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8 @settitle GNAT Reference Manual
13 @dircategory GNU Ada Tools
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24 GNAT Reference Manual , Oct 14, 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::
540 Implementation Advice
542 * RM 1.1.3(20); Error Detection: RM 1 1 3 20 Error Detection.
543 * RM 1.1.3(31); Child Units: RM 1 1 3 31 Child Units.
544 * RM 1.1.5(12); Bounded Errors: RM 1 1 5 12 Bounded Errors.
545 * RM 2.8(16); Pragmas: RM 2 8 16 Pragmas.
546 * RM 2.8(17-19); Pragmas: RM 2 8 17-19 Pragmas.
547 * RM 3.5.2(5); Alternative Character Sets: RM 3 5 2 5 Alternative Character Sets.
548 * RM 3.5.4(28); Integer Types: RM 3 5 4 28 Integer Types.
549 * RM 3.5.4(29); Integer Types: RM 3 5 4 29 Integer Types.
550 * RM 3.5.5(8); Enumeration Values: RM 3 5 5 8 Enumeration Values.
551 * RM 3.5.7(17); Float Types: RM 3 5 7 17 Float Types.
552 * RM 3.6.2(11); Multidimensional Arrays: RM 3 6 2 11 Multidimensional Arrays.
553 * RM 9.6(30-31); Duration'Small: RM 9 6 30-31 Duration'Small.
554 * RM 10.2.1(12); Consistent Representation: RM 10 2 1 12 Consistent Representation.
555 * RM 11.4.1(19); Exception Information: RM 11 4 1 19 Exception Information.
556 * RM 11.5(28); Suppression of Checks: RM 11 5 28 Suppression of Checks.
557 * RM 13.1 (21-24); Representation Clauses: RM 13 1 21-24 Representation Clauses.
558 * RM 13.2(6-8); Packed Types: RM 13 2 6-8 Packed Types.
559 * RM 13.3(14-19); Address Clauses: RM 13 3 14-19 Address Clauses.
560 * RM 13.3(29-35); Alignment Clauses: RM 13 3 29-35 Alignment Clauses.
561 * RM 13.3(42-43); Size Clauses: RM 13 3 42-43 Size Clauses.
562 * RM 13.3(50-56); Size Clauses: RM 13 3 50-56 Size Clauses.
563 * RM 13.3(71-73); Component Size Clauses: RM 13 3 71-73 Component Size Clauses.
564 * RM 13.4(9-10); Enumeration Representation Clauses: RM 13 4 9-10 Enumeration Representation Clauses.
565 * RM 13.5.1(17-22); Record Representation Clauses: RM 13 5 1 17-22 Record Representation Clauses.
566 * RM 13.5.2(5); Storage Place Attributes: RM 13 5 2 5 Storage Place Attributes.
567 * RM 13.5.3(7-8); Bit Ordering: RM 13 5 3 7-8 Bit Ordering.
568 * RM 13.7(37); Address as Private: RM 13 7 37 Address as Private.
569 * RM 13.7.1(16); Address Operations: RM 13 7 1 16 Address Operations.
570 * RM 13.9(14-17); Unchecked Conversion: RM 13 9 14-17 Unchecked Conversion.
571 * RM 13.11(23-25); Implicit Heap Usage: RM 13 11 23-25 Implicit Heap Usage.
572 * RM 13.11.2(17); Unchecked Deallocation: RM 13 11 2 17 Unchecked Deallocation.
573 * RM 13.13.2(17); Stream Oriented Attributes: RM 13 13 2 17 Stream Oriented Attributes.
574 * RM A.1(52); Names of Predefined Numeric Types: RM A 1 52 Names of Predefined Numeric Types.
575 * RM A.3.2(49); Ada.Characters.Handling: RM A 3 2 49 Ada Characters Handling.
576 * RM A.4.4(106); Bounded-Length String Handling: RM A 4 4 106 Bounded-Length String Handling.
577 * RM A.5.2(46-47); Random Number Generation: RM A 5 2 46-47 Random Number Generation.
578 * RM A.10.7(23); Get_Immediate: RM A 10 7 23 Get_Immediate.
579 * RM B.1(39-41); Pragma Export: RM B 1 39-41 Pragma Export.
580 * RM B.2(12-13); Package Interfaces: RM B 2 12-13 Package Interfaces.
581 * RM B.3(63-71); Interfacing with C: RM B 3 63-71 Interfacing with C.
582 * RM B.4(95-98); Interfacing with COBOL: RM B 4 95-98 Interfacing with COBOL.
583 * RM B.5(22-26); Interfacing with Fortran: RM B 5 22-26 Interfacing with Fortran.
584 * RM C.1(3-5); Access to Machine Operations: RM C 1 3-5 Access to Machine Operations.
585 * RM C.1(10-16); Access to Machine Operations: RM C 1 10-16 Access to Machine Operations.
586 * RM C.3(28); Interrupt Support: RM C 3 28 Interrupt Support.
587 * RM C.3.1(20-21); Protected Procedure Handlers: RM C 3 1 20-21 Protected Procedure Handlers.
588 * RM C.3.2(25); Package Interrupts: RM C 3 2 25 Package Interrupts.
589 * RM C.4(14); Pre-elaboration Requirements: RM C 4 14 Pre-elaboration Requirements.
590 * RM C.5(8); Pragma Discard_Names: RM C 5 8 Pragma Discard_Names.
591 * RM C.7.2(30); The Package Task_Attributes: RM C 7 2 30 The Package Task_Attributes.
592 * RM D.3(17); Locking Policies: RM D 3 17 Locking Policies.
593 * RM D.4(16); Entry Queuing Policies: RM D 4 16 Entry Queuing Policies.
594 * RM D.6(9-10); Preemptive Abort: RM D 6 9-10 Preemptive Abort.
595 * RM D.7(21); Tasking Restrictions: RM D 7 21 Tasking Restrictions.
596 * RM D.8(47-49); Monotonic Time: RM D 8 47-49 Monotonic Time.
597 * RM E.5(28-29); Partition Communication Subsystem: RM E 5 28-29 Partition Communication Subsystem.
598 * RM F(7); COBOL Support: RM F 7 COBOL Support.
599 * RM F.1(2); Decimal Radix Support: RM F 1 2 Decimal Radix Support.
600 * RM G; Numerics: RM G Numerics.
601 * RM G.1.1(56-58); Complex Types: RM G 1 1 56-58 Complex Types.
602 * RM G.1.2(49); Complex Elementary Functions: RM G 1 2 49 Complex Elementary Functions.
603 * RM G.2.4(19); Accuracy Requirements: RM G 2 4 19 Accuracy Requirements.
604 * RM G.2.6(15); Complex Arithmetic Accuracy: RM G 2 6 15 Complex Arithmetic Accuracy.
605 * RM H.6(15/2); Pragma Partition_Elaboration_Policy: RM H 6 15/2 Pragma Partition_Elaboration_Policy.
607 Intrinsic Subprograms
609 * Intrinsic Operators::
610 * Compilation_ISO_Date::
614 * Exception_Information::
615 * Exception_Message::
619 * Shifts and Rotates::
622 Representation Clauses and Pragmas
624 * Alignment Clauses::
626 * Storage_Size Clauses::
627 * Size of Variant Record Objects::
628 * Biased Representation::
629 * Value_Size and Object_Size Clauses::
630 * Component_Size Clauses::
631 * Bit_Order Clauses::
632 * Effect of Bit_Order on Byte Ordering::
633 * Pragma Pack for Arrays::
634 * Pragma Pack for Records::
635 * Record Representation Clauses::
636 * Handling of Records with Holes::
637 * Enumeration Clauses::
639 * Use of Address Clauses for Memory-Mapped I/O::
640 * Effect of Convention on Representation::
641 * Conventions and Anonymous Access Types::
642 * Determining the Representations chosen by GNAT::
644 The Implementation of Standard I/O
646 * Standard I/O Packages::
652 * Wide_Wide_Text_IO::
656 * Filenames encoding::
657 * File content encoding::
659 * Operations on C Streams::
660 * Interfacing to C Streams::
664 * Stream Pointer Positioning::
665 * Reading and Writing Non-Regular Files::
667 * Treating Text_IO Files as Streams::
668 * Text_IO Extensions::
669 * Text_IO Facilities for Unbounded Strings::
673 * Stream Pointer Positioning: Stream Pointer Positioning<2>.
674 * Reading and Writing Non-Regular Files: Reading and Writing Non-Regular Files<2>.
678 * Stream Pointer Positioning: Stream Pointer Positioning<3>.
679 * Reading and Writing Non-Regular Files: Reading and Writing Non-Regular Files<3>.
683 * Ada.Characters.Latin_9 (a-chlat9.ads): Ada Characters Latin_9 a-chlat9 ads.
684 * Ada.Characters.Wide_Latin_1 (a-cwila1.ads): Ada Characters Wide_Latin_1 a-cwila1 ads.
685 * Ada.Characters.Wide_Latin_9 (a-cwila1.ads): Ada Characters Wide_Latin_9 a-cwila1 ads.
686 * Ada.Characters.Wide_Wide_Latin_1 (a-chzla1.ads): Ada Characters Wide_Wide_Latin_1 a-chzla1 ads.
687 * Ada.Characters.Wide_Wide_Latin_9 (a-chzla9.ads): Ada Characters Wide_Wide_Latin_9 a-chzla9 ads.
688 * Ada.Containers.Formal_Doubly_Linked_Lists (a-cfdlli.ads): Ada Containers Formal_Doubly_Linked_Lists a-cfdlli ads.
689 * Ada.Containers.Formal_Hashed_Maps (a-cfhama.ads): Ada Containers Formal_Hashed_Maps a-cfhama ads.
690 * Ada.Containers.Formal_Hashed_Sets (a-cfhase.ads): Ada Containers Formal_Hashed_Sets a-cfhase ads.
691 * Ada.Containers.Formal_Ordered_Maps (a-cforma.ads): Ada Containers Formal_Ordered_Maps a-cforma ads.
692 * Ada.Containers.Formal_Ordered_Sets (a-cforse.ads): Ada Containers Formal_Ordered_Sets a-cforse ads.
693 * Ada.Containers.Formal_Vectors (a-cofove.ads): Ada Containers Formal_Vectors a-cofove ads.
694 * Ada.Containers.Formal_Indefinite_Vectors (a-cfinve.ads): Ada Containers Formal_Indefinite_Vectors a-cfinve ads.
695 * Ada.Containers.Functional_Vectors (a-cofuve.ads): Ada Containers Functional_Vectors a-cofuve ads.
696 * Ada.Containers.Functional_Sets (a-cofuse.ads): Ada Containers Functional_Sets a-cofuse ads.
697 * Ada.Containers.Functional_Maps (a-cofuma.ads): Ada Containers Functional_Maps a-cofuma ads.
698 * Ada.Containers.Bounded_Holders (a-coboho.ads): Ada Containers Bounded_Holders a-coboho ads.
699 * Ada.Command_Line.Environment (a-colien.ads): Ada Command_Line Environment a-colien ads.
700 * Ada.Command_Line.Remove (a-colire.ads): Ada Command_Line Remove a-colire ads.
701 * Ada.Command_Line.Response_File (a-clrefi.ads): Ada Command_Line Response_File a-clrefi ads.
702 * Ada.Direct_IO.C_Streams (a-diocst.ads): Ada Direct_IO C_Streams a-diocst ads.
703 * Ada.Exceptions.Is_Null_Occurrence (a-einuoc.ads): Ada Exceptions Is_Null_Occurrence a-einuoc ads.
704 * Ada.Exceptions.Last_Chance_Handler (a-elchha.ads): Ada Exceptions Last_Chance_Handler a-elchha ads.
705 * Ada.Exceptions.Traceback (a-exctra.ads): Ada Exceptions Traceback a-exctra ads.
706 * Ada.Sequential_IO.C_Streams (a-siocst.ads): Ada Sequential_IO C_Streams a-siocst ads.
707 * Ada.Streams.Stream_IO.C_Streams (a-ssicst.ads): Ada Streams Stream_IO C_Streams a-ssicst ads.
708 * Ada.Strings.Unbounded.Text_IO (a-suteio.ads): Ada Strings Unbounded Text_IO a-suteio ads.
709 * Ada.Strings.Wide_Unbounded.Wide_Text_IO (a-swuwti.ads): Ada Strings Wide_Unbounded Wide_Text_IO a-swuwti ads.
710 * Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO (a-szuzti.ads): Ada Strings Wide_Wide_Unbounded Wide_Wide_Text_IO a-szuzti ads.
711 * Ada.Text_IO.C_Streams (a-tiocst.ads): Ada Text_IO C_Streams a-tiocst ads.
712 * Ada.Text_IO.Reset_Standard_Files (a-tirsfi.ads): Ada Text_IO Reset_Standard_Files a-tirsfi ads.
713 * Ada.Wide_Characters.Unicode (a-wichun.ads): Ada Wide_Characters Unicode a-wichun ads.
714 * Ada.Wide_Text_IO.C_Streams (a-wtcstr.ads): Ada Wide_Text_IO C_Streams a-wtcstr ads.
715 * Ada.Wide_Text_IO.Reset_Standard_Files (a-wrstfi.ads): Ada Wide_Text_IO Reset_Standard_Files a-wrstfi ads.
716 * Ada.Wide_Wide_Characters.Unicode (a-zchuni.ads): Ada Wide_Wide_Characters Unicode a-zchuni ads.
717 * Ada.Wide_Wide_Text_IO.C_Streams (a-ztcstr.ads): Ada Wide_Wide_Text_IO C_Streams a-ztcstr ads.
718 * Ada.Wide_Wide_Text_IO.Reset_Standard_Files (a-zrstfi.ads): Ada Wide_Wide_Text_IO Reset_Standard_Files a-zrstfi ads.
719 * GNAT.Altivec (g-altive.ads): GNAT Altivec g-altive ads.
720 * GNAT.Altivec.Conversions (g-altcon.ads): GNAT Altivec Conversions g-altcon ads.
721 * GNAT.Altivec.Vector_Operations (g-alveop.ads): GNAT Altivec Vector_Operations g-alveop ads.
722 * GNAT.Altivec.Vector_Types (g-alvety.ads): GNAT Altivec Vector_Types g-alvety ads.
723 * GNAT.Altivec.Vector_Views (g-alvevi.ads): GNAT Altivec Vector_Views g-alvevi ads.
724 * GNAT.Array_Split (g-arrspl.ads): GNAT Array_Split g-arrspl ads.
725 * GNAT.AWK (g-awk.ads): GNAT AWK g-awk ads.
726 * GNAT.Bind_Environment (g-binenv.ads): GNAT Bind_Environment g-binenv ads.
727 * GNAT.Bounded_Buffers (g-boubuf.ads): GNAT Bounded_Buffers g-boubuf ads.
728 * GNAT.Bounded_Mailboxes (g-boumai.ads): GNAT Bounded_Mailboxes g-boumai ads.
729 * GNAT.Bubble_Sort (g-bubsor.ads): GNAT Bubble_Sort g-bubsor ads.
730 * GNAT.Bubble_Sort_A (g-busora.ads): GNAT Bubble_Sort_A g-busora ads.
731 * GNAT.Bubble_Sort_G (g-busorg.ads): GNAT Bubble_Sort_G g-busorg ads.
732 * GNAT.Byte_Order_Mark (g-byorma.ads): GNAT Byte_Order_Mark g-byorma ads.
733 * GNAT.Byte_Swapping (g-bytswa.ads): GNAT Byte_Swapping g-bytswa ads.
734 * GNAT.Calendar (g-calend.ads): GNAT Calendar g-calend ads.
735 * GNAT.Calendar.Time_IO (g-catiio.ads): GNAT Calendar Time_IO g-catiio ads.
736 * GNAT.CRC32 (g-crc32.ads): GNAT CRC32 g-crc32 ads.
737 * GNAT.Case_Util (g-casuti.ads): GNAT Case_Util g-casuti ads.
738 * GNAT.CGI (g-cgi.ads): GNAT CGI g-cgi ads.
739 * GNAT.CGI.Cookie (g-cgicoo.ads): GNAT CGI Cookie g-cgicoo ads.
740 * GNAT.CGI.Debug (g-cgideb.ads): GNAT CGI Debug g-cgideb ads.
741 * GNAT.Command_Line (g-comlin.ads): GNAT Command_Line g-comlin ads.
742 * GNAT.Compiler_Version (g-comver.ads): GNAT Compiler_Version g-comver ads.
743 * GNAT.Ctrl_C (g-ctrl_c.ads): GNAT Ctrl_C g-ctrl_c ads.
744 * GNAT.Current_Exception (g-curexc.ads): GNAT Current_Exception g-curexc ads.
745 * GNAT.Debug_Pools (g-debpoo.ads): GNAT Debug_Pools g-debpoo ads.
746 * GNAT.Debug_Utilities (g-debuti.ads): GNAT Debug_Utilities g-debuti ads.
747 * GNAT.Decode_String (g-decstr.ads): GNAT Decode_String g-decstr ads.
748 * GNAT.Decode_UTF8_String (g-deutst.ads): GNAT Decode_UTF8_String g-deutst ads.
749 * GNAT.Directory_Operations (g-dirope.ads): GNAT Directory_Operations g-dirope ads.
750 * GNAT.Directory_Operations.Iteration (g-diopit.ads): GNAT Directory_Operations Iteration g-diopit ads.
751 * GNAT.Dynamic_HTables (g-dynhta.ads): GNAT Dynamic_HTables g-dynhta ads.
752 * GNAT.Dynamic_Tables (g-dyntab.ads): GNAT Dynamic_Tables g-dyntab ads.
753 * GNAT.Encode_String (g-encstr.ads): GNAT Encode_String g-encstr ads.
754 * GNAT.Encode_UTF8_String (g-enutst.ads): GNAT Encode_UTF8_String g-enutst ads.
755 * GNAT.Exception_Actions (g-excact.ads): GNAT Exception_Actions g-excact ads.
756 * GNAT.Exception_Traces (g-exctra.ads): GNAT Exception_Traces g-exctra ads.
757 * GNAT.Exceptions (g-expect.ads): GNAT Exceptions g-expect ads.
758 * GNAT.Expect (g-expect.ads): GNAT Expect g-expect ads.
759 * GNAT.Expect.TTY (g-exptty.ads): GNAT Expect TTY g-exptty ads.
760 * GNAT.Float_Control (g-flocon.ads): GNAT Float_Control g-flocon ads.
761 * GNAT.Formatted_String (g-forstr.ads): GNAT Formatted_String g-forstr ads.
762 * GNAT.Heap_Sort (g-heasor.ads): GNAT Heap_Sort g-heasor ads.
763 * GNAT.Heap_Sort_A (g-hesora.ads): GNAT Heap_Sort_A g-hesora ads.
764 * GNAT.Heap_Sort_G (g-hesorg.ads): GNAT Heap_Sort_G g-hesorg ads.
765 * GNAT.HTable (g-htable.ads): GNAT HTable g-htable ads.
766 * GNAT.IO (g-io.ads): GNAT IO g-io ads.
767 * GNAT.IO_Aux (g-io_aux.ads): GNAT IO_Aux g-io_aux ads.
768 * GNAT.Lock_Files (g-locfil.ads): GNAT Lock_Files g-locfil ads.
769 * GNAT.MBBS_Discrete_Random (g-mbdira.ads): GNAT MBBS_Discrete_Random g-mbdira ads.
770 * GNAT.MBBS_Float_Random (g-mbflra.ads): GNAT MBBS_Float_Random g-mbflra ads.
771 * GNAT.MD5 (g-md5.ads): GNAT MD5 g-md5 ads.
772 * GNAT.Memory_Dump (g-memdum.ads): GNAT Memory_Dump g-memdum ads.
773 * GNAT.Most_Recent_Exception (g-moreex.ads): GNAT Most_Recent_Exception g-moreex ads.
774 * GNAT.OS_Lib (g-os_lib.ads): GNAT OS_Lib g-os_lib ads.
775 * GNAT.Perfect_Hash_Generators (g-pehage.ads): GNAT Perfect_Hash_Generators g-pehage ads.
776 * GNAT.Random_Numbers (g-rannum.ads): GNAT Random_Numbers g-rannum ads.
777 * GNAT.Regexp (g-regexp.ads): GNAT Regexp g-regexp ads.
778 * GNAT.Registry (g-regist.ads): GNAT Registry g-regist ads.
779 * GNAT.Regpat (g-regpat.ads): GNAT Regpat g-regpat ads.
780 * GNAT.Rewrite_Data (g-rewdat.ads): GNAT Rewrite_Data g-rewdat ads.
781 * GNAT.Secondary_Stack_Info (g-sestin.ads): GNAT Secondary_Stack_Info g-sestin ads.
782 * GNAT.Semaphores (g-semaph.ads): GNAT Semaphores g-semaph ads.
783 * GNAT.Serial_Communications (g-sercom.ads): GNAT Serial_Communications g-sercom ads.
784 * GNAT.SHA1 (g-sha1.ads): GNAT SHA1 g-sha1 ads.
785 * GNAT.SHA224 (g-sha224.ads): GNAT SHA224 g-sha224 ads.
786 * GNAT.SHA256 (g-sha256.ads): GNAT SHA256 g-sha256 ads.
787 * GNAT.SHA384 (g-sha384.ads): GNAT SHA384 g-sha384 ads.
788 * GNAT.SHA512 (g-sha512.ads): GNAT SHA512 g-sha512 ads.
789 * GNAT.Signals (g-signal.ads): GNAT Signals g-signal ads.
790 * GNAT.Sockets (g-socket.ads): GNAT Sockets g-socket ads.
791 * GNAT.Source_Info (g-souinf.ads): GNAT Source_Info g-souinf ads.
792 * GNAT.Spelling_Checker (g-speche.ads): GNAT Spelling_Checker g-speche ads.
793 * GNAT.Spelling_Checker_Generic (g-spchge.ads): GNAT Spelling_Checker_Generic g-spchge ads.
794 * GNAT.Spitbol.Patterns (g-spipat.ads): GNAT Spitbol Patterns g-spipat ads.
795 * GNAT.Spitbol (g-spitbo.ads): GNAT Spitbol g-spitbo ads.
796 * GNAT.Spitbol.Table_Boolean (g-sptabo.ads): GNAT Spitbol Table_Boolean g-sptabo ads.
797 * GNAT.Spitbol.Table_Integer (g-sptain.ads): GNAT Spitbol Table_Integer g-sptain ads.
798 * GNAT.Spitbol.Table_VString (g-sptavs.ads): GNAT Spitbol Table_VString g-sptavs ads.
799 * GNAT.SSE (g-sse.ads): GNAT SSE g-sse ads.
800 * GNAT.SSE.Vector_Types (g-ssvety.ads): GNAT SSE Vector_Types g-ssvety ads.
801 * GNAT.String_Hash (g-strhas.ads): GNAT String_Hash g-strhas ads.
802 * GNAT.Strings (g-string.ads): GNAT Strings g-string ads.
803 * GNAT.String_Split (g-strspl.ads): GNAT String_Split g-strspl ads.
804 * GNAT.Table (g-table.ads): GNAT Table g-table ads.
805 * GNAT.Task_Lock (g-tasloc.ads): GNAT Task_Lock g-tasloc ads.
806 * GNAT.Time_Stamp (g-timsta.ads): GNAT Time_Stamp g-timsta ads.
807 * GNAT.Threads (g-thread.ads): GNAT Threads g-thread ads.
808 * GNAT.Traceback (g-traceb.ads): GNAT Traceback g-traceb ads.
809 * GNAT.Traceback.Symbolic (g-trasym.ads): GNAT Traceback Symbolic g-trasym ads.
810 * GNAT.UTF_32 (g-table.ads): GNAT UTF_32 g-table ads.
811 * GNAT.Wide_Spelling_Checker (g-u3spch.ads): GNAT Wide_Spelling_Checker g-u3spch ads.
812 * GNAT.Wide_Spelling_Checker (g-wispch.ads): GNAT Wide_Spelling_Checker g-wispch ads.
813 * GNAT.Wide_String_Split (g-wistsp.ads): GNAT Wide_String_Split g-wistsp ads.
814 * GNAT.Wide_Wide_Spelling_Checker (g-zspche.ads): GNAT Wide_Wide_Spelling_Checker g-zspche ads.
815 * GNAT.Wide_Wide_String_Split (g-zistsp.ads): GNAT Wide_Wide_String_Split g-zistsp ads.
816 * Interfaces.C.Extensions (i-cexten.ads): Interfaces C Extensions i-cexten ads.
817 * Interfaces.C.Streams (i-cstrea.ads): Interfaces C Streams i-cstrea ads.
818 * Interfaces.Packed_Decimal (i-pacdec.ads): Interfaces Packed_Decimal i-pacdec ads.
819 * Interfaces.VxWorks (i-vxwork.ads): Interfaces VxWorks i-vxwork ads.
820 * Interfaces.VxWorks.Int_Connection (i-vxinco.ads): Interfaces VxWorks Int_Connection i-vxinco ads.
821 * Interfaces.VxWorks.IO (i-vxwoio.ads): Interfaces VxWorks IO i-vxwoio ads.
822 * System.Address_Image (s-addima.ads): System Address_Image s-addima ads.
823 * System.Assertions (s-assert.ads): System Assertions s-assert ads.
824 * System.Atomic_Counters (s-atocou.ads): System Atomic_Counters s-atocou ads.
825 * System.Memory (s-memory.ads): System Memory s-memory ads.
826 * System.Multiprocessors (s-multip.ads): System Multiprocessors s-multip ads.
827 * System.Multiprocessors.Dispatching_Domains (s-mudido.ads): System Multiprocessors Dispatching_Domains s-mudido ads.
828 * System.Partition_Interface (s-parint.ads): System Partition_Interface s-parint ads.
829 * System.Pool_Global (s-pooglo.ads): System Pool_Global s-pooglo ads.
830 * System.Pool_Local (s-pooloc.ads): System Pool_Local s-pooloc ads.
831 * System.Restrictions (s-restri.ads): System Restrictions s-restri ads.
832 * System.Rident (s-rident.ads): System Rident s-rident ads.
833 * System.Strings.Stream_Ops (s-ststop.ads): System Strings Stream_Ops s-ststop ads.
834 * System.Unsigned_Types (s-unstyp.ads): System Unsigned_Types s-unstyp ads.
835 * System.Wch_Cnv (s-wchcnv.ads): System Wch_Cnv s-wchcnv ads.
836 * System.Wch_Con (s-wchcon.ads): System Wch_Con s-wchcon ads.
838 Interfacing to Other Languages
841 * Interfacing to C++::
842 * Interfacing to COBOL::
843 * Interfacing to Fortran::
844 * Interfacing to non-GNAT Ada code::
846 Implementation of Specific Ada Features
848 * Machine Code Insertions::
849 * GNAT Implementation of Tasking::
850 * GNAT Implementation of Shared Passive Packages::
851 * Code Generation for Array Aggregates::
852 * The Size of Discriminated Records with Default Discriminants::
853 * Strict Conformance to the Ada Reference Manual::
855 GNAT Implementation of Tasking
857 * Mapping Ada Tasks onto the Underlying Kernel Threads::
858 * Ensuring Compliance with the Real-Time Annex::
859 * Support for Locking Policies::
861 Code Generation for Array Aggregates
863 * Static constant aggregates with static bounds::
864 * Constant aggregates with unconstrained nominal types::
865 * Aggregates with static bounds::
866 * Aggregates with nonstatic bounds::
867 * Aggregates in assignment statements::
871 * pragma No_Run_Time::
873 * pragma Restricted_Run_Time::
875 * package System.Task_Info (s-tasinf.ads): package System Task_Info s-tasinf ads.
877 Compatibility and Porting Guide
879 * Writing Portable Fixed-Point Declarations::
880 * Compatibility with Ada 83::
881 * Compatibility between Ada 95 and Ada 2005::
882 * Implementation-dependent characteristics::
883 * Compatibility with Other Ada Systems::
884 * Representation Clauses::
885 * Compatibility with HP Ada 83::
887 Compatibility with Ada 83
889 * Legal Ada 83 programs that are illegal in Ada 95::
890 * More deterministic semantics::
891 * Changed semantics::
892 * Other language compatibility issues::
894 Implementation-dependent characteristics
896 * Implementation-defined pragmas::
897 * Implementation-defined attributes::
899 * Elaboration order::
900 * Target-specific aspects::
905 @node About This Guide,Implementation Defined Pragmas,Top,Top
906 @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}
907 @chapter About This Guide
911 This manual contains useful information in writing programs using the
912 GNAT compiler. It includes information on implementation dependent
913 characteristics of GNAT, including all the information required by
914 Annex M of the Ada language standard.
916 GNAT implements Ada 95, Ada 2005 and Ada 2012, and it may also be
917 invoked in Ada 83 compatibility mode.
918 By default, GNAT assumes Ada 2012,
919 but you can override with a compiler switch
920 to explicitly specify the language version.
921 (Please refer to the @emph{GNAT User's Guide} for details on these switches.)
922 Throughout this manual, references to 'Ada' without a year suffix
923 apply to all the Ada versions of the language.
925 Ada is designed to be highly portable.
926 In general, a program will have the same effect even when compiled by
927 different compilers on different platforms.
928 However, since Ada is designed to be used in a
929 wide variety of applications, it also contains a number of system
930 dependent features to be used in interfacing to the external world.
932 @geindex Implementation-dependent features
936 Note: Any program that makes use of implementation-dependent features
937 may be non-portable. You should follow good programming practice and
938 isolate and clearly document any sections of your program that make use
939 of these features in a non-portable manner.
942 * What This Reference Manual Contains::
944 * Related Information::
948 @node What This Reference Manual Contains,Conventions,,About This Guide
949 @anchor{gnat_rm/about_this_guide what-this-reference-manual-contains}@anchor{6}
950 @section What This Reference Manual Contains
953 This reference manual contains the following chapters:
959 @ref{7,,Implementation Defined Pragmas}, lists GNAT implementation-dependent
960 pragmas, which can be used to extend and enhance the functionality of the
964 @ref{8,,Implementation Defined Attributes}, lists GNAT
965 implementation-dependent attributes, which can be used to extend and
966 enhance the functionality of the compiler.
969 @ref{9,,Standard and Implementation Defined Restrictions}, lists GNAT
970 implementation-dependent restrictions, which can be used to extend and
971 enhance the functionality of the compiler.
974 @ref{a,,Implementation Advice}, provides information on generally
975 desirable behavior which are not requirements that all compilers must
976 follow since it cannot be provided on all systems, or which may be
977 undesirable on some systems.
980 @ref{b,,Implementation Defined Characteristics}, provides a guide to
981 minimizing implementation dependent features.
984 @ref{c,,Intrinsic Subprograms}, describes the intrinsic subprograms
985 implemented by GNAT, and how they can be imported into user
986 application programs.
989 @ref{d,,Representation Clauses and Pragmas}, describes in detail the
990 way that GNAT represents data, and in particular the exact set
991 of representation clauses and pragmas that is accepted.
994 @ref{e,,Standard Library Routines}, provides a listing of packages and a
995 brief description of the functionality that is provided by Ada's
996 extensive set of standard library routines as implemented by GNAT.
999 @ref{f,,The Implementation of Standard I/O}, details how the GNAT
1000 implementation of the input-output facilities.
1003 @ref{10,,The GNAT Library}, is a catalog of packages that complement
1004 the Ada predefined library.
1007 @ref{11,,Interfacing to Other Languages}, describes how programs
1008 written in Ada using GNAT can be interfaced to other programming
1012 @ref{12,,Specialized Needs Annexes}, describes the GNAT implementation of all
1013 of the specialized needs annexes.
1016 @ref{13,,Implementation of Specific Ada Features}, discusses issues related
1017 to GNAT's implementation of machine code insertions, tasking, and several
1021 @ref{14,,Implementation of Ada 2012 Features}, describes the status of the
1022 GNAT implementation of the Ada 2012 language standard.
1025 @ref{15,,Obsolescent Features} documents implementation dependent features,
1026 including pragmas and attributes, which are considered obsolescent, since
1027 there are other preferred ways of achieving the same results. These
1028 obsolescent forms are retained for backwards compatibility.
1031 @ref{16,,Compatibility and Porting Guide} presents some guidelines for
1032 developing portable Ada code, describes the compatibility issues that
1033 may arise between GNAT and other Ada compilation systems (including those
1034 for Ada 83), and shows how GNAT can expedite porting applications
1035 developed in other Ada environments.
1038 @ref{1,,GNU Free Documentation License} contains the license for this document.
1041 @geindex Ada 95 Language Reference Manual
1043 @geindex Ada 2005 Language Reference Manual
1045 This reference manual assumes a basic familiarity with the Ada 95 language, as
1047 @cite{International Standard ANSI/ISO/IEC-8652:1995}.
1048 It does not require knowledge of the new features introduced by Ada 2005 or
1050 All three reference manuals are included in the GNAT documentation
1053 @node Conventions,Related Information,What This Reference Manual Contains,About This Guide
1054 @anchor{gnat_rm/about_this_guide conventions}@anchor{17}
1055 @section Conventions
1058 @geindex Conventions
1059 @geindex typographical
1061 @geindex Typographical conventions
1063 Following are examples of the typographical and graphic conventions used
1070 @code{Functions}, @code{utility program names}, @code{standard names},
1086 [optional information or parameters]
1089 Examples are described by text
1092 and then shown this way.
1096 Commands that are entered by the user are shown as preceded by a prompt string
1097 comprising the @code{$} character followed by a space.
1100 @node Related Information,,Conventions,About This Guide
1101 @anchor{gnat_rm/about_this_guide related-information}@anchor{18}
1102 @section Related Information
1105 See the following documents for further information on GNAT:
1111 @cite{GNAT User's Guide for Native Platforms},
1112 which provides information on how to use the
1113 GNAT development environment.
1116 @cite{Ada 95 Reference Manual}, the Ada 95 programming language standard.
1119 @cite{Ada 95 Annotated Reference Manual}, which is an annotated version
1120 of the Ada 95 standard. The annotations describe
1121 detailed aspects of the design decision, and in particular contain useful
1122 sections on Ada 83 compatibility.
1125 @cite{Ada 2005 Reference Manual}, the Ada 2005 programming language standard.
1128 @cite{Ada 2005 Annotated Reference Manual}, which is an annotated version
1129 of the Ada 2005 standard. The annotations describe
1130 detailed aspects of the design decision.
1133 @cite{Ada 2012 Reference Manual}, the Ada 2012 programming language standard.
1136 @cite{DEC Ada@comma{} Technical Overview and Comparison on DIGITAL Platforms},
1137 which contains specific information on compatibility between GNAT and
1141 @cite{DEC Ada@comma{} Language Reference Manual}, part number AA-PYZAB-TK, which
1142 describes in detail the pragmas and attributes provided by the DEC Ada 83
1146 @node Implementation Defined Pragmas,Implementation Defined Aspects,About This Guide,Top
1147 @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}
1148 @chapter Implementation Defined Pragmas
1151 Ada defines a set of pragmas that can be used to supply additional
1152 information to the compiler. These language defined pragmas are
1153 implemented in GNAT and work as described in the Ada Reference Manual.
1155 In addition, Ada allows implementations to define additional pragmas
1156 whose meaning is defined by the implementation. GNAT provides a number
1157 of these implementation-defined pragmas, which can be used to extend
1158 and enhance the functionality of the compiler. This section of the GNAT
1159 Reference Manual describes these additional pragmas.
1161 Note that any program using these pragmas might not be portable to other
1162 compilers (although GNAT implements this set of pragmas on all
1163 platforms). Therefore if portability to other compilers is an important
1164 consideration, the use of these pragmas should be minimized.
1167 * Pragma Abort_Defer::
1168 * Pragma Abstract_State::
1175 * Pragma Allow_Integer_Address::
1178 * Pragma Assert_And_Cut::
1179 * Pragma Assertion_Policy::
1181 * Pragma Assume_No_Invalid_Values::
1182 * Pragma Async_Readers::
1183 * Pragma Async_Writers::
1184 * Pragma Attribute_Definition::
1185 * Pragma C_Pass_By_Copy::
1187 * Pragma Check_Float_Overflow::
1188 * Pragma Check_Name::
1189 * Pragma Check_Policy::
1191 * Pragma Common_Object::
1192 * Pragma Compile_Time_Error::
1193 * Pragma Compile_Time_Warning::
1194 * Pragma Compiler_Unit::
1195 * Pragma Compiler_Unit_Warning::
1196 * Pragma Complete_Representation::
1197 * Pragma Complex_Representation::
1198 * Pragma Component_Alignment::
1199 * Pragma Constant_After_Elaboration::
1200 * Pragma Contract_Cases::
1201 * Pragma Convention_Identifier::
1202 * Pragma CPP_Class::
1203 * Pragma CPP_Constructor::
1204 * Pragma CPP_Virtual::
1205 * Pragma CPP_Vtable::
1207 * Pragma Deadline_Floor::
1208 * Pragma Default_Initial_Condition::
1210 * Pragma Debug_Policy::
1211 * Pragma Default_Scalar_Storage_Order::
1212 * Pragma Default_Storage_Pool::
1214 * Pragma Detect_Blocking::
1215 * Pragma Disable_Atomic_Synchronization::
1216 * Pragma Dispatching_Domain::
1217 * Pragma Effective_Reads::
1218 * Pragma Effective_Writes::
1219 * Pragma Elaboration_Checks::
1220 * Pragma Eliminate::
1221 * Pragma Enable_Atomic_Synchronization::
1222 * Pragma Export_Function::
1223 * Pragma Export_Object::
1224 * Pragma Export_Procedure::
1225 * Pragma Export_Value::
1226 * Pragma Export_Valued_Procedure::
1227 * Pragma Extend_System::
1228 * Pragma Extensions_Allowed::
1229 * Pragma Extensions_Visible::
1231 * Pragma External_Name_Casing::
1232 * Pragma Fast_Math::
1233 * Pragma Favor_Top_Level::
1234 * Pragma Finalize_Storage_Only::
1235 * Pragma Float_Representation::
1239 * Pragma Ignore_Pragma::
1240 * Pragma Implementation_Defined::
1241 * Pragma Implemented::
1242 * Pragma Implicit_Packing::
1243 * Pragma Import_Function::
1244 * Pragma Import_Object::
1245 * Pragma Import_Procedure::
1246 * Pragma Import_Valued_Procedure::
1247 * Pragma Independent::
1248 * Pragma Independent_Components::
1249 * Pragma Initial_Condition::
1250 * Pragma Initialize_Scalars::
1251 * Pragma Initializes::
1252 * Pragma Inline_Always::
1253 * Pragma Inline_Generic::
1254 * Pragma Interface::
1255 * Pragma Interface_Name::
1256 * Pragma Interrupt_Handler::
1257 * Pragma Interrupt_State::
1258 * Pragma Invariant::
1259 * Pragma Keep_Names::
1261 * Pragma Link_With::
1262 * Pragma Linker_Alias::
1263 * Pragma Linker_Constructor::
1264 * Pragma Linker_Destructor::
1265 * Pragma Linker_Section::
1266 * Pragma Lock_Free::
1267 * Pragma Loop_Invariant::
1268 * Pragma Loop_Optimize::
1269 * Pragma Loop_Variant::
1270 * Pragma Machine_Attribute::
1272 * Pragma Main_Storage::
1273 * Pragma Max_Queue_Length::
1275 * Pragma No_Component_Reordering::
1276 * Pragma No_Elaboration_Code_All::
1277 * Pragma No_Heap_Finalization::
1278 * Pragma No_Inline::
1279 * Pragma No_Return::
1280 * Pragma No_Run_Time::
1281 * Pragma No_Strict_Aliasing::
1282 * Pragma No_Tagged_Streams::
1283 * Pragma Normalize_Scalars::
1284 * Pragma Obsolescent::
1285 * Pragma Optimize_Alignment::
1287 * Pragma Overflow_Mode::
1288 * Pragma Overriding_Renamings::
1289 * Pragma Partition_Elaboration_Policy::
1292 * Pragma Persistent_BSS::
1295 * Pragma Postcondition::
1296 * Pragma Post_Class::
1297 * Pragma Rename_Pragma::
1299 * Pragma Precondition::
1300 * Pragma Predicate::
1301 * Pragma Predicate_Failure::
1302 * Pragma Preelaborable_Initialization::
1303 * Pragma Prefix_Exception_Messages::
1304 * Pragma Pre_Class::
1305 * Pragma Priority_Specific_Dispatching::
1307 * Pragma Profile_Warnings::
1308 * Pragma Propagate_Exceptions::
1309 * Pragma Provide_Shift_Operators::
1310 * Pragma Psect_Object::
1311 * Pragma Pure_Function::
1313 * Pragma Ravenscar::
1314 * Pragma Refined_Depends::
1315 * Pragma Refined_Global::
1316 * Pragma Refined_Post::
1317 * Pragma Refined_State::
1318 * Pragma Relative_Deadline::
1319 * Pragma Remote_Access_Type::
1320 * Pragma Restricted_Run_Time::
1321 * Pragma Restriction_Warnings::
1322 * Pragma Reviewable::
1323 * Pragma Secondary_Stack_Size::
1324 * Pragma Share_Generic::
1326 * Pragma Short_Circuit_And_Or::
1327 * Pragma Short_Descriptors::
1328 * Pragma Simple_Storage_Pool_Type::
1329 * Pragma Source_File_Name::
1330 * Pragma Source_File_Name_Project::
1331 * Pragma Source_Reference::
1332 * Pragma SPARK_Mode::
1333 * Pragma Static_Elaboration_Desired::
1334 * Pragma Stream_Convert::
1335 * Pragma Style_Checks::
1338 * Pragma Suppress_All::
1339 * Pragma Suppress_Debug_Info::
1340 * Pragma Suppress_Exception_Locations::
1341 * Pragma Suppress_Initialization::
1342 * Pragma Task_Name::
1343 * Pragma Task_Storage::
1344 * Pragma Test_Case::
1345 * Pragma Thread_Local_Storage::
1346 * Pragma Time_Slice::
1348 * Pragma Type_Invariant::
1349 * Pragma Type_Invariant_Class::
1350 * Pragma Unchecked_Union::
1351 * Pragma Unevaluated_Use_Of_Old::
1352 * Pragma Unimplemented_Unit::
1353 * Pragma Universal_Aliasing::
1354 * Pragma Universal_Data::
1355 * Pragma Unmodified::
1356 * Pragma Unreferenced::
1357 * Pragma Unreferenced_Objects::
1358 * Pragma Unreserve_All_Interrupts::
1359 * Pragma Unsuppress::
1360 * Pragma Use_VADS_Size::
1362 * Pragma Validity_Checks::
1364 * Pragma Volatile_Full_Access::
1365 * Pragma Volatile_Function::
1366 * Pragma Warning_As_Error::
1368 * Pragma Weak_External::
1369 * Pragma Wide_Character_Encoding::
1373 @node Pragma Abort_Defer,Pragma Abstract_State,,Implementation Defined Pragmas
1374 @anchor{gnat_rm/implementation_defined_pragmas pragma-abort-defer}@anchor{1b}
1375 @section Pragma Abort_Defer
1378 @geindex Deferring aborts
1386 This pragma must appear at the start of the statement sequence of a
1387 handled sequence of statements (right after the @code{begin}). It has
1388 the effect of deferring aborts for the sequence of statements (but not
1389 for the declarations or handlers, if any, associated with this statement
1392 @node Pragma Abstract_State,Pragma Ada_83,Pragma Abort_Defer,Implementation Defined Pragmas
1393 @anchor{gnat_rm/implementation_defined_pragmas pragma-abstract-state}@anchor{1c}@anchor{gnat_rm/implementation_defined_pragmas id2}@anchor{1d}
1394 @section Pragma Abstract_State
1400 pragma Abstract_State (ABSTRACT_STATE_LIST);
1402 ABSTRACT_STATE_LIST ::=
1404 | STATE_NAME_WITH_OPTIONS
1405 | (STATE_NAME_WITH_OPTIONS @{, STATE_NAME_WITH_OPTIONS@} )
1407 STATE_NAME_WITH_OPTIONS ::=
1409 | (STATE_NAME with OPTION_LIST)
1411 OPTION_LIST ::= OPTION @{, OPTION@}
1417 SIMPLE_OPTION ::= Ghost | Synchronous
1419 NAME_VALUE_OPTION ::=
1420 Part_Of => ABSTRACT_STATE
1421 | External [=> EXTERNAL_PROPERTY_LIST]
1423 EXTERNAL_PROPERTY_LIST ::=
1425 | (EXTERNAL_PROPERTY @{, EXTERNAL_PROPERTY@} )
1427 EXTERNAL_PROPERTY ::=
1428 Async_Readers [=> boolean_EXPRESSION]
1429 | Async_Writers [=> boolean_EXPRESSION]
1430 | Effective_Reads [=> boolean_EXPRESSION]
1431 | Effective_Writes [=> boolean_EXPRESSION]
1432 others => boolean_EXPRESSION
1434 STATE_NAME ::= defining_identifier
1436 ABSTRACT_STATE ::= name
1439 For the semantics of this pragma, see the entry for aspect @code{Abstract_State} in
1440 the SPARK 2014 Reference Manual, section 7.1.4.
1442 @node Pragma Ada_83,Pragma Ada_95,Pragma Abstract_State,Implementation Defined Pragmas
1443 @anchor{gnat_rm/implementation_defined_pragmas pragma-ada-83}@anchor{1e}
1444 @section Pragma Ada_83
1453 A configuration pragma that establishes Ada 83 mode for the unit to
1454 which it applies, regardless of the mode set by the command line
1455 switches. In Ada 83 mode, GNAT attempts to be as compatible with
1456 the syntax and semantics of Ada 83, as defined in the original Ada
1457 83 Reference Manual as possible. In particular, the keywords added by Ada 95
1458 and Ada 2005 are not recognized, optional package bodies are allowed,
1459 and generics may name types with unknown discriminants without using
1460 the @code{(<>)} notation. In addition, some but not all of the additional
1461 restrictions of Ada 83 are enforced.
1463 Ada 83 mode is intended for two purposes. Firstly, it allows existing
1464 Ada 83 code to be compiled and adapted to GNAT with less effort.
1465 Secondly, it aids in keeping code backwards compatible with Ada 83.
1466 However, there is no guarantee that code that is processed correctly
1467 by GNAT in Ada 83 mode will in fact compile and execute with an Ada
1468 83 compiler, since GNAT does not enforce all the additional checks
1471 @node Pragma Ada_95,Pragma Ada_05,Pragma Ada_83,Implementation Defined Pragmas
1472 @anchor{gnat_rm/implementation_defined_pragmas pragma-ada-95}@anchor{1f}
1473 @section Pragma Ada_95
1482 A configuration pragma that establishes Ada 95 mode for the unit to which
1483 it applies, regardless of the mode set by the command line switches.
1484 This mode is set automatically for the @code{Ada} and @code{System}
1485 packages and their children, so you need not specify it in these
1486 contexts. This pragma is useful when writing a reusable component that
1487 itself uses Ada 95 features, but which is intended to be usable from
1488 either Ada 83 or Ada 95 programs.
1490 @node Pragma Ada_05,Pragma Ada_2005,Pragma Ada_95,Implementation Defined Pragmas
1491 @anchor{gnat_rm/implementation_defined_pragmas pragma-ada-05}@anchor{20}
1492 @section Pragma Ada_05
1499 pragma Ada_05 (local_NAME);
1502 A configuration pragma that establishes Ada 2005 mode for the unit to which
1503 it applies, regardless of the mode set by the command line switches.
1504 This pragma is useful when writing a reusable component that
1505 itself uses Ada 2005 features, but which is intended to be usable from
1506 either Ada 83 or Ada 95 programs.
1508 The one argument form (which is not a configuration pragma)
1509 is used for managing the transition from
1510 Ada 95 to Ada 2005 in the run-time library. If an entity is marked
1511 as Ada_2005 only, then referencing the entity in Ada_83 or Ada_95
1512 mode will generate a warning. In addition, in Ada_83 or Ada_95
1513 mode, a preference rule is established which does not choose
1514 such an entity unless it is unambiguously specified. This avoids
1515 extra subprograms marked this way from generating ambiguities in
1516 otherwise legal pre-Ada_2005 programs. The one argument form is
1517 intended for exclusive use in the GNAT run-time library.
1519 @node Pragma Ada_2005,Pragma Ada_12,Pragma Ada_05,Implementation Defined Pragmas
1520 @anchor{gnat_rm/implementation_defined_pragmas pragma-ada-2005}@anchor{21}
1521 @section Pragma Ada_2005
1530 This configuration pragma is a synonym for pragma Ada_05 and has the
1531 same syntax and effect.
1533 @node Pragma Ada_12,Pragma Ada_2012,Pragma Ada_2005,Implementation Defined Pragmas
1534 @anchor{gnat_rm/implementation_defined_pragmas pragma-ada-12}@anchor{22}
1535 @section Pragma Ada_12
1542 pragma Ada_12 (local_NAME);
1545 A configuration pragma that establishes Ada 2012 mode for the unit to which
1546 it applies, regardless of the mode set by the command line switches.
1547 This mode is set automatically for the @code{Ada} and @code{System}
1548 packages and their children, so you need not specify it in these
1549 contexts. This pragma is useful when writing a reusable component that
1550 itself uses Ada 2012 features, but which is intended to be usable from
1551 Ada 83, Ada 95, or Ada 2005 programs.
1553 The one argument form, which is not a configuration pragma,
1554 is used for managing the transition from Ada
1555 2005 to Ada 2012 in the run-time library. If an entity is marked
1556 as Ada_2012 only, then referencing the entity in any pre-Ada_2012
1557 mode will generate a warning. In addition, in any pre-Ada_2012
1558 mode, a preference rule is established which does not choose
1559 such an entity unless it is unambiguously specified. This avoids
1560 extra subprograms marked this way from generating ambiguities in
1561 otherwise legal pre-Ada_2012 programs. The one argument form is
1562 intended for exclusive use in the GNAT run-time library.
1564 @node Pragma Ada_2012,Pragma Allow_Integer_Address,Pragma Ada_12,Implementation Defined Pragmas
1565 @anchor{gnat_rm/implementation_defined_pragmas pragma-ada-2012}@anchor{23}
1566 @section Pragma Ada_2012
1575 This configuration pragma is a synonym for pragma Ada_12 and has the
1576 same syntax and effect.
1578 @node Pragma Allow_Integer_Address,Pragma Annotate,Pragma Ada_2012,Implementation Defined Pragmas
1579 @anchor{gnat_rm/implementation_defined_pragmas pragma-allow-integer-address}@anchor{24}
1580 @section Pragma Allow_Integer_Address
1586 pragma Allow_Integer_Address;
1589 In almost all versions of GNAT, @code{System.Address} is a private
1590 type in accordance with the implementation advice in the RM. This
1591 means that integer values,
1592 in particular integer literals, are not allowed as address values.
1593 If the configuration pragma
1594 @code{Allow_Integer_Address} is given, then integer expressions may
1595 be used anywhere a value of type @code{System.Address} is required.
1596 The effect is to introduce an implicit unchecked conversion from the
1597 integer value to type @code{System.Address}. The reverse case of using
1598 an address where an integer type is required is handled analogously.
1599 The following example compiles without errors:
1602 pragma Allow_Integer_Address;
1603 with System; use System;
1604 package AddrAsInt is
1607 for X'Address use 16#1240#;
1608 for Y use at 16#3230#;
1609 m : Address := 16#4000#;
1610 n : constant Address := 4000;
1611 p : constant Address := Address (X + Y);
1612 v : Integer := y'Address;
1613 w : constant Integer := Integer (Y'Address);
1614 type R is new integer;
1617 for Z'Address use RR;
1621 Note that pragma @code{Allow_Integer_Address} is ignored if @code{System.Address}
1622 is not a private type. In implementations of @code{GNAT} where
1623 System.Address is a visible integer type,
1624 this pragma serves no purpose but is ignored
1625 rather than rejected to allow common sets of sources to be used
1626 in the two situations.
1628 @node Pragma Annotate,Pragma Assert,Pragma Allow_Integer_Address,Implementation Defined Pragmas
1629 @anchor{gnat_rm/implementation_defined_pragmas pragma-annotate}@anchor{25}@anchor{gnat_rm/implementation_defined_pragmas id3}@anchor{26}
1630 @section Pragma Annotate
1636 pragma Annotate (IDENTIFIER [, IDENTIFIER @{, ARG@}] [, entity => local_NAME]);
1638 ARG ::= NAME | EXPRESSION
1641 This pragma is used to annotate programs. IDENTIFIER identifies
1642 the type of annotation. GNAT verifies that it is an identifier, but does
1643 not otherwise analyze it. The second optional identifier is also left
1644 unanalyzed, and by convention is used to control the action of the tool to
1645 which the annotation is addressed. The remaining ARG arguments
1646 can be either string literals or more generally expressions.
1647 String literals are assumed to be either of type
1648 @code{Standard.String} or else @code{Wide_String} or @code{Wide_Wide_String}
1649 depending on the character literals they contain.
1650 All other kinds of arguments are analyzed as expressions, and must be
1651 unambiguous. The last argument if present must have the identifier
1652 @code{Entity} and GNAT verifies that a local name is given.
1654 The analyzed pragma is retained in the tree, but not otherwise processed
1655 by any part of the GNAT compiler, except to generate corresponding note
1656 lines in the generated ALI file. For the format of these note lines, see
1657 the compiler source file lib-writ.ads. This pragma is intended for use by
1658 external tools, including ASIS. The use of pragma Annotate does not
1659 affect the compilation process in any way. This pragma may be used as
1660 a configuration pragma.
1662 @node Pragma Assert,Pragma Assert_And_Cut,Pragma Annotate,Implementation Defined Pragmas
1663 @anchor{gnat_rm/implementation_defined_pragmas pragma-assert}@anchor{27}
1664 @section Pragma Assert
1672 [, string_EXPRESSION]);
1675 The effect of this pragma depends on whether the corresponding command
1676 line switch is set to activate assertions. The pragma expands into code
1677 equivalent to the following:
1680 if assertions-enabled then
1681 if not boolean_EXPRESSION then
1682 System.Assertions.Raise_Assert_Failure
1683 (string_EXPRESSION);
1688 The string argument, if given, is the message that will be associated
1689 with the exception occurrence if the exception is raised. If no second
1690 argument is given, the default message is @code{file}:@code{nnn},
1691 where @code{file} is the name of the source file containing the assert,
1692 and @code{nnn} is the line number of the assert.
1694 Note that, as with the @code{if} statement to which it is equivalent, the
1695 type of the expression is either @code{Standard.Boolean}, or any type derived
1696 from this standard type.
1698 Assert checks can be either checked or ignored. By default they are ignored.
1699 They will be checked if either the command line switch @emph{-gnata} is
1700 used, or if an @code{Assertion_Policy} or @code{Check_Policy} pragma is used
1701 to enable @code{Assert_Checks}.
1703 If assertions are ignored, then there
1704 is no run-time effect (and in particular, any side effects from the
1705 expression will not occur at run time). (The expression is still
1706 analyzed at compile time, and may cause types to be frozen if they are
1707 mentioned here for the first time).
1709 If assertions are checked, then the given expression is tested, and if
1710 it is @code{False} then @code{System.Assertions.Raise_Assert_Failure} is called
1711 which results in the raising of @code{Assert_Failure} with the given message.
1713 You should generally avoid side effects in the expression arguments of
1714 this pragma, because these side effects will turn on and off with the
1715 setting of the assertions mode, resulting in assertions that have an
1716 effect on the program. However, the expressions are analyzed for
1717 semantic correctness whether or not assertions are enabled, so turning
1718 assertions on and off cannot affect the legality of a program.
1720 Note that the implementation defined policy @code{DISABLE}, given in a
1721 pragma @code{Assertion_Policy}, can be used to suppress this semantic analysis.
1723 Note: this is a standard language-defined pragma in versions
1724 of Ada from 2005 on. In GNAT, it is implemented in all versions
1725 of Ada, and the DISABLE policy is an implementation-defined
1728 @node Pragma Assert_And_Cut,Pragma Assertion_Policy,Pragma Assert,Implementation Defined Pragmas
1729 @anchor{gnat_rm/implementation_defined_pragmas pragma-assert-and-cut}@anchor{28}
1730 @section Pragma Assert_And_Cut
1736 pragma Assert_And_Cut (
1738 [, string_EXPRESSION]);
1741 The effect of this pragma is identical to that of pragma @code{Assert},
1742 except that in an @code{Assertion_Policy} pragma, the identifier
1743 @code{Assert_And_Cut} is used to control whether it is ignored or checked
1746 The intention is that this be used within a subprogram when the
1747 given test expresion sums up all the work done so far in the
1748 subprogram, so that the rest of the subprogram can be verified
1749 (informally or formally) using only the entry preconditions,
1750 and the expression in this pragma. This allows dividing up
1751 a subprogram into sections for the purposes of testing or
1752 formal verification. The pragma also serves as useful
1755 @node Pragma Assertion_Policy,Pragma Assume,Pragma Assert_And_Cut,Implementation Defined Pragmas
1756 @anchor{gnat_rm/implementation_defined_pragmas pragma-assertion-policy}@anchor{29}
1757 @section Pragma Assertion_Policy
1763 pragma Assertion_Policy (CHECK | DISABLE | IGNORE);
1765 pragma Assertion_Policy (
1766 ASSERTION_KIND => POLICY_IDENTIFIER
1767 @{, ASSERTION_KIND => POLICY_IDENTIFIER@});
1769 ASSERTION_KIND ::= RM_ASSERTION_KIND | ID_ASSERTION_KIND
1771 RM_ASSERTION_KIND ::= Assert |
1779 Type_Invariant'Class
1781 ID_ASSERTION_KIND ::= Assertions |
1794 Statement_Assertions
1796 POLICY_IDENTIFIER ::= Check | Disable | Ignore | Suppressible
1799 This is a standard Ada 2012 pragma that is available as an
1800 implementation-defined pragma in earlier versions of Ada.
1801 The assertion kinds @code{RM_ASSERTION_KIND} are those defined in
1802 the Ada standard. The assertion kinds @code{ID_ASSERTION_KIND}
1803 are implementation defined additions recognized by the GNAT compiler.
1805 The pragma applies in both cases to pragmas and aspects with matching
1806 names, e.g. @code{Pre} applies to the Pre aspect, and @code{Precondition}
1807 applies to both the @code{Precondition} pragma
1808 and the aspect @code{Precondition}. Note that the identifiers for
1809 pragmas Pre_Class and Post_Class are Pre'Class and Post'Class (not
1810 Pre_Class and Post_Class), since these pragmas are intended to be
1811 identical to the corresponding aspects).
1813 If the policy is @code{CHECK}, then assertions are enabled, i.e.
1814 the corresponding pragma or aspect is activated.
1815 If the policy is @code{IGNORE}, then assertions are ignored, i.e.
1816 the corresponding pragma or aspect is deactivated.
1817 This pragma overrides the effect of the @emph{-gnata} switch on the
1819 If the policy is @code{SUPPRESSIBLE}, then assertions are enabled by default,
1820 however, if the @emph{-gnatp} switch is specified all assertions are ignored.
1822 The implementation defined policy @code{DISABLE} is like
1823 @code{IGNORE} except that it completely disables semantic
1824 checking of the corresponding pragma or aspect. This is
1825 useful when the pragma or aspect argument references subprograms
1826 in a with'ed package which is replaced by a dummy package
1827 for the final build.
1829 The implementation defined assertion kind @code{Assertions} applies to all
1830 assertion kinds. The form with no assertion kind given implies this
1831 choice, so it applies to all assertion kinds (RM defined, and
1832 implementation defined).
1834 The implementation defined assertion kind @code{Statement_Assertions}
1835 applies to @code{Assert}, @code{Assert_And_Cut},
1836 @code{Assume}, @code{Loop_Invariant}, and @code{Loop_Variant}.
1838 @node Pragma Assume,Pragma Assume_No_Invalid_Values,Pragma Assertion_Policy,Implementation Defined Pragmas
1839 @anchor{gnat_rm/implementation_defined_pragmas pragma-assume}@anchor{2a}
1840 @section Pragma Assume
1848 [, string_EXPRESSION]);
1851 The effect of this pragma is identical to that of pragma @code{Assert},
1852 except that in an @code{Assertion_Policy} pragma, the identifier
1853 @code{Assume} is used to control whether it is ignored or checked
1856 The intention is that this be used for assumptions about the
1857 external environment. So you cannot expect to verify formally
1858 or informally that the condition is met, this must be
1859 established by examining things outside the program itself.
1860 For example, we may have code that depends on the size of
1861 @code{Long_Long_Integer} being at least 64. So we could write:
1864 pragma Assume (Long_Long_Integer'Size >= 64);
1867 This assumption cannot be proved from the program itself,
1868 but it acts as a useful run-time check that the assumption
1869 is met, and documents the need to ensure that it is met by
1870 reference to information outside the program.
1872 @node Pragma Assume_No_Invalid_Values,Pragma Async_Readers,Pragma Assume,Implementation Defined Pragmas
1873 @anchor{gnat_rm/implementation_defined_pragmas pragma-assume-no-invalid-values}@anchor{2b}
1874 @section Pragma Assume_No_Invalid_Values
1877 @geindex Invalid representations
1879 @geindex Invalid values
1884 pragma Assume_No_Invalid_Values (On | Off);
1887 This is a configuration pragma that controls the assumptions made by the
1888 compiler about the occurrence of invalid representations (invalid values)
1891 The default behavior (corresponding to an Off argument for this pragma), is
1892 to assume that values may in general be invalid unless the compiler can
1893 prove they are valid. Consider the following example:
1896 V1 : Integer range 1 .. 10;
1897 V2 : Integer range 11 .. 20;
1899 for J in V2 .. V1 loop
1904 if V1 and V2 have valid values, then the loop is known at compile
1905 time not to execute since the lower bound must be greater than the
1906 upper bound. However in default mode, no such assumption is made,
1907 and the loop may execute. If @code{Assume_No_Invalid_Values (On)}
1908 is given, the compiler will assume that any occurrence of a variable
1909 other than in an explicit @code{'Valid} test always has a valid
1910 value, and the loop above will be optimized away.
1912 The use of @code{Assume_No_Invalid_Values (On)} is appropriate if
1913 you know your code is free of uninitialized variables and other
1914 possible sources of invalid representations, and may result in
1915 more efficient code. A program that accesses an invalid representation
1916 with this pragma in effect is erroneous, so no guarantees can be made
1919 It is peculiar though permissible to use this pragma in conjunction
1920 with validity checking (-gnatVa). In such cases, accessing invalid
1921 values will generally give an exception, though formally the program
1922 is erroneous so there are no guarantees that this will always be the
1923 case, and it is recommended that these two options not be used together.
1925 @node Pragma Async_Readers,Pragma Async_Writers,Pragma Assume_No_Invalid_Values,Implementation Defined Pragmas
1926 @anchor{gnat_rm/implementation_defined_pragmas pragma-async-readers}@anchor{2c}@anchor{gnat_rm/implementation_defined_pragmas id4}@anchor{2d}
1927 @section Pragma Async_Readers
1933 pragma Asynch_Readers [ (boolean_EXPRESSION) ];
1936 For the semantics of this pragma, see the entry for aspect @code{Async_Readers} in
1937 the SPARK 2014 Reference Manual, section 7.1.2.
1939 @node Pragma Async_Writers,Pragma Attribute_Definition,Pragma Async_Readers,Implementation Defined Pragmas
1940 @anchor{gnat_rm/implementation_defined_pragmas id5}@anchor{2e}@anchor{gnat_rm/implementation_defined_pragmas pragma-async-writers}@anchor{2f}
1941 @section Pragma Async_Writers
1947 pragma Asynch_Writers [ (boolean_EXPRESSION) ];
1950 For the semantics of this pragma, see the entry for aspect @code{Async_Writers} in
1951 the SPARK 2014 Reference Manual, section 7.1.2.
1953 @node Pragma Attribute_Definition,Pragma C_Pass_By_Copy,Pragma Async_Writers,Implementation Defined Pragmas
1954 @anchor{gnat_rm/implementation_defined_pragmas pragma-attribute-definition}@anchor{30}
1955 @section Pragma Attribute_Definition
1961 pragma Attribute_Definition
1962 ([Attribute =>] ATTRIBUTE_DESIGNATOR,
1963 [Entity =>] LOCAL_NAME,
1964 [Expression =>] EXPRESSION | NAME);
1967 If @code{Attribute} is a known attribute name, this pragma is equivalent to
1968 the attribute definition clause:
1971 for Entity'Attribute use Expression;
1974 If @code{Attribute} is not a recognized attribute name, the pragma is
1975 ignored, and a warning is emitted. This allows source
1976 code to be written that takes advantage of some new attribute, while remaining
1977 compilable with earlier compilers.
1979 @node Pragma C_Pass_By_Copy,Pragma Check,Pragma Attribute_Definition,Implementation Defined Pragmas
1980 @anchor{gnat_rm/implementation_defined_pragmas pragma-c-pass-by-copy}@anchor{31}
1981 @section Pragma C_Pass_By_Copy
1984 @geindex Passing by copy
1989 pragma C_Pass_By_Copy
1990 ([Max_Size =>] static_integer_EXPRESSION);
1993 Normally the default mechanism for passing C convention records to C
1994 convention subprograms is to pass them by reference, as suggested by RM
1995 B.3(69). Use the configuration pragma @code{C_Pass_By_Copy} to change
1996 this default, by requiring that record formal parameters be passed by
1997 copy if all of the following conditions are met:
2003 The size of the record type does not exceed the value specified for
2007 The record type has @code{Convention C}.
2010 The formal parameter has this record type, and the subprogram has a
2011 foreign (non-Ada) convention.
2014 If these conditions are met the argument is passed by copy; i.e., in a
2015 manner consistent with what C expects if the corresponding formal in the
2016 C prototype is a struct (rather than a pointer to a struct).
2018 You can also pass records by copy by specifying the convention
2019 @code{C_Pass_By_Copy} for the record type, or by using the extended
2020 @code{Import} and @code{Export} pragmas, which allow specification of
2021 passing mechanisms on a parameter by parameter basis.
2023 @node Pragma Check,Pragma Check_Float_Overflow,Pragma C_Pass_By_Copy,Implementation Defined Pragmas
2024 @anchor{gnat_rm/implementation_defined_pragmas pragma-check}@anchor{32}
2025 @section Pragma Check
2030 @geindex Named assertions
2036 [Name =>] CHECK_KIND,
2037 [Check =>] Boolean_EXPRESSION
2038 [, [Message =>] string_EXPRESSION] );
2040 CHECK_KIND ::= IDENTIFIER |
2043 Type_Invariant'Class |
2047 This pragma is similar to the predefined pragma @code{Assert} except that an
2048 extra identifier argument is present. In conjunction with pragma
2049 @code{Check_Policy}, this can be used to define groups of assertions that can
2050 be independently controlled. The identifier @code{Assertion} is special, it
2051 refers to the normal set of pragma @code{Assert} statements.
2053 Checks introduced by this pragma are normally deactivated by default. They can
2054 be activated either by the command line option @emph{-gnata}, which turns on
2055 all checks, or individually controlled using pragma @code{Check_Policy}.
2057 The identifiers @code{Assertions} and @code{Statement_Assertions} are not
2058 permitted as check kinds, since this would cause confusion with the use
2059 of these identifiers in @code{Assertion_Policy} and @code{Check_Policy}
2060 pragmas, where they are used to refer to sets of assertions.
2062 @node Pragma Check_Float_Overflow,Pragma Check_Name,Pragma Check,Implementation Defined Pragmas
2063 @anchor{gnat_rm/implementation_defined_pragmas pragma-check-float-overflow}@anchor{33}
2064 @section Pragma Check_Float_Overflow
2067 @geindex Floating-point overflow
2072 pragma Check_Float_Overflow;
2075 In Ada, the predefined floating-point types (@code{Short_Float},
2076 @code{Float}, @code{Long_Float}, @code{Long_Long_Float}) are
2077 defined to be @emph{unconstrained}. This means that even though each
2078 has a well-defined base range, an operation that delivers a result
2079 outside this base range is not required to raise an exception.
2080 This implementation permission accommodates the notion
2081 of infinities in IEEE floating-point, and corresponds to the
2082 efficient execution mode on most machines. GNAT will not raise
2083 overflow exceptions on these machines; instead it will generate
2084 infinities and NaN's as defined in the IEEE standard.
2086 Generating infinities, although efficient, is not always desirable.
2087 Often the preferable approach is to check for overflow, even at the
2088 (perhaps considerable) expense of run-time performance.
2089 This can be accomplished by defining your own constrained floating-point subtypes -- i.e., by supplying explicit
2090 range constraints -- and indeed such a subtype
2091 can have the same base range as its base type. For example:
2094 subtype My_Float is Float range Float'Range;
2097 Here @code{My_Float} has the same range as
2098 @code{Float} but is constrained, so operations on
2099 @code{My_Float} values will be checked for overflow
2102 This style will achieve the desired goal, but
2103 it is often more convenient to be able to simply use
2104 the standard predefined floating-point types as long
2105 as overflow checking could be guaranteed.
2106 The @code{Check_Float_Overflow}
2107 configuration pragma achieves this effect. If a unit is compiled
2108 subject to this configuration pragma, then all operations
2109 on predefined floating-point types including operations on
2110 base types of these floating-point types will be treated as
2111 though those types were constrained, and overflow checks
2112 will be generated. The @code{Constraint_Error}
2113 exception is raised if the result is out of range.
2115 This mode can also be set by use of the compiler
2116 switch @emph{-gnateF}.
2118 @node Pragma Check_Name,Pragma Check_Policy,Pragma Check_Float_Overflow,Implementation Defined Pragmas
2119 @anchor{gnat_rm/implementation_defined_pragmas pragma-check-name}@anchor{34}
2120 @section Pragma Check_Name
2123 @geindex Defining check names
2125 @geindex Check names
2131 pragma Check_Name (check_name_IDENTIFIER);
2134 This is a configuration pragma that defines a new implementation
2135 defined check name (unless IDENTIFIER matches one of the predefined
2136 check names, in which case the pragma has no effect). Check names
2137 are global to a partition, so if two or more configuration pragmas
2138 are present in a partition mentioning the same name, only one new
2139 check name is introduced.
2141 An implementation defined check name introduced with this pragma may
2142 be used in only three contexts: @code{pragma Suppress},
2143 @code{pragma Unsuppress},
2144 and as the prefix of a @code{Check_Name'Enabled} attribute reference. For
2145 any of these three cases, the check name must be visible. A check
2146 name is visible if it is in the configuration pragmas applying to
2147 the current unit, or if it appears at the start of any unit that
2148 is part of the dependency set of the current unit (e.g., units that
2149 are mentioned in @code{with} clauses).
2151 Check names introduced by this pragma are subject to control by compiler
2152 switches (in particular -gnatp) in the usual manner.
2154 @node Pragma Check_Policy,Pragma Comment,Pragma Check_Name,Implementation Defined Pragmas
2155 @anchor{gnat_rm/implementation_defined_pragmas pragma-check-policy}@anchor{35}
2156 @section Pragma Check_Policy
2159 @geindex Controlling assertions
2164 @geindex Check pragma control
2166 @geindex Named assertions
2172 ([Name =>] CHECK_KIND,
2173 [Policy =>] POLICY_IDENTIFIER);
2175 pragma Check_Policy (
2176 CHECK_KIND => POLICY_IDENTIFIER
2177 @{, CHECK_KIND => POLICY_IDENTIFIER@});
2179 ASSERTION_KIND ::= RM_ASSERTION_KIND | ID_ASSERTION_KIND
2181 CHECK_KIND ::= IDENTIFIER |
2184 Type_Invariant'Class |
2187 The identifiers Name and Policy are not allowed as CHECK_KIND values. This
2188 avoids confusion between the two possible syntax forms for this pragma.
2190 POLICY_IDENTIFIER ::= ON | OFF | CHECK | DISABLE | IGNORE
2193 This pragma is used to set the checking policy for assertions (specified
2194 by aspects or pragmas), the @code{Debug} pragma, or additional checks
2195 to be checked using the @code{Check} pragma. It may appear either as
2196 a configuration pragma, or within a declarative part of package. In the
2197 latter case, it applies from the point where it appears to the end of
2198 the declarative region (like pragma @code{Suppress}).
2200 The @code{Check_Policy} pragma is similar to the
2201 predefined @code{Assertion_Policy} pragma,
2202 and if the check kind corresponds to one of the assertion kinds that
2203 are allowed by @code{Assertion_Policy}, then the effect is identical.
2205 If the first argument is Debug, then the policy applies to Debug pragmas,
2206 disabling their effect if the policy is @code{OFF}, @code{DISABLE}, or
2207 @code{IGNORE}, and allowing them to execute with normal semantics if
2208 the policy is @code{ON} or @code{CHECK}. In addition if the policy is
2209 @code{DISABLE}, then the procedure call in @code{Debug} pragmas will
2210 be totally ignored and not analyzed semantically.
2212 Finally the first argument may be some other identifier than the above
2213 possibilities, in which case it controls a set of named assertions
2214 that can be checked using pragma @code{Check}. For example, if the pragma:
2217 pragma Check_Policy (Critical_Error, OFF);
2220 is given, then subsequent @code{Check} pragmas whose first argument is also
2221 @code{Critical_Error} will be disabled.
2223 The check policy is @code{OFF} to turn off corresponding checks, and @code{ON}
2224 to turn on corresponding checks. The default for a set of checks for which no
2225 @code{Check_Policy} is given is @code{OFF} unless the compiler switch
2226 @emph{-gnata} is given, which turns on all checks by default.
2228 The check policy settings @code{CHECK} and @code{IGNORE} are recognized
2229 as synonyms for @code{ON} and @code{OFF}. These synonyms are provided for
2230 compatibility with the standard @code{Assertion_Policy} pragma. The check
2231 policy setting @code{DISABLE} causes the second argument of a corresponding
2232 @code{Check} pragma to be completely ignored and not analyzed.
2234 @node Pragma Comment,Pragma Common_Object,Pragma Check_Policy,Implementation Defined Pragmas
2235 @anchor{gnat_rm/implementation_defined_pragmas pragma-comment}@anchor{36}
2236 @section Pragma Comment
2242 pragma Comment (static_string_EXPRESSION);
2245 This is almost identical in effect to pragma @code{Ident}. It allows the
2246 placement of a comment into the object file and hence into the
2247 executable file if the operating system permits such usage. The
2248 difference is that @code{Comment}, unlike @code{Ident}, has
2249 no limitations on placement of the pragma (it can be placed
2250 anywhere in the main source unit), and if more than one pragma
2251 is used, all comments are retained.
2253 @node Pragma Common_Object,Pragma Compile_Time_Error,Pragma Comment,Implementation Defined Pragmas
2254 @anchor{gnat_rm/implementation_defined_pragmas pragma-common-object}@anchor{37}
2255 @section Pragma Common_Object
2261 pragma Common_Object (
2262 [Internal =>] LOCAL_NAME
2263 [, [External =>] EXTERNAL_SYMBOL]
2264 [, [Size =>] EXTERNAL_SYMBOL] );
2268 | static_string_EXPRESSION
2271 This pragma enables the shared use of variables stored in overlaid
2272 linker areas corresponding to the use of @code{COMMON}
2273 in Fortran. The single
2274 object @code{LOCAL_NAME} is assigned to the area designated by
2275 the @code{External} argument.
2276 You may define a record to correspond to a series
2277 of fields. The @code{Size} argument
2278 is syntax checked in GNAT, but otherwise ignored.
2280 @code{Common_Object} is not supported on all platforms. If no
2281 support is available, then the code generator will issue a message
2282 indicating that the necessary attribute for implementation of this
2283 pragma is not available.
2285 @node Pragma Compile_Time_Error,Pragma Compile_Time_Warning,Pragma Common_Object,Implementation Defined Pragmas
2286 @anchor{gnat_rm/implementation_defined_pragmas pragma-compile-time-error}@anchor{38}
2287 @section Pragma Compile_Time_Error
2293 pragma Compile_Time_Error
2294 (boolean_EXPRESSION, static_string_EXPRESSION);
2297 This pragma can be used to generate additional compile time
2299 is particularly useful in generics, where errors can be issued for
2300 specific problematic instantiations. The first parameter is a boolean
2301 expression. The pragma is effective only if the value of this expression
2302 is known at compile time, and has the value True. The set of expressions
2303 whose values are known at compile time includes all static boolean
2304 expressions, and also other values which the compiler can determine
2305 at compile time (e.g., the size of a record type set by an explicit
2306 size representation clause, or the value of a variable which was
2307 initialized to a constant and is known not to have been modified).
2308 If these conditions are met, an error message is generated using
2309 the value given as the second argument. This string value may contain
2310 embedded ASCII.LF characters to break the message into multiple lines.
2312 @node Pragma Compile_Time_Warning,Pragma Compiler_Unit,Pragma Compile_Time_Error,Implementation Defined Pragmas
2313 @anchor{gnat_rm/implementation_defined_pragmas pragma-compile-time-warning}@anchor{39}
2314 @section Pragma Compile_Time_Warning
2320 pragma Compile_Time_Warning
2321 (boolean_EXPRESSION, static_string_EXPRESSION);
2324 Same as pragma Compile_Time_Error, except a warning is issued instead
2325 of an error message. Note that if this pragma is used in a package that
2326 is with'ed by a client, the client will get the warning even though it
2327 is issued by a with'ed package (normally warnings in with'ed units are
2328 suppressed, but this is a special exception to that rule).
2330 One typical use is within a generic where compile time known characteristics
2331 of formal parameters are tested, and warnings given appropriately. Another use
2332 with a first parameter of True is to warn a client about use of a package,
2333 for example that it is not fully implemented.
2335 @node Pragma Compiler_Unit,Pragma Compiler_Unit_Warning,Pragma Compile_Time_Warning,Implementation Defined Pragmas
2336 @anchor{gnat_rm/implementation_defined_pragmas pragma-compiler-unit}@anchor{3a}
2337 @section Pragma Compiler_Unit
2343 pragma Compiler_Unit;
2346 This pragma is obsolete. It is equivalent to Compiler_Unit_Warning. It is
2347 retained so that old versions of the GNAT run-time that use this pragma can
2348 be compiled with newer versions of the compiler.
2350 @node Pragma Compiler_Unit_Warning,Pragma Complete_Representation,Pragma Compiler_Unit,Implementation Defined Pragmas
2351 @anchor{gnat_rm/implementation_defined_pragmas pragma-compiler-unit-warning}@anchor{3b}
2352 @section Pragma Compiler_Unit_Warning
2358 pragma Compiler_Unit_Warning;
2361 This pragma is intended only for internal use in the GNAT run-time library.
2362 It indicates that the unit is used as part of the compiler build. The effect
2363 is to generate warnings for the use of constructs (for example, conditional
2364 expressions) that would cause trouble when bootstrapping using an older
2365 version of GNAT. For the exact list of restrictions, see the compiler sources
2366 and references to Check_Compiler_Unit.
2368 @node Pragma Complete_Representation,Pragma Complex_Representation,Pragma Compiler_Unit_Warning,Implementation Defined Pragmas
2369 @anchor{gnat_rm/implementation_defined_pragmas pragma-complete-representation}@anchor{3c}
2370 @section Pragma Complete_Representation
2376 pragma Complete_Representation;
2379 This pragma must appear immediately within a record representation
2380 clause. Typical placements are before the first component clause
2381 or after the last component clause. The effect is to give an error
2382 message if any component is missing a component clause. This pragma
2383 may be used to ensure that a record representation clause is
2384 complete, and that this invariant is maintained if fields are
2385 added to the record in the future.
2387 @node Pragma Complex_Representation,Pragma Component_Alignment,Pragma Complete_Representation,Implementation Defined Pragmas
2388 @anchor{gnat_rm/implementation_defined_pragmas pragma-complex-representation}@anchor{3d}
2389 @section Pragma Complex_Representation
2395 pragma Complex_Representation
2396 ([Entity =>] LOCAL_NAME);
2399 The @code{Entity} argument must be the name of a record type which has
2400 two fields of the same floating-point type. The effect of this pragma is
2401 to force gcc to use the special internal complex representation form for
2402 this record, which may be more efficient. Note that this may result in
2403 the code for this type not conforming to standard ABI (application
2404 binary interface) requirements for the handling of record types. For
2405 example, in some environments, there is a requirement for passing
2406 records by pointer, and the use of this pragma may result in passing
2407 this type in floating-point registers.
2409 @node Pragma Component_Alignment,Pragma Constant_After_Elaboration,Pragma Complex_Representation,Implementation Defined Pragmas
2410 @anchor{gnat_rm/implementation_defined_pragmas pragma-component-alignment}@anchor{3e}
2411 @section Pragma Component_Alignment
2414 @geindex Alignments of components
2416 @geindex Pragma Component_Alignment
2421 pragma Component_Alignment (
2422 [Form =>] ALIGNMENT_CHOICE
2423 [, [Name =>] type_LOCAL_NAME]);
2425 ALIGNMENT_CHOICE ::=
2432 Specifies the alignment of components in array or record types.
2433 The meaning of the @code{Form} argument is as follows:
2437 @geindex Component_Size (in pragma Component_Alignment)
2443 @item @emph{Component_Size}
2445 Aligns scalar components and subcomponents of the array or record type
2446 on boundaries appropriate to their inherent size (naturally
2447 aligned). For example, 1-byte components are aligned on byte boundaries,
2448 2-byte integer components are aligned on 2-byte boundaries, 4-byte
2449 integer components are aligned on 4-byte boundaries and so on. These
2450 alignment rules correspond to the normal rules for C compilers on all
2451 machines except the VAX.
2453 @geindex Component_Size_4 (in pragma Component_Alignment)
2455 @item @emph{Component_Size_4}
2457 Naturally aligns components with a size of four or fewer
2458 bytes. Components that are larger than 4 bytes are placed on the next
2461 @geindex Storage_Unit (in pragma Component_Alignment)
2463 @item @emph{Storage_Unit}
2465 Specifies that array or record components are byte aligned, i.e.,
2466 aligned on boundaries determined by the value of the constant
2467 @code{System.Storage_Unit}.
2469 @geindex Default (in pragma Component_Alignment)
2471 @item @emph{Default}
2473 Specifies that array or record components are aligned on default
2474 boundaries, appropriate to the underlying hardware or operating system or
2475 both. The @code{Default} choice is the same as @code{Component_Size} (natural
2479 If the @code{Name} parameter is present, @code{type_LOCAL_NAME} must
2480 refer to a local record or array type, and the specified alignment
2481 choice applies to the specified type. The use of
2482 @code{Component_Alignment} together with a pragma @code{Pack} causes the
2483 @code{Component_Alignment} pragma to be ignored. The use of
2484 @code{Component_Alignment} together with a record representation clause
2485 is only effective for fields not specified by the representation clause.
2487 If the @code{Name} parameter is absent, the pragma can be used as either
2488 a configuration pragma, in which case it applies to one or more units in
2489 accordance with the normal rules for configuration pragmas, or it can be
2490 used within a declarative part, in which case it applies to types that
2491 are declared within this declarative part, or within any nested scope
2492 within this declarative part. In either case it specifies the alignment
2493 to be applied to any record or array type which has otherwise standard
2496 If the alignment for a record or array type is not specified (using
2497 pragma @code{Pack}, pragma @code{Component_Alignment}, or a record rep
2498 clause), the GNAT uses the default alignment as described previously.
2500 @node Pragma Constant_After_Elaboration,Pragma Contract_Cases,Pragma Component_Alignment,Implementation Defined Pragmas
2501 @anchor{gnat_rm/implementation_defined_pragmas id6}@anchor{3f}@anchor{gnat_rm/implementation_defined_pragmas pragma-constant-after-elaboration}@anchor{40}
2502 @section Pragma Constant_After_Elaboration
2508 pragma Constant_After_Elaboration [ (boolean_EXPRESSION) ];
2511 For the semantics of this pragma, see the entry for aspect
2512 @code{Constant_After_Elaboration} in the SPARK 2014 Reference Manual, section 3.3.1.
2514 @node Pragma Contract_Cases,Pragma Convention_Identifier,Pragma Constant_After_Elaboration,Implementation Defined Pragmas
2515 @anchor{gnat_rm/implementation_defined_pragmas id7}@anchor{41}@anchor{gnat_rm/implementation_defined_pragmas pragma-contract-cases}@anchor{42}
2516 @section Pragma Contract_Cases
2519 @geindex Contract cases
2524 pragma Contract_Cases ((CONTRACT_CASE @{, CONTRACT_CASE));
2526 CONTRACT_CASE ::= CASE_GUARD => CONSEQUENCE
2528 CASE_GUARD ::= boolean_EXPRESSION | others
2530 CONSEQUENCE ::= boolean_EXPRESSION
2533 The @code{Contract_Cases} pragma allows defining fine-grain specifications
2534 that can complement or replace the contract given by a precondition and a
2535 postcondition. Additionally, the @code{Contract_Cases} pragma can be used
2536 by testing and formal verification tools. The compiler checks its validity and,
2537 depending on the assertion policy at the point of declaration of the pragma,
2538 it may insert a check in the executable. For code generation, the contract
2542 pragma Contract_Cases (
2550 C1 : constant Boolean := Cond1; -- evaluated at subprogram entry
2551 C2 : constant Boolean := Cond2; -- evaluated at subprogram entry
2552 pragma Precondition ((C1 and not C2) or (C2 and not C1));
2553 pragma Postcondition (if C1 then Pred1);
2554 pragma Postcondition (if C2 then Pred2);
2557 The precondition ensures that one and only one of the conditions is
2558 satisfied on entry to the subprogram.
2559 The postcondition ensures that for the condition that was True on entry,
2560 the corrresponding consequence is True on exit. Other consequence expressions
2563 A precondition @code{P} and postcondition @code{Q} can also be
2564 expressed as contract cases:
2567 pragma Contract_Cases (P => Q);
2570 The placement and visibility rules for @code{Contract_Cases} pragmas are
2571 identical to those described for preconditions and postconditions.
2573 The compiler checks that boolean expressions given in conditions and
2574 consequences are valid, where the rules for conditions are the same as
2575 the rule for an expression in @code{Precondition} and the rules for
2576 consequences are the same as the rule for an expression in
2577 @code{Postcondition}. In particular, attributes @code{'Old} and
2578 @code{'Result} can only be used within consequence expressions.
2579 The condition for the last contract case may be @code{others}, to denote
2580 any case not captured by the previous cases. The
2581 following is an example of use within a package spec:
2584 package Math_Functions is
2586 function Sqrt (Arg : Float) return Float;
2587 pragma Contract_Cases (((Arg in 0.0 .. 99.0) => Sqrt'Result < 10.0,
2588 Arg >= 100.0 => Sqrt'Result >= 10.0,
2589 others => Sqrt'Result = 0.0));
2594 The meaning of contract cases is that only one case should apply at each
2595 call, as determined by the corresponding condition evaluating to True,
2596 and that the consequence for this case should hold when the subprogram
2599 @node Pragma Convention_Identifier,Pragma CPP_Class,Pragma Contract_Cases,Implementation Defined Pragmas
2600 @anchor{gnat_rm/implementation_defined_pragmas pragma-convention-identifier}@anchor{43}
2601 @section Pragma Convention_Identifier
2604 @geindex Conventions
2610 pragma Convention_Identifier (
2611 [Name =>] IDENTIFIER,
2612 [Convention =>] convention_IDENTIFIER);
2615 This pragma provides a mechanism for supplying synonyms for existing
2616 convention identifiers. The @code{Name} identifier can subsequently
2617 be used as a synonym for the given convention in other pragmas (including
2618 for example pragma @code{Import} or another @code{Convention_Identifier}
2619 pragma). As an example of the use of this, suppose you had legacy code
2620 which used Fortran77 as the identifier for Fortran. Then the pragma:
2623 pragma Convention_Identifier (Fortran77, Fortran);
2626 would allow the use of the convention identifier @code{Fortran77} in
2627 subsequent code, avoiding the need to modify the sources. As another
2628 example, you could use this to parameterize convention requirements
2629 according to systems. Suppose you needed to use @code{Stdcall} on
2630 windows systems, and @code{C} on some other system, then you could
2631 define a convention identifier @code{Library} and use a single
2632 @code{Convention_Identifier} pragma to specify which convention
2633 would be used system-wide.
2635 @node Pragma CPP_Class,Pragma CPP_Constructor,Pragma Convention_Identifier,Implementation Defined Pragmas
2636 @anchor{gnat_rm/implementation_defined_pragmas pragma-cpp-class}@anchor{44}
2637 @section Pragma CPP_Class
2640 @geindex Interfacing with C++
2645 pragma CPP_Class ([Entity =>] LOCAL_NAME);
2648 The argument denotes an entity in the current declarative region that is
2649 declared as a record type. It indicates that the type corresponds to an
2650 externally declared C++ class type, and is to be laid out the same way
2651 that C++ would lay out the type. If the C++ class has virtual primitives
2652 then the record must be declared as a tagged record type.
2654 Types for which @code{CPP_Class} is specified do not have assignment or
2655 equality operators defined (such operations can be imported or declared
2656 as subprograms as required). Initialization is allowed only by constructor
2657 functions (see pragma @code{CPP_Constructor}). Such types are implicitly
2658 limited if not explicitly declared as limited or derived from a limited
2659 type, and an error is issued in that case.
2661 See @ref{45,,Interfacing to C++} for related information.
2663 Note: Pragma @code{CPP_Class} is currently obsolete. It is supported
2664 for backward compatibility but its functionality is available
2665 using pragma @code{Import} with @code{Convention} = @code{CPP}.
2667 @node Pragma CPP_Constructor,Pragma CPP_Virtual,Pragma CPP_Class,Implementation Defined Pragmas
2668 @anchor{gnat_rm/implementation_defined_pragmas pragma-cpp-constructor}@anchor{46}
2669 @section Pragma CPP_Constructor
2672 @geindex Interfacing with C++
2677 pragma CPP_Constructor ([Entity =>] LOCAL_NAME
2678 [, [External_Name =>] static_string_EXPRESSION ]
2679 [, [Link_Name =>] static_string_EXPRESSION ]);
2682 This pragma identifies an imported function (imported in the usual way
2683 with pragma @code{Import}) as corresponding to a C++ constructor. If
2684 @code{External_Name} and @code{Link_Name} are not specified then the
2685 @code{Entity} argument is a name that must have been previously mentioned
2686 in a pragma @code{Import} with @code{Convention} = @code{CPP}. Such name
2687 must be of one of the following forms:
2693 @strong{function} @code{Fname} @strong{return} T`
2696 @strong{function} @code{Fname} @strong{return} T'Class
2699 @strong{function} @code{Fname} (...) @strong{return} T`
2702 @strong{function} @code{Fname} (...) @strong{return} T'Class
2705 where @code{T} is a limited record type imported from C++ with pragma
2706 @code{Import} and @code{Convention} = @code{CPP}.
2708 The first two forms import the default constructor, used when an object
2709 of type @code{T} is created on the Ada side with no explicit constructor.
2710 The latter two forms cover all the non-default constructors of the type.
2711 See the GNAT User's Guide for details.
2713 If no constructors are imported, it is impossible to create any objects
2714 on the Ada side and the type is implicitly declared abstract.
2716 Pragma @code{CPP_Constructor} is intended primarily for automatic generation
2717 using an automatic binding generator tool (such as the @code{-fdump-ada-spec}
2719 See @ref{45,,Interfacing to C++} for more related information.
2721 Note: The use of functions returning class-wide types for constructors is
2722 currently obsolete. They are supported for backward compatibility. The
2723 use of functions returning the type T leave the Ada sources more clear
2724 because the imported C++ constructors always return an object of type T;
2725 that is, they never return an object whose type is a descendant of type T.
2727 @node Pragma CPP_Virtual,Pragma CPP_Vtable,Pragma CPP_Constructor,Implementation Defined Pragmas
2728 @anchor{gnat_rm/implementation_defined_pragmas pragma-cpp-virtual}@anchor{47}
2729 @section Pragma CPP_Virtual
2732 @geindex Interfacing to C++
2734 This pragma is now obsolete and, other than generating a warning if warnings
2735 on obsolescent features are enabled, is completely ignored.
2736 It is retained for compatibility
2737 purposes. It used to be required to ensure compoatibility with C++, but
2738 is no longer required for that purpose because GNAT generates
2739 the same object layout as the G++ compiler by default.
2741 See @ref{45,,Interfacing to C++} for related information.
2743 @node Pragma CPP_Vtable,Pragma CPU,Pragma CPP_Virtual,Implementation Defined Pragmas
2744 @anchor{gnat_rm/implementation_defined_pragmas pragma-cpp-vtable}@anchor{48}
2745 @section Pragma CPP_Vtable
2748 @geindex Interfacing with C++
2750 This pragma is now obsolete and, other than generating a warning if warnings
2751 on obsolescent features are enabled, is completely ignored.
2752 It used to be required to ensure compatibility with C++, but
2753 is no longer required for that purpose because GNAT generates
2754 the same object layout as the G++ compiler by default.
2756 See @ref{45,,Interfacing to C++} for related information.
2758 @node Pragma CPU,Pragma Deadline_Floor,Pragma CPP_Vtable,Implementation Defined Pragmas
2759 @anchor{gnat_rm/implementation_defined_pragmas pragma-cpu}@anchor{49}
2766 pragma CPU (EXPRESSION);
2769 This pragma is standard in Ada 2012, but is available in all earlier
2770 versions of Ada as an implementation-defined pragma.
2771 See Ada 2012 Reference Manual for details.
2773 @node Pragma Deadline_Floor,Pragma Default_Initial_Condition,Pragma CPU,Implementation Defined Pragmas
2774 @anchor{gnat_rm/implementation_defined_pragmas pragma-deadline-floor}@anchor{4a}
2775 @section Pragma Deadline_Floor
2781 pragma Deadline_Floor (time_span_EXPRESSION);
2784 This pragma applies only to protected types and specifies the floor
2785 deadline inherited by a task when the task enters a protected object.
2786 It is effective only when the EDF scheduling policy is used.
2788 @node Pragma Default_Initial_Condition,Pragma Debug,Pragma Deadline_Floor,Implementation Defined Pragmas
2789 @anchor{gnat_rm/implementation_defined_pragmas id8}@anchor{4b}@anchor{gnat_rm/implementation_defined_pragmas pragma-default-initial-condition}@anchor{4c}
2790 @section Pragma Default_Initial_Condition
2796 pragma Default_Initial_Condition [ (null | boolean_EXPRESSION) ];
2799 For the semantics of this pragma, see the entry for aspect
2800 @code{Default_Initial_Condition} in the SPARK 2014 Reference Manual, section 7.3.3.
2802 @node Pragma Debug,Pragma Debug_Policy,Pragma Default_Initial_Condition,Implementation Defined Pragmas
2803 @anchor{gnat_rm/implementation_defined_pragmas pragma-debug}@anchor{4d}
2804 @section Pragma Debug
2810 pragma Debug ([CONDITION, ]PROCEDURE_CALL_WITHOUT_SEMICOLON);
2812 PROCEDURE_CALL_WITHOUT_SEMICOLON ::=
2814 | PROCEDURE_PREFIX ACTUAL_PARAMETER_PART
2817 The procedure call argument has the syntactic form of an expression, meeting
2818 the syntactic requirements for pragmas.
2820 If debug pragmas are not enabled or if the condition is present and evaluates
2821 to False, this pragma has no effect. If debug pragmas are enabled, the
2822 semantics of the pragma is exactly equivalent to the procedure call statement
2823 corresponding to the argument with a terminating semicolon. Pragmas are
2824 permitted in sequences of declarations, so you can use pragma @code{Debug} to
2825 intersperse calls to debug procedures in the middle of declarations. Debug
2826 pragmas can be enabled either by use of the command line switch @emph{-gnata}
2827 or by use of the pragma @code{Check_Policy} with a first argument of
2830 @node Pragma Debug_Policy,Pragma Default_Scalar_Storage_Order,Pragma Debug,Implementation Defined Pragmas
2831 @anchor{gnat_rm/implementation_defined_pragmas pragma-debug-policy}@anchor{4e}
2832 @section Pragma Debug_Policy
2838 pragma Debug_Policy (CHECK | DISABLE | IGNORE | ON | OFF);
2841 This pragma is equivalent to a corresponding @code{Check_Policy} pragma
2842 with a first argument of @code{Debug}. It is retained for historical
2843 compatibility reasons.
2845 @node Pragma Default_Scalar_Storage_Order,Pragma Default_Storage_Pool,Pragma Debug_Policy,Implementation Defined Pragmas
2846 @anchor{gnat_rm/implementation_defined_pragmas pragma-default-scalar-storage-order}@anchor{4f}
2847 @section Pragma Default_Scalar_Storage_Order
2850 @geindex Default_Scalar_Storage_Order
2852 @geindex Scalar_Storage_Order
2857 pragma Default_Scalar_Storage_Order (High_Order_First | Low_Order_First);
2860 Normally if no explicit @code{Scalar_Storage_Order} is given for a record
2861 type or array type, then the scalar storage order defaults to the ordinary
2862 default for the target. But this default may be overridden using this pragma.
2863 The pragma may appear as a configuration pragma, or locally within a package
2864 spec or declarative part. In the latter case, it applies to all subsequent
2865 types declared within that package spec or declarative part.
2867 The following example shows the use of this pragma:
2870 pragma Default_Scalar_Storage_Order (High_Order_First);
2871 with System; use System;
2880 for L2'Scalar_Storage_Order use Low_Order_First;
2889 pragma Default_Scalar_Storage_Order (Low_Order_First);
2896 type H4a is new Inner.L4;
2904 In this example record types with names starting with @emph{L} have @cite{Low_Order_First} scalar
2905 storage order, and record types with names starting with @emph{H} have @code{High_Order_First}.
2906 Note that in the case of @code{H4a}, the order is not inherited
2907 from the parent type. Only an explicitly set @code{Scalar_Storage_Order}
2908 gets inherited on type derivation.
2910 If this pragma is used as a configuration pragma which appears within a
2911 configuration pragma file (as opposed to appearing explicitly at the start
2912 of a single unit), then the binder will require that all units in a partition
2913 be compiled in a similar manner, other than run-time units, which are not
2914 affected by this pragma. Note that the use of this form is discouraged because
2915 it may significantly degrade the run-time performance of the software, instead
2916 the default scalar storage order ought to be changed only on a local basis.
2918 @node Pragma Default_Storage_Pool,Pragma Depends,Pragma Default_Scalar_Storage_Order,Implementation Defined Pragmas
2919 @anchor{gnat_rm/implementation_defined_pragmas pragma-default-storage-pool}@anchor{50}
2920 @section Pragma Default_Storage_Pool
2923 @geindex Default_Storage_Pool
2928 pragma Default_Storage_Pool (storage_pool_NAME | null);
2931 This pragma is standard in Ada 2012, but is available in all earlier
2932 versions of Ada as an implementation-defined pragma.
2933 See Ada 2012 Reference Manual for details.
2935 @node Pragma Depends,Pragma Detect_Blocking,Pragma Default_Storage_Pool,Implementation Defined Pragmas
2936 @anchor{gnat_rm/implementation_defined_pragmas pragma-depends}@anchor{51}@anchor{gnat_rm/implementation_defined_pragmas id9}@anchor{52}
2937 @section Pragma Depends
2943 pragma Depends (DEPENDENCY_RELATION);
2945 DEPENDENCY_RELATION ::=
2947 | (DEPENDENCY_CLAUSE @{, DEPENDENCY_CLAUSE@})
2949 DEPENDENCY_CLAUSE ::=
2950 OUTPUT_LIST =>[+] INPUT_LIST
2951 | NULL_DEPENDENCY_CLAUSE
2953 NULL_DEPENDENCY_CLAUSE ::= null => INPUT_LIST
2955 OUTPUT_LIST ::= OUTPUT | (OUTPUT @{, OUTPUT@})
2957 INPUT_LIST ::= null | INPUT | (INPUT @{, INPUT@})
2959 OUTPUT ::= NAME | FUNCTION_RESULT
2962 where FUNCTION_RESULT is a function Result attribute_reference
2965 For the semantics of this pragma, see the entry for aspect @code{Depends} in the
2966 SPARK 2014 Reference Manual, section 6.1.5.
2968 @node Pragma Detect_Blocking,Pragma Disable_Atomic_Synchronization,Pragma Depends,Implementation Defined Pragmas
2969 @anchor{gnat_rm/implementation_defined_pragmas pragma-detect-blocking}@anchor{53}
2970 @section Pragma Detect_Blocking
2976 pragma Detect_Blocking;
2979 This is a standard pragma in Ada 2005, that is available in all earlier
2980 versions of Ada as an implementation-defined pragma.
2982 This is a configuration pragma that forces the detection of potentially
2983 blocking operations within a protected operation, and to raise Program_Error
2986 @node Pragma Disable_Atomic_Synchronization,Pragma Dispatching_Domain,Pragma Detect_Blocking,Implementation Defined Pragmas
2987 @anchor{gnat_rm/implementation_defined_pragmas pragma-disable-atomic-synchronization}@anchor{54}
2988 @section Pragma Disable_Atomic_Synchronization
2991 @geindex Atomic Synchronization
2996 pragma Disable_Atomic_Synchronization [(Entity)];
2999 Ada requires that accesses (reads or writes) of an atomic variable be
3000 regarded as synchronization points in the case of multiple tasks.
3001 Particularly in the case of multi-processors this may require special
3002 handling, e.g. the generation of memory barriers. This capability may
3003 be turned off using this pragma in cases where it is known not to be
3006 The placement and scope rules for this pragma are the same as those
3007 for @code{pragma Suppress}. In particular it can be used as a
3008 configuration pragma, or in a declaration sequence where it applies
3009 till the end of the scope. If an @code{Entity} argument is present,
3010 the action applies only to that entity.
3012 @node Pragma Dispatching_Domain,Pragma Effective_Reads,Pragma Disable_Atomic_Synchronization,Implementation Defined Pragmas
3013 @anchor{gnat_rm/implementation_defined_pragmas pragma-dispatching-domain}@anchor{55}
3014 @section Pragma Dispatching_Domain
3020 pragma Dispatching_Domain (EXPRESSION);
3023 This pragma is standard in Ada 2012, but is available in all earlier
3024 versions of Ada as an implementation-defined pragma.
3025 See Ada 2012 Reference Manual for details.
3027 @node Pragma Effective_Reads,Pragma Effective_Writes,Pragma Dispatching_Domain,Implementation Defined Pragmas
3028 @anchor{gnat_rm/implementation_defined_pragmas id10}@anchor{56}@anchor{gnat_rm/implementation_defined_pragmas pragma-effective-reads}@anchor{57}
3029 @section Pragma Effective_Reads
3035 pragma Effective_Reads [ (boolean_EXPRESSION) ];
3038 For the semantics of this pragma, see the entry for aspect @code{Effective_Reads} in
3039 the SPARK 2014 Reference Manual, section 7.1.2.
3041 @node Pragma Effective_Writes,Pragma Elaboration_Checks,Pragma Effective_Reads,Implementation Defined Pragmas
3042 @anchor{gnat_rm/implementation_defined_pragmas id11}@anchor{58}@anchor{gnat_rm/implementation_defined_pragmas pragma-effective-writes}@anchor{59}
3043 @section Pragma Effective_Writes
3049 pragma Effective_Writes [ (boolean_EXPRESSION) ];
3052 For the semantics of this pragma, see the entry for aspect @code{Effective_Writes}
3053 in the SPARK 2014 Reference Manual, section 7.1.2.
3055 @node Pragma Elaboration_Checks,Pragma Eliminate,Pragma Effective_Writes,Implementation Defined Pragmas
3056 @anchor{gnat_rm/implementation_defined_pragmas pragma-elaboration-checks}@anchor{5a}
3057 @section Pragma Elaboration_Checks
3060 @geindex Elaboration control
3065 pragma Elaboration_Checks (Dynamic | Static);
3068 This is a configuration pragma that provides control over the
3069 elaboration model used by the compilation affected by the
3070 pragma. If the parameter is @code{Dynamic},
3071 then the dynamic elaboration
3072 model described in the Ada Reference Manual is used, as though
3073 the @emph{-gnatE} switch had been specified on the command
3074 line. If the parameter is @code{Static}, then the default GNAT static
3075 model is used. This configuration pragma overrides the setting
3076 of the command line. For full details on the elaboration models
3077 used by the GNAT compiler, see the chapter on elaboration order handling
3078 in the @emph{GNAT User's Guide}.
3080 @node Pragma Eliminate,Pragma Enable_Atomic_Synchronization,Pragma Elaboration_Checks,Implementation Defined Pragmas
3081 @anchor{gnat_rm/implementation_defined_pragmas pragma-eliminate}@anchor{5b}
3082 @section Pragma Eliminate
3085 @geindex Elimination of unused subprograms
3091 [ Unit_Name => ] IDENTIFIER | SELECTED_COMPONENT ,
3092 [ Entity => ] IDENTIFIER |
3093 SELECTED_COMPONENT |
3095 [, Source_Location => SOURCE_TRACE ] );
3097 SOURCE_TRACE ::= STRING_LITERAL
3100 This pragma indicates that the given entity is not used in the program to be
3101 compiled and built, thus allowing the compiler to
3102 eliminate the code or data associated with the named entity. Any reference to
3103 an eliminated entity causes a compile-time or link-time error.
3105 The pragma has the following semantics, where @code{U} is the unit specified by
3106 the @code{Unit_Name} argument and @code{E} is the entity specified by the @code{Entity}
3113 @code{E} must be a subprogram that is explicitly declared either:
3115 o Within @code{U}, or
3117 o Within a generic package that is instantiated in @code{U}, or
3119 o As an instance of generic subprogram instantiated in @code{U}.
3121 Otherwise the pragma is ignored.
3124 If @code{E} is overloaded within @code{U} then, in the absence of a
3125 @code{Source_Location} argument, all overloadings are eliminated.
3128 If @code{E} is overloaded within @code{U} and only some overloadings
3129 are to be eliminated, then each overloading to be eliminated
3130 must be specified in a corresponding pragma @code{Eliminate}
3131 with a @code{Source_Location} argument identifying the line where the
3132 declaration appears, as described below.
3135 If @code{E} is declared as the result of a generic instantiation, then
3136 a @code{Source_Location} argument is needed, as described below
3139 Pragma @code{Eliminate} allows a program to be compiled in a system-independent
3140 manner, so that unused entities are eliminated but without
3141 needing to modify the source text. Normally the required set of
3142 @code{Eliminate} pragmas is constructed automatically using the @code{gnatelim} tool.
3144 Any source file change that removes, splits, or
3145 adds lines may make the set of @code{Eliminate} pragmas invalid because their
3146 @code{Source_Location} argument values may get out of date.
3148 Pragma @code{Eliminate} may be used where the referenced entity is a dispatching
3149 operation. In this case all the subprograms to which the given operation can
3150 dispatch are considered to be unused (are never called as a result of a direct
3151 or a dispatching call).
3153 The string literal given for the source location specifies the line number
3154 of the declaration of the entity, using the following syntax for @code{SOURCE_TRACE}:
3157 SOURCE_TRACE ::= SOURCE_REFERENCE [ LBRACKET SOURCE_TRACE RBRACKET ]
3162 SOURCE_REFERENCE ::= FILE_NAME : LINE_NUMBER
3164 LINE_NUMBER ::= DIGIT @{DIGIT@}
3167 Spaces around the colon in a @code{SOURCE_REFERENCE} are optional.
3169 The source trace that is given as the @code{Source_Location} must obey the
3170 following rules (or else the pragma is ignored), where @code{U} is
3171 the unit @code{U} specified by the @code{Unit_Name} argument and @code{E} is the
3172 subprogram specified by the @code{Entity} argument:
3178 @code{FILE_NAME} is the short name (with no directory
3179 information) of the Ada source file for @code{U}, using the required syntax
3180 for the underlying file system (e.g. case is significant if the underlying
3181 operating system is case sensitive).
3182 If @code{U} is a package and @code{E} is a subprogram declared in the package
3183 specification and its full declaration appears in the package body,
3184 then the relevant source file is the one for the package specification;
3185 analogously if @code{U} is a generic package.
3188 If @code{E} is not declared in a generic instantiation (this includes
3189 generic subprogram instances), the source trace includes only one source
3190 line reference. @code{LINE_NUMBER} gives the line number of the occurrence
3191 of the declaration of @code{E} within the source file (as a decimal literal
3192 without an exponent or point).
3195 If @code{E} is declared by a generic instantiation, its source trace
3196 (from left to right) starts with the source location of the
3197 declaration of @code{E} in the generic unit and ends with the source
3198 location of the instantiation, given in square brackets. This approach is
3199 applied recursively with nested instantiations: the rightmost (nested
3200 most deeply in square brackets) element of the source trace is the location
3201 of the outermost instantiation, and the leftmost element (that is, outside
3202 of any square brackets) is the location of the declaration of @code{E} in
3211 pragma Eliminate (Pkg0, Proc);
3212 -- Eliminate (all overloadings of) Proc in Pkg0
3214 pragma Eliminate (Pkg1, Proc,
3215 Source_Location => "pkg1.ads:8");
3216 -- Eliminate overloading of Proc at line 8 in pkg1.ads
3218 -- Assume the following file contents:
3221 -- 2: type T is private;
3222 -- 3: package Gen_Pkg is
3223 -- 4: procedure Proc(N : T);
3229 -- 2: procedure Q is
3230 -- 3: package Inst_Pkg is new Gen_Pkg(Integer);
3231 -- ... -- No calls on Inst_Pkg.Proc
3234 -- The following pragma eliminates Inst_Pkg.Proc from Q
3235 pragma Eliminate (Q, Proc,
3236 Source_Location => "gen_pkg.ads:4[q.adb:3]");
3240 @node Pragma Enable_Atomic_Synchronization,Pragma Export_Function,Pragma Eliminate,Implementation Defined Pragmas
3241 @anchor{gnat_rm/implementation_defined_pragmas pragma-enable-atomic-synchronization}@anchor{5c}
3242 @section Pragma Enable_Atomic_Synchronization
3245 @geindex Atomic Synchronization
3250 pragma Enable_Atomic_Synchronization [(Entity)];
3253 Ada requires that accesses (reads or writes) of an atomic variable be
3254 regarded as synchronization points in the case of multiple tasks.
3255 Particularly in the case of multi-processors this may require special
3256 handling, e.g. the generation of memory barriers. This synchronization
3257 is performed by default, but can be turned off using
3258 @code{pragma Disable_Atomic_Synchronization}. The
3259 @code{Enable_Atomic_Synchronization} pragma can be used to turn
3262 The placement and scope rules for this pragma are the same as those
3263 for @code{pragma Unsuppress}. In particular it can be used as a
3264 configuration pragma, or in a declaration sequence where it applies
3265 till the end of the scope. If an @code{Entity} argument is present,
3266 the action applies only to that entity.
3268 @node Pragma Export_Function,Pragma Export_Object,Pragma Enable_Atomic_Synchronization,Implementation Defined Pragmas
3269 @anchor{gnat_rm/implementation_defined_pragmas pragma-export-function}@anchor{5d}
3270 @section Pragma Export_Function
3273 @geindex Argument passing mechanisms
3278 pragma Export_Function (
3279 [Internal =>] LOCAL_NAME
3280 [, [External =>] EXTERNAL_SYMBOL]
3281 [, [Parameter_Types =>] PARAMETER_TYPES]
3282 [, [Result_Type =>] result_SUBTYPE_MARK]
3283 [, [Mechanism =>] MECHANISM]
3284 [, [Result_Mechanism =>] MECHANISM_NAME]);
3288 | static_string_EXPRESSION
3293 | TYPE_DESIGNATOR @{, TYPE_DESIGNATOR@}
3297 | subtype_Name ' Access
3301 | (MECHANISM_ASSOCIATION @{, MECHANISM_ASSOCIATION@})
3303 MECHANISM_ASSOCIATION ::=
3304 [formal_parameter_NAME =>] MECHANISM_NAME
3306 MECHANISM_NAME ::= Value | Reference
3309 Use this pragma to make a function externally callable and optionally
3310 provide information on mechanisms to be used for passing parameter and
3311 result values. We recommend, for the purposes of improving portability,
3312 this pragma always be used in conjunction with a separate pragma
3313 @code{Export}, which must precede the pragma @code{Export_Function}.
3314 GNAT does not require a separate pragma @code{Export}, but if none is
3315 present, @code{Convention Ada} is assumed, which is usually
3316 not what is wanted, so it is usually appropriate to use this
3317 pragma in conjunction with a @code{Export} or @code{Convention}
3318 pragma that specifies the desired foreign convention.
3319 Pragma @code{Export_Function}
3320 (and @code{Export}, if present) must appear in the same declarative
3321 region as the function to which they apply.
3323 The @code{internal_name} must uniquely designate the function to which the
3324 pragma applies. If more than one function name exists of this name in
3325 the declarative part you must use the @code{Parameter_Types} and
3326 @code{Result_Type} parameters to achieve the required
3327 unique designation. The @cite{subtype_mark}s in these parameters must
3328 exactly match the subtypes in the corresponding function specification,
3329 using positional notation to match parameters with subtype marks.
3330 The form with an @code{'Access} attribute can be used to match an
3331 anonymous access parameter.
3333 @geindex Suppressing external name
3335 Special treatment is given if the EXTERNAL is an explicit null
3336 string or a static string expressions that evaluates to the null
3337 string. In this case, no external name is generated. This form
3338 still allows the specification of parameter mechanisms.
3340 @node Pragma Export_Object,Pragma Export_Procedure,Pragma Export_Function,Implementation Defined Pragmas
3341 @anchor{gnat_rm/implementation_defined_pragmas pragma-export-object}@anchor{5e}
3342 @section Pragma Export_Object
3348 pragma Export_Object
3349 [Internal =>] LOCAL_NAME
3350 [, [External =>] EXTERNAL_SYMBOL]
3351 [, [Size =>] EXTERNAL_SYMBOL]
3355 | static_string_EXPRESSION
3358 This pragma designates an object as exported, and apart from the
3359 extended rules for external symbols, is identical in effect to the use of
3360 the normal @code{Export} pragma applied to an object. You may use a
3361 separate Export pragma (and you probably should from the point of view
3362 of portability), but it is not required. @code{Size} is syntax checked,
3363 but otherwise ignored by GNAT.
3365 @node Pragma Export_Procedure,Pragma Export_Value,Pragma Export_Object,Implementation Defined Pragmas
3366 @anchor{gnat_rm/implementation_defined_pragmas pragma-export-procedure}@anchor{5f}
3367 @section Pragma Export_Procedure
3373 pragma Export_Procedure (
3374 [Internal =>] LOCAL_NAME
3375 [, [External =>] EXTERNAL_SYMBOL]
3376 [, [Parameter_Types =>] PARAMETER_TYPES]
3377 [, [Mechanism =>] MECHANISM]);
3381 | static_string_EXPRESSION
3386 | TYPE_DESIGNATOR @{, TYPE_DESIGNATOR@}
3390 | subtype_Name ' Access
3394 | (MECHANISM_ASSOCIATION @{, MECHANISM_ASSOCIATION@})
3396 MECHANISM_ASSOCIATION ::=
3397 [formal_parameter_NAME =>] MECHANISM_NAME
3399 MECHANISM_NAME ::= Value | Reference
3402 This pragma is identical to @code{Export_Function} except that it
3403 applies to a procedure rather than a function and the parameters
3404 @code{Result_Type} and @code{Result_Mechanism} are not permitted.
3405 GNAT does not require a separate pragma @code{Export}, but if none is
3406 present, @code{Convention Ada} is assumed, which is usually
3407 not what is wanted, so it is usually appropriate to use this
3408 pragma in conjunction with a @code{Export} or @code{Convention}
3409 pragma that specifies the desired foreign convention.
3411 @geindex Suppressing external name
3413 Special treatment is given if the EXTERNAL is an explicit null
3414 string or a static string expressions that evaluates to the null
3415 string. In this case, no external name is generated. This form
3416 still allows the specification of parameter mechanisms.
3418 @node Pragma Export_Value,Pragma Export_Valued_Procedure,Pragma Export_Procedure,Implementation Defined Pragmas
3419 @anchor{gnat_rm/implementation_defined_pragmas pragma-export-value}@anchor{60}
3420 @section Pragma Export_Value
3426 pragma Export_Value (
3427 [Value =>] static_integer_EXPRESSION,
3428 [Link_Name =>] static_string_EXPRESSION);
3431 This pragma serves to export a static integer value for external use.
3432 The first argument specifies the value to be exported. The Link_Name
3433 argument specifies the symbolic name to be associated with the integer
3434 value. This pragma is useful for defining a named static value in Ada
3435 that can be referenced in assembly language units to be linked with
3436 the application. This pragma is currently supported only for the
3437 AAMP target and is ignored for other targets.
3439 @node Pragma Export_Valued_Procedure,Pragma Extend_System,Pragma Export_Value,Implementation Defined Pragmas
3440 @anchor{gnat_rm/implementation_defined_pragmas pragma-export-valued-procedure}@anchor{61}
3441 @section Pragma Export_Valued_Procedure
3447 pragma Export_Valued_Procedure (
3448 [Internal =>] LOCAL_NAME
3449 [, [External =>] EXTERNAL_SYMBOL]
3450 [, [Parameter_Types =>] PARAMETER_TYPES]
3451 [, [Mechanism =>] MECHANISM]);
3455 | static_string_EXPRESSION
3460 | TYPE_DESIGNATOR @{, TYPE_DESIGNATOR@}
3464 | subtype_Name ' Access
3468 | (MECHANISM_ASSOCIATION @{, MECHANISM_ASSOCIATION@})
3470 MECHANISM_ASSOCIATION ::=
3471 [formal_parameter_NAME =>] MECHANISM_NAME
3473 MECHANISM_NAME ::= Value | Reference
3476 This pragma is identical to @code{Export_Procedure} except that the
3477 first parameter of @code{LOCAL_NAME}, which must be present, must be of
3478 mode @code{out}, and externally the subprogram is treated as a function
3479 with this parameter as the result of the function. GNAT provides for
3480 this capability to allow the use of @code{out} and @code{in out}
3481 parameters in interfacing to external functions (which are not permitted
3483 GNAT does not require a separate pragma @code{Export}, but if none is
3484 present, @code{Convention Ada} is assumed, which is almost certainly
3485 not what is wanted since the whole point of this pragma is to interface
3486 with foreign language functions, so it is usually appropriate to use this
3487 pragma in conjunction with a @code{Export} or @code{Convention}
3488 pragma that specifies the desired foreign convention.
3490 @geindex Suppressing external name
3492 Special treatment is given if the EXTERNAL is an explicit null
3493 string or a static string expressions that evaluates to the null
3494 string. In this case, no external name is generated. This form
3495 still allows the specification of parameter mechanisms.
3497 @node Pragma Extend_System,Pragma Extensions_Allowed,Pragma Export_Valued_Procedure,Implementation Defined Pragmas
3498 @anchor{gnat_rm/implementation_defined_pragmas pragma-extend-system}@anchor{62}
3499 @section Pragma Extend_System
3510 pragma Extend_System ([Name =>] IDENTIFIER);
3513 This pragma is used to provide backwards compatibility with other
3514 implementations that extend the facilities of package @code{System}. In
3515 GNAT, @code{System} contains only the definitions that are present in
3516 the Ada RM. However, other implementations, notably the DEC Ada 83
3517 implementation, provide many extensions to package @code{System}.
3519 For each such implementation accommodated by this pragma, GNAT provides a
3520 package @code{Aux_@emph{xxx}}, e.g., @code{Aux_DEC} for the DEC Ada 83
3521 implementation, which provides the required additional definitions. You
3522 can use this package in two ways. You can @code{with} it in the normal
3523 way and access entities either by selection or using a @code{use}
3524 clause. In this case no special processing is required.
3526 However, if existing code contains references such as
3527 @code{System.@emph{xxx}} where @emph{xxx} is an entity in the extended
3528 definitions provided in package @code{System}, you may use this pragma
3529 to extend visibility in @code{System} in a non-standard way that
3530 provides greater compatibility with the existing code. Pragma
3531 @code{Extend_System} is a configuration pragma whose single argument is
3532 the name of the package containing the extended definition
3533 (e.g., @code{Aux_DEC} for the DEC Ada case). A unit compiled under
3534 control of this pragma will be processed using special visibility
3535 processing that looks in package @code{System.Aux_@emph{xxx}} where
3536 @code{Aux_@emph{xxx}} is the pragma argument for any entity referenced in
3537 package @code{System}, but not found in package @code{System}.
3539 You can use this pragma either to access a predefined @code{System}
3540 extension supplied with the compiler, for example @code{Aux_DEC} or
3541 you can construct your own extension unit following the above
3542 definition. Note that such a package is a child of @code{System}
3543 and thus is considered part of the implementation.
3544 To compile it you will have to use the @emph{-gnatg} switch
3545 for compiling System units, as explained in the
3548 @node Pragma Extensions_Allowed,Pragma Extensions_Visible,Pragma Extend_System,Implementation Defined Pragmas
3549 @anchor{gnat_rm/implementation_defined_pragmas pragma-extensions-allowed}@anchor{63}
3550 @section Pragma Extensions_Allowed
3553 @geindex Ada Extensions
3555 @geindex GNAT Extensions
3560 pragma Extensions_Allowed (On | Off);
3563 This configuration pragma enables or disables the implementation
3564 extension mode (the use of Off as a parameter cancels the effect
3565 of the @emph{-gnatX} command switch).
3567 In extension mode, the latest version of the Ada language is
3568 implemented (currently Ada 2012), and in addition a small number
3569 of GNAT specific extensions are recognized as follows:
3574 @item @emph{Constrained attribute for generic objects}
3576 The @code{Constrained} attribute is permitted for objects of
3577 generic types. The result indicates if the corresponding actual
3581 @node Pragma Extensions_Visible,Pragma External,Pragma Extensions_Allowed,Implementation Defined Pragmas
3582 @anchor{gnat_rm/implementation_defined_pragmas id12}@anchor{64}@anchor{gnat_rm/implementation_defined_pragmas pragma-extensions-visible}@anchor{65}
3583 @section Pragma Extensions_Visible
3589 pragma Extensions_Visible [ (boolean_EXPRESSION) ];
3592 For the semantics of this pragma, see the entry for aspect @code{Extensions_Visible}
3593 in the SPARK 2014 Reference Manual, section 6.1.7.
3595 @node Pragma External,Pragma External_Name_Casing,Pragma Extensions_Visible,Implementation Defined Pragmas
3596 @anchor{gnat_rm/implementation_defined_pragmas pragma-external}@anchor{66}
3597 @section Pragma External
3604 [ Convention =>] convention_IDENTIFIER,
3605 [ Entity =>] LOCAL_NAME
3606 [, [External_Name =>] static_string_EXPRESSION ]
3607 [, [Link_Name =>] static_string_EXPRESSION ]);
3610 This pragma is identical in syntax and semantics to pragma
3611 @code{Export} as defined in the Ada Reference Manual. It is
3612 provided for compatibility with some Ada 83 compilers that
3613 used this pragma for exactly the same purposes as pragma
3614 @code{Export} before the latter was standardized.
3616 @node Pragma External_Name_Casing,Pragma Fast_Math,Pragma External,Implementation Defined Pragmas
3617 @anchor{gnat_rm/implementation_defined_pragmas pragma-external-name-casing}@anchor{67}
3618 @section Pragma External_Name_Casing
3621 @geindex Dec Ada 83 casing compatibility
3623 @geindex External Names
3626 @geindex Casing of External names
3631 pragma External_Name_Casing (
3632 Uppercase | Lowercase
3633 [, Uppercase | Lowercase | As_Is]);
3636 This pragma provides control over the casing of external names associated
3637 with Import and Export pragmas. There are two cases to consider:
3643 Implicit external names
3645 Implicit external names are derived from identifiers. The most common case
3646 arises when a standard Ada Import or Export pragma is used with only two
3650 pragma Import (C, C_Routine);
3653 Since Ada is a case-insensitive language, the spelling of the identifier in
3654 the Ada source program does not provide any information on the desired
3655 casing of the external name, and so a convention is needed. In GNAT the
3656 default treatment is that such names are converted to all lower case
3657 letters. This corresponds to the normal C style in many environments.
3658 The first argument of pragma @code{External_Name_Casing} can be used to
3659 control this treatment. If @code{Uppercase} is specified, then the name
3660 will be forced to all uppercase letters. If @code{Lowercase} is specified,
3661 then the normal default of all lower case letters will be used.
3663 This same implicit treatment is also used in the case of extended DEC Ada 83
3664 compatible Import and Export pragmas where an external name is explicitly
3665 specified using an identifier rather than a string.
3668 Explicit external names
3670 Explicit external names are given as string literals. The most common case
3671 arises when a standard Ada Import or Export pragma is used with three
3675 pragma Import (C, C_Routine, "C_routine");
3678 In this case, the string literal normally provides the exact casing required
3679 for the external name. The second argument of pragma
3680 @code{External_Name_Casing} may be used to modify this behavior.
3681 If @code{Uppercase} is specified, then the name
3682 will be forced to all uppercase letters. If @code{Lowercase} is specified,
3683 then the name will be forced to all lowercase letters. A specification of
3684 @code{As_Is} provides the normal default behavior in which the casing is
3685 taken from the string provided.
3688 This pragma may appear anywhere that a pragma is valid. In particular, it
3689 can be used as a configuration pragma in the @code{gnat.adc} file, in which
3690 case it applies to all subsequent compilations, or it can be used as a program
3691 unit pragma, in which case it only applies to the current unit, or it can
3692 be used more locally to control individual Import/Export pragmas.
3694 It was primarily intended for use with OpenVMS systems, where many
3695 compilers convert all symbols to upper case by default. For interfacing to
3696 such compilers (e.g., the DEC C compiler), it may be convenient to use
3700 pragma External_Name_Casing (Uppercase, Uppercase);
3703 to enforce the upper casing of all external symbols.
3705 @node Pragma Fast_Math,Pragma Favor_Top_Level,Pragma External_Name_Casing,Implementation Defined Pragmas
3706 @anchor{gnat_rm/implementation_defined_pragmas pragma-fast-math}@anchor{68}
3707 @section Pragma Fast_Math
3716 This is a configuration pragma which activates a mode in which speed is
3717 considered more important for floating-point operations than absolutely
3718 accurate adherence to the requirements of the standard. Currently the
3719 following operations are affected:
3724 @item @emph{Complex Multiplication}
3726 The normal simple formula for complex multiplication can result in intermediate
3727 overflows for numbers near the end of the range. The Ada standard requires that
3728 this situation be detected and corrected by scaling, but in Fast_Math mode such
3729 cases will simply result in overflow. Note that to take advantage of this you
3730 must instantiate your own version of @code{Ada.Numerics.Generic_Complex_Types}
3731 under control of the pragma, rather than use the preinstantiated versions.
3734 @node Pragma Favor_Top_Level,Pragma Finalize_Storage_Only,Pragma Fast_Math,Implementation Defined Pragmas
3735 @anchor{gnat_rm/implementation_defined_pragmas id13}@anchor{69}@anchor{gnat_rm/implementation_defined_pragmas pragma-favor-top-level}@anchor{6a}
3736 @section Pragma Favor_Top_Level
3742 pragma Favor_Top_Level (type_NAME);
3745 The argument of pragma @code{Favor_Top_Level} must be a named access-to-subprogram
3746 type. This pragma is an efficiency hint to the compiler, regarding the use of
3747 @code{'Access} or @code{'Unrestricted_Access} on nested (non-library-level) subprograms.
3748 The pragma means that nested subprograms are not used with this type, or are
3749 rare, so that the generated code should be efficient in the top-level case.
3750 When this pragma is used, dynamically generated trampolines may be used on some
3751 targets for nested subprograms. See restriction @code{No_Implicit_Dynamic_Code}.
3753 @node Pragma Finalize_Storage_Only,Pragma Float_Representation,Pragma Favor_Top_Level,Implementation Defined Pragmas
3754 @anchor{gnat_rm/implementation_defined_pragmas pragma-finalize-storage-only}@anchor{6b}
3755 @section Pragma Finalize_Storage_Only
3761 pragma Finalize_Storage_Only (first_subtype_LOCAL_NAME);
3764 The argument of pragma @code{Finalize_Storage_Only} must denote a local type which
3765 is derived from @code{Ada.Finalization.Controlled} or @code{Limited_Controlled}. The
3766 pragma suppresses the call to @code{Finalize} for declared library-level objects
3767 of the argument type. This is mostly useful for types where finalization is
3768 only used to deal with storage reclamation since in most environments it is
3769 not necessary to reclaim memory just before terminating execution, hence the
3770 name. Note that this pragma does not suppress Finalize calls for library-level
3771 heap-allocated objects (see pragma @code{No_Heap_Finalization}).
3773 @node Pragma Float_Representation,Pragma Ghost,Pragma Finalize_Storage_Only,Implementation Defined Pragmas
3774 @anchor{gnat_rm/implementation_defined_pragmas pragma-float-representation}@anchor{6c}
3775 @section Pragma Float_Representation
3781 pragma Float_Representation (FLOAT_REP[, float_type_LOCAL_NAME]);
3783 FLOAT_REP ::= VAX_Float | IEEE_Float
3786 In the one argument form, this pragma is a configuration pragma which
3787 allows control over the internal representation chosen for the predefined
3788 floating point types declared in the packages @code{Standard} and
3789 @code{System}. This pragma is only provided for compatibility and has no effect.
3791 The two argument form specifies the representation to be used for
3792 the specified floating-point type. The argument must
3793 be @code{IEEE_Float} to specify the use of IEEE format, as follows:
3799 For a digits value of 6, 32-bit IEEE short format will be used.
3802 For a digits value of 15, 64-bit IEEE long format will be used.
3805 No other value of digits is permitted.
3808 @node Pragma Ghost,Pragma Global,Pragma Float_Representation,Implementation Defined Pragmas
3809 @anchor{gnat_rm/implementation_defined_pragmas pragma-ghost}@anchor{6d}@anchor{gnat_rm/implementation_defined_pragmas id14}@anchor{6e}
3810 @section Pragma Ghost
3816 pragma Ghost [ (boolean_EXPRESSION) ];
3819 For the semantics of this pragma, see the entry for aspect @code{Ghost} in the SPARK
3820 2014 Reference Manual, section 6.9.
3822 @node Pragma Global,Pragma Ident,Pragma Ghost,Implementation Defined Pragmas
3823 @anchor{gnat_rm/implementation_defined_pragmas pragma-global}@anchor{6f}@anchor{gnat_rm/implementation_defined_pragmas id15}@anchor{70}
3824 @section Pragma Global
3830 pragma Global (GLOBAL_SPECIFICATION);
3832 GLOBAL_SPECIFICATION ::=
3835 | (MODED_GLOBAL_LIST @{, MODED_GLOBAL_LIST@})
3837 MODED_GLOBAL_LIST ::= MODE_SELECTOR => GLOBAL_LIST
3839 MODE_SELECTOR ::= In_Out | Input | Output | Proof_In
3840 GLOBAL_LIST ::= GLOBAL_ITEM | (GLOBAL_ITEM @{, GLOBAL_ITEM@})
3841 GLOBAL_ITEM ::= NAME
3844 For the semantics of this pragma, see the entry for aspect @code{Global} in the
3845 SPARK 2014 Reference Manual, section 6.1.4.
3847 @node Pragma Ident,Pragma Ignore_Pragma,Pragma Global,Implementation Defined Pragmas
3848 @anchor{gnat_rm/implementation_defined_pragmas pragma-ident}@anchor{71}
3849 @section Pragma Ident
3855 pragma Ident (static_string_EXPRESSION);
3858 This pragma is identical in effect to pragma @code{Comment}. It is provided
3859 for compatibility with other Ada compilers providing this pragma.
3861 @node Pragma Ignore_Pragma,Pragma Implementation_Defined,Pragma Ident,Implementation Defined Pragmas
3862 @anchor{gnat_rm/implementation_defined_pragmas pragma-ignore-pragma}@anchor{72}
3863 @section Pragma Ignore_Pragma
3869 pragma Ignore_Pragma (pragma_IDENTIFIER);
3872 This is a configuration pragma
3873 that takes a single argument that is a simple identifier. Any subsequent
3874 use of a pragma whose pragma identifier matches this argument will be
3875 silently ignored. This may be useful when legacy code or code intended
3876 for compilation with some other compiler contains pragmas that match the
3877 name, but not the exact implementation, of a GNAT pragma. The use of this
3878 pragma allows such pragmas to be ignored, which may be useful in CodePeer
3879 mode, or during porting of legacy code.
3881 @node Pragma Implementation_Defined,Pragma Implemented,Pragma Ignore_Pragma,Implementation Defined Pragmas
3882 @anchor{gnat_rm/implementation_defined_pragmas pragma-implementation-defined}@anchor{73}
3883 @section Pragma Implementation_Defined
3889 pragma Implementation_Defined (local_NAME);
3892 This pragma marks a previously declared entity as implementation-defined.
3893 For an overloaded entity, applies to the most recent homonym.
3896 pragma Implementation_Defined;
3899 The form with no arguments appears anywhere within a scope, most
3900 typically a package spec, and indicates that all entities that are
3901 defined within the package spec are Implementation_Defined.
3903 This pragma is used within the GNAT runtime library to identify
3904 implementation-defined entities introduced in language-defined units,
3905 for the purpose of implementing the No_Implementation_Identifiers
3908 @node Pragma Implemented,Pragma Implicit_Packing,Pragma Implementation_Defined,Implementation Defined Pragmas
3909 @anchor{gnat_rm/implementation_defined_pragmas pragma-implemented}@anchor{74}
3910 @section Pragma Implemented
3916 pragma Implemented (procedure_LOCAL_NAME, implementation_kind);
3918 implementation_kind ::= By_Entry | By_Protected_Procedure | By_Any
3921 This is an Ada 2012 representation pragma which applies to protected, task
3922 and synchronized interface primitives. The use of pragma Implemented provides
3923 a way to impose a static requirement on the overriding operation by adhering
3924 to one of the three implementation kinds: entry, protected procedure or any of
3925 the above. This pragma is available in all earlier versions of Ada as an
3926 implementation-defined pragma.
3929 type Synch_Iface is synchronized interface;
3930 procedure Prim_Op (Obj : in out Iface) is abstract;
3931 pragma Implemented (Prim_Op, By_Protected_Procedure);
3933 protected type Prot_1 is new Synch_Iface with
3934 procedure Prim_Op; -- Legal
3937 protected type Prot_2 is new Synch_Iface with
3938 entry Prim_Op; -- Illegal
3941 task type Task_Typ is new Synch_Iface with
3942 entry Prim_Op; -- Illegal
3946 When applied to the procedure_or_entry_NAME of a requeue statement, pragma
3947 Implemented determines the runtime behavior of the requeue. Implementation kind
3948 By_Entry guarantees that the action of requeueing will proceed from an entry to
3949 another entry. Implementation kind By_Protected_Procedure transforms the
3950 requeue into a dispatching call, thus eliminating the chance of blocking. Kind
3951 By_Any shares the behavior of By_Entry and By_Protected_Procedure depending on
3952 the target's overriding subprogram kind.
3954 @node Pragma Implicit_Packing,Pragma Import_Function,Pragma Implemented,Implementation Defined Pragmas
3955 @anchor{gnat_rm/implementation_defined_pragmas pragma-implicit-packing}@anchor{75}
3956 @section Pragma Implicit_Packing
3959 @geindex Rational Profile
3964 pragma Implicit_Packing;
3967 This is a configuration pragma that requests implicit packing for packed
3968 arrays for which a size clause is given but no explicit pragma Pack or
3969 specification of Component_Size is present. It also applies to records
3970 where no record representation clause is present. Consider this example:
3973 type R is array (0 .. 7) of Boolean;
3977 In accordance with the recommendation in the RM (RM 13.3(53)), a Size clause
3978 does not change the layout of a composite object. So the Size clause in the
3979 above example is normally rejected, since the default layout of the array uses
3980 8-bit components, and thus the array requires a minimum of 64 bits.
3982 If this declaration is compiled in a region of code covered by an occurrence
3983 of the configuration pragma Implicit_Packing, then the Size clause in this
3984 and similar examples will cause implicit packing and thus be accepted. For
3985 this implicit packing to occur, the type in question must be an array of small
3986 components whose size is known at compile time, and the Size clause must
3987 specify the exact size that corresponds to the number of elements in the array
3988 multiplied by the size in bits of the component type (both single and
3989 multi-dimensioned arrays can be controlled with this pragma).
3991 @geindex Array packing
3993 Similarly, the following example shows the use in the record case
3997 a, b, c, d, e, f, g, h : boolean;
4003 Without a pragma Pack, each Boolean field requires 8 bits, so the
4004 minimum size is 72 bits, but with a pragma Pack, 16 bits would be
4005 sufficient. The use of pragma Implicit_Packing allows this record
4006 declaration to compile without an explicit pragma Pack.
4008 @node Pragma Import_Function,Pragma Import_Object,Pragma Implicit_Packing,Implementation Defined Pragmas
4009 @anchor{gnat_rm/implementation_defined_pragmas pragma-import-function}@anchor{76}
4010 @section Pragma Import_Function
4016 pragma Import_Function (
4017 [Internal =>] LOCAL_NAME,
4018 [, [External =>] EXTERNAL_SYMBOL]
4019 [, [Parameter_Types =>] PARAMETER_TYPES]
4020 [, [Result_Type =>] SUBTYPE_MARK]
4021 [, [Mechanism =>] MECHANISM]
4022 [, [Result_Mechanism =>] MECHANISM_NAME]);
4026 | static_string_EXPRESSION
4030 | TYPE_DESIGNATOR @{, TYPE_DESIGNATOR@}
4034 | subtype_Name ' Access
4038 | (MECHANISM_ASSOCIATION @{, MECHANISM_ASSOCIATION@})
4040 MECHANISM_ASSOCIATION ::=
4041 [formal_parameter_NAME =>] MECHANISM_NAME
4048 This pragma is used in conjunction with a pragma @code{Import} to
4049 specify additional information for an imported function. The pragma
4050 @code{Import} (or equivalent pragma @code{Interface}) must precede the
4051 @code{Import_Function} pragma and both must appear in the same
4052 declarative part as the function specification.
4054 The @code{Internal} argument must uniquely designate
4055 the function to which the
4056 pragma applies. If more than one function name exists of this name in
4057 the declarative part you must use the @code{Parameter_Types} and
4058 @code{Result_Type} parameters to achieve the required unique
4059 designation. Subtype marks in these parameters must exactly match the
4060 subtypes in the corresponding function specification, using positional
4061 notation to match parameters with subtype marks.
4062 The form with an @code{'Access} attribute can be used to match an
4063 anonymous access parameter.
4065 You may optionally use the @code{Mechanism} and @code{Result_Mechanism}
4066 parameters to specify passing mechanisms for the
4067 parameters and result. If you specify a single mechanism name, it
4068 applies to all parameters. Otherwise you may specify a mechanism on a
4069 parameter by parameter basis using either positional or named
4070 notation. If the mechanism is not specified, the default mechanism
4073 @node Pragma Import_Object,Pragma Import_Procedure,Pragma Import_Function,Implementation Defined Pragmas
4074 @anchor{gnat_rm/implementation_defined_pragmas pragma-import-object}@anchor{77}
4075 @section Pragma Import_Object
4081 pragma Import_Object
4082 [Internal =>] LOCAL_NAME
4083 [, [External =>] EXTERNAL_SYMBOL]
4084 [, [Size =>] EXTERNAL_SYMBOL]);
4088 | static_string_EXPRESSION
4091 This pragma designates an object as imported, and apart from the
4092 extended rules for external symbols, is identical in effect to the use of
4093 the normal @code{Import} pragma applied to an object. Unlike the
4094 subprogram case, you need not use a separate @code{Import} pragma,
4095 although you may do so (and probably should do so from a portability
4096 point of view). @code{size} is syntax checked, but otherwise ignored by
4099 @node Pragma Import_Procedure,Pragma Import_Valued_Procedure,Pragma Import_Object,Implementation Defined Pragmas
4100 @anchor{gnat_rm/implementation_defined_pragmas pragma-import-procedure}@anchor{78}
4101 @section Pragma Import_Procedure
4107 pragma Import_Procedure (
4108 [Internal =>] LOCAL_NAME
4109 [, [External =>] EXTERNAL_SYMBOL]
4110 [, [Parameter_Types =>] PARAMETER_TYPES]
4111 [, [Mechanism =>] MECHANISM]);
4115 | static_string_EXPRESSION
4119 | TYPE_DESIGNATOR @{, TYPE_DESIGNATOR@}
4123 | subtype_Name ' Access
4127 | (MECHANISM_ASSOCIATION @{, MECHANISM_ASSOCIATION@})
4129 MECHANISM_ASSOCIATION ::=
4130 [formal_parameter_NAME =>] MECHANISM_NAME
4132 MECHANISM_NAME ::= Value | Reference
4135 This pragma is identical to @code{Import_Function} except that it
4136 applies to a procedure rather than a function and the parameters
4137 @code{Result_Type} and @code{Result_Mechanism} are not permitted.
4139 @node Pragma Import_Valued_Procedure,Pragma Independent,Pragma Import_Procedure,Implementation Defined Pragmas
4140 @anchor{gnat_rm/implementation_defined_pragmas pragma-import-valued-procedure}@anchor{79}
4141 @section Pragma Import_Valued_Procedure
4147 pragma Import_Valued_Procedure (
4148 [Internal =>] LOCAL_NAME
4149 [, [External =>] EXTERNAL_SYMBOL]
4150 [, [Parameter_Types =>] PARAMETER_TYPES]
4151 [, [Mechanism =>] MECHANISM]);
4155 | static_string_EXPRESSION
4159 | TYPE_DESIGNATOR @{, TYPE_DESIGNATOR@}
4163 | subtype_Name ' Access
4167 | (MECHANISM_ASSOCIATION @{, MECHANISM_ASSOCIATION@})
4169 MECHANISM_ASSOCIATION ::=
4170 [formal_parameter_NAME =>] MECHANISM_NAME
4172 MECHANISM_NAME ::= Value | Reference
4175 This pragma is identical to @code{Import_Procedure} except that the
4176 first parameter of @code{LOCAL_NAME}, which must be present, must be of
4177 mode @code{out}, and externally the subprogram is treated as a function
4178 with this parameter as the result of the function. The purpose of this
4179 capability is to allow the use of @code{out} and @code{in out}
4180 parameters in interfacing to external functions (which are not permitted
4181 in Ada functions). You may optionally use the @code{Mechanism}
4182 parameters to specify passing mechanisms for the parameters.
4183 If you specify a single mechanism name, it applies to all parameters.
4184 Otherwise you may specify a mechanism on a parameter by parameter
4185 basis using either positional or named notation. If the mechanism is not
4186 specified, the default mechanism is used.
4188 Note that it is important to use this pragma in conjunction with a separate
4189 pragma Import that specifies the desired convention, since otherwise the
4190 default convention is Ada, which is almost certainly not what is required.
4192 @node Pragma Independent,Pragma Independent_Components,Pragma Import_Valued_Procedure,Implementation Defined Pragmas
4193 @anchor{gnat_rm/implementation_defined_pragmas pragma-independent}@anchor{7a}
4194 @section Pragma Independent
4200 pragma Independent (Local_NAME);
4203 This pragma is standard in Ada 2012 mode (which also provides an aspect
4204 of the same name). It is also available as an implementation-defined
4205 pragma in all earlier versions. It specifies that the
4206 designated object or all objects of the designated type must be
4207 independently addressable. This means that separate tasks can safely
4208 manipulate such objects. For example, if two components of a record are
4209 independent, then two separate tasks may access these two components.
4211 constraints on the representation of the object (for instance prohibiting
4214 @node Pragma Independent_Components,Pragma Initial_Condition,Pragma Independent,Implementation Defined Pragmas
4215 @anchor{gnat_rm/implementation_defined_pragmas pragma-independent-components}@anchor{7b}
4216 @section Pragma Independent_Components
4222 pragma Independent_Components (Local_NAME);
4225 This pragma is standard in Ada 2012 mode (which also provides an aspect
4226 of the same name). It is also available as an implementation-defined
4227 pragma in all earlier versions. It specifies that the components of the
4228 designated object, or the components of each object of the designated
4230 independently addressable. This means that separate tasks can safely
4231 manipulate separate components in the composite object. This may place
4232 constraints on the representation of the object (for instance prohibiting
4235 @node Pragma Initial_Condition,Pragma Initialize_Scalars,Pragma Independent_Components,Implementation Defined Pragmas
4236 @anchor{gnat_rm/implementation_defined_pragmas id16}@anchor{7c}@anchor{gnat_rm/implementation_defined_pragmas pragma-initial-condition}@anchor{7d}
4237 @section Pragma Initial_Condition
4243 pragma Initial_Condition (boolean_EXPRESSION);
4246 For the semantics of this pragma, see the entry for aspect @code{Initial_Condition}
4247 in the SPARK 2014 Reference Manual, section 7.1.6.
4249 @node Pragma Initialize_Scalars,Pragma Initializes,Pragma Initial_Condition,Implementation Defined Pragmas
4250 @anchor{gnat_rm/implementation_defined_pragmas pragma-initialize-scalars}@anchor{7e}
4251 @section Pragma Initialize_Scalars
4254 @geindex debugging with Initialize_Scalars
4259 pragma Initialize_Scalars;
4262 This pragma is similar to @code{Normalize_Scalars} conceptually but has
4263 two important differences. First, there is no requirement for the pragma
4264 to be used uniformly in all units of a partition, in particular, it is fine
4265 to use this just for some or all of the application units of a partition,
4266 without needing to recompile the run-time library.
4268 In the case where some units are compiled with the pragma, and some without,
4269 then a declaration of a variable where the type is defined in package
4270 Standard or is locally declared will always be subject to initialization,
4271 as will any declaration of a scalar variable. For composite variables,
4272 whether the variable is initialized may also depend on whether the package
4273 in which the type of the variable is declared is compiled with the pragma.
4275 The other important difference is that you can control the value used
4276 for initializing scalar objects. At bind time, you can select several
4277 options for initialization. You can
4278 initialize with invalid values (similar to Normalize_Scalars, though for
4279 Initialize_Scalars it is not always possible to determine the invalid
4280 values in complex cases like signed component fields with non-standard
4281 sizes). You can also initialize with high or
4282 low values, or with a specified bit pattern. See the GNAT
4283 User's Guide for binder options for specifying these cases.
4285 This means that you can compile a program, and then without having to
4286 recompile the program, you can run it with different values being used
4287 for initializing otherwise uninitialized values, to test if your program
4288 behavior depends on the choice. Of course the behavior should not change,
4289 and if it does, then most likely you have an incorrect reference to an
4290 uninitialized value.
4292 It is even possible to change the value at execution time eliminating even
4293 the need to rebind with a different switch using an environment variable.
4294 See the GNAT User's Guide for details.
4296 Note that pragma @code{Initialize_Scalars} is particularly useful in
4297 conjunction with the enhanced validity checking that is now provided
4298 in GNAT, which checks for invalid values under more conditions.
4299 Using this feature (see description of the @emph{-gnatV} flag in the
4300 GNAT User's Guide) in conjunction with
4301 pragma @code{Initialize_Scalars}
4302 provides a powerful new tool to assist in the detection of problems
4303 caused by uninitialized variables.
4305 Note: the use of @code{Initialize_Scalars} has a fairly extensive
4306 effect on the generated code. This may cause your code to be
4307 substantially larger. It may also cause an increase in the amount
4308 of stack required, so it is probably a good idea to turn on stack
4309 checking (see description of stack checking in the GNAT
4310 User's Guide) when using this pragma.
4312 @node Pragma Initializes,Pragma Inline_Always,Pragma Initialize_Scalars,Implementation Defined Pragmas
4313 @anchor{gnat_rm/implementation_defined_pragmas pragma-initializes}@anchor{7f}@anchor{gnat_rm/implementation_defined_pragmas id17}@anchor{80}
4314 @section Pragma Initializes
4320 pragma Initializes (INITIALIZATION_LIST);
4322 INITIALIZATION_LIST ::=
4324 | (INITIALIZATION_ITEM @{, INITIALIZATION_ITEM@})
4326 INITIALIZATION_ITEM ::= name [=> INPUT_LIST]
4331 | (INPUT @{, INPUT@})
4336 For the semantics of this pragma, see the entry for aspect @code{Initializes} in the
4337 SPARK 2014 Reference Manual, section 7.1.5.
4339 @node Pragma Inline_Always,Pragma Inline_Generic,Pragma Initializes,Implementation Defined Pragmas
4340 @anchor{gnat_rm/implementation_defined_pragmas id18}@anchor{81}@anchor{gnat_rm/implementation_defined_pragmas pragma-inline-always}@anchor{82}
4341 @section Pragma Inline_Always
4347 pragma Inline_Always (NAME [, NAME]);
4350 Similar to pragma @code{Inline} except that inlining is unconditional.
4351 Inline_Always instructs the compiler to inline every direct call to the
4352 subprogram or else to emit a compilation error, independently of any
4353 option, in particular @emph{-gnatn} or @emph{-gnatN} or the optimization level.
4354 It is an error to take the address or access of @code{NAME}. It is also an error to
4355 apply this pragma to a primitive operation of a tagged type. Thanks to such
4356 restrictions, the compiler is allowed to remove the out-of-line body of @code{NAME}.
4358 @node Pragma Inline_Generic,Pragma Interface,Pragma Inline_Always,Implementation Defined Pragmas
4359 @anchor{gnat_rm/implementation_defined_pragmas pragma-inline-generic}@anchor{83}
4360 @section Pragma Inline_Generic
4366 pragma Inline_Generic (GNAME @{, GNAME@});
4368 GNAME ::= generic_unit_NAME | generic_instance_NAME
4371 This pragma is provided for compatibility with Dec Ada 83. It has
4372 no effect in GNAT (which always inlines generics), other
4373 than to check that the given names are all names of generic units or
4376 @node Pragma Interface,Pragma Interface_Name,Pragma Inline_Generic,Implementation Defined Pragmas
4377 @anchor{gnat_rm/implementation_defined_pragmas pragma-interface}@anchor{84}
4378 @section Pragma Interface
4385 [Convention =>] convention_identifier,
4386 [Entity =>] local_NAME
4387 [, [External_Name =>] static_string_expression]
4388 [, [Link_Name =>] static_string_expression]);
4391 This pragma is identical in syntax and semantics to
4392 the standard Ada pragma @code{Import}. It is provided for compatibility
4393 with Ada 83. The definition is upwards compatible both with pragma
4394 @code{Interface} as defined in the Ada 83 Reference Manual, and also
4395 with some extended implementations of this pragma in certain Ada 83
4396 implementations. The only difference between pragma @code{Interface}
4397 and pragma @code{Import} is that there is special circuitry to allow
4398 both pragmas to appear for the same subprogram entity (normally it
4399 is illegal to have multiple @code{Import} pragmas. This is useful in
4400 maintaining Ada 83/Ada 95 compatibility and is compatible with other
4403 @node Pragma Interface_Name,Pragma Interrupt_Handler,Pragma Interface,Implementation Defined Pragmas
4404 @anchor{gnat_rm/implementation_defined_pragmas pragma-interface-name}@anchor{85}
4405 @section Pragma Interface_Name
4411 pragma Interface_Name (
4412 [Entity =>] LOCAL_NAME
4413 [, [External_Name =>] static_string_EXPRESSION]
4414 [, [Link_Name =>] static_string_EXPRESSION]);
4417 This pragma provides an alternative way of specifying the interface name
4418 for an interfaced subprogram, and is provided for compatibility with Ada
4419 83 compilers that use the pragma for this purpose. You must provide at
4420 least one of @code{External_Name} or @code{Link_Name}.
4422 @node Pragma Interrupt_Handler,Pragma Interrupt_State,Pragma Interface_Name,Implementation Defined Pragmas
4423 @anchor{gnat_rm/implementation_defined_pragmas pragma-interrupt-handler}@anchor{86}
4424 @section Pragma Interrupt_Handler
4430 pragma Interrupt_Handler (procedure_LOCAL_NAME);
4433 This program unit pragma is supported for parameterless protected procedures
4434 as described in Annex C of the Ada Reference Manual. On the AAMP target
4435 the pragma can also be specified for nonprotected parameterless procedures
4436 that are declared at the library level (which includes procedures
4437 declared at the top level of a library package). In the case of AAMP,
4438 when this pragma is applied to a nonprotected procedure, the instruction
4439 @code{IERET} is generated for returns from the procedure, enabling
4440 maskable interrupts, in place of the normal return instruction.
4442 @node Pragma Interrupt_State,Pragma Invariant,Pragma Interrupt_Handler,Implementation Defined Pragmas
4443 @anchor{gnat_rm/implementation_defined_pragmas pragma-interrupt-state}@anchor{87}
4444 @section Pragma Interrupt_State
4450 pragma Interrupt_State
4452 [State =>] SYSTEM | RUNTIME | USER);
4455 Normally certain interrupts are reserved to the implementation. Any attempt
4456 to attach an interrupt causes Program_Error to be raised, as described in
4457 RM C.3.2(22). A typical example is the @code{SIGINT} interrupt used in
4458 many systems for an @code{Ctrl-C} interrupt. Normally this interrupt is
4459 reserved to the implementation, so that @code{Ctrl-C} can be used to
4460 interrupt execution. Additionally, signals such as @code{SIGSEGV},
4461 @code{SIGABRT}, @code{SIGFPE} and @code{SIGILL} are often mapped to specific
4462 Ada exceptions, or used to implement run-time functions such as the
4463 @code{abort} statement and stack overflow checking.
4465 Pragma @code{Interrupt_State} provides a general mechanism for overriding
4466 such uses of interrupts. It subsumes the functionality of pragma
4467 @code{Unreserve_All_Interrupts}. Pragma @code{Interrupt_State} is not
4468 available on Windows or VMS. On all other platforms than VxWorks,
4469 it applies to signals; on VxWorks, it applies to vectored hardware interrupts
4470 and may be used to mark interrupts required by the board support package
4473 Interrupts can be in one of three states:
4481 The interrupt is reserved (no Ada handler can be installed), and the
4482 Ada run-time may not install a handler. As a result you are guaranteed
4483 standard system default action if this interrupt is raised. This also allows
4484 installing a low level handler via C APIs such as sigaction(), outside
4490 The interrupt is reserved (no Ada handler can be installed). The run time
4491 is allowed to install a handler for internal control purposes, but is
4492 not required to do so.
4497 The interrupt is unreserved. The user may install an Ada handler via
4498 Ada.Interrupts and pragma Interrupt_Handler or Attach_Handler to provide
4502 These states are the allowed values of the @code{State} parameter of the
4503 pragma. The @code{Name} parameter is a value of the type
4504 @code{Ada.Interrupts.Interrupt_ID}. Typically, it is a name declared in
4505 @code{Ada.Interrupts.Names}.
4507 This is a configuration pragma, and the binder will check that there
4508 are no inconsistencies between different units in a partition in how a
4509 given interrupt is specified. It may appear anywhere a pragma is legal.
4511 The effect is to move the interrupt to the specified state.
4513 By declaring interrupts to be SYSTEM, you guarantee the standard system
4514 action, such as a core dump.
4516 By declaring interrupts to be USER, you guarantee that you can install
4519 Note that certain signals on many operating systems cannot be caught and
4520 handled by applications. In such cases, the pragma is ignored. See the
4521 operating system documentation, or the value of the array @code{Reserved}
4522 declared in the spec of package @code{System.OS_Interface}.
4524 Overriding the default state of signals used by the Ada runtime may interfere
4525 with an application's runtime behavior in the cases of the synchronous signals,
4526 and in the case of the signal used to implement the @code{abort} statement.
4528 @node Pragma Invariant,Pragma Keep_Names,Pragma Interrupt_State,Implementation Defined Pragmas
4529 @anchor{gnat_rm/implementation_defined_pragmas id19}@anchor{88}@anchor{gnat_rm/implementation_defined_pragmas pragma-invariant}@anchor{89}
4530 @section Pragma Invariant
4537 ([Entity =>] private_type_LOCAL_NAME,
4538 [Check =>] EXPRESSION
4539 [,[Message =>] String_Expression]);
4542 This pragma provides exactly the same capabilities as the Type_Invariant aspect
4543 defined in AI05-0146-1, and in the Ada 2012 Reference Manual. The
4544 Type_Invariant aspect is fully implemented in Ada 2012 mode, but since it
4545 requires the use of the aspect syntax, which is not available except in 2012
4546 mode, it is not possible to use the Type_Invariant aspect in earlier versions
4547 of Ada. However the Invariant pragma may be used in any version of Ada. Also
4548 note that the aspect Invariant is a synonym in GNAT for the aspect
4549 Type_Invariant, but there is no pragma Type_Invariant.
4551 The pragma must appear within the visible part of the package specification,
4552 after the type to which its Entity argument appears. As with the Invariant
4553 aspect, the Check expression is not analyzed until the end of the visible
4554 part of the package, so it may contain forward references. The Message
4555 argument, if present, provides the exception message used if the invariant
4556 is violated. If no Message parameter is provided, a default message that
4557 identifies the line on which the pragma appears is used.
4559 It is permissible to have multiple Invariants for the same type entity, in
4560 which case they are and'ed together. It is permissible to use this pragma
4561 in Ada 2012 mode, but you cannot have both an invariant aspect and an
4562 invariant pragma for the same entity.
4564 For further details on the use of this pragma, see the Ada 2012 documentation
4565 of the Type_Invariant aspect.
4567 @node Pragma Keep_Names,Pragma License,Pragma Invariant,Implementation Defined Pragmas
4568 @anchor{gnat_rm/implementation_defined_pragmas pragma-keep-names}@anchor{8a}
4569 @section Pragma Keep_Names
4575 pragma Keep_Names ([On =>] enumeration_first_subtype_LOCAL_NAME);
4578 The @code{LOCAL_NAME} argument
4579 must refer to an enumeration first subtype
4580 in the current declarative part. The effect is to retain the enumeration
4581 literal names for use by @code{Image} and @code{Value} even if a global
4582 @code{Discard_Names} pragma applies. This is useful when you want to
4583 generally suppress enumeration literal names and for example you therefore
4584 use a @code{Discard_Names} pragma in the @code{gnat.adc} file, but you
4585 want to retain the names for specific enumeration types.
4587 @node Pragma License,Pragma Link_With,Pragma Keep_Names,Implementation Defined Pragmas
4588 @anchor{gnat_rm/implementation_defined_pragmas pragma-license}@anchor{8b}
4589 @section Pragma License
4592 @geindex License checking
4597 pragma License (Unrestricted | GPL | Modified_GPL | Restricted);
4600 This pragma is provided to allow automated checking for appropriate license
4601 conditions with respect to the standard and modified GPL. A pragma
4602 @code{License}, which is a configuration pragma that typically appears at
4603 the start of a source file or in a separate @code{gnat.adc} file, specifies
4604 the licensing conditions of a unit as follows:
4611 This is used for a unit that can be freely used with no license restrictions.
4612 Examples of such units are public domain units, and units from the Ada
4617 This is used for a unit that is licensed under the unmodified GPL, and which
4618 therefore cannot be @code{with}ed by a restricted unit.
4622 This is used for a unit licensed under the GNAT modified GPL that includes
4623 a special exception paragraph that specifically permits the inclusion of
4624 the unit in programs without requiring the entire program to be released
4629 This is used for a unit that is restricted in that it is not permitted to
4630 depend on units that are licensed under the GPL. Typical examples are
4631 proprietary code that is to be released under more restrictive license
4632 conditions. Note that restricted units are permitted to @code{with} units
4633 which are licensed under the modified GPL (this is the whole point of the
4637 Normally a unit with no @code{License} pragma is considered to have an
4638 unknown license, and no checking is done. However, standard GNAT headers
4639 are recognized, and license information is derived from them as follows.
4641 A GNAT license header starts with a line containing 78 hyphens. The following
4642 comment text is searched for the appearance of any of the following strings.
4644 If the string 'GNU General Public License' is found, then the unit is assumed
4645 to have GPL license, unless the string 'As a special exception' follows, in
4646 which case the license is assumed to be modified GPL.
4648 If one of the strings
4649 'This specification is adapted from the Ada Semantic Interface' or
4650 'This specification is derived from the Ada Reference Manual' is found
4651 then the unit is assumed to be unrestricted.
4653 These default actions means that a program with a restricted license pragma
4654 will automatically get warnings if a GPL unit is inappropriately
4655 @code{with}ed. For example, the program:
4660 procedure Secret_Stuff is
4665 if compiled with pragma @code{License} (@code{Restricted}) in a
4666 @code{gnat.adc} file will generate the warning:
4671 >>> license of withed unit "Sem_Ch3" is incompatible
4673 2. with GNAT.Sockets;
4674 3. procedure Secret_Stuff is
4677 Here we get a warning on @code{Sem_Ch3} since it is part of the GNAT
4678 compiler and is licensed under the
4679 GPL, but no warning for @code{GNAT.Sockets} which is part of the GNAT
4680 run time, and is therefore licensed under the modified GPL.
4682 @node Pragma Link_With,Pragma Linker_Alias,Pragma License,Implementation Defined Pragmas
4683 @anchor{gnat_rm/implementation_defined_pragmas pragma-link-with}@anchor{8c}
4684 @section Pragma Link_With
4690 pragma Link_With (static_string_EXPRESSION @{,static_string_EXPRESSION@});
4693 This pragma is provided for compatibility with certain Ada 83 compilers.
4694 It has exactly the same effect as pragma @code{Linker_Options} except
4695 that spaces occurring within one of the string expressions are treated
4696 as separators. For example, in the following case:
4699 pragma Link_With ("-labc -ldef");
4702 results in passing the strings @code{-labc} and @code{-ldef} as two
4703 separate arguments to the linker. In addition pragma Link_With allows
4704 multiple arguments, with the same effect as successive pragmas.
4706 @node Pragma Linker_Alias,Pragma Linker_Constructor,Pragma Link_With,Implementation Defined Pragmas
4707 @anchor{gnat_rm/implementation_defined_pragmas pragma-linker-alias}@anchor{8d}
4708 @section Pragma Linker_Alias
4714 pragma Linker_Alias (
4715 [Entity =>] LOCAL_NAME,
4716 [Target =>] static_string_EXPRESSION);
4719 @code{LOCAL_NAME} must refer to an object that is declared at the library
4720 level. This pragma establishes the given entity as a linker alias for the
4721 given target. It is equivalent to @code{__attribute__((alias))} in GNU C
4722 and causes @code{LOCAL_NAME} to be emitted as an alias for the symbol
4723 @code{static_string_EXPRESSION} in the object file, that is to say no space
4724 is reserved for @code{LOCAL_NAME} by the assembler and it will be resolved
4725 to the same address as @code{static_string_EXPRESSION} by the linker.
4727 The actual linker name for the target must be used (e.g., the fully
4728 encoded name with qualification in Ada, or the mangled name in C++),
4729 or it must be declared using the C convention with @code{pragma Import}
4730 or @code{pragma Export}.
4732 Not all target machines support this pragma. On some of them it is accepted
4733 only if @code{pragma Weak_External} has been applied to @code{LOCAL_NAME}.
4736 -- Example of the use of pragma Linker_Alias
4740 pragma Export (C, i);
4742 new_name_for_i : Integer;
4743 pragma Linker_Alias (new_name_for_i, "i");
4747 @node Pragma Linker_Constructor,Pragma Linker_Destructor,Pragma Linker_Alias,Implementation Defined Pragmas
4748 @anchor{gnat_rm/implementation_defined_pragmas pragma-linker-constructor}@anchor{8e}
4749 @section Pragma Linker_Constructor
4755 pragma Linker_Constructor (procedure_LOCAL_NAME);
4758 @code{procedure_LOCAL_NAME} must refer to a parameterless procedure that
4759 is declared at the library level. A procedure to which this pragma is
4760 applied will be treated as an initialization routine by the linker.
4761 It is equivalent to @code{__attribute__((constructor))} in GNU C and
4762 causes @code{procedure_LOCAL_NAME} to be invoked before the entry point
4763 of the executable is called (or immediately after the shared library is
4764 loaded if the procedure is linked in a shared library), in particular
4765 before the Ada run-time environment is set up.
4767 Because of these specific contexts, the set of operations such a procedure
4768 can perform is very limited and the type of objects it can manipulate is
4769 essentially restricted to the elementary types. In particular, it must only
4770 contain code to which pragma Restrictions (No_Elaboration_Code) applies.
4772 This pragma is used by GNAT to implement auto-initialization of shared Stand
4773 Alone Libraries, which provides a related capability without the restrictions
4774 listed above. Where possible, the use of Stand Alone Libraries is preferable
4775 to the use of this pragma.
4777 @node Pragma Linker_Destructor,Pragma Linker_Section,Pragma Linker_Constructor,Implementation Defined Pragmas
4778 @anchor{gnat_rm/implementation_defined_pragmas pragma-linker-destructor}@anchor{8f}
4779 @section Pragma Linker_Destructor
4785 pragma Linker_Destructor (procedure_LOCAL_NAME);
4788 @code{procedure_LOCAL_NAME} must refer to a parameterless procedure that
4789 is declared at the library level. A procedure to which this pragma is
4790 applied will be treated as a finalization routine by the linker.
4791 It is equivalent to @code{__attribute__((destructor))} in GNU C and
4792 causes @code{procedure_LOCAL_NAME} to be invoked after the entry point
4793 of the executable has exited (or immediately before the shared library
4794 is unloaded if the procedure is linked in a shared library), in particular
4795 after the Ada run-time environment is shut down.
4797 See @code{pragma Linker_Constructor} for the set of restrictions that apply
4798 because of these specific contexts.
4800 @node Pragma Linker_Section,Pragma Lock_Free,Pragma Linker_Destructor,Implementation Defined Pragmas
4801 @anchor{gnat_rm/implementation_defined_pragmas id20}@anchor{90}@anchor{gnat_rm/implementation_defined_pragmas pragma-linker-section}@anchor{91}
4802 @section Pragma Linker_Section
4808 pragma Linker_Section (
4809 [Entity =>] LOCAL_NAME,
4810 [Section =>] static_string_EXPRESSION);
4813 @code{LOCAL_NAME} must refer to an object, type, or subprogram that is
4814 declared at the library level. This pragma specifies the name of the
4815 linker section for the given entity. It is equivalent to
4816 @code{__attribute__((section))} in GNU C and causes @code{LOCAL_NAME} to
4817 be placed in the @code{static_string_EXPRESSION} section of the
4818 executable (assuming the linker doesn't rename the section).
4819 GNAT also provides an implementation defined aspect of the same name.
4821 In the case of specifying this aspect for a type, the effect is to
4822 specify the corresponding section for all library-level objects of
4823 the type that do not have an explicit linker section set. Note that
4824 this only applies to whole objects, not to components of composite objects.
4826 In the case of a subprogram, the linker section applies to all previously
4827 declared matching overloaded subprograms in the current declarative part
4828 which do not already have a linker section assigned. The linker section
4829 aspect is useful in this case for specifying different linker sections
4830 for different elements of such an overloaded set.
4832 Note that an empty string specifies that no linker section is specified.
4833 This is not quite the same as omitting the pragma or aspect, since it
4834 can be used to specify that one element of an overloaded set of subprograms
4835 has the default linker section, or that one object of a type for which a
4836 linker section is specified should has the default linker section.
4838 The compiler normally places library-level entities in standard sections
4839 depending on the class: procedures and functions generally go in the
4840 @code{.text} section, initialized variables in the @code{.data} section
4841 and uninitialized variables in the @code{.bss} section.
4843 Other, special sections may exist on given target machines to map special
4844 hardware, for example I/O ports or flash memory. This pragma is a means to
4845 defer the final layout of the executable to the linker, thus fully working
4846 at the symbolic level with the compiler.
4848 Some file formats do not support arbitrary sections so not all target
4849 machines support this pragma. The use of this pragma may cause a program
4850 execution to be erroneous if it is used to place an entity into an
4851 inappropriate section (e.g., a modified variable into the @code{.text}
4852 section). See also @code{pragma Persistent_BSS}.
4855 -- Example of the use of pragma Linker_Section
4859 pragma Volatile (Port_A);
4860 pragma Linker_Section (Port_A, ".bss.port_a");
4863 pragma Volatile (Port_B);
4864 pragma Linker_Section (Port_B, ".bss.port_b");
4866 type Port_Type is new Integer with Linker_Section => ".bss";
4867 PA : Port_Type with Linker_Section => ".bss.PA";
4868 PB : Port_Type; -- ends up in linker section ".bss"
4870 procedure Q with Linker_Section => "Qsection";
4874 @node Pragma Lock_Free,Pragma Loop_Invariant,Pragma Linker_Section,Implementation Defined Pragmas
4875 @anchor{gnat_rm/implementation_defined_pragmas id21}@anchor{92}@anchor{gnat_rm/implementation_defined_pragmas pragma-lock-free}@anchor{93}
4876 @section Pragma Lock_Free
4880 This pragma may be specified for protected types or objects. It specifies that
4881 the implementation of protected operations must be implemented without locks.
4882 Compilation fails if the compiler cannot generate lock-free code for the
4885 @node Pragma Loop_Invariant,Pragma Loop_Optimize,Pragma Lock_Free,Implementation Defined Pragmas
4886 @anchor{gnat_rm/implementation_defined_pragmas pragma-loop-invariant}@anchor{94}
4887 @section Pragma Loop_Invariant
4893 pragma Loop_Invariant ( boolean_EXPRESSION );
4896 The effect of this pragma is similar to that of pragma @code{Assert},
4897 except that in an @code{Assertion_Policy} pragma, the identifier
4898 @code{Loop_Invariant} is used to control whether it is ignored or checked
4901 @code{Loop_Invariant} can only appear as one of the items in the sequence
4902 of statements of a loop body, or nested inside block statements that
4903 appear in the sequence of statements of a loop body.
4904 The intention is that it be used to
4905 represent a "loop invariant" assertion, i.e. something that is true each
4906 time through the loop, and which can be used to show that the loop is
4907 achieving its purpose.
4909 Multiple @code{Loop_Invariant} and @code{Loop_Variant} pragmas that
4910 apply to the same loop should be grouped in the same sequence of
4913 To aid in writing such invariants, the special attribute @code{Loop_Entry}
4914 may be used to refer to the value of an expression on entry to the loop. This
4915 attribute can only be used within the expression of a @code{Loop_Invariant}
4916 pragma. For full details, see documentation of attribute @code{Loop_Entry}.
4918 @node Pragma Loop_Optimize,Pragma Loop_Variant,Pragma Loop_Invariant,Implementation Defined Pragmas
4919 @anchor{gnat_rm/implementation_defined_pragmas pragma-loop-optimize}@anchor{95}
4920 @section Pragma Loop_Optimize
4926 pragma Loop_Optimize (OPTIMIZATION_HINT @{, OPTIMIZATION_HINT@});
4928 OPTIMIZATION_HINT ::= Ivdep | No_Unroll | Unroll | No_Vector | Vector
4931 This pragma must appear immediately within a loop statement. It allows the
4932 programmer to specify optimization hints for the enclosing loop. The hints
4933 are not mutually exclusive and can be freely mixed, but not all combinations
4934 will yield a sensible outcome.
4936 There are five supported optimization hints for a loop:
4944 The programmer asserts that there are no loop-carried dependencies
4945 which would prevent consecutive iterations of the loop from being
4946 executed simultaneously.
4951 The loop must not be unrolled. This is a strong hint: the compiler will not
4952 unroll a loop marked with this hint.
4957 The loop should be unrolled. This is a weak hint: the compiler will try to
4958 apply unrolling to this loop preferably to other optimizations, notably
4959 vectorization, but there is no guarantee that the loop will be unrolled.
4964 The loop must not be vectorized. This is a strong hint: the compiler will not
4965 vectorize a loop marked with this hint.
4970 The loop should be vectorized. This is a weak hint: the compiler will try to
4971 apply vectorization to this loop preferably to other optimizations, notably
4972 unrolling, but there is no guarantee that the loop will be vectorized.
4975 These hints do not remove the need to pass the appropriate switches to the
4976 compiler in order to enable the relevant optimizations, that is to say
4977 @emph{-funroll-loops} for unrolling and @emph{-ftree-vectorize} for
4980 @node Pragma Loop_Variant,Pragma Machine_Attribute,Pragma Loop_Optimize,Implementation Defined Pragmas
4981 @anchor{gnat_rm/implementation_defined_pragmas pragma-loop-variant}@anchor{96}
4982 @section Pragma Loop_Variant
4988 pragma Loop_Variant ( LOOP_VARIANT_ITEM @{, LOOP_VARIANT_ITEM @} );
4989 LOOP_VARIANT_ITEM ::= CHANGE_DIRECTION => discrete_EXPRESSION
4990 CHANGE_DIRECTION ::= Increases | Decreases
4993 @code{Loop_Variant} can only appear as one of the items in the sequence
4994 of statements of a loop body, or nested inside block statements that
4995 appear in the sequence of statements of a loop body.
4996 It allows the specification of quantities which must always
4997 decrease or increase in successive iterations of the loop. In its simplest
4998 form, just one expression is specified, whose value must increase or decrease
4999 on each iteration of the loop.
5001 In a more complex form, multiple arguments can be given which are intepreted
5002 in a nesting lexicographic manner. For example:
5005 pragma Loop_Variant (Increases => X, Decreases => Y);
5008 specifies that each time through the loop either X increases, or X stays
5009 the same and Y decreases. A @code{Loop_Variant} pragma ensures that the
5010 loop is making progress. It can be useful in helping to show informally
5011 or prove formally that the loop always terminates.
5013 @code{Loop_Variant} is an assertion whose effect can be controlled using
5014 an @code{Assertion_Policy} with a check name of @code{Loop_Variant}. The
5015 policy can be @code{Check} to enable the loop variant check, @code{Ignore}
5016 to ignore the check (in which case the pragma has no effect on the program),
5017 or @code{Disable} in which case the pragma is not even checked for correct
5020 Multiple @code{Loop_Invariant} and @code{Loop_Variant} pragmas that
5021 apply to the same loop should be grouped in the same sequence of
5024 The @code{Loop_Entry} attribute may be used within the expressions of the
5025 @code{Loop_Variant} pragma to refer to values on entry to the loop.
5027 @node Pragma Machine_Attribute,Pragma Main,Pragma Loop_Variant,Implementation Defined Pragmas
5028 @anchor{gnat_rm/implementation_defined_pragmas pragma-machine-attribute}@anchor{97}
5029 @section Pragma Machine_Attribute
5035 pragma Machine_Attribute (
5036 [Entity =>] LOCAL_NAME,
5037 [Attribute_Name =>] static_string_EXPRESSION
5038 [, [Info =>] static_EXPRESSION] );
5041 Machine-dependent attributes can be specified for types and/or
5042 declarations. This pragma is semantically equivalent to
5043 @code{__attribute__((@emph{attribute_name}))} (if @code{info} is not
5044 specified) or @code{__attribute__((@emph{attribute_name(info})))}
5045 in GNU C, where @emph{attribute_name} is recognized by the
5046 compiler middle-end or the @code{TARGET_ATTRIBUTE_TABLE} machine
5047 specific macro. A string literal for the optional parameter @code{info}
5048 is transformed into an identifier, which may make this pragma unusable
5049 for some attributes.
5050 For further information see @cite{GNU Compiler Collection (GCC) Internals}.
5052 @node Pragma Main,Pragma Main_Storage,Pragma Machine_Attribute,Implementation Defined Pragmas
5053 @anchor{gnat_rm/implementation_defined_pragmas pragma-main}@anchor{98}
5054 @section Pragma Main
5061 (MAIN_OPTION [, MAIN_OPTION]);
5064 [Stack_Size =>] static_integer_EXPRESSION
5065 | [Task_Stack_Size_Default =>] static_integer_EXPRESSION
5066 | [Time_Slicing_Enabled =>] static_boolean_EXPRESSION
5069 This pragma is provided for compatibility with OpenVMS VAX Systems. It has
5070 no effect in GNAT, other than being syntax checked.
5072 @node Pragma Main_Storage,Pragma Max_Queue_Length,Pragma Main,Implementation Defined Pragmas
5073 @anchor{gnat_rm/implementation_defined_pragmas pragma-main-storage}@anchor{99}
5074 @section Pragma Main_Storage
5081 (MAIN_STORAGE_OPTION [, MAIN_STORAGE_OPTION]);
5083 MAIN_STORAGE_OPTION ::=
5084 [WORKING_STORAGE =>] static_SIMPLE_EXPRESSION
5085 | [TOP_GUARD =>] static_SIMPLE_EXPRESSION
5088 This pragma is provided for compatibility with OpenVMS VAX Systems. It has
5089 no effect in GNAT, other than being syntax checked.
5091 @node Pragma Max_Queue_Length,Pragma No_Body,Pragma Main_Storage,Implementation Defined Pragmas
5092 @anchor{gnat_rm/implementation_defined_pragmas id22}@anchor{9a}@anchor{gnat_rm/implementation_defined_pragmas pragma-max-queue-length}@anchor{9b}
5093 @section Pragma Max_Queue_Length
5099 pragma Max_Entry_Queue (static_integer_EXPRESSION);
5102 This pragma is used to specify the maximum callers per entry queue for
5103 individual protected entries and entry families. It accepts a single
5104 positive integer as a parameter and must appear after the declaration
5107 @node Pragma No_Body,Pragma No_Component_Reordering,Pragma Max_Queue_Length,Implementation Defined Pragmas
5108 @anchor{gnat_rm/implementation_defined_pragmas pragma-no-body}@anchor{9c}
5109 @section Pragma No_Body
5118 There are a number of cases in which a package spec does not require a body,
5119 and in fact a body is not permitted. GNAT will not permit the spec to be
5120 compiled if there is a body around. The pragma No_Body allows you to provide
5121 a body file, even in a case where no body is allowed. The body file must
5122 contain only comments and a single No_Body pragma. This is recognized by
5123 the compiler as indicating that no body is logically present.
5125 This is particularly useful during maintenance when a package is modified in
5126 such a way that a body needed before is no longer needed. The provision of a
5127 dummy body with a No_Body pragma ensures that there is no interference from
5128 earlier versions of the package body.
5130 @node Pragma No_Component_Reordering,Pragma No_Elaboration_Code_All,Pragma No_Body,Implementation Defined Pragmas
5131 @anchor{gnat_rm/implementation_defined_pragmas pragma-no-component-reordering}@anchor{9d}
5132 @section Pragma No_Component_Reordering
5138 pragma No_Component_Reordering [([Entity =>] type_LOCAL_NAME)];
5141 @code{type_LOCAL_NAME} must refer to a record type declaration in the current
5142 declarative part. The effect is to preclude any reordering of components
5143 for the layout of the record, i.e. the record is laid out by the compiler
5144 in the order in which the components are declared textually. The form with
5145 no argument is a configuration pragma which applies to all record types
5146 declared in units to which the pragma applies and there is a requirement
5147 that this pragma be used consistently within a partition.
5149 @node Pragma No_Elaboration_Code_All,Pragma No_Heap_Finalization,Pragma No_Component_Reordering,Implementation Defined Pragmas
5150 @anchor{gnat_rm/implementation_defined_pragmas id23}@anchor{9e}@anchor{gnat_rm/implementation_defined_pragmas pragma-no-elaboration-code-all}@anchor{9f}
5151 @section Pragma No_Elaboration_Code_All
5157 pragma No_Elaboration_Code_All [(program_unit_NAME)];
5160 This is a program unit pragma (there is also an equivalent aspect of the
5161 same name) that establishes the restriction @code{No_Elaboration_Code} for
5162 the current unit and any extended main source units (body and subunits).
5163 It also has the effect of enforcing a transitive application of this
5164 aspect, so that if any unit is implicitly or explicitly with'ed by the
5165 current unit, it must also have the No_Elaboration_Code_All aspect set.
5166 It may be applied to package or subprogram specs or their generic versions.
5168 @node Pragma No_Heap_Finalization,Pragma No_Inline,Pragma No_Elaboration_Code_All,Implementation Defined Pragmas
5169 @anchor{gnat_rm/implementation_defined_pragmas pragma-no-heap-finalization}@anchor{a0}
5170 @section Pragma No_Heap_Finalization
5176 pragma No_Heap_Finalization [ (first_subtype_LOCAL_NAME) ];
5179 Pragma @code{No_Heap_Finalization} may be used as a configuration pragma or as a
5180 type-specific pragma.
5182 In its configuration form, the pragma must appear within a configuration file
5183 such as gnat.adc, without an argument. The pragma suppresses the call to
5184 @code{Finalize} for heap-allocated objects created through library-level named
5185 access-to-object types in cases where the designated type requires finalization
5188 In its type-specific form, the argument of the pragma must denote a
5189 library-level named access-to-object type. The pragma suppresses the call to
5190 @code{Finalize} for heap-allocated objects created through the specific access type
5191 in cases where the designated type requires finalization actions.
5193 It is still possible to finalize such heap-allocated objects by explicitly
5196 A library-level named access-to-object type declared within a generic unit will
5197 lose its @code{No_Heap_Finalization} pragma when the corresponding instance does not
5198 appear at the library level.
5200 @node Pragma No_Inline,Pragma No_Return,Pragma No_Heap_Finalization,Implementation Defined Pragmas
5201 @anchor{gnat_rm/implementation_defined_pragmas id24}@anchor{a1}@anchor{gnat_rm/implementation_defined_pragmas pragma-no-inline}@anchor{a2}
5202 @section Pragma No_Inline
5208 pragma No_Inline (NAME @{, NAME@});
5211 This pragma suppresses inlining for the callable entity or the instances of
5212 the generic subprogram designated by @code{NAME}, including inlining that
5213 results from the use of pragma @code{Inline}. This pragma is always active,
5214 in particular it is not subject to the use of option @emph{-gnatn} or
5215 @emph{-gnatN}. It is illegal to specify both pragma @code{No_Inline} and
5216 pragma @code{Inline_Always} for the same @code{NAME}.
5218 @node Pragma No_Return,Pragma No_Run_Time,Pragma No_Inline,Implementation Defined Pragmas
5219 @anchor{gnat_rm/implementation_defined_pragmas pragma-no-return}@anchor{a3}
5220 @section Pragma No_Return
5226 pragma No_Return (procedure_LOCAL_NAME @{, procedure_LOCAL_NAME@});
5229 Each @code{procedure_LOCAL_NAME} argument must refer to one or more procedure
5230 declarations in the current declarative part. A procedure to which this
5231 pragma is applied may not contain any explicit @code{return} statements.
5232 In addition, if the procedure contains any implicit returns from falling
5233 off the end of a statement sequence, then execution of that implicit
5234 return will cause Program_Error to be raised.
5236 One use of this pragma is to identify procedures whose only purpose is to raise
5237 an exception. Another use of this pragma is to suppress incorrect warnings
5238 about missing returns in functions, where the last statement of a function
5239 statement sequence is a call to such a procedure.
5241 Note that in Ada 2005 mode, this pragma is part of the language. It is
5242 available in all earlier versions of Ada as an implementation-defined
5245 @node Pragma No_Run_Time,Pragma No_Strict_Aliasing,Pragma No_Return,Implementation Defined Pragmas
5246 @anchor{gnat_rm/implementation_defined_pragmas pragma-no-run-time}@anchor{a4}
5247 @section Pragma No_Run_Time
5256 This is an obsolete configuration pragma that historically was used to
5257 set up a runtime library with no object code. It is now used only for
5258 internal testing. The pragma has been superseded by the reconfigurable
5259 runtime capability of GNAT.
5261 @node Pragma No_Strict_Aliasing,Pragma No_Tagged_Streams,Pragma No_Run_Time,Implementation Defined Pragmas
5262 @anchor{gnat_rm/implementation_defined_pragmas pragma-no-strict-aliasing}@anchor{a5}
5263 @section Pragma No_Strict_Aliasing
5269 pragma No_Strict_Aliasing [([Entity =>] type_LOCAL_NAME)];
5272 @code{type_LOCAL_NAME} must refer to an access type
5273 declaration in the current declarative part. The effect is to inhibit
5274 strict aliasing optimization for the given type. The form with no
5275 arguments is a configuration pragma which applies to all access types
5276 declared in units to which the pragma applies. For a detailed
5277 description of the strict aliasing optimization, and the situations
5278 in which it must be suppressed, see the section on Optimization and Strict Aliasing
5279 in the @cite{GNAT User's Guide}.
5281 This pragma currently has no effects on access to unconstrained array types.
5283 @node Pragma No_Tagged_Streams,Pragma Normalize_Scalars,Pragma No_Strict_Aliasing,Implementation Defined Pragmas
5284 @anchor{gnat_rm/implementation_defined_pragmas pragma-no-tagged-streams}@anchor{a6}@anchor{gnat_rm/implementation_defined_pragmas id25}@anchor{a7}
5285 @section Pragma No_Tagged_Streams
5291 pragma No_Tagged_Streams [([Entity =>] tagged_type_LOCAL_NAME)];
5294 Normally when a tagged type is introduced using a full type declaration,
5295 part of the processing includes generating stream access routines to be
5296 used by stream attributes referencing the type (or one of its subtypes
5297 or derived types). This can involve the generation of significant amounts
5298 of code which is wasted space if stream routines are not needed for the
5301 The @code{No_Tagged_Streams} pragma causes the generation of these stream
5302 routines to be skipped, and any attempt to use stream operations on
5303 types subject to this pragma will be statically rejected as illegal.
5305 There are two forms of the pragma. The form with no arguments must appear
5306 in a declarative sequence or in the declarations of a package spec. This
5307 pragma affects all subsequent root tagged types declared in the declaration
5308 sequence, and specifies that no stream routines be generated. The form with
5309 an argument (for which there is also a corresponding aspect) specifies a
5310 single root tagged type for which stream routines are not to be generated.
5312 Once the pragma has been given for a particular root tagged type, all subtypes
5313 and derived types of this type inherit the pragma automatically, so the effect
5314 applies to a complete hierarchy (this is necessary to deal with the class-wide
5315 dispatching versions of the stream routines).
5317 @node Pragma Normalize_Scalars,Pragma Obsolescent,Pragma No_Tagged_Streams,Implementation Defined Pragmas
5318 @anchor{gnat_rm/implementation_defined_pragmas pragma-normalize-scalars}@anchor{a8}
5319 @section Pragma Normalize_Scalars
5325 pragma Normalize_Scalars;
5328 This is a language defined pragma which is fully implemented in GNAT. The
5329 effect is to cause all scalar objects that are not otherwise initialized
5330 to be initialized. The initial values are implementation dependent and
5336 @item @emph{Standard.Character}
5338 Objects whose root type is Standard.Character are initialized to
5339 Character'Last unless the subtype range excludes NUL (in which case
5340 NUL is used). This choice will always generate an invalid value if
5343 @item @emph{Standard.Wide_Character}
5345 Objects whose root type is Standard.Wide_Character are initialized to
5346 Wide_Character'Last unless the subtype range excludes NUL (in which case
5347 NUL is used). This choice will always generate an invalid value if
5350 @item @emph{Standard.Wide_Wide_Character}
5352 Objects whose root type is Standard.Wide_Wide_Character are initialized to
5353 the invalid value 16#FFFF_FFFF# unless the subtype range excludes NUL (in
5354 which case NUL is used). This choice will always generate an invalid value if
5357 @item @emph{Integer types}
5359 Objects of an integer type are treated differently depending on whether
5360 negative values are present in the subtype. If no negative values are
5361 present, then all one bits is used as the initial value except in the
5362 special case where zero is excluded from the subtype, in which case
5363 all zero bits are used. This choice will always generate an invalid
5364 value if one exists.
5366 For subtypes with negative values present, the largest negative number
5367 is used, except in the unusual case where this largest negative number
5368 is in the subtype, and the largest positive number is not, in which case
5369 the largest positive value is used. This choice will always generate
5370 an invalid value if one exists.
5372 @item @emph{Floating-Point Types}
5374 Objects of all floating-point types are initialized to all 1-bits. For
5375 standard IEEE format, this corresponds to a NaN (not a number) which is
5376 indeed an invalid value.
5378 @item @emph{Fixed-Point Types}
5380 Objects of all fixed-point types are treated as described above for integers,
5381 with the rules applying to the underlying integer value used to represent
5382 the fixed-point value.
5384 @item @emph{Modular types}
5386 Objects of a modular type are initialized to all one bits, except in
5387 the special case where zero is excluded from the subtype, in which
5388 case all zero bits are used. This choice will always generate an
5389 invalid value if one exists.
5391 @item @emph{Enumeration types}
5393 Objects of an enumeration type are initialized to all one-bits, i.e., to
5394 the value @code{2 ** typ'Size - 1} unless the subtype excludes the literal
5395 whose Pos value is zero, in which case a code of zero is used. This choice
5396 will always generate an invalid value if one exists.
5399 @node Pragma Obsolescent,Pragma Optimize_Alignment,Pragma Normalize_Scalars,Implementation Defined Pragmas
5400 @anchor{gnat_rm/implementation_defined_pragmas pragma-obsolescent}@anchor{a9}@anchor{gnat_rm/implementation_defined_pragmas id26}@anchor{aa}
5401 @section Pragma Obsolescent
5409 pragma Obsolescent (
5410 [Message =>] static_string_EXPRESSION
5411 [,[Version =>] Ada_05]]);
5413 pragma Obsolescent (
5415 [,[Message =>] static_string_EXPRESSION
5416 [,[Version =>] Ada_05]] );
5419 This pragma can occur immediately following a declaration of an entity,
5420 including the case of a record component. If no Entity argument is present,
5421 then this declaration is the one to which the pragma applies. If an Entity
5422 parameter is present, it must either match the name of the entity in this
5423 declaration, or alternatively, the pragma can immediately follow an enumeration
5424 type declaration, where the Entity argument names one of the enumeration
5427 This pragma is used to indicate that the named entity
5428 is considered obsolescent and should not be used. Typically this is
5429 used when an API must be modified by eventually removing or modifying
5430 existing subprograms or other entities. The pragma can be used at an
5431 intermediate stage when the entity is still present, but will be
5434 The effect of this pragma is to output a warning message on a reference to
5435 an entity thus marked that the subprogram is obsolescent if the appropriate
5436 warning option in the compiler is activated. If the @code{Message} parameter is
5437 present, then a second warning message is given containing this text. In
5438 addition, a reference to the entity is considered to be a violation of pragma
5439 @code{Restrictions (No_Obsolescent_Features)}.
5441 This pragma can also be used as a program unit pragma for a package,
5442 in which case the entity name is the name of the package, and the
5443 pragma indicates that the entire package is considered
5444 obsolescent. In this case a client @code{with}ing such a package
5445 violates the restriction, and the @code{with} clause is
5446 flagged with warnings if the warning option is set.
5448 If the @code{Version} parameter is present (which must be exactly
5449 the identifier @code{Ada_05}, no other argument is allowed), then the
5450 indication of obsolescence applies only when compiling in Ada 2005
5451 mode. This is primarily intended for dealing with the situations
5452 in the predefined library where subprograms or packages
5453 have become defined as obsolescent in Ada 2005
5454 (e.g., in @code{Ada.Characters.Handling}), but may be used anywhere.
5456 The following examples show typical uses of this pragma:
5460 pragma Obsolescent (p, Message => "use pp instead of p");
5465 pragma Obsolescent ("use q2new instead");
5467 type R is new integer;
5470 Message => "use RR in Ada 2005",
5480 type E is (a, bc, 'd', quack);
5481 pragma Obsolescent (Entity => bc)
5482 pragma Obsolescent (Entity => 'd')
5485 (a, b : character) return character;
5486 pragma Obsolescent (Entity => "+");
5490 Note that, as for all pragmas, if you use a pragma argument identifier,
5491 then all subsequent parameters must also use a pragma argument identifier.
5492 So if you specify @code{Entity =>} for the @code{Entity} argument, and a @code{Message}
5493 argument is present, it must be preceded by @code{Message =>}.
5495 @node Pragma Optimize_Alignment,Pragma Ordered,Pragma Obsolescent,Implementation Defined Pragmas
5496 @anchor{gnat_rm/implementation_defined_pragmas pragma-optimize-alignment}@anchor{ab}
5497 @section Pragma Optimize_Alignment
5501 @geindex default settings
5506 pragma Optimize_Alignment (TIME | SPACE | OFF);
5509 This is a configuration pragma which affects the choice of default alignments
5510 for types and objects where no alignment is explicitly specified. There is a
5511 time/space trade-off in the selection of these values. Large alignments result
5512 in more efficient code, at the expense of larger data space, since sizes have
5513 to be increased to match these alignments. Smaller alignments save space, but
5514 the access code is slower. The normal choice of default alignments for types
5515 and individual alignment promotions for objects (which is what you get if you
5516 do not use this pragma, or if you use an argument of OFF), tries to balance
5517 these two requirements.
5519 Specifying SPACE causes smaller default alignments to be chosen in two cases.
5520 First any packed record is given an alignment of 1. Second, if a size is given
5521 for the type, then the alignment is chosen to avoid increasing this size. For
5533 In the default mode, this type gets an alignment of 4, so that access to the
5534 Integer field X are efficient. But this means that objects of the type end up
5535 with a size of 8 bytes. This is a valid choice, since sizes of objects are
5536 allowed to be bigger than the size of the type, but it can waste space if for
5537 example fields of type R appear in an enclosing record. If the above type is
5538 compiled in @code{Optimize_Alignment (Space)} mode, the alignment is set to 1.
5540 However, there is one case in which SPACE is ignored. If a variable length
5541 record (that is a discriminated record with a component which is an array
5542 whose length depends on a discriminant), has a pragma Pack, then it is not
5543 in general possible to set the alignment of such a record to one, so the
5544 pragma is ignored in this case (with a warning).
5546 Specifying SPACE also disables alignment promotions for standalone objects,
5547 which occur when the compiler increases the alignment of a specific object
5548 without changing the alignment of its type.
5550 Specifying SPACE also disables component reordering in unpacked record types,
5551 which can result in larger sizes in order to meet alignment requirements.
5553 Specifying TIME causes larger default alignments to be chosen in the case of
5554 small types with sizes that are not a power of 2. For example, consider:
5567 The default alignment for this record is normally 1, but if this type is
5568 compiled in @code{Optimize_Alignment (Time)} mode, then the alignment is set
5569 to 4, which wastes space for objects of the type, since they are now 4 bytes
5570 long, but results in more efficient access when the whole record is referenced.
5572 As noted above, this is a configuration pragma, and there is a requirement
5573 that all units in a partition be compiled with a consistent setting of the
5574 optimization setting. This would normally be achieved by use of a configuration
5575 pragma file containing the appropriate setting. The exception to this rule is
5576 that units with an explicit configuration pragma in the same file as the source
5577 unit are excluded from the consistency check, as are all predefined units. The
5578 latter are compiled by default in pragma Optimize_Alignment (Off) mode if no
5579 pragma appears at the start of the file.
5581 @node Pragma Ordered,Pragma Overflow_Mode,Pragma Optimize_Alignment,Implementation Defined Pragmas
5582 @anchor{gnat_rm/implementation_defined_pragmas pragma-ordered}@anchor{ac}
5583 @section Pragma Ordered
5589 pragma Ordered (enumeration_first_subtype_LOCAL_NAME);
5592 Most enumeration types are from a conceptual point of view unordered.
5593 For example, consider:
5596 type Color is (Red, Blue, Green, Yellow);
5599 By Ada semantics @code{Blue > Red} and @code{Green > Blue},
5600 but really these relations make no sense; the enumeration type merely
5601 specifies a set of possible colors, and the order is unimportant.
5603 For unordered enumeration types, it is generally a good idea if
5604 clients avoid comparisons (other than equality or inequality) and
5605 explicit ranges. (A @emph{client} is a unit where the type is referenced,
5606 other than the unit where the type is declared, its body, and its subunits.)
5607 For example, if code buried in some client says:
5610 if Current_Color < Yellow then ...
5611 if Current_Color in Blue .. Green then ...
5614 then the client code is relying on the order, which is undesirable.
5615 It makes the code hard to read and creates maintenance difficulties if
5616 entries have to be added to the enumeration type. Instead,
5617 the code in the client should list the possibilities, or an
5618 appropriate subtype should be declared in the unit that declares
5619 the original enumeration type. E.g., the following subtype could
5620 be declared along with the type @code{Color}:
5623 subtype RBG is Color range Red .. Green;
5626 and then the client could write:
5629 if Current_Color in RBG then ...
5630 if Current_Color = Blue or Current_Color = Green then ...
5633 However, some enumeration types are legitimately ordered from a conceptual
5634 point of view. For example, if you declare:
5637 type Day is (Mon, Tue, Wed, Thu, Fri, Sat, Sun);
5640 then the ordering imposed by the language is reasonable, and
5641 clients can depend on it, writing for example:
5644 if D in Mon .. Fri then ...
5648 The pragma @emph{Ordered} is provided to mark enumeration types that
5649 are conceptually ordered, alerting the reader that clients may depend
5650 on the ordering. GNAT provides a pragma to mark enumerations as ordered
5651 rather than one to mark them as unordered, since in our experience,
5652 the great majority of enumeration types are conceptually unordered.
5654 The types @code{Boolean}, @code{Character}, @code{Wide_Character},
5655 and @code{Wide_Wide_Character}
5656 are considered to be ordered types, so each is declared with a
5657 pragma @code{Ordered} in package @code{Standard}.
5659 Normally pragma @code{Ordered} serves only as documentation and a guide for
5660 coding standards, but GNAT provides a warning switch @emph{-gnatw.u} that
5661 requests warnings for inappropriate uses (comparisons and explicit
5662 subranges) for unordered types. If this switch is used, then any
5663 enumeration type not marked with pragma @code{Ordered} will be considered
5664 as unordered, and will generate warnings for inappropriate uses.
5666 Note that generic types are not considered ordered or unordered (since the
5667 template can be instantiated for both cases), so we never generate warnings
5668 for the case of generic enumerated types.
5670 For additional information please refer to the description of the
5671 @emph{-gnatw.u} switch in the GNAT User's Guide.
5673 @node Pragma Overflow_Mode,Pragma Overriding_Renamings,Pragma Ordered,Implementation Defined Pragmas
5674 @anchor{gnat_rm/implementation_defined_pragmas pragma-overflow-mode}@anchor{ad}
5675 @section Pragma Overflow_Mode
5681 pragma Overflow_Mode
5683 [,[Assertions =>] MODE]);
5685 MODE ::= STRICT | MINIMIZED | ELIMINATED
5688 This pragma sets the current overflow mode to the given setting. For details
5689 of the meaning of these modes, please refer to the
5690 'Overflow Check Handling in GNAT' appendix in the
5691 GNAT User's Guide. If only the @code{General} parameter is present,
5692 the given mode applies to all expressions. If both parameters are present,
5693 the @code{General} mode applies to expressions outside assertions, and
5694 the @code{Eliminated} mode applies to expressions within assertions.
5696 The case of the @code{MODE} parameter is ignored,
5697 so @code{MINIMIZED}, @code{Minimized} and
5698 @code{minimized} all have the same effect.
5700 The @code{Overflow_Mode} pragma has the same scoping and placement
5701 rules as pragma @code{Suppress}, so it can occur either as a
5702 configuration pragma, specifying a default for the whole
5703 program, or in a declarative scope, where it applies to the
5704 remaining declarations and statements in that scope.
5706 The pragma @code{Suppress (Overflow_Check)} suppresses
5707 overflow checking, but does not affect the overflow mode.
5709 The pragma @code{Unsuppress (Overflow_Check)} unsuppresses (enables)
5710 overflow checking, but does not affect the overflow mode.
5712 @node Pragma Overriding_Renamings,Pragma Partition_Elaboration_Policy,Pragma Overflow_Mode,Implementation Defined Pragmas
5713 @anchor{gnat_rm/implementation_defined_pragmas pragma-overriding-renamings}@anchor{ae}
5714 @section Pragma Overriding_Renamings
5717 @geindex Rational profile
5719 @geindex Rational compatibility
5724 pragma Overriding_Renamings;
5727 This is a GNAT configuration pragma to simplify porting
5728 legacy code accepted by the Rational
5729 Ada compiler. In the presence of this pragma, a renaming declaration that
5730 renames an inherited operation declared in the same scope is legal if selected
5731 notation is used as in:
5734 pragma Overriding_Renamings;
5739 function F (..) renames R.F;
5744 RM 8.3 (15) stipulates that an overridden operation is not visible within the
5745 declaration of the overriding operation.
5747 @node Pragma Partition_Elaboration_Policy,Pragma Part_Of,Pragma Overriding_Renamings,Implementation Defined Pragmas
5748 @anchor{gnat_rm/implementation_defined_pragmas pragma-partition-elaboration-policy}@anchor{af}
5749 @section Pragma Partition_Elaboration_Policy
5755 pragma Partition_Elaboration_Policy (POLICY_IDENTIFIER);
5757 POLICY_IDENTIFIER ::= Concurrent | Sequential
5760 This pragma is standard in Ada 2005, but is available in all earlier
5761 versions of Ada as an implementation-defined pragma.
5762 See Ada 2012 Reference Manual for details.
5764 @node Pragma Part_Of,Pragma Passive,Pragma Partition_Elaboration_Policy,Implementation Defined Pragmas
5765 @anchor{gnat_rm/implementation_defined_pragmas id27}@anchor{b0}@anchor{gnat_rm/implementation_defined_pragmas pragma-part-of}@anchor{b1}
5766 @section Pragma Part_Of
5772 pragma Part_Of (ABSTRACT_STATE);
5774 ABSTRACT_STATE ::= NAME
5777 For the semantics of this pragma, see the entry for aspect @code{Part_Of} in the
5778 SPARK 2014 Reference Manual, section 7.2.6.
5780 @node Pragma Passive,Pragma Persistent_BSS,Pragma Part_Of,Implementation Defined Pragmas
5781 @anchor{gnat_rm/implementation_defined_pragmas pragma-passive}@anchor{b2}
5782 @section Pragma Passive
5788 pragma Passive [(Semaphore | No)];
5791 Syntax checked, but otherwise ignored by GNAT. This is recognized for
5792 compatibility with DEC Ada 83 implementations, where it is used within a
5793 task definition to request that a task be made passive. If the argument
5794 @code{Semaphore} is present, or the argument is omitted, then DEC Ada 83
5795 treats the pragma as an assertion that the containing task is passive
5796 and that optimization of context switch with this task is permitted and
5797 desired. If the argument @code{No} is present, the task must not be
5798 optimized. GNAT does not attempt to optimize any tasks in this manner
5799 (since protected objects are available in place of passive tasks).
5801 For more information on the subject of passive tasks, see the section
5802 'Passive Task Optimization' in the GNAT Users Guide.
5804 @node Pragma Persistent_BSS,Pragma Polling,Pragma Passive,Implementation Defined Pragmas
5805 @anchor{gnat_rm/implementation_defined_pragmas id28}@anchor{b3}@anchor{gnat_rm/implementation_defined_pragmas pragma-persistent-bss}@anchor{b4}
5806 @section Pragma Persistent_BSS
5812 pragma Persistent_BSS [(LOCAL_NAME)]
5815 This pragma allows selected objects to be placed in the @code{.persistent_bss}
5816 section. On some targets the linker and loader provide for special
5817 treatment of this section, allowing a program to be reloaded without
5818 affecting the contents of this data (hence the name persistent).
5820 There are two forms of usage. If an argument is given, it must be the
5821 local name of a library-level object, with no explicit initialization
5822 and whose type is potentially persistent. If no argument is given, then
5823 the pragma is a configuration pragma, and applies to all library-level
5824 objects with no explicit initialization of potentially persistent types.
5826 A potentially persistent type is a scalar type, or an untagged,
5827 non-discriminated record, all of whose components have no explicit
5828 initialization and are themselves of a potentially persistent type,
5829 or an array, all of whose constraints are static, and whose component
5830 type is potentially persistent.
5832 If this pragma is used on a target where this feature is not supported,
5833 then the pragma will be ignored. See also @code{pragma Linker_Section}.
5835 @node Pragma Polling,Pragma Post,Pragma Persistent_BSS,Implementation Defined Pragmas
5836 @anchor{gnat_rm/implementation_defined_pragmas pragma-polling}@anchor{b5}
5837 @section Pragma Polling
5843 pragma Polling (ON | OFF);
5846 This pragma controls the generation of polling code. This is normally off.
5847 If @code{pragma Polling (ON)} is used then periodic calls are generated to
5848 the routine @code{Ada.Exceptions.Poll}. This routine is a separate unit in the
5849 runtime library, and can be found in file @code{a-excpol.adb}.
5851 Pragma @code{Polling} can appear as a configuration pragma (for example it
5852 can be placed in the @code{gnat.adc} file) to enable polling globally, or it
5853 can be used in the statement or declaration sequence to control polling
5856 A call to the polling routine is generated at the start of every loop and
5857 at the start of every subprogram call. This guarantees that the @code{Poll}
5858 routine is called frequently, and places an upper bound (determined by
5859 the complexity of the code) on the period between two @code{Poll} calls.
5861 The primary purpose of the polling interface is to enable asynchronous
5862 aborts on targets that cannot otherwise support it (for example Windows
5863 NT), but it may be used for any other purpose requiring periodic polling.
5864 The standard version is null, and can be replaced by a user program. This
5865 will require re-compilation of the @code{Ada.Exceptions} package that can
5866 be found in files @code{a-except.ads} and @code{a-except.adb}.
5868 A standard alternative unit (in file @code{4wexcpol.adb} in the standard GNAT
5869 distribution) is used to enable the asynchronous abort capability on
5870 targets that do not normally support the capability. The version of
5871 @code{Poll} in this file makes a call to the appropriate runtime routine
5872 to test for an abort condition.
5874 Note that polling can also be enabled by use of the @emph{-gnatP} switch.
5875 See the section on switches for gcc in the @cite{GNAT User's Guide}.
5877 @node Pragma Post,Pragma Postcondition,Pragma Polling,Implementation Defined Pragmas
5878 @anchor{gnat_rm/implementation_defined_pragmas pragma-post}@anchor{b6}
5879 @section Pragma Post
5885 @geindex postconditions
5890 pragma Post (Boolean_Expression);
5893 The @code{Post} pragma is intended to be an exact replacement for
5894 the language-defined
5895 @code{Post} aspect, and shares its restrictions and semantics.
5896 It must appear either immediately following the corresponding
5897 subprogram declaration (only other pragmas may intervene), or
5898 if there is no separate subprogram declaration, then it can
5899 appear at the start of the declarations in a subprogram body
5900 (preceded only by other pragmas).
5902 @node Pragma Postcondition,Pragma Post_Class,Pragma Post,Implementation Defined Pragmas
5903 @anchor{gnat_rm/implementation_defined_pragmas pragma-postcondition}@anchor{b7}
5904 @section Pragma Postcondition
5907 @geindex Postcondition
5910 @geindex postconditions
5915 pragma Postcondition (
5916 [Check =>] Boolean_Expression
5917 [,[Message =>] String_Expression]);
5920 The @code{Postcondition} pragma allows specification of automatic
5921 postcondition checks for subprograms. These checks are similar to
5922 assertions, but are automatically inserted just prior to the return
5923 statements of the subprogram with which they are associated (including
5924 implicit returns at the end of procedure bodies and associated
5925 exception handlers).
5927 In addition, the boolean expression which is the condition which
5928 must be true may contain references to function'Result in the case
5929 of a function to refer to the returned value.
5931 @code{Postcondition} pragmas may appear either immediately following the
5932 (separate) declaration of a subprogram, or at the start of the
5933 declarations of a subprogram body. Only other pragmas may intervene
5934 (that is appear between the subprogram declaration and its
5935 postconditions, or appear before the postcondition in the
5936 declaration sequence in a subprogram body). In the case of a
5937 postcondition appearing after a subprogram declaration, the
5938 formal arguments of the subprogram are visible, and can be
5939 referenced in the postcondition expressions.
5941 The postconditions are collected and automatically tested just
5942 before any return (implicit or explicit) in the subprogram body.
5943 A postcondition is only recognized if postconditions are active
5944 at the time the pragma is encountered. The compiler switch @emph{gnata}
5945 turns on all postconditions by default, and pragma @code{Check_Policy}
5946 with an identifier of @code{Postcondition} can also be used to
5947 control whether postconditions are active.
5949 The general approach is that postconditions are placed in the spec
5950 if they represent functional aspects which make sense to the client.
5951 For example we might have:
5954 function Direction return Integer;
5955 pragma Postcondition
5956 (Direction'Result = +1
5958 Direction'Result = -1);
5961 which serves to document that the result must be +1 or -1, and
5962 will test that this is the case at run time if postcondition
5965 Postconditions within the subprogram body can be used to
5966 check that some internal aspect of the implementation,
5967 not visible to the client, is operating as expected.
5968 For instance if a square root routine keeps an internal
5969 counter of the number of times it is called, then we
5970 might have the following postcondition:
5973 Sqrt_Calls : Natural := 0;
5975 function Sqrt (Arg : Float) return Float is
5976 pragma Postcondition
5977 (Sqrt_Calls = Sqrt_Calls'Old + 1);
5982 As this example, shows, the use of the @code{Old} attribute
5983 is often useful in postconditions to refer to the state on
5984 entry to the subprogram.
5986 Note that postconditions are only checked on normal returns
5987 from the subprogram. If an abnormal return results from
5988 raising an exception, then the postconditions are not checked.
5990 If a postcondition fails, then the exception
5991 @code{System.Assertions.Assert_Failure} is raised. If
5992 a message argument was supplied, then the given string
5993 will be used as the exception message. If no message
5994 argument was supplied, then the default message has
5995 the form "Postcondition failed at file_name:line". The
5996 exception is raised in the context of the subprogram
5997 body, so it is possible to catch postcondition failures
5998 within the subprogram body itself.
6000 Within a package spec, normal visibility rules
6001 in Ada would prevent forward references within a
6002 postcondition pragma to functions defined later in
6003 the same package. This would introduce undesirable
6004 ordering constraints. To avoid this problem, all
6005 postcondition pragmas are analyzed at the end of
6006 the package spec, allowing forward references.
6008 The following example shows that this even allows
6009 mutually recursive postconditions as in:
6012 package Parity_Functions is
6013 function Odd (X : Natural) return Boolean;
6014 pragma Postcondition
6018 (x /= 0 and then Even (X - 1))));
6020 function Even (X : Natural) return Boolean;
6021 pragma Postcondition
6025 (x /= 1 and then Odd (X - 1))));
6027 end Parity_Functions;
6030 There are no restrictions on the complexity or form of
6031 conditions used within @code{Postcondition} pragmas.
6032 The following example shows that it is even possible
6033 to verify performance behavior.
6038 Performance : constant Float;
6039 -- Performance constant set by implementation
6040 -- to match target architecture behavior.
6042 procedure Treesort (Arg : String);
6043 -- Sorts characters of argument using N*logN sort
6044 pragma Postcondition
6045 (Float (Clock - Clock'Old) <=
6046 Float (Arg'Length) *
6047 log (Float (Arg'Length)) *
6052 Note: postcondition pragmas associated with subprograms that are
6053 marked as Inline_Always, or those marked as Inline with front-end
6054 inlining (-gnatN option set) are accepted and legality-checked
6055 by the compiler, but are ignored at run-time even if postcondition
6056 checking is enabled.
6058 Note that pragma @code{Postcondition} differs from the language-defined
6059 @code{Post} aspect (and corresponding @code{Post} pragma) in allowing
6060 multiple occurrences, allowing occurences in the body even if there
6061 is a separate spec, and allowing a second string parameter, and the
6062 use of the pragma identifier @code{Check}. Historically, pragma
6063 @code{Postcondition} was implemented prior to the development of
6064 Ada 2012, and has been retained in its original form for
6065 compatibility purposes.
6067 @node Pragma Post_Class,Pragma Rename_Pragma,Pragma Postcondition,Implementation Defined Pragmas
6068 @anchor{gnat_rm/implementation_defined_pragmas pragma-post-class}@anchor{b8}
6069 @section Pragma Post_Class
6075 @geindex postconditions
6080 pragma Post_Class (Boolean_Expression);
6083 The @code{Post_Class} pragma is intended to be an exact replacement for
6084 the language-defined
6085 @code{Post'Class} aspect, and shares its restrictions and semantics.
6086 It must appear either immediately following the corresponding
6087 subprogram declaration (only other pragmas may intervene), or
6088 if there is no separate subprogram declaration, then it can
6089 appear at the start of the declarations in a subprogram body
6090 (preceded only by other pragmas).
6092 Note: This pragma is called @code{Post_Class} rather than
6093 @code{Post'Class} because the latter would not be strictly
6094 conforming to the allowed syntax for pragmas. The motivation
6095 for provinding pragmas equivalent to the aspects is to allow a program
6096 to be written using the pragmas, and then compiled if necessary
6097 using an Ada compiler that does not recognize the pragmas or
6098 aspects, but is prepared to ignore the pragmas. The assertion
6099 policy that controls this pragma is @code{Post'Class}, not
6102 @node Pragma Rename_Pragma,Pragma Pre,Pragma Post_Class,Implementation Defined Pragmas
6103 @anchor{gnat_rm/implementation_defined_pragmas pragma-rename-pragma}@anchor{b9}
6104 @section Pragma Rename_Pragma
6113 pragma Rename_Pragma (
6114 [New_Name =>] IDENTIFIER,
6115 [Renamed =>] pragma_IDENTIFIER);
6118 This pragma provides a mechanism for supplying new names for existing
6119 pragmas. The @code{New_Name} identifier can subsequently be used as a synonym for
6120 the Renamed pragma. For example, suppose you have code that was originally
6121 developed on a compiler that supports Inline_Only as an implementation defined
6122 pragma. And suppose the semantics of pragma Inline_Only are identical to (or at
6123 least very similar to) the GNAT implementation defined pragma
6124 Inline_Always. You could globally replace Inline_Only with Inline_Always.
6126 However, to avoid that source modification, you could instead add a
6127 configuration pragma:
6130 pragma Rename_Pragma (
6131 New_Name => Inline_Only,
6132 Renamed => Inline_Always);
6135 Then GNAT will treat "pragma Inline_Only ..." as if you had written
6136 "pragma Inline_Always ...".
6138 Pragma Inline_Only will not necessarily mean the same thing as the other Ada
6139 compiler; it's up to you to make sure the semantics are close enough.
6141 @node Pragma Pre,Pragma Precondition,Pragma Rename_Pragma,Implementation Defined Pragmas
6142 @anchor{gnat_rm/implementation_defined_pragmas pragma-pre}@anchor{ba}
6149 @geindex preconditions
6154 pragma Pre (Boolean_Expression);
6157 The @code{Pre} pragma is intended to be an exact replacement for
6158 the language-defined
6159 @code{Pre} aspect, and shares its restrictions and semantics.
6160 It must appear either immediately following the corresponding
6161 subprogram declaration (only other pragmas may intervene), or
6162 if there is no separate subprogram declaration, then it can
6163 appear at the start of the declarations in a subprogram body
6164 (preceded only by other pragmas).
6166 @node Pragma Precondition,Pragma Predicate,Pragma Pre,Implementation Defined Pragmas
6167 @anchor{gnat_rm/implementation_defined_pragmas pragma-precondition}@anchor{bb}
6168 @section Pragma Precondition
6171 @geindex Preconditions
6174 @geindex preconditions
6179 pragma Precondition (
6180 [Check =>] Boolean_Expression
6181 [,[Message =>] String_Expression]);
6184 The @code{Precondition} pragma is similar to @code{Postcondition}
6185 except that the corresponding checks take place immediately upon
6186 entry to the subprogram, and if a precondition fails, the exception
6187 is raised in the context of the caller, and the attribute 'Result
6188 cannot be used within the precondition expression.
6190 Otherwise, the placement and visibility rules are identical to those
6191 described for postconditions. The following is an example of use
6192 within a package spec:
6195 package Math_Functions is
6197 function Sqrt (Arg : Float) return Float;
6198 pragma Precondition (Arg >= 0.0)
6203 @code{Precondition} pragmas may appear either immediately following the
6204 (separate) declaration of a subprogram, or at the start of the
6205 declarations of a subprogram body. Only other pragmas may intervene
6206 (that is appear between the subprogram declaration and its
6207 postconditions, or appear before the postcondition in the
6208 declaration sequence in a subprogram body).
6210 Note: precondition pragmas associated with subprograms that are
6211 marked as Inline_Always, or those marked as Inline with front-end
6212 inlining (-gnatN option set) are accepted and legality-checked
6213 by the compiler, but are ignored at run-time even if precondition
6214 checking is enabled.
6216 Note that pragma @code{Precondition} differs from the language-defined
6217 @code{Pre} aspect (and corresponding @code{Pre} pragma) in allowing
6218 multiple occurrences, allowing occurences in the body even if there
6219 is a separate spec, and allowing a second string parameter, and the
6220 use of the pragma identifier @code{Check}. Historically, pragma
6221 @code{Precondition} was implemented prior to the development of
6222 Ada 2012, and has been retained in its original form for
6223 compatibility purposes.
6225 @node Pragma Predicate,Pragma Predicate_Failure,Pragma Precondition,Implementation Defined Pragmas
6226 @anchor{gnat_rm/implementation_defined_pragmas id29}@anchor{bc}@anchor{gnat_rm/implementation_defined_pragmas pragma-predicate}@anchor{bd}
6227 @section Pragma Predicate
6234 ([Entity =>] type_LOCAL_NAME,
6235 [Check =>] EXPRESSION);
6238 This pragma (available in all versions of Ada in GNAT) encompasses both
6239 the @code{Static_Predicate} and @code{Dynamic_Predicate} aspects in
6240 Ada 2012. A predicate is regarded as static if it has an allowed form
6241 for @code{Static_Predicate} and is otherwise treated as a
6242 @code{Dynamic_Predicate}. Otherwise, predicates specified by this
6243 pragma behave exactly as described in the Ada 2012 reference manual.
6244 For example, if we have
6247 type R is range 1 .. 10;
6249 pragma Predicate (Entity => S, Check => S not in 4 .. 6);
6251 pragma Predicate (Entity => Q, Check => F(Q) or G(Q));
6254 the effect is identical to the following Ada 2012 code:
6257 type R is range 1 .. 10;
6259 Static_Predicate => S not in 4 .. 6;
6261 Dynamic_Predicate => F(Q) or G(Q);
6264 Note that there are no pragmas @code{Dynamic_Predicate}
6265 or @code{Static_Predicate}. That is
6266 because these pragmas would affect legality and semantics of
6267 the program and thus do not have a neutral effect if ignored.
6268 The motivation behind providing pragmas equivalent to
6269 corresponding aspects is to allow a program to be written
6270 using the pragmas, and then compiled with a compiler that
6271 will ignore the pragmas. That doesn't work in the case of
6272 static and dynamic predicates, since if the corresponding
6273 pragmas are ignored, then the behavior of the program is
6274 fundamentally changed (for example a membership test
6275 @code{A in B} would not take into account a predicate
6276 defined for subtype B). When following this approach, the
6277 use of predicates should be avoided.
6279 @node Pragma Predicate_Failure,Pragma Preelaborable_Initialization,Pragma Predicate,Implementation Defined Pragmas
6280 @anchor{gnat_rm/implementation_defined_pragmas pragma-predicate-failure}@anchor{be}
6281 @section Pragma Predicate_Failure
6287 pragma Predicate_Failure
6288 ([Entity =>] type_LOCAL_NAME,
6289 [Message =>] String_Expression);
6292 The @code{Predicate_Failure} pragma is intended to be an exact replacement for
6293 the language-defined
6294 @code{Predicate_Failure} aspect, and shares its restrictions and semantics.
6296 @node Pragma Preelaborable_Initialization,Pragma Prefix_Exception_Messages,Pragma Predicate_Failure,Implementation Defined Pragmas
6297 @anchor{gnat_rm/implementation_defined_pragmas pragma-preelaborable-initialization}@anchor{bf}
6298 @section Pragma Preelaborable_Initialization
6304 pragma Preelaborable_Initialization (DIRECT_NAME);
6307 This pragma is standard in Ada 2005, but is available in all earlier
6308 versions of Ada as an implementation-defined pragma.
6309 See Ada 2012 Reference Manual for details.
6311 @node Pragma Prefix_Exception_Messages,Pragma Pre_Class,Pragma Preelaborable_Initialization,Implementation Defined Pragmas
6312 @anchor{gnat_rm/implementation_defined_pragmas pragma-prefix-exception-messages}@anchor{c0}
6313 @section Pragma Prefix_Exception_Messages
6316 @geindex Prefix_Exception_Messages
6320 @geindex Exception_Message
6325 pragma Prefix_Exception_Messages;
6328 This is an implementation-defined configuration pragma that affects the
6329 behavior of raise statements with a message given as a static string
6330 constant (typically a string literal). In such cases, the string will
6331 be automatically prefixed by the name of the enclosing entity (giving
6332 the package and subprogram containing the raise statement). This helps
6333 to identify where messages are coming from, and this mode is automatic
6334 for the run-time library.
6336 The pragma has no effect if the message is computed with an expression other
6337 than a static string constant, since the assumption in this case is that
6338 the program computes exactly the string it wants. If you still want the
6339 prefixing in this case, you can always call
6340 @code{GNAT.Source_Info.Enclosing_Entity} and prepend the string manually.
6342 @node Pragma Pre_Class,Pragma Priority_Specific_Dispatching,Pragma Prefix_Exception_Messages,Implementation Defined Pragmas
6343 @anchor{gnat_rm/implementation_defined_pragmas pragma-pre-class}@anchor{c1}
6344 @section Pragma Pre_Class
6350 @geindex preconditions
6355 pragma Pre_Class (Boolean_Expression);
6358 The @code{Pre_Class} pragma is intended to be an exact replacement for
6359 the language-defined
6360 @code{Pre'Class} aspect, and shares its restrictions and semantics.
6361 It must appear either immediately following the corresponding
6362 subprogram declaration (only other pragmas may intervene), or
6363 if there is no separate subprogram declaration, then it can
6364 appear at the start of the declarations in a subprogram body
6365 (preceded only by other pragmas).
6367 Note: This pragma is called @code{Pre_Class} rather than
6368 @code{Pre'Class} because the latter would not be strictly
6369 conforming to the allowed syntax for pragmas. The motivation
6370 for providing pragmas equivalent to the aspects is to allow a program
6371 to be written using the pragmas, and then compiled if necessary
6372 using an Ada compiler that does not recognize the pragmas or
6373 aspects, but is prepared to ignore the pragmas. The assertion
6374 policy that controls this pragma is @code{Pre'Class}, not
6377 @node Pragma Priority_Specific_Dispatching,Pragma Profile,Pragma Pre_Class,Implementation Defined Pragmas
6378 @anchor{gnat_rm/implementation_defined_pragmas pragma-priority-specific-dispatching}@anchor{c2}
6379 @section Pragma Priority_Specific_Dispatching
6385 pragma Priority_Specific_Dispatching (
6387 first_priority_EXPRESSION,
6388 last_priority_EXPRESSION)
6390 POLICY_IDENTIFIER ::=
6391 EDF_Across_Priorities |
6392 FIFO_Within_Priorities |
6393 Non_Preemptive_Within_Priorities |
6394 Round_Robin_Within_Priorities
6397 This pragma is standard in Ada 2005, but is available in all earlier
6398 versions of Ada as an implementation-defined pragma.
6399 See Ada 2012 Reference Manual for details.
6401 @node Pragma Profile,Pragma Profile_Warnings,Pragma Priority_Specific_Dispatching,Implementation Defined Pragmas
6402 @anchor{gnat_rm/implementation_defined_pragmas pragma-profile}@anchor{c3}
6403 @section Pragma Profile
6409 pragma Profile (Ravenscar | Restricted | Rational |
6410 GNAT_Extended_Ravenscar | GNAT_Ravenscar_EDF );
6413 This pragma is standard in Ada 2005, but is available in all earlier
6414 versions of Ada as an implementation-defined pragma. This is a
6415 configuration pragma that establishes a set of configuration pragmas
6416 that depend on the argument. @code{Ravenscar} is standard in Ada 2005.
6417 The other possibilities (@code{Restricted}, @code{Rational},
6418 @code{GNAT_Extended_Ravenscar}, @code{GNAT_Ravenscar_EDF})
6419 are implementation-defined. The set of configuration pragmas
6420 is defined in the following sections.
6426 Pragma Profile (Ravenscar)
6428 The @code{Ravenscar} profile is standard in Ada 2005,
6429 but is available in all earlier
6430 versions of Ada as an implementation-defined pragma. This profile
6431 establishes the following set of configuration pragmas:
6437 @code{Task_Dispatching_Policy (FIFO_Within_Priorities)}
6439 [RM D.2.2] Tasks are dispatched following a preemptive
6440 priority-ordered scheduling policy.
6443 @code{Locking_Policy (Ceiling_Locking)}
6445 [RM D.3] While tasks and interrupts execute a protected action, they inherit
6446 the ceiling priority of the corresponding protected object.
6449 @code{Detect_Blocking}
6451 This pragma forces the detection of potentially blocking operations within a
6452 protected operation, and to raise Program_Error if that happens.
6455 plus the following set of restrictions:
6461 @code{Max_Entry_Queue_Length => 1}
6463 No task can be queued on a protected entry.
6466 @code{Max_Protected_Entries => 1}
6469 @code{Max_Task_Entries => 0}
6471 No rendezvous statements are allowed.
6474 @code{No_Abort_Statements}
6477 @code{No_Dynamic_Attachment}
6480 @code{No_Dynamic_Priorities}
6483 @code{No_Implicit_Heap_Allocations}
6486 @code{No_Local_Protected_Objects}
6489 @code{No_Local_Timing_Events}
6492 @code{No_Protected_Type_Allocators}
6495 @code{No_Relative_Delay}
6498 @code{No_Requeue_Statements}
6501 @code{No_Select_Statements}
6504 @code{No_Specific_Termination_Handlers}
6507 @code{No_Task_Allocators}
6510 @code{No_Task_Hierarchy}
6513 @code{No_Task_Termination}
6516 @code{Simple_Barriers}
6519 The Ravenscar profile also includes the following restrictions that specify
6520 that there are no semantic dependences on the corresponding predefined
6527 @code{No_Dependence => Ada.Asynchronous_Task_Control}
6530 @code{No_Dependence => Ada.Calendar}
6533 @code{No_Dependence => Ada.Execution_Time.Group_Budget}
6536 @code{No_Dependence => Ada.Execution_Time.Timers}
6539 @code{No_Dependence => Ada.Task_Attributes}
6542 @code{No_Dependence => System.Multiprocessors.Dispatching_Domains}
6545 This set of configuration pragmas and restrictions correspond to the
6546 definition of the 'Ravenscar Profile' for limited tasking, devised and
6547 published by the @cite{International Real-Time Ada Workshop@comma{} 1997}.
6548 A description is also available at
6549 @indicateurl{http://www-users.cs.york.ac.uk/~burns/ravenscar.ps}.
6551 The original definition of the profile was revised at subsequent IRTAW
6552 meetings. It has been included in the ISO
6553 @cite{Guide for the Use of the Ada Programming Language in High Integrity Systems},
6554 and was made part of the Ada 2005 standard.
6555 The formal definition given by
6556 the Ada Rapporteur Group (ARG) can be found in two Ada Issues (AI-249 and
6557 AI-305) available at
6558 @indicateurl{http://www.ada-auth.org/cgi-bin/cvsweb.cgi/ais/ai-00249.txt} and
6559 @indicateurl{http://www.ada-auth.org/cgi-bin/cvsweb.cgi/ais/ai-00305.txt}.
6561 The above set is a superset of the restrictions provided by pragma
6562 @code{Profile (Restricted)}, it includes six additional restrictions
6563 (@code{Simple_Barriers}, @code{No_Select_Statements},
6564 @code{No_Calendar}, @code{No_Implicit_Heap_Allocations},
6565 @code{No_Relative_Delay} and @code{No_Task_Termination}). This means
6566 that pragma @code{Profile (Ravenscar)}, like the pragma
6567 @code{Profile (Restricted)},
6568 automatically causes the use of a simplified,
6569 more efficient version of the tasking run-time library.
6572 Pragma Profile (GNAT_Extended_Ravenscar)
6574 This profile corresponds to a GNAT specific extension of the
6575 Ravenscar profile. The profile may change in the future although
6576 only in a compatible way: some restrictions may be removed or
6577 relaxed. It is defined as a variation of the Ravenscar profile.
6579 The @code{No_Implicit_Heap_Allocations} restriction has been replaced
6580 by @code{No_Implicit_Task_Allocations} and
6581 @code{No_Implicit_Protected_Object_Allocations}.
6583 The @code{Simple_Barriers} restriction has been replaced by
6584 @code{Pure_Barriers}.
6586 The @code{Max_Protected_Entries}, @code{Max_Entry_Queue_Length}, and
6587 @code{No_Relative_Delay} restrictions have been removed.
6590 Pragma Profile (GNAT_Ravenscar_EDF)
6592 This profile corresponds to the Ravenscar profile but using
6593 EDF_Across_Priority as the Task_Scheduling_Policy.
6596 Pragma Profile (Restricted)
6598 This profile corresponds to the GNAT restricted run time. It
6599 establishes the following set of restrictions:
6605 @code{No_Abort_Statements}
6608 @code{No_Entry_Queue}
6611 @code{No_Task_Hierarchy}
6614 @code{No_Task_Allocators}
6617 @code{No_Dynamic_Priorities}
6620 @code{No_Terminate_Alternatives}
6623 @code{No_Dynamic_Attachment}
6626 @code{No_Protected_Type_Allocators}
6629 @code{No_Local_Protected_Objects}
6632 @code{No_Requeue_Statements}
6635 @code{No_Task_Attributes_Package}
6638 @code{Max_Asynchronous_Select_Nesting = 0}
6641 @code{Max_Task_Entries = 0}
6644 @code{Max_Protected_Entries = 1}
6647 @code{Max_Select_Alternatives = 0}
6650 This set of restrictions causes the automatic selection of a simplified
6651 version of the run time that provides improved performance for the
6652 limited set of tasking functionality permitted by this set of restrictions.
6655 Pragma Profile (Rational)
6657 The Rational profile is intended to facilitate porting legacy code that
6658 compiles with the Rational APEX compiler, even when the code includes non-
6659 conforming Ada constructs. The profile enables the following three pragmas:
6665 @code{pragma Implicit_Packing}
6668 @code{pragma Overriding_Renamings}
6671 @code{pragma Use_VADS_Size}
6675 @node Pragma Profile_Warnings,Pragma Propagate_Exceptions,Pragma Profile,Implementation Defined Pragmas
6676 @anchor{gnat_rm/implementation_defined_pragmas pragma-profile-warnings}@anchor{c4}
6677 @section Pragma Profile_Warnings
6683 pragma Profile_Warnings (Ravenscar | Restricted | Rational);
6686 This is an implementation-defined pragma that is similar in
6687 effect to @code{pragma Profile} except that instead of
6688 generating @code{Restrictions} pragmas, it generates
6689 @code{Restriction_Warnings} pragmas. The result is that
6690 violations of the profile generate warning messages instead
6693 @node Pragma Propagate_Exceptions,Pragma Provide_Shift_Operators,Pragma Profile_Warnings,Implementation Defined Pragmas
6694 @anchor{gnat_rm/implementation_defined_pragmas pragma-propagate-exceptions}@anchor{c5}
6695 @section Pragma Propagate_Exceptions
6698 @geindex Interfacing to C++
6703 pragma Propagate_Exceptions;
6706 This pragma is now obsolete and, other than generating a warning if warnings
6707 on obsolescent features are enabled, is ignored.
6708 It is retained for compatibility
6709 purposes. It used to be used in connection with optimization of
6710 a now-obsolete mechanism for implementation of exceptions.
6712 @node Pragma Provide_Shift_Operators,Pragma Psect_Object,Pragma Propagate_Exceptions,Implementation Defined Pragmas
6713 @anchor{gnat_rm/implementation_defined_pragmas pragma-provide-shift-operators}@anchor{c6}
6714 @section Pragma Provide_Shift_Operators
6717 @geindex Shift operators
6722 pragma Provide_Shift_Operators (integer_first_subtype_LOCAL_NAME);
6725 This pragma can be applied to a first subtype local name that specifies
6726 either an unsigned or signed type. It has the effect of providing the
6727 five shift operators (Shift_Left, Shift_Right, Shift_Right_Arithmetic,
6728 Rotate_Left and Rotate_Right) for the given type. It is similar to
6729 including the function declarations for these five operators, together
6730 with the pragma Import (Intrinsic, ...) statements.
6732 @node Pragma Psect_Object,Pragma Pure_Function,Pragma Provide_Shift_Operators,Implementation Defined Pragmas
6733 @anchor{gnat_rm/implementation_defined_pragmas pragma-psect-object}@anchor{c7}
6734 @section Pragma Psect_Object
6740 pragma Psect_Object (
6741 [Internal =>] LOCAL_NAME,
6742 [, [External =>] EXTERNAL_SYMBOL]
6743 [, [Size =>] EXTERNAL_SYMBOL]);
6747 | static_string_EXPRESSION
6750 This pragma is identical in effect to pragma @code{Common_Object}.
6752 @node Pragma Pure_Function,Pragma Rational,Pragma Psect_Object,Implementation Defined Pragmas
6753 @anchor{gnat_rm/implementation_defined_pragmas pragma-pure-function}@anchor{c8}@anchor{gnat_rm/implementation_defined_pragmas id30}@anchor{c9}
6754 @section Pragma Pure_Function
6760 pragma Pure_Function ([Entity =>] function_LOCAL_NAME);
6763 This pragma appears in the same declarative part as a function
6764 declaration (or a set of function declarations if more than one
6765 overloaded declaration exists, in which case the pragma applies
6766 to all entities). It specifies that the function @code{Entity} is
6767 to be considered pure for the purposes of code generation. This means
6768 that the compiler can assume that there are no side effects, and
6769 in particular that two calls with identical arguments produce the
6770 same result. It also means that the function can be used in an
6773 Note that, quite deliberately, there are no static checks to try
6774 to ensure that this promise is met, so @code{Pure_Function} can be used
6775 with functions that are conceptually pure, even if they do modify
6776 global variables. For example, a square root function that is
6777 instrumented to count the number of times it is called is still
6778 conceptually pure, and can still be optimized, even though it
6779 modifies a global variable (the count). Memo functions are another
6780 example (where a table of previous calls is kept and consulted to
6781 avoid re-computation).
6783 Note also that the normal rules excluding optimization of subprograms
6784 in pure units (when parameter types are descended from System.Address,
6785 or when the full view of a parameter type is limited), do not apply
6786 for the Pure_Function case. If you explicitly specify Pure_Function,
6787 the compiler may optimize away calls with identical arguments, and
6788 if that results in unexpected behavior, the proper action is not to
6789 use the pragma for subprograms that are not (conceptually) pure.
6791 Note: Most functions in a @code{Pure} package are automatically pure, and
6792 there is no need to use pragma @code{Pure_Function} for such functions. One
6793 exception is any function that has at least one formal of type
6794 @code{System.Address} or a type derived from it. Such functions are not
6795 considered pure by default, since the compiler assumes that the
6796 @code{Address} parameter may be functioning as a pointer and that the
6797 referenced data may change even if the address value does not.
6798 Similarly, imported functions are not considered to be pure by default,
6799 since there is no way of checking that they are in fact pure. The use
6800 of pragma @code{Pure_Function} for such a function will override these default
6801 assumption, and cause the compiler to treat a designated subprogram as pure
6804 Note: If pragma @code{Pure_Function} is applied to a renamed function, it
6805 applies to the underlying renamed function. This can be used to
6806 disambiguate cases of overloading where some but not all functions
6807 in a set of overloaded functions are to be designated as pure.
6809 If pragma @code{Pure_Function} is applied to a library-level function, the
6810 function is also considered pure from an optimization point of view, but the
6811 unit is not a Pure unit in the categorization sense. So for example, a function
6812 thus marked is free to @code{with} non-pure units.
6814 @node Pragma Rational,Pragma Ravenscar,Pragma Pure_Function,Implementation Defined Pragmas
6815 @anchor{gnat_rm/implementation_defined_pragmas pragma-rational}@anchor{ca}
6816 @section Pragma Rational
6825 This pragma is considered obsolescent, but is retained for
6826 compatibility purposes. It is equivalent to:
6829 pragma Profile (Rational);
6832 @node Pragma Ravenscar,Pragma Refined_Depends,Pragma Rational,Implementation Defined Pragmas
6833 @anchor{gnat_rm/implementation_defined_pragmas pragma-ravenscar}@anchor{cb}
6834 @section Pragma Ravenscar
6843 This pragma is considered obsolescent, but is retained for
6844 compatibility purposes. It is equivalent to:
6847 pragma Profile (Ravenscar);
6850 which is the preferred method of setting the @code{Ravenscar} profile.
6852 @node Pragma Refined_Depends,Pragma Refined_Global,Pragma Ravenscar,Implementation Defined Pragmas
6853 @anchor{gnat_rm/implementation_defined_pragmas pragma-refined-depends}@anchor{cc}@anchor{gnat_rm/implementation_defined_pragmas id31}@anchor{cd}
6854 @section Pragma Refined_Depends
6860 pragma Refined_Depends (DEPENDENCY_RELATION);
6862 DEPENDENCY_RELATION ::=
6864 | (DEPENDENCY_CLAUSE @{, DEPENDENCY_CLAUSE@})
6866 DEPENDENCY_CLAUSE ::=
6867 OUTPUT_LIST =>[+] INPUT_LIST
6868 | NULL_DEPENDENCY_CLAUSE
6870 NULL_DEPENDENCY_CLAUSE ::= null => INPUT_LIST
6872 OUTPUT_LIST ::= OUTPUT | (OUTPUT @{, OUTPUT@})
6874 INPUT_LIST ::= null | INPUT | (INPUT @{, INPUT@})
6876 OUTPUT ::= NAME | FUNCTION_RESULT
6879 where FUNCTION_RESULT is a function Result attribute_reference
6882 For the semantics of this pragma, see the entry for aspect @code{Refined_Depends} in
6883 the SPARK 2014 Reference Manual, section 6.1.5.
6885 @node Pragma Refined_Global,Pragma Refined_Post,Pragma Refined_Depends,Implementation Defined Pragmas
6886 @anchor{gnat_rm/implementation_defined_pragmas pragma-refined-global}@anchor{ce}@anchor{gnat_rm/implementation_defined_pragmas id32}@anchor{cf}
6887 @section Pragma Refined_Global
6893 pragma Refined_Global (GLOBAL_SPECIFICATION);
6895 GLOBAL_SPECIFICATION ::=
6898 | (MODED_GLOBAL_LIST @{, MODED_GLOBAL_LIST@})
6900 MODED_GLOBAL_LIST ::= MODE_SELECTOR => GLOBAL_LIST
6902 MODE_SELECTOR ::= In_Out | Input | Output | Proof_In
6903 GLOBAL_LIST ::= GLOBAL_ITEM | (GLOBAL_ITEM @{, GLOBAL_ITEM@})
6904 GLOBAL_ITEM ::= NAME
6907 For the semantics of this pragma, see the entry for aspect @code{Refined_Global} in
6908 the SPARK 2014 Reference Manual, section 6.1.4.
6910 @node Pragma Refined_Post,Pragma Refined_State,Pragma Refined_Global,Implementation Defined Pragmas
6911 @anchor{gnat_rm/implementation_defined_pragmas pragma-refined-post}@anchor{d0}@anchor{gnat_rm/implementation_defined_pragmas id33}@anchor{d1}
6912 @section Pragma Refined_Post
6918 pragma Refined_Post (boolean_EXPRESSION);
6921 For the semantics of this pragma, see the entry for aspect @code{Refined_Post} in
6922 the SPARK 2014 Reference Manual, section 7.2.7.
6924 @node Pragma Refined_State,Pragma Relative_Deadline,Pragma Refined_Post,Implementation Defined Pragmas
6925 @anchor{gnat_rm/implementation_defined_pragmas pragma-refined-state}@anchor{d2}@anchor{gnat_rm/implementation_defined_pragmas id34}@anchor{d3}
6926 @section Pragma Refined_State
6932 pragma Refined_State (REFINEMENT_LIST);
6935 (REFINEMENT_CLAUSE @{, REFINEMENT_CLAUSE@})
6937 REFINEMENT_CLAUSE ::= state_NAME => CONSTITUENT_LIST
6939 CONSTITUENT_LIST ::=
6942 | (CONSTITUENT @{, CONSTITUENT@})
6944 CONSTITUENT ::= object_NAME | state_NAME
6947 For the semantics of this pragma, see the entry for aspect @code{Refined_State} in
6948 the SPARK 2014 Reference Manual, section 7.2.2.
6950 @node Pragma Relative_Deadline,Pragma Remote_Access_Type,Pragma Refined_State,Implementation Defined Pragmas
6951 @anchor{gnat_rm/implementation_defined_pragmas pragma-relative-deadline}@anchor{d4}
6952 @section Pragma Relative_Deadline
6958 pragma Relative_Deadline (time_span_EXPRESSION);
6961 This pragma is standard in Ada 2005, but is available in all earlier
6962 versions of Ada as an implementation-defined pragma.
6963 See Ada 2012 Reference Manual for details.
6965 @node Pragma Remote_Access_Type,Pragma Restricted_Run_Time,Pragma Relative_Deadline,Implementation Defined Pragmas
6966 @anchor{gnat_rm/implementation_defined_pragmas id35}@anchor{d5}@anchor{gnat_rm/implementation_defined_pragmas pragma-remote-access-type}@anchor{d6}
6967 @section Pragma Remote_Access_Type
6973 pragma Remote_Access_Type ([Entity =>] formal_access_type_LOCAL_NAME);
6976 This pragma appears in the formal part of a generic declaration.
6977 It specifies an exception to the RM rule from E.2.2(17/2), which forbids
6978 the use of a remote access to class-wide type as actual for a formal
6981 When this pragma applies to a formal access type @code{Entity}, that
6982 type is treated as a remote access to class-wide type in the generic.
6983 It must be a formal general access type, and its designated type must
6984 be the class-wide type of a formal tagged limited private type from the
6985 same generic declaration.
6987 In the generic unit, the formal type is subject to all restrictions
6988 pertaining to remote access to class-wide types. At instantiation, the
6989 actual type must be a remote access to class-wide type.
6991 @node Pragma Restricted_Run_Time,Pragma Restriction_Warnings,Pragma Remote_Access_Type,Implementation Defined Pragmas
6992 @anchor{gnat_rm/implementation_defined_pragmas pragma-restricted-run-time}@anchor{d7}
6993 @section Pragma Restricted_Run_Time
6999 pragma Restricted_Run_Time;
7002 This pragma is considered obsolescent, but is retained for
7003 compatibility purposes. It is equivalent to:
7006 pragma Profile (Restricted);
7009 which is the preferred method of setting the restricted run time
7012 @node Pragma Restriction_Warnings,Pragma Reviewable,Pragma Restricted_Run_Time,Implementation Defined Pragmas
7013 @anchor{gnat_rm/implementation_defined_pragmas pragma-restriction-warnings}@anchor{d8}
7014 @section Pragma Restriction_Warnings
7020 pragma Restriction_Warnings
7021 (restriction_IDENTIFIER @{, restriction_IDENTIFIER@});
7024 This pragma allows a series of restriction identifiers to be
7025 specified (the list of allowed identifiers is the same as for
7026 pragma @code{Restrictions}). For each of these identifiers
7027 the compiler checks for violations of the restriction, but
7028 generates a warning message rather than an error message
7029 if the restriction is violated.
7031 One use of this is in situations where you want to know
7032 about violations of a restriction, but you want to ignore some of
7033 these violations. Consider this example, where you want to set
7034 Ada_95 mode and enable style checks, but you want to know about
7035 any other use of implementation pragmas:
7038 pragma Restriction_Warnings (No_Implementation_Pragmas);
7039 pragma Warnings (Off, "violation of No_Implementation_Pragmas");
7041 pragma Style_Checks ("2bfhkM160");
7042 pragma Warnings (On, "violation of No_Implementation_Pragmas");
7045 By including the above lines in a configuration pragmas file,
7046 the Ada_95 and Style_Checks pragmas are accepted without
7047 generating a warning, but any other use of implementation
7048 defined pragmas will cause a warning to be generated.
7050 @node Pragma Reviewable,Pragma Secondary_Stack_Size,Pragma Restriction_Warnings,Implementation Defined Pragmas
7051 @anchor{gnat_rm/implementation_defined_pragmas pragma-reviewable}@anchor{d9}
7052 @section Pragma Reviewable
7061 This pragma is an RM-defined standard pragma, but has no effect on the
7062 program being compiled, or on the code generated for the program.
7064 To obtain the required output specified in RM H.3.1, the compiler must be
7065 run with various special switches as follows:
7071 @emph{Where compiler-generated run-time checks remain}
7073 The switch @emph{-gnatGL}
7074 may be used to list the expanded code in pseudo-Ada form.
7075 Runtime checks show up in the listing either as explicit
7076 checks or operators marked with @{@} to indicate a check is present.
7079 @emph{An identification of known exceptions at compile time}
7081 If the program is compiled with @emph{-gnatwa},
7082 the compiler warning messages will indicate all cases where the compiler
7083 detects that an exception is certain to occur at run time.
7086 @emph{Possible reads of uninitialized variables}
7088 The compiler warns of many such cases, but its output is incomplete.
7092 A supplemental static analysis tool
7093 may be used to obtain a comprehensive list of all
7094 possible points at which uninitialized data may be read.
7100 @emph{Where run-time support routines are implicitly invoked}
7102 In the output from @emph{-gnatGL},
7103 run-time calls are explicitly listed as calls to the relevant
7107 @emph{Object code listing}
7109 This may be obtained either by using the @emph{-S} switch,
7110 or the objdump utility.
7113 @emph{Constructs known to be erroneous at compile time}
7115 These are identified by warnings issued by the compiler (use @emph{-gnatwa}).
7118 @emph{Stack usage information}
7120 Static stack usage data (maximum per-subprogram) can be obtained via the
7121 @emph{-fstack-usage} switch to the compiler.
7122 Dynamic stack usage data (per task) can be obtained via the @emph{-u} switch
7131 @emph{Object code listing of entire partition}
7133 This can be obtained by compiling the partition with @emph{-S},
7134 or by applying objdump
7135 to all the object files that are part of the partition.
7138 @emph{A description of the run-time model}
7140 The full sources of the run-time are available, and the documentation of
7141 these routines describes how these run-time routines interface to the
7142 underlying operating system facilities.
7145 @emph{Control and data-flow information}
7149 A supplemental static analysis tool
7150 may be used to obtain complete control and data-flow information, as well as
7151 comprehensive messages identifying possible problems based on this
7154 @node Pragma Secondary_Stack_Size,Pragma Share_Generic,Pragma Reviewable,Implementation Defined Pragmas
7155 @anchor{gnat_rm/implementation_defined_pragmas id36}@anchor{da}@anchor{gnat_rm/implementation_defined_pragmas pragma-secondary-stack-size}@anchor{db}
7156 @section Pragma Secondary_Stack_Size
7162 pragma Secondary_Stack_Size (integer_EXPRESSION);
7165 This pragma appears within the task definition of a single task declaration
7166 or a task type declaration (like pragma @code{Storage_Size}) and applies to all
7167 task objects of that type. The argument specifies the size of the secondary
7168 stack to be used by these task objects, and must be of an integer type. The
7169 secondary stack is used to handle functions that return a variable-sized
7170 result, for example a function returning an unconstrained String.
7172 Note this pragma only applies to targets using fixed secondary stacks, like
7173 VxWorks 653 and bare board targets, where a fixed block for the
7174 secondary stack is allocated from the primary stack of the task. By default,
7175 these targets assign a percentage of the primary stack for the secondary stack,
7176 as defined by @code{System.Parameter.Sec_Stack_Percentage}. With this pragma,
7177 an @code{integer_EXPRESSION} of bytes is assigned from the primary stack instead.
7179 For most targets, the pragma does not apply as the secondary stack grows on
7180 demand: allocated as a chain of blocks in the heap. The default size of these
7181 blocks can be modified via the @code{-D} binder option as described in
7182 @cite{GNAT User's Guide}.
7184 Note that no check is made to see if the secondary stack can fit inside the
7187 Note the pragma cannot appear when the restriction @code{No_Secondary_Stack}
7190 @node Pragma Share_Generic,Pragma Shared,Pragma Secondary_Stack_Size,Implementation Defined Pragmas
7191 @anchor{gnat_rm/implementation_defined_pragmas pragma-share-generic}@anchor{dc}
7192 @section Pragma Share_Generic
7198 pragma Share_Generic (GNAME @{, GNAME@});
7200 GNAME ::= generic_unit_NAME | generic_instance_NAME
7203 This pragma is provided for compatibility with Dec Ada 83. It has
7204 no effect in GNAT (which does not implement shared generics), other
7205 than to check that the given names are all names of generic units or
7208 @node Pragma Shared,Pragma Short_Circuit_And_Or,Pragma Share_Generic,Implementation Defined Pragmas
7209 @anchor{gnat_rm/implementation_defined_pragmas id37}@anchor{dd}@anchor{gnat_rm/implementation_defined_pragmas pragma-shared}@anchor{de}
7210 @section Pragma Shared
7213 This pragma is provided for compatibility with Ada 83. The syntax and
7214 semantics are identical to pragma Atomic.
7216 @node Pragma Short_Circuit_And_Or,Pragma Short_Descriptors,Pragma Shared,Implementation Defined Pragmas
7217 @anchor{gnat_rm/implementation_defined_pragmas pragma-short-circuit-and-or}@anchor{df}
7218 @section Pragma Short_Circuit_And_Or
7224 pragma Short_Circuit_And_Or;
7227 This configuration pragma causes any occurrence of the AND operator applied to
7228 operands of type Standard.Boolean to be short-circuited (i.e. the AND operator
7229 is treated as if it were AND THEN). Or is similarly treated as OR ELSE. This
7230 may be useful in the context of certification protocols requiring the use of
7231 short-circuited logical operators. If this configuration pragma occurs locally
7232 within the file being compiled, it applies only to the file being compiled.
7233 There is no requirement that all units in a partition use this option.
7235 @node Pragma Short_Descriptors,Pragma Simple_Storage_Pool_Type,Pragma Short_Circuit_And_Or,Implementation Defined Pragmas
7236 @anchor{gnat_rm/implementation_defined_pragmas pragma-short-descriptors}@anchor{e0}
7237 @section Pragma Short_Descriptors
7243 pragma Short_Descriptors
7246 This pragma is provided for compatibility with other Ada implementations. It
7247 is recognized but ignored by all current versions of GNAT.
7249 @node Pragma Simple_Storage_Pool_Type,Pragma Source_File_Name,Pragma Short_Descriptors,Implementation Defined Pragmas
7250 @anchor{gnat_rm/implementation_defined_pragmas pragma-simple-storage-pool-type}@anchor{e1}@anchor{gnat_rm/implementation_defined_pragmas id38}@anchor{e2}
7251 @section Pragma Simple_Storage_Pool_Type
7254 @geindex Storage pool
7257 @geindex Simple storage pool
7262 pragma Simple_Storage_Pool_Type (type_LOCAL_NAME);
7265 A type can be established as a 'simple storage pool type' by applying
7266 the representation pragma @code{Simple_Storage_Pool_Type} to the type.
7267 A type named in the pragma must be a library-level immutably limited record
7268 type or limited tagged type declared immediately within a package declaration.
7269 The type can also be a limited private type whose full type is allowed as
7270 a simple storage pool type.
7272 For a simple storage pool type @code{SSP}, nonabstract primitive subprograms
7273 @code{Allocate}, @code{Deallocate}, and @code{Storage_Size} can be declared that
7274 are subtype conformant with the following subprogram declarations:
7279 Storage_Address : out System.Address;
7280 Size_In_Storage_Elements : System.Storage_Elements.Storage_Count;
7281 Alignment : System.Storage_Elements.Storage_Count);
7283 procedure Deallocate
7285 Storage_Address : System.Address;
7286 Size_In_Storage_Elements : System.Storage_Elements.Storage_Count;
7287 Alignment : System.Storage_Elements.Storage_Count);
7289 function Storage_Size (Pool : SSP)
7290 return System.Storage_Elements.Storage_Count;
7293 Procedure @code{Allocate} must be declared, whereas @code{Deallocate} and
7294 @code{Storage_Size} are optional. If @code{Deallocate} is not declared, then
7295 applying an unchecked deallocation has no effect other than to set its actual
7296 parameter to null. If @code{Storage_Size} is not declared, then the
7297 @code{Storage_Size} attribute applied to an access type associated with
7298 a pool object of type SSP returns zero. Additional operations can be declared
7299 for a simple storage pool type (such as for supporting a mark/release
7300 storage-management discipline).
7302 An object of a simple storage pool type can be associated with an access
7303 type by specifying the attribute
7304 @ref{e3,,Simple_Storage_Pool}. For example:
7307 My_Pool : My_Simple_Storage_Pool_Type;
7309 type Acc is access My_Data_Type;
7311 for Acc'Simple_Storage_Pool use My_Pool;
7314 See attribute @ref{e3,,Simple_Storage_Pool}
7315 for further details.
7317 @node Pragma Source_File_Name,Pragma Source_File_Name_Project,Pragma Simple_Storage_Pool_Type,Implementation Defined Pragmas
7318 @anchor{gnat_rm/implementation_defined_pragmas pragma-source-file-name}@anchor{e4}@anchor{gnat_rm/implementation_defined_pragmas id39}@anchor{e5}
7319 @section Pragma Source_File_Name
7325 pragma Source_File_Name (
7326 [Unit_Name =>] unit_NAME,
7327 Spec_File_Name => STRING_LITERAL,
7328 [Index => INTEGER_LITERAL]);
7330 pragma Source_File_Name (
7331 [Unit_Name =>] unit_NAME,
7332 Body_File_Name => STRING_LITERAL,
7333 [Index => INTEGER_LITERAL]);
7336 Use this to override the normal naming convention. It is a configuration
7337 pragma, and so has the usual applicability of configuration pragmas
7338 (i.e., it applies to either an entire partition, or to all units in a
7339 compilation, or to a single unit, depending on how it is used.
7340 @code{unit_name} is mapped to @code{file_name_literal}. The identifier for
7341 the second argument is required, and indicates whether this is the file
7342 name for the spec or for the body.
7344 The optional Index argument should be used when a file contains multiple
7345 units, and when you do not want to use @code{gnatchop} to separate then
7346 into multiple files (which is the recommended procedure to limit the
7347 number of recompilations that are needed when some sources change).
7348 For instance, if the source file @code{source.ada} contains
7362 you could use the following configuration pragmas:
7365 pragma Source_File_Name
7366 (B, Spec_File_Name => "source.ada", Index => 1);
7367 pragma Source_File_Name
7368 (A, Body_File_Name => "source.ada", Index => 2);
7371 Note that the @code{gnatname} utility can also be used to generate those
7372 configuration pragmas.
7374 Another form of the @code{Source_File_Name} pragma allows
7375 the specification of patterns defining alternative file naming schemes
7376 to apply to all files.
7379 pragma Source_File_Name
7380 ( [Spec_File_Name =>] STRING_LITERAL
7381 [,[Casing =>] CASING_SPEC]
7382 [,[Dot_Replacement =>] STRING_LITERAL]);
7384 pragma Source_File_Name
7385 ( [Body_File_Name =>] STRING_LITERAL
7386 [,[Casing =>] CASING_SPEC]
7387 [,[Dot_Replacement =>] STRING_LITERAL]);
7389 pragma Source_File_Name
7390 ( [Subunit_File_Name =>] STRING_LITERAL
7391 [,[Casing =>] CASING_SPEC]
7392 [,[Dot_Replacement =>] STRING_LITERAL]);
7394 CASING_SPEC ::= Lowercase | Uppercase | Mixedcase
7397 The first argument is a pattern that contains a single asterisk indicating
7398 the point at which the unit name is to be inserted in the pattern string
7399 to form the file name. The second argument is optional. If present it
7400 specifies the casing of the unit name in the resulting file name string.
7401 The default is lower case. Finally the third argument allows for systematic
7402 replacement of any dots in the unit name by the specified string literal.
7404 Note that Source_File_Name pragmas should not be used if you are using
7405 project files. The reason for this rule is that the project manager is not
7406 aware of these pragmas, and so other tools that use the projet file would not
7407 be aware of the intended naming conventions. If you are using project files,
7408 file naming is controlled by Source_File_Name_Project pragmas, which are
7409 usually supplied automatically by the project manager. A pragma
7410 Source_File_Name cannot appear after a @ref{e6,,Pragma Source_File_Name_Project}.
7412 For more details on the use of the @code{Source_File_Name} pragma, see the
7413 sections on @code{Using Other File Names} and @cite{Alternative File Naming Schemes' in the :title:`GNAT User's Guide}.
7415 @node Pragma Source_File_Name_Project,Pragma Source_Reference,Pragma Source_File_Name,Implementation Defined Pragmas
7416 @anchor{gnat_rm/implementation_defined_pragmas pragma-source-file-name-project}@anchor{e6}@anchor{gnat_rm/implementation_defined_pragmas id40}@anchor{e7}
7417 @section Pragma Source_File_Name_Project
7420 This pragma has the same syntax and semantics as pragma Source_File_Name.
7421 It is only allowed as a stand-alone configuration pragma.
7422 It cannot appear after a @ref{e4,,Pragma Source_File_Name}, and
7423 most importantly, once pragma Source_File_Name_Project appears,
7424 no further Source_File_Name pragmas are allowed.
7426 The intention is that Source_File_Name_Project pragmas are always
7427 generated by the Project Manager in a manner consistent with the naming
7428 specified in a project file, and when naming is controlled in this manner,
7429 it is not permissible to attempt to modify this naming scheme using
7430 Source_File_Name or Source_File_Name_Project pragmas (which would not be
7431 known to the project manager).
7433 @node Pragma Source_Reference,Pragma SPARK_Mode,Pragma Source_File_Name_Project,Implementation Defined Pragmas
7434 @anchor{gnat_rm/implementation_defined_pragmas pragma-source-reference}@anchor{e8}
7435 @section Pragma Source_Reference
7441 pragma Source_Reference (INTEGER_LITERAL, STRING_LITERAL);
7444 This pragma must appear as the first line of a source file.
7445 @code{integer_literal} is the logical line number of the line following
7446 the pragma line (for use in error messages and debugging
7447 information). @code{string_literal} is a static string constant that
7448 specifies the file name to be used in error messages and debugging
7449 information. This is most notably used for the output of @code{gnatchop}
7450 with the @emph{-r} switch, to make sure that the original unchopped
7451 source file is the one referred to.
7453 The second argument must be a string literal, it cannot be a static
7454 string expression other than a string literal. This is because its value
7455 is needed for error messages issued by all phases of the compiler.
7457 @node Pragma SPARK_Mode,Pragma Static_Elaboration_Desired,Pragma Source_Reference,Implementation Defined Pragmas
7458 @anchor{gnat_rm/implementation_defined_pragmas pragma-spark-mode}@anchor{e9}@anchor{gnat_rm/implementation_defined_pragmas id41}@anchor{ea}
7459 @section Pragma SPARK_Mode
7465 pragma SPARK_Mode [(On | Off)] ;
7468 In general a program can have some parts that are in SPARK 2014 (and
7469 follow all the rules in the SPARK Reference Manual), and some parts
7470 that are full Ada 2012.
7472 The SPARK_Mode pragma is used to identify which parts are in SPARK
7473 2014 (by default programs are in full Ada). The SPARK_Mode pragma can
7474 be used in the following places:
7480 As a configuration pragma, in which case it sets the default mode for
7481 all units compiled with this pragma.
7484 Immediately following a library-level subprogram spec
7487 Immediately within a library-level package body
7490 Immediately following the @code{private} keyword of a library-level
7494 Immediately following the @code{begin} keyword of a library-level
7498 Immediately within a library-level subprogram body
7501 Normally a subprogram or package spec/body inherits the current mode
7502 that is active at the point it is declared. But this can be overridden
7503 by pragma within the spec or body as above.
7505 The basic consistency rule is that you can't turn SPARK_Mode back
7506 @code{On}, once you have explicitly (with a pragma) turned if
7507 @code{Off}. So the following rules apply:
7509 If a subprogram spec has SPARK_Mode @code{Off}, then the body must
7510 also have SPARK_Mode @code{Off}.
7512 For a package, we have four parts:
7518 the package public declarations
7521 the package private part
7524 the body of the package
7527 the elaboration code after @code{begin}
7530 For a package, the rule is that if you explicitly turn SPARK_Mode
7531 @code{Off} for any part, then all the following parts must have
7532 SPARK_Mode @code{Off}. Note that this may require repeating a pragma
7533 SPARK_Mode (@code{Off}) in the body. For example, if we have a
7534 configuration pragma SPARK_Mode (@code{On}) that turns the mode on by
7535 default everywhere, and one particular package spec has pragma
7536 SPARK_Mode (@code{Off}), then that pragma will need to be repeated in
7539 @node Pragma Static_Elaboration_Desired,Pragma Stream_Convert,Pragma SPARK_Mode,Implementation Defined Pragmas
7540 @anchor{gnat_rm/implementation_defined_pragmas pragma-static-elaboration-desired}@anchor{eb}
7541 @section Pragma Static_Elaboration_Desired
7547 pragma Static_Elaboration_Desired;
7550 This pragma is used to indicate that the compiler should attempt to initialize
7551 statically the objects declared in the library unit to which the pragma applies,
7552 when these objects are initialized (explicitly or implicitly) by an aggregate.
7553 In the absence of this pragma, aggregates in object declarations are expanded
7554 into assignments and loops, even when the aggregate components are static
7555 constants. When the aggregate is present the compiler builds a static expression
7556 that requires no run-time code, so that the initialized object can be placed in
7557 read-only data space. If the components are not static, or the aggregate has
7558 more that 100 components, the compiler emits a warning that the pragma cannot
7559 be obeyed. (See also the restriction No_Implicit_Loops, which supports static
7560 construction of larger aggregates with static components that include an others
7563 @node Pragma Stream_Convert,Pragma Style_Checks,Pragma Static_Elaboration_Desired,Implementation Defined Pragmas
7564 @anchor{gnat_rm/implementation_defined_pragmas pragma-stream-convert}@anchor{ec}
7565 @section Pragma Stream_Convert
7571 pragma Stream_Convert (
7572 [Entity =>] type_LOCAL_NAME,
7573 [Read =>] function_NAME,
7574 [Write =>] function_NAME);
7577 This pragma provides an efficient way of providing user-defined stream
7578 attributes. Not only is it simpler to use than specifying the attributes
7579 directly, but more importantly, it allows the specification to be made in such
7580 a way that the predefined unit Ada.Streams is not loaded unless it is actually
7581 needed (i.e. unless the stream attributes are actually used); the use of
7582 the Stream_Convert pragma adds no overhead at all, unless the stream
7583 attributes are actually used on the designated type.
7585 The first argument specifies the type for which stream functions are
7586 provided. The second parameter provides a function used to read values
7587 of this type. It must name a function whose argument type may be any
7588 subtype, and whose returned type must be the type given as the first
7589 argument to the pragma.
7591 The meaning of the @code{Read} parameter is that if a stream attribute directly
7592 or indirectly specifies reading of the type given as the first parameter,
7593 then a value of the type given as the argument to the Read function is
7594 read from the stream, and then the Read function is used to convert this
7595 to the required target type.
7597 Similarly the @code{Write} parameter specifies how to treat write attributes
7598 that directly or indirectly apply to the type given as the first parameter.
7599 It must have an input parameter of the type specified by the first parameter,
7600 and the return type must be the same as the input type of the Read function.
7601 The effect is to first call the Write function to convert to the given stream
7602 type, and then write the result type to the stream.
7604 The Read and Write functions must not be overloaded subprograms. If necessary
7605 renamings can be supplied to meet this requirement.
7606 The usage of this attribute is best illustrated by a simple example, taken
7607 from the GNAT implementation of package Ada.Strings.Unbounded:
7610 function To_Unbounded (S : String) return Unbounded_String
7611 renames To_Unbounded_String;
7613 pragma Stream_Convert
7614 (Unbounded_String, To_Unbounded, To_String);
7617 The specifications of the referenced functions, as given in the Ada
7618 Reference Manual are:
7621 function To_Unbounded_String (Source : String)
7622 return Unbounded_String;
7624 function To_String (Source : Unbounded_String)
7628 The effect is that if the value of an unbounded string is written to a stream,
7629 then the representation of the item in the stream is in the same format that
7630 would be used for @code{Standard.String'Output}, and this same representation
7631 is expected when a value of this type is read from the stream. Note that the
7632 value written always includes the bounds, even for Unbounded_String'Write,
7633 since Unbounded_String is not an array type.
7635 Note that the @code{Stream_Convert} pragma is not effective in the case of
7636 a derived type of a non-limited tagged type. If such a type is specified then
7637 the pragma is silently ignored, and the default implementation of the stream
7638 attributes is used instead.
7640 @node Pragma Style_Checks,Pragma Subtitle,Pragma Stream_Convert,Implementation Defined Pragmas
7641 @anchor{gnat_rm/implementation_defined_pragmas pragma-style-checks}@anchor{ed}
7642 @section Pragma Style_Checks
7648 pragma Style_Checks (string_LITERAL | ALL_CHECKS |
7649 On | Off [, LOCAL_NAME]);
7652 This pragma is used in conjunction with compiler switches to control the
7653 built in style checking provided by GNAT. The compiler switches, if set,
7654 provide an initial setting for the switches, and this pragma may be used
7655 to modify these settings, or the settings may be provided entirely by
7656 the use of the pragma. This pragma can be used anywhere that a pragma
7657 is legal, including use as a configuration pragma (including use in
7658 the @code{gnat.adc} file).
7660 The form with a string literal specifies which style options are to be
7661 activated. These are additive, so they apply in addition to any previously
7662 set style check options. The codes for the options are the same as those
7663 used in the @emph{-gnaty} switch to @emph{gcc} or @emph{gnatmake}.
7664 For example the following two methods can be used to enable
7672 pragma Style_Checks ("l");
7681 The form @code{ALL_CHECKS} activates all standard checks (its use is equivalent
7682 to the use of the @code{gnaty} switch with no options.
7683 See the @cite{GNAT User's Guide} for details.)
7685 Note: the behavior is slightly different in GNAT mode (@code{-gnatg} used).
7686 In this case, @code{ALL_CHECKS} implies the standard set of GNAT mode style check
7687 options (i.e. equivalent to @code{-gnatyg}).
7689 The forms with @code{Off} and @code{On}
7690 can be used to temporarily disable style checks
7691 as shown in the following example:
7694 pragma Style_Checks ("k"); -- requires keywords in lower case
7695 pragma Style_Checks (Off); -- turn off style checks
7696 NULL; -- this will not generate an error message
7697 pragma Style_Checks (On); -- turn style checks back on
7698 NULL; -- this will generate an error message
7701 Finally the two argument form is allowed only if the first argument is
7702 @code{On} or @code{Off}. The effect is to turn of semantic style checks
7703 for the specified entity, as shown in the following example:
7706 pragma Style_Checks ("r"); -- require consistency of identifier casing
7708 Rf1 : Integer := ARG; -- incorrect, wrong case
7709 pragma Style_Checks (Off, Arg);
7710 Rf2 : Integer := ARG; -- OK, no error
7713 @node Pragma Subtitle,Pragma Suppress,Pragma Style_Checks,Implementation Defined Pragmas
7714 @anchor{gnat_rm/implementation_defined_pragmas pragma-subtitle}@anchor{ee}
7715 @section Pragma Subtitle
7721 pragma Subtitle ([Subtitle =>] STRING_LITERAL);
7724 This pragma is recognized for compatibility with other Ada compilers
7725 but is ignored by GNAT.
7727 @node Pragma Suppress,Pragma Suppress_All,Pragma Subtitle,Implementation Defined Pragmas
7728 @anchor{gnat_rm/implementation_defined_pragmas pragma-suppress}@anchor{ef}
7729 @section Pragma Suppress
7735 pragma Suppress (Identifier [, [On =>] Name]);
7738 This is a standard pragma, and supports all the check names required in
7739 the RM. It is included here because GNAT recognizes some additional check
7740 names that are implementation defined (as permitted by the RM):
7746 @code{Alignment_Check} can be used to suppress alignment checks
7747 on addresses used in address clauses. Such checks can also be suppressed
7748 by suppressing range checks, but the specific use of @code{Alignment_Check}
7749 allows suppression of alignment checks without suppressing other range checks.
7750 Note that @code{Alignment_Check} is suppressed by default on machines (such as
7751 the x86) with non-strict alignment.
7754 @code{Atomic_Synchronization} can be used to suppress the special memory
7755 synchronization instructions that are normally generated for access to
7756 @code{Atomic} variables to ensure correct synchronization between tasks
7757 that use such variables for synchronization purposes.
7760 @code{Duplicated_Tag_Check} Can be used to suppress the check that is generated
7761 for a duplicated tag value when a tagged type is declared.
7764 @code{Container_Checks} Can be used to suppress all checks within Ada.Containers
7765 and instances of its children, including Tampering_Check.
7768 @code{Tampering_Check} Can be used to suppress tampering check in the containers.
7771 @code{Predicate_Check} can be used to control whether predicate checks are
7772 active. It is applicable only to predicates for which the policy is
7773 @code{Check}. Unlike @code{Assertion_Policy}, which determines if a given
7774 predicate is ignored or checked for the whole program, the use of
7775 @code{Suppress} and @code{Unsuppress} with this check name allows a given
7776 predicate to be turned on and off at specific points in the program.
7779 @code{Validity_Check} can be used specifically to control validity checks.
7780 If @code{Suppress} is used to suppress validity checks, then no validity
7781 checks are performed, including those specified by the appropriate compiler
7782 switch or the @code{Validity_Checks} pragma.
7785 Additional check names previously introduced by use of the @code{Check_Name}
7786 pragma are also allowed.
7789 Note that pragma Suppress gives the compiler permission to omit
7790 checks, but does not require the compiler to omit checks. The compiler
7791 will generate checks if they are essentially free, even when they are
7792 suppressed. In particular, if the compiler can prove that a certain
7793 check will necessarily fail, it will generate code to do an
7794 unconditional 'raise', even if checks are suppressed. The compiler
7797 Of course, run-time checks are omitted whenever the compiler can prove
7798 that they will not fail, whether or not checks are suppressed.
7800 @node Pragma Suppress_All,Pragma Suppress_Debug_Info,Pragma Suppress,Implementation Defined Pragmas
7801 @anchor{gnat_rm/implementation_defined_pragmas pragma-suppress-all}@anchor{f0}
7802 @section Pragma Suppress_All
7808 pragma Suppress_All;
7811 This pragma can appear anywhere within a unit.
7812 The effect is to apply @code{Suppress (All_Checks)} to the unit
7813 in which it appears. This pragma is implemented for compatibility with DEC
7814 Ada 83 usage where it appears at the end of a unit, and for compatibility
7815 with Rational Ada, where it appears as a program unit pragma.
7816 The use of the standard Ada pragma @code{Suppress (All_Checks)}
7817 as a normal configuration pragma is the preferred usage in GNAT.
7819 @node Pragma Suppress_Debug_Info,Pragma Suppress_Exception_Locations,Pragma Suppress_All,Implementation Defined Pragmas
7820 @anchor{gnat_rm/implementation_defined_pragmas pragma-suppress-debug-info}@anchor{f1}@anchor{gnat_rm/implementation_defined_pragmas id42}@anchor{f2}
7821 @section Pragma Suppress_Debug_Info
7827 pragma Suppress_Debug_Info ([Entity =>] LOCAL_NAME);
7830 This pragma can be used to suppress generation of debug information
7831 for the specified entity. It is intended primarily for use in debugging
7832 the debugger, and navigating around debugger problems.
7834 @node Pragma Suppress_Exception_Locations,Pragma Suppress_Initialization,Pragma Suppress_Debug_Info,Implementation Defined Pragmas
7835 @anchor{gnat_rm/implementation_defined_pragmas pragma-suppress-exception-locations}@anchor{f3}
7836 @section Pragma Suppress_Exception_Locations
7842 pragma Suppress_Exception_Locations;
7845 In normal mode, a raise statement for an exception by default generates
7846 an exception message giving the file name and line number for the location
7847 of the raise. This is useful for debugging and logging purposes, but this
7848 entails extra space for the strings for the messages. The configuration
7849 pragma @code{Suppress_Exception_Locations} can be used to suppress the
7850 generation of these strings, with the result that space is saved, but the
7851 exception message for such raises is null. This configuration pragma may
7852 appear in a global configuration pragma file, or in a specific unit as
7853 usual. It is not required that this pragma be used consistently within
7854 a partition, so it is fine to have some units within a partition compiled
7855 with this pragma and others compiled in normal mode without it.
7857 @node Pragma Suppress_Initialization,Pragma Task_Name,Pragma Suppress_Exception_Locations,Implementation Defined Pragmas
7858 @anchor{gnat_rm/implementation_defined_pragmas id43}@anchor{f4}@anchor{gnat_rm/implementation_defined_pragmas pragma-suppress-initialization}@anchor{f5}
7859 @section Pragma Suppress_Initialization
7862 @geindex Suppressing initialization
7864 @geindex Initialization
7865 @geindex suppression of
7870 pragma Suppress_Initialization ([Entity =>] variable_or_subtype_Name);
7873 Here variable_or_subtype_Name is the name introduced by a type declaration
7874 or subtype declaration or the name of a variable introduced by an
7877 In the case of a type or subtype
7878 this pragma suppresses any implicit or explicit initialization
7879 for all variables of the given type or subtype,
7880 including initialization resulting from the use of pragmas
7881 Normalize_Scalars or Initialize_Scalars.
7883 This is considered a representation item, so it cannot be given after
7884 the type is frozen. It applies to all subsequent object declarations,
7885 and also any allocator that creates objects of the type.
7887 If the pragma is given for the first subtype, then it is considered
7888 to apply to the base type and all its subtypes. If the pragma is given
7889 for other than a first subtype, then it applies only to the given subtype.
7890 The pragma may not be given after the type is frozen.
7892 Note that this includes eliminating initialization of discriminants
7893 for discriminated types, and tags for tagged types. In these cases,
7894 you will have to use some non-portable mechanism (e.g. address
7895 overlays or unchecked conversion) to achieve required initialization
7896 of these fields before accessing any object of the corresponding type.
7898 For the variable case, implicit initialization for the named variable
7899 is suppressed, just as though its subtype had been given in a pragma
7900 Suppress_Initialization, as described above.
7902 @node Pragma Task_Name,Pragma Task_Storage,Pragma Suppress_Initialization,Implementation Defined Pragmas
7903 @anchor{gnat_rm/implementation_defined_pragmas pragma-task-name}@anchor{f6}
7904 @section Pragma Task_Name
7910 pragma Task_Name (string_EXPRESSION);
7913 This pragma appears within a task definition (like pragma
7914 @code{Priority}) and applies to the task in which it appears. The
7915 argument must be of type String, and provides a name to be used for
7916 the task instance when the task is created. Note that this expression
7917 is not required to be static, and in particular, it can contain
7918 references to task discriminants. This facility can be used to
7919 provide different names for different tasks as they are created,
7920 as illustrated in the example below.
7922 The task name is recorded internally in the run-time structures
7923 and is accessible to tools like the debugger. In addition the
7924 routine @code{Ada.Task_Identification.Image} will return this
7925 string, with a unique task address appended.
7928 -- Example of the use of pragma Task_Name
7930 with Ada.Task_Identification;
7931 use Ada.Task_Identification;
7932 with Text_IO; use Text_IO;
7935 type Astring is access String;
7937 task type Task_Typ (Name : access String) is
7938 pragma Task_Name (Name.all);
7941 task body Task_Typ is
7942 Nam : constant String := Image (Current_Task);
7944 Put_Line ("-->" & Nam (1 .. 14) & "<--");
7947 type Ptr_Task is access Task_Typ;
7948 Task_Var : Ptr_Task;
7952 new Task_Typ (new String'("This is task 1"));
7954 new Task_Typ (new String'("This is task 2"));
7958 @node Pragma Task_Storage,Pragma Test_Case,Pragma Task_Name,Implementation Defined Pragmas
7959 @anchor{gnat_rm/implementation_defined_pragmas pragma-task-storage}@anchor{f7}
7960 @section Pragma Task_Storage
7966 pragma Task_Storage (
7967 [Task_Type =>] LOCAL_NAME,
7968 [Top_Guard =>] static_integer_EXPRESSION);
7971 This pragma specifies the length of the guard area for tasks. The guard
7972 area is an additional storage area allocated to a task. A value of zero
7973 means that either no guard area is created or a minimal guard area is
7974 created, depending on the target. This pragma can appear anywhere a
7975 @code{Storage_Size} attribute definition clause is allowed for a task
7978 @node Pragma Test_Case,Pragma Thread_Local_Storage,Pragma Task_Storage,Implementation Defined Pragmas
7979 @anchor{gnat_rm/implementation_defined_pragmas pragma-test-case}@anchor{f8}@anchor{gnat_rm/implementation_defined_pragmas id44}@anchor{f9}
7980 @section Pragma Test_Case
7989 [Name =>] static_string_Expression
7990 ,[Mode =>] (Nominal | Robustness)
7991 [, Requires => Boolean_Expression]
7992 [, Ensures => Boolean_Expression]);
7995 The @code{Test_Case} pragma allows defining fine-grain specifications
7996 for use by testing tools.
7997 The compiler checks the validity of the @code{Test_Case} pragma, but its
7998 presence does not lead to any modification of the code generated by the
8001 @code{Test_Case} pragmas may only appear immediately following the
8002 (separate) declaration of a subprogram in a package declaration, inside
8003 a package spec unit. Only other pragmas may intervene (that is appear
8004 between the subprogram declaration and a test case).
8006 The compiler checks that boolean expressions given in @code{Requires} and
8007 @code{Ensures} are valid, where the rules for @code{Requires} are the
8008 same as the rule for an expression in @code{Precondition} and the rules
8009 for @code{Ensures} are the same as the rule for an expression in
8010 @code{Postcondition}. In particular, attributes @code{'Old} and
8011 @code{'Result} can only be used within the @code{Ensures}
8012 expression. The following is an example of use within a package spec:
8015 package Math_Functions is
8017 function Sqrt (Arg : Float) return Float;
8018 pragma Test_Case (Name => "Test 1",
8020 Requires => Arg < 10000,
8021 Ensures => Sqrt'Result < 10);
8026 The meaning of a test case is that there is at least one context where
8027 @code{Requires} holds such that, if the associated subprogram is executed in
8028 that context, then @code{Ensures} holds when the subprogram returns.
8029 Mode @code{Nominal} indicates that the input context should also satisfy the
8030 precondition of the subprogram, and the output context should also satisfy its
8031 postcondition. Mode @code{Robustness} indicates that the precondition and
8032 postcondition of the subprogram should be ignored for this test case.
8034 @node Pragma Thread_Local_Storage,Pragma Time_Slice,Pragma Test_Case,Implementation Defined Pragmas
8035 @anchor{gnat_rm/implementation_defined_pragmas pragma-thread-local-storage}@anchor{fa}@anchor{gnat_rm/implementation_defined_pragmas id45}@anchor{fb}
8036 @section Pragma Thread_Local_Storage
8039 @geindex Task specific storage
8041 @geindex TLS (Thread Local Storage)
8043 @geindex Task_Attributes
8048 pragma Thread_Local_Storage ([Entity =>] LOCAL_NAME);
8051 This pragma specifies that the specified entity, which must be
8052 a variable declared in a library-level package, is to be marked as
8053 "Thread Local Storage" (@code{TLS}). On systems supporting this (which
8054 include Windows, Solaris, GNU/Linux and VxWorks 6), this causes each
8055 thread (and hence each Ada task) to see a distinct copy of the variable.
8057 The variable may not have default initialization, and if there is
8058 an explicit initialization, it must be either @code{null} for an
8059 access variable, or a static expression for a scalar variable.
8060 This provides a low level mechanism similar to that provided by
8061 the @code{Ada.Task_Attributes} package, but much more efficient
8062 and is also useful in writing interface code that will interact
8063 with foreign threads.
8065 If this pragma is used on a system where @code{TLS} is not supported,
8066 then an error message will be generated and the program will be rejected.
8068 @node Pragma Time_Slice,Pragma Title,Pragma Thread_Local_Storage,Implementation Defined Pragmas
8069 @anchor{gnat_rm/implementation_defined_pragmas pragma-time-slice}@anchor{fc}
8070 @section Pragma Time_Slice
8076 pragma Time_Slice (static_duration_EXPRESSION);
8079 For implementations of GNAT on operating systems where it is possible
8080 to supply a time slice value, this pragma may be used for this purpose.
8081 It is ignored if it is used in a system that does not allow this control,
8082 or if it appears in other than the main program unit.
8084 @node Pragma Title,Pragma Type_Invariant,Pragma Time_Slice,Implementation Defined Pragmas
8085 @anchor{gnat_rm/implementation_defined_pragmas pragma-title}@anchor{fd}
8086 @section Pragma Title
8092 pragma Title (TITLING_OPTION [, TITLING OPTION]);
8095 [Title =>] STRING_LITERAL,
8096 | [Subtitle =>] STRING_LITERAL
8099 Syntax checked but otherwise ignored by GNAT. This is a listing control
8100 pragma used in DEC Ada 83 implementations to provide a title and/or
8101 subtitle for the program listing. The program listing generated by GNAT
8102 does not have titles or subtitles.
8104 Unlike other pragmas, the full flexibility of named notation is allowed
8105 for this pragma, i.e., the parameters may be given in any order if named
8106 notation is used, and named and positional notation can be mixed
8107 following the normal rules for procedure calls in Ada.
8109 @node Pragma Type_Invariant,Pragma Type_Invariant_Class,Pragma Title,Implementation Defined Pragmas
8110 @anchor{gnat_rm/implementation_defined_pragmas pragma-type-invariant}@anchor{fe}
8111 @section Pragma Type_Invariant
8117 pragma Type_Invariant
8118 ([Entity =>] type_LOCAL_NAME,
8119 [Check =>] EXPRESSION);
8122 The @code{Type_Invariant} pragma is intended to be an exact
8123 replacement for the language-defined @code{Type_Invariant}
8124 aspect, and shares its restrictions and semantics. It differs
8125 from the language defined @code{Invariant} pragma in that it
8126 does not permit a string parameter, and it is
8127 controlled by the assertion identifier @code{Type_Invariant}
8128 rather than @code{Invariant}.
8130 @node Pragma Type_Invariant_Class,Pragma Unchecked_Union,Pragma Type_Invariant,Implementation Defined Pragmas
8131 @anchor{gnat_rm/implementation_defined_pragmas id46}@anchor{ff}@anchor{gnat_rm/implementation_defined_pragmas pragma-type-invariant-class}@anchor{100}
8132 @section Pragma Type_Invariant_Class
8138 pragma Type_Invariant_Class
8139 ([Entity =>] type_LOCAL_NAME,
8140 [Check =>] EXPRESSION);
8143 The @code{Type_Invariant_Class} pragma is intended to be an exact
8144 replacement for the language-defined @code{Type_Invariant'Class}
8145 aspect, and shares its restrictions and semantics.
8147 Note: This pragma is called @code{Type_Invariant_Class} rather than
8148 @code{Type_Invariant'Class} because the latter would not be strictly
8149 conforming to the allowed syntax for pragmas. The motivation
8150 for providing pragmas equivalent to the aspects is to allow a program
8151 to be written using the pragmas, and then compiled if necessary
8152 using an Ada compiler that does not recognize the pragmas or
8153 aspects, but is prepared to ignore the pragmas. The assertion
8154 policy that controls this pragma is @code{Type_Invariant'Class},
8155 not @code{Type_Invariant_Class}.
8157 @node Pragma Unchecked_Union,Pragma Unevaluated_Use_Of_Old,Pragma Type_Invariant_Class,Implementation Defined Pragmas
8158 @anchor{gnat_rm/implementation_defined_pragmas pragma-unchecked-union}@anchor{101}
8159 @section Pragma Unchecked_Union
8162 @geindex Unions in C
8167 pragma Unchecked_Union (first_subtype_LOCAL_NAME);
8170 This pragma is used to specify a representation of a record type that is
8171 equivalent to a C union. It was introduced as a GNAT implementation defined
8172 pragma in the GNAT Ada 95 mode. Ada 2005 includes an extended version of this
8173 pragma, making it language defined, and GNAT fully implements this extended
8174 version in all language modes (Ada 83, Ada 95, and Ada 2005). For full
8175 details, consult the Ada 2012 Reference Manual, section B.3.3.
8177 @node Pragma Unevaluated_Use_Of_Old,Pragma Unimplemented_Unit,Pragma Unchecked_Union,Implementation Defined Pragmas
8178 @anchor{gnat_rm/implementation_defined_pragmas pragma-unevaluated-use-of-old}@anchor{102}
8179 @section Pragma Unevaluated_Use_Of_Old
8182 @geindex Attribute Old
8184 @geindex Attribute Loop_Entry
8186 @geindex Unevaluated_Use_Of_Old
8191 pragma Unevaluated_Use_Of_Old (Error | Warn | Allow);
8194 This pragma controls the processing of attributes Old and Loop_Entry.
8195 If either of these attributes is used in a potentially unevaluated
8196 expression (e.g. the then or else parts of an if expression), then
8197 normally this usage is considered illegal if the prefix of the attribute
8198 is other than an entity name. The language requires this
8199 behavior for Old, and GNAT copies the same rule for Loop_Entry.
8201 The reason for this rule is that otherwise, we can have a situation
8202 where we save the Old value, and this results in an exception, even
8203 though we might not evaluate the attribute. Consider this example:
8206 package UnevalOld is
8208 procedure U (A : String; C : Boolean) -- ERROR
8209 with Post => (if C then A(1)'Old = K else True);
8213 If procedure U is called with a string with a lower bound of 2, and
8214 C false, then an exception would be raised trying to evaluate A(1)
8215 on entry even though the value would not be actually used.
8217 Although the rule guarantees against this possibility, it is sometimes
8218 too restrictive. For example if we know that the string has a lower
8219 bound of 1, then we will never raise an exception.
8220 The pragma @code{Unevaluated_Use_Of_Old} can be
8221 used to modify this behavior. If the argument is @code{Error} then an
8222 error is given (this is the default RM behavior). If the argument is
8223 @code{Warn} then the usage is allowed as legal but with a warning
8224 that an exception might be raised. If the argument is @code{Allow}
8225 then the usage is allowed as legal without generating a warning.
8227 This pragma may appear as a configuration pragma, or in a declarative
8228 part or package specification. In the latter case it applies to
8229 uses up to the end of the corresponding statement sequence or
8230 sequence of package declarations.
8232 @node Pragma Unimplemented_Unit,Pragma Universal_Aliasing,Pragma Unevaluated_Use_Of_Old,Implementation Defined Pragmas
8233 @anchor{gnat_rm/implementation_defined_pragmas pragma-unimplemented-unit}@anchor{103}
8234 @section Pragma Unimplemented_Unit
8240 pragma Unimplemented_Unit;
8243 If this pragma occurs in a unit that is processed by the compiler, GNAT
8244 aborts with the message @code{xxx not implemented}, where
8245 @code{xxx} is the name of the current compilation unit. This pragma is
8246 intended to allow the compiler to handle unimplemented library units in
8249 The abort only happens if code is being generated. Thus you can use
8250 specs of unimplemented packages in syntax or semantic checking mode.
8252 @node Pragma Universal_Aliasing,Pragma Universal_Data,Pragma Unimplemented_Unit,Implementation Defined Pragmas
8253 @anchor{gnat_rm/implementation_defined_pragmas id47}@anchor{104}@anchor{gnat_rm/implementation_defined_pragmas pragma-universal-aliasing}@anchor{105}
8254 @section Pragma Universal_Aliasing
8260 pragma Universal_Aliasing [([Entity =>] type_LOCAL_NAME)];
8263 @code{type_LOCAL_NAME} must refer to a type declaration in the current
8264 declarative part. The effect is to inhibit strict type-based aliasing
8265 optimization for the given type. In other words, the effect is as though
8266 access types designating this type were subject to pragma No_Strict_Aliasing.
8267 For a detailed description of the strict aliasing optimization, and the
8268 situations in which it must be suppressed, see the section on
8269 @code{Optimization and Strict Aliasing} in the @cite{GNAT User's Guide}.
8271 @node Pragma Universal_Data,Pragma Unmodified,Pragma Universal_Aliasing,Implementation Defined Pragmas
8272 @anchor{gnat_rm/implementation_defined_pragmas pragma-universal-data}@anchor{106}@anchor{gnat_rm/implementation_defined_pragmas id48}@anchor{107}
8273 @section Pragma Universal_Data
8279 pragma Universal_Data [(library_unit_Name)];
8282 This pragma is supported only for the AAMP target and is ignored for
8283 other targets. The pragma specifies that all library-level objects
8284 (Counter 0 data) associated with the library unit are to be accessed
8285 and updated using universal addressing (24-bit addresses for AAMP5)
8286 rather than the default of 16-bit Data Environment (DENV) addressing.
8287 Use of this pragma will generally result in less efficient code for
8288 references to global data associated with the library unit, but
8289 allows such data to be located anywhere in memory. This pragma is
8290 a library unit pragma, but can also be used as a configuration pragma
8291 (including use in the @code{gnat.adc} file). The functionality
8292 of this pragma is also available by applying the -univ switch on the
8293 compilations of units where universal addressing of the data is desired.
8295 @node Pragma Unmodified,Pragma Unreferenced,Pragma Universal_Data,Implementation Defined Pragmas
8296 @anchor{gnat_rm/implementation_defined_pragmas pragma-unmodified}@anchor{108}@anchor{gnat_rm/implementation_defined_pragmas id49}@anchor{109}
8297 @section Pragma Unmodified
8306 pragma Unmodified (LOCAL_NAME @{, LOCAL_NAME@});
8309 This pragma signals that the assignable entities (variables,
8310 @code{out} parameters, @code{in out} parameters) whose names are listed are
8311 deliberately not assigned in the current source unit. This
8312 suppresses warnings about the
8313 entities being referenced but not assigned, and in addition a warning will be
8314 generated if one of these entities is in fact assigned in the
8315 same unit as the pragma (or in the corresponding body, or one
8318 This is particularly useful for clearly signaling that a particular
8319 parameter is not modified, even though the spec suggests that it might
8322 For the variable case, warnings are never given for unreferenced variables
8323 whose name contains one of the substrings
8324 @code{DISCARD, DUMMY, IGNORE, JUNK, UNUSED} in any casing. Such names
8325 are typically to be used in cases where such warnings are expected.
8326 Thus it is never necessary to use @code{pragma Unmodified} for such
8327 variables, though it is harmless to do so.
8329 @node Pragma Unreferenced,Pragma Unreferenced_Objects,Pragma Unmodified,Implementation Defined Pragmas
8330 @anchor{gnat_rm/implementation_defined_pragmas pragma-unreferenced}@anchor{10a}@anchor{gnat_rm/implementation_defined_pragmas id50}@anchor{10b}
8331 @section Pragma Unreferenced
8335 @geindex unreferenced
8340 pragma Unreferenced (LOCAL_NAME @{, LOCAL_NAME@});
8341 pragma Unreferenced (library_unit_NAME @{, library_unit_NAME@});
8344 This pragma signals that the entities whose names are listed are
8345 deliberately not referenced in the current source unit after the
8346 occurrence of the pragma. This
8347 suppresses warnings about the
8348 entities being unreferenced, and in addition a warning will be
8349 generated if one of these entities is in fact subsequently referenced in the
8350 same unit as the pragma (or in the corresponding body, or one
8353 This is particularly useful for clearly signaling that a particular
8354 parameter is not referenced in some particular subprogram implementation
8355 and that this is deliberate. It can also be useful in the case of
8356 objects declared only for their initialization or finalization side
8359 If @code{LOCAL_NAME} identifies more than one matching homonym in the
8360 current scope, then the entity most recently declared is the one to which
8361 the pragma applies. Note that in the case of accept formals, the pragma
8362 Unreferenced may appear immediately after the keyword @code{do} which
8363 allows the indication of whether or not accept formals are referenced
8364 or not to be given individually for each accept statement.
8366 The left hand side of an assignment does not count as a reference for the
8367 purpose of this pragma. Thus it is fine to assign to an entity for which
8368 pragma Unreferenced is given.
8370 Note that if a warning is desired for all calls to a given subprogram,
8371 regardless of whether they occur in the same unit as the subprogram
8372 declaration, then this pragma should not be used (calls from another
8373 unit would not be flagged); pragma Obsolescent can be used instead
8374 for this purpose, see @ref{a9,,Pragma Obsolescent}.
8376 The second form of pragma @code{Unreferenced} is used within a context
8377 clause. In this case the arguments must be unit names of units previously
8378 mentioned in @code{with} clauses (similar to the usage of pragma
8379 @code{Elaborate_All}. The effect is to suppress warnings about unreferenced
8380 units and unreferenced entities within these units.
8382 For the variable case, warnings are never given for unreferenced variables
8383 whose name contains one of the substrings
8384 @code{DISCARD, DUMMY, IGNORE, JUNK, UNUSED} in any casing. Such names
8385 are typically to be used in cases where such warnings are expected.
8386 Thus it is never necessary to use @code{pragma Unreferenced} for such
8387 variables, though it is harmless to do so.
8389 @node Pragma Unreferenced_Objects,Pragma Unreserve_All_Interrupts,Pragma Unreferenced,Implementation Defined Pragmas
8390 @anchor{gnat_rm/implementation_defined_pragmas pragma-unreferenced-objects}@anchor{10c}@anchor{gnat_rm/implementation_defined_pragmas id51}@anchor{10d}
8391 @section Pragma Unreferenced_Objects
8395 @geindex unreferenced
8400 pragma Unreferenced_Objects (local_subtype_NAME @{, local_subtype_NAME@});
8403 This pragma signals that for the types or subtypes whose names are
8404 listed, objects which are declared with one of these types or subtypes may
8405 not be referenced, and if no references appear, no warnings are given.
8407 This is particularly useful for objects which are declared solely for their
8408 initialization and finalization effect. Such variables are sometimes referred
8409 to as RAII variables (Resource Acquisition Is Initialization). Using this
8410 pragma on the relevant type (most typically a limited controlled type), the
8411 compiler will automatically suppress unwanted warnings about these variables
8412 not being referenced.
8414 @node Pragma Unreserve_All_Interrupts,Pragma Unsuppress,Pragma Unreferenced_Objects,Implementation Defined Pragmas
8415 @anchor{gnat_rm/implementation_defined_pragmas pragma-unreserve-all-interrupts}@anchor{10e}
8416 @section Pragma Unreserve_All_Interrupts
8422 pragma Unreserve_All_Interrupts;
8425 Normally certain interrupts are reserved to the implementation. Any attempt
8426 to attach an interrupt causes Program_Error to be raised, as described in
8427 RM C.3.2(22). A typical example is the @code{SIGINT} interrupt used in
8428 many systems for a @code{Ctrl-C} interrupt. Normally this interrupt is
8429 reserved to the implementation, so that @code{Ctrl-C} can be used to
8430 interrupt execution.
8432 If the pragma @code{Unreserve_All_Interrupts} appears anywhere in any unit in
8433 a program, then all such interrupts are unreserved. This allows the
8434 program to handle these interrupts, but disables their standard
8435 functions. For example, if this pragma is used, then pressing
8436 @code{Ctrl-C} will not automatically interrupt execution. However,
8437 a program can then handle the @code{SIGINT} interrupt as it chooses.
8439 For a full list of the interrupts handled in a specific implementation,
8440 see the source code for the spec of @code{Ada.Interrupts.Names} in
8441 file @code{a-intnam.ads}. This is a target dependent file that contains the
8442 list of interrupts recognized for a given target. The documentation in
8443 this file also specifies what interrupts are affected by the use of
8444 the @code{Unreserve_All_Interrupts} pragma.
8446 For a more general facility for controlling what interrupts can be
8447 handled, see pragma @code{Interrupt_State}, which subsumes the functionality
8448 of the @code{Unreserve_All_Interrupts} pragma.
8450 @node Pragma Unsuppress,Pragma Use_VADS_Size,Pragma Unreserve_All_Interrupts,Implementation Defined Pragmas
8451 @anchor{gnat_rm/implementation_defined_pragmas pragma-unsuppress}@anchor{10f}
8452 @section Pragma Unsuppress
8458 pragma Unsuppress (IDENTIFIER [, [On =>] NAME]);
8461 This pragma undoes the effect of a previous pragma @code{Suppress}. If
8462 there is no corresponding pragma @code{Suppress} in effect, it has no
8463 effect. The range of the effect is the same as for pragma
8464 @code{Suppress}. The meaning of the arguments is identical to that used
8465 in pragma @code{Suppress}.
8467 One important application is to ensure that checks are on in cases where
8468 code depends on the checks for its correct functioning, so that the code
8469 will compile correctly even if the compiler switches are set to suppress
8470 checks. For example, in a program that depends on external names of tagged
8471 types and wants to ensure that the duplicated tag check occurs even if all
8472 run-time checks are suppressed by a compiler switch, the following
8473 configuration pragma will ensure this test is not suppressed:
8476 pragma Unsuppress (Duplicated_Tag_Check);
8479 This pragma is standard in Ada 2005. It is available in all earlier versions
8480 of Ada as an implementation-defined pragma.
8482 Note that in addition to the checks defined in the Ada RM, GNAT recogizes a
8483 number of implementation-defined check names. See the description of pragma
8484 @code{Suppress} for full details.
8486 @node Pragma Use_VADS_Size,Pragma Unused,Pragma Unsuppress,Implementation Defined Pragmas
8487 @anchor{gnat_rm/implementation_defined_pragmas pragma-use-vads-size}@anchor{110}
8488 @section Pragma Use_VADS_Size
8492 @geindex VADS compatibility
8494 @geindex Rational profile
8499 pragma Use_VADS_Size;
8502 This is a configuration pragma. In a unit to which it applies, any use
8503 of the 'Size attribute is automatically interpreted as a use of the
8504 'VADS_Size attribute. Note that this may result in incorrect semantic
8505 processing of valid Ada 95 or Ada 2005 programs. This is intended to aid in
8506 the handling of existing code which depends on the interpretation of Size
8507 as implemented in the VADS compiler. See description of the VADS_Size
8508 attribute for further details.
8510 @node Pragma Unused,Pragma Validity_Checks,Pragma Use_VADS_Size,Implementation Defined Pragmas
8511 @anchor{gnat_rm/implementation_defined_pragmas pragma-unused}@anchor{111}@anchor{gnat_rm/implementation_defined_pragmas id52}@anchor{112}
8512 @section Pragma Unused
8521 pragma Unused (LOCAL_NAME @{, LOCAL_NAME@});
8524 This pragma signals that the assignable entities (variables,
8525 @code{out} parameters, and @code{in out} parameters) whose names are listed
8526 deliberately do not get assigned or referenced in the current source unit
8527 after the occurrence of the pragma in the current source unit. This
8528 suppresses warnings about the entities that are unreferenced and/or not
8529 assigned, and, in addition, a warning will be generated if one of these
8530 entities gets assigned or subsequently referenced in the same unit as the
8531 pragma (in the corresponding body or one of its subunits).
8533 This is particularly useful for clearly signaling that a particular
8534 parameter is not modified or referenced, even though the spec suggests
8537 For the variable case, warnings are never given for unreferenced
8538 variables whose name contains one of the substrings
8539 @code{DISCARD, DUMMY, IGNORE, JUNK, UNUSED} in any casing. Such names
8540 are typically to be used in cases where such warnings are expected.
8541 Thus it is never necessary to use @code{pragma Unmodified} for such
8542 variables, though it is harmless to do so.
8544 @node Pragma Validity_Checks,Pragma Volatile,Pragma Unused,Implementation Defined Pragmas
8545 @anchor{gnat_rm/implementation_defined_pragmas pragma-validity-checks}@anchor{113}
8546 @section Pragma Validity_Checks
8552 pragma Validity_Checks (string_LITERAL | ALL_CHECKS | On | Off);
8555 This pragma is used in conjunction with compiler switches to control the
8556 built-in validity checking provided by GNAT. The compiler switches, if set
8557 provide an initial setting for the switches, and this pragma may be used
8558 to modify these settings, or the settings may be provided entirely by
8559 the use of the pragma. This pragma can be used anywhere that a pragma
8560 is legal, including use as a configuration pragma (including use in
8561 the @code{gnat.adc} file).
8563 The form with a string literal specifies which validity options are to be
8564 activated. The validity checks are first set to include only the default
8565 reference manual settings, and then a string of letters in the string
8566 specifies the exact set of options required. The form of this string
8567 is exactly as described for the @emph{-gnatVx} compiler switch (see the
8568 GNAT User's Guide for details). For example the following two
8569 methods can be used to enable validity checking for mode @code{in} and
8570 @code{in out} subprogram parameters:
8577 pragma Validity_Checks ("im");
8582 $ gcc -c -gnatVim ...
8586 The form ALL_CHECKS activates all standard checks (its use is equivalent
8587 to the use of the @code{gnatva} switch.
8589 The forms with @code{Off} and @code{On}
8590 can be used to temporarily disable validity checks
8591 as shown in the following example:
8594 pragma Validity_Checks ("c"); -- validity checks for copies
8595 pragma Validity_Checks (Off); -- turn off validity checks
8596 A := B; -- B will not be validity checked
8597 pragma Validity_Checks (On); -- turn validity checks back on
8598 A := C; -- C will be validity checked
8601 @node Pragma Volatile,Pragma Volatile_Full_Access,Pragma Validity_Checks,Implementation Defined Pragmas
8602 @anchor{gnat_rm/implementation_defined_pragmas pragma-volatile}@anchor{114}
8603 @section Pragma Volatile
8609 pragma Volatile (LOCAL_NAME);
8612 This pragma is defined by the Ada Reference Manual, and the GNAT
8613 implementation is fully conformant with this definition. The reason it
8614 is mentioned in this section is that a pragma of the same name was supplied
8615 in some Ada 83 compilers, including DEC Ada 83. The Ada 95 / Ada 2005
8616 implementation of pragma Volatile is upwards compatible with the
8617 implementation in DEC Ada 83.
8619 @node Pragma Volatile_Full_Access,Pragma Volatile_Function,Pragma Volatile,Implementation Defined Pragmas
8620 @anchor{gnat_rm/implementation_defined_pragmas pragma-volatile-full-access}@anchor{115}@anchor{gnat_rm/implementation_defined_pragmas id53}@anchor{116}
8621 @section Pragma Volatile_Full_Access
8627 pragma Volatile_Full_Access (LOCAL_NAME);
8630 This is similar in effect to pragma Volatile, except that any reference to the
8631 object is guaranteed to be done only with instructions that read or write all
8632 the bits of the object. Furthermore, if the object is of a composite type,
8633 then any reference to a component of the object is guaranteed to read and/or
8634 write all the bits of the object.
8636 The intention is that this be suitable for use with memory-mapped I/O devices
8637 on some machines. Note that there are two important respects in which this is
8638 different from @code{pragma Atomic}. First a reference to a @code{Volatile_Full_Access}
8639 object is not a sequential action in the RM 9.10 sense and, therefore, does
8640 not create a synchronization point. Second, in the case of @code{pragma Atomic},
8641 there is no guarantee that all the bits will be accessed if the reference
8642 is not to the whole object; the compiler is allowed (and generally will)
8643 access only part of the object in this case.
8645 It is not permissible to specify @code{Atomic} and @code{Volatile_Full_Access} for
8648 It is not permissible to specify @code{Volatile_Full_Access} for a composite
8649 (record or array) type or object that has at least one @code{Aliased} component.
8651 @node Pragma Volatile_Function,Pragma Warning_As_Error,Pragma Volatile_Full_Access,Implementation Defined Pragmas
8652 @anchor{gnat_rm/implementation_defined_pragmas id54}@anchor{117}@anchor{gnat_rm/implementation_defined_pragmas pragma-volatile-function}@anchor{118}
8653 @section Pragma Volatile_Function
8659 pragma Volatile_Function [ (boolean_EXPRESSION) ];
8662 For the semantics of this pragma, see the entry for aspect @code{Volatile_Function}
8663 in the SPARK 2014 Reference Manual, section 7.1.2.
8665 @node Pragma Warning_As_Error,Pragma Warnings,Pragma Volatile_Function,Implementation Defined Pragmas
8666 @anchor{gnat_rm/implementation_defined_pragmas pragma-warning-as-error}@anchor{119}
8667 @section Pragma Warning_As_Error
8673 pragma Warning_As_Error (static_string_EXPRESSION);
8676 This configuration pragma allows the programmer to specify a set
8677 of warnings that will be treated as errors. Any warning which
8678 matches the pattern given by the pragma argument will be treated
8679 as an error. This gives much more precise control that -gnatwe
8680 which treats all warnings as errors.
8682 The pattern may contain asterisks, which match zero or more characters in
8683 the message. For example, you can use
8684 @code{pragma Warning_As_Error ("bits of*unused")} to treat the warning
8685 message @code{warning: 960 bits of "a" unused} as an error. No other regular
8686 expression notations are permitted. All characters other than asterisk in
8687 these three specific cases are treated as literal characters in the match.
8688 The match is case insensitive, for example XYZ matches xyz.
8690 Note that the pattern matches if it occurs anywhere within the warning
8691 message string (it is not necessary to put an asterisk at the start and
8692 the end of the message, since this is implied).
8694 Another possibility for the static_string_EXPRESSION which works whether
8695 or not error tags are enabled (@emph{-gnatw.d}) is to use the
8696 @emph{-gnatw} tag string, enclosed in brackets,
8697 as shown in the example below, to treat a class of warnings as errors.
8699 The above use of patterns to match the message applies only to warning
8700 messages generated by the front end. This pragma can also be applied to
8701 warnings provided by the back end and mentioned in @ref{11a,,Pragma Warnings}.
8702 By using a single full @emph{-Wxxx} switch in the pragma, such warnings
8703 can also be treated as errors.
8705 The pragma can appear either in a global configuration pragma file
8706 (e.g. @code{gnat.adc}), or at the start of a file. Given a global
8707 configuration pragma file containing:
8710 pragma Warning_As_Error ("[-gnatwj]");
8713 which will treat all obsolescent feature warnings as errors, the
8714 following program compiles as shown (compile options here are
8715 @emph{-gnatwa.d -gnatl -gnatj55}).
8718 1. pragma Warning_As_Error ("*never assigned*");
8719 2. function Warnerr return String is
8722 >>> error: variable "X" is never read and
8723 never assigned [-gnatwv] [warning-as-error]
8727 >>> warning: variable "Y" is assigned but
8728 never read [-gnatwu]
8734 >>> error: use of "%" is an obsolescent
8735 feature (RM J.2(4)), use """ instead
8736 [-gnatwj] [warning-as-error]
8740 8 lines: No errors, 3 warnings (2 treated as errors)
8743 Note that this pragma does not affect the set of warnings issued in
8744 any way, it merely changes the effect of a matching warning if one
8745 is produced as a result of other warnings options. As shown in this
8746 example, if the pragma results in a warning being treated as an error,
8747 the tag is changed from "warning:" to "error:" and the string
8748 "[warning-as-error]" is appended to the end of the message.
8750 @node Pragma Warnings,Pragma Weak_External,Pragma Warning_As_Error,Implementation Defined Pragmas
8751 @anchor{gnat_rm/implementation_defined_pragmas id55}@anchor{11b}@anchor{gnat_rm/implementation_defined_pragmas pragma-warnings}@anchor{11a}
8752 @section Pragma Warnings
8758 pragma Warnings ([TOOL_NAME,] DETAILS [, REASON]);
8760 DETAILS ::= On | Off
8761 DETAILS ::= On | Off, local_NAME
8762 DETAILS ::= static_string_EXPRESSION
8763 DETAILS ::= On | Off, static_string_EXPRESSION
8765 TOOL_NAME ::= GNAT | GNATProve
8767 REASON ::= Reason => STRING_LITERAL @{& STRING_LITERAL@}
8770 Note: in Ada 83 mode, a string literal may be used in place of a static string
8771 expression (which does not exist in Ada 83).
8773 Note if the second argument of @code{DETAILS} is a @code{local_NAME} then the
8774 second form is always understood. If the intention is to use
8775 the fourth form, then you can write @code{NAME & ""} to force the
8776 intepretation as a @emph{static_string_EXPRESSION}.
8778 Note: if the first argument is a valid @code{TOOL_NAME}, it will be interpreted
8779 that way. The use of the @code{TOOL_NAME} argument is relevant only to users
8780 of SPARK and GNATprove, see last part of this section for details.
8782 Normally warnings are enabled, with the output being controlled by
8783 the command line switch. Warnings (@code{Off}) turns off generation of
8784 warnings until a Warnings (@code{On}) is encountered or the end of the
8785 current unit. If generation of warnings is turned off using this
8786 pragma, then some or all of the warning messages are suppressed,
8787 regardless of the setting of the command line switches.
8789 The @code{Reason} parameter may optionally appear as the last argument
8790 in any of the forms of this pragma. It is intended purely for the
8791 purposes of documenting the reason for the @code{Warnings} pragma.
8792 The compiler will check that the argument is a static string but
8793 otherwise ignore this argument. Other tools may provide specialized
8794 processing for this string.
8796 The form with a single argument (or two arguments if Reason present),
8797 where the first argument is @code{ON} or @code{OFF}
8798 may be used as a configuration pragma.
8800 If the @code{LOCAL_NAME} parameter is present, warnings are suppressed for
8801 the specified entity. This suppression is effective from the point where
8802 it occurs till the end of the extended scope of the variable (similar to
8803 the scope of @code{Suppress}). This form cannot be used as a configuration
8806 In the case where the first argument is other than @code{ON} or
8808 the third form with a single static_string_EXPRESSION argument (and possible
8809 reason) provides more precise
8810 control over which warnings are active. The string is a list of letters
8811 specifying which warnings are to be activated and which deactivated. The
8812 code for these letters is the same as the string used in the command
8813 line switch controlling warnings. For a brief summary, use the gnatmake
8814 command with no arguments, which will generate usage information containing
8815 the list of warnings switches supported. For
8816 full details see the section on @code{Warning Message Control} in the
8817 @cite{GNAT User's Guide}.
8818 This form can also be used as a configuration pragma.
8820 The warnings controlled by the @code{-gnatw} switch are generated by the
8821 front end of the compiler. The GCC back end can provide additional warnings
8822 and they are controlled by the @code{-W} switch. Such warnings can be
8823 identified by the appearance of a string of the form @code{[-W@{xxx@}]} in the
8824 message which designates the @code{-W@emph{xxx}} switch that controls the message.
8825 The form with a single @emph{static_string_EXPRESSION} argument also works for these
8826 warnings, but the string must be a single full @code{-W@emph{xxx}} switch in this
8827 case. The above reference lists a few examples of these additional warnings.
8829 The specified warnings will be in effect until the end of the program
8830 or another pragma @code{Warnings} is encountered. The effect of the pragma is
8831 cumulative. Initially the set of warnings is the standard default set
8832 as possibly modified by compiler switches. Then each pragma Warning
8833 modifies this set of warnings as specified. This form of the pragma may
8834 also be used as a configuration pragma.
8836 The fourth form, with an @code{On|Off} parameter and a string, is used to
8837 control individual messages, based on their text. The string argument
8838 is a pattern that is used to match against the text of individual
8839 warning messages (not including the initial "warning: " tag).
8841 The pattern may contain asterisks, which match zero or more characters in
8842 the message. For example, you can use
8843 @code{pragma Warnings (Off, "bits of*unused")} to suppress the warning
8844 message @code{warning: 960 bits of "a" unused}. No other regular
8845 expression notations are permitted. All characters other than asterisk in
8846 these three specific cases are treated as literal characters in the match.
8847 The match is case insensitive, for example XYZ matches xyz.
8849 Note that the pattern matches if it occurs anywhere within the warning
8850 message string (it is not necessary to put an asterisk at the start and
8851 the end of the message, since this is implied).
8853 The above use of patterns to match the message applies only to warning
8854 messages generated by the front end. This form of the pragma with a string
8855 argument can also be used to control warnings provided by the back end and
8856 mentioned above. By using a single full @code{-W@emph{xxx}} switch in the pragma,
8857 such warnings can be turned on and off.
8859 There are two ways to use the pragma in this form. The OFF form can be used
8860 as a configuration pragma. The effect is to suppress all warnings (if any)
8861 that match the pattern string throughout the compilation (or match the
8862 -W switch in the back end case).
8864 The second usage is to suppress a warning locally, and in this case, two
8865 pragmas must appear in sequence:
8868 pragma Warnings (Off, Pattern);
8869 ... code where given warning is to be suppressed
8870 pragma Warnings (On, Pattern);
8873 In this usage, the pattern string must match in the Off and On
8874 pragmas, and (if @emph{-gnatw.w} is given) at least one matching
8875 warning must be suppressed.
8877 Note: to write a string that will match any warning, use the string
8878 @code{"***"}. It will not work to use a single asterisk or two
8879 asterisks since this looks like an operator name. This form with three
8880 asterisks is similar in effect to specifying @code{pragma Warnings (Off)} except (if @code{-gnatw.w} is given) that a matching
8881 @code{pragma Warnings (On, "***")} will be required. This can be
8882 helpful in avoiding forgetting to turn warnings back on.
8884 Note: the debug flag @code{-gnatd.i} (@code{/NOWARNINGS_PRAGMAS} in VMS) can be
8885 used to cause the compiler to entirely ignore all WARNINGS pragmas. This can
8886 be useful in checking whether obsolete pragmas in existing programs are hiding
8889 Note: pragma Warnings does not affect the processing of style messages. See
8890 separate entry for pragma Style_Checks for control of style messages.
8892 Users of the formal verification tool GNATprove for the SPARK subset of Ada may
8893 use the version of the pragma with a @code{TOOL_NAME} parameter.
8895 If present, @code{TOOL_NAME} is the name of a tool, currently either @code{GNAT} for the
8896 compiler or @code{GNATprove} for the formal verification tool. A given tool only
8897 takes into account pragma Warnings that do not specify a tool name, or that
8898 specify the matching tool name. This makes it possible to disable warnings
8899 selectively for each tool, and as a consequence to detect useless pragma
8900 Warnings with switch @code{-gnatw.w}.
8902 @node Pragma Weak_External,Pragma Wide_Character_Encoding,Pragma Warnings,Implementation Defined Pragmas
8903 @anchor{gnat_rm/implementation_defined_pragmas pragma-weak-external}@anchor{11c}
8904 @section Pragma Weak_External
8910 pragma Weak_External ([Entity =>] LOCAL_NAME);
8913 @code{LOCAL_NAME} must refer to an object that is declared at the library
8914 level. This pragma specifies that the given entity should be marked as a
8915 weak symbol for the linker. It is equivalent to @code{__attribute__((weak))}
8916 in GNU C and causes @code{LOCAL_NAME} to be emitted as a weak symbol instead
8917 of a regular symbol, that is to say a symbol that does not have to be
8918 resolved by the linker if used in conjunction with a pragma Import.
8920 When a weak symbol is not resolved by the linker, its address is set to
8921 zero. This is useful in writing interfaces to external modules that may
8922 or may not be linked in the final executable, for example depending on
8923 configuration settings.
8925 If a program references at run time an entity to which this pragma has been
8926 applied, and the corresponding symbol was not resolved at link time, then
8927 the execution of the program is erroneous. It is not erroneous to take the
8928 Address of such an entity, for example to guard potential references,
8929 as shown in the example below.
8931 Some file formats do not support weak symbols so not all target machines
8932 support this pragma.
8935 -- Example of the use of pragma Weak_External
8937 package External_Module is
8939 pragma Import (C, key);
8940 pragma Weak_External (key);
8941 function Present return boolean;
8942 end External_Module;
8944 with System; use System;
8945 package body External_Module is
8946 function Present return boolean is
8948 return key'Address /= System.Null_Address;
8950 end External_Module;
8953 @node Pragma Wide_Character_Encoding,,Pragma Weak_External,Implementation Defined Pragmas
8954 @anchor{gnat_rm/implementation_defined_pragmas pragma-wide-character-encoding}@anchor{11d}
8955 @section Pragma Wide_Character_Encoding
8961 pragma Wide_Character_Encoding (IDENTIFIER | CHARACTER_LITERAL);
8964 This pragma specifies the wide character encoding to be used in program
8965 source text appearing subsequently. It is a configuration pragma, but may
8966 also be used at any point that a pragma is allowed, and it is permissible
8967 to have more than one such pragma in a file, allowing multiple encodings
8968 to appear within the same file.
8970 However, note that the pragma cannot immediately precede the relevant
8971 wide character, because then the previous encoding will still be in
8972 effect, causing "illegal character" errors.
8974 The argument can be an identifier or a character literal. In the identifier
8975 case, it is one of @code{HEX}, @code{UPPER}, @code{SHIFT_JIS},
8976 @code{EUC}, @code{UTF8}, or @code{BRACKETS}. In the character literal
8977 case it is correspondingly one of the characters @code{h}, @code{u},
8978 @code{s}, @code{e}, @code{8}, or @code{b}.
8980 Note that when the pragma is used within a file, it affects only the
8981 encoding within that file, and does not affect withed units, specs,
8984 @node Implementation Defined Aspects,Implementation Defined Attributes,Implementation Defined Pragmas,Top
8985 @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}
8986 @chapter Implementation Defined Aspects
8989 Ada defines (throughout the Ada 2012 reference manual, summarized
8990 in Annex K) a set of aspects that can be specified for certain entities.
8991 These language defined aspects are implemented in GNAT in Ada 2012 mode
8992 and work as described in the Ada 2012 Reference Manual.
8994 In addition, Ada 2012 allows implementations to define additional aspects
8995 whose meaning is defined by the implementation. GNAT provides
8996 a number of these implementation-defined aspects which can be used
8997 to extend and enhance the functionality of the compiler. This section of
8998 the GNAT reference manual describes these additional aspects.
9000 Note that any program using these aspects may not be portable to
9001 other compilers (although GNAT implements this set of aspects on all
9002 platforms). Therefore if portability to other compilers is an important
9003 consideration, you should minimize the use of these aspects.
9005 Note that for many of these aspects, the effect is essentially similar
9006 to the use of a pragma or attribute specification with the same name
9007 applied to the entity. For example, if we write:
9010 type R is range 1 .. 100
9011 with Value_Size => 10;
9014 then the effect is the same as:
9017 type R is range 1 .. 100;
9018 for R'Value_Size use 10;
9024 type R is new Integer
9025 with Shared => True;
9028 then the effect is the same as:
9031 type R is new Integer;
9035 In the documentation below, such cases are simply marked
9036 as being boolean aspects equivalent to the corresponding pragma
9037 or attribute definition clause.
9040 * Aspect Abstract_State::
9042 * Aspect Async_Readers::
9043 * Aspect Async_Writers::
9044 * Aspect Constant_After_Elaboration::
9045 * Aspect Contract_Cases::
9047 * Aspect Default_Initial_Condition::
9048 * Aspect Dimension::
9049 * Aspect Dimension_System::
9050 * Aspect Disable_Controlled::
9051 * Aspect Effective_Reads::
9052 * Aspect Effective_Writes::
9053 * Aspect Extensions_Visible::
9054 * Aspect Favor_Top_Level::
9057 * Aspect Initial_Condition::
9058 * Aspect Initializes::
9059 * Aspect Inline_Always::
9060 * Aspect Invariant::
9061 * Aspect Invariant'Class::
9063 * Aspect Linker_Section::
9064 * Aspect Lock_Free::
9065 * Aspect Max_Queue_Length::
9066 * Aspect No_Elaboration_Code_All::
9067 * Aspect No_Inline::
9068 * Aspect No_Tagged_Streams::
9069 * Aspect Object_Size::
9070 * Aspect Obsolescent::
9072 * Aspect Persistent_BSS::
9073 * Aspect Predicate::
9074 * Aspect Pure_Function::
9075 * Aspect Refined_Depends::
9076 * Aspect Refined_Global::
9077 * Aspect Refined_Post::
9078 * Aspect Refined_State::
9079 * Aspect Remote_Access_Type::
9080 * Aspect Secondary_Stack_Size::
9081 * Aspect Scalar_Storage_Order::
9083 * Aspect Simple_Storage_Pool::
9084 * Aspect Simple_Storage_Pool_Type::
9085 * Aspect SPARK_Mode::
9086 * Aspect Suppress_Debug_Info::
9087 * Aspect Suppress_Initialization::
9088 * Aspect Test_Case::
9089 * Aspect Thread_Local_Storage::
9090 * Aspect Universal_Aliasing::
9091 * Aspect Universal_Data::
9092 * Aspect Unmodified::
9093 * Aspect Unreferenced::
9094 * Aspect Unreferenced_Objects::
9095 * Aspect Value_Size::
9096 * Aspect Volatile_Full_Access::
9097 * Aspect Volatile_Function::
9102 @node Aspect Abstract_State,Aspect Annotate,,Implementation Defined Aspects
9103 @anchor{gnat_rm/implementation_defined_aspects aspect-abstract-state}@anchor{121}
9104 @section Aspect Abstract_State
9107 @geindex Abstract_State
9109 This aspect is equivalent to @ref{1c,,pragma Abstract_State}.
9111 @node Aspect Annotate,Aspect Async_Readers,Aspect Abstract_State,Implementation Defined Aspects
9112 @anchor{gnat_rm/implementation_defined_aspects aspect-annotate}@anchor{122}
9113 @section Aspect Annotate
9118 There are three forms of this aspect (where ID is an identifier,
9119 and ARG is a general expression),
9120 corresponding to @ref{25,,pragma Annotate}.
9125 @item @emph{Annotate => ID}
9127 Equivalent to @code{pragma Annotate (ID, Entity => Name);}
9129 @item @emph{Annotate => (ID)}
9131 Equivalent to @code{pragma Annotate (ID, Entity => Name);}
9133 @item @emph{Annotate => (ID ,ID @{, ARG@})}
9135 Equivalent to @code{pragma Annotate (ID, ID @{, ARG@}, Entity => Name);}
9138 @node Aspect Async_Readers,Aspect Async_Writers,Aspect Annotate,Implementation Defined Aspects
9139 @anchor{gnat_rm/implementation_defined_aspects aspect-async-readers}@anchor{123}
9140 @section Aspect Async_Readers
9143 @geindex Async_Readers
9145 This boolean aspect is equivalent to @ref{2c,,pragma Async_Readers}.
9147 @node Aspect Async_Writers,Aspect Constant_After_Elaboration,Aspect Async_Readers,Implementation Defined Aspects
9148 @anchor{gnat_rm/implementation_defined_aspects aspect-async-writers}@anchor{124}
9149 @section Aspect Async_Writers
9152 @geindex Async_Writers
9154 This boolean aspect is equivalent to @ref{2f,,pragma Async_Writers}.
9156 @node Aspect Constant_After_Elaboration,Aspect Contract_Cases,Aspect Async_Writers,Implementation Defined Aspects
9157 @anchor{gnat_rm/implementation_defined_aspects aspect-constant-after-elaboration}@anchor{125}
9158 @section Aspect Constant_After_Elaboration
9161 @geindex Constant_After_Elaboration
9163 This aspect is equivalent to @ref{40,,pragma Constant_After_Elaboration}.
9165 @node Aspect Contract_Cases,Aspect Depends,Aspect Constant_After_Elaboration,Implementation Defined Aspects
9166 @anchor{gnat_rm/implementation_defined_aspects aspect-contract-cases}@anchor{126}
9167 @section Aspect Contract_Cases
9170 @geindex Contract_Cases
9172 This aspect is equivalent to @ref{42,,pragma Contract_Cases}, the sequence
9173 of clauses being enclosed in parentheses so that syntactically it is an
9176 @node Aspect Depends,Aspect Default_Initial_Condition,Aspect Contract_Cases,Implementation Defined Aspects
9177 @anchor{gnat_rm/implementation_defined_aspects aspect-depends}@anchor{127}
9178 @section Aspect Depends
9183 This aspect is equivalent to @ref{51,,pragma Depends}.
9185 @node Aspect Default_Initial_Condition,Aspect Dimension,Aspect Depends,Implementation Defined Aspects
9186 @anchor{gnat_rm/implementation_defined_aspects aspect-default-initial-condition}@anchor{128}
9187 @section Aspect Default_Initial_Condition
9190 @geindex Default_Initial_Condition
9192 This aspect is equivalent to @ref{4c,,pragma Default_Initial_Condition}.
9194 @node Aspect Dimension,Aspect Dimension_System,Aspect Default_Initial_Condition,Implementation Defined Aspects
9195 @anchor{gnat_rm/implementation_defined_aspects aspect-dimension}@anchor{129}
9196 @section Aspect Dimension
9201 The @code{Dimension} aspect is used to specify the dimensions of a given
9202 subtype of a dimensioned numeric type. The aspect also specifies a symbol
9203 used when doing formatted output of dimensioned quantities. The syntax is:
9207 ([Symbol =>] SYMBOL, DIMENSION_VALUE @{, DIMENSION_Value@})
9209 SYMBOL ::= STRING_LITERAL | CHARACTER_LITERAL
9213 | others => RATIONAL
9214 | DISCRETE_CHOICE_LIST => RATIONAL
9216 RATIONAL ::= [-] NUMERIC_LITERAL [/ NUMERIC_LITERAL]
9219 This aspect can only be applied to a subtype whose parent type has
9220 a @code{Dimension_System} aspect. The aspect must specify values for
9221 all dimensions of the system. The rational values are the powers of the
9222 corresponding dimensions that are used by the compiler to verify that
9223 physical (numeric) computations are dimensionally consistent. For example,
9224 the computation of a force must result in dimensions (L => 1, M => 1, T => -2).
9225 For further examples of the usage
9226 of this aspect, see package @code{System.Dim.Mks}.
9227 Note that when the dimensioned type is an integer type, then any
9228 dimension value must be an integer literal.
9230 @node Aspect Dimension_System,Aspect Disable_Controlled,Aspect Dimension,Implementation Defined Aspects
9231 @anchor{gnat_rm/implementation_defined_aspects aspect-dimension-system}@anchor{12a}
9232 @section Aspect Dimension_System
9235 @geindex Dimension_System
9237 The @code{Dimension_System} aspect is used to define a system of
9238 dimensions that will be used in subsequent subtype declarations with
9239 @code{Dimension} aspects that reference this system. The syntax is:
9242 with Dimension_System => (DIMENSION @{, DIMENSION@});
9244 DIMENSION ::= ([Unit_Name =>] IDENTIFIER,
9245 [Unit_Symbol =>] SYMBOL,
9246 [Dim_Symbol =>] SYMBOL)
9248 SYMBOL ::= CHARACTER_LITERAL | STRING_LITERAL
9251 This aspect is applied to a type, which must be a numeric derived type
9252 (typically a floating-point type), that
9253 will represent values within the dimension system. Each @code{DIMENSION}
9254 corresponds to one particular dimension. A maximum of 7 dimensions may
9255 be specified. @code{Unit_Name} is the name of the dimension (for example
9256 @code{Meter}). @code{Unit_Symbol} is the shorthand used for quantities
9257 of this dimension (for example @code{m} for @code{Meter}).
9258 @code{Dim_Symbol} gives
9259 the identification within the dimension system (typically this is a
9260 single letter, e.g. @code{L} standing for length for unit name @code{Meter}).
9261 The @code{Unit_Symbol} is used in formatted output of dimensioned quantities.
9262 The @code{Dim_Symbol} is used in error messages when numeric operations have
9263 inconsistent dimensions.
9265 GNAT provides the standard definition of the International MKS system in
9266 the run-time package @code{System.Dim.Mks}. You can easily define
9267 similar packages for cgs units or British units, and define conversion factors
9268 between values in different systems. The MKS system is characterized by the
9272 type Mks_Type is new Long_Long_Float with
9273 Dimension_System => (
9274 (Unit_Name => Meter, Unit_Symbol => 'm', Dim_Symbol => 'L'),
9275 (Unit_Name => Kilogram, Unit_Symbol => "kg", Dim_Symbol => 'M'),
9276 (Unit_Name => Second, Unit_Symbol => 's', Dim_Symbol => 'T'),
9277 (Unit_Name => Ampere, Unit_Symbol => 'A', Dim_Symbol => 'I'),
9278 (Unit_Name => Kelvin, Unit_Symbol => 'K', Dim_Symbol => '@@'),
9279 (Unit_Name => Mole, Unit_Symbol => "mol", Dim_Symbol => 'N'),
9280 (Unit_Name => Candela, Unit_Symbol => "cd", Dim_Symbol => 'J'));
9283 Note that in the above type definition, we use the @code{at} symbol (@code{@@}) to
9284 represent a theta character (avoiding the use of extended Latin-1
9285 characters in this context).
9287 See section 'Performing Dimensionality Analysis in GNAT' in the GNAT Users
9288 Guide for detailed examples of use of the dimension system.
9290 @node Aspect Disable_Controlled,Aspect Effective_Reads,Aspect Dimension_System,Implementation Defined Aspects
9291 @anchor{gnat_rm/implementation_defined_aspects aspect-disable-controlled}@anchor{12b}
9292 @section Aspect Disable_Controlled
9295 @geindex Disable_Controlled
9297 The aspect @code{Disable_Controlled} is defined for controlled record types. If
9298 active, this aspect causes suppression of all related calls to @code{Initialize},
9299 @code{Adjust}, and @code{Finalize}. The intended use is for conditional compilation,
9300 where for example you might want a record to be controlled or not depending on
9301 whether some run-time check is enabled or suppressed.
9303 @node Aspect Effective_Reads,Aspect Effective_Writes,Aspect Disable_Controlled,Implementation Defined Aspects
9304 @anchor{gnat_rm/implementation_defined_aspects aspect-effective-reads}@anchor{12c}
9305 @section Aspect Effective_Reads
9308 @geindex Effective_Reads
9310 This aspect is equivalent to @ref{57,,pragma Effective_Reads}.
9312 @node Aspect Effective_Writes,Aspect Extensions_Visible,Aspect Effective_Reads,Implementation Defined Aspects
9313 @anchor{gnat_rm/implementation_defined_aspects aspect-effective-writes}@anchor{12d}
9314 @section Aspect Effective_Writes
9317 @geindex Effective_Writes
9319 This aspect is equivalent to @ref{59,,pragma Effective_Writes}.
9321 @node Aspect Extensions_Visible,Aspect Favor_Top_Level,Aspect Effective_Writes,Implementation Defined Aspects
9322 @anchor{gnat_rm/implementation_defined_aspects aspect-extensions-visible}@anchor{12e}
9323 @section Aspect Extensions_Visible
9326 @geindex Extensions_Visible
9328 This aspect is equivalent to @ref{65,,pragma Extensions_Visible}.
9330 @node Aspect Favor_Top_Level,Aspect Ghost,Aspect Extensions_Visible,Implementation Defined Aspects
9331 @anchor{gnat_rm/implementation_defined_aspects aspect-favor-top-level}@anchor{12f}
9332 @section Aspect Favor_Top_Level
9335 @geindex Favor_Top_Level
9337 This boolean aspect is equivalent to @ref{6a,,pragma Favor_Top_Level}.
9339 @node Aspect Ghost,Aspect Global,Aspect Favor_Top_Level,Implementation Defined Aspects
9340 @anchor{gnat_rm/implementation_defined_aspects aspect-ghost}@anchor{130}
9341 @section Aspect Ghost
9346 This aspect is equivalent to @ref{6d,,pragma Ghost}.
9348 @node Aspect Global,Aspect Initial_Condition,Aspect Ghost,Implementation Defined Aspects
9349 @anchor{gnat_rm/implementation_defined_aspects aspect-global}@anchor{131}
9350 @section Aspect Global
9355 This aspect is equivalent to @ref{6f,,pragma Global}.
9357 @node Aspect Initial_Condition,Aspect Initializes,Aspect Global,Implementation Defined Aspects
9358 @anchor{gnat_rm/implementation_defined_aspects aspect-initial-condition}@anchor{132}
9359 @section Aspect Initial_Condition
9362 @geindex Initial_Condition
9364 This aspect is equivalent to @ref{7d,,pragma Initial_Condition}.
9366 @node Aspect Initializes,Aspect Inline_Always,Aspect Initial_Condition,Implementation Defined Aspects
9367 @anchor{gnat_rm/implementation_defined_aspects aspect-initializes}@anchor{133}
9368 @section Aspect Initializes
9371 @geindex Initializes
9373 This aspect is equivalent to @ref{7f,,pragma Initializes}.
9375 @node Aspect Inline_Always,Aspect Invariant,Aspect Initializes,Implementation Defined Aspects
9376 @anchor{gnat_rm/implementation_defined_aspects aspect-inline-always}@anchor{134}
9377 @section Aspect Inline_Always
9380 @geindex Inline_Always
9382 This boolean aspect is equivalent to @ref{82,,pragma Inline_Always}.
9384 @node Aspect Invariant,Aspect Invariant'Class,Aspect Inline_Always,Implementation Defined Aspects
9385 @anchor{gnat_rm/implementation_defined_aspects aspect-invariant}@anchor{135}
9386 @section Aspect Invariant
9391 This aspect is equivalent to @ref{89,,pragma Invariant}. It is a
9392 synonym for the language defined aspect @code{Type_Invariant} except
9393 that it is separately controllable using pragma @code{Assertion_Policy}.
9395 @node Aspect Invariant'Class,Aspect Iterable,Aspect Invariant,Implementation Defined Aspects
9396 @anchor{gnat_rm/implementation_defined_aspects aspect-invariant-class}@anchor{136}
9397 @section Aspect Invariant'Class
9400 @geindex Invariant'Class
9402 This aspect is equivalent to @ref{100,,pragma Type_Invariant_Class}. It is a
9403 synonym for the language defined aspect @code{Type_Invariant'Class} except
9404 that it is separately controllable using pragma @code{Assertion_Policy}.
9406 @node Aspect Iterable,Aspect Linker_Section,Aspect Invariant'Class,Implementation Defined Aspects
9407 @anchor{gnat_rm/implementation_defined_aspects aspect-iterable}@anchor{137}
9408 @section Aspect Iterable
9413 This aspect provides a light-weight mechanism for loops and quantified
9414 expressions over container types, without the overhead imposed by the tampering
9415 checks of standard Ada 2012 iterators. The value of the aspect is an aggregate
9416 with six named components, or which the last three are optional: @code{First},
9420 @code{Next}, @code{Has_Element},`@w{`}Element`@w{`}, @code{Last}, and @code{Previous}.
9423 When only the first three components are specified, only the
9424 @code{for .. in} form of iteration over cursors is available. When @code{Element}
9425 is specified, both this form and the @code{for .. of} form of iteration over
9426 elements are available. If the last two components are specified, reverse
9427 iterations over the container can be specified (analogous to what can be done
9428 over predefined containers that support the Reverse_Iterator interface).
9429 The following is a typical example of use:
9432 type List is private with
9433 Iterable => (First => First_Cursor,
9435 Has_Element => Cursor_Has_Element,
9436 [Element => Get_Element]);
9443 The value denoted by @code{First} must denote a primitive operation of the
9444 container type that returns a @code{Cursor}, which must a be a type declared in
9445 the container package or visible from it. For example:
9449 function First_Cursor (Cont : Container) return Cursor;
9456 The value of @code{Next} is a primitive operation of the container type that takes
9457 both a container and a cursor and yields a cursor. For example:
9461 function Advance (Cont : Container; Position : Cursor) return Cursor;
9468 The value of @code{Has_Element} is a primitive operation of the container type
9469 that takes both a container and a cursor and yields a boolean. For example:
9473 function Cursor_Has_Element (Cont : Container; Position : Cursor) return Boolean;
9480 The value of @code{Element} is a primitive operation of the container type that
9481 takes both a container and a cursor and yields an @code{Element_Type}, which must
9482 be a type declared in the container package or visible from it. For example:
9486 function Get_Element (Cont : Container; Position : Cursor) return Element_Type;
9489 This aspect is used in the GNAT-defined formal container packages.
9491 @node Aspect Linker_Section,Aspect Lock_Free,Aspect Iterable,Implementation Defined Aspects
9492 @anchor{gnat_rm/implementation_defined_aspects aspect-linker-section}@anchor{138}
9493 @section Aspect Linker_Section
9496 @geindex Linker_Section
9498 This aspect is equivalent to @ref{91,,pragma Linker_Section}.
9500 @node Aspect Lock_Free,Aspect Max_Queue_Length,Aspect Linker_Section,Implementation Defined Aspects
9501 @anchor{gnat_rm/implementation_defined_aspects aspect-lock-free}@anchor{139}
9502 @section Aspect Lock_Free
9507 This boolean aspect is equivalent to @ref{93,,pragma Lock_Free}.
9509 @node Aspect Max_Queue_Length,Aspect No_Elaboration_Code_All,Aspect Lock_Free,Implementation Defined Aspects
9510 @anchor{gnat_rm/implementation_defined_aspects aspect-max-queue-length}@anchor{13a}
9511 @section Aspect Max_Queue_Length
9514 @geindex Max_Queue_Length
9516 This aspect is equivalent to @ref{9b,,pragma Max_Queue_Length}.
9518 @node Aspect No_Elaboration_Code_All,Aspect No_Inline,Aspect Max_Queue_Length,Implementation Defined Aspects
9519 @anchor{gnat_rm/implementation_defined_aspects aspect-no-elaboration-code-all}@anchor{13b}
9520 @section Aspect No_Elaboration_Code_All
9523 @geindex No_Elaboration_Code_All
9525 This aspect is equivalent to @ref{9f,,pragma No_Elaboration_Code_All}
9528 @node Aspect No_Inline,Aspect No_Tagged_Streams,Aspect No_Elaboration_Code_All,Implementation Defined Aspects
9529 @anchor{gnat_rm/implementation_defined_aspects aspect-no-inline}@anchor{13c}
9530 @section Aspect No_Inline
9535 This boolean aspect is equivalent to @ref{a2,,pragma No_Inline}.
9537 @node Aspect No_Tagged_Streams,Aspect Object_Size,Aspect No_Inline,Implementation Defined Aspects
9538 @anchor{gnat_rm/implementation_defined_aspects aspect-no-tagged-streams}@anchor{13d}
9539 @section Aspect No_Tagged_Streams
9542 @geindex No_Tagged_Streams
9544 This aspect is equivalent to @ref{a6,,pragma No_Tagged_Streams} with an
9545 argument specifying a root tagged type (thus this aspect can only be
9546 applied to such a type).
9548 @node Aspect Object_Size,Aspect Obsolescent,Aspect No_Tagged_Streams,Implementation Defined Aspects
9549 @anchor{gnat_rm/implementation_defined_aspects aspect-object-size}@anchor{13e}
9550 @section Aspect Object_Size
9553 @geindex Object_Size
9555 This aspect is equivalent to @ref{13f,,attribute Object_Size}.
9557 @node Aspect Obsolescent,Aspect Part_Of,Aspect Object_Size,Implementation Defined Aspects
9558 @anchor{gnat_rm/implementation_defined_aspects aspect-obsolescent}@anchor{140}
9559 @section Aspect Obsolescent
9562 @geindex Obsolsecent
9564 This aspect is equivalent to @ref{a9,,pragma Obsolescent}. Note that the
9565 evaluation of this aspect happens at the point of occurrence, it is not
9566 delayed until the freeze point.
9568 @node Aspect Part_Of,Aspect Persistent_BSS,Aspect Obsolescent,Implementation Defined Aspects
9569 @anchor{gnat_rm/implementation_defined_aspects aspect-part-of}@anchor{141}
9570 @section Aspect Part_Of
9575 This aspect is equivalent to @ref{b1,,pragma Part_Of}.
9577 @node Aspect Persistent_BSS,Aspect Predicate,Aspect Part_Of,Implementation Defined Aspects
9578 @anchor{gnat_rm/implementation_defined_aspects aspect-persistent-bss}@anchor{142}
9579 @section Aspect Persistent_BSS
9582 @geindex Persistent_BSS
9584 This boolean aspect is equivalent to @ref{b4,,pragma Persistent_BSS}.
9586 @node Aspect Predicate,Aspect Pure_Function,Aspect Persistent_BSS,Implementation Defined Aspects
9587 @anchor{gnat_rm/implementation_defined_aspects aspect-predicate}@anchor{143}
9588 @section Aspect Predicate
9593 This aspect is equivalent to @ref{bd,,pragma Predicate}. It is thus
9594 similar to the language defined aspects @code{Dynamic_Predicate}
9595 and @code{Static_Predicate} except that whether the resulting
9596 predicate is static or dynamic is controlled by the form of the
9597 expression. It is also separately controllable using pragma
9598 @code{Assertion_Policy}.
9600 @node Aspect Pure_Function,Aspect Refined_Depends,Aspect Predicate,Implementation Defined Aspects
9601 @anchor{gnat_rm/implementation_defined_aspects aspect-pure-function}@anchor{144}
9602 @section Aspect Pure_Function
9605 @geindex Pure_Function
9607 This boolean aspect is equivalent to @ref{c8,,pragma Pure_Function}.
9609 @node Aspect Refined_Depends,Aspect Refined_Global,Aspect Pure_Function,Implementation Defined Aspects
9610 @anchor{gnat_rm/implementation_defined_aspects aspect-refined-depends}@anchor{145}
9611 @section Aspect Refined_Depends
9614 @geindex Refined_Depends
9616 This aspect is equivalent to @ref{cc,,pragma Refined_Depends}.
9618 @node Aspect Refined_Global,Aspect Refined_Post,Aspect Refined_Depends,Implementation Defined Aspects
9619 @anchor{gnat_rm/implementation_defined_aspects aspect-refined-global}@anchor{146}
9620 @section Aspect Refined_Global
9623 @geindex Refined_Global
9625 This aspect is equivalent to @ref{ce,,pragma Refined_Global}.
9627 @node Aspect Refined_Post,Aspect Refined_State,Aspect Refined_Global,Implementation Defined Aspects
9628 @anchor{gnat_rm/implementation_defined_aspects aspect-refined-post}@anchor{147}
9629 @section Aspect Refined_Post
9632 @geindex Refined_Post
9634 This aspect is equivalent to @ref{d0,,pragma Refined_Post}.
9636 @node Aspect Refined_State,Aspect Remote_Access_Type,Aspect Refined_Post,Implementation Defined Aspects
9637 @anchor{gnat_rm/implementation_defined_aspects aspect-refined-state}@anchor{148}
9638 @section Aspect Refined_State
9641 @geindex Refined_State
9643 This aspect is equivalent to @ref{d2,,pragma Refined_State}.
9645 @node Aspect Remote_Access_Type,Aspect Secondary_Stack_Size,Aspect Refined_State,Implementation Defined Aspects
9646 @anchor{gnat_rm/implementation_defined_aspects aspect-remote-access-type}@anchor{149}
9647 @section Aspect Remote_Access_Type
9650 @geindex Remote_Access_Type
9652 This aspect is equivalent to @ref{d6,,pragma Remote_Access_Type}.
9654 @node Aspect Secondary_Stack_Size,Aspect Scalar_Storage_Order,Aspect Remote_Access_Type,Implementation Defined Aspects
9655 @anchor{gnat_rm/implementation_defined_aspects aspect-secondary-stack-size}@anchor{14a}
9656 @section Aspect Secondary_Stack_Size
9659 @geindex Secondary_Stack_Size
9661 This aspect is equivalent to @ref{db,,pragma Secondary_Stack_Size}.
9663 @node Aspect Scalar_Storage_Order,Aspect Shared,Aspect Secondary_Stack_Size,Implementation Defined Aspects
9664 @anchor{gnat_rm/implementation_defined_aspects aspect-scalar-storage-order}@anchor{14b}
9665 @section Aspect Scalar_Storage_Order
9668 @geindex Scalar_Storage_Order
9670 This aspect is equivalent to a @ref{14c,,attribute Scalar_Storage_Order}.
9672 @node Aspect Shared,Aspect Simple_Storage_Pool,Aspect Scalar_Storage_Order,Implementation Defined Aspects
9673 @anchor{gnat_rm/implementation_defined_aspects aspect-shared}@anchor{14d}
9674 @section Aspect Shared
9679 This boolean aspect is equivalent to @ref{de,,pragma Shared}
9680 and is thus a synonym for aspect @code{Atomic}.
9682 @node Aspect Simple_Storage_Pool,Aspect Simple_Storage_Pool_Type,Aspect Shared,Implementation Defined Aspects
9683 @anchor{gnat_rm/implementation_defined_aspects aspect-simple-storage-pool}@anchor{14e}
9684 @section Aspect Simple_Storage_Pool
9687 @geindex Simple_Storage_Pool
9689 This aspect is equivalent to @ref{e3,,attribute Simple_Storage_Pool}.
9691 @node Aspect Simple_Storage_Pool_Type,Aspect SPARK_Mode,Aspect Simple_Storage_Pool,Implementation Defined Aspects
9692 @anchor{gnat_rm/implementation_defined_aspects aspect-simple-storage-pool-type}@anchor{14f}
9693 @section Aspect Simple_Storage_Pool_Type
9696 @geindex Simple_Storage_Pool_Type
9698 This boolean aspect is equivalent to @ref{e1,,pragma Simple_Storage_Pool_Type}.
9700 @node Aspect SPARK_Mode,Aspect Suppress_Debug_Info,Aspect Simple_Storage_Pool_Type,Implementation Defined Aspects
9701 @anchor{gnat_rm/implementation_defined_aspects aspect-spark-mode}@anchor{150}
9702 @section Aspect SPARK_Mode
9707 This aspect is equivalent to @ref{e9,,pragma SPARK_Mode} and
9708 may be specified for either or both of the specification and body
9709 of a subprogram or package.
9711 @node Aspect Suppress_Debug_Info,Aspect Suppress_Initialization,Aspect SPARK_Mode,Implementation Defined Aspects
9712 @anchor{gnat_rm/implementation_defined_aspects aspect-suppress-debug-info}@anchor{151}
9713 @section Aspect Suppress_Debug_Info
9716 @geindex Suppress_Debug_Info
9718 This boolean aspect is equivalent to @ref{f1,,pragma Suppress_Debug_Info}.
9720 @node Aspect Suppress_Initialization,Aspect Test_Case,Aspect Suppress_Debug_Info,Implementation Defined Aspects
9721 @anchor{gnat_rm/implementation_defined_aspects aspect-suppress-initialization}@anchor{152}
9722 @section Aspect Suppress_Initialization
9725 @geindex Suppress_Initialization
9727 This boolean aspect is equivalent to @ref{f5,,pragma Suppress_Initialization}.
9729 @node Aspect Test_Case,Aspect Thread_Local_Storage,Aspect Suppress_Initialization,Implementation Defined Aspects
9730 @anchor{gnat_rm/implementation_defined_aspects aspect-test-case}@anchor{153}
9731 @section Aspect Test_Case
9736 This aspect is equivalent to @ref{f8,,pragma Test_Case}.
9738 @node Aspect Thread_Local_Storage,Aspect Universal_Aliasing,Aspect Test_Case,Implementation Defined Aspects
9739 @anchor{gnat_rm/implementation_defined_aspects aspect-thread-local-storage}@anchor{154}
9740 @section Aspect Thread_Local_Storage
9743 @geindex Thread_Local_Storage
9745 This boolean aspect is equivalent to @ref{fa,,pragma Thread_Local_Storage}.
9747 @node Aspect Universal_Aliasing,Aspect Universal_Data,Aspect Thread_Local_Storage,Implementation Defined Aspects
9748 @anchor{gnat_rm/implementation_defined_aspects aspect-universal-aliasing}@anchor{155}
9749 @section Aspect Universal_Aliasing
9752 @geindex Universal_Aliasing
9754 This boolean aspect is equivalent to @ref{105,,pragma Universal_Aliasing}.
9756 @node Aspect Universal_Data,Aspect Unmodified,Aspect Universal_Aliasing,Implementation Defined Aspects
9757 @anchor{gnat_rm/implementation_defined_aspects aspect-universal-data}@anchor{156}
9758 @section Aspect Universal_Data
9761 @geindex Universal_Data
9763 This aspect is equivalent to @ref{106,,pragma Universal_Data}.
9765 @node Aspect Unmodified,Aspect Unreferenced,Aspect Universal_Data,Implementation Defined Aspects
9766 @anchor{gnat_rm/implementation_defined_aspects aspect-unmodified}@anchor{157}
9767 @section Aspect Unmodified
9772 This boolean aspect is equivalent to @ref{108,,pragma Unmodified}.
9774 @node Aspect Unreferenced,Aspect Unreferenced_Objects,Aspect Unmodified,Implementation Defined Aspects
9775 @anchor{gnat_rm/implementation_defined_aspects aspect-unreferenced}@anchor{158}
9776 @section Aspect Unreferenced
9779 @geindex Unreferenced
9781 This boolean aspect is equivalent to @ref{10a,,pragma Unreferenced}. Note that
9782 in the case of formal parameters, it is not permitted to have aspects for
9783 a formal parameter, so in this case the pragma form must be used.
9785 @node Aspect Unreferenced_Objects,Aspect Value_Size,Aspect Unreferenced,Implementation Defined Aspects
9786 @anchor{gnat_rm/implementation_defined_aspects aspect-unreferenced-objects}@anchor{159}
9787 @section Aspect Unreferenced_Objects
9790 @geindex Unreferenced_Objects
9792 This boolean aspect is equivalent to @ref{10c,,pragma Unreferenced_Objects}.
9794 @node Aspect Value_Size,Aspect Volatile_Full_Access,Aspect Unreferenced_Objects,Implementation Defined Aspects
9795 @anchor{gnat_rm/implementation_defined_aspects aspect-value-size}@anchor{15a}
9796 @section Aspect Value_Size
9801 This aspect is equivalent to @ref{15b,,attribute Value_Size}.
9803 @node Aspect Volatile_Full_Access,Aspect Volatile_Function,Aspect Value_Size,Implementation Defined Aspects
9804 @anchor{gnat_rm/implementation_defined_aspects aspect-volatile-full-access}@anchor{15c}
9805 @section Aspect Volatile_Full_Access
9808 @geindex Volatile_Full_Access
9810 This boolean aspect is equivalent to @ref{115,,pragma Volatile_Full_Access}.
9812 @node Aspect Volatile_Function,Aspect Warnings,Aspect Volatile_Full_Access,Implementation Defined Aspects
9813 @anchor{gnat_rm/implementation_defined_aspects aspect-volatile-function}@anchor{15d}
9814 @section Aspect Volatile_Function
9817 @geindex Volatile_Function
9819 This boolean aspect is equivalent to @ref{118,,pragma Volatile_Function}.
9821 @node Aspect Warnings,,Aspect Volatile_Function,Implementation Defined Aspects
9822 @anchor{gnat_rm/implementation_defined_aspects aspect-warnings}@anchor{15e}
9823 @section Aspect Warnings
9828 This aspect is equivalent to the two argument form of @ref{11a,,pragma Warnings},
9829 where the first argument is @code{ON} or @code{OFF} and the second argument
9832 @node Implementation Defined Attributes,Standard and Implementation Defined Restrictions,Implementation Defined Aspects,Top
9833 @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}
9834 @chapter Implementation Defined Attributes
9837 Ada defines (throughout the Ada reference manual,
9838 summarized in Annex K),
9839 a set of attributes that provide useful additional functionality in all
9840 areas of the language. These language defined attributes are implemented
9841 in GNAT and work as described in the Ada Reference Manual.
9843 In addition, Ada allows implementations to define additional
9844 attributes whose meaning is defined by the implementation. GNAT provides
9845 a number of these implementation-dependent attributes which can be used
9846 to extend and enhance the functionality of the compiler. This section of
9847 the GNAT reference manual describes these additional attributes. It also
9848 describes additional implementation-dependent features of standard
9849 language-defined attributes.
9851 Note that any program using these attributes may not be portable to
9852 other compilers (although GNAT implements this set of attributes on all
9853 platforms). Therefore if portability to other compilers is an important
9854 consideration, you should minimize the use of these attributes.
9857 * Attribute Abort_Signal::
9858 * Attribute Address_Size::
9859 * Attribute Asm_Input::
9860 * Attribute Asm_Output::
9861 * Attribute Atomic_Always_Lock_Free::
9863 * Attribute Bit_Position::
9864 * Attribute Code_Address::
9865 * Attribute Compiler_Version::
9866 * Attribute Constrained::
9867 * Attribute Default_Bit_Order::
9868 * Attribute Default_Scalar_Storage_Order::
9870 * Attribute Descriptor_Size::
9871 * Attribute Elaborated::
9872 * Attribute Elab_Body::
9873 * Attribute Elab_Spec::
9874 * Attribute Elab_Subp_Body::
9876 * Attribute Enabled::
9877 * Attribute Enum_Rep::
9878 * Attribute Enum_Val::
9879 * Attribute Epsilon::
9880 * Attribute Fast_Math::
9881 * Attribute Finalization_Size::
9882 * Attribute Fixed_Value::
9883 * Attribute From_Any::
9884 * Attribute Has_Access_Values::
9885 * Attribute Has_Discriminants::
9887 * Attribute Integer_Value::
9888 * Attribute Invalid_Value::
9889 * Attribute Iterable::
9891 * Attribute Library_Level::
9892 * Attribute Lock_Free::
9893 * Attribute Loop_Entry::
9894 * Attribute Machine_Size::
9895 * Attribute Mantissa::
9896 * Attribute Maximum_Alignment::
9897 * Attribute Mechanism_Code::
9898 * Attribute Null_Parameter::
9899 * Attribute Object_Size::
9901 * Attribute Passed_By_Reference::
9902 * Attribute Pool_Address::
9903 * Attribute Range_Length::
9904 * Attribute Restriction_Set::
9905 * Attribute Result::
9906 * Attribute Safe_Emax::
9907 * Attribute Safe_Large::
9908 * Attribute Safe_Small::
9909 * Attribute Scalar_Storage_Order::
9910 * Attribute Simple_Storage_Pool::
9912 * Attribute Storage_Unit::
9913 * Attribute Stub_Type::
9914 * Attribute System_Allocator_Alignment::
9915 * Attribute Target_Name::
9916 * Attribute To_Address::
9917 * Attribute To_Any::
9918 * Attribute Type_Class::
9919 * Attribute Type_Key::
9920 * Attribute TypeCode::
9921 * Attribute Unconstrained_Array::
9922 * Attribute Universal_Literal_String::
9923 * Attribute Unrestricted_Access::
9924 * Attribute Update::
9925 * Attribute Valid_Scalars::
9926 * Attribute VADS_Size::
9927 * Attribute Value_Size::
9928 * Attribute Wchar_T_Size::
9929 * Attribute Word_Size::
9933 @node Attribute Abort_Signal,Attribute Address_Size,,Implementation Defined Attributes
9934 @anchor{gnat_rm/implementation_defined_attributes attribute-abort-signal}@anchor{161}
9935 @section Attribute Abort_Signal
9938 @geindex Abort_Signal
9940 @code{Standard'Abort_Signal} (@code{Standard} is the only allowed
9941 prefix) provides the entity for the special exception used to signal
9942 task abort or asynchronous transfer of control. Normally this attribute
9943 should only be used in the tasking runtime (it is highly peculiar, and
9944 completely outside the normal semantics of Ada, for a user program to
9945 intercept the abort exception).
9947 @node Attribute Address_Size,Attribute Asm_Input,Attribute Abort_Signal,Implementation Defined Attributes
9948 @anchor{gnat_rm/implementation_defined_attributes attribute-address-size}@anchor{162}
9949 @section Attribute Address_Size
9952 @geindex Size of `@w{`}Address`@w{`}
9954 @geindex Address_Size
9956 @code{Standard'Address_Size} (@code{Standard} is the only allowed
9957 prefix) is a static constant giving the number of bits in an
9958 @code{Address}. It is the same value as System.Address'Size,
9959 but has the advantage of being static, while a direct
9960 reference to System.Address'Size is nonstatic because Address
9963 @node Attribute Asm_Input,Attribute Asm_Output,Attribute Address_Size,Implementation Defined Attributes
9964 @anchor{gnat_rm/implementation_defined_attributes attribute-asm-input}@anchor{163}
9965 @section Attribute Asm_Input
9970 The @code{Asm_Input} attribute denotes a function that takes two
9971 parameters. The first is a string, the second is an expression of the
9972 type designated by the prefix. The first (string) argument is required
9973 to be a static expression, and is the constraint for the parameter,
9974 (e.g., what kind of register is required). The second argument is the
9975 value to be used as the input argument. The possible values for the
9976 constant are the same as those used in the RTL, and are dependent on
9977 the configuration file used to built the GCC back end.
9978 @ref{164,,Machine Code Insertions}
9980 @node Attribute Asm_Output,Attribute Atomic_Always_Lock_Free,Attribute Asm_Input,Implementation Defined Attributes
9981 @anchor{gnat_rm/implementation_defined_attributes attribute-asm-output}@anchor{165}
9982 @section Attribute Asm_Output
9987 The @code{Asm_Output} attribute denotes a function that takes two
9988 parameters. The first is a string, the second is the name of a variable
9989 of the type designated by the attribute prefix. The first (string)
9990 argument is required to be a static expression and designates the
9991 constraint for the parameter (e.g., what kind of register is
9992 required). The second argument is the variable to be updated with the
9993 result. The possible values for constraint are the same as those used in
9994 the RTL, and are dependent on the configuration file used to build the
9995 GCC back end. If there are no output operands, then this argument may
9996 either be omitted, or explicitly given as @code{No_Output_Operands}.
9997 @ref{164,,Machine Code Insertions}
9999 @node Attribute Atomic_Always_Lock_Free,Attribute Bit,Attribute Asm_Output,Implementation Defined Attributes
10000 @anchor{gnat_rm/implementation_defined_attributes attribute-atomic-always-lock-free}@anchor{166}
10001 @section Attribute Atomic_Always_Lock_Free
10004 @geindex Atomic_Always_Lock_Free
10006 The prefix of the @code{Atomic_Always_Lock_Free} attribute is a type.
10007 The result is a Boolean value which is True if the type has discriminants,
10008 and False otherwise. The result indicate whether atomic operations are
10009 supported by the target for the given type.
10011 @node Attribute Bit,Attribute Bit_Position,Attribute Atomic_Always_Lock_Free,Implementation Defined Attributes
10012 @anchor{gnat_rm/implementation_defined_attributes attribute-bit}@anchor{167}
10013 @section Attribute Bit
10018 @code{obj'Bit}, where @code{obj} is any object, yields the bit
10019 offset within the storage unit (byte) that contains the first bit of
10020 storage allocated for the object. The value of this attribute is of the
10021 type @emph{universal_integer}, and is always a non-negative number not
10022 exceeding the value of @code{System.Storage_Unit}.
10024 For an object that is a variable or a constant allocated in a register,
10025 the value is zero. (The use of this attribute does not force the
10026 allocation of a variable to memory).
10028 For an object that is a formal parameter, this attribute applies
10029 to either the matching actual parameter or to a copy of the
10030 matching actual parameter.
10032 For an access object the value is zero. Note that
10033 @code{obj.all'Bit} is subject to an @code{Access_Check} for the
10034 designated object. Similarly for a record component
10035 @code{X.C'Bit} is subject to a discriminant check and
10036 @code{X(I).Bit} and @code{X(I1..I2)'Bit}
10037 are subject to index checks.
10039 This attribute is designed to be compatible with the DEC Ada 83 definition
10040 and implementation of the @code{Bit} attribute.
10042 @node Attribute Bit_Position,Attribute Code_Address,Attribute Bit,Implementation Defined Attributes
10043 @anchor{gnat_rm/implementation_defined_attributes attribute-bit-position}@anchor{168}
10044 @section Attribute Bit_Position
10047 @geindex Bit_Position
10049 @code{R.C'Bit_Position}, where @code{R} is a record object and @code{C} is one
10050 of the fields of the record type, yields the bit
10051 offset within the record contains the first bit of
10052 storage allocated for the object. The value of this attribute is of the
10053 type @emph{universal_integer}. The value depends only on the field
10054 @code{C} and is independent of the alignment of
10055 the containing record @code{R}.
10057 @node Attribute Code_Address,Attribute Compiler_Version,Attribute Bit_Position,Implementation Defined Attributes
10058 @anchor{gnat_rm/implementation_defined_attributes attribute-code-address}@anchor{169}
10059 @section Attribute Code_Address
10062 @geindex Code_Address
10064 @geindex Subprogram address
10066 @geindex Address of subprogram code
10068 The @code{'Address}
10069 attribute may be applied to subprograms in Ada 95 and Ada 2005, but the
10070 intended effect seems to be to provide
10071 an address value which can be used to call the subprogram by means of
10072 an address clause as in the following example:
10078 for L'Address use K'Address;
10079 pragma Import (Ada, L);
10082 A call to @code{L} is then expected to result in a call to @code{K}.
10083 In Ada 83, where there were no access-to-subprogram values, this was
10084 a common work-around for getting the effect of an indirect call.
10085 GNAT implements the above use of @code{Address} and the technique
10086 illustrated by the example code works correctly.
10088 However, for some purposes, it is useful to have the address of the start
10089 of the generated code for the subprogram. On some architectures, this is
10090 not necessarily the same as the @code{Address} value described above.
10091 For example, the @code{Address} value may reference a subprogram
10092 descriptor rather than the subprogram itself.
10094 The @code{'Code_Address} attribute, which can only be applied to
10095 subprogram entities, always returns the address of the start of the
10096 generated code of the specified subprogram, which may or may not be
10097 the same value as is returned by the corresponding @code{'Address}
10100 @node Attribute Compiler_Version,Attribute Constrained,Attribute Code_Address,Implementation Defined Attributes
10101 @anchor{gnat_rm/implementation_defined_attributes attribute-compiler-version}@anchor{16a}
10102 @section Attribute Compiler_Version
10105 @geindex Compiler_Version
10107 @code{Standard'Compiler_Version} (@code{Standard} is the only allowed
10108 prefix) yields a static string identifying the version of the compiler
10109 being used to compile the unit containing the attribute reference.
10111 @node Attribute Constrained,Attribute Default_Bit_Order,Attribute Compiler_Version,Implementation Defined Attributes
10112 @anchor{gnat_rm/implementation_defined_attributes attribute-constrained}@anchor{16b}
10113 @section Attribute Constrained
10116 @geindex Constrained
10118 In addition to the usage of this attribute in the Ada RM, GNAT
10119 also permits the use of the @code{'Constrained} attribute
10120 in a generic template
10121 for any type, including types without discriminants. The value of this
10122 attribute in the generic instance when applied to a scalar type or a
10123 record type without discriminants is always @code{True}. This usage is
10124 compatible with older Ada compilers, including notably DEC Ada.
10126 @node Attribute Default_Bit_Order,Attribute Default_Scalar_Storage_Order,Attribute Constrained,Implementation Defined Attributes
10127 @anchor{gnat_rm/implementation_defined_attributes attribute-default-bit-order}@anchor{16c}
10128 @section Attribute Default_Bit_Order
10131 @geindex Big endian
10133 @geindex Little endian
10135 @geindex Default_Bit_Order
10137 @code{Standard'Default_Bit_Order} (@code{Standard} is the only
10138 permissible prefix), provides the value @code{System.Default_Bit_Order}
10139 as a @code{Pos} value (0 for @code{High_Order_First}, 1 for
10140 @code{Low_Order_First}). This is used to construct the definition of
10141 @code{Default_Bit_Order} in package @code{System}.
10143 @node Attribute Default_Scalar_Storage_Order,Attribute Deref,Attribute Default_Bit_Order,Implementation Defined Attributes
10144 @anchor{gnat_rm/implementation_defined_attributes attribute-default-scalar-storage-order}@anchor{16d}
10145 @section Attribute Default_Scalar_Storage_Order
10148 @geindex Big endian
10150 @geindex Little endian
10152 @geindex Default_Scalar_Storage_Order
10154 @code{Standard'Default_Scalar_Storage_Order} (@code{Standard} is the only
10155 permissible prefix), provides the current value of the default scalar storage
10156 order (as specified using pragma @code{Default_Scalar_Storage_Order}, or
10157 equal to @code{Default_Bit_Order} if unspecified) as a
10158 @code{System.Bit_Order} value. This is a static attribute.
10160 @node Attribute Deref,Attribute Descriptor_Size,Attribute Default_Scalar_Storage_Order,Implementation Defined Attributes
10161 @anchor{gnat_rm/implementation_defined_attributes attribute-deref}@anchor{16e}
10162 @section Attribute Deref
10167 The attribute @code{typ'Deref(expr)} where @code{expr} is of type @code{System.Address} yields
10168 the variable of type @code{typ} that is located at the given address. It is similar
10169 to @code{(totyp (expr).all)}, where @code{totyp} is an unchecked conversion from address to
10170 a named access-to-@cite{typ} type, except that it yields a variable, so it can be
10171 used on the left side of an assignment.
10173 @node Attribute Descriptor_Size,Attribute Elaborated,Attribute Deref,Implementation Defined Attributes
10174 @anchor{gnat_rm/implementation_defined_attributes attribute-descriptor-size}@anchor{16f}
10175 @section Attribute Descriptor_Size
10178 @geindex Descriptor
10180 @geindex Dope vector
10182 @geindex Descriptor_Size
10184 Nonstatic attribute @code{Descriptor_Size} returns the size in bits of the
10185 descriptor allocated for a type. The result is non-zero only for unconstrained
10186 array types and the returned value is of type universal integer. In GNAT, an
10187 array descriptor contains bounds information and is located immediately before
10188 the first element of the array.
10191 type Unconstr_Array is array (Positive range <>) of Boolean;
10192 Put_Line ("Descriptor size = " & Unconstr_Array'Descriptor_Size'Img);
10195 The attribute takes into account any additional padding due to type alignment.
10196 In the example above, the descriptor contains two values of type
10197 @code{Positive} representing the low and high bound. Since @code{Positive} has
10198 a size of 31 bits and an alignment of 4, the descriptor size is @code{2 * Positive'Size + 2} or 64 bits.
10200 @node Attribute Elaborated,Attribute Elab_Body,Attribute Descriptor_Size,Implementation Defined Attributes
10201 @anchor{gnat_rm/implementation_defined_attributes attribute-elaborated}@anchor{170}
10202 @section Attribute Elaborated
10205 @geindex Elaborated
10207 The prefix of the @code{'Elaborated} attribute must be a unit name. The
10208 value is a Boolean which indicates whether or not the given unit has been
10209 elaborated. This attribute is primarily intended for internal use by the
10210 generated code for dynamic elaboration checking, but it can also be used
10211 in user programs. The value will always be True once elaboration of all
10212 units has been completed. An exception is for units which need no
10213 elaboration, the value is always False for such units.
10215 @node Attribute Elab_Body,Attribute Elab_Spec,Attribute Elaborated,Implementation Defined Attributes
10216 @anchor{gnat_rm/implementation_defined_attributes attribute-elab-body}@anchor{171}
10217 @section Attribute Elab_Body
10222 This attribute can only be applied to a program unit name. It returns
10223 the entity for the corresponding elaboration procedure for elaborating
10224 the body of the referenced unit. This is used in the main generated
10225 elaboration procedure by the binder and is not normally used in any
10226 other context. However, there may be specialized situations in which it
10227 is useful to be able to call this elaboration procedure from Ada code,
10228 e.g., if it is necessary to do selective re-elaboration to fix some
10231 @node Attribute Elab_Spec,Attribute Elab_Subp_Body,Attribute Elab_Body,Implementation Defined Attributes
10232 @anchor{gnat_rm/implementation_defined_attributes attribute-elab-spec}@anchor{172}
10233 @section Attribute Elab_Spec
10238 This attribute can only be applied to a program unit name. It returns
10239 the entity for the corresponding elaboration procedure for elaborating
10240 the spec of the referenced unit. This is used in the main
10241 generated elaboration procedure by the binder and is not normally used
10242 in any other context. However, there may be specialized situations in
10243 which it is useful to be able to call this elaboration procedure from
10244 Ada code, e.g., if it is necessary to do selective re-elaboration to fix
10247 @node Attribute Elab_Subp_Body,Attribute Emax,Attribute Elab_Spec,Implementation Defined Attributes
10248 @anchor{gnat_rm/implementation_defined_attributes attribute-elab-subp-body}@anchor{173}
10249 @section Attribute Elab_Subp_Body
10252 @geindex Elab_Subp_Body
10254 This attribute can only be applied to a library level subprogram
10255 name and is only allowed in CodePeer mode. It returns the entity
10256 for the corresponding elaboration procedure for elaborating the body
10257 of the referenced subprogram unit. This is used in the main generated
10258 elaboration procedure by the binder in CodePeer mode only and is unrecognized
10261 @node Attribute Emax,Attribute Enabled,Attribute Elab_Subp_Body,Implementation Defined Attributes
10262 @anchor{gnat_rm/implementation_defined_attributes attribute-emax}@anchor{174}
10263 @section Attribute Emax
10266 @geindex Ada 83 attributes
10270 The @code{Emax} attribute is provided for compatibility with Ada 83. See
10271 the Ada 83 reference manual for an exact description of the semantics of
10274 @node Attribute Enabled,Attribute Enum_Rep,Attribute Emax,Implementation Defined Attributes
10275 @anchor{gnat_rm/implementation_defined_attributes attribute-enabled}@anchor{175}
10276 @section Attribute Enabled
10281 The @code{Enabled} attribute allows an application program to check at compile
10282 time to see if the designated check is currently enabled. The prefix is a
10283 simple identifier, referencing any predefined check name (other than
10284 @code{All_Checks}) or a check name introduced by pragma Check_Name. If
10285 no argument is given for the attribute, the check is for the general state
10286 of the check, if an argument is given, then it is an entity name, and the
10287 check indicates whether an @code{Suppress} or @code{Unsuppress} has been
10288 given naming the entity (if not, then the argument is ignored).
10290 Note that instantiations inherit the check status at the point of the
10291 instantiation, so a useful idiom is to have a library package that
10292 introduces a check name with @code{pragma Check_Name}, and then contains
10293 generic packages or subprograms which use the @code{Enabled} attribute
10294 to see if the check is enabled. A user of this package can then issue
10295 a @code{pragma Suppress} or @code{pragma Unsuppress} before instantiating
10296 the package or subprogram, controlling whether the check will be present.
10298 @node Attribute Enum_Rep,Attribute Enum_Val,Attribute Enabled,Implementation Defined Attributes
10299 @anchor{gnat_rm/implementation_defined_attributes attribute-enum-rep}@anchor{176}
10300 @section Attribute Enum_Rep
10303 @geindex Representation of enums
10307 For every enumeration subtype @code{S}, @code{S'Enum_Rep} denotes a
10308 function with the following spec:
10311 function S'Enum_Rep (Arg : S'Base) return <Universal_Integer>;
10314 It is also allowable to apply @code{Enum_Rep} directly to an object of an
10315 enumeration type or to a non-overloaded enumeration
10316 literal. In this case @code{S'Enum_Rep} is equivalent to
10317 @code{typ'Enum_Rep(S)} where @code{typ} is the type of the
10318 enumeration literal or object.
10320 The function returns the representation value for the given enumeration
10321 value. This will be equal to value of the @code{Pos} attribute in the
10322 absence of an enumeration representation clause. This is a static
10323 attribute (i.e.,:the result is static if the argument is static).
10325 @code{S'Enum_Rep} can also be used with integer types and objects,
10326 in which case it simply returns the integer value. The reason for this
10327 is to allow it to be used for @code{(<>)} discrete formal arguments in
10328 a generic unit that can be instantiated with either enumeration types
10329 or integer types. Note that if @code{Enum_Rep} is used on a modular
10330 type whose upper bound exceeds the upper bound of the largest signed
10331 integer type, and the argument is a variable, so that the universal
10332 integer calculation is done at run time, then the call to @code{Enum_Rep}
10333 may raise @code{Constraint_Error}.
10335 @node Attribute Enum_Val,Attribute Epsilon,Attribute Enum_Rep,Implementation Defined Attributes
10336 @anchor{gnat_rm/implementation_defined_attributes attribute-enum-val}@anchor{177}
10337 @section Attribute Enum_Val
10340 @geindex Representation of enums
10344 For every enumeration subtype @code{S}, @code{S'Enum_Val} denotes a
10345 function with the following spec:
10348 function S'Enum_Val (Arg : <Universal_Integer>) return S'Base;
10351 The function returns the enumeration value whose representation matches the
10352 argument, or raises Constraint_Error if no enumeration literal of the type
10353 has the matching value.
10354 This will be equal to value of the @code{Val} attribute in the
10355 absence of an enumeration representation clause. This is a static
10356 attribute (i.e., the result is static if the argument is static).
10358 @node Attribute Epsilon,Attribute Fast_Math,Attribute Enum_Val,Implementation Defined Attributes
10359 @anchor{gnat_rm/implementation_defined_attributes attribute-epsilon}@anchor{178}
10360 @section Attribute Epsilon
10363 @geindex Ada 83 attributes
10367 The @code{Epsilon} attribute is provided for compatibility with Ada 83. See
10368 the Ada 83 reference manual for an exact description of the semantics of
10371 @node Attribute Fast_Math,Attribute Finalization_Size,Attribute Epsilon,Implementation Defined Attributes
10372 @anchor{gnat_rm/implementation_defined_attributes attribute-fast-math}@anchor{179}
10373 @section Attribute Fast_Math
10378 @code{Standard'Fast_Math} (@code{Standard} is the only allowed
10379 prefix) yields a static Boolean value that is True if pragma
10380 @code{Fast_Math} is active, and False otherwise.
10382 @node Attribute Finalization_Size,Attribute Fixed_Value,Attribute Fast_Math,Implementation Defined Attributes
10383 @anchor{gnat_rm/implementation_defined_attributes attribute-finalization-size}@anchor{17a}
10384 @section Attribute Finalization_Size
10387 @geindex Finalization_Size
10389 The prefix of attribute @code{Finalization_Size} must be an object or
10390 a non-class-wide type. This attribute returns the size of any hidden data
10391 reserved by the compiler to handle finalization-related actions. The type of
10392 the attribute is @emph{universal_integer}.
10394 @code{Finalization_Size} yields a value of zero for a type with no controlled
10395 parts, an object whose type has no controlled parts, or an object of a
10396 class-wide type whose tag denotes a type with no controlled parts.
10398 Note that only heap-allocated objects contain finalization data.
10400 @node Attribute Fixed_Value,Attribute From_Any,Attribute Finalization_Size,Implementation Defined Attributes
10401 @anchor{gnat_rm/implementation_defined_attributes attribute-fixed-value}@anchor{17b}
10402 @section Attribute Fixed_Value
10405 @geindex Fixed_Value
10407 For every fixed-point type @code{S}, @code{S'Fixed_Value} denotes a
10408 function with the following specification:
10411 function S'Fixed_Value (Arg : <Universal_Integer>) return S;
10414 The value returned is the fixed-point value @code{V} such that:
10420 The effect is thus similar to first converting the argument to the
10421 integer type used to represent @code{S}, and then doing an unchecked
10422 conversion to the fixed-point type. The difference is
10423 that there are full range checks, to ensure that the result is in range.
10424 This attribute is primarily intended for use in implementation of the
10425 input-output functions for fixed-point values.
10427 @node Attribute From_Any,Attribute Has_Access_Values,Attribute Fixed_Value,Implementation Defined Attributes
10428 @anchor{gnat_rm/implementation_defined_attributes attribute-from-any}@anchor{17c}
10429 @section Attribute From_Any
10434 This internal attribute is used for the generation of remote subprogram
10435 stubs in the context of the Distributed Systems Annex.
10437 @node Attribute Has_Access_Values,Attribute Has_Discriminants,Attribute From_Any,Implementation Defined Attributes
10438 @anchor{gnat_rm/implementation_defined_attributes attribute-has-access-values}@anchor{17d}
10439 @section Attribute Has_Access_Values
10442 @geindex Access values
10443 @geindex testing for
10445 @geindex Has_Access_Values
10447 The prefix of the @code{Has_Access_Values} attribute is a type. The result
10448 is a Boolean value which is True if the is an access type, or is a composite
10449 type with a component (at any nesting depth) that is an access type, and is
10451 The intended use of this attribute is in conjunction with generic
10452 definitions. If the attribute is applied to a generic private type, it
10453 indicates whether or not the corresponding actual type has access values.
10455 @node Attribute Has_Discriminants,Attribute Img,Attribute Has_Access_Values,Implementation Defined Attributes
10456 @anchor{gnat_rm/implementation_defined_attributes attribute-has-discriminants}@anchor{17e}
10457 @section Attribute Has_Discriminants
10460 @geindex Discriminants
10461 @geindex testing for
10463 @geindex Has_Discriminants
10465 The prefix of the @code{Has_Discriminants} attribute is a type. The result
10466 is a Boolean value which is True if the type has discriminants, and False
10467 otherwise. The intended use of this attribute is in conjunction with generic
10468 definitions. If the attribute is applied to a generic private type, it
10469 indicates whether or not the corresponding actual type has discriminants.
10471 @node Attribute Img,Attribute Integer_Value,Attribute Has_Discriminants,Implementation Defined Attributes
10472 @anchor{gnat_rm/implementation_defined_attributes attribute-img}@anchor{17f}
10473 @section Attribute Img
10478 The @code{Img} attribute differs from @code{Image} in that it is applied
10479 directly to an object, and yields the same result as
10480 @code{Image} for the subtype of the object. This is convenient for
10484 Put_Line ("X = " & X'Img);
10487 has the same meaning as the more verbose:
10490 Put_Line ("X = " & T'Image (X));
10493 where @code{T} is the (sub)type of the object @code{X}.
10495 Note that technically, in analogy to @code{Image},
10496 @code{X'Img} returns a parameterless function
10497 that returns the appropriate string when called. This means that
10498 @code{X'Img} can be renamed as a function-returning-string, or used
10499 in an instantiation as a function parameter.
10501 @node Attribute Integer_Value,Attribute Invalid_Value,Attribute Img,Implementation Defined Attributes
10502 @anchor{gnat_rm/implementation_defined_attributes attribute-integer-value}@anchor{180}
10503 @section Attribute Integer_Value
10506 @geindex Integer_Value
10508 For every integer type @code{S}, @code{S'Integer_Value} denotes a
10509 function with the following spec:
10512 function S'Integer_Value (Arg : <Universal_Fixed>) return S;
10515 The value returned is the integer value @code{V}, such that:
10521 where @code{T} is the type of @code{Arg}.
10522 The effect is thus similar to first doing an unchecked conversion from
10523 the fixed-point type to its corresponding implementation type, and then
10524 converting the result to the target integer type. The difference is
10525 that there are full range checks, to ensure that the result is in range.
10526 This attribute is primarily intended for use in implementation of the
10527 standard input-output functions for fixed-point values.
10529 @node Attribute Invalid_Value,Attribute Iterable,Attribute Integer_Value,Implementation Defined Attributes
10530 @anchor{gnat_rm/implementation_defined_attributes attribute-invalid-value}@anchor{181}
10531 @section Attribute Invalid_Value
10534 @geindex Invalid_Value
10536 For every scalar type S, S'Invalid_Value returns an undefined value of the
10537 type. If possible this value is an invalid representation for the type. The
10538 value returned is identical to the value used to initialize an otherwise
10539 uninitialized value of the type if pragma Initialize_Scalars is used,
10540 including the ability to modify the value with the binder -Sxx flag and
10541 relevant environment variables at run time.
10543 @node Attribute Iterable,Attribute Large,Attribute Invalid_Value,Implementation Defined Attributes
10544 @anchor{gnat_rm/implementation_defined_attributes attribute-iterable}@anchor{182}
10545 @section Attribute Iterable
10550 Equivalent to Aspect Iterable.
10552 @node Attribute Large,Attribute Library_Level,Attribute Iterable,Implementation Defined Attributes
10553 @anchor{gnat_rm/implementation_defined_attributes attribute-large}@anchor{183}
10554 @section Attribute Large
10557 @geindex Ada 83 attributes
10561 The @code{Large} attribute is provided for compatibility with Ada 83. See
10562 the Ada 83 reference manual for an exact description of the semantics of
10565 @node Attribute Library_Level,Attribute Lock_Free,Attribute Large,Implementation Defined Attributes
10566 @anchor{gnat_rm/implementation_defined_attributes attribute-library-level}@anchor{184}
10567 @section Attribute Library_Level
10570 @geindex Library_Level
10572 @code{P'Library_Level}, where P is an entity name,
10573 returns a Boolean value which is True if the entity is declared
10574 at the library level, and False otherwise. Note that within a
10575 generic instantition, the name of the generic unit denotes the
10576 instance, which means that this attribute can be used to test
10577 if a generic is instantiated at the library level, as shown
10584 pragma Compile_Time_Error
10585 (not Gen'Library_Level,
10586 "Gen can only be instantiated at library level");
10591 @node Attribute Lock_Free,Attribute Loop_Entry,Attribute Library_Level,Implementation Defined Attributes
10592 @anchor{gnat_rm/implementation_defined_attributes attribute-lock-free}@anchor{185}
10593 @section Attribute Lock_Free
10598 @code{P'Lock_Free}, where P is a protected object, returns True if a
10599 pragma @code{Lock_Free} applies to P.
10601 @node Attribute Loop_Entry,Attribute Machine_Size,Attribute Lock_Free,Implementation Defined Attributes
10602 @anchor{gnat_rm/implementation_defined_attributes attribute-loop-entry}@anchor{186}
10603 @section Attribute Loop_Entry
10606 @geindex Loop_Entry
10611 X'Loop_Entry [(loop_name)]
10614 The @code{Loop_Entry} attribute is used to refer to the value that an
10615 expression had upon entry to a given loop in much the same way that the
10616 @code{Old} attribute in a subprogram postcondition can be used to refer
10617 to the value an expression had upon entry to the subprogram. The
10618 relevant loop is either identified by the given loop name, or it is the
10619 innermost enclosing loop when no loop name is given.
10621 A @code{Loop_Entry} attribute can only occur within a
10622 @code{Loop_Variant} or @code{Loop_Invariant} pragma. A common use of
10623 @code{Loop_Entry} is to compare the current value of objects with their
10624 initial value at loop entry, in a @code{Loop_Invariant} pragma.
10626 The effect of using @code{X'Loop_Entry} is the same as declaring
10627 a constant initialized with the initial value of @code{X} at loop
10628 entry. This copy is not performed if the loop is not entered, or if the
10629 corresponding pragmas are ignored or disabled.
10631 @node Attribute Machine_Size,Attribute Mantissa,Attribute Loop_Entry,Implementation Defined Attributes
10632 @anchor{gnat_rm/implementation_defined_attributes attribute-machine-size}@anchor{187}
10633 @section Attribute Machine_Size
10636 @geindex Machine_Size
10638 This attribute is identical to the @code{Object_Size} attribute. It is
10639 provided for compatibility with the DEC Ada 83 attribute of this name.
10641 @node Attribute Mantissa,Attribute Maximum_Alignment,Attribute Machine_Size,Implementation Defined Attributes
10642 @anchor{gnat_rm/implementation_defined_attributes attribute-mantissa}@anchor{188}
10643 @section Attribute Mantissa
10646 @geindex Ada 83 attributes
10650 The @code{Mantissa} attribute is provided for compatibility with Ada 83. See
10651 the Ada 83 reference manual for an exact description of the semantics of
10654 @node Attribute Maximum_Alignment,Attribute Mechanism_Code,Attribute Mantissa,Implementation Defined Attributes
10655 @anchor{gnat_rm/implementation_defined_attributes attribute-maximum-alignment}@anchor{189}@anchor{gnat_rm/implementation_defined_attributes id2}@anchor{18a}
10656 @section Attribute Maximum_Alignment
10662 @geindex Maximum_Alignment
10664 @code{Standard'Maximum_Alignment} (@code{Standard} is the only
10665 permissible prefix) provides the maximum useful alignment value for the
10666 target. This is a static value that can be used to specify the alignment
10667 for an object, guaranteeing that it is properly aligned in all
10670 @node Attribute Mechanism_Code,Attribute Null_Parameter,Attribute Maximum_Alignment,Implementation Defined Attributes
10671 @anchor{gnat_rm/implementation_defined_attributes attribute-mechanism-code}@anchor{18b}
10672 @section Attribute Mechanism_Code
10675 @geindex Return values
10676 @geindex passing mechanism
10678 @geindex Parameters
10679 @geindex passing mechanism
10681 @geindex Mechanism_Code
10683 @code{func'Mechanism_Code} yields an integer code for the
10684 mechanism used for the result of function @code{func}, and
10685 @code{subprog'Mechanism_Code (n)} yields the mechanism
10686 used for formal parameter number @emph{n} (a static integer value, with 1
10687 meaning the first parameter) of subprogram @code{subprog}. The code returned is:
10701 @node Attribute Null_Parameter,Attribute Object_Size,Attribute Mechanism_Code,Implementation Defined Attributes
10702 @anchor{gnat_rm/implementation_defined_attributes attribute-null-parameter}@anchor{18c}
10703 @section Attribute Null_Parameter
10706 @geindex Zero address
10709 @geindex Null_Parameter
10711 A reference @code{T'Null_Parameter} denotes an imaginary object of
10712 type or subtype @code{T} allocated at machine address zero. The attribute
10713 is allowed only as the default expression of a formal parameter, or as
10714 an actual expression of a subprogram call. In either case, the
10715 subprogram must be imported.
10717 The identity of the object is represented by the address zero in the
10718 argument list, independent of the passing mechanism (explicit or
10721 This capability is needed to specify that a zero address should be
10722 passed for a record or other composite object passed by reference.
10723 There is no way of indicating this without the @code{Null_Parameter}
10726 @node Attribute Object_Size,Attribute Old,Attribute Null_Parameter,Implementation Defined Attributes
10727 @anchor{gnat_rm/implementation_defined_attributes attribute-object-size}@anchor{13f}@anchor{gnat_rm/implementation_defined_attributes id3}@anchor{18d}
10728 @section Attribute Object_Size
10732 @geindex used for objects
10734 @geindex Object_Size
10736 The size of an object is not necessarily the same as the size of the type
10737 of an object. This is because by default object sizes are increased to be
10738 a multiple of the alignment of the object. For example,
10739 @code{Natural'Size} is
10740 31, but by default objects of type @code{Natural} will have a size of 32 bits.
10741 Similarly, a record containing an integer and a character:
10750 will have a size of 40 (that is @code{Rec'Size} will be 40). The
10751 alignment will be 4, because of the
10752 integer field, and so the default size of record objects for this type
10753 will be 64 (8 bytes).
10755 If the alignment of the above record is specified to be 1, then the
10756 object size will be 40 (5 bytes). This is true by default, and also
10757 an object size of 40 can be explicitly specified in this case.
10759 A consequence of this capability is that different object sizes can be
10760 given to subtypes that would otherwise be considered in Ada to be
10761 statically matching. But it makes no sense to consider such subtypes
10762 as statically matching. Consequently, GNAT adds a rule
10763 to the static matching rules that requires object sizes to match.
10764 Consider this example:
10767 1. procedure BadAVConvert is
10768 2. type R is new Integer;
10769 3. subtype R1 is R range 1 .. 10;
10770 4. subtype R2 is R range 1 .. 10;
10771 5. for R1'Object_Size use 8;
10772 6. for R2'Object_Size use 16;
10773 7. type R1P is access all R1;
10774 8. type R2P is access all R2;
10775 9. R1PV : R1P := new R1'(4);
10778 12. R2PV := R2P (R1PV);
10780 >>> target designated subtype not compatible with
10781 type "R1" defined at line 3
10786 In the absence of lines 5 and 6,
10787 types @code{R1} and @code{R2} statically match and
10788 hence the conversion on line 12 is legal. But since lines 5 and 6
10789 cause the object sizes to differ, GNAT considers that types
10790 @code{R1} and @code{R2} are not statically matching, and line 12
10791 generates the diagnostic shown above.
10793 Similar additional checks are performed in other contexts requiring
10794 statically matching subtypes.
10796 @node Attribute Old,Attribute Passed_By_Reference,Attribute Object_Size,Implementation Defined Attributes
10797 @anchor{gnat_rm/implementation_defined_attributes attribute-old}@anchor{18e}
10798 @section Attribute Old
10803 In addition to the usage of @code{Old} defined in the Ada 2012 RM (usage
10804 within @code{Post} aspect), GNAT also permits the use of this attribute
10805 in implementation defined pragmas @code{Postcondition},
10806 @code{Contract_Cases} and @code{Test_Case}. Also usages of
10807 @code{Old} which would be illegal according to the Ada 2012 RM
10808 definition are allowed under control of
10809 implementation defined pragma @code{Unevaluated_Use_Of_Old}.
10811 @node Attribute Passed_By_Reference,Attribute Pool_Address,Attribute Old,Implementation Defined Attributes
10812 @anchor{gnat_rm/implementation_defined_attributes attribute-passed-by-reference}@anchor{18f}
10813 @section Attribute Passed_By_Reference
10816 @geindex Parameters
10817 @geindex when passed by reference
10819 @geindex Passed_By_Reference
10821 @code{typ'Passed_By_Reference} for any subtype @cite{typ} returns
10822 a value of type @code{Boolean} value that is @code{True} if the type is
10823 normally passed by reference and @code{False} if the type is normally
10824 passed by copy in calls. For scalar types, the result is always @code{False}
10825 and is static. For non-scalar types, the result is nonstatic.
10827 @node Attribute Pool_Address,Attribute Range_Length,Attribute Passed_By_Reference,Implementation Defined Attributes
10828 @anchor{gnat_rm/implementation_defined_attributes attribute-pool-address}@anchor{190}
10829 @section Attribute Pool_Address
10832 @geindex Parameters
10833 @geindex when passed by reference
10835 @geindex Pool_Address
10837 @code{X'Pool_Address} for any object @code{X} returns the address
10838 of X within its storage pool. This is the same as
10839 @code{X'Address}, except that for an unconstrained array whose
10840 bounds are allocated just before the first component,
10841 @code{X'Pool_Address} returns the address of those bounds,
10842 whereas @code{X'Address} returns the address of the first
10845 Here, we are interpreting 'storage pool' broadly to mean
10846 @code{wherever the object is allocated}, which could be a
10847 user-defined storage pool,
10848 the global heap, on the stack, or in a static memory area.
10849 For an object created by @code{new}, @code{Ptr.all'Pool_Address} is
10850 what is passed to @code{Allocate} and returned from @code{Deallocate}.
10852 @node Attribute Range_Length,Attribute Restriction_Set,Attribute Pool_Address,Implementation Defined Attributes
10853 @anchor{gnat_rm/implementation_defined_attributes attribute-range-length}@anchor{191}
10854 @section Attribute Range_Length
10857 @geindex Range_Length
10859 @code{typ'Range_Length} for any discrete type @cite{typ} yields
10860 the number of values represented by the subtype (zero for a null
10861 range). The result is static for static subtypes. @code{Range_Length}
10862 applied to the index subtype of a one dimensional array always gives the
10863 same result as @code{Length} applied to the array itself.
10865 @node Attribute Restriction_Set,Attribute Result,Attribute Range_Length,Implementation Defined Attributes
10866 @anchor{gnat_rm/implementation_defined_attributes attribute-restriction-set}@anchor{192}
10867 @section Attribute Restriction_Set
10870 @geindex Restriction_Set
10872 @geindex Restrictions
10874 This attribute allows compile time testing of restrictions that
10875 are currently in effect. It is primarily intended for specializing
10876 code in the run-time based on restrictions that are active (e.g.
10877 don't need to save fpt registers if restriction No_Floating_Point
10878 is known to be in effect), but can be used anywhere.
10880 There are two forms:
10883 System'Restriction_Set (partition_boolean_restriction_NAME)
10884 System'Restriction_Set (No_Dependence => library_unit_NAME);
10887 In the case of the first form, the only restriction names
10888 allowed are parameterless restrictions that are checked
10889 for consistency at bind time. For a complete list see the
10890 subtype @code{System.Rident.Partition_Boolean_Restrictions}.
10892 The result returned is True if the restriction is known to
10893 be in effect, and False if the restriction is known not to
10894 be in effect. An important guarantee is that the value of
10895 a Restriction_Set attribute is known to be consistent throughout
10896 all the code of a partition.
10898 This is trivially achieved if the entire partition is compiled
10899 with a consistent set of restriction pragmas. However, the
10900 compilation model does not require this. It is possible to
10901 compile one set of units with one set of pragmas, and another
10902 set of units with another set of pragmas. It is even possible
10903 to compile a spec with one set of pragmas, and then WITH the
10904 same spec with a different set of pragmas. Inconsistencies
10905 in the actual use of the restriction are checked at bind time.
10907 In order to achieve the guarantee of consistency for the
10908 Restriction_Set pragma, we consider that a use of the pragma
10909 that yields False is equivalent to a violation of the
10912 So for example if you write
10915 if System'Restriction_Set (No_Floating_Point) then
10922 And the result is False, so that the else branch is executed,
10923 you can assume that this restriction is not set for any unit
10924 in the partition. This is checked by considering this use of
10925 the restriction pragma to be a violation of the restriction
10926 No_Floating_Point. This means that no other unit can attempt
10927 to set this restriction (if some unit does attempt to set it,
10928 the binder will refuse to bind the partition).
10930 Technical note: The restriction name and the unit name are
10931 intepreted entirely syntactically, as in the corresponding
10932 Restrictions pragma, they are not analyzed semantically,
10933 so they do not have a type.
10935 @node Attribute Result,Attribute Safe_Emax,Attribute Restriction_Set,Implementation Defined Attributes
10936 @anchor{gnat_rm/implementation_defined_attributes attribute-result}@anchor{193}
10937 @section Attribute Result
10942 @code{function'Result} can only be used with in a Postcondition pragma
10943 for a function. The prefix must be the name of the corresponding function. This
10944 is used to refer to the result of the function in the postcondition expression.
10945 For a further discussion of the use of this attribute and examples of its use,
10946 see the description of pragma Postcondition.
10948 @node Attribute Safe_Emax,Attribute Safe_Large,Attribute Result,Implementation Defined Attributes
10949 @anchor{gnat_rm/implementation_defined_attributes attribute-safe-emax}@anchor{194}
10950 @section Attribute Safe_Emax
10953 @geindex Ada 83 attributes
10957 The @code{Safe_Emax} attribute is provided for compatibility with Ada 83. See
10958 the Ada 83 reference manual for an exact description of the semantics of
10961 @node Attribute Safe_Large,Attribute Safe_Small,Attribute Safe_Emax,Implementation Defined Attributes
10962 @anchor{gnat_rm/implementation_defined_attributes attribute-safe-large}@anchor{195}
10963 @section Attribute Safe_Large
10966 @geindex Ada 83 attributes
10968 @geindex Safe_Large
10970 The @code{Safe_Large} attribute is provided for compatibility with Ada 83. See
10971 the Ada 83 reference manual for an exact description of the semantics of
10974 @node Attribute Safe_Small,Attribute Scalar_Storage_Order,Attribute Safe_Large,Implementation Defined Attributes
10975 @anchor{gnat_rm/implementation_defined_attributes attribute-safe-small}@anchor{196}
10976 @section Attribute Safe_Small
10979 @geindex Ada 83 attributes
10981 @geindex Safe_Small
10983 The @code{Safe_Small} attribute is provided for compatibility with Ada 83. See
10984 the Ada 83 reference manual for an exact description of the semantics of
10987 @node Attribute Scalar_Storage_Order,Attribute Simple_Storage_Pool,Attribute Safe_Small,Implementation Defined Attributes
10988 @anchor{gnat_rm/implementation_defined_attributes id4}@anchor{197}@anchor{gnat_rm/implementation_defined_attributes attribute-scalar-storage-order}@anchor{14c}
10989 @section Attribute Scalar_Storage_Order
10992 @geindex Endianness
10994 @geindex Scalar storage order
10996 @geindex Scalar_Storage_Order
10998 For every array or record type @code{S}, the representation attribute
10999 @code{Scalar_Storage_Order} denotes the order in which storage elements
11000 that make up scalar components are ordered within S. The value given must
11001 be a static expression of type System.Bit_Order. The following is an example
11002 of the use of this feature:
11005 -- Component type definitions
11007 subtype Yr_Type is Natural range 0 .. 127;
11008 subtype Mo_Type is Natural range 1 .. 12;
11009 subtype Da_Type is Natural range 1 .. 31;
11011 -- Record declaration
11013 type Date is record
11014 Years_Since_1980 : Yr_Type;
11016 Day_Of_Month : Da_Type;
11019 -- Record representation clause
11021 for Date use record
11022 Years_Since_1980 at 0 range 0 .. 6;
11023 Month at 0 range 7 .. 10;
11024 Day_Of_Month at 0 range 11 .. 15;
11027 -- Attribute definition clauses
11029 for Date'Bit_Order use System.High_Order_First;
11030 for Date'Scalar_Storage_Order use System.High_Order_First;
11031 -- If Scalar_Storage_Order is specified, it must be consistent with
11032 -- Bit_Order, so it's best to always define the latter explicitly if
11033 -- the former is used.
11036 Other properties are as for standard representation attribute @code{Bit_Order},
11037 as defined by Ada RM 13.5.3(4). The default is @code{System.Default_Bit_Order}.
11039 For a record type @code{T}, if @code{T'Scalar_Storage_Order} is
11040 specified explicitly, it shall be equal to @code{T'Bit_Order}. Note:
11041 this means that if a @code{Scalar_Storage_Order} attribute definition
11042 clause is not confirming, then the type's @code{Bit_Order} shall be
11043 specified explicitly and set to the same value.
11045 Derived types inherit an explicitly set scalar storage order from their parent
11046 types. This may be overridden for the derived type by giving an explicit scalar
11047 storage order for the derived type. For a record extension, the derived type
11048 must have the same scalar storage order as the parent type.
11050 A component of a record type that is itself a record or an array and that does
11051 not start and end on a byte boundary must have have the same scalar storage
11052 order as the record type. A component of a bit-packed array type that is itself
11053 a record or an array must have the same scalar storage order as the array type.
11055 No component of a type that has an explicit @code{Scalar_Storage_Order}
11056 attribute definition may be aliased.
11058 A confirming @code{Scalar_Storage_Order} attribute definition clause (i.e.
11059 with a value equal to @code{System.Default_Bit_Order}) has no effect.
11061 If the opposite storage order is specified, then whenever the value of
11062 a scalar component of an object of type @code{S} is read, the storage
11063 elements of the enclosing machine scalar are first reversed (before
11064 retrieving the component value, possibly applying some shift and mask
11065 operatings on the enclosing machine scalar), and the opposite operation
11066 is done for writes.
11068 In that case, the restrictions set forth in 13.5.1(10.3/2) for scalar components
11069 are relaxed. Instead, the following rules apply:
11075 the underlying storage elements are those at positions
11076 @code{(position + first_bit / storage_element_size) .. (position + (last_bit + storage_element_size - 1) / storage_element_size)}
11079 the sequence of underlying storage elements shall have
11080 a size no greater than the largest machine scalar
11083 the enclosing machine scalar is defined as the smallest machine
11084 scalar starting at a position no greater than
11085 @code{position + first_bit / storage_element_size} and covering
11086 storage elements at least up to @code{position + (last_bit + storage_element_size - 1) / storage_element_size`}
11089 the position of the component is interpreted relative to that machine
11093 If no scalar storage order is specified for a type (either directly, or by
11094 inheritance in the case of a derived type), then the default is normally
11095 the native ordering of the target, but this default can be overridden using
11096 pragma @code{Default_Scalar_Storage_Order}.
11098 Note that if a component of @code{T} is itself of a record or array type,
11099 the specfied @code{Scalar_Storage_Order} does @emph{not} apply to that nested type:
11100 an explicit attribute definition clause must be provided for the component
11101 type as well if desired.
11103 Note that the scalar storage order only affects the in-memory data
11104 representation. It has no effect on the representation used by stream
11107 @node Attribute Simple_Storage_Pool,Attribute Small,Attribute Scalar_Storage_Order,Implementation Defined Attributes
11108 @anchor{gnat_rm/implementation_defined_attributes attribute-simple-storage-pool}@anchor{e3}@anchor{gnat_rm/implementation_defined_attributes id5}@anchor{198}
11109 @section Attribute Simple_Storage_Pool
11112 @geindex Storage pool
11115 @geindex Simple storage pool
11117 @geindex Simple_Storage_Pool
11119 For every nonformal, nonderived access-to-object type @code{Acc}, the
11120 representation attribute @code{Simple_Storage_Pool} may be specified
11121 via an attribute_definition_clause (or by specifying the equivalent aspect):
11124 My_Pool : My_Simple_Storage_Pool_Type;
11126 type Acc is access My_Data_Type;
11128 for Acc'Simple_Storage_Pool use My_Pool;
11131 The name given in an attribute_definition_clause for the
11132 @code{Simple_Storage_Pool} attribute shall denote a variable of
11133 a 'simple storage pool type' (see pragma @cite{Simple_Storage_Pool_Type}).
11135 The use of this attribute is only allowed for a prefix denoting a type
11136 for which it has been specified. The type of the attribute is the type
11137 of the variable specified as the simple storage pool of the access type,
11138 and the attribute denotes that variable.
11140 It is illegal to specify both @code{Storage_Pool} and @code{Simple_Storage_Pool}
11141 for the same access type.
11143 If the @code{Simple_Storage_Pool} attribute has been specified for an access
11144 type, then applying the @code{Storage_Pool} attribute to the type is flagged
11145 with a warning and its evaluation raises the exception @code{Program_Error}.
11147 If the Simple_Storage_Pool attribute has been specified for an access
11148 type @code{S}, then the evaluation of the attribute @code{S'Storage_Size}
11149 returns the result of calling @code{Storage_Size (S'Simple_Storage_Pool)},
11150 which is intended to indicate the number of storage elements reserved for
11151 the simple storage pool. If the Storage_Size function has not been defined
11152 for the simple storage pool type, then this attribute returns zero.
11154 If an access type @code{S} has a specified simple storage pool of type
11155 @code{SSP}, then the evaluation of an allocator for that access type calls
11156 the primitive @code{Allocate} procedure for type @code{SSP}, passing
11157 @code{S'Simple_Storage_Pool} as the pool parameter. The detailed
11158 semantics of such allocators is the same as those defined for allocators
11159 in section 13.11 of the @cite{Ada Reference Manual}, with the term
11160 @emph{simple storage pool} substituted for @emph{storage pool}.
11162 If an access type @code{S} has a specified simple storage pool of type
11163 @code{SSP}, then a call to an instance of the @code{Ada.Unchecked_Deallocation}
11164 for that access type invokes the primitive @code{Deallocate} procedure
11165 for type @code{SSP}, passing @code{S'Simple_Storage_Pool} as the pool
11166 parameter. The detailed semantics of such unchecked deallocations is the same
11167 as defined in section 13.11.2 of the Ada Reference Manual, except that the
11168 term @emph{simple storage pool} is substituted for @emph{storage pool}.
11170 @node Attribute Small,Attribute Storage_Unit,Attribute Simple_Storage_Pool,Implementation Defined Attributes
11171 @anchor{gnat_rm/implementation_defined_attributes attribute-small}@anchor{199}
11172 @section Attribute Small
11175 @geindex Ada 83 attributes
11179 The @code{Small} attribute is defined in Ada 95 (and Ada 2005) only for
11181 GNAT also allows this attribute to be applied to floating-point types
11182 for compatibility with Ada 83. See
11183 the Ada 83 reference manual for an exact description of the semantics of
11184 this attribute when applied to floating-point types.
11186 @node Attribute Storage_Unit,Attribute Stub_Type,Attribute Small,Implementation Defined Attributes
11187 @anchor{gnat_rm/implementation_defined_attributes attribute-storage-unit}@anchor{19a}
11188 @section Attribute Storage_Unit
11191 @geindex Storage_Unit
11193 @code{Standard'Storage_Unit} (@code{Standard} is the only permissible
11194 prefix) provides the same value as @code{System.Storage_Unit}.
11196 @node Attribute Stub_Type,Attribute System_Allocator_Alignment,Attribute Storage_Unit,Implementation Defined Attributes
11197 @anchor{gnat_rm/implementation_defined_attributes attribute-stub-type}@anchor{19b}
11198 @section Attribute Stub_Type
11203 The GNAT implementation of remote access-to-classwide types is
11204 organized as described in AARM section E.4 (20.t): a value of an RACW type
11205 (designating a remote object) is represented as a normal access
11206 value, pointing to a "stub" object which in turn contains the
11207 necessary information to contact the designated remote object. A
11208 call on any dispatching operation of such a stub object does the
11209 remote call, if necessary, using the information in the stub object
11210 to locate the target partition, etc.
11212 For a prefix @code{T} that denotes a remote access-to-classwide type,
11213 @code{T'Stub_Type} denotes the type of the corresponding stub objects.
11215 By construction, the layout of @code{T'Stub_Type} is identical to that of
11216 type @code{RACW_Stub_Type} declared in the internal implementation-defined
11217 unit @code{System.Partition_Interface}. Use of this attribute will create
11218 an implicit dependency on this unit.
11220 @node Attribute System_Allocator_Alignment,Attribute Target_Name,Attribute Stub_Type,Implementation Defined Attributes
11221 @anchor{gnat_rm/implementation_defined_attributes attribute-system-allocator-alignment}@anchor{19c}
11222 @section Attribute System_Allocator_Alignment
11228 @geindex System_Allocator_Alignment
11230 @code{Standard'System_Allocator_Alignment} (@code{Standard} is the only
11231 permissible prefix) provides the observable guaranted to be honored by
11232 the system allocator (malloc). This is a static value that can be used
11233 in user storage pools based on malloc either to reject allocation
11234 with alignment too large or to enable a realignment circuitry if the
11235 alignment request is larger than this value.
11237 @node Attribute Target_Name,Attribute To_Address,Attribute System_Allocator_Alignment,Implementation Defined Attributes
11238 @anchor{gnat_rm/implementation_defined_attributes attribute-target-name}@anchor{19d}
11239 @section Attribute Target_Name
11242 @geindex Target_Name
11244 @code{Standard'Target_Name} (@code{Standard} is the only permissible
11245 prefix) provides a static string value that identifies the target
11246 for the current compilation. For GCC implementations, this is the
11247 standard gcc target name without the terminating slash (for
11248 example, GNAT 5.0 on windows yields "i586-pc-mingw32msv").
11250 @node Attribute To_Address,Attribute To_Any,Attribute Target_Name,Implementation Defined Attributes
11251 @anchor{gnat_rm/implementation_defined_attributes attribute-to-address}@anchor{19e}
11252 @section Attribute To_Address
11255 @geindex To_Address
11257 The @code{System'To_Address}
11258 (@code{System} is the only permissible prefix)
11259 denotes a function identical to
11260 @code{System.Storage_Elements.To_Address} except that
11261 it is a static attribute. This means that if its argument is
11262 a static expression, then the result of the attribute is a
11263 static expression. This means that such an expression can be
11264 used in contexts (e.g., preelaborable packages) which require a
11265 static expression and where the function call could not be used
11266 (since the function call is always nonstatic, even if its
11267 argument is static). The argument must be in the range
11268 -(2**(m-1)) .. 2**m-1, where m is the memory size
11269 (typically 32 or 64). Negative values are intepreted in a
11270 modular manner (e.g., -1 means the same as 16#FFFF_FFFF# on
11271 a 32 bits machine).
11273 @node Attribute To_Any,Attribute Type_Class,Attribute To_Address,Implementation Defined Attributes
11274 @anchor{gnat_rm/implementation_defined_attributes attribute-to-any}@anchor{19f}
11275 @section Attribute To_Any
11280 This internal attribute is used for the generation of remote subprogram
11281 stubs in the context of the Distributed Systems Annex.
11283 @node Attribute Type_Class,Attribute Type_Key,Attribute To_Any,Implementation Defined Attributes
11284 @anchor{gnat_rm/implementation_defined_attributes attribute-type-class}@anchor{1a0}
11285 @section Attribute Type_Class
11288 @geindex Type_Class
11290 @code{typ'Type_Class} for any type or subtype @cite{typ} yields
11291 the value of the type class for the full type of @cite{typ}. If
11292 @cite{typ} is a generic formal type, the value is the value for the
11293 corresponding actual subtype. The value of this attribute is of type
11294 @code{System.Aux_DEC.Type_Class}, which has the following definition:
11298 (Type_Class_Enumeration,
11299 Type_Class_Integer,
11300 Type_Class_Fixed_Point,
11301 Type_Class_Floating_Point,
11306 Type_Class_Address);
11309 Protected types yield the value @code{Type_Class_Task}, which thus
11310 applies to all concurrent types. This attribute is designed to
11311 be compatible with the DEC Ada 83 attribute of the same name.
11313 @node Attribute Type_Key,Attribute TypeCode,Attribute Type_Class,Implementation Defined Attributes
11314 @anchor{gnat_rm/implementation_defined_attributes attribute-type-key}@anchor{1a1}
11315 @section Attribute Type_Key
11320 The @code{Type_Key} attribute is applicable to a type or subtype and
11321 yields a value of type Standard.String containing encoded information
11322 about the type or subtype. This provides improved compatibility with
11323 other implementations that support this attribute.
11325 @node Attribute TypeCode,Attribute Unconstrained_Array,Attribute Type_Key,Implementation Defined Attributes
11326 @anchor{gnat_rm/implementation_defined_attributes attribute-typecode}@anchor{1a2}
11327 @section Attribute TypeCode
11332 This internal attribute is used for the generation of remote subprogram
11333 stubs in the context of the Distributed Systems Annex.
11335 @node Attribute Unconstrained_Array,Attribute Universal_Literal_String,Attribute TypeCode,Implementation Defined Attributes
11336 @anchor{gnat_rm/implementation_defined_attributes attribute-unconstrained-array}@anchor{1a3}
11337 @section Attribute Unconstrained_Array
11340 @geindex Unconstrained_Array
11342 The @code{Unconstrained_Array} attribute can be used with a prefix that
11343 denotes any type or subtype. It is a static attribute that yields
11344 @code{True} if the prefix designates an unconstrained array,
11345 and @code{False} otherwise. In a generic instance, the result is
11346 still static, and yields the result of applying this test to the
11349 @node Attribute Universal_Literal_String,Attribute Unrestricted_Access,Attribute Unconstrained_Array,Implementation Defined Attributes
11350 @anchor{gnat_rm/implementation_defined_attributes attribute-universal-literal-string}@anchor{1a4}
11351 @section Attribute Universal_Literal_String
11354 @geindex Named numbers
11355 @geindex representation of
11357 @geindex Universal_Literal_String
11359 The prefix of @code{Universal_Literal_String} must be a named
11360 number. The static result is the string consisting of the characters of
11361 the number as defined in the original source. This allows the user
11362 program to access the actual text of named numbers without intermediate
11363 conversions and without the need to enclose the strings in quotes (which
11364 would preclude their use as numbers).
11366 For example, the following program prints the first 50 digits of pi:
11369 with Text_IO; use Text_IO;
11373 Put (Ada.Numerics.Pi'Universal_Literal_String);
11377 @node Attribute Unrestricted_Access,Attribute Update,Attribute Universal_Literal_String,Implementation Defined Attributes
11378 @anchor{gnat_rm/implementation_defined_attributes attribute-unrestricted-access}@anchor{1a5}
11379 @section Attribute Unrestricted_Access
11383 @geindex unrestricted
11385 @geindex Unrestricted_Access
11387 The @code{Unrestricted_Access} attribute is similar to @code{Access}
11388 except that all accessibility and aliased view checks are omitted. This
11389 is a user-beware attribute.
11391 For objects, it is similar to @code{Address}, for which it is a
11392 desirable replacement where the value desired is an access type.
11393 In other words, its effect is similar to first applying the
11394 @code{Address} attribute and then doing an unchecked conversion to a
11395 desired access type.
11397 For subprograms, @code{P'Unrestricted_Access} may be used where
11398 @code{P'Access} would be illegal, to construct a value of a
11399 less-nested named access type that designates a more-nested
11400 subprogram. This value may be used in indirect calls, so long as the
11401 more-nested subprogram still exists; once the subprogram containing it
11402 has returned, such calls are erroneous. For example:
11407 type Less_Nested is not null access procedure;
11408 Global : Less_Nested;
11416 Local_Var : Integer;
11418 procedure More_Nested is
11423 Global := More_Nested'Unrestricted_Access;
11430 When P1 is called from P2, the call via Global is OK, but if P1 were
11431 called after P2 returns, it would be an erroneous use of a dangling
11434 For objects, it is possible to use @code{Unrestricted_Access} for any
11435 type. However, if the result is of an access-to-unconstrained array
11436 subtype, then the resulting pointer has the same scope as the context
11437 of the attribute, and must not be returned to some enclosing scope.
11438 For instance, if a function uses @code{Unrestricted_Access} to create
11439 an access-to-unconstrained-array and returns that value to the caller,
11440 the result will involve dangling pointers. In addition, it is only
11441 valid to create pointers to unconstrained arrays using this attribute
11442 if the pointer has the normal default 'fat' representation where a
11443 pointer has two components, one points to the array and one points to
11444 the bounds. If a size clause is used to force 'thin' representation
11445 for a pointer to unconstrained where there is only space for a single
11446 pointer, then the resulting pointer is not usable.
11448 In the simple case where a direct use of Unrestricted_Access attempts
11449 to make a thin pointer for a non-aliased object, the compiler will
11450 reject the use as illegal, as shown in the following example:
11453 with System; use System;
11454 procedure SliceUA2 is
11455 type A is access all String;
11456 for A'Size use Standard'Address_Size;
11458 procedure P (Arg : A) is
11463 X : String := "hello world!";
11464 X2 : aliased String := "hello world!";
11466 AV : A := X'Unrestricted_Access; -- ERROR
11468 >>> illegal use of Unrestricted_Access attribute
11469 >>> attempt to generate thin pointer to unaliased object
11472 P (X'Unrestricted_Access); -- ERROR
11474 >>> illegal use of Unrestricted_Access attribute
11475 >>> attempt to generate thin pointer to unaliased object
11477 P (X(7 .. 12)'Unrestricted_Access); -- ERROR
11479 >>> illegal use of Unrestricted_Access attribute
11480 >>> attempt to generate thin pointer to unaliased object
11482 P (X2'Unrestricted_Access); -- OK
11486 but other cases cannot be detected by the compiler, and are
11487 considered to be erroneous. Consider the following example:
11490 with System; use System;
11491 with System; use System;
11492 procedure SliceUA is
11493 type AF is access all String;
11495 type A is access all String;
11496 for A'Size use Standard'Address_Size;
11498 procedure P (Arg : A) is
11500 if Arg'Length /= 6 then
11501 raise Program_Error;
11505 X : String := "hello world!";
11506 Y : AF := X (7 .. 12)'Unrestricted_Access;
11513 A normal unconstrained array value
11514 or a constrained array object marked as aliased has the bounds in memory
11515 just before the array, so a thin pointer can retrieve both the data and
11516 the bounds. But in this case, the non-aliased object @code{X} does not have the
11517 bounds before the string. If the size clause for type @code{A}
11518 were not present, then the pointer
11519 would be a fat pointer, where one component is a pointer to the bounds,
11520 and all would be well. But with the size clause present, the conversion from
11521 fat pointer to thin pointer in the call loses the bounds, and so this
11522 is erroneous, and the program likely raises a @code{Program_Error} exception.
11524 In general, it is advisable to completely
11525 avoid mixing the use of thin pointers and the use of
11526 @code{Unrestricted_Access} where the designated type is an
11527 unconstrained array. The use of thin pointers should be restricted to
11528 cases of porting legacy code that implicitly assumes the size of pointers,
11529 and such code should not in any case be using this attribute.
11531 Another erroneous situation arises if the attribute is
11532 applied to a constant. The resulting pointer can be used to access the
11533 constant, but the effect of trying to modify a constant in this manner
11534 is not well-defined. Consider this example:
11537 P : constant Integer := 4;
11538 type R is access all Integer;
11539 RV : R := P'Unrestricted_Access;
11544 Here we attempt to modify the constant P from 4 to 3, but the compiler may
11545 or may not notice this attempt, and subsequent references to P may yield
11546 either the value 3 or the value 4 or the assignment may blow up if the
11547 compiler decides to put P in read-only memory. One particular case where
11548 @code{Unrestricted_Access} can be used in this way is to modify the
11549 value of an @code{in} parameter:
11552 procedure K (S : in String) is
11553 type R is access all Character;
11554 RV : R := S (3)'Unrestricted_Access;
11560 In general this is a risky approach. It may appear to "work" but such uses of
11561 @code{Unrestricted_Access} are potentially non-portable, even from one version
11562 of GNAT to another, so are best avoided if possible.
11564 @node Attribute Update,Attribute Valid_Scalars,Attribute Unrestricted_Access,Implementation Defined Attributes
11565 @anchor{gnat_rm/implementation_defined_attributes attribute-update}@anchor{1a6}
11566 @section Attribute Update
11571 The @code{Update} attribute creates a copy of an array or record value
11572 with one or more modified components. The syntax is:
11575 PREFIX'Update ( RECORD_COMPONENT_ASSOCIATION_LIST )
11576 PREFIX'Update ( ARRAY_COMPONENT_ASSOCIATION @{, ARRAY_COMPONENT_ASSOCIATION @} )
11577 PREFIX'Update ( MULTIDIMENSIONAL_ARRAY_COMPONENT_ASSOCIATION
11578 @{, MULTIDIMENSIONAL_ARRAY_COMPONENT_ASSOCIATION @} )
11580 MULTIDIMENSIONAL_ARRAY_COMPONENT_ASSOCIATION ::= INDEX_EXPRESSION_LIST_LIST => EXPRESSION
11581 INDEX_EXPRESSION_LIST_LIST ::= INDEX_EXPRESSION_LIST @{| INDEX_EXPRESSION_LIST @}
11582 INDEX_EXPRESSION_LIST ::= ( EXPRESSION @{, EXPRESSION @} )
11585 where @code{PREFIX} is the name of an array or record object, the
11586 association list in parentheses does not contain an @code{others}
11587 choice and the box symbol @code{<>} may not appear in any
11588 expression. The effect is to yield a copy of the array or record value
11589 which is unchanged apart from the components mentioned in the
11590 association list, which are changed to the indicated value. The
11591 original value of the array or record value is not affected. For
11595 type Arr is Array (1 .. 5) of Integer;
11597 Avar1 : Arr := (1,2,3,4,5);
11598 Avar2 : Arr := Avar1'Update (2 => 10, 3 .. 4 => 20);
11601 yields a value for @code{Avar2} of 1,10,20,20,5 with @code{Avar1}
11602 begin unmodified. Similarly:
11605 type Rec is A, B, C : Integer;
11607 Rvar1 : Rec := (A => 1, B => 2, C => 3);
11608 Rvar2 : Rec := Rvar1'Update (B => 20);
11611 yields a value for @code{Rvar2} of (A => 1, B => 20, C => 3),
11612 with @code{Rvar1} being unmodifed.
11613 Note that the value of the attribute reference is computed
11614 completely before it is used. This means that if you write:
11617 Avar1 := Avar1'Update (1 => 10, 2 => Function_Call);
11620 then the value of @code{Avar1} is not modified if @code{Function_Call}
11621 raises an exception, unlike the effect of a series of direct assignments
11622 to elements of @code{Avar1}. In general this requires that
11623 two extra complete copies of the object are required, which should be
11624 kept in mind when considering efficiency.
11626 The @code{Update} attribute cannot be applied to prefixes of a limited
11627 type, and cannot reference discriminants in the case of a record type.
11628 The accessibility level of an Update attribute result object is defined
11629 as for an aggregate.
11631 In the record case, no component can be mentioned more than once. In
11632 the array case, two overlapping ranges can appear in the association list,
11633 in which case the modifications are processed left to right.
11635 Multi-dimensional arrays can be modified, as shown by this example:
11638 A : array (1 .. 10, 1 .. 10) of Integer;
11640 A := A'Update ((1, 2) => 20, (3, 4) => 30);
11643 which changes element (1,2) to 20 and (3,4) to 30.
11645 @node Attribute Valid_Scalars,Attribute VADS_Size,Attribute Update,Implementation Defined Attributes
11646 @anchor{gnat_rm/implementation_defined_attributes attribute-valid-scalars}@anchor{1a7}
11647 @section Attribute Valid_Scalars
11650 @geindex Valid_Scalars
11652 The @code{'Valid_Scalars} attribute is intended to make it easier to
11653 check the validity of scalar subcomponents of composite objects. It
11654 is defined for any prefix @code{X} that denotes an object.
11655 The value of this attribute is of the predefined type Boolean.
11656 @code{X'Valid_Scalars} yields True if and only if evaluation of
11657 @code{P'Valid} yields True for every scalar part P of X or if X has
11658 no scalar parts. It is not specified in what order the scalar parts
11659 are checked, nor whether any more are checked after any one of them
11660 is determined to be invalid. If the prefix @code{X} is of a class-wide
11661 type @code{T'Class} (where @code{T} is the associated specific type),
11662 or if the prefix @code{X} is of a specific tagged type @code{T}, then
11663 only the scalar parts of components of @code{T} are traversed; in other
11664 words, components of extensions of @code{T} are not traversed even if
11665 @code{T'Class (X)'Tag /= T'Tag} . The compiler will issue a warning if it can
11666 be determined at compile time that the prefix of the attribute has no
11667 scalar parts (e.g., if the prefix is of an access type, an interface type,
11668 an undiscriminated task type, or an undiscriminated protected type).
11670 For scalar types, @code{Valid_Scalars} is equivalent to @code{Valid}. The use
11671 of this attribute is not permitted for @code{Unchecked_Union} types for which
11672 in general it is not possible to determine the values of the discriminants.
11674 Note: @code{Valid_Scalars} can generate a lot of code, especially in the case
11675 of a large variant record. If the attribute is called in many places in the
11676 same program applied to objects of the same type, it can reduce program size
11677 to write a function with a single use of the attribute, and then call that
11678 function from multiple places.
11680 @node Attribute VADS_Size,Attribute Value_Size,Attribute Valid_Scalars,Implementation Defined Attributes
11681 @anchor{gnat_rm/implementation_defined_attributes attribute-vads-size}@anchor{1a8}
11682 @section Attribute VADS_Size
11686 @geindex VADS compatibility
11690 The @code{'VADS_Size} attribute is intended to make it easier to port
11691 legacy code which relies on the semantics of @code{'Size} as implemented
11692 by the VADS Ada 83 compiler. GNAT makes a best effort at duplicating the
11693 same semantic interpretation. In particular, @code{'VADS_Size} applied
11694 to a predefined or other primitive type with no Size clause yields the
11695 Object_Size (for example, @code{Natural'Size} is 32 rather than 31 on
11696 typical machines). In addition @code{'VADS_Size} applied to an object
11697 gives the result that would be obtained by applying the attribute to
11698 the corresponding type.
11700 @node Attribute Value_Size,Attribute Wchar_T_Size,Attribute VADS_Size,Implementation Defined Attributes
11701 @anchor{gnat_rm/implementation_defined_attributes id6}@anchor{1a9}@anchor{gnat_rm/implementation_defined_attributes attribute-value-size}@anchor{15b}
11702 @section Attribute Value_Size
11706 @geindex setting for not-first subtype
11708 @geindex Value_Size
11710 @code{type'Value_Size} is the number of bits required to represent
11711 a value of the given subtype. It is the same as @code{type'Size},
11712 but, unlike @code{Size}, may be set for non-first subtypes.
11714 @node Attribute Wchar_T_Size,Attribute Word_Size,Attribute Value_Size,Implementation Defined Attributes
11715 @anchor{gnat_rm/implementation_defined_attributes attribute-wchar-t-size}@anchor{1aa}
11716 @section Attribute Wchar_T_Size
11719 @geindex Wchar_T_Size
11721 @code{Standard'Wchar_T_Size} (@code{Standard} is the only permissible
11722 prefix) provides the size in bits of the C @code{wchar_t} type
11723 primarily for constructing the definition of this type in
11724 package @code{Interfaces.C}. The result is a static constant.
11726 @node Attribute Word_Size,,Attribute Wchar_T_Size,Implementation Defined Attributes
11727 @anchor{gnat_rm/implementation_defined_attributes attribute-word-size}@anchor{1ab}
11728 @section Attribute Word_Size
11733 @code{Standard'Word_Size} (@code{Standard} is the only permissible
11734 prefix) provides the value @code{System.Word_Size}. The result is
11737 @node Standard and Implementation Defined Restrictions,Implementation Advice,Implementation Defined Attributes,Top
11738 @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}
11739 @chapter Standard and Implementation Defined Restrictions
11742 All Ada Reference Manual-defined Restriction identifiers are implemented:
11748 language-defined restrictions (see 13.12.1)
11751 tasking restrictions (see D.7)
11754 high integrity restrictions (see H.4)
11757 GNAT implements additional restriction identifiers. All restrictions, whether
11758 language defined or GNAT-specific, are listed in the following.
11761 * Partition-Wide Restrictions::
11762 * Program Unit Level Restrictions::
11766 @node Partition-Wide Restrictions,Program Unit Level Restrictions,,Standard and Implementation Defined Restrictions
11767 @anchor{gnat_rm/standard_and_implementation_defined_restrictions partition-wide-restrictions}@anchor{1ae}@anchor{gnat_rm/standard_and_implementation_defined_restrictions id2}@anchor{1af}
11768 @section Partition-Wide Restrictions
11771 There are two separate lists of restriction identifiers. The first
11772 set requires consistency throughout a partition (in other words, if the
11773 restriction identifier is used for any compilation unit in the partition,
11774 then all compilation units in the partition must obey the restriction).
11777 * Immediate_Reclamation::
11778 * Max_Asynchronous_Select_Nesting::
11779 * Max_Entry_Queue_Length::
11780 * Max_Protected_Entries::
11781 * Max_Select_Alternatives::
11782 * Max_Storage_At_Blocking::
11783 * Max_Task_Entries::
11785 * No_Abort_Statements::
11786 * No_Access_Parameter_Allocators::
11787 * No_Access_Subprograms::
11789 * No_Anonymous_Allocators::
11790 * No_Asynchronous_Control::
11792 * No_Coextensions::
11793 * No_Default_Initialization::
11796 * No_Direct_Boolean_Operators::
11798 * No_Dispatching_Calls::
11799 * No_Dynamic_Attachment::
11800 * No_Dynamic_Priorities::
11801 * No_Entry_Calls_In_Elaboration_Code::
11802 * No_Enumeration_Maps::
11803 * No_Exception_Handlers::
11804 * No_Exception_Propagation::
11805 * No_Exception_Registration::
11807 * No_Finalization::
11809 * No_Floating_Point::
11810 * No_Implicit_Conditionals::
11811 * No_Implicit_Dynamic_Code::
11812 * No_Implicit_Heap_Allocations::
11813 * No_Implicit_Protected_Object_Allocations::
11814 * No_Implicit_Task_Allocations::
11815 * No_Initialize_Scalars::
11817 * No_Local_Allocators::
11818 * No_Local_Protected_Objects::
11819 * No_Local_Timing_Events::
11820 * No_Long_Long_Integers::
11821 * No_Multiple_Elaboration::
11822 * No_Nested_Finalization::
11823 * No_Protected_Type_Allocators::
11824 * No_Protected_Types::
11827 * No_Relative_Delay::
11828 * No_Requeue_Statements::
11829 * No_Secondary_Stack::
11830 * No_Select_Statements::
11831 * No_Specific_Termination_Handlers::
11832 * No_Specification_of_Aspect::
11833 * No_Standard_Allocators_After_Elaboration::
11834 * No_Standard_Storage_Pools::
11835 * No_Stream_Optimizations::
11837 * No_Task_Allocators::
11838 * No_Task_At_Interrupt_Priority::
11839 * No_Task_Attributes_Package::
11840 * No_Task_Hierarchy::
11841 * No_Task_Termination::
11843 * No_Terminate_Alternatives::
11844 * No_Unchecked_Access::
11845 * No_Unchecked_Conversion::
11846 * No_Unchecked_Deallocation::
11847 * No_Use_Of_Entity::
11849 * Simple_Barriers::
11850 * Static_Priorities::
11851 * Static_Storage_Size::
11855 @node Immediate_Reclamation,Max_Asynchronous_Select_Nesting,,Partition-Wide Restrictions
11856 @anchor{gnat_rm/standard_and_implementation_defined_restrictions immediate-reclamation}@anchor{1b0}
11857 @subsection Immediate_Reclamation
11860 @geindex Immediate_Reclamation
11862 [RM H.4] This restriction ensures that, except for storage occupied by
11863 objects created by allocators and not deallocated via unchecked
11864 deallocation, any storage reserved at run time for an object is
11865 immediately reclaimed when the object no longer exists.
11867 @node Max_Asynchronous_Select_Nesting,Max_Entry_Queue_Length,Immediate_Reclamation,Partition-Wide Restrictions
11868 @anchor{gnat_rm/standard_and_implementation_defined_restrictions max-asynchronous-select-nesting}@anchor{1b1}
11869 @subsection Max_Asynchronous_Select_Nesting
11872 @geindex Max_Asynchronous_Select_Nesting
11874 [RM D.7] Specifies the maximum dynamic nesting level of asynchronous
11875 selects. Violations of this restriction with a value of zero are
11876 detected at compile time. Violations of this restriction with values
11877 other than zero cause Storage_Error to be raised.
11879 @node Max_Entry_Queue_Length,Max_Protected_Entries,Max_Asynchronous_Select_Nesting,Partition-Wide Restrictions
11880 @anchor{gnat_rm/standard_and_implementation_defined_restrictions max-entry-queue-length}@anchor{1b2}
11881 @subsection Max_Entry_Queue_Length
11884 @geindex Max_Entry_Queue_Length
11886 [RM D.7] This restriction is a declaration that any protected entry compiled in
11887 the scope of the restriction has at most the specified number of
11888 tasks waiting on the entry at any one time, and so no queue is required.
11889 Note that this restriction is checked at run time. Violation of this
11890 restriction results in the raising of Program_Error exception at the point of
11893 @geindex Max_Entry_Queue_Depth
11895 The restriction @code{Max_Entry_Queue_Depth} is recognized as a
11896 synonym for @code{Max_Entry_Queue_Length}. This is retained for historical
11897 compatibility purposes (and a warning will be generated for its use if
11898 warnings on obsolescent features are activated).
11900 @node Max_Protected_Entries,Max_Select_Alternatives,Max_Entry_Queue_Length,Partition-Wide Restrictions
11901 @anchor{gnat_rm/standard_and_implementation_defined_restrictions max-protected-entries}@anchor{1b3}
11902 @subsection Max_Protected_Entries
11905 @geindex Max_Protected_Entries
11907 [RM D.7] Specifies the maximum number of entries per protected type. The
11908 bounds of every entry family of a protected unit shall be static, or shall be
11909 defined by a discriminant of a subtype whose corresponding bound is static.
11911 @node Max_Select_Alternatives,Max_Storage_At_Blocking,Max_Protected_Entries,Partition-Wide Restrictions
11912 @anchor{gnat_rm/standard_and_implementation_defined_restrictions max-select-alternatives}@anchor{1b4}
11913 @subsection Max_Select_Alternatives
11916 @geindex Max_Select_Alternatives
11918 [RM D.7] Specifies the maximum number of alternatives in a selective accept.
11920 @node Max_Storage_At_Blocking,Max_Task_Entries,Max_Select_Alternatives,Partition-Wide Restrictions
11921 @anchor{gnat_rm/standard_and_implementation_defined_restrictions max-storage-at-blocking}@anchor{1b5}
11922 @subsection Max_Storage_At_Blocking
11925 @geindex Max_Storage_At_Blocking
11927 [RM D.7] Specifies the maximum portion (in storage elements) of a task's
11928 Storage_Size that can be retained by a blocked task. A violation of this
11929 restriction causes Storage_Error to be raised.
11931 @node Max_Task_Entries,Max_Tasks,Max_Storage_At_Blocking,Partition-Wide Restrictions
11932 @anchor{gnat_rm/standard_and_implementation_defined_restrictions max-task-entries}@anchor{1b6}
11933 @subsection Max_Task_Entries
11936 @geindex Max_Task_Entries
11938 [RM D.7] Specifies the maximum number of entries
11939 per task. The bounds of every entry family
11940 of a task unit shall be static, or shall be
11941 defined by a discriminant of a subtype whose
11942 corresponding bound is static.
11944 @node Max_Tasks,No_Abort_Statements,Max_Task_Entries,Partition-Wide Restrictions
11945 @anchor{gnat_rm/standard_and_implementation_defined_restrictions max-tasks}@anchor{1b7}
11946 @subsection Max_Tasks
11951 [RM D.7] Specifies the maximum number of task that may be created, not
11952 counting the creation of the environment task. Violations of this
11953 restriction with a value of zero are detected at compile
11954 time. Violations of this restriction with values other than zero cause
11955 Storage_Error to be raised.
11957 @node No_Abort_Statements,No_Access_Parameter_Allocators,Max_Tasks,Partition-Wide Restrictions
11958 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-abort-statements}@anchor{1b8}
11959 @subsection No_Abort_Statements
11962 @geindex No_Abort_Statements
11964 [RM D.7] There are no abort_statements, and there are
11965 no calls to Task_Identification.Abort_Task.
11967 @node No_Access_Parameter_Allocators,No_Access_Subprograms,No_Abort_Statements,Partition-Wide Restrictions
11968 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-access-parameter-allocators}@anchor{1b9}
11969 @subsection No_Access_Parameter_Allocators
11972 @geindex No_Access_Parameter_Allocators
11974 [RM H.4] This restriction ensures at compile time that there are no
11975 occurrences of an allocator as the actual parameter to an access
11978 @node No_Access_Subprograms,No_Allocators,No_Access_Parameter_Allocators,Partition-Wide Restrictions
11979 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-access-subprograms}@anchor{1ba}
11980 @subsection No_Access_Subprograms
11983 @geindex No_Access_Subprograms
11985 [RM H.4] This restriction ensures at compile time that there are no
11986 declarations of access-to-subprogram types.
11988 @node No_Allocators,No_Anonymous_Allocators,No_Access_Subprograms,Partition-Wide Restrictions
11989 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-allocators}@anchor{1bb}
11990 @subsection No_Allocators
11993 @geindex No_Allocators
11995 [RM H.4] This restriction ensures at compile time that there are no
11996 occurrences of an allocator.
11998 @node No_Anonymous_Allocators,No_Asynchronous_Control,No_Allocators,Partition-Wide Restrictions
11999 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-anonymous-allocators}@anchor{1bc}
12000 @subsection No_Anonymous_Allocators
12003 @geindex No_Anonymous_Allocators
12005 [RM H.4] This restriction ensures at compile time that there are no
12006 occurrences of an allocator of anonymous access type.
12008 @node No_Asynchronous_Control,No_Calendar,No_Anonymous_Allocators,Partition-Wide Restrictions
12009 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-asynchronous-control}@anchor{1bd}
12010 @subsection No_Asynchronous_Control
12013 @geindex No_Asynchronous_Control
12015 [RM J.13] This restriction ensures at compile time that there are no semantic
12016 dependences on the predefined package Asynchronous_Task_Control.
12018 @node No_Calendar,No_Coextensions,No_Asynchronous_Control,Partition-Wide Restrictions
12019 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-calendar}@anchor{1be}
12020 @subsection No_Calendar
12023 @geindex No_Calendar
12025 [GNAT] This restriction ensures at compile time that there are no semantic
12026 dependences on package Calendar.
12028 @node No_Coextensions,No_Default_Initialization,No_Calendar,Partition-Wide Restrictions
12029 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-coextensions}@anchor{1bf}
12030 @subsection No_Coextensions
12033 @geindex No_Coextensions
12035 [RM H.4] This restriction ensures at compile time that there are no
12036 coextensions. See 3.10.2.
12038 @node No_Default_Initialization,No_Delay,No_Coextensions,Partition-Wide Restrictions
12039 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-default-initialization}@anchor{1c0}
12040 @subsection No_Default_Initialization
12043 @geindex No_Default_Initialization
12045 [GNAT] This restriction prohibits any instance of default initialization
12046 of variables. The binder implements a consistency rule which prevents
12047 any unit compiled without the restriction from with'ing a unit with the
12048 restriction (this allows the generation of initialization procedures to
12049 be skipped, since you can be sure that no call is ever generated to an
12050 initialization procedure in a unit with the restriction active). If used
12051 in conjunction with Initialize_Scalars or Normalize_Scalars, the effect
12052 is to prohibit all cases of variables declared without a specific
12053 initializer (including the case of OUT scalar parameters).
12055 @node No_Delay,No_Dependence,No_Default_Initialization,Partition-Wide Restrictions
12056 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-delay}@anchor{1c1}
12057 @subsection No_Delay
12062 [RM H.4] This restriction ensures at compile time that there are no
12063 delay statements and no semantic dependences on package Calendar.
12065 @node No_Dependence,No_Direct_Boolean_Operators,No_Delay,Partition-Wide Restrictions
12066 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-dependence}@anchor{1c2}
12067 @subsection No_Dependence
12070 @geindex No_Dependence
12072 [RM 13.12.1] This restriction ensures at compile time that there are no
12073 dependences on a library unit.
12075 @node No_Direct_Boolean_Operators,No_Dispatch,No_Dependence,Partition-Wide Restrictions
12076 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-direct-boolean-operators}@anchor{1c3}
12077 @subsection No_Direct_Boolean_Operators
12080 @geindex No_Direct_Boolean_Operators
12082 [GNAT] This restriction ensures that no logical operators (and/or/xor)
12083 are used on operands of type Boolean (or any type derived from Boolean).
12084 This is intended for use in safety critical programs where the certification
12085 protocol requires the use of short-circuit (and then, or else) forms for all
12086 composite boolean operations.
12088 @node No_Dispatch,No_Dispatching_Calls,No_Direct_Boolean_Operators,Partition-Wide Restrictions
12089 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-dispatch}@anchor{1c4}
12090 @subsection No_Dispatch
12093 @geindex No_Dispatch
12095 [RM H.4] This restriction ensures at compile time that there are no
12096 occurrences of @code{T'Class}, for any (tagged) subtype @code{T}.
12098 @node No_Dispatching_Calls,No_Dynamic_Attachment,No_Dispatch,Partition-Wide Restrictions
12099 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-dispatching-calls}@anchor{1c5}
12100 @subsection No_Dispatching_Calls
12103 @geindex No_Dispatching_Calls
12105 [GNAT] This restriction ensures at compile time that the code generated by the
12106 compiler involves no dispatching calls. The use of this restriction allows the
12107 safe use of record extensions, classwide membership tests and other classwide
12108 features not involving implicit dispatching. This restriction ensures that
12109 the code contains no indirect calls through a dispatching mechanism. Note that
12110 this includes internally-generated calls created by the compiler, for example
12111 in the implementation of class-wide objects assignments. The
12112 membership test is allowed in the presence of this restriction, because its
12113 implementation requires no dispatching.
12114 This restriction is comparable to the official Ada restriction
12115 @code{No_Dispatch} except that it is a bit less restrictive in that it allows
12116 all classwide constructs that do not imply dispatching.
12117 The following example indicates constructs that violate this restriction.
12121 type T is tagged record
12124 procedure P (X : T);
12126 type DT is new T with record
12127 More_Data : Natural;
12129 procedure Q (X : DT);
12133 procedure Example is
12134 procedure Test (O : T'Class) is
12135 N : Natural := O'Size;-- Error: Dispatching call
12136 C : T'Class := O; -- Error: implicit Dispatching Call
12138 if O in DT'Class then -- OK : Membership test
12139 Q (DT (O)); -- OK : Type conversion plus direct call
12141 P (O); -- Error: Dispatching call
12147 P (Obj); -- OK : Direct call
12148 P (T (Obj)); -- OK : Type conversion plus direct call
12149 P (T'Class (Obj)); -- Error: Dispatching call
12151 Test (Obj); -- OK : Type conversion
12153 if Obj in T'Class then -- OK : Membership test
12159 @node No_Dynamic_Attachment,No_Dynamic_Priorities,No_Dispatching_Calls,Partition-Wide Restrictions
12160 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-dynamic-attachment}@anchor{1c6}
12161 @subsection No_Dynamic_Attachment
12164 @geindex No_Dynamic_Attachment
12166 [RM D.7] This restriction ensures that there is no call to any of the
12167 operations defined in package Ada.Interrupts
12168 (Is_Reserved, Is_Attached, Current_Handler, Attach_Handler, Exchange_Handler,
12169 Detach_Handler, and Reference).
12171 @geindex No_Dynamic_Interrupts
12173 The restriction @code{No_Dynamic_Interrupts} is recognized as a
12174 synonym for @code{No_Dynamic_Attachment}. This is retained for historical
12175 compatibility purposes (and a warning will be generated for its use if
12176 warnings on obsolescent features are activated).
12178 @node No_Dynamic_Priorities,No_Entry_Calls_In_Elaboration_Code,No_Dynamic_Attachment,Partition-Wide Restrictions
12179 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-dynamic-priorities}@anchor{1c7}
12180 @subsection No_Dynamic_Priorities
12183 @geindex No_Dynamic_Priorities
12185 [RM D.7] There are no semantic dependencies on the package Dynamic_Priorities.
12187 @node No_Entry_Calls_In_Elaboration_Code,No_Enumeration_Maps,No_Dynamic_Priorities,Partition-Wide Restrictions
12188 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-entry-calls-in-elaboration-code}@anchor{1c8}
12189 @subsection No_Entry_Calls_In_Elaboration_Code
12192 @geindex No_Entry_Calls_In_Elaboration_Code
12194 [GNAT] This restriction ensures at compile time that no task or protected entry
12195 calls are made during elaboration code. As a result of the use of this
12196 restriction, the compiler can assume that no code past an accept statement
12197 in a task can be executed at elaboration time.
12199 @node No_Enumeration_Maps,No_Exception_Handlers,No_Entry_Calls_In_Elaboration_Code,Partition-Wide Restrictions
12200 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-enumeration-maps}@anchor{1c9}
12201 @subsection No_Enumeration_Maps
12204 @geindex No_Enumeration_Maps
12206 [GNAT] This restriction ensures at compile time that no operations requiring
12207 enumeration maps are used (that is Image and Value attributes applied
12208 to enumeration types).
12210 @node No_Exception_Handlers,No_Exception_Propagation,No_Enumeration_Maps,Partition-Wide Restrictions
12211 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-exception-handlers}@anchor{1ca}
12212 @subsection No_Exception_Handlers
12215 @geindex No_Exception_Handlers
12217 [GNAT] This restriction ensures at compile time that there are no explicit
12218 exception handlers. It also indicates that no exception propagation will
12219 be provided. In this mode, exceptions may be raised but will result in
12220 an immediate call to the last chance handler, a routine that the user
12221 must define with the following profile:
12224 procedure Last_Chance_Handler
12225 (Source_Location : System.Address; Line : Integer);
12226 pragma Export (C, Last_Chance_Handler,
12227 "__gnat_last_chance_handler");
12230 The parameter is a C null-terminated string representing a message to be
12231 associated with the exception (typically the source location of the raise
12232 statement generated by the compiler). The Line parameter when nonzero
12233 represents the line number in the source program where the raise occurs.
12235 @node No_Exception_Propagation,No_Exception_Registration,No_Exception_Handlers,Partition-Wide Restrictions
12236 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-exception-propagation}@anchor{1cb}
12237 @subsection No_Exception_Propagation
12240 @geindex No_Exception_Propagation
12242 [GNAT] This restriction guarantees that exceptions are never propagated
12243 to an outer subprogram scope. The only case in which an exception may
12244 be raised is when the handler is statically in the same subprogram, so
12245 that the effect of a raise is essentially like a goto statement. Any
12246 other raise statement (implicit or explicit) will be considered
12247 unhandled. Exception handlers are allowed, but may not contain an
12248 exception occurrence identifier (exception choice). In addition, use of
12249 the package GNAT.Current_Exception is not permitted, and reraise
12250 statements (raise with no operand) are not permitted.
12252 @node No_Exception_Registration,No_Exceptions,No_Exception_Propagation,Partition-Wide Restrictions
12253 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-exception-registration}@anchor{1cc}
12254 @subsection No_Exception_Registration
12257 @geindex No_Exception_Registration
12259 [GNAT] This restriction ensures at compile time that no stream operations for
12260 types Exception_Id or Exception_Occurrence are used. This also makes it
12261 impossible to pass exceptions to or from a partition with this restriction
12262 in a distributed environment. If this restriction is active, the generated
12263 code is simplified by omitting the otherwise-required global registration
12264 of exceptions when they are declared.
12266 @node No_Exceptions,No_Finalization,No_Exception_Registration,Partition-Wide Restrictions
12267 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-exceptions}@anchor{1cd}
12268 @subsection No_Exceptions
12271 @geindex No_Exceptions
12273 [RM H.4] This restriction ensures at compile time that there are no
12274 raise statements and no exception handlers.
12276 @node No_Finalization,No_Fixed_Point,No_Exceptions,Partition-Wide Restrictions
12277 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-finalization}@anchor{1ce}
12278 @subsection No_Finalization
12281 @geindex No_Finalization
12283 [GNAT] This restriction disables the language features described in
12284 chapter 7.6 of the Ada 2005 RM as well as all form of code generation
12285 performed by the compiler to support these features. The following types
12286 are no longer considered controlled when this restriction is in effect:
12292 @code{Ada.Finalization.Controlled}
12295 @code{Ada.Finalization.Limited_Controlled}
12298 Derivations from @code{Controlled} or @code{Limited_Controlled}
12310 Array and record types with controlled components
12313 The compiler no longer generates code to initialize, finalize or adjust an
12314 object or a nested component, either declared on the stack or on the heap. The
12315 deallocation of a controlled object no longer finalizes its contents.
12317 @node No_Fixed_Point,No_Floating_Point,No_Finalization,Partition-Wide Restrictions
12318 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-fixed-point}@anchor{1cf}
12319 @subsection No_Fixed_Point
12322 @geindex No_Fixed_Point
12324 [RM H.4] This restriction ensures at compile time that there are no
12325 occurrences of fixed point types and operations.
12327 @node No_Floating_Point,No_Implicit_Conditionals,No_Fixed_Point,Partition-Wide Restrictions
12328 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-floating-point}@anchor{1d0}
12329 @subsection No_Floating_Point
12332 @geindex No_Floating_Point
12334 [RM H.4] This restriction ensures at compile time that there are no
12335 occurrences of floating point types and operations.
12337 @node No_Implicit_Conditionals,No_Implicit_Dynamic_Code,No_Floating_Point,Partition-Wide Restrictions
12338 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-conditionals}@anchor{1d1}
12339 @subsection No_Implicit_Conditionals
12342 @geindex No_Implicit_Conditionals
12344 [GNAT] This restriction ensures that the generated code does not contain any
12345 implicit conditionals, either by modifying the generated code where possible,
12346 or by rejecting any construct that would otherwise generate an implicit
12347 conditional. Note that this check does not include run time constraint
12348 checks, which on some targets may generate implicit conditionals as
12349 well. To control the latter, constraint checks can be suppressed in the
12350 normal manner. Constructs generating implicit conditionals include comparisons
12351 of composite objects and the Max/Min attributes.
12353 @node No_Implicit_Dynamic_Code,No_Implicit_Heap_Allocations,No_Implicit_Conditionals,Partition-Wide Restrictions
12354 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-dynamic-code}@anchor{1d2}
12355 @subsection No_Implicit_Dynamic_Code
12358 @geindex No_Implicit_Dynamic_Code
12360 @geindex trampoline
12362 [GNAT] This restriction prevents the compiler from building 'trampolines'.
12363 This is a structure that is built on the stack and contains dynamic
12364 code to be executed at run time. On some targets, a trampoline is
12365 built for the following features: @code{Access},
12366 @code{Unrestricted_Access}, or @code{Address} of a nested subprogram;
12367 nested task bodies; primitive operations of nested tagged types.
12368 Trampolines do not work on machines that prevent execution of stack
12369 data. For example, on windows systems, enabling DEP (data execution
12370 protection) will cause trampolines to raise an exception.
12371 Trampolines are also quite slow at run time.
12373 On many targets, trampolines have been largely eliminated. Look at the
12374 version of system.ads for your target --- if it has
12375 Always_Compatible_Rep equal to False, then trampolines are largely
12376 eliminated. In particular, a trampoline is built for the following
12377 features: @code{Address} of a nested subprogram;
12378 @code{Access} or @code{Unrestricted_Access} of a nested subprogram,
12379 but only if pragma Favor_Top_Level applies, or the access type has a
12380 foreign-language convention; primitive operations of nested tagged
12383 @node No_Implicit_Heap_Allocations,No_Implicit_Protected_Object_Allocations,No_Implicit_Dynamic_Code,Partition-Wide Restrictions
12384 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-heap-allocations}@anchor{1d3}
12385 @subsection No_Implicit_Heap_Allocations
12388 @geindex No_Implicit_Heap_Allocations
12390 [RM D.7] No constructs are allowed to cause implicit heap allocation.
12392 @node No_Implicit_Protected_Object_Allocations,No_Implicit_Task_Allocations,No_Implicit_Heap_Allocations,Partition-Wide Restrictions
12393 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-protected-object-allocations}@anchor{1d4}
12394 @subsection No_Implicit_Protected_Object_Allocations
12397 @geindex No_Implicit_Protected_Object_Allocations
12399 [GNAT] No constructs are allowed to cause implicit heap allocation of a
12402 @node No_Implicit_Task_Allocations,No_Initialize_Scalars,No_Implicit_Protected_Object_Allocations,Partition-Wide Restrictions
12403 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-task-allocations}@anchor{1d5}
12404 @subsection No_Implicit_Task_Allocations
12407 @geindex No_Implicit_Task_Allocations
12409 [GNAT] No constructs are allowed to cause implicit heap allocation of a task.
12411 @node No_Initialize_Scalars,No_IO,No_Implicit_Task_Allocations,Partition-Wide Restrictions
12412 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-initialize-scalars}@anchor{1d6}
12413 @subsection No_Initialize_Scalars
12416 @geindex No_Initialize_Scalars
12418 [GNAT] This restriction ensures that no unit in the partition is compiled with
12419 pragma Initialize_Scalars. This allows the generation of more efficient
12420 code, and in particular eliminates dummy null initialization routines that
12421 are otherwise generated for some record and array types.
12423 @node No_IO,No_Local_Allocators,No_Initialize_Scalars,Partition-Wide Restrictions
12424 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-io}@anchor{1d7}
12430 [RM H.4] This restriction ensures at compile time that there are no
12431 dependences on any of the library units Sequential_IO, Direct_IO,
12432 Text_IO, Wide_Text_IO, Wide_Wide_Text_IO, or Stream_IO.
12434 @node No_Local_Allocators,No_Local_Protected_Objects,No_IO,Partition-Wide Restrictions
12435 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-local-allocators}@anchor{1d8}
12436 @subsection No_Local_Allocators
12439 @geindex No_Local_Allocators
12441 [RM H.4] This restriction ensures at compile time that there are no
12442 occurrences of an allocator in subprograms, generic subprograms, tasks,
12445 @node No_Local_Protected_Objects,No_Local_Timing_Events,No_Local_Allocators,Partition-Wide Restrictions
12446 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-local-protected-objects}@anchor{1d9}
12447 @subsection No_Local_Protected_Objects
12450 @geindex No_Local_Protected_Objects
12452 [RM D.7] This restriction ensures at compile time that protected objects are
12453 only declared at the library level.
12455 @node No_Local_Timing_Events,No_Long_Long_Integers,No_Local_Protected_Objects,Partition-Wide Restrictions
12456 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-local-timing-events}@anchor{1da}
12457 @subsection No_Local_Timing_Events
12460 @geindex No_Local_Timing_Events
12462 [RM D.7] All objects of type Ada.Timing_Events.Timing_Event are
12463 declared at the library level.
12465 @node No_Long_Long_Integers,No_Multiple_Elaboration,No_Local_Timing_Events,Partition-Wide Restrictions
12466 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-long-long-integers}@anchor{1db}
12467 @subsection No_Long_Long_Integers
12470 @geindex No_Long_Long_Integers
12472 [GNAT] This partition-wide restriction forbids any explicit reference to
12473 type Standard.Long_Long_Integer, and also forbids declaring range types whose
12474 implicit base type is Long_Long_Integer, and modular types whose size exceeds
12477 @node No_Multiple_Elaboration,No_Nested_Finalization,No_Long_Long_Integers,Partition-Wide Restrictions
12478 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-multiple-elaboration}@anchor{1dc}
12479 @subsection No_Multiple_Elaboration
12482 @geindex No_Multiple_Elaboration
12484 [GNAT] When this restriction is active, we are not requesting control-flow
12485 preservation with -fpreserve-control-flow, and the static elaboration model is
12486 used, the compiler is allowed to suppress the elaboration counter normally
12487 associated with the unit, even if the unit has elaboration code. This counter
12488 is typically used to check for access before elaboration and to control
12489 multiple elaboration attempts. If the restriction is used, then the
12490 situations in which multiple elaboration is possible, including non-Ada main
12491 programs and Stand Alone libraries, are not permitted and will be diagnosed
12494 @node No_Nested_Finalization,No_Protected_Type_Allocators,No_Multiple_Elaboration,Partition-Wide Restrictions
12495 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-nested-finalization}@anchor{1dd}
12496 @subsection No_Nested_Finalization
12499 @geindex No_Nested_Finalization
12501 [RM D.7] All objects requiring finalization are declared at the library level.
12503 @node No_Protected_Type_Allocators,No_Protected_Types,No_Nested_Finalization,Partition-Wide Restrictions
12504 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-protected-type-allocators}@anchor{1de}
12505 @subsection No_Protected_Type_Allocators
12508 @geindex No_Protected_Type_Allocators
12510 [RM D.7] This restriction ensures at compile time that there are no allocator
12511 expressions that attempt to allocate protected objects.
12513 @node No_Protected_Types,No_Recursion,No_Protected_Type_Allocators,Partition-Wide Restrictions
12514 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-protected-types}@anchor{1df}
12515 @subsection No_Protected_Types
12518 @geindex No_Protected_Types
12520 [RM H.4] This restriction ensures at compile time that there are no
12521 declarations of protected types or protected objects.
12523 @node No_Recursion,No_Reentrancy,No_Protected_Types,Partition-Wide Restrictions
12524 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-recursion}@anchor{1e0}
12525 @subsection No_Recursion
12528 @geindex No_Recursion
12530 [RM H.4] A program execution is erroneous if a subprogram is invoked as
12531 part of its execution.
12533 @node No_Reentrancy,No_Relative_Delay,No_Recursion,Partition-Wide Restrictions
12534 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-reentrancy}@anchor{1e1}
12535 @subsection No_Reentrancy
12538 @geindex No_Reentrancy
12540 [RM H.4] A program execution is erroneous if a subprogram is executed by
12541 two tasks at the same time.
12543 @node No_Relative_Delay,No_Requeue_Statements,No_Reentrancy,Partition-Wide Restrictions
12544 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-relative-delay}@anchor{1e2}
12545 @subsection No_Relative_Delay
12548 @geindex No_Relative_Delay
12550 [RM D.7] This restriction ensures at compile time that there are no delay
12551 relative statements and prevents expressions such as @code{delay 1.23;} from
12552 appearing in source code.
12554 @node No_Requeue_Statements,No_Secondary_Stack,No_Relative_Delay,Partition-Wide Restrictions
12555 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-requeue-statements}@anchor{1e3}
12556 @subsection No_Requeue_Statements
12559 @geindex No_Requeue_Statements
12561 [RM D.7] This restriction ensures at compile time that no requeue statements
12562 are permitted and prevents keyword @code{requeue} from being used in source
12565 @geindex No_Requeue
12567 The restriction @code{No_Requeue} is recognized as a
12568 synonym for @code{No_Requeue_Statements}. This is retained for historical
12569 compatibility purposes (and a warning will be generated for its use if
12570 warnings on oNobsolescent features are activated).
12572 @node No_Secondary_Stack,No_Select_Statements,No_Requeue_Statements,Partition-Wide Restrictions
12573 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-secondary-stack}@anchor{1e4}
12574 @subsection No_Secondary_Stack
12577 @geindex No_Secondary_Stack
12579 [GNAT] This restriction ensures at compile time that the generated code
12580 does not contain any reference to the secondary stack. The secondary
12581 stack is used to implement functions returning unconstrained objects
12582 (arrays or records) on some targets. Suppresses the allocation of
12583 secondary stacks for tasks (excluding the environment task) at run time.
12585 @node No_Select_Statements,No_Specific_Termination_Handlers,No_Secondary_Stack,Partition-Wide Restrictions
12586 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-select-statements}@anchor{1e5}
12587 @subsection No_Select_Statements
12590 @geindex No_Select_Statements
12592 [RM D.7] This restriction ensures at compile time no select statements of any
12593 kind are permitted, that is the keyword @code{select} may not appear.
12595 @node No_Specific_Termination_Handlers,No_Specification_of_Aspect,No_Select_Statements,Partition-Wide Restrictions
12596 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-specific-termination-handlers}@anchor{1e6}
12597 @subsection No_Specific_Termination_Handlers
12600 @geindex No_Specific_Termination_Handlers
12602 [RM D.7] There are no calls to Ada.Task_Termination.Set_Specific_Handler
12603 or to Ada.Task_Termination.Specific_Handler.
12605 @node No_Specification_of_Aspect,No_Standard_Allocators_After_Elaboration,No_Specific_Termination_Handlers,Partition-Wide Restrictions
12606 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-specification-of-aspect}@anchor{1e7}
12607 @subsection No_Specification_of_Aspect
12610 @geindex No_Specification_of_Aspect
12612 [RM 13.12.1] This restriction checks at compile time that no aspect
12613 specification, attribute definition clause, or pragma is given for a
12616 @node No_Standard_Allocators_After_Elaboration,No_Standard_Storage_Pools,No_Specification_of_Aspect,Partition-Wide Restrictions
12617 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-standard-allocators-after-elaboration}@anchor{1e8}
12618 @subsection No_Standard_Allocators_After_Elaboration
12621 @geindex No_Standard_Allocators_After_Elaboration
12623 [RM D.7] Specifies that an allocator using a standard storage pool
12624 should never be evaluated at run time after the elaboration of the
12625 library items of the partition has completed. Otherwise, Storage_Error
12628 @node No_Standard_Storage_Pools,No_Stream_Optimizations,No_Standard_Allocators_After_Elaboration,Partition-Wide Restrictions
12629 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-standard-storage-pools}@anchor{1e9}
12630 @subsection No_Standard_Storage_Pools
12633 @geindex No_Standard_Storage_Pools
12635 [GNAT] This restriction ensures at compile time that no access types
12636 use the standard default storage pool. Any access type declared must
12637 have an explicit Storage_Pool attribute defined specifying a
12638 user-defined storage pool.
12640 @node No_Stream_Optimizations,No_Streams,No_Standard_Storage_Pools,Partition-Wide Restrictions
12641 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-stream-optimizations}@anchor{1ea}
12642 @subsection No_Stream_Optimizations
12645 @geindex No_Stream_Optimizations
12647 [GNAT] This restriction affects the performance of stream operations on types
12648 @code{String}, @code{Wide_String} and @code{Wide_Wide_String}. By default, the
12649 compiler uses block reads and writes when manipulating @code{String} objects
12650 due to their supperior performance. When this restriction is in effect, the
12651 compiler performs all IO operations on a per-character basis.
12653 @node No_Streams,No_Task_Allocators,No_Stream_Optimizations,Partition-Wide Restrictions
12654 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-streams}@anchor{1eb}
12655 @subsection No_Streams
12658 @geindex No_Streams
12660 [GNAT] This restriction ensures at compile/bind time that there are no
12661 stream objects created and no use of stream attributes.
12662 This restriction does not forbid dependences on the package
12663 @code{Ada.Streams}. So it is permissible to with
12664 @code{Ada.Streams} (or another package that does so itself)
12665 as long as no actual stream objects are created and no
12666 stream attributes are used.
12668 Note that the use of restriction allows optimization of tagged types,
12669 since they do not need to worry about dispatching stream operations.
12670 To take maximum advantage of this space-saving optimization, any
12671 unit declaring a tagged type should be compiled with the restriction,
12672 though this is not required.
12674 @node No_Task_Allocators,No_Task_At_Interrupt_Priority,No_Streams,Partition-Wide Restrictions
12675 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-task-allocators}@anchor{1ec}
12676 @subsection No_Task_Allocators
12679 @geindex No_Task_Allocators
12681 [RM D.7] There are no allocators for task types
12682 or types containing task subcomponents.
12684 @node No_Task_At_Interrupt_Priority,No_Task_Attributes_Package,No_Task_Allocators,Partition-Wide Restrictions
12685 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-task-at-interrupt-priority}@anchor{1ed}
12686 @subsection No_Task_At_Interrupt_Priority
12689 @geindex No_Task_At_Interrupt_Priority
12691 [GNAT] This restriction ensures at compile time that there is no
12692 Interrupt_Priority aspect or pragma for a task or a task type. As
12693 a consequence, the tasks are always created with a priority below
12694 that an interrupt priority.
12696 @node No_Task_Attributes_Package,No_Task_Hierarchy,No_Task_At_Interrupt_Priority,Partition-Wide Restrictions
12697 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-task-attributes-package}@anchor{1ee}
12698 @subsection No_Task_Attributes_Package
12701 @geindex No_Task_Attributes_Package
12703 [GNAT] This restriction ensures at compile time that there are no implicit or
12704 explicit dependencies on the package @code{Ada.Task_Attributes}.
12706 @geindex No_Task_Attributes
12708 The restriction @code{No_Task_Attributes} is recognized as a synonym
12709 for @code{No_Task_Attributes_Package}. This is retained for historical
12710 compatibility purposes (and a warning will be generated for its use if
12711 warnings on obsolescent features are activated).
12713 @node No_Task_Hierarchy,No_Task_Termination,No_Task_Attributes_Package,Partition-Wide Restrictions
12714 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-task-hierarchy}@anchor{1ef}
12715 @subsection No_Task_Hierarchy
12718 @geindex No_Task_Hierarchy
12720 [RM D.7] All (non-environment) tasks depend
12721 directly on the environment task of the partition.
12723 @node No_Task_Termination,No_Tasking,No_Task_Hierarchy,Partition-Wide Restrictions
12724 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-task-termination}@anchor{1f0}
12725 @subsection No_Task_Termination
12728 @geindex No_Task_Termination
12730 [RM D.7] Tasks that terminate are erroneous.
12732 @node No_Tasking,No_Terminate_Alternatives,No_Task_Termination,Partition-Wide Restrictions
12733 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-tasking}@anchor{1f1}
12734 @subsection No_Tasking
12737 @geindex No_Tasking
12739 [GNAT] This restriction prevents the declaration of tasks or task types
12740 throughout the partition. It is similar in effect to the use of
12741 @code{Max_Tasks => 0} except that violations are caught at compile time
12742 and cause an error message to be output either by the compiler or
12745 @node No_Terminate_Alternatives,No_Unchecked_Access,No_Tasking,Partition-Wide Restrictions
12746 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-terminate-alternatives}@anchor{1f2}
12747 @subsection No_Terminate_Alternatives
12750 @geindex No_Terminate_Alternatives
12752 [RM D.7] There are no selective accepts with terminate alternatives.
12754 @node No_Unchecked_Access,No_Unchecked_Conversion,No_Terminate_Alternatives,Partition-Wide Restrictions
12755 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-unchecked-access}@anchor{1f3}
12756 @subsection No_Unchecked_Access
12759 @geindex No_Unchecked_Access
12761 [RM H.4] This restriction ensures at compile time that there are no
12762 occurrences of the Unchecked_Access attribute.
12764 @node No_Unchecked_Conversion,No_Unchecked_Deallocation,No_Unchecked_Access,Partition-Wide Restrictions
12765 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-unchecked-conversion}@anchor{1f4}
12766 @subsection No_Unchecked_Conversion
12769 @geindex No_Unchecked_Conversion
12771 [RM J.13] This restriction ensures at compile time that there are no semantic
12772 dependences on the predefined generic function Unchecked_Conversion.
12774 @node No_Unchecked_Deallocation,No_Use_Of_Entity,No_Unchecked_Conversion,Partition-Wide Restrictions
12775 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-unchecked-deallocation}@anchor{1f5}
12776 @subsection No_Unchecked_Deallocation
12779 @geindex No_Unchecked_Deallocation
12781 [RM J.13] This restriction ensures at compile time that there are no semantic
12782 dependences on the predefined generic procedure Unchecked_Deallocation.
12784 @node No_Use_Of_Entity,Pure_Barriers,No_Unchecked_Deallocation,Partition-Wide Restrictions
12785 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-use-of-entity}@anchor{1f6}
12786 @subsection No_Use_Of_Entity
12789 @geindex No_Use_Of_Entity
12791 [GNAT] This restriction ensures at compile time that there are no references
12792 to the entity given in the form
12795 No_Use_Of_Entity => Name
12798 where @code{Name} is the fully qualified entity, for example
12801 No_Use_Of_Entity => Ada.Text_IO.Put_Line
12804 @node Pure_Barriers,Simple_Barriers,No_Use_Of_Entity,Partition-Wide Restrictions
12805 @anchor{gnat_rm/standard_and_implementation_defined_restrictions pure-barriers}@anchor{1f7}
12806 @subsection Pure_Barriers
12809 @geindex Pure_Barriers
12811 [GNAT] This restriction ensures at compile time that protected entry
12812 barriers are restricted to:
12818 components of the protected object (excluding selection from dereferences),
12821 constant declarations,
12827 enumeration literals,
12836 character literals,
12839 implicitly defined comparison operators,
12842 uses of the Standard."not" operator,
12845 short-circuit operator,
12848 the Count attribute
12851 This restriction is a relaxation of the Simple_Barriers restriction,
12852 but still ensures absence of side effects, exceptions, and recursion
12853 during the evaluation of the barriers.
12855 @node Simple_Barriers,Static_Priorities,Pure_Barriers,Partition-Wide Restrictions
12856 @anchor{gnat_rm/standard_and_implementation_defined_restrictions simple-barriers}@anchor{1f8}
12857 @subsection Simple_Barriers
12860 @geindex Simple_Barriers
12862 [RM D.7] This restriction ensures at compile time that barriers in entry
12863 declarations for protected types are restricted to either static boolean
12864 expressions or references to simple boolean variables defined in the private
12865 part of the protected type. No other form of entry barriers is permitted.
12867 @geindex Boolean_Entry_Barriers
12869 The restriction @code{Boolean_Entry_Barriers} is recognized as a
12870 synonym for @code{Simple_Barriers}. This is retained for historical
12871 compatibility purposes (and a warning will be generated for its use if
12872 warnings on obsolescent features are activated).
12874 @node Static_Priorities,Static_Storage_Size,Simple_Barriers,Partition-Wide Restrictions
12875 @anchor{gnat_rm/standard_and_implementation_defined_restrictions static-priorities}@anchor{1f9}
12876 @subsection Static_Priorities
12879 @geindex Static_Priorities
12881 [GNAT] This restriction ensures at compile time that all priority expressions
12882 are static, and that there are no dependences on the package
12883 @code{Ada.Dynamic_Priorities}.
12885 @node Static_Storage_Size,,Static_Priorities,Partition-Wide Restrictions
12886 @anchor{gnat_rm/standard_and_implementation_defined_restrictions static-storage-size}@anchor{1fa}
12887 @subsection Static_Storage_Size
12890 @geindex Static_Storage_Size
12892 [GNAT] This restriction ensures at compile time that any expression appearing
12893 in a Storage_Size pragma or attribute definition clause is static.
12895 @node Program Unit Level Restrictions,,Partition-Wide Restrictions,Standard and Implementation Defined Restrictions
12896 @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}
12897 @section Program Unit Level Restrictions
12900 The second set of restriction identifiers
12901 does not require partition-wide consistency.
12902 The restriction may be enforced for a single
12903 compilation unit without any effect on any of the
12904 other compilation units in the partition.
12907 * No_Elaboration_Code::
12908 * No_Dynamic_Sized_Objects::
12910 * No_Implementation_Aspect_Specifications::
12911 * No_Implementation_Attributes::
12912 * No_Implementation_Identifiers::
12913 * No_Implementation_Pragmas::
12914 * No_Implementation_Restrictions::
12915 * No_Implementation_Units::
12916 * No_Implicit_Aliasing::
12917 * No_Implicit_Loops::
12918 * No_Obsolescent_Features::
12919 * No_Wide_Characters::
12924 @node No_Elaboration_Code,No_Dynamic_Sized_Objects,,Program Unit Level Restrictions
12925 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-elaboration-code}@anchor{1fd}
12926 @subsection No_Elaboration_Code
12929 @geindex No_Elaboration_Code
12931 [GNAT] This restriction ensures at compile time that no elaboration code is
12932 generated. Note that this is not the same condition as is enforced
12933 by pragma @code{Preelaborate}. There are cases in which pragma
12934 @code{Preelaborate} still permits code to be generated (e.g., code
12935 to initialize a large array to all zeroes), and there are cases of units
12936 which do not meet the requirements for pragma @code{Preelaborate},
12937 but for which no elaboration code is generated. Generally, it is
12938 the case that preelaborable units will meet the restrictions, with
12939 the exception of large aggregates initialized with an others_clause,
12940 and exception declarations (which generate calls to a run-time
12941 registry procedure). This restriction is enforced on
12942 a unit by unit basis, it need not be obeyed consistently
12943 throughout a partition.
12945 In the case of aggregates with others, if the aggregate has a dynamic
12946 size, there is no way to eliminate the elaboration code (such dynamic
12947 bounds would be incompatible with @code{Preelaborate} in any case). If
12948 the bounds are static, then use of this restriction actually modifies
12949 the code choice of the compiler to avoid generating a loop, and instead
12950 generate the aggregate statically if possible, no matter how many times
12951 the data for the others clause must be repeatedly generated.
12953 It is not possible to precisely document
12954 the constructs which are compatible with this restriction, since,
12955 unlike most other restrictions, this is not a restriction on the
12956 source code, but a restriction on the generated object code. For
12957 example, if the source contains a declaration:
12960 Val : constant Integer := X;
12963 where X is not a static constant, it may be possible, depending
12964 on complex optimization circuitry, for the compiler to figure
12965 out the value of X at compile time, in which case this initialization
12966 can be done by the loader, and requires no initialization code. It
12967 is not possible to document the precise conditions under which the
12968 optimizer can figure this out.
12970 Note that this the implementation of this restriction requires full
12971 code generation. If it is used in conjunction with "semantics only"
12972 checking, then some cases of violations may be missed.
12974 When this restriction is active, we are not requesting control-flow
12975 preservation with -fpreserve-control-flow, and the static elaboration model is
12976 used, the compiler is allowed to suppress the elaboration counter normally
12977 associated with the unit. This counter is typically used to check for access
12978 before elaboration and to control multiple elaboration attempts.
12980 @node No_Dynamic_Sized_Objects,No_Entry_Queue,No_Elaboration_Code,Program Unit Level Restrictions
12981 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-dynamic-sized-objects}@anchor{1fe}
12982 @subsection No_Dynamic_Sized_Objects
12985 @geindex No_Dynamic_Sized_Objects
12987 [GNAT] This restriction disallows certain constructs that might lead to the
12988 creation of dynamic-sized composite objects (or array or discriminated type).
12989 An array subtype indication is illegal if the bounds are not static
12990 or references to discriminants of an enclosing type.
12991 A discriminated subtype indication is illegal if the type has
12992 discriminant-dependent array components or a variant part, and the
12993 discriminants are not static. In addition, array and record aggregates are
12994 illegal in corresponding cases. Note that this restriction does not forbid
12995 access discriminants. It is often a good idea to combine this restriction
12996 with No_Secondary_Stack.
12998 @node No_Entry_Queue,No_Implementation_Aspect_Specifications,No_Dynamic_Sized_Objects,Program Unit Level Restrictions
12999 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-entry-queue}@anchor{1ff}
13000 @subsection No_Entry_Queue
13003 @geindex No_Entry_Queue
13005 [GNAT] This restriction is a declaration that any protected entry compiled in
13006 the scope of the restriction has at most one task waiting on the entry
13007 at any one time, and so no queue is required. This restriction is not
13008 checked at compile time. A program execution is erroneous if an attempt
13009 is made to queue a second task on such an entry.
13011 @node No_Implementation_Aspect_Specifications,No_Implementation_Attributes,No_Entry_Queue,Program Unit Level Restrictions
13012 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implementation-aspect-specifications}@anchor{200}
13013 @subsection No_Implementation_Aspect_Specifications
13016 @geindex No_Implementation_Aspect_Specifications
13018 [RM 13.12.1] This restriction checks at compile time that no
13019 GNAT-defined aspects are present. With this restriction, the only
13020 aspects that can be used are those defined in the Ada Reference Manual.
13022 @node No_Implementation_Attributes,No_Implementation_Identifiers,No_Implementation_Aspect_Specifications,Program Unit Level Restrictions
13023 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implementation-attributes}@anchor{201}
13024 @subsection No_Implementation_Attributes
13027 @geindex No_Implementation_Attributes
13029 [RM 13.12.1] This restriction checks at compile time that no
13030 GNAT-defined attributes are present. With this restriction, the only
13031 attributes that can be used are those defined in the Ada Reference
13034 @node No_Implementation_Identifiers,No_Implementation_Pragmas,No_Implementation_Attributes,Program Unit Level Restrictions
13035 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implementation-identifiers}@anchor{202}
13036 @subsection No_Implementation_Identifiers
13039 @geindex No_Implementation_Identifiers
13041 [RM 13.12.1] This restriction checks at compile time that no
13042 implementation-defined identifiers (marked with pragma Implementation_Defined)
13043 occur within language-defined packages.
13045 @node No_Implementation_Pragmas,No_Implementation_Restrictions,No_Implementation_Identifiers,Program Unit Level Restrictions
13046 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implementation-pragmas}@anchor{203}
13047 @subsection No_Implementation_Pragmas
13050 @geindex No_Implementation_Pragmas
13052 [RM 13.12.1] This restriction checks at compile time that no
13053 GNAT-defined pragmas are present. With this restriction, the only
13054 pragmas that can be used are those defined in the Ada Reference Manual.
13056 @node No_Implementation_Restrictions,No_Implementation_Units,No_Implementation_Pragmas,Program Unit Level Restrictions
13057 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implementation-restrictions}@anchor{204}
13058 @subsection No_Implementation_Restrictions
13061 @geindex No_Implementation_Restrictions
13063 [GNAT] This restriction checks at compile time that no GNAT-defined restriction
13064 identifiers (other than @code{No_Implementation_Restrictions} itself)
13065 are present. With this restriction, the only other restriction identifiers
13066 that can be used are those defined in the Ada Reference Manual.
13068 @node No_Implementation_Units,No_Implicit_Aliasing,No_Implementation_Restrictions,Program Unit Level Restrictions
13069 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implementation-units}@anchor{205}
13070 @subsection No_Implementation_Units
13073 @geindex No_Implementation_Units
13075 [RM 13.12.1] This restriction checks at compile time that there is no
13076 mention in the context clause of any implementation-defined descendants
13077 of packages Ada, Interfaces, or System.
13079 @node No_Implicit_Aliasing,No_Implicit_Loops,No_Implementation_Units,Program Unit Level Restrictions
13080 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-aliasing}@anchor{206}
13081 @subsection No_Implicit_Aliasing
13084 @geindex No_Implicit_Aliasing
13086 [GNAT] This restriction, which is not required to be partition-wide consistent,
13087 requires an explicit aliased keyword for an object to which 'Access,
13088 'Unchecked_Access, or 'Address is applied, and forbids entirely the use of
13089 the 'Unrestricted_Access attribute for objects. Note: the reason that
13090 Unrestricted_Access is forbidden is that it would require the prefix
13091 to be aliased, and in such cases, it can always be replaced by
13092 the standard attribute Unchecked_Access which is preferable.
13094 @node No_Implicit_Loops,No_Obsolescent_Features,No_Implicit_Aliasing,Program Unit Level Restrictions
13095 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-loops}@anchor{207}
13096 @subsection No_Implicit_Loops
13099 @geindex No_Implicit_Loops
13101 [GNAT] This restriction ensures that the generated code of the unit marked
13102 with this restriction does not contain any implicit @code{for} loops, either by
13103 modifying the generated code where possible, or by rejecting any construct
13104 that would otherwise generate an implicit @code{for} loop. If this restriction is
13105 active, it is possible to build large array aggregates with all static
13106 components without generating an intermediate temporary, and without generating
13107 a loop to initialize individual components. Otherwise, a loop is created for
13108 arrays larger than about 5000 scalar components. Note that if this restriction
13109 is set in the spec of a package, it will not apply to its body.
13111 @node No_Obsolescent_Features,No_Wide_Characters,No_Implicit_Loops,Program Unit Level Restrictions
13112 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-obsolescent-features}@anchor{208}
13113 @subsection No_Obsolescent_Features
13116 @geindex No_Obsolescent_Features
13118 [RM 13.12.1] This restriction checks at compile time that no obsolescent
13119 features are used, as defined in Annex J of the Ada Reference Manual.
13121 @node No_Wide_Characters,SPARK_05,No_Obsolescent_Features,Program Unit Level Restrictions
13122 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-wide-characters}@anchor{209}
13123 @subsection No_Wide_Characters
13126 @geindex No_Wide_Characters
13128 [GNAT] This restriction ensures at compile time that no uses of the types
13129 @code{Wide_Character} or @code{Wide_String} or corresponding wide
13131 appear, and that no wide or wide wide string or character literals
13132 appear in the program (that is literals representing characters not in
13133 type @code{Character}).
13135 @node SPARK_05,,No_Wide_Characters,Program Unit Level Restrictions
13136 @anchor{gnat_rm/standard_and_implementation_defined_restrictions spark-05}@anchor{20a}
13137 @subsection SPARK_05
13142 [GNAT] This restriction checks at compile time that some constructs
13143 forbidden in SPARK 2005 are not present. Error messages related to
13144 SPARK restriction have the form:
13147 violation of restriction "SPARK_05" at <source-location>
13153 The restriction @code{SPARK} is recognized as a
13154 synonym for @code{SPARK_05}. This is retained for historical
13155 compatibility purposes (and an unconditional warning will be generated
13156 for its use, advising replacement by @code{SPARK}).
13158 This is not a replacement for the semantic checks performed by the
13159 SPARK Examiner tool, as the compiler currently only deals with code,
13160 not SPARK 2005 annotations, and does not guarantee catching all
13161 cases of constructs forbidden by SPARK 2005.
13163 Thus it may well be the case that code which passes the compiler with
13164 the SPARK restriction is rejected by the SPARK Examiner, e.g. due to
13165 the different visibility rules of the Examiner based on SPARK 2005
13166 @code{inherit} annotations.
13168 This restriction can be useful in providing an initial filter for code
13169 developed using SPARK 2005, or in examining legacy code to see how far
13170 it is from meeting SPARK restrictions.
13172 The list below summarizes the checks that are performed when this
13173 restriction is in force:
13179 No block statements
13182 No case statements with only an others clause
13185 Exit statements in loops must respect the SPARK 2005 language restrictions
13191 Return can only appear as last statement in function
13194 Function must have return statement
13197 Loop parameter specification must include subtype mark
13200 Prefix of expanded name cannot be a loop statement
13203 Abstract subprogram not allowed
13206 User-defined operators not allowed
13209 Access type parameters not allowed
13212 Default expressions for parameters not allowed
13215 Default expressions for record fields not allowed
13218 No tasking constructs allowed
13221 Label needed at end of subprograms and packages
13224 No mixing of positional and named parameter association
13227 No access types as result type
13230 No unconstrained arrays as result types
13236 Initial and later declarations must be in correct order (declaration can't come after body)
13239 No attributes on private types if full declaration not visible
13242 No package declaration within package specification
13245 No controlled types
13248 No discriminant types
13254 Selector name cannot be operator symbol (i.e. operator symbol cannot be prefixed)
13257 Access attribute not allowed
13260 Allocator not allowed
13263 Result of catenation must be String
13266 Operands of catenation must be string literal, static char or another catenation
13269 No conditional expressions
13272 No explicit dereference
13275 Quantified expression not allowed
13278 Slicing not allowed
13281 No exception renaming
13284 No generic renaming
13293 Aggregates must be qualified
13296 Nonstatic choice in array aggregates not allowed
13299 The only view conversions which are allowed as in-out parameters are conversions of a tagged type to an ancestor type
13302 No mixing of positional and named association in aggregate, no multi choice
13305 AND, OR and XOR for arrays only allowed when operands have same static bounds
13308 Fixed point operands to * or / must be qualified or converted
13311 Comparison operators not allowed for Booleans or arrays (except strings)
13314 Equality not allowed for arrays with non-matching static bounds (except strings)
13317 Conversion / qualification not allowed for arrays with non-matching static bounds
13320 Subprogram declaration only allowed in package spec (unless followed by import)
13323 Access types not allowed
13326 Incomplete type declaration not allowed
13329 Object and subtype declarations must respect SPARK restrictions
13332 Digits or delta constraint not allowed
13335 Decimal fixed point type not allowed
13338 Aliasing of objects not allowed
13341 Modular type modulus must be power of 2
13344 Base not allowed on subtype mark
13347 Unary operators not allowed on modular types (except not)
13350 Untagged record cannot be null
13353 No class-wide operations
13356 Initialization expressions must respect SPARK restrictions
13359 Nonstatic ranges not allowed except in iteration schemes
13362 String subtypes must have lower bound of 1
13365 Subtype of Boolean cannot have constraint
13368 At most one tagged type or extension per package
13371 Interface is not allowed
13374 Character literal cannot be prefixed (selector name cannot be character literal)
13377 Record aggregate cannot contain 'others'
13380 Component association in record aggregate must contain a single choice
13383 Ancestor part cannot be a type mark
13386 Attributes 'Image, 'Width and 'Value not allowed
13389 Functions may not update globals
13392 Subprograms may not contain direct calls to themselves (prevents recursion within unit)
13395 Call to subprogram not allowed in same unit before body has been seen (prevents recursion within unit)
13398 The following restrictions are enforced, but note that they are actually more
13399 strict that the latest SPARK 2005 language definition:
13405 No derived types other than tagged type extensions
13408 Subtype of unconstrained array must have constraint
13411 This list summarises the main SPARK 2005 language rules that are not
13412 currently checked by the SPARK_05 restriction:
13418 SPARK annotations are treated as comments so are not checked at all
13421 Based real literals not allowed
13424 Objects cannot be initialized at declaration by calls to user-defined functions
13427 Objects cannot be initialized at declaration by assignments from variables
13430 Objects cannot be initialized at declaration by assignments from indexed/selected components
13433 Ranges shall not be null
13436 A fixed point delta expression must be a simple expression
13439 Restrictions on where renaming declarations may be placed
13442 Externals of mode 'out' cannot be referenced
13445 Externals of mode 'in' cannot be updated
13448 Loop with no iteration scheme or exits only allowed as last statement in main program or task
13451 Subprogram cannot have parent unit name
13454 SPARK 2005 inherited subprogram must be prefixed with overriding
13457 External variables (or functions that reference them) may not be passed as actual parameters
13460 Globals must be explicitly mentioned in contract
13463 Deferred constants cannot be completed by pragma Import
13466 Package initialization cannot read/write variables from other packages
13469 Prefix not allowed for entities that are directly visible
13472 Identifier declaration can't override inherited package name
13475 Cannot use Standard or other predefined packages as identifiers
13478 After renaming, cannot use the original name
13481 Subprograms can only be renamed to remove package prefix
13484 Pragma import must be immediately after entity it names
13487 No mutual recursion between multiple units (this can be checked with gnatcheck)
13490 Note that if a unit is compiled in Ada 95 mode with the SPARK restriction,
13491 violations will be reported for constructs forbidden in SPARK 95,
13492 instead of SPARK 2005.
13494 @node Implementation Advice,Implementation Defined Characteristics,Standard and Implementation Defined Restrictions,Top
13495 @anchor{gnat_rm/implementation_advice doc}@anchor{20b}@anchor{gnat_rm/implementation_advice implementation-advice}@anchor{a}@anchor{gnat_rm/implementation_advice id1}@anchor{20c}
13496 @chapter Implementation Advice
13499 The main text of the Ada Reference Manual describes the required
13500 behavior of all Ada compilers, and the GNAT compiler conforms to
13501 these requirements.
13503 In addition, there are sections throughout the Ada Reference Manual headed
13504 by the phrase 'Implementation advice'. These sections are not normative,
13505 i.e., they do not specify requirements that all compilers must
13506 follow. Rather they provide advice on generally desirable behavior.
13507 They are not requirements, because they describe behavior that cannot
13508 be provided on all systems, or may be undesirable on some systems.
13510 As far as practical, GNAT follows the implementation advice in
13511 the Ada Reference Manual. Each such RM section corresponds to a section
13512 in this chapter whose title specifies the
13513 RM section number and paragraph number and the subject of
13514 the advice. The contents of each section consists of the RM text within
13516 followed by the GNAT interpretation of the advice. Most often, this simply says
13517 'followed', which means that GNAT follows the advice. However, in a
13518 number of cases, GNAT deliberately deviates from this advice, in which
13519 case the text describes what GNAT does and why.
13521 @geindex Error detection
13524 * RM 1.1.3(20); Error Detection: RM 1 1 3 20 Error Detection.
13525 * RM 1.1.3(31); Child Units: RM 1 1 3 31 Child Units.
13526 * RM 1.1.5(12); Bounded Errors: RM 1 1 5 12 Bounded Errors.
13527 * RM 2.8(16); Pragmas: RM 2 8 16 Pragmas.
13528 * RM 2.8(17-19); Pragmas: RM 2 8 17-19 Pragmas.
13529 * RM 3.5.2(5); Alternative Character Sets: RM 3 5 2 5 Alternative Character Sets.
13530 * RM 3.5.4(28); Integer Types: RM 3 5 4 28 Integer Types.
13531 * RM 3.5.4(29); Integer Types: RM 3 5 4 29 Integer Types.
13532 * RM 3.5.5(8); Enumeration Values: RM 3 5 5 8 Enumeration Values.
13533 * RM 3.5.7(17); Float Types: RM 3 5 7 17 Float Types.
13534 * RM 3.6.2(11); Multidimensional Arrays: RM 3 6 2 11 Multidimensional Arrays.
13535 * RM 9.6(30-31); Duration'Small: RM 9 6 30-31 Duration'Small.
13536 * RM 10.2.1(12); Consistent Representation: RM 10 2 1 12 Consistent Representation.
13537 * RM 11.4.1(19); Exception Information: RM 11 4 1 19 Exception Information.
13538 * RM 11.5(28); Suppression of Checks: RM 11 5 28 Suppression of Checks.
13539 * RM 13.1 (21-24); Representation Clauses: RM 13 1 21-24 Representation Clauses.
13540 * RM 13.2(6-8); Packed Types: RM 13 2 6-8 Packed Types.
13541 * RM 13.3(14-19); Address Clauses: RM 13 3 14-19 Address Clauses.
13542 * RM 13.3(29-35); Alignment Clauses: RM 13 3 29-35 Alignment Clauses.
13543 * RM 13.3(42-43); Size Clauses: RM 13 3 42-43 Size Clauses.
13544 * RM 13.3(50-56); Size Clauses: RM 13 3 50-56 Size Clauses.
13545 * RM 13.3(71-73); Component Size Clauses: RM 13 3 71-73 Component Size Clauses.
13546 * RM 13.4(9-10); Enumeration Representation Clauses: RM 13 4 9-10 Enumeration Representation Clauses.
13547 * RM 13.5.1(17-22); Record Representation Clauses: RM 13 5 1 17-22 Record Representation Clauses.
13548 * RM 13.5.2(5); Storage Place Attributes: RM 13 5 2 5 Storage Place Attributes.
13549 * RM 13.5.3(7-8); Bit Ordering: RM 13 5 3 7-8 Bit Ordering.
13550 * RM 13.7(37); Address as Private: RM 13 7 37 Address as Private.
13551 * RM 13.7.1(16); Address Operations: RM 13 7 1 16 Address Operations.
13552 * RM 13.9(14-17); Unchecked Conversion: RM 13 9 14-17 Unchecked Conversion.
13553 * RM 13.11(23-25); Implicit Heap Usage: RM 13 11 23-25 Implicit Heap Usage.
13554 * RM 13.11.2(17); Unchecked Deallocation: RM 13 11 2 17 Unchecked Deallocation.
13555 * RM 13.13.2(17); Stream Oriented Attributes: RM 13 13 2 17 Stream Oriented Attributes.
13556 * RM A.1(52); Names of Predefined Numeric Types: RM A 1 52 Names of Predefined Numeric Types.
13557 * RM A.3.2(49); Ada.Characters.Handling: RM A 3 2 49 Ada Characters Handling.
13558 * RM A.4.4(106); Bounded-Length String Handling: RM A 4 4 106 Bounded-Length String Handling.
13559 * RM A.5.2(46-47); Random Number Generation: RM A 5 2 46-47 Random Number Generation.
13560 * RM A.10.7(23); Get_Immediate: RM A 10 7 23 Get_Immediate.
13561 * RM B.1(39-41); Pragma Export: RM B 1 39-41 Pragma Export.
13562 * RM B.2(12-13); Package Interfaces: RM B 2 12-13 Package Interfaces.
13563 * RM B.3(63-71); Interfacing with C: RM B 3 63-71 Interfacing with C.
13564 * RM B.4(95-98); Interfacing with COBOL: RM B 4 95-98 Interfacing with COBOL.
13565 * RM B.5(22-26); Interfacing with Fortran: RM B 5 22-26 Interfacing with Fortran.
13566 * RM C.1(3-5); Access to Machine Operations: RM C 1 3-5 Access to Machine Operations.
13567 * RM C.1(10-16); Access to Machine Operations: RM C 1 10-16 Access to Machine Operations.
13568 * RM C.3(28); Interrupt Support: RM C 3 28 Interrupt Support.
13569 * RM C.3.1(20-21); Protected Procedure Handlers: RM C 3 1 20-21 Protected Procedure Handlers.
13570 * RM C.3.2(25); Package Interrupts: RM C 3 2 25 Package Interrupts.
13571 * RM C.4(14); Pre-elaboration Requirements: RM C 4 14 Pre-elaboration Requirements.
13572 * RM C.5(8); Pragma Discard_Names: RM C 5 8 Pragma Discard_Names.
13573 * RM C.7.2(30); The Package Task_Attributes: RM C 7 2 30 The Package Task_Attributes.
13574 * RM D.3(17); Locking Policies: RM D 3 17 Locking Policies.
13575 * RM D.4(16); Entry Queuing Policies: RM D 4 16 Entry Queuing Policies.
13576 * RM D.6(9-10); Preemptive Abort: RM D 6 9-10 Preemptive Abort.
13577 * RM D.7(21); Tasking Restrictions: RM D 7 21 Tasking Restrictions.
13578 * RM D.8(47-49); Monotonic Time: RM D 8 47-49 Monotonic Time.
13579 * RM E.5(28-29); Partition Communication Subsystem: RM E 5 28-29 Partition Communication Subsystem.
13580 * RM F(7); COBOL Support: RM F 7 COBOL Support.
13581 * RM F.1(2); Decimal Radix Support: RM F 1 2 Decimal Radix Support.
13582 * RM G; Numerics: RM G Numerics.
13583 * RM G.1.1(56-58); Complex Types: RM G 1 1 56-58 Complex Types.
13584 * RM G.1.2(49); Complex Elementary Functions: RM G 1 2 49 Complex Elementary Functions.
13585 * RM G.2.4(19); Accuracy Requirements: RM G 2 4 19 Accuracy Requirements.
13586 * RM G.2.6(15); Complex Arithmetic Accuracy: RM G 2 6 15 Complex Arithmetic Accuracy.
13587 * RM H.6(15/2); Pragma Partition_Elaboration_Policy: RM H 6 15/2 Pragma Partition_Elaboration_Policy.
13591 @node RM 1 1 3 20 Error Detection,RM 1 1 3 31 Child Units,,Implementation Advice
13592 @anchor{gnat_rm/implementation_advice rm-1-1-3-20-error-detection}@anchor{20d}
13593 @section RM 1.1.3(20): Error Detection
13598 "If an implementation detects the use of an unsupported Specialized Needs
13599 Annex feature at run time, it should raise @code{Program_Error} if
13603 Not relevant. All specialized needs annex features are either supported,
13604 or diagnosed at compile time.
13606 @geindex Child Units
13608 @node RM 1 1 3 31 Child Units,RM 1 1 5 12 Bounded Errors,RM 1 1 3 20 Error Detection,Implementation Advice
13609 @anchor{gnat_rm/implementation_advice rm-1-1-3-31-child-units}@anchor{20e}
13610 @section RM 1.1.3(31): Child Units
13615 "If an implementation wishes to provide implementation-defined
13616 extensions to the functionality of a language-defined library unit, it
13617 should normally do so by adding children to the library unit."
13622 @geindex Bounded errors
13624 @node RM 1 1 5 12 Bounded Errors,RM 2 8 16 Pragmas,RM 1 1 3 31 Child Units,Implementation Advice
13625 @anchor{gnat_rm/implementation_advice rm-1-1-5-12-bounded-errors}@anchor{20f}
13626 @section RM 1.1.5(12): Bounded Errors
13631 "If an implementation detects a bounded error or erroneous
13632 execution, it should raise @code{Program_Error}."
13635 Followed in all cases in which the implementation detects a bounded
13636 error or erroneous execution. Not all such situations are detected at
13641 @node RM 2 8 16 Pragmas,RM 2 8 17-19 Pragmas,RM 1 1 5 12 Bounded Errors,Implementation Advice
13642 @anchor{gnat_rm/implementation_advice id2}@anchor{210}@anchor{gnat_rm/implementation_advice rm-2-8-16-pragmas}@anchor{211}
13643 @section RM 2.8(16): Pragmas
13648 "Normally, implementation-defined pragmas should have no semantic effect
13649 for error-free programs; that is, if the implementation-defined pragmas
13650 are removed from a working program, the program should still be legal,
13651 and should still have the same semantics."
13654 The following implementation defined pragmas are exceptions to this
13658 @multitable {xxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxx}
13701 @emph{CPP_Constructor}
13717 @emph{Interface_Name}
13725 @emph{Machine_Attribute}
13733 @emph{Unimplemented_Unit}
13741 @emph{Unchecked_Union}
13750 In each of the above cases, it is essential to the purpose of the pragma
13751 that this advice not be followed. For details see
13752 @ref{7,,Implementation Defined Pragmas}.
13754 @node RM 2 8 17-19 Pragmas,RM 3 5 2 5 Alternative Character Sets,RM 2 8 16 Pragmas,Implementation Advice
13755 @anchor{gnat_rm/implementation_advice rm-2-8-17-19-pragmas}@anchor{212}
13756 @section RM 2.8(17-19): Pragmas
13761 "Normally, an implementation should not define pragmas that can
13762 make an illegal program legal, except as follows:
13768 A pragma used to complete a declaration, such as a pragma @code{Import};
13771 A pragma used to configure the environment by adding, removing, or
13772 replacing @code{library_items}."
13776 See @ref{211,,RM 2.8(16); Pragmas}.
13778 @geindex Character Sets
13780 @geindex Alternative Character Sets
13782 @node RM 3 5 2 5 Alternative Character Sets,RM 3 5 4 28 Integer Types,RM 2 8 17-19 Pragmas,Implementation Advice
13783 @anchor{gnat_rm/implementation_advice rm-3-5-2-5-alternative-character-sets}@anchor{213}
13784 @section RM 3.5.2(5): Alternative Character Sets
13789 "If an implementation supports a mode with alternative interpretations
13790 for @code{Character} and @code{Wide_Character}, the set of graphic
13791 characters of @code{Character} should nevertheless remain a proper
13792 subset of the set of graphic characters of @code{Wide_Character}. Any
13793 character set 'localizations' should be reflected in the results of
13794 the subprograms defined in the language-defined package
13795 @code{Characters.Handling} (see A.3) available in such a mode. In a mode with
13796 an alternative interpretation of @code{Character}, the implementation should
13797 also support a corresponding change in what is a legal
13798 @code{identifier_letter}."
13801 Not all wide character modes follow this advice, in particular the JIS
13802 and IEC modes reflect standard usage in Japan, and in these encoding,
13803 the upper half of the Latin-1 set is not part of the wide-character
13804 subset, since the most significant bit is used for wide character
13805 encoding. However, this only applies to the external forms. Internally
13806 there is no such restriction.
13808 @geindex Integer types
13810 @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
13811 @anchor{gnat_rm/implementation_advice rm-3-5-4-28-integer-types}@anchor{214}
13812 @section RM 3.5.4(28): Integer Types
13817 "An implementation should support @code{Long_Integer} in addition to
13818 @code{Integer} if the target machine supports 32-bit (or longer)
13819 arithmetic. No other named integer subtypes are recommended for package
13820 @code{Standard}. Instead, appropriate named integer subtypes should be
13821 provided in the library package @code{Interfaces} (see B.2)."
13824 @code{Long_Integer} is supported. Other standard integer types are supported
13825 so this advice is not fully followed. These types
13826 are supported for convenient interface to C, and so that all hardware
13827 types of the machine are easily available.
13829 @node RM 3 5 4 29 Integer Types,RM 3 5 5 8 Enumeration Values,RM 3 5 4 28 Integer Types,Implementation Advice
13830 @anchor{gnat_rm/implementation_advice rm-3-5-4-29-integer-types}@anchor{215}
13831 @section RM 3.5.4(29): Integer Types
13836 "An implementation for a two's complement machine should support
13837 modular types with a binary modulus up to @code{System.Max_Int*2+2}. An
13838 implementation should support a non-binary modules up to @code{Integer'Last}."
13843 @geindex Enumeration values
13845 @node RM 3 5 5 8 Enumeration Values,RM 3 5 7 17 Float Types,RM 3 5 4 29 Integer Types,Implementation Advice
13846 @anchor{gnat_rm/implementation_advice rm-3-5-5-8-enumeration-values}@anchor{216}
13847 @section RM 3.5.5(8): Enumeration Values
13852 "For the evaluation of a call on @code{S'Pos} for an enumeration
13853 subtype, if the value of the operand does not correspond to the internal
13854 code for any enumeration literal of its type (perhaps due to an
13855 un-initialized variable), then the implementation should raise
13856 @code{Program_Error}. This is particularly important for enumeration
13857 types with noncontiguous internal codes specified by an
13858 enumeration_representation_clause."
13863 @geindex Float types
13865 @node RM 3 5 7 17 Float Types,RM 3 6 2 11 Multidimensional Arrays,RM 3 5 5 8 Enumeration Values,Implementation Advice
13866 @anchor{gnat_rm/implementation_advice rm-3-5-7-17-float-types}@anchor{217}
13867 @section RM 3.5.7(17): Float Types
13872 "An implementation should support @code{Long_Float} in addition to
13873 @code{Float} if the target machine supports 11 or more digits of
13874 precision. No other named floating point subtypes are recommended for
13875 package @code{Standard}. Instead, appropriate named floating point subtypes
13876 should be provided in the library package @code{Interfaces} (see B.2)."
13879 @code{Short_Float} and @code{Long_Long_Float} are also provided. The
13880 former provides improved compatibility with other implementations
13881 supporting this type. The latter corresponds to the highest precision
13882 floating-point type supported by the hardware. On most machines, this
13883 will be the same as @code{Long_Float}, but on some machines, it will
13884 correspond to the IEEE extended form. The notable case is all ia32
13885 (x86) implementations, where @code{Long_Long_Float} corresponds to
13886 the 80-bit extended precision format supported in hardware on this
13887 processor. Note that the 128-bit format on SPARC is not supported,
13888 since this is a software rather than a hardware format.
13890 @geindex Multidimensional arrays
13893 @geindex multidimensional
13895 @node RM 3 6 2 11 Multidimensional Arrays,RM 9 6 30-31 Duration'Small,RM 3 5 7 17 Float Types,Implementation Advice
13896 @anchor{gnat_rm/implementation_advice rm-3-6-2-11-multidimensional-arrays}@anchor{218}
13897 @section RM 3.6.2(11): Multidimensional Arrays
13902 "An implementation should normally represent multidimensional arrays in
13903 row-major order, consistent with the notation used for multidimensional
13904 array aggregates (see 4.3.3). However, if a pragma @code{Convention}
13905 (@code{Fortran}, ...) applies to a multidimensional array type, then
13906 column-major order should be used instead (see B.5, @emph{Interfacing with Fortran})."
13911 @geindex Duration'Small
13913 @node RM 9 6 30-31 Duration'Small,RM 10 2 1 12 Consistent Representation,RM 3 6 2 11 Multidimensional Arrays,Implementation Advice
13914 @anchor{gnat_rm/implementation_advice rm-9-6-30-31-duration-small}@anchor{219}
13915 @section RM 9.6(30-31): Duration'Small
13920 "Whenever possible in an implementation, the value of @code{Duration'Small}
13921 should be no greater than 100 microseconds."
13924 Followed. (@code{Duration'Small} = 10**(-9)).
13928 "The time base for @code{delay_relative_statements} should be monotonic;
13929 it need not be the same time base as used for @code{Calendar.Clock}."
13934 @node RM 10 2 1 12 Consistent Representation,RM 11 4 1 19 Exception Information,RM 9 6 30-31 Duration'Small,Implementation Advice
13935 @anchor{gnat_rm/implementation_advice rm-10-2-1-12-consistent-representation}@anchor{21a}
13936 @section RM 10.2.1(12): Consistent Representation
13941 "In an implementation, a type declared in a pre-elaborated package should
13942 have the same representation in every elaboration of a given version of
13943 the package, whether the elaborations occur in distinct executions of
13944 the same program, or in executions of distinct programs or partitions
13945 that include the given version."
13948 Followed, except in the case of tagged types. Tagged types involve
13949 implicit pointers to a local copy of a dispatch table, and these pointers
13950 have representations which thus depend on a particular elaboration of the
13951 package. It is not easy to see how it would be possible to follow this
13952 advice without severely impacting efficiency of execution.
13954 @geindex Exception information
13956 @node RM 11 4 1 19 Exception Information,RM 11 5 28 Suppression of Checks,RM 10 2 1 12 Consistent Representation,Implementation Advice
13957 @anchor{gnat_rm/implementation_advice rm-11-4-1-19-exception-information}@anchor{21b}
13958 @section RM 11.4.1(19): Exception Information
13963 "@code{Exception_Message} by default and @code{Exception_Information}
13964 should produce information useful for
13965 debugging. @code{Exception_Message} should be short, about one
13966 line. @code{Exception_Information} can be long. @code{Exception_Message}
13967 should not include the
13968 @code{Exception_Name}. @code{Exception_Information} should include both
13969 the @code{Exception_Name} and the @code{Exception_Message}."
13972 Followed. For each exception that doesn't have a specified
13973 @code{Exception_Message}, the compiler generates one containing the location
13974 of the raise statement. This location has the form 'file_name:line', where
13975 file_name is the short file name (without path information) and line is the line
13976 number in the file. Note that in the case of the Zero Cost Exception
13977 mechanism, these messages become redundant with the Exception_Information that
13978 contains a full backtrace of the calling sequence, so they are disabled.
13979 To disable explicitly the generation of the source location message, use the
13980 Pragma @code{Discard_Names}.
13982 @geindex Suppression of checks
13985 @geindex suppression of
13987 @node RM 11 5 28 Suppression of Checks,RM 13 1 21-24 Representation Clauses,RM 11 4 1 19 Exception Information,Implementation Advice
13988 @anchor{gnat_rm/implementation_advice rm-11-5-28-suppression-of-checks}@anchor{21c}
13989 @section RM 11.5(28): Suppression of Checks
13994 "The implementation should minimize the code executed for checks that
13995 have been suppressed."
14000 @geindex Representation clauses
14002 @node RM 13 1 21-24 Representation Clauses,RM 13 2 6-8 Packed Types,RM 11 5 28 Suppression of Checks,Implementation Advice
14003 @anchor{gnat_rm/implementation_advice rm-13-1-21-24-representation-clauses}@anchor{21d}
14004 @section RM 13.1 (21-24): Representation Clauses
14009 "The recommended level of support for all representation items is
14010 qualified as follows:
14012 An implementation need not support representation items containing
14013 nonstatic expressions, except that an implementation should support a
14014 representation item for a given entity if each nonstatic expression in
14015 the representation item is a name that statically denotes a constant
14016 declared before the entity."
14019 Followed. In fact, GNAT goes beyond the recommended level of support
14020 by allowing nonstatic expressions in some representation clauses even
14021 without the need to declare constants initialized with the values of
14028 for Y'Address use X'Address;>>
14031 "An implementation need not support a specification for the `@w{`}Size`@w{`}
14032 for a given composite subtype, nor the size or storage place for an
14033 object (including a component) of a given composite subtype, unless the
14034 constraints on the subtype and its composite subcomponents (if any) are
14035 all static constraints."
14038 Followed. Size Clauses are not permitted on nonstatic components, as
14043 "An aliased component, or a component whose type is by-reference, should
14044 always be allocated at an addressable location."
14049 @geindex Packed types
14051 @node RM 13 2 6-8 Packed Types,RM 13 3 14-19 Address Clauses,RM 13 1 21-24 Representation Clauses,Implementation Advice
14052 @anchor{gnat_rm/implementation_advice rm-13-2-6-8-packed-types}@anchor{21e}
14053 @section RM 13.2(6-8): Packed Types
14058 "If a type is packed, then the implementation should try to minimize
14059 storage allocated to objects of the type, possibly at the expense of
14060 speed of accessing components, subject to reasonable complexity in
14061 addressing calculations.
14063 The recommended level of support pragma @code{Pack} is:
14065 For a packed record type, the components should be packed as tightly as
14066 possible subject to the Sizes of the component subtypes, and subject to
14067 any @emph{record_representation_clause} that applies to the type; the
14068 implementation may, but need not, reorder components or cross aligned
14069 word boundaries to improve the packing. A component whose @code{Size} is
14070 greater than the word size may be allocated an integral number of words."
14073 Followed. Tight packing of arrays is supported for all component sizes
14074 up to 64-bits. If the array component size is 1 (that is to say, if
14075 the component is a boolean type or an enumeration type with two values)
14076 then values of the type are implicitly initialized to zero. This
14077 happens both for objects of the packed type, and for objects that have a
14078 subcomponent of the packed type.
14082 "An implementation should support Address clauses for imported
14088 @geindex Address clauses
14090 @node RM 13 3 14-19 Address Clauses,RM 13 3 29-35 Alignment Clauses,RM 13 2 6-8 Packed Types,Implementation Advice
14091 @anchor{gnat_rm/implementation_advice rm-13-3-14-19-address-clauses}@anchor{21f}
14092 @section RM 13.3(14-19): Address Clauses
14097 "For an array @code{X}, @code{X'Address} should point at the first
14098 component of the array, and not at the array bounds."
14105 "The recommended level of support for the @code{Address} attribute is:
14107 @code{X'Address} should produce a useful result if @code{X} is an
14108 object that is aliased or of a by-reference type, or is an entity whose
14109 @code{Address} has been specified."
14112 Followed. A valid address will be produced even if none of those
14113 conditions have been met. If necessary, the object is forced into
14114 memory to ensure the address is valid.
14118 "An implementation should support @code{Address} clauses for imported
14126 "Objects (including subcomponents) that are aliased or of a by-reference
14127 type should be allocated on storage element boundaries."
14134 "If the @code{Address} of an object is specified, or it is imported or exported,
14135 then the implementation should not perform optimizations based on
14136 assumptions of no aliases."
14141 @geindex Alignment clauses
14143 @node RM 13 3 29-35 Alignment Clauses,RM 13 3 42-43 Size Clauses,RM 13 3 14-19 Address Clauses,Implementation Advice
14144 @anchor{gnat_rm/implementation_advice rm-13-3-29-35-alignment-clauses}@anchor{220}
14145 @section RM 13.3(29-35): Alignment Clauses
14150 "The recommended level of support for the @code{Alignment} attribute for
14153 An implementation should support specified Alignments that are factors
14154 and multiples of the number of storage elements per word, subject to the
14162 "An implementation need not support specified Alignments for
14163 combinations of Sizes and Alignments that cannot be easily
14164 loaded and stored by available machine instructions."
14171 "An implementation need not support specified Alignments that are
14172 greater than the maximum @code{Alignment} the implementation ever returns by
14180 "The recommended level of support for the @code{Alignment} attribute for
14183 Same as above, for subtypes, but in addition:"
14190 "For stand-alone library-level objects of statically constrained
14191 subtypes, the implementation should support all alignments
14192 supported by the target linker. For example, page alignment is likely to
14193 be supported for such objects, but not for subtypes."
14198 @geindex Size clauses
14200 @node RM 13 3 42-43 Size Clauses,RM 13 3 50-56 Size Clauses,RM 13 3 29-35 Alignment Clauses,Implementation Advice
14201 @anchor{gnat_rm/implementation_advice rm-13-3-42-43-size-clauses}@anchor{221}
14202 @section RM 13.3(42-43): Size Clauses
14207 "The recommended level of support for the @code{Size} attribute of
14210 A @code{Size} clause should be supported for an object if the specified
14211 @code{Size} is at least as large as its subtype's @code{Size}, and
14212 corresponds to a size in storage elements that is a multiple of the
14213 object's @code{Alignment} (if the @code{Alignment} is nonzero)."
14218 @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
14219 @anchor{gnat_rm/implementation_advice rm-13-3-50-56-size-clauses}@anchor{222}
14220 @section RM 13.3(50-56): Size Clauses
14225 "If the @code{Size} of a subtype is specified, and allows for efficient
14226 independent addressability (see 9.10) on the target architecture, then
14227 the @code{Size} of the following objects of the subtype should equal the
14228 @code{Size} of the subtype:
14230 Aliased objects (including components)."
14237 "@cite{Size} clause on a composite subtype should not affect the
14238 internal layout of components."
14241 Followed. But note that this can be overridden by use of the implementation
14242 pragma Implicit_Packing in the case of packed arrays.
14246 "The recommended level of support for the @code{Size} attribute of subtypes is:
14248 The @code{Size} (if not specified) of a static discrete or fixed point
14249 subtype should be the number of bits needed to represent each value
14250 belonging to the subtype using an unbiased representation, leaving space
14251 for a sign bit only if the subtype contains negative values. If such a
14252 subtype is a first subtype, then an implementation should support a
14253 specified @code{Size} for it that reflects this representation."
14260 "For a subtype implemented with levels of indirection, the @code{Size}
14261 should include the size of the pointers, but not the size of what they
14267 @geindex Component_Size clauses
14269 @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
14270 @anchor{gnat_rm/implementation_advice rm-13-3-71-73-component-size-clauses}@anchor{223}
14271 @section RM 13.3(71-73): Component Size Clauses
14276 "The recommended level of support for the @code{Component_Size}
14279 An implementation need not support specified @code{Component_Sizes} that are
14280 less than the @code{Size} of the component subtype."
14287 "An implementation should support specified Component_Sizes that
14288 are factors and multiples of the word size. For such
14289 Component_Sizes, the array should contain no gaps between
14290 components. For other Component_Sizes (if supported), the array
14291 should contain no gaps between components when packing is also
14292 specified; the implementation should forbid this combination in cases
14293 where it cannot support a no-gaps representation."
14298 @geindex Enumeration representation clauses
14300 @geindex Representation clauses
14301 @geindex enumeration
14303 @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
14304 @anchor{gnat_rm/implementation_advice rm-13-4-9-10-enumeration-representation-clauses}@anchor{224}
14305 @section RM 13.4(9-10): Enumeration Representation Clauses
14310 "The recommended level of support for enumeration representation clauses
14313 An implementation need not support enumeration representation clauses
14314 for boolean types, but should at minimum support the internal codes in
14315 the range @code{System.Min_Int .. System.Max_Int}."
14320 @geindex Record representation clauses
14322 @geindex Representation clauses
14325 @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
14326 @anchor{gnat_rm/implementation_advice rm-13-5-1-17-22-record-representation-clauses}@anchor{225}
14327 @section RM 13.5.1(17-22): Record Representation Clauses
14332 "The recommended level of support for
14333 @emph{record_representation_clause}s is:
14335 An implementation should support storage places that can be extracted
14336 with a load, mask, shift sequence of machine code, and set with a load,
14337 shift, mask, store sequence, given the available machine instructions
14338 and run-time model."
14345 "A storage place should be supported if its size is equal to the
14346 @code{Size} of the component subtype, and it starts and ends on a
14347 boundary that obeys the @code{Alignment} of the component subtype."
14354 "If the default bit ordering applies to the declaration of a given type,
14355 then for a component whose subtype's @code{Size} is less than the word
14356 size, any storage place that does not cross an aligned word boundary
14357 should be supported."
14364 "An implementation may reserve a storage place for the tag field of a
14365 tagged type, and disallow other components from overlapping that place."
14368 Followed. The storage place for the tag field is the beginning of the tagged
14369 record, and its size is Address'Size. GNAT will reject an explicit component
14370 clause for the tag field.
14374 "An implementation need not support a @emph{component_clause} for a
14375 component of an extension part if the storage place is not after the
14376 storage places of all components of the parent type, whether or not
14377 those storage places had been specified."
14380 Followed. The above advice on record representation clauses is followed,
14381 and all mentioned features are implemented.
14383 @geindex Storage place attributes
14385 @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
14386 @anchor{gnat_rm/implementation_advice rm-13-5-2-5-storage-place-attributes}@anchor{226}
14387 @section RM 13.5.2(5): Storage Place Attributes
14392 "If a component is represented using some form of pointer (such as an
14393 offset) to the actual data of the component, and this data is contiguous
14394 with the rest of the object, then the storage place attributes should
14395 reflect the place of the actual data, not the pointer. If a component is
14396 allocated discontinuously from the rest of the object, then a warning
14397 should be generated upon reference to one of its storage place
14401 Followed. There are no such components in GNAT.
14403 @geindex Bit ordering
14405 @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
14406 @anchor{gnat_rm/implementation_advice rm-13-5-3-7-8-bit-ordering}@anchor{227}
14407 @section RM 13.5.3(7-8): Bit Ordering
14412 "The recommended level of support for the non-default bit ordering is:
14414 If @code{Word_Size} = @code{Storage_Unit}, then the implementation
14415 should support the non-default bit ordering in addition to the default
14419 Followed. Word size does not equal storage size in this implementation.
14420 Thus non-default bit ordering is not supported.
14423 @geindex as private type
14425 @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
14426 @anchor{gnat_rm/implementation_advice rm-13-7-37-address-as-private}@anchor{228}
14427 @section RM 13.7(37): Address as Private
14432 "@cite{Address} should be of a private type."
14437 @geindex Operations
14438 @geindex on `@w{`}Address`@w{`}
14441 @geindex operations of
14443 @node RM 13 7 1 16 Address Operations,RM 13 9 14-17 Unchecked Conversion,RM 13 7 37 Address as Private,Implementation Advice
14444 @anchor{gnat_rm/implementation_advice rm-13-7-1-16-address-operations}@anchor{229}
14445 @section RM 13.7.1(16): Address Operations
14450 "Operations in @code{System} and its children should reflect the target
14451 environment semantics as closely as is reasonable. For example, on most
14452 machines, it makes sense for address arithmetic to 'wrap around'.
14453 Operations that do not make sense should raise @code{Program_Error}."
14456 Followed. Address arithmetic is modular arithmetic that wraps around. No
14457 operation raises @code{Program_Error}, since all operations make sense.
14459 @geindex Unchecked conversion
14461 @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
14462 @anchor{gnat_rm/implementation_advice rm-13-9-14-17-unchecked-conversion}@anchor{22a}
14463 @section RM 13.9(14-17): Unchecked Conversion
14468 "The @code{Size} of an array object should not include its bounds; hence,
14469 the bounds should not be part of the converted data."
14476 "The implementation should not generate unnecessary run-time checks to
14477 ensure that the representation of @code{S} is a representation of the
14478 target type. It should take advantage of the permission to return by
14479 reference when possible. Restrictions on unchecked conversions should be
14480 avoided unless required by the target environment."
14483 Followed. There are no restrictions on unchecked conversion. A warning is
14484 generated if the source and target types do not have the same size since
14485 the semantics in this case may be target dependent.
14489 "The recommended level of support for unchecked conversions is:
14491 Unchecked conversions should be supported and should be reversible in
14492 the cases where this clause defines the result. To enable meaningful use
14493 of unchecked conversion, a contiguous representation should be used for
14494 elementary subtypes, for statically constrained array subtypes whose
14495 component subtype is one of the subtypes described in this paragraph,
14496 and for record subtypes without discriminants whose component subtypes
14497 are described in this paragraph."
14502 @geindex Heap usage
14505 @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
14506 @anchor{gnat_rm/implementation_advice rm-13-11-23-25-implicit-heap-usage}@anchor{22b}
14507 @section RM 13.11(23-25): Implicit Heap Usage
14512 "An implementation should document any cases in which it dynamically
14513 allocates heap storage for a purpose other than the evaluation of an
14517 Followed, the only other points at which heap storage is dynamically
14518 allocated are as follows:
14524 At initial elaboration time, to allocate dynamically sized global
14528 To allocate space for a task when a task is created.
14531 To extend the secondary stack dynamically when needed. The secondary
14532 stack is used for returning variable length results.
14538 "A default (implementation-provided) storage pool for an
14539 access-to-constant type should not have overhead to support deallocation of
14540 individual objects."
14547 "A storage pool for an anonymous access type should be created at the
14548 point of an allocator for the type, and be reclaimed when the designated
14549 object becomes inaccessible."
14554 @geindex Unchecked deallocation
14556 @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
14557 @anchor{gnat_rm/implementation_advice rm-13-11-2-17-unchecked-deallocation}@anchor{22c}
14558 @section RM 13.11.2(17): Unchecked Deallocation
14563 "For a standard storage pool, @code{Free} should actually reclaim the
14569 @geindex Stream oriented attributes
14571 @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
14572 @anchor{gnat_rm/implementation_advice rm-13-13-2-17-stream-oriented-attributes}@anchor{22d}
14573 @section RM 13.13.2(17): Stream Oriented Attributes
14578 "If a stream element is the same size as a storage element, then the
14579 normal in-memory representation should be used by @code{Read} and
14580 @code{Write} for scalar objects. Otherwise, @code{Read} and @code{Write}
14581 should use the smallest number of stream elements needed to represent
14582 all values in the base range of the scalar type."
14585 Followed. By default, GNAT uses the interpretation suggested by AI-195,
14586 which specifies using the size of the first subtype.
14587 However, such an implementation is based on direct binary
14588 representations and is therefore target- and endianness-dependent.
14589 To address this issue, GNAT also supplies an alternate implementation
14590 of the stream attributes @code{Read} and @code{Write},
14591 which uses the target-independent XDR standard representation
14594 @geindex XDR representation
14596 @geindex Read attribute
14598 @geindex Write attribute
14600 @geindex Stream oriented attributes
14602 The XDR implementation is provided as an alternative body of the
14603 @code{System.Stream_Attributes} package, in the file
14604 @code{s-stratt-xdr.adb} in the GNAT library.
14605 There is no @code{s-stratt-xdr.ads} file.
14606 In order to install the XDR implementation, do the following:
14612 Replace the default implementation of the
14613 @code{System.Stream_Attributes} package with the XDR implementation.
14614 For example on a Unix platform issue the commands:
14617 $ mv s-stratt.adb s-stratt-default.adb
14618 $ mv s-stratt-xdr.adb s-stratt.adb
14622 Rebuild the GNAT run-time library as documented in
14623 the @emph{GNAT and Libraries} section of the @cite{GNAT User's Guide}.
14626 @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
14627 @anchor{gnat_rm/implementation_advice rm-a-1-52-names-of-predefined-numeric-types}@anchor{22e}
14628 @section RM A.1(52): Names of Predefined Numeric Types
14633 "If an implementation provides additional named predefined integer types,
14634 then the names should end with @code{Integer} as in
14635 @code{Long_Integer}. If an implementation provides additional named
14636 predefined floating point types, then the names should end with
14637 @code{Float} as in @code{Long_Float}."
14642 @geindex Ada.Characters.Handling
14644 @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
14645 @anchor{gnat_rm/implementation_advice rm-a-3-2-49-ada-characters-handling}@anchor{22f}
14646 @section RM A.3.2(49): @code{Ada.Characters.Handling}
14651 "If an implementation provides a localized definition of @code{Character}
14652 or @code{Wide_Character}, then the effects of the subprograms in
14653 @code{Characters.Handling} should reflect the localizations.
14657 Followed. GNAT provides no such localized definitions.
14659 @geindex Bounded-length strings
14661 @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
14662 @anchor{gnat_rm/implementation_advice rm-a-4-4-106-bounded-length-string-handling}@anchor{230}
14663 @section RM A.4.4(106): Bounded-Length String Handling
14668 "Bounded string objects should not be implemented by implicit pointers
14669 and dynamic allocation."
14672 Followed. No implicit pointers or dynamic allocation are used.
14674 @geindex Random number generation
14676 @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
14677 @anchor{gnat_rm/implementation_advice rm-a-5-2-46-47-random-number-generation}@anchor{231}
14678 @section RM A.5.2(46-47): Random Number Generation
14683 "Any storage associated with an object of type @code{Generator} should be
14684 reclaimed on exit from the scope of the object."
14691 "If the generator period is sufficiently long in relation to the number
14692 of distinct initiator values, then each possible value of
14693 @code{Initiator} passed to @code{Reset} should initiate a sequence of
14694 random numbers that does not, in a practical sense, overlap the sequence
14695 initiated by any other value. If this is not possible, then the mapping
14696 between initiator values and generator states should be a rapidly
14697 varying function of the initiator value."
14700 Followed. The generator period is sufficiently long for the first
14701 condition here to hold true.
14703 @geindex Get_Immediate
14705 @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
14706 @anchor{gnat_rm/implementation_advice rm-a-10-7-23-get-immediate}@anchor{232}
14707 @section RM A.10.7(23): @code{Get_Immediate}
14712 "The @code{Get_Immediate} procedures should be implemented with
14713 unbuffered input. For a device such as a keyboard, input should be
14714 available if a key has already been typed, whereas for a disk
14715 file, input should always be available except at end of file. For a file
14716 associated with a keyboard-like device, any line-editing features of the
14717 underlying operating system should be disabled during the execution of
14718 @code{Get_Immediate}."
14721 Followed on all targets except VxWorks. For VxWorks, there is no way to
14722 provide this functionality that does not result in the input buffer being
14723 flushed before the @code{Get_Immediate} call. A special unit
14724 @code{Interfaces.Vxworks.IO} is provided that contains routines to enable
14725 this functionality.
14729 @node RM B 1 39-41 Pragma Export,RM B 2 12-13 Package Interfaces,RM A 10 7 23 Get_Immediate,Implementation Advice
14730 @anchor{gnat_rm/implementation_advice rm-b-1-39-41-pragma-export}@anchor{233}
14731 @section RM B.1(39-41): Pragma @code{Export}
14736 "If an implementation supports pragma @code{Export} to a given language,
14737 then it should also allow the main subprogram to be written in that
14738 language. It should support some mechanism for invoking the elaboration
14739 of the Ada library units included in the system, and for invoking the
14740 finalization of the environment task. On typical systems, the
14741 recommended mechanism is to provide two subprograms whose link names are
14742 @code{adainit} and @code{adafinal}. @code{adainit} should contain the
14743 elaboration code for library units. @code{adafinal} should contain the
14744 finalization code. These subprograms should have no effect the second
14745 and subsequent time they are called."
14752 "Automatic elaboration of pre-elaborated packages should be
14753 provided when pragma @code{Export} is supported."
14756 Followed when the main program is in Ada. If the main program is in a
14757 foreign language, then
14758 @code{adainit} must be called to elaborate pre-elaborated
14763 "For each supported convention @emph{L} other than @code{Intrinsic}, an
14764 implementation should support @code{Import} and @code{Export} pragmas
14765 for objects of @emph{L}-compatible types and for subprograms, and pragma
14766 @cite{Convention} for @emph{L}-eligible types and for subprograms,
14767 presuming the other language has corresponding features. Pragma
14768 @code{Convention} need not be supported for scalar types."
14773 @geindex Package Interfaces
14775 @geindex Interfaces
14777 @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
14778 @anchor{gnat_rm/implementation_advice rm-b-2-12-13-package-interfaces}@anchor{234}
14779 @section RM B.2(12-13): Package @code{Interfaces}
14784 "For each implementation-defined convention identifier, there should be a
14785 child package of package Interfaces with the corresponding name. This
14786 package should contain any declarations that would be useful for
14787 interfacing to the language (implementation) represented by the
14788 convention. Any declarations useful for interfacing to any language on
14789 the given hardware architecture should be provided directly in
14790 @code{Interfaces}."
14797 "An implementation supporting an interface to C, COBOL, or Fortran should
14798 provide the corresponding package or packages described in the following
14802 Followed. GNAT provides all the packages described in this section.
14805 @geindex interfacing with
14807 @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
14808 @anchor{gnat_rm/implementation_advice rm-b-3-63-71-interfacing-with-c}@anchor{235}
14809 @section RM B.3(63-71): Interfacing with C
14814 "An implementation should support the following interface correspondences
14815 between Ada and C."
14822 "An Ada procedure corresponds to a void-returning C function."
14829 "An Ada function corresponds to a non-void C function."
14836 "An Ada @code{in} scalar parameter is passed as a scalar argument to a C
14844 "An Ada @code{in} parameter of an access-to-object type with designated
14845 type @code{T} is passed as a @code{t*} argument to a C function,
14846 where @code{t} is the C type corresponding to the Ada type @code{T}."
14853 "An Ada access @code{T} parameter, or an Ada @code{out} or @code{in out}
14854 parameter of an elementary type @code{T}, is passed as a @code{t*}
14855 argument to a C function, where @code{t} is the C type corresponding to
14856 the Ada type @code{T}. In the case of an elementary @code{out} or
14857 @code{in out} parameter, a pointer to a temporary copy is used to
14858 preserve by-copy semantics."
14865 "An Ada parameter of a record type @code{T}, of any mode, is passed as a
14866 @code{t*} argument to a C function, where @code{t} is the C
14867 structure corresponding to the Ada type @code{T}."
14870 Followed. This convention may be overridden by the use of the C_Pass_By_Copy
14871 pragma, or Convention, or by explicitly specifying the mechanism for a given
14872 call using an extended import or export pragma.
14876 "An Ada parameter of an array type with component type @code{T}, of any
14877 mode, is passed as a @code{t*} argument to a C function, where
14878 @code{t} is the C type corresponding to the Ada type @code{T}."
14885 "An Ada parameter of an access-to-subprogram type is passed as a pointer
14886 to a C function whose prototype corresponds to the designated
14887 subprogram's specification."
14893 @geindex interfacing with
14895 @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
14896 @anchor{gnat_rm/implementation_advice rm-b-4-95-98-interfacing-with-cobol}@anchor{236}
14897 @section RM B.4(95-98): Interfacing with COBOL
14902 "An Ada implementation should support the following interface
14903 correspondences between Ada and COBOL."
14910 "An Ada access @code{T} parameter is passed as a @code{BY REFERENCE} data item of
14911 the COBOL type corresponding to @code{T}."
14918 "An Ada in scalar parameter is passed as a @code{BY CONTENT} data item of
14919 the corresponding COBOL type."
14926 "Any other Ada parameter is passed as a @code{BY REFERENCE} data item of the
14927 COBOL type corresponding to the Ada parameter type; for scalars, a local
14928 copy is used if necessary to ensure by-copy semantics."
14934 @geindex interfacing with
14936 @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
14937 @anchor{gnat_rm/implementation_advice rm-b-5-22-26-interfacing-with-fortran}@anchor{237}
14938 @section RM B.5(22-26): Interfacing with Fortran
14943 "An Ada implementation should support the following interface
14944 correspondences between Ada and Fortran:"
14951 "An Ada procedure corresponds to a Fortran subroutine."
14958 "An Ada function corresponds to a Fortran function."
14965 "An Ada parameter of an elementary, array, or record type @code{T} is
14966 passed as a @code{T} argument to a Fortran procedure, where @code{T} is
14967 the Fortran type corresponding to the Ada type @code{T}, and where the
14968 INTENT attribute of the corresponding dummy argument matches the Ada
14969 formal parameter mode; the Fortran implementation's parameter passing
14970 conventions are used. For elementary types, a local copy is used if
14971 necessary to ensure by-copy semantics."
14978 "An Ada parameter of an access-to-subprogram type is passed as a
14979 reference to a Fortran procedure whose interface corresponds to the
14980 designated subprogram's specification."
14985 @geindex Machine operations
14987 @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
14988 @anchor{gnat_rm/implementation_advice rm-c-1-3-5-access-to-machine-operations}@anchor{238}
14989 @section RM C.1(3-5): Access to Machine Operations
14994 "The machine code or intrinsic support should allow access to all
14995 operations normally available to assembly language programmers for the
14996 target environment, including privileged instructions, if any."
15003 "The interfacing pragmas (see Annex B) should support interface to
15004 assembler; the default assembler should be associated with the
15005 convention identifier @code{Assembler}."
15012 "If an entity is exported to assembly language, then the implementation
15013 should allocate it at an addressable location, and should ensure that it
15014 is retained by the linking process, even if not otherwise referenced
15015 from the Ada code. The implementation should assume that any call to a
15016 machine code or assembler subprogram is allowed to read or update every
15017 object that is specified as exported."
15022 @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
15023 @anchor{gnat_rm/implementation_advice rm-c-1-10-16-access-to-machine-operations}@anchor{239}
15024 @section RM C.1(10-16): Access to Machine Operations
15029 "The implementation should ensure that little or no overhead is
15030 associated with calling intrinsic and machine-code subprograms."
15033 Followed for both intrinsics and machine-code subprograms.
15037 "It is recommended that intrinsic subprograms be provided for convenient
15038 access to any machine operations that provide special capabilities or
15039 efficiency and that are not otherwise available through the language
15043 Followed. A full set of machine operation intrinsic subprograms is provided.
15047 "Atomic read-modify-write operations---e.g., test and set, compare and
15048 swap, decrement and test, enqueue/dequeue."
15051 Followed on any target supporting such operations.
15055 "Standard numeric functions---e.g.:, sin, log."
15058 Followed on any target supporting such operations.
15062 "String manipulation operations---e.g.:, translate and test."
15065 Followed on any target supporting such operations.
15069 "Vector operations---e.g.:, compare vector against thresholds."
15072 Followed on any target supporting such operations.
15076 "Direct operations on I/O ports."
15079 Followed on any target supporting such operations.
15081 @geindex Interrupt support
15083 @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
15084 @anchor{gnat_rm/implementation_advice rm-c-3-28-interrupt-support}@anchor{23a}
15085 @section RM C.3(28): Interrupt Support
15090 "If the @code{Ceiling_Locking} policy is not in effect, the
15091 implementation should provide means for the application to specify which
15092 interrupts are to be blocked during protected actions, if the underlying
15093 system allows for a finer-grain control of interrupt blocking."
15096 Followed. The underlying system does not allow for finer-grain control
15097 of interrupt blocking.
15099 @geindex Protected procedure handlers
15101 @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
15102 @anchor{gnat_rm/implementation_advice rm-c-3-1-20-21-protected-procedure-handlers}@anchor{23b}
15103 @section RM C.3.1(20-21): Protected Procedure Handlers
15108 "Whenever possible, the implementation should allow interrupt handlers to
15109 be called directly by the hardware."
15112 Followed on any target where the underlying operating system permits
15117 "Whenever practical, violations of any
15118 implementation-defined restrictions should be detected before run time."
15121 Followed. Compile time warnings are given when possible.
15123 @geindex Package `@w{`}Interrupts`@w{`}
15125 @geindex Interrupts
15127 @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
15128 @anchor{gnat_rm/implementation_advice rm-c-3-2-25-package-interrupts}@anchor{23c}
15129 @section RM C.3.2(25): Package @code{Interrupts}
15134 "If implementation-defined forms of interrupt handler procedures are
15135 supported, such as protected procedures with parameters, then for each
15136 such form of a handler, a type analogous to @code{Parameterless_Handler}
15137 should be specified in a child package of @code{Interrupts}, with the
15138 same operations as in the predefined package Interrupts."
15143 @geindex Pre-elaboration requirements
15145 @node RM C 4 14 Pre-elaboration Requirements,RM C 5 8 Pragma Discard_Names,RM C 3 2 25 Package Interrupts,Implementation Advice
15146 @anchor{gnat_rm/implementation_advice rm-c-4-14-pre-elaboration-requirements}@anchor{23d}
15147 @section RM C.4(14): Pre-elaboration Requirements
15152 "It is recommended that pre-elaborated packages be implemented in such a
15153 way that there should be little or no code executed at run time for the
15154 elaboration of entities not already covered by the Implementation
15158 Followed. Executable code is generated in some cases, e.g., loops
15159 to initialize large arrays.
15161 @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
15162 @anchor{gnat_rm/implementation_advice rm-c-5-8-pragma-discard-names}@anchor{23e}
15163 @section RM C.5(8): Pragma @code{Discard_Names}
15168 "If the pragma applies to an entity, then the implementation should
15169 reduce the amount of storage used for storing names associated with that
15175 @geindex Package Task_Attributes
15177 @geindex Task_Attributes
15179 @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
15180 @anchor{gnat_rm/implementation_advice rm-c-7-2-30-the-package-task-attributes}@anchor{23f}
15181 @section RM C.7.2(30): The Package Task_Attributes
15186 "Some implementations are targeted to domains in which memory use at run
15187 time must be completely deterministic. For such implementations, it is
15188 recommended that the storage for task attributes will be pre-allocated
15189 statically and not from the heap. This can be accomplished by either
15190 placing restrictions on the number and the size of the task's
15191 attributes, or by using the pre-allocated storage for the first @code{N}
15192 attribute objects, and the heap for the others. In the latter case,
15193 @code{N} should be documented."
15196 Not followed. This implementation is not targeted to such a domain.
15198 @geindex Locking Policies
15200 @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
15201 @anchor{gnat_rm/implementation_advice rm-d-3-17-locking-policies}@anchor{240}
15202 @section RM D.3(17): Locking Policies
15207 "The implementation should use names that end with @code{_Locking} for
15208 locking policies defined by the implementation."
15211 Followed. Two implementation-defined locking policies are defined,
15212 whose names (@code{Inheritance_Locking} and
15213 @code{Concurrent_Readers_Locking}) follow this suggestion.
15215 @geindex Entry queuing policies
15217 @node RM D 4 16 Entry Queuing Policies,RM D 6 9-10 Preemptive Abort,RM D 3 17 Locking Policies,Implementation Advice
15218 @anchor{gnat_rm/implementation_advice rm-d-4-16-entry-queuing-policies}@anchor{241}
15219 @section RM D.4(16): Entry Queuing Policies
15224 "Names that end with @code{_Queuing} should be used
15225 for all implementation-defined queuing policies."
15228 Followed. No such implementation-defined queuing policies exist.
15230 @geindex Preemptive abort
15232 @node RM D 6 9-10 Preemptive Abort,RM D 7 21 Tasking Restrictions,RM D 4 16 Entry Queuing Policies,Implementation Advice
15233 @anchor{gnat_rm/implementation_advice rm-d-6-9-10-preemptive-abort}@anchor{242}
15234 @section RM D.6(9-10): Preemptive Abort
15239 "Even though the @emph{abort_statement} is included in the list of
15240 potentially blocking operations (see 9.5.1), it is recommended that this
15241 statement be implemented in a way that never requires the task executing
15242 the @emph{abort_statement} to block."
15249 "On a multi-processor, the delay associated with aborting a task on
15250 another processor should be bounded; the implementation should use
15251 periodic polling, if necessary, to achieve this."
15256 @geindex Tasking restrictions
15258 @node RM D 7 21 Tasking Restrictions,RM D 8 47-49 Monotonic Time,RM D 6 9-10 Preemptive Abort,Implementation Advice
15259 @anchor{gnat_rm/implementation_advice rm-d-7-21-tasking-restrictions}@anchor{243}
15260 @section RM D.7(21): Tasking Restrictions
15265 "When feasible, the implementation should take advantage of the specified
15266 restrictions to produce a more efficient implementation."
15269 GNAT currently takes advantage of these restrictions by providing an optimized
15270 run time when the Ravenscar profile and the GNAT restricted run time set
15271 of restrictions are specified. See pragma @code{Profile (Ravenscar)} and
15272 pragma @code{Profile (Restricted)} for more details.
15277 @node RM D 8 47-49 Monotonic Time,RM E 5 28-29 Partition Communication Subsystem,RM D 7 21 Tasking Restrictions,Implementation Advice
15278 @anchor{gnat_rm/implementation_advice rm-d-8-47-49-monotonic-time}@anchor{244}
15279 @section RM D.8(47-49): Monotonic Time
15284 "When appropriate, implementations should provide configuration
15285 mechanisms to change the value of @code{Tick}."
15288 Such configuration mechanisms are not appropriate to this implementation
15289 and are thus not supported.
15293 "It is recommended that @code{Calendar.Clock} and @code{Real_Time.Clock}
15294 be implemented as transformations of the same time base."
15301 "It is recommended that the best time base which exists in
15302 the underlying system be available to the application through
15303 @code{Clock}. @cite{Best} may mean highest accuracy or largest range."
15308 @geindex Partition communication subsystem
15312 @node RM E 5 28-29 Partition Communication Subsystem,RM F 7 COBOL Support,RM D 8 47-49 Monotonic Time,Implementation Advice
15313 @anchor{gnat_rm/implementation_advice rm-e-5-28-29-partition-communication-subsystem}@anchor{245}
15314 @section RM E.5(28-29): Partition Communication Subsystem
15319 "Whenever possible, the PCS on the called partition should allow for
15320 multiple tasks to call the RPC-receiver with different messages and
15321 should allow them to block until the corresponding subprogram body
15325 Followed by GLADE, a separately supplied PCS that can be used with
15330 "The @code{Write} operation on a stream of type @code{Params_Stream_Type}
15331 should raise @code{Storage_Error} if it runs out of space trying to
15332 write the @code{Item} into the stream."
15335 Followed by GLADE, a separately supplied PCS that can be used with
15338 @geindex COBOL support
15340 @node RM F 7 COBOL Support,RM F 1 2 Decimal Radix Support,RM E 5 28-29 Partition Communication Subsystem,Implementation Advice
15341 @anchor{gnat_rm/implementation_advice rm-f-7-cobol-support}@anchor{246}
15342 @section RM F(7): COBOL Support
15347 "If COBOL (respectively, C) is widely supported in the target
15348 environment, implementations supporting the Information Systems Annex
15349 should provide the child package @code{Interfaces.COBOL} (respectively,
15350 @code{Interfaces.C}) specified in Annex B and should support a
15351 @code{convention_identifier} of COBOL (respectively, C) in the interfacing
15352 pragmas (see Annex B), thus allowing Ada programs to interface with
15353 programs written in that language."
15358 @geindex Decimal radix support
15360 @node RM F 1 2 Decimal Radix Support,RM G Numerics,RM F 7 COBOL Support,Implementation Advice
15361 @anchor{gnat_rm/implementation_advice rm-f-1-2-decimal-radix-support}@anchor{247}
15362 @section RM F.1(2): Decimal Radix Support
15367 "Packed decimal should be used as the internal representation for objects
15368 of subtype @code{S} when @code{S}'Machine_Radix = 10."
15371 Not followed. GNAT ignores @code{S}'Machine_Radix and always uses binary
15376 @node RM G Numerics,RM G 1 1 56-58 Complex Types,RM F 1 2 Decimal Radix Support,Implementation Advice
15377 @anchor{gnat_rm/implementation_advice rm-g-numerics}@anchor{248}
15378 @section RM G: Numerics
15383 "If Fortran (respectively, C) is widely supported in the target
15384 environment, implementations supporting the Numerics Annex
15385 should provide the child package @code{Interfaces.Fortran} (respectively,
15386 @code{Interfaces.C}) specified in Annex B and should support a
15387 @code{convention_identifier} of Fortran (respectively, C) in the interfacing
15388 pragmas (see Annex B), thus allowing Ada programs to interface with
15389 programs written in that language."
15394 @geindex Complex types
15396 @node RM G 1 1 56-58 Complex Types,RM G 1 2 49 Complex Elementary Functions,RM G Numerics,Implementation Advice
15397 @anchor{gnat_rm/implementation_advice rm-g-1-1-56-58-complex-types}@anchor{249}
15398 @section RM G.1.1(56-58): Complex Types
15403 "Because the usual mathematical meaning of multiplication of a complex
15404 operand and a real operand is that of the scaling of both components of
15405 the former by the latter, an implementation should not perform this
15406 operation by first promoting the real operand to complex type and then
15407 performing a full complex multiplication. In systems that, in the
15408 future, support an Ada binding to IEC 559:1989, the latter technique
15409 will not generate the required result when one of the components of the
15410 complex operand is infinite. (Explicit multiplication of the infinite
15411 component by the zero component obtained during promotion yields a NaN
15412 that propagates into the final result.) Analogous advice applies in the
15413 case of multiplication of a complex operand and a pure-imaginary
15414 operand, and in the case of division of a complex operand by a real or
15415 pure-imaginary operand."
15422 "Similarly, because the usual mathematical meaning of addition of a
15423 complex operand and a real operand is that the imaginary operand remains
15424 unchanged, an implementation should not perform this operation by first
15425 promoting the real operand to complex type and then performing a full
15426 complex addition. In implementations in which the @code{Signed_Zeros}
15427 attribute of the component type is @code{True} (and which therefore
15428 conform to IEC 559:1989 in regard to the handling of the sign of zero in
15429 predefined arithmetic operations), the latter technique will not
15430 generate the required result when the imaginary component of the complex
15431 operand is a negatively signed zero. (Explicit addition of the negative
15432 zero to the zero obtained during promotion yields a positive zero.)
15433 Analogous advice applies in the case of addition of a complex operand
15434 and a pure-imaginary operand, and in the case of subtraction of a
15435 complex operand and a real or pure-imaginary operand."
15442 "Implementations in which @code{Real'Signed_Zeros} is @code{True} should
15443 attempt to provide a rational treatment of the signs of zero results and
15444 result components. As one example, the result of the @code{Argument}
15445 function should have the sign of the imaginary component of the
15446 parameter @code{X} when the point represented by that parameter lies on
15447 the positive real axis; as another, the sign of the imaginary component
15448 of the @code{Compose_From_Polar} function should be the same as
15449 (respectively, the opposite of) that of the @code{Argument} parameter when that
15450 parameter has a value of zero and the @code{Modulus} parameter has a
15451 nonnegative (respectively, negative) value."
15456 @geindex Complex elementary functions
15458 @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
15459 @anchor{gnat_rm/implementation_advice rm-g-1-2-49-complex-elementary-functions}@anchor{24a}
15460 @section RM G.1.2(49): Complex Elementary Functions
15465 "Implementations in which @code{Complex_Types.Real'Signed_Zeros} is
15466 @code{True} should attempt to provide a rational treatment of the signs
15467 of zero results and result components. For example, many of the complex
15468 elementary functions have components that are odd functions of one of
15469 the parameter components; in these cases, the result component should
15470 have the sign of the parameter component at the origin. Other complex
15471 elementary functions have zero components whose sign is opposite that of
15472 a parameter component at the origin, or is always positive or always
15478 @geindex Accuracy requirements
15480 @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
15481 @anchor{gnat_rm/implementation_advice rm-g-2-4-19-accuracy-requirements}@anchor{24b}
15482 @section RM G.2.4(19): Accuracy Requirements
15487 "The versions of the forward trigonometric functions without a
15488 @code{Cycle} parameter should not be implemented by calling the
15489 corresponding version with a @code{Cycle} parameter of
15490 @code{2.0*Numerics.Pi}, since this will not provide the required
15491 accuracy in some portions of the domain. For the same reason, the
15492 version of @code{Log} without a @code{Base} parameter should not be
15493 implemented by calling the corresponding version with a @code{Base}
15494 parameter of @code{Numerics.e}."
15499 @geindex Complex arithmetic accuracy
15502 @geindex complex arithmetic
15504 @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
15505 @anchor{gnat_rm/implementation_advice rm-g-2-6-15-complex-arithmetic-accuracy}@anchor{24c}
15506 @section RM G.2.6(15): Complex Arithmetic Accuracy
15511 "The version of the @code{Compose_From_Polar} function without a
15512 @code{Cycle} parameter should not be implemented by calling the
15513 corresponding version with a @code{Cycle} parameter of
15514 @code{2.0*Numerics.Pi}, since this will not provide the required
15515 accuracy in some portions of the domain."
15520 @geindex Sequential elaboration policy
15522 @node RM H 6 15/2 Pragma Partition_Elaboration_Policy,,RM G 2 6 15 Complex Arithmetic Accuracy,Implementation Advice
15523 @anchor{gnat_rm/implementation_advice rm-h-6-15-2-pragma-partition-elaboration-policy}@anchor{24d}
15524 @section RM H.6(15/2): Pragma Partition_Elaboration_Policy
15529 "If the partition elaboration policy is @code{Sequential} and the
15530 Environment task becomes permanently blocked during elaboration then the
15531 partition is deadlocked and it is recommended that the partition be
15532 immediately terminated."
15537 @node Implementation Defined Characteristics,Intrinsic Subprograms,Implementation Advice,Top
15538 @anchor{gnat_rm/implementation_defined_characteristics implementation-defined-characteristics}@anchor{b}@anchor{gnat_rm/implementation_defined_characteristics doc}@anchor{24e}@anchor{gnat_rm/implementation_defined_characteristics id1}@anchor{24f}
15539 @chapter Implementation Defined Characteristics
15542 In addition to the implementation dependent pragmas and attributes, and the
15543 implementation advice, there are a number of other Ada features that are
15544 potentially implementation dependent and are designated as
15545 implementation-defined. These are mentioned throughout the Ada Reference
15546 Manual, and are summarized in Annex M.
15548 A requirement for conforming Ada compilers is that they provide
15549 documentation describing how the implementation deals with each of these
15550 issues. In this chapter you will find each point in Annex M listed,
15551 followed by a description of how GNAT
15552 handles the implementation dependence.
15554 You can use this chapter as a guide to minimizing implementation
15555 dependent features in your programs if portability to other compilers
15556 and other operating systems is an important consideration. The numbers
15557 in each entry below correspond to the paragraph numbers in the Ada
15564 "Whether or not each recommendation given in Implementation
15565 Advice is followed. See 1.1.2(37)."
15568 See @ref{a,,Implementation Advice}.
15574 "Capacity limitations of the implementation. See 1.1.3(3)."
15577 The complexity of programs that can be processed is limited only by the
15578 total amount of available virtual memory, and disk space for the
15579 generated object files.
15585 "Variations from the standard that are impractical to avoid
15586 given the implementation's execution environment. See 1.1.3(6)."
15589 There are no variations from the standard.
15595 "Which code_statements cause external
15596 interactions. See 1.1.3(10)."
15599 Any @emph{code_statement} can potentially cause external interactions.
15605 "The coded representation for the text of an Ada
15606 program. See 2.1(4)."
15609 See separate section on source representation.
15615 "The control functions allowed in comments. See 2.1(14)."
15618 See separate section on source representation.
15624 "The representation for an end of line. See 2.2(2)."
15627 See separate section on source representation.
15633 "Maximum supported line length and lexical element
15634 length. See 2.2(15)."
15637 The maximum line length is 255 characters and the maximum length of
15638 a lexical element is also 255 characters. This is the default setting
15639 if not overridden by the use of compiler switch @emph{-gnaty} (which
15640 sets the maximum to 79) or @emph{-gnatyMnn} which allows the maximum
15641 line length to be specified to be any value up to 32767. The maximum
15642 length of a lexical element is the same as the maximum line length.
15648 "Implementation defined pragmas. See 2.8(14)."
15651 See @ref{7,,Implementation Defined Pragmas}.
15657 "Effect of pragma @code{Optimize}. See 2.8(27)."
15660 Pragma @code{Optimize}, if given with a @code{Time} or @code{Space}
15661 parameter, checks that the optimization flag is set, and aborts if it is
15668 "The sequence of characters of the value returned by
15669 @code{S'Image} when some of the graphic characters of
15670 @code{S'Wide_Image} are not defined in @code{Character}. See
15674 The sequence of characters is as defined by the wide character encoding
15675 method used for the source. See section on source representation for
15682 "The predefined integer types declared in
15683 @code{Standard}. See 3.5.4(25)."
15687 @multitable {xxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
15698 @emph{Short_Short_Integer}
15706 @emph{Short_Integer}
15710 (Short) 16 bit signed
15722 @emph{Long_Integer}
15726 64 bit signed (on most 64 bit targets,
15727 depending on the C definition of long).
15728 32 bit signed (all other targets)
15732 @emph{Long_Long_Integer}
15745 "Any nonstandard integer types and the operators defined
15746 for them. See 3.5.4(26)."
15749 There are no nonstandard integer types.
15755 "Any nonstandard real types and the operators defined for
15756 them. See 3.5.6(8)."
15759 There are no nonstandard real types.
15765 "What combinations of requested decimal precision and range
15766 are supported for floating point types. See 3.5.7(7)."
15769 The precision and range is as defined by the IEEE standard.
15775 "The predefined floating point types declared in
15776 @code{Standard}. See 3.5.7(16)."
15780 @multitable {xxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
15803 (Short) 32 bit IEEE short
15815 @emph{Long_Long_Float}
15819 64 bit IEEE long (80 bit IEEE long on x86 processors)
15828 "The small of an ordinary fixed point type. See 3.5.9(8)."
15831 @code{Fine_Delta} is 2**(-63)
15837 "What combinations of small, range, and digits are
15838 supported for fixed point types. See 3.5.9(10)."
15841 Any combinations are permitted that do not result in a small less than
15842 @code{Fine_Delta} and do not result in a mantissa larger than 63 bits.
15843 If the mantissa is larger than 53 bits on machines where Long_Long_Float
15844 is 64 bits (true of all architectures except ia32), then the output from
15845 Text_IO is accurate to only 53 bits, rather than the full mantissa. This
15846 is because floating-point conversions are used to convert fixed point.
15852 "The result of @code{Tags.Expanded_Name} for types declared
15853 within an unnamed @emph{block_statement}. See 3.9(10)."
15856 Block numbers of the form @code{B@emph{nnn}}, where @emph{nnn} is a
15857 decimal integer are allocated.
15863 "Implementation-defined attributes. See 4.1.4(12)."
15866 See @ref{8,,Implementation Defined Attributes}.
15872 "Any implementation-defined time types. See 9.6(6)."
15875 There are no implementation-defined time types.
15881 "The time base associated with relative delays."
15884 See 9.6(20). The time base used is that provided by the C library
15885 function @code{gettimeofday}.
15891 "The time base of the type @code{Calendar.Time}. See
15895 The time base used is that provided by the C library function
15896 @code{gettimeofday}.
15902 "The time zone used for package @code{Calendar}
15903 operations. See 9.6(24)."
15906 The time zone used by package @code{Calendar} is the current system time zone
15907 setting for local time, as accessed by the C library function
15914 "Any limit on @emph{delay_until_statements} of
15915 @emph{select_statements}. See 9.6(29)."
15918 There are no such limits.
15924 "Whether or not two non-overlapping parts of a composite
15925 object are independently addressable, in the case where packing, record
15926 layout, or @code{Component_Size} is specified for the object. See
15930 Separate components are independently addressable if they do not share
15931 overlapping storage units.
15937 "The representation for a compilation. See 10.1(2)."
15940 A compilation is represented by a sequence of files presented to the
15941 compiler in a single invocation of the @emph{gcc} command.
15947 "Any restrictions on compilations that contain multiple
15948 compilation_units. See 10.1(4)."
15951 No single file can contain more than one compilation unit, but any
15952 sequence of files can be presented to the compiler as a single
15959 "The mechanisms for creating an environment and for adding
15960 and replacing compilation units. See 10.1.4(3)."
15963 See separate section on compilation model.
15969 "The manner of explicitly assigning library units to a
15970 partition. See 10.2(2)."
15973 If a unit contains an Ada main program, then the Ada units for the partition
15974 are determined by recursive application of the rules in the Ada Reference
15975 Manual section 10.2(2-6). In other words, the Ada units will be those that
15976 are needed by the main program, and then this definition of need is applied
15977 recursively to those units, and the partition contains the transitive
15978 closure determined by this relationship. In short, all the necessary units
15979 are included, with no need to explicitly specify the list. If additional
15980 units are required, e.g., by foreign language units, then all units must be
15981 mentioned in the context clause of one of the needed Ada units.
15983 If the partition contains no main program, or if the main program is in
15984 a language other than Ada, then GNAT
15985 provides the binder options @emph{-z} and @emph{-n} respectively, and in
15986 this case a list of units can be explicitly supplied to the binder for
15987 inclusion in the partition (all units needed by these units will also
15988 be included automatically). For full details on the use of these
15989 options, refer to @emph{GNAT Make Program gnatmake} in the
15990 @cite{GNAT User's Guide}.
15996 "The implementation-defined means, if any, of specifying
15997 which compilation units are needed by a given compilation unit. See
16001 The units needed by a given compilation unit are as defined in
16002 the Ada Reference Manual section 10.2(2-6). There are no
16003 implementation-defined pragmas or other implementation-defined
16004 means for specifying needed units.
16010 "The manner of designating the main subprogram of a
16011 partition. See 10.2(7)."
16014 The main program is designated by providing the name of the
16015 corresponding @code{ALI} file as the input parameter to the binder.
16021 "The order of elaboration of @emph{library_items}. See
16025 The first constraint on ordering is that it meets the requirements of
16026 Chapter 10 of the Ada Reference Manual. This still leaves some
16027 implementation dependent choices, which are resolved by first
16028 elaborating bodies as early as possible (i.e., in preference to specs
16029 where there is a choice), and second by evaluating the immediate with
16030 clauses of a unit to determine the probably best choice, and
16031 third by elaborating in alphabetical order of unit names
16032 where a choice still remains.
16038 "Parameter passing and function return for the main
16039 subprogram. See 10.2(21)."
16042 The main program has no parameters. It may be a procedure, or a function
16043 returning an integer type. In the latter case, the returned integer
16044 value is the return code of the program (overriding any value that
16045 may have been set by a call to @code{Ada.Command_Line.Set_Exit_Status}).
16051 "The mechanisms for building and running partitions. See
16055 GNAT itself supports programs with only a single partition. The GNATDIST
16056 tool provided with the GLADE package (which also includes an implementation
16057 of the PCS) provides a completely flexible method for building and running
16058 programs consisting of multiple partitions. See the separate GLADE manual
16065 "The details of program execution, including program
16066 termination. See 10.2(25)."
16069 See separate section on compilation model.
16075 "The semantics of any non-active partitions supported by the
16076 implementation. See 10.2(28)."
16079 Passive partitions are supported on targets where shared memory is
16080 provided by the operating system. See the GLADE reference manual for
16087 "The information returned by @code{Exception_Message}. See
16091 Exception message returns the null string unless a specific message has
16092 been passed by the program.
16098 "The result of @code{Exceptions.Exception_Name} for types
16099 declared within an unnamed @emph{block_statement}. See 11.4.1(12)."
16102 Blocks have implementation defined names of the form @code{B@emph{nnn}}
16103 where @emph{nnn} is an integer.
16109 "The information returned by
16110 @code{Exception_Information}. See 11.4.1(13)."
16113 @code{Exception_Information} returns a string in the following format:
16116 *Exception_Name:* nnnnn
16119 *Load address:* 0xhhhh
16120 *Call stack traceback locations:*
16121 0xhhhh 0xhhhh 0xhhhh ... 0xhhh
16132 @code{nnnn} is the fully qualified name of the exception in all upper
16133 case letters. This line is always present.
16136 @code{mmmm} is the message (this line present only if message is non-null)
16139 @code{ppp} is the Process Id value as a decimal integer (this line is
16140 present only if the Process Id is nonzero). Currently we are
16141 not making use of this field.
16144 The Load address line, the Call stack traceback locations line and the
16145 following values are present only if at least one traceback location was
16146 recorded. The Load address indicates the address at which the main executable
16147 was loaded; this line may not be present if operating system hasn't relocated
16148 the main executable. The values are given in C style format, with lower case
16149 letters for a-f, and only as many digits present as are necessary.
16150 The line terminator sequence at the end of each line, including
16151 the last line is a single @code{LF} character (@code{16#0A#}).
16159 "Implementation-defined check names. See 11.5(27)."
16162 The implementation defined check names include Alignment_Check,
16163 Atomic_Synchronization, Duplicated_Tag_Check, Container_Checks,
16164 Tampering_Check, Predicate_Check, and Validity_Check. In addition, a user
16165 program can add implementation-defined check names by means of the pragma
16166 Check_Name. See the description of pragma @code{Suppress} for full details.
16172 "The interpretation of each aspect of representation. See
16176 See separate section on data representations.
16182 "Any restrictions placed upon representation items. See
16186 See separate section on data representations.
16192 "The meaning of @code{Size} for indefinite subtypes. See
16196 Size for an indefinite subtype is the maximum possible size, except that
16197 for the case of a subprogram parameter, the size of the parameter object
16198 is the actual size.
16204 "The default external representation for a type tag. See
16208 The default external representation for a type tag is the fully expanded
16209 name of the type in upper case letters.
16215 "What determines whether a compilation unit is the same in
16216 two different partitions. See 13.3(76)."
16219 A compilation unit is the same in two different partitions if and only
16220 if it derives from the same source file.
16226 "Implementation-defined components. See 13.5.1(15)."
16229 The only implementation defined component is the tag for a tagged type,
16230 which contains a pointer to the dispatching table.
16236 "If @code{Word_Size} = @code{Storage_Unit}, the default bit
16237 ordering. See 13.5.3(5)."
16240 @code{Word_Size} (32) is not the same as @code{Storage_Unit} (8) for this
16241 implementation, so no non-default bit ordering is supported. The default
16242 bit ordering corresponds to the natural endianness of the target architecture.
16248 "The contents of the visible part of package @code{System}
16249 and its language-defined children. See 13.7(2)."
16252 See the definition of these packages in files @code{system.ads} and
16253 @code{s-stoele.ads}. Note that two declarations are added to package
16257 Max_Priority : constant Positive := Priority'Last;
16258 Max_Interrupt_Priority : constant Positive := Interrupt_Priority'Last;
16265 "The contents of the visible part of package
16266 @code{System.Machine_Code}, and the meaning of
16267 @emph{code_statements}. See 13.8(7)."
16270 See the definition and documentation in file @code{s-maccod.ads}.
16276 "The effect of unchecked conversion. See 13.9(11)."
16279 Unchecked conversion between types of the same size
16280 results in an uninterpreted transmission of the bits from one type
16281 to the other. If the types are of unequal sizes, then in the case of
16282 discrete types, a shorter source is first zero or sign extended as
16283 necessary, and a shorter target is simply truncated on the left.
16284 For all non-discrete types, the source is first copied if necessary
16285 to ensure that the alignment requirements of the target are met, then
16286 a pointer is constructed to the source value, and the result is obtained
16287 by dereferencing this pointer after converting it to be a pointer to the
16288 target type. Unchecked conversions where the target subtype is an
16289 unconstrained array are not permitted. If the target alignment is
16290 greater than the source alignment, then a copy of the result is
16291 made with appropriate alignment
16297 "The semantics of operations on invalid representations.
16298 See 13.9.2(10-11)."
16301 For assignments and other operations where the use of invalid values cannot
16302 result in erroneous behavior, the compiler ignores the possibility of invalid
16303 values. An exception is raised at the point where an invalid value would
16304 result in erroneous behavior. For example executing:
16307 procedure invalidvals is
16309 Y : Natural range 1 .. 10;
16310 for Y'Address use X'Address;
16311 Z : Natural range 1 .. 10;
16312 A : array (Natural range 1 .. 10) of Integer;
16314 Z := Y; -- no exception
16315 A (Z) := 3; -- exception raised;
16319 As indicated, an exception is raised on the array assignment, but not
16320 on the simple assignment of the invalid negative value from Y to Z.
16326 "The manner of choosing a storage pool for an access type
16327 when @code{Storage_Pool} is not specified for the type. See 13.11(17)."
16330 There are 3 different standard pools used by the compiler when
16331 @code{Storage_Pool} is not specified depending whether the type is local
16332 to a subprogram or defined at the library level and whether
16333 @code{Storage_Size`@w{`}is specified or not. See documentation in the runtime
16334 library units `@w{`}System.Pool_Global}, @code{System.Pool_Size} and
16335 @code{System.Pool_Local} in files @code{s-poosiz.ads},
16336 @code{s-pooglo.ads} and @code{s-pooloc.ads} for full details on the
16337 default pools used.
16343 "Whether or not the implementation provides user-accessible
16344 names for the standard pool type(s). See 13.11(17)."
16347 See documentation in the sources of the run time mentioned in the previous
16348 paragraph. All these pools are accessible by means of @cite{with}ing
16355 "The meaning of @code{Storage_Size}. See 13.11(18)."
16358 @code{Storage_Size} is measured in storage units, and refers to the
16359 total space available for an access type collection, or to the primary
16360 stack space for a task.
16366 "Implementation-defined aspects of storage pools. See
16370 See documentation in the sources of the run time mentioned in the
16371 paragraph about standard storage pools above
16372 for details on GNAT-defined aspects of storage pools.
16378 "The set of restrictions allowed in a pragma
16379 @code{Restrictions}. See 13.12(7)."
16382 See @ref{9,,Standard and Implementation Defined Restrictions}.
16388 "The consequences of violating limitations on
16389 @code{Restrictions} pragmas. See 13.12(9)."
16392 Restrictions that can be checked at compile time result in illegalities
16393 if violated. Currently there are no other consequences of violating
16400 "The representation used by the @code{Read} and
16401 @code{Write} attributes of elementary types in terms of stream
16402 elements. See 13.13.2(9)."
16405 The representation is the in-memory representation of the base type of
16406 the type, using the number of bits corresponding to the
16407 @code{type'Size} value, and the natural ordering of the machine.
16413 "The names and characteristics of the numeric subtypes
16414 declared in the visible part of package @code{Standard}. See A.1(3)."
16417 See items describing the integer and floating-point types supported.
16423 "The string returned by @code{Character_Set_Version}.
16427 @code{Ada.Wide_Characters.Handling.Character_Set_Version} returns
16428 the string "Unicode 4.0", referring to version 4.0 of the
16429 Unicode specification.
16435 "The accuracy actually achieved by the elementary
16436 functions. See A.5.1(1)."
16439 The elementary functions correspond to the functions available in the C
16440 library. Only fast math mode is implemented.
16446 "The sign of a zero result from some of the operators or
16447 functions in @code{Numerics.Generic_Elementary_Functions}, when
16448 @code{Float_Type'Signed_Zeros} is @code{True}. See A.5.1(46)."
16451 The sign of zeroes follows the requirements of the IEEE 754 standard on
16459 @code{Numerics.Float_Random.Max_Image_Width}. See A.5.2(27)."
16462 Maximum image width is 6864, see library file @code{s-rannum.ads}.
16469 @code{Numerics.Discrete_Random.Max_Image_Width}. See A.5.2(27)."
16472 Maximum image width is 6864, see library file @code{s-rannum.ads}.
16478 "The algorithms for random number generation. See
16482 The algorithm is the Mersenne Twister, as documented in the source file
16483 @code{s-rannum.adb}. This version of the algorithm has a period of
16490 "The string representation of a random number generator's
16491 state. See A.5.2(38)."
16494 The value returned by the Image function is the concatenation of
16495 the fixed-width decimal representations of the 624 32-bit integers
16496 of the state vector.
16502 "The minimum time interval between calls to the
16503 time-dependent Reset procedure that are guaranteed to initiate different
16504 random number sequences. See A.5.2(45)."
16507 The minimum period between reset calls to guarantee distinct series of
16508 random numbers is one microsecond.
16514 "The values of the @code{Model_Mantissa},
16515 @code{Model_Emin}, @code{Model_Epsilon}, @code{Model},
16516 @code{Safe_First}, and @code{Safe_Last} attributes, if the Numerics
16517 Annex is not supported. See A.5.3(72)."
16520 Run the compiler with @emph{-gnatS} to produce a listing of package
16521 @code{Standard}, has the values of all numeric attributes.
16527 "Any implementation-defined characteristics of the
16528 input-output packages. See A.7(14)."
16531 There are no special implementation defined characteristics for these
16538 "The value of @code{Buffer_Size} in @code{Storage_IO}. See
16542 All type representations are contiguous, and the @code{Buffer_Size} is
16543 the value of @code{type'Size} rounded up to the next storage unit
16550 "External files for standard input, standard output, and
16551 standard error See A.10(5)."
16554 These files are mapped onto the files provided by the C streams
16555 libraries. See source file @code{i-cstrea.ads} for further details.
16561 "The accuracy of the value produced by @code{Put}. See
16565 If more digits are requested in the output than are represented by the
16566 precision of the value, zeroes are output in the corresponding least
16567 significant digit positions.
16573 "The meaning of @code{Argument_Count}, @code{Argument}, and
16574 @code{Command_Name}. See A.15(1)."
16577 These are mapped onto the @code{argv} and @code{argc} parameters of the
16578 main program in the natural manner.
16584 "The interpretation of the @code{Form} parameter in procedure
16585 @code{Create_Directory}. See A.16(56)."
16588 The @code{Form} parameter is not used.
16594 "The interpretation of the @code{Form} parameter in procedure
16595 @code{Create_Path}. See A.16(60)."
16598 The @code{Form} parameter is not used.
16604 "The interpretation of the @code{Form} parameter in procedure
16605 @code{Copy_File}. See A.16(68)."
16608 The @code{Form} parameter is case-insensitive.
16609 Two fields are recognized in the @code{Form} parameter:
16616 <value> starts immediately after the character '=' and ends with the
16617 character immediately preceding the next comma (',') or with the last
16618 character of the parameter.
16620 The only possible values for preserve= are:
16623 @multitable {xxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
16634 @emph{no_attributes}
16638 Do not try to preserve any file attributes. This is the
16639 default if no preserve= is found in Form.
16643 @emph{all_attributes}
16647 Try to preserve all file attributes (timestamps, access rights).
16655 Preserve the timestamp of the copied file, but not the other
16661 The only possible values for mode= are:
16664 @multitable {xxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
16679 Only do the copy if the destination file does not already exist.
16680 If it already exists, Copy_File fails.
16688 Copy the file in all cases. Overwrite an already existing destination file.
16696 Append the original file to the destination file. If the destination file
16697 does not exist, the destination file is a copy of the source file.
16698 When mode=append, the field preserve=, if it exists, is not taken into account.
16703 If the Form parameter includes one or both of the fields and the value or
16704 values are incorrect, Copy_file fails with Use_Error.
16706 Examples of correct Forms:
16709 Form => "preserve=no_attributes,mode=overwrite" (the default)
16710 Form => "mode=append"
16711 Form => "mode=copy, preserve=all_attributes"
16714 Examples of incorrect Forms:
16717 Form => "preserve=junk"
16718 Form => "mode=internal, preserve=timestamps"
16725 "The interpretation of the @code{Pattern} parameter, when not the null string,
16726 in the @code{Start_Search} and @code{Search} procedures.
16727 See A.16(104) and A.16(112)."
16730 When the @code{Pattern} parameter is not the null string, it is interpreted
16731 according to the syntax of regular expressions as defined in the
16732 @code{GNAT.Regexp} package.
16734 See @ref{250,,GNAT.Regexp (g-regexp.ads)}.
16740 "Implementation-defined convention names. See B.1(11)."
16743 The following convention names are supported
16746 @multitable {xxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
16765 @emph{Ada_Pass_By_Copy}
16769 Allowed for any types except by-reference types such as limited
16770 records. Compatible with convention Ada, but causes any parameters
16771 with this convention to be passed by copy.
16775 @emph{Ada_Pass_By_Reference}
16779 Allowed for any types except by-copy types such as scalars.
16780 Compatible with convention Ada, but causes any parameters
16781 with this convention to be passed by reference.
16797 Synonym for Assembler
16805 Synonym for Assembler
16817 @emph{C_Pass_By_Copy}
16821 Allowed only for record types, like C, but also notes that record
16822 is to be passed by copy rather than reference.
16834 @emph{C_Plus_Plus (or CPP)}
16846 Treated the same as C
16854 Treated the same as C
16870 For support of pragma @code{Import} with convention Intrinsic, see
16871 separate section on Intrinsic Subprograms.
16879 Stdcall (used for Windows implementations only). This convention correspond
16880 to the WINAPI (previously called Pascal convention) C/C++ convention under
16881 Windows. A routine with this convention cleans the stack before
16882 exit. This pragma cannot be applied to a dispatching call.
16890 Synonym for Stdcall
16898 Synonym for Stdcall
16906 Stubbed is a special convention used to indicate that the body of the
16907 subprogram will be entirely ignored. Any call to the subprogram
16908 is converted into a raise of the @code{Program_Error} exception. If a
16909 pragma @code{Import} specifies convention @code{stubbed} then no body need
16910 be present at all. This convention is useful during development for the
16911 inclusion of subprograms whose body has not yet been written.
16912 In addition, all otherwise unrecognized convention names are also
16913 treated as being synonymous with convention C. In all implementations
16914 except for VMS, use of such other names results in a warning. In VMS
16915 implementations, these names are accepted silently.
16924 "The meaning of link names. See B.1(36)."
16927 Link names are the actual names used by the linker.
16933 "The manner of choosing link names when neither the link
16934 name nor the address of an imported or exported entity is specified. See
16938 The default linker name is that which would be assigned by the relevant
16939 external language, interpreting the Ada name as being in all lower case
16946 "The effect of pragma @code{Linker_Options}. See B.1(37)."
16949 The string passed to @code{Linker_Options} is presented uninterpreted as
16950 an argument to the link command, unless it contains ASCII.NUL characters.
16951 NUL characters if they appear act as argument separators, so for example
16954 pragma Linker_Options ("-labc" & ASCII.NUL & "-ldef");
16957 causes two separate arguments @code{-labc} and @code{-ldef} to be passed to the
16958 linker. The order of linker options is preserved for a given unit. The final
16959 list of options passed to the linker is in reverse order of the elaboration
16960 order. For example, linker options for a body always appear before the options
16961 from the corresponding package spec.
16967 "The contents of the visible part of package
16968 @code{Interfaces} and its language-defined descendants. See B.2(1)."
16971 See files with prefix @code{i-} in the distributed library.
16977 "Implementation-defined children of package
16978 @code{Interfaces}. The contents of the visible part of package
16979 @code{Interfaces}. See B.2(11)."
16982 See files with prefix @code{i-} in the distributed library.
16988 "The types @code{Floating}, @code{Long_Floating},
16989 @code{Binary}, @code{Long_Binary}, @code{Decimal_ Element}, and
16990 @code{COBOL_Character}; and the initialization of the variables
16991 @code{Ada_To_COBOL} and @code{COBOL_To_Ada}, in
16992 @code{Interfaces.COBOL}. See B.4(50)."
16996 @multitable {xxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
17015 @emph{Long_Floating}
17019 (Floating) Long_Float
17039 @emph{Decimal_Element}
17047 @emph{COBOL_Character}
17056 For initialization, see the file @code{i-cobol.ads} in the distributed library.
17062 "Support for access to machine instructions. See C.1(1)."
17065 See documentation in file @code{s-maccod.ads} in the distributed library.
17071 "Implementation-defined aspects of access to machine
17072 operations. See C.1(9)."
17075 See documentation in file @code{s-maccod.ads} in the distributed library.
17081 "Implementation-defined aspects of interrupts. See C.3(2)."
17084 Interrupts are mapped to signals or conditions as appropriate. See
17086 @code{Ada.Interrupt_Names} in source file @code{a-intnam.ads} for details
17087 on the interrupts supported on a particular target.
17093 "Implementation-defined aspects of pre-elaboration. See
17097 GNAT does not permit a partition to be restarted without reloading,
17098 except under control of the debugger.
17104 "The semantics of pragma @code{Discard_Names}. See C.5(7)."
17107 Pragma @code{Discard_Names} causes names of enumeration literals to
17108 be suppressed. In the presence of this pragma, the Image attribute
17109 provides the image of the Pos of the literal, and Value accepts
17116 "The result of the @code{Task_Identification.Image}
17117 attribute. See C.7.1(7)."
17120 The result of this attribute is a string that identifies
17121 the object or component that denotes a given task. If a variable @code{Var}
17122 has a task type, the image for this task will have the form @code{Var_@emph{XXXXXXXX}},
17123 where the suffix @emph{XXXXXXXX}
17124 is the hexadecimal representation of the virtual address of the corresponding
17125 task control block. If the variable is an array of tasks, the image of each
17126 task will have the form of an indexed component indicating the position of a
17127 given task in the array, e.g., @code{Group(5)_@emph{XXXXXXX}}. If the task is a
17128 component of a record, the image of the task will have the form of a selected
17129 component. These rules are fully recursive, so that the image of a task that
17130 is a subcomponent of a composite object corresponds to the expression that
17131 designates this task.
17133 If a task is created by an allocator, its image depends on the context. If the
17134 allocator is part of an object declaration, the rules described above are used
17135 to construct its image, and this image is not affected by subsequent
17136 assignments. If the allocator appears within an expression, the image
17137 includes only the name of the task type.
17139 If the configuration pragma Discard_Names is present, or if the restriction
17140 No_Implicit_Heap_Allocation is in effect, the image reduces to
17141 the numeric suffix, that is to say the hexadecimal representation of the
17142 virtual address of the control block of the task.
17148 "The value of @code{Current_Task} when in a protected entry
17149 or interrupt handler. See C.7.1(17)."
17152 Protected entries or interrupt handlers can be executed by any
17153 convenient thread, so the value of @code{Current_Task} is undefined.
17159 "The effect of calling @code{Current_Task} from an entry
17160 body or interrupt handler. See C.7.1(19)."
17163 When GNAT can determine statically that @code{Current_Task} is called directly in
17164 the body of an entry (or barrier) then a warning is emitted and @code{Program_Error}
17165 is raised at run time. Otherwise, the effect of calling @code{Current_Task} from an
17166 entry body or interrupt handler is to return the identification of the task
17167 currently executing the code.
17173 "Implementation-defined aspects of
17174 @code{Task_Attributes}. See C.7.2(19)."
17177 There are no implementation-defined aspects of @code{Task_Attributes}.
17183 "Values of all @code{Metrics}. See D(2)."
17186 The metrics information for GNAT depends on the performance of the
17187 underlying operating system. The sources of the run-time for tasking
17188 implementation, together with the output from @emph{-gnatG} can be
17189 used to determine the exact sequence of operating systems calls made
17190 to implement various tasking constructs. Together with appropriate
17191 information on the performance of the underlying operating system,
17192 on the exact target in use, this information can be used to determine
17193 the required metrics.
17199 "The declarations of @code{Any_Priority} and
17200 @code{Priority}. See D.1(11)."
17203 See declarations in file @code{system.ads}.
17209 "Implementation-defined execution resources. See D.1(15)."
17212 There are no implementation-defined execution resources.
17218 "Whether, on a multiprocessor, a task that is waiting for
17219 access to a protected object keeps its processor busy. See D.2.1(3)."
17222 On a multi-processor, a task that is waiting for access to a protected
17223 object does not keep its processor busy.
17229 "The affect of implementation defined execution resources
17230 on task dispatching. See D.2.1(9)."
17233 Tasks map to threads in the threads package used by GNAT. Where possible
17234 and appropriate, these threads correspond to native threads of the
17235 underlying operating system.
17241 "Implementation-defined @emph{policy_identifiers} allowed
17242 in a pragma @code{Task_Dispatching_Policy}. See D.2.2(3)."
17245 There are no implementation-defined policy-identifiers allowed in this
17252 "Implementation-defined aspects of priority inversion. See
17256 Execution of a task cannot be preempted by the implementation processing
17257 of delay expirations for lower priority tasks.
17263 "Implementation-defined task dispatching. See D.2.2(18)."
17266 The policy is the same as that of the underlying threads implementation.
17272 "Implementation-defined @emph{policy_identifiers} allowed
17273 in a pragma @code{Locking_Policy}. See D.3(4)."
17276 The two implementation defined policies permitted in GNAT are
17277 @code{Inheritance_Locking} and @code{Concurrent_Readers_Locking}. On
17278 targets that support the @code{Inheritance_Locking} policy, locking is
17279 implemented by inheritance, i.e., the task owning the lock operates
17280 at a priority equal to the highest priority of any task currently
17281 requesting the lock. On targets that support the
17282 @code{Concurrent_Readers_Locking} policy, locking is implemented with a
17283 read/write lock allowing multiple protected object functions to enter
17290 "Default ceiling priorities. See D.3(10)."
17293 The ceiling priority of protected objects of the type
17294 @code{System.Interrupt_Priority'Last} as described in the Ada
17295 Reference Manual D.3(10),
17301 "The ceiling of any protected object used internally by
17302 the implementation. See D.3(16)."
17305 The ceiling priority of internal protected objects is
17306 @code{System.Priority'Last}.
17312 "Implementation-defined queuing policies. See D.4(1)."
17315 There are no implementation-defined queuing policies.
17321 "On a multiprocessor, any conditions that cause the
17322 completion of an aborted construct to be delayed later than what is
17323 specified for a single processor. See D.6(3)."
17326 The semantics for abort on a multi-processor is the same as on a single
17327 processor, there are no further delays.
17333 "Any operations that implicitly require heap storage
17334 allocation. See D.7(8)."
17337 The only operation that implicitly requires heap storage allocation is
17344 "What happens when a task terminates in the presence of
17345 pragma @code{No_Task_Termination}. See D.7(15)."
17348 Execution is erroneous in that case.
17354 "Implementation-defined aspects of pragma
17355 @code{Restrictions}. See D.7(20)."
17358 There are no such implementation-defined aspects.
17364 "Implementation-defined aspects of package
17365 @code{Real_Time}. See D.8(17)."
17368 There are no implementation defined aspects of package @code{Real_Time}.
17374 "Implementation-defined aspects of
17375 @emph{delay_statements}. See D.9(8)."
17378 Any difference greater than one microsecond will cause the task to be
17379 delayed (see D.9(7)).
17385 "The upper bound on the duration of interrupt blocking
17386 caused by the implementation. See D.12(5)."
17389 The upper bound is determined by the underlying operating system. In
17390 no cases is it more than 10 milliseconds.
17396 "The means for creating and executing distributed
17397 programs. See E(5)."
17400 The GLADE package provides a utility GNATDIST for creating and executing
17401 distributed programs. See the GLADE reference manual for further details.
17407 "Any events that can result in a partition becoming
17408 inaccessible. See E.1(7)."
17411 See the GLADE reference manual for full details on such events.
17417 "The scheduling policies, treatment of priorities, and
17418 management of shared resources between partitions in certain cases. See
17422 See the GLADE reference manual for full details on these aspects of
17423 multi-partition execution.
17429 "Events that cause the version of a compilation unit to
17430 change. See E.3(5)."
17433 Editing the source file of a compilation unit, or the source files of
17434 any units on which it is dependent in a significant way cause the version
17435 to change. No other actions cause the version number to change. All changes
17436 are significant except those which affect only layout, capitalization or
17443 "Whether the execution of the remote subprogram is
17444 immediately aborted as a result of cancellation. See E.4(13)."
17447 See the GLADE reference manual for details on the effect of abort in
17448 a distributed application.
17454 "Implementation-defined aspects of the PCS. See E.5(25)."
17457 See the GLADE reference manual for a full description of all implementation
17458 defined aspects of the PCS.
17464 "Implementation-defined interfaces in the PCS. See
17468 See the GLADE reference manual for a full description of all
17469 implementation defined interfaces.
17475 "The values of named numbers in the package
17476 @code{Decimal}. See F.2(7)."
17480 @multitable {xxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxx}
17523 @emph{Max_Decimal_Digits}
17536 "The value of @code{Max_Picture_Length} in the package
17537 @code{Text_IO.Editing}. See F.3.3(16)."
17546 "The value of @code{Max_Picture_Length} in the package
17547 @code{Wide_Text_IO.Editing}. See F.3.4(5)."
17556 "The accuracy actually achieved by the complex elementary
17557 functions and by other complex arithmetic operations. See G.1(1)."
17560 Standard library functions are used for the complex arithmetic
17561 operations. Only fast math mode is currently supported.
17567 "The sign of a zero result (or a component thereof) from
17568 any operator or function in @code{Numerics.Generic_Complex_Types}, when
17569 @code{Real'Signed_Zeros} is True. See G.1.1(53)."
17572 The signs of zero values are as recommended by the relevant
17573 implementation advice.
17579 "The sign of a zero result (or a component thereof) from
17580 any operator or function in
17581 @code{Numerics.Generic_Complex_Elementary_Functions}, when
17582 @code{Real'Signed_Zeros} is @code{True}. See G.1.2(45)."
17585 The signs of zero values are as recommended by the relevant
17586 implementation advice.
17592 "Whether the strict mode or the relaxed mode is the
17593 default. See G.2(2)."
17596 The strict mode is the default. There is no separate relaxed mode. GNAT
17597 provides a highly efficient implementation of strict mode.
17603 "The result interval in certain cases of fixed-to-float
17604 conversion. See G.2.1(10)."
17607 For cases where the result interval is implementation dependent, the
17608 accuracy is that provided by performing all operations in 64-bit IEEE
17609 floating-point format.
17615 "The result of a floating point arithmetic operation in
17616 overflow situations, when the @code{Machine_Overflows} attribute of the
17617 result type is @code{False}. See G.2.1(13)."
17620 Infinite and NaN values are produced as dictated by the IEEE
17621 floating-point standard.
17622 Note that on machines that are not fully compliant with the IEEE
17623 floating-point standard, such as Alpha, the @emph{-mieee} compiler flag
17624 must be used for achieving IEEE conforming behavior (although at the cost
17625 of a significant performance penalty), so infinite and NaN values are
17626 properly generated.
17632 "The result interval for division (or exponentiation by a
17633 negative exponent), when the floating point hardware implements division
17634 as multiplication by a reciprocal. See G.2.1(16)."
17637 Not relevant, division is IEEE exact.
17643 "The definition of close result set, which determines the
17644 accuracy of certain fixed point multiplications and divisions. See
17648 Operations in the close result set are performed using IEEE long format
17649 floating-point arithmetic. The input operands are converted to
17650 floating-point, the operation is done in floating-point, and the result
17651 is converted to the target type.
17657 "Conditions on a @emph{universal_real} operand of a fixed
17658 point multiplication or division for which the result shall be in the
17659 perfect result set. See G.2.3(22)."
17662 The result is only defined to be in the perfect result set if the result
17663 can be computed by a single scaling operation involving a scale factor
17664 representable in 64-bits.
17670 "The result of a fixed point arithmetic operation in
17671 overflow situations, when the @code{Machine_Overflows} attribute of the
17672 result type is @code{False}. See G.2.3(27)."
17675 Not relevant, @code{Machine_Overflows} is @code{True} for fixed-point
17682 "The result of an elementary function reference in
17683 overflow situations, when the @code{Machine_Overflows} attribute of the
17684 result type is @code{False}. See G.2.4(4)."
17687 IEEE infinite and Nan values are produced as appropriate.
17693 "The value of the angle threshold, within which certain
17694 elementary functions, complex arithmetic operations, and complex
17695 elementary functions yield results conforming to a maximum relative
17696 error bound. See G.2.4(10)."
17699 Information on this subject is not yet available.
17705 "The accuracy of certain elementary functions for
17706 parameters beyond the angle threshold. See G.2.4(10)."
17709 Information on this subject is not yet available.
17715 "The result of a complex arithmetic operation or complex
17716 elementary function reference in overflow situations, when the
17717 @code{Machine_Overflows} attribute of the corresponding real type is
17718 @code{False}. See G.2.6(5)."
17721 IEEE infinite and Nan values are produced as appropriate.
17727 "The accuracy of certain complex arithmetic operations and
17728 certain complex elementary functions for parameters (or components
17729 thereof) beyond the angle threshold. See G.2.6(8)."
17732 Information on those subjects is not yet available.
17738 "Information regarding bounded errors and erroneous
17739 execution. See H.2(1)."
17742 Information on this subject is not yet available.
17748 "Implementation-defined aspects of pragma
17749 @code{Inspection_Point}. See H.3.2(8)."
17752 Pragma @code{Inspection_Point} ensures that the variable is live and can
17753 be examined by the debugger at the inspection point.
17759 "Implementation-defined aspects of pragma
17760 @code{Restrictions}. See H.4(25)."
17763 There are no implementation-defined aspects of pragma @code{Restrictions}. The
17764 use of pragma @code{Restrictions [No_Exceptions]} has no effect on the
17765 generated code. Checks must suppressed by use of pragma @code{Suppress}.
17771 "Any restrictions on pragma @code{Restrictions}. See
17775 There are no restrictions on pragma @code{Restrictions}.
17777 @node Intrinsic Subprograms,Representation Clauses and Pragmas,Implementation Defined Characteristics,Top
17778 @anchor{gnat_rm/intrinsic_subprograms doc}@anchor{251}@anchor{gnat_rm/intrinsic_subprograms intrinsic-subprograms}@anchor{c}@anchor{gnat_rm/intrinsic_subprograms id1}@anchor{252}
17779 @chapter Intrinsic Subprograms
17782 @geindex Intrinsic Subprograms
17784 GNAT allows a user application program to write the declaration:
17787 pragma Import (Intrinsic, name);
17790 providing that the name corresponds to one of the implemented intrinsic
17791 subprograms in GNAT, and that the parameter profile of the referenced
17792 subprogram meets the requirements. This chapter describes the set of
17793 implemented intrinsic subprograms, and the requirements on parameter profiles.
17794 Note that no body is supplied; as with other uses of pragma Import, the
17795 body is supplied elsewhere (in this case by the compiler itself). Note
17796 that any use of this feature is potentially non-portable, since the
17797 Ada standard does not require Ada compilers to implement this feature.
17800 * Intrinsic Operators::
17801 * Compilation_ISO_Date::
17802 * Compilation_Date::
17803 * Compilation_Time::
17804 * Enclosing_Entity::
17805 * Exception_Information::
17806 * Exception_Message::
17810 * Shifts and Rotates::
17811 * Source_Location::
17815 @node Intrinsic Operators,Compilation_ISO_Date,,Intrinsic Subprograms
17816 @anchor{gnat_rm/intrinsic_subprograms id2}@anchor{253}@anchor{gnat_rm/intrinsic_subprograms intrinsic-operators}@anchor{254}
17817 @section Intrinsic Operators
17820 @geindex Intrinsic operator
17822 All the predefined numeric operators in package Standard
17823 in @code{pragma Import (Intrinsic,..)}
17824 declarations. In the binary operator case, the operands must have the same
17825 size. The operand or operands must also be appropriate for
17826 the operator. For example, for addition, the operands must
17827 both be floating-point or both be fixed-point, and the
17828 right operand for @code{"**"} must have a root type of
17829 @code{Standard.Integer'Base}.
17830 You can use an intrinsic operator declaration as in the following example:
17833 type Int1 is new Integer;
17834 type Int2 is new Integer;
17836 function "+" (X1 : Int1; X2 : Int2) return Int1;
17837 function "+" (X1 : Int1; X2 : Int2) return Int2;
17838 pragma Import (Intrinsic, "+");
17841 This declaration would permit 'mixed mode' arithmetic on items
17842 of the differing types @code{Int1} and @code{Int2}.
17843 It is also possible to specify such operators for private types, if the
17844 full views are appropriate arithmetic types.
17846 @node Compilation_ISO_Date,Compilation_Date,Intrinsic Operators,Intrinsic Subprograms
17847 @anchor{gnat_rm/intrinsic_subprograms id3}@anchor{255}@anchor{gnat_rm/intrinsic_subprograms compilation-iso-date}@anchor{256}
17848 @section Compilation_ISO_Date
17851 @geindex Compilation_ISO_Date
17853 This intrinsic subprogram is used in the implementation of the
17854 library package @code{GNAT.Source_Info}. The only useful use of the
17855 intrinsic import in this case is the one in this unit, so an
17856 application program should simply call the function
17857 @code{GNAT.Source_Info.Compilation_ISO_Date} to obtain the date of
17858 the current compilation (in local time format YYYY-MM-DD).
17860 @node Compilation_Date,Compilation_Time,Compilation_ISO_Date,Intrinsic Subprograms
17861 @anchor{gnat_rm/intrinsic_subprograms compilation-date}@anchor{257}@anchor{gnat_rm/intrinsic_subprograms id4}@anchor{258}
17862 @section Compilation_Date
17865 @geindex Compilation_Date
17867 Same as Compilation_ISO_Date, except the string is in the form
17870 @node Compilation_Time,Enclosing_Entity,Compilation_Date,Intrinsic Subprograms
17871 @anchor{gnat_rm/intrinsic_subprograms compilation-time}@anchor{259}@anchor{gnat_rm/intrinsic_subprograms id5}@anchor{25a}
17872 @section Compilation_Time
17875 @geindex Compilation_Time
17877 This intrinsic subprogram is used in the implementation of the
17878 library package @code{GNAT.Source_Info}. The only useful use of the
17879 intrinsic import in this case is the one in this unit, so an
17880 application program should simply call the function
17881 @code{GNAT.Source_Info.Compilation_Time} to obtain the time of
17882 the current compilation (in local time format HH:MM:SS).
17884 @node Enclosing_Entity,Exception_Information,Compilation_Time,Intrinsic Subprograms
17885 @anchor{gnat_rm/intrinsic_subprograms id6}@anchor{25b}@anchor{gnat_rm/intrinsic_subprograms enclosing-entity}@anchor{25c}
17886 @section Enclosing_Entity
17889 @geindex Enclosing_Entity
17891 This intrinsic subprogram is used in the implementation of the
17892 library package @code{GNAT.Source_Info}. The only useful use of the
17893 intrinsic import in this case is the one in this unit, so an
17894 application program should simply call the function
17895 @code{GNAT.Source_Info.Enclosing_Entity} to obtain the name of
17896 the current subprogram, package, task, entry, or protected subprogram.
17898 @node Exception_Information,Exception_Message,Enclosing_Entity,Intrinsic Subprograms
17899 @anchor{gnat_rm/intrinsic_subprograms id7}@anchor{25d}@anchor{gnat_rm/intrinsic_subprograms exception-information}@anchor{25e}
17900 @section Exception_Information
17903 @geindex Exception_Information'
17905 This intrinsic subprogram is used in the implementation of the
17906 library package @code{GNAT.Current_Exception}. The only useful
17907 use of the intrinsic import in this case is the one in this unit,
17908 so an application program should simply call the function
17909 @code{GNAT.Current_Exception.Exception_Information} to obtain
17910 the exception information associated with the current exception.
17912 @node Exception_Message,Exception_Name,Exception_Information,Intrinsic Subprograms
17913 @anchor{gnat_rm/intrinsic_subprograms exception-message}@anchor{25f}@anchor{gnat_rm/intrinsic_subprograms id8}@anchor{260}
17914 @section Exception_Message
17917 @geindex Exception_Message
17919 This intrinsic subprogram is used in the implementation of the
17920 library package @code{GNAT.Current_Exception}. The only useful
17921 use of the intrinsic import in this case is the one in this unit,
17922 so an application program should simply call the function
17923 @code{GNAT.Current_Exception.Exception_Message} to obtain
17924 the message associated with the current exception.
17926 @node Exception_Name,File,Exception_Message,Intrinsic Subprograms
17927 @anchor{gnat_rm/intrinsic_subprograms exception-name}@anchor{261}@anchor{gnat_rm/intrinsic_subprograms id9}@anchor{262}
17928 @section Exception_Name
17931 @geindex Exception_Name
17933 This intrinsic subprogram is used in the implementation of the
17934 library package @code{GNAT.Current_Exception}. The only useful
17935 use of the intrinsic import in this case is the one in this unit,
17936 so an application program should simply call the function
17937 @code{GNAT.Current_Exception.Exception_Name} to obtain
17938 the name of the current exception.
17940 @node File,Line,Exception_Name,Intrinsic Subprograms
17941 @anchor{gnat_rm/intrinsic_subprograms id10}@anchor{263}@anchor{gnat_rm/intrinsic_subprograms file}@anchor{264}
17947 This intrinsic subprogram is used in the implementation of the
17948 library package @code{GNAT.Source_Info}. The only useful use of the
17949 intrinsic import in this case is the one in this unit, so an
17950 application program should simply call the function
17951 @code{GNAT.Source_Info.File} to obtain the name of the current
17954 @node Line,Shifts and Rotates,File,Intrinsic Subprograms
17955 @anchor{gnat_rm/intrinsic_subprograms id11}@anchor{265}@anchor{gnat_rm/intrinsic_subprograms line}@anchor{266}
17961 This intrinsic subprogram is used in the implementation of the
17962 library package @code{GNAT.Source_Info}. The only useful use of the
17963 intrinsic import in this case is the one in this unit, so an
17964 application program should simply call the function
17965 @code{GNAT.Source_Info.Line} to obtain the number of the current
17968 @node Shifts and Rotates,Source_Location,Line,Intrinsic Subprograms
17969 @anchor{gnat_rm/intrinsic_subprograms shifts-and-rotates}@anchor{267}@anchor{gnat_rm/intrinsic_subprograms id12}@anchor{268}
17970 @section Shifts and Rotates
17973 @geindex Shift_Left
17975 @geindex Shift_Right
17977 @geindex Shift_Right_Arithmetic
17979 @geindex Rotate_Left
17981 @geindex Rotate_Right
17983 In standard Ada, the shift and rotate functions are available only
17984 for the predefined modular types in package @code{Interfaces}. However, in
17985 GNAT it is possible to define these functions for any integer
17986 type (signed or modular), as in this example:
17989 function Shift_Left
17991 Amount : Natural) return T;
17994 The function name must be one of
17995 Shift_Left, Shift_Right, Shift_Right_Arithmetic, Rotate_Left, or
17996 Rotate_Right. T must be an integer type. T'Size must be
17997 8, 16, 32 or 64 bits; if T is modular, the modulus
17998 must be 2**8, 2**16, 2**32 or 2**64.
17999 The result type must be the same as the type of @code{Value}.
18000 The shift amount must be Natural.
18001 The formal parameter names can be anything.
18003 A more convenient way of providing these shift operators is to use
18004 the Provide_Shift_Operators pragma, which provides the function declarations
18005 and corresponding pragma Import's for all five shift functions.
18007 @node Source_Location,,Shifts and Rotates,Intrinsic Subprograms
18008 @anchor{gnat_rm/intrinsic_subprograms source-location}@anchor{269}@anchor{gnat_rm/intrinsic_subprograms id13}@anchor{26a}
18009 @section Source_Location
18012 @geindex Source_Location
18014 This intrinsic subprogram is used in the implementation of the
18015 library routine @code{GNAT.Source_Info}. The only useful use of the
18016 intrinsic import in this case is the one in this unit, so an
18017 application program should simply call the function
18018 @code{GNAT.Source_Info.Source_Location} to obtain the current
18019 source file location.
18021 @node Representation Clauses and Pragmas,Standard Library Routines,Intrinsic Subprograms,Top
18022 @anchor{gnat_rm/representation_clauses_and_pragmas representation-clauses-and-pragmas}@anchor{d}@anchor{gnat_rm/representation_clauses_and_pragmas doc}@anchor{26b}@anchor{gnat_rm/representation_clauses_and_pragmas id1}@anchor{26c}
18023 @chapter Representation Clauses and Pragmas
18026 @geindex Representation Clauses
18028 @geindex Representation Clause
18030 @geindex Representation Pragma
18033 @geindex representation
18035 This section describes the representation clauses accepted by GNAT, and
18036 their effect on the representation of corresponding data objects.
18038 GNAT fully implements Annex C (Systems Programming). This means that all
18039 the implementation advice sections in chapter 13 are fully implemented.
18040 However, these sections only require a minimal level of support for
18041 representation clauses. GNAT provides much more extensive capabilities,
18042 and this section describes the additional capabilities provided.
18045 * Alignment Clauses::
18047 * Storage_Size Clauses::
18048 * Size of Variant Record Objects::
18049 * Biased Representation::
18050 * Value_Size and Object_Size Clauses::
18051 * Component_Size Clauses::
18052 * Bit_Order Clauses::
18053 * Effect of Bit_Order on Byte Ordering::
18054 * Pragma Pack for Arrays::
18055 * Pragma Pack for Records::
18056 * Record Representation Clauses::
18057 * Handling of Records with Holes::
18058 * Enumeration Clauses::
18059 * Address Clauses::
18060 * Use of Address Clauses for Memory-Mapped I/O::
18061 * Effect of Convention on Representation::
18062 * Conventions and Anonymous Access Types::
18063 * Determining the Representations chosen by GNAT::
18067 @node Alignment Clauses,Size Clauses,,Representation Clauses and Pragmas
18068 @anchor{gnat_rm/representation_clauses_and_pragmas id2}@anchor{26d}@anchor{gnat_rm/representation_clauses_and_pragmas alignment-clauses}@anchor{26e}
18069 @section Alignment Clauses
18072 @geindex Alignment Clause
18074 GNAT requires that all alignment clauses specify a power of 2, and all
18075 default alignments are always a power of 2. The default alignment
18076 values are as follows:
18082 @emph{Elementary Types}.
18084 For elementary types, the alignment is the minimum of the actual size of
18085 objects of the type divided by @code{Storage_Unit},
18086 and the maximum alignment supported by the target.
18087 (This maximum alignment is given by the GNAT-specific attribute
18088 @code{Standard'Maximum_Alignment}; see @ref{189,,Attribute Maximum_Alignment}.)
18090 @geindex Maximum_Alignment attribute
18092 For example, for type @code{Long_Float}, the object size is 8 bytes, and the
18093 default alignment will be 8 on any target that supports alignments
18094 this large, but on some targets, the maximum alignment may be smaller
18095 than 8, in which case objects of type @code{Long_Float} will be maximally
18101 For arrays, the alignment is equal to the alignment of the component type
18102 for the normal case where no packing or component size is given. If the
18103 array is packed, and the packing is effective (see separate section on
18104 packed arrays), then the alignment will be either 4, 2, or 1 for long packed
18105 arrays or arrays whose length is not known at compile time, depending on
18106 whether the component size is divisible by 4, 2, or is odd. For short packed
18107 arrays, which are handled internally as modular types, the alignment
18108 will be as described for elementary types, e.g. a packed array of length
18109 31 bits will have an object size of four bytes, and an alignment of 4.
18114 For the normal unpacked case, the alignment of a record is equal to
18115 the maximum alignment of any of its components. For tagged records, this
18116 includes the implicit access type used for the tag. If a pragma @code{Pack}
18117 is used and all components are packable (see separate section on pragma
18118 @code{Pack}), then the resulting alignment is 1, unless the layout of the
18119 record makes it profitable to increase it.
18121 A special case is when:
18127 the size of the record is given explicitly, or a
18128 full record representation clause is given, and
18131 the size of the record is 2, 4, or 8 bytes.
18134 In this case, an alignment is chosen to match the
18135 size of the record. For example, if we have:
18138 type Small is record
18141 for Small'Size use 16;
18144 then the default alignment of the record type @code{Small} is 2, not 1. This
18145 leads to more efficient code when the record is treated as a unit, and also
18146 allows the type to specified as @code{Atomic} on architectures requiring
18150 An alignment clause may specify a larger alignment than the default value
18151 up to some maximum value dependent on the target (obtainable by using the
18152 attribute reference @code{Standard'Maximum_Alignment}). It may also specify
18153 a smaller alignment than the default value for enumeration, integer and
18154 fixed point types, as well as for record types, for example
18161 for V'alignment use 1;
18167 The default alignment for the type @code{V} is 4, as a result of the
18168 Integer field in the record, but it is permissible, as shown, to
18169 override the default alignment of the record with a smaller value.
18174 Note that according to the Ada standard, an alignment clause applies only
18175 to the first named subtype. If additional subtypes are declared, then the
18176 compiler is allowed to choose any alignment it likes, and there is no way
18177 to control this choice. Consider:
18180 type R is range 1 .. 10_000;
18181 for R'Alignment use 1;
18182 subtype RS is R range 1 .. 1000;
18185 The alignment clause specifies an alignment of 1 for the first named subtype
18186 @code{R} but this does not necessarily apply to @code{RS}. When writing
18187 portable Ada code, you should avoid writing code that explicitly or
18188 implicitly relies on the alignment of such subtypes.
18190 For the GNAT compiler, if an explicit alignment clause is given, this
18191 value is also used for any subsequent subtypes. So for GNAT, in the
18192 above example, you can count on the alignment of @code{RS} being 1. But this
18193 assumption is non-portable, and other compilers may choose different
18194 alignments for the subtype @code{RS}.
18196 @node Size Clauses,Storage_Size Clauses,Alignment Clauses,Representation Clauses and Pragmas
18197 @anchor{gnat_rm/representation_clauses_and_pragmas id3}@anchor{26f}@anchor{gnat_rm/representation_clauses_and_pragmas size-clauses}@anchor{270}
18198 @section Size Clauses
18201 @geindex Size Clause
18203 The default size for a type @code{T} is obtainable through the
18204 language-defined attribute @code{T'Size} and also through the
18205 equivalent GNAT-defined attribute @code{T'Value_Size}.
18206 For objects of type @code{T}, GNAT will generally increase the type size
18207 so that the object size (obtainable through the GNAT-defined attribute
18208 @code{T'Object_Size})
18209 is a multiple of @code{T'Alignment * Storage_Unit}.
18214 type Smallint is range 1 .. 6;
18222 In this example, @code{Smallint'Size} = @code{Smallint'Value_Size} = 3,
18223 as specified by the RM rules,
18224 but objects of this type will have a size of 8
18225 (@code{Smallint'Object_Size} = 8),
18226 since objects by default occupy an integral number
18227 of storage units. On some targets, notably older
18228 versions of the Digital Alpha, the size of stand
18229 alone objects of this type may be 32, reflecting
18230 the inability of the hardware to do byte load/stores.
18232 Similarly, the size of type @code{Rec} is 40 bits
18233 (@code{Rec'Size} = @code{Rec'Value_Size} = 40), but
18234 the alignment is 4, so objects of this type will have
18235 their size increased to 64 bits so that it is a multiple
18236 of the alignment (in bits). This decision is
18237 in accordance with the specific Implementation Advice in RM 13.3(43):
18241 "A @code{Size} clause should be supported for an object if the specified
18242 @code{Size} is at least as large as its subtype's @code{Size}, and corresponds
18243 to a size in storage elements that is a multiple of the object's
18244 @code{Alignment} (if the @code{Alignment} is nonzero)."
18247 An explicit size clause may be used to override the default size by
18248 increasing it. For example, if we have:
18251 type My_Boolean is new Boolean;
18252 for My_Boolean'Size use 32;
18255 then values of this type will always be 32 bits long. In the case of
18256 discrete types, the size can be increased up to 64 bits, with the effect
18257 that the entire specified field is used to hold the value, sign- or
18258 zero-extended as appropriate. If more than 64 bits is specified, then
18259 padding space is allocated after the value, and a warning is issued that
18260 there are unused bits.
18262 Similarly the size of records and arrays may be increased, and the effect
18263 is to add padding bits after the value. This also causes a warning message
18266 The largest Size value permitted in GNAT is 2**31-1. Since this is a
18267 Size in bits, this corresponds to an object of size 256 megabytes (minus
18268 one). This limitation is true on all targets. The reason for this
18269 limitation is that it improves the quality of the code in many cases
18270 if it is known that a Size value can be accommodated in an object of
18273 @node Storage_Size Clauses,Size of Variant Record Objects,Size Clauses,Representation Clauses and Pragmas
18274 @anchor{gnat_rm/representation_clauses_and_pragmas storage-size-clauses}@anchor{271}@anchor{gnat_rm/representation_clauses_and_pragmas id4}@anchor{272}
18275 @section Storage_Size Clauses
18278 @geindex Storage_Size Clause
18280 For tasks, the @code{Storage_Size} clause specifies the amount of space
18281 to be allocated for the task stack. This cannot be extended, and if the
18282 stack is exhausted, then @code{Storage_Error} will be raised (if stack
18283 checking is enabled). Use a @code{Storage_Size} attribute definition clause,
18284 or a @code{Storage_Size} pragma in the task definition to set the
18285 appropriate required size. A useful technique is to include in every
18286 task definition a pragma of the form:
18289 pragma Storage_Size (Default_Stack_Size);
18292 Then @code{Default_Stack_Size} can be defined in a global package, and
18293 modified as required. Any tasks requiring stack sizes different from the
18294 default can have an appropriate alternative reference in the pragma.
18296 You can also use the @emph{-d} binder switch to modify the default stack
18299 For access types, the @code{Storage_Size} clause specifies the maximum
18300 space available for allocation of objects of the type. If this space is
18301 exceeded then @code{Storage_Error} will be raised by an allocation attempt.
18302 In the case where the access type is declared local to a subprogram, the
18303 use of a @code{Storage_Size} clause triggers automatic use of a special
18304 predefined storage pool (@code{System.Pool_Size}) that ensures that all
18305 space for the pool is automatically reclaimed on exit from the scope in
18306 which the type is declared.
18308 A special case recognized by the compiler is the specification of a
18309 @code{Storage_Size} of zero for an access type. This means that no
18310 items can be allocated from the pool, and this is recognized at compile
18311 time, and all the overhead normally associated with maintaining a fixed
18312 size storage pool is eliminated. Consider the following example:
18316 type R is array (Natural) of Character;
18317 type P is access all R;
18318 for P'Storage_Size use 0;
18319 -- Above access type intended only for interfacing purposes
18323 procedure g (m : P);
18324 pragma Import (C, g);
18334 As indicated in this example, these dummy storage pools are often useful in
18335 connection with interfacing where no object will ever be allocated. If you
18336 compile the above example, you get the warning:
18339 p.adb:16:09: warning: allocation from empty storage pool
18340 p.adb:16:09: warning: Storage_Error will be raised at run time
18343 Of course in practice, there will not be any explicit allocators in the
18344 case of such an access declaration.
18346 @node Size of Variant Record Objects,Biased Representation,Storage_Size Clauses,Representation Clauses and Pragmas
18347 @anchor{gnat_rm/representation_clauses_and_pragmas id5}@anchor{273}@anchor{gnat_rm/representation_clauses_and_pragmas size-of-variant-record-objects}@anchor{274}
18348 @section Size of Variant Record Objects
18352 @geindex variant record objects
18354 @geindex Variant record objects
18357 In the case of variant record objects, there is a question whether Size gives
18358 information about a particular variant, or the maximum size required
18359 for any variant. Consider the following program
18362 with Text_IO; use Text_IO;
18364 type R1 (A : Boolean := False) is record
18366 when True => X : Character;
18367 when False => null;
18375 Put_Line (Integer'Image (V1'Size));
18376 Put_Line (Integer'Image (V2'Size));
18380 Here we are dealing with a variant record, where the True variant
18381 requires 16 bits, and the False variant requires 8 bits.
18382 In the above example, both V1 and V2 contain the False variant,
18383 which is only 8 bits long. However, the result of running the
18391 The reason for the difference here is that the discriminant value of
18392 V1 is fixed, and will always be False. It is not possible to assign
18393 a True variant value to V1, therefore 8 bits is sufficient. On the
18394 other hand, in the case of V2, the initial discriminant value is
18395 False (from the default), but it is possible to assign a True
18396 variant value to V2, therefore 16 bits must be allocated for V2
18397 in the general case, even fewer bits may be needed at any particular
18398 point during the program execution.
18400 As can be seen from the output of this program, the @code{'Size}
18401 attribute applied to such an object in GNAT gives the actual allocated
18402 size of the variable, which is the largest size of any of the variants.
18403 The Ada Reference Manual is not completely clear on what choice should
18404 be made here, but the GNAT behavior seems most consistent with the
18405 language in the RM.
18407 In some cases, it may be desirable to obtain the size of the current
18408 variant, rather than the size of the largest variant. This can be
18409 achieved in GNAT by making use of the fact that in the case of a
18410 subprogram parameter, GNAT does indeed return the size of the current
18411 variant (because a subprogram has no way of knowing how much space
18412 is actually allocated for the actual).
18414 Consider the following modified version of the above program:
18417 with Text_IO; use Text_IO;
18419 type R1 (A : Boolean := False) is record
18421 when True => X : Character;
18422 when False => null;
18428 function Size (V : R1) return Integer is
18434 Put_Line (Integer'Image (V2'Size));
18435 Put_Line (Integer'Image (Size (V2)));
18437 Put_Line (Integer'Image (V2'Size));
18438 Put_Line (Integer'Image (Size (V2)));
18442 The output from this program is
18451 Here we see that while the @code{'Size} attribute always returns
18452 the maximum size, regardless of the current variant value, the
18453 @code{Size} function does indeed return the size of the current
18456 @node Biased Representation,Value_Size and Object_Size Clauses,Size of Variant Record Objects,Representation Clauses and Pragmas
18457 @anchor{gnat_rm/representation_clauses_and_pragmas id6}@anchor{275}@anchor{gnat_rm/representation_clauses_and_pragmas biased-representation}@anchor{276}
18458 @section Biased Representation
18461 @geindex Size for biased representation
18463 @geindex Biased representation
18465 In the case of scalars with a range starting at other than zero, it is
18466 possible in some cases to specify a size smaller than the default minimum
18467 value, and in such cases, GNAT uses an unsigned biased representation,
18468 in which zero is used to represent the lower bound, and successive values
18469 represent successive values of the type.
18471 For example, suppose we have the declaration:
18474 type Small is range -7 .. -4;
18475 for Small'Size use 2;
18478 Although the default size of type @code{Small} is 4, the @code{Size}
18479 clause is accepted by GNAT and results in the following representation
18483 -7 is represented as 2#00#
18484 -6 is represented as 2#01#
18485 -5 is represented as 2#10#
18486 -4 is represented as 2#11#
18489 Biased representation is only used if the specified @code{Size} clause
18490 cannot be accepted in any other manner. These reduced sizes that force
18491 biased representation can be used for all discrete types except for
18492 enumeration types for which a representation clause is given.
18494 @node Value_Size and Object_Size Clauses,Component_Size Clauses,Biased Representation,Representation Clauses and Pragmas
18495 @anchor{gnat_rm/representation_clauses_and_pragmas id7}@anchor{277}@anchor{gnat_rm/representation_clauses_and_pragmas value-size-and-object-size-clauses}@anchor{278}
18496 @section Value_Size and Object_Size Clauses
18499 @geindex Value_Size
18501 @geindex Object_Size
18504 @geindex of objects
18506 In Ada 95 and Ada 2005, @code{T'Size} for a type @code{T} is the minimum
18507 number of bits required to hold values of type @code{T}.
18508 Although this interpretation was allowed in Ada 83, it was not required,
18509 and this requirement in practice can cause some significant difficulties.
18510 For example, in most Ada 83 compilers, @code{Natural'Size} was 32.
18511 However, in Ada 95 and Ada 2005,
18512 @code{Natural'Size} is
18513 typically 31. This means that code may change in behavior when moving
18514 from Ada 83 to Ada 95 or Ada 2005. For example, consider:
18517 type Rec is record;
18523 at 0 range 0 .. Natural'Size - 1;
18524 at 0 range Natural'Size .. 2 * Natural'Size - 1;
18528 In the above code, since the typical size of @code{Natural} objects
18529 is 32 bits and @code{Natural'Size} is 31, the above code can cause
18530 unexpected inefficient packing in Ada 95 and Ada 2005, and in general
18531 there are cases where the fact that the object size can exceed the
18532 size of the type causes surprises.
18534 To help get around this problem GNAT provides two implementation
18535 defined attributes, @code{Value_Size} and @code{Object_Size}. When
18536 applied to a type, these attributes yield the size of the type
18537 (corresponding to the RM defined size attribute), and the size of
18538 objects of the type respectively.
18540 The @code{Object_Size} is used for determining the default size of
18541 objects and components. This size value can be referred to using the
18542 @code{Object_Size} attribute. The phrase 'is used' here means that it is
18543 the basis of the determination of the size. The backend is free to
18544 pad this up if necessary for efficiency, e.g., an 8-bit stand-alone
18545 character might be stored in 32 bits on a machine with no efficient
18546 byte access instructions such as the Alpha.
18548 The default rules for the value of @code{Object_Size} for
18549 discrete types are as follows:
18555 The @code{Object_Size} for base subtypes reflect the natural hardware
18556 size in bits (run the compiler with @emph{-gnatS} to find those values
18557 for numeric types). Enumeration types and fixed-point base subtypes have
18558 8, 16, 32, or 64 bits for this size, depending on the range of values
18562 The @code{Object_Size} of a subtype is the same as the
18563 @code{Object_Size} of
18564 the type from which it is obtained.
18567 The @code{Object_Size} of a derived base type is copied from the parent
18568 base type, and the @code{Object_Size} of a derived first subtype is copied
18569 from the parent first subtype.
18572 The @code{Value_Size} attribute
18573 is the (minimum) number of bits required to store a value
18575 This value is used to determine how tightly to pack
18576 records or arrays with components of this type, and also affects
18577 the semantics of unchecked conversion (unchecked conversions where
18578 the @code{Value_Size} values differ generate a warning, and are potentially
18581 The default rules for the value of @code{Value_Size} are as follows:
18587 The @code{Value_Size} for a base subtype is the minimum number of bits
18588 required to store all values of the type (including the sign bit
18589 only if negative values are possible).
18592 If a subtype statically matches the first subtype of a given type, then it has
18593 by default the same @code{Value_Size} as the first subtype. This is a
18594 consequence of RM 13.1(14): "if two subtypes statically match,
18595 then their subtype-specific aspects are the same".)
18598 All other subtypes have a @code{Value_Size} corresponding to the minimum
18599 number of bits required to store all values of the subtype. For
18600 dynamic bounds, it is assumed that the value can range down or up
18601 to the corresponding bound of the ancestor
18604 The RM defined attribute @code{Size} corresponds to the
18605 @code{Value_Size} attribute.
18607 The @code{Size} attribute may be defined for a first-named subtype. This sets
18608 the @code{Value_Size} of
18609 the first-named subtype to the given value, and the
18610 @code{Object_Size} of this first-named subtype to the given value padded up
18611 to an appropriate boundary. It is a consequence of the default rules
18612 above that this @code{Object_Size} will apply to all further subtypes. On the
18613 other hand, @code{Value_Size} is affected only for the first subtype, any
18614 dynamic subtypes obtained from it directly, and any statically matching
18615 subtypes. The @code{Value_Size} of any other static subtypes is not affected.
18617 @code{Value_Size} and
18618 @code{Object_Size} may be explicitly set for any subtype using
18619 an attribute definition clause. Note that the use of these attributes
18620 can cause the RM 13.1(14) rule to be violated. If two access types
18621 reference aliased objects whose subtypes have differing @code{Object_Size}
18622 values as a result of explicit attribute definition clauses, then it
18623 is illegal to convert from one access subtype to the other. For a more
18624 complete description of this additional legality rule, see the
18625 description of the @code{Object_Size} attribute.
18627 To get a feel for the difference, consider the following examples (note
18628 that in each case the base is @code{Short_Short_Integer} with a size of 8):
18631 @multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxx}
18634 Type or subtype declaration
18646 @code{type x1 is range 0 .. 5;}
18658 @code{type x2 is range 0 .. 5;}
18659 @code{for x2'size use 12;}
18671 @code{subtype x3 is x2 range 0 .. 3;}
18683 @code{subtype x4 is x2'base range 0 .. 10;}
18695 @code{dynamic : x2'Base range -64 .. +63;}
18703 @code{subtype x5 is x2 range 0 .. dynamic;}
18715 @code{subtype x6 is x2'base range 0 .. dynamic;}
18728 Note: the entries marked '*' are not actually specified by the Ada
18729 Reference Manual, which has nothing to say about size in the dynamic
18730 case. What GNAT does is to allocate sufficient bits to accomodate any
18731 possible dynamic values for the bounds at run-time.
18733 So far, so good, but GNAT has to obey the RM rules, so the question is
18734 under what conditions must the RM @code{Size} be used.
18735 The following is a list
18736 of the occasions on which the RM @code{Size} must be used:
18742 Component size for packed arrays or records
18745 Value of the attribute @code{Size} for a type
18748 Warning about sizes not matching for unchecked conversion
18751 For record types, the @code{Object_Size} is always a multiple of the
18752 alignment of the type (this is true for all types). In some cases the
18753 @code{Value_Size} can be smaller. Consider:
18762 On a typical 32-bit architecture, the X component will be four bytes, and
18763 require four-byte alignment, and the Y component will be one byte. In this
18764 case @code{R'Value_Size} will be 40 (bits) since this is the minimum size
18765 required to store a value of this type, and for example, it is permissible
18766 to have a component of type R in an outer array whose component size is
18767 specified to be 48 bits. However, @code{R'Object_Size} will be 64 (bits),
18768 since it must be rounded up so that this value is a multiple of the
18769 alignment (4 bytes = 32 bits).
18771 For all other types, the @code{Object_Size}
18772 and @code{Value_Size} are the same (and equivalent to the RM attribute @code{Size}).
18773 Only @code{Size} may be specified for such types.
18775 Note that @code{Value_Size} can be used to force biased representation
18776 for a particular subtype. Consider this example:
18779 type R is (A, B, C, D, E, F);
18780 subtype RAB is R range A .. B;
18781 subtype REF is R range E .. F;
18784 By default, @code{RAB}
18785 has a size of 1 (sufficient to accommodate the representation
18786 of @code{A} and @code{B}, 0 and 1), and @code{REF}
18787 has a size of 3 (sufficient to accommodate the representation
18788 of @code{E} and @code{F}, 4 and 5). But if we add the
18789 following @code{Value_Size} attribute definition clause:
18792 for REF'Value_Size use 1;
18795 then biased representation is forced for @code{REF},
18796 and 0 will represent @code{E} and 1 will represent @code{F}.
18797 A warning is issued when a @code{Value_Size} attribute
18798 definition clause forces biased representation. This
18799 warning can be turned off using @code{-gnatw.B}.
18801 @node Component_Size Clauses,Bit_Order Clauses,Value_Size and Object_Size Clauses,Representation Clauses and Pragmas
18802 @anchor{gnat_rm/representation_clauses_and_pragmas id8}@anchor{279}@anchor{gnat_rm/representation_clauses_and_pragmas component-size-clauses}@anchor{27a}
18803 @section Component_Size Clauses
18806 @geindex Component_Size Clause
18808 Normally, the value specified in a component size clause must be consistent
18809 with the subtype of the array component with regard to size and alignment.
18810 In other words, the value specified must be at least equal to the size
18811 of this subtype, and must be a multiple of the alignment value.
18813 In addition, component size clauses are allowed which cause the array
18814 to be packed, by specifying a smaller value. A first case is for
18815 component size values in the range 1 through 63. The value specified
18816 must not be smaller than the Size of the subtype. GNAT will accurately
18817 honor all packing requests in this range. For example, if we have:
18820 type r is array (1 .. 8) of Natural;
18821 for r'Component_Size use 31;
18824 then the resulting array has a length of 31 bytes (248 bits = 8 * 31).
18825 Of course access to the components of such an array is considerably
18826 less efficient than if the natural component size of 32 is used.
18827 A second case is when the subtype of the component is a record type
18828 padded because of its default alignment. For example, if we have:
18837 type a is array (1 .. 8) of r;
18838 for a'Component_Size use 72;
18841 then the resulting array has a length of 72 bytes, instead of 96 bytes
18842 if the alignment of the record (4) was obeyed.
18844 Note that there is no point in giving both a component size clause
18845 and a pragma Pack for the same array type. if such duplicate
18846 clauses are given, the pragma Pack will be ignored.
18848 @node Bit_Order Clauses,Effect of Bit_Order on Byte Ordering,Component_Size Clauses,Representation Clauses and Pragmas
18849 @anchor{gnat_rm/representation_clauses_and_pragmas bit-order-clauses}@anchor{27b}@anchor{gnat_rm/representation_clauses_and_pragmas id9}@anchor{27c}
18850 @section Bit_Order Clauses
18853 @geindex Bit_Order Clause
18855 @geindex bit ordering
18860 For record subtypes, GNAT permits the specification of the @code{Bit_Order}
18861 attribute. The specification may either correspond to the default bit
18862 order for the target, in which case the specification has no effect and
18863 places no additional restrictions, or it may be for the non-standard
18864 setting (that is the opposite of the default).
18866 In the case where the non-standard value is specified, the effect is
18867 to renumber bits within each byte, but the ordering of bytes is not
18868 affected. There are certain
18869 restrictions placed on component clauses as follows:
18875 Components fitting within a single storage unit.
18877 These are unrestricted, and the effect is merely to renumber bits. For
18878 example if we are on a little-endian machine with @code{Low_Order_First}
18879 being the default, then the following two declarations have exactly
18885 B : Integer range 1 .. 120;
18889 A at 0 range 0 .. 0;
18890 B at 0 range 1 .. 7;
18895 B : Integer range 1 .. 120;
18898 for R2'Bit_Order use High_Order_First;
18901 A at 0 range 7 .. 7;
18902 B at 0 range 0 .. 6;
18906 The useful application here is to write the second declaration with the
18907 @code{Bit_Order} attribute definition clause, and know that it will be treated
18908 the same, regardless of whether the target is little-endian or big-endian.
18911 Components occupying an integral number of bytes.
18913 These are components that exactly fit in two or more bytes. Such component
18914 declarations are allowed, but have no effect, since it is important to realize
18915 that the @code{Bit_Order} specification does not affect the ordering of bytes.
18916 In particular, the following attempt at getting an endian-independent integer
18924 for R2'Bit_Order use High_Order_First;
18927 A at 0 range 0 .. 31;
18931 This declaration will result in a little-endian integer on a
18932 little-endian machine, and a big-endian integer on a big-endian machine.
18933 If byte flipping is required for interoperability between big- and
18934 little-endian machines, this must be explicitly programmed. This capability
18935 is not provided by @code{Bit_Order}.
18938 Components that are positioned across byte boundaries.
18940 but do not occupy an integral number of bytes. Given that bytes are not
18941 reordered, such fields would occupy a non-contiguous sequence of bits
18942 in memory, requiring non-trivial code to reassemble. They are for this
18943 reason not permitted, and any component clause specifying such a layout
18944 will be flagged as illegal by GNAT.
18947 Since the misconception that Bit_Order automatically deals with all
18948 endian-related incompatibilities is a common one, the specification of
18949 a component field that is an integral number of bytes will always
18950 generate a warning. This warning may be suppressed using @code{pragma Warnings (Off)}
18951 if desired. The following section contains additional
18952 details regarding the issue of byte ordering.
18954 @node Effect of Bit_Order on Byte Ordering,Pragma Pack for Arrays,Bit_Order Clauses,Representation Clauses and Pragmas
18955 @anchor{gnat_rm/representation_clauses_and_pragmas id10}@anchor{27d}@anchor{gnat_rm/representation_clauses_and_pragmas effect-of-bit-order-on-byte-ordering}@anchor{27e}
18956 @section Effect of Bit_Order on Byte Ordering
18959 @geindex byte ordering
18964 In this section we will review the effect of the @code{Bit_Order} attribute
18965 definition clause on byte ordering. Briefly, it has no effect at all, but
18966 a detailed example will be helpful. Before giving this
18967 example, let us review the precise
18968 definition of the effect of defining @code{Bit_Order}. The effect of a
18969 non-standard bit order is described in section 13.5.3 of the Ada
18974 "2 A bit ordering is a method of interpreting the meaning of
18975 the storage place attributes."
18978 To understand the precise definition of storage place attributes in
18979 this context, we visit section 13.5.1 of the manual:
18983 "13 A record_representation_clause (without the mod_clause)
18984 specifies the layout. The storage place attributes (see 13.5.2)
18985 are taken from the values of the position, first_bit, and last_bit
18986 expressions after normalizing those values so that first_bit is
18987 less than Storage_Unit."
18990 The critical point here is that storage places are taken from
18991 the values after normalization, not before. So the @code{Bit_Order}
18992 interpretation applies to normalized values. The interpretation
18993 is described in the later part of the 13.5.3 paragraph:
18997 "2 A bit ordering is a method of interpreting the meaning of
18998 the storage place attributes. High_Order_First (known in the
18999 vernacular as 'big endian') means that the first bit of a
19000 storage element (bit 0) is the most significant bit (interpreting
19001 the sequence of bits that represent a component as an unsigned
19002 integer value). Low_Order_First (known in the vernacular as
19003 'little endian') means the opposite: the first bit is the
19004 least significant."
19007 Note that the numbering is with respect to the bits of a storage
19008 unit. In other words, the specification affects only the numbering
19009 of bits within a single storage unit.
19011 We can make the effect clearer by giving an example.
19013 Suppose that we have an external device which presents two bytes, the first
19014 byte presented, which is the first (low addressed byte) of the two byte
19015 record is called Master, and the second byte is called Slave.
19017 The left most (most significant bit is called Control for each byte, and
19018 the remaining 7 bits are called V1, V2, ... V7, where V7 is the rightmost
19019 (least significant) bit.
19021 On a big-endian machine, we can write the following representation clause
19024 type Data is record
19025 Master_Control : Bit;
19033 Slave_Control : Bit;
19043 for Data use record
19044 Master_Control at 0 range 0 .. 0;
19045 Master_V1 at 0 range 1 .. 1;
19046 Master_V2 at 0 range 2 .. 2;
19047 Master_V3 at 0 range 3 .. 3;
19048 Master_V4 at 0 range 4 .. 4;
19049 Master_V5 at 0 range 5 .. 5;
19050 Master_V6 at 0 range 6 .. 6;
19051 Master_V7 at 0 range 7 .. 7;
19052 Slave_Control at 1 range 0 .. 0;
19053 Slave_V1 at 1 range 1 .. 1;
19054 Slave_V2 at 1 range 2 .. 2;
19055 Slave_V3 at 1 range 3 .. 3;
19056 Slave_V4 at 1 range 4 .. 4;
19057 Slave_V5 at 1 range 5 .. 5;
19058 Slave_V6 at 1 range 6 .. 6;
19059 Slave_V7 at 1 range 7 .. 7;
19063 Now if we move this to a little endian machine, then the bit ordering within
19064 the byte is backwards, so we have to rewrite the record rep clause as:
19067 for Data use record
19068 Master_Control at 0 range 7 .. 7;
19069 Master_V1 at 0 range 6 .. 6;
19070 Master_V2 at 0 range 5 .. 5;
19071 Master_V3 at 0 range 4 .. 4;
19072 Master_V4 at 0 range 3 .. 3;
19073 Master_V5 at 0 range 2 .. 2;
19074 Master_V6 at 0 range 1 .. 1;
19075 Master_V7 at 0 range 0 .. 0;
19076 Slave_Control at 1 range 7 .. 7;
19077 Slave_V1 at 1 range 6 .. 6;
19078 Slave_V2 at 1 range 5 .. 5;
19079 Slave_V3 at 1 range 4 .. 4;
19080 Slave_V4 at 1 range 3 .. 3;
19081 Slave_V5 at 1 range 2 .. 2;
19082 Slave_V6 at 1 range 1 .. 1;
19083 Slave_V7 at 1 range 0 .. 0;
19087 It is a nuisance to have to rewrite the clause, especially if
19088 the code has to be maintained on both machines. However,
19089 this is a case that we can handle with the
19090 @code{Bit_Order} attribute if it is implemented.
19091 Note that the implementation is not required on byte addressed
19092 machines, but it is indeed implemented in GNAT.
19093 This means that we can simply use the
19094 first record clause, together with the declaration
19097 for Data'Bit_Order use High_Order_First;
19100 and the effect is what is desired, namely the layout is exactly the same,
19101 independent of whether the code is compiled on a big-endian or little-endian
19104 The important point to understand is that byte ordering is not affected.
19105 A @code{Bit_Order} attribute definition never affects which byte a field
19106 ends up in, only where it ends up in that byte.
19107 To make this clear, let us rewrite the record rep clause of the previous
19111 for Data'Bit_Order use High_Order_First;
19112 for Data use record
19113 Master_Control at 0 range 0 .. 0;
19114 Master_V1 at 0 range 1 .. 1;
19115 Master_V2 at 0 range 2 .. 2;
19116 Master_V3 at 0 range 3 .. 3;
19117 Master_V4 at 0 range 4 .. 4;
19118 Master_V5 at 0 range 5 .. 5;
19119 Master_V6 at 0 range 6 .. 6;
19120 Master_V7 at 0 range 7 .. 7;
19121 Slave_Control at 0 range 8 .. 8;
19122 Slave_V1 at 0 range 9 .. 9;
19123 Slave_V2 at 0 range 10 .. 10;
19124 Slave_V3 at 0 range 11 .. 11;
19125 Slave_V4 at 0 range 12 .. 12;
19126 Slave_V5 at 0 range 13 .. 13;
19127 Slave_V6 at 0 range 14 .. 14;
19128 Slave_V7 at 0 range 15 .. 15;
19132 This is exactly equivalent to saying (a repeat of the first example):
19135 for Data'Bit_Order use High_Order_First;
19136 for Data use record
19137 Master_Control at 0 range 0 .. 0;
19138 Master_V1 at 0 range 1 .. 1;
19139 Master_V2 at 0 range 2 .. 2;
19140 Master_V3 at 0 range 3 .. 3;
19141 Master_V4 at 0 range 4 .. 4;
19142 Master_V5 at 0 range 5 .. 5;
19143 Master_V6 at 0 range 6 .. 6;
19144 Master_V7 at 0 range 7 .. 7;
19145 Slave_Control at 1 range 0 .. 0;
19146 Slave_V1 at 1 range 1 .. 1;
19147 Slave_V2 at 1 range 2 .. 2;
19148 Slave_V3 at 1 range 3 .. 3;
19149 Slave_V4 at 1 range 4 .. 4;
19150 Slave_V5 at 1 range 5 .. 5;
19151 Slave_V6 at 1 range 6 .. 6;
19152 Slave_V7 at 1 range 7 .. 7;
19156 Why are they equivalent? Well take a specific field, the @code{Slave_V2}
19157 field. The storage place attributes are obtained by normalizing the
19158 values given so that the @code{First_Bit} value is less than 8. After
19159 normalizing the values (0,10,10) we get (1,2,2) which is exactly what
19160 we specified in the other case.
19162 Now one might expect that the @code{Bit_Order} attribute might affect
19163 bit numbering within the entire record component (two bytes in this
19164 case, thus affecting which byte fields end up in), but that is not
19165 the way this feature is defined, it only affects numbering of bits,
19166 not which byte they end up in.
19168 Consequently it never makes sense to specify a starting bit number
19169 greater than 7 (for a byte addressable field) if an attribute
19170 definition for @code{Bit_Order} has been given, and indeed it
19171 may be actively confusing to specify such a value, so the compiler
19172 generates a warning for such usage.
19174 If you do need to control byte ordering then appropriate conditional
19175 values must be used. If in our example, the slave byte came first on
19176 some machines we might write:
19179 Master_Byte_First constant Boolean := ...;
19181 Master_Byte : constant Natural :=
19182 1 - Boolean'Pos (Master_Byte_First);
19183 Slave_Byte : constant Natural :=
19184 Boolean'Pos (Master_Byte_First);
19186 for Data'Bit_Order use High_Order_First;
19187 for Data use record
19188 Master_Control at Master_Byte range 0 .. 0;
19189 Master_V1 at Master_Byte range 1 .. 1;
19190 Master_V2 at Master_Byte range 2 .. 2;
19191 Master_V3 at Master_Byte range 3 .. 3;
19192 Master_V4 at Master_Byte range 4 .. 4;
19193 Master_V5 at Master_Byte range 5 .. 5;
19194 Master_V6 at Master_Byte range 6 .. 6;
19195 Master_V7 at Master_Byte range 7 .. 7;
19196 Slave_Control at Slave_Byte range 0 .. 0;
19197 Slave_V1 at Slave_Byte range 1 .. 1;
19198 Slave_V2 at Slave_Byte range 2 .. 2;
19199 Slave_V3 at Slave_Byte range 3 .. 3;
19200 Slave_V4 at Slave_Byte range 4 .. 4;
19201 Slave_V5 at Slave_Byte range 5 .. 5;
19202 Slave_V6 at Slave_Byte range 6 .. 6;
19203 Slave_V7 at Slave_Byte range 7 .. 7;
19207 Now to switch between machines, all that is necessary is
19208 to set the boolean constant @code{Master_Byte_First} in
19209 an appropriate manner.
19211 @node Pragma Pack for Arrays,Pragma Pack for Records,Effect of Bit_Order on Byte Ordering,Representation Clauses and Pragmas
19212 @anchor{gnat_rm/representation_clauses_and_pragmas pragma-pack-for-arrays}@anchor{27f}@anchor{gnat_rm/representation_clauses_and_pragmas id11}@anchor{280}
19213 @section Pragma Pack for Arrays
19216 @geindex Pragma Pack (for arrays)
19218 Pragma @code{Pack} applied to an array has an effect that depends upon whether the
19219 component type is @emph{packable}. For a component type to be @emph{packable}, it must
19220 be one of the following cases:
19226 Any elementary type.
19229 Any small packed array type with a static size.
19232 Any small simple record type with a static size.
19235 For all these cases, if the component subtype size is in the range
19236 1 through 64, then the effect of the pragma @code{Pack} is exactly as though a
19237 component size were specified giving the component subtype size.
19239 All other types are non-packable, they occupy an integral number of storage
19240 units and the only effect of pragma Pack is to remove alignment gaps.
19242 For example if we have:
19245 type r is range 0 .. 17;
19247 type ar is array (1 .. 8) of r;
19251 Then the component size of @code{ar} will be set to 5 (i.e., to @code{r'size},
19252 and the size of the array @code{ar} will be exactly 40 bits).
19254 Note that in some cases this rather fierce approach to packing can produce
19255 unexpected effects. For example, in Ada 95 and Ada 2005,
19256 subtype @code{Natural} typically has a size of 31, meaning that if you
19257 pack an array of @code{Natural}, you get 31-bit
19258 close packing, which saves a few bits, but results in far less efficient
19259 access. Since many other Ada compilers will ignore such a packing request,
19260 GNAT will generate a warning on some uses of pragma @code{Pack} that it guesses
19261 might not be what is intended. You can easily remove this warning by
19262 using an explicit @code{Component_Size} setting instead, which never generates
19263 a warning, since the intention of the programmer is clear in this case.
19265 GNAT treats packed arrays in one of two ways. If the size of the array is
19266 known at compile time and is less than 64 bits, then internally the array
19267 is represented as a single modular type, of exactly the appropriate number
19268 of bits. If the length is greater than 63 bits, or is not known at compile
19269 time, then the packed array is represented as an array of bytes, and the
19270 length is always a multiple of 8 bits.
19272 Note that to represent a packed array as a modular type, the alignment must
19273 be suitable for the modular type involved. For example, on typical machines
19274 a 32-bit packed array will be represented by a 32-bit modular integer with
19275 an alignment of four bytes. If you explicitly override the default alignment
19276 with an alignment clause that is too small, the modular representation
19277 cannot be used. For example, consider the following set of declarations:
19280 type R is range 1 .. 3;
19281 type S is array (1 .. 31) of R;
19282 for S'Component_Size use 2;
19284 for S'Alignment use 1;
19287 If the alignment clause were not present, then a 62-bit modular
19288 representation would be chosen (typically with an alignment of 4 or 8
19289 bytes depending on the target). But the default alignment is overridden
19290 with the explicit alignment clause. This means that the modular
19291 representation cannot be used, and instead the array of bytes
19292 representation must be used, meaning that the length must be a multiple
19293 of 8. Thus the above set of declarations will result in a diagnostic
19294 rejecting the size clause and noting that the minimum size allowed is 64.
19296 @geindex Pragma Pack (for type Natural)
19298 @geindex Pragma Pack warning
19300 One special case that is worth noting occurs when the base type of the
19301 component size is 8/16/32 and the subtype is one bit less. Notably this
19302 occurs with subtype @code{Natural}. Consider:
19305 type Arr is array (1 .. 32) of Natural;
19309 In all commonly used Ada 83 compilers, this pragma Pack would be ignored,
19310 since typically @code{Natural'Size} is 32 in Ada 83, and in any case most
19311 Ada 83 compilers did not attempt 31 bit packing.
19313 In Ada 95 and Ada 2005, @code{Natural'Size} is required to be 31. Furthermore,
19314 GNAT really does pack 31-bit subtype to 31 bits. This may result in a
19315 substantial unintended performance penalty when porting legacy Ada 83 code.
19316 To help prevent this, GNAT generates a warning in such cases. If you really
19317 want 31 bit packing in a case like this, you can set the component size
19321 type Arr is array (1 .. 32) of Natural;
19322 for Arr'Component_Size use 31;
19325 Here 31-bit packing is achieved as required, and no warning is generated,
19326 since in this case the programmer intention is clear.
19328 @node Pragma Pack for Records,Record Representation Clauses,Pragma Pack for Arrays,Representation Clauses and Pragmas
19329 @anchor{gnat_rm/representation_clauses_and_pragmas pragma-pack-for-records}@anchor{281}@anchor{gnat_rm/representation_clauses_and_pragmas id12}@anchor{282}
19330 @section Pragma Pack for Records
19333 @geindex Pragma Pack (for records)
19335 Pragma @code{Pack} applied to a record will pack the components to reduce
19336 wasted space from alignment gaps and by reducing the amount of space
19337 taken by components. We distinguish between @emph{packable} components and
19338 @emph{non-packable} components.
19339 Components of the following types are considered packable:
19345 Components of an elementary type are packable unless they are aliased,
19346 independent, or of an atomic type.
19349 Small packed arrays, where the size is statically known, are represented
19350 internally as modular integers, and so they are also packable.
19353 Small simple records, where the size is statically known, are also packable.
19356 For all these cases, if the @code{'Size} value is in the range 1 through 64, the
19357 components occupy the exact number of bits corresponding to this value
19358 and are packed with no padding bits, i.e. they can start on an arbitrary
19361 All other types are non-packable, they occupy an integral number of storage
19362 units and the only effect of pragma @code{Pack} is to remove alignment gaps.
19364 For example, consider the record
19367 type Rb1 is array (1 .. 13) of Boolean;
19370 type Rb2 is array (1 .. 65) of Boolean;
19373 type AF is new Float with Atomic;
19386 The representation for the record @code{X2} is as follows:
19389 for X2'Size use 224;
19391 L1 at 0 range 0 .. 0;
19392 L2 at 0 range 1 .. 64;
19393 L3 at 12 range 0 .. 31;
19394 L4 at 16 range 0 .. 0;
19395 L5 at 16 range 1 .. 13;
19396 L6 at 18 range 0 .. 71;
19400 Studying this example, we see that the packable fields @code{L1}
19402 of length equal to their sizes, and placed at specific bit boundaries (and
19403 not byte boundaries) to
19404 eliminate padding. But @code{L3} is of a non-packable float type (because
19405 it is aliased), so it is on the next appropriate alignment boundary.
19407 The next two fields are fully packable, so @code{L4} and @code{L5} are
19408 minimally packed with no gaps. However, type @code{Rb2} is a packed
19409 array that is longer than 64 bits, so it is itself non-packable. Thus
19410 the @code{L6} field is aligned to the next byte boundary, and takes an
19411 integral number of bytes, i.e., 72 bits.
19413 @node Record Representation Clauses,Handling of Records with Holes,Pragma Pack for Records,Representation Clauses and Pragmas
19414 @anchor{gnat_rm/representation_clauses_and_pragmas id13}@anchor{283}@anchor{gnat_rm/representation_clauses_and_pragmas record-representation-clauses}@anchor{284}
19415 @section Record Representation Clauses
19418 @geindex Record Representation Clause
19420 Record representation clauses may be given for all record types, including
19421 types obtained by record extension. Component clauses are allowed for any
19422 static component. The restrictions on component clauses depend on the type
19425 @geindex Component Clause
19427 For all components of an elementary type, the only restriction on component
19428 clauses is that the size must be at least the @code{'Size} value of the type
19429 (actually the Value_Size). There are no restrictions due to alignment,
19430 and such components may freely cross storage boundaries.
19432 Packed arrays with a size up to and including 64 bits are represented
19433 internally using a modular type with the appropriate number of bits, and
19434 thus the same lack of restriction applies. For example, if you declare:
19437 type R is array (1 .. 49) of Boolean;
19442 then a component clause for a component of type @code{R} may start on any
19443 specified bit boundary, and may specify a value of 49 bits or greater.
19445 For packed bit arrays that are longer than 64 bits, there are two
19446 cases. If the component size is a power of 2 (1,2,4,8,16,32 bits),
19447 including the important case of single bits or boolean values, then
19448 there are no limitations on placement of such components, and they
19449 may start and end at arbitrary bit boundaries.
19451 If the component size is not a power of 2 (e.g., 3 or 5), then
19452 an array of this type longer than 64 bits must always be placed on
19453 on a storage unit (byte) boundary and occupy an integral number
19454 of storage units (bytes). Any component clause that does not
19455 meet this requirement will be rejected.
19457 Any aliased component, or component of an aliased type, must
19458 have its normal alignment and size. A component clause that
19459 does not meet this requirement will be rejected.
19461 The tag field of a tagged type always occupies an address sized field at
19462 the start of the record. No component clause may attempt to overlay this
19463 tag. When a tagged type appears as a component, the tag field must have
19466 In the case of a record extension @code{T1}, of a type @code{T}, no component clause applied
19467 to the type @code{T1} can specify a storage location that would overlap the first
19468 @code{T'Size} bytes of the record.
19470 For all other component types, including non-bit-packed arrays,
19471 the component can be placed at an arbitrary bit boundary,
19472 so for example, the following is permitted:
19475 type R is array (1 .. 10) of Boolean;
19484 G at 0 range 0 .. 0;
19485 H at 0 range 1 .. 1;
19486 L at 0 range 2 .. 81;
19487 R at 0 range 82 .. 161;
19491 @node Handling of Records with Holes,Enumeration Clauses,Record Representation Clauses,Representation Clauses and Pragmas
19492 @anchor{gnat_rm/representation_clauses_and_pragmas handling-of-records-with-holes}@anchor{285}@anchor{gnat_rm/representation_clauses_and_pragmas id14}@anchor{286}
19493 @section Handling of Records with Holes
19496 @geindex Handling of Records with Holes
19498 As a result of alignment considerations, records may contain "holes"
19500 which do not correspond to the data bits of any of the components.
19501 Record representation clauses can also result in holes in records.
19503 GNAT does not attempt to clear these holes, so in record objects,
19504 they should be considered to hold undefined rubbish. The generated
19505 equality routine just tests components so does not access these
19506 undefined bits, and assignment and copy operations may or may not
19507 preserve the contents of these holes (for assignments, the holes
19508 in the target will in practice contain either the bits that are
19509 present in the holes in the source, or the bits that were present
19510 in the target before the assignment).
19512 If it is necessary to ensure that holes in records have all zero
19513 bits, then record objects for which this initialization is desired
19514 should be explicitly set to all zero values using Unchecked_Conversion
19515 or address overlays. For example
19518 type HRec is record
19524 On typical machines, integers need to be aligned on a four-byte
19525 boundary, resulting in three bytes of undefined rubbish following
19526 the 8-bit field for C. To ensure that the hole in a variable of
19527 type HRec is set to all zero bits,
19528 you could for example do:
19531 type Base is record
19532 Dummy1, Dummy2 : Integer := 0;
19537 for RealVar'Address use BaseVar'Address;
19540 Now the 8-bytes of the value of RealVar start out containing all zero
19541 bits. A safer approach is to just define dummy fields, avoiding the
19545 type HRec is record
19547 Dummy1 : Short_Short_Integer := 0;
19548 Dummy2 : Short_Short_Integer := 0;
19549 Dummy3 : Short_Short_Integer := 0;
19554 And to make absolutely sure that the intent of this is followed, you
19555 can use representation clauses:
19558 for Hrec use record
19559 C at 0 range 0 .. 7;
19560 Dummy1 at 1 range 0 .. 7;
19561 Dummy2 at 2 range 0 .. 7;
19562 Dummy3 at 3 range 0 .. 7;
19563 I at 4 range 0 .. 31;
19565 for Hrec'Size use 64;
19568 @node Enumeration Clauses,Address Clauses,Handling of Records with Holes,Representation Clauses and Pragmas
19569 @anchor{gnat_rm/representation_clauses_and_pragmas enumeration-clauses}@anchor{287}@anchor{gnat_rm/representation_clauses_and_pragmas id15}@anchor{288}
19570 @section Enumeration Clauses
19573 The only restriction on enumeration clauses is that the range of values
19574 must be representable. For the signed case, if one or more of the
19575 representation values are negative, all values must be in the range:
19578 System.Min_Int .. System.Max_Int
19581 For the unsigned case, where all values are nonnegative, the values must
19585 0 .. System.Max_Binary_Modulus;
19588 A @emph{confirming} representation clause is one in which the values range
19589 from 0 in sequence, i.e., a clause that confirms the default representation
19590 for an enumeration type.
19591 Such a confirming representation
19592 is permitted by these rules, and is specially recognized by the compiler so
19593 that no extra overhead results from the use of such a clause.
19595 If an array has an index type which is an enumeration type to which an
19596 enumeration clause has been applied, then the array is stored in a compact
19597 manner. Consider the declarations:
19600 type r is (A, B, C);
19601 for r use (A => 1, B => 5, C => 10);
19602 type t is array (r) of Character;
19605 The array type t corresponds to a vector with exactly three elements and
19606 has a default size equal to @code{3*Character'Size}. This ensures efficient
19607 use of space, but means that accesses to elements of the array will incur
19608 the overhead of converting representation values to the corresponding
19609 positional values, (i.e., the value delivered by the @code{Pos} attribute).
19611 @node Address Clauses,Use of Address Clauses for Memory-Mapped I/O,Enumeration Clauses,Representation Clauses and Pragmas
19612 @anchor{gnat_rm/representation_clauses_and_pragmas id16}@anchor{289}@anchor{gnat_rm/representation_clauses_and_pragmas address-clauses}@anchor{28a}
19613 @section Address Clauses
19616 @geindex Address Clause
19618 The reference manual allows a general restriction on representation clauses,
19619 as found in RM 13.1(22):
19623 "An implementation need not support representation
19624 items containing nonstatic expressions, except that
19625 an implementation should support a representation item
19626 for a given entity if each nonstatic expression in the
19627 representation item is a name that statically denotes
19628 a constant declared before the entity."
19631 In practice this is applicable only to address clauses, since this is the
19632 only case in which a nonstatic expression is permitted by the syntax. As
19633 the AARM notes in sections 13.1 (22.a-22.h):
19637 22.a Reason: This is to avoid the following sort of thing:
19639 22.b X : Integer := F(...);
19640 Y : Address := G(...);
19641 for X'Address use Y;
19643 22.c In the above, we have to evaluate the
19644 initialization expression for X before we
19645 know where to put the result. This seems
19646 like an unreasonable implementation burden.
19648 22.d The above code should instead be written
19651 22.e Y : constant Address := G(...);
19652 X : Integer := F(...);
19653 for X'Address use Y;
19655 22.f This allows the expression 'Y' to be safely
19656 evaluated before X is created.
19658 22.g The constant could be a formal parameter of mode in.
19660 22.h An implementation can support other nonstatic
19661 expressions if it wants to. Expressions of type
19662 Address are hardly ever static, but their value
19663 might be known at compile time anyway in many
19667 GNAT does indeed permit many additional cases of nonstatic expressions. In
19668 particular, if the type involved is elementary there are no restrictions
19669 (since in this case, holding a temporary copy of the initialization value,
19670 if one is present, is inexpensive). In addition, if there is no implicit or
19671 explicit initialization, then there are no restrictions. GNAT will reject
19672 only the case where all three of these conditions hold:
19678 The type of the item is non-elementary (e.g., a record or array).
19681 There is explicit or implicit initialization required for the object.
19682 Note that access values are always implicitly initialized.
19685 The address value is nonstatic. Here GNAT is more permissive than the
19686 RM, and allows the address value to be the address of a previously declared
19687 stand-alone variable, as long as it does not itself have an address clause.
19690 Anchor : Some_Initialized_Type;
19691 Overlay : Some_Initialized_Type;
19692 for Overlay'Address use Anchor'Address;
19695 However, the prefix of the address clause cannot be an array component, or
19696 a component of a discriminated record.
19699 As noted above in section 22.h, address values are typically nonstatic. In
19700 particular the To_Address function, even if applied to a literal value, is
19701 a nonstatic function call. To avoid this minor annoyance, GNAT provides
19702 the implementation defined attribute 'To_Address. The following two
19703 expressions have identical values:
19707 @geindex To_Address
19710 To_Address (16#1234_0000#)
19711 System'To_Address (16#1234_0000#);
19714 except that the second form is considered to be a static expression, and
19715 thus when used as an address clause value is always permitted.
19717 Additionally, GNAT treats as static an address clause that is an
19718 unchecked_conversion of a static integer value. This simplifies the porting
19719 of legacy code, and provides a portable equivalent to the GNAT attribute
19722 Another issue with address clauses is the interaction with alignment
19723 requirements. When an address clause is given for an object, the address
19724 value must be consistent with the alignment of the object (which is usually
19725 the same as the alignment of the type of the object). If an address clause
19726 is given that specifies an inappropriately aligned address value, then the
19727 program execution is erroneous.
19729 Since this source of erroneous behavior can have unfortunate effects on
19730 machines with strict alignment requirements, GNAT
19731 checks (at compile time if possible, generating a warning, or at execution
19732 time with a run-time check) that the alignment is appropriate. If the
19733 run-time check fails, then @code{Program_Error} is raised. This run-time
19734 check is suppressed if range checks are suppressed, or if the special GNAT
19735 check Alignment_Check is suppressed, or if
19736 @code{pragma Restrictions (No_Elaboration_Code)} is in effect. It is also
19737 suppressed by default on non-strict alignment machines (such as the x86).
19739 Finally, GNAT does not permit overlaying of objects of class-wide types. In
19740 most cases, the compiler can detect an attempt at such overlays and will
19741 generate a warning at compile time and a Program_Error exception at run time.
19745 An address clause cannot be given for an exported object. More
19746 understandably the real restriction is that objects with an address
19747 clause cannot be exported. This is because such variables are not
19748 defined by the Ada program, so there is no external object to export.
19752 It is permissible to give an address clause and a pragma Import for the
19753 same object. In this case, the variable is not really defined by the
19754 Ada program, so there is no external symbol to be linked. The link name
19755 and the external name are ignored in this case. The reason that we allow this
19756 combination is that it provides a useful idiom to avoid unwanted
19757 initializations on objects with address clauses.
19759 When an address clause is given for an object that has implicit or
19760 explicit initialization, then by default initialization takes place. This
19761 means that the effect of the object declaration is to overwrite the
19762 memory at the specified address. This is almost always not what the
19763 programmer wants, so GNAT will output a warning:
19773 for Ext'Address use System'To_Address (16#1234_1234#);
19775 >>> warning: implicit initialization of "Ext" may
19776 modify overlaid storage
19777 >>> warning: use pragma Import for "Ext" to suppress
19778 initialization (RM B(24))
19783 As indicated by the warning message, the solution is to use a (dummy) pragma
19784 Import to suppress this initialization. The pragma tell the compiler that the
19785 object is declared and initialized elsewhere. The following package compiles
19786 without warnings (and the initialization is suppressed):
19796 for Ext'Address use System'To_Address (16#1234_1234#);
19797 pragma Import (Ada, Ext);
19801 A final issue with address clauses involves their use for overlaying
19802 variables, as in the following example:
19804 @geindex Overlaying of objects
19809 for B'Address use A'Address;
19812 or alternatively, using the form recommended by the RM:
19816 Addr : constant Address := A'Address;
19818 for B'Address use Addr;
19821 In both of these cases, @code{A} and @code{B} become aliased to one another
19822 via the address clause. This use of address clauses to overlay
19823 variables, achieving an effect similar to unchecked conversion
19824 was erroneous in Ada 83, but in Ada 95 and Ada 2005
19825 the effect is implementation defined. Furthermore, the
19826 Ada RM specifically recommends that in a situation
19827 like this, @code{B} should be subject to the following
19828 implementation advice (RM 13.3(19)):
19832 "19 If the Address of an object is specified, or it is imported
19833 or exported, then the implementation should not perform
19834 optimizations based on assumptions of no aliases."
19837 GNAT follows this recommendation, and goes further by also applying
19838 this recommendation to the overlaid variable (@code{A} in the above example)
19839 in this case. This means that the overlay works "as expected", in that
19840 a modification to one of the variables will affect the value of the other.
19842 More generally, GNAT interprets this recommendation conservatively for
19843 address clauses: in the cases other than overlays, it considers that the
19844 object is effectively subject to pragma @code{Volatile} and implements the
19845 associated semantics.
19847 Note that when address clause overlays are used in this way, there is an
19848 issue of unintentional initialization, as shown by this example:
19851 package Overwrite_Record is
19853 A : Character := 'C';
19854 B : Character := 'A';
19856 X : Short_Integer := 3;
19858 for Y'Address use X'Address;
19860 >>> warning: default initialization of "Y" may
19861 modify "X", use pragma Import for "Y" to
19862 suppress initialization (RM B.1(24))
19864 end Overwrite_Record;
19867 Here the default initialization of @code{Y} will clobber the value
19868 of @code{X}, which justifies the warning. The warning notes that
19869 this effect can be eliminated by adding a @code{pragma Import}
19870 which suppresses the initialization:
19873 package Overwrite_Record is
19875 A : Character := 'C';
19876 B : Character := 'A';
19878 X : Short_Integer := 3;
19880 for Y'Address use X'Address;
19881 pragma Import (Ada, Y);
19882 end Overwrite_Record;
19885 Note that the use of @code{pragma Initialize_Scalars} may cause variables to
19886 be initialized when they would not otherwise have been in the absence
19887 of the use of this pragma. This may cause an overlay to have this
19888 unintended clobbering effect. The compiler avoids this for scalar
19889 types, but not for composite objects (where in general the effect
19890 of @code{Initialize_Scalars} is part of the initialization routine
19891 for the composite object:
19894 pragma Initialize_Scalars;
19895 with Ada.Text_IO; use Ada.Text_IO;
19896 procedure Overwrite_Array is
19897 type Arr is array (1 .. 5) of Integer;
19898 X : Arr := (others => 1);
19900 for A'Address use X'Address;
19902 >>> warning: default initialization of "A" may
19903 modify "X", use pragma Import for "A" to
19904 suppress initialization (RM B.1(24))
19907 if X /= Arr'(others => 1) then
19908 Put_Line ("X was clobbered");
19910 Put_Line ("X was not clobbered");
19912 end Overwrite_Array;
19915 The above program generates the warning as shown, and at execution
19916 time, prints @code{X was clobbered}. If the @code{pragma Import} is
19917 added as suggested:
19920 pragma Initialize_Scalars;
19921 with Ada.Text_IO; use Ada.Text_IO;
19922 procedure Overwrite_Array is
19923 type Arr is array (1 .. 5) of Integer;
19924 X : Arr := (others => 1);
19926 for A'Address use X'Address;
19927 pragma Import (Ada, A);
19929 if X /= Arr'(others => 1) then
19930 Put_Line ("X was clobbered");
19932 Put_Line ("X was not clobbered");
19934 end Overwrite_Array;
19937 then the program compiles without the warning and when run will generate
19938 the output @code{X was not clobbered}.
19940 @node Use of Address Clauses for Memory-Mapped I/O,Effect of Convention on Representation,Address Clauses,Representation Clauses and Pragmas
19941 @anchor{gnat_rm/representation_clauses_and_pragmas id17}@anchor{28b}@anchor{gnat_rm/representation_clauses_and_pragmas use-of-address-clauses-for-memory-mapped-i-o}@anchor{28c}
19942 @section Use of Address Clauses for Memory-Mapped I/O
19945 @geindex Memory-mapped I/O
19947 A common pattern is to use an address clause to map an atomic variable to
19948 a location in memory that corresponds to a memory-mapped I/O operation or
19949 operations, for example:
19952 type Mem_Word is record
19955 pragma Atomic (Mem_Word);
19956 for Mem_Word_Size use 32;
19959 for Mem'Address use some-address;
19966 For a full access (reference or modification) of the variable (Mem) in this
19967 case, as in the above examples, GNAT guarantees that the entire atomic word
19968 will be accessed, in accordance with the RM C.6(15) clause.
19970 A problem arises with a component access such as:
19976 Note that the component A is not declared as atomic. This means that it is
19977 not clear what this assignment means. It could correspond to full word read
19978 and write as given in the first example, or on architectures that supported
19979 such an operation it might be a single byte store instruction. The RM does
19980 not have anything to say in this situation, and GNAT does not make any
19981 guarantee. The code generated may vary from target to target. GNAT will issue
19982 a warning in such a case:
19987 >>> warning: access to non-atomic component of atomic array,
19988 may cause unexpected accesses to atomic object
19991 It is best to be explicit in this situation, by either declaring the
19992 components to be atomic if you want the byte store, or explicitly writing
19993 the full word access sequence if that is what the hardware requires.
19994 Alternatively, if the full word access sequence is required, GNAT also
19995 provides the pragma @code{Volatile_Full_Access} which can be used in lieu of
19996 pragma @code{Atomic} and will give the additional guarantee.
19998 @node Effect of Convention on Representation,Conventions and Anonymous Access Types,Use of Address Clauses for Memory-Mapped I/O,Representation Clauses and Pragmas
19999 @anchor{gnat_rm/representation_clauses_and_pragmas id18}@anchor{28d}@anchor{gnat_rm/representation_clauses_and_pragmas effect-of-convention-on-representation}@anchor{28e}
20000 @section Effect of Convention on Representation
20003 @geindex Convention
20004 @geindex effect on representation
20006 Normally the specification of a foreign language convention for a type or
20007 an object has no effect on the chosen representation. In particular, the
20008 representation chosen for data in GNAT generally meets the standard system
20009 conventions, and for example records are laid out in a manner that is
20010 consistent with C. This means that specifying convention C (for example)
20013 There are four exceptions to this general rule:
20019 @emph{Convention Fortran and array subtypes}.
20021 If pragma Convention Fortran is specified for an array subtype, then in
20022 accordance with the implementation advice in section 3.6.2(11) of the
20023 Ada Reference Manual, the array will be stored in a Fortran-compatible
20024 column-major manner, instead of the normal default row-major order.
20027 @emph{Convention C and enumeration types}
20029 GNAT normally stores enumeration types in 8, 16, or 32 bits as required
20030 to accommodate all values of the type. For example, for the enumeration
20034 type Color is (Red, Green, Blue);
20037 8 bits is sufficient to store all values of the type, so by default, objects
20038 of type @code{Color} will be represented using 8 bits. However, normal C
20039 convention is to use 32 bits for all enum values in C, since enum values
20040 are essentially of type int. If pragma @code{Convention C} is specified for an
20041 Ada enumeration type, then the size is modified as necessary (usually to
20042 32 bits) to be consistent with the C convention for enum values.
20044 Note that this treatment applies only to types. If Convention C is given for
20045 an enumeration object, where the enumeration type is not Convention C, then
20046 Object_Size bits are allocated. For example, for a normal enumeration type,
20047 with less than 256 elements, only 8 bits will be allocated for the object.
20048 Since this may be a surprise in terms of what C expects, GNAT will issue a
20049 warning in this situation. The warning can be suppressed by giving an explicit
20050 size clause specifying the desired size.
20053 @emph{Convention C/Fortran and Boolean types}
20055 In C, the usual convention for boolean values, that is values used for
20056 conditions, is that zero represents false, and nonzero values represent
20057 true. In Ada, the normal convention is that two specific values, typically
20058 0/1, are used to represent false/true respectively.
20060 Fortran has a similar convention for @code{LOGICAL} values (any nonzero
20061 value represents true).
20063 To accommodate the Fortran and C conventions, if a pragma Convention specifies
20064 C or Fortran convention for a derived Boolean, as in the following example:
20067 type C_Switch is new Boolean;
20068 pragma Convention (C, C_Switch);
20071 then the GNAT generated code will treat any nonzero value as true. For truth
20072 values generated by GNAT, the conventional value 1 will be used for True, but
20073 when one of these values is read, any nonzero value is treated as True.
20076 @node Conventions and Anonymous Access Types,Determining the Representations chosen by GNAT,Effect of Convention on Representation,Representation Clauses and Pragmas
20077 @anchor{gnat_rm/representation_clauses_and_pragmas conventions-and-anonymous-access-types}@anchor{28f}@anchor{gnat_rm/representation_clauses_and_pragmas id19}@anchor{290}
20078 @section Conventions and Anonymous Access Types
20081 @geindex Anonymous access types
20083 @geindex Convention for anonymous access types
20085 The RM is not entirely clear on convention handling in a number of cases,
20086 and in particular, it is not clear on the convention to be given to
20087 anonymous access types in general, and in particular what is to be
20088 done for the case of anonymous access-to-subprogram.
20090 In GNAT, we decide that if an explicit Convention is applied
20091 to an object or component, and its type is such an anonymous type,
20092 then the convention will apply to this anonymous type as well. This
20093 seems to make sense since it is anomolous in any case to have a
20094 different convention for an object and its type, and there is clearly
20095 no way to explicitly specify a convention for an anonymous type, since
20096 it doesn't have a name to specify!
20098 Furthermore, we decide that if a convention is applied to a record type,
20099 then this convention is inherited by any of its components that are of an
20100 anonymous access type which do not have an explicitly specified convention.
20102 The following program shows these conventions in action:
20105 package ConvComp is
20106 type Foo is range 1 .. 10;
20108 A : access function (X : Foo) return Integer;
20111 pragma Convention (C, T1);
20114 A : access function (X : Foo) return Integer;
20115 pragma Convention (C, A);
20118 pragma Convention (COBOL, T2);
20121 A : access function (X : Foo) return Integer;
20122 pragma Convention (COBOL, A);
20125 pragma Convention (C, T3);
20128 A : access function (X : Foo) return Integer;
20131 pragma Convention (COBOL, T4);
20133 function F (X : Foo) return Integer;
20134 pragma Convention (C, F);
20136 function F (X : Foo) return Integer is (13);
20138 TV1 : T1 := (F'Access, 12); -- OK
20139 TV2 : T2 := (F'Access, 13); -- OK
20141 TV3 : T3 := (F'Access, 13); -- ERROR
20143 >>> subprogram "F" has wrong convention
20144 >>> does not match access to subprogram declared at line 17
20145 38. TV4 : T4 := (F'Access, 13); -- ERROR
20147 >>> subprogram "F" has wrong convention
20148 >>> does not match access to subprogram declared at line 24
20152 @node Determining the Representations chosen by GNAT,,Conventions and Anonymous Access Types,Representation Clauses and Pragmas
20153 @anchor{gnat_rm/representation_clauses_and_pragmas id20}@anchor{291}@anchor{gnat_rm/representation_clauses_and_pragmas determining-the-representations-chosen-by-gnat}@anchor{292}
20154 @section Determining the Representations chosen by GNAT
20157 @geindex Representation
20158 @geindex determination of
20160 @geindex -gnatR (gcc)
20162 Although the descriptions in this section are intended to be complete, it is
20163 often easier to simply experiment to see what GNAT accepts and what the
20164 effect is on the layout of types and objects.
20166 As required by the Ada RM, if a representation clause is not accepted, then
20167 it must be rejected as illegal by the compiler. However, when a
20168 representation clause or pragma is accepted, there can still be questions
20169 of what the compiler actually does. For example, if a partial record
20170 representation clause specifies the location of some components and not
20171 others, then where are the non-specified components placed? Or if pragma
20172 @code{Pack} is used on a record, then exactly where are the resulting
20173 fields placed? The section on pragma @code{Pack} in this chapter can be
20174 used to answer the second question, but it is often easier to just see
20175 what the compiler does.
20177 For this purpose, GNAT provides the option @emph{-gnatR}. If you compile
20178 with this option, then the compiler will output information on the actual
20179 representations chosen, in a format similar to source representation
20180 clauses. For example, if we compile the package:
20184 type r (x : boolean) is tagged record
20186 when True => S : String (1 .. 100);
20187 when False => null;
20191 type r2 is new r (false) with record
20196 y2 at 16 range 0 .. 31;
20203 type x1 is array (1 .. 10) of x;
20204 for x1'component_size use 11;
20206 type ia is access integer;
20208 type Rb1 is array (1 .. 13) of Boolean;
20211 type Rb2 is array (1 .. 65) of Boolean;
20226 using the switch @emph{-gnatR} we obtain the following output:
20229 Representation information for unit q
20230 -------------------------------------
20233 for r'Alignment use 4;
20235 x at 4 range 0 .. 7;
20236 _tag at 0 range 0 .. 31;
20237 s at 5 range 0 .. 799;
20240 for r2'Size use 160;
20241 for r2'Alignment use 4;
20243 x at 4 range 0 .. 7;
20244 _tag at 0 range 0 .. 31;
20245 _parent at 0 range 0 .. 63;
20246 y2 at 16 range 0 .. 31;
20250 for x'Alignment use 1;
20252 y at 0 range 0 .. 7;
20255 for x1'Size use 112;
20256 for x1'Alignment use 1;
20257 for x1'Component_Size use 11;
20259 for rb1'Size use 13;
20260 for rb1'Alignment use 2;
20261 for rb1'Component_Size use 1;
20263 for rb2'Size use 72;
20264 for rb2'Alignment use 1;
20265 for rb2'Component_Size use 1;
20267 for x2'Size use 224;
20268 for x2'Alignment use 4;
20270 l1 at 0 range 0 .. 0;
20271 l2 at 0 range 1 .. 64;
20272 l3 at 12 range 0 .. 31;
20273 l4 at 16 range 0 .. 0;
20274 l5 at 16 range 1 .. 13;
20275 l6 at 18 range 0 .. 71;
20279 The Size values are actually the Object_Size, i.e., the default size that
20280 will be allocated for objects of the type.
20281 The @code{??} size for type r indicates that we have a variant record, and the
20282 actual size of objects will depend on the discriminant value.
20284 The Alignment values show the actual alignment chosen by the compiler
20285 for each record or array type.
20287 The record representation clause for type r shows where all fields
20288 are placed, including the compiler generated tag field (whose location
20289 cannot be controlled by the programmer).
20291 The record representation clause for the type extension r2 shows all the
20292 fields present, including the parent field, which is a copy of the fields
20293 of the parent type of r2, i.e., r1.
20295 The component size and size clauses for types rb1 and rb2 show
20296 the exact effect of pragma @code{Pack} on these arrays, and the record
20297 representation clause for type x2 shows how pragma @cite{Pack} affects
20300 In some cases, it may be useful to cut and paste the representation clauses
20301 generated by the compiler into the original source to fix and guarantee
20302 the actual representation to be used.
20304 @node Standard Library Routines,The Implementation of Standard I/O,Representation Clauses and Pragmas,Top
20305 @anchor{gnat_rm/standard_library_routines standard-library-routines}@anchor{e}@anchor{gnat_rm/standard_library_routines doc}@anchor{293}@anchor{gnat_rm/standard_library_routines id1}@anchor{294}
20306 @chapter Standard Library Routines
20309 The Ada Reference Manual contains in Annex A a full description of an
20310 extensive set of standard library routines that can be used in any Ada
20311 program, and which must be provided by all Ada compilers. They are
20312 analogous to the standard C library used by C programs.
20314 GNAT implements all of the facilities described in annex A, and for most
20315 purposes the description in the Ada Reference Manual, or appropriate Ada
20316 text book, will be sufficient for making use of these facilities.
20318 In the case of the input-output facilities,
20319 @ref{f,,The Implementation of Standard I/O},
20320 gives details on exactly how GNAT interfaces to the
20321 file system. For the remaining packages, the Ada Reference Manual
20322 should be sufficient. The following is a list of the packages included,
20323 together with a brief description of the functionality that is provided.
20325 For completeness, references are included to other predefined library
20326 routines defined in other sections of the Ada Reference Manual (these are
20327 cross-indexed from Annex A). For further details see the relevant
20328 package declarations in the run-time library. In particular, a few units
20329 are not implemented, as marked by the presence of pragma Unimplemented_Unit,
20330 and in this case the package declaration contains comments explaining why
20331 the unit is not implemented.
20336 @item @code{Ada} @emph{(A.2)}
20338 This is a parent package for all the standard library packages. It is
20339 usually included implicitly in your program, and itself contains no
20340 useful data or routines.
20342 @item @code{Ada.Assertions} @emph{(11.4.2)}
20344 @code{Assertions} provides the @code{Assert} subprograms, and also
20345 the declaration of the @code{Assertion_Error} exception.
20347 @item @code{Ada.Asynchronous_Task_Control} @emph{(D.11)}
20349 @code{Asynchronous_Task_Control} provides low level facilities for task
20350 synchronization. It is typically not implemented. See package spec for details.
20352 @item @code{Ada.Calendar} @emph{(9.6)}
20354 @code{Calendar} provides time of day access, and routines for
20355 manipulating times and durations.
20357 @item @code{Ada.Calendar.Arithmetic} @emph{(9.6.1)}
20359 This package provides additional arithmetic
20360 operations for @code{Calendar}.
20362 @item @code{Ada.Calendar.Formatting} @emph{(9.6.1)}
20364 This package provides formatting operations for @code{Calendar}.
20366 @item @code{Ada.Calendar.Time_Zones} @emph{(9.6.1)}
20368 This package provides additional @code{Calendar} facilities
20369 for handling time zones.
20371 @item @code{Ada.Characters} @emph{(A.3.1)}
20373 This is a dummy parent package that contains no useful entities
20375 @item @code{Ada.Characters.Conversions} @emph{(A.3.2)}
20377 This package provides character conversion functions.
20379 @item @code{Ada.Characters.Handling} @emph{(A.3.2)}
20381 This package provides some basic character handling capabilities,
20382 including classification functions for classes of characters (e.g., test
20383 for letters, or digits).
20385 @item @code{Ada.Characters.Latin_1} @emph{(A.3.3)}
20387 This package includes a complete set of definitions of the characters
20388 that appear in type CHARACTER. It is useful for writing programs that
20389 will run in international environments. For example, if you want an
20390 upper case E with an acute accent in a string, it is often better to use
20391 the definition of @code{UC_E_Acute} in this package. Then your program
20392 will print in an understandable manner even if your environment does not
20393 support these extended characters.
20395 @item @code{Ada.Command_Line} @emph{(A.15)}
20397 This package provides access to the command line parameters and the name
20398 of the current program (analogous to the use of @code{argc} and @code{argv}
20399 in C), and also allows the exit status for the program to be set in a
20400 system-independent manner.
20402 @item @code{Ada.Complex_Text_IO} @emph{(G.1.3)}
20404 This package provides text input and output of complex numbers.
20406 @item @code{Ada.Containers} @emph{(A.18.1)}
20408 A top level package providing a few basic definitions used by all the
20409 following specific child packages that provide specific kinds of
20413 @code{Ada.Containers.Bounded_Priority_Queues} @emph{(A.18.31)}
20415 @code{Ada.Containers.Bounded_Synchronized_Queues} @emph{(A.18.29)}
20417 @code{Ada.Containers.Doubly_Linked_Lists} @emph{(A.18.3)}
20419 @code{Ada.Containers.Generic_Array_Sort} @emph{(A.18.26)}
20421 @code{Ada.Containers.Generic_Constrained_Array_Sort} @emph{(A.18.26)}
20423 @code{Ada.Containers.Generic_Sort} @emph{(A.18.26)}
20425 @code{Ada.Containers.Hashed_Maps} @emph{(A.18.5)}
20427 @code{Ada.Containers.Hashed_Sets} @emph{(A.18.8)}
20429 @code{Ada.Containers.Indefinite_Doubly_Linked_Lists} @emph{(A.18.12)}
20431 @code{Ada.Containers.Indefinite_Hashed_Maps} @emph{(A.18.13)}
20433 @code{Ada.Containers.Indefinite_Hashed_Sets} @emph{(A.18.15)}
20435 @code{Ada.Containers.Indefinite_Holders} @emph{(A.18.18)}
20437 @code{Ada.Containers.Indefinite_Multiway_Trees} @emph{(A.18.17)}
20439 @code{Ada.Containers.Indefinite_Ordered_Maps} @emph{(A.18.14)}
20441 @code{Ada.Containers.Indefinite_Ordered_Sets} @emph{(A.18.16)}
20443 @code{Ada.Containers.Indefinite_Vectors} @emph{(A.18.11)}
20445 @code{Ada.Containers.Multiway_Trees} @emph{(A.18.10)}
20447 @code{Ada.Containers.Ordered_Maps} @emph{(A.18.6)}
20449 @code{Ada.Containers.Ordered_Sets} @emph{(A.18.9)}
20451 @code{Ada.Containers.Synchronized_Queue_Interfaces} @emph{(A.18.27)}
20453 @code{Ada.Containers.Unbounded_Priority_Queues} @emph{(A.18.30)}
20455 @code{Ada.Containers.Unbounded_Synchronized_Queues} @emph{(A.18.28)}
20457 @code{Ada.Containers.Vectors} @emph{(A.18.2)}
20462 @item @code{Ada.Directories} @emph{(A.16)}
20464 This package provides operations on directories.
20466 @item @code{Ada.Directories.Hierarchical_File_Names} @emph{(A.16.1)}
20468 This package provides additional directory operations handling
20469 hiearchical file names.
20471 @item @code{Ada.Directories.Information} @emph{(A.16)}
20473 This is an implementation defined package for additional directory
20474 operations, which is not implemented in GNAT.
20476 @item @code{Ada.Decimal} @emph{(F.2)}
20478 This package provides constants describing the range of decimal numbers
20479 implemented, and also a decimal divide routine (analogous to the COBOL
20480 verb DIVIDE ... GIVING ... REMAINDER ...)
20482 @item @code{Ada.Direct_IO} @emph{(A.8.4)}
20484 This package provides input-output using a model of a set of records of
20485 fixed-length, containing an arbitrary definite Ada type, indexed by an
20486 integer record number.
20488 @item @code{Ada.Dispatching} @emph{(D.2.1)}
20490 A parent package containing definitions for task dispatching operations.
20492 @item @code{Ada.Dispatching.EDF} @emph{(D.2.6)}
20494 Not implemented in GNAT.
20496 @item @code{Ada.Dispatching.Non_Preemptive} @emph{(D.2.4)}
20498 Not implemented in GNAT.
20500 @item @code{Ada.Dispatching.Round_Robin} @emph{(D.2.5)}
20502 Not implemented in GNAT.
20504 @item @code{Ada.Dynamic_Priorities} @emph{(D.5)}
20506 This package allows the priorities of a task to be adjusted dynamically
20507 as the task is running.
20509 @item @code{Ada.Environment_Variables} @emph{(A.17)}
20511 This package provides facilities for accessing environment variables.
20513 @item @code{Ada.Exceptions} @emph{(11.4.1)}
20515 This package provides additional information on exceptions, and also
20516 contains facilities for treating exceptions as data objects, and raising
20517 exceptions with associated messages.
20519 @item @code{Ada.Execution_Time} @emph{(D.14)}
20521 This package provides CPU clock functionalities. It is not implemented on
20522 all targets (see package spec for details).
20524 @item @code{Ada.Execution_Time.Group_Budgets} @emph{(D.14.2)}
20526 Not implemented in GNAT.
20528 @item @code{Ada.Execution_Time.Timers} @emph{(D.14.1)'}
20530 Not implemented in GNAT.
20532 @item @code{Ada.Finalization} @emph{(7.6)}
20534 This package contains the declarations and subprograms to support the
20535 use of controlled types, providing for automatic initialization and
20536 finalization (analogous to the constructors and destructors of C++).
20538 @item @code{Ada.Float_Text_IO} @emph{(A.10.9)}
20540 A library level instantiation of Text_IO.Float_IO for type Float.
20542 @item @code{Ada.Float_Wide_Text_IO} @emph{(A.10.9)}
20544 A library level instantiation of Wide_Text_IO.Float_IO for type Float.
20546 @item @code{Ada.Float_Wide_Wide_Text_IO} @emph{(A.10.9)}
20548 A library level instantiation of Wide_Wide_Text_IO.Float_IO for type Float.
20550 @item @code{Ada.Integer_Text_IO} @emph{(A.10.9)}
20552 A library level instantiation of Text_IO.Integer_IO for type Integer.
20554 @item @code{Ada.Integer_Wide_Text_IO} @emph{(A.10.9)}
20556 A library level instantiation of Wide_Text_IO.Integer_IO for type Integer.
20558 @item @code{Ada.Integer_Wide_Wide_Text_IO} @emph{(A.10.9)}
20560 A library level instantiation of Wide_Wide_Text_IO.Integer_IO for type Integer.
20562 @item @code{Ada.Interrupts} @emph{(C.3.2)}
20564 This package provides facilities for interfacing to interrupts, which
20565 includes the set of signals or conditions that can be raised and
20566 recognized as interrupts.
20568 @item @code{Ada.Interrupts.Names} @emph{(C.3.2)}
20570 This package provides the set of interrupt names (actually signal
20571 or condition names) that can be handled by GNAT.
20573 @item @code{Ada.IO_Exceptions} @emph{(A.13)}
20575 This package defines the set of exceptions that can be raised by use of
20576 the standard IO packages.
20578 @item @code{Ada.Iterator_Interfaces} @emph{(5.5.1)}
20580 This package provides a generic interface to generalized iterators.
20582 @item @code{Ada.Locales} @emph{(A.19)}
20584 This package provides declarations providing information (Language
20585 and Country) about the current locale. This package is currently not
20586 implemented other than by providing stubs which will always return
20587 Language_Unknown/Country_Unknown.
20589 @item @code{Ada.Numerics}
20591 This package contains some standard constants and exceptions used
20592 throughout the numerics packages. Note that the constants pi and e are
20593 defined here, and it is better to use these definitions than rolling
20596 @item @code{Ada.Numerics.Complex_Arrays} @emph{(G.3.2)}
20598 Provides operations on arrays of complex numbers.
20600 @item @code{Ada.Numerics.Complex_Elementary_Functions}
20602 Provides the implementation of standard elementary functions (such as
20603 log and trigonometric functions) operating on complex numbers using the
20604 standard @code{Float} and the @code{Complex} and @code{Imaginary} types
20605 created by the package @code{Numerics.Complex_Types}.
20607 @item @code{Ada.Numerics.Complex_Types}
20609 This is a predefined instantiation of
20610 @code{Numerics.Generic_Complex_Types} using @code{Standard.Float} to
20611 build the type @code{Complex} and @code{Imaginary}.
20613 @item @code{Ada.Numerics.Discrete_Random}
20615 This generic package provides a random number generator suitable for generating
20616 uniformly distributed values of a specified discrete subtype.
20618 @item @code{Ada.Numerics.Float_Random}
20620 This package provides a random number generator suitable for generating
20621 uniformly distributed floating point values in the unit interval.
20623 @item @code{Ada.Numerics.Generic_Complex_Elementary_Functions}
20625 This is a generic version of the package that provides the
20626 implementation of standard elementary functions (such as log and
20627 trigonometric functions) for an arbitrary complex type.
20629 The following predefined instantiations of this package are provided:
20637 @code{Ada.Numerics.Short_Complex_Elementary_Functions}
20642 @code{Ada.Numerics.Complex_Elementary_Functions}
20647 @code{Ada.Numerics.Long_Complex_Elementary_Functions}
20650 @item @code{Ada.Numerics.Generic_Complex_Types}
20652 This is a generic package that allows the creation of complex types,
20653 with associated complex arithmetic operations.
20655 The following predefined instantiations of this package exist
20663 @code{Ada.Numerics.Short_Complex_Complex_Types}
20668 @code{Ada.Numerics.Complex_Complex_Types}
20673 @code{Ada.Numerics.Long_Complex_Complex_Types}
20676 @item @code{Ada.Numerics.Generic_Elementary_Functions}
20678 This is a generic package that provides the implementation of standard
20679 elementary functions (such as log an trigonometric functions) for an
20680 arbitrary float type.
20682 The following predefined instantiations of this package exist
20690 @code{Ada.Numerics.Short_Elementary_Functions}
20695 @code{Ada.Numerics.Elementary_Functions}
20700 @code{Ada.Numerics.Long_Elementary_Functions}
20703 @item @code{Ada.Numerics.Generic_Real_Arrays} @emph{(G.3.1)}
20705 Generic operations on arrays of reals
20707 @item @code{Ada.Numerics.Real_Arrays} @emph{(G.3.1)}
20709 Preinstantiation of Ada.Numerics.Generic_Real_Arrays (Float).
20711 @item @code{Ada.Real_Time} @emph{(D.8)}
20713 This package provides facilities similar to those of @code{Calendar}, but
20714 operating with a finer clock suitable for real time control. Note that
20715 annex D requires that there be no backward clock jumps, and GNAT generally
20716 guarantees this behavior, but of course if the external clock on which
20717 the GNAT runtime depends is deliberately reset by some external event,
20718 then such a backward jump may occur.
20720 @item @code{Ada.Real_Time.Timing_Events} @emph{(D.15)}
20722 Not implemented in GNAT.
20724 @item @code{Ada.Sequential_IO} @emph{(A.8.1)}
20726 This package provides input-output facilities for sequential files,
20727 which can contain a sequence of values of a single type, which can be
20728 any Ada type, including indefinite (unconstrained) types.
20730 @item @code{Ada.Storage_IO} @emph{(A.9)}
20732 This package provides a facility for mapping arbitrary Ada types to and
20733 from a storage buffer. It is primarily intended for the creation of new
20736 @item @code{Ada.Streams} @emph{(13.13.1)}
20738 This is a generic package that provides the basic support for the
20739 concept of streams as used by the stream attributes (@code{Input},
20740 @code{Output}, @code{Read} and @code{Write}).
20742 @item @code{Ada.Streams.Stream_IO} @emph{(A.12.1)}
20744 This package is a specialization of the type @code{Streams} defined in
20745 package @code{Streams} together with a set of operations providing
20746 Stream_IO capability. The Stream_IO model permits both random and
20747 sequential access to a file which can contain an arbitrary set of values
20748 of one or more Ada types.
20750 @item @code{Ada.Strings} @emph{(A.4.1)}
20752 This package provides some basic constants used by the string handling
20755 @item @code{Ada.Strings.Bounded} @emph{(A.4.4)}
20757 This package provides facilities for handling variable length
20758 strings. The bounded model requires a maximum length. It is thus
20759 somewhat more limited than the unbounded model, but avoids the use of
20760 dynamic allocation or finalization.
20762 @item @code{Ada.Strings.Bounded.Equal_Case_Insensitive} @emph{(A.4.10)}
20764 Provides case-insensitive comparisons of bounded strings
20766 @item @code{Ada.Strings.Bounded.Hash} @emph{(A.4.9)}
20768 This package provides a generic hash function for bounded strings
20770 @item @code{Ada.Strings.Bounded.Hash_Case_Insensitive} @emph{(A.4.9)}
20772 This package provides a generic hash function for bounded strings that
20773 converts the string to be hashed to lower case.
20775 @item @code{Ada.Strings.Bounded.Less_Case_Insensitive} @emph{(A.4.10)}
20777 This package provides a comparison function for bounded strings that works
20778 in a case insensitive manner by converting to lower case before the comparison.
20780 @item @code{Ada.Strings.Fixed} @emph{(A.4.3)}
20782 This package provides facilities for handling fixed length strings.
20784 @item @code{Ada.Strings.Fixed.Equal_Case_Insensitive} @emph{(A.4.10)}
20786 This package provides an equality function for fixed strings that compares
20787 the strings after converting both to lower case.
20789 @item @code{Ada.Strings.Fixed.Hash_Case_Insensitive} @emph{(A.4.9)}
20791 This package provides a case insensitive hash function for fixed strings that
20792 converts the string to lower case before computing the hash.
20794 @item @code{Ada.Strings.Fixed.Less_Case_Insensitive} @emph{(A.4.10)}
20796 This package provides a comparison function for fixed strings that works
20797 in a case insensitive manner by converting to lower case before the comparison.
20799 @item @code{Ada.Strings.Hash} @emph{(A.4.9)}
20801 This package provides a hash function for strings.
20803 @item @code{Ada.Strings.Hash_Case_Insensitive} @emph{(A.4.9)}
20805 This package provides a hash function for strings that is case insensitive.
20806 The string is converted to lower case before computing the hash.
20808 @item @code{Ada.Strings.Less_Case_Insensitive} @emph{(A.4.10)}
20810 This package provides a comparison function for\strings that works
20811 in a case insensitive manner by converting to lower case before the comparison.
20813 @item @code{Ada.Strings.Maps} @emph{(A.4.2)}
20815 This package provides facilities for handling character mappings and
20816 arbitrarily defined subsets of characters. For instance it is useful in
20817 defining specialized translation tables.
20819 @item @code{Ada.Strings.Maps.Constants} @emph{(A.4.6)}
20821 This package provides a standard set of predefined mappings and
20822 predefined character sets. For example, the standard upper to lower case
20823 conversion table is found in this package. Note that upper to lower case
20824 conversion is non-trivial if you want to take the entire set of
20825 characters, including extended characters like E with an acute accent,
20826 into account. You should use the mappings in this package (rather than
20827 adding 32 yourself) to do case mappings.
20829 @item @code{Ada.Strings.Unbounded} @emph{(A.4.5)}
20831 This package provides facilities for handling variable length
20832 strings. The unbounded model allows arbitrary length strings, but
20833 requires the use of dynamic allocation and finalization.
20835 @item @code{Ada.Strings.Unbounded.Equal_Case_Insensitive} @emph{(A.4.10)}
20837 Provides case-insensitive comparisons of unbounded strings
20839 @item @code{Ada.Strings.Unbounded.Hash} @emph{(A.4.9)}
20841 This package provides a generic hash function for unbounded strings
20843 @item @code{Ada.Strings.Unbounded.Hash_Case_Insensitive} @emph{(A.4.9)}
20845 This package provides a generic hash function for unbounded strings that
20846 converts the string to be hashed to lower case.
20848 @item @code{Ada.Strings.Unbounded.Less_Case_Insensitive} @emph{(A.4.10)}
20850 This package provides a comparison function for unbounded strings that works
20851 in a case insensitive manner by converting to lower case before the comparison.
20853 @item @code{Ada.Strings.UTF_Encoding} @emph{(A.4.11)}
20855 This package provides basic definitions for dealing with UTF-encoded strings.
20857 @item @code{Ada.Strings.UTF_Encoding.Conversions} @emph{(A.4.11)}
20859 This package provides conversion functions for UTF-encoded strings.
20862 @code{Ada.Strings.UTF_Encoding.Strings} @emph{(A.4.11)}
20864 @code{Ada.Strings.UTF_Encoding.Wide_Strings} @emph{(A.4.11)}
20869 @item @code{Ada.Strings.UTF_Encoding.Wide_Wide_Strings} @emph{(A.4.11)}
20871 These packages provide facilities for handling UTF encodings for
20872 Strings, Wide_Strings and Wide_Wide_Strings.
20875 @code{Ada.Strings.Wide_Bounded} @emph{(A.4.7)}
20877 @code{Ada.Strings.Wide_Fixed} @emph{(A.4.7)}
20879 @code{Ada.Strings.Wide_Maps} @emph{(A.4.7)}
20884 @item @code{Ada.Strings.Wide_Unbounded} @emph{(A.4.7)}
20886 These packages provide analogous capabilities to the corresponding
20887 packages without @code{Wide_} in the name, but operate with the types
20888 @code{Wide_String} and @code{Wide_Character} instead of @code{String}
20889 and @code{Character}. Versions of all the child packages are available.
20892 @code{Ada.Strings.Wide_Wide_Bounded} @emph{(A.4.7)}
20894 @code{Ada.Strings.Wide_Wide_Fixed} @emph{(A.4.7)}
20896 @code{Ada.Strings.Wide_Wide_Maps} @emph{(A.4.7)}
20901 @item @code{Ada.Strings.Wide_Wide_Unbounded} @emph{(A.4.7)}
20903 These packages provide analogous capabilities to the corresponding
20904 packages without @code{Wide_} in the name, but operate with the types
20905 @code{Wide_Wide_String} and @code{Wide_Wide_Character} instead
20906 of @code{String} and @code{Character}.
20908 @item @code{Ada.Synchronous_Barriers} @emph{(D.10.1)}
20910 This package provides facilities for synchronizing tasks at a low level
20913 @item @code{Ada.Synchronous_Task_Control} @emph{(D.10)}
20915 This package provides some standard facilities for controlling task
20916 communication in a synchronous manner.
20918 @item @code{Ada.Synchronous_Task_Control.EDF} @emph{(D.10)}
20920 Not implemented in GNAT.
20922 @item @code{Ada.Tags}
20924 This package contains definitions for manipulation of the tags of tagged
20927 @item @code{Ada.Tags.Generic_Dispatching_Constructor} @emph{(3.9)}
20929 This package provides a way of constructing tagged class-wide values given
20930 only the tag value.
20932 @item @code{Ada.Task_Attributes} @emph{(C.7.2)}
20934 This package provides the capability of associating arbitrary
20935 task-specific data with separate tasks.
20937 @item @code{Ada.Task_Identifification} @emph{(C.7.1)}
20939 This package provides capabilities for task identification.
20941 @item @code{Ada.Task_Termination} @emph{(C.7.3)}
20943 This package provides control over task termination.
20945 @item @code{Ada.Text_IO}
20947 This package provides basic text input-output capabilities for
20948 character, string and numeric data. The subpackages of this
20949 package are listed next. Note that although these are defined
20950 as subpackages in the RM, they are actually transparently
20951 implemented as child packages in GNAT, meaning that they
20952 are only loaded if needed.
20954 @item @code{Ada.Text_IO.Decimal_IO}
20956 Provides input-output facilities for decimal fixed-point types
20958 @item @code{Ada.Text_IO.Enumeration_IO}
20960 Provides input-output facilities for enumeration types.
20962 @item @code{Ada.Text_IO.Fixed_IO}
20964 Provides input-output facilities for ordinary fixed-point types.
20966 @item @code{Ada.Text_IO.Float_IO}
20968 Provides input-output facilities for float types. The following
20969 predefined instantiations of this generic package are available:
20977 @code{Short_Float_Text_IO}
20982 @code{Float_Text_IO}
20987 @code{Long_Float_Text_IO}
20990 @item @code{Ada.Text_IO.Integer_IO}
20992 Provides input-output facilities for integer types. The following
20993 predefined instantiations of this generic package are available:
20999 @code{Short_Short_Integer}
21001 @code{Ada.Short_Short_Integer_Text_IO}
21004 @code{Short_Integer}
21006 @code{Ada.Short_Integer_Text_IO}
21011 @code{Ada.Integer_Text_IO}
21014 @code{Long_Integer}
21016 @code{Ada.Long_Integer_Text_IO}
21019 @code{Long_Long_Integer}
21021 @code{Ada.Long_Long_Integer_Text_IO}
21024 @item @code{Ada.Text_IO.Modular_IO}
21026 Provides input-output facilities for modular (unsigned) types.
21028 @item @code{Ada.Text_IO.Bounded_IO (A.10.11)}
21030 Provides input-output facilities for bounded strings.
21032 @item @code{Ada.Text_IO.Complex_IO (G.1.3)}
21034 This package provides basic text input-output capabilities for complex
21037 @item @code{Ada.Text_IO.Editing (F.3.3)}
21039 This package contains routines for edited output, analogous to the use
21040 of pictures in COBOL. The picture formats used by this package are a
21041 close copy of the facility in COBOL.
21043 @item @code{Ada.Text_IO.Text_Streams (A.12.2)}
21045 This package provides a facility that allows Text_IO files to be treated
21046 as streams, so that the stream attributes can be used for writing
21047 arbitrary data, including binary data, to Text_IO files.
21049 @item @code{Ada.Text_IO.Unbounded_IO (A.10.12)}
21051 This package provides input-output facilities for unbounded strings.
21053 @item @code{Ada.Unchecked_Conversion (13.9)}
21055 This generic package allows arbitrary conversion from one type to
21056 another of the same size, providing for breaking the type safety in
21057 special circumstances.
21059 If the types have the same Size (more accurately the same Value_Size),
21060 then the effect is simply to transfer the bits from the source to the
21061 target type without any modification. This usage is well defined, and
21062 for simple types whose representation is typically the same across
21063 all implementations, gives a portable method of performing such
21066 If the types do not have the same size, then the result is implementation
21067 defined, and thus may be non-portable. The following describes how GNAT
21068 handles such unchecked conversion cases.
21070 If the types are of different sizes, and are both discrete types, then
21071 the effect is of a normal type conversion without any constraint checking.
21072 In particular if the result type has a larger size, the result will be
21073 zero or sign extended. If the result type has a smaller size, the result
21074 will be truncated by ignoring high order bits.
21076 If the types are of different sizes, and are not both discrete types,
21077 then the conversion works as though pointers were created to the source
21078 and target, and the pointer value is converted. The effect is that bits
21079 are copied from successive low order storage units and bits of the source
21080 up to the length of the target type.
21082 A warning is issued if the lengths differ, since the effect in this
21083 case is implementation dependent, and the above behavior may not match
21084 that of some other compiler.
21086 A pointer to one type may be converted to a pointer to another type using
21087 unchecked conversion. The only case in which the effect is undefined is
21088 when one or both pointers are pointers to unconstrained array types. In
21089 this case, the bounds information may get incorrectly transferred, and in
21090 particular, GNAT uses double size pointers for such types, and it is
21091 meaningless to convert between such pointer types. GNAT will issue a
21092 warning if the alignment of the target designated type is more strict
21093 than the alignment of the source designated type (since the result may
21094 be unaligned in this case).
21096 A pointer other than a pointer to an unconstrained array type may be
21097 converted to and from System.Address. Such usage is common in Ada 83
21098 programs, but note that Ada.Address_To_Access_Conversions is the
21099 preferred method of performing such conversions in Ada 95 and Ada 2005.
21101 unchecked conversion nor Ada.Address_To_Access_Conversions should be
21102 used in conjunction with pointers to unconstrained objects, since
21103 the bounds information cannot be handled correctly in this case.
21105 @item @code{Ada.Unchecked_Deallocation} @emph{(13.11.2)}
21107 This generic package allows explicit freeing of storage previously
21108 allocated by use of an allocator.
21110 @item @code{Ada.Wide_Text_IO} @emph{(A.11)}
21112 This package is similar to @code{Ada.Text_IO}, except that the external
21113 file supports wide character representations, and the internal types are
21114 @code{Wide_Character} and @code{Wide_String} instead of @code{Character}
21115 and @code{String}. The corresponding set of nested packages and child
21116 packages are defined.
21118 @item @code{Ada.Wide_Wide_Text_IO} @emph{(A.11)}
21120 This package is similar to @code{Ada.Text_IO}, except that the external
21121 file supports wide character representations, and the internal types are
21122 @code{Wide_Character} and @code{Wide_String} instead of @code{Character}
21123 and @code{String}. The corresponding set of nested packages and child
21124 packages are defined.
21127 For packages in Interfaces and System, all the RM defined packages are
21128 available in GNAT, see the Ada 2012 RM for full details.
21130 @node The Implementation of Standard I/O,The GNAT Library,Standard Library Routines,Top
21131 @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{295}@anchor{gnat_rm/the_implementation_of_standard_i_o id1}@anchor{296}
21132 @chapter The Implementation of Standard I/O
21135 GNAT implements all the required input-output facilities described in
21136 A.6 through A.14. These sections of the Ada Reference Manual describe the
21137 required behavior of these packages from the Ada point of view, and if
21138 you are writing a portable Ada program that does not need to know the
21139 exact manner in which Ada maps to the outside world when it comes to
21140 reading or writing external files, then you do not need to read this
21141 chapter. As long as your files are all regular files (not pipes or
21142 devices), and as long as you write and read the files only from Ada, the
21143 description in the Ada Reference Manual is sufficient.
21145 However, if you want to do input-output to pipes or other devices, such
21146 as the keyboard or screen, or if the files you are dealing with are
21147 either generated by some other language, or to be read by some other
21148 language, then you need to know more about the details of how the GNAT
21149 implementation of these input-output facilities behaves.
21151 In this chapter we give a detailed description of exactly how GNAT
21152 interfaces to the file system. As always, the sources of the system are
21153 available to you for answering questions at an even more detailed level,
21154 but for most purposes the information in this chapter will suffice.
21156 Another reason that you may need to know more about how input-output is
21157 implemented arises when you have a program written in mixed languages
21158 where, for example, files are shared between the C and Ada sections of
21159 the same program. GNAT provides some additional facilities, in the form
21160 of additional child library packages, that facilitate this sharing, and
21161 these additional facilities are also described in this chapter.
21164 * Standard I/O Packages::
21170 * Wide_Wide_Text_IO::
21172 * Text Translation::
21174 * Filenames encoding::
21175 * File content encoding::
21177 * Operations on C Streams::
21178 * Interfacing to C Streams::
21182 @node Standard I/O Packages,FORM Strings,,The Implementation of Standard I/O
21183 @anchor{gnat_rm/the_implementation_of_standard_i_o standard-i-o-packages}@anchor{297}@anchor{gnat_rm/the_implementation_of_standard_i_o id2}@anchor{298}
21184 @section Standard I/O Packages
21187 The Standard I/O packages described in Annex A for
21196 Ada.Text_IO.Complex_IO
21199 Ada.Text_IO.Text_Streams
21205 Ada.Wide_Text_IO.Complex_IO
21208 Ada.Wide_Text_IO.Text_Streams
21211 Ada.Wide_Wide_Text_IO
21214 Ada.Wide_Wide_Text_IO.Complex_IO
21217 Ada.Wide_Wide_Text_IO.Text_Streams
21229 are implemented using the C
21230 library streams facility; where
21236 All files are opened using @code{fopen}.
21239 All input/output operations use @code{fread}/@cite{fwrite}.
21242 There is no internal buffering of any kind at the Ada library level. The only
21243 buffering is that provided at the system level in the implementation of the
21244 library routines that support streams. This facilitates shared use of these
21245 streams by mixed language programs. Note though that system level buffering is
21246 explicitly enabled at elaboration of the standard I/O packages and that can
21247 have an impact on mixed language programs, in particular those using I/O before
21248 calling the Ada elaboration routine (e.g., adainit). It is recommended to call
21249 the Ada elaboration routine before performing any I/O or when impractical,
21250 flush the common I/O streams and in particular Standard_Output before
21251 elaborating the Ada code.
21253 @node FORM Strings,Direct_IO,Standard I/O Packages,The Implementation of Standard I/O
21254 @anchor{gnat_rm/the_implementation_of_standard_i_o form-strings}@anchor{299}@anchor{gnat_rm/the_implementation_of_standard_i_o id3}@anchor{29a}
21255 @section FORM Strings
21258 The format of a FORM string in GNAT is:
21261 "keyword=value,keyword=value,...,keyword=value"
21264 where letters may be in upper or lower case, and there are no spaces
21265 between values. The order of the entries is not important. Currently
21266 the following keywords defined.
21269 TEXT_TRANSLATION=[YES|NO|TEXT|BINARY|U8TEXT|WTEXT|U16TEXT]
21271 WCEM=[n|h|u|s|e|8|b]
21272 ENCODING=[UTF8|8BITS]
21275 The use of these parameters is described later in this section. If an
21276 unrecognized keyword appears in a form string, it is silently ignored
21277 and not considered invalid.
21279 @node Direct_IO,Sequential_IO,FORM Strings,The Implementation of Standard I/O
21280 @anchor{gnat_rm/the_implementation_of_standard_i_o direct-io}@anchor{29b}@anchor{gnat_rm/the_implementation_of_standard_i_o id4}@anchor{29c}
21284 Direct_IO can only be instantiated for definite types. This is a
21285 restriction of the Ada language, which means that the records are fixed
21286 length (the length being determined by @code{type'Size}, rounded
21287 up to the next storage unit boundary if necessary).
21289 The records of a Direct_IO file are simply written to the file in index
21290 sequence, with the first record starting at offset zero, and subsequent
21291 records following. There is no control information of any kind. For
21292 example, if 32-bit integers are being written, each record takes
21293 4-bytes, so the record at index @code{K} starts at offset
21296 There is no limit on the size of Direct_IO files, they are expanded as
21297 necessary to accommodate whatever records are written to the file.
21299 @node Sequential_IO,Text_IO,Direct_IO,The Implementation of Standard I/O
21300 @anchor{gnat_rm/the_implementation_of_standard_i_o sequential-io}@anchor{29d}@anchor{gnat_rm/the_implementation_of_standard_i_o id5}@anchor{29e}
21301 @section Sequential_IO
21304 Sequential_IO may be instantiated with either a definite (constrained)
21305 or indefinite (unconstrained) type.
21307 For the definite type case, the elements written to the file are simply
21308 the memory images of the data values with no control information of any
21309 kind. The resulting file should be read using the same type, no validity
21310 checking is performed on input.
21312 For the indefinite type case, the elements written consist of two
21313 parts. First is the size of the data item, written as the memory image
21314 of a @code{Interfaces.C.size_t} value, followed by the memory image of
21315 the data value. The resulting file can only be read using the same
21316 (unconstrained) type. Normal assignment checks are performed on these
21317 read operations, and if these checks fail, @code{Data_Error} is
21318 raised. In particular, in the array case, the lengths must match, and in
21319 the variant record case, if the variable for a particular read operation
21320 is constrained, the discriminants must match.
21322 Note that it is not possible to use Sequential_IO to write variable
21323 length array items, and then read the data back into different length
21324 arrays. For example, the following will raise @code{Data_Error}:
21327 package IO is new Sequential_IO (String);
21332 IO.Write (F, "hello!")
21333 IO.Reset (F, Mode=>In_File);
21338 On some Ada implementations, this will print @code{hell}, but the program is
21339 clearly incorrect, since there is only one element in the file, and that
21340 element is the string @code{hello!}.
21342 In Ada 95 and Ada 2005, this kind of behavior can be legitimately achieved
21343 using Stream_IO, and this is the preferred mechanism. In particular, the
21344 above program fragment rewritten to use Stream_IO will work correctly.
21346 @node Text_IO,Wide_Text_IO,Sequential_IO,The Implementation of Standard I/O
21347 @anchor{gnat_rm/the_implementation_of_standard_i_o id6}@anchor{29f}@anchor{gnat_rm/the_implementation_of_standard_i_o text-io}@anchor{2a0}
21351 Text_IO files consist of a stream of characters containing the following
21352 special control characters:
21355 LF (line feed, 16#0A#) Line Mark
21356 FF (form feed, 16#0C#) Page Mark
21359 A canonical Text_IO file is defined as one in which the following
21360 conditions are met:
21366 The character @code{LF} is used only as a line mark, i.e., to mark the end
21370 The character @code{FF} is used only as a page mark, i.e., to mark the
21371 end of a page and consequently can appear only immediately following a
21372 @code{LF} (line mark) character.
21375 The file ends with either @code{LF} (line mark) or @code{LF}-@cite{FF}
21376 (line mark, page mark). In the former case, the page mark is implicitly
21377 assumed to be present.
21380 A file written using Text_IO will be in canonical form provided that no
21381 explicit @code{LF} or @code{FF} characters are written using @code{Put}
21382 or @code{Put_Line}. There will be no @code{FF} character at the end of
21383 the file unless an explicit @code{New_Page} operation was performed
21384 before closing the file.
21386 A canonical Text_IO file that is a regular file (i.e., not a device or a
21387 pipe) can be read using any of the routines in Text_IO. The
21388 semantics in this case will be exactly as defined in the Ada Reference
21389 Manual, and all the routines in Text_IO are fully implemented.
21391 A text file that does not meet the requirements for a canonical Text_IO
21392 file has one of the following:
21398 The file contains @code{FF} characters not immediately following a
21399 @code{LF} character.
21402 The file contains @code{LF} or @code{FF} characters written by
21403 @code{Put} or @code{Put_Line}, which are not logically considered to be
21404 line marks or page marks.
21407 The file ends in a character other than @code{LF} or @code{FF},
21408 i.e., there is no explicit line mark or page mark at the end of the file.
21411 Text_IO can be used to read such non-standard text files but subprograms
21412 to do with line or page numbers do not have defined meanings. In
21413 particular, a @code{FF} character that does not follow a @code{LF}
21414 character may or may not be treated as a page mark from the point of
21415 view of page and line numbering. Every @code{LF} character is considered
21416 to end a line, and there is an implied @code{LF} character at the end of
21420 * Stream Pointer Positioning::
21421 * Reading and Writing Non-Regular Files::
21423 * Treating Text_IO Files as Streams::
21424 * Text_IO Extensions::
21425 * Text_IO Facilities for Unbounded Strings::
21429 @node Stream Pointer Positioning,Reading and Writing Non-Regular Files,,Text_IO
21430 @anchor{gnat_rm/the_implementation_of_standard_i_o id7}@anchor{2a1}@anchor{gnat_rm/the_implementation_of_standard_i_o stream-pointer-positioning}@anchor{2a2}
21431 @subsection Stream Pointer Positioning
21434 @code{Ada.Text_IO} has a definition of current position for a file that
21435 is being read. No internal buffering occurs in Text_IO, and usually the
21436 physical position in the stream used to implement the file corresponds
21437 to this logical position defined by Text_IO. There are two exceptions:
21443 After a call to @code{End_Of_Page} that returns @code{True}, the stream
21444 is positioned past the @code{LF} (line mark) that precedes the page
21445 mark. Text_IO maintains an internal flag so that subsequent read
21446 operations properly handle the logical position which is unchanged by
21447 the @code{End_Of_Page} call.
21450 After a call to @code{End_Of_File} that returns @code{True}, if the
21451 Text_IO file was positioned before the line mark at the end of file
21452 before the call, then the logical position is unchanged, but the stream
21453 is physically positioned right at the end of file (past the line mark,
21454 and past a possible page mark following the line mark. Again Text_IO
21455 maintains internal flags so that subsequent read operations properly
21456 handle the logical position.
21459 These discrepancies have no effect on the observable behavior of
21460 Text_IO, but if a single Ada stream is shared between a C program and
21461 Ada program, or shared (using @code{shared=yes} in the form string)
21462 between two Ada files, then the difference may be observable in some
21465 @node Reading and Writing Non-Regular Files,Get_Immediate,Stream Pointer Positioning,Text_IO
21466 @anchor{gnat_rm/the_implementation_of_standard_i_o reading-and-writing-non-regular-files}@anchor{2a3}@anchor{gnat_rm/the_implementation_of_standard_i_o id8}@anchor{2a4}
21467 @subsection Reading and Writing Non-Regular Files
21470 A non-regular file is a device (such as a keyboard), or a pipe. Text_IO
21471 can be used for reading and writing. Writing is not affected and the
21472 sequence of characters output is identical to the normal file case, but
21473 for reading, the behavior of Text_IO is modified to avoid undesirable
21474 look-ahead as follows:
21476 An input file that is not a regular file is considered to have no page
21477 marks. Any @code{Ascii.FF} characters (the character normally used for a
21478 page mark) appearing in the file are considered to be data
21479 characters. In particular:
21485 @code{Get_Line} and @code{Skip_Line} do not test for a page mark
21486 following a line mark. If a page mark appears, it will be treated as a
21490 This avoids the need to wait for an extra character to be typed or
21491 entered from the pipe to complete one of these operations.
21494 @code{End_Of_Page} always returns @code{False}
21497 @code{End_Of_File} will return @code{False} if there is a page mark at
21498 the end of the file.
21501 Output to non-regular files is the same as for regular files. Page marks
21502 may be written to non-regular files using @code{New_Page}, but as noted
21503 above they will not be treated as page marks on input if the output is
21504 piped to another Ada program.
21506 Another important discrepancy when reading non-regular files is that the end
21507 of file indication is not 'sticky'. If an end of file is entered, e.g., by
21508 pressing the @code{EOT} key,
21510 is signaled once (i.e., the test @code{End_Of_File}
21511 will yield @code{True}, or a read will
21512 raise @code{End_Error}), but then reading can resume
21513 to read data past that end of
21514 file indication, until another end of file indication is entered.
21516 @node Get_Immediate,Treating Text_IO Files as Streams,Reading and Writing Non-Regular Files,Text_IO
21517 @anchor{gnat_rm/the_implementation_of_standard_i_o get-immediate}@anchor{2a5}@anchor{gnat_rm/the_implementation_of_standard_i_o id9}@anchor{2a6}
21518 @subsection Get_Immediate
21521 @geindex Get_Immediate
21523 Get_Immediate returns the next character (including control characters)
21524 from the input file. In particular, Get_Immediate will return LF or FF
21525 characters used as line marks or page marks. Such operations leave the
21526 file positioned past the control character, and it is thus not treated
21527 as having its normal function. This means that page, line and column
21528 counts after this kind of Get_Immediate call are set as though the mark
21529 did not occur. In the case where a Get_Immediate leaves the file
21530 positioned between the line mark and page mark (which is not normally
21531 possible), it is undefined whether the FF character will be treated as a
21534 @node Treating Text_IO Files as Streams,Text_IO Extensions,Get_Immediate,Text_IO
21535 @anchor{gnat_rm/the_implementation_of_standard_i_o id10}@anchor{2a7}@anchor{gnat_rm/the_implementation_of_standard_i_o treating-text-io-files-as-streams}@anchor{2a8}
21536 @subsection Treating Text_IO Files as Streams
21539 @geindex Stream files
21541 The package @code{Text_IO.Streams} allows a @code{Text_IO} file to be treated
21542 as a stream. Data written to a @code{Text_IO} file in this stream mode is
21543 binary data. If this binary data contains bytes 16#0A# (@code{LF}) or
21544 16#0C# (@code{FF}), the resulting file may have non-standard
21545 format. Similarly if read operations are used to read from a Text_IO
21546 file treated as a stream, then @code{LF} and @code{FF} characters may be
21547 skipped and the effect is similar to that described above for
21548 @code{Get_Immediate}.
21550 @node Text_IO Extensions,Text_IO Facilities for Unbounded Strings,Treating Text_IO Files as Streams,Text_IO
21551 @anchor{gnat_rm/the_implementation_of_standard_i_o id11}@anchor{2a9}@anchor{gnat_rm/the_implementation_of_standard_i_o text-io-extensions}@anchor{2aa}
21552 @subsection Text_IO Extensions
21555 @geindex Text_IO extensions
21557 A package GNAT.IO_Aux in the GNAT library provides some useful extensions
21558 to the standard @code{Text_IO} package:
21564 function File_Exists (Name : String) return Boolean;
21565 Determines if a file of the given name exists.
21568 function Get_Line return String;
21569 Reads a string from the standard input file. The value returned is exactly
21570 the length of the line that was read.
21573 function Get_Line (File : Ada.Text_IO.File_Type) return String;
21574 Similar, except that the parameter File specifies the file from which
21575 the string is to be read.
21578 @node Text_IO Facilities for Unbounded Strings,,Text_IO Extensions,Text_IO
21579 @anchor{gnat_rm/the_implementation_of_standard_i_o text-io-facilities-for-unbounded-strings}@anchor{2ab}@anchor{gnat_rm/the_implementation_of_standard_i_o id12}@anchor{2ac}
21580 @subsection Text_IO Facilities for Unbounded Strings
21583 @geindex Text_IO for unbounded strings
21585 @geindex Unbounded_String
21586 @geindex Text_IO operations
21588 The package @code{Ada.Strings.Unbounded.Text_IO}
21589 in library files @code{a-suteio.ads/adb} contains some GNAT-specific
21590 subprograms useful for Text_IO operations on unbounded strings:
21596 function Get_Line (File : File_Type) return Unbounded_String;
21597 Reads a line from the specified file
21598 and returns the result as an unbounded string.
21601 procedure Put (File : File_Type; U : Unbounded_String);
21602 Writes the value of the given unbounded string to the specified file
21603 Similar to the effect of
21604 @code{Put (To_String (U))} except that an extra copy is avoided.
21607 procedure Put_Line (File : File_Type; U : Unbounded_String);
21608 Writes the value of the given unbounded string to the specified file,
21609 followed by a @code{New_Line}.
21610 Similar to the effect of @code{Put_Line (To_String (U))} except
21611 that an extra copy is avoided.
21614 In the above procedures, @code{File} is of type @code{Ada.Text_IO.File_Type}
21615 and is optional. If the parameter is omitted, then the standard input or
21616 output file is referenced as appropriate.
21618 The package @code{Ada.Strings.Wide_Unbounded.Wide_Text_IO} in library
21619 files @code{a-swuwti.ads} and @code{a-swuwti.adb} provides similar extended
21620 @code{Wide_Text_IO} functionality for unbounded wide strings.
21622 The package @code{Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO} in library
21623 files @code{a-szuzti.ads} and @code{a-szuzti.adb} provides similar extended
21624 @code{Wide_Wide_Text_IO} functionality for unbounded wide wide strings.
21626 @node Wide_Text_IO,Wide_Wide_Text_IO,Text_IO,The Implementation of Standard I/O
21627 @anchor{gnat_rm/the_implementation_of_standard_i_o wide-text-io}@anchor{2ad}@anchor{gnat_rm/the_implementation_of_standard_i_o id13}@anchor{2ae}
21628 @section Wide_Text_IO
21631 @code{Wide_Text_IO} is similar in most respects to Text_IO, except that
21632 both input and output files may contain special sequences that represent
21633 wide character values. The encoding scheme for a given file may be
21634 specified using a FORM parameter:
21640 as part of the FORM string (WCEM = wide character encoding method),
21641 where @code{x} is one of the following characters
21644 @multitable {xxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxx}
21667 Upper half encoding
21704 The encoding methods match those that
21705 can be used in a source
21706 program, but there is no requirement that the encoding method used for
21707 the source program be the same as the encoding method used for files,
21708 and different files may use different encoding methods.
21710 The default encoding method for the standard files, and for opened files
21711 for which no WCEM parameter is given in the FORM string matches the
21712 wide character encoding specified for the main program (the default
21713 being brackets encoding if no coding method was specified with -gnatW).
21718 @item @emph{Hex Coding}
21720 In this encoding, a wide character is represented by a five character
21731 where @code{a}, @code{b}, @code{c}, @code{d} are the four hexadecimal
21732 characters (using upper case letters) of the wide character code. For
21733 example, ESC A345 is used to represent the wide character with code
21734 16#A345#. This scheme is compatible with use of the full
21735 @code{Wide_Character} set.
21741 @item @emph{Upper Half Coding}
21743 The wide character with encoding 16#abcd#, where the upper bit is on
21744 (i.e., a is in the range 8-F) is represented as two bytes 16#ab# and
21745 16#cd#. The second byte may never be a format control character, but is
21746 not required to be in the upper half. This method can be also used for
21747 shift-JIS or EUC where the internal coding matches the external coding.
21749 @item @emph{Shift JIS Coding}
21751 A wide character is represented by a two character sequence 16#ab# and
21752 16#cd#, with the restrictions described for upper half encoding as
21753 described above. The internal character code is the corresponding JIS
21754 character according to the standard algorithm for Shift-JIS
21755 conversion. Only characters defined in the JIS code set table can be
21756 used with this encoding method.
21758 @item @emph{EUC Coding}
21760 A wide character is represented by a two character sequence 16#ab# and
21761 16#cd#, with both characters being in the upper half. The internal
21762 character code is the corresponding JIS character according to the EUC
21763 encoding algorithm. Only characters defined in the JIS code set table
21764 can be used with this encoding method.
21766 @item @emph{UTF-8 Coding}
21768 A wide character is represented using
21769 UCS Transformation Format 8 (UTF-8) as defined in Annex R of ISO
21770 10646-1/Am.2. Depending on the character value, the representation
21771 is a one, two, or three byte sequence:
21775 16#0000#-16#007f#: 2#0xxxxxxx#
21776 16#0080#-16#07ff#: 2#110xxxxx# 2#10xxxxxx#
21777 16#0800#-16#ffff#: 2#1110xxxx# 2#10xxxxxx# 2#10xxxxxx#
21783 where the @code{xxx} bits correspond to the left-padded bits of the
21784 16-bit character value. Note that all lower half ASCII characters
21785 are represented as ASCII bytes and all upper half characters and
21786 other wide characters are represented as sequences of upper-half
21787 (The full UTF-8 scheme allows for encoding 31-bit characters as
21788 6-byte sequences, but in this implementation, all UTF-8 sequences
21789 of four or more bytes length will raise a Constraint_Error, as
21790 will all invalid UTF-8 sequences.)
21796 @item @emph{Brackets Coding}
21798 In this encoding, a wide character is represented by the following eight
21799 character sequence:
21809 where @code{a}, @code{b}, @code{c}, @code{d} are the four hexadecimal
21810 characters (using uppercase letters) of the wide character code. For
21811 example, @code{["A345"]} is used to represent the wide character with code
21813 This scheme is compatible with use of the full Wide_Character set.
21814 On input, brackets coding can also be used for upper half characters,
21815 e.g., @code{["C1"]} for lower case a. However, on output, brackets notation
21816 is only used for wide characters with a code greater than @code{16#FF#}.
21818 Note that brackets coding is not normally used in the context of
21819 Wide_Text_IO or Wide_Wide_Text_IO, since it is really just designed as
21820 a portable way of encoding source files. In the context of Wide_Text_IO
21821 or Wide_Wide_Text_IO, it can only be used if the file does not contain
21822 any instance of the left bracket character other than to encode wide
21823 character values using the brackets encoding method. In practice it is
21824 expected that some standard wide character encoding method such
21825 as UTF-8 will be used for text input output.
21827 If brackets notation is used, then any occurrence of a left bracket
21828 in the input file which is not the start of a valid wide character
21829 sequence will cause Constraint_Error to be raised. It is possible to
21830 encode a left bracket as ["5B"] and Wide_Text_IO and Wide_Wide_Text_IO
21831 input will interpret this as a left bracket.
21833 However, when a left bracket is output, it will be output as a left bracket
21834 and not as ["5B"]. We make this decision because for normal use of
21835 Wide_Text_IO for outputting messages, it is unpleasant to clobber left
21836 brackets. For example, if we write:
21839 Put_Line ("Start of output [first run]");
21842 we really do not want to have the left bracket in this message clobbered so
21843 that the output reads:
21847 Start of output ["5B"]first run]
21853 In practice brackets encoding is reasonably useful for normal Put_Line use
21854 since we won't get confused between left brackets and wide character
21855 sequences in the output. But for input, or when files are written out
21856 and read back in, it really makes better sense to use one of the standard
21857 encoding methods such as UTF-8.
21860 For the coding schemes other than UTF-8, Hex, or Brackets encoding,
21861 not all wide character
21862 values can be represented. An attempt to output a character that cannot
21863 be represented using the encoding scheme for the file causes
21864 Constraint_Error to be raised. An invalid wide character sequence on
21865 input also causes Constraint_Error to be raised.
21868 * Stream Pointer Positioning: Stream Pointer Positioning<2>.
21869 * Reading and Writing Non-Regular Files: Reading and Writing Non-Regular Files<2>.
21873 @node Stream Pointer Positioning<2>,Reading and Writing Non-Regular Files<2>,,Wide_Text_IO
21874 @anchor{gnat_rm/the_implementation_of_standard_i_o stream-pointer-positioning-1}@anchor{2af}@anchor{gnat_rm/the_implementation_of_standard_i_o id14}@anchor{2b0}
21875 @subsection Stream Pointer Positioning
21878 @code{Ada.Wide_Text_IO} is similar to @code{Ada.Text_IO} in its handling
21879 of stream pointer positioning (@ref{2a0,,Text_IO}). There is one additional
21882 If @code{Ada.Wide_Text_IO.Look_Ahead} reads a character outside the
21883 normal lower ASCII set (i.e., a character in the range:
21886 Wide_Character'Val (16#0080#) .. Wide_Character'Val (16#FFFF#)
21889 then although the logical position of the file pointer is unchanged by
21890 the @code{Look_Ahead} call, the stream is physically positioned past the
21891 wide character sequence. Again this is to avoid the need for buffering
21892 or backup, and all @code{Wide_Text_IO} routines check the internal
21893 indication that this situation has occurred so that this is not visible
21894 to a normal program using @code{Wide_Text_IO}. However, this discrepancy
21895 can be observed if the wide text file shares a stream with another file.
21897 @node Reading and Writing Non-Regular Files<2>,,Stream Pointer Positioning<2>,Wide_Text_IO
21898 @anchor{gnat_rm/the_implementation_of_standard_i_o reading-and-writing-non-regular-files-1}@anchor{2b1}@anchor{gnat_rm/the_implementation_of_standard_i_o id15}@anchor{2b2}
21899 @subsection Reading and Writing Non-Regular Files
21902 As in the case of Text_IO, when a non-regular file is read, it is
21903 assumed that the file contains no page marks (any form characters are
21904 treated as data characters), and @code{End_Of_Page} always returns
21905 @code{False}. Similarly, the end of file indication is not sticky, so
21906 it is possible to read beyond an end of file.
21908 @node Wide_Wide_Text_IO,Stream_IO,Wide_Text_IO,The Implementation of Standard I/O
21909 @anchor{gnat_rm/the_implementation_of_standard_i_o id16}@anchor{2b3}@anchor{gnat_rm/the_implementation_of_standard_i_o wide-wide-text-io}@anchor{2b4}
21910 @section Wide_Wide_Text_IO
21913 @code{Wide_Wide_Text_IO} is similar in most respects to Text_IO, except that
21914 both input and output files may contain special sequences that represent
21915 wide wide character values. The encoding scheme for a given file may be
21916 specified using a FORM parameter:
21922 as part of the FORM string (WCEM = wide character encoding method),
21923 where @code{x} is one of the following characters
21926 @multitable {xxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxx}
21949 Upper half encoding
21986 The encoding methods match those that
21987 can be used in a source
21988 program, but there is no requirement that the encoding method used for
21989 the source program be the same as the encoding method used for files,
21990 and different files may use different encoding methods.
21992 The default encoding method for the standard files, and for opened files
21993 for which no WCEM parameter is given in the FORM string matches the
21994 wide character encoding specified for the main program (the default
21995 being brackets encoding if no coding method was specified with -gnatW).
22000 @item @emph{UTF-8 Coding}
22002 A wide character is represented using
22003 UCS Transformation Format 8 (UTF-8) as defined in Annex R of ISO
22004 10646-1/Am.2. Depending on the character value, the representation
22005 is a one, two, three, or four byte sequence:
22009 16#000000#-16#00007f#: 2#0xxxxxxx#
22010 16#000080#-16#0007ff#: 2#110xxxxx# 2#10xxxxxx#
22011 16#000800#-16#00ffff#: 2#1110xxxx# 2#10xxxxxx# 2#10xxxxxx#
22012 16#010000#-16#10ffff#: 2#11110xxx# 2#10xxxxxx# 2#10xxxxxx# 2#10xxxxxx#
22018 where the @code{xxx} bits correspond to the left-padded bits of the
22019 21-bit character value. Note that all lower half ASCII characters
22020 are represented as ASCII bytes and all upper half characters and
22021 other wide characters are represented as sequences of upper-half
22028 @item @emph{Brackets Coding}
22030 In this encoding, a wide wide character is represented by the following eight
22031 character sequence if is in wide character range
22041 and by the following ten character sequence if not
22045 [ " a b c d e f " ]
22051 where @code{a}, @code{b}, @code{c}, @code{d}, @code{e}, and @code{f}
22052 are the four or six hexadecimal
22053 characters (using uppercase letters) of the wide wide character code. For
22054 example, @code{["01A345"]} is used to represent the wide wide character
22055 with code @code{16#01A345#}.
22057 This scheme is compatible with use of the full Wide_Wide_Character set.
22058 On input, brackets coding can also be used for upper half characters,
22059 e.g., @code{["C1"]} for lower case a. However, on output, brackets notation
22060 is only used for wide characters with a code greater than @code{16#FF#}.
22063 If is also possible to use the other Wide_Character encoding methods,
22064 such as Shift-JIS, but the other schemes cannot support the full range
22065 of wide wide characters.
22066 An attempt to output a character that cannot
22067 be represented using the encoding scheme for the file causes
22068 Constraint_Error to be raised. An invalid wide character sequence on
22069 input also causes Constraint_Error to be raised.
22072 * Stream Pointer Positioning: Stream Pointer Positioning<3>.
22073 * Reading and Writing Non-Regular Files: Reading and Writing Non-Regular Files<3>.
22077 @node Stream Pointer Positioning<3>,Reading and Writing Non-Regular Files<3>,,Wide_Wide_Text_IO
22078 @anchor{gnat_rm/the_implementation_of_standard_i_o stream-pointer-positioning-2}@anchor{2b5}@anchor{gnat_rm/the_implementation_of_standard_i_o id17}@anchor{2b6}
22079 @subsection Stream Pointer Positioning
22082 @code{Ada.Wide_Wide_Text_IO} is similar to @code{Ada.Text_IO} in its handling
22083 of stream pointer positioning (@ref{2a0,,Text_IO}). There is one additional
22086 If @code{Ada.Wide_Wide_Text_IO.Look_Ahead} reads a character outside the
22087 normal lower ASCII set (i.e., a character in the range:
22090 Wide_Wide_Character'Val (16#0080#) .. Wide_Wide_Character'Val (16#10FFFF#)
22093 then although the logical position of the file pointer is unchanged by
22094 the @code{Look_Ahead} call, the stream is physically positioned past the
22095 wide character sequence. Again this is to avoid the need for buffering
22096 or backup, and all @code{Wide_Wide_Text_IO} routines check the internal
22097 indication that this situation has occurred so that this is not visible
22098 to a normal program using @code{Wide_Wide_Text_IO}. However, this discrepancy
22099 can be observed if the wide text file shares a stream with another file.
22101 @node Reading and Writing Non-Regular Files<3>,,Stream Pointer Positioning<3>,Wide_Wide_Text_IO
22102 @anchor{gnat_rm/the_implementation_of_standard_i_o id18}@anchor{2b7}@anchor{gnat_rm/the_implementation_of_standard_i_o reading-and-writing-non-regular-files-2}@anchor{2b8}
22103 @subsection Reading and Writing Non-Regular Files
22106 As in the case of Text_IO, when a non-regular file is read, it is
22107 assumed that the file contains no page marks (any form characters are
22108 treated as data characters), and @code{End_Of_Page} always returns
22109 @code{False}. Similarly, the end of file indication is not sticky, so
22110 it is possible to read beyond an end of file.
22112 @node Stream_IO,Text Translation,Wide_Wide_Text_IO,The Implementation of Standard I/O
22113 @anchor{gnat_rm/the_implementation_of_standard_i_o id19}@anchor{2b9}@anchor{gnat_rm/the_implementation_of_standard_i_o stream-io}@anchor{2ba}
22117 A stream file is a sequence of bytes, where individual elements are
22118 written to the file as described in the Ada Reference Manual. The type
22119 @code{Stream_Element} is simply a byte. There are two ways to read or
22120 write a stream file.
22126 The operations @code{Read} and @code{Write} directly read or write a
22127 sequence of stream elements with no control information.
22130 The stream attributes applied to a stream file transfer data in the
22131 manner described for stream attributes.
22134 @node Text Translation,Shared Files,Stream_IO,The Implementation of Standard I/O
22135 @anchor{gnat_rm/the_implementation_of_standard_i_o id20}@anchor{2bb}@anchor{gnat_rm/the_implementation_of_standard_i_o text-translation}@anchor{2bc}
22136 @section Text Translation
22139 @code{Text_Translation=xxx} may be used as the Form parameter
22140 passed to Text_IO.Create and Text_IO.Open. @code{Text_Translation=xxx}
22141 has no effect on Unix systems. Possible values are:
22147 @code{Yes} or @code{Text} is the default, which means to
22148 translate LF to/from CR/LF on Windows systems.
22150 @code{No} disables this translation; i.e. it
22151 uses binary mode. For output files, @code{Text_Translation=No}
22152 may be used to create Unix-style files on
22156 @code{wtext} translation enabled in Unicode mode.
22157 (corresponds to _O_WTEXT).
22160 @code{u8text} translation enabled in Unicode UTF-8 mode.
22161 (corresponds to O_U8TEXT).
22164 @code{u16text} translation enabled in Unicode UTF-16
22165 mode. (corresponds to_O_U16TEXT).
22168 @node Shared Files,Filenames encoding,Text Translation,The Implementation of Standard I/O
22169 @anchor{gnat_rm/the_implementation_of_standard_i_o id21}@anchor{2bd}@anchor{gnat_rm/the_implementation_of_standard_i_o shared-files}@anchor{2be}
22170 @section Shared Files
22173 Section A.14 of the Ada Reference Manual allows implementations to
22174 provide a wide variety of behavior if an attempt is made to access the
22175 same external file with two or more internal files.
22177 To provide a full range of functionality, while at the same time
22178 minimizing the problems of portability caused by this implementation
22179 dependence, GNAT handles file sharing as follows:
22185 In the absence of a @code{shared=xxx} form parameter, an attempt
22186 to open two or more files with the same full name is considered an error
22187 and is not supported. The exception @code{Use_Error} will be
22188 raised. Note that a file that is not explicitly closed by the program
22189 remains open until the program terminates.
22192 If the form parameter @code{shared=no} appears in the form string, the
22193 file can be opened or created with its own separate stream identifier,
22194 regardless of whether other files sharing the same external file are
22195 opened. The exact effect depends on how the C stream routines handle
22196 multiple accesses to the same external files using separate streams.
22199 If the form parameter @code{shared=yes} appears in the form string for
22200 each of two or more files opened using the same full name, the same
22201 stream is shared between these files, and the semantics are as described
22202 in Ada Reference Manual, Section A.14.
22205 When a program that opens multiple files with the same name is ported
22206 from another Ada compiler to GNAT, the effect will be that
22207 @code{Use_Error} is raised.
22209 The documentation of the original compiler and the documentation of the
22210 program should then be examined to determine if file sharing was
22211 expected, and @code{shared=xxx} parameters added to @code{Open}
22212 and @code{Create} calls as required.
22214 When a program is ported from GNAT to some other Ada compiler, no
22215 special attention is required unless the @code{shared=xxx} form
22216 parameter is used in the program. In this case, you must examine the
22217 documentation of the new compiler to see if it supports the required
22218 file sharing semantics, and form strings modified appropriately. Of
22219 course it may be the case that the program cannot be ported if the
22220 target compiler does not support the required functionality. The best
22221 approach in writing portable code is to avoid file sharing (and hence
22222 the use of the @code{shared=xxx} parameter in the form string)
22225 One common use of file sharing in Ada 83 is the use of instantiations of
22226 Sequential_IO on the same file with different types, to achieve
22227 heterogeneous input-output. Although this approach will work in GNAT if
22228 @code{shared=yes} is specified, it is preferable in Ada to use Stream_IO
22229 for this purpose (using the stream attributes)
22231 @node Filenames encoding,File content encoding,Shared Files,The Implementation of Standard I/O
22232 @anchor{gnat_rm/the_implementation_of_standard_i_o filenames-encoding}@anchor{2bf}@anchor{gnat_rm/the_implementation_of_standard_i_o id22}@anchor{2c0}
22233 @section Filenames encoding
22236 An encoding form parameter can be used to specify the filename
22237 encoding @code{encoding=xxx}.
22243 If the form parameter @code{encoding=utf8} appears in the form string, the
22244 filename must be encoded in UTF-8.
22247 If the form parameter @code{encoding=8bits} appears in the form
22248 string, the filename must be a standard 8bits string.
22251 In the absence of a @code{encoding=xxx} form parameter, the
22252 encoding is controlled by the @code{GNAT_CODE_PAGE} environment
22253 variable. And if not set @code{utf8} is assumed.
22258 @item @emph{CP_ACP}
22260 The current system Windows ANSI code page.
22262 @item @emph{CP_UTF8}
22267 This encoding form parameter is only supported on the Windows
22268 platform. On the other Operating Systems the run-time is supporting
22271 @node File content encoding,Open Modes,Filenames encoding,The Implementation of Standard I/O
22272 @anchor{gnat_rm/the_implementation_of_standard_i_o file-content-encoding}@anchor{2c1}@anchor{gnat_rm/the_implementation_of_standard_i_o id23}@anchor{2c2}
22273 @section File content encoding
22276 For text files it is possible to specify the encoding to use. This is
22277 controlled by the by the @code{GNAT_CCS_ENCODING} environment
22278 variable. And if not set @code{TEXT} is assumed.
22280 The possible values are those supported on Windows:
22287 Translated text mode
22291 Translated unicode encoding
22293 @item @emph{U16TEXT}
22295 Unicode 16-bit encoding
22297 @item @emph{U8TEXT}
22299 Unicode 8-bit encoding
22302 This encoding is only supported on the Windows platform.
22304 @node Open Modes,Operations on C Streams,File content encoding,The Implementation of Standard I/O
22305 @anchor{gnat_rm/the_implementation_of_standard_i_o open-modes}@anchor{2c3}@anchor{gnat_rm/the_implementation_of_standard_i_o id24}@anchor{2c4}
22306 @section Open Modes
22309 @code{Open} and @code{Create} calls result in a call to @code{fopen}
22310 using the mode shown in the following table:
22313 @multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxx}
22316 @code{Open} and @code{Create} Call Modes
22358 Out_File (Direct_IO)
22370 Out_File (all other cases)
22395 If text file translation is required, then either @code{b} or @code{t}
22396 is added to the mode, depending on the setting of Text. Text file
22397 translation refers to the mapping of CR/LF sequences in an external file
22398 to LF characters internally. This mapping only occurs in DOS and
22399 DOS-like systems, and is not relevant to other systems.
22401 A special case occurs with Stream_IO. As shown in the above table, the
22402 file is initially opened in @code{r} or @code{w} mode for the
22403 @code{In_File} and @code{Out_File} cases. If a @code{Set_Mode} operation
22404 subsequently requires switching from reading to writing or vice-versa,
22405 then the file is reopened in @code{r+} mode to permit the required operation.
22407 @node Operations on C Streams,Interfacing to C Streams,Open Modes,The Implementation of Standard I/O
22408 @anchor{gnat_rm/the_implementation_of_standard_i_o operations-on-c-streams}@anchor{2c5}@anchor{gnat_rm/the_implementation_of_standard_i_o id25}@anchor{2c6}
22409 @section Operations on C Streams
22412 The package @code{Interfaces.C_Streams} provides an Ada program with direct
22413 access to the C library functions for operations on C streams:
22416 package Interfaces.C_Streams is
22417 -- Note: the reason we do not use the types that are in
22418 -- Interfaces.C is that we want to avoid dragging in the
22419 -- code in this unit if possible.
22420 subtype chars is System.Address;
22421 -- Pointer to null-terminated array of characters
22422 subtype FILEs is System.Address;
22423 -- Corresponds to the C type FILE*
22424 subtype voids is System.Address;
22425 -- Corresponds to the C type void*
22426 subtype int is Integer;
22427 subtype long is Long_Integer;
22428 -- Note: the above types are subtypes deliberately, and it
22429 -- is part of this spec that the above correspondences are
22430 -- guaranteed. This means that it is legitimate to, for
22431 -- example, use Integer instead of int. We provide these
22432 -- synonyms for clarity, but in some cases it may be
22433 -- convenient to use the underlying types (for example to
22434 -- avoid an unnecessary dependency of a spec on the spec
22436 type size_t is mod 2 ** Standard'Address_Size;
22437 NULL_Stream : constant FILEs;
22438 -- Value returned (NULL in C) to indicate an
22439 -- fdopen/fopen/tmpfile error
22440 ----------------------------------
22441 -- Constants Defined in stdio.h --
22442 ----------------------------------
22443 EOF : constant int;
22444 -- Used by a number of routines to indicate error or
22446 IOFBF : constant int;
22447 IOLBF : constant int;
22448 IONBF : constant int;
22449 -- Used to indicate buffering mode for setvbuf call
22450 SEEK_CUR : constant int;
22451 SEEK_END : constant int;
22452 SEEK_SET : constant int;
22453 -- Used to indicate origin for fseek call
22454 function stdin return FILEs;
22455 function stdout return FILEs;
22456 function stderr return FILEs;
22457 -- Streams associated with standard files
22458 --------------------------
22459 -- Standard C functions --
22460 --------------------------
22461 -- The functions selected below are ones that are
22462 -- available in UNIX (but not necessarily in ANSI C).
22463 -- These are very thin interfaces
22464 -- which copy exactly the C headers. For more
22465 -- documentation on these functions, see the Microsoft C
22466 -- "Run-Time Library Reference" (Microsoft Press, 1990,
22467 -- ISBN 1-55615-225-6), which includes useful information
22468 -- on system compatibility.
22469 procedure clearerr (stream : FILEs);
22470 function fclose (stream : FILEs) return int;
22471 function fdopen (handle : int; mode : chars) return FILEs;
22472 function feof (stream : FILEs) return int;
22473 function ferror (stream : FILEs) return int;
22474 function fflush (stream : FILEs) return int;
22475 function fgetc (stream : FILEs) return int;
22476 function fgets (strng : chars; n : int; stream : FILEs)
22478 function fileno (stream : FILEs) return int;
22479 function fopen (filename : chars; Mode : chars)
22481 -- Note: to maintain target independence, use
22482 -- text_translation_required, a boolean variable defined in
22483 -- a-sysdep.c to deal with the target dependent text
22484 -- translation requirement. If this variable is set,
22485 -- then b/t should be appended to the standard mode
22486 -- argument to set the text translation mode off or on
22488 function fputc (C : int; stream : FILEs) return int;
22489 function fputs (Strng : chars; Stream : FILEs) return int;
22506 function ftell (stream : FILEs) return long;
22513 function isatty (handle : int) return int;
22514 procedure mktemp (template : chars);
22515 -- The return value (which is just a pointer to template)
22517 procedure rewind (stream : FILEs);
22518 function rmtmp return int;
22526 function tmpfile return FILEs;
22527 function ungetc (c : int; stream : FILEs) return int;
22528 function unlink (filename : chars) return int;
22529 ---------------------
22530 -- Extra functions --
22531 ---------------------
22532 -- These functions supply slightly thicker bindings than
22533 -- those above. They are derived from functions in the
22534 -- C Run-Time Library, but may do a bit more work than
22535 -- just directly calling one of the Library functions.
22536 function is_regular_file (handle : int) return int;
22537 -- Tests if given handle is for a regular file (result 1)
22538 -- or for a non-regular file (pipe or device, result 0).
22539 ---------------------------------
22540 -- Control of Text/Binary Mode --
22541 ---------------------------------
22542 -- If text_translation_required is true, then the following
22543 -- functions may be used to dynamically switch a file from
22544 -- binary to text mode or vice versa. These functions have
22545 -- no effect if text_translation_required is false (i.e., in
22546 -- normal UNIX mode). Use fileno to get a stream handle.
22547 procedure set_binary_mode (handle : int);
22548 procedure set_text_mode (handle : int);
22549 ----------------------------
22550 -- Full Path Name support --
22551 ----------------------------
22552 procedure full_name (nam : chars; buffer : chars);
22553 -- Given a NUL terminated string representing a file
22554 -- name, returns in buffer a NUL terminated string
22555 -- representing the full path name for the file name.
22556 -- On systems where it is relevant the drive is also
22557 -- part of the full path name. It is the responsibility
22558 -- of the caller to pass an actual parameter for buffer
22559 -- that is big enough for any full path name. Use
22560 -- max_path_len given below as the size of buffer.
22561 max_path_len : integer;
22562 -- Maximum length of an allowable full path name on the
22563 -- system, including a terminating NUL character.
22564 end Interfaces.C_Streams;
22567 @node Interfacing to C Streams,,Operations on C Streams,The Implementation of Standard I/O
22568 @anchor{gnat_rm/the_implementation_of_standard_i_o interfacing-to-c-streams}@anchor{2c7}@anchor{gnat_rm/the_implementation_of_standard_i_o id26}@anchor{2c8}
22569 @section Interfacing to C Streams
22572 The packages in this section permit interfacing Ada files to C Stream
22576 with Interfaces.C_Streams;
22577 package Ada.Sequential_IO.C_Streams is
22578 function C_Stream (F : File_Type)
22579 return Interfaces.C_Streams.FILEs;
22581 (File : in out File_Type;
22582 Mode : in File_Mode;
22583 C_Stream : in Interfaces.C_Streams.FILEs;
22584 Form : in String := "");
22585 end Ada.Sequential_IO.C_Streams;
22587 with Interfaces.C_Streams;
22588 package Ada.Direct_IO.C_Streams is
22589 function C_Stream (F : File_Type)
22590 return Interfaces.C_Streams.FILEs;
22592 (File : in out File_Type;
22593 Mode : in File_Mode;
22594 C_Stream : in Interfaces.C_Streams.FILEs;
22595 Form : in String := "");
22596 end Ada.Direct_IO.C_Streams;
22598 with Interfaces.C_Streams;
22599 package Ada.Text_IO.C_Streams is
22600 function C_Stream (F : File_Type)
22601 return Interfaces.C_Streams.FILEs;
22603 (File : in out File_Type;
22604 Mode : in File_Mode;
22605 C_Stream : in Interfaces.C_Streams.FILEs;
22606 Form : in String := "");
22607 end Ada.Text_IO.C_Streams;
22609 with Interfaces.C_Streams;
22610 package Ada.Wide_Text_IO.C_Streams is
22611 function C_Stream (F : File_Type)
22612 return Interfaces.C_Streams.FILEs;
22614 (File : in out File_Type;
22615 Mode : in File_Mode;
22616 C_Stream : in Interfaces.C_Streams.FILEs;
22617 Form : in String := "");
22618 end Ada.Wide_Text_IO.C_Streams;
22620 with Interfaces.C_Streams;
22621 package Ada.Wide_Wide_Text_IO.C_Streams is
22622 function C_Stream (F : File_Type)
22623 return Interfaces.C_Streams.FILEs;
22625 (File : in out File_Type;
22626 Mode : in File_Mode;
22627 C_Stream : in Interfaces.C_Streams.FILEs;
22628 Form : in String := "");
22629 end Ada.Wide_Wide_Text_IO.C_Streams;
22631 with Interfaces.C_Streams;
22632 package Ada.Stream_IO.C_Streams is
22633 function C_Stream (F : File_Type)
22634 return Interfaces.C_Streams.FILEs;
22636 (File : in out File_Type;
22637 Mode : in File_Mode;
22638 C_Stream : in Interfaces.C_Streams.FILEs;
22639 Form : in String := "");
22640 end Ada.Stream_IO.C_Streams;
22643 In each of these six packages, the @code{C_Stream} function obtains the
22644 @code{FILE} pointer from a currently opened Ada file. It is then
22645 possible to use the @code{Interfaces.C_Streams} package to operate on
22646 this stream, or the stream can be passed to a C program which can
22647 operate on it directly. Of course the program is responsible for
22648 ensuring that only appropriate sequences of operations are executed.
22650 One particular use of relevance to an Ada program is that the
22651 @code{setvbuf} function can be used to control the buffering of the
22652 stream used by an Ada file. In the absence of such a call the standard
22653 default buffering is used.
22655 The @code{Open} procedures in these packages open a file giving an
22656 existing C Stream instead of a file name. Typically this stream is
22657 imported from a C program, allowing an Ada file to operate on an
22660 @node The GNAT Library,Interfacing to Other Languages,The Implementation of Standard I/O,Top
22661 @anchor{gnat_rm/the_gnat_library the-gnat-library}@anchor{10}@anchor{gnat_rm/the_gnat_library doc}@anchor{2c9}@anchor{gnat_rm/the_gnat_library id1}@anchor{2ca}
22662 @chapter The GNAT Library
22665 The GNAT library contains a number of general and special purpose packages.
22666 It represents functionality that the GNAT developers have found useful, and
22667 which is made available to GNAT users. The packages described here are fully
22668 supported, and upwards compatibility will be maintained in future releases,
22669 so you can use these facilities with the confidence that the same functionality
22670 will be available in future releases.
22672 The chapter here simply gives a brief summary of the facilities available.
22673 The full documentation is found in the spec file for the package. The full
22674 sources of these library packages, including both spec and body, are provided
22675 with all GNAT releases. For example, to find out the full specifications of
22676 the SPITBOL pattern matching capability, including a full tutorial and
22677 extensive examples, look in the @code{g-spipat.ads} file in the library.
22679 For each entry here, the package name (as it would appear in a @code{with}
22680 clause) is given, followed by the name of the corresponding spec file in
22681 parentheses. The packages are children in four hierarchies, @code{Ada},
22682 @code{Interfaces}, @code{System}, and @code{GNAT}, the latter being a
22683 GNAT-specific hierarchy.
22685 Note that an application program should only use packages in one of these
22686 four hierarchies if the package is defined in the Ada Reference Manual,
22687 or is listed in this section of the GNAT Programmers Reference Manual.
22688 All other units should be considered internal implementation units and
22689 should not be directly @code{with}ed by application code. The use of
22690 a @code{with} clause that references one of these internal implementation
22691 units makes an application potentially dependent on changes in versions
22692 of GNAT, and will generate a warning message.
22695 * Ada.Characters.Latin_9 (a-chlat9.ads): Ada Characters Latin_9 a-chlat9 ads.
22696 * Ada.Characters.Wide_Latin_1 (a-cwila1.ads): Ada Characters Wide_Latin_1 a-cwila1 ads.
22697 * Ada.Characters.Wide_Latin_9 (a-cwila1.ads): Ada Characters Wide_Latin_9 a-cwila1 ads.
22698 * Ada.Characters.Wide_Wide_Latin_1 (a-chzla1.ads): Ada Characters Wide_Wide_Latin_1 a-chzla1 ads.
22699 * Ada.Characters.Wide_Wide_Latin_9 (a-chzla9.ads): Ada Characters Wide_Wide_Latin_9 a-chzla9 ads.
22700 * Ada.Containers.Formal_Doubly_Linked_Lists (a-cfdlli.ads): Ada Containers Formal_Doubly_Linked_Lists a-cfdlli ads.
22701 * Ada.Containers.Formal_Hashed_Maps (a-cfhama.ads): Ada Containers Formal_Hashed_Maps a-cfhama ads.
22702 * Ada.Containers.Formal_Hashed_Sets (a-cfhase.ads): Ada Containers Formal_Hashed_Sets a-cfhase ads.
22703 * Ada.Containers.Formal_Ordered_Maps (a-cforma.ads): Ada Containers Formal_Ordered_Maps a-cforma ads.
22704 * Ada.Containers.Formal_Ordered_Sets (a-cforse.ads): Ada Containers Formal_Ordered_Sets a-cforse ads.
22705 * Ada.Containers.Formal_Vectors (a-cofove.ads): Ada Containers Formal_Vectors a-cofove ads.
22706 * Ada.Containers.Formal_Indefinite_Vectors (a-cfinve.ads): Ada Containers Formal_Indefinite_Vectors a-cfinve ads.
22707 * Ada.Containers.Functional_Vectors (a-cofuve.ads): Ada Containers Functional_Vectors a-cofuve ads.
22708 * Ada.Containers.Functional_Sets (a-cofuse.ads): Ada Containers Functional_Sets a-cofuse ads.
22709 * Ada.Containers.Functional_Maps (a-cofuma.ads): Ada Containers Functional_Maps a-cofuma ads.
22710 * Ada.Containers.Bounded_Holders (a-coboho.ads): Ada Containers Bounded_Holders a-coboho ads.
22711 * Ada.Command_Line.Environment (a-colien.ads): Ada Command_Line Environment a-colien ads.
22712 * Ada.Command_Line.Remove (a-colire.ads): Ada Command_Line Remove a-colire ads.
22713 * Ada.Command_Line.Response_File (a-clrefi.ads): Ada Command_Line Response_File a-clrefi ads.
22714 * Ada.Direct_IO.C_Streams (a-diocst.ads): Ada Direct_IO C_Streams a-diocst ads.
22715 * Ada.Exceptions.Is_Null_Occurrence (a-einuoc.ads): Ada Exceptions Is_Null_Occurrence a-einuoc ads.
22716 * Ada.Exceptions.Last_Chance_Handler (a-elchha.ads): Ada Exceptions Last_Chance_Handler a-elchha ads.
22717 * Ada.Exceptions.Traceback (a-exctra.ads): Ada Exceptions Traceback a-exctra ads.
22718 * Ada.Sequential_IO.C_Streams (a-siocst.ads): Ada Sequential_IO C_Streams a-siocst ads.
22719 * Ada.Streams.Stream_IO.C_Streams (a-ssicst.ads): Ada Streams Stream_IO C_Streams a-ssicst ads.
22720 * Ada.Strings.Unbounded.Text_IO (a-suteio.ads): Ada Strings Unbounded Text_IO a-suteio ads.
22721 * Ada.Strings.Wide_Unbounded.Wide_Text_IO (a-swuwti.ads): Ada Strings Wide_Unbounded Wide_Text_IO a-swuwti ads.
22722 * Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO (a-szuzti.ads): Ada Strings Wide_Wide_Unbounded Wide_Wide_Text_IO a-szuzti ads.
22723 * Ada.Text_IO.C_Streams (a-tiocst.ads): Ada Text_IO C_Streams a-tiocst ads.
22724 * Ada.Text_IO.Reset_Standard_Files (a-tirsfi.ads): Ada Text_IO Reset_Standard_Files a-tirsfi ads.
22725 * Ada.Wide_Characters.Unicode (a-wichun.ads): Ada Wide_Characters Unicode a-wichun ads.
22726 * Ada.Wide_Text_IO.C_Streams (a-wtcstr.ads): Ada Wide_Text_IO C_Streams a-wtcstr ads.
22727 * Ada.Wide_Text_IO.Reset_Standard_Files (a-wrstfi.ads): Ada Wide_Text_IO Reset_Standard_Files a-wrstfi ads.
22728 * Ada.Wide_Wide_Characters.Unicode (a-zchuni.ads): Ada Wide_Wide_Characters Unicode a-zchuni ads.
22729 * Ada.Wide_Wide_Text_IO.C_Streams (a-ztcstr.ads): Ada Wide_Wide_Text_IO C_Streams a-ztcstr ads.
22730 * Ada.Wide_Wide_Text_IO.Reset_Standard_Files (a-zrstfi.ads): Ada Wide_Wide_Text_IO Reset_Standard_Files a-zrstfi ads.
22731 * GNAT.Altivec (g-altive.ads): GNAT Altivec g-altive ads.
22732 * GNAT.Altivec.Conversions (g-altcon.ads): GNAT Altivec Conversions g-altcon ads.
22733 * GNAT.Altivec.Vector_Operations (g-alveop.ads): GNAT Altivec Vector_Operations g-alveop ads.
22734 * GNAT.Altivec.Vector_Types (g-alvety.ads): GNAT Altivec Vector_Types g-alvety ads.
22735 * GNAT.Altivec.Vector_Views (g-alvevi.ads): GNAT Altivec Vector_Views g-alvevi ads.
22736 * GNAT.Array_Split (g-arrspl.ads): GNAT Array_Split g-arrspl ads.
22737 * GNAT.AWK (g-awk.ads): GNAT AWK g-awk ads.
22738 * GNAT.Bind_Environment (g-binenv.ads): GNAT Bind_Environment g-binenv ads.
22739 * GNAT.Bounded_Buffers (g-boubuf.ads): GNAT Bounded_Buffers g-boubuf ads.
22740 * GNAT.Bounded_Mailboxes (g-boumai.ads): GNAT Bounded_Mailboxes g-boumai ads.
22741 * GNAT.Bubble_Sort (g-bubsor.ads): GNAT Bubble_Sort g-bubsor ads.
22742 * GNAT.Bubble_Sort_A (g-busora.ads): GNAT Bubble_Sort_A g-busora ads.
22743 * GNAT.Bubble_Sort_G (g-busorg.ads): GNAT Bubble_Sort_G g-busorg ads.
22744 * GNAT.Byte_Order_Mark (g-byorma.ads): GNAT Byte_Order_Mark g-byorma ads.
22745 * GNAT.Byte_Swapping (g-bytswa.ads): GNAT Byte_Swapping g-bytswa ads.
22746 * GNAT.Calendar (g-calend.ads): GNAT Calendar g-calend ads.
22747 * GNAT.Calendar.Time_IO (g-catiio.ads): GNAT Calendar Time_IO g-catiio ads.
22748 * GNAT.CRC32 (g-crc32.ads): GNAT CRC32 g-crc32 ads.
22749 * GNAT.Case_Util (g-casuti.ads): GNAT Case_Util g-casuti ads.
22750 * GNAT.CGI (g-cgi.ads): GNAT CGI g-cgi ads.
22751 * GNAT.CGI.Cookie (g-cgicoo.ads): GNAT CGI Cookie g-cgicoo ads.
22752 * GNAT.CGI.Debug (g-cgideb.ads): GNAT CGI Debug g-cgideb ads.
22753 * GNAT.Command_Line (g-comlin.ads): GNAT Command_Line g-comlin ads.
22754 * GNAT.Compiler_Version (g-comver.ads): GNAT Compiler_Version g-comver ads.
22755 * GNAT.Ctrl_C (g-ctrl_c.ads): GNAT Ctrl_C g-ctrl_c ads.
22756 * GNAT.Current_Exception (g-curexc.ads): GNAT Current_Exception g-curexc ads.
22757 * GNAT.Debug_Pools (g-debpoo.ads): GNAT Debug_Pools g-debpoo ads.
22758 * GNAT.Debug_Utilities (g-debuti.ads): GNAT Debug_Utilities g-debuti ads.
22759 * GNAT.Decode_String (g-decstr.ads): GNAT Decode_String g-decstr ads.
22760 * GNAT.Decode_UTF8_String (g-deutst.ads): GNAT Decode_UTF8_String g-deutst ads.
22761 * GNAT.Directory_Operations (g-dirope.ads): GNAT Directory_Operations g-dirope ads.
22762 * GNAT.Directory_Operations.Iteration (g-diopit.ads): GNAT Directory_Operations Iteration g-diopit ads.
22763 * GNAT.Dynamic_HTables (g-dynhta.ads): GNAT Dynamic_HTables g-dynhta ads.
22764 * GNAT.Dynamic_Tables (g-dyntab.ads): GNAT Dynamic_Tables g-dyntab ads.
22765 * GNAT.Encode_String (g-encstr.ads): GNAT Encode_String g-encstr ads.
22766 * GNAT.Encode_UTF8_String (g-enutst.ads): GNAT Encode_UTF8_String g-enutst ads.
22767 * GNAT.Exception_Actions (g-excact.ads): GNAT Exception_Actions g-excact ads.
22768 * GNAT.Exception_Traces (g-exctra.ads): GNAT Exception_Traces g-exctra ads.
22769 * GNAT.Exceptions (g-expect.ads): GNAT Exceptions g-expect ads.
22770 * GNAT.Expect (g-expect.ads): GNAT Expect g-expect ads.
22771 * GNAT.Expect.TTY (g-exptty.ads): GNAT Expect TTY g-exptty ads.
22772 * GNAT.Float_Control (g-flocon.ads): GNAT Float_Control g-flocon ads.
22773 * GNAT.Formatted_String (g-forstr.ads): GNAT Formatted_String g-forstr ads.
22774 * GNAT.Heap_Sort (g-heasor.ads): GNAT Heap_Sort g-heasor ads.
22775 * GNAT.Heap_Sort_A (g-hesora.ads): GNAT Heap_Sort_A g-hesora ads.
22776 * GNAT.Heap_Sort_G (g-hesorg.ads): GNAT Heap_Sort_G g-hesorg ads.
22777 * GNAT.HTable (g-htable.ads): GNAT HTable g-htable ads.
22778 * GNAT.IO (g-io.ads): GNAT IO g-io ads.
22779 * GNAT.IO_Aux (g-io_aux.ads): GNAT IO_Aux g-io_aux ads.
22780 * GNAT.Lock_Files (g-locfil.ads): GNAT Lock_Files g-locfil ads.
22781 * GNAT.MBBS_Discrete_Random (g-mbdira.ads): GNAT MBBS_Discrete_Random g-mbdira ads.
22782 * GNAT.MBBS_Float_Random (g-mbflra.ads): GNAT MBBS_Float_Random g-mbflra ads.
22783 * GNAT.MD5 (g-md5.ads): GNAT MD5 g-md5 ads.
22784 * GNAT.Memory_Dump (g-memdum.ads): GNAT Memory_Dump g-memdum ads.
22785 * GNAT.Most_Recent_Exception (g-moreex.ads): GNAT Most_Recent_Exception g-moreex ads.
22786 * GNAT.OS_Lib (g-os_lib.ads): GNAT OS_Lib g-os_lib ads.
22787 * GNAT.Perfect_Hash_Generators (g-pehage.ads): GNAT Perfect_Hash_Generators g-pehage ads.
22788 * GNAT.Random_Numbers (g-rannum.ads): GNAT Random_Numbers g-rannum ads.
22789 * GNAT.Regexp (g-regexp.ads): GNAT Regexp g-regexp ads.
22790 * GNAT.Registry (g-regist.ads): GNAT Registry g-regist ads.
22791 * GNAT.Regpat (g-regpat.ads): GNAT Regpat g-regpat ads.
22792 * GNAT.Rewrite_Data (g-rewdat.ads): GNAT Rewrite_Data g-rewdat ads.
22793 * GNAT.Secondary_Stack_Info (g-sestin.ads): GNAT Secondary_Stack_Info g-sestin ads.
22794 * GNAT.Semaphores (g-semaph.ads): GNAT Semaphores g-semaph ads.
22795 * GNAT.Serial_Communications (g-sercom.ads): GNAT Serial_Communications g-sercom ads.
22796 * GNAT.SHA1 (g-sha1.ads): GNAT SHA1 g-sha1 ads.
22797 * GNAT.SHA224 (g-sha224.ads): GNAT SHA224 g-sha224 ads.
22798 * GNAT.SHA256 (g-sha256.ads): GNAT SHA256 g-sha256 ads.
22799 * GNAT.SHA384 (g-sha384.ads): GNAT SHA384 g-sha384 ads.
22800 * GNAT.SHA512 (g-sha512.ads): GNAT SHA512 g-sha512 ads.
22801 * GNAT.Signals (g-signal.ads): GNAT Signals g-signal ads.
22802 * GNAT.Sockets (g-socket.ads): GNAT Sockets g-socket ads.
22803 * GNAT.Source_Info (g-souinf.ads): GNAT Source_Info g-souinf ads.
22804 * GNAT.Spelling_Checker (g-speche.ads): GNAT Spelling_Checker g-speche ads.
22805 * GNAT.Spelling_Checker_Generic (g-spchge.ads): GNAT Spelling_Checker_Generic g-spchge ads.
22806 * GNAT.Spitbol.Patterns (g-spipat.ads): GNAT Spitbol Patterns g-spipat ads.
22807 * GNAT.Spitbol (g-spitbo.ads): GNAT Spitbol g-spitbo ads.
22808 * GNAT.Spitbol.Table_Boolean (g-sptabo.ads): GNAT Spitbol Table_Boolean g-sptabo ads.
22809 * GNAT.Spitbol.Table_Integer (g-sptain.ads): GNAT Spitbol Table_Integer g-sptain ads.
22810 * GNAT.Spitbol.Table_VString (g-sptavs.ads): GNAT Spitbol Table_VString g-sptavs ads.
22811 * GNAT.SSE (g-sse.ads): GNAT SSE g-sse ads.
22812 * GNAT.SSE.Vector_Types (g-ssvety.ads): GNAT SSE Vector_Types g-ssvety ads.
22813 * GNAT.String_Hash (g-strhas.ads): GNAT String_Hash g-strhas ads.
22814 * GNAT.Strings (g-string.ads): GNAT Strings g-string ads.
22815 * GNAT.String_Split (g-strspl.ads): GNAT String_Split g-strspl ads.
22816 * GNAT.Table (g-table.ads): GNAT Table g-table ads.
22817 * GNAT.Task_Lock (g-tasloc.ads): GNAT Task_Lock g-tasloc ads.
22818 * GNAT.Time_Stamp (g-timsta.ads): GNAT Time_Stamp g-timsta ads.
22819 * GNAT.Threads (g-thread.ads): GNAT Threads g-thread ads.
22820 * GNAT.Traceback (g-traceb.ads): GNAT Traceback g-traceb ads.
22821 * GNAT.Traceback.Symbolic (g-trasym.ads): GNAT Traceback Symbolic g-trasym ads.
22822 * GNAT.UTF_32 (g-table.ads): GNAT UTF_32 g-table ads.
22823 * GNAT.Wide_Spelling_Checker (g-u3spch.ads): GNAT Wide_Spelling_Checker g-u3spch ads.
22824 * GNAT.Wide_Spelling_Checker (g-wispch.ads): GNAT Wide_Spelling_Checker g-wispch ads.
22825 * GNAT.Wide_String_Split (g-wistsp.ads): GNAT Wide_String_Split g-wistsp ads.
22826 * GNAT.Wide_Wide_Spelling_Checker (g-zspche.ads): GNAT Wide_Wide_Spelling_Checker g-zspche ads.
22827 * GNAT.Wide_Wide_String_Split (g-zistsp.ads): GNAT Wide_Wide_String_Split g-zistsp ads.
22828 * Interfaces.C.Extensions (i-cexten.ads): Interfaces C Extensions i-cexten ads.
22829 * Interfaces.C.Streams (i-cstrea.ads): Interfaces C Streams i-cstrea ads.
22830 * Interfaces.Packed_Decimal (i-pacdec.ads): Interfaces Packed_Decimal i-pacdec ads.
22831 * Interfaces.VxWorks (i-vxwork.ads): Interfaces VxWorks i-vxwork ads.
22832 * Interfaces.VxWorks.Int_Connection (i-vxinco.ads): Interfaces VxWorks Int_Connection i-vxinco ads.
22833 * Interfaces.VxWorks.IO (i-vxwoio.ads): Interfaces VxWorks IO i-vxwoio ads.
22834 * System.Address_Image (s-addima.ads): System Address_Image s-addima ads.
22835 * System.Assertions (s-assert.ads): System Assertions s-assert ads.
22836 * System.Atomic_Counters (s-atocou.ads): System Atomic_Counters s-atocou ads.
22837 * System.Memory (s-memory.ads): System Memory s-memory ads.
22838 * System.Multiprocessors (s-multip.ads): System Multiprocessors s-multip ads.
22839 * System.Multiprocessors.Dispatching_Domains (s-mudido.ads): System Multiprocessors Dispatching_Domains s-mudido ads.
22840 * System.Partition_Interface (s-parint.ads): System Partition_Interface s-parint ads.
22841 * System.Pool_Global (s-pooglo.ads): System Pool_Global s-pooglo ads.
22842 * System.Pool_Local (s-pooloc.ads): System Pool_Local s-pooloc ads.
22843 * System.Restrictions (s-restri.ads): System Restrictions s-restri ads.
22844 * System.Rident (s-rident.ads): System Rident s-rident ads.
22845 * System.Strings.Stream_Ops (s-ststop.ads): System Strings Stream_Ops s-ststop ads.
22846 * System.Unsigned_Types (s-unstyp.ads): System Unsigned_Types s-unstyp ads.
22847 * System.Wch_Cnv (s-wchcnv.ads): System Wch_Cnv s-wchcnv ads.
22848 * System.Wch_Con (s-wchcon.ads): System Wch_Con s-wchcon ads.
22852 @node Ada Characters Latin_9 a-chlat9 ads,Ada Characters Wide_Latin_1 a-cwila1 ads,,The GNAT Library
22853 @anchor{gnat_rm/the_gnat_library id2}@anchor{2cb}@anchor{gnat_rm/the_gnat_library ada-characters-latin-9-a-chlat9-ads}@anchor{2cc}
22854 @section @code{Ada.Characters.Latin_9} (@code{a-chlat9.ads})
22857 @geindex Ada.Characters.Latin_9 (a-chlat9.ads)
22859 @geindex Latin_9 constants for Character
22861 This child of @code{Ada.Characters}
22862 provides a set of definitions corresponding to those in the
22863 RM-defined package @code{Ada.Characters.Latin_1} but with the
22864 few modifications required for @code{Latin-9}
22865 The provision of such a package
22866 is specifically authorized by the Ada Reference Manual
22869 @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
22870 @anchor{gnat_rm/the_gnat_library ada-characters-wide-latin-1-a-cwila1-ads}@anchor{2cd}@anchor{gnat_rm/the_gnat_library id3}@anchor{2ce}
22871 @section @code{Ada.Characters.Wide_Latin_1} (@code{a-cwila1.ads})
22874 @geindex Ada.Characters.Wide_Latin_1 (a-cwila1.ads)
22876 @geindex Latin_1 constants for Wide_Character
22878 This child of @code{Ada.Characters}
22879 provides a set of definitions corresponding to those in the
22880 RM-defined package @code{Ada.Characters.Latin_1} but with the
22881 types of the constants being @code{Wide_Character}
22882 instead of @code{Character}. The provision of such a package
22883 is specifically authorized by the Ada Reference Manual
22886 @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
22887 @anchor{gnat_rm/the_gnat_library id4}@anchor{2cf}@anchor{gnat_rm/the_gnat_library ada-characters-wide-latin-9-a-cwila1-ads}@anchor{2d0}
22888 @section @code{Ada.Characters.Wide_Latin_9} (@code{a-cwila1.ads})
22891 @geindex Ada.Characters.Wide_Latin_9 (a-cwila1.ads)
22893 @geindex Latin_9 constants for Wide_Character
22895 This child of @code{Ada.Characters}
22896 provides a set of definitions corresponding to those in the
22897 GNAT defined package @code{Ada.Characters.Latin_9} but with the
22898 types of the constants being @code{Wide_Character}
22899 instead of @code{Character}. The provision of such a package
22900 is specifically authorized by the Ada Reference Manual
22903 @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
22904 @anchor{gnat_rm/the_gnat_library ada-characters-wide-wide-latin-1-a-chzla1-ads}@anchor{2d1}@anchor{gnat_rm/the_gnat_library id5}@anchor{2d2}
22905 @section @code{Ada.Characters.Wide_Wide_Latin_1} (@code{a-chzla1.ads})
22908 @geindex Ada.Characters.Wide_Wide_Latin_1 (a-chzla1.ads)
22910 @geindex Latin_1 constants for Wide_Wide_Character
22912 This child of @code{Ada.Characters}
22913 provides a set of definitions corresponding to those in the
22914 RM-defined package @code{Ada.Characters.Latin_1} but with the
22915 types of the constants being @code{Wide_Wide_Character}
22916 instead of @code{Character}. The provision of such a package
22917 is specifically authorized by the Ada Reference Manual
22920 @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
22921 @anchor{gnat_rm/the_gnat_library ada-characters-wide-wide-latin-9-a-chzla9-ads}@anchor{2d3}@anchor{gnat_rm/the_gnat_library id6}@anchor{2d4}
22922 @section @code{Ada.Characters.Wide_Wide_Latin_9} (@code{a-chzla9.ads})
22925 @geindex Ada.Characters.Wide_Wide_Latin_9 (a-chzla9.ads)
22927 @geindex Latin_9 constants for Wide_Wide_Character
22929 This child of @code{Ada.Characters}
22930 provides a set of definitions corresponding to those in the
22931 GNAT defined package @code{Ada.Characters.Latin_9} but with the
22932 types of the constants being @code{Wide_Wide_Character}
22933 instead of @code{Character}. The provision of such a package
22934 is specifically authorized by the Ada Reference Manual
22937 @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
22938 @anchor{gnat_rm/the_gnat_library id7}@anchor{2d5}@anchor{gnat_rm/the_gnat_library ada-containers-formal-doubly-linked-lists-a-cfdlli-ads}@anchor{2d6}
22939 @section @code{Ada.Containers.Formal_Doubly_Linked_Lists} (@code{a-cfdlli.ads})
22942 @geindex Ada.Containers.Formal_Doubly_Linked_Lists (a-cfdlli.ads)
22944 @geindex Formal container for doubly linked lists
22946 This child of @code{Ada.Containers} defines a modified version of the
22947 Ada 2005 container for doubly linked lists, meant to facilitate formal
22948 verification of code using such containers. The specification of this
22949 unit is compatible with SPARK 2014.
22951 Note that although this container was designed with formal verification
22952 in mind, it may well be generally useful in that it is a simplified more
22953 efficient version than the one defined in the standard. In particular it
22954 does not have the complex overhead required to detect cursor tampering.
22956 @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
22957 @anchor{gnat_rm/the_gnat_library id8}@anchor{2d7}@anchor{gnat_rm/the_gnat_library ada-containers-formal-hashed-maps-a-cfhama-ads}@anchor{2d8}
22958 @section @code{Ada.Containers.Formal_Hashed_Maps} (@code{a-cfhama.ads})
22961 @geindex Ada.Containers.Formal_Hashed_Maps (a-cfhama.ads)
22963 @geindex Formal container for hashed maps
22965 This child of @code{Ada.Containers} defines a modified version of the
22966 Ada 2005 container for hashed maps, meant to facilitate formal
22967 verification of code using such containers. The specification of this
22968 unit is compatible with SPARK 2014.
22970 Note that although this container was designed with formal verification
22971 in mind, it may well be generally useful in that it is a simplified more
22972 efficient version than the one defined in the standard. In particular it
22973 does not have the complex overhead required to detect cursor tampering.
22975 @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
22976 @anchor{gnat_rm/the_gnat_library id9}@anchor{2d9}@anchor{gnat_rm/the_gnat_library ada-containers-formal-hashed-sets-a-cfhase-ads}@anchor{2da}
22977 @section @code{Ada.Containers.Formal_Hashed_Sets} (@code{a-cfhase.ads})
22980 @geindex Ada.Containers.Formal_Hashed_Sets (a-cfhase.ads)
22982 @geindex Formal container for hashed sets
22984 This child of @code{Ada.Containers} defines a modified version of the
22985 Ada 2005 container for hashed sets, meant to facilitate formal
22986 verification of code using such containers. The specification of this
22987 unit is compatible with SPARK 2014.
22989 Note that although this container was designed with formal verification
22990 in mind, it may well be generally useful in that it is a simplified more
22991 efficient version than the one defined in the standard. In particular it
22992 does not have the complex overhead required to detect cursor tampering.
22994 @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
22995 @anchor{gnat_rm/the_gnat_library id10}@anchor{2db}@anchor{gnat_rm/the_gnat_library ada-containers-formal-ordered-maps-a-cforma-ads}@anchor{2dc}
22996 @section @code{Ada.Containers.Formal_Ordered_Maps} (@code{a-cforma.ads})
22999 @geindex Ada.Containers.Formal_Ordered_Maps (a-cforma.ads)
23001 @geindex Formal container for ordered maps
23003 This child of @code{Ada.Containers} defines a modified version of the
23004 Ada 2005 container for ordered maps, meant to facilitate formal
23005 verification of code using such containers. The specification of this
23006 unit is compatible with SPARK 2014.
23008 Note that although this container was designed with formal verification
23009 in mind, it may well be generally useful in that it is a simplified more
23010 efficient version than the one defined in the standard. In particular it
23011 does not have the complex overhead required to detect cursor tampering.
23013 @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
23014 @anchor{gnat_rm/the_gnat_library ada-containers-formal-ordered-sets-a-cforse-ads}@anchor{2dd}@anchor{gnat_rm/the_gnat_library id11}@anchor{2de}
23015 @section @code{Ada.Containers.Formal_Ordered_Sets} (@code{a-cforse.ads})
23018 @geindex Ada.Containers.Formal_Ordered_Sets (a-cforse.ads)
23020 @geindex Formal container for ordered sets
23022 This child of @code{Ada.Containers} defines a modified version of the
23023 Ada 2005 container for ordered sets, meant to facilitate formal
23024 verification of code using such containers. The specification of this
23025 unit is compatible with SPARK 2014.
23027 Note that although this container was designed with formal verification
23028 in mind, it may well be generally useful in that it is a simplified more
23029 efficient version than the one defined in the standard. In particular it
23030 does not have the complex overhead required to detect cursor tampering.
23032 @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
23033 @anchor{gnat_rm/the_gnat_library id12}@anchor{2df}@anchor{gnat_rm/the_gnat_library ada-containers-formal-vectors-a-cofove-ads}@anchor{2e0}
23034 @section @code{Ada.Containers.Formal_Vectors} (@code{a-cofove.ads})
23037 @geindex Ada.Containers.Formal_Vectors (a-cofove.ads)
23039 @geindex Formal container for vectors
23041 This child of @code{Ada.Containers} defines a modified version of the
23042 Ada 2005 container for vectors, meant to facilitate formal
23043 verification of code using such containers. The specification of this
23044 unit is compatible with SPARK 2014.
23046 Note that although this container was designed with formal verification
23047 in mind, it may well be generally useful in that it is a simplified more
23048 efficient version than the one defined in the standard. In particular it
23049 does not have the complex overhead required to detect cursor tampering.
23051 @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
23052 @anchor{gnat_rm/the_gnat_library id13}@anchor{2e1}@anchor{gnat_rm/the_gnat_library ada-containers-formal-indefinite-vectors-a-cfinve-ads}@anchor{2e2}
23053 @section @code{Ada.Containers.Formal_Indefinite_Vectors} (@code{a-cfinve.ads})
23056 @geindex Ada.Containers.Formal_Indefinite_Vectors (a-cfinve.ads)
23058 @geindex Formal container for vectors
23060 This child of @code{Ada.Containers} defines a modified version of the
23061 Ada 2005 container for vectors of indefinite elements, meant to
23062 facilitate formal verification of code using such containers. The
23063 specification of this unit is compatible with SPARK 2014.
23065 Note that although this container was designed with formal verification
23066 in mind, it may well be generally useful in that it is a simplified more
23067 efficient version than the one defined in the standard. In particular it
23068 does not have the complex overhead required to detect cursor tampering.
23070 @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
23071 @anchor{gnat_rm/the_gnat_library id14}@anchor{2e3}@anchor{gnat_rm/the_gnat_library ada-containers-functional-vectors-a-cofuve-ads}@anchor{2e4}
23072 @section @code{Ada.Containers.Functional_Vectors} (@code{a-cofuve.ads})
23075 @geindex Ada.Containers.Functional_Vectors (a-cofuve.ads)
23077 @geindex Functional vectors
23079 This child of @code{Ada.Containers} defines immutable vectors. These
23080 containers are unbounded and may contain indefinite elements. Furthermore, to
23081 be usable in every context, they are neither controlled nor limited. As they
23082 are functional, that is, no primitives are provided which would allow modifying
23083 an existing container, these containers can still be used safely.
23085 Their API features functions creating new containers from existing ones.
23086 As a consequence, these containers are highly inefficient. They are also
23087 memory consuming, as the allocated memory is not reclaimed when the container
23088 is no longer referenced. Thus, they should in general be used in ghost code
23089 and annotations, so that they can be removed from the final executable. The
23090 specification of this unit is compatible with SPARK 2014.
23092 @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
23093 @anchor{gnat_rm/the_gnat_library ada-containers-functional-sets-a-cofuse-ads}@anchor{2e5}@anchor{gnat_rm/the_gnat_library id15}@anchor{2e6}
23094 @section @code{Ada.Containers.Functional_Sets} (@code{a-cofuse.ads})
23097 @geindex Ada.Containers.Functional_Sets (a-cofuse.ads)
23099 @geindex Functional sets
23101 This child of @code{Ada.Containers} defines immutable sets. These containers are
23102 unbounded and may contain indefinite elements. Furthermore, to be usable in
23103 every context, they are neither controlled nor limited. As they are functional,
23104 that is, no primitives are provided which would allow modifying an existing
23105 container, these containers can still be used safely.
23107 Their API features functions creating new containers from existing ones.
23108 As a consequence, these containers are highly inefficient. They are also
23109 memory consuming, as the allocated memory is not reclaimed when the container
23110 is no longer referenced. Thus, they should in general be used in ghost code
23111 and annotations, so that they can be removed from the final executable. The
23112 specification of this unit is compatible with SPARK 2014.
23114 @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
23115 @anchor{gnat_rm/the_gnat_library id16}@anchor{2e7}@anchor{gnat_rm/the_gnat_library ada-containers-functional-maps-a-cofuma-ads}@anchor{2e8}
23116 @section @code{Ada.Containers.Functional_Maps} (@code{a-cofuma.ads})
23119 @geindex Ada.Containers.Functional_Maps (a-cofuma.ads)
23121 @geindex Functional maps
23123 This child of @code{Ada.Containers} defines immutable maps. These containers are
23124 unbounded and may contain indefinite elements. Furthermore, to be usable in
23125 every context, they are neither controlled nor limited. As they are functional,
23126 that is, no primitives are provided which would allow modifying an existing
23127 container, these containers can still be used safely.
23129 Their API features functions creating new containers from existing ones.
23130 As a consequence, these containers are highly inefficient. They are also
23131 memory consuming, as the allocated memory is not reclaimed when the container
23132 is no longer referenced. Thus, they should in general be used in ghost code
23133 and annotations, so that they can be removed from the final executable. The
23134 specification of this unit is compatible with SPARK 2014.
23136 @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
23137 @anchor{gnat_rm/the_gnat_library ada-containers-bounded-holders-a-coboho-ads}@anchor{2e9}@anchor{gnat_rm/the_gnat_library id17}@anchor{2ea}
23138 @section @code{Ada.Containers.Bounded_Holders} (@code{a-coboho.ads})
23141 @geindex Ada.Containers.Bounded_Holders (a-coboho.ads)
23143 @geindex Formal container for vectors
23145 This child of @code{Ada.Containers} defines a modified version of
23146 Indefinite_Holders that avoids heap allocation.
23148 @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
23149 @anchor{gnat_rm/the_gnat_library ada-command-line-environment-a-colien-ads}@anchor{2eb}@anchor{gnat_rm/the_gnat_library id18}@anchor{2ec}
23150 @section @code{Ada.Command_Line.Environment} (@code{a-colien.ads})
23153 @geindex Ada.Command_Line.Environment (a-colien.ads)
23155 @geindex Environment entries
23157 This child of @code{Ada.Command_Line}
23158 provides a mechanism for obtaining environment values on systems
23159 where this concept makes sense.
23161 @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
23162 @anchor{gnat_rm/the_gnat_library id19}@anchor{2ed}@anchor{gnat_rm/the_gnat_library ada-command-line-remove-a-colire-ads}@anchor{2ee}
23163 @section @code{Ada.Command_Line.Remove} (@code{a-colire.ads})
23166 @geindex Ada.Command_Line.Remove (a-colire.ads)
23168 @geindex Removing command line arguments
23170 @geindex Command line
23171 @geindex argument removal
23173 This child of @code{Ada.Command_Line}
23174 provides a mechanism for logically removing
23175 arguments from the argument list. Once removed, an argument is not visible
23176 to further calls on the subprograms in @code{Ada.Command_Line} will not
23177 see the removed argument.
23179 @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
23180 @anchor{gnat_rm/the_gnat_library id20}@anchor{2ef}@anchor{gnat_rm/the_gnat_library ada-command-line-response-file-a-clrefi-ads}@anchor{2f0}
23181 @section @code{Ada.Command_Line.Response_File} (@code{a-clrefi.ads})
23184 @geindex Ada.Command_Line.Response_File (a-clrefi.ads)
23186 @geindex Response file for command line
23188 @geindex Command line
23189 @geindex response file
23191 @geindex Command line
23192 @geindex handling long command lines
23194 This child of @code{Ada.Command_Line} provides a mechanism facilities for
23195 getting command line arguments from a text file, called a "response file".
23196 Using a response file allow passing a set of arguments to an executable longer
23197 than the maximum allowed by the system on the command line.
23199 @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
23200 @anchor{gnat_rm/the_gnat_library id21}@anchor{2f1}@anchor{gnat_rm/the_gnat_library ada-direct-io-c-streams-a-diocst-ads}@anchor{2f2}
23201 @section @code{Ada.Direct_IO.C_Streams} (@code{a-diocst.ads})
23204 @geindex Ada.Direct_IO.C_Streams (a-diocst.ads)
23207 @geindex Interfacing with Direct_IO
23209 This package provides subprograms that allow interfacing between
23210 C streams and @code{Direct_IO}. The stream identifier can be
23211 extracted from a file opened on the Ada side, and an Ada file
23212 can be constructed from a stream opened on the C side.
23214 @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
23215 @anchor{gnat_rm/the_gnat_library id22}@anchor{2f3}@anchor{gnat_rm/the_gnat_library ada-exceptions-is-null-occurrence-a-einuoc-ads}@anchor{2f4}
23216 @section @code{Ada.Exceptions.Is_Null_Occurrence} (@code{a-einuoc.ads})
23219 @geindex Ada.Exceptions.Is_Null_Occurrence (a-einuoc.ads)
23221 @geindex Null_Occurrence
23222 @geindex testing for
23224 This child subprogram provides a way of testing for the null
23225 exception occurrence (@code{Null_Occurrence}) without raising
23228 @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
23229 @anchor{gnat_rm/the_gnat_library id23}@anchor{2f5}@anchor{gnat_rm/the_gnat_library ada-exceptions-last-chance-handler-a-elchha-ads}@anchor{2f6}
23230 @section @code{Ada.Exceptions.Last_Chance_Handler} (@code{a-elchha.ads})
23233 @geindex Ada.Exceptions.Last_Chance_Handler (a-elchha.ads)
23235 @geindex Null_Occurrence
23236 @geindex testing for
23238 This child subprogram is used for handling otherwise unhandled
23239 exceptions (hence the name last chance), and perform clean ups before
23240 terminating the program. Note that this subprogram never returns.
23242 @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
23243 @anchor{gnat_rm/the_gnat_library ada-exceptions-traceback-a-exctra-ads}@anchor{2f7}@anchor{gnat_rm/the_gnat_library id24}@anchor{2f8}
23244 @section @code{Ada.Exceptions.Traceback} (@code{a-exctra.ads})
23247 @geindex Ada.Exceptions.Traceback (a-exctra.ads)
23249 @geindex Traceback for Exception Occurrence
23251 This child package provides the subprogram (@code{Tracebacks}) to
23252 give a traceback array of addresses based on an exception
23255 @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
23256 @anchor{gnat_rm/the_gnat_library ada-sequential-io-c-streams-a-siocst-ads}@anchor{2f9}@anchor{gnat_rm/the_gnat_library id25}@anchor{2fa}
23257 @section @code{Ada.Sequential_IO.C_Streams} (@code{a-siocst.ads})
23260 @geindex Ada.Sequential_IO.C_Streams (a-siocst.ads)
23263 @geindex Interfacing with Sequential_IO
23265 This package provides subprograms that allow interfacing between
23266 C streams and @code{Sequential_IO}. The stream identifier can be
23267 extracted from a file opened on the Ada side, and an Ada file
23268 can be constructed from a stream opened on the C side.
23270 @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
23271 @anchor{gnat_rm/the_gnat_library id26}@anchor{2fb}@anchor{gnat_rm/the_gnat_library ada-streams-stream-io-c-streams-a-ssicst-ads}@anchor{2fc}
23272 @section @code{Ada.Streams.Stream_IO.C_Streams} (@code{a-ssicst.ads})
23275 @geindex Ada.Streams.Stream_IO.C_Streams (a-ssicst.ads)
23278 @geindex Interfacing with Stream_IO
23280 This package provides subprograms that allow interfacing between
23281 C streams and @code{Stream_IO}. The stream identifier can be
23282 extracted from a file opened on the Ada side, and an Ada file
23283 can be constructed from a stream opened on the C side.
23285 @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
23286 @anchor{gnat_rm/the_gnat_library ada-strings-unbounded-text-io-a-suteio-ads}@anchor{2fd}@anchor{gnat_rm/the_gnat_library id27}@anchor{2fe}
23287 @section @code{Ada.Strings.Unbounded.Text_IO} (@code{a-suteio.ads})
23290 @geindex Ada.Strings.Unbounded.Text_IO (a-suteio.ads)
23292 @geindex Unbounded_String
23293 @geindex IO support
23296 @geindex extensions for unbounded strings
23298 This package provides subprograms for Text_IO for unbounded
23299 strings, avoiding the necessity for an intermediate operation
23300 with ordinary strings.
23302 @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
23303 @anchor{gnat_rm/the_gnat_library id28}@anchor{2ff}@anchor{gnat_rm/the_gnat_library ada-strings-wide-unbounded-wide-text-io-a-swuwti-ads}@anchor{300}
23304 @section @code{Ada.Strings.Wide_Unbounded.Wide_Text_IO} (@code{a-swuwti.ads})
23307 @geindex Ada.Strings.Wide_Unbounded.Wide_Text_IO (a-swuwti.ads)
23309 @geindex Unbounded_Wide_String
23310 @geindex IO support
23313 @geindex extensions for unbounded wide strings
23315 This package provides subprograms for Text_IO for unbounded
23316 wide strings, avoiding the necessity for an intermediate operation
23317 with ordinary wide strings.
23319 @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
23320 @anchor{gnat_rm/the_gnat_library id29}@anchor{301}@anchor{gnat_rm/the_gnat_library ada-strings-wide-wide-unbounded-wide-wide-text-io-a-szuzti-ads}@anchor{302}
23321 @section @code{Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO} (@code{a-szuzti.ads})
23324 @geindex Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO (a-szuzti.ads)
23326 @geindex Unbounded_Wide_Wide_String
23327 @geindex IO support
23330 @geindex extensions for unbounded wide wide strings
23332 This package provides subprograms for Text_IO for unbounded
23333 wide wide strings, avoiding the necessity for an intermediate operation
23334 with ordinary wide wide strings.
23336 @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
23337 @anchor{gnat_rm/the_gnat_library ada-text-io-c-streams-a-tiocst-ads}@anchor{303}@anchor{gnat_rm/the_gnat_library id30}@anchor{304}
23338 @section @code{Ada.Text_IO.C_Streams} (@code{a-tiocst.ads})
23341 @geindex Ada.Text_IO.C_Streams (a-tiocst.ads)
23344 @geindex Interfacing with `@w{`}Text_IO`@w{`}
23346 This package provides subprograms that allow interfacing between
23347 C streams and @code{Text_IO}. The stream identifier can be
23348 extracted from a file opened on the Ada side, and an Ada file
23349 can be constructed from a stream opened on the C side.
23351 @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
23352 @anchor{gnat_rm/the_gnat_library ada-text-io-reset-standard-files-a-tirsfi-ads}@anchor{305}@anchor{gnat_rm/the_gnat_library id31}@anchor{306}
23353 @section @code{Ada.Text_IO.Reset_Standard_Files} (@code{a-tirsfi.ads})
23356 @geindex Ada.Text_IO.Reset_Standard_Files (a-tirsfi.ads)
23358 @geindex Text_IO resetting standard files
23360 This procedure is used to reset the status of the standard files used
23361 by Ada.Text_IO. This is useful in a situation (such as a restart in an
23362 embedded application) where the status of the files may change during
23363 execution (for example a standard input file may be redefined to be
23366 @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
23367 @anchor{gnat_rm/the_gnat_library id32}@anchor{307}@anchor{gnat_rm/the_gnat_library ada-wide-characters-unicode-a-wichun-ads}@anchor{308}
23368 @section @code{Ada.Wide_Characters.Unicode} (@code{a-wichun.ads})
23371 @geindex Ada.Wide_Characters.Unicode (a-wichun.ads)
23373 @geindex Unicode categorization
23374 @geindex Wide_Character
23376 This package provides subprograms that allow categorization of
23377 Wide_Character values according to Unicode categories.
23379 @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
23380 @anchor{gnat_rm/the_gnat_library ada-wide-text-io-c-streams-a-wtcstr-ads}@anchor{309}@anchor{gnat_rm/the_gnat_library id33}@anchor{30a}
23381 @section @code{Ada.Wide_Text_IO.C_Streams} (@code{a-wtcstr.ads})
23384 @geindex Ada.Wide_Text_IO.C_Streams (a-wtcstr.ads)
23387 @geindex Interfacing with `@w{`}Wide_Text_IO`@w{`}
23389 This package provides subprograms that allow interfacing between
23390 C streams and @code{Wide_Text_IO}. The stream identifier can be
23391 extracted from a file opened on the Ada side, and an Ada file
23392 can be constructed from a stream opened on the C side.
23394 @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
23395 @anchor{gnat_rm/the_gnat_library ada-wide-text-io-reset-standard-files-a-wrstfi-ads}@anchor{30b}@anchor{gnat_rm/the_gnat_library id34}@anchor{30c}
23396 @section @code{Ada.Wide_Text_IO.Reset_Standard_Files} (@code{a-wrstfi.ads})
23399 @geindex Ada.Wide_Text_IO.Reset_Standard_Files (a-wrstfi.ads)
23401 @geindex Wide_Text_IO resetting standard files
23403 This procedure is used to reset the status of the standard files used
23404 by Ada.Wide_Text_IO. This is useful in a situation (such as a restart in an
23405 embedded application) where the status of the files may change during
23406 execution (for example a standard input file may be redefined to be
23409 @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
23410 @anchor{gnat_rm/the_gnat_library id35}@anchor{30d}@anchor{gnat_rm/the_gnat_library ada-wide-wide-characters-unicode-a-zchuni-ads}@anchor{30e}
23411 @section @code{Ada.Wide_Wide_Characters.Unicode} (@code{a-zchuni.ads})
23414 @geindex Ada.Wide_Wide_Characters.Unicode (a-zchuni.ads)
23416 @geindex Unicode categorization
23417 @geindex Wide_Wide_Character
23419 This package provides subprograms that allow categorization of
23420 Wide_Wide_Character values according to Unicode categories.
23422 @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
23423 @anchor{gnat_rm/the_gnat_library id36}@anchor{30f}@anchor{gnat_rm/the_gnat_library ada-wide-wide-text-io-c-streams-a-ztcstr-ads}@anchor{310}
23424 @section @code{Ada.Wide_Wide_Text_IO.C_Streams} (@code{a-ztcstr.ads})
23427 @geindex Ada.Wide_Wide_Text_IO.C_Streams (a-ztcstr.ads)
23430 @geindex Interfacing with `@w{`}Wide_Wide_Text_IO`@w{`}
23432 This package provides subprograms that allow interfacing between
23433 C streams and @code{Wide_Wide_Text_IO}. The stream identifier can be
23434 extracted from a file opened on the Ada side, and an Ada file
23435 can be constructed from a stream opened on the C side.
23437 @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
23438 @anchor{gnat_rm/the_gnat_library id37}@anchor{311}@anchor{gnat_rm/the_gnat_library ada-wide-wide-text-io-reset-standard-files-a-zrstfi-ads}@anchor{312}
23439 @section @code{Ada.Wide_Wide_Text_IO.Reset_Standard_Files} (@code{a-zrstfi.ads})
23442 @geindex Ada.Wide_Wide_Text_IO.Reset_Standard_Files (a-zrstfi.ads)
23444 @geindex Wide_Wide_Text_IO resetting standard files
23446 This procedure is used to reset the status of the standard files used
23447 by Ada.Wide_Wide_Text_IO. This is useful in a situation (such as a
23448 restart in an embedded application) where the status of the files may
23449 change during execution (for example a standard input file may be
23450 redefined to be interactive).
23452 @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
23453 @anchor{gnat_rm/the_gnat_library gnat-altivec-g-altive-ads}@anchor{313}@anchor{gnat_rm/the_gnat_library id38}@anchor{314}
23454 @section @code{GNAT.Altivec} (@code{g-altive.ads})
23457 @geindex GNAT.Altivec (g-altive.ads)
23461 This is the root package of the GNAT AltiVec binding. It provides
23462 definitions of constants and types common to all the versions of the
23465 @node GNAT Altivec Conversions g-altcon ads,GNAT Altivec Vector_Operations g-alveop ads,GNAT Altivec g-altive ads,The GNAT Library
23466 @anchor{gnat_rm/the_gnat_library gnat-altivec-conversions-g-altcon-ads}@anchor{315}@anchor{gnat_rm/the_gnat_library id39}@anchor{316}
23467 @section @code{GNAT.Altivec.Conversions} (@code{g-altcon.ads})
23470 @geindex GNAT.Altivec.Conversions (g-altcon.ads)
23474 This package provides the Vector/View conversion routines.
23476 @node GNAT Altivec Vector_Operations g-alveop ads,GNAT Altivec Vector_Types g-alvety ads,GNAT Altivec Conversions g-altcon ads,The GNAT Library
23477 @anchor{gnat_rm/the_gnat_library gnat-altivec-vector-operations-g-alveop-ads}@anchor{317}@anchor{gnat_rm/the_gnat_library id40}@anchor{318}
23478 @section @code{GNAT.Altivec.Vector_Operations} (@code{g-alveop.ads})
23481 @geindex GNAT.Altivec.Vector_Operations (g-alveop.ads)
23485 This package exposes the Ada interface to the AltiVec operations on
23486 vector objects. A soft emulation is included by default in the GNAT
23487 library. The hard binding is provided as a separate package. This unit
23488 is common to both bindings.
23490 @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
23491 @anchor{gnat_rm/the_gnat_library gnat-altivec-vector-types-g-alvety-ads}@anchor{319}@anchor{gnat_rm/the_gnat_library id41}@anchor{31a}
23492 @section @code{GNAT.Altivec.Vector_Types} (@code{g-alvety.ads})
23495 @geindex GNAT.Altivec.Vector_Types (g-alvety.ads)
23499 This package exposes the various vector types part of the Ada binding
23500 to AltiVec facilities.
23502 @node GNAT Altivec Vector_Views g-alvevi ads,GNAT Array_Split g-arrspl ads,GNAT Altivec Vector_Types g-alvety ads,The GNAT Library
23503 @anchor{gnat_rm/the_gnat_library gnat-altivec-vector-views-g-alvevi-ads}@anchor{31b}@anchor{gnat_rm/the_gnat_library id42}@anchor{31c}
23504 @section @code{GNAT.Altivec.Vector_Views} (@code{g-alvevi.ads})
23507 @geindex GNAT.Altivec.Vector_Views (g-alvevi.ads)
23511 This package provides public 'View' data types from/to which private
23512 vector representations can be converted via
23513 GNAT.Altivec.Conversions. This allows convenient access to individual
23514 vector elements and provides a simple way to initialize vector
23517 @node GNAT Array_Split g-arrspl ads,GNAT AWK g-awk ads,GNAT Altivec Vector_Views g-alvevi ads,The GNAT Library
23518 @anchor{gnat_rm/the_gnat_library gnat-array-split-g-arrspl-ads}@anchor{31d}@anchor{gnat_rm/the_gnat_library id43}@anchor{31e}
23519 @section @code{GNAT.Array_Split} (@code{g-arrspl.ads})
23522 @geindex GNAT.Array_Split (g-arrspl.ads)
23524 @geindex Array splitter
23526 Useful array-manipulation routines: given a set of separators, split
23527 an array wherever the separators appear, and provide direct access
23528 to the resulting slices.
23530 @node GNAT AWK g-awk ads,GNAT Bind_Environment g-binenv ads,GNAT Array_Split g-arrspl ads,The GNAT Library
23531 @anchor{gnat_rm/the_gnat_library id44}@anchor{31f}@anchor{gnat_rm/the_gnat_library gnat-awk-g-awk-ads}@anchor{320}
23532 @section @code{GNAT.AWK} (@code{g-awk.ads})
23535 @geindex GNAT.AWK (g-awk.ads)
23541 Provides AWK-like parsing functions, with an easy interface for parsing one
23542 or more files containing formatted data. The file is viewed as a database
23543 where each record is a line and a field is a data element in this line.
23545 @node GNAT Bind_Environment g-binenv ads,GNAT Bounded_Buffers g-boubuf ads,GNAT AWK g-awk ads,The GNAT Library
23546 @anchor{gnat_rm/the_gnat_library gnat-bind-environment-g-binenv-ads}@anchor{321}@anchor{gnat_rm/the_gnat_library id45}@anchor{322}
23547 @section @code{GNAT.Bind_Environment} (@code{g-binenv.ads})
23550 @geindex GNAT.Bind_Environment (g-binenv.ads)
23552 @geindex Bind environment
23554 Provides access to key=value associations captured at bind time.
23555 These associations can be specified using the @code{-V} binder command
23558 @node GNAT Bounded_Buffers g-boubuf ads,GNAT Bounded_Mailboxes g-boumai ads,GNAT Bind_Environment g-binenv ads,The GNAT Library
23559 @anchor{gnat_rm/the_gnat_library id46}@anchor{323}@anchor{gnat_rm/the_gnat_library gnat-bounded-buffers-g-boubuf-ads}@anchor{324}
23560 @section @code{GNAT.Bounded_Buffers} (@code{g-boubuf.ads})
23563 @geindex GNAT.Bounded_Buffers (g-boubuf.ads)
23567 @geindex Bounded Buffers
23569 Provides a concurrent generic bounded buffer abstraction. Instances are
23570 useful directly or as parts of the implementations of other abstractions,
23573 @node GNAT Bounded_Mailboxes g-boumai ads,GNAT Bubble_Sort g-bubsor ads,GNAT Bounded_Buffers g-boubuf ads,The GNAT Library
23574 @anchor{gnat_rm/the_gnat_library id47}@anchor{325}@anchor{gnat_rm/the_gnat_library gnat-bounded-mailboxes-g-boumai-ads}@anchor{326}
23575 @section @code{GNAT.Bounded_Mailboxes} (@code{g-boumai.ads})
23578 @geindex GNAT.Bounded_Mailboxes (g-boumai.ads)
23584 Provides a thread-safe asynchronous intertask mailbox communication facility.
23586 @node GNAT Bubble_Sort g-bubsor ads,GNAT Bubble_Sort_A g-busora ads,GNAT Bounded_Mailboxes g-boumai ads,The GNAT Library
23587 @anchor{gnat_rm/the_gnat_library gnat-bubble-sort-g-bubsor-ads}@anchor{327}@anchor{gnat_rm/the_gnat_library id48}@anchor{328}
23588 @section @code{GNAT.Bubble_Sort} (@code{g-bubsor.ads})
23591 @geindex GNAT.Bubble_Sort (g-bubsor.ads)
23595 @geindex Bubble sort
23597 Provides a general implementation of bubble sort usable for sorting arbitrary
23598 data items. Exchange and comparison procedures are provided by passing
23599 access-to-procedure values.
23601 @node GNAT Bubble_Sort_A g-busora ads,GNAT Bubble_Sort_G g-busorg ads,GNAT Bubble_Sort g-bubsor ads,The GNAT Library
23602 @anchor{gnat_rm/the_gnat_library id49}@anchor{329}@anchor{gnat_rm/the_gnat_library gnat-bubble-sort-a-g-busora-ads}@anchor{32a}
23603 @section @code{GNAT.Bubble_Sort_A} (@code{g-busora.ads})
23606 @geindex GNAT.Bubble_Sort_A (g-busora.ads)
23610 @geindex Bubble sort
23612 Provides a general implementation of bubble sort usable for sorting arbitrary
23613 data items. Move and comparison procedures are provided by passing
23614 access-to-procedure values. This is an older version, retained for
23615 compatibility. Usually @code{GNAT.Bubble_Sort} will be preferable.
23617 @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
23618 @anchor{gnat_rm/the_gnat_library gnat-bubble-sort-g-g-busorg-ads}@anchor{32b}@anchor{gnat_rm/the_gnat_library id50}@anchor{32c}
23619 @section @code{GNAT.Bubble_Sort_G} (@code{g-busorg.ads})
23622 @geindex GNAT.Bubble_Sort_G (g-busorg.ads)
23626 @geindex Bubble sort
23628 Similar to @code{Bubble_Sort_A} except that the move and sorting procedures
23629 are provided as generic parameters, this improves efficiency, especially
23630 if the procedures can be inlined, at the expense of duplicating code for
23631 multiple instantiations.
23633 @node GNAT Byte_Order_Mark g-byorma ads,GNAT Byte_Swapping g-bytswa ads,GNAT Bubble_Sort_G g-busorg ads,The GNAT Library
23634 @anchor{gnat_rm/the_gnat_library gnat-byte-order-mark-g-byorma-ads}@anchor{32d}@anchor{gnat_rm/the_gnat_library id51}@anchor{32e}
23635 @section @code{GNAT.Byte_Order_Mark} (@code{g-byorma.ads})
23638 @geindex GNAT.Byte_Order_Mark (g-byorma.ads)
23640 @geindex UTF-8 representation
23642 @geindex Wide characte representations
23644 Provides a routine which given a string, reads the start of the string to
23645 see whether it is one of the standard byte order marks (BOM's) which signal
23646 the encoding of the string. The routine includes detection of special XML
23647 sequences for various UCS input formats.
23649 @node GNAT Byte_Swapping g-bytswa ads,GNAT Calendar g-calend ads,GNAT Byte_Order_Mark g-byorma ads,The GNAT Library
23650 @anchor{gnat_rm/the_gnat_library gnat-byte-swapping-g-bytswa-ads}@anchor{32f}@anchor{gnat_rm/the_gnat_library id52}@anchor{330}
23651 @section @code{GNAT.Byte_Swapping} (@code{g-bytswa.ads})
23654 @geindex GNAT.Byte_Swapping (g-bytswa.ads)
23656 @geindex Byte swapping
23658 @geindex Endianness
23660 General routines for swapping the bytes in 2-, 4-, and 8-byte quantities.
23661 Machine-specific implementations are available in some cases.
23663 @node GNAT Calendar g-calend ads,GNAT Calendar Time_IO g-catiio ads,GNAT Byte_Swapping g-bytswa ads,The GNAT Library
23664 @anchor{gnat_rm/the_gnat_library gnat-calendar-g-calend-ads}@anchor{331}@anchor{gnat_rm/the_gnat_library id53}@anchor{332}
23665 @section @code{GNAT.Calendar} (@code{g-calend.ads})
23668 @geindex GNAT.Calendar (g-calend.ads)
23672 Extends the facilities provided by @code{Ada.Calendar} to include handling
23673 of days of the week, an extended @code{Split} and @code{Time_Of} capability.
23674 Also provides conversion of @code{Ada.Calendar.Time} values to and from the
23675 C @code{timeval} format.
23677 @node GNAT Calendar Time_IO g-catiio ads,GNAT CRC32 g-crc32 ads,GNAT Calendar g-calend ads,The GNAT Library
23678 @anchor{gnat_rm/the_gnat_library id54}@anchor{333}@anchor{gnat_rm/the_gnat_library gnat-calendar-time-io-g-catiio-ads}@anchor{334}
23679 @section @code{GNAT.Calendar.Time_IO} (@code{g-catiio.ads})
23686 @geindex GNAT.Calendar.Time_IO (g-catiio.ads)
23688 @node GNAT CRC32 g-crc32 ads,GNAT Case_Util g-casuti ads,GNAT Calendar Time_IO g-catiio ads,The GNAT Library
23689 @anchor{gnat_rm/the_gnat_library id55}@anchor{335}@anchor{gnat_rm/the_gnat_library gnat-crc32-g-crc32-ads}@anchor{336}
23690 @section @code{GNAT.CRC32} (@code{g-crc32.ads})
23693 @geindex GNAT.CRC32 (g-crc32.ads)
23697 @geindex Cyclic Redundancy Check
23699 This package implements the CRC-32 algorithm. For a full description
23700 of this algorithm see
23701 @emph{Computation of Cyclic Redundancy Checks via Table Look-Up},
23702 @cite{Communications of the ACM}, Vol. 31 No. 8, pp. 1008-1013,
23703 Aug. 1988. Sarwate, D.V.
23705 @node GNAT Case_Util g-casuti ads,GNAT CGI g-cgi ads,GNAT CRC32 g-crc32 ads,The GNAT Library
23706 @anchor{gnat_rm/the_gnat_library id56}@anchor{337}@anchor{gnat_rm/the_gnat_library gnat-case-util-g-casuti-ads}@anchor{338}
23707 @section @code{GNAT.Case_Util} (@code{g-casuti.ads})
23710 @geindex GNAT.Case_Util (g-casuti.ads)
23712 @geindex Casing utilities
23714 @geindex Character handling (`@w{`}GNAT.Case_Util`@w{`})
23716 A set of simple routines for handling upper and lower casing of strings
23717 without the overhead of the full casing tables
23718 in @code{Ada.Characters.Handling}.
23720 @node GNAT CGI g-cgi ads,GNAT CGI Cookie g-cgicoo ads,GNAT Case_Util g-casuti ads,The GNAT Library
23721 @anchor{gnat_rm/the_gnat_library id57}@anchor{339}@anchor{gnat_rm/the_gnat_library gnat-cgi-g-cgi-ads}@anchor{33a}
23722 @section @code{GNAT.CGI} (@code{g-cgi.ads})
23725 @geindex GNAT.CGI (g-cgi.ads)
23727 @geindex CGI (Common Gateway Interface)
23729 This is a package for interfacing a GNAT program with a Web server via the
23730 Common Gateway Interface (CGI). Basically this package parses the CGI
23731 parameters, which are a set of key/value pairs sent by the Web server. It
23732 builds a table whose index is the key and provides some services to deal
23735 @node GNAT CGI Cookie g-cgicoo ads,GNAT CGI Debug g-cgideb ads,GNAT CGI g-cgi ads,The GNAT Library
23736 @anchor{gnat_rm/the_gnat_library gnat-cgi-cookie-g-cgicoo-ads}@anchor{33b}@anchor{gnat_rm/the_gnat_library id58}@anchor{33c}
23737 @section @code{GNAT.CGI.Cookie} (@code{g-cgicoo.ads})
23740 @geindex GNAT.CGI.Cookie (g-cgicoo.ads)
23742 @geindex CGI (Common Gateway Interface) cookie support
23744 @geindex Cookie support in CGI
23746 This is a package to interface a GNAT program with a Web server via the
23747 Common Gateway Interface (CGI). It exports services to deal with Web
23748 cookies (piece of information kept in the Web client software).
23750 @node GNAT CGI Debug g-cgideb ads,GNAT Command_Line g-comlin ads,GNAT CGI Cookie g-cgicoo ads,The GNAT Library
23751 @anchor{gnat_rm/the_gnat_library gnat-cgi-debug-g-cgideb-ads}@anchor{33d}@anchor{gnat_rm/the_gnat_library id59}@anchor{33e}
23752 @section @code{GNAT.CGI.Debug} (@code{g-cgideb.ads})
23755 @geindex GNAT.CGI.Debug (g-cgideb.ads)
23757 @geindex CGI (Common Gateway Interface) debugging
23759 This is a package to help debugging CGI (Common Gateway Interface)
23760 programs written in Ada.
23762 @node GNAT Command_Line g-comlin ads,GNAT Compiler_Version g-comver ads,GNAT CGI Debug g-cgideb ads,The GNAT Library
23763 @anchor{gnat_rm/the_gnat_library id60}@anchor{33f}@anchor{gnat_rm/the_gnat_library gnat-command-line-g-comlin-ads}@anchor{340}
23764 @section @code{GNAT.Command_Line} (@code{g-comlin.ads})
23767 @geindex GNAT.Command_Line (g-comlin.ads)
23769 @geindex Command line
23771 Provides a high level interface to @code{Ada.Command_Line} facilities,
23772 including the ability to scan for named switches with optional parameters
23773 and expand file names using wild card notations.
23775 @node GNAT Compiler_Version g-comver ads,GNAT Ctrl_C g-ctrl_c ads,GNAT Command_Line g-comlin ads,The GNAT Library
23776 @anchor{gnat_rm/the_gnat_library gnat-compiler-version-g-comver-ads}@anchor{341}@anchor{gnat_rm/the_gnat_library id61}@anchor{342}
23777 @section @code{GNAT.Compiler_Version} (@code{g-comver.ads})
23780 @geindex GNAT.Compiler_Version (g-comver.ads)
23782 @geindex Compiler Version
23785 @geindex of compiler
23787 Provides a routine for obtaining the version of the compiler used to
23788 compile the program. More accurately this is the version of the binder
23789 used to bind the program (this will normally be the same as the version
23790 of the compiler if a consistent tool set is used to compile all units
23793 @node GNAT Ctrl_C g-ctrl_c ads,GNAT Current_Exception g-curexc ads,GNAT Compiler_Version g-comver ads,The GNAT Library
23794 @anchor{gnat_rm/the_gnat_library gnat-ctrl-c-g-ctrl-c-ads}@anchor{343}@anchor{gnat_rm/the_gnat_library id62}@anchor{344}
23795 @section @code{GNAT.Ctrl_C} (@code{g-ctrl_c.ads})
23798 @geindex GNAT.Ctrl_C (g-ctrl_c.ads)
23802 Provides a simple interface to handle Ctrl-C keyboard events.
23804 @node GNAT Current_Exception g-curexc ads,GNAT Debug_Pools g-debpoo ads,GNAT Ctrl_C g-ctrl_c ads,The GNAT Library
23805 @anchor{gnat_rm/the_gnat_library id63}@anchor{345}@anchor{gnat_rm/the_gnat_library gnat-current-exception-g-curexc-ads}@anchor{346}
23806 @section @code{GNAT.Current_Exception} (@code{g-curexc.ads})
23809 @geindex GNAT.Current_Exception (g-curexc.ads)
23811 @geindex Current exception
23813 @geindex Exception retrieval
23815 Provides access to information on the current exception that has been raised
23816 without the need for using the Ada 95 / Ada 2005 exception choice parameter
23817 specification syntax.
23818 This is particularly useful in simulating typical facilities for
23819 obtaining information about exceptions provided by Ada 83 compilers.
23821 @node GNAT Debug_Pools g-debpoo ads,GNAT Debug_Utilities g-debuti ads,GNAT Current_Exception g-curexc ads,The GNAT Library
23822 @anchor{gnat_rm/the_gnat_library gnat-debug-pools-g-debpoo-ads}@anchor{347}@anchor{gnat_rm/the_gnat_library id64}@anchor{348}
23823 @section @code{GNAT.Debug_Pools} (@code{g-debpoo.ads})
23826 @geindex GNAT.Debug_Pools (g-debpoo.ads)
23830 @geindex Debug pools
23832 @geindex Memory corruption debugging
23834 Provide a debugging storage pools that helps tracking memory corruption
23836 See @code{The GNAT Debug_Pool Facility} section in the @cite{GNAT User's Guide}.
23838 @node GNAT Debug_Utilities g-debuti ads,GNAT Decode_String g-decstr ads,GNAT Debug_Pools g-debpoo ads,The GNAT Library
23839 @anchor{gnat_rm/the_gnat_library id65}@anchor{349}@anchor{gnat_rm/the_gnat_library gnat-debug-utilities-g-debuti-ads}@anchor{34a}
23840 @section @code{GNAT.Debug_Utilities} (@code{g-debuti.ads})
23843 @geindex GNAT.Debug_Utilities (g-debuti.ads)
23847 Provides a few useful utilities for debugging purposes, including conversion
23848 to and from string images of address values. Supports both C and Ada formats
23849 for hexadecimal literals.
23851 @node GNAT Decode_String g-decstr ads,GNAT Decode_UTF8_String g-deutst ads,GNAT Debug_Utilities g-debuti ads,The GNAT Library
23852 @anchor{gnat_rm/the_gnat_library gnat-decode-string-g-decstr-ads}@anchor{34b}@anchor{gnat_rm/the_gnat_library id66}@anchor{34c}
23853 @section @code{GNAT.Decode_String} (@code{g-decstr.ads})
23856 @geindex GNAT.Decode_String (g-decstr.ads)
23858 @geindex Decoding strings
23860 @geindex String decoding
23862 @geindex Wide character encoding
23868 A generic package providing routines for decoding wide character and wide wide
23869 character strings encoded as sequences of 8-bit characters using a specified
23870 encoding method. Includes validation routines, and also routines for stepping
23871 to next or previous encoded character in an encoded string.
23872 Useful in conjunction with Unicode character coding. Note there is a
23873 preinstantiation for UTF-8. See next entry.
23875 @node GNAT Decode_UTF8_String g-deutst ads,GNAT Directory_Operations g-dirope ads,GNAT Decode_String g-decstr ads,The GNAT Library
23876 @anchor{gnat_rm/the_gnat_library gnat-decode-utf8-string-g-deutst-ads}@anchor{34d}@anchor{gnat_rm/the_gnat_library id67}@anchor{34e}
23877 @section @code{GNAT.Decode_UTF8_String} (@code{g-deutst.ads})
23880 @geindex GNAT.Decode_UTF8_String (g-deutst.ads)
23882 @geindex Decoding strings
23884 @geindex Decoding UTF-8 strings
23886 @geindex UTF-8 string decoding
23888 @geindex Wide character decoding
23894 A preinstantiation of GNAT.Decode_Strings for UTF-8 encoding.
23896 @node GNAT Directory_Operations g-dirope ads,GNAT Directory_Operations Iteration g-diopit ads,GNAT Decode_UTF8_String g-deutst ads,The GNAT Library
23897 @anchor{gnat_rm/the_gnat_library gnat-directory-operations-g-dirope-ads}@anchor{34f}@anchor{gnat_rm/the_gnat_library id68}@anchor{350}
23898 @section @code{GNAT.Directory_Operations} (@code{g-dirope.ads})
23901 @geindex GNAT.Directory_Operations (g-dirope.ads)
23903 @geindex Directory operations
23905 Provides a set of routines for manipulating directories, including changing
23906 the current directory, making new directories, and scanning the files in a
23909 @node GNAT Directory_Operations Iteration g-diopit ads,GNAT Dynamic_HTables g-dynhta ads,GNAT Directory_Operations g-dirope ads,The GNAT Library
23910 @anchor{gnat_rm/the_gnat_library id69}@anchor{351}@anchor{gnat_rm/the_gnat_library gnat-directory-operations-iteration-g-diopit-ads}@anchor{352}
23911 @section @code{GNAT.Directory_Operations.Iteration} (@code{g-diopit.ads})
23914 @geindex GNAT.Directory_Operations.Iteration (g-diopit.ads)
23916 @geindex Directory operations iteration
23918 A child unit of GNAT.Directory_Operations providing additional operations
23919 for iterating through directories.
23921 @node GNAT Dynamic_HTables g-dynhta ads,GNAT Dynamic_Tables g-dyntab ads,GNAT Directory_Operations Iteration g-diopit ads,The GNAT Library
23922 @anchor{gnat_rm/the_gnat_library id70}@anchor{353}@anchor{gnat_rm/the_gnat_library gnat-dynamic-htables-g-dynhta-ads}@anchor{354}
23923 @section @code{GNAT.Dynamic_HTables} (@code{g-dynhta.ads})
23926 @geindex GNAT.Dynamic_HTables (g-dynhta.ads)
23928 @geindex Hash tables
23930 A generic implementation of hash tables that can be used to hash arbitrary
23931 data. Provided in two forms, a simple form with built in hash functions,
23932 and a more complex form in which the hash function is supplied.
23934 This package provides a facility similar to that of @code{GNAT.HTable},
23935 except that this package declares a type that can be used to define
23936 dynamic instances of the hash table, while an instantiation of
23937 @code{GNAT.HTable} creates a single instance of the hash table.
23939 @node GNAT Dynamic_Tables g-dyntab ads,GNAT Encode_String g-encstr ads,GNAT Dynamic_HTables g-dynhta ads,The GNAT Library
23940 @anchor{gnat_rm/the_gnat_library gnat-dynamic-tables-g-dyntab-ads}@anchor{355}@anchor{gnat_rm/the_gnat_library id71}@anchor{356}
23941 @section @code{GNAT.Dynamic_Tables} (@code{g-dyntab.ads})
23944 @geindex GNAT.Dynamic_Tables (g-dyntab.ads)
23946 @geindex Table implementation
23949 @geindex extendable
23951 A generic package providing a single dimension array abstraction where the
23952 length of the array can be dynamically modified.
23954 This package provides a facility similar to that of @code{GNAT.Table},
23955 except that this package declares a type that can be used to define
23956 dynamic instances of the table, while an instantiation of
23957 @code{GNAT.Table} creates a single instance of the table type.
23959 @node GNAT Encode_String g-encstr ads,GNAT Encode_UTF8_String g-enutst ads,GNAT Dynamic_Tables g-dyntab ads,The GNAT Library
23960 @anchor{gnat_rm/the_gnat_library id72}@anchor{357}@anchor{gnat_rm/the_gnat_library gnat-encode-string-g-encstr-ads}@anchor{358}
23961 @section @code{GNAT.Encode_String} (@code{g-encstr.ads})
23964 @geindex GNAT.Encode_String (g-encstr.ads)
23966 @geindex Encoding strings
23968 @geindex String encoding
23970 @geindex Wide character encoding
23976 A generic package providing routines for encoding wide character and wide
23977 wide character strings as sequences of 8-bit characters using a specified
23978 encoding method. Useful in conjunction with Unicode character coding.
23979 Note there is a preinstantiation for UTF-8. See next entry.
23981 @node GNAT Encode_UTF8_String g-enutst ads,GNAT Exception_Actions g-excact ads,GNAT Encode_String g-encstr ads,The GNAT Library
23982 @anchor{gnat_rm/the_gnat_library gnat-encode-utf8-string-g-enutst-ads}@anchor{359}@anchor{gnat_rm/the_gnat_library id73}@anchor{35a}
23983 @section @code{GNAT.Encode_UTF8_String} (@code{g-enutst.ads})
23986 @geindex GNAT.Encode_UTF8_String (g-enutst.ads)
23988 @geindex Encoding strings
23990 @geindex Encoding UTF-8 strings
23992 @geindex UTF-8 string encoding
23994 @geindex Wide character encoding
24000 A preinstantiation of GNAT.Encode_Strings for UTF-8 encoding.
24002 @node GNAT Exception_Actions g-excact ads,GNAT Exception_Traces g-exctra ads,GNAT Encode_UTF8_String g-enutst ads,The GNAT Library
24003 @anchor{gnat_rm/the_gnat_library gnat-exception-actions-g-excact-ads}@anchor{35b}@anchor{gnat_rm/the_gnat_library id74}@anchor{35c}
24004 @section @code{GNAT.Exception_Actions} (@code{g-excact.ads})
24007 @geindex GNAT.Exception_Actions (g-excact.ads)
24009 @geindex Exception actions
24011 Provides callbacks when an exception is raised. Callbacks can be registered
24012 for specific exceptions, or when any exception is raised. This
24013 can be used for instance to force a core dump to ease debugging.
24015 @node GNAT Exception_Traces g-exctra ads,GNAT Exceptions g-expect ads,GNAT Exception_Actions g-excact ads,The GNAT Library
24016 @anchor{gnat_rm/the_gnat_library gnat-exception-traces-g-exctra-ads}@anchor{35d}@anchor{gnat_rm/the_gnat_library id75}@anchor{35e}
24017 @section @code{GNAT.Exception_Traces} (@code{g-exctra.ads})
24020 @geindex GNAT.Exception_Traces (g-exctra.ads)
24022 @geindex Exception traces
24026 Provides an interface allowing to control automatic output upon exception
24029 @node GNAT Exceptions g-expect ads,GNAT Expect g-expect ads,GNAT Exception_Traces g-exctra ads,The GNAT Library
24030 @anchor{gnat_rm/the_gnat_library id76}@anchor{35f}@anchor{gnat_rm/the_gnat_library gnat-exceptions-g-expect-ads}@anchor{360}
24031 @section @code{GNAT.Exceptions} (@code{g-expect.ads})
24034 @geindex GNAT.Exceptions (g-expect.ads)
24036 @geindex Exceptions
24039 @geindex Pure packages
24040 @geindex exceptions
24042 Normally it is not possible to raise an exception with
24043 a message from a subprogram in a pure package, since the
24044 necessary types and subprograms are in @code{Ada.Exceptions}
24045 which is not a pure unit. @code{GNAT.Exceptions} provides a
24046 facility for getting around this limitation for a few
24047 predefined exceptions, and for example allow raising
24048 @code{Constraint_Error} with a message from a pure subprogram.
24050 @node GNAT Expect g-expect ads,GNAT Expect TTY g-exptty ads,GNAT Exceptions g-expect ads,The GNAT Library
24051 @anchor{gnat_rm/the_gnat_library gnat-expect-g-expect-ads}@anchor{361}@anchor{gnat_rm/the_gnat_library id77}@anchor{362}
24052 @section @code{GNAT.Expect} (@code{g-expect.ads})
24055 @geindex GNAT.Expect (g-expect.ads)
24057 Provides a set of subprograms similar to what is available
24058 with the standard Tcl Expect tool.
24059 It allows you to easily spawn and communicate with an external process.
24060 You can send commands or inputs to the process, and compare the output
24061 with some expected regular expression. Currently @code{GNAT.Expect}
24062 is implemented on all native GNAT ports.
24063 It is not implemented for cross ports, and in particular is not
24064 implemented for VxWorks or LynxOS.
24066 @node GNAT Expect TTY g-exptty ads,GNAT Float_Control g-flocon ads,GNAT Expect g-expect ads,The GNAT Library
24067 @anchor{gnat_rm/the_gnat_library id78}@anchor{363}@anchor{gnat_rm/the_gnat_library gnat-expect-tty-g-exptty-ads}@anchor{364}
24068 @section @code{GNAT.Expect.TTY} (@code{g-exptty.ads})
24071 @geindex GNAT.Expect.TTY (g-exptty.ads)
24073 As GNAT.Expect but using pseudo-terminal.
24074 Currently @code{GNAT.Expect.TTY} is implemented on all native GNAT
24075 ports. It is not implemented for cross ports, and
24076 in particular is not implemented for VxWorks or LynxOS.
24078 @node GNAT Float_Control g-flocon ads,GNAT Formatted_String g-forstr ads,GNAT Expect TTY g-exptty ads,The GNAT Library
24079 @anchor{gnat_rm/the_gnat_library id79}@anchor{365}@anchor{gnat_rm/the_gnat_library gnat-float-control-g-flocon-ads}@anchor{366}
24080 @section @code{GNAT.Float_Control} (@code{g-flocon.ads})
24083 @geindex GNAT.Float_Control (g-flocon.ads)
24085 @geindex Floating-Point Processor
24087 Provides an interface for resetting the floating-point processor into the
24088 mode required for correct semantic operation in Ada. Some third party
24089 library calls may cause this mode to be modified, and the Reset procedure
24090 in this package can be used to reestablish the required mode.
24092 @node GNAT Formatted_String g-forstr ads,GNAT Heap_Sort g-heasor ads,GNAT Float_Control g-flocon ads,The GNAT Library
24093 @anchor{gnat_rm/the_gnat_library id80}@anchor{367}@anchor{gnat_rm/the_gnat_library gnat-formatted-string-g-forstr-ads}@anchor{368}
24094 @section @code{GNAT.Formatted_String} (@code{g-forstr.ads})
24097 @geindex GNAT.Formatted_String (g-forstr.ads)
24099 @geindex Formatted String
24101 Provides support for C/C++ printf() formatted strings. The format is
24102 copied from the printf() routine and should therefore gives identical
24103 output. Some generic routines are provided to be able to use types
24104 derived from Integer, Float or enumerations as values for the
24107 @node GNAT Heap_Sort g-heasor ads,GNAT Heap_Sort_A g-hesora ads,GNAT Formatted_String g-forstr ads,The GNAT Library
24108 @anchor{gnat_rm/the_gnat_library gnat-heap-sort-g-heasor-ads}@anchor{369}@anchor{gnat_rm/the_gnat_library id81}@anchor{36a}
24109 @section @code{GNAT.Heap_Sort} (@code{g-heasor.ads})
24112 @geindex GNAT.Heap_Sort (g-heasor.ads)
24116 Provides a general implementation of heap sort usable for sorting arbitrary
24117 data items. Exchange and comparison procedures are provided by passing
24118 access-to-procedure values. The algorithm used is a modified heap sort
24119 that performs approximately N*log(N) comparisons in the worst case.
24121 @node GNAT Heap_Sort_A g-hesora ads,GNAT Heap_Sort_G g-hesorg ads,GNAT Heap_Sort g-heasor ads,The GNAT Library
24122 @anchor{gnat_rm/the_gnat_library id82}@anchor{36b}@anchor{gnat_rm/the_gnat_library gnat-heap-sort-a-g-hesora-ads}@anchor{36c}
24123 @section @code{GNAT.Heap_Sort_A} (@code{g-hesora.ads})
24126 @geindex GNAT.Heap_Sort_A (g-hesora.ads)
24130 Provides a general implementation of heap sort usable for sorting arbitrary
24131 data items. Move and comparison procedures are provided by passing
24132 access-to-procedure values. The algorithm used is a modified heap sort
24133 that performs approximately N*log(N) comparisons in the worst case.
24134 This differs from @code{GNAT.Heap_Sort} in having a less convenient
24135 interface, but may be slightly more efficient.
24137 @node GNAT Heap_Sort_G g-hesorg ads,GNAT HTable g-htable ads,GNAT Heap_Sort_A g-hesora ads,The GNAT Library
24138 @anchor{gnat_rm/the_gnat_library id83}@anchor{36d}@anchor{gnat_rm/the_gnat_library gnat-heap-sort-g-g-hesorg-ads}@anchor{36e}
24139 @section @code{GNAT.Heap_Sort_G} (@code{g-hesorg.ads})
24142 @geindex GNAT.Heap_Sort_G (g-hesorg.ads)
24146 Similar to @code{Heap_Sort_A} except that the move and sorting procedures
24147 are provided as generic parameters, this improves efficiency, especially
24148 if the procedures can be inlined, at the expense of duplicating code for
24149 multiple instantiations.
24151 @node GNAT HTable g-htable ads,GNAT IO g-io ads,GNAT Heap_Sort_G g-hesorg ads,The GNAT Library
24152 @anchor{gnat_rm/the_gnat_library id84}@anchor{36f}@anchor{gnat_rm/the_gnat_library gnat-htable-g-htable-ads}@anchor{370}
24153 @section @code{GNAT.HTable} (@code{g-htable.ads})
24156 @geindex GNAT.HTable (g-htable.ads)
24158 @geindex Hash tables
24160 A generic implementation of hash tables that can be used to hash arbitrary
24161 data. Provides two approaches, one a simple static approach, and the other
24162 allowing arbitrary dynamic hash tables.
24164 @node GNAT IO g-io ads,GNAT IO_Aux g-io_aux ads,GNAT HTable g-htable ads,The GNAT Library
24165 @anchor{gnat_rm/the_gnat_library id85}@anchor{371}@anchor{gnat_rm/the_gnat_library gnat-io-g-io-ads}@anchor{372}
24166 @section @code{GNAT.IO} (@code{g-io.ads})
24169 @geindex GNAT.IO (g-io.ads)
24171 @geindex Simple I/O
24173 @geindex Input/Output facilities
24175 A simple preelaborable input-output package that provides a subset of
24176 simple Text_IO functions for reading characters and strings from
24177 Standard_Input, and writing characters, strings and integers to either
24178 Standard_Output or Standard_Error.
24180 @node GNAT IO_Aux g-io_aux ads,GNAT Lock_Files g-locfil ads,GNAT IO g-io ads,The GNAT Library
24181 @anchor{gnat_rm/the_gnat_library gnat-io-aux-g-io-aux-ads}@anchor{373}@anchor{gnat_rm/the_gnat_library id86}@anchor{374}
24182 @section @code{GNAT.IO_Aux} (@code{g-io_aux.ads})
24185 @geindex GNAT.IO_Aux (g-io_aux.ads)
24189 @geindex Input/Output facilities
24191 Provides some auxiliary functions for use with Text_IO, including a test
24192 for whether a file exists, and functions for reading a line of text.
24194 @node GNAT Lock_Files g-locfil ads,GNAT MBBS_Discrete_Random g-mbdira ads,GNAT IO_Aux g-io_aux ads,The GNAT Library
24195 @anchor{gnat_rm/the_gnat_library id87}@anchor{375}@anchor{gnat_rm/the_gnat_library gnat-lock-files-g-locfil-ads}@anchor{376}
24196 @section @code{GNAT.Lock_Files} (@code{g-locfil.ads})
24199 @geindex GNAT.Lock_Files (g-locfil.ads)
24201 @geindex File locking
24203 @geindex Locking using files
24205 Provides a general interface for using files as locks. Can be used for
24206 providing program level synchronization.
24208 @node GNAT MBBS_Discrete_Random g-mbdira ads,GNAT MBBS_Float_Random g-mbflra ads,GNAT Lock_Files g-locfil ads,The GNAT Library
24209 @anchor{gnat_rm/the_gnat_library id88}@anchor{377}@anchor{gnat_rm/the_gnat_library gnat-mbbs-discrete-random-g-mbdira-ads}@anchor{378}
24210 @section @code{GNAT.MBBS_Discrete_Random} (@code{g-mbdira.ads})
24213 @geindex GNAT.MBBS_Discrete_Random (g-mbdira.ads)
24215 @geindex Random number generation
24217 The original implementation of @code{Ada.Numerics.Discrete_Random}. Uses
24218 a modified version of the Blum-Blum-Shub generator.
24220 @node GNAT MBBS_Float_Random g-mbflra ads,GNAT MD5 g-md5 ads,GNAT MBBS_Discrete_Random g-mbdira ads,The GNAT Library
24221 @anchor{gnat_rm/the_gnat_library id89}@anchor{379}@anchor{gnat_rm/the_gnat_library gnat-mbbs-float-random-g-mbflra-ads}@anchor{37a}
24222 @section @code{GNAT.MBBS_Float_Random} (@code{g-mbflra.ads})
24225 @geindex GNAT.MBBS_Float_Random (g-mbflra.ads)
24227 @geindex Random number generation
24229 The original implementation of @code{Ada.Numerics.Float_Random}. Uses
24230 a modified version of the Blum-Blum-Shub generator.
24232 @node GNAT MD5 g-md5 ads,GNAT Memory_Dump g-memdum ads,GNAT MBBS_Float_Random g-mbflra ads,The GNAT Library
24233 @anchor{gnat_rm/the_gnat_library id90}@anchor{37b}@anchor{gnat_rm/the_gnat_library gnat-md5-g-md5-ads}@anchor{37c}
24234 @section @code{GNAT.MD5} (@code{g-md5.ads})
24237 @geindex GNAT.MD5 (g-md5.ads)
24239 @geindex Message Digest MD5
24241 Implements the MD5 Message-Digest Algorithm as described in RFC 1321, and
24242 the HMAC-MD5 message authentication function as described in RFC 2104 and
24245 @node GNAT Memory_Dump g-memdum ads,GNAT Most_Recent_Exception g-moreex ads,GNAT MD5 g-md5 ads,The GNAT Library
24246 @anchor{gnat_rm/the_gnat_library id91}@anchor{37d}@anchor{gnat_rm/the_gnat_library gnat-memory-dump-g-memdum-ads}@anchor{37e}
24247 @section @code{GNAT.Memory_Dump} (@code{g-memdum.ads})
24250 @geindex GNAT.Memory_Dump (g-memdum.ads)
24252 @geindex Dump Memory
24254 Provides a convenient routine for dumping raw memory to either the
24255 standard output or standard error files. Uses GNAT.IO for actual
24258 @node GNAT Most_Recent_Exception g-moreex ads,GNAT OS_Lib g-os_lib ads,GNAT Memory_Dump g-memdum ads,The GNAT Library
24259 @anchor{gnat_rm/the_gnat_library id92}@anchor{37f}@anchor{gnat_rm/the_gnat_library gnat-most-recent-exception-g-moreex-ads}@anchor{380}
24260 @section @code{GNAT.Most_Recent_Exception} (@code{g-moreex.ads})
24263 @geindex GNAT.Most_Recent_Exception (g-moreex.ads)
24266 @geindex obtaining most recent
24268 Provides access to the most recently raised exception. Can be used for
24269 various logging purposes, including duplicating functionality of some
24270 Ada 83 implementation dependent extensions.
24272 @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
24273 @anchor{gnat_rm/the_gnat_library gnat-os-lib-g-os-lib-ads}@anchor{381}@anchor{gnat_rm/the_gnat_library id93}@anchor{382}
24274 @section @code{GNAT.OS_Lib} (@code{g-os_lib.ads})
24277 @geindex GNAT.OS_Lib (g-os_lib.ads)
24279 @geindex Operating System interface
24281 @geindex Spawn capability
24283 Provides a range of target independent operating system interface functions,
24284 including time/date management, file operations, subprocess management,
24285 including a portable spawn procedure, and access to environment variables
24286 and error return codes.
24288 @node GNAT Perfect_Hash_Generators g-pehage ads,GNAT Random_Numbers g-rannum ads,GNAT OS_Lib g-os_lib ads,The GNAT Library
24289 @anchor{gnat_rm/the_gnat_library gnat-perfect-hash-generators-g-pehage-ads}@anchor{383}@anchor{gnat_rm/the_gnat_library id94}@anchor{384}
24290 @section @code{GNAT.Perfect_Hash_Generators} (@code{g-pehage.ads})
24293 @geindex GNAT.Perfect_Hash_Generators (g-pehage.ads)
24295 @geindex Hash functions
24297 Provides a generator of static minimal perfect hash functions. No
24298 collisions occur and each item can be retrieved from the table in one
24299 probe (perfect property). The hash table size corresponds to the exact
24300 size of the key set and no larger (minimal property). The key set has to
24301 be know in advance (static property). The hash functions are also order
24302 preserving. If w2 is inserted after w1 in the generator, their
24303 hashcode are in the same order. These hashing functions are very
24304 convenient for use with realtime applications.
24306 @node GNAT Random_Numbers g-rannum ads,GNAT Regexp g-regexp ads,GNAT Perfect_Hash_Generators g-pehage ads,The GNAT Library
24307 @anchor{gnat_rm/the_gnat_library gnat-random-numbers-g-rannum-ads}@anchor{385}@anchor{gnat_rm/the_gnat_library id95}@anchor{386}
24308 @section @code{GNAT.Random_Numbers} (@code{g-rannum.ads})
24311 @geindex GNAT.Random_Numbers (g-rannum.ads)
24313 @geindex Random number generation
24315 Provides random number capabilities which extend those available in the
24316 standard Ada library and are more convenient to use.
24318 @node GNAT Regexp g-regexp ads,GNAT Registry g-regist ads,GNAT Random_Numbers g-rannum ads,The GNAT Library
24319 @anchor{gnat_rm/the_gnat_library gnat-regexp-g-regexp-ads}@anchor{250}@anchor{gnat_rm/the_gnat_library id96}@anchor{387}
24320 @section @code{GNAT.Regexp} (@code{g-regexp.ads})
24323 @geindex GNAT.Regexp (g-regexp.ads)
24325 @geindex Regular expressions
24327 @geindex Pattern matching
24329 A simple implementation of regular expressions, using a subset of regular
24330 expression syntax copied from familiar Unix style utilities. This is the
24331 simplest of the three pattern matching packages provided, and is particularly
24332 suitable for 'file globbing' applications.
24334 @node GNAT Registry g-regist ads,GNAT Regpat g-regpat ads,GNAT Regexp g-regexp ads,The GNAT Library
24335 @anchor{gnat_rm/the_gnat_library gnat-registry-g-regist-ads}@anchor{388}@anchor{gnat_rm/the_gnat_library id97}@anchor{389}
24336 @section @code{GNAT.Registry} (@code{g-regist.ads})
24339 @geindex GNAT.Registry (g-regist.ads)
24341 @geindex Windows Registry
24343 This is a high level binding to the Windows registry. It is possible to
24344 do simple things like reading a key value, creating a new key. For full
24345 registry API, but at a lower level of abstraction, refer to the Win32.Winreg
24346 package provided with the Win32Ada binding
24348 @node GNAT Regpat g-regpat ads,GNAT Rewrite_Data g-rewdat ads,GNAT Registry g-regist ads,The GNAT Library
24349 @anchor{gnat_rm/the_gnat_library id98}@anchor{38a}@anchor{gnat_rm/the_gnat_library gnat-regpat-g-regpat-ads}@anchor{38b}
24350 @section @code{GNAT.Regpat} (@code{g-regpat.ads})
24353 @geindex GNAT.Regpat (g-regpat.ads)
24355 @geindex Regular expressions
24357 @geindex Pattern matching
24359 A complete implementation of Unix-style regular expression matching, copied
24360 from the original V7 style regular expression library written in C by
24361 Henry Spencer (and binary compatible with this C library).
24363 @node GNAT Rewrite_Data g-rewdat ads,GNAT Secondary_Stack_Info g-sestin ads,GNAT Regpat g-regpat ads,The GNAT Library
24364 @anchor{gnat_rm/the_gnat_library id99}@anchor{38c}@anchor{gnat_rm/the_gnat_library gnat-rewrite-data-g-rewdat-ads}@anchor{38d}
24365 @section @code{GNAT.Rewrite_Data} (@code{g-rewdat.ads})
24368 @geindex GNAT.Rewrite_Data (g-rewdat.ads)
24370 @geindex Rewrite data
24372 A unit to rewrite on-the-fly string occurrences in a stream of
24373 data. The implementation has a very minimal memory footprint as the
24374 full content to be processed is not loaded into memory all at once. This makes
24375 this interface usable for large files or socket streams.
24377 @node GNAT Secondary_Stack_Info g-sestin ads,GNAT Semaphores g-semaph ads,GNAT Rewrite_Data g-rewdat ads,The GNAT Library
24378 @anchor{gnat_rm/the_gnat_library id100}@anchor{38e}@anchor{gnat_rm/the_gnat_library gnat-secondary-stack-info-g-sestin-ads}@anchor{38f}
24379 @section @code{GNAT.Secondary_Stack_Info} (@code{g-sestin.ads})
24382 @geindex GNAT.Secondary_Stack_Info (g-sestin.ads)
24384 @geindex Secondary Stack Info
24386 Provide the capability to query the high water mark of the current task's
24389 @node GNAT Semaphores g-semaph ads,GNAT Serial_Communications g-sercom ads,GNAT Secondary_Stack_Info g-sestin ads,The GNAT Library
24390 @anchor{gnat_rm/the_gnat_library id101}@anchor{390}@anchor{gnat_rm/the_gnat_library gnat-semaphores-g-semaph-ads}@anchor{391}
24391 @section @code{GNAT.Semaphores} (@code{g-semaph.ads})
24394 @geindex GNAT.Semaphores (g-semaph.ads)
24396 @geindex Semaphores
24398 Provides classic counting and binary semaphores using protected types.
24400 @node GNAT Serial_Communications g-sercom ads,GNAT SHA1 g-sha1 ads,GNAT Semaphores g-semaph ads,The GNAT Library
24401 @anchor{gnat_rm/the_gnat_library gnat-serial-communications-g-sercom-ads}@anchor{392}@anchor{gnat_rm/the_gnat_library id102}@anchor{393}
24402 @section @code{GNAT.Serial_Communications} (@code{g-sercom.ads})
24405 @geindex GNAT.Serial_Communications (g-sercom.ads)
24407 @geindex Serial_Communications
24409 Provides a simple interface to send and receive data over a serial
24410 port. This is only supported on GNU/Linux and Windows.
24412 @node GNAT SHA1 g-sha1 ads,GNAT SHA224 g-sha224 ads,GNAT Serial_Communications g-sercom ads,The GNAT Library
24413 @anchor{gnat_rm/the_gnat_library gnat-sha1-g-sha1-ads}@anchor{394}@anchor{gnat_rm/the_gnat_library id103}@anchor{395}
24414 @section @code{GNAT.SHA1} (@code{g-sha1.ads})
24417 @geindex GNAT.SHA1 (g-sha1.ads)
24419 @geindex Secure Hash Algorithm SHA-1
24421 Implements the SHA-1 Secure Hash Algorithm as described in FIPS PUB 180-3
24422 and RFC 3174, and the HMAC-SHA1 message authentication function as described
24423 in RFC 2104 and FIPS PUB 198.
24425 @node GNAT SHA224 g-sha224 ads,GNAT SHA256 g-sha256 ads,GNAT SHA1 g-sha1 ads,The GNAT Library
24426 @anchor{gnat_rm/the_gnat_library gnat-sha224-g-sha224-ads}@anchor{396}@anchor{gnat_rm/the_gnat_library id104}@anchor{397}
24427 @section @code{GNAT.SHA224} (@code{g-sha224.ads})
24430 @geindex GNAT.SHA224 (g-sha224.ads)
24432 @geindex Secure Hash Algorithm SHA-224
24434 Implements the SHA-224 Secure Hash Algorithm as described in FIPS PUB 180-3,
24435 and the HMAC-SHA224 message authentication function as described
24436 in RFC 2104 and FIPS PUB 198.
24438 @node GNAT SHA256 g-sha256 ads,GNAT SHA384 g-sha384 ads,GNAT SHA224 g-sha224 ads,The GNAT Library
24439 @anchor{gnat_rm/the_gnat_library id105}@anchor{398}@anchor{gnat_rm/the_gnat_library gnat-sha256-g-sha256-ads}@anchor{399}
24440 @section @code{GNAT.SHA256} (@code{g-sha256.ads})
24443 @geindex GNAT.SHA256 (g-sha256.ads)
24445 @geindex Secure Hash Algorithm SHA-256
24447 Implements the SHA-256 Secure Hash Algorithm as described in FIPS PUB 180-3,
24448 and the HMAC-SHA256 message authentication function as described
24449 in RFC 2104 and FIPS PUB 198.
24451 @node GNAT SHA384 g-sha384 ads,GNAT SHA512 g-sha512 ads,GNAT SHA256 g-sha256 ads,The GNAT Library
24452 @anchor{gnat_rm/the_gnat_library gnat-sha384-g-sha384-ads}@anchor{39a}@anchor{gnat_rm/the_gnat_library id106}@anchor{39b}
24453 @section @code{GNAT.SHA384} (@code{g-sha384.ads})
24456 @geindex GNAT.SHA384 (g-sha384.ads)
24458 @geindex Secure Hash Algorithm SHA-384
24460 Implements the SHA-384 Secure Hash Algorithm as described in FIPS PUB 180-3,
24461 and the HMAC-SHA384 message authentication function as described
24462 in RFC 2104 and FIPS PUB 198.
24464 @node GNAT SHA512 g-sha512 ads,GNAT Signals g-signal ads,GNAT SHA384 g-sha384 ads,The GNAT Library
24465 @anchor{gnat_rm/the_gnat_library gnat-sha512-g-sha512-ads}@anchor{39c}@anchor{gnat_rm/the_gnat_library id107}@anchor{39d}
24466 @section @code{GNAT.SHA512} (@code{g-sha512.ads})
24469 @geindex GNAT.SHA512 (g-sha512.ads)
24471 @geindex Secure Hash Algorithm SHA-512
24473 Implements the SHA-512 Secure Hash Algorithm as described in FIPS PUB 180-3,
24474 and the HMAC-SHA512 message authentication function as described
24475 in RFC 2104 and FIPS PUB 198.
24477 @node GNAT Signals g-signal ads,GNAT Sockets g-socket ads,GNAT SHA512 g-sha512 ads,The GNAT Library
24478 @anchor{gnat_rm/the_gnat_library gnat-signals-g-signal-ads}@anchor{39e}@anchor{gnat_rm/the_gnat_library id108}@anchor{39f}
24479 @section @code{GNAT.Signals} (@code{g-signal.ads})
24482 @geindex GNAT.Signals (g-signal.ads)
24486 Provides the ability to manipulate the blocked status of signals on supported
24489 @node GNAT Sockets g-socket ads,GNAT Source_Info g-souinf ads,GNAT Signals g-signal ads,The GNAT Library
24490 @anchor{gnat_rm/the_gnat_library id109}@anchor{3a0}@anchor{gnat_rm/the_gnat_library gnat-sockets-g-socket-ads}@anchor{3a1}
24491 @section @code{GNAT.Sockets} (@code{g-socket.ads})
24494 @geindex GNAT.Sockets (g-socket.ads)
24498 A high level and portable interface to develop sockets based applications.
24499 This package is based on the sockets thin binding found in
24500 @code{GNAT.Sockets.Thin}. Currently @code{GNAT.Sockets} is implemented
24501 on all native GNAT ports and on VxWorks cross prots. It is not implemented for
24502 the LynxOS cross port.
24504 @node GNAT Source_Info g-souinf ads,GNAT Spelling_Checker g-speche ads,GNAT Sockets g-socket ads,The GNAT Library
24505 @anchor{gnat_rm/the_gnat_library gnat-source-info-g-souinf-ads}@anchor{3a2}@anchor{gnat_rm/the_gnat_library id110}@anchor{3a3}
24506 @section @code{GNAT.Source_Info} (@code{g-souinf.ads})
24509 @geindex GNAT.Source_Info (g-souinf.ads)
24511 @geindex Source Information
24513 Provides subprograms that give access to source code information known at
24514 compile time, such as the current file name and line number. Also provides
24515 subprograms yielding the date and time of the current compilation (like the
24516 C macros @code{__DATE__} and @code{__TIME__})
24518 @node GNAT Spelling_Checker g-speche ads,GNAT Spelling_Checker_Generic g-spchge ads,GNAT Source_Info g-souinf ads,The GNAT Library
24519 @anchor{gnat_rm/the_gnat_library gnat-spelling-checker-g-speche-ads}@anchor{3a4}@anchor{gnat_rm/the_gnat_library id111}@anchor{3a5}
24520 @section @code{GNAT.Spelling_Checker} (@code{g-speche.ads})
24523 @geindex GNAT.Spelling_Checker (g-speche.ads)
24525 @geindex Spell checking
24527 Provides a function for determining whether one string is a plausible
24528 near misspelling of another string.
24530 @node GNAT Spelling_Checker_Generic g-spchge ads,GNAT Spitbol Patterns g-spipat ads,GNAT Spelling_Checker g-speche ads,The GNAT Library
24531 @anchor{gnat_rm/the_gnat_library id112}@anchor{3a6}@anchor{gnat_rm/the_gnat_library gnat-spelling-checker-generic-g-spchge-ads}@anchor{3a7}
24532 @section @code{GNAT.Spelling_Checker_Generic} (@code{g-spchge.ads})
24535 @geindex GNAT.Spelling_Checker_Generic (g-spchge.ads)
24537 @geindex Spell checking
24539 Provides a generic function that can be instantiated with a string type for
24540 determining whether one string is a plausible near misspelling of another
24543 @node GNAT Spitbol Patterns g-spipat ads,GNAT Spitbol g-spitbo ads,GNAT Spelling_Checker_Generic g-spchge ads,The GNAT Library
24544 @anchor{gnat_rm/the_gnat_library id113}@anchor{3a8}@anchor{gnat_rm/the_gnat_library gnat-spitbol-patterns-g-spipat-ads}@anchor{3a9}
24545 @section @code{GNAT.Spitbol.Patterns} (@code{g-spipat.ads})
24548 @geindex GNAT.Spitbol.Patterns (g-spipat.ads)
24550 @geindex SPITBOL pattern matching
24552 @geindex Pattern matching
24554 A complete implementation of SNOBOL4 style pattern matching. This is the
24555 most elaborate of the pattern matching packages provided. It fully duplicates
24556 the SNOBOL4 dynamic pattern construction and matching capabilities, using the
24557 efficient algorithm developed by Robert Dewar for the SPITBOL system.
24559 @node GNAT Spitbol g-spitbo ads,GNAT Spitbol Table_Boolean g-sptabo ads,GNAT Spitbol Patterns g-spipat ads,The GNAT Library
24560 @anchor{gnat_rm/the_gnat_library gnat-spitbol-g-spitbo-ads}@anchor{3aa}@anchor{gnat_rm/the_gnat_library id114}@anchor{3ab}
24561 @section @code{GNAT.Spitbol} (@code{g-spitbo.ads})
24564 @geindex GNAT.Spitbol (g-spitbo.ads)
24566 @geindex SPITBOL interface
24568 The top level package of the collection of SPITBOL-style functionality, this
24569 package provides basic SNOBOL4 string manipulation functions, such as
24570 Pad, Reverse, Trim, Substr capability, as well as a generic table function
24571 useful for constructing arbitrary mappings from strings in the style of
24572 the SNOBOL4 TABLE function.
24574 @node GNAT Spitbol Table_Boolean g-sptabo ads,GNAT Spitbol Table_Integer g-sptain ads,GNAT Spitbol g-spitbo ads,The GNAT Library
24575 @anchor{gnat_rm/the_gnat_library gnat-spitbol-table-boolean-g-sptabo-ads}@anchor{3ac}@anchor{gnat_rm/the_gnat_library id115}@anchor{3ad}
24576 @section @code{GNAT.Spitbol.Table_Boolean} (@code{g-sptabo.ads})
24579 @geindex GNAT.Spitbol.Table_Boolean (g-sptabo.ads)
24581 @geindex Sets of strings
24583 @geindex SPITBOL Tables
24585 A library level of instantiation of @code{GNAT.Spitbol.Patterns.Table}
24586 for type @code{Standard.Boolean}, giving an implementation of sets of
24589 @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
24590 @anchor{gnat_rm/the_gnat_library gnat-spitbol-table-integer-g-sptain-ads}@anchor{3ae}@anchor{gnat_rm/the_gnat_library id116}@anchor{3af}
24591 @section @code{GNAT.Spitbol.Table_Integer} (@code{g-sptain.ads})
24594 @geindex GNAT.Spitbol.Table_Integer (g-sptain.ads)
24596 @geindex Integer maps
24600 @geindex SPITBOL Tables
24602 A library level of instantiation of @code{GNAT.Spitbol.Patterns.Table}
24603 for type @code{Standard.Integer}, giving an implementation of maps
24604 from string to integer values.
24606 @node GNAT Spitbol Table_VString g-sptavs ads,GNAT SSE g-sse ads,GNAT Spitbol Table_Integer g-sptain ads,The GNAT Library
24607 @anchor{gnat_rm/the_gnat_library id117}@anchor{3b0}@anchor{gnat_rm/the_gnat_library gnat-spitbol-table-vstring-g-sptavs-ads}@anchor{3b1}
24608 @section @code{GNAT.Spitbol.Table_VString} (@code{g-sptavs.ads})
24611 @geindex GNAT.Spitbol.Table_VString (g-sptavs.ads)
24613 @geindex String maps
24617 @geindex SPITBOL Tables
24619 A library level of instantiation of @code{GNAT.Spitbol.Patterns.Table} for
24620 a variable length string type, giving an implementation of general
24621 maps from strings to strings.
24623 @node GNAT SSE g-sse ads,GNAT SSE Vector_Types g-ssvety ads,GNAT Spitbol Table_VString g-sptavs ads,The GNAT Library
24624 @anchor{gnat_rm/the_gnat_library id118}@anchor{3b2}@anchor{gnat_rm/the_gnat_library gnat-sse-g-sse-ads}@anchor{3b3}
24625 @section @code{GNAT.SSE} (@code{g-sse.ads})
24628 @geindex GNAT.SSE (g-sse.ads)
24630 Root of a set of units aimed at offering Ada bindings to a subset of
24631 the Intel(r) Streaming SIMD Extensions with GNAT on the x86 family of
24632 targets. It exposes vector component types together with a general
24633 introduction to the binding contents and use.
24635 @node GNAT SSE Vector_Types g-ssvety ads,GNAT String_Hash g-strhas ads,GNAT SSE g-sse ads,The GNAT Library
24636 @anchor{gnat_rm/the_gnat_library gnat-sse-vector-types-g-ssvety-ads}@anchor{3b4}@anchor{gnat_rm/the_gnat_library id119}@anchor{3b5}
24637 @section @code{GNAT.SSE.Vector_Types} (@code{g-ssvety.ads})
24640 @geindex GNAT.SSE.Vector_Types (g-ssvety.ads)
24642 SSE vector types for use with SSE related intrinsics.
24644 @node GNAT String_Hash g-strhas ads,GNAT Strings g-string ads,GNAT SSE Vector_Types g-ssvety ads,The GNAT Library
24645 @anchor{gnat_rm/the_gnat_library gnat-string-hash-g-strhas-ads}@anchor{3b6}@anchor{gnat_rm/the_gnat_library id120}@anchor{3b7}
24646 @section @code{GNAT.String_Hash} (@code{g-strhas.ads})
24649 @geindex GNAT.String_Hash (g-strhas.ads)
24651 @geindex Hash functions
24653 Provides a generic hash function working on arrays of scalars. Both the scalar
24654 type and the hash result type are parameters.
24656 @node GNAT Strings g-string ads,GNAT String_Split g-strspl ads,GNAT String_Hash g-strhas ads,The GNAT Library
24657 @anchor{gnat_rm/the_gnat_library gnat-strings-g-string-ads}@anchor{3b8}@anchor{gnat_rm/the_gnat_library id121}@anchor{3b9}
24658 @section @code{GNAT.Strings} (@code{g-string.ads})
24661 @geindex GNAT.Strings (g-string.ads)
24663 Common String access types and related subprograms. Basically it
24664 defines a string access and an array of string access types.
24666 @node GNAT String_Split g-strspl ads,GNAT Table g-table ads,GNAT Strings g-string ads,The GNAT Library
24667 @anchor{gnat_rm/the_gnat_library gnat-string-split-g-strspl-ads}@anchor{3ba}@anchor{gnat_rm/the_gnat_library id122}@anchor{3bb}
24668 @section @code{GNAT.String_Split} (@code{g-strspl.ads})
24671 @geindex GNAT.String_Split (g-strspl.ads)
24673 @geindex String splitter
24675 Useful string manipulation routines: given a set of separators, split
24676 a string wherever the separators appear, and provide direct access
24677 to the resulting slices. This package is instantiated from
24678 @code{GNAT.Array_Split}.
24680 @node GNAT Table g-table ads,GNAT Task_Lock g-tasloc ads,GNAT String_Split g-strspl ads,The GNAT Library
24681 @anchor{gnat_rm/the_gnat_library gnat-table-g-table-ads}@anchor{3bc}@anchor{gnat_rm/the_gnat_library id123}@anchor{3bd}
24682 @section @code{GNAT.Table} (@code{g-table.ads})
24685 @geindex GNAT.Table (g-table.ads)
24687 @geindex Table implementation
24690 @geindex extendable
24692 A generic package providing a single dimension array abstraction where the
24693 length of the array can be dynamically modified.
24695 This package provides a facility similar to that of @code{GNAT.Dynamic_Tables},
24696 except that this package declares a single instance of the table type,
24697 while an instantiation of @code{GNAT.Dynamic_Tables} creates a type that can be
24698 used to define dynamic instances of the table.
24700 @node GNAT Task_Lock g-tasloc ads,GNAT Time_Stamp g-timsta ads,GNAT Table g-table ads,The GNAT Library
24701 @anchor{gnat_rm/the_gnat_library id124}@anchor{3be}@anchor{gnat_rm/the_gnat_library gnat-task-lock-g-tasloc-ads}@anchor{3bf}
24702 @section @code{GNAT.Task_Lock} (@code{g-tasloc.ads})
24705 @geindex GNAT.Task_Lock (g-tasloc.ads)
24707 @geindex Task synchronization
24709 @geindex Task locking
24713 A very simple facility for locking and unlocking sections of code using a
24714 single global task lock. Appropriate for use in situations where contention
24715 between tasks is very rarely expected.
24717 @node GNAT Time_Stamp g-timsta ads,GNAT Threads g-thread ads,GNAT Task_Lock g-tasloc ads,The GNAT Library
24718 @anchor{gnat_rm/the_gnat_library id125}@anchor{3c0}@anchor{gnat_rm/the_gnat_library gnat-time-stamp-g-timsta-ads}@anchor{3c1}
24719 @section @code{GNAT.Time_Stamp} (@code{g-timsta.ads})
24722 @geindex GNAT.Time_Stamp (g-timsta.ads)
24724 @geindex Time stamp
24726 @geindex Current time
24728 Provides a simple function that returns a string YYYY-MM-DD HH:MM:SS.SS that
24729 represents the current date and time in ISO 8601 format. This is a very simple
24730 routine with minimal code and there are no dependencies on any other unit.
24732 @node GNAT Threads g-thread ads,GNAT Traceback g-traceb ads,GNAT Time_Stamp g-timsta ads,The GNAT Library
24733 @anchor{gnat_rm/the_gnat_library gnat-threads-g-thread-ads}@anchor{3c2}@anchor{gnat_rm/the_gnat_library id126}@anchor{3c3}
24734 @section @code{GNAT.Threads} (@code{g-thread.ads})
24737 @geindex GNAT.Threads (g-thread.ads)
24739 @geindex Foreign threads
24744 Provides facilities for dealing with foreign threads which need to be known
24745 by the GNAT run-time system. Consult the documentation of this package for
24746 further details if your program has threads that are created by a non-Ada
24747 environment which then accesses Ada code.
24749 @node GNAT Traceback g-traceb ads,GNAT Traceback Symbolic g-trasym ads,GNAT Threads g-thread ads,The GNAT Library
24750 @anchor{gnat_rm/the_gnat_library id127}@anchor{3c4}@anchor{gnat_rm/the_gnat_library gnat-traceback-g-traceb-ads}@anchor{3c5}
24751 @section @code{GNAT.Traceback} (@code{g-traceb.ads})
24754 @geindex GNAT.Traceback (g-traceb.ads)
24756 @geindex Trace back facilities
24758 Provides a facility for obtaining non-symbolic traceback information, useful
24759 in various debugging situations.
24761 @node GNAT Traceback Symbolic g-trasym ads,GNAT UTF_32 g-table ads,GNAT Traceback g-traceb ads,The GNAT Library
24762 @anchor{gnat_rm/the_gnat_library gnat-traceback-symbolic-g-trasym-ads}@anchor{3c6}@anchor{gnat_rm/the_gnat_library id128}@anchor{3c7}
24763 @section @code{GNAT.Traceback.Symbolic} (@code{g-trasym.ads})
24766 @geindex GNAT.Traceback.Symbolic (g-trasym.ads)
24768 @geindex Trace back facilities
24770 @node GNAT UTF_32 g-table ads,GNAT Wide_Spelling_Checker g-u3spch ads,GNAT Traceback Symbolic g-trasym ads,The GNAT Library
24771 @anchor{gnat_rm/the_gnat_library id129}@anchor{3c8}@anchor{gnat_rm/the_gnat_library gnat-utf-32-g-table-ads}@anchor{3c9}
24772 @section @code{GNAT.UTF_32} (@code{g-table.ads})
24775 @geindex GNAT.UTF_32 (g-table.ads)
24777 @geindex Wide character codes
24779 This is a package intended to be used in conjunction with the
24780 @code{Wide_Character} type in Ada 95 and the
24781 @code{Wide_Wide_Character} type in Ada 2005 (available
24782 in @code{GNAT} in Ada 2005 mode). This package contains
24783 Unicode categorization routines, as well as lexical
24784 categorization routines corresponding to the Ada 2005
24785 lexical rules for identifiers and strings, and also a
24786 lower case to upper case fold routine corresponding to
24787 the Ada 2005 rules for identifier equivalence.
24789 @node GNAT Wide_Spelling_Checker g-u3spch ads,GNAT Wide_Spelling_Checker g-wispch ads,GNAT UTF_32 g-table ads,The GNAT Library
24790 @anchor{gnat_rm/the_gnat_library gnat-wide-spelling-checker-g-u3spch-ads}@anchor{3ca}@anchor{gnat_rm/the_gnat_library id130}@anchor{3cb}
24791 @section @code{GNAT.Wide_Spelling_Checker} (@code{g-u3spch.ads})
24794 @geindex GNAT.Wide_Spelling_Checker (g-u3spch.ads)
24796 @geindex Spell checking
24798 Provides a function for determining whether one wide wide string is a plausible
24799 near misspelling of another wide wide string, where the strings are represented
24800 using the UTF_32_String type defined in System.Wch_Cnv.
24802 @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
24803 @anchor{gnat_rm/the_gnat_library gnat-wide-spelling-checker-g-wispch-ads}@anchor{3cc}@anchor{gnat_rm/the_gnat_library id131}@anchor{3cd}
24804 @section @code{GNAT.Wide_Spelling_Checker} (@code{g-wispch.ads})
24807 @geindex GNAT.Wide_Spelling_Checker (g-wispch.ads)
24809 @geindex Spell checking
24811 Provides a function for determining whether one wide string is a plausible
24812 near misspelling of another wide string.
24814 @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
24815 @anchor{gnat_rm/the_gnat_library id132}@anchor{3ce}@anchor{gnat_rm/the_gnat_library gnat-wide-string-split-g-wistsp-ads}@anchor{3cf}
24816 @section @code{GNAT.Wide_String_Split} (@code{g-wistsp.ads})
24819 @geindex GNAT.Wide_String_Split (g-wistsp.ads)
24821 @geindex Wide_String splitter
24823 Useful wide string manipulation routines: given a set of separators, split
24824 a wide string wherever the separators appear, and provide direct access
24825 to the resulting slices. This package is instantiated from
24826 @code{GNAT.Array_Split}.
24828 @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
24829 @anchor{gnat_rm/the_gnat_library gnat-wide-wide-spelling-checker-g-zspche-ads}@anchor{3d0}@anchor{gnat_rm/the_gnat_library id133}@anchor{3d1}
24830 @section @code{GNAT.Wide_Wide_Spelling_Checker} (@code{g-zspche.ads})
24833 @geindex GNAT.Wide_Wide_Spelling_Checker (g-zspche.ads)
24835 @geindex Spell checking
24837 Provides a function for determining whether one wide wide string is a plausible
24838 near misspelling of another wide wide string.
24840 @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
24841 @anchor{gnat_rm/the_gnat_library gnat-wide-wide-string-split-g-zistsp-ads}@anchor{3d2}@anchor{gnat_rm/the_gnat_library id134}@anchor{3d3}
24842 @section @code{GNAT.Wide_Wide_String_Split} (@code{g-zistsp.ads})
24845 @geindex GNAT.Wide_Wide_String_Split (g-zistsp.ads)
24847 @geindex Wide_Wide_String splitter
24849 Useful wide wide string manipulation routines: given a set of separators, split
24850 a wide wide string wherever the separators appear, and provide direct access
24851 to the resulting slices. This package is instantiated from
24852 @code{GNAT.Array_Split}.
24854 @node Interfaces C Extensions i-cexten ads,Interfaces C Streams i-cstrea ads,GNAT Wide_Wide_String_Split g-zistsp ads,The GNAT Library
24855 @anchor{gnat_rm/the_gnat_library interfaces-c-extensions-i-cexten-ads}@anchor{3d4}@anchor{gnat_rm/the_gnat_library id135}@anchor{3d5}
24856 @section @code{Interfaces.C.Extensions} (@code{i-cexten.ads})
24859 @geindex Interfaces.C.Extensions (i-cexten.ads)
24861 This package contains additional C-related definitions, intended
24862 for use with either manually or automatically generated bindings
24865 @node Interfaces C Streams i-cstrea ads,Interfaces Packed_Decimal i-pacdec ads,Interfaces C Extensions i-cexten ads,The GNAT Library
24866 @anchor{gnat_rm/the_gnat_library interfaces-c-streams-i-cstrea-ads}@anchor{3d6}@anchor{gnat_rm/the_gnat_library id136}@anchor{3d7}
24867 @section @code{Interfaces.C.Streams} (@code{i-cstrea.ads})
24870 @geindex Interfaces.C.Streams (i-cstrea.ads)
24873 @geindex interfacing
24875 This package is a binding for the most commonly used operations
24878 @node Interfaces Packed_Decimal i-pacdec ads,Interfaces VxWorks i-vxwork ads,Interfaces C Streams i-cstrea ads,The GNAT Library
24879 @anchor{gnat_rm/the_gnat_library interfaces-packed-decimal-i-pacdec-ads}@anchor{3d8}@anchor{gnat_rm/the_gnat_library id137}@anchor{3d9}
24880 @section @code{Interfaces.Packed_Decimal} (@code{i-pacdec.ads})
24883 @geindex Interfaces.Packed_Decimal (i-pacdec.ads)
24885 @geindex IBM Packed Format
24887 @geindex Packed Decimal
24889 This package provides a set of routines for conversions to and
24890 from a packed decimal format compatible with that used on IBM
24893 @node Interfaces VxWorks i-vxwork ads,Interfaces VxWorks Int_Connection i-vxinco ads,Interfaces Packed_Decimal i-pacdec ads,The GNAT Library
24894 @anchor{gnat_rm/the_gnat_library id138}@anchor{3da}@anchor{gnat_rm/the_gnat_library interfaces-vxworks-i-vxwork-ads}@anchor{3db}
24895 @section @code{Interfaces.VxWorks} (@code{i-vxwork.ads})
24898 @geindex Interfaces.VxWorks (i-vxwork.ads)
24900 @geindex Interfacing to VxWorks
24903 @geindex interfacing
24905 This package provides a limited binding to the VxWorks API.
24906 In particular, it interfaces with the
24907 VxWorks hardware interrupt facilities.
24909 @node Interfaces VxWorks Int_Connection i-vxinco ads,Interfaces VxWorks IO i-vxwoio ads,Interfaces VxWorks i-vxwork ads,The GNAT Library
24910 @anchor{gnat_rm/the_gnat_library interfaces-vxworks-int-connection-i-vxinco-ads}@anchor{3dc}@anchor{gnat_rm/the_gnat_library id139}@anchor{3dd}
24911 @section @code{Interfaces.VxWorks.Int_Connection} (@code{i-vxinco.ads})
24914 @geindex Interfaces.VxWorks.Int_Connection (i-vxinco.ads)
24916 @geindex Interfacing to VxWorks
24919 @geindex interfacing
24921 This package provides a way for users to replace the use of
24922 intConnect() with a custom routine for installing interrupt
24925 @node Interfaces VxWorks IO i-vxwoio ads,System Address_Image s-addima ads,Interfaces VxWorks Int_Connection i-vxinco ads,The GNAT Library
24926 @anchor{gnat_rm/the_gnat_library interfaces-vxworks-io-i-vxwoio-ads}@anchor{3de}@anchor{gnat_rm/the_gnat_library id140}@anchor{3df}
24927 @section @code{Interfaces.VxWorks.IO} (@code{i-vxwoio.ads})
24930 @geindex Interfaces.VxWorks.IO (i-vxwoio.ads)
24932 @geindex Interfacing to VxWorks' I/O
24935 @geindex I/O interfacing
24938 @geindex Get_Immediate
24940 @geindex Get_Immediate
24943 This package provides a binding to the ioctl (IO/Control)
24944 function of VxWorks, defining a set of option values and
24945 function codes. A particular use of this package is
24946 to enable the use of Get_Immediate under VxWorks.
24948 @node System Address_Image s-addima ads,System Assertions s-assert ads,Interfaces VxWorks IO i-vxwoio ads,The GNAT Library
24949 @anchor{gnat_rm/the_gnat_library id141}@anchor{3e0}@anchor{gnat_rm/the_gnat_library system-address-image-s-addima-ads}@anchor{3e1}
24950 @section @code{System.Address_Image} (@code{s-addima.ads})
24953 @geindex System.Address_Image (s-addima.ads)
24955 @geindex Address image
24958 @geindex of an address
24960 This function provides a useful debugging
24961 function that gives an (implementation dependent)
24962 string which identifies an address.
24964 @node System Assertions s-assert ads,System Atomic_Counters s-atocou ads,System Address_Image s-addima ads,The GNAT Library
24965 @anchor{gnat_rm/the_gnat_library system-assertions-s-assert-ads}@anchor{3e2}@anchor{gnat_rm/the_gnat_library id142}@anchor{3e3}
24966 @section @code{System.Assertions} (@code{s-assert.ads})
24969 @geindex System.Assertions (s-assert.ads)
24971 @geindex Assertions
24973 @geindex Assert_Failure
24976 This package provides the declaration of the exception raised
24977 by an run-time assertion failure, as well as the routine that
24978 is used internally to raise this assertion.
24980 @node System Atomic_Counters s-atocou ads,System Memory s-memory ads,System Assertions s-assert ads,The GNAT Library
24981 @anchor{gnat_rm/the_gnat_library id143}@anchor{3e4}@anchor{gnat_rm/the_gnat_library system-atomic-counters-s-atocou-ads}@anchor{3e5}
24982 @section @code{System.Atomic_Counters} (@code{s-atocou.ads})
24985 @geindex System.Atomic_Counters (s-atocou.ads)
24987 This package provides the declaration of an atomic counter type,
24988 together with efficient routines (using hardware
24989 synchronization primitives) for incrementing, decrementing,
24990 and testing of these counters. This package is implemented
24991 on most targets, including all Alpha, ia64, PowerPC, SPARC V9,
24992 x86, and x86_64 platforms.
24994 @node System Memory s-memory ads,System Multiprocessors s-multip ads,System Atomic_Counters s-atocou ads,The GNAT Library
24995 @anchor{gnat_rm/the_gnat_library system-memory-s-memory-ads}@anchor{3e6}@anchor{gnat_rm/the_gnat_library id144}@anchor{3e7}
24996 @section @code{System.Memory} (@code{s-memory.ads})
24999 @geindex System.Memory (s-memory.ads)
25001 @geindex Memory allocation
25003 This package provides the interface to the low level routines used
25004 by the generated code for allocation and freeing storage for the
25005 default storage pool (analogous to the C routines malloc and free.
25006 It also provides a reallocation interface analogous to the C routine
25007 realloc. The body of this unit may be modified to provide alternative
25008 allocation mechanisms for the default pool, and in addition, direct
25009 calls to this unit may be made for low level allocation uses (for
25010 example see the body of @code{GNAT.Tables}).
25012 @node System Multiprocessors s-multip ads,System Multiprocessors Dispatching_Domains s-mudido ads,System Memory s-memory ads,The GNAT Library
25013 @anchor{gnat_rm/the_gnat_library id145}@anchor{3e8}@anchor{gnat_rm/the_gnat_library system-multiprocessors-s-multip-ads}@anchor{3e9}
25014 @section @code{System.Multiprocessors} (@code{s-multip.ads})
25017 @geindex System.Multiprocessors (s-multip.ads)
25019 @geindex Multiprocessor interface
25021 This is an Ada 2012 unit defined in the Ada 2012 Reference Manual, but
25022 in GNAT we also make it available in Ada 95 and Ada 2005 (where it is
25023 technically an implementation-defined addition).
25025 @node System Multiprocessors Dispatching_Domains s-mudido ads,System Partition_Interface s-parint ads,System Multiprocessors s-multip ads,The GNAT Library
25026 @anchor{gnat_rm/the_gnat_library system-multiprocessors-dispatching-domains-s-mudido-ads}@anchor{3ea}@anchor{gnat_rm/the_gnat_library id146}@anchor{3eb}
25027 @section @code{System.Multiprocessors.Dispatching_Domains} (@code{s-mudido.ads})
25030 @geindex System.Multiprocessors.Dispatching_Domains (s-mudido.ads)
25032 @geindex Multiprocessor interface
25034 This is an Ada 2012 unit defined in the Ada 2012 Reference Manual, but
25035 in GNAT we also make it available in Ada 95 and Ada 2005 (where it is
25036 technically an implementation-defined addition).
25038 @node System Partition_Interface s-parint ads,System Pool_Global s-pooglo ads,System Multiprocessors Dispatching_Domains s-mudido ads,The GNAT Library
25039 @anchor{gnat_rm/the_gnat_library id147}@anchor{3ec}@anchor{gnat_rm/the_gnat_library system-partition-interface-s-parint-ads}@anchor{3ed}
25040 @section @code{System.Partition_Interface} (@code{s-parint.ads})
25043 @geindex System.Partition_Interface (s-parint.ads)
25045 @geindex Partition interfacing functions
25047 This package provides facilities for partition interfacing. It
25048 is used primarily in a distribution context when using Annex E
25051 @node System Pool_Global s-pooglo ads,System Pool_Local s-pooloc ads,System Partition_Interface s-parint ads,The GNAT Library
25052 @anchor{gnat_rm/the_gnat_library id148}@anchor{3ee}@anchor{gnat_rm/the_gnat_library system-pool-global-s-pooglo-ads}@anchor{3ef}
25053 @section @code{System.Pool_Global} (@code{s-pooglo.ads})
25056 @geindex System.Pool_Global (s-pooglo.ads)
25058 @geindex Storage pool
25061 @geindex Global storage pool
25063 This package provides a storage pool that is equivalent to the default
25064 storage pool used for access types for which no pool is specifically
25065 declared. It uses malloc/free to allocate/free and does not attempt to
25066 do any automatic reclamation.
25068 @node System Pool_Local s-pooloc ads,System Restrictions s-restri ads,System Pool_Global s-pooglo ads,The GNAT Library
25069 @anchor{gnat_rm/the_gnat_library system-pool-local-s-pooloc-ads}@anchor{3f0}@anchor{gnat_rm/the_gnat_library id149}@anchor{3f1}
25070 @section @code{System.Pool_Local} (@code{s-pooloc.ads})
25073 @geindex System.Pool_Local (s-pooloc.ads)
25075 @geindex Storage pool
25078 @geindex Local storage pool
25080 This package provides a storage pool that is intended for use with locally
25081 defined access types. It uses malloc/free for allocate/free, and maintains
25082 a list of allocated blocks, so that all storage allocated for the pool can
25083 be freed automatically when the pool is finalized.
25085 @node System Restrictions s-restri ads,System Rident s-rident ads,System Pool_Local s-pooloc ads,The GNAT Library
25086 @anchor{gnat_rm/the_gnat_library id150}@anchor{3f2}@anchor{gnat_rm/the_gnat_library system-restrictions-s-restri-ads}@anchor{3f3}
25087 @section @code{System.Restrictions} (@code{s-restri.ads})
25090 @geindex System.Restrictions (s-restri.ads)
25092 @geindex Run-time restrictions access
25094 This package provides facilities for accessing at run time
25095 the status of restrictions specified at compile time for
25096 the partition. Information is available both with regard
25097 to actual restrictions specified, and with regard to
25098 compiler determined information on which restrictions
25099 are violated by one or more packages in the partition.
25101 @node System Rident s-rident ads,System Strings Stream_Ops s-ststop ads,System Restrictions s-restri ads,The GNAT Library
25102 @anchor{gnat_rm/the_gnat_library system-rident-s-rident-ads}@anchor{3f4}@anchor{gnat_rm/the_gnat_library id151}@anchor{3f5}
25103 @section @code{System.Rident} (@code{s-rident.ads})
25106 @geindex System.Rident (s-rident.ads)
25108 @geindex Restrictions definitions
25110 This package provides definitions of the restrictions
25111 identifiers supported by GNAT, and also the format of
25112 the restrictions provided in package System.Restrictions.
25113 It is not normally necessary to @code{with} this generic package
25114 since the necessary instantiation is included in
25115 package System.Restrictions.
25117 @node System Strings Stream_Ops s-ststop ads,System Unsigned_Types s-unstyp ads,System Rident s-rident ads,The GNAT Library
25118 @anchor{gnat_rm/the_gnat_library id152}@anchor{3f6}@anchor{gnat_rm/the_gnat_library system-strings-stream-ops-s-ststop-ads}@anchor{3f7}
25119 @section @code{System.Strings.Stream_Ops} (@code{s-ststop.ads})
25122 @geindex System.Strings.Stream_Ops (s-ststop.ads)
25124 @geindex Stream operations
25126 @geindex String stream operations
25128 This package provides a set of stream subprograms for standard string types.
25129 It is intended primarily to support implicit use of such subprograms when
25130 stream attributes are applied to string types, but the subprograms in this
25131 package can be used directly by application programs.
25133 @node System Unsigned_Types s-unstyp ads,System Wch_Cnv s-wchcnv ads,System Strings Stream_Ops s-ststop ads,The GNAT Library
25134 @anchor{gnat_rm/the_gnat_library system-unsigned-types-s-unstyp-ads}@anchor{3f8}@anchor{gnat_rm/the_gnat_library id153}@anchor{3f9}
25135 @section @code{System.Unsigned_Types} (@code{s-unstyp.ads})
25138 @geindex System.Unsigned_Types (s-unstyp.ads)
25140 This package contains definitions of standard unsigned types that
25141 correspond in size to the standard signed types declared in Standard,
25142 and (unlike the types in Interfaces) have corresponding names. It
25143 also contains some related definitions for other specialized types
25144 used by the compiler in connection with packed array types.
25146 @node System Wch_Cnv s-wchcnv ads,System Wch_Con s-wchcon ads,System Unsigned_Types s-unstyp ads,The GNAT Library
25147 @anchor{gnat_rm/the_gnat_library system-wch-cnv-s-wchcnv-ads}@anchor{3fa}@anchor{gnat_rm/the_gnat_library id154}@anchor{3fb}
25148 @section @code{System.Wch_Cnv} (@code{s-wchcnv.ads})
25151 @geindex System.Wch_Cnv (s-wchcnv.ads)
25153 @geindex Wide Character
25154 @geindex Representation
25156 @geindex Wide String
25157 @geindex Conversion
25159 @geindex Representation of wide characters
25161 This package provides routines for converting between
25162 wide and wide wide characters and a representation as a value of type
25163 @code{Standard.String}, using a specified wide character
25164 encoding method. It uses definitions in
25165 package @code{System.Wch_Con}.
25167 @node System Wch_Con s-wchcon ads,,System Wch_Cnv s-wchcnv ads,The GNAT Library
25168 @anchor{gnat_rm/the_gnat_library system-wch-con-s-wchcon-ads}@anchor{3fc}@anchor{gnat_rm/the_gnat_library id155}@anchor{3fd}
25169 @section @code{System.Wch_Con} (@code{s-wchcon.ads})
25172 @geindex System.Wch_Con (s-wchcon.ads)
25174 This package provides definitions and descriptions of
25175 the various methods used for encoding wide characters
25176 in ordinary strings. These definitions are used by
25177 the package @code{System.Wch_Cnv}.
25179 @node Interfacing to Other Languages,Specialized Needs Annexes,The GNAT Library,Top
25180 @anchor{gnat_rm/interfacing_to_other_languages interfacing-to-other-languages}@anchor{11}@anchor{gnat_rm/interfacing_to_other_languages doc}@anchor{3fe}@anchor{gnat_rm/interfacing_to_other_languages id1}@anchor{3ff}
25181 @chapter Interfacing to Other Languages
25184 The facilities in Annex B of the Ada Reference Manual are fully
25185 implemented in GNAT, and in addition, a full interface to C++ is
25189 * Interfacing to C::
25190 * Interfacing to C++::
25191 * Interfacing to COBOL::
25192 * Interfacing to Fortran::
25193 * Interfacing to non-GNAT Ada code::
25197 @node Interfacing to C,Interfacing to C++,,Interfacing to Other Languages
25198 @anchor{gnat_rm/interfacing_to_other_languages interfacing-to-c}@anchor{400}@anchor{gnat_rm/interfacing_to_other_languages id2}@anchor{401}
25199 @section Interfacing to C
25202 Interfacing to C with GNAT can use one of two approaches:
25208 The types in the package @code{Interfaces.C} may be used.
25211 Standard Ada types may be used directly. This may be less portable to
25212 other compilers, but will work on all GNAT compilers, which guarantee
25213 correspondence between the C and Ada types.
25216 Pragma @code{Convention C} may be applied to Ada types, but mostly has no
25217 effect, since this is the default. The following table shows the
25218 correspondence between Ada scalar types and the corresponding C types.
25221 @multitable {xxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
25240 @code{Short_Integer}
25248 @code{Short_Short_Integer}
25256 @code{Long_Integer}
25264 @code{Long_Long_Integer}
25296 @code{Long_Long_Float}
25300 This is the longest floating-point type supported by the hardware.
25305 Additionally, there are the following general correspondences between Ada
25312 Ada enumeration types map to C enumeration types directly if pragma
25313 @code{Convention C} is specified, which causes them to have int
25314 length. Without pragma @code{Convention C}, Ada enumeration types map to
25315 8, 16, or 32 bits (i.e., C types @code{signed char}, @code{short},
25316 @code{int}, respectively) depending on the number of values passed.
25317 This is the only case in which pragma @code{Convention C} affects the
25318 representation of an Ada type.
25321 Ada access types map to C pointers, except for the case of pointers to
25322 unconstrained types in Ada, which have no direct C equivalent.
25325 Ada arrays map directly to C arrays.
25328 Ada records map directly to C structures.
25331 Packed Ada records map to C structures where all members are bit fields
25332 of the length corresponding to the @code{type'Size} value in Ada.
25335 @node Interfacing to C++,Interfacing to COBOL,Interfacing to C,Interfacing to Other Languages
25336 @anchor{gnat_rm/interfacing_to_other_languages id4}@anchor{402}@anchor{gnat_rm/interfacing_to_other_languages id3}@anchor{45}
25337 @section Interfacing to C++
25340 The interface to C++ makes use of the following pragmas, which are
25341 primarily intended to be constructed automatically using a binding generator
25342 tool, although it is possible to construct them by hand.
25344 Using these pragmas it is possible to achieve complete
25345 inter-operability between Ada tagged types and C++ class definitions.
25346 See @ref{7,,Implementation Defined Pragmas}, for more details.
25351 @item @code{pragma CPP_Class ([Entity =>] @emph{LOCAL_NAME})}
25353 The argument denotes an entity in the current declarative region that is
25354 declared as a tagged or untagged record type. It indicates that the type
25355 corresponds to an externally declared C++ class type, and is to be laid
25356 out the same way that C++ would lay out the type.
25358 Note: Pragma @code{CPP_Class} is currently obsolete. It is supported
25359 for backward compatibility but its functionality is available
25360 using pragma @code{Import} with @code{Convention} = @code{CPP}.
25362 @item @code{pragma CPP_Constructor ([Entity =>] @emph{LOCAL_NAME})}
25364 This pragma identifies an imported function (imported in the usual way
25365 with pragma @code{Import}) as corresponding to a C++ constructor.
25368 A few restrictions are placed on the use of the @code{Access} attribute
25369 in conjunction with subprograms subject to convention @code{CPP}: the
25370 attribute may be used neither on primitive operations of a tagged
25371 record type with convention @code{CPP}, imported or not, nor on
25372 subprograms imported with pragma @code{CPP_Constructor}.
25374 In addition, C++ exceptions are propagated and can be handled in an
25375 @code{others} choice of an exception handler. The corresponding Ada
25376 occurrence has no message, and the simple name of the exception identity
25377 contains @code{Foreign_Exception}. Finalization and awaiting dependent
25378 tasks works properly when such foreign exceptions are propagated.
25380 It is also possible to import a C++ exception using the following syntax:
25383 LOCAL_NAME : exception;
25384 pragma Import (Cpp,
25385 [Entity =>] LOCAL_NAME,
25386 [External_Name =>] static_string_EXPRESSION);
25389 The @code{External_Name} is the name of the C++ RTTI symbol. You can then
25390 cover a specific C++ exception in an exception handler.
25392 @node Interfacing to COBOL,Interfacing to Fortran,Interfacing to C++,Interfacing to Other Languages
25393 @anchor{gnat_rm/interfacing_to_other_languages id5}@anchor{403}@anchor{gnat_rm/interfacing_to_other_languages interfacing-to-cobol}@anchor{404}
25394 @section Interfacing to COBOL
25397 Interfacing to COBOL is achieved as described in section B.4 of
25398 the Ada Reference Manual.
25400 @node Interfacing to Fortran,Interfacing to non-GNAT Ada code,Interfacing to COBOL,Interfacing to Other Languages
25401 @anchor{gnat_rm/interfacing_to_other_languages id6}@anchor{405}@anchor{gnat_rm/interfacing_to_other_languages interfacing-to-fortran}@anchor{406}
25402 @section Interfacing to Fortran
25405 Interfacing to Fortran is achieved as described in section B.5 of the
25406 Ada Reference Manual. The pragma @code{Convention Fortran}, applied to a
25407 multi-dimensional array causes the array to be stored in column-major
25408 order as required for convenient interface to Fortran.
25410 @node Interfacing to non-GNAT Ada code,,Interfacing to Fortran,Interfacing to Other Languages
25411 @anchor{gnat_rm/interfacing_to_other_languages interfacing-to-non-gnat-ada-code}@anchor{407}@anchor{gnat_rm/interfacing_to_other_languages id7}@anchor{408}
25412 @section Interfacing to non-GNAT Ada code
25415 It is possible to specify the convention @code{Ada} in a pragma
25416 @code{Import} or pragma @code{Export}. However this refers to
25417 the calling conventions used by GNAT, which may or may not be
25418 similar enough to those used by some other Ada 83 / Ada 95 / Ada 2005
25419 compiler to allow interoperation.
25421 If arguments types are kept simple, and if the foreign compiler generally
25422 follows system calling conventions, then it may be possible to integrate
25423 files compiled by other Ada compilers, provided that the elaboration
25424 issues are adequately addressed (for example by eliminating the
25425 need for any load time elaboration).
25427 In particular, GNAT running on VMS is designed to
25428 be highly compatible with the DEC Ada 83 compiler, so this is one
25429 case in which it is possible to import foreign units of this type,
25430 provided that the data items passed are restricted to simple scalar
25431 values or simple record types without variants, or simple array
25432 types with fixed bounds.
25434 @node Specialized Needs Annexes,Implementation of Specific Ada Features,Interfacing to Other Languages,Top
25435 @anchor{gnat_rm/specialized_needs_annexes specialized-needs-annexes}@anchor{12}@anchor{gnat_rm/specialized_needs_annexes doc}@anchor{409}@anchor{gnat_rm/specialized_needs_annexes id1}@anchor{40a}
25436 @chapter Specialized Needs Annexes
25439 Ada 95, Ada 2005, and Ada 2012 define a number of Specialized Needs Annexes, which are not
25440 required in all implementations. However, as described in this chapter,
25441 GNAT implements all of these annexes:
25446 @item @emph{Systems Programming (Annex C)}
25448 The Systems Programming Annex is fully implemented.
25450 @item @emph{Real-Time Systems (Annex D)}
25452 The Real-Time Systems Annex is fully implemented.
25454 @item @emph{Distributed Systems (Annex E)}
25456 Stub generation is fully implemented in the GNAT compiler. In addition,
25457 a complete compatible PCS is available as part of the GLADE system,
25458 a separate product. When the two
25459 products are used in conjunction, this annex is fully implemented.
25461 @item @emph{Information Systems (Annex F)}
25463 The Information Systems annex is fully implemented.
25465 @item @emph{Numerics (Annex G)}
25467 The Numerics Annex is fully implemented.
25469 @item @emph{Safety and Security / High-Integrity Systems (Annex H)}
25471 The Safety and Security Annex (termed the High-Integrity Systems Annex
25472 in Ada 2005) is fully implemented.
25475 @node Implementation of Specific Ada Features,Implementation of Ada 2012 Features,Specialized Needs Annexes,Top
25476 @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{40b}@anchor{gnat_rm/implementation_of_specific_ada_features id1}@anchor{40c}
25477 @chapter Implementation of Specific Ada Features
25480 This chapter describes the GNAT implementation of several Ada language
25484 * Machine Code Insertions::
25485 * GNAT Implementation of Tasking::
25486 * GNAT Implementation of Shared Passive Packages::
25487 * Code Generation for Array Aggregates::
25488 * The Size of Discriminated Records with Default Discriminants::
25489 * Strict Conformance to the Ada Reference Manual::
25493 @node Machine Code Insertions,GNAT Implementation of Tasking,,Implementation of Specific Ada Features
25494 @anchor{gnat_rm/implementation_of_specific_ada_features machine-code-insertions}@anchor{164}@anchor{gnat_rm/implementation_of_specific_ada_features id2}@anchor{40d}
25495 @section Machine Code Insertions
25498 @geindex Machine Code insertions
25500 Package @code{Machine_Code} provides machine code support as described
25501 in the Ada Reference Manual in two separate forms:
25507 Machine code statements, consisting of qualified expressions that
25508 fit the requirements of RM section 13.8.
25511 An intrinsic callable procedure, providing an alternative mechanism of
25512 including machine instructions in a subprogram.
25515 The two features are similar, and both are closely related to the mechanism
25516 provided by the asm instruction in the GNU C compiler. Full understanding
25517 and use of the facilities in this package requires understanding the asm
25518 instruction, see the section on Extended Asm in
25519 @cite{Using_the_GNU_Compiler_Collection_(GCC)}.
25521 Calls to the function @code{Asm} and the procedure @code{Asm} have identical
25522 semantic restrictions and effects as described below. Both are provided so
25523 that the procedure call can be used as a statement, and the function call
25524 can be used to form a code_statement.
25526 Consider this C @code{asm} instruction:
25529 asm ("fsinx %1 %0" : "=f" (result) : "f" (angle));
25532 The equivalent can be written for GNAT as:
25535 Asm ("fsinx %1 %0",
25536 My_Float'Asm_Output ("=f", result),
25537 My_Float'Asm_Input ("f", angle));
25540 The first argument to @code{Asm} is the assembler template, and is
25541 identical to what is used in GNU C. This string must be a static
25542 expression. The second argument is the output operand list. It is
25543 either a single @code{Asm_Output} attribute reference, or a list of such
25544 references enclosed in parentheses (technically an array aggregate of
25547 The @code{Asm_Output} attribute denotes a function that takes two
25548 parameters. The first is a string, the second is the name of a variable
25549 of the type designated by the attribute prefix. The first (string)
25550 argument is required to be a static expression and designates the
25551 constraint (see the section on Constraints in
25552 @cite{Using_the_GNU_Compiler_Collection_(GCC)})
25553 for the parameter; e.g., what kind of register is required. The second
25554 argument is the variable to be written or updated with the
25555 result. The possible values for constraint are the same as those used in
25556 the RTL, and are dependent on the configuration file used to build the
25557 GCC back end. If there are no output operands, then this argument may
25558 either be omitted, or explicitly given as @code{No_Output_Operands}.
25559 No support is provided for GNU C's symbolic names for output parameters.
25561 The second argument of @code{my_float'Asm_Output} functions as
25562 though it were an @code{out} parameter, which is a little curious, but
25563 all names have the form of expressions, so there is no syntactic
25564 irregularity, even though normally functions would not be permitted
25565 @code{out} parameters. The third argument is the list of input
25566 operands. It is either a single @code{Asm_Input} attribute reference, or
25567 a list of such references enclosed in parentheses (technically an array
25568 aggregate of such references).
25570 The @code{Asm_Input} attribute denotes a function that takes two
25571 parameters. The first is a string, the second is an expression of the
25572 type designated by the prefix. The first (string) argument is required
25573 to be a static expression, and is the constraint for the parameter,
25574 (e.g., what kind of register is required). The second argument is the
25575 value to be used as the input argument. The possible values for the
25576 constraint are the same as those used in the RTL, and are dependent on
25577 the configuration file used to built the GCC back end.
25578 No support is provided for GNU C's symbolic names for input parameters.
25580 If there are no input operands, this argument may either be omitted, or
25581 explicitly given as @code{No_Input_Operands}. The fourth argument, not
25582 present in the above example, is a list of register names, called the
25583 @emph{clobber} argument. This argument, if given, must be a static string
25584 expression, and is a space or comma separated list of names of registers
25585 that must be considered destroyed as a result of the @code{Asm} call. If
25586 this argument is the null string (the default value), then the code
25587 generator assumes that no additional registers are destroyed.
25588 In addition to registers, the special clobbers @code{memory} and
25589 @code{cc} as described in the GNU C docs are both supported.
25591 The fifth argument, not present in the above example, called the
25592 @emph{volatile} argument, is by default @code{False}. It can be set to
25593 the literal value @code{True} to indicate to the code generator that all
25594 optimizations with respect to the instruction specified should be
25595 suppressed, and in particular an instruction that has outputs
25596 will still be generated, even if none of the outputs are
25597 used. See @cite{Using_the_GNU_Compiler_Collection_(GCC)}
25598 for the full description.
25599 Generally it is strongly advisable to use Volatile for any ASM statement
25600 that is missing either input or output operands or to avoid unwanted
25601 optimizations. A warning is generated if this advice is not followed.
25603 No support is provided for GNU C's @code{asm goto} feature.
25605 The @code{Asm} subprograms may be used in two ways. First the procedure
25606 forms can be used anywhere a procedure call would be valid, and
25607 correspond to what the RM calls 'intrinsic' routines. Such calls can
25608 be used to intersperse machine instructions with other Ada statements.
25609 Second, the function forms, which return a dummy value of the limited
25610 private type @code{Asm_Insn}, can be used in code statements, and indeed
25611 this is the only context where such calls are allowed. Code statements
25612 appear as aggregates of the form:
25615 Asm_Insn'(Asm (...));
25616 Asm_Insn'(Asm_Volatile (...));
25619 In accordance with RM rules, such code statements are allowed only
25620 within subprograms whose entire body consists of such statements. It is
25621 not permissible to intermix such statements with other Ada statements.
25623 Typically the form using intrinsic procedure calls is more convenient
25624 and more flexible. The code statement form is provided to meet the RM
25625 suggestion that such a facility should be made available. The following
25626 is the exact syntax of the call to @code{Asm}. As usual, if named notation
25627 is used, the arguments may be given in arbitrary order, following the
25628 normal rules for use of positional and named arguments:
25632 [Template =>] static_string_EXPRESSION
25633 [,[Outputs =>] OUTPUT_OPERAND_LIST ]
25634 [,[Inputs =>] INPUT_OPERAND_LIST ]
25635 [,[Clobber =>] static_string_EXPRESSION ]
25636 [,[Volatile =>] static_boolean_EXPRESSION] )
25638 OUTPUT_OPERAND_LIST ::=
25639 [PREFIX.]No_Output_Operands
25640 | OUTPUT_OPERAND_ATTRIBUTE
25641 | (OUTPUT_OPERAND_ATTRIBUTE @{,OUTPUT_OPERAND_ATTRIBUTE@})
25643 OUTPUT_OPERAND_ATTRIBUTE ::=
25644 SUBTYPE_MARK'Asm_Output (static_string_EXPRESSION, NAME)
25646 INPUT_OPERAND_LIST ::=
25647 [PREFIX.]No_Input_Operands
25648 | INPUT_OPERAND_ATTRIBUTE
25649 | (INPUT_OPERAND_ATTRIBUTE @{,INPUT_OPERAND_ATTRIBUTE@})
25651 INPUT_OPERAND_ATTRIBUTE ::=
25652 SUBTYPE_MARK'Asm_Input (static_string_EXPRESSION, EXPRESSION)
25655 The identifiers @code{No_Input_Operands} and @code{No_Output_Operands}
25656 are declared in the package @code{Machine_Code} and must be referenced
25657 according to normal visibility rules. In particular if there is no
25658 @code{use} clause for this package, then appropriate package name
25659 qualification is required.
25661 @node GNAT Implementation of Tasking,GNAT Implementation of Shared Passive Packages,Machine Code Insertions,Implementation of Specific Ada Features
25662 @anchor{gnat_rm/implementation_of_specific_ada_features id3}@anchor{40e}@anchor{gnat_rm/implementation_of_specific_ada_features gnat-implementation-of-tasking}@anchor{40f}
25663 @section GNAT Implementation of Tasking
25666 This chapter outlines the basic GNAT approach to tasking (in particular,
25667 a multi-layered library for portability) and discusses issues related
25668 to compliance with the Real-Time Systems Annex.
25671 * Mapping Ada Tasks onto the Underlying Kernel Threads::
25672 * Ensuring Compliance with the Real-Time Annex::
25673 * Support for Locking Policies::
25677 @node Mapping Ada Tasks onto the Underlying Kernel Threads,Ensuring Compliance with the Real-Time Annex,,GNAT Implementation of Tasking
25678 @anchor{gnat_rm/implementation_of_specific_ada_features mapping-ada-tasks-onto-the-underlying-kernel-threads}@anchor{410}@anchor{gnat_rm/implementation_of_specific_ada_features id4}@anchor{411}
25679 @subsection Mapping Ada Tasks onto the Underlying Kernel Threads
25682 GNAT's run-time support comprises two layers:
25688 GNARL (GNAT Run-time Layer)
25691 GNULL (GNAT Low-level Library)
25694 In GNAT, Ada's tasking services rely on a platform and OS independent
25695 layer known as GNARL. This code is responsible for implementing the
25696 correct semantics of Ada's task creation, rendezvous, protected
25699 GNARL decomposes Ada's tasking semantics into simpler lower level
25700 operations such as create a thread, set the priority of a thread,
25701 yield, create a lock, lock/unlock, etc. The spec for these low-level
25702 operations constitutes GNULLI, the GNULL Interface. This interface is
25703 directly inspired from the POSIX real-time API.
25705 If the underlying executive or OS implements the POSIX standard
25706 faithfully, the GNULL Interface maps as is to the services offered by
25707 the underlying kernel. Otherwise, some target dependent glue code maps
25708 the services offered by the underlying kernel to the semantics expected
25711 Whatever the underlying OS (VxWorks, UNIX, Windows, etc.) the
25712 key point is that each Ada task is mapped on a thread in the underlying
25713 kernel. For example, in the case of VxWorks, one Ada task = one VxWorks task.
25715 In addition Ada task priorities map onto the underlying thread priorities.
25716 Mapping Ada tasks onto the underlying kernel threads has several advantages:
25722 The underlying scheduler is used to schedule the Ada tasks. This
25723 makes Ada tasks as efficient as kernel threads from a scheduling
25727 Interaction with code written in C containing threads is eased
25728 since at the lowest level Ada tasks and C threads map onto the same
25729 underlying kernel concept.
25732 When an Ada task is blocked during I/O the remaining Ada tasks are
25736 On multiprocessor systems Ada tasks can execute in parallel.
25739 Some threads libraries offer a mechanism to fork a new process, with the
25740 child process duplicating the threads from the parent.
25742 support this functionality when the parent contains more than one task.
25744 @geindex Forking a new process
25746 @node Ensuring Compliance with the Real-Time Annex,Support for Locking Policies,Mapping Ada Tasks onto the Underlying Kernel Threads,GNAT Implementation of Tasking
25747 @anchor{gnat_rm/implementation_of_specific_ada_features id5}@anchor{412}@anchor{gnat_rm/implementation_of_specific_ada_features ensuring-compliance-with-the-real-time-annex}@anchor{413}
25748 @subsection Ensuring Compliance with the Real-Time Annex
25751 @geindex Real-Time Systems Annex compliance
25753 Although mapping Ada tasks onto
25754 the underlying threads has significant advantages, it does create some
25755 complications when it comes to respecting the scheduling semantics
25756 specified in the real-time annex (Annex D).
25758 For instance the Annex D requirement for the @code{FIFO_Within_Priorities}
25759 scheduling policy states:
25763 @emph{When the active priority of a ready task that is not running
25764 changes, or the setting of its base priority takes effect, the
25765 task is removed from the ready queue for its old active priority
25766 and is added at the tail of the ready queue for its new active
25767 priority, except in the case where the active priority is lowered
25768 due to the loss of inherited priority, in which case the task is
25769 added at the head of the ready queue for its new active priority.}
25772 While most kernels do put tasks at the end of the priority queue when
25773 a task changes its priority, (which respects the main
25774 FIFO_Within_Priorities requirement), almost none keep a thread at the
25775 beginning of its priority queue when its priority drops from the loss
25776 of inherited priority.
25778 As a result most vendors have provided incomplete Annex D implementations.
25780 The GNAT run-time, has a nice cooperative solution to this problem
25781 which ensures that accurate FIFO_Within_Priorities semantics are
25784 The principle is as follows. When an Ada task T is about to start
25785 running, it checks whether some other Ada task R with the same
25786 priority as T has been suspended due to the loss of priority
25787 inheritance. If this is the case, T yields and is placed at the end of
25788 its priority queue. When R arrives at the front of the queue it
25791 Note that this simple scheme preserves the relative order of the tasks
25792 that were ready to execute in the priority queue where R has been
25795 @c Support_for_Locking_Policies
25797 @node Support for Locking Policies,,Ensuring Compliance with the Real-Time Annex,GNAT Implementation of Tasking
25798 @anchor{gnat_rm/implementation_of_specific_ada_features support-for-locking-policies}@anchor{414}
25799 @subsection Support for Locking Policies
25802 This section specifies which policies specified by pragma Locking_Policy
25803 are supported on which platforms.
25805 GNAT supports the standard @code{Ceiling_Locking} policy, and the
25806 implementation defined @code{Inheritance_Locking} and
25807 @code{Concurrent_Readers_Locking} policies.
25809 @code{Ceiling_Locking} is supported on all platforms if the operating system
25810 supports it. In particular, @code{Ceiling_Locking} is not supported on
25812 @code{Inheritance_Locking} is supported on
25817 @code{Concurrent_Readers_Locking} is supported on Linux.
25819 Notes about @code{Ceiling_Locking} on Linux:
25820 If the process is running as 'root', ceiling locking is used.
25821 If the capabilities facility is installed
25822 ("sudo apt-get --assume-yes install libcap-dev" on Ubuntu,
25824 and the program is linked against that library
25826 and the executable file has the cap_sys_nice capability
25827 ("sudo /sbin/setcap cap_sys_nice=ep executable_file_name"),
25828 then ceiling locking is used.
25829 Otherwise, the @code{Ceiling_Locking} policy is ignored.
25831 @node GNAT Implementation of Shared Passive Packages,Code Generation for Array Aggregates,GNAT Implementation of Tasking,Implementation of Specific Ada Features
25832 @anchor{gnat_rm/implementation_of_specific_ada_features id6}@anchor{415}@anchor{gnat_rm/implementation_of_specific_ada_features gnat-implementation-of-shared-passive-packages}@anchor{416}
25833 @section GNAT Implementation of Shared Passive Packages
25836 @geindex Shared passive packages
25838 GNAT fully implements the
25839 @geindex pragma Shared_Passive
25841 @code{Shared_Passive} for
25842 the purpose of designating shared passive packages.
25843 This allows the use of passive partitions in the
25844 context described in the Ada Reference Manual; i.e., for communication
25845 between separate partitions of a distributed application using the
25846 features in Annex E.
25850 @geindex Distribution Systems Annex
25852 However, the implementation approach used by GNAT provides for more
25853 extensive usage as follows:
25858 @item @emph{Communication between separate programs}
25860 This allows separate programs to access the data in passive
25861 partitions, using protected objects for synchronization where
25862 needed. The only requirement is that the two programs have a
25863 common shared file system. It is even possible for programs
25864 running on different machines with different architectures
25865 (e.g., different endianness) to communicate via the data in
25866 a passive partition.
25868 @item @emph{Persistence between program runs}
25870 The data in a passive package can persist from one run of a
25871 program to another, so that a later program sees the final
25872 values stored by a previous run of the same program.
25875 The implementation approach used is to store the data in files. A
25876 separate stream file is created for each object in the package, and
25877 an access to an object causes the corresponding file to be read or
25880 @geindex SHARED_MEMORY_DIRECTORY environment variable
25882 The environment variable @code{SHARED_MEMORY_DIRECTORY} should be
25883 set to the directory to be used for these files.
25884 The files in this directory
25885 have names that correspond to their fully qualified names. For
25886 example, if we have the package
25890 pragma Shared_Passive (X);
25896 and the environment variable is set to @code{/stemp/}, then the files created
25897 will have the names:
25904 These files are created when a value is initially written to the object, and
25905 the files are retained until manually deleted. This provides the persistence
25906 semantics. If no file exists, it means that no partition has assigned a value
25907 to the variable; in this case the initial value declared in the package
25908 will be used. This model ensures that there are no issues in synchronizing
25909 the elaboration process, since elaboration of passive packages elaborates the
25910 initial values, but does not create the files.
25912 The files are written using normal @code{Stream_IO} access.
25913 If you want to be able
25914 to communicate between programs or partitions running on different
25915 architectures, then you should use the XDR versions of the stream attribute
25916 routines, since these are architecture independent.
25918 If active synchronization is required for access to the variables in the
25919 shared passive package, then as described in the Ada Reference Manual, the
25920 package may contain protected objects used for this purpose. In this case
25921 a lock file (whose name is @code{___lock} (three underscores)
25922 is created in the shared memory directory.
25924 @geindex ___lock file (for shared passive packages)
25926 This is used to provide the required locking
25927 semantics for proper protected object synchronization.
25929 GNAT supports shared passive packages on all platforms
25930 except for OpenVMS.
25932 @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
25933 @anchor{gnat_rm/implementation_of_specific_ada_features code-generation-for-array-aggregates}@anchor{417}@anchor{gnat_rm/implementation_of_specific_ada_features id7}@anchor{418}
25934 @section Code Generation for Array Aggregates
25937 Aggregates have a rich syntax and allow the user to specify the values of
25938 complex data structures by means of a single construct. As a result, the
25939 code generated for aggregates can be quite complex and involve loops, case
25940 statements and multiple assignments. In the simplest cases, however, the
25941 compiler will recognize aggregates whose components and constraints are
25942 fully static, and in those cases the compiler will generate little or no
25943 executable code. The following is an outline of the code that GNAT generates
25944 for various aggregate constructs. For further details, you will find it
25945 useful to examine the output produced by the -gnatG flag to see the expanded
25946 source that is input to the code generator. You may also want to examine
25947 the assembly code generated at various levels of optimization.
25949 The code generated for aggregates depends on the context, the component values,
25950 and the type. In the context of an object declaration the code generated is
25951 generally simpler than in the case of an assignment. As a general rule, static
25952 component values and static subtypes also lead to simpler code.
25955 * Static constant aggregates with static bounds::
25956 * Constant aggregates with unconstrained nominal types::
25957 * Aggregates with static bounds::
25958 * Aggregates with nonstatic bounds::
25959 * Aggregates in assignment statements::
25963 @node Static constant aggregates with static bounds,Constant aggregates with unconstrained nominal types,,Code Generation for Array Aggregates
25964 @anchor{gnat_rm/implementation_of_specific_ada_features static-constant-aggregates-with-static-bounds}@anchor{419}@anchor{gnat_rm/implementation_of_specific_ada_features id8}@anchor{41a}
25965 @subsection Static constant aggregates with static bounds
25968 For the declarations:
25971 type One_Dim is array (1..10) of integer;
25972 ar0 : constant One_Dim := (1, 2, 3, 4, 5, 6, 7, 8, 9, 0);
25975 GNAT generates no executable code: the constant ar0 is placed in static memory.
25976 The same is true for constant aggregates with named associations:
25979 Cr1 : constant One_Dim := (4 => 16, 2 => 4, 3 => 9, 1 => 1, 5 .. 10 => 0);
25980 Cr3 : constant One_Dim := (others => 7777);
25983 The same is true for multidimensional constant arrays such as:
25986 type two_dim is array (1..3, 1..3) of integer;
25987 Unit : constant two_dim := ( (1,0,0), (0,1,0), (0,0,1));
25990 The same is true for arrays of one-dimensional arrays: the following are
25994 type ar1b is array (1..3) of boolean;
25995 type ar_ar is array (1..3) of ar1b;
25996 None : constant ar1b := (others => false); -- fully static
25997 None2 : constant ar_ar := (1..3 => None); -- fully static
26000 However, for multidimensional aggregates with named associations, GNAT will
26001 generate assignments and loops, even if all associations are static. The
26002 following two declarations generate a loop for the first dimension, and
26003 individual component assignments for the second dimension:
26006 Zero1: constant two_dim := (1..3 => (1..3 => 0));
26007 Zero2: constant two_dim := (others => (others => 0));
26010 @node Constant aggregates with unconstrained nominal types,Aggregates with static bounds,Static constant aggregates with static bounds,Code Generation for Array Aggregates
26011 @anchor{gnat_rm/implementation_of_specific_ada_features constant-aggregates-with-unconstrained-nominal-types}@anchor{41b}@anchor{gnat_rm/implementation_of_specific_ada_features id9}@anchor{41c}
26012 @subsection Constant aggregates with unconstrained nominal types
26015 In such cases the aggregate itself establishes the subtype, so that
26016 associations with @code{others} cannot be used. GNAT determines the
26017 bounds for the actual subtype of the aggregate, and allocates the
26018 aggregate statically as well. No code is generated for the following:
26021 type One_Unc is array (natural range <>) of integer;
26022 Cr_Unc : constant One_Unc := (12,24,36);
26025 @node Aggregates with static bounds,Aggregates with nonstatic bounds,Constant aggregates with unconstrained nominal types,Code Generation for Array Aggregates
26026 @anchor{gnat_rm/implementation_of_specific_ada_features id10}@anchor{41d}@anchor{gnat_rm/implementation_of_specific_ada_features aggregates-with-static-bounds}@anchor{41e}
26027 @subsection Aggregates with static bounds
26030 In all previous examples the aggregate was the initial (and immutable) value
26031 of a constant. If the aggregate initializes a variable, then code is generated
26032 for it as a combination of individual assignments and loops over the target
26033 object. The declarations
26036 Cr_Var1 : One_Dim := (2, 5, 7, 11, 0, 0, 0, 0, 0, 0);
26037 Cr_Var2 : One_Dim := (others > -1);
26040 generate the equivalent of
26048 for I in Cr_Var2'range loop
26053 @node Aggregates with nonstatic bounds,Aggregates in assignment statements,Aggregates with static bounds,Code Generation for Array Aggregates
26054 @anchor{gnat_rm/implementation_of_specific_ada_features id11}@anchor{41f}@anchor{gnat_rm/implementation_of_specific_ada_features aggregates-with-nonstatic-bounds}@anchor{420}
26055 @subsection Aggregates with nonstatic bounds
26058 If the bounds of the aggregate are not statically compatible with the bounds
26059 of the nominal subtype of the target, then constraint checks have to be
26060 generated on the bounds. For a multidimensional array, constraint checks may
26061 have to be applied to sub-arrays individually, if they do not have statically
26062 compatible subtypes.
26064 @node Aggregates in assignment statements,,Aggregates with nonstatic bounds,Code Generation for Array Aggregates
26065 @anchor{gnat_rm/implementation_of_specific_ada_features id12}@anchor{421}@anchor{gnat_rm/implementation_of_specific_ada_features aggregates-in-assignment-statements}@anchor{422}
26066 @subsection Aggregates in assignment statements
26069 In general, aggregate assignment requires the construction of a temporary,
26070 and a copy from the temporary to the target of the assignment. This is because
26071 it is not always possible to convert the assignment into a series of individual
26072 component assignments. For example, consider the simple case:
26078 This cannot be converted into:
26085 So the aggregate has to be built first in a separate location, and then
26086 copied into the target. GNAT recognizes simple cases where this intermediate
26087 step is not required, and the assignments can be performed in place, directly
26088 into the target. The following sufficient criteria are applied:
26094 The bounds of the aggregate are static, and the associations are static.
26097 The components of the aggregate are static constants, names of
26098 simple variables that are not renamings, or expressions not involving
26099 indexed components whose operands obey these rules.
26102 If any of these conditions are violated, the aggregate will be built in
26103 a temporary (created either by the front-end or the code generator) and then
26104 that temporary will be copied onto the target.
26106 @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
26107 @anchor{gnat_rm/implementation_of_specific_ada_features id13}@anchor{423}@anchor{gnat_rm/implementation_of_specific_ada_features the-size-of-discriminated-records-with-default-discriminants}@anchor{424}
26108 @section The Size of Discriminated Records with Default Discriminants
26111 If a discriminated type @code{T} has discriminants with default values, it is
26112 possible to declare an object of this type without providing an explicit
26116 type Size is range 1..100;
26118 type Rec (D : Size := 15) is record
26119 Name : String (1..D);
26125 Such an object is said to be @emph{unconstrained}.
26126 The discriminant of the object
26127 can be modified by a full assignment to the object, as long as it preserves the
26128 relation between the value of the discriminant, and the value of the components
26132 Word := (3, "yes");
26134 Word := (5, "maybe");
26136 Word := (5, "no"); -- raises Constraint_Error
26139 In order to support this behavior efficiently, an unconstrained object is
26140 given the maximum size that any value of the type requires. In the case
26141 above, @code{Word} has storage for the discriminant and for
26142 a @code{String} of length 100.
26143 It is important to note that unconstrained objects do not require dynamic
26144 allocation. It would be an improper implementation to place on the heap those
26145 components whose size depends on discriminants. (This improper implementation
26146 was used by some Ada83 compilers, where the @code{Name} component above
26148 been stored as a pointer to a dynamic string). Following the principle that
26149 dynamic storage management should never be introduced implicitly,
26150 an Ada compiler should reserve the full size for an unconstrained declared
26151 object, and place it on the stack.
26153 This maximum size approach
26154 has been a source of surprise to some users, who expect the default
26155 values of the discriminants to determine the size reserved for an
26156 unconstrained object: "If the default is 15, why should the object occupy
26158 The answer, of course, is that the discriminant may be later modified,
26159 and its full range of values must be taken into account. This is why the
26163 type Rec (D : Positive := 15) is record
26164 Name : String (1..D);
26170 is flagged by the compiler with a warning:
26171 an attempt to create @code{Too_Large} will raise @code{Storage_Error},
26172 because the required size includes @code{Positive'Last}
26173 bytes. As the first example indicates, the proper approach is to declare an
26174 index type of 'reasonable' range so that unconstrained objects are not too
26177 One final wrinkle: if the object is declared to be @code{aliased}, or if it is
26178 created in the heap by means of an allocator, then it is @emph{not}
26180 it is constrained by the default values of the discriminants, and those values
26181 cannot be modified by full assignment. This is because in the presence of
26182 aliasing all views of the object (which may be manipulated by different tasks,
26183 say) must be consistent, so it is imperative that the object, once created,
26186 @node Strict Conformance to the Ada Reference Manual,,The Size of Discriminated Records with Default Discriminants,Implementation of Specific Ada Features
26187 @anchor{gnat_rm/implementation_of_specific_ada_features strict-conformance-to-the-ada-reference-manual}@anchor{425}@anchor{gnat_rm/implementation_of_specific_ada_features id14}@anchor{426}
26188 @section Strict Conformance to the Ada Reference Manual
26191 The dynamic semantics defined by the Ada Reference Manual impose a set of
26192 run-time checks to be generated. By default, the GNAT compiler will insert many
26193 run-time checks into the compiled code, including most of those required by the
26194 Ada Reference Manual. However, there are two checks that are not enabled in
26195 the default mode for efficiency reasons: checks for access before elaboration
26196 on subprogram calls, and stack overflow checking (most operating systems do not
26197 perform this check by default).
26199 Strict conformance to the Ada Reference Manual can be achieved by adding two
26200 compiler options for dynamic checks for access-before-elaboration on subprogram
26201 calls and generic instantiations (@emph{-gnatE}), and stack overflow checking
26202 (@emph{-fstack-check}).
26204 Note that the result of a floating point arithmetic operation in overflow and
26205 invalid situations, when the @code{Machine_Overflows} attribute of the result
26206 type is @code{False}, is to generate IEEE NaN and infinite values. This is the
26207 case for machines compliant with the IEEE floating-point standard, but on
26208 machines that are not fully compliant with this standard, such as Alpha, the
26209 @emph{-mieee} compiler flag must be used for achieving IEEE confirming
26210 behavior (although at the cost of a significant performance penalty), so
26211 infinite and NaN values are properly generated.
26213 @node Implementation of Ada 2012 Features,Obsolescent Features,Implementation of Specific Ada Features,Top
26214 @anchor{gnat_rm/implementation_of_ada_2012_features doc}@anchor{427}@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{428}
26215 @chapter Implementation of Ada 2012 Features
26218 @geindex Ada 2012 implementation status
26220 @geindex -gnat12 option (gcc)
26222 @geindex pragma Ada_2012
26224 @geindex configuration pragma Ada_2012
26226 @geindex Ada_2012 configuration pragma
26228 This chapter contains a complete list of Ada 2012 features that have been
26230 Generally, these features are only
26231 available if the @emph{-gnat12} (Ada 2012 features enabled) option is set,
26232 which is the default behavior,
26233 or if the configuration pragma @code{Ada_2012} is used.
26235 However, new pragmas, attributes, and restrictions are
26236 unconditionally available, since the Ada 95 standard allows the addition of
26237 new pragmas, attributes, and restrictions (there are exceptions, which are
26238 documented in the individual descriptions), and also certain packages
26239 were made available in earlier versions of Ada.
26241 An ISO date (YYYY-MM-DD) appears in parentheses on the description line.
26242 This date shows the implementation date of the feature. Any wavefront
26243 subsequent to this date will contain the indicated feature, as will any
26244 subsequent releases. A date of 0000-00-00 means that GNAT has always
26245 implemented the feature, or implemented it as soon as it appeared as a
26246 binding interpretation.
26248 Each feature corresponds to an Ada Issue ('AI') approved by the Ada
26249 standardization group (ISO/IEC JTC1/SC22/WG9) for inclusion in Ada 2012.
26250 The features are ordered based on the relevant sections of the Ada
26251 Reference Manual ("RM"). When a given AI relates to multiple points
26252 in the RM, the earliest is used.
26254 A complete description of the AIs may be found in
26255 @indicateurl{http://www.ada-auth.org/ai05-summary.html}.
26257 @geindex AI-0176 (Ada 2012 feature)
26263 @emph{AI-0176 Quantified expressions (2010-09-29)}
26265 Both universally and existentially quantified expressions are implemented.
26266 They use the new syntax for iterators proposed in AI05-139-2, as well as
26267 the standard Ada loop syntax.
26269 RM References: 1.01.04 (12) 2.09 (2/2) 4.04 (7) 4.05.09 (0)
26272 @geindex AI-0079 (Ada 2012 feature)
26278 @emph{AI-0079 Allow other_format characters in source (2010-07-10)}
26280 Wide characters in the unicode category @emph{other_format} are now allowed in
26281 source programs between tokens, but not within a token such as an identifier.
26283 RM References: 2.01 (4/2) 2.02 (7)
26286 @geindex AI-0091 (Ada 2012 feature)
26292 @emph{AI-0091 Do not allow other_format in identifiers (0000-00-00)}
26294 Wide characters in the unicode category @emph{other_format} are not permitted
26295 within an identifier, since this can be a security problem. The error
26296 message for this case has been improved to be more specific, but GNAT has
26297 never allowed such characters to appear in identifiers.
26299 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)
26302 @geindex AI-0100 (Ada 2012 feature)
26308 @emph{AI-0100 Placement of pragmas (2010-07-01)}
26310 This AI is an earlier version of AI-163. It simplifies the rules
26311 for legal placement of pragmas. In the case of lists that allow pragmas, if
26312 the list may have no elements, then the list may consist solely of pragmas.
26314 RM References: 2.08 (7)
26317 @geindex AI-0163 (Ada 2012 feature)
26323 @emph{AI-0163 Pragmas in place of null (2010-07-01)}
26325 A statement sequence may be composed entirely of pragmas. It is no longer
26326 necessary to add a dummy @code{null} statement to make the sequence legal.
26328 RM References: 2.08 (7) 2.08 (16)
26331 @geindex AI-0080 (Ada 2012 feature)
26337 @emph{AI-0080 'View of' not needed if clear from context (0000-00-00)}
26339 This is an editorial change only, described as non-testable in the AI.
26341 RM References: 3.01 (7)
26344 @geindex AI-0183 (Ada 2012 feature)
26350 @emph{AI-0183 Aspect specifications (2010-08-16)}
26352 Aspect specifications have been fully implemented except for pre and post-
26353 conditions, and type invariants, which have their own separate AI's. All
26354 forms of declarations listed in the AI are supported. The following is a
26355 list of the aspects supported (with GNAT implementation aspects marked)
26359 @multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxx}
26404 @code{Atomic_Components}
26416 @code{Component_Size}
26422 @code{Contract_Cases}
26430 @code{Discard_Names}
26436 @code{External_Tag}
26442 @code{Favor_Top_Level}
26456 @code{Inline_Always}
26472 @code{Machine_Radix}
26498 @code{Persistent_BSS}
26524 @code{Preelaborable_Initialization}
26530 @code{Pure_Function}
26538 @code{Remote_Access_Type}
26560 @code{Storage_Pool}
26566 @code{Storage_Size}
26584 @code{Suppress_Debug_Info}
26600 @code{Thread_Local_Storage}
26608 @code{Type_Invariant}
26614 @code{Unchecked_Union}
26620 @code{Universal_Aliasing}
26636 @code{Unreferenced}
26644 @code{Unreferenced_Objects}
26672 @code{Volatile_Components}
26689 Note that for aspects with an expression, e.g. @code{Size}, the expression is
26690 treated like a default expression (visibility is analyzed at the point of
26691 occurrence of the aspect, but evaluation of the expression occurs at the
26692 freeze point of the entity involved).
26694 RM References: 3.02.01 (3) 3.02.02 (2) 3.03.01 (2/2) 3.08 (6)
26695 3.09.03 (1.1/2) 6.01 (2/2) 6.07 (2/2) 9.05.02 (2/2) 7.01 (3) 7.03
26696 (2) 7.03 (3) 9.01 (2/2) 9.01 (3/2) 9.04 (2/2) 9.04 (3/2)
26697 9.05.02 (2/2) 11.01 (2) 12.01 (3) 12.03 (2/2) 12.04 (2/2) 12.05 (2)
26698 12.06 (2.1/2) 12.06 (2.2/2) 12.07 (2) 13.01 (0.1/2) 13.03 (5/1)
26702 @geindex AI-0128 (Ada 2012 feature)
26708 @emph{AI-0128 Inequality is a primitive operation (0000-00-00)}
26710 If an equality operator ("=") is declared for a type, then the implicitly
26711 declared inequality operator ("/=") is a primitive operation of the type.
26712 This is the only reasonable interpretation, and is the one always implemented
26713 by GNAT, but the RM was not entirely clear in making this point.
26715 RM References: 3.02.03 (6) 6.06 (6)
26718 @geindex AI-0003 (Ada 2012 feature)
26724 @emph{AI-0003 Qualified expressions as names (2010-07-11)}
26726 In Ada 2012, a qualified expression is considered to be syntactically a name,
26727 meaning that constructs such as @code{A'(F(X)).B} are now legal. This is
26728 useful in disambiguating some cases of overloading.
26730 RM References: 3.03 (11) 3.03 (21) 4.01 (2) 4.04 (7) 4.07 (3)
26734 @geindex AI-0120 (Ada 2012 feature)
26740 @emph{AI-0120 Constant instance of protected object (0000-00-00)}
26742 This is an RM editorial change only. The section that lists objects that are
26743 constant failed to include the current instance of a protected object
26744 within a protected function. This has always been treated as a constant
26747 RM References: 3.03 (21)
26750 @geindex AI-0008 (Ada 2012 feature)
26756 @emph{AI-0008 General access to constrained objects (0000-00-00)}
26758 The wording in the RM implied that if you have a general access to a
26759 constrained object, it could be used to modify the discriminants. This was
26760 obviously not intended. @code{Constraint_Error} should be raised, and GNAT
26761 has always done so in this situation.
26763 RM References: 3.03 (23) 3.10.02 (26/2) 4.01 (9) 6.04.01 (17) 8.05.01 (5/2)
26766 @geindex AI-0093 (Ada 2012 feature)
26772 @emph{AI-0093 Additional rules use immutably limited (0000-00-00)}
26774 This is an editorial change only, to make more widespread use of the Ada 2012
26775 'immutably limited'.
26777 RM References: 3.03 (23.4/3)
26780 @geindex AI-0096 (Ada 2012 feature)
26786 @emph{AI-0096 Deriving from formal private types (2010-07-20)}
26788 In general it is illegal for a type derived from a formal limited type to be
26789 nonlimited. This AI makes an exception to this rule: derivation is legal
26790 if it appears in the private part of the generic, and the formal type is not
26791 tagged. If the type is tagged, the legality check must be applied to the
26792 private part of the package.
26794 RM References: 3.04 (5.1/2) 6.02 (7)
26797 @geindex AI-0181 (Ada 2012 feature)
26803 @emph{AI-0181 Soft hyphen is a non-graphic character (2010-07-23)}
26805 From Ada 2005 on, soft hyphen is considered a non-graphic character, which
26806 means that it has a special name (@code{SOFT_HYPHEN}) in conjunction with the
26807 @code{Image} and @code{Value} attributes for the character types. Strictly
26808 speaking this is an inconsistency with Ada 95, but in practice the use of
26809 these attributes is so obscure that it will not cause problems.
26811 RM References: 3.05.02 (2/2) A.01 (35/2) A.03.03 (21)
26814 @geindex AI-0182 (Ada 2012 feature)
26820 @emph{AI-0182 Additional forms for} @code{Character'Value} @emph{(0000-00-00)}
26822 This AI allows @code{Character'Value} to accept the string @code{'?'} where
26823 @code{?} is any character including non-graphic control characters. GNAT has
26824 always accepted such strings. It also allows strings such as
26825 @code{HEX_00000041} to be accepted, but GNAT does not take advantage of this
26826 permission and raises @code{Constraint_Error}, as is certainly still
26829 RM References: 3.05 (56/2)
26832 @geindex AI-0214 (Ada 2012 feature)
26838 @emph{AI-0214 Defaulted discriminants for limited tagged (2010-10-01)}
26840 Ada 2012 relaxes the restriction that forbids discriminants of tagged types
26841 to have default expressions by allowing them when the type is limited. It
26842 is often useful to define a default value for a discriminant even though
26843 it can't be changed by assignment.
26845 RM References: 3.07 (9.1/2) 3.07.02 (3)
26848 @geindex AI-0102 (Ada 2012 feature)
26854 @emph{AI-0102 Some implicit conversions are illegal (0000-00-00)}
26856 It is illegal to assign an anonymous access constant to an anonymous access
26857 variable. The RM did not have a clear rule to prevent this, but GNAT has
26858 always generated an error for this usage.
26860 RM References: 3.07 (16) 3.07.01 (9) 6.04.01 (6) 8.06 (27/2)
26863 @geindex AI-0158 (Ada 2012 feature)
26869 @emph{AI-0158 Generalizing membership tests (2010-09-16)}
26871 This AI extends the syntax of membership tests to simplify complex conditions
26872 that can be expressed as membership in a subset of values of any type. It
26873 introduces syntax for a list of expressions that may be used in loop contexts
26876 RM References: 3.08.01 (5) 4.04 (3) 4.05.02 (3) 4.05.02 (5) 4.05.02 (27)
26879 @geindex AI-0173 (Ada 2012 feature)
26885 @emph{AI-0173 Testing if tags represent abstract types (2010-07-03)}
26887 The function @code{Ada.Tags.Type_Is_Abstract} returns @code{True} if invoked
26888 with the tag of an abstract type, and @code{False} otherwise.
26890 RM References: 3.09 (7.4/2) 3.09 (12.4/2)
26893 @geindex AI-0076 (Ada 2012 feature)
26899 @emph{AI-0076 function with controlling result (0000-00-00)}
26901 This is an editorial change only. The RM defines calls with controlling
26902 results, but uses the term 'function with controlling result' without an
26903 explicit definition.
26905 RM References: 3.09.02 (2/2)
26908 @geindex AI-0126 (Ada 2012 feature)
26914 @emph{AI-0126 Dispatching with no declared operation (0000-00-00)}
26916 This AI clarifies dispatching rules, and simply confirms that dispatching
26917 executes the operation of the parent type when there is no explicitly or
26918 implicitly declared operation for the descendant type. This has always been
26919 the case in all versions of GNAT.
26921 RM References: 3.09.02 (20/2) 3.09.02 (20.1/2) 3.09.02 (20.2/2)
26924 @geindex AI-0097 (Ada 2012 feature)
26930 @emph{AI-0097 Treatment of abstract null extension (2010-07-19)}
26932 The RM as written implied that in some cases it was possible to create an
26933 object of an abstract type, by having an abstract extension inherit a non-
26934 abstract constructor from its parent type. This mistake has been corrected
26935 in GNAT and in the RM, and this construct is now illegal.
26937 RM References: 3.09.03 (4/2)
26940 @geindex AI-0203 (Ada 2012 feature)
26946 @emph{AI-0203 Extended return cannot be abstract (0000-00-00)}
26948 A return_subtype_indication cannot denote an abstract subtype. GNAT has never
26949 permitted such usage.
26951 RM References: 3.09.03 (8/3)
26954 @geindex AI-0198 (Ada 2012 feature)
26960 @emph{AI-0198 Inheriting abstract operators (0000-00-00)}
26962 This AI resolves a conflict between two rules involving inherited abstract
26963 operations and predefined operators. If a derived numeric type inherits
26964 an abstract operator, it overrides the predefined one. This interpretation
26965 was always the one implemented in GNAT.
26967 RM References: 3.09.03 (4/3)
26970 @geindex AI-0073 (Ada 2012 feature)
26976 @emph{AI-0073 Functions returning abstract types (2010-07-10)}
26978 This AI covers a number of issues regarding returning abstract types. In
26979 particular generic functions cannot have abstract result types or access
26980 result types designated an abstract type. There are some other cases which
26981 are detailed in the AI. Note that this binding interpretation has not been
26982 retrofitted to operate before Ada 2012 mode, since it caused a significant
26983 number of regressions.
26985 RM References: 3.09.03 (8) 3.09.03 (10) 6.05 (8/2)
26988 @geindex AI-0070 (Ada 2012 feature)
26994 @emph{AI-0070 Elaboration of interface types (0000-00-00)}
26996 This is an editorial change only, there are no testable consequences short of
26997 checking for the absence of generated code for an interface declaration.
26999 RM References: 3.09.04 (18/2)
27002 @geindex AI-0208 (Ada 2012 feature)
27008 @emph{AI-0208 Characteristics of incomplete views (0000-00-00)}
27010 The wording in the Ada 2005 RM concerning characteristics of incomplete views
27011 was incorrect and implied that some programs intended to be legal were now
27012 illegal. GNAT had never considered such programs illegal, so it has always
27013 implemented the intent of this AI.
27015 RM References: 3.10.01 (2.4/2) 3.10.01 (2.6/2)
27018 @geindex AI-0162 (Ada 2012 feature)
27024 @emph{AI-0162 Incomplete type completed by partial view (2010-09-15)}
27026 Incomplete types are made more useful by allowing them to be completed by
27027 private types and private extensions.
27029 RM References: 3.10.01 (2.5/2) 3.10.01 (2.6/2) 3.10.01 (3) 3.10.01 (4/2)
27032 @geindex AI-0098 (Ada 2012 feature)
27038 @emph{AI-0098 Anonymous subprogram access restrictions (0000-00-00)}
27040 An unintentional omission in the RM implied some inconsistent restrictions on
27041 the use of anonymous access to subprogram values. These restrictions were not
27042 intentional, and have never been enforced by GNAT.
27044 RM References: 3.10.01 (6) 3.10.01 (9.2/2)
27047 @geindex AI-0199 (Ada 2012 feature)
27053 @emph{AI-0199 Aggregate with anonymous access components (2010-07-14)}
27055 A choice list in a record aggregate can include several components of
27056 (distinct) anonymous access types as long as they have matching designated
27059 RM References: 4.03.01 (16)
27062 @geindex AI-0220 (Ada 2012 feature)
27068 @emph{AI-0220 Needed components for aggregates (0000-00-00)}
27070 This AI addresses a wording problem in the RM that appears to permit some
27071 complex cases of aggregates with nonstatic discriminants. GNAT has always
27072 implemented the intended semantics.
27074 RM References: 4.03.01 (17)
27077 @geindex AI-0147 (Ada 2012 feature)
27083 @emph{AI-0147 Conditional expressions (2009-03-29)}
27085 Conditional expressions are permitted. The form of such an expression is:
27088 (if expr then expr @{elsif expr then expr@} [else expr])
27091 The parentheses can be omitted in contexts where parentheses are present
27092 anyway, such as subprogram arguments and pragma arguments. If the @strong{else}
27093 clause is omitted, @strong{else} @emph{True} is assumed;
27094 thus @code{(if A then B)} is a way to conveniently represent
27095 @emph{(A implies B)} in standard logic.
27097 RM References: 4.03.03 (15) 4.04 (1) 4.04 (7) 4.05.07 (0) 4.07 (2)
27098 4.07 (3) 4.09 (12) 4.09 (33) 5.03 (3) 5.03 (4) 7.05 (2.1/2)
27101 @geindex AI-0037 (Ada 2012 feature)
27107 @emph{AI-0037 Out-of-range box associations in aggregate (0000-00-00)}
27109 This AI confirms that an association of the form @code{Indx => <>} in an
27110 array aggregate must raise @code{Constraint_Error} if @code{Indx}
27111 is out of range. The RM specified a range check on other associations, but
27112 not when the value of the association was defaulted. GNAT has always inserted
27113 a constraint check on the index value.
27115 RM References: 4.03.03 (29)
27118 @geindex AI-0123 (Ada 2012 feature)
27124 @emph{AI-0123 Composability of equality (2010-04-13)}
27126 Equality of untagged record composes, so that the predefined equality for a
27127 composite type that includes a component of some untagged record type
27128 @code{R} uses the equality operation of @code{R} (which may be user-defined
27129 or predefined). This makes the behavior of untagged records identical to that
27130 of tagged types in this respect.
27132 This change is an incompatibility with previous versions of Ada, but it
27133 corrects a non-uniformity that was often a source of confusion. Analysis of
27134 a large number of industrial programs indicates that in those rare cases
27135 where a composite type had an untagged record component with a user-defined
27136 equality, either there was no use of the composite equality, or else the code
27137 expected the same composability as for tagged types, and thus had a bug that
27138 would be fixed by this change.
27140 RM References: 4.05.02 (9.7/2) 4.05.02 (14) 4.05.02 (15) 4.05.02 (24)
27144 @geindex AI-0088 (Ada 2012 feature)
27150 @emph{AI-0088 The value of exponentiation (0000-00-00)}
27152 This AI clarifies the equivalence rule given for the dynamic semantics of
27153 exponentiation: the value of the operation can be obtained by repeated
27154 multiplication, but the operation can be implemented otherwise (for example
27155 using the familiar divide-by-two-and-square algorithm, even if this is less
27156 accurate), and does not imply repeated reads of a volatile base.
27158 RM References: 4.05.06 (11)
27161 @geindex AI-0188 (Ada 2012 feature)
27167 @emph{AI-0188 Case expressions (2010-01-09)}
27169 Case expressions are permitted. This allows use of constructs such as:
27172 X := (case Y is when 1 => 2, when 2 => 3, when others => 31)
27175 RM References: 4.05.07 (0) 4.05.08 (0) 4.09 (12) 4.09 (33)
27178 @geindex AI-0104 (Ada 2012 feature)
27184 @emph{AI-0104 Null exclusion and uninitialized allocator (2010-07-15)}
27186 The assignment @code{Ptr := new not null Some_Ptr;} will raise
27187 @code{Constraint_Error} because the default value of the allocated object is
27188 @strong{null}. This useless construct is illegal in Ada 2012.
27190 RM References: 4.08 (2)
27193 @geindex AI-0157 (Ada 2012 feature)
27199 @emph{AI-0157 Allocation/Deallocation from empty pool (2010-07-11)}
27201 Allocation and Deallocation from an empty storage pool (i.e. allocation or
27202 deallocation of a pointer for which a static storage size clause of zero
27203 has been given) is now illegal and is detected as such. GNAT
27204 previously gave a warning but not an error.
27206 RM References: 4.08 (5.3/2) 13.11.02 (4) 13.11.02 (17)
27209 @geindex AI-0179 (Ada 2012 feature)
27215 @emph{AI-0179 Statement not required after label (2010-04-10)}
27217 It is not necessary to have a statement following a label, so a label
27218 can appear at the end of a statement sequence without the need for putting a
27219 null statement afterwards, but it is not allowable to have only labels and
27220 no real statements in a statement sequence.
27222 RM References: 5.01 (2)
27225 @geindex AI-0139-2 (Ada 2012 feature)
27231 @emph{AI-0139-2 Syntactic sugar for iterators (2010-09-29)}
27233 The new syntax for iterating over arrays and containers is now implemented.
27234 Iteration over containers is for now limited to read-only iterators. Only
27235 default iterators are supported, with the syntax: @code{for Elem of C}.
27237 RM References: 5.05
27240 @geindex AI-0134 (Ada 2012 feature)
27246 @emph{AI-0134 Profiles must match for full conformance (0000-00-00)}
27248 For full conformance, the profiles of anonymous-access-to-subprogram
27249 parameters must match. GNAT has always enforced this rule.
27251 RM References: 6.03.01 (18)
27254 @geindex AI-0207 (Ada 2012 feature)
27260 @emph{AI-0207 Mode conformance and access constant (0000-00-00)}
27262 This AI confirms that access_to_constant indication must match for mode
27263 conformance. This was implemented in GNAT when the qualifier was originally
27264 introduced in Ada 2005.
27266 RM References: 6.03.01 (16/2)
27269 @geindex AI-0046 (Ada 2012 feature)
27275 @emph{AI-0046 Null exclusion match for full conformance (2010-07-17)}
27277 For full conformance, in the case of access parameters, the null exclusion
27278 must match (either both or neither must have @code{not null}).
27280 RM References: 6.03.02 (18)
27283 @geindex AI-0118 (Ada 2012 feature)
27289 @emph{AI-0118 The association of parameter associations (0000-00-00)}
27291 This AI clarifies the rules for named associations in subprogram calls and
27292 generic instantiations. The rules have been in place since Ada 83.
27294 RM References: 6.04.01 (2) 12.03 (9)
27297 @geindex AI-0196 (Ada 2012 feature)
27303 @emph{AI-0196 Null exclusion tests for out parameters (0000-00-00)}
27305 Null exclusion checks are not made for @code{out} parameters when
27306 evaluating the actual parameters. GNAT has never generated these checks.
27308 RM References: 6.04.01 (13)
27311 @geindex AI-0015 (Ada 2012 feature)
27317 @emph{AI-0015 Constant return objects (0000-00-00)}
27319 The return object declared in an @emph{extended_return_statement} may be
27320 declared constant. This was always intended, and GNAT has always allowed it.
27322 RM References: 6.05 (2.1/2) 3.03 (10/2) 3.03 (21) 6.05 (5/2)
27326 @geindex AI-0032 (Ada 2012 feature)
27332 @emph{AI-0032 Extended return for class-wide functions (0000-00-00)}
27334 If a function returns a class-wide type, the object of an extended return
27335 statement can be declared with a specific type that is covered by the class-
27336 wide type. This has been implemented in GNAT since the introduction of
27337 extended returns. Note AI-0103 complements this AI by imposing matching
27338 rules for constrained return types.
27340 RM References: 6.05 (5.2/2) 6.05 (5.3/2) 6.05 (5.6/2) 6.05 (5.8/2)
27344 @geindex AI-0103 (Ada 2012 feature)
27350 @emph{AI-0103 Static matching for extended return (2010-07-23)}
27352 If the return subtype of a function is an elementary type or a constrained
27353 type, the subtype indication in an extended return statement must match
27354 statically this return subtype.
27356 RM References: 6.05 (5.2/2)
27359 @geindex AI-0058 (Ada 2012 feature)
27365 @emph{AI-0058 Abnormal completion of an extended return (0000-00-00)}
27367 The RM had some incorrect wording implying wrong treatment of abnormal
27368 completion in an extended return. GNAT has always implemented the intended
27369 correct semantics as described by this AI.
27371 RM References: 6.05 (22/2)
27374 @geindex AI-0050 (Ada 2012 feature)
27380 @emph{AI-0050 Raising Constraint_Error early for function call (0000-00-00)}
27382 The implementation permissions for raising @code{Constraint_Error} early on a function call
27383 when it was clear an exception would be raised were over-permissive and allowed
27384 mishandling of discriminants in some cases. GNAT did
27385 not take advantage of these incorrect permissions in any case.
27387 RM References: 6.05 (24/2)
27390 @geindex AI-0125 (Ada 2012 feature)
27396 @emph{AI-0125 Nonoverridable operations of an ancestor (2010-09-28)}
27398 In Ada 2012, the declaration of a primitive operation of a type extension
27399 or private extension can also override an inherited primitive that is not
27400 visible at the point of this declaration.
27402 RM References: 7.03.01 (6) 8.03 (23) 8.03.01 (5/2) 8.03.01 (6/2)
27405 @geindex AI-0062 (Ada 2012 feature)
27411 @emph{AI-0062 Null exclusions and deferred constants (0000-00-00)}
27413 A full constant may have a null exclusion even if its associated deferred
27414 constant does not. GNAT has always allowed this.
27416 RM References: 7.04 (6/2) 7.04 (7.1/2)
27419 @geindex AI-0178 (Ada 2012 feature)
27425 @emph{AI-0178 Incomplete views are limited (0000-00-00)}
27427 This AI clarifies the role of incomplete views and plugs an omission in the
27428 RM. GNAT always correctly restricted the use of incomplete views and types.
27430 RM References: 7.05 (3/2) 7.05 (6/2)
27433 @geindex AI-0087 (Ada 2012 feature)
27439 @emph{AI-0087 Actual for formal nonlimited derived type (2010-07-15)}
27441 The actual for a formal nonlimited derived type cannot be limited. In
27442 particular, a formal derived type that extends a limited interface but which
27443 is not explicitly limited cannot be instantiated with a limited type.
27445 RM References: 7.05 (5/2) 12.05.01 (5.1/2)
27448 @geindex AI-0099 (Ada 2012 feature)
27454 @emph{AI-0099 Tag determines whether finalization needed (0000-00-00)}
27456 This AI clarifies that 'needs finalization' is part of dynamic semantics,
27457 and therefore depends on the run-time characteristics of an object (i.e. its
27458 tag) and not on its nominal type. As the AI indicates: "we do not expect
27459 this to affect any implementation'@w{'}.
27461 RM References: 7.06.01 (6) 7.06.01 (7) 7.06.01 (8) 7.06.01 (9/2)
27464 @geindex AI-0064 (Ada 2012 feature)
27470 @emph{AI-0064 Redundant finalization rule (0000-00-00)}
27472 This is an editorial change only. The intended behavior is already checked
27473 by an existing ACATS test, which GNAT has always executed correctly.
27475 RM References: 7.06.01 (17.1/1)
27478 @geindex AI-0026 (Ada 2012 feature)
27484 @emph{AI-0026 Missing rules for Unchecked_Union (2010-07-07)}
27486 Record representation clauses concerning Unchecked_Union types cannot mention
27487 the discriminant of the type. The type of a component declared in the variant
27488 part of an Unchecked_Union cannot be controlled, have controlled components,
27489 nor have protected or task parts. If an Unchecked_Union type is declared
27490 within the body of a generic unit or its descendants, then the type of a
27491 component declared in the variant part cannot be a formal private type or a
27492 formal private extension declared within the same generic unit.
27494 RM References: 7.06 (9.4/2) B.03.03 (9/2) B.03.03 (10/2)
27497 @geindex AI-0205 (Ada 2012 feature)
27503 @emph{AI-0205 Extended return declares visible name (0000-00-00)}
27505 This AI corrects a simple omission in the RM. Return objects have always
27506 been visible within an extended return statement.
27508 RM References: 8.03 (17)
27511 @geindex AI-0042 (Ada 2012 feature)
27517 @emph{AI-0042 Overriding versus implemented-by (0000-00-00)}
27519 This AI fixes a wording gap in the RM. An operation of a synchronized
27520 interface can be implemented by a protected or task entry, but the abstract
27521 operation is not being overridden in the usual sense, and it must be stated
27522 separately that this implementation is legal. This has always been the case
27525 RM References: 9.01 (9.2/2) 9.04 (11.1/2)
27528 @geindex AI-0030 (Ada 2012 feature)
27534 @emph{AI-0030 Requeue on synchronized interfaces (2010-07-19)}
27536 Requeue is permitted to a protected, synchronized or task interface primitive
27537 providing it is known that the overriding operation is an entry. Otherwise
27538 the requeue statement has the same effect as a procedure call. Use of pragma
27539 @code{Implemented} provides a way to impose a static requirement on the
27540 overriding operation by adhering to one of the implementation kinds: entry,
27541 protected procedure or any of the above.
27543 RM References: 9.05 (9) 9.05.04 (2) 9.05.04 (3) 9.05.04 (5)
27544 9.05.04 (6) 9.05.04 (7) 9.05.04 (12)
27547 @geindex AI-0201 (Ada 2012 feature)
27553 @emph{AI-0201 Independence of atomic object components (2010-07-22)}
27555 If an Atomic object has a pragma @code{Pack} or a @code{Component_Size}
27556 attribute, then individual components may not be addressable by independent
27557 tasks. However, if the representation clause has no effect (is confirming),
27558 then independence is not compromised. Furthermore, in GNAT, specification of
27559 other appropriately addressable component sizes (e.g. 16 for 8-bit
27560 characters) also preserves independence. GNAT now gives very clear warnings
27561 both for the declaration of such a type, and for any assignment to its components.
27563 RM References: 9.10 (1/3) C.06 (22/2) C.06 (23/2)
27566 @geindex AI-0009 (Ada 2012 feature)
27572 @emph{AI-0009 Pragma Independent[_Components] (2010-07-23)}
27574 This AI introduces the new pragmas @code{Independent} and
27575 @code{Independent_Components},
27576 which control guaranteeing independence of access to objects and components.
27577 The AI also requires independence not unaffected by confirming rep clauses.
27579 RM References: 9.10 (1) 13.01 (15/1) 13.02 (9) 13.03 (13) C.06 (2)
27580 C.06 (4) C.06 (6) C.06 (9) C.06 (13) C.06 (14)
27583 @geindex AI-0072 (Ada 2012 feature)
27589 @emph{AI-0072 Task signalling using 'Terminated (0000-00-00)}
27591 This AI clarifies that task signalling for reading @code{'Terminated} only
27592 occurs if the result is True. GNAT semantics has always been consistent with
27593 this notion of task signalling.
27595 RM References: 9.10 (6.1/1)
27598 @geindex AI-0108 (Ada 2012 feature)
27604 @emph{AI-0108 Limited incomplete view and discriminants (0000-00-00)}
27606 This AI confirms that an incomplete type from a limited view does not have
27607 discriminants. This has always been the case in GNAT.
27609 RM References: 10.01.01 (12.3/2)
27612 @geindex AI-0129 (Ada 2012 feature)
27618 @emph{AI-0129 Limited views and incomplete types (0000-00-00)}
27620 This AI clarifies the description of limited views: a limited view of a
27621 package includes only one view of a type that has an incomplete declaration
27622 and a full declaration (there is no possible ambiguity in a client package).
27623 This AI also fixes an omission: a nested package in the private part has no
27624 limited view. GNAT always implemented this correctly.
27626 RM References: 10.01.01 (12.2/2) 10.01.01 (12.3/2)
27629 @geindex AI-0077 (Ada 2012 feature)
27635 @emph{AI-0077 Limited withs and scope of declarations (0000-00-00)}
27637 This AI clarifies that a declaration does not include a context clause,
27638 and confirms that it is illegal to have a context in which both a limited
27639 and a nonlimited view of a package are accessible. Such double visibility
27640 was always rejected by GNAT.
27642 RM References: 10.01.02 (12/2) 10.01.02 (21/2) 10.01.02 (22/2)
27645 @geindex AI-0122 (Ada 2012 feature)
27651 @emph{AI-0122 Private with and children of generics (0000-00-00)}
27653 This AI clarifies the visibility of private children of generic units within
27654 instantiations of a parent. GNAT has always handled this correctly.
27656 RM References: 10.01.02 (12/2)
27659 @geindex AI-0040 (Ada 2012 feature)
27665 @emph{AI-0040 Limited with clauses on descendant (0000-00-00)}
27667 This AI confirms that a limited with clause in a child unit cannot name
27668 an ancestor of the unit. This has always been checked in GNAT.
27670 RM References: 10.01.02 (20/2)
27673 @geindex AI-0132 (Ada 2012 feature)
27679 @emph{AI-0132 Placement of library unit pragmas (0000-00-00)}
27681 This AI fills a gap in the description of library unit pragmas. The pragma
27682 clearly must apply to a library unit, even if it does not carry the name
27683 of the enclosing unit. GNAT has always enforced the required check.
27685 RM References: 10.01.05 (7)
27688 @geindex AI-0034 (Ada 2012 feature)
27694 @emph{AI-0034 Categorization of limited views (0000-00-00)}
27696 The RM makes certain limited with clauses illegal because of categorization
27697 considerations, when the corresponding normal with would be legal. This is
27698 not intended, and GNAT has always implemented the recommended behavior.
27700 RM References: 10.02.01 (11/1) 10.02.01 (17/2)
27703 @geindex AI-0035 (Ada 2012 feature)
27709 @emph{AI-0035 Inconsistencies with Pure units (0000-00-00)}
27711 This AI remedies some inconsistencies in the legality rules for Pure units.
27712 Derived access types are legal in a pure unit (on the assumption that the
27713 rule for a zero storage pool size has been enforced on the ancestor type).
27714 The rules are enforced in generic instances and in subunits. GNAT has always
27715 implemented the recommended behavior.
27717 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)
27720 @geindex AI-0219 (Ada 2012 feature)
27726 @emph{AI-0219 Pure permissions and limited parameters (2010-05-25)}
27728 This AI refines the rules for the cases with limited parameters which do not
27729 allow the implementations to omit 'redundant'. GNAT now properly conforms
27730 to the requirements of this binding interpretation.
27732 RM References: 10.02.01 (18/2)
27735 @geindex AI-0043 (Ada 2012 feature)
27741 @emph{AI-0043 Rules about raising exceptions (0000-00-00)}
27743 This AI covers various omissions in the RM regarding the raising of
27744 exceptions. GNAT has always implemented the intended semantics.
27746 RM References: 11.04.01 (10.1/2) 11 (2)
27749 @geindex AI-0200 (Ada 2012 feature)
27755 @emph{AI-0200 Mismatches in formal package declarations (0000-00-00)}
27757 This AI plugs a gap in the RM which appeared to allow some obviously intended
27758 illegal instantiations. GNAT has never allowed these instantiations.
27760 RM References: 12.07 (16)
27763 @geindex AI-0112 (Ada 2012 feature)
27769 @emph{AI-0112 Detection of duplicate pragmas (2010-07-24)}
27771 This AI concerns giving names to various representation aspects, but the
27772 practical effect is simply to make the use of duplicate
27773 @code{Atomic[_Components]},
27774 @code{Volatile[_Components]}, and
27775 @code{Independent[_Components]} pragmas illegal, and GNAT
27776 now performs this required check.
27778 RM References: 13.01 (8)
27781 @geindex AI-0106 (Ada 2012 feature)
27787 @emph{AI-0106 No representation pragmas on generic formals (0000-00-00)}
27789 The RM appeared to allow representation pragmas on generic formal parameters,
27790 but this was not intended, and GNAT has never permitted this usage.
27792 RM References: 13.01 (9.1/1)
27795 @geindex AI-0012 (Ada 2012 feature)
27801 @emph{AI-0012 Pack/Component_Size for aliased/atomic (2010-07-15)}
27803 It is now illegal to give an inappropriate component size or a pragma
27804 @code{Pack} that attempts to change the component size in the case of atomic
27805 or aliased components. Previously GNAT ignored such an attempt with a
27808 RM References: 13.02 (6.1/2) 13.02 (7) C.06 (10) C.06 (11) C.06 (21)
27811 @geindex AI-0039 (Ada 2012 feature)
27817 @emph{AI-0039 Stream attributes cannot be dynamic (0000-00-00)}
27819 The RM permitted the use of dynamic expressions (such as @code{ptr.all})`
27820 for stream attributes, but these were never useful and are now illegal. GNAT
27821 has always regarded such expressions as illegal.
27823 RM References: 13.03 (4) 13.03 (6) 13.13.02 (38/2)
27826 @geindex AI-0095 (Ada 2012 feature)
27832 @emph{AI-0095 Address of intrinsic subprograms (0000-00-00)}
27834 The prefix of @code{'Address} cannot statically denote a subprogram with
27835 convention @code{Intrinsic}. The use of the @code{Address} attribute raises
27836 @code{Program_Error} if the prefix denotes a subprogram with convention
27839 RM References: 13.03 (11/1)
27842 @geindex AI-0116 (Ada 2012 feature)
27848 @emph{AI-0116 Alignment of class-wide objects (0000-00-00)}
27850 This AI requires that the alignment of a class-wide object be no greater
27851 than the alignment of any type in the class. GNAT has always followed this
27854 RM References: 13.03 (29) 13.11 (16)
27857 @geindex AI-0146 (Ada 2012 feature)
27863 @emph{AI-0146 Type invariants (2009-09-21)}
27865 Type invariants may be specified for private types using the aspect notation.
27866 Aspect @code{Type_Invariant} may be specified for any private type,
27867 @code{Type_Invariant'Class} can
27868 only be specified for tagged types, and is inherited by any descendent of the
27869 tagged types. The invariant is a boolean expression that is tested for being
27870 true in the following situations: conversions to the private type, object
27871 declarations for the private type that are default initialized, and
27872 [@strong{in}] @strong{out}
27873 parameters and returned result on return from any primitive operation for
27874 the type that is visible to a client.
27875 GNAT defines the synonyms @code{Invariant} for @code{Type_Invariant} and
27876 @code{Invariant'Class} for @code{Type_Invariant'Class}.
27878 RM References: 13.03.03 (00)
27881 @geindex AI-0078 (Ada 2012 feature)
27887 @emph{AI-0078 Relax Unchecked_Conversion alignment rules (0000-00-00)}
27889 In Ada 2012, compilers are required to support unchecked conversion where the
27890 target alignment is a multiple of the source alignment. GNAT always supported
27891 this case (and indeed all cases of differing alignments, doing copies where
27892 required if the alignment was reduced).
27894 RM References: 13.09 (7)
27897 @geindex AI-0195 (Ada 2012 feature)
27903 @emph{AI-0195 Invalid value handling is implementation defined (2010-07-03)}
27905 The handling of invalid values is now designated to be implementation
27906 defined. This is a documentation change only, requiring Annex M in the GNAT
27907 Reference Manual to document this handling.
27908 In GNAT, checks for invalid values are made
27909 only when necessary to avoid erroneous behavior. Operations like assignments
27910 which cannot cause erroneous behavior ignore the possibility of invalid
27911 values and do not do a check. The date given above applies only to the
27912 documentation change, this behavior has always been implemented by GNAT.
27914 RM References: 13.09.01 (10)
27917 @geindex AI-0193 (Ada 2012 feature)
27923 @emph{AI-0193 Alignment of allocators (2010-09-16)}
27925 This AI introduces a new attribute @code{Max_Alignment_For_Allocation},
27926 analogous to @code{Max_Size_In_Storage_Elements}, but for alignment instead
27929 RM References: 13.11 (16) 13.11 (21) 13.11.01 (0) 13.11.01 (1)
27930 13.11.01 (2) 13.11.01 (3)
27933 @geindex AI-0177 (Ada 2012 feature)
27939 @emph{AI-0177 Parameterized expressions (2010-07-10)}
27941 The new Ada 2012 notion of parameterized expressions is implemented. The form
27945 function-specification is (expression)
27948 This is exactly equivalent to the
27949 corresponding function body that returns the expression, but it can appear
27950 in a package spec. Note that the expression must be parenthesized.
27952 RM References: 13.11.01 (3/2)
27955 @geindex AI-0033 (Ada 2012 feature)
27961 @emph{AI-0033 Attach/Interrupt_Handler in generic (2010-07-24)}
27963 Neither of these two pragmas may appear within a generic template, because
27964 the generic might be instantiated at other than the library level.
27966 RM References: 13.11.02 (16) C.03.01 (7/2) C.03.01 (8/2)
27969 @geindex AI-0161 (Ada 2012 feature)
27975 @emph{AI-0161 Restriction No_Default_Stream_Attributes (2010-09-11)}
27977 A new restriction @code{No_Default_Stream_Attributes} prevents the use of any
27978 of the default stream attributes for elementary types. If this restriction is
27979 in force, then it is necessary to provide explicit subprograms for any
27980 stream attributes used.
27982 RM References: 13.12.01 (4/2) 13.13.02 (40/2) 13.13.02 (52/2)
27985 @geindex AI-0194 (Ada 2012 feature)
27991 @emph{AI-0194 Value of Stream_Size attribute (0000-00-00)}
27993 The @code{Stream_Size} attribute returns the default number of bits in the
27994 stream representation of the given type.
27995 This value is not affected by the presence
27996 of stream subprogram attributes for the type. GNAT has always implemented
27997 this interpretation.
27999 RM References: 13.13.02 (1.2/2)
28002 @geindex AI-0109 (Ada 2012 feature)
28008 @emph{AI-0109 Redundant check in S'Class'Input (0000-00-00)}
28010 This AI is an editorial change only. It removes the need for a tag check
28011 that can never fail.
28013 RM References: 13.13.02 (34/2)
28016 @geindex AI-0007 (Ada 2012 feature)
28022 @emph{AI-0007 Stream read and private scalar types (0000-00-00)}
28024 The RM as written appeared to limit the possibilities of declaring read
28025 attribute procedures for private scalar types. This limitation was not
28026 intended, and has never been enforced by GNAT.
28028 RM References: 13.13.02 (50/2) 13.13.02 (51/2)
28031 @geindex AI-0065 (Ada 2012 feature)
28037 @emph{AI-0065 Remote access types and external streaming (0000-00-00)}
28039 This AI clarifies the fact that all remote access types support external
28040 streaming. This fixes an obvious oversight in the definition of the
28041 language, and GNAT always implemented the intended correct rules.
28043 RM References: 13.13.02 (52/2)
28046 @geindex AI-0019 (Ada 2012 feature)
28052 @emph{AI-0019 Freezing of primitives for tagged types (0000-00-00)}
28054 The RM suggests that primitive subprograms of a specific tagged type are
28055 frozen when the tagged type is frozen. This would be an incompatible change
28056 and is not intended. GNAT has never attempted this kind of freezing and its
28057 behavior is consistent with the recommendation of this AI.
28059 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)
28062 @geindex AI-0017 (Ada 2012 feature)
28068 @emph{AI-0017 Freezing and incomplete types (0000-00-00)}
28070 So-called 'Taft-amendment types' (i.e., types that are completed in package
28071 bodies) are not frozen by the occurrence of bodies in the
28072 enclosing declarative part. GNAT always implemented this properly.
28074 RM References: 13.14 (3/1)
28077 @geindex AI-0060 (Ada 2012 feature)
28083 @emph{AI-0060 Extended definition of remote access types (0000-00-00)}
28085 This AI extends the definition of remote access types to include access
28086 to limited, synchronized, protected or task class-wide interface types.
28087 GNAT already implemented this extension.
28089 RM References: A (4) E.02.02 (9/1) E.02.02 (9.2/1) E.02.02 (14/2) E.02.02 (18)
28092 @geindex AI-0114 (Ada 2012 feature)
28098 @emph{AI-0114 Classification of letters (0000-00-00)}
28100 The code points 170 (@code{FEMININE ORDINAL INDICATOR}),
28101 181 (@code{MICRO SIGN}), and
28102 186 (@code{MASCULINE ORDINAL INDICATOR}) are technically considered
28103 lower case letters by Unicode.
28104 However, they are not allowed in identifiers, and they
28105 return @code{False} to @code{Ada.Characters.Handling.Is_Letter/Is_Lower}.
28106 This behavior is consistent with that defined in Ada 95.
28108 RM References: A.03.02 (59) A.04.06 (7)
28111 @geindex AI-0185 (Ada 2012 feature)
28117 @emph{AI-0185 Ada.Wide_[Wide_]Characters.Handling (2010-07-06)}
28119 Two new packages @code{Ada.Wide_[Wide_]Characters.Handling} provide
28120 classification functions for @code{Wide_Character} and
28121 @code{Wide_Wide_Character}, as well as providing
28122 case folding routines for @code{Wide_[Wide_]Character} and
28123 @code{Wide_[Wide_]String}.
28125 RM References: A.03.05 (0) A.03.06 (0)
28128 @geindex AI-0031 (Ada 2012 feature)
28134 @emph{AI-0031 Add From parameter to Find_Token (2010-07-25)}
28136 A new version of @code{Find_Token} is added to all relevant string packages,
28137 with an extra parameter @code{From}. Instead of starting at the first
28138 character of the string, the search for a matching Token starts at the
28139 character indexed by the value of @code{From}.
28140 These procedures are available in all versions of Ada
28141 but if used in versions earlier than Ada 2012 they will generate a warning
28142 that an Ada 2012 subprogram is being used.
28144 RM References: A.04.03 (16) A.04.03 (67) A.04.03 (68/1) A.04.04 (51)
28148 @geindex AI-0056 (Ada 2012 feature)
28154 @emph{AI-0056 Index on null string returns zero (0000-00-00)}
28156 The wording in the Ada 2005 RM implied an incompatible handling of the
28157 @code{Index} functions, resulting in raising an exception instead of
28158 returning zero in some situations.
28159 This was not intended and has been corrected.
28160 GNAT always returned zero, and is thus consistent with this AI.
28162 RM References: A.04.03 (56.2/2) A.04.03 (58.5/2)
28165 @geindex AI-0137 (Ada 2012 feature)
28171 @emph{AI-0137 String encoding package (2010-03-25)}
28173 The packages @code{Ada.Strings.UTF_Encoding}, together with its child
28174 packages, @code{Conversions}, @code{Strings}, @code{Wide_Strings},
28175 and @code{Wide_Wide_Strings} have been
28176 implemented. These packages (whose documentation can be found in the spec
28177 files @code{a-stuten.ads}, @code{a-suenco.ads}, @code{a-suenst.ads},
28178 @code{a-suewst.ads}, @code{a-suezst.ads}) allow encoding and decoding of
28179 @code{String}, @code{Wide_String}, and @code{Wide_Wide_String}
28180 values using UTF coding schemes (including UTF-8, UTF-16LE, UTF-16BE, and
28181 UTF-16), as well as conversions between the different UTF encodings. With
28182 the exception of @code{Wide_Wide_Strings}, these packages are available in
28183 Ada 95 and Ada 2005 mode as well as Ada 2012 mode.
28184 The @code{Wide_Wide_Strings} package
28185 is available in Ada 2005 mode as well as Ada 2012 mode (but not in Ada 95
28186 mode since it uses @code{Wide_Wide_Character}).
28188 RM References: A.04.11
28191 @geindex AI-0038 (Ada 2012 feature)
28197 @emph{AI-0038 Minor errors in Text_IO (0000-00-00)}
28199 These are minor errors in the description on three points. The intent on
28200 all these points has always been clear, and GNAT has always implemented the
28201 correct intended semantics.
28203 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)
28206 @geindex AI-0044 (Ada 2012 feature)
28212 @emph{AI-0044 Restrictions on container instantiations (0000-00-00)}
28214 This AI places restrictions on allowed instantiations of generic containers.
28215 These restrictions are not checked by the compiler, so there is nothing to
28216 change in the implementation. This affects only the RM documentation.
28218 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)
28221 @geindex AI-0127 (Ada 2012 feature)
28227 @emph{AI-0127 Adding Locale Capabilities (2010-09-29)}
28229 This package provides an interface for identifying the current locale.
28231 RM References: A.19 A.19.01 A.19.02 A.19.03 A.19.05 A.19.06
28232 A.19.07 A.19.08 A.19.09 A.19.10 A.19.11 A.19.12 A.19.13
28235 @geindex AI-0002 (Ada 2012 feature)
28241 @emph{AI-0002 Export C with unconstrained arrays (0000-00-00)}
28243 The compiler is not required to support exporting an Ada subprogram with
28244 convention C if there are parameters or a return type of an unconstrained
28245 array type (such as @code{String}). GNAT allows such declarations but
28246 generates warnings. It is possible, but complicated, to write the
28247 corresponding C code and certainly such code would be specific to GNAT and
28250 RM References: B.01 (17) B.03 (62) B.03 (71.1/2)
28253 @geindex AI05-0216 (Ada 2012 feature)
28259 @emph{AI-0216 No_Task_Hierarchy forbids local tasks (0000-00-00)}
28261 It is clearly the intention that @code{No_Task_Hierarchy} is intended to
28262 forbid tasks declared locally within subprograms, or functions returning task
28263 objects, and that is the implementation that GNAT has always provided.
28264 However the language in the RM was not sufficiently clear on this point.
28265 Thus this is a documentation change in the RM only.
28267 RM References: D.07 (3/3)
28270 @geindex AI-0211 (Ada 2012 feature)
28276 @emph{AI-0211 No_Relative_Delays forbids Set_Handler use (2010-07-09)}
28278 The restriction @code{No_Relative_Delays} forbids any calls to the subprogram
28279 @code{Ada.Real_Time.Timing_Events.Set_Handler}.
28281 RM References: D.07 (5) D.07 (10/2) D.07 (10.4/2) D.07 (10.7/2)
28284 @geindex AI-0190 (Ada 2012 feature)
28290 @emph{AI-0190 pragma Default_Storage_Pool (2010-09-15)}
28292 This AI introduces a new pragma @code{Default_Storage_Pool}, which can be
28293 used to control storage pools globally.
28294 In particular, you can force every access
28295 type that is used for allocation (@strong{new}) to have an explicit storage pool,
28296 or you can declare a pool globally to be used for all access types that lack
28299 RM References: D.07 (8)
28302 @geindex AI-0189 (Ada 2012 feature)
28308 @emph{AI-0189 No_Allocators_After_Elaboration (2010-01-23)}
28310 This AI introduces a new restriction @code{No_Allocators_After_Elaboration},
28311 which says that no dynamic allocation will occur once elaboration is
28313 In general this requires a run-time check, which is not required, and which
28314 GNAT does not attempt. But the static cases of allocators in a task body or
28315 in the body of the main program are detected and flagged at compile or bind
28318 RM References: D.07 (19.1/2) H.04 (23.3/2)
28321 @geindex AI-0171 (Ada 2012 feature)
28327 @emph{AI-0171 Pragma CPU and Ravenscar Profile (2010-09-24)}
28329 A new package @code{System.Multiprocessors} is added, together with the
28330 definition of pragma @code{CPU} for controlling task affinity. A new no
28331 dependence restriction, on @code{System.Multiprocessors.Dispatching_Domains},
28332 is added to the Ravenscar profile.
28334 RM References: D.13.01 (4/2) D.16
28337 @geindex AI-0210 (Ada 2012 feature)
28343 @emph{AI-0210 Correct Timing_Events metric (0000-00-00)}
28345 This is a documentation only issue regarding wording of metric requirements,
28346 that does not affect the implementation of the compiler.
28348 RM References: D.15 (24/2)
28351 @geindex AI-0206 (Ada 2012 feature)
28357 @emph{AI-0206 Remote types packages and preelaborate (2010-07-24)}
28359 Remote types packages are now allowed to depend on preelaborated packages.
28360 This was formerly considered illegal.
28362 RM References: E.02.02 (6)
28365 @geindex AI-0152 (Ada 2012 feature)
28371 @emph{AI-0152 Restriction No_Anonymous_Allocators (2010-09-08)}
28373 Restriction @code{No_Anonymous_Allocators} prevents the use of allocators
28374 where the type of the returned value is an anonymous access type.
28376 RM References: H.04 (8/1)
28379 @node Obsolescent Features,Compatibility and Porting Guide,Implementation of Ada 2012 Features,Top
28380 @anchor{gnat_rm/obsolescent_features id1}@anchor{429}@anchor{gnat_rm/obsolescent_features doc}@anchor{42a}@anchor{gnat_rm/obsolescent_features obsolescent-features}@anchor{15}
28381 @chapter Obsolescent Features
28384 This chapter describes features that are provided by GNAT, but are
28385 considered obsolescent since there are preferred ways of achieving
28386 the same effect. These features are provided solely for historical
28387 compatibility purposes.
28390 * pragma No_Run_Time::
28391 * pragma Ravenscar::
28392 * pragma Restricted_Run_Time::
28393 * pragma Task_Info::
28394 * package System.Task_Info (s-tasinf.ads): package System Task_Info s-tasinf ads.
28398 @node pragma No_Run_Time,pragma Ravenscar,,Obsolescent Features
28399 @anchor{gnat_rm/obsolescent_features id2}@anchor{42b}@anchor{gnat_rm/obsolescent_features pragma-no-run-time}@anchor{42c}
28400 @section pragma No_Run_Time
28403 The pragma @code{No_Run_Time} is used to achieve an affect similar
28404 to the use of the "Zero Foot Print" configurable run time, but without
28405 requiring a specially configured run time. The result of using this
28406 pragma, which must be used for all units in a partition, is to restrict
28407 the use of any language features requiring run-time support code. The
28408 preferred usage is to use an appropriately configured run-time that
28409 includes just those features that are to be made accessible.
28411 @node pragma Ravenscar,pragma Restricted_Run_Time,pragma No_Run_Time,Obsolescent Features
28412 @anchor{gnat_rm/obsolescent_features id3}@anchor{42d}@anchor{gnat_rm/obsolescent_features pragma-ravenscar}@anchor{42e}
28413 @section pragma Ravenscar
28416 The pragma @code{Ravenscar} has exactly the same effect as pragma
28417 @code{Profile (Ravenscar)}. The latter usage is preferred since it
28418 is part of the new Ada 2005 standard.
28420 @node pragma Restricted_Run_Time,pragma Task_Info,pragma Ravenscar,Obsolescent Features
28421 @anchor{gnat_rm/obsolescent_features pragma-restricted-run-time}@anchor{42f}@anchor{gnat_rm/obsolescent_features id4}@anchor{430}
28422 @section pragma Restricted_Run_Time
28425 The pragma @code{Restricted_Run_Time} has exactly the same effect as
28426 pragma @code{Profile (Restricted)}. The latter usage is
28427 preferred since the Ada 2005 pragma @code{Profile} is intended for
28428 this kind of implementation dependent addition.
28430 @node pragma Task_Info,package System Task_Info s-tasinf ads,pragma Restricted_Run_Time,Obsolescent Features
28431 @anchor{gnat_rm/obsolescent_features pragma-task-info}@anchor{431}@anchor{gnat_rm/obsolescent_features id5}@anchor{432}
28432 @section pragma Task_Info
28435 The functionality provided by pragma @code{Task_Info} is now part of the
28436 Ada language. The @code{CPU} aspect and the package
28437 @code{System.Multiprocessors} offer a less system-dependent way to specify
28438 task affinity or to query the number of processsors.
28443 pragma Task_Info (EXPRESSION);
28446 This pragma appears within a task definition (like pragma
28447 @code{Priority}) and applies to the task in which it appears. The
28448 argument must be of type @code{System.Task_Info.Task_Info_Type}.
28449 The @code{Task_Info} pragma provides system dependent control over
28450 aspects of tasking implementation, for example, the ability to map
28451 tasks to specific processors. For details on the facilities available
28452 for the version of GNAT that you are using, see the documentation
28453 in the spec of package System.Task_Info in the runtime
28456 @node package System Task_Info s-tasinf ads,,pragma Task_Info,Obsolescent Features
28457 @anchor{gnat_rm/obsolescent_features package-system-task-info}@anchor{433}@anchor{gnat_rm/obsolescent_features package-system-task-info-s-tasinf-ads}@anchor{434}
28458 @section package System.Task_Info (@code{s-tasinf.ads})
28461 This package provides target dependent functionality that is used
28462 to support the @code{Task_Info} pragma. The predefined Ada package
28463 @code{System.Multiprocessors} and the @code{CPU} aspect now provide a
28464 standard replacement for GNAT's @code{Task_Info} functionality.
28466 @node Compatibility and Porting Guide,GNU Free Documentation License,Obsolescent Features,Top
28467 @anchor{gnat_rm/compatibility_and_porting_guide compatibility-and-porting-guide}@anchor{16}@anchor{gnat_rm/compatibility_and_porting_guide doc}@anchor{435}@anchor{gnat_rm/compatibility_and_porting_guide id1}@anchor{436}
28468 @chapter Compatibility and Porting Guide
28471 This chapter presents some guidelines for developing portable Ada code,
28472 describes the compatibility issues that may arise between
28473 GNAT and other Ada compilation systems (including those for Ada 83),
28474 and shows how GNAT can expedite porting
28475 applications developed in other Ada environments.
28478 * Writing Portable Fixed-Point Declarations::
28479 * Compatibility with Ada 83::
28480 * Compatibility between Ada 95 and Ada 2005::
28481 * Implementation-dependent characteristics::
28482 * Compatibility with Other Ada Systems::
28483 * Representation Clauses::
28484 * Compatibility with HP Ada 83::
28488 @node Writing Portable Fixed-Point Declarations,Compatibility with Ada 83,,Compatibility and Porting Guide
28489 @anchor{gnat_rm/compatibility_and_porting_guide id2}@anchor{437}@anchor{gnat_rm/compatibility_and_porting_guide writing-portable-fixed-point-declarations}@anchor{438}
28490 @section Writing Portable Fixed-Point Declarations
28493 The Ada Reference Manual gives an implementation freedom to choose bounds
28494 that are narrower by @code{Small} from the given bounds.
28495 For example, if we write
28498 type F1 is delta 1.0 range -128.0 .. +128.0;
28501 then the implementation is allowed to choose -128.0 .. +127.0 if it
28502 likes, but is not required to do so.
28504 This leads to possible portability problems, so let's have a closer
28505 look at this, and figure out how to avoid these problems.
28507 First, why does this freedom exist, and why would an implementation
28508 take advantage of it? To answer this, take a closer look at the type
28509 declaration for @code{F1} above. If the compiler uses the given bounds,
28510 it would need 9 bits to hold the largest positive value (and typically
28511 that means 16 bits on all machines). But if the implementation chooses
28512 the +127.0 bound then it can fit values of the type in 8 bits.
28514 Why not make the user write +127.0 if that's what is wanted?
28515 The rationale is that if you are thinking of fixed point
28516 as a kind of 'poor man's floating-point', then you don't want
28517 to be thinking about the scaled integers that are used in its
28518 representation. Let's take another example:
28521 type F2 is delta 2.0**(-15) range -1.0 .. +1.0;
28524 Looking at this declaration, it seems casually as though
28525 it should fit in 16 bits, but again that extra positive value
28526 +1.0 has the scaled integer equivalent of 2**15 which is one too
28527 big for signed 16 bits. The implementation can treat this as:
28530 type F2 is delta 2.0**(-15) range -1.0 .. +1.0-(2.0**(-15));
28533 and the Ada language design team felt that this was too annoying
28534 to require. We don't need to debate this decision at this point,
28535 since it is well established (the rule about narrowing the ranges
28538 But the important point is that an implementation is not required
28539 to do this narrowing, so we have a potential portability problem.
28540 We could imagine three types of implementation:
28546 those that narrow the range automatically if they can figure
28547 out that the narrower range will allow storage in a smaller machine unit,
28550 those that will narrow only if forced to by a @code{'Size} clause, and
28553 those that will never narrow.
28556 Now if we are language theoreticians, we can imagine a fourth
28557 approach: to narrow all the time, e.g. to treat
28560 type F3 is delta 1.0 range -10.0 .. +23.0;
28563 as though it had been written:
28566 type F3 is delta 1.0 range -9.0 .. +22.0;
28569 But although technically allowed, such a behavior would be hostile and silly,
28570 and no real compiler would do this. All real compilers will fall into one of
28571 the categories (a), (b) or (c) above.
28573 So, how do you get the compiler to do what you want? The answer is give the
28574 actual bounds you want, and then use a @code{'Small} clause and a
28575 @code{'Size} clause to absolutely pin down what the compiler does.
28576 E.g., for @code{F2} above, we will write:
28579 My_Small : constant := 2.0**(-15);
28580 My_First : constant := -1.0;
28581 My_Last : constant := +1.0 - My_Small;
28583 type F2 is delta My_Small range My_First .. My_Last;
28589 for F2'Small use my_Small;
28590 for F2'Size use 16;
28593 In practice all compilers will do the same thing here and will give you
28594 what you want, so the above declarations are fully portable. If you really
28595 want to play language lawyer and guard against ludicrous behavior by the
28596 compiler you could add
28599 Test1 : constant := 1 / Boolean'Pos (F2'First = My_First);
28600 Test2 : constant := 1 / Boolean'Pos (F2'Last = My_Last);
28603 One or other or both are allowed to be illegal if the compiler is
28604 behaving in a silly manner, but at least the silly compiler will not
28605 get away with silently messing with your (very clear) intentions.
28607 If you follow this scheme you will be guaranteed that your fixed-point
28608 types will be portable.
28610 @node Compatibility with Ada 83,Compatibility between Ada 95 and Ada 2005,Writing Portable Fixed-Point Declarations,Compatibility and Porting Guide
28611 @anchor{gnat_rm/compatibility_and_porting_guide compatibility-with-ada-83}@anchor{439}@anchor{gnat_rm/compatibility_and_porting_guide id3}@anchor{43a}
28612 @section Compatibility with Ada 83
28615 @geindex Compatibility (between Ada 83 and Ada 95 / Ada 2005 / Ada 2012)
28617 Ada 95 and the subsequent revisions Ada 2005 and Ada 2012
28618 are highly upwards compatible with Ada 83. In
28619 particular, the design intention was that the difficulties associated
28620 with moving from Ada 83 to later versions of the standard should be no greater
28621 than those that occur when moving from one Ada 83 system to another.
28623 However, there are a number of points at which there are minor
28624 incompatibilities. The @cite{Ada 95 Annotated Reference Manual} contains
28625 full details of these issues as they relate to Ada 95,
28626 and should be consulted for a complete treatment.
28628 following subsections treat the most likely issues to be encountered.
28631 * Legal Ada 83 programs that are illegal in Ada 95::
28632 * More deterministic semantics::
28633 * Changed semantics::
28634 * Other language compatibility issues::
28638 @node Legal Ada 83 programs that are illegal in Ada 95,More deterministic semantics,,Compatibility with Ada 83
28639 @anchor{gnat_rm/compatibility_and_porting_guide id4}@anchor{43b}@anchor{gnat_rm/compatibility_and_porting_guide legal-ada-83-programs-that-are-illegal-in-ada-95}@anchor{43c}
28640 @subsection Legal Ada 83 programs that are illegal in Ada 95
28643 Some legal Ada 83 programs are illegal (i.e., they will fail to compile) in
28644 Ada 95 and later versions of the standard:
28650 @emph{Character literals}
28652 Some uses of character literals are ambiguous. Since Ada 95 has introduced
28653 @code{Wide_Character} as a new predefined character type, some uses of
28654 character literals that were legal in Ada 83 are illegal in Ada 95.
28658 for Char in 'A' .. 'Z' loop ... end loop;
28661 The problem is that 'A' and 'Z' could be from either
28662 @code{Character} or @code{Wide_Character}. The simplest correction
28663 is to make the type explicit; e.g.:
28666 for Char in Character range 'A' .. 'Z' loop ... end loop;
28670 @emph{New reserved words}
28672 The identifiers @code{abstract}, @code{aliased}, @code{protected},
28673 @code{requeue}, @code{tagged}, and @code{until} are reserved in Ada 95.
28674 Existing Ada 83 code using any of these identifiers must be edited to
28675 use some alternative name.
28678 @emph{Freezing rules}
28680 The rules in Ada 95 are slightly different with regard to the point at
28681 which entities are frozen, and representation pragmas and clauses are
28682 not permitted past the freeze point. This shows up most typically in
28683 the form of an error message complaining that a representation item
28684 appears too late, and the appropriate corrective action is to move
28685 the item nearer to the declaration of the entity to which it refers.
28687 A particular case is that representation pragmas
28688 cannot be applied to a subprogram body. If necessary, a separate subprogram
28689 declaration must be introduced to which the pragma can be applied.
28692 @emph{Optional bodies for library packages}
28694 In Ada 83, a package that did not require a package body was nevertheless
28695 allowed to have one. This lead to certain surprises in compiling large
28696 systems (situations in which the body could be unexpectedly ignored by the
28697 binder). In Ada 95, if a package does not require a body then it is not
28698 permitted to have a body. To fix this problem, simply remove a redundant
28699 body if it is empty, or, if it is non-empty, introduce a dummy declaration
28700 into the spec that makes the body required. One approach is to add a private
28701 part to the package declaration (if necessary), and define a parameterless
28702 procedure called @code{Requires_Body}, which must then be given a dummy
28703 procedure body in the package body, which then becomes required.
28704 Another approach (assuming that this does not introduce elaboration
28705 circularities) is to add an @code{Elaborate_Body} pragma to the package spec,
28706 since one effect of this pragma is to require the presence of a package body.
28709 @emph{Numeric_Error is the same exception as Constraint_Error}
28711 In Ada 95, the exception @code{Numeric_Error} is a renaming of @code{Constraint_Error}.
28712 This means that it is illegal to have separate exception handlers for
28713 the two exceptions. The fix is simply to remove the handler for the
28714 @code{Numeric_Error} case (since even in Ada 83, a compiler was free to raise
28715 @code{Constraint_Error} in place of @code{Numeric_Error} in all cases).
28718 @emph{Indefinite subtypes in generics}
28720 In Ada 83, it was permissible to pass an indefinite type (e.g, @code{String})
28721 as the actual for a generic formal private type, but then the instantiation
28722 would be illegal if there were any instances of declarations of variables
28723 of this type in the generic body. In Ada 95, to avoid this clear violation
28724 of the methodological principle known as the 'contract model',
28725 the generic declaration explicitly indicates whether
28726 or not such instantiations are permitted. If a generic formal parameter
28727 has explicit unknown discriminants, indicated by using @code{(<>)} after the
28728 subtype name, then it can be instantiated with indefinite types, but no
28729 stand-alone variables can be declared of this type. Any attempt to declare
28730 such a variable will result in an illegality at the time the generic is
28731 declared. If the @code{(<>)} notation is not used, then it is illegal
28732 to instantiate the generic with an indefinite type.
28733 This is the potential incompatibility issue when porting Ada 83 code to Ada 95.
28734 It will show up as a compile time error, and
28735 the fix is usually simply to add the @code{(<>)} to the generic declaration.
28738 @node More deterministic semantics,Changed semantics,Legal Ada 83 programs that are illegal in Ada 95,Compatibility with Ada 83
28739 @anchor{gnat_rm/compatibility_and_porting_guide more-deterministic-semantics}@anchor{43d}@anchor{gnat_rm/compatibility_and_porting_guide id5}@anchor{43e}
28740 @subsection More deterministic semantics
28749 Conversions from real types to integer types round away from 0. In Ada 83
28750 the conversion Integer(2.5) could deliver either 2 or 3 as its value. This
28751 implementation freedom was intended to support unbiased rounding in
28752 statistical applications, but in practice it interfered with portability.
28753 In Ada 95 the conversion semantics are unambiguous, and rounding away from 0
28754 is required. Numeric code may be affected by this change in semantics.
28755 Note, though, that this issue is no worse than already existed in Ada 83
28756 when porting code from one vendor to another.
28761 The Real-Time Annex introduces a set of policies that define the behavior of
28762 features that were implementation dependent in Ada 83, such as the order in
28763 which open select branches are executed.
28766 @node Changed semantics,Other language compatibility issues,More deterministic semantics,Compatibility with Ada 83
28767 @anchor{gnat_rm/compatibility_and_porting_guide id6}@anchor{43f}@anchor{gnat_rm/compatibility_and_porting_guide changed-semantics}@anchor{440}
28768 @subsection Changed semantics
28771 The worst kind of incompatibility is one where a program that is legal in
28772 Ada 83 is also legal in Ada 95 but can have an effect in Ada 95 that was not
28773 possible in Ada 83. Fortunately this is extremely rare, but the one
28774 situation that you should be alert to is the change in the predefined type
28775 @code{Character} from 7-bit ASCII to 8-bit Latin-1.
28786 @emph{Range of type `@w{`}Character`@w{`}}
28788 The range of @code{Standard.Character} is now the full 256 characters
28789 of Latin-1, whereas in most Ada 83 implementations it was restricted
28790 to 128 characters. Although some of the effects of
28791 this change will be manifest in compile-time rejection of legal
28792 Ada 83 programs it is possible for a working Ada 83 program to have
28793 a different effect in Ada 95, one that was not permitted in Ada 83.
28794 As an example, the expression
28795 @code{Character'Pos(Character'Last)} returned @code{127} in Ada 83 and now
28796 delivers @code{255} as its value.
28797 In general, you should look at the logic of any
28798 character-processing Ada 83 program and see whether it needs to be adapted
28799 to work correctly with Latin-1. Note that the predefined Ada 95 API has a
28800 character handling package that may be relevant if code needs to be adapted
28801 to account for the additional Latin-1 elements.
28802 The desirable fix is to
28803 modify the program to accommodate the full character set, but in some cases
28804 it may be convenient to define a subtype or derived type of Character that
28805 covers only the restricted range.
28808 @node Other language compatibility issues,,Changed semantics,Compatibility with Ada 83
28809 @anchor{gnat_rm/compatibility_and_porting_guide other-language-compatibility-issues}@anchor{441}@anchor{gnat_rm/compatibility_and_porting_guide id7}@anchor{442}
28810 @subsection Other language compatibility issues
28817 @emph{-gnat83} switch
28819 All implementations of GNAT provide a switch that causes GNAT to operate
28820 in Ada 83 mode. In this mode, some but not all compatibility problems
28821 of the type described above are handled automatically. For example, the
28822 new reserved words introduced in Ada 95 and Ada 2005 are treated simply
28823 as identifiers as in Ada 83. However,
28824 in practice, it is usually advisable to make the necessary modifications
28825 to the program to remove the need for using this switch.
28826 See the @code{Compiling Different Versions of Ada} section in
28827 the @cite{GNAT User's Guide}.
28830 Support for removed Ada 83 pragmas and attributes
28832 A number of pragmas and attributes from Ada 83 were removed from Ada 95,
28833 generally because they were replaced by other mechanisms. Ada 95 and Ada 2005
28834 compilers are allowed, but not required, to implement these missing
28835 elements. In contrast with some other compilers, GNAT implements all
28836 such pragmas and attributes, eliminating this compatibility concern. These
28837 include @code{pragma Interface} and the floating point type attributes
28838 (@code{Emax}, @code{Mantissa}, etc.), among other items.
28841 @node Compatibility between Ada 95 and Ada 2005,Implementation-dependent characteristics,Compatibility with Ada 83,Compatibility and Porting Guide
28842 @anchor{gnat_rm/compatibility_and_porting_guide compatibility-between-ada-95-and-ada-2005}@anchor{443}@anchor{gnat_rm/compatibility_and_porting_guide id8}@anchor{444}
28843 @section Compatibility between Ada 95 and Ada 2005
28846 @geindex Compatibility between Ada 95 and Ada 2005
28848 Although Ada 2005 was designed to be upwards compatible with Ada 95, there are
28849 a number of incompatibilities. Several are enumerated below;
28850 for a complete description please see the
28851 @cite{Annotated Ada 2005 Reference Manual}, or section 9.1.1 in
28852 @cite{Rationale for Ada 2005}.
28858 @emph{New reserved words.}
28860 The words @code{interface}, @code{overriding} and @code{synchronized} are
28861 reserved in Ada 2005.
28862 A pre-Ada 2005 program that uses any of these as an identifier will be
28866 @emph{New declarations in predefined packages.}
28868 A number of packages in the predefined environment contain new declarations:
28869 @code{Ada.Exceptions}, @code{Ada.Real_Time}, @code{Ada.Strings},
28870 @code{Ada.Strings.Fixed}, @code{Ada.Strings.Bounded},
28871 @code{Ada.Strings.Unbounded}, @code{Ada.Strings.Wide_Fixed},
28872 @code{Ada.Strings.Wide_Bounded}, @code{Ada.Strings.Wide_Unbounded},
28873 @code{Ada.Tags}, @code{Ada.Text_IO}, and @code{Interfaces.C}.
28874 If an Ada 95 program does a @code{with} and @code{use} of any of these
28875 packages, the new declarations may cause name clashes.
28878 @emph{Access parameters.}
28880 A nondispatching subprogram with an access parameter cannot be renamed
28881 as a dispatching operation. This was permitted in Ada 95.
28884 @emph{Access types, discriminants, and constraints.}
28886 Rule changes in this area have led to some incompatibilities; for example,
28887 constrained subtypes of some access types are not permitted in Ada 2005.
28890 @emph{Aggregates for limited types.}
28892 The allowance of aggregates for limited types in Ada 2005 raises the
28893 possibility of ambiguities in legal Ada 95 programs, since additional types
28894 now need to be considered in expression resolution.
28897 @emph{Fixed-point multiplication and division.}
28899 Certain expressions involving '*' or '/' for a fixed-point type, which
28900 were legal in Ada 95 and invoked the predefined versions of these operations,
28902 The ambiguity may be resolved either by applying a type conversion to the
28903 expression, or by explicitly invoking the operation from package
28907 @emph{Return-by-reference types.}
28909 The Ada 95 return-by-reference mechanism has been removed. Instead, the user
28910 can declare a function returning a value from an anonymous access type.
28913 @node Implementation-dependent characteristics,Compatibility with Other Ada Systems,Compatibility between Ada 95 and Ada 2005,Compatibility and Porting Guide
28914 @anchor{gnat_rm/compatibility_and_porting_guide implementation-dependent-characteristics}@anchor{445}@anchor{gnat_rm/compatibility_and_porting_guide id9}@anchor{446}
28915 @section Implementation-dependent characteristics
28918 Although the Ada language defines the semantics of each construct as
28919 precisely as practical, in some situations (for example for reasons of
28920 efficiency, or where the effect is heavily dependent on the host or target
28921 platform) the implementation is allowed some freedom. In porting Ada 83
28922 code to GNAT, you need to be aware of whether / how the existing code
28923 exercised such implementation dependencies. Such characteristics fall into
28924 several categories, and GNAT offers specific support in assisting the
28925 transition from certain Ada 83 compilers.
28928 * Implementation-defined pragmas::
28929 * Implementation-defined attributes::
28931 * Elaboration order::
28932 * Target-specific aspects::
28936 @node Implementation-defined pragmas,Implementation-defined attributes,,Implementation-dependent characteristics
28937 @anchor{gnat_rm/compatibility_and_porting_guide implementation-defined-pragmas}@anchor{447}@anchor{gnat_rm/compatibility_and_porting_guide id10}@anchor{448}
28938 @subsection Implementation-defined pragmas
28941 Ada compilers are allowed to supplement the language-defined pragmas, and
28942 these are a potential source of non-portability. All GNAT-defined pragmas
28943 are described in @ref{7,,Implementation Defined Pragmas},
28944 and these include several that are specifically
28945 intended to correspond to other vendors' Ada 83 pragmas.
28946 For migrating from VADS, the pragma @code{Use_VADS_Size} may be useful.
28947 For compatibility with HP Ada 83, GNAT supplies the pragmas
28948 @code{Extend_System}, @code{Ident}, @code{Inline_Generic},
28949 @code{Interface_Name}, @code{Passive}, @code{Suppress_All},
28950 and @code{Volatile}.
28951 Other relevant pragmas include @code{External} and @code{Link_With}.
28952 Some vendor-specific
28953 Ada 83 pragmas (@code{Share_Generic}, @code{Subtitle}, and @code{Title}) are
28955 avoiding compiler rejection of units that contain such pragmas; they are not
28956 relevant in a GNAT context and hence are not otherwise implemented.
28958 @node Implementation-defined attributes,Libraries,Implementation-defined pragmas,Implementation-dependent characteristics
28959 @anchor{gnat_rm/compatibility_and_porting_guide id11}@anchor{449}@anchor{gnat_rm/compatibility_and_porting_guide implementation-defined-attributes}@anchor{44a}
28960 @subsection Implementation-defined attributes
28963 Analogous to pragmas, the set of attributes may be extended by an
28964 implementation. All GNAT-defined attributes are described in
28965 @ref{8,,Implementation Defined Attributes},
28966 and these include several that are specifically intended
28967 to correspond to other vendors' Ada 83 attributes. For migrating from VADS,
28968 the attribute @code{VADS_Size} may be useful. For compatibility with HP
28969 Ada 83, GNAT supplies the attributes @code{Bit}, @code{Machine_Size} and
28972 @node Libraries,Elaboration order,Implementation-defined attributes,Implementation-dependent characteristics
28973 @anchor{gnat_rm/compatibility_and_porting_guide libraries}@anchor{44b}@anchor{gnat_rm/compatibility_and_porting_guide id12}@anchor{44c}
28974 @subsection Libraries
28977 Vendors may supply libraries to supplement the standard Ada API. If Ada 83
28978 code uses vendor-specific libraries then there are several ways to manage
28979 this in Ada 95 and later versions of the standard:
28985 If the source code for the libraries (specs and bodies) are
28986 available, then the libraries can be migrated in the same way as the
28990 If the source code for the specs but not the bodies are
28991 available, then you can reimplement the bodies.
28994 Some features introduced by Ada 95 obviate the need for library support. For
28995 example most Ada 83 vendors supplied a package for unsigned integers. The
28996 Ada 95 modular type feature is the preferred way to handle this need, so
28997 instead of migrating or reimplementing the unsigned integer package it may
28998 be preferable to retrofit the application using modular types.
29001 @node Elaboration order,Target-specific aspects,Libraries,Implementation-dependent characteristics
29002 @anchor{gnat_rm/compatibility_and_porting_guide elaboration-order}@anchor{44d}@anchor{gnat_rm/compatibility_and_porting_guide id13}@anchor{44e}
29003 @subsection Elaboration order
29006 The implementation can choose any elaboration order consistent with the unit
29007 dependency relationship. This freedom means that some orders can result in
29008 Program_Error being raised due to an 'Access Before Elaboration': an attempt
29009 to invoke a subprogram before its body has been elaborated, or to instantiate
29010 a generic before the generic body has been elaborated. By default GNAT
29011 attempts to choose a safe order (one that will not encounter access before
29012 elaboration problems) by implicitly inserting @code{Elaborate} or
29013 @code{Elaborate_All} pragmas where
29014 needed. However, this can lead to the creation of elaboration circularities
29015 and a resulting rejection of the program by gnatbind. This issue is
29016 thoroughly described in the @emph{Elaboration Order Handling in GNAT} appendix
29017 in the @cite{GNAT User's Guide}.
29018 In brief, there are several
29019 ways to deal with this situation:
29025 Modify the program to eliminate the circularities, e.g., by moving
29026 elaboration-time code into explicitly-invoked procedures
29029 Constrain the elaboration order by including explicit @code{Elaborate_Body} or
29030 @code{Elaborate} pragmas, and then inhibit the generation of implicit
29031 @code{Elaborate_All}
29032 pragmas either globally (as an effect of the @emph{-gnatE} switch) or locally
29033 (by selectively suppressing elaboration checks via pragma
29034 @code{Suppress(Elaboration_Check)} when it is safe to do so).
29037 @node Target-specific aspects,,Elaboration order,Implementation-dependent characteristics
29038 @anchor{gnat_rm/compatibility_and_porting_guide target-specific-aspects}@anchor{44f}@anchor{gnat_rm/compatibility_and_porting_guide id14}@anchor{450}
29039 @subsection Target-specific aspects
29042 Low-level applications need to deal with machine addresses, data
29043 representations, interfacing with assembler code, and similar issues. If
29044 such an Ada 83 application is being ported to different target hardware (for
29045 example where the byte endianness has changed) then you will need to
29046 carefully examine the program logic; the porting effort will heavily depend
29047 on the robustness of the original design. Moreover, Ada 95 (and thus
29048 Ada 2005 and Ada 2012) are sometimes
29049 incompatible with typical Ada 83 compiler practices regarding implicit
29050 packing, the meaning of the Size attribute, and the size of access values.
29051 GNAT's approach to these issues is described in @ref{451,,Representation Clauses}.
29053 @node Compatibility with Other Ada Systems,Representation Clauses,Implementation-dependent characteristics,Compatibility and Porting Guide
29054 @anchor{gnat_rm/compatibility_and_porting_guide id15}@anchor{452}@anchor{gnat_rm/compatibility_and_porting_guide compatibility-with-other-ada-systems}@anchor{453}
29055 @section Compatibility with Other Ada Systems
29058 If programs avoid the use of implementation dependent and
29059 implementation defined features, as documented in the
29060 @cite{Ada Reference Manual}, there should be a high degree of portability between
29061 GNAT and other Ada systems. The following are specific items which
29062 have proved troublesome in moving Ada 95 programs from GNAT to other Ada 95
29063 compilers, but do not affect porting code to GNAT.
29064 (As of January 2007, GNAT is the only compiler available for Ada 2005;
29065 the following issues may or may not arise for Ada 2005 programs
29066 when other compilers appear.)
29072 @emph{Ada 83 Pragmas and Attributes}
29074 Ada 95 compilers are allowed, but not required, to implement the missing
29075 Ada 83 pragmas and attributes that are no longer defined in Ada 95.
29076 GNAT implements all such pragmas and attributes, eliminating this as
29077 a compatibility concern, but some other Ada 95 compilers reject these
29078 pragmas and attributes.
29081 @emph{Specialized Needs Annexes}
29083 GNAT implements the full set of special needs annexes. At the
29084 current time, it is the only Ada 95 compiler to do so. This means that
29085 programs making use of these features may not be portable to other Ada
29086 95 compilation systems.
29089 @emph{Representation Clauses}
29091 Some other Ada 95 compilers implement only the minimal set of
29092 representation clauses required by the Ada 95 reference manual. GNAT goes
29093 far beyond this minimal set, as described in the next section.
29096 @node Representation Clauses,Compatibility with HP Ada 83,Compatibility with Other Ada Systems,Compatibility and Porting Guide
29097 @anchor{gnat_rm/compatibility_and_porting_guide representation-clauses}@anchor{451}@anchor{gnat_rm/compatibility_and_porting_guide id16}@anchor{454}
29098 @section Representation Clauses
29101 The Ada 83 reference manual was quite vague in describing both the minimal
29102 required implementation of representation clauses, and also their precise
29103 effects. Ada 95 (and thus also Ada 2005) are much more explicit, but the
29104 minimal set of capabilities required is still quite limited.
29106 GNAT implements the full required set of capabilities in
29107 Ada 95 and Ada 2005, but also goes much further, and in particular
29108 an effort has been made to be compatible with existing Ada 83 usage to the
29109 greatest extent possible.
29111 A few cases exist in which Ada 83 compiler behavior is incompatible with
29112 the requirements in Ada 95 (and thus also Ada 2005). These are instances of
29113 intentional or accidental dependence on specific implementation dependent
29114 characteristics of these Ada 83 compilers. The following is a list of
29115 the cases most likely to arise in existing Ada 83 code.
29121 @emph{Implicit Packing}
29123 Some Ada 83 compilers allowed a Size specification to cause implicit
29124 packing of an array or record. This could cause expensive implicit
29125 conversions for change of representation in the presence of derived
29126 types, and the Ada design intends to avoid this possibility.
29127 Subsequent AI's were issued to make it clear that such implicit
29128 change of representation in response to a Size clause is inadvisable,
29129 and this recommendation is represented explicitly in the Ada 95 (and Ada 2005)
29130 Reference Manuals as implementation advice that is followed by GNAT.
29131 The problem will show up as an error
29132 message rejecting the size clause. The fix is simply to provide
29133 the explicit pragma @code{Pack}, or for more fine tuned control, provide
29134 a Component_Size clause.
29137 @emph{Meaning of Size Attribute}
29139 The Size attribute in Ada 95 (and Ada 2005) for discrete types is defined as
29140 the minimal number of bits required to hold values of the type. For example,
29141 on a 32-bit machine, the size of @code{Natural} will typically be 31 and not
29142 32 (since no sign bit is required). Some Ada 83 compilers gave 31, and
29143 some 32 in this situation. This problem will usually show up as a compile
29144 time error, but not always. It is a good idea to check all uses of the
29145 'Size attribute when porting Ada 83 code. The GNAT specific attribute
29146 Object_Size can provide a useful way of duplicating the behavior of
29147 some Ada 83 compiler systems.
29150 @emph{Size of Access Types}
29152 A common assumption in Ada 83 code is that an access type is in fact a pointer,
29153 and that therefore it will be the same size as a System.Address value. This
29154 assumption is true for GNAT in most cases with one exception. For the case of
29155 a pointer to an unconstrained array type (where the bounds may vary from one
29156 value of the access type to another), the default is to use a 'fat pointer',
29157 which is represented as two separate pointers, one to the bounds, and one to
29158 the array. This representation has a number of advantages, including improved
29159 efficiency. However, it may cause some difficulties in porting existing Ada 83
29160 code which makes the assumption that, for example, pointers fit in 32 bits on
29161 a machine with 32-bit addressing.
29163 To get around this problem, GNAT also permits the use of 'thin pointers' for
29164 access types in this case (where the designated type is an unconstrained array
29165 type). These thin pointers are indeed the same size as a System.Address value.
29166 To specify a thin pointer, use a size clause for the type, for example:
29169 type X is access all String;
29170 for X'Size use Standard'Address_Size;
29173 which will cause the type X to be represented using a single pointer.
29174 When using this representation, the bounds are right behind the array.
29175 This representation is slightly less efficient, and does not allow quite
29176 such flexibility in the use of foreign pointers or in using the
29177 Unrestricted_Access attribute to create pointers to non-aliased objects.
29178 But for any standard portable use of the access type it will work in
29179 a functionally correct manner and allow porting of existing code.
29180 Note that another way of forcing a thin pointer representation
29181 is to use a component size clause for the element size in an array,
29182 or a record representation clause for an access field in a record.
29184 See the documentation of Unrestricted_Access in the GNAT RM for a
29185 full discussion of possible problems using this attribute in conjunction
29186 with thin pointers.
29189 @node Compatibility with HP Ada 83,,Representation Clauses,Compatibility and Porting Guide
29190 @anchor{gnat_rm/compatibility_and_porting_guide compatibility-with-hp-ada-83}@anchor{455}@anchor{gnat_rm/compatibility_and_porting_guide id17}@anchor{456}
29191 @section Compatibility with HP Ada 83
29194 All the HP Ada 83 pragmas and attributes are recognized, although only a subset
29195 of them can sensibly be implemented. The description of pragmas in
29196 @ref{7,,Implementation Defined Pragmas} indicates whether or not they are
29197 applicable to GNAT.
29203 @emph{Default floating-point representation}
29205 In GNAT, the default floating-point format is IEEE, whereas in HP Ada 83,
29211 the package System in GNAT exactly corresponds to the definition in the
29212 Ada 95 reference manual, which means that it excludes many of the
29213 HP Ada 83 extensions. However, a separate package Aux_DEC is provided
29214 that contains the additional definitions, and a special pragma,
29215 Extend_System allows this package to be treated transparently as an
29216 extension of package System.
29219 @node GNU Free Documentation License,Index,Compatibility and Porting Guide,Top
29220 @anchor{share/gnu_free_documentation_license gnu-fdl}@anchor{1}@anchor{share/gnu_free_documentation_license doc}@anchor{457}@anchor{share/gnu_free_documentation_license gnu-free-documentation-license}@anchor{458}
29221 @chapter GNU Free Documentation License
29224 Version 1.3, 3 November 2008
29226 Copyright 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc
29227 @indicateurl{http://fsf.org/}
29229 Everyone is permitted to copy and distribute verbatim copies of this
29230 license document, but changing it is not allowed.
29234 The purpose of this License is to make a manual, textbook, or other
29235 functional and useful document "free" in the sense of freedom: to
29236 assure everyone the effective freedom to copy and redistribute it,
29237 with or without modifying it, either commercially or noncommercially.
29238 Secondarily, this License preserves for the author and publisher a way
29239 to get credit for their work, while not being considered responsible
29240 for modifications made by others.
29242 This License is a kind of "copyleft", which means that derivative
29243 works of the document must themselves be free in the same sense. It
29244 complements the GNU General Public License, which is a copyleft
29245 license designed for free software.
29247 We have designed this License in order to use it for manuals for free
29248 software, because free software needs free documentation: a free
29249 program should come with manuals providing the same freedoms that the
29250 software does. But this License is not limited to software manuals;
29251 it can be used for any textual work, regardless of subject matter or
29252 whether it is published as a printed book. We recommend this License
29253 principally for works whose purpose is instruction or reference.
29255 @strong{1. APPLICABILITY AND DEFINITIONS}
29257 This License applies to any manual or other work, in any medium, that
29258 contains a notice placed by the copyright holder saying it can be
29259 distributed under the terms of this License. Such a notice grants a
29260 world-wide, royalty-free license, unlimited in duration, to use that
29261 work under the conditions stated herein. The @strong{Document}, below,
29262 refers to any such manual or work. Any member of the public is a
29263 licensee, and is addressed as "@strong{you}". You accept the license if you
29264 copy, modify or distribute the work in a way requiring permission
29265 under copyright law.
29267 A "@strong{Modified Version}" of the Document means any work containing the
29268 Document or a portion of it, either copied verbatim, or with
29269 modifications and/or translated into another language.
29271 A "@strong{Secondary Section}" is a named appendix or a front-matter section of
29272 the Document that deals exclusively with the relationship of the
29273 publishers or authors of the Document to the Document's overall subject
29274 (or to related matters) and contains nothing that could fall directly
29275 within that overall subject. (Thus, if the Document is in part a
29276 textbook of mathematics, a Secondary Section may not explain any
29277 mathematics.) The relationship could be a matter of historical
29278 connection with the subject or with related matters, or of legal,
29279 commercial, philosophical, ethical or political position regarding
29282 The "@strong{Invariant Sections}" are certain Secondary Sections whose titles
29283 are designated, as being those of Invariant Sections, in the notice
29284 that says that the Document is released under this License. If a
29285 section does not fit the above definition of Secondary then it is not
29286 allowed to be designated as Invariant. The Document may contain zero
29287 Invariant Sections. If the Document does not identify any Invariant
29288 Sections then there are none.
29290 The "@strong{Cover Texts}" are certain short passages of text that are listed,
29291 as Front-Cover Texts or Back-Cover Texts, in the notice that says that
29292 the Document is released under this License. A Front-Cover Text may
29293 be at most 5 words, and a Back-Cover Text may be at most 25 words.
29295 A "@strong{Transparent}" copy of the Document means a machine-readable copy,
29296 represented in a format whose specification is available to the
29297 general public, that is suitable for revising the document
29298 straightforwardly with generic text editors or (for images composed of
29299 pixels) generic paint programs or (for drawings) some widely available
29300 drawing editor, and that is suitable for input to text formatters or
29301 for automatic translation to a variety of formats suitable for input
29302 to text formatters. A copy made in an otherwise Transparent file
29303 format whose markup, or absence of markup, has been arranged to thwart
29304 or discourage subsequent modification by readers is not Transparent.
29305 An image format is not Transparent if used for any substantial amount
29306 of text. A copy that is not "Transparent" is called @strong{Opaque}.
29308 Examples of suitable formats for Transparent copies include plain
29309 ASCII without markup, Texinfo input format, LaTeX input format, SGML
29310 or XML using a publicly available DTD, and standard-conforming simple
29311 HTML, PostScript or PDF designed for human modification. Examples of
29312 transparent image formats include PNG, XCF and JPG. Opaque formats
29313 include proprietary formats that can be read and edited only by
29314 proprietary word processors, SGML or XML for which the DTD and/or
29315 processing tools are not generally available, and the
29316 machine-generated HTML, PostScript or PDF produced by some word
29317 processors for output purposes only.
29319 The "@strong{Title Page}" means, for a printed book, the title page itself,
29320 plus such following pages as are needed to hold, legibly, the material
29321 this License requires to appear in the title page. For works in
29322 formats which do not have any title page as such, "Title Page" means
29323 the text near the most prominent appearance of the work's title,
29324 preceding the beginning of the body of the text.
29326 The "@strong{publisher}" means any person or entity that distributes
29327 copies of the Document to the public.
29329 A section "@strong{Entitled XYZ}" means a named subunit of the Document whose
29330 title either is precisely XYZ or contains XYZ in parentheses following
29331 text that translates XYZ in another language. (Here XYZ stands for a
29332 specific section name mentioned below, such as "@strong{Acknowledgements}",
29333 "@strong{Dedications}", "@strong{Endorsements}", or "@strong{History}".)
29334 To "@strong{Preserve the Title}"
29335 of such a section when you modify the Document means that it remains a
29336 section "Entitled XYZ" according to this definition.
29338 The Document may include Warranty Disclaimers next to the notice which
29339 states that this License applies to the Document. These Warranty
29340 Disclaimers are considered to be included by reference in this
29341 License, but only as regards disclaiming warranties: any other
29342 implication that these Warranty Disclaimers may have is void and has
29343 no effect on the meaning of this License.
29345 @strong{2. VERBATIM COPYING}
29347 You may copy and distribute the Document in any medium, either
29348 commercially or noncommercially, provided that this License, the
29349 copyright notices, and the license notice saying this License applies
29350 to the Document are reproduced in all copies, and that you add no other
29351 conditions whatsoever to those of this License. You may not use
29352 technical measures to obstruct or control the reading or further
29353 copying of the copies you make or distribute. However, you may accept
29354 compensation in exchange for copies. If you distribute a large enough
29355 number of copies you must also follow the conditions in section 3.
29357 You may also lend copies, under the same conditions stated above, and
29358 you may publicly display copies.
29360 @strong{3. COPYING IN QUANTITY}
29362 If you publish printed copies (or copies in media that commonly have
29363 printed covers) of the Document, numbering more than 100, and the
29364 Document's license notice requires Cover Texts, you must enclose the
29365 copies in covers that carry, clearly and legibly, all these Cover
29366 Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on
29367 the back cover. Both covers must also clearly and legibly identify
29368 you as the publisher of these copies. The front cover must present
29369 the full title with all words of the title equally prominent and
29370 visible. You may add other material on the covers in addition.
29371 Copying with changes limited to the covers, as long as they preserve
29372 the title of the Document and satisfy these conditions, can be treated
29373 as verbatim copying in other respects.
29375 If the required texts for either cover are too voluminous to fit
29376 legibly, you should put the first ones listed (as many as fit
29377 reasonably) on the actual cover, and continue the rest onto adjacent
29380 If you publish or distribute Opaque copies of the Document numbering
29381 more than 100, you must either include a machine-readable Transparent
29382 copy along with each Opaque copy, or state in or with each Opaque copy
29383 a computer-network location from which the general network-using
29384 public has access to download using public-standard network protocols
29385 a complete Transparent copy of the Document, free of added material.
29386 If you use the latter option, you must take reasonably prudent steps,
29387 when you begin distribution of Opaque copies in quantity, to ensure
29388 that this Transparent copy will remain thus accessible at the stated
29389 location until at least one year after the last time you distribute an
29390 Opaque copy (directly or through your agents or retailers) of that
29391 edition to the public.
29393 It is requested, but not required, that you contact the authors of the
29394 Document well before redistributing any large number of copies, to give
29395 them a chance to provide you with an updated version of the Document.
29397 @strong{4. MODIFICATIONS}
29399 You may copy and distribute a Modified Version of the Document under
29400 the conditions of sections 2 and 3 above, provided that you release
29401 the Modified Version under precisely this License, with the Modified
29402 Version filling the role of the Document, thus licensing distribution
29403 and modification of the Modified Version to whoever possesses a copy
29404 of it. In addition, you must do these things in the Modified Version:
29410 Use in the Title Page (and on the covers, if any) a title distinct
29411 from that of the Document, and from those of previous versions
29412 (which should, if there were any, be listed in the History section
29413 of the Document). You may use the same title as a previous version
29414 if the original publisher of that version gives permission.
29417 List on the Title Page, as authors, one or more persons or entities
29418 responsible for authorship of the modifications in the Modified
29419 Version, together with at least five of the principal authors of the
29420 Document (all of its principal authors, if it has fewer than five),
29421 unless they release you from this requirement.
29424 State on the Title page the name of the publisher of the
29425 Modified Version, as the publisher.
29428 Preserve all the copyright notices of the Document.
29431 Add an appropriate copyright notice for your modifications
29432 adjacent to the other copyright notices.
29435 Include, immediately after the copyright notices, a license notice
29436 giving the public permission to use the Modified Version under the
29437 terms of this License, in the form shown in the Addendum below.
29440 Preserve in that license notice the full lists of Invariant Sections
29441 and required Cover Texts given in the Document's license notice.
29444 Include an unaltered copy of this License.
29447 Preserve the section Entitled "History", Preserve its Title, and add
29448 to it an item stating at least the title, year, new authors, and
29449 publisher of the Modified Version as given on the Title Page. If
29450 there is no section Entitled "History" in the Document, create one
29451 stating the title, year, authors, and publisher of the Document as
29452 given on its Title Page, then add an item describing the Modified
29453 Version as stated in the previous sentence.
29456 Preserve the network location, if any, given in the Document for
29457 public access to a Transparent copy of the Document, and likewise
29458 the network locations given in the Document for previous versions
29459 it was based on. These may be placed in the "History" section.
29460 You may omit a network location for a work that was published at
29461 least four years before the Document itself, or if the original
29462 publisher of the version it refers to gives permission.
29465 For any section Entitled "Acknowledgements" or "Dedications",
29466 Preserve the Title of the section, and preserve in the section all
29467 the substance and tone of each of the contributor acknowledgements
29468 and/or dedications given therein.
29471 Preserve all the Invariant Sections of the Document,
29472 unaltered in their text and in their titles. Section numbers
29473 or the equivalent are not considered part of the section titles.
29476 Delete any section Entitled "Endorsements". Such a section
29477 may not be included in the Modified Version.
29480 Do not retitle any existing section to be Entitled "Endorsements"
29481 or to conflict in title with any Invariant Section.
29484 Preserve any Warranty Disclaimers.
29487 If the Modified Version includes new front-matter sections or
29488 appendices that qualify as Secondary Sections and contain no material
29489 copied from the Document, you may at your option designate some or all
29490 of these sections as invariant. To do this, add their titles to the
29491 list of Invariant Sections in the Modified Version's license notice.
29492 These titles must be distinct from any other section titles.
29494 You may add a section Entitled "Endorsements", provided it contains
29495 nothing but endorsements of your Modified Version by various
29496 parties---for example, statements of peer review or that the text has
29497 been approved by an organization as the authoritative definition of a
29500 You may add a passage of up to five words as a Front-Cover Text, and a
29501 passage of up to 25 words as a Back-Cover Text, to the end of the list
29502 of Cover Texts in the Modified Version. Only one passage of
29503 Front-Cover Text and one of Back-Cover Text may be added by (or
29504 through arrangements made by) any one entity. If the Document already
29505 includes a cover text for the same cover, previously added by you or
29506 by arrangement made by the same entity you are acting on behalf of,
29507 you may not add another; but you may replace the old one, on explicit
29508 permission from the previous publisher that added the old one.
29510 The author(s) and publisher(s) of the Document do not by this License
29511 give permission to use their names for publicity for or to assert or
29512 imply endorsement of any Modified Version.
29514 @strong{5. COMBINING DOCUMENTS}
29516 You may combine the Document with other documents released under this
29517 License, under the terms defined in section 4 above for modified
29518 versions, provided that you include in the combination all of the
29519 Invariant Sections of all of the original documents, unmodified, and
29520 list them all as Invariant Sections of your combined work in its
29521 license notice, and that you preserve all their Warranty Disclaimers.
29523 The combined work need only contain one copy of this License, and
29524 multiple identical Invariant Sections may be replaced with a single
29525 copy. If there are multiple Invariant Sections with the same name but
29526 different contents, make the title of each such section unique by
29527 adding at the end of it, in parentheses, the name of the original
29528 author or publisher of that section if known, or else a unique number.
29529 Make the same adjustment to the section titles in the list of
29530 Invariant Sections in the license notice of the combined work.
29532 In the combination, you must combine any sections Entitled "History"
29533 in the various original documents, forming one section Entitled
29534 "History"; likewise combine any sections Entitled "Acknowledgements",
29535 and any sections Entitled "Dedications". You must delete all sections
29536 Entitled "Endorsements".
29538 @strong{6. COLLECTIONS OF DOCUMENTS}
29540 You may make a collection consisting of the Document and other documents
29541 released under this License, and replace the individual copies of this
29542 License in the various documents with a single copy that is included in
29543 the collection, provided that you follow the rules of this License for
29544 verbatim copying of each of the documents in all other respects.
29546 You may extract a single document from such a collection, and distribute
29547 it individually under this License, provided you insert a copy of this
29548 License into the extracted document, and follow this License in all
29549 other respects regarding verbatim copying of that document.
29551 @strong{7. AGGREGATION WITH INDEPENDENT WORKS}
29553 A compilation of the Document or its derivatives with other separate
29554 and independent documents or works, in or on a volume of a storage or
29555 distribution medium, is called an "aggregate" if the copyright
29556 resulting from the compilation is not used to limit the legal rights
29557 of the compilation's users beyond what the individual works permit.
29558 When the Document is included in an aggregate, this License does not
29559 apply to the other works in the aggregate which are not themselves
29560 derivative works of the Document.
29562 If the Cover Text requirement of section 3 is applicable to these
29563 copies of the Document, then if the Document is less than one half of
29564 the entire aggregate, the Document's Cover Texts may be placed on
29565 covers that bracket the Document within the aggregate, or the
29566 electronic equivalent of covers if the Document is in electronic form.
29567 Otherwise they must appear on printed covers that bracket the whole
29570 @strong{8. TRANSLATION}
29572 Translation is considered a kind of modification, so you may
29573 distribute translations of the Document under the terms of section 4.
29574 Replacing Invariant Sections with translations requires special
29575 permission from their copyright holders, but you may include
29576 translations of some or all Invariant Sections in addition to the
29577 original versions of these Invariant Sections. You may include a
29578 translation of this License, and all the license notices in the
29579 Document, and any Warranty Disclaimers, provided that you also include
29580 the original English version of this License and the original versions
29581 of those notices and disclaimers. In case of a disagreement between
29582 the translation and the original version of this License or a notice
29583 or disclaimer, the original version will prevail.
29585 If a section in the Document is Entitled "Acknowledgements",
29586 "Dedications", or "History", the requirement (section 4) to Preserve
29587 its Title (section 1) will typically require changing the actual
29590 @strong{9. TERMINATION}
29592 You may not copy, modify, sublicense, or distribute the Document
29593 except as expressly provided under this License. Any attempt
29594 otherwise to copy, modify, sublicense, or distribute it is void, and
29595 will automatically terminate your rights under this License.
29597 However, if you cease all violation of this License, then your license
29598 from a particular copyright holder is reinstated (a) provisionally,
29599 unless and until the copyright holder explicitly and finally
29600 terminates your license, and (b) permanently, if the copyright holder
29601 fails to notify you of the violation by some reasonable means prior to
29602 60 days after the cessation.
29604 Moreover, your license from a particular copyright holder is
29605 reinstated permanently if the copyright holder notifies you of the
29606 violation by some reasonable means, this is the first time you have
29607 received notice of violation of this License (for any work) from that
29608 copyright holder, and you cure the violation prior to 30 days after
29609 your receipt of the notice.
29611 Termination of your rights under this section does not terminate the
29612 licenses of parties who have received copies or rights from you under
29613 this License. If your rights have been terminated and not permanently
29614 reinstated, receipt of a copy of some or all of the same material does
29615 not give you any rights to use it.
29617 @strong{10. FUTURE REVISIONS OF THIS LICENSE}
29619 The Free Software Foundation may publish new, revised versions
29620 of the GNU Free Documentation License from time to time. Such new
29621 versions will be similar in spirit to the present version, but may
29622 differ in detail to address new problems or concerns. See
29623 @indicateurl{http://www.gnu.org/copyleft/}.
29625 Each version of the License is given a distinguishing version number.
29626 If the Document specifies that a particular numbered version of this
29627 License "or any later version" applies to it, you have the option of
29628 following the terms and conditions either of that specified version or
29629 of any later version that has been published (not as a draft) by the
29630 Free Software Foundation. If the Document does not specify a version
29631 number of this License, you may choose any version ever published (not
29632 as a draft) by the Free Software Foundation. If the Document
29633 specifies that a proxy can decide which future versions of this
29634 License can be used, that proxy's public statement of acceptance of a
29635 version permanently authorizes you to choose that version for the
29638 @strong{11. RELICENSING}
29640 "Massive Multiauthor Collaboration Site" (or "MMC Site") means any
29641 World Wide Web server that publishes copyrightable works and also
29642 provides prominent facilities for anybody to edit those works. A
29643 public wiki that anybody can edit is an example of such a server. A
29644 "Massive Multiauthor Collaboration" (or "MMC") contained in the
29645 site means any set of copyrightable works thus published on the MMC
29648 "CC-BY-SA" means the Creative Commons Attribution-Share Alike 3.0
29649 license published by Creative Commons Corporation, a not-for-profit
29650 corporation with a principal place of business in San Francisco,
29651 California, as well as future copyleft versions of that license
29652 published by that same organization.
29654 "Incorporate" means to publish or republish a Document, in whole or
29655 in part, as part of another Document.
29657 An MMC is "eligible for relicensing" if it is licensed under this
29658 License, and if all works that were first published under this License
29659 somewhere other than this MMC, and subsequently incorporated in whole
29660 or in part into the MMC, (1) had no cover texts or invariant sections,
29661 and (2) were thus incorporated prior to November 1, 2008.
29663 The operator of an MMC Site may republish an MMC contained in the site
29664 under CC-BY-SA on the same site at any time before August 1, 2009,
29665 provided the MMC is eligible for relicensing.
29667 @strong{ADDENDUM: How to use this License for your documents}
29669 To use this License in a document you have written, include a copy of
29670 the License in the document and put the following copyright and
29671 license notices just after the title page:
29675 Copyright © YEAR YOUR NAME.
29676 Permission is granted to copy, distribute and/or modify this document
29677 under the terms of the GNU Free Documentation License, Version 1.3
29678 or any later version published by the Free Software Foundation;
29679 with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
29680 A copy of the license is included in the section entitled "GNU
29681 Free Documentation License".
29684 If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts,
29685 replace the "with ... Texts." line with this:
29689 with the Invariant Sections being LIST THEIR TITLES, with the
29690 Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST.
29693 If you have Invariant Sections without Cover Texts, or some other
29694 combination of the three, merge those two alternatives to suit the
29697 If your document contains nontrivial examples of program code, we
29698 recommend releasing these examples in parallel under your choice of
29699 free software license, such as the GNU General Public License,
29700 to permit their use in free software.
29702 @node Index,,GNU Free Documentation License,Top