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8 @settitle GNAT Reference Manual
13 @dircategory GNU Ada Tools
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24 GNAT Reference Manual , Nov 09, 2017
28 Copyright @copyright{} 2008-2017, Free Software Foundation
34 @title GNAT Reference Manual
39 @c %** start of user preamble
41 @c %** end of user preamble
45 @top GNAT Reference Manual
50 @anchor{gnat_rm doc}@anchor{0}
51 @emph{GNAT, The GNU Ada Development Environment}
54 @include gcc-common.texi
55 GCC version @value{version-GCC}@*
58 Permission is granted to copy, distribute and/or modify this document
59 under the terms of the GNU Free Documentation License, Version 1.3 or
60 any later version published by the Free Software Foundation; with no
61 Invariant Sections, with the Front-Cover Texts being "GNAT Reference
62 Manual", and with no Back-Cover Texts. A copy of the license is
63 included in the section entitled @ref{1,,GNU Free Documentation License}.
67 * Implementation Defined Pragmas::
68 * Implementation Defined Aspects::
69 * Implementation Defined Attributes::
70 * Standard and Implementation Defined Restrictions::
71 * Implementation Advice::
72 * Implementation Defined Characteristics::
73 * Intrinsic Subprograms::
74 * Representation Clauses and Pragmas::
75 * Standard Library Routines::
76 * The Implementation of Standard I/O::
78 * Interfacing to Other Languages::
79 * Specialized Needs Annexes::
80 * Implementation of Specific Ada Features::
81 * Implementation of Ada 2012 Features::
82 * Obsolescent Features::
83 * Compatibility and Porting Guide::
84 * GNU Free Documentation License::
88 --- The Detailed Node Listing ---
92 * What This Reference Manual Contains::
94 * Related Information::
96 Implementation Defined Pragmas
98 * Pragma Abort_Defer::
99 * Pragma Abstract_State::
106 * Pragma Allow_Integer_Address::
109 * Pragma Assert_And_Cut::
110 * Pragma Assertion_Policy::
112 * Pragma Assume_No_Invalid_Values::
113 * Pragma Async_Readers::
114 * Pragma Async_Writers::
115 * Pragma Attribute_Definition::
116 * Pragma C_Pass_By_Copy::
118 * Pragma Check_Float_Overflow::
119 * Pragma Check_Name::
120 * Pragma Check_Policy::
122 * Pragma Common_Object::
123 * Pragma Compile_Time_Error::
124 * Pragma Compile_Time_Warning::
125 * Pragma Compiler_Unit::
126 * Pragma Compiler_Unit_Warning::
127 * Pragma Complete_Representation::
128 * Pragma Complex_Representation::
129 * Pragma Component_Alignment::
130 * Pragma Constant_After_Elaboration::
131 * Pragma Contract_Cases::
132 * Pragma Convention_Identifier::
134 * Pragma CPP_Constructor::
135 * Pragma CPP_Virtual::
136 * Pragma CPP_Vtable::
138 * Pragma Deadline_Floor::
139 * Pragma Default_Initial_Condition::
141 * Pragma Debug_Policy::
142 * Pragma Default_Scalar_Storage_Order::
143 * Pragma Default_Storage_Pool::
145 * Pragma Detect_Blocking::
146 * Pragma Disable_Atomic_Synchronization::
147 * Pragma Dispatching_Domain::
148 * Pragma Effective_Reads::
149 * Pragma Effective_Writes::
150 * Pragma Elaboration_Checks::
152 * Pragma Enable_Atomic_Synchronization::
153 * Pragma Export_Function::
154 * Pragma Export_Object::
155 * Pragma Export_Procedure::
156 * Pragma Export_Value::
157 * Pragma Export_Valued_Procedure::
158 * Pragma Extend_System::
159 * Pragma Extensions_Allowed::
160 * Pragma Extensions_Visible::
162 * Pragma External_Name_Casing::
164 * Pragma Favor_Top_Level::
165 * Pragma Finalize_Storage_Only::
166 * Pragma Float_Representation::
170 * Pragma Ignore_Pragma::
171 * Pragma Implementation_Defined::
172 * Pragma Implemented::
173 * Pragma Implicit_Packing::
174 * Pragma Import_Function::
175 * Pragma Import_Object::
176 * Pragma Import_Procedure::
177 * Pragma Import_Valued_Procedure::
178 * Pragma Independent::
179 * Pragma Independent_Components::
180 * Pragma Initial_Condition::
181 * Pragma Initialize_Scalars::
182 * Pragma Initializes::
183 * Pragma Inline_Always::
184 * Pragma Inline_Generic::
186 * Pragma Interface_Name::
187 * Pragma Interrupt_Handler::
188 * Pragma Interrupt_State::
190 * Pragma Keep_Names::
193 * Pragma Linker_Alias::
194 * Pragma Linker_Constructor::
195 * Pragma Linker_Destructor::
196 * Pragma Linker_Section::
198 * Pragma Loop_Invariant::
199 * Pragma Loop_Optimize::
200 * Pragma Loop_Variant::
201 * Pragma Machine_Attribute::
203 * Pragma Main_Storage::
204 * Pragma Max_Queue_Length::
206 * Pragma No_Component_Reordering::
207 * Pragma No_Elaboration_Code_All::
208 * Pragma No_Heap_Finalization::
211 * Pragma No_Run_Time::
212 * Pragma No_Strict_Aliasing::
213 * Pragma No_Tagged_Streams::
214 * Pragma Normalize_Scalars::
215 * Pragma Obsolescent::
216 * Pragma Optimize_Alignment::
218 * Pragma Overflow_Mode::
219 * Pragma Overriding_Renamings::
220 * Pragma Partition_Elaboration_Policy::
223 * Pragma Persistent_BSS::
226 * Pragma Postcondition::
227 * Pragma Post_Class::
228 * Pragma Rename_Pragma::
230 * Pragma Precondition::
232 * Pragma Predicate_Failure::
233 * Pragma Preelaborable_Initialization::
234 * Pragma Prefix_Exception_Messages::
236 * Pragma Priority_Specific_Dispatching::
238 * Pragma Profile_Warnings::
239 * Pragma Propagate_Exceptions::
240 * Pragma Provide_Shift_Operators::
241 * Pragma Psect_Object::
242 * Pragma Pure_Function::
245 * Pragma Refined_Depends::
246 * Pragma Refined_Global::
247 * Pragma Refined_Post::
248 * Pragma Refined_State::
249 * Pragma Relative_Deadline::
250 * Pragma Remote_Access_Type::
251 * Pragma Restricted_Run_Time::
252 * Pragma Restriction_Warnings::
253 * Pragma Reviewable::
254 * Pragma Secondary_Stack_Size::
255 * Pragma Share_Generic::
257 * Pragma Short_Circuit_And_Or::
258 * Pragma Short_Descriptors::
259 * Pragma Simple_Storage_Pool_Type::
260 * Pragma Source_File_Name::
261 * Pragma Source_File_Name_Project::
262 * Pragma Source_Reference::
263 * Pragma SPARK_Mode::
264 * Pragma Static_Elaboration_Desired::
265 * Pragma Stream_Convert::
266 * Pragma Style_Checks::
269 * Pragma Suppress_All::
270 * Pragma Suppress_Debug_Info::
271 * Pragma Suppress_Exception_Locations::
272 * Pragma Suppress_Initialization::
274 * Pragma Task_Storage::
276 * Pragma Thread_Local_Storage::
277 * Pragma Time_Slice::
279 * Pragma Type_Invariant::
280 * Pragma Type_Invariant_Class::
281 * Pragma Unchecked_Union::
282 * Pragma Unevaluated_Use_Of_Old::
283 * Pragma Unimplemented_Unit::
284 * Pragma Universal_Aliasing::
285 * Pragma Universal_Data::
286 * Pragma Unmodified::
287 * Pragma Unreferenced::
288 * Pragma Unreferenced_Objects::
289 * Pragma Unreserve_All_Interrupts::
290 * Pragma Unsuppress::
291 * Pragma Use_VADS_Size::
293 * Pragma Validity_Checks::
295 * Pragma Volatile_Full_Access::
296 * Pragma Volatile_Function::
297 * Pragma Warning_As_Error::
299 * Pragma Weak_External::
300 * Pragma Wide_Character_Encoding::
302 Implementation Defined Aspects
304 * Aspect Abstract_State::
306 * Aspect Async_Readers::
307 * Aspect Async_Writers::
308 * Aspect Constant_After_Elaboration::
309 * Aspect Contract_Cases::
311 * Aspect Default_Initial_Condition::
313 * Aspect Dimension_System::
314 * Aspect Disable_Controlled::
315 * Aspect Effective_Reads::
316 * Aspect Effective_Writes::
317 * Aspect Extensions_Visible::
318 * Aspect Favor_Top_Level::
321 * Aspect Initial_Condition::
322 * Aspect Initializes::
323 * Aspect Inline_Always::
325 * Aspect Invariant'Class::
327 * Aspect Linker_Section::
329 * Aspect Max_Queue_Length::
330 * Aspect No_Elaboration_Code_All::
332 * Aspect No_Tagged_Streams::
333 * Aspect Object_Size::
334 * Aspect Obsolescent::
336 * Aspect Persistent_BSS::
338 * Aspect Pure_Function::
339 * Aspect Refined_Depends::
340 * Aspect Refined_Global::
341 * Aspect Refined_Post::
342 * Aspect Refined_State::
343 * Aspect Remote_Access_Type::
344 * Aspect Secondary_Stack_Size::
345 * Aspect Scalar_Storage_Order::
347 * Aspect Simple_Storage_Pool::
348 * Aspect Simple_Storage_Pool_Type::
349 * Aspect SPARK_Mode::
350 * Aspect Suppress_Debug_Info::
351 * Aspect Suppress_Initialization::
353 * Aspect Thread_Local_Storage::
354 * Aspect Universal_Aliasing::
355 * Aspect Universal_Data::
356 * Aspect Unmodified::
357 * Aspect Unreferenced::
358 * Aspect Unreferenced_Objects::
359 * Aspect Value_Size::
360 * Aspect Volatile_Full_Access::
361 * Aspect Volatile_Function::
364 Implementation Defined Attributes
366 * Attribute Abort_Signal::
367 * Attribute Address_Size::
368 * Attribute Asm_Input::
369 * Attribute Asm_Output::
370 * Attribute Atomic_Always_Lock_Free::
372 * Attribute Bit_Position::
373 * Attribute Code_Address::
374 * Attribute Compiler_Version::
375 * Attribute Constrained::
376 * Attribute Default_Bit_Order::
377 * Attribute Default_Scalar_Storage_Order::
379 * Attribute Descriptor_Size::
380 * Attribute Elaborated::
381 * Attribute Elab_Body::
382 * Attribute Elab_Spec::
383 * Attribute Elab_Subp_Body::
385 * Attribute Enabled::
386 * Attribute Enum_Rep::
387 * Attribute Enum_Val::
388 * Attribute Epsilon::
389 * Attribute Fast_Math::
390 * Attribute Finalization_Size::
391 * Attribute Fixed_Value::
392 * Attribute From_Any::
393 * Attribute Has_Access_Values::
394 * Attribute Has_Discriminants::
396 * Attribute Integer_Value::
397 * Attribute Invalid_Value::
398 * Attribute Iterable::
400 * Attribute Library_Level::
401 * Attribute Lock_Free::
402 * Attribute Loop_Entry::
403 * Attribute Machine_Size::
404 * Attribute Mantissa::
405 * Attribute Maximum_Alignment::
406 * Attribute Mechanism_Code::
407 * Attribute Null_Parameter::
408 * Attribute Object_Size::
410 * Attribute Passed_By_Reference::
411 * Attribute Pool_Address::
412 * Attribute Range_Length::
413 * Attribute Restriction_Set::
415 * Attribute Safe_Emax::
416 * Attribute Safe_Large::
417 * Attribute Safe_Small::
418 * Attribute Scalar_Storage_Order::
419 * Attribute Simple_Storage_Pool::
421 * Attribute Storage_Unit::
422 * Attribute Stub_Type::
423 * Attribute System_Allocator_Alignment::
424 * Attribute Target_Name::
425 * Attribute To_Address::
427 * Attribute Type_Class::
428 * Attribute Type_Key::
429 * Attribute TypeCode::
430 * Attribute Unconstrained_Array::
431 * Attribute Universal_Literal_String::
432 * Attribute Unrestricted_Access::
434 * Attribute Valid_Scalars::
435 * Attribute VADS_Size::
436 * Attribute Value_Size::
437 * Attribute Wchar_T_Size::
438 * Attribute Word_Size::
440 Standard and Implementation Defined Restrictions
442 * Partition-Wide Restrictions::
443 * Program Unit Level Restrictions::
445 Partition-Wide Restrictions
447 * Immediate_Reclamation::
448 * Max_Asynchronous_Select_Nesting::
449 * Max_Entry_Queue_Length::
450 * Max_Protected_Entries::
451 * Max_Select_Alternatives::
452 * Max_Storage_At_Blocking::
455 * No_Abort_Statements::
456 * No_Access_Parameter_Allocators::
457 * No_Access_Subprograms::
459 * No_Anonymous_Allocators::
460 * No_Asynchronous_Control::
463 * No_Default_Initialization::
466 * No_Direct_Boolean_Operators::
468 * No_Dispatching_Calls::
469 * No_Dynamic_Attachment::
470 * No_Dynamic_Priorities::
471 * No_Entry_Calls_In_Elaboration_Code::
472 * No_Enumeration_Maps::
473 * No_Exception_Handlers::
474 * No_Exception_Propagation::
475 * No_Exception_Registration::
479 * No_Floating_Point::
480 * No_Implicit_Conditionals::
481 * No_Implicit_Dynamic_Code::
482 * No_Implicit_Heap_Allocations::
483 * No_Implicit_Protected_Object_Allocations::
484 * No_Implicit_Task_Allocations::
485 * No_Initialize_Scalars::
487 * No_Local_Allocators::
488 * No_Local_Protected_Objects::
489 * No_Local_Timing_Events::
490 * No_Long_Long_Integers::
491 * No_Multiple_Elaboration::
492 * No_Nested_Finalization::
493 * No_Protected_Type_Allocators::
494 * No_Protected_Types::
497 * No_Relative_Delay::
498 * No_Requeue_Statements::
499 * No_Secondary_Stack::
500 * No_Select_Statements::
501 * No_Specific_Termination_Handlers::
502 * No_Specification_of_Aspect::
503 * No_Standard_Allocators_After_Elaboration::
504 * No_Standard_Storage_Pools::
505 * No_Stream_Optimizations::
507 * No_Task_Allocators::
508 * No_Task_At_Interrupt_Priority::
509 * No_Task_Attributes_Package::
510 * No_Task_Hierarchy::
511 * No_Task_Termination::
513 * No_Terminate_Alternatives::
514 * No_Unchecked_Access::
515 * No_Unchecked_Conversion::
516 * No_Unchecked_Deallocation::
520 * Static_Priorities::
521 * Static_Storage_Size::
523 Program Unit Level Restrictions
525 * No_Elaboration_Code::
526 * No_Dynamic_Sized_Objects::
528 * No_Implementation_Aspect_Specifications::
529 * No_Implementation_Attributes::
530 * No_Implementation_Identifiers::
531 * No_Implementation_Pragmas::
532 * No_Implementation_Restrictions::
533 * No_Implementation_Units::
534 * No_Implicit_Aliasing::
535 * No_Implicit_Loops::
536 * No_Obsolescent_Features::
537 * No_Wide_Characters::
538 * Static_Dispatch_Tables::
541 Implementation Advice
543 * RM 1.1.3(20); Error Detection: RM 1 1 3 20 Error Detection.
544 * RM 1.1.3(31); Child Units: RM 1 1 3 31 Child Units.
545 * RM 1.1.5(12); Bounded Errors: RM 1 1 5 12 Bounded Errors.
546 * RM 2.8(16); Pragmas: RM 2 8 16 Pragmas.
547 * RM 2.8(17-19); Pragmas: RM 2 8 17-19 Pragmas.
548 * RM 3.5.2(5); Alternative Character Sets: RM 3 5 2 5 Alternative Character Sets.
549 * RM 3.5.4(28); Integer Types: RM 3 5 4 28 Integer Types.
550 * RM 3.5.4(29); Integer Types: RM 3 5 4 29 Integer Types.
551 * RM 3.5.5(8); Enumeration Values: RM 3 5 5 8 Enumeration Values.
552 * RM 3.5.7(17); Float Types: RM 3 5 7 17 Float Types.
553 * RM 3.6.2(11); Multidimensional Arrays: RM 3 6 2 11 Multidimensional Arrays.
554 * RM 9.6(30-31); Duration'Small: RM 9 6 30-31 Duration'Small.
555 * RM 10.2.1(12); Consistent Representation: RM 10 2 1 12 Consistent Representation.
556 * RM 11.4.1(19); Exception Information: RM 11 4 1 19 Exception Information.
557 * RM 11.5(28); Suppression of Checks: RM 11 5 28 Suppression of Checks.
558 * RM 13.1 (21-24); Representation Clauses: RM 13 1 21-24 Representation Clauses.
559 * RM 13.2(6-8); Packed Types: RM 13 2 6-8 Packed Types.
560 * RM 13.3(14-19); Address Clauses: RM 13 3 14-19 Address Clauses.
561 * RM 13.3(29-35); Alignment Clauses: RM 13 3 29-35 Alignment Clauses.
562 * RM 13.3(42-43); Size Clauses: RM 13 3 42-43 Size Clauses.
563 * RM 13.3(50-56); Size Clauses: RM 13 3 50-56 Size Clauses.
564 * RM 13.3(71-73); Component Size Clauses: RM 13 3 71-73 Component Size Clauses.
565 * RM 13.4(9-10); Enumeration Representation Clauses: RM 13 4 9-10 Enumeration Representation Clauses.
566 * RM 13.5.1(17-22); Record Representation Clauses: RM 13 5 1 17-22 Record Representation Clauses.
567 * RM 13.5.2(5); Storage Place Attributes: RM 13 5 2 5 Storage Place Attributes.
568 * RM 13.5.3(7-8); Bit Ordering: RM 13 5 3 7-8 Bit Ordering.
569 * RM 13.7(37); Address as Private: RM 13 7 37 Address as Private.
570 * RM 13.7.1(16); Address Operations: RM 13 7 1 16 Address Operations.
571 * RM 13.9(14-17); Unchecked Conversion: RM 13 9 14-17 Unchecked Conversion.
572 * RM 13.11(23-25); Implicit Heap Usage: RM 13 11 23-25 Implicit Heap Usage.
573 * RM 13.11.2(17); Unchecked Deallocation: RM 13 11 2 17 Unchecked Deallocation.
574 * RM 13.13.2(17); Stream Oriented Attributes: RM 13 13 2 17 Stream Oriented Attributes.
575 * RM A.1(52); Names of Predefined Numeric Types: RM A 1 52 Names of Predefined Numeric Types.
576 * RM A.3.2(49); Ada.Characters.Handling: RM A 3 2 49 Ada Characters Handling.
577 * RM A.4.4(106); Bounded-Length String Handling: RM A 4 4 106 Bounded-Length String Handling.
578 * RM A.5.2(46-47); Random Number Generation: RM A 5 2 46-47 Random Number Generation.
579 * RM A.10.7(23); Get_Immediate: RM A 10 7 23 Get_Immediate.
580 * RM B.1(39-41); Pragma Export: RM B 1 39-41 Pragma Export.
581 * RM B.2(12-13); Package Interfaces: RM B 2 12-13 Package Interfaces.
582 * RM B.3(63-71); Interfacing with C: RM B 3 63-71 Interfacing with C.
583 * RM B.4(95-98); Interfacing with COBOL: RM B 4 95-98 Interfacing with COBOL.
584 * RM B.5(22-26); Interfacing with Fortran: RM B 5 22-26 Interfacing with Fortran.
585 * RM C.1(3-5); Access to Machine Operations: RM C 1 3-5 Access to Machine Operations.
586 * RM C.1(10-16); Access to Machine Operations: RM C 1 10-16 Access to Machine Operations.
587 * RM C.3(28); Interrupt Support: RM C 3 28 Interrupt Support.
588 * RM C.3.1(20-21); Protected Procedure Handlers: RM C 3 1 20-21 Protected Procedure Handlers.
589 * RM C.3.2(25); Package Interrupts: RM C 3 2 25 Package Interrupts.
590 * RM C.4(14); Pre-elaboration Requirements: RM C 4 14 Pre-elaboration Requirements.
591 * RM C.5(8); Pragma Discard_Names: RM C 5 8 Pragma Discard_Names.
592 * RM C.7.2(30); The Package Task_Attributes: RM C 7 2 30 The Package Task_Attributes.
593 * RM D.3(17); Locking Policies: RM D 3 17 Locking Policies.
594 * RM D.4(16); Entry Queuing Policies: RM D 4 16 Entry Queuing Policies.
595 * RM D.6(9-10); Preemptive Abort: RM D 6 9-10 Preemptive Abort.
596 * RM D.7(21); Tasking Restrictions: RM D 7 21 Tasking Restrictions.
597 * RM D.8(47-49); Monotonic Time: RM D 8 47-49 Monotonic Time.
598 * RM E.5(28-29); Partition Communication Subsystem: RM E 5 28-29 Partition Communication Subsystem.
599 * RM F(7); COBOL Support: RM F 7 COBOL Support.
600 * RM F.1(2); Decimal Radix Support: RM F 1 2 Decimal Radix Support.
601 * RM G; Numerics: RM G Numerics.
602 * RM G.1.1(56-58); Complex Types: RM G 1 1 56-58 Complex Types.
603 * RM G.1.2(49); Complex Elementary Functions: RM G 1 2 49 Complex Elementary Functions.
604 * RM G.2.4(19); Accuracy Requirements: RM G 2 4 19 Accuracy Requirements.
605 * RM G.2.6(15); Complex Arithmetic Accuracy: RM G 2 6 15 Complex Arithmetic Accuracy.
606 * RM H.6(15/2); Pragma Partition_Elaboration_Policy: RM H 6 15/2 Pragma Partition_Elaboration_Policy.
608 Intrinsic Subprograms
610 * Intrinsic Operators::
611 * Compilation_ISO_Date::
615 * Exception_Information::
616 * Exception_Message::
620 * Shifts and Rotates::
623 Representation Clauses and Pragmas
625 * Alignment Clauses::
627 * Storage_Size Clauses::
628 * Size of Variant Record Objects::
629 * Biased Representation::
630 * Value_Size and Object_Size Clauses::
631 * Component_Size Clauses::
632 * Bit_Order Clauses::
633 * Effect of Bit_Order on Byte Ordering::
634 * Pragma Pack for Arrays::
635 * Pragma Pack for Records::
636 * Record Representation Clauses::
637 * Handling of Records with Holes::
638 * Enumeration Clauses::
640 * Use of Address Clauses for Memory-Mapped I/O::
641 * Effect of Convention on Representation::
642 * Conventions and Anonymous Access Types::
643 * Determining the Representations chosen by GNAT::
645 The Implementation of Standard I/O
647 * Standard I/O Packages::
653 * Wide_Wide_Text_IO::
657 * Filenames encoding::
658 * File content encoding::
660 * Operations on C Streams::
661 * Interfacing to C Streams::
665 * Stream Pointer Positioning::
666 * Reading and Writing Non-Regular Files::
668 * Treating Text_IO Files as Streams::
669 * Text_IO Extensions::
670 * Text_IO Facilities for Unbounded Strings::
674 * Stream Pointer Positioning: Stream Pointer Positioning<2>.
675 * Reading and Writing Non-Regular Files: Reading and Writing Non-Regular Files<2>.
679 * Stream Pointer Positioning: Stream Pointer Positioning<3>.
680 * Reading and Writing Non-Regular Files: Reading and Writing Non-Regular Files<3>.
684 * Ada.Characters.Latin_9 (a-chlat9.ads): Ada Characters Latin_9 a-chlat9 ads.
685 * Ada.Characters.Wide_Latin_1 (a-cwila1.ads): Ada Characters Wide_Latin_1 a-cwila1 ads.
686 * Ada.Characters.Wide_Latin_9 (a-cwila1.ads): Ada Characters Wide_Latin_9 a-cwila1 ads.
687 * Ada.Characters.Wide_Wide_Latin_1 (a-chzla1.ads): Ada Characters Wide_Wide_Latin_1 a-chzla1 ads.
688 * Ada.Characters.Wide_Wide_Latin_9 (a-chzla9.ads): Ada Characters Wide_Wide_Latin_9 a-chzla9 ads.
689 * Ada.Containers.Formal_Doubly_Linked_Lists (a-cfdlli.ads): Ada Containers Formal_Doubly_Linked_Lists a-cfdlli ads.
690 * Ada.Containers.Formal_Hashed_Maps (a-cfhama.ads): Ada Containers Formal_Hashed_Maps a-cfhama ads.
691 * Ada.Containers.Formal_Hashed_Sets (a-cfhase.ads): Ada Containers Formal_Hashed_Sets a-cfhase ads.
692 * Ada.Containers.Formal_Ordered_Maps (a-cforma.ads): Ada Containers Formal_Ordered_Maps a-cforma ads.
693 * Ada.Containers.Formal_Ordered_Sets (a-cforse.ads): Ada Containers Formal_Ordered_Sets a-cforse ads.
694 * Ada.Containers.Formal_Vectors (a-cofove.ads): Ada Containers Formal_Vectors a-cofove ads.
695 * Ada.Containers.Formal_Indefinite_Vectors (a-cfinve.ads): Ada Containers Formal_Indefinite_Vectors a-cfinve ads.
696 * Ada.Containers.Functional_Vectors (a-cofuve.ads): Ada Containers Functional_Vectors a-cofuve ads.
697 * Ada.Containers.Functional_Sets (a-cofuse.ads): Ada Containers Functional_Sets a-cofuse ads.
698 * Ada.Containers.Functional_Maps (a-cofuma.ads): Ada Containers Functional_Maps a-cofuma ads.
699 * Ada.Containers.Bounded_Holders (a-coboho.ads): Ada Containers Bounded_Holders a-coboho ads.
700 * Ada.Command_Line.Environment (a-colien.ads): Ada Command_Line Environment a-colien ads.
701 * Ada.Command_Line.Remove (a-colire.ads): Ada Command_Line Remove a-colire ads.
702 * Ada.Command_Line.Response_File (a-clrefi.ads): Ada Command_Line Response_File a-clrefi ads.
703 * Ada.Direct_IO.C_Streams (a-diocst.ads): Ada Direct_IO C_Streams a-diocst ads.
704 * Ada.Exceptions.Is_Null_Occurrence (a-einuoc.ads): Ada Exceptions Is_Null_Occurrence a-einuoc ads.
705 * Ada.Exceptions.Last_Chance_Handler (a-elchha.ads): Ada Exceptions Last_Chance_Handler a-elchha ads.
706 * Ada.Exceptions.Traceback (a-exctra.ads): Ada Exceptions Traceback a-exctra ads.
707 * Ada.Sequential_IO.C_Streams (a-siocst.ads): Ada Sequential_IO C_Streams a-siocst ads.
708 * Ada.Streams.Stream_IO.C_Streams (a-ssicst.ads): Ada Streams Stream_IO C_Streams a-ssicst ads.
709 * Ada.Strings.Unbounded.Text_IO (a-suteio.ads): Ada Strings Unbounded Text_IO a-suteio ads.
710 * Ada.Strings.Wide_Unbounded.Wide_Text_IO (a-swuwti.ads): Ada Strings Wide_Unbounded Wide_Text_IO a-swuwti ads.
711 * Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO (a-szuzti.ads): Ada Strings Wide_Wide_Unbounded Wide_Wide_Text_IO a-szuzti ads.
712 * Ada.Text_IO.C_Streams (a-tiocst.ads): Ada Text_IO C_Streams a-tiocst ads.
713 * Ada.Text_IO.Reset_Standard_Files (a-tirsfi.ads): Ada Text_IO Reset_Standard_Files a-tirsfi ads.
714 * Ada.Wide_Characters.Unicode (a-wichun.ads): Ada Wide_Characters Unicode a-wichun ads.
715 * Ada.Wide_Text_IO.C_Streams (a-wtcstr.ads): Ada Wide_Text_IO C_Streams a-wtcstr ads.
716 * Ada.Wide_Text_IO.Reset_Standard_Files (a-wrstfi.ads): Ada Wide_Text_IO Reset_Standard_Files a-wrstfi ads.
717 * Ada.Wide_Wide_Characters.Unicode (a-zchuni.ads): Ada Wide_Wide_Characters Unicode a-zchuni ads.
718 * Ada.Wide_Wide_Text_IO.C_Streams (a-ztcstr.ads): Ada Wide_Wide_Text_IO C_Streams a-ztcstr ads.
719 * Ada.Wide_Wide_Text_IO.Reset_Standard_Files (a-zrstfi.ads): Ada Wide_Wide_Text_IO Reset_Standard_Files a-zrstfi ads.
720 * GNAT.Altivec (g-altive.ads): GNAT Altivec g-altive ads.
721 * GNAT.Altivec.Conversions (g-altcon.ads): GNAT Altivec Conversions g-altcon ads.
722 * GNAT.Altivec.Vector_Operations (g-alveop.ads): GNAT Altivec Vector_Operations g-alveop ads.
723 * GNAT.Altivec.Vector_Types (g-alvety.ads): GNAT Altivec Vector_Types g-alvety ads.
724 * GNAT.Altivec.Vector_Views (g-alvevi.ads): GNAT Altivec Vector_Views g-alvevi ads.
725 * GNAT.Array_Split (g-arrspl.ads): GNAT Array_Split g-arrspl ads.
726 * GNAT.AWK (g-awk.ads): GNAT AWK g-awk ads.
727 * GNAT.Bind_Environment (g-binenv.ads): GNAT Bind_Environment g-binenv ads.
728 * GNAT.Bounded_Buffers (g-boubuf.ads): GNAT Bounded_Buffers g-boubuf ads.
729 * GNAT.Bounded_Mailboxes (g-boumai.ads): GNAT Bounded_Mailboxes g-boumai ads.
730 * GNAT.Bubble_Sort (g-bubsor.ads): GNAT Bubble_Sort g-bubsor ads.
731 * GNAT.Bubble_Sort_A (g-busora.ads): GNAT Bubble_Sort_A g-busora ads.
732 * GNAT.Bubble_Sort_G (g-busorg.ads): GNAT Bubble_Sort_G g-busorg ads.
733 * GNAT.Byte_Order_Mark (g-byorma.ads): GNAT Byte_Order_Mark g-byorma ads.
734 * GNAT.Byte_Swapping (g-bytswa.ads): GNAT Byte_Swapping g-bytswa ads.
735 * GNAT.Calendar (g-calend.ads): GNAT Calendar g-calend ads.
736 * GNAT.Calendar.Time_IO (g-catiio.ads): GNAT Calendar Time_IO g-catiio ads.
737 * GNAT.CRC32 (g-crc32.ads): GNAT CRC32 g-crc32 ads.
738 * GNAT.Case_Util (g-casuti.ads): GNAT Case_Util g-casuti ads.
739 * GNAT.CGI (g-cgi.ads): GNAT CGI g-cgi ads.
740 * GNAT.CGI.Cookie (g-cgicoo.ads): GNAT CGI Cookie g-cgicoo ads.
741 * GNAT.CGI.Debug (g-cgideb.ads): GNAT CGI Debug g-cgideb ads.
742 * GNAT.Command_Line (g-comlin.ads): GNAT Command_Line g-comlin ads.
743 * GNAT.Compiler_Version (g-comver.ads): GNAT Compiler_Version g-comver ads.
744 * GNAT.Ctrl_C (g-ctrl_c.ads): GNAT Ctrl_C g-ctrl_c ads.
745 * GNAT.Current_Exception (g-curexc.ads): GNAT Current_Exception g-curexc ads.
746 * GNAT.Debug_Pools (g-debpoo.ads): GNAT Debug_Pools g-debpoo ads.
747 * GNAT.Debug_Utilities (g-debuti.ads): GNAT Debug_Utilities g-debuti ads.
748 * GNAT.Decode_String (g-decstr.ads): GNAT Decode_String g-decstr ads.
749 * GNAT.Decode_UTF8_String (g-deutst.ads): GNAT Decode_UTF8_String g-deutst ads.
750 * GNAT.Directory_Operations (g-dirope.ads): GNAT Directory_Operations g-dirope ads.
751 * GNAT.Directory_Operations.Iteration (g-diopit.ads): GNAT Directory_Operations Iteration g-diopit ads.
752 * GNAT.Dynamic_HTables (g-dynhta.ads): GNAT Dynamic_HTables g-dynhta ads.
753 * GNAT.Dynamic_Tables (g-dyntab.ads): GNAT Dynamic_Tables g-dyntab ads.
754 * GNAT.Encode_String (g-encstr.ads): GNAT Encode_String g-encstr ads.
755 * GNAT.Encode_UTF8_String (g-enutst.ads): GNAT Encode_UTF8_String g-enutst ads.
756 * GNAT.Exception_Actions (g-excact.ads): GNAT Exception_Actions g-excact ads.
757 * GNAT.Exception_Traces (g-exctra.ads): GNAT Exception_Traces g-exctra ads.
758 * GNAT.Exceptions (g-expect.ads): GNAT Exceptions g-expect ads.
759 * GNAT.Expect (g-expect.ads): GNAT Expect g-expect ads.
760 * GNAT.Expect.TTY (g-exptty.ads): GNAT Expect TTY g-exptty ads.
761 * GNAT.Float_Control (g-flocon.ads): GNAT Float_Control g-flocon ads.
762 * GNAT.Formatted_String (g-forstr.ads): GNAT Formatted_String g-forstr ads.
763 * GNAT.Heap_Sort (g-heasor.ads): GNAT Heap_Sort g-heasor ads.
764 * GNAT.Heap_Sort_A (g-hesora.ads): GNAT Heap_Sort_A g-hesora ads.
765 * GNAT.Heap_Sort_G (g-hesorg.ads): GNAT Heap_Sort_G g-hesorg ads.
766 * GNAT.HTable (g-htable.ads): GNAT HTable g-htable ads.
767 * GNAT.IO (g-io.ads): GNAT IO g-io ads.
768 * GNAT.IO_Aux (g-io_aux.ads): GNAT IO_Aux g-io_aux ads.
769 * GNAT.Lock_Files (g-locfil.ads): GNAT Lock_Files g-locfil ads.
770 * GNAT.MBBS_Discrete_Random (g-mbdira.ads): GNAT MBBS_Discrete_Random g-mbdira ads.
771 * GNAT.MBBS_Float_Random (g-mbflra.ads): GNAT MBBS_Float_Random g-mbflra ads.
772 * GNAT.MD5 (g-md5.ads): GNAT MD5 g-md5 ads.
773 * GNAT.Memory_Dump (g-memdum.ads): GNAT Memory_Dump g-memdum ads.
774 * GNAT.Most_Recent_Exception (g-moreex.ads): GNAT Most_Recent_Exception g-moreex ads.
775 * GNAT.OS_Lib (g-os_lib.ads): GNAT OS_Lib g-os_lib ads.
776 * GNAT.Perfect_Hash_Generators (g-pehage.ads): GNAT Perfect_Hash_Generators g-pehage ads.
777 * GNAT.Random_Numbers (g-rannum.ads): GNAT Random_Numbers g-rannum ads.
778 * GNAT.Regexp (g-regexp.ads): GNAT Regexp g-regexp ads.
779 * GNAT.Registry (g-regist.ads): GNAT Registry g-regist ads.
780 * GNAT.Regpat (g-regpat.ads): GNAT Regpat g-regpat ads.
781 * GNAT.Rewrite_Data (g-rewdat.ads): GNAT Rewrite_Data g-rewdat ads.
782 * GNAT.Secondary_Stack_Info (g-sestin.ads): GNAT Secondary_Stack_Info g-sestin ads.
783 * GNAT.Semaphores (g-semaph.ads): GNAT Semaphores g-semaph ads.
784 * GNAT.Serial_Communications (g-sercom.ads): GNAT Serial_Communications g-sercom ads.
785 * GNAT.SHA1 (g-sha1.ads): GNAT SHA1 g-sha1 ads.
786 * GNAT.SHA224 (g-sha224.ads): GNAT SHA224 g-sha224 ads.
787 * GNAT.SHA256 (g-sha256.ads): GNAT SHA256 g-sha256 ads.
788 * GNAT.SHA384 (g-sha384.ads): GNAT SHA384 g-sha384 ads.
789 * GNAT.SHA512 (g-sha512.ads): GNAT SHA512 g-sha512 ads.
790 * GNAT.Signals (g-signal.ads): GNAT Signals g-signal ads.
791 * GNAT.Sockets (g-socket.ads): GNAT Sockets g-socket ads.
792 * GNAT.Source_Info (g-souinf.ads): GNAT Source_Info g-souinf ads.
793 * GNAT.Spelling_Checker (g-speche.ads): GNAT Spelling_Checker g-speche ads.
794 * GNAT.Spelling_Checker_Generic (g-spchge.ads): GNAT Spelling_Checker_Generic g-spchge ads.
795 * GNAT.Spitbol.Patterns (g-spipat.ads): GNAT Spitbol Patterns g-spipat ads.
796 * GNAT.Spitbol (g-spitbo.ads): GNAT Spitbol g-spitbo ads.
797 * GNAT.Spitbol.Table_Boolean (g-sptabo.ads): GNAT Spitbol Table_Boolean g-sptabo ads.
798 * GNAT.Spitbol.Table_Integer (g-sptain.ads): GNAT Spitbol Table_Integer g-sptain ads.
799 * GNAT.Spitbol.Table_VString (g-sptavs.ads): GNAT Spitbol Table_VString g-sptavs ads.
800 * GNAT.SSE (g-sse.ads): GNAT SSE g-sse ads.
801 * GNAT.SSE.Vector_Types (g-ssvety.ads): GNAT SSE Vector_Types g-ssvety ads.
802 * GNAT.String_Hash (g-strhas.ads): GNAT String_Hash g-strhas ads.
803 * GNAT.Strings (g-string.ads): GNAT Strings g-string ads.
804 * GNAT.String_Split (g-strspl.ads): GNAT String_Split g-strspl ads.
805 * GNAT.Table (g-table.ads): GNAT Table g-table ads.
806 * GNAT.Task_Lock (g-tasloc.ads): GNAT Task_Lock g-tasloc ads.
807 * GNAT.Time_Stamp (g-timsta.ads): GNAT Time_Stamp g-timsta ads.
808 * GNAT.Threads (g-thread.ads): GNAT Threads g-thread ads.
809 * GNAT.Traceback (g-traceb.ads): GNAT Traceback g-traceb ads.
810 * GNAT.Traceback.Symbolic (g-trasym.ads): GNAT Traceback Symbolic g-trasym ads.
811 * GNAT.UTF_32 (g-table.ads): GNAT UTF_32 g-table ads.
812 * GNAT.Wide_Spelling_Checker (g-u3spch.ads): GNAT Wide_Spelling_Checker g-u3spch ads.
813 * GNAT.Wide_Spelling_Checker (g-wispch.ads): GNAT Wide_Spelling_Checker g-wispch ads.
814 * GNAT.Wide_String_Split (g-wistsp.ads): GNAT Wide_String_Split g-wistsp ads.
815 * GNAT.Wide_Wide_Spelling_Checker (g-zspche.ads): GNAT Wide_Wide_Spelling_Checker g-zspche ads.
816 * GNAT.Wide_Wide_String_Split (g-zistsp.ads): GNAT Wide_Wide_String_Split g-zistsp ads.
817 * Interfaces.C.Extensions (i-cexten.ads): Interfaces C Extensions i-cexten ads.
818 * Interfaces.C.Streams (i-cstrea.ads): Interfaces C Streams i-cstrea ads.
819 * Interfaces.Packed_Decimal (i-pacdec.ads): Interfaces Packed_Decimal i-pacdec ads.
820 * Interfaces.VxWorks (i-vxwork.ads): Interfaces VxWorks i-vxwork ads.
821 * Interfaces.VxWorks.Int_Connection (i-vxinco.ads): Interfaces VxWorks Int_Connection i-vxinco ads.
822 * Interfaces.VxWorks.IO (i-vxwoio.ads): Interfaces VxWorks IO i-vxwoio ads.
823 * System.Address_Image (s-addima.ads): System Address_Image s-addima ads.
824 * System.Assertions (s-assert.ads): System Assertions s-assert ads.
825 * System.Atomic_Counters (s-atocou.ads): System Atomic_Counters s-atocou ads.
826 * System.Memory (s-memory.ads): System Memory s-memory ads.
827 * System.Multiprocessors (s-multip.ads): System Multiprocessors s-multip ads.
828 * System.Multiprocessors.Dispatching_Domains (s-mudido.ads): System Multiprocessors Dispatching_Domains s-mudido ads.
829 * System.Partition_Interface (s-parint.ads): System Partition_Interface s-parint ads.
830 * System.Pool_Global (s-pooglo.ads): System Pool_Global s-pooglo ads.
831 * System.Pool_Local (s-pooloc.ads): System Pool_Local s-pooloc ads.
832 * System.Restrictions (s-restri.ads): System Restrictions s-restri ads.
833 * System.Rident (s-rident.ads): System Rident s-rident ads.
834 * System.Strings.Stream_Ops (s-ststop.ads): System Strings Stream_Ops s-ststop ads.
835 * System.Unsigned_Types (s-unstyp.ads): System Unsigned_Types s-unstyp ads.
836 * System.Wch_Cnv (s-wchcnv.ads): System Wch_Cnv s-wchcnv ads.
837 * System.Wch_Con (s-wchcon.ads): System Wch_Con s-wchcon ads.
839 Interfacing to Other Languages
842 * Interfacing to C++::
843 * Interfacing to COBOL::
844 * Interfacing to Fortran::
845 * Interfacing to non-GNAT Ada code::
847 Implementation of Specific Ada Features
849 * Machine Code Insertions::
850 * GNAT Implementation of Tasking::
851 * GNAT Implementation of Shared Passive Packages::
852 * Code Generation for Array Aggregates::
853 * The Size of Discriminated Records with Default Discriminants::
854 * Strict Conformance to the Ada Reference Manual::
856 GNAT Implementation of Tasking
858 * Mapping Ada Tasks onto the Underlying Kernel Threads::
859 * Ensuring Compliance with the Real-Time Annex::
860 * Support for Locking Policies::
862 Code Generation for Array Aggregates
864 * Static constant aggregates with static bounds::
865 * Constant aggregates with unconstrained nominal types::
866 * Aggregates with static bounds::
867 * Aggregates with nonstatic bounds::
868 * Aggregates in assignment statements::
872 * pragma No_Run_Time::
874 * pragma Restricted_Run_Time::
876 * package System.Task_Info (s-tasinf.ads): package System Task_Info s-tasinf ads.
878 Compatibility and Porting Guide
880 * Writing Portable Fixed-Point Declarations::
881 * Compatibility with Ada 83::
882 * Compatibility between Ada 95 and Ada 2005::
883 * Implementation-dependent characteristics::
884 * Compatibility with Other Ada Systems::
885 * Representation Clauses::
886 * Compatibility with HP Ada 83::
888 Compatibility with Ada 83
890 * Legal Ada 83 programs that are illegal in Ada 95::
891 * More deterministic semantics::
892 * Changed semantics::
893 * Other language compatibility issues::
895 Implementation-dependent characteristics
897 * Implementation-defined pragmas::
898 * Implementation-defined attributes::
900 * Elaboration order::
901 * Target-specific aspects::
906 @node About This Guide,Implementation Defined Pragmas,Top,Top
907 @anchor{gnat_rm/about_this_guide about-this-guide}@anchor{2}@anchor{gnat_rm/about_this_guide doc}@anchor{3}@anchor{gnat_rm/about_this_guide gnat-reference-manual}@anchor{4}@anchor{gnat_rm/about_this_guide id1}@anchor{5}
908 @chapter About This Guide
912 This manual contains useful information in writing programs using the
913 GNAT compiler. It includes information on implementation dependent
914 characteristics of GNAT, including all the information required by
915 Annex M of the Ada language standard.
917 GNAT implements Ada 95, Ada 2005 and Ada 2012, and it may also be
918 invoked in Ada 83 compatibility mode.
919 By default, GNAT assumes Ada 2012,
920 but you can override with a compiler switch
921 to explicitly specify the language version.
922 (Please refer to the @emph{GNAT User's Guide} for details on these switches.)
923 Throughout this manual, references to 'Ada' without a year suffix
924 apply to all the Ada versions of the language.
926 Ada is designed to be highly portable.
927 In general, a program will have the same effect even when compiled by
928 different compilers on different platforms.
929 However, since Ada is designed to be used in a
930 wide variety of applications, it also contains a number of system
931 dependent features to be used in interfacing to the external world.
933 @geindex Implementation-dependent features
937 Note: Any program that makes use of implementation-dependent features
938 may be non-portable. You should follow good programming practice and
939 isolate and clearly document any sections of your program that make use
940 of these features in a non-portable manner.
943 * What This Reference Manual Contains::
945 * Related Information::
949 @node What This Reference Manual Contains,Conventions,,About This Guide
950 @anchor{gnat_rm/about_this_guide what-this-reference-manual-contains}@anchor{6}
951 @section What This Reference Manual Contains
954 This reference manual contains the following chapters:
960 @ref{7,,Implementation Defined Pragmas}, lists GNAT implementation-dependent
961 pragmas, which can be used to extend and enhance the functionality of the
965 @ref{8,,Implementation Defined Attributes}, lists GNAT
966 implementation-dependent attributes, which can be used to extend and
967 enhance the functionality of the compiler.
970 @ref{9,,Standard and Implementation Defined Restrictions}, lists GNAT
971 implementation-dependent restrictions, which can be used to extend and
972 enhance the functionality of the compiler.
975 @ref{a,,Implementation Advice}, provides information on generally
976 desirable behavior which are not requirements that all compilers must
977 follow since it cannot be provided on all systems, or which may be
978 undesirable on some systems.
981 @ref{b,,Implementation Defined Characteristics}, provides a guide to
982 minimizing implementation dependent features.
985 @ref{c,,Intrinsic Subprograms}, describes the intrinsic subprograms
986 implemented by GNAT, and how they can be imported into user
987 application programs.
990 @ref{d,,Representation Clauses and Pragmas}, describes in detail the
991 way that GNAT represents data, and in particular the exact set
992 of representation clauses and pragmas that is accepted.
995 @ref{e,,Standard Library Routines}, provides a listing of packages and a
996 brief description of the functionality that is provided by Ada's
997 extensive set of standard library routines as implemented by GNAT.
1000 @ref{f,,The Implementation of Standard I/O}, details how the GNAT
1001 implementation of the input-output facilities.
1004 @ref{10,,The GNAT Library}, is a catalog of packages that complement
1005 the Ada predefined library.
1008 @ref{11,,Interfacing to Other Languages}, describes how programs
1009 written in Ada using GNAT can be interfaced to other programming
1013 @ref{12,,Specialized Needs Annexes}, describes the GNAT implementation of all
1014 of the specialized needs annexes.
1017 @ref{13,,Implementation of Specific Ada Features}, discusses issues related
1018 to GNAT's implementation of machine code insertions, tasking, and several
1022 @ref{14,,Implementation of Ada 2012 Features}, describes the status of the
1023 GNAT implementation of the Ada 2012 language standard.
1026 @ref{15,,Obsolescent Features} documents implementation dependent features,
1027 including pragmas and attributes, which are considered obsolescent, since
1028 there are other preferred ways of achieving the same results. These
1029 obsolescent forms are retained for backwards compatibility.
1032 @ref{16,,Compatibility and Porting Guide} presents some guidelines for
1033 developing portable Ada code, describes the compatibility issues that
1034 may arise between GNAT and other Ada compilation systems (including those
1035 for Ada 83), and shows how GNAT can expedite porting applications
1036 developed in other Ada environments.
1039 @ref{1,,GNU Free Documentation License} contains the license for this document.
1042 @geindex Ada 95 Language Reference Manual
1044 @geindex Ada 2005 Language Reference Manual
1046 This reference manual assumes a basic familiarity with the Ada 95 language, as
1048 @cite{International Standard ANSI/ISO/IEC-8652:1995}.
1049 It does not require knowledge of the new features introduced by Ada 2005 or
1051 All three reference manuals are included in the GNAT documentation
1054 @node Conventions,Related Information,What This Reference Manual Contains,About This Guide
1055 @anchor{gnat_rm/about_this_guide conventions}@anchor{17}
1056 @section Conventions
1059 @geindex Conventions
1060 @geindex typographical
1062 @geindex Typographical conventions
1064 Following are examples of the typographical and graphic conventions used
1071 @code{Functions}, @code{utility program names}, @code{standard names},
1087 [optional information or parameters]
1090 Examples are described by text
1093 and then shown this way.
1097 Commands that are entered by the user are shown as preceded by a prompt string
1098 comprising the @code{$} character followed by a space.
1101 @node Related Information,,Conventions,About This Guide
1102 @anchor{gnat_rm/about_this_guide related-information}@anchor{18}
1103 @section Related Information
1106 See the following documents for further information on GNAT:
1112 @cite{GNAT User's Guide for Native Platforms},
1113 which provides information on how to use the
1114 GNAT development environment.
1117 @cite{Ada 95 Reference Manual}, the Ada 95 programming language standard.
1120 @cite{Ada 95 Annotated Reference Manual}, which is an annotated version
1121 of the Ada 95 standard. The annotations describe
1122 detailed aspects of the design decision, and in particular contain useful
1123 sections on Ada 83 compatibility.
1126 @cite{Ada 2005 Reference Manual}, the Ada 2005 programming language standard.
1129 @cite{Ada 2005 Annotated Reference Manual}, which is an annotated version
1130 of the Ada 2005 standard. The annotations describe
1131 detailed aspects of the design decision.
1134 @cite{Ada 2012 Reference Manual}, the Ada 2012 programming language standard.
1137 @cite{DEC Ada@comma{} Technical Overview and Comparison on DIGITAL Platforms},
1138 which contains specific information on compatibility between GNAT and
1142 @cite{DEC Ada@comma{} Language Reference Manual}, part number AA-PYZAB-TK, which
1143 describes in detail the pragmas and attributes provided by the DEC Ada 83
1147 @node Implementation Defined Pragmas,Implementation Defined Aspects,About This Guide,Top
1148 @anchor{gnat_rm/implementation_defined_pragmas implementation-defined-pragmas}@anchor{7}@anchor{gnat_rm/implementation_defined_pragmas doc}@anchor{19}@anchor{gnat_rm/implementation_defined_pragmas id1}@anchor{1a}
1149 @chapter Implementation Defined Pragmas
1152 Ada defines a set of pragmas that can be used to supply additional
1153 information to the compiler. These language defined pragmas are
1154 implemented in GNAT and work as described in the Ada Reference Manual.
1156 In addition, Ada allows implementations to define additional pragmas
1157 whose meaning is defined by the implementation. GNAT provides a number
1158 of these implementation-defined pragmas, which can be used to extend
1159 and enhance the functionality of the compiler. This section of the GNAT
1160 Reference Manual describes these additional pragmas.
1162 Note that any program using these pragmas might not be portable to other
1163 compilers (although GNAT implements this set of pragmas on all
1164 platforms). Therefore if portability to other compilers is an important
1165 consideration, the use of these pragmas should be minimized.
1168 * Pragma Abort_Defer::
1169 * Pragma Abstract_State::
1176 * Pragma Allow_Integer_Address::
1179 * Pragma Assert_And_Cut::
1180 * Pragma Assertion_Policy::
1182 * Pragma Assume_No_Invalid_Values::
1183 * Pragma Async_Readers::
1184 * Pragma Async_Writers::
1185 * Pragma Attribute_Definition::
1186 * Pragma C_Pass_By_Copy::
1188 * Pragma Check_Float_Overflow::
1189 * Pragma Check_Name::
1190 * Pragma Check_Policy::
1192 * Pragma Common_Object::
1193 * Pragma Compile_Time_Error::
1194 * Pragma Compile_Time_Warning::
1195 * Pragma Compiler_Unit::
1196 * Pragma Compiler_Unit_Warning::
1197 * Pragma Complete_Representation::
1198 * Pragma Complex_Representation::
1199 * Pragma Component_Alignment::
1200 * Pragma Constant_After_Elaboration::
1201 * Pragma Contract_Cases::
1202 * Pragma Convention_Identifier::
1203 * Pragma CPP_Class::
1204 * Pragma CPP_Constructor::
1205 * Pragma CPP_Virtual::
1206 * Pragma CPP_Vtable::
1208 * Pragma Deadline_Floor::
1209 * Pragma Default_Initial_Condition::
1211 * Pragma Debug_Policy::
1212 * Pragma Default_Scalar_Storage_Order::
1213 * Pragma Default_Storage_Pool::
1215 * Pragma Detect_Blocking::
1216 * Pragma Disable_Atomic_Synchronization::
1217 * Pragma Dispatching_Domain::
1218 * Pragma Effective_Reads::
1219 * Pragma Effective_Writes::
1220 * Pragma Elaboration_Checks::
1221 * Pragma Eliminate::
1222 * Pragma Enable_Atomic_Synchronization::
1223 * Pragma Export_Function::
1224 * Pragma Export_Object::
1225 * Pragma Export_Procedure::
1226 * Pragma Export_Value::
1227 * Pragma Export_Valued_Procedure::
1228 * Pragma Extend_System::
1229 * Pragma Extensions_Allowed::
1230 * Pragma Extensions_Visible::
1232 * Pragma External_Name_Casing::
1233 * Pragma Fast_Math::
1234 * Pragma Favor_Top_Level::
1235 * Pragma Finalize_Storage_Only::
1236 * Pragma Float_Representation::
1240 * Pragma Ignore_Pragma::
1241 * Pragma Implementation_Defined::
1242 * Pragma Implemented::
1243 * Pragma Implicit_Packing::
1244 * Pragma Import_Function::
1245 * Pragma Import_Object::
1246 * Pragma Import_Procedure::
1247 * Pragma Import_Valued_Procedure::
1248 * Pragma Independent::
1249 * Pragma Independent_Components::
1250 * Pragma Initial_Condition::
1251 * Pragma Initialize_Scalars::
1252 * Pragma Initializes::
1253 * Pragma Inline_Always::
1254 * Pragma Inline_Generic::
1255 * Pragma Interface::
1256 * Pragma Interface_Name::
1257 * Pragma Interrupt_Handler::
1258 * Pragma Interrupt_State::
1259 * Pragma Invariant::
1260 * Pragma Keep_Names::
1262 * Pragma Link_With::
1263 * Pragma Linker_Alias::
1264 * Pragma Linker_Constructor::
1265 * Pragma Linker_Destructor::
1266 * Pragma Linker_Section::
1267 * Pragma Lock_Free::
1268 * Pragma Loop_Invariant::
1269 * Pragma Loop_Optimize::
1270 * Pragma Loop_Variant::
1271 * Pragma Machine_Attribute::
1273 * Pragma Main_Storage::
1274 * Pragma Max_Queue_Length::
1276 * Pragma No_Component_Reordering::
1277 * Pragma No_Elaboration_Code_All::
1278 * Pragma No_Heap_Finalization::
1279 * Pragma No_Inline::
1280 * Pragma No_Return::
1281 * Pragma No_Run_Time::
1282 * Pragma No_Strict_Aliasing::
1283 * Pragma No_Tagged_Streams::
1284 * Pragma Normalize_Scalars::
1285 * Pragma Obsolescent::
1286 * Pragma Optimize_Alignment::
1288 * Pragma Overflow_Mode::
1289 * Pragma Overriding_Renamings::
1290 * Pragma Partition_Elaboration_Policy::
1293 * Pragma Persistent_BSS::
1296 * Pragma Postcondition::
1297 * Pragma Post_Class::
1298 * Pragma Rename_Pragma::
1300 * Pragma Precondition::
1301 * Pragma Predicate::
1302 * Pragma Predicate_Failure::
1303 * Pragma Preelaborable_Initialization::
1304 * Pragma Prefix_Exception_Messages::
1305 * Pragma Pre_Class::
1306 * Pragma Priority_Specific_Dispatching::
1308 * Pragma Profile_Warnings::
1309 * Pragma Propagate_Exceptions::
1310 * Pragma Provide_Shift_Operators::
1311 * Pragma Psect_Object::
1312 * Pragma Pure_Function::
1314 * Pragma Ravenscar::
1315 * Pragma Refined_Depends::
1316 * Pragma Refined_Global::
1317 * Pragma Refined_Post::
1318 * Pragma Refined_State::
1319 * Pragma Relative_Deadline::
1320 * Pragma Remote_Access_Type::
1321 * Pragma Restricted_Run_Time::
1322 * Pragma Restriction_Warnings::
1323 * Pragma Reviewable::
1324 * Pragma Secondary_Stack_Size::
1325 * Pragma Share_Generic::
1327 * Pragma Short_Circuit_And_Or::
1328 * Pragma Short_Descriptors::
1329 * Pragma Simple_Storage_Pool_Type::
1330 * Pragma Source_File_Name::
1331 * Pragma Source_File_Name_Project::
1332 * Pragma Source_Reference::
1333 * Pragma SPARK_Mode::
1334 * Pragma Static_Elaboration_Desired::
1335 * Pragma Stream_Convert::
1336 * Pragma Style_Checks::
1339 * Pragma Suppress_All::
1340 * Pragma Suppress_Debug_Info::
1341 * Pragma Suppress_Exception_Locations::
1342 * Pragma Suppress_Initialization::
1343 * Pragma Task_Name::
1344 * Pragma Task_Storage::
1345 * Pragma Test_Case::
1346 * Pragma Thread_Local_Storage::
1347 * Pragma Time_Slice::
1349 * Pragma Type_Invariant::
1350 * Pragma Type_Invariant_Class::
1351 * Pragma Unchecked_Union::
1352 * Pragma Unevaluated_Use_Of_Old::
1353 * Pragma Unimplemented_Unit::
1354 * Pragma Universal_Aliasing::
1355 * Pragma Universal_Data::
1356 * Pragma Unmodified::
1357 * Pragma Unreferenced::
1358 * Pragma Unreferenced_Objects::
1359 * Pragma Unreserve_All_Interrupts::
1360 * Pragma Unsuppress::
1361 * Pragma Use_VADS_Size::
1363 * Pragma Validity_Checks::
1365 * Pragma Volatile_Full_Access::
1366 * Pragma Volatile_Function::
1367 * Pragma Warning_As_Error::
1369 * Pragma Weak_External::
1370 * Pragma Wide_Character_Encoding::
1374 @node Pragma Abort_Defer,Pragma Abstract_State,,Implementation Defined Pragmas
1375 @anchor{gnat_rm/implementation_defined_pragmas pragma-abort-defer}@anchor{1b}
1376 @section Pragma Abort_Defer
1379 @geindex Deferring aborts
1387 This pragma must appear at the start of the statement sequence of a
1388 handled sequence of statements (right after the @code{begin}). It has
1389 the effect of deferring aborts for the sequence of statements (but not
1390 for the declarations or handlers, if any, associated with this statement
1393 @node Pragma Abstract_State,Pragma Ada_83,Pragma Abort_Defer,Implementation Defined Pragmas
1394 @anchor{gnat_rm/implementation_defined_pragmas pragma-abstract-state}@anchor{1c}@anchor{gnat_rm/implementation_defined_pragmas id2}@anchor{1d}
1395 @section Pragma Abstract_State
1401 pragma Abstract_State (ABSTRACT_STATE_LIST);
1403 ABSTRACT_STATE_LIST ::=
1405 | STATE_NAME_WITH_OPTIONS
1406 | (STATE_NAME_WITH_OPTIONS @{, STATE_NAME_WITH_OPTIONS@} )
1408 STATE_NAME_WITH_OPTIONS ::=
1410 | (STATE_NAME with OPTION_LIST)
1412 OPTION_LIST ::= OPTION @{, OPTION@}
1418 SIMPLE_OPTION ::= Ghost | Synchronous
1420 NAME_VALUE_OPTION ::=
1421 Part_Of => ABSTRACT_STATE
1422 | External [=> EXTERNAL_PROPERTY_LIST]
1424 EXTERNAL_PROPERTY_LIST ::=
1426 | (EXTERNAL_PROPERTY @{, EXTERNAL_PROPERTY@} )
1428 EXTERNAL_PROPERTY ::=
1429 Async_Readers [=> boolean_EXPRESSION]
1430 | Async_Writers [=> boolean_EXPRESSION]
1431 | Effective_Reads [=> boolean_EXPRESSION]
1432 | Effective_Writes [=> boolean_EXPRESSION]
1433 others => boolean_EXPRESSION
1435 STATE_NAME ::= defining_identifier
1437 ABSTRACT_STATE ::= name
1440 For the semantics of this pragma, see the entry for aspect @code{Abstract_State} in
1441 the SPARK 2014 Reference Manual, section 7.1.4.
1443 @node Pragma Ada_83,Pragma Ada_95,Pragma Abstract_State,Implementation Defined Pragmas
1444 @anchor{gnat_rm/implementation_defined_pragmas pragma-ada-83}@anchor{1e}
1445 @section Pragma Ada_83
1454 A configuration pragma that establishes Ada 83 mode for the unit to
1455 which it applies, regardless of the mode set by the command line
1456 switches. In Ada 83 mode, GNAT attempts to be as compatible with
1457 the syntax and semantics of Ada 83, as defined in the original Ada
1458 83 Reference Manual as possible. In particular, the keywords added by Ada 95
1459 and Ada 2005 are not recognized, optional package bodies are allowed,
1460 and generics may name types with unknown discriminants without using
1461 the @code{(<>)} notation. In addition, some but not all of the additional
1462 restrictions of Ada 83 are enforced.
1464 Ada 83 mode is intended for two purposes. Firstly, it allows existing
1465 Ada 83 code to be compiled and adapted to GNAT with less effort.
1466 Secondly, it aids in keeping code backwards compatible with Ada 83.
1467 However, there is no guarantee that code that is processed correctly
1468 by GNAT in Ada 83 mode will in fact compile and execute with an Ada
1469 83 compiler, since GNAT does not enforce all the additional checks
1472 @node Pragma Ada_95,Pragma Ada_05,Pragma Ada_83,Implementation Defined Pragmas
1473 @anchor{gnat_rm/implementation_defined_pragmas pragma-ada-95}@anchor{1f}
1474 @section Pragma Ada_95
1483 A configuration pragma that establishes Ada 95 mode for the unit to which
1484 it applies, regardless of the mode set by the command line switches.
1485 This mode is set automatically for the @code{Ada} and @code{System}
1486 packages and their children, so you need not specify it in these
1487 contexts. This pragma is useful when writing a reusable component that
1488 itself uses Ada 95 features, but which is intended to be usable from
1489 either Ada 83 or Ada 95 programs.
1491 @node Pragma Ada_05,Pragma Ada_2005,Pragma Ada_95,Implementation Defined Pragmas
1492 @anchor{gnat_rm/implementation_defined_pragmas pragma-ada-05}@anchor{20}
1493 @section Pragma Ada_05
1500 pragma Ada_05 (local_NAME);
1503 A configuration pragma that establishes Ada 2005 mode for the unit to which
1504 it applies, regardless of the mode set by the command line switches.
1505 This pragma is useful when writing a reusable component that
1506 itself uses Ada 2005 features, but which is intended to be usable from
1507 either Ada 83 or Ada 95 programs.
1509 The one argument form (which is not a configuration pragma)
1510 is used for managing the transition from
1511 Ada 95 to Ada 2005 in the run-time library. If an entity is marked
1512 as Ada_2005 only, then referencing the entity in Ada_83 or Ada_95
1513 mode will generate a warning. In addition, in Ada_83 or Ada_95
1514 mode, a preference rule is established which does not choose
1515 such an entity unless it is unambiguously specified. This avoids
1516 extra subprograms marked this way from generating ambiguities in
1517 otherwise legal pre-Ada_2005 programs. The one argument form is
1518 intended for exclusive use in the GNAT run-time library.
1520 @node Pragma Ada_2005,Pragma Ada_12,Pragma Ada_05,Implementation Defined Pragmas
1521 @anchor{gnat_rm/implementation_defined_pragmas pragma-ada-2005}@anchor{21}
1522 @section Pragma Ada_2005
1531 This configuration pragma is a synonym for pragma Ada_05 and has the
1532 same syntax and effect.
1534 @node Pragma Ada_12,Pragma Ada_2012,Pragma Ada_2005,Implementation Defined Pragmas
1535 @anchor{gnat_rm/implementation_defined_pragmas pragma-ada-12}@anchor{22}
1536 @section Pragma Ada_12
1543 pragma Ada_12 (local_NAME);
1546 A configuration pragma that establishes Ada 2012 mode for the unit to which
1547 it applies, regardless of the mode set by the command line switches.
1548 This mode is set automatically for the @code{Ada} and @code{System}
1549 packages and their children, so you need not specify it in these
1550 contexts. This pragma is useful when writing a reusable component that
1551 itself uses Ada 2012 features, but which is intended to be usable from
1552 Ada 83, Ada 95, or Ada 2005 programs.
1554 The one argument form, which is not a configuration pragma,
1555 is used for managing the transition from Ada
1556 2005 to Ada 2012 in the run-time library. If an entity is marked
1557 as Ada_2012 only, then referencing the entity in any pre-Ada_2012
1558 mode will generate a warning. In addition, in any pre-Ada_2012
1559 mode, a preference rule is established which does not choose
1560 such an entity unless it is unambiguously specified. This avoids
1561 extra subprograms marked this way from generating ambiguities in
1562 otherwise legal pre-Ada_2012 programs. The one argument form is
1563 intended for exclusive use in the GNAT run-time library.
1565 @node Pragma Ada_2012,Pragma Allow_Integer_Address,Pragma Ada_12,Implementation Defined Pragmas
1566 @anchor{gnat_rm/implementation_defined_pragmas pragma-ada-2012}@anchor{23}
1567 @section Pragma Ada_2012
1576 This configuration pragma is a synonym for pragma Ada_12 and has the
1577 same syntax and effect.
1579 @node Pragma Allow_Integer_Address,Pragma Annotate,Pragma Ada_2012,Implementation Defined Pragmas
1580 @anchor{gnat_rm/implementation_defined_pragmas pragma-allow-integer-address}@anchor{24}
1581 @section Pragma Allow_Integer_Address
1587 pragma Allow_Integer_Address;
1590 In almost all versions of GNAT, @code{System.Address} is a private
1591 type in accordance with the implementation advice in the RM. This
1592 means that integer values,
1593 in particular integer literals, are not allowed as address values.
1594 If the configuration pragma
1595 @code{Allow_Integer_Address} is given, then integer expressions may
1596 be used anywhere a value of type @code{System.Address} is required.
1597 The effect is to introduce an implicit unchecked conversion from the
1598 integer value to type @code{System.Address}. The reverse case of using
1599 an address where an integer type is required is handled analogously.
1600 The following example compiles without errors:
1603 pragma Allow_Integer_Address;
1604 with System; use System;
1605 package AddrAsInt is
1608 for X'Address use 16#1240#;
1609 for Y use at 16#3230#;
1610 m : Address := 16#4000#;
1611 n : constant Address := 4000;
1612 p : constant Address := Address (X + Y);
1613 v : Integer := y'Address;
1614 w : constant Integer := Integer (Y'Address);
1615 type R is new integer;
1618 for Z'Address use RR;
1622 Note that pragma @code{Allow_Integer_Address} is ignored if @code{System.Address}
1623 is not a private type. In implementations of @code{GNAT} where
1624 System.Address is a visible integer type,
1625 this pragma serves no purpose but is ignored
1626 rather than rejected to allow common sets of sources to be used
1627 in the two situations.
1629 @node Pragma Annotate,Pragma Assert,Pragma Allow_Integer_Address,Implementation Defined Pragmas
1630 @anchor{gnat_rm/implementation_defined_pragmas pragma-annotate}@anchor{25}@anchor{gnat_rm/implementation_defined_pragmas id3}@anchor{26}
1631 @section Pragma Annotate
1637 pragma Annotate (IDENTIFIER [, IDENTIFIER @{, ARG@}] [, entity => local_NAME]);
1639 ARG ::= NAME | EXPRESSION
1642 This pragma is used to annotate programs. IDENTIFIER identifies
1643 the type of annotation. GNAT verifies that it is an identifier, but does
1644 not otherwise analyze it. The second optional identifier is also left
1645 unanalyzed, and by convention is used to control the action of the tool to
1646 which the annotation is addressed. The remaining ARG arguments
1647 can be either string literals or more generally expressions.
1648 String literals are assumed to be either of type
1649 @code{Standard.String} or else @code{Wide_String} or @code{Wide_Wide_String}
1650 depending on the character literals they contain.
1651 All other kinds of arguments are analyzed as expressions, and must be
1652 unambiguous. The last argument if present must have the identifier
1653 @code{Entity} and GNAT verifies that a local name is given.
1655 The analyzed pragma is retained in the tree, but not otherwise processed
1656 by any part of the GNAT compiler, except to generate corresponding note
1657 lines in the generated ALI file. For the format of these note lines, see
1658 the compiler source file lib-writ.ads. This pragma is intended for use by
1659 external tools, including ASIS. The use of pragma Annotate does not
1660 affect the compilation process in any way. This pragma may be used as
1661 a configuration pragma.
1663 @node Pragma Assert,Pragma Assert_And_Cut,Pragma Annotate,Implementation Defined Pragmas
1664 @anchor{gnat_rm/implementation_defined_pragmas pragma-assert}@anchor{27}
1665 @section Pragma Assert
1673 [, string_EXPRESSION]);
1676 The effect of this pragma depends on whether the corresponding command
1677 line switch is set to activate assertions. The pragma expands into code
1678 equivalent to the following:
1681 if assertions-enabled then
1682 if not boolean_EXPRESSION then
1683 System.Assertions.Raise_Assert_Failure
1684 (string_EXPRESSION);
1689 The string argument, if given, is the message that will be associated
1690 with the exception occurrence if the exception is raised. If no second
1691 argument is given, the default message is @code{file}:@code{nnn},
1692 where @code{file} is the name of the source file containing the assert,
1693 and @code{nnn} is the line number of the assert.
1695 Note that, as with the @code{if} statement to which it is equivalent, the
1696 type of the expression is either @code{Standard.Boolean}, or any type derived
1697 from this standard type.
1699 Assert checks can be either checked or ignored. By default they are ignored.
1700 They will be checked if either the command line switch @emph{-gnata} is
1701 used, or if an @code{Assertion_Policy} or @code{Check_Policy} pragma is used
1702 to enable @code{Assert_Checks}.
1704 If assertions are ignored, then there
1705 is no run-time effect (and in particular, any side effects from the
1706 expression will not occur at run time). (The expression is still
1707 analyzed at compile time, and may cause types to be frozen if they are
1708 mentioned here for the first time).
1710 If assertions are checked, then the given expression is tested, and if
1711 it is @code{False} then @code{System.Assertions.Raise_Assert_Failure} is called
1712 which results in the raising of @code{Assert_Failure} with the given message.
1714 You should generally avoid side effects in the expression arguments of
1715 this pragma, because these side effects will turn on and off with the
1716 setting of the assertions mode, resulting in assertions that have an
1717 effect on the program. However, the expressions are analyzed for
1718 semantic correctness whether or not assertions are enabled, so turning
1719 assertions on and off cannot affect the legality of a program.
1721 Note that the implementation defined policy @code{DISABLE}, given in a
1722 pragma @code{Assertion_Policy}, can be used to suppress this semantic analysis.
1724 Note: this is a standard language-defined pragma in versions
1725 of Ada from 2005 on. In GNAT, it is implemented in all versions
1726 of Ada, and the DISABLE policy is an implementation-defined
1729 @node Pragma Assert_And_Cut,Pragma Assertion_Policy,Pragma Assert,Implementation Defined Pragmas
1730 @anchor{gnat_rm/implementation_defined_pragmas pragma-assert-and-cut}@anchor{28}
1731 @section Pragma Assert_And_Cut
1737 pragma Assert_And_Cut (
1739 [, string_EXPRESSION]);
1742 The effect of this pragma is identical to that of pragma @code{Assert},
1743 except that in an @code{Assertion_Policy} pragma, the identifier
1744 @code{Assert_And_Cut} is used to control whether it is ignored or checked
1747 The intention is that this be used within a subprogram when the
1748 given test expresion sums up all the work done so far in the
1749 subprogram, so that the rest of the subprogram can be verified
1750 (informally or formally) using only the entry preconditions,
1751 and the expression in this pragma. This allows dividing up
1752 a subprogram into sections for the purposes of testing or
1753 formal verification. The pragma also serves as useful
1756 @node Pragma Assertion_Policy,Pragma Assume,Pragma Assert_And_Cut,Implementation Defined Pragmas
1757 @anchor{gnat_rm/implementation_defined_pragmas pragma-assertion-policy}@anchor{29}
1758 @section Pragma Assertion_Policy
1764 pragma Assertion_Policy (CHECK | DISABLE | IGNORE);
1766 pragma Assertion_Policy (
1767 ASSERTION_KIND => POLICY_IDENTIFIER
1768 @{, ASSERTION_KIND => POLICY_IDENTIFIER@});
1770 ASSERTION_KIND ::= RM_ASSERTION_KIND | ID_ASSERTION_KIND
1772 RM_ASSERTION_KIND ::= Assert |
1780 Type_Invariant'Class
1782 ID_ASSERTION_KIND ::= Assertions |
1795 Statement_Assertions
1797 POLICY_IDENTIFIER ::= Check | Disable | Ignore | Suppressible
1800 This is a standard Ada 2012 pragma that is available as an
1801 implementation-defined pragma in earlier versions of Ada.
1802 The assertion kinds @code{RM_ASSERTION_KIND} are those defined in
1803 the Ada standard. The assertion kinds @code{ID_ASSERTION_KIND}
1804 are implementation defined additions recognized by the GNAT compiler.
1806 The pragma applies in both cases to pragmas and aspects with matching
1807 names, e.g. @code{Pre} applies to the Pre aspect, and @code{Precondition}
1808 applies to both the @code{Precondition} pragma
1809 and the aspect @code{Precondition}. Note that the identifiers for
1810 pragmas Pre_Class and Post_Class are Pre'Class and Post'Class (not
1811 Pre_Class and Post_Class), since these pragmas are intended to be
1812 identical to the corresponding aspects).
1814 If the policy is @code{CHECK}, then assertions are enabled, i.e.
1815 the corresponding pragma or aspect is activated.
1816 If the policy is @code{IGNORE}, then assertions are ignored, i.e.
1817 the corresponding pragma or aspect is deactivated.
1818 This pragma overrides the effect of the @emph{-gnata} switch on the
1820 If the policy is @code{SUPPRESSIBLE}, then assertions are enabled by default,
1821 however, if the @emph{-gnatp} switch is specified all assertions are ignored.
1823 The implementation defined policy @code{DISABLE} is like
1824 @code{IGNORE} except that it completely disables semantic
1825 checking of the corresponding pragma or aspect. This is
1826 useful when the pragma or aspect argument references subprograms
1827 in a with'ed package which is replaced by a dummy package
1828 for the final build.
1830 The implementation defined assertion kind @code{Assertions} applies to all
1831 assertion kinds. The form with no assertion kind given implies this
1832 choice, so it applies to all assertion kinds (RM defined, and
1833 implementation defined).
1835 The implementation defined assertion kind @code{Statement_Assertions}
1836 applies to @code{Assert}, @code{Assert_And_Cut},
1837 @code{Assume}, @code{Loop_Invariant}, and @code{Loop_Variant}.
1839 @node Pragma Assume,Pragma Assume_No_Invalid_Values,Pragma Assertion_Policy,Implementation Defined Pragmas
1840 @anchor{gnat_rm/implementation_defined_pragmas pragma-assume}@anchor{2a}
1841 @section Pragma Assume
1849 [, string_EXPRESSION]);
1852 The effect of this pragma is identical to that of pragma @code{Assert},
1853 except that in an @code{Assertion_Policy} pragma, the identifier
1854 @code{Assume} is used to control whether it is ignored or checked
1857 The intention is that this be used for assumptions about the
1858 external environment. So you cannot expect to verify formally
1859 or informally that the condition is met, this must be
1860 established by examining things outside the program itself.
1861 For example, we may have code that depends on the size of
1862 @code{Long_Long_Integer} being at least 64. So we could write:
1865 pragma Assume (Long_Long_Integer'Size >= 64);
1868 This assumption cannot be proved from the program itself,
1869 but it acts as a useful run-time check that the assumption
1870 is met, and documents the need to ensure that it is met by
1871 reference to information outside the program.
1873 @node Pragma Assume_No_Invalid_Values,Pragma Async_Readers,Pragma Assume,Implementation Defined Pragmas
1874 @anchor{gnat_rm/implementation_defined_pragmas pragma-assume-no-invalid-values}@anchor{2b}
1875 @section Pragma Assume_No_Invalid_Values
1878 @geindex Invalid representations
1880 @geindex Invalid values
1885 pragma Assume_No_Invalid_Values (On | Off);
1888 This is a configuration pragma that controls the assumptions made by the
1889 compiler about the occurrence of invalid representations (invalid values)
1892 The default behavior (corresponding to an Off argument for this pragma), is
1893 to assume that values may in general be invalid unless the compiler can
1894 prove they are valid. Consider the following example:
1897 V1 : Integer range 1 .. 10;
1898 V2 : Integer range 11 .. 20;
1900 for J in V2 .. V1 loop
1905 if V1 and V2 have valid values, then the loop is known at compile
1906 time not to execute since the lower bound must be greater than the
1907 upper bound. However in default mode, no such assumption is made,
1908 and the loop may execute. If @code{Assume_No_Invalid_Values (On)}
1909 is given, the compiler will assume that any occurrence of a variable
1910 other than in an explicit @code{'Valid} test always has a valid
1911 value, and the loop above will be optimized away.
1913 The use of @code{Assume_No_Invalid_Values (On)} is appropriate if
1914 you know your code is free of uninitialized variables and other
1915 possible sources of invalid representations, and may result in
1916 more efficient code. A program that accesses an invalid representation
1917 with this pragma in effect is erroneous, so no guarantees can be made
1920 It is peculiar though permissible to use this pragma in conjunction
1921 with validity checking (-gnatVa). In such cases, accessing invalid
1922 values will generally give an exception, though formally the program
1923 is erroneous so there are no guarantees that this will always be the
1924 case, and it is recommended that these two options not be used together.
1926 @node Pragma Async_Readers,Pragma Async_Writers,Pragma Assume_No_Invalid_Values,Implementation Defined Pragmas
1927 @anchor{gnat_rm/implementation_defined_pragmas pragma-async-readers}@anchor{2c}@anchor{gnat_rm/implementation_defined_pragmas id4}@anchor{2d}
1928 @section Pragma Async_Readers
1934 pragma Asynch_Readers [ (boolean_EXPRESSION) ];
1937 For the semantics of this pragma, see the entry for aspect @code{Async_Readers} in
1938 the SPARK 2014 Reference Manual, section 7.1.2.
1940 @node Pragma Async_Writers,Pragma Attribute_Definition,Pragma Async_Readers,Implementation Defined Pragmas
1941 @anchor{gnat_rm/implementation_defined_pragmas id5}@anchor{2e}@anchor{gnat_rm/implementation_defined_pragmas pragma-async-writers}@anchor{2f}
1942 @section Pragma Async_Writers
1948 pragma Asynch_Writers [ (boolean_EXPRESSION) ];
1951 For the semantics of this pragma, see the entry for aspect @code{Async_Writers} in
1952 the SPARK 2014 Reference Manual, section 7.1.2.
1954 @node Pragma Attribute_Definition,Pragma C_Pass_By_Copy,Pragma Async_Writers,Implementation Defined Pragmas
1955 @anchor{gnat_rm/implementation_defined_pragmas pragma-attribute-definition}@anchor{30}
1956 @section Pragma Attribute_Definition
1962 pragma Attribute_Definition
1963 ([Attribute =>] ATTRIBUTE_DESIGNATOR,
1964 [Entity =>] LOCAL_NAME,
1965 [Expression =>] EXPRESSION | NAME);
1968 If @code{Attribute} is a known attribute name, this pragma is equivalent to
1969 the attribute definition clause:
1972 for Entity'Attribute use Expression;
1975 If @code{Attribute} is not a recognized attribute name, the pragma is
1976 ignored, and a warning is emitted. This allows source
1977 code to be written that takes advantage of some new attribute, while remaining
1978 compilable with earlier compilers.
1980 @node Pragma C_Pass_By_Copy,Pragma Check,Pragma Attribute_Definition,Implementation Defined Pragmas
1981 @anchor{gnat_rm/implementation_defined_pragmas pragma-c-pass-by-copy}@anchor{31}
1982 @section Pragma C_Pass_By_Copy
1985 @geindex Passing by copy
1990 pragma C_Pass_By_Copy
1991 ([Max_Size =>] static_integer_EXPRESSION);
1994 Normally the default mechanism for passing C convention records to C
1995 convention subprograms is to pass them by reference, as suggested by RM
1996 B.3(69). Use the configuration pragma @code{C_Pass_By_Copy} to change
1997 this default, by requiring that record formal parameters be passed by
1998 copy if all of the following conditions are met:
2004 The size of the record type does not exceed the value specified for
2008 The record type has @code{Convention C}.
2011 The formal parameter has this record type, and the subprogram has a
2012 foreign (non-Ada) convention.
2015 If these conditions are met the argument is passed by copy; i.e., in a
2016 manner consistent with what C expects if the corresponding formal in the
2017 C prototype is a struct (rather than a pointer to a struct).
2019 You can also pass records by copy by specifying the convention
2020 @code{C_Pass_By_Copy} for the record type, or by using the extended
2021 @code{Import} and @code{Export} pragmas, which allow specification of
2022 passing mechanisms on a parameter by parameter basis.
2024 @node Pragma Check,Pragma Check_Float_Overflow,Pragma C_Pass_By_Copy,Implementation Defined Pragmas
2025 @anchor{gnat_rm/implementation_defined_pragmas pragma-check}@anchor{32}
2026 @section Pragma Check
2031 @geindex Named assertions
2037 [Name =>] CHECK_KIND,
2038 [Check =>] Boolean_EXPRESSION
2039 [, [Message =>] string_EXPRESSION] );
2041 CHECK_KIND ::= IDENTIFIER |
2044 Type_Invariant'Class |
2048 This pragma is similar to the predefined pragma @code{Assert} except that an
2049 extra identifier argument is present. In conjunction with pragma
2050 @code{Check_Policy}, this can be used to define groups of assertions that can
2051 be independently controlled. The identifier @code{Assertion} is special, it
2052 refers to the normal set of pragma @code{Assert} statements.
2054 Checks introduced by this pragma are normally deactivated by default. They can
2055 be activated either by the command line option @emph{-gnata}, which turns on
2056 all checks, or individually controlled using pragma @code{Check_Policy}.
2058 The identifiers @code{Assertions} and @code{Statement_Assertions} are not
2059 permitted as check kinds, since this would cause confusion with the use
2060 of these identifiers in @code{Assertion_Policy} and @code{Check_Policy}
2061 pragmas, where they are used to refer to sets of assertions.
2063 @node Pragma Check_Float_Overflow,Pragma Check_Name,Pragma Check,Implementation Defined Pragmas
2064 @anchor{gnat_rm/implementation_defined_pragmas pragma-check-float-overflow}@anchor{33}
2065 @section Pragma Check_Float_Overflow
2068 @geindex Floating-point overflow
2073 pragma Check_Float_Overflow;
2076 In Ada, the predefined floating-point types (@code{Short_Float},
2077 @code{Float}, @code{Long_Float}, @code{Long_Long_Float}) are
2078 defined to be @emph{unconstrained}. This means that even though each
2079 has a well-defined base range, an operation that delivers a result
2080 outside this base range is not required to raise an exception.
2081 This implementation permission accommodates the notion
2082 of infinities in IEEE floating-point, and corresponds to the
2083 efficient execution mode on most machines. GNAT will not raise
2084 overflow exceptions on these machines; instead it will generate
2085 infinities and NaN's as defined in the IEEE standard.
2087 Generating infinities, although efficient, is not always desirable.
2088 Often the preferable approach is to check for overflow, even at the
2089 (perhaps considerable) expense of run-time performance.
2090 This can be accomplished by defining your own constrained floating-point subtypes -- i.e., by supplying explicit
2091 range constraints -- and indeed such a subtype
2092 can have the same base range as its base type. For example:
2095 subtype My_Float is Float range Float'Range;
2098 Here @code{My_Float} has the same range as
2099 @code{Float} but is constrained, so operations on
2100 @code{My_Float} values will be checked for overflow
2103 This style will achieve the desired goal, but
2104 it is often more convenient to be able to simply use
2105 the standard predefined floating-point types as long
2106 as overflow checking could be guaranteed.
2107 The @code{Check_Float_Overflow}
2108 configuration pragma achieves this effect. If a unit is compiled
2109 subject to this configuration pragma, then all operations
2110 on predefined floating-point types including operations on
2111 base types of these floating-point types will be treated as
2112 though those types were constrained, and overflow checks
2113 will be generated. The @code{Constraint_Error}
2114 exception is raised if the result is out of range.
2116 This mode can also be set by use of the compiler
2117 switch @emph{-gnateF}.
2119 @node Pragma Check_Name,Pragma Check_Policy,Pragma Check_Float_Overflow,Implementation Defined Pragmas
2120 @anchor{gnat_rm/implementation_defined_pragmas pragma-check-name}@anchor{34}
2121 @section Pragma Check_Name
2124 @geindex Defining check names
2126 @geindex Check names
2132 pragma Check_Name (check_name_IDENTIFIER);
2135 This is a configuration pragma that defines a new implementation
2136 defined check name (unless IDENTIFIER matches one of the predefined
2137 check names, in which case the pragma has no effect). Check names
2138 are global to a partition, so if two or more configuration pragmas
2139 are present in a partition mentioning the same name, only one new
2140 check name is introduced.
2142 An implementation defined check name introduced with this pragma may
2143 be used in only three contexts: @code{pragma Suppress},
2144 @code{pragma Unsuppress},
2145 and as the prefix of a @code{Check_Name'Enabled} attribute reference. For
2146 any of these three cases, the check name must be visible. A check
2147 name is visible if it is in the configuration pragmas applying to
2148 the current unit, or if it appears at the start of any unit that
2149 is part of the dependency set of the current unit (e.g., units that
2150 are mentioned in @code{with} clauses).
2152 Check names introduced by this pragma are subject to control by compiler
2153 switches (in particular -gnatp) in the usual manner.
2155 @node Pragma Check_Policy,Pragma Comment,Pragma Check_Name,Implementation Defined Pragmas
2156 @anchor{gnat_rm/implementation_defined_pragmas pragma-check-policy}@anchor{35}
2157 @section Pragma Check_Policy
2160 @geindex Controlling assertions
2165 @geindex Check pragma control
2167 @geindex Named assertions
2173 ([Name =>] CHECK_KIND,
2174 [Policy =>] POLICY_IDENTIFIER);
2176 pragma Check_Policy (
2177 CHECK_KIND => POLICY_IDENTIFIER
2178 @{, CHECK_KIND => POLICY_IDENTIFIER@});
2180 ASSERTION_KIND ::= RM_ASSERTION_KIND | ID_ASSERTION_KIND
2182 CHECK_KIND ::= IDENTIFIER |
2185 Type_Invariant'Class |
2188 The identifiers Name and Policy are not allowed as CHECK_KIND values. This
2189 avoids confusion between the two possible syntax forms for this pragma.
2191 POLICY_IDENTIFIER ::= ON | OFF | CHECK | DISABLE | IGNORE
2194 This pragma is used to set the checking policy for assertions (specified
2195 by aspects or pragmas), the @code{Debug} pragma, or additional checks
2196 to be checked using the @code{Check} pragma. It may appear either as
2197 a configuration pragma, or within a declarative part of package. In the
2198 latter case, it applies from the point where it appears to the end of
2199 the declarative region (like pragma @code{Suppress}).
2201 The @code{Check_Policy} pragma is similar to the
2202 predefined @code{Assertion_Policy} pragma,
2203 and if the check kind corresponds to one of the assertion kinds that
2204 are allowed by @code{Assertion_Policy}, then the effect is identical.
2206 If the first argument is Debug, then the policy applies to Debug pragmas,
2207 disabling their effect if the policy is @code{OFF}, @code{DISABLE}, or
2208 @code{IGNORE}, and allowing them to execute with normal semantics if
2209 the policy is @code{ON} or @code{CHECK}. In addition if the policy is
2210 @code{DISABLE}, then the procedure call in @code{Debug} pragmas will
2211 be totally ignored and not analyzed semantically.
2213 Finally the first argument may be some other identifier than the above
2214 possibilities, in which case it controls a set of named assertions
2215 that can be checked using pragma @code{Check}. For example, if the pragma:
2218 pragma Check_Policy (Critical_Error, OFF);
2221 is given, then subsequent @code{Check} pragmas whose first argument is also
2222 @code{Critical_Error} will be disabled.
2224 The check policy is @code{OFF} to turn off corresponding checks, and @code{ON}
2225 to turn on corresponding checks. The default for a set of checks for which no
2226 @code{Check_Policy} is given is @code{OFF} unless the compiler switch
2227 @emph{-gnata} is given, which turns on all checks by default.
2229 The check policy settings @code{CHECK} and @code{IGNORE} are recognized
2230 as synonyms for @code{ON} and @code{OFF}. These synonyms are provided for
2231 compatibility with the standard @code{Assertion_Policy} pragma. The check
2232 policy setting @code{DISABLE} causes the second argument of a corresponding
2233 @code{Check} pragma to be completely ignored and not analyzed.
2235 @node Pragma Comment,Pragma Common_Object,Pragma Check_Policy,Implementation Defined Pragmas
2236 @anchor{gnat_rm/implementation_defined_pragmas pragma-comment}@anchor{36}
2237 @section Pragma Comment
2243 pragma Comment (static_string_EXPRESSION);
2246 This is almost identical in effect to pragma @code{Ident}. It allows the
2247 placement of a comment into the object file and hence into the
2248 executable file if the operating system permits such usage. The
2249 difference is that @code{Comment}, unlike @code{Ident}, has
2250 no limitations on placement of the pragma (it can be placed
2251 anywhere in the main source unit), and if more than one pragma
2252 is used, all comments are retained.
2254 @node Pragma Common_Object,Pragma Compile_Time_Error,Pragma Comment,Implementation Defined Pragmas
2255 @anchor{gnat_rm/implementation_defined_pragmas pragma-common-object}@anchor{37}
2256 @section Pragma Common_Object
2262 pragma Common_Object (
2263 [Internal =>] LOCAL_NAME
2264 [, [External =>] EXTERNAL_SYMBOL]
2265 [, [Size =>] EXTERNAL_SYMBOL] );
2269 | static_string_EXPRESSION
2272 This pragma enables the shared use of variables stored in overlaid
2273 linker areas corresponding to the use of @code{COMMON}
2274 in Fortran. The single
2275 object @code{LOCAL_NAME} is assigned to the area designated by
2276 the @code{External} argument.
2277 You may define a record to correspond to a series
2278 of fields. The @code{Size} argument
2279 is syntax checked in GNAT, but otherwise ignored.
2281 @code{Common_Object} is not supported on all platforms. If no
2282 support is available, then the code generator will issue a message
2283 indicating that the necessary attribute for implementation of this
2284 pragma is not available.
2286 @node Pragma Compile_Time_Error,Pragma Compile_Time_Warning,Pragma Common_Object,Implementation Defined Pragmas
2287 @anchor{gnat_rm/implementation_defined_pragmas pragma-compile-time-error}@anchor{38}
2288 @section Pragma Compile_Time_Error
2294 pragma Compile_Time_Error
2295 (boolean_EXPRESSION, static_string_EXPRESSION);
2298 This pragma can be used to generate additional compile time
2300 is particularly useful in generics, where errors can be issued for
2301 specific problematic instantiations. The first parameter is a boolean
2302 expression. The pragma is effective only if the value of this expression
2303 is known at compile time, and has the value True. The set of expressions
2304 whose values are known at compile time includes all static boolean
2305 expressions, and also other values which the compiler can determine
2306 at compile time (e.g., the size of a record type set by an explicit
2307 size representation clause, or the value of a variable which was
2308 initialized to a constant and is known not to have been modified).
2309 If these conditions are met, an error message is generated using
2310 the value given as the second argument. This string value may contain
2311 embedded ASCII.LF characters to break the message into multiple lines.
2313 @node Pragma Compile_Time_Warning,Pragma Compiler_Unit,Pragma Compile_Time_Error,Implementation Defined Pragmas
2314 @anchor{gnat_rm/implementation_defined_pragmas pragma-compile-time-warning}@anchor{39}
2315 @section Pragma Compile_Time_Warning
2321 pragma Compile_Time_Warning
2322 (boolean_EXPRESSION, static_string_EXPRESSION);
2325 Same as pragma Compile_Time_Error, except a warning is issued instead
2326 of an error message. Note that if this pragma is used in a package that
2327 is with'ed by a client, the client will get the warning even though it
2328 is issued by a with'ed package (normally warnings in with'ed units are
2329 suppressed, but this is a special exception to that rule).
2331 One typical use is within a generic where compile time known characteristics
2332 of formal parameters are tested, and warnings given appropriately. Another use
2333 with a first parameter of True is to warn a client about use of a package,
2334 for example that it is not fully implemented.
2336 @node Pragma Compiler_Unit,Pragma Compiler_Unit_Warning,Pragma Compile_Time_Warning,Implementation Defined Pragmas
2337 @anchor{gnat_rm/implementation_defined_pragmas pragma-compiler-unit}@anchor{3a}
2338 @section Pragma Compiler_Unit
2344 pragma Compiler_Unit;
2347 This pragma is obsolete. It is equivalent to Compiler_Unit_Warning. It is
2348 retained so that old versions of the GNAT run-time that use this pragma can
2349 be compiled with newer versions of the compiler.
2351 @node Pragma Compiler_Unit_Warning,Pragma Complete_Representation,Pragma Compiler_Unit,Implementation Defined Pragmas
2352 @anchor{gnat_rm/implementation_defined_pragmas pragma-compiler-unit-warning}@anchor{3b}
2353 @section Pragma Compiler_Unit_Warning
2359 pragma Compiler_Unit_Warning;
2362 This pragma is intended only for internal use in the GNAT run-time library.
2363 It indicates that the unit is used as part of the compiler build. The effect
2364 is to generate warnings for the use of constructs (for example, conditional
2365 expressions) that would cause trouble when bootstrapping using an older
2366 version of GNAT. For the exact list of restrictions, see the compiler sources
2367 and references to Check_Compiler_Unit.
2369 @node Pragma Complete_Representation,Pragma Complex_Representation,Pragma Compiler_Unit_Warning,Implementation Defined Pragmas
2370 @anchor{gnat_rm/implementation_defined_pragmas pragma-complete-representation}@anchor{3c}
2371 @section Pragma Complete_Representation
2377 pragma Complete_Representation;
2380 This pragma must appear immediately within a record representation
2381 clause. Typical placements are before the first component clause
2382 or after the last component clause. The effect is to give an error
2383 message if any component is missing a component clause. This pragma
2384 may be used to ensure that a record representation clause is
2385 complete, and that this invariant is maintained if fields are
2386 added to the record in the future.
2388 @node Pragma Complex_Representation,Pragma Component_Alignment,Pragma Complete_Representation,Implementation Defined Pragmas
2389 @anchor{gnat_rm/implementation_defined_pragmas pragma-complex-representation}@anchor{3d}
2390 @section Pragma Complex_Representation
2396 pragma Complex_Representation
2397 ([Entity =>] LOCAL_NAME);
2400 The @code{Entity} argument must be the name of a record type which has
2401 two fields of the same floating-point type. The effect of this pragma is
2402 to force gcc to use the special internal complex representation form for
2403 this record, which may be more efficient. Note that this may result in
2404 the code for this type not conforming to standard ABI (application
2405 binary interface) requirements for the handling of record types. For
2406 example, in some environments, there is a requirement for passing
2407 records by pointer, and the use of this pragma may result in passing
2408 this type in floating-point registers.
2410 @node Pragma Component_Alignment,Pragma Constant_After_Elaboration,Pragma Complex_Representation,Implementation Defined Pragmas
2411 @anchor{gnat_rm/implementation_defined_pragmas pragma-component-alignment}@anchor{3e}
2412 @section Pragma Component_Alignment
2415 @geindex Alignments of components
2417 @geindex Pragma Component_Alignment
2422 pragma Component_Alignment (
2423 [Form =>] ALIGNMENT_CHOICE
2424 [, [Name =>] type_LOCAL_NAME]);
2426 ALIGNMENT_CHOICE ::=
2433 Specifies the alignment of components in array or record types.
2434 The meaning of the @code{Form} argument is as follows:
2438 @geindex Component_Size (in pragma Component_Alignment)
2444 @item @emph{Component_Size}
2446 Aligns scalar components and subcomponents of the array or record type
2447 on boundaries appropriate to their inherent size (naturally
2448 aligned). For example, 1-byte components are aligned on byte boundaries,
2449 2-byte integer components are aligned on 2-byte boundaries, 4-byte
2450 integer components are aligned on 4-byte boundaries and so on. These
2451 alignment rules correspond to the normal rules for C compilers on all
2452 machines except the VAX.
2454 @geindex Component_Size_4 (in pragma Component_Alignment)
2456 @item @emph{Component_Size_4}
2458 Naturally aligns components with a size of four or fewer
2459 bytes. Components that are larger than 4 bytes are placed on the next
2462 @geindex Storage_Unit (in pragma Component_Alignment)
2464 @item @emph{Storage_Unit}
2466 Specifies that array or record components are byte aligned, i.e.,
2467 aligned on boundaries determined by the value of the constant
2468 @code{System.Storage_Unit}.
2470 @geindex Default (in pragma Component_Alignment)
2472 @item @emph{Default}
2474 Specifies that array or record components are aligned on default
2475 boundaries, appropriate to the underlying hardware or operating system or
2476 both. The @code{Default} choice is the same as @code{Component_Size} (natural
2480 If the @code{Name} parameter is present, @code{type_LOCAL_NAME} must
2481 refer to a local record or array type, and the specified alignment
2482 choice applies to the specified type. The use of
2483 @code{Component_Alignment} together with a pragma @code{Pack} causes the
2484 @code{Component_Alignment} pragma to be ignored. The use of
2485 @code{Component_Alignment} together with a record representation clause
2486 is only effective for fields not specified by the representation clause.
2488 If the @code{Name} parameter is absent, the pragma can be used as either
2489 a configuration pragma, in which case it applies to one or more units in
2490 accordance with the normal rules for configuration pragmas, or it can be
2491 used within a declarative part, in which case it applies to types that
2492 are declared within this declarative part, or within any nested scope
2493 within this declarative part. In either case it specifies the alignment
2494 to be applied to any record or array type which has otherwise standard
2497 If the alignment for a record or array type is not specified (using
2498 pragma @code{Pack}, pragma @code{Component_Alignment}, or a record rep
2499 clause), the GNAT uses the default alignment as described previously.
2501 @node Pragma Constant_After_Elaboration,Pragma Contract_Cases,Pragma Component_Alignment,Implementation Defined Pragmas
2502 @anchor{gnat_rm/implementation_defined_pragmas id6}@anchor{3f}@anchor{gnat_rm/implementation_defined_pragmas pragma-constant-after-elaboration}@anchor{40}
2503 @section Pragma Constant_After_Elaboration
2509 pragma Constant_After_Elaboration [ (boolean_EXPRESSION) ];
2512 For the semantics of this pragma, see the entry for aspect
2513 @code{Constant_After_Elaboration} in the SPARK 2014 Reference Manual, section 3.3.1.
2515 @node Pragma Contract_Cases,Pragma Convention_Identifier,Pragma Constant_After_Elaboration,Implementation Defined Pragmas
2516 @anchor{gnat_rm/implementation_defined_pragmas id7}@anchor{41}@anchor{gnat_rm/implementation_defined_pragmas pragma-contract-cases}@anchor{42}
2517 @section Pragma Contract_Cases
2520 @geindex Contract cases
2525 pragma Contract_Cases ((CONTRACT_CASE @{, CONTRACT_CASE));
2527 CONTRACT_CASE ::= CASE_GUARD => CONSEQUENCE
2529 CASE_GUARD ::= boolean_EXPRESSION | others
2531 CONSEQUENCE ::= boolean_EXPRESSION
2534 The @code{Contract_Cases} pragma allows defining fine-grain specifications
2535 that can complement or replace the contract given by a precondition and a
2536 postcondition. Additionally, the @code{Contract_Cases} pragma can be used
2537 by testing and formal verification tools. The compiler checks its validity and,
2538 depending on the assertion policy at the point of declaration of the pragma,
2539 it may insert a check in the executable. For code generation, the contract
2543 pragma Contract_Cases (
2551 C1 : constant Boolean := Cond1; -- evaluated at subprogram entry
2552 C2 : constant Boolean := Cond2; -- evaluated at subprogram entry
2553 pragma Precondition ((C1 and not C2) or (C2 and not C1));
2554 pragma Postcondition (if C1 then Pred1);
2555 pragma Postcondition (if C2 then Pred2);
2558 The precondition ensures that one and only one of the conditions is
2559 satisfied on entry to the subprogram.
2560 The postcondition ensures that for the condition that was True on entry,
2561 the corrresponding consequence is True on exit. Other consequence expressions
2564 A precondition @code{P} and postcondition @code{Q} can also be
2565 expressed as contract cases:
2568 pragma Contract_Cases (P => Q);
2571 The placement and visibility rules for @code{Contract_Cases} pragmas are
2572 identical to those described for preconditions and postconditions.
2574 The compiler checks that boolean expressions given in conditions and
2575 consequences are valid, where the rules for conditions are the same as
2576 the rule for an expression in @code{Precondition} and the rules for
2577 consequences are the same as the rule for an expression in
2578 @code{Postcondition}. In particular, attributes @code{'Old} and
2579 @code{'Result} can only be used within consequence expressions.
2580 The condition for the last contract case may be @code{others}, to denote
2581 any case not captured by the previous cases. The
2582 following is an example of use within a package spec:
2585 package Math_Functions is
2587 function Sqrt (Arg : Float) return Float;
2588 pragma Contract_Cases (((Arg in 0.0 .. 99.0) => Sqrt'Result < 10.0,
2589 Arg >= 100.0 => Sqrt'Result >= 10.0,
2590 others => Sqrt'Result = 0.0));
2595 The meaning of contract cases is that only one case should apply at each
2596 call, as determined by the corresponding condition evaluating to True,
2597 and that the consequence for this case should hold when the subprogram
2600 @node Pragma Convention_Identifier,Pragma CPP_Class,Pragma Contract_Cases,Implementation Defined Pragmas
2601 @anchor{gnat_rm/implementation_defined_pragmas pragma-convention-identifier}@anchor{43}
2602 @section Pragma Convention_Identifier
2605 @geindex Conventions
2611 pragma Convention_Identifier (
2612 [Name =>] IDENTIFIER,
2613 [Convention =>] convention_IDENTIFIER);
2616 This pragma provides a mechanism for supplying synonyms for existing
2617 convention identifiers. The @code{Name} identifier can subsequently
2618 be used as a synonym for the given convention in other pragmas (including
2619 for example pragma @code{Import} or another @code{Convention_Identifier}
2620 pragma). As an example of the use of this, suppose you had legacy code
2621 which used Fortran77 as the identifier for Fortran. Then the pragma:
2624 pragma Convention_Identifier (Fortran77, Fortran);
2627 would allow the use of the convention identifier @code{Fortran77} in
2628 subsequent code, avoiding the need to modify the sources. As another
2629 example, you could use this to parameterize convention requirements
2630 according to systems. Suppose you needed to use @code{Stdcall} on
2631 windows systems, and @code{C} on some other system, then you could
2632 define a convention identifier @code{Library} and use a single
2633 @code{Convention_Identifier} pragma to specify which convention
2634 would be used system-wide.
2636 @node Pragma CPP_Class,Pragma CPP_Constructor,Pragma Convention_Identifier,Implementation Defined Pragmas
2637 @anchor{gnat_rm/implementation_defined_pragmas pragma-cpp-class}@anchor{44}
2638 @section Pragma CPP_Class
2641 @geindex Interfacing with C++
2646 pragma CPP_Class ([Entity =>] LOCAL_NAME);
2649 The argument denotes an entity in the current declarative region that is
2650 declared as a record type. It indicates that the type corresponds to an
2651 externally declared C++ class type, and is to be laid out the same way
2652 that C++ would lay out the type. If the C++ class has virtual primitives
2653 then the record must be declared as a tagged record type.
2655 Types for which @code{CPP_Class} is specified do not have assignment or
2656 equality operators defined (such operations can be imported or declared
2657 as subprograms as required). Initialization is allowed only by constructor
2658 functions (see pragma @code{CPP_Constructor}). Such types are implicitly
2659 limited if not explicitly declared as limited or derived from a limited
2660 type, and an error is issued in that case.
2662 See @ref{45,,Interfacing to C++} for related information.
2664 Note: Pragma @code{CPP_Class} is currently obsolete. It is supported
2665 for backward compatibility but its functionality is available
2666 using pragma @code{Import} with @code{Convention} = @code{CPP}.
2668 @node Pragma CPP_Constructor,Pragma CPP_Virtual,Pragma CPP_Class,Implementation Defined Pragmas
2669 @anchor{gnat_rm/implementation_defined_pragmas pragma-cpp-constructor}@anchor{46}
2670 @section Pragma CPP_Constructor
2673 @geindex Interfacing with C++
2678 pragma CPP_Constructor ([Entity =>] LOCAL_NAME
2679 [, [External_Name =>] static_string_EXPRESSION ]
2680 [, [Link_Name =>] static_string_EXPRESSION ]);
2683 This pragma identifies an imported function (imported in the usual way
2684 with pragma @code{Import}) as corresponding to a C++ constructor. If
2685 @code{External_Name} and @code{Link_Name} are not specified then the
2686 @code{Entity} argument is a name that must have been previously mentioned
2687 in a pragma @code{Import} with @code{Convention} = @code{CPP}. Such name
2688 must be of one of the following forms:
2694 @strong{function} @code{Fname} @strong{return} T`
2697 @strong{function} @code{Fname} @strong{return} T'Class
2700 @strong{function} @code{Fname} (...) @strong{return} T`
2703 @strong{function} @code{Fname} (...) @strong{return} T'Class
2706 where @code{T} is a limited record type imported from C++ with pragma
2707 @code{Import} and @code{Convention} = @code{CPP}.
2709 The first two forms import the default constructor, used when an object
2710 of type @code{T} is created on the Ada side with no explicit constructor.
2711 The latter two forms cover all the non-default constructors of the type.
2712 See the GNAT User's Guide for details.
2714 If no constructors are imported, it is impossible to create any objects
2715 on the Ada side and the type is implicitly declared abstract.
2717 Pragma @code{CPP_Constructor} is intended primarily for automatic generation
2718 using an automatic binding generator tool (such as the @code{-fdump-ada-spec}
2720 See @ref{45,,Interfacing to C++} for more related information.
2722 Note: The use of functions returning class-wide types for constructors is
2723 currently obsolete. They are supported for backward compatibility. The
2724 use of functions returning the type T leave the Ada sources more clear
2725 because the imported C++ constructors always return an object of type T;
2726 that is, they never return an object whose type is a descendant of type T.
2728 @node Pragma CPP_Virtual,Pragma CPP_Vtable,Pragma CPP_Constructor,Implementation Defined Pragmas
2729 @anchor{gnat_rm/implementation_defined_pragmas pragma-cpp-virtual}@anchor{47}
2730 @section Pragma CPP_Virtual
2733 @geindex Interfacing to C++
2735 This pragma is now obsolete and, other than generating a warning if warnings
2736 on obsolescent features are enabled, is completely ignored.
2737 It is retained for compatibility
2738 purposes. It used to be required to ensure compoatibility with C++, but
2739 is no longer required for that purpose because GNAT generates
2740 the same object layout as the G++ compiler by default.
2742 See @ref{45,,Interfacing to C++} for related information.
2744 @node Pragma CPP_Vtable,Pragma CPU,Pragma CPP_Virtual,Implementation Defined Pragmas
2745 @anchor{gnat_rm/implementation_defined_pragmas pragma-cpp-vtable}@anchor{48}
2746 @section Pragma CPP_Vtable
2749 @geindex Interfacing with C++
2751 This pragma is now obsolete and, other than generating a warning if warnings
2752 on obsolescent features are enabled, is completely ignored.
2753 It used to be required to ensure compatibility with C++, but
2754 is no longer required for that purpose because GNAT generates
2755 the same object layout as the G++ compiler by default.
2757 See @ref{45,,Interfacing to C++} for related information.
2759 @node Pragma CPU,Pragma Deadline_Floor,Pragma CPP_Vtable,Implementation Defined Pragmas
2760 @anchor{gnat_rm/implementation_defined_pragmas pragma-cpu}@anchor{49}
2767 pragma CPU (EXPRESSION);
2770 This pragma is standard in Ada 2012, but is available in all earlier
2771 versions of Ada as an implementation-defined pragma.
2772 See Ada 2012 Reference Manual for details.
2774 @node Pragma Deadline_Floor,Pragma Default_Initial_Condition,Pragma CPU,Implementation Defined Pragmas
2775 @anchor{gnat_rm/implementation_defined_pragmas pragma-deadline-floor}@anchor{4a}
2776 @section Pragma Deadline_Floor
2782 pragma Deadline_Floor (time_span_EXPRESSION);
2785 This pragma applies only to protected types and specifies the floor
2786 deadline inherited by a task when the task enters a protected object.
2787 It is effective only when the EDF scheduling policy is used.
2789 @node Pragma Default_Initial_Condition,Pragma Debug,Pragma Deadline_Floor,Implementation Defined Pragmas
2790 @anchor{gnat_rm/implementation_defined_pragmas id8}@anchor{4b}@anchor{gnat_rm/implementation_defined_pragmas pragma-default-initial-condition}@anchor{4c}
2791 @section Pragma Default_Initial_Condition
2797 pragma Default_Initial_Condition [ (null | boolean_EXPRESSION) ];
2800 For the semantics of this pragma, see the entry for aspect
2801 @code{Default_Initial_Condition} in the SPARK 2014 Reference Manual, section 7.3.3.
2803 @node Pragma Debug,Pragma Debug_Policy,Pragma Default_Initial_Condition,Implementation Defined Pragmas
2804 @anchor{gnat_rm/implementation_defined_pragmas pragma-debug}@anchor{4d}
2805 @section Pragma Debug
2811 pragma Debug ([CONDITION, ]PROCEDURE_CALL_WITHOUT_SEMICOLON);
2813 PROCEDURE_CALL_WITHOUT_SEMICOLON ::=
2815 | PROCEDURE_PREFIX ACTUAL_PARAMETER_PART
2818 The procedure call argument has the syntactic form of an expression, meeting
2819 the syntactic requirements for pragmas.
2821 If debug pragmas are not enabled or if the condition is present and evaluates
2822 to False, this pragma has no effect. If debug pragmas are enabled, the
2823 semantics of the pragma is exactly equivalent to the procedure call statement
2824 corresponding to the argument with a terminating semicolon. Pragmas are
2825 permitted in sequences of declarations, so you can use pragma @code{Debug} to
2826 intersperse calls to debug procedures in the middle of declarations. Debug
2827 pragmas can be enabled either by use of the command line switch @emph{-gnata}
2828 or by use of the pragma @code{Check_Policy} with a first argument of
2831 @node Pragma Debug_Policy,Pragma Default_Scalar_Storage_Order,Pragma Debug,Implementation Defined Pragmas
2832 @anchor{gnat_rm/implementation_defined_pragmas pragma-debug-policy}@anchor{4e}
2833 @section Pragma Debug_Policy
2839 pragma Debug_Policy (CHECK | DISABLE | IGNORE | ON | OFF);
2842 This pragma is equivalent to a corresponding @code{Check_Policy} pragma
2843 with a first argument of @code{Debug}. It is retained for historical
2844 compatibility reasons.
2846 @node Pragma Default_Scalar_Storage_Order,Pragma Default_Storage_Pool,Pragma Debug_Policy,Implementation Defined Pragmas
2847 @anchor{gnat_rm/implementation_defined_pragmas pragma-default-scalar-storage-order}@anchor{4f}
2848 @section Pragma Default_Scalar_Storage_Order
2851 @geindex Default_Scalar_Storage_Order
2853 @geindex Scalar_Storage_Order
2858 pragma Default_Scalar_Storage_Order (High_Order_First | Low_Order_First);
2861 Normally if no explicit @code{Scalar_Storage_Order} is given for a record
2862 type or array type, then the scalar storage order defaults to the ordinary
2863 default for the target. But this default may be overridden using this pragma.
2864 The pragma may appear as a configuration pragma, or locally within a package
2865 spec or declarative part. In the latter case, it applies to all subsequent
2866 types declared within that package spec or declarative part.
2868 The following example shows the use of this pragma:
2871 pragma Default_Scalar_Storage_Order (High_Order_First);
2872 with System; use System;
2881 for L2'Scalar_Storage_Order use Low_Order_First;
2890 pragma Default_Scalar_Storage_Order (Low_Order_First);
2897 type H4a is new Inner.L4;
2905 In this example record types with names starting with @emph{L} have @cite{Low_Order_First} scalar
2906 storage order, and record types with names starting with @emph{H} have @code{High_Order_First}.
2907 Note that in the case of @code{H4a}, the order is not inherited
2908 from the parent type. Only an explicitly set @code{Scalar_Storage_Order}
2909 gets inherited on type derivation.
2911 If this pragma is used as a configuration pragma which appears within a
2912 configuration pragma file (as opposed to appearing explicitly at the start
2913 of a single unit), then the binder will require that all units in a partition
2914 be compiled in a similar manner, other than run-time units, which are not
2915 affected by this pragma. Note that the use of this form is discouraged because
2916 it may significantly degrade the run-time performance of the software, instead
2917 the default scalar storage order ought to be changed only on a local basis.
2919 @node Pragma Default_Storage_Pool,Pragma Depends,Pragma Default_Scalar_Storage_Order,Implementation Defined Pragmas
2920 @anchor{gnat_rm/implementation_defined_pragmas pragma-default-storage-pool}@anchor{50}
2921 @section Pragma Default_Storage_Pool
2924 @geindex Default_Storage_Pool
2929 pragma Default_Storage_Pool (storage_pool_NAME | null);
2932 This pragma is standard in Ada 2012, but is available in all earlier
2933 versions of Ada as an implementation-defined pragma.
2934 See Ada 2012 Reference Manual for details.
2936 @node Pragma Depends,Pragma Detect_Blocking,Pragma Default_Storage_Pool,Implementation Defined Pragmas
2937 @anchor{gnat_rm/implementation_defined_pragmas pragma-depends}@anchor{51}@anchor{gnat_rm/implementation_defined_pragmas id9}@anchor{52}
2938 @section Pragma Depends
2944 pragma Depends (DEPENDENCY_RELATION);
2946 DEPENDENCY_RELATION ::=
2948 | (DEPENDENCY_CLAUSE @{, DEPENDENCY_CLAUSE@})
2950 DEPENDENCY_CLAUSE ::=
2951 OUTPUT_LIST =>[+] INPUT_LIST
2952 | NULL_DEPENDENCY_CLAUSE
2954 NULL_DEPENDENCY_CLAUSE ::= null => INPUT_LIST
2956 OUTPUT_LIST ::= OUTPUT | (OUTPUT @{, OUTPUT@})
2958 INPUT_LIST ::= null | INPUT | (INPUT @{, INPUT@})
2960 OUTPUT ::= NAME | FUNCTION_RESULT
2963 where FUNCTION_RESULT is a function Result attribute_reference
2966 For the semantics of this pragma, see the entry for aspect @code{Depends} in the
2967 SPARK 2014 Reference Manual, section 6.1.5.
2969 @node Pragma Detect_Blocking,Pragma Disable_Atomic_Synchronization,Pragma Depends,Implementation Defined Pragmas
2970 @anchor{gnat_rm/implementation_defined_pragmas pragma-detect-blocking}@anchor{53}
2971 @section Pragma Detect_Blocking
2977 pragma Detect_Blocking;
2980 This is a standard pragma in Ada 2005, that is available in all earlier
2981 versions of Ada as an implementation-defined pragma.
2983 This is a configuration pragma that forces the detection of potentially
2984 blocking operations within a protected operation, and to raise Program_Error
2987 @node Pragma Disable_Atomic_Synchronization,Pragma Dispatching_Domain,Pragma Detect_Blocking,Implementation Defined Pragmas
2988 @anchor{gnat_rm/implementation_defined_pragmas pragma-disable-atomic-synchronization}@anchor{54}
2989 @section Pragma Disable_Atomic_Synchronization
2992 @geindex Atomic Synchronization
2997 pragma Disable_Atomic_Synchronization [(Entity)];
3000 Ada requires that accesses (reads or writes) of an atomic variable be
3001 regarded as synchronization points in the case of multiple tasks.
3002 Particularly in the case of multi-processors this may require special
3003 handling, e.g. the generation of memory barriers. This capability may
3004 be turned off using this pragma in cases where it is known not to be
3007 The placement and scope rules for this pragma are the same as those
3008 for @code{pragma Suppress}. In particular it can be used as a
3009 configuration pragma, or in a declaration sequence where it applies
3010 till the end of the scope. If an @code{Entity} argument is present,
3011 the action applies only to that entity.
3013 @node Pragma Dispatching_Domain,Pragma Effective_Reads,Pragma Disable_Atomic_Synchronization,Implementation Defined Pragmas
3014 @anchor{gnat_rm/implementation_defined_pragmas pragma-dispatching-domain}@anchor{55}
3015 @section Pragma Dispatching_Domain
3021 pragma Dispatching_Domain (EXPRESSION);
3024 This pragma is standard in Ada 2012, but is available in all earlier
3025 versions of Ada as an implementation-defined pragma.
3026 See Ada 2012 Reference Manual for details.
3028 @node Pragma Effective_Reads,Pragma Effective_Writes,Pragma Dispatching_Domain,Implementation Defined Pragmas
3029 @anchor{gnat_rm/implementation_defined_pragmas id10}@anchor{56}@anchor{gnat_rm/implementation_defined_pragmas pragma-effective-reads}@anchor{57}
3030 @section Pragma Effective_Reads
3036 pragma Effective_Reads [ (boolean_EXPRESSION) ];
3039 For the semantics of this pragma, see the entry for aspect @code{Effective_Reads} in
3040 the SPARK 2014 Reference Manual, section 7.1.2.
3042 @node Pragma Effective_Writes,Pragma Elaboration_Checks,Pragma Effective_Reads,Implementation Defined Pragmas
3043 @anchor{gnat_rm/implementation_defined_pragmas id11}@anchor{58}@anchor{gnat_rm/implementation_defined_pragmas pragma-effective-writes}@anchor{59}
3044 @section Pragma Effective_Writes
3050 pragma Effective_Writes [ (boolean_EXPRESSION) ];
3053 For the semantics of this pragma, see the entry for aspect @code{Effective_Writes}
3054 in the SPARK 2014 Reference Manual, section 7.1.2.
3056 @node Pragma Elaboration_Checks,Pragma Eliminate,Pragma Effective_Writes,Implementation Defined Pragmas
3057 @anchor{gnat_rm/implementation_defined_pragmas pragma-elaboration-checks}@anchor{5a}
3058 @section Pragma Elaboration_Checks
3061 @geindex Elaboration control
3066 pragma Elaboration_Checks (Dynamic | Static);
3069 This is a configuration pragma that provides control over the
3070 elaboration model used by the compilation affected by the
3071 pragma. If the parameter is @code{Dynamic},
3072 then the dynamic elaboration
3073 model described in the Ada Reference Manual is used, as though
3074 the @emph{-gnatE} switch had been specified on the command
3075 line. If the parameter is @code{Static}, then the default GNAT static
3076 model is used. This configuration pragma overrides the setting
3077 of the command line. For full details on the elaboration models
3078 used by the GNAT compiler, see the chapter on elaboration order handling
3079 in the @emph{GNAT User's Guide}.
3081 @node Pragma Eliminate,Pragma Enable_Atomic_Synchronization,Pragma Elaboration_Checks,Implementation Defined Pragmas
3082 @anchor{gnat_rm/implementation_defined_pragmas pragma-eliminate}@anchor{5b}
3083 @section Pragma Eliminate
3086 @geindex Elimination of unused subprograms
3092 [ Unit_Name => ] IDENTIFIER | SELECTED_COMPONENT ,
3093 [ Entity => ] IDENTIFIER |
3094 SELECTED_COMPONENT |
3096 [, Source_Location => SOURCE_TRACE ] );
3098 SOURCE_TRACE ::= STRING_LITERAL
3101 This pragma indicates that the given entity is not used in the program to be
3102 compiled and built, thus allowing the compiler to
3103 eliminate the code or data associated with the named entity. Any reference to
3104 an eliminated entity causes a compile-time or link-time error.
3106 The pragma has the following semantics, where @code{U} is the unit specified by
3107 the @code{Unit_Name} argument and @code{E} is the entity specified by the @code{Entity}
3114 @code{E} must be a subprogram that is explicitly declared either:
3116 o Within @code{U}, or
3118 o Within a generic package that is instantiated in @code{U}, or
3120 o As an instance of generic subprogram instantiated in @code{U}.
3122 Otherwise the pragma is ignored.
3125 If @code{E} is overloaded within @code{U} then, in the absence of a
3126 @code{Source_Location} argument, all overloadings are eliminated.
3129 If @code{E} is overloaded within @code{U} and only some overloadings
3130 are to be eliminated, then each overloading to be eliminated
3131 must be specified in a corresponding pragma @code{Eliminate}
3132 with a @code{Source_Location} argument identifying the line where the
3133 declaration appears, as described below.
3136 If @code{E} is declared as the result of a generic instantiation, then
3137 a @code{Source_Location} argument is needed, as described below
3140 Pragma @code{Eliminate} allows a program to be compiled in a system-independent
3141 manner, so that unused entities are eliminated but without
3142 needing to modify the source text. Normally the required set of
3143 @code{Eliminate} pragmas is constructed automatically using the @code{gnatelim} tool.
3145 Any source file change that removes, splits, or
3146 adds lines may make the set of @code{Eliminate} pragmas invalid because their
3147 @code{Source_Location} argument values may get out of date.
3149 Pragma @code{Eliminate} may be used where the referenced entity is a dispatching
3150 operation. In this case all the subprograms to which the given operation can
3151 dispatch are considered to be unused (are never called as a result of a direct
3152 or a dispatching call).
3154 The string literal given for the source location specifies the line number
3155 of the declaration of the entity, using the following syntax for @code{SOURCE_TRACE}:
3158 SOURCE_TRACE ::= SOURCE_REFERENCE [ LBRACKET SOURCE_TRACE RBRACKET ]
3163 SOURCE_REFERENCE ::= FILE_NAME : LINE_NUMBER
3165 LINE_NUMBER ::= DIGIT @{DIGIT@}
3168 Spaces around the colon in a @code{SOURCE_REFERENCE} are optional.
3170 The source trace that is given as the @code{Source_Location} must obey the
3171 following rules (or else the pragma is ignored), where @code{U} is
3172 the unit @code{U} specified by the @code{Unit_Name} argument and @code{E} is the
3173 subprogram specified by the @code{Entity} argument:
3179 @code{FILE_NAME} is the short name (with no directory
3180 information) of the Ada source file for @code{U}, using the required syntax
3181 for the underlying file system (e.g. case is significant if the underlying
3182 operating system is case sensitive).
3183 If @code{U} is a package and @code{E} is a subprogram declared in the package
3184 specification and its full declaration appears in the package body,
3185 then the relevant source file is the one for the package specification;
3186 analogously if @code{U} is a generic package.
3189 If @code{E} is not declared in a generic instantiation (this includes
3190 generic subprogram instances), the source trace includes only one source
3191 line reference. @code{LINE_NUMBER} gives the line number of the occurrence
3192 of the declaration of @code{E} within the source file (as a decimal literal
3193 without an exponent or point).
3196 If @code{E} is declared by a generic instantiation, its source trace
3197 (from left to right) starts with the source location of the
3198 declaration of @code{E} in the generic unit and ends with the source
3199 location of the instantiation, given in square brackets. This approach is
3200 applied recursively with nested instantiations: the rightmost (nested
3201 most deeply in square brackets) element of the source trace is the location
3202 of the outermost instantiation, and the leftmost element (that is, outside
3203 of any square brackets) is the location of the declaration of @code{E} in
3212 pragma Eliminate (Pkg0, Proc);
3213 -- Eliminate (all overloadings of) Proc in Pkg0
3215 pragma Eliminate (Pkg1, Proc,
3216 Source_Location => "pkg1.ads:8");
3217 -- Eliminate overloading of Proc at line 8 in pkg1.ads
3219 -- Assume the following file contents:
3222 -- 2: type T is private;
3223 -- 3: package Gen_Pkg is
3224 -- 4: procedure Proc(N : T);
3230 -- 2: procedure Q is
3231 -- 3: package Inst_Pkg is new Gen_Pkg(Integer);
3232 -- ... -- No calls on Inst_Pkg.Proc
3235 -- The following pragma eliminates Inst_Pkg.Proc from Q
3236 pragma Eliminate (Q, Proc,
3237 Source_Location => "gen_pkg.ads:4[q.adb:3]");
3241 @node Pragma Enable_Atomic_Synchronization,Pragma Export_Function,Pragma Eliminate,Implementation Defined Pragmas
3242 @anchor{gnat_rm/implementation_defined_pragmas pragma-enable-atomic-synchronization}@anchor{5c}
3243 @section Pragma Enable_Atomic_Synchronization
3246 @geindex Atomic Synchronization
3251 pragma Enable_Atomic_Synchronization [(Entity)];
3254 Ada requires that accesses (reads or writes) of an atomic variable be
3255 regarded as synchronization points in the case of multiple tasks.
3256 Particularly in the case of multi-processors this may require special
3257 handling, e.g. the generation of memory barriers. This synchronization
3258 is performed by default, but can be turned off using
3259 @code{pragma Disable_Atomic_Synchronization}. The
3260 @code{Enable_Atomic_Synchronization} pragma can be used to turn
3263 The placement and scope rules for this pragma are the same as those
3264 for @code{pragma Unsuppress}. In particular it can be used as a
3265 configuration pragma, or in a declaration sequence where it applies
3266 till the end of the scope. If an @code{Entity} argument is present,
3267 the action applies only to that entity.
3269 @node Pragma Export_Function,Pragma Export_Object,Pragma Enable_Atomic_Synchronization,Implementation Defined Pragmas
3270 @anchor{gnat_rm/implementation_defined_pragmas pragma-export-function}@anchor{5d}
3271 @section Pragma Export_Function
3274 @geindex Argument passing mechanisms
3279 pragma Export_Function (
3280 [Internal =>] LOCAL_NAME
3281 [, [External =>] EXTERNAL_SYMBOL]
3282 [, [Parameter_Types =>] PARAMETER_TYPES]
3283 [, [Result_Type =>] result_SUBTYPE_MARK]
3284 [, [Mechanism =>] MECHANISM]
3285 [, [Result_Mechanism =>] MECHANISM_NAME]);
3289 | static_string_EXPRESSION
3294 | TYPE_DESIGNATOR @{, TYPE_DESIGNATOR@}
3298 | subtype_Name ' Access
3302 | (MECHANISM_ASSOCIATION @{, MECHANISM_ASSOCIATION@})
3304 MECHANISM_ASSOCIATION ::=
3305 [formal_parameter_NAME =>] MECHANISM_NAME
3307 MECHANISM_NAME ::= Value | Reference
3310 Use this pragma to make a function externally callable and optionally
3311 provide information on mechanisms to be used for passing parameter and
3312 result values. We recommend, for the purposes of improving portability,
3313 this pragma always be used in conjunction with a separate pragma
3314 @code{Export}, which must precede the pragma @code{Export_Function}.
3315 GNAT does not require a separate pragma @code{Export}, but if none is
3316 present, @code{Convention Ada} is assumed, which is usually
3317 not what is wanted, so it is usually appropriate to use this
3318 pragma in conjunction with a @code{Export} or @code{Convention}
3319 pragma that specifies the desired foreign convention.
3320 Pragma @code{Export_Function}
3321 (and @code{Export}, if present) must appear in the same declarative
3322 region as the function to which they apply.
3324 The @code{internal_name} must uniquely designate the function to which the
3325 pragma applies. If more than one function name exists of this name in
3326 the declarative part you must use the @code{Parameter_Types} and
3327 @code{Result_Type} parameters to achieve the required
3328 unique designation. The @cite{subtype_mark}s in these parameters must
3329 exactly match the subtypes in the corresponding function specification,
3330 using positional notation to match parameters with subtype marks.
3331 The form with an @code{'Access} attribute can be used to match an
3332 anonymous access parameter.
3334 @geindex Suppressing external name
3336 Special treatment is given if the EXTERNAL is an explicit null
3337 string or a static string expressions that evaluates to the null
3338 string. In this case, no external name is generated. This form
3339 still allows the specification of parameter mechanisms.
3341 @node Pragma Export_Object,Pragma Export_Procedure,Pragma Export_Function,Implementation Defined Pragmas
3342 @anchor{gnat_rm/implementation_defined_pragmas pragma-export-object}@anchor{5e}
3343 @section Pragma Export_Object
3349 pragma Export_Object
3350 [Internal =>] LOCAL_NAME
3351 [, [External =>] EXTERNAL_SYMBOL]
3352 [, [Size =>] EXTERNAL_SYMBOL]
3356 | static_string_EXPRESSION
3359 This pragma designates an object as exported, and apart from the
3360 extended rules for external symbols, is identical in effect to the use of
3361 the normal @code{Export} pragma applied to an object. You may use a
3362 separate Export pragma (and you probably should from the point of view
3363 of portability), but it is not required. @code{Size} is syntax checked,
3364 but otherwise ignored by GNAT.
3366 @node Pragma Export_Procedure,Pragma Export_Value,Pragma Export_Object,Implementation Defined Pragmas
3367 @anchor{gnat_rm/implementation_defined_pragmas pragma-export-procedure}@anchor{5f}
3368 @section Pragma Export_Procedure
3374 pragma Export_Procedure (
3375 [Internal =>] LOCAL_NAME
3376 [, [External =>] EXTERNAL_SYMBOL]
3377 [, [Parameter_Types =>] PARAMETER_TYPES]
3378 [, [Mechanism =>] MECHANISM]);
3382 | static_string_EXPRESSION
3387 | TYPE_DESIGNATOR @{, TYPE_DESIGNATOR@}
3391 | subtype_Name ' Access
3395 | (MECHANISM_ASSOCIATION @{, MECHANISM_ASSOCIATION@})
3397 MECHANISM_ASSOCIATION ::=
3398 [formal_parameter_NAME =>] MECHANISM_NAME
3400 MECHANISM_NAME ::= Value | Reference
3403 This pragma is identical to @code{Export_Function} except that it
3404 applies to a procedure rather than a function and the parameters
3405 @code{Result_Type} and @code{Result_Mechanism} are not permitted.
3406 GNAT does not require a separate pragma @code{Export}, but if none is
3407 present, @code{Convention Ada} is assumed, which is usually
3408 not what is wanted, so it is usually appropriate to use this
3409 pragma in conjunction with a @code{Export} or @code{Convention}
3410 pragma that specifies the desired foreign convention.
3412 @geindex Suppressing external name
3414 Special treatment is given if the EXTERNAL is an explicit null
3415 string or a static string expressions that evaluates to the null
3416 string. In this case, no external name is generated. This form
3417 still allows the specification of parameter mechanisms.
3419 @node Pragma Export_Value,Pragma Export_Valued_Procedure,Pragma Export_Procedure,Implementation Defined Pragmas
3420 @anchor{gnat_rm/implementation_defined_pragmas pragma-export-value}@anchor{60}
3421 @section Pragma Export_Value
3427 pragma Export_Value (
3428 [Value =>] static_integer_EXPRESSION,
3429 [Link_Name =>] static_string_EXPRESSION);
3432 This pragma serves to export a static integer value for external use.
3433 The first argument specifies the value to be exported. The Link_Name
3434 argument specifies the symbolic name to be associated with the integer
3435 value. This pragma is useful for defining a named static value in Ada
3436 that can be referenced in assembly language units to be linked with
3437 the application. This pragma is currently supported only for the
3438 AAMP target and is ignored for other targets.
3440 @node Pragma Export_Valued_Procedure,Pragma Extend_System,Pragma Export_Value,Implementation Defined Pragmas
3441 @anchor{gnat_rm/implementation_defined_pragmas pragma-export-valued-procedure}@anchor{61}
3442 @section Pragma Export_Valued_Procedure
3448 pragma Export_Valued_Procedure (
3449 [Internal =>] LOCAL_NAME
3450 [, [External =>] EXTERNAL_SYMBOL]
3451 [, [Parameter_Types =>] PARAMETER_TYPES]
3452 [, [Mechanism =>] MECHANISM]);
3456 | static_string_EXPRESSION
3461 | TYPE_DESIGNATOR @{, TYPE_DESIGNATOR@}
3465 | subtype_Name ' Access
3469 | (MECHANISM_ASSOCIATION @{, MECHANISM_ASSOCIATION@})
3471 MECHANISM_ASSOCIATION ::=
3472 [formal_parameter_NAME =>] MECHANISM_NAME
3474 MECHANISM_NAME ::= Value | Reference
3477 This pragma is identical to @code{Export_Procedure} except that the
3478 first parameter of @code{LOCAL_NAME}, which must be present, must be of
3479 mode @code{out}, and externally the subprogram is treated as a function
3480 with this parameter as the result of the function. GNAT provides for
3481 this capability to allow the use of @code{out} and @code{in out}
3482 parameters in interfacing to external functions (which are not permitted
3484 GNAT does not require a separate pragma @code{Export}, but if none is
3485 present, @code{Convention Ada} is assumed, which is almost certainly
3486 not what is wanted since the whole point of this pragma is to interface
3487 with foreign language functions, so it is usually appropriate to use this
3488 pragma in conjunction with a @code{Export} or @code{Convention}
3489 pragma that specifies the desired foreign convention.
3491 @geindex Suppressing external name
3493 Special treatment is given if the EXTERNAL is an explicit null
3494 string or a static string expressions that evaluates to the null
3495 string. In this case, no external name is generated. This form
3496 still allows the specification of parameter mechanisms.
3498 @node Pragma Extend_System,Pragma Extensions_Allowed,Pragma Export_Valued_Procedure,Implementation Defined Pragmas
3499 @anchor{gnat_rm/implementation_defined_pragmas pragma-extend-system}@anchor{62}
3500 @section Pragma Extend_System
3511 pragma Extend_System ([Name =>] IDENTIFIER);
3514 This pragma is used to provide backwards compatibility with other
3515 implementations that extend the facilities of package @code{System}. In
3516 GNAT, @code{System} contains only the definitions that are present in
3517 the Ada RM. However, other implementations, notably the DEC Ada 83
3518 implementation, provide many extensions to package @code{System}.
3520 For each such implementation accommodated by this pragma, GNAT provides a
3521 package @code{Aux_@emph{xxx}}, e.g., @code{Aux_DEC} for the DEC Ada 83
3522 implementation, which provides the required additional definitions. You
3523 can use this package in two ways. You can @code{with} it in the normal
3524 way and access entities either by selection or using a @code{use}
3525 clause. In this case no special processing is required.
3527 However, if existing code contains references such as
3528 @code{System.@emph{xxx}} where @emph{xxx} is an entity in the extended
3529 definitions provided in package @code{System}, you may use this pragma
3530 to extend visibility in @code{System} in a non-standard way that
3531 provides greater compatibility with the existing code. Pragma
3532 @code{Extend_System} is a configuration pragma whose single argument is
3533 the name of the package containing the extended definition
3534 (e.g., @code{Aux_DEC} for the DEC Ada case). A unit compiled under
3535 control of this pragma will be processed using special visibility
3536 processing that looks in package @code{System.Aux_@emph{xxx}} where
3537 @code{Aux_@emph{xxx}} is the pragma argument for any entity referenced in
3538 package @code{System}, but not found in package @code{System}.
3540 You can use this pragma either to access a predefined @code{System}
3541 extension supplied with the compiler, for example @code{Aux_DEC} or
3542 you can construct your own extension unit following the above
3543 definition. Note that such a package is a child of @code{System}
3544 and thus is considered part of the implementation.
3545 To compile it you will have to use the @emph{-gnatg} switch
3546 for compiling System units, as explained in the
3549 @node Pragma Extensions_Allowed,Pragma Extensions_Visible,Pragma Extend_System,Implementation Defined Pragmas
3550 @anchor{gnat_rm/implementation_defined_pragmas pragma-extensions-allowed}@anchor{63}
3551 @section Pragma Extensions_Allowed
3554 @geindex Ada Extensions
3556 @geindex GNAT Extensions
3561 pragma Extensions_Allowed (On | Off);
3564 This configuration pragma enables or disables the implementation
3565 extension mode (the use of Off as a parameter cancels the effect
3566 of the @emph{-gnatX} command switch).
3568 In extension mode, the latest version of the Ada language is
3569 implemented (currently Ada 2012), and in addition a small number
3570 of GNAT specific extensions are recognized as follows:
3575 @item @emph{Constrained attribute for generic objects}
3577 The @code{Constrained} attribute is permitted for objects of
3578 generic types. The result indicates if the corresponding actual
3582 @node Pragma Extensions_Visible,Pragma External,Pragma Extensions_Allowed,Implementation Defined Pragmas
3583 @anchor{gnat_rm/implementation_defined_pragmas id12}@anchor{64}@anchor{gnat_rm/implementation_defined_pragmas pragma-extensions-visible}@anchor{65}
3584 @section Pragma Extensions_Visible
3590 pragma Extensions_Visible [ (boolean_EXPRESSION) ];
3593 For the semantics of this pragma, see the entry for aspect @code{Extensions_Visible}
3594 in the SPARK 2014 Reference Manual, section 6.1.7.
3596 @node Pragma External,Pragma External_Name_Casing,Pragma Extensions_Visible,Implementation Defined Pragmas
3597 @anchor{gnat_rm/implementation_defined_pragmas pragma-external}@anchor{66}
3598 @section Pragma External
3605 [ Convention =>] convention_IDENTIFIER,
3606 [ Entity =>] LOCAL_NAME
3607 [, [External_Name =>] static_string_EXPRESSION ]
3608 [, [Link_Name =>] static_string_EXPRESSION ]);
3611 This pragma is identical in syntax and semantics to pragma
3612 @code{Export} as defined in the Ada Reference Manual. It is
3613 provided for compatibility with some Ada 83 compilers that
3614 used this pragma for exactly the same purposes as pragma
3615 @code{Export} before the latter was standardized.
3617 @node Pragma External_Name_Casing,Pragma Fast_Math,Pragma External,Implementation Defined Pragmas
3618 @anchor{gnat_rm/implementation_defined_pragmas pragma-external-name-casing}@anchor{67}
3619 @section Pragma External_Name_Casing
3622 @geindex Dec Ada 83 casing compatibility
3624 @geindex External Names
3627 @geindex Casing of External names
3632 pragma External_Name_Casing (
3633 Uppercase | Lowercase
3634 [, Uppercase | Lowercase | As_Is]);
3637 This pragma provides control over the casing of external names associated
3638 with Import and Export pragmas. There are two cases to consider:
3644 Implicit external names
3646 Implicit external names are derived from identifiers. The most common case
3647 arises when a standard Ada Import or Export pragma is used with only two
3651 pragma Import (C, C_Routine);
3654 Since Ada is a case-insensitive language, the spelling of the identifier in
3655 the Ada source program does not provide any information on the desired
3656 casing of the external name, and so a convention is needed. In GNAT the
3657 default treatment is that such names are converted to all lower case
3658 letters. This corresponds to the normal C style in many environments.
3659 The first argument of pragma @code{External_Name_Casing} can be used to
3660 control this treatment. If @code{Uppercase} is specified, then the name
3661 will be forced to all uppercase letters. If @code{Lowercase} is specified,
3662 then the normal default of all lower case letters will be used.
3664 This same implicit treatment is also used in the case of extended DEC Ada 83
3665 compatible Import and Export pragmas where an external name is explicitly
3666 specified using an identifier rather than a string.
3669 Explicit external names
3671 Explicit external names are given as string literals. The most common case
3672 arises when a standard Ada Import or Export pragma is used with three
3676 pragma Import (C, C_Routine, "C_routine");
3679 In this case, the string literal normally provides the exact casing required
3680 for the external name. The second argument of pragma
3681 @code{External_Name_Casing} may be used to modify this behavior.
3682 If @code{Uppercase} is specified, then the name
3683 will be forced to all uppercase letters. If @code{Lowercase} is specified,
3684 then the name will be forced to all lowercase letters. A specification of
3685 @code{As_Is} provides the normal default behavior in which the casing is
3686 taken from the string provided.
3689 This pragma may appear anywhere that a pragma is valid. In particular, it
3690 can be used as a configuration pragma in the @code{gnat.adc} file, in which
3691 case it applies to all subsequent compilations, or it can be used as a program
3692 unit pragma, in which case it only applies to the current unit, or it can
3693 be used more locally to control individual Import/Export pragmas.
3695 It was primarily intended for use with OpenVMS systems, where many
3696 compilers convert all symbols to upper case by default. For interfacing to
3697 such compilers (e.g., the DEC C compiler), it may be convenient to use
3701 pragma External_Name_Casing (Uppercase, Uppercase);
3704 to enforce the upper casing of all external symbols.
3706 @node Pragma Fast_Math,Pragma Favor_Top_Level,Pragma External_Name_Casing,Implementation Defined Pragmas
3707 @anchor{gnat_rm/implementation_defined_pragmas pragma-fast-math}@anchor{68}
3708 @section Pragma Fast_Math
3717 This is a configuration pragma which activates a mode in which speed is
3718 considered more important for floating-point operations than absolutely
3719 accurate adherence to the requirements of the standard. Currently the
3720 following operations are affected:
3725 @item @emph{Complex Multiplication}
3727 The normal simple formula for complex multiplication can result in intermediate
3728 overflows for numbers near the end of the range. The Ada standard requires that
3729 this situation be detected and corrected by scaling, but in Fast_Math mode such
3730 cases will simply result in overflow. Note that to take advantage of this you
3731 must instantiate your own version of @code{Ada.Numerics.Generic_Complex_Types}
3732 under control of the pragma, rather than use the preinstantiated versions.
3735 @node Pragma Favor_Top_Level,Pragma Finalize_Storage_Only,Pragma Fast_Math,Implementation Defined Pragmas
3736 @anchor{gnat_rm/implementation_defined_pragmas id13}@anchor{69}@anchor{gnat_rm/implementation_defined_pragmas pragma-favor-top-level}@anchor{6a}
3737 @section Pragma Favor_Top_Level
3743 pragma Favor_Top_Level (type_NAME);
3746 The argument of pragma @code{Favor_Top_Level} must be a named access-to-subprogram
3747 type. This pragma is an efficiency hint to the compiler, regarding the use of
3748 @code{'Access} or @code{'Unrestricted_Access} on nested (non-library-level) subprograms.
3749 The pragma means that nested subprograms are not used with this type, or are
3750 rare, so that the generated code should be efficient in the top-level case.
3751 When this pragma is used, dynamically generated trampolines may be used on some
3752 targets for nested subprograms. See restriction @code{No_Implicit_Dynamic_Code}.
3754 @node Pragma Finalize_Storage_Only,Pragma Float_Representation,Pragma Favor_Top_Level,Implementation Defined Pragmas
3755 @anchor{gnat_rm/implementation_defined_pragmas pragma-finalize-storage-only}@anchor{6b}
3756 @section Pragma Finalize_Storage_Only
3762 pragma Finalize_Storage_Only (first_subtype_LOCAL_NAME);
3765 The argument of pragma @code{Finalize_Storage_Only} must denote a local type which
3766 is derived from @code{Ada.Finalization.Controlled} or @code{Limited_Controlled}. The
3767 pragma suppresses the call to @code{Finalize} for declared library-level objects
3768 of the argument type. This is mostly useful for types where finalization is
3769 only used to deal with storage reclamation since in most environments it is
3770 not necessary to reclaim memory just before terminating execution, hence the
3771 name. Note that this pragma does not suppress Finalize calls for library-level
3772 heap-allocated objects (see pragma @code{No_Heap_Finalization}).
3774 @node Pragma Float_Representation,Pragma Ghost,Pragma Finalize_Storage_Only,Implementation Defined Pragmas
3775 @anchor{gnat_rm/implementation_defined_pragmas pragma-float-representation}@anchor{6c}
3776 @section Pragma Float_Representation
3782 pragma Float_Representation (FLOAT_REP[, float_type_LOCAL_NAME]);
3784 FLOAT_REP ::= VAX_Float | IEEE_Float
3787 In the one argument form, this pragma is a configuration pragma which
3788 allows control over the internal representation chosen for the predefined
3789 floating point types declared in the packages @code{Standard} and
3790 @code{System}. This pragma is only provided for compatibility and has no effect.
3792 The two argument form specifies the representation to be used for
3793 the specified floating-point type. The argument must
3794 be @code{IEEE_Float} to specify the use of IEEE format, as follows:
3800 For a digits value of 6, 32-bit IEEE short format will be used.
3803 For a digits value of 15, 64-bit IEEE long format will be used.
3806 No other value of digits is permitted.
3809 @node Pragma Ghost,Pragma Global,Pragma Float_Representation,Implementation Defined Pragmas
3810 @anchor{gnat_rm/implementation_defined_pragmas pragma-ghost}@anchor{6d}@anchor{gnat_rm/implementation_defined_pragmas id14}@anchor{6e}
3811 @section Pragma Ghost
3817 pragma Ghost [ (boolean_EXPRESSION) ];
3820 For the semantics of this pragma, see the entry for aspect @code{Ghost} in the SPARK
3821 2014 Reference Manual, section 6.9.
3823 @node Pragma Global,Pragma Ident,Pragma Ghost,Implementation Defined Pragmas
3824 @anchor{gnat_rm/implementation_defined_pragmas pragma-global}@anchor{6f}@anchor{gnat_rm/implementation_defined_pragmas id15}@anchor{70}
3825 @section Pragma Global
3831 pragma Global (GLOBAL_SPECIFICATION);
3833 GLOBAL_SPECIFICATION ::=
3836 | (MODED_GLOBAL_LIST @{, MODED_GLOBAL_LIST@})
3838 MODED_GLOBAL_LIST ::= MODE_SELECTOR => GLOBAL_LIST
3840 MODE_SELECTOR ::= In_Out | Input | Output | Proof_In
3841 GLOBAL_LIST ::= GLOBAL_ITEM | (GLOBAL_ITEM @{, GLOBAL_ITEM@})
3842 GLOBAL_ITEM ::= NAME
3845 For the semantics of this pragma, see the entry for aspect @code{Global} in the
3846 SPARK 2014 Reference Manual, section 6.1.4.
3848 @node Pragma Ident,Pragma Ignore_Pragma,Pragma Global,Implementation Defined Pragmas
3849 @anchor{gnat_rm/implementation_defined_pragmas pragma-ident}@anchor{71}
3850 @section Pragma Ident
3856 pragma Ident (static_string_EXPRESSION);
3859 This pragma is identical in effect to pragma @code{Comment}. It is provided
3860 for compatibility with other Ada compilers providing this pragma.
3862 @node Pragma Ignore_Pragma,Pragma Implementation_Defined,Pragma Ident,Implementation Defined Pragmas
3863 @anchor{gnat_rm/implementation_defined_pragmas pragma-ignore-pragma}@anchor{72}
3864 @section Pragma Ignore_Pragma
3870 pragma Ignore_Pragma (pragma_IDENTIFIER);
3873 This is a configuration pragma
3874 that takes a single argument that is a simple identifier. Any subsequent
3875 use of a pragma whose pragma identifier matches this argument will be
3876 silently ignored. This may be useful when legacy code or code intended
3877 for compilation with some other compiler contains pragmas that match the
3878 name, but not the exact implementation, of a GNAT pragma. The use of this
3879 pragma allows such pragmas to be ignored, which may be useful in CodePeer
3880 mode, or during porting of legacy code.
3882 @node Pragma Implementation_Defined,Pragma Implemented,Pragma Ignore_Pragma,Implementation Defined Pragmas
3883 @anchor{gnat_rm/implementation_defined_pragmas pragma-implementation-defined}@anchor{73}
3884 @section Pragma Implementation_Defined
3890 pragma Implementation_Defined (local_NAME);
3893 This pragma marks a previously declared entity as implementation-defined.
3894 For an overloaded entity, applies to the most recent homonym.
3897 pragma Implementation_Defined;
3900 The form with no arguments appears anywhere within a scope, most
3901 typically a package spec, and indicates that all entities that are
3902 defined within the package spec are Implementation_Defined.
3904 This pragma is used within the GNAT runtime library to identify
3905 implementation-defined entities introduced in language-defined units,
3906 for the purpose of implementing the No_Implementation_Identifiers
3909 @node Pragma Implemented,Pragma Implicit_Packing,Pragma Implementation_Defined,Implementation Defined Pragmas
3910 @anchor{gnat_rm/implementation_defined_pragmas pragma-implemented}@anchor{74}
3911 @section Pragma Implemented
3917 pragma Implemented (procedure_LOCAL_NAME, implementation_kind);
3919 implementation_kind ::= By_Entry | By_Protected_Procedure | By_Any
3922 This is an Ada 2012 representation pragma which applies to protected, task
3923 and synchronized interface primitives. The use of pragma Implemented provides
3924 a way to impose a static requirement on the overriding operation by adhering
3925 to one of the three implementation kinds: entry, protected procedure or any of
3926 the above. This pragma is available in all earlier versions of Ada as an
3927 implementation-defined pragma.
3930 type Synch_Iface is synchronized interface;
3931 procedure Prim_Op (Obj : in out Iface) is abstract;
3932 pragma Implemented (Prim_Op, By_Protected_Procedure);
3934 protected type Prot_1 is new Synch_Iface with
3935 procedure Prim_Op; -- Legal
3938 protected type Prot_2 is new Synch_Iface with
3939 entry Prim_Op; -- Illegal
3942 task type Task_Typ is new Synch_Iface with
3943 entry Prim_Op; -- Illegal
3947 When applied to the procedure_or_entry_NAME of a requeue statement, pragma
3948 Implemented determines the runtime behavior of the requeue. Implementation kind
3949 By_Entry guarantees that the action of requeueing will proceed from an entry to
3950 another entry. Implementation kind By_Protected_Procedure transforms the
3951 requeue into a dispatching call, thus eliminating the chance of blocking. Kind
3952 By_Any shares the behavior of By_Entry and By_Protected_Procedure depending on
3953 the target's overriding subprogram kind.
3955 @node Pragma Implicit_Packing,Pragma Import_Function,Pragma Implemented,Implementation Defined Pragmas
3956 @anchor{gnat_rm/implementation_defined_pragmas pragma-implicit-packing}@anchor{75}
3957 @section Pragma Implicit_Packing
3960 @geindex Rational Profile
3965 pragma Implicit_Packing;
3968 This is a configuration pragma that requests implicit packing for packed
3969 arrays for which a size clause is given but no explicit pragma Pack or
3970 specification of Component_Size is present. It also applies to records
3971 where no record representation clause is present. Consider this example:
3974 type R is array (0 .. 7) of Boolean;
3978 In accordance with the recommendation in the RM (RM 13.3(53)), a Size clause
3979 does not change the layout of a composite object. So the Size clause in the
3980 above example is normally rejected, since the default layout of the array uses
3981 8-bit components, and thus the array requires a minimum of 64 bits.
3983 If this declaration is compiled in a region of code covered by an occurrence
3984 of the configuration pragma Implicit_Packing, then the Size clause in this
3985 and similar examples will cause implicit packing and thus be accepted. For
3986 this implicit packing to occur, the type in question must be an array of small
3987 components whose size is known at compile time, and the Size clause must
3988 specify the exact size that corresponds to the number of elements in the array
3989 multiplied by the size in bits of the component type (both single and
3990 multi-dimensioned arrays can be controlled with this pragma).
3992 @geindex Array packing
3994 Similarly, the following example shows the use in the record case
3998 a, b, c, d, e, f, g, h : boolean;
4004 Without a pragma Pack, each Boolean field requires 8 bits, so the
4005 minimum size is 72 bits, but with a pragma Pack, 16 bits would be
4006 sufficient. The use of pragma Implicit_Packing allows this record
4007 declaration to compile without an explicit pragma Pack.
4009 @node Pragma Import_Function,Pragma Import_Object,Pragma Implicit_Packing,Implementation Defined Pragmas
4010 @anchor{gnat_rm/implementation_defined_pragmas pragma-import-function}@anchor{76}
4011 @section Pragma Import_Function
4017 pragma Import_Function (
4018 [Internal =>] LOCAL_NAME,
4019 [, [External =>] EXTERNAL_SYMBOL]
4020 [, [Parameter_Types =>] PARAMETER_TYPES]
4021 [, [Result_Type =>] SUBTYPE_MARK]
4022 [, [Mechanism =>] MECHANISM]
4023 [, [Result_Mechanism =>] MECHANISM_NAME]);
4027 | static_string_EXPRESSION
4031 | TYPE_DESIGNATOR @{, TYPE_DESIGNATOR@}
4035 | subtype_Name ' Access
4039 | (MECHANISM_ASSOCIATION @{, MECHANISM_ASSOCIATION@})
4041 MECHANISM_ASSOCIATION ::=
4042 [formal_parameter_NAME =>] MECHANISM_NAME
4049 This pragma is used in conjunction with a pragma @code{Import} to
4050 specify additional information for an imported function. The pragma
4051 @code{Import} (or equivalent pragma @code{Interface}) must precede the
4052 @code{Import_Function} pragma and both must appear in the same
4053 declarative part as the function specification.
4055 The @code{Internal} argument must uniquely designate
4056 the function to which the
4057 pragma applies. If more than one function name exists of this name in
4058 the declarative part you must use the @code{Parameter_Types} and
4059 @code{Result_Type} parameters to achieve the required unique
4060 designation. Subtype marks in these parameters must exactly match the
4061 subtypes in the corresponding function specification, using positional
4062 notation to match parameters with subtype marks.
4063 The form with an @code{'Access} attribute can be used to match an
4064 anonymous access parameter.
4066 You may optionally use the @code{Mechanism} and @code{Result_Mechanism}
4067 parameters to specify passing mechanisms for the
4068 parameters and result. If you specify a single mechanism name, it
4069 applies to all parameters. Otherwise you may specify a mechanism on a
4070 parameter by parameter basis using either positional or named
4071 notation. If the mechanism is not specified, the default mechanism
4074 @node Pragma Import_Object,Pragma Import_Procedure,Pragma Import_Function,Implementation Defined Pragmas
4075 @anchor{gnat_rm/implementation_defined_pragmas pragma-import-object}@anchor{77}
4076 @section Pragma Import_Object
4082 pragma Import_Object
4083 [Internal =>] LOCAL_NAME
4084 [, [External =>] EXTERNAL_SYMBOL]
4085 [, [Size =>] EXTERNAL_SYMBOL]);
4089 | static_string_EXPRESSION
4092 This pragma designates an object as imported, and apart from the
4093 extended rules for external symbols, is identical in effect to the use of
4094 the normal @code{Import} pragma applied to an object. Unlike the
4095 subprogram case, you need not use a separate @code{Import} pragma,
4096 although you may do so (and probably should do so from a portability
4097 point of view). @code{size} is syntax checked, but otherwise ignored by
4100 @node Pragma Import_Procedure,Pragma Import_Valued_Procedure,Pragma Import_Object,Implementation Defined Pragmas
4101 @anchor{gnat_rm/implementation_defined_pragmas pragma-import-procedure}@anchor{78}
4102 @section Pragma Import_Procedure
4108 pragma Import_Procedure (
4109 [Internal =>] LOCAL_NAME
4110 [, [External =>] EXTERNAL_SYMBOL]
4111 [, [Parameter_Types =>] PARAMETER_TYPES]
4112 [, [Mechanism =>] MECHANISM]);
4116 | static_string_EXPRESSION
4120 | TYPE_DESIGNATOR @{, TYPE_DESIGNATOR@}
4124 | subtype_Name ' Access
4128 | (MECHANISM_ASSOCIATION @{, MECHANISM_ASSOCIATION@})
4130 MECHANISM_ASSOCIATION ::=
4131 [formal_parameter_NAME =>] MECHANISM_NAME
4133 MECHANISM_NAME ::= Value | Reference
4136 This pragma is identical to @code{Import_Function} except that it
4137 applies to a procedure rather than a function and the parameters
4138 @code{Result_Type} and @code{Result_Mechanism} are not permitted.
4140 @node Pragma Import_Valued_Procedure,Pragma Independent,Pragma Import_Procedure,Implementation Defined Pragmas
4141 @anchor{gnat_rm/implementation_defined_pragmas pragma-import-valued-procedure}@anchor{79}
4142 @section Pragma Import_Valued_Procedure
4148 pragma Import_Valued_Procedure (
4149 [Internal =>] LOCAL_NAME
4150 [, [External =>] EXTERNAL_SYMBOL]
4151 [, [Parameter_Types =>] PARAMETER_TYPES]
4152 [, [Mechanism =>] MECHANISM]);
4156 | static_string_EXPRESSION
4160 | TYPE_DESIGNATOR @{, TYPE_DESIGNATOR@}
4164 | subtype_Name ' Access
4168 | (MECHANISM_ASSOCIATION @{, MECHANISM_ASSOCIATION@})
4170 MECHANISM_ASSOCIATION ::=
4171 [formal_parameter_NAME =>] MECHANISM_NAME
4173 MECHANISM_NAME ::= Value | Reference
4176 This pragma is identical to @code{Import_Procedure} except that the
4177 first parameter of @code{LOCAL_NAME}, which must be present, must be of
4178 mode @code{out}, and externally the subprogram is treated as a function
4179 with this parameter as the result of the function. The purpose of this
4180 capability is to allow the use of @code{out} and @code{in out}
4181 parameters in interfacing to external functions (which are not permitted
4182 in Ada functions). You may optionally use the @code{Mechanism}
4183 parameters to specify passing mechanisms for the parameters.
4184 If you specify a single mechanism name, it applies to all parameters.
4185 Otherwise you may specify a mechanism on a parameter by parameter
4186 basis using either positional or named notation. If the mechanism is not
4187 specified, the default mechanism is used.
4189 Note that it is important to use this pragma in conjunction with a separate
4190 pragma Import that specifies the desired convention, since otherwise the
4191 default convention is Ada, which is almost certainly not what is required.
4193 @node Pragma Independent,Pragma Independent_Components,Pragma Import_Valued_Procedure,Implementation Defined Pragmas
4194 @anchor{gnat_rm/implementation_defined_pragmas pragma-independent}@anchor{7a}
4195 @section Pragma Independent
4201 pragma Independent (Local_NAME);
4204 This pragma is standard in Ada 2012 mode (which also provides an aspect
4205 of the same name). It is also available as an implementation-defined
4206 pragma in all earlier versions. It specifies that the
4207 designated object or all objects of the designated type must be
4208 independently addressable. This means that separate tasks can safely
4209 manipulate such objects. For example, if two components of a record are
4210 independent, then two separate tasks may access these two components.
4212 constraints on the representation of the object (for instance prohibiting
4215 @node Pragma Independent_Components,Pragma Initial_Condition,Pragma Independent,Implementation Defined Pragmas
4216 @anchor{gnat_rm/implementation_defined_pragmas pragma-independent-components}@anchor{7b}
4217 @section Pragma Independent_Components
4223 pragma Independent_Components (Local_NAME);
4226 This pragma is standard in Ada 2012 mode (which also provides an aspect
4227 of the same name). It is also available as an implementation-defined
4228 pragma in all earlier versions. It specifies that the components of the
4229 designated object, or the components of each object of the designated
4231 independently addressable. This means that separate tasks can safely
4232 manipulate separate components in the composite object. This may place
4233 constraints on the representation of the object (for instance prohibiting
4236 @node Pragma Initial_Condition,Pragma Initialize_Scalars,Pragma Independent_Components,Implementation Defined Pragmas
4237 @anchor{gnat_rm/implementation_defined_pragmas id16}@anchor{7c}@anchor{gnat_rm/implementation_defined_pragmas pragma-initial-condition}@anchor{7d}
4238 @section Pragma Initial_Condition
4244 pragma Initial_Condition (boolean_EXPRESSION);
4247 For the semantics of this pragma, see the entry for aspect @code{Initial_Condition}
4248 in the SPARK 2014 Reference Manual, section 7.1.6.
4250 @node Pragma Initialize_Scalars,Pragma Initializes,Pragma Initial_Condition,Implementation Defined Pragmas
4251 @anchor{gnat_rm/implementation_defined_pragmas pragma-initialize-scalars}@anchor{7e}
4252 @section Pragma Initialize_Scalars
4255 @geindex debugging with Initialize_Scalars
4260 pragma Initialize_Scalars;
4263 This pragma is similar to @code{Normalize_Scalars} conceptually but has
4264 two important differences. First, there is no requirement for the pragma
4265 to be used uniformly in all units of a partition, in particular, it is fine
4266 to use this just for some or all of the application units of a partition,
4267 without needing to recompile the run-time library.
4269 In the case where some units are compiled with the pragma, and some without,
4270 then a declaration of a variable where the type is defined in package
4271 Standard or is locally declared will always be subject to initialization,
4272 as will any declaration of a scalar variable. For composite variables,
4273 whether the variable is initialized may also depend on whether the package
4274 in which the type of the variable is declared is compiled with the pragma.
4276 The other important difference is that you can control the value used
4277 for initializing scalar objects. At bind time, you can select several
4278 options for initialization. You can
4279 initialize with invalid values (similar to Normalize_Scalars, though for
4280 Initialize_Scalars it is not always possible to determine the invalid
4281 values in complex cases like signed component fields with non-standard
4282 sizes). You can also initialize with high or
4283 low values, or with a specified bit pattern. See the GNAT
4284 User's Guide for binder options for specifying these cases.
4286 This means that you can compile a program, and then without having to
4287 recompile the program, you can run it with different values being used
4288 for initializing otherwise uninitialized values, to test if your program
4289 behavior depends on the choice. Of course the behavior should not change,
4290 and if it does, then most likely you have an incorrect reference to an
4291 uninitialized value.
4293 It is even possible to change the value at execution time eliminating even
4294 the need to rebind with a different switch using an environment variable.
4295 See the GNAT User's Guide for details.
4297 Note that pragma @code{Initialize_Scalars} is particularly useful in
4298 conjunction with the enhanced validity checking that is now provided
4299 in GNAT, which checks for invalid values under more conditions.
4300 Using this feature (see description of the @emph{-gnatV} flag in the
4301 GNAT User's Guide) in conjunction with
4302 pragma @code{Initialize_Scalars}
4303 provides a powerful new tool to assist in the detection of problems
4304 caused by uninitialized variables.
4306 Note: the use of @code{Initialize_Scalars} has a fairly extensive
4307 effect on the generated code. This may cause your code to be
4308 substantially larger. It may also cause an increase in the amount
4309 of stack required, so it is probably a good idea to turn on stack
4310 checking (see description of stack checking in the GNAT
4311 User's Guide) when using this pragma.
4313 @node Pragma Initializes,Pragma Inline_Always,Pragma Initialize_Scalars,Implementation Defined Pragmas
4314 @anchor{gnat_rm/implementation_defined_pragmas pragma-initializes}@anchor{7f}@anchor{gnat_rm/implementation_defined_pragmas id17}@anchor{80}
4315 @section Pragma Initializes
4321 pragma Initializes (INITIALIZATION_LIST);
4323 INITIALIZATION_LIST ::=
4325 | (INITIALIZATION_ITEM @{, INITIALIZATION_ITEM@})
4327 INITIALIZATION_ITEM ::= name [=> INPUT_LIST]
4332 | (INPUT @{, INPUT@})
4337 For the semantics of this pragma, see the entry for aspect @code{Initializes} in the
4338 SPARK 2014 Reference Manual, section 7.1.5.
4340 @node Pragma Inline_Always,Pragma Inline_Generic,Pragma Initializes,Implementation Defined Pragmas
4341 @anchor{gnat_rm/implementation_defined_pragmas id18}@anchor{81}@anchor{gnat_rm/implementation_defined_pragmas pragma-inline-always}@anchor{82}
4342 @section Pragma Inline_Always
4348 pragma Inline_Always (NAME [, NAME]);
4351 Similar to pragma @code{Inline} except that inlining is unconditional.
4352 Inline_Always instructs the compiler to inline every direct call to the
4353 subprogram or else to emit a compilation error, independently of any
4354 option, in particular @emph{-gnatn} or @emph{-gnatN} or the optimization level.
4355 It is an error to take the address or access of @code{NAME}. It is also an error to
4356 apply this pragma to a primitive operation of a tagged type. Thanks to such
4357 restrictions, the compiler is allowed to remove the out-of-line body of @code{NAME}.
4359 @node Pragma Inline_Generic,Pragma Interface,Pragma Inline_Always,Implementation Defined Pragmas
4360 @anchor{gnat_rm/implementation_defined_pragmas pragma-inline-generic}@anchor{83}
4361 @section Pragma Inline_Generic
4367 pragma Inline_Generic (GNAME @{, GNAME@});
4369 GNAME ::= generic_unit_NAME | generic_instance_NAME
4372 This pragma is provided for compatibility with Dec Ada 83. It has
4373 no effect in GNAT (which always inlines generics), other
4374 than to check that the given names are all names of generic units or
4377 @node Pragma Interface,Pragma Interface_Name,Pragma Inline_Generic,Implementation Defined Pragmas
4378 @anchor{gnat_rm/implementation_defined_pragmas pragma-interface}@anchor{84}
4379 @section Pragma Interface
4386 [Convention =>] convention_identifier,
4387 [Entity =>] local_NAME
4388 [, [External_Name =>] static_string_expression]
4389 [, [Link_Name =>] static_string_expression]);
4392 This pragma is identical in syntax and semantics to
4393 the standard Ada pragma @code{Import}. It is provided for compatibility
4394 with Ada 83. The definition is upwards compatible both with pragma
4395 @code{Interface} as defined in the Ada 83 Reference Manual, and also
4396 with some extended implementations of this pragma in certain Ada 83
4397 implementations. The only difference between pragma @code{Interface}
4398 and pragma @code{Import} is that there is special circuitry to allow
4399 both pragmas to appear for the same subprogram entity (normally it
4400 is illegal to have multiple @code{Import} pragmas. This is useful in
4401 maintaining Ada 83/Ada 95 compatibility and is compatible with other
4404 @node Pragma Interface_Name,Pragma Interrupt_Handler,Pragma Interface,Implementation Defined Pragmas
4405 @anchor{gnat_rm/implementation_defined_pragmas pragma-interface-name}@anchor{85}
4406 @section Pragma Interface_Name
4412 pragma Interface_Name (
4413 [Entity =>] LOCAL_NAME
4414 [, [External_Name =>] static_string_EXPRESSION]
4415 [, [Link_Name =>] static_string_EXPRESSION]);
4418 This pragma provides an alternative way of specifying the interface name
4419 for an interfaced subprogram, and is provided for compatibility with Ada
4420 83 compilers that use the pragma for this purpose. You must provide at
4421 least one of @code{External_Name} or @code{Link_Name}.
4423 @node Pragma Interrupt_Handler,Pragma Interrupt_State,Pragma Interface_Name,Implementation Defined Pragmas
4424 @anchor{gnat_rm/implementation_defined_pragmas pragma-interrupt-handler}@anchor{86}
4425 @section Pragma Interrupt_Handler
4431 pragma Interrupt_Handler (procedure_LOCAL_NAME);
4434 This program unit pragma is supported for parameterless protected procedures
4435 as described in Annex C of the Ada Reference Manual. On the AAMP target
4436 the pragma can also be specified for nonprotected parameterless procedures
4437 that are declared at the library level (which includes procedures
4438 declared at the top level of a library package). In the case of AAMP,
4439 when this pragma is applied to a nonprotected procedure, the instruction
4440 @code{IERET} is generated for returns from the procedure, enabling
4441 maskable interrupts, in place of the normal return instruction.
4443 @node Pragma Interrupt_State,Pragma Invariant,Pragma Interrupt_Handler,Implementation Defined Pragmas
4444 @anchor{gnat_rm/implementation_defined_pragmas pragma-interrupt-state}@anchor{87}
4445 @section Pragma Interrupt_State
4451 pragma Interrupt_State
4453 [State =>] SYSTEM | RUNTIME | USER);
4456 Normally certain interrupts are reserved to the implementation. Any attempt
4457 to attach an interrupt causes Program_Error to be raised, as described in
4458 RM C.3.2(22). A typical example is the @code{SIGINT} interrupt used in
4459 many systems for an @code{Ctrl-C} interrupt. Normally this interrupt is
4460 reserved to the implementation, so that @code{Ctrl-C} can be used to
4461 interrupt execution. Additionally, signals such as @code{SIGSEGV},
4462 @code{SIGABRT}, @code{SIGFPE} and @code{SIGILL} are often mapped to specific
4463 Ada exceptions, or used to implement run-time functions such as the
4464 @code{abort} statement and stack overflow checking.
4466 Pragma @code{Interrupt_State} provides a general mechanism for overriding
4467 such uses of interrupts. It subsumes the functionality of pragma
4468 @code{Unreserve_All_Interrupts}. Pragma @code{Interrupt_State} is not
4469 available on Windows or VMS. On all other platforms than VxWorks,
4470 it applies to signals; on VxWorks, it applies to vectored hardware interrupts
4471 and may be used to mark interrupts required by the board support package
4474 Interrupts can be in one of three states:
4482 The interrupt is reserved (no Ada handler can be installed), and the
4483 Ada run-time may not install a handler. As a result you are guaranteed
4484 standard system default action if this interrupt is raised. This also allows
4485 installing a low level handler via C APIs such as sigaction(), outside
4491 The interrupt is reserved (no Ada handler can be installed). The run time
4492 is allowed to install a handler for internal control purposes, but is
4493 not required to do so.
4498 The interrupt is unreserved. The user may install an Ada handler via
4499 Ada.Interrupts and pragma Interrupt_Handler or Attach_Handler to provide
4503 These states are the allowed values of the @code{State} parameter of the
4504 pragma. The @code{Name} parameter is a value of the type
4505 @code{Ada.Interrupts.Interrupt_ID}. Typically, it is a name declared in
4506 @code{Ada.Interrupts.Names}.
4508 This is a configuration pragma, and the binder will check that there
4509 are no inconsistencies between different units in a partition in how a
4510 given interrupt is specified. It may appear anywhere a pragma is legal.
4512 The effect is to move the interrupt to the specified state.
4514 By declaring interrupts to be SYSTEM, you guarantee the standard system
4515 action, such as a core dump.
4517 By declaring interrupts to be USER, you guarantee that you can install
4520 Note that certain signals on many operating systems cannot be caught and
4521 handled by applications. In such cases, the pragma is ignored. See the
4522 operating system documentation, or the value of the array @code{Reserved}
4523 declared in the spec of package @code{System.OS_Interface}.
4525 Overriding the default state of signals used by the Ada runtime may interfere
4526 with an application's runtime behavior in the cases of the synchronous signals,
4527 and in the case of the signal used to implement the @code{abort} statement.
4529 @node Pragma Invariant,Pragma Keep_Names,Pragma Interrupt_State,Implementation Defined Pragmas
4530 @anchor{gnat_rm/implementation_defined_pragmas id19}@anchor{88}@anchor{gnat_rm/implementation_defined_pragmas pragma-invariant}@anchor{89}
4531 @section Pragma Invariant
4538 ([Entity =>] private_type_LOCAL_NAME,
4539 [Check =>] EXPRESSION
4540 [,[Message =>] String_Expression]);
4543 This pragma provides exactly the same capabilities as the Type_Invariant aspect
4544 defined in AI05-0146-1, and in the Ada 2012 Reference Manual. The
4545 Type_Invariant aspect is fully implemented in Ada 2012 mode, but since it
4546 requires the use of the aspect syntax, which is not available except in 2012
4547 mode, it is not possible to use the Type_Invariant aspect in earlier versions
4548 of Ada. However the Invariant pragma may be used in any version of Ada. Also
4549 note that the aspect Invariant is a synonym in GNAT for the aspect
4550 Type_Invariant, but there is no pragma Type_Invariant.
4552 The pragma must appear within the visible part of the package specification,
4553 after the type to which its Entity argument appears. As with the Invariant
4554 aspect, the Check expression is not analyzed until the end of the visible
4555 part of the package, so it may contain forward references. The Message
4556 argument, if present, provides the exception message used if the invariant
4557 is violated. If no Message parameter is provided, a default message that
4558 identifies the line on which the pragma appears is used.
4560 It is permissible to have multiple Invariants for the same type entity, in
4561 which case they are and'ed together. It is permissible to use this pragma
4562 in Ada 2012 mode, but you cannot have both an invariant aspect and an
4563 invariant pragma for the same entity.
4565 For further details on the use of this pragma, see the Ada 2012 documentation
4566 of the Type_Invariant aspect.
4568 @node Pragma Keep_Names,Pragma License,Pragma Invariant,Implementation Defined Pragmas
4569 @anchor{gnat_rm/implementation_defined_pragmas pragma-keep-names}@anchor{8a}
4570 @section Pragma Keep_Names
4576 pragma Keep_Names ([On =>] enumeration_first_subtype_LOCAL_NAME);
4579 The @code{LOCAL_NAME} argument
4580 must refer to an enumeration first subtype
4581 in the current declarative part. The effect is to retain the enumeration
4582 literal names for use by @code{Image} and @code{Value} even if a global
4583 @code{Discard_Names} pragma applies. This is useful when you want to
4584 generally suppress enumeration literal names and for example you therefore
4585 use a @code{Discard_Names} pragma in the @code{gnat.adc} file, but you
4586 want to retain the names for specific enumeration types.
4588 @node Pragma License,Pragma Link_With,Pragma Keep_Names,Implementation Defined Pragmas
4589 @anchor{gnat_rm/implementation_defined_pragmas pragma-license}@anchor{8b}
4590 @section Pragma License
4593 @geindex License checking
4598 pragma License (Unrestricted | GPL | Modified_GPL | Restricted);
4601 This pragma is provided to allow automated checking for appropriate license
4602 conditions with respect to the standard and modified GPL. A pragma
4603 @code{License}, which is a configuration pragma that typically appears at
4604 the start of a source file or in a separate @code{gnat.adc} file, specifies
4605 the licensing conditions of a unit as follows:
4612 This is used for a unit that can be freely used with no license restrictions.
4613 Examples of such units are public domain units, and units from the Ada
4618 This is used for a unit that is licensed under the unmodified GPL, and which
4619 therefore cannot be @code{with}ed by a restricted unit.
4623 This is used for a unit licensed under the GNAT modified GPL that includes
4624 a special exception paragraph that specifically permits the inclusion of
4625 the unit in programs without requiring the entire program to be released
4630 This is used for a unit that is restricted in that it is not permitted to
4631 depend on units that are licensed under the GPL. Typical examples are
4632 proprietary code that is to be released under more restrictive license
4633 conditions. Note that restricted units are permitted to @code{with} units
4634 which are licensed under the modified GPL (this is the whole point of the
4638 Normally a unit with no @code{License} pragma is considered to have an
4639 unknown license, and no checking is done. However, standard GNAT headers
4640 are recognized, and license information is derived from them as follows.
4642 A GNAT license header starts with a line containing 78 hyphens. The following
4643 comment text is searched for the appearance of any of the following strings.
4645 If the string 'GNU General Public License' is found, then the unit is assumed
4646 to have GPL license, unless the string 'As a special exception' follows, in
4647 which case the license is assumed to be modified GPL.
4649 If one of the strings
4650 'This specification is adapted from the Ada Semantic Interface' or
4651 'This specification is derived from the Ada Reference Manual' is found
4652 then the unit is assumed to be unrestricted.
4654 These default actions means that a program with a restricted license pragma
4655 will automatically get warnings if a GPL unit is inappropriately
4656 @code{with}ed. For example, the program:
4661 procedure Secret_Stuff is
4666 if compiled with pragma @code{License} (@code{Restricted}) in a
4667 @code{gnat.adc} file will generate the warning:
4672 >>> license of withed unit "Sem_Ch3" is incompatible
4674 2. with GNAT.Sockets;
4675 3. procedure Secret_Stuff is
4678 Here we get a warning on @code{Sem_Ch3} since it is part of the GNAT
4679 compiler and is licensed under the
4680 GPL, but no warning for @code{GNAT.Sockets} which is part of the GNAT
4681 run time, and is therefore licensed under the modified GPL.
4683 @node Pragma Link_With,Pragma Linker_Alias,Pragma License,Implementation Defined Pragmas
4684 @anchor{gnat_rm/implementation_defined_pragmas pragma-link-with}@anchor{8c}
4685 @section Pragma Link_With
4691 pragma Link_With (static_string_EXPRESSION @{,static_string_EXPRESSION@});
4694 This pragma is provided for compatibility with certain Ada 83 compilers.
4695 It has exactly the same effect as pragma @code{Linker_Options} except
4696 that spaces occurring within one of the string expressions are treated
4697 as separators. For example, in the following case:
4700 pragma Link_With ("-labc -ldef");
4703 results in passing the strings @code{-labc} and @code{-ldef} as two
4704 separate arguments to the linker. In addition pragma Link_With allows
4705 multiple arguments, with the same effect as successive pragmas.
4707 @node Pragma Linker_Alias,Pragma Linker_Constructor,Pragma Link_With,Implementation Defined Pragmas
4708 @anchor{gnat_rm/implementation_defined_pragmas pragma-linker-alias}@anchor{8d}
4709 @section Pragma Linker_Alias
4715 pragma Linker_Alias (
4716 [Entity =>] LOCAL_NAME,
4717 [Target =>] static_string_EXPRESSION);
4720 @code{LOCAL_NAME} must refer to an object that is declared at the library
4721 level. This pragma establishes the given entity as a linker alias for the
4722 given target. It is equivalent to @code{__attribute__((alias))} in GNU C
4723 and causes @code{LOCAL_NAME} to be emitted as an alias for the symbol
4724 @code{static_string_EXPRESSION} in the object file, that is to say no space
4725 is reserved for @code{LOCAL_NAME} by the assembler and it will be resolved
4726 to the same address as @code{static_string_EXPRESSION} by the linker.
4728 The actual linker name for the target must be used (e.g., the fully
4729 encoded name with qualification in Ada, or the mangled name in C++),
4730 or it must be declared using the C convention with @code{pragma Import}
4731 or @code{pragma Export}.
4733 Not all target machines support this pragma. On some of them it is accepted
4734 only if @code{pragma Weak_External} has been applied to @code{LOCAL_NAME}.
4737 -- Example of the use of pragma Linker_Alias
4741 pragma Export (C, i);
4743 new_name_for_i : Integer;
4744 pragma Linker_Alias (new_name_for_i, "i");
4748 @node Pragma Linker_Constructor,Pragma Linker_Destructor,Pragma Linker_Alias,Implementation Defined Pragmas
4749 @anchor{gnat_rm/implementation_defined_pragmas pragma-linker-constructor}@anchor{8e}
4750 @section Pragma Linker_Constructor
4756 pragma Linker_Constructor (procedure_LOCAL_NAME);
4759 @code{procedure_LOCAL_NAME} must refer to a parameterless procedure that
4760 is declared at the library level. A procedure to which this pragma is
4761 applied will be treated as an initialization routine by the linker.
4762 It is equivalent to @code{__attribute__((constructor))} in GNU C and
4763 causes @code{procedure_LOCAL_NAME} to be invoked before the entry point
4764 of the executable is called (or immediately after the shared library is
4765 loaded if the procedure is linked in a shared library), in particular
4766 before the Ada run-time environment is set up.
4768 Because of these specific contexts, the set of operations such a procedure
4769 can perform is very limited and the type of objects it can manipulate is
4770 essentially restricted to the elementary types. In particular, it must only
4771 contain code to which pragma Restrictions (No_Elaboration_Code) applies.
4773 This pragma is used by GNAT to implement auto-initialization of shared Stand
4774 Alone Libraries, which provides a related capability without the restrictions
4775 listed above. Where possible, the use of Stand Alone Libraries is preferable
4776 to the use of this pragma.
4778 @node Pragma Linker_Destructor,Pragma Linker_Section,Pragma Linker_Constructor,Implementation Defined Pragmas
4779 @anchor{gnat_rm/implementation_defined_pragmas pragma-linker-destructor}@anchor{8f}
4780 @section Pragma Linker_Destructor
4786 pragma Linker_Destructor (procedure_LOCAL_NAME);
4789 @code{procedure_LOCAL_NAME} must refer to a parameterless procedure that
4790 is declared at the library level. A procedure to which this pragma is
4791 applied will be treated as a finalization routine by the linker.
4792 It is equivalent to @code{__attribute__((destructor))} in GNU C and
4793 causes @code{procedure_LOCAL_NAME} to be invoked after the entry point
4794 of the executable has exited (or immediately before the shared library
4795 is unloaded if the procedure is linked in a shared library), in particular
4796 after the Ada run-time environment is shut down.
4798 See @code{pragma Linker_Constructor} for the set of restrictions that apply
4799 because of these specific contexts.
4801 @node Pragma Linker_Section,Pragma Lock_Free,Pragma Linker_Destructor,Implementation Defined Pragmas
4802 @anchor{gnat_rm/implementation_defined_pragmas id20}@anchor{90}@anchor{gnat_rm/implementation_defined_pragmas pragma-linker-section}@anchor{91}
4803 @section Pragma Linker_Section
4809 pragma Linker_Section (
4810 [Entity =>] LOCAL_NAME,
4811 [Section =>] static_string_EXPRESSION);
4814 @code{LOCAL_NAME} must refer to an object, type, or subprogram that is
4815 declared at the library level. This pragma specifies the name of the
4816 linker section for the given entity. It is equivalent to
4817 @code{__attribute__((section))} in GNU C and causes @code{LOCAL_NAME} to
4818 be placed in the @code{static_string_EXPRESSION} section of the
4819 executable (assuming the linker doesn't rename the section).
4820 GNAT also provides an implementation defined aspect of the same name.
4822 In the case of specifying this aspect for a type, the effect is to
4823 specify the corresponding section for all library-level objects of
4824 the type that do not have an explicit linker section set. Note that
4825 this only applies to whole objects, not to components of composite objects.
4827 In the case of a subprogram, the linker section applies to all previously
4828 declared matching overloaded subprograms in the current declarative part
4829 which do not already have a linker section assigned. The linker section
4830 aspect is useful in this case for specifying different linker sections
4831 for different elements of such an overloaded set.
4833 Note that an empty string specifies that no linker section is specified.
4834 This is not quite the same as omitting the pragma or aspect, since it
4835 can be used to specify that one element of an overloaded set of subprograms
4836 has the default linker section, or that one object of a type for which a
4837 linker section is specified should has the default linker section.
4839 The compiler normally places library-level entities in standard sections
4840 depending on the class: procedures and functions generally go in the
4841 @code{.text} section, initialized variables in the @code{.data} section
4842 and uninitialized variables in the @code{.bss} section.
4844 Other, special sections may exist on given target machines to map special
4845 hardware, for example I/O ports or flash memory. This pragma is a means to
4846 defer the final layout of the executable to the linker, thus fully working
4847 at the symbolic level with the compiler.
4849 Some file formats do not support arbitrary sections so not all target
4850 machines support this pragma. The use of this pragma may cause a program
4851 execution to be erroneous if it is used to place an entity into an
4852 inappropriate section (e.g., a modified variable into the @code{.text}
4853 section). See also @code{pragma Persistent_BSS}.
4856 -- Example of the use of pragma Linker_Section
4860 pragma Volatile (Port_A);
4861 pragma Linker_Section (Port_A, ".bss.port_a");
4864 pragma Volatile (Port_B);
4865 pragma Linker_Section (Port_B, ".bss.port_b");
4867 type Port_Type is new Integer with Linker_Section => ".bss";
4868 PA : Port_Type with Linker_Section => ".bss.PA";
4869 PB : Port_Type; -- ends up in linker section ".bss"
4871 procedure Q with Linker_Section => "Qsection";
4875 @node Pragma Lock_Free,Pragma Loop_Invariant,Pragma Linker_Section,Implementation Defined Pragmas
4876 @anchor{gnat_rm/implementation_defined_pragmas id21}@anchor{92}@anchor{gnat_rm/implementation_defined_pragmas pragma-lock-free}@anchor{93}
4877 @section Pragma Lock_Free
4881 This pragma may be specified for protected types or objects. It specifies that
4882 the implementation of protected operations must be implemented without locks.
4883 Compilation fails if the compiler cannot generate lock-free code for the
4886 @node Pragma Loop_Invariant,Pragma Loop_Optimize,Pragma Lock_Free,Implementation Defined Pragmas
4887 @anchor{gnat_rm/implementation_defined_pragmas pragma-loop-invariant}@anchor{94}
4888 @section Pragma Loop_Invariant
4894 pragma Loop_Invariant ( boolean_EXPRESSION );
4897 The effect of this pragma is similar to that of pragma @code{Assert},
4898 except that in an @code{Assertion_Policy} pragma, the identifier
4899 @code{Loop_Invariant} is used to control whether it is ignored or checked
4902 @code{Loop_Invariant} can only appear as one of the items in the sequence
4903 of statements of a loop body, or nested inside block statements that
4904 appear in the sequence of statements of a loop body.
4905 The intention is that it be used to
4906 represent a "loop invariant" assertion, i.e. something that is true each
4907 time through the loop, and which can be used to show that the loop is
4908 achieving its purpose.
4910 Multiple @code{Loop_Invariant} and @code{Loop_Variant} pragmas that
4911 apply to the same loop should be grouped in the same sequence of
4914 To aid in writing such invariants, the special attribute @code{Loop_Entry}
4915 may be used to refer to the value of an expression on entry to the loop. This
4916 attribute can only be used within the expression of a @code{Loop_Invariant}
4917 pragma. For full details, see documentation of attribute @code{Loop_Entry}.
4919 @node Pragma Loop_Optimize,Pragma Loop_Variant,Pragma Loop_Invariant,Implementation Defined Pragmas
4920 @anchor{gnat_rm/implementation_defined_pragmas pragma-loop-optimize}@anchor{95}
4921 @section Pragma Loop_Optimize
4927 pragma Loop_Optimize (OPTIMIZATION_HINT @{, OPTIMIZATION_HINT@});
4929 OPTIMIZATION_HINT ::= Ivdep | No_Unroll | Unroll | No_Vector | Vector
4932 This pragma must appear immediately within a loop statement. It allows the
4933 programmer to specify optimization hints for the enclosing loop. The hints
4934 are not mutually exclusive and can be freely mixed, but not all combinations
4935 will yield a sensible outcome.
4937 There are five supported optimization hints for a loop:
4945 The programmer asserts that there are no loop-carried dependencies
4946 which would prevent consecutive iterations of the loop from being
4947 executed simultaneously.
4952 The loop must not be unrolled. This is a strong hint: the compiler will not
4953 unroll a loop marked with this hint.
4958 The loop should be unrolled. This is a weak hint: the compiler will try to
4959 apply unrolling to this loop preferably to other optimizations, notably
4960 vectorization, but there is no guarantee that the loop will be unrolled.
4965 The loop must not be vectorized. This is a strong hint: the compiler will not
4966 vectorize a loop marked with this hint.
4971 The loop should be vectorized. This is a weak hint: the compiler will try to
4972 apply vectorization to this loop preferably to other optimizations, notably
4973 unrolling, but there is no guarantee that the loop will be vectorized.
4976 These hints do not remove the need to pass the appropriate switches to the
4977 compiler in order to enable the relevant optimizations, that is to say
4978 @emph{-funroll-loops} for unrolling and @emph{-ftree-vectorize} for
4981 @node Pragma Loop_Variant,Pragma Machine_Attribute,Pragma Loop_Optimize,Implementation Defined Pragmas
4982 @anchor{gnat_rm/implementation_defined_pragmas pragma-loop-variant}@anchor{96}
4983 @section Pragma Loop_Variant
4989 pragma Loop_Variant ( LOOP_VARIANT_ITEM @{, LOOP_VARIANT_ITEM @} );
4990 LOOP_VARIANT_ITEM ::= CHANGE_DIRECTION => discrete_EXPRESSION
4991 CHANGE_DIRECTION ::= Increases | Decreases
4994 @code{Loop_Variant} can only appear as one of the items in the sequence
4995 of statements of a loop body, or nested inside block statements that
4996 appear in the sequence of statements of a loop body.
4997 It allows the specification of quantities which must always
4998 decrease or increase in successive iterations of the loop. In its simplest
4999 form, just one expression is specified, whose value must increase or decrease
5000 on each iteration of the loop.
5002 In a more complex form, multiple arguments can be given which are intepreted
5003 in a nesting lexicographic manner. For example:
5006 pragma Loop_Variant (Increases => X, Decreases => Y);
5009 specifies that each time through the loop either X increases, or X stays
5010 the same and Y decreases. A @code{Loop_Variant} pragma ensures that the
5011 loop is making progress. It can be useful in helping to show informally
5012 or prove formally that the loop always terminates.
5014 @code{Loop_Variant} is an assertion whose effect can be controlled using
5015 an @code{Assertion_Policy} with a check name of @code{Loop_Variant}. The
5016 policy can be @code{Check} to enable the loop variant check, @code{Ignore}
5017 to ignore the check (in which case the pragma has no effect on the program),
5018 or @code{Disable} in which case the pragma is not even checked for correct
5021 Multiple @code{Loop_Invariant} and @code{Loop_Variant} pragmas that
5022 apply to the same loop should be grouped in the same sequence of
5025 The @code{Loop_Entry} attribute may be used within the expressions of the
5026 @code{Loop_Variant} pragma to refer to values on entry to the loop.
5028 @node Pragma Machine_Attribute,Pragma Main,Pragma Loop_Variant,Implementation Defined Pragmas
5029 @anchor{gnat_rm/implementation_defined_pragmas pragma-machine-attribute}@anchor{97}
5030 @section Pragma Machine_Attribute
5036 pragma Machine_Attribute (
5037 [Entity =>] LOCAL_NAME,
5038 [Attribute_Name =>] static_string_EXPRESSION
5039 [, [Info =>] static_EXPRESSION] );
5042 Machine-dependent attributes can be specified for types and/or
5043 declarations. This pragma is semantically equivalent to
5044 @code{__attribute__((@emph{attribute_name}))} (if @code{info} is not
5045 specified) or @code{__attribute__((@emph{attribute_name(info})))}
5046 in GNU C, where @emph{attribute_name} is recognized by the
5047 compiler middle-end or the @code{TARGET_ATTRIBUTE_TABLE} machine
5048 specific macro. A string literal for the optional parameter @code{info}
5049 is transformed into an identifier, which may make this pragma unusable
5050 for some attributes.
5051 For further information see @cite{GNU Compiler Collection (GCC) Internals}.
5053 @node Pragma Main,Pragma Main_Storage,Pragma Machine_Attribute,Implementation Defined Pragmas
5054 @anchor{gnat_rm/implementation_defined_pragmas pragma-main}@anchor{98}
5055 @section Pragma Main
5062 (MAIN_OPTION [, MAIN_OPTION]);
5065 [Stack_Size =>] static_integer_EXPRESSION
5066 | [Task_Stack_Size_Default =>] static_integer_EXPRESSION
5067 | [Time_Slicing_Enabled =>] static_boolean_EXPRESSION
5070 This pragma is provided for compatibility with OpenVMS VAX Systems. It has
5071 no effect in GNAT, other than being syntax checked.
5073 @node Pragma Main_Storage,Pragma Max_Queue_Length,Pragma Main,Implementation Defined Pragmas
5074 @anchor{gnat_rm/implementation_defined_pragmas pragma-main-storage}@anchor{99}
5075 @section Pragma Main_Storage
5082 (MAIN_STORAGE_OPTION [, MAIN_STORAGE_OPTION]);
5084 MAIN_STORAGE_OPTION ::=
5085 [WORKING_STORAGE =>] static_SIMPLE_EXPRESSION
5086 | [TOP_GUARD =>] static_SIMPLE_EXPRESSION
5089 This pragma is provided for compatibility with OpenVMS VAX Systems. It has
5090 no effect in GNAT, other than being syntax checked.
5092 @node Pragma Max_Queue_Length,Pragma No_Body,Pragma Main_Storage,Implementation Defined Pragmas
5093 @anchor{gnat_rm/implementation_defined_pragmas id22}@anchor{9a}@anchor{gnat_rm/implementation_defined_pragmas pragma-max-queue-length}@anchor{9b}
5094 @section Pragma Max_Queue_Length
5100 pragma Max_Entry_Queue (static_integer_EXPRESSION);
5103 This pragma is used to specify the maximum callers per entry queue for
5104 individual protected entries and entry families. It accepts a single
5105 positive integer as a parameter and must appear after the declaration
5108 @node Pragma No_Body,Pragma No_Component_Reordering,Pragma Max_Queue_Length,Implementation Defined Pragmas
5109 @anchor{gnat_rm/implementation_defined_pragmas pragma-no-body}@anchor{9c}
5110 @section Pragma No_Body
5119 There are a number of cases in which a package spec does not require a body,
5120 and in fact a body is not permitted. GNAT will not permit the spec to be
5121 compiled if there is a body around. The pragma No_Body allows you to provide
5122 a body file, even in a case where no body is allowed. The body file must
5123 contain only comments and a single No_Body pragma. This is recognized by
5124 the compiler as indicating that no body is logically present.
5126 This is particularly useful during maintenance when a package is modified in
5127 such a way that a body needed before is no longer needed. The provision of a
5128 dummy body with a No_Body pragma ensures that there is no interference from
5129 earlier versions of the package body.
5131 @node Pragma No_Component_Reordering,Pragma No_Elaboration_Code_All,Pragma No_Body,Implementation Defined Pragmas
5132 @anchor{gnat_rm/implementation_defined_pragmas pragma-no-component-reordering}@anchor{9d}
5133 @section Pragma No_Component_Reordering
5139 pragma No_Component_Reordering [([Entity =>] type_LOCAL_NAME)];
5142 @code{type_LOCAL_NAME} must refer to a record type declaration in the current
5143 declarative part. The effect is to preclude any reordering of components
5144 for the layout of the record, i.e. the record is laid out by the compiler
5145 in the order in which the components are declared textually. The form with
5146 no argument is a configuration pragma which applies to all record types
5147 declared in units to which the pragma applies and there is a requirement
5148 that this pragma be used consistently within a partition.
5150 @node Pragma No_Elaboration_Code_All,Pragma No_Heap_Finalization,Pragma No_Component_Reordering,Implementation Defined Pragmas
5151 @anchor{gnat_rm/implementation_defined_pragmas id23}@anchor{9e}@anchor{gnat_rm/implementation_defined_pragmas pragma-no-elaboration-code-all}@anchor{9f}
5152 @section Pragma No_Elaboration_Code_All
5158 pragma No_Elaboration_Code_All [(program_unit_NAME)];
5161 This is a program unit pragma (there is also an equivalent aspect of the
5162 same name) that establishes the restriction @code{No_Elaboration_Code} for
5163 the current unit and any extended main source units (body and subunits).
5164 It also has the effect of enforcing a transitive application of this
5165 aspect, so that if any unit is implicitly or explicitly with'ed by the
5166 current unit, it must also have the No_Elaboration_Code_All aspect set.
5167 It may be applied to package or subprogram specs or their generic versions.
5169 @node Pragma No_Heap_Finalization,Pragma No_Inline,Pragma No_Elaboration_Code_All,Implementation Defined Pragmas
5170 @anchor{gnat_rm/implementation_defined_pragmas pragma-no-heap-finalization}@anchor{a0}
5171 @section Pragma No_Heap_Finalization
5177 pragma No_Heap_Finalization [ (first_subtype_LOCAL_NAME) ];
5180 Pragma @code{No_Heap_Finalization} may be used as a configuration pragma or as a
5181 type-specific pragma.
5183 In its configuration form, the pragma must appear within a configuration file
5184 such as gnat.adc, without an argument. The pragma suppresses the call to
5185 @code{Finalize} for heap-allocated objects created through library-level named
5186 access-to-object types in cases where the designated type requires finalization
5189 In its type-specific form, the argument of the pragma must denote a
5190 library-level named access-to-object type. The pragma suppresses the call to
5191 @code{Finalize} for heap-allocated objects created through the specific access type
5192 in cases where the designated type requires finalization actions.
5194 It is still possible to finalize such heap-allocated objects by explicitly
5197 A library-level named access-to-object type declared within a generic unit will
5198 lose its @code{No_Heap_Finalization} pragma when the corresponding instance does not
5199 appear at the library level.
5201 @node Pragma No_Inline,Pragma No_Return,Pragma No_Heap_Finalization,Implementation Defined Pragmas
5202 @anchor{gnat_rm/implementation_defined_pragmas id24}@anchor{a1}@anchor{gnat_rm/implementation_defined_pragmas pragma-no-inline}@anchor{a2}
5203 @section Pragma No_Inline
5209 pragma No_Inline (NAME @{, NAME@});
5212 This pragma suppresses inlining for the callable entity or the instances of
5213 the generic subprogram designated by @code{NAME}, including inlining that
5214 results from the use of pragma @code{Inline}. This pragma is always active,
5215 in particular it is not subject to the use of option @emph{-gnatn} or
5216 @emph{-gnatN}. It is illegal to specify both pragma @code{No_Inline} and
5217 pragma @code{Inline_Always} for the same @code{NAME}.
5219 @node Pragma No_Return,Pragma No_Run_Time,Pragma No_Inline,Implementation Defined Pragmas
5220 @anchor{gnat_rm/implementation_defined_pragmas pragma-no-return}@anchor{a3}
5221 @section Pragma No_Return
5227 pragma No_Return (procedure_LOCAL_NAME @{, procedure_LOCAL_NAME@});
5230 Each @code{procedure_LOCAL_NAME} argument must refer to one or more procedure
5231 declarations in the current declarative part. A procedure to which this
5232 pragma is applied may not contain any explicit @code{return} statements.
5233 In addition, if the procedure contains any implicit returns from falling
5234 off the end of a statement sequence, then execution of that implicit
5235 return will cause Program_Error to be raised.
5237 One use of this pragma is to identify procedures whose only purpose is to raise
5238 an exception. Another use of this pragma is to suppress incorrect warnings
5239 about missing returns in functions, where the last statement of a function
5240 statement sequence is a call to such a procedure.
5242 Note that in Ada 2005 mode, this pragma is part of the language. It is
5243 available in all earlier versions of Ada as an implementation-defined
5246 @node Pragma No_Run_Time,Pragma No_Strict_Aliasing,Pragma No_Return,Implementation Defined Pragmas
5247 @anchor{gnat_rm/implementation_defined_pragmas pragma-no-run-time}@anchor{a4}
5248 @section Pragma No_Run_Time
5257 This is an obsolete configuration pragma that historically was used to
5258 set up a runtime library with no object code. It is now used only for
5259 internal testing. The pragma has been superseded by the reconfigurable
5260 runtime capability of GNAT.
5262 @node Pragma No_Strict_Aliasing,Pragma No_Tagged_Streams,Pragma No_Run_Time,Implementation Defined Pragmas
5263 @anchor{gnat_rm/implementation_defined_pragmas pragma-no-strict-aliasing}@anchor{a5}
5264 @section Pragma No_Strict_Aliasing
5270 pragma No_Strict_Aliasing [([Entity =>] type_LOCAL_NAME)];
5273 @code{type_LOCAL_NAME} must refer to an access type
5274 declaration in the current declarative part. The effect is to inhibit
5275 strict aliasing optimization for the given type. The form with no
5276 arguments is a configuration pragma which applies to all access types
5277 declared in units to which the pragma applies. For a detailed
5278 description of the strict aliasing optimization, and the situations
5279 in which it must be suppressed, see the section on Optimization and Strict Aliasing
5280 in the @cite{GNAT User's Guide}.
5282 This pragma currently has no effects on access to unconstrained array types.
5284 @node Pragma No_Tagged_Streams,Pragma Normalize_Scalars,Pragma No_Strict_Aliasing,Implementation Defined Pragmas
5285 @anchor{gnat_rm/implementation_defined_pragmas pragma-no-tagged-streams}@anchor{a6}@anchor{gnat_rm/implementation_defined_pragmas id25}@anchor{a7}
5286 @section Pragma No_Tagged_Streams
5292 pragma No_Tagged_Streams [([Entity =>] tagged_type_LOCAL_NAME)];
5295 Normally when a tagged type is introduced using a full type declaration,
5296 part of the processing includes generating stream access routines to be
5297 used by stream attributes referencing the type (or one of its subtypes
5298 or derived types). This can involve the generation of significant amounts
5299 of code which is wasted space if stream routines are not needed for the
5302 The @code{No_Tagged_Streams} pragma causes the generation of these stream
5303 routines to be skipped, and any attempt to use stream operations on
5304 types subject to this pragma will be statically rejected as illegal.
5306 There are two forms of the pragma. The form with no arguments must appear
5307 in a declarative sequence or in the declarations of a package spec. This
5308 pragma affects all subsequent root tagged types declared in the declaration
5309 sequence, and specifies that no stream routines be generated. The form with
5310 an argument (for which there is also a corresponding aspect) specifies a
5311 single root tagged type for which stream routines are not to be generated.
5313 Once the pragma has been given for a particular root tagged type, all subtypes
5314 and derived types of this type inherit the pragma automatically, so the effect
5315 applies to a complete hierarchy (this is necessary to deal with the class-wide
5316 dispatching versions of the stream routines).
5318 @node Pragma Normalize_Scalars,Pragma Obsolescent,Pragma No_Tagged_Streams,Implementation Defined Pragmas
5319 @anchor{gnat_rm/implementation_defined_pragmas pragma-normalize-scalars}@anchor{a8}
5320 @section Pragma Normalize_Scalars
5326 pragma Normalize_Scalars;
5329 This is a language defined pragma which is fully implemented in GNAT. The
5330 effect is to cause all scalar objects that are not otherwise initialized
5331 to be initialized. The initial values are implementation dependent and
5337 @item @emph{Standard.Character}
5339 Objects whose root type is Standard.Character are initialized to
5340 Character'Last unless the subtype range excludes NUL (in which case
5341 NUL is used). This choice will always generate an invalid value if
5344 @item @emph{Standard.Wide_Character}
5346 Objects whose root type is Standard.Wide_Character are initialized to
5347 Wide_Character'Last unless the subtype range excludes NUL (in which case
5348 NUL is used). This choice will always generate an invalid value if
5351 @item @emph{Standard.Wide_Wide_Character}
5353 Objects whose root type is Standard.Wide_Wide_Character are initialized to
5354 the invalid value 16#FFFF_FFFF# unless the subtype range excludes NUL (in
5355 which case NUL is used). This choice will always generate an invalid value if
5358 @item @emph{Integer types}
5360 Objects of an integer type are treated differently depending on whether
5361 negative values are present in the subtype. If no negative values are
5362 present, then all one bits is used as the initial value except in the
5363 special case where zero is excluded from the subtype, in which case
5364 all zero bits are used. This choice will always generate an invalid
5365 value if one exists.
5367 For subtypes with negative values present, the largest negative number
5368 is used, except in the unusual case where this largest negative number
5369 is in the subtype, and the largest positive number is not, in which case
5370 the largest positive value is used. This choice will always generate
5371 an invalid value if one exists.
5373 @item @emph{Floating-Point Types}
5375 Objects of all floating-point types are initialized to all 1-bits. For
5376 standard IEEE format, this corresponds to a NaN (not a number) which is
5377 indeed an invalid value.
5379 @item @emph{Fixed-Point Types}
5381 Objects of all fixed-point types are treated as described above for integers,
5382 with the rules applying to the underlying integer value used to represent
5383 the fixed-point value.
5385 @item @emph{Modular types}
5387 Objects of a modular type are initialized to all one bits, except in
5388 the special case where zero is excluded from the subtype, in which
5389 case all zero bits are used. This choice will always generate an
5390 invalid value if one exists.
5392 @item @emph{Enumeration types}
5394 Objects of an enumeration type are initialized to all one-bits, i.e., to
5395 the value @code{2 ** typ'Size - 1} unless the subtype excludes the literal
5396 whose Pos value is zero, in which case a code of zero is used. This choice
5397 will always generate an invalid value if one exists.
5400 @node Pragma Obsolescent,Pragma Optimize_Alignment,Pragma Normalize_Scalars,Implementation Defined Pragmas
5401 @anchor{gnat_rm/implementation_defined_pragmas pragma-obsolescent}@anchor{a9}@anchor{gnat_rm/implementation_defined_pragmas id26}@anchor{aa}
5402 @section Pragma Obsolescent
5410 pragma Obsolescent (
5411 [Message =>] static_string_EXPRESSION
5412 [,[Version =>] Ada_05]]);
5414 pragma Obsolescent (
5416 [,[Message =>] static_string_EXPRESSION
5417 [,[Version =>] Ada_05]] );
5420 This pragma can occur immediately following a declaration of an entity,
5421 including the case of a record component. If no Entity argument is present,
5422 then this declaration is the one to which the pragma applies. If an Entity
5423 parameter is present, it must either match the name of the entity in this
5424 declaration, or alternatively, the pragma can immediately follow an enumeration
5425 type declaration, where the Entity argument names one of the enumeration
5428 This pragma is used to indicate that the named entity
5429 is considered obsolescent and should not be used. Typically this is
5430 used when an API must be modified by eventually removing or modifying
5431 existing subprograms or other entities. The pragma can be used at an
5432 intermediate stage when the entity is still present, but will be
5435 The effect of this pragma is to output a warning message on a reference to
5436 an entity thus marked that the subprogram is obsolescent if the appropriate
5437 warning option in the compiler is activated. If the @code{Message} parameter is
5438 present, then a second warning message is given containing this text. In
5439 addition, a reference to the entity is considered to be a violation of pragma
5440 @code{Restrictions (No_Obsolescent_Features)}.
5442 This pragma can also be used as a program unit pragma for a package,
5443 in which case the entity name is the name of the package, and the
5444 pragma indicates that the entire package is considered
5445 obsolescent. In this case a client @code{with}ing such a package
5446 violates the restriction, and the @code{with} clause is
5447 flagged with warnings if the warning option is set.
5449 If the @code{Version} parameter is present (which must be exactly
5450 the identifier @code{Ada_05}, no other argument is allowed), then the
5451 indication of obsolescence applies only when compiling in Ada 2005
5452 mode. This is primarily intended for dealing with the situations
5453 in the predefined library where subprograms or packages
5454 have become defined as obsolescent in Ada 2005
5455 (e.g., in @code{Ada.Characters.Handling}), but may be used anywhere.
5457 The following examples show typical uses of this pragma:
5461 pragma Obsolescent (p, Message => "use pp instead of p");
5466 pragma Obsolescent ("use q2new instead");
5468 type R is new integer;
5471 Message => "use RR in Ada 2005",
5481 type E is (a, bc, 'd', quack);
5482 pragma Obsolescent (Entity => bc)
5483 pragma Obsolescent (Entity => 'd')
5486 (a, b : character) return character;
5487 pragma Obsolescent (Entity => "+");
5491 Note that, as for all pragmas, if you use a pragma argument identifier,
5492 then all subsequent parameters must also use a pragma argument identifier.
5493 So if you specify @code{Entity =>} for the @code{Entity} argument, and a @code{Message}
5494 argument is present, it must be preceded by @code{Message =>}.
5496 @node Pragma Optimize_Alignment,Pragma Ordered,Pragma Obsolescent,Implementation Defined Pragmas
5497 @anchor{gnat_rm/implementation_defined_pragmas pragma-optimize-alignment}@anchor{ab}
5498 @section Pragma Optimize_Alignment
5502 @geindex default settings
5507 pragma Optimize_Alignment (TIME | SPACE | OFF);
5510 This is a configuration pragma which affects the choice of default alignments
5511 for types and objects where no alignment is explicitly specified. There is a
5512 time/space trade-off in the selection of these values. Large alignments result
5513 in more efficient code, at the expense of larger data space, since sizes have
5514 to be increased to match these alignments. Smaller alignments save space, but
5515 the access code is slower. The normal choice of default alignments for types
5516 and individual alignment promotions for objects (which is what you get if you
5517 do not use this pragma, or if you use an argument of OFF), tries to balance
5518 these two requirements.
5520 Specifying SPACE causes smaller default alignments to be chosen in two cases.
5521 First any packed record is given an alignment of 1. Second, if a size is given
5522 for the type, then the alignment is chosen to avoid increasing this size. For
5534 In the default mode, this type gets an alignment of 4, so that access to the
5535 Integer field X are efficient. But this means that objects of the type end up
5536 with a size of 8 bytes. This is a valid choice, since sizes of objects are
5537 allowed to be bigger than the size of the type, but it can waste space if for
5538 example fields of type R appear in an enclosing record. If the above type is
5539 compiled in @code{Optimize_Alignment (Space)} mode, the alignment is set to 1.
5541 However, there is one case in which SPACE is ignored. If a variable length
5542 record (that is a discriminated record with a component which is an array
5543 whose length depends on a discriminant), has a pragma Pack, then it is not
5544 in general possible to set the alignment of such a record to one, so the
5545 pragma is ignored in this case (with a warning).
5547 Specifying SPACE also disables alignment promotions for standalone objects,
5548 which occur when the compiler increases the alignment of a specific object
5549 without changing the alignment of its type.
5551 Specifying SPACE also disables component reordering in unpacked record types,
5552 which can result in larger sizes in order to meet alignment requirements.
5554 Specifying TIME causes larger default alignments to be chosen in the case of
5555 small types with sizes that are not a power of 2. For example, consider:
5568 The default alignment for this record is normally 1, but if this type is
5569 compiled in @code{Optimize_Alignment (Time)} mode, then the alignment is set
5570 to 4, which wastes space for objects of the type, since they are now 4 bytes
5571 long, but results in more efficient access when the whole record is referenced.
5573 As noted above, this is a configuration pragma, and there is a requirement
5574 that all units in a partition be compiled with a consistent setting of the
5575 optimization setting. This would normally be achieved by use of a configuration
5576 pragma file containing the appropriate setting. The exception to this rule is
5577 that units with an explicit configuration pragma in the same file as the source
5578 unit are excluded from the consistency check, as are all predefined units. The
5579 latter are compiled by default in pragma Optimize_Alignment (Off) mode if no
5580 pragma appears at the start of the file.
5582 @node Pragma Ordered,Pragma Overflow_Mode,Pragma Optimize_Alignment,Implementation Defined Pragmas
5583 @anchor{gnat_rm/implementation_defined_pragmas pragma-ordered}@anchor{ac}
5584 @section Pragma Ordered
5590 pragma Ordered (enumeration_first_subtype_LOCAL_NAME);
5593 Most enumeration types are from a conceptual point of view unordered.
5594 For example, consider:
5597 type Color is (Red, Blue, Green, Yellow);
5600 By Ada semantics @code{Blue > Red} and @code{Green > Blue},
5601 but really these relations make no sense; the enumeration type merely
5602 specifies a set of possible colors, and the order is unimportant.
5604 For unordered enumeration types, it is generally a good idea if
5605 clients avoid comparisons (other than equality or inequality) and
5606 explicit ranges. (A @emph{client} is a unit where the type is referenced,
5607 other than the unit where the type is declared, its body, and its subunits.)
5608 For example, if code buried in some client says:
5611 if Current_Color < Yellow then ...
5612 if Current_Color in Blue .. Green then ...
5615 then the client code is relying on the order, which is undesirable.
5616 It makes the code hard to read and creates maintenance difficulties if
5617 entries have to be added to the enumeration type. Instead,
5618 the code in the client should list the possibilities, or an
5619 appropriate subtype should be declared in the unit that declares
5620 the original enumeration type. E.g., the following subtype could
5621 be declared along with the type @code{Color}:
5624 subtype RBG is Color range Red .. Green;
5627 and then the client could write:
5630 if Current_Color in RBG then ...
5631 if Current_Color = Blue or Current_Color = Green then ...
5634 However, some enumeration types are legitimately ordered from a conceptual
5635 point of view. For example, if you declare:
5638 type Day is (Mon, Tue, Wed, Thu, Fri, Sat, Sun);
5641 then the ordering imposed by the language is reasonable, and
5642 clients can depend on it, writing for example:
5645 if D in Mon .. Fri then ...
5649 The pragma @emph{Ordered} is provided to mark enumeration types that
5650 are conceptually ordered, alerting the reader that clients may depend
5651 on the ordering. GNAT provides a pragma to mark enumerations as ordered
5652 rather than one to mark them as unordered, since in our experience,
5653 the great majority of enumeration types are conceptually unordered.
5655 The types @code{Boolean}, @code{Character}, @code{Wide_Character},
5656 and @code{Wide_Wide_Character}
5657 are considered to be ordered types, so each is declared with a
5658 pragma @code{Ordered} in package @code{Standard}.
5660 Normally pragma @code{Ordered} serves only as documentation and a guide for
5661 coding standards, but GNAT provides a warning switch @emph{-gnatw.u} that
5662 requests warnings for inappropriate uses (comparisons and explicit
5663 subranges) for unordered types. If this switch is used, then any
5664 enumeration type not marked with pragma @code{Ordered} will be considered
5665 as unordered, and will generate warnings for inappropriate uses.
5667 Note that generic types are not considered ordered or unordered (since the
5668 template can be instantiated for both cases), so we never generate warnings
5669 for the case of generic enumerated types.
5671 For additional information please refer to the description of the
5672 @emph{-gnatw.u} switch in the GNAT User's Guide.
5674 @node Pragma Overflow_Mode,Pragma Overriding_Renamings,Pragma Ordered,Implementation Defined Pragmas
5675 @anchor{gnat_rm/implementation_defined_pragmas pragma-overflow-mode}@anchor{ad}
5676 @section Pragma Overflow_Mode
5682 pragma Overflow_Mode
5684 [,[Assertions =>] MODE]);
5686 MODE ::= STRICT | MINIMIZED | ELIMINATED
5689 This pragma sets the current overflow mode to the given setting. For details
5690 of the meaning of these modes, please refer to the
5691 'Overflow Check Handling in GNAT' appendix in the
5692 GNAT User's Guide. If only the @code{General} parameter is present,
5693 the given mode applies to all expressions. If both parameters are present,
5694 the @code{General} mode applies to expressions outside assertions, and
5695 the @code{Eliminated} mode applies to expressions within assertions.
5697 The case of the @code{MODE} parameter is ignored,
5698 so @code{MINIMIZED}, @code{Minimized} and
5699 @code{minimized} all have the same effect.
5701 The @code{Overflow_Mode} pragma has the same scoping and placement
5702 rules as pragma @code{Suppress}, so it can occur either as a
5703 configuration pragma, specifying a default for the whole
5704 program, or in a declarative scope, where it applies to the
5705 remaining declarations and statements in that scope.
5707 The pragma @code{Suppress (Overflow_Check)} suppresses
5708 overflow checking, but does not affect the overflow mode.
5710 The pragma @code{Unsuppress (Overflow_Check)} unsuppresses (enables)
5711 overflow checking, but does not affect the overflow mode.
5713 @node Pragma Overriding_Renamings,Pragma Partition_Elaboration_Policy,Pragma Overflow_Mode,Implementation Defined Pragmas
5714 @anchor{gnat_rm/implementation_defined_pragmas pragma-overriding-renamings}@anchor{ae}
5715 @section Pragma Overriding_Renamings
5718 @geindex Rational profile
5720 @geindex Rational compatibility
5725 pragma Overriding_Renamings;
5728 This is a GNAT configuration pragma to simplify porting
5729 legacy code accepted by the Rational
5730 Ada compiler. In the presence of this pragma, a renaming declaration that
5731 renames an inherited operation declared in the same scope is legal if selected
5732 notation is used as in:
5735 pragma Overriding_Renamings;
5740 function F (..) renames R.F;
5745 RM 8.3 (15) stipulates that an overridden operation is not visible within the
5746 declaration of the overriding operation.
5748 @node Pragma Partition_Elaboration_Policy,Pragma Part_Of,Pragma Overriding_Renamings,Implementation Defined Pragmas
5749 @anchor{gnat_rm/implementation_defined_pragmas pragma-partition-elaboration-policy}@anchor{af}
5750 @section Pragma Partition_Elaboration_Policy
5756 pragma Partition_Elaboration_Policy (POLICY_IDENTIFIER);
5758 POLICY_IDENTIFIER ::= Concurrent | Sequential
5761 This pragma is standard in Ada 2005, but is available in all earlier
5762 versions of Ada as an implementation-defined pragma.
5763 See Ada 2012 Reference Manual for details.
5765 @node Pragma Part_Of,Pragma Passive,Pragma Partition_Elaboration_Policy,Implementation Defined Pragmas
5766 @anchor{gnat_rm/implementation_defined_pragmas id27}@anchor{b0}@anchor{gnat_rm/implementation_defined_pragmas pragma-part-of}@anchor{b1}
5767 @section Pragma Part_Of
5773 pragma Part_Of (ABSTRACT_STATE);
5775 ABSTRACT_STATE ::= NAME
5778 For the semantics of this pragma, see the entry for aspect @code{Part_Of} in the
5779 SPARK 2014 Reference Manual, section 7.2.6.
5781 @node Pragma Passive,Pragma Persistent_BSS,Pragma Part_Of,Implementation Defined Pragmas
5782 @anchor{gnat_rm/implementation_defined_pragmas pragma-passive}@anchor{b2}
5783 @section Pragma Passive
5789 pragma Passive [(Semaphore | No)];
5792 Syntax checked, but otherwise ignored by GNAT. This is recognized for
5793 compatibility with DEC Ada 83 implementations, where it is used within a
5794 task definition to request that a task be made passive. If the argument
5795 @code{Semaphore} is present, or the argument is omitted, then DEC Ada 83
5796 treats the pragma as an assertion that the containing task is passive
5797 and that optimization of context switch with this task is permitted and
5798 desired. If the argument @code{No} is present, the task must not be
5799 optimized. GNAT does not attempt to optimize any tasks in this manner
5800 (since protected objects are available in place of passive tasks).
5802 For more information on the subject of passive tasks, see the section
5803 'Passive Task Optimization' in the GNAT Users Guide.
5805 @node Pragma Persistent_BSS,Pragma Polling,Pragma Passive,Implementation Defined Pragmas
5806 @anchor{gnat_rm/implementation_defined_pragmas id28}@anchor{b3}@anchor{gnat_rm/implementation_defined_pragmas pragma-persistent-bss}@anchor{b4}
5807 @section Pragma Persistent_BSS
5813 pragma Persistent_BSS [(LOCAL_NAME)]
5816 This pragma allows selected objects to be placed in the @code{.persistent_bss}
5817 section. On some targets the linker and loader provide for special
5818 treatment of this section, allowing a program to be reloaded without
5819 affecting the contents of this data (hence the name persistent).
5821 There are two forms of usage. If an argument is given, it must be the
5822 local name of a library-level object, with no explicit initialization
5823 and whose type is potentially persistent. If no argument is given, then
5824 the pragma is a configuration pragma, and applies to all library-level
5825 objects with no explicit initialization of potentially persistent types.
5827 A potentially persistent type is a scalar type, or an untagged,
5828 non-discriminated record, all of whose components have no explicit
5829 initialization and are themselves of a potentially persistent type,
5830 or an array, all of whose constraints are static, and whose component
5831 type is potentially persistent.
5833 If this pragma is used on a target where this feature is not supported,
5834 then the pragma will be ignored. See also @code{pragma Linker_Section}.
5836 @node Pragma Polling,Pragma Post,Pragma Persistent_BSS,Implementation Defined Pragmas
5837 @anchor{gnat_rm/implementation_defined_pragmas pragma-polling}@anchor{b5}
5838 @section Pragma Polling
5844 pragma Polling (ON | OFF);
5847 This pragma controls the generation of polling code. This is normally off.
5848 If @code{pragma Polling (ON)} is used then periodic calls are generated to
5849 the routine @code{Ada.Exceptions.Poll}. This routine is a separate unit in the
5850 runtime library, and can be found in file @code{a-excpol.adb}.
5852 Pragma @code{Polling} can appear as a configuration pragma (for example it
5853 can be placed in the @code{gnat.adc} file) to enable polling globally, or it
5854 can be used in the statement or declaration sequence to control polling
5857 A call to the polling routine is generated at the start of every loop and
5858 at the start of every subprogram call. This guarantees that the @code{Poll}
5859 routine is called frequently, and places an upper bound (determined by
5860 the complexity of the code) on the period between two @code{Poll} calls.
5862 The primary purpose of the polling interface is to enable asynchronous
5863 aborts on targets that cannot otherwise support it (for example Windows
5864 NT), but it may be used for any other purpose requiring periodic polling.
5865 The standard version is null, and can be replaced by a user program. This
5866 will require re-compilation of the @code{Ada.Exceptions} package that can
5867 be found in files @code{a-except.ads} and @code{a-except.adb}.
5869 A standard alternative unit (in file @code{4wexcpol.adb} in the standard GNAT
5870 distribution) is used to enable the asynchronous abort capability on
5871 targets that do not normally support the capability. The version of
5872 @code{Poll} in this file makes a call to the appropriate runtime routine
5873 to test for an abort condition.
5875 Note that polling can also be enabled by use of the @emph{-gnatP} switch.
5876 See the section on switches for gcc in the @cite{GNAT User's Guide}.
5878 @node Pragma Post,Pragma Postcondition,Pragma Polling,Implementation Defined Pragmas
5879 @anchor{gnat_rm/implementation_defined_pragmas pragma-post}@anchor{b6}
5880 @section Pragma Post
5886 @geindex postconditions
5891 pragma Post (Boolean_Expression);
5894 The @code{Post} pragma is intended to be an exact replacement for
5895 the language-defined
5896 @code{Post} aspect, and shares its restrictions and semantics.
5897 It must appear either immediately following the corresponding
5898 subprogram declaration (only other pragmas may intervene), or
5899 if there is no separate subprogram declaration, then it can
5900 appear at the start of the declarations in a subprogram body
5901 (preceded only by other pragmas).
5903 @node Pragma Postcondition,Pragma Post_Class,Pragma Post,Implementation Defined Pragmas
5904 @anchor{gnat_rm/implementation_defined_pragmas pragma-postcondition}@anchor{b7}
5905 @section Pragma Postcondition
5908 @geindex Postcondition
5911 @geindex postconditions
5916 pragma Postcondition (
5917 [Check =>] Boolean_Expression
5918 [,[Message =>] String_Expression]);
5921 The @code{Postcondition} pragma allows specification of automatic
5922 postcondition checks for subprograms. These checks are similar to
5923 assertions, but are automatically inserted just prior to the return
5924 statements of the subprogram with which they are associated (including
5925 implicit returns at the end of procedure bodies and associated
5926 exception handlers).
5928 In addition, the boolean expression which is the condition which
5929 must be true may contain references to function'Result in the case
5930 of a function to refer to the returned value.
5932 @code{Postcondition} pragmas may appear either immediately following the
5933 (separate) declaration of a subprogram, or at the start of the
5934 declarations of a subprogram body. Only other pragmas may intervene
5935 (that is appear between the subprogram declaration and its
5936 postconditions, or appear before the postcondition in the
5937 declaration sequence in a subprogram body). In the case of a
5938 postcondition appearing after a subprogram declaration, the
5939 formal arguments of the subprogram are visible, and can be
5940 referenced in the postcondition expressions.
5942 The postconditions are collected and automatically tested just
5943 before any return (implicit or explicit) in the subprogram body.
5944 A postcondition is only recognized if postconditions are active
5945 at the time the pragma is encountered. The compiler switch @emph{gnata}
5946 turns on all postconditions by default, and pragma @code{Check_Policy}
5947 with an identifier of @code{Postcondition} can also be used to
5948 control whether postconditions are active.
5950 The general approach is that postconditions are placed in the spec
5951 if they represent functional aspects which make sense to the client.
5952 For example we might have:
5955 function Direction return Integer;
5956 pragma Postcondition
5957 (Direction'Result = +1
5959 Direction'Result = -1);
5962 which serves to document that the result must be +1 or -1, and
5963 will test that this is the case at run time if postcondition
5966 Postconditions within the subprogram body can be used to
5967 check that some internal aspect of the implementation,
5968 not visible to the client, is operating as expected.
5969 For instance if a square root routine keeps an internal
5970 counter of the number of times it is called, then we
5971 might have the following postcondition:
5974 Sqrt_Calls : Natural := 0;
5976 function Sqrt (Arg : Float) return Float is
5977 pragma Postcondition
5978 (Sqrt_Calls = Sqrt_Calls'Old + 1);
5983 As this example, shows, the use of the @code{Old} attribute
5984 is often useful in postconditions to refer to the state on
5985 entry to the subprogram.
5987 Note that postconditions are only checked on normal returns
5988 from the subprogram. If an abnormal return results from
5989 raising an exception, then the postconditions are not checked.
5991 If a postcondition fails, then the exception
5992 @code{System.Assertions.Assert_Failure} is raised. If
5993 a message argument was supplied, then the given string
5994 will be used as the exception message. If no message
5995 argument was supplied, then the default message has
5996 the form "Postcondition failed at file_name:line". The
5997 exception is raised in the context of the subprogram
5998 body, so it is possible to catch postcondition failures
5999 within the subprogram body itself.
6001 Within a package spec, normal visibility rules
6002 in Ada would prevent forward references within a
6003 postcondition pragma to functions defined later in
6004 the same package. This would introduce undesirable
6005 ordering constraints. To avoid this problem, all
6006 postcondition pragmas are analyzed at the end of
6007 the package spec, allowing forward references.
6009 The following example shows that this even allows
6010 mutually recursive postconditions as in:
6013 package Parity_Functions is
6014 function Odd (X : Natural) return Boolean;
6015 pragma Postcondition
6019 (x /= 0 and then Even (X - 1))));
6021 function Even (X : Natural) return Boolean;
6022 pragma Postcondition
6026 (x /= 1 and then Odd (X - 1))));
6028 end Parity_Functions;
6031 There are no restrictions on the complexity or form of
6032 conditions used within @code{Postcondition} pragmas.
6033 The following example shows that it is even possible
6034 to verify performance behavior.
6039 Performance : constant Float;
6040 -- Performance constant set by implementation
6041 -- to match target architecture behavior.
6043 procedure Treesort (Arg : String);
6044 -- Sorts characters of argument using N*logN sort
6045 pragma Postcondition
6046 (Float (Clock - Clock'Old) <=
6047 Float (Arg'Length) *
6048 log (Float (Arg'Length)) *
6053 Note: postcondition pragmas associated with subprograms that are
6054 marked as Inline_Always, or those marked as Inline with front-end
6055 inlining (-gnatN option set) are accepted and legality-checked
6056 by the compiler, but are ignored at run-time even if postcondition
6057 checking is enabled.
6059 Note that pragma @code{Postcondition} differs from the language-defined
6060 @code{Post} aspect (and corresponding @code{Post} pragma) in allowing
6061 multiple occurrences, allowing occurences in the body even if there
6062 is a separate spec, and allowing a second string parameter, and the
6063 use of the pragma identifier @code{Check}. Historically, pragma
6064 @code{Postcondition} was implemented prior to the development of
6065 Ada 2012, and has been retained in its original form for
6066 compatibility purposes.
6068 @node Pragma Post_Class,Pragma Rename_Pragma,Pragma Postcondition,Implementation Defined Pragmas
6069 @anchor{gnat_rm/implementation_defined_pragmas pragma-post-class}@anchor{b8}
6070 @section Pragma Post_Class
6076 @geindex postconditions
6081 pragma Post_Class (Boolean_Expression);
6084 The @code{Post_Class} pragma is intended to be an exact replacement for
6085 the language-defined
6086 @code{Post'Class} aspect, and shares its restrictions and semantics.
6087 It must appear either immediately following the corresponding
6088 subprogram declaration (only other pragmas may intervene), or
6089 if there is no separate subprogram declaration, then it can
6090 appear at the start of the declarations in a subprogram body
6091 (preceded only by other pragmas).
6093 Note: This pragma is called @code{Post_Class} rather than
6094 @code{Post'Class} because the latter would not be strictly
6095 conforming to the allowed syntax for pragmas. The motivation
6096 for provinding pragmas equivalent to the aspects is to allow a program
6097 to be written using the pragmas, and then compiled if necessary
6098 using an Ada compiler that does not recognize the pragmas or
6099 aspects, but is prepared to ignore the pragmas. The assertion
6100 policy that controls this pragma is @code{Post'Class}, not
6103 @node Pragma Rename_Pragma,Pragma Pre,Pragma Post_Class,Implementation Defined Pragmas
6104 @anchor{gnat_rm/implementation_defined_pragmas pragma-rename-pragma}@anchor{b9}
6105 @section Pragma Rename_Pragma
6114 pragma Rename_Pragma (
6115 [New_Name =>] IDENTIFIER,
6116 [Renamed =>] pragma_IDENTIFIER);
6119 This pragma provides a mechanism for supplying new names for existing
6120 pragmas. The @code{New_Name} identifier can subsequently be used as a synonym for
6121 the Renamed pragma. For example, suppose you have code that was originally
6122 developed on a compiler that supports Inline_Only as an implementation defined
6123 pragma. And suppose the semantics of pragma Inline_Only are identical to (or at
6124 least very similar to) the GNAT implementation defined pragma
6125 Inline_Always. You could globally replace Inline_Only with Inline_Always.
6127 However, to avoid that source modification, you could instead add a
6128 configuration pragma:
6131 pragma Rename_Pragma (
6132 New_Name => Inline_Only,
6133 Renamed => Inline_Always);
6136 Then GNAT will treat "pragma Inline_Only ..." as if you had written
6137 "pragma Inline_Always ...".
6139 Pragma Inline_Only will not necessarily mean the same thing as the other Ada
6140 compiler; it's up to you to make sure the semantics are close enough.
6142 @node Pragma Pre,Pragma Precondition,Pragma Rename_Pragma,Implementation Defined Pragmas
6143 @anchor{gnat_rm/implementation_defined_pragmas pragma-pre}@anchor{ba}
6150 @geindex preconditions
6155 pragma Pre (Boolean_Expression);
6158 The @code{Pre} pragma is intended to be an exact replacement for
6159 the language-defined
6160 @code{Pre} aspect, and shares its restrictions and semantics.
6161 It must appear either immediately following the corresponding
6162 subprogram declaration (only other pragmas may intervene), or
6163 if there is no separate subprogram declaration, then it can
6164 appear at the start of the declarations in a subprogram body
6165 (preceded only by other pragmas).
6167 @node Pragma Precondition,Pragma Predicate,Pragma Pre,Implementation Defined Pragmas
6168 @anchor{gnat_rm/implementation_defined_pragmas pragma-precondition}@anchor{bb}
6169 @section Pragma Precondition
6172 @geindex Preconditions
6175 @geindex preconditions
6180 pragma Precondition (
6181 [Check =>] Boolean_Expression
6182 [,[Message =>] String_Expression]);
6185 The @code{Precondition} pragma is similar to @code{Postcondition}
6186 except that the corresponding checks take place immediately upon
6187 entry to the subprogram, and if a precondition fails, the exception
6188 is raised in the context of the caller, and the attribute 'Result
6189 cannot be used within the precondition expression.
6191 Otherwise, the placement and visibility rules are identical to those
6192 described for postconditions. The following is an example of use
6193 within a package spec:
6196 package Math_Functions is
6198 function Sqrt (Arg : Float) return Float;
6199 pragma Precondition (Arg >= 0.0)
6204 @code{Precondition} pragmas may appear either immediately following the
6205 (separate) declaration of a subprogram, or at the start of the
6206 declarations of a subprogram body. Only other pragmas may intervene
6207 (that is appear between the subprogram declaration and its
6208 postconditions, or appear before the postcondition in the
6209 declaration sequence in a subprogram body).
6211 Note: precondition pragmas associated with subprograms that are
6212 marked as Inline_Always, or those marked as Inline with front-end
6213 inlining (-gnatN option set) are accepted and legality-checked
6214 by the compiler, but are ignored at run-time even if precondition
6215 checking is enabled.
6217 Note that pragma @code{Precondition} differs from the language-defined
6218 @code{Pre} aspect (and corresponding @code{Pre} pragma) in allowing
6219 multiple occurrences, allowing occurences in the body even if there
6220 is a separate spec, and allowing a second string parameter, and the
6221 use of the pragma identifier @code{Check}. Historically, pragma
6222 @code{Precondition} was implemented prior to the development of
6223 Ada 2012, and has been retained in its original form for
6224 compatibility purposes.
6226 @node Pragma Predicate,Pragma Predicate_Failure,Pragma Precondition,Implementation Defined Pragmas
6227 @anchor{gnat_rm/implementation_defined_pragmas id29}@anchor{bc}@anchor{gnat_rm/implementation_defined_pragmas pragma-predicate}@anchor{bd}
6228 @section Pragma Predicate
6235 ([Entity =>] type_LOCAL_NAME,
6236 [Check =>] EXPRESSION);
6239 This pragma (available in all versions of Ada in GNAT) encompasses both
6240 the @code{Static_Predicate} and @code{Dynamic_Predicate} aspects in
6241 Ada 2012. A predicate is regarded as static if it has an allowed form
6242 for @code{Static_Predicate} and is otherwise treated as a
6243 @code{Dynamic_Predicate}. Otherwise, predicates specified by this
6244 pragma behave exactly as described in the Ada 2012 reference manual.
6245 For example, if we have
6248 type R is range 1 .. 10;
6250 pragma Predicate (Entity => S, Check => S not in 4 .. 6);
6252 pragma Predicate (Entity => Q, Check => F(Q) or G(Q));
6255 the effect is identical to the following Ada 2012 code:
6258 type R is range 1 .. 10;
6260 Static_Predicate => S not in 4 .. 6;
6262 Dynamic_Predicate => F(Q) or G(Q);
6265 Note that there are no pragmas @code{Dynamic_Predicate}
6266 or @code{Static_Predicate}. That is
6267 because these pragmas would affect legality and semantics of
6268 the program and thus do not have a neutral effect if ignored.
6269 The motivation behind providing pragmas equivalent to
6270 corresponding aspects is to allow a program to be written
6271 using the pragmas, and then compiled with a compiler that
6272 will ignore the pragmas. That doesn't work in the case of
6273 static and dynamic predicates, since if the corresponding
6274 pragmas are ignored, then the behavior of the program is
6275 fundamentally changed (for example a membership test
6276 @code{A in B} would not take into account a predicate
6277 defined for subtype B). When following this approach, the
6278 use of predicates should be avoided.
6280 @node Pragma Predicate_Failure,Pragma Preelaborable_Initialization,Pragma Predicate,Implementation Defined Pragmas
6281 @anchor{gnat_rm/implementation_defined_pragmas pragma-predicate-failure}@anchor{be}
6282 @section Pragma Predicate_Failure
6288 pragma Predicate_Failure
6289 ([Entity =>] type_LOCAL_NAME,
6290 [Message =>] String_Expression);
6293 The @code{Predicate_Failure} pragma is intended to be an exact replacement for
6294 the language-defined
6295 @code{Predicate_Failure} aspect, and shares its restrictions and semantics.
6297 @node Pragma Preelaborable_Initialization,Pragma Prefix_Exception_Messages,Pragma Predicate_Failure,Implementation Defined Pragmas
6298 @anchor{gnat_rm/implementation_defined_pragmas pragma-preelaborable-initialization}@anchor{bf}
6299 @section Pragma Preelaborable_Initialization
6305 pragma Preelaborable_Initialization (DIRECT_NAME);
6308 This pragma is standard in Ada 2005, but is available in all earlier
6309 versions of Ada as an implementation-defined pragma.
6310 See Ada 2012 Reference Manual for details.
6312 @node Pragma Prefix_Exception_Messages,Pragma Pre_Class,Pragma Preelaborable_Initialization,Implementation Defined Pragmas
6313 @anchor{gnat_rm/implementation_defined_pragmas pragma-prefix-exception-messages}@anchor{c0}
6314 @section Pragma Prefix_Exception_Messages
6317 @geindex Prefix_Exception_Messages
6321 @geindex Exception_Message
6326 pragma Prefix_Exception_Messages;
6329 This is an implementation-defined configuration pragma that affects the
6330 behavior of raise statements with a message given as a static string
6331 constant (typically a string literal). In such cases, the string will
6332 be automatically prefixed by the name of the enclosing entity (giving
6333 the package and subprogram containing the raise statement). This helps
6334 to identify where messages are coming from, and this mode is automatic
6335 for the run-time library.
6337 The pragma has no effect if the message is computed with an expression other
6338 than a static string constant, since the assumption in this case is that
6339 the program computes exactly the string it wants. If you still want the
6340 prefixing in this case, you can always call
6341 @code{GNAT.Source_Info.Enclosing_Entity} and prepend the string manually.
6343 @node Pragma Pre_Class,Pragma Priority_Specific_Dispatching,Pragma Prefix_Exception_Messages,Implementation Defined Pragmas
6344 @anchor{gnat_rm/implementation_defined_pragmas pragma-pre-class}@anchor{c1}
6345 @section Pragma Pre_Class
6351 @geindex preconditions
6356 pragma Pre_Class (Boolean_Expression);
6359 The @code{Pre_Class} pragma is intended to be an exact replacement for
6360 the language-defined
6361 @code{Pre'Class} aspect, and shares its restrictions and semantics.
6362 It must appear either immediately following the corresponding
6363 subprogram declaration (only other pragmas may intervene), or
6364 if there is no separate subprogram declaration, then it can
6365 appear at the start of the declarations in a subprogram body
6366 (preceded only by other pragmas).
6368 Note: This pragma is called @code{Pre_Class} rather than
6369 @code{Pre'Class} because the latter would not be strictly
6370 conforming to the allowed syntax for pragmas. The motivation
6371 for providing pragmas equivalent to the aspects is to allow a program
6372 to be written using the pragmas, and then compiled if necessary
6373 using an Ada compiler that does not recognize the pragmas or
6374 aspects, but is prepared to ignore the pragmas. The assertion
6375 policy that controls this pragma is @code{Pre'Class}, not
6378 @node Pragma Priority_Specific_Dispatching,Pragma Profile,Pragma Pre_Class,Implementation Defined Pragmas
6379 @anchor{gnat_rm/implementation_defined_pragmas pragma-priority-specific-dispatching}@anchor{c2}
6380 @section Pragma Priority_Specific_Dispatching
6386 pragma Priority_Specific_Dispatching (
6388 first_priority_EXPRESSION,
6389 last_priority_EXPRESSION)
6391 POLICY_IDENTIFIER ::=
6392 EDF_Across_Priorities |
6393 FIFO_Within_Priorities |
6394 Non_Preemptive_Within_Priorities |
6395 Round_Robin_Within_Priorities
6398 This pragma is standard in Ada 2005, but is available in all earlier
6399 versions of Ada as an implementation-defined pragma.
6400 See Ada 2012 Reference Manual for details.
6402 @node Pragma Profile,Pragma Profile_Warnings,Pragma Priority_Specific_Dispatching,Implementation Defined Pragmas
6403 @anchor{gnat_rm/implementation_defined_pragmas pragma-profile}@anchor{c3}
6404 @section Pragma Profile
6410 pragma Profile (Ravenscar | Restricted | Rational |
6411 GNAT_Extended_Ravenscar | GNAT_Ravenscar_EDF );
6414 This pragma is standard in Ada 2005, but is available in all earlier
6415 versions of Ada as an implementation-defined pragma. This is a
6416 configuration pragma that establishes a set of configuration pragmas
6417 that depend on the argument. @code{Ravenscar} is standard in Ada 2005.
6418 The other possibilities (@code{Restricted}, @code{Rational},
6419 @code{GNAT_Extended_Ravenscar}, @code{GNAT_Ravenscar_EDF})
6420 are implementation-defined. The set of configuration pragmas
6421 is defined in the following sections.
6427 Pragma Profile (Ravenscar)
6429 The @code{Ravenscar} profile is standard in Ada 2005,
6430 but is available in all earlier
6431 versions of Ada as an implementation-defined pragma. This profile
6432 establishes the following set of configuration pragmas:
6438 @code{Task_Dispatching_Policy (FIFO_Within_Priorities)}
6440 [RM D.2.2] Tasks are dispatched following a preemptive
6441 priority-ordered scheduling policy.
6444 @code{Locking_Policy (Ceiling_Locking)}
6446 [RM D.3] While tasks and interrupts execute a protected action, they inherit
6447 the ceiling priority of the corresponding protected object.
6450 @code{Detect_Blocking}
6452 This pragma forces the detection of potentially blocking operations within a
6453 protected operation, and to raise Program_Error if that happens.
6456 plus the following set of restrictions:
6462 @code{Max_Entry_Queue_Length => 1}
6464 No task can be queued on a protected entry.
6467 @code{Max_Protected_Entries => 1}
6470 @code{Max_Task_Entries => 0}
6472 No rendezvous statements are allowed.
6475 @code{No_Abort_Statements}
6478 @code{No_Dynamic_Attachment}
6481 @code{No_Dynamic_Priorities}
6484 @code{No_Implicit_Heap_Allocations}
6487 @code{No_Local_Protected_Objects}
6490 @code{No_Local_Timing_Events}
6493 @code{No_Protected_Type_Allocators}
6496 @code{No_Relative_Delay}
6499 @code{No_Requeue_Statements}
6502 @code{No_Select_Statements}
6505 @code{No_Specific_Termination_Handlers}
6508 @code{No_Task_Allocators}
6511 @code{No_Task_Hierarchy}
6514 @code{No_Task_Termination}
6517 @code{Simple_Barriers}
6520 The Ravenscar profile also includes the following restrictions that specify
6521 that there are no semantic dependences on the corresponding predefined
6528 @code{No_Dependence => Ada.Asynchronous_Task_Control}
6531 @code{No_Dependence => Ada.Calendar}
6534 @code{No_Dependence => Ada.Execution_Time.Group_Budget}
6537 @code{No_Dependence => Ada.Execution_Time.Timers}
6540 @code{No_Dependence => Ada.Task_Attributes}
6543 @code{No_Dependence => System.Multiprocessors.Dispatching_Domains}
6546 This set of configuration pragmas and restrictions correspond to the
6547 definition of the 'Ravenscar Profile' for limited tasking, devised and
6548 published by the @cite{International Real-Time Ada Workshop@comma{} 1997}.
6549 A description is also available at
6550 @indicateurl{http://www-users.cs.york.ac.uk/~burns/ravenscar.ps}.
6552 The original definition of the profile was revised at subsequent IRTAW
6553 meetings. It has been included in the ISO
6554 @cite{Guide for the Use of the Ada Programming Language in High Integrity Systems},
6555 and was made part of the Ada 2005 standard.
6556 The formal definition given by
6557 the Ada Rapporteur Group (ARG) can be found in two Ada Issues (AI-249 and
6558 AI-305) available at
6559 @indicateurl{http://www.ada-auth.org/cgi-bin/cvsweb.cgi/ais/ai-00249.txt} and
6560 @indicateurl{http://www.ada-auth.org/cgi-bin/cvsweb.cgi/ais/ai-00305.txt}.
6562 The above set is a superset of the restrictions provided by pragma
6563 @code{Profile (Restricted)}, it includes six additional restrictions
6564 (@code{Simple_Barriers}, @code{No_Select_Statements},
6565 @code{No_Calendar}, @code{No_Implicit_Heap_Allocations},
6566 @code{No_Relative_Delay} and @code{No_Task_Termination}). This means
6567 that pragma @code{Profile (Ravenscar)}, like the pragma
6568 @code{Profile (Restricted)},
6569 automatically causes the use of a simplified,
6570 more efficient version of the tasking run-time library.
6573 Pragma Profile (GNAT_Extended_Ravenscar)
6575 This profile corresponds to a GNAT specific extension of the
6576 Ravenscar profile. The profile may change in the future although
6577 only in a compatible way: some restrictions may be removed or
6578 relaxed. It is defined as a variation of the Ravenscar profile.
6580 The @code{No_Implicit_Heap_Allocations} restriction has been replaced
6581 by @code{No_Implicit_Task_Allocations} and
6582 @code{No_Implicit_Protected_Object_Allocations}.
6584 The @code{Simple_Barriers} restriction has been replaced by
6585 @code{Pure_Barriers}.
6587 The @code{Max_Protected_Entries}, @code{Max_Entry_Queue_Length}, and
6588 @code{No_Relative_Delay} restrictions have been removed.
6591 Pragma Profile (GNAT_Ravenscar_EDF)
6593 This profile corresponds to the Ravenscar profile but using
6594 EDF_Across_Priority as the Task_Scheduling_Policy.
6597 Pragma Profile (Restricted)
6599 This profile corresponds to the GNAT restricted run time. It
6600 establishes the following set of restrictions:
6606 @code{No_Abort_Statements}
6609 @code{No_Entry_Queue}
6612 @code{No_Task_Hierarchy}
6615 @code{No_Task_Allocators}
6618 @code{No_Dynamic_Priorities}
6621 @code{No_Terminate_Alternatives}
6624 @code{No_Dynamic_Attachment}
6627 @code{No_Protected_Type_Allocators}
6630 @code{No_Local_Protected_Objects}
6633 @code{No_Requeue_Statements}
6636 @code{No_Task_Attributes_Package}
6639 @code{Max_Asynchronous_Select_Nesting = 0}
6642 @code{Max_Task_Entries = 0}
6645 @code{Max_Protected_Entries = 1}
6648 @code{Max_Select_Alternatives = 0}
6651 This set of restrictions causes the automatic selection of a simplified
6652 version of the run time that provides improved performance for the
6653 limited set of tasking functionality permitted by this set of restrictions.
6656 Pragma Profile (Rational)
6658 The Rational profile is intended to facilitate porting legacy code that
6659 compiles with the Rational APEX compiler, even when the code includes non-
6660 conforming Ada constructs. The profile enables the following three pragmas:
6666 @code{pragma Implicit_Packing}
6669 @code{pragma Overriding_Renamings}
6672 @code{pragma Use_VADS_Size}
6676 @node Pragma Profile_Warnings,Pragma Propagate_Exceptions,Pragma Profile,Implementation Defined Pragmas
6677 @anchor{gnat_rm/implementation_defined_pragmas pragma-profile-warnings}@anchor{c4}
6678 @section Pragma Profile_Warnings
6684 pragma Profile_Warnings (Ravenscar | Restricted | Rational);
6687 This is an implementation-defined pragma that is similar in
6688 effect to @code{pragma Profile} except that instead of
6689 generating @code{Restrictions} pragmas, it generates
6690 @code{Restriction_Warnings} pragmas. The result is that
6691 violations of the profile generate warning messages instead
6694 @node Pragma Propagate_Exceptions,Pragma Provide_Shift_Operators,Pragma Profile_Warnings,Implementation Defined Pragmas
6695 @anchor{gnat_rm/implementation_defined_pragmas pragma-propagate-exceptions}@anchor{c5}
6696 @section Pragma Propagate_Exceptions
6699 @geindex Interfacing to C++
6704 pragma Propagate_Exceptions;
6707 This pragma is now obsolete and, other than generating a warning if warnings
6708 on obsolescent features are enabled, is ignored.
6709 It is retained for compatibility
6710 purposes. It used to be used in connection with optimization of
6711 a now-obsolete mechanism for implementation of exceptions.
6713 @node Pragma Provide_Shift_Operators,Pragma Psect_Object,Pragma Propagate_Exceptions,Implementation Defined Pragmas
6714 @anchor{gnat_rm/implementation_defined_pragmas pragma-provide-shift-operators}@anchor{c6}
6715 @section Pragma Provide_Shift_Operators
6718 @geindex Shift operators
6723 pragma Provide_Shift_Operators (integer_first_subtype_LOCAL_NAME);
6726 This pragma can be applied to a first subtype local name that specifies
6727 either an unsigned or signed type. It has the effect of providing the
6728 five shift operators (Shift_Left, Shift_Right, Shift_Right_Arithmetic,
6729 Rotate_Left and Rotate_Right) for the given type. It is similar to
6730 including the function declarations for these five operators, together
6731 with the pragma Import (Intrinsic, ...) statements.
6733 @node Pragma Psect_Object,Pragma Pure_Function,Pragma Provide_Shift_Operators,Implementation Defined Pragmas
6734 @anchor{gnat_rm/implementation_defined_pragmas pragma-psect-object}@anchor{c7}
6735 @section Pragma Psect_Object
6741 pragma Psect_Object (
6742 [Internal =>] LOCAL_NAME,
6743 [, [External =>] EXTERNAL_SYMBOL]
6744 [, [Size =>] EXTERNAL_SYMBOL]);
6748 | static_string_EXPRESSION
6751 This pragma is identical in effect to pragma @code{Common_Object}.
6753 @node Pragma Pure_Function,Pragma Rational,Pragma Psect_Object,Implementation Defined Pragmas
6754 @anchor{gnat_rm/implementation_defined_pragmas pragma-pure-function}@anchor{c8}@anchor{gnat_rm/implementation_defined_pragmas id30}@anchor{c9}
6755 @section Pragma Pure_Function
6761 pragma Pure_Function ([Entity =>] function_LOCAL_NAME);
6764 This pragma appears in the same declarative part as a function
6765 declaration (or a set of function declarations if more than one
6766 overloaded declaration exists, in which case the pragma applies
6767 to all entities). It specifies that the function @code{Entity} is
6768 to be considered pure for the purposes of code generation. This means
6769 that the compiler can assume that there are no side effects, and
6770 in particular that two calls with identical arguments produce the
6771 same result. It also means that the function can be used in an
6774 Note that, quite deliberately, there are no static checks to try
6775 to ensure that this promise is met, so @code{Pure_Function} can be used
6776 with functions that are conceptually pure, even if they do modify
6777 global variables. For example, a square root function that is
6778 instrumented to count the number of times it is called is still
6779 conceptually pure, and can still be optimized, even though it
6780 modifies a global variable (the count). Memo functions are another
6781 example (where a table of previous calls is kept and consulted to
6782 avoid re-computation).
6784 Note also that the normal rules excluding optimization of subprograms
6785 in pure units (when parameter types are descended from System.Address,
6786 or when the full view of a parameter type is limited), do not apply
6787 for the Pure_Function case. If you explicitly specify Pure_Function,
6788 the compiler may optimize away calls with identical arguments, and
6789 if that results in unexpected behavior, the proper action is not to
6790 use the pragma for subprograms that are not (conceptually) pure.
6792 Note: Most functions in a @code{Pure} package are automatically pure, and
6793 there is no need to use pragma @code{Pure_Function} for such functions. One
6794 exception is any function that has at least one formal of type
6795 @code{System.Address} or a type derived from it. Such functions are not
6796 considered pure by default, since the compiler assumes that the
6797 @code{Address} parameter may be functioning as a pointer and that the
6798 referenced data may change even if the address value does not.
6799 Similarly, imported functions are not considered to be pure by default,
6800 since there is no way of checking that they are in fact pure. The use
6801 of pragma @code{Pure_Function} for such a function will override these default
6802 assumption, and cause the compiler to treat a designated subprogram as pure
6805 Note: If pragma @code{Pure_Function} is applied to a renamed function, it
6806 applies to the underlying renamed function. This can be used to
6807 disambiguate cases of overloading where some but not all functions
6808 in a set of overloaded functions are to be designated as pure.
6810 If pragma @code{Pure_Function} is applied to a library-level function, the
6811 function is also considered pure from an optimization point of view, but the
6812 unit is not a Pure unit in the categorization sense. So for example, a function
6813 thus marked is free to @code{with} non-pure units.
6815 @node Pragma Rational,Pragma Ravenscar,Pragma Pure_Function,Implementation Defined Pragmas
6816 @anchor{gnat_rm/implementation_defined_pragmas pragma-rational}@anchor{ca}
6817 @section Pragma Rational
6826 This pragma is considered obsolescent, but is retained for
6827 compatibility purposes. It is equivalent to:
6830 pragma Profile (Rational);
6833 @node Pragma Ravenscar,Pragma Refined_Depends,Pragma Rational,Implementation Defined Pragmas
6834 @anchor{gnat_rm/implementation_defined_pragmas pragma-ravenscar}@anchor{cb}
6835 @section Pragma Ravenscar
6844 This pragma is considered obsolescent, but is retained for
6845 compatibility purposes. It is equivalent to:
6848 pragma Profile (Ravenscar);
6851 which is the preferred method of setting the @code{Ravenscar} profile.
6853 @node Pragma Refined_Depends,Pragma Refined_Global,Pragma Ravenscar,Implementation Defined Pragmas
6854 @anchor{gnat_rm/implementation_defined_pragmas pragma-refined-depends}@anchor{cc}@anchor{gnat_rm/implementation_defined_pragmas id31}@anchor{cd}
6855 @section Pragma Refined_Depends
6861 pragma Refined_Depends (DEPENDENCY_RELATION);
6863 DEPENDENCY_RELATION ::=
6865 | (DEPENDENCY_CLAUSE @{, DEPENDENCY_CLAUSE@})
6867 DEPENDENCY_CLAUSE ::=
6868 OUTPUT_LIST =>[+] INPUT_LIST
6869 | NULL_DEPENDENCY_CLAUSE
6871 NULL_DEPENDENCY_CLAUSE ::= null => INPUT_LIST
6873 OUTPUT_LIST ::= OUTPUT | (OUTPUT @{, OUTPUT@})
6875 INPUT_LIST ::= null | INPUT | (INPUT @{, INPUT@})
6877 OUTPUT ::= NAME | FUNCTION_RESULT
6880 where FUNCTION_RESULT is a function Result attribute_reference
6883 For the semantics of this pragma, see the entry for aspect @code{Refined_Depends} in
6884 the SPARK 2014 Reference Manual, section 6.1.5.
6886 @node Pragma Refined_Global,Pragma Refined_Post,Pragma Refined_Depends,Implementation Defined Pragmas
6887 @anchor{gnat_rm/implementation_defined_pragmas pragma-refined-global}@anchor{ce}@anchor{gnat_rm/implementation_defined_pragmas id32}@anchor{cf}
6888 @section Pragma Refined_Global
6894 pragma Refined_Global (GLOBAL_SPECIFICATION);
6896 GLOBAL_SPECIFICATION ::=
6899 | (MODED_GLOBAL_LIST @{, MODED_GLOBAL_LIST@})
6901 MODED_GLOBAL_LIST ::= MODE_SELECTOR => GLOBAL_LIST
6903 MODE_SELECTOR ::= In_Out | Input | Output | Proof_In
6904 GLOBAL_LIST ::= GLOBAL_ITEM | (GLOBAL_ITEM @{, GLOBAL_ITEM@})
6905 GLOBAL_ITEM ::= NAME
6908 For the semantics of this pragma, see the entry for aspect @code{Refined_Global} in
6909 the SPARK 2014 Reference Manual, section 6.1.4.
6911 @node Pragma Refined_Post,Pragma Refined_State,Pragma Refined_Global,Implementation Defined Pragmas
6912 @anchor{gnat_rm/implementation_defined_pragmas pragma-refined-post}@anchor{d0}@anchor{gnat_rm/implementation_defined_pragmas id33}@anchor{d1}
6913 @section Pragma Refined_Post
6919 pragma Refined_Post (boolean_EXPRESSION);
6922 For the semantics of this pragma, see the entry for aspect @code{Refined_Post} in
6923 the SPARK 2014 Reference Manual, section 7.2.7.
6925 @node Pragma Refined_State,Pragma Relative_Deadline,Pragma Refined_Post,Implementation Defined Pragmas
6926 @anchor{gnat_rm/implementation_defined_pragmas pragma-refined-state}@anchor{d2}@anchor{gnat_rm/implementation_defined_pragmas id34}@anchor{d3}
6927 @section Pragma Refined_State
6933 pragma Refined_State (REFINEMENT_LIST);
6936 (REFINEMENT_CLAUSE @{, REFINEMENT_CLAUSE@})
6938 REFINEMENT_CLAUSE ::= state_NAME => CONSTITUENT_LIST
6940 CONSTITUENT_LIST ::=
6943 | (CONSTITUENT @{, CONSTITUENT@})
6945 CONSTITUENT ::= object_NAME | state_NAME
6948 For the semantics of this pragma, see the entry for aspect @code{Refined_State} in
6949 the SPARK 2014 Reference Manual, section 7.2.2.
6951 @node Pragma Relative_Deadline,Pragma Remote_Access_Type,Pragma Refined_State,Implementation Defined Pragmas
6952 @anchor{gnat_rm/implementation_defined_pragmas pragma-relative-deadline}@anchor{d4}
6953 @section Pragma Relative_Deadline
6959 pragma Relative_Deadline (time_span_EXPRESSION);
6962 This pragma is standard in Ada 2005, but is available in all earlier
6963 versions of Ada as an implementation-defined pragma.
6964 See Ada 2012 Reference Manual for details.
6966 @node Pragma Remote_Access_Type,Pragma Restricted_Run_Time,Pragma Relative_Deadline,Implementation Defined Pragmas
6967 @anchor{gnat_rm/implementation_defined_pragmas id35}@anchor{d5}@anchor{gnat_rm/implementation_defined_pragmas pragma-remote-access-type}@anchor{d6}
6968 @section Pragma Remote_Access_Type
6974 pragma Remote_Access_Type ([Entity =>] formal_access_type_LOCAL_NAME);
6977 This pragma appears in the formal part of a generic declaration.
6978 It specifies an exception to the RM rule from E.2.2(17/2), which forbids
6979 the use of a remote access to class-wide type as actual for a formal
6982 When this pragma applies to a formal access type @code{Entity}, that
6983 type is treated as a remote access to class-wide type in the generic.
6984 It must be a formal general access type, and its designated type must
6985 be the class-wide type of a formal tagged limited private type from the
6986 same generic declaration.
6988 In the generic unit, the formal type is subject to all restrictions
6989 pertaining to remote access to class-wide types. At instantiation, the
6990 actual type must be a remote access to class-wide type.
6992 @node Pragma Restricted_Run_Time,Pragma Restriction_Warnings,Pragma Remote_Access_Type,Implementation Defined Pragmas
6993 @anchor{gnat_rm/implementation_defined_pragmas pragma-restricted-run-time}@anchor{d7}
6994 @section Pragma Restricted_Run_Time
7000 pragma Restricted_Run_Time;
7003 This pragma is considered obsolescent, but is retained for
7004 compatibility purposes. It is equivalent to:
7007 pragma Profile (Restricted);
7010 which is the preferred method of setting the restricted run time
7013 @node Pragma Restriction_Warnings,Pragma Reviewable,Pragma Restricted_Run_Time,Implementation Defined Pragmas
7014 @anchor{gnat_rm/implementation_defined_pragmas pragma-restriction-warnings}@anchor{d8}
7015 @section Pragma Restriction_Warnings
7021 pragma Restriction_Warnings
7022 (restriction_IDENTIFIER @{, restriction_IDENTIFIER@});
7025 This pragma allows a series of restriction identifiers to be
7026 specified (the list of allowed identifiers is the same as for
7027 pragma @code{Restrictions}). For each of these identifiers
7028 the compiler checks for violations of the restriction, but
7029 generates a warning message rather than an error message
7030 if the restriction is violated.
7032 One use of this is in situations where you want to know
7033 about violations of a restriction, but you want to ignore some of
7034 these violations. Consider this example, where you want to set
7035 Ada_95 mode and enable style checks, but you want to know about
7036 any other use of implementation pragmas:
7039 pragma Restriction_Warnings (No_Implementation_Pragmas);
7040 pragma Warnings (Off, "violation of No_Implementation_Pragmas");
7042 pragma Style_Checks ("2bfhkM160");
7043 pragma Warnings (On, "violation of No_Implementation_Pragmas");
7046 By including the above lines in a configuration pragmas file,
7047 the Ada_95 and Style_Checks pragmas are accepted without
7048 generating a warning, but any other use of implementation
7049 defined pragmas will cause a warning to be generated.
7051 @node Pragma Reviewable,Pragma Secondary_Stack_Size,Pragma Restriction_Warnings,Implementation Defined Pragmas
7052 @anchor{gnat_rm/implementation_defined_pragmas pragma-reviewable}@anchor{d9}
7053 @section Pragma Reviewable
7062 This pragma is an RM-defined standard pragma, but has no effect on the
7063 program being compiled, or on the code generated for the program.
7065 To obtain the required output specified in RM H.3.1, the compiler must be
7066 run with various special switches as follows:
7072 @emph{Where compiler-generated run-time checks remain}
7074 The switch @emph{-gnatGL}
7075 may be used to list the expanded code in pseudo-Ada form.
7076 Runtime checks show up in the listing either as explicit
7077 checks or operators marked with @{@} to indicate a check is present.
7080 @emph{An identification of known exceptions at compile time}
7082 If the program is compiled with @emph{-gnatwa},
7083 the compiler warning messages will indicate all cases where the compiler
7084 detects that an exception is certain to occur at run time.
7087 @emph{Possible reads of uninitialized variables}
7089 The compiler warns of many such cases, but its output is incomplete.
7093 A supplemental static analysis tool
7094 may be used to obtain a comprehensive list of all
7095 possible points at which uninitialized data may be read.
7101 @emph{Where run-time support routines are implicitly invoked}
7103 In the output from @emph{-gnatGL},
7104 run-time calls are explicitly listed as calls to the relevant
7108 @emph{Object code listing}
7110 This may be obtained either by using the @emph{-S} switch,
7111 or the objdump utility.
7114 @emph{Constructs known to be erroneous at compile time}
7116 These are identified by warnings issued by the compiler (use @emph{-gnatwa}).
7119 @emph{Stack usage information}
7121 Static stack usage data (maximum per-subprogram) can be obtained via the
7122 @emph{-fstack-usage} switch to the compiler.
7123 Dynamic stack usage data (per task) can be obtained via the @emph{-u} switch
7132 @emph{Object code listing of entire partition}
7134 This can be obtained by compiling the partition with @emph{-S},
7135 or by applying objdump
7136 to all the object files that are part of the partition.
7139 @emph{A description of the run-time model}
7141 The full sources of the run-time are available, and the documentation of
7142 these routines describes how these run-time routines interface to the
7143 underlying operating system facilities.
7146 @emph{Control and data-flow information}
7150 A supplemental static analysis tool
7151 may be used to obtain complete control and data-flow information, as well as
7152 comprehensive messages identifying possible problems based on this
7155 @node Pragma Secondary_Stack_Size,Pragma Share_Generic,Pragma Reviewable,Implementation Defined Pragmas
7156 @anchor{gnat_rm/implementation_defined_pragmas id36}@anchor{da}@anchor{gnat_rm/implementation_defined_pragmas pragma-secondary-stack-size}@anchor{db}
7157 @section Pragma Secondary_Stack_Size
7163 pragma Secondary_Stack_Size (integer_EXPRESSION);
7166 This pragma appears within the task definition of a single task declaration
7167 or a task type declaration (like pragma @code{Storage_Size}) and applies to all
7168 task objects of that type. The argument specifies the size of the secondary
7169 stack to be used by these task objects, and must be of an integer type. The
7170 secondary stack is used to handle functions that return a variable-sized
7171 result, for example a function returning an unconstrained String.
7173 Note this pragma only applies to targets using fixed secondary stacks, like
7174 VxWorks 653 and bare board targets, where a fixed block for the
7175 secondary stack is allocated from the primary stack of the task. By default,
7176 these targets assign a percentage of the primary stack for the secondary stack,
7177 as defined by @code{System.Parameter.Sec_Stack_Percentage}. With this pragma,
7178 an @code{integer_EXPRESSION} of bytes is assigned from the primary stack instead.
7180 For most targets, the pragma does not apply as the secondary stack grows on
7181 demand: allocated as a chain of blocks in the heap. The default size of these
7182 blocks can be modified via the @code{-D} binder option as described in
7183 @cite{GNAT User's Guide}.
7185 Note that no check is made to see if the secondary stack can fit inside the
7188 Note the pragma cannot appear when the restriction @code{No_Secondary_Stack}
7191 @node Pragma Share_Generic,Pragma Shared,Pragma Secondary_Stack_Size,Implementation Defined Pragmas
7192 @anchor{gnat_rm/implementation_defined_pragmas pragma-share-generic}@anchor{dc}
7193 @section Pragma Share_Generic
7199 pragma Share_Generic (GNAME @{, GNAME@});
7201 GNAME ::= generic_unit_NAME | generic_instance_NAME
7204 This pragma is provided for compatibility with Dec Ada 83. It has
7205 no effect in GNAT (which does not implement shared generics), other
7206 than to check that the given names are all names of generic units or
7209 @node Pragma Shared,Pragma Short_Circuit_And_Or,Pragma Share_Generic,Implementation Defined Pragmas
7210 @anchor{gnat_rm/implementation_defined_pragmas id37}@anchor{dd}@anchor{gnat_rm/implementation_defined_pragmas pragma-shared}@anchor{de}
7211 @section Pragma Shared
7214 This pragma is provided for compatibility with Ada 83. The syntax and
7215 semantics are identical to pragma Atomic.
7217 @node Pragma Short_Circuit_And_Or,Pragma Short_Descriptors,Pragma Shared,Implementation Defined Pragmas
7218 @anchor{gnat_rm/implementation_defined_pragmas pragma-short-circuit-and-or}@anchor{df}
7219 @section Pragma Short_Circuit_And_Or
7225 pragma Short_Circuit_And_Or;
7228 This configuration pragma causes any occurrence of the AND operator applied to
7229 operands of type Standard.Boolean to be short-circuited (i.e. the AND operator
7230 is treated as if it were AND THEN). Or is similarly treated as OR ELSE. This
7231 may be useful in the context of certification protocols requiring the use of
7232 short-circuited logical operators. If this configuration pragma occurs locally
7233 within the file being compiled, it applies only to the file being compiled.
7234 There is no requirement that all units in a partition use this option.
7236 @node Pragma Short_Descriptors,Pragma Simple_Storage_Pool_Type,Pragma Short_Circuit_And_Or,Implementation Defined Pragmas
7237 @anchor{gnat_rm/implementation_defined_pragmas pragma-short-descriptors}@anchor{e0}
7238 @section Pragma Short_Descriptors
7244 pragma Short_Descriptors
7247 This pragma is provided for compatibility with other Ada implementations. It
7248 is recognized but ignored by all current versions of GNAT.
7250 @node Pragma Simple_Storage_Pool_Type,Pragma Source_File_Name,Pragma Short_Descriptors,Implementation Defined Pragmas
7251 @anchor{gnat_rm/implementation_defined_pragmas pragma-simple-storage-pool-type}@anchor{e1}@anchor{gnat_rm/implementation_defined_pragmas id38}@anchor{e2}
7252 @section Pragma Simple_Storage_Pool_Type
7255 @geindex Storage pool
7258 @geindex Simple storage pool
7263 pragma Simple_Storage_Pool_Type (type_LOCAL_NAME);
7266 A type can be established as a 'simple storage pool type' by applying
7267 the representation pragma @code{Simple_Storage_Pool_Type} to the type.
7268 A type named in the pragma must be a library-level immutably limited record
7269 type or limited tagged type declared immediately within a package declaration.
7270 The type can also be a limited private type whose full type is allowed as
7271 a simple storage pool type.
7273 For a simple storage pool type @code{SSP}, nonabstract primitive subprograms
7274 @code{Allocate}, @code{Deallocate}, and @code{Storage_Size} can be declared that
7275 are subtype conformant with the following subprogram declarations:
7280 Storage_Address : out System.Address;
7281 Size_In_Storage_Elements : System.Storage_Elements.Storage_Count;
7282 Alignment : System.Storage_Elements.Storage_Count);
7284 procedure Deallocate
7286 Storage_Address : System.Address;
7287 Size_In_Storage_Elements : System.Storage_Elements.Storage_Count;
7288 Alignment : System.Storage_Elements.Storage_Count);
7290 function Storage_Size (Pool : SSP)
7291 return System.Storage_Elements.Storage_Count;
7294 Procedure @code{Allocate} must be declared, whereas @code{Deallocate} and
7295 @code{Storage_Size} are optional. If @code{Deallocate} is not declared, then
7296 applying an unchecked deallocation has no effect other than to set its actual
7297 parameter to null. If @code{Storage_Size} is not declared, then the
7298 @code{Storage_Size} attribute applied to an access type associated with
7299 a pool object of type SSP returns zero. Additional operations can be declared
7300 for a simple storage pool type (such as for supporting a mark/release
7301 storage-management discipline).
7303 An object of a simple storage pool type can be associated with an access
7304 type by specifying the attribute
7305 @ref{e3,,Simple_Storage_Pool}. For example:
7308 My_Pool : My_Simple_Storage_Pool_Type;
7310 type Acc is access My_Data_Type;
7312 for Acc'Simple_Storage_Pool use My_Pool;
7315 See attribute @ref{e3,,Simple_Storage_Pool}
7316 for further details.
7318 @node Pragma Source_File_Name,Pragma Source_File_Name_Project,Pragma Simple_Storage_Pool_Type,Implementation Defined Pragmas
7319 @anchor{gnat_rm/implementation_defined_pragmas pragma-source-file-name}@anchor{e4}@anchor{gnat_rm/implementation_defined_pragmas id39}@anchor{e5}
7320 @section Pragma Source_File_Name
7326 pragma Source_File_Name (
7327 [Unit_Name =>] unit_NAME,
7328 Spec_File_Name => STRING_LITERAL,
7329 [Index => INTEGER_LITERAL]);
7331 pragma Source_File_Name (
7332 [Unit_Name =>] unit_NAME,
7333 Body_File_Name => STRING_LITERAL,
7334 [Index => INTEGER_LITERAL]);
7337 Use this to override the normal naming convention. It is a configuration
7338 pragma, and so has the usual applicability of configuration pragmas
7339 (i.e., it applies to either an entire partition, or to all units in a
7340 compilation, or to a single unit, depending on how it is used.
7341 @code{unit_name} is mapped to @code{file_name_literal}. The identifier for
7342 the second argument is required, and indicates whether this is the file
7343 name for the spec or for the body.
7345 The optional Index argument should be used when a file contains multiple
7346 units, and when you do not want to use @code{gnatchop} to separate then
7347 into multiple files (which is the recommended procedure to limit the
7348 number of recompilations that are needed when some sources change).
7349 For instance, if the source file @code{source.ada} contains
7363 you could use the following configuration pragmas:
7366 pragma Source_File_Name
7367 (B, Spec_File_Name => "source.ada", Index => 1);
7368 pragma Source_File_Name
7369 (A, Body_File_Name => "source.ada", Index => 2);
7372 Note that the @code{gnatname} utility can also be used to generate those
7373 configuration pragmas.
7375 Another form of the @code{Source_File_Name} pragma allows
7376 the specification of patterns defining alternative file naming schemes
7377 to apply to all files.
7380 pragma Source_File_Name
7381 ( [Spec_File_Name =>] STRING_LITERAL
7382 [,[Casing =>] CASING_SPEC]
7383 [,[Dot_Replacement =>] STRING_LITERAL]);
7385 pragma Source_File_Name
7386 ( [Body_File_Name =>] STRING_LITERAL
7387 [,[Casing =>] CASING_SPEC]
7388 [,[Dot_Replacement =>] STRING_LITERAL]);
7390 pragma Source_File_Name
7391 ( [Subunit_File_Name =>] STRING_LITERAL
7392 [,[Casing =>] CASING_SPEC]
7393 [,[Dot_Replacement =>] STRING_LITERAL]);
7395 CASING_SPEC ::= Lowercase | Uppercase | Mixedcase
7398 The first argument is a pattern that contains a single asterisk indicating
7399 the point at which the unit name is to be inserted in the pattern string
7400 to form the file name. The second argument is optional. If present it
7401 specifies the casing of the unit name in the resulting file name string.
7402 The default is lower case. Finally the third argument allows for systematic
7403 replacement of any dots in the unit name by the specified string literal.
7405 Note that Source_File_Name pragmas should not be used if you are using
7406 project files. The reason for this rule is that the project manager is not
7407 aware of these pragmas, and so other tools that use the projet file would not
7408 be aware of the intended naming conventions. If you are using project files,
7409 file naming is controlled by Source_File_Name_Project pragmas, which are
7410 usually supplied automatically by the project manager. A pragma
7411 Source_File_Name cannot appear after a @ref{e6,,Pragma Source_File_Name_Project}.
7413 For more details on the use of the @code{Source_File_Name} pragma, see the
7414 sections on @code{Using Other File Names} and @cite{Alternative File Naming Schemes' in the :title:`GNAT User's Guide}.
7416 @node Pragma Source_File_Name_Project,Pragma Source_Reference,Pragma Source_File_Name,Implementation Defined Pragmas
7417 @anchor{gnat_rm/implementation_defined_pragmas pragma-source-file-name-project}@anchor{e6}@anchor{gnat_rm/implementation_defined_pragmas id40}@anchor{e7}
7418 @section Pragma Source_File_Name_Project
7421 This pragma has the same syntax and semantics as pragma Source_File_Name.
7422 It is only allowed as a stand-alone configuration pragma.
7423 It cannot appear after a @ref{e4,,Pragma Source_File_Name}, and
7424 most importantly, once pragma Source_File_Name_Project appears,
7425 no further Source_File_Name pragmas are allowed.
7427 The intention is that Source_File_Name_Project pragmas are always
7428 generated by the Project Manager in a manner consistent with the naming
7429 specified in a project file, and when naming is controlled in this manner,
7430 it is not permissible to attempt to modify this naming scheme using
7431 Source_File_Name or Source_File_Name_Project pragmas (which would not be
7432 known to the project manager).
7434 @node Pragma Source_Reference,Pragma SPARK_Mode,Pragma Source_File_Name_Project,Implementation Defined Pragmas
7435 @anchor{gnat_rm/implementation_defined_pragmas pragma-source-reference}@anchor{e8}
7436 @section Pragma Source_Reference
7442 pragma Source_Reference (INTEGER_LITERAL, STRING_LITERAL);
7445 This pragma must appear as the first line of a source file.
7446 @code{integer_literal} is the logical line number of the line following
7447 the pragma line (for use in error messages and debugging
7448 information). @code{string_literal} is a static string constant that
7449 specifies the file name to be used in error messages and debugging
7450 information. This is most notably used for the output of @code{gnatchop}
7451 with the @emph{-r} switch, to make sure that the original unchopped
7452 source file is the one referred to.
7454 The second argument must be a string literal, it cannot be a static
7455 string expression other than a string literal. This is because its value
7456 is needed for error messages issued by all phases of the compiler.
7458 @node Pragma SPARK_Mode,Pragma Static_Elaboration_Desired,Pragma Source_Reference,Implementation Defined Pragmas
7459 @anchor{gnat_rm/implementation_defined_pragmas pragma-spark-mode}@anchor{e9}@anchor{gnat_rm/implementation_defined_pragmas id41}@anchor{ea}
7460 @section Pragma SPARK_Mode
7466 pragma SPARK_Mode [(On | Off)] ;
7469 In general a program can have some parts that are in SPARK 2014 (and
7470 follow all the rules in the SPARK Reference Manual), and some parts
7471 that are full Ada 2012.
7473 The SPARK_Mode pragma is used to identify which parts are in SPARK
7474 2014 (by default programs are in full Ada). The SPARK_Mode pragma can
7475 be used in the following places:
7481 As a configuration pragma, in which case it sets the default mode for
7482 all units compiled with this pragma.
7485 Immediately following a library-level subprogram spec
7488 Immediately within a library-level package body
7491 Immediately following the @code{private} keyword of a library-level
7495 Immediately following the @code{begin} keyword of a library-level
7499 Immediately within a library-level subprogram body
7502 Normally a subprogram or package spec/body inherits the current mode
7503 that is active at the point it is declared. But this can be overridden
7504 by pragma within the spec or body as above.
7506 The basic consistency rule is that you can't turn SPARK_Mode back
7507 @code{On}, once you have explicitly (with a pragma) turned if
7508 @code{Off}. So the following rules apply:
7510 If a subprogram spec has SPARK_Mode @code{Off}, then the body must
7511 also have SPARK_Mode @code{Off}.
7513 For a package, we have four parts:
7519 the package public declarations
7522 the package private part
7525 the body of the package
7528 the elaboration code after @code{begin}
7531 For a package, the rule is that if you explicitly turn SPARK_Mode
7532 @code{Off} for any part, then all the following parts must have
7533 SPARK_Mode @code{Off}. Note that this may require repeating a pragma
7534 SPARK_Mode (@code{Off}) in the body. For example, if we have a
7535 configuration pragma SPARK_Mode (@code{On}) that turns the mode on by
7536 default everywhere, and one particular package spec has pragma
7537 SPARK_Mode (@code{Off}), then that pragma will need to be repeated in
7540 @node Pragma Static_Elaboration_Desired,Pragma Stream_Convert,Pragma SPARK_Mode,Implementation Defined Pragmas
7541 @anchor{gnat_rm/implementation_defined_pragmas pragma-static-elaboration-desired}@anchor{eb}
7542 @section Pragma Static_Elaboration_Desired
7548 pragma Static_Elaboration_Desired;
7551 This pragma is used to indicate that the compiler should attempt to initialize
7552 statically the objects declared in the library unit to which the pragma applies,
7553 when these objects are initialized (explicitly or implicitly) by an aggregate.
7554 In the absence of this pragma, aggregates in object declarations are expanded
7555 into assignments and loops, even when the aggregate components are static
7556 constants. When the aggregate is present the compiler builds a static expression
7557 that requires no run-time code, so that the initialized object can be placed in
7558 read-only data space. If the components are not static, or the aggregate has
7559 more that 100 components, the compiler emits a warning that the pragma cannot
7560 be obeyed. (See also the restriction No_Implicit_Loops, which supports static
7561 construction of larger aggregates with static components that include an others
7564 @node Pragma Stream_Convert,Pragma Style_Checks,Pragma Static_Elaboration_Desired,Implementation Defined Pragmas
7565 @anchor{gnat_rm/implementation_defined_pragmas pragma-stream-convert}@anchor{ec}
7566 @section Pragma Stream_Convert
7572 pragma Stream_Convert (
7573 [Entity =>] type_LOCAL_NAME,
7574 [Read =>] function_NAME,
7575 [Write =>] function_NAME);
7578 This pragma provides an efficient way of providing user-defined stream
7579 attributes. Not only is it simpler to use than specifying the attributes
7580 directly, but more importantly, it allows the specification to be made in such
7581 a way that the predefined unit Ada.Streams is not loaded unless it is actually
7582 needed (i.e. unless the stream attributes are actually used); the use of
7583 the Stream_Convert pragma adds no overhead at all, unless the stream
7584 attributes are actually used on the designated type.
7586 The first argument specifies the type for which stream functions are
7587 provided. The second parameter provides a function used to read values
7588 of this type. It must name a function whose argument type may be any
7589 subtype, and whose returned type must be the type given as the first
7590 argument to the pragma.
7592 The meaning of the @code{Read} parameter is that if a stream attribute directly
7593 or indirectly specifies reading of the type given as the first parameter,
7594 then a value of the type given as the argument to the Read function is
7595 read from the stream, and then the Read function is used to convert this
7596 to the required target type.
7598 Similarly the @code{Write} parameter specifies how to treat write attributes
7599 that directly or indirectly apply to the type given as the first parameter.
7600 It must have an input parameter of the type specified by the first parameter,
7601 and the return type must be the same as the input type of the Read function.
7602 The effect is to first call the Write function to convert to the given stream
7603 type, and then write the result type to the stream.
7605 The Read and Write functions must not be overloaded subprograms. If necessary
7606 renamings can be supplied to meet this requirement.
7607 The usage of this attribute is best illustrated by a simple example, taken
7608 from the GNAT implementation of package Ada.Strings.Unbounded:
7611 function To_Unbounded (S : String) return Unbounded_String
7612 renames To_Unbounded_String;
7614 pragma Stream_Convert
7615 (Unbounded_String, To_Unbounded, To_String);
7618 The specifications of the referenced functions, as given in the Ada
7619 Reference Manual are:
7622 function To_Unbounded_String (Source : String)
7623 return Unbounded_String;
7625 function To_String (Source : Unbounded_String)
7629 The effect is that if the value of an unbounded string is written to a stream,
7630 then the representation of the item in the stream is in the same format that
7631 would be used for @code{Standard.String'Output}, and this same representation
7632 is expected when a value of this type is read from the stream. Note that the
7633 value written always includes the bounds, even for Unbounded_String'Write,
7634 since Unbounded_String is not an array type.
7636 Note that the @code{Stream_Convert} pragma is not effective in the case of
7637 a derived type of a non-limited tagged type. If such a type is specified then
7638 the pragma is silently ignored, and the default implementation of the stream
7639 attributes is used instead.
7641 @node Pragma Style_Checks,Pragma Subtitle,Pragma Stream_Convert,Implementation Defined Pragmas
7642 @anchor{gnat_rm/implementation_defined_pragmas pragma-style-checks}@anchor{ed}
7643 @section Pragma Style_Checks
7649 pragma Style_Checks (string_LITERAL | ALL_CHECKS |
7650 On | Off [, LOCAL_NAME]);
7653 This pragma is used in conjunction with compiler switches to control the
7654 built in style checking provided by GNAT. The compiler switches, if set,
7655 provide an initial setting for the switches, and this pragma may be used
7656 to modify these settings, or the settings may be provided entirely by
7657 the use of the pragma. This pragma can be used anywhere that a pragma
7658 is legal, including use as a configuration pragma (including use in
7659 the @code{gnat.adc} file).
7661 The form with a string literal specifies which style options are to be
7662 activated. These are additive, so they apply in addition to any previously
7663 set style check options. The codes for the options are the same as those
7664 used in the @emph{-gnaty} switch to @emph{gcc} or @emph{gnatmake}.
7665 For example the following two methods can be used to enable
7673 pragma Style_Checks ("l");
7682 The form @code{ALL_CHECKS} activates all standard checks (its use is equivalent
7683 to the use of the @code{gnaty} switch with no options.
7684 See the @cite{GNAT User's Guide} for details.)
7686 Note: the behavior is slightly different in GNAT mode (@code{-gnatg} used).
7687 In this case, @code{ALL_CHECKS} implies the standard set of GNAT mode style check
7688 options (i.e. equivalent to @code{-gnatyg}).
7690 The forms with @code{Off} and @code{On}
7691 can be used to temporarily disable style checks
7692 as shown in the following example:
7695 pragma Style_Checks ("k"); -- requires keywords in lower case
7696 pragma Style_Checks (Off); -- turn off style checks
7697 NULL; -- this will not generate an error message
7698 pragma Style_Checks (On); -- turn style checks back on
7699 NULL; -- this will generate an error message
7702 Finally the two argument form is allowed only if the first argument is
7703 @code{On} or @code{Off}. The effect is to turn of semantic style checks
7704 for the specified entity, as shown in the following example:
7707 pragma Style_Checks ("r"); -- require consistency of identifier casing
7709 Rf1 : Integer := ARG; -- incorrect, wrong case
7710 pragma Style_Checks (Off, Arg);
7711 Rf2 : Integer := ARG; -- OK, no error
7714 @node Pragma Subtitle,Pragma Suppress,Pragma Style_Checks,Implementation Defined Pragmas
7715 @anchor{gnat_rm/implementation_defined_pragmas pragma-subtitle}@anchor{ee}
7716 @section Pragma Subtitle
7722 pragma Subtitle ([Subtitle =>] STRING_LITERAL);
7725 This pragma is recognized for compatibility with other Ada compilers
7726 but is ignored by GNAT.
7728 @node Pragma Suppress,Pragma Suppress_All,Pragma Subtitle,Implementation Defined Pragmas
7729 @anchor{gnat_rm/implementation_defined_pragmas pragma-suppress}@anchor{ef}
7730 @section Pragma Suppress
7736 pragma Suppress (Identifier [, [On =>] Name]);
7739 This is a standard pragma, and supports all the check names required in
7740 the RM. It is included here because GNAT recognizes some additional check
7741 names that are implementation defined (as permitted by the RM):
7747 @code{Alignment_Check} can be used to suppress alignment checks
7748 on addresses used in address clauses. Such checks can also be suppressed
7749 by suppressing range checks, but the specific use of @code{Alignment_Check}
7750 allows suppression of alignment checks without suppressing other range checks.
7751 Note that @code{Alignment_Check} is suppressed by default on machines (such as
7752 the x86) with non-strict alignment.
7755 @code{Atomic_Synchronization} can be used to suppress the special memory
7756 synchronization instructions that are normally generated for access to
7757 @code{Atomic} variables to ensure correct synchronization between tasks
7758 that use such variables for synchronization purposes.
7761 @code{Duplicated_Tag_Check} Can be used to suppress the check that is generated
7762 for a duplicated tag value when a tagged type is declared.
7765 @code{Container_Checks} Can be used to suppress all checks within Ada.Containers
7766 and instances of its children, including Tampering_Check.
7769 @code{Tampering_Check} Can be used to suppress tampering check in the containers.
7772 @code{Predicate_Check} can be used to control whether predicate checks are
7773 active. It is applicable only to predicates for which the policy is
7774 @code{Check}. Unlike @code{Assertion_Policy}, which determines if a given
7775 predicate is ignored or checked for the whole program, the use of
7776 @code{Suppress} and @code{Unsuppress} with this check name allows a given
7777 predicate to be turned on and off at specific points in the program.
7780 @code{Validity_Check} can be used specifically to control validity checks.
7781 If @code{Suppress} is used to suppress validity checks, then no validity
7782 checks are performed, including those specified by the appropriate compiler
7783 switch or the @code{Validity_Checks} pragma.
7786 Additional check names previously introduced by use of the @code{Check_Name}
7787 pragma are also allowed.
7790 Note that pragma Suppress gives the compiler permission to omit
7791 checks, but does not require the compiler to omit checks. The compiler
7792 will generate checks if they are essentially free, even when they are
7793 suppressed. In particular, if the compiler can prove that a certain
7794 check will necessarily fail, it will generate code to do an
7795 unconditional 'raise', even if checks are suppressed. The compiler
7798 Of course, run-time checks are omitted whenever the compiler can prove
7799 that they will not fail, whether or not checks are suppressed.
7801 @node Pragma Suppress_All,Pragma Suppress_Debug_Info,Pragma Suppress,Implementation Defined Pragmas
7802 @anchor{gnat_rm/implementation_defined_pragmas pragma-suppress-all}@anchor{f0}
7803 @section Pragma Suppress_All
7809 pragma Suppress_All;
7812 This pragma can appear anywhere within a unit.
7813 The effect is to apply @code{Suppress (All_Checks)} to the unit
7814 in which it appears. This pragma is implemented for compatibility with DEC
7815 Ada 83 usage where it appears at the end of a unit, and for compatibility
7816 with Rational Ada, where it appears as a program unit pragma.
7817 The use of the standard Ada pragma @code{Suppress (All_Checks)}
7818 as a normal configuration pragma is the preferred usage in GNAT.
7820 @node Pragma Suppress_Debug_Info,Pragma Suppress_Exception_Locations,Pragma Suppress_All,Implementation Defined Pragmas
7821 @anchor{gnat_rm/implementation_defined_pragmas pragma-suppress-debug-info}@anchor{f1}@anchor{gnat_rm/implementation_defined_pragmas id42}@anchor{f2}
7822 @section Pragma Suppress_Debug_Info
7828 pragma Suppress_Debug_Info ([Entity =>] LOCAL_NAME);
7831 This pragma can be used to suppress generation of debug information
7832 for the specified entity. It is intended primarily for use in debugging
7833 the debugger, and navigating around debugger problems.
7835 @node Pragma Suppress_Exception_Locations,Pragma Suppress_Initialization,Pragma Suppress_Debug_Info,Implementation Defined Pragmas
7836 @anchor{gnat_rm/implementation_defined_pragmas pragma-suppress-exception-locations}@anchor{f3}
7837 @section Pragma Suppress_Exception_Locations
7843 pragma Suppress_Exception_Locations;
7846 In normal mode, a raise statement for an exception by default generates
7847 an exception message giving the file name and line number for the location
7848 of the raise. This is useful for debugging and logging purposes, but this
7849 entails extra space for the strings for the messages. The configuration
7850 pragma @code{Suppress_Exception_Locations} can be used to suppress the
7851 generation of these strings, with the result that space is saved, but the
7852 exception message for such raises is null. This configuration pragma may
7853 appear in a global configuration pragma file, or in a specific unit as
7854 usual. It is not required that this pragma be used consistently within
7855 a partition, so it is fine to have some units within a partition compiled
7856 with this pragma and others compiled in normal mode without it.
7858 @node Pragma Suppress_Initialization,Pragma Task_Name,Pragma Suppress_Exception_Locations,Implementation Defined Pragmas
7859 @anchor{gnat_rm/implementation_defined_pragmas id43}@anchor{f4}@anchor{gnat_rm/implementation_defined_pragmas pragma-suppress-initialization}@anchor{f5}
7860 @section Pragma Suppress_Initialization
7863 @geindex Suppressing initialization
7865 @geindex Initialization
7866 @geindex suppression of
7871 pragma Suppress_Initialization ([Entity =>] variable_or_subtype_Name);
7874 Here variable_or_subtype_Name is the name introduced by a type declaration
7875 or subtype declaration or the name of a variable introduced by an
7878 In the case of a type or subtype
7879 this pragma suppresses any implicit or explicit initialization
7880 for all variables of the given type or subtype,
7881 including initialization resulting from the use of pragmas
7882 Normalize_Scalars or Initialize_Scalars.
7884 This is considered a representation item, so it cannot be given after
7885 the type is frozen. It applies to all subsequent object declarations,
7886 and also any allocator that creates objects of the type.
7888 If the pragma is given for the first subtype, then it is considered
7889 to apply to the base type and all its subtypes. If the pragma is given
7890 for other than a first subtype, then it applies only to the given subtype.
7891 The pragma may not be given after the type is frozen.
7893 Note that this includes eliminating initialization of discriminants
7894 for discriminated types, and tags for tagged types. In these cases,
7895 you will have to use some non-portable mechanism (e.g. address
7896 overlays or unchecked conversion) to achieve required initialization
7897 of these fields before accessing any object of the corresponding type.
7899 For the variable case, implicit initialization for the named variable
7900 is suppressed, just as though its subtype had been given in a pragma
7901 Suppress_Initialization, as described above.
7903 @node Pragma Task_Name,Pragma Task_Storage,Pragma Suppress_Initialization,Implementation Defined Pragmas
7904 @anchor{gnat_rm/implementation_defined_pragmas pragma-task-name}@anchor{f6}
7905 @section Pragma Task_Name
7911 pragma Task_Name (string_EXPRESSION);
7914 This pragma appears within a task definition (like pragma
7915 @code{Priority}) and applies to the task in which it appears. The
7916 argument must be of type String, and provides a name to be used for
7917 the task instance when the task is created. Note that this expression
7918 is not required to be static, and in particular, it can contain
7919 references to task discriminants. This facility can be used to
7920 provide different names for different tasks as they are created,
7921 as illustrated in the example below.
7923 The task name is recorded internally in the run-time structures
7924 and is accessible to tools like the debugger. In addition the
7925 routine @code{Ada.Task_Identification.Image} will return this
7926 string, with a unique task address appended.
7929 -- Example of the use of pragma Task_Name
7931 with Ada.Task_Identification;
7932 use Ada.Task_Identification;
7933 with Text_IO; use Text_IO;
7936 type Astring is access String;
7938 task type Task_Typ (Name : access String) is
7939 pragma Task_Name (Name.all);
7942 task body Task_Typ is
7943 Nam : constant String := Image (Current_Task);
7945 Put_Line ("-->" & Nam (1 .. 14) & "<--");
7948 type Ptr_Task is access Task_Typ;
7949 Task_Var : Ptr_Task;
7953 new Task_Typ (new String'("This is task 1"));
7955 new Task_Typ (new String'("This is task 2"));
7959 @node Pragma Task_Storage,Pragma Test_Case,Pragma Task_Name,Implementation Defined Pragmas
7960 @anchor{gnat_rm/implementation_defined_pragmas pragma-task-storage}@anchor{f7}
7961 @section Pragma Task_Storage
7967 pragma Task_Storage (
7968 [Task_Type =>] LOCAL_NAME,
7969 [Top_Guard =>] static_integer_EXPRESSION);
7972 This pragma specifies the length of the guard area for tasks. The guard
7973 area is an additional storage area allocated to a task. A value of zero
7974 means that either no guard area is created or a minimal guard area is
7975 created, depending on the target. This pragma can appear anywhere a
7976 @code{Storage_Size} attribute definition clause is allowed for a task
7979 @node Pragma Test_Case,Pragma Thread_Local_Storage,Pragma Task_Storage,Implementation Defined Pragmas
7980 @anchor{gnat_rm/implementation_defined_pragmas pragma-test-case}@anchor{f8}@anchor{gnat_rm/implementation_defined_pragmas id44}@anchor{f9}
7981 @section Pragma Test_Case
7990 [Name =>] static_string_Expression
7991 ,[Mode =>] (Nominal | Robustness)
7992 [, Requires => Boolean_Expression]
7993 [, Ensures => Boolean_Expression]);
7996 The @code{Test_Case} pragma allows defining fine-grain specifications
7997 for use by testing tools.
7998 The compiler checks the validity of the @code{Test_Case} pragma, but its
7999 presence does not lead to any modification of the code generated by the
8002 @code{Test_Case} pragmas may only appear immediately following the
8003 (separate) declaration of a subprogram in a package declaration, inside
8004 a package spec unit. Only other pragmas may intervene (that is appear
8005 between the subprogram declaration and a test case).
8007 The compiler checks that boolean expressions given in @code{Requires} and
8008 @code{Ensures} are valid, where the rules for @code{Requires} are the
8009 same as the rule for an expression in @code{Precondition} and the rules
8010 for @code{Ensures} are the same as the rule for an expression in
8011 @code{Postcondition}. In particular, attributes @code{'Old} and
8012 @code{'Result} can only be used within the @code{Ensures}
8013 expression. The following is an example of use within a package spec:
8016 package Math_Functions is
8018 function Sqrt (Arg : Float) return Float;
8019 pragma Test_Case (Name => "Test 1",
8021 Requires => Arg < 10000,
8022 Ensures => Sqrt'Result < 10);
8027 The meaning of a test case is that there is at least one context where
8028 @code{Requires} holds such that, if the associated subprogram is executed in
8029 that context, then @code{Ensures} holds when the subprogram returns.
8030 Mode @code{Nominal} indicates that the input context should also satisfy the
8031 precondition of the subprogram, and the output context should also satisfy its
8032 postcondition. Mode @code{Robustness} indicates that the precondition and
8033 postcondition of the subprogram should be ignored for this test case.
8035 @node Pragma Thread_Local_Storage,Pragma Time_Slice,Pragma Test_Case,Implementation Defined Pragmas
8036 @anchor{gnat_rm/implementation_defined_pragmas pragma-thread-local-storage}@anchor{fa}@anchor{gnat_rm/implementation_defined_pragmas id45}@anchor{fb}
8037 @section Pragma Thread_Local_Storage
8040 @geindex Task specific storage
8042 @geindex TLS (Thread Local Storage)
8044 @geindex Task_Attributes
8049 pragma Thread_Local_Storage ([Entity =>] LOCAL_NAME);
8052 This pragma specifies that the specified entity, which must be
8053 a variable declared in a library-level package, is to be marked as
8054 "Thread Local Storage" (@code{TLS}). On systems supporting this (which
8055 include Windows, Solaris, GNU/Linux and VxWorks 6), this causes each
8056 thread (and hence each Ada task) to see a distinct copy of the variable.
8058 The variable may not have default initialization, and if there is
8059 an explicit initialization, it must be either @code{null} for an
8060 access variable, or a static expression for a scalar variable.
8061 This provides a low level mechanism similar to that provided by
8062 the @code{Ada.Task_Attributes} package, but much more efficient
8063 and is also useful in writing interface code that will interact
8064 with foreign threads.
8066 If this pragma is used on a system where @code{TLS} is not supported,
8067 then an error message will be generated and the program will be rejected.
8069 @node Pragma Time_Slice,Pragma Title,Pragma Thread_Local_Storage,Implementation Defined Pragmas
8070 @anchor{gnat_rm/implementation_defined_pragmas pragma-time-slice}@anchor{fc}
8071 @section Pragma Time_Slice
8077 pragma Time_Slice (static_duration_EXPRESSION);
8080 For implementations of GNAT on operating systems where it is possible
8081 to supply a time slice value, this pragma may be used for this purpose.
8082 It is ignored if it is used in a system that does not allow this control,
8083 or if it appears in other than the main program unit.
8085 @node Pragma Title,Pragma Type_Invariant,Pragma Time_Slice,Implementation Defined Pragmas
8086 @anchor{gnat_rm/implementation_defined_pragmas pragma-title}@anchor{fd}
8087 @section Pragma Title
8093 pragma Title (TITLING_OPTION [, TITLING OPTION]);
8096 [Title =>] STRING_LITERAL,
8097 | [Subtitle =>] STRING_LITERAL
8100 Syntax checked but otherwise ignored by GNAT. This is a listing control
8101 pragma used in DEC Ada 83 implementations to provide a title and/or
8102 subtitle for the program listing. The program listing generated by GNAT
8103 does not have titles or subtitles.
8105 Unlike other pragmas, the full flexibility of named notation is allowed
8106 for this pragma, i.e., the parameters may be given in any order if named
8107 notation is used, and named and positional notation can be mixed
8108 following the normal rules for procedure calls in Ada.
8110 @node Pragma Type_Invariant,Pragma Type_Invariant_Class,Pragma Title,Implementation Defined Pragmas
8111 @anchor{gnat_rm/implementation_defined_pragmas pragma-type-invariant}@anchor{fe}
8112 @section Pragma Type_Invariant
8118 pragma Type_Invariant
8119 ([Entity =>] type_LOCAL_NAME,
8120 [Check =>] EXPRESSION);
8123 The @code{Type_Invariant} pragma is intended to be an exact
8124 replacement for the language-defined @code{Type_Invariant}
8125 aspect, and shares its restrictions and semantics. It differs
8126 from the language defined @code{Invariant} pragma in that it
8127 does not permit a string parameter, and it is
8128 controlled by the assertion identifier @code{Type_Invariant}
8129 rather than @code{Invariant}.
8131 @node Pragma Type_Invariant_Class,Pragma Unchecked_Union,Pragma Type_Invariant,Implementation Defined Pragmas
8132 @anchor{gnat_rm/implementation_defined_pragmas id46}@anchor{ff}@anchor{gnat_rm/implementation_defined_pragmas pragma-type-invariant-class}@anchor{100}
8133 @section Pragma Type_Invariant_Class
8139 pragma Type_Invariant_Class
8140 ([Entity =>] type_LOCAL_NAME,
8141 [Check =>] EXPRESSION);
8144 The @code{Type_Invariant_Class} pragma is intended to be an exact
8145 replacement for the language-defined @code{Type_Invariant'Class}
8146 aspect, and shares its restrictions and semantics.
8148 Note: This pragma is called @code{Type_Invariant_Class} rather than
8149 @code{Type_Invariant'Class} because the latter would not be strictly
8150 conforming to the allowed syntax for pragmas. The motivation
8151 for providing pragmas equivalent to the aspects is to allow a program
8152 to be written using the pragmas, and then compiled if necessary
8153 using an Ada compiler that does not recognize the pragmas or
8154 aspects, but is prepared to ignore the pragmas. The assertion
8155 policy that controls this pragma is @code{Type_Invariant'Class},
8156 not @code{Type_Invariant_Class}.
8158 @node Pragma Unchecked_Union,Pragma Unevaluated_Use_Of_Old,Pragma Type_Invariant_Class,Implementation Defined Pragmas
8159 @anchor{gnat_rm/implementation_defined_pragmas pragma-unchecked-union}@anchor{101}
8160 @section Pragma Unchecked_Union
8163 @geindex Unions in C
8168 pragma Unchecked_Union (first_subtype_LOCAL_NAME);
8171 This pragma is used to specify a representation of a record type that is
8172 equivalent to a C union. It was introduced as a GNAT implementation defined
8173 pragma in the GNAT Ada 95 mode. Ada 2005 includes an extended version of this
8174 pragma, making it language defined, and GNAT fully implements this extended
8175 version in all language modes (Ada 83, Ada 95, and Ada 2005). For full
8176 details, consult the Ada 2012 Reference Manual, section B.3.3.
8178 @node Pragma Unevaluated_Use_Of_Old,Pragma Unimplemented_Unit,Pragma Unchecked_Union,Implementation Defined Pragmas
8179 @anchor{gnat_rm/implementation_defined_pragmas pragma-unevaluated-use-of-old}@anchor{102}
8180 @section Pragma Unevaluated_Use_Of_Old
8183 @geindex Attribute Old
8185 @geindex Attribute Loop_Entry
8187 @geindex Unevaluated_Use_Of_Old
8192 pragma Unevaluated_Use_Of_Old (Error | Warn | Allow);
8195 This pragma controls the processing of attributes Old and Loop_Entry.
8196 If either of these attributes is used in a potentially unevaluated
8197 expression (e.g. the then or else parts of an if expression), then
8198 normally this usage is considered illegal if the prefix of the attribute
8199 is other than an entity name. The language requires this
8200 behavior for Old, and GNAT copies the same rule for Loop_Entry.
8202 The reason for this rule is that otherwise, we can have a situation
8203 where we save the Old value, and this results in an exception, even
8204 though we might not evaluate the attribute. Consider this example:
8207 package UnevalOld is
8209 procedure U (A : String; C : Boolean) -- ERROR
8210 with Post => (if C then A(1)'Old = K else True);
8214 If procedure U is called with a string with a lower bound of 2, and
8215 C false, then an exception would be raised trying to evaluate A(1)
8216 on entry even though the value would not be actually used.
8218 Although the rule guarantees against this possibility, it is sometimes
8219 too restrictive. For example if we know that the string has a lower
8220 bound of 1, then we will never raise an exception.
8221 The pragma @code{Unevaluated_Use_Of_Old} can be
8222 used to modify this behavior. If the argument is @code{Error} then an
8223 error is given (this is the default RM behavior). If the argument is
8224 @code{Warn} then the usage is allowed as legal but with a warning
8225 that an exception might be raised. If the argument is @code{Allow}
8226 then the usage is allowed as legal without generating a warning.
8228 This pragma may appear as a configuration pragma, or in a declarative
8229 part or package specification. In the latter case it applies to
8230 uses up to the end of the corresponding statement sequence or
8231 sequence of package declarations.
8233 @node Pragma Unimplemented_Unit,Pragma Universal_Aliasing,Pragma Unevaluated_Use_Of_Old,Implementation Defined Pragmas
8234 @anchor{gnat_rm/implementation_defined_pragmas pragma-unimplemented-unit}@anchor{103}
8235 @section Pragma Unimplemented_Unit
8241 pragma Unimplemented_Unit;
8244 If this pragma occurs in a unit that is processed by the compiler, GNAT
8245 aborts with the message @code{xxx not implemented}, where
8246 @code{xxx} is the name of the current compilation unit. This pragma is
8247 intended to allow the compiler to handle unimplemented library units in
8250 The abort only happens if code is being generated. Thus you can use
8251 specs of unimplemented packages in syntax or semantic checking mode.
8253 @node Pragma Universal_Aliasing,Pragma Universal_Data,Pragma Unimplemented_Unit,Implementation Defined Pragmas
8254 @anchor{gnat_rm/implementation_defined_pragmas id47}@anchor{104}@anchor{gnat_rm/implementation_defined_pragmas pragma-universal-aliasing}@anchor{105}
8255 @section Pragma Universal_Aliasing
8261 pragma Universal_Aliasing [([Entity =>] type_LOCAL_NAME)];
8264 @code{type_LOCAL_NAME} must refer to a type declaration in the current
8265 declarative part. The effect is to inhibit strict type-based aliasing
8266 optimization for the given type. In other words, the effect is as though
8267 access types designating this type were subject to pragma No_Strict_Aliasing.
8268 For a detailed description of the strict aliasing optimization, and the
8269 situations in which it must be suppressed, see the section on
8270 @code{Optimization and Strict Aliasing} in the @cite{GNAT User's Guide}.
8272 @node Pragma Universal_Data,Pragma Unmodified,Pragma Universal_Aliasing,Implementation Defined Pragmas
8273 @anchor{gnat_rm/implementation_defined_pragmas pragma-universal-data}@anchor{106}@anchor{gnat_rm/implementation_defined_pragmas id48}@anchor{107}
8274 @section Pragma Universal_Data
8280 pragma Universal_Data [(library_unit_Name)];
8283 This pragma is supported only for the AAMP target and is ignored for
8284 other targets. The pragma specifies that all library-level objects
8285 (Counter 0 data) associated with the library unit are to be accessed
8286 and updated using universal addressing (24-bit addresses for AAMP5)
8287 rather than the default of 16-bit Data Environment (DENV) addressing.
8288 Use of this pragma will generally result in less efficient code for
8289 references to global data associated with the library unit, but
8290 allows such data to be located anywhere in memory. This pragma is
8291 a library unit pragma, but can also be used as a configuration pragma
8292 (including use in the @code{gnat.adc} file). The functionality
8293 of this pragma is also available by applying the -univ switch on the
8294 compilations of units where universal addressing of the data is desired.
8296 @node Pragma Unmodified,Pragma Unreferenced,Pragma Universal_Data,Implementation Defined Pragmas
8297 @anchor{gnat_rm/implementation_defined_pragmas pragma-unmodified}@anchor{108}@anchor{gnat_rm/implementation_defined_pragmas id49}@anchor{109}
8298 @section Pragma Unmodified
8307 pragma Unmodified (LOCAL_NAME @{, LOCAL_NAME@});
8310 This pragma signals that the assignable entities (variables,
8311 @code{out} parameters, @code{in out} parameters) whose names are listed are
8312 deliberately not assigned in the current source unit. This
8313 suppresses warnings about the
8314 entities being referenced but not assigned, and in addition a warning will be
8315 generated if one of these entities is in fact assigned in the
8316 same unit as the pragma (or in the corresponding body, or one
8319 This is particularly useful for clearly signaling that a particular
8320 parameter is not modified, even though the spec suggests that it might
8323 For the variable case, warnings are never given for unreferenced variables
8324 whose name contains one of the substrings
8325 @code{DISCARD, DUMMY, IGNORE, JUNK, UNUSED} in any casing. Such names
8326 are typically to be used in cases where such warnings are expected.
8327 Thus it is never necessary to use @code{pragma Unmodified} for such
8328 variables, though it is harmless to do so.
8330 @node Pragma Unreferenced,Pragma Unreferenced_Objects,Pragma Unmodified,Implementation Defined Pragmas
8331 @anchor{gnat_rm/implementation_defined_pragmas pragma-unreferenced}@anchor{10a}@anchor{gnat_rm/implementation_defined_pragmas id50}@anchor{10b}
8332 @section Pragma Unreferenced
8336 @geindex unreferenced
8341 pragma Unreferenced (LOCAL_NAME @{, LOCAL_NAME@});
8342 pragma Unreferenced (library_unit_NAME @{, library_unit_NAME@});
8345 This pragma signals that the entities whose names are listed are
8346 deliberately not referenced in the current source unit after the
8347 occurrence of the pragma. This
8348 suppresses warnings about the
8349 entities being unreferenced, and in addition a warning will be
8350 generated if one of these entities is in fact subsequently referenced in the
8351 same unit as the pragma (or in the corresponding body, or one
8354 This is particularly useful for clearly signaling that a particular
8355 parameter is not referenced in some particular subprogram implementation
8356 and that this is deliberate. It can also be useful in the case of
8357 objects declared only for their initialization or finalization side
8360 If @code{LOCAL_NAME} identifies more than one matching homonym in the
8361 current scope, then the entity most recently declared is the one to which
8362 the pragma applies. Note that in the case of accept formals, the pragma
8363 Unreferenced may appear immediately after the keyword @code{do} which
8364 allows the indication of whether or not accept formals are referenced
8365 or not to be given individually for each accept statement.
8367 The left hand side of an assignment does not count as a reference for the
8368 purpose of this pragma. Thus it is fine to assign to an entity for which
8369 pragma Unreferenced is given.
8371 Note that if a warning is desired for all calls to a given subprogram,
8372 regardless of whether they occur in the same unit as the subprogram
8373 declaration, then this pragma should not be used (calls from another
8374 unit would not be flagged); pragma Obsolescent can be used instead
8375 for this purpose, see @ref{a9,,Pragma Obsolescent}.
8377 The second form of pragma @code{Unreferenced} is used within a context
8378 clause. In this case the arguments must be unit names of units previously
8379 mentioned in @code{with} clauses (similar to the usage of pragma
8380 @code{Elaborate_All}. The effect is to suppress warnings about unreferenced
8381 units and unreferenced entities within these units.
8383 For the variable case, warnings are never given for unreferenced variables
8384 whose name contains one of the substrings
8385 @code{DISCARD, DUMMY, IGNORE, JUNK, UNUSED} in any casing. Such names
8386 are typically to be used in cases where such warnings are expected.
8387 Thus it is never necessary to use @code{pragma Unreferenced} for such
8388 variables, though it is harmless to do so.
8390 @node Pragma Unreferenced_Objects,Pragma Unreserve_All_Interrupts,Pragma Unreferenced,Implementation Defined Pragmas
8391 @anchor{gnat_rm/implementation_defined_pragmas pragma-unreferenced-objects}@anchor{10c}@anchor{gnat_rm/implementation_defined_pragmas id51}@anchor{10d}
8392 @section Pragma Unreferenced_Objects
8396 @geindex unreferenced
8401 pragma Unreferenced_Objects (local_subtype_NAME @{, local_subtype_NAME@});
8404 This pragma signals that for the types or subtypes whose names are
8405 listed, objects which are declared with one of these types or subtypes may
8406 not be referenced, and if no references appear, no warnings are given.
8408 This is particularly useful for objects which are declared solely for their
8409 initialization and finalization effect. Such variables are sometimes referred
8410 to as RAII variables (Resource Acquisition Is Initialization). Using this
8411 pragma on the relevant type (most typically a limited controlled type), the
8412 compiler will automatically suppress unwanted warnings about these variables
8413 not being referenced.
8415 @node Pragma Unreserve_All_Interrupts,Pragma Unsuppress,Pragma Unreferenced_Objects,Implementation Defined Pragmas
8416 @anchor{gnat_rm/implementation_defined_pragmas pragma-unreserve-all-interrupts}@anchor{10e}
8417 @section Pragma Unreserve_All_Interrupts
8423 pragma Unreserve_All_Interrupts;
8426 Normally certain interrupts are reserved to the implementation. Any attempt
8427 to attach an interrupt causes Program_Error to be raised, as described in
8428 RM C.3.2(22). A typical example is the @code{SIGINT} interrupt used in
8429 many systems for a @code{Ctrl-C} interrupt. Normally this interrupt is
8430 reserved to the implementation, so that @code{Ctrl-C} can be used to
8431 interrupt execution.
8433 If the pragma @code{Unreserve_All_Interrupts} appears anywhere in any unit in
8434 a program, then all such interrupts are unreserved. This allows the
8435 program to handle these interrupts, but disables their standard
8436 functions. For example, if this pragma is used, then pressing
8437 @code{Ctrl-C} will not automatically interrupt execution. However,
8438 a program can then handle the @code{SIGINT} interrupt as it chooses.
8440 For a full list of the interrupts handled in a specific implementation,
8441 see the source code for the spec of @code{Ada.Interrupts.Names} in
8442 file @code{a-intnam.ads}. This is a target dependent file that contains the
8443 list of interrupts recognized for a given target. The documentation in
8444 this file also specifies what interrupts are affected by the use of
8445 the @code{Unreserve_All_Interrupts} pragma.
8447 For a more general facility for controlling what interrupts can be
8448 handled, see pragma @code{Interrupt_State}, which subsumes the functionality
8449 of the @code{Unreserve_All_Interrupts} pragma.
8451 @node Pragma Unsuppress,Pragma Use_VADS_Size,Pragma Unreserve_All_Interrupts,Implementation Defined Pragmas
8452 @anchor{gnat_rm/implementation_defined_pragmas pragma-unsuppress}@anchor{10f}
8453 @section Pragma Unsuppress
8459 pragma Unsuppress (IDENTIFIER [, [On =>] NAME]);
8462 This pragma undoes the effect of a previous pragma @code{Suppress}. If
8463 there is no corresponding pragma @code{Suppress} in effect, it has no
8464 effect. The range of the effect is the same as for pragma
8465 @code{Suppress}. The meaning of the arguments is identical to that used
8466 in pragma @code{Suppress}.
8468 One important application is to ensure that checks are on in cases where
8469 code depends on the checks for its correct functioning, so that the code
8470 will compile correctly even if the compiler switches are set to suppress
8471 checks. For example, in a program that depends on external names of tagged
8472 types and wants to ensure that the duplicated tag check occurs even if all
8473 run-time checks are suppressed by a compiler switch, the following
8474 configuration pragma will ensure this test is not suppressed:
8477 pragma Unsuppress (Duplicated_Tag_Check);
8480 This pragma is standard in Ada 2005. It is available in all earlier versions
8481 of Ada as an implementation-defined pragma.
8483 Note that in addition to the checks defined in the Ada RM, GNAT recogizes a
8484 number of implementation-defined check names. See the description of pragma
8485 @code{Suppress} for full details.
8487 @node Pragma Use_VADS_Size,Pragma Unused,Pragma Unsuppress,Implementation Defined Pragmas
8488 @anchor{gnat_rm/implementation_defined_pragmas pragma-use-vads-size}@anchor{110}
8489 @section Pragma Use_VADS_Size
8493 @geindex VADS compatibility
8495 @geindex Rational profile
8500 pragma Use_VADS_Size;
8503 This is a configuration pragma. In a unit to which it applies, any use
8504 of the 'Size attribute is automatically interpreted as a use of the
8505 'VADS_Size attribute. Note that this may result in incorrect semantic
8506 processing of valid Ada 95 or Ada 2005 programs. This is intended to aid in
8507 the handling of existing code which depends on the interpretation of Size
8508 as implemented in the VADS compiler. See description of the VADS_Size
8509 attribute for further details.
8511 @node Pragma Unused,Pragma Validity_Checks,Pragma Use_VADS_Size,Implementation Defined Pragmas
8512 @anchor{gnat_rm/implementation_defined_pragmas pragma-unused}@anchor{111}@anchor{gnat_rm/implementation_defined_pragmas id52}@anchor{112}
8513 @section Pragma Unused
8522 pragma Unused (LOCAL_NAME @{, LOCAL_NAME@});
8525 This pragma signals that the assignable entities (variables,
8526 @code{out} parameters, and @code{in out} parameters) whose names are listed
8527 deliberately do not get assigned or referenced in the current source unit
8528 after the occurrence of the pragma in the current source unit. This
8529 suppresses warnings about the entities that are unreferenced and/or not
8530 assigned, and, in addition, a warning will be generated if one of these
8531 entities gets assigned or subsequently referenced in the same unit as the
8532 pragma (in the corresponding body or one of its subunits).
8534 This is particularly useful for clearly signaling that a particular
8535 parameter is not modified or referenced, even though the spec suggests
8538 For the variable case, warnings are never given for unreferenced
8539 variables whose name contains one of the substrings
8540 @code{DISCARD, DUMMY, IGNORE, JUNK, UNUSED} in any casing. Such names
8541 are typically to be used in cases where such warnings are expected.
8542 Thus it is never necessary to use @code{pragma Unmodified} for such
8543 variables, though it is harmless to do so.
8545 @node Pragma Validity_Checks,Pragma Volatile,Pragma Unused,Implementation Defined Pragmas
8546 @anchor{gnat_rm/implementation_defined_pragmas pragma-validity-checks}@anchor{113}
8547 @section Pragma Validity_Checks
8553 pragma Validity_Checks (string_LITERAL | ALL_CHECKS | On | Off);
8556 This pragma is used in conjunction with compiler switches to control the
8557 built-in validity checking provided by GNAT. The compiler switches, if set
8558 provide an initial setting for the switches, and this pragma may be used
8559 to modify these settings, or the settings may be provided entirely by
8560 the use of the pragma. This pragma can be used anywhere that a pragma
8561 is legal, including use as a configuration pragma (including use in
8562 the @code{gnat.adc} file).
8564 The form with a string literal specifies which validity options are to be
8565 activated. The validity checks are first set to include only the default
8566 reference manual settings, and then a string of letters in the string
8567 specifies the exact set of options required. The form of this string
8568 is exactly as described for the @emph{-gnatVx} compiler switch (see the
8569 GNAT User's Guide for details). For example the following two
8570 methods can be used to enable validity checking for mode @code{in} and
8571 @code{in out} subprogram parameters:
8578 pragma Validity_Checks ("im");
8583 $ gcc -c -gnatVim ...
8587 The form ALL_CHECKS activates all standard checks (its use is equivalent
8588 to the use of the @code{gnatva} switch.
8590 The forms with @code{Off} and @code{On}
8591 can be used to temporarily disable validity checks
8592 as shown in the following example:
8595 pragma Validity_Checks ("c"); -- validity checks for copies
8596 pragma Validity_Checks (Off); -- turn off validity checks
8597 A := B; -- B will not be validity checked
8598 pragma Validity_Checks (On); -- turn validity checks back on
8599 A := C; -- C will be validity checked
8602 @node Pragma Volatile,Pragma Volatile_Full_Access,Pragma Validity_Checks,Implementation Defined Pragmas
8603 @anchor{gnat_rm/implementation_defined_pragmas pragma-volatile}@anchor{114}
8604 @section Pragma Volatile
8610 pragma Volatile (LOCAL_NAME);
8613 This pragma is defined by the Ada Reference Manual, and the GNAT
8614 implementation is fully conformant with this definition. The reason it
8615 is mentioned in this section is that a pragma of the same name was supplied
8616 in some Ada 83 compilers, including DEC Ada 83. The Ada 95 / Ada 2005
8617 implementation of pragma Volatile is upwards compatible with the
8618 implementation in DEC Ada 83.
8620 @node Pragma Volatile_Full_Access,Pragma Volatile_Function,Pragma Volatile,Implementation Defined Pragmas
8621 @anchor{gnat_rm/implementation_defined_pragmas pragma-volatile-full-access}@anchor{115}@anchor{gnat_rm/implementation_defined_pragmas id53}@anchor{116}
8622 @section Pragma Volatile_Full_Access
8628 pragma Volatile_Full_Access (LOCAL_NAME);
8631 This is similar in effect to pragma Volatile, except that any reference to the
8632 object is guaranteed to be done only with instructions that read or write all
8633 the bits of the object. Furthermore, if the object is of a composite type,
8634 then any reference to a component of the object is guaranteed to read and/or
8635 write all the bits of the object.
8637 The intention is that this be suitable for use with memory-mapped I/O devices
8638 on some machines. Note that there are two important respects in which this is
8639 different from @code{pragma Atomic}. First a reference to a @code{Volatile_Full_Access}
8640 object is not a sequential action in the RM 9.10 sense and, therefore, does
8641 not create a synchronization point. Second, in the case of @code{pragma Atomic},
8642 there is no guarantee that all the bits will be accessed if the reference
8643 is not to the whole object; the compiler is allowed (and generally will)
8644 access only part of the object in this case.
8646 It is not permissible to specify @code{Atomic} and @code{Volatile_Full_Access} for
8649 It is not permissible to specify @code{Volatile_Full_Access} for a composite
8650 (record or array) type or object that has at least one @code{Aliased} component.
8652 @node Pragma Volatile_Function,Pragma Warning_As_Error,Pragma Volatile_Full_Access,Implementation Defined Pragmas
8653 @anchor{gnat_rm/implementation_defined_pragmas id54}@anchor{117}@anchor{gnat_rm/implementation_defined_pragmas pragma-volatile-function}@anchor{118}
8654 @section Pragma Volatile_Function
8660 pragma Volatile_Function [ (boolean_EXPRESSION) ];
8663 For the semantics of this pragma, see the entry for aspect @code{Volatile_Function}
8664 in the SPARK 2014 Reference Manual, section 7.1.2.
8666 @node Pragma Warning_As_Error,Pragma Warnings,Pragma Volatile_Function,Implementation Defined Pragmas
8667 @anchor{gnat_rm/implementation_defined_pragmas pragma-warning-as-error}@anchor{119}
8668 @section Pragma Warning_As_Error
8674 pragma Warning_As_Error (static_string_EXPRESSION);
8677 This configuration pragma allows the programmer to specify a set
8678 of warnings that will be treated as errors. Any warning which
8679 matches the pattern given by the pragma argument will be treated
8680 as an error. This gives much more precise control that -gnatwe
8681 which treats all warnings as errors.
8683 The pattern may contain asterisks, which match zero or more characters in
8684 the message. For example, you can use
8685 @code{pragma Warning_As_Error ("bits of*unused")} to treat the warning
8686 message @code{warning: 960 bits of "a" unused} as an error. No other regular
8687 expression notations are permitted. All characters other than asterisk in
8688 these three specific cases are treated as literal characters in the match.
8689 The match is case insensitive, for example XYZ matches xyz.
8691 Note that the pattern matches if it occurs anywhere within the warning
8692 message string (it is not necessary to put an asterisk at the start and
8693 the end of the message, since this is implied).
8695 Another possibility for the static_string_EXPRESSION which works whether
8696 or not error tags are enabled (@emph{-gnatw.d}) is to use the
8697 @emph{-gnatw} tag string, enclosed in brackets,
8698 as shown in the example below, to treat a class of warnings as errors.
8700 The above use of patterns to match the message applies only to warning
8701 messages generated by the front end. This pragma can also be applied to
8702 warnings provided by the back end and mentioned in @ref{11a,,Pragma Warnings}.
8703 By using a single full @emph{-Wxxx} switch in the pragma, such warnings
8704 can also be treated as errors.
8706 The pragma can appear either in a global configuration pragma file
8707 (e.g. @code{gnat.adc}), or at the start of a file. Given a global
8708 configuration pragma file containing:
8711 pragma Warning_As_Error ("[-gnatwj]");
8714 which will treat all obsolescent feature warnings as errors, the
8715 following program compiles as shown (compile options here are
8716 @emph{-gnatwa.d -gnatl -gnatj55}).
8719 1. pragma Warning_As_Error ("*never assigned*");
8720 2. function Warnerr return String is
8723 >>> error: variable "X" is never read and
8724 never assigned [-gnatwv] [warning-as-error]
8728 >>> warning: variable "Y" is assigned but
8729 never read [-gnatwu]
8735 >>> error: use of "%" is an obsolescent
8736 feature (RM J.2(4)), use """ instead
8737 [-gnatwj] [warning-as-error]
8741 8 lines: No errors, 3 warnings (2 treated as errors)
8744 Note that this pragma does not affect the set of warnings issued in
8745 any way, it merely changes the effect of a matching warning if one
8746 is produced as a result of other warnings options. As shown in this
8747 example, if the pragma results in a warning being treated as an error,
8748 the tag is changed from "warning:" to "error:" and the string
8749 "[warning-as-error]" is appended to the end of the message.
8751 @node Pragma Warnings,Pragma Weak_External,Pragma Warning_As_Error,Implementation Defined Pragmas
8752 @anchor{gnat_rm/implementation_defined_pragmas id55}@anchor{11b}@anchor{gnat_rm/implementation_defined_pragmas pragma-warnings}@anchor{11a}
8753 @section Pragma Warnings
8759 pragma Warnings ([TOOL_NAME,] DETAILS [, REASON]);
8761 DETAILS ::= On | Off
8762 DETAILS ::= On | Off, local_NAME
8763 DETAILS ::= static_string_EXPRESSION
8764 DETAILS ::= On | Off, static_string_EXPRESSION
8766 TOOL_NAME ::= GNAT | GNATProve
8768 REASON ::= Reason => STRING_LITERAL @{& STRING_LITERAL@}
8771 Note: in Ada 83 mode, a string literal may be used in place of a static string
8772 expression (which does not exist in Ada 83).
8774 Note if the second argument of @code{DETAILS} is a @code{local_NAME} then the
8775 second form is always understood. If the intention is to use
8776 the fourth form, then you can write @code{NAME & ""} to force the
8777 intepretation as a @emph{static_string_EXPRESSION}.
8779 Note: if the first argument is a valid @code{TOOL_NAME}, it will be interpreted
8780 that way. The use of the @code{TOOL_NAME} argument is relevant only to users
8781 of SPARK and GNATprove, see last part of this section for details.
8783 Normally warnings are enabled, with the output being controlled by
8784 the command line switch. Warnings (@code{Off}) turns off generation of
8785 warnings until a Warnings (@code{On}) is encountered or the end of the
8786 current unit. If generation of warnings is turned off using this
8787 pragma, then some or all of the warning messages are suppressed,
8788 regardless of the setting of the command line switches.
8790 The @code{Reason} parameter may optionally appear as the last argument
8791 in any of the forms of this pragma. It is intended purely for the
8792 purposes of documenting the reason for the @code{Warnings} pragma.
8793 The compiler will check that the argument is a static string but
8794 otherwise ignore this argument. Other tools may provide specialized
8795 processing for this string.
8797 The form with a single argument (or two arguments if Reason present),
8798 where the first argument is @code{ON} or @code{OFF}
8799 may be used as a configuration pragma.
8801 If the @code{LOCAL_NAME} parameter is present, warnings are suppressed for
8802 the specified entity. This suppression is effective from the point where
8803 it occurs till the end of the extended scope of the variable (similar to
8804 the scope of @code{Suppress}). This form cannot be used as a configuration
8807 In the case where the first argument is other than @code{ON} or
8809 the third form with a single static_string_EXPRESSION argument (and possible
8810 reason) provides more precise
8811 control over which warnings are active. The string is a list of letters
8812 specifying which warnings are to be activated and which deactivated. The
8813 code for these letters is the same as the string used in the command
8814 line switch controlling warnings. For a brief summary, use the gnatmake
8815 command with no arguments, which will generate usage information containing
8816 the list of warnings switches supported. For
8817 full details see the section on @code{Warning Message Control} in the
8818 @cite{GNAT User's Guide}.
8819 This form can also be used as a configuration pragma.
8821 The warnings controlled by the @code{-gnatw} switch are generated by the
8822 front end of the compiler. The GCC back end can provide additional warnings
8823 and they are controlled by the @code{-W} switch. Such warnings can be
8824 identified by the appearance of a string of the form @code{[-W@{xxx@}]} in the
8825 message which designates the @code{-W@emph{xxx}} switch that controls the message.
8826 The form with a single @emph{static_string_EXPRESSION} argument also works for these
8827 warnings, but the string must be a single full @code{-W@emph{xxx}} switch in this
8828 case. The above reference lists a few examples of these additional warnings.
8830 The specified warnings will be in effect until the end of the program
8831 or another pragma @code{Warnings} is encountered. The effect of the pragma is
8832 cumulative. Initially the set of warnings is the standard default set
8833 as possibly modified by compiler switches. Then each pragma Warning
8834 modifies this set of warnings as specified. This form of the pragma may
8835 also be used as a configuration pragma.
8837 The fourth form, with an @code{On|Off} parameter and a string, is used to
8838 control individual messages, based on their text. The string argument
8839 is a pattern that is used to match against the text of individual
8840 warning messages (not including the initial "warning: " tag).
8842 The pattern may contain asterisks, which match zero or more characters in
8843 the message. For example, you can use
8844 @code{pragma Warnings (Off, "bits of*unused")} to suppress the warning
8845 message @code{warning: 960 bits of "a" unused}. No other regular
8846 expression notations are permitted. All characters other than asterisk in
8847 these three specific cases are treated as literal characters in the match.
8848 The match is case insensitive, for example XYZ matches xyz.
8850 Note that the pattern matches if it occurs anywhere within the warning
8851 message string (it is not necessary to put an asterisk at the start and
8852 the end of the message, since this is implied).
8854 The above use of patterns to match the message applies only to warning
8855 messages generated by the front end. This form of the pragma with a string
8856 argument can also be used to control warnings provided by the back end and
8857 mentioned above. By using a single full @code{-W@emph{xxx}} switch in the pragma,
8858 such warnings can be turned on and off.
8860 There are two ways to use the pragma in this form. The OFF form can be used
8861 as a configuration pragma. The effect is to suppress all warnings (if any)
8862 that match the pattern string throughout the compilation (or match the
8863 -W switch in the back end case).
8865 The second usage is to suppress a warning locally, and in this case, two
8866 pragmas must appear in sequence:
8869 pragma Warnings (Off, Pattern);
8870 ... code where given warning is to be suppressed
8871 pragma Warnings (On, Pattern);
8874 In this usage, the pattern string must match in the Off and On
8875 pragmas, and (if @emph{-gnatw.w} is given) at least one matching
8876 warning must be suppressed.
8878 Note: to write a string that will match any warning, use the string
8879 @code{"***"}. It will not work to use a single asterisk or two
8880 asterisks since this looks like an operator name. This form with three
8881 asterisks is similar in effect to specifying @code{pragma Warnings (Off)} except (if @code{-gnatw.w} is given) that a matching
8882 @code{pragma Warnings (On, "***")} will be required. This can be
8883 helpful in avoiding forgetting to turn warnings back on.
8885 Note: the debug flag @code{-gnatd.i} (@code{/NOWARNINGS_PRAGMAS} in VMS) can be
8886 used to cause the compiler to entirely ignore all WARNINGS pragmas. This can
8887 be useful in checking whether obsolete pragmas in existing programs are hiding
8890 Note: pragma Warnings does not affect the processing of style messages. See
8891 separate entry for pragma Style_Checks for control of style messages.
8893 Users of the formal verification tool GNATprove for the SPARK subset of Ada may
8894 use the version of the pragma with a @code{TOOL_NAME} parameter.
8896 If present, @code{TOOL_NAME} is the name of a tool, currently either @code{GNAT} for the
8897 compiler or @code{GNATprove} for the formal verification tool. A given tool only
8898 takes into account pragma Warnings that do not specify a tool name, or that
8899 specify the matching tool name. This makes it possible to disable warnings
8900 selectively for each tool, and as a consequence to detect useless pragma
8901 Warnings with switch @code{-gnatw.w}.
8903 @node Pragma Weak_External,Pragma Wide_Character_Encoding,Pragma Warnings,Implementation Defined Pragmas
8904 @anchor{gnat_rm/implementation_defined_pragmas pragma-weak-external}@anchor{11c}
8905 @section Pragma Weak_External
8911 pragma Weak_External ([Entity =>] LOCAL_NAME);
8914 @code{LOCAL_NAME} must refer to an object that is declared at the library
8915 level. This pragma specifies that the given entity should be marked as a
8916 weak symbol for the linker. It is equivalent to @code{__attribute__((weak))}
8917 in GNU C and causes @code{LOCAL_NAME} to be emitted as a weak symbol instead
8918 of a regular symbol, that is to say a symbol that does not have to be
8919 resolved by the linker if used in conjunction with a pragma Import.
8921 When a weak symbol is not resolved by the linker, its address is set to
8922 zero. This is useful in writing interfaces to external modules that may
8923 or may not be linked in the final executable, for example depending on
8924 configuration settings.
8926 If a program references at run time an entity to which this pragma has been
8927 applied, and the corresponding symbol was not resolved at link time, then
8928 the execution of the program is erroneous. It is not erroneous to take the
8929 Address of such an entity, for example to guard potential references,
8930 as shown in the example below.
8932 Some file formats do not support weak symbols so not all target machines
8933 support this pragma.
8936 -- Example of the use of pragma Weak_External
8938 package External_Module is
8940 pragma Import (C, key);
8941 pragma Weak_External (key);
8942 function Present return boolean;
8943 end External_Module;
8945 with System; use System;
8946 package body External_Module is
8947 function Present return boolean is
8949 return key'Address /= System.Null_Address;
8951 end External_Module;
8954 @node Pragma Wide_Character_Encoding,,Pragma Weak_External,Implementation Defined Pragmas
8955 @anchor{gnat_rm/implementation_defined_pragmas pragma-wide-character-encoding}@anchor{11d}
8956 @section Pragma Wide_Character_Encoding
8962 pragma Wide_Character_Encoding (IDENTIFIER | CHARACTER_LITERAL);
8965 This pragma specifies the wide character encoding to be used in program
8966 source text appearing subsequently. It is a configuration pragma, but may
8967 also be used at any point that a pragma is allowed, and it is permissible
8968 to have more than one such pragma in a file, allowing multiple encodings
8969 to appear within the same file.
8971 However, note that the pragma cannot immediately precede the relevant
8972 wide character, because then the previous encoding will still be in
8973 effect, causing "illegal character" errors.
8975 The argument can be an identifier or a character literal. In the identifier
8976 case, it is one of @code{HEX}, @code{UPPER}, @code{SHIFT_JIS},
8977 @code{EUC}, @code{UTF8}, or @code{BRACKETS}. In the character literal
8978 case it is correspondingly one of the characters @code{h}, @code{u},
8979 @code{s}, @code{e}, @code{8}, or @code{b}.
8981 Note that when the pragma is used within a file, it affects only the
8982 encoding within that file, and does not affect withed units, specs,
8985 @node Implementation Defined Aspects,Implementation Defined Attributes,Implementation Defined Pragmas,Top
8986 @anchor{gnat_rm/implementation_defined_aspects implementation-defined-aspects}@anchor{11e}@anchor{gnat_rm/implementation_defined_aspects doc}@anchor{11f}@anchor{gnat_rm/implementation_defined_aspects id1}@anchor{120}
8987 @chapter Implementation Defined Aspects
8990 Ada defines (throughout the Ada 2012 reference manual, summarized
8991 in Annex K) a set of aspects that can be specified for certain entities.
8992 These language defined aspects are implemented in GNAT in Ada 2012 mode
8993 and work as described in the Ada 2012 Reference Manual.
8995 In addition, Ada 2012 allows implementations to define additional aspects
8996 whose meaning is defined by the implementation. GNAT provides
8997 a number of these implementation-defined aspects which can be used
8998 to extend and enhance the functionality of the compiler. This section of
8999 the GNAT reference manual describes these additional aspects.
9001 Note that any program using these aspects may not be portable to
9002 other compilers (although GNAT implements this set of aspects on all
9003 platforms). Therefore if portability to other compilers is an important
9004 consideration, you should minimize the use of these aspects.
9006 Note that for many of these aspects, the effect is essentially similar
9007 to the use of a pragma or attribute specification with the same name
9008 applied to the entity. For example, if we write:
9011 type R is range 1 .. 100
9012 with Value_Size => 10;
9015 then the effect is the same as:
9018 type R is range 1 .. 100;
9019 for R'Value_Size use 10;
9025 type R is new Integer
9026 with Shared => True;
9029 then the effect is the same as:
9032 type R is new Integer;
9036 In the documentation below, such cases are simply marked
9037 as being boolean aspects equivalent to the corresponding pragma
9038 or attribute definition clause.
9041 * Aspect Abstract_State::
9043 * Aspect Async_Readers::
9044 * Aspect Async_Writers::
9045 * Aspect Constant_After_Elaboration::
9046 * Aspect Contract_Cases::
9048 * Aspect Default_Initial_Condition::
9049 * Aspect Dimension::
9050 * Aspect Dimension_System::
9051 * Aspect Disable_Controlled::
9052 * Aspect Effective_Reads::
9053 * Aspect Effective_Writes::
9054 * Aspect Extensions_Visible::
9055 * Aspect Favor_Top_Level::
9058 * Aspect Initial_Condition::
9059 * Aspect Initializes::
9060 * Aspect Inline_Always::
9061 * Aspect Invariant::
9062 * Aspect Invariant'Class::
9064 * Aspect Linker_Section::
9065 * Aspect Lock_Free::
9066 * Aspect Max_Queue_Length::
9067 * Aspect No_Elaboration_Code_All::
9068 * Aspect No_Inline::
9069 * Aspect No_Tagged_Streams::
9070 * Aspect Object_Size::
9071 * Aspect Obsolescent::
9073 * Aspect Persistent_BSS::
9074 * Aspect Predicate::
9075 * Aspect Pure_Function::
9076 * Aspect Refined_Depends::
9077 * Aspect Refined_Global::
9078 * Aspect Refined_Post::
9079 * Aspect Refined_State::
9080 * Aspect Remote_Access_Type::
9081 * Aspect Secondary_Stack_Size::
9082 * Aspect Scalar_Storage_Order::
9084 * Aspect Simple_Storage_Pool::
9085 * Aspect Simple_Storage_Pool_Type::
9086 * Aspect SPARK_Mode::
9087 * Aspect Suppress_Debug_Info::
9088 * Aspect Suppress_Initialization::
9089 * Aspect Test_Case::
9090 * Aspect Thread_Local_Storage::
9091 * Aspect Universal_Aliasing::
9092 * Aspect Universal_Data::
9093 * Aspect Unmodified::
9094 * Aspect Unreferenced::
9095 * Aspect Unreferenced_Objects::
9096 * Aspect Value_Size::
9097 * Aspect Volatile_Full_Access::
9098 * Aspect Volatile_Function::
9103 @node Aspect Abstract_State,Aspect Annotate,,Implementation Defined Aspects
9104 @anchor{gnat_rm/implementation_defined_aspects aspect-abstract-state}@anchor{121}
9105 @section Aspect Abstract_State
9108 @geindex Abstract_State
9110 This aspect is equivalent to @ref{1c,,pragma Abstract_State}.
9112 @node Aspect Annotate,Aspect Async_Readers,Aspect Abstract_State,Implementation Defined Aspects
9113 @anchor{gnat_rm/implementation_defined_aspects aspect-annotate}@anchor{122}
9114 @section Aspect Annotate
9119 There are three forms of this aspect (where ID is an identifier,
9120 and ARG is a general expression),
9121 corresponding to @ref{25,,pragma Annotate}.
9126 @item @emph{Annotate => ID}
9128 Equivalent to @code{pragma Annotate (ID, Entity => Name);}
9130 @item @emph{Annotate => (ID)}
9132 Equivalent to @code{pragma Annotate (ID, Entity => Name);}
9134 @item @emph{Annotate => (ID ,ID @{, ARG@})}
9136 Equivalent to @code{pragma Annotate (ID, ID @{, ARG@}, Entity => Name);}
9139 @node Aspect Async_Readers,Aspect Async_Writers,Aspect Annotate,Implementation Defined Aspects
9140 @anchor{gnat_rm/implementation_defined_aspects aspect-async-readers}@anchor{123}
9141 @section Aspect Async_Readers
9144 @geindex Async_Readers
9146 This boolean aspect is equivalent to @ref{2c,,pragma Async_Readers}.
9148 @node Aspect Async_Writers,Aspect Constant_After_Elaboration,Aspect Async_Readers,Implementation Defined Aspects
9149 @anchor{gnat_rm/implementation_defined_aspects aspect-async-writers}@anchor{124}
9150 @section Aspect Async_Writers
9153 @geindex Async_Writers
9155 This boolean aspect is equivalent to @ref{2f,,pragma Async_Writers}.
9157 @node Aspect Constant_After_Elaboration,Aspect Contract_Cases,Aspect Async_Writers,Implementation Defined Aspects
9158 @anchor{gnat_rm/implementation_defined_aspects aspect-constant-after-elaboration}@anchor{125}
9159 @section Aspect Constant_After_Elaboration
9162 @geindex Constant_After_Elaboration
9164 This aspect is equivalent to @ref{40,,pragma Constant_After_Elaboration}.
9166 @node Aspect Contract_Cases,Aspect Depends,Aspect Constant_After_Elaboration,Implementation Defined Aspects
9167 @anchor{gnat_rm/implementation_defined_aspects aspect-contract-cases}@anchor{126}
9168 @section Aspect Contract_Cases
9171 @geindex Contract_Cases
9173 This aspect is equivalent to @ref{42,,pragma Contract_Cases}, the sequence
9174 of clauses being enclosed in parentheses so that syntactically it is an
9177 @node Aspect Depends,Aspect Default_Initial_Condition,Aspect Contract_Cases,Implementation Defined Aspects
9178 @anchor{gnat_rm/implementation_defined_aspects aspect-depends}@anchor{127}
9179 @section Aspect Depends
9184 This aspect is equivalent to @ref{51,,pragma Depends}.
9186 @node Aspect Default_Initial_Condition,Aspect Dimension,Aspect Depends,Implementation Defined Aspects
9187 @anchor{gnat_rm/implementation_defined_aspects aspect-default-initial-condition}@anchor{128}
9188 @section Aspect Default_Initial_Condition
9191 @geindex Default_Initial_Condition
9193 This aspect is equivalent to @ref{4c,,pragma Default_Initial_Condition}.
9195 @node Aspect Dimension,Aspect Dimension_System,Aspect Default_Initial_Condition,Implementation Defined Aspects
9196 @anchor{gnat_rm/implementation_defined_aspects aspect-dimension}@anchor{129}
9197 @section Aspect Dimension
9202 The @code{Dimension} aspect is used to specify the dimensions of a given
9203 subtype of a dimensioned numeric type. The aspect also specifies a symbol
9204 used when doing formatted output of dimensioned quantities. The syntax is:
9208 ([Symbol =>] SYMBOL, DIMENSION_VALUE @{, DIMENSION_Value@})
9210 SYMBOL ::= STRING_LITERAL | CHARACTER_LITERAL
9214 | others => RATIONAL
9215 | DISCRETE_CHOICE_LIST => RATIONAL
9217 RATIONAL ::= [-] NUMERIC_LITERAL [/ NUMERIC_LITERAL]
9220 This aspect can only be applied to a subtype whose parent type has
9221 a @code{Dimension_System} aspect. The aspect must specify values for
9222 all dimensions of the system. The rational values are the powers of the
9223 corresponding dimensions that are used by the compiler to verify that
9224 physical (numeric) computations are dimensionally consistent. For example,
9225 the computation of a force must result in dimensions (L => 1, M => 1, T => -2).
9226 For further examples of the usage
9227 of this aspect, see package @code{System.Dim.Mks}.
9228 Note that when the dimensioned type is an integer type, then any
9229 dimension value must be an integer literal.
9231 @node Aspect Dimension_System,Aspect Disable_Controlled,Aspect Dimension,Implementation Defined Aspects
9232 @anchor{gnat_rm/implementation_defined_aspects aspect-dimension-system}@anchor{12a}
9233 @section Aspect Dimension_System
9236 @geindex Dimension_System
9238 The @code{Dimension_System} aspect is used to define a system of
9239 dimensions that will be used in subsequent subtype declarations with
9240 @code{Dimension} aspects that reference this system. The syntax is:
9243 with Dimension_System => (DIMENSION @{, DIMENSION@});
9245 DIMENSION ::= ([Unit_Name =>] IDENTIFIER,
9246 [Unit_Symbol =>] SYMBOL,
9247 [Dim_Symbol =>] SYMBOL)
9249 SYMBOL ::= CHARACTER_LITERAL | STRING_LITERAL
9252 This aspect is applied to a type, which must be a numeric derived type
9253 (typically a floating-point type), that
9254 will represent values within the dimension system. Each @code{DIMENSION}
9255 corresponds to one particular dimension. A maximum of 7 dimensions may
9256 be specified. @code{Unit_Name} is the name of the dimension (for example
9257 @code{Meter}). @code{Unit_Symbol} is the shorthand used for quantities
9258 of this dimension (for example @code{m} for @code{Meter}).
9259 @code{Dim_Symbol} gives
9260 the identification within the dimension system (typically this is a
9261 single letter, e.g. @code{L} standing for length for unit name @code{Meter}).
9262 The @code{Unit_Symbol} is used in formatted output of dimensioned quantities.
9263 The @code{Dim_Symbol} is used in error messages when numeric operations have
9264 inconsistent dimensions.
9266 GNAT provides the standard definition of the International MKS system in
9267 the run-time package @code{System.Dim.Mks}. You can easily define
9268 similar packages for cgs units or British units, and define conversion factors
9269 between values in different systems. The MKS system is characterized by the
9273 type Mks_Type is new Long_Long_Float with
9274 Dimension_System => (
9275 (Unit_Name => Meter, Unit_Symbol => 'm', Dim_Symbol => 'L'),
9276 (Unit_Name => Kilogram, Unit_Symbol => "kg", Dim_Symbol => 'M'),
9277 (Unit_Name => Second, Unit_Symbol => 's', Dim_Symbol => 'T'),
9278 (Unit_Name => Ampere, Unit_Symbol => 'A', Dim_Symbol => 'I'),
9279 (Unit_Name => Kelvin, Unit_Symbol => 'K', Dim_Symbol => '@@'),
9280 (Unit_Name => Mole, Unit_Symbol => "mol", Dim_Symbol => 'N'),
9281 (Unit_Name => Candela, Unit_Symbol => "cd", Dim_Symbol => 'J'));
9284 Note that in the above type definition, we use the @code{at} symbol (@code{@@}) to
9285 represent a theta character (avoiding the use of extended Latin-1
9286 characters in this context).
9288 See section 'Performing Dimensionality Analysis in GNAT' in the GNAT Users
9289 Guide for detailed examples of use of the dimension system.
9291 @node Aspect Disable_Controlled,Aspect Effective_Reads,Aspect Dimension_System,Implementation Defined Aspects
9292 @anchor{gnat_rm/implementation_defined_aspects aspect-disable-controlled}@anchor{12b}
9293 @section Aspect Disable_Controlled
9296 @geindex Disable_Controlled
9298 The aspect @code{Disable_Controlled} is defined for controlled record types. If
9299 active, this aspect causes suppression of all related calls to @code{Initialize},
9300 @code{Adjust}, and @code{Finalize}. The intended use is for conditional compilation,
9301 where for example you might want a record to be controlled or not depending on
9302 whether some run-time check is enabled or suppressed.
9304 @node Aspect Effective_Reads,Aspect Effective_Writes,Aspect Disable_Controlled,Implementation Defined Aspects
9305 @anchor{gnat_rm/implementation_defined_aspects aspect-effective-reads}@anchor{12c}
9306 @section Aspect Effective_Reads
9309 @geindex Effective_Reads
9311 This aspect is equivalent to @ref{57,,pragma Effective_Reads}.
9313 @node Aspect Effective_Writes,Aspect Extensions_Visible,Aspect Effective_Reads,Implementation Defined Aspects
9314 @anchor{gnat_rm/implementation_defined_aspects aspect-effective-writes}@anchor{12d}
9315 @section Aspect Effective_Writes
9318 @geindex Effective_Writes
9320 This aspect is equivalent to @ref{59,,pragma Effective_Writes}.
9322 @node Aspect Extensions_Visible,Aspect Favor_Top_Level,Aspect Effective_Writes,Implementation Defined Aspects
9323 @anchor{gnat_rm/implementation_defined_aspects aspect-extensions-visible}@anchor{12e}
9324 @section Aspect Extensions_Visible
9327 @geindex Extensions_Visible
9329 This aspect is equivalent to @ref{65,,pragma Extensions_Visible}.
9331 @node Aspect Favor_Top_Level,Aspect Ghost,Aspect Extensions_Visible,Implementation Defined Aspects
9332 @anchor{gnat_rm/implementation_defined_aspects aspect-favor-top-level}@anchor{12f}
9333 @section Aspect Favor_Top_Level
9336 @geindex Favor_Top_Level
9338 This boolean aspect is equivalent to @ref{6a,,pragma Favor_Top_Level}.
9340 @node Aspect Ghost,Aspect Global,Aspect Favor_Top_Level,Implementation Defined Aspects
9341 @anchor{gnat_rm/implementation_defined_aspects aspect-ghost}@anchor{130}
9342 @section Aspect Ghost
9347 This aspect is equivalent to @ref{6d,,pragma Ghost}.
9349 @node Aspect Global,Aspect Initial_Condition,Aspect Ghost,Implementation Defined Aspects
9350 @anchor{gnat_rm/implementation_defined_aspects aspect-global}@anchor{131}
9351 @section Aspect Global
9356 This aspect is equivalent to @ref{6f,,pragma Global}.
9358 @node Aspect Initial_Condition,Aspect Initializes,Aspect Global,Implementation Defined Aspects
9359 @anchor{gnat_rm/implementation_defined_aspects aspect-initial-condition}@anchor{132}
9360 @section Aspect Initial_Condition
9363 @geindex Initial_Condition
9365 This aspect is equivalent to @ref{7d,,pragma Initial_Condition}.
9367 @node Aspect Initializes,Aspect Inline_Always,Aspect Initial_Condition,Implementation Defined Aspects
9368 @anchor{gnat_rm/implementation_defined_aspects aspect-initializes}@anchor{133}
9369 @section Aspect Initializes
9372 @geindex Initializes
9374 This aspect is equivalent to @ref{7f,,pragma Initializes}.
9376 @node Aspect Inline_Always,Aspect Invariant,Aspect Initializes,Implementation Defined Aspects
9377 @anchor{gnat_rm/implementation_defined_aspects aspect-inline-always}@anchor{134}
9378 @section Aspect Inline_Always
9381 @geindex Inline_Always
9383 This boolean aspect is equivalent to @ref{82,,pragma Inline_Always}.
9385 @node Aspect Invariant,Aspect Invariant'Class,Aspect Inline_Always,Implementation Defined Aspects
9386 @anchor{gnat_rm/implementation_defined_aspects aspect-invariant}@anchor{135}
9387 @section Aspect Invariant
9392 This aspect is equivalent to @ref{89,,pragma Invariant}. It is a
9393 synonym for the language defined aspect @code{Type_Invariant} except
9394 that it is separately controllable using pragma @code{Assertion_Policy}.
9396 @node Aspect Invariant'Class,Aspect Iterable,Aspect Invariant,Implementation Defined Aspects
9397 @anchor{gnat_rm/implementation_defined_aspects aspect-invariant-class}@anchor{136}
9398 @section Aspect Invariant'Class
9401 @geindex Invariant'Class
9403 This aspect is equivalent to @ref{100,,pragma Type_Invariant_Class}. It is a
9404 synonym for the language defined aspect @code{Type_Invariant'Class} except
9405 that it is separately controllable using pragma @code{Assertion_Policy}.
9407 @node Aspect Iterable,Aspect Linker_Section,Aspect Invariant'Class,Implementation Defined Aspects
9408 @anchor{gnat_rm/implementation_defined_aspects aspect-iterable}@anchor{137}
9409 @section Aspect Iterable
9414 This aspect provides a light-weight mechanism for loops and quantified
9415 expressions over container types, without the overhead imposed by the tampering
9416 checks of standard Ada 2012 iterators. The value of the aspect is an aggregate
9417 with six named components, or which the last three are optional: @code{First},
9421 @code{Next}, @code{Has_Element},`@w{`}Element`@w{`}, @code{Last}, and @code{Previous}.
9424 When only the first three components are specified, only the
9425 @code{for .. in} form of iteration over cursors is available. When @code{Element}
9426 is specified, both this form and the @code{for .. of} form of iteration over
9427 elements are available. If the last two components are specified, reverse
9428 iterations over the container can be specified (analogous to what can be done
9429 over predefined containers that support the Reverse_Iterator interface).
9430 The following is a typical example of use:
9433 type List is private with
9434 Iterable => (First => First_Cursor,
9436 Has_Element => Cursor_Has_Element,
9437 [Element => Get_Element]);
9444 The value denoted by @code{First} must denote a primitive operation of the
9445 container type that returns a @code{Cursor}, which must a be a type declared in
9446 the container package or visible from it. For example:
9450 function First_Cursor (Cont : Container) return Cursor;
9457 The value of @code{Next} is a primitive operation of the container type that takes
9458 both a container and a cursor and yields a cursor. For example:
9462 function Advance (Cont : Container; Position : Cursor) return Cursor;
9469 The value of @code{Has_Element} is a primitive operation of the container type
9470 that takes both a container and a cursor and yields a boolean. For example:
9474 function Cursor_Has_Element (Cont : Container; Position : Cursor) return Boolean;
9481 The value of @code{Element} is a primitive operation of the container type that
9482 takes both a container and a cursor and yields an @code{Element_Type}, which must
9483 be a type declared in the container package or visible from it. For example:
9487 function Get_Element (Cont : Container; Position : Cursor) return Element_Type;
9490 This aspect is used in the GNAT-defined formal container packages.
9492 @node Aspect Linker_Section,Aspect Lock_Free,Aspect Iterable,Implementation Defined Aspects
9493 @anchor{gnat_rm/implementation_defined_aspects aspect-linker-section}@anchor{138}
9494 @section Aspect Linker_Section
9497 @geindex Linker_Section
9499 This aspect is equivalent to @ref{91,,pragma Linker_Section}.
9501 @node Aspect Lock_Free,Aspect Max_Queue_Length,Aspect Linker_Section,Implementation Defined Aspects
9502 @anchor{gnat_rm/implementation_defined_aspects aspect-lock-free}@anchor{139}
9503 @section Aspect Lock_Free
9508 This boolean aspect is equivalent to @ref{93,,pragma Lock_Free}.
9510 @node Aspect Max_Queue_Length,Aspect No_Elaboration_Code_All,Aspect Lock_Free,Implementation Defined Aspects
9511 @anchor{gnat_rm/implementation_defined_aspects aspect-max-queue-length}@anchor{13a}
9512 @section Aspect Max_Queue_Length
9515 @geindex Max_Queue_Length
9517 This aspect is equivalent to @ref{9b,,pragma Max_Queue_Length}.
9519 @node Aspect No_Elaboration_Code_All,Aspect No_Inline,Aspect Max_Queue_Length,Implementation Defined Aspects
9520 @anchor{gnat_rm/implementation_defined_aspects aspect-no-elaboration-code-all}@anchor{13b}
9521 @section Aspect No_Elaboration_Code_All
9524 @geindex No_Elaboration_Code_All
9526 This aspect is equivalent to @ref{9f,,pragma No_Elaboration_Code_All}
9529 @node Aspect No_Inline,Aspect No_Tagged_Streams,Aspect No_Elaboration_Code_All,Implementation Defined Aspects
9530 @anchor{gnat_rm/implementation_defined_aspects aspect-no-inline}@anchor{13c}
9531 @section Aspect No_Inline
9536 This boolean aspect is equivalent to @ref{a2,,pragma No_Inline}.
9538 @node Aspect No_Tagged_Streams,Aspect Object_Size,Aspect No_Inline,Implementation Defined Aspects
9539 @anchor{gnat_rm/implementation_defined_aspects aspect-no-tagged-streams}@anchor{13d}
9540 @section Aspect No_Tagged_Streams
9543 @geindex No_Tagged_Streams
9545 This aspect is equivalent to @ref{a6,,pragma No_Tagged_Streams} with an
9546 argument specifying a root tagged type (thus this aspect can only be
9547 applied to such a type).
9549 @node Aspect Object_Size,Aspect Obsolescent,Aspect No_Tagged_Streams,Implementation Defined Aspects
9550 @anchor{gnat_rm/implementation_defined_aspects aspect-object-size}@anchor{13e}
9551 @section Aspect Object_Size
9554 @geindex Object_Size
9556 This aspect is equivalent to @ref{13f,,attribute Object_Size}.
9558 @node Aspect Obsolescent,Aspect Part_Of,Aspect Object_Size,Implementation Defined Aspects
9559 @anchor{gnat_rm/implementation_defined_aspects aspect-obsolescent}@anchor{140}
9560 @section Aspect Obsolescent
9563 @geindex Obsolsecent
9565 This aspect is equivalent to @ref{a9,,pragma Obsolescent}. Note that the
9566 evaluation of this aspect happens at the point of occurrence, it is not
9567 delayed until the freeze point.
9569 @node Aspect Part_Of,Aspect Persistent_BSS,Aspect Obsolescent,Implementation Defined Aspects
9570 @anchor{gnat_rm/implementation_defined_aspects aspect-part-of}@anchor{141}
9571 @section Aspect Part_Of
9576 This aspect is equivalent to @ref{b1,,pragma Part_Of}.
9578 @node Aspect Persistent_BSS,Aspect Predicate,Aspect Part_Of,Implementation Defined Aspects
9579 @anchor{gnat_rm/implementation_defined_aspects aspect-persistent-bss}@anchor{142}
9580 @section Aspect Persistent_BSS
9583 @geindex Persistent_BSS
9585 This boolean aspect is equivalent to @ref{b4,,pragma Persistent_BSS}.
9587 @node Aspect Predicate,Aspect Pure_Function,Aspect Persistent_BSS,Implementation Defined Aspects
9588 @anchor{gnat_rm/implementation_defined_aspects aspect-predicate}@anchor{143}
9589 @section Aspect Predicate
9594 This aspect is equivalent to @ref{bd,,pragma Predicate}. It is thus
9595 similar to the language defined aspects @code{Dynamic_Predicate}
9596 and @code{Static_Predicate} except that whether the resulting
9597 predicate is static or dynamic is controlled by the form of the
9598 expression. It is also separately controllable using pragma
9599 @code{Assertion_Policy}.
9601 @node Aspect Pure_Function,Aspect Refined_Depends,Aspect Predicate,Implementation Defined Aspects
9602 @anchor{gnat_rm/implementation_defined_aspects aspect-pure-function}@anchor{144}
9603 @section Aspect Pure_Function
9606 @geindex Pure_Function
9608 This boolean aspect is equivalent to @ref{c8,,pragma Pure_Function}.
9610 @node Aspect Refined_Depends,Aspect Refined_Global,Aspect Pure_Function,Implementation Defined Aspects
9611 @anchor{gnat_rm/implementation_defined_aspects aspect-refined-depends}@anchor{145}
9612 @section Aspect Refined_Depends
9615 @geindex Refined_Depends
9617 This aspect is equivalent to @ref{cc,,pragma Refined_Depends}.
9619 @node Aspect Refined_Global,Aspect Refined_Post,Aspect Refined_Depends,Implementation Defined Aspects
9620 @anchor{gnat_rm/implementation_defined_aspects aspect-refined-global}@anchor{146}
9621 @section Aspect Refined_Global
9624 @geindex Refined_Global
9626 This aspect is equivalent to @ref{ce,,pragma Refined_Global}.
9628 @node Aspect Refined_Post,Aspect Refined_State,Aspect Refined_Global,Implementation Defined Aspects
9629 @anchor{gnat_rm/implementation_defined_aspects aspect-refined-post}@anchor{147}
9630 @section Aspect Refined_Post
9633 @geindex Refined_Post
9635 This aspect is equivalent to @ref{d0,,pragma Refined_Post}.
9637 @node Aspect Refined_State,Aspect Remote_Access_Type,Aspect Refined_Post,Implementation Defined Aspects
9638 @anchor{gnat_rm/implementation_defined_aspects aspect-refined-state}@anchor{148}
9639 @section Aspect Refined_State
9642 @geindex Refined_State
9644 This aspect is equivalent to @ref{d2,,pragma Refined_State}.
9646 @node Aspect Remote_Access_Type,Aspect Secondary_Stack_Size,Aspect Refined_State,Implementation Defined Aspects
9647 @anchor{gnat_rm/implementation_defined_aspects aspect-remote-access-type}@anchor{149}
9648 @section Aspect Remote_Access_Type
9651 @geindex Remote_Access_Type
9653 This aspect is equivalent to @ref{d6,,pragma Remote_Access_Type}.
9655 @node Aspect Secondary_Stack_Size,Aspect Scalar_Storage_Order,Aspect Remote_Access_Type,Implementation Defined Aspects
9656 @anchor{gnat_rm/implementation_defined_aspects aspect-secondary-stack-size}@anchor{14a}
9657 @section Aspect Secondary_Stack_Size
9660 @geindex Secondary_Stack_Size
9662 This aspect is equivalent to @ref{db,,pragma Secondary_Stack_Size}.
9664 @node Aspect Scalar_Storage_Order,Aspect Shared,Aspect Secondary_Stack_Size,Implementation Defined Aspects
9665 @anchor{gnat_rm/implementation_defined_aspects aspect-scalar-storage-order}@anchor{14b}
9666 @section Aspect Scalar_Storage_Order
9669 @geindex Scalar_Storage_Order
9671 This aspect is equivalent to a @ref{14c,,attribute Scalar_Storage_Order}.
9673 @node Aspect Shared,Aspect Simple_Storage_Pool,Aspect Scalar_Storage_Order,Implementation Defined Aspects
9674 @anchor{gnat_rm/implementation_defined_aspects aspect-shared}@anchor{14d}
9675 @section Aspect Shared
9680 This boolean aspect is equivalent to @ref{de,,pragma Shared}
9681 and is thus a synonym for aspect @code{Atomic}.
9683 @node Aspect Simple_Storage_Pool,Aspect Simple_Storage_Pool_Type,Aspect Shared,Implementation Defined Aspects
9684 @anchor{gnat_rm/implementation_defined_aspects aspect-simple-storage-pool}@anchor{14e}
9685 @section Aspect Simple_Storage_Pool
9688 @geindex Simple_Storage_Pool
9690 This aspect is equivalent to @ref{e3,,attribute Simple_Storage_Pool}.
9692 @node Aspect Simple_Storage_Pool_Type,Aspect SPARK_Mode,Aspect Simple_Storage_Pool,Implementation Defined Aspects
9693 @anchor{gnat_rm/implementation_defined_aspects aspect-simple-storage-pool-type}@anchor{14f}
9694 @section Aspect Simple_Storage_Pool_Type
9697 @geindex Simple_Storage_Pool_Type
9699 This boolean aspect is equivalent to @ref{e1,,pragma Simple_Storage_Pool_Type}.
9701 @node Aspect SPARK_Mode,Aspect Suppress_Debug_Info,Aspect Simple_Storage_Pool_Type,Implementation Defined Aspects
9702 @anchor{gnat_rm/implementation_defined_aspects aspect-spark-mode}@anchor{150}
9703 @section Aspect SPARK_Mode
9708 This aspect is equivalent to @ref{e9,,pragma SPARK_Mode} and
9709 may be specified for either or both of the specification and body
9710 of a subprogram or package.
9712 @node Aspect Suppress_Debug_Info,Aspect Suppress_Initialization,Aspect SPARK_Mode,Implementation Defined Aspects
9713 @anchor{gnat_rm/implementation_defined_aspects aspect-suppress-debug-info}@anchor{151}
9714 @section Aspect Suppress_Debug_Info
9717 @geindex Suppress_Debug_Info
9719 This boolean aspect is equivalent to @ref{f1,,pragma Suppress_Debug_Info}.
9721 @node Aspect Suppress_Initialization,Aspect Test_Case,Aspect Suppress_Debug_Info,Implementation Defined Aspects
9722 @anchor{gnat_rm/implementation_defined_aspects aspect-suppress-initialization}@anchor{152}
9723 @section Aspect Suppress_Initialization
9726 @geindex Suppress_Initialization
9728 This boolean aspect is equivalent to @ref{f5,,pragma Suppress_Initialization}.
9730 @node Aspect Test_Case,Aspect Thread_Local_Storage,Aspect Suppress_Initialization,Implementation Defined Aspects
9731 @anchor{gnat_rm/implementation_defined_aspects aspect-test-case}@anchor{153}
9732 @section Aspect Test_Case
9737 This aspect is equivalent to @ref{f8,,pragma Test_Case}.
9739 @node Aspect Thread_Local_Storage,Aspect Universal_Aliasing,Aspect Test_Case,Implementation Defined Aspects
9740 @anchor{gnat_rm/implementation_defined_aspects aspect-thread-local-storage}@anchor{154}
9741 @section Aspect Thread_Local_Storage
9744 @geindex Thread_Local_Storage
9746 This boolean aspect is equivalent to @ref{fa,,pragma Thread_Local_Storage}.
9748 @node Aspect Universal_Aliasing,Aspect Universal_Data,Aspect Thread_Local_Storage,Implementation Defined Aspects
9749 @anchor{gnat_rm/implementation_defined_aspects aspect-universal-aliasing}@anchor{155}
9750 @section Aspect Universal_Aliasing
9753 @geindex Universal_Aliasing
9755 This boolean aspect is equivalent to @ref{105,,pragma Universal_Aliasing}.
9757 @node Aspect Universal_Data,Aspect Unmodified,Aspect Universal_Aliasing,Implementation Defined Aspects
9758 @anchor{gnat_rm/implementation_defined_aspects aspect-universal-data}@anchor{156}
9759 @section Aspect Universal_Data
9762 @geindex Universal_Data
9764 This aspect is equivalent to @ref{106,,pragma Universal_Data}.
9766 @node Aspect Unmodified,Aspect Unreferenced,Aspect Universal_Data,Implementation Defined Aspects
9767 @anchor{gnat_rm/implementation_defined_aspects aspect-unmodified}@anchor{157}
9768 @section Aspect Unmodified
9773 This boolean aspect is equivalent to @ref{108,,pragma Unmodified}.
9775 @node Aspect Unreferenced,Aspect Unreferenced_Objects,Aspect Unmodified,Implementation Defined Aspects
9776 @anchor{gnat_rm/implementation_defined_aspects aspect-unreferenced}@anchor{158}
9777 @section Aspect Unreferenced
9780 @geindex Unreferenced
9782 This boolean aspect is equivalent to @ref{10a,,pragma Unreferenced}. Note that
9783 in the case of formal parameters, it is not permitted to have aspects for
9784 a formal parameter, so in this case the pragma form must be used.
9786 @node Aspect Unreferenced_Objects,Aspect Value_Size,Aspect Unreferenced,Implementation Defined Aspects
9787 @anchor{gnat_rm/implementation_defined_aspects aspect-unreferenced-objects}@anchor{159}
9788 @section Aspect Unreferenced_Objects
9791 @geindex Unreferenced_Objects
9793 This boolean aspect is equivalent to @ref{10c,,pragma Unreferenced_Objects}.
9795 @node Aspect Value_Size,Aspect Volatile_Full_Access,Aspect Unreferenced_Objects,Implementation Defined Aspects
9796 @anchor{gnat_rm/implementation_defined_aspects aspect-value-size}@anchor{15a}
9797 @section Aspect Value_Size
9802 This aspect is equivalent to @ref{15b,,attribute Value_Size}.
9804 @node Aspect Volatile_Full_Access,Aspect Volatile_Function,Aspect Value_Size,Implementation Defined Aspects
9805 @anchor{gnat_rm/implementation_defined_aspects aspect-volatile-full-access}@anchor{15c}
9806 @section Aspect Volatile_Full_Access
9809 @geindex Volatile_Full_Access
9811 This boolean aspect is equivalent to @ref{115,,pragma Volatile_Full_Access}.
9813 @node Aspect Volatile_Function,Aspect Warnings,Aspect Volatile_Full_Access,Implementation Defined Aspects
9814 @anchor{gnat_rm/implementation_defined_aspects aspect-volatile-function}@anchor{15d}
9815 @section Aspect Volatile_Function
9818 @geindex Volatile_Function
9820 This boolean aspect is equivalent to @ref{118,,pragma Volatile_Function}.
9822 @node Aspect Warnings,,Aspect Volatile_Function,Implementation Defined Aspects
9823 @anchor{gnat_rm/implementation_defined_aspects aspect-warnings}@anchor{15e}
9824 @section Aspect Warnings
9829 This aspect is equivalent to the two argument form of @ref{11a,,pragma Warnings},
9830 where the first argument is @code{ON} or @code{OFF} and the second argument
9833 @node Implementation Defined Attributes,Standard and Implementation Defined Restrictions,Implementation Defined Aspects,Top
9834 @anchor{gnat_rm/implementation_defined_attributes doc}@anchor{15f}@anchor{gnat_rm/implementation_defined_attributes implementation-defined-attributes}@anchor{8}@anchor{gnat_rm/implementation_defined_attributes id1}@anchor{160}
9835 @chapter Implementation Defined Attributes
9838 Ada defines (throughout the Ada reference manual,
9839 summarized in Annex K),
9840 a set of attributes that provide useful additional functionality in all
9841 areas of the language. These language defined attributes are implemented
9842 in GNAT and work as described in the Ada Reference Manual.
9844 In addition, Ada allows implementations to define additional
9845 attributes whose meaning is defined by the implementation. GNAT provides
9846 a number of these implementation-dependent attributes which can be used
9847 to extend and enhance the functionality of the compiler. This section of
9848 the GNAT reference manual describes these additional attributes. It also
9849 describes additional implementation-dependent features of standard
9850 language-defined attributes.
9852 Note that any program using these attributes may not be portable to
9853 other compilers (although GNAT implements this set of attributes on all
9854 platforms). Therefore if portability to other compilers is an important
9855 consideration, you should minimize the use of these attributes.
9858 * Attribute Abort_Signal::
9859 * Attribute Address_Size::
9860 * Attribute Asm_Input::
9861 * Attribute Asm_Output::
9862 * Attribute Atomic_Always_Lock_Free::
9864 * Attribute Bit_Position::
9865 * Attribute Code_Address::
9866 * Attribute Compiler_Version::
9867 * Attribute Constrained::
9868 * Attribute Default_Bit_Order::
9869 * Attribute Default_Scalar_Storage_Order::
9871 * Attribute Descriptor_Size::
9872 * Attribute Elaborated::
9873 * Attribute Elab_Body::
9874 * Attribute Elab_Spec::
9875 * Attribute Elab_Subp_Body::
9877 * Attribute Enabled::
9878 * Attribute Enum_Rep::
9879 * Attribute Enum_Val::
9880 * Attribute Epsilon::
9881 * Attribute Fast_Math::
9882 * Attribute Finalization_Size::
9883 * Attribute Fixed_Value::
9884 * Attribute From_Any::
9885 * Attribute Has_Access_Values::
9886 * Attribute Has_Discriminants::
9888 * Attribute Integer_Value::
9889 * Attribute Invalid_Value::
9890 * Attribute Iterable::
9892 * Attribute Library_Level::
9893 * Attribute Lock_Free::
9894 * Attribute Loop_Entry::
9895 * Attribute Machine_Size::
9896 * Attribute Mantissa::
9897 * Attribute Maximum_Alignment::
9898 * Attribute Mechanism_Code::
9899 * Attribute Null_Parameter::
9900 * Attribute Object_Size::
9902 * Attribute Passed_By_Reference::
9903 * Attribute Pool_Address::
9904 * Attribute Range_Length::
9905 * Attribute Restriction_Set::
9906 * Attribute Result::
9907 * Attribute Safe_Emax::
9908 * Attribute Safe_Large::
9909 * Attribute Safe_Small::
9910 * Attribute Scalar_Storage_Order::
9911 * Attribute Simple_Storage_Pool::
9913 * Attribute Storage_Unit::
9914 * Attribute Stub_Type::
9915 * Attribute System_Allocator_Alignment::
9916 * Attribute Target_Name::
9917 * Attribute To_Address::
9918 * Attribute To_Any::
9919 * Attribute Type_Class::
9920 * Attribute Type_Key::
9921 * Attribute TypeCode::
9922 * Attribute Unconstrained_Array::
9923 * Attribute Universal_Literal_String::
9924 * Attribute Unrestricted_Access::
9925 * Attribute Update::
9926 * Attribute Valid_Scalars::
9927 * Attribute VADS_Size::
9928 * Attribute Value_Size::
9929 * Attribute Wchar_T_Size::
9930 * Attribute Word_Size::
9934 @node Attribute Abort_Signal,Attribute Address_Size,,Implementation Defined Attributes
9935 @anchor{gnat_rm/implementation_defined_attributes attribute-abort-signal}@anchor{161}
9936 @section Attribute Abort_Signal
9939 @geindex Abort_Signal
9941 @code{Standard'Abort_Signal} (@code{Standard} is the only allowed
9942 prefix) provides the entity for the special exception used to signal
9943 task abort or asynchronous transfer of control. Normally this attribute
9944 should only be used in the tasking runtime (it is highly peculiar, and
9945 completely outside the normal semantics of Ada, for a user program to
9946 intercept the abort exception).
9948 @node Attribute Address_Size,Attribute Asm_Input,Attribute Abort_Signal,Implementation Defined Attributes
9949 @anchor{gnat_rm/implementation_defined_attributes attribute-address-size}@anchor{162}
9950 @section Attribute Address_Size
9953 @geindex Size of `@w{`}Address`@w{`}
9955 @geindex Address_Size
9957 @code{Standard'Address_Size} (@code{Standard} is the only allowed
9958 prefix) is a static constant giving the number of bits in an
9959 @code{Address}. It is the same value as System.Address'Size,
9960 but has the advantage of being static, while a direct
9961 reference to System.Address'Size is nonstatic because Address
9964 @node Attribute Asm_Input,Attribute Asm_Output,Attribute Address_Size,Implementation Defined Attributes
9965 @anchor{gnat_rm/implementation_defined_attributes attribute-asm-input}@anchor{163}
9966 @section Attribute Asm_Input
9971 The @code{Asm_Input} attribute denotes a function that takes two
9972 parameters. The first is a string, the second is an expression of the
9973 type designated by the prefix. The first (string) argument is required
9974 to be a static expression, and is the constraint for the parameter,
9975 (e.g., what kind of register is required). The second argument is the
9976 value to be used as the input argument. The possible values for the
9977 constant are the same as those used in the RTL, and are dependent on
9978 the configuration file used to built the GCC back end.
9979 @ref{164,,Machine Code Insertions}
9981 @node Attribute Asm_Output,Attribute Atomic_Always_Lock_Free,Attribute Asm_Input,Implementation Defined Attributes
9982 @anchor{gnat_rm/implementation_defined_attributes attribute-asm-output}@anchor{165}
9983 @section Attribute Asm_Output
9988 The @code{Asm_Output} attribute denotes a function that takes two
9989 parameters. The first is a string, the second is the name of a variable
9990 of the type designated by the attribute prefix. The first (string)
9991 argument is required to be a static expression and designates the
9992 constraint for the parameter (e.g., what kind of register is
9993 required). The second argument is the variable to be updated with the
9994 result. The possible values for constraint are the same as those used in
9995 the RTL, and are dependent on the configuration file used to build the
9996 GCC back end. If there are no output operands, then this argument may
9997 either be omitted, or explicitly given as @code{No_Output_Operands}.
9998 @ref{164,,Machine Code Insertions}
10000 @node Attribute Atomic_Always_Lock_Free,Attribute Bit,Attribute Asm_Output,Implementation Defined Attributes
10001 @anchor{gnat_rm/implementation_defined_attributes attribute-atomic-always-lock-free}@anchor{166}
10002 @section Attribute Atomic_Always_Lock_Free
10005 @geindex Atomic_Always_Lock_Free
10007 The prefix of the @code{Atomic_Always_Lock_Free} attribute is a type.
10008 The result is a Boolean value which is True if the type has discriminants,
10009 and False otherwise. The result indicate whether atomic operations are
10010 supported by the target for the given type.
10012 @node Attribute Bit,Attribute Bit_Position,Attribute Atomic_Always_Lock_Free,Implementation Defined Attributes
10013 @anchor{gnat_rm/implementation_defined_attributes attribute-bit}@anchor{167}
10014 @section Attribute Bit
10019 @code{obj'Bit}, where @code{obj} is any object, yields the bit
10020 offset within the storage unit (byte) that contains the first bit of
10021 storage allocated for the object. The value of this attribute is of the
10022 type @emph{universal_integer}, and is always a non-negative number not
10023 exceeding the value of @code{System.Storage_Unit}.
10025 For an object that is a variable or a constant allocated in a register,
10026 the value is zero. (The use of this attribute does not force the
10027 allocation of a variable to memory).
10029 For an object that is a formal parameter, this attribute applies
10030 to either the matching actual parameter or to a copy of the
10031 matching actual parameter.
10033 For an access object the value is zero. Note that
10034 @code{obj.all'Bit} is subject to an @code{Access_Check} for the
10035 designated object. Similarly for a record component
10036 @code{X.C'Bit} is subject to a discriminant check and
10037 @code{X(I).Bit} and @code{X(I1..I2)'Bit}
10038 are subject to index checks.
10040 This attribute is designed to be compatible with the DEC Ada 83 definition
10041 and implementation of the @code{Bit} attribute.
10043 @node Attribute Bit_Position,Attribute Code_Address,Attribute Bit,Implementation Defined Attributes
10044 @anchor{gnat_rm/implementation_defined_attributes attribute-bit-position}@anchor{168}
10045 @section Attribute Bit_Position
10048 @geindex Bit_Position
10050 @code{R.C'Bit_Position}, where @code{R} is a record object and @code{C} is one
10051 of the fields of the record type, yields the bit
10052 offset within the record contains the first bit of
10053 storage allocated for the object. The value of this attribute is of the
10054 type @emph{universal_integer}. The value depends only on the field
10055 @code{C} and is independent of the alignment of
10056 the containing record @code{R}.
10058 @node Attribute Code_Address,Attribute Compiler_Version,Attribute Bit_Position,Implementation Defined Attributes
10059 @anchor{gnat_rm/implementation_defined_attributes attribute-code-address}@anchor{169}
10060 @section Attribute Code_Address
10063 @geindex Code_Address
10065 @geindex Subprogram address
10067 @geindex Address of subprogram code
10069 The @code{'Address}
10070 attribute may be applied to subprograms in Ada 95 and Ada 2005, but the
10071 intended effect seems to be to provide
10072 an address value which can be used to call the subprogram by means of
10073 an address clause as in the following example:
10079 for L'Address use K'Address;
10080 pragma Import (Ada, L);
10083 A call to @code{L} is then expected to result in a call to @code{K}.
10084 In Ada 83, where there were no access-to-subprogram values, this was
10085 a common work-around for getting the effect of an indirect call.
10086 GNAT implements the above use of @code{Address} and the technique
10087 illustrated by the example code works correctly.
10089 However, for some purposes, it is useful to have the address of the start
10090 of the generated code for the subprogram. On some architectures, this is
10091 not necessarily the same as the @code{Address} value described above.
10092 For example, the @code{Address} value may reference a subprogram
10093 descriptor rather than the subprogram itself.
10095 The @code{'Code_Address} attribute, which can only be applied to
10096 subprogram entities, always returns the address of the start of the
10097 generated code of the specified subprogram, which may or may not be
10098 the same value as is returned by the corresponding @code{'Address}
10101 @node Attribute Compiler_Version,Attribute Constrained,Attribute Code_Address,Implementation Defined Attributes
10102 @anchor{gnat_rm/implementation_defined_attributes attribute-compiler-version}@anchor{16a}
10103 @section Attribute Compiler_Version
10106 @geindex Compiler_Version
10108 @code{Standard'Compiler_Version} (@code{Standard} is the only allowed
10109 prefix) yields a static string identifying the version of the compiler
10110 being used to compile the unit containing the attribute reference.
10112 @node Attribute Constrained,Attribute Default_Bit_Order,Attribute Compiler_Version,Implementation Defined Attributes
10113 @anchor{gnat_rm/implementation_defined_attributes attribute-constrained}@anchor{16b}
10114 @section Attribute Constrained
10117 @geindex Constrained
10119 In addition to the usage of this attribute in the Ada RM, GNAT
10120 also permits the use of the @code{'Constrained} attribute
10121 in a generic template
10122 for any type, including types without discriminants. The value of this
10123 attribute in the generic instance when applied to a scalar type or a
10124 record type without discriminants is always @code{True}. This usage is
10125 compatible with older Ada compilers, including notably DEC Ada.
10127 @node Attribute Default_Bit_Order,Attribute Default_Scalar_Storage_Order,Attribute Constrained,Implementation Defined Attributes
10128 @anchor{gnat_rm/implementation_defined_attributes attribute-default-bit-order}@anchor{16c}
10129 @section Attribute Default_Bit_Order
10132 @geindex Big endian
10134 @geindex Little endian
10136 @geindex Default_Bit_Order
10138 @code{Standard'Default_Bit_Order} (@code{Standard} is the only
10139 permissible prefix), provides the value @code{System.Default_Bit_Order}
10140 as a @code{Pos} value (0 for @code{High_Order_First}, 1 for
10141 @code{Low_Order_First}). This is used to construct the definition of
10142 @code{Default_Bit_Order} in package @code{System}.
10144 @node Attribute Default_Scalar_Storage_Order,Attribute Deref,Attribute Default_Bit_Order,Implementation Defined Attributes
10145 @anchor{gnat_rm/implementation_defined_attributes attribute-default-scalar-storage-order}@anchor{16d}
10146 @section Attribute Default_Scalar_Storage_Order
10149 @geindex Big endian
10151 @geindex Little endian
10153 @geindex Default_Scalar_Storage_Order
10155 @code{Standard'Default_Scalar_Storage_Order} (@code{Standard} is the only
10156 permissible prefix), provides the current value of the default scalar storage
10157 order (as specified using pragma @code{Default_Scalar_Storage_Order}, or
10158 equal to @code{Default_Bit_Order} if unspecified) as a
10159 @code{System.Bit_Order} value. This is a static attribute.
10161 @node Attribute Deref,Attribute Descriptor_Size,Attribute Default_Scalar_Storage_Order,Implementation Defined Attributes
10162 @anchor{gnat_rm/implementation_defined_attributes attribute-deref}@anchor{16e}
10163 @section Attribute Deref
10168 The attribute @code{typ'Deref(expr)} where @code{expr} is of type @code{System.Address} yields
10169 the variable of type @code{typ} that is located at the given address. It is similar
10170 to @code{(totyp (expr).all)}, where @code{totyp} is an unchecked conversion from address to
10171 a named access-to-@cite{typ} type, except that it yields a variable, so it can be
10172 used on the left side of an assignment.
10174 @node Attribute Descriptor_Size,Attribute Elaborated,Attribute Deref,Implementation Defined Attributes
10175 @anchor{gnat_rm/implementation_defined_attributes attribute-descriptor-size}@anchor{16f}
10176 @section Attribute Descriptor_Size
10179 @geindex Descriptor
10181 @geindex Dope vector
10183 @geindex Descriptor_Size
10185 Nonstatic attribute @code{Descriptor_Size} returns the size in bits of the
10186 descriptor allocated for a type. The result is non-zero only for unconstrained
10187 array types and the returned value is of type universal integer. In GNAT, an
10188 array descriptor contains bounds information and is located immediately before
10189 the first element of the array.
10192 type Unconstr_Array is array (Positive range <>) of Boolean;
10193 Put_Line ("Descriptor size = " & Unconstr_Array'Descriptor_Size'Img);
10196 The attribute takes into account any additional padding due to type alignment.
10197 In the example above, the descriptor contains two values of type
10198 @code{Positive} representing the low and high bound. Since @code{Positive} has
10199 a size of 31 bits and an alignment of 4, the descriptor size is @code{2 * Positive'Size + 2} or 64 bits.
10201 @node Attribute Elaborated,Attribute Elab_Body,Attribute Descriptor_Size,Implementation Defined Attributes
10202 @anchor{gnat_rm/implementation_defined_attributes attribute-elaborated}@anchor{170}
10203 @section Attribute Elaborated
10206 @geindex Elaborated
10208 The prefix of the @code{'Elaborated} attribute must be a unit name. The
10209 value is a Boolean which indicates whether or not the given unit has been
10210 elaborated. This attribute is primarily intended for internal use by the
10211 generated code for dynamic elaboration checking, but it can also be used
10212 in user programs. The value will always be True once elaboration of all
10213 units has been completed. An exception is for units which need no
10214 elaboration, the value is always False for such units.
10216 @node Attribute Elab_Body,Attribute Elab_Spec,Attribute Elaborated,Implementation Defined Attributes
10217 @anchor{gnat_rm/implementation_defined_attributes attribute-elab-body}@anchor{171}
10218 @section Attribute Elab_Body
10223 This attribute can only be applied to a program unit name. It returns
10224 the entity for the corresponding elaboration procedure for elaborating
10225 the body of the referenced unit. This is used in the main generated
10226 elaboration procedure by the binder and is not normally used in any
10227 other context. However, there may be specialized situations in which it
10228 is useful to be able to call this elaboration procedure from Ada code,
10229 e.g., if it is necessary to do selective re-elaboration to fix some
10232 @node Attribute Elab_Spec,Attribute Elab_Subp_Body,Attribute Elab_Body,Implementation Defined Attributes
10233 @anchor{gnat_rm/implementation_defined_attributes attribute-elab-spec}@anchor{172}
10234 @section Attribute Elab_Spec
10239 This attribute can only be applied to a program unit name. It returns
10240 the entity for the corresponding elaboration procedure for elaborating
10241 the spec of the referenced unit. This is used in the main
10242 generated elaboration procedure by the binder and is not normally used
10243 in any other context. However, there may be specialized situations in
10244 which it is useful to be able to call this elaboration procedure from
10245 Ada code, e.g., if it is necessary to do selective re-elaboration to fix
10248 @node Attribute Elab_Subp_Body,Attribute Emax,Attribute Elab_Spec,Implementation Defined Attributes
10249 @anchor{gnat_rm/implementation_defined_attributes attribute-elab-subp-body}@anchor{173}
10250 @section Attribute Elab_Subp_Body
10253 @geindex Elab_Subp_Body
10255 This attribute can only be applied to a library level subprogram
10256 name and is only allowed in CodePeer mode. It returns the entity
10257 for the corresponding elaboration procedure for elaborating the body
10258 of the referenced subprogram unit. This is used in the main generated
10259 elaboration procedure by the binder in CodePeer mode only and is unrecognized
10262 @node Attribute Emax,Attribute Enabled,Attribute Elab_Subp_Body,Implementation Defined Attributes
10263 @anchor{gnat_rm/implementation_defined_attributes attribute-emax}@anchor{174}
10264 @section Attribute Emax
10267 @geindex Ada 83 attributes
10271 The @code{Emax} attribute is provided for compatibility with Ada 83. See
10272 the Ada 83 reference manual for an exact description of the semantics of
10275 @node Attribute Enabled,Attribute Enum_Rep,Attribute Emax,Implementation Defined Attributes
10276 @anchor{gnat_rm/implementation_defined_attributes attribute-enabled}@anchor{175}
10277 @section Attribute Enabled
10282 The @code{Enabled} attribute allows an application program to check at compile
10283 time to see if the designated check is currently enabled. The prefix is a
10284 simple identifier, referencing any predefined check name (other than
10285 @code{All_Checks}) or a check name introduced by pragma Check_Name. If
10286 no argument is given for the attribute, the check is for the general state
10287 of the check, if an argument is given, then it is an entity name, and the
10288 check indicates whether an @code{Suppress} or @code{Unsuppress} has been
10289 given naming the entity (if not, then the argument is ignored).
10291 Note that instantiations inherit the check status at the point of the
10292 instantiation, so a useful idiom is to have a library package that
10293 introduces a check name with @code{pragma Check_Name}, and then contains
10294 generic packages or subprograms which use the @code{Enabled} attribute
10295 to see if the check is enabled. A user of this package can then issue
10296 a @code{pragma Suppress} or @code{pragma Unsuppress} before instantiating
10297 the package or subprogram, controlling whether the check will be present.
10299 @node Attribute Enum_Rep,Attribute Enum_Val,Attribute Enabled,Implementation Defined Attributes
10300 @anchor{gnat_rm/implementation_defined_attributes attribute-enum-rep}@anchor{176}
10301 @section Attribute Enum_Rep
10304 @geindex Representation of enums
10308 For every enumeration subtype @code{S}, @code{S'Enum_Rep} denotes a
10309 function with the following spec:
10312 function S'Enum_Rep (Arg : S'Base) return <Universal_Integer>;
10315 It is also allowable to apply @code{Enum_Rep} directly to an object of an
10316 enumeration type or to a non-overloaded enumeration
10317 literal. In this case @code{S'Enum_Rep} is equivalent to
10318 @code{typ'Enum_Rep(S)} where @code{typ} is the type of the
10319 enumeration literal or object.
10321 The function returns the representation value for the given enumeration
10322 value. This will be equal to value of the @code{Pos} attribute in the
10323 absence of an enumeration representation clause. This is a static
10324 attribute (i.e.,:the result is static if the argument is static).
10326 @code{S'Enum_Rep} can also be used with integer types and objects,
10327 in which case it simply returns the integer value. The reason for this
10328 is to allow it to be used for @code{(<>)} discrete formal arguments in
10329 a generic unit that can be instantiated with either enumeration types
10330 or integer types. Note that if @code{Enum_Rep} is used on a modular
10331 type whose upper bound exceeds the upper bound of the largest signed
10332 integer type, and the argument is a variable, so that the universal
10333 integer calculation is done at run time, then the call to @code{Enum_Rep}
10334 may raise @code{Constraint_Error}.
10336 @node Attribute Enum_Val,Attribute Epsilon,Attribute Enum_Rep,Implementation Defined Attributes
10337 @anchor{gnat_rm/implementation_defined_attributes attribute-enum-val}@anchor{177}
10338 @section Attribute Enum_Val
10341 @geindex Representation of enums
10345 For every enumeration subtype @code{S}, @code{S'Enum_Val} denotes a
10346 function with the following spec:
10349 function S'Enum_Val (Arg : <Universal_Integer>) return S'Base;
10352 The function returns the enumeration value whose representation matches the
10353 argument, or raises Constraint_Error if no enumeration literal of the type
10354 has the matching value.
10355 This will be equal to value of the @code{Val} attribute in the
10356 absence of an enumeration representation clause. This is a static
10357 attribute (i.e., the result is static if the argument is static).
10359 @node Attribute Epsilon,Attribute Fast_Math,Attribute Enum_Val,Implementation Defined Attributes
10360 @anchor{gnat_rm/implementation_defined_attributes attribute-epsilon}@anchor{178}
10361 @section Attribute Epsilon
10364 @geindex Ada 83 attributes
10368 The @code{Epsilon} attribute is provided for compatibility with Ada 83. See
10369 the Ada 83 reference manual for an exact description of the semantics of
10372 @node Attribute Fast_Math,Attribute Finalization_Size,Attribute Epsilon,Implementation Defined Attributes
10373 @anchor{gnat_rm/implementation_defined_attributes attribute-fast-math}@anchor{179}
10374 @section Attribute Fast_Math
10379 @code{Standard'Fast_Math} (@code{Standard} is the only allowed
10380 prefix) yields a static Boolean value that is True if pragma
10381 @code{Fast_Math} is active, and False otherwise.
10383 @node Attribute Finalization_Size,Attribute Fixed_Value,Attribute Fast_Math,Implementation Defined Attributes
10384 @anchor{gnat_rm/implementation_defined_attributes attribute-finalization-size}@anchor{17a}
10385 @section Attribute Finalization_Size
10388 @geindex Finalization_Size
10390 The prefix of attribute @code{Finalization_Size} must be an object or
10391 a non-class-wide type. This attribute returns the size of any hidden data
10392 reserved by the compiler to handle finalization-related actions. The type of
10393 the attribute is @emph{universal_integer}.
10395 @code{Finalization_Size} yields a value of zero for a type with no controlled
10396 parts, an object whose type has no controlled parts, or an object of a
10397 class-wide type whose tag denotes a type with no controlled parts.
10399 Note that only heap-allocated objects contain finalization data.
10401 @node Attribute Fixed_Value,Attribute From_Any,Attribute Finalization_Size,Implementation Defined Attributes
10402 @anchor{gnat_rm/implementation_defined_attributes attribute-fixed-value}@anchor{17b}
10403 @section Attribute Fixed_Value
10406 @geindex Fixed_Value
10408 For every fixed-point type @code{S}, @code{S'Fixed_Value} denotes a
10409 function with the following specification:
10412 function S'Fixed_Value (Arg : <Universal_Integer>) return S;
10415 The value returned is the fixed-point value @code{V} such that:
10421 The effect is thus similar to first converting the argument to the
10422 integer type used to represent @code{S}, and then doing an unchecked
10423 conversion to the fixed-point type. The difference is
10424 that there are full range checks, to ensure that the result is in range.
10425 This attribute is primarily intended for use in implementation of the
10426 input-output functions for fixed-point values.
10428 @node Attribute From_Any,Attribute Has_Access_Values,Attribute Fixed_Value,Implementation Defined Attributes
10429 @anchor{gnat_rm/implementation_defined_attributes attribute-from-any}@anchor{17c}
10430 @section Attribute From_Any
10435 This internal attribute is used for the generation of remote subprogram
10436 stubs in the context of the Distributed Systems Annex.
10438 @node Attribute Has_Access_Values,Attribute Has_Discriminants,Attribute From_Any,Implementation Defined Attributes
10439 @anchor{gnat_rm/implementation_defined_attributes attribute-has-access-values}@anchor{17d}
10440 @section Attribute Has_Access_Values
10443 @geindex Access values
10444 @geindex testing for
10446 @geindex Has_Access_Values
10448 The prefix of the @code{Has_Access_Values} attribute is a type. The result
10449 is a Boolean value which is True if the is an access type, or is a composite
10450 type with a component (at any nesting depth) that is an access type, and is
10452 The intended use of this attribute is in conjunction with generic
10453 definitions. If the attribute is applied to a generic private type, it
10454 indicates whether or not the corresponding actual type has access values.
10456 @node Attribute Has_Discriminants,Attribute Img,Attribute Has_Access_Values,Implementation Defined Attributes
10457 @anchor{gnat_rm/implementation_defined_attributes attribute-has-discriminants}@anchor{17e}
10458 @section Attribute Has_Discriminants
10461 @geindex Discriminants
10462 @geindex testing for
10464 @geindex Has_Discriminants
10466 The prefix of the @code{Has_Discriminants} attribute is a type. The result
10467 is a Boolean value which is True if the type has discriminants, and False
10468 otherwise. The intended use of this attribute is in conjunction with generic
10469 definitions. If the attribute is applied to a generic private type, it
10470 indicates whether or not the corresponding actual type has discriminants.
10472 @node Attribute Img,Attribute Integer_Value,Attribute Has_Discriminants,Implementation Defined Attributes
10473 @anchor{gnat_rm/implementation_defined_attributes attribute-img}@anchor{17f}
10474 @section Attribute Img
10479 The @code{Img} attribute differs from @code{Image} in that it is applied
10480 directly to an object, and yields the same result as
10481 @code{Image} for the subtype of the object. This is convenient for
10485 Put_Line ("X = " & X'Img);
10488 has the same meaning as the more verbose:
10491 Put_Line ("X = " & T'Image (X));
10494 where @code{T} is the (sub)type of the object @code{X}.
10496 Note that technically, in analogy to @code{Image},
10497 @code{X'Img} returns a parameterless function
10498 that returns the appropriate string when called. This means that
10499 @code{X'Img} can be renamed as a function-returning-string, or used
10500 in an instantiation as a function parameter.
10502 @node Attribute Integer_Value,Attribute Invalid_Value,Attribute Img,Implementation Defined Attributes
10503 @anchor{gnat_rm/implementation_defined_attributes attribute-integer-value}@anchor{180}
10504 @section Attribute Integer_Value
10507 @geindex Integer_Value
10509 For every integer type @code{S}, @code{S'Integer_Value} denotes a
10510 function with the following spec:
10513 function S'Integer_Value (Arg : <Universal_Fixed>) return S;
10516 The value returned is the integer value @code{V}, such that:
10522 where @code{T} is the type of @code{Arg}.
10523 The effect is thus similar to first doing an unchecked conversion from
10524 the fixed-point type to its corresponding implementation type, and then
10525 converting the result to the target integer type. The difference is
10526 that there are full range checks, to ensure that the result is in range.
10527 This attribute is primarily intended for use in implementation of the
10528 standard input-output functions for fixed-point values.
10530 @node Attribute Invalid_Value,Attribute Iterable,Attribute Integer_Value,Implementation Defined Attributes
10531 @anchor{gnat_rm/implementation_defined_attributes attribute-invalid-value}@anchor{181}
10532 @section Attribute Invalid_Value
10535 @geindex Invalid_Value
10537 For every scalar type S, S'Invalid_Value returns an undefined value of the
10538 type. If possible this value is an invalid representation for the type. The
10539 value returned is identical to the value used to initialize an otherwise
10540 uninitialized value of the type if pragma Initialize_Scalars is used,
10541 including the ability to modify the value with the binder -Sxx flag and
10542 relevant environment variables at run time.
10544 @node Attribute Iterable,Attribute Large,Attribute Invalid_Value,Implementation Defined Attributes
10545 @anchor{gnat_rm/implementation_defined_attributes attribute-iterable}@anchor{182}
10546 @section Attribute Iterable
10551 Equivalent to Aspect Iterable.
10553 @node Attribute Large,Attribute Library_Level,Attribute Iterable,Implementation Defined Attributes
10554 @anchor{gnat_rm/implementation_defined_attributes attribute-large}@anchor{183}
10555 @section Attribute Large
10558 @geindex Ada 83 attributes
10562 The @code{Large} attribute is provided for compatibility with Ada 83. See
10563 the Ada 83 reference manual for an exact description of the semantics of
10566 @node Attribute Library_Level,Attribute Lock_Free,Attribute Large,Implementation Defined Attributes
10567 @anchor{gnat_rm/implementation_defined_attributes attribute-library-level}@anchor{184}
10568 @section Attribute Library_Level
10571 @geindex Library_Level
10573 @code{P'Library_Level}, where P is an entity name,
10574 returns a Boolean value which is True if the entity is declared
10575 at the library level, and False otherwise. Note that within a
10576 generic instantition, the name of the generic unit denotes the
10577 instance, which means that this attribute can be used to test
10578 if a generic is instantiated at the library level, as shown
10585 pragma Compile_Time_Error
10586 (not Gen'Library_Level,
10587 "Gen can only be instantiated at library level");
10592 @node Attribute Lock_Free,Attribute Loop_Entry,Attribute Library_Level,Implementation Defined Attributes
10593 @anchor{gnat_rm/implementation_defined_attributes attribute-lock-free}@anchor{185}
10594 @section Attribute Lock_Free
10599 @code{P'Lock_Free}, where P is a protected object, returns True if a
10600 pragma @code{Lock_Free} applies to P.
10602 @node Attribute Loop_Entry,Attribute Machine_Size,Attribute Lock_Free,Implementation Defined Attributes
10603 @anchor{gnat_rm/implementation_defined_attributes attribute-loop-entry}@anchor{186}
10604 @section Attribute Loop_Entry
10607 @geindex Loop_Entry
10612 X'Loop_Entry [(loop_name)]
10615 The @code{Loop_Entry} attribute is used to refer to the value that an
10616 expression had upon entry to a given loop in much the same way that the
10617 @code{Old} attribute in a subprogram postcondition can be used to refer
10618 to the value an expression had upon entry to the subprogram. The
10619 relevant loop is either identified by the given loop name, or it is the
10620 innermost enclosing loop when no loop name is given.
10622 A @code{Loop_Entry} attribute can only occur within a
10623 @code{Loop_Variant} or @code{Loop_Invariant} pragma. A common use of
10624 @code{Loop_Entry} is to compare the current value of objects with their
10625 initial value at loop entry, in a @code{Loop_Invariant} pragma.
10627 The effect of using @code{X'Loop_Entry} is the same as declaring
10628 a constant initialized with the initial value of @code{X} at loop
10629 entry. This copy is not performed if the loop is not entered, or if the
10630 corresponding pragmas are ignored or disabled.
10632 @node Attribute Machine_Size,Attribute Mantissa,Attribute Loop_Entry,Implementation Defined Attributes
10633 @anchor{gnat_rm/implementation_defined_attributes attribute-machine-size}@anchor{187}
10634 @section Attribute Machine_Size
10637 @geindex Machine_Size
10639 This attribute is identical to the @code{Object_Size} attribute. It is
10640 provided for compatibility with the DEC Ada 83 attribute of this name.
10642 @node Attribute Mantissa,Attribute Maximum_Alignment,Attribute Machine_Size,Implementation Defined Attributes
10643 @anchor{gnat_rm/implementation_defined_attributes attribute-mantissa}@anchor{188}
10644 @section Attribute Mantissa
10647 @geindex Ada 83 attributes
10651 The @code{Mantissa} attribute is provided for compatibility with Ada 83. See
10652 the Ada 83 reference manual for an exact description of the semantics of
10655 @node Attribute Maximum_Alignment,Attribute Mechanism_Code,Attribute Mantissa,Implementation Defined Attributes
10656 @anchor{gnat_rm/implementation_defined_attributes attribute-maximum-alignment}@anchor{189}@anchor{gnat_rm/implementation_defined_attributes id2}@anchor{18a}
10657 @section Attribute Maximum_Alignment
10663 @geindex Maximum_Alignment
10665 @code{Standard'Maximum_Alignment} (@code{Standard} is the only
10666 permissible prefix) provides the maximum useful alignment value for the
10667 target. This is a static value that can be used to specify the alignment
10668 for an object, guaranteeing that it is properly aligned in all
10671 @node Attribute Mechanism_Code,Attribute Null_Parameter,Attribute Maximum_Alignment,Implementation Defined Attributes
10672 @anchor{gnat_rm/implementation_defined_attributes attribute-mechanism-code}@anchor{18b}
10673 @section Attribute Mechanism_Code
10676 @geindex Return values
10677 @geindex passing mechanism
10679 @geindex Parameters
10680 @geindex passing mechanism
10682 @geindex Mechanism_Code
10684 @code{func'Mechanism_Code} yields an integer code for the
10685 mechanism used for the result of function @code{func}, and
10686 @code{subprog'Mechanism_Code (n)} yields the mechanism
10687 used for formal parameter number @emph{n} (a static integer value, with 1
10688 meaning the first parameter) of subprogram @code{subprog}. The code returned is:
10702 @node Attribute Null_Parameter,Attribute Object_Size,Attribute Mechanism_Code,Implementation Defined Attributes
10703 @anchor{gnat_rm/implementation_defined_attributes attribute-null-parameter}@anchor{18c}
10704 @section Attribute Null_Parameter
10707 @geindex Zero address
10710 @geindex Null_Parameter
10712 A reference @code{T'Null_Parameter} denotes an imaginary object of
10713 type or subtype @code{T} allocated at machine address zero. The attribute
10714 is allowed only as the default expression of a formal parameter, or as
10715 an actual expression of a subprogram call. In either case, the
10716 subprogram must be imported.
10718 The identity of the object is represented by the address zero in the
10719 argument list, independent of the passing mechanism (explicit or
10722 This capability is needed to specify that a zero address should be
10723 passed for a record or other composite object passed by reference.
10724 There is no way of indicating this without the @code{Null_Parameter}
10727 @node Attribute Object_Size,Attribute Old,Attribute Null_Parameter,Implementation Defined Attributes
10728 @anchor{gnat_rm/implementation_defined_attributes attribute-object-size}@anchor{13f}@anchor{gnat_rm/implementation_defined_attributes id3}@anchor{18d}
10729 @section Attribute Object_Size
10733 @geindex used for objects
10735 @geindex Object_Size
10737 The size of an object is not necessarily the same as the size of the type
10738 of an object. This is because by default object sizes are increased to be
10739 a multiple of the alignment of the object. For example,
10740 @code{Natural'Size} is
10741 31, but by default objects of type @code{Natural} will have a size of 32 bits.
10742 Similarly, a record containing an integer and a character:
10751 will have a size of 40 (that is @code{Rec'Size} will be 40). The
10752 alignment will be 4, because of the
10753 integer field, and so the default size of record objects for this type
10754 will be 64 (8 bytes).
10756 If the alignment of the above record is specified to be 1, then the
10757 object size will be 40 (5 bytes). This is true by default, and also
10758 an object size of 40 can be explicitly specified in this case.
10760 A consequence of this capability is that different object sizes can be
10761 given to subtypes that would otherwise be considered in Ada to be
10762 statically matching. But it makes no sense to consider such subtypes
10763 as statically matching. Consequently, GNAT adds a rule
10764 to the static matching rules that requires object sizes to match.
10765 Consider this example:
10768 1. procedure BadAVConvert is
10769 2. type R is new Integer;
10770 3. subtype R1 is R range 1 .. 10;
10771 4. subtype R2 is R range 1 .. 10;
10772 5. for R1'Object_Size use 8;
10773 6. for R2'Object_Size use 16;
10774 7. type R1P is access all R1;
10775 8. type R2P is access all R2;
10776 9. R1PV : R1P := new R1'(4);
10779 12. R2PV := R2P (R1PV);
10781 >>> target designated subtype not compatible with
10782 type "R1" defined at line 3
10787 In the absence of lines 5 and 6,
10788 types @code{R1} and @code{R2} statically match and
10789 hence the conversion on line 12 is legal. But since lines 5 and 6
10790 cause the object sizes to differ, GNAT considers that types
10791 @code{R1} and @code{R2} are not statically matching, and line 12
10792 generates the diagnostic shown above.
10794 Similar additional checks are performed in other contexts requiring
10795 statically matching subtypes.
10797 @node Attribute Old,Attribute Passed_By_Reference,Attribute Object_Size,Implementation Defined Attributes
10798 @anchor{gnat_rm/implementation_defined_attributes attribute-old}@anchor{18e}
10799 @section Attribute Old
10804 In addition to the usage of @code{Old} defined in the Ada 2012 RM (usage
10805 within @code{Post} aspect), GNAT also permits the use of this attribute
10806 in implementation defined pragmas @code{Postcondition},
10807 @code{Contract_Cases} and @code{Test_Case}. Also usages of
10808 @code{Old} which would be illegal according to the Ada 2012 RM
10809 definition are allowed under control of
10810 implementation defined pragma @code{Unevaluated_Use_Of_Old}.
10812 @node Attribute Passed_By_Reference,Attribute Pool_Address,Attribute Old,Implementation Defined Attributes
10813 @anchor{gnat_rm/implementation_defined_attributes attribute-passed-by-reference}@anchor{18f}
10814 @section Attribute Passed_By_Reference
10817 @geindex Parameters
10818 @geindex when passed by reference
10820 @geindex Passed_By_Reference
10822 @code{typ'Passed_By_Reference} for any subtype @cite{typ} returns
10823 a value of type @code{Boolean} value that is @code{True} if the type is
10824 normally passed by reference and @code{False} if the type is normally
10825 passed by copy in calls. For scalar types, the result is always @code{False}
10826 and is static. For non-scalar types, the result is nonstatic.
10828 @node Attribute Pool_Address,Attribute Range_Length,Attribute Passed_By_Reference,Implementation Defined Attributes
10829 @anchor{gnat_rm/implementation_defined_attributes attribute-pool-address}@anchor{190}
10830 @section Attribute Pool_Address
10833 @geindex Parameters
10834 @geindex when passed by reference
10836 @geindex Pool_Address
10838 @code{X'Pool_Address} for any object @code{X} returns the address
10839 of X within its storage pool. This is the same as
10840 @code{X'Address}, except that for an unconstrained array whose
10841 bounds are allocated just before the first component,
10842 @code{X'Pool_Address} returns the address of those bounds,
10843 whereas @code{X'Address} returns the address of the first
10846 Here, we are interpreting 'storage pool' broadly to mean
10847 @code{wherever the object is allocated}, which could be a
10848 user-defined storage pool,
10849 the global heap, on the stack, or in a static memory area.
10850 For an object created by @code{new}, @code{Ptr.all'Pool_Address} is
10851 what is passed to @code{Allocate} and returned from @code{Deallocate}.
10853 @node Attribute Range_Length,Attribute Restriction_Set,Attribute Pool_Address,Implementation Defined Attributes
10854 @anchor{gnat_rm/implementation_defined_attributes attribute-range-length}@anchor{191}
10855 @section Attribute Range_Length
10858 @geindex Range_Length
10860 @code{typ'Range_Length} for any discrete type @cite{typ} yields
10861 the number of values represented by the subtype (zero for a null
10862 range). The result is static for static subtypes. @code{Range_Length}
10863 applied to the index subtype of a one dimensional array always gives the
10864 same result as @code{Length} applied to the array itself.
10866 @node Attribute Restriction_Set,Attribute Result,Attribute Range_Length,Implementation Defined Attributes
10867 @anchor{gnat_rm/implementation_defined_attributes attribute-restriction-set}@anchor{192}
10868 @section Attribute Restriction_Set
10871 @geindex Restriction_Set
10873 @geindex Restrictions
10875 This attribute allows compile time testing of restrictions that
10876 are currently in effect. It is primarily intended for specializing
10877 code in the run-time based on restrictions that are active (e.g.
10878 don't need to save fpt registers if restriction No_Floating_Point
10879 is known to be in effect), but can be used anywhere.
10881 There are two forms:
10884 System'Restriction_Set (partition_boolean_restriction_NAME)
10885 System'Restriction_Set (No_Dependence => library_unit_NAME);
10888 In the case of the first form, the only restriction names
10889 allowed are parameterless restrictions that are checked
10890 for consistency at bind time. For a complete list see the
10891 subtype @code{System.Rident.Partition_Boolean_Restrictions}.
10893 The result returned is True if the restriction is known to
10894 be in effect, and False if the restriction is known not to
10895 be in effect. An important guarantee is that the value of
10896 a Restriction_Set attribute is known to be consistent throughout
10897 all the code of a partition.
10899 This is trivially achieved if the entire partition is compiled
10900 with a consistent set of restriction pragmas. However, the
10901 compilation model does not require this. It is possible to
10902 compile one set of units with one set of pragmas, and another
10903 set of units with another set of pragmas. It is even possible
10904 to compile a spec with one set of pragmas, and then WITH the
10905 same spec with a different set of pragmas. Inconsistencies
10906 in the actual use of the restriction are checked at bind time.
10908 In order to achieve the guarantee of consistency for the
10909 Restriction_Set pragma, we consider that a use of the pragma
10910 that yields False is equivalent to a violation of the
10913 So for example if you write
10916 if System'Restriction_Set (No_Floating_Point) then
10923 And the result is False, so that the else branch is executed,
10924 you can assume that this restriction is not set for any unit
10925 in the partition. This is checked by considering this use of
10926 the restriction pragma to be a violation of the restriction
10927 No_Floating_Point. This means that no other unit can attempt
10928 to set this restriction (if some unit does attempt to set it,
10929 the binder will refuse to bind the partition).
10931 Technical note: The restriction name and the unit name are
10932 intepreted entirely syntactically, as in the corresponding
10933 Restrictions pragma, they are not analyzed semantically,
10934 so they do not have a type.
10936 @node Attribute Result,Attribute Safe_Emax,Attribute Restriction_Set,Implementation Defined Attributes
10937 @anchor{gnat_rm/implementation_defined_attributes attribute-result}@anchor{193}
10938 @section Attribute Result
10943 @code{function'Result} can only be used with in a Postcondition pragma
10944 for a function. The prefix must be the name of the corresponding function. This
10945 is used to refer to the result of the function in the postcondition expression.
10946 For a further discussion of the use of this attribute and examples of its use,
10947 see the description of pragma Postcondition.
10949 @node Attribute Safe_Emax,Attribute Safe_Large,Attribute Result,Implementation Defined Attributes
10950 @anchor{gnat_rm/implementation_defined_attributes attribute-safe-emax}@anchor{194}
10951 @section Attribute Safe_Emax
10954 @geindex Ada 83 attributes
10958 The @code{Safe_Emax} attribute is provided for compatibility with Ada 83. See
10959 the Ada 83 reference manual for an exact description of the semantics of
10962 @node Attribute Safe_Large,Attribute Safe_Small,Attribute Safe_Emax,Implementation Defined Attributes
10963 @anchor{gnat_rm/implementation_defined_attributes attribute-safe-large}@anchor{195}
10964 @section Attribute Safe_Large
10967 @geindex Ada 83 attributes
10969 @geindex Safe_Large
10971 The @code{Safe_Large} attribute is provided for compatibility with Ada 83. See
10972 the Ada 83 reference manual for an exact description of the semantics of
10975 @node Attribute Safe_Small,Attribute Scalar_Storage_Order,Attribute Safe_Large,Implementation Defined Attributes
10976 @anchor{gnat_rm/implementation_defined_attributes attribute-safe-small}@anchor{196}
10977 @section Attribute Safe_Small
10980 @geindex Ada 83 attributes
10982 @geindex Safe_Small
10984 The @code{Safe_Small} attribute is provided for compatibility with Ada 83. See
10985 the Ada 83 reference manual for an exact description of the semantics of
10988 @node Attribute Scalar_Storage_Order,Attribute Simple_Storage_Pool,Attribute Safe_Small,Implementation Defined Attributes
10989 @anchor{gnat_rm/implementation_defined_attributes id4}@anchor{197}@anchor{gnat_rm/implementation_defined_attributes attribute-scalar-storage-order}@anchor{14c}
10990 @section Attribute Scalar_Storage_Order
10993 @geindex Endianness
10995 @geindex Scalar storage order
10997 @geindex Scalar_Storage_Order
10999 For every array or record type @code{S}, the representation attribute
11000 @code{Scalar_Storage_Order} denotes the order in which storage elements
11001 that make up scalar components are ordered within S. The value given must
11002 be a static expression of type System.Bit_Order. The following is an example
11003 of the use of this feature:
11006 -- Component type definitions
11008 subtype Yr_Type is Natural range 0 .. 127;
11009 subtype Mo_Type is Natural range 1 .. 12;
11010 subtype Da_Type is Natural range 1 .. 31;
11012 -- Record declaration
11014 type Date is record
11015 Years_Since_1980 : Yr_Type;
11017 Day_Of_Month : Da_Type;
11020 -- Record representation clause
11022 for Date use record
11023 Years_Since_1980 at 0 range 0 .. 6;
11024 Month at 0 range 7 .. 10;
11025 Day_Of_Month at 0 range 11 .. 15;
11028 -- Attribute definition clauses
11030 for Date'Bit_Order use System.High_Order_First;
11031 for Date'Scalar_Storage_Order use System.High_Order_First;
11032 -- If Scalar_Storage_Order is specified, it must be consistent with
11033 -- Bit_Order, so it's best to always define the latter explicitly if
11034 -- the former is used.
11037 Other properties are as for standard representation attribute @code{Bit_Order},
11038 as defined by Ada RM 13.5.3(4). The default is @code{System.Default_Bit_Order}.
11040 For a record type @code{T}, if @code{T'Scalar_Storage_Order} is
11041 specified explicitly, it shall be equal to @code{T'Bit_Order}. Note:
11042 this means that if a @code{Scalar_Storage_Order} attribute definition
11043 clause is not confirming, then the type's @code{Bit_Order} shall be
11044 specified explicitly and set to the same value.
11046 Derived types inherit an explicitly set scalar storage order from their parent
11047 types. This may be overridden for the derived type by giving an explicit scalar
11048 storage order for the derived type. For a record extension, the derived type
11049 must have the same scalar storage order as the parent type.
11051 A component of a record type that is itself a record or an array and that does
11052 not start and end on a byte boundary must have have the same scalar storage
11053 order as the record type. A component of a bit-packed array type that is itself
11054 a record or an array must have the same scalar storage order as the array type.
11056 No component of a type that has an explicit @code{Scalar_Storage_Order}
11057 attribute definition may be aliased.
11059 A confirming @code{Scalar_Storage_Order} attribute definition clause (i.e.
11060 with a value equal to @code{System.Default_Bit_Order}) has no effect.
11062 If the opposite storage order is specified, then whenever the value of
11063 a scalar component of an object of type @code{S} is read, the storage
11064 elements of the enclosing machine scalar are first reversed (before
11065 retrieving the component value, possibly applying some shift and mask
11066 operatings on the enclosing machine scalar), and the opposite operation
11067 is done for writes.
11069 In that case, the restrictions set forth in 13.5.1(10.3/2) for scalar components
11070 are relaxed. Instead, the following rules apply:
11076 the underlying storage elements are those at positions
11077 @code{(position + first_bit / storage_element_size) .. (position + (last_bit + storage_element_size - 1) / storage_element_size)}
11080 the sequence of underlying storage elements shall have
11081 a size no greater than the largest machine scalar
11084 the enclosing machine scalar is defined as the smallest machine
11085 scalar starting at a position no greater than
11086 @code{position + first_bit / storage_element_size} and covering
11087 storage elements at least up to @code{position + (last_bit + storage_element_size - 1) / storage_element_size`}
11090 the position of the component is interpreted relative to that machine
11094 If no scalar storage order is specified for a type (either directly, or by
11095 inheritance in the case of a derived type), then the default is normally
11096 the native ordering of the target, but this default can be overridden using
11097 pragma @code{Default_Scalar_Storage_Order}.
11099 Note that if a component of @code{T} is itself of a record or array type,
11100 the specfied @code{Scalar_Storage_Order} does @emph{not} apply to that nested type:
11101 an explicit attribute definition clause must be provided for the component
11102 type as well if desired.
11104 Note that the scalar storage order only affects the in-memory data
11105 representation. It has no effect on the representation used by stream
11108 @node Attribute Simple_Storage_Pool,Attribute Small,Attribute Scalar_Storage_Order,Implementation Defined Attributes
11109 @anchor{gnat_rm/implementation_defined_attributes attribute-simple-storage-pool}@anchor{e3}@anchor{gnat_rm/implementation_defined_attributes id5}@anchor{198}
11110 @section Attribute Simple_Storage_Pool
11113 @geindex Storage pool
11116 @geindex Simple storage pool
11118 @geindex Simple_Storage_Pool
11120 For every nonformal, nonderived access-to-object type @code{Acc}, the
11121 representation attribute @code{Simple_Storage_Pool} may be specified
11122 via an attribute_definition_clause (or by specifying the equivalent aspect):
11125 My_Pool : My_Simple_Storage_Pool_Type;
11127 type Acc is access My_Data_Type;
11129 for Acc'Simple_Storage_Pool use My_Pool;
11132 The name given in an attribute_definition_clause for the
11133 @code{Simple_Storage_Pool} attribute shall denote a variable of
11134 a 'simple storage pool type' (see pragma @cite{Simple_Storage_Pool_Type}).
11136 The use of this attribute is only allowed for a prefix denoting a type
11137 for which it has been specified. The type of the attribute is the type
11138 of the variable specified as the simple storage pool of the access type,
11139 and the attribute denotes that variable.
11141 It is illegal to specify both @code{Storage_Pool} and @code{Simple_Storage_Pool}
11142 for the same access type.
11144 If the @code{Simple_Storage_Pool} attribute has been specified for an access
11145 type, then applying the @code{Storage_Pool} attribute to the type is flagged
11146 with a warning and its evaluation raises the exception @code{Program_Error}.
11148 If the Simple_Storage_Pool attribute has been specified for an access
11149 type @code{S}, then the evaluation of the attribute @code{S'Storage_Size}
11150 returns the result of calling @code{Storage_Size (S'Simple_Storage_Pool)},
11151 which is intended to indicate the number of storage elements reserved for
11152 the simple storage pool. If the Storage_Size function has not been defined
11153 for the simple storage pool type, then this attribute returns zero.
11155 If an access type @code{S} has a specified simple storage pool of type
11156 @code{SSP}, then the evaluation of an allocator for that access type calls
11157 the primitive @code{Allocate} procedure for type @code{SSP}, passing
11158 @code{S'Simple_Storage_Pool} as the pool parameter. The detailed
11159 semantics of such allocators is the same as those defined for allocators
11160 in section 13.11 of the @cite{Ada Reference Manual}, with the term
11161 @emph{simple storage pool} substituted for @emph{storage pool}.
11163 If an access type @code{S} has a specified simple storage pool of type
11164 @code{SSP}, then a call to an instance of the @code{Ada.Unchecked_Deallocation}
11165 for that access type invokes the primitive @code{Deallocate} procedure
11166 for type @code{SSP}, passing @code{S'Simple_Storage_Pool} as the pool
11167 parameter. The detailed semantics of such unchecked deallocations is the same
11168 as defined in section 13.11.2 of the Ada Reference Manual, except that the
11169 term @emph{simple storage pool} is substituted for @emph{storage pool}.
11171 @node Attribute Small,Attribute Storage_Unit,Attribute Simple_Storage_Pool,Implementation Defined Attributes
11172 @anchor{gnat_rm/implementation_defined_attributes attribute-small}@anchor{199}
11173 @section Attribute Small
11176 @geindex Ada 83 attributes
11180 The @code{Small} attribute is defined in Ada 95 (and Ada 2005) only for
11182 GNAT also allows this attribute to be applied to floating-point types
11183 for compatibility with Ada 83. See
11184 the Ada 83 reference manual for an exact description of the semantics of
11185 this attribute when applied to floating-point types.
11187 @node Attribute Storage_Unit,Attribute Stub_Type,Attribute Small,Implementation Defined Attributes
11188 @anchor{gnat_rm/implementation_defined_attributes attribute-storage-unit}@anchor{19a}
11189 @section Attribute Storage_Unit
11192 @geindex Storage_Unit
11194 @code{Standard'Storage_Unit} (@code{Standard} is the only permissible
11195 prefix) provides the same value as @code{System.Storage_Unit}.
11197 @node Attribute Stub_Type,Attribute System_Allocator_Alignment,Attribute Storage_Unit,Implementation Defined Attributes
11198 @anchor{gnat_rm/implementation_defined_attributes attribute-stub-type}@anchor{19b}
11199 @section Attribute Stub_Type
11204 The GNAT implementation of remote access-to-classwide types is
11205 organized as described in AARM section E.4 (20.t): a value of an RACW type
11206 (designating a remote object) is represented as a normal access
11207 value, pointing to a "stub" object which in turn contains the
11208 necessary information to contact the designated remote object. A
11209 call on any dispatching operation of such a stub object does the
11210 remote call, if necessary, using the information in the stub object
11211 to locate the target partition, etc.
11213 For a prefix @code{T} that denotes a remote access-to-classwide type,
11214 @code{T'Stub_Type} denotes the type of the corresponding stub objects.
11216 By construction, the layout of @code{T'Stub_Type} is identical to that of
11217 type @code{RACW_Stub_Type} declared in the internal implementation-defined
11218 unit @code{System.Partition_Interface}. Use of this attribute will create
11219 an implicit dependency on this unit.
11221 @node Attribute System_Allocator_Alignment,Attribute Target_Name,Attribute Stub_Type,Implementation Defined Attributes
11222 @anchor{gnat_rm/implementation_defined_attributes attribute-system-allocator-alignment}@anchor{19c}
11223 @section Attribute System_Allocator_Alignment
11229 @geindex System_Allocator_Alignment
11231 @code{Standard'System_Allocator_Alignment} (@code{Standard} is the only
11232 permissible prefix) provides the observable guaranted to be honored by
11233 the system allocator (malloc). This is a static value that can be used
11234 in user storage pools based on malloc either to reject allocation
11235 with alignment too large or to enable a realignment circuitry if the
11236 alignment request is larger than this value.
11238 @node Attribute Target_Name,Attribute To_Address,Attribute System_Allocator_Alignment,Implementation Defined Attributes
11239 @anchor{gnat_rm/implementation_defined_attributes attribute-target-name}@anchor{19d}
11240 @section Attribute Target_Name
11243 @geindex Target_Name
11245 @code{Standard'Target_Name} (@code{Standard} is the only permissible
11246 prefix) provides a static string value that identifies the target
11247 for the current compilation. For GCC implementations, this is the
11248 standard gcc target name without the terminating slash (for
11249 example, GNAT 5.0 on windows yields "i586-pc-mingw32msv").
11251 @node Attribute To_Address,Attribute To_Any,Attribute Target_Name,Implementation Defined Attributes
11252 @anchor{gnat_rm/implementation_defined_attributes attribute-to-address}@anchor{19e}
11253 @section Attribute To_Address
11256 @geindex To_Address
11258 The @code{System'To_Address}
11259 (@code{System} is the only permissible prefix)
11260 denotes a function identical to
11261 @code{System.Storage_Elements.To_Address} except that
11262 it is a static attribute. This means that if its argument is
11263 a static expression, then the result of the attribute is a
11264 static expression. This means that such an expression can be
11265 used in contexts (e.g., preelaborable packages) which require a
11266 static expression and where the function call could not be used
11267 (since the function call is always nonstatic, even if its
11268 argument is static). The argument must be in the range
11269 -(2**(m-1)) .. 2**m-1, where m is the memory size
11270 (typically 32 or 64). Negative values are intepreted in a
11271 modular manner (e.g., -1 means the same as 16#FFFF_FFFF# on
11272 a 32 bits machine).
11274 @node Attribute To_Any,Attribute Type_Class,Attribute To_Address,Implementation Defined Attributes
11275 @anchor{gnat_rm/implementation_defined_attributes attribute-to-any}@anchor{19f}
11276 @section Attribute To_Any
11281 This internal attribute is used for the generation of remote subprogram
11282 stubs in the context of the Distributed Systems Annex.
11284 @node Attribute Type_Class,Attribute Type_Key,Attribute To_Any,Implementation Defined Attributes
11285 @anchor{gnat_rm/implementation_defined_attributes attribute-type-class}@anchor{1a0}
11286 @section Attribute Type_Class
11289 @geindex Type_Class
11291 @code{typ'Type_Class} for any type or subtype @cite{typ} yields
11292 the value of the type class for the full type of @cite{typ}. If
11293 @cite{typ} is a generic formal type, the value is the value for the
11294 corresponding actual subtype. The value of this attribute is of type
11295 @code{System.Aux_DEC.Type_Class}, which has the following definition:
11299 (Type_Class_Enumeration,
11300 Type_Class_Integer,
11301 Type_Class_Fixed_Point,
11302 Type_Class_Floating_Point,
11307 Type_Class_Address);
11310 Protected types yield the value @code{Type_Class_Task}, which thus
11311 applies to all concurrent types. This attribute is designed to
11312 be compatible with the DEC Ada 83 attribute of the same name.
11314 @node Attribute Type_Key,Attribute TypeCode,Attribute Type_Class,Implementation Defined Attributes
11315 @anchor{gnat_rm/implementation_defined_attributes attribute-type-key}@anchor{1a1}
11316 @section Attribute Type_Key
11321 The @code{Type_Key} attribute is applicable to a type or subtype and
11322 yields a value of type Standard.String containing encoded information
11323 about the type or subtype. This provides improved compatibility with
11324 other implementations that support this attribute.
11326 @node Attribute TypeCode,Attribute Unconstrained_Array,Attribute Type_Key,Implementation Defined Attributes
11327 @anchor{gnat_rm/implementation_defined_attributes attribute-typecode}@anchor{1a2}
11328 @section Attribute TypeCode
11333 This internal attribute is used for the generation of remote subprogram
11334 stubs in the context of the Distributed Systems Annex.
11336 @node Attribute Unconstrained_Array,Attribute Universal_Literal_String,Attribute TypeCode,Implementation Defined Attributes
11337 @anchor{gnat_rm/implementation_defined_attributes attribute-unconstrained-array}@anchor{1a3}
11338 @section Attribute Unconstrained_Array
11341 @geindex Unconstrained_Array
11343 The @code{Unconstrained_Array} attribute can be used with a prefix that
11344 denotes any type or subtype. It is a static attribute that yields
11345 @code{True} if the prefix designates an unconstrained array,
11346 and @code{False} otherwise. In a generic instance, the result is
11347 still static, and yields the result of applying this test to the
11350 @node Attribute Universal_Literal_String,Attribute Unrestricted_Access,Attribute Unconstrained_Array,Implementation Defined Attributes
11351 @anchor{gnat_rm/implementation_defined_attributes attribute-universal-literal-string}@anchor{1a4}
11352 @section Attribute Universal_Literal_String
11355 @geindex Named numbers
11356 @geindex representation of
11358 @geindex Universal_Literal_String
11360 The prefix of @code{Universal_Literal_String} must be a named
11361 number. The static result is the string consisting of the characters of
11362 the number as defined in the original source. This allows the user
11363 program to access the actual text of named numbers without intermediate
11364 conversions and without the need to enclose the strings in quotes (which
11365 would preclude their use as numbers).
11367 For example, the following program prints the first 50 digits of pi:
11370 with Text_IO; use Text_IO;
11374 Put (Ada.Numerics.Pi'Universal_Literal_String);
11378 @node Attribute Unrestricted_Access,Attribute Update,Attribute Universal_Literal_String,Implementation Defined Attributes
11379 @anchor{gnat_rm/implementation_defined_attributes attribute-unrestricted-access}@anchor{1a5}
11380 @section Attribute Unrestricted_Access
11384 @geindex unrestricted
11386 @geindex Unrestricted_Access
11388 The @code{Unrestricted_Access} attribute is similar to @code{Access}
11389 except that all accessibility and aliased view checks are omitted. This
11390 is a user-beware attribute.
11392 For objects, it is similar to @code{Address}, for which it is a
11393 desirable replacement where the value desired is an access type.
11394 In other words, its effect is similar to first applying the
11395 @code{Address} attribute and then doing an unchecked conversion to a
11396 desired access type.
11398 For subprograms, @code{P'Unrestricted_Access} may be used where
11399 @code{P'Access} would be illegal, to construct a value of a
11400 less-nested named access type that designates a more-nested
11401 subprogram. This value may be used in indirect calls, so long as the
11402 more-nested subprogram still exists; once the subprogram containing it
11403 has returned, such calls are erroneous. For example:
11408 type Less_Nested is not null access procedure;
11409 Global : Less_Nested;
11417 Local_Var : Integer;
11419 procedure More_Nested is
11424 Global := More_Nested'Unrestricted_Access;
11431 When P1 is called from P2, the call via Global is OK, but if P1 were
11432 called after P2 returns, it would be an erroneous use of a dangling
11435 For objects, it is possible to use @code{Unrestricted_Access} for any
11436 type. However, if the result is of an access-to-unconstrained array
11437 subtype, then the resulting pointer has the same scope as the context
11438 of the attribute, and must not be returned to some enclosing scope.
11439 For instance, if a function uses @code{Unrestricted_Access} to create
11440 an access-to-unconstrained-array and returns that value to the caller,
11441 the result will involve dangling pointers. In addition, it is only
11442 valid to create pointers to unconstrained arrays using this attribute
11443 if the pointer has the normal default 'fat' representation where a
11444 pointer has two components, one points to the array and one points to
11445 the bounds. If a size clause is used to force 'thin' representation
11446 for a pointer to unconstrained where there is only space for a single
11447 pointer, then the resulting pointer is not usable.
11449 In the simple case where a direct use of Unrestricted_Access attempts
11450 to make a thin pointer for a non-aliased object, the compiler will
11451 reject the use as illegal, as shown in the following example:
11454 with System; use System;
11455 procedure SliceUA2 is
11456 type A is access all String;
11457 for A'Size use Standard'Address_Size;
11459 procedure P (Arg : A) is
11464 X : String := "hello world!";
11465 X2 : aliased String := "hello world!";
11467 AV : A := X'Unrestricted_Access; -- ERROR
11469 >>> illegal use of Unrestricted_Access attribute
11470 >>> attempt to generate thin pointer to unaliased object
11473 P (X'Unrestricted_Access); -- ERROR
11475 >>> illegal use of Unrestricted_Access attribute
11476 >>> attempt to generate thin pointer to unaliased object
11478 P (X(7 .. 12)'Unrestricted_Access); -- ERROR
11480 >>> illegal use of Unrestricted_Access attribute
11481 >>> attempt to generate thin pointer to unaliased object
11483 P (X2'Unrestricted_Access); -- OK
11487 but other cases cannot be detected by the compiler, and are
11488 considered to be erroneous. Consider the following example:
11491 with System; use System;
11492 with System; use System;
11493 procedure SliceUA is
11494 type AF is access all String;
11496 type A is access all String;
11497 for A'Size use Standard'Address_Size;
11499 procedure P (Arg : A) is
11501 if Arg'Length /= 6 then
11502 raise Program_Error;
11506 X : String := "hello world!";
11507 Y : AF := X (7 .. 12)'Unrestricted_Access;
11514 A normal unconstrained array value
11515 or a constrained array object marked as aliased has the bounds in memory
11516 just before the array, so a thin pointer can retrieve both the data and
11517 the bounds. But in this case, the non-aliased object @code{X} does not have the
11518 bounds before the string. If the size clause for type @code{A}
11519 were not present, then the pointer
11520 would be a fat pointer, where one component is a pointer to the bounds,
11521 and all would be well. But with the size clause present, the conversion from
11522 fat pointer to thin pointer in the call loses the bounds, and so this
11523 is erroneous, and the program likely raises a @code{Program_Error} exception.
11525 In general, it is advisable to completely
11526 avoid mixing the use of thin pointers and the use of
11527 @code{Unrestricted_Access} where the designated type is an
11528 unconstrained array. The use of thin pointers should be restricted to
11529 cases of porting legacy code that implicitly assumes the size of pointers,
11530 and such code should not in any case be using this attribute.
11532 Another erroneous situation arises if the attribute is
11533 applied to a constant. The resulting pointer can be used to access the
11534 constant, but the effect of trying to modify a constant in this manner
11535 is not well-defined. Consider this example:
11538 P : constant Integer := 4;
11539 type R is access all Integer;
11540 RV : R := P'Unrestricted_Access;
11545 Here we attempt to modify the constant P from 4 to 3, but the compiler may
11546 or may not notice this attempt, and subsequent references to P may yield
11547 either the value 3 or the value 4 or the assignment may blow up if the
11548 compiler decides to put P in read-only memory. One particular case where
11549 @code{Unrestricted_Access} can be used in this way is to modify the
11550 value of an @code{in} parameter:
11553 procedure K (S : in String) is
11554 type R is access all Character;
11555 RV : R := S (3)'Unrestricted_Access;
11561 In general this is a risky approach. It may appear to "work" but such uses of
11562 @code{Unrestricted_Access} are potentially non-portable, even from one version
11563 of GNAT to another, so are best avoided if possible.
11565 @node Attribute Update,Attribute Valid_Scalars,Attribute Unrestricted_Access,Implementation Defined Attributes
11566 @anchor{gnat_rm/implementation_defined_attributes attribute-update}@anchor{1a6}
11567 @section Attribute Update
11572 The @code{Update} attribute creates a copy of an array or record value
11573 with one or more modified components. The syntax is:
11576 PREFIX'Update ( RECORD_COMPONENT_ASSOCIATION_LIST )
11577 PREFIX'Update ( ARRAY_COMPONENT_ASSOCIATION @{, ARRAY_COMPONENT_ASSOCIATION @} )
11578 PREFIX'Update ( MULTIDIMENSIONAL_ARRAY_COMPONENT_ASSOCIATION
11579 @{, MULTIDIMENSIONAL_ARRAY_COMPONENT_ASSOCIATION @} )
11581 MULTIDIMENSIONAL_ARRAY_COMPONENT_ASSOCIATION ::= INDEX_EXPRESSION_LIST_LIST => EXPRESSION
11582 INDEX_EXPRESSION_LIST_LIST ::= INDEX_EXPRESSION_LIST @{| INDEX_EXPRESSION_LIST @}
11583 INDEX_EXPRESSION_LIST ::= ( EXPRESSION @{, EXPRESSION @} )
11586 where @code{PREFIX} is the name of an array or record object, the
11587 association list in parentheses does not contain an @code{others}
11588 choice and the box symbol @code{<>} may not appear in any
11589 expression. The effect is to yield a copy of the array or record value
11590 which is unchanged apart from the components mentioned in the
11591 association list, which are changed to the indicated value. The
11592 original value of the array or record value is not affected. For
11596 type Arr is Array (1 .. 5) of Integer;
11598 Avar1 : Arr := (1,2,3,4,5);
11599 Avar2 : Arr := Avar1'Update (2 => 10, 3 .. 4 => 20);
11602 yields a value for @code{Avar2} of 1,10,20,20,5 with @code{Avar1}
11603 begin unmodified. Similarly:
11606 type Rec is A, B, C : Integer;
11608 Rvar1 : Rec := (A => 1, B => 2, C => 3);
11609 Rvar2 : Rec := Rvar1'Update (B => 20);
11612 yields a value for @code{Rvar2} of (A => 1, B => 20, C => 3),
11613 with @code{Rvar1} being unmodifed.
11614 Note that the value of the attribute reference is computed
11615 completely before it is used. This means that if you write:
11618 Avar1 := Avar1'Update (1 => 10, 2 => Function_Call);
11621 then the value of @code{Avar1} is not modified if @code{Function_Call}
11622 raises an exception, unlike the effect of a series of direct assignments
11623 to elements of @code{Avar1}. In general this requires that
11624 two extra complete copies of the object are required, which should be
11625 kept in mind when considering efficiency.
11627 The @code{Update} attribute cannot be applied to prefixes of a limited
11628 type, and cannot reference discriminants in the case of a record type.
11629 The accessibility level of an Update attribute result object is defined
11630 as for an aggregate.
11632 In the record case, no component can be mentioned more than once. In
11633 the array case, two overlapping ranges can appear in the association list,
11634 in which case the modifications are processed left to right.
11636 Multi-dimensional arrays can be modified, as shown by this example:
11639 A : array (1 .. 10, 1 .. 10) of Integer;
11641 A := A'Update ((1, 2) => 20, (3, 4) => 30);
11644 which changes element (1,2) to 20 and (3,4) to 30.
11646 @node Attribute Valid_Scalars,Attribute VADS_Size,Attribute Update,Implementation Defined Attributes
11647 @anchor{gnat_rm/implementation_defined_attributes attribute-valid-scalars}@anchor{1a7}
11648 @section Attribute Valid_Scalars
11651 @geindex Valid_Scalars
11653 The @code{'Valid_Scalars} attribute is intended to make it easier to
11654 check the validity of scalar subcomponents of composite objects. It
11655 is defined for any prefix @code{X} that denotes an object.
11656 The value of this attribute is of the predefined type Boolean.
11657 @code{X'Valid_Scalars} yields True if and only if evaluation of
11658 @code{P'Valid} yields True for every scalar part P of X or if X has
11659 no scalar parts. It is not specified in what order the scalar parts
11660 are checked, nor whether any more are checked after any one of them
11661 is determined to be invalid. If the prefix @code{X} is of a class-wide
11662 type @code{T'Class} (where @code{T} is the associated specific type),
11663 or if the prefix @code{X} is of a specific tagged type @code{T}, then
11664 only the scalar parts of components of @code{T} are traversed; in other
11665 words, components of extensions of @code{T} are not traversed even if
11666 @code{T'Class (X)'Tag /= T'Tag} . The compiler will issue a warning if it can
11667 be determined at compile time that the prefix of the attribute has no
11668 scalar parts (e.g., if the prefix is of an access type, an interface type,
11669 an undiscriminated task type, or an undiscriminated protected type).
11671 For scalar types, @code{Valid_Scalars} is equivalent to @code{Valid}. The use
11672 of this attribute is not permitted for @code{Unchecked_Union} types for which
11673 in general it is not possible to determine the values of the discriminants.
11675 Note: @code{Valid_Scalars} can generate a lot of code, especially in the case
11676 of a large variant record. If the attribute is called in many places in the
11677 same program applied to objects of the same type, it can reduce program size
11678 to write a function with a single use of the attribute, and then call that
11679 function from multiple places.
11681 @node Attribute VADS_Size,Attribute Value_Size,Attribute Valid_Scalars,Implementation Defined Attributes
11682 @anchor{gnat_rm/implementation_defined_attributes attribute-vads-size}@anchor{1a8}
11683 @section Attribute VADS_Size
11687 @geindex VADS compatibility
11691 The @code{'VADS_Size} attribute is intended to make it easier to port
11692 legacy code which relies on the semantics of @code{'Size} as implemented
11693 by the VADS Ada 83 compiler. GNAT makes a best effort at duplicating the
11694 same semantic interpretation. In particular, @code{'VADS_Size} applied
11695 to a predefined or other primitive type with no Size clause yields the
11696 Object_Size (for example, @code{Natural'Size} is 32 rather than 31 on
11697 typical machines). In addition @code{'VADS_Size} applied to an object
11698 gives the result that would be obtained by applying the attribute to
11699 the corresponding type.
11701 @node Attribute Value_Size,Attribute Wchar_T_Size,Attribute VADS_Size,Implementation Defined Attributes
11702 @anchor{gnat_rm/implementation_defined_attributes id6}@anchor{1a9}@anchor{gnat_rm/implementation_defined_attributes attribute-value-size}@anchor{15b}
11703 @section Attribute Value_Size
11707 @geindex setting for not-first subtype
11709 @geindex Value_Size
11711 @code{type'Value_Size} is the number of bits required to represent
11712 a value of the given subtype. It is the same as @code{type'Size},
11713 but, unlike @code{Size}, may be set for non-first subtypes.
11715 @node Attribute Wchar_T_Size,Attribute Word_Size,Attribute Value_Size,Implementation Defined Attributes
11716 @anchor{gnat_rm/implementation_defined_attributes attribute-wchar-t-size}@anchor{1aa}
11717 @section Attribute Wchar_T_Size
11720 @geindex Wchar_T_Size
11722 @code{Standard'Wchar_T_Size} (@code{Standard} is the only permissible
11723 prefix) provides the size in bits of the C @code{wchar_t} type
11724 primarily for constructing the definition of this type in
11725 package @code{Interfaces.C}. The result is a static constant.
11727 @node Attribute Word_Size,,Attribute Wchar_T_Size,Implementation Defined Attributes
11728 @anchor{gnat_rm/implementation_defined_attributes attribute-word-size}@anchor{1ab}
11729 @section Attribute Word_Size
11734 @code{Standard'Word_Size} (@code{Standard} is the only permissible
11735 prefix) provides the value @code{System.Word_Size}. The result is
11738 @node Standard and Implementation Defined Restrictions,Implementation Advice,Implementation Defined Attributes,Top
11739 @anchor{gnat_rm/standard_and_implementation_defined_restrictions standard-and-implementation-defined-restrictions}@anchor{9}@anchor{gnat_rm/standard_and_implementation_defined_restrictions doc}@anchor{1ac}@anchor{gnat_rm/standard_and_implementation_defined_restrictions id1}@anchor{1ad}
11740 @chapter Standard and Implementation Defined Restrictions
11743 All Ada Reference Manual-defined Restriction identifiers are implemented:
11749 language-defined restrictions (see 13.12.1)
11752 tasking restrictions (see D.7)
11755 high integrity restrictions (see H.4)
11758 GNAT implements additional restriction identifiers. All restrictions, whether
11759 language defined or GNAT-specific, are listed in the following.
11762 * Partition-Wide Restrictions::
11763 * Program Unit Level Restrictions::
11767 @node Partition-Wide Restrictions,Program Unit Level Restrictions,,Standard and Implementation Defined Restrictions
11768 @anchor{gnat_rm/standard_and_implementation_defined_restrictions partition-wide-restrictions}@anchor{1ae}@anchor{gnat_rm/standard_and_implementation_defined_restrictions id2}@anchor{1af}
11769 @section Partition-Wide Restrictions
11772 There are two separate lists of restriction identifiers. The first
11773 set requires consistency throughout a partition (in other words, if the
11774 restriction identifier is used for any compilation unit in the partition,
11775 then all compilation units in the partition must obey the restriction).
11778 * Immediate_Reclamation::
11779 * Max_Asynchronous_Select_Nesting::
11780 * Max_Entry_Queue_Length::
11781 * Max_Protected_Entries::
11782 * Max_Select_Alternatives::
11783 * Max_Storage_At_Blocking::
11784 * Max_Task_Entries::
11786 * No_Abort_Statements::
11787 * No_Access_Parameter_Allocators::
11788 * No_Access_Subprograms::
11790 * No_Anonymous_Allocators::
11791 * No_Asynchronous_Control::
11793 * No_Coextensions::
11794 * No_Default_Initialization::
11797 * No_Direct_Boolean_Operators::
11799 * No_Dispatching_Calls::
11800 * No_Dynamic_Attachment::
11801 * No_Dynamic_Priorities::
11802 * No_Entry_Calls_In_Elaboration_Code::
11803 * No_Enumeration_Maps::
11804 * No_Exception_Handlers::
11805 * No_Exception_Propagation::
11806 * No_Exception_Registration::
11808 * No_Finalization::
11810 * No_Floating_Point::
11811 * No_Implicit_Conditionals::
11812 * No_Implicit_Dynamic_Code::
11813 * No_Implicit_Heap_Allocations::
11814 * No_Implicit_Protected_Object_Allocations::
11815 * No_Implicit_Task_Allocations::
11816 * No_Initialize_Scalars::
11818 * No_Local_Allocators::
11819 * No_Local_Protected_Objects::
11820 * No_Local_Timing_Events::
11821 * No_Long_Long_Integers::
11822 * No_Multiple_Elaboration::
11823 * No_Nested_Finalization::
11824 * No_Protected_Type_Allocators::
11825 * No_Protected_Types::
11828 * No_Relative_Delay::
11829 * No_Requeue_Statements::
11830 * No_Secondary_Stack::
11831 * No_Select_Statements::
11832 * No_Specific_Termination_Handlers::
11833 * No_Specification_of_Aspect::
11834 * No_Standard_Allocators_After_Elaboration::
11835 * No_Standard_Storage_Pools::
11836 * No_Stream_Optimizations::
11838 * No_Task_Allocators::
11839 * No_Task_At_Interrupt_Priority::
11840 * No_Task_Attributes_Package::
11841 * No_Task_Hierarchy::
11842 * No_Task_Termination::
11844 * No_Terminate_Alternatives::
11845 * No_Unchecked_Access::
11846 * No_Unchecked_Conversion::
11847 * No_Unchecked_Deallocation::
11848 * No_Use_Of_Entity::
11850 * Simple_Barriers::
11851 * Static_Priorities::
11852 * Static_Storage_Size::
11856 @node Immediate_Reclamation,Max_Asynchronous_Select_Nesting,,Partition-Wide Restrictions
11857 @anchor{gnat_rm/standard_and_implementation_defined_restrictions immediate-reclamation}@anchor{1b0}
11858 @subsection Immediate_Reclamation
11861 @geindex Immediate_Reclamation
11863 [RM H.4] This restriction ensures that, except for storage occupied by
11864 objects created by allocators and not deallocated via unchecked
11865 deallocation, any storage reserved at run time for an object is
11866 immediately reclaimed when the object no longer exists.
11868 @node Max_Asynchronous_Select_Nesting,Max_Entry_Queue_Length,Immediate_Reclamation,Partition-Wide Restrictions
11869 @anchor{gnat_rm/standard_and_implementation_defined_restrictions max-asynchronous-select-nesting}@anchor{1b1}
11870 @subsection Max_Asynchronous_Select_Nesting
11873 @geindex Max_Asynchronous_Select_Nesting
11875 [RM D.7] Specifies the maximum dynamic nesting level of asynchronous
11876 selects. Violations of this restriction with a value of zero are
11877 detected at compile time. Violations of this restriction with values
11878 other than zero cause Storage_Error to be raised.
11880 @node Max_Entry_Queue_Length,Max_Protected_Entries,Max_Asynchronous_Select_Nesting,Partition-Wide Restrictions
11881 @anchor{gnat_rm/standard_and_implementation_defined_restrictions max-entry-queue-length}@anchor{1b2}
11882 @subsection Max_Entry_Queue_Length
11885 @geindex Max_Entry_Queue_Length
11887 [RM D.7] This restriction is a declaration that any protected entry compiled in
11888 the scope of the restriction has at most the specified number of
11889 tasks waiting on the entry at any one time, and so no queue is required.
11890 Note that this restriction is checked at run time. Violation of this
11891 restriction results in the raising of Program_Error exception at the point of
11894 @geindex Max_Entry_Queue_Depth
11896 The restriction @code{Max_Entry_Queue_Depth} is recognized as a
11897 synonym for @code{Max_Entry_Queue_Length}. This is retained for historical
11898 compatibility purposes (and a warning will be generated for its use if
11899 warnings on obsolescent features are activated).
11901 @node Max_Protected_Entries,Max_Select_Alternatives,Max_Entry_Queue_Length,Partition-Wide Restrictions
11902 @anchor{gnat_rm/standard_and_implementation_defined_restrictions max-protected-entries}@anchor{1b3}
11903 @subsection Max_Protected_Entries
11906 @geindex Max_Protected_Entries
11908 [RM D.7] Specifies the maximum number of entries per protected type. The
11909 bounds of every entry family of a protected unit shall be static, or shall be
11910 defined by a discriminant of a subtype whose corresponding bound is static.
11912 @node Max_Select_Alternatives,Max_Storage_At_Blocking,Max_Protected_Entries,Partition-Wide Restrictions
11913 @anchor{gnat_rm/standard_and_implementation_defined_restrictions max-select-alternatives}@anchor{1b4}
11914 @subsection Max_Select_Alternatives
11917 @geindex Max_Select_Alternatives
11919 [RM D.7] Specifies the maximum number of alternatives in a selective accept.
11921 @node Max_Storage_At_Blocking,Max_Task_Entries,Max_Select_Alternatives,Partition-Wide Restrictions
11922 @anchor{gnat_rm/standard_and_implementation_defined_restrictions max-storage-at-blocking}@anchor{1b5}
11923 @subsection Max_Storage_At_Blocking
11926 @geindex Max_Storage_At_Blocking
11928 [RM D.7] Specifies the maximum portion (in storage elements) of a task's
11929 Storage_Size that can be retained by a blocked task. A violation of this
11930 restriction causes Storage_Error to be raised.
11932 @node Max_Task_Entries,Max_Tasks,Max_Storage_At_Blocking,Partition-Wide Restrictions
11933 @anchor{gnat_rm/standard_and_implementation_defined_restrictions max-task-entries}@anchor{1b6}
11934 @subsection Max_Task_Entries
11937 @geindex Max_Task_Entries
11939 [RM D.7] Specifies the maximum number of entries
11940 per task. The bounds of every entry family
11941 of a task unit shall be static, or shall be
11942 defined by a discriminant of a subtype whose
11943 corresponding bound is static.
11945 @node Max_Tasks,No_Abort_Statements,Max_Task_Entries,Partition-Wide Restrictions
11946 @anchor{gnat_rm/standard_and_implementation_defined_restrictions max-tasks}@anchor{1b7}
11947 @subsection Max_Tasks
11952 [RM D.7] Specifies the maximum number of task that may be created, not
11953 counting the creation of the environment task. Violations of this
11954 restriction with a value of zero are detected at compile
11955 time. Violations of this restriction with values other than zero cause
11956 Storage_Error to be raised.
11958 @node No_Abort_Statements,No_Access_Parameter_Allocators,Max_Tasks,Partition-Wide Restrictions
11959 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-abort-statements}@anchor{1b8}
11960 @subsection No_Abort_Statements
11963 @geindex No_Abort_Statements
11965 [RM D.7] There are no abort_statements, and there are
11966 no calls to Task_Identification.Abort_Task.
11968 @node No_Access_Parameter_Allocators,No_Access_Subprograms,No_Abort_Statements,Partition-Wide Restrictions
11969 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-access-parameter-allocators}@anchor{1b9}
11970 @subsection No_Access_Parameter_Allocators
11973 @geindex No_Access_Parameter_Allocators
11975 [RM H.4] This restriction ensures at compile time that there are no
11976 occurrences of an allocator as the actual parameter to an access
11979 @node No_Access_Subprograms,No_Allocators,No_Access_Parameter_Allocators,Partition-Wide Restrictions
11980 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-access-subprograms}@anchor{1ba}
11981 @subsection No_Access_Subprograms
11984 @geindex No_Access_Subprograms
11986 [RM H.4] This restriction ensures at compile time that there are no
11987 declarations of access-to-subprogram types.
11989 @node No_Allocators,No_Anonymous_Allocators,No_Access_Subprograms,Partition-Wide Restrictions
11990 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-allocators}@anchor{1bb}
11991 @subsection No_Allocators
11994 @geindex No_Allocators
11996 [RM H.4] This restriction ensures at compile time that there are no
11997 occurrences of an allocator.
11999 @node No_Anonymous_Allocators,No_Asynchronous_Control,No_Allocators,Partition-Wide Restrictions
12000 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-anonymous-allocators}@anchor{1bc}
12001 @subsection No_Anonymous_Allocators
12004 @geindex No_Anonymous_Allocators
12006 [RM H.4] This restriction ensures at compile time that there are no
12007 occurrences of an allocator of anonymous access type.
12009 @node No_Asynchronous_Control,No_Calendar,No_Anonymous_Allocators,Partition-Wide Restrictions
12010 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-asynchronous-control}@anchor{1bd}
12011 @subsection No_Asynchronous_Control
12014 @geindex No_Asynchronous_Control
12016 [RM J.13] This restriction ensures at compile time that there are no semantic
12017 dependences on the predefined package Asynchronous_Task_Control.
12019 @node No_Calendar,No_Coextensions,No_Asynchronous_Control,Partition-Wide Restrictions
12020 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-calendar}@anchor{1be}
12021 @subsection No_Calendar
12024 @geindex No_Calendar
12026 [GNAT] This restriction ensures at compile time that there are no semantic
12027 dependences on package Calendar.
12029 @node No_Coextensions,No_Default_Initialization,No_Calendar,Partition-Wide Restrictions
12030 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-coextensions}@anchor{1bf}
12031 @subsection No_Coextensions
12034 @geindex No_Coextensions
12036 [RM H.4] This restriction ensures at compile time that there are no
12037 coextensions. See 3.10.2.
12039 @node No_Default_Initialization,No_Delay,No_Coextensions,Partition-Wide Restrictions
12040 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-default-initialization}@anchor{1c0}
12041 @subsection No_Default_Initialization
12044 @geindex No_Default_Initialization
12046 [GNAT] This restriction prohibits any instance of default initialization
12047 of variables. The binder implements a consistency rule which prevents
12048 any unit compiled without the restriction from with'ing a unit with the
12049 restriction (this allows the generation of initialization procedures to
12050 be skipped, since you can be sure that no call is ever generated to an
12051 initialization procedure in a unit with the restriction active). If used
12052 in conjunction with Initialize_Scalars or Normalize_Scalars, the effect
12053 is to prohibit all cases of variables declared without a specific
12054 initializer (including the case of OUT scalar parameters).
12056 @node No_Delay,No_Dependence,No_Default_Initialization,Partition-Wide Restrictions
12057 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-delay}@anchor{1c1}
12058 @subsection No_Delay
12063 [RM H.4] This restriction ensures at compile time that there are no
12064 delay statements and no semantic dependences on package Calendar.
12066 @node No_Dependence,No_Direct_Boolean_Operators,No_Delay,Partition-Wide Restrictions
12067 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-dependence}@anchor{1c2}
12068 @subsection No_Dependence
12071 @geindex No_Dependence
12073 [RM 13.12.1] This restriction ensures at compile time that there are no
12074 dependences on a library unit.
12076 @node No_Direct_Boolean_Operators,No_Dispatch,No_Dependence,Partition-Wide Restrictions
12077 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-direct-boolean-operators}@anchor{1c3}
12078 @subsection No_Direct_Boolean_Operators
12081 @geindex No_Direct_Boolean_Operators
12083 [GNAT] This restriction ensures that no logical operators (and/or/xor)
12084 are used on operands of type Boolean (or any type derived from Boolean).
12085 This is intended for use in safety critical programs where the certification
12086 protocol requires the use of short-circuit (and then, or else) forms for all
12087 composite boolean operations.
12089 @node No_Dispatch,No_Dispatching_Calls,No_Direct_Boolean_Operators,Partition-Wide Restrictions
12090 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-dispatch}@anchor{1c4}
12091 @subsection No_Dispatch
12094 @geindex No_Dispatch
12096 [RM H.4] This restriction ensures at compile time that there are no
12097 occurrences of @code{T'Class}, for any (tagged) subtype @code{T}.
12099 @node No_Dispatching_Calls,No_Dynamic_Attachment,No_Dispatch,Partition-Wide Restrictions
12100 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-dispatching-calls}@anchor{1c5}
12101 @subsection No_Dispatching_Calls
12104 @geindex No_Dispatching_Calls
12106 [GNAT] This restriction ensures at compile time that the code generated by the
12107 compiler involves no dispatching calls. The use of this restriction allows the
12108 safe use of record extensions, classwide membership tests and other classwide
12109 features not involving implicit dispatching. This restriction ensures that
12110 the code contains no indirect calls through a dispatching mechanism. Note that
12111 this includes internally-generated calls created by the compiler, for example
12112 in the implementation of class-wide objects assignments. The
12113 membership test is allowed in the presence of this restriction, because its
12114 implementation requires no dispatching.
12115 This restriction is comparable to the official Ada restriction
12116 @code{No_Dispatch} except that it is a bit less restrictive in that it allows
12117 all classwide constructs that do not imply dispatching.
12118 The following example indicates constructs that violate this restriction.
12122 type T is tagged record
12125 procedure P (X : T);
12127 type DT is new T with record
12128 More_Data : Natural;
12130 procedure Q (X : DT);
12134 procedure Example is
12135 procedure Test (O : T'Class) is
12136 N : Natural := O'Size;-- Error: Dispatching call
12137 C : T'Class := O; -- Error: implicit Dispatching Call
12139 if O in DT'Class then -- OK : Membership test
12140 Q (DT (O)); -- OK : Type conversion plus direct call
12142 P (O); -- Error: Dispatching call
12148 P (Obj); -- OK : Direct call
12149 P (T (Obj)); -- OK : Type conversion plus direct call
12150 P (T'Class (Obj)); -- Error: Dispatching call
12152 Test (Obj); -- OK : Type conversion
12154 if Obj in T'Class then -- OK : Membership test
12160 @node No_Dynamic_Attachment,No_Dynamic_Priorities,No_Dispatching_Calls,Partition-Wide Restrictions
12161 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-dynamic-attachment}@anchor{1c6}
12162 @subsection No_Dynamic_Attachment
12165 @geindex No_Dynamic_Attachment
12167 [RM D.7] This restriction ensures that there is no call to any of the
12168 operations defined in package Ada.Interrupts
12169 (Is_Reserved, Is_Attached, Current_Handler, Attach_Handler, Exchange_Handler,
12170 Detach_Handler, and Reference).
12172 @geindex No_Dynamic_Interrupts
12174 The restriction @code{No_Dynamic_Interrupts} is recognized as a
12175 synonym for @code{No_Dynamic_Attachment}. This is retained for historical
12176 compatibility purposes (and a warning will be generated for its use if
12177 warnings on obsolescent features are activated).
12179 @node No_Dynamic_Priorities,No_Entry_Calls_In_Elaboration_Code,No_Dynamic_Attachment,Partition-Wide Restrictions
12180 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-dynamic-priorities}@anchor{1c7}
12181 @subsection No_Dynamic_Priorities
12184 @geindex No_Dynamic_Priorities
12186 [RM D.7] There are no semantic dependencies on the package Dynamic_Priorities.
12188 @node No_Entry_Calls_In_Elaboration_Code,No_Enumeration_Maps,No_Dynamic_Priorities,Partition-Wide Restrictions
12189 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-entry-calls-in-elaboration-code}@anchor{1c8}
12190 @subsection No_Entry_Calls_In_Elaboration_Code
12193 @geindex No_Entry_Calls_In_Elaboration_Code
12195 [GNAT] This restriction ensures at compile time that no task or protected entry
12196 calls are made during elaboration code. As a result of the use of this
12197 restriction, the compiler can assume that no code past an accept statement
12198 in a task can be executed at elaboration time.
12200 @node No_Enumeration_Maps,No_Exception_Handlers,No_Entry_Calls_In_Elaboration_Code,Partition-Wide Restrictions
12201 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-enumeration-maps}@anchor{1c9}
12202 @subsection No_Enumeration_Maps
12205 @geindex No_Enumeration_Maps
12207 [GNAT] This restriction ensures at compile time that no operations requiring
12208 enumeration maps are used (that is Image and Value attributes applied
12209 to enumeration types).
12211 @node No_Exception_Handlers,No_Exception_Propagation,No_Enumeration_Maps,Partition-Wide Restrictions
12212 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-exception-handlers}@anchor{1ca}
12213 @subsection No_Exception_Handlers
12216 @geindex No_Exception_Handlers
12218 [GNAT] This restriction ensures at compile time that there are no explicit
12219 exception handlers. It also indicates that no exception propagation will
12220 be provided. In this mode, exceptions may be raised but will result in
12221 an immediate call to the last chance handler, a routine that the user
12222 must define with the following profile:
12225 procedure Last_Chance_Handler
12226 (Source_Location : System.Address; Line : Integer);
12227 pragma Export (C, Last_Chance_Handler,
12228 "__gnat_last_chance_handler");
12231 The parameter is a C null-terminated string representing a message to be
12232 associated with the exception (typically the source location of the raise
12233 statement generated by the compiler). The Line parameter when nonzero
12234 represents the line number in the source program where the raise occurs.
12236 @node No_Exception_Propagation,No_Exception_Registration,No_Exception_Handlers,Partition-Wide Restrictions
12237 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-exception-propagation}@anchor{1cb}
12238 @subsection No_Exception_Propagation
12241 @geindex No_Exception_Propagation
12243 [GNAT] This restriction guarantees that exceptions are never propagated
12244 to an outer subprogram scope. The only case in which an exception may
12245 be raised is when the handler is statically in the same subprogram, so
12246 that the effect of a raise is essentially like a goto statement. Any
12247 other raise statement (implicit or explicit) will be considered
12248 unhandled. Exception handlers are allowed, but may not contain an
12249 exception occurrence identifier (exception choice). In addition, use of
12250 the package GNAT.Current_Exception is not permitted, and reraise
12251 statements (raise with no operand) are not permitted.
12253 @node No_Exception_Registration,No_Exceptions,No_Exception_Propagation,Partition-Wide Restrictions
12254 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-exception-registration}@anchor{1cc}
12255 @subsection No_Exception_Registration
12258 @geindex No_Exception_Registration
12260 [GNAT] This restriction ensures at compile time that no stream operations for
12261 types Exception_Id or Exception_Occurrence are used. This also makes it
12262 impossible to pass exceptions to or from a partition with this restriction
12263 in a distributed environment. If this restriction is active, the generated
12264 code is simplified by omitting the otherwise-required global registration
12265 of exceptions when they are declared.
12267 @node No_Exceptions,No_Finalization,No_Exception_Registration,Partition-Wide Restrictions
12268 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-exceptions}@anchor{1cd}
12269 @subsection No_Exceptions
12272 @geindex No_Exceptions
12274 [RM H.4] This restriction ensures at compile time that there are no
12275 raise statements and no exception handlers.
12277 @node No_Finalization,No_Fixed_Point,No_Exceptions,Partition-Wide Restrictions
12278 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-finalization}@anchor{1ce}
12279 @subsection No_Finalization
12282 @geindex No_Finalization
12284 [GNAT] This restriction disables the language features described in
12285 chapter 7.6 of the Ada 2005 RM as well as all form of code generation
12286 performed by the compiler to support these features. The following types
12287 are no longer considered controlled when this restriction is in effect:
12293 @code{Ada.Finalization.Controlled}
12296 @code{Ada.Finalization.Limited_Controlled}
12299 Derivations from @code{Controlled} or @code{Limited_Controlled}
12311 Array and record types with controlled components
12314 The compiler no longer generates code to initialize, finalize or adjust an
12315 object or a nested component, either declared on the stack or on the heap. The
12316 deallocation of a controlled object no longer finalizes its contents.
12318 @node No_Fixed_Point,No_Floating_Point,No_Finalization,Partition-Wide Restrictions
12319 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-fixed-point}@anchor{1cf}
12320 @subsection No_Fixed_Point
12323 @geindex No_Fixed_Point
12325 [RM H.4] This restriction ensures at compile time that there are no
12326 occurrences of fixed point types and operations.
12328 @node No_Floating_Point,No_Implicit_Conditionals,No_Fixed_Point,Partition-Wide Restrictions
12329 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-floating-point}@anchor{1d0}
12330 @subsection No_Floating_Point
12333 @geindex No_Floating_Point
12335 [RM H.4] This restriction ensures at compile time that there are no
12336 occurrences of floating point types and operations.
12338 @node No_Implicit_Conditionals,No_Implicit_Dynamic_Code,No_Floating_Point,Partition-Wide Restrictions
12339 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-conditionals}@anchor{1d1}
12340 @subsection No_Implicit_Conditionals
12343 @geindex No_Implicit_Conditionals
12345 [GNAT] This restriction ensures that the generated code does not contain any
12346 implicit conditionals, either by modifying the generated code where possible,
12347 or by rejecting any construct that would otherwise generate an implicit
12348 conditional. Note that this check does not include run time constraint
12349 checks, which on some targets may generate implicit conditionals as
12350 well. To control the latter, constraint checks can be suppressed in the
12351 normal manner. Constructs generating implicit conditionals include comparisons
12352 of composite objects and the Max/Min attributes.
12354 @node No_Implicit_Dynamic_Code,No_Implicit_Heap_Allocations,No_Implicit_Conditionals,Partition-Wide Restrictions
12355 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-dynamic-code}@anchor{1d2}
12356 @subsection No_Implicit_Dynamic_Code
12359 @geindex No_Implicit_Dynamic_Code
12361 @geindex trampoline
12363 [GNAT] This restriction prevents the compiler from building 'trampolines'.
12364 This is a structure that is built on the stack and contains dynamic
12365 code to be executed at run time. On some targets, a trampoline is
12366 built for the following features: @code{Access},
12367 @code{Unrestricted_Access}, or @code{Address} of a nested subprogram;
12368 nested task bodies; primitive operations of nested tagged types.
12369 Trampolines do not work on machines that prevent execution of stack
12370 data. For example, on windows systems, enabling DEP (data execution
12371 protection) will cause trampolines to raise an exception.
12372 Trampolines are also quite slow at run time.
12374 On many targets, trampolines have been largely eliminated. Look at the
12375 version of system.ads for your target --- if it has
12376 Always_Compatible_Rep equal to False, then trampolines are largely
12377 eliminated. In particular, a trampoline is built for the following
12378 features: @code{Address} of a nested subprogram;
12379 @code{Access} or @code{Unrestricted_Access} of a nested subprogram,
12380 but only if pragma Favor_Top_Level applies, or the access type has a
12381 foreign-language convention; primitive operations of nested tagged
12384 @node No_Implicit_Heap_Allocations,No_Implicit_Protected_Object_Allocations,No_Implicit_Dynamic_Code,Partition-Wide Restrictions
12385 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-heap-allocations}@anchor{1d3}
12386 @subsection No_Implicit_Heap_Allocations
12389 @geindex No_Implicit_Heap_Allocations
12391 [RM D.7] No constructs are allowed to cause implicit heap allocation.
12393 @node No_Implicit_Protected_Object_Allocations,No_Implicit_Task_Allocations,No_Implicit_Heap_Allocations,Partition-Wide Restrictions
12394 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-protected-object-allocations}@anchor{1d4}
12395 @subsection No_Implicit_Protected_Object_Allocations
12398 @geindex No_Implicit_Protected_Object_Allocations
12400 [GNAT] No constructs are allowed to cause implicit heap allocation of a
12403 @node No_Implicit_Task_Allocations,No_Initialize_Scalars,No_Implicit_Protected_Object_Allocations,Partition-Wide Restrictions
12404 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-task-allocations}@anchor{1d5}
12405 @subsection No_Implicit_Task_Allocations
12408 @geindex No_Implicit_Task_Allocations
12410 [GNAT] No constructs are allowed to cause implicit heap allocation of a task.
12412 @node No_Initialize_Scalars,No_IO,No_Implicit_Task_Allocations,Partition-Wide Restrictions
12413 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-initialize-scalars}@anchor{1d6}
12414 @subsection No_Initialize_Scalars
12417 @geindex No_Initialize_Scalars
12419 [GNAT] This restriction ensures that no unit in the partition is compiled with
12420 pragma Initialize_Scalars. This allows the generation of more efficient
12421 code, and in particular eliminates dummy null initialization routines that
12422 are otherwise generated for some record and array types.
12424 @node No_IO,No_Local_Allocators,No_Initialize_Scalars,Partition-Wide Restrictions
12425 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-io}@anchor{1d7}
12431 [RM H.4] This restriction ensures at compile time that there are no
12432 dependences on any of the library units Sequential_IO, Direct_IO,
12433 Text_IO, Wide_Text_IO, Wide_Wide_Text_IO, or Stream_IO.
12435 @node No_Local_Allocators,No_Local_Protected_Objects,No_IO,Partition-Wide Restrictions
12436 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-local-allocators}@anchor{1d8}
12437 @subsection No_Local_Allocators
12440 @geindex No_Local_Allocators
12442 [RM H.4] This restriction ensures at compile time that there are no
12443 occurrences of an allocator in subprograms, generic subprograms, tasks,
12446 @node No_Local_Protected_Objects,No_Local_Timing_Events,No_Local_Allocators,Partition-Wide Restrictions
12447 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-local-protected-objects}@anchor{1d9}
12448 @subsection No_Local_Protected_Objects
12451 @geindex No_Local_Protected_Objects
12453 [RM D.7] This restriction ensures at compile time that protected objects are
12454 only declared at the library level.
12456 @node No_Local_Timing_Events,No_Long_Long_Integers,No_Local_Protected_Objects,Partition-Wide Restrictions
12457 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-local-timing-events}@anchor{1da}
12458 @subsection No_Local_Timing_Events
12461 @geindex No_Local_Timing_Events
12463 [RM D.7] All objects of type Ada.Timing_Events.Timing_Event are
12464 declared at the library level.
12466 @node No_Long_Long_Integers,No_Multiple_Elaboration,No_Local_Timing_Events,Partition-Wide Restrictions
12467 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-long-long-integers}@anchor{1db}
12468 @subsection No_Long_Long_Integers
12471 @geindex No_Long_Long_Integers
12473 [GNAT] This partition-wide restriction forbids any explicit reference to
12474 type Standard.Long_Long_Integer, and also forbids declaring range types whose
12475 implicit base type is Long_Long_Integer, and modular types whose size exceeds
12478 @node No_Multiple_Elaboration,No_Nested_Finalization,No_Long_Long_Integers,Partition-Wide Restrictions
12479 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-multiple-elaboration}@anchor{1dc}
12480 @subsection No_Multiple_Elaboration
12483 @geindex No_Multiple_Elaboration
12485 [GNAT] When this restriction is active, we are not requesting control-flow
12486 preservation with -fpreserve-control-flow, and the static elaboration model is
12487 used, the compiler is allowed to suppress the elaboration counter normally
12488 associated with the unit, even if the unit has elaboration code. This counter
12489 is typically used to check for access before elaboration and to control
12490 multiple elaboration attempts. If the restriction is used, then the
12491 situations in which multiple elaboration is possible, including non-Ada main
12492 programs and Stand Alone libraries, are not permitted and will be diagnosed
12495 @node No_Nested_Finalization,No_Protected_Type_Allocators,No_Multiple_Elaboration,Partition-Wide Restrictions
12496 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-nested-finalization}@anchor{1dd}
12497 @subsection No_Nested_Finalization
12500 @geindex No_Nested_Finalization
12502 [RM D.7] All objects requiring finalization are declared at the library level.
12504 @node No_Protected_Type_Allocators,No_Protected_Types,No_Nested_Finalization,Partition-Wide Restrictions
12505 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-protected-type-allocators}@anchor{1de}
12506 @subsection No_Protected_Type_Allocators
12509 @geindex No_Protected_Type_Allocators
12511 [RM D.7] This restriction ensures at compile time that there are no allocator
12512 expressions that attempt to allocate protected objects.
12514 @node No_Protected_Types,No_Recursion,No_Protected_Type_Allocators,Partition-Wide Restrictions
12515 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-protected-types}@anchor{1df}
12516 @subsection No_Protected_Types
12519 @geindex No_Protected_Types
12521 [RM H.4] This restriction ensures at compile time that there are no
12522 declarations of protected types or protected objects.
12524 @node No_Recursion,No_Reentrancy,No_Protected_Types,Partition-Wide Restrictions
12525 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-recursion}@anchor{1e0}
12526 @subsection No_Recursion
12529 @geindex No_Recursion
12531 [RM H.4] A program execution is erroneous if a subprogram is invoked as
12532 part of its execution.
12534 @node No_Reentrancy,No_Relative_Delay,No_Recursion,Partition-Wide Restrictions
12535 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-reentrancy}@anchor{1e1}
12536 @subsection No_Reentrancy
12539 @geindex No_Reentrancy
12541 [RM H.4] A program execution is erroneous if a subprogram is executed by
12542 two tasks at the same time.
12544 @node No_Relative_Delay,No_Requeue_Statements,No_Reentrancy,Partition-Wide Restrictions
12545 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-relative-delay}@anchor{1e2}
12546 @subsection No_Relative_Delay
12549 @geindex No_Relative_Delay
12551 [RM D.7] This restriction ensures at compile time that there are no delay
12552 relative statements and prevents expressions such as @code{delay 1.23;} from
12553 appearing in source code.
12555 @node No_Requeue_Statements,No_Secondary_Stack,No_Relative_Delay,Partition-Wide Restrictions
12556 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-requeue-statements}@anchor{1e3}
12557 @subsection No_Requeue_Statements
12560 @geindex No_Requeue_Statements
12562 [RM D.7] This restriction ensures at compile time that no requeue statements
12563 are permitted and prevents keyword @code{requeue} from being used in source
12566 @geindex No_Requeue
12568 The restriction @code{No_Requeue} is recognized as a
12569 synonym for @code{No_Requeue_Statements}. This is retained for historical
12570 compatibility purposes (and a warning will be generated for its use if
12571 warnings on oNobsolescent features are activated).
12573 @node No_Secondary_Stack,No_Select_Statements,No_Requeue_Statements,Partition-Wide Restrictions
12574 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-secondary-stack}@anchor{1e4}
12575 @subsection No_Secondary_Stack
12578 @geindex No_Secondary_Stack
12580 [GNAT] This restriction ensures at compile time that the generated code
12581 does not contain any reference to the secondary stack. The secondary
12582 stack is used to implement functions returning unconstrained objects
12583 (arrays or records) on some targets. Suppresses the allocation of
12584 secondary stacks for tasks (excluding the environment task) at run time.
12586 @node No_Select_Statements,No_Specific_Termination_Handlers,No_Secondary_Stack,Partition-Wide Restrictions
12587 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-select-statements}@anchor{1e5}
12588 @subsection No_Select_Statements
12591 @geindex No_Select_Statements
12593 [RM D.7] This restriction ensures at compile time no select statements of any
12594 kind are permitted, that is the keyword @code{select} may not appear.
12596 @node No_Specific_Termination_Handlers,No_Specification_of_Aspect,No_Select_Statements,Partition-Wide Restrictions
12597 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-specific-termination-handlers}@anchor{1e6}
12598 @subsection No_Specific_Termination_Handlers
12601 @geindex No_Specific_Termination_Handlers
12603 [RM D.7] There are no calls to Ada.Task_Termination.Set_Specific_Handler
12604 or to Ada.Task_Termination.Specific_Handler.
12606 @node No_Specification_of_Aspect,No_Standard_Allocators_After_Elaboration,No_Specific_Termination_Handlers,Partition-Wide Restrictions
12607 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-specification-of-aspect}@anchor{1e7}
12608 @subsection No_Specification_of_Aspect
12611 @geindex No_Specification_of_Aspect
12613 [RM 13.12.1] This restriction checks at compile time that no aspect
12614 specification, attribute definition clause, or pragma is given for a
12617 @node No_Standard_Allocators_After_Elaboration,No_Standard_Storage_Pools,No_Specification_of_Aspect,Partition-Wide Restrictions
12618 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-standard-allocators-after-elaboration}@anchor{1e8}
12619 @subsection No_Standard_Allocators_After_Elaboration
12622 @geindex No_Standard_Allocators_After_Elaboration
12624 [RM D.7] Specifies that an allocator using a standard storage pool
12625 should never be evaluated at run time after the elaboration of the
12626 library items of the partition has completed. Otherwise, Storage_Error
12629 @node No_Standard_Storage_Pools,No_Stream_Optimizations,No_Standard_Allocators_After_Elaboration,Partition-Wide Restrictions
12630 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-standard-storage-pools}@anchor{1e9}
12631 @subsection No_Standard_Storage_Pools
12634 @geindex No_Standard_Storage_Pools
12636 [GNAT] This restriction ensures at compile time that no access types
12637 use the standard default storage pool. Any access type declared must
12638 have an explicit Storage_Pool attribute defined specifying a
12639 user-defined storage pool.
12641 @node No_Stream_Optimizations,No_Streams,No_Standard_Storage_Pools,Partition-Wide Restrictions
12642 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-stream-optimizations}@anchor{1ea}
12643 @subsection No_Stream_Optimizations
12646 @geindex No_Stream_Optimizations
12648 [GNAT] This restriction affects the performance of stream operations on types
12649 @code{String}, @code{Wide_String} and @code{Wide_Wide_String}. By default, the
12650 compiler uses block reads and writes when manipulating @code{String} objects
12651 due to their supperior performance. When this restriction is in effect, the
12652 compiler performs all IO operations on a per-character basis.
12654 @node No_Streams,No_Task_Allocators,No_Stream_Optimizations,Partition-Wide Restrictions
12655 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-streams}@anchor{1eb}
12656 @subsection No_Streams
12659 @geindex No_Streams
12661 [GNAT] This restriction ensures at compile/bind time that there are no
12662 stream objects created and no use of stream attributes.
12663 This restriction does not forbid dependences on the package
12664 @code{Ada.Streams}. So it is permissible to with
12665 @code{Ada.Streams} (or another package that does so itself)
12666 as long as no actual stream objects are created and no
12667 stream attributes are used.
12669 Note that the use of restriction allows optimization of tagged types,
12670 since they do not need to worry about dispatching stream operations.
12671 To take maximum advantage of this space-saving optimization, any
12672 unit declaring a tagged type should be compiled with the restriction,
12673 though this is not required.
12675 @node No_Task_Allocators,No_Task_At_Interrupt_Priority,No_Streams,Partition-Wide Restrictions
12676 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-task-allocators}@anchor{1ec}
12677 @subsection No_Task_Allocators
12680 @geindex No_Task_Allocators
12682 [RM D.7] There are no allocators for task types
12683 or types containing task subcomponents.
12685 @node No_Task_At_Interrupt_Priority,No_Task_Attributes_Package,No_Task_Allocators,Partition-Wide Restrictions
12686 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-task-at-interrupt-priority}@anchor{1ed}
12687 @subsection No_Task_At_Interrupt_Priority
12690 @geindex No_Task_At_Interrupt_Priority
12692 [GNAT] This restriction ensures at compile time that there is no
12693 Interrupt_Priority aspect or pragma for a task or a task type. As
12694 a consequence, the tasks are always created with a priority below
12695 that an interrupt priority.
12697 @node No_Task_Attributes_Package,No_Task_Hierarchy,No_Task_At_Interrupt_Priority,Partition-Wide Restrictions
12698 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-task-attributes-package}@anchor{1ee}
12699 @subsection No_Task_Attributes_Package
12702 @geindex No_Task_Attributes_Package
12704 [GNAT] This restriction ensures at compile time that there are no implicit or
12705 explicit dependencies on the package @code{Ada.Task_Attributes}.
12707 @geindex No_Task_Attributes
12709 The restriction @code{No_Task_Attributes} is recognized as a synonym
12710 for @code{No_Task_Attributes_Package}. This is retained for historical
12711 compatibility purposes (and a warning will be generated for its use if
12712 warnings on obsolescent features are activated).
12714 @node No_Task_Hierarchy,No_Task_Termination,No_Task_Attributes_Package,Partition-Wide Restrictions
12715 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-task-hierarchy}@anchor{1ef}
12716 @subsection No_Task_Hierarchy
12719 @geindex No_Task_Hierarchy
12721 [RM D.7] All (non-environment) tasks depend
12722 directly on the environment task of the partition.
12724 @node No_Task_Termination,No_Tasking,No_Task_Hierarchy,Partition-Wide Restrictions
12725 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-task-termination}@anchor{1f0}
12726 @subsection No_Task_Termination
12729 @geindex No_Task_Termination
12731 [RM D.7] Tasks that terminate are erroneous.
12733 @node No_Tasking,No_Terminate_Alternatives,No_Task_Termination,Partition-Wide Restrictions
12734 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-tasking}@anchor{1f1}
12735 @subsection No_Tasking
12738 @geindex No_Tasking
12740 [GNAT] This restriction prevents the declaration of tasks or task types
12741 throughout the partition. It is similar in effect to the use of
12742 @code{Max_Tasks => 0} except that violations are caught at compile time
12743 and cause an error message to be output either by the compiler or
12746 @node No_Terminate_Alternatives,No_Unchecked_Access,No_Tasking,Partition-Wide Restrictions
12747 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-terminate-alternatives}@anchor{1f2}
12748 @subsection No_Terminate_Alternatives
12751 @geindex No_Terminate_Alternatives
12753 [RM D.7] There are no selective accepts with terminate alternatives.
12755 @node No_Unchecked_Access,No_Unchecked_Conversion,No_Terminate_Alternatives,Partition-Wide Restrictions
12756 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-unchecked-access}@anchor{1f3}
12757 @subsection No_Unchecked_Access
12760 @geindex No_Unchecked_Access
12762 [RM H.4] This restriction ensures at compile time that there are no
12763 occurrences of the Unchecked_Access attribute.
12765 @node No_Unchecked_Conversion,No_Unchecked_Deallocation,No_Unchecked_Access,Partition-Wide Restrictions
12766 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-unchecked-conversion}@anchor{1f4}
12767 @subsection No_Unchecked_Conversion
12770 @geindex No_Unchecked_Conversion
12772 [RM J.13] This restriction ensures at compile time that there are no semantic
12773 dependences on the predefined generic function Unchecked_Conversion.
12775 @node No_Unchecked_Deallocation,No_Use_Of_Entity,No_Unchecked_Conversion,Partition-Wide Restrictions
12776 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-unchecked-deallocation}@anchor{1f5}
12777 @subsection No_Unchecked_Deallocation
12780 @geindex No_Unchecked_Deallocation
12782 [RM J.13] This restriction ensures at compile time that there are no semantic
12783 dependences on the predefined generic procedure Unchecked_Deallocation.
12785 @node No_Use_Of_Entity,Pure_Barriers,No_Unchecked_Deallocation,Partition-Wide Restrictions
12786 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-use-of-entity}@anchor{1f6}
12787 @subsection No_Use_Of_Entity
12790 @geindex No_Use_Of_Entity
12792 [GNAT] This restriction ensures at compile time that there are no references
12793 to the entity given in the form
12796 No_Use_Of_Entity => Name
12799 where @code{Name} is the fully qualified entity, for example
12802 No_Use_Of_Entity => Ada.Text_IO.Put_Line
12805 @node Pure_Barriers,Simple_Barriers,No_Use_Of_Entity,Partition-Wide Restrictions
12806 @anchor{gnat_rm/standard_and_implementation_defined_restrictions pure-barriers}@anchor{1f7}
12807 @subsection Pure_Barriers
12810 @geindex Pure_Barriers
12812 [GNAT] This restriction ensures at compile time that protected entry
12813 barriers are restricted to:
12819 components of the protected object (excluding selection from dereferences),
12822 constant declarations,
12828 enumeration literals,
12837 character literals,
12840 implicitly defined comparison operators,
12843 uses of the Standard."not" operator,
12846 short-circuit operator,
12849 the Count attribute
12852 This restriction is a relaxation of the Simple_Barriers restriction,
12853 but still ensures absence of side effects, exceptions, and recursion
12854 during the evaluation of the barriers.
12856 @node Simple_Barriers,Static_Priorities,Pure_Barriers,Partition-Wide Restrictions
12857 @anchor{gnat_rm/standard_and_implementation_defined_restrictions simple-barriers}@anchor{1f8}
12858 @subsection Simple_Barriers
12861 @geindex Simple_Barriers
12863 [RM D.7] This restriction ensures at compile time that barriers in entry
12864 declarations for protected types are restricted to either static boolean
12865 expressions or references to simple boolean variables defined in the private
12866 part of the protected type. No other form of entry barriers is permitted.
12868 @geindex Boolean_Entry_Barriers
12870 The restriction @code{Boolean_Entry_Barriers} is recognized as a
12871 synonym for @code{Simple_Barriers}. This is retained for historical
12872 compatibility purposes (and a warning will be generated for its use if
12873 warnings on obsolescent features are activated).
12875 @node Static_Priorities,Static_Storage_Size,Simple_Barriers,Partition-Wide Restrictions
12876 @anchor{gnat_rm/standard_and_implementation_defined_restrictions static-priorities}@anchor{1f9}
12877 @subsection Static_Priorities
12880 @geindex Static_Priorities
12882 [GNAT] This restriction ensures at compile time that all priority expressions
12883 are static, and that there are no dependences on the package
12884 @code{Ada.Dynamic_Priorities}.
12886 @node Static_Storage_Size,,Static_Priorities,Partition-Wide Restrictions
12887 @anchor{gnat_rm/standard_and_implementation_defined_restrictions static-storage-size}@anchor{1fa}
12888 @subsection Static_Storage_Size
12891 @geindex Static_Storage_Size
12893 [GNAT] This restriction ensures at compile time that any expression appearing
12894 in a Storage_Size pragma or attribute definition clause is static.
12896 @node Program Unit Level Restrictions,,Partition-Wide Restrictions,Standard and Implementation Defined Restrictions
12897 @anchor{gnat_rm/standard_and_implementation_defined_restrictions program-unit-level-restrictions}@anchor{1fb}@anchor{gnat_rm/standard_and_implementation_defined_restrictions id3}@anchor{1fc}
12898 @section Program Unit Level Restrictions
12901 The second set of restriction identifiers
12902 does not require partition-wide consistency.
12903 The restriction may be enforced for a single
12904 compilation unit without any effect on any of the
12905 other compilation units in the partition.
12908 * No_Elaboration_Code::
12909 * No_Dynamic_Sized_Objects::
12911 * No_Implementation_Aspect_Specifications::
12912 * No_Implementation_Attributes::
12913 * No_Implementation_Identifiers::
12914 * No_Implementation_Pragmas::
12915 * No_Implementation_Restrictions::
12916 * No_Implementation_Units::
12917 * No_Implicit_Aliasing::
12918 * No_Implicit_Loops::
12919 * No_Obsolescent_Features::
12920 * No_Wide_Characters::
12921 * Static_Dispatch_Tables::
12926 @node No_Elaboration_Code,No_Dynamic_Sized_Objects,,Program Unit Level Restrictions
12927 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-elaboration-code}@anchor{1fd}
12928 @subsection No_Elaboration_Code
12931 @geindex No_Elaboration_Code
12933 [GNAT] This restriction ensures at compile time that no elaboration code is
12934 generated. Note that this is not the same condition as is enforced
12935 by pragma @code{Preelaborate}. There are cases in which pragma
12936 @code{Preelaborate} still permits code to be generated (e.g., code
12937 to initialize a large array to all zeroes), and there are cases of units
12938 which do not meet the requirements for pragma @code{Preelaborate},
12939 but for which no elaboration code is generated. Generally, it is
12940 the case that preelaborable units will meet the restrictions, with
12941 the exception of large aggregates initialized with an others_clause,
12942 and exception declarations (which generate calls to a run-time
12943 registry procedure). This restriction is enforced on
12944 a unit by unit basis, it need not be obeyed consistently
12945 throughout a partition.
12947 In the case of aggregates with others, if the aggregate has a dynamic
12948 size, there is no way to eliminate the elaboration code (such dynamic
12949 bounds would be incompatible with @code{Preelaborate} in any case). If
12950 the bounds are static, then use of this restriction actually modifies
12951 the code choice of the compiler to avoid generating a loop, and instead
12952 generate the aggregate statically if possible, no matter how many times
12953 the data for the others clause must be repeatedly generated.
12955 It is not possible to precisely document
12956 the constructs which are compatible with this restriction, since,
12957 unlike most other restrictions, this is not a restriction on the
12958 source code, but a restriction on the generated object code. For
12959 example, if the source contains a declaration:
12962 Val : constant Integer := X;
12965 where X is not a static constant, it may be possible, depending
12966 on complex optimization circuitry, for the compiler to figure
12967 out the value of X at compile time, in which case this initialization
12968 can be done by the loader, and requires no initialization code. It
12969 is not possible to document the precise conditions under which the
12970 optimizer can figure this out.
12972 Note that this the implementation of this restriction requires full
12973 code generation. If it is used in conjunction with "semantics only"
12974 checking, then some cases of violations may be missed.
12976 When this restriction is active, we are not requesting control-flow
12977 preservation with -fpreserve-control-flow, and the static elaboration model is
12978 used, the compiler is allowed to suppress the elaboration counter normally
12979 associated with the unit. This counter is typically used to check for access
12980 before elaboration and to control multiple elaboration attempts.
12982 @node No_Dynamic_Sized_Objects,No_Entry_Queue,No_Elaboration_Code,Program Unit Level Restrictions
12983 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-dynamic-sized-objects}@anchor{1fe}
12984 @subsection No_Dynamic_Sized_Objects
12987 @geindex No_Dynamic_Sized_Objects
12989 [GNAT] This restriction disallows certain constructs that might lead to the
12990 creation of dynamic-sized composite objects (or array or discriminated type).
12991 An array subtype indication is illegal if the bounds are not static
12992 or references to discriminants of an enclosing type.
12993 A discriminated subtype indication is illegal if the type has
12994 discriminant-dependent array components or a variant part, and the
12995 discriminants are not static. In addition, array and record aggregates are
12996 illegal in corresponding cases. Note that this restriction does not forbid
12997 access discriminants. It is often a good idea to combine this restriction
12998 with No_Secondary_Stack.
13000 @node No_Entry_Queue,No_Implementation_Aspect_Specifications,No_Dynamic_Sized_Objects,Program Unit Level Restrictions
13001 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-entry-queue}@anchor{1ff}
13002 @subsection No_Entry_Queue
13005 @geindex No_Entry_Queue
13007 [GNAT] This restriction is a declaration that any protected entry compiled in
13008 the scope of the restriction has at most one task waiting on the entry
13009 at any one time, and so no queue is required. This restriction is not
13010 checked at compile time. A program execution is erroneous if an attempt
13011 is made to queue a second task on such an entry.
13013 @node No_Implementation_Aspect_Specifications,No_Implementation_Attributes,No_Entry_Queue,Program Unit Level Restrictions
13014 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implementation-aspect-specifications}@anchor{200}
13015 @subsection No_Implementation_Aspect_Specifications
13018 @geindex No_Implementation_Aspect_Specifications
13020 [RM 13.12.1] This restriction checks at compile time that no
13021 GNAT-defined aspects are present. With this restriction, the only
13022 aspects that can be used are those defined in the Ada Reference Manual.
13024 @node No_Implementation_Attributes,No_Implementation_Identifiers,No_Implementation_Aspect_Specifications,Program Unit Level Restrictions
13025 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implementation-attributes}@anchor{201}
13026 @subsection No_Implementation_Attributes
13029 @geindex No_Implementation_Attributes
13031 [RM 13.12.1] This restriction checks at compile time that no
13032 GNAT-defined attributes are present. With this restriction, the only
13033 attributes that can be used are those defined in the Ada Reference
13036 @node No_Implementation_Identifiers,No_Implementation_Pragmas,No_Implementation_Attributes,Program Unit Level Restrictions
13037 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implementation-identifiers}@anchor{202}
13038 @subsection No_Implementation_Identifiers
13041 @geindex No_Implementation_Identifiers
13043 [RM 13.12.1] This restriction checks at compile time that no
13044 implementation-defined identifiers (marked with pragma Implementation_Defined)
13045 occur within language-defined packages.
13047 @node No_Implementation_Pragmas,No_Implementation_Restrictions,No_Implementation_Identifiers,Program Unit Level Restrictions
13048 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implementation-pragmas}@anchor{203}
13049 @subsection No_Implementation_Pragmas
13052 @geindex No_Implementation_Pragmas
13054 [RM 13.12.1] This restriction checks at compile time that no
13055 GNAT-defined pragmas are present. With this restriction, the only
13056 pragmas that can be used are those defined in the Ada Reference Manual.
13058 @node No_Implementation_Restrictions,No_Implementation_Units,No_Implementation_Pragmas,Program Unit Level Restrictions
13059 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implementation-restrictions}@anchor{204}
13060 @subsection No_Implementation_Restrictions
13063 @geindex No_Implementation_Restrictions
13065 [GNAT] This restriction checks at compile time that no GNAT-defined restriction
13066 identifiers (other than @code{No_Implementation_Restrictions} itself)
13067 are present. With this restriction, the only other restriction identifiers
13068 that can be used are those defined in the Ada Reference Manual.
13070 @node No_Implementation_Units,No_Implicit_Aliasing,No_Implementation_Restrictions,Program Unit Level Restrictions
13071 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implementation-units}@anchor{205}
13072 @subsection No_Implementation_Units
13075 @geindex No_Implementation_Units
13077 [RM 13.12.1] This restriction checks at compile time that there is no
13078 mention in the context clause of any implementation-defined descendants
13079 of packages Ada, Interfaces, or System.
13081 @node No_Implicit_Aliasing,No_Implicit_Loops,No_Implementation_Units,Program Unit Level Restrictions
13082 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-aliasing}@anchor{206}
13083 @subsection No_Implicit_Aliasing
13086 @geindex No_Implicit_Aliasing
13088 [GNAT] This restriction, which is not required to be partition-wide consistent,
13089 requires an explicit aliased keyword for an object to which 'Access,
13090 'Unchecked_Access, or 'Address is applied, and forbids entirely the use of
13091 the 'Unrestricted_Access attribute for objects. Note: the reason that
13092 Unrestricted_Access is forbidden is that it would require the prefix
13093 to be aliased, and in such cases, it can always be replaced by
13094 the standard attribute Unchecked_Access which is preferable.
13096 @node No_Implicit_Loops,No_Obsolescent_Features,No_Implicit_Aliasing,Program Unit Level Restrictions
13097 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-loops}@anchor{207}
13098 @subsection No_Implicit_Loops
13101 @geindex No_Implicit_Loops
13103 [GNAT] This restriction ensures that the generated code of the unit marked
13104 with this restriction does not contain any implicit @code{for} loops, either by
13105 modifying the generated code where possible, or by rejecting any construct
13106 that would otherwise generate an implicit @code{for} loop. If this restriction is
13107 active, it is possible to build large array aggregates with all static
13108 components without generating an intermediate temporary, and without generating
13109 a loop to initialize individual components. Otherwise, a loop is created for
13110 arrays larger than about 5000 scalar components. Note that if this restriction
13111 is set in the spec of a package, it will not apply to its body.
13113 @node No_Obsolescent_Features,No_Wide_Characters,No_Implicit_Loops,Program Unit Level Restrictions
13114 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-obsolescent-features}@anchor{208}
13115 @subsection No_Obsolescent_Features
13118 @geindex No_Obsolescent_Features
13120 [RM 13.12.1] This restriction checks at compile time that no obsolescent
13121 features are used, as defined in Annex J of the Ada Reference Manual.
13123 @node No_Wide_Characters,Static_Dispatch_Tables,No_Obsolescent_Features,Program Unit Level Restrictions
13124 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-wide-characters}@anchor{209}
13125 @subsection No_Wide_Characters
13128 @geindex No_Wide_Characters
13130 [GNAT] This restriction ensures at compile time that no uses of the types
13131 @code{Wide_Character} or @code{Wide_String} or corresponding wide
13133 appear, and that no wide or wide wide string or character literals
13134 appear in the program (that is literals representing characters not in
13135 type @code{Character}).
13137 @node Static_Dispatch_Tables,SPARK_05,No_Wide_Characters,Program Unit Level Restrictions
13138 @anchor{gnat_rm/standard_and_implementation_defined_restrictions static-dispatch-tables}@anchor{20a}
13139 @subsection Static_Dispatch_Tables
13142 @geindex Static_Dispatch_Tables
13144 [GNAT] This restriction checks at compile time that all the artifacts
13145 associated with dispatch tables can be placed in read-only memory.
13147 @node SPARK_05,,Static_Dispatch_Tables,Program Unit Level Restrictions
13148 @anchor{gnat_rm/standard_and_implementation_defined_restrictions spark-05}@anchor{20b}
13149 @subsection SPARK_05
13154 [GNAT] This restriction checks at compile time that some constructs
13155 forbidden in SPARK 2005 are not present. Error messages related to
13156 SPARK restriction have the form:
13159 violation of restriction "SPARK_05" at <source-location>
13165 The restriction @code{SPARK} is recognized as a
13166 synonym for @code{SPARK_05}. This is retained for historical
13167 compatibility purposes (and an unconditional warning will be generated
13168 for its use, advising replacement by @code{SPARK}).
13170 This is not a replacement for the semantic checks performed by the
13171 SPARK Examiner tool, as the compiler currently only deals with code,
13172 not SPARK 2005 annotations, and does not guarantee catching all
13173 cases of constructs forbidden by SPARK 2005.
13175 Thus it may well be the case that code which passes the compiler with
13176 the SPARK restriction is rejected by the SPARK Examiner, e.g. due to
13177 the different visibility rules of the Examiner based on SPARK 2005
13178 @code{inherit} annotations.
13180 This restriction can be useful in providing an initial filter for code
13181 developed using SPARK 2005, or in examining legacy code to see how far
13182 it is from meeting SPARK restrictions.
13184 The list below summarizes the checks that are performed when this
13185 restriction is in force:
13191 No block statements
13194 No case statements with only an others clause
13197 Exit statements in loops must respect the SPARK 2005 language restrictions
13203 Return can only appear as last statement in function
13206 Function must have return statement
13209 Loop parameter specification must include subtype mark
13212 Prefix of expanded name cannot be a loop statement
13215 Abstract subprogram not allowed
13218 User-defined operators not allowed
13221 Access type parameters not allowed
13224 Default expressions for parameters not allowed
13227 Default expressions for record fields not allowed
13230 No tasking constructs allowed
13233 Label needed at end of subprograms and packages
13236 No mixing of positional and named parameter association
13239 No access types as result type
13242 No unconstrained arrays as result types
13248 Initial and later declarations must be in correct order (declaration can't come after body)
13251 No attributes on private types if full declaration not visible
13254 No package declaration within package specification
13257 No controlled types
13260 No discriminant types
13266 Selector name cannot be operator symbol (i.e. operator symbol cannot be prefixed)
13269 Access attribute not allowed
13272 Allocator not allowed
13275 Result of catenation must be String
13278 Operands of catenation must be string literal, static char or another catenation
13281 No conditional expressions
13284 No explicit dereference
13287 Quantified expression not allowed
13290 Slicing not allowed
13293 No exception renaming
13296 No generic renaming
13305 Aggregates must be qualified
13308 Nonstatic choice in array aggregates not allowed
13311 The only view conversions which are allowed as in-out parameters are conversions of a tagged type to an ancestor type
13314 No mixing of positional and named association in aggregate, no multi choice
13317 AND, OR and XOR for arrays only allowed when operands have same static bounds
13320 Fixed point operands to * or / must be qualified or converted
13323 Comparison operators not allowed for Booleans or arrays (except strings)
13326 Equality not allowed for arrays with non-matching static bounds (except strings)
13329 Conversion / qualification not allowed for arrays with non-matching static bounds
13332 Subprogram declaration only allowed in package spec (unless followed by import)
13335 Access types not allowed
13338 Incomplete type declaration not allowed
13341 Object and subtype declarations must respect SPARK restrictions
13344 Digits or delta constraint not allowed
13347 Decimal fixed point type not allowed
13350 Aliasing of objects not allowed
13353 Modular type modulus must be power of 2
13356 Base not allowed on subtype mark
13359 Unary operators not allowed on modular types (except not)
13362 Untagged record cannot be null
13365 No class-wide operations
13368 Initialization expressions must respect SPARK restrictions
13371 Nonstatic ranges not allowed except in iteration schemes
13374 String subtypes must have lower bound of 1
13377 Subtype of Boolean cannot have constraint
13380 At most one tagged type or extension per package
13383 Interface is not allowed
13386 Character literal cannot be prefixed (selector name cannot be character literal)
13389 Record aggregate cannot contain 'others'
13392 Component association in record aggregate must contain a single choice
13395 Ancestor part cannot be a type mark
13398 Attributes 'Image, 'Width and 'Value not allowed
13401 Functions may not update globals
13404 Subprograms may not contain direct calls to themselves (prevents recursion within unit)
13407 Call to subprogram not allowed in same unit before body has been seen (prevents recursion within unit)
13410 The following restrictions are enforced, but note that they are actually more
13411 strict that the latest SPARK 2005 language definition:
13417 No derived types other than tagged type extensions
13420 Subtype of unconstrained array must have constraint
13423 This list summarises the main SPARK 2005 language rules that are not
13424 currently checked by the SPARK_05 restriction:
13430 SPARK annotations are treated as comments so are not checked at all
13433 Based real literals not allowed
13436 Objects cannot be initialized at declaration by calls to user-defined functions
13439 Objects cannot be initialized at declaration by assignments from variables
13442 Objects cannot be initialized at declaration by assignments from indexed/selected components
13445 Ranges shall not be null
13448 A fixed point delta expression must be a simple expression
13451 Restrictions on where renaming declarations may be placed
13454 Externals of mode 'out' cannot be referenced
13457 Externals of mode 'in' cannot be updated
13460 Loop with no iteration scheme or exits only allowed as last statement in main program or task
13463 Subprogram cannot have parent unit name
13466 SPARK 2005 inherited subprogram must be prefixed with overriding
13469 External variables (or functions that reference them) may not be passed as actual parameters
13472 Globals must be explicitly mentioned in contract
13475 Deferred constants cannot be completed by pragma Import
13478 Package initialization cannot read/write variables from other packages
13481 Prefix not allowed for entities that are directly visible
13484 Identifier declaration can't override inherited package name
13487 Cannot use Standard or other predefined packages as identifiers
13490 After renaming, cannot use the original name
13493 Subprograms can only be renamed to remove package prefix
13496 Pragma import must be immediately after entity it names
13499 No mutual recursion between multiple units (this can be checked with gnatcheck)
13502 Note that if a unit is compiled in Ada 95 mode with the SPARK restriction,
13503 violations will be reported for constructs forbidden in SPARK 95,
13504 instead of SPARK 2005.
13506 @node Implementation Advice,Implementation Defined Characteristics,Standard and Implementation Defined Restrictions,Top
13507 @anchor{gnat_rm/implementation_advice doc}@anchor{20c}@anchor{gnat_rm/implementation_advice implementation-advice}@anchor{a}@anchor{gnat_rm/implementation_advice id1}@anchor{20d}
13508 @chapter Implementation Advice
13511 The main text of the Ada Reference Manual describes the required
13512 behavior of all Ada compilers, and the GNAT compiler conforms to
13513 these requirements.
13515 In addition, there are sections throughout the Ada Reference Manual headed
13516 by the phrase 'Implementation advice'. These sections are not normative,
13517 i.e., they do not specify requirements that all compilers must
13518 follow. Rather they provide advice on generally desirable behavior.
13519 They are not requirements, because they describe behavior that cannot
13520 be provided on all systems, or may be undesirable on some systems.
13522 As far as practical, GNAT follows the implementation advice in
13523 the Ada Reference Manual. Each such RM section corresponds to a section
13524 in this chapter whose title specifies the
13525 RM section number and paragraph number and the subject of
13526 the advice. The contents of each section consists of the RM text within
13528 followed by the GNAT interpretation of the advice. Most often, this simply says
13529 'followed', which means that GNAT follows the advice. However, in a
13530 number of cases, GNAT deliberately deviates from this advice, in which
13531 case the text describes what GNAT does and why.
13533 @geindex Error detection
13536 * RM 1.1.3(20); Error Detection: RM 1 1 3 20 Error Detection.
13537 * RM 1.1.3(31); Child Units: RM 1 1 3 31 Child Units.
13538 * RM 1.1.5(12); Bounded Errors: RM 1 1 5 12 Bounded Errors.
13539 * RM 2.8(16); Pragmas: RM 2 8 16 Pragmas.
13540 * RM 2.8(17-19); Pragmas: RM 2 8 17-19 Pragmas.
13541 * RM 3.5.2(5); Alternative Character Sets: RM 3 5 2 5 Alternative Character Sets.
13542 * RM 3.5.4(28); Integer Types: RM 3 5 4 28 Integer Types.
13543 * RM 3.5.4(29); Integer Types: RM 3 5 4 29 Integer Types.
13544 * RM 3.5.5(8); Enumeration Values: RM 3 5 5 8 Enumeration Values.
13545 * RM 3.5.7(17); Float Types: RM 3 5 7 17 Float Types.
13546 * RM 3.6.2(11); Multidimensional Arrays: RM 3 6 2 11 Multidimensional Arrays.
13547 * RM 9.6(30-31); Duration'Small: RM 9 6 30-31 Duration'Small.
13548 * RM 10.2.1(12); Consistent Representation: RM 10 2 1 12 Consistent Representation.
13549 * RM 11.4.1(19); Exception Information: RM 11 4 1 19 Exception Information.
13550 * RM 11.5(28); Suppression of Checks: RM 11 5 28 Suppression of Checks.
13551 * RM 13.1 (21-24); Representation Clauses: RM 13 1 21-24 Representation Clauses.
13552 * RM 13.2(6-8); Packed Types: RM 13 2 6-8 Packed Types.
13553 * RM 13.3(14-19); Address Clauses: RM 13 3 14-19 Address Clauses.
13554 * RM 13.3(29-35); Alignment Clauses: RM 13 3 29-35 Alignment Clauses.
13555 * RM 13.3(42-43); Size Clauses: RM 13 3 42-43 Size Clauses.
13556 * RM 13.3(50-56); Size Clauses: RM 13 3 50-56 Size Clauses.
13557 * RM 13.3(71-73); Component Size Clauses: RM 13 3 71-73 Component Size Clauses.
13558 * RM 13.4(9-10); Enumeration Representation Clauses: RM 13 4 9-10 Enumeration Representation Clauses.
13559 * RM 13.5.1(17-22); Record Representation Clauses: RM 13 5 1 17-22 Record Representation Clauses.
13560 * RM 13.5.2(5); Storage Place Attributes: RM 13 5 2 5 Storage Place Attributes.
13561 * RM 13.5.3(7-8); Bit Ordering: RM 13 5 3 7-8 Bit Ordering.
13562 * RM 13.7(37); Address as Private: RM 13 7 37 Address as Private.
13563 * RM 13.7.1(16); Address Operations: RM 13 7 1 16 Address Operations.
13564 * RM 13.9(14-17); Unchecked Conversion: RM 13 9 14-17 Unchecked Conversion.
13565 * RM 13.11(23-25); Implicit Heap Usage: RM 13 11 23-25 Implicit Heap Usage.
13566 * RM 13.11.2(17); Unchecked Deallocation: RM 13 11 2 17 Unchecked Deallocation.
13567 * RM 13.13.2(17); Stream Oriented Attributes: RM 13 13 2 17 Stream Oriented Attributes.
13568 * RM A.1(52); Names of Predefined Numeric Types: RM A 1 52 Names of Predefined Numeric Types.
13569 * RM A.3.2(49); Ada.Characters.Handling: RM A 3 2 49 Ada Characters Handling.
13570 * RM A.4.4(106); Bounded-Length String Handling: RM A 4 4 106 Bounded-Length String Handling.
13571 * RM A.5.2(46-47); Random Number Generation: RM A 5 2 46-47 Random Number Generation.
13572 * RM A.10.7(23); Get_Immediate: RM A 10 7 23 Get_Immediate.
13573 * RM B.1(39-41); Pragma Export: RM B 1 39-41 Pragma Export.
13574 * RM B.2(12-13); Package Interfaces: RM B 2 12-13 Package Interfaces.
13575 * RM B.3(63-71); Interfacing with C: RM B 3 63-71 Interfacing with C.
13576 * RM B.4(95-98); Interfacing with COBOL: RM B 4 95-98 Interfacing with COBOL.
13577 * RM B.5(22-26); Interfacing with Fortran: RM B 5 22-26 Interfacing with Fortran.
13578 * RM C.1(3-5); Access to Machine Operations: RM C 1 3-5 Access to Machine Operations.
13579 * RM C.1(10-16); Access to Machine Operations: RM C 1 10-16 Access to Machine Operations.
13580 * RM C.3(28); Interrupt Support: RM C 3 28 Interrupt Support.
13581 * RM C.3.1(20-21); Protected Procedure Handlers: RM C 3 1 20-21 Protected Procedure Handlers.
13582 * RM C.3.2(25); Package Interrupts: RM C 3 2 25 Package Interrupts.
13583 * RM C.4(14); Pre-elaboration Requirements: RM C 4 14 Pre-elaboration Requirements.
13584 * RM C.5(8); Pragma Discard_Names: RM C 5 8 Pragma Discard_Names.
13585 * RM C.7.2(30); The Package Task_Attributes: RM C 7 2 30 The Package Task_Attributes.
13586 * RM D.3(17); Locking Policies: RM D 3 17 Locking Policies.
13587 * RM D.4(16); Entry Queuing Policies: RM D 4 16 Entry Queuing Policies.
13588 * RM D.6(9-10); Preemptive Abort: RM D 6 9-10 Preemptive Abort.
13589 * RM D.7(21); Tasking Restrictions: RM D 7 21 Tasking Restrictions.
13590 * RM D.8(47-49); Monotonic Time: RM D 8 47-49 Monotonic Time.
13591 * RM E.5(28-29); Partition Communication Subsystem: RM E 5 28-29 Partition Communication Subsystem.
13592 * RM F(7); COBOL Support: RM F 7 COBOL Support.
13593 * RM F.1(2); Decimal Radix Support: RM F 1 2 Decimal Radix Support.
13594 * RM G; Numerics: RM G Numerics.
13595 * RM G.1.1(56-58); Complex Types: RM G 1 1 56-58 Complex Types.
13596 * RM G.1.2(49); Complex Elementary Functions: RM G 1 2 49 Complex Elementary Functions.
13597 * RM G.2.4(19); Accuracy Requirements: RM G 2 4 19 Accuracy Requirements.
13598 * RM G.2.6(15); Complex Arithmetic Accuracy: RM G 2 6 15 Complex Arithmetic Accuracy.
13599 * RM H.6(15/2); Pragma Partition_Elaboration_Policy: RM H 6 15/2 Pragma Partition_Elaboration_Policy.
13603 @node RM 1 1 3 20 Error Detection,RM 1 1 3 31 Child Units,,Implementation Advice
13604 @anchor{gnat_rm/implementation_advice rm-1-1-3-20-error-detection}@anchor{20e}
13605 @section RM 1.1.3(20): Error Detection
13610 "If an implementation detects the use of an unsupported Specialized Needs
13611 Annex feature at run time, it should raise @code{Program_Error} if
13615 Not relevant. All specialized needs annex features are either supported,
13616 or diagnosed at compile time.
13618 @geindex Child Units
13620 @node RM 1 1 3 31 Child Units,RM 1 1 5 12 Bounded Errors,RM 1 1 3 20 Error Detection,Implementation Advice
13621 @anchor{gnat_rm/implementation_advice rm-1-1-3-31-child-units}@anchor{20f}
13622 @section RM 1.1.3(31): Child Units
13627 "If an implementation wishes to provide implementation-defined
13628 extensions to the functionality of a language-defined library unit, it
13629 should normally do so by adding children to the library unit."
13634 @geindex Bounded errors
13636 @node RM 1 1 5 12 Bounded Errors,RM 2 8 16 Pragmas,RM 1 1 3 31 Child Units,Implementation Advice
13637 @anchor{gnat_rm/implementation_advice rm-1-1-5-12-bounded-errors}@anchor{210}
13638 @section RM 1.1.5(12): Bounded Errors
13643 "If an implementation detects a bounded error or erroneous
13644 execution, it should raise @code{Program_Error}."
13647 Followed in all cases in which the implementation detects a bounded
13648 error or erroneous execution. Not all such situations are detected at
13653 @node RM 2 8 16 Pragmas,RM 2 8 17-19 Pragmas,RM 1 1 5 12 Bounded Errors,Implementation Advice
13654 @anchor{gnat_rm/implementation_advice id2}@anchor{211}@anchor{gnat_rm/implementation_advice rm-2-8-16-pragmas}@anchor{212}
13655 @section RM 2.8(16): Pragmas
13660 "Normally, implementation-defined pragmas should have no semantic effect
13661 for error-free programs; that is, if the implementation-defined pragmas
13662 are removed from a working program, the program should still be legal,
13663 and should still have the same semantics."
13666 The following implementation defined pragmas are exceptions to this
13670 @multitable {xxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxx}
13713 @emph{CPP_Constructor}
13729 @emph{Interface_Name}
13737 @emph{Machine_Attribute}
13745 @emph{Unimplemented_Unit}
13753 @emph{Unchecked_Union}
13762 In each of the above cases, it is essential to the purpose of the pragma
13763 that this advice not be followed. For details see
13764 @ref{7,,Implementation Defined Pragmas}.
13766 @node RM 2 8 17-19 Pragmas,RM 3 5 2 5 Alternative Character Sets,RM 2 8 16 Pragmas,Implementation Advice
13767 @anchor{gnat_rm/implementation_advice rm-2-8-17-19-pragmas}@anchor{213}
13768 @section RM 2.8(17-19): Pragmas
13773 "Normally, an implementation should not define pragmas that can
13774 make an illegal program legal, except as follows:
13780 A pragma used to complete a declaration, such as a pragma @code{Import};
13783 A pragma used to configure the environment by adding, removing, or
13784 replacing @code{library_items}."
13788 See @ref{212,,RM 2.8(16); Pragmas}.
13790 @geindex Character Sets
13792 @geindex Alternative Character Sets
13794 @node RM 3 5 2 5 Alternative Character Sets,RM 3 5 4 28 Integer Types,RM 2 8 17-19 Pragmas,Implementation Advice
13795 @anchor{gnat_rm/implementation_advice rm-3-5-2-5-alternative-character-sets}@anchor{214}
13796 @section RM 3.5.2(5): Alternative Character Sets
13801 "If an implementation supports a mode with alternative interpretations
13802 for @code{Character} and @code{Wide_Character}, the set of graphic
13803 characters of @code{Character} should nevertheless remain a proper
13804 subset of the set of graphic characters of @code{Wide_Character}. Any
13805 character set 'localizations' should be reflected in the results of
13806 the subprograms defined in the language-defined package
13807 @code{Characters.Handling} (see A.3) available in such a mode. In a mode with
13808 an alternative interpretation of @code{Character}, the implementation should
13809 also support a corresponding change in what is a legal
13810 @code{identifier_letter}."
13813 Not all wide character modes follow this advice, in particular the JIS
13814 and IEC modes reflect standard usage in Japan, and in these encoding,
13815 the upper half of the Latin-1 set is not part of the wide-character
13816 subset, since the most significant bit is used for wide character
13817 encoding. However, this only applies to the external forms. Internally
13818 there is no such restriction.
13820 @geindex Integer types
13822 @node RM 3 5 4 28 Integer Types,RM 3 5 4 29 Integer Types,RM 3 5 2 5 Alternative Character Sets,Implementation Advice
13823 @anchor{gnat_rm/implementation_advice rm-3-5-4-28-integer-types}@anchor{215}
13824 @section RM 3.5.4(28): Integer Types
13829 "An implementation should support @code{Long_Integer} in addition to
13830 @code{Integer} if the target machine supports 32-bit (or longer)
13831 arithmetic. No other named integer subtypes are recommended for package
13832 @code{Standard}. Instead, appropriate named integer subtypes should be
13833 provided in the library package @code{Interfaces} (see B.2)."
13836 @code{Long_Integer} is supported. Other standard integer types are supported
13837 so this advice is not fully followed. These types
13838 are supported for convenient interface to C, and so that all hardware
13839 types of the machine are easily available.
13841 @node RM 3 5 4 29 Integer Types,RM 3 5 5 8 Enumeration Values,RM 3 5 4 28 Integer Types,Implementation Advice
13842 @anchor{gnat_rm/implementation_advice rm-3-5-4-29-integer-types}@anchor{216}
13843 @section RM 3.5.4(29): Integer Types
13848 "An implementation for a two's complement machine should support
13849 modular types with a binary modulus up to @code{System.Max_Int*2+2}. An
13850 implementation should support a non-binary modules up to @code{Integer'Last}."
13855 @geindex Enumeration values
13857 @node RM 3 5 5 8 Enumeration Values,RM 3 5 7 17 Float Types,RM 3 5 4 29 Integer Types,Implementation Advice
13858 @anchor{gnat_rm/implementation_advice rm-3-5-5-8-enumeration-values}@anchor{217}
13859 @section RM 3.5.5(8): Enumeration Values
13864 "For the evaluation of a call on @code{S'Pos} for an enumeration
13865 subtype, if the value of the operand does not correspond to the internal
13866 code for any enumeration literal of its type (perhaps due to an
13867 un-initialized variable), then the implementation should raise
13868 @code{Program_Error}. This is particularly important for enumeration
13869 types with noncontiguous internal codes specified by an
13870 enumeration_representation_clause."
13875 @geindex Float types
13877 @node RM 3 5 7 17 Float Types,RM 3 6 2 11 Multidimensional Arrays,RM 3 5 5 8 Enumeration Values,Implementation Advice
13878 @anchor{gnat_rm/implementation_advice rm-3-5-7-17-float-types}@anchor{218}
13879 @section RM 3.5.7(17): Float Types
13884 "An implementation should support @code{Long_Float} in addition to
13885 @code{Float} if the target machine supports 11 or more digits of
13886 precision. No other named floating point subtypes are recommended for
13887 package @code{Standard}. Instead, appropriate named floating point subtypes
13888 should be provided in the library package @code{Interfaces} (see B.2)."
13891 @code{Short_Float} and @code{Long_Long_Float} are also provided. The
13892 former provides improved compatibility with other implementations
13893 supporting this type. The latter corresponds to the highest precision
13894 floating-point type supported by the hardware. On most machines, this
13895 will be the same as @code{Long_Float}, but on some machines, it will
13896 correspond to the IEEE extended form. The notable case is all ia32
13897 (x86) implementations, where @code{Long_Long_Float} corresponds to
13898 the 80-bit extended precision format supported in hardware on this
13899 processor. Note that the 128-bit format on SPARC is not supported,
13900 since this is a software rather than a hardware format.
13902 @geindex Multidimensional arrays
13905 @geindex multidimensional
13907 @node RM 3 6 2 11 Multidimensional Arrays,RM 9 6 30-31 Duration'Small,RM 3 5 7 17 Float Types,Implementation Advice
13908 @anchor{gnat_rm/implementation_advice rm-3-6-2-11-multidimensional-arrays}@anchor{219}
13909 @section RM 3.6.2(11): Multidimensional Arrays
13914 "An implementation should normally represent multidimensional arrays in
13915 row-major order, consistent with the notation used for multidimensional
13916 array aggregates (see 4.3.3). However, if a pragma @code{Convention}
13917 (@code{Fortran}, ...) applies to a multidimensional array type, then
13918 column-major order should be used instead (see B.5, @emph{Interfacing with Fortran})."
13923 @geindex Duration'Small
13925 @node RM 9 6 30-31 Duration'Small,RM 10 2 1 12 Consistent Representation,RM 3 6 2 11 Multidimensional Arrays,Implementation Advice
13926 @anchor{gnat_rm/implementation_advice rm-9-6-30-31-duration-small}@anchor{21a}
13927 @section RM 9.6(30-31): Duration'Small
13932 "Whenever possible in an implementation, the value of @code{Duration'Small}
13933 should be no greater than 100 microseconds."
13936 Followed. (@code{Duration'Small} = 10**(-9)).
13940 "The time base for @code{delay_relative_statements} should be monotonic;
13941 it need not be the same time base as used for @code{Calendar.Clock}."
13946 @node RM 10 2 1 12 Consistent Representation,RM 11 4 1 19 Exception Information,RM 9 6 30-31 Duration'Small,Implementation Advice
13947 @anchor{gnat_rm/implementation_advice rm-10-2-1-12-consistent-representation}@anchor{21b}
13948 @section RM 10.2.1(12): Consistent Representation
13953 "In an implementation, a type declared in a pre-elaborated package should
13954 have the same representation in every elaboration of a given version of
13955 the package, whether the elaborations occur in distinct executions of
13956 the same program, or in executions of distinct programs or partitions
13957 that include the given version."
13960 Followed, except in the case of tagged types. Tagged types involve
13961 implicit pointers to a local copy of a dispatch table, and these pointers
13962 have representations which thus depend on a particular elaboration of the
13963 package. It is not easy to see how it would be possible to follow this
13964 advice without severely impacting efficiency of execution.
13966 @geindex Exception information
13968 @node RM 11 4 1 19 Exception Information,RM 11 5 28 Suppression of Checks,RM 10 2 1 12 Consistent Representation,Implementation Advice
13969 @anchor{gnat_rm/implementation_advice rm-11-4-1-19-exception-information}@anchor{21c}
13970 @section RM 11.4.1(19): Exception Information
13975 "@code{Exception_Message} by default and @code{Exception_Information}
13976 should produce information useful for
13977 debugging. @code{Exception_Message} should be short, about one
13978 line. @code{Exception_Information} can be long. @code{Exception_Message}
13979 should not include the
13980 @code{Exception_Name}. @code{Exception_Information} should include both
13981 the @code{Exception_Name} and the @code{Exception_Message}."
13984 Followed. For each exception that doesn't have a specified
13985 @code{Exception_Message}, the compiler generates one containing the location
13986 of the raise statement. This location has the form 'file_name:line', where
13987 file_name is the short file name (without path information) and line is the line
13988 number in the file. Note that in the case of the Zero Cost Exception
13989 mechanism, these messages become redundant with the Exception_Information that
13990 contains a full backtrace of the calling sequence, so they are disabled.
13991 To disable explicitly the generation of the source location message, use the
13992 Pragma @code{Discard_Names}.
13994 @geindex Suppression of checks
13997 @geindex suppression of
13999 @node RM 11 5 28 Suppression of Checks,RM 13 1 21-24 Representation Clauses,RM 11 4 1 19 Exception Information,Implementation Advice
14000 @anchor{gnat_rm/implementation_advice rm-11-5-28-suppression-of-checks}@anchor{21d}
14001 @section RM 11.5(28): Suppression of Checks
14006 "The implementation should minimize the code executed for checks that
14007 have been suppressed."
14012 @geindex Representation clauses
14014 @node RM 13 1 21-24 Representation Clauses,RM 13 2 6-8 Packed Types,RM 11 5 28 Suppression of Checks,Implementation Advice
14015 @anchor{gnat_rm/implementation_advice rm-13-1-21-24-representation-clauses}@anchor{21e}
14016 @section RM 13.1 (21-24): Representation Clauses
14021 "The recommended level of support for all representation items is
14022 qualified as follows:
14024 An implementation need not support representation items containing
14025 nonstatic expressions, except that an implementation should support a
14026 representation item for a given entity if each nonstatic expression in
14027 the representation item is a name that statically denotes a constant
14028 declared before the entity."
14031 Followed. In fact, GNAT goes beyond the recommended level of support
14032 by allowing nonstatic expressions in some representation clauses even
14033 without the need to declare constants initialized with the values of
14040 for Y'Address use X'Address;>>
14043 "An implementation need not support a specification for the `@w{`}Size`@w{`}
14044 for a given composite subtype, nor the size or storage place for an
14045 object (including a component) of a given composite subtype, unless the
14046 constraints on the subtype and its composite subcomponents (if any) are
14047 all static constraints."
14050 Followed. Size Clauses are not permitted on nonstatic components, as
14055 "An aliased component, or a component whose type is by-reference, should
14056 always be allocated at an addressable location."
14061 @geindex Packed types
14063 @node RM 13 2 6-8 Packed Types,RM 13 3 14-19 Address Clauses,RM 13 1 21-24 Representation Clauses,Implementation Advice
14064 @anchor{gnat_rm/implementation_advice rm-13-2-6-8-packed-types}@anchor{21f}
14065 @section RM 13.2(6-8): Packed Types
14070 "If a type is packed, then the implementation should try to minimize
14071 storage allocated to objects of the type, possibly at the expense of
14072 speed of accessing components, subject to reasonable complexity in
14073 addressing calculations.
14075 The recommended level of support pragma @code{Pack} is:
14077 For a packed record type, the components should be packed as tightly as
14078 possible subject to the Sizes of the component subtypes, and subject to
14079 any @emph{record_representation_clause} that applies to the type; the
14080 implementation may, but need not, reorder components or cross aligned
14081 word boundaries to improve the packing. A component whose @code{Size} is
14082 greater than the word size may be allocated an integral number of words."
14085 Followed. Tight packing of arrays is supported for all component sizes
14086 up to 64-bits. If the array component size is 1 (that is to say, if
14087 the component is a boolean type or an enumeration type with two values)
14088 then values of the type are implicitly initialized to zero. This
14089 happens both for objects of the packed type, and for objects that have a
14090 subcomponent of the packed type.
14094 "An implementation should support Address clauses for imported
14100 @geindex Address clauses
14102 @node RM 13 3 14-19 Address Clauses,RM 13 3 29-35 Alignment Clauses,RM 13 2 6-8 Packed Types,Implementation Advice
14103 @anchor{gnat_rm/implementation_advice rm-13-3-14-19-address-clauses}@anchor{220}
14104 @section RM 13.3(14-19): Address Clauses
14109 "For an array @code{X}, @code{X'Address} should point at the first
14110 component of the array, and not at the array bounds."
14117 "The recommended level of support for the @code{Address} attribute is:
14119 @code{X'Address} should produce a useful result if @code{X} is an
14120 object that is aliased or of a by-reference type, or is an entity whose
14121 @code{Address} has been specified."
14124 Followed. A valid address will be produced even if none of those
14125 conditions have been met. If necessary, the object is forced into
14126 memory to ensure the address is valid.
14130 "An implementation should support @code{Address} clauses for imported
14138 "Objects (including subcomponents) that are aliased or of a by-reference
14139 type should be allocated on storage element boundaries."
14146 "If the @code{Address} of an object is specified, or it is imported or exported,
14147 then the implementation should not perform optimizations based on
14148 assumptions of no aliases."
14153 @geindex Alignment clauses
14155 @node RM 13 3 29-35 Alignment Clauses,RM 13 3 42-43 Size Clauses,RM 13 3 14-19 Address Clauses,Implementation Advice
14156 @anchor{gnat_rm/implementation_advice rm-13-3-29-35-alignment-clauses}@anchor{221}
14157 @section RM 13.3(29-35): Alignment Clauses
14162 "The recommended level of support for the @code{Alignment} attribute for
14165 An implementation should support specified Alignments that are factors
14166 and multiples of the number of storage elements per word, subject to the
14174 "An implementation need not support specified Alignments for
14175 combinations of Sizes and Alignments that cannot be easily
14176 loaded and stored by available machine instructions."
14183 "An implementation need not support specified Alignments that are
14184 greater than the maximum @code{Alignment} the implementation ever returns by
14192 "The recommended level of support for the @code{Alignment} attribute for
14195 Same as above, for subtypes, but in addition:"
14202 "For stand-alone library-level objects of statically constrained
14203 subtypes, the implementation should support all alignments
14204 supported by the target linker. For example, page alignment is likely to
14205 be supported for such objects, but not for subtypes."
14210 @geindex Size clauses
14212 @node RM 13 3 42-43 Size Clauses,RM 13 3 50-56 Size Clauses,RM 13 3 29-35 Alignment Clauses,Implementation Advice
14213 @anchor{gnat_rm/implementation_advice rm-13-3-42-43-size-clauses}@anchor{222}
14214 @section RM 13.3(42-43): Size Clauses
14219 "The recommended level of support for the @code{Size} attribute of
14222 A @code{Size} clause should be supported for an object if the specified
14223 @code{Size} is at least as large as its subtype's @code{Size}, and
14224 corresponds to a size in storage elements that is a multiple of the
14225 object's @code{Alignment} (if the @code{Alignment} is nonzero)."
14230 @node RM 13 3 50-56 Size Clauses,RM 13 3 71-73 Component Size Clauses,RM 13 3 42-43 Size Clauses,Implementation Advice
14231 @anchor{gnat_rm/implementation_advice rm-13-3-50-56-size-clauses}@anchor{223}
14232 @section RM 13.3(50-56): Size Clauses
14237 "If the @code{Size} of a subtype is specified, and allows for efficient
14238 independent addressability (see 9.10) on the target architecture, then
14239 the @code{Size} of the following objects of the subtype should equal the
14240 @code{Size} of the subtype:
14242 Aliased objects (including components)."
14249 "@cite{Size} clause on a composite subtype should not affect the
14250 internal layout of components."
14253 Followed. But note that this can be overridden by use of the implementation
14254 pragma Implicit_Packing in the case of packed arrays.
14258 "The recommended level of support for the @code{Size} attribute of subtypes is:
14260 The @code{Size} (if not specified) of a static discrete or fixed point
14261 subtype should be the number of bits needed to represent each value
14262 belonging to the subtype using an unbiased representation, leaving space
14263 for a sign bit only if the subtype contains negative values. If such a
14264 subtype is a first subtype, then an implementation should support a
14265 specified @code{Size} for it that reflects this representation."
14272 "For a subtype implemented with levels of indirection, the @code{Size}
14273 should include the size of the pointers, but not the size of what they
14279 @geindex Component_Size clauses
14281 @node RM 13 3 71-73 Component Size Clauses,RM 13 4 9-10 Enumeration Representation Clauses,RM 13 3 50-56 Size Clauses,Implementation Advice
14282 @anchor{gnat_rm/implementation_advice rm-13-3-71-73-component-size-clauses}@anchor{224}
14283 @section RM 13.3(71-73): Component Size Clauses
14288 "The recommended level of support for the @code{Component_Size}
14291 An implementation need not support specified @code{Component_Sizes} that are
14292 less than the @code{Size} of the component subtype."
14299 "An implementation should support specified Component_Sizes that
14300 are factors and multiples of the word size. For such
14301 Component_Sizes, the array should contain no gaps between
14302 components. For other Component_Sizes (if supported), the array
14303 should contain no gaps between components when packing is also
14304 specified; the implementation should forbid this combination in cases
14305 where it cannot support a no-gaps representation."
14310 @geindex Enumeration representation clauses
14312 @geindex Representation clauses
14313 @geindex enumeration
14315 @node RM 13 4 9-10 Enumeration Representation Clauses,RM 13 5 1 17-22 Record Representation Clauses,RM 13 3 71-73 Component Size Clauses,Implementation Advice
14316 @anchor{gnat_rm/implementation_advice rm-13-4-9-10-enumeration-representation-clauses}@anchor{225}
14317 @section RM 13.4(9-10): Enumeration Representation Clauses
14322 "The recommended level of support for enumeration representation clauses
14325 An implementation need not support enumeration representation clauses
14326 for boolean types, but should at minimum support the internal codes in
14327 the range @code{System.Min_Int .. System.Max_Int}."
14332 @geindex Record representation clauses
14334 @geindex Representation clauses
14337 @node RM 13 5 1 17-22 Record Representation Clauses,RM 13 5 2 5 Storage Place Attributes,RM 13 4 9-10 Enumeration Representation Clauses,Implementation Advice
14338 @anchor{gnat_rm/implementation_advice rm-13-5-1-17-22-record-representation-clauses}@anchor{226}
14339 @section RM 13.5.1(17-22): Record Representation Clauses
14344 "The recommended level of support for
14345 @emph{record_representation_clause}s is:
14347 An implementation should support storage places that can be extracted
14348 with a load, mask, shift sequence of machine code, and set with a load,
14349 shift, mask, store sequence, given the available machine instructions
14350 and run-time model."
14357 "A storage place should be supported if its size is equal to the
14358 @code{Size} of the component subtype, and it starts and ends on a
14359 boundary that obeys the @code{Alignment} of the component subtype."
14366 "If the default bit ordering applies to the declaration of a given type,
14367 then for a component whose subtype's @code{Size} is less than the word
14368 size, any storage place that does not cross an aligned word boundary
14369 should be supported."
14376 "An implementation may reserve a storage place for the tag field of a
14377 tagged type, and disallow other components from overlapping that place."
14380 Followed. The storage place for the tag field is the beginning of the tagged
14381 record, and its size is Address'Size. GNAT will reject an explicit component
14382 clause for the tag field.
14386 "An implementation need not support a @emph{component_clause} for a
14387 component of an extension part if the storage place is not after the
14388 storage places of all components of the parent type, whether or not
14389 those storage places had been specified."
14392 Followed. The above advice on record representation clauses is followed,
14393 and all mentioned features are implemented.
14395 @geindex Storage place attributes
14397 @node RM 13 5 2 5 Storage Place Attributes,RM 13 5 3 7-8 Bit Ordering,RM 13 5 1 17-22 Record Representation Clauses,Implementation Advice
14398 @anchor{gnat_rm/implementation_advice rm-13-5-2-5-storage-place-attributes}@anchor{227}
14399 @section RM 13.5.2(5): Storage Place Attributes
14404 "If a component is represented using some form of pointer (such as an
14405 offset) to the actual data of the component, and this data is contiguous
14406 with the rest of the object, then the storage place attributes should
14407 reflect the place of the actual data, not the pointer. If a component is
14408 allocated discontinuously from the rest of the object, then a warning
14409 should be generated upon reference to one of its storage place
14413 Followed. There are no such components in GNAT.
14415 @geindex Bit ordering
14417 @node RM 13 5 3 7-8 Bit Ordering,RM 13 7 37 Address as Private,RM 13 5 2 5 Storage Place Attributes,Implementation Advice
14418 @anchor{gnat_rm/implementation_advice rm-13-5-3-7-8-bit-ordering}@anchor{228}
14419 @section RM 13.5.3(7-8): Bit Ordering
14424 "The recommended level of support for the non-default bit ordering is:
14426 If @code{Word_Size} = @code{Storage_Unit}, then the implementation
14427 should support the non-default bit ordering in addition to the default
14431 Followed. Word size does not equal storage size in this implementation.
14432 Thus non-default bit ordering is not supported.
14435 @geindex as private type
14437 @node RM 13 7 37 Address as Private,RM 13 7 1 16 Address Operations,RM 13 5 3 7-8 Bit Ordering,Implementation Advice
14438 @anchor{gnat_rm/implementation_advice rm-13-7-37-address-as-private}@anchor{229}
14439 @section RM 13.7(37): Address as Private
14444 "@cite{Address} should be of a private type."
14449 @geindex Operations
14450 @geindex on `@w{`}Address`@w{`}
14453 @geindex operations of
14455 @node RM 13 7 1 16 Address Operations,RM 13 9 14-17 Unchecked Conversion,RM 13 7 37 Address as Private,Implementation Advice
14456 @anchor{gnat_rm/implementation_advice rm-13-7-1-16-address-operations}@anchor{22a}
14457 @section RM 13.7.1(16): Address Operations
14462 "Operations in @code{System} and its children should reflect the target
14463 environment semantics as closely as is reasonable. For example, on most
14464 machines, it makes sense for address arithmetic to 'wrap around'.
14465 Operations that do not make sense should raise @code{Program_Error}."
14468 Followed. Address arithmetic is modular arithmetic that wraps around. No
14469 operation raises @code{Program_Error}, since all operations make sense.
14471 @geindex Unchecked conversion
14473 @node RM 13 9 14-17 Unchecked Conversion,RM 13 11 23-25 Implicit Heap Usage,RM 13 7 1 16 Address Operations,Implementation Advice
14474 @anchor{gnat_rm/implementation_advice rm-13-9-14-17-unchecked-conversion}@anchor{22b}
14475 @section RM 13.9(14-17): Unchecked Conversion
14480 "The @code{Size} of an array object should not include its bounds; hence,
14481 the bounds should not be part of the converted data."
14488 "The implementation should not generate unnecessary run-time checks to
14489 ensure that the representation of @code{S} is a representation of the
14490 target type. It should take advantage of the permission to return by
14491 reference when possible. Restrictions on unchecked conversions should be
14492 avoided unless required by the target environment."
14495 Followed. There are no restrictions on unchecked conversion. A warning is
14496 generated if the source and target types do not have the same size since
14497 the semantics in this case may be target dependent.
14501 "The recommended level of support for unchecked conversions is:
14503 Unchecked conversions should be supported and should be reversible in
14504 the cases where this clause defines the result. To enable meaningful use
14505 of unchecked conversion, a contiguous representation should be used for
14506 elementary subtypes, for statically constrained array subtypes whose
14507 component subtype is one of the subtypes described in this paragraph,
14508 and for record subtypes without discriminants whose component subtypes
14509 are described in this paragraph."
14514 @geindex Heap usage
14517 @node RM 13 11 23-25 Implicit Heap Usage,RM 13 11 2 17 Unchecked Deallocation,RM 13 9 14-17 Unchecked Conversion,Implementation Advice
14518 @anchor{gnat_rm/implementation_advice rm-13-11-23-25-implicit-heap-usage}@anchor{22c}
14519 @section RM 13.11(23-25): Implicit Heap Usage
14524 "An implementation should document any cases in which it dynamically
14525 allocates heap storage for a purpose other than the evaluation of an
14529 Followed, the only other points at which heap storage is dynamically
14530 allocated are as follows:
14536 At initial elaboration time, to allocate dynamically sized global
14540 To allocate space for a task when a task is created.
14543 To extend the secondary stack dynamically when needed. The secondary
14544 stack is used for returning variable length results.
14550 "A default (implementation-provided) storage pool for an
14551 access-to-constant type should not have overhead to support deallocation of
14552 individual objects."
14559 "A storage pool for an anonymous access type should be created at the
14560 point of an allocator for the type, and be reclaimed when the designated
14561 object becomes inaccessible."
14566 @geindex Unchecked deallocation
14568 @node RM 13 11 2 17 Unchecked Deallocation,RM 13 13 2 17 Stream Oriented Attributes,RM 13 11 23-25 Implicit Heap Usage,Implementation Advice
14569 @anchor{gnat_rm/implementation_advice rm-13-11-2-17-unchecked-deallocation}@anchor{22d}
14570 @section RM 13.11.2(17): Unchecked Deallocation
14575 "For a standard storage pool, @code{Free} should actually reclaim the
14581 @geindex Stream oriented attributes
14583 @node RM 13 13 2 17 Stream Oriented Attributes,RM A 1 52 Names of Predefined Numeric Types,RM 13 11 2 17 Unchecked Deallocation,Implementation Advice
14584 @anchor{gnat_rm/implementation_advice rm-13-13-2-17-stream-oriented-attributes}@anchor{22e}
14585 @section RM 13.13.2(17): Stream Oriented Attributes
14590 "If a stream element is the same size as a storage element, then the
14591 normal in-memory representation should be used by @code{Read} and
14592 @code{Write} for scalar objects. Otherwise, @code{Read} and @code{Write}
14593 should use the smallest number of stream elements needed to represent
14594 all values in the base range of the scalar type."
14597 Followed. By default, GNAT uses the interpretation suggested by AI-195,
14598 which specifies using the size of the first subtype.
14599 However, such an implementation is based on direct binary
14600 representations and is therefore target- and endianness-dependent.
14601 To address this issue, GNAT also supplies an alternate implementation
14602 of the stream attributes @code{Read} and @code{Write},
14603 which uses the target-independent XDR standard representation
14606 @geindex XDR representation
14608 @geindex Read attribute
14610 @geindex Write attribute
14612 @geindex Stream oriented attributes
14614 The XDR implementation is provided as an alternative body of the
14615 @code{System.Stream_Attributes} package, in the file
14616 @code{s-stratt-xdr.adb} in the GNAT library.
14617 There is no @code{s-stratt-xdr.ads} file.
14618 In order to install the XDR implementation, do the following:
14624 Replace the default implementation of the
14625 @code{System.Stream_Attributes} package with the XDR implementation.
14626 For example on a Unix platform issue the commands:
14629 $ mv s-stratt.adb s-stratt-default.adb
14630 $ mv s-stratt-xdr.adb s-stratt.adb
14634 Rebuild the GNAT run-time library as documented in
14635 the @emph{GNAT and Libraries} section of the @cite{GNAT User's Guide}.
14638 @node RM A 1 52 Names of Predefined Numeric Types,RM A 3 2 49 Ada Characters Handling,RM 13 13 2 17 Stream Oriented Attributes,Implementation Advice
14639 @anchor{gnat_rm/implementation_advice rm-a-1-52-names-of-predefined-numeric-types}@anchor{22f}
14640 @section RM A.1(52): Names of Predefined Numeric Types
14645 "If an implementation provides additional named predefined integer types,
14646 then the names should end with @code{Integer} as in
14647 @code{Long_Integer}. If an implementation provides additional named
14648 predefined floating point types, then the names should end with
14649 @code{Float} as in @code{Long_Float}."
14654 @geindex Ada.Characters.Handling
14656 @node RM A 3 2 49 Ada Characters Handling,RM A 4 4 106 Bounded-Length String Handling,RM A 1 52 Names of Predefined Numeric Types,Implementation Advice
14657 @anchor{gnat_rm/implementation_advice rm-a-3-2-49-ada-characters-handling}@anchor{230}
14658 @section RM A.3.2(49): @code{Ada.Characters.Handling}
14663 "If an implementation provides a localized definition of @code{Character}
14664 or @code{Wide_Character}, then the effects of the subprograms in
14665 @code{Characters.Handling} should reflect the localizations.
14669 Followed. GNAT provides no such localized definitions.
14671 @geindex Bounded-length strings
14673 @node RM A 4 4 106 Bounded-Length String Handling,RM A 5 2 46-47 Random Number Generation,RM A 3 2 49 Ada Characters Handling,Implementation Advice
14674 @anchor{gnat_rm/implementation_advice rm-a-4-4-106-bounded-length-string-handling}@anchor{231}
14675 @section RM A.4.4(106): Bounded-Length String Handling
14680 "Bounded string objects should not be implemented by implicit pointers
14681 and dynamic allocation."
14684 Followed. No implicit pointers or dynamic allocation are used.
14686 @geindex Random number generation
14688 @node RM A 5 2 46-47 Random Number Generation,RM A 10 7 23 Get_Immediate,RM A 4 4 106 Bounded-Length String Handling,Implementation Advice
14689 @anchor{gnat_rm/implementation_advice rm-a-5-2-46-47-random-number-generation}@anchor{232}
14690 @section RM A.5.2(46-47): Random Number Generation
14695 "Any storage associated with an object of type @code{Generator} should be
14696 reclaimed on exit from the scope of the object."
14703 "If the generator period is sufficiently long in relation to the number
14704 of distinct initiator values, then each possible value of
14705 @code{Initiator} passed to @code{Reset} should initiate a sequence of
14706 random numbers that does not, in a practical sense, overlap the sequence
14707 initiated by any other value. If this is not possible, then the mapping
14708 between initiator values and generator states should be a rapidly
14709 varying function of the initiator value."
14712 Followed. The generator period is sufficiently long for the first
14713 condition here to hold true.
14715 @geindex Get_Immediate
14717 @node RM A 10 7 23 Get_Immediate,RM B 1 39-41 Pragma Export,RM A 5 2 46-47 Random Number Generation,Implementation Advice
14718 @anchor{gnat_rm/implementation_advice rm-a-10-7-23-get-immediate}@anchor{233}
14719 @section RM A.10.7(23): @code{Get_Immediate}
14724 "The @code{Get_Immediate} procedures should be implemented with
14725 unbuffered input. For a device such as a keyboard, input should be
14726 available if a key has already been typed, whereas for a disk
14727 file, input should always be available except at end of file. For a file
14728 associated with a keyboard-like device, any line-editing features of the
14729 underlying operating system should be disabled during the execution of
14730 @code{Get_Immediate}."
14733 Followed on all targets except VxWorks. For VxWorks, there is no way to
14734 provide this functionality that does not result in the input buffer being
14735 flushed before the @code{Get_Immediate} call. A special unit
14736 @code{Interfaces.Vxworks.IO} is provided that contains routines to enable
14737 this functionality.
14741 @node RM B 1 39-41 Pragma Export,RM B 2 12-13 Package Interfaces,RM A 10 7 23 Get_Immediate,Implementation Advice
14742 @anchor{gnat_rm/implementation_advice rm-b-1-39-41-pragma-export}@anchor{234}
14743 @section RM B.1(39-41): Pragma @code{Export}
14748 "If an implementation supports pragma @code{Export} to a given language,
14749 then it should also allow the main subprogram to be written in that
14750 language. It should support some mechanism for invoking the elaboration
14751 of the Ada library units included in the system, and for invoking the
14752 finalization of the environment task. On typical systems, the
14753 recommended mechanism is to provide two subprograms whose link names are
14754 @code{adainit} and @code{adafinal}. @code{adainit} should contain the
14755 elaboration code for library units. @code{adafinal} should contain the
14756 finalization code. These subprograms should have no effect the second
14757 and subsequent time they are called."
14764 "Automatic elaboration of pre-elaborated packages should be
14765 provided when pragma @code{Export} is supported."
14768 Followed when the main program is in Ada. If the main program is in a
14769 foreign language, then
14770 @code{adainit} must be called to elaborate pre-elaborated
14775 "For each supported convention @emph{L} other than @code{Intrinsic}, an
14776 implementation should support @code{Import} and @code{Export} pragmas
14777 for objects of @emph{L}-compatible types and for subprograms, and pragma
14778 @cite{Convention} for @emph{L}-eligible types and for subprograms,
14779 presuming the other language has corresponding features. Pragma
14780 @code{Convention} need not be supported for scalar types."
14785 @geindex Package Interfaces
14787 @geindex Interfaces
14789 @node RM B 2 12-13 Package Interfaces,RM B 3 63-71 Interfacing with C,RM B 1 39-41 Pragma Export,Implementation Advice
14790 @anchor{gnat_rm/implementation_advice rm-b-2-12-13-package-interfaces}@anchor{235}
14791 @section RM B.2(12-13): Package @code{Interfaces}
14796 "For each implementation-defined convention identifier, there should be a
14797 child package of package Interfaces with the corresponding name. This
14798 package should contain any declarations that would be useful for
14799 interfacing to the language (implementation) represented by the
14800 convention. Any declarations useful for interfacing to any language on
14801 the given hardware architecture should be provided directly in
14802 @code{Interfaces}."
14809 "An implementation supporting an interface to C, COBOL, or Fortran should
14810 provide the corresponding package or packages described in the following
14814 Followed. GNAT provides all the packages described in this section.
14817 @geindex interfacing with
14819 @node RM B 3 63-71 Interfacing with C,RM B 4 95-98 Interfacing with COBOL,RM B 2 12-13 Package Interfaces,Implementation Advice
14820 @anchor{gnat_rm/implementation_advice rm-b-3-63-71-interfacing-with-c}@anchor{236}
14821 @section RM B.3(63-71): Interfacing with C
14826 "An implementation should support the following interface correspondences
14827 between Ada and C."
14834 "An Ada procedure corresponds to a void-returning C function."
14841 "An Ada function corresponds to a non-void C function."
14848 "An Ada @code{in} scalar parameter is passed as a scalar argument to a C
14856 "An Ada @code{in} parameter of an access-to-object type with designated
14857 type @code{T} is passed as a @code{t*} argument to a C function,
14858 where @code{t} is the C type corresponding to the Ada type @code{T}."
14865 "An Ada access @code{T} parameter, or an Ada @code{out} or @code{in out}
14866 parameter of an elementary type @code{T}, is passed as a @code{t*}
14867 argument to a C function, where @code{t} is the C type corresponding to
14868 the Ada type @code{T}. In the case of an elementary @code{out} or
14869 @code{in out} parameter, a pointer to a temporary copy is used to
14870 preserve by-copy semantics."
14877 "An Ada parameter of a record type @code{T}, of any mode, is passed as a
14878 @code{t*} argument to a C function, where @code{t} is the C
14879 structure corresponding to the Ada type @code{T}."
14882 Followed. This convention may be overridden by the use of the C_Pass_By_Copy
14883 pragma, or Convention, or by explicitly specifying the mechanism for a given
14884 call using an extended import or export pragma.
14888 "An Ada parameter of an array type with component type @code{T}, of any
14889 mode, is passed as a @code{t*} argument to a C function, where
14890 @code{t} is the C type corresponding to the Ada type @code{T}."
14897 "An Ada parameter of an access-to-subprogram type is passed as a pointer
14898 to a C function whose prototype corresponds to the designated
14899 subprogram's specification."
14905 @geindex interfacing with
14907 @node RM B 4 95-98 Interfacing with COBOL,RM B 5 22-26 Interfacing with Fortran,RM B 3 63-71 Interfacing with C,Implementation Advice
14908 @anchor{gnat_rm/implementation_advice rm-b-4-95-98-interfacing-with-cobol}@anchor{237}
14909 @section RM B.4(95-98): Interfacing with COBOL
14914 "An Ada implementation should support the following interface
14915 correspondences between Ada and COBOL."
14922 "An Ada access @code{T} parameter is passed as a @code{BY REFERENCE} data item of
14923 the COBOL type corresponding to @code{T}."
14930 "An Ada in scalar parameter is passed as a @code{BY CONTENT} data item of
14931 the corresponding COBOL type."
14938 "Any other Ada parameter is passed as a @code{BY REFERENCE} data item of the
14939 COBOL type corresponding to the Ada parameter type; for scalars, a local
14940 copy is used if necessary to ensure by-copy semantics."
14946 @geindex interfacing with
14948 @node RM B 5 22-26 Interfacing with Fortran,RM C 1 3-5 Access to Machine Operations,RM B 4 95-98 Interfacing with COBOL,Implementation Advice
14949 @anchor{gnat_rm/implementation_advice rm-b-5-22-26-interfacing-with-fortran}@anchor{238}
14950 @section RM B.5(22-26): Interfacing with Fortran
14955 "An Ada implementation should support the following interface
14956 correspondences between Ada and Fortran:"
14963 "An Ada procedure corresponds to a Fortran subroutine."
14970 "An Ada function corresponds to a Fortran function."
14977 "An Ada parameter of an elementary, array, or record type @code{T} is
14978 passed as a @code{T} argument to a Fortran procedure, where @code{T} is
14979 the Fortran type corresponding to the Ada type @code{T}, and where the
14980 INTENT attribute of the corresponding dummy argument matches the Ada
14981 formal parameter mode; the Fortran implementation's parameter passing
14982 conventions are used. For elementary types, a local copy is used if
14983 necessary to ensure by-copy semantics."
14990 "An Ada parameter of an access-to-subprogram type is passed as a
14991 reference to a Fortran procedure whose interface corresponds to the
14992 designated subprogram's specification."
14997 @geindex Machine operations
14999 @node RM C 1 3-5 Access to Machine Operations,RM C 1 10-16 Access to Machine Operations,RM B 5 22-26 Interfacing with Fortran,Implementation Advice
15000 @anchor{gnat_rm/implementation_advice rm-c-1-3-5-access-to-machine-operations}@anchor{239}
15001 @section RM C.1(3-5): Access to Machine Operations
15006 "The machine code or intrinsic support should allow access to all
15007 operations normally available to assembly language programmers for the
15008 target environment, including privileged instructions, if any."
15015 "The interfacing pragmas (see Annex B) should support interface to
15016 assembler; the default assembler should be associated with the
15017 convention identifier @code{Assembler}."
15024 "If an entity is exported to assembly language, then the implementation
15025 should allocate it at an addressable location, and should ensure that it
15026 is retained by the linking process, even if not otherwise referenced
15027 from the Ada code. The implementation should assume that any call to a
15028 machine code or assembler subprogram is allowed to read or update every
15029 object that is specified as exported."
15034 @node RM C 1 10-16 Access to Machine Operations,RM C 3 28 Interrupt Support,RM C 1 3-5 Access to Machine Operations,Implementation Advice
15035 @anchor{gnat_rm/implementation_advice rm-c-1-10-16-access-to-machine-operations}@anchor{23a}
15036 @section RM C.1(10-16): Access to Machine Operations
15041 "The implementation should ensure that little or no overhead is
15042 associated with calling intrinsic and machine-code subprograms."
15045 Followed for both intrinsics and machine-code subprograms.
15049 "It is recommended that intrinsic subprograms be provided for convenient
15050 access to any machine operations that provide special capabilities or
15051 efficiency and that are not otherwise available through the language
15055 Followed. A full set of machine operation intrinsic subprograms is provided.
15059 "Atomic read-modify-write operations---e.g., test and set, compare and
15060 swap, decrement and test, enqueue/dequeue."
15063 Followed on any target supporting such operations.
15067 "Standard numeric functions---e.g.:, sin, log."
15070 Followed on any target supporting such operations.
15074 "String manipulation operations---e.g.:, translate and test."
15077 Followed on any target supporting such operations.
15081 "Vector operations---e.g.:, compare vector against thresholds."
15084 Followed on any target supporting such operations.
15088 "Direct operations on I/O ports."
15091 Followed on any target supporting such operations.
15093 @geindex Interrupt support
15095 @node RM C 3 28 Interrupt Support,RM C 3 1 20-21 Protected Procedure Handlers,RM C 1 10-16 Access to Machine Operations,Implementation Advice
15096 @anchor{gnat_rm/implementation_advice rm-c-3-28-interrupt-support}@anchor{23b}
15097 @section RM C.3(28): Interrupt Support
15102 "If the @code{Ceiling_Locking} policy is not in effect, the
15103 implementation should provide means for the application to specify which
15104 interrupts are to be blocked during protected actions, if the underlying
15105 system allows for a finer-grain control of interrupt blocking."
15108 Followed. The underlying system does not allow for finer-grain control
15109 of interrupt blocking.
15111 @geindex Protected procedure handlers
15113 @node RM C 3 1 20-21 Protected Procedure Handlers,RM C 3 2 25 Package Interrupts,RM C 3 28 Interrupt Support,Implementation Advice
15114 @anchor{gnat_rm/implementation_advice rm-c-3-1-20-21-protected-procedure-handlers}@anchor{23c}
15115 @section RM C.3.1(20-21): Protected Procedure Handlers
15120 "Whenever possible, the implementation should allow interrupt handlers to
15121 be called directly by the hardware."
15124 Followed on any target where the underlying operating system permits
15129 "Whenever practical, violations of any
15130 implementation-defined restrictions should be detected before run time."
15133 Followed. Compile time warnings are given when possible.
15135 @geindex Package `@w{`}Interrupts`@w{`}
15137 @geindex Interrupts
15139 @node RM C 3 2 25 Package Interrupts,RM C 4 14 Pre-elaboration Requirements,RM C 3 1 20-21 Protected Procedure Handlers,Implementation Advice
15140 @anchor{gnat_rm/implementation_advice rm-c-3-2-25-package-interrupts}@anchor{23d}
15141 @section RM C.3.2(25): Package @code{Interrupts}
15146 "If implementation-defined forms of interrupt handler procedures are
15147 supported, such as protected procedures with parameters, then for each
15148 such form of a handler, a type analogous to @code{Parameterless_Handler}
15149 should be specified in a child package of @code{Interrupts}, with the
15150 same operations as in the predefined package Interrupts."
15155 @geindex Pre-elaboration requirements
15157 @node RM C 4 14 Pre-elaboration Requirements,RM C 5 8 Pragma Discard_Names,RM C 3 2 25 Package Interrupts,Implementation Advice
15158 @anchor{gnat_rm/implementation_advice rm-c-4-14-pre-elaboration-requirements}@anchor{23e}
15159 @section RM C.4(14): Pre-elaboration Requirements
15164 "It is recommended that pre-elaborated packages be implemented in such a
15165 way that there should be little or no code executed at run time for the
15166 elaboration of entities not already covered by the Implementation
15170 Followed. Executable code is generated in some cases, e.g., loops
15171 to initialize large arrays.
15173 @node RM C 5 8 Pragma Discard_Names,RM C 7 2 30 The Package Task_Attributes,RM C 4 14 Pre-elaboration Requirements,Implementation Advice
15174 @anchor{gnat_rm/implementation_advice rm-c-5-8-pragma-discard-names}@anchor{23f}
15175 @section RM C.5(8): Pragma @code{Discard_Names}
15180 "If the pragma applies to an entity, then the implementation should
15181 reduce the amount of storage used for storing names associated with that
15187 @geindex Package Task_Attributes
15189 @geindex Task_Attributes
15191 @node RM C 7 2 30 The Package Task_Attributes,RM D 3 17 Locking Policies,RM C 5 8 Pragma Discard_Names,Implementation Advice
15192 @anchor{gnat_rm/implementation_advice rm-c-7-2-30-the-package-task-attributes}@anchor{240}
15193 @section RM C.7.2(30): The Package Task_Attributes
15198 "Some implementations are targeted to domains in which memory use at run
15199 time must be completely deterministic. For such implementations, it is
15200 recommended that the storage for task attributes will be pre-allocated
15201 statically and not from the heap. This can be accomplished by either
15202 placing restrictions on the number and the size of the task's
15203 attributes, or by using the pre-allocated storage for the first @code{N}
15204 attribute objects, and the heap for the others. In the latter case,
15205 @code{N} should be documented."
15208 Not followed. This implementation is not targeted to such a domain.
15210 @geindex Locking Policies
15212 @node RM D 3 17 Locking Policies,RM D 4 16 Entry Queuing Policies,RM C 7 2 30 The Package Task_Attributes,Implementation Advice
15213 @anchor{gnat_rm/implementation_advice rm-d-3-17-locking-policies}@anchor{241}
15214 @section RM D.3(17): Locking Policies
15219 "The implementation should use names that end with @code{_Locking} for
15220 locking policies defined by the implementation."
15223 Followed. Two implementation-defined locking policies are defined,
15224 whose names (@code{Inheritance_Locking} and
15225 @code{Concurrent_Readers_Locking}) follow this suggestion.
15227 @geindex Entry queuing policies
15229 @node RM D 4 16 Entry Queuing Policies,RM D 6 9-10 Preemptive Abort,RM D 3 17 Locking Policies,Implementation Advice
15230 @anchor{gnat_rm/implementation_advice rm-d-4-16-entry-queuing-policies}@anchor{242}
15231 @section RM D.4(16): Entry Queuing Policies
15236 "Names that end with @code{_Queuing} should be used
15237 for all implementation-defined queuing policies."
15240 Followed. No such implementation-defined queuing policies exist.
15242 @geindex Preemptive abort
15244 @node RM D 6 9-10 Preemptive Abort,RM D 7 21 Tasking Restrictions,RM D 4 16 Entry Queuing Policies,Implementation Advice
15245 @anchor{gnat_rm/implementation_advice rm-d-6-9-10-preemptive-abort}@anchor{243}
15246 @section RM D.6(9-10): Preemptive Abort
15251 "Even though the @emph{abort_statement} is included in the list of
15252 potentially blocking operations (see 9.5.1), it is recommended that this
15253 statement be implemented in a way that never requires the task executing
15254 the @emph{abort_statement} to block."
15261 "On a multi-processor, the delay associated with aborting a task on
15262 another processor should be bounded; the implementation should use
15263 periodic polling, if necessary, to achieve this."
15268 @geindex Tasking restrictions
15270 @node RM D 7 21 Tasking Restrictions,RM D 8 47-49 Monotonic Time,RM D 6 9-10 Preemptive Abort,Implementation Advice
15271 @anchor{gnat_rm/implementation_advice rm-d-7-21-tasking-restrictions}@anchor{244}
15272 @section RM D.7(21): Tasking Restrictions
15277 "When feasible, the implementation should take advantage of the specified
15278 restrictions to produce a more efficient implementation."
15281 GNAT currently takes advantage of these restrictions by providing an optimized
15282 run time when the Ravenscar profile and the GNAT restricted run time set
15283 of restrictions are specified. See pragma @code{Profile (Ravenscar)} and
15284 pragma @code{Profile (Restricted)} for more details.
15289 @node RM D 8 47-49 Monotonic Time,RM E 5 28-29 Partition Communication Subsystem,RM D 7 21 Tasking Restrictions,Implementation Advice
15290 @anchor{gnat_rm/implementation_advice rm-d-8-47-49-monotonic-time}@anchor{245}
15291 @section RM D.8(47-49): Monotonic Time
15296 "When appropriate, implementations should provide configuration
15297 mechanisms to change the value of @code{Tick}."
15300 Such configuration mechanisms are not appropriate to this implementation
15301 and are thus not supported.
15305 "It is recommended that @code{Calendar.Clock} and @code{Real_Time.Clock}
15306 be implemented as transformations of the same time base."
15313 "It is recommended that the best time base which exists in
15314 the underlying system be available to the application through
15315 @code{Clock}. @cite{Best} may mean highest accuracy or largest range."
15320 @geindex Partition communication subsystem
15324 @node RM E 5 28-29 Partition Communication Subsystem,RM F 7 COBOL Support,RM D 8 47-49 Monotonic Time,Implementation Advice
15325 @anchor{gnat_rm/implementation_advice rm-e-5-28-29-partition-communication-subsystem}@anchor{246}
15326 @section RM E.5(28-29): Partition Communication Subsystem
15331 "Whenever possible, the PCS on the called partition should allow for
15332 multiple tasks to call the RPC-receiver with different messages and
15333 should allow them to block until the corresponding subprogram body
15337 Followed by GLADE, a separately supplied PCS that can be used with
15342 "The @code{Write} operation on a stream of type @code{Params_Stream_Type}
15343 should raise @code{Storage_Error} if it runs out of space trying to
15344 write the @code{Item} into the stream."
15347 Followed by GLADE, a separately supplied PCS that can be used with
15350 @geindex COBOL support
15352 @node RM F 7 COBOL Support,RM F 1 2 Decimal Radix Support,RM E 5 28-29 Partition Communication Subsystem,Implementation Advice
15353 @anchor{gnat_rm/implementation_advice rm-f-7-cobol-support}@anchor{247}
15354 @section RM F(7): COBOL Support
15359 "If COBOL (respectively, C) is widely supported in the target
15360 environment, implementations supporting the Information Systems Annex
15361 should provide the child package @code{Interfaces.COBOL} (respectively,
15362 @code{Interfaces.C}) specified in Annex B and should support a
15363 @code{convention_identifier} of COBOL (respectively, C) in the interfacing
15364 pragmas (see Annex B), thus allowing Ada programs to interface with
15365 programs written in that language."
15370 @geindex Decimal radix support
15372 @node RM F 1 2 Decimal Radix Support,RM G Numerics,RM F 7 COBOL Support,Implementation Advice
15373 @anchor{gnat_rm/implementation_advice rm-f-1-2-decimal-radix-support}@anchor{248}
15374 @section RM F.1(2): Decimal Radix Support
15379 "Packed decimal should be used as the internal representation for objects
15380 of subtype @code{S} when @code{S}'Machine_Radix = 10."
15383 Not followed. GNAT ignores @code{S}'Machine_Radix and always uses binary
15388 @node RM G Numerics,RM G 1 1 56-58 Complex Types,RM F 1 2 Decimal Radix Support,Implementation Advice
15389 @anchor{gnat_rm/implementation_advice rm-g-numerics}@anchor{249}
15390 @section RM G: Numerics
15395 "If Fortran (respectively, C) is widely supported in the target
15396 environment, implementations supporting the Numerics Annex
15397 should provide the child package @code{Interfaces.Fortran} (respectively,
15398 @code{Interfaces.C}) specified in Annex B and should support a
15399 @code{convention_identifier} of Fortran (respectively, C) in the interfacing
15400 pragmas (see Annex B), thus allowing Ada programs to interface with
15401 programs written in that language."
15406 @geindex Complex types
15408 @node RM G 1 1 56-58 Complex Types,RM G 1 2 49 Complex Elementary Functions,RM G Numerics,Implementation Advice
15409 @anchor{gnat_rm/implementation_advice rm-g-1-1-56-58-complex-types}@anchor{24a}
15410 @section RM G.1.1(56-58): Complex Types
15415 "Because the usual mathematical meaning of multiplication of a complex
15416 operand and a real operand is that of the scaling of both components of
15417 the former by the latter, an implementation should not perform this
15418 operation by first promoting the real operand to complex type and then
15419 performing a full complex multiplication. In systems that, in the
15420 future, support an Ada binding to IEC 559:1989, the latter technique
15421 will not generate the required result when one of the components of the
15422 complex operand is infinite. (Explicit multiplication of the infinite
15423 component by the zero component obtained during promotion yields a NaN
15424 that propagates into the final result.) Analogous advice applies in the
15425 case of multiplication of a complex operand and a pure-imaginary
15426 operand, and in the case of division of a complex operand by a real or
15427 pure-imaginary operand."
15434 "Similarly, because the usual mathematical meaning of addition of a
15435 complex operand and a real operand is that the imaginary operand remains
15436 unchanged, an implementation should not perform this operation by first
15437 promoting the real operand to complex type and then performing a full
15438 complex addition. In implementations in which the @code{Signed_Zeros}
15439 attribute of the component type is @code{True} (and which therefore
15440 conform to IEC 559:1989 in regard to the handling of the sign of zero in
15441 predefined arithmetic operations), the latter technique will not
15442 generate the required result when the imaginary component of the complex
15443 operand is a negatively signed zero. (Explicit addition of the negative
15444 zero to the zero obtained during promotion yields a positive zero.)
15445 Analogous advice applies in the case of addition of a complex operand
15446 and a pure-imaginary operand, and in the case of subtraction of a
15447 complex operand and a real or pure-imaginary operand."
15454 "Implementations in which @code{Real'Signed_Zeros} is @code{True} should
15455 attempt to provide a rational treatment of the signs of zero results and
15456 result components. As one example, the result of the @code{Argument}
15457 function should have the sign of the imaginary component of the
15458 parameter @code{X} when the point represented by that parameter lies on
15459 the positive real axis; as another, the sign of the imaginary component
15460 of the @code{Compose_From_Polar} function should be the same as
15461 (respectively, the opposite of) that of the @code{Argument} parameter when that
15462 parameter has a value of zero and the @code{Modulus} parameter has a
15463 nonnegative (respectively, negative) value."
15468 @geindex Complex elementary functions
15470 @node RM G 1 2 49 Complex Elementary Functions,RM G 2 4 19 Accuracy Requirements,RM G 1 1 56-58 Complex Types,Implementation Advice
15471 @anchor{gnat_rm/implementation_advice rm-g-1-2-49-complex-elementary-functions}@anchor{24b}
15472 @section RM G.1.2(49): Complex Elementary Functions
15477 "Implementations in which @code{Complex_Types.Real'Signed_Zeros} is
15478 @code{True} should attempt to provide a rational treatment of the signs
15479 of zero results and result components. For example, many of the complex
15480 elementary functions have components that are odd functions of one of
15481 the parameter components; in these cases, the result component should
15482 have the sign of the parameter component at the origin. Other complex
15483 elementary functions have zero components whose sign is opposite that of
15484 a parameter component at the origin, or is always positive or always
15490 @geindex Accuracy requirements
15492 @node RM G 2 4 19 Accuracy Requirements,RM G 2 6 15 Complex Arithmetic Accuracy,RM G 1 2 49 Complex Elementary Functions,Implementation Advice
15493 @anchor{gnat_rm/implementation_advice rm-g-2-4-19-accuracy-requirements}@anchor{24c}
15494 @section RM G.2.4(19): Accuracy Requirements
15499 "The versions of the forward trigonometric functions without a
15500 @code{Cycle} parameter should not be implemented by calling the
15501 corresponding version with a @code{Cycle} parameter of
15502 @code{2.0*Numerics.Pi}, since this will not provide the required
15503 accuracy in some portions of the domain. For the same reason, the
15504 version of @code{Log} without a @code{Base} parameter should not be
15505 implemented by calling the corresponding version with a @code{Base}
15506 parameter of @code{Numerics.e}."
15511 @geindex Complex arithmetic accuracy
15514 @geindex complex arithmetic
15516 @node RM G 2 6 15 Complex Arithmetic Accuracy,RM H 6 15/2 Pragma Partition_Elaboration_Policy,RM G 2 4 19 Accuracy Requirements,Implementation Advice
15517 @anchor{gnat_rm/implementation_advice rm-g-2-6-15-complex-arithmetic-accuracy}@anchor{24d}
15518 @section RM G.2.6(15): Complex Arithmetic Accuracy
15523 "The version of the @code{Compose_From_Polar} function without a
15524 @code{Cycle} parameter should not be implemented by calling the
15525 corresponding version with a @code{Cycle} parameter of
15526 @code{2.0*Numerics.Pi}, since this will not provide the required
15527 accuracy in some portions of the domain."
15532 @geindex Sequential elaboration policy
15534 @node RM H 6 15/2 Pragma Partition_Elaboration_Policy,,RM G 2 6 15 Complex Arithmetic Accuracy,Implementation Advice
15535 @anchor{gnat_rm/implementation_advice rm-h-6-15-2-pragma-partition-elaboration-policy}@anchor{24e}
15536 @section RM H.6(15/2): Pragma Partition_Elaboration_Policy
15541 "If the partition elaboration policy is @code{Sequential} and the
15542 Environment task becomes permanently blocked during elaboration then the
15543 partition is deadlocked and it is recommended that the partition be
15544 immediately terminated."
15549 @node Implementation Defined Characteristics,Intrinsic Subprograms,Implementation Advice,Top
15550 @anchor{gnat_rm/implementation_defined_characteristics implementation-defined-characteristics}@anchor{b}@anchor{gnat_rm/implementation_defined_characteristics doc}@anchor{24f}@anchor{gnat_rm/implementation_defined_characteristics id1}@anchor{250}
15551 @chapter Implementation Defined Characteristics
15554 In addition to the implementation dependent pragmas and attributes, and the
15555 implementation advice, there are a number of other Ada features that are
15556 potentially implementation dependent and are designated as
15557 implementation-defined. These are mentioned throughout the Ada Reference
15558 Manual, and are summarized in Annex M.
15560 A requirement for conforming Ada compilers is that they provide
15561 documentation describing how the implementation deals with each of these
15562 issues. In this chapter you will find each point in Annex M listed,
15563 followed by a description of how GNAT
15564 handles the implementation dependence.
15566 You can use this chapter as a guide to minimizing implementation
15567 dependent features in your programs if portability to other compilers
15568 and other operating systems is an important consideration. The numbers
15569 in each entry below correspond to the paragraph numbers in the Ada
15576 "Whether or not each recommendation given in Implementation
15577 Advice is followed. See 1.1.2(37)."
15580 See @ref{a,,Implementation Advice}.
15586 "Capacity limitations of the implementation. See 1.1.3(3)."
15589 The complexity of programs that can be processed is limited only by the
15590 total amount of available virtual memory, and disk space for the
15591 generated object files.
15597 "Variations from the standard that are impractical to avoid
15598 given the implementation's execution environment. See 1.1.3(6)."
15601 There are no variations from the standard.
15607 "Which code_statements cause external
15608 interactions. See 1.1.3(10)."
15611 Any @emph{code_statement} can potentially cause external interactions.
15617 "The coded representation for the text of an Ada
15618 program. See 2.1(4)."
15621 See separate section on source representation.
15627 "The control functions allowed in comments. See 2.1(14)."
15630 See separate section on source representation.
15636 "The representation for an end of line. See 2.2(2)."
15639 See separate section on source representation.
15645 "Maximum supported line length and lexical element
15646 length. See 2.2(15)."
15649 The maximum line length is 255 characters and the maximum length of
15650 a lexical element is also 255 characters. This is the default setting
15651 if not overridden by the use of compiler switch @emph{-gnaty} (which
15652 sets the maximum to 79) or @emph{-gnatyMnn} which allows the maximum
15653 line length to be specified to be any value up to 32767. The maximum
15654 length of a lexical element is the same as the maximum line length.
15660 "Implementation defined pragmas. See 2.8(14)."
15663 See @ref{7,,Implementation Defined Pragmas}.
15669 "Effect of pragma @code{Optimize}. See 2.8(27)."
15672 Pragma @code{Optimize}, if given with a @code{Time} or @code{Space}
15673 parameter, checks that the optimization flag is set, and aborts if it is
15680 "The sequence of characters of the value returned by
15681 @code{S'Image} when some of the graphic characters of
15682 @code{S'Wide_Image} are not defined in @code{Character}. See
15686 The sequence of characters is as defined by the wide character encoding
15687 method used for the source. See section on source representation for
15694 "The predefined integer types declared in
15695 @code{Standard}. See 3.5.4(25)."
15699 @multitable {xxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
15710 @emph{Short_Short_Integer}
15718 @emph{Short_Integer}
15722 (Short) 16 bit signed
15734 @emph{Long_Integer}
15738 64 bit signed (on most 64 bit targets,
15739 depending on the C definition of long).
15740 32 bit signed (all other targets)
15744 @emph{Long_Long_Integer}
15757 "Any nonstandard integer types and the operators defined
15758 for them. See 3.5.4(26)."
15761 There are no nonstandard integer types.
15767 "Any nonstandard real types and the operators defined for
15768 them. See 3.5.6(8)."
15771 There are no nonstandard real types.
15777 "What combinations of requested decimal precision and range
15778 are supported for floating point types. See 3.5.7(7)."
15781 The precision and range is as defined by the IEEE standard.
15787 "The predefined floating point types declared in
15788 @code{Standard}. See 3.5.7(16)."
15792 @multitable {xxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
15815 (Short) 32 bit IEEE short
15827 @emph{Long_Long_Float}
15831 64 bit IEEE long (80 bit IEEE long on x86 processors)
15840 "The small of an ordinary fixed point type. See 3.5.9(8)."
15843 @code{Fine_Delta} is 2**(-63)
15849 "What combinations of small, range, and digits are
15850 supported for fixed point types. See 3.5.9(10)."
15853 Any combinations are permitted that do not result in a small less than
15854 @code{Fine_Delta} and do not result in a mantissa larger than 63 bits.
15855 If the mantissa is larger than 53 bits on machines where Long_Long_Float
15856 is 64 bits (true of all architectures except ia32), then the output from
15857 Text_IO is accurate to only 53 bits, rather than the full mantissa. This
15858 is because floating-point conversions are used to convert fixed point.
15864 "The result of @code{Tags.Expanded_Name} for types declared
15865 within an unnamed @emph{block_statement}. See 3.9(10)."
15868 Block numbers of the form @code{B@emph{nnn}}, where @emph{nnn} is a
15869 decimal integer are allocated.
15875 "Implementation-defined attributes. See 4.1.4(12)."
15878 See @ref{8,,Implementation Defined Attributes}.
15884 "Any implementation-defined time types. See 9.6(6)."
15887 There are no implementation-defined time types.
15893 "The time base associated with relative delays."
15896 See 9.6(20). The time base used is that provided by the C library
15897 function @code{gettimeofday}.
15903 "The time base of the type @code{Calendar.Time}. See
15907 The time base used is that provided by the C library function
15908 @code{gettimeofday}.
15914 "The time zone used for package @code{Calendar}
15915 operations. See 9.6(24)."
15918 The time zone used by package @code{Calendar} is the current system time zone
15919 setting for local time, as accessed by the C library function
15926 "Any limit on @emph{delay_until_statements} of
15927 @emph{select_statements}. See 9.6(29)."
15930 There are no such limits.
15936 "Whether or not two non-overlapping parts of a composite
15937 object are independently addressable, in the case where packing, record
15938 layout, or @code{Component_Size} is specified for the object. See
15942 Separate components are independently addressable if they do not share
15943 overlapping storage units.
15949 "The representation for a compilation. See 10.1(2)."
15952 A compilation is represented by a sequence of files presented to the
15953 compiler in a single invocation of the @emph{gcc} command.
15959 "Any restrictions on compilations that contain multiple
15960 compilation_units. See 10.1(4)."
15963 No single file can contain more than one compilation unit, but any
15964 sequence of files can be presented to the compiler as a single
15971 "The mechanisms for creating an environment and for adding
15972 and replacing compilation units. See 10.1.4(3)."
15975 See separate section on compilation model.
15981 "The manner of explicitly assigning library units to a
15982 partition. See 10.2(2)."
15985 If a unit contains an Ada main program, then the Ada units for the partition
15986 are determined by recursive application of the rules in the Ada Reference
15987 Manual section 10.2(2-6). In other words, the Ada units will be those that
15988 are needed by the main program, and then this definition of need is applied
15989 recursively to those units, and the partition contains the transitive
15990 closure determined by this relationship. In short, all the necessary units
15991 are included, with no need to explicitly specify the list. If additional
15992 units are required, e.g., by foreign language units, then all units must be
15993 mentioned in the context clause of one of the needed Ada units.
15995 If the partition contains no main program, or if the main program is in
15996 a language other than Ada, then GNAT
15997 provides the binder options @emph{-z} and @emph{-n} respectively, and in
15998 this case a list of units can be explicitly supplied to the binder for
15999 inclusion in the partition (all units needed by these units will also
16000 be included automatically). For full details on the use of these
16001 options, refer to @emph{GNAT Make Program gnatmake} in the
16002 @cite{GNAT User's Guide}.
16008 "The implementation-defined means, if any, of specifying
16009 which compilation units are needed by a given compilation unit. See
16013 The units needed by a given compilation unit are as defined in
16014 the Ada Reference Manual section 10.2(2-6). There are no
16015 implementation-defined pragmas or other implementation-defined
16016 means for specifying needed units.
16022 "The manner of designating the main subprogram of a
16023 partition. See 10.2(7)."
16026 The main program is designated by providing the name of the
16027 corresponding @code{ALI} file as the input parameter to the binder.
16033 "The order of elaboration of @emph{library_items}. See
16037 The first constraint on ordering is that it meets the requirements of
16038 Chapter 10 of the Ada Reference Manual. This still leaves some
16039 implementation dependent choices, which are resolved by first
16040 elaborating bodies as early as possible (i.e., in preference to specs
16041 where there is a choice), and second by evaluating the immediate with
16042 clauses of a unit to determine the probably best choice, and
16043 third by elaborating in alphabetical order of unit names
16044 where a choice still remains.
16050 "Parameter passing and function return for the main
16051 subprogram. See 10.2(21)."
16054 The main program has no parameters. It may be a procedure, or a function
16055 returning an integer type. In the latter case, the returned integer
16056 value is the return code of the program (overriding any value that
16057 may have been set by a call to @code{Ada.Command_Line.Set_Exit_Status}).
16063 "The mechanisms for building and running partitions. See
16067 GNAT itself supports programs with only a single partition. The GNATDIST
16068 tool provided with the GLADE package (which also includes an implementation
16069 of the PCS) provides a completely flexible method for building and running
16070 programs consisting of multiple partitions. See the separate GLADE manual
16077 "The details of program execution, including program
16078 termination. See 10.2(25)."
16081 See separate section on compilation model.
16087 "The semantics of any non-active partitions supported by the
16088 implementation. See 10.2(28)."
16091 Passive partitions are supported on targets where shared memory is
16092 provided by the operating system. See the GLADE reference manual for
16099 "The information returned by @code{Exception_Message}. See
16103 Exception message returns the null string unless a specific message has
16104 been passed by the program.
16110 "The result of @code{Exceptions.Exception_Name} for types
16111 declared within an unnamed @emph{block_statement}. See 11.4.1(12)."
16114 Blocks have implementation defined names of the form @code{B@emph{nnn}}
16115 where @emph{nnn} is an integer.
16121 "The information returned by
16122 @code{Exception_Information}. See 11.4.1(13)."
16125 @code{Exception_Information} returns a string in the following format:
16128 *Exception_Name:* nnnnn
16131 *Load address:* 0xhhhh
16132 *Call stack traceback locations:*
16133 0xhhhh 0xhhhh 0xhhhh ... 0xhhh
16144 @code{nnnn} is the fully qualified name of the exception in all upper
16145 case letters. This line is always present.
16148 @code{mmmm} is the message (this line present only if message is non-null)
16151 @code{ppp} is the Process Id value as a decimal integer (this line is
16152 present only if the Process Id is nonzero). Currently we are
16153 not making use of this field.
16156 The Load address line, the Call stack traceback locations line and the
16157 following values are present only if at least one traceback location was
16158 recorded. The Load address indicates the address at which the main executable
16159 was loaded; this line may not be present if operating system hasn't relocated
16160 the main executable. The values are given in C style format, with lower case
16161 letters for a-f, and only as many digits present as are necessary.
16162 The line terminator sequence at the end of each line, including
16163 the last line is a single @code{LF} character (@code{16#0A#}).
16171 "Implementation-defined check names. See 11.5(27)."
16174 The implementation defined check names include Alignment_Check,
16175 Atomic_Synchronization, Duplicated_Tag_Check, Container_Checks,
16176 Tampering_Check, Predicate_Check, and Validity_Check. In addition, a user
16177 program can add implementation-defined check names by means of the pragma
16178 Check_Name. See the description of pragma @code{Suppress} for full details.
16184 "The interpretation of each aspect of representation. See
16188 See separate section on data representations.
16194 "Any restrictions placed upon representation items. See
16198 See separate section on data representations.
16204 "The meaning of @code{Size} for indefinite subtypes. See
16208 Size for an indefinite subtype is the maximum possible size, except that
16209 for the case of a subprogram parameter, the size of the parameter object
16210 is the actual size.
16216 "The default external representation for a type tag. See
16220 The default external representation for a type tag is the fully expanded
16221 name of the type in upper case letters.
16227 "What determines whether a compilation unit is the same in
16228 two different partitions. See 13.3(76)."
16231 A compilation unit is the same in two different partitions if and only
16232 if it derives from the same source file.
16238 "Implementation-defined components. See 13.5.1(15)."
16241 The only implementation defined component is the tag for a tagged type,
16242 which contains a pointer to the dispatching table.
16248 "If @code{Word_Size} = @code{Storage_Unit}, the default bit
16249 ordering. See 13.5.3(5)."
16252 @code{Word_Size} (32) is not the same as @code{Storage_Unit} (8) for this
16253 implementation, so no non-default bit ordering is supported. The default
16254 bit ordering corresponds to the natural endianness of the target architecture.
16260 "The contents of the visible part of package @code{System}
16261 and its language-defined children. See 13.7(2)."
16264 See the definition of these packages in files @code{system.ads} and
16265 @code{s-stoele.ads}. Note that two declarations are added to package
16269 Max_Priority : constant Positive := Priority'Last;
16270 Max_Interrupt_Priority : constant Positive := Interrupt_Priority'Last;
16277 "The contents of the visible part of package
16278 @code{System.Machine_Code}, and the meaning of
16279 @emph{code_statements}. See 13.8(7)."
16282 See the definition and documentation in file @code{s-maccod.ads}.
16288 "The effect of unchecked conversion. See 13.9(11)."
16291 Unchecked conversion between types of the same size
16292 results in an uninterpreted transmission of the bits from one type
16293 to the other. If the types are of unequal sizes, then in the case of
16294 discrete types, a shorter source is first zero or sign extended as
16295 necessary, and a shorter target is simply truncated on the left.
16296 For all non-discrete types, the source is first copied if necessary
16297 to ensure that the alignment requirements of the target are met, then
16298 a pointer is constructed to the source value, and the result is obtained
16299 by dereferencing this pointer after converting it to be a pointer to the
16300 target type. Unchecked conversions where the target subtype is an
16301 unconstrained array are not permitted. If the target alignment is
16302 greater than the source alignment, then a copy of the result is
16303 made with appropriate alignment
16309 "The semantics of operations on invalid representations.
16310 See 13.9.2(10-11)."
16313 For assignments and other operations where the use of invalid values cannot
16314 result in erroneous behavior, the compiler ignores the possibility of invalid
16315 values. An exception is raised at the point where an invalid value would
16316 result in erroneous behavior. For example executing:
16319 procedure invalidvals is
16321 Y : Natural range 1 .. 10;
16322 for Y'Address use X'Address;
16323 Z : Natural range 1 .. 10;
16324 A : array (Natural range 1 .. 10) of Integer;
16326 Z := Y; -- no exception
16327 A (Z) := 3; -- exception raised;
16331 As indicated, an exception is raised on the array assignment, but not
16332 on the simple assignment of the invalid negative value from Y to Z.
16338 "The manner of choosing a storage pool for an access type
16339 when @code{Storage_Pool} is not specified for the type. See 13.11(17)."
16342 There are 3 different standard pools used by the compiler when
16343 @code{Storage_Pool} is not specified depending whether the type is local
16344 to a subprogram or defined at the library level and whether
16345 @code{Storage_Size`@w{`}is specified or not. See documentation in the runtime
16346 library units `@w{`}System.Pool_Global}, @code{System.Pool_Size} and
16347 @code{System.Pool_Local} in files @code{s-poosiz.ads},
16348 @code{s-pooglo.ads} and @code{s-pooloc.ads} for full details on the
16349 default pools used.
16355 "Whether or not the implementation provides user-accessible
16356 names for the standard pool type(s). See 13.11(17)."
16359 See documentation in the sources of the run time mentioned in the previous
16360 paragraph. All these pools are accessible by means of @cite{with}ing
16367 "The meaning of @code{Storage_Size}. See 13.11(18)."
16370 @code{Storage_Size} is measured in storage units, and refers to the
16371 total space available for an access type collection, or to the primary
16372 stack space for a task.
16378 "Implementation-defined aspects of storage pools. See
16382 See documentation in the sources of the run time mentioned in the
16383 paragraph about standard storage pools above
16384 for details on GNAT-defined aspects of storage pools.
16390 "The set of restrictions allowed in a pragma
16391 @code{Restrictions}. See 13.12(7)."
16394 See @ref{9,,Standard and Implementation Defined Restrictions}.
16400 "The consequences of violating limitations on
16401 @code{Restrictions} pragmas. See 13.12(9)."
16404 Restrictions that can be checked at compile time result in illegalities
16405 if violated. Currently there are no other consequences of violating
16412 "The representation used by the @code{Read} and
16413 @code{Write} attributes of elementary types in terms of stream
16414 elements. See 13.13.2(9)."
16417 The representation is the in-memory representation of the base type of
16418 the type, using the number of bits corresponding to the
16419 @code{type'Size} value, and the natural ordering of the machine.
16425 "The names and characteristics of the numeric subtypes
16426 declared in the visible part of package @code{Standard}. See A.1(3)."
16429 See items describing the integer and floating-point types supported.
16435 "The string returned by @code{Character_Set_Version}.
16439 @code{Ada.Wide_Characters.Handling.Character_Set_Version} returns
16440 the string "Unicode 4.0", referring to version 4.0 of the
16441 Unicode specification.
16447 "The accuracy actually achieved by the elementary
16448 functions. See A.5.1(1)."
16451 The elementary functions correspond to the functions available in the C
16452 library. Only fast math mode is implemented.
16458 "The sign of a zero result from some of the operators or
16459 functions in @code{Numerics.Generic_Elementary_Functions}, when
16460 @code{Float_Type'Signed_Zeros} is @code{True}. See A.5.1(46)."
16463 The sign of zeroes follows the requirements of the IEEE 754 standard on
16471 @code{Numerics.Float_Random.Max_Image_Width}. See A.5.2(27)."
16474 Maximum image width is 6864, see library file @code{s-rannum.ads}.
16481 @code{Numerics.Discrete_Random.Max_Image_Width}. See A.5.2(27)."
16484 Maximum image width is 6864, see library file @code{s-rannum.ads}.
16490 "The algorithms for random number generation. See
16494 The algorithm is the Mersenne Twister, as documented in the source file
16495 @code{s-rannum.adb}. This version of the algorithm has a period of
16502 "The string representation of a random number generator's
16503 state. See A.5.2(38)."
16506 The value returned by the Image function is the concatenation of
16507 the fixed-width decimal representations of the 624 32-bit integers
16508 of the state vector.
16514 "The minimum time interval between calls to the
16515 time-dependent Reset procedure that are guaranteed to initiate different
16516 random number sequences. See A.5.2(45)."
16519 The minimum period between reset calls to guarantee distinct series of
16520 random numbers is one microsecond.
16526 "The values of the @code{Model_Mantissa},
16527 @code{Model_Emin}, @code{Model_Epsilon}, @code{Model},
16528 @code{Safe_First}, and @code{Safe_Last} attributes, if the Numerics
16529 Annex is not supported. See A.5.3(72)."
16532 Run the compiler with @emph{-gnatS} to produce a listing of package
16533 @code{Standard}, has the values of all numeric attributes.
16539 "Any implementation-defined characteristics of the
16540 input-output packages. See A.7(14)."
16543 There are no special implementation defined characteristics for these
16550 "The value of @code{Buffer_Size} in @code{Storage_IO}. See
16554 All type representations are contiguous, and the @code{Buffer_Size} is
16555 the value of @code{type'Size} rounded up to the next storage unit
16562 "External files for standard input, standard output, and
16563 standard error See A.10(5)."
16566 These files are mapped onto the files provided by the C streams
16567 libraries. See source file @code{i-cstrea.ads} for further details.
16573 "The accuracy of the value produced by @code{Put}. See
16577 If more digits are requested in the output than are represented by the
16578 precision of the value, zeroes are output in the corresponding least
16579 significant digit positions.
16585 "The meaning of @code{Argument_Count}, @code{Argument}, and
16586 @code{Command_Name}. See A.15(1)."
16589 These are mapped onto the @code{argv} and @code{argc} parameters of the
16590 main program in the natural manner.
16596 "The interpretation of the @code{Form} parameter in procedure
16597 @code{Create_Directory}. See A.16(56)."
16600 The @code{Form} parameter is not used.
16606 "The interpretation of the @code{Form} parameter in procedure
16607 @code{Create_Path}. See A.16(60)."
16610 The @code{Form} parameter is not used.
16616 "The interpretation of the @code{Form} parameter in procedure
16617 @code{Copy_File}. See A.16(68)."
16620 The @code{Form} parameter is case-insensitive.
16621 Two fields are recognized in the @code{Form} parameter:
16628 <value> starts immediately after the character '=' and ends with the
16629 character immediately preceding the next comma (',') or with the last
16630 character of the parameter.
16632 The only possible values for preserve= are:
16635 @multitable {xxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
16646 @emph{no_attributes}
16650 Do not try to preserve any file attributes. This is the
16651 default if no preserve= is found in Form.
16655 @emph{all_attributes}
16659 Try to preserve all file attributes (timestamps, access rights).
16667 Preserve the timestamp of the copied file, but not the other
16673 The only possible values for mode= are:
16676 @multitable {xxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
16691 Only do the copy if the destination file does not already exist.
16692 If it already exists, Copy_File fails.
16700 Copy the file in all cases. Overwrite an already existing destination file.
16708 Append the original file to the destination file. If the destination file
16709 does not exist, the destination file is a copy of the source file.
16710 When mode=append, the field preserve=, if it exists, is not taken into account.
16715 If the Form parameter includes one or both of the fields and the value or
16716 values are incorrect, Copy_file fails with Use_Error.
16718 Examples of correct Forms:
16721 Form => "preserve=no_attributes,mode=overwrite" (the default)
16722 Form => "mode=append"
16723 Form => "mode=copy, preserve=all_attributes"
16726 Examples of incorrect Forms:
16729 Form => "preserve=junk"
16730 Form => "mode=internal, preserve=timestamps"
16737 "The interpretation of the @code{Pattern} parameter, when not the null string,
16738 in the @code{Start_Search} and @code{Search} procedures.
16739 See A.16(104) and A.16(112)."
16742 When the @code{Pattern} parameter is not the null string, it is interpreted
16743 according to the syntax of regular expressions as defined in the
16744 @code{GNAT.Regexp} package.
16746 See @ref{251,,GNAT.Regexp (g-regexp.ads)}.
16752 "Implementation-defined convention names. See B.1(11)."
16755 The following convention names are supported
16758 @multitable {xxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
16777 @emph{Ada_Pass_By_Copy}
16781 Allowed for any types except by-reference types such as limited
16782 records. Compatible with convention Ada, but causes any parameters
16783 with this convention to be passed by copy.
16787 @emph{Ada_Pass_By_Reference}
16791 Allowed for any types except by-copy types such as scalars.
16792 Compatible with convention Ada, but causes any parameters
16793 with this convention to be passed by reference.
16809 Synonym for Assembler
16817 Synonym for Assembler
16829 @emph{C_Pass_By_Copy}
16833 Allowed only for record types, like C, but also notes that record
16834 is to be passed by copy rather than reference.
16846 @emph{C_Plus_Plus (or CPP)}
16858 Treated the same as C
16866 Treated the same as C
16882 For support of pragma @code{Import} with convention Intrinsic, see
16883 separate section on Intrinsic Subprograms.
16891 Stdcall (used for Windows implementations only). This convention correspond
16892 to the WINAPI (previously called Pascal convention) C/C++ convention under
16893 Windows. A routine with this convention cleans the stack before
16894 exit. This pragma cannot be applied to a dispatching call.
16902 Synonym for Stdcall
16910 Synonym for Stdcall
16918 Stubbed is a special convention used to indicate that the body of the
16919 subprogram will be entirely ignored. Any call to the subprogram
16920 is converted into a raise of the @code{Program_Error} exception. If a
16921 pragma @code{Import} specifies convention @code{stubbed} then no body need
16922 be present at all. This convention is useful during development for the
16923 inclusion of subprograms whose body has not yet been written.
16924 In addition, all otherwise unrecognized convention names are also
16925 treated as being synonymous with convention C. In all implementations
16926 except for VMS, use of such other names results in a warning. In VMS
16927 implementations, these names are accepted silently.
16936 "The meaning of link names. See B.1(36)."
16939 Link names are the actual names used by the linker.
16945 "The manner of choosing link names when neither the link
16946 name nor the address of an imported or exported entity is specified. See
16950 The default linker name is that which would be assigned by the relevant
16951 external language, interpreting the Ada name as being in all lower case
16958 "The effect of pragma @code{Linker_Options}. See B.1(37)."
16961 The string passed to @code{Linker_Options} is presented uninterpreted as
16962 an argument to the link command, unless it contains ASCII.NUL characters.
16963 NUL characters if they appear act as argument separators, so for example
16966 pragma Linker_Options ("-labc" & ASCII.NUL & "-ldef");
16969 causes two separate arguments @code{-labc} and @code{-ldef} to be passed to the
16970 linker. The order of linker options is preserved for a given unit. The final
16971 list of options passed to the linker is in reverse order of the elaboration
16972 order. For example, linker options for a body always appear before the options
16973 from the corresponding package spec.
16979 "The contents of the visible part of package
16980 @code{Interfaces} and its language-defined descendants. See B.2(1)."
16983 See files with prefix @code{i-} in the distributed library.
16989 "Implementation-defined children of package
16990 @code{Interfaces}. The contents of the visible part of package
16991 @code{Interfaces}. See B.2(11)."
16994 See files with prefix @code{i-} in the distributed library.
17000 "The types @code{Floating}, @code{Long_Floating},
17001 @code{Binary}, @code{Long_Binary}, @code{Decimal_ Element}, and
17002 @code{COBOL_Character}; and the initialization of the variables
17003 @code{Ada_To_COBOL} and @code{COBOL_To_Ada}, in
17004 @code{Interfaces.COBOL}. See B.4(50)."
17008 @multitable {xxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
17027 @emph{Long_Floating}
17031 (Floating) Long_Float
17051 @emph{Decimal_Element}
17059 @emph{COBOL_Character}
17068 For initialization, see the file @code{i-cobol.ads} in the distributed library.
17074 "Support for access to machine instructions. See C.1(1)."
17077 See documentation in file @code{s-maccod.ads} in the distributed library.
17083 "Implementation-defined aspects of access to machine
17084 operations. See C.1(9)."
17087 See documentation in file @code{s-maccod.ads} in the distributed library.
17093 "Implementation-defined aspects of interrupts. See C.3(2)."
17096 Interrupts are mapped to signals or conditions as appropriate. See
17098 @code{Ada.Interrupt_Names} in source file @code{a-intnam.ads} for details
17099 on the interrupts supported on a particular target.
17105 "Implementation-defined aspects of pre-elaboration. See
17109 GNAT does not permit a partition to be restarted without reloading,
17110 except under control of the debugger.
17116 "The semantics of pragma @code{Discard_Names}. See C.5(7)."
17119 Pragma @code{Discard_Names} causes names of enumeration literals to
17120 be suppressed. In the presence of this pragma, the Image attribute
17121 provides the image of the Pos of the literal, and Value accepts
17128 "The result of the @code{Task_Identification.Image}
17129 attribute. See C.7.1(7)."
17132 The result of this attribute is a string that identifies
17133 the object or component that denotes a given task. If a variable @code{Var}
17134 has a task type, the image for this task will have the form @code{Var_@emph{XXXXXXXX}},
17135 where the suffix @emph{XXXXXXXX}
17136 is the hexadecimal representation of the virtual address of the corresponding
17137 task control block. If the variable is an array of tasks, the image of each
17138 task will have the form of an indexed component indicating the position of a
17139 given task in the array, e.g., @code{Group(5)_@emph{XXXXXXX}}. If the task is a
17140 component of a record, the image of the task will have the form of a selected
17141 component. These rules are fully recursive, so that the image of a task that
17142 is a subcomponent of a composite object corresponds to the expression that
17143 designates this task.
17145 If a task is created by an allocator, its image depends on the context. If the
17146 allocator is part of an object declaration, the rules described above are used
17147 to construct its image, and this image is not affected by subsequent
17148 assignments. If the allocator appears within an expression, the image
17149 includes only the name of the task type.
17151 If the configuration pragma Discard_Names is present, or if the restriction
17152 No_Implicit_Heap_Allocation is in effect, the image reduces to
17153 the numeric suffix, that is to say the hexadecimal representation of the
17154 virtual address of the control block of the task.
17160 "The value of @code{Current_Task} when in a protected entry
17161 or interrupt handler. See C.7.1(17)."
17164 Protected entries or interrupt handlers can be executed by any
17165 convenient thread, so the value of @code{Current_Task} is undefined.
17171 "The effect of calling @code{Current_Task} from an entry
17172 body or interrupt handler. See C.7.1(19)."
17175 When GNAT can determine statically that @code{Current_Task} is called directly in
17176 the body of an entry (or barrier) then a warning is emitted and @code{Program_Error}
17177 is raised at run time. Otherwise, the effect of calling @code{Current_Task} from an
17178 entry body or interrupt handler is to return the identification of the task
17179 currently executing the code.
17185 "Implementation-defined aspects of
17186 @code{Task_Attributes}. See C.7.2(19)."
17189 There are no implementation-defined aspects of @code{Task_Attributes}.
17195 "Values of all @code{Metrics}. See D(2)."
17198 The metrics information for GNAT depends on the performance of the
17199 underlying operating system. The sources of the run-time for tasking
17200 implementation, together with the output from @emph{-gnatG} can be
17201 used to determine the exact sequence of operating systems calls made
17202 to implement various tasking constructs. Together with appropriate
17203 information on the performance of the underlying operating system,
17204 on the exact target in use, this information can be used to determine
17205 the required metrics.
17211 "The declarations of @code{Any_Priority} and
17212 @code{Priority}. See D.1(11)."
17215 See declarations in file @code{system.ads}.
17221 "Implementation-defined execution resources. See D.1(15)."
17224 There are no implementation-defined execution resources.
17230 "Whether, on a multiprocessor, a task that is waiting for
17231 access to a protected object keeps its processor busy. See D.2.1(3)."
17234 On a multi-processor, a task that is waiting for access to a protected
17235 object does not keep its processor busy.
17241 "The affect of implementation defined execution resources
17242 on task dispatching. See D.2.1(9)."
17245 Tasks map to threads in the threads package used by GNAT. Where possible
17246 and appropriate, these threads correspond to native threads of the
17247 underlying operating system.
17253 "Implementation-defined @emph{policy_identifiers} allowed
17254 in a pragma @code{Task_Dispatching_Policy}. See D.2.2(3)."
17257 There are no implementation-defined policy-identifiers allowed in this
17264 "Implementation-defined aspects of priority inversion. See
17268 Execution of a task cannot be preempted by the implementation processing
17269 of delay expirations for lower priority tasks.
17275 "Implementation-defined task dispatching. See D.2.2(18)."
17278 The policy is the same as that of the underlying threads implementation.
17284 "Implementation-defined @emph{policy_identifiers} allowed
17285 in a pragma @code{Locking_Policy}. See D.3(4)."
17288 The two implementation defined policies permitted in GNAT are
17289 @code{Inheritance_Locking} and @code{Concurrent_Readers_Locking}. On
17290 targets that support the @code{Inheritance_Locking} policy, locking is
17291 implemented by inheritance, i.e., the task owning the lock operates
17292 at a priority equal to the highest priority of any task currently
17293 requesting the lock. On targets that support the
17294 @code{Concurrent_Readers_Locking} policy, locking is implemented with a
17295 read/write lock allowing multiple protected object functions to enter
17302 "Default ceiling priorities. See D.3(10)."
17305 The ceiling priority of protected objects of the type
17306 @code{System.Interrupt_Priority'Last} as described in the Ada
17307 Reference Manual D.3(10),
17313 "The ceiling of any protected object used internally by
17314 the implementation. See D.3(16)."
17317 The ceiling priority of internal protected objects is
17318 @code{System.Priority'Last}.
17324 "Implementation-defined queuing policies. See D.4(1)."
17327 There are no implementation-defined queuing policies.
17333 "On a multiprocessor, any conditions that cause the
17334 completion of an aborted construct to be delayed later than what is
17335 specified for a single processor. See D.6(3)."
17338 The semantics for abort on a multi-processor is the same as on a single
17339 processor, there are no further delays.
17345 "Any operations that implicitly require heap storage
17346 allocation. See D.7(8)."
17349 The only operation that implicitly requires heap storage allocation is
17356 "What happens when a task terminates in the presence of
17357 pragma @code{No_Task_Termination}. See D.7(15)."
17360 Execution is erroneous in that case.
17366 "Implementation-defined aspects of pragma
17367 @code{Restrictions}. See D.7(20)."
17370 There are no such implementation-defined aspects.
17376 "Implementation-defined aspects of package
17377 @code{Real_Time}. See D.8(17)."
17380 There are no implementation defined aspects of package @code{Real_Time}.
17386 "Implementation-defined aspects of
17387 @emph{delay_statements}. See D.9(8)."
17390 Any difference greater than one microsecond will cause the task to be
17391 delayed (see D.9(7)).
17397 "The upper bound on the duration of interrupt blocking
17398 caused by the implementation. See D.12(5)."
17401 The upper bound is determined by the underlying operating system. In
17402 no cases is it more than 10 milliseconds.
17408 "The means for creating and executing distributed
17409 programs. See E(5)."
17412 The GLADE package provides a utility GNATDIST for creating and executing
17413 distributed programs. See the GLADE reference manual for further details.
17419 "Any events that can result in a partition becoming
17420 inaccessible. See E.1(7)."
17423 See the GLADE reference manual for full details on such events.
17429 "The scheduling policies, treatment of priorities, and
17430 management of shared resources between partitions in certain cases. See
17434 See the GLADE reference manual for full details on these aspects of
17435 multi-partition execution.
17441 "Events that cause the version of a compilation unit to
17442 change. See E.3(5)."
17445 Editing the source file of a compilation unit, or the source files of
17446 any units on which it is dependent in a significant way cause the version
17447 to change. No other actions cause the version number to change. All changes
17448 are significant except those which affect only layout, capitalization or
17455 "Whether the execution of the remote subprogram is
17456 immediately aborted as a result of cancellation. See E.4(13)."
17459 See the GLADE reference manual for details on the effect of abort in
17460 a distributed application.
17466 "Implementation-defined aspects of the PCS. See E.5(25)."
17469 See the GLADE reference manual for a full description of all implementation
17470 defined aspects of the PCS.
17476 "Implementation-defined interfaces in the PCS. See
17480 See the GLADE reference manual for a full description of all
17481 implementation defined interfaces.
17487 "The values of named numbers in the package
17488 @code{Decimal}. See F.2(7)."
17492 @multitable {xxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxx}
17535 @emph{Max_Decimal_Digits}
17548 "The value of @code{Max_Picture_Length} in the package
17549 @code{Text_IO.Editing}. See F.3.3(16)."
17558 "The value of @code{Max_Picture_Length} in the package
17559 @code{Wide_Text_IO.Editing}. See F.3.4(5)."
17568 "The accuracy actually achieved by the complex elementary
17569 functions and by other complex arithmetic operations. See G.1(1)."
17572 Standard library functions are used for the complex arithmetic
17573 operations. Only fast math mode is currently supported.
17579 "The sign of a zero result (or a component thereof) from
17580 any operator or function in @code{Numerics.Generic_Complex_Types}, when
17581 @code{Real'Signed_Zeros} is True. See G.1.1(53)."
17584 The signs of zero values are as recommended by the relevant
17585 implementation advice.
17591 "The sign of a zero result (or a component thereof) from
17592 any operator or function in
17593 @code{Numerics.Generic_Complex_Elementary_Functions}, when
17594 @code{Real'Signed_Zeros} is @code{True}. See G.1.2(45)."
17597 The signs of zero values are as recommended by the relevant
17598 implementation advice.
17604 "Whether the strict mode or the relaxed mode is the
17605 default. See G.2(2)."
17608 The strict mode is the default. There is no separate relaxed mode. GNAT
17609 provides a highly efficient implementation of strict mode.
17615 "The result interval in certain cases of fixed-to-float
17616 conversion. See G.2.1(10)."
17619 For cases where the result interval is implementation dependent, the
17620 accuracy is that provided by performing all operations in 64-bit IEEE
17621 floating-point format.
17627 "The result of a floating point arithmetic operation in
17628 overflow situations, when the @code{Machine_Overflows} attribute of the
17629 result type is @code{False}. See G.2.1(13)."
17632 Infinite and NaN values are produced as dictated by the IEEE
17633 floating-point standard.
17634 Note that on machines that are not fully compliant with the IEEE
17635 floating-point standard, such as Alpha, the @emph{-mieee} compiler flag
17636 must be used for achieving IEEE conforming behavior (although at the cost
17637 of a significant performance penalty), so infinite and NaN values are
17638 properly generated.
17644 "The result interval for division (or exponentiation by a
17645 negative exponent), when the floating point hardware implements division
17646 as multiplication by a reciprocal. See G.2.1(16)."
17649 Not relevant, division is IEEE exact.
17655 "The definition of close result set, which determines the
17656 accuracy of certain fixed point multiplications and divisions. See
17660 Operations in the close result set are performed using IEEE long format
17661 floating-point arithmetic. The input operands are converted to
17662 floating-point, the operation is done in floating-point, and the result
17663 is converted to the target type.
17669 "Conditions on a @emph{universal_real} operand of a fixed
17670 point multiplication or division for which the result shall be in the
17671 perfect result set. See G.2.3(22)."
17674 The result is only defined to be in the perfect result set if the result
17675 can be computed by a single scaling operation involving a scale factor
17676 representable in 64-bits.
17682 "The result of a fixed point arithmetic operation in
17683 overflow situations, when the @code{Machine_Overflows} attribute of the
17684 result type is @code{False}. See G.2.3(27)."
17687 Not relevant, @code{Machine_Overflows} is @code{True} for fixed-point
17694 "The result of an elementary function reference in
17695 overflow situations, when the @code{Machine_Overflows} attribute of the
17696 result type is @code{False}. See G.2.4(4)."
17699 IEEE infinite and Nan values are produced as appropriate.
17705 "The value of the angle threshold, within which certain
17706 elementary functions, complex arithmetic operations, and complex
17707 elementary functions yield results conforming to a maximum relative
17708 error bound. See G.2.4(10)."
17711 Information on this subject is not yet available.
17717 "The accuracy of certain elementary functions for
17718 parameters beyond the angle threshold. See G.2.4(10)."
17721 Information on this subject is not yet available.
17727 "The result of a complex arithmetic operation or complex
17728 elementary function reference in overflow situations, when the
17729 @code{Machine_Overflows} attribute of the corresponding real type is
17730 @code{False}. See G.2.6(5)."
17733 IEEE infinite and Nan values are produced as appropriate.
17739 "The accuracy of certain complex arithmetic operations and
17740 certain complex elementary functions for parameters (or components
17741 thereof) beyond the angle threshold. See G.2.6(8)."
17744 Information on those subjects is not yet available.
17750 "Information regarding bounded errors and erroneous
17751 execution. See H.2(1)."
17754 Information on this subject is not yet available.
17760 "Implementation-defined aspects of pragma
17761 @code{Inspection_Point}. See H.3.2(8)."
17764 Pragma @code{Inspection_Point} ensures that the variable is live and can
17765 be examined by the debugger at the inspection point.
17771 "Implementation-defined aspects of pragma
17772 @code{Restrictions}. See H.4(25)."
17775 There are no implementation-defined aspects of pragma @code{Restrictions}. The
17776 use of pragma @code{Restrictions [No_Exceptions]} has no effect on the
17777 generated code. Checks must suppressed by use of pragma @code{Suppress}.
17783 "Any restrictions on pragma @code{Restrictions}. See
17787 There are no restrictions on pragma @code{Restrictions}.
17789 @node Intrinsic Subprograms,Representation Clauses and Pragmas,Implementation Defined Characteristics,Top
17790 @anchor{gnat_rm/intrinsic_subprograms doc}@anchor{252}@anchor{gnat_rm/intrinsic_subprograms intrinsic-subprograms}@anchor{c}@anchor{gnat_rm/intrinsic_subprograms id1}@anchor{253}
17791 @chapter Intrinsic Subprograms
17794 @geindex Intrinsic Subprograms
17796 GNAT allows a user application program to write the declaration:
17799 pragma Import (Intrinsic, name);
17802 providing that the name corresponds to one of the implemented intrinsic
17803 subprograms in GNAT, and that the parameter profile of the referenced
17804 subprogram meets the requirements. This chapter describes the set of
17805 implemented intrinsic subprograms, and the requirements on parameter profiles.
17806 Note that no body is supplied; as with other uses of pragma Import, the
17807 body is supplied elsewhere (in this case by the compiler itself). Note
17808 that any use of this feature is potentially non-portable, since the
17809 Ada standard does not require Ada compilers to implement this feature.
17812 * Intrinsic Operators::
17813 * Compilation_ISO_Date::
17814 * Compilation_Date::
17815 * Compilation_Time::
17816 * Enclosing_Entity::
17817 * Exception_Information::
17818 * Exception_Message::
17822 * Shifts and Rotates::
17823 * Source_Location::
17827 @node Intrinsic Operators,Compilation_ISO_Date,,Intrinsic Subprograms
17828 @anchor{gnat_rm/intrinsic_subprograms id2}@anchor{254}@anchor{gnat_rm/intrinsic_subprograms intrinsic-operators}@anchor{255}
17829 @section Intrinsic Operators
17832 @geindex Intrinsic operator
17834 All the predefined numeric operators in package Standard
17835 in @code{pragma Import (Intrinsic,..)}
17836 declarations. In the binary operator case, the operands must have the same
17837 size. The operand or operands must also be appropriate for
17838 the operator. For example, for addition, the operands must
17839 both be floating-point or both be fixed-point, and the
17840 right operand for @code{"**"} must have a root type of
17841 @code{Standard.Integer'Base}.
17842 You can use an intrinsic operator declaration as in the following example:
17845 type Int1 is new Integer;
17846 type Int2 is new Integer;
17848 function "+" (X1 : Int1; X2 : Int2) return Int1;
17849 function "+" (X1 : Int1; X2 : Int2) return Int2;
17850 pragma Import (Intrinsic, "+");
17853 This declaration would permit 'mixed mode' arithmetic on items
17854 of the differing types @code{Int1} and @code{Int2}.
17855 It is also possible to specify such operators for private types, if the
17856 full views are appropriate arithmetic types.
17858 @node Compilation_ISO_Date,Compilation_Date,Intrinsic Operators,Intrinsic Subprograms
17859 @anchor{gnat_rm/intrinsic_subprograms id3}@anchor{256}@anchor{gnat_rm/intrinsic_subprograms compilation-iso-date}@anchor{257}
17860 @section Compilation_ISO_Date
17863 @geindex Compilation_ISO_Date
17865 This intrinsic subprogram is used in the implementation of the
17866 library package @code{GNAT.Source_Info}. The only useful use of the
17867 intrinsic import in this case is the one in this unit, so an
17868 application program should simply call the function
17869 @code{GNAT.Source_Info.Compilation_ISO_Date} to obtain the date of
17870 the current compilation (in local time format YYYY-MM-DD).
17872 @node Compilation_Date,Compilation_Time,Compilation_ISO_Date,Intrinsic Subprograms
17873 @anchor{gnat_rm/intrinsic_subprograms compilation-date}@anchor{258}@anchor{gnat_rm/intrinsic_subprograms id4}@anchor{259}
17874 @section Compilation_Date
17877 @geindex Compilation_Date
17879 Same as Compilation_ISO_Date, except the string is in the form
17882 @node Compilation_Time,Enclosing_Entity,Compilation_Date,Intrinsic Subprograms
17883 @anchor{gnat_rm/intrinsic_subprograms compilation-time}@anchor{25a}@anchor{gnat_rm/intrinsic_subprograms id5}@anchor{25b}
17884 @section Compilation_Time
17887 @geindex Compilation_Time
17889 This intrinsic subprogram is used in the implementation of the
17890 library package @code{GNAT.Source_Info}. The only useful use of the
17891 intrinsic import in this case is the one in this unit, so an
17892 application program should simply call the function
17893 @code{GNAT.Source_Info.Compilation_Time} to obtain the time of
17894 the current compilation (in local time format HH:MM:SS).
17896 @node Enclosing_Entity,Exception_Information,Compilation_Time,Intrinsic Subprograms
17897 @anchor{gnat_rm/intrinsic_subprograms id6}@anchor{25c}@anchor{gnat_rm/intrinsic_subprograms enclosing-entity}@anchor{25d}
17898 @section Enclosing_Entity
17901 @geindex Enclosing_Entity
17903 This intrinsic subprogram is used in the implementation of the
17904 library package @code{GNAT.Source_Info}. The only useful use of the
17905 intrinsic import in this case is the one in this unit, so an
17906 application program should simply call the function
17907 @code{GNAT.Source_Info.Enclosing_Entity} to obtain the name of
17908 the current subprogram, package, task, entry, or protected subprogram.
17910 @node Exception_Information,Exception_Message,Enclosing_Entity,Intrinsic Subprograms
17911 @anchor{gnat_rm/intrinsic_subprograms id7}@anchor{25e}@anchor{gnat_rm/intrinsic_subprograms exception-information}@anchor{25f}
17912 @section Exception_Information
17915 @geindex Exception_Information'
17917 This intrinsic subprogram is used in the implementation of the
17918 library package @code{GNAT.Current_Exception}. The only useful
17919 use of the intrinsic import in this case is the one in this unit,
17920 so an application program should simply call the function
17921 @code{GNAT.Current_Exception.Exception_Information} to obtain
17922 the exception information associated with the current exception.
17924 @node Exception_Message,Exception_Name,Exception_Information,Intrinsic Subprograms
17925 @anchor{gnat_rm/intrinsic_subprograms exception-message}@anchor{260}@anchor{gnat_rm/intrinsic_subprograms id8}@anchor{261}
17926 @section Exception_Message
17929 @geindex Exception_Message
17931 This intrinsic subprogram is used in the implementation of the
17932 library package @code{GNAT.Current_Exception}. The only useful
17933 use of the intrinsic import in this case is the one in this unit,
17934 so an application program should simply call the function
17935 @code{GNAT.Current_Exception.Exception_Message} to obtain
17936 the message associated with the current exception.
17938 @node Exception_Name,File,Exception_Message,Intrinsic Subprograms
17939 @anchor{gnat_rm/intrinsic_subprograms exception-name}@anchor{262}@anchor{gnat_rm/intrinsic_subprograms id9}@anchor{263}
17940 @section Exception_Name
17943 @geindex Exception_Name
17945 This intrinsic subprogram is used in the implementation of the
17946 library package @code{GNAT.Current_Exception}. The only useful
17947 use of the intrinsic import in this case is the one in this unit,
17948 so an application program should simply call the function
17949 @code{GNAT.Current_Exception.Exception_Name} to obtain
17950 the name of the current exception.
17952 @node File,Line,Exception_Name,Intrinsic Subprograms
17953 @anchor{gnat_rm/intrinsic_subprograms id10}@anchor{264}@anchor{gnat_rm/intrinsic_subprograms file}@anchor{265}
17959 This intrinsic subprogram is used in the implementation of the
17960 library package @code{GNAT.Source_Info}. The only useful use of the
17961 intrinsic import in this case is the one in this unit, so an
17962 application program should simply call the function
17963 @code{GNAT.Source_Info.File} to obtain the name of the current
17966 @node Line,Shifts and Rotates,File,Intrinsic Subprograms
17967 @anchor{gnat_rm/intrinsic_subprograms id11}@anchor{266}@anchor{gnat_rm/intrinsic_subprograms line}@anchor{267}
17973 This intrinsic subprogram is used in the implementation of the
17974 library package @code{GNAT.Source_Info}. The only useful use of the
17975 intrinsic import in this case is the one in this unit, so an
17976 application program should simply call the function
17977 @code{GNAT.Source_Info.Line} to obtain the number of the current
17980 @node Shifts and Rotates,Source_Location,Line,Intrinsic Subprograms
17981 @anchor{gnat_rm/intrinsic_subprograms shifts-and-rotates}@anchor{268}@anchor{gnat_rm/intrinsic_subprograms id12}@anchor{269}
17982 @section Shifts and Rotates
17985 @geindex Shift_Left
17987 @geindex Shift_Right
17989 @geindex Shift_Right_Arithmetic
17991 @geindex Rotate_Left
17993 @geindex Rotate_Right
17995 In standard Ada, the shift and rotate functions are available only
17996 for the predefined modular types in package @code{Interfaces}. However, in
17997 GNAT it is possible to define these functions for any integer
17998 type (signed or modular), as in this example:
18001 function Shift_Left
18003 Amount : Natural) return T;
18006 The function name must be one of
18007 Shift_Left, Shift_Right, Shift_Right_Arithmetic, Rotate_Left, or
18008 Rotate_Right. T must be an integer type. T'Size must be
18009 8, 16, 32 or 64 bits; if T is modular, the modulus
18010 must be 2**8, 2**16, 2**32 or 2**64.
18011 The result type must be the same as the type of @code{Value}.
18012 The shift amount must be Natural.
18013 The formal parameter names can be anything.
18015 A more convenient way of providing these shift operators is to use
18016 the Provide_Shift_Operators pragma, which provides the function declarations
18017 and corresponding pragma Import's for all five shift functions.
18019 @node Source_Location,,Shifts and Rotates,Intrinsic Subprograms
18020 @anchor{gnat_rm/intrinsic_subprograms source-location}@anchor{26a}@anchor{gnat_rm/intrinsic_subprograms id13}@anchor{26b}
18021 @section Source_Location
18024 @geindex Source_Location
18026 This intrinsic subprogram is used in the implementation of the
18027 library routine @code{GNAT.Source_Info}. The only useful use of the
18028 intrinsic import in this case is the one in this unit, so an
18029 application program should simply call the function
18030 @code{GNAT.Source_Info.Source_Location} to obtain the current
18031 source file location.
18033 @node Representation Clauses and Pragmas,Standard Library Routines,Intrinsic Subprograms,Top
18034 @anchor{gnat_rm/representation_clauses_and_pragmas representation-clauses-and-pragmas}@anchor{d}@anchor{gnat_rm/representation_clauses_and_pragmas doc}@anchor{26c}@anchor{gnat_rm/representation_clauses_and_pragmas id1}@anchor{26d}
18035 @chapter Representation Clauses and Pragmas
18038 @geindex Representation Clauses
18040 @geindex Representation Clause
18042 @geindex Representation Pragma
18045 @geindex representation
18047 This section describes the representation clauses accepted by GNAT, and
18048 their effect on the representation of corresponding data objects.
18050 GNAT fully implements Annex C (Systems Programming). This means that all
18051 the implementation advice sections in chapter 13 are fully implemented.
18052 However, these sections only require a minimal level of support for
18053 representation clauses. GNAT provides much more extensive capabilities,
18054 and this section describes the additional capabilities provided.
18057 * Alignment Clauses::
18059 * Storage_Size Clauses::
18060 * Size of Variant Record Objects::
18061 * Biased Representation::
18062 * Value_Size and Object_Size Clauses::
18063 * Component_Size Clauses::
18064 * Bit_Order Clauses::
18065 * Effect of Bit_Order on Byte Ordering::
18066 * Pragma Pack for Arrays::
18067 * Pragma Pack for Records::
18068 * Record Representation Clauses::
18069 * Handling of Records with Holes::
18070 * Enumeration Clauses::
18071 * Address Clauses::
18072 * Use of Address Clauses for Memory-Mapped I/O::
18073 * Effect of Convention on Representation::
18074 * Conventions and Anonymous Access Types::
18075 * Determining the Representations chosen by GNAT::
18079 @node Alignment Clauses,Size Clauses,,Representation Clauses and Pragmas
18080 @anchor{gnat_rm/representation_clauses_and_pragmas id2}@anchor{26e}@anchor{gnat_rm/representation_clauses_and_pragmas alignment-clauses}@anchor{26f}
18081 @section Alignment Clauses
18084 @geindex Alignment Clause
18086 GNAT requires that all alignment clauses specify a power of 2, and all
18087 default alignments are always a power of 2. The default alignment
18088 values are as follows:
18094 @emph{Elementary Types}.
18096 For elementary types, the alignment is the minimum of the actual size of
18097 objects of the type divided by @code{Storage_Unit},
18098 and the maximum alignment supported by the target.
18099 (This maximum alignment is given by the GNAT-specific attribute
18100 @code{Standard'Maximum_Alignment}; see @ref{189,,Attribute Maximum_Alignment}.)
18102 @geindex Maximum_Alignment attribute
18104 For example, for type @code{Long_Float}, the object size is 8 bytes, and the
18105 default alignment will be 8 on any target that supports alignments
18106 this large, but on some targets, the maximum alignment may be smaller
18107 than 8, in which case objects of type @code{Long_Float} will be maximally
18113 For arrays, the alignment is equal to the alignment of the component type
18114 for the normal case where no packing or component size is given. If the
18115 array is packed, and the packing is effective (see separate section on
18116 packed arrays), then the alignment will be either 4, 2, or 1 for long packed
18117 arrays or arrays whose length is not known at compile time, depending on
18118 whether the component size is divisible by 4, 2, or is odd. For short packed
18119 arrays, which are handled internally as modular types, the alignment
18120 will be as described for elementary types, e.g. a packed array of length
18121 31 bits will have an object size of four bytes, and an alignment of 4.
18126 For the normal unpacked case, the alignment of a record is equal to
18127 the maximum alignment of any of its components. For tagged records, this
18128 includes the implicit access type used for the tag. If a pragma @code{Pack}
18129 is used and all components are packable (see separate section on pragma
18130 @code{Pack}), then the resulting alignment is 1, unless the layout of the
18131 record makes it profitable to increase it.
18133 A special case is when:
18139 the size of the record is given explicitly, or a
18140 full record representation clause is given, and
18143 the size of the record is 2, 4, or 8 bytes.
18146 In this case, an alignment is chosen to match the
18147 size of the record. For example, if we have:
18150 type Small is record
18153 for Small'Size use 16;
18156 then the default alignment of the record type @code{Small} is 2, not 1. This
18157 leads to more efficient code when the record is treated as a unit, and also
18158 allows the type to specified as @code{Atomic} on architectures requiring
18162 An alignment clause may specify a larger alignment than the default value
18163 up to some maximum value dependent on the target (obtainable by using the
18164 attribute reference @code{Standard'Maximum_Alignment}). It may also specify
18165 a smaller alignment than the default value for enumeration, integer and
18166 fixed point types, as well as for record types, for example
18173 for V'alignment use 1;
18179 The default alignment for the type @code{V} is 4, as a result of the
18180 Integer field in the record, but it is permissible, as shown, to
18181 override the default alignment of the record with a smaller value.
18186 Note that according to the Ada standard, an alignment clause applies only
18187 to the first named subtype. If additional subtypes are declared, then the
18188 compiler is allowed to choose any alignment it likes, and there is no way
18189 to control this choice. Consider:
18192 type R is range 1 .. 10_000;
18193 for R'Alignment use 1;
18194 subtype RS is R range 1 .. 1000;
18197 The alignment clause specifies an alignment of 1 for the first named subtype
18198 @code{R} but this does not necessarily apply to @code{RS}. When writing
18199 portable Ada code, you should avoid writing code that explicitly or
18200 implicitly relies on the alignment of such subtypes.
18202 For the GNAT compiler, if an explicit alignment clause is given, this
18203 value is also used for any subsequent subtypes. So for GNAT, in the
18204 above example, you can count on the alignment of @code{RS} being 1. But this
18205 assumption is non-portable, and other compilers may choose different
18206 alignments for the subtype @code{RS}.
18208 @node Size Clauses,Storage_Size Clauses,Alignment Clauses,Representation Clauses and Pragmas
18209 @anchor{gnat_rm/representation_clauses_and_pragmas id3}@anchor{270}@anchor{gnat_rm/representation_clauses_and_pragmas size-clauses}@anchor{271}
18210 @section Size Clauses
18213 @geindex Size Clause
18215 The default size for a type @code{T} is obtainable through the
18216 language-defined attribute @code{T'Size} and also through the
18217 equivalent GNAT-defined attribute @code{T'Value_Size}.
18218 For objects of type @code{T}, GNAT will generally increase the type size
18219 so that the object size (obtainable through the GNAT-defined attribute
18220 @code{T'Object_Size})
18221 is a multiple of @code{T'Alignment * Storage_Unit}.
18226 type Smallint is range 1 .. 6;
18234 In this example, @code{Smallint'Size} = @code{Smallint'Value_Size} = 3,
18235 as specified by the RM rules,
18236 but objects of this type will have a size of 8
18237 (@code{Smallint'Object_Size} = 8),
18238 since objects by default occupy an integral number
18239 of storage units. On some targets, notably older
18240 versions of the Digital Alpha, the size of stand
18241 alone objects of this type may be 32, reflecting
18242 the inability of the hardware to do byte load/stores.
18244 Similarly, the size of type @code{Rec} is 40 bits
18245 (@code{Rec'Size} = @code{Rec'Value_Size} = 40), but
18246 the alignment is 4, so objects of this type will have
18247 their size increased to 64 bits so that it is a multiple
18248 of the alignment (in bits). This decision is
18249 in accordance with the specific Implementation Advice in RM 13.3(43):
18253 "A @code{Size} clause should be supported for an object if the specified
18254 @code{Size} is at least as large as its subtype's @code{Size}, and corresponds
18255 to a size in storage elements that is a multiple of the object's
18256 @code{Alignment} (if the @code{Alignment} is nonzero)."
18259 An explicit size clause may be used to override the default size by
18260 increasing it. For example, if we have:
18263 type My_Boolean is new Boolean;
18264 for My_Boolean'Size use 32;
18267 then values of this type will always be 32 bits long. In the case of
18268 discrete types, the size can be increased up to 64 bits, with the effect
18269 that the entire specified field is used to hold the value, sign- or
18270 zero-extended as appropriate. If more than 64 bits is specified, then
18271 padding space is allocated after the value, and a warning is issued that
18272 there are unused bits.
18274 Similarly the size of records and arrays may be increased, and the effect
18275 is to add padding bits after the value. This also causes a warning message
18278 The largest Size value permitted in GNAT is 2**31-1. Since this is a
18279 Size in bits, this corresponds to an object of size 256 megabytes (minus
18280 one). This limitation is true on all targets. The reason for this
18281 limitation is that it improves the quality of the code in many cases
18282 if it is known that a Size value can be accommodated in an object of
18285 @node Storage_Size Clauses,Size of Variant Record Objects,Size Clauses,Representation Clauses and Pragmas
18286 @anchor{gnat_rm/representation_clauses_and_pragmas storage-size-clauses}@anchor{272}@anchor{gnat_rm/representation_clauses_and_pragmas id4}@anchor{273}
18287 @section Storage_Size Clauses
18290 @geindex Storage_Size Clause
18292 For tasks, the @code{Storage_Size} clause specifies the amount of space
18293 to be allocated for the task stack. This cannot be extended, and if the
18294 stack is exhausted, then @code{Storage_Error} will be raised (if stack
18295 checking is enabled). Use a @code{Storage_Size} attribute definition clause,
18296 or a @code{Storage_Size} pragma in the task definition to set the
18297 appropriate required size. A useful technique is to include in every
18298 task definition a pragma of the form:
18301 pragma Storage_Size (Default_Stack_Size);
18304 Then @code{Default_Stack_Size} can be defined in a global package, and
18305 modified as required. Any tasks requiring stack sizes different from the
18306 default can have an appropriate alternative reference in the pragma.
18308 You can also use the @emph{-d} binder switch to modify the default stack
18311 For access types, the @code{Storage_Size} clause specifies the maximum
18312 space available for allocation of objects of the type. If this space is
18313 exceeded then @code{Storage_Error} will be raised by an allocation attempt.
18314 In the case where the access type is declared local to a subprogram, the
18315 use of a @code{Storage_Size} clause triggers automatic use of a special
18316 predefined storage pool (@code{System.Pool_Size}) that ensures that all
18317 space for the pool is automatically reclaimed on exit from the scope in
18318 which the type is declared.
18320 A special case recognized by the compiler is the specification of a
18321 @code{Storage_Size} of zero for an access type. This means that no
18322 items can be allocated from the pool, and this is recognized at compile
18323 time, and all the overhead normally associated with maintaining a fixed
18324 size storage pool is eliminated. Consider the following example:
18328 type R is array (Natural) of Character;
18329 type P is access all R;
18330 for P'Storage_Size use 0;
18331 -- Above access type intended only for interfacing purposes
18335 procedure g (m : P);
18336 pragma Import (C, g);
18346 As indicated in this example, these dummy storage pools are often useful in
18347 connection with interfacing where no object will ever be allocated. If you
18348 compile the above example, you get the warning:
18351 p.adb:16:09: warning: allocation from empty storage pool
18352 p.adb:16:09: warning: Storage_Error will be raised at run time
18355 Of course in practice, there will not be any explicit allocators in the
18356 case of such an access declaration.
18358 @node Size of Variant Record Objects,Biased Representation,Storage_Size Clauses,Representation Clauses and Pragmas
18359 @anchor{gnat_rm/representation_clauses_and_pragmas id5}@anchor{274}@anchor{gnat_rm/representation_clauses_and_pragmas size-of-variant-record-objects}@anchor{275}
18360 @section Size of Variant Record Objects
18364 @geindex variant record objects
18366 @geindex Variant record objects
18369 In the case of variant record objects, there is a question whether Size gives
18370 information about a particular variant, or the maximum size required
18371 for any variant. Consider the following program
18374 with Text_IO; use Text_IO;
18376 type R1 (A : Boolean := False) is record
18378 when True => X : Character;
18379 when False => null;
18387 Put_Line (Integer'Image (V1'Size));
18388 Put_Line (Integer'Image (V2'Size));
18392 Here we are dealing with a variant record, where the True variant
18393 requires 16 bits, and the False variant requires 8 bits.
18394 In the above example, both V1 and V2 contain the False variant,
18395 which is only 8 bits long. However, the result of running the
18403 The reason for the difference here is that the discriminant value of
18404 V1 is fixed, and will always be False. It is not possible to assign
18405 a True variant value to V1, therefore 8 bits is sufficient. On the
18406 other hand, in the case of V2, the initial discriminant value is
18407 False (from the default), but it is possible to assign a True
18408 variant value to V2, therefore 16 bits must be allocated for V2
18409 in the general case, even fewer bits may be needed at any particular
18410 point during the program execution.
18412 As can be seen from the output of this program, the @code{'Size}
18413 attribute applied to such an object in GNAT gives the actual allocated
18414 size of the variable, which is the largest size of any of the variants.
18415 The Ada Reference Manual is not completely clear on what choice should
18416 be made here, but the GNAT behavior seems most consistent with the
18417 language in the RM.
18419 In some cases, it may be desirable to obtain the size of the current
18420 variant, rather than the size of the largest variant. This can be
18421 achieved in GNAT by making use of the fact that in the case of a
18422 subprogram parameter, GNAT does indeed return the size of the current
18423 variant (because a subprogram has no way of knowing how much space
18424 is actually allocated for the actual).
18426 Consider the following modified version of the above program:
18429 with Text_IO; use Text_IO;
18431 type R1 (A : Boolean := False) is record
18433 when True => X : Character;
18434 when False => null;
18440 function Size (V : R1) return Integer is
18446 Put_Line (Integer'Image (V2'Size));
18447 Put_Line (Integer'Image (Size (V2)));
18449 Put_Line (Integer'Image (V2'Size));
18450 Put_Line (Integer'Image (Size (V2)));
18454 The output from this program is
18463 Here we see that while the @code{'Size} attribute always returns
18464 the maximum size, regardless of the current variant value, the
18465 @code{Size} function does indeed return the size of the current
18468 @node Biased Representation,Value_Size and Object_Size Clauses,Size of Variant Record Objects,Representation Clauses and Pragmas
18469 @anchor{gnat_rm/representation_clauses_and_pragmas id6}@anchor{276}@anchor{gnat_rm/representation_clauses_and_pragmas biased-representation}@anchor{277}
18470 @section Biased Representation
18473 @geindex Size for biased representation
18475 @geindex Biased representation
18477 In the case of scalars with a range starting at other than zero, it is
18478 possible in some cases to specify a size smaller than the default minimum
18479 value, and in such cases, GNAT uses an unsigned biased representation,
18480 in which zero is used to represent the lower bound, and successive values
18481 represent successive values of the type.
18483 For example, suppose we have the declaration:
18486 type Small is range -7 .. -4;
18487 for Small'Size use 2;
18490 Although the default size of type @code{Small} is 4, the @code{Size}
18491 clause is accepted by GNAT and results in the following representation
18495 -7 is represented as 2#00#
18496 -6 is represented as 2#01#
18497 -5 is represented as 2#10#
18498 -4 is represented as 2#11#
18501 Biased representation is only used if the specified @code{Size} clause
18502 cannot be accepted in any other manner. These reduced sizes that force
18503 biased representation can be used for all discrete types except for
18504 enumeration types for which a representation clause is given.
18506 @node Value_Size and Object_Size Clauses,Component_Size Clauses,Biased Representation,Representation Clauses and Pragmas
18507 @anchor{gnat_rm/representation_clauses_and_pragmas id7}@anchor{278}@anchor{gnat_rm/representation_clauses_and_pragmas value-size-and-object-size-clauses}@anchor{279}
18508 @section Value_Size and Object_Size Clauses
18511 @geindex Value_Size
18513 @geindex Object_Size
18516 @geindex of objects
18518 In Ada 95 and Ada 2005, @code{T'Size} for a type @code{T} is the minimum
18519 number of bits required to hold values of type @code{T}.
18520 Although this interpretation was allowed in Ada 83, it was not required,
18521 and this requirement in practice can cause some significant difficulties.
18522 For example, in most Ada 83 compilers, @code{Natural'Size} was 32.
18523 However, in Ada 95 and Ada 2005,
18524 @code{Natural'Size} is
18525 typically 31. This means that code may change in behavior when moving
18526 from Ada 83 to Ada 95 or Ada 2005. For example, consider:
18529 type Rec is record;
18535 at 0 range 0 .. Natural'Size - 1;
18536 at 0 range Natural'Size .. 2 * Natural'Size - 1;
18540 In the above code, since the typical size of @code{Natural} objects
18541 is 32 bits and @code{Natural'Size} is 31, the above code can cause
18542 unexpected inefficient packing in Ada 95 and Ada 2005, and in general
18543 there are cases where the fact that the object size can exceed the
18544 size of the type causes surprises.
18546 To help get around this problem GNAT provides two implementation
18547 defined attributes, @code{Value_Size} and @code{Object_Size}. When
18548 applied to a type, these attributes yield the size of the type
18549 (corresponding to the RM defined size attribute), and the size of
18550 objects of the type respectively.
18552 The @code{Object_Size} is used for determining the default size of
18553 objects and components. This size value can be referred to using the
18554 @code{Object_Size} attribute. The phrase 'is used' here means that it is
18555 the basis of the determination of the size. The backend is free to
18556 pad this up if necessary for efficiency, e.g., an 8-bit stand-alone
18557 character might be stored in 32 bits on a machine with no efficient
18558 byte access instructions such as the Alpha.
18560 The default rules for the value of @code{Object_Size} for
18561 discrete types are as follows:
18567 The @code{Object_Size} for base subtypes reflect the natural hardware
18568 size in bits (run the compiler with @emph{-gnatS} to find those values
18569 for numeric types). Enumeration types and fixed-point base subtypes have
18570 8, 16, 32, or 64 bits for this size, depending on the range of values
18574 The @code{Object_Size} of a subtype is the same as the
18575 @code{Object_Size} of
18576 the type from which it is obtained.
18579 The @code{Object_Size} of a derived base type is copied from the parent
18580 base type, and the @code{Object_Size} of a derived first subtype is copied
18581 from the parent first subtype.
18584 The @code{Value_Size} attribute
18585 is the (minimum) number of bits required to store a value
18587 This value is used to determine how tightly to pack
18588 records or arrays with components of this type, and also affects
18589 the semantics of unchecked conversion (unchecked conversions where
18590 the @code{Value_Size} values differ generate a warning, and are potentially
18593 The default rules for the value of @code{Value_Size} are as follows:
18599 The @code{Value_Size} for a base subtype is the minimum number of bits
18600 required to store all values of the type (including the sign bit
18601 only if negative values are possible).
18604 If a subtype statically matches the first subtype of a given type, then it has
18605 by default the same @code{Value_Size} as the first subtype. This is a
18606 consequence of RM 13.1(14): "if two subtypes statically match,
18607 then their subtype-specific aspects are the same".)
18610 All other subtypes have a @code{Value_Size} corresponding to the minimum
18611 number of bits required to store all values of the subtype. For
18612 dynamic bounds, it is assumed that the value can range down or up
18613 to the corresponding bound of the ancestor
18616 The RM defined attribute @code{Size} corresponds to the
18617 @code{Value_Size} attribute.
18619 The @code{Size} attribute may be defined for a first-named subtype. This sets
18620 the @code{Value_Size} of
18621 the first-named subtype to the given value, and the
18622 @code{Object_Size} of this first-named subtype to the given value padded up
18623 to an appropriate boundary. It is a consequence of the default rules
18624 above that this @code{Object_Size} will apply to all further subtypes. On the
18625 other hand, @code{Value_Size} is affected only for the first subtype, any
18626 dynamic subtypes obtained from it directly, and any statically matching
18627 subtypes. The @code{Value_Size} of any other static subtypes is not affected.
18629 @code{Value_Size} and
18630 @code{Object_Size} may be explicitly set for any subtype using
18631 an attribute definition clause. Note that the use of these attributes
18632 can cause the RM 13.1(14) rule to be violated. If two access types
18633 reference aliased objects whose subtypes have differing @code{Object_Size}
18634 values as a result of explicit attribute definition clauses, then it
18635 is illegal to convert from one access subtype to the other. For a more
18636 complete description of this additional legality rule, see the
18637 description of the @code{Object_Size} attribute.
18639 To get a feel for the difference, consider the following examples (note
18640 that in each case the base is @code{Short_Short_Integer} with a size of 8):
18643 @multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxx}
18646 Type or subtype declaration
18658 @code{type x1 is range 0 .. 5;}
18670 @code{type x2 is range 0 .. 5;}
18671 @code{for x2'size use 12;}
18683 @code{subtype x3 is x2 range 0 .. 3;}
18695 @code{subtype x4 is x2'base range 0 .. 10;}
18707 @code{dynamic : x2'Base range -64 .. +63;}
18715 @code{subtype x5 is x2 range 0 .. dynamic;}
18727 @code{subtype x6 is x2'base range 0 .. dynamic;}
18740 Note: the entries marked '*' are not actually specified by the Ada
18741 Reference Manual, which has nothing to say about size in the dynamic
18742 case. What GNAT does is to allocate sufficient bits to accomodate any
18743 possible dynamic values for the bounds at run-time.
18745 So far, so good, but GNAT has to obey the RM rules, so the question is
18746 under what conditions must the RM @code{Size} be used.
18747 The following is a list
18748 of the occasions on which the RM @code{Size} must be used:
18754 Component size for packed arrays or records
18757 Value of the attribute @code{Size} for a type
18760 Warning about sizes not matching for unchecked conversion
18763 For record types, the @code{Object_Size} is always a multiple of the
18764 alignment of the type (this is true for all types). In some cases the
18765 @code{Value_Size} can be smaller. Consider:
18774 On a typical 32-bit architecture, the X component will be four bytes, and
18775 require four-byte alignment, and the Y component will be one byte. In this
18776 case @code{R'Value_Size} will be 40 (bits) since this is the minimum size
18777 required to store a value of this type, and for example, it is permissible
18778 to have a component of type R in an outer array whose component size is
18779 specified to be 48 bits. However, @code{R'Object_Size} will be 64 (bits),
18780 since it must be rounded up so that this value is a multiple of the
18781 alignment (4 bytes = 32 bits).
18783 For all other types, the @code{Object_Size}
18784 and @code{Value_Size} are the same (and equivalent to the RM attribute @code{Size}).
18785 Only @code{Size} may be specified for such types.
18787 Note that @code{Value_Size} can be used to force biased representation
18788 for a particular subtype. Consider this example:
18791 type R is (A, B, C, D, E, F);
18792 subtype RAB is R range A .. B;
18793 subtype REF is R range E .. F;
18796 By default, @code{RAB}
18797 has a size of 1 (sufficient to accommodate the representation
18798 of @code{A} and @code{B}, 0 and 1), and @code{REF}
18799 has a size of 3 (sufficient to accommodate the representation
18800 of @code{E} and @code{F}, 4 and 5). But if we add the
18801 following @code{Value_Size} attribute definition clause:
18804 for REF'Value_Size use 1;
18807 then biased representation is forced for @code{REF},
18808 and 0 will represent @code{E} and 1 will represent @code{F}.
18809 A warning is issued when a @code{Value_Size} attribute
18810 definition clause forces biased representation. This
18811 warning can be turned off using @code{-gnatw.B}.
18813 @node Component_Size Clauses,Bit_Order Clauses,Value_Size and Object_Size Clauses,Representation Clauses and Pragmas
18814 @anchor{gnat_rm/representation_clauses_and_pragmas id8}@anchor{27a}@anchor{gnat_rm/representation_clauses_and_pragmas component-size-clauses}@anchor{27b}
18815 @section Component_Size Clauses
18818 @geindex Component_Size Clause
18820 Normally, the value specified in a component size clause must be consistent
18821 with the subtype of the array component with regard to size and alignment.
18822 In other words, the value specified must be at least equal to the size
18823 of this subtype, and must be a multiple of the alignment value.
18825 In addition, component size clauses are allowed which cause the array
18826 to be packed, by specifying a smaller value. A first case is for
18827 component size values in the range 1 through 63. The value specified
18828 must not be smaller than the Size of the subtype. GNAT will accurately
18829 honor all packing requests in this range. For example, if we have:
18832 type r is array (1 .. 8) of Natural;
18833 for r'Component_Size use 31;
18836 then the resulting array has a length of 31 bytes (248 bits = 8 * 31).
18837 Of course access to the components of such an array is considerably
18838 less efficient than if the natural component size of 32 is used.
18839 A second case is when the subtype of the component is a record type
18840 padded because of its default alignment. For example, if we have:
18849 type a is array (1 .. 8) of r;
18850 for a'Component_Size use 72;
18853 then the resulting array has a length of 72 bytes, instead of 96 bytes
18854 if the alignment of the record (4) was obeyed.
18856 Note that there is no point in giving both a component size clause
18857 and a pragma Pack for the same array type. if such duplicate
18858 clauses are given, the pragma Pack will be ignored.
18860 @node Bit_Order Clauses,Effect of Bit_Order on Byte Ordering,Component_Size Clauses,Representation Clauses and Pragmas
18861 @anchor{gnat_rm/representation_clauses_and_pragmas bit-order-clauses}@anchor{27c}@anchor{gnat_rm/representation_clauses_and_pragmas id9}@anchor{27d}
18862 @section Bit_Order Clauses
18865 @geindex Bit_Order Clause
18867 @geindex bit ordering
18872 For record subtypes, GNAT permits the specification of the @code{Bit_Order}
18873 attribute. The specification may either correspond to the default bit
18874 order for the target, in which case the specification has no effect and
18875 places no additional restrictions, or it may be for the non-standard
18876 setting (that is the opposite of the default).
18878 In the case where the non-standard value is specified, the effect is
18879 to renumber bits within each byte, but the ordering of bytes is not
18880 affected. There are certain
18881 restrictions placed on component clauses as follows:
18887 Components fitting within a single storage unit.
18889 These are unrestricted, and the effect is merely to renumber bits. For
18890 example if we are on a little-endian machine with @code{Low_Order_First}
18891 being the default, then the following two declarations have exactly
18897 B : Integer range 1 .. 120;
18901 A at 0 range 0 .. 0;
18902 B at 0 range 1 .. 7;
18907 B : Integer range 1 .. 120;
18910 for R2'Bit_Order use High_Order_First;
18913 A at 0 range 7 .. 7;
18914 B at 0 range 0 .. 6;
18918 The useful application here is to write the second declaration with the
18919 @code{Bit_Order} attribute definition clause, and know that it will be treated
18920 the same, regardless of whether the target is little-endian or big-endian.
18923 Components occupying an integral number of bytes.
18925 These are components that exactly fit in two or more bytes. Such component
18926 declarations are allowed, but have no effect, since it is important to realize
18927 that the @code{Bit_Order} specification does not affect the ordering of bytes.
18928 In particular, the following attempt at getting an endian-independent integer
18936 for R2'Bit_Order use High_Order_First;
18939 A at 0 range 0 .. 31;
18943 This declaration will result in a little-endian integer on a
18944 little-endian machine, and a big-endian integer on a big-endian machine.
18945 If byte flipping is required for interoperability between big- and
18946 little-endian machines, this must be explicitly programmed. This capability
18947 is not provided by @code{Bit_Order}.
18950 Components that are positioned across byte boundaries.
18952 but do not occupy an integral number of bytes. Given that bytes are not
18953 reordered, such fields would occupy a non-contiguous sequence of bits
18954 in memory, requiring non-trivial code to reassemble. They are for this
18955 reason not permitted, and any component clause specifying such a layout
18956 will be flagged as illegal by GNAT.
18959 Since the misconception that Bit_Order automatically deals with all
18960 endian-related incompatibilities is a common one, the specification of
18961 a component field that is an integral number of bytes will always
18962 generate a warning. This warning may be suppressed using @code{pragma Warnings (Off)}
18963 if desired. The following section contains additional
18964 details regarding the issue of byte ordering.
18966 @node Effect of Bit_Order on Byte Ordering,Pragma Pack for Arrays,Bit_Order Clauses,Representation Clauses and Pragmas
18967 @anchor{gnat_rm/representation_clauses_and_pragmas id10}@anchor{27e}@anchor{gnat_rm/representation_clauses_and_pragmas effect-of-bit-order-on-byte-ordering}@anchor{27f}
18968 @section Effect of Bit_Order on Byte Ordering
18971 @geindex byte ordering
18976 In this section we will review the effect of the @code{Bit_Order} attribute
18977 definition clause on byte ordering. Briefly, it has no effect at all, but
18978 a detailed example will be helpful. Before giving this
18979 example, let us review the precise
18980 definition of the effect of defining @code{Bit_Order}. The effect of a
18981 non-standard bit order is described in section 13.5.3 of the Ada
18986 "2 A bit ordering is a method of interpreting the meaning of
18987 the storage place attributes."
18990 To understand the precise definition of storage place attributes in
18991 this context, we visit section 13.5.1 of the manual:
18995 "13 A record_representation_clause (without the mod_clause)
18996 specifies the layout. The storage place attributes (see 13.5.2)
18997 are taken from the values of the position, first_bit, and last_bit
18998 expressions after normalizing those values so that first_bit is
18999 less than Storage_Unit."
19002 The critical point here is that storage places are taken from
19003 the values after normalization, not before. So the @code{Bit_Order}
19004 interpretation applies to normalized values. The interpretation
19005 is described in the later part of the 13.5.3 paragraph:
19009 "2 A bit ordering is a method of interpreting the meaning of
19010 the storage place attributes. High_Order_First (known in the
19011 vernacular as 'big endian') means that the first bit of a
19012 storage element (bit 0) is the most significant bit (interpreting
19013 the sequence of bits that represent a component as an unsigned
19014 integer value). Low_Order_First (known in the vernacular as
19015 'little endian') means the opposite: the first bit is the
19016 least significant."
19019 Note that the numbering is with respect to the bits of a storage
19020 unit. In other words, the specification affects only the numbering
19021 of bits within a single storage unit.
19023 We can make the effect clearer by giving an example.
19025 Suppose that we have an external device which presents two bytes, the first
19026 byte presented, which is the first (low addressed byte) of the two byte
19027 record is called Master, and the second byte is called Slave.
19029 The left most (most significant bit is called Control for each byte, and
19030 the remaining 7 bits are called V1, V2, ... V7, where V7 is the rightmost
19031 (least significant) bit.
19033 On a big-endian machine, we can write the following representation clause
19036 type Data is record
19037 Master_Control : Bit;
19045 Slave_Control : Bit;
19055 for Data use record
19056 Master_Control at 0 range 0 .. 0;
19057 Master_V1 at 0 range 1 .. 1;
19058 Master_V2 at 0 range 2 .. 2;
19059 Master_V3 at 0 range 3 .. 3;
19060 Master_V4 at 0 range 4 .. 4;
19061 Master_V5 at 0 range 5 .. 5;
19062 Master_V6 at 0 range 6 .. 6;
19063 Master_V7 at 0 range 7 .. 7;
19064 Slave_Control at 1 range 0 .. 0;
19065 Slave_V1 at 1 range 1 .. 1;
19066 Slave_V2 at 1 range 2 .. 2;
19067 Slave_V3 at 1 range 3 .. 3;
19068 Slave_V4 at 1 range 4 .. 4;
19069 Slave_V5 at 1 range 5 .. 5;
19070 Slave_V6 at 1 range 6 .. 6;
19071 Slave_V7 at 1 range 7 .. 7;
19075 Now if we move this to a little endian machine, then the bit ordering within
19076 the byte is backwards, so we have to rewrite the record rep clause as:
19079 for Data use record
19080 Master_Control at 0 range 7 .. 7;
19081 Master_V1 at 0 range 6 .. 6;
19082 Master_V2 at 0 range 5 .. 5;
19083 Master_V3 at 0 range 4 .. 4;
19084 Master_V4 at 0 range 3 .. 3;
19085 Master_V5 at 0 range 2 .. 2;
19086 Master_V6 at 0 range 1 .. 1;
19087 Master_V7 at 0 range 0 .. 0;
19088 Slave_Control at 1 range 7 .. 7;
19089 Slave_V1 at 1 range 6 .. 6;
19090 Slave_V2 at 1 range 5 .. 5;
19091 Slave_V3 at 1 range 4 .. 4;
19092 Slave_V4 at 1 range 3 .. 3;
19093 Slave_V5 at 1 range 2 .. 2;
19094 Slave_V6 at 1 range 1 .. 1;
19095 Slave_V7 at 1 range 0 .. 0;
19099 It is a nuisance to have to rewrite the clause, especially if
19100 the code has to be maintained on both machines. However,
19101 this is a case that we can handle with the
19102 @code{Bit_Order} attribute if it is implemented.
19103 Note that the implementation is not required on byte addressed
19104 machines, but it is indeed implemented in GNAT.
19105 This means that we can simply use the
19106 first record clause, together with the declaration
19109 for Data'Bit_Order use High_Order_First;
19112 and the effect is what is desired, namely the layout is exactly the same,
19113 independent of whether the code is compiled on a big-endian or little-endian
19116 The important point to understand is that byte ordering is not affected.
19117 A @code{Bit_Order} attribute definition never affects which byte a field
19118 ends up in, only where it ends up in that byte.
19119 To make this clear, let us rewrite the record rep clause of the previous
19123 for Data'Bit_Order use High_Order_First;
19124 for Data use record
19125 Master_Control at 0 range 0 .. 0;
19126 Master_V1 at 0 range 1 .. 1;
19127 Master_V2 at 0 range 2 .. 2;
19128 Master_V3 at 0 range 3 .. 3;
19129 Master_V4 at 0 range 4 .. 4;
19130 Master_V5 at 0 range 5 .. 5;
19131 Master_V6 at 0 range 6 .. 6;
19132 Master_V7 at 0 range 7 .. 7;
19133 Slave_Control at 0 range 8 .. 8;
19134 Slave_V1 at 0 range 9 .. 9;
19135 Slave_V2 at 0 range 10 .. 10;
19136 Slave_V3 at 0 range 11 .. 11;
19137 Slave_V4 at 0 range 12 .. 12;
19138 Slave_V5 at 0 range 13 .. 13;
19139 Slave_V6 at 0 range 14 .. 14;
19140 Slave_V7 at 0 range 15 .. 15;
19144 This is exactly equivalent to saying (a repeat of the first example):
19147 for Data'Bit_Order use High_Order_First;
19148 for Data use record
19149 Master_Control at 0 range 0 .. 0;
19150 Master_V1 at 0 range 1 .. 1;
19151 Master_V2 at 0 range 2 .. 2;
19152 Master_V3 at 0 range 3 .. 3;
19153 Master_V4 at 0 range 4 .. 4;
19154 Master_V5 at 0 range 5 .. 5;
19155 Master_V6 at 0 range 6 .. 6;
19156 Master_V7 at 0 range 7 .. 7;
19157 Slave_Control at 1 range 0 .. 0;
19158 Slave_V1 at 1 range 1 .. 1;
19159 Slave_V2 at 1 range 2 .. 2;
19160 Slave_V3 at 1 range 3 .. 3;
19161 Slave_V4 at 1 range 4 .. 4;
19162 Slave_V5 at 1 range 5 .. 5;
19163 Slave_V6 at 1 range 6 .. 6;
19164 Slave_V7 at 1 range 7 .. 7;
19168 Why are they equivalent? Well take a specific field, the @code{Slave_V2}
19169 field. The storage place attributes are obtained by normalizing the
19170 values given so that the @code{First_Bit} value is less than 8. After
19171 normalizing the values (0,10,10) we get (1,2,2) which is exactly what
19172 we specified in the other case.
19174 Now one might expect that the @code{Bit_Order} attribute might affect
19175 bit numbering within the entire record component (two bytes in this
19176 case, thus affecting which byte fields end up in), but that is not
19177 the way this feature is defined, it only affects numbering of bits,
19178 not which byte they end up in.
19180 Consequently it never makes sense to specify a starting bit number
19181 greater than 7 (for a byte addressable field) if an attribute
19182 definition for @code{Bit_Order} has been given, and indeed it
19183 may be actively confusing to specify such a value, so the compiler
19184 generates a warning for such usage.
19186 If you do need to control byte ordering then appropriate conditional
19187 values must be used. If in our example, the slave byte came first on
19188 some machines we might write:
19191 Master_Byte_First constant Boolean := ...;
19193 Master_Byte : constant Natural :=
19194 1 - Boolean'Pos (Master_Byte_First);
19195 Slave_Byte : constant Natural :=
19196 Boolean'Pos (Master_Byte_First);
19198 for Data'Bit_Order use High_Order_First;
19199 for Data use record
19200 Master_Control at Master_Byte range 0 .. 0;
19201 Master_V1 at Master_Byte range 1 .. 1;
19202 Master_V2 at Master_Byte range 2 .. 2;
19203 Master_V3 at Master_Byte range 3 .. 3;
19204 Master_V4 at Master_Byte range 4 .. 4;
19205 Master_V5 at Master_Byte range 5 .. 5;
19206 Master_V6 at Master_Byte range 6 .. 6;
19207 Master_V7 at Master_Byte range 7 .. 7;
19208 Slave_Control at Slave_Byte range 0 .. 0;
19209 Slave_V1 at Slave_Byte range 1 .. 1;
19210 Slave_V2 at Slave_Byte range 2 .. 2;
19211 Slave_V3 at Slave_Byte range 3 .. 3;
19212 Slave_V4 at Slave_Byte range 4 .. 4;
19213 Slave_V5 at Slave_Byte range 5 .. 5;
19214 Slave_V6 at Slave_Byte range 6 .. 6;
19215 Slave_V7 at Slave_Byte range 7 .. 7;
19219 Now to switch between machines, all that is necessary is
19220 to set the boolean constant @code{Master_Byte_First} in
19221 an appropriate manner.
19223 @node Pragma Pack for Arrays,Pragma Pack for Records,Effect of Bit_Order on Byte Ordering,Representation Clauses and Pragmas
19224 @anchor{gnat_rm/representation_clauses_and_pragmas pragma-pack-for-arrays}@anchor{280}@anchor{gnat_rm/representation_clauses_and_pragmas id11}@anchor{281}
19225 @section Pragma Pack for Arrays
19228 @geindex Pragma Pack (for arrays)
19230 Pragma @code{Pack} applied to an array has an effect that depends upon whether the
19231 component type is @emph{packable}. For a component type to be @emph{packable}, it must
19232 be one of the following cases:
19238 Any elementary type.
19241 Any small packed array type with a static size.
19244 Any small simple record type with a static size.
19247 For all these cases, if the component subtype size is in the range
19248 1 through 64, then the effect of the pragma @code{Pack} is exactly as though a
19249 component size were specified giving the component subtype size.
19251 All other types are non-packable, they occupy an integral number of storage
19252 units and the only effect of pragma Pack is to remove alignment gaps.
19254 For example if we have:
19257 type r is range 0 .. 17;
19259 type ar is array (1 .. 8) of r;
19263 Then the component size of @code{ar} will be set to 5 (i.e., to @code{r'size},
19264 and the size of the array @code{ar} will be exactly 40 bits).
19266 Note that in some cases this rather fierce approach to packing can produce
19267 unexpected effects. For example, in Ada 95 and Ada 2005,
19268 subtype @code{Natural} typically has a size of 31, meaning that if you
19269 pack an array of @code{Natural}, you get 31-bit
19270 close packing, which saves a few bits, but results in far less efficient
19271 access. Since many other Ada compilers will ignore such a packing request,
19272 GNAT will generate a warning on some uses of pragma @code{Pack} that it guesses
19273 might not be what is intended. You can easily remove this warning by
19274 using an explicit @code{Component_Size} setting instead, which never generates
19275 a warning, since the intention of the programmer is clear in this case.
19277 GNAT treats packed arrays in one of two ways. If the size of the array is
19278 known at compile time and is less than 64 bits, then internally the array
19279 is represented as a single modular type, of exactly the appropriate number
19280 of bits. If the length is greater than 63 bits, or is not known at compile
19281 time, then the packed array is represented as an array of bytes, and the
19282 length is always a multiple of 8 bits.
19284 Note that to represent a packed array as a modular type, the alignment must
19285 be suitable for the modular type involved. For example, on typical machines
19286 a 32-bit packed array will be represented by a 32-bit modular integer with
19287 an alignment of four bytes. If you explicitly override the default alignment
19288 with an alignment clause that is too small, the modular representation
19289 cannot be used. For example, consider the following set of declarations:
19292 type R is range 1 .. 3;
19293 type S is array (1 .. 31) of R;
19294 for S'Component_Size use 2;
19296 for S'Alignment use 1;
19299 If the alignment clause were not present, then a 62-bit modular
19300 representation would be chosen (typically with an alignment of 4 or 8
19301 bytes depending on the target). But the default alignment is overridden
19302 with the explicit alignment clause. This means that the modular
19303 representation cannot be used, and instead the array of bytes
19304 representation must be used, meaning that the length must be a multiple
19305 of 8. Thus the above set of declarations will result in a diagnostic
19306 rejecting the size clause and noting that the minimum size allowed is 64.
19308 @geindex Pragma Pack (for type Natural)
19310 @geindex Pragma Pack warning
19312 One special case that is worth noting occurs when the base type of the
19313 component size is 8/16/32 and the subtype is one bit less. Notably this
19314 occurs with subtype @code{Natural}. Consider:
19317 type Arr is array (1 .. 32) of Natural;
19321 In all commonly used Ada 83 compilers, this pragma Pack would be ignored,
19322 since typically @code{Natural'Size} is 32 in Ada 83, and in any case most
19323 Ada 83 compilers did not attempt 31 bit packing.
19325 In Ada 95 and Ada 2005, @code{Natural'Size} is required to be 31. Furthermore,
19326 GNAT really does pack 31-bit subtype to 31 bits. This may result in a
19327 substantial unintended performance penalty when porting legacy Ada 83 code.
19328 To help prevent this, GNAT generates a warning in such cases. If you really
19329 want 31 bit packing in a case like this, you can set the component size
19333 type Arr is array (1 .. 32) of Natural;
19334 for Arr'Component_Size use 31;
19337 Here 31-bit packing is achieved as required, and no warning is generated,
19338 since in this case the programmer intention is clear.
19340 @node Pragma Pack for Records,Record Representation Clauses,Pragma Pack for Arrays,Representation Clauses and Pragmas
19341 @anchor{gnat_rm/representation_clauses_and_pragmas pragma-pack-for-records}@anchor{282}@anchor{gnat_rm/representation_clauses_and_pragmas id12}@anchor{283}
19342 @section Pragma Pack for Records
19345 @geindex Pragma Pack (for records)
19347 Pragma @code{Pack} applied to a record will pack the components to reduce
19348 wasted space from alignment gaps and by reducing the amount of space
19349 taken by components. We distinguish between @emph{packable} components and
19350 @emph{non-packable} components.
19351 Components of the following types are considered packable:
19357 Components of an elementary type are packable unless they are aliased,
19358 independent, or of an atomic type.
19361 Small packed arrays, where the size is statically known, are represented
19362 internally as modular integers, and so they are also packable.
19365 Small simple records, where the size is statically known, are also packable.
19368 For all these cases, if the @code{'Size} value is in the range 1 through 64, the
19369 components occupy the exact number of bits corresponding to this value
19370 and are packed with no padding bits, i.e. they can start on an arbitrary
19373 All other types are non-packable, they occupy an integral number of storage
19374 units and the only effect of pragma @code{Pack} is to remove alignment gaps.
19376 For example, consider the record
19379 type Rb1 is array (1 .. 13) of Boolean;
19382 type Rb2 is array (1 .. 65) of Boolean;
19385 type AF is new Float with Atomic;
19398 The representation for the record @code{X2} is as follows:
19401 for X2'Size use 224;
19403 L1 at 0 range 0 .. 0;
19404 L2 at 0 range 1 .. 64;
19405 L3 at 12 range 0 .. 31;
19406 L4 at 16 range 0 .. 0;
19407 L5 at 16 range 1 .. 13;
19408 L6 at 18 range 0 .. 71;
19412 Studying this example, we see that the packable fields @code{L1}
19414 of length equal to their sizes, and placed at specific bit boundaries (and
19415 not byte boundaries) to
19416 eliminate padding. But @code{L3} is of a non-packable float type (because
19417 it is aliased), so it is on the next appropriate alignment boundary.
19419 The next two fields are fully packable, so @code{L4} and @code{L5} are
19420 minimally packed with no gaps. However, type @code{Rb2} is a packed
19421 array that is longer than 64 bits, so it is itself non-packable. Thus
19422 the @code{L6} field is aligned to the next byte boundary, and takes an
19423 integral number of bytes, i.e., 72 bits.
19425 @node Record Representation Clauses,Handling of Records with Holes,Pragma Pack for Records,Representation Clauses and Pragmas
19426 @anchor{gnat_rm/representation_clauses_and_pragmas id13}@anchor{284}@anchor{gnat_rm/representation_clauses_and_pragmas record-representation-clauses}@anchor{285}
19427 @section Record Representation Clauses
19430 @geindex Record Representation Clause
19432 Record representation clauses may be given for all record types, including
19433 types obtained by record extension. Component clauses are allowed for any
19434 static component. The restrictions on component clauses depend on the type
19437 @geindex Component Clause
19439 For all components of an elementary type, the only restriction on component
19440 clauses is that the size must be at least the @code{'Size} value of the type
19441 (actually the Value_Size). There are no restrictions due to alignment,
19442 and such components may freely cross storage boundaries.
19444 Packed arrays with a size up to and including 64 bits are represented
19445 internally using a modular type with the appropriate number of bits, and
19446 thus the same lack of restriction applies. For example, if you declare:
19449 type R is array (1 .. 49) of Boolean;
19454 then a component clause for a component of type @code{R} may start on any
19455 specified bit boundary, and may specify a value of 49 bits or greater.
19457 For packed bit arrays that are longer than 64 bits, there are two
19458 cases. If the component size is a power of 2 (1,2,4,8,16,32 bits),
19459 including the important case of single bits or boolean values, then
19460 there are no limitations on placement of such components, and they
19461 may start and end at arbitrary bit boundaries.
19463 If the component size is not a power of 2 (e.g., 3 or 5), then
19464 an array of this type longer than 64 bits must always be placed on
19465 on a storage unit (byte) boundary and occupy an integral number
19466 of storage units (bytes). Any component clause that does not
19467 meet this requirement will be rejected.
19469 Any aliased component, or component of an aliased type, must
19470 have its normal alignment and size. A component clause that
19471 does not meet this requirement will be rejected.
19473 The tag field of a tagged type always occupies an address sized field at
19474 the start of the record. No component clause may attempt to overlay this
19475 tag. When a tagged type appears as a component, the tag field must have
19478 In the case of a record extension @code{T1}, of a type @code{T}, no component clause applied
19479 to the type @code{T1} can specify a storage location that would overlap the first
19480 @code{T'Size} bytes of the record.
19482 For all other component types, including non-bit-packed arrays,
19483 the component can be placed at an arbitrary bit boundary,
19484 so for example, the following is permitted:
19487 type R is array (1 .. 10) of Boolean;
19496 G at 0 range 0 .. 0;
19497 H at 0 range 1 .. 1;
19498 L at 0 range 2 .. 81;
19499 R at 0 range 82 .. 161;
19503 @node Handling of Records with Holes,Enumeration Clauses,Record Representation Clauses,Representation Clauses and Pragmas
19504 @anchor{gnat_rm/representation_clauses_and_pragmas handling-of-records-with-holes}@anchor{286}@anchor{gnat_rm/representation_clauses_and_pragmas id14}@anchor{287}
19505 @section Handling of Records with Holes
19508 @geindex Handling of Records with Holes
19510 As a result of alignment considerations, records may contain "holes"
19512 which do not correspond to the data bits of any of the components.
19513 Record representation clauses can also result in holes in records.
19515 GNAT does not attempt to clear these holes, so in record objects,
19516 they should be considered to hold undefined rubbish. The generated
19517 equality routine just tests components so does not access these
19518 undefined bits, and assignment and copy operations may or may not
19519 preserve the contents of these holes (for assignments, the holes
19520 in the target will in practice contain either the bits that are
19521 present in the holes in the source, or the bits that were present
19522 in the target before the assignment).
19524 If it is necessary to ensure that holes in records have all zero
19525 bits, then record objects for which this initialization is desired
19526 should be explicitly set to all zero values using Unchecked_Conversion
19527 or address overlays. For example
19530 type HRec is record
19536 On typical machines, integers need to be aligned on a four-byte
19537 boundary, resulting in three bytes of undefined rubbish following
19538 the 8-bit field for C. To ensure that the hole in a variable of
19539 type HRec is set to all zero bits,
19540 you could for example do:
19543 type Base is record
19544 Dummy1, Dummy2 : Integer := 0;
19549 for RealVar'Address use BaseVar'Address;
19552 Now the 8-bytes of the value of RealVar start out containing all zero
19553 bits. A safer approach is to just define dummy fields, avoiding the
19557 type HRec is record
19559 Dummy1 : Short_Short_Integer := 0;
19560 Dummy2 : Short_Short_Integer := 0;
19561 Dummy3 : Short_Short_Integer := 0;
19566 And to make absolutely sure that the intent of this is followed, you
19567 can use representation clauses:
19570 for Hrec use record
19571 C at 0 range 0 .. 7;
19572 Dummy1 at 1 range 0 .. 7;
19573 Dummy2 at 2 range 0 .. 7;
19574 Dummy3 at 3 range 0 .. 7;
19575 I at 4 range 0 .. 31;
19577 for Hrec'Size use 64;
19580 @node Enumeration Clauses,Address Clauses,Handling of Records with Holes,Representation Clauses and Pragmas
19581 @anchor{gnat_rm/representation_clauses_and_pragmas enumeration-clauses}@anchor{288}@anchor{gnat_rm/representation_clauses_and_pragmas id15}@anchor{289}
19582 @section Enumeration Clauses
19585 The only restriction on enumeration clauses is that the range of values
19586 must be representable. For the signed case, if one or more of the
19587 representation values are negative, all values must be in the range:
19590 System.Min_Int .. System.Max_Int
19593 For the unsigned case, where all values are nonnegative, the values must
19597 0 .. System.Max_Binary_Modulus;
19600 A @emph{confirming} representation clause is one in which the values range
19601 from 0 in sequence, i.e., a clause that confirms the default representation
19602 for an enumeration type.
19603 Such a confirming representation
19604 is permitted by these rules, and is specially recognized by the compiler so
19605 that no extra overhead results from the use of such a clause.
19607 If an array has an index type which is an enumeration type to which an
19608 enumeration clause has been applied, then the array is stored in a compact
19609 manner. Consider the declarations:
19612 type r is (A, B, C);
19613 for r use (A => 1, B => 5, C => 10);
19614 type t is array (r) of Character;
19617 The array type t corresponds to a vector with exactly three elements and
19618 has a default size equal to @code{3*Character'Size}. This ensures efficient
19619 use of space, but means that accesses to elements of the array will incur
19620 the overhead of converting representation values to the corresponding
19621 positional values, (i.e., the value delivered by the @code{Pos} attribute).
19623 @node Address Clauses,Use of Address Clauses for Memory-Mapped I/O,Enumeration Clauses,Representation Clauses and Pragmas
19624 @anchor{gnat_rm/representation_clauses_and_pragmas id16}@anchor{28a}@anchor{gnat_rm/representation_clauses_and_pragmas address-clauses}@anchor{28b}
19625 @section Address Clauses
19628 @geindex Address Clause
19630 The reference manual allows a general restriction on representation clauses,
19631 as found in RM 13.1(22):
19635 "An implementation need not support representation
19636 items containing nonstatic expressions, except that
19637 an implementation should support a representation item
19638 for a given entity if each nonstatic expression in the
19639 representation item is a name that statically denotes
19640 a constant declared before the entity."
19643 In practice this is applicable only to address clauses, since this is the
19644 only case in which a nonstatic expression is permitted by the syntax. As
19645 the AARM notes in sections 13.1 (22.a-22.h):
19649 22.a Reason: This is to avoid the following sort of thing:
19651 22.b X : Integer := F(...);
19652 Y : Address := G(...);
19653 for X'Address use Y;
19655 22.c In the above, we have to evaluate the
19656 initialization expression for X before we
19657 know where to put the result. This seems
19658 like an unreasonable implementation burden.
19660 22.d The above code should instead be written
19663 22.e Y : constant Address := G(...);
19664 X : Integer := F(...);
19665 for X'Address use Y;
19667 22.f This allows the expression 'Y' to be safely
19668 evaluated before X is created.
19670 22.g The constant could be a formal parameter of mode in.
19672 22.h An implementation can support other nonstatic
19673 expressions if it wants to. Expressions of type
19674 Address are hardly ever static, but their value
19675 might be known at compile time anyway in many
19679 GNAT does indeed permit many additional cases of nonstatic expressions. In
19680 particular, if the type involved is elementary there are no restrictions
19681 (since in this case, holding a temporary copy of the initialization value,
19682 if one is present, is inexpensive). In addition, if there is no implicit or
19683 explicit initialization, then there are no restrictions. GNAT will reject
19684 only the case where all three of these conditions hold:
19690 The type of the item is non-elementary (e.g., a record or array).
19693 There is explicit or implicit initialization required for the object.
19694 Note that access values are always implicitly initialized.
19697 The address value is nonstatic. Here GNAT is more permissive than the
19698 RM, and allows the address value to be the address of a previously declared
19699 stand-alone variable, as long as it does not itself have an address clause.
19702 Anchor : Some_Initialized_Type;
19703 Overlay : Some_Initialized_Type;
19704 for Overlay'Address use Anchor'Address;
19707 However, the prefix of the address clause cannot be an array component, or
19708 a component of a discriminated record.
19711 As noted above in section 22.h, address values are typically nonstatic. In
19712 particular the To_Address function, even if applied to a literal value, is
19713 a nonstatic function call. To avoid this minor annoyance, GNAT provides
19714 the implementation defined attribute 'To_Address. The following two
19715 expressions have identical values:
19719 @geindex To_Address
19722 To_Address (16#1234_0000#)
19723 System'To_Address (16#1234_0000#);
19726 except that the second form is considered to be a static expression, and
19727 thus when used as an address clause value is always permitted.
19729 Additionally, GNAT treats as static an address clause that is an
19730 unchecked_conversion of a static integer value. This simplifies the porting
19731 of legacy code, and provides a portable equivalent to the GNAT attribute
19734 Another issue with address clauses is the interaction with alignment
19735 requirements. When an address clause is given for an object, the address
19736 value must be consistent with the alignment of the object (which is usually
19737 the same as the alignment of the type of the object). If an address clause
19738 is given that specifies an inappropriately aligned address value, then the
19739 program execution is erroneous.
19741 Since this source of erroneous behavior can have unfortunate effects on
19742 machines with strict alignment requirements, GNAT
19743 checks (at compile time if possible, generating a warning, or at execution
19744 time with a run-time check) that the alignment is appropriate. If the
19745 run-time check fails, then @code{Program_Error} is raised. This run-time
19746 check is suppressed if range checks are suppressed, or if the special GNAT
19747 check Alignment_Check is suppressed, or if
19748 @code{pragma Restrictions (No_Elaboration_Code)} is in effect. It is also
19749 suppressed by default on non-strict alignment machines (such as the x86).
19751 Finally, GNAT does not permit overlaying of objects of class-wide types. In
19752 most cases, the compiler can detect an attempt at such overlays and will
19753 generate a warning at compile time and a Program_Error exception at run time.
19757 An address clause cannot be given for an exported object. More
19758 understandably the real restriction is that objects with an address
19759 clause cannot be exported. This is because such variables are not
19760 defined by the Ada program, so there is no external object to export.
19764 It is permissible to give an address clause and a pragma Import for the
19765 same object. In this case, the variable is not really defined by the
19766 Ada program, so there is no external symbol to be linked. The link name
19767 and the external name are ignored in this case. The reason that we allow this
19768 combination is that it provides a useful idiom to avoid unwanted
19769 initializations on objects with address clauses.
19771 When an address clause is given for an object that has implicit or
19772 explicit initialization, then by default initialization takes place. This
19773 means that the effect of the object declaration is to overwrite the
19774 memory at the specified address. This is almost always not what the
19775 programmer wants, so GNAT will output a warning:
19785 for Ext'Address use System'To_Address (16#1234_1234#);
19787 >>> warning: implicit initialization of "Ext" may
19788 modify overlaid storage
19789 >>> warning: use pragma Import for "Ext" to suppress
19790 initialization (RM B(24))
19795 As indicated by the warning message, the solution is to use a (dummy) pragma
19796 Import to suppress this initialization. The pragma tell the compiler that the
19797 object is declared and initialized elsewhere. The following package compiles
19798 without warnings (and the initialization is suppressed):
19808 for Ext'Address use System'To_Address (16#1234_1234#);
19809 pragma Import (Ada, Ext);
19813 A final issue with address clauses involves their use for overlaying
19814 variables, as in the following example:
19816 @geindex Overlaying of objects
19821 for B'Address use A'Address;
19824 or alternatively, using the form recommended by the RM:
19828 Addr : constant Address := A'Address;
19830 for B'Address use Addr;
19833 In both of these cases, @code{A} and @code{B} become aliased to one another
19834 via the address clause. This use of address clauses to overlay
19835 variables, achieving an effect similar to unchecked conversion
19836 was erroneous in Ada 83, but in Ada 95 and Ada 2005
19837 the effect is implementation defined. Furthermore, the
19838 Ada RM specifically recommends that in a situation
19839 like this, @code{B} should be subject to the following
19840 implementation advice (RM 13.3(19)):
19844 "19 If the Address of an object is specified, or it is imported
19845 or exported, then the implementation should not perform
19846 optimizations based on assumptions of no aliases."
19849 GNAT follows this recommendation, and goes further by also applying
19850 this recommendation to the overlaid variable (@code{A} in the above example)
19851 in this case. This means that the overlay works "as expected", in that
19852 a modification to one of the variables will affect the value of the other.
19854 More generally, GNAT interprets this recommendation conservatively for
19855 address clauses: in the cases other than overlays, it considers that the
19856 object is effectively subject to pragma @code{Volatile} and implements the
19857 associated semantics.
19859 Note that when address clause overlays are used in this way, there is an
19860 issue of unintentional initialization, as shown by this example:
19863 package Overwrite_Record is
19865 A : Character := 'C';
19866 B : Character := 'A';
19868 X : Short_Integer := 3;
19870 for Y'Address use X'Address;
19872 >>> warning: default initialization of "Y" may
19873 modify "X", use pragma Import for "Y" to
19874 suppress initialization (RM B.1(24))
19876 end Overwrite_Record;
19879 Here the default initialization of @code{Y} will clobber the value
19880 of @code{X}, which justifies the warning. The warning notes that
19881 this effect can be eliminated by adding a @code{pragma Import}
19882 which suppresses the initialization:
19885 package Overwrite_Record is
19887 A : Character := 'C';
19888 B : Character := 'A';
19890 X : Short_Integer := 3;
19892 for Y'Address use X'Address;
19893 pragma Import (Ada, Y);
19894 end Overwrite_Record;
19897 Note that the use of @code{pragma Initialize_Scalars} may cause variables to
19898 be initialized when they would not otherwise have been in the absence
19899 of the use of this pragma. This may cause an overlay to have this
19900 unintended clobbering effect. The compiler avoids this for scalar
19901 types, but not for composite objects (where in general the effect
19902 of @code{Initialize_Scalars} is part of the initialization routine
19903 for the composite object:
19906 pragma Initialize_Scalars;
19907 with Ada.Text_IO; use Ada.Text_IO;
19908 procedure Overwrite_Array is
19909 type Arr is array (1 .. 5) of Integer;
19910 X : Arr := (others => 1);
19912 for A'Address use X'Address;
19914 >>> warning: default initialization of "A" may
19915 modify "X", use pragma Import for "A" to
19916 suppress initialization (RM B.1(24))
19919 if X /= Arr'(others => 1) then
19920 Put_Line ("X was clobbered");
19922 Put_Line ("X was not clobbered");
19924 end Overwrite_Array;
19927 The above program generates the warning as shown, and at execution
19928 time, prints @code{X was clobbered}. If the @code{pragma Import} is
19929 added as suggested:
19932 pragma Initialize_Scalars;
19933 with Ada.Text_IO; use Ada.Text_IO;
19934 procedure Overwrite_Array is
19935 type Arr is array (1 .. 5) of Integer;
19936 X : Arr := (others => 1);
19938 for A'Address use X'Address;
19939 pragma Import (Ada, A);
19941 if X /= Arr'(others => 1) then
19942 Put_Line ("X was clobbered");
19944 Put_Line ("X was not clobbered");
19946 end Overwrite_Array;
19949 then the program compiles without the warning and when run will generate
19950 the output @code{X was not clobbered}.
19952 @node Use of Address Clauses for Memory-Mapped I/O,Effect of Convention on Representation,Address Clauses,Representation Clauses and Pragmas
19953 @anchor{gnat_rm/representation_clauses_and_pragmas id17}@anchor{28c}@anchor{gnat_rm/representation_clauses_and_pragmas use-of-address-clauses-for-memory-mapped-i-o}@anchor{28d}
19954 @section Use of Address Clauses for Memory-Mapped I/O
19957 @geindex Memory-mapped I/O
19959 A common pattern is to use an address clause to map an atomic variable to
19960 a location in memory that corresponds to a memory-mapped I/O operation or
19961 operations, for example:
19964 type Mem_Word is record
19967 pragma Atomic (Mem_Word);
19968 for Mem_Word_Size use 32;
19971 for Mem'Address use some-address;
19978 For a full access (reference or modification) of the variable (Mem) in this
19979 case, as in the above examples, GNAT guarantees that the entire atomic word
19980 will be accessed, in accordance with the RM C.6(15) clause.
19982 A problem arises with a component access such as:
19988 Note that the component A is not declared as atomic. This means that it is
19989 not clear what this assignment means. It could correspond to full word read
19990 and write as given in the first example, or on architectures that supported
19991 such an operation it might be a single byte store instruction. The RM does
19992 not have anything to say in this situation, and GNAT does not make any
19993 guarantee. The code generated may vary from target to target. GNAT will issue
19994 a warning in such a case:
19999 >>> warning: access to non-atomic component of atomic array,
20000 may cause unexpected accesses to atomic object
20003 It is best to be explicit in this situation, by either declaring the
20004 components to be atomic if you want the byte store, or explicitly writing
20005 the full word access sequence if that is what the hardware requires.
20006 Alternatively, if the full word access sequence is required, GNAT also
20007 provides the pragma @code{Volatile_Full_Access} which can be used in lieu of
20008 pragma @code{Atomic} and will give the additional guarantee.
20010 @node Effect of Convention on Representation,Conventions and Anonymous Access Types,Use of Address Clauses for Memory-Mapped I/O,Representation Clauses and Pragmas
20011 @anchor{gnat_rm/representation_clauses_and_pragmas id18}@anchor{28e}@anchor{gnat_rm/representation_clauses_and_pragmas effect-of-convention-on-representation}@anchor{28f}
20012 @section Effect of Convention on Representation
20015 @geindex Convention
20016 @geindex effect on representation
20018 Normally the specification of a foreign language convention for a type or
20019 an object has no effect on the chosen representation. In particular, the
20020 representation chosen for data in GNAT generally meets the standard system
20021 conventions, and for example records are laid out in a manner that is
20022 consistent with C. This means that specifying convention C (for example)
20025 There are four exceptions to this general rule:
20031 @emph{Convention Fortran and array subtypes}.
20033 If pragma Convention Fortran is specified for an array subtype, then in
20034 accordance with the implementation advice in section 3.6.2(11) of the
20035 Ada Reference Manual, the array will be stored in a Fortran-compatible
20036 column-major manner, instead of the normal default row-major order.
20039 @emph{Convention C and enumeration types}
20041 GNAT normally stores enumeration types in 8, 16, or 32 bits as required
20042 to accommodate all values of the type. For example, for the enumeration
20046 type Color is (Red, Green, Blue);
20049 8 bits is sufficient to store all values of the type, so by default, objects
20050 of type @code{Color} will be represented using 8 bits. However, normal C
20051 convention is to use 32 bits for all enum values in C, since enum values
20052 are essentially of type int. If pragma @code{Convention C} is specified for an
20053 Ada enumeration type, then the size is modified as necessary (usually to
20054 32 bits) to be consistent with the C convention for enum values.
20056 Note that this treatment applies only to types. If Convention C is given for
20057 an enumeration object, where the enumeration type is not Convention C, then
20058 Object_Size bits are allocated. For example, for a normal enumeration type,
20059 with less than 256 elements, only 8 bits will be allocated for the object.
20060 Since this may be a surprise in terms of what C expects, GNAT will issue a
20061 warning in this situation. The warning can be suppressed by giving an explicit
20062 size clause specifying the desired size.
20065 @emph{Convention C/Fortran and Boolean types}
20067 In C, the usual convention for boolean values, that is values used for
20068 conditions, is that zero represents false, and nonzero values represent
20069 true. In Ada, the normal convention is that two specific values, typically
20070 0/1, are used to represent false/true respectively.
20072 Fortran has a similar convention for @code{LOGICAL} values (any nonzero
20073 value represents true).
20075 To accommodate the Fortran and C conventions, if a pragma Convention specifies
20076 C or Fortran convention for a derived Boolean, as in the following example:
20079 type C_Switch is new Boolean;
20080 pragma Convention (C, C_Switch);
20083 then the GNAT generated code will treat any nonzero value as true. For truth
20084 values generated by GNAT, the conventional value 1 will be used for True, but
20085 when one of these values is read, any nonzero value is treated as True.
20088 @node Conventions and Anonymous Access Types,Determining the Representations chosen by GNAT,Effect of Convention on Representation,Representation Clauses and Pragmas
20089 @anchor{gnat_rm/representation_clauses_and_pragmas conventions-and-anonymous-access-types}@anchor{290}@anchor{gnat_rm/representation_clauses_and_pragmas id19}@anchor{291}
20090 @section Conventions and Anonymous Access Types
20093 @geindex Anonymous access types
20095 @geindex Convention for anonymous access types
20097 The RM is not entirely clear on convention handling in a number of cases,
20098 and in particular, it is not clear on the convention to be given to
20099 anonymous access types in general, and in particular what is to be
20100 done for the case of anonymous access-to-subprogram.
20102 In GNAT, we decide that if an explicit Convention is applied
20103 to an object or component, and its type is such an anonymous type,
20104 then the convention will apply to this anonymous type as well. This
20105 seems to make sense since it is anomolous in any case to have a
20106 different convention for an object and its type, and there is clearly
20107 no way to explicitly specify a convention for an anonymous type, since
20108 it doesn't have a name to specify!
20110 Furthermore, we decide that if a convention is applied to a record type,
20111 then this convention is inherited by any of its components that are of an
20112 anonymous access type which do not have an explicitly specified convention.
20114 The following program shows these conventions in action:
20117 package ConvComp is
20118 type Foo is range 1 .. 10;
20120 A : access function (X : Foo) return Integer;
20123 pragma Convention (C, T1);
20126 A : access function (X : Foo) return Integer;
20127 pragma Convention (C, A);
20130 pragma Convention (COBOL, T2);
20133 A : access function (X : Foo) return Integer;
20134 pragma Convention (COBOL, A);
20137 pragma Convention (C, T3);
20140 A : access function (X : Foo) return Integer;
20143 pragma Convention (COBOL, T4);
20145 function F (X : Foo) return Integer;
20146 pragma Convention (C, F);
20148 function F (X : Foo) return Integer is (13);
20150 TV1 : T1 := (F'Access, 12); -- OK
20151 TV2 : T2 := (F'Access, 13); -- OK
20153 TV3 : T3 := (F'Access, 13); -- ERROR
20155 >>> subprogram "F" has wrong convention
20156 >>> does not match access to subprogram declared at line 17
20157 38. TV4 : T4 := (F'Access, 13); -- ERROR
20159 >>> subprogram "F" has wrong convention
20160 >>> does not match access to subprogram declared at line 24
20164 @node Determining the Representations chosen by GNAT,,Conventions and Anonymous Access Types,Representation Clauses and Pragmas
20165 @anchor{gnat_rm/representation_clauses_and_pragmas id20}@anchor{292}@anchor{gnat_rm/representation_clauses_and_pragmas determining-the-representations-chosen-by-gnat}@anchor{293}
20166 @section Determining the Representations chosen by GNAT
20169 @geindex Representation
20170 @geindex determination of
20172 @geindex -gnatR (gcc)
20174 Although the descriptions in this section are intended to be complete, it is
20175 often easier to simply experiment to see what GNAT accepts and what the
20176 effect is on the layout of types and objects.
20178 As required by the Ada RM, if a representation clause is not accepted, then
20179 it must be rejected as illegal by the compiler. However, when a
20180 representation clause or pragma is accepted, there can still be questions
20181 of what the compiler actually does. For example, if a partial record
20182 representation clause specifies the location of some components and not
20183 others, then where are the non-specified components placed? Or if pragma
20184 @code{Pack} is used on a record, then exactly where are the resulting
20185 fields placed? The section on pragma @code{Pack} in this chapter can be
20186 used to answer the second question, but it is often easier to just see
20187 what the compiler does.
20189 For this purpose, GNAT provides the option @emph{-gnatR}. If you compile
20190 with this option, then the compiler will output information on the actual
20191 representations chosen, in a format similar to source representation
20192 clauses. For example, if we compile the package:
20196 type r (x : boolean) is tagged record
20198 when True => S : String (1 .. 100);
20199 when False => null;
20203 type r2 is new r (false) with record
20208 y2 at 16 range 0 .. 31;
20215 type x1 is array (1 .. 10) of x;
20216 for x1'component_size use 11;
20218 type ia is access integer;
20220 type Rb1 is array (1 .. 13) of Boolean;
20223 type Rb2 is array (1 .. 65) of Boolean;
20238 using the switch @emph{-gnatR} we obtain the following output:
20241 Representation information for unit q
20242 -------------------------------------
20245 for r'Alignment use 4;
20247 x at 4 range 0 .. 7;
20248 _tag at 0 range 0 .. 31;
20249 s at 5 range 0 .. 799;
20252 for r2'Size use 160;
20253 for r2'Alignment use 4;
20255 x at 4 range 0 .. 7;
20256 _tag at 0 range 0 .. 31;
20257 _parent at 0 range 0 .. 63;
20258 y2 at 16 range 0 .. 31;
20262 for x'Alignment use 1;
20264 y at 0 range 0 .. 7;
20267 for x1'Size use 112;
20268 for x1'Alignment use 1;
20269 for x1'Component_Size use 11;
20271 for rb1'Size use 13;
20272 for rb1'Alignment use 2;
20273 for rb1'Component_Size use 1;
20275 for rb2'Size use 72;
20276 for rb2'Alignment use 1;
20277 for rb2'Component_Size use 1;
20279 for x2'Size use 224;
20280 for x2'Alignment use 4;
20282 l1 at 0 range 0 .. 0;
20283 l2 at 0 range 1 .. 64;
20284 l3 at 12 range 0 .. 31;
20285 l4 at 16 range 0 .. 0;
20286 l5 at 16 range 1 .. 13;
20287 l6 at 18 range 0 .. 71;
20291 The Size values are actually the Object_Size, i.e., the default size that
20292 will be allocated for objects of the type.
20293 The @code{??} size for type r indicates that we have a variant record, and the
20294 actual size of objects will depend on the discriminant value.
20296 The Alignment values show the actual alignment chosen by the compiler
20297 for each record or array type.
20299 The record representation clause for type r shows where all fields
20300 are placed, including the compiler generated tag field (whose location
20301 cannot be controlled by the programmer).
20303 The record representation clause for the type extension r2 shows all the
20304 fields present, including the parent field, which is a copy of the fields
20305 of the parent type of r2, i.e., r1.
20307 The component size and size clauses for types rb1 and rb2 show
20308 the exact effect of pragma @code{Pack} on these arrays, and the record
20309 representation clause for type x2 shows how pragma @cite{Pack} affects
20312 In some cases, it may be useful to cut and paste the representation clauses
20313 generated by the compiler into the original source to fix and guarantee
20314 the actual representation to be used.
20316 @node Standard Library Routines,The Implementation of Standard I/O,Representation Clauses and Pragmas,Top
20317 @anchor{gnat_rm/standard_library_routines standard-library-routines}@anchor{e}@anchor{gnat_rm/standard_library_routines doc}@anchor{294}@anchor{gnat_rm/standard_library_routines id1}@anchor{295}
20318 @chapter Standard Library Routines
20321 The Ada Reference Manual contains in Annex A a full description of an
20322 extensive set of standard library routines that can be used in any Ada
20323 program, and which must be provided by all Ada compilers. They are
20324 analogous to the standard C library used by C programs.
20326 GNAT implements all of the facilities described in annex A, and for most
20327 purposes the description in the Ada Reference Manual, or appropriate Ada
20328 text book, will be sufficient for making use of these facilities.
20330 In the case of the input-output facilities,
20331 @ref{f,,The Implementation of Standard I/O},
20332 gives details on exactly how GNAT interfaces to the
20333 file system. For the remaining packages, the Ada Reference Manual
20334 should be sufficient. The following is a list of the packages included,
20335 together with a brief description of the functionality that is provided.
20337 For completeness, references are included to other predefined library
20338 routines defined in other sections of the Ada Reference Manual (these are
20339 cross-indexed from Annex A). For further details see the relevant
20340 package declarations in the run-time library. In particular, a few units
20341 are not implemented, as marked by the presence of pragma Unimplemented_Unit,
20342 and in this case the package declaration contains comments explaining why
20343 the unit is not implemented.
20348 @item @code{Ada} @emph{(A.2)}
20350 This is a parent package for all the standard library packages. It is
20351 usually included implicitly in your program, and itself contains no
20352 useful data or routines.
20354 @item @code{Ada.Assertions} @emph{(11.4.2)}
20356 @code{Assertions} provides the @code{Assert} subprograms, and also
20357 the declaration of the @code{Assertion_Error} exception.
20359 @item @code{Ada.Asynchronous_Task_Control} @emph{(D.11)}
20361 @code{Asynchronous_Task_Control} provides low level facilities for task
20362 synchronization. It is typically not implemented. See package spec for details.
20364 @item @code{Ada.Calendar} @emph{(9.6)}
20366 @code{Calendar} provides time of day access, and routines for
20367 manipulating times and durations.
20369 @item @code{Ada.Calendar.Arithmetic} @emph{(9.6.1)}
20371 This package provides additional arithmetic
20372 operations for @code{Calendar}.
20374 @item @code{Ada.Calendar.Formatting} @emph{(9.6.1)}
20376 This package provides formatting operations for @code{Calendar}.
20378 @item @code{Ada.Calendar.Time_Zones} @emph{(9.6.1)}
20380 This package provides additional @code{Calendar} facilities
20381 for handling time zones.
20383 @item @code{Ada.Characters} @emph{(A.3.1)}
20385 This is a dummy parent package that contains no useful entities
20387 @item @code{Ada.Characters.Conversions} @emph{(A.3.2)}
20389 This package provides character conversion functions.
20391 @item @code{Ada.Characters.Handling} @emph{(A.3.2)}
20393 This package provides some basic character handling capabilities,
20394 including classification functions for classes of characters (e.g., test
20395 for letters, or digits).
20397 @item @code{Ada.Characters.Latin_1} @emph{(A.3.3)}
20399 This package includes a complete set of definitions of the characters
20400 that appear in type CHARACTER. It is useful for writing programs that
20401 will run in international environments. For example, if you want an
20402 upper case E with an acute accent in a string, it is often better to use
20403 the definition of @code{UC_E_Acute} in this package. Then your program
20404 will print in an understandable manner even if your environment does not
20405 support these extended characters.
20407 @item @code{Ada.Command_Line} @emph{(A.15)}
20409 This package provides access to the command line parameters and the name
20410 of the current program (analogous to the use of @code{argc} and @code{argv}
20411 in C), and also allows the exit status for the program to be set in a
20412 system-independent manner.
20414 @item @code{Ada.Complex_Text_IO} @emph{(G.1.3)}
20416 This package provides text input and output of complex numbers.
20418 @item @code{Ada.Containers} @emph{(A.18.1)}
20420 A top level package providing a few basic definitions used by all the
20421 following specific child packages that provide specific kinds of
20425 @code{Ada.Containers.Bounded_Priority_Queues} @emph{(A.18.31)}
20427 @code{Ada.Containers.Bounded_Synchronized_Queues} @emph{(A.18.29)}
20429 @code{Ada.Containers.Doubly_Linked_Lists} @emph{(A.18.3)}
20431 @code{Ada.Containers.Generic_Array_Sort} @emph{(A.18.26)}
20433 @code{Ada.Containers.Generic_Constrained_Array_Sort} @emph{(A.18.26)}
20435 @code{Ada.Containers.Generic_Sort} @emph{(A.18.26)}
20437 @code{Ada.Containers.Hashed_Maps} @emph{(A.18.5)}
20439 @code{Ada.Containers.Hashed_Sets} @emph{(A.18.8)}
20441 @code{Ada.Containers.Indefinite_Doubly_Linked_Lists} @emph{(A.18.12)}
20443 @code{Ada.Containers.Indefinite_Hashed_Maps} @emph{(A.18.13)}
20445 @code{Ada.Containers.Indefinite_Hashed_Sets} @emph{(A.18.15)}
20447 @code{Ada.Containers.Indefinite_Holders} @emph{(A.18.18)}
20449 @code{Ada.Containers.Indefinite_Multiway_Trees} @emph{(A.18.17)}
20451 @code{Ada.Containers.Indefinite_Ordered_Maps} @emph{(A.18.14)}
20453 @code{Ada.Containers.Indefinite_Ordered_Sets} @emph{(A.18.16)}
20455 @code{Ada.Containers.Indefinite_Vectors} @emph{(A.18.11)}
20457 @code{Ada.Containers.Multiway_Trees} @emph{(A.18.10)}
20459 @code{Ada.Containers.Ordered_Maps} @emph{(A.18.6)}
20461 @code{Ada.Containers.Ordered_Sets} @emph{(A.18.9)}
20463 @code{Ada.Containers.Synchronized_Queue_Interfaces} @emph{(A.18.27)}
20465 @code{Ada.Containers.Unbounded_Priority_Queues} @emph{(A.18.30)}
20467 @code{Ada.Containers.Unbounded_Synchronized_Queues} @emph{(A.18.28)}
20469 @code{Ada.Containers.Vectors} @emph{(A.18.2)}
20474 @item @code{Ada.Directories} @emph{(A.16)}
20476 This package provides operations on directories.
20478 @item @code{Ada.Directories.Hierarchical_File_Names} @emph{(A.16.1)}
20480 This package provides additional directory operations handling
20481 hiearchical file names.
20483 @item @code{Ada.Directories.Information} @emph{(A.16)}
20485 This is an implementation defined package for additional directory
20486 operations, which is not implemented in GNAT.
20488 @item @code{Ada.Decimal} @emph{(F.2)}
20490 This package provides constants describing the range of decimal numbers
20491 implemented, and also a decimal divide routine (analogous to the COBOL
20492 verb DIVIDE ... GIVING ... REMAINDER ...)
20494 @item @code{Ada.Direct_IO} @emph{(A.8.4)}
20496 This package provides input-output using a model of a set of records of
20497 fixed-length, containing an arbitrary definite Ada type, indexed by an
20498 integer record number.
20500 @item @code{Ada.Dispatching} @emph{(D.2.1)}
20502 A parent package containing definitions for task dispatching operations.
20504 @item @code{Ada.Dispatching.EDF} @emph{(D.2.6)}
20506 Not implemented in GNAT.
20508 @item @code{Ada.Dispatching.Non_Preemptive} @emph{(D.2.4)}
20510 Not implemented in GNAT.
20512 @item @code{Ada.Dispatching.Round_Robin} @emph{(D.2.5)}
20514 Not implemented in GNAT.
20516 @item @code{Ada.Dynamic_Priorities} @emph{(D.5)}
20518 This package allows the priorities of a task to be adjusted dynamically
20519 as the task is running.
20521 @item @code{Ada.Environment_Variables} @emph{(A.17)}
20523 This package provides facilities for accessing environment variables.
20525 @item @code{Ada.Exceptions} @emph{(11.4.1)}
20527 This package provides additional information on exceptions, and also
20528 contains facilities for treating exceptions as data objects, and raising
20529 exceptions with associated messages.
20531 @item @code{Ada.Execution_Time} @emph{(D.14)}
20533 This package provides CPU clock functionalities. It is not implemented on
20534 all targets (see package spec for details).
20536 @item @code{Ada.Execution_Time.Group_Budgets} @emph{(D.14.2)}
20538 Not implemented in GNAT.
20540 @item @code{Ada.Execution_Time.Timers} @emph{(D.14.1)'}
20542 Not implemented in GNAT.
20544 @item @code{Ada.Finalization} @emph{(7.6)}
20546 This package contains the declarations and subprograms to support the
20547 use of controlled types, providing for automatic initialization and
20548 finalization (analogous to the constructors and destructors of C++).
20550 @item @code{Ada.Float_Text_IO} @emph{(A.10.9)}
20552 A library level instantiation of Text_IO.Float_IO for type Float.
20554 @item @code{Ada.Float_Wide_Text_IO} @emph{(A.10.9)}
20556 A library level instantiation of Wide_Text_IO.Float_IO for type Float.
20558 @item @code{Ada.Float_Wide_Wide_Text_IO} @emph{(A.10.9)}
20560 A library level instantiation of Wide_Wide_Text_IO.Float_IO for type Float.
20562 @item @code{Ada.Integer_Text_IO} @emph{(A.10.9)}
20564 A library level instantiation of Text_IO.Integer_IO for type Integer.
20566 @item @code{Ada.Integer_Wide_Text_IO} @emph{(A.10.9)}
20568 A library level instantiation of Wide_Text_IO.Integer_IO for type Integer.
20570 @item @code{Ada.Integer_Wide_Wide_Text_IO} @emph{(A.10.9)}
20572 A library level instantiation of Wide_Wide_Text_IO.Integer_IO for type Integer.
20574 @item @code{Ada.Interrupts} @emph{(C.3.2)}
20576 This package provides facilities for interfacing to interrupts, which
20577 includes the set of signals or conditions that can be raised and
20578 recognized as interrupts.
20580 @item @code{Ada.Interrupts.Names} @emph{(C.3.2)}
20582 This package provides the set of interrupt names (actually signal
20583 or condition names) that can be handled by GNAT.
20585 @item @code{Ada.IO_Exceptions} @emph{(A.13)}
20587 This package defines the set of exceptions that can be raised by use of
20588 the standard IO packages.
20590 @item @code{Ada.Iterator_Interfaces} @emph{(5.5.1)}
20592 This package provides a generic interface to generalized iterators.
20594 @item @code{Ada.Locales} @emph{(A.19)}
20596 This package provides declarations providing information (Language
20597 and Country) about the current locale. This package is currently not
20598 implemented other than by providing stubs which will always return
20599 Language_Unknown/Country_Unknown.
20601 @item @code{Ada.Numerics}
20603 This package contains some standard constants and exceptions used
20604 throughout the numerics packages. Note that the constants pi and e are
20605 defined here, and it is better to use these definitions than rolling
20608 @item @code{Ada.Numerics.Complex_Arrays} @emph{(G.3.2)}
20610 Provides operations on arrays of complex numbers.
20612 @item @code{Ada.Numerics.Complex_Elementary_Functions}
20614 Provides the implementation of standard elementary functions (such as
20615 log and trigonometric functions) operating on complex numbers using the
20616 standard @code{Float} and the @code{Complex} and @code{Imaginary} types
20617 created by the package @code{Numerics.Complex_Types}.
20619 @item @code{Ada.Numerics.Complex_Types}
20621 This is a predefined instantiation of
20622 @code{Numerics.Generic_Complex_Types} using @code{Standard.Float} to
20623 build the type @code{Complex} and @code{Imaginary}.
20625 @item @code{Ada.Numerics.Discrete_Random}
20627 This generic package provides a random number generator suitable for generating
20628 uniformly distributed values of a specified discrete subtype.
20630 @item @code{Ada.Numerics.Float_Random}
20632 This package provides a random number generator suitable for generating
20633 uniformly distributed floating point values in the unit interval.
20635 @item @code{Ada.Numerics.Generic_Complex_Elementary_Functions}
20637 This is a generic version of the package that provides the
20638 implementation of standard elementary functions (such as log and
20639 trigonometric functions) for an arbitrary complex type.
20641 The following predefined instantiations of this package are provided:
20649 @code{Ada.Numerics.Short_Complex_Elementary_Functions}
20654 @code{Ada.Numerics.Complex_Elementary_Functions}
20659 @code{Ada.Numerics.Long_Complex_Elementary_Functions}
20662 @item @code{Ada.Numerics.Generic_Complex_Types}
20664 This is a generic package that allows the creation of complex types,
20665 with associated complex arithmetic operations.
20667 The following predefined instantiations of this package exist
20675 @code{Ada.Numerics.Short_Complex_Complex_Types}
20680 @code{Ada.Numerics.Complex_Complex_Types}
20685 @code{Ada.Numerics.Long_Complex_Complex_Types}
20688 @item @code{Ada.Numerics.Generic_Elementary_Functions}
20690 This is a generic package that provides the implementation of standard
20691 elementary functions (such as log an trigonometric functions) for an
20692 arbitrary float type.
20694 The following predefined instantiations of this package exist
20702 @code{Ada.Numerics.Short_Elementary_Functions}
20707 @code{Ada.Numerics.Elementary_Functions}
20712 @code{Ada.Numerics.Long_Elementary_Functions}
20715 @item @code{Ada.Numerics.Generic_Real_Arrays} @emph{(G.3.1)}
20717 Generic operations on arrays of reals
20719 @item @code{Ada.Numerics.Real_Arrays} @emph{(G.3.1)}
20721 Preinstantiation of Ada.Numerics.Generic_Real_Arrays (Float).
20723 @item @code{Ada.Real_Time} @emph{(D.8)}
20725 This package provides facilities similar to those of @code{Calendar}, but
20726 operating with a finer clock suitable for real time control. Note that
20727 annex D requires that there be no backward clock jumps, and GNAT generally
20728 guarantees this behavior, but of course if the external clock on which
20729 the GNAT runtime depends is deliberately reset by some external event,
20730 then such a backward jump may occur.
20732 @item @code{Ada.Real_Time.Timing_Events} @emph{(D.15)}
20734 Not implemented in GNAT.
20736 @item @code{Ada.Sequential_IO} @emph{(A.8.1)}
20738 This package provides input-output facilities for sequential files,
20739 which can contain a sequence of values of a single type, which can be
20740 any Ada type, including indefinite (unconstrained) types.
20742 @item @code{Ada.Storage_IO} @emph{(A.9)}
20744 This package provides a facility for mapping arbitrary Ada types to and
20745 from a storage buffer. It is primarily intended for the creation of new
20748 @item @code{Ada.Streams} @emph{(13.13.1)}
20750 This is a generic package that provides the basic support for the
20751 concept of streams as used by the stream attributes (@code{Input},
20752 @code{Output}, @code{Read} and @code{Write}).
20754 @item @code{Ada.Streams.Stream_IO} @emph{(A.12.1)}
20756 This package is a specialization of the type @code{Streams} defined in
20757 package @code{Streams} together with a set of operations providing
20758 Stream_IO capability. The Stream_IO model permits both random and
20759 sequential access to a file which can contain an arbitrary set of values
20760 of one or more Ada types.
20762 @item @code{Ada.Strings} @emph{(A.4.1)}
20764 This package provides some basic constants used by the string handling
20767 @item @code{Ada.Strings.Bounded} @emph{(A.4.4)}
20769 This package provides facilities for handling variable length
20770 strings. The bounded model requires a maximum length. It is thus
20771 somewhat more limited than the unbounded model, but avoids the use of
20772 dynamic allocation or finalization.
20774 @item @code{Ada.Strings.Bounded.Equal_Case_Insensitive} @emph{(A.4.10)}
20776 Provides case-insensitive comparisons of bounded strings
20778 @item @code{Ada.Strings.Bounded.Hash} @emph{(A.4.9)}
20780 This package provides a generic hash function for bounded strings
20782 @item @code{Ada.Strings.Bounded.Hash_Case_Insensitive} @emph{(A.4.9)}
20784 This package provides a generic hash function for bounded strings that
20785 converts the string to be hashed to lower case.
20787 @item @code{Ada.Strings.Bounded.Less_Case_Insensitive} @emph{(A.4.10)}
20789 This package provides a comparison function for bounded strings that works
20790 in a case insensitive manner by converting to lower case before the comparison.
20792 @item @code{Ada.Strings.Fixed} @emph{(A.4.3)}
20794 This package provides facilities for handling fixed length strings.
20796 @item @code{Ada.Strings.Fixed.Equal_Case_Insensitive} @emph{(A.4.10)}
20798 This package provides an equality function for fixed strings that compares
20799 the strings after converting both to lower case.
20801 @item @code{Ada.Strings.Fixed.Hash_Case_Insensitive} @emph{(A.4.9)}
20803 This package provides a case insensitive hash function for fixed strings that
20804 converts the string to lower case before computing the hash.
20806 @item @code{Ada.Strings.Fixed.Less_Case_Insensitive} @emph{(A.4.10)}
20808 This package provides a comparison function for fixed strings that works
20809 in a case insensitive manner by converting to lower case before the comparison.
20811 @item @code{Ada.Strings.Hash} @emph{(A.4.9)}
20813 This package provides a hash function for strings.
20815 @item @code{Ada.Strings.Hash_Case_Insensitive} @emph{(A.4.9)}
20817 This package provides a hash function for strings that is case insensitive.
20818 The string is converted to lower case before computing the hash.
20820 @item @code{Ada.Strings.Less_Case_Insensitive} @emph{(A.4.10)}
20822 This package provides a comparison function for\strings that works
20823 in a case insensitive manner by converting to lower case before the comparison.
20825 @item @code{Ada.Strings.Maps} @emph{(A.4.2)}
20827 This package provides facilities for handling character mappings and
20828 arbitrarily defined subsets of characters. For instance it is useful in
20829 defining specialized translation tables.
20831 @item @code{Ada.Strings.Maps.Constants} @emph{(A.4.6)}
20833 This package provides a standard set of predefined mappings and
20834 predefined character sets. For example, the standard upper to lower case
20835 conversion table is found in this package. Note that upper to lower case
20836 conversion is non-trivial if you want to take the entire set of
20837 characters, including extended characters like E with an acute accent,
20838 into account. You should use the mappings in this package (rather than
20839 adding 32 yourself) to do case mappings.
20841 @item @code{Ada.Strings.Unbounded} @emph{(A.4.5)}
20843 This package provides facilities for handling variable length
20844 strings. The unbounded model allows arbitrary length strings, but
20845 requires the use of dynamic allocation and finalization.
20847 @item @code{Ada.Strings.Unbounded.Equal_Case_Insensitive} @emph{(A.4.10)}
20849 Provides case-insensitive comparisons of unbounded strings
20851 @item @code{Ada.Strings.Unbounded.Hash} @emph{(A.4.9)}
20853 This package provides a generic hash function for unbounded strings
20855 @item @code{Ada.Strings.Unbounded.Hash_Case_Insensitive} @emph{(A.4.9)}
20857 This package provides a generic hash function for unbounded strings that
20858 converts the string to be hashed to lower case.
20860 @item @code{Ada.Strings.Unbounded.Less_Case_Insensitive} @emph{(A.4.10)}
20862 This package provides a comparison function for unbounded strings that works
20863 in a case insensitive manner by converting to lower case before the comparison.
20865 @item @code{Ada.Strings.UTF_Encoding} @emph{(A.4.11)}
20867 This package provides basic definitions for dealing with UTF-encoded strings.
20869 @item @code{Ada.Strings.UTF_Encoding.Conversions} @emph{(A.4.11)}
20871 This package provides conversion functions for UTF-encoded strings.
20874 @code{Ada.Strings.UTF_Encoding.Strings} @emph{(A.4.11)}
20876 @code{Ada.Strings.UTF_Encoding.Wide_Strings} @emph{(A.4.11)}
20881 @item @code{Ada.Strings.UTF_Encoding.Wide_Wide_Strings} @emph{(A.4.11)}
20883 These packages provide facilities for handling UTF encodings for
20884 Strings, Wide_Strings and Wide_Wide_Strings.
20887 @code{Ada.Strings.Wide_Bounded} @emph{(A.4.7)}
20889 @code{Ada.Strings.Wide_Fixed} @emph{(A.4.7)}
20891 @code{Ada.Strings.Wide_Maps} @emph{(A.4.7)}
20896 @item @code{Ada.Strings.Wide_Unbounded} @emph{(A.4.7)}
20898 These packages provide analogous capabilities to the corresponding
20899 packages without @code{Wide_} in the name, but operate with the types
20900 @code{Wide_String} and @code{Wide_Character} instead of @code{String}
20901 and @code{Character}. Versions of all the child packages are available.
20904 @code{Ada.Strings.Wide_Wide_Bounded} @emph{(A.4.7)}
20906 @code{Ada.Strings.Wide_Wide_Fixed} @emph{(A.4.7)}
20908 @code{Ada.Strings.Wide_Wide_Maps} @emph{(A.4.7)}
20913 @item @code{Ada.Strings.Wide_Wide_Unbounded} @emph{(A.4.7)}
20915 These packages provide analogous capabilities to the corresponding
20916 packages without @code{Wide_} in the name, but operate with the types
20917 @code{Wide_Wide_String} and @code{Wide_Wide_Character} instead
20918 of @code{String} and @code{Character}.
20920 @item @code{Ada.Synchronous_Barriers} @emph{(D.10.1)}
20922 This package provides facilities for synchronizing tasks at a low level
20925 @item @code{Ada.Synchronous_Task_Control} @emph{(D.10)}
20927 This package provides some standard facilities for controlling task
20928 communication in a synchronous manner.
20930 @item @code{Ada.Synchronous_Task_Control.EDF} @emph{(D.10)}
20932 Not implemented in GNAT.
20934 @item @code{Ada.Tags}
20936 This package contains definitions for manipulation of the tags of tagged
20939 @item @code{Ada.Tags.Generic_Dispatching_Constructor} @emph{(3.9)}
20941 This package provides a way of constructing tagged class-wide values given
20942 only the tag value.
20944 @item @code{Ada.Task_Attributes} @emph{(C.7.2)}
20946 This package provides the capability of associating arbitrary
20947 task-specific data with separate tasks.
20949 @item @code{Ada.Task_Identifification} @emph{(C.7.1)}
20951 This package provides capabilities for task identification.
20953 @item @code{Ada.Task_Termination} @emph{(C.7.3)}
20955 This package provides control over task termination.
20957 @item @code{Ada.Text_IO}
20959 This package provides basic text input-output capabilities for
20960 character, string and numeric data. The subpackages of this
20961 package are listed next. Note that although these are defined
20962 as subpackages in the RM, they are actually transparently
20963 implemented as child packages in GNAT, meaning that they
20964 are only loaded if needed.
20966 @item @code{Ada.Text_IO.Decimal_IO}
20968 Provides input-output facilities for decimal fixed-point types
20970 @item @code{Ada.Text_IO.Enumeration_IO}
20972 Provides input-output facilities for enumeration types.
20974 @item @code{Ada.Text_IO.Fixed_IO}
20976 Provides input-output facilities for ordinary fixed-point types.
20978 @item @code{Ada.Text_IO.Float_IO}
20980 Provides input-output facilities for float types. The following
20981 predefined instantiations of this generic package are available:
20989 @code{Short_Float_Text_IO}
20994 @code{Float_Text_IO}
20999 @code{Long_Float_Text_IO}
21002 @item @code{Ada.Text_IO.Integer_IO}
21004 Provides input-output facilities for integer types. The following
21005 predefined instantiations of this generic package are available:
21011 @code{Short_Short_Integer}
21013 @code{Ada.Short_Short_Integer_Text_IO}
21016 @code{Short_Integer}
21018 @code{Ada.Short_Integer_Text_IO}
21023 @code{Ada.Integer_Text_IO}
21026 @code{Long_Integer}
21028 @code{Ada.Long_Integer_Text_IO}
21031 @code{Long_Long_Integer}
21033 @code{Ada.Long_Long_Integer_Text_IO}
21036 @item @code{Ada.Text_IO.Modular_IO}
21038 Provides input-output facilities for modular (unsigned) types.
21040 @item @code{Ada.Text_IO.Bounded_IO (A.10.11)}
21042 Provides input-output facilities for bounded strings.
21044 @item @code{Ada.Text_IO.Complex_IO (G.1.3)}
21046 This package provides basic text input-output capabilities for complex
21049 @item @code{Ada.Text_IO.Editing (F.3.3)}
21051 This package contains routines for edited output, analogous to the use
21052 of pictures in COBOL. The picture formats used by this package are a
21053 close copy of the facility in COBOL.
21055 @item @code{Ada.Text_IO.Text_Streams (A.12.2)}
21057 This package provides a facility that allows Text_IO files to be treated
21058 as streams, so that the stream attributes can be used for writing
21059 arbitrary data, including binary data, to Text_IO files.
21061 @item @code{Ada.Text_IO.Unbounded_IO (A.10.12)}
21063 This package provides input-output facilities for unbounded strings.
21065 @item @code{Ada.Unchecked_Conversion (13.9)}
21067 This generic package allows arbitrary conversion from one type to
21068 another of the same size, providing for breaking the type safety in
21069 special circumstances.
21071 If the types have the same Size (more accurately the same Value_Size),
21072 then the effect is simply to transfer the bits from the source to the
21073 target type without any modification. This usage is well defined, and
21074 for simple types whose representation is typically the same across
21075 all implementations, gives a portable method of performing such
21078 If the types do not have the same size, then the result is implementation
21079 defined, and thus may be non-portable. The following describes how GNAT
21080 handles such unchecked conversion cases.
21082 If the types are of different sizes, and are both discrete types, then
21083 the effect is of a normal type conversion without any constraint checking.
21084 In particular if the result type has a larger size, the result will be
21085 zero or sign extended. If the result type has a smaller size, the result
21086 will be truncated by ignoring high order bits.
21088 If the types are of different sizes, and are not both discrete types,
21089 then the conversion works as though pointers were created to the source
21090 and target, and the pointer value is converted. The effect is that bits
21091 are copied from successive low order storage units and bits of the source
21092 up to the length of the target type.
21094 A warning is issued if the lengths differ, since the effect in this
21095 case is implementation dependent, and the above behavior may not match
21096 that of some other compiler.
21098 A pointer to one type may be converted to a pointer to another type using
21099 unchecked conversion. The only case in which the effect is undefined is
21100 when one or both pointers are pointers to unconstrained array types. In
21101 this case, the bounds information may get incorrectly transferred, and in
21102 particular, GNAT uses double size pointers for such types, and it is
21103 meaningless to convert between such pointer types. GNAT will issue a
21104 warning if the alignment of the target designated type is more strict
21105 than the alignment of the source designated type (since the result may
21106 be unaligned in this case).
21108 A pointer other than a pointer to an unconstrained array type may be
21109 converted to and from System.Address. Such usage is common in Ada 83
21110 programs, but note that Ada.Address_To_Access_Conversions is the
21111 preferred method of performing such conversions in Ada 95 and Ada 2005.
21113 unchecked conversion nor Ada.Address_To_Access_Conversions should be
21114 used in conjunction with pointers to unconstrained objects, since
21115 the bounds information cannot be handled correctly in this case.
21117 @item @code{Ada.Unchecked_Deallocation} @emph{(13.11.2)}
21119 This generic package allows explicit freeing of storage previously
21120 allocated by use of an allocator.
21122 @item @code{Ada.Wide_Text_IO} @emph{(A.11)}
21124 This package is similar to @code{Ada.Text_IO}, except that the external
21125 file supports wide character representations, and the internal types are
21126 @code{Wide_Character} and @code{Wide_String} instead of @code{Character}
21127 and @code{String}. The corresponding set of nested packages and child
21128 packages are defined.
21130 @item @code{Ada.Wide_Wide_Text_IO} @emph{(A.11)}
21132 This package is similar to @code{Ada.Text_IO}, except that the external
21133 file supports wide character representations, and the internal types are
21134 @code{Wide_Character} and @code{Wide_String} instead of @code{Character}
21135 and @code{String}. The corresponding set of nested packages and child
21136 packages are defined.
21139 For packages in Interfaces and System, all the RM defined packages are
21140 available in GNAT, see the Ada 2012 RM for full details.
21142 @node The Implementation of Standard I/O,The GNAT Library,Standard Library Routines,Top
21143 @anchor{gnat_rm/the_implementation_of_standard_i_o the-implementation-of-standard-i-o}@anchor{f}@anchor{gnat_rm/the_implementation_of_standard_i_o doc}@anchor{296}@anchor{gnat_rm/the_implementation_of_standard_i_o id1}@anchor{297}
21144 @chapter The Implementation of Standard I/O
21147 GNAT implements all the required input-output facilities described in
21148 A.6 through A.14. These sections of the Ada Reference Manual describe the
21149 required behavior of these packages from the Ada point of view, and if
21150 you are writing a portable Ada program that does not need to know the
21151 exact manner in which Ada maps to the outside world when it comes to
21152 reading or writing external files, then you do not need to read this
21153 chapter. As long as your files are all regular files (not pipes or
21154 devices), and as long as you write and read the files only from Ada, the
21155 description in the Ada Reference Manual is sufficient.
21157 However, if you want to do input-output to pipes or other devices, such
21158 as the keyboard or screen, or if the files you are dealing with are
21159 either generated by some other language, or to be read by some other
21160 language, then you need to know more about the details of how the GNAT
21161 implementation of these input-output facilities behaves.
21163 In this chapter we give a detailed description of exactly how GNAT
21164 interfaces to the file system. As always, the sources of the system are
21165 available to you for answering questions at an even more detailed level,
21166 but for most purposes the information in this chapter will suffice.
21168 Another reason that you may need to know more about how input-output is
21169 implemented arises when you have a program written in mixed languages
21170 where, for example, files are shared between the C and Ada sections of
21171 the same program. GNAT provides some additional facilities, in the form
21172 of additional child library packages, that facilitate this sharing, and
21173 these additional facilities are also described in this chapter.
21176 * Standard I/O Packages::
21182 * Wide_Wide_Text_IO::
21184 * Text Translation::
21186 * Filenames encoding::
21187 * File content encoding::
21189 * Operations on C Streams::
21190 * Interfacing to C Streams::
21194 @node Standard I/O Packages,FORM Strings,,The Implementation of Standard I/O
21195 @anchor{gnat_rm/the_implementation_of_standard_i_o standard-i-o-packages}@anchor{298}@anchor{gnat_rm/the_implementation_of_standard_i_o id2}@anchor{299}
21196 @section Standard I/O Packages
21199 The Standard I/O packages described in Annex A for
21208 Ada.Text_IO.Complex_IO
21211 Ada.Text_IO.Text_Streams
21217 Ada.Wide_Text_IO.Complex_IO
21220 Ada.Wide_Text_IO.Text_Streams
21223 Ada.Wide_Wide_Text_IO
21226 Ada.Wide_Wide_Text_IO.Complex_IO
21229 Ada.Wide_Wide_Text_IO.Text_Streams
21241 are implemented using the C
21242 library streams facility; where
21248 All files are opened using @code{fopen}.
21251 All input/output operations use @code{fread}/@cite{fwrite}.
21254 There is no internal buffering of any kind at the Ada library level. The only
21255 buffering is that provided at the system level in the implementation of the
21256 library routines that support streams. This facilitates shared use of these
21257 streams by mixed language programs. Note though that system level buffering is
21258 explicitly enabled at elaboration of the standard I/O packages and that can
21259 have an impact on mixed language programs, in particular those using I/O before
21260 calling the Ada elaboration routine (e.g., adainit). It is recommended to call
21261 the Ada elaboration routine before performing any I/O or when impractical,
21262 flush the common I/O streams and in particular Standard_Output before
21263 elaborating the Ada code.
21265 @node FORM Strings,Direct_IO,Standard I/O Packages,The Implementation of Standard I/O
21266 @anchor{gnat_rm/the_implementation_of_standard_i_o form-strings}@anchor{29a}@anchor{gnat_rm/the_implementation_of_standard_i_o id3}@anchor{29b}
21267 @section FORM Strings
21270 The format of a FORM string in GNAT is:
21273 "keyword=value,keyword=value,...,keyword=value"
21276 where letters may be in upper or lower case, and there are no spaces
21277 between values. The order of the entries is not important. Currently
21278 the following keywords defined.
21281 TEXT_TRANSLATION=[YES|NO|TEXT|BINARY|U8TEXT|WTEXT|U16TEXT]
21283 WCEM=[n|h|u|s|e|8|b]
21284 ENCODING=[UTF8|8BITS]
21287 The use of these parameters is described later in this section. If an
21288 unrecognized keyword appears in a form string, it is silently ignored
21289 and not considered invalid.
21291 @node Direct_IO,Sequential_IO,FORM Strings,The Implementation of Standard I/O
21292 @anchor{gnat_rm/the_implementation_of_standard_i_o direct-io}@anchor{29c}@anchor{gnat_rm/the_implementation_of_standard_i_o id4}@anchor{29d}
21296 Direct_IO can only be instantiated for definite types. This is a
21297 restriction of the Ada language, which means that the records are fixed
21298 length (the length being determined by @code{type'Size}, rounded
21299 up to the next storage unit boundary if necessary).
21301 The records of a Direct_IO file are simply written to the file in index
21302 sequence, with the first record starting at offset zero, and subsequent
21303 records following. There is no control information of any kind. For
21304 example, if 32-bit integers are being written, each record takes
21305 4-bytes, so the record at index @code{K} starts at offset
21308 There is no limit on the size of Direct_IO files, they are expanded as
21309 necessary to accommodate whatever records are written to the file.
21311 @node Sequential_IO,Text_IO,Direct_IO,The Implementation of Standard I/O
21312 @anchor{gnat_rm/the_implementation_of_standard_i_o sequential-io}@anchor{29e}@anchor{gnat_rm/the_implementation_of_standard_i_o id5}@anchor{29f}
21313 @section Sequential_IO
21316 Sequential_IO may be instantiated with either a definite (constrained)
21317 or indefinite (unconstrained) type.
21319 For the definite type case, the elements written to the file are simply
21320 the memory images of the data values with no control information of any
21321 kind. The resulting file should be read using the same type, no validity
21322 checking is performed on input.
21324 For the indefinite type case, the elements written consist of two
21325 parts. First is the size of the data item, written as the memory image
21326 of a @code{Interfaces.C.size_t} value, followed by the memory image of
21327 the data value. The resulting file can only be read using the same
21328 (unconstrained) type. Normal assignment checks are performed on these
21329 read operations, and if these checks fail, @code{Data_Error} is
21330 raised. In particular, in the array case, the lengths must match, and in
21331 the variant record case, if the variable for a particular read operation
21332 is constrained, the discriminants must match.
21334 Note that it is not possible to use Sequential_IO to write variable
21335 length array items, and then read the data back into different length
21336 arrays. For example, the following will raise @code{Data_Error}:
21339 package IO is new Sequential_IO (String);
21344 IO.Write (F, "hello!")
21345 IO.Reset (F, Mode=>In_File);
21350 On some Ada implementations, this will print @code{hell}, but the program is
21351 clearly incorrect, since there is only one element in the file, and that
21352 element is the string @code{hello!}.
21354 In Ada 95 and Ada 2005, this kind of behavior can be legitimately achieved
21355 using Stream_IO, and this is the preferred mechanism. In particular, the
21356 above program fragment rewritten to use Stream_IO will work correctly.
21358 @node Text_IO,Wide_Text_IO,Sequential_IO,The Implementation of Standard I/O
21359 @anchor{gnat_rm/the_implementation_of_standard_i_o id6}@anchor{2a0}@anchor{gnat_rm/the_implementation_of_standard_i_o text-io}@anchor{2a1}
21363 Text_IO files consist of a stream of characters containing the following
21364 special control characters:
21367 LF (line feed, 16#0A#) Line Mark
21368 FF (form feed, 16#0C#) Page Mark
21371 A canonical Text_IO file is defined as one in which the following
21372 conditions are met:
21378 The character @code{LF} is used only as a line mark, i.e., to mark the end
21382 The character @code{FF} is used only as a page mark, i.e., to mark the
21383 end of a page and consequently can appear only immediately following a
21384 @code{LF} (line mark) character.
21387 The file ends with either @code{LF} (line mark) or @code{LF}-@cite{FF}
21388 (line mark, page mark). In the former case, the page mark is implicitly
21389 assumed to be present.
21392 A file written using Text_IO will be in canonical form provided that no
21393 explicit @code{LF} or @code{FF} characters are written using @code{Put}
21394 or @code{Put_Line}. There will be no @code{FF} character at the end of
21395 the file unless an explicit @code{New_Page} operation was performed
21396 before closing the file.
21398 A canonical Text_IO file that is a regular file (i.e., not a device or a
21399 pipe) can be read using any of the routines in Text_IO. The
21400 semantics in this case will be exactly as defined in the Ada Reference
21401 Manual, and all the routines in Text_IO are fully implemented.
21403 A text file that does not meet the requirements for a canonical Text_IO
21404 file has one of the following:
21410 The file contains @code{FF} characters not immediately following a
21411 @code{LF} character.
21414 The file contains @code{LF} or @code{FF} characters written by
21415 @code{Put} or @code{Put_Line}, which are not logically considered to be
21416 line marks or page marks.
21419 The file ends in a character other than @code{LF} or @code{FF},
21420 i.e., there is no explicit line mark or page mark at the end of the file.
21423 Text_IO can be used to read such non-standard text files but subprograms
21424 to do with line or page numbers do not have defined meanings. In
21425 particular, a @code{FF} character that does not follow a @code{LF}
21426 character may or may not be treated as a page mark from the point of
21427 view of page and line numbering. Every @code{LF} character is considered
21428 to end a line, and there is an implied @code{LF} character at the end of
21432 * Stream Pointer Positioning::
21433 * Reading and Writing Non-Regular Files::
21435 * Treating Text_IO Files as Streams::
21436 * Text_IO Extensions::
21437 * Text_IO Facilities for Unbounded Strings::
21441 @node Stream Pointer Positioning,Reading and Writing Non-Regular Files,,Text_IO
21442 @anchor{gnat_rm/the_implementation_of_standard_i_o id7}@anchor{2a2}@anchor{gnat_rm/the_implementation_of_standard_i_o stream-pointer-positioning}@anchor{2a3}
21443 @subsection Stream Pointer Positioning
21446 @code{Ada.Text_IO} has a definition of current position for a file that
21447 is being read. No internal buffering occurs in Text_IO, and usually the
21448 physical position in the stream used to implement the file corresponds
21449 to this logical position defined by Text_IO. There are two exceptions:
21455 After a call to @code{End_Of_Page} that returns @code{True}, the stream
21456 is positioned past the @code{LF} (line mark) that precedes the page
21457 mark. Text_IO maintains an internal flag so that subsequent read
21458 operations properly handle the logical position which is unchanged by
21459 the @code{End_Of_Page} call.
21462 After a call to @code{End_Of_File} that returns @code{True}, if the
21463 Text_IO file was positioned before the line mark at the end of file
21464 before the call, then the logical position is unchanged, but the stream
21465 is physically positioned right at the end of file (past the line mark,
21466 and past a possible page mark following the line mark. Again Text_IO
21467 maintains internal flags so that subsequent read operations properly
21468 handle the logical position.
21471 These discrepancies have no effect on the observable behavior of
21472 Text_IO, but if a single Ada stream is shared between a C program and
21473 Ada program, or shared (using @code{shared=yes} in the form string)
21474 between two Ada files, then the difference may be observable in some
21477 @node Reading and Writing Non-Regular Files,Get_Immediate,Stream Pointer Positioning,Text_IO
21478 @anchor{gnat_rm/the_implementation_of_standard_i_o reading-and-writing-non-regular-files}@anchor{2a4}@anchor{gnat_rm/the_implementation_of_standard_i_o id8}@anchor{2a5}
21479 @subsection Reading and Writing Non-Regular Files
21482 A non-regular file is a device (such as a keyboard), or a pipe. Text_IO
21483 can be used for reading and writing. Writing is not affected and the
21484 sequence of characters output is identical to the normal file case, but
21485 for reading, the behavior of Text_IO is modified to avoid undesirable
21486 look-ahead as follows:
21488 An input file that is not a regular file is considered to have no page
21489 marks. Any @code{Ascii.FF} characters (the character normally used for a
21490 page mark) appearing in the file are considered to be data
21491 characters. In particular:
21497 @code{Get_Line} and @code{Skip_Line} do not test for a page mark
21498 following a line mark. If a page mark appears, it will be treated as a
21502 This avoids the need to wait for an extra character to be typed or
21503 entered from the pipe to complete one of these operations.
21506 @code{End_Of_Page} always returns @code{False}
21509 @code{End_Of_File} will return @code{False} if there is a page mark at
21510 the end of the file.
21513 Output to non-regular files is the same as for regular files. Page marks
21514 may be written to non-regular files using @code{New_Page}, but as noted
21515 above they will not be treated as page marks on input if the output is
21516 piped to another Ada program.
21518 Another important discrepancy when reading non-regular files is that the end
21519 of file indication is not 'sticky'. If an end of file is entered, e.g., by
21520 pressing the @code{EOT} key,
21522 is signaled once (i.e., the test @code{End_Of_File}
21523 will yield @code{True}, or a read will
21524 raise @code{End_Error}), but then reading can resume
21525 to read data past that end of
21526 file indication, until another end of file indication is entered.
21528 @node Get_Immediate,Treating Text_IO Files as Streams,Reading and Writing Non-Regular Files,Text_IO
21529 @anchor{gnat_rm/the_implementation_of_standard_i_o get-immediate}@anchor{2a6}@anchor{gnat_rm/the_implementation_of_standard_i_o id9}@anchor{2a7}
21530 @subsection Get_Immediate
21533 @geindex Get_Immediate
21535 Get_Immediate returns the next character (including control characters)
21536 from the input file. In particular, Get_Immediate will return LF or FF
21537 characters used as line marks or page marks. Such operations leave the
21538 file positioned past the control character, and it is thus not treated
21539 as having its normal function. This means that page, line and column
21540 counts after this kind of Get_Immediate call are set as though the mark
21541 did not occur. In the case where a Get_Immediate leaves the file
21542 positioned between the line mark and page mark (which is not normally
21543 possible), it is undefined whether the FF character will be treated as a
21546 @node Treating Text_IO Files as Streams,Text_IO Extensions,Get_Immediate,Text_IO
21547 @anchor{gnat_rm/the_implementation_of_standard_i_o id10}@anchor{2a8}@anchor{gnat_rm/the_implementation_of_standard_i_o treating-text-io-files-as-streams}@anchor{2a9}
21548 @subsection Treating Text_IO Files as Streams
21551 @geindex Stream files
21553 The package @code{Text_IO.Streams} allows a @code{Text_IO} file to be treated
21554 as a stream. Data written to a @code{Text_IO} file in this stream mode is
21555 binary data. If this binary data contains bytes 16#0A# (@code{LF}) or
21556 16#0C# (@code{FF}), the resulting file may have non-standard
21557 format. Similarly if read operations are used to read from a Text_IO
21558 file treated as a stream, then @code{LF} and @code{FF} characters may be
21559 skipped and the effect is similar to that described above for
21560 @code{Get_Immediate}.
21562 @node Text_IO Extensions,Text_IO Facilities for Unbounded Strings,Treating Text_IO Files as Streams,Text_IO
21563 @anchor{gnat_rm/the_implementation_of_standard_i_o id11}@anchor{2aa}@anchor{gnat_rm/the_implementation_of_standard_i_o text-io-extensions}@anchor{2ab}
21564 @subsection Text_IO Extensions
21567 @geindex Text_IO extensions
21569 A package GNAT.IO_Aux in the GNAT library provides some useful extensions
21570 to the standard @code{Text_IO} package:
21576 function File_Exists (Name : String) return Boolean;
21577 Determines if a file of the given name exists.
21580 function Get_Line return String;
21581 Reads a string from the standard input file. The value returned is exactly
21582 the length of the line that was read.
21585 function Get_Line (File : Ada.Text_IO.File_Type) return String;
21586 Similar, except that the parameter File specifies the file from which
21587 the string is to be read.
21590 @node Text_IO Facilities for Unbounded Strings,,Text_IO Extensions,Text_IO
21591 @anchor{gnat_rm/the_implementation_of_standard_i_o text-io-facilities-for-unbounded-strings}@anchor{2ac}@anchor{gnat_rm/the_implementation_of_standard_i_o id12}@anchor{2ad}
21592 @subsection Text_IO Facilities for Unbounded Strings
21595 @geindex Text_IO for unbounded strings
21597 @geindex Unbounded_String
21598 @geindex Text_IO operations
21600 The package @code{Ada.Strings.Unbounded.Text_IO}
21601 in library files @code{a-suteio.ads/adb} contains some GNAT-specific
21602 subprograms useful for Text_IO operations on unbounded strings:
21608 function Get_Line (File : File_Type) return Unbounded_String;
21609 Reads a line from the specified file
21610 and returns the result as an unbounded string.
21613 procedure Put (File : File_Type; U : Unbounded_String);
21614 Writes the value of the given unbounded string to the specified file
21615 Similar to the effect of
21616 @code{Put (To_String (U))} except that an extra copy is avoided.
21619 procedure Put_Line (File : File_Type; U : Unbounded_String);
21620 Writes the value of the given unbounded string to the specified file,
21621 followed by a @code{New_Line}.
21622 Similar to the effect of @code{Put_Line (To_String (U))} except
21623 that an extra copy is avoided.
21626 In the above procedures, @code{File} is of type @code{Ada.Text_IO.File_Type}
21627 and is optional. If the parameter is omitted, then the standard input or
21628 output file is referenced as appropriate.
21630 The package @code{Ada.Strings.Wide_Unbounded.Wide_Text_IO} in library
21631 files @code{a-swuwti.ads} and @code{a-swuwti.adb} provides similar extended
21632 @code{Wide_Text_IO} functionality for unbounded wide strings.
21634 The package @code{Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO} in library
21635 files @code{a-szuzti.ads} and @code{a-szuzti.adb} provides similar extended
21636 @code{Wide_Wide_Text_IO} functionality for unbounded wide wide strings.
21638 @node Wide_Text_IO,Wide_Wide_Text_IO,Text_IO,The Implementation of Standard I/O
21639 @anchor{gnat_rm/the_implementation_of_standard_i_o wide-text-io}@anchor{2ae}@anchor{gnat_rm/the_implementation_of_standard_i_o id13}@anchor{2af}
21640 @section Wide_Text_IO
21643 @code{Wide_Text_IO} is similar in most respects to Text_IO, except that
21644 both input and output files may contain special sequences that represent
21645 wide character values. The encoding scheme for a given file may be
21646 specified using a FORM parameter:
21652 as part of the FORM string (WCEM = wide character encoding method),
21653 where @code{x} is one of the following characters
21656 @multitable {xxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxx}
21679 Upper half encoding
21716 The encoding methods match those that
21717 can be used in a source
21718 program, but there is no requirement that the encoding method used for
21719 the source program be the same as the encoding method used for files,
21720 and different files may use different encoding methods.
21722 The default encoding method for the standard files, and for opened files
21723 for which no WCEM parameter is given in the FORM string matches the
21724 wide character encoding specified for the main program (the default
21725 being brackets encoding if no coding method was specified with -gnatW).
21730 @item @emph{Hex Coding}
21732 In this encoding, a wide character is represented by a five character
21743 where @code{a}, @code{b}, @code{c}, @code{d} are the four hexadecimal
21744 characters (using upper case letters) of the wide character code. For
21745 example, ESC A345 is used to represent the wide character with code
21746 16#A345#. This scheme is compatible with use of the full
21747 @code{Wide_Character} set.
21753 @item @emph{Upper Half Coding}
21755 The wide character with encoding 16#abcd#, where the upper bit is on
21756 (i.e., a is in the range 8-F) is represented as two bytes 16#ab# and
21757 16#cd#. The second byte may never be a format control character, but is
21758 not required to be in the upper half. This method can be also used for
21759 shift-JIS or EUC where the internal coding matches the external coding.
21761 @item @emph{Shift JIS Coding}
21763 A wide character is represented by a two character sequence 16#ab# and
21764 16#cd#, with the restrictions described for upper half encoding as
21765 described above. The internal character code is the corresponding JIS
21766 character according to the standard algorithm for Shift-JIS
21767 conversion. Only characters defined in the JIS code set table can be
21768 used with this encoding method.
21770 @item @emph{EUC Coding}
21772 A wide character is represented by a two character sequence 16#ab# and
21773 16#cd#, with both characters being in the upper half. The internal
21774 character code is the corresponding JIS character according to the EUC
21775 encoding algorithm. Only characters defined in the JIS code set table
21776 can be used with this encoding method.
21778 @item @emph{UTF-8 Coding}
21780 A wide character is represented using
21781 UCS Transformation Format 8 (UTF-8) as defined in Annex R of ISO
21782 10646-1/Am.2. Depending on the character value, the representation
21783 is a one, two, or three byte sequence:
21787 16#0000#-16#007f#: 2#0xxxxxxx#
21788 16#0080#-16#07ff#: 2#110xxxxx# 2#10xxxxxx#
21789 16#0800#-16#ffff#: 2#1110xxxx# 2#10xxxxxx# 2#10xxxxxx#
21795 where the @code{xxx} bits correspond to the left-padded bits of the
21796 16-bit character value. Note that all lower half ASCII characters
21797 are represented as ASCII bytes and all upper half characters and
21798 other wide characters are represented as sequences of upper-half
21799 (The full UTF-8 scheme allows for encoding 31-bit characters as
21800 6-byte sequences, but in this implementation, all UTF-8 sequences
21801 of four or more bytes length will raise a Constraint_Error, as
21802 will all invalid UTF-8 sequences.)
21808 @item @emph{Brackets Coding}
21810 In this encoding, a wide character is represented by the following eight
21811 character sequence:
21821 where @code{a}, @code{b}, @code{c}, @code{d} are the four hexadecimal
21822 characters (using uppercase letters) of the wide character code. For
21823 example, @code{["A345"]} is used to represent the wide character with code
21825 This scheme is compatible with use of the full Wide_Character set.
21826 On input, brackets coding can also be used for upper half characters,
21827 e.g., @code{["C1"]} for lower case a. However, on output, brackets notation
21828 is only used for wide characters with a code greater than @code{16#FF#}.
21830 Note that brackets coding is not normally used in the context of
21831 Wide_Text_IO or Wide_Wide_Text_IO, since it is really just designed as
21832 a portable way of encoding source files. In the context of Wide_Text_IO
21833 or Wide_Wide_Text_IO, it can only be used if the file does not contain
21834 any instance of the left bracket character other than to encode wide
21835 character values using the brackets encoding method. In practice it is
21836 expected that some standard wide character encoding method such
21837 as UTF-8 will be used for text input output.
21839 If brackets notation is used, then any occurrence of a left bracket
21840 in the input file which is not the start of a valid wide character
21841 sequence will cause Constraint_Error to be raised. It is possible to
21842 encode a left bracket as ["5B"] and Wide_Text_IO and Wide_Wide_Text_IO
21843 input will interpret this as a left bracket.
21845 However, when a left bracket is output, it will be output as a left bracket
21846 and not as ["5B"]. We make this decision because for normal use of
21847 Wide_Text_IO for outputting messages, it is unpleasant to clobber left
21848 brackets. For example, if we write:
21851 Put_Line ("Start of output [first run]");
21854 we really do not want to have the left bracket in this message clobbered so
21855 that the output reads:
21859 Start of output ["5B"]first run]
21865 In practice brackets encoding is reasonably useful for normal Put_Line use
21866 since we won't get confused between left brackets and wide character
21867 sequences in the output. But for input, or when files are written out
21868 and read back in, it really makes better sense to use one of the standard
21869 encoding methods such as UTF-8.
21872 For the coding schemes other than UTF-8, Hex, or Brackets encoding,
21873 not all wide character
21874 values can be represented. An attempt to output a character that cannot
21875 be represented using the encoding scheme for the file causes
21876 Constraint_Error to be raised. An invalid wide character sequence on
21877 input also causes Constraint_Error to be raised.
21880 * Stream Pointer Positioning: Stream Pointer Positioning<2>.
21881 * Reading and Writing Non-Regular Files: Reading and Writing Non-Regular Files<2>.
21885 @node Stream Pointer Positioning<2>,Reading and Writing Non-Regular Files<2>,,Wide_Text_IO
21886 @anchor{gnat_rm/the_implementation_of_standard_i_o stream-pointer-positioning-1}@anchor{2b0}@anchor{gnat_rm/the_implementation_of_standard_i_o id14}@anchor{2b1}
21887 @subsection Stream Pointer Positioning
21890 @code{Ada.Wide_Text_IO} is similar to @code{Ada.Text_IO} in its handling
21891 of stream pointer positioning (@ref{2a1,,Text_IO}). There is one additional
21894 If @code{Ada.Wide_Text_IO.Look_Ahead} reads a character outside the
21895 normal lower ASCII set (i.e., a character in the range:
21898 Wide_Character'Val (16#0080#) .. Wide_Character'Val (16#FFFF#)
21901 then although the logical position of the file pointer is unchanged by
21902 the @code{Look_Ahead} call, the stream is physically positioned past the
21903 wide character sequence. Again this is to avoid the need for buffering
21904 or backup, and all @code{Wide_Text_IO} routines check the internal
21905 indication that this situation has occurred so that this is not visible
21906 to a normal program using @code{Wide_Text_IO}. However, this discrepancy
21907 can be observed if the wide text file shares a stream with another file.
21909 @node Reading and Writing Non-Regular Files<2>,,Stream Pointer Positioning<2>,Wide_Text_IO
21910 @anchor{gnat_rm/the_implementation_of_standard_i_o reading-and-writing-non-regular-files-1}@anchor{2b2}@anchor{gnat_rm/the_implementation_of_standard_i_o id15}@anchor{2b3}
21911 @subsection Reading and Writing Non-Regular Files
21914 As in the case of Text_IO, when a non-regular file is read, it is
21915 assumed that the file contains no page marks (any form characters are
21916 treated as data characters), and @code{End_Of_Page} always returns
21917 @code{False}. Similarly, the end of file indication is not sticky, so
21918 it is possible to read beyond an end of file.
21920 @node Wide_Wide_Text_IO,Stream_IO,Wide_Text_IO,The Implementation of Standard I/O
21921 @anchor{gnat_rm/the_implementation_of_standard_i_o id16}@anchor{2b4}@anchor{gnat_rm/the_implementation_of_standard_i_o wide-wide-text-io}@anchor{2b5}
21922 @section Wide_Wide_Text_IO
21925 @code{Wide_Wide_Text_IO} is similar in most respects to Text_IO, except that
21926 both input and output files may contain special sequences that represent
21927 wide wide character values. The encoding scheme for a given file may be
21928 specified using a FORM parameter:
21934 as part of the FORM string (WCEM = wide character encoding method),
21935 where @code{x} is one of the following characters
21938 @multitable {xxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxx}
21961 Upper half encoding
21998 The encoding methods match those that
21999 can be used in a source
22000 program, but there is no requirement that the encoding method used for
22001 the source program be the same as the encoding method used for files,
22002 and different files may use different encoding methods.
22004 The default encoding method for the standard files, and for opened files
22005 for which no WCEM parameter is given in the FORM string matches the
22006 wide character encoding specified for the main program (the default
22007 being brackets encoding if no coding method was specified with -gnatW).
22012 @item @emph{UTF-8 Coding}
22014 A wide character is represented using
22015 UCS Transformation Format 8 (UTF-8) as defined in Annex R of ISO
22016 10646-1/Am.2. Depending on the character value, the representation
22017 is a one, two, three, or four byte sequence:
22021 16#000000#-16#00007f#: 2#0xxxxxxx#
22022 16#000080#-16#0007ff#: 2#110xxxxx# 2#10xxxxxx#
22023 16#000800#-16#00ffff#: 2#1110xxxx# 2#10xxxxxx# 2#10xxxxxx#
22024 16#010000#-16#10ffff#: 2#11110xxx# 2#10xxxxxx# 2#10xxxxxx# 2#10xxxxxx#
22030 where the @code{xxx} bits correspond to the left-padded bits of the
22031 21-bit character value. Note that all lower half ASCII characters
22032 are represented as ASCII bytes and all upper half characters and
22033 other wide characters are represented as sequences of upper-half
22040 @item @emph{Brackets Coding}
22042 In this encoding, a wide wide character is represented by the following eight
22043 character sequence if is in wide character range
22053 and by the following ten character sequence if not
22057 [ " a b c d e f " ]
22063 where @code{a}, @code{b}, @code{c}, @code{d}, @code{e}, and @code{f}
22064 are the four or six hexadecimal
22065 characters (using uppercase letters) of the wide wide character code. For
22066 example, @code{["01A345"]} is used to represent the wide wide character
22067 with code @code{16#01A345#}.
22069 This scheme is compatible with use of the full Wide_Wide_Character set.
22070 On input, brackets coding can also be used for upper half characters,
22071 e.g., @code{["C1"]} for lower case a. However, on output, brackets notation
22072 is only used for wide characters with a code greater than @code{16#FF#}.
22075 If is also possible to use the other Wide_Character encoding methods,
22076 such as Shift-JIS, but the other schemes cannot support the full range
22077 of wide wide characters.
22078 An attempt to output a character that cannot
22079 be represented using the encoding scheme for the file causes
22080 Constraint_Error to be raised. An invalid wide character sequence on
22081 input also causes Constraint_Error to be raised.
22084 * Stream Pointer Positioning: Stream Pointer Positioning<3>.
22085 * Reading and Writing Non-Regular Files: Reading and Writing Non-Regular Files<3>.
22089 @node Stream Pointer Positioning<3>,Reading and Writing Non-Regular Files<3>,,Wide_Wide_Text_IO
22090 @anchor{gnat_rm/the_implementation_of_standard_i_o stream-pointer-positioning-2}@anchor{2b6}@anchor{gnat_rm/the_implementation_of_standard_i_o id17}@anchor{2b7}
22091 @subsection Stream Pointer Positioning
22094 @code{Ada.Wide_Wide_Text_IO} is similar to @code{Ada.Text_IO} in its handling
22095 of stream pointer positioning (@ref{2a1,,Text_IO}). There is one additional
22098 If @code{Ada.Wide_Wide_Text_IO.Look_Ahead} reads a character outside the
22099 normal lower ASCII set (i.e., a character in the range:
22102 Wide_Wide_Character'Val (16#0080#) .. Wide_Wide_Character'Val (16#10FFFF#)
22105 then although the logical position of the file pointer is unchanged by
22106 the @code{Look_Ahead} call, the stream is physically positioned past the
22107 wide character sequence. Again this is to avoid the need for buffering
22108 or backup, and all @code{Wide_Wide_Text_IO} routines check the internal
22109 indication that this situation has occurred so that this is not visible
22110 to a normal program using @code{Wide_Wide_Text_IO}. However, this discrepancy
22111 can be observed if the wide text file shares a stream with another file.
22113 @node Reading and Writing Non-Regular Files<3>,,Stream Pointer Positioning<3>,Wide_Wide_Text_IO
22114 @anchor{gnat_rm/the_implementation_of_standard_i_o id18}@anchor{2b8}@anchor{gnat_rm/the_implementation_of_standard_i_o reading-and-writing-non-regular-files-2}@anchor{2b9}
22115 @subsection Reading and Writing Non-Regular Files
22118 As in the case of Text_IO, when a non-regular file is read, it is
22119 assumed that the file contains no page marks (any form characters are
22120 treated as data characters), and @code{End_Of_Page} always returns
22121 @code{False}. Similarly, the end of file indication is not sticky, so
22122 it is possible to read beyond an end of file.
22124 @node Stream_IO,Text Translation,Wide_Wide_Text_IO,The Implementation of Standard I/O
22125 @anchor{gnat_rm/the_implementation_of_standard_i_o id19}@anchor{2ba}@anchor{gnat_rm/the_implementation_of_standard_i_o stream-io}@anchor{2bb}
22129 A stream file is a sequence of bytes, where individual elements are
22130 written to the file as described in the Ada Reference Manual. The type
22131 @code{Stream_Element} is simply a byte. There are two ways to read or
22132 write a stream file.
22138 The operations @code{Read} and @code{Write} directly read or write a
22139 sequence of stream elements with no control information.
22142 The stream attributes applied to a stream file transfer data in the
22143 manner described for stream attributes.
22146 @node Text Translation,Shared Files,Stream_IO,The Implementation of Standard I/O
22147 @anchor{gnat_rm/the_implementation_of_standard_i_o id20}@anchor{2bc}@anchor{gnat_rm/the_implementation_of_standard_i_o text-translation}@anchor{2bd}
22148 @section Text Translation
22151 @code{Text_Translation=xxx} may be used as the Form parameter
22152 passed to Text_IO.Create and Text_IO.Open. @code{Text_Translation=xxx}
22153 has no effect on Unix systems. Possible values are:
22159 @code{Yes} or @code{Text} is the default, which means to
22160 translate LF to/from CR/LF on Windows systems.
22162 @code{No} disables this translation; i.e. it
22163 uses binary mode. For output files, @code{Text_Translation=No}
22164 may be used to create Unix-style files on
22168 @code{wtext} translation enabled in Unicode mode.
22169 (corresponds to _O_WTEXT).
22172 @code{u8text} translation enabled in Unicode UTF-8 mode.
22173 (corresponds to O_U8TEXT).
22176 @code{u16text} translation enabled in Unicode UTF-16
22177 mode. (corresponds to_O_U16TEXT).
22180 @node Shared Files,Filenames encoding,Text Translation,The Implementation of Standard I/O
22181 @anchor{gnat_rm/the_implementation_of_standard_i_o id21}@anchor{2be}@anchor{gnat_rm/the_implementation_of_standard_i_o shared-files}@anchor{2bf}
22182 @section Shared Files
22185 Section A.14 of the Ada Reference Manual allows implementations to
22186 provide a wide variety of behavior if an attempt is made to access the
22187 same external file with two or more internal files.
22189 To provide a full range of functionality, while at the same time
22190 minimizing the problems of portability caused by this implementation
22191 dependence, GNAT handles file sharing as follows:
22197 In the absence of a @code{shared=xxx} form parameter, an attempt
22198 to open two or more files with the same full name is considered an error
22199 and is not supported. The exception @code{Use_Error} will be
22200 raised. Note that a file that is not explicitly closed by the program
22201 remains open until the program terminates.
22204 If the form parameter @code{shared=no} appears in the form string, the
22205 file can be opened or created with its own separate stream identifier,
22206 regardless of whether other files sharing the same external file are
22207 opened. The exact effect depends on how the C stream routines handle
22208 multiple accesses to the same external files using separate streams.
22211 If the form parameter @code{shared=yes} appears in the form string for
22212 each of two or more files opened using the same full name, the same
22213 stream is shared between these files, and the semantics are as described
22214 in Ada Reference Manual, Section A.14.
22217 When a program that opens multiple files with the same name is ported
22218 from another Ada compiler to GNAT, the effect will be that
22219 @code{Use_Error} is raised.
22221 The documentation of the original compiler and the documentation of the
22222 program should then be examined to determine if file sharing was
22223 expected, and @code{shared=xxx} parameters added to @code{Open}
22224 and @code{Create} calls as required.
22226 When a program is ported from GNAT to some other Ada compiler, no
22227 special attention is required unless the @code{shared=xxx} form
22228 parameter is used in the program. In this case, you must examine the
22229 documentation of the new compiler to see if it supports the required
22230 file sharing semantics, and form strings modified appropriately. Of
22231 course it may be the case that the program cannot be ported if the
22232 target compiler does not support the required functionality. The best
22233 approach in writing portable code is to avoid file sharing (and hence
22234 the use of the @code{shared=xxx} parameter in the form string)
22237 One common use of file sharing in Ada 83 is the use of instantiations of
22238 Sequential_IO on the same file with different types, to achieve
22239 heterogeneous input-output. Although this approach will work in GNAT if
22240 @code{shared=yes} is specified, it is preferable in Ada to use Stream_IO
22241 for this purpose (using the stream attributes)
22243 @node Filenames encoding,File content encoding,Shared Files,The Implementation of Standard I/O
22244 @anchor{gnat_rm/the_implementation_of_standard_i_o filenames-encoding}@anchor{2c0}@anchor{gnat_rm/the_implementation_of_standard_i_o id22}@anchor{2c1}
22245 @section Filenames encoding
22248 An encoding form parameter can be used to specify the filename
22249 encoding @code{encoding=xxx}.
22255 If the form parameter @code{encoding=utf8} appears in the form string, the
22256 filename must be encoded in UTF-8.
22259 If the form parameter @code{encoding=8bits} appears in the form
22260 string, the filename must be a standard 8bits string.
22263 In the absence of a @code{encoding=xxx} form parameter, the
22264 encoding is controlled by the @code{GNAT_CODE_PAGE} environment
22265 variable. And if not set @code{utf8} is assumed.
22270 @item @emph{CP_ACP}
22272 The current system Windows ANSI code page.
22274 @item @emph{CP_UTF8}
22279 This encoding form parameter is only supported on the Windows
22280 platform. On the other Operating Systems the run-time is supporting
22283 @node File content encoding,Open Modes,Filenames encoding,The Implementation of Standard I/O
22284 @anchor{gnat_rm/the_implementation_of_standard_i_o file-content-encoding}@anchor{2c2}@anchor{gnat_rm/the_implementation_of_standard_i_o id23}@anchor{2c3}
22285 @section File content encoding
22288 For text files it is possible to specify the encoding to use. This is
22289 controlled by the by the @code{GNAT_CCS_ENCODING} environment
22290 variable. And if not set @code{TEXT} is assumed.
22292 The possible values are those supported on Windows:
22299 Translated text mode
22303 Translated unicode encoding
22305 @item @emph{U16TEXT}
22307 Unicode 16-bit encoding
22309 @item @emph{U8TEXT}
22311 Unicode 8-bit encoding
22314 This encoding is only supported on the Windows platform.
22316 @node Open Modes,Operations on C Streams,File content encoding,The Implementation of Standard I/O
22317 @anchor{gnat_rm/the_implementation_of_standard_i_o open-modes}@anchor{2c4}@anchor{gnat_rm/the_implementation_of_standard_i_o id24}@anchor{2c5}
22318 @section Open Modes
22321 @code{Open} and @code{Create} calls result in a call to @code{fopen}
22322 using the mode shown in the following table:
22325 @multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxx}
22328 @code{Open} and @code{Create} Call Modes
22370 Out_File (Direct_IO)
22382 Out_File (all other cases)
22407 If text file translation is required, then either @code{b} or @code{t}
22408 is added to the mode, depending on the setting of Text. Text file
22409 translation refers to the mapping of CR/LF sequences in an external file
22410 to LF characters internally. This mapping only occurs in DOS and
22411 DOS-like systems, and is not relevant to other systems.
22413 A special case occurs with Stream_IO. As shown in the above table, the
22414 file is initially opened in @code{r} or @code{w} mode for the
22415 @code{In_File} and @code{Out_File} cases. If a @code{Set_Mode} operation
22416 subsequently requires switching from reading to writing or vice-versa,
22417 then the file is reopened in @code{r+} mode to permit the required operation.
22419 @node Operations on C Streams,Interfacing to C Streams,Open Modes,The Implementation of Standard I/O
22420 @anchor{gnat_rm/the_implementation_of_standard_i_o operations-on-c-streams}@anchor{2c6}@anchor{gnat_rm/the_implementation_of_standard_i_o id25}@anchor{2c7}
22421 @section Operations on C Streams
22424 The package @code{Interfaces.C_Streams} provides an Ada program with direct
22425 access to the C library functions for operations on C streams:
22428 package Interfaces.C_Streams is
22429 -- Note: the reason we do not use the types that are in
22430 -- Interfaces.C is that we want to avoid dragging in the
22431 -- code in this unit if possible.
22432 subtype chars is System.Address;
22433 -- Pointer to null-terminated array of characters
22434 subtype FILEs is System.Address;
22435 -- Corresponds to the C type FILE*
22436 subtype voids is System.Address;
22437 -- Corresponds to the C type void*
22438 subtype int is Integer;
22439 subtype long is Long_Integer;
22440 -- Note: the above types are subtypes deliberately, and it
22441 -- is part of this spec that the above correspondences are
22442 -- guaranteed. This means that it is legitimate to, for
22443 -- example, use Integer instead of int. We provide these
22444 -- synonyms for clarity, but in some cases it may be
22445 -- convenient to use the underlying types (for example to
22446 -- avoid an unnecessary dependency of a spec on the spec
22448 type size_t is mod 2 ** Standard'Address_Size;
22449 NULL_Stream : constant FILEs;
22450 -- Value returned (NULL in C) to indicate an
22451 -- fdopen/fopen/tmpfile error
22452 ----------------------------------
22453 -- Constants Defined in stdio.h --
22454 ----------------------------------
22455 EOF : constant int;
22456 -- Used by a number of routines to indicate error or
22458 IOFBF : constant int;
22459 IOLBF : constant int;
22460 IONBF : constant int;
22461 -- Used to indicate buffering mode for setvbuf call
22462 SEEK_CUR : constant int;
22463 SEEK_END : constant int;
22464 SEEK_SET : constant int;
22465 -- Used to indicate origin for fseek call
22466 function stdin return FILEs;
22467 function stdout return FILEs;
22468 function stderr return FILEs;
22469 -- Streams associated with standard files
22470 --------------------------
22471 -- Standard C functions --
22472 --------------------------
22473 -- The functions selected below are ones that are
22474 -- available in UNIX (but not necessarily in ANSI C).
22475 -- These are very thin interfaces
22476 -- which copy exactly the C headers. For more
22477 -- documentation on these functions, see the Microsoft C
22478 -- "Run-Time Library Reference" (Microsoft Press, 1990,
22479 -- ISBN 1-55615-225-6), which includes useful information
22480 -- on system compatibility.
22481 procedure clearerr (stream : FILEs);
22482 function fclose (stream : FILEs) return int;
22483 function fdopen (handle : int; mode : chars) return FILEs;
22484 function feof (stream : FILEs) return int;
22485 function ferror (stream : FILEs) return int;
22486 function fflush (stream : FILEs) return int;
22487 function fgetc (stream : FILEs) return int;
22488 function fgets (strng : chars; n : int; stream : FILEs)
22490 function fileno (stream : FILEs) return int;
22491 function fopen (filename : chars; Mode : chars)
22493 -- Note: to maintain target independence, use
22494 -- text_translation_required, a boolean variable defined in
22495 -- a-sysdep.c to deal with the target dependent text
22496 -- translation requirement. If this variable is set,
22497 -- then b/t should be appended to the standard mode
22498 -- argument to set the text translation mode off or on
22500 function fputc (C : int; stream : FILEs) return int;
22501 function fputs (Strng : chars; Stream : FILEs) return int;
22518 function ftell (stream : FILEs) return long;
22525 function isatty (handle : int) return int;
22526 procedure mktemp (template : chars);
22527 -- The return value (which is just a pointer to template)
22529 procedure rewind (stream : FILEs);
22530 function rmtmp return int;
22538 function tmpfile return FILEs;
22539 function ungetc (c : int; stream : FILEs) return int;
22540 function unlink (filename : chars) return int;
22541 ---------------------
22542 -- Extra functions --
22543 ---------------------
22544 -- These functions supply slightly thicker bindings than
22545 -- those above. They are derived from functions in the
22546 -- C Run-Time Library, but may do a bit more work than
22547 -- just directly calling one of the Library functions.
22548 function is_regular_file (handle : int) return int;
22549 -- Tests if given handle is for a regular file (result 1)
22550 -- or for a non-regular file (pipe or device, result 0).
22551 ---------------------------------
22552 -- Control of Text/Binary Mode --
22553 ---------------------------------
22554 -- If text_translation_required is true, then the following
22555 -- functions may be used to dynamically switch a file from
22556 -- binary to text mode or vice versa. These functions have
22557 -- no effect if text_translation_required is false (i.e., in
22558 -- normal UNIX mode). Use fileno to get a stream handle.
22559 procedure set_binary_mode (handle : int);
22560 procedure set_text_mode (handle : int);
22561 ----------------------------
22562 -- Full Path Name support --
22563 ----------------------------
22564 procedure full_name (nam : chars; buffer : chars);
22565 -- Given a NUL terminated string representing a file
22566 -- name, returns in buffer a NUL terminated string
22567 -- representing the full path name for the file name.
22568 -- On systems where it is relevant the drive is also
22569 -- part of the full path name. It is the responsibility
22570 -- of the caller to pass an actual parameter for buffer
22571 -- that is big enough for any full path name. Use
22572 -- max_path_len given below as the size of buffer.
22573 max_path_len : integer;
22574 -- Maximum length of an allowable full path name on the
22575 -- system, including a terminating NUL character.
22576 end Interfaces.C_Streams;
22579 @node Interfacing to C Streams,,Operations on C Streams,The Implementation of Standard I/O
22580 @anchor{gnat_rm/the_implementation_of_standard_i_o interfacing-to-c-streams}@anchor{2c8}@anchor{gnat_rm/the_implementation_of_standard_i_o id26}@anchor{2c9}
22581 @section Interfacing to C Streams
22584 The packages in this section permit interfacing Ada files to C Stream
22588 with Interfaces.C_Streams;
22589 package Ada.Sequential_IO.C_Streams is
22590 function C_Stream (F : File_Type)
22591 return Interfaces.C_Streams.FILEs;
22593 (File : in out File_Type;
22594 Mode : in File_Mode;
22595 C_Stream : in Interfaces.C_Streams.FILEs;
22596 Form : in String := "");
22597 end Ada.Sequential_IO.C_Streams;
22599 with Interfaces.C_Streams;
22600 package Ada.Direct_IO.C_Streams is
22601 function C_Stream (F : File_Type)
22602 return Interfaces.C_Streams.FILEs;
22604 (File : in out File_Type;
22605 Mode : in File_Mode;
22606 C_Stream : in Interfaces.C_Streams.FILEs;
22607 Form : in String := "");
22608 end Ada.Direct_IO.C_Streams;
22610 with Interfaces.C_Streams;
22611 package Ada.Text_IO.C_Streams is
22612 function C_Stream (F : File_Type)
22613 return Interfaces.C_Streams.FILEs;
22615 (File : in out File_Type;
22616 Mode : in File_Mode;
22617 C_Stream : in Interfaces.C_Streams.FILEs;
22618 Form : in String := "");
22619 end Ada.Text_IO.C_Streams;
22621 with Interfaces.C_Streams;
22622 package Ada.Wide_Text_IO.C_Streams is
22623 function C_Stream (F : File_Type)
22624 return Interfaces.C_Streams.FILEs;
22626 (File : in out File_Type;
22627 Mode : in File_Mode;
22628 C_Stream : in Interfaces.C_Streams.FILEs;
22629 Form : in String := "");
22630 end Ada.Wide_Text_IO.C_Streams;
22632 with Interfaces.C_Streams;
22633 package Ada.Wide_Wide_Text_IO.C_Streams is
22634 function C_Stream (F : File_Type)
22635 return Interfaces.C_Streams.FILEs;
22637 (File : in out File_Type;
22638 Mode : in File_Mode;
22639 C_Stream : in Interfaces.C_Streams.FILEs;
22640 Form : in String := "");
22641 end Ada.Wide_Wide_Text_IO.C_Streams;
22643 with Interfaces.C_Streams;
22644 package Ada.Stream_IO.C_Streams is
22645 function C_Stream (F : File_Type)
22646 return Interfaces.C_Streams.FILEs;
22648 (File : in out File_Type;
22649 Mode : in File_Mode;
22650 C_Stream : in Interfaces.C_Streams.FILEs;
22651 Form : in String := "");
22652 end Ada.Stream_IO.C_Streams;
22655 In each of these six packages, the @code{C_Stream} function obtains the
22656 @code{FILE} pointer from a currently opened Ada file. It is then
22657 possible to use the @code{Interfaces.C_Streams} package to operate on
22658 this stream, or the stream can be passed to a C program which can
22659 operate on it directly. Of course the program is responsible for
22660 ensuring that only appropriate sequences of operations are executed.
22662 One particular use of relevance to an Ada program is that the
22663 @code{setvbuf} function can be used to control the buffering of the
22664 stream used by an Ada file. In the absence of such a call the standard
22665 default buffering is used.
22667 The @code{Open} procedures in these packages open a file giving an
22668 existing C Stream instead of a file name. Typically this stream is
22669 imported from a C program, allowing an Ada file to operate on an
22672 @node The GNAT Library,Interfacing to Other Languages,The Implementation of Standard I/O,Top
22673 @anchor{gnat_rm/the_gnat_library the-gnat-library}@anchor{10}@anchor{gnat_rm/the_gnat_library doc}@anchor{2ca}@anchor{gnat_rm/the_gnat_library id1}@anchor{2cb}
22674 @chapter The GNAT Library
22677 The GNAT library contains a number of general and special purpose packages.
22678 It represents functionality that the GNAT developers have found useful, and
22679 which is made available to GNAT users. The packages described here are fully
22680 supported, and upwards compatibility will be maintained in future releases,
22681 so you can use these facilities with the confidence that the same functionality
22682 will be available in future releases.
22684 The chapter here simply gives a brief summary of the facilities available.
22685 The full documentation is found in the spec file for the package. The full
22686 sources of these library packages, including both spec and body, are provided
22687 with all GNAT releases. For example, to find out the full specifications of
22688 the SPITBOL pattern matching capability, including a full tutorial and
22689 extensive examples, look in the @code{g-spipat.ads} file in the library.
22691 For each entry here, the package name (as it would appear in a @code{with}
22692 clause) is given, followed by the name of the corresponding spec file in
22693 parentheses. The packages are children in four hierarchies, @code{Ada},
22694 @code{Interfaces}, @code{System}, and @code{GNAT}, the latter being a
22695 GNAT-specific hierarchy.
22697 Note that an application program should only use packages in one of these
22698 four hierarchies if the package is defined in the Ada Reference Manual,
22699 or is listed in this section of the GNAT Programmers Reference Manual.
22700 All other units should be considered internal implementation units and
22701 should not be directly @code{with}ed by application code. The use of
22702 a @code{with} clause that references one of these internal implementation
22703 units makes an application potentially dependent on changes in versions
22704 of GNAT, and will generate a warning message.
22707 * Ada.Characters.Latin_9 (a-chlat9.ads): Ada Characters Latin_9 a-chlat9 ads.
22708 * Ada.Characters.Wide_Latin_1 (a-cwila1.ads): Ada Characters Wide_Latin_1 a-cwila1 ads.
22709 * Ada.Characters.Wide_Latin_9 (a-cwila1.ads): Ada Characters Wide_Latin_9 a-cwila1 ads.
22710 * Ada.Characters.Wide_Wide_Latin_1 (a-chzla1.ads): Ada Characters Wide_Wide_Latin_1 a-chzla1 ads.
22711 * Ada.Characters.Wide_Wide_Latin_9 (a-chzla9.ads): Ada Characters Wide_Wide_Latin_9 a-chzla9 ads.
22712 * Ada.Containers.Formal_Doubly_Linked_Lists (a-cfdlli.ads): Ada Containers Formal_Doubly_Linked_Lists a-cfdlli ads.
22713 * Ada.Containers.Formal_Hashed_Maps (a-cfhama.ads): Ada Containers Formal_Hashed_Maps a-cfhama ads.
22714 * Ada.Containers.Formal_Hashed_Sets (a-cfhase.ads): Ada Containers Formal_Hashed_Sets a-cfhase ads.
22715 * Ada.Containers.Formal_Ordered_Maps (a-cforma.ads): Ada Containers Formal_Ordered_Maps a-cforma ads.
22716 * Ada.Containers.Formal_Ordered_Sets (a-cforse.ads): Ada Containers Formal_Ordered_Sets a-cforse ads.
22717 * Ada.Containers.Formal_Vectors (a-cofove.ads): Ada Containers Formal_Vectors a-cofove ads.
22718 * Ada.Containers.Formal_Indefinite_Vectors (a-cfinve.ads): Ada Containers Formal_Indefinite_Vectors a-cfinve ads.
22719 * Ada.Containers.Functional_Vectors (a-cofuve.ads): Ada Containers Functional_Vectors a-cofuve ads.
22720 * Ada.Containers.Functional_Sets (a-cofuse.ads): Ada Containers Functional_Sets a-cofuse ads.
22721 * Ada.Containers.Functional_Maps (a-cofuma.ads): Ada Containers Functional_Maps a-cofuma ads.
22722 * Ada.Containers.Bounded_Holders (a-coboho.ads): Ada Containers Bounded_Holders a-coboho ads.
22723 * Ada.Command_Line.Environment (a-colien.ads): Ada Command_Line Environment a-colien ads.
22724 * Ada.Command_Line.Remove (a-colire.ads): Ada Command_Line Remove a-colire ads.
22725 * Ada.Command_Line.Response_File (a-clrefi.ads): Ada Command_Line Response_File a-clrefi ads.
22726 * Ada.Direct_IO.C_Streams (a-diocst.ads): Ada Direct_IO C_Streams a-diocst ads.
22727 * Ada.Exceptions.Is_Null_Occurrence (a-einuoc.ads): Ada Exceptions Is_Null_Occurrence a-einuoc ads.
22728 * Ada.Exceptions.Last_Chance_Handler (a-elchha.ads): Ada Exceptions Last_Chance_Handler a-elchha ads.
22729 * Ada.Exceptions.Traceback (a-exctra.ads): Ada Exceptions Traceback a-exctra ads.
22730 * Ada.Sequential_IO.C_Streams (a-siocst.ads): Ada Sequential_IO C_Streams a-siocst ads.
22731 * Ada.Streams.Stream_IO.C_Streams (a-ssicst.ads): Ada Streams Stream_IO C_Streams a-ssicst ads.
22732 * Ada.Strings.Unbounded.Text_IO (a-suteio.ads): Ada Strings Unbounded Text_IO a-suteio ads.
22733 * Ada.Strings.Wide_Unbounded.Wide_Text_IO (a-swuwti.ads): Ada Strings Wide_Unbounded Wide_Text_IO a-swuwti ads.
22734 * Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO (a-szuzti.ads): Ada Strings Wide_Wide_Unbounded Wide_Wide_Text_IO a-szuzti ads.
22735 * Ada.Text_IO.C_Streams (a-tiocst.ads): Ada Text_IO C_Streams a-tiocst ads.
22736 * Ada.Text_IO.Reset_Standard_Files (a-tirsfi.ads): Ada Text_IO Reset_Standard_Files a-tirsfi ads.
22737 * Ada.Wide_Characters.Unicode (a-wichun.ads): Ada Wide_Characters Unicode a-wichun ads.
22738 * Ada.Wide_Text_IO.C_Streams (a-wtcstr.ads): Ada Wide_Text_IO C_Streams a-wtcstr ads.
22739 * Ada.Wide_Text_IO.Reset_Standard_Files (a-wrstfi.ads): Ada Wide_Text_IO Reset_Standard_Files a-wrstfi ads.
22740 * Ada.Wide_Wide_Characters.Unicode (a-zchuni.ads): Ada Wide_Wide_Characters Unicode a-zchuni ads.
22741 * Ada.Wide_Wide_Text_IO.C_Streams (a-ztcstr.ads): Ada Wide_Wide_Text_IO C_Streams a-ztcstr ads.
22742 * Ada.Wide_Wide_Text_IO.Reset_Standard_Files (a-zrstfi.ads): Ada Wide_Wide_Text_IO Reset_Standard_Files a-zrstfi ads.
22743 * GNAT.Altivec (g-altive.ads): GNAT Altivec g-altive ads.
22744 * GNAT.Altivec.Conversions (g-altcon.ads): GNAT Altivec Conversions g-altcon ads.
22745 * GNAT.Altivec.Vector_Operations (g-alveop.ads): GNAT Altivec Vector_Operations g-alveop ads.
22746 * GNAT.Altivec.Vector_Types (g-alvety.ads): GNAT Altivec Vector_Types g-alvety ads.
22747 * GNAT.Altivec.Vector_Views (g-alvevi.ads): GNAT Altivec Vector_Views g-alvevi ads.
22748 * GNAT.Array_Split (g-arrspl.ads): GNAT Array_Split g-arrspl ads.
22749 * GNAT.AWK (g-awk.ads): GNAT AWK g-awk ads.
22750 * GNAT.Bind_Environment (g-binenv.ads): GNAT Bind_Environment g-binenv ads.
22751 * GNAT.Bounded_Buffers (g-boubuf.ads): GNAT Bounded_Buffers g-boubuf ads.
22752 * GNAT.Bounded_Mailboxes (g-boumai.ads): GNAT Bounded_Mailboxes g-boumai ads.
22753 * GNAT.Bubble_Sort (g-bubsor.ads): GNAT Bubble_Sort g-bubsor ads.
22754 * GNAT.Bubble_Sort_A (g-busora.ads): GNAT Bubble_Sort_A g-busora ads.
22755 * GNAT.Bubble_Sort_G (g-busorg.ads): GNAT Bubble_Sort_G g-busorg ads.
22756 * GNAT.Byte_Order_Mark (g-byorma.ads): GNAT Byte_Order_Mark g-byorma ads.
22757 * GNAT.Byte_Swapping (g-bytswa.ads): GNAT Byte_Swapping g-bytswa ads.
22758 * GNAT.Calendar (g-calend.ads): GNAT Calendar g-calend ads.
22759 * GNAT.Calendar.Time_IO (g-catiio.ads): GNAT Calendar Time_IO g-catiio ads.
22760 * GNAT.CRC32 (g-crc32.ads): GNAT CRC32 g-crc32 ads.
22761 * GNAT.Case_Util (g-casuti.ads): GNAT Case_Util g-casuti ads.
22762 * GNAT.CGI (g-cgi.ads): GNAT CGI g-cgi ads.
22763 * GNAT.CGI.Cookie (g-cgicoo.ads): GNAT CGI Cookie g-cgicoo ads.
22764 * GNAT.CGI.Debug (g-cgideb.ads): GNAT CGI Debug g-cgideb ads.
22765 * GNAT.Command_Line (g-comlin.ads): GNAT Command_Line g-comlin ads.
22766 * GNAT.Compiler_Version (g-comver.ads): GNAT Compiler_Version g-comver ads.
22767 * GNAT.Ctrl_C (g-ctrl_c.ads): GNAT Ctrl_C g-ctrl_c ads.
22768 * GNAT.Current_Exception (g-curexc.ads): GNAT Current_Exception g-curexc ads.
22769 * GNAT.Debug_Pools (g-debpoo.ads): GNAT Debug_Pools g-debpoo ads.
22770 * GNAT.Debug_Utilities (g-debuti.ads): GNAT Debug_Utilities g-debuti ads.
22771 * GNAT.Decode_String (g-decstr.ads): GNAT Decode_String g-decstr ads.
22772 * GNAT.Decode_UTF8_String (g-deutst.ads): GNAT Decode_UTF8_String g-deutst ads.
22773 * GNAT.Directory_Operations (g-dirope.ads): GNAT Directory_Operations g-dirope ads.
22774 * GNAT.Directory_Operations.Iteration (g-diopit.ads): GNAT Directory_Operations Iteration g-diopit ads.
22775 * GNAT.Dynamic_HTables (g-dynhta.ads): GNAT Dynamic_HTables g-dynhta ads.
22776 * GNAT.Dynamic_Tables (g-dyntab.ads): GNAT Dynamic_Tables g-dyntab ads.
22777 * GNAT.Encode_String (g-encstr.ads): GNAT Encode_String g-encstr ads.
22778 * GNAT.Encode_UTF8_String (g-enutst.ads): GNAT Encode_UTF8_String g-enutst ads.
22779 * GNAT.Exception_Actions (g-excact.ads): GNAT Exception_Actions g-excact ads.
22780 * GNAT.Exception_Traces (g-exctra.ads): GNAT Exception_Traces g-exctra ads.
22781 * GNAT.Exceptions (g-expect.ads): GNAT Exceptions g-expect ads.
22782 * GNAT.Expect (g-expect.ads): GNAT Expect g-expect ads.
22783 * GNAT.Expect.TTY (g-exptty.ads): GNAT Expect TTY g-exptty ads.
22784 * GNAT.Float_Control (g-flocon.ads): GNAT Float_Control g-flocon ads.
22785 * GNAT.Formatted_String (g-forstr.ads): GNAT Formatted_String g-forstr ads.
22786 * GNAT.Heap_Sort (g-heasor.ads): GNAT Heap_Sort g-heasor ads.
22787 * GNAT.Heap_Sort_A (g-hesora.ads): GNAT Heap_Sort_A g-hesora ads.
22788 * GNAT.Heap_Sort_G (g-hesorg.ads): GNAT Heap_Sort_G g-hesorg ads.
22789 * GNAT.HTable (g-htable.ads): GNAT HTable g-htable ads.
22790 * GNAT.IO (g-io.ads): GNAT IO g-io ads.
22791 * GNAT.IO_Aux (g-io_aux.ads): GNAT IO_Aux g-io_aux ads.
22792 * GNAT.Lock_Files (g-locfil.ads): GNAT Lock_Files g-locfil ads.
22793 * GNAT.MBBS_Discrete_Random (g-mbdira.ads): GNAT MBBS_Discrete_Random g-mbdira ads.
22794 * GNAT.MBBS_Float_Random (g-mbflra.ads): GNAT MBBS_Float_Random g-mbflra ads.
22795 * GNAT.MD5 (g-md5.ads): GNAT MD5 g-md5 ads.
22796 * GNAT.Memory_Dump (g-memdum.ads): GNAT Memory_Dump g-memdum ads.
22797 * GNAT.Most_Recent_Exception (g-moreex.ads): GNAT Most_Recent_Exception g-moreex ads.
22798 * GNAT.OS_Lib (g-os_lib.ads): GNAT OS_Lib g-os_lib ads.
22799 * GNAT.Perfect_Hash_Generators (g-pehage.ads): GNAT Perfect_Hash_Generators g-pehage ads.
22800 * GNAT.Random_Numbers (g-rannum.ads): GNAT Random_Numbers g-rannum ads.
22801 * GNAT.Regexp (g-regexp.ads): GNAT Regexp g-regexp ads.
22802 * GNAT.Registry (g-regist.ads): GNAT Registry g-regist ads.
22803 * GNAT.Regpat (g-regpat.ads): GNAT Regpat g-regpat ads.
22804 * GNAT.Rewrite_Data (g-rewdat.ads): GNAT Rewrite_Data g-rewdat ads.
22805 * GNAT.Secondary_Stack_Info (g-sestin.ads): GNAT Secondary_Stack_Info g-sestin ads.
22806 * GNAT.Semaphores (g-semaph.ads): GNAT Semaphores g-semaph ads.
22807 * GNAT.Serial_Communications (g-sercom.ads): GNAT Serial_Communications g-sercom ads.
22808 * GNAT.SHA1 (g-sha1.ads): GNAT SHA1 g-sha1 ads.
22809 * GNAT.SHA224 (g-sha224.ads): GNAT SHA224 g-sha224 ads.
22810 * GNAT.SHA256 (g-sha256.ads): GNAT SHA256 g-sha256 ads.
22811 * GNAT.SHA384 (g-sha384.ads): GNAT SHA384 g-sha384 ads.
22812 * GNAT.SHA512 (g-sha512.ads): GNAT SHA512 g-sha512 ads.
22813 * GNAT.Signals (g-signal.ads): GNAT Signals g-signal ads.
22814 * GNAT.Sockets (g-socket.ads): GNAT Sockets g-socket ads.
22815 * GNAT.Source_Info (g-souinf.ads): GNAT Source_Info g-souinf ads.
22816 * GNAT.Spelling_Checker (g-speche.ads): GNAT Spelling_Checker g-speche ads.
22817 * GNAT.Spelling_Checker_Generic (g-spchge.ads): GNAT Spelling_Checker_Generic g-spchge ads.
22818 * GNAT.Spitbol.Patterns (g-spipat.ads): GNAT Spitbol Patterns g-spipat ads.
22819 * GNAT.Spitbol (g-spitbo.ads): GNAT Spitbol g-spitbo ads.
22820 * GNAT.Spitbol.Table_Boolean (g-sptabo.ads): GNAT Spitbol Table_Boolean g-sptabo ads.
22821 * GNAT.Spitbol.Table_Integer (g-sptain.ads): GNAT Spitbol Table_Integer g-sptain ads.
22822 * GNAT.Spitbol.Table_VString (g-sptavs.ads): GNAT Spitbol Table_VString g-sptavs ads.
22823 * GNAT.SSE (g-sse.ads): GNAT SSE g-sse ads.
22824 * GNAT.SSE.Vector_Types (g-ssvety.ads): GNAT SSE Vector_Types g-ssvety ads.
22825 * GNAT.String_Hash (g-strhas.ads): GNAT String_Hash g-strhas ads.
22826 * GNAT.Strings (g-string.ads): GNAT Strings g-string ads.
22827 * GNAT.String_Split (g-strspl.ads): GNAT String_Split g-strspl ads.
22828 * GNAT.Table (g-table.ads): GNAT Table g-table ads.
22829 * GNAT.Task_Lock (g-tasloc.ads): GNAT Task_Lock g-tasloc ads.
22830 * GNAT.Time_Stamp (g-timsta.ads): GNAT Time_Stamp g-timsta ads.
22831 * GNAT.Threads (g-thread.ads): GNAT Threads g-thread ads.
22832 * GNAT.Traceback (g-traceb.ads): GNAT Traceback g-traceb ads.
22833 * GNAT.Traceback.Symbolic (g-trasym.ads): GNAT Traceback Symbolic g-trasym ads.
22834 * GNAT.UTF_32 (g-table.ads): GNAT UTF_32 g-table ads.
22835 * GNAT.Wide_Spelling_Checker (g-u3spch.ads): GNAT Wide_Spelling_Checker g-u3spch ads.
22836 * GNAT.Wide_Spelling_Checker (g-wispch.ads): GNAT Wide_Spelling_Checker g-wispch ads.
22837 * GNAT.Wide_String_Split (g-wistsp.ads): GNAT Wide_String_Split g-wistsp ads.
22838 * GNAT.Wide_Wide_Spelling_Checker (g-zspche.ads): GNAT Wide_Wide_Spelling_Checker g-zspche ads.
22839 * GNAT.Wide_Wide_String_Split (g-zistsp.ads): GNAT Wide_Wide_String_Split g-zistsp ads.
22840 * Interfaces.C.Extensions (i-cexten.ads): Interfaces C Extensions i-cexten ads.
22841 * Interfaces.C.Streams (i-cstrea.ads): Interfaces C Streams i-cstrea ads.
22842 * Interfaces.Packed_Decimal (i-pacdec.ads): Interfaces Packed_Decimal i-pacdec ads.
22843 * Interfaces.VxWorks (i-vxwork.ads): Interfaces VxWorks i-vxwork ads.
22844 * Interfaces.VxWorks.Int_Connection (i-vxinco.ads): Interfaces VxWorks Int_Connection i-vxinco ads.
22845 * Interfaces.VxWorks.IO (i-vxwoio.ads): Interfaces VxWorks IO i-vxwoio ads.
22846 * System.Address_Image (s-addima.ads): System Address_Image s-addima ads.
22847 * System.Assertions (s-assert.ads): System Assertions s-assert ads.
22848 * System.Atomic_Counters (s-atocou.ads): System Atomic_Counters s-atocou ads.
22849 * System.Memory (s-memory.ads): System Memory s-memory ads.
22850 * System.Multiprocessors (s-multip.ads): System Multiprocessors s-multip ads.
22851 * System.Multiprocessors.Dispatching_Domains (s-mudido.ads): System Multiprocessors Dispatching_Domains s-mudido ads.
22852 * System.Partition_Interface (s-parint.ads): System Partition_Interface s-parint ads.
22853 * System.Pool_Global (s-pooglo.ads): System Pool_Global s-pooglo ads.
22854 * System.Pool_Local (s-pooloc.ads): System Pool_Local s-pooloc ads.
22855 * System.Restrictions (s-restri.ads): System Restrictions s-restri ads.
22856 * System.Rident (s-rident.ads): System Rident s-rident ads.
22857 * System.Strings.Stream_Ops (s-ststop.ads): System Strings Stream_Ops s-ststop ads.
22858 * System.Unsigned_Types (s-unstyp.ads): System Unsigned_Types s-unstyp ads.
22859 * System.Wch_Cnv (s-wchcnv.ads): System Wch_Cnv s-wchcnv ads.
22860 * System.Wch_Con (s-wchcon.ads): System Wch_Con s-wchcon ads.
22864 @node Ada Characters Latin_9 a-chlat9 ads,Ada Characters Wide_Latin_1 a-cwila1 ads,,The GNAT Library
22865 @anchor{gnat_rm/the_gnat_library id2}@anchor{2cc}@anchor{gnat_rm/the_gnat_library ada-characters-latin-9-a-chlat9-ads}@anchor{2cd}
22866 @section @code{Ada.Characters.Latin_9} (@code{a-chlat9.ads})
22869 @geindex Ada.Characters.Latin_9 (a-chlat9.ads)
22871 @geindex Latin_9 constants for Character
22873 This child of @code{Ada.Characters}
22874 provides a set of definitions corresponding to those in the
22875 RM-defined package @code{Ada.Characters.Latin_1} but with the
22876 few modifications required for @code{Latin-9}
22877 The provision of such a package
22878 is specifically authorized by the Ada Reference Manual
22881 @node Ada Characters Wide_Latin_1 a-cwila1 ads,Ada Characters Wide_Latin_9 a-cwila1 ads,Ada Characters Latin_9 a-chlat9 ads,The GNAT Library
22882 @anchor{gnat_rm/the_gnat_library ada-characters-wide-latin-1-a-cwila1-ads}@anchor{2ce}@anchor{gnat_rm/the_gnat_library id3}@anchor{2cf}
22883 @section @code{Ada.Characters.Wide_Latin_1} (@code{a-cwila1.ads})
22886 @geindex Ada.Characters.Wide_Latin_1 (a-cwila1.ads)
22888 @geindex Latin_1 constants for Wide_Character
22890 This child of @code{Ada.Characters}
22891 provides a set of definitions corresponding to those in the
22892 RM-defined package @code{Ada.Characters.Latin_1} but with the
22893 types of the constants being @code{Wide_Character}
22894 instead of @code{Character}. The provision of such a package
22895 is specifically authorized by the Ada Reference Manual
22898 @node Ada Characters Wide_Latin_9 a-cwila1 ads,Ada Characters Wide_Wide_Latin_1 a-chzla1 ads,Ada Characters Wide_Latin_1 a-cwila1 ads,The GNAT Library
22899 @anchor{gnat_rm/the_gnat_library id4}@anchor{2d0}@anchor{gnat_rm/the_gnat_library ada-characters-wide-latin-9-a-cwila1-ads}@anchor{2d1}
22900 @section @code{Ada.Characters.Wide_Latin_9} (@code{a-cwila1.ads})
22903 @geindex Ada.Characters.Wide_Latin_9 (a-cwila1.ads)
22905 @geindex Latin_9 constants for Wide_Character
22907 This child of @code{Ada.Characters}
22908 provides a set of definitions corresponding to those in the
22909 GNAT defined package @code{Ada.Characters.Latin_9} but with the
22910 types of the constants being @code{Wide_Character}
22911 instead of @code{Character}. The provision of such a package
22912 is specifically authorized by the Ada Reference Manual
22915 @node Ada Characters Wide_Wide_Latin_1 a-chzla1 ads,Ada Characters Wide_Wide_Latin_9 a-chzla9 ads,Ada Characters Wide_Latin_9 a-cwila1 ads,The GNAT Library
22916 @anchor{gnat_rm/the_gnat_library ada-characters-wide-wide-latin-1-a-chzla1-ads}@anchor{2d2}@anchor{gnat_rm/the_gnat_library id5}@anchor{2d3}
22917 @section @code{Ada.Characters.Wide_Wide_Latin_1} (@code{a-chzla1.ads})
22920 @geindex Ada.Characters.Wide_Wide_Latin_1 (a-chzla1.ads)
22922 @geindex Latin_1 constants for Wide_Wide_Character
22924 This child of @code{Ada.Characters}
22925 provides a set of definitions corresponding to those in the
22926 RM-defined package @code{Ada.Characters.Latin_1} but with the
22927 types of the constants being @code{Wide_Wide_Character}
22928 instead of @code{Character}. The provision of such a package
22929 is specifically authorized by the Ada Reference Manual
22932 @node Ada Characters Wide_Wide_Latin_9 a-chzla9 ads,Ada Containers Formal_Doubly_Linked_Lists a-cfdlli ads,Ada Characters Wide_Wide_Latin_1 a-chzla1 ads,The GNAT Library
22933 @anchor{gnat_rm/the_gnat_library ada-characters-wide-wide-latin-9-a-chzla9-ads}@anchor{2d4}@anchor{gnat_rm/the_gnat_library id6}@anchor{2d5}
22934 @section @code{Ada.Characters.Wide_Wide_Latin_9} (@code{a-chzla9.ads})
22937 @geindex Ada.Characters.Wide_Wide_Latin_9 (a-chzla9.ads)
22939 @geindex Latin_9 constants for Wide_Wide_Character
22941 This child of @code{Ada.Characters}
22942 provides a set of definitions corresponding to those in the
22943 GNAT defined package @code{Ada.Characters.Latin_9} but with the
22944 types of the constants being @code{Wide_Wide_Character}
22945 instead of @code{Character}. The provision of such a package
22946 is specifically authorized by the Ada Reference Manual
22949 @node Ada Containers Formal_Doubly_Linked_Lists a-cfdlli ads,Ada Containers Formal_Hashed_Maps a-cfhama ads,Ada Characters Wide_Wide_Latin_9 a-chzla9 ads,The GNAT Library
22950 @anchor{gnat_rm/the_gnat_library id7}@anchor{2d6}@anchor{gnat_rm/the_gnat_library ada-containers-formal-doubly-linked-lists-a-cfdlli-ads}@anchor{2d7}
22951 @section @code{Ada.Containers.Formal_Doubly_Linked_Lists} (@code{a-cfdlli.ads})
22954 @geindex Ada.Containers.Formal_Doubly_Linked_Lists (a-cfdlli.ads)
22956 @geindex Formal container for doubly linked lists
22958 This child of @code{Ada.Containers} defines a modified version of the
22959 Ada 2005 container for doubly linked lists, meant to facilitate formal
22960 verification of code using such containers. The specification of this
22961 unit is compatible with SPARK 2014.
22963 Note that although this container was designed with formal verification
22964 in mind, it may well be generally useful in that it is a simplified more
22965 efficient version than the one defined in the standard. In particular it
22966 does not have the complex overhead required to detect cursor tampering.
22968 @node Ada Containers Formal_Hashed_Maps a-cfhama ads,Ada Containers Formal_Hashed_Sets a-cfhase ads,Ada Containers Formal_Doubly_Linked_Lists a-cfdlli ads,The GNAT Library
22969 @anchor{gnat_rm/the_gnat_library id8}@anchor{2d8}@anchor{gnat_rm/the_gnat_library ada-containers-formal-hashed-maps-a-cfhama-ads}@anchor{2d9}
22970 @section @code{Ada.Containers.Formal_Hashed_Maps} (@code{a-cfhama.ads})
22973 @geindex Ada.Containers.Formal_Hashed_Maps (a-cfhama.ads)
22975 @geindex Formal container for hashed maps
22977 This child of @code{Ada.Containers} defines a modified version of the
22978 Ada 2005 container for hashed maps, meant to facilitate formal
22979 verification of code using such containers. The specification of this
22980 unit is compatible with SPARK 2014.
22982 Note that although this container was designed with formal verification
22983 in mind, it may well be generally useful in that it is a simplified more
22984 efficient version than the one defined in the standard. In particular it
22985 does not have the complex overhead required to detect cursor tampering.
22987 @node Ada Containers Formal_Hashed_Sets a-cfhase ads,Ada Containers Formal_Ordered_Maps a-cforma ads,Ada Containers Formal_Hashed_Maps a-cfhama ads,The GNAT Library
22988 @anchor{gnat_rm/the_gnat_library id9}@anchor{2da}@anchor{gnat_rm/the_gnat_library ada-containers-formal-hashed-sets-a-cfhase-ads}@anchor{2db}
22989 @section @code{Ada.Containers.Formal_Hashed_Sets} (@code{a-cfhase.ads})
22992 @geindex Ada.Containers.Formal_Hashed_Sets (a-cfhase.ads)
22994 @geindex Formal container for hashed sets
22996 This child of @code{Ada.Containers} defines a modified version of the
22997 Ada 2005 container for hashed sets, meant to facilitate formal
22998 verification of code using such containers. The specification of this
22999 unit is compatible with SPARK 2014.
23001 Note that although this container was designed with formal verification
23002 in mind, it may well be generally useful in that it is a simplified more
23003 efficient version than the one defined in the standard. In particular it
23004 does not have the complex overhead required to detect cursor tampering.
23006 @node Ada Containers Formal_Ordered_Maps a-cforma ads,Ada Containers Formal_Ordered_Sets a-cforse ads,Ada Containers Formal_Hashed_Sets a-cfhase ads,The GNAT Library
23007 @anchor{gnat_rm/the_gnat_library id10}@anchor{2dc}@anchor{gnat_rm/the_gnat_library ada-containers-formal-ordered-maps-a-cforma-ads}@anchor{2dd}
23008 @section @code{Ada.Containers.Formal_Ordered_Maps} (@code{a-cforma.ads})
23011 @geindex Ada.Containers.Formal_Ordered_Maps (a-cforma.ads)
23013 @geindex Formal container for ordered maps
23015 This child of @code{Ada.Containers} defines a modified version of the
23016 Ada 2005 container for ordered maps, meant to facilitate formal
23017 verification of code using such containers. The specification of this
23018 unit is compatible with SPARK 2014.
23020 Note that although this container was designed with formal verification
23021 in mind, it may well be generally useful in that it is a simplified more
23022 efficient version than the one defined in the standard. In particular it
23023 does not have the complex overhead required to detect cursor tampering.
23025 @node Ada Containers Formal_Ordered_Sets a-cforse ads,Ada Containers Formal_Vectors a-cofove ads,Ada Containers Formal_Ordered_Maps a-cforma ads,The GNAT Library
23026 @anchor{gnat_rm/the_gnat_library ada-containers-formal-ordered-sets-a-cforse-ads}@anchor{2de}@anchor{gnat_rm/the_gnat_library id11}@anchor{2df}
23027 @section @code{Ada.Containers.Formal_Ordered_Sets} (@code{a-cforse.ads})
23030 @geindex Ada.Containers.Formal_Ordered_Sets (a-cforse.ads)
23032 @geindex Formal container for ordered sets
23034 This child of @code{Ada.Containers} defines a modified version of the
23035 Ada 2005 container for ordered sets, meant to facilitate formal
23036 verification of code using such containers. The specification of this
23037 unit is compatible with SPARK 2014.
23039 Note that although this container was designed with formal verification
23040 in mind, it may well be generally useful in that it is a simplified more
23041 efficient version than the one defined in the standard. In particular it
23042 does not have the complex overhead required to detect cursor tampering.
23044 @node Ada Containers Formal_Vectors a-cofove ads,Ada Containers Formal_Indefinite_Vectors a-cfinve ads,Ada Containers Formal_Ordered_Sets a-cforse ads,The GNAT Library
23045 @anchor{gnat_rm/the_gnat_library id12}@anchor{2e0}@anchor{gnat_rm/the_gnat_library ada-containers-formal-vectors-a-cofove-ads}@anchor{2e1}
23046 @section @code{Ada.Containers.Formal_Vectors} (@code{a-cofove.ads})
23049 @geindex Ada.Containers.Formal_Vectors (a-cofove.ads)
23051 @geindex Formal container for vectors
23053 This child of @code{Ada.Containers} defines a modified version of the
23054 Ada 2005 container for vectors, meant to facilitate formal
23055 verification of code using such containers. The specification of this
23056 unit is compatible with SPARK 2014.
23058 Note that although this container was designed with formal verification
23059 in mind, it may well be generally useful in that it is a simplified more
23060 efficient version than the one defined in the standard. In particular it
23061 does not have the complex overhead required to detect cursor tampering.
23063 @node Ada Containers Formal_Indefinite_Vectors a-cfinve ads,Ada Containers Functional_Vectors a-cofuve ads,Ada Containers Formal_Vectors a-cofove ads,The GNAT Library
23064 @anchor{gnat_rm/the_gnat_library id13}@anchor{2e2}@anchor{gnat_rm/the_gnat_library ada-containers-formal-indefinite-vectors-a-cfinve-ads}@anchor{2e3}
23065 @section @code{Ada.Containers.Formal_Indefinite_Vectors} (@code{a-cfinve.ads})
23068 @geindex Ada.Containers.Formal_Indefinite_Vectors (a-cfinve.ads)
23070 @geindex Formal container for vectors
23072 This child of @code{Ada.Containers} defines a modified version of the
23073 Ada 2005 container for vectors of indefinite elements, meant to
23074 facilitate formal verification of code using such containers. The
23075 specification of this unit is compatible with SPARK 2014.
23077 Note that although this container was designed with formal verification
23078 in mind, it may well be generally useful in that it is a simplified more
23079 efficient version than the one defined in the standard. In particular it
23080 does not have the complex overhead required to detect cursor tampering.
23082 @node Ada Containers Functional_Vectors a-cofuve ads,Ada Containers Functional_Sets a-cofuse ads,Ada Containers Formal_Indefinite_Vectors a-cfinve ads,The GNAT Library
23083 @anchor{gnat_rm/the_gnat_library id14}@anchor{2e4}@anchor{gnat_rm/the_gnat_library ada-containers-functional-vectors-a-cofuve-ads}@anchor{2e5}
23084 @section @code{Ada.Containers.Functional_Vectors} (@code{a-cofuve.ads})
23087 @geindex Ada.Containers.Functional_Vectors (a-cofuve.ads)
23089 @geindex Functional vectors
23091 This child of @code{Ada.Containers} defines immutable vectors. These
23092 containers are unbounded and may contain indefinite elements. Furthermore, to
23093 be usable in every context, they are neither controlled nor limited. As they
23094 are functional, that is, no primitives are provided which would allow modifying
23095 an existing container, these containers can still be used safely.
23097 Their API features functions creating new containers from existing ones.
23098 As a consequence, these containers are highly inefficient. They are also
23099 memory consuming, as the allocated memory is not reclaimed when the container
23100 is no longer referenced. Thus, they should in general be used in ghost code
23101 and annotations, so that they can be removed from the final executable. The
23102 specification of this unit is compatible with SPARK 2014.
23104 @node Ada Containers Functional_Sets a-cofuse ads,Ada Containers Functional_Maps a-cofuma ads,Ada Containers Functional_Vectors a-cofuve ads,The GNAT Library
23105 @anchor{gnat_rm/the_gnat_library ada-containers-functional-sets-a-cofuse-ads}@anchor{2e6}@anchor{gnat_rm/the_gnat_library id15}@anchor{2e7}
23106 @section @code{Ada.Containers.Functional_Sets} (@code{a-cofuse.ads})
23109 @geindex Ada.Containers.Functional_Sets (a-cofuse.ads)
23111 @geindex Functional sets
23113 This child of @code{Ada.Containers} defines immutable sets. These containers are
23114 unbounded and may contain indefinite elements. Furthermore, to be usable in
23115 every context, they are neither controlled nor limited. As they are functional,
23116 that is, no primitives are provided which would allow modifying an existing
23117 container, these containers can still be used safely.
23119 Their API features functions creating new containers from existing ones.
23120 As a consequence, these containers are highly inefficient. They are also
23121 memory consuming, as the allocated memory is not reclaimed when the container
23122 is no longer referenced. Thus, they should in general be used in ghost code
23123 and annotations, so that they can be removed from the final executable. The
23124 specification of this unit is compatible with SPARK 2014.
23126 @node Ada Containers Functional_Maps a-cofuma ads,Ada Containers Bounded_Holders a-coboho ads,Ada Containers Functional_Sets a-cofuse ads,The GNAT Library
23127 @anchor{gnat_rm/the_gnat_library id16}@anchor{2e8}@anchor{gnat_rm/the_gnat_library ada-containers-functional-maps-a-cofuma-ads}@anchor{2e9}
23128 @section @code{Ada.Containers.Functional_Maps} (@code{a-cofuma.ads})
23131 @geindex Ada.Containers.Functional_Maps (a-cofuma.ads)
23133 @geindex Functional maps
23135 This child of @code{Ada.Containers} defines immutable maps. These containers are
23136 unbounded and may contain indefinite elements. Furthermore, to be usable in
23137 every context, they are neither controlled nor limited. As they are functional,
23138 that is, no primitives are provided which would allow modifying an existing
23139 container, these containers can still be used safely.
23141 Their API features functions creating new containers from existing ones.
23142 As a consequence, these containers are highly inefficient. They are also
23143 memory consuming, as the allocated memory is not reclaimed when the container
23144 is no longer referenced. Thus, they should in general be used in ghost code
23145 and annotations, so that they can be removed from the final executable. The
23146 specification of this unit is compatible with SPARK 2014.
23148 @node Ada Containers Bounded_Holders a-coboho ads,Ada Command_Line Environment a-colien ads,Ada Containers Functional_Maps a-cofuma ads,The GNAT Library
23149 @anchor{gnat_rm/the_gnat_library ada-containers-bounded-holders-a-coboho-ads}@anchor{2ea}@anchor{gnat_rm/the_gnat_library id17}@anchor{2eb}
23150 @section @code{Ada.Containers.Bounded_Holders} (@code{a-coboho.ads})
23153 @geindex Ada.Containers.Bounded_Holders (a-coboho.ads)
23155 @geindex Formal container for vectors
23157 This child of @code{Ada.Containers} defines a modified version of
23158 Indefinite_Holders that avoids heap allocation.
23160 @node Ada Command_Line Environment a-colien ads,Ada Command_Line Remove a-colire ads,Ada Containers Bounded_Holders a-coboho ads,The GNAT Library
23161 @anchor{gnat_rm/the_gnat_library ada-command-line-environment-a-colien-ads}@anchor{2ec}@anchor{gnat_rm/the_gnat_library id18}@anchor{2ed}
23162 @section @code{Ada.Command_Line.Environment} (@code{a-colien.ads})
23165 @geindex Ada.Command_Line.Environment (a-colien.ads)
23167 @geindex Environment entries
23169 This child of @code{Ada.Command_Line}
23170 provides a mechanism for obtaining environment values on systems
23171 where this concept makes sense.
23173 @node Ada Command_Line Remove a-colire ads,Ada Command_Line Response_File a-clrefi ads,Ada Command_Line Environment a-colien ads,The GNAT Library
23174 @anchor{gnat_rm/the_gnat_library id19}@anchor{2ee}@anchor{gnat_rm/the_gnat_library ada-command-line-remove-a-colire-ads}@anchor{2ef}
23175 @section @code{Ada.Command_Line.Remove} (@code{a-colire.ads})
23178 @geindex Ada.Command_Line.Remove (a-colire.ads)
23180 @geindex Removing command line arguments
23182 @geindex Command line
23183 @geindex argument removal
23185 This child of @code{Ada.Command_Line}
23186 provides a mechanism for logically removing
23187 arguments from the argument list. Once removed, an argument is not visible
23188 to further calls on the subprograms in @code{Ada.Command_Line} will not
23189 see the removed argument.
23191 @node Ada Command_Line Response_File a-clrefi ads,Ada Direct_IO C_Streams a-diocst ads,Ada Command_Line Remove a-colire ads,The GNAT Library
23192 @anchor{gnat_rm/the_gnat_library id20}@anchor{2f0}@anchor{gnat_rm/the_gnat_library ada-command-line-response-file-a-clrefi-ads}@anchor{2f1}
23193 @section @code{Ada.Command_Line.Response_File} (@code{a-clrefi.ads})
23196 @geindex Ada.Command_Line.Response_File (a-clrefi.ads)
23198 @geindex Response file for command line
23200 @geindex Command line
23201 @geindex response file
23203 @geindex Command line
23204 @geindex handling long command lines
23206 This child of @code{Ada.Command_Line} provides a mechanism facilities for
23207 getting command line arguments from a text file, called a "response file".
23208 Using a response file allow passing a set of arguments to an executable longer
23209 than the maximum allowed by the system on the command line.
23211 @node Ada Direct_IO C_Streams a-diocst ads,Ada Exceptions Is_Null_Occurrence a-einuoc ads,Ada Command_Line Response_File a-clrefi ads,The GNAT Library
23212 @anchor{gnat_rm/the_gnat_library id21}@anchor{2f2}@anchor{gnat_rm/the_gnat_library ada-direct-io-c-streams-a-diocst-ads}@anchor{2f3}
23213 @section @code{Ada.Direct_IO.C_Streams} (@code{a-diocst.ads})
23216 @geindex Ada.Direct_IO.C_Streams (a-diocst.ads)
23219 @geindex Interfacing with Direct_IO
23221 This package provides subprograms that allow interfacing between
23222 C streams and @code{Direct_IO}. The stream identifier can be
23223 extracted from a file opened on the Ada side, and an Ada file
23224 can be constructed from a stream opened on the C side.
23226 @node Ada Exceptions Is_Null_Occurrence a-einuoc ads,Ada Exceptions Last_Chance_Handler a-elchha ads,Ada Direct_IO C_Streams a-diocst ads,The GNAT Library
23227 @anchor{gnat_rm/the_gnat_library id22}@anchor{2f4}@anchor{gnat_rm/the_gnat_library ada-exceptions-is-null-occurrence-a-einuoc-ads}@anchor{2f5}
23228 @section @code{Ada.Exceptions.Is_Null_Occurrence} (@code{a-einuoc.ads})
23231 @geindex Ada.Exceptions.Is_Null_Occurrence (a-einuoc.ads)
23233 @geindex Null_Occurrence
23234 @geindex testing for
23236 This child subprogram provides a way of testing for the null
23237 exception occurrence (@code{Null_Occurrence}) without raising
23240 @node Ada Exceptions Last_Chance_Handler a-elchha ads,Ada Exceptions Traceback a-exctra ads,Ada Exceptions Is_Null_Occurrence a-einuoc ads,The GNAT Library
23241 @anchor{gnat_rm/the_gnat_library id23}@anchor{2f6}@anchor{gnat_rm/the_gnat_library ada-exceptions-last-chance-handler-a-elchha-ads}@anchor{2f7}
23242 @section @code{Ada.Exceptions.Last_Chance_Handler} (@code{a-elchha.ads})
23245 @geindex Ada.Exceptions.Last_Chance_Handler (a-elchha.ads)
23247 @geindex Null_Occurrence
23248 @geindex testing for
23250 This child subprogram is used for handling otherwise unhandled
23251 exceptions (hence the name last chance), and perform clean ups before
23252 terminating the program. Note that this subprogram never returns.
23254 @node Ada Exceptions Traceback a-exctra ads,Ada Sequential_IO C_Streams a-siocst ads,Ada Exceptions Last_Chance_Handler a-elchha ads,The GNAT Library
23255 @anchor{gnat_rm/the_gnat_library ada-exceptions-traceback-a-exctra-ads}@anchor{2f8}@anchor{gnat_rm/the_gnat_library id24}@anchor{2f9}
23256 @section @code{Ada.Exceptions.Traceback} (@code{a-exctra.ads})
23259 @geindex Ada.Exceptions.Traceback (a-exctra.ads)
23261 @geindex Traceback for Exception Occurrence
23263 This child package provides the subprogram (@code{Tracebacks}) to
23264 give a traceback array of addresses based on an exception
23267 @node Ada Sequential_IO C_Streams a-siocst ads,Ada Streams Stream_IO C_Streams a-ssicst ads,Ada Exceptions Traceback a-exctra ads,The GNAT Library
23268 @anchor{gnat_rm/the_gnat_library ada-sequential-io-c-streams-a-siocst-ads}@anchor{2fa}@anchor{gnat_rm/the_gnat_library id25}@anchor{2fb}
23269 @section @code{Ada.Sequential_IO.C_Streams} (@code{a-siocst.ads})
23272 @geindex Ada.Sequential_IO.C_Streams (a-siocst.ads)
23275 @geindex Interfacing with Sequential_IO
23277 This package provides subprograms that allow interfacing between
23278 C streams and @code{Sequential_IO}. The stream identifier can be
23279 extracted from a file opened on the Ada side, and an Ada file
23280 can be constructed from a stream opened on the C side.
23282 @node Ada Streams Stream_IO C_Streams a-ssicst ads,Ada Strings Unbounded Text_IO a-suteio ads,Ada Sequential_IO C_Streams a-siocst ads,The GNAT Library
23283 @anchor{gnat_rm/the_gnat_library id26}@anchor{2fc}@anchor{gnat_rm/the_gnat_library ada-streams-stream-io-c-streams-a-ssicst-ads}@anchor{2fd}
23284 @section @code{Ada.Streams.Stream_IO.C_Streams} (@code{a-ssicst.ads})
23287 @geindex Ada.Streams.Stream_IO.C_Streams (a-ssicst.ads)
23290 @geindex Interfacing with Stream_IO
23292 This package provides subprograms that allow interfacing between
23293 C streams and @code{Stream_IO}. The stream identifier can be
23294 extracted from a file opened on the Ada side, and an Ada file
23295 can be constructed from a stream opened on the C side.
23297 @node Ada Strings Unbounded Text_IO a-suteio ads,Ada Strings Wide_Unbounded Wide_Text_IO a-swuwti ads,Ada Streams Stream_IO C_Streams a-ssicst ads,The GNAT Library
23298 @anchor{gnat_rm/the_gnat_library ada-strings-unbounded-text-io-a-suteio-ads}@anchor{2fe}@anchor{gnat_rm/the_gnat_library id27}@anchor{2ff}
23299 @section @code{Ada.Strings.Unbounded.Text_IO} (@code{a-suteio.ads})
23302 @geindex Ada.Strings.Unbounded.Text_IO (a-suteio.ads)
23304 @geindex Unbounded_String
23305 @geindex IO support
23308 @geindex extensions for unbounded strings
23310 This package provides subprograms for Text_IO for unbounded
23311 strings, avoiding the necessity for an intermediate operation
23312 with ordinary strings.
23314 @node Ada Strings Wide_Unbounded Wide_Text_IO a-swuwti ads,Ada Strings Wide_Wide_Unbounded Wide_Wide_Text_IO a-szuzti ads,Ada Strings Unbounded Text_IO a-suteio ads,The GNAT Library
23315 @anchor{gnat_rm/the_gnat_library id28}@anchor{300}@anchor{gnat_rm/the_gnat_library ada-strings-wide-unbounded-wide-text-io-a-swuwti-ads}@anchor{301}
23316 @section @code{Ada.Strings.Wide_Unbounded.Wide_Text_IO} (@code{a-swuwti.ads})
23319 @geindex Ada.Strings.Wide_Unbounded.Wide_Text_IO (a-swuwti.ads)
23321 @geindex Unbounded_Wide_String
23322 @geindex IO support
23325 @geindex extensions for unbounded wide strings
23327 This package provides subprograms for Text_IO for unbounded
23328 wide strings, avoiding the necessity for an intermediate operation
23329 with ordinary wide strings.
23331 @node Ada Strings Wide_Wide_Unbounded Wide_Wide_Text_IO a-szuzti ads,Ada Text_IO C_Streams a-tiocst ads,Ada Strings Wide_Unbounded Wide_Text_IO a-swuwti ads,The GNAT Library
23332 @anchor{gnat_rm/the_gnat_library id29}@anchor{302}@anchor{gnat_rm/the_gnat_library ada-strings-wide-wide-unbounded-wide-wide-text-io-a-szuzti-ads}@anchor{303}
23333 @section @code{Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO} (@code{a-szuzti.ads})
23336 @geindex Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO (a-szuzti.ads)
23338 @geindex Unbounded_Wide_Wide_String
23339 @geindex IO support
23342 @geindex extensions for unbounded wide wide strings
23344 This package provides subprograms for Text_IO for unbounded
23345 wide wide strings, avoiding the necessity for an intermediate operation
23346 with ordinary wide wide strings.
23348 @node Ada Text_IO C_Streams a-tiocst ads,Ada Text_IO Reset_Standard_Files a-tirsfi ads,Ada Strings Wide_Wide_Unbounded Wide_Wide_Text_IO a-szuzti ads,The GNAT Library
23349 @anchor{gnat_rm/the_gnat_library ada-text-io-c-streams-a-tiocst-ads}@anchor{304}@anchor{gnat_rm/the_gnat_library id30}@anchor{305}
23350 @section @code{Ada.Text_IO.C_Streams} (@code{a-tiocst.ads})
23353 @geindex Ada.Text_IO.C_Streams (a-tiocst.ads)
23356 @geindex Interfacing with `@w{`}Text_IO`@w{`}
23358 This package provides subprograms that allow interfacing between
23359 C streams and @code{Text_IO}. The stream identifier can be
23360 extracted from a file opened on the Ada side, and an Ada file
23361 can be constructed from a stream opened on the C side.
23363 @node Ada Text_IO Reset_Standard_Files a-tirsfi ads,Ada Wide_Characters Unicode a-wichun ads,Ada Text_IO C_Streams a-tiocst ads,The GNAT Library
23364 @anchor{gnat_rm/the_gnat_library ada-text-io-reset-standard-files-a-tirsfi-ads}@anchor{306}@anchor{gnat_rm/the_gnat_library id31}@anchor{307}
23365 @section @code{Ada.Text_IO.Reset_Standard_Files} (@code{a-tirsfi.ads})
23368 @geindex Ada.Text_IO.Reset_Standard_Files (a-tirsfi.ads)
23370 @geindex Text_IO resetting standard files
23372 This procedure is used to reset the status of the standard files used
23373 by Ada.Text_IO. This is useful in a situation (such as a restart in an
23374 embedded application) where the status of the files may change during
23375 execution (for example a standard input file may be redefined to be
23378 @node Ada Wide_Characters Unicode a-wichun ads,Ada Wide_Text_IO C_Streams a-wtcstr ads,Ada Text_IO Reset_Standard_Files a-tirsfi ads,The GNAT Library
23379 @anchor{gnat_rm/the_gnat_library id32}@anchor{308}@anchor{gnat_rm/the_gnat_library ada-wide-characters-unicode-a-wichun-ads}@anchor{309}
23380 @section @code{Ada.Wide_Characters.Unicode} (@code{a-wichun.ads})
23383 @geindex Ada.Wide_Characters.Unicode (a-wichun.ads)
23385 @geindex Unicode categorization
23386 @geindex Wide_Character
23388 This package provides subprograms that allow categorization of
23389 Wide_Character values according to Unicode categories.
23391 @node Ada Wide_Text_IO C_Streams a-wtcstr ads,Ada Wide_Text_IO Reset_Standard_Files a-wrstfi ads,Ada Wide_Characters Unicode a-wichun ads,The GNAT Library
23392 @anchor{gnat_rm/the_gnat_library ada-wide-text-io-c-streams-a-wtcstr-ads}@anchor{30a}@anchor{gnat_rm/the_gnat_library id33}@anchor{30b}
23393 @section @code{Ada.Wide_Text_IO.C_Streams} (@code{a-wtcstr.ads})
23396 @geindex Ada.Wide_Text_IO.C_Streams (a-wtcstr.ads)
23399 @geindex Interfacing with `@w{`}Wide_Text_IO`@w{`}
23401 This package provides subprograms that allow interfacing between
23402 C streams and @code{Wide_Text_IO}. The stream identifier can be
23403 extracted from a file opened on the Ada side, and an Ada file
23404 can be constructed from a stream opened on the C side.
23406 @node Ada Wide_Text_IO Reset_Standard_Files a-wrstfi ads,Ada Wide_Wide_Characters Unicode a-zchuni ads,Ada Wide_Text_IO C_Streams a-wtcstr ads,The GNAT Library
23407 @anchor{gnat_rm/the_gnat_library ada-wide-text-io-reset-standard-files-a-wrstfi-ads}@anchor{30c}@anchor{gnat_rm/the_gnat_library id34}@anchor{30d}
23408 @section @code{Ada.Wide_Text_IO.Reset_Standard_Files} (@code{a-wrstfi.ads})
23411 @geindex Ada.Wide_Text_IO.Reset_Standard_Files (a-wrstfi.ads)
23413 @geindex Wide_Text_IO resetting standard files
23415 This procedure is used to reset the status of the standard files used
23416 by Ada.Wide_Text_IO. This is useful in a situation (such as a restart in an
23417 embedded application) where the status of the files may change during
23418 execution (for example a standard input file may be redefined to be
23421 @node Ada Wide_Wide_Characters Unicode a-zchuni ads,Ada Wide_Wide_Text_IO C_Streams a-ztcstr ads,Ada Wide_Text_IO Reset_Standard_Files a-wrstfi ads,The GNAT Library
23422 @anchor{gnat_rm/the_gnat_library id35}@anchor{30e}@anchor{gnat_rm/the_gnat_library ada-wide-wide-characters-unicode-a-zchuni-ads}@anchor{30f}
23423 @section @code{Ada.Wide_Wide_Characters.Unicode} (@code{a-zchuni.ads})
23426 @geindex Ada.Wide_Wide_Characters.Unicode (a-zchuni.ads)
23428 @geindex Unicode categorization
23429 @geindex Wide_Wide_Character
23431 This package provides subprograms that allow categorization of
23432 Wide_Wide_Character values according to Unicode categories.
23434 @node Ada Wide_Wide_Text_IO C_Streams a-ztcstr ads,Ada Wide_Wide_Text_IO Reset_Standard_Files a-zrstfi ads,Ada Wide_Wide_Characters Unicode a-zchuni ads,The GNAT Library
23435 @anchor{gnat_rm/the_gnat_library id36}@anchor{310}@anchor{gnat_rm/the_gnat_library ada-wide-wide-text-io-c-streams-a-ztcstr-ads}@anchor{311}
23436 @section @code{Ada.Wide_Wide_Text_IO.C_Streams} (@code{a-ztcstr.ads})
23439 @geindex Ada.Wide_Wide_Text_IO.C_Streams (a-ztcstr.ads)
23442 @geindex Interfacing with `@w{`}Wide_Wide_Text_IO`@w{`}
23444 This package provides subprograms that allow interfacing between
23445 C streams and @code{Wide_Wide_Text_IO}. The stream identifier can be
23446 extracted from a file opened on the Ada side, and an Ada file
23447 can be constructed from a stream opened on the C side.
23449 @node Ada Wide_Wide_Text_IO Reset_Standard_Files a-zrstfi ads,GNAT Altivec g-altive ads,Ada Wide_Wide_Text_IO C_Streams a-ztcstr ads,The GNAT Library
23450 @anchor{gnat_rm/the_gnat_library id37}@anchor{312}@anchor{gnat_rm/the_gnat_library ada-wide-wide-text-io-reset-standard-files-a-zrstfi-ads}@anchor{313}
23451 @section @code{Ada.Wide_Wide_Text_IO.Reset_Standard_Files} (@code{a-zrstfi.ads})
23454 @geindex Ada.Wide_Wide_Text_IO.Reset_Standard_Files (a-zrstfi.ads)
23456 @geindex Wide_Wide_Text_IO resetting standard files
23458 This procedure is used to reset the status of the standard files used
23459 by Ada.Wide_Wide_Text_IO. This is useful in a situation (such as a
23460 restart in an embedded application) where the status of the files may
23461 change during execution (for example a standard input file may be
23462 redefined to be interactive).
23464 @node GNAT Altivec g-altive ads,GNAT Altivec Conversions g-altcon ads,Ada Wide_Wide_Text_IO Reset_Standard_Files a-zrstfi ads,The GNAT Library
23465 @anchor{gnat_rm/the_gnat_library gnat-altivec-g-altive-ads}@anchor{314}@anchor{gnat_rm/the_gnat_library id38}@anchor{315}
23466 @section @code{GNAT.Altivec} (@code{g-altive.ads})
23469 @geindex GNAT.Altivec (g-altive.ads)
23473 This is the root package of the GNAT AltiVec binding. It provides
23474 definitions of constants and types common to all the versions of the
23477 @node GNAT Altivec Conversions g-altcon ads,GNAT Altivec Vector_Operations g-alveop ads,GNAT Altivec g-altive ads,The GNAT Library
23478 @anchor{gnat_rm/the_gnat_library gnat-altivec-conversions-g-altcon-ads}@anchor{316}@anchor{gnat_rm/the_gnat_library id39}@anchor{317}
23479 @section @code{GNAT.Altivec.Conversions} (@code{g-altcon.ads})
23482 @geindex GNAT.Altivec.Conversions (g-altcon.ads)
23486 This package provides the Vector/View conversion routines.
23488 @node GNAT Altivec Vector_Operations g-alveop ads,GNAT Altivec Vector_Types g-alvety ads,GNAT Altivec Conversions g-altcon ads,The GNAT Library
23489 @anchor{gnat_rm/the_gnat_library gnat-altivec-vector-operations-g-alveop-ads}@anchor{318}@anchor{gnat_rm/the_gnat_library id40}@anchor{319}
23490 @section @code{GNAT.Altivec.Vector_Operations} (@code{g-alveop.ads})
23493 @geindex GNAT.Altivec.Vector_Operations (g-alveop.ads)
23497 This package exposes the Ada interface to the AltiVec operations on
23498 vector objects. A soft emulation is included by default in the GNAT
23499 library. The hard binding is provided as a separate package. This unit
23500 is common to both bindings.
23502 @node GNAT Altivec Vector_Types g-alvety ads,GNAT Altivec Vector_Views g-alvevi ads,GNAT Altivec Vector_Operations g-alveop ads,The GNAT Library
23503 @anchor{gnat_rm/the_gnat_library gnat-altivec-vector-types-g-alvety-ads}@anchor{31a}@anchor{gnat_rm/the_gnat_library id41}@anchor{31b}
23504 @section @code{GNAT.Altivec.Vector_Types} (@code{g-alvety.ads})
23507 @geindex GNAT.Altivec.Vector_Types (g-alvety.ads)
23511 This package exposes the various vector types part of the Ada binding
23512 to AltiVec facilities.
23514 @node GNAT Altivec Vector_Views g-alvevi ads,GNAT Array_Split g-arrspl ads,GNAT Altivec Vector_Types g-alvety ads,The GNAT Library
23515 @anchor{gnat_rm/the_gnat_library gnat-altivec-vector-views-g-alvevi-ads}@anchor{31c}@anchor{gnat_rm/the_gnat_library id42}@anchor{31d}
23516 @section @code{GNAT.Altivec.Vector_Views} (@code{g-alvevi.ads})
23519 @geindex GNAT.Altivec.Vector_Views (g-alvevi.ads)
23523 This package provides public 'View' data types from/to which private
23524 vector representations can be converted via
23525 GNAT.Altivec.Conversions. This allows convenient access to individual
23526 vector elements and provides a simple way to initialize vector
23529 @node GNAT Array_Split g-arrspl ads,GNAT AWK g-awk ads,GNAT Altivec Vector_Views g-alvevi ads,The GNAT Library
23530 @anchor{gnat_rm/the_gnat_library gnat-array-split-g-arrspl-ads}@anchor{31e}@anchor{gnat_rm/the_gnat_library id43}@anchor{31f}
23531 @section @code{GNAT.Array_Split} (@code{g-arrspl.ads})
23534 @geindex GNAT.Array_Split (g-arrspl.ads)
23536 @geindex Array splitter
23538 Useful array-manipulation routines: given a set of separators, split
23539 an array wherever the separators appear, and provide direct access
23540 to the resulting slices.
23542 @node GNAT AWK g-awk ads,GNAT Bind_Environment g-binenv ads,GNAT Array_Split g-arrspl ads,The GNAT Library
23543 @anchor{gnat_rm/the_gnat_library id44}@anchor{320}@anchor{gnat_rm/the_gnat_library gnat-awk-g-awk-ads}@anchor{321}
23544 @section @code{GNAT.AWK} (@code{g-awk.ads})
23547 @geindex GNAT.AWK (g-awk.ads)
23553 Provides AWK-like parsing functions, with an easy interface for parsing one
23554 or more files containing formatted data. The file is viewed as a database
23555 where each record is a line and a field is a data element in this line.
23557 @node GNAT Bind_Environment g-binenv ads,GNAT Bounded_Buffers g-boubuf ads,GNAT AWK g-awk ads,The GNAT Library
23558 @anchor{gnat_rm/the_gnat_library gnat-bind-environment-g-binenv-ads}@anchor{322}@anchor{gnat_rm/the_gnat_library id45}@anchor{323}
23559 @section @code{GNAT.Bind_Environment} (@code{g-binenv.ads})
23562 @geindex GNAT.Bind_Environment (g-binenv.ads)
23564 @geindex Bind environment
23566 Provides access to key=value associations captured at bind time.
23567 These associations can be specified using the @code{-V} binder command
23570 @node GNAT Bounded_Buffers g-boubuf ads,GNAT Bounded_Mailboxes g-boumai ads,GNAT Bind_Environment g-binenv ads,The GNAT Library
23571 @anchor{gnat_rm/the_gnat_library id46}@anchor{324}@anchor{gnat_rm/the_gnat_library gnat-bounded-buffers-g-boubuf-ads}@anchor{325}
23572 @section @code{GNAT.Bounded_Buffers} (@code{g-boubuf.ads})
23575 @geindex GNAT.Bounded_Buffers (g-boubuf.ads)
23579 @geindex Bounded Buffers
23581 Provides a concurrent generic bounded buffer abstraction. Instances are
23582 useful directly or as parts of the implementations of other abstractions,
23585 @node GNAT Bounded_Mailboxes g-boumai ads,GNAT Bubble_Sort g-bubsor ads,GNAT Bounded_Buffers g-boubuf ads,The GNAT Library
23586 @anchor{gnat_rm/the_gnat_library id47}@anchor{326}@anchor{gnat_rm/the_gnat_library gnat-bounded-mailboxes-g-boumai-ads}@anchor{327}
23587 @section @code{GNAT.Bounded_Mailboxes} (@code{g-boumai.ads})
23590 @geindex GNAT.Bounded_Mailboxes (g-boumai.ads)
23596 Provides a thread-safe asynchronous intertask mailbox communication facility.
23598 @node GNAT Bubble_Sort g-bubsor ads,GNAT Bubble_Sort_A g-busora ads,GNAT Bounded_Mailboxes g-boumai ads,The GNAT Library
23599 @anchor{gnat_rm/the_gnat_library gnat-bubble-sort-g-bubsor-ads}@anchor{328}@anchor{gnat_rm/the_gnat_library id48}@anchor{329}
23600 @section @code{GNAT.Bubble_Sort} (@code{g-bubsor.ads})
23603 @geindex GNAT.Bubble_Sort (g-bubsor.ads)
23607 @geindex Bubble sort
23609 Provides a general implementation of bubble sort usable for sorting arbitrary
23610 data items. Exchange and comparison procedures are provided by passing
23611 access-to-procedure values.
23613 @node GNAT Bubble_Sort_A g-busora ads,GNAT Bubble_Sort_G g-busorg ads,GNAT Bubble_Sort g-bubsor ads,The GNAT Library
23614 @anchor{gnat_rm/the_gnat_library id49}@anchor{32a}@anchor{gnat_rm/the_gnat_library gnat-bubble-sort-a-g-busora-ads}@anchor{32b}
23615 @section @code{GNAT.Bubble_Sort_A} (@code{g-busora.ads})
23618 @geindex GNAT.Bubble_Sort_A (g-busora.ads)
23622 @geindex Bubble sort
23624 Provides a general implementation of bubble sort usable for sorting arbitrary
23625 data items. Move and comparison procedures are provided by passing
23626 access-to-procedure values. This is an older version, retained for
23627 compatibility. Usually @code{GNAT.Bubble_Sort} will be preferable.
23629 @node GNAT Bubble_Sort_G g-busorg ads,GNAT Byte_Order_Mark g-byorma ads,GNAT Bubble_Sort_A g-busora ads,The GNAT Library
23630 @anchor{gnat_rm/the_gnat_library gnat-bubble-sort-g-g-busorg-ads}@anchor{32c}@anchor{gnat_rm/the_gnat_library id50}@anchor{32d}
23631 @section @code{GNAT.Bubble_Sort_G} (@code{g-busorg.ads})
23634 @geindex GNAT.Bubble_Sort_G (g-busorg.ads)
23638 @geindex Bubble sort
23640 Similar to @code{Bubble_Sort_A} except that the move and sorting procedures
23641 are provided as generic parameters, this improves efficiency, especially
23642 if the procedures can be inlined, at the expense of duplicating code for
23643 multiple instantiations.
23645 @node GNAT Byte_Order_Mark g-byorma ads,GNAT Byte_Swapping g-bytswa ads,GNAT Bubble_Sort_G g-busorg ads,The GNAT Library
23646 @anchor{gnat_rm/the_gnat_library gnat-byte-order-mark-g-byorma-ads}@anchor{32e}@anchor{gnat_rm/the_gnat_library id51}@anchor{32f}
23647 @section @code{GNAT.Byte_Order_Mark} (@code{g-byorma.ads})
23650 @geindex GNAT.Byte_Order_Mark (g-byorma.ads)
23652 @geindex UTF-8 representation
23654 @geindex Wide characte representations
23656 Provides a routine which given a string, reads the start of the string to
23657 see whether it is one of the standard byte order marks (BOM's) which signal
23658 the encoding of the string. The routine includes detection of special XML
23659 sequences for various UCS input formats.
23661 @node GNAT Byte_Swapping g-bytswa ads,GNAT Calendar g-calend ads,GNAT Byte_Order_Mark g-byorma ads,The GNAT Library
23662 @anchor{gnat_rm/the_gnat_library gnat-byte-swapping-g-bytswa-ads}@anchor{330}@anchor{gnat_rm/the_gnat_library id52}@anchor{331}
23663 @section @code{GNAT.Byte_Swapping} (@code{g-bytswa.ads})
23666 @geindex GNAT.Byte_Swapping (g-bytswa.ads)
23668 @geindex Byte swapping
23670 @geindex Endianness
23672 General routines for swapping the bytes in 2-, 4-, and 8-byte quantities.
23673 Machine-specific implementations are available in some cases.
23675 @node GNAT Calendar g-calend ads,GNAT Calendar Time_IO g-catiio ads,GNAT Byte_Swapping g-bytswa ads,The GNAT Library
23676 @anchor{gnat_rm/the_gnat_library gnat-calendar-g-calend-ads}@anchor{332}@anchor{gnat_rm/the_gnat_library id53}@anchor{333}
23677 @section @code{GNAT.Calendar} (@code{g-calend.ads})
23680 @geindex GNAT.Calendar (g-calend.ads)
23684 Extends the facilities provided by @code{Ada.Calendar} to include handling
23685 of days of the week, an extended @code{Split} and @code{Time_Of} capability.
23686 Also provides conversion of @code{Ada.Calendar.Time} values to and from the
23687 C @code{timeval} format.
23689 @node GNAT Calendar Time_IO g-catiio ads,GNAT CRC32 g-crc32 ads,GNAT Calendar g-calend ads,The GNAT Library
23690 @anchor{gnat_rm/the_gnat_library id54}@anchor{334}@anchor{gnat_rm/the_gnat_library gnat-calendar-time-io-g-catiio-ads}@anchor{335}
23691 @section @code{GNAT.Calendar.Time_IO} (@code{g-catiio.ads})
23698 @geindex GNAT.Calendar.Time_IO (g-catiio.ads)
23700 @node GNAT CRC32 g-crc32 ads,GNAT Case_Util g-casuti ads,GNAT Calendar Time_IO g-catiio ads,The GNAT Library
23701 @anchor{gnat_rm/the_gnat_library id55}@anchor{336}@anchor{gnat_rm/the_gnat_library gnat-crc32-g-crc32-ads}@anchor{337}
23702 @section @code{GNAT.CRC32} (@code{g-crc32.ads})
23705 @geindex GNAT.CRC32 (g-crc32.ads)
23709 @geindex Cyclic Redundancy Check
23711 This package implements the CRC-32 algorithm. For a full description
23712 of this algorithm see
23713 @emph{Computation of Cyclic Redundancy Checks via Table Look-Up},
23714 @cite{Communications of the ACM}, Vol. 31 No. 8, pp. 1008-1013,
23715 Aug. 1988. Sarwate, D.V.
23717 @node GNAT Case_Util g-casuti ads,GNAT CGI g-cgi ads,GNAT CRC32 g-crc32 ads,The GNAT Library
23718 @anchor{gnat_rm/the_gnat_library id56}@anchor{338}@anchor{gnat_rm/the_gnat_library gnat-case-util-g-casuti-ads}@anchor{339}
23719 @section @code{GNAT.Case_Util} (@code{g-casuti.ads})
23722 @geindex GNAT.Case_Util (g-casuti.ads)
23724 @geindex Casing utilities
23726 @geindex Character handling (`@w{`}GNAT.Case_Util`@w{`})
23728 A set of simple routines for handling upper and lower casing of strings
23729 without the overhead of the full casing tables
23730 in @code{Ada.Characters.Handling}.
23732 @node GNAT CGI g-cgi ads,GNAT CGI Cookie g-cgicoo ads,GNAT Case_Util g-casuti ads,The GNAT Library
23733 @anchor{gnat_rm/the_gnat_library id57}@anchor{33a}@anchor{gnat_rm/the_gnat_library gnat-cgi-g-cgi-ads}@anchor{33b}
23734 @section @code{GNAT.CGI} (@code{g-cgi.ads})
23737 @geindex GNAT.CGI (g-cgi.ads)
23739 @geindex CGI (Common Gateway Interface)
23741 This is a package for interfacing a GNAT program with a Web server via the
23742 Common Gateway Interface (CGI). Basically this package parses the CGI
23743 parameters, which are a set of key/value pairs sent by the Web server. It
23744 builds a table whose index is the key and provides some services to deal
23747 @node GNAT CGI Cookie g-cgicoo ads,GNAT CGI Debug g-cgideb ads,GNAT CGI g-cgi ads,The GNAT Library
23748 @anchor{gnat_rm/the_gnat_library gnat-cgi-cookie-g-cgicoo-ads}@anchor{33c}@anchor{gnat_rm/the_gnat_library id58}@anchor{33d}
23749 @section @code{GNAT.CGI.Cookie} (@code{g-cgicoo.ads})
23752 @geindex GNAT.CGI.Cookie (g-cgicoo.ads)
23754 @geindex CGI (Common Gateway Interface) cookie support
23756 @geindex Cookie support in CGI
23758 This is a package to interface a GNAT program with a Web server via the
23759 Common Gateway Interface (CGI). It exports services to deal with Web
23760 cookies (piece of information kept in the Web client software).
23762 @node GNAT CGI Debug g-cgideb ads,GNAT Command_Line g-comlin ads,GNAT CGI Cookie g-cgicoo ads,The GNAT Library
23763 @anchor{gnat_rm/the_gnat_library gnat-cgi-debug-g-cgideb-ads}@anchor{33e}@anchor{gnat_rm/the_gnat_library id59}@anchor{33f}
23764 @section @code{GNAT.CGI.Debug} (@code{g-cgideb.ads})
23767 @geindex GNAT.CGI.Debug (g-cgideb.ads)
23769 @geindex CGI (Common Gateway Interface) debugging
23771 This is a package to help debugging CGI (Common Gateway Interface)
23772 programs written in Ada.
23774 @node GNAT Command_Line g-comlin ads,GNAT Compiler_Version g-comver ads,GNAT CGI Debug g-cgideb ads,The GNAT Library
23775 @anchor{gnat_rm/the_gnat_library id60}@anchor{340}@anchor{gnat_rm/the_gnat_library gnat-command-line-g-comlin-ads}@anchor{341}
23776 @section @code{GNAT.Command_Line} (@code{g-comlin.ads})
23779 @geindex GNAT.Command_Line (g-comlin.ads)
23781 @geindex Command line
23783 Provides a high level interface to @code{Ada.Command_Line} facilities,
23784 including the ability to scan for named switches with optional parameters
23785 and expand file names using wild card notations.
23787 @node GNAT Compiler_Version g-comver ads,GNAT Ctrl_C g-ctrl_c ads,GNAT Command_Line g-comlin ads,The GNAT Library
23788 @anchor{gnat_rm/the_gnat_library gnat-compiler-version-g-comver-ads}@anchor{342}@anchor{gnat_rm/the_gnat_library id61}@anchor{343}
23789 @section @code{GNAT.Compiler_Version} (@code{g-comver.ads})
23792 @geindex GNAT.Compiler_Version (g-comver.ads)
23794 @geindex Compiler Version
23797 @geindex of compiler
23799 Provides a routine for obtaining the version of the compiler used to
23800 compile the program. More accurately this is the version of the binder
23801 used to bind the program (this will normally be the same as the version
23802 of the compiler if a consistent tool set is used to compile all units
23805 @node GNAT Ctrl_C g-ctrl_c ads,GNAT Current_Exception g-curexc ads,GNAT Compiler_Version g-comver ads,The GNAT Library
23806 @anchor{gnat_rm/the_gnat_library gnat-ctrl-c-g-ctrl-c-ads}@anchor{344}@anchor{gnat_rm/the_gnat_library id62}@anchor{345}
23807 @section @code{GNAT.Ctrl_C} (@code{g-ctrl_c.ads})
23810 @geindex GNAT.Ctrl_C (g-ctrl_c.ads)
23814 Provides a simple interface to handle Ctrl-C keyboard events.
23816 @node GNAT Current_Exception g-curexc ads,GNAT Debug_Pools g-debpoo ads,GNAT Ctrl_C g-ctrl_c ads,The GNAT Library
23817 @anchor{gnat_rm/the_gnat_library id63}@anchor{346}@anchor{gnat_rm/the_gnat_library gnat-current-exception-g-curexc-ads}@anchor{347}
23818 @section @code{GNAT.Current_Exception} (@code{g-curexc.ads})
23821 @geindex GNAT.Current_Exception (g-curexc.ads)
23823 @geindex Current exception
23825 @geindex Exception retrieval
23827 Provides access to information on the current exception that has been raised
23828 without the need for using the Ada 95 / Ada 2005 exception choice parameter
23829 specification syntax.
23830 This is particularly useful in simulating typical facilities for
23831 obtaining information about exceptions provided by Ada 83 compilers.
23833 @node GNAT Debug_Pools g-debpoo ads,GNAT Debug_Utilities g-debuti ads,GNAT Current_Exception g-curexc ads,The GNAT Library
23834 @anchor{gnat_rm/the_gnat_library gnat-debug-pools-g-debpoo-ads}@anchor{348}@anchor{gnat_rm/the_gnat_library id64}@anchor{349}
23835 @section @code{GNAT.Debug_Pools} (@code{g-debpoo.ads})
23838 @geindex GNAT.Debug_Pools (g-debpoo.ads)
23842 @geindex Debug pools
23844 @geindex Memory corruption debugging
23846 Provide a debugging storage pools that helps tracking memory corruption
23848 See @code{The GNAT Debug_Pool Facility} section in the @cite{GNAT User's Guide}.
23850 @node GNAT Debug_Utilities g-debuti ads,GNAT Decode_String g-decstr ads,GNAT Debug_Pools g-debpoo ads,The GNAT Library
23851 @anchor{gnat_rm/the_gnat_library id65}@anchor{34a}@anchor{gnat_rm/the_gnat_library gnat-debug-utilities-g-debuti-ads}@anchor{34b}
23852 @section @code{GNAT.Debug_Utilities} (@code{g-debuti.ads})
23855 @geindex GNAT.Debug_Utilities (g-debuti.ads)
23859 Provides a few useful utilities for debugging purposes, including conversion
23860 to and from string images of address values. Supports both C and Ada formats
23861 for hexadecimal literals.
23863 @node GNAT Decode_String g-decstr ads,GNAT Decode_UTF8_String g-deutst ads,GNAT Debug_Utilities g-debuti ads,The GNAT Library
23864 @anchor{gnat_rm/the_gnat_library gnat-decode-string-g-decstr-ads}@anchor{34c}@anchor{gnat_rm/the_gnat_library id66}@anchor{34d}
23865 @section @code{GNAT.Decode_String} (@code{g-decstr.ads})
23868 @geindex GNAT.Decode_String (g-decstr.ads)
23870 @geindex Decoding strings
23872 @geindex String decoding
23874 @geindex Wide character encoding
23880 A generic package providing routines for decoding wide character and wide wide
23881 character strings encoded as sequences of 8-bit characters using a specified
23882 encoding method. Includes validation routines, and also routines for stepping
23883 to next or previous encoded character in an encoded string.
23884 Useful in conjunction with Unicode character coding. Note there is a
23885 preinstantiation for UTF-8. See next entry.
23887 @node GNAT Decode_UTF8_String g-deutst ads,GNAT Directory_Operations g-dirope ads,GNAT Decode_String g-decstr ads,The GNAT Library
23888 @anchor{gnat_rm/the_gnat_library gnat-decode-utf8-string-g-deutst-ads}@anchor{34e}@anchor{gnat_rm/the_gnat_library id67}@anchor{34f}
23889 @section @code{GNAT.Decode_UTF8_String} (@code{g-deutst.ads})
23892 @geindex GNAT.Decode_UTF8_String (g-deutst.ads)
23894 @geindex Decoding strings
23896 @geindex Decoding UTF-8 strings
23898 @geindex UTF-8 string decoding
23900 @geindex Wide character decoding
23906 A preinstantiation of GNAT.Decode_Strings for UTF-8 encoding.
23908 @node GNAT Directory_Operations g-dirope ads,GNAT Directory_Operations Iteration g-diopit ads,GNAT Decode_UTF8_String g-deutst ads,The GNAT Library
23909 @anchor{gnat_rm/the_gnat_library gnat-directory-operations-g-dirope-ads}@anchor{350}@anchor{gnat_rm/the_gnat_library id68}@anchor{351}
23910 @section @code{GNAT.Directory_Operations} (@code{g-dirope.ads})
23913 @geindex GNAT.Directory_Operations (g-dirope.ads)
23915 @geindex Directory operations
23917 Provides a set of routines for manipulating directories, including changing
23918 the current directory, making new directories, and scanning the files in a
23921 @node GNAT Directory_Operations Iteration g-diopit ads,GNAT Dynamic_HTables g-dynhta ads,GNAT Directory_Operations g-dirope ads,The GNAT Library
23922 @anchor{gnat_rm/the_gnat_library id69}@anchor{352}@anchor{gnat_rm/the_gnat_library gnat-directory-operations-iteration-g-diopit-ads}@anchor{353}
23923 @section @code{GNAT.Directory_Operations.Iteration} (@code{g-diopit.ads})
23926 @geindex GNAT.Directory_Operations.Iteration (g-diopit.ads)
23928 @geindex Directory operations iteration
23930 A child unit of GNAT.Directory_Operations providing additional operations
23931 for iterating through directories.
23933 @node GNAT Dynamic_HTables g-dynhta ads,GNAT Dynamic_Tables g-dyntab ads,GNAT Directory_Operations Iteration g-diopit ads,The GNAT Library
23934 @anchor{gnat_rm/the_gnat_library id70}@anchor{354}@anchor{gnat_rm/the_gnat_library gnat-dynamic-htables-g-dynhta-ads}@anchor{355}
23935 @section @code{GNAT.Dynamic_HTables} (@code{g-dynhta.ads})
23938 @geindex GNAT.Dynamic_HTables (g-dynhta.ads)
23940 @geindex Hash tables
23942 A generic implementation of hash tables that can be used to hash arbitrary
23943 data. Provided in two forms, a simple form with built in hash functions,
23944 and a more complex form in which the hash function is supplied.
23946 This package provides a facility similar to that of @code{GNAT.HTable},
23947 except that this package declares a type that can be used to define
23948 dynamic instances of the hash table, while an instantiation of
23949 @code{GNAT.HTable} creates a single instance of the hash table.
23951 @node GNAT Dynamic_Tables g-dyntab ads,GNAT Encode_String g-encstr ads,GNAT Dynamic_HTables g-dynhta ads,The GNAT Library
23952 @anchor{gnat_rm/the_gnat_library gnat-dynamic-tables-g-dyntab-ads}@anchor{356}@anchor{gnat_rm/the_gnat_library id71}@anchor{357}
23953 @section @code{GNAT.Dynamic_Tables} (@code{g-dyntab.ads})
23956 @geindex GNAT.Dynamic_Tables (g-dyntab.ads)
23958 @geindex Table implementation
23961 @geindex extendable
23963 A generic package providing a single dimension array abstraction where the
23964 length of the array can be dynamically modified.
23966 This package provides a facility similar to that of @code{GNAT.Table},
23967 except that this package declares a type that can be used to define
23968 dynamic instances of the table, while an instantiation of
23969 @code{GNAT.Table} creates a single instance of the table type.
23971 @node GNAT Encode_String g-encstr ads,GNAT Encode_UTF8_String g-enutst ads,GNAT Dynamic_Tables g-dyntab ads,The GNAT Library
23972 @anchor{gnat_rm/the_gnat_library id72}@anchor{358}@anchor{gnat_rm/the_gnat_library gnat-encode-string-g-encstr-ads}@anchor{359}
23973 @section @code{GNAT.Encode_String} (@code{g-encstr.ads})
23976 @geindex GNAT.Encode_String (g-encstr.ads)
23978 @geindex Encoding strings
23980 @geindex String encoding
23982 @geindex Wide character encoding
23988 A generic package providing routines for encoding wide character and wide
23989 wide character strings as sequences of 8-bit characters using a specified
23990 encoding method. Useful in conjunction with Unicode character coding.
23991 Note there is a preinstantiation for UTF-8. See next entry.
23993 @node GNAT Encode_UTF8_String g-enutst ads,GNAT Exception_Actions g-excact ads,GNAT Encode_String g-encstr ads,The GNAT Library
23994 @anchor{gnat_rm/the_gnat_library gnat-encode-utf8-string-g-enutst-ads}@anchor{35a}@anchor{gnat_rm/the_gnat_library id73}@anchor{35b}
23995 @section @code{GNAT.Encode_UTF8_String} (@code{g-enutst.ads})
23998 @geindex GNAT.Encode_UTF8_String (g-enutst.ads)
24000 @geindex Encoding strings
24002 @geindex Encoding UTF-8 strings
24004 @geindex UTF-8 string encoding
24006 @geindex Wide character encoding
24012 A preinstantiation of GNAT.Encode_Strings for UTF-8 encoding.
24014 @node GNAT Exception_Actions g-excact ads,GNAT Exception_Traces g-exctra ads,GNAT Encode_UTF8_String g-enutst ads,The GNAT Library
24015 @anchor{gnat_rm/the_gnat_library gnat-exception-actions-g-excact-ads}@anchor{35c}@anchor{gnat_rm/the_gnat_library id74}@anchor{35d}
24016 @section @code{GNAT.Exception_Actions} (@code{g-excact.ads})
24019 @geindex GNAT.Exception_Actions (g-excact.ads)
24021 @geindex Exception actions
24023 Provides callbacks when an exception is raised. Callbacks can be registered
24024 for specific exceptions, or when any exception is raised. This
24025 can be used for instance to force a core dump to ease debugging.
24027 @node GNAT Exception_Traces g-exctra ads,GNAT Exceptions g-expect ads,GNAT Exception_Actions g-excact ads,The GNAT Library
24028 @anchor{gnat_rm/the_gnat_library gnat-exception-traces-g-exctra-ads}@anchor{35e}@anchor{gnat_rm/the_gnat_library id75}@anchor{35f}
24029 @section @code{GNAT.Exception_Traces} (@code{g-exctra.ads})
24032 @geindex GNAT.Exception_Traces (g-exctra.ads)
24034 @geindex Exception traces
24038 Provides an interface allowing to control automatic output upon exception
24041 @node GNAT Exceptions g-expect ads,GNAT Expect g-expect ads,GNAT Exception_Traces g-exctra ads,The GNAT Library
24042 @anchor{gnat_rm/the_gnat_library id76}@anchor{360}@anchor{gnat_rm/the_gnat_library gnat-exceptions-g-expect-ads}@anchor{361}
24043 @section @code{GNAT.Exceptions} (@code{g-expect.ads})
24046 @geindex GNAT.Exceptions (g-expect.ads)
24048 @geindex Exceptions
24051 @geindex Pure packages
24052 @geindex exceptions
24054 Normally it is not possible to raise an exception with
24055 a message from a subprogram in a pure package, since the
24056 necessary types and subprograms are in @code{Ada.Exceptions}
24057 which is not a pure unit. @code{GNAT.Exceptions} provides a
24058 facility for getting around this limitation for a few
24059 predefined exceptions, and for example allow raising
24060 @code{Constraint_Error} with a message from a pure subprogram.
24062 @node GNAT Expect g-expect ads,GNAT Expect TTY g-exptty ads,GNAT Exceptions g-expect ads,The GNAT Library
24063 @anchor{gnat_rm/the_gnat_library gnat-expect-g-expect-ads}@anchor{362}@anchor{gnat_rm/the_gnat_library id77}@anchor{363}
24064 @section @code{GNAT.Expect} (@code{g-expect.ads})
24067 @geindex GNAT.Expect (g-expect.ads)
24069 Provides a set of subprograms similar to what is available
24070 with the standard Tcl Expect tool.
24071 It allows you to easily spawn and communicate with an external process.
24072 You can send commands or inputs to the process, and compare the output
24073 with some expected regular expression. Currently @code{GNAT.Expect}
24074 is implemented on all native GNAT ports.
24075 It is not implemented for cross ports, and in particular is not
24076 implemented for VxWorks or LynxOS.
24078 @node GNAT Expect TTY g-exptty ads,GNAT Float_Control g-flocon ads,GNAT Expect g-expect ads,The GNAT Library
24079 @anchor{gnat_rm/the_gnat_library id78}@anchor{364}@anchor{gnat_rm/the_gnat_library gnat-expect-tty-g-exptty-ads}@anchor{365}
24080 @section @code{GNAT.Expect.TTY} (@code{g-exptty.ads})
24083 @geindex GNAT.Expect.TTY (g-exptty.ads)
24085 As GNAT.Expect but using pseudo-terminal.
24086 Currently @code{GNAT.Expect.TTY} is implemented on all native GNAT
24087 ports. It is not implemented for cross ports, and
24088 in particular is not implemented for VxWorks or LynxOS.
24090 @node GNAT Float_Control g-flocon ads,GNAT Formatted_String g-forstr ads,GNAT Expect TTY g-exptty ads,The GNAT Library
24091 @anchor{gnat_rm/the_gnat_library id79}@anchor{366}@anchor{gnat_rm/the_gnat_library gnat-float-control-g-flocon-ads}@anchor{367}
24092 @section @code{GNAT.Float_Control} (@code{g-flocon.ads})
24095 @geindex GNAT.Float_Control (g-flocon.ads)
24097 @geindex Floating-Point Processor
24099 Provides an interface for resetting the floating-point processor into the
24100 mode required for correct semantic operation in Ada. Some third party
24101 library calls may cause this mode to be modified, and the Reset procedure
24102 in this package can be used to reestablish the required mode.
24104 @node GNAT Formatted_String g-forstr ads,GNAT Heap_Sort g-heasor ads,GNAT Float_Control g-flocon ads,The GNAT Library
24105 @anchor{gnat_rm/the_gnat_library id80}@anchor{368}@anchor{gnat_rm/the_gnat_library gnat-formatted-string-g-forstr-ads}@anchor{369}
24106 @section @code{GNAT.Formatted_String} (@code{g-forstr.ads})
24109 @geindex GNAT.Formatted_String (g-forstr.ads)
24111 @geindex Formatted String
24113 Provides support for C/C++ printf() formatted strings. The format is
24114 copied from the printf() routine and should therefore gives identical
24115 output. Some generic routines are provided to be able to use types
24116 derived from Integer, Float or enumerations as values for the
24119 @node GNAT Heap_Sort g-heasor ads,GNAT Heap_Sort_A g-hesora ads,GNAT Formatted_String g-forstr ads,The GNAT Library
24120 @anchor{gnat_rm/the_gnat_library gnat-heap-sort-g-heasor-ads}@anchor{36a}@anchor{gnat_rm/the_gnat_library id81}@anchor{36b}
24121 @section @code{GNAT.Heap_Sort} (@code{g-heasor.ads})
24124 @geindex GNAT.Heap_Sort (g-heasor.ads)
24128 Provides a general implementation of heap sort usable for sorting arbitrary
24129 data items. Exchange and comparison procedures are provided by passing
24130 access-to-procedure values. The algorithm used is a modified heap sort
24131 that performs approximately N*log(N) comparisons in the worst case.
24133 @node GNAT Heap_Sort_A g-hesora ads,GNAT Heap_Sort_G g-hesorg ads,GNAT Heap_Sort g-heasor ads,The GNAT Library
24134 @anchor{gnat_rm/the_gnat_library id82}@anchor{36c}@anchor{gnat_rm/the_gnat_library gnat-heap-sort-a-g-hesora-ads}@anchor{36d}
24135 @section @code{GNAT.Heap_Sort_A} (@code{g-hesora.ads})
24138 @geindex GNAT.Heap_Sort_A (g-hesora.ads)
24142 Provides a general implementation of heap sort usable for sorting arbitrary
24143 data items. Move and comparison procedures are provided by passing
24144 access-to-procedure values. The algorithm used is a modified heap sort
24145 that performs approximately N*log(N) comparisons in the worst case.
24146 This differs from @code{GNAT.Heap_Sort} in having a less convenient
24147 interface, but may be slightly more efficient.
24149 @node GNAT Heap_Sort_G g-hesorg ads,GNAT HTable g-htable ads,GNAT Heap_Sort_A g-hesora ads,The GNAT Library
24150 @anchor{gnat_rm/the_gnat_library id83}@anchor{36e}@anchor{gnat_rm/the_gnat_library gnat-heap-sort-g-g-hesorg-ads}@anchor{36f}
24151 @section @code{GNAT.Heap_Sort_G} (@code{g-hesorg.ads})
24154 @geindex GNAT.Heap_Sort_G (g-hesorg.ads)
24158 Similar to @code{Heap_Sort_A} except that the move and sorting procedures
24159 are provided as generic parameters, this improves efficiency, especially
24160 if the procedures can be inlined, at the expense of duplicating code for
24161 multiple instantiations.
24163 @node GNAT HTable g-htable ads,GNAT IO g-io ads,GNAT Heap_Sort_G g-hesorg ads,The GNAT Library
24164 @anchor{gnat_rm/the_gnat_library id84}@anchor{370}@anchor{gnat_rm/the_gnat_library gnat-htable-g-htable-ads}@anchor{371}
24165 @section @code{GNAT.HTable} (@code{g-htable.ads})
24168 @geindex GNAT.HTable (g-htable.ads)
24170 @geindex Hash tables
24172 A generic implementation of hash tables that can be used to hash arbitrary
24173 data. Provides two approaches, one a simple static approach, and the other
24174 allowing arbitrary dynamic hash tables.
24176 @node GNAT IO g-io ads,GNAT IO_Aux g-io_aux ads,GNAT HTable g-htable ads,The GNAT Library
24177 @anchor{gnat_rm/the_gnat_library id85}@anchor{372}@anchor{gnat_rm/the_gnat_library gnat-io-g-io-ads}@anchor{373}
24178 @section @code{GNAT.IO} (@code{g-io.ads})
24181 @geindex GNAT.IO (g-io.ads)
24183 @geindex Simple I/O
24185 @geindex Input/Output facilities
24187 A simple preelaborable input-output package that provides a subset of
24188 simple Text_IO functions for reading characters and strings from
24189 Standard_Input, and writing characters, strings and integers to either
24190 Standard_Output or Standard_Error.
24192 @node GNAT IO_Aux g-io_aux ads,GNAT Lock_Files g-locfil ads,GNAT IO g-io ads,The GNAT Library
24193 @anchor{gnat_rm/the_gnat_library gnat-io-aux-g-io-aux-ads}@anchor{374}@anchor{gnat_rm/the_gnat_library id86}@anchor{375}
24194 @section @code{GNAT.IO_Aux} (@code{g-io_aux.ads})
24197 @geindex GNAT.IO_Aux (g-io_aux.ads)
24201 @geindex Input/Output facilities
24203 Provides some auxiliary functions for use with Text_IO, including a test
24204 for whether a file exists, and functions for reading a line of text.
24206 @node GNAT Lock_Files g-locfil ads,GNAT MBBS_Discrete_Random g-mbdira ads,GNAT IO_Aux g-io_aux ads,The GNAT Library
24207 @anchor{gnat_rm/the_gnat_library id87}@anchor{376}@anchor{gnat_rm/the_gnat_library gnat-lock-files-g-locfil-ads}@anchor{377}
24208 @section @code{GNAT.Lock_Files} (@code{g-locfil.ads})
24211 @geindex GNAT.Lock_Files (g-locfil.ads)
24213 @geindex File locking
24215 @geindex Locking using files
24217 Provides a general interface for using files as locks. Can be used for
24218 providing program level synchronization.
24220 @node GNAT MBBS_Discrete_Random g-mbdira ads,GNAT MBBS_Float_Random g-mbflra ads,GNAT Lock_Files g-locfil ads,The GNAT Library
24221 @anchor{gnat_rm/the_gnat_library id88}@anchor{378}@anchor{gnat_rm/the_gnat_library gnat-mbbs-discrete-random-g-mbdira-ads}@anchor{379}
24222 @section @code{GNAT.MBBS_Discrete_Random} (@code{g-mbdira.ads})
24225 @geindex GNAT.MBBS_Discrete_Random (g-mbdira.ads)
24227 @geindex Random number generation
24229 The original implementation of @code{Ada.Numerics.Discrete_Random}. Uses
24230 a modified version of the Blum-Blum-Shub generator.
24232 @node GNAT MBBS_Float_Random g-mbflra ads,GNAT MD5 g-md5 ads,GNAT MBBS_Discrete_Random g-mbdira ads,The GNAT Library
24233 @anchor{gnat_rm/the_gnat_library id89}@anchor{37a}@anchor{gnat_rm/the_gnat_library gnat-mbbs-float-random-g-mbflra-ads}@anchor{37b}
24234 @section @code{GNAT.MBBS_Float_Random} (@code{g-mbflra.ads})
24237 @geindex GNAT.MBBS_Float_Random (g-mbflra.ads)
24239 @geindex Random number generation
24241 The original implementation of @code{Ada.Numerics.Float_Random}. Uses
24242 a modified version of the Blum-Blum-Shub generator.
24244 @node GNAT MD5 g-md5 ads,GNAT Memory_Dump g-memdum ads,GNAT MBBS_Float_Random g-mbflra ads,The GNAT Library
24245 @anchor{gnat_rm/the_gnat_library id90}@anchor{37c}@anchor{gnat_rm/the_gnat_library gnat-md5-g-md5-ads}@anchor{37d}
24246 @section @code{GNAT.MD5} (@code{g-md5.ads})
24249 @geindex GNAT.MD5 (g-md5.ads)
24251 @geindex Message Digest MD5
24253 Implements the MD5 Message-Digest Algorithm as described in RFC 1321, and
24254 the HMAC-MD5 message authentication function as described in RFC 2104 and
24257 @node GNAT Memory_Dump g-memdum ads,GNAT Most_Recent_Exception g-moreex ads,GNAT MD5 g-md5 ads,The GNAT Library
24258 @anchor{gnat_rm/the_gnat_library id91}@anchor{37e}@anchor{gnat_rm/the_gnat_library gnat-memory-dump-g-memdum-ads}@anchor{37f}
24259 @section @code{GNAT.Memory_Dump} (@code{g-memdum.ads})
24262 @geindex GNAT.Memory_Dump (g-memdum.ads)
24264 @geindex Dump Memory
24266 Provides a convenient routine for dumping raw memory to either the
24267 standard output or standard error files. Uses GNAT.IO for actual
24270 @node GNAT Most_Recent_Exception g-moreex ads,GNAT OS_Lib g-os_lib ads,GNAT Memory_Dump g-memdum ads,The GNAT Library
24271 @anchor{gnat_rm/the_gnat_library id92}@anchor{380}@anchor{gnat_rm/the_gnat_library gnat-most-recent-exception-g-moreex-ads}@anchor{381}
24272 @section @code{GNAT.Most_Recent_Exception} (@code{g-moreex.ads})
24275 @geindex GNAT.Most_Recent_Exception (g-moreex.ads)
24278 @geindex obtaining most recent
24280 Provides access to the most recently raised exception. Can be used for
24281 various logging purposes, including duplicating functionality of some
24282 Ada 83 implementation dependent extensions.
24284 @node GNAT OS_Lib g-os_lib ads,GNAT Perfect_Hash_Generators g-pehage ads,GNAT Most_Recent_Exception g-moreex ads,The GNAT Library
24285 @anchor{gnat_rm/the_gnat_library gnat-os-lib-g-os-lib-ads}@anchor{382}@anchor{gnat_rm/the_gnat_library id93}@anchor{383}
24286 @section @code{GNAT.OS_Lib} (@code{g-os_lib.ads})
24289 @geindex GNAT.OS_Lib (g-os_lib.ads)
24291 @geindex Operating System interface
24293 @geindex Spawn capability
24295 Provides a range of target independent operating system interface functions,
24296 including time/date management, file operations, subprocess management,
24297 including a portable spawn procedure, and access to environment variables
24298 and error return codes.
24300 @node GNAT Perfect_Hash_Generators g-pehage ads,GNAT Random_Numbers g-rannum ads,GNAT OS_Lib g-os_lib ads,The GNAT Library
24301 @anchor{gnat_rm/the_gnat_library gnat-perfect-hash-generators-g-pehage-ads}@anchor{384}@anchor{gnat_rm/the_gnat_library id94}@anchor{385}
24302 @section @code{GNAT.Perfect_Hash_Generators} (@code{g-pehage.ads})
24305 @geindex GNAT.Perfect_Hash_Generators (g-pehage.ads)
24307 @geindex Hash functions
24309 Provides a generator of static minimal perfect hash functions. No
24310 collisions occur and each item can be retrieved from the table in one
24311 probe (perfect property). The hash table size corresponds to the exact
24312 size of the key set and no larger (minimal property). The key set has to
24313 be know in advance (static property). The hash functions are also order
24314 preserving. If w2 is inserted after w1 in the generator, their
24315 hashcode are in the same order. These hashing functions are very
24316 convenient for use with realtime applications.
24318 @node GNAT Random_Numbers g-rannum ads,GNAT Regexp g-regexp ads,GNAT Perfect_Hash_Generators g-pehage ads,The GNAT Library
24319 @anchor{gnat_rm/the_gnat_library gnat-random-numbers-g-rannum-ads}@anchor{386}@anchor{gnat_rm/the_gnat_library id95}@anchor{387}
24320 @section @code{GNAT.Random_Numbers} (@code{g-rannum.ads})
24323 @geindex GNAT.Random_Numbers (g-rannum.ads)
24325 @geindex Random number generation
24327 Provides random number capabilities which extend those available in the
24328 standard Ada library and are more convenient to use.
24330 @node GNAT Regexp g-regexp ads,GNAT Registry g-regist ads,GNAT Random_Numbers g-rannum ads,The GNAT Library
24331 @anchor{gnat_rm/the_gnat_library gnat-regexp-g-regexp-ads}@anchor{251}@anchor{gnat_rm/the_gnat_library id96}@anchor{388}
24332 @section @code{GNAT.Regexp} (@code{g-regexp.ads})
24335 @geindex GNAT.Regexp (g-regexp.ads)
24337 @geindex Regular expressions
24339 @geindex Pattern matching
24341 A simple implementation of regular expressions, using a subset of regular
24342 expression syntax copied from familiar Unix style utilities. This is the
24343 simplest of the three pattern matching packages provided, and is particularly
24344 suitable for 'file globbing' applications.
24346 @node GNAT Registry g-regist ads,GNAT Regpat g-regpat ads,GNAT Regexp g-regexp ads,The GNAT Library
24347 @anchor{gnat_rm/the_gnat_library gnat-registry-g-regist-ads}@anchor{389}@anchor{gnat_rm/the_gnat_library id97}@anchor{38a}
24348 @section @code{GNAT.Registry} (@code{g-regist.ads})
24351 @geindex GNAT.Registry (g-regist.ads)
24353 @geindex Windows Registry
24355 This is a high level binding to the Windows registry. It is possible to
24356 do simple things like reading a key value, creating a new key. For full
24357 registry API, but at a lower level of abstraction, refer to the Win32.Winreg
24358 package provided with the Win32Ada binding
24360 @node GNAT Regpat g-regpat ads,GNAT Rewrite_Data g-rewdat ads,GNAT Registry g-regist ads,The GNAT Library
24361 @anchor{gnat_rm/the_gnat_library id98}@anchor{38b}@anchor{gnat_rm/the_gnat_library gnat-regpat-g-regpat-ads}@anchor{38c}
24362 @section @code{GNAT.Regpat} (@code{g-regpat.ads})
24365 @geindex GNAT.Regpat (g-regpat.ads)
24367 @geindex Regular expressions
24369 @geindex Pattern matching
24371 A complete implementation of Unix-style regular expression matching, copied
24372 from the original V7 style regular expression library written in C by
24373 Henry Spencer (and binary compatible with this C library).
24375 @node GNAT Rewrite_Data g-rewdat ads,GNAT Secondary_Stack_Info g-sestin ads,GNAT Regpat g-regpat ads,The GNAT Library
24376 @anchor{gnat_rm/the_gnat_library id99}@anchor{38d}@anchor{gnat_rm/the_gnat_library gnat-rewrite-data-g-rewdat-ads}@anchor{38e}
24377 @section @code{GNAT.Rewrite_Data} (@code{g-rewdat.ads})
24380 @geindex GNAT.Rewrite_Data (g-rewdat.ads)
24382 @geindex Rewrite data
24384 A unit to rewrite on-the-fly string occurrences in a stream of
24385 data. The implementation has a very minimal memory footprint as the
24386 full content to be processed is not loaded into memory all at once. This makes
24387 this interface usable for large files or socket streams.
24389 @node GNAT Secondary_Stack_Info g-sestin ads,GNAT Semaphores g-semaph ads,GNAT Rewrite_Data g-rewdat ads,The GNAT Library
24390 @anchor{gnat_rm/the_gnat_library id100}@anchor{38f}@anchor{gnat_rm/the_gnat_library gnat-secondary-stack-info-g-sestin-ads}@anchor{390}
24391 @section @code{GNAT.Secondary_Stack_Info} (@code{g-sestin.ads})
24394 @geindex GNAT.Secondary_Stack_Info (g-sestin.ads)
24396 @geindex Secondary Stack Info
24398 Provide the capability to query the high water mark of the current task's
24401 @node GNAT Semaphores g-semaph ads,GNAT Serial_Communications g-sercom ads,GNAT Secondary_Stack_Info g-sestin ads,The GNAT Library
24402 @anchor{gnat_rm/the_gnat_library id101}@anchor{391}@anchor{gnat_rm/the_gnat_library gnat-semaphores-g-semaph-ads}@anchor{392}
24403 @section @code{GNAT.Semaphores} (@code{g-semaph.ads})
24406 @geindex GNAT.Semaphores (g-semaph.ads)
24408 @geindex Semaphores
24410 Provides classic counting and binary semaphores using protected types.
24412 @node GNAT Serial_Communications g-sercom ads,GNAT SHA1 g-sha1 ads,GNAT Semaphores g-semaph ads,The GNAT Library
24413 @anchor{gnat_rm/the_gnat_library gnat-serial-communications-g-sercom-ads}@anchor{393}@anchor{gnat_rm/the_gnat_library id102}@anchor{394}
24414 @section @code{GNAT.Serial_Communications} (@code{g-sercom.ads})
24417 @geindex GNAT.Serial_Communications (g-sercom.ads)
24419 @geindex Serial_Communications
24421 Provides a simple interface to send and receive data over a serial
24422 port. This is only supported on GNU/Linux and Windows.
24424 @node GNAT SHA1 g-sha1 ads,GNAT SHA224 g-sha224 ads,GNAT Serial_Communications g-sercom ads,The GNAT Library
24425 @anchor{gnat_rm/the_gnat_library gnat-sha1-g-sha1-ads}@anchor{395}@anchor{gnat_rm/the_gnat_library id103}@anchor{396}
24426 @section @code{GNAT.SHA1} (@code{g-sha1.ads})
24429 @geindex GNAT.SHA1 (g-sha1.ads)
24431 @geindex Secure Hash Algorithm SHA-1
24433 Implements the SHA-1 Secure Hash Algorithm as described in FIPS PUB 180-3
24434 and RFC 3174, and the HMAC-SHA1 message authentication function as described
24435 in RFC 2104 and FIPS PUB 198.
24437 @node GNAT SHA224 g-sha224 ads,GNAT SHA256 g-sha256 ads,GNAT SHA1 g-sha1 ads,The GNAT Library
24438 @anchor{gnat_rm/the_gnat_library gnat-sha224-g-sha224-ads}@anchor{397}@anchor{gnat_rm/the_gnat_library id104}@anchor{398}
24439 @section @code{GNAT.SHA224} (@code{g-sha224.ads})
24442 @geindex GNAT.SHA224 (g-sha224.ads)
24444 @geindex Secure Hash Algorithm SHA-224
24446 Implements the SHA-224 Secure Hash Algorithm as described in FIPS PUB 180-3,
24447 and the HMAC-SHA224 message authentication function as described
24448 in RFC 2104 and FIPS PUB 198.
24450 @node GNAT SHA256 g-sha256 ads,GNAT SHA384 g-sha384 ads,GNAT SHA224 g-sha224 ads,The GNAT Library
24451 @anchor{gnat_rm/the_gnat_library id105}@anchor{399}@anchor{gnat_rm/the_gnat_library gnat-sha256-g-sha256-ads}@anchor{39a}
24452 @section @code{GNAT.SHA256} (@code{g-sha256.ads})
24455 @geindex GNAT.SHA256 (g-sha256.ads)
24457 @geindex Secure Hash Algorithm SHA-256
24459 Implements the SHA-256 Secure Hash Algorithm as described in FIPS PUB 180-3,
24460 and the HMAC-SHA256 message authentication function as described
24461 in RFC 2104 and FIPS PUB 198.
24463 @node GNAT SHA384 g-sha384 ads,GNAT SHA512 g-sha512 ads,GNAT SHA256 g-sha256 ads,The GNAT Library
24464 @anchor{gnat_rm/the_gnat_library gnat-sha384-g-sha384-ads}@anchor{39b}@anchor{gnat_rm/the_gnat_library id106}@anchor{39c}
24465 @section @code{GNAT.SHA384} (@code{g-sha384.ads})
24468 @geindex GNAT.SHA384 (g-sha384.ads)
24470 @geindex Secure Hash Algorithm SHA-384
24472 Implements the SHA-384 Secure Hash Algorithm as described in FIPS PUB 180-3,
24473 and the HMAC-SHA384 message authentication function as described
24474 in RFC 2104 and FIPS PUB 198.
24476 @node GNAT SHA512 g-sha512 ads,GNAT Signals g-signal ads,GNAT SHA384 g-sha384 ads,The GNAT Library
24477 @anchor{gnat_rm/the_gnat_library gnat-sha512-g-sha512-ads}@anchor{39d}@anchor{gnat_rm/the_gnat_library id107}@anchor{39e}
24478 @section @code{GNAT.SHA512} (@code{g-sha512.ads})
24481 @geindex GNAT.SHA512 (g-sha512.ads)
24483 @geindex Secure Hash Algorithm SHA-512
24485 Implements the SHA-512 Secure Hash Algorithm as described in FIPS PUB 180-3,
24486 and the HMAC-SHA512 message authentication function as described
24487 in RFC 2104 and FIPS PUB 198.
24489 @node GNAT Signals g-signal ads,GNAT Sockets g-socket ads,GNAT SHA512 g-sha512 ads,The GNAT Library
24490 @anchor{gnat_rm/the_gnat_library gnat-signals-g-signal-ads}@anchor{39f}@anchor{gnat_rm/the_gnat_library id108}@anchor{3a0}
24491 @section @code{GNAT.Signals} (@code{g-signal.ads})
24494 @geindex GNAT.Signals (g-signal.ads)
24498 Provides the ability to manipulate the blocked status of signals on supported
24501 @node GNAT Sockets g-socket ads,GNAT Source_Info g-souinf ads,GNAT Signals g-signal ads,The GNAT Library
24502 @anchor{gnat_rm/the_gnat_library id109}@anchor{3a1}@anchor{gnat_rm/the_gnat_library gnat-sockets-g-socket-ads}@anchor{3a2}
24503 @section @code{GNAT.Sockets} (@code{g-socket.ads})
24506 @geindex GNAT.Sockets (g-socket.ads)
24510 A high level and portable interface to develop sockets based applications.
24511 This package is based on the sockets thin binding found in
24512 @code{GNAT.Sockets.Thin}. Currently @code{GNAT.Sockets} is implemented
24513 on all native GNAT ports and on VxWorks cross prots. It is not implemented for
24514 the LynxOS cross port.
24516 @node GNAT Source_Info g-souinf ads,GNAT Spelling_Checker g-speche ads,GNAT Sockets g-socket ads,The GNAT Library
24517 @anchor{gnat_rm/the_gnat_library gnat-source-info-g-souinf-ads}@anchor{3a3}@anchor{gnat_rm/the_gnat_library id110}@anchor{3a4}
24518 @section @code{GNAT.Source_Info} (@code{g-souinf.ads})
24521 @geindex GNAT.Source_Info (g-souinf.ads)
24523 @geindex Source Information
24525 Provides subprograms that give access to source code information known at
24526 compile time, such as the current file name and line number. Also provides
24527 subprograms yielding the date and time of the current compilation (like the
24528 C macros @code{__DATE__} and @code{__TIME__})
24530 @node GNAT Spelling_Checker g-speche ads,GNAT Spelling_Checker_Generic g-spchge ads,GNAT Source_Info g-souinf ads,The GNAT Library
24531 @anchor{gnat_rm/the_gnat_library gnat-spelling-checker-g-speche-ads}@anchor{3a5}@anchor{gnat_rm/the_gnat_library id111}@anchor{3a6}
24532 @section @code{GNAT.Spelling_Checker} (@code{g-speche.ads})
24535 @geindex GNAT.Spelling_Checker (g-speche.ads)
24537 @geindex Spell checking
24539 Provides a function for determining whether one string is a plausible
24540 near misspelling of another string.
24542 @node GNAT Spelling_Checker_Generic g-spchge ads,GNAT Spitbol Patterns g-spipat ads,GNAT Spelling_Checker g-speche ads,The GNAT Library
24543 @anchor{gnat_rm/the_gnat_library id112}@anchor{3a7}@anchor{gnat_rm/the_gnat_library gnat-spelling-checker-generic-g-spchge-ads}@anchor{3a8}
24544 @section @code{GNAT.Spelling_Checker_Generic} (@code{g-spchge.ads})
24547 @geindex GNAT.Spelling_Checker_Generic (g-spchge.ads)
24549 @geindex Spell checking
24551 Provides a generic function that can be instantiated with a string type for
24552 determining whether one string is a plausible near misspelling of another
24555 @node GNAT Spitbol Patterns g-spipat ads,GNAT Spitbol g-spitbo ads,GNAT Spelling_Checker_Generic g-spchge ads,The GNAT Library
24556 @anchor{gnat_rm/the_gnat_library id113}@anchor{3a9}@anchor{gnat_rm/the_gnat_library gnat-spitbol-patterns-g-spipat-ads}@anchor{3aa}
24557 @section @code{GNAT.Spitbol.Patterns} (@code{g-spipat.ads})
24560 @geindex GNAT.Spitbol.Patterns (g-spipat.ads)
24562 @geindex SPITBOL pattern matching
24564 @geindex Pattern matching
24566 A complete implementation of SNOBOL4 style pattern matching. This is the
24567 most elaborate of the pattern matching packages provided. It fully duplicates
24568 the SNOBOL4 dynamic pattern construction and matching capabilities, using the
24569 efficient algorithm developed by Robert Dewar for the SPITBOL system.
24571 @node GNAT Spitbol g-spitbo ads,GNAT Spitbol Table_Boolean g-sptabo ads,GNAT Spitbol Patterns g-spipat ads,The GNAT Library
24572 @anchor{gnat_rm/the_gnat_library gnat-spitbol-g-spitbo-ads}@anchor{3ab}@anchor{gnat_rm/the_gnat_library id114}@anchor{3ac}
24573 @section @code{GNAT.Spitbol} (@code{g-spitbo.ads})
24576 @geindex GNAT.Spitbol (g-spitbo.ads)
24578 @geindex SPITBOL interface
24580 The top level package of the collection of SPITBOL-style functionality, this
24581 package provides basic SNOBOL4 string manipulation functions, such as
24582 Pad, Reverse, Trim, Substr capability, as well as a generic table function
24583 useful for constructing arbitrary mappings from strings in the style of
24584 the SNOBOL4 TABLE function.
24586 @node GNAT Spitbol Table_Boolean g-sptabo ads,GNAT Spitbol Table_Integer g-sptain ads,GNAT Spitbol g-spitbo ads,The GNAT Library
24587 @anchor{gnat_rm/the_gnat_library gnat-spitbol-table-boolean-g-sptabo-ads}@anchor{3ad}@anchor{gnat_rm/the_gnat_library id115}@anchor{3ae}
24588 @section @code{GNAT.Spitbol.Table_Boolean} (@code{g-sptabo.ads})
24591 @geindex GNAT.Spitbol.Table_Boolean (g-sptabo.ads)
24593 @geindex Sets of strings
24595 @geindex SPITBOL Tables
24597 A library level of instantiation of @code{GNAT.Spitbol.Patterns.Table}
24598 for type @code{Standard.Boolean}, giving an implementation of sets of
24601 @node GNAT Spitbol Table_Integer g-sptain ads,GNAT Spitbol Table_VString g-sptavs ads,GNAT Spitbol Table_Boolean g-sptabo ads,The GNAT Library
24602 @anchor{gnat_rm/the_gnat_library gnat-spitbol-table-integer-g-sptain-ads}@anchor{3af}@anchor{gnat_rm/the_gnat_library id116}@anchor{3b0}
24603 @section @code{GNAT.Spitbol.Table_Integer} (@code{g-sptain.ads})
24606 @geindex GNAT.Spitbol.Table_Integer (g-sptain.ads)
24608 @geindex Integer maps
24612 @geindex SPITBOL Tables
24614 A library level of instantiation of @code{GNAT.Spitbol.Patterns.Table}
24615 for type @code{Standard.Integer}, giving an implementation of maps
24616 from string to integer values.
24618 @node GNAT Spitbol Table_VString g-sptavs ads,GNAT SSE g-sse ads,GNAT Spitbol Table_Integer g-sptain ads,The GNAT Library
24619 @anchor{gnat_rm/the_gnat_library id117}@anchor{3b1}@anchor{gnat_rm/the_gnat_library gnat-spitbol-table-vstring-g-sptavs-ads}@anchor{3b2}
24620 @section @code{GNAT.Spitbol.Table_VString} (@code{g-sptavs.ads})
24623 @geindex GNAT.Spitbol.Table_VString (g-sptavs.ads)
24625 @geindex String maps
24629 @geindex SPITBOL Tables
24631 A library level of instantiation of @code{GNAT.Spitbol.Patterns.Table} for
24632 a variable length string type, giving an implementation of general
24633 maps from strings to strings.
24635 @node GNAT SSE g-sse ads,GNAT SSE Vector_Types g-ssvety ads,GNAT Spitbol Table_VString g-sptavs ads,The GNAT Library
24636 @anchor{gnat_rm/the_gnat_library id118}@anchor{3b3}@anchor{gnat_rm/the_gnat_library gnat-sse-g-sse-ads}@anchor{3b4}
24637 @section @code{GNAT.SSE} (@code{g-sse.ads})
24640 @geindex GNAT.SSE (g-sse.ads)
24642 Root of a set of units aimed at offering Ada bindings to a subset of
24643 the Intel(r) Streaming SIMD Extensions with GNAT on the x86 family of
24644 targets. It exposes vector component types together with a general
24645 introduction to the binding contents and use.
24647 @node GNAT SSE Vector_Types g-ssvety ads,GNAT String_Hash g-strhas ads,GNAT SSE g-sse ads,The GNAT Library
24648 @anchor{gnat_rm/the_gnat_library gnat-sse-vector-types-g-ssvety-ads}@anchor{3b5}@anchor{gnat_rm/the_gnat_library id119}@anchor{3b6}
24649 @section @code{GNAT.SSE.Vector_Types} (@code{g-ssvety.ads})
24652 @geindex GNAT.SSE.Vector_Types (g-ssvety.ads)
24654 SSE vector types for use with SSE related intrinsics.
24656 @node GNAT String_Hash g-strhas ads,GNAT Strings g-string ads,GNAT SSE Vector_Types g-ssvety ads,The GNAT Library
24657 @anchor{gnat_rm/the_gnat_library gnat-string-hash-g-strhas-ads}@anchor{3b7}@anchor{gnat_rm/the_gnat_library id120}@anchor{3b8}
24658 @section @code{GNAT.String_Hash} (@code{g-strhas.ads})
24661 @geindex GNAT.String_Hash (g-strhas.ads)
24663 @geindex Hash functions
24665 Provides a generic hash function working on arrays of scalars. Both the scalar
24666 type and the hash result type are parameters.
24668 @node GNAT Strings g-string ads,GNAT String_Split g-strspl ads,GNAT String_Hash g-strhas ads,The GNAT Library
24669 @anchor{gnat_rm/the_gnat_library gnat-strings-g-string-ads}@anchor{3b9}@anchor{gnat_rm/the_gnat_library id121}@anchor{3ba}
24670 @section @code{GNAT.Strings} (@code{g-string.ads})
24673 @geindex GNAT.Strings (g-string.ads)
24675 Common String access types and related subprograms. Basically it
24676 defines a string access and an array of string access types.
24678 @node GNAT String_Split g-strspl ads,GNAT Table g-table ads,GNAT Strings g-string ads,The GNAT Library
24679 @anchor{gnat_rm/the_gnat_library gnat-string-split-g-strspl-ads}@anchor{3bb}@anchor{gnat_rm/the_gnat_library id122}@anchor{3bc}
24680 @section @code{GNAT.String_Split} (@code{g-strspl.ads})
24683 @geindex GNAT.String_Split (g-strspl.ads)
24685 @geindex String splitter
24687 Useful string manipulation routines: given a set of separators, split
24688 a string wherever the separators appear, and provide direct access
24689 to the resulting slices. This package is instantiated from
24690 @code{GNAT.Array_Split}.
24692 @node GNAT Table g-table ads,GNAT Task_Lock g-tasloc ads,GNAT String_Split g-strspl ads,The GNAT Library
24693 @anchor{gnat_rm/the_gnat_library gnat-table-g-table-ads}@anchor{3bd}@anchor{gnat_rm/the_gnat_library id123}@anchor{3be}
24694 @section @code{GNAT.Table} (@code{g-table.ads})
24697 @geindex GNAT.Table (g-table.ads)
24699 @geindex Table implementation
24702 @geindex extendable
24704 A generic package providing a single dimension array abstraction where the
24705 length of the array can be dynamically modified.
24707 This package provides a facility similar to that of @code{GNAT.Dynamic_Tables},
24708 except that this package declares a single instance of the table type,
24709 while an instantiation of @code{GNAT.Dynamic_Tables} creates a type that can be
24710 used to define dynamic instances of the table.
24712 @node GNAT Task_Lock g-tasloc ads,GNAT Time_Stamp g-timsta ads,GNAT Table g-table ads,The GNAT Library
24713 @anchor{gnat_rm/the_gnat_library id124}@anchor{3bf}@anchor{gnat_rm/the_gnat_library gnat-task-lock-g-tasloc-ads}@anchor{3c0}
24714 @section @code{GNAT.Task_Lock} (@code{g-tasloc.ads})
24717 @geindex GNAT.Task_Lock (g-tasloc.ads)
24719 @geindex Task synchronization
24721 @geindex Task locking
24725 A very simple facility for locking and unlocking sections of code using a
24726 single global task lock. Appropriate for use in situations where contention
24727 between tasks is very rarely expected.
24729 @node GNAT Time_Stamp g-timsta ads,GNAT Threads g-thread ads,GNAT Task_Lock g-tasloc ads,The GNAT Library
24730 @anchor{gnat_rm/the_gnat_library id125}@anchor{3c1}@anchor{gnat_rm/the_gnat_library gnat-time-stamp-g-timsta-ads}@anchor{3c2}
24731 @section @code{GNAT.Time_Stamp} (@code{g-timsta.ads})
24734 @geindex GNAT.Time_Stamp (g-timsta.ads)
24736 @geindex Time stamp
24738 @geindex Current time
24740 Provides a simple function that returns a string YYYY-MM-DD HH:MM:SS.SS that
24741 represents the current date and time in ISO 8601 format. This is a very simple
24742 routine with minimal code and there are no dependencies on any other unit.
24744 @node GNAT Threads g-thread ads,GNAT Traceback g-traceb ads,GNAT Time_Stamp g-timsta ads,The GNAT Library
24745 @anchor{gnat_rm/the_gnat_library gnat-threads-g-thread-ads}@anchor{3c3}@anchor{gnat_rm/the_gnat_library id126}@anchor{3c4}
24746 @section @code{GNAT.Threads} (@code{g-thread.ads})
24749 @geindex GNAT.Threads (g-thread.ads)
24751 @geindex Foreign threads
24756 Provides facilities for dealing with foreign threads which need to be known
24757 by the GNAT run-time system. Consult the documentation of this package for
24758 further details if your program has threads that are created by a non-Ada
24759 environment which then accesses Ada code.
24761 @node GNAT Traceback g-traceb ads,GNAT Traceback Symbolic g-trasym ads,GNAT Threads g-thread ads,The GNAT Library
24762 @anchor{gnat_rm/the_gnat_library id127}@anchor{3c5}@anchor{gnat_rm/the_gnat_library gnat-traceback-g-traceb-ads}@anchor{3c6}
24763 @section @code{GNAT.Traceback} (@code{g-traceb.ads})
24766 @geindex GNAT.Traceback (g-traceb.ads)
24768 @geindex Trace back facilities
24770 Provides a facility for obtaining non-symbolic traceback information, useful
24771 in various debugging situations.
24773 @node GNAT Traceback Symbolic g-trasym ads,GNAT UTF_32 g-table ads,GNAT Traceback g-traceb ads,The GNAT Library
24774 @anchor{gnat_rm/the_gnat_library gnat-traceback-symbolic-g-trasym-ads}@anchor{3c7}@anchor{gnat_rm/the_gnat_library id128}@anchor{3c8}
24775 @section @code{GNAT.Traceback.Symbolic} (@code{g-trasym.ads})
24778 @geindex GNAT.Traceback.Symbolic (g-trasym.ads)
24780 @geindex Trace back facilities
24782 @node GNAT UTF_32 g-table ads,GNAT Wide_Spelling_Checker g-u3spch ads,GNAT Traceback Symbolic g-trasym ads,The GNAT Library
24783 @anchor{gnat_rm/the_gnat_library id129}@anchor{3c9}@anchor{gnat_rm/the_gnat_library gnat-utf-32-g-table-ads}@anchor{3ca}
24784 @section @code{GNAT.UTF_32} (@code{g-table.ads})
24787 @geindex GNAT.UTF_32 (g-table.ads)
24789 @geindex Wide character codes
24791 This is a package intended to be used in conjunction with the
24792 @code{Wide_Character} type in Ada 95 and the
24793 @code{Wide_Wide_Character} type in Ada 2005 (available
24794 in @code{GNAT} in Ada 2005 mode). This package contains
24795 Unicode categorization routines, as well as lexical
24796 categorization routines corresponding to the Ada 2005
24797 lexical rules for identifiers and strings, and also a
24798 lower case to upper case fold routine corresponding to
24799 the Ada 2005 rules for identifier equivalence.
24801 @node GNAT Wide_Spelling_Checker g-u3spch ads,GNAT Wide_Spelling_Checker g-wispch ads,GNAT UTF_32 g-table ads,The GNAT Library
24802 @anchor{gnat_rm/the_gnat_library gnat-wide-spelling-checker-g-u3spch-ads}@anchor{3cb}@anchor{gnat_rm/the_gnat_library id130}@anchor{3cc}
24803 @section @code{GNAT.Wide_Spelling_Checker} (@code{g-u3spch.ads})
24806 @geindex GNAT.Wide_Spelling_Checker (g-u3spch.ads)
24808 @geindex Spell checking
24810 Provides a function for determining whether one wide wide string is a plausible
24811 near misspelling of another wide wide string, where the strings are represented
24812 using the UTF_32_String type defined in System.Wch_Cnv.
24814 @node GNAT Wide_Spelling_Checker g-wispch ads,GNAT Wide_String_Split g-wistsp ads,GNAT Wide_Spelling_Checker g-u3spch ads,The GNAT Library
24815 @anchor{gnat_rm/the_gnat_library gnat-wide-spelling-checker-g-wispch-ads}@anchor{3cd}@anchor{gnat_rm/the_gnat_library id131}@anchor{3ce}
24816 @section @code{GNAT.Wide_Spelling_Checker} (@code{g-wispch.ads})
24819 @geindex GNAT.Wide_Spelling_Checker (g-wispch.ads)
24821 @geindex Spell checking
24823 Provides a function for determining whether one wide string is a plausible
24824 near misspelling of another wide string.
24826 @node GNAT Wide_String_Split g-wistsp ads,GNAT Wide_Wide_Spelling_Checker g-zspche ads,GNAT Wide_Spelling_Checker g-wispch ads,The GNAT Library
24827 @anchor{gnat_rm/the_gnat_library id132}@anchor{3cf}@anchor{gnat_rm/the_gnat_library gnat-wide-string-split-g-wistsp-ads}@anchor{3d0}
24828 @section @code{GNAT.Wide_String_Split} (@code{g-wistsp.ads})
24831 @geindex GNAT.Wide_String_Split (g-wistsp.ads)
24833 @geindex Wide_String splitter
24835 Useful wide string manipulation routines: given a set of separators, split
24836 a wide string wherever the separators appear, and provide direct access
24837 to the resulting slices. This package is instantiated from
24838 @code{GNAT.Array_Split}.
24840 @node GNAT Wide_Wide_Spelling_Checker g-zspche ads,GNAT Wide_Wide_String_Split g-zistsp ads,GNAT Wide_String_Split g-wistsp ads,The GNAT Library
24841 @anchor{gnat_rm/the_gnat_library gnat-wide-wide-spelling-checker-g-zspche-ads}@anchor{3d1}@anchor{gnat_rm/the_gnat_library id133}@anchor{3d2}
24842 @section @code{GNAT.Wide_Wide_Spelling_Checker} (@code{g-zspche.ads})
24845 @geindex GNAT.Wide_Wide_Spelling_Checker (g-zspche.ads)
24847 @geindex Spell checking
24849 Provides a function for determining whether one wide wide string is a plausible
24850 near misspelling of another wide wide string.
24852 @node GNAT Wide_Wide_String_Split g-zistsp ads,Interfaces C Extensions i-cexten ads,GNAT Wide_Wide_Spelling_Checker g-zspche ads,The GNAT Library
24853 @anchor{gnat_rm/the_gnat_library gnat-wide-wide-string-split-g-zistsp-ads}@anchor{3d3}@anchor{gnat_rm/the_gnat_library id134}@anchor{3d4}
24854 @section @code{GNAT.Wide_Wide_String_Split} (@code{g-zistsp.ads})
24857 @geindex GNAT.Wide_Wide_String_Split (g-zistsp.ads)
24859 @geindex Wide_Wide_String splitter
24861 Useful wide wide string manipulation routines: given a set of separators, split
24862 a wide wide string wherever the separators appear, and provide direct access
24863 to the resulting slices. This package is instantiated from
24864 @code{GNAT.Array_Split}.
24866 @node Interfaces C Extensions i-cexten ads,Interfaces C Streams i-cstrea ads,GNAT Wide_Wide_String_Split g-zistsp ads,The GNAT Library
24867 @anchor{gnat_rm/the_gnat_library interfaces-c-extensions-i-cexten-ads}@anchor{3d5}@anchor{gnat_rm/the_gnat_library id135}@anchor{3d6}
24868 @section @code{Interfaces.C.Extensions} (@code{i-cexten.ads})
24871 @geindex Interfaces.C.Extensions (i-cexten.ads)
24873 This package contains additional C-related definitions, intended
24874 for use with either manually or automatically generated bindings
24877 @node Interfaces C Streams i-cstrea ads,Interfaces Packed_Decimal i-pacdec ads,Interfaces C Extensions i-cexten ads,The GNAT Library
24878 @anchor{gnat_rm/the_gnat_library interfaces-c-streams-i-cstrea-ads}@anchor{3d7}@anchor{gnat_rm/the_gnat_library id136}@anchor{3d8}
24879 @section @code{Interfaces.C.Streams} (@code{i-cstrea.ads})
24882 @geindex Interfaces.C.Streams (i-cstrea.ads)
24885 @geindex interfacing
24887 This package is a binding for the most commonly used operations
24890 @node Interfaces Packed_Decimal i-pacdec ads,Interfaces VxWorks i-vxwork ads,Interfaces C Streams i-cstrea ads,The GNAT Library
24891 @anchor{gnat_rm/the_gnat_library interfaces-packed-decimal-i-pacdec-ads}@anchor{3d9}@anchor{gnat_rm/the_gnat_library id137}@anchor{3da}
24892 @section @code{Interfaces.Packed_Decimal} (@code{i-pacdec.ads})
24895 @geindex Interfaces.Packed_Decimal (i-pacdec.ads)
24897 @geindex IBM Packed Format
24899 @geindex Packed Decimal
24901 This package provides a set of routines for conversions to and
24902 from a packed decimal format compatible with that used on IBM
24905 @node Interfaces VxWorks i-vxwork ads,Interfaces VxWorks Int_Connection i-vxinco ads,Interfaces Packed_Decimal i-pacdec ads,The GNAT Library
24906 @anchor{gnat_rm/the_gnat_library id138}@anchor{3db}@anchor{gnat_rm/the_gnat_library interfaces-vxworks-i-vxwork-ads}@anchor{3dc}
24907 @section @code{Interfaces.VxWorks} (@code{i-vxwork.ads})
24910 @geindex Interfaces.VxWorks (i-vxwork.ads)
24912 @geindex Interfacing to VxWorks
24915 @geindex interfacing
24917 This package provides a limited binding to the VxWorks API.
24918 In particular, it interfaces with the
24919 VxWorks hardware interrupt facilities.
24921 @node Interfaces VxWorks Int_Connection i-vxinco ads,Interfaces VxWorks IO i-vxwoio ads,Interfaces VxWorks i-vxwork ads,The GNAT Library
24922 @anchor{gnat_rm/the_gnat_library interfaces-vxworks-int-connection-i-vxinco-ads}@anchor{3dd}@anchor{gnat_rm/the_gnat_library id139}@anchor{3de}
24923 @section @code{Interfaces.VxWorks.Int_Connection} (@code{i-vxinco.ads})
24926 @geindex Interfaces.VxWorks.Int_Connection (i-vxinco.ads)
24928 @geindex Interfacing to VxWorks
24931 @geindex interfacing
24933 This package provides a way for users to replace the use of
24934 intConnect() with a custom routine for installing interrupt
24937 @node Interfaces VxWorks IO i-vxwoio ads,System Address_Image s-addima ads,Interfaces VxWorks Int_Connection i-vxinco ads,The GNAT Library
24938 @anchor{gnat_rm/the_gnat_library interfaces-vxworks-io-i-vxwoio-ads}@anchor{3df}@anchor{gnat_rm/the_gnat_library id140}@anchor{3e0}
24939 @section @code{Interfaces.VxWorks.IO} (@code{i-vxwoio.ads})
24942 @geindex Interfaces.VxWorks.IO (i-vxwoio.ads)
24944 @geindex Interfacing to VxWorks' I/O
24947 @geindex I/O interfacing
24950 @geindex Get_Immediate
24952 @geindex Get_Immediate
24955 This package provides a binding to the ioctl (IO/Control)
24956 function of VxWorks, defining a set of option values and
24957 function codes. A particular use of this package is
24958 to enable the use of Get_Immediate under VxWorks.
24960 @node System Address_Image s-addima ads,System Assertions s-assert ads,Interfaces VxWorks IO i-vxwoio ads,The GNAT Library
24961 @anchor{gnat_rm/the_gnat_library id141}@anchor{3e1}@anchor{gnat_rm/the_gnat_library system-address-image-s-addima-ads}@anchor{3e2}
24962 @section @code{System.Address_Image} (@code{s-addima.ads})
24965 @geindex System.Address_Image (s-addima.ads)
24967 @geindex Address image
24970 @geindex of an address
24972 This function provides a useful debugging
24973 function that gives an (implementation dependent)
24974 string which identifies an address.
24976 @node System Assertions s-assert ads,System Atomic_Counters s-atocou ads,System Address_Image s-addima ads,The GNAT Library
24977 @anchor{gnat_rm/the_gnat_library system-assertions-s-assert-ads}@anchor{3e3}@anchor{gnat_rm/the_gnat_library id142}@anchor{3e4}
24978 @section @code{System.Assertions} (@code{s-assert.ads})
24981 @geindex System.Assertions (s-assert.ads)
24983 @geindex Assertions
24985 @geindex Assert_Failure
24988 This package provides the declaration of the exception raised
24989 by an run-time assertion failure, as well as the routine that
24990 is used internally to raise this assertion.
24992 @node System Atomic_Counters s-atocou ads,System Memory s-memory ads,System Assertions s-assert ads,The GNAT Library
24993 @anchor{gnat_rm/the_gnat_library id143}@anchor{3e5}@anchor{gnat_rm/the_gnat_library system-atomic-counters-s-atocou-ads}@anchor{3e6}
24994 @section @code{System.Atomic_Counters} (@code{s-atocou.ads})
24997 @geindex System.Atomic_Counters (s-atocou.ads)
24999 This package provides the declaration of an atomic counter type,
25000 together with efficient routines (using hardware
25001 synchronization primitives) for incrementing, decrementing,
25002 and testing of these counters. This package is implemented
25003 on most targets, including all Alpha, ia64, PowerPC, SPARC V9,
25004 x86, and x86_64 platforms.
25006 @node System Memory s-memory ads,System Multiprocessors s-multip ads,System Atomic_Counters s-atocou ads,The GNAT Library
25007 @anchor{gnat_rm/the_gnat_library system-memory-s-memory-ads}@anchor{3e7}@anchor{gnat_rm/the_gnat_library id144}@anchor{3e8}
25008 @section @code{System.Memory} (@code{s-memory.ads})
25011 @geindex System.Memory (s-memory.ads)
25013 @geindex Memory allocation
25015 This package provides the interface to the low level routines used
25016 by the generated code for allocation and freeing storage for the
25017 default storage pool (analogous to the C routines malloc and free.
25018 It also provides a reallocation interface analogous to the C routine
25019 realloc. The body of this unit may be modified to provide alternative
25020 allocation mechanisms for the default pool, and in addition, direct
25021 calls to this unit may be made for low level allocation uses (for
25022 example see the body of @code{GNAT.Tables}).
25024 @node System Multiprocessors s-multip ads,System Multiprocessors Dispatching_Domains s-mudido ads,System Memory s-memory ads,The GNAT Library
25025 @anchor{gnat_rm/the_gnat_library id145}@anchor{3e9}@anchor{gnat_rm/the_gnat_library system-multiprocessors-s-multip-ads}@anchor{3ea}
25026 @section @code{System.Multiprocessors} (@code{s-multip.ads})
25029 @geindex System.Multiprocessors (s-multip.ads)
25031 @geindex Multiprocessor interface
25033 This is an Ada 2012 unit defined in the Ada 2012 Reference Manual, but
25034 in GNAT we also make it available in Ada 95 and Ada 2005 (where it is
25035 technically an implementation-defined addition).
25037 @node System Multiprocessors Dispatching_Domains s-mudido ads,System Partition_Interface s-parint ads,System Multiprocessors s-multip ads,The GNAT Library
25038 @anchor{gnat_rm/the_gnat_library system-multiprocessors-dispatching-domains-s-mudido-ads}@anchor{3eb}@anchor{gnat_rm/the_gnat_library id146}@anchor{3ec}
25039 @section @code{System.Multiprocessors.Dispatching_Domains} (@code{s-mudido.ads})
25042 @geindex System.Multiprocessors.Dispatching_Domains (s-mudido.ads)
25044 @geindex Multiprocessor interface
25046 This is an Ada 2012 unit defined in the Ada 2012 Reference Manual, but
25047 in GNAT we also make it available in Ada 95 and Ada 2005 (where it is
25048 technically an implementation-defined addition).
25050 @node System Partition_Interface s-parint ads,System Pool_Global s-pooglo ads,System Multiprocessors Dispatching_Domains s-mudido ads,The GNAT Library
25051 @anchor{gnat_rm/the_gnat_library id147}@anchor{3ed}@anchor{gnat_rm/the_gnat_library system-partition-interface-s-parint-ads}@anchor{3ee}
25052 @section @code{System.Partition_Interface} (@code{s-parint.ads})
25055 @geindex System.Partition_Interface (s-parint.ads)
25057 @geindex Partition interfacing functions
25059 This package provides facilities for partition interfacing. It
25060 is used primarily in a distribution context when using Annex E
25063 @node System Pool_Global s-pooglo ads,System Pool_Local s-pooloc ads,System Partition_Interface s-parint ads,The GNAT Library
25064 @anchor{gnat_rm/the_gnat_library id148}@anchor{3ef}@anchor{gnat_rm/the_gnat_library system-pool-global-s-pooglo-ads}@anchor{3f0}
25065 @section @code{System.Pool_Global} (@code{s-pooglo.ads})
25068 @geindex System.Pool_Global (s-pooglo.ads)
25070 @geindex Storage pool
25073 @geindex Global storage pool
25075 This package provides a storage pool that is equivalent to the default
25076 storage pool used for access types for which no pool is specifically
25077 declared. It uses malloc/free to allocate/free and does not attempt to
25078 do any automatic reclamation.
25080 @node System Pool_Local s-pooloc ads,System Restrictions s-restri ads,System Pool_Global s-pooglo ads,The GNAT Library
25081 @anchor{gnat_rm/the_gnat_library system-pool-local-s-pooloc-ads}@anchor{3f1}@anchor{gnat_rm/the_gnat_library id149}@anchor{3f2}
25082 @section @code{System.Pool_Local} (@code{s-pooloc.ads})
25085 @geindex System.Pool_Local (s-pooloc.ads)
25087 @geindex Storage pool
25090 @geindex Local storage pool
25092 This package provides a storage pool that is intended for use with locally
25093 defined access types. It uses malloc/free for allocate/free, and maintains
25094 a list of allocated blocks, so that all storage allocated for the pool can
25095 be freed automatically when the pool is finalized.
25097 @node System Restrictions s-restri ads,System Rident s-rident ads,System Pool_Local s-pooloc ads,The GNAT Library
25098 @anchor{gnat_rm/the_gnat_library id150}@anchor{3f3}@anchor{gnat_rm/the_gnat_library system-restrictions-s-restri-ads}@anchor{3f4}
25099 @section @code{System.Restrictions} (@code{s-restri.ads})
25102 @geindex System.Restrictions (s-restri.ads)
25104 @geindex Run-time restrictions access
25106 This package provides facilities for accessing at run time
25107 the status of restrictions specified at compile time for
25108 the partition. Information is available both with regard
25109 to actual restrictions specified, and with regard to
25110 compiler determined information on which restrictions
25111 are violated by one or more packages in the partition.
25113 @node System Rident s-rident ads,System Strings Stream_Ops s-ststop ads,System Restrictions s-restri ads,The GNAT Library
25114 @anchor{gnat_rm/the_gnat_library system-rident-s-rident-ads}@anchor{3f5}@anchor{gnat_rm/the_gnat_library id151}@anchor{3f6}
25115 @section @code{System.Rident} (@code{s-rident.ads})
25118 @geindex System.Rident (s-rident.ads)
25120 @geindex Restrictions definitions
25122 This package provides definitions of the restrictions
25123 identifiers supported by GNAT, and also the format of
25124 the restrictions provided in package System.Restrictions.
25125 It is not normally necessary to @code{with} this generic package
25126 since the necessary instantiation is included in
25127 package System.Restrictions.
25129 @node System Strings Stream_Ops s-ststop ads,System Unsigned_Types s-unstyp ads,System Rident s-rident ads,The GNAT Library
25130 @anchor{gnat_rm/the_gnat_library id152}@anchor{3f7}@anchor{gnat_rm/the_gnat_library system-strings-stream-ops-s-ststop-ads}@anchor{3f8}
25131 @section @code{System.Strings.Stream_Ops} (@code{s-ststop.ads})
25134 @geindex System.Strings.Stream_Ops (s-ststop.ads)
25136 @geindex Stream operations
25138 @geindex String stream operations
25140 This package provides a set of stream subprograms for standard string types.
25141 It is intended primarily to support implicit use of such subprograms when
25142 stream attributes are applied to string types, but the subprograms in this
25143 package can be used directly by application programs.
25145 @node System Unsigned_Types s-unstyp ads,System Wch_Cnv s-wchcnv ads,System Strings Stream_Ops s-ststop ads,The GNAT Library
25146 @anchor{gnat_rm/the_gnat_library system-unsigned-types-s-unstyp-ads}@anchor{3f9}@anchor{gnat_rm/the_gnat_library id153}@anchor{3fa}
25147 @section @code{System.Unsigned_Types} (@code{s-unstyp.ads})
25150 @geindex System.Unsigned_Types (s-unstyp.ads)
25152 This package contains definitions of standard unsigned types that
25153 correspond in size to the standard signed types declared in Standard,
25154 and (unlike the types in Interfaces) have corresponding names. It
25155 also contains some related definitions for other specialized types
25156 used by the compiler in connection with packed array types.
25158 @node System Wch_Cnv s-wchcnv ads,System Wch_Con s-wchcon ads,System Unsigned_Types s-unstyp ads,The GNAT Library
25159 @anchor{gnat_rm/the_gnat_library system-wch-cnv-s-wchcnv-ads}@anchor{3fb}@anchor{gnat_rm/the_gnat_library id154}@anchor{3fc}
25160 @section @code{System.Wch_Cnv} (@code{s-wchcnv.ads})
25163 @geindex System.Wch_Cnv (s-wchcnv.ads)
25165 @geindex Wide Character
25166 @geindex Representation
25168 @geindex Wide String
25169 @geindex Conversion
25171 @geindex Representation of wide characters
25173 This package provides routines for converting between
25174 wide and wide wide characters and a representation as a value of type
25175 @code{Standard.String}, using a specified wide character
25176 encoding method. It uses definitions in
25177 package @code{System.Wch_Con}.
25179 @node System Wch_Con s-wchcon ads,,System Wch_Cnv s-wchcnv ads,The GNAT Library
25180 @anchor{gnat_rm/the_gnat_library system-wch-con-s-wchcon-ads}@anchor{3fd}@anchor{gnat_rm/the_gnat_library id155}@anchor{3fe}
25181 @section @code{System.Wch_Con} (@code{s-wchcon.ads})
25184 @geindex System.Wch_Con (s-wchcon.ads)
25186 This package provides definitions and descriptions of
25187 the various methods used for encoding wide characters
25188 in ordinary strings. These definitions are used by
25189 the package @code{System.Wch_Cnv}.
25191 @node Interfacing to Other Languages,Specialized Needs Annexes,The GNAT Library,Top
25192 @anchor{gnat_rm/interfacing_to_other_languages interfacing-to-other-languages}@anchor{11}@anchor{gnat_rm/interfacing_to_other_languages doc}@anchor{3ff}@anchor{gnat_rm/interfacing_to_other_languages id1}@anchor{400}
25193 @chapter Interfacing to Other Languages
25196 The facilities in Annex B of the Ada Reference Manual are fully
25197 implemented in GNAT, and in addition, a full interface to C++ is
25201 * Interfacing to C::
25202 * Interfacing to C++::
25203 * Interfacing to COBOL::
25204 * Interfacing to Fortran::
25205 * Interfacing to non-GNAT Ada code::
25209 @node Interfacing to C,Interfacing to C++,,Interfacing to Other Languages
25210 @anchor{gnat_rm/interfacing_to_other_languages interfacing-to-c}@anchor{401}@anchor{gnat_rm/interfacing_to_other_languages id2}@anchor{402}
25211 @section Interfacing to C
25214 Interfacing to C with GNAT can use one of two approaches:
25220 The types in the package @code{Interfaces.C} may be used.
25223 Standard Ada types may be used directly. This may be less portable to
25224 other compilers, but will work on all GNAT compilers, which guarantee
25225 correspondence between the C and Ada types.
25228 Pragma @code{Convention C} may be applied to Ada types, but mostly has no
25229 effect, since this is the default. The following table shows the
25230 correspondence between Ada scalar types and the corresponding C types.
25233 @multitable {xxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
25252 @code{Short_Integer}
25260 @code{Short_Short_Integer}
25268 @code{Long_Integer}
25276 @code{Long_Long_Integer}
25308 @code{Long_Long_Float}
25312 This is the longest floating-point type supported by the hardware.
25317 Additionally, there are the following general correspondences between Ada
25324 Ada enumeration types map to C enumeration types directly if pragma
25325 @code{Convention C} is specified, which causes them to have int
25326 length. Without pragma @code{Convention C}, Ada enumeration types map to
25327 8, 16, or 32 bits (i.e., C types @code{signed char}, @code{short},
25328 @code{int}, respectively) depending on the number of values passed.
25329 This is the only case in which pragma @code{Convention C} affects the
25330 representation of an Ada type.
25333 Ada access types map to C pointers, except for the case of pointers to
25334 unconstrained types in Ada, which have no direct C equivalent.
25337 Ada arrays map directly to C arrays.
25340 Ada records map directly to C structures.
25343 Packed Ada records map to C structures where all members are bit fields
25344 of the length corresponding to the @code{type'Size} value in Ada.
25347 @node Interfacing to C++,Interfacing to COBOL,Interfacing to C,Interfacing to Other Languages
25348 @anchor{gnat_rm/interfacing_to_other_languages id4}@anchor{403}@anchor{gnat_rm/interfacing_to_other_languages id3}@anchor{45}
25349 @section Interfacing to C++
25352 The interface to C++ makes use of the following pragmas, which are
25353 primarily intended to be constructed automatically using a binding generator
25354 tool, although it is possible to construct them by hand.
25356 Using these pragmas it is possible to achieve complete
25357 inter-operability between Ada tagged types and C++ class definitions.
25358 See @ref{7,,Implementation Defined Pragmas}, for more details.
25363 @item @code{pragma CPP_Class ([Entity =>] @emph{LOCAL_NAME})}
25365 The argument denotes an entity in the current declarative region that is
25366 declared as a tagged or untagged record type. It indicates that the type
25367 corresponds to an externally declared C++ class type, and is to be laid
25368 out the same way that C++ would lay out the type.
25370 Note: Pragma @code{CPP_Class} is currently obsolete. It is supported
25371 for backward compatibility but its functionality is available
25372 using pragma @code{Import} with @code{Convention} = @code{CPP}.
25374 @item @code{pragma CPP_Constructor ([Entity =>] @emph{LOCAL_NAME})}
25376 This pragma identifies an imported function (imported in the usual way
25377 with pragma @code{Import}) as corresponding to a C++ constructor.
25380 A few restrictions are placed on the use of the @code{Access} attribute
25381 in conjunction with subprograms subject to convention @code{CPP}: the
25382 attribute may be used neither on primitive operations of a tagged
25383 record type with convention @code{CPP}, imported or not, nor on
25384 subprograms imported with pragma @code{CPP_Constructor}.
25386 In addition, C++ exceptions are propagated and can be handled in an
25387 @code{others} choice of an exception handler. The corresponding Ada
25388 occurrence has no message, and the simple name of the exception identity
25389 contains @code{Foreign_Exception}. Finalization and awaiting dependent
25390 tasks works properly when such foreign exceptions are propagated.
25392 It is also possible to import a C++ exception using the following syntax:
25395 LOCAL_NAME : exception;
25396 pragma Import (Cpp,
25397 [Entity =>] LOCAL_NAME,
25398 [External_Name =>] static_string_EXPRESSION);
25401 The @code{External_Name} is the name of the C++ RTTI symbol. You can then
25402 cover a specific C++ exception in an exception handler.
25404 @node Interfacing to COBOL,Interfacing to Fortran,Interfacing to C++,Interfacing to Other Languages
25405 @anchor{gnat_rm/interfacing_to_other_languages id5}@anchor{404}@anchor{gnat_rm/interfacing_to_other_languages interfacing-to-cobol}@anchor{405}
25406 @section Interfacing to COBOL
25409 Interfacing to COBOL is achieved as described in section B.4 of
25410 the Ada Reference Manual.
25412 @node Interfacing to Fortran,Interfacing to non-GNAT Ada code,Interfacing to COBOL,Interfacing to Other Languages
25413 @anchor{gnat_rm/interfacing_to_other_languages id6}@anchor{406}@anchor{gnat_rm/interfacing_to_other_languages interfacing-to-fortran}@anchor{407}
25414 @section Interfacing to Fortran
25417 Interfacing to Fortran is achieved as described in section B.5 of the
25418 Ada Reference Manual. The pragma @code{Convention Fortran}, applied to a
25419 multi-dimensional array causes the array to be stored in column-major
25420 order as required for convenient interface to Fortran.
25422 @node Interfacing to non-GNAT Ada code,,Interfacing to Fortran,Interfacing to Other Languages
25423 @anchor{gnat_rm/interfacing_to_other_languages interfacing-to-non-gnat-ada-code}@anchor{408}@anchor{gnat_rm/interfacing_to_other_languages id7}@anchor{409}
25424 @section Interfacing to non-GNAT Ada code
25427 It is possible to specify the convention @code{Ada} in a pragma
25428 @code{Import} or pragma @code{Export}. However this refers to
25429 the calling conventions used by GNAT, which may or may not be
25430 similar enough to those used by some other Ada 83 / Ada 95 / Ada 2005
25431 compiler to allow interoperation.
25433 If arguments types are kept simple, and if the foreign compiler generally
25434 follows system calling conventions, then it may be possible to integrate
25435 files compiled by other Ada compilers, provided that the elaboration
25436 issues are adequately addressed (for example by eliminating the
25437 need for any load time elaboration).
25439 In particular, GNAT running on VMS is designed to
25440 be highly compatible with the DEC Ada 83 compiler, so this is one
25441 case in which it is possible to import foreign units of this type,
25442 provided that the data items passed are restricted to simple scalar
25443 values or simple record types without variants, or simple array
25444 types with fixed bounds.
25446 @node Specialized Needs Annexes,Implementation of Specific Ada Features,Interfacing to Other Languages,Top
25447 @anchor{gnat_rm/specialized_needs_annexes specialized-needs-annexes}@anchor{12}@anchor{gnat_rm/specialized_needs_annexes doc}@anchor{40a}@anchor{gnat_rm/specialized_needs_annexes id1}@anchor{40b}
25448 @chapter Specialized Needs Annexes
25451 Ada 95, Ada 2005, and Ada 2012 define a number of Specialized Needs Annexes, which are not
25452 required in all implementations. However, as described in this chapter,
25453 GNAT implements all of these annexes:
25458 @item @emph{Systems Programming (Annex C)}
25460 The Systems Programming Annex is fully implemented.
25462 @item @emph{Real-Time Systems (Annex D)}
25464 The Real-Time Systems Annex is fully implemented.
25466 @item @emph{Distributed Systems (Annex E)}
25468 Stub generation is fully implemented in the GNAT compiler. In addition,
25469 a complete compatible PCS is available as part of the GLADE system,
25470 a separate product. When the two
25471 products are used in conjunction, this annex is fully implemented.
25473 @item @emph{Information Systems (Annex F)}
25475 The Information Systems annex is fully implemented.
25477 @item @emph{Numerics (Annex G)}
25479 The Numerics Annex is fully implemented.
25481 @item @emph{Safety and Security / High-Integrity Systems (Annex H)}
25483 The Safety and Security Annex (termed the High-Integrity Systems Annex
25484 in Ada 2005) is fully implemented.
25487 @node Implementation of Specific Ada Features,Implementation of Ada 2012 Features,Specialized Needs Annexes,Top
25488 @anchor{gnat_rm/implementation_of_specific_ada_features implementation-of-specific-ada-features}@anchor{13}@anchor{gnat_rm/implementation_of_specific_ada_features doc}@anchor{40c}@anchor{gnat_rm/implementation_of_specific_ada_features id1}@anchor{40d}
25489 @chapter Implementation of Specific Ada Features
25492 This chapter describes the GNAT implementation of several Ada language
25496 * Machine Code Insertions::
25497 * GNAT Implementation of Tasking::
25498 * GNAT Implementation of Shared Passive Packages::
25499 * Code Generation for Array Aggregates::
25500 * The Size of Discriminated Records with Default Discriminants::
25501 * Strict Conformance to the Ada Reference Manual::
25505 @node Machine Code Insertions,GNAT Implementation of Tasking,,Implementation of Specific Ada Features
25506 @anchor{gnat_rm/implementation_of_specific_ada_features machine-code-insertions}@anchor{164}@anchor{gnat_rm/implementation_of_specific_ada_features id2}@anchor{40e}
25507 @section Machine Code Insertions
25510 @geindex Machine Code insertions
25512 Package @code{Machine_Code} provides machine code support as described
25513 in the Ada Reference Manual in two separate forms:
25519 Machine code statements, consisting of qualified expressions that
25520 fit the requirements of RM section 13.8.
25523 An intrinsic callable procedure, providing an alternative mechanism of
25524 including machine instructions in a subprogram.
25527 The two features are similar, and both are closely related to the mechanism
25528 provided by the asm instruction in the GNU C compiler. Full understanding
25529 and use of the facilities in this package requires understanding the asm
25530 instruction, see the section on Extended Asm in
25531 @cite{Using_the_GNU_Compiler_Collection_(GCC)}.
25533 Calls to the function @code{Asm} and the procedure @code{Asm} have identical
25534 semantic restrictions and effects as described below. Both are provided so
25535 that the procedure call can be used as a statement, and the function call
25536 can be used to form a code_statement.
25538 Consider this C @code{asm} instruction:
25541 asm ("fsinx %1 %0" : "=f" (result) : "f" (angle));
25544 The equivalent can be written for GNAT as:
25547 Asm ("fsinx %1 %0",
25548 My_Float'Asm_Output ("=f", result),
25549 My_Float'Asm_Input ("f", angle));
25552 The first argument to @code{Asm} is the assembler template, and is
25553 identical to what is used in GNU C. This string must be a static
25554 expression. The second argument is the output operand list. It is
25555 either a single @code{Asm_Output} attribute reference, or a list of such
25556 references enclosed in parentheses (technically an array aggregate of
25559 The @code{Asm_Output} attribute denotes a function that takes two
25560 parameters. The first is a string, the second is the name of a variable
25561 of the type designated by the attribute prefix. The first (string)
25562 argument is required to be a static expression and designates the
25563 constraint (see the section on Constraints in
25564 @cite{Using_the_GNU_Compiler_Collection_(GCC)})
25565 for the parameter; e.g., what kind of register is required. The second
25566 argument is the variable to be written or updated with the
25567 result. The possible values for constraint are the same as those used in
25568 the RTL, and are dependent on the configuration file used to build the
25569 GCC back end. If there are no output operands, then this argument may
25570 either be omitted, or explicitly given as @code{No_Output_Operands}.
25571 No support is provided for GNU C's symbolic names for output parameters.
25573 The second argument of @code{my_float'Asm_Output} functions as
25574 though it were an @code{out} parameter, which is a little curious, but
25575 all names have the form of expressions, so there is no syntactic
25576 irregularity, even though normally functions would not be permitted
25577 @code{out} parameters. The third argument is the list of input
25578 operands. It is either a single @code{Asm_Input} attribute reference, or
25579 a list of such references enclosed in parentheses (technically an array
25580 aggregate of such references).
25582 The @code{Asm_Input} attribute denotes a function that takes two
25583 parameters. The first is a string, the second is an expression of the
25584 type designated by the prefix. The first (string) argument is required
25585 to be a static expression, and is the constraint for the parameter,
25586 (e.g., what kind of register is required). The second argument is the
25587 value to be used as the input argument. The possible values for the
25588 constraint are the same as those used in the RTL, and are dependent on
25589 the configuration file used to built the GCC back end.
25590 No support is provided for GNU C's symbolic names for input parameters.
25592 If there are no input operands, this argument may either be omitted, or
25593 explicitly given as @code{No_Input_Operands}. The fourth argument, not
25594 present in the above example, is a list of register names, called the
25595 @emph{clobber} argument. This argument, if given, must be a static string
25596 expression, and is a space or comma separated list of names of registers
25597 that must be considered destroyed as a result of the @code{Asm} call. If
25598 this argument is the null string (the default value), then the code
25599 generator assumes that no additional registers are destroyed.
25600 In addition to registers, the special clobbers @code{memory} and
25601 @code{cc} as described in the GNU C docs are both supported.
25603 The fifth argument, not present in the above example, called the
25604 @emph{volatile} argument, is by default @code{False}. It can be set to
25605 the literal value @code{True} to indicate to the code generator that all
25606 optimizations with respect to the instruction specified should be
25607 suppressed, and in particular an instruction that has outputs
25608 will still be generated, even if none of the outputs are
25609 used. See @cite{Using_the_GNU_Compiler_Collection_(GCC)}
25610 for the full description.
25611 Generally it is strongly advisable to use Volatile for any ASM statement
25612 that is missing either input or output operands or to avoid unwanted
25613 optimizations. A warning is generated if this advice is not followed.
25615 No support is provided for GNU C's @code{asm goto} feature.
25617 The @code{Asm} subprograms may be used in two ways. First the procedure
25618 forms can be used anywhere a procedure call would be valid, and
25619 correspond to what the RM calls 'intrinsic' routines. Such calls can
25620 be used to intersperse machine instructions with other Ada statements.
25621 Second, the function forms, which return a dummy value of the limited
25622 private type @code{Asm_Insn}, can be used in code statements, and indeed
25623 this is the only context where such calls are allowed. Code statements
25624 appear as aggregates of the form:
25627 Asm_Insn'(Asm (...));
25628 Asm_Insn'(Asm_Volatile (...));
25631 In accordance with RM rules, such code statements are allowed only
25632 within subprograms whose entire body consists of such statements. It is
25633 not permissible to intermix such statements with other Ada statements.
25635 Typically the form using intrinsic procedure calls is more convenient
25636 and more flexible. The code statement form is provided to meet the RM
25637 suggestion that such a facility should be made available. The following
25638 is the exact syntax of the call to @code{Asm}. As usual, if named notation
25639 is used, the arguments may be given in arbitrary order, following the
25640 normal rules for use of positional and named arguments:
25644 [Template =>] static_string_EXPRESSION
25645 [,[Outputs =>] OUTPUT_OPERAND_LIST ]
25646 [,[Inputs =>] INPUT_OPERAND_LIST ]
25647 [,[Clobber =>] static_string_EXPRESSION ]
25648 [,[Volatile =>] static_boolean_EXPRESSION] )
25650 OUTPUT_OPERAND_LIST ::=
25651 [PREFIX.]No_Output_Operands
25652 | OUTPUT_OPERAND_ATTRIBUTE
25653 | (OUTPUT_OPERAND_ATTRIBUTE @{,OUTPUT_OPERAND_ATTRIBUTE@})
25655 OUTPUT_OPERAND_ATTRIBUTE ::=
25656 SUBTYPE_MARK'Asm_Output (static_string_EXPRESSION, NAME)
25658 INPUT_OPERAND_LIST ::=
25659 [PREFIX.]No_Input_Operands
25660 | INPUT_OPERAND_ATTRIBUTE
25661 | (INPUT_OPERAND_ATTRIBUTE @{,INPUT_OPERAND_ATTRIBUTE@})
25663 INPUT_OPERAND_ATTRIBUTE ::=
25664 SUBTYPE_MARK'Asm_Input (static_string_EXPRESSION, EXPRESSION)
25667 The identifiers @code{No_Input_Operands} and @code{No_Output_Operands}
25668 are declared in the package @code{Machine_Code} and must be referenced
25669 according to normal visibility rules. In particular if there is no
25670 @code{use} clause for this package, then appropriate package name
25671 qualification is required.
25673 @node GNAT Implementation of Tasking,GNAT Implementation of Shared Passive Packages,Machine Code Insertions,Implementation of Specific Ada Features
25674 @anchor{gnat_rm/implementation_of_specific_ada_features id3}@anchor{40f}@anchor{gnat_rm/implementation_of_specific_ada_features gnat-implementation-of-tasking}@anchor{410}
25675 @section GNAT Implementation of Tasking
25678 This chapter outlines the basic GNAT approach to tasking (in particular,
25679 a multi-layered library for portability) and discusses issues related
25680 to compliance with the Real-Time Systems Annex.
25683 * Mapping Ada Tasks onto the Underlying Kernel Threads::
25684 * Ensuring Compliance with the Real-Time Annex::
25685 * Support for Locking Policies::
25689 @node Mapping Ada Tasks onto the Underlying Kernel Threads,Ensuring Compliance with the Real-Time Annex,,GNAT Implementation of Tasking
25690 @anchor{gnat_rm/implementation_of_specific_ada_features mapping-ada-tasks-onto-the-underlying-kernel-threads}@anchor{411}@anchor{gnat_rm/implementation_of_specific_ada_features id4}@anchor{412}
25691 @subsection Mapping Ada Tasks onto the Underlying Kernel Threads
25694 GNAT's run-time support comprises two layers:
25700 GNARL (GNAT Run-time Layer)
25703 GNULL (GNAT Low-level Library)
25706 In GNAT, Ada's tasking services rely on a platform and OS independent
25707 layer known as GNARL. This code is responsible for implementing the
25708 correct semantics of Ada's task creation, rendezvous, protected
25711 GNARL decomposes Ada's tasking semantics into simpler lower level
25712 operations such as create a thread, set the priority of a thread,
25713 yield, create a lock, lock/unlock, etc. The spec for these low-level
25714 operations constitutes GNULLI, the GNULL Interface. This interface is
25715 directly inspired from the POSIX real-time API.
25717 If the underlying executive or OS implements the POSIX standard
25718 faithfully, the GNULL Interface maps as is to the services offered by
25719 the underlying kernel. Otherwise, some target dependent glue code maps
25720 the services offered by the underlying kernel to the semantics expected
25723 Whatever the underlying OS (VxWorks, UNIX, Windows, etc.) the
25724 key point is that each Ada task is mapped on a thread in the underlying
25725 kernel. For example, in the case of VxWorks, one Ada task = one VxWorks task.
25727 In addition Ada task priorities map onto the underlying thread priorities.
25728 Mapping Ada tasks onto the underlying kernel threads has several advantages:
25734 The underlying scheduler is used to schedule the Ada tasks. This
25735 makes Ada tasks as efficient as kernel threads from a scheduling
25739 Interaction with code written in C containing threads is eased
25740 since at the lowest level Ada tasks and C threads map onto the same
25741 underlying kernel concept.
25744 When an Ada task is blocked during I/O the remaining Ada tasks are
25748 On multiprocessor systems Ada tasks can execute in parallel.
25751 Some threads libraries offer a mechanism to fork a new process, with the
25752 child process duplicating the threads from the parent.
25754 support this functionality when the parent contains more than one task.
25756 @geindex Forking a new process
25758 @node Ensuring Compliance with the Real-Time Annex,Support for Locking Policies,Mapping Ada Tasks onto the Underlying Kernel Threads,GNAT Implementation of Tasking
25759 @anchor{gnat_rm/implementation_of_specific_ada_features id5}@anchor{413}@anchor{gnat_rm/implementation_of_specific_ada_features ensuring-compliance-with-the-real-time-annex}@anchor{414}
25760 @subsection Ensuring Compliance with the Real-Time Annex
25763 @geindex Real-Time Systems Annex compliance
25765 Although mapping Ada tasks onto
25766 the underlying threads has significant advantages, it does create some
25767 complications when it comes to respecting the scheduling semantics
25768 specified in the real-time annex (Annex D).
25770 For instance the Annex D requirement for the @code{FIFO_Within_Priorities}
25771 scheduling policy states:
25775 @emph{When the active priority of a ready task that is not running
25776 changes, or the setting of its base priority takes effect, the
25777 task is removed from the ready queue for its old active priority
25778 and is added at the tail of the ready queue for its new active
25779 priority, except in the case where the active priority is lowered
25780 due to the loss of inherited priority, in which case the task is
25781 added at the head of the ready queue for its new active priority.}
25784 While most kernels do put tasks at the end of the priority queue when
25785 a task changes its priority, (which respects the main
25786 FIFO_Within_Priorities requirement), almost none keep a thread at the
25787 beginning of its priority queue when its priority drops from the loss
25788 of inherited priority.
25790 As a result most vendors have provided incomplete Annex D implementations.
25792 The GNAT run-time, has a nice cooperative solution to this problem
25793 which ensures that accurate FIFO_Within_Priorities semantics are
25796 The principle is as follows. When an Ada task T is about to start
25797 running, it checks whether some other Ada task R with the same
25798 priority as T has been suspended due to the loss of priority
25799 inheritance. If this is the case, T yields and is placed at the end of
25800 its priority queue. When R arrives at the front of the queue it
25803 Note that this simple scheme preserves the relative order of the tasks
25804 that were ready to execute in the priority queue where R has been
25807 @c Support_for_Locking_Policies
25809 @node Support for Locking Policies,,Ensuring Compliance with the Real-Time Annex,GNAT Implementation of Tasking
25810 @anchor{gnat_rm/implementation_of_specific_ada_features support-for-locking-policies}@anchor{415}
25811 @subsection Support for Locking Policies
25814 This section specifies which policies specified by pragma Locking_Policy
25815 are supported on which platforms.
25817 GNAT supports the standard @code{Ceiling_Locking} policy, and the
25818 implementation defined @code{Inheritance_Locking} and
25819 @code{Concurrent_Readers_Locking} policies.
25821 @code{Ceiling_Locking} is supported on all platforms if the operating system
25822 supports it. In particular, @code{Ceiling_Locking} is not supported on
25824 @code{Inheritance_Locking} is supported on
25829 @code{Concurrent_Readers_Locking} is supported on Linux.
25831 Notes about @code{Ceiling_Locking} on Linux:
25832 If the process is running as 'root', ceiling locking is used.
25833 If the capabilities facility is installed
25834 ("sudo apt-get --assume-yes install libcap-dev" on Ubuntu,
25836 and the program is linked against that library
25838 and the executable file has the cap_sys_nice capability
25839 ("sudo /sbin/setcap cap_sys_nice=ep executable_file_name"),
25840 then ceiling locking is used.
25841 Otherwise, the @code{Ceiling_Locking} policy is ignored.
25843 @node GNAT Implementation of Shared Passive Packages,Code Generation for Array Aggregates,GNAT Implementation of Tasking,Implementation of Specific Ada Features
25844 @anchor{gnat_rm/implementation_of_specific_ada_features id6}@anchor{416}@anchor{gnat_rm/implementation_of_specific_ada_features gnat-implementation-of-shared-passive-packages}@anchor{417}
25845 @section GNAT Implementation of Shared Passive Packages
25848 @geindex Shared passive packages
25850 GNAT fully implements the
25851 @geindex pragma Shared_Passive
25853 @code{Shared_Passive} for
25854 the purpose of designating shared passive packages.
25855 This allows the use of passive partitions in the
25856 context described in the Ada Reference Manual; i.e., for communication
25857 between separate partitions of a distributed application using the
25858 features in Annex E.
25862 @geindex Distribution Systems Annex
25864 However, the implementation approach used by GNAT provides for more
25865 extensive usage as follows:
25870 @item @emph{Communication between separate programs}
25872 This allows separate programs to access the data in passive
25873 partitions, using protected objects for synchronization where
25874 needed. The only requirement is that the two programs have a
25875 common shared file system. It is even possible for programs
25876 running on different machines with different architectures
25877 (e.g., different endianness) to communicate via the data in
25878 a passive partition.
25880 @item @emph{Persistence between program runs}
25882 The data in a passive package can persist from one run of a
25883 program to another, so that a later program sees the final
25884 values stored by a previous run of the same program.
25887 The implementation approach used is to store the data in files. A
25888 separate stream file is created for each object in the package, and
25889 an access to an object causes the corresponding file to be read or
25892 @geindex SHARED_MEMORY_DIRECTORY environment variable
25894 The environment variable @code{SHARED_MEMORY_DIRECTORY} should be
25895 set to the directory to be used for these files.
25896 The files in this directory
25897 have names that correspond to their fully qualified names. For
25898 example, if we have the package
25902 pragma Shared_Passive (X);
25908 and the environment variable is set to @code{/stemp/}, then the files created
25909 will have the names:
25916 These files are created when a value is initially written to the object, and
25917 the files are retained until manually deleted. This provides the persistence
25918 semantics. If no file exists, it means that no partition has assigned a value
25919 to the variable; in this case the initial value declared in the package
25920 will be used. This model ensures that there are no issues in synchronizing
25921 the elaboration process, since elaboration of passive packages elaborates the
25922 initial values, but does not create the files.
25924 The files are written using normal @code{Stream_IO} access.
25925 If you want to be able
25926 to communicate between programs or partitions running on different
25927 architectures, then you should use the XDR versions of the stream attribute
25928 routines, since these are architecture independent.
25930 If active synchronization is required for access to the variables in the
25931 shared passive package, then as described in the Ada Reference Manual, the
25932 package may contain protected objects used for this purpose. In this case
25933 a lock file (whose name is @code{___lock} (three underscores)
25934 is created in the shared memory directory.
25936 @geindex ___lock file (for shared passive packages)
25938 This is used to provide the required locking
25939 semantics for proper protected object synchronization.
25941 GNAT supports shared passive packages on all platforms
25942 except for OpenVMS.
25944 @node Code Generation for Array Aggregates,The Size of Discriminated Records with Default Discriminants,GNAT Implementation of Shared Passive Packages,Implementation of Specific Ada Features
25945 @anchor{gnat_rm/implementation_of_specific_ada_features code-generation-for-array-aggregates}@anchor{418}@anchor{gnat_rm/implementation_of_specific_ada_features id7}@anchor{419}
25946 @section Code Generation for Array Aggregates
25949 Aggregates have a rich syntax and allow the user to specify the values of
25950 complex data structures by means of a single construct. As a result, the
25951 code generated for aggregates can be quite complex and involve loops, case
25952 statements and multiple assignments. In the simplest cases, however, the
25953 compiler will recognize aggregates whose components and constraints are
25954 fully static, and in those cases the compiler will generate little or no
25955 executable code. The following is an outline of the code that GNAT generates
25956 for various aggregate constructs. For further details, you will find it
25957 useful to examine the output produced by the -gnatG flag to see the expanded
25958 source that is input to the code generator. You may also want to examine
25959 the assembly code generated at various levels of optimization.
25961 The code generated for aggregates depends on the context, the component values,
25962 and the type. In the context of an object declaration the code generated is
25963 generally simpler than in the case of an assignment. As a general rule, static
25964 component values and static subtypes also lead to simpler code.
25967 * Static constant aggregates with static bounds::
25968 * Constant aggregates with unconstrained nominal types::
25969 * Aggregates with static bounds::
25970 * Aggregates with nonstatic bounds::
25971 * Aggregates in assignment statements::
25975 @node Static constant aggregates with static bounds,Constant aggregates with unconstrained nominal types,,Code Generation for Array Aggregates
25976 @anchor{gnat_rm/implementation_of_specific_ada_features static-constant-aggregates-with-static-bounds}@anchor{41a}@anchor{gnat_rm/implementation_of_specific_ada_features id8}@anchor{41b}
25977 @subsection Static constant aggregates with static bounds
25980 For the declarations:
25983 type One_Dim is array (1..10) of integer;
25984 ar0 : constant One_Dim := (1, 2, 3, 4, 5, 6, 7, 8, 9, 0);
25987 GNAT generates no executable code: the constant ar0 is placed in static memory.
25988 The same is true for constant aggregates with named associations:
25991 Cr1 : constant One_Dim := (4 => 16, 2 => 4, 3 => 9, 1 => 1, 5 .. 10 => 0);
25992 Cr3 : constant One_Dim := (others => 7777);
25995 The same is true for multidimensional constant arrays such as:
25998 type two_dim is array (1..3, 1..3) of integer;
25999 Unit : constant two_dim := ( (1,0,0), (0,1,0), (0,0,1));
26002 The same is true for arrays of one-dimensional arrays: the following are
26006 type ar1b is array (1..3) of boolean;
26007 type ar_ar is array (1..3) of ar1b;
26008 None : constant ar1b := (others => false); -- fully static
26009 None2 : constant ar_ar := (1..3 => None); -- fully static
26012 However, for multidimensional aggregates with named associations, GNAT will
26013 generate assignments and loops, even if all associations are static. The
26014 following two declarations generate a loop for the first dimension, and
26015 individual component assignments for the second dimension:
26018 Zero1: constant two_dim := (1..3 => (1..3 => 0));
26019 Zero2: constant two_dim := (others => (others => 0));
26022 @node Constant aggregates with unconstrained nominal types,Aggregates with static bounds,Static constant aggregates with static bounds,Code Generation for Array Aggregates
26023 @anchor{gnat_rm/implementation_of_specific_ada_features constant-aggregates-with-unconstrained-nominal-types}@anchor{41c}@anchor{gnat_rm/implementation_of_specific_ada_features id9}@anchor{41d}
26024 @subsection Constant aggregates with unconstrained nominal types
26027 In such cases the aggregate itself establishes the subtype, so that
26028 associations with @code{others} cannot be used. GNAT determines the
26029 bounds for the actual subtype of the aggregate, and allocates the
26030 aggregate statically as well. No code is generated for the following:
26033 type One_Unc is array (natural range <>) of integer;
26034 Cr_Unc : constant One_Unc := (12,24,36);
26037 @node Aggregates with static bounds,Aggregates with nonstatic bounds,Constant aggregates with unconstrained nominal types,Code Generation for Array Aggregates
26038 @anchor{gnat_rm/implementation_of_specific_ada_features id10}@anchor{41e}@anchor{gnat_rm/implementation_of_specific_ada_features aggregates-with-static-bounds}@anchor{41f}
26039 @subsection Aggregates with static bounds
26042 In all previous examples the aggregate was the initial (and immutable) value
26043 of a constant. If the aggregate initializes a variable, then code is generated
26044 for it as a combination of individual assignments and loops over the target
26045 object. The declarations
26048 Cr_Var1 : One_Dim := (2, 5, 7, 11, 0, 0, 0, 0, 0, 0);
26049 Cr_Var2 : One_Dim := (others > -1);
26052 generate the equivalent of
26060 for I in Cr_Var2'range loop
26065 @node Aggregates with nonstatic bounds,Aggregates in assignment statements,Aggregates with static bounds,Code Generation for Array Aggregates
26066 @anchor{gnat_rm/implementation_of_specific_ada_features id11}@anchor{420}@anchor{gnat_rm/implementation_of_specific_ada_features aggregates-with-nonstatic-bounds}@anchor{421}
26067 @subsection Aggregates with nonstatic bounds
26070 If the bounds of the aggregate are not statically compatible with the bounds
26071 of the nominal subtype of the target, then constraint checks have to be
26072 generated on the bounds. For a multidimensional array, constraint checks may
26073 have to be applied to sub-arrays individually, if they do not have statically
26074 compatible subtypes.
26076 @node Aggregates in assignment statements,,Aggregates with nonstatic bounds,Code Generation for Array Aggregates
26077 @anchor{gnat_rm/implementation_of_specific_ada_features id12}@anchor{422}@anchor{gnat_rm/implementation_of_specific_ada_features aggregates-in-assignment-statements}@anchor{423}
26078 @subsection Aggregates in assignment statements
26081 In general, aggregate assignment requires the construction of a temporary,
26082 and a copy from the temporary to the target of the assignment. This is because
26083 it is not always possible to convert the assignment into a series of individual
26084 component assignments. For example, consider the simple case:
26090 This cannot be converted into:
26097 So the aggregate has to be built first in a separate location, and then
26098 copied into the target. GNAT recognizes simple cases where this intermediate
26099 step is not required, and the assignments can be performed in place, directly
26100 into the target. The following sufficient criteria are applied:
26106 The bounds of the aggregate are static, and the associations are static.
26109 The components of the aggregate are static constants, names of
26110 simple variables that are not renamings, or expressions not involving
26111 indexed components whose operands obey these rules.
26114 If any of these conditions are violated, the aggregate will be built in
26115 a temporary (created either by the front-end or the code generator) and then
26116 that temporary will be copied onto the target.
26118 @node The Size of Discriminated Records with Default Discriminants,Strict Conformance to the Ada Reference Manual,Code Generation for Array Aggregates,Implementation of Specific Ada Features
26119 @anchor{gnat_rm/implementation_of_specific_ada_features id13}@anchor{424}@anchor{gnat_rm/implementation_of_specific_ada_features the-size-of-discriminated-records-with-default-discriminants}@anchor{425}
26120 @section The Size of Discriminated Records with Default Discriminants
26123 If a discriminated type @code{T} has discriminants with default values, it is
26124 possible to declare an object of this type without providing an explicit
26128 type Size is range 1..100;
26130 type Rec (D : Size := 15) is record
26131 Name : String (1..D);
26137 Such an object is said to be @emph{unconstrained}.
26138 The discriminant of the object
26139 can be modified by a full assignment to the object, as long as it preserves the
26140 relation between the value of the discriminant, and the value of the components
26144 Word := (3, "yes");
26146 Word := (5, "maybe");
26148 Word := (5, "no"); -- raises Constraint_Error
26151 In order to support this behavior efficiently, an unconstrained object is
26152 given the maximum size that any value of the type requires. In the case
26153 above, @code{Word} has storage for the discriminant and for
26154 a @code{String} of length 100.
26155 It is important to note that unconstrained objects do not require dynamic
26156 allocation. It would be an improper implementation to place on the heap those
26157 components whose size depends on discriminants. (This improper implementation
26158 was used by some Ada83 compilers, where the @code{Name} component above
26160 been stored as a pointer to a dynamic string). Following the principle that
26161 dynamic storage management should never be introduced implicitly,
26162 an Ada compiler should reserve the full size for an unconstrained declared
26163 object, and place it on the stack.
26165 This maximum size approach
26166 has been a source of surprise to some users, who expect the default
26167 values of the discriminants to determine the size reserved for an
26168 unconstrained object: "If the default is 15, why should the object occupy
26170 The answer, of course, is that the discriminant may be later modified,
26171 and its full range of values must be taken into account. This is why the
26175 type Rec (D : Positive := 15) is record
26176 Name : String (1..D);
26182 is flagged by the compiler with a warning:
26183 an attempt to create @code{Too_Large} will raise @code{Storage_Error},
26184 because the required size includes @code{Positive'Last}
26185 bytes. As the first example indicates, the proper approach is to declare an
26186 index type of 'reasonable' range so that unconstrained objects are not too
26189 One final wrinkle: if the object is declared to be @code{aliased}, or if it is
26190 created in the heap by means of an allocator, then it is @emph{not}
26192 it is constrained by the default values of the discriminants, and those values
26193 cannot be modified by full assignment. This is because in the presence of
26194 aliasing all views of the object (which may be manipulated by different tasks,
26195 say) must be consistent, so it is imperative that the object, once created,
26198 @node Strict Conformance to the Ada Reference Manual,,The Size of Discriminated Records with Default Discriminants,Implementation of Specific Ada Features
26199 @anchor{gnat_rm/implementation_of_specific_ada_features strict-conformance-to-the-ada-reference-manual}@anchor{426}@anchor{gnat_rm/implementation_of_specific_ada_features id14}@anchor{427}
26200 @section Strict Conformance to the Ada Reference Manual
26203 The dynamic semantics defined by the Ada Reference Manual impose a set of
26204 run-time checks to be generated. By default, the GNAT compiler will insert many
26205 run-time checks into the compiled code, including most of those required by the
26206 Ada Reference Manual. However, there are two checks that are not enabled in
26207 the default mode for efficiency reasons: checks for access before elaboration
26208 on subprogram calls, and stack overflow checking (most operating systems do not
26209 perform this check by default).
26211 Strict conformance to the Ada Reference Manual can be achieved by adding two
26212 compiler options for dynamic checks for access-before-elaboration on subprogram
26213 calls and generic instantiations (@emph{-gnatE}), and stack overflow checking
26214 (@emph{-fstack-check}).
26216 Note that the result of a floating point arithmetic operation in overflow and
26217 invalid situations, when the @code{Machine_Overflows} attribute of the result
26218 type is @code{False}, is to generate IEEE NaN and infinite values. This is the
26219 case for machines compliant with the IEEE floating-point standard, but on
26220 machines that are not fully compliant with this standard, such as Alpha, the
26221 @emph{-mieee} compiler flag must be used for achieving IEEE confirming
26222 behavior (although at the cost of a significant performance penalty), so
26223 infinite and NaN values are properly generated.
26225 @node Implementation of Ada 2012 Features,Obsolescent Features,Implementation of Specific Ada Features,Top
26226 @anchor{gnat_rm/implementation_of_ada_2012_features doc}@anchor{428}@anchor{gnat_rm/implementation_of_ada_2012_features implementation-of-ada-2012-features}@anchor{14}@anchor{gnat_rm/implementation_of_ada_2012_features id1}@anchor{429}
26227 @chapter Implementation of Ada 2012 Features
26230 @geindex Ada 2012 implementation status
26232 @geindex -gnat12 option (gcc)
26234 @geindex pragma Ada_2012
26236 @geindex configuration pragma Ada_2012
26238 @geindex Ada_2012 configuration pragma
26240 This chapter contains a complete list of Ada 2012 features that have been
26242 Generally, these features are only
26243 available if the @emph{-gnat12} (Ada 2012 features enabled) option is set,
26244 which is the default behavior,
26245 or if the configuration pragma @code{Ada_2012} is used.
26247 However, new pragmas, attributes, and restrictions are
26248 unconditionally available, since the Ada 95 standard allows the addition of
26249 new pragmas, attributes, and restrictions (there are exceptions, which are
26250 documented in the individual descriptions), and also certain packages
26251 were made available in earlier versions of Ada.
26253 An ISO date (YYYY-MM-DD) appears in parentheses on the description line.
26254 This date shows the implementation date of the feature. Any wavefront
26255 subsequent to this date will contain the indicated feature, as will any
26256 subsequent releases. A date of 0000-00-00 means that GNAT has always
26257 implemented the feature, or implemented it as soon as it appeared as a
26258 binding interpretation.
26260 Each feature corresponds to an Ada Issue ('AI') approved by the Ada
26261 standardization group (ISO/IEC JTC1/SC22/WG9) for inclusion in Ada 2012.
26262 The features are ordered based on the relevant sections of the Ada
26263 Reference Manual ("RM"). When a given AI relates to multiple points
26264 in the RM, the earliest is used.
26266 A complete description of the AIs may be found in
26267 @indicateurl{http://www.ada-auth.org/ai05-summary.html}.
26269 @geindex AI-0176 (Ada 2012 feature)
26275 @emph{AI-0176 Quantified expressions (2010-09-29)}
26277 Both universally and existentially quantified expressions are implemented.
26278 They use the new syntax for iterators proposed in AI05-139-2, as well as
26279 the standard Ada loop syntax.
26281 RM References: 1.01.04 (12) 2.09 (2/2) 4.04 (7) 4.05.09 (0)
26284 @geindex AI-0079 (Ada 2012 feature)
26290 @emph{AI-0079 Allow other_format characters in source (2010-07-10)}
26292 Wide characters in the unicode category @emph{other_format} are now allowed in
26293 source programs between tokens, but not within a token such as an identifier.
26295 RM References: 2.01 (4/2) 2.02 (7)
26298 @geindex AI-0091 (Ada 2012 feature)
26304 @emph{AI-0091 Do not allow other_format in identifiers (0000-00-00)}
26306 Wide characters in the unicode category @emph{other_format} are not permitted
26307 within an identifier, since this can be a security problem. The error
26308 message for this case has been improved to be more specific, but GNAT has
26309 never allowed such characters to appear in identifiers.
26311 RM References: 2.03 (3.1/2) 2.03 (4/2) 2.03 (5/2) 2.03 (5.1/2) 2.03 (5.2/2) 2.03 (5.3/2) 2.09 (2/2)
26314 @geindex AI-0100 (Ada 2012 feature)
26320 @emph{AI-0100 Placement of pragmas (2010-07-01)}
26322 This AI is an earlier version of AI-163. It simplifies the rules
26323 for legal placement of pragmas. In the case of lists that allow pragmas, if
26324 the list may have no elements, then the list may consist solely of pragmas.
26326 RM References: 2.08 (7)
26329 @geindex AI-0163 (Ada 2012 feature)
26335 @emph{AI-0163 Pragmas in place of null (2010-07-01)}
26337 A statement sequence may be composed entirely of pragmas. It is no longer
26338 necessary to add a dummy @code{null} statement to make the sequence legal.
26340 RM References: 2.08 (7) 2.08 (16)
26343 @geindex AI-0080 (Ada 2012 feature)
26349 @emph{AI-0080 'View of' not needed if clear from context (0000-00-00)}
26351 This is an editorial change only, described as non-testable in the AI.
26353 RM References: 3.01 (7)
26356 @geindex AI-0183 (Ada 2012 feature)
26362 @emph{AI-0183 Aspect specifications (2010-08-16)}
26364 Aspect specifications have been fully implemented except for pre and post-
26365 conditions, and type invariants, which have their own separate AI's. All
26366 forms of declarations listed in the AI are supported. The following is a
26367 list of the aspects supported (with GNAT implementation aspects marked)
26371 @multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxx}
26416 @code{Atomic_Components}
26428 @code{Component_Size}
26434 @code{Contract_Cases}
26442 @code{Discard_Names}
26448 @code{External_Tag}
26454 @code{Favor_Top_Level}
26468 @code{Inline_Always}
26484 @code{Machine_Radix}
26510 @code{Persistent_BSS}
26536 @code{Preelaborable_Initialization}
26542 @code{Pure_Function}
26550 @code{Remote_Access_Type}
26572 @code{Storage_Pool}
26578 @code{Storage_Size}
26596 @code{Suppress_Debug_Info}
26612 @code{Thread_Local_Storage}
26620 @code{Type_Invariant}
26626 @code{Unchecked_Union}
26632 @code{Universal_Aliasing}
26648 @code{Unreferenced}
26656 @code{Unreferenced_Objects}
26684 @code{Volatile_Components}
26701 Note that for aspects with an expression, e.g. @code{Size}, the expression is
26702 treated like a default expression (visibility is analyzed at the point of
26703 occurrence of the aspect, but evaluation of the expression occurs at the
26704 freeze point of the entity involved).
26706 RM References: 3.02.01 (3) 3.02.02 (2) 3.03.01 (2/2) 3.08 (6)
26707 3.09.03 (1.1/2) 6.01 (2/2) 6.07 (2/2) 9.05.02 (2/2) 7.01 (3) 7.03
26708 (2) 7.03 (3) 9.01 (2/2) 9.01 (3/2) 9.04 (2/2) 9.04 (3/2)
26709 9.05.02 (2/2) 11.01 (2) 12.01 (3) 12.03 (2/2) 12.04 (2/2) 12.05 (2)
26710 12.06 (2.1/2) 12.06 (2.2/2) 12.07 (2) 13.01 (0.1/2) 13.03 (5/1)
26714 @geindex AI-0128 (Ada 2012 feature)
26720 @emph{AI-0128 Inequality is a primitive operation (0000-00-00)}
26722 If an equality operator ("=") is declared for a type, then the implicitly
26723 declared inequality operator ("/=") is a primitive operation of the type.
26724 This is the only reasonable interpretation, and is the one always implemented
26725 by GNAT, but the RM was not entirely clear in making this point.
26727 RM References: 3.02.03 (6) 6.06 (6)
26730 @geindex AI-0003 (Ada 2012 feature)
26736 @emph{AI-0003 Qualified expressions as names (2010-07-11)}
26738 In Ada 2012, a qualified expression is considered to be syntactically a name,
26739 meaning that constructs such as @code{A'(F(X)).B} are now legal. This is
26740 useful in disambiguating some cases of overloading.
26742 RM References: 3.03 (11) 3.03 (21) 4.01 (2) 4.04 (7) 4.07 (3)
26746 @geindex AI-0120 (Ada 2012 feature)
26752 @emph{AI-0120 Constant instance of protected object (0000-00-00)}
26754 This is an RM editorial change only. The section that lists objects that are
26755 constant failed to include the current instance of a protected object
26756 within a protected function. This has always been treated as a constant
26759 RM References: 3.03 (21)
26762 @geindex AI-0008 (Ada 2012 feature)
26768 @emph{AI-0008 General access to constrained objects (0000-00-00)}
26770 The wording in the RM implied that if you have a general access to a
26771 constrained object, it could be used to modify the discriminants. This was
26772 obviously not intended. @code{Constraint_Error} should be raised, and GNAT
26773 has always done so in this situation.
26775 RM References: 3.03 (23) 3.10.02 (26/2) 4.01 (9) 6.04.01 (17) 8.05.01 (5/2)
26778 @geindex AI-0093 (Ada 2012 feature)
26784 @emph{AI-0093 Additional rules use immutably limited (0000-00-00)}
26786 This is an editorial change only, to make more widespread use of the Ada 2012
26787 'immutably limited'.
26789 RM References: 3.03 (23.4/3)
26792 @geindex AI-0096 (Ada 2012 feature)
26798 @emph{AI-0096 Deriving from formal private types (2010-07-20)}
26800 In general it is illegal for a type derived from a formal limited type to be
26801 nonlimited. This AI makes an exception to this rule: derivation is legal
26802 if it appears in the private part of the generic, and the formal type is not
26803 tagged. If the type is tagged, the legality check must be applied to the
26804 private part of the package.
26806 RM References: 3.04 (5.1/2) 6.02 (7)
26809 @geindex AI-0181 (Ada 2012 feature)
26815 @emph{AI-0181 Soft hyphen is a non-graphic character (2010-07-23)}
26817 From Ada 2005 on, soft hyphen is considered a non-graphic character, which
26818 means that it has a special name (@code{SOFT_HYPHEN}) in conjunction with the
26819 @code{Image} and @code{Value} attributes for the character types. Strictly
26820 speaking this is an inconsistency with Ada 95, but in practice the use of
26821 these attributes is so obscure that it will not cause problems.
26823 RM References: 3.05.02 (2/2) A.01 (35/2) A.03.03 (21)
26826 @geindex AI-0182 (Ada 2012 feature)
26832 @emph{AI-0182 Additional forms for} @code{Character'Value} @emph{(0000-00-00)}
26834 This AI allows @code{Character'Value} to accept the string @code{'?'} where
26835 @code{?} is any character including non-graphic control characters. GNAT has
26836 always accepted such strings. It also allows strings such as
26837 @code{HEX_00000041} to be accepted, but GNAT does not take advantage of this
26838 permission and raises @code{Constraint_Error}, as is certainly still
26841 RM References: 3.05 (56/2)
26844 @geindex AI-0214 (Ada 2012 feature)
26850 @emph{AI-0214 Defaulted discriminants for limited tagged (2010-10-01)}
26852 Ada 2012 relaxes the restriction that forbids discriminants of tagged types
26853 to have default expressions by allowing them when the type is limited. It
26854 is often useful to define a default value for a discriminant even though
26855 it can't be changed by assignment.
26857 RM References: 3.07 (9.1/2) 3.07.02 (3)
26860 @geindex AI-0102 (Ada 2012 feature)
26866 @emph{AI-0102 Some implicit conversions are illegal (0000-00-00)}
26868 It is illegal to assign an anonymous access constant to an anonymous access
26869 variable. The RM did not have a clear rule to prevent this, but GNAT has
26870 always generated an error for this usage.
26872 RM References: 3.07 (16) 3.07.01 (9) 6.04.01 (6) 8.06 (27/2)
26875 @geindex AI-0158 (Ada 2012 feature)
26881 @emph{AI-0158 Generalizing membership tests (2010-09-16)}
26883 This AI extends the syntax of membership tests to simplify complex conditions
26884 that can be expressed as membership in a subset of values of any type. It
26885 introduces syntax for a list of expressions that may be used in loop contexts
26888 RM References: 3.08.01 (5) 4.04 (3) 4.05.02 (3) 4.05.02 (5) 4.05.02 (27)
26891 @geindex AI-0173 (Ada 2012 feature)
26897 @emph{AI-0173 Testing if tags represent abstract types (2010-07-03)}
26899 The function @code{Ada.Tags.Type_Is_Abstract} returns @code{True} if invoked
26900 with the tag of an abstract type, and @code{False} otherwise.
26902 RM References: 3.09 (7.4/2) 3.09 (12.4/2)
26905 @geindex AI-0076 (Ada 2012 feature)
26911 @emph{AI-0076 function with controlling result (0000-00-00)}
26913 This is an editorial change only. The RM defines calls with controlling
26914 results, but uses the term 'function with controlling result' without an
26915 explicit definition.
26917 RM References: 3.09.02 (2/2)
26920 @geindex AI-0126 (Ada 2012 feature)
26926 @emph{AI-0126 Dispatching with no declared operation (0000-00-00)}
26928 This AI clarifies dispatching rules, and simply confirms that dispatching
26929 executes the operation of the parent type when there is no explicitly or
26930 implicitly declared operation for the descendant type. This has always been
26931 the case in all versions of GNAT.
26933 RM References: 3.09.02 (20/2) 3.09.02 (20.1/2) 3.09.02 (20.2/2)
26936 @geindex AI-0097 (Ada 2012 feature)
26942 @emph{AI-0097 Treatment of abstract null extension (2010-07-19)}
26944 The RM as written implied that in some cases it was possible to create an
26945 object of an abstract type, by having an abstract extension inherit a non-
26946 abstract constructor from its parent type. This mistake has been corrected
26947 in GNAT and in the RM, and this construct is now illegal.
26949 RM References: 3.09.03 (4/2)
26952 @geindex AI-0203 (Ada 2012 feature)
26958 @emph{AI-0203 Extended return cannot be abstract (0000-00-00)}
26960 A return_subtype_indication cannot denote an abstract subtype. GNAT has never
26961 permitted such usage.
26963 RM References: 3.09.03 (8/3)
26966 @geindex AI-0198 (Ada 2012 feature)
26972 @emph{AI-0198 Inheriting abstract operators (0000-00-00)}
26974 This AI resolves a conflict between two rules involving inherited abstract
26975 operations and predefined operators. If a derived numeric type inherits
26976 an abstract operator, it overrides the predefined one. This interpretation
26977 was always the one implemented in GNAT.
26979 RM References: 3.09.03 (4/3)
26982 @geindex AI-0073 (Ada 2012 feature)
26988 @emph{AI-0073 Functions returning abstract types (2010-07-10)}
26990 This AI covers a number of issues regarding returning abstract types. In
26991 particular generic functions cannot have abstract result types or access
26992 result types designated an abstract type. There are some other cases which
26993 are detailed in the AI. Note that this binding interpretation has not been
26994 retrofitted to operate before Ada 2012 mode, since it caused a significant
26995 number of regressions.
26997 RM References: 3.09.03 (8) 3.09.03 (10) 6.05 (8/2)
27000 @geindex AI-0070 (Ada 2012 feature)
27006 @emph{AI-0070 Elaboration of interface types (0000-00-00)}
27008 This is an editorial change only, there are no testable consequences short of
27009 checking for the absence of generated code for an interface declaration.
27011 RM References: 3.09.04 (18/2)
27014 @geindex AI-0208 (Ada 2012 feature)
27020 @emph{AI-0208 Characteristics of incomplete views (0000-00-00)}
27022 The wording in the Ada 2005 RM concerning characteristics of incomplete views
27023 was incorrect and implied that some programs intended to be legal were now
27024 illegal. GNAT had never considered such programs illegal, so it has always
27025 implemented the intent of this AI.
27027 RM References: 3.10.01 (2.4/2) 3.10.01 (2.6/2)
27030 @geindex AI-0162 (Ada 2012 feature)
27036 @emph{AI-0162 Incomplete type completed by partial view (2010-09-15)}
27038 Incomplete types are made more useful by allowing them to be completed by
27039 private types and private extensions.
27041 RM References: 3.10.01 (2.5/2) 3.10.01 (2.6/2) 3.10.01 (3) 3.10.01 (4/2)
27044 @geindex AI-0098 (Ada 2012 feature)
27050 @emph{AI-0098 Anonymous subprogram access restrictions (0000-00-00)}
27052 An unintentional omission in the RM implied some inconsistent restrictions on
27053 the use of anonymous access to subprogram values. These restrictions were not
27054 intentional, and have never been enforced by GNAT.
27056 RM References: 3.10.01 (6) 3.10.01 (9.2/2)
27059 @geindex AI-0199 (Ada 2012 feature)
27065 @emph{AI-0199 Aggregate with anonymous access components (2010-07-14)}
27067 A choice list in a record aggregate can include several components of
27068 (distinct) anonymous access types as long as they have matching designated
27071 RM References: 4.03.01 (16)
27074 @geindex AI-0220 (Ada 2012 feature)
27080 @emph{AI-0220 Needed components for aggregates (0000-00-00)}
27082 This AI addresses a wording problem in the RM that appears to permit some
27083 complex cases of aggregates with nonstatic discriminants. GNAT has always
27084 implemented the intended semantics.
27086 RM References: 4.03.01 (17)
27089 @geindex AI-0147 (Ada 2012 feature)
27095 @emph{AI-0147 Conditional expressions (2009-03-29)}
27097 Conditional expressions are permitted. The form of such an expression is:
27100 (if expr then expr @{elsif expr then expr@} [else expr])
27103 The parentheses can be omitted in contexts where parentheses are present
27104 anyway, such as subprogram arguments and pragma arguments. If the @strong{else}
27105 clause is omitted, @strong{else} @emph{True} is assumed;
27106 thus @code{(if A then B)} is a way to conveniently represent
27107 @emph{(A implies B)} in standard logic.
27109 RM References: 4.03.03 (15) 4.04 (1) 4.04 (7) 4.05.07 (0) 4.07 (2)
27110 4.07 (3) 4.09 (12) 4.09 (33) 5.03 (3) 5.03 (4) 7.05 (2.1/2)
27113 @geindex AI-0037 (Ada 2012 feature)
27119 @emph{AI-0037 Out-of-range box associations in aggregate (0000-00-00)}
27121 This AI confirms that an association of the form @code{Indx => <>} in an
27122 array aggregate must raise @code{Constraint_Error} if @code{Indx}
27123 is out of range. The RM specified a range check on other associations, but
27124 not when the value of the association was defaulted. GNAT has always inserted
27125 a constraint check on the index value.
27127 RM References: 4.03.03 (29)
27130 @geindex AI-0123 (Ada 2012 feature)
27136 @emph{AI-0123 Composability of equality (2010-04-13)}
27138 Equality of untagged record composes, so that the predefined equality for a
27139 composite type that includes a component of some untagged record type
27140 @code{R} uses the equality operation of @code{R} (which may be user-defined
27141 or predefined). This makes the behavior of untagged records identical to that
27142 of tagged types in this respect.
27144 This change is an incompatibility with previous versions of Ada, but it
27145 corrects a non-uniformity that was often a source of confusion. Analysis of
27146 a large number of industrial programs indicates that in those rare cases
27147 where a composite type had an untagged record component with a user-defined
27148 equality, either there was no use of the composite equality, or else the code
27149 expected the same composability as for tagged types, and thus had a bug that
27150 would be fixed by this change.
27152 RM References: 4.05.02 (9.7/2) 4.05.02 (14) 4.05.02 (15) 4.05.02 (24)
27156 @geindex AI-0088 (Ada 2012 feature)
27162 @emph{AI-0088 The value of exponentiation (0000-00-00)}
27164 This AI clarifies the equivalence rule given for the dynamic semantics of
27165 exponentiation: the value of the operation can be obtained by repeated
27166 multiplication, but the operation can be implemented otherwise (for example
27167 using the familiar divide-by-two-and-square algorithm, even if this is less
27168 accurate), and does not imply repeated reads of a volatile base.
27170 RM References: 4.05.06 (11)
27173 @geindex AI-0188 (Ada 2012 feature)
27179 @emph{AI-0188 Case expressions (2010-01-09)}
27181 Case expressions are permitted. This allows use of constructs such as:
27184 X := (case Y is when 1 => 2, when 2 => 3, when others => 31)
27187 RM References: 4.05.07 (0) 4.05.08 (0) 4.09 (12) 4.09 (33)
27190 @geindex AI-0104 (Ada 2012 feature)
27196 @emph{AI-0104 Null exclusion and uninitialized allocator (2010-07-15)}
27198 The assignment @code{Ptr := new not null Some_Ptr;} will raise
27199 @code{Constraint_Error} because the default value of the allocated object is
27200 @strong{null}. This useless construct is illegal in Ada 2012.
27202 RM References: 4.08 (2)
27205 @geindex AI-0157 (Ada 2012 feature)
27211 @emph{AI-0157 Allocation/Deallocation from empty pool (2010-07-11)}
27213 Allocation and Deallocation from an empty storage pool (i.e. allocation or
27214 deallocation of a pointer for which a static storage size clause of zero
27215 has been given) is now illegal and is detected as such. GNAT
27216 previously gave a warning but not an error.
27218 RM References: 4.08 (5.3/2) 13.11.02 (4) 13.11.02 (17)
27221 @geindex AI-0179 (Ada 2012 feature)
27227 @emph{AI-0179 Statement not required after label (2010-04-10)}
27229 It is not necessary to have a statement following a label, so a label
27230 can appear at the end of a statement sequence without the need for putting a
27231 null statement afterwards, but it is not allowable to have only labels and
27232 no real statements in a statement sequence.
27234 RM References: 5.01 (2)
27237 @geindex AI-0139-2 (Ada 2012 feature)
27243 @emph{AI-0139-2 Syntactic sugar for iterators (2010-09-29)}
27245 The new syntax for iterating over arrays and containers is now implemented.
27246 Iteration over containers is for now limited to read-only iterators. Only
27247 default iterators are supported, with the syntax: @code{for Elem of C}.
27249 RM References: 5.05
27252 @geindex AI-0134 (Ada 2012 feature)
27258 @emph{AI-0134 Profiles must match for full conformance (0000-00-00)}
27260 For full conformance, the profiles of anonymous-access-to-subprogram
27261 parameters must match. GNAT has always enforced this rule.
27263 RM References: 6.03.01 (18)
27266 @geindex AI-0207 (Ada 2012 feature)
27272 @emph{AI-0207 Mode conformance and access constant (0000-00-00)}
27274 This AI confirms that access_to_constant indication must match for mode
27275 conformance. This was implemented in GNAT when the qualifier was originally
27276 introduced in Ada 2005.
27278 RM References: 6.03.01 (16/2)
27281 @geindex AI-0046 (Ada 2012 feature)
27287 @emph{AI-0046 Null exclusion match for full conformance (2010-07-17)}
27289 For full conformance, in the case of access parameters, the null exclusion
27290 must match (either both or neither must have @code{not null}).
27292 RM References: 6.03.02 (18)
27295 @geindex AI-0118 (Ada 2012 feature)
27301 @emph{AI-0118 The association of parameter associations (0000-00-00)}
27303 This AI clarifies the rules for named associations in subprogram calls and
27304 generic instantiations. The rules have been in place since Ada 83.
27306 RM References: 6.04.01 (2) 12.03 (9)
27309 @geindex AI-0196 (Ada 2012 feature)
27315 @emph{AI-0196 Null exclusion tests for out parameters (0000-00-00)}
27317 Null exclusion checks are not made for @code{out} parameters when
27318 evaluating the actual parameters. GNAT has never generated these checks.
27320 RM References: 6.04.01 (13)
27323 @geindex AI-0015 (Ada 2012 feature)
27329 @emph{AI-0015 Constant return objects (0000-00-00)}
27331 The return object declared in an @emph{extended_return_statement} may be
27332 declared constant. This was always intended, and GNAT has always allowed it.
27334 RM References: 6.05 (2.1/2) 3.03 (10/2) 3.03 (21) 6.05 (5/2)
27338 @geindex AI-0032 (Ada 2012 feature)
27344 @emph{AI-0032 Extended return for class-wide functions (0000-00-00)}
27346 If a function returns a class-wide type, the object of an extended return
27347 statement can be declared with a specific type that is covered by the class-
27348 wide type. This has been implemented in GNAT since the introduction of
27349 extended returns. Note AI-0103 complements this AI by imposing matching
27350 rules for constrained return types.
27352 RM References: 6.05 (5.2/2) 6.05 (5.3/2) 6.05 (5.6/2) 6.05 (5.8/2)
27356 @geindex AI-0103 (Ada 2012 feature)
27362 @emph{AI-0103 Static matching for extended return (2010-07-23)}
27364 If the return subtype of a function is an elementary type or a constrained
27365 type, the subtype indication in an extended return statement must match
27366 statically this return subtype.
27368 RM References: 6.05 (5.2/2)
27371 @geindex AI-0058 (Ada 2012 feature)
27377 @emph{AI-0058 Abnormal completion of an extended return (0000-00-00)}
27379 The RM had some incorrect wording implying wrong treatment of abnormal
27380 completion in an extended return. GNAT has always implemented the intended
27381 correct semantics as described by this AI.
27383 RM References: 6.05 (22/2)
27386 @geindex AI-0050 (Ada 2012 feature)
27392 @emph{AI-0050 Raising Constraint_Error early for function call (0000-00-00)}
27394 The implementation permissions for raising @code{Constraint_Error} early on a function call
27395 when it was clear an exception would be raised were over-permissive and allowed
27396 mishandling of discriminants in some cases. GNAT did
27397 not take advantage of these incorrect permissions in any case.
27399 RM References: 6.05 (24/2)
27402 @geindex AI-0125 (Ada 2012 feature)
27408 @emph{AI-0125 Nonoverridable operations of an ancestor (2010-09-28)}
27410 In Ada 2012, the declaration of a primitive operation of a type extension
27411 or private extension can also override an inherited primitive that is not
27412 visible at the point of this declaration.
27414 RM References: 7.03.01 (6) 8.03 (23) 8.03.01 (5/2) 8.03.01 (6/2)
27417 @geindex AI-0062 (Ada 2012 feature)
27423 @emph{AI-0062 Null exclusions and deferred constants (0000-00-00)}
27425 A full constant may have a null exclusion even if its associated deferred
27426 constant does not. GNAT has always allowed this.
27428 RM References: 7.04 (6/2) 7.04 (7.1/2)
27431 @geindex AI-0178 (Ada 2012 feature)
27437 @emph{AI-0178 Incomplete views are limited (0000-00-00)}
27439 This AI clarifies the role of incomplete views and plugs an omission in the
27440 RM. GNAT always correctly restricted the use of incomplete views and types.
27442 RM References: 7.05 (3/2) 7.05 (6/2)
27445 @geindex AI-0087 (Ada 2012 feature)
27451 @emph{AI-0087 Actual for formal nonlimited derived type (2010-07-15)}
27453 The actual for a formal nonlimited derived type cannot be limited. In
27454 particular, a formal derived type that extends a limited interface but which
27455 is not explicitly limited cannot be instantiated with a limited type.
27457 RM References: 7.05 (5/2) 12.05.01 (5.1/2)
27460 @geindex AI-0099 (Ada 2012 feature)
27466 @emph{AI-0099 Tag determines whether finalization needed (0000-00-00)}
27468 This AI clarifies that 'needs finalization' is part of dynamic semantics,
27469 and therefore depends on the run-time characteristics of an object (i.e. its
27470 tag) and not on its nominal type. As the AI indicates: "we do not expect
27471 this to affect any implementation'@w{'}.
27473 RM References: 7.06.01 (6) 7.06.01 (7) 7.06.01 (8) 7.06.01 (9/2)
27476 @geindex AI-0064 (Ada 2012 feature)
27482 @emph{AI-0064 Redundant finalization rule (0000-00-00)}
27484 This is an editorial change only. The intended behavior is already checked
27485 by an existing ACATS test, which GNAT has always executed correctly.
27487 RM References: 7.06.01 (17.1/1)
27490 @geindex AI-0026 (Ada 2012 feature)
27496 @emph{AI-0026 Missing rules for Unchecked_Union (2010-07-07)}
27498 Record representation clauses concerning Unchecked_Union types cannot mention
27499 the discriminant of the type. The type of a component declared in the variant
27500 part of an Unchecked_Union cannot be controlled, have controlled components,
27501 nor have protected or task parts. If an Unchecked_Union type is declared
27502 within the body of a generic unit or its descendants, then the type of a
27503 component declared in the variant part cannot be a formal private type or a
27504 formal private extension declared within the same generic unit.
27506 RM References: 7.06 (9.4/2) B.03.03 (9/2) B.03.03 (10/2)
27509 @geindex AI-0205 (Ada 2012 feature)
27515 @emph{AI-0205 Extended return declares visible name (0000-00-00)}
27517 This AI corrects a simple omission in the RM. Return objects have always
27518 been visible within an extended return statement.
27520 RM References: 8.03 (17)
27523 @geindex AI-0042 (Ada 2012 feature)
27529 @emph{AI-0042 Overriding versus implemented-by (0000-00-00)}
27531 This AI fixes a wording gap in the RM. An operation of a synchronized
27532 interface can be implemented by a protected or task entry, but the abstract
27533 operation is not being overridden in the usual sense, and it must be stated
27534 separately that this implementation is legal. This has always been the case
27537 RM References: 9.01 (9.2/2) 9.04 (11.1/2)
27540 @geindex AI-0030 (Ada 2012 feature)
27546 @emph{AI-0030 Requeue on synchronized interfaces (2010-07-19)}
27548 Requeue is permitted to a protected, synchronized or task interface primitive
27549 providing it is known that the overriding operation is an entry. Otherwise
27550 the requeue statement has the same effect as a procedure call. Use of pragma
27551 @code{Implemented} provides a way to impose a static requirement on the
27552 overriding operation by adhering to one of the implementation kinds: entry,
27553 protected procedure or any of the above.
27555 RM References: 9.05 (9) 9.05.04 (2) 9.05.04 (3) 9.05.04 (5)
27556 9.05.04 (6) 9.05.04 (7) 9.05.04 (12)
27559 @geindex AI-0201 (Ada 2012 feature)
27565 @emph{AI-0201 Independence of atomic object components (2010-07-22)}
27567 If an Atomic object has a pragma @code{Pack} or a @code{Component_Size}
27568 attribute, then individual components may not be addressable by independent
27569 tasks. However, if the representation clause has no effect (is confirming),
27570 then independence is not compromised. Furthermore, in GNAT, specification of
27571 other appropriately addressable component sizes (e.g. 16 for 8-bit
27572 characters) also preserves independence. GNAT now gives very clear warnings
27573 both for the declaration of such a type, and for any assignment to its components.
27575 RM References: 9.10 (1/3) C.06 (22/2) C.06 (23/2)
27578 @geindex AI-0009 (Ada 2012 feature)
27584 @emph{AI-0009 Pragma Independent[_Components] (2010-07-23)}
27586 This AI introduces the new pragmas @code{Independent} and
27587 @code{Independent_Components},
27588 which control guaranteeing independence of access to objects and components.
27589 The AI also requires independence not unaffected by confirming rep clauses.
27591 RM References: 9.10 (1) 13.01 (15/1) 13.02 (9) 13.03 (13) C.06 (2)
27592 C.06 (4) C.06 (6) C.06 (9) C.06 (13) C.06 (14)
27595 @geindex AI-0072 (Ada 2012 feature)
27601 @emph{AI-0072 Task signalling using 'Terminated (0000-00-00)}
27603 This AI clarifies that task signalling for reading @code{'Terminated} only
27604 occurs if the result is True. GNAT semantics has always been consistent with
27605 this notion of task signalling.
27607 RM References: 9.10 (6.1/1)
27610 @geindex AI-0108 (Ada 2012 feature)
27616 @emph{AI-0108 Limited incomplete view and discriminants (0000-00-00)}
27618 This AI confirms that an incomplete type from a limited view does not have
27619 discriminants. This has always been the case in GNAT.
27621 RM References: 10.01.01 (12.3/2)
27624 @geindex AI-0129 (Ada 2012 feature)
27630 @emph{AI-0129 Limited views and incomplete types (0000-00-00)}
27632 This AI clarifies the description of limited views: a limited view of a
27633 package includes only one view of a type that has an incomplete declaration
27634 and a full declaration (there is no possible ambiguity in a client package).
27635 This AI also fixes an omission: a nested package in the private part has no
27636 limited view. GNAT always implemented this correctly.
27638 RM References: 10.01.01 (12.2/2) 10.01.01 (12.3/2)
27641 @geindex AI-0077 (Ada 2012 feature)
27647 @emph{AI-0077 Limited withs and scope of declarations (0000-00-00)}
27649 This AI clarifies that a declaration does not include a context clause,
27650 and confirms that it is illegal to have a context in which both a limited
27651 and a nonlimited view of a package are accessible. Such double visibility
27652 was always rejected by GNAT.
27654 RM References: 10.01.02 (12/2) 10.01.02 (21/2) 10.01.02 (22/2)
27657 @geindex AI-0122 (Ada 2012 feature)
27663 @emph{AI-0122 Private with and children of generics (0000-00-00)}
27665 This AI clarifies the visibility of private children of generic units within
27666 instantiations of a parent. GNAT has always handled this correctly.
27668 RM References: 10.01.02 (12/2)
27671 @geindex AI-0040 (Ada 2012 feature)
27677 @emph{AI-0040 Limited with clauses on descendant (0000-00-00)}
27679 This AI confirms that a limited with clause in a child unit cannot name
27680 an ancestor of the unit. This has always been checked in GNAT.
27682 RM References: 10.01.02 (20/2)
27685 @geindex AI-0132 (Ada 2012 feature)
27691 @emph{AI-0132 Placement of library unit pragmas (0000-00-00)}
27693 This AI fills a gap in the description of library unit pragmas. The pragma
27694 clearly must apply to a library unit, even if it does not carry the name
27695 of the enclosing unit. GNAT has always enforced the required check.
27697 RM References: 10.01.05 (7)
27700 @geindex AI-0034 (Ada 2012 feature)
27706 @emph{AI-0034 Categorization of limited views (0000-00-00)}
27708 The RM makes certain limited with clauses illegal because of categorization
27709 considerations, when the corresponding normal with would be legal. This is
27710 not intended, and GNAT has always implemented the recommended behavior.
27712 RM References: 10.02.01 (11/1) 10.02.01 (17/2)
27715 @geindex AI-0035 (Ada 2012 feature)
27721 @emph{AI-0035 Inconsistencies with Pure units (0000-00-00)}
27723 This AI remedies some inconsistencies in the legality rules for Pure units.
27724 Derived access types are legal in a pure unit (on the assumption that the
27725 rule for a zero storage pool size has been enforced on the ancestor type).
27726 The rules are enforced in generic instances and in subunits. GNAT has always
27727 implemented the recommended behavior.
27729 RM References: 10.02.01 (15.1/2) 10.02.01 (15.4/2) 10.02.01 (15.5/2) 10.02.01 (17/2)
27732 @geindex AI-0219 (Ada 2012 feature)
27738 @emph{AI-0219 Pure permissions and limited parameters (2010-05-25)}
27740 This AI refines the rules for the cases with limited parameters which do not
27741 allow the implementations to omit 'redundant'. GNAT now properly conforms
27742 to the requirements of this binding interpretation.
27744 RM References: 10.02.01 (18/2)
27747 @geindex AI-0043 (Ada 2012 feature)
27753 @emph{AI-0043 Rules about raising exceptions (0000-00-00)}
27755 This AI covers various omissions in the RM regarding the raising of
27756 exceptions. GNAT has always implemented the intended semantics.
27758 RM References: 11.04.01 (10.1/2) 11 (2)
27761 @geindex AI-0200 (Ada 2012 feature)
27767 @emph{AI-0200 Mismatches in formal package declarations (0000-00-00)}
27769 This AI plugs a gap in the RM which appeared to allow some obviously intended
27770 illegal instantiations. GNAT has never allowed these instantiations.
27772 RM References: 12.07 (16)
27775 @geindex AI-0112 (Ada 2012 feature)
27781 @emph{AI-0112 Detection of duplicate pragmas (2010-07-24)}
27783 This AI concerns giving names to various representation aspects, but the
27784 practical effect is simply to make the use of duplicate
27785 @code{Atomic[_Components]},
27786 @code{Volatile[_Components]}, and
27787 @code{Independent[_Components]} pragmas illegal, and GNAT
27788 now performs this required check.
27790 RM References: 13.01 (8)
27793 @geindex AI-0106 (Ada 2012 feature)
27799 @emph{AI-0106 No representation pragmas on generic formals (0000-00-00)}
27801 The RM appeared to allow representation pragmas on generic formal parameters,
27802 but this was not intended, and GNAT has never permitted this usage.
27804 RM References: 13.01 (9.1/1)
27807 @geindex AI-0012 (Ada 2012 feature)
27813 @emph{AI-0012 Pack/Component_Size for aliased/atomic (2010-07-15)}
27815 It is now illegal to give an inappropriate component size or a pragma
27816 @code{Pack} that attempts to change the component size in the case of atomic
27817 or aliased components. Previously GNAT ignored such an attempt with a
27820 RM References: 13.02 (6.1/2) 13.02 (7) C.06 (10) C.06 (11) C.06 (21)
27823 @geindex AI-0039 (Ada 2012 feature)
27829 @emph{AI-0039 Stream attributes cannot be dynamic (0000-00-00)}
27831 The RM permitted the use of dynamic expressions (such as @code{ptr.all})`
27832 for stream attributes, but these were never useful and are now illegal. GNAT
27833 has always regarded such expressions as illegal.
27835 RM References: 13.03 (4) 13.03 (6) 13.13.02 (38/2)
27838 @geindex AI-0095 (Ada 2012 feature)
27844 @emph{AI-0095 Address of intrinsic subprograms (0000-00-00)}
27846 The prefix of @code{'Address} cannot statically denote a subprogram with
27847 convention @code{Intrinsic}. The use of the @code{Address} attribute raises
27848 @code{Program_Error} if the prefix denotes a subprogram with convention
27851 RM References: 13.03 (11/1)
27854 @geindex AI-0116 (Ada 2012 feature)
27860 @emph{AI-0116 Alignment of class-wide objects (0000-00-00)}
27862 This AI requires that the alignment of a class-wide object be no greater
27863 than the alignment of any type in the class. GNAT has always followed this
27866 RM References: 13.03 (29) 13.11 (16)
27869 @geindex AI-0146 (Ada 2012 feature)
27875 @emph{AI-0146 Type invariants (2009-09-21)}
27877 Type invariants may be specified for private types using the aspect notation.
27878 Aspect @code{Type_Invariant} may be specified for any private type,
27879 @code{Type_Invariant'Class} can
27880 only be specified for tagged types, and is inherited by any descendent of the
27881 tagged types. The invariant is a boolean expression that is tested for being
27882 true in the following situations: conversions to the private type, object
27883 declarations for the private type that are default initialized, and
27884 [@strong{in}] @strong{out}
27885 parameters and returned result on return from any primitive operation for
27886 the type that is visible to a client.
27887 GNAT defines the synonyms @code{Invariant} for @code{Type_Invariant} and
27888 @code{Invariant'Class} for @code{Type_Invariant'Class}.
27890 RM References: 13.03.03 (00)
27893 @geindex AI-0078 (Ada 2012 feature)
27899 @emph{AI-0078 Relax Unchecked_Conversion alignment rules (0000-00-00)}
27901 In Ada 2012, compilers are required to support unchecked conversion where the
27902 target alignment is a multiple of the source alignment. GNAT always supported
27903 this case (and indeed all cases of differing alignments, doing copies where
27904 required if the alignment was reduced).
27906 RM References: 13.09 (7)
27909 @geindex AI-0195 (Ada 2012 feature)
27915 @emph{AI-0195 Invalid value handling is implementation defined (2010-07-03)}
27917 The handling of invalid values is now designated to be implementation
27918 defined. This is a documentation change only, requiring Annex M in the GNAT
27919 Reference Manual to document this handling.
27920 In GNAT, checks for invalid values are made
27921 only when necessary to avoid erroneous behavior. Operations like assignments
27922 which cannot cause erroneous behavior ignore the possibility of invalid
27923 values and do not do a check. The date given above applies only to the
27924 documentation change, this behavior has always been implemented by GNAT.
27926 RM References: 13.09.01 (10)
27929 @geindex AI-0193 (Ada 2012 feature)
27935 @emph{AI-0193 Alignment of allocators (2010-09-16)}
27937 This AI introduces a new attribute @code{Max_Alignment_For_Allocation},
27938 analogous to @code{Max_Size_In_Storage_Elements}, but for alignment instead
27941 RM References: 13.11 (16) 13.11 (21) 13.11.01 (0) 13.11.01 (1)
27942 13.11.01 (2) 13.11.01 (3)
27945 @geindex AI-0177 (Ada 2012 feature)
27951 @emph{AI-0177 Parameterized expressions (2010-07-10)}
27953 The new Ada 2012 notion of parameterized expressions is implemented. The form
27957 function-specification is (expression)
27960 This is exactly equivalent to the
27961 corresponding function body that returns the expression, but it can appear
27962 in a package spec. Note that the expression must be parenthesized.
27964 RM References: 13.11.01 (3/2)
27967 @geindex AI-0033 (Ada 2012 feature)
27973 @emph{AI-0033 Attach/Interrupt_Handler in generic (2010-07-24)}
27975 Neither of these two pragmas may appear within a generic template, because
27976 the generic might be instantiated at other than the library level.
27978 RM References: 13.11.02 (16) C.03.01 (7/2) C.03.01 (8/2)
27981 @geindex AI-0161 (Ada 2012 feature)
27987 @emph{AI-0161 Restriction No_Default_Stream_Attributes (2010-09-11)}
27989 A new restriction @code{No_Default_Stream_Attributes} prevents the use of any
27990 of the default stream attributes for elementary types. If this restriction is
27991 in force, then it is necessary to provide explicit subprograms for any
27992 stream attributes used.
27994 RM References: 13.12.01 (4/2) 13.13.02 (40/2) 13.13.02 (52/2)
27997 @geindex AI-0194 (Ada 2012 feature)
28003 @emph{AI-0194 Value of Stream_Size attribute (0000-00-00)}
28005 The @code{Stream_Size} attribute returns the default number of bits in the
28006 stream representation of the given type.
28007 This value is not affected by the presence
28008 of stream subprogram attributes for the type. GNAT has always implemented
28009 this interpretation.
28011 RM References: 13.13.02 (1.2/2)
28014 @geindex AI-0109 (Ada 2012 feature)
28020 @emph{AI-0109 Redundant check in S'Class'Input (0000-00-00)}
28022 This AI is an editorial change only. It removes the need for a tag check
28023 that can never fail.
28025 RM References: 13.13.02 (34/2)
28028 @geindex AI-0007 (Ada 2012 feature)
28034 @emph{AI-0007 Stream read and private scalar types (0000-00-00)}
28036 The RM as written appeared to limit the possibilities of declaring read
28037 attribute procedures for private scalar types. This limitation was not
28038 intended, and has never been enforced by GNAT.
28040 RM References: 13.13.02 (50/2) 13.13.02 (51/2)
28043 @geindex AI-0065 (Ada 2012 feature)
28049 @emph{AI-0065 Remote access types and external streaming (0000-00-00)}
28051 This AI clarifies the fact that all remote access types support external
28052 streaming. This fixes an obvious oversight in the definition of the
28053 language, and GNAT always implemented the intended correct rules.
28055 RM References: 13.13.02 (52/2)
28058 @geindex AI-0019 (Ada 2012 feature)
28064 @emph{AI-0019 Freezing of primitives for tagged types (0000-00-00)}
28066 The RM suggests that primitive subprograms of a specific tagged type are
28067 frozen when the tagged type is frozen. This would be an incompatible change
28068 and is not intended. GNAT has never attempted this kind of freezing and its
28069 behavior is consistent with the recommendation of this AI.
28071 RM References: 13.14 (2) 13.14 (3/1) 13.14 (8.1/1) 13.14 (10) 13.14 (14) 13.14 (15.1/2)
28074 @geindex AI-0017 (Ada 2012 feature)
28080 @emph{AI-0017 Freezing and incomplete types (0000-00-00)}
28082 So-called 'Taft-amendment types' (i.e., types that are completed in package
28083 bodies) are not frozen by the occurrence of bodies in the
28084 enclosing declarative part. GNAT always implemented this properly.
28086 RM References: 13.14 (3/1)
28089 @geindex AI-0060 (Ada 2012 feature)
28095 @emph{AI-0060 Extended definition of remote access types (0000-00-00)}
28097 This AI extends the definition of remote access types to include access
28098 to limited, synchronized, protected or task class-wide interface types.
28099 GNAT already implemented this extension.
28101 RM References: A (4) E.02.02 (9/1) E.02.02 (9.2/1) E.02.02 (14/2) E.02.02 (18)
28104 @geindex AI-0114 (Ada 2012 feature)
28110 @emph{AI-0114 Classification of letters (0000-00-00)}
28112 The code points 170 (@code{FEMININE ORDINAL INDICATOR}),
28113 181 (@code{MICRO SIGN}), and
28114 186 (@code{MASCULINE ORDINAL INDICATOR}) are technically considered
28115 lower case letters by Unicode.
28116 However, they are not allowed in identifiers, and they
28117 return @code{False} to @code{Ada.Characters.Handling.Is_Letter/Is_Lower}.
28118 This behavior is consistent with that defined in Ada 95.
28120 RM References: A.03.02 (59) A.04.06 (7)
28123 @geindex AI-0185 (Ada 2012 feature)
28129 @emph{AI-0185 Ada.Wide_[Wide_]Characters.Handling (2010-07-06)}
28131 Two new packages @code{Ada.Wide_[Wide_]Characters.Handling} provide
28132 classification functions for @code{Wide_Character} and
28133 @code{Wide_Wide_Character}, as well as providing
28134 case folding routines for @code{Wide_[Wide_]Character} and
28135 @code{Wide_[Wide_]String}.
28137 RM References: A.03.05 (0) A.03.06 (0)
28140 @geindex AI-0031 (Ada 2012 feature)
28146 @emph{AI-0031 Add From parameter to Find_Token (2010-07-25)}
28148 A new version of @code{Find_Token} is added to all relevant string packages,
28149 with an extra parameter @code{From}. Instead of starting at the first
28150 character of the string, the search for a matching Token starts at the
28151 character indexed by the value of @code{From}.
28152 These procedures are available in all versions of Ada
28153 but if used in versions earlier than Ada 2012 they will generate a warning
28154 that an Ada 2012 subprogram is being used.
28156 RM References: A.04.03 (16) A.04.03 (67) A.04.03 (68/1) A.04.04 (51)
28160 @geindex AI-0056 (Ada 2012 feature)
28166 @emph{AI-0056 Index on null string returns zero (0000-00-00)}
28168 The wording in the Ada 2005 RM implied an incompatible handling of the
28169 @code{Index} functions, resulting in raising an exception instead of
28170 returning zero in some situations.
28171 This was not intended and has been corrected.
28172 GNAT always returned zero, and is thus consistent with this AI.
28174 RM References: A.04.03 (56.2/2) A.04.03 (58.5/2)
28177 @geindex AI-0137 (Ada 2012 feature)
28183 @emph{AI-0137 String encoding package (2010-03-25)}
28185 The packages @code{Ada.Strings.UTF_Encoding}, together with its child
28186 packages, @code{Conversions}, @code{Strings}, @code{Wide_Strings},
28187 and @code{Wide_Wide_Strings} have been
28188 implemented. These packages (whose documentation can be found in the spec
28189 files @code{a-stuten.ads}, @code{a-suenco.ads}, @code{a-suenst.ads},
28190 @code{a-suewst.ads}, @code{a-suezst.ads}) allow encoding and decoding of
28191 @code{String}, @code{Wide_String}, and @code{Wide_Wide_String}
28192 values using UTF coding schemes (including UTF-8, UTF-16LE, UTF-16BE, and
28193 UTF-16), as well as conversions between the different UTF encodings. With
28194 the exception of @code{Wide_Wide_Strings}, these packages are available in
28195 Ada 95 and Ada 2005 mode as well as Ada 2012 mode.
28196 The @code{Wide_Wide_Strings} package
28197 is available in Ada 2005 mode as well as Ada 2012 mode (but not in Ada 95
28198 mode since it uses @code{Wide_Wide_Character}).
28200 RM References: A.04.11
28203 @geindex AI-0038 (Ada 2012 feature)
28209 @emph{AI-0038 Minor errors in Text_IO (0000-00-00)}
28211 These are minor errors in the description on three points. The intent on
28212 all these points has always been clear, and GNAT has always implemented the
28213 correct intended semantics.
28215 RM References: A.10.05 (37) A.10.07 (8/1) A.10.07 (10) A.10.07 (12) A.10.08 (10) A.10.08 (24)
28218 @geindex AI-0044 (Ada 2012 feature)
28224 @emph{AI-0044 Restrictions on container instantiations (0000-00-00)}
28226 This AI places restrictions on allowed instantiations of generic containers.
28227 These restrictions are not checked by the compiler, so there is nothing to
28228 change in the implementation. This affects only the RM documentation.
28230 RM References: A.18 (4/2) A.18.02 (231/2) A.18.03 (145/2) A.18.06 (56/2) A.18.08 (66/2) A.18.09 (79/2) A.18.26 (5/2) A.18.26 (9/2)
28233 @geindex AI-0127 (Ada 2012 feature)
28239 @emph{AI-0127 Adding Locale Capabilities (2010-09-29)}
28241 This package provides an interface for identifying the current locale.
28243 RM References: A.19 A.19.01 A.19.02 A.19.03 A.19.05 A.19.06
28244 A.19.07 A.19.08 A.19.09 A.19.10 A.19.11 A.19.12 A.19.13
28247 @geindex AI-0002 (Ada 2012 feature)
28253 @emph{AI-0002 Export C with unconstrained arrays (0000-00-00)}
28255 The compiler is not required to support exporting an Ada subprogram with
28256 convention C if there are parameters or a return type of an unconstrained
28257 array type (such as @code{String}). GNAT allows such declarations but
28258 generates warnings. It is possible, but complicated, to write the
28259 corresponding C code and certainly such code would be specific to GNAT and
28262 RM References: B.01 (17) B.03 (62) B.03 (71.1/2)
28265 @geindex AI05-0216 (Ada 2012 feature)
28271 @emph{AI-0216 No_Task_Hierarchy forbids local tasks (0000-00-00)}
28273 It is clearly the intention that @code{No_Task_Hierarchy} is intended to
28274 forbid tasks declared locally within subprograms, or functions returning task
28275 objects, and that is the implementation that GNAT has always provided.
28276 However the language in the RM was not sufficiently clear on this point.
28277 Thus this is a documentation change in the RM only.
28279 RM References: D.07 (3/3)
28282 @geindex AI-0211 (Ada 2012 feature)
28288 @emph{AI-0211 No_Relative_Delays forbids Set_Handler use (2010-07-09)}
28290 The restriction @code{No_Relative_Delays} forbids any calls to the subprogram
28291 @code{Ada.Real_Time.Timing_Events.Set_Handler}.
28293 RM References: D.07 (5) D.07 (10/2) D.07 (10.4/2) D.07 (10.7/2)
28296 @geindex AI-0190 (Ada 2012 feature)
28302 @emph{AI-0190 pragma Default_Storage_Pool (2010-09-15)}
28304 This AI introduces a new pragma @code{Default_Storage_Pool}, which can be
28305 used to control storage pools globally.
28306 In particular, you can force every access
28307 type that is used for allocation (@strong{new}) to have an explicit storage pool,
28308 or you can declare a pool globally to be used for all access types that lack
28311 RM References: D.07 (8)
28314 @geindex AI-0189 (Ada 2012 feature)
28320 @emph{AI-0189 No_Allocators_After_Elaboration (2010-01-23)}
28322 This AI introduces a new restriction @code{No_Allocators_After_Elaboration},
28323 which says that no dynamic allocation will occur once elaboration is
28325 In general this requires a run-time check, which is not required, and which
28326 GNAT does not attempt. But the static cases of allocators in a task body or
28327 in the body of the main program are detected and flagged at compile or bind
28330 RM References: D.07 (19.1/2) H.04 (23.3/2)
28333 @geindex AI-0171 (Ada 2012 feature)
28339 @emph{AI-0171 Pragma CPU and Ravenscar Profile (2010-09-24)}
28341 A new package @code{System.Multiprocessors} is added, together with the
28342 definition of pragma @code{CPU} for controlling task affinity. A new no
28343 dependence restriction, on @code{System.Multiprocessors.Dispatching_Domains},
28344 is added to the Ravenscar profile.
28346 RM References: D.13.01 (4/2) D.16
28349 @geindex AI-0210 (Ada 2012 feature)
28355 @emph{AI-0210 Correct Timing_Events metric (0000-00-00)}
28357 This is a documentation only issue regarding wording of metric requirements,
28358 that does not affect the implementation of the compiler.
28360 RM References: D.15 (24/2)
28363 @geindex AI-0206 (Ada 2012 feature)
28369 @emph{AI-0206 Remote types packages and preelaborate (2010-07-24)}
28371 Remote types packages are now allowed to depend on preelaborated packages.
28372 This was formerly considered illegal.
28374 RM References: E.02.02 (6)
28377 @geindex AI-0152 (Ada 2012 feature)
28383 @emph{AI-0152 Restriction No_Anonymous_Allocators (2010-09-08)}
28385 Restriction @code{No_Anonymous_Allocators} prevents the use of allocators
28386 where the type of the returned value is an anonymous access type.
28388 RM References: H.04 (8/1)
28391 @node Obsolescent Features,Compatibility and Porting Guide,Implementation of Ada 2012 Features,Top
28392 @anchor{gnat_rm/obsolescent_features id1}@anchor{42a}@anchor{gnat_rm/obsolescent_features doc}@anchor{42b}@anchor{gnat_rm/obsolescent_features obsolescent-features}@anchor{15}
28393 @chapter Obsolescent Features
28396 This chapter describes features that are provided by GNAT, but are
28397 considered obsolescent since there are preferred ways of achieving
28398 the same effect. These features are provided solely for historical
28399 compatibility purposes.
28402 * pragma No_Run_Time::
28403 * pragma Ravenscar::
28404 * pragma Restricted_Run_Time::
28405 * pragma Task_Info::
28406 * package System.Task_Info (s-tasinf.ads): package System Task_Info s-tasinf ads.
28410 @node pragma No_Run_Time,pragma Ravenscar,,Obsolescent Features
28411 @anchor{gnat_rm/obsolescent_features id2}@anchor{42c}@anchor{gnat_rm/obsolescent_features pragma-no-run-time}@anchor{42d}
28412 @section pragma No_Run_Time
28415 The pragma @code{No_Run_Time} is used to achieve an affect similar
28416 to the use of the "Zero Foot Print" configurable run time, but without
28417 requiring a specially configured run time. The result of using this
28418 pragma, which must be used for all units in a partition, is to restrict
28419 the use of any language features requiring run-time support code. The
28420 preferred usage is to use an appropriately configured run-time that
28421 includes just those features that are to be made accessible.
28423 @node pragma Ravenscar,pragma Restricted_Run_Time,pragma No_Run_Time,Obsolescent Features
28424 @anchor{gnat_rm/obsolescent_features id3}@anchor{42e}@anchor{gnat_rm/obsolescent_features pragma-ravenscar}@anchor{42f}
28425 @section pragma Ravenscar
28428 The pragma @code{Ravenscar} has exactly the same effect as pragma
28429 @code{Profile (Ravenscar)}. The latter usage is preferred since it
28430 is part of the new Ada 2005 standard.
28432 @node pragma Restricted_Run_Time,pragma Task_Info,pragma Ravenscar,Obsolescent Features
28433 @anchor{gnat_rm/obsolescent_features pragma-restricted-run-time}@anchor{430}@anchor{gnat_rm/obsolescent_features id4}@anchor{431}
28434 @section pragma Restricted_Run_Time
28437 The pragma @code{Restricted_Run_Time} has exactly the same effect as
28438 pragma @code{Profile (Restricted)}. The latter usage is
28439 preferred since the Ada 2005 pragma @code{Profile} is intended for
28440 this kind of implementation dependent addition.
28442 @node pragma Task_Info,package System Task_Info s-tasinf ads,pragma Restricted_Run_Time,Obsolescent Features
28443 @anchor{gnat_rm/obsolescent_features pragma-task-info}@anchor{432}@anchor{gnat_rm/obsolescent_features id5}@anchor{433}
28444 @section pragma Task_Info
28447 The functionality provided by pragma @code{Task_Info} is now part of the
28448 Ada language. The @code{CPU} aspect and the package
28449 @code{System.Multiprocessors} offer a less system-dependent way to specify
28450 task affinity or to query the number of processsors.
28455 pragma Task_Info (EXPRESSION);
28458 This pragma appears within a task definition (like pragma
28459 @code{Priority}) and applies to the task in which it appears. The
28460 argument must be of type @code{System.Task_Info.Task_Info_Type}.
28461 The @code{Task_Info} pragma provides system dependent control over
28462 aspects of tasking implementation, for example, the ability to map
28463 tasks to specific processors. For details on the facilities available
28464 for the version of GNAT that you are using, see the documentation
28465 in the spec of package System.Task_Info in the runtime
28468 @node package System Task_Info s-tasinf ads,,pragma Task_Info,Obsolescent Features
28469 @anchor{gnat_rm/obsolescent_features package-system-task-info}@anchor{434}@anchor{gnat_rm/obsolescent_features package-system-task-info-s-tasinf-ads}@anchor{435}
28470 @section package System.Task_Info (@code{s-tasinf.ads})
28473 This package provides target dependent functionality that is used
28474 to support the @code{Task_Info} pragma. The predefined Ada package
28475 @code{System.Multiprocessors} and the @code{CPU} aspect now provide a
28476 standard replacement for GNAT's @code{Task_Info} functionality.
28478 @node Compatibility and Porting Guide,GNU Free Documentation License,Obsolescent Features,Top
28479 @anchor{gnat_rm/compatibility_and_porting_guide compatibility-and-porting-guide}@anchor{16}@anchor{gnat_rm/compatibility_and_porting_guide doc}@anchor{436}@anchor{gnat_rm/compatibility_and_porting_guide id1}@anchor{437}
28480 @chapter Compatibility and Porting Guide
28483 This chapter presents some guidelines for developing portable Ada code,
28484 describes the compatibility issues that may arise between
28485 GNAT and other Ada compilation systems (including those for Ada 83),
28486 and shows how GNAT can expedite porting
28487 applications developed in other Ada environments.
28490 * Writing Portable Fixed-Point Declarations::
28491 * Compatibility with Ada 83::
28492 * Compatibility between Ada 95 and Ada 2005::
28493 * Implementation-dependent characteristics::
28494 * Compatibility with Other Ada Systems::
28495 * Representation Clauses::
28496 * Compatibility with HP Ada 83::
28500 @node Writing Portable Fixed-Point Declarations,Compatibility with Ada 83,,Compatibility and Porting Guide
28501 @anchor{gnat_rm/compatibility_and_porting_guide id2}@anchor{438}@anchor{gnat_rm/compatibility_and_porting_guide writing-portable-fixed-point-declarations}@anchor{439}
28502 @section Writing Portable Fixed-Point Declarations
28505 The Ada Reference Manual gives an implementation freedom to choose bounds
28506 that are narrower by @code{Small} from the given bounds.
28507 For example, if we write
28510 type F1 is delta 1.0 range -128.0 .. +128.0;
28513 then the implementation is allowed to choose -128.0 .. +127.0 if it
28514 likes, but is not required to do so.
28516 This leads to possible portability problems, so let's have a closer
28517 look at this, and figure out how to avoid these problems.
28519 First, why does this freedom exist, and why would an implementation
28520 take advantage of it? To answer this, take a closer look at the type
28521 declaration for @code{F1} above. If the compiler uses the given bounds,
28522 it would need 9 bits to hold the largest positive value (and typically
28523 that means 16 bits on all machines). But if the implementation chooses
28524 the +127.0 bound then it can fit values of the type in 8 bits.
28526 Why not make the user write +127.0 if that's what is wanted?
28527 The rationale is that if you are thinking of fixed point
28528 as a kind of 'poor man's floating-point', then you don't want
28529 to be thinking about the scaled integers that are used in its
28530 representation. Let's take another example:
28533 type F2 is delta 2.0**(-15) range -1.0 .. +1.0;
28536 Looking at this declaration, it seems casually as though
28537 it should fit in 16 bits, but again that extra positive value
28538 +1.0 has the scaled integer equivalent of 2**15 which is one too
28539 big for signed 16 bits. The implementation can treat this as:
28542 type F2 is delta 2.0**(-15) range -1.0 .. +1.0-(2.0**(-15));
28545 and the Ada language design team felt that this was too annoying
28546 to require. We don't need to debate this decision at this point,
28547 since it is well established (the rule about narrowing the ranges
28550 But the important point is that an implementation is not required
28551 to do this narrowing, so we have a potential portability problem.
28552 We could imagine three types of implementation:
28558 those that narrow the range automatically if they can figure
28559 out that the narrower range will allow storage in a smaller machine unit,
28562 those that will narrow only if forced to by a @code{'Size} clause, and
28565 those that will never narrow.
28568 Now if we are language theoreticians, we can imagine a fourth
28569 approach: to narrow all the time, e.g. to treat
28572 type F3 is delta 1.0 range -10.0 .. +23.0;
28575 as though it had been written:
28578 type F3 is delta 1.0 range -9.0 .. +22.0;
28581 But although technically allowed, such a behavior would be hostile and silly,
28582 and no real compiler would do this. All real compilers will fall into one of
28583 the categories (a), (b) or (c) above.
28585 So, how do you get the compiler to do what you want? The answer is give the
28586 actual bounds you want, and then use a @code{'Small} clause and a
28587 @code{'Size} clause to absolutely pin down what the compiler does.
28588 E.g., for @code{F2} above, we will write:
28591 My_Small : constant := 2.0**(-15);
28592 My_First : constant := -1.0;
28593 My_Last : constant := +1.0 - My_Small;
28595 type F2 is delta My_Small range My_First .. My_Last;
28601 for F2'Small use my_Small;
28602 for F2'Size use 16;
28605 In practice all compilers will do the same thing here and will give you
28606 what you want, so the above declarations are fully portable. If you really
28607 want to play language lawyer and guard against ludicrous behavior by the
28608 compiler you could add
28611 Test1 : constant := 1 / Boolean'Pos (F2'First = My_First);
28612 Test2 : constant := 1 / Boolean'Pos (F2'Last = My_Last);
28615 One or other or both are allowed to be illegal if the compiler is
28616 behaving in a silly manner, but at least the silly compiler will not
28617 get away with silently messing with your (very clear) intentions.
28619 If you follow this scheme you will be guaranteed that your fixed-point
28620 types will be portable.
28622 @node Compatibility with Ada 83,Compatibility between Ada 95 and Ada 2005,Writing Portable Fixed-Point Declarations,Compatibility and Porting Guide
28623 @anchor{gnat_rm/compatibility_and_porting_guide compatibility-with-ada-83}@anchor{43a}@anchor{gnat_rm/compatibility_and_porting_guide id3}@anchor{43b}
28624 @section Compatibility with Ada 83
28627 @geindex Compatibility (between Ada 83 and Ada 95 / Ada 2005 / Ada 2012)
28629 Ada 95 and the subsequent revisions Ada 2005 and Ada 2012
28630 are highly upwards compatible with Ada 83. In
28631 particular, the design intention was that the difficulties associated
28632 with moving from Ada 83 to later versions of the standard should be no greater
28633 than those that occur when moving from one Ada 83 system to another.
28635 However, there are a number of points at which there are minor
28636 incompatibilities. The @cite{Ada 95 Annotated Reference Manual} contains
28637 full details of these issues as they relate to Ada 95,
28638 and should be consulted for a complete treatment.
28640 following subsections treat the most likely issues to be encountered.
28643 * Legal Ada 83 programs that are illegal in Ada 95::
28644 * More deterministic semantics::
28645 * Changed semantics::
28646 * Other language compatibility issues::
28650 @node Legal Ada 83 programs that are illegal in Ada 95,More deterministic semantics,,Compatibility with Ada 83
28651 @anchor{gnat_rm/compatibility_and_porting_guide id4}@anchor{43c}@anchor{gnat_rm/compatibility_and_porting_guide legal-ada-83-programs-that-are-illegal-in-ada-95}@anchor{43d}
28652 @subsection Legal Ada 83 programs that are illegal in Ada 95
28655 Some legal Ada 83 programs are illegal (i.e., they will fail to compile) in
28656 Ada 95 and later versions of the standard:
28662 @emph{Character literals}
28664 Some uses of character literals are ambiguous. Since Ada 95 has introduced
28665 @code{Wide_Character} as a new predefined character type, some uses of
28666 character literals that were legal in Ada 83 are illegal in Ada 95.
28670 for Char in 'A' .. 'Z' loop ... end loop;
28673 The problem is that 'A' and 'Z' could be from either
28674 @code{Character} or @code{Wide_Character}. The simplest correction
28675 is to make the type explicit; e.g.:
28678 for Char in Character range 'A' .. 'Z' loop ... end loop;
28682 @emph{New reserved words}
28684 The identifiers @code{abstract}, @code{aliased}, @code{protected},
28685 @code{requeue}, @code{tagged}, and @code{until} are reserved in Ada 95.
28686 Existing Ada 83 code using any of these identifiers must be edited to
28687 use some alternative name.
28690 @emph{Freezing rules}
28692 The rules in Ada 95 are slightly different with regard to the point at
28693 which entities are frozen, and representation pragmas and clauses are
28694 not permitted past the freeze point. This shows up most typically in
28695 the form of an error message complaining that a representation item
28696 appears too late, and the appropriate corrective action is to move
28697 the item nearer to the declaration of the entity to which it refers.
28699 A particular case is that representation pragmas
28700 cannot be applied to a subprogram body. If necessary, a separate subprogram
28701 declaration must be introduced to which the pragma can be applied.
28704 @emph{Optional bodies for library packages}
28706 In Ada 83, a package that did not require a package body was nevertheless
28707 allowed to have one. This lead to certain surprises in compiling large
28708 systems (situations in which the body could be unexpectedly ignored by the
28709 binder). In Ada 95, if a package does not require a body then it is not
28710 permitted to have a body. To fix this problem, simply remove a redundant
28711 body if it is empty, or, if it is non-empty, introduce a dummy declaration
28712 into the spec that makes the body required. One approach is to add a private
28713 part to the package declaration (if necessary), and define a parameterless
28714 procedure called @code{Requires_Body}, which must then be given a dummy
28715 procedure body in the package body, which then becomes required.
28716 Another approach (assuming that this does not introduce elaboration
28717 circularities) is to add an @code{Elaborate_Body} pragma to the package spec,
28718 since one effect of this pragma is to require the presence of a package body.
28721 @emph{Numeric_Error is the same exception as Constraint_Error}
28723 In Ada 95, the exception @code{Numeric_Error} is a renaming of @code{Constraint_Error}.
28724 This means that it is illegal to have separate exception handlers for
28725 the two exceptions. The fix is simply to remove the handler for the
28726 @code{Numeric_Error} case (since even in Ada 83, a compiler was free to raise
28727 @code{Constraint_Error} in place of @code{Numeric_Error} in all cases).
28730 @emph{Indefinite subtypes in generics}
28732 In Ada 83, it was permissible to pass an indefinite type (e.g, @code{String})
28733 as the actual for a generic formal private type, but then the instantiation
28734 would be illegal if there were any instances of declarations of variables
28735 of this type in the generic body. In Ada 95, to avoid this clear violation
28736 of the methodological principle known as the 'contract model',
28737 the generic declaration explicitly indicates whether
28738 or not such instantiations are permitted. If a generic formal parameter
28739 has explicit unknown discriminants, indicated by using @code{(<>)} after the
28740 subtype name, then it can be instantiated with indefinite types, but no
28741 stand-alone variables can be declared of this type. Any attempt to declare
28742 such a variable will result in an illegality at the time the generic is
28743 declared. If the @code{(<>)} notation is not used, then it is illegal
28744 to instantiate the generic with an indefinite type.
28745 This is the potential incompatibility issue when porting Ada 83 code to Ada 95.
28746 It will show up as a compile time error, and
28747 the fix is usually simply to add the @code{(<>)} to the generic declaration.
28750 @node More deterministic semantics,Changed semantics,Legal Ada 83 programs that are illegal in Ada 95,Compatibility with Ada 83
28751 @anchor{gnat_rm/compatibility_and_porting_guide more-deterministic-semantics}@anchor{43e}@anchor{gnat_rm/compatibility_and_porting_guide id5}@anchor{43f}
28752 @subsection More deterministic semantics
28761 Conversions from real types to integer types round away from 0. In Ada 83
28762 the conversion Integer(2.5) could deliver either 2 or 3 as its value. This
28763 implementation freedom was intended to support unbiased rounding in
28764 statistical applications, but in practice it interfered with portability.
28765 In Ada 95 the conversion semantics are unambiguous, and rounding away from 0
28766 is required. Numeric code may be affected by this change in semantics.
28767 Note, though, that this issue is no worse than already existed in Ada 83
28768 when porting code from one vendor to another.
28773 The Real-Time Annex introduces a set of policies that define the behavior of
28774 features that were implementation dependent in Ada 83, such as the order in
28775 which open select branches are executed.
28778 @node Changed semantics,Other language compatibility issues,More deterministic semantics,Compatibility with Ada 83
28779 @anchor{gnat_rm/compatibility_and_porting_guide id6}@anchor{440}@anchor{gnat_rm/compatibility_and_porting_guide changed-semantics}@anchor{441}
28780 @subsection Changed semantics
28783 The worst kind of incompatibility is one where a program that is legal in
28784 Ada 83 is also legal in Ada 95 but can have an effect in Ada 95 that was not
28785 possible in Ada 83. Fortunately this is extremely rare, but the one
28786 situation that you should be alert to is the change in the predefined type
28787 @code{Character} from 7-bit ASCII to 8-bit Latin-1.
28798 @emph{Range of type `@w{`}Character`@w{`}}
28800 The range of @code{Standard.Character} is now the full 256 characters
28801 of Latin-1, whereas in most Ada 83 implementations it was restricted
28802 to 128 characters. Although some of the effects of
28803 this change will be manifest in compile-time rejection of legal
28804 Ada 83 programs it is possible for a working Ada 83 program to have
28805 a different effect in Ada 95, one that was not permitted in Ada 83.
28806 As an example, the expression
28807 @code{Character'Pos(Character'Last)} returned @code{127} in Ada 83 and now
28808 delivers @code{255} as its value.
28809 In general, you should look at the logic of any
28810 character-processing Ada 83 program and see whether it needs to be adapted
28811 to work correctly with Latin-1. Note that the predefined Ada 95 API has a
28812 character handling package that may be relevant if code needs to be adapted
28813 to account for the additional Latin-1 elements.
28814 The desirable fix is to
28815 modify the program to accommodate the full character set, but in some cases
28816 it may be convenient to define a subtype or derived type of Character that
28817 covers only the restricted range.
28820 @node Other language compatibility issues,,Changed semantics,Compatibility with Ada 83
28821 @anchor{gnat_rm/compatibility_and_porting_guide other-language-compatibility-issues}@anchor{442}@anchor{gnat_rm/compatibility_and_porting_guide id7}@anchor{443}
28822 @subsection Other language compatibility issues
28829 @emph{-gnat83} switch
28831 All implementations of GNAT provide a switch that causes GNAT to operate
28832 in Ada 83 mode. In this mode, some but not all compatibility problems
28833 of the type described above are handled automatically. For example, the
28834 new reserved words introduced in Ada 95 and Ada 2005 are treated simply
28835 as identifiers as in Ada 83. However,
28836 in practice, it is usually advisable to make the necessary modifications
28837 to the program to remove the need for using this switch.
28838 See the @code{Compiling Different Versions of Ada} section in
28839 the @cite{GNAT User's Guide}.
28842 Support for removed Ada 83 pragmas and attributes
28844 A number of pragmas and attributes from Ada 83 were removed from Ada 95,
28845 generally because they were replaced by other mechanisms. Ada 95 and Ada 2005
28846 compilers are allowed, but not required, to implement these missing
28847 elements. In contrast with some other compilers, GNAT implements all
28848 such pragmas and attributes, eliminating this compatibility concern. These
28849 include @code{pragma Interface} and the floating point type attributes
28850 (@code{Emax}, @code{Mantissa}, etc.), among other items.
28853 @node Compatibility between Ada 95 and Ada 2005,Implementation-dependent characteristics,Compatibility with Ada 83,Compatibility and Porting Guide
28854 @anchor{gnat_rm/compatibility_and_porting_guide compatibility-between-ada-95-and-ada-2005}@anchor{444}@anchor{gnat_rm/compatibility_and_porting_guide id8}@anchor{445}
28855 @section Compatibility between Ada 95 and Ada 2005
28858 @geindex Compatibility between Ada 95 and Ada 2005
28860 Although Ada 2005 was designed to be upwards compatible with Ada 95, there are
28861 a number of incompatibilities. Several are enumerated below;
28862 for a complete description please see the
28863 @cite{Annotated Ada 2005 Reference Manual}, or section 9.1.1 in
28864 @cite{Rationale for Ada 2005}.
28870 @emph{New reserved words.}
28872 The words @code{interface}, @code{overriding} and @code{synchronized} are
28873 reserved in Ada 2005.
28874 A pre-Ada 2005 program that uses any of these as an identifier will be
28878 @emph{New declarations in predefined packages.}
28880 A number of packages in the predefined environment contain new declarations:
28881 @code{Ada.Exceptions}, @code{Ada.Real_Time}, @code{Ada.Strings},
28882 @code{Ada.Strings.Fixed}, @code{Ada.Strings.Bounded},
28883 @code{Ada.Strings.Unbounded}, @code{Ada.Strings.Wide_Fixed},
28884 @code{Ada.Strings.Wide_Bounded}, @code{Ada.Strings.Wide_Unbounded},
28885 @code{Ada.Tags}, @code{Ada.Text_IO}, and @code{Interfaces.C}.
28886 If an Ada 95 program does a @code{with} and @code{use} of any of these
28887 packages, the new declarations may cause name clashes.
28890 @emph{Access parameters.}
28892 A nondispatching subprogram with an access parameter cannot be renamed
28893 as a dispatching operation. This was permitted in Ada 95.
28896 @emph{Access types, discriminants, and constraints.}
28898 Rule changes in this area have led to some incompatibilities; for example,
28899 constrained subtypes of some access types are not permitted in Ada 2005.
28902 @emph{Aggregates for limited types.}
28904 The allowance of aggregates for limited types in Ada 2005 raises the
28905 possibility of ambiguities in legal Ada 95 programs, since additional types
28906 now need to be considered in expression resolution.
28909 @emph{Fixed-point multiplication and division.}
28911 Certain expressions involving '*' or '/' for a fixed-point type, which
28912 were legal in Ada 95 and invoked the predefined versions of these operations,
28914 The ambiguity may be resolved either by applying a type conversion to the
28915 expression, or by explicitly invoking the operation from package
28919 @emph{Return-by-reference types.}
28921 The Ada 95 return-by-reference mechanism has been removed. Instead, the user
28922 can declare a function returning a value from an anonymous access type.
28925 @node Implementation-dependent characteristics,Compatibility with Other Ada Systems,Compatibility between Ada 95 and Ada 2005,Compatibility and Porting Guide
28926 @anchor{gnat_rm/compatibility_and_porting_guide implementation-dependent-characteristics}@anchor{446}@anchor{gnat_rm/compatibility_and_porting_guide id9}@anchor{447}
28927 @section Implementation-dependent characteristics
28930 Although the Ada language defines the semantics of each construct as
28931 precisely as practical, in some situations (for example for reasons of
28932 efficiency, or where the effect is heavily dependent on the host or target
28933 platform) the implementation is allowed some freedom. In porting Ada 83
28934 code to GNAT, you need to be aware of whether / how the existing code
28935 exercised such implementation dependencies. Such characteristics fall into
28936 several categories, and GNAT offers specific support in assisting the
28937 transition from certain Ada 83 compilers.
28940 * Implementation-defined pragmas::
28941 * Implementation-defined attributes::
28943 * Elaboration order::
28944 * Target-specific aspects::
28948 @node Implementation-defined pragmas,Implementation-defined attributes,,Implementation-dependent characteristics
28949 @anchor{gnat_rm/compatibility_and_porting_guide implementation-defined-pragmas}@anchor{448}@anchor{gnat_rm/compatibility_and_porting_guide id10}@anchor{449}
28950 @subsection Implementation-defined pragmas
28953 Ada compilers are allowed to supplement the language-defined pragmas, and
28954 these are a potential source of non-portability. All GNAT-defined pragmas
28955 are described in @ref{7,,Implementation Defined Pragmas},
28956 and these include several that are specifically
28957 intended to correspond to other vendors' Ada 83 pragmas.
28958 For migrating from VADS, the pragma @code{Use_VADS_Size} may be useful.
28959 For compatibility with HP Ada 83, GNAT supplies the pragmas
28960 @code{Extend_System}, @code{Ident}, @code{Inline_Generic},
28961 @code{Interface_Name}, @code{Passive}, @code{Suppress_All},
28962 and @code{Volatile}.
28963 Other relevant pragmas include @code{External} and @code{Link_With}.
28964 Some vendor-specific
28965 Ada 83 pragmas (@code{Share_Generic}, @code{Subtitle}, and @code{Title}) are
28967 avoiding compiler rejection of units that contain such pragmas; they are not
28968 relevant in a GNAT context and hence are not otherwise implemented.
28970 @node Implementation-defined attributes,Libraries,Implementation-defined pragmas,Implementation-dependent characteristics
28971 @anchor{gnat_rm/compatibility_and_porting_guide id11}@anchor{44a}@anchor{gnat_rm/compatibility_and_porting_guide implementation-defined-attributes}@anchor{44b}
28972 @subsection Implementation-defined attributes
28975 Analogous to pragmas, the set of attributes may be extended by an
28976 implementation. All GNAT-defined attributes are described in
28977 @ref{8,,Implementation Defined Attributes},
28978 and these include several that are specifically intended
28979 to correspond to other vendors' Ada 83 attributes. For migrating from VADS,
28980 the attribute @code{VADS_Size} may be useful. For compatibility with HP
28981 Ada 83, GNAT supplies the attributes @code{Bit}, @code{Machine_Size} and
28984 @node Libraries,Elaboration order,Implementation-defined attributes,Implementation-dependent characteristics
28985 @anchor{gnat_rm/compatibility_and_porting_guide libraries}@anchor{44c}@anchor{gnat_rm/compatibility_and_porting_guide id12}@anchor{44d}
28986 @subsection Libraries
28989 Vendors may supply libraries to supplement the standard Ada API. If Ada 83
28990 code uses vendor-specific libraries then there are several ways to manage
28991 this in Ada 95 and later versions of the standard:
28997 If the source code for the libraries (specs and bodies) are
28998 available, then the libraries can be migrated in the same way as the
29002 If the source code for the specs but not the bodies are
29003 available, then you can reimplement the bodies.
29006 Some features introduced by Ada 95 obviate the need for library support. For
29007 example most Ada 83 vendors supplied a package for unsigned integers. The
29008 Ada 95 modular type feature is the preferred way to handle this need, so
29009 instead of migrating or reimplementing the unsigned integer package it may
29010 be preferable to retrofit the application using modular types.
29013 @node Elaboration order,Target-specific aspects,Libraries,Implementation-dependent characteristics
29014 @anchor{gnat_rm/compatibility_and_porting_guide elaboration-order}@anchor{44e}@anchor{gnat_rm/compatibility_and_porting_guide id13}@anchor{44f}
29015 @subsection Elaboration order
29018 The implementation can choose any elaboration order consistent with the unit
29019 dependency relationship. This freedom means that some orders can result in
29020 Program_Error being raised due to an 'Access Before Elaboration': an attempt
29021 to invoke a subprogram before its body has been elaborated, or to instantiate
29022 a generic before the generic body has been elaborated. By default GNAT
29023 attempts to choose a safe order (one that will not encounter access before
29024 elaboration problems) by implicitly inserting @code{Elaborate} or
29025 @code{Elaborate_All} pragmas where
29026 needed. However, this can lead to the creation of elaboration circularities
29027 and a resulting rejection of the program by gnatbind. This issue is
29028 thoroughly described in the @emph{Elaboration Order Handling in GNAT} appendix
29029 in the @cite{GNAT User's Guide}.
29030 In brief, there are several
29031 ways to deal with this situation:
29037 Modify the program to eliminate the circularities, e.g., by moving
29038 elaboration-time code into explicitly-invoked procedures
29041 Constrain the elaboration order by including explicit @code{Elaborate_Body} or
29042 @code{Elaborate} pragmas, and then inhibit the generation of implicit
29043 @code{Elaborate_All}
29044 pragmas either globally (as an effect of the @emph{-gnatE} switch) or locally
29045 (by selectively suppressing elaboration checks via pragma
29046 @code{Suppress(Elaboration_Check)} when it is safe to do so).
29049 @node Target-specific aspects,,Elaboration order,Implementation-dependent characteristics
29050 @anchor{gnat_rm/compatibility_and_porting_guide target-specific-aspects}@anchor{450}@anchor{gnat_rm/compatibility_and_porting_guide id14}@anchor{451}
29051 @subsection Target-specific aspects
29054 Low-level applications need to deal with machine addresses, data
29055 representations, interfacing with assembler code, and similar issues. If
29056 such an Ada 83 application is being ported to different target hardware (for
29057 example where the byte endianness has changed) then you will need to
29058 carefully examine the program logic; the porting effort will heavily depend
29059 on the robustness of the original design. Moreover, Ada 95 (and thus
29060 Ada 2005 and Ada 2012) are sometimes
29061 incompatible with typical Ada 83 compiler practices regarding implicit
29062 packing, the meaning of the Size attribute, and the size of access values.
29063 GNAT's approach to these issues is described in @ref{452,,Representation Clauses}.
29065 @node Compatibility with Other Ada Systems,Representation Clauses,Implementation-dependent characteristics,Compatibility and Porting Guide
29066 @anchor{gnat_rm/compatibility_and_porting_guide id15}@anchor{453}@anchor{gnat_rm/compatibility_and_porting_guide compatibility-with-other-ada-systems}@anchor{454}
29067 @section Compatibility with Other Ada Systems
29070 If programs avoid the use of implementation dependent and
29071 implementation defined features, as documented in the
29072 @cite{Ada Reference Manual}, there should be a high degree of portability between
29073 GNAT and other Ada systems. The following are specific items which
29074 have proved troublesome in moving Ada 95 programs from GNAT to other Ada 95
29075 compilers, but do not affect porting code to GNAT.
29076 (As of January 2007, GNAT is the only compiler available for Ada 2005;
29077 the following issues may or may not arise for Ada 2005 programs
29078 when other compilers appear.)
29084 @emph{Ada 83 Pragmas and Attributes}
29086 Ada 95 compilers are allowed, but not required, to implement the missing
29087 Ada 83 pragmas and attributes that are no longer defined in Ada 95.
29088 GNAT implements all such pragmas and attributes, eliminating this as
29089 a compatibility concern, but some other Ada 95 compilers reject these
29090 pragmas and attributes.
29093 @emph{Specialized Needs Annexes}
29095 GNAT implements the full set of special needs annexes. At the
29096 current time, it is the only Ada 95 compiler to do so. This means that
29097 programs making use of these features may not be portable to other Ada
29098 95 compilation systems.
29101 @emph{Representation Clauses}
29103 Some other Ada 95 compilers implement only the minimal set of
29104 representation clauses required by the Ada 95 reference manual. GNAT goes
29105 far beyond this minimal set, as described in the next section.
29108 @node Representation Clauses,Compatibility with HP Ada 83,Compatibility with Other Ada Systems,Compatibility and Porting Guide
29109 @anchor{gnat_rm/compatibility_and_porting_guide representation-clauses}@anchor{452}@anchor{gnat_rm/compatibility_and_porting_guide id16}@anchor{455}
29110 @section Representation Clauses
29113 The Ada 83 reference manual was quite vague in describing both the minimal
29114 required implementation of representation clauses, and also their precise
29115 effects. Ada 95 (and thus also Ada 2005) are much more explicit, but the
29116 minimal set of capabilities required is still quite limited.
29118 GNAT implements the full required set of capabilities in
29119 Ada 95 and Ada 2005, but also goes much further, and in particular
29120 an effort has been made to be compatible with existing Ada 83 usage to the
29121 greatest extent possible.
29123 A few cases exist in which Ada 83 compiler behavior is incompatible with
29124 the requirements in Ada 95 (and thus also Ada 2005). These are instances of
29125 intentional or accidental dependence on specific implementation dependent
29126 characteristics of these Ada 83 compilers. The following is a list of
29127 the cases most likely to arise in existing Ada 83 code.
29133 @emph{Implicit Packing}
29135 Some Ada 83 compilers allowed a Size specification to cause implicit
29136 packing of an array or record. This could cause expensive implicit
29137 conversions for change of representation in the presence of derived
29138 types, and the Ada design intends to avoid this possibility.
29139 Subsequent AI's were issued to make it clear that such implicit
29140 change of representation in response to a Size clause is inadvisable,
29141 and this recommendation is represented explicitly in the Ada 95 (and Ada 2005)
29142 Reference Manuals as implementation advice that is followed by GNAT.
29143 The problem will show up as an error
29144 message rejecting the size clause. The fix is simply to provide
29145 the explicit pragma @code{Pack}, or for more fine tuned control, provide
29146 a Component_Size clause.
29149 @emph{Meaning of Size Attribute}
29151 The Size attribute in Ada 95 (and Ada 2005) for discrete types is defined as
29152 the minimal number of bits required to hold values of the type. For example,
29153 on a 32-bit machine, the size of @code{Natural} will typically be 31 and not
29154 32 (since no sign bit is required). Some Ada 83 compilers gave 31, and
29155 some 32 in this situation. This problem will usually show up as a compile
29156 time error, but not always. It is a good idea to check all uses of the
29157 'Size attribute when porting Ada 83 code. The GNAT specific attribute
29158 Object_Size can provide a useful way of duplicating the behavior of
29159 some Ada 83 compiler systems.
29162 @emph{Size of Access Types}
29164 A common assumption in Ada 83 code is that an access type is in fact a pointer,
29165 and that therefore it will be the same size as a System.Address value. This
29166 assumption is true for GNAT in most cases with one exception. For the case of
29167 a pointer to an unconstrained array type (where the bounds may vary from one
29168 value of the access type to another), the default is to use a 'fat pointer',
29169 which is represented as two separate pointers, one to the bounds, and one to
29170 the array. This representation has a number of advantages, including improved
29171 efficiency. However, it may cause some difficulties in porting existing Ada 83
29172 code which makes the assumption that, for example, pointers fit in 32 bits on
29173 a machine with 32-bit addressing.
29175 To get around this problem, GNAT also permits the use of 'thin pointers' for
29176 access types in this case (where the designated type is an unconstrained array
29177 type). These thin pointers are indeed the same size as a System.Address value.
29178 To specify a thin pointer, use a size clause for the type, for example:
29181 type X is access all String;
29182 for X'Size use Standard'Address_Size;
29185 which will cause the type X to be represented using a single pointer.
29186 When using this representation, the bounds are right behind the array.
29187 This representation is slightly less efficient, and does not allow quite
29188 such flexibility in the use of foreign pointers or in using the
29189 Unrestricted_Access attribute to create pointers to non-aliased objects.
29190 But for any standard portable use of the access type it will work in
29191 a functionally correct manner and allow porting of existing code.
29192 Note that another way of forcing a thin pointer representation
29193 is to use a component size clause for the element size in an array,
29194 or a record representation clause for an access field in a record.
29196 See the documentation of Unrestricted_Access in the GNAT RM for a
29197 full discussion of possible problems using this attribute in conjunction
29198 with thin pointers.
29201 @node Compatibility with HP Ada 83,,Representation Clauses,Compatibility and Porting Guide
29202 @anchor{gnat_rm/compatibility_and_porting_guide compatibility-with-hp-ada-83}@anchor{456}@anchor{gnat_rm/compatibility_and_porting_guide id17}@anchor{457}
29203 @section Compatibility with HP Ada 83
29206 All the HP Ada 83 pragmas and attributes are recognized, although only a subset
29207 of them can sensibly be implemented. The description of pragmas in
29208 @ref{7,,Implementation Defined Pragmas} indicates whether or not they are
29209 applicable to GNAT.
29215 @emph{Default floating-point representation}
29217 In GNAT, the default floating-point format is IEEE, whereas in HP Ada 83,
29223 the package System in GNAT exactly corresponds to the definition in the
29224 Ada 95 reference manual, which means that it excludes many of the
29225 HP Ada 83 extensions. However, a separate package Aux_DEC is provided
29226 that contains the additional definitions, and a special pragma,
29227 Extend_System allows this package to be treated transparently as an
29228 extension of package System.
29231 @node GNU Free Documentation License,Index,Compatibility and Porting Guide,Top
29232 @anchor{share/gnu_free_documentation_license gnu-fdl}@anchor{1}@anchor{share/gnu_free_documentation_license doc}@anchor{458}@anchor{share/gnu_free_documentation_license gnu-free-documentation-license}@anchor{459}
29233 @chapter GNU Free Documentation License
29236 Version 1.3, 3 November 2008
29238 Copyright 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc
29239 @indicateurl{http://fsf.org/}
29241 Everyone is permitted to copy and distribute verbatim copies of this
29242 license document, but changing it is not allowed.
29246 The purpose of this License is to make a manual, textbook, or other
29247 functional and useful document "free" in the sense of freedom: to
29248 assure everyone the effective freedom to copy and redistribute it,
29249 with or without modifying it, either commercially or noncommercially.
29250 Secondarily, this License preserves for the author and publisher a way
29251 to get credit for their work, while not being considered responsible
29252 for modifications made by others.
29254 This License is a kind of "copyleft", which means that derivative
29255 works of the document must themselves be free in the same sense. It
29256 complements the GNU General Public License, which is a copyleft
29257 license designed for free software.
29259 We have designed this License in order to use it for manuals for free
29260 software, because free software needs free documentation: a free
29261 program should come with manuals providing the same freedoms that the
29262 software does. But this License is not limited to software manuals;
29263 it can be used for any textual work, regardless of subject matter or
29264 whether it is published as a printed book. We recommend this License
29265 principally for works whose purpose is instruction or reference.
29267 @strong{1. APPLICABILITY AND DEFINITIONS}
29269 This License applies to any manual or other work, in any medium, that
29270 contains a notice placed by the copyright holder saying it can be
29271 distributed under the terms of this License. Such a notice grants a
29272 world-wide, royalty-free license, unlimited in duration, to use that
29273 work under the conditions stated herein. The @strong{Document}, below,
29274 refers to any such manual or work. Any member of the public is a
29275 licensee, and is addressed as "@strong{you}". You accept the license if you
29276 copy, modify or distribute the work in a way requiring permission
29277 under copyright law.
29279 A "@strong{Modified Version}" of the Document means any work containing the
29280 Document or a portion of it, either copied verbatim, or with
29281 modifications and/or translated into another language.
29283 A "@strong{Secondary Section}" is a named appendix or a front-matter section of
29284 the Document that deals exclusively with the relationship of the
29285 publishers or authors of the Document to the Document's overall subject
29286 (or to related matters) and contains nothing that could fall directly
29287 within that overall subject. (Thus, if the Document is in part a
29288 textbook of mathematics, a Secondary Section may not explain any
29289 mathematics.) The relationship could be a matter of historical
29290 connection with the subject or with related matters, or of legal,
29291 commercial, philosophical, ethical or political position regarding
29294 The "@strong{Invariant Sections}" are certain Secondary Sections whose titles
29295 are designated, as being those of Invariant Sections, in the notice
29296 that says that the Document is released under this License. If a
29297 section does not fit the above definition of Secondary then it is not
29298 allowed to be designated as Invariant. The Document may contain zero
29299 Invariant Sections. If the Document does not identify any Invariant
29300 Sections then there are none.
29302 The "@strong{Cover Texts}" are certain short passages of text that are listed,
29303 as Front-Cover Texts or Back-Cover Texts, in the notice that says that
29304 the Document is released under this License. A Front-Cover Text may
29305 be at most 5 words, and a Back-Cover Text may be at most 25 words.
29307 A "@strong{Transparent}" copy of the Document means a machine-readable copy,
29308 represented in a format whose specification is available to the
29309 general public, that is suitable for revising the document
29310 straightforwardly with generic text editors or (for images composed of
29311 pixels) generic paint programs or (for drawings) some widely available
29312 drawing editor, and that is suitable for input to text formatters or
29313 for automatic translation to a variety of formats suitable for input
29314 to text formatters. A copy made in an otherwise Transparent file
29315 format whose markup, or absence of markup, has been arranged to thwart
29316 or discourage subsequent modification by readers is not Transparent.
29317 An image format is not Transparent if used for any substantial amount
29318 of text. A copy that is not "Transparent" is called @strong{Opaque}.
29320 Examples of suitable formats for Transparent copies include plain
29321 ASCII without markup, Texinfo input format, LaTeX input format, SGML
29322 or XML using a publicly available DTD, and standard-conforming simple
29323 HTML, PostScript or PDF designed for human modification. Examples of
29324 transparent image formats include PNG, XCF and JPG. Opaque formats
29325 include proprietary formats that can be read and edited only by
29326 proprietary word processors, SGML or XML for which the DTD and/or
29327 processing tools are not generally available, and the
29328 machine-generated HTML, PostScript or PDF produced by some word
29329 processors for output purposes only.
29331 The "@strong{Title Page}" means, for a printed book, the title page itself,
29332 plus such following pages as are needed to hold, legibly, the material
29333 this License requires to appear in the title page. For works in
29334 formats which do not have any title page as such, "Title Page" means
29335 the text near the most prominent appearance of the work's title,
29336 preceding the beginning of the body of the text.
29338 The "@strong{publisher}" means any person or entity that distributes
29339 copies of the Document to the public.
29341 A section "@strong{Entitled XYZ}" means a named subunit of the Document whose
29342 title either is precisely XYZ or contains XYZ in parentheses following
29343 text that translates XYZ in another language. (Here XYZ stands for a
29344 specific section name mentioned below, such as "@strong{Acknowledgements}",
29345 "@strong{Dedications}", "@strong{Endorsements}", or "@strong{History}".)
29346 To "@strong{Preserve the Title}"
29347 of such a section when you modify the Document means that it remains a
29348 section "Entitled XYZ" according to this definition.
29350 The Document may include Warranty Disclaimers next to the notice which
29351 states that this License applies to the Document. These Warranty
29352 Disclaimers are considered to be included by reference in this
29353 License, but only as regards disclaiming warranties: any other
29354 implication that these Warranty Disclaimers may have is void and has
29355 no effect on the meaning of this License.
29357 @strong{2. VERBATIM COPYING}
29359 You may copy and distribute the Document in any medium, either
29360 commercially or noncommercially, provided that this License, the
29361 copyright notices, and the license notice saying this License applies
29362 to the Document are reproduced in all copies, and that you add no other
29363 conditions whatsoever to those of this License. You may not use
29364 technical measures to obstruct or control the reading or further
29365 copying of the copies you make or distribute. However, you may accept
29366 compensation in exchange for copies. If you distribute a large enough
29367 number of copies you must also follow the conditions in section 3.
29369 You may also lend copies, under the same conditions stated above, and
29370 you may publicly display copies.
29372 @strong{3. COPYING IN QUANTITY}
29374 If you publish printed copies (or copies in media that commonly have
29375 printed covers) of the Document, numbering more than 100, and the
29376 Document's license notice requires Cover Texts, you must enclose the
29377 copies in covers that carry, clearly and legibly, all these Cover
29378 Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on
29379 the back cover. Both covers must also clearly and legibly identify
29380 you as the publisher of these copies. The front cover must present
29381 the full title with all words of the title equally prominent and
29382 visible. You may add other material on the covers in addition.
29383 Copying with changes limited to the covers, as long as they preserve
29384 the title of the Document and satisfy these conditions, can be treated
29385 as verbatim copying in other respects.
29387 If the required texts for either cover are too voluminous to fit
29388 legibly, you should put the first ones listed (as many as fit
29389 reasonably) on the actual cover, and continue the rest onto adjacent
29392 If you publish or distribute Opaque copies of the Document numbering
29393 more than 100, you must either include a machine-readable Transparent
29394 copy along with each Opaque copy, or state in or with each Opaque copy
29395 a computer-network location from which the general network-using
29396 public has access to download using public-standard network protocols
29397 a complete Transparent copy of the Document, free of added material.
29398 If you use the latter option, you must take reasonably prudent steps,
29399 when you begin distribution of Opaque copies in quantity, to ensure
29400 that this Transparent copy will remain thus accessible at the stated
29401 location until at least one year after the last time you distribute an
29402 Opaque copy (directly or through your agents or retailers) of that
29403 edition to the public.
29405 It is requested, but not required, that you contact the authors of the
29406 Document well before redistributing any large number of copies, to give
29407 them a chance to provide you with an updated version of the Document.
29409 @strong{4. MODIFICATIONS}
29411 You may copy and distribute a Modified Version of the Document under
29412 the conditions of sections 2 and 3 above, provided that you release
29413 the Modified Version under precisely this License, with the Modified
29414 Version filling the role of the Document, thus licensing distribution
29415 and modification of the Modified Version to whoever possesses a copy
29416 of it. In addition, you must do these things in the Modified Version:
29422 Use in the Title Page (and on the covers, if any) a title distinct
29423 from that of the Document, and from those of previous versions
29424 (which should, if there were any, be listed in the History section
29425 of the Document). You may use the same title as a previous version
29426 if the original publisher of that version gives permission.
29429 List on the Title Page, as authors, one or more persons or entities
29430 responsible for authorship of the modifications in the Modified
29431 Version, together with at least five of the principal authors of the
29432 Document (all of its principal authors, if it has fewer than five),
29433 unless they release you from this requirement.
29436 State on the Title page the name of the publisher of the
29437 Modified Version, as the publisher.
29440 Preserve all the copyright notices of the Document.
29443 Add an appropriate copyright notice for your modifications
29444 adjacent to the other copyright notices.
29447 Include, immediately after the copyright notices, a license notice
29448 giving the public permission to use the Modified Version under the
29449 terms of this License, in the form shown in the Addendum below.
29452 Preserve in that license notice the full lists of Invariant Sections
29453 and required Cover Texts given in the Document's license notice.
29456 Include an unaltered copy of this License.
29459 Preserve the section Entitled "History", Preserve its Title, and add
29460 to it an item stating at least the title, year, new authors, and
29461 publisher of the Modified Version as given on the Title Page. If
29462 there is no section Entitled "History" in the Document, create one
29463 stating the title, year, authors, and publisher of the Document as
29464 given on its Title Page, then add an item describing the Modified
29465 Version as stated in the previous sentence.
29468 Preserve the network location, if any, given in the Document for
29469 public access to a Transparent copy of the Document, and likewise
29470 the network locations given in the Document for previous versions
29471 it was based on. These may be placed in the "History" section.
29472 You may omit a network location for a work that was published at
29473 least four years before the Document itself, or if the original
29474 publisher of the version it refers to gives permission.
29477 For any section Entitled "Acknowledgements" or "Dedications",
29478 Preserve the Title of the section, and preserve in the section all
29479 the substance and tone of each of the contributor acknowledgements
29480 and/or dedications given therein.
29483 Preserve all the Invariant Sections of the Document,
29484 unaltered in their text and in their titles. Section numbers
29485 or the equivalent are not considered part of the section titles.
29488 Delete any section Entitled "Endorsements". Such a section
29489 may not be included in the Modified Version.
29492 Do not retitle any existing section to be Entitled "Endorsements"
29493 or to conflict in title with any Invariant Section.
29496 Preserve any Warranty Disclaimers.
29499 If the Modified Version includes new front-matter sections or
29500 appendices that qualify as Secondary Sections and contain no material
29501 copied from the Document, you may at your option designate some or all
29502 of these sections as invariant. To do this, add their titles to the
29503 list of Invariant Sections in the Modified Version's license notice.
29504 These titles must be distinct from any other section titles.
29506 You may add a section Entitled "Endorsements", provided it contains
29507 nothing but endorsements of your Modified Version by various
29508 parties---for example, statements of peer review or that the text has
29509 been approved by an organization as the authoritative definition of a
29512 You may add a passage of up to five words as a Front-Cover Text, and a
29513 passage of up to 25 words as a Back-Cover Text, to the end of the list
29514 of Cover Texts in the Modified Version. Only one passage of
29515 Front-Cover Text and one of Back-Cover Text may be added by (or
29516 through arrangements made by) any one entity. If the Document already
29517 includes a cover text for the same cover, previously added by you or
29518 by arrangement made by the same entity you are acting on behalf of,
29519 you may not add another; but you may replace the old one, on explicit
29520 permission from the previous publisher that added the old one.
29522 The author(s) and publisher(s) of the Document do not by this License
29523 give permission to use their names for publicity for or to assert or
29524 imply endorsement of any Modified Version.
29526 @strong{5. COMBINING DOCUMENTS}
29528 You may combine the Document with other documents released under this
29529 License, under the terms defined in section 4 above for modified
29530 versions, provided that you include in the combination all of the
29531 Invariant Sections of all of the original documents, unmodified, and
29532 list them all as Invariant Sections of your combined work in its
29533 license notice, and that you preserve all their Warranty Disclaimers.
29535 The combined work need only contain one copy of this License, and
29536 multiple identical Invariant Sections may be replaced with a single
29537 copy. If there are multiple Invariant Sections with the same name but
29538 different contents, make the title of each such section unique by
29539 adding at the end of it, in parentheses, the name of the original
29540 author or publisher of that section if known, or else a unique number.
29541 Make the same adjustment to the section titles in the list of
29542 Invariant Sections in the license notice of the combined work.
29544 In the combination, you must combine any sections Entitled "History"
29545 in the various original documents, forming one section Entitled
29546 "History"; likewise combine any sections Entitled "Acknowledgements",
29547 and any sections Entitled "Dedications". You must delete all sections
29548 Entitled "Endorsements".
29550 @strong{6. COLLECTIONS OF DOCUMENTS}
29552 You may make a collection consisting of the Document and other documents
29553 released under this License, and replace the individual copies of this
29554 License in the various documents with a single copy that is included in
29555 the collection, provided that you follow the rules of this License for
29556 verbatim copying of each of the documents in all other respects.
29558 You may extract a single document from such a collection, and distribute
29559 it individually under this License, provided you insert a copy of this
29560 License into the extracted document, and follow this License in all
29561 other respects regarding verbatim copying of that document.
29563 @strong{7. AGGREGATION WITH INDEPENDENT WORKS}
29565 A compilation of the Document or its derivatives with other separate
29566 and independent documents or works, in or on a volume of a storage or
29567 distribution medium, is called an "aggregate" if the copyright
29568 resulting from the compilation is not used to limit the legal rights
29569 of the compilation's users beyond what the individual works permit.
29570 When the Document is included in an aggregate, this License does not
29571 apply to the other works in the aggregate which are not themselves
29572 derivative works of the Document.
29574 If the Cover Text requirement of section 3 is applicable to these
29575 copies of the Document, then if the Document is less than one half of
29576 the entire aggregate, the Document's Cover Texts may be placed on
29577 covers that bracket the Document within the aggregate, or the
29578 electronic equivalent of covers if the Document is in electronic form.
29579 Otherwise they must appear on printed covers that bracket the whole
29582 @strong{8. TRANSLATION}
29584 Translation is considered a kind of modification, so you may
29585 distribute translations of the Document under the terms of section 4.
29586 Replacing Invariant Sections with translations requires special
29587 permission from their copyright holders, but you may include
29588 translations of some or all Invariant Sections in addition to the
29589 original versions of these Invariant Sections. You may include a
29590 translation of this License, and all the license notices in the
29591 Document, and any Warranty Disclaimers, provided that you also include
29592 the original English version of this License and the original versions
29593 of those notices and disclaimers. In case of a disagreement between
29594 the translation and the original version of this License or a notice
29595 or disclaimer, the original version will prevail.
29597 If a section in the Document is Entitled "Acknowledgements",
29598 "Dedications", or "History", the requirement (section 4) to Preserve
29599 its Title (section 1) will typically require changing the actual
29602 @strong{9. TERMINATION}
29604 You may not copy, modify, sublicense, or distribute the Document
29605 except as expressly provided under this License. Any attempt
29606 otherwise to copy, modify, sublicense, or distribute it is void, and
29607 will automatically terminate your rights under this License.
29609 However, if you cease all violation of this License, then your license
29610 from a particular copyright holder is reinstated (a) provisionally,
29611 unless and until the copyright holder explicitly and finally
29612 terminates your license, and (b) permanently, if the copyright holder
29613 fails to notify you of the violation by some reasonable means prior to
29614 60 days after the cessation.
29616 Moreover, your license from a particular copyright holder is
29617 reinstated permanently if the copyright holder notifies you of the
29618 violation by some reasonable means, this is the first time you have
29619 received notice of violation of this License (for any work) from that
29620 copyright holder, and you cure the violation prior to 30 days after
29621 your receipt of the notice.
29623 Termination of your rights under this section does not terminate the
29624 licenses of parties who have received copies or rights from you under
29625 this License. If your rights have been terminated and not permanently
29626 reinstated, receipt of a copy of some or all of the same material does
29627 not give you any rights to use it.
29629 @strong{10. FUTURE REVISIONS OF THIS LICENSE}
29631 The Free Software Foundation may publish new, revised versions
29632 of the GNU Free Documentation License from time to time. Such new
29633 versions will be similar in spirit to the present version, but may
29634 differ in detail to address new problems or concerns. See
29635 @indicateurl{http://www.gnu.org/copyleft/}.
29637 Each version of the License is given a distinguishing version number.
29638 If the Document specifies that a particular numbered version of this
29639 License "or any later version" applies to it, you have the option of
29640 following the terms and conditions either of that specified version or
29641 of any later version that has been published (not as a draft) by the
29642 Free Software Foundation. If the Document does not specify a version
29643 number of this License, you may choose any version ever published (not
29644 as a draft) by the Free Software Foundation. If the Document
29645 specifies that a proxy can decide which future versions of this
29646 License can be used, that proxy's public statement of acceptance of a
29647 version permanently authorizes you to choose that version for the
29650 @strong{11. RELICENSING}
29652 "Massive Multiauthor Collaboration Site" (or "MMC Site") means any
29653 World Wide Web server that publishes copyrightable works and also
29654 provides prominent facilities for anybody to edit those works. A
29655 public wiki that anybody can edit is an example of such a server. A
29656 "Massive Multiauthor Collaboration" (or "MMC") contained in the
29657 site means any set of copyrightable works thus published on the MMC
29660 "CC-BY-SA" means the Creative Commons Attribution-Share Alike 3.0
29661 license published by Creative Commons Corporation, a not-for-profit
29662 corporation with a principal place of business in San Francisco,
29663 California, as well as future copyleft versions of that license
29664 published by that same organization.
29666 "Incorporate" means to publish or republish a Document, in whole or
29667 in part, as part of another Document.
29669 An MMC is "eligible for relicensing" if it is licensed under this
29670 License, and if all works that were first published under this License
29671 somewhere other than this MMC, and subsequently incorporated in whole
29672 or in part into the MMC, (1) had no cover texts or invariant sections,
29673 and (2) were thus incorporated prior to November 1, 2008.
29675 The operator of an MMC Site may republish an MMC contained in the site
29676 under CC-BY-SA on the same site at any time before August 1, 2009,
29677 provided the MMC is eligible for relicensing.
29679 @strong{ADDENDUM: How to use this License for your documents}
29681 To use this License in a document you have written, include a copy of
29682 the License in the document and put the following copyright and
29683 license notices just after the title page:
29687 Copyright © YEAR YOUR NAME.
29688 Permission is granted to copy, distribute and/or modify this document
29689 under the terms of the GNU Free Documentation License, Version 1.3
29690 or any later version published by the Free Software Foundation;
29691 with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
29692 A copy of the license is included in the section entitled "GNU
29693 Free Documentation License".
29696 If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts,
29697 replace the "with ... Texts." line with this:
29701 with the Invariant Sections being LIST THEIR TITLES, with the
29702 Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST.
29705 If you have Invariant Sections without Cover Texts, or some other
29706 combination of the three, merge those two alternatives to suit the
29709 If your document contains nontrivial examples of program code, we
29710 recommend releasing these examples in parallel under your choice of
29711 free software license, such as the GNU General Public License,
29712 to permit their use in free software.
29714 @node Index,,GNU Free Documentation License,Top