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8 @settitle GNAT Reference Manual
13 @dircategory GNU Ada Tools
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24 GNAT Reference Manual , Sep 08, 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::
613 * Exception_Information::
614 * Exception_Message::
618 * Shifts and Rotates::
621 Representation Clauses and Pragmas
623 * Alignment Clauses::
625 * Storage_Size Clauses::
626 * Size of Variant Record Objects::
627 * Biased Representation::
628 * Value_Size and Object_Size Clauses::
629 * Component_Size Clauses::
630 * Bit_Order Clauses::
631 * Effect of Bit_Order on Byte Ordering::
632 * Pragma Pack for Arrays::
633 * Pragma Pack for Records::
634 * Record Representation Clauses::
635 * Handling of Records with Holes::
636 * Enumeration Clauses::
638 * Use of Address Clauses for Memory-Mapped I/O::
639 * Effect of Convention on Representation::
640 * Conventions and Anonymous Access Types::
641 * Determining the Representations chosen by GNAT::
643 The Implementation of Standard I/O
645 * Standard I/O Packages::
651 * Wide_Wide_Text_IO::
655 * Filenames encoding::
656 * File content encoding::
658 * Operations on C Streams::
659 * Interfacing to C Streams::
663 * Stream Pointer Positioning::
664 * Reading and Writing Non-Regular Files::
666 * Treating Text_IO Files as Streams::
667 * Text_IO Extensions::
668 * Text_IO Facilities for Unbounded Strings::
672 * Stream Pointer Positioning: Stream Pointer Positioning<2>.
673 * Reading and Writing Non-Regular Files: Reading and Writing Non-Regular Files<2>.
677 * Stream Pointer Positioning: Stream Pointer Positioning<3>.
678 * Reading and Writing Non-Regular Files: Reading and Writing Non-Regular Files<3>.
682 * Ada.Characters.Latin_9 (a-chlat9.ads): Ada Characters Latin_9 a-chlat9 ads.
683 * Ada.Characters.Wide_Latin_1 (a-cwila1.ads): Ada Characters Wide_Latin_1 a-cwila1 ads.
684 * Ada.Characters.Wide_Latin_9 (a-cwila1.ads): Ada Characters Wide_Latin_9 a-cwila1 ads.
685 * Ada.Characters.Wide_Wide_Latin_1 (a-chzla1.ads): Ada Characters Wide_Wide_Latin_1 a-chzla1 ads.
686 * Ada.Characters.Wide_Wide_Latin_9 (a-chzla9.ads): Ada Characters Wide_Wide_Latin_9 a-chzla9 ads.
687 * Ada.Containers.Formal_Doubly_Linked_Lists (a-cfdlli.ads): Ada Containers Formal_Doubly_Linked_Lists a-cfdlli ads.
688 * Ada.Containers.Formal_Hashed_Maps (a-cfhama.ads): Ada Containers Formal_Hashed_Maps a-cfhama ads.
689 * Ada.Containers.Formal_Hashed_Sets (a-cfhase.ads): Ada Containers Formal_Hashed_Sets a-cfhase ads.
690 * Ada.Containers.Formal_Ordered_Maps (a-cforma.ads): Ada Containers Formal_Ordered_Maps a-cforma ads.
691 * Ada.Containers.Formal_Ordered_Sets (a-cforse.ads): Ada Containers Formal_Ordered_Sets a-cforse ads.
692 * Ada.Containers.Formal_Vectors (a-cofove.ads): Ada Containers Formal_Vectors a-cofove ads.
693 * Ada.Containers.Formal_Indefinite_Vectors (a-cfinve.ads): Ada Containers Formal_Indefinite_Vectors a-cfinve ads.
694 * Ada.Containers.Functional_Vectors (a-cofuve.ads): Ada Containers Functional_Vectors a-cofuve ads.
695 * Ada.Containers.Functional_Sets (a-cofuse.ads): Ada Containers Functional_Sets a-cofuse ads.
696 * Ada.Containers.Functional_Maps (a-cofuma.ads): Ada Containers Functional_Maps a-cofuma ads.
697 * Ada.Containers.Bounded_Holders (a-coboho.ads): Ada Containers Bounded_Holders a-coboho ads.
698 * Ada.Command_Line.Environment (a-colien.ads): Ada Command_Line Environment a-colien ads.
699 * Ada.Command_Line.Remove (a-colire.ads): Ada Command_Line Remove a-colire ads.
700 * Ada.Command_Line.Response_File (a-clrefi.ads): Ada Command_Line Response_File a-clrefi ads.
701 * Ada.Direct_IO.C_Streams (a-diocst.ads): Ada Direct_IO C_Streams a-diocst ads.
702 * Ada.Exceptions.Is_Null_Occurrence (a-einuoc.ads): Ada Exceptions Is_Null_Occurrence a-einuoc ads.
703 * Ada.Exceptions.Last_Chance_Handler (a-elchha.ads): Ada Exceptions Last_Chance_Handler a-elchha ads.
704 * Ada.Exceptions.Traceback (a-exctra.ads): Ada Exceptions Traceback a-exctra ads.
705 * Ada.Sequential_IO.C_Streams (a-siocst.ads): Ada Sequential_IO C_Streams a-siocst ads.
706 * Ada.Streams.Stream_IO.C_Streams (a-ssicst.ads): Ada Streams Stream_IO C_Streams a-ssicst ads.
707 * Ada.Strings.Unbounded.Text_IO (a-suteio.ads): Ada Strings Unbounded Text_IO a-suteio ads.
708 * Ada.Strings.Wide_Unbounded.Wide_Text_IO (a-swuwti.ads): Ada Strings Wide_Unbounded Wide_Text_IO a-swuwti ads.
709 * Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO (a-szuzti.ads): Ada Strings Wide_Wide_Unbounded Wide_Wide_Text_IO a-szuzti ads.
710 * Ada.Text_IO.C_Streams (a-tiocst.ads): Ada Text_IO C_Streams a-tiocst ads.
711 * Ada.Text_IO.Reset_Standard_Files (a-tirsfi.ads): Ada Text_IO Reset_Standard_Files a-tirsfi ads.
712 * Ada.Wide_Characters.Unicode (a-wichun.ads): Ada Wide_Characters Unicode a-wichun ads.
713 * Ada.Wide_Text_IO.C_Streams (a-wtcstr.ads): Ada Wide_Text_IO C_Streams a-wtcstr ads.
714 * Ada.Wide_Text_IO.Reset_Standard_Files (a-wrstfi.ads): Ada Wide_Text_IO Reset_Standard_Files a-wrstfi ads.
715 * Ada.Wide_Wide_Characters.Unicode (a-zchuni.ads): Ada Wide_Wide_Characters Unicode a-zchuni ads.
716 * Ada.Wide_Wide_Text_IO.C_Streams (a-ztcstr.ads): Ada Wide_Wide_Text_IO C_Streams a-ztcstr ads.
717 * Ada.Wide_Wide_Text_IO.Reset_Standard_Files (a-zrstfi.ads): Ada Wide_Wide_Text_IO Reset_Standard_Files a-zrstfi ads.
718 * GNAT.Altivec (g-altive.ads): GNAT Altivec g-altive ads.
719 * GNAT.Altivec.Conversions (g-altcon.ads): GNAT Altivec Conversions g-altcon ads.
720 * GNAT.Altivec.Vector_Operations (g-alveop.ads): GNAT Altivec Vector_Operations g-alveop ads.
721 * GNAT.Altivec.Vector_Types (g-alvety.ads): GNAT Altivec Vector_Types g-alvety ads.
722 * GNAT.Altivec.Vector_Views (g-alvevi.ads): GNAT Altivec Vector_Views g-alvevi ads.
723 * GNAT.Array_Split (g-arrspl.ads): GNAT Array_Split g-arrspl ads.
724 * GNAT.AWK (g-awk.ads): GNAT AWK g-awk ads.
725 * GNAT.Bind_Environment (g-binenv.ads): GNAT Bind_Environment g-binenv ads.
726 * GNAT.Bounded_Buffers (g-boubuf.ads): GNAT Bounded_Buffers g-boubuf ads.
727 * GNAT.Bounded_Mailboxes (g-boumai.ads): GNAT Bounded_Mailboxes g-boumai ads.
728 * GNAT.Bubble_Sort (g-bubsor.ads): GNAT Bubble_Sort g-bubsor ads.
729 * GNAT.Bubble_Sort_A (g-busora.ads): GNAT Bubble_Sort_A g-busora ads.
730 * GNAT.Bubble_Sort_G (g-busorg.ads): GNAT Bubble_Sort_G g-busorg ads.
731 * GNAT.Byte_Order_Mark (g-byorma.ads): GNAT Byte_Order_Mark g-byorma ads.
732 * GNAT.Byte_Swapping (g-bytswa.ads): GNAT Byte_Swapping g-bytswa ads.
733 * GNAT.Calendar (g-calend.ads): GNAT Calendar g-calend ads.
734 * GNAT.Calendar.Time_IO (g-catiio.ads): GNAT Calendar Time_IO g-catiio ads.
735 * GNAT.CRC32 (g-crc32.ads): GNAT CRC32 g-crc32 ads.
736 * GNAT.Case_Util (g-casuti.ads): GNAT Case_Util g-casuti ads.
737 * GNAT.CGI (g-cgi.ads): GNAT CGI g-cgi ads.
738 * GNAT.CGI.Cookie (g-cgicoo.ads): GNAT CGI Cookie g-cgicoo ads.
739 * GNAT.CGI.Debug (g-cgideb.ads): GNAT CGI Debug g-cgideb ads.
740 * GNAT.Command_Line (g-comlin.ads): GNAT Command_Line g-comlin ads.
741 * GNAT.Compiler_Version (g-comver.ads): GNAT Compiler_Version g-comver ads.
742 * GNAT.Ctrl_C (g-ctrl_c.ads): GNAT Ctrl_C g-ctrl_c ads.
743 * GNAT.Current_Exception (g-curexc.ads): GNAT Current_Exception g-curexc ads.
744 * GNAT.Debug_Pools (g-debpoo.ads): GNAT Debug_Pools g-debpoo ads.
745 * GNAT.Debug_Utilities (g-debuti.ads): GNAT Debug_Utilities g-debuti ads.
746 * GNAT.Decode_String (g-decstr.ads): GNAT Decode_String g-decstr ads.
747 * GNAT.Decode_UTF8_String (g-deutst.ads): GNAT Decode_UTF8_String g-deutst ads.
748 * GNAT.Directory_Operations (g-dirope.ads): GNAT Directory_Operations g-dirope ads.
749 * GNAT.Directory_Operations.Iteration (g-diopit.ads): GNAT Directory_Operations Iteration g-diopit ads.
750 * GNAT.Dynamic_HTables (g-dynhta.ads): GNAT Dynamic_HTables g-dynhta ads.
751 * GNAT.Dynamic_Tables (g-dyntab.ads): GNAT Dynamic_Tables g-dyntab ads.
752 * GNAT.Encode_String (g-encstr.ads): GNAT Encode_String g-encstr ads.
753 * GNAT.Encode_UTF8_String (g-enutst.ads): GNAT Encode_UTF8_String g-enutst ads.
754 * GNAT.Exception_Actions (g-excact.ads): GNAT Exception_Actions g-excact ads.
755 * GNAT.Exception_Traces (g-exctra.ads): GNAT Exception_Traces g-exctra ads.
756 * GNAT.Exceptions (g-expect.ads): GNAT Exceptions g-expect ads.
757 * GNAT.Expect (g-expect.ads): GNAT Expect g-expect ads.
758 * GNAT.Expect.TTY (g-exptty.ads): GNAT Expect TTY g-exptty ads.
759 * GNAT.Float_Control (g-flocon.ads): GNAT Float_Control g-flocon ads.
760 * GNAT.Formatted_String (g-forstr.ads): GNAT Formatted_String g-forstr ads.
761 * GNAT.Heap_Sort (g-heasor.ads): GNAT Heap_Sort g-heasor ads.
762 * GNAT.Heap_Sort_A (g-hesora.ads): GNAT Heap_Sort_A g-hesora ads.
763 * GNAT.Heap_Sort_G (g-hesorg.ads): GNAT Heap_Sort_G g-hesorg ads.
764 * GNAT.HTable (g-htable.ads): GNAT HTable g-htable ads.
765 * GNAT.IO (g-io.ads): GNAT IO g-io ads.
766 * GNAT.IO_Aux (g-io_aux.ads): GNAT IO_Aux g-io_aux ads.
767 * GNAT.Lock_Files (g-locfil.ads): GNAT Lock_Files g-locfil ads.
768 * GNAT.MBBS_Discrete_Random (g-mbdira.ads): GNAT MBBS_Discrete_Random g-mbdira ads.
769 * GNAT.MBBS_Float_Random (g-mbflra.ads): GNAT MBBS_Float_Random g-mbflra ads.
770 * GNAT.MD5 (g-md5.ads): GNAT MD5 g-md5 ads.
771 * GNAT.Memory_Dump (g-memdum.ads): GNAT Memory_Dump g-memdum ads.
772 * GNAT.Most_Recent_Exception (g-moreex.ads): GNAT Most_Recent_Exception g-moreex ads.
773 * GNAT.OS_Lib (g-os_lib.ads): GNAT OS_Lib g-os_lib ads.
774 * GNAT.Perfect_Hash_Generators (g-pehage.ads): GNAT Perfect_Hash_Generators g-pehage ads.
775 * GNAT.Random_Numbers (g-rannum.ads): GNAT Random_Numbers g-rannum ads.
776 * GNAT.Regexp (g-regexp.ads): GNAT Regexp g-regexp ads.
777 * GNAT.Registry (g-regist.ads): GNAT Registry g-regist ads.
778 * GNAT.Regpat (g-regpat.ads): GNAT Regpat g-regpat ads.
779 * GNAT.Rewrite_Data (g-rewdat.ads): GNAT Rewrite_Data g-rewdat ads.
780 * GNAT.Secondary_Stack_Info (g-sestin.ads): GNAT Secondary_Stack_Info g-sestin ads.
781 * GNAT.Semaphores (g-semaph.ads): GNAT Semaphores g-semaph ads.
782 * GNAT.Serial_Communications (g-sercom.ads): GNAT Serial_Communications g-sercom ads.
783 * GNAT.SHA1 (g-sha1.ads): GNAT SHA1 g-sha1 ads.
784 * GNAT.SHA224 (g-sha224.ads): GNAT SHA224 g-sha224 ads.
785 * GNAT.SHA256 (g-sha256.ads): GNAT SHA256 g-sha256 ads.
786 * GNAT.SHA384 (g-sha384.ads): GNAT SHA384 g-sha384 ads.
787 * GNAT.SHA512 (g-sha512.ads): GNAT SHA512 g-sha512 ads.
788 * GNAT.Signals (g-signal.ads): GNAT Signals g-signal ads.
789 * GNAT.Sockets (g-socket.ads): GNAT Sockets g-socket ads.
790 * GNAT.Source_Info (g-souinf.ads): GNAT Source_Info g-souinf ads.
791 * GNAT.Spelling_Checker (g-speche.ads): GNAT Spelling_Checker g-speche ads.
792 * GNAT.Spelling_Checker_Generic (g-spchge.ads): GNAT Spelling_Checker_Generic g-spchge ads.
793 * GNAT.Spitbol.Patterns (g-spipat.ads): GNAT Spitbol Patterns g-spipat ads.
794 * GNAT.Spitbol (g-spitbo.ads): GNAT Spitbol g-spitbo ads.
795 * GNAT.Spitbol.Table_Boolean (g-sptabo.ads): GNAT Spitbol Table_Boolean g-sptabo ads.
796 * GNAT.Spitbol.Table_Integer (g-sptain.ads): GNAT Spitbol Table_Integer g-sptain ads.
797 * GNAT.Spitbol.Table_VString (g-sptavs.ads): GNAT Spitbol Table_VString g-sptavs ads.
798 * GNAT.SSE (g-sse.ads): GNAT SSE g-sse ads.
799 * GNAT.SSE.Vector_Types (g-ssvety.ads): GNAT SSE Vector_Types g-ssvety ads.
800 * GNAT.String_Hash (g-strhas.ads): GNAT String_Hash g-strhas ads.
801 * GNAT.Strings (g-string.ads): GNAT Strings g-string ads.
802 * GNAT.String_Split (g-strspl.ads): GNAT String_Split g-strspl ads.
803 * GNAT.Table (g-table.ads): GNAT Table g-table ads.
804 * GNAT.Task_Lock (g-tasloc.ads): GNAT Task_Lock g-tasloc ads.
805 * GNAT.Time_Stamp (g-timsta.ads): GNAT Time_Stamp g-timsta ads.
806 * GNAT.Threads (g-thread.ads): GNAT Threads g-thread ads.
807 * GNAT.Traceback (g-traceb.ads): GNAT Traceback g-traceb ads.
808 * GNAT.Traceback.Symbolic (g-trasym.ads): GNAT Traceback Symbolic g-trasym ads.
809 * GNAT.UTF_32 (g-table.ads): GNAT UTF_32 g-table ads.
810 * GNAT.Wide_Spelling_Checker (g-u3spch.ads): GNAT Wide_Spelling_Checker g-u3spch ads.
811 * GNAT.Wide_Spelling_Checker (g-wispch.ads): GNAT Wide_Spelling_Checker g-wispch ads.
812 * GNAT.Wide_String_Split (g-wistsp.ads): GNAT Wide_String_Split g-wistsp ads.
813 * GNAT.Wide_Wide_Spelling_Checker (g-zspche.ads): GNAT Wide_Wide_Spelling_Checker g-zspche ads.
814 * GNAT.Wide_Wide_String_Split (g-zistsp.ads): GNAT Wide_Wide_String_Split g-zistsp ads.
815 * Interfaces.C.Extensions (i-cexten.ads): Interfaces C Extensions i-cexten ads.
816 * Interfaces.C.Streams (i-cstrea.ads): Interfaces C Streams i-cstrea ads.
817 * Interfaces.Packed_Decimal (i-pacdec.ads): Interfaces Packed_Decimal i-pacdec ads.
818 * Interfaces.VxWorks (i-vxwork.ads): Interfaces VxWorks i-vxwork ads.
819 * Interfaces.VxWorks.Int_Connection (i-vxinco.ads): Interfaces VxWorks Int_Connection i-vxinco ads.
820 * Interfaces.VxWorks.IO (i-vxwoio.ads): Interfaces VxWorks IO i-vxwoio ads.
821 * System.Address_Image (s-addima.ads): System Address_Image s-addima ads.
822 * System.Assertions (s-assert.ads): System Assertions s-assert ads.
823 * System.Atomic_Counters (s-atocou.ads): System Atomic_Counters s-atocou ads.
824 * System.Memory (s-memory.ads): System Memory s-memory ads.
825 * System.Multiprocessors (s-multip.ads): System Multiprocessors s-multip ads.
826 * System.Multiprocessors.Dispatching_Domains (s-mudido.ads): System Multiprocessors Dispatching_Domains s-mudido ads.
827 * System.Partition_Interface (s-parint.ads): System Partition_Interface s-parint ads.
828 * System.Pool_Global (s-pooglo.ads): System Pool_Global s-pooglo ads.
829 * System.Pool_Local (s-pooloc.ads): System Pool_Local s-pooloc ads.
830 * System.Restrictions (s-restri.ads): System Restrictions s-restri ads.
831 * System.Rident (s-rident.ads): System Rident s-rident ads.
832 * System.Strings.Stream_Ops (s-ststop.ads): System Strings Stream_Ops s-ststop ads.
833 * System.Unsigned_Types (s-unstyp.ads): System Unsigned_Types s-unstyp ads.
834 * System.Wch_Cnv (s-wchcnv.ads): System Wch_Cnv s-wchcnv ads.
835 * System.Wch_Con (s-wchcon.ads): System Wch_Con s-wchcon ads.
837 Interfacing to Other Languages
840 * Interfacing to C++::
841 * Interfacing to COBOL::
842 * Interfacing to Fortran::
843 * Interfacing to non-GNAT Ada code::
845 Implementation of Specific Ada Features
847 * Machine Code Insertions::
848 * GNAT Implementation of Tasking::
849 * GNAT Implementation of Shared Passive Packages::
850 * Code Generation for Array Aggregates::
851 * The Size of Discriminated Records with Default Discriminants::
852 * Strict Conformance to the Ada Reference Manual::
854 GNAT Implementation of Tasking
856 * Mapping Ada Tasks onto the Underlying Kernel Threads::
857 * Ensuring Compliance with the Real-Time Annex::
858 * Support for Locking Policies::
860 Code Generation for Array Aggregates
862 * Static constant aggregates with static bounds::
863 * Constant aggregates with unconstrained nominal types::
864 * Aggregates with static bounds::
865 * Aggregates with nonstatic bounds::
866 * Aggregates in assignment statements::
870 * pragma No_Run_Time::
872 * pragma Restricted_Run_Time::
874 * package System.Task_Info (s-tasinf.ads): package System Task_Info s-tasinf ads.
876 Compatibility and Porting Guide
878 * Writing Portable Fixed-Point Declarations::
879 * Compatibility with Ada 83::
880 * Compatibility between Ada 95 and Ada 2005::
881 * Implementation-dependent characteristics::
882 * Compatibility with Other Ada Systems::
883 * Representation Clauses::
884 * Compatibility with HP Ada 83::
886 Compatibility with Ada 83
888 * Legal Ada 83 programs that are illegal in Ada 95::
889 * More deterministic semantics::
890 * Changed semantics::
891 * Other language compatibility issues::
893 Implementation-dependent characteristics
895 * Implementation-defined pragmas::
896 * Implementation-defined attributes::
898 * Elaboration order::
899 * Target-specific aspects::
904 @node About This Guide,Implementation Defined Pragmas,Top,Top
905 @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}
906 @chapter About This Guide
910 This manual contains useful information in writing programs using the
911 GNAT compiler. It includes information on implementation dependent
912 characteristics of GNAT, including all the information required by
913 Annex M of the Ada language standard.
915 GNAT implements Ada 95, Ada 2005 and Ada 2012, and it may also be
916 invoked in Ada 83 compatibility mode.
917 By default, GNAT assumes Ada 2012,
918 but you can override with a compiler switch
919 to explicitly specify the language version.
920 (Please refer to the @emph{GNAT User's Guide} for details on these switches.)
921 Throughout this manual, references to 'Ada' without a year suffix
922 apply to all the Ada versions of the language.
924 Ada is designed to be highly portable.
925 In general, a program will have the same effect even when compiled by
926 different compilers on different platforms.
927 However, since Ada is designed to be used in a
928 wide variety of applications, it also contains a number of system
929 dependent features to be used in interfacing to the external world.
931 @geindex Implementation-dependent features
935 Note: Any program that makes use of implementation-dependent features
936 may be non-portable. You should follow good programming practice and
937 isolate and clearly document any sections of your program that make use
938 of these features in a non-portable manner.
941 * What This Reference Manual Contains::
943 * Related Information::
947 @node What This Reference Manual Contains,Conventions,,About This Guide
948 @anchor{gnat_rm/about_this_guide what-this-reference-manual-contains}@anchor{6}
949 @section What This Reference Manual Contains
952 This reference manual contains the following chapters:
958 @ref{7,,Implementation Defined Pragmas}, lists GNAT implementation-dependent
959 pragmas, which can be used to extend and enhance the functionality of the
963 @ref{8,,Implementation Defined Attributes}, lists GNAT
964 implementation-dependent attributes, which can be used to extend and
965 enhance the functionality of the compiler.
968 @ref{9,,Standard and Implementation Defined Restrictions}, lists GNAT
969 implementation-dependent restrictions, which can be used to extend and
970 enhance the functionality of the compiler.
973 @ref{a,,Implementation Advice}, provides information on generally
974 desirable behavior which are not requirements that all compilers must
975 follow since it cannot be provided on all systems, or which may be
976 undesirable on some systems.
979 @ref{b,,Implementation Defined Characteristics}, provides a guide to
980 minimizing implementation dependent features.
983 @ref{c,,Intrinsic Subprograms}, describes the intrinsic subprograms
984 implemented by GNAT, and how they can be imported into user
985 application programs.
988 @ref{d,,Representation Clauses and Pragmas}, describes in detail the
989 way that GNAT represents data, and in particular the exact set
990 of representation clauses and pragmas that is accepted.
993 @ref{e,,Standard Library Routines}, provides a listing of packages and a
994 brief description of the functionality that is provided by Ada's
995 extensive set of standard library routines as implemented by GNAT.
998 @ref{f,,The Implementation of Standard I/O}, details how the GNAT
999 implementation of the input-output facilities.
1002 @ref{10,,The GNAT Library}, is a catalog of packages that complement
1003 the Ada predefined library.
1006 @ref{11,,Interfacing to Other Languages}, describes how programs
1007 written in Ada using GNAT can be interfaced to other programming
1011 @ref{12,,Specialized Needs Annexes}, describes the GNAT implementation of all
1012 of the specialized needs annexes.
1015 @ref{13,,Implementation of Specific Ada Features}, discusses issues related
1016 to GNAT's implementation of machine code insertions, tasking, and several
1020 @ref{14,,Implementation of Ada 2012 Features}, describes the status of the
1021 GNAT implementation of the Ada 2012 language standard.
1024 @ref{15,,Obsolescent Features} documents implementation dependent features,
1025 including pragmas and attributes, which are considered obsolescent, since
1026 there are other preferred ways of achieving the same results. These
1027 obsolescent forms are retained for backwards compatibility.
1030 @ref{16,,Compatibility and Porting Guide} presents some guidelines for
1031 developing portable Ada code, describes the compatibility issues that
1032 may arise between GNAT and other Ada compilation systems (including those
1033 for Ada 83), and shows how GNAT can expedite porting applications
1034 developed in other Ada environments.
1037 @ref{1,,GNU Free Documentation License} contains the license for this document.
1040 @geindex Ada 95 Language Reference Manual
1042 @geindex Ada 2005 Language Reference Manual
1044 This reference manual assumes a basic familiarity with the Ada 95 language, as
1046 @cite{International Standard ANSI/ISO/IEC-8652:1995}.
1047 It does not require knowledge of the new features introduced by Ada 2005 or
1049 All three reference manuals are included in the GNAT documentation
1052 @node Conventions,Related Information,What This Reference Manual Contains,About This Guide
1053 @anchor{gnat_rm/about_this_guide conventions}@anchor{17}
1054 @section Conventions
1057 @geindex Conventions
1058 @geindex typographical
1060 @geindex Typographical conventions
1062 Following are examples of the typographical and graphic conventions used
1069 @code{Functions}, @code{utility program names}, @code{standard names},
1085 [optional information or parameters]
1088 Examples are described by text
1091 and then shown this way.
1095 Commands that are entered by the user are shown as preceded by a prompt string
1096 comprising the @code{$} character followed by a space.
1099 @node Related Information,,Conventions,About This Guide
1100 @anchor{gnat_rm/about_this_guide related-information}@anchor{18}
1101 @section Related Information
1104 See the following documents for further information on GNAT:
1110 @cite{GNAT User's Guide for Native Platforms},
1111 which provides information on how to use the
1112 GNAT development environment.
1115 @cite{Ada 95 Reference Manual}, the Ada 95 programming language standard.
1118 @cite{Ada 95 Annotated Reference Manual}, which is an annotated version
1119 of the Ada 95 standard. The annotations describe
1120 detailed aspects of the design decision, and in particular contain useful
1121 sections on Ada 83 compatibility.
1124 @cite{Ada 2005 Reference Manual}, the Ada 2005 programming language standard.
1127 @cite{Ada 2005 Annotated Reference Manual}, which is an annotated version
1128 of the Ada 2005 standard. The annotations describe
1129 detailed aspects of the design decision.
1132 @cite{Ada 2012 Reference Manual}, the Ada 2012 programming language standard.
1135 @cite{DEC Ada@comma{} Technical Overview and Comparison on DIGITAL Platforms},
1136 which contains specific information on compatibility between GNAT and
1140 @cite{DEC Ada@comma{} Language Reference Manual}, part number AA-PYZAB-TK, which
1141 describes in detail the pragmas and attributes provided by the DEC Ada 83
1145 @node Implementation Defined Pragmas,Implementation Defined Aspects,About This Guide,Top
1146 @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}
1147 @chapter Implementation Defined Pragmas
1150 Ada defines a set of pragmas that can be used to supply additional
1151 information to the compiler. These language defined pragmas are
1152 implemented in GNAT and work as described in the Ada Reference Manual.
1154 In addition, Ada allows implementations to define additional pragmas
1155 whose meaning is defined by the implementation. GNAT provides a number
1156 of these implementation-defined pragmas, which can be used to extend
1157 and enhance the functionality of the compiler. This section of the GNAT
1158 Reference Manual describes these additional pragmas.
1160 Note that any program using these pragmas might not be portable to other
1161 compilers (although GNAT implements this set of pragmas on all
1162 platforms). Therefore if portability to other compilers is an important
1163 consideration, the use of these pragmas should be minimized.
1166 * Pragma Abort_Defer::
1167 * Pragma Abstract_State::
1174 * Pragma Allow_Integer_Address::
1177 * Pragma Assert_And_Cut::
1178 * Pragma Assertion_Policy::
1180 * Pragma Assume_No_Invalid_Values::
1181 * Pragma Async_Readers::
1182 * Pragma Async_Writers::
1183 * Pragma Attribute_Definition::
1184 * Pragma C_Pass_By_Copy::
1186 * Pragma Check_Float_Overflow::
1187 * Pragma Check_Name::
1188 * Pragma Check_Policy::
1190 * Pragma Common_Object::
1191 * Pragma Compile_Time_Error::
1192 * Pragma Compile_Time_Warning::
1193 * Pragma Compiler_Unit::
1194 * Pragma Compiler_Unit_Warning::
1195 * Pragma Complete_Representation::
1196 * Pragma Complex_Representation::
1197 * Pragma Component_Alignment::
1198 * Pragma Constant_After_Elaboration::
1199 * Pragma Contract_Cases::
1200 * Pragma Convention_Identifier::
1201 * Pragma CPP_Class::
1202 * Pragma CPP_Constructor::
1203 * Pragma CPP_Virtual::
1204 * Pragma CPP_Vtable::
1206 * Pragma Deadline_Floor::
1207 * Pragma Default_Initial_Condition::
1209 * Pragma Debug_Policy::
1210 * Pragma Default_Scalar_Storage_Order::
1211 * Pragma Default_Storage_Pool::
1213 * Pragma Detect_Blocking::
1214 * Pragma Disable_Atomic_Synchronization::
1215 * Pragma Dispatching_Domain::
1216 * Pragma Effective_Reads::
1217 * Pragma Effective_Writes::
1218 * Pragma Elaboration_Checks::
1219 * Pragma Eliminate::
1220 * Pragma Enable_Atomic_Synchronization::
1221 * Pragma Export_Function::
1222 * Pragma Export_Object::
1223 * Pragma Export_Procedure::
1224 * Pragma Export_Value::
1225 * Pragma Export_Valued_Procedure::
1226 * Pragma Extend_System::
1227 * Pragma Extensions_Allowed::
1228 * Pragma Extensions_Visible::
1230 * Pragma External_Name_Casing::
1231 * Pragma Fast_Math::
1232 * Pragma Favor_Top_Level::
1233 * Pragma Finalize_Storage_Only::
1234 * Pragma Float_Representation::
1238 * Pragma Ignore_Pragma::
1239 * Pragma Implementation_Defined::
1240 * Pragma Implemented::
1241 * Pragma Implicit_Packing::
1242 * Pragma Import_Function::
1243 * Pragma Import_Object::
1244 * Pragma Import_Procedure::
1245 * Pragma Import_Valued_Procedure::
1246 * Pragma Independent::
1247 * Pragma Independent_Components::
1248 * Pragma Initial_Condition::
1249 * Pragma Initialize_Scalars::
1250 * Pragma Initializes::
1251 * Pragma Inline_Always::
1252 * Pragma Inline_Generic::
1253 * Pragma Interface::
1254 * Pragma Interface_Name::
1255 * Pragma Interrupt_Handler::
1256 * Pragma Interrupt_State::
1257 * Pragma Invariant::
1258 * Pragma Keep_Names::
1260 * Pragma Link_With::
1261 * Pragma Linker_Alias::
1262 * Pragma Linker_Constructor::
1263 * Pragma Linker_Destructor::
1264 * Pragma Linker_Section::
1265 * Pragma Lock_Free::
1266 * Pragma Loop_Invariant::
1267 * Pragma Loop_Optimize::
1268 * Pragma Loop_Variant::
1269 * Pragma Machine_Attribute::
1271 * Pragma Main_Storage::
1272 * Pragma Max_Queue_Length::
1274 * Pragma No_Component_Reordering::
1275 * Pragma No_Elaboration_Code_All::
1276 * Pragma No_Heap_Finalization::
1277 * Pragma No_Inline::
1278 * Pragma No_Return::
1279 * Pragma No_Run_Time::
1280 * Pragma No_Strict_Aliasing::
1281 * Pragma No_Tagged_Streams::
1282 * Pragma Normalize_Scalars::
1283 * Pragma Obsolescent::
1284 * Pragma Optimize_Alignment::
1286 * Pragma Overflow_Mode::
1287 * Pragma Overriding_Renamings::
1288 * Pragma Partition_Elaboration_Policy::
1291 * Pragma Persistent_BSS::
1294 * Pragma Postcondition::
1295 * Pragma Post_Class::
1296 * Pragma Rename_Pragma::
1298 * Pragma Precondition::
1299 * Pragma Predicate::
1300 * Pragma Predicate_Failure::
1301 * Pragma Preelaborable_Initialization::
1302 * Pragma Prefix_Exception_Messages::
1303 * Pragma Pre_Class::
1304 * Pragma Priority_Specific_Dispatching::
1306 * Pragma Profile_Warnings::
1307 * Pragma Propagate_Exceptions::
1308 * Pragma Provide_Shift_Operators::
1309 * Pragma Psect_Object::
1310 * Pragma Pure_Function::
1312 * Pragma Ravenscar::
1313 * Pragma Refined_Depends::
1314 * Pragma Refined_Global::
1315 * Pragma Refined_Post::
1316 * Pragma Refined_State::
1317 * Pragma Relative_Deadline::
1318 * Pragma Remote_Access_Type::
1319 * Pragma Restricted_Run_Time::
1320 * Pragma Restriction_Warnings::
1321 * Pragma Reviewable::
1322 * Pragma Secondary_Stack_Size::
1323 * Pragma Share_Generic::
1325 * Pragma Short_Circuit_And_Or::
1326 * Pragma Short_Descriptors::
1327 * Pragma Simple_Storage_Pool_Type::
1328 * Pragma Source_File_Name::
1329 * Pragma Source_File_Name_Project::
1330 * Pragma Source_Reference::
1331 * Pragma SPARK_Mode::
1332 * Pragma Static_Elaboration_Desired::
1333 * Pragma Stream_Convert::
1334 * Pragma Style_Checks::
1337 * Pragma Suppress_All::
1338 * Pragma Suppress_Debug_Info::
1339 * Pragma Suppress_Exception_Locations::
1340 * Pragma Suppress_Initialization::
1341 * Pragma Task_Name::
1342 * Pragma Task_Storage::
1343 * Pragma Test_Case::
1344 * Pragma Thread_Local_Storage::
1345 * Pragma Time_Slice::
1347 * Pragma Type_Invariant::
1348 * Pragma Type_Invariant_Class::
1349 * Pragma Unchecked_Union::
1350 * Pragma Unevaluated_Use_Of_Old::
1351 * Pragma Unimplemented_Unit::
1352 * Pragma Universal_Aliasing::
1353 * Pragma Universal_Data::
1354 * Pragma Unmodified::
1355 * Pragma Unreferenced::
1356 * Pragma Unreferenced_Objects::
1357 * Pragma Unreserve_All_Interrupts::
1358 * Pragma Unsuppress::
1359 * Pragma Use_VADS_Size::
1361 * Pragma Validity_Checks::
1363 * Pragma Volatile_Full_Access::
1364 * Pragma Volatile_Function::
1365 * Pragma Warning_As_Error::
1367 * Pragma Weak_External::
1368 * Pragma Wide_Character_Encoding::
1372 @node Pragma Abort_Defer,Pragma Abstract_State,,Implementation Defined Pragmas
1373 @anchor{gnat_rm/implementation_defined_pragmas pragma-abort-defer}@anchor{1b}
1374 @section Pragma Abort_Defer
1377 @geindex Deferring aborts
1385 This pragma must appear at the start of the statement sequence of a
1386 handled sequence of statements (right after the @code{begin}). It has
1387 the effect of deferring aborts for the sequence of statements (but not
1388 for the declarations or handlers, if any, associated with this statement
1391 @node Pragma Abstract_State,Pragma Ada_83,Pragma Abort_Defer,Implementation Defined Pragmas
1392 @anchor{gnat_rm/implementation_defined_pragmas pragma-abstract-state}@anchor{1c}@anchor{gnat_rm/implementation_defined_pragmas id2}@anchor{1d}
1393 @section Pragma Abstract_State
1399 pragma Abstract_State (ABSTRACT_STATE_LIST);
1401 ABSTRACT_STATE_LIST ::=
1403 | STATE_NAME_WITH_OPTIONS
1404 | (STATE_NAME_WITH_OPTIONS @{, STATE_NAME_WITH_OPTIONS@} )
1406 STATE_NAME_WITH_OPTIONS ::=
1408 | (STATE_NAME with OPTION_LIST)
1410 OPTION_LIST ::= OPTION @{, OPTION@}
1416 SIMPLE_OPTION ::= Ghost | Synchronous
1418 NAME_VALUE_OPTION ::=
1419 Part_Of => ABSTRACT_STATE
1420 | External [=> EXTERNAL_PROPERTY_LIST]
1422 EXTERNAL_PROPERTY_LIST ::=
1424 | (EXTERNAL_PROPERTY @{, EXTERNAL_PROPERTY@} )
1426 EXTERNAL_PROPERTY ::=
1427 Async_Readers [=> boolean_EXPRESSION]
1428 | Async_Writers [=> boolean_EXPRESSION]
1429 | Effective_Reads [=> boolean_EXPRESSION]
1430 | Effective_Writes [=> boolean_EXPRESSION]
1431 others => boolean_EXPRESSION
1433 STATE_NAME ::= defining_identifier
1435 ABSTRACT_STATE ::= name
1438 For the semantics of this pragma, see the entry for aspect @code{Abstract_State} in
1439 the SPARK 2014 Reference Manual, section 7.1.4.
1441 @node Pragma Ada_83,Pragma Ada_95,Pragma Abstract_State,Implementation Defined Pragmas
1442 @anchor{gnat_rm/implementation_defined_pragmas pragma-ada-83}@anchor{1e}
1443 @section Pragma Ada_83
1452 A configuration pragma that establishes Ada 83 mode for the unit to
1453 which it applies, regardless of the mode set by the command line
1454 switches. In Ada 83 mode, GNAT attempts to be as compatible with
1455 the syntax and semantics of Ada 83, as defined in the original Ada
1456 83 Reference Manual as possible. In particular, the keywords added by Ada 95
1457 and Ada 2005 are not recognized, optional package bodies are allowed,
1458 and generics may name types with unknown discriminants without using
1459 the @code{(<>)} notation. In addition, some but not all of the additional
1460 restrictions of Ada 83 are enforced.
1462 Ada 83 mode is intended for two purposes. Firstly, it allows existing
1463 Ada 83 code to be compiled and adapted to GNAT with less effort.
1464 Secondly, it aids in keeping code backwards compatible with Ada 83.
1465 However, there is no guarantee that code that is processed correctly
1466 by GNAT in Ada 83 mode will in fact compile and execute with an Ada
1467 83 compiler, since GNAT does not enforce all the additional checks
1470 @node Pragma Ada_95,Pragma Ada_05,Pragma Ada_83,Implementation Defined Pragmas
1471 @anchor{gnat_rm/implementation_defined_pragmas pragma-ada-95}@anchor{1f}
1472 @section Pragma Ada_95
1481 A configuration pragma that establishes Ada 95 mode for the unit to which
1482 it applies, regardless of the mode set by the command line switches.
1483 This mode is set automatically for the @code{Ada} and @code{System}
1484 packages and their children, so you need not specify it in these
1485 contexts. This pragma is useful when writing a reusable component that
1486 itself uses Ada 95 features, but which is intended to be usable from
1487 either Ada 83 or Ada 95 programs.
1489 @node Pragma Ada_05,Pragma Ada_2005,Pragma Ada_95,Implementation Defined Pragmas
1490 @anchor{gnat_rm/implementation_defined_pragmas pragma-ada-05}@anchor{20}
1491 @section Pragma Ada_05
1498 pragma Ada_05 (local_NAME);
1501 A configuration pragma that establishes Ada 2005 mode for the unit to which
1502 it applies, regardless of the mode set by the command line switches.
1503 This pragma is useful when writing a reusable component that
1504 itself uses Ada 2005 features, but which is intended to be usable from
1505 either Ada 83 or Ada 95 programs.
1507 The one argument form (which is not a configuration pragma)
1508 is used for managing the transition from
1509 Ada 95 to Ada 2005 in the run-time library. If an entity is marked
1510 as Ada_2005 only, then referencing the entity in Ada_83 or Ada_95
1511 mode will generate a warning. In addition, in Ada_83 or Ada_95
1512 mode, a preference rule is established which does not choose
1513 such an entity unless it is unambiguously specified. This avoids
1514 extra subprograms marked this way from generating ambiguities in
1515 otherwise legal pre-Ada_2005 programs. The one argument form is
1516 intended for exclusive use in the GNAT run-time library.
1518 @node Pragma Ada_2005,Pragma Ada_12,Pragma Ada_05,Implementation Defined Pragmas
1519 @anchor{gnat_rm/implementation_defined_pragmas pragma-ada-2005}@anchor{21}
1520 @section Pragma Ada_2005
1529 This configuration pragma is a synonym for pragma Ada_05 and has the
1530 same syntax and effect.
1532 @node Pragma Ada_12,Pragma Ada_2012,Pragma Ada_2005,Implementation Defined Pragmas
1533 @anchor{gnat_rm/implementation_defined_pragmas pragma-ada-12}@anchor{22}
1534 @section Pragma Ada_12
1541 pragma Ada_12 (local_NAME);
1544 A configuration pragma that establishes Ada 2012 mode for the unit to which
1545 it applies, regardless of the mode set by the command line switches.
1546 This mode is set automatically for the @code{Ada} and @code{System}
1547 packages and their children, so you need not specify it in these
1548 contexts. This pragma is useful when writing a reusable component that
1549 itself uses Ada 2012 features, but which is intended to be usable from
1550 Ada 83, Ada 95, or Ada 2005 programs.
1552 The one argument form, which is not a configuration pragma,
1553 is used for managing the transition from Ada
1554 2005 to Ada 2012 in the run-time library. If an entity is marked
1555 as Ada_2012 only, then referencing the entity in any pre-Ada_2012
1556 mode will generate a warning. In addition, in any pre-Ada_2012
1557 mode, a preference rule is established which does not choose
1558 such an entity unless it is unambiguously specified. This avoids
1559 extra subprograms marked this way from generating ambiguities in
1560 otherwise legal pre-Ada_2012 programs. The one argument form is
1561 intended for exclusive use in the GNAT run-time library.
1563 @node Pragma Ada_2012,Pragma Allow_Integer_Address,Pragma Ada_12,Implementation Defined Pragmas
1564 @anchor{gnat_rm/implementation_defined_pragmas pragma-ada-2012}@anchor{23}
1565 @section Pragma Ada_2012
1574 This configuration pragma is a synonym for pragma Ada_12 and has the
1575 same syntax and effect.
1577 @node Pragma Allow_Integer_Address,Pragma Annotate,Pragma Ada_2012,Implementation Defined Pragmas
1578 @anchor{gnat_rm/implementation_defined_pragmas pragma-allow-integer-address}@anchor{24}
1579 @section Pragma Allow_Integer_Address
1585 pragma Allow_Integer_Address;
1588 In almost all versions of GNAT, @code{System.Address} is a private
1589 type in accordance with the implementation advice in the RM. This
1590 means that integer values,
1591 in particular integer literals, are not allowed as address values.
1592 If the configuration pragma
1593 @code{Allow_Integer_Address} is given, then integer expressions may
1594 be used anywhere a value of type @code{System.Address} is required.
1595 The effect is to introduce an implicit unchecked conversion from the
1596 integer value to type @code{System.Address}. The reverse case of using
1597 an address where an integer type is required is handled analogously.
1598 The following example compiles without errors:
1601 pragma Allow_Integer_Address;
1602 with System; use System;
1603 package AddrAsInt is
1606 for X'Address use 16#1240#;
1607 for Y use at 16#3230#;
1608 m : Address := 16#4000#;
1609 n : constant Address := 4000;
1610 p : constant Address := Address (X + Y);
1611 v : Integer := y'Address;
1612 w : constant Integer := Integer (Y'Address);
1613 type R is new integer;
1616 for Z'Address use RR;
1620 Note that pragma @code{Allow_Integer_Address} is ignored if @code{System.Address}
1621 is not a private type. In implementations of @code{GNAT} where
1622 System.Address is a visible integer type,
1623 this pragma serves no purpose but is ignored
1624 rather than rejected to allow common sets of sources to be used
1625 in the two situations.
1627 @node Pragma Annotate,Pragma Assert,Pragma Allow_Integer_Address,Implementation Defined Pragmas
1628 @anchor{gnat_rm/implementation_defined_pragmas pragma-annotate}@anchor{25}@anchor{gnat_rm/implementation_defined_pragmas id3}@anchor{26}
1629 @section Pragma Annotate
1635 pragma Annotate (IDENTIFIER [, IDENTIFIER @{, ARG@}] [, entity => local_NAME]);
1637 ARG ::= NAME | EXPRESSION
1640 This pragma is used to annotate programs. IDENTIFIER identifies
1641 the type of annotation. GNAT verifies that it is an identifier, but does
1642 not otherwise analyze it. The second optional identifier is also left
1643 unanalyzed, and by convention is used to control the action of the tool to
1644 which the annotation is addressed. The remaining ARG arguments
1645 can be either string literals or more generally expressions.
1646 String literals are assumed to be either of type
1647 @code{Standard.String} or else @code{Wide_String} or @code{Wide_Wide_String}
1648 depending on the character literals they contain.
1649 All other kinds of arguments are analyzed as expressions, and must be
1650 unambiguous. The last argument if present must have the identifier
1651 @code{Entity} and GNAT verifies that a local name is given.
1653 The analyzed pragma is retained in the tree, but not otherwise processed
1654 by any part of the GNAT compiler, except to generate corresponding note
1655 lines in the generated ALI file. For the format of these note lines, see
1656 the compiler source file lib-writ.ads. This pragma is intended for use by
1657 external tools, including ASIS. The use of pragma Annotate does not
1658 affect the compilation process in any way. This pragma may be used as
1659 a configuration pragma.
1661 @node Pragma Assert,Pragma Assert_And_Cut,Pragma Annotate,Implementation Defined Pragmas
1662 @anchor{gnat_rm/implementation_defined_pragmas pragma-assert}@anchor{27}
1663 @section Pragma Assert
1671 [, string_EXPRESSION]);
1674 The effect of this pragma depends on whether the corresponding command
1675 line switch is set to activate assertions. The pragma expands into code
1676 equivalent to the following:
1679 if assertions-enabled then
1680 if not boolean_EXPRESSION then
1681 System.Assertions.Raise_Assert_Failure
1682 (string_EXPRESSION);
1687 The string argument, if given, is the message that will be associated
1688 with the exception occurrence if the exception is raised. If no second
1689 argument is given, the default message is @code{file}:@code{nnn},
1690 where @code{file} is the name of the source file containing the assert,
1691 and @code{nnn} is the line number of the assert.
1693 Note that, as with the @code{if} statement to which it is equivalent, the
1694 type of the expression is either @code{Standard.Boolean}, or any type derived
1695 from this standard type.
1697 Assert checks can be either checked or ignored. By default they are ignored.
1698 They will be checked if either the command line switch @emph{-gnata} is
1699 used, or if an @code{Assertion_Policy} or @code{Check_Policy} pragma is used
1700 to enable @code{Assert_Checks}.
1702 If assertions are ignored, then there
1703 is no run-time effect (and in particular, any side effects from the
1704 expression will not occur at run time). (The expression is still
1705 analyzed at compile time, and may cause types to be frozen if they are
1706 mentioned here for the first time).
1708 If assertions are checked, then the given expression is tested, and if
1709 it is @code{False} then @code{System.Assertions.Raise_Assert_Failure} is called
1710 which results in the raising of @code{Assert_Failure} with the given message.
1712 You should generally avoid side effects in the expression arguments of
1713 this pragma, because these side effects will turn on and off with the
1714 setting of the assertions mode, resulting in assertions that have an
1715 effect on the program. However, the expressions are analyzed for
1716 semantic correctness whether or not assertions are enabled, so turning
1717 assertions on and off cannot affect the legality of a program.
1719 Note that the implementation defined policy @code{DISABLE}, given in a
1720 pragma @code{Assertion_Policy}, can be used to suppress this semantic analysis.
1722 Note: this is a standard language-defined pragma in versions
1723 of Ada from 2005 on. In GNAT, it is implemented in all versions
1724 of Ada, and the DISABLE policy is an implementation-defined
1727 @node Pragma Assert_And_Cut,Pragma Assertion_Policy,Pragma Assert,Implementation Defined Pragmas
1728 @anchor{gnat_rm/implementation_defined_pragmas pragma-assert-and-cut}@anchor{28}
1729 @section Pragma Assert_And_Cut
1735 pragma Assert_And_Cut (
1737 [, string_EXPRESSION]);
1740 The effect of this pragma is identical to that of pragma @code{Assert},
1741 except that in an @code{Assertion_Policy} pragma, the identifier
1742 @code{Assert_And_Cut} is used to control whether it is ignored or checked
1745 The intention is that this be used within a subprogram when the
1746 given test expresion sums up all the work done so far in the
1747 subprogram, so that the rest of the subprogram can be verified
1748 (informally or formally) using only the entry preconditions,
1749 and the expression in this pragma. This allows dividing up
1750 a subprogram into sections for the purposes of testing or
1751 formal verification. The pragma also serves as useful
1754 @node Pragma Assertion_Policy,Pragma Assume,Pragma Assert_And_Cut,Implementation Defined Pragmas
1755 @anchor{gnat_rm/implementation_defined_pragmas pragma-assertion-policy}@anchor{29}
1756 @section Pragma Assertion_Policy
1762 pragma Assertion_Policy (CHECK | DISABLE | IGNORE);
1764 pragma Assertion_Policy (
1765 ASSERTION_KIND => POLICY_IDENTIFIER
1766 @{, ASSERTION_KIND => POLICY_IDENTIFIER@});
1768 ASSERTION_KIND ::= RM_ASSERTION_KIND | ID_ASSERTION_KIND
1770 RM_ASSERTION_KIND ::= Assert |
1778 Type_Invariant'Class
1780 ID_ASSERTION_KIND ::= Assertions |
1793 Statement_Assertions
1795 POLICY_IDENTIFIER ::= Check | Disable | Ignore | Suppressible
1798 This is a standard Ada 2012 pragma that is available as an
1799 implementation-defined pragma in earlier versions of Ada.
1800 The assertion kinds @code{RM_ASSERTION_KIND} are those defined in
1801 the Ada standard. The assertion kinds @code{ID_ASSERTION_KIND}
1802 are implementation defined additions recognized by the GNAT compiler.
1804 The pragma applies in both cases to pragmas and aspects with matching
1805 names, e.g. @code{Pre} applies to the Pre aspect, and @code{Precondition}
1806 applies to both the @code{Precondition} pragma
1807 and the aspect @code{Precondition}. Note that the identifiers for
1808 pragmas Pre_Class and Post_Class are Pre'Class and Post'Class (not
1809 Pre_Class and Post_Class), since these pragmas are intended to be
1810 identical to the corresponding aspects).
1812 If the policy is @code{CHECK}, then assertions are enabled, i.e.
1813 the corresponding pragma or aspect is activated.
1814 If the policy is @code{IGNORE}, then assertions are ignored, i.e.
1815 the corresponding pragma or aspect is deactivated.
1816 This pragma overrides the effect of the @emph{-gnata} switch on the
1818 If the policy is @code{SUPPRESSIBLE}, then assertions are enabled by default,
1819 however, if the @emph{-gnatp} switch is specified all assertions are ignored.
1821 The implementation defined policy @code{DISABLE} is like
1822 @code{IGNORE} except that it completely disables semantic
1823 checking of the corresponding pragma or aspect. This is
1824 useful when the pragma or aspect argument references subprograms
1825 in a with'ed package which is replaced by a dummy package
1826 for the final build.
1828 The implementation defined assertion kind @code{Assertions} applies to all
1829 assertion kinds. The form with no assertion kind given implies this
1830 choice, so it applies to all assertion kinds (RM defined, and
1831 implementation defined).
1833 The implementation defined assertion kind @code{Statement_Assertions}
1834 applies to @code{Assert}, @code{Assert_And_Cut},
1835 @code{Assume}, @code{Loop_Invariant}, and @code{Loop_Variant}.
1837 @node Pragma Assume,Pragma Assume_No_Invalid_Values,Pragma Assertion_Policy,Implementation Defined Pragmas
1838 @anchor{gnat_rm/implementation_defined_pragmas pragma-assume}@anchor{2a}
1839 @section Pragma Assume
1847 [, string_EXPRESSION]);
1850 The effect of this pragma is identical to that of pragma @code{Assert},
1851 except that in an @code{Assertion_Policy} pragma, the identifier
1852 @code{Assume} is used to control whether it is ignored or checked
1855 The intention is that this be used for assumptions about the
1856 external environment. So you cannot expect to verify formally
1857 or informally that the condition is met, this must be
1858 established by examining things outside the program itself.
1859 For example, we may have code that depends on the size of
1860 @code{Long_Long_Integer} being at least 64. So we could write:
1863 pragma Assume (Long_Long_Integer'Size >= 64);
1866 This assumption cannot be proved from the program itself,
1867 but it acts as a useful run-time check that the assumption
1868 is met, and documents the need to ensure that it is met by
1869 reference to information outside the program.
1871 @node Pragma Assume_No_Invalid_Values,Pragma Async_Readers,Pragma Assume,Implementation Defined Pragmas
1872 @anchor{gnat_rm/implementation_defined_pragmas pragma-assume-no-invalid-values}@anchor{2b}
1873 @section Pragma Assume_No_Invalid_Values
1876 @geindex Invalid representations
1878 @geindex Invalid values
1883 pragma Assume_No_Invalid_Values (On | Off);
1886 This is a configuration pragma that controls the assumptions made by the
1887 compiler about the occurrence of invalid representations (invalid values)
1890 The default behavior (corresponding to an Off argument for this pragma), is
1891 to assume that values may in general be invalid unless the compiler can
1892 prove they are valid. Consider the following example:
1895 V1 : Integer range 1 .. 10;
1896 V2 : Integer range 11 .. 20;
1898 for J in V2 .. V1 loop
1903 if V1 and V2 have valid values, then the loop is known at compile
1904 time not to execute since the lower bound must be greater than the
1905 upper bound. However in default mode, no such assumption is made,
1906 and the loop may execute. If @code{Assume_No_Invalid_Values (On)}
1907 is given, the compiler will assume that any occurrence of a variable
1908 other than in an explicit @code{'Valid} test always has a valid
1909 value, and the loop above will be optimized away.
1911 The use of @code{Assume_No_Invalid_Values (On)} is appropriate if
1912 you know your code is free of uninitialized variables and other
1913 possible sources of invalid representations, and may result in
1914 more efficient code. A program that accesses an invalid representation
1915 with this pragma in effect is erroneous, so no guarantees can be made
1918 It is peculiar though permissible to use this pragma in conjunction
1919 with validity checking (-gnatVa). In such cases, accessing invalid
1920 values will generally give an exception, though formally the program
1921 is erroneous so there are no guarantees that this will always be the
1922 case, and it is recommended that these two options not be used together.
1924 @node Pragma Async_Readers,Pragma Async_Writers,Pragma Assume_No_Invalid_Values,Implementation Defined Pragmas
1925 @anchor{gnat_rm/implementation_defined_pragmas pragma-async-readers}@anchor{2c}@anchor{gnat_rm/implementation_defined_pragmas id4}@anchor{2d}
1926 @section Pragma Async_Readers
1932 pragma Asynch_Readers [ (boolean_EXPRESSION) ];
1935 For the semantics of this pragma, see the entry for aspect @code{Async_Readers} in
1936 the SPARK 2014 Reference Manual, section 7.1.2.
1938 @node Pragma Async_Writers,Pragma Attribute_Definition,Pragma Async_Readers,Implementation Defined Pragmas
1939 @anchor{gnat_rm/implementation_defined_pragmas id5}@anchor{2e}@anchor{gnat_rm/implementation_defined_pragmas pragma-async-writers}@anchor{2f}
1940 @section Pragma Async_Writers
1946 pragma Asynch_Writers [ (boolean_EXPRESSION) ];
1949 For the semantics of this pragma, see the entry for aspect @code{Async_Writers} in
1950 the SPARK 2014 Reference Manual, section 7.1.2.
1952 @node Pragma Attribute_Definition,Pragma C_Pass_By_Copy,Pragma Async_Writers,Implementation Defined Pragmas
1953 @anchor{gnat_rm/implementation_defined_pragmas pragma-attribute-definition}@anchor{30}
1954 @section Pragma Attribute_Definition
1960 pragma Attribute_Definition
1961 ([Attribute =>] ATTRIBUTE_DESIGNATOR,
1962 [Entity =>] LOCAL_NAME,
1963 [Expression =>] EXPRESSION | NAME);
1966 If @code{Attribute} is a known attribute name, this pragma is equivalent to
1967 the attribute definition clause:
1970 for Entity'Attribute use Expression;
1973 If @code{Attribute} is not a recognized attribute name, the pragma is
1974 ignored, and a warning is emitted. This allows source
1975 code to be written that takes advantage of some new attribute, while remaining
1976 compilable with earlier compilers.
1978 @node Pragma C_Pass_By_Copy,Pragma Check,Pragma Attribute_Definition,Implementation Defined Pragmas
1979 @anchor{gnat_rm/implementation_defined_pragmas pragma-c-pass-by-copy}@anchor{31}
1980 @section Pragma C_Pass_By_Copy
1983 @geindex Passing by copy
1988 pragma C_Pass_By_Copy
1989 ([Max_Size =>] static_integer_EXPRESSION);
1992 Normally the default mechanism for passing C convention records to C
1993 convention subprograms is to pass them by reference, as suggested by RM
1994 B.3(69). Use the configuration pragma @code{C_Pass_By_Copy} to change
1995 this default, by requiring that record formal parameters be passed by
1996 copy if all of the following conditions are met:
2002 The size of the record type does not exceed the value specified for
2006 The record type has @code{Convention C}.
2009 The formal parameter has this record type, and the subprogram has a
2010 foreign (non-Ada) convention.
2013 If these conditions are met the argument is passed by copy; i.e., in a
2014 manner consistent with what C expects if the corresponding formal in the
2015 C prototype is a struct (rather than a pointer to a struct).
2017 You can also pass records by copy by specifying the convention
2018 @code{C_Pass_By_Copy} for the record type, or by using the extended
2019 @code{Import} and @code{Export} pragmas, which allow specification of
2020 passing mechanisms on a parameter by parameter basis.
2022 @node Pragma Check,Pragma Check_Float_Overflow,Pragma C_Pass_By_Copy,Implementation Defined Pragmas
2023 @anchor{gnat_rm/implementation_defined_pragmas pragma-check}@anchor{32}
2024 @section Pragma Check
2029 @geindex Named assertions
2035 [Name =>] CHECK_KIND,
2036 [Check =>] Boolean_EXPRESSION
2037 [, [Message =>] string_EXPRESSION] );
2039 CHECK_KIND ::= IDENTIFIER |
2042 Type_Invariant'Class |
2046 This pragma is similar to the predefined pragma @code{Assert} except that an
2047 extra identifier argument is present. In conjunction with pragma
2048 @code{Check_Policy}, this can be used to define groups of assertions that can
2049 be independently controlled. The identifier @code{Assertion} is special, it
2050 refers to the normal set of pragma @code{Assert} statements.
2052 Checks introduced by this pragma are normally deactivated by default. They can
2053 be activated either by the command line option @emph{-gnata}, which turns on
2054 all checks, or individually controlled using pragma @code{Check_Policy}.
2056 The identifiers @code{Assertions} and @code{Statement_Assertions} are not
2057 permitted as check kinds, since this would cause confusion with the use
2058 of these identifiers in @code{Assertion_Policy} and @code{Check_Policy}
2059 pragmas, where they are used to refer to sets of assertions.
2061 @node Pragma Check_Float_Overflow,Pragma Check_Name,Pragma Check,Implementation Defined Pragmas
2062 @anchor{gnat_rm/implementation_defined_pragmas pragma-check-float-overflow}@anchor{33}
2063 @section Pragma Check_Float_Overflow
2066 @geindex Floating-point overflow
2071 pragma Check_Float_Overflow;
2074 In Ada, the predefined floating-point types (@code{Short_Float},
2075 @code{Float}, @code{Long_Float}, @code{Long_Long_Float}) are
2076 defined to be @emph{unconstrained}. This means that even though each
2077 has a well-defined base range, an operation that delivers a result
2078 outside this base range is not required to raise an exception.
2079 This implementation permission accommodates the notion
2080 of infinities in IEEE floating-point, and corresponds to the
2081 efficient execution mode on most machines. GNAT will not raise
2082 overflow exceptions on these machines; instead it will generate
2083 infinities and NaN's as defined in the IEEE standard.
2085 Generating infinities, although efficient, is not always desirable.
2086 Often the preferable approach is to check for overflow, even at the
2087 (perhaps considerable) expense of run-time performance.
2088 This can be accomplished by defining your own constrained floating-point subtypes -- i.e., by supplying explicit
2089 range constraints -- and indeed such a subtype
2090 can have the same base range as its base type. For example:
2093 subtype My_Float is Float range Float'Range;
2096 Here @code{My_Float} has the same range as
2097 @code{Float} but is constrained, so operations on
2098 @code{My_Float} values will be checked for overflow
2101 This style will achieve the desired goal, but
2102 it is often more convenient to be able to simply use
2103 the standard predefined floating-point types as long
2104 as overflow checking could be guaranteed.
2105 The @code{Check_Float_Overflow}
2106 configuration pragma achieves this effect. If a unit is compiled
2107 subject to this configuration pragma, then all operations
2108 on predefined floating-point types including operations on
2109 base types of these floating-point types will be treated as
2110 though those types were constrained, and overflow checks
2111 will be generated. The @code{Constraint_Error}
2112 exception is raised if the result is out of range.
2114 This mode can also be set by use of the compiler
2115 switch @emph{-gnateF}.
2117 @node Pragma Check_Name,Pragma Check_Policy,Pragma Check_Float_Overflow,Implementation Defined Pragmas
2118 @anchor{gnat_rm/implementation_defined_pragmas pragma-check-name}@anchor{34}
2119 @section Pragma Check_Name
2122 @geindex Defining check names
2124 @geindex Check names
2130 pragma Check_Name (check_name_IDENTIFIER);
2133 This is a configuration pragma that defines a new implementation
2134 defined check name (unless IDENTIFIER matches one of the predefined
2135 check names, in which case the pragma has no effect). Check names
2136 are global to a partition, so if two or more configuration pragmas
2137 are present in a partition mentioning the same name, only one new
2138 check name is introduced.
2140 An implementation defined check name introduced with this pragma may
2141 be used in only three contexts: @code{pragma Suppress},
2142 @code{pragma Unsuppress},
2143 and as the prefix of a @code{Check_Name'Enabled} attribute reference. For
2144 any of these three cases, the check name must be visible. A check
2145 name is visible if it is in the configuration pragmas applying to
2146 the current unit, or if it appears at the start of any unit that
2147 is part of the dependency set of the current unit (e.g., units that
2148 are mentioned in @code{with} clauses).
2150 Check names introduced by this pragma are subject to control by compiler
2151 switches (in particular -gnatp) in the usual manner.
2153 @node Pragma Check_Policy,Pragma Comment,Pragma Check_Name,Implementation Defined Pragmas
2154 @anchor{gnat_rm/implementation_defined_pragmas pragma-check-policy}@anchor{35}
2155 @section Pragma Check_Policy
2158 @geindex Controlling assertions
2163 @geindex Check pragma control
2165 @geindex Named assertions
2171 ([Name =>] CHECK_KIND,
2172 [Policy =>] POLICY_IDENTIFIER);
2174 pragma Check_Policy (
2175 CHECK_KIND => POLICY_IDENTIFIER
2176 @{, CHECK_KIND => POLICY_IDENTIFIER@});
2178 ASSERTION_KIND ::= RM_ASSERTION_KIND | ID_ASSERTION_KIND
2180 CHECK_KIND ::= IDENTIFIER |
2183 Type_Invariant'Class |
2186 The identifiers Name and Policy are not allowed as CHECK_KIND values. This
2187 avoids confusion between the two possible syntax forms for this pragma.
2189 POLICY_IDENTIFIER ::= ON | OFF | CHECK | DISABLE | IGNORE
2192 This pragma is used to set the checking policy for assertions (specified
2193 by aspects or pragmas), the @code{Debug} pragma, or additional checks
2194 to be checked using the @code{Check} pragma. It may appear either as
2195 a configuration pragma, or within a declarative part of package. In the
2196 latter case, it applies from the point where it appears to the end of
2197 the declarative region (like pragma @code{Suppress}).
2199 The @code{Check_Policy} pragma is similar to the
2200 predefined @code{Assertion_Policy} pragma,
2201 and if the check kind corresponds to one of the assertion kinds that
2202 are allowed by @code{Assertion_Policy}, then the effect is identical.
2204 If the first argument is Debug, then the policy applies to Debug pragmas,
2205 disabling their effect if the policy is @code{OFF}, @code{DISABLE}, or
2206 @code{IGNORE}, and allowing them to execute with normal semantics if
2207 the policy is @code{ON} or @code{CHECK}. In addition if the policy is
2208 @code{DISABLE}, then the procedure call in @code{Debug} pragmas will
2209 be totally ignored and not analyzed semantically.
2211 Finally the first argument may be some other identifier than the above
2212 possibilities, in which case it controls a set of named assertions
2213 that can be checked using pragma @code{Check}. For example, if the pragma:
2216 pragma Check_Policy (Critical_Error, OFF);
2219 is given, then subsequent @code{Check} pragmas whose first argument is also
2220 @code{Critical_Error} will be disabled.
2222 The check policy is @code{OFF} to turn off corresponding checks, and @code{ON}
2223 to turn on corresponding checks. The default for a set of checks for which no
2224 @code{Check_Policy} is given is @code{OFF} unless the compiler switch
2225 @emph{-gnata} is given, which turns on all checks by default.
2227 The check policy settings @code{CHECK} and @code{IGNORE} are recognized
2228 as synonyms for @code{ON} and @code{OFF}. These synonyms are provided for
2229 compatibility with the standard @code{Assertion_Policy} pragma. The check
2230 policy setting @code{DISABLE} causes the second argument of a corresponding
2231 @code{Check} pragma to be completely ignored and not analyzed.
2233 @node Pragma Comment,Pragma Common_Object,Pragma Check_Policy,Implementation Defined Pragmas
2234 @anchor{gnat_rm/implementation_defined_pragmas pragma-comment}@anchor{36}
2235 @section Pragma Comment
2241 pragma Comment (static_string_EXPRESSION);
2244 This is almost identical in effect to pragma @code{Ident}. It allows the
2245 placement of a comment into the object file and hence into the
2246 executable file if the operating system permits such usage. The
2247 difference is that @code{Comment}, unlike @code{Ident}, has
2248 no limitations on placement of the pragma (it can be placed
2249 anywhere in the main source unit), and if more than one pragma
2250 is used, all comments are retained.
2252 @node Pragma Common_Object,Pragma Compile_Time_Error,Pragma Comment,Implementation Defined Pragmas
2253 @anchor{gnat_rm/implementation_defined_pragmas pragma-common-object}@anchor{37}
2254 @section Pragma Common_Object
2260 pragma Common_Object (
2261 [Internal =>] LOCAL_NAME
2262 [, [External =>] EXTERNAL_SYMBOL]
2263 [, [Size =>] EXTERNAL_SYMBOL] );
2267 | static_string_EXPRESSION
2270 This pragma enables the shared use of variables stored in overlaid
2271 linker areas corresponding to the use of @code{COMMON}
2272 in Fortran. The single
2273 object @code{LOCAL_NAME} is assigned to the area designated by
2274 the @code{External} argument.
2275 You may define a record to correspond to a series
2276 of fields. The @code{Size} argument
2277 is syntax checked in GNAT, but otherwise ignored.
2279 @code{Common_Object} is not supported on all platforms. If no
2280 support is available, then the code generator will issue a message
2281 indicating that the necessary attribute for implementation of this
2282 pragma is not available.
2284 @node Pragma Compile_Time_Error,Pragma Compile_Time_Warning,Pragma Common_Object,Implementation Defined Pragmas
2285 @anchor{gnat_rm/implementation_defined_pragmas pragma-compile-time-error}@anchor{38}
2286 @section Pragma Compile_Time_Error
2292 pragma Compile_Time_Error
2293 (boolean_EXPRESSION, static_string_EXPRESSION);
2296 This pragma can be used to generate additional compile time
2298 is particularly useful in generics, where errors can be issued for
2299 specific problematic instantiations. The first parameter is a boolean
2300 expression. The pragma is effective only if the value of this expression
2301 is known at compile time, and has the value True. The set of expressions
2302 whose values are known at compile time includes all static boolean
2303 expressions, and also other values which the compiler can determine
2304 at compile time (e.g., the size of a record type set by an explicit
2305 size representation clause, or the value of a variable which was
2306 initialized to a constant and is known not to have been modified).
2307 If these conditions are met, an error message is generated using
2308 the value given as the second argument. This string value may contain
2309 embedded ASCII.LF characters to break the message into multiple lines.
2311 @node Pragma Compile_Time_Warning,Pragma Compiler_Unit,Pragma Compile_Time_Error,Implementation Defined Pragmas
2312 @anchor{gnat_rm/implementation_defined_pragmas pragma-compile-time-warning}@anchor{39}
2313 @section Pragma Compile_Time_Warning
2319 pragma Compile_Time_Warning
2320 (boolean_EXPRESSION, static_string_EXPRESSION);
2323 Same as pragma Compile_Time_Error, except a warning is issued instead
2324 of an error message. Note that if this pragma is used in a package that
2325 is with'ed by a client, the client will get the warning even though it
2326 is issued by a with'ed package (normally warnings in with'ed units are
2327 suppressed, but this is a special exception to that rule).
2329 One typical use is within a generic where compile time known characteristics
2330 of formal parameters are tested, and warnings given appropriately. Another use
2331 with a first parameter of True is to warn a client about use of a package,
2332 for example that it is not fully implemented.
2334 @node Pragma Compiler_Unit,Pragma Compiler_Unit_Warning,Pragma Compile_Time_Warning,Implementation Defined Pragmas
2335 @anchor{gnat_rm/implementation_defined_pragmas pragma-compiler-unit}@anchor{3a}
2336 @section Pragma Compiler_Unit
2342 pragma Compiler_Unit;
2345 This pragma is obsolete. It is equivalent to Compiler_Unit_Warning. It is
2346 retained so that old versions of the GNAT run-time that use this pragma can
2347 be compiled with newer versions of the compiler.
2349 @node Pragma Compiler_Unit_Warning,Pragma Complete_Representation,Pragma Compiler_Unit,Implementation Defined Pragmas
2350 @anchor{gnat_rm/implementation_defined_pragmas pragma-compiler-unit-warning}@anchor{3b}
2351 @section Pragma Compiler_Unit_Warning
2357 pragma Compiler_Unit_Warning;
2360 This pragma is intended only for internal use in the GNAT run-time library.
2361 It indicates that the unit is used as part of the compiler build. The effect
2362 is to generate warnings for the use of constructs (for example, conditional
2363 expressions) that would cause trouble when bootstrapping using an older
2364 version of GNAT. For the exact list of restrictions, see the compiler sources
2365 and references to Check_Compiler_Unit.
2367 @node Pragma Complete_Representation,Pragma Complex_Representation,Pragma Compiler_Unit_Warning,Implementation Defined Pragmas
2368 @anchor{gnat_rm/implementation_defined_pragmas pragma-complete-representation}@anchor{3c}
2369 @section Pragma Complete_Representation
2375 pragma Complete_Representation;
2378 This pragma must appear immediately within a record representation
2379 clause. Typical placements are before the first component clause
2380 or after the last component clause. The effect is to give an error
2381 message if any component is missing a component clause. This pragma
2382 may be used to ensure that a record representation clause is
2383 complete, and that this invariant is maintained if fields are
2384 added to the record in the future.
2386 @node Pragma Complex_Representation,Pragma Component_Alignment,Pragma Complete_Representation,Implementation Defined Pragmas
2387 @anchor{gnat_rm/implementation_defined_pragmas pragma-complex-representation}@anchor{3d}
2388 @section Pragma Complex_Representation
2394 pragma Complex_Representation
2395 ([Entity =>] LOCAL_NAME);
2398 The @code{Entity} argument must be the name of a record type which has
2399 two fields of the same floating-point type. The effect of this pragma is
2400 to force gcc to use the special internal complex representation form for
2401 this record, which may be more efficient. Note that this may result in
2402 the code for this type not conforming to standard ABI (application
2403 binary interface) requirements for the handling of record types. For
2404 example, in some environments, there is a requirement for passing
2405 records by pointer, and the use of this pragma may result in passing
2406 this type in floating-point registers.
2408 @node Pragma Component_Alignment,Pragma Constant_After_Elaboration,Pragma Complex_Representation,Implementation Defined Pragmas
2409 @anchor{gnat_rm/implementation_defined_pragmas pragma-component-alignment}@anchor{3e}
2410 @section Pragma Component_Alignment
2413 @geindex Alignments of components
2415 @geindex Pragma Component_Alignment
2420 pragma Component_Alignment (
2421 [Form =>] ALIGNMENT_CHOICE
2422 [, [Name =>] type_LOCAL_NAME]);
2424 ALIGNMENT_CHOICE ::=
2431 Specifies the alignment of components in array or record types.
2432 The meaning of the @code{Form} argument is as follows:
2436 @geindex Component_Size (in pragma Component_Alignment)
2442 @item @emph{Component_Size}
2444 Aligns scalar components and subcomponents of the array or record type
2445 on boundaries appropriate to their inherent size (naturally
2446 aligned). For example, 1-byte components are aligned on byte boundaries,
2447 2-byte integer components are aligned on 2-byte boundaries, 4-byte
2448 integer components are aligned on 4-byte boundaries and so on. These
2449 alignment rules correspond to the normal rules for C compilers on all
2450 machines except the VAX.
2452 @geindex Component_Size_4 (in pragma Component_Alignment)
2454 @item @emph{Component_Size_4}
2456 Naturally aligns components with a size of four or fewer
2457 bytes. Components that are larger than 4 bytes are placed on the next
2460 @geindex Storage_Unit (in pragma Component_Alignment)
2462 @item @emph{Storage_Unit}
2464 Specifies that array or record components are byte aligned, i.e.,
2465 aligned on boundaries determined by the value of the constant
2466 @code{System.Storage_Unit}.
2468 @geindex Default (in pragma Component_Alignment)
2470 @item @emph{Default}
2472 Specifies that array or record components are aligned on default
2473 boundaries, appropriate to the underlying hardware or operating system or
2474 both. The @code{Default} choice is the same as @code{Component_Size} (natural
2478 If the @code{Name} parameter is present, @code{type_LOCAL_NAME} must
2479 refer to a local record or array type, and the specified alignment
2480 choice applies to the specified type. The use of
2481 @code{Component_Alignment} together with a pragma @code{Pack} causes the
2482 @code{Component_Alignment} pragma to be ignored. The use of
2483 @code{Component_Alignment} together with a record representation clause
2484 is only effective for fields not specified by the representation clause.
2486 If the @code{Name} parameter is absent, the pragma can be used as either
2487 a configuration pragma, in which case it applies to one or more units in
2488 accordance with the normal rules for configuration pragmas, or it can be
2489 used within a declarative part, in which case it applies to types that
2490 are declared within this declarative part, or within any nested scope
2491 within this declarative part. In either case it specifies the alignment
2492 to be applied to any record or array type which has otherwise standard
2495 If the alignment for a record or array type is not specified (using
2496 pragma @code{Pack}, pragma @code{Component_Alignment}, or a record rep
2497 clause), the GNAT uses the default alignment as described previously.
2499 @node Pragma Constant_After_Elaboration,Pragma Contract_Cases,Pragma Component_Alignment,Implementation Defined Pragmas
2500 @anchor{gnat_rm/implementation_defined_pragmas id6}@anchor{3f}@anchor{gnat_rm/implementation_defined_pragmas pragma-constant-after-elaboration}@anchor{40}
2501 @section Pragma Constant_After_Elaboration
2507 pragma Constant_After_Elaboration [ (boolean_EXPRESSION) ];
2510 For the semantics of this pragma, see the entry for aspect
2511 @code{Constant_After_Elaboration} in the SPARK 2014 Reference Manual, section 3.3.1.
2513 @node Pragma Contract_Cases,Pragma Convention_Identifier,Pragma Constant_After_Elaboration,Implementation Defined Pragmas
2514 @anchor{gnat_rm/implementation_defined_pragmas id7}@anchor{41}@anchor{gnat_rm/implementation_defined_pragmas pragma-contract-cases}@anchor{42}
2515 @section Pragma Contract_Cases
2518 @geindex Contract cases
2523 pragma Contract_Cases ((CONTRACT_CASE @{, CONTRACT_CASE));
2525 CONTRACT_CASE ::= CASE_GUARD => CONSEQUENCE
2527 CASE_GUARD ::= boolean_EXPRESSION | others
2529 CONSEQUENCE ::= boolean_EXPRESSION
2532 The @code{Contract_Cases} pragma allows defining fine-grain specifications
2533 that can complement or replace the contract given by a precondition and a
2534 postcondition. Additionally, the @code{Contract_Cases} pragma can be used
2535 by testing and formal verification tools. The compiler checks its validity and,
2536 depending on the assertion policy at the point of declaration of the pragma,
2537 it may insert a check in the executable. For code generation, the contract
2541 pragma Contract_Cases (
2549 C1 : constant Boolean := Cond1; -- evaluated at subprogram entry
2550 C2 : constant Boolean := Cond2; -- evaluated at subprogram entry
2551 pragma Precondition ((C1 and not C2) or (C2 and not C1));
2552 pragma Postcondition (if C1 then Pred1);
2553 pragma Postcondition (if C2 then Pred2);
2556 The precondition ensures that one and only one of the conditions is
2557 satisfied on entry to the subprogram.
2558 The postcondition ensures that for the condition that was True on entry,
2559 the corrresponding consequence is True on exit. Other consequence expressions
2562 A precondition @code{P} and postcondition @code{Q} can also be
2563 expressed as contract cases:
2566 pragma Contract_Cases (P => Q);
2569 The placement and visibility rules for @code{Contract_Cases} pragmas are
2570 identical to those described for preconditions and postconditions.
2572 The compiler checks that boolean expressions given in conditions and
2573 consequences are valid, where the rules for conditions are the same as
2574 the rule for an expression in @code{Precondition} and the rules for
2575 consequences are the same as the rule for an expression in
2576 @code{Postcondition}. In particular, attributes @code{'Old} and
2577 @code{'Result} can only be used within consequence expressions.
2578 The condition for the last contract case may be @code{others}, to denote
2579 any case not captured by the previous cases. The
2580 following is an example of use within a package spec:
2583 package Math_Functions is
2585 function Sqrt (Arg : Float) return Float;
2586 pragma Contract_Cases (((Arg in 0.0 .. 99.0) => Sqrt'Result < 10.0,
2587 Arg >= 100.0 => Sqrt'Result >= 10.0,
2588 others => Sqrt'Result = 0.0));
2593 The meaning of contract cases is that only one case should apply at each
2594 call, as determined by the corresponding condition evaluating to True,
2595 and that the consequence for this case should hold when the subprogram
2598 @node Pragma Convention_Identifier,Pragma CPP_Class,Pragma Contract_Cases,Implementation Defined Pragmas
2599 @anchor{gnat_rm/implementation_defined_pragmas pragma-convention-identifier}@anchor{43}
2600 @section Pragma Convention_Identifier
2603 @geindex Conventions
2609 pragma Convention_Identifier (
2610 [Name =>] IDENTIFIER,
2611 [Convention =>] convention_IDENTIFIER);
2614 This pragma provides a mechanism for supplying synonyms for existing
2615 convention identifiers. The @code{Name} identifier can subsequently
2616 be used as a synonym for the given convention in other pragmas (including
2617 for example pragma @code{Import} or another @code{Convention_Identifier}
2618 pragma). As an example of the use of this, suppose you had legacy code
2619 which used Fortran77 as the identifier for Fortran. Then the pragma:
2622 pragma Convention_Identifier (Fortran77, Fortran);
2625 would allow the use of the convention identifier @code{Fortran77} in
2626 subsequent code, avoiding the need to modify the sources. As another
2627 example, you could use this to parameterize convention requirements
2628 according to systems. Suppose you needed to use @code{Stdcall} on
2629 windows systems, and @code{C} on some other system, then you could
2630 define a convention identifier @code{Library} and use a single
2631 @code{Convention_Identifier} pragma to specify which convention
2632 would be used system-wide.
2634 @node Pragma CPP_Class,Pragma CPP_Constructor,Pragma Convention_Identifier,Implementation Defined Pragmas
2635 @anchor{gnat_rm/implementation_defined_pragmas pragma-cpp-class}@anchor{44}
2636 @section Pragma CPP_Class
2639 @geindex Interfacing with C++
2644 pragma CPP_Class ([Entity =>] LOCAL_NAME);
2647 The argument denotes an entity in the current declarative region that is
2648 declared as a record type. It indicates that the type corresponds to an
2649 externally declared C++ class type, and is to be laid out the same way
2650 that C++ would lay out the type. If the C++ class has virtual primitives
2651 then the record must be declared as a tagged record type.
2653 Types for which @code{CPP_Class} is specified do not have assignment or
2654 equality operators defined (such operations can be imported or declared
2655 as subprograms as required). Initialization is allowed only by constructor
2656 functions (see pragma @code{CPP_Constructor}). Such types are implicitly
2657 limited if not explicitly declared as limited or derived from a limited
2658 type, and an error is issued in that case.
2660 See @ref{45,,Interfacing to C++} for related information.
2662 Note: Pragma @code{CPP_Class} is currently obsolete. It is supported
2663 for backward compatibility but its functionality is available
2664 using pragma @code{Import} with @code{Convention} = @code{CPP}.
2666 @node Pragma CPP_Constructor,Pragma CPP_Virtual,Pragma CPP_Class,Implementation Defined Pragmas
2667 @anchor{gnat_rm/implementation_defined_pragmas pragma-cpp-constructor}@anchor{46}
2668 @section Pragma CPP_Constructor
2671 @geindex Interfacing with C++
2676 pragma CPP_Constructor ([Entity =>] LOCAL_NAME
2677 [, [External_Name =>] static_string_EXPRESSION ]
2678 [, [Link_Name =>] static_string_EXPRESSION ]);
2681 This pragma identifies an imported function (imported in the usual way
2682 with pragma @code{Import}) as corresponding to a C++ constructor. If
2683 @code{External_Name} and @code{Link_Name} are not specified then the
2684 @code{Entity} argument is a name that must have been previously mentioned
2685 in a pragma @code{Import} with @code{Convention} = @code{CPP}. Such name
2686 must be of one of the following forms:
2692 @strong{function} @code{Fname} @strong{return} T`
2695 @strong{function} @code{Fname} @strong{return} T'Class
2698 @strong{function} @code{Fname} (...) @strong{return} T`
2701 @strong{function} @code{Fname} (...) @strong{return} T'Class
2704 where @code{T} is a limited record type imported from C++ with pragma
2705 @code{Import} and @code{Convention} = @code{CPP}.
2707 The first two forms import the default constructor, used when an object
2708 of type @code{T} is created on the Ada side with no explicit constructor.
2709 The latter two forms cover all the non-default constructors of the type.
2710 See the GNAT User's Guide for details.
2712 If no constructors are imported, it is impossible to create any objects
2713 on the Ada side and the type is implicitly declared abstract.
2715 Pragma @code{CPP_Constructor} is intended primarily for automatic generation
2716 using an automatic binding generator tool (such as the @code{-fdump-ada-spec}
2718 See @ref{45,,Interfacing to C++} for more related information.
2720 Note: The use of functions returning class-wide types for constructors is
2721 currently obsolete. They are supported for backward compatibility. The
2722 use of functions returning the type T leave the Ada sources more clear
2723 because the imported C++ constructors always return an object of type T;
2724 that is, they never return an object whose type is a descendant of type T.
2726 @node Pragma CPP_Virtual,Pragma CPP_Vtable,Pragma CPP_Constructor,Implementation Defined Pragmas
2727 @anchor{gnat_rm/implementation_defined_pragmas pragma-cpp-virtual}@anchor{47}
2728 @section Pragma CPP_Virtual
2731 @geindex Interfacing to C++
2733 This pragma is now obsolete and, other than generating a warning if warnings
2734 on obsolescent features are enabled, is completely ignored.
2735 It is retained for compatibility
2736 purposes. It used to be required to ensure compoatibility with C++, but
2737 is no longer required for that purpose because GNAT generates
2738 the same object layout as the G++ compiler by default.
2740 See @ref{45,,Interfacing to C++} for related information.
2742 @node Pragma CPP_Vtable,Pragma CPU,Pragma CPP_Virtual,Implementation Defined Pragmas
2743 @anchor{gnat_rm/implementation_defined_pragmas pragma-cpp-vtable}@anchor{48}
2744 @section Pragma CPP_Vtable
2747 @geindex Interfacing with C++
2749 This pragma is now obsolete and, other than generating a warning if warnings
2750 on obsolescent features are enabled, is completely ignored.
2751 It used to be required to ensure compatibility with C++, but
2752 is no longer required for that purpose because GNAT generates
2753 the same object layout as the G++ compiler by default.
2755 See @ref{45,,Interfacing to C++} for related information.
2757 @node Pragma CPU,Pragma Deadline_Floor,Pragma CPP_Vtable,Implementation Defined Pragmas
2758 @anchor{gnat_rm/implementation_defined_pragmas pragma-cpu}@anchor{49}
2765 pragma CPU (EXPRESSION);
2768 This pragma is standard in Ada 2012, but is available in all earlier
2769 versions of Ada as an implementation-defined pragma.
2770 See Ada 2012 Reference Manual for details.
2772 @node Pragma Deadline_Floor,Pragma Default_Initial_Condition,Pragma CPU,Implementation Defined Pragmas
2773 @anchor{gnat_rm/implementation_defined_pragmas pragma-deadline-floor}@anchor{4a}
2774 @section Pragma Deadline_Floor
2780 pragma Deadline_Floor (time_span_EXPRESSION);
2783 This pragma applies only to protected types and specifies the floor
2784 deadline inherited by a task when the task enters a protected object.
2785 It is effective only when the EDF scheduling policy is used.
2787 @node Pragma Default_Initial_Condition,Pragma Debug,Pragma Deadline_Floor,Implementation Defined Pragmas
2788 @anchor{gnat_rm/implementation_defined_pragmas id8}@anchor{4b}@anchor{gnat_rm/implementation_defined_pragmas pragma-default-initial-condition}@anchor{4c}
2789 @section Pragma Default_Initial_Condition
2795 pragma Default_Initial_Condition [ (null | boolean_EXPRESSION) ];
2798 For the semantics of this pragma, see the entry for aspect
2799 @code{Default_Initial_Condition} in the SPARK 2014 Reference Manual, section 7.3.3.
2801 @node Pragma Debug,Pragma Debug_Policy,Pragma Default_Initial_Condition,Implementation Defined Pragmas
2802 @anchor{gnat_rm/implementation_defined_pragmas pragma-debug}@anchor{4d}
2803 @section Pragma Debug
2809 pragma Debug ([CONDITION, ]PROCEDURE_CALL_WITHOUT_SEMICOLON);
2811 PROCEDURE_CALL_WITHOUT_SEMICOLON ::=
2813 | PROCEDURE_PREFIX ACTUAL_PARAMETER_PART
2816 The procedure call argument has the syntactic form of an expression, meeting
2817 the syntactic requirements for pragmas.
2819 If debug pragmas are not enabled or if the condition is present and evaluates
2820 to False, this pragma has no effect. If debug pragmas are enabled, the
2821 semantics of the pragma is exactly equivalent to the procedure call statement
2822 corresponding to the argument with a terminating semicolon. Pragmas are
2823 permitted in sequences of declarations, so you can use pragma @code{Debug} to
2824 intersperse calls to debug procedures in the middle of declarations. Debug
2825 pragmas can be enabled either by use of the command line switch @emph{-gnata}
2826 or by use of the pragma @code{Check_Policy} with a first argument of
2829 @node Pragma Debug_Policy,Pragma Default_Scalar_Storage_Order,Pragma Debug,Implementation Defined Pragmas
2830 @anchor{gnat_rm/implementation_defined_pragmas pragma-debug-policy}@anchor{4e}
2831 @section Pragma Debug_Policy
2837 pragma Debug_Policy (CHECK | DISABLE | IGNORE | ON | OFF);
2840 This pragma is equivalent to a corresponding @code{Check_Policy} pragma
2841 with a first argument of @code{Debug}. It is retained for historical
2842 compatibility reasons.
2844 @node Pragma Default_Scalar_Storage_Order,Pragma Default_Storage_Pool,Pragma Debug_Policy,Implementation Defined Pragmas
2845 @anchor{gnat_rm/implementation_defined_pragmas pragma-default-scalar-storage-order}@anchor{4f}
2846 @section Pragma Default_Scalar_Storage_Order
2849 @geindex Default_Scalar_Storage_Order
2851 @geindex Scalar_Storage_Order
2856 pragma Default_Scalar_Storage_Order (High_Order_First | Low_Order_First);
2859 Normally if no explicit @code{Scalar_Storage_Order} is given for a record
2860 type or array type, then the scalar storage order defaults to the ordinary
2861 default for the target. But this default may be overridden using this pragma.
2862 The pragma may appear as a configuration pragma, or locally within a package
2863 spec or declarative part. In the latter case, it applies to all subsequent
2864 types declared within that package spec or declarative part.
2866 The following example shows the use of this pragma:
2869 pragma Default_Scalar_Storage_Order (High_Order_First);
2870 with System; use System;
2879 for L2'Scalar_Storage_Order use Low_Order_First;
2888 pragma Default_Scalar_Storage_Order (Low_Order_First);
2895 type H4a is new Inner.L4;
2903 In this example record types with names starting with @emph{L} have @cite{Low_Order_First} scalar
2904 storage order, and record types with names starting with @emph{H} have @code{High_Order_First}.
2905 Note that in the case of @code{H4a}, the order is not inherited
2906 from the parent type. Only an explicitly set @code{Scalar_Storage_Order}
2907 gets inherited on type derivation.
2909 If this pragma is used as a configuration pragma which appears within a
2910 configuration pragma file (as opposed to appearing explicitly at the start
2911 of a single unit), then the binder will require that all units in a partition
2912 be compiled in a similar manner, other than run-time units, which are not
2913 affected by this pragma. Note that the use of this form is discouraged because
2914 it may significantly degrade the run-time performance of the software, instead
2915 the default scalar storage order ought to be changed only on a local basis.
2917 @node Pragma Default_Storage_Pool,Pragma Depends,Pragma Default_Scalar_Storage_Order,Implementation Defined Pragmas
2918 @anchor{gnat_rm/implementation_defined_pragmas pragma-default-storage-pool}@anchor{50}
2919 @section Pragma Default_Storage_Pool
2922 @geindex Default_Storage_Pool
2927 pragma Default_Storage_Pool (storage_pool_NAME | null);
2930 This pragma is standard in Ada 2012, but is available in all earlier
2931 versions of Ada as an implementation-defined pragma.
2932 See Ada 2012 Reference Manual for details.
2934 @node Pragma Depends,Pragma Detect_Blocking,Pragma Default_Storage_Pool,Implementation Defined Pragmas
2935 @anchor{gnat_rm/implementation_defined_pragmas pragma-depends}@anchor{51}@anchor{gnat_rm/implementation_defined_pragmas id9}@anchor{52}
2936 @section Pragma Depends
2942 pragma Depends (DEPENDENCY_RELATION);
2944 DEPENDENCY_RELATION ::=
2946 | (DEPENDENCY_CLAUSE @{, DEPENDENCY_CLAUSE@})
2948 DEPENDENCY_CLAUSE ::=
2949 OUTPUT_LIST =>[+] INPUT_LIST
2950 | NULL_DEPENDENCY_CLAUSE
2952 NULL_DEPENDENCY_CLAUSE ::= null => INPUT_LIST
2954 OUTPUT_LIST ::= OUTPUT | (OUTPUT @{, OUTPUT@})
2956 INPUT_LIST ::= null | INPUT | (INPUT @{, INPUT@})
2958 OUTPUT ::= NAME | FUNCTION_RESULT
2961 where FUNCTION_RESULT is a function Result attribute_reference
2964 For the semantics of this pragma, see the entry for aspect @code{Depends} in the
2965 SPARK 2014 Reference Manual, section 6.1.5.
2967 @node Pragma Detect_Blocking,Pragma Disable_Atomic_Synchronization,Pragma Depends,Implementation Defined Pragmas
2968 @anchor{gnat_rm/implementation_defined_pragmas pragma-detect-blocking}@anchor{53}
2969 @section Pragma Detect_Blocking
2975 pragma Detect_Blocking;
2978 This is a standard pragma in Ada 2005, that is available in all earlier
2979 versions of Ada as an implementation-defined pragma.
2981 This is a configuration pragma that forces the detection of potentially
2982 blocking operations within a protected operation, and to raise Program_Error
2985 @node Pragma Disable_Atomic_Synchronization,Pragma Dispatching_Domain,Pragma Detect_Blocking,Implementation Defined Pragmas
2986 @anchor{gnat_rm/implementation_defined_pragmas pragma-disable-atomic-synchronization}@anchor{54}
2987 @section Pragma Disable_Atomic_Synchronization
2990 @geindex Atomic Synchronization
2995 pragma Disable_Atomic_Synchronization [(Entity)];
2998 Ada requires that accesses (reads or writes) of an atomic variable be
2999 regarded as synchronization points in the case of multiple tasks.
3000 Particularly in the case of multi-processors this may require special
3001 handling, e.g. the generation of memory barriers. This capability may
3002 be turned off using this pragma in cases where it is known not to be
3005 The placement and scope rules for this pragma are the same as those
3006 for @code{pragma Suppress}. In particular it can be used as a
3007 configuration pragma, or in a declaration sequence where it applies
3008 till the end of the scope. If an @code{Entity} argument is present,
3009 the action applies only to that entity.
3011 @node Pragma Dispatching_Domain,Pragma Effective_Reads,Pragma Disable_Atomic_Synchronization,Implementation Defined Pragmas
3012 @anchor{gnat_rm/implementation_defined_pragmas pragma-dispatching-domain}@anchor{55}
3013 @section Pragma Dispatching_Domain
3019 pragma Dispatching_Domain (EXPRESSION);
3022 This pragma is standard in Ada 2012, but is available in all earlier
3023 versions of Ada as an implementation-defined pragma.
3024 See Ada 2012 Reference Manual for details.
3026 @node Pragma Effective_Reads,Pragma Effective_Writes,Pragma Dispatching_Domain,Implementation Defined Pragmas
3027 @anchor{gnat_rm/implementation_defined_pragmas id10}@anchor{56}@anchor{gnat_rm/implementation_defined_pragmas pragma-effective-reads}@anchor{57}
3028 @section Pragma Effective_Reads
3034 pragma Effective_Reads [ (boolean_EXPRESSION) ];
3037 For the semantics of this pragma, see the entry for aspect @code{Effective_Reads} in
3038 the SPARK 2014 Reference Manual, section 7.1.2.
3040 @node Pragma Effective_Writes,Pragma Elaboration_Checks,Pragma Effective_Reads,Implementation Defined Pragmas
3041 @anchor{gnat_rm/implementation_defined_pragmas id11}@anchor{58}@anchor{gnat_rm/implementation_defined_pragmas pragma-effective-writes}@anchor{59}
3042 @section Pragma Effective_Writes
3048 pragma Effective_Writes [ (boolean_EXPRESSION) ];
3051 For the semantics of this pragma, see the entry for aspect @code{Effective_Writes}
3052 in the SPARK 2014 Reference Manual, section 7.1.2.
3054 @node Pragma Elaboration_Checks,Pragma Eliminate,Pragma Effective_Writes,Implementation Defined Pragmas
3055 @anchor{gnat_rm/implementation_defined_pragmas pragma-elaboration-checks}@anchor{5a}
3056 @section Pragma Elaboration_Checks
3059 @geindex Elaboration control
3064 pragma Elaboration_Checks (Dynamic | Static);
3067 This is a configuration pragma that provides control over the
3068 elaboration model used by the compilation affected by the
3069 pragma. If the parameter is @code{Dynamic},
3070 then the dynamic elaboration
3071 model described in the Ada Reference Manual is used, as though
3072 the @emph{-gnatE} switch had been specified on the command
3073 line. If the parameter is @code{Static}, then the default GNAT static
3074 model is used. This configuration pragma overrides the setting
3075 of the command line. For full details on the elaboration models
3076 used by the GNAT compiler, see the chapter on elaboration order handling
3077 in the @emph{GNAT User's Guide}.
3079 @node Pragma Eliminate,Pragma Enable_Atomic_Synchronization,Pragma Elaboration_Checks,Implementation Defined Pragmas
3080 @anchor{gnat_rm/implementation_defined_pragmas pragma-eliminate}@anchor{5b}
3081 @section Pragma Eliminate
3084 @geindex Elimination of unused subprograms
3090 [ Unit_Name => ] IDENTIFIER | SELECTED_COMPONENT ,
3091 [ Entity => ] IDENTIFIER |
3092 SELECTED_COMPONENT |
3094 [, Source_Location => SOURCE_TRACE ] );
3096 SOURCE_TRACE ::= STRING_LITERAL
3099 This pragma indicates that the given entity is not used in the program to be
3100 compiled and built, thus allowing the compiler to
3101 eliminate the code or data associated with the named entity. Any reference to
3102 an eliminated entity causes a compile-time or link-time error.
3104 The pragma has the following semantics, where @code{U} is the unit specified by
3105 the @code{Unit_Name} argument and @code{E} is the entity specified by the @code{Entity}
3112 @code{E} must be a subprogram that is explicitly declared either:
3114 o Within @code{U}, or
3116 o Within a generic package that is instantiated in @code{U}, or
3118 o As an instance of generic subprogram instantiated in @code{U}.
3120 Otherwise the pragma is ignored.
3123 If @code{E} is overloaded within @code{U} then, in the absence of a
3124 @code{Source_Location} argument, all overloadings are eliminated.
3127 If @code{E} is overloaded within @code{U} and only some overloadings
3128 are to be eliminated, then each overloading to be eliminated
3129 must be specified in a corresponding pragma @code{Eliminate}
3130 with a @code{Source_Location} argument identifying the line where the
3131 declaration appears, as described below.
3134 If @code{E} is declared as the result of a generic instantiation, then
3135 a @code{Source_Location} argument is needed, as described below
3138 Pragma @code{Eliminate} allows a program to be compiled in a system-independent
3139 manner, so that unused entities are eliminated but without
3140 needing to modify the source text. Normally the required set of
3141 @code{Eliminate} pragmas is constructed automatically using the @code{gnatelim} tool.
3143 Any source file change that removes, splits, or
3144 adds lines may make the set of @code{Eliminate} pragmas invalid because their
3145 @code{Source_Location} argument values may get out of date.
3147 Pragma @code{Eliminate} may be used where the referenced entity is a dispatching
3148 operation. In this case all the subprograms to which the given operation can
3149 dispatch are considered to be unused (are never called as a result of a direct
3150 or a dispatching call).
3152 The string literal given for the source location specifies the line number
3153 of the declaration of the entity, using the following syntax for @code{SOURCE_TRACE}:
3156 SOURCE_TRACE ::= SOURCE_REFERENCE [ LBRACKET SOURCE_TRACE RBRACKET ]
3161 SOURCE_REFERENCE ::= FILE_NAME : LINE_NUMBER
3163 LINE_NUMBER ::= DIGIT @{DIGIT@}
3166 Spaces around the colon in a @code{SOURCE_REFERENCE} are optional.
3168 The source trace that is given as the @code{Source_Location} must obey the
3169 following rules (or else the pragma is ignored), where @code{U} is
3170 the unit @code{U} specified by the @code{Unit_Name} argument and @code{E} is the
3171 subprogram specified by the @code{Entity} argument:
3177 @code{FILE_NAME} is the short name (with no directory
3178 information) of the Ada source file for @code{U}, using the required syntax
3179 for the underlying file system (e.g. case is significant if the underlying
3180 operating system is case sensitive).
3181 If @code{U} is a package and @code{E} is a subprogram declared in the package
3182 specification and its full declaration appears in the package body,
3183 then the relevant source file is the one for the package specification;
3184 analogously if @code{U} is a generic package.
3187 If @code{E} is not declared in a generic instantiation (this includes
3188 generic subprogram instances), the source trace includes only one source
3189 line reference. @code{LINE_NUMBER} gives the line number of the occurrence
3190 of the declaration of @code{E} within the source file (as a decimal literal
3191 without an exponent or point).
3194 If @code{E} is declared by a generic instantiation, its source trace
3195 (from left to right) starts with the source location of the
3196 declaration of @code{E} in the generic unit and ends with the source
3197 location of the instantiation, given in square brackets. This approach is
3198 applied recursively with nested instantiations: the rightmost (nested
3199 most deeply in square brackets) element of the source trace is the location
3200 of the outermost instantiation, and the leftmost element (that is, outside
3201 of any square brackets) is the location of the declaration of @code{E} in
3210 pragma Eliminate (Pkg0, Proc);
3211 -- Eliminate (all overloadings of) Proc in Pkg0
3213 pragma Eliminate (Pkg1, Proc,
3214 Source_Location => "pkg1.ads:8");
3215 -- Eliminate overloading of Proc at line 8 in pkg1.ads
3217 -- Assume the following file contents:
3220 -- 2: type T is private;
3221 -- 3: package Gen_Pkg is
3222 -- 4: procedure Proc(N : T);
3228 -- 2: procedure Q is
3229 -- 3: package Inst_Pkg is new Gen_Pkg(Integer);
3230 -- ... -- No calls on Inst_Pkg.Proc
3233 -- The following pragma eliminates Inst_Pkg.Proc from Q
3234 pragma Eliminate (Q, Proc,
3235 Source_Location => "gen_pkg.ads:4[q.adb:3]");
3239 @node Pragma Enable_Atomic_Synchronization,Pragma Export_Function,Pragma Eliminate,Implementation Defined Pragmas
3240 @anchor{gnat_rm/implementation_defined_pragmas pragma-enable-atomic-synchronization}@anchor{5c}
3241 @section Pragma Enable_Atomic_Synchronization
3244 @geindex Atomic Synchronization
3249 pragma Enable_Atomic_Synchronization [(Entity)];
3252 Ada requires that accesses (reads or writes) of an atomic variable be
3253 regarded as synchronization points in the case of multiple tasks.
3254 Particularly in the case of multi-processors this may require special
3255 handling, e.g. the generation of memory barriers. This synchronization
3256 is performed by default, but can be turned off using
3257 @code{pragma Disable_Atomic_Synchronization}. The
3258 @code{Enable_Atomic_Synchronization} pragma can be used to turn
3261 The placement and scope rules for this pragma are the same as those
3262 for @code{pragma Unsuppress}. In particular it can be used as a
3263 configuration pragma, or in a declaration sequence where it applies
3264 till the end of the scope. If an @code{Entity} argument is present,
3265 the action applies only to that entity.
3267 @node Pragma Export_Function,Pragma Export_Object,Pragma Enable_Atomic_Synchronization,Implementation Defined Pragmas
3268 @anchor{gnat_rm/implementation_defined_pragmas pragma-export-function}@anchor{5d}
3269 @section Pragma Export_Function
3272 @geindex Argument passing mechanisms
3277 pragma Export_Function (
3278 [Internal =>] LOCAL_NAME
3279 [, [External =>] EXTERNAL_SYMBOL]
3280 [, [Parameter_Types =>] PARAMETER_TYPES]
3281 [, [Result_Type =>] result_SUBTYPE_MARK]
3282 [, [Mechanism =>] MECHANISM]
3283 [, [Result_Mechanism =>] MECHANISM_NAME]);
3287 | static_string_EXPRESSION
3292 | TYPE_DESIGNATOR @{, TYPE_DESIGNATOR@}
3296 | subtype_Name ' Access
3300 | (MECHANISM_ASSOCIATION @{, MECHANISM_ASSOCIATION@})
3302 MECHANISM_ASSOCIATION ::=
3303 [formal_parameter_NAME =>] MECHANISM_NAME
3305 MECHANISM_NAME ::= Value | Reference
3308 Use this pragma to make a function externally callable and optionally
3309 provide information on mechanisms to be used for passing parameter and
3310 result values. We recommend, for the purposes of improving portability,
3311 this pragma always be used in conjunction with a separate pragma
3312 @code{Export}, which must precede the pragma @code{Export_Function}.
3313 GNAT does not require a separate pragma @code{Export}, but if none is
3314 present, @code{Convention Ada} is assumed, which is usually
3315 not what is wanted, so it is usually appropriate to use this
3316 pragma in conjunction with a @code{Export} or @code{Convention}
3317 pragma that specifies the desired foreign convention.
3318 Pragma @code{Export_Function}
3319 (and @code{Export}, if present) must appear in the same declarative
3320 region as the function to which they apply.
3322 The @code{internal_name} must uniquely designate the function to which the
3323 pragma applies. If more than one function name exists of this name in
3324 the declarative part you must use the @code{Parameter_Types} and
3325 @code{Result_Type} parameters to achieve the required
3326 unique designation. The @cite{subtype_mark}s in these parameters must
3327 exactly match the subtypes in the corresponding function specification,
3328 using positional notation to match parameters with subtype marks.
3329 The form with an @code{'Access} attribute can be used to match an
3330 anonymous access parameter.
3332 @geindex Suppressing external name
3334 Special treatment is given if the EXTERNAL is an explicit null
3335 string or a static string expressions that evaluates to the null
3336 string. In this case, no external name is generated. This form
3337 still allows the specification of parameter mechanisms.
3339 @node Pragma Export_Object,Pragma Export_Procedure,Pragma Export_Function,Implementation Defined Pragmas
3340 @anchor{gnat_rm/implementation_defined_pragmas pragma-export-object}@anchor{5e}
3341 @section Pragma Export_Object
3347 pragma Export_Object
3348 [Internal =>] LOCAL_NAME
3349 [, [External =>] EXTERNAL_SYMBOL]
3350 [, [Size =>] EXTERNAL_SYMBOL]
3354 | static_string_EXPRESSION
3357 This pragma designates an object as exported, and apart from the
3358 extended rules for external symbols, is identical in effect to the use of
3359 the normal @code{Export} pragma applied to an object. You may use a
3360 separate Export pragma (and you probably should from the point of view
3361 of portability), but it is not required. @code{Size} is syntax checked,
3362 but otherwise ignored by GNAT.
3364 @node Pragma Export_Procedure,Pragma Export_Value,Pragma Export_Object,Implementation Defined Pragmas
3365 @anchor{gnat_rm/implementation_defined_pragmas pragma-export-procedure}@anchor{5f}
3366 @section Pragma Export_Procedure
3372 pragma Export_Procedure (
3373 [Internal =>] LOCAL_NAME
3374 [, [External =>] EXTERNAL_SYMBOL]
3375 [, [Parameter_Types =>] PARAMETER_TYPES]
3376 [, [Mechanism =>] MECHANISM]);
3380 | static_string_EXPRESSION
3385 | TYPE_DESIGNATOR @{, TYPE_DESIGNATOR@}
3389 | subtype_Name ' Access
3393 | (MECHANISM_ASSOCIATION @{, MECHANISM_ASSOCIATION@})
3395 MECHANISM_ASSOCIATION ::=
3396 [formal_parameter_NAME =>] MECHANISM_NAME
3398 MECHANISM_NAME ::= Value | Reference
3401 This pragma is identical to @code{Export_Function} except that it
3402 applies to a procedure rather than a function and the parameters
3403 @code{Result_Type} and @code{Result_Mechanism} are not permitted.
3404 GNAT does not require a separate pragma @code{Export}, but if none is
3405 present, @code{Convention Ada} is assumed, which is usually
3406 not what is wanted, so it is usually appropriate to use this
3407 pragma in conjunction with a @code{Export} or @code{Convention}
3408 pragma that specifies the desired foreign convention.
3410 @geindex Suppressing external name
3412 Special treatment is given if the EXTERNAL is an explicit null
3413 string or a static string expressions that evaluates to the null
3414 string. In this case, no external name is generated. This form
3415 still allows the specification of parameter mechanisms.
3417 @node Pragma Export_Value,Pragma Export_Valued_Procedure,Pragma Export_Procedure,Implementation Defined Pragmas
3418 @anchor{gnat_rm/implementation_defined_pragmas pragma-export-value}@anchor{60}
3419 @section Pragma Export_Value
3425 pragma Export_Value (
3426 [Value =>] static_integer_EXPRESSION,
3427 [Link_Name =>] static_string_EXPRESSION);
3430 This pragma serves to export a static integer value for external use.
3431 The first argument specifies the value to be exported. The Link_Name
3432 argument specifies the symbolic name to be associated with the integer
3433 value. This pragma is useful for defining a named static value in Ada
3434 that can be referenced in assembly language units to be linked with
3435 the application. This pragma is currently supported only for the
3436 AAMP target and is ignored for other targets.
3438 @node Pragma Export_Valued_Procedure,Pragma Extend_System,Pragma Export_Value,Implementation Defined Pragmas
3439 @anchor{gnat_rm/implementation_defined_pragmas pragma-export-valued-procedure}@anchor{61}
3440 @section Pragma Export_Valued_Procedure
3446 pragma Export_Valued_Procedure (
3447 [Internal =>] LOCAL_NAME
3448 [, [External =>] EXTERNAL_SYMBOL]
3449 [, [Parameter_Types =>] PARAMETER_TYPES]
3450 [, [Mechanism =>] MECHANISM]);
3454 | static_string_EXPRESSION
3459 | TYPE_DESIGNATOR @{, TYPE_DESIGNATOR@}
3463 | subtype_Name ' Access
3467 | (MECHANISM_ASSOCIATION @{, MECHANISM_ASSOCIATION@})
3469 MECHANISM_ASSOCIATION ::=
3470 [formal_parameter_NAME =>] MECHANISM_NAME
3472 MECHANISM_NAME ::= Value | Reference
3475 This pragma is identical to @code{Export_Procedure} except that the
3476 first parameter of @code{LOCAL_NAME}, which must be present, must be of
3477 mode @code{out}, and externally the subprogram is treated as a function
3478 with this parameter as the result of the function. GNAT provides for
3479 this capability to allow the use of @code{out} and @code{in out}
3480 parameters in interfacing to external functions (which are not permitted
3482 GNAT does not require a separate pragma @code{Export}, but if none is
3483 present, @code{Convention Ada} is assumed, which is almost certainly
3484 not what is wanted since the whole point of this pragma is to interface
3485 with foreign language functions, so it is usually appropriate to use this
3486 pragma in conjunction with a @code{Export} or @code{Convention}
3487 pragma that specifies the desired foreign convention.
3489 @geindex Suppressing external name
3491 Special treatment is given if the EXTERNAL is an explicit null
3492 string or a static string expressions that evaluates to the null
3493 string. In this case, no external name is generated. This form
3494 still allows the specification of parameter mechanisms.
3496 @node Pragma Extend_System,Pragma Extensions_Allowed,Pragma Export_Valued_Procedure,Implementation Defined Pragmas
3497 @anchor{gnat_rm/implementation_defined_pragmas pragma-extend-system}@anchor{62}
3498 @section Pragma Extend_System
3509 pragma Extend_System ([Name =>] IDENTIFIER);
3512 This pragma is used to provide backwards compatibility with other
3513 implementations that extend the facilities of package @code{System}. In
3514 GNAT, @code{System} contains only the definitions that are present in
3515 the Ada RM. However, other implementations, notably the DEC Ada 83
3516 implementation, provide many extensions to package @code{System}.
3518 For each such implementation accommodated by this pragma, GNAT provides a
3519 package @code{Aux_@emph{xxx}}, e.g., @code{Aux_DEC} for the DEC Ada 83
3520 implementation, which provides the required additional definitions. You
3521 can use this package in two ways. You can @code{with} it in the normal
3522 way and access entities either by selection or using a @code{use}
3523 clause. In this case no special processing is required.
3525 However, if existing code contains references such as
3526 @code{System.@emph{xxx}} where @emph{xxx} is an entity in the extended
3527 definitions provided in package @code{System}, you may use this pragma
3528 to extend visibility in @code{System} in a non-standard way that
3529 provides greater compatibility with the existing code. Pragma
3530 @code{Extend_System} is a configuration pragma whose single argument is
3531 the name of the package containing the extended definition
3532 (e.g., @code{Aux_DEC} for the DEC Ada case). A unit compiled under
3533 control of this pragma will be processed using special visibility
3534 processing that looks in package @code{System.Aux_@emph{xxx}} where
3535 @code{Aux_@emph{xxx}} is the pragma argument for any entity referenced in
3536 package @code{System}, but not found in package @code{System}.
3538 You can use this pragma either to access a predefined @code{System}
3539 extension supplied with the compiler, for example @code{Aux_DEC} or
3540 you can construct your own extension unit following the above
3541 definition. Note that such a package is a child of @code{System}
3542 and thus is considered part of the implementation.
3543 To compile it you will have to use the @emph{-gnatg} switch
3544 for compiling System units, as explained in the
3547 @node Pragma Extensions_Allowed,Pragma Extensions_Visible,Pragma Extend_System,Implementation Defined Pragmas
3548 @anchor{gnat_rm/implementation_defined_pragmas pragma-extensions-allowed}@anchor{63}
3549 @section Pragma Extensions_Allowed
3552 @geindex Ada Extensions
3554 @geindex GNAT Extensions
3559 pragma Extensions_Allowed (On | Off);
3562 This configuration pragma enables or disables the implementation
3563 extension mode (the use of Off as a parameter cancels the effect
3564 of the @emph{-gnatX} command switch).
3566 In extension mode, the latest version of the Ada language is
3567 implemented (currently Ada 2012), and in addition a small number
3568 of GNAT specific extensions are recognized as follows:
3573 @item @emph{Constrained attribute for generic objects}
3575 The @code{Constrained} attribute is permitted for objects of
3576 generic types. The result indicates if the corresponding actual
3580 @node Pragma Extensions_Visible,Pragma External,Pragma Extensions_Allowed,Implementation Defined Pragmas
3581 @anchor{gnat_rm/implementation_defined_pragmas id12}@anchor{64}@anchor{gnat_rm/implementation_defined_pragmas pragma-extensions-visible}@anchor{65}
3582 @section Pragma Extensions_Visible
3588 pragma Extensions_Visible [ (boolean_EXPRESSION) ];
3591 For the semantics of this pragma, see the entry for aspect @code{Extensions_Visible}
3592 in the SPARK 2014 Reference Manual, section 6.1.7.
3594 @node Pragma External,Pragma External_Name_Casing,Pragma Extensions_Visible,Implementation Defined Pragmas
3595 @anchor{gnat_rm/implementation_defined_pragmas pragma-external}@anchor{66}
3596 @section Pragma External
3603 [ Convention =>] convention_IDENTIFIER,
3604 [ Entity =>] LOCAL_NAME
3605 [, [External_Name =>] static_string_EXPRESSION ]
3606 [, [Link_Name =>] static_string_EXPRESSION ]);
3609 This pragma is identical in syntax and semantics to pragma
3610 @code{Export} as defined in the Ada Reference Manual. It is
3611 provided for compatibility with some Ada 83 compilers that
3612 used this pragma for exactly the same purposes as pragma
3613 @code{Export} before the latter was standardized.
3615 @node Pragma External_Name_Casing,Pragma Fast_Math,Pragma External,Implementation Defined Pragmas
3616 @anchor{gnat_rm/implementation_defined_pragmas pragma-external-name-casing}@anchor{67}
3617 @section Pragma External_Name_Casing
3620 @geindex Dec Ada 83 casing compatibility
3622 @geindex External Names
3625 @geindex Casing of External names
3630 pragma External_Name_Casing (
3631 Uppercase | Lowercase
3632 [, Uppercase | Lowercase | As_Is]);
3635 This pragma provides control over the casing of external names associated
3636 with Import and Export pragmas. There are two cases to consider:
3642 Implicit external names
3644 Implicit external names are derived from identifiers. The most common case
3645 arises when a standard Ada Import or Export pragma is used with only two
3649 pragma Import (C, C_Routine);
3652 Since Ada is a case-insensitive language, the spelling of the identifier in
3653 the Ada source program does not provide any information on the desired
3654 casing of the external name, and so a convention is needed. In GNAT the
3655 default treatment is that such names are converted to all lower case
3656 letters. This corresponds to the normal C style in many environments.
3657 The first argument of pragma @code{External_Name_Casing} can be used to
3658 control this treatment. If @code{Uppercase} is specified, then the name
3659 will be forced to all uppercase letters. If @code{Lowercase} is specified,
3660 then the normal default of all lower case letters will be used.
3662 This same implicit treatment is also used in the case of extended DEC Ada 83
3663 compatible Import and Export pragmas where an external name is explicitly
3664 specified using an identifier rather than a string.
3667 Explicit external names
3669 Explicit external names are given as string literals. The most common case
3670 arises when a standard Ada Import or Export pragma is used with three
3674 pragma Import (C, C_Routine, "C_routine");
3677 In this case, the string literal normally provides the exact casing required
3678 for the external name. The second argument of pragma
3679 @code{External_Name_Casing} may be used to modify this behavior.
3680 If @code{Uppercase} is specified, then the name
3681 will be forced to all uppercase letters. If @code{Lowercase} is specified,
3682 then the name will be forced to all lowercase letters. A specification of
3683 @code{As_Is} provides the normal default behavior in which the casing is
3684 taken from the string provided.
3687 This pragma may appear anywhere that a pragma is valid. In particular, it
3688 can be used as a configuration pragma in the @code{gnat.adc} file, in which
3689 case it applies to all subsequent compilations, or it can be used as a program
3690 unit pragma, in which case it only applies to the current unit, or it can
3691 be used more locally to control individual Import/Export pragmas.
3693 It was primarily intended for use with OpenVMS systems, where many
3694 compilers convert all symbols to upper case by default. For interfacing to
3695 such compilers (e.g., the DEC C compiler), it may be convenient to use
3699 pragma External_Name_Casing (Uppercase, Uppercase);
3702 to enforce the upper casing of all external symbols.
3704 @node Pragma Fast_Math,Pragma Favor_Top_Level,Pragma External_Name_Casing,Implementation Defined Pragmas
3705 @anchor{gnat_rm/implementation_defined_pragmas pragma-fast-math}@anchor{68}
3706 @section Pragma Fast_Math
3715 This is a configuration pragma which activates a mode in which speed is
3716 considered more important for floating-point operations than absolutely
3717 accurate adherence to the requirements of the standard. Currently the
3718 following operations are affected:
3723 @item @emph{Complex Multiplication}
3725 The normal simple formula for complex multiplication can result in intermediate
3726 overflows for numbers near the end of the range. The Ada standard requires that
3727 this situation be detected and corrected by scaling, but in Fast_Math mode such
3728 cases will simply result in overflow. Note that to take advantage of this you
3729 must instantiate your own version of @code{Ada.Numerics.Generic_Complex_Types}
3730 under control of the pragma, rather than use the preinstantiated versions.
3733 @node Pragma Favor_Top_Level,Pragma Finalize_Storage_Only,Pragma Fast_Math,Implementation Defined Pragmas
3734 @anchor{gnat_rm/implementation_defined_pragmas id13}@anchor{69}@anchor{gnat_rm/implementation_defined_pragmas pragma-favor-top-level}@anchor{6a}
3735 @section Pragma Favor_Top_Level
3741 pragma Favor_Top_Level (type_NAME);
3744 The argument of pragma @code{Favor_Top_Level} must be a named access-to-subprogram
3745 type. This pragma is an efficiency hint to the compiler, regarding the use of
3746 @code{'Access} or @code{'Unrestricted_Access} on nested (non-library-level) subprograms.
3747 The pragma means that nested subprograms are not used with this type, or are
3748 rare, so that the generated code should be efficient in the top-level case.
3749 When this pragma is used, dynamically generated trampolines may be used on some
3750 targets for nested subprograms. See restriction @code{No_Implicit_Dynamic_Code}.
3752 @node Pragma Finalize_Storage_Only,Pragma Float_Representation,Pragma Favor_Top_Level,Implementation Defined Pragmas
3753 @anchor{gnat_rm/implementation_defined_pragmas pragma-finalize-storage-only}@anchor{6b}
3754 @section Pragma Finalize_Storage_Only
3760 pragma Finalize_Storage_Only (first_subtype_LOCAL_NAME);
3763 The argument of pragma @code{Finalize_Storage_Only} must denote a local type which
3764 is derived from @code{Ada.Finalization.Controlled} or @code{Limited_Controlled}. The
3765 pragma suppresses the call to @code{Finalize} for declared library-level objects
3766 of the argument type. This is mostly useful for types where finalization is
3767 only used to deal with storage reclamation since in most environments it is
3768 not necessary to reclaim memory just before terminating execution, hence the
3769 name. Note that this pragma does not suppress Finalize calls for library-level
3770 heap-allocated objects (see pragma @code{No_Heap_Finalization}).
3772 @node Pragma Float_Representation,Pragma Ghost,Pragma Finalize_Storage_Only,Implementation Defined Pragmas
3773 @anchor{gnat_rm/implementation_defined_pragmas pragma-float-representation}@anchor{6c}
3774 @section Pragma Float_Representation
3780 pragma Float_Representation (FLOAT_REP[, float_type_LOCAL_NAME]);
3782 FLOAT_REP ::= VAX_Float | IEEE_Float
3785 In the one argument form, this pragma is a configuration pragma which
3786 allows control over the internal representation chosen for the predefined
3787 floating point types declared in the packages @code{Standard} and
3788 @code{System}. This pragma is only provided for compatibility and has no effect.
3790 The two argument form specifies the representation to be used for
3791 the specified floating-point type. The argument must
3792 be @code{IEEE_Float} to specify the use of IEEE format, as follows:
3798 For a digits value of 6, 32-bit IEEE short format will be used.
3801 For a digits value of 15, 64-bit IEEE long format will be used.
3804 No other value of digits is permitted.
3807 @node Pragma Ghost,Pragma Global,Pragma Float_Representation,Implementation Defined Pragmas
3808 @anchor{gnat_rm/implementation_defined_pragmas pragma-ghost}@anchor{6d}@anchor{gnat_rm/implementation_defined_pragmas id14}@anchor{6e}
3809 @section Pragma Ghost
3815 pragma Ghost [ (boolean_EXPRESSION) ];
3818 For the semantics of this pragma, see the entry for aspect @code{Ghost} in the SPARK
3819 2014 Reference Manual, section 6.9.
3821 @node Pragma Global,Pragma Ident,Pragma Ghost,Implementation Defined Pragmas
3822 @anchor{gnat_rm/implementation_defined_pragmas pragma-global}@anchor{6f}@anchor{gnat_rm/implementation_defined_pragmas id15}@anchor{70}
3823 @section Pragma Global
3829 pragma Global (GLOBAL_SPECIFICATION);
3831 GLOBAL_SPECIFICATION ::=
3834 | (MODED_GLOBAL_LIST @{, MODED_GLOBAL_LIST@})
3836 MODED_GLOBAL_LIST ::= MODE_SELECTOR => GLOBAL_LIST
3838 MODE_SELECTOR ::= In_Out | Input | Output | Proof_In
3839 GLOBAL_LIST ::= GLOBAL_ITEM | (GLOBAL_ITEM @{, GLOBAL_ITEM@})
3840 GLOBAL_ITEM ::= NAME
3843 For the semantics of this pragma, see the entry for aspect @code{Global} in the
3844 SPARK 2014 Reference Manual, section 6.1.4.
3846 @node Pragma Ident,Pragma Ignore_Pragma,Pragma Global,Implementation Defined Pragmas
3847 @anchor{gnat_rm/implementation_defined_pragmas pragma-ident}@anchor{71}
3848 @section Pragma Ident
3854 pragma Ident (static_string_EXPRESSION);
3857 This pragma is identical in effect to pragma @code{Comment}. It is provided
3858 for compatibility with other Ada compilers providing this pragma.
3860 @node Pragma Ignore_Pragma,Pragma Implementation_Defined,Pragma Ident,Implementation Defined Pragmas
3861 @anchor{gnat_rm/implementation_defined_pragmas pragma-ignore-pragma}@anchor{72}
3862 @section Pragma Ignore_Pragma
3868 pragma Ignore_Pragma (pragma_IDENTIFIER);
3871 This is a configuration pragma
3872 that takes a single argument that is a simple identifier. Any subsequent
3873 use of a pragma whose pragma identifier matches this argument will be
3874 silently ignored. This may be useful when legacy code or code intended
3875 for compilation with some other compiler contains pragmas that match the
3876 name, but not the exact implementation, of a GNAT pragma. The use of this
3877 pragma allows such pragmas to be ignored, which may be useful in CodePeer
3878 mode, or during porting of legacy code.
3880 @node Pragma Implementation_Defined,Pragma Implemented,Pragma Ignore_Pragma,Implementation Defined Pragmas
3881 @anchor{gnat_rm/implementation_defined_pragmas pragma-implementation-defined}@anchor{73}
3882 @section Pragma Implementation_Defined
3888 pragma Implementation_Defined (local_NAME);
3891 This pragma marks a previously declared entity as implementation-defined.
3892 For an overloaded entity, applies to the most recent homonym.
3895 pragma Implementation_Defined;
3898 The form with no arguments appears anywhere within a scope, most
3899 typically a package spec, and indicates that all entities that are
3900 defined within the package spec are Implementation_Defined.
3902 This pragma is used within the GNAT runtime library to identify
3903 implementation-defined entities introduced in language-defined units,
3904 for the purpose of implementing the No_Implementation_Identifiers
3907 @node Pragma Implemented,Pragma Implicit_Packing,Pragma Implementation_Defined,Implementation Defined Pragmas
3908 @anchor{gnat_rm/implementation_defined_pragmas pragma-implemented}@anchor{74}
3909 @section Pragma Implemented
3915 pragma Implemented (procedure_LOCAL_NAME, implementation_kind);
3917 implementation_kind ::= By_Entry | By_Protected_Procedure | By_Any
3920 This is an Ada 2012 representation pragma which applies to protected, task
3921 and synchronized interface primitives. The use of pragma Implemented provides
3922 a way to impose a static requirement on the overriding operation by adhering
3923 to one of the three implementation kinds: entry, protected procedure or any of
3924 the above. This pragma is available in all earlier versions of Ada as an
3925 implementation-defined pragma.
3928 type Synch_Iface is synchronized interface;
3929 procedure Prim_Op (Obj : in out Iface) is abstract;
3930 pragma Implemented (Prim_Op, By_Protected_Procedure);
3932 protected type Prot_1 is new Synch_Iface with
3933 procedure Prim_Op; -- Legal
3936 protected type Prot_2 is new Synch_Iface with
3937 entry Prim_Op; -- Illegal
3940 task type Task_Typ is new Synch_Iface with
3941 entry Prim_Op; -- Illegal
3945 When applied to the procedure_or_entry_NAME of a requeue statement, pragma
3946 Implemented determines the runtime behavior of the requeue. Implementation kind
3947 By_Entry guarantees that the action of requeueing will proceed from an entry to
3948 another entry. Implementation kind By_Protected_Procedure transforms the
3949 requeue into a dispatching call, thus eliminating the chance of blocking. Kind
3950 By_Any shares the behavior of By_Entry and By_Protected_Procedure depending on
3951 the target's overriding subprogram kind.
3953 @node Pragma Implicit_Packing,Pragma Import_Function,Pragma Implemented,Implementation Defined Pragmas
3954 @anchor{gnat_rm/implementation_defined_pragmas pragma-implicit-packing}@anchor{75}
3955 @section Pragma Implicit_Packing
3958 @geindex Rational Profile
3963 pragma Implicit_Packing;
3966 This is a configuration pragma that requests implicit packing for packed
3967 arrays for which a size clause is given but no explicit pragma Pack or
3968 specification of Component_Size is present. It also applies to records
3969 where no record representation clause is present. Consider this example:
3972 type R is array (0 .. 7) of Boolean;
3976 In accordance with the recommendation in the RM (RM 13.3(53)), a Size clause
3977 does not change the layout of a composite object. So the Size clause in the
3978 above example is normally rejected, since the default layout of the array uses
3979 8-bit components, and thus the array requires a minimum of 64 bits.
3981 If this declaration is compiled in a region of code covered by an occurrence
3982 of the configuration pragma Implicit_Packing, then the Size clause in this
3983 and similar examples will cause implicit packing and thus be accepted. For
3984 this implicit packing to occur, the type in question must be an array of small
3985 components whose size is known at compile time, and the Size clause must
3986 specify the exact size that corresponds to the number of elements in the array
3987 multiplied by the size in bits of the component type (both single and
3988 multi-dimensioned arrays can be controlled with this pragma).
3990 @geindex Array packing
3992 Similarly, the following example shows the use in the record case
3996 a, b, c, d, e, f, g, h : boolean;
4002 Without a pragma Pack, each Boolean field requires 8 bits, so the
4003 minimum size is 72 bits, but with a pragma Pack, 16 bits would be
4004 sufficient. The use of pragma Implicit_Packing allows this record
4005 declaration to compile without an explicit pragma Pack.
4007 @node Pragma Import_Function,Pragma Import_Object,Pragma Implicit_Packing,Implementation Defined Pragmas
4008 @anchor{gnat_rm/implementation_defined_pragmas pragma-import-function}@anchor{76}
4009 @section Pragma Import_Function
4015 pragma Import_Function (
4016 [Internal =>] LOCAL_NAME,
4017 [, [External =>] EXTERNAL_SYMBOL]
4018 [, [Parameter_Types =>] PARAMETER_TYPES]
4019 [, [Result_Type =>] SUBTYPE_MARK]
4020 [, [Mechanism =>] MECHANISM]
4021 [, [Result_Mechanism =>] MECHANISM_NAME]);
4025 | static_string_EXPRESSION
4029 | TYPE_DESIGNATOR @{, TYPE_DESIGNATOR@}
4033 | subtype_Name ' Access
4037 | (MECHANISM_ASSOCIATION @{, MECHANISM_ASSOCIATION@})
4039 MECHANISM_ASSOCIATION ::=
4040 [formal_parameter_NAME =>] MECHANISM_NAME
4047 This pragma is used in conjunction with a pragma @code{Import} to
4048 specify additional information for an imported function. The pragma
4049 @code{Import} (or equivalent pragma @code{Interface}) must precede the
4050 @code{Import_Function} pragma and both must appear in the same
4051 declarative part as the function specification.
4053 The @code{Internal} argument must uniquely designate
4054 the function to which the
4055 pragma applies. If more than one function name exists of this name in
4056 the declarative part you must use the @code{Parameter_Types} and
4057 @code{Result_Type} parameters to achieve the required unique
4058 designation. Subtype marks in these parameters must exactly match the
4059 subtypes in the corresponding function specification, using positional
4060 notation to match parameters with subtype marks.
4061 The form with an @code{'Access} attribute can be used to match an
4062 anonymous access parameter.
4064 You may optionally use the @code{Mechanism} and @code{Result_Mechanism}
4065 parameters to specify passing mechanisms for the
4066 parameters and result. If you specify a single mechanism name, it
4067 applies to all parameters. Otherwise you may specify a mechanism on a
4068 parameter by parameter basis using either positional or named
4069 notation. If the mechanism is not specified, the default mechanism
4072 @node Pragma Import_Object,Pragma Import_Procedure,Pragma Import_Function,Implementation Defined Pragmas
4073 @anchor{gnat_rm/implementation_defined_pragmas pragma-import-object}@anchor{77}
4074 @section Pragma Import_Object
4080 pragma Import_Object
4081 [Internal =>] LOCAL_NAME
4082 [, [External =>] EXTERNAL_SYMBOL]
4083 [, [Size =>] EXTERNAL_SYMBOL]);
4087 | static_string_EXPRESSION
4090 This pragma designates an object as imported, and apart from the
4091 extended rules for external symbols, is identical in effect to the use of
4092 the normal @code{Import} pragma applied to an object. Unlike the
4093 subprogram case, you need not use a separate @code{Import} pragma,
4094 although you may do so (and probably should do so from a portability
4095 point of view). @code{size} is syntax checked, but otherwise ignored by
4098 @node Pragma Import_Procedure,Pragma Import_Valued_Procedure,Pragma Import_Object,Implementation Defined Pragmas
4099 @anchor{gnat_rm/implementation_defined_pragmas pragma-import-procedure}@anchor{78}
4100 @section Pragma Import_Procedure
4106 pragma Import_Procedure (
4107 [Internal =>] LOCAL_NAME
4108 [, [External =>] EXTERNAL_SYMBOL]
4109 [, [Parameter_Types =>] PARAMETER_TYPES]
4110 [, [Mechanism =>] MECHANISM]);
4114 | static_string_EXPRESSION
4118 | TYPE_DESIGNATOR @{, TYPE_DESIGNATOR@}
4122 | subtype_Name ' Access
4126 | (MECHANISM_ASSOCIATION @{, MECHANISM_ASSOCIATION@})
4128 MECHANISM_ASSOCIATION ::=
4129 [formal_parameter_NAME =>] MECHANISM_NAME
4131 MECHANISM_NAME ::= Value | Reference
4134 This pragma is identical to @code{Import_Function} except that it
4135 applies to a procedure rather than a function and the parameters
4136 @code{Result_Type} and @code{Result_Mechanism} are not permitted.
4138 @node Pragma Import_Valued_Procedure,Pragma Independent,Pragma Import_Procedure,Implementation Defined Pragmas
4139 @anchor{gnat_rm/implementation_defined_pragmas pragma-import-valued-procedure}@anchor{79}
4140 @section Pragma Import_Valued_Procedure
4146 pragma Import_Valued_Procedure (
4147 [Internal =>] LOCAL_NAME
4148 [, [External =>] EXTERNAL_SYMBOL]
4149 [, [Parameter_Types =>] PARAMETER_TYPES]
4150 [, [Mechanism =>] MECHANISM]);
4154 | static_string_EXPRESSION
4158 | TYPE_DESIGNATOR @{, TYPE_DESIGNATOR@}
4162 | subtype_Name ' Access
4166 | (MECHANISM_ASSOCIATION @{, MECHANISM_ASSOCIATION@})
4168 MECHANISM_ASSOCIATION ::=
4169 [formal_parameter_NAME =>] MECHANISM_NAME
4171 MECHANISM_NAME ::= Value | Reference
4174 This pragma is identical to @code{Import_Procedure} except that the
4175 first parameter of @code{LOCAL_NAME}, which must be present, must be of
4176 mode @code{out}, and externally the subprogram is treated as a function
4177 with this parameter as the result of the function. The purpose of this
4178 capability is to allow the use of @code{out} and @code{in out}
4179 parameters in interfacing to external functions (which are not permitted
4180 in Ada functions). You may optionally use the @code{Mechanism}
4181 parameters to specify passing mechanisms for the parameters.
4182 If you specify a single mechanism name, it applies to all parameters.
4183 Otherwise you may specify a mechanism on a parameter by parameter
4184 basis using either positional or named notation. If the mechanism is not
4185 specified, the default mechanism is used.
4187 Note that it is important to use this pragma in conjunction with a separate
4188 pragma Import that specifies the desired convention, since otherwise the
4189 default convention is Ada, which is almost certainly not what is required.
4191 @node Pragma Independent,Pragma Independent_Components,Pragma Import_Valued_Procedure,Implementation Defined Pragmas
4192 @anchor{gnat_rm/implementation_defined_pragmas pragma-independent}@anchor{7a}
4193 @section Pragma Independent
4199 pragma Independent (Local_NAME);
4202 This pragma is standard in Ada 2012 mode (which also provides an aspect
4203 of the same name). It is also available as an implementation-defined
4204 pragma in all earlier versions. It specifies that the
4205 designated object or all objects of the designated type must be
4206 independently addressable. This means that separate tasks can safely
4207 manipulate such objects. For example, if two components of a record are
4208 independent, then two separate tasks may access these two components.
4210 constraints on the representation of the object (for instance prohibiting
4213 @node Pragma Independent_Components,Pragma Initial_Condition,Pragma Independent,Implementation Defined Pragmas
4214 @anchor{gnat_rm/implementation_defined_pragmas pragma-independent-components}@anchor{7b}
4215 @section Pragma Independent_Components
4221 pragma Independent_Components (Local_NAME);
4224 This pragma is standard in Ada 2012 mode (which also provides an aspect
4225 of the same name). It is also available as an implementation-defined
4226 pragma in all earlier versions. It specifies that the components of the
4227 designated object, or the components of each object of the designated
4229 independently addressable. This means that separate tasks can safely
4230 manipulate separate components in the composite object. This may place
4231 constraints on the representation of the object (for instance prohibiting
4234 @node Pragma Initial_Condition,Pragma Initialize_Scalars,Pragma Independent_Components,Implementation Defined Pragmas
4235 @anchor{gnat_rm/implementation_defined_pragmas id16}@anchor{7c}@anchor{gnat_rm/implementation_defined_pragmas pragma-initial-condition}@anchor{7d}
4236 @section Pragma Initial_Condition
4242 pragma Initial_Condition (boolean_EXPRESSION);
4245 For the semantics of this pragma, see the entry for aspect @code{Initial_Condition}
4246 in the SPARK 2014 Reference Manual, section 7.1.6.
4248 @node Pragma Initialize_Scalars,Pragma Initializes,Pragma Initial_Condition,Implementation Defined Pragmas
4249 @anchor{gnat_rm/implementation_defined_pragmas pragma-initialize-scalars}@anchor{7e}
4250 @section Pragma Initialize_Scalars
4253 @geindex debugging with Initialize_Scalars
4258 pragma Initialize_Scalars;
4261 This pragma is similar to @code{Normalize_Scalars} conceptually but has
4262 two important differences. First, there is no requirement for the pragma
4263 to be used uniformly in all units of a partition, in particular, it is fine
4264 to use this just for some or all of the application units of a partition,
4265 without needing to recompile the run-time library.
4267 In the case where some units are compiled with the pragma, and some without,
4268 then a declaration of a variable where the type is defined in package
4269 Standard or is locally declared will always be subject to initialization,
4270 as will any declaration of a scalar variable. For composite variables,
4271 whether the variable is initialized may also depend on whether the package
4272 in which the type of the variable is declared is compiled with the pragma.
4274 The other important difference is that you can control the value used
4275 for initializing scalar objects. At bind time, you can select several
4276 options for initialization. You can
4277 initialize with invalid values (similar to Normalize_Scalars, though for
4278 Initialize_Scalars it is not always possible to determine the invalid
4279 values in complex cases like signed component fields with non-standard
4280 sizes). You can also initialize with high or
4281 low values, or with a specified bit pattern. See the GNAT
4282 User's Guide for binder options for specifying these cases.
4284 This means that you can compile a program, and then without having to
4285 recompile the program, you can run it with different values being used
4286 for initializing otherwise uninitialized values, to test if your program
4287 behavior depends on the choice. Of course the behavior should not change,
4288 and if it does, then most likely you have an incorrect reference to an
4289 uninitialized value.
4291 It is even possible to change the value at execution time eliminating even
4292 the need to rebind with a different switch using an environment variable.
4293 See the GNAT User's Guide for details.
4295 Note that pragma @code{Initialize_Scalars} is particularly useful in
4296 conjunction with the enhanced validity checking that is now provided
4297 in GNAT, which checks for invalid values under more conditions.
4298 Using this feature (see description of the @emph{-gnatV} flag in the
4299 GNAT User's Guide) in conjunction with
4300 pragma @code{Initialize_Scalars}
4301 provides a powerful new tool to assist in the detection of problems
4302 caused by uninitialized variables.
4304 Note: the use of @code{Initialize_Scalars} has a fairly extensive
4305 effect on the generated code. This may cause your code to be
4306 substantially larger. It may also cause an increase in the amount
4307 of stack required, so it is probably a good idea to turn on stack
4308 checking (see description of stack checking in the GNAT
4309 User's Guide) when using this pragma.
4311 @node Pragma Initializes,Pragma Inline_Always,Pragma Initialize_Scalars,Implementation Defined Pragmas
4312 @anchor{gnat_rm/implementation_defined_pragmas pragma-initializes}@anchor{7f}@anchor{gnat_rm/implementation_defined_pragmas id17}@anchor{80}
4313 @section Pragma Initializes
4319 pragma Initializes (INITIALIZATION_LIST);
4321 INITIALIZATION_LIST ::=
4323 | (INITIALIZATION_ITEM @{, INITIALIZATION_ITEM@})
4325 INITIALIZATION_ITEM ::= name [=> INPUT_LIST]
4330 | (INPUT @{, INPUT@})
4335 For the semantics of this pragma, see the entry for aspect @code{Initializes} in the
4336 SPARK 2014 Reference Manual, section 7.1.5.
4338 @node Pragma Inline_Always,Pragma Inline_Generic,Pragma Initializes,Implementation Defined Pragmas
4339 @anchor{gnat_rm/implementation_defined_pragmas id18}@anchor{81}@anchor{gnat_rm/implementation_defined_pragmas pragma-inline-always}@anchor{82}
4340 @section Pragma Inline_Always
4346 pragma Inline_Always (NAME [, NAME]);
4349 Similar to pragma @code{Inline} except that inlining is unconditional.
4350 Inline_Always instructs the compiler to inline every direct call to the
4351 subprogram or else to emit a compilation error, independently of any
4352 option, in particular @emph{-gnatn} or @emph{-gnatN} or the optimization level.
4353 It is an error to take the address or access of @code{NAME}. It is also an error to
4354 apply this pragma to a primitive operation of a tagged type. Thanks to such
4355 restrictions, the compiler is allowed to remove the out-of-line body of @code{NAME}.
4357 @node Pragma Inline_Generic,Pragma Interface,Pragma Inline_Always,Implementation Defined Pragmas
4358 @anchor{gnat_rm/implementation_defined_pragmas pragma-inline-generic}@anchor{83}
4359 @section Pragma Inline_Generic
4365 pragma Inline_Generic (GNAME @{, GNAME@});
4367 GNAME ::= generic_unit_NAME | generic_instance_NAME
4370 This pragma is provided for compatibility with Dec Ada 83. It has
4371 no effect in GNAT (which always inlines generics), other
4372 than to check that the given names are all names of generic units or
4375 @node Pragma Interface,Pragma Interface_Name,Pragma Inline_Generic,Implementation Defined Pragmas
4376 @anchor{gnat_rm/implementation_defined_pragmas pragma-interface}@anchor{84}
4377 @section Pragma Interface
4384 [Convention =>] convention_identifier,
4385 [Entity =>] local_NAME
4386 [, [External_Name =>] static_string_expression]
4387 [, [Link_Name =>] static_string_expression]);
4390 This pragma is identical in syntax and semantics to
4391 the standard Ada pragma @code{Import}. It is provided for compatibility
4392 with Ada 83. The definition is upwards compatible both with pragma
4393 @code{Interface} as defined in the Ada 83 Reference Manual, and also
4394 with some extended implementations of this pragma in certain Ada 83
4395 implementations. The only difference between pragma @code{Interface}
4396 and pragma @code{Import} is that there is special circuitry to allow
4397 both pragmas to appear for the same subprogram entity (normally it
4398 is illegal to have multiple @code{Import} pragmas. This is useful in
4399 maintaining Ada 83/Ada 95 compatibility and is compatible with other
4402 @node Pragma Interface_Name,Pragma Interrupt_Handler,Pragma Interface,Implementation Defined Pragmas
4403 @anchor{gnat_rm/implementation_defined_pragmas pragma-interface-name}@anchor{85}
4404 @section Pragma Interface_Name
4410 pragma Interface_Name (
4411 [Entity =>] LOCAL_NAME
4412 [, [External_Name =>] static_string_EXPRESSION]
4413 [, [Link_Name =>] static_string_EXPRESSION]);
4416 This pragma provides an alternative way of specifying the interface name
4417 for an interfaced subprogram, and is provided for compatibility with Ada
4418 83 compilers that use the pragma for this purpose. You must provide at
4419 least one of @code{External_Name} or @code{Link_Name}.
4421 @node Pragma Interrupt_Handler,Pragma Interrupt_State,Pragma Interface_Name,Implementation Defined Pragmas
4422 @anchor{gnat_rm/implementation_defined_pragmas pragma-interrupt-handler}@anchor{86}
4423 @section Pragma Interrupt_Handler
4429 pragma Interrupt_Handler (procedure_LOCAL_NAME);
4432 This program unit pragma is supported for parameterless protected procedures
4433 as described in Annex C of the Ada Reference Manual. On the AAMP target
4434 the pragma can also be specified for nonprotected parameterless procedures
4435 that are declared at the library level (which includes procedures
4436 declared at the top level of a library package). In the case of AAMP,
4437 when this pragma is applied to a nonprotected procedure, the instruction
4438 @code{IERET} is generated for returns from the procedure, enabling
4439 maskable interrupts, in place of the normal return instruction.
4441 @node Pragma Interrupt_State,Pragma Invariant,Pragma Interrupt_Handler,Implementation Defined Pragmas
4442 @anchor{gnat_rm/implementation_defined_pragmas pragma-interrupt-state}@anchor{87}
4443 @section Pragma Interrupt_State
4449 pragma Interrupt_State
4451 [State =>] SYSTEM | RUNTIME | USER);
4454 Normally certain interrupts are reserved to the implementation. Any attempt
4455 to attach an interrupt causes Program_Error to be raised, as described in
4456 RM C.3.2(22). A typical example is the @code{SIGINT} interrupt used in
4457 many systems for an @code{Ctrl-C} interrupt. Normally this interrupt is
4458 reserved to the implementation, so that @code{Ctrl-C} can be used to
4459 interrupt execution. Additionally, signals such as @code{SIGSEGV},
4460 @code{SIGABRT}, @code{SIGFPE} and @code{SIGILL} are often mapped to specific
4461 Ada exceptions, or used to implement run-time functions such as the
4462 @code{abort} statement and stack overflow checking.
4464 Pragma @code{Interrupt_State} provides a general mechanism for overriding
4465 such uses of interrupts. It subsumes the functionality of pragma
4466 @code{Unreserve_All_Interrupts}. Pragma @code{Interrupt_State} is not
4467 available on Windows or VMS. On all other platforms than VxWorks,
4468 it applies to signals; on VxWorks, it applies to vectored hardware interrupts
4469 and may be used to mark interrupts required by the board support package
4472 Interrupts can be in one of three states:
4480 The interrupt is reserved (no Ada handler can be installed), and the
4481 Ada run-time may not install a handler. As a result you are guaranteed
4482 standard system default action if this interrupt is raised. This also allows
4483 installing a low level handler via C APIs such as sigaction(), outside
4489 The interrupt is reserved (no Ada handler can be installed). The run time
4490 is allowed to install a handler for internal control purposes, but is
4491 not required to do so.
4496 The interrupt is unreserved. The user may install an Ada handler via
4497 Ada.Interrupts and pragma Interrupt_Handler or Attach_Handler to provide
4501 These states are the allowed values of the @code{State} parameter of the
4502 pragma. The @code{Name} parameter is a value of the type
4503 @code{Ada.Interrupts.Interrupt_ID}. Typically, it is a name declared in
4504 @code{Ada.Interrupts.Names}.
4506 This is a configuration pragma, and the binder will check that there
4507 are no inconsistencies between different units in a partition in how a
4508 given interrupt is specified. It may appear anywhere a pragma is legal.
4510 The effect is to move the interrupt to the specified state.
4512 By declaring interrupts to be SYSTEM, you guarantee the standard system
4513 action, such as a core dump.
4515 By declaring interrupts to be USER, you guarantee that you can install
4518 Note that certain signals on many operating systems cannot be caught and
4519 handled by applications. In such cases, the pragma is ignored. See the
4520 operating system documentation, or the value of the array @code{Reserved}
4521 declared in the spec of package @code{System.OS_Interface}.
4523 Overriding the default state of signals used by the Ada runtime may interfere
4524 with an application's runtime behavior in the cases of the synchronous signals,
4525 and in the case of the signal used to implement the @code{abort} statement.
4527 @node Pragma Invariant,Pragma Keep_Names,Pragma Interrupt_State,Implementation Defined Pragmas
4528 @anchor{gnat_rm/implementation_defined_pragmas id19}@anchor{88}@anchor{gnat_rm/implementation_defined_pragmas pragma-invariant}@anchor{89}
4529 @section Pragma Invariant
4536 ([Entity =>] private_type_LOCAL_NAME,
4537 [Check =>] EXPRESSION
4538 [,[Message =>] String_Expression]);
4541 This pragma provides exactly the same capabilities as the Type_Invariant aspect
4542 defined in AI05-0146-1, and in the Ada 2012 Reference Manual. The
4543 Type_Invariant aspect is fully implemented in Ada 2012 mode, but since it
4544 requires the use of the aspect syntax, which is not available except in 2012
4545 mode, it is not possible to use the Type_Invariant aspect in earlier versions
4546 of Ada. However the Invariant pragma may be used in any version of Ada. Also
4547 note that the aspect Invariant is a synonym in GNAT for the aspect
4548 Type_Invariant, but there is no pragma Type_Invariant.
4550 The pragma must appear within the visible part of the package specification,
4551 after the type to which its Entity argument appears. As with the Invariant
4552 aspect, the Check expression is not analyzed until the end of the visible
4553 part of the package, so it may contain forward references. The Message
4554 argument, if present, provides the exception message used if the invariant
4555 is violated. If no Message parameter is provided, a default message that
4556 identifies the line on which the pragma appears is used.
4558 It is permissible to have multiple Invariants for the same type entity, in
4559 which case they are and'ed together. It is permissible to use this pragma
4560 in Ada 2012 mode, but you cannot have both an invariant aspect and an
4561 invariant pragma for the same entity.
4563 For further details on the use of this pragma, see the Ada 2012 documentation
4564 of the Type_Invariant aspect.
4566 @node Pragma Keep_Names,Pragma License,Pragma Invariant,Implementation Defined Pragmas
4567 @anchor{gnat_rm/implementation_defined_pragmas pragma-keep-names}@anchor{8a}
4568 @section Pragma Keep_Names
4574 pragma Keep_Names ([On =>] enumeration_first_subtype_LOCAL_NAME);
4577 The @code{LOCAL_NAME} argument
4578 must refer to an enumeration first subtype
4579 in the current declarative part. The effect is to retain the enumeration
4580 literal names for use by @code{Image} and @code{Value} even if a global
4581 @code{Discard_Names} pragma applies. This is useful when you want to
4582 generally suppress enumeration literal names and for example you therefore
4583 use a @code{Discard_Names} pragma in the @code{gnat.adc} file, but you
4584 want to retain the names for specific enumeration types.
4586 @node Pragma License,Pragma Link_With,Pragma Keep_Names,Implementation Defined Pragmas
4587 @anchor{gnat_rm/implementation_defined_pragmas pragma-license}@anchor{8b}
4588 @section Pragma License
4591 @geindex License checking
4596 pragma License (Unrestricted | GPL | Modified_GPL | Restricted);
4599 This pragma is provided to allow automated checking for appropriate license
4600 conditions with respect to the standard and modified GPL. A pragma
4601 @code{License}, which is a configuration pragma that typically appears at
4602 the start of a source file or in a separate @code{gnat.adc} file, specifies
4603 the licensing conditions of a unit as follows:
4610 This is used for a unit that can be freely used with no license restrictions.
4611 Examples of such units are public domain units, and units from the Ada
4616 This is used for a unit that is licensed under the unmodified GPL, and which
4617 therefore cannot be @code{with}ed by a restricted unit.
4621 This is used for a unit licensed under the GNAT modified GPL that includes
4622 a special exception paragraph that specifically permits the inclusion of
4623 the unit in programs without requiring the entire program to be released
4628 This is used for a unit that is restricted in that it is not permitted to
4629 depend on units that are licensed under the GPL. Typical examples are
4630 proprietary code that is to be released under more restrictive license
4631 conditions. Note that restricted units are permitted to @code{with} units
4632 which are licensed under the modified GPL (this is the whole point of the
4636 Normally a unit with no @code{License} pragma is considered to have an
4637 unknown license, and no checking is done. However, standard GNAT headers
4638 are recognized, and license information is derived from them as follows.
4640 A GNAT license header starts with a line containing 78 hyphens. The following
4641 comment text is searched for the appearance of any of the following strings.
4643 If the string 'GNU General Public License' is found, then the unit is assumed
4644 to have GPL license, unless the string 'As a special exception' follows, in
4645 which case the license is assumed to be modified GPL.
4647 If one of the strings
4648 'This specification is adapted from the Ada Semantic Interface' or
4649 'This specification is derived from the Ada Reference Manual' is found
4650 then the unit is assumed to be unrestricted.
4652 These default actions means that a program with a restricted license pragma
4653 will automatically get warnings if a GPL unit is inappropriately
4654 @code{with}ed. For example, the program:
4659 procedure Secret_Stuff is
4664 if compiled with pragma @code{License} (@code{Restricted}) in a
4665 @code{gnat.adc} file will generate the warning:
4670 >>> license of withed unit "Sem_Ch3" is incompatible
4672 2. with GNAT.Sockets;
4673 3. procedure Secret_Stuff is
4676 Here we get a warning on @code{Sem_Ch3} since it is part of the GNAT
4677 compiler and is licensed under the
4678 GPL, but no warning for @code{GNAT.Sockets} which is part of the GNAT
4679 run time, and is therefore licensed under the modified GPL.
4681 @node Pragma Link_With,Pragma Linker_Alias,Pragma License,Implementation Defined Pragmas
4682 @anchor{gnat_rm/implementation_defined_pragmas pragma-link-with}@anchor{8c}
4683 @section Pragma Link_With
4689 pragma Link_With (static_string_EXPRESSION @{,static_string_EXPRESSION@});
4692 This pragma is provided for compatibility with certain Ada 83 compilers.
4693 It has exactly the same effect as pragma @code{Linker_Options} except
4694 that spaces occurring within one of the string expressions are treated
4695 as separators. For example, in the following case:
4698 pragma Link_With ("-labc -ldef");
4701 results in passing the strings @code{-labc} and @code{-ldef} as two
4702 separate arguments to the linker. In addition pragma Link_With allows
4703 multiple arguments, with the same effect as successive pragmas.
4705 @node Pragma Linker_Alias,Pragma Linker_Constructor,Pragma Link_With,Implementation Defined Pragmas
4706 @anchor{gnat_rm/implementation_defined_pragmas pragma-linker-alias}@anchor{8d}
4707 @section Pragma Linker_Alias
4713 pragma Linker_Alias (
4714 [Entity =>] LOCAL_NAME,
4715 [Target =>] static_string_EXPRESSION);
4718 @code{LOCAL_NAME} must refer to an object that is declared at the library
4719 level. This pragma establishes the given entity as a linker alias for the
4720 given target. It is equivalent to @code{__attribute__((alias))} in GNU C
4721 and causes @code{LOCAL_NAME} to be emitted as an alias for the symbol
4722 @code{static_string_EXPRESSION} in the object file, that is to say no space
4723 is reserved for @code{LOCAL_NAME} by the assembler and it will be resolved
4724 to the same address as @code{static_string_EXPRESSION} by the linker.
4726 The actual linker name for the target must be used (e.g., the fully
4727 encoded name with qualification in Ada, or the mangled name in C++),
4728 or it must be declared using the C convention with @code{pragma Import}
4729 or @code{pragma Export}.
4731 Not all target machines support this pragma. On some of them it is accepted
4732 only if @code{pragma Weak_External} has been applied to @code{LOCAL_NAME}.
4735 -- Example of the use of pragma Linker_Alias
4739 pragma Export (C, i);
4741 new_name_for_i : Integer;
4742 pragma Linker_Alias (new_name_for_i, "i");
4746 @node Pragma Linker_Constructor,Pragma Linker_Destructor,Pragma Linker_Alias,Implementation Defined Pragmas
4747 @anchor{gnat_rm/implementation_defined_pragmas pragma-linker-constructor}@anchor{8e}
4748 @section Pragma Linker_Constructor
4754 pragma Linker_Constructor (procedure_LOCAL_NAME);
4757 @code{procedure_LOCAL_NAME} must refer to a parameterless procedure that
4758 is declared at the library level. A procedure to which this pragma is
4759 applied will be treated as an initialization routine by the linker.
4760 It is equivalent to @code{__attribute__((constructor))} in GNU C and
4761 causes @code{procedure_LOCAL_NAME} to be invoked before the entry point
4762 of the executable is called (or immediately after the shared library is
4763 loaded if the procedure is linked in a shared library), in particular
4764 before the Ada run-time environment is set up.
4766 Because of these specific contexts, the set of operations such a procedure
4767 can perform is very limited and the type of objects it can manipulate is
4768 essentially restricted to the elementary types. In particular, it must only
4769 contain code to which pragma Restrictions (No_Elaboration_Code) applies.
4771 This pragma is used by GNAT to implement auto-initialization of shared Stand
4772 Alone Libraries, which provides a related capability without the restrictions
4773 listed above. Where possible, the use of Stand Alone Libraries is preferable
4774 to the use of this pragma.
4776 @node Pragma Linker_Destructor,Pragma Linker_Section,Pragma Linker_Constructor,Implementation Defined Pragmas
4777 @anchor{gnat_rm/implementation_defined_pragmas pragma-linker-destructor}@anchor{8f}
4778 @section Pragma Linker_Destructor
4784 pragma Linker_Destructor (procedure_LOCAL_NAME);
4787 @code{procedure_LOCAL_NAME} must refer to a parameterless procedure that
4788 is declared at the library level. A procedure to which this pragma is
4789 applied will be treated as a finalization routine by the linker.
4790 It is equivalent to @code{__attribute__((destructor))} in GNU C and
4791 causes @code{procedure_LOCAL_NAME} to be invoked after the entry point
4792 of the executable has exited (or immediately before the shared library
4793 is unloaded if the procedure is linked in a shared library), in particular
4794 after the Ada run-time environment is shut down.
4796 See @code{pragma Linker_Constructor} for the set of restrictions that apply
4797 because of these specific contexts.
4799 @node Pragma Linker_Section,Pragma Lock_Free,Pragma Linker_Destructor,Implementation Defined Pragmas
4800 @anchor{gnat_rm/implementation_defined_pragmas id20}@anchor{90}@anchor{gnat_rm/implementation_defined_pragmas pragma-linker-section}@anchor{91}
4801 @section Pragma Linker_Section
4807 pragma Linker_Section (
4808 [Entity =>] LOCAL_NAME,
4809 [Section =>] static_string_EXPRESSION);
4812 @code{LOCAL_NAME} must refer to an object, type, or subprogram that is
4813 declared at the library level. This pragma specifies the name of the
4814 linker section for the given entity. It is equivalent to
4815 @code{__attribute__((section))} in GNU C and causes @code{LOCAL_NAME} to
4816 be placed in the @code{static_string_EXPRESSION} section of the
4817 executable (assuming the linker doesn't rename the section).
4818 GNAT also provides an implementation defined aspect of the same name.
4820 In the case of specifying this aspect for a type, the effect is to
4821 specify the corresponding section for all library-level objects of
4822 the type that do not have an explicit linker section set. Note that
4823 this only applies to whole objects, not to components of composite objects.
4825 In the case of a subprogram, the linker section applies to all previously
4826 declared matching overloaded subprograms in the current declarative part
4827 which do not already have a linker section assigned. The linker section
4828 aspect is useful in this case for specifying different linker sections
4829 for different elements of such an overloaded set.
4831 Note that an empty string specifies that no linker section is specified.
4832 This is not quite the same as omitting the pragma or aspect, since it
4833 can be used to specify that one element of an overloaded set of subprograms
4834 has the default linker section, or that one object of a type for which a
4835 linker section is specified should has the default linker section.
4837 The compiler normally places library-level entities in standard sections
4838 depending on the class: procedures and functions generally go in the
4839 @code{.text} section, initialized variables in the @code{.data} section
4840 and uninitialized variables in the @code{.bss} section.
4842 Other, special sections may exist on given target machines to map special
4843 hardware, for example I/O ports or flash memory. This pragma is a means to
4844 defer the final layout of the executable to the linker, thus fully working
4845 at the symbolic level with the compiler.
4847 Some file formats do not support arbitrary sections so not all target
4848 machines support this pragma. The use of this pragma may cause a program
4849 execution to be erroneous if it is used to place an entity into an
4850 inappropriate section (e.g., a modified variable into the @code{.text}
4851 section). See also @code{pragma Persistent_BSS}.
4854 -- Example of the use of pragma Linker_Section
4858 pragma Volatile (Port_A);
4859 pragma Linker_Section (Port_A, ".bss.port_a");
4862 pragma Volatile (Port_B);
4863 pragma Linker_Section (Port_B, ".bss.port_b");
4865 type Port_Type is new Integer with Linker_Section => ".bss";
4866 PA : Port_Type with Linker_Section => ".bss.PA";
4867 PB : Port_Type; -- ends up in linker section ".bss"
4869 procedure Q with Linker_Section => "Qsection";
4873 @node Pragma Lock_Free,Pragma Loop_Invariant,Pragma Linker_Section,Implementation Defined Pragmas
4874 @anchor{gnat_rm/implementation_defined_pragmas id21}@anchor{92}@anchor{gnat_rm/implementation_defined_pragmas pragma-lock-free}@anchor{93}
4875 @section Pragma Lock_Free
4879 This pragma may be specified for protected types or objects. It specifies that
4880 the implementation of protected operations must be implemented without locks.
4881 Compilation fails if the compiler cannot generate lock-free code for the
4884 @node Pragma Loop_Invariant,Pragma Loop_Optimize,Pragma Lock_Free,Implementation Defined Pragmas
4885 @anchor{gnat_rm/implementation_defined_pragmas pragma-loop-invariant}@anchor{94}
4886 @section Pragma Loop_Invariant
4892 pragma Loop_Invariant ( boolean_EXPRESSION );
4895 The effect of this pragma is similar to that of pragma @code{Assert},
4896 except that in an @code{Assertion_Policy} pragma, the identifier
4897 @code{Loop_Invariant} is used to control whether it is ignored or checked
4900 @code{Loop_Invariant} can only appear as one of the items in the sequence
4901 of statements of a loop body, or nested inside block statements that
4902 appear in the sequence of statements of a loop body.
4903 The intention is that it be used to
4904 represent a "loop invariant" assertion, i.e. something that is true each
4905 time through the loop, and which can be used to show that the loop is
4906 achieving its purpose.
4908 Multiple @code{Loop_Invariant} and @code{Loop_Variant} pragmas that
4909 apply to the same loop should be grouped in the same sequence of
4912 To aid in writing such invariants, the special attribute @code{Loop_Entry}
4913 may be used to refer to the value of an expression on entry to the loop. This
4914 attribute can only be used within the expression of a @code{Loop_Invariant}
4915 pragma. For full details, see documentation of attribute @code{Loop_Entry}.
4917 @node Pragma Loop_Optimize,Pragma Loop_Variant,Pragma Loop_Invariant,Implementation Defined Pragmas
4918 @anchor{gnat_rm/implementation_defined_pragmas pragma-loop-optimize}@anchor{95}
4919 @section Pragma Loop_Optimize
4925 pragma Loop_Optimize (OPTIMIZATION_HINT @{, OPTIMIZATION_HINT@});
4927 OPTIMIZATION_HINT ::= Ivdep | No_Unroll | Unroll | No_Vector | Vector
4930 This pragma must appear immediately within a loop statement. It allows the
4931 programmer to specify optimization hints for the enclosing loop. The hints
4932 are not mutually exclusive and can be freely mixed, but not all combinations
4933 will yield a sensible outcome.
4935 There are five supported optimization hints for a loop:
4943 The programmer asserts that there are no loop-carried dependencies
4944 which would prevent consecutive iterations of the loop from being
4945 executed simultaneously.
4950 The loop must not be unrolled. This is a strong hint: the compiler will not
4951 unroll a loop marked with this hint.
4956 The loop should be unrolled. This is a weak hint: the compiler will try to
4957 apply unrolling to this loop preferably to other optimizations, notably
4958 vectorization, but there is no guarantee that the loop will be unrolled.
4963 The loop must not be vectorized. This is a strong hint: the compiler will not
4964 vectorize a loop marked with this hint.
4969 The loop should be vectorized. This is a weak hint: the compiler will try to
4970 apply vectorization to this loop preferably to other optimizations, notably
4971 unrolling, but there is no guarantee that the loop will be vectorized.
4974 These hints do not remove the need to pass the appropriate switches to the
4975 compiler in order to enable the relevant optimizations, that is to say
4976 @emph{-funroll-loops} for unrolling and @emph{-ftree-vectorize} for
4979 @node Pragma Loop_Variant,Pragma Machine_Attribute,Pragma Loop_Optimize,Implementation Defined Pragmas
4980 @anchor{gnat_rm/implementation_defined_pragmas pragma-loop-variant}@anchor{96}
4981 @section Pragma Loop_Variant
4987 pragma Loop_Variant ( LOOP_VARIANT_ITEM @{, LOOP_VARIANT_ITEM @} );
4988 LOOP_VARIANT_ITEM ::= CHANGE_DIRECTION => discrete_EXPRESSION
4989 CHANGE_DIRECTION ::= Increases | Decreases
4992 @code{Loop_Variant} can only appear as one of the items in the sequence
4993 of statements of a loop body, or nested inside block statements that
4994 appear in the sequence of statements of a loop body.
4995 It allows the specification of quantities which must always
4996 decrease or increase in successive iterations of the loop. In its simplest
4997 form, just one expression is specified, whose value must increase or decrease
4998 on each iteration of the loop.
5000 In a more complex form, multiple arguments can be given which are intepreted
5001 in a nesting lexicographic manner. For example:
5004 pragma Loop_Variant (Increases => X, Decreases => Y);
5007 specifies that each time through the loop either X increases, or X stays
5008 the same and Y decreases. A @code{Loop_Variant} pragma ensures that the
5009 loop is making progress. It can be useful in helping to show informally
5010 or prove formally that the loop always terminates.
5012 @code{Loop_Variant} is an assertion whose effect can be controlled using
5013 an @code{Assertion_Policy} with a check name of @code{Loop_Variant}. The
5014 policy can be @code{Check} to enable the loop variant check, @code{Ignore}
5015 to ignore the check (in which case the pragma has no effect on the program),
5016 or @code{Disable} in which case the pragma is not even checked for correct
5019 Multiple @code{Loop_Invariant} and @code{Loop_Variant} pragmas that
5020 apply to the same loop should be grouped in the same sequence of
5023 The @code{Loop_Entry} attribute may be used within the expressions of the
5024 @code{Loop_Variant} pragma to refer to values on entry to the loop.
5026 @node Pragma Machine_Attribute,Pragma Main,Pragma Loop_Variant,Implementation Defined Pragmas
5027 @anchor{gnat_rm/implementation_defined_pragmas pragma-machine-attribute}@anchor{97}
5028 @section Pragma Machine_Attribute
5034 pragma Machine_Attribute (
5035 [Entity =>] LOCAL_NAME,
5036 [Attribute_Name =>] static_string_EXPRESSION
5037 [, [Info =>] static_EXPRESSION] );
5040 Machine-dependent attributes can be specified for types and/or
5041 declarations. This pragma is semantically equivalent to
5042 @code{__attribute__((@emph{attribute_name}))} (if @code{info} is not
5043 specified) or @code{__attribute__((@emph{attribute_name(info})))}
5044 in GNU C, where @emph{attribute_name} is recognized by the
5045 compiler middle-end or the @code{TARGET_ATTRIBUTE_TABLE} machine
5046 specific macro. A string literal for the optional parameter @code{info}
5047 is transformed into an identifier, which may make this pragma unusable
5048 for some attributes.
5049 For further information see @cite{GNU Compiler Collection (GCC) Internals}.
5051 @node Pragma Main,Pragma Main_Storage,Pragma Machine_Attribute,Implementation Defined Pragmas
5052 @anchor{gnat_rm/implementation_defined_pragmas pragma-main}@anchor{98}
5053 @section Pragma Main
5060 (MAIN_OPTION [, MAIN_OPTION]);
5063 [Stack_Size =>] static_integer_EXPRESSION
5064 | [Task_Stack_Size_Default =>] static_integer_EXPRESSION
5065 | [Time_Slicing_Enabled =>] static_boolean_EXPRESSION
5068 This pragma is provided for compatibility with OpenVMS VAX Systems. It has
5069 no effect in GNAT, other than being syntax checked.
5071 @node Pragma Main_Storage,Pragma Max_Queue_Length,Pragma Main,Implementation Defined Pragmas
5072 @anchor{gnat_rm/implementation_defined_pragmas pragma-main-storage}@anchor{99}
5073 @section Pragma Main_Storage
5080 (MAIN_STORAGE_OPTION [, MAIN_STORAGE_OPTION]);
5082 MAIN_STORAGE_OPTION ::=
5083 [WORKING_STORAGE =>] static_SIMPLE_EXPRESSION
5084 | [TOP_GUARD =>] static_SIMPLE_EXPRESSION
5087 This pragma is provided for compatibility with OpenVMS VAX Systems. It has
5088 no effect in GNAT, other than being syntax checked.
5090 @node Pragma Max_Queue_Length,Pragma No_Body,Pragma Main_Storage,Implementation Defined Pragmas
5091 @anchor{gnat_rm/implementation_defined_pragmas id22}@anchor{9a}@anchor{gnat_rm/implementation_defined_pragmas pragma-max-queue-length}@anchor{9b}
5092 @section Pragma Max_Queue_Length
5098 pragma Max_Entry_Queue (static_integer_EXPRESSION);
5101 This pragma is used to specify the maximum callers per entry queue for
5102 individual protected entries and entry families. It accepts a single
5103 positive integer as a parameter and must appear after the declaration
5106 @node Pragma No_Body,Pragma No_Component_Reordering,Pragma Max_Queue_Length,Implementation Defined Pragmas
5107 @anchor{gnat_rm/implementation_defined_pragmas pragma-no-body}@anchor{9c}
5108 @section Pragma No_Body
5117 There are a number of cases in which a package spec does not require a body,
5118 and in fact a body is not permitted. GNAT will not permit the spec to be
5119 compiled if there is a body around. The pragma No_Body allows you to provide
5120 a body file, even in a case where no body is allowed. The body file must
5121 contain only comments and a single No_Body pragma. This is recognized by
5122 the compiler as indicating that no body is logically present.
5124 This is particularly useful during maintenance when a package is modified in
5125 such a way that a body needed before is no longer needed. The provision of a
5126 dummy body with a No_Body pragma ensures that there is no interference from
5127 earlier versions of the package body.
5129 @node Pragma No_Component_Reordering,Pragma No_Elaboration_Code_All,Pragma No_Body,Implementation Defined Pragmas
5130 @anchor{gnat_rm/implementation_defined_pragmas pragma-no-component-reordering}@anchor{9d}
5131 @section Pragma No_Component_Reordering
5137 pragma No_Component_Reordering [([Entity =>] type_LOCAL_NAME)];
5140 @code{type_LOCAL_NAME} must refer to a record type declaration in the current
5141 declarative part. The effect is to preclude any reordering of components
5142 for the layout of the record, i.e. the record is laid out by the compiler
5143 in the order in which the components are declared textually. The form with
5144 no argument is a configuration pragma which applies to all record types
5145 declared in units to which the pragma applies and there is a requirement
5146 that this pragma be used consistently within a partition.
5148 @node Pragma No_Elaboration_Code_All,Pragma No_Heap_Finalization,Pragma No_Component_Reordering,Implementation Defined Pragmas
5149 @anchor{gnat_rm/implementation_defined_pragmas id23}@anchor{9e}@anchor{gnat_rm/implementation_defined_pragmas pragma-no-elaboration-code-all}@anchor{9f}
5150 @section Pragma No_Elaboration_Code_All
5156 pragma No_Elaboration_Code_All [(program_unit_NAME)];
5159 This is a program unit pragma (there is also an equivalent aspect of the
5160 same name) that establishes the restriction @code{No_Elaboration_Code} for
5161 the current unit and any extended main source units (body and subunits).
5162 It also has the effect of enforcing a transitive application of this
5163 aspect, so that if any unit is implicitly or explicitly with'ed by the
5164 current unit, it must also have the No_Elaboration_Code_All aspect set.
5165 It may be applied to package or subprogram specs or their generic versions.
5167 @node Pragma No_Heap_Finalization,Pragma No_Inline,Pragma No_Elaboration_Code_All,Implementation Defined Pragmas
5168 @anchor{gnat_rm/implementation_defined_pragmas pragma-no-heap-finalization}@anchor{a0}
5169 @section Pragma No_Heap_Finalization
5175 pragma No_Heap_Finalization [ (first_subtype_LOCAL_NAME) ];
5178 Pragma @code{No_Heap_Finalization} may be used as a configuration pragma or as a
5179 type-specific pragma.
5181 In its configuration form, the pragma must appear within a configuration file
5182 such as gnat.adc, without an argument. The pragma suppresses the call to
5183 @code{Finalize} for heap-allocated objects created through library-level named
5184 access-to-object types in cases where the designated type requires finalization
5187 In its type-specific form, the argument of the pragma must denote a
5188 library-level named access-to-object type. The pragma suppresses the call to
5189 @code{Finalize} for heap-allocated objects created through the specific access type
5190 in cases where the designated type requires finalization actions.
5192 It is still possible to finalize such heap-allocated objects by explicitly
5195 A library-level named access-to-object type declared within a generic unit will
5196 lose its @code{No_Heap_Finalization} pragma when the corresponding instance does not
5197 appear at the library level.
5199 @node Pragma No_Inline,Pragma No_Return,Pragma No_Heap_Finalization,Implementation Defined Pragmas
5200 @anchor{gnat_rm/implementation_defined_pragmas id24}@anchor{a1}@anchor{gnat_rm/implementation_defined_pragmas pragma-no-inline}@anchor{a2}
5201 @section Pragma No_Inline
5207 pragma No_Inline (NAME @{, NAME@});
5210 This pragma suppresses inlining for the callable entity or the instances of
5211 the generic subprogram designated by @code{NAME}, including inlining that
5212 results from the use of pragma @code{Inline}. This pragma is always active,
5213 in particular it is not subject to the use of option @emph{-gnatn} or
5214 @emph{-gnatN}. It is illegal to specify both pragma @code{No_Inline} and
5215 pragma @code{Inline_Always} for the same @code{NAME}.
5217 @node Pragma No_Return,Pragma No_Run_Time,Pragma No_Inline,Implementation Defined Pragmas
5218 @anchor{gnat_rm/implementation_defined_pragmas pragma-no-return}@anchor{a3}
5219 @section Pragma No_Return
5225 pragma No_Return (procedure_LOCAL_NAME @{, procedure_LOCAL_NAME@});
5228 Each @code{procedure_LOCAL_NAME} argument must refer to one or more procedure
5229 declarations in the current declarative part. A procedure to which this
5230 pragma is applied may not contain any explicit @code{return} statements.
5231 In addition, if the procedure contains any implicit returns from falling
5232 off the end of a statement sequence, then execution of that implicit
5233 return will cause Program_Error to be raised.
5235 One use of this pragma is to identify procedures whose only purpose is to raise
5236 an exception. Another use of this pragma is to suppress incorrect warnings
5237 about missing returns in functions, where the last statement of a function
5238 statement sequence is a call to such a procedure.
5240 Note that in Ada 2005 mode, this pragma is part of the language. It is
5241 available in all earlier versions of Ada as an implementation-defined
5244 @node Pragma No_Run_Time,Pragma No_Strict_Aliasing,Pragma No_Return,Implementation Defined Pragmas
5245 @anchor{gnat_rm/implementation_defined_pragmas pragma-no-run-time}@anchor{a4}
5246 @section Pragma No_Run_Time
5255 This is an obsolete configuration pragma that historically was used to
5256 set up a runtime library with no object code. It is now used only for
5257 internal testing. The pragma has been superseded by the reconfigurable
5258 runtime capability of GNAT.
5260 @node Pragma No_Strict_Aliasing,Pragma No_Tagged_Streams,Pragma No_Run_Time,Implementation Defined Pragmas
5261 @anchor{gnat_rm/implementation_defined_pragmas pragma-no-strict-aliasing}@anchor{a5}
5262 @section Pragma No_Strict_Aliasing
5268 pragma No_Strict_Aliasing [([Entity =>] type_LOCAL_NAME)];
5271 @code{type_LOCAL_NAME} must refer to an access type
5272 declaration in the current declarative part. The effect is to inhibit
5273 strict aliasing optimization for the given type. The form with no
5274 arguments is a configuration pragma which applies to all access types
5275 declared in units to which the pragma applies. For a detailed
5276 description of the strict aliasing optimization, and the situations
5277 in which it must be suppressed, see the section on Optimization and Strict Aliasing
5278 in the @cite{GNAT User's Guide}.
5280 This pragma currently has no effects on access to unconstrained array types.
5282 @node Pragma No_Tagged_Streams,Pragma Normalize_Scalars,Pragma No_Strict_Aliasing,Implementation Defined Pragmas
5283 @anchor{gnat_rm/implementation_defined_pragmas pragma-no-tagged-streams}@anchor{a6}@anchor{gnat_rm/implementation_defined_pragmas id25}@anchor{a7}
5284 @section Pragma No_Tagged_Streams
5290 pragma No_Tagged_Streams [([Entity =>] tagged_type_LOCAL_NAME)];
5293 Normally when a tagged type is introduced using a full type declaration,
5294 part of the processing includes generating stream access routines to be
5295 used by stream attributes referencing the type (or one of its subtypes
5296 or derived types). This can involve the generation of significant amounts
5297 of code which is wasted space if stream routines are not needed for the
5300 The @code{No_Tagged_Streams} pragma causes the generation of these stream
5301 routines to be skipped, and any attempt to use stream operations on
5302 types subject to this pragma will be statically rejected as illegal.
5304 There are two forms of the pragma. The form with no arguments must appear
5305 in a declarative sequence or in the declarations of a package spec. This
5306 pragma affects all subsequent root tagged types declared in the declaration
5307 sequence, and specifies that no stream routines be generated. The form with
5308 an argument (for which there is also a corresponding aspect) specifies a
5309 single root tagged type for which stream routines are not to be generated.
5311 Once the pragma has been given for a particular root tagged type, all subtypes
5312 and derived types of this type inherit the pragma automatically, so the effect
5313 applies to a complete hierarchy (this is necessary to deal with the class-wide
5314 dispatching versions of the stream routines).
5316 @node Pragma Normalize_Scalars,Pragma Obsolescent,Pragma No_Tagged_Streams,Implementation Defined Pragmas
5317 @anchor{gnat_rm/implementation_defined_pragmas pragma-normalize-scalars}@anchor{a8}
5318 @section Pragma Normalize_Scalars
5324 pragma Normalize_Scalars;
5327 This is a language defined pragma which is fully implemented in GNAT. The
5328 effect is to cause all scalar objects that are not otherwise initialized
5329 to be initialized. The initial values are implementation dependent and
5335 @item @emph{Standard.Character}
5337 Objects whose root type is Standard.Character are initialized to
5338 Character'Last unless the subtype range excludes NUL (in which case
5339 NUL is used). This choice will always generate an invalid value if
5342 @item @emph{Standard.Wide_Character}
5344 Objects whose root type is Standard.Wide_Character are initialized to
5345 Wide_Character'Last unless the subtype range excludes NUL (in which case
5346 NUL is used). This choice will always generate an invalid value if
5349 @item @emph{Standard.Wide_Wide_Character}
5351 Objects whose root type is Standard.Wide_Wide_Character are initialized to
5352 the invalid value 16#FFFF_FFFF# unless the subtype range excludes NUL (in
5353 which case NUL is used). This choice will always generate an invalid value if
5356 @item @emph{Integer types}
5358 Objects of an integer type are treated differently depending on whether
5359 negative values are present in the subtype. If no negative values are
5360 present, then all one bits is used as the initial value except in the
5361 special case where zero is excluded from the subtype, in which case
5362 all zero bits are used. This choice will always generate an invalid
5363 value if one exists.
5365 For subtypes with negative values present, the largest negative number
5366 is used, except in the unusual case where this largest negative number
5367 is in the subtype, and the largest positive number is not, in which case
5368 the largest positive value is used. This choice will always generate
5369 an invalid value if one exists.
5371 @item @emph{Floating-Point Types}
5373 Objects of all floating-point types are initialized to all 1-bits. For
5374 standard IEEE format, this corresponds to a NaN (not a number) which is
5375 indeed an invalid value.
5377 @item @emph{Fixed-Point Types}
5379 Objects of all fixed-point types are treated as described above for integers,
5380 with the rules applying to the underlying integer value used to represent
5381 the fixed-point value.
5383 @item @emph{Modular types}
5385 Objects of a modular type are initialized to all one bits, except in
5386 the special case where zero is excluded from the subtype, in which
5387 case all zero bits are used. This choice will always generate an
5388 invalid value if one exists.
5390 @item @emph{Enumeration types}
5392 Objects of an enumeration type are initialized to all one-bits, i.e., to
5393 the value @code{2 ** typ'Size - 1} unless the subtype excludes the literal
5394 whose Pos value is zero, in which case a code of zero is used. This choice
5395 will always generate an invalid value if one exists.
5398 @node Pragma Obsolescent,Pragma Optimize_Alignment,Pragma Normalize_Scalars,Implementation Defined Pragmas
5399 @anchor{gnat_rm/implementation_defined_pragmas pragma-obsolescent}@anchor{a9}@anchor{gnat_rm/implementation_defined_pragmas id26}@anchor{aa}
5400 @section Pragma Obsolescent
5408 pragma Obsolescent (
5409 [Message =>] static_string_EXPRESSION
5410 [,[Version =>] Ada_05]]);
5412 pragma Obsolescent (
5414 [,[Message =>] static_string_EXPRESSION
5415 [,[Version =>] Ada_05]] );
5418 This pragma can occur immediately following a declaration of an entity,
5419 including the case of a record component. If no Entity argument is present,
5420 then this declaration is the one to which the pragma applies. If an Entity
5421 parameter is present, it must either match the name of the entity in this
5422 declaration, or alternatively, the pragma can immediately follow an enumeration
5423 type declaration, where the Entity argument names one of the enumeration
5426 This pragma is used to indicate that the named entity
5427 is considered obsolescent and should not be used. Typically this is
5428 used when an API must be modified by eventually removing or modifying
5429 existing subprograms or other entities. The pragma can be used at an
5430 intermediate stage when the entity is still present, but will be
5433 The effect of this pragma is to output a warning message on a reference to
5434 an entity thus marked that the subprogram is obsolescent if the appropriate
5435 warning option in the compiler is activated. If the @code{Message} parameter is
5436 present, then a second warning message is given containing this text. In
5437 addition, a reference to the entity is considered to be a violation of pragma
5438 @code{Restrictions (No_Obsolescent_Features)}.
5440 This pragma can also be used as a program unit pragma for a package,
5441 in which case the entity name is the name of the package, and the
5442 pragma indicates that the entire package is considered
5443 obsolescent. In this case a client @code{with}ing such a package
5444 violates the restriction, and the @code{with} clause is
5445 flagged with warnings if the warning option is set.
5447 If the @code{Version} parameter is present (which must be exactly
5448 the identifier @code{Ada_05}, no other argument is allowed), then the
5449 indication of obsolescence applies only when compiling in Ada 2005
5450 mode. This is primarily intended for dealing with the situations
5451 in the predefined library where subprograms or packages
5452 have become defined as obsolescent in Ada 2005
5453 (e.g., in @code{Ada.Characters.Handling}), but may be used anywhere.
5455 The following examples show typical uses of this pragma:
5459 pragma Obsolescent (p, Message => "use pp instead of p");
5464 pragma Obsolescent ("use q2new instead");
5466 type R is new integer;
5469 Message => "use RR in Ada 2005",
5479 type E is (a, bc, 'd', quack);
5480 pragma Obsolescent (Entity => bc)
5481 pragma Obsolescent (Entity => 'd')
5484 (a, b : character) return character;
5485 pragma Obsolescent (Entity => "+");
5489 Note that, as for all pragmas, if you use a pragma argument identifier,
5490 then all subsequent parameters must also use a pragma argument identifier.
5491 So if you specify @code{Entity =>} for the @code{Entity} argument, and a @code{Message}
5492 argument is present, it must be preceded by @code{Message =>}.
5494 @node Pragma Optimize_Alignment,Pragma Ordered,Pragma Obsolescent,Implementation Defined Pragmas
5495 @anchor{gnat_rm/implementation_defined_pragmas pragma-optimize-alignment}@anchor{ab}
5496 @section Pragma Optimize_Alignment
5500 @geindex default settings
5505 pragma Optimize_Alignment (TIME | SPACE | OFF);
5508 This is a configuration pragma which affects the choice of default alignments
5509 for types and objects where no alignment is explicitly specified. There is a
5510 time/space trade-off in the selection of these values. Large alignments result
5511 in more efficient code, at the expense of larger data space, since sizes have
5512 to be increased to match these alignments. Smaller alignments save space, but
5513 the access code is slower. The normal choice of default alignments for types
5514 and individual alignment promotions for objects (which is what you get if you
5515 do not use this pragma, or if you use an argument of OFF), tries to balance
5516 these two requirements.
5518 Specifying SPACE causes smaller default alignments to be chosen in two cases.
5519 First any packed record is given an alignment of 1. Second, if a size is given
5520 for the type, then the alignment is chosen to avoid increasing this size. For
5532 In the default mode, this type gets an alignment of 4, so that access to the
5533 Integer field X are efficient. But this means that objects of the type end up
5534 with a size of 8 bytes. This is a valid choice, since sizes of objects are
5535 allowed to be bigger than the size of the type, but it can waste space if for
5536 example fields of type R appear in an enclosing record. If the above type is
5537 compiled in @code{Optimize_Alignment (Space)} mode, the alignment is set to 1.
5539 However, there is one case in which SPACE is ignored. If a variable length
5540 record (that is a discriminated record with a component which is an array
5541 whose length depends on a discriminant), has a pragma Pack, then it is not
5542 in general possible to set the alignment of such a record to one, so the
5543 pragma is ignored in this case (with a warning).
5545 Specifying SPACE also disables alignment promotions for standalone objects,
5546 which occur when the compiler increases the alignment of a specific object
5547 without changing the alignment of its type.
5549 Specifying TIME causes larger default alignments to be chosen in the case of
5550 small types with sizes that are not a power of 2. For example, consider:
5563 The default alignment for this record is normally 1, but if this type is
5564 compiled in @code{Optimize_Alignment (Time)} mode, then the alignment is set
5565 to 4, which wastes space for objects of the type, since they are now 4 bytes
5566 long, but results in more efficient access when the whole record is referenced.
5568 As noted above, this is a configuration pragma, and there is a requirement
5569 that all units in a partition be compiled with a consistent setting of the
5570 optimization setting. This would normally be achieved by use of a configuration
5571 pragma file containing the appropriate setting. The exception to this rule is
5572 that units with an explicit configuration pragma in the same file as the source
5573 unit are excluded from the consistency check, as are all predefined units. The
5574 latter are compiled by default in pragma Optimize_Alignment (Off) mode if no
5575 pragma appears at the start of the file.
5577 @node Pragma Ordered,Pragma Overflow_Mode,Pragma Optimize_Alignment,Implementation Defined Pragmas
5578 @anchor{gnat_rm/implementation_defined_pragmas pragma-ordered}@anchor{ac}
5579 @section Pragma Ordered
5585 pragma Ordered (enumeration_first_subtype_LOCAL_NAME);
5588 Most enumeration types are from a conceptual point of view unordered.
5589 For example, consider:
5592 type Color is (Red, Blue, Green, Yellow);
5595 By Ada semantics @code{Blue > Red} and @code{Green > Blue},
5596 but really these relations make no sense; the enumeration type merely
5597 specifies a set of possible colors, and the order is unimportant.
5599 For unordered enumeration types, it is generally a good idea if
5600 clients avoid comparisons (other than equality or inequality) and
5601 explicit ranges. (A @emph{client} is a unit where the type is referenced,
5602 other than the unit where the type is declared, its body, and its subunits.)
5603 For example, if code buried in some client says:
5606 if Current_Color < Yellow then ...
5607 if Current_Color in Blue .. Green then ...
5610 then the client code is relying on the order, which is undesirable.
5611 It makes the code hard to read and creates maintenance difficulties if
5612 entries have to be added to the enumeration type. Instead,
5613 the code in the client should list the possibilities, or an
5614 appropriate subtype should be declared in the unit that declares
5615 the original enumeration type. E.g., the following subtype could
5616 be declared along with the type @code{Color}:
5619 subtype RBG is Color range Red .. Green;
5622 and then the client could write:
5625 if Current_Color in RBG then ...
5626 if Current_Color = Blue or Current_Color = Green then ...
5629 However, some enumeration types are legitimately ordered from a conceptual
5630 point of view. For example, if you declare:
5633 type Day is (Mon, Tue, Wed, Thu, Fri, Sat, Sun);
5636 then the ordering imposed by the language is reasonable, and
5637 clients can depend on it, writing for example:
5640 if D in Mon .. Fri then ...
5644 The pragma @emph{Ordered} is provided to mark enumeration types that
5645 are conceptually ordered, alerting the reader that clients may depend
5646 on the ordering. GNAT provides a pragma to mark enumerations as ordered
5647 rather than one to mark them as unordered, since in our experience,
5648 the great majority of enumeration types are conceptually unordered.
5650 The types @code{Boolean}, @code{Character}, @code{Wide_Character},
5651 and @code{Wide_Wide_Character}
5652 are considered to be ordered types, so each is declared with a
5653 pragma @code{Ordered} in package @code{Standard}.
5655 Normally pragma @code{Ordered} serves only as documentation and a guide for
5656 coding standards, but GNAT provides a warning switch @emph{-gnatw.u} that
5657 requests warnings for inappropriate uses (comparisons and explicit
5658 subranges) for unordered types. If this switch is used, then any
5659 enumeration type not marked with pragma @code{Ordered} will be considered
5660 as unordered, and will generate warnings for inappropriate uses.
5662 Note that generic types are not considered ordered or unordered (since the
5663 template can be instantiated for both cases), so we never generate warnings
5664 for the case of generic enumerated types.
5666 For additional information please refer to the description of the
5667 @emph{-gnatw.u} switch in the GNAT User's Guide.
5669 @node Pragma Overflow_Mode,Pragma Overriding_Renamings,Pragma Ordered,Implementation Defined Pragmas
5670 @anchor{gnat_rm/implementation_defined_pragmas pragma-overflow-mode}@anchor{ad}
5671 @section Pragma Overflow_Mode
5677 pragma Overflow_Mode
5679 [,[Assertions =>] MODE]);
5681 MODE ::= STRICT | MINIMIZED | ELIMINATED
5684 This pragma sets the current overflow mode to the given setting. For details
5685 of the meaning of these modes, please refer to the
5686 'Overflow Check Handling in GNAT' appendix in the
5687 GNAT User's Guide. If only the @code{General} parameter is present,
5688 the given mode applies to all expressions. If both parameters are present,
5689 the @code{General} mode applies to expressions outside assertions, and
5690 the @code{Eliminated} mode applies to expressions within assertions.
5692 The case of the @code{MODE} parameter is ignored,
5693 so @code{MINIMIZED}, @code{Minimized} and
5694 @code{minimized} all have the same effect.
5696 The @code{Overflow_Mode} pragma has the same scoping and placement
5697 rules as pragma @code{Suppress}, so it can occur either as a
5698 configuration pragma, specifying a default for the whole
5699 program, or in a declarative scope, where it applies to the
5700 remaining declarations and statements in that scope.
5702 The pragma @code{Suppress (Overflow_Check)} suppresses
5703 overflow checking, but does not affect the overflow mode.
5705 The pragma @code{Unsuppress (Overflow_Check)} unsuppresses (enables)
5706 overflow checking, but does not affect the overflow mode.
5708 @node Pragma Overriding_Renamings,Pragma Partition_Elaboration_Policy,Pragma Overflow_Mode,Implementation Defined Pragmas
5709 @anchor{gnat_rm/implementation_defined_pragmas pragma-overriding-renamings}@anchor{ae}
5710 @section Pragma Overriding_Renamings
5713 @geindex Rational profile
5715 @geindex Rational compatibility
5720 pragma Overriding_Renamings;
5723 This is a GNAT configuration pragma to simplify porting
5724 legacy code accepted by the Rational
5725 Ada compiler. In the presence of this pragma, a renaming declaration that
5726 renames an inherited operation declared in the same scope is legal if selected
5727 notation is used as in:
5730 pragma Overriding_Renamings;
5735 function F (..) renames R.F;
5740 RM 8.3 (15) stipulates that an overridden operation is not visible within the
5741 declaration of the overriding operation.
5743 @node Pragma Partition_Elaboration_Policy,Pragma Part_Of,Pragma Overriding_Renamings,Implementation Defined Pragmas
5744 @anchor{gnat_rm/implementation_defined_pragmas pragma-partition-elaboration-policy}@anchor{af}
5745 @section Pragma Partition_Elaboration_Policy
5751 pragma Partition_Elaboration_Policy (POLICY_IDENTIFIER);
5753 POLICY_IDENTIFIER ::= Concurrent | Sequential
5756 This pragma is standard in Ada 2005, but is available in all earlier
5757 versions of Ada as an implementation-defined pragma.
5758 See Ada 2012 Reference Manual for details.
5760 @node Pragma Part_Of,Pragma Passive,Pragma Partition_Elaboration_Policy,Implementation Defined Pragmas
5761 @anchor{gnat_rm/implementation_defined_pragmas id27}@anchor{b0}@anchor{gnat_rm/implementation_defined_pragmas pragma-part-of}@anchor{b1}
5762 @section Pragma Part_Of
5768 pragma Part_Of (ABSTRACT_STATE);
5770 ABSTRACT_STATE ::= NAME
5773 For the semantics of this pragma, see the entry for aspect @code{Part_Of} in the
5774 SPARK 2014 Reference Manual, section 7.2.6.
5776 @node Pragma Passive,Pragma Persistent_BSS,Pragma Part_Of,Implementation Defined Pragmas
5777 @anchor{gnat_rm/implementation_defined_pragmas pragma-passive}@anchor{b2}
5778 @section Pragma Passive
5784 pragma Passive [(Semaphore | No)];
5787 Syntax checked, but otherwise ignored by GNAT. This is recognized for
5788 compatibility with DEC Ada 83 implementations, where it is used within a
5789 task definition to request that a task be made passive. If the argument
5790 @code{Semaphore} is present, or the argument is omitted, then DEC Ada 83
5791 treats the pragma as an assertion that the containing task is passive
5792 and that optimization of context switch with this task is permitted and
5793 desired. If the argument @code{No} is present, the task must not be
5794 optimized. GNAT does not attempt to optimize any tasks in this manner
5795 (since protected objects are available in place of passive tasks).
5797 For more information on the subject of passive tasks, see the section
5798 'Passive Task Optimization' in the GNAT Users Guide.
5800 @node Pragma Persistent_BSS,Pragma Polling,Pragma Passive,Implementation Defined Pragmas
5801 @anchor{gnat_rm/implementation_defined_pragmas id28}@anchor{b3}@anchor{gnat_rm/implementation_defined_pragmas pragma-persistent-bss}@anchor{b4}
5802 @section Pragma Persistent_BSS
5808 pragma Persistent_BSS [(LOCAL_NAME)]
5811 This pragma allows selected objects to be placed in the @code{.persistent_bss}
5812 section. On some targets the linker and loader provide for special
5813 treatment of this section, allowing a program to be reloaded without
5814 affecting the contents of this data (hence the name persistent).
5816 There are two forms of usage. If an argument is given, it must be the
5817 local name of a library-level object, with no explicit initialization
5818 and whose type is potentially persistent. If no argument is given, then
5819 the pragma is a configuration pragma, and applies to all library-level
5820 objects with no explicit initialization of potentially persistent types.
5822 A potentially persistent type is a scalar type, or an untagged,
5823 non-discriminated record, all of whose components have no explicit
5824 initialization and are themselves of a potentially persistent type,
5825 or an array, all of whose constraints are static, and whose component
5826 type is potentially persistent.
5828 If this pragma is used on a target where this feature is not supported,
5829 then the pragma will be ignored. See also @code{pragma Linker_Section}.
5831 @node Pragma Polling,Pragma Post,Pragma Persistent_BSS,Implementation Defined Pragmas
5832 @anchor{gnat_rm/implementation_defined_pragmas pragma-polling}@anchor{b5}
5833 @section Pragma Polling
5839 pragma Polling (ON | OFF);
5842 This pragma controls the generation of polling code. This is normally off.
5843 If @code{pragma Polling (ON)} is used then periodic calls are generated to
5844 the routine @code{Ada.Exceptions.Poll}. This routine is a separate unit in the
5845 runtime library, and can be found in file @code{a-excpol.adb}.
5847 Pragma @code{Polling} can appear as a configuration pragma (for example it
5848 can be placed in the @code{gnat.adc} file) to enable polling globally, or it
5849 can be used in the statement or declaration sequence to control polling
5852 A call to the polling routine is generated at the start of every loop and
5853 at the start of every subprogram call. This guarantees that the @code{Poll}
5854 routine is called frequently, and places an upper bound (determined by
5855 the complexity of the code) on the period between two @code{Poll} calls.
5857 The primary purpose of the polling interface is to enable asynchronous
5858 aborts on targets that cannot otherwise support it (for example Windows
5859 NT), but it may be used for any other purpose requiring periodic polling.
5860 The standard version is null, and can be replaced by a user program. This
5861 will require re-compilation of the @code{Ada.Exceptions} package that can
5862 be found in files @code{a-except.ads} and @code{a-except.adb}.
5864 A standard alternative unit (in file @code{4wexcpol.adb} in the standard GNAT
5865 distribution) is used to enable the asynchronous abort capability on
5866 targets that do not normally support the capability. The version of
5867 @code{Poll} in this file makes a call to the appropriate runtime routine
5868 to test for an abort condition.
5870 Note that polling can also be enabled by use of the @emph{-gnatP} switch.
5871 See the section on switches for gcc in the @cite{GNAT User's Guide}.
5873 @node Pragma Post,Pragma Postcondition,Pragma Polling,Implementation Defined Pragmas
5874 @anchor{gnat_rm/implementation_defined_pragmas pragma-post}@anchor{b6}
5875 @section Pragma Post
5881 @geindex postconditions
5886 pragma Post (Boolean_Expression);
5889 The @code{Post} pragma is intended to be an exact replacement for
5890 the language-defined
5891 @code{Post} aspect, and shares its restrictions and semantics.
5892 It must appear either immediately following the corresponding
5893 subprogram declaration (only other pragmas may intervene), or
5894 if there is no separate subprogram declaration, then it can
5895 appear at the start of the declarations in a subprogram body
5896 (preceded only by other pragmas).
5898 @node Pragma Postcondition,Pragma Post_Class,Pragma Post,Implementation Defined Pragmas
5899 @anchor{gnat_rm/implementation_defined_pragmas pragma-postcondition}@anchor{b7}
5900 @section Pragma Postcondition
5903 @geindex Postcondition
5906 @geindex postconditions
5911 pragma Postcondition (
5912 [Check =>] Boolean_Expression
5913 [,[Message =>] String_Expression]);
5916 The @code{Postcondition} pragma allows specification of automatic
5917 postcondition checks for subprograms. These checks are similar to
5918 assertions, but are automatically inserted just prior to the return
5919 statements of the subprogram with which they are associated (including
5920 implicit returns at the end of procedure bodies and associated
5921 exception handlers).
5923 In addition, the boolean expression which is the condition which
5924 must be true may contain references to function'Result in the case
5925 of a function to refer to the returned value.
5927 @code{Postcondition} pragmas may appear either immediately following the
5928 (separate) declaration of a subprogram, or at the start of the
5929 declarations of a subprogram body. Only other pragmas may intervene
5930 (that is appear between the subprogram declaration and its
5931 postconditions, or appear before the postcondition in the
5932 declaration sequence in a subprogram body). In the case of a
5933 postcondition appearing after a subprogram declaration, the
5934 formal arguments of the subprogram are visible, and can be
5935 referenced in the postcondition expressions.
5937 The postconditions are collected and automatically tested just
5938 before any return (implicit or explicit) in the subprogram body.
5939 A postcondition is only recognized if postconditions are active
5940 at the time the pragma is encountered. The compiler switch @emph{gnata}
5941 turns on all postconditions by default, and pragma @code{Check_Policy}
5942 with an identifier of @code{Postcondition} can also be used to
5943 control whether postconditions are active.
5945 The general approach is that postconditions are placed in the spec
5946 if they represent functional aspects which make sense to the client.
5947 For example we might have:
5950 function Direction return Integer;
5951 pragma Postcondition
5952 (Direction'Result = +1
5954 Direction'Result = -1);
5957 which serves to document that the result must be +1 or -1, and
5958 will test that this is the case at run time if postcondition
5961 Postconditions within the subprogram body can be used to
5962 check that some internal aspect of the implementation,
5963 not visible to the client, is operating as expected.
5964 For instance if a square root routine keeps an internal
5965 counter of the number of times it is called, then we
5966 might have the following postcondition:
5969 Sqrt_Calls : Natural := 0;
5971 function Sqrt (Arg : Float) return Float is
5972 pragma Postcondition
5973 (Sqrt_Calls = Sqrt_Calls'Old + 1);
5978 As this example, shows, the use of the @code{Old} attribute
5979 is often useful in postconditions to refer to the state on
5980 entry to the subprogram.
5982 Note that postconditions are only checked on normal returns
5983 from the subprogram. If an abnormal return results from
5984 raising an exception, then the postconditions are not checked.
5986 If a postcondition fails, then the exception
5987 @code{System.Assertions.Assert_Failure} is raised. If
5988 a message argument was supplied, then the given string
5989 will be used as the exception message. If no message
5990 argument was supplied, then the default message has
5991 the form "Postcondition failed at file_name:line". The
5992 exception is raised in the context of the subprogram
5993 body, so it is possible to catch postcondition failures
5994 within the subprogram body itself.
5996 Within a package spec, normal visibility rules
5997 in Ada would prevent forward references within a
5998 postcondition pragma to functions defined later in
5999 the same package. This would introduce undesirable
6000 ordering constraints. To avoid this problem, all
6001 postcondition pragmas are analyzed at the end of
6002 the package spec, allowing forward references.
6004 The following example shows that this even allows
6005 mutually recursive postconditions as in:
6008 package Parity_Functions is
6009 function Odd (X : Natural) return Boolean;
6010 pragma Postcondition
6014 (x /= 0 and then Even (X - 1))));
6016 function Even (X : Natural) return Boolean;
6017 pragma Postcondition
6021 (x /= 1 and then Odd (X - 1))));
6023 end Parity_Functions;
6026 There are no restrictions on the complexity or form of
6027 conditions used within @code{Postcondition} pragmas.
6028 The following example shows that it is even possible
6029 to verify performance behavior.
6034 Performance : constant Float;
6035 -- Performance constant set by implementation
6036 -- to match target architecture behavior.
6038 procedure Treesort (Arg : String);
6039 -- Sorts characters of argument using N*logN sort
6040 pragma Postcondition
6041 (Float (Clock - Clock'Old) <=
6042 Float (Arg'Length) *
6043 log (Float (Arg'Length)) *
6048 Note: postcondition pragmas associated with subprograms that are
6049 marked as Inline_Always, or those marked as Inline with front-end
6050 inlining (-gnatN option set) are accepted and legality-checked
6051 by the compiler, but are ignored at run-time even if postcondition
6052 checking is enabled.
6054 Note that pragma @code{Postcondition} differs from the language-defined
6055 @code{Post} aspect (and corresponding @code{Post} pragma) in allowing
6056 multiple occurrences, allowing occurences in the body even if there
6057 is a separate spec, and allowing a second string parameter, and the
6058 use of the pragma identifier @code{Check}. Historically, pragma
6059 @code{Postcondition} was implemented prior to the development of
6060 Ada 2012, and has been retained in its original form for
6061 compatibility purposes.
6063 @node Pragma Post_Class,Pragma Rename_Pragma,Pragma Postcondition,Implementation Defined Pragmas
6064 @anchor{gnat_rm/implementation_defined_pragmas pragma-post-class}@anchor{b8}
6065 @section Pragma Post_Class
6071 @geindex postconditions
6076 pragma Post_Class (Boolean_Expression);
6079 The @code{Post_Class} pragma is intended to be an exact replacement for
6080 the language-defined
6081 @code{Post'Class} aspect, and shares its restrictions and semantics.
6082 It must appear either immediately following the corresponding
6083 subprogram declaration (only other pragmas may intervene), or
6084 if there is no separate subprogram declaration, then it can
6085 appear at the start of the declarations in a subprogram body
6086 (preceded only by other pragmas).
6088 Note: This pragma is called @code{Post_Class} rather than
6089 @code{Post'Class} because the latter would not be strictly
6090 conforming to the allowed syntax for pragmas. The motivation
6091 for provinding pragmas equivalent to the aspects is to allow a program
6092 to be written using the pragmas, and then compiled if necessary
6093 using an Ada compiler that does not recognize the pragmas or
6094 aspects, but is prepared to ignore the pragmas. The assertion
6095 policy that controls this pragma is @code{Post'Class}, not
6098 @node Pragma Rename_Pragma,Pragma Pre,Pragma Post_Class,Implementation Defined Pragmas
6099 @anchor{gnat_rm/implementation_defined_pragmas pragma-rename-pragma}@anchor{b9}
6100 @section Pragma Rename_Pragma
6109 pragma Rename_Pragma (
6110 [New_Name =>] IDENTIFIER,
6111 [Renamed =>] pragma_IDENTIFIER);
6114 This pragma provides a mechanism for supplying new names for existing
6115 pragmas. The @code{New_Name} identifier can subsequently be used as a synonym for
6116 the Renamed pragma. For example, suppose you have code that was originally
6117 developed on a compiler that supports Inline_Only as an implementation defined
6118 pragma. And suppose the semantics of pragma Inline_Only are identical to (or at
6119 least very similar to) the GNAT implementation defined pragma
6120 Inline_Always. You could globally replace Inline_Only with Inline_Always.
6122 However, to avoid that source modification, you could instead add a
6123 configuration pragma:
6126 pragma Rename_Pragma (
6127 New_Name => Inline_Only,
6128 Renamed => Inline_Always);
6131 Then GNAT will treat "pragma Inline_Only ..." as if you had written
6132 "pragma Inline_Always ...".
6134 Pragma Inline_Only will not necessarily mean the same thing as the other Ada
6135 compiler; it's up to you to make sure the semantics are close enough.
6137 @node Pragma Pre,Pragma Precondition,Pragma Rename_Pragma,Implementation Defined Pragmas
6138 @anchor{gnat_rm/implementation_defined_pragmas pragma-pre}@anchor{ba}
6145 @geindex preconditions
6150 pragma Pre (Boolean_Expression);
6153 The @code{Pre} pragma is intended to be an exact replacement for
6154 the language-defined
6155 @code{Pre} aspect, and shares its restrictions and semantics.
6156 It must appear either immediately following the corresponding
6157 subprogram declaration (only other pragmas may intervene), or
6158 if there is no separate subprogram declaration, then it can
6159 appear at the start of the declarations in a subprogram body
6160 (preceded only by other pragmas).
6162 @node Pragma Precondition,Pragma Predicate,Pragma Pre,Implementation Defined Pragmas
6163 @anchor{gnat_rm/implementation_defined_pragmas pragma-precondition}@anchor{bb}
6164 @section Pragma Precondition
6167 @geindex Preconditions
6170 @geindex preconditions
6175 pragma Precondition (
6176 [Check =>] Boolean_Expression
6177 [,[Message =>] String_Expression]);
6180 The @code{Precondition} pragma is similar to @code{Postcondition}
6181 except that the corresponding checks take place immediately upon
6182 entry to the subprogram, and if a precondition fails, the exception
6183 is raised in the context of the caller, and the attribute 'Result
6184 cannot be used within the precondition expression.
6186 Otherwise, the placement and visibility rules are identical to those
6187 described for postconditions. The following is an example of use
6188 within a package spec:
6191 package Math_Functions is
6193 function Sqrt (Arg : Float) return Float;
6194 pragma Precondition (Arg >= 0.0)
6199 @code{Precondition} pragmas may appear either immediately following the
6200 (separate) declaration of a subprogram, or at the start of the
6201 declarations of a subprogram body. Only other pragmas may intervene
6202 (that is appear between the subprogram declaration and its
6203 postconditions, or appear before the postcondition in the
6204 declaration sequence in a subprogram body).
6206 Note: precondition pragmas associated with subprograms that are
6207 marked as Inline_Always, or those marked as Inline with front-end
6208 inlining (-gnatN option set) are accepted and legality-checked
6209 by the compiler, but are ignored at run-time even if precondition
6210 checking is enabled.
6212 Note that pragma @code{Precondition} differs from the language-defined
6213 @code{Pre} aspect (and corresponding @code{Pre} pragma) in allowing
6214 multiple occurrences, allowing occurences in the body even if there
6215 is a separate spec, and allowing a second string parameter, and the
6216 use of the pragma identifier @code{Check}. Historically, pragma
6217 @code{Precondition} was implemented prior to the development of
6218 Ada 2012, and has been retained in its original form for
6219 compatibility purposes.
6221 @node Pragma Predicate,Pragma Predicate_Failure,Pragma Precondition,Implementation Defined Pragmas
6222 @anchor{gnat_rm/implementation_defined_pragmas id29}@anchor{bc}@anchor{gnat_rm/implementation_defined_pragmas pragma-predicate}@anchor{bd}
6223 @section Pragma Predicate
6230 ([Entity =>] type_LOCAL_NAME,
6231 [Check =>] EXPRESSION);
6234 This pragma (available in all versions of Ada in GNAT) encompasses both
6235 the @code{Static_Predicate} and @code{Dynamic_Predicate} aspects in
6236 Ada 2012. A predicate is regarded as static if it has an allowed form
6237 for @code{Static_Predicate} and is otherwise treated as a
6238 @code{Dynamic_Predicate}. Otherwise, predicates specified by this
6239 pragma behave exactly as described in the Ada 2012 reference manual.
6240 For example, if we have
6243 type R is range 1 .. 10;
6245 pragma Predicate (Entity => S, Check => S not in 4 .. 6);
6247 pragma Predicate (Entity => Q, Check => F(Q) or G(Q));
6250 the effect is identical to the following Ada 2012 code:
6253 type R is range 1 .. 10;
6255 Static_Predicate => S not in 4 .. 6;
6257 Dynamic_Predicate => F(Q) or G(Q);
6260 Note that there are no pragmas @code{Dynamic_Predicate}
6261 or @code{Static_Predicate}. That is
6262 because these pragmas would affect legality and semantics of
6263 the program and thus do not have a neutral effect if ignored.
6264 The motivation behind providing pragmas equivalent to
6265 corresponding aspects is to allow a program to be written
6266 using the pragmas, and then compiled with a compiler that
6267 will ignore the pragmas. That doesn't work in the case of
6268 static and dynamic predicates, since if the corresponding
6269 pragmas are ignored, then the behavior of the program is
6270 fundamentally changed (for example a membership test
6271 @code{A in B} would not take into account a predicate
6272 defined for subtype B). When following this approach, the
6273 use of predicates should be avoided.
6275 @node Pragma Predicate_Failure,Pragma Preelaborable_Initialization,Pragma Predicate,Implementation Defined Pragmas
6276 @anchor{gnat_rm/implementation_defined_pragmas pragma-predicate-failure}@anchor{be}
6277 @section Pragma Predicate_Failure
6283 pragma Predicate_Failure
6284 ([Entity =>] type_LOCAL_NAME,
6285 [Message =>] String_Expression);
6288 The @code{Predicate_Failure} pragma is intended to be an exact replacement for
6289 the language-defined
6290 @code{Predicate_Failure} aspect, and shares its restrictions and semantics.
6292 @node Pragma Preelaborable_Initialization,Pragma Prefix_Exception_Messages,Pragma Predicate_Failure,Implementation Defined Pragmas
6293 @anchor{gnat_rm/implementation_defined_pragmas pragma-preelaborable-initialization}@anchor{bf}
6294 @section Pragma Preelaborable_Initialization
6300 pragma Preelaborable_Initialization (DIRECT_NAME);
6303 This pragma is standard in Ada 2005, but is available in all earlier
6304 versions of Ada as an implementation-defined pragma.
6305 See Ada 2012 Reference Manual for details.
6307 @node Pragma Prefix_Exception_Messages,Pragma Pre_Class,Pragma Preelaborable_Initialization,Implementation Defined Pragmas
6308 @anchor{gnat_rm/implementation_defined_pragmas pragma-prefix-exception-messages}@anchor{c0}
6309 @section Pragma Prefix_Exception_Messages
6312 @geindex Prefix_Exception_Messages
6316 @geindex Exception_Message
6321 pragma Prefix_Exception_Messages;
6324 This is an implementation-defined configuration pragma that affects the
6325 behavior of raise statements with a message given as a static string
6326 constant (typically a string literal). In such cases, the string will
6327 be automatically prefixed by the name of the enclosing entity (giving
6328 the package and subprogram containing the raise statement). This helps
6329 to identify where messages are coming from, and this mode is automatic
6330 for the run-time library.
6332 The pragma has no effect if the message is computed with an expression other
6333 than a static string constant, since the assumption in this case is that
6334 the program computes exactly the string it wants. If you still want the
6335 prefixing in this case, you can always call
6336 @code{GNAT.Source_Info.Enclosing_Entity} and prepend the string manually.
6338 @node Pragma Pre_Class,Pragma Priority_Specific_Dispatching,Pragma Prefix_Exception_Messages,Implementation Defined Pragmas
6339 @anchor{gnat_rm/implementation_defined_pragmas pragma-pre-class}@anchor{c1}
6340 @section Pragma Pre_Class
6346 @geindex preconditions
6351 pragma Pre_Class (Boolean_Expression);
6354 The @code{Pre_Class} pragma is intended to be an exact replacement for
6355 the language-defined
6356 @code{Pre'Class} aspect, and shares its restrictions and semantics.
6357 It must appear either immediately following the corresponding
6358 subprogram declaration (only other pragmas may intervene), or
6359 if there is no separate subprogram declaration, then it can
6360 appear at the start of the declarations in a subprogram body
6361 (preceded only by other pragmas).
6363 Note: This pragma is called @code{Pre_Class} rather than
6364 @code{Pre'Class} because the latter would not be strictly
6365 conforming to the allowed syntax for pragmas. The motivation
6366 for providing pragmas equivalent to the aspects is to allow a program
6367 to be written using the pragmas, and then compiled if necessary
6368 using an Ada compiler that does not recognize the pragmas or
6369 aspects, but is prepared to ignore the pragmas. The assertion
6370 policy that controls this pragma is @code{Pre'Class}, not
6373 @node Pragma Priority_Specific_Dispatching,Pragma Profile,Pragma Pre_Class,Implementation Defined Pragmas
6374 @anchor{gnat_rm/implementation_defined_pragmas pragma-priority-specific-dispatching}@anchor{c2}
6375 @section Pragma Priority_Specific_Dispatching
6381 pragma Priority_Specific_Dispatching (
6383 first_priority_EXPRESSION,
6384 last_priority_EXPRESSION)
6386 POLICY_IDENTIFIER ::=
6387 EDF_Across_Priorities |
6388 FIFO_Within_Priorities |
6389 Non_Preemptive_Within_Priorities |
6390 Round_Robin_Within_Priorities
6393 This pragma is standard in Ada 2005, but is available in all earlier
6394 versions of Ada as an implementation-defined pragma.
6395 See Ada 2012 Reference Manual for details.
6397 @node Pragma Profile,Pragma Profile_Warnings,Pragma Priority_Specific_Dispatching,Implementation Defined Pragmas
6398 @anchor{gnat_rm/implementation_defined_pragmas pragma-profile}@anchor{c3}
6399 @section Pragma Profile
6405 pragma Profile (Ravenscar | Restricted | Rational |
6406 GNAT_Extended_Ravenscar | GNAT_Ravenscar_EDF );
6409 This pragma is standard in Ada 2005, but is available in all earlier
6410 versions of Ada as an implementation-defined pragma. This is a
6411 configuration pragma that establishes a set of configuration pragmas
6412 that depend on the argument. @code{Ravenscar} is standard in Ada 2005.
6413 The other possibilities (@code{Restricted}, @code{Rational},
6414 @code{GNAT_Extended_Ravenscar}, @code{GNAT_Ravenscar_EDF})
6415 are implementation-defined. The set of configuration pragmas
6416 is defined in the following sections.
6422 Pragma Profile (Ravenscar)
6424 The @code{Ravenscar} profile is standard in Ada 2005,
6425 but is available in all earlier
6426 versions of Ada as an implementation-defined pragma. This profile
6427 establishes the following set of configuration pragmas:
6433 @code{Task_Dispatching_Policy (FIFO_Within_Priorities)}
6435 [RM D.2.2] Tasks are dispatched following a preemptive
6436 priority-ordered scheduling policy.
6439 @code{Locking_Policy (Ceiling_Locking)}
6441 [RM D.3] While tasks and interrupts execute a protected action, they inherit
6442 the ceiling priority of the corresponding protected object.
6445 @code{Detect_Blocking}
6447 This pragma forces the detection of potentially blocking operations within a
6448 protected operation, and to raise Program_Error if that happens.
6451 plus the following set of restrictions:
6457 @code{Max_Entry_Queue_Length => 1}
6459 No task can be queued on a protected entry.
6462 @code{Max_Protected_Entries => 1}
6465 @code{Max_Task_Entries => 0}
6467 No rendezvous statements are allowed.
6470 @code{No_Abort_Statements}
6473 @code{No_Dynamic_Attachment}
6476 @code{No_Dynamic_Priorities}
6479 @code{No_Implicit_Heap_Allocations}
6482 @code{No_Local_Protected_Objects}
6485 @code{No_Local_Timing_Events}
6488 @code{No_Protected_Type_Allocators}
6491 @code{No_Relative_Delay}
6494 @code{No_Requeue_Statements}
6497 @code{No_Select_Statements}
6500 @code{No_Specific_Termination_Handlers}
6503 @code{No_Task_Allocators}
6506 @code{No_Task_Hierarchy}
6509 @code{No_Task_Termination}
6512 @code{Simple_Barriers}
6515 The Ravenscar profile also includes the following restrictions that specify
6516 that there are no semantic dependences on the corresponding predefined
6523 @code{No_Dependence => Ada.Asynchronous_Task_Control}
6526 @code{No_Dependence => Ada.Calendar}
6529 @code{No_Dependence => Ada.Execution_Time.Group_Budget}
6532 @code{No_Dependence => Ada.Execution_Time.Timers}
6535 @code{No_Dependence => Ada.Task_Attributes}
6538 @code{No_Dependence => System.Multiprocessors.Dispatching_Domains}
6541 This set of configuration pragmas and restrictions correspond to the
6542 definition of the 'Ravenscar Profile' for limited tasking, devised and
6543 published by the @cite{International Real-Time Ada Workshop@comma{} 1997}.
6544 A description is also available at
6545 @indicateurl{http://www-users.cs.york.ac.uk/~burns/ravenscar.ps}.
6547 The original definition of the profile was revised at subsequent IRTAW
6548 meetings. It has been included in the ISO
6549 @cite{Guide for the Use of the Ada Programming Language in High Integrity Systems},
6550 and was made part of the Ada 2005 standard.
6551 The formal definition given by
6552 the Ada Rapporteur Group (ARG) can be found in two Ada Issues (AI-249 and
6553 AI-305) available at
6554 @indicateurl{http://www.ada-auth.org/cgi-bin/cvsweb.cgi/ais/ai-00249.txt} and
6555 @indicateurl{http://www.ada-auth.org/cgi-bin/cvsweb.cgi/ais/ai-00305.txt}.
6557 The above set is a superset of the restrictions provided by pragma
6558 @code{Profile (Restricted)}, it includes six additional restrictions
6559 (@code{Simple_Barriers}, @code{No_Select_Statements},
6560 @code{No_Calendar}, @code{No_Implicit_Heap_Allocations},
6561 @code{No_Relative_Delay} and @code{No_Task_Termination}). This means
6562 that pragma @code{Profile (Ravenscar)}, like the pragma
6563 @code{Profile (Restricted)},
6564 automatically causes the use of a simplified,
6565 more efficient version of the tasking run-time library.
6568 Pragma Profile (GNAT_Extended_Ravenscar)
6570 This profile corresponds to a GNAT specific extension of the
6571 Ravenscar profile. The profile may change in the future although
6572 only in a compatible way: some restrictions may be removed or
6573 relaxed. It is defined as a variation of the Ravenscar profile.
6575 The @code{No_Implicit_Heap_Allocations} restriction has been replaced
6576 by @code{No_Implicit_Task_Allocations} and
6577 @code{No_Implicit_Protected_Object_Allocations}.
6579 The @code{Simple_Barriers} restriction has been replaced by
6580 @code{Pure_Barriers}.
6582 The @code{Max_Protected_Entries}, @code{Max_Entry_Queue_Length}, and
6583 @code{No_Relative_Delay} restrictions have been removed.
6586 Pragma Profile (GNAT_Ravenscar_EDF)
6588 This profile corresponds to the Ravenscar profile but using
6589 EDF_Across_Priority as the Task_Scheduling_Policy.
6592 Pragma Profile (Restricted)
6594 This profile corresponds to the GNAT restricted run time. It
6595 establishes the following set of restrictions:
6601 @code{No_Abort_Statements}
6604 @code{No_Entry_Queue}
6607 @code{No_Task_Hierarchy}
6610 @code{No_Task_Allocators}
6613 @code{No_Dynamic_Priorities}
6616 @code{No_Terminate_Alternatives}
6619 @code{No_Dynamic_Attachment}
6622 @code{No_Protected_Type_Allocators}
6625 @code{No_Local_Protected_Objects}
6628 @code{No_Requeue_Statements}
6631 @code{No_Task_Attributes_Package}
6634 @code{Max_Asynchronous_Select_Nesting = 0}
6637 @code{Max_Task_Entries = 0}
6640 @code{Max_Protected_Entries = 1}
6643 @code{Max_Select_Alternatives = 0}
6646 This set of restrictions causes the automatic selection of a simplified
6647 version of the run time that provides improved performance for the
6648 limited set of tasking functionality permitted by this set of restrictions.
6651 Pragma Profile (Rational)
6653 The Rational profile is intended to facilitate porting legacy code that
6654 compiles with the Rational APEX compiler, even when the code includes non-
6655 conforming Ada constructs. The profile enables the following three pragmas:
6661 @code{pragma Implicit_Packing}
6664 @code{pragma Overriding_Renamings}
6667 @code{pragma Use_VADS_Size}
6671 @node Pragma Profile_Warnings,Pragma Propagate_Exceptions,Pragma Profile,Implementation Defined Pragmas
6672 @anchor{gnat_rm/implementation_defined_pragmas pragma-profile-warnings}@anchor{c4}
6673 @section Pragma Profile_Warnings
6679 pragma Profile_Warnings (Ravenscar | Restricted | Rational);
6682 This is an implementation-defined pragma that is similar in
6683 effect to @code{pragma Profile} except that instead of
6684 generating @code{Restrictions} pragmas, it generates
6685 @code{Restriction_Warnings} pragmas. The result is that
6686 violations of the profile generate warning messages instead
6689 @node Pragma Propagate_Exceptions,Pragma Provide_Shift_Operators,Pragma Profile_Warnings,Implementation Defined Pragmas
6690 @anchor{gnat_rm/implementation_defined_pragmas pragma-propagate-exceptions}@anchor{c5}
6691 @section Pragma Propagate_Exceptions
6694 @geindex Interfacing to C++
6699 pragma Propagate_Exceptions;
6702 This pragma is now obsolete and, other than generating a warning if warnings
6703 on obsolescent features are enabled, is ignored.
6704 It is retained for compatibility
6705 purposes. It used to be used in connection with optimization of
6706 a now-obsolete mechanism for implementation of exceptions.
6708 @node Pragma Provide_Shift_Operators,Pragma Psect_Object,Pragma Propagate_Exceptions,Implementation Defined Pragmas
6709 @anchor{gnat_rm/implementation_defined_pragmas pragma-provide-shift-operators}@anchor{c6}
6710 @section Pragma Provide_Shift_Operators
6713 @geindex Shift operators
6718 pragma Provide_Shift_Operators (integer_first_subtype_LOCAL_NAME);
6721 This pragma can be applied to a first subtype local name that specifies
6722 either an unsigned or signed type. It has the effect of providing the
6723 five shift operators (Shift_Left, Shift_Right, Shift_Right_Arithmetic,
6724 Rotate_Left and Rotate_Right) for the given type. It is similar to
6725 including the function declarations for these five operators, together
6726 with the pragma Import (Intrinsic, ...) statements.
6728 @node Pragma Psect_Object,Pragma Pure_Function,Pragma Provide_Shift_Operators,Implementation Defined Pragmas
6729 @anchor{gnat_rm/implementation_defined_pragmas pragma-psect-object}@anchor{c7}
6730 @section Pragma Psect_Object
6736 pragma Psect_Object (
6737 [Internal =>] LOCAL_NAME,
6738 [, [External =>] EXTERNAL_SYMBOL]
6739 [, [Size =>] EXTERNAL_SYMBOL]);
6743 | static_string_EXPRESSION
6746 This pragma is identical in effect to pragma @code{Common_Object}.
6748 @node Pragma Pure_Function,Pragma Rational,Pragma Psect_Object,Implementation Defined Pragmas
6749 @anchor{gnat_rm/implementation_defined_pragmas pragma-pure-function}@anchor{c8}@anchor{gnat_rm/implementation_defined_pragmas id30}@anchor{c9}
6750 @section Pragma Pure_Function
6756 pragma Pure_Function ([Entity =>] function_LOCAL_NAME);
6759 This pragma appears in the same declarative part as a function
6760 declaration (or a set of function declarations if more than one
6761 overloaded declaration exists, in which case the pragma applies
6762 to all entities). It specifies that the function @code{Entity} is
6763 to be considered pure for the purposes of code generation. This means
6764 that the compiler can assume that there are no side effects, and
6765 in particular that two calls with identical arguments produce the
6766 same result. It also means that the function can be used in an
6769 Note that, quite deliberately, there are no static checks to try
6770 to ensure that this promise is met, so @code{Pure_Function} can be used
6771 with functions that are conceptually pure, even if they do modify
6772 global variables. For example, a square root function that is
6773 instrumented to count the number of times it is called is still
6774 conceptually pure, and can still be optimized, even though it
6775 modifies a global variable (the count). Memo functions are another
6776 example (where a table of previous calls is kept and consulted to
6777 avoid re-computation).
6779 Note also that the normal rules excluding optimization of subprograms
6780 in pure units (when parameter types are descended from System.Address,
6781 or when the full view of a parameter type is limited), do not apply
6782 for the Pure_Function case. If you explicitly specify Pure_Function,
6783 the compiler may optimize away calls with identical arguments, and
6784 if that results in unexpected behavior, the proper action is not to
6785 use the pragma for subprograms that are not (conceptually) pure.
6787 Note: Most functions in a @code{Pure} package are automatically pure, and
6788 there is no need to use pragma @code{Pure_Function} for such functions. One
6789 exception is any function that has at least one formal of type
6790 @code{System.Address} or a type derived from it. Such functions are not
6791 considered pure by default, since the compiler assumes that the
6792 @code{Address} parameter may be functioning as a pointer and that the
6793 referenced data may change even if the address value does not.
6794 Similarly, imported functions are not considered to be pure by default,
6795 since there is no way of checking that they are in fact pure. The use
6796 of pragma @code{Pure_Function} for such a function will override these default
6797 assumption, and cause the compiler to treat a designated subprogram as pure
6800 Note: If pragma @code{Pure_Function} is applied to a renamed function, it
6801 applies to the underlying renamed function. This can be used to
6802 disambiguate cases of overloading where some but not all functions
6803 in a set of overloaded functions are to be designated as pure.
6805 If pragma @code{Pure_Function} is applied to a library-level function, the
6806 function is also considered pure from an optimization point of view, but the
6807 unit is not a Pure unit in the categorization sense. So for example, a function
6808 thus marked is free to @code{with} non-pure units.
6810 @node Pragma Rational,Pragma Ravenscar,Pragma Pure_Function,Implementation Defined Pragmas
6811 @anchor{gnat_rm/implementation_defined_pragmas pragma-rational}@anchor{ca}
6812 @section Pragma Rational
6821 This pragma is considered obsolescent, but is retained for
6822 compatibility purposes. It is equivalent to:
6825 pragma Profile (Rational);
6828 @node Pragma Ravenscar,Pragma Refined_Depends,Pragma Rational,Implementation Defined Pragmas
6829 @anchor{gnat_rm/implementation_defined_pragmas pragma-ravenscar}@anchor{cb}
6830 @section Pragma Ravenscar
6839 This pragma is considered obsolescent, but is retained for
6840 compatibility purposes. It is equivalent to:
6843 pragma Profile (Ravenscar);
6846 which is the preferred method of setting the @code{Ravenscar} profile.
6848 @node Pragma Refined_Depends,Pragma Refined_Global,Pragma Ravenscar,Implementation Defined Pragmas
6849 @anchor{gnat_rm/implementation_defined_pragmas pragma-refined-depends}@anchor{cc}@anchor{gnat_rm/implementation_defined_pragmas id31}@anchor{cd}
6850 @section Pragma Refined_Depends
6856 pragma Refined_Depends (DEPENDENCY_RELATION);
6858 DEPENDENCY_RELATION ::=
6860 | (DEPENDENCY_CLAUSE @{, DEPENDENCY_CLAUSE@})
6862 DEPENDENCY_CLAUSE ::=
6863 OUTPUT_LIST =>[+] INPUT_LIST
6864 | NULL_DEPENDENCY_CLAUSE
6866 NULL_DEPENDENCY_CLAUSE ::= null => INPUT_LIST
6868 OUTPUT_LIST ::= OUTPUT | (OUTPUT @{, OUTPUT@})
6870 INPUT_LIST ::= null | INPUT | (INPUT @{, INPUT@})
6872 OUTPUT ::= NAME | FUNCTION_RESULT
6875 where FUNCTION_RESULT is a function Result attribute_reference
6878 For the semantics of this pragma, see the entry for aspect @code{Refined_Depends} in
6879 the SPARK 2014 Reference Manual, section 6.1.5.
6881 @node Pragma Refined_Global,Pragma Refined_Post,Pragma Refined_Depends,Implementation Defined Pragmas
6882 @anchor{gnat_rm/implementation_defined_pragmas pragma-refined-global}@anchor{ce}@anchor{gnat_rm/implementation_defined_pragmas id32}@anchor{cf}
6883 @section Pragma Refined_Global
6889 pragma Refined_Global (GLOBAL_SPECIFICATION);
6891 GLOBAL_SPECIFICATION ::=
6894 | (MODED_GLOBAL_LIST @{, MODED_GLOBAL_LIST@})
6896 MODED_GLOBAL_LIST ::= MODE_SELECTOR => GLOBAL_LIST
6898 MODE_SELECTOR ::= In_Out | Input | Output | Proof_In
6899 GLOBAL_LIST ::= GLOBAL_ITEM | (GLOBAL_ITEM @{, GLOBAL_ITEM@})
6900 GLOBAL_ITEM ::= NAME
6903 For the semantics of this pragma, see the entry for aspect @code{Refined_Global} in
6904 the SPARK 2014 Reference Manual, section 6.1.4.
6906 @node Pragma Refined_Post,Pragma Refined_State,Pragma Refined_Global,Implementation Defined Pragmas
6907 @anchor{gnat_rm/implementation_defined_pragmas pragma-refined-post}@anchor{d0}@anchor{gnat_rm/implementation_defined_pragmas id33}@anchor{d1}
6908 @section Pragma Refined_Post
6914 pragma Refined_Post (boolean_EXPRESSION);
6917 For the semantics of this pragma, see the entry for aspect @code{Refined_Post} in
6918 the SPARK 2014 Reference Manual, section 7.2.7.
6920 @node Pragma Refined_State,Pragma Relative_Deadline,Pragma Refined_Post,Implementation Defined Pragmas
6921 @anchor{gnat_rm/implementation_defined_pragmas pragma-refined-state}@anchor{d2}@anchor{gnat_rm/implementation_defined_pragmas id34}@anchor{d3}
6922 @section Pragma Refined_State
6928 pragma Refined_State (REFINEMENT_LIST);
6931 (REFINEMENT_CLAUSE @{, REFINEMENT_CLAUSE@})
6933 REFINEMENT_CLAUSE ::= state_NAME => CONSTITUENT_LIST
6935 CONSTITUENT_LIST ::=
6938 | (CONSTITUENT @{, CONSTITUENT@})
6940 CONSTITUENT ::= object_NAME | state_NAME
6943 For the semantics of this pragma, see the entry for aspect @code{Refined_State} in
6944 the SPARK 2014 Reference Manual, section 7.2.2.
6946 @node Pragma Relative_Deadline,Pragma Remote_Access_Type,Pragma Refined_State,Implementation Defined Pragmas
6947 @anchor{gnat_rm/implementation_defined_pragmas pragma-relative-deadline}@anchor{d4}
6948 @section Pragma Relative_Deadline
6954 pragma Relative_Deadline (time_span_EXPRESSION);
6957 This pragma is standard in Ada 2005, but is available in all earlier
6958 versions of Ada as an implementation-defined pragma.
6959 See Ada 2012 Reference Manual for details.
6961 @node Pragma Remote_Access_Type,Pragma Restricted_Run_Time,Pragma Relative_Deadline,Implementation Defined Pragmas
6962 @anchor{gnat_rm/implementation_defined_pragmas id35}@anchor{d5}@anchor{gnat_rm/implementation_defined_pragmas pragma-remote-access-type}@anchor{d6}
6963 @section Pragma Remote_Access_Type
6969 pragma Remote_Access_Type ([Entity =>] formal_access_type_LOCAL_NAME);
6972 This pragma appears in the formal part of a generic declaration.
6973 It specifies an exception to the RM rule from E.2.2(17/2), which forbids
6974 the use of a remote access to class-wide type as actual for a formal
6977 When this pragma applies to a formal access type @code{Entity}, that
6978 type is treated as a remote access to class-wide type in the generic.
6979 It must be a formal general access type, and its designated type must
6980 be the class-wide type of a formal tagged limited private type from the
6981 same generic declaration.
6983 In the generic unit, the formal type is subject to all restrictions
6984 pertaining to remote access to class-wide types. At instantiation, the
6985 actual type must be a remote access to class-wide type.
6987 @node Pragma Restricted_Run_Time,Pragma Restriction_Warnings,Pragma Remote_Access_Type,Implementation Defined Pragmas
6988 @anchor{gnat_rm/implementation_defined_pragmas pragma-restricted-run-time}@anchor{d7}
6989 @section Pragma Restricted_Run_Time
6995 pragma Restricted_Run_Time;
6998 This pragma is considered obsolescent, but is retained for
6999 compatibility purposes. It is equivalent to:
7002 pragma Profile (Restricted);
7005 which is the preferred method of setting the restricted run time
7008 @node Pragma Restriction_Warnings,Pragma Reviewable,Pragma Restricted_Run_Time,Implementation Defined Pragmas
7009 @anchor{gnat_rm/implementation_defined_pragmas pragma-restriction-warnings}@anchor{d8}
7010 @section Pragma Restriction_Warnings
7016 pragma Restriction_Warnings
7017 (restriction_IDENTIFIER @{, restriction_IDENTIFIER@});
7020 This pragma allows a series of restriction identifiers to be
7021 specified (the list of allowed identifiers is the same as for
7022 pragma @code{Restrictions}). For each of these identifiers
7023 the compiler checks for violations of the restriction, but
7024 generates a warning message rather than an error message
7025 if the restriction is violated.
7027 One use of this is in situations where you want to know
7028 about violations of a restriction, but you want to ignore some of
7029 these violations. Consider this example, where you want to set
7030 Ada_95 mode and enable style checks, but you want to know about
7031 any other use of implementation pragmas:
7034 pragma Restriction_Warnings (No_Implementation_Pragmas);
7035 pragma Warnings (Off, "violation of No_Implementation_Pragmas");
7037 pragma Style_Checks ("2bfhkM160");
7038 pragma Warnings (On, "violation of No_Implementation_Pragmas");
7041 By including the above lines in a configuration pragmas file,
7042 the Ada_95 and Style_Checks pragmas are accepted without
7043 generating a warning, but any other use of implementation
7044 defined pragmas will cause a warning to be generated.
7046 @node Pragma Reviewable,Pragma Secondary_Stack_Size,Pragma Restriction_Warnings,Implementation Defined Pragmas
7047 @anchor{gnat_rm/implementation_defined_pragmas pragma-reviewable}@anchor{d9}
7048 @section Pragma Reviewable
7057 This pragma is an RM-defined standard pragma, but has no effect on the
7058 program being compiled, or on the code generated for the program.
7060 To obtain the required output specified in RM H.3.1, the compiler must be
7061 run with various special switches as follows:
7067 @emph{Where compiler-generated run-time checks remain}
7069 The switch @emph{-gnatGL}
7070 may be used to list the expanded code in pseudo-Ada form.
7071 Runtime checks show up in the listing either as explicit
7072 checks or operators marked with @{@} to indicate a check is present.
7075 @emph{An identification of known exceptions at compile time}
7077 If the program is compiled with @emph{-gnatwa},
7078 the compiler warning messages will indicate all cases where the compiler
7079 detects that an exception is certain to occur at run time.
7082 @emph{Possible reads of uninitialized variables}
7084 The compiler warns of many such cases, but its output is incomplete.
7088 A supplemental static analysis tool
7089 may be used to obtain a comprehensive list of all
7090 possible points at which uninitialized data may be read.
7096 @emph{Where run-time support routines are implicitly invoked}
7098 In the output from @emph{-gnatGL},
7099 run-time calls are explicitly listed as calls to the relevant
7103 @emph{Object code listing}
7105 This may be obtained either by using the @emph{-S} switch,
7106 or the objdump utility.
7109 @emph{Constructs known to be erroneous at compile time}
7111 These are identified by warnings issued by the compiler (use @emph{-gnatwa}).
7114 @emph{Stack usage information}
7116 Static stack usage data (maximum per-subprogram) can be obtained via the
7117 @emph{-fstack-usage} switch to the compiler.
7118 Dynamic stack usage data (per task) can be obtained via the @emph{-u} switch
7127 @emph{Object code listing of entire partition}
7129 This can be obtained by compiling the partition with @emph{-S},
7130 or by applying objdump
7131 to all the object files that are part of the partition.
7134 @emph{A description of the run-time model}
7136 The full sources of the run-time are available, and the documentation of
7137 these routines describes how these run-time routines interface to the
7138 underlying operating system facilities.
7141 @emph{Control and data-flow information}
7145 A supplemental static analysis tool
7146 may be used to obtain complete control and data-flow information, as well as
7147 comprehensive messages identifying possible problems based on this
7150 @node Pragma Secondary_Stack_Size,Pragma Share_Generic,Pragma Reviewable,Implementation Defined Pragmas
7151 @anchor{gnat_rm/implementation_defined_pragmas id36}@anchor{da}@anchor{gnat_rm/implementation_defined_pragmas pragma-secondary-stack-size}@anchor{db}
7152 @section Pragma Secondary_Stack_Size
7158 pragma Secondary_Stack_Size (integer_EXPRESSION);
7161 This pragma appears within the task definition of a single task declaration
7162 or a task type declaration (like pragma @code{Storage_Size}) and applies to all
7163 task objects of that type. The argument specifies the size of the secondary
7164 stack to be used by these task objects, and must be of an integer type. The
7165 secondary stack is used to handle functions that return a variable-sized
7166 result, for example a function returning an unconstrained String.
7168 Note this pragma only applies to targets using fixed secondary stacks, like
7169 VxWorks 653 and bare board targets, where a fixed block for the
7170 secondary stack is allocated from the primary stack of the task. By default,
7171 these targets assign a percentage of the primary stack for the secondary stack,
7172 as defined by @code{System.Parameter.Sec_Stack_Percentage}. With this pragma,
7173 an @code{integer_EXPRESSION} of bytes is assigned from the primary stack instead.
7175 For most targets, the pragma does not apply as the secondary stack grows on
7176 demand: allocated as a chain of blocks in the heap. The default size of these
7177 blocks can be modified via the @code{-D} binder option as described in
7178 @cite{GNAT User's Guide}.
7180 Note that no check is made to see if the secondary stack can fit inside the
7183 Note the pragma cannot appear when the restriction @code{No_Secondary_Stack}
7186 @node Pragma Share_Generic,Pragma Shared,Pragma Secondary_Stack_Size,Implementation Defined Pragmas
7187 @anchor{gnat_rm/implementation_defined_pragmas pragma-share-generic}@anchor{dc}
7188 @section Pragma Share_Generic
7194 pragma Share_Generic (GNAME @{, GNAME@});
7196 GNAME ::= generic_unit_NAME | generic_instance_NAME
7199 This pragma is provided for compatibility with Dec Ada 83. It has
7200 no effect in GNAT (which does not implement shared generics), other
7201 than to check that the given names are all names of generic units or
7204 @node Pragma Shared,Pragma Short_Circuit_And_Or,Pragma Share_Generic,Implementation Defined Pragmas
7205 @anchor{gnat_rm/implementation_defined_pragmas id37}@anchor{dd}@anchor{gnat_rm/implementation_defined_pragmas pragma-shared}@anchor{de}
7206 @section Pragma Shared
7209 This pragma is provided for compatibility with Ada 83. The syntax and
7210 semantics are identical to pragma Atomic.
7212 @node Pragma Short_Circuit_And_Or,Pragma Short_Descriptors,Pragma Shared,Implementation Defined Pragmas
7213 @anchor{gnat_rm/implementation_defined_pragmas pragma-short-circuit-and-or}@anchor{df}
7214 @section Pragma Short_Circuit_And_Or
7220 pragma Short_Circuit_And_Or;
7223 This configuration pragma causes any occurrence of the AND operator applied to
7224 operands of type Standard.Boolean to be short-circuited (i.e. the AND operator
7225 is treated as if it were AND THEN). Or is similarly treated as OR ELSE. This
7226 may be useful in the context of certification protocols requiring the use of
7227 short-circuited logical operators. If this configuration pragma occurs locally
7228 within the file being compiled, it applies only to the file being compiled.
7229 There is no requirement that all units in a partition use this option.
7231 @node Pragma Short_Descriptors,Pragma Simple_Storage_Pool_Type,Pragma Short_Circuit_And_Or,Implementation Defined Pragmas
7232 @anchor{gnat_rm/implementation_defined_pragmas pragma-short-descriptors}@anchor{e0}
7233 @section Pragma Short_Descriptors
7239 pragma Short_Descriptors
7242 This pragma is provided for compatibility with other Ada implementations. It
7243 is recognized but ignored by all current versions of GNAT.
7245 @node Pragma Simple_Storage_Pool_Type,Pragma Source_File_Name,Pragma Short_Descriptors,Implementation Defined Pragmas
7246 @anchor{gnat_rm/implementation_defined_pragmas pragma-simple-storage-pool-type}@anchor{e1}@anchor{gnat_rm/implementation_defined_pragmas id38}@anchor{e2}
7247 @section Pragma Simple_Storage_Pool_Type
7250 @geindex Storage pool
7253 @geindex Simple storage pool
7258 pragma Simple_Storage_Pool_Type (type_LOCAL_NAME);
7261 A type can be established as a 'simple storage pool type' by applying
7262 the representation pragma @code{Simple_Storage_Pool_Type} to the type.
7263 A type named in the pragma must be a library-level immutably limited record
7264 type or limited tagged type declared immediately within a package declaration.
7265 The type can also be a limited private type whose full type is allowed as
7266 a simple storage pool type.
7268 For a simple storage pool type @code{SSP}, nonabstract primitive subprograms
7269 @code{Allocate}, @code{Deallocate}, and @code{Storage_Size} can be declared that
7270 are subtype conformant with the following subprogram declarations:
7275 Storage_Address : out System.Address;
7276 Size_In_Storage_Elements : System.Storage_Elements.Storage_Count;
7277 Alignment : System.Storage_Elements.Storage_Count);
7279 procedure Deallocate
7281 Storage_Address : System.Address;
7282 Size_In_Storage_Elements : System.Storage_Elements.Storage_Count;
7283 Alignment : System.Storage_Elements.Storage_Count);
7285 function Storage_Size (Pool : SSP)
7286 return System.Storage_Elements.Storage_Count;
7289 Procedure @code{Allocate} must be declared, whereas @code{Deallocate} and
7290 @code{Storage_Size} are optional. If @code{Deallocate} is not declared, then
7291 applying an unchecked deallocation has no effect other than to set its actual
7292 parameter to null. If @code{Storage_Size} is not declared, then the
7293 @code{Storage_Size} attribute applied to an access type associated with
7294 a pool object of type SSP returns zero. Additional operations can be declared
7295 for a simple storage pool type (such as for supporting a mark/release
7296 storage-management discipline).
7298 An object of a simple storage pool type can be associated with an access
7299 type by specifying the attribute
7300 @ref{e3,,Simple_Storage_Pool}. For example:
7303 My_Pool : My_Simple_Storage_Pool_Type;
7305 type Acc is access My_Data_Type;
7307 for Acc'Simple_Storage_Pool use My_Pool;
7310 See attribute @ref{e3,,Simple_Storage_Pool}
7311 for further details.
7313 @node Pragma Source_File_Name,Pragma Source_File_Name_Project,Pragma Simple_Storage_Pool_Type,Implementation Defined Pragmas
7314 @anchor{gnat_rm/implementation_defined_pragmas pragma-source-file-name}@anchor{e4}@anchor{gnat_rm/implementation_defined_pragmas id39}@anchor{e5}
7315 @section Pragma Source_File_Name
7321 pragma Source_File_Name (
7322 [Unit_Name =>] unit_NAME,
7323 Spec_File_Name => STRING_LITERAL,
7324 [Index => INTEGER_LITERAL]);
7326 pragma Source_File_Name (
7327 [Unit_Name =>] unit_NAME,
7328 Body_File_Name => STRING_LITERAL,
7329 [Index => INTEGER_LITERAL]);
7332 Use this to override the normal naming convention. It is a configuration
7333 pragma, and so has the usual applicability of configuration pragmas
7334 (i.e., it applies to either an entire partition, or to all units in a
7335 compilation, or to a single unit, depending on how it is used.
7336 @code{unit_name} is mapped to @code{file_name_literal}. The identifier for
7337 the second argument is required, and indicates whether this is the file
7338 name for the spec or for the body.
7340 The optional Index argument should be used when a file contains multiple
7341 units, and when you do not want to use @code{gnatchop} to separate then
7342 into multiple files (which is the recommended procedure to limit the
7343 number of recompilations that are needed when some sources change).
7344 For instance, if the source file @code{source.ada} contains
7358 you could use the following configuration pragmas:
7361 pragma Source_File_Name
7362 (B, Spec_File_Name => "source.ada", Index => 1);
7363 pragma Source_File_Name
7364 (A, Body_File_Name => "source.ada", Index => 2);
7367 Note that the @code{gnatname} utility can also be used to generate those
7368 configuration pragmas.
7370 Another form of the @code{Source_File_Name} pragma allows
7371 the specification of patterns defining alternative file naming schemes
7372 to apply to all files.
7375 pragma Source_File_Name
7376 ( [Spec_File_Name =>] STRING_LITERAL
7377 [,[Casing =>] CASING_SPEC]
7378 [,[Dot_Replacement =>] STRING_LITERAL]);
7380 pragma Source_File_Name
7381 ( [Body_File_Name =>] STRING_LITERAL
7382 [,[Casing =>] CASING_SPEC]
7383 [,[Dot_Replacement =>] STRING_LITERAL]);
7385 pragma Source_File_Name
7386 ( [Subunit_File_Name =>] STRING_LITERAL
7387 [,[Casing =>] CASING_SPEC]
7388 [,[Dot_Replacement =>] STRING_LITERAL]);
7390 CASING_SPEC ::= Lowercase | Uppercase | Mixedcase
7393 The first argument is a pattern that contains a single asterisk indicating
7394 the point at which the unit name is to be inserted in the pattern string
7395 to form the file name. The second argument is optional. If present it
7396 specifies the casing of the unit name in the resulting file name string.
7397 The default is lower case. Finally the third argument allows for systematic
7398 replacement of any dots in the unit name by the specified string literal.
7400 Note that Source_File_Name pragmas should not be used if you are using
7401 project files. The reason for this rule is that the project manager is not
7402 aware of these pragmas, and so other tools that use the projet file would not
7403 be aware of the intended naming conventions. If you are using project files,
7404 file naming is controlled by Source_File_Name_Project pragmas, which are
7405 usually supplied automatically by the project manager. A pragma
7406 Source_File_Name cannot appear after a @ref{e6,,Pragma Source_File_Name_Project}.
7408 For more details on the use of the @code{Source_File_Name} pragma, see the
7409 sections on @code{Using Other File Names} and @cite{Alternative File Naming Schemes' in the :title:`GNAT User's Guide}.
7411 @node Pragma Source_File_Name_Project,Pragma Source_Reference,Pragma Source_File_Name,Implementation Defined Pragmas
7412 @anchor{gnat_rm/implementation_defined_pragmas pragma-source-file-name-project}@anchor{e6}@anchor{gnat_rm/implementation_defined_pragmas id40}@anchor{e7}
7413 @section Pragma Source_File_Name_Project
7416 This pragma has the same syntax and semantics as pragma Source_File_Name.
7417 It is only allowed as a stand-alone configuration pragma.
7418 It cannot appear after a @ref{e4,,Pragma Source_File_Name}, and
7419 most importantly, once pragma Source_File_Name_Project appears,
7420 no further Source_File_Name pragmas are allowed.
7422 The intention is that Source_File_Name_Project pragmas are always
7423 generated by the Project Manager in a manner consistent with the naming
7424 specified in a project file, and when naming is controlled in this manner,
7425 it is not permissible to attempt to modify this naming scheme using
7426 Source_File_Name or Source_File_Name_Project pragmas (which would not be
7427 known to the project manager).
7429 @node Pragma Source_Reference,Pragma SPARK_Mode,Pragma Source_File_Name_Project,Implementation Defined Pragmas
7430 @anchor{gnat_rm/implementation_defined_pragmas pragma-source-reference}@anchor{e8}
7431 @section Pragma Source_Reference
7437 pragma Source_Reference (INTEGER_LITERAL, STRING_LITERAL);
7440 This pragma must appear as the first line of a source file.
7441 @code{integer_literal} is the logical line number of the line following
7442 the pragma line (for use in error messages and debugging
7443 information). @code{string_literal} is a static string constant that
7444 specifies the file name to be used in error messages and debugging
7445 information. This is most notably used for the output of @code{gnatchop}
7446 with the @emph{-r} switch, to make sure that the original unchopped
7447 source file is the one referred to.
7449 The second argument must be a string literal, it cannot be a static
7450 string expression other than a string literal. This is because its value
7451 is needed for error messages issued by all phases of the compiler.
7453 @node Pragma SPARK_Mode,Pragma Static_Elaboration_Desired,Pragma Source_Reference,Implementation Defined Pragmas
7454 @anchor{gnat_rm/implementation_defined_pragmas pragma-spark-mode}@anchor{e9}@anchor{gnat_rm/implementation_defined_pragmas id41}@anchor{ea}
7455 @section Pragma SPARK_Mode
7461 pragma SPARK_Mode [(On | Off)] ;
7464 In general a program can have some parts that are in SPARK 2014 (and
7465 follow all the rules in the SPARK Reference Manual), and some parts
7466 that are full Ada 2012.
7468 The SPARK_Mode pragma is used to identify which parts are in SPARK
7469 2014 (by default programs are in full Ada). The SPARK_Mode pragma can
7470 be used in the following places:
7476 As a configuration pragma, in which case it sets the default mode for
7477 all units compiled with this pragma.
7480 Immediately following a library-level subprogram spec
7483 Immediately within a library-level package body
7486 Immediately following the @code{private} keyword of a library-level
7490 Immediately following the @code{begin} keyword of a library-level
7494 Immediately within a library-level subprogram body
7497 Normally a subprogram or package spec/body inherits the current mode
7498 that is active at the point it is declared. But this can be overridden
7499 by pragma within the spec or body as above.
7501 The basic consistency rule is that you can't turn SPARK_Mode back
7502 @code{On}, once you have explicitly (with a pragma) turned if
7503 @code{Off}. So the following rules apply:
7505 If a subprogram spec has SPARK_Mode @code{Off}, then the body must
7506 also have SPARK_Mode @code{Off}.
7508 For a package, we have four parts:
7514 the package public declarations
7517 the package private part
7520 the body of the package
7523 the elaboration code after @code{begin}
7526 For a package, the rule is that if you explicitly turn SPARK_Mode
7527 @code{Off} for any part, then all the following parts must have
7528 SPARK_Mode @code{Off}. Note that this may require repeating a pragma
7529 SPARK_Mode (@code{Off}) in the body. For example, if we have a
7530 configuration pragma SPARK_Mode (@code{On}) that turns the mode on by
7531 default everywhere, and one particular package spec has pragma
7532 SPARK_Mode (@code{Off}), then that pragma will need to be repeated in
7535 @node Pragma Static_Elaboration_Desired,Pragma Stream_Convert,Pragma SPARK_Mode,Implementation Defined Pragmas
7536 @anchor{gnat_rm/implementation_defined_pragmas pragma-static-elaboration-desired}@anchor{eb}
7537 @section Pragma Static_Elaboration_Desired
7543 pragma Static_Elaboration_Desired;
7546 This pragma is used to indicate that the compiler should attempt to initialize
7547 statically the objects declared in the library unit to which the pragma applies,
7548 when these objects are initialized (explicitly or implicitly) by an aggregate.
7549 In the absence of this pragma, aggregates in object declarations are expanded
7550 into assignments and loops, even when the aggregate components are static
7551 constants. When the aggregate is present the compiler builds a static expression
7552 that requires no run-time code, so that the initialized object can be placed in
7553 read-only data space. If the components are not static, or the aggregate has
7554 more that 100 components, the compiler emits a warning that the pragma cannot
7555 be obeyed. (See also the restriction No_Implicit_Loops, which supports static
7556 construction of larger aggregates with static components that include an others
7559 @node Pragma Stream_Convert,Pragma Style_Checks,Pragma Static_Elaboration_Desired,Implementation Defined Pragmas
7560 @anchor{gnat_rm/implementation_defined_pragmas pragma-stream-convert}@anchor{ec}
7561 @section Pragma Stream_Convert
7567 pragma Stream_Convert (
7568 [Entity =>] type_LOCAL_NAME,
7569 [Read =>] function_NAME,
7570 [Write =>] function_NAME);
7573 This pragma provides an efficient way of providing user-defined stream
7574 attributes. Not only is it simpler to use than specifying the attributes
7575 directly, but more importantly, it allows the specification to be made in such
7576 a way that the predefined unit Ada.Streams is not loaded unless it is actually
7577 needed (i.e. unless the stream attributes are actually used); the use of
7578 the Stream_Convert pragma adds no overhead at all, unless the stream
7579 attributes are actually used on the designated type.
7581 The first argument specifies the type for which stream functions are
7582 provided. The second parameter provides a function used to read values
7583 of this type. It must name a function whose argument type may be any
7584 subtype, and whose returned type must be the type given as the first
7585 argument to the pragma.
7587 The meaning of the @code{Read} parameter is that if a stream attribute directly
7588 or indirectly specifies reading of the type given as the first parameter,
7589 then a value of the type given as the argument to the Read function is
7590 read from the stream, and then the Read function is used to convert this
7591 to the required target type.
7593 Similarly the @code{Write} parameter specifies how to treat write attributes
7594 that directly or indirectly apply to the type given as the first parameter.
7595 It must have an input parameter of the type specified by the first parameter,
7596 and the return type must be the same as the input type of the Read function.
7597 The effect is to first call the Write function to convert to the given stream
7598 type, and then write the result type to the stream.
7600 The Read and Write functions must not be overloaded subprograms. If necessary
7601 renamings can be supplied to meet this requirement.
7602 The usage of this attribute is best illustrated by a simple example, taken
7603 from the GNAT implementation of package Ada.Strings.Unbounded:
7606 function To_Unbounded (S : String) return Unbounded_String
7607 renames To_Unbounded_String;
7609 pragma Stream_Convert
7610 (Unbounded_String, To_Unbounded, To_String);
7613 The specifications of the referenced functions, as given in the Ada
7614 Reference Manual are:
7617 function To_Unbounded_String (Source : String)
7618 return Unbounded_String;
7620 function To_String (Source : Unbounded_String)
7624 The effect is that if the value of an unbounded string is written to a stream,
7625 then the representation of the item in the stream is in the same format that
7626 would be used for @code{Standard.String'Output}, and this same representation
7627 is expected when a value of this type is read from the stream. Note that the
7628 value written always includes the bounds, even for Unbounded_String'Write,
7629 since Unbounded_String is not an array type.
7631 Note that the @code{Stream_Convert} pragma is not effective in the case of
7632 a derived type of a non-limited tagged type. If such a type is specified then
7633 the pragma is silently ignored, and the default implementation of the stream
7634 attributes is used instead.
7636 @node Pragma Style_Checks,Pragma Subtitle,Pragma Stream_Convert,Implementation Defined Pragmas
7637 @anchor{gnat_rm/implementation_defined_pragmas pragma-style-checks}@anchor{ed}
7638 @section Pragma Style_Checks
7644 pragma Style_Checks (string_LITERAL | ALL_CHECKS |
7645 On | Off [, LOCAL_NAME]);
7648 This pragma is used in conjunction with compiler switches to control the
7649 built in style checking provided by GNAT. The compiler switches, if set,
7650 provide an initial setting for the switches, and this pragma may be used
7651 to modify these settings, or the settings may be provided entirely by
7652 the use of the pragma. This pragma can be used anywhere that a pragma
7653 is legal, including use as a configuration pragma (including use in
7654 the @code{gnat.adc} file).
7656 The form with a string literal specifies which style options are to be
7657 activated. These are additive, so they apply in addition to any previously
7658 set style check options. The codes for the options are the same as those
7659 used in the @emph{-gnaty} switch to @emph{gcc} or @emph{gnatmake}.
7660 For example the following two methods can be used to enable
7668 pragma Style_Checks ("l");
7677 The form @code{ALL_CHECKS} activates all standard checks (its use is equivalent
7678 to the use of the @code{gnaty} switch with no options.
7679 See the @cite{GNAT User's Guide} for details.)
7681 Note: the behavior is slightly different in GNAT mode (@code{-gnatg} used).
7682 In this case, @code{ALL_CHECKS} implies the standard set of GNAT mode style check
7683 options (i.e. equivalent to @code{-gnatyg}).
7685 The forms with @code{Off} and @code{On}
7686 can be used to temporarily disable style checks
7687 as shown in the following example:
7690 pragma Style_Checks ("k"); -- requires keywords in lower case
7691 pragma Style_Checks (Off); -- turn off style checks
7692 NULL; -- this will not generate an error message
7693 pragma Style_Checks (On); -- turn style checks back on
7694 NULL; -- this will generate an error message
7697 Finally the two argument form is allowed only if the first argument is
7698 @code{On} or @code{Off}. The effect is to turn of semantic style checks
7699 for the specified entity, as shown in the following example:
7702 pragma Style_Checks ("r"); -- require consistency of identifier casing
7704 Rf1 : Integer := ARG; -- incorrect, wrong case
7705 pragma Style_Checks (Off, Arg);
7706 Rf2 : Integer := ARG; -- OK, no error
7709 @node Pragma Subtitle,Pragma Suppress,Pragma Style_Checks,Implementation Defined Pragmas
7710 @anchor{gnat_rm/implementation_defined_pragmas pragma-subtitle}@anchor{ee}
7711 @section Pragma Subtitle
7717 pragma Subtitle ([Subtitle =>] STRING_LITERAL);
7720 This pragma is recognized for compatibility with other Ada compilers
7721 but is ignored by GNAT.
7723 @node Pragma Suppress,Pragma Suppress_All,Pragma Subtitle,Implementation Defined Pragmas
7724 @anchor{gnat_rm/implementation_defined_pragmas pragma-suppress}@anchor{ef}
7725 @section Pragma Suppress
7731 pragma Suppress (Identifier [, [On =>] Name]);
7734 This is a standard pragma, and supports all the check names required in
7735 the RM. It is included here because GNAT recognizes some additional check
7736 names that are implementation defined (as permitted by the RM):
7742 @code{Alignment_Check} can be used to suppress alignment checks
7743 on addresses used in address clauses. Such checks can also be suppressed
7744 by suppressing range checks, but the specific use of @code{Alignment_Check}
7745 allows suppression of alignment checks without suppressing other range checks.
7746 Note that @code{Alignment_Check} is suppressed by default on machines (such as
7747 the x86) with non-strict alignment.
7750 @code{Atomic_Synchronization} can be used to suppress the special memory
7751 synchronization instructions that are normally generated for access to
7752 @code{Atomic} variables to ensure correct synchronization between tasks
7753 that use such variables for synchronization purposes.
7756 @code{Duplicated_Tag_Check} Can be used to suppress the check that is generated
7757 for a duplicated tag value when a tagged type is declared.
7760 @code{Container_Checks} Can be used to suppress all checks within Ada.Containers
7761 and instances of its children, including Tampering_Check.
7764 @code{Tampering_Check} Can be used to suppress tampering check in the containers.
7767 @code{Predicate_Check} can be used to control whether predicate checks are
7768 active. It is applicable only to predicates for which the policy is
7769 @code{Check}. Unlike @code{Assertion_Policy}, which determines if a given
7770 predicate is ignored or checked for the whole program, the use of
7771 @code{Suppress} and @code{Unsuppress} with this check name allows a given
7772 predicate to be turned on and off at specific points in the program.
7775 @code{Validity_Check} can be used specifically to control validity checks.
7776 If @code{Suppress} is used to suppress validity checks, then no validity
7777 checks are performed, including those specified by the appropriate compiler
7778 switch or the @code{Validity_Checks} pragma.
7781 Additional check names previously introduced by use of the @code{Check_Name}
7782 pragma are also allowed.
7785 Note that pragma Suppress gives the compiler permission to omit
7786 checks, but does not require the compiler to omit checks. The compiler
7787 will generate checks if they are essentially free, even when they are
7788 suppressed. In particular, if the compiler can prove that a certain
7789 check will necessarily fail, it will generate code to do an
7790 unconditional 'raise', even if checks are suppressed. The compiler
7793 Of course, run-time checks are omitted whenever the compiler can prove
7794 that they will not fail, whether or not checks are suppressed.
7796 @node Pragma Suppress_All,Pragma Suppress_Debug_Info,Pragma Suppress,Implementation Defined Pragmas
7797 @anchor{gnat_rm/implementation_defined_pragmas pragma-suppress-all}@anchor{f0}
7798 @section Pragma Suppress_All
7804 pragma Suppress_All;
7807 This pragma can appear anywhere within a unit.
7808 The effect is to apply @code{Suppress (All_Checks)} to the unit
7809 in which it appears. This pragma is implemented for compatibility with DEC
7810 Ada 83 usage where it appears at the end of a unit, and for compatibility
7811 with Rational Ada, where it appears as a program unit pragma.
7812 The use of the standard Ada pragma @code{Suppress (All_Checks)}
7813 as a normal configuration pragma is the preferred usage in GNAT.
7815 @node Pragma Suppress_Debug_Info,Pragma Suppress_Exception_Locations,Pragma Suppress_All,Implementation Defined Pragmas
7816 @anchor{gnat_rm/implementation_defined_pragmas pragma-suppress-debug-info}@anchor{f1}@anchor{gnat_rm/implementation_defined_pragmas id42}@anchor{f2}
7817 @section Pragma Suppress_Debug_Info
7823 pragma Suppress_Debug_Info ([Entity =>] LOCAL_NAME);
7826 This pragma can be used to suppress generation of debug information
7827 for the specified entity. It is intended primarily for use in debugging
7828 the debugger, and navigating around debugger problems.
7830 @node Pragma Suppress_Exception_Locations,Pragma Suppress_Initialization,Pragma Suppress_Debug_Info,Implementation Defined Pragmas
7831 @anchor{gnat_rm/implementation_defined_pragmas pragma-suppress-exception-locations}@anchor{f3}
7832 @section Pragma Suppress_Exception_Locations
7838 pragma Suppress_Exception_Locations;
7841 In normal mode, a raise statement for an exception by default generates
7842 an exception message giving the file name and line number for the location
7843 of the raise. This is useful for debugging and logging purposes, but this
7844 entails extra space for the strings for the messages. The configuration
7845 pragma @code{Suppress_Exception_Locations} can be used to suppress the
7846 generation of these strings, with the result that space is saved, but the
7847 exception message for such raises is null. This configuration pragma may
7848 appear in a global configuration pragma file, or in a specific unit as
7849 usual. It is not required that this pragma be used consistently within
7850 a partition, so it is fine to have some units within a partition compiled
7851 with this pragma and others compiled in normal mode without it.
7853 @node Pragma Suppress_Initialization,Pragma Task_Name,Pragma Suppress_Exception_Locations,Implementation Defined Pragmas
7854 @anchor{gnat_rm/implementation_defined_pragmas id43}@anchor{f4}@anchor{gnat_rm/implementation_defined_pragmas pragma-suppress-initialization}@anchor{f5}
7855 @section Pragma Suppress_Initialization
7858 @geindex Suppressing initialization
7860 @geindex Initialization
7861 @geindex suppression of
7866 pragma Suppress_Initialization ([Entity =>] variable_or_subtype_Name);
7869 Here variable_or_subtype_Name is the name introduced by a type declaration
7870 or subtype declaration or the name of a variable introduced by an
7873 In the case of a type or subtype
7874 this pragma suppresses any implicit or explicit initialization
7875 for all variables of the given type or subtype,
7876 including initialization resulting from the use of pragmas
7877 Normalize_Scalars or Initialize_Scalars.
7879 This is considered a representation item, so it cannot be given after
7880 the type is frozen. It applies to all subsequent object declarations,
7881 and also any allocator that creates objects of the type.
7883 If the pragma is given for the first subtype, then it is considered
7884 to apply to the base type and all its subtypes. If the pragma is given
7885 for other than a first subtype, then it applies only to the given subtype.
7886 The pragma may not be given after the type is frozen.
7888 Note that this includes eliminating initialization of discriminants
7889 for discriminated types, and tags for tagged types. In these cases,
7890 you will have to use some non-portable mechanism (e.g. address
7891 overlays or unchecked conversion) to achieve required initialization
7892 of these fields before accessing any object of the corresponding type.
7894 For the variable case, implicit initialization for the named variable
7895 is suppressed, just as though its subtype had been given in a pragma
7896 Suppress_Initialization, as described above.
7898 @node Pragma Task_Name,Pragma Task_Storage,Pragma Suppress_Initialization,Implementation Defined Pragmas
7899 @anchor{gnat_rm/implementation_defined_pragmas pragma-task-name}@anchor{f6}
7900 @section Pragma Task_Name
7906 pragma Task_Name (string_EXPRESSION);
7909 This pragma appears within a task definition (like pragma
7910 @code{Priority}) and applies to the task in which it appears. The
7911 argument must be of type String, and provides a name to be used for
7912 the task instance when the task is created. Note that this expression
7913 is not required to be static, and in particular, it can contain
7914 references to task discriminants. This facility can be used to
7915 provide different names for different tasks as they are created,
7916 as illustrated in the example below.
7918 The task name is recorded internally in the run-time structures
7919 and is accessible to tools like the debugger. In addition the
7920 routine @code{Ada.Task_Identification.Image} will return this
7921 string, with a unique task address appended.
7924 -- Example of the use of pragma Task_Name
7926 with Ada.Task_Identification;
7927 use Ada.Task_Identification;
7928 with Text_IO; use Text_IO;
7931 type Astring is access String;
7933 task type Task_Typ (Name : access String) is
7934 pragma Task_Name (Name.all);
7937 task body Task_Typ is
7938 Nam : constant String := Image (Current_Task);
7940 Put_Line ("-->" & Nam (1 .. 14) & "<--");
7943 type Ptr_Task is access Task_Typ;
7944 Task_Var : Ptr_Task;
7948 new Task_Typ (new String'("This is task 1"));
7950 new Task_Typ (new String'("This is task 2"));
7954 @node Pragma Task_Storage,Pragma Test_Case,Pragma Task_Name,Implementation Defined Pragmas
7955 @anchor{gnat_rm/implementation_defined_pragmas pragma-task-storage}@anchor{f7}
7956 @section Pragma Task_Storage
7962 pragma Task_Storage (
7963 [Task_Type =>] LOCAL_NAME,
7964 [Top_Guard =>] static_integer_EXPRESSION);
7967 This pragma specifies the length of the guard area for tasks. The guard
7968 area is an additional storage area allocated to a task. A value of zero
7969 means that either no guard area is created or a minimal guard area is
7970 created, depending on the target. This pragma can appear anywhere a
7971 @code{Storage_Size} attribute definition clause is allowed for a task
7974 @node Pragma Test_Case,Pragma Thread_Local_Storage,Pragma Task_Storage,Implementation Defined Pragmas
7975 @anchor{gnat_rm/implementation_defined_pragmas pragma-test-case}@anchor{f8}@anchor{gnat_rm/implementation_defined_pragmas id44}@anchor{f9}
7976 @section Pragma Test_Case
7985 [Name =>] static_string_Expression
7986 ,[Mode =>] (Nominal | Robustness)
7987 [, Requires => Boolean_Expression]
7988 [, Ensures => Boolean_Expression]);
7991 The @code{Test_Case} pragma allows defining fine-grain specifications
7992 for use by testing tools.
7993 The compiler checks the validity of the @code{Test_Case} pragma, but its
7994 presence does not lead to any modification of the code generated by the
7997 @code{Test_Case} pragmas may only appear immediately following the
7998 (separate) declaration of a subprogram in a package declaration, inside
7999 a package spec unit. Only other pragmas may intervene (that is appear
8000 between the subprogram declaration and a test case).
8002 The compiler checks that boolean expressions given in @code{Requires} and
8003 @code{Ensures} are valid, where the rules for @code{Requires} are the
8004 same as the rule for an expression in @code{Precondition} and the rules
8005 for @code{Ensures} are the same as the rule for an expression in
8006 @code{Postcondition}. In particular, attributes @code{'Old} and
8007 @code{'Result} can only be used within the @code{Ensures}
8008 expression. The following is an example of use within a package spec:
8011 package Math_Functions is
8013 function Sqrt (Arg : Float) return Float;
8014 pragma Test_Case (Name => "Test 1",
8016 Requires => Arg < 10000,
8017 Ensures => Sqrt'Result < 10);
8022 The meaning of a test case is that there is at least one context where
8023 @code{Requires} holds such that, if the associated subprogram is executed in
8024 that context, then @code{Ensures} holds when the subprogram returns.
8025 Mode @code{Nominal} indicates that the input context should also satisfy the
8026 precondition of the subprogram, and the output context should also satisfy its
8027 postcondition. Mode @code{Robustness} indicates that the precondition and
8028 postcondition of the subprogram should be ignored for this test case.
8030 @node Pragma Thread_Local_Storage,Pragma Time_Slice,Pragma Test_Case,Implementation Defined Pragmas
8031 @anchor{gnat_rm/implementation_defined_pragmas pragma-thread-local-storage}@anchor{fa}@anchor{gnat_rm/implementation_defined_pragmas id45}@anchor{fb}
8032 @section Pragma Thread_Local_Storage
8035 @geindex Task specific storage
8037 @geindex TLS (Thread Local Storage)
8039 @geindex Task_Attributes
8044 pragma Thread_Local_Storage ([Entity =>] LOCAL_NAME);
8047 This pragma specifies that the specified entity, which must be
8048 a variable declared in a library-level package, is to be marked as
8049 "Thread Local Storage" (@code{TLS}). On systems supporting this (which
8050 include Windows, Solaris, GNU/Linux and VxWorks 6), this causes each
8051 thread (and hence each Ada task) to see a distinct copy of the variable.
8053 The variable may not have default initialization, and if there is
8054 an explicit initialization, it must be either @code{null} for an
8055 access variable, or a static expression for a scalar variable.
8056 This provides a low level mechanism similar to that provided by
8057 the @code{Ada.Task_Attributes} package, but much more efficient
8058 and is also useful in writing interface code that will interact
8059 with foreign threads.
8061 If this pragma is used on a system where @code{TLS} is not supported,
8062 then an error message will be generated and the program will be rejected.
8064 @node Pragma Time_Slice,Pragma Title,Pragma Thread_Local_Storage,Implementation Defined Pragmas
8065 @anchor{gnat_rm/implementation_defined_pragmas pragma-time-slice}@anchor{fc}
8066 @section Pragma Time_Slice
8072 pragma Time_Slice (static_duration_EXPRESSION);
8075 For implementations of GNAT on operating systems where it is possible
8076 to supply a time slice value, this pragma may be used for this purpose.
8077 It is ignored if it is used in a system that does not allow this control,
8078 or if it appears in other than the main program unit.
8080 @node Pragma Title,Pragma Type_Invariant,Pragma Time_Slice,Implementation Defined Pragmas
8081 @anchor{gnat_rm/implementation_defined_pragmas pragma-title}@anchor{fd}
8082 @section Pragma Title
8088 pragma Title (TITLING_OPTION [, TITLING OPTION]);
8091 [Title =>] STRING_LITERAL,
8092 | [Subtitle =>] STRING_LITERAL
8095 Syntax checked but otherwise ignored by GNAT. This is a listing control
8096 pragma used in DEC Ada 83 implementations to provide a title and/or
8097 subtitle for the program listing. The program listing generated by GNAT
8098 does not have titles or subtitles.
8100 Unlike other pragmas, the full flexibility of named notation is allowed
8101 for this pragma, i.e., the parameters may be given in any order if named
8102 notation is used, and named and positional notation can be mixed
8103 following the normal rules for procedure calls in Ada.
8105 @node Pragma Type_Invariant,Pragma Type_Invariant_Class,Pragma Title,Implementation Defined Pragmas
8106 @anchor{gnat_rm/implementation_defined_pragmas pragma-type-invariant}@anchor{fe}
8107 @section Pragma Type_Invariant
8113 pragma Type_Invariant
8114 ([Entity =>] type_LOCAL_NAME,
8115 [Check =>] EXPRESSION);
8118 The @code{Type_Invariant} pragma is intended to be an exact
8119 replacement for the language-defined @code{Type_Invariant}
8120 aspect, and shares its restrictions and semantics. It differs
8121 from the language defined @code{Invariant} pragma in that it
8122 does not permit a string parameter, and it is
8123 controlled by the assertion identifier @code{Type_Invariant}
8124 rather than @code{Invariant}.
8126 @node Pragma Type_Invariant_Class,Pragma Unchecked_Union,Pragma Type_Invariant,Implementation Defined Pragmas
8127 @anchor{gnat_rm/implementation_defined_pragmas id46}@anchor{ff}@anchor{gnat_rm/implementation_defined_pragmas pragma-type-invariant-class}@anchor{100}
8128 @section Pragma Type_Invariant_Class
8134 pragma Type_Invariant_Class
8135 ([Entity =>] type_LOCAL_NAME,
8136 [Check =>] EXPRESSION);
8139 The @code{Type_Invariant_Class} pragma is intended to be an exact
8140 replacement for the language-defined @code{Type_Invariant'Class}
8141 aspect, and shares its restrictions and semantics.
8143 Note: This pragma is called @code{Type_Invariant_Class} rather than
8144 @code{Type_Invariant'Class} because the latter would not be strictly
8145 conforming to the allowed syntax for pragmas. The motivation
8146 for providing pragmas equivalent to the aspects is to allow a program
8147 to be written using the pragmas, and then compiled if necessary
8148 using an Ada compiler that does not recognize the pragmas or
8149 aspects, but is prepared to ignore the pragmas. The assertion
8150 policy that controls this pragma is @code{Type_Invariant'Class},
8151 not @code{Type_Invariant_Class}.
8153 @node Pragma Unchecked_Union,Pragma Unevaluated_Use_Of_Old,Pragma Type_Invariant_Class,Implementation Defined Pragmas
8154 @anchor{gnat_rm/implementation_defined_pragmas pragma-unchecked-union}@anchor{101}
8155 @section Pragma Unchecked_Union
8158 @geindex Unions in C
8163 pragma Unchecked_Union (first_subtype_LOCAL_NAME);
8166 This pragma is used to specify a representation of a record type that is
8167 equivalent to a C union. It was introduced as a GNAT implementation defined
8168 pragma in the GNAT Ada 95 mode. Ada 2005 includes an extended version of this
8169 pragma, making it language defined, and GNAT fully implements this extended
8170 version in all language modes (Ada 83, Ada 95, and Ada 2005). For full
8171 details, consult the Ada 2012 Reference Manual, section B.3.3.
8173 @node Pragma Unevaluated_Use_Of_Old,Pragma Unimplemented_Unit,Pragma Unchecked_Union,Implementation Defined Pragmas
8174 @anchor{gnat_rm/implementation_defined_pragmas pragma-unevaluated-use-of-old}@anchor{102}
8175 @section Pragma Unevaluated_Use_Of_Old
8178 @geindex Attribute Old
8180 @geindex Attribute Loop_Entry
8182 @geindex Unevaluated_Use_Of_Old
8187 pragma Unevaluated_Use_Of_Old (Error | Warn | Allow);
8190 This pragma controls the processing of attributes Old and Loop_Entry.
8191 If either of these attributes is used in a potentially unevaluated
8192 expression (e.g. the then or else parts of an if expression), then
8193 normally this usage is considered illegal if the prefix of the attribute
8194 is other than an entity name. The language requires this
8195 behavior for Old, and GNAT copies the same rule for Loop_Entry.
8197 The reason for this rule is that otherwise, we can have a situation
8198 where we save the Old value, and this results in an exception, even
8199 though we might not evaluate the attribute. Consider this example:
8202 package UnevalOld is
8204 procedure U (A : String; C : Boolean) -- ERROR
8205 with Post => (if C then A(1)'Old = K else True);
8209 If procedure U is called with a string with a lower bound of 2, and
8210 C false, then an exception would be raised trying to evaluate A(1)
8211 on entry even though the value would not be actually used.
8213 Although the rule guarantees against this possibility, it is sometimes
8214 too restrictive. For example if we know that the string has a lower
8215 bound of 1, then we will never raise an exception.
8216 The pragma @code{Unevaluated_Use_Of_Old} can be
8217 used to modify this behavior. If the argument is @code{Error} then an
8218 error is given (this is the default RM behavior). If the argument is
8219 @code{Warn} then the usage is allowed as legal but with a warning
8220 that an exception might be raised. If the argument is @code{Allow}
8221 then the usage is allowed as legal without generating a warning.
8223 This pragma may appear as a configuration pragma, or in a declarative
8224 part or package specification. In the latter case it applies to
8225 uses up to the end of the corresponding statement sequence or
8226 sequence of package declarations.
8228 @node Pragma Unimplemented_Unit,Pragma Universal_Aliasing,Pragma Unevaluated_Use_Of_Old,Implementation Defined Pragmas
8229 @anchor{gnat_rm/implementation_defined_pragmas pragma-unimplemented-unit}@anchor{103}
8230 @section Pragma Unimplemented_Unit
8236 pragma Unimplemented_Unit;
8239 If this pragma occurs in a unit that is processed by the compiler, GNAT
8240 aborts with the message @code{xxx not implemented}, where
8241 @code{xxx} is the name of the current compilation unit. This pragma is
8242 intended to allow the compiler to handle unimplemented library units in
8245 The abort only happens if code is being generated. Thus you can use
8246 specs of unimplemented packages in syntax or semantic checking mode.
8248 @node Pragma Universal_Aliasing,Pragma Universal_Data,Pragma Unimplemented_Unit,Implementation Defined Pragmas
8249 @anchor{gnat_rm/implementation_defined_pragmas id47}@anchor{104}@anchor{gnat_rm/implementation_defined_pragmas pragma-universal-aliasing}@anchor{105}
8250 @section Pragma Universal_Aliasing
8256 pragma Universal_Aliasing [([Entity =>] type_LOCAL_NAME)];
8259 @code{type_LOCAL_NAME} must refer to a type declaration in the current
8260 declarative part. The effect is to inhibit strict type-based aliasing
8261 optimization for the given type. In other words, the effect is as though
8262 access types designating this type were subject to pragma No_Strict_Aliasing.
8263 For a detailed description of the strict aliasing optimization, and the
8264 situations in which it must be suppressed, see the section on
8265 @code{Optimization and Strict Aliasing} in the @cite{GNAT User's Guide}.
8267 @node Pragma Universal_Data,Pragma Unmodified,Pragma Universal_Aliasing,Implementation Defined Pragmas
8268 @anchor{gnat_rm/implementation_defined_pragmas pragma-universal-data}@anchor{106}@anchor{gnat_rm/implementation_defined_pragmas id48}@anchor{107}
8269 @section Pragma Universal_Data
8275 pragma Universal_Data [(library_unit_Name)];
8278 This pragma is supported only for the AAMP target and is ignored for
8279 other targets. The pragma specifies that all library-level objects
8280 (Counter 0 data) associated with the library unit are to be accessed
8281 and updated using universal addressing (24-bit addresses for AAMP5)
8282 rather than the default of 16-bit Data Environment (DENV) addressing.
8283 Use of this pragma will generally result in less efficient code for
8284 references to global data associated with the library unit, but
8285 allows such data to be located anywhere in memory. This pragma is
8286 a library unit pragma, but can also be used as a configuration pragma
8287 (including use in the @code{gnat.adc} file). The functionality
8288 of this pragma is also available by applying the -univ switch on the
8289 compilations of units where universal addressing of the data is desired.
8291 @node Pragma Unmodified,Pragma Unreferenced,Pragma Universal_Data,Implementation Defined Pragmas
8292 @anchor{gnat_rm/implementation_defined_pragmas pragma-unmodified}@anchor{108}@anchor{gnat_rm/implementation_defined_pragmas id49}@anchor{109}
8293 @section Pragma Unmodified
8302 pragma Unmodified (LOCAL_NAME @{, LOCAL_NAME@});
8305 This pragma signals that the assignable entities (variables,
8306 @code{out} parameters, @code{in out} parameters) whose names are listed are
8307 deliberately not assigned in the current source unit. This
8308 suppresses warnings about the
8309 entities being referenced but not assigned, and in addition a warning will be
8310 generated if one of these entities is in fact assigned in the
8311 same unit as the pragma (or in the corresponding body, or one
8314 This is particularly useful for clearly signaling that a particular
8315 parameter is not modified, even though the spec suggests that it might
8318 For the variable case, warnings are never given for unreferenced variables
8319 whose name contains one of the substrings
8320 @code{DISCARD, DUMMY, IGNORE, JUNK, UNUSED} in any casing. Such names
8321 are typically to be used in cases where such warnings are expected.
8322 Thus it is never necessary to use @code{pragma Unmodified} for such
8323 variables, though it is harmless to do so.
8325 @node Pragma Unreferenced,Pragma Unreferenced_Objects,Pragma Unmodified,Implementation Defined Pragmas
8326 @anchor{gnat_rm/implementation_defined_pragmas pragma-unreferenced}@anchor{10a}@anchor{gnat_rm/implementation_defined_pragmas id50}@anchor{10b}
8327 @section Pragma Unreferenced
8331 @geindex unreferenced
8336 pragma Unreferenced (LOCAL_NAME @{, LOCAL_NAME@});
8337 pragma Unreferenced (library_unit_NAME @{, library_unit_NAME@});
8340 This pragma signals that the entities whose names are listed are
8341 deliberately not referenced in the current source unit after the
8342 occurrence of the pragma. This
8343 suppresses warnings about the
8344 entities being unreferenced, and in addition a warning will be
8345 generated if one of these entities is in fact subsequently referenced in the
8346 same unit as the pragma (or in the corresponding body, or one
8349 This is particularly useful for clearly signaling that a particular
8350 parameter is not referenced in some particular subprogram implementation
8351 and that this is deliberate. It can also be useful in the case of
8352 objects declared only for their initialization or finalization side
8355 If @code{LOCAL_NAME} identifies more than one matching homonym in the
8356 current scope, then the entity most recently declared is the one to which
8357 the pragma applies. Note that in the case of accept formals, the pragma
8358 Unreferenced may appear immediately after the keyword @code{do} which
8359 allows the indication of whether or not accept formals are referenced
8360 or not to be given individually for each accept statement.
8362 The left hand side of an assignment does not count as a reference for the
8363 purpose of this pragma. Thus it is fine to assign to an entity for which
8364 pragma Unreferenced is given.
8366 Note that if a warning is desired for all calls to a given subprogram,
8367 regardless of whether they occur in the same unit as the subprogram
8368 declaration, then this pragma should not be used (calls from another
8369 unit would not be flagged); pragma Obsolescent can be used instead
8370 for this purpose, see @ref{a9,,Pragma Obsolescent}.
8372 The second form of pragma @code{Unreferenced} is used within a context
8373 clause. In this case the arguments must be unit names of units previously
8374 mentioned in @code{with} clauses (similar to the usage of pragma
8375 @code{Elaborate_All}. The effect is to suppress warnings about unreferenced
8376 units and unreferenced entities within these units.
8378 For the variable case, warnings are never given for unreferenced variables
8379 whose name contains one of the substrings
8380 @code{DISCARD, DUMMY, IGNORE, JUNK, UNUSED} in any casing. Such names
8381 are typically to be used in cases where such warnings are expected.
8382 Thus it is never necessary to use @code{pragma Unreferenced} for such
8383 variables, though it is harmless to do so.
8385 @node Pragma Unreferenced_Objects,Pragma Unreserve_All_Interrupts,Pragma Unreferenced,Implementation Defined Pragmas
8386 @anchor{gnat_rm/implementation_defined_pragmas pragma-unreferenced-objects}@anchor{10c}@anchor{gnat_rm/implementation_defined_pragmas id51}@anchor{10d}
8387 @section Pragma Unreferenced_Objects
8391 @geindex unreferenced
8396 pragma Unreferenced_Objects (local_subtype_NAME @{, local_subtype_NAME@});
8399 This pragma signals that for the types or subtypes whose names are
8400 listed, objects which are declared with one of these types or subtypes may
8401 not be referenced, and if no references appear, no warnings are given.
8403 This is particularly useful for objects which are declared solely for their
8404 initialization and finalization effect. Such variables are sometimes referred
8405 to as RAII variables (Resource Acquisition Is Initialization). Using this
8406 pragma on the relevant type (most typically a limited controlled type), the
8407 compiler will automatically suppress unwanted warnings about these variables
8408 not being referenced.
8410 @node Pragma Unreserve_All_Interrupts,Pragma Unsuppress,Pragma Unreferenced_Objects,Implementation Defined Pragmas
8411 @anchor{gnat_rm/implementation_defined_pragmas pragma-unreserve-all-interrupts}@anchor{10e}
8412 @section Pragma Unreserve_All_Interrupts
8418 pragma Unreserve_All_Interrupts;
8421 Normally certain interrupts are reserved to the implementation. Any attempt
8422 to attach an interrupt causes Program_Error to be raised, as described in
8423 RM C.3.2(22). A typical example is the @code{SIGINT} interrupt used in
8424 many systems for a @code{Ctrl-C} interrupt. Normally this interrupt is
8425 reserved to the implementation, so that @code{Ctrl-C} can be used to
8426 interrupt execution.
8428 If the pragma @code{Unreserve_All_Interrupts} appears anywhere in any unit in
8429 a program, then all such interrupts are unreserved. This allows the
8430 program to handle these interrupts, but disables their standard
8431 functions. For example, if this pragma is used, then pressing
8432 @code{Ctrl-C} will not automatically interrupt execution. However,
8433 a program can then handle the @code{SIGINT} interrupt as it chooses.
8435 For a full list of the interrupts handled in a specific implementation,
8436 see the source code for the spec of @code{Ada.Interrupts.Names} in
8437 file @code{a-intnam.ads}. This is a target dependent file that contains the
8438 list of interrupts recognized for a given target. The documentation in
8439 this file also specifies what interrupts are affected by the use of
8440 the @code{Unreserve_All_Interrupts} pragma.
8442 For a more general facility for controlling what interrupts can be
8443 handled, see pragma @code{Interrupt_State}, which subsumes the functionality
8444 of the @code{Unreserve_All_Interrupts} pragma.
8446 @node Pragma Unsuppress,Pragma Use_VADS_Size,Pragma Unreserve_All_Interrupts,Implementation Defined Pragmas
8447 @anchor{gnat_rm/implementation_defined_pragmas pragma-unsuppress}@anchor{10f}
8448 @section Pragma Unsuppress
8454 pragma Unsuppress (IDENTIFIER [, [On =>] NAME]);
8457 This pragma undoes the effect of a previous pragma @code{Suppress}. If
8458 there is no corresponding pragma @code{Suppress} in effect, it has no
8459 effect. The range of the effect is the same as for pragma
8460 @code{Suppress}. The meaning of the arguments is identical to that used
8461 in pragma @code{Suppress}.
8463 One important application is to ensure that checks are on in cases where
8464 code depends on the checks for its correct functioning, so that the code
8465 will compile correctly even if the compiler switches are set to suppress
8466 checks. For example, in a program that depends on external names of tagged
8467 types and wants to ensure that the duplicated tag check occurs even if all
8468 run-time checks are suppressed by a compiler switch, the following
8469 configuration pragma will ensure this test is not suppressed:
8472 pragma Unsuppress (Duplicated_Tag_Check);
8475 This pragma is standard in Ada 2005. It is available in all earlier versions
8476 of Ada as an implementation-defined pragma.
8478 Note that in addition to the checks defined in the Ada RM, GNAT recogizes a
8479 number of implementation-defined check names. See the description of pragma
8480 @code{Suppress} for full details.
8482 @node Pragma Use_VADS_Size,Pragma Unused,Pragma Unsuppress,Implementation Defined Pragmas
8483 @anchor{gnat_rm/implementation_defined_pragmas pragma-use-vads-size}@anchor{110}
8484 @section Pragma Use_VADS_Size
8488 @geindex VADS compatibility
8490 @geindex Rational profile
8495 pragma Use_VADS_Size;
8498 This is a configuration pragma. In a unit to which it applies, any use
8499 of the 'Size attribute is automatically interpreted as a use of the
8500 'VADS_Size attribute. Note that this may result in incorrect semantic
8501 processing of valid Ada 95 or Ada 2005 programs. This is intended to aid in
8502 the handling of existing code which depends on the interpretation of Size
8503 as implemented in the VADS compiler. See description of the VADS_Size
8504 attribute for further details.
8506 @node Pragma Unused,Pragma Validity_Checks,Pragma Use_VADS_Size,Implementation Defined Pragmas
8507 @anchor{gnat_rm/implementation_defined_pragmas pragma-unused}@anchor{111}@anchor{gnat_rm/implementation_defined_pragmas id52}@anchor{112}
8508 @section Pragma Unused
8517 pragma Unused (LOCAL_NAME @{, LOCAL_NAME@});
8520 This pragma signals that the assignable entities (variables,
8521 @code{out} parameters, and @code{in out} parameters) whose names are listed
8522 deliberately do not get assigned or referenced in the current source unit
8523 after the occurrence of the pragma in the current source unit. This
8524 suppresses warnings about the entities that are unreferenced and/or not
8525 assigned, and, in addition, a warning will be generated if one of these
8526 entities gets assigned or subsequently referenced in the same unit as the
8527 pragma (in the corresponding body or one of its subunits).
8529 This is particularly useful for clearly signaling that a particular
8530 parameter is not modified or referenced, even though the spec suggests
8533 For the variable case, warnings are never given for unreferenced
8534 variables whose name contains one of the substrings
8535 @code{DISCARD, DUMMY, IGNORE, JUNK, UNUSED} in any casing. Such names
8536 are typically to be used in cases where such warnings are expected.
8537 Thus it is never necessary to use @code{pragma Unmodified} for such
8538 variables, though it is harmless to do so.
8540 @node Pragma Validity_Checks,Pragma Volatile,Pragma Unused,Implementation Defined Pragmas
8541 @anchor{gnat_rm/implementation_defined_pragmas pragma-validity-checks}@anchor{113}
8542 @section Pragma Validity_Checks
8548 pragma Validity_Checks (string_LITERAL | ALL_CHECKS | On | Off);
8551 This pragma is used in conjunction with compiler switches to control the
8552 built-in validity checking provided by GNAT. The compiler switches, if set
8553 provide an initial setting for the switches, and this pragma may be used
8554 to modify these settings, or the settings may be provided entirely by
8555 the use of the pragma. This pragma can be used anywhere that a pragma
8556 is legal, including use as a configuration pragma (including use in
8557 the @code{gnat.adc} file).
8559 The form with a string literal specifies which validity options are to be
8560 activated. The validity checks are first set to include only the default
8561 reference manual settings, and then a string of letters in the string
8562 specifies the exact set of options required. The form of this string
8563 is exactly as described for the @emph{-gnatVx} compiler switch (see the
8564 GNAT User's Guide for details). For example the following two
8565 methods can be used to enable validity checking for mode @code{in} and
8566 @code{in out} subprogram parameters:
8573 pragma Validity_Checks ("im");
8578 $ gcc -c -gnatVim ...
8582 The form ALL_CHECKS activates all standard checks (its use is equivalent
8583 to the use of the @code{gnatva} switch.
8585 The forms with @code{Off} and @code{On}
8586 can be used to temporarily disable validity checks
8587 as shown in the following example:
8590 pragma Validity_Checks ("c"); -- validity checks for copies
8591 pragma Validity_Checks (Off); -- turn off validity checks
8592 A := B; -- B will not be validity checked
8593 pragma Validity_Checks (On); -- turn validity checks back on
8594 A := C; -- C will be validity checked
8597 @node Pragma Volatile,Pragma Volatile_Full_Access,Pragma Validity_Checks,Implementation Defined Pragmas
8598 @anchor{gnat_rm/implementation_defined_pragmas pragma-volatile}@anchor{114}
8599 @section Pragma Volatile
8605 pragma Volatile (LOCAL_NAME);
8608 This pragma is defined by the Ada Reference Manual, and the GNAT
8609 implementation is fully conformant with this definition. The reason it
8610 is mentioned in this section is that a pragma of the same name was supplied
8611 in some Ada 83 compilers, including DEC Ada 83. The Ada 95 / Ada 2005
8612 implementation of pragma Volatile is upwards compatible with the
8613 implementation in DEC Ada 83.
8615 @node Pragma Volatile_Full_Access,Pragma Volatile_Function,Pragma Volatile,Implementation Defined Pragmas
8616 @anchor{gnat_rm/implementation_defined_pragmas pragma-volatile-full-access}@anchor{115}@anchor{gnat_rm/implementation_defined_pragmas id53}@anchor{116}
8617 @section Pragma Volatile_Full_Access
8623 pragma Volatile_Full_Access (LOCAL_NAME);
8626 This is similar in effect to pragma Volatile, except that any reference to the
8627 object is guaranteed to be done only with instructions that read or write all
8628 the bits of the object. Furthermore, if the object is of a composite type,
8629 then any reference to a component of the object is guaranteed to read and/or
8630 write all the bits of the object.
8632 The intention is that this be suitable for use with memory-mapped I/O devices
8633 on some machines. Note that there are two important respects in which this is
8634 different from @code{pragma Atomic}. First a reference to a @code{Volatile_Full_Access}
8635 object is not a sequential action in the RM 9.10 sense and, therefore, does
8636 not create a synchronization point. Second, in the case of @code{pragma Atomic},
8637 there is no guarantee that all the bits will be accessed if the reference
8638 is not to the whole object; the compiler is allowed (and generally will)
8639 access only part of the object in this case.
8641 It is not permissible to specify @code{Atomic} and @code{Volatile_Full_Access} for
8644 It is not permissible to specify @code{Volatile_Full_Access} for a composite
8645 (record or array) type or object that has at least one @code{Aliased} component.
8647 @node Pragma Volatile_Function,Pragma Warning_As_Error,Pragma Volatile_Full_Access,Implementation Defined Pragmas
8648 @anchor{gnat_rm/implementation_defined_pragmas id54}@anchor{117}@anchor{gnat_rm/implementation_defined_pragmas pragma-volatile-function}@anchor{118}
8649 @section Pragma Volatile_Function
8655 pragma Volatile_Function [ (boolean_EXPRESSION) ];
8658 For the semantics of this pragma, see the entry for aspect @code{Volatile_Function}
8659 in the SPARK 2014 Reference Manual, section 7.1.2.
8661 @node Pragma Warning_As_Error,Pragma Warnings,Pragma Volatile_Function,Implementation Defined Pragmas
8662 @anchor{gnat_rm/implementation_defined_pragmas pragma-warning-as-error}@anchor{119}
8663 @section Pragma Warning_As_Error
8669 pragma Warning_As_Error (static_string_EXPRESSION);
8672 This configuration pragma allows the programmer to specify a set
8673 of warnings that will be treated as errors. Any warning which
8674 matches the pattern given by the pragma argument will be treated
8675 as an error. This gives much more precise control that -gnatwe
8676 which treats all warnings as errors.
8678 The pattern may contain asterisks, which match zero or more characters in
8679 the message. For example, you can use
8680 @code{pragma Warning_As_Error ("bits of*unused")} to treat the warning
8681 message @code{warning: 960 bits of "a" unused} as an error. No other regular
8682 expression notations are permitted. All characters other than asterisk in
8683 these three specific cases are treated as literal characters in the match.
8684 The match is case insensitive, for example XYZ matches xyz.
8686 Note that the pattern matches if it occurs anywhere within the warning
8687 message string (it is not necessary to put an asterisk at the start and
8688 the end of the message, since this is implied).
8690 Another possibility for the static_string_EXPRESSION which works whether
8691 or not error tags are enabled (@emph{-gnatw.d}) is to use the
8692 @emph{-gnatw} tag string, enclosed in brackets,
8693 as shown in the example below, to treat a class of warnings as errors.
8695 The above use of patterns to match the message applies only to warning
8696 messages generated by the front end. This pragma can also be applied to
8697 warnings provided by the back end and mentioned in @ref{11a,,Pragma Warnings}.
8698 By using a single full @emph{-Wxxx} switch in the pragma, such warnings
8699 can also be treated as errors.
8701 The pragma can appear either in a global configuration pragma file
8702 (e.g. @code{gnat.adc}), or at the start of a file. Given a global
8703 configuration pragma file containing:
8706 pragma Warning_As_Error ("[-gnatwj]");
8709 which will treat all obsolescent feature warnings as errors, the
8710 following program compiles as shown (compile options here are
8711 @emph{-gnatwa.d -gnatl -gnatj55}).
8714 1. pragma Warning_As_Error ("*never assigned*");
8715 2. function Warnerr return String is
8718 >>> error: variable "X" is never read and
8719 never assigned [-gnatwv] [warning-as-error]
8723 >>> warning: variable "Y" is assigned but
8724 never read [-gnatwu]
8730 >>> error: use of "%" is an obsolescent
8731 feature (RM J.2(4)), use """ instead
8732 [-gnatwj] [warning-as-error]
8736 8 lines: No errors, 3 warnings (2 treated as errors)
8739 Note that this pragma does not affect the set of warnings issued in
8740 any way, it merely changes the effect of a matching warning if one
8741 is produced as a result of other warnings options. As shown in this
8742 example, if the pragma results in a warning being treated as an error,
8743 the tag is changed from "warning:" to "error:" and the string
8744 "[warning-as-error]" is appended to the end of the message.
8746 @node Pragma Warnings,Pragma Weak_External,Pragma Warning_As_Error,Implementation Defined Pragmas
8747 @anchor{gnat_rm/implementation_defined_pragmas id55}@anchor{11b}@anchor{gnat_rm/implementation_defined_pragmas pragma-warnings}@anchor{11a}
8748 @section Pragma Warnings
8754 pragma Warnings ([TOOL_NAME,] DETAILS [, REASON]);
8756 DETAILS ::= On | Off
8757 DETAILS ::= On | Off, local_NAME
8758 DETAILS ::= static_string_EXPRESSION
8759 DETAILS ::= On | Off, static_string_EXPRESSION
8761 TOOL_NAME ::= GNAT | GNATProve
8763 REASON ::= Reason => STRING_LITERAL @{& STRING_LITERAL@}
8766 Note: in Ada 83 mode, a string literal may be used in place of a static string
8767 expression (which does not exist in Ada 83).
8769 Note if the second argument of @code{DETAILS} is a @code{local_NAME} then the
8770 second form is always understood. If the intention is to use
8771 the fourth form, then you can write @code{NAME & ""} to force the
8772 intepretation as a @emph{static_string_EXPRESSION}.
8774 Note: if the first argument is a valid @code{TOOL_NAME}, it will be interpreted
8775 that way. The use of the @code{TOOL_NAME} argument is relevant only to users
8776 of SPARK and GNATprove, see last part of this section for details.
8778 Normally warnings are enabled, with the output being controlled by
8779 the command line switch. Warnings (@code{Off}) turns off generation of
8780 warnings until a Warnings (@code{On}) is encountered or the end of the
8781 current unit. If generation of warnings is turned off using this
8782 pragma, then some or all of the warning messages are suppressed,
8783 regardless of the setting of the command line switches.
8785 The @code{Reason} parameter may optionally appear as the last argument
8786 in any of the forms of this pragma. It is intended purely for the
8787 purposes of documenting the reason for the @code{Warnings} pragma.
8788 The compiler will check that the argument is a static string but
8789 otherwise ignore this argument. Other tools may provide specialized
8790 processing for this string.
8792 The form with a single argument (or two arguments if Reason present),
8793 where the first argument is @code{ON} or @code{OFF}
8794 may be used as a configuration pragma.
8796 If the @code{LOCAL_NAME} parameter is present, warnings are suppressed for
8797 the specified entity. This suppression is effective from the point where
8798 it occurs till the end of the extended scope of the variable (similar to
8799 the scope of @code{Suppress}). This form cannot be used as a configuration
8802 In the case where the first argument is other than @code{ON} or
8804 the third form with a single static_string_EXPRESSION argument (and possible
8805 reason) provides more precise
8806 control over which warnings are active. The string is a list of letters
8807 specifying which warnings are to be activated and which deactivated. The
8808 code for these letters is the same as the string used in the command
8809 line switch controlling warnings. For a brief summary, use the gnatmake
8810 command with no arguments, which will generate usage information containing
8811 the list of warnings switches supported. For
8812 full details see the section on @code{Warning Message Control} in the
8813 @cite{GNAT User's Guide}.
8814 This form can also be used as a configuration pragma.
8816 The warnings controlled by the @code{-gnatw} switch are generated by the
8817 front end of the compiler. The GCC back end can provide additional warnings
8818 and they are controlled by the @code{-W} switch. Such warnings can be
8819 identified by the appearance of a string of the form @code{[-W@{xxx@}]} in the
8820 message which designates the @code{-W@emph{xxx}} switch that controls the message.
8821 The form with a single @emph{static_string_EXPRESSION} argument also works for these
8822 warnings, but the string must be a single full @code{-W@emph{xxx}} switch in this
8823 case. The above reference lists a few examples of these additional warnings.
8825 The specified warnings will be in effect until the end of the program
8826 or another pragma @code{Warnings} is encountered. The effect of the pragma is
8827 cumulative. Initially the set of warnings is the standard default set
8828 as possibly modified by compiler switches. Then each pragma Warning
8829 modifies this set of warnings as specified. This form of the pragma may
8830 also be used as a configuration pragma.
8832 The fourth form, with an @code{On|Off} parameter and a string, is used to
8833 control individual messages, based on their text. The string argument
8834 is a pattern that is used to match against the text of individual
8835 warning messages (not including the initial "warning: " tag).
8837 The pattern may contain asterisks, which match zero or more characters in
8838 the message. For example, you can use
8839 @code{pragma Warnings (Off, "bits of*unused")} to suppress the warning
8840 message @code{warning: 960 bits of "a" unused}. No other regular
8841 expression notations are permitted. All characters other than asterisk in
8842 these three specific cases are treated as literal characters in the match.
8843 The match is case insensitive, for example XYZ matches xyz.
8845 Note that the pattern matches if it occurs anywhere within the warning
8846 message string (it is not necessary to put an asterisk at the start and
8847 the end of the message, since this is implied).
8849 The above use of patterns to match the message applies only to warning
8850 messages generated by the front end. This form of the pragma with a string
8851 argument can also be used to control warnings provided by the back end and
8852 mentioned above. By using a single full @code{-W@emph{xxx}} switch in the pragma,
8853 such warnings can be turned on and off.
8855 There are two ways to use the pragma in this form. The OFF form can be used
8856 as a configuration pragma. The effect is to suppress all warnings (if any)
8857 that match the pattern string throughout the compilation (or match the
8858 -W switch in the back end case).
8860 The second usage is to suppress a warning locally, and in this case, two
8861 pragmas must appear in sequence:
8864 pragma Warnings (Off, Pattern);
8865 ... code where given warning is to be suppressed
8866 pragma Warnings (On, Pattern);
8869 In this usage, the pattern string must match in the Off and On
8870 pragmas, and (if @emph{-gnatw.w} is given) at least one matching
8871 warning must be suppressed.
8873 Note: to write a string that will match any warning, use the string
8874 @code{"***"}. It will not work to use a single asterisk or two
8875 asterisks since this looks like an operator name. This form with three
8876 asterisks is similar in effect to specifying @code{pragma Warnings (Off)} except (if @code{-gnatw.w} is given) that a matching
8877 @code{pragma Warnings (On, "***")} will be required. This can be
8878 helpful in avoiding forgetting to turn warnings back on.
8880 Note: the debug flag @code{-gnatd.i} (@code{/NOWARNINGS_PRAGMAS} in VMS) can be
8881 used to cause the compiler to entirely ignore all WARNINGS pragmas. This can
8882 be useful in checking whether obsolete pragmas in existing programs are hiding
8885 Note: pragma Warnings does not affect the processing of style messages. See
8886 separate entry for pragma Style_Checks for control of style messages.
8888 Users of the formal verification tool GNATprove for the SPARK subset of Ada may
8889 use the version of the pragma with a @code{TOOL_NAME} parameter.
8891 If present, @code{TOOL_NAME} is the name of a tool, currently either @code{GNAT} for the
8892 compiler or @code{GNATprove} for the formal verification tool. A given tool only
8893 takes into account pragma Warnings that do not specify a tool name, or that
8894 specify the matching tool name. This makes it possible to disable warnings
8895 selectively for each tool, and as a consequence to detect useless pragma
8896 Warnings with switch @code{-gnatw.w}.
8898 @node Pragma Weak_External,Pragma Wide_Character_Encoding,Pragma Warnings,Implementation Defined Pragmas
8899 @anchor{gnat_rm/implementation_defined_pragmas pragma-weak-external}@anchor{11c}
8900 @section Pragma Weak_External
8906 pragma Weak_External ([Entity =>] LOCAL_NAME);
8909 @code{LOCAL_NAME} must refer to an object that is declared at the library
8910 level. This pragma specifies that the given entity should be marked as a
8911 weak symbol for the linker. It is equivalent to @code{__attribute__((weak))}
8912 in GNU C and causes @code{LOCAL_NAME} to be emitted as a weak symbol instead
8913 of a regular symbol, that is to say a symbol that does not have to be
8914 resolved by the linker if used in conjunction with a pragma Import.
8916 When a weak symbol is not resolved by the linker, its address is set to
8917 zero. This is useful in writing interfaces to external modules that may
8918 or may not be linked in the final executable, for example depending on
8919 configuration settings.
8921 If a program references at run time an entity to which this pragma has been
8922 applied, and the corresponding symbol was not resolved at link time, then
8923 the execution of the program is erroneous. It is not erroneous to take the
8924 Address of such an entity, for example to guard potential references,
8925 as shown in the example below.
8927 Some file formats do not support weak symbols so not all target machines
8928 support this pragma.
8931 -- Example of the use of pragma Weak_External
8933 package External_Module is
8935 pragma Import (C, key);
8936 pragma Weak_External (key);
8937 function Present return boolean;
8938 end External_Module;
8940 with System; use System;
8941 package body External_Module is
8942 function Present return boolean is
8944 return key'Address /= System.Null_Address;
8946 end External_Module;
8949 @node Pragma Wide_Character_Encoding,,Pragma Weak_External,Implementation Defined Pragmas
8950 @anchor{gnat_rm/implementation_defined_pragmas pragma-wide-character-encoding}@anchor{11d}
8951 @section Pragma Wide_Character_Encoding
8957 pragma Wide_Character_Encoding (IDENTIFIER | CHARACTER_LITERAL);
8960 This pragma specifies the wide character encoding to be used in program
8961 source text appearing subsequently. It is a configuration pragma, but may
8962 also be used at any point that a pragma is allowed, and it is permissible
8963 to have more than one such pragma in a file, allowing multiple encodings
8964 to appear within the same file.
8966 However, note that the pragma cannot immediately precede the relevant
8967 wide character, because then the previous encoding will still be in
8968 effect, causing "illegal character" errors.
8970 The argument can be an identifier or a character literal. In the identifier
8971 case, it is one of @code{HEX}, @code{UPPER}, @code{SHIFT_JIS},
8972 @code{EUC}, @code{UTF8}, or @code{BRACKETS}. In the character literal
8973 case it is correspondingly one of the characters @code{h}, @code{u},
8974 @code{s}, @code{e}, @code{8}, or @code{b}.
8976 Note that when the pragma is used within a file, it affects only the
8977 encoding within that file, and does not affect withed units, specs,
8980 @node Implementation Defined Aspects,Implementation Defined Attributes,Implementation Defined Pragmas,Top
8981 @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}
8982 @chapter Implementation Defined Aspects
8985 Ada defines (throughout the Ada 2012 reference manual, summarized
8986 in Annex K) a set of aspects that can be specified for certain entities.
8987 These language defined aspects are implemented in GNAT in Ada 2012 mode
8988 and work as described in the Ada 2012 Reference Manual.
8990 In addition, Ada 2012 allows implementations to define additional aspects
8991 whose meaning is defined by the implementation. GNAT provides
8992 a number of these implementation-defined aspects which can be used
8993 to extend and enhance the functionality of the compiler. This section of
8994 the GNAT reference manual describes these additional aspects.
8996 Note that any program using these aspects may not be portable to
8997 other compilers (although GNAT implements this set of aspects on all
8998 platforms). Therefore if portability to other compilers is an important
8999 consideration, you should minimize the use of these aspects.
9001 Note that for many of these aspects, the effect is essentially similar
9002 to the use of a pragma or attribute specification with the same name
9003 applied to the entity. For example, if we write:
9006 type R is range 1 .. 100
9007 with Value_Size => 10;
9010 then the effect is the same as:
9013 type R is range 1 .. 100;
9014 for R'Value_Size use 10;
9020 type R is new Integer
9021 with Shared => True;
9024 then the effect is the same as:
9027 type R is new Integer;
9031 In the documentation below, such cases are simply marked
9032 as being boolean aspects equivalent to the corresponding pragma
9033 or attribute definition clause.
9036 * Aspect Abstract_State::
9038 * Aspect Async_Readers::
9039 * Aspect Async_Writers::
9040 * Aspect Constant_After_Elaboration::
9041 * Aspect Contract_Cases::
9043 * Aspect Default_Initial_Condition::
9044 * Aspect Dimension::
9045 * Aspect Dimension_System::
9046 * Aspect Disable_Controlled::
9047 * Aspect Effective_Reads::
9048 * Aspect Effective_Writes::
9049 * Aspect Extensions_Visible::
9050 * Aspect Favor_Top_Level::
9053 * Aspect Initial_Condition::
9054 * Aspect Initializes::
9055 * Aspect Inline_Always::
9056 * Aspect Invariant::
9057 * Aspect Invariant'Class::
9059 * Aspect Linker_Section::
9060 * Aspect Lock_Free::
9061 * Aspect Max_Queue_Length::
9062 * Aspect No_Elaboration_Code_All::
9063 * Aspect No_Inline::
9064 * Aspect No_Tagged_Streams::
9065 * Aspect Object_Size::
9066 * Aspect Obsolescent::
9068 * Aspect Persistent_BSS::
9069 * Aspect Predicate::
9070 * Aspect Pure_Function::
9071 * Aspect Refined_Depends::
9072 * Aspect Refined_Global::
9073 * Aspect Refined_Post::
9074 * Aspect Refined_State::
9075 * Aspect Remote_Access_Type::
9076 * Aspect Secondary_Stack_Size::
9077 * Aspect Scalar_Storage_Order::
9079 * Aspect Simple_Storage_Pool::
9080 * Aspect Simple_Storage_Pool_Type::
9081 * Aspect SPARK_Mode::
9082 * Aspect Suppress_Debug_Info::
9083 * Aspect Suppress_Initialization::
9084 * Aspect Test_Case::
9085 * Aspect Thread_Local_Storage::
9086 * Aspect Universal_Aliasing::
9087 * Aspect Universal_Data::
9088 * Aspect Unmodified::
9089 * Aspect Unreferenced::
9090 * Aspect Unreferenced_Objects::
9091 * Aspect Value_Size::
9092 * Aspect Volatile_Full_Access::
9093 * Aspect Volatile_Function::
9098 @node Aspect Abstract_State,Aspect Annotate,,Implementation Defined Aspects
9099 @anchor{gnat_rm/implementation_defined_aspects aspect-abstract-state}@anchor{121}
9100 @section Aspect Abstract_State
9103 @geindex Abstract_State
9105 This aspect is equivalent to @ref{1c,,pragma Abstract_State}.
9107 @node Aspect Annotate,Aspect Async_Readers,Aspect Abstract_State,Implementation Defined Aspects
9108 @anchor{gnat_rm/implementation_defined_aspects aspect-annotate}@anchor{122}
9109 @section Aspect Annotate
9114 There are three forms of this aspect (where ID is an identifier,
9115 and ARG is a general expression),
9116 corresponding to @ref{25,,pragma Annotate}.
9121 @item @emph{Annotate => ID}
9123 Equivalent to @code{pragma Annotate (ID, Entity => Name);}
9125 @item @emph{Annotate => (ID)}
9127 Equivalent to @code{pragma Annotate (ID, Entity => Name);}
9129 @item @emph{Annotate => (ID ,ID @{, ARG@})}
9131 Equivalent to @code{pragma Annotate (ID, ID @{, ARG@}, Entity => Name);}
9134 @node Aspect Async_Readers,Aspect Async_Writers,Aspect Annotate,Implementation Defined Aspects
9135 @anchor{gnat_rm/implementation_defined_aspects aspect-async-readers}@anchor{123}
9136 @section Aspect Async_Readers
9139 @geindex Async_Readers
9141 This boolean aspect is equivalent to @ref{2c,,pragma Async_Readers}.
9143 @node Aspect Async_Writers,Aspect Constant_After_Elaboration,Aspect Async_Readers,Implementation Defined Aspects
9144 @anchor{gnat_rm/implementation_defined_aspects aspect-async-writers}@anchor{124}
9145 @section Aspect Async_Writers
9148 @geindex Async_Writers
9150 This boolean aspect is equivalent to @ref{2f,,pragma Async_Writers}.
9152 @node Aspect Constant_After_Elaboration,Aspect Contract_Cases,Aspect Async_Writers,Implementation Defined Aspects
9153 @anchor{gnat_rm/implementation_defined_aspects aspect-constant-after-elaboration}@anchor{125}
9154 @section Aspect Constant_After_Elaboration
9157 @geindex Constant_After_Elaboration
9159 This aspect is equivalent to @ref{40,,pragma Constant_After_Elaboration}.
9161 @node Aspect Contract_Cases,Aspect Depends,Aspect Constant_After_Elaboration,Implementation Defined Aspects
9162 @anchor{gnat_rm/implementation_defined_aspects aspect-contract-cases}@anchor{126}
9163 @section Aspect Contract_Cases
9166 @geindex Contract_Cases
9168 This aspect is equivalent to @ref{42,,pragma Contract_Cases}, the sequence
9169 of clauses being enclosed in parentheses so that syntactically it is an
9172 @node Aspect Depends,Aspect Default_Initial_Condition,Aspect Contract_Cases,Implementation Defined Aspects
9173 @anchor{gnat_rm/implementation_defined_aspects aspect-depends}@anchor{127}
9174 @section Aspect Depends
9179 This aspect is equivalent to @ref{51,,pragma Depends}.
9181 @node Aspect Default_Initial_Condition,Aspect Dimension,Aspect Depends,Implementation Defined Aspects
9182 @anchor{gnat_rm/implementation_defined_aspects aspect-default-initial-condition}@anchor{128}
9183 @section Aspect Default_Initial_Condition
9186 @geindex Default_Initial_Condition
9188 This aspect is equivalent to @ref{4c,,pragma Default_Initial_Condition}.
9190 @node Aspect Dimension,Aspect Dimension_System,Aspect Default_Initial_Condition,Implementation Defined Aspects
9191 @anchor{gnat_rm/implementation_defined_aspects aspect-dimension}@anchor{129}
9192 @section Aspect Dimension
9197 The @code{Dimension} aspect is used to specify the dimensions of a given
9198 subtype of a dimensioned numeric type. The aspect also specifies a symbol
9199 used when doing formatted output of dimensioned quantities. The syntax is:
9203 ([Symbol =>] SYMBOL, DIMENSION_VALUE @{, DIMENSION_Value@})
9205 SYMBOL ::= STRING_LITERAL | CHARACTER_LITERAL
9209 | others => RATIONAL
9210 | DISCRETE_CHOICE_LIST => RATIONAL
9212 RATIONAL ::= [-] NUMERIC_LITERAL [/ NUMERIC_LITERAL]
9215 This aspect can only be applied to a subtype whose parent type has
9216 a @code{Dimension_System} aspect. The aspect must specify values for
9217 all dimensions of the system. The rational values are the powers of the
9218 corresponding dimensions that are used by the compiler to verify that
9219 physical (numeric) computations are dimensionally consistent. For example,
9220 the computation of a force must result in dimensions (L => 1, M => 1, T => -2).
9221 For further examples of the usage
9222 of this aspect, see package @code{System.Dim.Mks}.
9223 Note that when the dimensioned type is an integer type, then any
9224 dimension value must be an integer literal.
9226 @node Aspect Dimension_System,Aspect Disable_Controlled,Aspect Dimension,Implementation Defined Aspects
9227 @anchor{gnat_rm/implementation_defined_aspects aspect-dimension-system}@anchor{12a}
9228 @section Aspect Dimension_System
9231 @geindex Dimension_System
9233 The @code{Dimension_System} aspect is used to define a system of
9234 dimensions that will be used in subsequent subtype declarations with
9235 @code{Dimension} aspects that reference this system. The syntax is:
9238 with Dimension_System => (DIMENSION @{, DIMENSION@});
9240 DIMENSION ::= ([Unit_Name =>] IDENTIFIER,
9241 [Unit_Symbol =>] SYMBOL,
9242 [Dim_Symbol =>] SYMBOL)
9244 SYMBOL ::= CHARACTER_LITERAL | STRING_LITERAL
9247 This aspect is applied to a type, which must be a numeric derived type
9248 (typically a floating-point type), that
9249 will represent values within the dimension system. Each @code{DIMENSION}
9250 corresponds to one particular dimension. A maximum of 7 dimensions may
9251 be specified. @code{Unit_Name} is the name of the dimension (for example
9252 @code{Meter}). @code{Unit_Symbol} is the shorthand used for quantities
9253 of this dimension (for example @code{m} for @code{Meter}).
9254 @code{Dim_Symbol} gives
9255 the identification within the dimension system (typically this is a
9256 single letter, e.g. @code{L} standing for length for unit name @code{Meter}).
9257 The @code{Unit_Symbol} is used in formatted output of dimensioned quantities.
9258 The @code{Dim_Symbol} is used in error messages when numeric operations have
9259 inconsistent dimensions.
9261 GNAT provides the standard definition of the International MKS system in
9262 the run-time package @code{System.Dim.Mks}. You can easily define
9263 similar packages for cgs units or British units, and define conversion factors
9264 between values in different systems. The MKS system is characterized by the
9268 type Mks_Type is new Long_Long_Float with
9269 Dimension_System => (
9270 (Unit_Name => Meter, Unit_Symbol => 'm', Dim_Symbol => 'L'),
9271 (Unit_Name => Kilogram, Unit_Symbol => "kg", Dim_Symbol => 'M'),
9272 (Unit_Name => Second, Unit_Symbol => 's', Dim_Symbol => 'T'),
9273 (Unit_Name => Ampere, Unit_Symbol => 'A', Dim_Symbol => 'I'),
9274 (Unit_Name => Kelvin, Unit_Symbol => 'K', Dim_Symbol => '@@'),
9275 (Unit_Name => Mole, Unit_Symbol => "mol", Dim_Symbol => 'N'),
9276 (Unit_Name => Candela, Unit_Symbol => "cd", Dim_Symbol => 'J'));
9279 Note that in the above type definition, we use the @code{at} symbol (@code{@@}) to
9280 represent a theta character (avoiding the use of extended Latin-1
9281 characters in this context).
9283 See section 'Performing Dimensionality Analysis in GNAT' in the GNAT Users
9284 Guide for detailed examples of use of the dimension system.
9286 @node Aspect Disable_Controlled,Aspect Effective_Reads,Aspect Dimension_System,Implementation Defined Aspects
9287 @anchor{gnat_rm/implementation_defined_aspects aspect-disable-controlled}@anchor{12b}
9288 @section Aspect Disable_Controlled
9291 @geindex Disable_Controlled
9293 The aspect @code{Disable_Controlled} is defined for controlled record types. If
9294 active, this aspect causes suppression of all related calls to @code{Initialize},
9295 @code{Adjust}, and @code{Finalize}. The intended use is for conditional compilation,
9296 where for example you might want a record to be controlled or not depending on
9297 whether some run-time check is enabled or suppressed.
9299 @node Aspect Effective_Reads,Aspect Effective_Writes,Aspect Disable_Controlled,Implementation Defined Aspects
9300 @anchor{gnat_rm/implementation_defined_aspects aspect-effective-reads}@anchor{12c}
9301 @section Aspect Effective_Reads
9304 @geindex Effective_Reads
9306 This aspect is equivalent to @ref{57,,pragma Effective_Reads}.
9308 @node Aspect Effective_Writes,Aspect Extensions_Visible,Aspect Effective_Reads,Implementation Defined Aspects
9309 @anchor{gnat_rm/implementation_defined_aspects aspect-effective-writes}@anchor{12d}
9310 @section Aspect Effective_Writes
9313 @geindex Effective_Writes
9315 This aspect is equivalent to @ref{59,,pragma Effective_Writes}.
9317 @node Aspect Extensions_Visible,Aspect Favor_Top_Level,Aspect Effective_Writes,Implementation Defined Aspects
9318 @anchor{gnat_rm/implementation_defined_aspects aspect-extensions-visible}@anchor{12e}
9319 @section Aspect Extensions_Visible
9322 @geindex Extensions_Visible
9324 This aspect is equivalent to @ref{65,,pragma Extensions_Visible}.
9326 @node Aspect Favor_Top_Level,Aspect Ghost,Aspect Extensions_Visible,Implementation Defined Aspects
9327 @anchor{gnat_rm/implementation_defined_aspects aspect-favor-top-level}@anchor{12f}
9328 @section Aspect Favor_Top_Level
9331 @geindex Favor_Top_Level
9333 This boolean aspect is equivalent to @ref{6a,,pragma Favor_Top_Level}.
9335 @node Aspect Ghost,Aspect Global,Aspect Favor_Top_Level,Implementation Defined Aspects
9336 @anchor{gnat_rm/implementation_defined_aspects aspect-ghost}@anchor{130}
9337 @section Aspect Ghost
9342 This aspect is equivalent to @ref{6d,,pragma Ghost}.
9344 @node Aspect Global,Aspect Initial_Condition,Aspect Ghost,Implementation Defined Aspects
9345 @anchor{gnat_rm/implementation_defined_aspects aspect-global}@anchor{131}
9346 @section Aspect Global
9351 This aspect is equivalent to @ref{6f,,pragma Global}.
9353 @node Aspect Initial_Condition,Aspect Initializes,Aspect Global,Implementation Defined Aspects
9354 @anchor{gnat_rm/implementation_defined_aspects aspect-initial-condition}@anchor{132}
9355 @section Aspect Initial_Condition
9358 @geindex Initial_Condition
9360 This aspect is equivalent to @ref{7d,,pragma Initial_Condition}.
9362 @node Aspect Initializes,Aspect Inline_Always,Aspect Initial_Condition,Implementation Defined Aspects
9363 @anchor{gnat_rm/implementation_defined_aspects aspect-initializes}@anchor{133}
9364 @section Aspect Initializes
9367 @geindex Initializes
9369 This aspect is equivalent to @ref{7f,,pragma Initializes}.
9371 @node Aspect Inline_Always,Aspect Invariant,Aspect Initializes,Implementation Defined Aspects
9372 @anchor{gnat_rm/implementation_defined_aspects aspect-inline-always}@anchor{134}
9373 @section Aspect Inline_Always
9376 @geindex Inline_Always
9378 This boolean aspect is equivalent to @ref{82,,pragma Inline_Always}.
9380 @node Aspect Invariant,Aspect Invariant'Class,Aspect Inline_Always,Implementation Defined Aspects
9381 @anchor{gnat_rm/implementation_defined_aspects aspect-invariant}@anchor{135}
9382 @section Aspect Invariant
9387 This aspect is equivalent to @ref{89,,pragma Invariant}. It is a
9388 synonym for the language defined aspect @code{Type_Invariant} except
9389 that it is separately controllable using pragma @code{Assertion_Policy}.
9391 @node Aspect Invariant'Class,Aspect Iterable,Aspect Invariant,Implementation Defined Aspects
9392 @anchor{gnat_rm/implementation_defined_aspects aspect-invariant-class}@anchor{136}
9393 @section Aspect Invariant'Class
9396 @geindex Invariant'Class
9398 This aspect is equivalent to @ref{100,,pragma Type_Invariant_Class}. It is a
9399 synonym for the language defined aspect @code{Type_Invariant'Class} except
9400 that it is separately controllable using pragma @code{Assertion_Policy}.
9402 @node Aspect Iterable,Aspect Linker_Section,Aspect Invariant'Class,Implementation Defined Aspects
9403 @anchor{gnat_rm/implementation_defined_aspects aspect-iterable}@anchor{137}
9404 @section Aspect Iterable
9409 This aspect provides a light-weight mechanism for loops and quantified
9410 expressions over container types, without the overhead imposed by the tampering
9411 checks of standard Ada 2012 iterators. The value of the aspect is an aggregate
9412 with four named components: @code{First}, @code{Next}, @code{Has_Element}, and @code{Element} (the
9413 last one being optional). When only 3 components are specified, only the
9414 @code{for .. in} form of iteration over cursors is available. When all 4 components
9415 are specified, both this form and the @code{for .. of} form of iteration over
9416 elements are available. The following is a typical example of use:
9419 type List is private with
9420 Iterable => (First => First_Cursor,
9422 Has_Element => Cursor_Has_Element,
9423 [Element => Get_Element]);
9430 The value denoted by @code{First} must denote a primitive operation of the
9431 container type that returns a @code{Cursor}, which must a be a type declared in
9432 the container package or visible from it. For example:
9436 function First_Cursor (Cont : Container) return Cursor;
9443 The value of @code{Next} is a primitive operation of the container type that takes
9444 both a container and a cursor and yields a cursor. For example:
9448 function Advance (Cont : Container; Position : Cursor) return Cursor;
9455 The value of @code{Has_Element} is a primitive operation of the container type
9456 that takes both a container and a cursor and yields a boolean. For example:
9460 function Cursor_Has_Element (Cont : Container; Position : Cursor) return Boolean;
9467 The value of @code{Element} is a primitive operation of the container type that
9468 takes both a container and a cursor and yields an @code{Element_Type}, which must
9469 be a type declared in the container package or visible from it. For example:
9473 function Get_Element (Cont : Container; Position : Cursor) return Element_Type;
9476 This aspect is used in the GNAT-defined formal container packages.
9478 @node Aspect Linker_Section,Aspect Lock_Free,Aspect Iterable,Implementation Defined Aspects
9479 @anchor{gnat_rm/implementation_defined_aspects aspect-linker-section}@anchor{138}
9480 @section Aspect Linker_Section
9483 @geindex Linker_Section
9485 This aspect is equivalent to @ref{91,,pragma Linker_Section}.
9487 @node Aspect Lock_Free,Aspect Max_Queue_Length,Aspect Linker_Section,Implementation Defined Aspects
9488 @anchor{gnat_rm/implementation_defined_aspects aspect-lock-free}@anchor{139}
9489 @section Aspect Lock_Free
9494 This boolean aspect is equivalent to @ref{93,,pragma Lock_Free}.
9496 @node Aspect Max_Queue_Length,Aspect No_Elaboration_Code_All,Aspect Lock_Free,Implementation Defined Aspects
9497 @anchor{gnat_rm/implementation_defined_aspects aspect-max-queue-length}@anchor{13a}
9498 @section Aspect Max_Queue_Length
9501 @geindex Max_Queue_Length
9503 This aspect is equivalent to @ref{9b,,pragma Max_Queue_Length}.
9505 @node Aspect No_Elaboration_Code_All,Aspect No_Inline,Aspect Max_Queue_Length,Implementation Defined Aspects
9506 @anchor{gnat_rm/implementation_defined_aspects aspect-no-elaboration-code-all}@anchor{13b}
9507 @section Aspect No_Elaboration_Code_All
9510 @geindex No_Elaboration_Code_All
9512 This aspect is equivalent to @ref{9f,,pragma No_Elaboration_Code_All}
9515 @node Aspect No_Inline,Aspect No_Tagged_Streams,Aspect No_Elaboration_Code_All,Implementation Defined Aspects
9516 @anchor{gnat_rm/implementation_defined_aspects aspect-no-inline}@anchor{13c}
9517 @section Aspect No_Inline
9522 This boolean aspect is equivalent to @ref{a2,,pragma No_Inline}.
9524 @node Aspect No_Tagged_Streams,Aspect Object_Size,Aspect No_Inline,Implementation Defined Aspects
9525 @anchor{gnat_rm/implementation_defined_aspects aspect-no-tagged-streams}@anchor{13d}
9526 @section Aspect No_Tagged_Streams
9529 @geindex No_Tagged_Streams
9531 This aspect is equivalent to @ref{a6,,pragma No_Tagged_Streams} with an
9532 argument specifying a root tagged type (thus this aspect can only be
9533 applied to such a type).
9535 @node Aspect Object_Size,Aspect Obsolescent,Aspect No_Tagged_Streams,Implementation Defined Aspects
9536 @anchor{gnat_rm/implementation_defined_aspects aspect-object-size}@anchor{13e}
9537 @section Aspect Object_Size
9540 @geindex Object_Size
9542 This aspect is equivalent to @ref{13f,,attribute Object_Size}.
9544 @node Aspect Obsolescent,Aspect Part_Of,Aspect Object_Size,Implementation Defined Aspects
9545 @anchor{gnat_rm/implementation_defined_aspects aspect-obsolescent}@anchor{140}
9546 @section Aspect Obsolescent
9549 @geindex Obsolsecent
9551 This aspect is equivalent to @ref{a9,,pragma Obsolescent}. Note that the
9552 evaluation of this aspect happens at the point of occurrence, it is not
9553 delayed until the freeze point.
9555 @node Aspect Part_Of,Aspect Persistent_BSS,Aspect Obsolescent,Implementation Defined Aspects
9556 @anchor{gnat_rm/implementation_defined_aspects aspect-part-of}@anchor{141}
9557 @section Aspect Part_Of
9562 This aspect is equivalent to @ref{b1,,pragma Part_Of}.
9564 @node Aspect Persistent_BSS,Aspect Predicate,Aspect Part_Of,Implementation Defined Aspects
9565 @anchor{gnat_rm/implementation_defined_aspects aspect-persistent-bss}@anchor{142}
9566 @section Aspect Persistent_BSS
9569 @geindex Persistent_BSS
9571 This boolean aspect is equivalent to @ref{b4,,pragma Persistent_BSS}.
9573 @node Aspect Predicate,Aspect Pure_Function,Aspect Persistent_BSS,Implementation Defined Aspects
9574 @anchor{gnat_rm/implementation_defined_aspects aspect-predicate}@anchor{143}
9575 @section Aspect Predicate
9580 This aspect is equivalent to @ref{bd,,pragma Predicate}. It is thus
9581 similar to the language defined aspects @code{Dynamic_Predicate}
9582 and @code{Static_Predicate} except that whether the resulting
9583 predicate is static or dynamic is controlled by the form of the
9584 expression. It is also separately controllable using pragma
9585 @code{Assertion_Policy}.
9587 @node Aspect Pure_Function,Aspect Refined_Depends,Aspect Predicate,Implementation Defined Aspects
9588 @anchor{gnat_rm/implementation_defined_aspects aspect-pure-function}@anchor{144}
9589 @section Aspect Pure_Function
9592 @geindex Pure_Function
9594 This boolean aspect is equivalent to @ref{c8,,pragma Pure_Function}.
9596 @node Aspect Refined_Depends,Aspect Refined_Global,Aspect Pure_Function,Implementation Defined Aspects
9597 @anchor{gnat_rm/implementation_defined_aspects aspect-refined-depends}@anchor{145}
9598 @section Aspect Refined_Depends
9601 @geindex Refined_Depends
9603 This aspect is equivalent to @ref{cc,,pragma Refined_Depends}.
9605 @node Aspect Refined_Global,Aspect Refined_Post,Aspect Refined_Depends,Implementation Defined Aspects
9606 @anchor{gnat_rm/implementation_defined_aspects aspect-refined-global}@anchor{146}
9607 @section Aspect Refined_Global
9610 @geindex Refined_Global
9612 This aspect is equivalent to @ref{ce,,pragma Refined_Global}.
9614 @node Aspect Refined_Post,Aspect Refined_State,Aspect Refined_Global,Implementation Defined Aspects
9615 @anchor{gnat_rm/implementation_defined_aspects aspect-refined-post}@anchor{147}
9616 @section Aspect Refined_Post
9619 @geindex Refined_Post
9621 This aspect is equivalent to @ref{d0,,pragma Refined_Post}.
9623 @node Aspect Refined_State,Aspect Remote_Access_Type,Aspect Refined_Post,Implementation Defined Aspects
9624 @anchor{gnat_rm/implementation_defined_aspects aspect-refined-state}@anchor{148}
9625 @section Aspect Refined_State
9628 @geindex Refined_State
9630 This aspect is equivalent to @ref{d2,,pragma Refined_State}.
9632 @node Aspect Remote_Access_Type,Aspect Secondary_Stack_Size,Aspect Refined_State,Implementation Defined Aspects
9633 @anchor{gnat_rm/implementation_defined_aspects aspect-remote-access-type}@anchor{149}
9634 @section Aspect Remote_Access_Type
9637 @geindex Remote_Access_Type
9639 This aspect is equivalent to @ref{d6,,pragma Remote_Access_Type}.
9641 @node Aspect Secondary_Stack_Size,Aspect Scalar_Storage_Order,Aspect Remote_Access_Type,Implementation Defined Aspects
9642 @anchor{gnat_rm/implementation_defined_aspects aspect-secondary-stack-size}@anchor{14a}
9643 @section Aspect Secondary_Stack_Size
9646 @geindex Secondary_Stack_Size
9648 This aspect is equivalent to @ref{db,,pragma Secondary_Stack_Size}.
9650 @node Aspect Scalar_Storage_Order,Aspect Shared,Aspect Secondary_Stack_Size,Implementation Defined Aspects
9651 @anchor{gnat_rm/implementation_defined_aspects aspect-scalar-storage-order}@anchor{14b}
9652 @section Aspect Scalar_Storage_Order
9655 @geindex Scalar_Storage_Order
9657 This aspect is equivalent to a @ref{14c,,attribute Scalar_Storage_Order}.
9659 @node Aspect Shared,Aspect Simple_Storage_Pool,Aspect Scalar_Storage_Order,Implementation Defined Aspects
9660 @anchor{gnat_rm/implementation_defined_aspects aspect-shared}@anchor{14d}
9661 @section Aspect Shared
9666 This boolean aspect is equivalent to @ref{de,,pragma Shared}
9667 and is thus a synonym for aspect @code{Atomic}.
9669 @node Aspect Simple_Storage_Pool,Aspect Simple_Storage_Pool_Type,Aspect Shared,Implementation Defined Aspects
9670 @anchor{gnat_rm/implementation_defined_aspects aspect-simple-storage-pool}@anchor{14e}
9671 @section Aspect Simple_Storage_Pool
9674 @geindex Simple_Storage_Pool
9676 This aspect is equivalent to @ref{e3,,attribute Simple_Storage_Pool}.
9678 @node Aspect Simple_Storage_Pool_Type,Aspect SPARK_Mode,Aspect Simple_Storage_Pool,Implementation Defined Aspects
9679 @anchor{gnat_rm/implementation_defined_aspects aspect-simple-storage-pool-type}@anchor{14f}
9680 @section Aspect Simple_Storage_Pool_Type
9683 @geindex Simple_Storage_Pool_Type
9685 This boolean aspect is equivalent to @ref{e1,,pragma Simple_Storage_Pool_Type}.
9687 @node Aspect SPARK_Mode,Aspect Suppress_Debug_Info,Aspect Simple_Storage_Pool_Type,Implementation Defined Aspects
9688 @anchor{gnat_rm/implementation_defined_aspects aspect-spark-mode}@anchor{150}
9689 @section Aspect SPARK_Mode
9694 This aspect is equivalent to @ref{e9,,pragma SPARK_Mode} and
9695 may be specified for either or both of the specification and body
9696 of a subprogram or package.
9698 @node Aspect Suppress_Debug_Info,Aspect Suppress_Initialization,Aspect SPARK_Mode,Implementation Defined Aspects
9699 @anchor{gnat_rm/implementation_defined_aspects aspect-suppress-debug-info}@anchor{151}
9700 @section Aspect Suppress_Debug_Info
9703 @geindex Suppress_Debug_Info
9705 This boolean aspect is equivalent to @ref{f1,,pragma Suppress_Debug_Info}.
9707 @node Aspect Suppress_Initialization,Aspect Test_Case,Aspect Suppress_Debug_Info,Implementation Defined Aspects
9708 @anchor{gnat_rm/implementation_defined_aspects aspect-suppress-initialization}@anchor{152}
9709 @section Aspect Suppress_Initialization
9712 @geindex Suppress_Initialization
9714 This boolean aspect is equivalent to @ref{f5,,pragma Suppress_Initialization}.
9716 @node Aspect Test_Case,Aspect Thread_Local_Storage,Aspect Suppress_Initialization,Implementation Defined Aspects
9717 @anchor{gnat_rm/implementation_defined_aspects aspect-test-case}@anchor{153}
9718 @section Aspect Test_Case
9723 This aspect is equivalent to @ref{f8,,pragma Test_Case}.
9725 @node Aspect Thread_Local_Storage,Aspect Universal_Aliasing,Aspect Test_Case,Implementation Defined Aspects
9726 @anchor{gnat_rm/implementation_defined_aspects aspect-thread-local-storage}@anchor{154}
9727 @section Aspect Thread_Local_Storage
9730 @geindex Thread_Local_Storage
9732 This boolean aspect is equivalent to @ref{fa,,pragma Thread_Local_Storage}.
9734 @node Aspect Universal_Aliasing,Aspect Universal_Data,Aspect Thread_Local_Storage,Implementation Defined Aspects
9735 @anchor{gnat_rm/implementation_defined_aspects aspect-universal-aliasing}@anchor{155}
9736 @section Aspect Universal_Aliasing
9739 @geindex Universal_Aliasing
9741 This boolean aspect is equivalent to @ref{105,,pragma Universal_Aliasing}.
9743 @node Aspect Universal_Data,Aspect Unmodified,Aspect Universal_Aliasing,Implementation Defined Aspects
9744 @anchor{gnat_rm/implementation_defined_aspects aspect-universal-data}@anchor{156}
9745 @section Aspect Universal_Data
9748 @geindex Universal_Data
9750 This aspect is equivalent to @ref{106,,pragma Universal_Data}.
9752 @node Aspect Unmodified,Aspect Unreferenced,Aspect Universal_Data,Implementation Defined Aspects
9753 @anchor{gnat_rm/implementation_defined_aspects aspect-unmodified}@anchor{157}
9754 @section Aspect Unmodified
9759 This boolean aspect is equivalent to @ref{108,,pragma Unmodified}.
9761 @node Aspect Unreferenced,Aspect Unreferenced_Objects,Aspect Unmodified,Implementation Defined Aspects
9762 @anchor{gnat_rm/implementation_defined_aspects aspect-unreferenced}@anchor{158}
9763 @section Aspect Unreferenced
9766 @geindex Unreferenced
9768 This boolean aspect is equivalent to @ref{10a,,pragma Unreferenced}. Note that
9769 in the case of formal parameters, it is not permitted to have aspects for
9770 a formal parameter, so in this case the pragma form must be used.
9772 @node Aspect Unreferenced_Objects,Aspect Value_Size,Aspect Unreferenced,Implementation Defined Aspects
9773 @anchor{gnat_rm/implementation_defined_aspects aspect-unreferenced-objects}@anchor{159}
9774 @section Aspect Unreferenced_Objects
9777 @geindex Unreferenced_Objects
9779 This boolean aspect is equivalent to @ref{10c,,pragma Unreferenced_Objects}.
9781 @node Aspect Value_Size,Aspect Volatile_Full_Access,Aspect Unreferenced_Objects,Implementation Defined Aspects
9782 @anchor{gnat_rm/implementation_defined_aspects aspect-value-size}@anchor{15a}
9783 @section Aspect Value_Size
9788 This aspect is equivalent to @ref{15b,,attribute Value_Size}.
9790 @node Aspect Volatile_Full_Access,Aspect Volatile_Function,Aspect Value_Size,Implementation Defined Aspects
9791 @anchor{gnat_rm/implementation_defined_aspects aspect-volatile-full-access}@anchor{15c}
9792 @section Aspect Volatile_Full_Access
9795 @geindex Volatile_Full_Access
9797 This boolean aspect is equivalent to @ref{115,,pragma Volatile_Full_Access}.
9799 @node Aspect Volatile_Function,Aspect Warnings,Aspect Volatile_Full_Access,Implementation Defined Aspects
9800 @anchor{gnat_rm/implementation_defined_aspects aspect-volatile-function}@anchor{15d}
9801 @section Aspect Volatile_Function
9804 @geindex Volatile_Function
9806 This boolean aspect is equivalent to @ref{118,,pragma Volatile_Function}.
9808 @node Aspect Warnings,,Aspect Volatile_Function,Implementation Defined Aspects
9809 @anchor{gnat_rm/implementation_defined_aspects aspect-warnings}@anchor{15e}
9810 @section Aspect Warnings
9815 This aspect is equivalent to the two argument form of @ref{11a,,pragma Warnings},
9816 where the first argument is @code{ON} or @code{OFF} and the second argument
9819 @node Implementation Defined Attributes,Standard and Implementation Defined Restrictions,Implementation Defined Aspects,Top
9820 @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}
9821 @chapter Implementation Defined Attributes
9824 Ada defines (throughout the Ada reference manual,
9825 summarized in Annex K),
9826 a set of attributes that provide useful additional functionality in all
9827 areas of the language. These language defined attributes are implemented
9828 in GNAT and work as described in the Ada Reference Manual.
9830 In addition, Ada allows implementations to define additional
9831 attributes whose meaning is defined by the implementation. GNAT provides
9832 a number of these implementation-dependent attributes which can be used
9833 to extend and enhance the functionality of the compiler. This section of
9834 the GNAT reference manual describes these additional attributes. It also
9835 describes additional implementation-dependent features of standard
9836 language-defined attributes.
9838 Note that any program using these attributes may not be portable to
9839 other compilers (although GNAT implements this set of attributes on all
9840 platforms). Therefore if portability to other compilers is an important
9841 consideration, you should minimize the use of these attributes.
9844 * Attribute Abort_Signal::
9845 * Attribute Address_Size::
9846 * Attribute Asm_Input::
9847 * Attribute Asm_Output::
9848 * Attribute Atomic_Always_Lock_Free::
9850 * Attribute Bit_Position::
9851 * Attribute Code_Address::
9852 * Attribute Compiler_Version::
9853 * Attribute Constrained::
9854 * Attribute Default_Bit_Order::
9855 * Attribute Default_Scalar_Storage_Order::
9857 * Attribute Descriptor_Size::
9858 * Attribute Elaborated::
9859 * Attribute Elab_Body::
9860 * Attribute Elab_Spec::
9861 * Attribute Elab_Subp_Body::
9863 * Attribute Enabled::
9864 * Attribute Enum_Rep::
9865 * Attribute Enum_Val::
9866 * Attribute Epsilon::
9867 * Attribute Fast_Math::
9868 * Attribute Finalization_Size::
9869 * Attribute Fixed_Value::
9870 * Attribute From_Any::
9871 * Attribute Has_Access_Values::
9872 * Attribute Has_Discriminants::
9874 * Attribute Integer_Value::
9875 * Attribute Invalid_Value::
9876 * Attribute Iterable::
9878 * Attribute Library_Level::
9879 * Attribute Lock_Free::
9880 * Attribute Loop_Entry::
9881 * Attribute Machine_Size::
9882 * Attribute Mantissa::
9883 * Attribute Maximum_Alignment::
9884 * Attribute Mechanism_Code::
9885 * Attribute Null_Parameter::
9886 * Attribute Object_Size::
9888 * Attribute Passed_By_Reference::
9889 * Attribute Pool_Address::
9890 * Attribute Range_Length::
9891 * Attribute Restriction_Set::
9892 * Attribute Result::
9893 * Attribute Safe_Emax::
9894 * Attribute Safe_Large::
9895 * Attribute Safe_Small::
9896 * Attribute Scalar_Storage_Order::
9897 * Attribute Simple_Storage_Pool::
9899 * Attribute Storage_Unit::
9900 * Attribute Stub_Type::
9901 * Attribute System_Allocator_Alignment::
9902 * Attribute Target_Name::
9903 * Attribute To_Address::
9904 * Attribute To_Any::
9905 * Attribute Type_Class::
9906 * Attribute Type_Key::
9907 * Attribute TypeCode::
9908 * Attribute Unconstrained_Array::
9909 * Attribute Universal_Literal_String::
9910 * Attribute Unrestricted_Access::
9911 * Attribute Update::
9912 * Attribute Valid_Scalars::
9913 * Attribute VADS_Size::
9914 * Attribute Value_Size::
9915 * Attribute Wchar_T_Size::
9916 * Attribute Word_Size::
9920 @node Attribute Abort_Signal,Attribute Address_Size,,Implementation Defined Attributes
9921 @anchor{gnat_rm/implementation_defined_attributes attribute-abort-signal}@anchor{161}
9922 @section Attribute Abort_Signal
9925 @geindex Abort_Signal
9927 @code{Standard'Abort_Signal} (@code{Standard} is the only allowed
9928 prefix) provides the entity for the special exception used to signal
9929 task abort or asynchronous transfer of control. Normally this attribute
9930 should only be used in the tasking runtime (it is highly peculiar, and
9931 completely outside the normal semantics of Ada, for a user program to
9932 intercept the abort exception).
9934 @node Attribute Address_Size,Attribute Asm_Input,Attribute Abort_Signal,Implementation Defined Attributes
9935 @anchor{gnat_rm/implementation_defined_attributes attribute-address-size}@anchor{162}
9936 @section Attribute Address_Size
9939 @geindex Size of `@w{`}Address`@w{`}
9941 @geindex Address_Size
9943 @code{Standard'Address_Size} (@code{Standard} is the only allowed
9944 prefix) is a static constant giving the number of bits in an
9945 @code{Address}. It is the same value as System.Address'Size,
9946 but has the advantage of being static, while a direct
9947 reference to System.Address'Size is nonstatic because Address
9950 @node Attribute Asm_Input,Attribute Asm_Output,Attribute Address_Size,Implementation Defined Attributes
9951 @anchor{gnat_rm/implementation_defined_attributes attribute-asm-input}@anchor{163}
9952 @section Attribute Asm_Input
9957 The @code{Asm_Input} attribute denotes a function that takes two
9958 parameters. The first is a string, the second is an expression of the
9959 type designated by the prefix. The first (string) argument is required
9960 to be a static expression, and is the constraint for the parameter,
9961 (e.g., what kind of register is required). The second argument is the
9962 value to be used as the input argument. The possible values for the
9963 constant are the same as those used in the RTL, and are dependent on
9964 the configuration file used to built the GCC back end.
9965 @ref{164,,Machine Code Insertions}
9967 @node Attribute Asm_Output,Attribute Atomic_Always_Lock_Free,Attribute Asm_Input,Implementation Defined Attributes
9968 @anchor{gnat_rm/implementation_defined_attributes attribute-asm-output}@anchor{165}
9969 @section Attribute Asm_Output
9974 The @code{Asm_Output} attribute denotes a function that takes two
9975 parameters. The first is a string, the second is the name of a variable
9976 of the type designated by the attribute prefix. The first (string)
9977 argument is required to be a static expression and designates the
9978 constraint for the parameter (e.g., what kind of register is
9979 required). The second argument is the variable to be updated with the
9980 result. The possible values for constraint are the same as those used in
9981 the RTL, and are dependent on the configuration file used to build the
9982 GCC back end. If there are no output operands, then this argument may
9983 either be omitted, or explicitly given as @code{No_Output_Operands}.
9984 @ref{164,,Machine Code Insertions}
9986 @node Attribute Atomic_Always_Lock_Free,Attribute Bit,Attribute Asm_Output,Implementation Defined Attributes
9987 @anchor{gnat_rm/implementation_defined_attributes attribute-atomic-always-lock-free}@anchor{166}
9988 @section Attribute Atomic_Always_Lock_Free
9991 @geindex Atomic_Always_Lock_Free
9993 The prefix of the @code{Atomic_Always_Lock_Free} attribute is a type.
9994 The result is a Boolean value which is True if the type has discriminants,
9995 and False otherwise. The result indicate whether atomic operations are
9996 supported by the target for the given type.
9998 @node Attribute Bit,Attribute Bit_Position,Attribute Atomic_Always_Lock_Free,Implementation Defined Attributes
9999 @anchor{gnat_rm/implementation_defined_attributes attribute-bit}@anchor{167}
10000 @section Attribute Bit
10005 @code{obj'Bit}, where @code{obj} is any object, yields the bit
10006 offset within the storage unit (byte) that contains the first bit of
10007 storage allocated for the object. The value of this attribute is of the
10008 type @emph{universal_integer}, and is always a non-negative number not
10009 exceeding the value of @code{System.Storage_Unit}.
10011 For an object that is a variable or a constant allocated in a register,
10012 the value is zero. (The use of this attribute does not force the
10013 allocation of a variable to memory).
10015 For an object that is a formal parameter, this attribute applies
10016 to either the matching actual parameter or to a copy of the
10017 matching actual parameter.
10019 For an access object the value is zero. Note that
10020 @code{obj.all'Bit} is subject to an @code{Access_Check} for the
10021 designated object. Similarly for a record component
10022 @code{X.C'Bit} is subject to a discriminant check and
10023 @code{X(I).Bit} and @code{X(I1..I2)'Bit}
10024 are subject to index checks.
10026 This attribute is designed to be compatible with the DEC Ada 83 definition
10027 and implementation of the @code{Bit} attribute.
10029 @node Attribute Bit_Position,Attribute Code_Address,Attribute Bit,Implementation Defined Attributes
10030 @anchor{gnat_rm/implementation_defined_attributes attribute-bit-position}@anchor{168}
10031 @section Attribute Bit_Position
10034 @geindex Bit_Position
10036 @code{R.C'Bit_Position}, where @code{R} is a record object and @code{C} is one
10037 of the fields of the record type, yields the bit
10038 offset within the record contains the first bit of
10039 storage allocated for the object. The value of this attribute is of the
10040 type @emph{universal_integer}. The value depends only on the field
10041 @code{C} and is independent of the alignment of
10042 the containing record @code{R}.
10044 @node Attribute Code_Address,Attribute Compiler_Version,Attribute Bit_Position,Implementation Defined Attributes
10045 @anchor{gnat_rm/implementation_defined_attributes attribute-code-address}@anchor{169}
10046 @section Attribute Code_Address
10049 @geindex Code_Address
10051 @geindex Subprogram address
10053 @geindex Address of subprogram code
10055 The @code{'Address}
10056 attribute may be applied to subprograms in Ada 95 and Ada 2005, but the
10057 intended effect seems to be to provide
10058 an address value which can be used to call the subprogram by means of
10059 an address clause as in the following example:
10065 for L'Address use K'Address;
10066 pragma Import (Ada, L);
10069 A call to @code{L} is then expected to result in a call to @code{K}.
10070 In Ada 83, where there were no access-to-subprogram values, this was
10071 a common work-around for getting the effect of an indirect call.
10072 GNAT implements the above use of @code{Address} and the technique
10073 illustrated by the example code works correctly.
10075 However, for some purposes, it is useful to have the address of the start
10076 of the generated code for the subprogram. On some architectures, this is
10077 not necessarily the same as the @code{Address} value described above.
10078 For example, the @code{Address} value may reference a subprogram
10079 descriptor rather than the subprogram itself.
10081 The @code{'Code_Address} attribute, which can only be applied to
10082 subprogram entities, always returns the address of the start of the
10083 generated code of the specified subprogram, which may or may not be
10084 the same value as is returned by the corresponding @code{'Address}
10087 @node Attribute Compiler_Version,Attribute Constrained,Attribute Code_Address,Implementation Defined Attributes
10088 @anchor{gnat_rm/implementation_defined_attributes attribute-compiler-version}@anchor{16a}
10089 @section Attribute Compiler_Version
10092 @geindex Compiler_Version
10094 @code{Standard'Compiler_Version} (@code{Standard} is the only allowed
10095 prefix) yields a static string identifying the version of the compiler
10096 being used to compile the unit containing the attribute reference.
10098 @node Attribute Constrained,Attribute Default_Bit_Order,Attribute Compiler_Version,Implementation Defined Attributes
10099 @anchor{gnat_rm/implementation_defined_attributes attribute-constrained}@anchor{16b}
10100 @section Attribute Constrained
10103 @geindex Constrained
10105 In addition to the usage of this attribute in the Ada RM, GNAT
10106 also permits the use of the @code{'Constrained} attribute
10107 in a generic template
10108 for any type, including types without discriminants. The value of this
10109 attribute in the generic instance when applied to a scalar type or a
10110 record type without discriminants is always @code{True}. This usage is
10111 compatible with older Ada compilers, including notably DEC Ada.
10113 @node Attribute Default_Bit_Order,Attribute Default_Scalar_Storage_Order,Attribute Constrained,Implementation Defined Attributes
10114 @anchor{gnat_rm/implementation_defined_attributes attribute-default-bit-order}@anchor{16c}
10115 @section Attribute Default_Bit_Order
10118 @geindex Big endian
10120 @geindex Little endian
10122 @geindex Default_Bit_Order
10124 @code{Standard'Default_Bit_Order} (@code{Standard} is the only
10125 permissible prefix), provides the value @code{System.Default_Bit_Order}
10126 as a @code{Pos} value (0 for @code{High_Order_First}, 1 for
10127 @code{Low_Order_First}). This is used to construct the definition of
10128 @code{Default_Bit_Order} in package @code{System}.
10130 @node Attribute Default_Scalar_Storage_Order,Attribute Deref,Attribute Default_Bit_Order,Implementation Defined Attributes
10131 @anchor{gnat_rm/implementation_defined_attributes attribute-default-scalar-storage-order}@anchor{16d}
10132 @section Attribute Default_Scalar_Storage_Order
10135 @geindex Big endian
10137 @geindex Little endian
10139 @geindex Default_Scalar_Storage_Order
10141 @code{Standard'Default_Scalar_Storage_Order} (@code{Standard} is the only
10142 permissible prefix), provides the current value of the default scalar storage
10143 order (as specified using pragma @code{Default_Scalar_Storage_Order}, or
10144 equal to @code{Default_Bit_Order} if unspecified) as a
10145 @code{System.Bit_Order} value. This is a static attribute.
10147 @node Attribute Deref,Attribute Descriptor_Size,Attribute Default_Scalar_Storage_Order,Implementation Defined Attributes
10148 @anchor{gnat_rm/implementation_defined_attributes attribute-deref}@anchor{16e}
10149 @section Attribute Deref
10154 The attribute @code{typ'Deref(expr)} where @code{expr} is of type @code{System.Address} yields
10155 the variable of type @code{typ} that is located at the given address. It is similar
10156 to @code{(totyp (expr).all)}, where @code{totyp} is an unchecked conversion from address to
10157 a named access-to-@cite{typ} type, except that it yields a variable, so it can be
10158 used on the left side of an assignment.
10160 @node Attribute Descriptor_Size,Attribute Elaborated,Attribute Deref,Implementation Defined Attributes
10161 @anchor{gnat_rm/implementation_defined_attributes attribute-descriptor-size}@anchor{16f}
10162 @section Attribute Descriptor_Size
10165 @geindex Descriptor
10167 @geindex Dope vector
10169 @geindex Descriptor_Size
10171 Nonstatic attribute @code{Descriptor_Size} returns the size in bits of the
10172 descriptor allocated for a type. The result is non-zero only for unconstrained
10173 array types and the returned value is of type universal integer. In GNAT, an
10174 array descriptor contains bounds information and is located immediately before
10175 the first element of the array.
10178 type Unconstr_Array is array (Positive range <>) of Boolean;
10179 Put_Line ("Descriptor size = " & Unconstr_Array'Descriptor_Size'Img);
10182 The attribute takes into account any additional padding due to type alignment.
10183 In the example above, the descriptor contains two values of type
10184 @code{Positive} representing the low and high bound. Since @code{Positive} has
10185 a size of 31 bits and an alignment of 4, the descriptor size is @code{2 * Positive'Size + 2} or 64 bits.
10187 @node Attribute Elaborated,Attribute Elab_Body,Attribute Descriptor_Size,Implementation Defined Attributes
10188 @anchor{gnat_rm/implementation_defined_attributes attribute-elaborated}@anchor{170}
10189 @section Attribute Elaborated
10192 @geindex Elaborated
10194 The prefix of the @code{'Elaborated} attribute must be a unit name. The
10195 value is a Boolean which indicates whether or not the given unit has been
10196 elaborated. This attribute is primarily intended for internal use by the
10197 generated code for dynamic elaboration checking, but it can also be used
10198 in user programs. The value will always be True once elaboration of all
10199 units has been completed. An exception is for units which need no
10200 elaboration, the value is always False for such units.
10202 @node Attribute Elab_Body,Attribute Elab_Spec,Attribute Elaborated,Implementation Defined Attributes
10203 @anchor{gnat_rm/implementation_defined_attributes attribute-elab-body}@anchor{171}
10204 @section Attribute Elab_Body
10209 This attribute can only be applied to a program unit name. It returns
10210 the entity for the corresponding elaboration procedure for elaborating
10211 the body of the referenced unit. This is used in the main generated
10212 elaboration procedure by the binder and is not normally used in any
10213 other context. However, there may be specialized situations in which it
10214 is useful to be able to call this elaboration procedure from Ada code,
10215 e.g., if it is necessary to do selective re-elaboration to fix some
10218 @node Attribute Elab_Spec,Attribute Elab_Subp_Body,Attribute Elab_Body,Implementation Defined Attributes
10219 @anchor{gnat_rm/implementation_defined_attributes attribute-elab-spec}@anchor{172}
10220 @section Attribute Elab_Spec
10225 This attribute can only be applied to a program unit name. It returns
10226 the entity for the corresponding elaboration procedure for elaborating
10227 the spec of the referenced unit. This is used in the main
10228 generated elaboration procedure by the binder and is not normally used
10229 in any other context. However, there may be specialized situations in
10230 which it is useful to be able to call this elaboration procedure from
10231 Ada code, e.g., if it is necessary to do selective re-elaboration to fix
10234 @node Attribute Elab_Subp_Body,Attribute Emax,Attribute Elab_Spec,Implementation Defined Attributes
10235 @anchor{gnat_rm/implementation_defined_attributes attribute-elab-subp-body}@anchor{173}
10236 @section Attribute Elab_Subp_Body
10239 @geindex Elab_Subp_Body
10241 This attribute can only be applied to a library level subprogram
10242 name and is only allowed in CodePeer mode. It returns the entity
10243 for the corresponding elaboration procedure for elaborating the body
10244 of the referenced subprogram unit. This is used in the main generated
10245 elaboration procedure by the binder in CodePeer mode only and is unrecognized
10248 @node Attribute Emax,Attribute Enabled,Attribute Elab_Subp_Body,Implementation Defined Attributes
10249 @anchor{gnat_rm/implementation_defined_attributes attribute-emax}@anchor{174}
10250 @section Attribute Emax
10253 @geindex Ada 83 attributes
10257 The @code{Emax} attribute is provided for compatibility with Ada 83. See
10258 the Ada 83 reference manual for an exact description of the semantics of
10261 @node Attribute Enabled,Attribute Enum_Rep,Attribute Emax,Implementation Defined Attributes
10262 @anchor{gnat_rm/implementation_defined_attributes attribute-enabled}@anchor{175}
10263 @section Attribute Enabled
10268 The @code{Enabled} attribute allows an application program to check at compile
10269 time to see if the designated check is currently enabled. The prefix is a
10270 simple identifier, referencing any predefined check name (other than
10271 @code{All_Checks}) or a check name introduced by pragma Check_Name. If
10272 no argument is given for the attribute, the check is for the general state
10273 of the check, if an argument is given, then it is an entity name, and the
10274 check indicates whether an @code{Suppress} or @code{Unsuppress} has been
10275 given naming the entity (if not, then the argument is ignored).
10277 Note that instantiations inherit the check status at the point of the
10278 instantiation, so a useful idiom is to have a library package that
10279 introduces a check name with @code{pragma Check_Name}, and then contains
10280 generic packages or subprograms which use the @code{Enabled} attribute
10281 to see if the check is enabled. A user of this package can then issue
10282 a @code{pragma Suppress} or @code{pragma Unsuppress} before instantiating
10283 the package or subprogram, controlling whether the check will be present.
10285 @node Attribute Enum_Rep,Attribute Enum_Val,Attribute Enabled,Implementation Defined Attributes
10286 @anchor{gnat_rm/implementation_defined_attributes attribute-enum-rep}@anchor{176}
10287 @section Attribute Enum_Rep
10290 @geindex Representation of enums
10294 For every enumeration subtype @code{S}, @code{S'Enum_Rep} denotes a
10295 function with the following spec:
10298 function S'Enum_Rep (Arg : S'Base) return <Universal_Integer>;
10301 It is also allowable to apply @code{Enum_Rep} directly to an object of an
10302 enumeration type or to a non-overloaded enumeration
10303 literal. In this case @code{S'Enum_Rep} is equivalent to
10304 @code{typ'Enum_Rep(S)} where @code{typ} is the type of the
10305 enumeration literal or object.
10307 The function returns the representation value for the given enumeration
10308 value. This will be equal to value of the @code{Pos} attribute in the
10309 absence of an enumeration representation clause. This is a static
10310 attribute (i.e.,:the result is static if the argument is static).
10312 @code{S'Enum_Rep} can also be used with integer types and objects,
10313 in which case it simply returns the integer value. The reason for this
10314 is to allow it to be used for @code{(<>)} discrete formal arguments in
10315 a generic unit that can be instantiated with either enumeration types
10316 or integer types. Note that if @code{Enum_Rep} is used on a modular
10317 type whose upper bound exceeds the upper bound of the largest signed
10318 integer type, and the argument is a variable, so that the universal
10319 integer calculation is done at run time, then the call to @code{Enum_Rep}
10320 may raise @code{Constraint_Error}.
10322 @node Attribute Enum_Val,Attribute Epsilon,Attribute Enum_Rep,Implementation Defined Attributes
10323 @anchor{gnat_rm/implementation_defined_attributes attribute-enum-val}@anchor{177}
10324 @section Attribute Enum_Val
10327 @geindex Representation of enums
10331 For every enumeration subtype @code{S}, @code{S'Enum_Val} denotes a
10332 function with the following spec:
10335 function S'Enum_Val (Arg : <Universal_Integer>) return S'Base;
10338 The function returns the enumeration value whose representation matches the
10339 argument, or raises Constraint_Error if no enumeration literal of the type
10340 has the matching value.
10341 This will be equal to value of the @code{Val} attribute in the
10342 absence of an enumeration representation clause. This is a static
10343 attribute (i.e., the result is static if the argument is static).
10345 @node Attribute Epsilon,Attribute Fast_Math,Attribute Enum_Val,Implementation Defined Attributes
10346 @anchor{gnat_rm/implementation_defined_attributes attribute-epsilon}@anchor{178}
10347 @section Attribute Epsilon
10350 @geindex Ada 83 attributes
10354 The @code{Epsilon} attribute is provided for compatibility with Ada 83. See
10355 the Ada 83 reference manual for an exact description of the semantics of
10358 @node Attribute Fast_Math,Attribute Finalization_Size,Attribute Epsilon,Implementation Defined Attributes
10359 @anchor{gnat_rm/implementation_defined_attributes attribute-fast-math}@anchor{179}
10360 @section Attribute Fast_Math
10365 @code{Standard'Fast_Math} (@code{Standard} is the only allowed
10366 prefix) yields a static Boolean value that is True if pragma
10367 @code{Fast_Math} is active, and False otherwise.
10369 @node Attribute Finalization_Size,Attribute Fixed_Value,Attribute Fast_Math,Implementation Defined Attributes
10370 @anchor{gnat_rm/implementation_defined_attributes attribute-finalization-size}@anchor{17a}
10371 @section Attribute Finalization_Size
10374 @geindex Finalization_Size
10376 The prefix of attribute @code{Finalization_Size} must be an object or
10377 a non-class-wide type. This attribute returns the size of any hidden data
10378 reserved by the compiler to handle finalization-related actions. The type of
10379 the attribute is @emph{universal_integer}.
10381 @code{Finalization_Size} yields a value of zero for a type with no controlled
10382 parts, an object whose type has no controlled parts, or an object of a
10383 class-wide type whose tag denotes a type with no controlled parts.
10385 Note that only heap-allocated objects contain finalization data.
10387 @node Attribute Fixed_Value,Attribute From_Any,Attribute Finalization_Size,Implementation Defined Attributes
10388 @anchor{gnat_rm/implementation_defined_attributes attribute-fixed-value}@anchor{17b}
10389 @section Attribute Fixed_Value
10392 @geindex Fixed_Value
10394 For every fixed-point type @code{S}, @code{S'Fixed_Value} denotes a
10395 function with the following specification:
10398 function S'Fixed_Value (Arg : <Universal_Integer>) return S;
10401 The value returned is the fixed-point value @code{V} such that:
10407 The effect is thus similar to first converting the argument to the
10408 integer type used to represent @code{S}, and then doing an unchecked
10409 conversion to the fixed-point type. The difference is
10410 that there are full range checks, to ensure that the result is in range.
10411 This attribute is primarily intended for use in implementation of the
10412 input-output functions for fixed-point values.
10414 @node Attribute From_Any,Attribute Has_Access_Values,Attribute Fixed_Value,Implementation Defined Attributes
10415 @anchor{gnat_rm/implementation_defined_attributes attribute-from-any}@anchor{17c}
10416 @section Attribute From_Any
10421 This internal attribute is used for the generation of remote subprogram
10422 stubs in the context of the Distributed Systems Annex.
10424 @node Attribute Has_Access_Values,Attribute Has_Discriminants,Attribute From_Any,Implementation Defined Attributes
10425 @anchor{gnat_rm/implementation_defined_attributes attribute-has-access-values}@anchor{17d}
10426 @section Attribute Has_Access_Values
10429 @geindex Access values
10430 @geindex testing for
10432 @geindex Has_Access_Values
10434 The prefix of the @code{Has_Access_Values} attribute is a type. The result
10435 is a Boolean value which is True if the is an access type, or is a composite
10436 type with a component (at any nesting depth) that is an access type, and is
10438 The intended use of this attribute is in conjunction with generic
10439 definitions. If the attribute is applied to a generic private type, it
10440 indicates whether or not the corresponding actual type has access values.
10442 @node Attribute Has_Discriminants,Attribute Img,Attribute Has_Access_Values,Implementation Defined Attributes
10443 @anchor{gnat_rm/implementation_defined_attributes attribute-has-discriminants}@anchor{17e}
10444 @section Attribute Has_Discriminants
10447 @geindex Discriminants
10448 @geindex testing for
10450 @geindex Has_Discriminants
10452 The prefix of the @code{Has_Discriminants} attribute is a type. The result
10453 is a Boolean value which is True if the type has discriminants, and False
10454 otherwise. The intended use of this attribute is in conjunction with generic
10455 definitions. If the attribute is applied to a generic private type, it
10456 indicates whether or not the corresponding actual type has discriminants.
10458 @node Attribute Img,Attribute Integer_Value,Attribute Has_Discriminants,Implementation Defined Attributes
10459 @anchor{gnat_rm/implementation_defined_attributes attribute-img}@anchor{17f}
10460 @section Attribute Img
10465 The @code{Img} attribute differs from @code{Image} in that it is applied
10466 directly to an object, and yields the same result as
10467 @code{Image} for the subtype of the object. This is convenient for
10471 Put_Line ("X = " & X'Img);
10474 has the same meaning as the more verbose:
10477 Put_Line ("X = " & T'Image (X));
10480 where @code{T} is the (sub)type of the object @code{X}.
10482 Note that technically, in analogy to @code{Image},
10483 @code{X'Img} returns a parameterless function
10484 that returns the appropriate string when called. This means that
10485 @code{X'Img} can be renamed as a function-returning-string, or used
10486 in an instantiation as a function parameter.
10488 @node Attribute Integer_Value,Attribute Invalid_Value,Attribute Img,Implementation Defined Attributes
10489 @anchor{gnat_rm/implementation_defined_attributes attribute-integer-value}@anchor{180}
10490 @section Attribute Integer_Value
10493 @geindex Integer_Value
10495 For every integer type @code{S}, @code{S'Integer_Value} denotes a
10496 function with the following spec:
10499 function S'Integer_Value (Arg : <Universal_Fixed>) return S;
10502 The value returned is the integer value @code{V}, such that:
10508 where @code{T} is the type of @code{Arg}.
10509 The effect is thus similar to first doing an unchecked conversion from
10510 the fixed-point type to its corresponding implementation type, and then
10511 converting the result to the target integer type. The difference is
10512 that there are full range checks, to ensure that the result is in range.
10513 This attribute is primarily intended for use in implementation of the
10514 standard input-output functions for fixed-point values.
10516 @node Attribute Invalid_Value,Attribute Iterable,Attribute Integer_Value,Implementation Defined Attributes
10517 @anchor{gnat_rm/implementation_defined_attributes attribute-invalid-value}@anchor{181}
10518 @section Attribute Invalid_Value
10521 @geindex Invalid_Value
10523 For every scalar type S, S'Invalid_Value returns an undefined value of the
10524 type. If possible this value is an invalid representation for the type. The
10525 value returned is identical to the value used to initialize an otherwise
10526 uninitialized value of the type if pragma Initialize_Scalars is used,
10527 including the ability to modify the value with the binder -Sxx flag and
10528 relevant environment variables at run time.
10530 @node Attribute Iterable,Attribute Large,Attribute Invalid_Value,Implementation Defined Attributes
10531 @anchor{gnat_rm/implementation_defined_attributes attribute-iterable}@anchor{182}
10532 @section Attribute Iterable
10537 Equivalent to Aspect Iterable.
10539 @node Attribute Large,Attribute Library_Level,Attribute Iterable,Implementation Defined Attributes
10540 @anchor{gnat_rm/implementation_defined_attributes attribute-large}@anchor{183}
10541 @section Attribute Large
10544 @geindex Ada 83 attributes
10548 The @code{Large} attribute is provided for compatibility with Ada 83. See
10549 the Ada 83 reference manual for an exact description of the semantics of
10552 @node Attribute Library_Level,Attribute Lock_Free,Attribute Large,Implementation Defined Attributes
10553 @anchor{gnat_rm/implementation_defined_attributes attribute-library-level}@anchor{184}
10554 @section Attribute Library_Level
10557 @geindex Library_Level
10559 @code{P'Library_Level}, where P is an entity name,
10560 returns a Boolean value which is True if the entity is declared
10561 at the library level, and False otherwise. Note that within a
10562 generic instantition, the name of the generic unit denotes the
10563 instance, which means that this attribute can be used to test
10564 if a generic is instantiated at the library level, as shown
10571 pragma Compile_Time_Error
10572 (not Gen'Library_Level,
10573 "Gen can only be instantiated at library level");
10578 @node Attribute Lock_Free,Attribute Loop_Entry,Attribute Library_Level,Implementation Defined Attributes
10579 @anchor{gnat_rm/implementation_defined_attributes attribute-lock-free}@anchor{185}
10580 @section Attribute Lock_Free
10585 @code{P'Lock_Free}, where P is a protected object, returns True if a
10586 pragma @code{Lock_Free} applies to P.
10588 @node Attribute Loop_Entry,Attribute Machine_Size,Attribute Lock_Free,Implementation Defined Attributes
10589 @anchor{gnat_rm/implementation_defined_attributes attribute-loop-entry}@anchor{186}
10590 @section Attribute Loop_Entry
10593 @geindex Loop_Entry
10598 X'Loop_Entry [(loop_name)]
10601 The @code{Loop_Entry} attribute is used to refer to the value that an
10602 expression had upon entry to a given loop in much the same way that the
10603 @code{Old} attribute in a subprogram postcondition can be used to refer
10604 to the value an expression had upon entry to the subprogram. The
10605 relevant loop is either identified by the given loop name, or it is the
10606 innermost enclosing loop when no loop name is given.
10608 A @code{Loop_Entry} attribute can only occur within a
10609 @code{Loop_Variant} or @code{Loop_Invariant} pragma. A common use of
10610 @code{Loop_Entry} is to compare the current value of objects with their
10611 initial value at loop entry, in a @code{Loop_Invariant} pragma.
10613 The effect of using @code{X'Loop_Entry} is the same as declaring
10614 a constant initialized with the initial value of @code{X} at loop
10615 entry. This copy is not performed if the loop is not entered, or if the
10616 corresponding pragmas are ignored or disabled.
10618 @node Attribute Machine_Size,Attribute Mantissa,Attribute Loop_Entry,Implementation Defined Attributes
10619 @anchor{gnat_rm/implementation_defined_attributes attribute-machine-size}@anchor{187}
10620 @section Attribute Machine_Size
10623 @geindex Machine_Size
10625 This attribute is identical to the @code{Object_Size} attribute. It is
10626 provided for compatibility with the DEC Ada 83 attribute of this name.
10628 @node Attribute Mantissa,Attribute Maximum_Alignment,Attribute Machine_Size,Implementation Defined Attributes
10629 @anchor{gnat_rm/implementation_defined_attributes attribute-mantissa}@anchor{188}
10630 @section Attribute Mantissa
10633 @geindex Ada 83 attributes
10637 The @code{Mantissa} attribute is provided for compatibility with Ada 83. See
10638 the Ada 83 reference manual for an exact description of the semantics of
10641 @node Attribute Maximum_Alignment,Attribute Mechanism_Code,Attribute Mantissa,Implementation Defined Attributes
10642 @anchor{gnat_rm/implementation_defined_attributes attribute-maximum-alignment}@anchor{189}@anchor{gnat_rm/implementation_defined_attributes id2}@anchor{18a}
10643 @section Attribute Maximum_Alignment
10649 @geindex Maximum_Alignment
10651 @code{Standard'Maximum_Alignment} (@code{Standard} is the only
10652 permissible prefix) provides the maximum useful alignment value for the
10653 target. This is a static value that can be used to specify the alignment
10654 for an object, guaranteeing that it is properly aligned in all
10657 @node Attribute Mechanism_Code,Attribute Null_Parameter,Attribute Maximum_Alignment,Implementation Defined Attributes
10658 @anchor{gnat_rm/implementation_defined_attributes attribute-mechanism-code}@anchor{18b}
10659 @section Attribute Mechanism_Code
10662 @geindex Return values
10663 @geindex passing mechanism
10665 @geindex Parameters
10666 @geindex passing mechanism
10668 @geindex Mechanism_Code
10670 @code{func'Mechanism_Code} yields an integer code for the
10671 mechanism used for the result of function @code{func}, and
10672 @code{subprog'Mechanism_Code (n)} yields the mechanism
10673 used for formal parameter number @emph{n} (a static integer value, with 1
10674 meaning the first parameter) of subprogram @code{subprog}. The code returned is:
10688 @node Attribute Null_Parameter,Attribute Object_Size,Attribute Mechanism_Code,Implementation Defined Attributes
10689 @anchor{gnat_rm/implementation_defined_attributes attribute-null-parameter}@anchor{18c}
10690 @section Attribute Null_Parameter
10693 @geindex Zero address
10696 @geindex Null_Parameter
10698 A reference @code{T'Null_Parameter} denotes an imaginary object of
10699 type or subtype @code{T} allocated at machine address zero. The attribute
10700 is allowed only as the default expression of a formal parameter, or as
10701 an actual expression of a subprogram call. In either case, the
10702 subprogram must be imported.
10704 The identity of the object is represented by the address zero in the
10705 argument list, independent of the passing mechanism (explicit or
10708 This capability is needed to specify that a zero address should be
10709 passed for a record or other composite object passed by reference.
10710 There is no way of indicating this without the @code{Null_Parameter}
10713 @node Attribute Object_Size,Attribute Old,Attribute Null_Parameter,Implementation Defined Attributes
10714 @anchor{gnat_rm/implementation_defined_attributes attribute-object-size}@anchor{13f}@anchor{gnat_rm/implementation_defined_attributes id3}@anchor{18d}
10715 @section Attribute Object_Size
10719 @geindex used for objects
10721 @geindex Object_Size
10723 The size of an object is not necessarily the same as the size of the type
10724 of an object. This is because by default object sizes are increased to be
10725 a multiple of the alignment of the object. For example,
10726 @code{Natural'Size} is
10727 31, but by default objects of type @code{Natural} will have a size of 32 bits.
10728 Similarly, a record containing an integer and a character:
10737 will have a size of 40 (that is @code{Rec'Size} will be 40). The
10738 alignment will be 4, because of the
10739 integer field, and so the default size of record objects for this type
10740 will be 64 (8 bytes).
10742 If the alignment of the above record is specified to be 1, then the
10743 object size will be 40 (5 bytes). This is true by default, and also
10744 an object size of 40 can be explicitly specified in this case.
10746 A consequence of this capability is that different object sizes can be
10747 given to subtypes that would otherwise be considered in Ada to be
10748 statically matching. But it makes no sense to consider such subtypes
10749 as statically matching. Consequently, GNAT adds a rule
10750 to the static matching rules that requires object sizes to match.
10751 Consider this example:
10754 1. procedure BadAVConvert is
10755 2. type R is new Integer;
10756 3. subtype R1 is R range 1 .. 10;
10757 4. subtype R2 is R range 1 .. 10;
10758 5. for R1'Object_Size use 8;
10759 6. for R2'Object_Size use 16;
10760 7. type R1P is access all R1;
10761 8. type R2P is access all R2;
10762 9. R1PV : R1P := new R1'(4);
10765 12. R2PV := R2P (R1PV);
10767 >>> target designated subtype not compatible with
10768 type "R1" defined at line 3
10773 In the absence of lines 5 and 6,
10774 types @code{R1} and @code{R2} statically match and
10775 hence the conversion on line 12 is legal. But since lines 5 and 6
10776 cause the object sizes to differ, GNAT considers that types
10777 @code{R1} and @code{R2} are not statically matching, and line 12
10778 generates the diagnostic shown above.
10780 Similar additional checks are performed in other contexts requiring
10781 statically matching subtypes.
10783 @node Attribute Old,Attribute Passed_By_Reference,Attribute Object_Size,Implementation Defined Attributes
10784 @anchor{gnat_rm/implementation_defined_attributes attribute-old}@anchor{18e}
10785 @section Attribute Old
10790 In addition to the usage of @code{Old} defined in the Ada 2012 RM (usage
10791 within @code{Post} aspect), GNAT also permits the use of this attribute
10792 in implementation defined pragmas @code{Postcondition},
10793 @code{Contract_Cases} and @code{Test_Case}. Also usages of
10794 @code{Old} which would be illegal according to the Ada 2012 RM
10795 definition are allowed under control of
10796 implementation defined pragma @code{Unevaluated_Use_Of_Old}.
10798 @node Attribute Passed_By_Reference,Attribute Pool_Address,Attribute Old,Implementation Defined Attributes
10799 @anchor{gnat_rm/implementation_defined_attributes attribute-passed-by-reference}@anchor{18f}
10800 @section Attribute Passed_By_Reference
10803 @geindex Parameters
10804 @geindex when passed by reference
10806 @geindex Passed_By_Reference
10808 @code{typ'Passed_By_Reference} for any subtype @cite{typ} returns
10809 a value of type @code{Boolean} value that is @code{True} if the type is
10810 normally passed by reference and @code{False} if the type is normally
10811 passed by copy in calls. For scalar types, the result is always @code{False}
10812 and is static. For non-scalar types, the result is nonstatic.
10814 @node Attribute Pool_Address,Attribute Range_Length,Attribute Passed_By_Reference,Implementation Defined Attributes
10815 @anchor{gnat_rm/implementation_defined_attributes attribute-pool-address}@anchor{190}
10816 @section Attribute Pool_Address
10819 @geindex Parameters
10820 @geindex when passed by reference
10822 @geindex Pool_Address
10824 @code{X'Pool_Address} for any object @code{X} returns the address
10825 of X within its storage pool. This is the same as
10826 @code{X'Address}, except that for an unconstrained array whose
10827 bounds are allocated just before the first component,
10828 @code{X'Pool_Address} returns the address of those bounds,
10829 whereas @code{X'Address} returns the address of the first
10832 Here, we are interpreting 'storage pool' broadly to mean
10833 @code{wherever the object is allocated}, which could be a
10834 user-defined storage pool,
10835 the global heap, on the stack, or in a static memory area.
10836 For an object created by @code{new}, @code{Ptr.all'Pool_Address} is
10837 what is passed to @code{Allocate} and returned from @code{Deallocate}.
10839 @node Attribute Range_Length,Attribute Restriction_Set,Attribute Pool_Address,Implementation Defined Attributes
10840 @anchor{gnat_rm/implementation_defined_attributes attribute-range-length}@anchor{191}
10841 @section Attribute Range_Length
10844 @geindex Range_Length
10846 @code{typ'Range_Length} for any discrete type @cite{typ} yields
10847 the number of values represented by the subtype (zero for a null
10848 range). The result is static for static subtypes. @code{Range_Length}
10849 applied to the index subtype of a one dimensional array always gives the
10850 same result as @code{Length} applied to the array itself.
10852 @node Attribute Restriction_Set,Attribute Result,Attribute Range_Length,Implementation Defined Attributes
10853 @anchor{gnat_rm/implementation_defined_attributes attribute-restriction-set}@anchor{192}
10854 @section Attribute Restriction_Set
10857 @geindex Restriction_Set
10859 @geindex Restrictions
10861 This attribute allows compile time testing of restrictions that
10862 are currently in effect. It is primarily intended for specializing
10863 code in the run-time based on restrictions that are active (e.g.
10864 don't need to save fpt registers if restriction No_Floating_Point
10865 is known to be in effect), but can be used anywhere.
10867 There are two forms:
10870 System'Restriction_Set (partition_boolean_restriction_NAME)
10871 System'Restriction_Set (No_Dependence => library_unit_NAME);
10874 In the case of the first form, the only restriction names
10875 allowed are parameterless restrictions that are checked
10876 for consistency at bind time. For a complete list see the
10877 subtype @code{System.Rident.Partition_Boolean_Restrictions}.
10879 The result returned is True if the restriction is known to
10880 be in effect, and False if the restriction is known not to
10881 be in effect. An important guarantee is that the value of
10882 a Restriction_Set attribute is known to be consistent throughout
10883 all the code of a partition.
10885 This is trivially achieved if the entire partition is compiled
10886 with a consistent set of restriction pragmas. However, the
10887 compilation model does not require this. It is possible to
10888 compile one set of units with one set of pragmas, and another
10889 set of units with another set of pragmas. It is even possible
10890 to compile a spec with one set of pragmas, and then WITH the
10891 same spec with a different set of pragmas. Inconsistencies
10892 in the actual use of the restriction are checked at bind time.
10894 In order to achieve the guarantee of consistency for the
10895 Restriction_Set pragma, we consider that a use of the pragma
10896 that yields False is equivalent to a violation of the
10899 So for example if you write
10902 if System'Restriction_Set (No_Floating_Point) then
10909 And the result is False, so that the else branch is executed,
10910 you can assume that this restriction is not set for any unit
10911 in the partition. This is checked by considering this use of
10912 the restriction pragma to be a violation of the restriction
10913 No_Floating_Point. This means that no other unit can attempt
10914 to set this restriction (if some unit does attempt to set it,
10915 the binder will refuse to bind the partition).
10917 Technical note: The restriction name and the unit name are
10918 intepreted entirely syntactically, as in the corresponding
10919 Restrictions pragma, they are not analyzed semantically,
10920 so they do not have a type.
10922 @node Attribute Result,Attribute Safe_Emax,Attribute Restriction_Set,Implementation Defined Attributes
10923 @anchor{gnat_rm/implementation_defined_attributes attribute-result}@anchor{193}
10924 @section Attribute Result
10929 @code{function'Result} can only be used with in a Postcondition pragma
10930 for a function. The prefix must be the name of the corresponding function. This
10931 is used to refer to the result of the function in the postcondition expression.
10932 For a further discussion of the use of this attribute and examples of its use,
10933 see the description of pragma Postcondition.
10935 @node Attribute Safe_Emax,Attribute Safe_Large,Attribute Result,Implementation Defined Attributes
10936 @anchor{gnat_rm/implementation_defined_attributes attribute-safe-emax}@anchor{194}
10937 @section Attribute Safe_Emax
10940 @geindex Ada 83 attributes
10944 The @code{Safe_Emax} attribute is provided for compatibility with Ada 83. See
10945 the Ada 83 reference manual for an exact description of the semantics of
10948 @node Attribute Safe_Large,Attribute Safe_Small,Attribute Safe_Emax,Implementation Defined Attributes
10949 @anchor{gnat_rm/implementation_defined_attributes attribute-safe-large}@anchor{195}
10950 @section Attribute Safe_Large
10953 @geindex Ada 83 attributes
10955 @geindex Safe_Large
10957 The @code{Safe_Large} 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_Small,Attribute Scalar_Storage_Order,Attribute Safe_Large,Implementation Defined Attributes
10962 @anchor{gnat_rm/implementation_defined_attributes attribute-safe-small}@anchor{196}
10963 @section Attribute Safe_Small
10966 @geindex Ada 83 attributes
10968 @geindex Safe_Small
10970 The @code{Safe_Small} 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 Scalar_Storage_Order,Attribute Simple_Storage_Pool,Attribute Safe_Small,Implementation Defined Attributes
10975 @anchor{gnat_rm/implementation_defined_attributes id4}@anchor{197}@anchor{gnat_rm/implementation_defined_attributes attribute-scalar-storage-order}@anchor{14c}
10976 @section Attribute Scalar_Storage_Order
10979 @geindex Endianness
10981 @geindex Scalar storage order
10983 @geindex Scalar_Storage_Order
10985 For every array or record type @code{S}, the representation attribute
10986 @code{Scalar_Storage_Order} denotes the order in which storage elements
10987 that make up scalar components are ordered within S. The value given must
10988 be a static expression of type System.Bit_Order. The following is an example
10989 of the use of this feature:
10992 -- Component type definitions
10994 subtype Yr_Type is Natural range 0 .. 127;
10995 subtype Mo_Type is Natural range 1 .. 12;
10996 subtype Da_Type is Natural range 1 .. 31;
10998 -- Record declaration
11000 type Date is record
11001 Years_Since_1980 : Yr_Type;
11003 Day_Of_Month : Da_Type;
11006 -- Record representation clause
11008 for Date use record
11009 Years_Since_1980 at 0 range 0 .. 6;
11010 Month at 0 range 7 .. 10;
11011 Day_Of_Month at 0 range 11 .. 15;
11014 -- Attribute definition clauses
11016 for Date'Bit_Order use System.High_Order_First;
11017 for Date'Scalar_Storage_Order use System.High_Order_First;
11018 -- If Scalar_Storage_Order is specified, it must be consistent with
11019 -- Bit_Order, so it's best to always define the latter explicitly if
11020 -- the former is used.
11023 Other properties are as for standard representation attribute @code{Bit_Order},
11024 as defined by Ada RM 13.5.3(4). The default is @code{System.Default_Bit_Order}.
11026 For a record type @code{T}, if @code{T'Scalar_Storage_Order} is
11027 specified explicitly, it shall be equal to @code{T'Bit_Order}. Note:
11028 this means that if a @code{Scalar_Storage_Order} attribute definition
11029 clause is not confirming, then the type's @code{Bit_Order} shall be
11030 specified explicitly and set to the same value.
11032 Derived types inherit an explicitly set scalar storage order from their parent
11033 types. This may be overridden for the derived type by giving an explicit scalar
11034 storage order for the derived type. For a record extension, the derived type
11035 must have the same scalar storage order as the parent type.
11037 A component of a record type that is itself a record or an array and that does
11038 not start and end on a byte boundary must have have the same scalar storage
11039 order as the record type. A component of a bit-packed array type that is itself
11040 a record or an array must have the same scalar storage order as the array type.
11042 No component of a type that has an explicit @code{Scalar_Storage_Order}
11043 attribute definition may be aliased.
11045 A confirming @code{Scalar_Storage_Order} attribute definition clause (i.e.
11046 with a value equal to @code{System.Default_Bit_Order}) has no effect.
11048 If the opposite storage order is specified, then whenever the value of
11049 a scalar component of an object of type @code{S} is read, the storage
11050 elements of the enclosing machine scalar are first reversed (before
11051 retrieving the component value, possibly applying some shift and mask
11052 operatings on the enclosing machine scalar), and the opposite operation
11053 is done for writes.
11055 In that case, the restrictions set forth in 13.5.1(10.3/2) for scalar components
11056 are relaxed. Instead, the following rules apply:
11062 the underlying storage elements are those at positions
11063 @code{(position + first_bit / storage_element_size) .. (position + (last_bit + storage_element_size - 1) / storage_element_size)}
11066 the sequence of underlying storage elements shall have
11067 a size no greater than the largest machine scalar
11070 the enclosing machine scalar is defined as the smallest machine
11071 scalar starting at a position no greater than
11072 @code{position + first_bit / storage_element_size} and covering
11073 storage elements at least up to @code{position + (last_bit + storage_element_size - 1) / storage_element_size`}
11076 the position of the component is interpreted relative to that machine
11080 If no scalar storage order is specified for a type (either directly, or by
11081 inheritance in the case of a derived type), then the default is normally
11082 the native ordering of the target, but this default can be overridden using
11083 pragma @code{Default_Scalar_Storage_Order}.
11085 Note that if a component of @code{T} is itself of a record or array type,
11086 the specfied @code{Scalar_Storage_Order} does @emph{not} apply to that nested type:
11087 an explicit attribute definition clause must be provided for the component
11088 type as well if desired.
11090 Note that the scalar storage order only affects the in-memory data
11091 representation. It has no effect on the representation used by stream
11094 @node Attribute Simple_Storage_Pool,Attribute Small,Attribute Scalar_Storage_Order,Implementation Defined Attributes
11095 @anchor{gnat_rm/implementation_defined_attributes attribute-simple-storage-pool}@anchor{e3}@anchor{gnat_rm/implementation_defined_attributes id5}@anchor{198}
11096 @section Attribute Simple_Storage_Pool
11099 @geindex Storage pool
11102 @geindex Simple storage pool
11104 @geindex Simple_Storage_Pool
11106 For every nonformal, nonderived access-to-object type @code{Acc}, the
11107 representation attribute @code{Simple_Storage_Pool} may be specified
11108 via an attribute_definition_clause (or by specifying the equivalent aspect):
11111 My_Pool : My_Simple_Storage_Pool_Type;
11113 type Acc is access My_Data_Type;
11115 for Acc'Simple_Storage_Pool use My_Pool;
11118 The name given in an attribute_definition_clause for the
11119 @code{Simple_Storage_Pool} attribute shall denote a variable of
11120 a 'simple storage pool type' (see pragma @cite{Simple_Storage_Pool_Type}).
11122 The use of this attribute is only allowed for a prefix denoting a type
11123 for which it has been specified. The type of the attribute is the type
11124 of the variable specified as the simple storage pool of the access type,
11125 and the attribute denotes that variable.
11127 It is illegal to specify both @code{Storage_Pool} and @code{Simple_Storage_Pool}
11128 for the same access type.
11130 If the @code{Simple_Storage_Pool} attribute has been specified for an access
11131 type, then applying the @code{Storage_Pool} attribute to the type is flagged
11132 with a warning and its evaluation raises the exception @code{Program_Error}.
11134 If the Simple_Storage_Pool attribute has been specified for an access
11135 type @code{S}, then the evaluation of the attribute @code{S'Storage_Size}
11136 returns the result of calling @code{Storage_Size (S'Simple_Storage_Pool)},
11137 which is intended to indicate the number of storage elements reserved for
11138 the simple storage pool. If the Storage_Size function has not been defined
11139 for the simple storage pool type, then this attribute returns zero.
11141 If an access type @code{S} has a specified simple storage pool of type
11142 @code{SSP}, then the evaluation of an allocator for that access type calls
11143 the primitive @code{Allocate} procedure for type @code{SSP}, passing
11144 @code{S'Simple_Storage_Pool} as the pool parameter. The detailed
11145 semantics of such allocators is the same as those defined for allocators
11146 in section 13.11 of the @cite{Ada Reference Manual}, with the term
11147 @emph{simple storage pool} substituted for @emph{storage pool}.
11149 If an access type @code{S} has a specified simple storage pool of type
11150 @code{SSP}, then a call to an instance of the @code{Ada.Unchecked_Deallocation}
11151 for that access type invokes the primitive @code{Deallocate} procedure
11152 for type @code{SSP}, passing @code{S'Simple_Storage_Pool} as the pool
11153 parameter. The detailed semantics of such unchecked deallocations is the same
11154 as defined in section 13.11.2 of the Ada Reference Manual, except that the
11155 term @emph{simple storage pool} is substituted for @emph{storage pool}.
11157 @node Attribute Small,Attribute Storage_Unit,Attribute Simple_Storage_Pool,Implementation Defined Attributes
11158 @anchor{gnat_rm/implementation_defined_attributes attribute-small}@anchor{199}
11159 @section Attribute Small
11162 @geindex Ada 83 attributes
11166 The @code{Small} attribute is defined in Ada 95 (and Ada 2005) only for
11168 GNAT also allows this attribute to be applied to floating-point types
11169 for compatibility with Ada 83. See
11170 the Ada 83 reference manual for an exact description of the semantics of
11171 this attribute when applied to floating-point types.
11173 @node Attribute Storage_Unit,Attribute Stub_Type,Attribute Small,Implementation Defined Attributes
11174 @anchor{gnat_rm/implementation_defined_attributes attribute-storage-unit}@anchor{19a}
11175 @section Attribute Storage_Unit
11178 @geindex Storage_Unit
11180 @code{Standard'Storage_Unit} (@code{Standard} is the only permissible
11181 prefix) provides the same value as @code{System.Storage_Unit}.
11183 @node Attribute Stub_Type,Attribute System_Allocator_Alignment,Attribute Storage_Unit,Implementation Defined Attributes
11184 @anchor{gnat_rm/implementation_defined_attributes attribute-stub-type}@anchor{19b}
11185 @section Attribute Stub_Type
11190 The GNAT implementation of remote access-to-classwide types is
11191 organized as described in AARM section E.4 (20.t): a value of an RACW type
11192 (designating a remote object) is represented as a normal access
11193 value, pointing to a "stub" object which in turn contains the
11194 necessary information to contact the designated remote object. A
11195 call on any dispatching operation of such a stub object does the
11196 remote call, if necessary, using the information in the stub object
11197 to locate the target partition, etc.
11199 For a prefix @code{T} that denotes a remote access-to-classwide type,
11200 @code{T'Stub_Type} denotes the type of the corresponding stub objects.
11202 By construction, the layout of @code{T'Stub_Type} is identical to that of
11203 type @code{RACW_Stub_Type} declared in the internal implementation-defined
11204 unit @code{System.Partition_Interface}. Use of this attribute will create
11205 an implicit dependency on this unit.
11207 @node Attribute System_Allocator_Alignment,Attribute Target_Name,Attribute Stub_Type,Implementation Defined Attributes
11208 @anchor{gnat_rm/implementation_defined_attributes attribute-system-allocator-alignment}@anchor{19c}
11209 @section Attribute System_Allocator_Alignment
11215 @geindex System_Allocator_Alignment
11217 @code{Standard'System_Allocator_Alignment} (@code{Standard} is the only
11218 permissible prefix) provides the observable guaranted to be honored by
11219 the system allocator (malloc). This is a static value that can be used
11220 in user storage pools based on malloc either to reject allocation
11221 with alignment too large or to enable a realignment circuitry if the
11222 alignment request is larger than this value.
11224 @node Attribute Target_Name,Attribute To_Address,Attribute System_Allocator_Alignment,Implementation Defined Attributes
11225 @anchor{gnat_rm/implementation_defined_attributes attribute-target-name}@anchor{19d}
11226 @section Attribute Target_Name
11229 @geindex Target_Name
11231 @code{Standard'Target_Name} (@code{Standard} is the only permissible
11232 prefix) provides a static string value that identifies the target
11233 for the current compilation. For GCC implementations, this is the
11234 standard gcc target name without the terminating slash (for
11235 example, GNAT 5.0 on windows yields "i586-pc-mingw32msv").
11237 @node Attribute To_Address,Attribute To_Any,Attribute Target_Name,Implementation Defined Attributes
11238 @anchor{gnat_rm/implementation_defined_attributes attribute-to-address}@anchor{19e}
11239 @section Attribute To_Address
11242 @geindex To_Address
11244 The @code{System'To_Address}
11245 (@code{System} is the only permissible prefix)
11246 denotes a function identical to
11247 @code{System.Storage_Elements.To_Address} except that
11248 it is a static attribute. This means that if its argument is
11249 a static expression, then the result of the attribute is a
11250 static expression. This means that such an expression can be
11251 used in contexts (e.g., preelaborable packages) which require a
11252 static expression and where the function call could not be used
11253 (since the function call is always nonstatic, even if its
11254 argument is static). The argument must be in the range
11255 -(2**(m-1)) .. 2**m-1, where m is the memory size
11256 (typically 32 or 64). Negative values are intepreted in a
11257 modular manner (e.g., -1 means the same as 16#FFFF_FFFF# on
11258 a 32 bits machine).
11260 @node Attribute To_Any,Attribute Type_Class,Attribute To_Address,Implementation Defined Attributes
11261 @anchor{gnat_rm/implementation_defined_attributes attribute-to-any}@anchor{19f}
11262 @section Attribute To_Any
11267 This internal attribute is used for the generation of remote subprogram
11268 stubs in the context of the Distributed Systems Annex.
11270 @node Attribute Type_Class,Attribute Type_Key,Attribute To_Any,Implementation Defined Attributes
11271 @anchor{gnat_rm/implementation_defined_attributes attribute-type-class}@anchor{1a0}
11272 @section Attribute Type_Class
11275 @geindex Type_Class
11277 @code{typ'Type_Class} for any type or subtype @cite{typ} yields
11278 the value of the type class for the full type of @cite{typ}. If
11279 @cite{typ} is a generic formal type, the value is the value for the
11280 corresponding actual subtype. The value of this attribute is of type
11281 @code{System.Aux_DEC.Type_Class}, which has the following definition:
11285 (Type_Class_Enumeration,
11286 Type_Class_Integer,
11287 Type_Class_Fixed_Point,
11288 Type_Class_Floating_Point,
11293 Type_Class_Address);
11296 Protected types yield the value @code{Type_Class_Task}, which thus
11297 applies to all concurrent types. This attribute is designed to
11298 be compatible with the DEC Ada 83 attribute of the same name.
11300 @node Attribute Type_Key,Attribute TypeCode,Attribute Type_Class,Implementation Defined Attributes
11301 @anchor{gnat_rm/implementation_defined_attributes attribute-type-key}@anchor{1a1}
11302 @section Attribute Type_Key
11307 The @code{Type_Key} attribute is applicable to a type or subtype and
11308 yields a value of type Standard.String containing encoded information
11309 about the type or subtype. This provides improved compatibility with
11310 other implementations that support this attribute.
11312 @node Attribute TypeCode,Attribute Unconstrained_Array,Attribute Type_Key,Implementation Defined Attributes
11313 @anchor{gnat_rm/implementation_defined_attributes attribute-typecode}@anchor{1a2}
11314 @section Attribute TypeCode
11319 This internal attribute is used for the generation of remote subprogram
11320 stubs in the context of the Distributed Systems Annex.
11322 @node Attribute Unconstrained_Array,Attribute Universal_Literal_String,Attribute TypeCode,Implementation Defined Attributes
11323 @anchor{gnat_rm/implementation_defined_attributes attribute-unconstrained-array}@anchor{1a3}
11324 @section Attribute Unconstrained_Array
11327 @geindex Unconstrained_Array
11329 The @code{Unconstrained_Array} attribute can be used with a prefix that
11330 denotes any type or subtype. It is a static attribute that yields
11331 @code{True} if the prefix designates an unconstrained array,
11332 and @code{False} otherwise. In a generic instance, the result is
11333 still static, and yields the result of applying this test to the
11336 @node Attribute Universal_Literal_String,Attribute Unrestricted_Access,Attribute Unconstrained_Array,Implementation Defined Attributes
11337 @anchor{gnat_rm/implementation_defined_attributes attribute-universal-literal-string}@anchor{1a4}
11338 @section Attribute Universal_Literal_String
11341 @geindex Named numbers
11342 @geindex representation of
11344 @geindex Universal_Literal_String
11346 The prefix of @code{Universal_Literal_String} must be a named
11347 number. The static result is the string consisting of the characters of
11348 the number as defined in the original source. This allows the user
11349 program to access the actual text of named numbers without intermediate
11350 conversions and without the need to enclose the strings in quotes (which
11351 would preclude their use as numbers).
11353 For example, the following program prints the first 50 digits of pi:
11356 with Text_IO; use Text_IO;
11360 Put (Ada.Numerics.Pi'Universal_Literal_String);
11364 @node Attribute Unrestricted_Access,Attribute Update,Attribute Universal_Literal_String,Implementation Defined Attributes
11365 @anchor{gnat_rm/implementation_defined_attributes attribute-unrestricted-access}@anchor{1a5}
11366 @section Attribute Unrestricted_Access
11370 @geindex unrestricted
11372 @geindex Unrestricted_Access
11374 The @code{Unrestricted_Access} attribute is similar to @code{Access}
11375 except that all accessibility and aliased view checks are omitted. This
11376 is a user-beware attribute.
11378 For objects, it is similar to @code{Address}, for which it is a
11379 desirable replacement where the value desired is an access type.
11380 In other words, its effect is similar to first applying the
11381 @code{Address} attribute and then doing an unchecked conversion to a
11382 desired access type.
11384 For subprograms, @code{P'Unrestricted_Access} may be used where
11385 @code{P'Access} would be illegal, to construct a value of a
11386 less-nested named access type that designates a more-nested
11387 subprogram. This value may be used in indirect calls, so long as the
11388 more-nested subprogram still exists; once the subprogram containing it
11389 has returned, such calls are erroneous. For example:
11394 type Less_Nested is not null access procedure;
11395 Global : Less_Nested;
11403 Local_Var : Integer;
11405 procedure More_Nested is
11410 Global := More_Nested'Unrestricted_Access;
11417 When P1 is called from P2, the call via Global is OK, but if P1 were
11418 called after P2 returns, it would be an erroneous use of a dangling
11421 For objects, it is possible to use @code{Unrestricted_Access} for any
11422 type. However, if the result is of an access-to-unconstrained array
11423 subtype, then the resulting pointer has the same scope as the context
11424 of the attribute, and must not be returned to some enclosing scope.
11425 For instance, if a function uses @code{Unrestricted_Access} to create
11426 an access-to-unconstrained-array and returns that value to the caller,
11427 the result will involve dangling pointers. In addition, it is only
11428 valid to create pointers to unconstrained arrays using this attribute
11429 if the pointer has the normal default 'fat' representation where a
11430 pointer has two components, one points to the array and one points to
11431 the bounds. If a size clause is used to force 'thin' representation
11432 for a pointer to unconstrained where there is only space for a single
11433 pointer, then the resulting pointer is not usable.
11435 In the simple case where a direct use of Unrestricted_Access attempts
11436 to make a thin pointer for a non-aliased object, the compiler will
11437 reject the use as illegal, as shown in the following example:
11440 with System; use System;
11441 procedure SliceUA2 is
11442 type A is access all String;
11443 for A'Size use Standard'Address_Size;
11445 procedure P (Arg : A) is
11450 X : String := "hello world!";
11451 X2 : aliased String := "hello world!";
11453 AV : A := X'Unrestricted_Access; -- ERROR
11455 >>> illegal use of Unrestricted_Access attribute
11456 >>> attempt to generate thin pointer to unaliased object
11459 P (X'Unrestricted_Access); -- ERROR
11461 >>> illegal use of Unrestricted_Access attribute
11462 >>> attempt to generate thin pointer to unaliased object
11464 P (X(7 .. 12)'Unrestricted_Access); -- ERROR
11466 >>> illegal use of Unrestricted_Access attribute
11467 >>> attempt to generate thin pointer to unaliased object
11469 P (X2'Unrestricted_Access); -- OK
11473 but other cases cannot be detected by the compiler, and are
11474 considered to be erroneous. Consider the following example:
11477 with System; use System;
11478 with System; use System;
11479 procedure SliceUA is
11480 type AF is access all String;
11482 type A is access all String;
11483 for A'Size use Standard'Address_Size;
11485 procedure P (Arg : A) is
11487 if Arg'Length /= 6 then
11488 raise Program_Error;
11492 X : String := "hello world!";
11493 Y : AF := X (7 .. 12)'Unrestricted_Access;
11500 A normal unconstrained array value
11501 or a constrained array object marked as aliased has the bounds in memory
11502 just before the array, so a thin pointer can retrieve both the data and
11503 the bounds. But in this case, the non-aliased object @code{X} does not have the
11504 bounds before the string. If the size clause for type @code{A}
11505 were not present, then the pointer
11506 would be a fat pointer, where one component is a pointer to the bounds,
11507 and all would be well. But with the size clause present, the conversion from
11508 fat pointer to thin pointer in the call loses the bounds, and so this
11509 is erroneous, and the program likely raises a @code{Program_Error} exception.
11511 In general, it is advisable to completely
11512 avoid mixing the use of thin pointers and the use of
11513 @code{Unrestricted_Access} where the designated type is an
11514 unconstrained array. The use of thin pointers should be restricted to
11515 cases of porting legacy code that implicitly assumes the size of pointers,
11516 and such code should not in any case be using this attribute.
11518 Another erroneous situation arises if the attribute is
11519 applied to a constant. The resulting pointer can be used to access the
11520 constant, but the effect of trying to modify a constant in this manner
11521 is not well-defined. Consider this example:
11524 P : constant Integer := 4;
11525 type R is access all Integer;
11526 RV : R := P'Unrestricted_Access;
11531 Here we attempt to modify the constant P from 4 to 3, but the compiler may
11532 or may not notice this attempt, and subsequent references to P may yield
11533 either the value 3 or the value 4 or the assignment may blow up if the
11534 compiler decides to put P in read-only memory. One particular case where
11535 @code{Unrestricted_Access} can be used in this way is to modify the
11536 value of an @code{in} parameter:
11539 procedure K (S : in String) is
11540 type R is access all Character;
11541 RV : R := S (3)'Unrestricted_Access;
11547 In general this is a risky approach. It may appear to "work" but such uses of
11548 @code{Unrestricted_Access} are potentially non-portable, even from one version
11549 of GNAT to another, so are best avoided if possible.
11551 @node Attribute Update,Attribute Valid_Scalars,Attribute Unrestricted_Access,Implementation Defined Attributes
11552 @anchor{gnat_rm/implementation_defined_attributes attribute-update}@anchor{1a6}
11553 @section Attribute Update
11558 The @code{Update} attribute creates a copy of an array or record value
11559 with one or more modified components. The syntax is:
11562 PREFIX'Update ( RECORD_COMPONENT_ASSOCIATION_LIST )
11563 PREFIX'Update ( ARRAY_COMPONENT_ASSOCIATION @{, ARRAY_COMPONENT_ASSOCIATION @} )
11564 PREFIX'Update ( MULTIDIMENSIONAL_ARRAY_COMPONENT_ASSOCIATION
11565 @{, MULTIDIMENSIONAL_ARRAY_COMPONENT_ASSOCIATION @} )
11567 MULTIDIMENSIONAL_ARRAY_COMPONENT_ASSOCIATION ::= INDEX_EXPRESSION_LIST_LIST => EXPRESSION
11568 INDEX_EXPRESSION_LIST_LIST ::= INDEX_EXPRESSION_LIST @{| INDEX_EXPRESSION_LIST @}
11569 INDEX_EXPRESSION_LIST ::= ( EXPRESSION @{, EXPRESSION @} )
11572 where @code{PREFIX} is the name of an array or record object, the
11573 association list in parentheses does not contain an @code{others}
11574 choice and the box symbol @code{<>} may not appear in any
11575 expression. The effect is to yield a copy of the array or record value
11576 which is unchanged apart from the components mentioned in the
11577 association list, which are changed to the indicated value. The
11578 original value of the array or record value is not affected. For
11582 type Arr is Array (1 .. 5) of Integer;
11584 Avar1 : Arr := (1,2,3,4,5);
11585 Avar2 : Arr := Avar1'Update (2 => 10, 3 .. 4 => 20);
11588 yields a value for @code{Avar2} of 1,10,20,20,5 with @code{Avar1}
11589 begin unmodified. Similarly:
11592 type Rec is A, B, C : Integer;
11594 Rvar1 : Rec := (A => 1, B => 2, C => 3);
11595 Rvar2 : Rec := Rvar1'Update (B => 20);
11598 yields a value for @code{Rvar2} of (A => 1, B => 20, C => 3),
11599 with @code{Rvar1} being unmodifed.
11600 Note that the value of the attribute reference is computed
11601 completely before it is used. This means that if you write:
11604 Avar1 := Avar1'Update (1 => 10, 2 => Function_Call);
11607 then the value of @code{Avar1} is not modified if @code{Function_Call}
11608 raises an exception, unlike the effect of a series of direct assignments
11609 to elements of @code{Avar1}. In general this requires that
11610 two extra complete copies of the object are required, which should be
11611 kept in mind when considering efficiency.
11613 The @code{Update} attribute cannot be applied to prefixes of a limited
11614 type, and cannot reference discriminants in the case of a record type.
11615 The accessibility level of an Update attribute result object is defined
11616 as for an aggregate.
11618 In the record case, no component can be mentioned more than once. In
11619 the array case, two overlapping ranges can appear in the association list,
11620 in which case the modifications are processed left to right.
11622 Multi-dimensional arrays can be modified, as shown by this example:
11625 A : array (1 .. 10, 1 .. 10) of Integer;
11627 A := A'Update ((1, 2) => 20, (3, 4) => 30);
11630 which changes element (1,2) to 20 and (3,4) to 30.
11632 @node Attribute Valid_Scalars,Attribute VADS_Size,Attribute Update,Implementation Defined Attributes
11633 @anchor{gnat_rm/implementation_defined_attributes attribute-valid-scalars}@anchor{1a7}
11634 @section Attribute Valid_Scalars
11637 @geindex Valid_Scalars
11639 The @code{'Valid_Scalars} attribute is intended to make it easier to
11640 check the validity of scalar subcomponents of composite objects. It
11641 is defined for any prefix @code{X} that denotes an object.
11642 The value of this attribute is of the predefined type Boolean.
11643 @code{X'Valid_Scalars} yields True if and only if evaluation of
11644 @code{P'Valid} yields True for every scalar part P of X or if X has
11645 no scalar parts. It is not specified in what order the scalar parts
11646 are checked, nor whether any more are checked after any one of them
11647 is determined to be invalid. If the prefix @code{X} is of a class-wide
11648 type @code{T'Class} (where @code{T} is the associated specific type),
11649 or if the prefix @code{X} is of a specific tagged type @code{T}, then
11650 only the scalar parts of components of @code{T} are traversed; in other
11651 words, components of extensions of @code{T} are not traversed even if
11652 @code{T'Class (X)'Tag /= T'Tag} . The compiler will issue a warning if it can
11653 be determined at compile time that the prefix of the attribute has no
11654 scalar parts (e.g., if the prefix is of an access type, an interface type,
11655 an undiscriminated task type, or an undiscriminated protected type).
11657 For scalar types, @code{Valid_Scalars} is equivalent to @code{Valid}. The use
11658 of this attribute is not permitted for @code{Unchecked_Union} types for which
11659 in general it is not possible to determine the values of the discriminants.
11661 Note: @code{Valid_Scalars} can generate a lot of code, especially in the case
11662 of a large variant record. If the attribute is called in many places in the
11663 same program applied to objects of the same type, it can reduce program size
11664 to write a function with a single use of the attribute, and then call that
11665 function from multiple places.
11667 @node Attribute VADS_Size,Attribute Value_Size,Attribute Valid_Scalars,Implementation Defined Attributes
11668 @anchor{gnat_rm/implementation_defined_attributes attribute-vads-size}@anchor{1a8}
11669 @section Attribute VADS_Size
11673 @geindex VADS compatibility
11677 The @code{'VADS_Size} attribute is intended to make it easier to port
11678 legacy code which relies on the semantics of @code{'Size} as implemented
11679 by the VADS Ada 83 compiler. GNAT makes a best effort at duplicating the
11680 same semantic interpretation. In particular, @code{'VADS_Size} applied
11681 to a predefined or other primitive type with no Size clause yields the
11682 Object_Size (for example, @code{Natural'Size} is 32 rather than 31 on
11683 typical machines). In addition @code{'VADS_Size} applied to an object
11684 gives the result that would be obtained by applying the attribute to
11685 the corresponding type.
11687 @node Attribute Value_Size,Attribute Wchar_T_Size,Attribute VADS_Size,Implementation Defined Attributes
11688 @anchor{gnat_rm/implementation_defined_attributes id6}@anchor{1a9}@anchor{gnat_rm/implementation_defined_attributes attribute-value-size}@anchor{15b}
11689 @section Attribute Value_Size
11693 @geindex setting for not-first subtype
11695 @geindex Value_Size
11697 @code{type'Value_Size} is the number of bits required to represent
11698 a value of the given subtype. It is the same as @code{type'Size},
11699 but, unlike @code{Size}, may be set for non-first subtypes.
11701 @node Attribute Wchar_T_Size,Attribute Word_Size,Attribute Value_Size,Implementation Defined Attributes
11702 @anchor{gnat_rm/implementation_defined_attributes attribute-wchar-t-size}@anchor{1aa}
11703 @section Attribute Wchar_T_Size
11706 @geindex Wchar_T_Size
11708 @code{Standard'Wchar_T_Size} (@code{Standard} is the only permissible
11709 prefix) provides the size in bits of the C @code{wchar_t} type
11710 primarily for constructing the definition of this type in
11711 package @code{Interfaces.C}. The result is a static constant.
11713 @node Attribute Word_Size,,Attribute Wchar_T_Size,Implementation Defined Attributes
11714 @anchor{gnat_rm/implementation_defined_attributes attribute-word-size}@anchor{1ab}
11715 @section Attribute Word_Size
11720 @code{Standard'Word_Size} (@code{Standard} is the only permissible
11721 prefix) provides the value @code{System.Word_Size}. The result is
11724 @node Standard and Implementation Defined Restrictions,Implementation Advice,Implementation Defined Attributes,Top
11725 @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}
11726 @chapter Standard and Implementation Defined Restrictions
11729 All Ada Reference Manual-defined Restriction identifiers are implemented:
11735 language-defined restrictions (see 13.12.1)
11738 tasking restrictions (see D.7)
11741 high integrity restrictions (see H.4)
11744 GNAT implements additional restriction identifiers. All restrictions, whether
11745 language defined or GNAT-specific, are listed in the following.
11748 * Partition-Wide Restrictions::
11749 * Program Unit Level Restrictions::
11753 @node Partition-Wide Restrictions,Program Unit Level Restrictions,,Standard and Implementation Defined Restrictions
11754 @anchor{gnat_rm/standard_and_implementation_defined_restrictions partition-wide-restrictions}@anchor{1ae}@anchor{gnat_rm/standard_and_implementation_defined_restrictions id2}@anchor{1af}
11755 @section Partition-Wide Restrictions
11758 There are two separate lists of restriction identifiers. The first
11759 set requires consistency throughout a partition (in other words, if the
11760 restriction identifier is used for any compilation unit in the partition,
11761 then all compilation units in the partition must obey the restriction).
11764 * Immediate_Reclamation::
11765 * Max_Asynchronous_Select_Nesting::
11766 * Max_Entry_Queue_Length::
11767 * Max_Protected_Entries::
11768 * Max_Select_Alternatives::
11769 * Max_Storage_At_Blocking::
11770 * Max_Task_Entries::
11772 * No_Abort_Statements::
11773 * No_Access_Parameter_Allocators::
11774 * No_Access_Subprograms::
11776 * No_Anonymous_Allocators::
11777 * No_Asynchronous_Control::
11779 * No_Coextensions::
11780 * No_Default_Initialization::
11783 * No_Direct_Boolean_Operators::
11785 * No_Dispatching_Calls::
11786 * No_Dynamic_Attachment::
11787 * No_Dynamic_Priorities::
11788 * No_Entry_Calls_In_Elaboration_Code::
11789 * No_Enumeration_Maps::
11790 * No_Exception_Handlers::
11791 * No_Exception_Propagation::
11792 * No_Exception_Registration::
11794 * No_Finalization::
11796 * No_Floating_Point::
11797 * No_Implicit_Conditionals::
11798 * No_Implicit_Dynamic_Code::
11799 * No_Implicit_Heap_Allocations::
11800 * No_Implicit_Protected_Object_Allocations::
11801 * No_Implicit_Task_Allocations::
11802 * No_Initialize_Scalars::
11804 * No_Local_Allocators::
11805 * No_Local_Protected_Objects::
11806 * No_Local_Timing_Events::
11807 * No_Long_Long_Integers::
11808 * No_Multiple_Elaboration::
11809 * No_Nested_Finalization::
11810 * No_Protected_Type_Allocators::
11811 * No_Protected_Types::
11814 * No_Relative_Delay::
11815 * No_Requeue_Statements::
11816 * No_Secondary_Stack::
11817 * No_Select_Statements::
11818 * No_Specific_Termination_Handlers::
11819 * No_Specification_of_Aspect::
11820 * No_Standard_Allocators_After_Elaboration::
11821 * No_Standard_Storage_Pools::
11822 * No_Stream_Optimizations::
11824 * No_Task_Allocators::
11825 * No_Task_At_Interrupt_Priority::
11826 * No_Task_Attributes_Package::
11827 * No_Task_Hierarchy::
11828 * No_Task_Termination::
11830 * No_Terminate_Alternatives::
11831 * No_Unchecked_Access::
11832 * No_Unchecked_Conversion::
11833 * No_Unchecked_Deallocation::
11834 * No_Use_Of_Entity::
11836 * Simple_Barriers::
11837 * Static_Priorities::
11838 * Static_Storage_Size::
11842 @node Immediate_Reclamation,Max_Asynchronous_Select_Nesting,,Partition-Wide Restrictions
11843 @anchor{gnat_rm/standard_and_implementation_defined_restrictions immediate-reclamation}@anchor{1b0}
11844 @subsection Immediate_Reclamation
11847 @geindex Immediate_Reclamation
11849 [RM H.4] This restriction ensures that, except for storage occupied by
11850 objects created by allocators and not deallocated via unchecked
11851 deallocation, any storage reserved at run time for an object is
11852 immediately reclaimed when the object no longer exists.
11854 @node Max_Asynchronous_Select_Nesting,Max_Entry_Queue_Length,Immediate_Reclamation,Partition-Wide Restrictions
11855 @anchor{gnat_rm/standard_and_implementation_defined_restrictions max-asynchronous-select-nesting}@anchor{1b1}
11856 @subsection Max_Asynchronous_Select_Nesting
11859 @geindex Max_Asynchronous_Select_Nesting
11861 [RM D.7] Specifies the maximum dynamic nesting level of asynchronous
11862 selects. Violations of this restriction with a value of zero are
11863 detected at compile time. Violations of this restriction with values
11864 other than zero cause Storage_Error to be raised.
11866 @node Max_Entry_Queue_Length,Max_Protected_Entries,Max_Asynchronous_Select_Nesting,Partition-Wide Restrictions
11867 @anchor{gnat_rm/standard_and_implementation_defined_restrictions max-entry-queue-length}@anchor{1b2}
11868 @subsection Max_Entry_Queue_Length
11871 @geindex Max_Entry_Queue_Length
11873 [RM D.7] This restriction is a declaration that any protected entry compiled in
11874 the scope of the restriction has at most the specified number of
11875 tasks waiting on the entry at any one time, and so no queue is required.
11876 Note that this restriction is checked at run time. Violation of this
11877 restriction results in the raising of Program_Error exception at the point of
11880 @geindex Max_Entry_Queue_Depth
11882 The restriction @code{Max_Entry_Queue_Depth} is recognized as a
11883 synonym for @code{Max_Entry_Queue_Length}. This is retained for historical
11884 compatibility purposes (and a warning will be generated for its use if
11885 warnings on obsolescent features are activated).
11887 @node Max_Protected_Entries,Max_Select_Alternatives,Max_Entry_Queue_Length,Partition-Wide Restrictions
11888 @anchor{gnat_rm/standard_and_implementation_defined_restrictions max-protected-entries}@anchor{1b3}
11889 @subsection Max_Protected_Entries
11892 @geindex Max_Protected_Entries
11894 [RM D.7] Specifies the maximum number of entries per protected type. The
11895 bounds of every entry family of a protected unit shall be static, or shall be
11896 defined by a discriminant of a subtype whose corresponding bound is static.
11898 @node Max_Select_Alternatives,Max_Storage_At_Blocking,Max_Protected_Entries,Partition-Wide Restrictions
11899 @anchor{gnat_rm/standard_and_implementation_defined_restrictions max-select-alternatives}@anchor{1b4}
11900 @subsection Max_Select_Alternatives
11903 @geindex Max_Select_Alternatives
11905 [RM D.7] Specifies the maximum number of alternatives in a selective accept.
11907 @node Max_Storage_At_Blocking,Max_Task_Entries,Max_Select_Alternatives,Partition-Wide Restrictions
11908 @anchor{gnat_rm/standard_and_implementation_defined_restrictions max-storage-at-blocking}@anchor{1b5}
11909 @subsection Max_Storage_At_Blocking
11912 @geindex Max_Storage_At_Blocking
11914 [RM D.7] Specifies the maximum portion (in storage elements) of a task's
11915 Storage_Size that can be retained by a blocked task. A violation of this
11916 restriction causes Storage_Error to be raised.
11918 @node Max_Task_Entries,Max_Tasks,Max_Storage_At_Blocking,Partition-Wide Restrictions
11919 @anchor{gnat_rm/standard_and_implementation_defined_restrictions max-task-entries}@anchor{1b6}
11920 @subsection Max_Task_Entries
11923 @geindex Max_Task_Entries
11925 [RM D.7] Specifies the maximum number of entries
11926 per task. The bounds of every entry family
11927 of a task unit shall be static, or shall be
11928 defined by a discriminant of a subtype whose
11929 corresponding bound is static.
11931 @node Max_Tasks,No_Abort_Statements,Max_Task_Entries,Partition-Wide Restrictions
11932 @anchor{gnat_rm/standard_and_implementation_defined_restrictions max-tasks}@anchor{1b7}
11933 @subsection Max_Tasks
11938 [RM D.7] Specifies the maximum number of task that may be created, not
11939 counting the creation of the environment task. Violations of this
11940 restriction with a value of zero are detected at compile
11941 time. Violations of this restriction with values other than zero cause
11942 Storage_Error to be raised.
11944 @node No_Abort_Statements,No_Access_Parameter_Allocators,Max_Tasks,Partition-Wide Restrictions
11945 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-abort-statements}@anchor{1b8}
11946 @subsection No_Abort_Statements
11949 @geindex No_Abort_Statements
11951 [RM D.7] There are no abort_statements, and there are
11952 no calls to Task_Identification.Abort_Task.
11954 @node No_Access_Parameter_Allocators,No_Access_Subprograms,No_Abort_Statements,Partition-Wide Restrictions
11955 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-access-parameter-allocators}@anchor{1b9}
11956 @subsection No_Access_Parameter_Allocators
11959 @geindex No_Access_Parameter_Allocators
11961 [RM H.4] This restriction ensures at compile time that there are no
11962 occurrences of an allocator as the actual parameter to an access
11965 @node No_Access_Subprograms,No_Allocators,No_Access_Parameter_Allocators,Partition-Wide Restrictions
11966 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-access-subprograms}@anchor{1ba}
11967 @subsection No_Access_Subprograms
11970 @geindex No_Access_Subprograms
11972 [RM H.4] This restriction ensures at compile time that there are no
11973 declarations of access-to-subprogram types.
11975 @node No_Allocators,No_Anonymous_Allocators,No_Access_Subprograms,Partition-Wide Restrictions
11976 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-allocators}@anchor{1bb}
11977 @subsection No_Allocators
11980 @geindex No_Allocators
11982 [RM H.4] This restriction ensures at compile time that there are no
11983 occurrences of an allocator.
11985 @node No_Anonymous_Allocators,No_Asynchronous_Control,No_Allocators,Partition-Wide Restrictions
11986 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-anonymous-allocators}@anchor{1bc}
11987 @subsection No_Anonymous_Allocators
11990 @geindex No_Anonymous_Allocators
11992 [RM H.4] This restriction ensures at compile time that there are no
11993 occurrences of an allocator of anonymous access type.
11995 @node No_Asynchronous_Control,No_Calendar,No_Anonymous_Allocators,Partition-Wide Restrictions
11996 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-asynchronous-control}@anchor{1bd}
11997 @subsection No_Asynchronous_Control
12000 @geindex No_Asynchronous_Control
12002 [RM J.13] This restriction ensures at compile time that there are no semantic
12003 dependences on the predefined package Asynchronous_Task_Control.
12005 @node No_Calendar,No_Coextensions,No_Asynchronous_Control,Partition-Wide Restrictions
12006 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-calendar}@anchor{1be}
12007 @subsection No_Calendar
12010 @geindex No_Calendar
12012 [GNAT] This restriction ensures at compile time that there are no semantic
12013 dependences on package Calendar.
12015 @node No_Coextensions,No_Default_Initialization,No_Calendar,Partition-Wide Restrictions
12016 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-coextensions}@anchor{1bf}
12017 @subsection No_Coextensions
12020 @geindex No_Coextensions
12022 [RM H.4] This restriction ensures at compile time that there are no
12023 coextensions. See 3.10.2.
12025 @node No_Default_Initialization,No_Delay,No_Coextensions,Partition-Wide Restrictions
12026 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-default-initialization}@anchor{1c0}
12027 @subsection No_Default_Initialization
12030 @geindex No_Default_Initialization
12032 [GNAT] This restriction prohibits any instance of default initialization
12033 of variables. The binder implements a consistency rule which prevents
12034 any unit compiled without the restriction from with'ing a unit with the
12035 restriction (this allows the generation of initialization procedures to
12036 be skipped, since you can be sure that no call is ever generated to an
12037 initialization procedure in a unit with the restriction active). If used
12038 in conjunction with Initialize_Scalars or Normalize_Scalars, the effect
12039 is to prohibit all cases of variables declared without a specific
12040 initializer (including the case of OUT scalar parameters).
12042 @node No_Delay,No_Dependence,No_Default_Initialization,Partition-Wide Restrictions
12043 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-delay}@anchor{1c1}
12044 @subsection No_Delay
12049 [RM H.4] This restriction ensures at compile time that there are no
12050 delay statements and no semantic dependences on package Calendar.
12052 @node No_Dependence,No_Direct_Boolean_Operators,No_Delay,Partition-Wide Restrictions
12053 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-dependence}@anchor{1c2}
12054 @subsection No_Dependence
12057 @geindex No_Dependence
12059 [RM 13.12.1] This restriction ensures at compile time that there are no
12060 dependences on a library unit.
12062 @node No_Direct_Boolean_Operators,No_Dispatch,No_Dependence,Partition-Wide Restrictions
12063 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-direct-boolean-operators}@anchor{1c3}
12064 @subsection No_Direct_Boolean_Operators
12067 @geindex No_Direct_Boolean_Operators
12069 [GNAT] This restriction ensures that no logical operators (and/or/xor)
12070 are used on operands of type Boolean (or any type derived from Boolean).
12071 This is intended for use in safety critical programs where the certification
12072 protocol requires the use of short-circuit (and then, or else) forms for all
12073 composite boolean operations.
12075 @node No_Dispatch,No_Dispatching_Calls,No_Direct_Boolean_Operators,Partition-Wide Restrictions
12076 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-dispatch}@anchor{1c4}
12077 @subsection No_Dispatch
12080 @geindex No_Dispatch
12082 [RM H.4] This restriction ensures at compile time that there are no
12083 occurrences of @code{T'Class}, for any (tagged) subtype @code{T}.
12085 @node No_Dispatching_Calls,No_Dynamic_Attachment,No_Dispatch,Partition-Wide Restrictions
12086 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-dispatching-calls}@anchor{1c5}
12087 @subsection No_Dispatching_Calls
12090 @geindex No_Dispatching_Calls
12092 [GNAT] This restriction ensures at compile time that the code generated by the
12093 compiler involves no dispatching calls. The use of this restriction allows the
12094 safe use of record extensions, classwide membership tests and other classwide
12095 features not involving implicit dispatching. This restriction ensures that
12096 the code contains no indirect calls through a dispatching mechanism. Note that
12097 this includes internally-generated calls created by the compiler, for example
12098 in the implementation of class-wide objects assignments. The
12099 membership test is allowed in the presence of this restriction, because its
12100 implementation requires no dispatching.
12101 This restriction is comparable to the official Ada restriction
12102 @code{No_Dispatch} except that it is a bit less restrictive in that it allows
12103 all classwide constructs that do not imply dispatching.
12104 The following example indicates constructs that violate this restriction.
12108 type T is tagged record
12111 procedure P (X : T);
12113 type DT is new T with record
12114 More_Data : Natural;
12116 procedure Q (X : DT);
12120 procedure Example is
12121 procedure Test (O : T'Class) is
12122 N : Natural := O'Size;-- Error: Dispatching call
12123 C : T'Class := O; -- Error: implicit Dispatching Call
12125 if O in DT'Class then -- OK : Membership test
12126 Q (DT (O)); -- OK : Type conversion plus direct call
12128 P (O); -- Error: Dispatching call
12134 P (Obj); -- OK : Direct call
12135 P (T (Obj)); -- OK : Type conversion plus direct call
12136 P (T'Class (Obj)); -- Error: Dispatching call
12138 Test (Obj); -- OK : Type conversion
12140 if Obj in T'Class then -- OK : Membership test
12146 @node No_Dynamic_Attachment,No_Dynamic_Priorities,No_Dispatching_Calls,Partition-Wide Restrictions
12147 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-dynamic-attachment}@anchor{1c6}
12148 @subsection No_Dynamic_Attachment
12151 @geindex No_Dynamic_Attachment
12153 [RM D.7] This restriction ensures that there is no call to any of the
12154 operations defined in package Ada.Interrupts
12155 (Is_Reserved, Is_Attached, Current_Handler, Attach_Handler, Exchange_Handler,
12156 Detach_Handler, and Reference).
12158 @geindex No_Dynamic_Interrupts
12160 The restriction @code{No_Dynamic_Interrupts} is recognized as a
12161 synonym for @code{No_Dynamic_Attachment}. This is retained for historical
12162 compatibility purposes (and a warning will be generated for its use if
12163 warnings on obsolescent features are activated).
12165 @node No_Dynamic_Priorities,No_Entry_Calls_In_Elaboration_Code,No_Dynamic_Attachment,Partition-Wide Restrictions
12166 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-dynamic-priorities}@anchor{1c7}
12167 @subsection No_Dynamic_Priorities
12170 @geindex No_Dynamic_Priorities
12172 [RM D.7] There are no semantic dependencies on the package Dynamic_Priorities.
12174 @node No_Entry_Calls_In_Elaboration_Code,No_Enumeration_Maps,No_Dynamic_Priorities,Partition-Wide Restrictions
12175 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-entry-calls-in-elaboration-code}@anchor{1c8}
12176 @subsection No_Entry_Calls_In_Elaboration_Code
12179 @geindex No_Entry_Calls_In_Elaboration_Code
12181 [GNAT] This restriction ensures at compile time that no task or protected entry
12182 calls are made during elaboration code. As a result of the use of this
12183 restriction, the compiler can assume that no code past an accept statement
12184 in a task can be executed at elaboration time.
12186 @node No_Enumeration_Maps,No_Exception_Handlers,No_Entry_Calls_In_Elaboration_Code,Partition-Wide Restrictions
12187 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-enumeration-maps}@anchor{1c9}
12188 @subsection No_Enumeration_Maps
12191 @geindex No_Enumeration_Maps
12193 [GNAT] This restriction ensures at compile time that no operations requiring
12194 enumeration maps are used (that is Image and Value attributes applied
12195 to enumeration types).
12197 @node No_Exception_Handlers,No_Exception_Propagation,No_Enumeration_Maps,Partition-Wide Restrictions
12198 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-exception-handlers}@anchor{1ca}
12199 @subsection No_Exception_Handlers
12202 @geindex No_Exception_Handlers
12204 [GNAT] This restriction ensures at compile time that there are no explicit
12205 exception handlers. It also indicates that no exception propagation will
12206 be provided. In this mode, exceptions may be raised but will result in
12207 an immediate call to the last chance handler, a routine that the user
12208 must define with the following profile:
12211 procedure Last_Chance_Handler
12212 (Source_Location : System.Address; Line : Integer);
12213 pragma Export (C, Last_Chance_Handler,
12214 "__gnat_last_chance_handler");
12217 The parameter is a C null-terminated string representing a message to be
12218 associated with the exception (typically the source location of the raise
12219 statement generated by the compiler). The Line parameter when nonzero
12220 represents the line number in the source program where the raise occurs.
12222 @node No_Exception_Propagation,No_Exception_Registration,No_Exception_Handlers,Partition-Wide Restrictions
12223 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-exception-propagation}@anchor{1cb}
12224 @subsection No_Exception_Propagation
12227 @geindex No_Exception_Propagation
12229 [GNAT] This restriction guarantees that exceptions are never propagated
12230 to an outer subprogram scope. The only case in which an exception may
12231 be raised is when the handler is statically in the same subprogram, so
12232 that the effect of a raise is essentially like a goto statement. Any
12233 other raise statement (implicit or explicit) will be considered
12234 unhandled. Exception handlers are allowed, but may not contain an
12235 exception occurrence identifier (exception choice). In addition, use of
12236 the package GNAT.Current_Exception is not permitted, and reraise
12237 statements (raise with no operand) are not permitted.
12239 @node No_Exception_Registration,No_Exceptions,No_Exception_Propagation,Partition-Wide Restrictions
12240 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-exception-registration}@anchor{1cc}
12241 @subsection No_Exception_Registration
12244 @geindex No_Exception_Registration
12246 [GNAT] This restriction ensures at compile time that no stream operations for
12247 types Exception_Id or Exception_Occurrence are used. This also makes it
12248 impossible to pass exceptions to or from a partition with this restriction
12249 in a distributed environment. If this restriction is active, the generated
12250 code is simplified by omitting the otherwise-required global registration
12251 of exceptions when they are declared.
12253 @node No_Exceptions,No_Finalization,No_Exception_Registration,Partition-Wide Restrictions
12254 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-exceptions}@anchor{1cd}
12255 @subsection No_Exceptions
12258 @geindex No_Exceptions
12260 [RM H.4] This restriction ensures at compile time that there are no
12261 raise statements and no exception handlers.
12263 @node No_Finalization,No_Fixed_Point,No_Exceptions,Partition-Wide Restrictions
12264 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-finalization}@anchor{1ce}
12265 @subsection No_Finalization
12268 @geindex No_Finalization
12270 [GNAT] This restriction disables the language features described in
12271 chapter 7.6 of the Ada 2005 RM as well as all form of code generation
12272 performed by the compiler to support these features. The following types
12273 are no longer considered controlled when this restriction is in effect:
12279 @code{Ada.Finalization.Controlled}
12282 @code{Ada.Finalization.Limited_Controlled}
12285 Derivations from @code{Controlled} or @code{Limited_Controlled}
12297 Array and record types with controlled components
12300 The compiler no longer generates code to initialize, finalize or adjust an
12301 object or a nested component, either declared on the stack or on the heap. The
12302 deallocation of a controlled object no longer finalizes its contents.
12304 @node No_Fixed_Point,No_Floating_Point,No_Finalization,Partition-Wide Restrictions
12305 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-fixed-point}@anchor{1cf}
12306 @subsection No_Fixed_Point
12309 @geindex No_Fixed_Point
12311 [RM H.4] This restriction ensures at compile time that there are no
12312 occurrences of fixed point types and operations.
12314 @node No_Floating_Point,No_Implicit_Conditionals,No_Fixed_Point,Partition-Wide Restrictions
12315 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-floating-point}@anchor{1d0}
12316 @subsection No_Floating_Point
12319 @geindex No_Floating_Point
12321 [RM H.4] This restriction ensures at compile time that there are no
12322 occurrences of floating point types and operations.
12324 @node No_Implicit_Conditionals,No_Implicit_Dynamic_Code,No_Floating_Point,Partition-Wide Restrictions
12325 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-conditionals}@anchor{1d1}
12326 @subsection No_Implicit_Conditionals
12329 @geindex No_Implicit_Conditionals
12331 [GNAT] This restriction ensures that the generated code does not contain any
12332 implicit conditionals, either by modifying the generated code where possible,
12333 or by rejecting any construct that would otherwise generate an implicit
12334 conditional. Note that this check does not include run time constraint
12335 checks, which on some targets may generate implicit conditionals as
12336 well. To control the latter, constraint checks can be suppressed in the
12337 normal manner. Constructs generating implicit conditionals include comparisons
12338 of composite objects and the Max/Min attributes.
12340 @node No_Implicit_Dynamic_Code,No_Implicit_Heap_Allocations,No_Implicit_Conditionals,Partition-Wide Restrictions
12341 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-dynamic-code}@anchor{1d2}
12342 @subsection No_Implicit_Dynamic_Code
12345 @geindex No_Implicit_Dynamic_Code
12347 @geindex trampoline
12349 [GNAT] This restriction prevents the compiler from building 'trampolines'.
12350 This is a structure that is built on the stack and contains dynamic
12351 code to be executed at run time. On some targets, a trampoline is
12352 built for the following features: @code{Access},
12353 @code{Unrestricted_Access}, or @code{Address} of a nested subprogram;
12354 nested task bodies; primitive operations of nested tagged types.
12355 Trampolines do not work on machines that prevent execution of stack
12356 data. For example, on windows systems, enabling DEP (data execution
12357 protection) will cause trampolines to raise an exception.
12358 Trampolines are also quite slow at run time.
12360 On many targets, trampolines have been largely eliminated. Look at the
12361 version of system.ads for your target --- if it has
12362 Always_Compatible_Rep equal to False, then trampolines are largely
12363 eliminated. In particular, a trampoline is built for the following
12364 features: @code{Address} of a nested subprogram;
12365 @code{Access} or @code{Unrestricted_Access} of a nested subprogram,
12366 but only if pragma Favor_Top_Level applies, or the access type has a
12367 foreign-language convention; primitive operations of nested tagged
12370 @node No_Implicit_Heap_Allocations,No_Implicit_Protected_Object_Allocations,No_Implicit_Dynamic_Code,Partition-Wide Restrictions
12371 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-heap-allocations}@anchor{1d3}
12372 @subsection No_Implicit_Heap_Allocations
12375 @geindex No_Implicit_Heap_Allocations
12377 [RM D.7] No constructs are allowed to cause implicit heap allocation.
12379 @node No_Implicit_Protected_Object_Allocations,No_Implicit_Task_Allocations,No_Implicit_Heap_Allocations,Partition-Wide Restrictions
12380 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-protected-object-allocations}@anchor{1d4}
12381 @subsection No_Implicit_Protected_Object_Allocations
12384 @geindex No_Implicit_Protected_Object_Allocations
12386 [GNAT] No constructs are allowed to cause implicit heap allocation of a
12389 @node No_Implicit_Task_Allocations,No_Initialize_Scalars,No_Implicit_Protected_Object_Allocations,Partition-Wide Restrictions
12390 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-task-allocations}@anchor{1d5}
12391 @subsection No_Implicit_Task_Allocations
12394 @geindex No_Implicit_Task_Allocations
12396 [GNAT] No constructs are allowed to cause implicit heap allocation of a task.
12398 @node No_Initialize_Scalars,No_IO,No_Implicit_Task_Allocations,Partition-Wide Restrictions
12399 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-initialize-scalars}@anchor{1d6}
12400 @subsection No_Initialize_Scalars
12403 @geindex No_Initialize_Scalars
12405 [GNAT] This restriction ensures that no unit in the partition is compiled with
12406 pragma Initialize_Scalars. This allows the generation of more efficient
12407 code, and in particular eliminates dummy null initialization routines that
12408 are otherwise generated for some record and array types.
12410 @node No_IO,No_Local_Allocators,No_Initialize_Scalars,Partition-Wide Restrictions
12411 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-io}@anchor{1d7}
12417 [RM H.4] This restriction ensures at compile time that there are no
12418 dependences on any of the library units Sequential_IO, Direct_IO,
12419 Text_IO, Wide_Text_IO, Wide_Wide_Text_IO, or Stream_IO.
12421 @node No_Local_Allocators,No_Local_Protected_Objects,No_IO,Partition-Wide Restrictions
12422 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-local-allocators}@anchor{1d8}
12423 @subsection No_Local_Allocators
12426 @geindex No_Local_Allocators
12428 [RM H.4] This restriction ensures at compile time that there are no
12429 occurrences of an allocator in subprograms, generic subprograms, tasks,
12432 @node No_Local_Protected_Objects,No_Local_Timing_Events,No_Local_Allocators,Partition-Wide Restrictions
12433 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-local-protected-objects}@anchor{1d9}
12434 @subsection No_Local_Protected_Objects
12437 @geindex No_Local_Protected_Objects
12439 [RM D.7] This restriction ensures at compile time that protected objects are
12440 only declared at the library level.
12442 @node No_Local_Timing_Events,No_Long_Long_Integers,No_Local_Protected_Objects,Partition-Wide Restrictions
12443 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-local-timing-events}@anchor{1da}
12444 @subsection No_Local_Timing_Events
12447 @geindex No_Local_Timing_Events
12449 [RM D.7] All objects of type Ada.Timing_Events.Timing_Event are
12450 declared at the library level.
12452 @node No_Long_Long_Integers,No_Multiple_Elaboration,No_Local_Timing_Events,Partition-Wide Restrictions
12453 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-long-long-integers}@anchor{1db}
12454 @subsection No_Long_Long_Integers
12457 @geindex No_Long_Long_Integers
12459 [GNAT] This partition-wide restriction forbids any explicit reference to
12460 type Standard.Long_Long_Integer, and also forbids declaring range types whose
12461 implicit base type is Long_Long_Integer, and modular types whose size exceeds
12464 @node No_Multiple_Elaboration,No_Nested_Finalization,No_Long_Long_Integers,Partition-Wide Restrictions
12465 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-multiple-elaboration}@anchor{1dc}
12466 @subsection No_Multiple_Elaboration
12469 @geindex No_Multiple_Elaboration
12471 [GNAT] When this restriction is active, we are not requesting control-flow
12472 preservation with -fpreserve-control-flow, and the static elaboration model is
12473 used, the compiler is allowed to suppress the elaboration counter normally
12474 associated with the unit, even if the unit has elaboration code. This counter
12475 is typically used to check for access before elaboration and to control
12476 multiple elaboration attempts. If the restriction is used, then the
12477 situations in which multiple elaboration is possible, including non-Ada main
12478 programs and Stand Alone libraries, are not permitted and will be diagnosed
12481 @node No_Nested_Finalization,No_Protected_Type_Allocators,No_Multiple_Elaboration,Partition-Wide Restrictions
12482 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-nested-finalization}@anchor{1dd}
12483 @subsection No_Nested_Finalization
12486 @geindex No_Nested_Finalization
12488 [RM D.7] All objects requiring finalization are declared at the library level.
12490 @node No_Protected_Type_Allocators,No_Protected_Types,No_Nested_Finalization,Partition-Wide Restrictions
12491 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-protected-type-allocators}@anchor{1de}
12492 @subsection No_Protected_Type_Allocators
12495 @geindex No_Protected_Type_Allocators
12497 [RM D.7] This restriction ensures at compile time that there are no allocator
12498 expressions that attempt to allocate protected objects.
12500 @node No_Protected_Types,No_Recursion,No_Protected_Type_Allocators,Partition-Wide Restrictions
12501 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-protected-types}@anchor{1df}
12502 @subsection No_Protected_Types
12505 @geindex No_Protected_Types
12507 [RM H.4] This restriction ensures at compile time that there are no
12508 declarations of protected types or protected objects.
12510 @node No_Recursion,No_Reentrancy,No_Protected_Types,Partition-Wide Restrictions
12511 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-recursion}@anchor{1e0}
12512 @subsection No_Recursion
12515 @geindex No_Recursion
12517 [RM H.4] A program execution is erroneous if a subprogram is invoked as
12518 part of its execution.
12520 @node No_Reentrancy,No_Relative_Delay,No_Recursion,Partition-Wide Restrictions
12521 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-reentrancy}@anchor{1e1}
12522 @subsection No_Reentrancy
12525 @geindex No_Reentrancy
12527 [RM H.4] A program execution is erroneous if a subprogram is executed by
12528 two tasks at the same time.
12530 @node No_Relative_Delay,No_Requeue_Statements,No_Reentrancy,Partition-Wide Restrictions
12531 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-relative-delay}@anchor{1e2}
12532 @subsection No_Relative_Delay
12535 @geindex No_Relative_Delay
12537 [RM D.7] This restriction ensures at compile time that there are no delay
12538 relative statements and prevents expressions such as @code{delay 1.23;} from
12539 appearing in source code.
12541 @node No_Requeue_Statements,No_Secondary_Stack,No_Relative_Delay,Partition-Wide Restrictions
12542 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-requeue-statements}@anchor{1e3}
12543 @subsection No_Requeue_Statements
12546 @geindex No_Requeue_Statements
12548 [RM D.7] This restriction ensures at compile time that no requeue statements
12549 are permitted and prevents keyword @code{requeue} from being used in source
12552 @geindex No_Requeue
12554 The restriction @code{No_Requeue} is recognized as a
12555 synonym for @code{No_Requeue_Statements}. This is retained for historical
12556 compatibility purposes (and a warning will be generated for its use if
12557 warnings on oNobsolescent features are activated).
12559 @node No_Secondary_Stack,No_Select_Statements,No_Requeue_Statements,Partition-Wide Restrictions
12560 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-secondary-stack}@anchor{1e4}
12561 @subsection No_Secondary_Stack
12564 @geindex No_Secondary_Stack
12566 [GNAT] This restriction ensures at compile time that the generated code
12567 does not contain any reference to the secondary stack. The secondary
12568 stack is used to implement functions returning unconstrained objects
12569 (arrays or records) on some targets. Suppresses the allocation of
12570 secondary stacks for tasks (excluding the environment task) at run time.
12572 @node No_Select_Statements,No_Specific_Termination_Handlers,No_Secondary_Stack,Partition-Wide Restrictions
12573 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-select-statements}@anchor{1e5}
12574 @subsection No_Select_Statements
12577 @geindex No_Select_Statements
12579 [RM D.7] This restriction ensures at compile time no select statements of any
12580 kind are permitted, that is the keyword @code{select} may not appear.
12582 @node No_Specific_Termination_Handlers,No_Specification_of_Aspect,No_Select_Statements,Partition-Wide Restrictions
12583 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-specific-termination-handlers}@anchor{1e6}
12584 @subsection No_Specific_Termination_Handlers
12587 @geindex No_Specific_Termination_Handlers
12589 [RM D.7] There are no calls to Ada.Task_Termination.Set_Specific_Handler
12590 or to Ada.Task_Termination.Specific_Handler.
12592 @node No_Specification_of_Aspect,No_Standard_Allocators_After_Elaboration,No_Specific_Termination_Handlers,Partition-Wide Restrictions
12593 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-specification-of-aspect}@anchor{1e7}
12594 @subsection No_Specification_of_Aspect
12597 @geindex No_Specification_of_Aspect
12599 [RM 13.12.1] This restriction checks at compile time that no aspect
12600 specification, attribute definition clause, or pragma is given for a
12603 @node No_Standard_Allocators_After_Elaboration,No_Standard_Storage_Pools,No_Specification_of_Aspect,Partition-Wide Restrictions
12604 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-standard-allocators-after-elaboration}@anchor{1e8}
12605 @subsection No_Standard_Allocators_After_Elaboration
12608 @geindex No_Standard_Allocators_After_Elaboration
12610 [RM D.7] Specifies that an allocator using a standard storage pool
12611 should never be evaluated at run time after the elaboration of the
12612 library items of the partition has completed. Otherwise, Storage_Error
12615 @node No_Standard_Storage_Pools,No_Stream_Optimizations,No_Standard_Allocators_After_Elaboration,Partition-Wide Restrictions
12616 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-standard-storage-pools}@anchor{1e9}
12617 @subsection No_Standard_Storage_Pools
12620 @geindex No_Standard_Storage_Pools
12622 [GNAT] This restriction ensures at compile time that no access types
12623 use the standard default storage pool. Any access type declared must
12624 have an explicit Storage_Pool attribute defined specifying a
12625 user-defined storage pool.
12627 @node No_Stream_Optimizations,No_Streams,No_Standard_Storage_Pools,Partition-Wide Restrictions
12628 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-stream-optimizations}@anchor{1ea}
12629 @subsection No_Stream_Optimizations
12632 @geindex No_Stream_Optimizations
12634 [GNAT] This restriction affects the performance of stream operations on types
12635 @code{String}, @code{Wide_String} and @code{Wide_Wide_String}. By default, the
12636 compiler uses block reads and writes when manipulating @code{String} objects
12637 due to their supperior performance. When this restriction is in effect, the
12638 compiler performs all IO operations on a per-character basis.
12640 @node No_Streams,No_Task_Allocators,No_Stream_Optimizations,Partition-Wide Restrictions
12641 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-streams}@anchor{1eb}
12642 @subsection No_Streams
12645 @geindex No_Streams
12647 [GNAT] This restriction ensures at compile/bind time that there are no
12648 stream objects created and no use of stream attributes.
12649 This restriction does not forbid dependences on the package
12650 @code{Ada.Streams}. So it is permissible to with
12651 @code{Ada.Streams} (or another package that does so itself)
12652 as long as no actual stream objects are created and no
12653 stream attributes are used.
12655 Note that the use of restriction allows optimization of tagged types,
12656 since they do not need to worry about dispatching stream operations.
12657 To take maximum advantage of this space-saving optimization, any
12658 unit declaring a tagged type should be compiled with the restriction,
12659 though this is not required.
12661 @node No_Task_Allocators,No_Task_At_Interrupt_Priority,No_Streams,Partition-Wide Restrictions
12662 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-task-allocators}@anchor{1ec}
12663 @subsection No_Task_Allocators
12666 @geindex No_Task_Allocators
12668 [RM D.7] There are no allocators for task types
12669 or types containing task subcomponents.
12671 @node No_Task_At_Interrupt_Priority,No_Task_Attributes_Package,No_Task_Allocators,Partition-Wide Restrictions
12672 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-task-at-interrupt-priority}@anchor{1ed}
12673 @subsection No_Task_At_Interrupt_Priority
12676 @geindex No_Task_At_Interrupt_Priority
12678 [GNAT] This restriction ensures at compile time that there is no
12679 Interrupt_Priority aspect or pragma for a task or a task type. As
12680 a consequence, the tasks are always created with a priority below
12681 that an interrupt priority.
12683 @node No_Task_Attributes_Package,No_Task_Hierarchy,No_Task_At_Interrupt_Priority,Partition-Wide Restrictions
12684 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-task-attributes-package}@anchor{1ee}
12685 @subsection No_Task_Attributes_Package
12688 @geindex No_Task_Attributes_Package
12690 [GNAT] This restriction ensures at compile time that there are no implicit or
12691 explicit dependencies on the package @code{Ada.Task_Attributes}.
12693 @geindex No_Task_Attributes
12695 The restriction @code{No_Task_Attributes} is recognized as a synonym
12696 for @code{No_Task_Attributes_Package}. This is retained for historical
12697 compatibility purposes (and a warning will be generated for its use if
12698 warnings on obsolescent features are activated).
12700 @node No_Task_Hierarchy,No_Task_Termination,No_Task_Attributes_Package,Partition-Wide Restrictions
12701 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-task-hierarchy}@anchor{1ef}
12702 @subsection No_Task_Hierarchy
12705 @geindex No_Task_Hierarchy
12707 [RM D.7] All (non-environment) tasks depend
12708 directly on the environment task of the partition.
12710 @node No_Task_Termination,No_Tasking,No_Task_Hierarchy,Partition-Wide Restrictions
12711 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-task-termination}@anchor{1f0}
12712 @subsection No_Task_Termination
12715 @geindex No_Task_Termination
12717 [RM D.7] Tasks that terminate are erroneous.
12719 @node No_Tasking,No_Terminate_Alternatives,No_Task_Termination,Partition-Wide Restrictions
12720 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-tasking}@anchor{1f1}
12721 @subsection No_Tasking
12724 @geindex No_Tasking
12726 [GNAT] This restriction prevents the declaration of tasks or task types
12727 throughout the partition. It is similar in effect to the use of
12728 @code{Max_Tasks => 0} except that violations are caught at compile time
12729 and cause an error message to be output either by the compiler or
12732 @node No_Terminate_Alternatives,No_Unchecked_Access,No_Tasking,Partition-Wide Restrictions
12733 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-terminate-alternatives}@anchor{1f2}
12734 @subsection No_Terminate_Alternatives
12737 @geindex No_Terminate_Alternatives
12739 [RM D.7] There are no selective accepts with terminate alternatives.
12741 @node No_Unchecked_Access,No_Unchecked_Conversion,No_Terminate_Alternatives,Partition-Wide Restrictions
12742 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-unchecked-access}@anchor{1f3}
12743 @subsection No_Unchecked_Access
12746 @geindex No_Unchecked_Access
12748 [RM H.4] This restriction ensures at compile time that there are no
12749 occurrences of the Unchecked_Access attribute.
12751 @node No_Unchecked_Conversion,No_Unchecked_Deallocation,No_Unchecked_Access,Partition-Wide Restrictions
12752 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-unchecked-conversion}@anchor{1f4}
12753 @subsection No_Unchecked_Conversion
12756 @geindex No_Unchecked_Conversion
12758 [RM J.13] This restriction ensures at compile time that there are no semantic
12759 dependences on the predefined generic function Unchecked_Conversion.
12761 @node No_Unchecked_Deallocation,No_Use_Of_Entity,No_Unchecked_Conversion,Partition-Wide Restrictions
12762 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-unchecked-deallocation}@anchor{1f5}
12763 @subsection No_Unchecked_Deallocation
12766 @geindex No_Unchecked_Deallocation
12768 [RM J.13] This restriction ensures at compile time that there are no semantic
12769 dependences on the predefined generic procedure Unchecked_Deallocation.
12771 @node No_Use_Of_Entity,Pure_Barriers,No_Unchecked_Deallocation,Partition-Wide Restrictions
12772 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-use-of-entity}@anchor{1f6}
12773 @subsection No_Use_Of_Entity
12776 @geindex No_Use_Of_Entity
12778 [GNAT] This restriction ensures at compile time that there are no references
12779 to the entity given in the form
12782 No_Use_Of_Entity => Name
12785 where @code{Name} is the fully qualified entity, for example
12788 No_Use_Of_Entity => Ada.Text_IO.Put_Line
12791 @node Pure_Barriers,Simple_Barriers,No_Use_Of_Entity,Partition-Wide Restrictions
12792 @anchor{gnat_rm/standard_and_implementation_defined_restrictions pure-barriers}@anchor{1f7}
12793 @subsection Pure_Barriers
12796 @geindex Pure_Barriers
12798 [GNAT] This restriction ensures at compile time that protected entry
12799 barriers are restricted to:
12805 components of the protected object (excluding selection from dereferences),
12808 constant declarations,
12814 enumeration literals,
12823 character literals,
12826 implicitly defined comparison operators,
12829 uses of the Standard."not" operator,
12832 short-circuit operator,
12835 the Count attribute
12838 This restriction is a relaxation of the Simple_Barriers restriction,
12839 but still ensures absence of side effects, exceptions, and recursion
12840 during the evaluation of the barriers.
12842 @node Simple_Barriers,Static_Priorities,Pure_Barriers,Partition-Wide Restrictions
12843 @anchor{gnat_rm/standard_and_implementation_defined_restrictions simple-barriers}@anchor{1f8}
12844 @subsection Simple_Barriers
12847 @geindex Simple_Barriers
12849 [RM D.7] This restriction ensures at compile time that barriers in entry
12850 declarations for protected types are restricted to either static boolean
12851 expressions or references to simple boolean variables defined in the private
12852 part of the protected type. No other form of entry barriers is permitted.
12854 @geindex Boolean_Entry_Barriers
12856 The restriction @code{Boolean_Entry_Barriers} is recognized as a
12857 synonym for @code{Simple_Barriers}. This is retained for historical
12858 compatibility purposes (and a warning will be generated for its use if
12859 warnings on obsolescent features are activated).
12861 @node Static_Priorities,Static_Storage_Size,Simple_Barriers,Partition-Wide Restrictions
12862 @anchor{gnat_rm/standard_and_implementation_defined_restrictions static-priorities}@anchor{1f9}
12863 @subsection Static_Priorities
12866 @geindex Static_Priorities
12868 [GNAT] This restriction ensures at compile time that all priority expressions
12869 are static, and that there are no dependences on the package
12870 @code{Ada.Dynamic_Priorities}.
12872 @node Static_Storage_Size,,Static_Priorities,Partition-Wide Restrictions
12873 @anchor{gnat_rm/standard_and_implementation_defined_restrictions static-storage-size}@anchor{1fa}
12874 @subsection Static_Storage_Size
12877 @geindex Static_Storage_Size
12879 [GNAT] This restriction ensures at compile time that any expression appearing
12880 in a Storage_Size pragma or attribute definition clause is static.
12882 @node Program Unit Level Restrictions,,Partition-Wide Restrictions,Standard and Implementation Defined Restrictions
12883 @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}
12884 @section Program Unit Level Restrictions
12887 The second set of restriction identifiers
12888 does not require partition-wide consistency.
12889 The restriction may be enforced for a single
12890 compilation unit without any effect on any of the
12891 other compilation units in the partition.
12894 * No_Elaboration_Code::
12895 * No_Dynamic_Sized_Objects::
12897 * No_Implementation_Aspect_Specifications::
12898 * No_Implementation_Attributes::
12899 * No_Implementation_Identifiers::
12900 * No_Implementation_Pragmas::
12901 * No_Implementation_Restrictions::
12902 * No_Implementation_Units::
12903 * No_Implicit_Aliasing::
12904 * No_Implicit_Loops::
12905 * No_Obsolescent_Features::
12906 * No_Wide_Characters::
12911 @node No_Elaboration_Code,No_Dynamic_Sized_Objects,,Program Unit Level Restrictions
12912 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-elaboration-code}@anchor{1fd}
12913 @subsection No_Elaboration_Code
12916 @geindex No_Elaboration_Code
12918 [GNAT] This restriction ensures at compile time that no elaboration code is
12919 generated. Note that this is not the same condition as is enforced
12920 by pragma @code{Preelaborate}. There are cases in which pragma
12921 @code{Preelaborate} still permits code to be generated (e.g., code
12922 to initialize a large array to all zeroes), and there are cases of units
12923 which do not meet the requirements for pragma @code{Preelaborate},
12924 but for which no elaboration code is generated. Generally, it is
12925 the case that preelaborable units will meet the restrictions, with
12926 the exception of large aggregates initialized with an others_clause,
12927 and exception declarations (which generate calls to a run-time
12928 registry procedure). This restriction is enforced on
12929 a unit by unit basis, it need not be obeyed consistently
12930 throughout a partition.
12932 In the case of aggregates with others, if the aggregate has a dynamic
12933 size, there is no way to eliminate the elaboration code (such dynamic
12934 bounds would be incompatible with @code{Preelaborate} in any case). If
12935 the bounds are static, then use of this restriction actually modifies
12936 the code choice of the compiler to avoid generating a loop, and instead
12937 generate the aggregate statically if possible, no matter how many times
12938 the data for the others clause must be repeatedly generated.
12940 It is not possible to precisely document
12941 the constructs which are compatible with this restriction, since,
12942 unlike most other restrictions, this is not a restriction on the
12943 source code, but a restriction on the generated object code. For
12944 example, if the source contains a declaration:
12947 Val : constant Integer := X;
12950 where X is not a static constant, it may be possible, depending
12951 on complex optimization circuitry, for the compiler to figure
12952 out the value of X at compile time, in which case this initialization
12953 can be done by the loader, and requires no initialization code. It
12954 is not possible to document the precise conditions under which the
12955 optimizer can figure this out.
12957 Note that this the implementation of this restriction requires full
12958 code generation. If it is used in conjunction with "semantics only"
12959 checking, then some cases of violations may be missed.
12961 When this restriction is active, we are not requesting control-flow
12962 preservation with -fpreserve-control-flow, and the static elaboration model is
12963 used, the compiler is allowed to suppress the elaboration counter normally
12964 associated with the unit. This counter is typically used to check for access
12965 before elaboration and to control multiple elaboration attempts.
12967 @node No_Dynamic_Sized_Objects,No_Entry_Queue,No_Elaboration_Code,Program Unit Level Restrictions
12968 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-dynamic-sized-objects}@anchor{1fe}
12969 @subsection No_Dynamic_Sized_Objects
12972 @geindex No_Dynamic_Sized_Objects
12974 [GNAT] This restriction disallows certain constructs that might lead to the
12975 creation of dynamic-sized composite objects (or array or discriminated type).
12976 An array subtype indication is illegal if the bounds are not static
12977 or references to discriminants of an enclosing type.
12978 A discriminated subtype indication is illegal if the type has
12979 discriminant-dependent array components or a variant part, and the
12980 discriminants are not static. In addition, array and record aggregates are
12981 illegal in corresponding cases. Note that this restriction does not forbid
12982 access discriminants. It is often a good idea to combine this restriction
12983 with No_Secondary_Stack.
12985 @node No_Entry_Queue,No_Implementation_Aspect_Specifications,No_Dynamic_Sized_Objects,Program Unit Level Restrictions
12986 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-entry-queue}@anchor{1ff}
12987 @subsection No_Entry_Queue
12990 @geindex No_Entry_Queue
12992 [GNAT] This restriction is a declaration that any protected entry compiled in
12993 the scope of the restriction has at most one task waiting on the entry
12994 at any one time, and so no queue is required. This restriction is not
12995 checked at compile time. A program execution is erroneous if an attempt
12996 is made to queue a second task on such an entry.
12998 @node No_Implementation_Aspect_Specifications,No_Implementation_Attributes,No_Entry_Queue,Program Unit Level Restrictions
12999 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implementation-aspect-specifications}@anchor{200}
13000 @subsection No_Implementation_Aspect_Specifications
13003 @geindex No_Implementation_Aspect_Specifications
13005 [RM 13.12.1] This restriction checks at compile time that no
13006 GNAT-defined aspects are present. With this restriction, the only
13007 aspects that can be used are those defined in the Ada Reference Manual.
13009 @node No_Implementation_Attributes,No_Implementation_Identifiers,No_Implementation_Aspect_Specifications,Program Unit Level Restrictions
13010 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implementation-attributes}@anchor{201}
13011 @subsection No_Implementation_Attributes
13014 @geindex No_Implementation_Attributes
13016 [RM 13.12.1] This restriction checks at compile time that no
13017 GNAT-defined attributes are present. With this restriction, the only
13018 attributes that can be used are those defined in the Ada Reference
13021 @node No_Implementation_Identifiers,No_Implementation_Pragmas,No_Implementation_Attributes,Program Unit Level Restrictions
13022 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implementation-identifiers}@anchor{202}
13023 @subsection No_Implementation_Identifiers
13026 @geindex No_Implementation_Identifiers
13028 [RM 13.12.1] This restriction checks at compile time that no
13029 implementation-defined identifiers (marked with pragma Implementation_Defined)
13030 occur within language-defined packages.
13032 @node No_Implementation_Pragmas,No_Implementation_Restrictions,No_Implementation_Identifiers,Program Unit Level Restrictions
13033 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implementation-pragmas}@anchor{203}
13034 @subsection No_Implementation_Pragmas
13037 @geindex No_Implementation_Pragmas
13039 [RM 13.12.1] This restriction checks at compile time that no
13040 GNAT-defined pragmas are present. With this restriction, the only
13041 pragmas that can be used are those defined in the Ada Reference Manual.
13043 @node No_Implementation_Restrictions,No_Implementation_Units,No_Implementation_Pragmas,Program Unit Level Restrictions
13044 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implementation-restrictions}@anchor{204}
13045 @subsection No_Implementation_Restrictions
13048 @geindex No_Implementation_Restrictions
13050 [GNAT] This restriction checks at compile time that no GNAT-defined restriction
13051 identifiers (other than @code{No_Implementation_Restrictions} itself)
13052 are present. With this restriction, the only other restriction identifiers
13053 that can be used are those defined in the Ada Reference Manual.
13055 @node No_Implementation_Units,No_Implicit_Aliasing,No_Implementation_Restrictions,Program Unit Level Restrictions
13056 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implementation-units}@anchor{205}
13057 @subsection No_Implementation_Units
13060 @geindex No_Implementation_Units
13062 [RM 13.12.1] This restriction checks at compile time that there is no
13063 mention in the context clause of any implementation-defined descendants
13064 of packages Ada, Interfaces, or System.
13066 @node No_Implicit_Aliasing,No_Implicit_Loops,No_Implementation_Units,Program Unit Level Restrictions
13067 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-aliasing}@anchor{206}
13068 @subsection No_Implicit_Aliasing
13071 @geindex No_Implicit_Aliasing
13073 [GNAT] This restriction, which is not required to be partition-wide consistent,
13074 requires an explicit aliased keyword for an object to which 'Access,
13075 'Unchecked_Access, or 'Address is applied, and forbids entirely the use of
13076 the 'Unrestricted_Access attribute for objects. Note: the reason that
13077 Unrestricted_Access is forbidden is that it would require the prefix
13078 to be aliased, and in such cases, it can always be replaced by
13079 the standard attribute Unchecked_Access which is preferable.
13081 @node No_Implicit_Loops,No_Obsolescent_Features,No_Implicit_Aliasing,Program Unit Level Restrictions
13082 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-loops}@anchor{207}
13083 @subsection No_Implicit_Loops
13086 @geindex No_Implicit_Loops
13088 [GNAT] This restriction ensures that the generated code of the unit marked
13089 with this restriction does not contain any implicit @code{for} loops, either by
13090 modifying the generated code where possible, or by rejecting any construct
13091 that would otherwise generate an implicit @code{for} loop. If this restriction is
13092 active, it is possible to build large array aggregates with all static
13093 components without generating an intermediate temporary, and without generating
13094 a loop to initialize individual components. Otherwise, a loop is created for
13095 arrays larger than about 5000 scalar components. Note that if this restriction
13096 is set in the spec of a package, it will not apply to its body.
13098 @node No_Obsolescent_Features,No_Wide_Characters,No_Implicit_Loops,Program Unit Level Restrictions
13099 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-obsolescent-features}@anchor{208}
13100 @subsection No_Obsolescent_Features
13103 @geindex No_Obsolescent_Features
13105 [RM 13.12.1] This restriction checks at compile time that no obsolescent
13106 features are used, as defined in Annex J of the Ada Reference Manual.
13108 @node No_Wide_Characters,SPARK_05,No_Obsolescent_Features,Program Unit Level Restrictions
13109 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-wide-characters}@anchor{209}
13110 @subsection No_Wide_Characters
13113 @geindex No_Wide_Characters
13115 [GNAT] This restriction ensures at compile time that no uses of the types
13116 @code{Wide_Character} or @code{Wide_String} or corresponding wide
13118 appear, and that no wide or wide wide string or character literals
13119 appear in the program (that is literals representing characters not in
13120 type @code{Character}).
13122 @node SPARK_05,,No_Wide_Characters,Program Unit Level Restrictions
13123 @anchor{gnat_rm/standard_and_implementation_defined_restrictions spark-05}@anchor{20a}
13124 @subsection SPARK_05
13129 [GNAT] This restriction checks at compile time that some constructs
13130 forbidden in SPARK 2005 are not present. Error messages related to
13131 SPARK restriction have the form:
13134 violation of restriction "SPARK_05" at <source-location>
13140 The restriction @code{SPARK} is recognized as a
13141 synonym for @code{SPARK_05}. This is retained for historical
13142 compatibility purposes (and an unconditional warning will be generated
13143 for its use, advising replacement by @code{SPARK}).
13145 This is not a replacement for the semantic checks performed by the
13146 SPARK Examiner tool, as the compiler currently only deals with code,
13147 not SPARK 2005 annotations, and does not guarantee catching all
13148 cases of constructs forbidden by SPARK 2005.
13150 Thus it may well be the case that code which passes the compiler with
13151 the SPARK restriction is rejected by the SPARK Examiner, e.g. due to
13152 the different visibility rules of the Examiner based on SPARK 2005
13153 @code{inherit} annotations.
13155 This restriction can be useful in providing an initial filter for code
13156 developed using SPARK 2005, or in examining legacy code to see how far
13157 it is from meeting SPARK restrictions.
13159 The list below summarizes the checks that are performed when this
13160 restriction is in force:
13166 No block statements
13169 No case statements with only an others clause
13172 Exit statements in loops must respect the SPARK 2005 language restrictions
13178 Return can only appear as last statement in function
13181 Function must have return statement
13184 Loop parameter specification must include subtype mark
13187 Prefix of expanded name cannot be a loop statement
13190 Abstract subprogram not allowed
13193 User-defined operators not allowed
13196 Access type parameters not allowed
13199 Default expressions for parameters not allowed
13202 Default expressions for record fields not allowed
13205 No tasking constructs allowed
13208 Label needed at end of subprograms and packages
13211 No mixing of positional and named parameter association
13214 No access types as result type
13217 No unconstrained arrays as result types
13223 Initial and later declarations must be in correct order (declaration can't come after body)
13226 No attributes on private types if full declaration not visible
13229 No package declaration within package specification
13232 No controlled types
13235 No discriminant types
13241 Selector name cannot be operator symbol (i.e. operator symbol cannot be prefixed)
13244 Access attribute not allowed
13247 Allocator not allowed
13250 Result of catenation must be String
13253 Operands of catenation must be string literal, static char or another catenation
13256 No conditional expressions
13259 No explicit dereference
13262 Quantified expression not allowed
13265 Slicing not allowed
13268 No exception renaming
13271 No generic renaming
13280 Aggregates must be qualified
13283 Nonstatic choice in array aggregates not allowed
13286 The only view conversions which are allowed as in-out parameters are conversions of a tagged type to an ancestor type
13289 No mixing of positional and named association in aggregate, no multi choice
13292 AND, OR and XOR for arrays only allowed when operands have same static bounds
13295 Fixed point operands to * or / must be qualified or converted
13298 Comparison operators not allowed for Booleans or arrays (except strings)
13301 Equality not allowed for arrays with non-matching static bounds (except strings)
13304 Conversion / qualification not allowed for arrays with non-matching static bounds
13307 Subprogram declaration only allowed in package spec (unless followed by import)
13310 Access types not allowed
13313 Incomplete type declaration not allowed
13316 Object and subtype declarations must respect SPARK restrictions
13319 Digits or delta constraint not allowed
13322 Decimal fixed point type not allowed
13325 Aliasing of objects not allowed
13328 Modular type modulus must be power of 2
13331 Base not allowed on subtype mark
13334 Unary operators not allowed on modular types (except not)
13337 Untagged record cannot be null
13340 No class-wide operations
13343 Initialization expressions must respect SPARK restrictions
13346 Nonstatic ranges not allowed except in iteration schemes
13349 String subtypes must have lower bound of 1
13352 Subtype of Boolean cannot have constraint
13355 At most one tagged type or extension per package
13358 Interface is not allowed
13361 Character literal cannot be prefixed (selector name cannot be character literal)
13364 Record aggregate cannot contain 'others'
13367 Component association in record aggregate must contain a single choice
13370 Ancestor part cannot be a type mark
13373 Attributes 'Image, 'Width and 'Value not allowed
13376 Functions may not update globals
13379 Subprograms may not contain direct calls to themselves (prevents recursion within unit)
13382 Call to subprogram not allowed in same unit before body has been seen (prevents recursion within unit)
13385 The following restrictions are enforced, but note that they are actually more
13386 strict that the latest SPARK 2005 language definition:
13392 No derived types other than tagged type extensions
13395 Subtype of unconstrained array must have constraint
13398 This list summarises the main SPARK 2005 language rules that are not
13399 currently checked by the SPARK_05 restriction:
13405 SPARK annotations are treated as comments so are not checked at all
13408 Based real literals not allowed
13411 Objects cannot be initialized at declaration by calls to user-defined functions
13414 Objects cannot be initialized at declaration by assignments from variables
13417 Objects cannot be initialized at declaration by assignments from indexed/selected components
13420 Ranges shall not be null
13423 A fixed point delta expression must be a simple expression
13426 Restrictions on where renaming declarations may be placed
13429 Externals of mode 'out' cannot be referenced
13432 Externals of mode 'in' cannot be updated
13435 Loop with no iteration scheme or exits only allowed as last statement in main program or task
13438 Subprogram cannot have parent unit name
13441 SPARK 2005 inherited subprogram must be prefixed with overriding
13444 External variables (or functions that reference them) may not be passed as actual parameters
13447 Globals must be explicitly mentioned in contract
13450 Deferred constants cannot be completed by pragma Import
13453 Package initialization cannot read/write variables from other packages
13456 Prefix not allowed for entities that are directly visible
13459 Identifier declaration can't override inherited package name
13462 Cannot use Standard or other predefined packages as identifiers
13465 After renaming, cannot use the original name
13468 Subprograms can only be renamed to remove package prefix
13471 Pragma import must be immediately after entity it names
13474 No mutual recursion between multiple units (this can be checked with gnatcheck)
13477 Note that if a unit is compiled in Ada 95 mode with the SPARK restriction,
13478 violations will be reported for constructs forbidden in SPARK 95,
13479 instead of SPARK 2005.
13481 @node Implementation Advice,Implementation Defined Characteristics,Standard and Implementation Defined Restrictions,Top
13482 @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}
13483 @chapter Implementation Advice
13486 The main text of the Ada Reference Manual describes the required
13487 behavior of all Ada compilers, and the GNAT compiler conforms to
13488 these requirements.
13490 In addition, there are sections throughout the Ada Reference Manual headed
13491 by the phrase 'Implementation advice'. These sections are not normative,
13492 i.e., they do not specify requirements that all compilers must
13493 follow. Rather they provide advice on generally desirable behavior.
13494 They are not requirements, because they describe behavior that cannot
13495 be provided on all systems, or may be undesirable on some systems.
13497 As far as practical, GNAT follows the implementation advice in
13498 the Ada Reference Manual. Each such RM section corresponds to a section
13499 in this chapter whose title specifies the
13500 RM section number and paragraph number and the subject of
13501 the advice. The contents of each section consists of the RM text within
13503 followed by the GNAT interpretation of the advice. Most often, this simply says
13504 'followed', which means that GNAT follows the advice. However, in a
13505 number of cases, GNAT deliberately deviates from this advice, in which
13506 case the text describes what GNAT does and why.
13508 @geindex Error detection
13511 * RM 1.1.3(20); Error Detection: RM 1 1 3 20 Error Detection.
13512 * RM 1.1.3(31); Child Units: RM 1 1 3 31 Child Units.
13513 * RM 1.1.5(12); Bounded Errors: RM 1 1 5 12 Bounded Errors.
13514 * RM 2.8(16); Pragmas: RM 2 8 16 Pragmas.
13515 * RM 2.8(17-19); Pragmas: RM 2 8 17-19 Pragmas.
13516 * RM 3.5.2(5); Alternative Character Sets: RM 3 5 2 5 Alternative Character Sets.
13517 * RM 3.5.4(28); Integer Types: RM 3 5 4 28 Integer Types.
13518 * RM 3.5.4(29); Integer Types: RM 3 5 4 29 Integer Types.
13519 * RM 3.5.5(8); Enumeration Values: RM 3 5 5 8 Enumeration Values.
13520 * RM 3.5.7(17); Float Types: RM 3 5 7 17 Float Types.
13521 * RM 3.6.2(11); Multidimensional Arrays: RM 3 6 2 11 Multidimensional Arrays.
13522 * RM 9.6(30-31); Duration'Small: RM 9 6 30-31 Duration'Small.
13523 * RM 10.2.1(12); Consistent Representation: RM 10 2 1 12 Consistent Representation.
13524 * RM 11.4.1(19); Exception Information: RM 11 4 1 19 Exception Information.
13525 * RM 11.5(28); Suppression of Checks: RM 11 5 28 Suppression of Checks.
13526 * RM 13.1 (21-24); Representation Clauses: RM 13 1 21-24 Representation Clauses.
13527 * RM 13.2(6-8); Packed Types: RM 13 2 6-8 Packed Types.
13528 * RM 13.3(14-19); Address Clauses: RM 13 3 14-19 Address Clauses.
13529 * RM 13.3(29-35); Alignment Clauses: RM 13 3 29-35 Alignment Clauses.
13530 * RM 13.3(42-43); Size Clauses: RM 13 3 42-43 Size Clauses.
13531 * RM 13.3(50-56); Size Clauses: RM 13 3 50-56 Size Clauses.
13532 * RM 13.3(71-73); Component Size Clauses: RM 13 3 71-73 Component Size Clauses.
13533 * RM 13.4(9-10); Enumeration Representation Clauses: RM 13 4 9-10 Enumeration Representation Clauses.
13534 * RM 13.5.1(17-22); Record Representation Clauses: RM 13 5 1 17-22 Record Representation Clauses.
13535 * RM 13.5.2(5); Storage Place Attributes: RM 13 5 2 5 Storage Place Attributes.
13536 * RM 13.5.3(7-8); Bit Ordering: RM 13 5 3 7-8 Bit Ordering.
13537 * RM 13.7(37); Address as Private: RM 13 7 37 Address as Private.
13538 * RM 13.7.1(16); Address Operations: RM 13 7 1 16 Address Operations.
13539 * RM 13.9(14-17); Unchecked Conversion: RM 13 9 14-17 Unchecked Conversion.
13540 * RM 13.11(23-25); Implicit Heap Usage: RM 13 11 23-25 Implicit Heap Usage.
13541 * RM 13.11.2(17); Unchecked Deallocation: RM 13 11 2 17 Unchecked Deallocation.
13542 * RM 13.13.2(17); Stream Oriented Attributes: RM 13 13 2 17 Stream Oriented Attributes.
13543 * RM A.1(52); Names of Predefined Numeric Types: RM A 1 52 Names of Predefined Numeric Types.
13544 * RM A.3.2(49); Ada.Characters.Handling: RM A 3 2 49 Ada Characters Handling.
13545 * RM A.4.4(106); Bounded-Length String Handling: RM A 4 4 106 Bounded-Length String Handling.
13546 * RM A.5.2(46-47); Random Number Generation: RM A 5 2 46-47 Random Number Generation.
13547 * RM A.10.7(23); Get_Immediate: RM A 10 7 23 Get_Immediate.
13548 * RM B.1(39-41); Pragma Export: RM B 1 39-41 Pragma Export.
13549 * RM B.2(12-13); Package Interfaces: RM B 2 12-13 Package Interfaces.
13550 * RM B.3(63-71); Interfacing with C: RM B 3 63-71 Interfacing with C.
13551 * RM B.4(95-98); Interfacing with COBOL: RM B 4 95-98 Interfacing with COBOL.
13552 * RM B.5(22-26); Interfacing with Fortran: RM B 5 22-26 Interfacing with Fortran.
13553 * RM C.1(3-5); Access to Machine Operations: RM C 1 3-5 Access to Machine Operations.
13554 * RM C.1(10-16); Access to Machine Operations: RM C 1 10-16 Access to Machine Operations.
13555 * RM C.3(28); Interrupt Support: RM C 3 28 Interrupt Support.
13556 * RM C.3.1(20-21); Protected Procedure Handlers: RM C 3 1 20-21 Protected Procedure Handlers.
13557 * RM C.3.2(25); Package Interrupts: RM C 3 2 25 Package Interrupts.
13558 * RM C.4(14); Pre-elaboration Requirements: RM C 4 14 Pre-elaboration Requirements.
13559 * RM C.5(8); Pragma Discard_Names: RM C 5 8 Pragma Discard_Names.
13560 * RM C.7.2(30); The Package Task_Attributes: RM C 7 2 30 The Package Task_Attributes.
13561 * RM D.3(17); Locking Policies: RM D 3 17 Locking Policies.
13562 * RM D.4(16); Entry Queuing Policies: RM D 4 16 Entry Queuing Policies.
13563 * RM D.6(9-10); Preemptive Abort: RM D 6 9-10 Preemptive Abort.
13564 * RM D.7(21); Tasking Restrictions: RM D 7 21 Tasking Restrictions.
13565 * RM D.8(47-49); Monotonic Time: RM D 8 47-49 Monotonic Time.
13566 * RM E.5(28-29); Partition Communication Subsystem: RM E 5 28-29 Partition Communication Subsystem.
13567 * RM F(7); COBOL Support: RM F 7 COBOL Support.
13568 * RM F.1(2); Decimal Radix Support: RM F 1 2 Decimal Radix Support.
13569 * RM G; Numerics: RM G Numerics.
13570 * RM G.1.1(56-58); Complex Types: RM G 1 1 56-58 Complex Types.
13571 * RM G.1.2(49); Complex Elementary Functions: RM G 1 2 49 Complex Elementary Functions.
13572 * RM G.2.4(19); Accuracy Requirements: RM G 2 4 19 Accuracy Requirements.
13573 * RM G.2.6(15); Complex Arithmetic Accuracy: RM G 2 6 15 Complex Arithmetic Accuracy.
13574 * RM H.6(15/2); Pragma Partition_Elaboration_Policy: RM H 6 15/2 Pragma Partition_Elaboration_Policy.
13578 @node RM 1 1 3 20 Error Detection,RM 1 1 3 31 Child Units,,Implementation Advice
13579 @anchor{gnat_rm/implementation_advice rm-1-1-3-20-error-detection}@anchor{20d}
13580 @section RM 1.1.3(20): Error Detection
13585 "If an implementation detects the use of an unsupported Specialized Needs
13586 Annex feature at run time, it should raise @code{Program_Error} if
13590 Not relevant. All specialized needs annex features are either supported,
13591 or diagnosed at compile time.
13593 @geindex Child Units
13595 @node RM 1 1 3 31 Child Units,RM 1 1 5 12 Bounded Errors,RM 1 1 3 20 Error Detection,Implementation Advice
13596 @anchor{gnat_rm/implementation_advice rm-1-1-3-31-child-units}@anchor{20e}
13597 @section RM 1.1.3(31): Child Units
13602 "If an implementation wishes to provide implementation-defined
13603 extensions to the functionality of a language-defined library unit, it
13604 should normally do so by adding children to the library unit."
13609 @geindex Bounded errors
13611 @node RM 1 1 5 12 Bounded Errors,RM 2 8 16 Pragmas,RM 1 1 3 31 Child Units,Implementation Advice
13612 @anchor{gnat_rm/implementation_advice rm-1-1-5-12-bounded-errors}@anchor{20f}
13613 @section RM 1.1.5(12): Bounded Errors
13618 "If an implementation detects a bounded error or erroneous
13619 execution, it should raise @code{Program_Error}."
13622 Followed in all cases in which the implementation detects a bounded
13623 error or erroneous execution. Not all such situations are detected at
13628 @node RM 2 8 16 Pragmas,RM 2 8 17-19 Pragmas,RM 1 1 5 12 Bounded Errors,Implementation Advice
13629 @anchor{gnat_rm/implementation_advice id2}@anchor{210}@anchor{gnat_rm/implementation_advice rm-2-8-16-pragmas}@anchor{211}
13630 @section RM 2.8(16): Pragmas
13635 "Normally, implementation-defined pragmas should have no semantic effect
13636 for error-free programs; that is, if the implementation-defined pragmas
13637 are removed from a working program, the program should still be legal,
13638 and should still have the same semantics."
13641 The following implementation defined pragmas are exceptions to this
13645 @multitable {xxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxx}
13688 @emph{CPP_Constructor}
13704 @emph{Interface_Name}
13712 @emph{Machine_Attribute}
13720 @emph{Unimplemented_Unit}
13728 @emph{Unchecked_Union}
13737 In each of the above cases, it is essential to the purpose of the pragma
13738 that this advice not be followed. For details see
13739 @ref{7,,Implementation Defined Pragmas}.
13741 @node RM 2 8 17-19 Pragmas,RM 3 5 2 5 Alternative Character Sets,RM 2 8 16 Pragmas,Implementation Advice
13742 @anchor{gnat_rm/implementation_advice rm-2-8-17-19-pragmas}@anchor{212}
13743 @section RM 2.8(17-19): Pragmas
13748 "Normally, an implementation should not define pragmas that can
13749 make an illegal program legal, except as follows:
13755 A pragma used to complete a declaration, such as a pragma @code{Import};
13758 A pragma used to configure the environment by adding, removing, or
13759 replacing @code{library_items}."
13763 See @ref{211,,RM 2.8(16); Pragmas}.
13765 @geindex Character Sets
13767 @geindex Alternative Character Sets
13769 @node RM 3 5 2 5 Alternative Character Sets,RM 3 5 4 28 Integer Types,RM 2 8 17-19 Pragmas,Implementation Advice
13770 @anchor{gnat_rm/implementation_advice rm-3-5-2-5-alternative-character-sets}@anchor{213}
13771 @section RM 3.5.2(5): Alternative Character Sets
13776 "If an implementation supports a mode with alternative interpretations
13777 for @code{Character} and @code{Wide_Character}, the set of graphic
13778 characters of @code{Character} should nevertheless remain a proper
13779 subset of the set of graphic characters of @code{Wide_Character}. Any
13780 character set 'localizations' should be reflected in the results of
13781 the subprograms defined in the language-defined package
13782 @code{Characters.Handling} (see A.3) available in such a mode. In a mode with
13783 an alternative interpretation of @code{Character}, the implementation should
13784 also support a corresponding change in what is a legal
13785 @code{identifier_letter}."
13788 Not all wide character modes follow this advice, in particular the JIS
13789 and IEC modes reflect standard usage in Japan, and in these encoding,
13790 the upper half of the Latin-1 set is not part of the wide-character
13791 subset, since the most significant bit is used for wide character
13792 encoding. However, this only applies to the external forms. Internally
13793 there is no such restriction.
13795 @geindex Integer types
13797 @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
13798 @anchor{gnat_rm/implementation_advice rm-3-5-4-28-integer-types}@anchor{214}
13799 @section RM 3.5.4(28): Integer Types
13804 "An implementation should support @code{Long_Integer} in addition to
13805 @code{Integer} if the target machine supports 32-bit (or longer)
13806 arithmetic. No other named integer subtypes are recommended for package
13807 @code{Standard}. Instead, appropriate named integer subtypes should be
13808 provided in the library package @code{Interfaces} (see B.2)."
13811 @code{Long_Integer} is supported. Other standard integer types are supported
13812 so this advice is not fully followed. These types
13813 are supported for convenient interface to C, and so that all hardware
13814 types of the machine are easily available.
13816 @node RM 3 5 4 29 Integer Types,RM 3 5 5 8 Enumeration Values,RM 3 5 4 28 Integer Types,Implementation Advice
13817 @anchor{gnat_rm/implementation_advice rm-3-5-4-29-integer-types}@anchor{215}
13818 @section RM 3.5.4(29): Integer Types
13823 "An implementation for a two's complement machine should support
13824 modular types with a binary modulus up to @code{System.Max_Int*2+2}. An
13825 implementation should support a non-binary modules up to @code{Integer'Last}."
13830 @geindex Enumeration values
13832 @node RM 3 5 5 8 Enumeration Values,RM 3 5 7 17 Float Types,RM 3 5 4 29 Integer Types,Implementation Advice
13833 @anchor{gnat_rm/implementation_advice rm-3-5-5-8-enumeration-values}@anchor{216}
13834 @section RM 3.5.5(8): Enumeration Values
13839 "For the evaluation of a call on @code{S'Pos} for an enumeration
13840 subtype, if the value of the operand does not correspond to the internal
13841 code for any enumeration literal of its type (perhaps due to an
13842 un-initialized variable), then the implementation should raise
13843 @code{Program_Error}. This is particularly important for enumeration
13844 types with noncontiguous internal codes specified by an
13845 enumeration_representation_clause."
13850 @geindex Float types
13852 @node RM 3 5 7 17 Float Types,RM 3 6 2 11 Multidimensional Arrays,RM 3 5 5 8 Enumeration Values,Implementation Advice
13853 @anchor{gnat_rm/implementation_advice rm-3-5-7-17-float-types}@anchor{217}
13854 @section RM 3.5.7(17): Float Types
13859 "An implementation should support @code{Long_Float} in addition to
13860 @code{Float} if the target machine supports 11 or more digits of
13861 precision. No other named floating point subtypes are recommended for
13862 package @code{Standard}. Instead, appropriate named floating point subtypes
13863 should be provided in the library package @code{Interfaces} (see B.2)."
13866 @code{Short_Float} and @code{Long_Long_Float} are also provided. The
13867 former provides improved compatibility with other implementations
13868 supporting this type. The latter corresponds to the highest precision
13869 floating-point type supported by the hardware. On most machines, this
13870 will be the same as @code{Long_Float}, but on some machines, it will
13871 correspond to the IEEE extended form. The notable case is all ia32
13872 (x86) implementations, where @code{Long_Long_Float} corresponds to
13873 the 80-bit extended precision format supported in hardware on this
13874 processor. Note that the 128-bit format on SPARC is not supported,
13875 since this is a software rather than a hardware format.
13877 @geindex Multidimensional arrays
13880 @geindex multidimensional
13882 @node RM 3 6 2 11 Multidimensional Arrays,RM 9 6 30-31 Duration'Small,RM 3 5 7 17 Float Types,Implementation Advice
13883 @anchor{gnat_rm/implementation_advice rm-3-6-2-11-multidimensional-arrays}@anchor{218}
13884 @section RM 3.6.2(11): Multidimensional Arrays
13889 "An implementation should normally represent multidimensional arrays in
13890 row-major order, consistent with the notation used for multidimensional
13891 array aggregates (see 4.3.3). However, if a pragma @code{Convention}
13892 (@code{Fortran}, ...) applies to a multidimensional array type, then
13893 column-major order should be used instead (see B.5, @emph{Interfacing with Fortran})."
13898 @geindex Duration'Small
13900 @node RM 9 6 30-31 Duration'Small,RM 10 2 1 12 Consistent Representation,RM 3 6 2 11 Multidimensional Arrays,Implementation Advice
13901 @anchor{gnat_rm/implementation_advice rm-9-6-30-31-duration-small}@anchor{219}
13902 @section RM 9.6(30-31): Duration'Small
13907 "Whenever possible in an implementation, the value of @code{Duration'Small}
13908 should be no greater than 100 microseconds."
13911 Followed. (@code{Duration'Small} = 10**(-9)).
13915 "The time base for @code{delay_relative_statements} should be monotonic;
13916 it need not be the same time base as used for @code{Calendar.Clock}."
13921 @node RM 10 2 1 12 Consistent Representation,RM 11 4 1 19 Exception Information,RM 9 6 30-31 Duration'Small,Implementation Advice
13922 @anchor{gnat_rm/implementation_advice rm-10-2-1-12-consistent-representation}@anchor{21a}
13923 @section RM 10.2.1(12): Consistent Representation
13928 "In an implementation, a type declared in a pre-elaborated package should
13929 have the same representation in every elaboration of a given version of
13930 the package, whether the elaborations occur in distinct executions of
13931 the same program, or in executions of distinct programs or partitions
13932 that include the given version."
13935 Followed, except in the case of tagged types. Tagged types involve
13936 implicit pointers to a local copy of a dispatch table, and these pointers
13937 have representations which thus depend on a particular elaboration of the
13938 package. It is not easy to see how it would be possible to follow this
13939 advice without severely impacting efficiency of execution.
13941 @geindex Exception information
13943 @node RM 11 4 1 19 Exception Information,RM 11 5 28 Suppression of Checks,RM 10 2 1 12 Consistent Representation,Implementation Advice
13944 @anchor{gnat_rm/implementation_advice rm-11-4-1-19-exception-information}@anchor{21b}
13945 @section RM 11.4.1(19): Exception Information
13950 "@code{Exception_Message} by default and @code{Exception_Information}
13951 should produce information useful for
13952 debugging. @code{Exception_Message} should be short, about one
13953 line. @code{Exception_Information} can be long. @code{Exception_Message}
13954 should not include the
13955 @code{Exception_Name}. @code{Exception_Information} should include both
13956 the @code{Exception_Name} and the @code{Exception_Message}."
13959 Followed. For each exception that doesn't have a specified
13960 @code{Exception_Message}, the compiler generates one containing the location
13961 of the raise statement. This location has the form 'file_name:line', where
13962 file_name is the short file name (without path information) and line is the line
13963 number in the file. Note that in the case of the Zero Cost Exception
13964 mechanism, these messages become redundant with the Exception_Information that
13965 contains a full backtrace of the calling sequence, so they are disabled.
13966 To disable explicitly the generation of the source location message, use the
13967 Pragma @code{Discard_Names}.
13969 @geindex Suppression of checks
13972 @geindex suppression of
13974 @node RM 11 5 28 Suppression of Checks,RM 13 1 21-24 Representation Clauses,RM 11 4 1 19 Exception Information,Implementation Advice
13975 @anchor{gnat_rm/implementation_advice rm-11-5-28-suppression-of-checks}@anchor{21c}
13976 @section RM 11.5(28): Suppression of Checks
13981 "The implementation should minimize the code executed for checks that
13982 have been suppressed."
13987 @geindex Representation clauses
13989 @node RM 13 1 21-24 Representation Clauses,RM 13 2 6-8 Packed Types,RM 11 5 28 Suppression of Checks,Implementation Advice
13990 @anchor{gnat_rm/implementation_advice rm-13-1-21-24-representation-clauses}@anchor{21d}
13991 @section RM 13.1 (21-24): Representation Clauses
13996 "The recommended level of support for all representation items is
13997 qualified as follows:
13999 An implementation need not support representation items containing
14000 nonstatic expressions, except that an implementation should support a
14001 representation item for a given entity if each nonstatic expression in
14002 the representation item is a name that statically denotes a constant
14003 declared before the entity."
14006 Followed. In fact, GNAT goes beyond the recommended level of support
14007 by allowing nonstatic expressions in some representation clauses even
14008 without the need to declare constants initialized with the values of
14015 for Y'Address use X'Address;>>
14018 "An implementation need not support a specification for the `@w{`}Size`@w{`}
14019 for a given composite subtype, nor the size or storage place for an
14020 object (including a component) of a given composite subtype, unless the
14021 constraints on the subtype and its composite subcomponents (if any) are
14022 all static constraints."
14025 Followed. Size Clauses are not permitted on nonstatic components, as
14030 "An aliased component, or a component whose type is by-reference, should
14031 always be allocated at an addressable location."
14036 @geindex Packed types
14038 @node RM 13 2 6-8 Packed Types,RM 13 3 14-19 Address Clauses,RM 13 1 21-24 Representation Clauses,Implementation Advice
14039 @anchor{gnat_rm/implementation_advice rm-13-2-6-8-packed-types}@anchor{21e}
14040 @section RM 13.2(6-8): Packed Types
14045 "If a type is packed, then the implementation should try to minimize
14046 storage allocated to objects of the type, possibly at the expense of
14047 speed of accessing components, subject to reasonable complexity in
14048 addressing calculations.
14050 The recommended level of support pragma @code{Pack} is:
14052 For a packed record type, the components should be packed as tightly as
14053 possible subject to the Sizes of the component subtypes, and subject to
14054 any @emph{record_representation_clause} that applies to the type; the
14055 implementation may, but need not, reorder components or cross aligned
14056 word boundaries to improve the packing. A component whose @code{Size} is
14057 greater than the word size may be allocated an integral number of words."
14060 Followed. Tight packing of arrays is supported for all component sizes
14061 up to 64-bits. If the array component size is 1 (that is to say, if
14062 the component is a boolean type or an enumeration type with two values)
14063 then values of the type are implicitly initialized to zero. This
14064 happens both for objects of the packed type, and for objects that have a
14065 subcomponent of the packed type.
14069 "An implementation should support Address clauses for imported
14075 @geindex Address clauses
14077 @node RM 13 3 14-19 Address Clauses,RM 13 3 29-35 Alignment Clauses,RM 13 2 6-8 Packed Types,Implementation Advice
14078 @anchor{gnat_rm/implementation_advice rm-13-3-14-19-address-clauses}@anchor{21f}
14079 @section RM 13.3(14-19): Address Clauses
14084 "For an array @code{X}, @code{X'Address} should point at the first
14085 component of the array, and not at the array bounds."
14092 "The recommended level of support for the @code{Address} attribute is:
14094 @code{X'Address} should produce a useful result if @code{X} is an
14095 object that is aliased or of a by-reference type, or is an entity whose
14096 @code{Address} has been specified."
14099 Followed. A valid address will be produced even if none of those
14100 conditions have been met. If necessary, the object is forced into
14101 memory to ensure the address is valid.
14105 "An implementation should support @code{Address} clauses for imported
14113 "Objects (including subcomponents) that are aliased or of a by-reference
14114 type should be allocated on storage element boundaries."
14121 "If the @code{Address} of an object is specified, or it is imported or exported,
14122 then the implementation should not perform optimizations based on
14123 assumptions of no aliases."
14128 @geindex Alignment clauses
14130 @node RM 13 3 29-35 Alignment Clauses,RM 13 3 42-43 Size Clauses,RM 13 3 14-19 Address Clauses,Implementation Advice
14131 @anchor{gnat_rm/implementation_advice rm-13-3-29-35-alignment-clauses}@anchor{220}
14132 @section RM 13.3(29-35): Alignment Clauses
14137 "The recommended level of support for the @code{Alignment} attribute for
14140 An implementation should support specified Alignments that are factors
14141 and multiples of the number of storage elements per word, subject to the
14149 "An implementation need not support specified Alignments for
14150 combinations of Sizes and Alignments that cannot be easily
14151 loaded and stored by available machine instructions."
14158 "An implementation need not support specified Alignments that are
14159 greater than the maximum @code{Alignment} the implementation ever returns by
14167 "The recommended level of support for the @code{Alignment} attribute for
14170 Same as above, for subtypes, but in addition:"
14177 "For stand-alone library-level objects of statically constrained
14178 subtypes, the implementation should support all alignments
14179 supported by the target linker. For example, page alignment is likely to
14180 be supported for such objects, but not for subtypes."
14185 @geindex Size clauses
14187 @node RM 13 3 42-43 Size Clauses,RM 13 3 50-56 Size Clauses,RM 13 3 29-35 Alignment Clauses,Implementation Advice
14188 @anchor{gnat_rm/implementation_advice rm-13-3-42-43-size-clauses}@anchor{221}
14189 @section RM 13.3(42-43): Size Clauses
14194 "The recommended level of support for the @code{Size} attribute of
14197 A @code{Size} clause should be supported for an object if the specified
14198 @code{Size} is at least as large as its subtype's @code{Size}, and
14199 corresponds to a size in storage elements that is a multiple of the
14200 object's @code{Alignment} (if the @code{Alignment} is nonzero)."
14205 @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
14206 @anchor{gnat_rm/implementation_advice rm-13-3-50-56-size-clauses}@anchor{222}
14207 @section RM 13.3(50-56): Size Clauses
14212 "If the @code{Size} of a subtype is specified, and allows for efficient
14213 independent addressability (see 9.10) on the target architecture, then
14214 the @code{Size} of the following objects of the subtype should equal the
14215 @code{Size} of the subtype:
14217 Aliased objects (including components)."
14224 "@cite{Size} clause on a composite subtype should not affect the
14225 internal layout of components."
14228 Followed. But note that this can be overridden by use of the implementation
14229 pragma Implicit_Packing in the case of packed arrays.
14233 "The recommended level of support for the @code{Size} attribute of subtypes is:
14235 The @code{Size} (if not specified) of a static discrete or fixed point
14236 subtype should be the number of bits needed to represent each value
14237 belonging to the subtype using an unbiased representation, leaving space
14238 for a sign bit only if the subtype contains negative values. If such a
14239 subtype is a first subtype, then an implementation should support a
14240 specified @code{Size} for it that reflects this representation."
14247 "For a subtype implemented with levels of indirection, the @code{Size}
14248 should include the size of the pointers, but not the size of what they
14254 @geindex Component_Size clauses
14256 @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
14257 @anchor{gnat_rm/implementation_advice rm-13-3-71-73-component-size-clauses}@anchor{223}
14258 @section RM 13.3(71-73): Component Size Clauses
14263 "The recommended level of support for the @code{Component_Size}
14266 An implementation need not support specified @code{Component_Sizes} that are
14267 less than the @code{Size} of the component subtype."
14274 "An implementation should support specified Component_Sizes that
14275 are factors and multiples of the word size. For such
14276 Component_Sizes, the array should contain no gaps between
14277 components. For other Component_Sizes (if supported), the array
14278 should contain no gaps between components when packing is also
14279 specified; the implementation should forbid this combination in cases
14280 where it cannot support a no-gaps representation."
14285 @geindex Enumeration representation clauses
14287 @geindex Representation clauses
14288 @geindex enumeration
14290 @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
14291 @anchor{gnat_rm/implementation_advice rm-13-4-9-10-enumeration-representation-clauses}@anchor{224}
14292 @section RM 13.4(9-10): Enumeration Representation Clauses
14297 "The recommended level of support for enumeration representation clauses
14300 An implementation need not support enumeration representation clauses
14301 for boolean types, but should at minimum support the internal codes in
14302 the range @code{System.Min_Int .. System.Max_Int}."
14307 @geindex Record representation clauses
14309 @geindex Representation clauses
14312 @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
14313 @anchor{gnat_rm/implementation_advice rm-13-5-1-17-22-record-representation-clauses}@anchor{225}
14314 @section RM 13.5.1(17-22): Record Representation Clauses
14319 "The recommended level of support for
14320 @emph{record_representation_clause}s is:
14322 An implementation should support storage places that can be extracted
14323 with a load, mask, shift sequence of machine code, and set with a load,
14324 shift, mask, store sequence, given the available machine instructions
14325 and run-time model."
14332 "A storage place should be supported if its size is equal to the
14333 @code{Size} of the component subtype, and it starts and ends on a
14334 boundary that obeys the @code{Alignment} of the component subtype."
14341 "If the default bit ordering applies to the declaration of a given type,
14342 then for a component whose subtype's @code{Size} is less than the word
14343 size, any storage place that does not cross an aligned word boundary
14344 should be supported."
14351 "An implementation may reserve a storage place for the tag field of a
14352 tagged type, and disallow other components from overlapping that place."
14355 Followed. The storage place for the tag field is the beginning of the tagged
14356 record, and its size is Address'Size. GNAT will reject an explicit component
14357 clause for the tag field.
14361 "An implementation need not support a @emph{component_clause} for a
14362 component of an extension part if the storage place is not after the
14363 storage places of all components of the parent type, whether or not
14364 those storage places had been specified."
14367 Followed. The above advice on record representation clauses is followed,
14368 and all mentioned features are implemented.
14370 @geindex Storage place attributes
14372 @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
14373 @anchor{gnat_rm/implementation_advice rm-13-5-2-5-storage-place-attributes}@anchor{226}
14374 @section RM 13.5.2(5): Storage Place Attributes
14379 "If a component is represented using some form of pointer (such as an
14380 offset) to the actual data of the component, and this data is contiguous
14381 with the rest of the object, then the storage place attributes should
14382 reflect the place of the actual data, not the pointer. If a component is
14383 allocated discontinuously from the rest of the object, then a warning
14384 should be generated upon reference to one of its storage place
14388 Followed. There are no such components in GNAT.
14390 @geindex Bit ordering
14392 @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
14393 @anchor{gnat_rm/implementation_advice rm-13-5-3-7-8-bit-ordering}@anchor{227}
14394 @section RM 13.5.3(7-8): Bit Ordering
14399 "The recommended level of support for the non-default bit ordering is:
14401 If @code{Word_Size} = @code{Storage_Unit}, then the implementation
14402 should support the non-default bit ordering in addition to the default
14406 Followed. Word size does not equal storage size in this implementation.
14407 Thus non-default bit ordering is not supported.
14410 @geindex as private type
14412 @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
14413 @anchor{gnat_rm/implementation_advice rm-13-7-37-address-as-private}@anchor{228}
14414 @section RM 13.7(37): Address as Private
14419 "@cite{Address} should be of a private type."
14424 @geindex Operations
14425 @geindex on `@w{`}Address`@w{`}
14428 @geindex operations of
14430 @node RM 13 7 1 16 Address Operations,RM 13 9 14-17 Unchecked Conversion,RM 13 7 37 Address as Private,Implementation Advice
14431 @anchor{gnat_rm/implementation_advice rm-13-7-1-16-address-operations}@anchor{229}
14432 @section RM 13.7.1(16): Address Operations
14437 "Operations in @code{System} and its children should reflect the target
14438 environment semantics as closely as is reasonable. For example, on most
14439 machines, it makes sense for address arithmetic to 'wrap around'.
14440 Operations that do not make sense should raise @code{Program_Error}."
14443 Followed. Address arithmetic is modular arithmetic that wraps around. No
14444 operation raises @code{Program_Error}, since all operations make sense.
14446 @geindex Unchecked conversion
14448 @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
14449 @anchor{gnat_rm/implementation_advice rm-13-9-14-17-unchecked-conversion}@anchor{22a}
14450 @section RM 13.9(14-17): Unchecked Conversion
14455 "The @code{Size} of an array object should not include its bounds; hence,
14456 the bounds should not be part of the converted data."
14463 "The implementation should not generate unnecessary run-time checks to
14464 ensure that the representation of @code{S} is a representation of the
14465 target type. It should take advantage of the permission to return by
14466 reference when possible. Restrictions on unchecked conversions should be
14467 avoided unless required by the target environment."
14470 Followed. There are no restrictions on unchecked conversion. A warning is
14471 generated if the source and target types do not have the same size since
14472 the semantics in this case may be target dependent.
14476 "The recommended level of support for unchecked conversions is:
14478 Unchecked conversions should be supported and should be reversible in
14479 the cases where this clause defines the result. To enable meaningful use
14480 of unchecked conversion, a contiguous representation should be used for
14481 elementary subtypes, for statically constrained array subtypes whose
14482 component subtype is one of the subtypes described in this paragraph,
14483 and for record subtypes without discriminants whose component subtypes
14484 are described in this paragraph."
14489 @geindex Heap usage
14492 @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
14493 @anchor{gnat_rm/implementation_advice rm-13-11-23-25-implicit-heap-usage}@anchor{22b}
14494 @section RM 13.11(23-25): Implicit Heap Usage
14499 "An implementation should document any cases in which it dynamically
14500 allocates heap storage for a purpose other than the evaluation of an
14504 Followed, the only other points at which heap storage is dynamically
14505 allocated are as follows:
14511 At initial elaboration time, to allocate dynamically sized global
14515 To allocate space for a task when a task is created.
14518 To extend the secondary stack dynamically when needed. The secondary
14519 stack is used for returning variable length results.
14525 "A default (implementation-provided) storage pool for an
14526 access-to-constant type should not have overhead to support deallocation of
14527 individual objects."
14534 "A storage pool for an anonymous access type should be created at the
14535 point of an allocator for the type, and be reclaimed when the designated
14536 object becomes inaccessible."
14541 @geindex Unchecked deallocation
14543 @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
14544 @anchor{gnat_rm/implementation_advice rm-13-11-2-17-unchecked-deallocation}@anchor{22c}
14545 @section RM 13.11.2(17): Unchecked Deallocation
14550 "For a standard storage pool, @code{Free} should actually reclaim the
14556 @geindex Stream oriented attributes
14558 @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
14559 @anchor{gnat_rm/implementation_advice rm-13-13-2-17-stream-oriented-attributes}@anchor{22d}
14560 @section RM 13.13.2(17): Stream Oriented Attributes
14565 "If a stream element is the same size as a storage element, then the
14566 normal in-memory representation should be used by @code{Read} and
14567 @code{Write} for scalar objects. Otherwise, @code{Read} and @code{Write}
14568 should use the smallest number of stream elements needed to represent
14569 all values in the base range of the scalar type."
14572 Followed. By default, GNAT uses the interpretation suggested by AI-195,
14573 which specifies using the size of the first subtype.
14574 However, such an implementation is based on direct binary
14575 representations and is therefore target- and endianness-dependent.
14576 To address this issue, GNAT also supplies an alternate implementation
14577 of the stream attributes @code{Read} and @code{Write},
14578 which uses the target-independent XDR standard representation
14581 @geindex XDR representation
14583 @geindex Read attribute
14585 @geindex Write attribute
14587 @geindex Stream oriented attributes
14589 The XDR implementation is provided as an alternative body of the
14590 @code{System.Stream_Attributes} package, in the file
14591 @code{s-stratt-xdr.adb} in the GNAT library.
14592 There is no @code{s-stratt-xdr.ads} file.
14593 In order to install the XDR implementation, do the following:
14599 Replace the default implementation of the
14600 @code{System.Stream_Attributes} package with the XDR implementation.
14601 For example on a Unix platform issue the commands:
14604 $ mv s-stratt.adb s-stratt-default.adb
14605 $ mv s-stratt-xdr.adb s-stratt.adb
14609 Rebuild the GNAT run-time library as documented in
14610 the @emph{GNAT and Libraries} section of the @cite{GNAT User's Guide}.
14613 @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
14614 @anchor{gnat_rm/implementation_advice rm-a-1-52-names-of-predefined-numeric-types}@anchor{22e}
14615 @section RM A.1(52): Names of Predefined Numeric Types
14620 "If an implementation provides additional named predefined integer types,
14621 then the names should end with @code{Integer} as in
14622 @code{Long_Integer}. If an implementation provides additional named
14623 predefined floating point types, then the names should end with
14624 @code{Float} as in @code{Long_Float}."
14629 @geindex Ada.Characters.Handling
14631 @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
14632 @anchor{gnat_rm/implementation_advice rm-a-3-2-49-ada-characters-handling}@anchor{22f}
14633 @section RM A.3.2(49): @code{Ada.Characters.Handling}
14638 "If an implementation provides a localized definition of @code{Character}
14639 or @code{Wide_Character}, then the effects of the subprograms in
14640 @code{Characters.Handling} should reflect the localizations.
14644 Followed. GNAT provides no such localized definitions.
14646 @geindex Bounded-length strings
14648 @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
14649 @anchor{gnat_rm/implementation_advice rm-a-4-4-106-bounded-length-string-handling}@anchor{230}
14650 @section RM A.4.4(106): Bounded-Length String Handling
14655 "Bounded string objects should not be implemented by implicit pointers
14656 and dynamic allocation."
14659 Followed. No implicit pointers or dynamic allocation are used.
14661 @geindex Random number generation
14663 @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
14664 @anchor{gnat_rm/implementation_advice rm-a-5-2-46-47-random-number-generation}@anchor{231}
14665 @section RM A.5.2(46-47): Random Number Generation
14670 "Any storage associated with an object of type @code{Generator} should be
14671 reclaimed on exit from the scope of the object."
14678 "If the generator period is sufficiently long in relation to the number
14679 of distinct initiator values, then each possible value of
14680 @code{Initiator} passed to @code{Reset} should initiate a sequence of
14681 random numbers that does not, in a practical sense, overlap the sequence
14682 initiated by any other value. If this is not possible, then the mapping
14683 between initiator values and generator states should be a rapidly
14684 varying function of the initiator value."
14687 Followed. The generator period is sufficiently long for the first
14688 condition here to hold true.
14690 @geindex Get_Immediate
14692 @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
14693 @anchor{gnat_rm/implementation_advice rm-a-10-7-23-get-immediate}@anchor{232}
14694 @section RM A.10.7(23): @code{Get_Immediate}
14699 "The @code{Get_Immediate} procedures should be implemented with
14700 unbuffered input. For a device such as a keyboard, input should be
14701 available if a key has already been typed, whereas for a disk
14702 file, input should always be available except at end of file. For a file
14703 associated with a keyboard-like device, any line-editing features of the
14704 underlying operating system should be disabled during the execution of
14705 @code{Get_Immediate}."
14708 Followed on all targets except VxWorks. For VxWorks, there is no way to
14709 provide this functionality that does not result in the input buffer being
14710 flushed before the @code{Get_Immediate} call. A special unit
14711 @code{Interfaces.Vxworks.IO} is provided that contains routines to enable
14712 this functionality.
14716 @node RM B 1 39-41 Pragma Export,RM B 2 12-13 Package Interfaces,RM A 10 7 23 Get_Immediate,Implementation Advice
14717 @anchor{gnat_rm/implementation_advice rm-b-1-39-41-pragma-export}@anchor{233}
14718 @section RM B.1(39-41): Pragma @code{Export}
14723 "If an implementation supports pragma @code{Export} to a given language,
14724 then it should also allow the main subprogram to be written in that
14725 language. It should support some mechanism for invoking the elaboration
14726 of the Ada library units included in the system, and for invoking the
14727 finalization of the environment task. On typical systems, the
14728 recommended mechanism is to provide two subprograms whose link names are
14729 @code{adainit} and @code{adafinal}. @code{adainit} should contain the
14730 elaboration code for library units. @code{adafinal} should contain the
14731 finalization code. These subprograms should have no effect the second
14732 and subsequent time they are called."
14739 "Automatic elaboration of pre-elaborated packages should be
14740 provided when pragma @code{Export} is supported."
14743 Followed when the main program is in Ada. If the main program is in a
14744 foreign language, then
14745 @code{adainit} must be called to elaborate pre-elaborated
14750 "For each supported convention @emph{L} other than @code{Intrinsic}, an
14751 implementation should support @code{Import} and @code{Export} pragmas
14752 for objects of @emph{L}-compatible types and for subprograms, and pragma
14753 @cite{Convention} for @emph{L}-eligible types and for subprograms,
14754 presuming the other language has corresponding features. Pragma
14755 @code{Convention} need not be supported for scalar types."
14760 @geindex Package Interfaces
14762 @geindex Interfaces
14764 @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
14765 @anchor{gnat_rm/implementation_advice rm-b-2-12-13-package-interfaces}@anchor{234}
14766 @section RM B.2(12-13): Package @code{Interfaces}
14771 "For each implementation-defined convention identifier, there should be a
14772 child package of package Interfaces with the corresponding name. This
14773 package should contain any declarations that would be useful for
14774 interfacing to the language (implementation) represented by the
14775 convention. Any declarations useful for interfacing to any language on
14776 the given hardware architecture should be provided directly in
14777 @code{Interfaces}."
14784 "An implementation supporting an interface to C, COBOL, or Fortran should
14785 provide the corresponding package or packages described in the following
14789 Followed. GNAT provides all the packages described in this section.
14792 @geindex interfacing with
14794 @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
14795 @anchor{gnat_rm/implementation_advice rm-b-3-63-71-interfacing-with-c}@anchor{235}
14796 @section RM B.3(63-71): Interfacing with C
14801 "An implementation should support the following interface correspondences
14802 between Ada and C."
14809 "An Ada procedure corresponds to a void-returning C function."
14816 "An Ada function corresponds to a non-void C function."
14823 "An Ada @code{in} scalar parameter is passed as a scalar argument to a C
14831 "An Ada @code{in} parameter of an access-to-object type with designated
14832 type @code{T} is passed as a @code{t*} argument to a C function,
14833 where @code{t} is the C type corresponding to the Ada type @code{T}."
14840 "An Ada access @code{T} parameter, or an Ada @code{out} or @code{in out}
14841 parameter of an elementary type @code{T}, is passed as a @code{t*}
14842 argument to a C function, where @code{t} is the C type corresponding to
14843 the Ada type @code{T}. In the case of an elementary @code{out} or
14844 @code{in out} parameter, a pointer to a temporary copy is used to
14845 preserve by-copy semantics."
14852 "An Ada parameter of a record type @code{T}, of any mode, is passed as a
14853 @code{t*} argument to a C function, where @code{t} is the C
14854 structure corresponding to the Ada type @code{T}."
14857 Followed. This convention may be overridden by the use of the C_Pass_By_Copy
14858 pragma, or Convention, or by explicitly specifying the mechanism for a given
14859 call using an extended import or export pragma.
14863 "An Ada parameter of an array type with component type @code{T}, of any
14864 mode, is passed as a @code{t*} argument to a C function, where
14865 @code{t} is the C type corresponding to the Ada type @code{T}."
14872 "An Ada parameter of an access-to-subprogram type is passed as a pointer
14873 to a C function whose prototype corresponds to the designated
14874 subprogram's specification."
14880 @geindex interfacing with
14882 @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
14883 @anchor{gnat_rm/implementation_advice rm-b-4-95-98-interfacing-with-cobol}@anchor{236}
14884 @section RM B.4(95-98): Interfacing with COBOL
14889 "An Ada implementation should support the following interface
14890 correspondences between Ada and COBOL."
14897 "An Ada access @code{T} parameter is passed as a @code{BY REFERENCE} data item of
14898 the COBOL type corresponding to @code{T}."
14905 "An Ada in scalar parameter is passed as a @code{BY CONTENT} data item of
14906 the corresponding COBOL type."
14913 "Any other Ada parameter is passed as a @code{BY REFERENCE} data item of the
14914 COBOL type corresponding to the Ada parameter type; for scalars, a local
14915 copy is used if necessary to ensure by-copy semantics."
14921 @geindex interfacing with
14923 @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
14924 @anchor{gnat_rm/implementation_advice rm-b-5-22-26-interfacing-with-fortran}@anchor{237}
14925 @section RM B.5(22-26): Interfacing with Fortran
14930 "An Ada implementation should support the following interface
14931 correspondences between Ada and Fortran:"
14938 "An Ada procedure corresponds to a Fortran subroutine."
14945 "An Ada function corresponds to a Fortran function."
14952 "An Ada parameter of an elementary, array, or record type @code{T} is
14953 passed as a @code{T} argument to a Fortran procedure, where @code{T} is
14954 the Fortran type corresponding to the Ada type @code{T}, and where the
14955 INTENT attribute of the corresponding dummy argument matches the Ada
14956 formal parameter mode; the Fortran implementation's parameter passing
14957 conventions are used. For elementary types, a local copy is used if
14958 necessary to ensure by-copy semantics."
14965 "An Ada parameter of an access-to-subprogram type is passed as a
14966 reference to a Fortran procedure whose interface corresponds to the
14967 designated subprogram's specification."
14972 @geindex Machine operations
14974 @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
14975 @anchor{gnat_rm/implementation_advice rm-c-1-3-5-access-to-machine-operations}@anchor{238}
14976 @section RM C.1(3-5): Access to Machine Operations
14981 "The machine code or intrinsic support should allow access to all
14982 operations normally available to assembly language programmers for the
14983 target environment, including privileged instructions, if any."
14990 "The interfacing pragmas (see Annex B) should support interface to
14991 assembler; the default assembler should be associated with the
14992 convention identifier @code{Assembler}."
14999 "If an entity is exported to assembly language, then the implementation
15000 should allocate it at an addressable location, and should ensure that it
15001 is retained by the linking process, even if not otherwise referenced
15002 from the Ada code. The implementation should assume that any call to a
15003 machine code or assembler subprogram is allowed to read or update every
15004 object that is specified as exported."
15009 @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
15010 @anchor{gnat_rm/implementation_advice rm-c-1-10-16-access-to-machine-operations}@anchor{239}
15011 @section RM C.1(10-16): Access to Machine Operations
15016 "The implementation should ensure that little or no overhead is
15017 associated with calling intrinsic and machine-code subprograms."
15020 Followed for both intrinsics and machine-code subprograms.
15024 "It is recommended that intrinsic subprograms be provided for convenient
15025 access to any machine operations that provide special capabilities or
15026 efficiency and that are not otherwise available through the language
15030 Followed. A full set of machine operation intrinsic subprograms is provided.
15034 "Atomic read-modify-write operations---e.g., test and set, compare and
15035 swap, decrement and test, enqueue/dequeue."
15038 Followed on any target supporting such operations.
15042 "Standard numeric functions---e.g.:, sin, log."
15045 Followed on any target supporting such operations.
15049 "String manipulation operations---e.g.:, translate and test."
15052 Followed on any target supporting such operations.
15056 "Vector operations---e.g.:, compare vector against thresholds."
15059 Followed on any target supporting such operations.
15063 "Direct operations on I/O ports."
15066 Followed on any target supporting such operations.
15068 @geindex Interrupt support
15070 @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
15071 @anchor{gnat_rm/implementation_advice rm-c-3-28-interrupt-support}@anchor{23a}
15072 @section RM C.3(28): Interrupt Support
15077 "If the @code{Ceiling_Locking} policy is not in effect, the
15078 implementation should provide means for the application to specify which
15079 interrupts are to be blocked during protected actions, if the underlying
15080 system allows for a finer-grain control of interrupt blocking."
15083 Followed. The underlying system does not allow for finer-grain control
15084 of interrupt blocking.
15086 @geindex Protected procedure handlers
15088 @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
15089 @anchor{gnat_rm/implementation_advice rm-c-3-1-20-21-protected-procedure-handlers}@anchor{23b}
15090 @section RM C.3.1(20-21): Protected Procedure Handlers
15095 "Whenever possible, the implementation should allow interrupt handlers to
15096 be called directly by the hardware."
15099 Followed on any target where the underlying operating system permits
15104 "Whenever practical, violations of any
15105 implementation-defined restrictions should be detected before run time."
15108 Followed. Compile time warnings are given when possible.
15110 @geindex Package `@w{`}Interrupts`@w{`}
15112 @geindex Interrupts
15114 @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
15115 @anchor{gnat_rm/implementation_advice rm-c-3-2-25-package-interrupts}@anchor{23c}
15116 @section RM C.3.2(25): Package @code{Interrupts}
15121 "If implementation-defined forms of interrupt handler procedures are
15122 supported, such as protected procedures with parameters, then for each
15123 such form of a handler, a type analogous to @code{Parameterless_Handler}
15124 should be specified in a child package of @code{Interrupts}, with the
15125 same operations as in the predefined package Interrupts."
15130 @geindex Pre-elaboration requirements
15132 @node RM C 4 14 Pre-elaboration Requirements,RM C 5 8 Pragma Discard_Names,RM C 3 2 25 Package Interrupts,Implementation Advice
15133 @anchor{gnat_rm/implementation_advice rm-c-4-14-pre-elaboration-requirements}@anchor{23d}
15134 @section RM C.4(14): Pre-elaboration Requirements
15139 "It is recommended that pre-elaborated packages be implemented in such a
15140 way that there should be little or no code executed at run time for the
15141 elaboration of entities not already covered by the Implementation
15145 Followed. Executable code is generated in some cases, e.g., loops
15146 to initialize large arrays.
15148 @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
15149 @anchor{gnat_rm/implementation_advice rm-c-5-8-pragma-discard-names}@anchor{23e}
15150 @section RM C.5(8): Pragma @code{Discard_Names}
15155 "If the pragma applies to an entity, then the implementation should
15156 reduce the amount of storage used for storing names associated with that
15162 @geindex Package Task_Attributes
15164 @geindex Task_Attributes
15166 @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
15167 @anchor{gnat_rm/implementation_advice rm-c-7-2-30-the-package-task-attributes}@anchor{23f}
15168 @section RM C.7.2(30): The Package Task_Attributes
15173 "Some implementations are targeted to domains in which memory use at run
15174 time must be completely deterministic. For such implementations, it is
15175 recommended that the storage for task attributes will be pre-allocated
15176 statically and not from the heap. This can be accomplished by either
15177 placing restrictions on the number and the size of the task's
15178 attributes, or by using the pre-allocated storage for the first @code{N}
15179 attribute objects, and the heap for the others. In the latter case,
15180 @code{N} should be documented."
15183 Not followed. This implementation is not targeted to such a domain.
15185 @geindex Locking Policies
15187 @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
15188 @anchor{gnat_rm/implementation_advice rm-d-3-17-locking-policies}@anchor{240}
15189 @section RM D.3(17): Locking Policies
15194 "The implementation should use names that end with @code{_Locking} for
15195 locking policies defined by the implementation."
15198 Followed. Two implementation-defined locking policies are defined,
15199 whose names (@code{Inheritance_Locking} and
15200 @code{Concurrent_Readers_Locking}) follow this suggestion.
15202 @geindex Entry queuing policies
15204 @node RM D 4 16 Entry Queuing Policies,RM D 6 9-10 Preemptive Abort,RM D 3 17 Locking Policies,Implementation Advice
15205 @anchor{gnat_rm/implementation_advice rm-d-4-16-entry-queuing-policies}@anchor{241}
15206 @section RM D.4(16): Entry Queuing Policies
15211 "Names that end with @code{_Queuing} should be used
15212 for all implementation-defined queuing policies."
15215 Followed. No such implementation-defined queuing policies exist.
15217 @geindex Preemptive abort
15219 @node RM D 6 9-10 Preemptive Abort,RM D 7 21 Tasking Restrictions,RM D 4 16 Entry Queuing Policies,Implementation Advice
15220 @anchor{gnat_rm/implementation_advice rm-d-6-9-10-preemptive-abort}@anchor{242}
15221 @section RM D.6(9-10): Preemptive Abort
15226 "Even though the @emph{abort_statement} is included in the list of
15227 potentially blocking operations (see 9.5.1), it is recommended that this
15228 statement be implemented in a way that never requires the task executing
15229 the @emph{abort_statement} to block."
15236 "On a multi-processor, the delay associated with aborting a task on
15237 another processor should be bounded; the implementation should use
15238 periodic polling, if necessary, to achieve this."
15243 @geindex Tasking restrictions
15245 @node RM D 7 21 Tasking Restrictions,RM D 8 47-49 Monotonic Time,RM D 6 9-10 Preemptive Abort,Implementation Advice
15246 @anchor{gnat_rm/implementation_advice rm-d-7-21-tasking-restrictions}@anchor{243}
15247 @section RM D.7(21): Tasking Restrictions
15252 "When feasible, the implementation should take advantage of the specified
15253 restrictions to produce a more efficient implementation."
15256 GNAT currently takes advantage of these restrictions by providing an optimized
15257 run time when the Ravenscar profile and the GNAT restricted run time set
15258 of restrictions are specified. See pragma @code{Profile (Ravenscar)} and
15259 pragma @code{Profile (Restricted)} for more details.
15264 @node RM D 8 47-49 Monotonic Time,RM E 5 28-29 Partition Communication Subsystem,RM D 7 21 Tasking Restrictions,Implementation Advice
15265 @anchor{gnat_rm/implementation_advice rm-d-8-47-49-monotonic-time}@anchor{244}
15266 @section RM D.8(47-49): Monotonic Time
15271 "When appropriate, implementations should provide configuration
15272 mechanisms to change the value of @code{Tick}."
15275 Such configuration mechanisms are not appropriate to this implementation
15276 and are thus not supported.
15280 "It is recommended that @code{Calendar.Clock} and @code{Real_Time.Clock}
15281 be implemented as transformations of the same time base."
15288 "It is recommended that the best time base which exists in
15289 the underlying system be available to the application through
15290 @code{Clock}. @cite{Best} may mean highest accuracy or largest range."
15295 @geindex Partition communication subsystem
15299 @node RM E 5 28-29 Partition Communication Subsystem,RM F 7 COBOL Support,RM D 8 47-49 Monotonic Time,Implementation Advice
15300 @anchor{gnat_rm/implementation_advice rm-e-5-28-29-partition-communication-subsystem}@anchor{245}
15301 @section RM E.5(28-29): Partition Communication Subsystem
15306 "Whenever possible, the PCS on the called partition should allow for
15307 multiple tasks to call the RPC-receiver with different messages and
15308 should allow them to block until the corresponding subprogram body
15312 Followed by GLADE, a separately supplied PCS that can be used with
15317 "The @code{Write} operation on a stream of type @code{Params_Stream_Type}
15318 should raise @code{Storage_Error} if it runs out of space trying to
15319 write the @code{Item} into the stream."
15322 Followed by GLADE, a separately supplied PCS that can be used with
15325 @geindex COBOL support
15327 @node RM F 7 COBOL Support,RM F 1 2 Decimal Radix Support,RM E 5 28-29 Partition Communication Subsystem,Implementation Advice
15328 @anchor{gnat_rm/implementation_advice rm-f-7-cobol-support}@anchor{246}
15329 @section RM F(7): COBOL Support
15334 "If COBOL (respectively, C) is widely supported in the target
15335 environment, implementations supporting the Information Systems Annex
15336 should provide the child package @code{Interfaces.COBOL} (respectively,
15337 @code{Interfaces.C}) specified in Annex B and should support a
15338 @code{convention_identifier} of COBOL (respectively, C) in the interfacing
15339 pragmas (see Annex B), thus allowing Ada programs to interface with
15340 programs written in that language."
15345 @geindex Decimal radix support
15347 @node RM F 1 2 Decimal Radix Support,RM G Numerics,RM F 7 COBOL Support,Implementation Advice
15348 @anchor{gnat_rm/implementation_advice rm-f-1-2-decimal-radix-support}@anchor{247}
15349 @section RM F.1(2): Decimal Radix Support
15354 "Packed decimal should be used as the internal representation for objects
15355 of subtype @code{S} when @code{S}'Machine_Radix = 10."
15358 Not followed. GNAT ignores @code{S}'Machine_Radix and always uses binary
15363 @node RM G Numerics,RM G 1 1 56-58 Complex Types,RM F 1 2 Decimal Radix Support,Implementation Advice
15364 @anchor{gnat_rm/implementation_advice rm-g-numerics}@anchor{248}
15365 @section RM G: Numerics
15370 "If Fortran (respectively, C) is widely supported in the target
15371 environment, implementations supporting the Numerics Annex
15372 should provide the child package @code{Interfaces.Fortran} (respectively,
15373 @code{Interfaces.C}) specified in Annex B and should support a
15374 @code{convention_identifier} of Fortran (respectively, C) in the interfacing
15375 pragmas (see Annex B), thus allowing Ada programs to interface with
15376 programs written in that language."
15381 @geindex Complex types
15383 @node RM G 1 1 56-58 Complex Types,RM G 1 2 49 Complex Elementary Functions,RM G Numerics,Implementation Advice
15384 @anchor{gnat_rm/implementation_advice rm-g-1-1-56-58-complex-types}@anchor{249}
15385 @section RM G.1.1(56-58): Complex Types
15390 "Because the usual mathematical meaning of multiplication of a complex
15391 operand and a real operand is that of the scaling of both components of
15392 the former by the latter, an implementation should not perform this
15393 operation by first promoting the real operand to complex type and then
15394 performing a full complex multiplication. In systems that, in the
15395 future, support an Ada binding to IEC 559:1989, the latter technique
15396 will not generate the required result when one of the components of the
15397 complex operand is infinite. (Explicit multiplication of the infinite
15398 component by the zero component obtained during promotion yields a NaN
15399 that propagates into the final result.) Analogous advice applies in the
15400 case of multiplication of a complex operand and a pure-imaginary
15401 operand, and in the case of division of a complex operand by a real or
15402 pure-imaginary operand."
15409 "Similarly, because the usual mathematical meaning of addition of a
15410 complex operand and a real operand is that the imaginary operand remains
15411 unchanged, an implementation should not perform this operation by first
15412 promoting the real operand to complex type and then performing a full
15413 complex addition. In implementations in which the @code{Signed_Zeros}
15414 attribute of the component type is @code{True} (and which therefore
15415 conform to IEC 559:1989 in regard to the handling of the sign of zero in
15416 predefined arithmetic operations), the latter technique will not
15417 generate the required result when the imaginary component of the complex
15418 operand is a negatively signed zero. (Explicit addition of the negative
15419 zero to the zero obtained during promotion yields a positive zero.)
15420 Analogous advice applies in the case of addition of a complex operand
15421 and a pure-imaginary operand, and in the case of subtraction of a
15422 complex operand and a real or pure-imaginary operand."
15429 "Implementations in which @code{Real'Signed_Zeros} is @code{True} should
15430 attempt to provide a rational treatment of the signs of zero results and
15431 result components. As one example, the result of the @code{Argument}
15432 function should have the sign of the imaginary component of the
15433 parameter @code{X} when the point represented by that parameter lies on
15434 the positive real axis; as another, the sign of the imaginary component
15435 of the @code{Compose_From_Polar} function should be the same as
15436 (respectively, the opposite of) that of the @code{Argument} parameter when that
15437 parameter has a value of zero and the @code{Modulus} parameter has a
15438 nonnegative (respectively, negative) value."
15443 @geindex Complex elementary functions
15445 @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
15446 @anchor{gnat_rm/implementation_advice rm-g-1-2-49-complex-elementary-functions}@anchor{24a}
15447 @section RM G.1.2(49): Complex Elementary Functions
15452 "Implementations in which @code{Complex_Types.Real'Signed_Zeros} is
15453 @code{True} should attempt to provide a rational treatment of the signs
15454 of zero results and result components. For example, many of the complex
15455 elementary functions have components that are odd functions of one of
15456 the parameter components; in these cases, the result component should
15457 have the sign of the parameter component at the origin. Other complex
15458 elementary functions have zero components whose sign is opposite that of
15459 a parameter component at the origin, or is always positive or always
15465 @geindex Accuracy requirements
15467 @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
15468 @anchor{gnat_rm/implementation_advice rm-g-2-4-19-accuracy-requirements}@anchor{24b}
15469 @section RM G.2.4(19): Accuracy Requirements
15474 "The versions of the forward trigonometric functions without a
15475 @code{Cycle} parameter should not be implemented by calling the
15476 corresponding version with a @code{Cycle} parameter of
15477 @code{2.0*Numerics.Pi}, since this will not provide the required
15478 accuracy in some portions of the domain. For the same reason, the
15479 version of @code{Log} without a @code{Base} parameter should not be
15480 implemented by calling the corresponding version with a @code{Base}
15481 parameter of @code{Numerics.e}."
15486 @geindex Complex arithmetic accuracy
15489 @geindex complex arithmetic
15491 @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
15492 @anchor{gnat_rm/implementation_advice rm-g-2-6-15-complex-arithmetic-accuracy}@anchor{24c}
15493 @section RM G.2.6(15): Complex Arithmetic Accuracy
15498 "The version of the @code{Compose_From_Polar} function without a
15499 @code{Cycle} parameter should not be implemented by calling the
15500 corresponding version with a @code{Cycle} parameter of
15501 @code{2.0*Numerics.Pi}, since this will not provide the required
15502 accuracy in some portions of the domain."
15507 @geindex Sequential elaboration policy
15509 @node RM H 6 15/2 Pragma Partition_Elaboration_Policy,,RM G 2 6 15 Complex Arithmetic Accuracy,Implementation Advice
15510 @anchor{gnat_rm/implementation_advice rm-h-6-15-2-pragma-partition-elaboration-policy}@anchor{24d}
15511 @section RM H.6(15/2): Pragma Partition_Elaboration_Policy
15516 "If the partition elaboration policy is @code{Sequential} and the
15517 Environment task becomes permanently blocked during elaboration then the
15518 partition is deadlocked and it is recommended that the partition be
15519 immediately terminated."
15524 @node Implementation Defined Characteristics,Intrinsic Subprograms,Implementation Advice,Top
15525 @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}
15526 @chapter Implementation Defined Characteristics
15529 In addition to the implementation dependent pragmas and attributes, and the
15530 implementation advice, there are a number of other Ada features that are
15531 potentially implementation dependent and are designated as
15532 implementation-defined. These are mentioned throughout the Ada Reference
15533 Manual, and are summarized in Annex M.
15535 A requirement for conforming Ada compilers is that they provide
15536 documentation describing how the implementation deals with each of these
15537 issues. In this chapter you will find each point in Annex M listed,
15538 followed by a description of how GNAT
15539 handles the implementation dependence.
15541 You can use this chapter as a guide to minimizing implementation
15542 dependent features in your programs if portability to other compilers
15543 and other operating systems is an important consideration. The numbers
15544 in each entry below correspond to the paragraph numbers in the Ada
15551 "Whether or not each recommendation given in Implementation
15552 Advice is followed. See 1.1.2(37)."
15555 See @ref{a,,Implementation Advice}.
15561 "Capacity limitations of the implementation. See 1.1.3(3)."
15564 The complexity of programs that can be processed is limited only by the
15565 total amount of available virtual memory, and disk space for the
15566 generated object files.
15572 "Variations from the standard that are impractical to avoid
15573 given the implementation's execution environment. See 1.1.3(6)."
15576 There are no variations from the standard.
15582 "Which code_statements cause external
15583 interactions. See 1.1.3(10)."
15586 Any @emph{code_statement} can potentially cause external interactions.
15592 "The coded representation for the text of an Ada
15593 program. See 2.1(4)."
15596 See separate section on source representation.
15602 "The control functions allowed in comments. See 2.1(14)."
15605 See separate section on source representation.
15611 "The representation for an end of line. See 2.2(2)."
15614 See separate section on source representation.
15620 "Maximum supported line length and lexical element
15621 length. See 2.2(15)."
15624 The maximum line length is 255 characters and the maximum length of
15625 a lexical element is also 255 characters. This is the default setting
15626 if not overridden by the use of compiler switch @emph{-gnaty} (which
15627 sets the maximum to 79) or @emph{-gnatyMnn} which allows the maximum
15628 line length to be specified to be any value up to 32767. The maximum
15629 length of a lexical element is the same as the maximum line length.
15635 "Implementation defined pragmas. See 2.8(14)."
15638 See @ref{7,,Implementation Defined Pragmas}.
15644 "Effect of pragma @code{Optimize}. See 2.8(27)."
15647 Pragma @code{Optimize}, if given with a @code{Time} or @code{Space}
15648 parameter, checks that the optimization flag is set, and aborts if it is
15655 "The sequence of characters of the value returned by
15656 @code{S'Image} when some of the graphic characters of
15657 @code{S'Wide_Image} are not defined in @code{Character}. See
15661 The sequence of characters is as defined by the wide character encoding
15662 method used for the source. See section on source representation for
15669 "The predefined integer types declared in
15670 @code{Standard}. See 3.5.4(25)."
15674 @multitable {xxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
15685 @emph{Short_Short_Integer}
15693 @emph{Short_Integer}
15697 (Short) 16 bit signed
15709 @emph{Long_Integer}
15713 64 bit signed (on most 64 bit targets,
15714 depending on the C definition of long).
15715 32 bit signed (all other targets)
15719 @emph{Long_Long_Integer}
15732 "Any nonstandard integer types and the operators defined
15733 for them. See 3.5.4(26)."
15736 There are no nonstandard integer types.
15742 "Any nonstandard real types and the operators defined for
15743 them. See 3.5.6(8)."
15746 There are no nonstandard real types.
15752 "What combinations of requested decimal precision and range
15753 are supported for floating point types. See 3.5.7(7)."
15756 The precision and range is as defined by the IEEE standard.
15762 "The predefined floating point types declared in
15763 @code{Standard}. See 3.5.7(16)."
15767 @multitable {xxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
15790 (Short) 32 bit IEEE short
15802 @emph{Long_Long_Float}
15806 64 bit IEEE long (80 bit IEEE long on x86 processors)
15815 "The small of an ordinary fixed point type. See 3.5.9(8)."
15818 @code{Fine_Delta} is 2**(-63)
15824 "What combinations of small, range, and digits are
15825 supported for fixed point types. See 3.5.9(10)."
15828 Any combinations are permitted that do not result in a small less than
15829 @code{Fine_Delta} and do not result in a mantissa larger than 63 bits.
15830 If the mantissa is larger than 53 bits on machines where Long_Long_Float
15831 is 64 bits (true of all architectures except ia32), then the output from
15832 Text_IO is accurate to only 53 bits, rather than the full mantissa. This
15833 is because floating-point conversions are used to convert fixed point.
15839 "The result of @code{Tags.Expanded_Name} for types declared
15840 within an unnamed @emph{block_statement}. See 3.9(10)."
15843 Block numbers of the form @code{B@emph{nnn}}, where @emph{nnn} is a
15844 decimal integer are allocated.
15850 "Implementation-defined attributes. See 4.1.4(12)."
15853 See @ref{8,,Implementation Defined Attributes}.
15859 "Any implementation-defined time types. See 9.6(6)."
15862 There are no implementation-defined time types.
15868 "The time base associated with relative delays."
15871 See 9.6(20). The time base used is that provided by the C library
15872 function @code{gettimeofday}.
15878 "The time base of the type @code{Calendar.Time}. See
15882 The time base used is that provided by the C library function
15883 @code{gettimeofday}.
15889 "The time zone used for package @code{Calendar}
15890 operations. See 9.6(24)."
15893 The time zone used by package @code{Calendar} is the current system time zone
15894 setting for local time, as accessed by the C library function
15901 "Any limit on @emph{delay_until_statements} of
15902 @emph{select_statements}. See 9.6(29)."
15905 There are no such limits.
15911 "Whether or not two non-overlapping parts of a composite
15912 object are independently addressable, in the case where packing, record
15913 layout, or @code{Component_Size} is specified for the object. See
15917 Separate components are independently addressable if they do not share
15918 overlapping storage units.
15924 "The representation for a compilation. See 10.1(2)."
15927 A compilation is represented by a sequence of files presented to the
15928 compiler in a single invocation of the @emph{gcc} command.
15934 "Any restrictions on compilations that contain multiple
15935 compilation_units. See 10.1(4)."
15938 No single file can contain more than one compilation unit, but any
15939 sequence of files can be presented to the compiler as a single
15946 "The mechanisms for creating an environment and for adding
15947 and replacing compilation units. See 10.1.4(3)."
15950 See separate section on compilation model.
15956 "The manner of explicitly assigning library units to a
15957 partition. See 10.2(2)."
15960 If a unit contains an Ada main program, then the Ada units for the partition
15961 are determined by recursive application of the rules in the Ada Reference
15962 Manual section 10.2(2-6). In other words, the Ada units will be those that
15963 are needed by the main program, and then this definition of need is applied
15964 recursively to those units, and the partition contains the transitive
15965 closure determined by this relationship. In short, all the necessary units
15966 are included, with no need to explicitly specify the list. If additional
15967 units are required, e.g., by foreign language units, then all units must be
15968 mentioned in the context clause of one of the needed Ada units.
15970 If the partition contains no main program, or if the main program is in
15971 a language other than Ada, then GNAT
15972 provides the binder options @emph{-z} and @emph{-n} respectively, and in
15973 this case a list of units can be explicitly supplied to the binder for
15974 inclusion in the partition (all units needed by these units will also
15975 be included automatically). For full details on the use of these
15976 options, refer to @emph{GNAT Make Program gnatmake} in the
15977 @cite{GNAT User's Guide}.
15983 "The implementation-defined means, if any, of specifying
15984 which compilation units are needed by a given compilation unit. See
15988 The units needed by a given compilation unit are as defined in
15989 the Ada Reference Manual section 10.2(2-6). There are no
15990 implementation-defined pragmas or other implementation-defined
15991 means for specifying needed units.
15997 "The manner of designating the main subprogram of a
15998 partition. See 10.2(7)."
16001 The main program is designated by providing the name of the
16002 corresponding @code{ALI} file as the input parameter to the binder.
16008 "The order of elaboration of @emph{library_items}. See
16012 The first constraint on ordering is that it meets the requirements of
16013 Chapter 10 of the Ada Reference Manual. This still leaves some
16014 implementation dependent choices, which are resolved by first
16015 elaborating bodies as early as possible (i.e., in preference to specs
16016 where there is a choice), and second by evaluating the immediate with
16017 clauses of a unit to determine the probably best choice, and
16018 third by elaborating in alphabetical order of unit names
16019 where a choice still remains.
16025 "Parameter passing and function return for the main
16026 subprogram. See 10.2(21)."
16029 The main program has no parameters. It may be a procedure, or a function
16030 returning an integer type. In the latter case, the returned integer
16031 value is the return code of the program (overriding any value that
16032 may have been set by a call to @code{Ada.Command_Line.Set_Exit_Status}).
16038 "The mechanisms for building and running partitions. See
16042 GNAT itself supports programs with only a single partition. The GNATDIST
16043 tool provided with the GLADE package (which also includes an implementation
16044 of the PCS) provides a completely flexible method for building and running
16045 programs consisting of multiple partitions. See the separate GLADE manual
16052 "The details of program execution, including program
16053 termination. See 10.2(25)."
16056 See separate section on compilation model.
16062 "The semantics of any non-active partitions supported by the
16063 implementation. See 10.2(28)."
16066 Passive partitions are supported on targets where shared memory is
16067 provided by the operating system. See the GLADE reference manual for
16074 "The information returned by @code{Exception_Message}. See
16078 Exception message returns the null string unless a specific message has
16079 been passed by the program.
16085 "The result of @code{Exceptions.Exception_Name} for types
16086 declared within an unnamed @emph{block_statement}. See 11.4.1(12)."
16089 Blocks have implementation defined names of the form @code{B@emph{nnn}}
16090 where @emph{nnn} is an integer.
16096 "The information returned by
16097 @code{Exception_Information}. See 11.4.1(13)."
16100 @code{Exception_Information} returns a string in the following format:
16103 *Exception_Name:* nnnnn
16106 *Load address:* 0xhhhh
16107 *Call stack traceback locations:*
16108 0xhhhh 0xhhhh 0xhhhh ... 0xhhh
16119 @code{nnnn} is the fully qualified name of the exception in all upper
16120 case letters. This line is always present.
16123 @code{mmmm} is the message (this line present only if message is non-null)
16126 @code{ppp} is the Process Id value as a decimal integer (this line is
16127 present only if the Process Id is nonzero). Currently we are
16128 not making use of this field.
16131 The Load address line, the Call stack traceback locations line and the
16132 following values are present only if at least one traceback location was
16133 recorded. The Load address indicates the address at which the main executable
16134 was loaded; this line may not be present if operating system hasn't relocated
16135 the main executable. The values are given in C style format, with lower case
16136 letters for a-f, and only as many digits present as are necessary.
16137 The line terminator sequence at the end of each line, including
16138 the last line is a single @code{LF} character (@code{16#0A#}).
16146 "Implementation-defined check names. See 11.5(27)."
16149 The implementation defined check names include Alignment_Check,
16150 Atomic_Synchronization, Duplicated_Tag_Check, Container_Checks,
16151 Tampering_Check, Predicate_Check, and Validity_Check. In addition, a user
16152 program can add implementation-defined check names by means of the pragma
16153 Check_Name. See the description of pragma @code{Suppress} for full details.
16159 "The interpretation of each aspect of representation. See
16163 See separate section on data representations.
16169 "Any restrictions placed upon representation items. See
16173 See separate section on data representations.
16179 "The meaning of @code{Size} for indefinite subtypes. See
16183 Size for an indefinite subtype is the maximum possible size, except that
16184 for the case of a subprogram parameter, the size of the parameter object
16185 is the actual size.
16191 "The default external representation for a type tag. See
16195 The default external representation for a type tag is the fully expanded
16196 name of the type in upper case letters.
16202 "What determines whether a compilation unit is the same in
16203 two different partitions. See 13.3(76)."
16206 A compilation unit is the same in two different partitions if and only
16207 if it derives from the same source file.
16213 "Implementation-defined components. See 13.5.1(15)."
16216 The only implementation defined component is the tag for a tagged type,
16217 which contains a pointer to the dispatching table.
16223 "If @code{Word_Size} = @code{Storage_Unit}, the default bit
16224 ordering. See 13.5.3(5)."
16227 @code{Word_Size} (32) is not the same as @code{Storage_Unit} (8) for this
16228 implementation, so no non-default bit ordering is supported. The default
16229 bit ordering corresponds to the natural endianness of the target architecture.
16235 "The contents of the visible part of package @code{System}
16236 and its language-defined children. See 13.7(2)."
16239 See the definition of these packages in files @code{system.ads} and
16240 @code{s-stoele.ads}. Note that two declarations are added to package
16244 Max_Priority : constant Positive := Priority'Last;
16245 Max_Interrupt_Priority : constant Positive := Interrupt_Priority'Last;
16252 "The contents of the visible part of package
16253 @code{System.Machine_Code}, and the meaning of
16254 @emph{code_statements}. See 13.8(7)."
16257 See the definition and documentation in file @code{s-maccod.ads}.
16263 "The effect of unchecked conversion. See 13.9(11)."
16266 Unchecked conversion between types of the same size
16267 results in an uninterpreted transmission of the bits from one type
16268 to the other. If the types are of unequal sizes, then in the case of
16269 discrete types, a shorter source is first zero or sign extended as
16270 necessary, and a shorter target is simply truncated on the left.
16271 For all non-discrete types, the source is first copied if necessary
16272 to ensure that the alignment requirements of the target are met, then
16273 a pointer is constructed to the source value, and the result is obtained
16274 by dereferencing this pointer after converting it to be a pointer to the
16275 target type. Unchecked conversions where the target subtype is an
16276 unconstrained array are not permitted. If the target alignment is
16277 greater than the source alignment, then a copy of the result is
16278 made with appropriate alignment
16284 "The semantics of operations on invalid representations.
16285 See 13.9.2(10-11)."
16288 For assignments and other operations where the use of invalid values cannot
16289 result in erroneous behavior, the compiler ignores the possibility of invalid
16290 values. An exception is raised at the point where an invalid value would
16291 result in erroneous behavior. For example executing:
16294 procedure invalidvals is
16296 Y : Natural range 1 .. 10;
16297 for Y'Address use X'Address;
16298 Z : Natural range 1 .. 10;
16299 A : array (Natural range 1 .. 10) of Integer;
16301 Z := Y; -- no exception
16302 A (Z) := 3; -- exception raised;
16306 As indicated, an exception is raised on the array assignment, but not
16307 on the simple assignment of the invalid negative value from Y to Z.
16313 "The manner of choosing a storage pool for an access type
16314 when @code{Storage_Pool} is not specified for the type. See 13.11(17)."
16317 There are 3 different standard pools used by the compiler when
16318 @code{Storage_Pool} is not specified depending whether the type is local
16319 to a subprogram or defined at the library level and whether
16320 @code{Storage_Size`@w{`}is specified or not. See documentation in the runtime
16321 library units `@w{`}System.Pool_Global}, @code{System.Pool_Size} and
16322 @code{System.Pool_Local} in files @code{s-poosiz.ads},
16323 @code{s-pooglo.ads} and @code{s-pooloc.ads} for full details on the
16324 default pools used.
16330 "Whether or not the implementation provides user-accessible
16331 names for the standard pool type(s). See 13.11(17)."
16334 See documentation in the sources of the run time mentioned in the previous
16335 paragraph. All these pools are accessible by means of @cite{with}ing
16342 "The meaning of @code{Storage_Size}. See 13.11(18)."
16345 @code{Storage_Size} is measured in storage units, and refers to the
16346 total space available for an access type collection, or to the primary
16347 stack space for a task.
16353 "Implementation-defined aspects of storage pools. See
16357 See documentation in the sources of the run time mentioned in the
16358 paragraph about standard storage pools above
16359 for details on GNAT-defined aspects of storage pools.
16365 "The set of restrictions allowed in a pragma
16366 @code{Restrictions}. See 13.12(7)."
16369 See @ref{9,,Standard and Implementation Defined Restrictions}.
16375 "The consequences of violating limitations on
16376 @code{Restrictions} pragmas. See 13.12(9)."
16379 Restrictions that can be checked at compile time result in illegalities
16380 if violated. Currently there are no other consequences of violating
16387 "The representation used by the @code{Read} and
16388 @code{Write} attributes of elementary types in terms of stream
16389 elements. See 13.13.2(9)."
16392 The representation is the in-memory representation of the base type of
16393 the type, using the number of bits corresponding to the
16394 @code{type'Size} value, and the natural ordering of the machine.
16400 "The names and characteristics of the numeric subtypes
16401 declared in the visible part of package @code{Standard}. See A.1(3)."
16404 See items describing the integer and floating-point types supported.
16410 "The string returned by @code{Character_Set_Version}.
16414 @code{Ada.Wide_Characters.Handling.Character_Set_Version} returns
16415 the string "Unicode 4.0", referring to version 4.0 of the
16416 Unicode specification.
16422 "The accuracy actually achieved by the elementary
16423 functions. See A.5.1(1)."
16426 The elementary functions correspond to the functions available in the C
16427 library. Only fast math mode is implemented.
16433 "The sign of a zero result from some of the operators or
16434 functions in @code{Numerics.Generic_Elementary_Functions}, when
16435 @code{Float_Type'Signed_Zeros} is @code{True}. See A.5.1(46)."
16438 The sign of zeroes follows the requirements of the IEEE 754 standard on
16446 @code{Numerics.Float_Random.Max_Image_Width}. See A.5.2(27)."
16449 Maximum image width is 6864, see library file @code{s-rannum.ads}.
16456 @code{Numerics.Discrete_Random.Max_Image_Width}. See A.5.2(27)."
16459 Maximum image width is 6864, see library file @code{s-rannum.ads}.
16465 "The algorithms for random number generation. See
16469 The algorithm is the Mersenne Twister, as documented in the source file
16470 @code{s-rannum.adb}. This version of the algorithm has a period of
16477 "The string representation of a random number generator's
16478 state. See A.5.2(38)."
16481 The value returned by the Image function is the concatenation of
16482 the fixed-width decimal representations of the 624 32-bit integers
16483 of the state vector.
16489 "The minimum time interval between calls to the
16490 time-dependent Reset procedure that are guaranteed to initiate different
16491 random number sequences. See A.5.2(45)."
16494 The minimum period between reset calls to guarantee distinct series of
16495 random numbers is one microsecond.
16501 "The values of the @code{Model_Mantissa},
16502 @code{Model_Emin}, @code{Model_Epsilon}, @code{Model},
16503 @code{Safe_First}, and @code{Safe_Last} attributes, if the Numerics
16504 Annex is not supported. See A.5.3(72)."
16507 Run the compiler with @emph{-gnatS} to produce a listing of package
16508 @code{Standard}, has the values of all numeric attributes.
16514 "Any implementation-defined characteristics of the
16515 input-output packages. See A.7(14)."
16518 There are no special implementation defined characteristics for these
16525 "The value of @code{Buffer_Size} in @code{Storage_IO}. See
16529 All type representations are contiguous, and the @code{Buffer_Size} is
16530 the value of @code{type'Size} rounded up to the next storage unit
16537 "External files for standard input, standard output, and
16538 standard error See A.10(5)."
16541 These files are mapped onto the files provided by the C streams
16542 libraries. See source file @code{i-cstrea.ads} for further details.
16548 "The accuracy of the value produced by @code{Put}. See
16552 If more digits are requested in the output than are represented by the
16553 precision of the value, zeroes are output in the corresponding least
16554 significant digit positions.
16560 "The meaning of @code{Argument_Count}, @code{Argument}, and
16561 @code{Command_Name}. See A.15(1)."
16564 These are mapped onto the @code{argv} and @code{argc} parameters of the
16565 main program in the natural manner.
16571 "The interpretation of the @code{Form} parameter in procedure
16572 @code{Create_Directory}. See A.16(56)."
16575 The @code{Form} parameter is not used.
16581 "The interpretation of the @code{Form} parameter in procedure
16582 @code{Create_Path}. See A.16(60)."
16585 The @code{Form} parameter is not used.
16591 "The interpretation of the @code{Form} parameter in procedure
16592 @code{Copy_File}. See A.16(68)."
16595 The @code{Form} parameter is case-insensitive.
16596 Two fields are recognized in the @code{Form} parameter:
16603 <value> starts immediately after the character '=' and ends with the
16604 character immediately preceding the next comma (',') or with the last
16605 character of the parameter.
16607 The only possible values for preserve= are:
16610 @multitable {xxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
16621 @emph{no_attributes}
16625 Do not try to preserve any file attributes. This is the
16626 default if no preserve= is found in Form.
16630 @emph{all_attributes}
16634 Try to preserve all file attributes (timestamps, access rights).
16642 Preserve the timestamp of the copied file, but not the other
16648 The only possible values for mode= are:
16651 @multitable {xxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
16666 Only do the copy if the destination file does not already exist.
16667 If it already exists, Copy_File fails.
16675 Copy the file in all cases. Overwrite an already existing destination file.
16683 Append the original file to the destination file. If the destination file
16684 does not exist, the destination file is a copy of the source file.
16685 When mode=append, the field preserve=, if it exists, is not taken into account.
16690 If the Form parameter includes one or both of the fields and the value or
16691 values are incorrect, Copy_file fails with Use_Error.
16693 Examples of correct Forms:
16696 Form => "preserve=no_attributes,mode=overwrite" (the default)
16697 Form => "mode=append"
16698 Form => "mode=copy, preserve=all_attributes"
16701 Examples of incorrect Forms:
16704 Form => "preserve=junk"
16705 Form => "mode=internal, preserve=timestamps"
16712 "The interpretation of the @code{Pattern} parameter, when not the null string,
16713 in the @code{Start_Search} and @code{Search} procedures.
16714 See A.16(104) and A.16(112)."
16717 When the @code{Pattern} parameter is not the null string, it is interpreted
16718 according to the syntax of regular expressions as defined in the
16719 @code{GNAT.Regexp} package.
16721 See @ref{250,,GNAT.Regexp (g-regexp.ads)}.
16727 "Implementation-defined convention names. See B.1(11)."
16730 The following convention names are supported
16733 @multitable {xxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
16752 @emph{Ada_Pass_By_Copy}
16756 Allowed for any types except by-reference types such as limited
16757 records. Compatible with convention Ada, but causes any parameters
16758 with this convention to be passed by copy.
16762 @emph{Ada_Pass_By_Reference}
16766 Allowed for any types except by-copy types such as scalars.
16767 Compatible with convention Ada, but causes any parameters
16768 with this convention to be passed by reference.
16784 Synonym for Assembler
16792 Synonym for Assembler
16804 @emph{C_Pass_By_Copy}
16808 Allowed only for record types, like C, but also notes that record
16809 is to be passed by copy rather than reference.
16821 @emph{C_Plus_Plus (or CPP)}
16833 Treated the same as C
16841 Treated the same as C
16857 For support of pragma @code{Import} with convention Intrinsic, see
16858 separate section on Intrinsic Subprograms.
16866 Stdcall (used for Windows implementations only). This convention correspond
16867 to the WINAPI (previously called Pascal convention) C/C++ convention under
16868 Windows. A routine with this convention cleans the stack before
16869 exit. This pragma cannot be applied to a dispatching call.
16877 Synonym for Stdcall
16885 Synonym for Stdcall
16893 Stubbed is a special convention used to indicate that the body of the
16894 subprogram will be entirely ignored. Any call to the subprogram
16895 is converted into a raise of the @code{Program_Error} exception. If a
16896 pragma @code{Import} specifies convention @code{stubbed} then no body need
16897 be present at all. This convention is useful during development for the
16898 inclusion of subprograms whose body has not yet been written.
16899 In addition, all otherwise unrecognized convention names are also
16900 treated as being synonymous with convention C. In all implementations
16901 except for VMS, use of such other names results in a warning. In VMS
16902 implementations, these names are accepted silently.
16911 "The meaning of link names. See B.1(36)."
16914 Link names are the actual names used by the linker.
16920 "The manner of choosing link names when neither the link
16921 name nor the address of an imported or exported entity is specified. See
16925 The default linker name is that which would be assigned by the relevant
16926 external language, interpreting the Ada name as being in all lower case
16933 "The effect of pragma @code{Linker_Options}. See B.1(37)."
16936 The string passed to @code{Linker_Options} is presented uninterpreted as
16937 an argument to the link command, unless it contains ASCII.NUL characters.
16938 NUL characters if they appear act as argument separators, so for example
16941 pragma Linker_Options ("-labc" & ASCII.NUL & "-ldef");
16944 causes two separate arguments @code{-labc} and @code{-ldef} to be passed to the
16945 linker. The order of linker options is preserved for a given unit. The final
16946 list of options passed to the linker is in reverse order of the elaboration
16947 order. For example, linker options for a body always appear before the options
16948 from the corresponding package spec.
16954 "The contents of the visible part of package
16955 @code{Interfaces} and its language-defined descendants. See B.2(1)."
16958 See files with prefix @code{i-} in the distributed library.
16964 "Implementation-defined children of package
16965 @code{Interfaces}. The contents of the visible part of package
16966 @code{Interfaces}. See B.2(11)."
16969 See files with prefix @code{i-} in the distributed library.
16975 "The types @code{Floating}, @code{Long_Floating},
16976 @code{Binary}, @code{Long_Binary}, @code{Decimal_ Element}, and
16977 @code{COBOL_Character}; and the initialization of the variables
16978 @code{Ada_To_COBOL} and @code{COBOL_To_Ada}, in
16979 @code{Interfaces.COBOL}. See B.4(50)."
16983 @multitable {xxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
17002 @emph{Long_Floating}
17006 (Floating) Long_Float
17026 @emph{Decimal_Element}
17034 @emph{COBOL_Character}
17043 For initialization, see the file @code{i-cobol.ads} in the distributed library.
17049 "Support for access to machine instructions. See C.1(1)."
17052 See documentation in file @code{s-maccod.ads} in the distributed library.
17058 "Implementation-defined aspects of access to machine
17059 operations. See C.1(9)."
17062 See documentation in file @code{s-maccod.ads} in the distributed library.
17068 "Implementation-defined aspects of interrupts. See C.3(2)."
17071 Interrupts are mapped to signals or conditions as appropriate. See
17073 @code{Ada.Interrupt_Names} in source file @code{a-intnam.ads} for details
17074 on the interrupts supported on a particular target.
17080 "Implementation-defined aspects of pre-elaboration. See
17084 GNAT does not permit a partition to be restarted without reloading,
17085 except under control of the debugger.
17091 "The semantics of pragma @code{Discard_Names}. See C.5(7)."
17094 Pragma @code{Discard_Names} causes names of enumeration literals to
17095 be suppressed. In the presence of this pragma, the Image attribute
17096 provides the image of the Pos of the literal, and Value accepts
17103 "The result of the @code{Task_Identification.Image}
17104 attribute. See C.7.1(7)."
17107 The result of this attribute is a string that identifies
17108 the object or component that denotes a given task. If a variable @code{Var}
17109 has a task type, the image for this task will have the form @code{Var_@emph{XXXXXXXX}},
17110 where the suffix @emph{XXXXXXXX}
17111 is the hexadecimal representation of the virtual address of the corresponding
17112 task control block. If the variable is an array of tasks, the image of each
17113 task will have the form of an indexed component indicating the position of a
17114 given task in the array, e.g., @code{Group(5)_@emph{XXXXXXX}}. If the task is a
17115 component of a record, the image of the task will have the form of a selected
17116 component. These rules are fully recursive, so that the image of a task that
17117 is a subcomponent of a composite object corresponds to the expression that
17118 designates this task.
17120 If a task is created by an allocator, its image depends on the context. If the
17121 allocator is part of an object declaration, the rules described above are used
17122 to construct its image, and this image is not affected by subsequent
17123 assignments. If the allocator appears within an expression, the image
17124 includes only the name of the task type.
17126 If the configuration pragma Discard_Names is present, or if the restriction
17127 No_Implicit_Heap_Allocation is in effect, the image reduces to
17128 the numeric suffix, that is to say the hexadecimal representation of the
17129 virtual address of the control block of the task.
17135 "The value of @code{Current_Task} when in a protected entry
17136 or interrupt handler. See C.7.1(17)."
17139 Protected entries or interrupt handlers can be executed by any
17140 convenient thread, so the value of @code{Current_Task} is undefined.
17146 "The effect of calling @code{Current_Task} from an entry
17147 body or interrupt handler. See C.7.1(19)."
17150 When GNAT can determine statically that @code{Current_Task} is called directly in
17151 the body of an entry (or barrier) then a warning is emitted and @code{Program_Error}
17152 is raised at run time. Otherwise, the effect of calling @code{Current_Task} from an
17153 entry body or interrupt handler is to return the identification of the task
17154 currently executing the code.
17160 "Implementation-defined aspects of
17161 @code{Task_Attributes}. See C.7.2(19)."
17164 There are no implementation-defined aspects of @code{Task_Attributes}.
17170 "Values of all @code{Metrics}. See D(2)."
17173 The metrics information for GNAT depends on the performance of the
17174 underlying operating system. The sources of the run-time for tasking
17175 implementation, together with the output from @emph{-gnatG} can be
17176 used to determine the exact sequence of operating systems calls made
17177 to implement various tasking constructs. Together with appropriate
17178 information on the performance of the underlying operating system,
17179 on the exact target in use, this information can be used to determine
17180 the required metrics.
17186 "The declarations of @code{Any_Priority} and
17187 @code{Priority}. See D.1(11)."
17190 See declarations in file @code{system.ads}.
17196 "Implementation-defined execution resources. See D.1(15)."
17199 There are no implementation-defined execution resources.
17205 "Whether, on a multiprocessor, a task that is waiting for
17206 access to a protected object keeps its processor busy. See D.2.1(3)."
17209 On a multi-processor, a task that is waiting for access to a protected
17210 object does not keep its processor busy.
17216 "The affect of implementation defined execution resources
17217 on task dispatching. See D.2.1(9)."
17220 Tasks map to threads in the threads package used by GNAT. Where possible
17221 and appropriate, these threads correspond to native threads of the
17222 underlying operating system.
17228 "Implementation-defined @emph{policy_identifiers} allowed
17229 in a pragma @code{Task_Dispatching_Policy}. See D.2.2(3)."
17232 There are no implementation-defined policy-identifiers allowed in this
17239 "Implementation-defined aspects of priority inversion. See
17243 Execution of a task cannot be preempted by the implementation processing
17244 of delay expirations for lower priority tasks.
17250 "Implementation-defined task dispatching. See D.2.2(18)."
17253 The policy is the same as that of the underlying threads implementation.
17259 "Implementation-defined @emph{policy_identifiers} allowed
17260 in a pragma @code{Locking_Policy}. See D.3(4)."
17263 The two implementation defined policies permitted in GNAT are
17264 @code{Inheritance_Locking} and @code{Concurrent_Readers_Locking}. On
17265 targets that support the @code{Inheritance_Locking} policy, locking is
17266 implemented by inheritance, i.e., the task owning the lock operates
17267 at a priority equal to the highest priority of any task currently
17268 requesting the lock. On targets that support the
17269 @code{Concurrent_Readers_Locking} policy, locking is implemented with a
17270 read/write lock allowing multiple protected object functions to enter
17277 "Default ceiling priorities. See D.3(10)."
17280 The ceiling priority of protected objects of the type
17281 @code{System.Interrupt_Priority'Last} as described in the Ada
17282 Reference Manual D.3(10),
17288 "The ceiling of any protected object used internally by
17289 the implementation. See D.3(16)."
17292 The ceiling priority of internal protected objects is
17293 @code{System.Priority'Last}.
17299 "Implementation-defined queuing policies. See D.4(1)."
17302 There are no implementation-defined queuing policies.
17308 "On a multiprocessor, any conditions that cause the
17309 completion of an aborted construct to be delayed later than what is
17310 specified for a single processor. See D.6(3)."
17313 The semantics for abort on a multi-processor is the same as on a single
17314 processor, there are no further delays.
17320 "Any operations that implicitly require heap storage
17321 allocation. See D.7(8)."
17324 The only operation that implicitly requires heap storage allocation is
17331 "What happens when a task terminates in the presence of
17332 pragma @code{No_Task_Termination}. See D.7(15)."
17335 Execution is erroneous in that case.
17341 "Implementation-defined aspects of pragma
17342 @code{Restrictions}. See D.7(20)."
17345 There are no such implementation-defined aspects.
17351 "Implementation-defined aspects of package
17352 @code{Real_Time}. See D.8(17)."
17355 There are no implementation defined aspects of package @code{Real_Time}.
17361 "Implementation-defined aspects of
17362 @emph{delay_statements}. See D.9(8)."
17365 Any difference greater than one microsecond will cause the task to be
17366 delayed (see D.9(7)).
17372 "The upper bound on the duration of interrupt blocking
17373 caused by the implementation. See D.12(5)."
17376 The upper bound is determined by the underlying operating system. In
17377 no cases is it more than 10 milliseconds.
17383 "The means for creating and executing distributed
17384 programs. See E(5)."
17387 The GLADE package provides a utility GNATDIST for creating and executing
17388 distributed programs. See the GLADE reference manual for further details.
17394 "Any events that can result in a partition becoming
17395 inaccessible. See E.1(7)."
17398 See the GLADE reference manual for full details on such events.
17404 "The scheduling policies, treatment of priorities, and
17405 management of shared resources between partitions in certain cases. See
17409 See the GLADE reference manual for full details on these aspects of
17410 multi-partition execution.
17416 "Events that cause the version of a compilation unit to
17417 change. See E.3(5)."
17420 Editing the source file of a compilation unit, or the source files of
17421 any units on which it is dependent in a significant way cause the version
17422 to change. No other actions cause the version number to change. All changes
17423 are significant except those which affect only layout, capitalization or
17430 "Whether the execution of the remote subprogram is
17431 immediately aborted as a result of cancellation. See E.4(13)."
17434 See the GLADE reference manual for details on the effect of abort in
17435 a distributed application.
17441 "Implementation-defined aspects of the PCS. See E.5(25)."
17444 See the GLADE reference manual for a full description of all implementation
17445 defined aspects of the PCS.
17451 "Implementation-defined interfaces in the PCS. See
17455 See the GLADE reference manual for a full description of all
17456 implementation defined interfaces.
17462 "The values of named numbers in the package
17463 @code{Decimal}. See F.2(7)."
17467 @multitable {xxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxx}
17510 @emph{Max_Decimal_Digits}
17523 "The value of @code{Max_Picture_Length} in the package
17524 @code{Text_IO.Editing}. See F.3.3(16)."
17533 "The value of @code{Max_Picture_Length} in the package
17534 @code{Wide_Text_IO.Editing}. See F.3.4(5)."
17543 "The accuracy actually achieved by the complex elementary
17544 functions and by other complex arithmetic operations. See G.1(1)."
17547 Standard library functions are used for the complex arithmetic
17548 operations. Only fast math mode is currently supported.
17554 "The sign of a zero result (or a component thereof) from
17555 any operator or function in @code{Numerics.Generic_Complex_Types}, when
17556 @code{Real'Signed_Zeros} is True. See G.1.1(53)."
17559 The signs of zero values are as recommended by the relevant
17560 implementation advice.
17566 "The sign of a zero result (or a component thereof) from
17567 any operator or function in
17568 @code{Numerics.Generic_Complex_Elementary_Functions}, when
17569 @code{Real'Signed_Zeros} is @code{True}. See G.1.2(45)."
17572 The signs of zero values are as recommended by the relevant
17573 implementation advice.
17579 "Whether the strict mode or the relaxed mode is the
17580 default. See G.2(2)."
17583 The strict mode is the default. There is no separate relaxed mode. GNAT
17584 provides a highly efficient implementation of strict mode.
17590 "The result interval in certain cases of fixed-to-float
17591 conversion. See G.2.1(10)."
17594 For cases where the result interval is implementation dependent, the
17595 accuracy is that provided by performing all operations in 64-bit IEEE
17596 floating-point format.
17602 "The result of a floating point arithmetic operation in
17603 overflow situations, when the @code{Machine_Overflows} attribute of the
17604 result type is @code{False}. See G.2.1(13)."
17607 Infinite and NaN values are produced as dictated by the IEEE
17608 floating-point standard.
17609 Note that on machines that are not fully compliant with the IEEE
17610 floating-point standard, such as Alpha, the @emph{-mieee} compiler flag
17611 must be used for achieving IEEE conforming behavior (although at the cost
17612 of a significant performance penalty), so infinite and NaN values are
17613 properly generated.
17619 "The result interval for division (or exponentiation by a
17620 negative exponent), when the floating point hardware implements division
17621 as multiplication by a reciprocal. See G.2.1(16)."
17624 Not relevant, division is IEEE exact.
17630 "The definition of close result set, which determines the
17631 accuracy of certain fixed point multiplications and divisions. See
17635 Operations in the close result set are performed using IEEE long format
17636 floating-point arithmetic. The input operands are converted to
17637 floating-point, the operation is done in floating-point, and the result
17638 is converted to the target type.
17644 "Conditions on a @emph{universal_real} operand of a fixed
17645 point multiplication or division for which the result shall be in the
17646 perfect result set. See G.2.3(22)."
17649 The result is only defined to be in the perfect result set if the result
17650 can be computed by a single scaling operation involving a scale factor
17651 representable in 64-bits.
17657 "The result of a fixed point arithmetic operation in
17658 overflow situations, when the @code{Machine_Overflows} attribute of the
17659 result type is @code{False}. See G.2.3(27)."
17662 Not relevant, @code{Machine_Overflows} is @code{True} for fixed-point
17669 "The result of an elementary function reference in
17670 overflow situations, when the @code{Machine_Overflows} attribute of the
17671 result type is @code{False}. See G.2.4(4)."
17674 IEEE infinite and Nan values are produced as appropriate.
17680 "The value of the angle threshold, within which certain
17681 elementary functions, complex arithmetic operations, and complex
17682 elementary functions yield results conforming to a maximum relative
17683 error bound. See G.2.4(10)."
17686 Information on this subject is not yet available.
17692 "The accuracy of certain elementary functions for
17693 parameters beyond the angle threshold. See G.2.4(10)."
17696 Information on this subject is not yet available.
17702 "The result of a complex arithmetic operation or complex
17703 elementary function reference in overflow situations, when the
17704 @code{Machine_Overflows} attribute of the corresponding real type is
17705 @code{False}. See G.2.6(5)."
17708 IEEE infinite and Nan values are produced as appropriate.
17714 "The accuracy of certain complex arithmetic operations and
17715 certain complex elementary functions for parameters (or components
17716 thereof) beyond the angle threshold. See G.2.6(8)."
17719 Information on those subjects is not yet available.
17725 "Information regarding bounded errors and erroneous
17726 execution. See H.2(1)."
17729 Information on this subject is not yet available.
17735 "Implementation-defined aspects of pragma
17736 @code{Inspection_Point}. See H.3.2(8)."
17739 Pragma @code{Inspection_Point} ensures that the variable is live and can
17740 be examined by the debugger at the inspection point.
17746 "Implementation-defined aspects of pragma
17747 @code{Restrictions}. See H.4(25)."
17750 There are no implementation-defined aspects of pragma @code{Restrictions}. The
17751 use of pragma @code{Restrictions [No_Exceptions]} has no effect on the
17752 generated code. Checks must suppressed by use of pragma @code{Suppress}.
17758 "Any restrictions on pragma @code{Restrictions}. See
17762 There are no restrictions on pragma @code{Restrictions}.
17764 @node Intrinsic Subprograms,Representation Clauses and Pragmas,Implementation Defined Characteristics,Top
17765 @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}
17766 @chapter Intrinsic Subprograms
17769 @geindex Intrinsic Subprograms
17771 GNAT allows a user application program to write the declaration:
17774 pragma Import (Intrinsic, name);
17777 providing that the name corresponds to one of the implemented intrinsic
17778 subprograms in GNAT, and that the parameter profile of the referenced
17779 subprogram meets the requirements. This chapter describes the set of
17780 implemented intrinsic subprograms, and the requirements on parameter profiles.
17781 Note that no body is supplied; as with other uses of pragma Import, the
17782 body is supplied elsewhere (in this case by the compiler itself). Note
17783 that any use of this feature is potentially non-portable, since the
17784 Ada standard does not require Ada compilers to implement this feature.
17787 * Intrinsic Operators::
17788 * Compilation_Date::
17789 * Compilation_Time::
17790 * Enclosing_Entity::
17791 * Exception_Information::
17792 * Exception_Message::
17796 * Shifts and Rotates::
17797 * Source_Location::
17801 @node Intrinsic Operators,Compilation_Date,,Intrinsic Subprograms
17802 @anchor{gnat_rm/intrinsic_subprograms id2}@anchor{253}@anchor{gnat_rm/intrinsic_subprograms intrinsic-operators}@anchor{254}
17803 @section Intrinsic Operators
17806 @geindex Intrinsic operator
17808 All the predefined numeric operators in package Standard
17809 in @code{pragma Import (Intrinsic,..)}
17810 declarations. In the binary operator case, the operands must have the same
17811 size. The operand or operands must also be appropriate for
17812 the operator. For example, for addition, the operands must
17813 both be floating-point or both be fixed-point, and the
17814 right operand for @code{"**"} must have a root type of
17815 @code{Standard.Integer'Base}.
17816 You can use an intrinsic operator declaration as in the following example:
17819 type Int1 is new Integer;
17820 type Int2 is new Integer;
17822 function "+" (X1 : Int1; X2 : Int2) return Int1;
17823 function "+" (X1 : Int1; X2 : Int2) return Int2;
17824 pragma Import (Intrinsic, "+");
17827 This declaration would permit 'mixed mode' arithmetic on items
17828 of the differing types @code{Int1} and @code{Int2}.
17829 It is also possible to specify such operators for private types, if the
17830 full views are appropriate arithmetic types.
17832 @node Compilation_Date,Compilation_Time,Intrinsic Operators,Intrinsic Subprograms
17833 @anchor{gnat_rm/intrinsic_subprograms compilation-date}@anchor{255}@anchor{gnat_rm/intrinsic_subprograms id3}@anchor{256}
17834 @section Compilation_Date
17837 @geindex Compilation_Date
17839 This intrinsic subprogram is used in the implementation of the
17840 library package @code{GNAT.Source_Info}. The only useful use of the
17841 intrinsic import in this case is the one in this unit, so an
17842 application program should simply call the function
17843 @code{GNAT.Source_Info.Compilation_ISO_Date} to obtain the date of
17844 the current compilation (in local time format YYYY-MM-DD).
17846 @node Compilation_Time,Enclosing_Entity,Compilation_Date,Intrinsic Subprograms
17847 @anchor{gnat_rm/intrinsic_subprograms compilation-time}@anchor{257}@anchor{gnat_rm/intrinsic_subprograms id4}@anchor{258}
17848 @section Compilation_Time
17851 @geindex Compilation_Time
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_Time} to obtain the time of
17858 the current compilation (in local time format HH:MM:SS).
17860 @node Enclosing_Entity,Exception_Information,Compilation_Time,Intrinsic Subprograms
17861 @anchor{gnat_rm/intrinsic_subprograms id5}@anchor{259}@anchor{gnat_rm/intrinsic_subprograms enclosing-entity}@anchor{25a}
17862 @section Enclosing_Entity
17865 @geindex Enclosing_Entity
17867 This intrinsic subprogram is used in the implementation of the
17868 library package @code{GNAT.Source_Info}. The only useful use of the
17869 intrinsic import in this case is the one in this unit, so an
17870 application program should simply call the function
17871 @code{GNAT.Source_Info.Enclosing_Entity} to obtain the name of
17872 the current subprogram, package, task, entry, or protected subprogram.
17874 @node Exception_Information,Exception_Message,Enclosing_Entity,Intrinsic Subprograms
17875 @anchor{gnat_rm/intrinsic_subprograms id6}@anchor{25b}@anchor{gnat_rm/intrinsic_subprograms exception-information}@anchor{25c}
17876 @section Exception_Information
17879 @geindex Exception_Information'
17881 This intrinsic subprogram is used in the implementation of the
17882 library package @code{GNAT.Current_Exception}. The only useful
17883 use of the intrinsic import in this case is the one in this unit,
17884 so an application program should simply call the function
17885 @code{GNAT.Current_Exception.Exception_Information} to obtain
17886 the exception information associated with the current exception.
17888 @node Exception_Message,Exception_Name,Exception_Information,Intrinsic Subprograms
17889 @anchor{gnat_rm/intrinsic_subprograms exception-message}@anchor{25d}@anchor{gnat_rm/intrinsic_subprograms id7}@anchor{25e}
17890 @section Exception_Message
17893 @geindex Exception_Message
17895 This intrinsic subprogram is used in the implementation of the
17896 library package @code{GNAT.Current_Exception}. The only useful
17897 use of the intrinsic import in this case is the one in this unit,
17898 so an application program should simply call the function
17899 @code{GNAT.Current_Exception.Exception_Message} to obtain
17900 the message associated with the current exception.
17902 @node Exception_Name,File,Exception_Message,Intrinsic Subprograms
17903 @anchor{gnat_rm/intrinsic_subprograms exception-name}@anchor{25f}@anchor{gnat_rm/intrinsic_subprograms id8}@anchor{260}
17904 @section Exception_Name
17907 @geindex Exception_Name
17909 This intrinsic subprogram is used in the implementation of the
17910 library package @code{GNAT.Current_Exception}. The only useful
17911 use of the intrinsic import in this case is the one in this unit,
17912 so an application program should simply call the function
17913 @code{GNAT.Current_Exception.Exception_Name} to obtain
17914 the name of the current exception.
17916 @node File,Line,Exception_Name,Intrinsic Subprograms
17917 @anchor{gnat_rm/intrinsic_subprograms file}@anchor{261}@anchor{gnat_rm/intrinsic_subprograms id9}@anchor{262}
17923 This intrinsic subprogram is used in the implementation of the
17924 library package @code{GNAT.Source_Info}. The only useful use of the
17925 intrinsic import in this case is the one in this unit, so an
17926 application program should simply call the function
17927 @code{GNAT.Source_Info.File} to obtain the name of the current
17930 @node Line,Shifts and Rotates,File,Intrinsic Subprograms
17931 @anchor{gnat_rm/intrinsic_subprograms id10}@anchor{263}@anchor{gnat_rm/intrinsic_subprograms line}@anchor{264}
17937 This intrinsic subprogram is used in the implementation of the
17938 library package @code{GNAT.Source_Info}. The only useful use of the
17939 intrinsic import in this case is the one in this unit, so an
17940 application program should simply call the function
17941 @code{GNAT.Source_Info.Line} to obtain the number of the current
17944 @node Shifts and Rotates,Source_Location,Line,Intrinsic Subprograms
17945 @anchor{gnat_rm/intrinsic_subprograms id11}@anchor{265}@anchor{gnat_rm/intrinsic_subprograms shifts-and-rotates}@anchor{266}
17946 @section Shifts and Rotates
17949 @geindex Shift_Left
17951 @geindex Shift_Right
17953 @geindex Shift_Right_Arithmetic
17955 @geindex Rotate_Left
17957 @geindex Rotate_Right
17959 In standard Ada, the shift and rotate functions are available only
17960 for the predefined modular types in package @code{Interfaces}. However, in
17961 GNAT it is possible to define these functions for any integer
17962 type (signed or modular), as in this example:
17965 function Shift_Left
17967 Amount : Natural) return T;
17970 The function name must be one of
17971 Shift_Left, Shift_Right, Shift_Right_Arithmetic, Rotate_Left, or
17972 Rotate_Right. T must be an integer type. T'Size must be
17973 8, 16, 32 or 64 bits; if T is modular, the modulus
17974 must be 2**8, 2**16, 2**32 or 2**64.
17975 The result type must be the same as the type of @code{Value}.
17976 The shift amount must be Natural.
17977 The formal parameter names can be anything.
17979 A more convenient way of providing these shift operators is to use
17980 the Provide_Shift_Operators pragma, which provides the function declarations
17981 and corresponding pragma Import's for all five shift functions.
17983 @node Source_Location,,Shifts and Rotates,Intrinsic Subprograms
17984 @anchor{gnat_rm/intrinsic_subprograms source-location}@anchor{267}@anchor{gnat_rm/intrinsic_subprograms id12}@anchor{268}
17985 @section Source_Location
17988 @geindex Source_Location
17990 This intrinsic subprogram is used in the implementation of the
17991 library routine @code{GNAT.Source_Info}. The only useful use of the
17992 intrinsic import in this case is the one in this unit, so an
17993 application program should simply call the function
17994 @code{GNAT.Source_Info.Source_Location} to obtain the current
17995 source file location.
17997 @node Representation Clauses and Pragmas,Standard Library Routines,Intrinsic Subprograms,Top
17998 @anchor{gnat_rm/representation_clauses_and_pragmas representation-clauses-and-pragmas}@anchor{d}@anchor{gnat_rm/representation_clauses_and_pragmas doc}@anchor{269}@anchor{gnat_rm/representation_clauses_and_pragmas id1}@anchor{26a}
17999 @chapter Representation Clauses and Pragmas
18002 @geindex Representation Clauses
18004 @geindex Representation Clause
18006 @geindex Representation Pragma
18009 @geindex representation
18011 This section describes the representation clauses accepted by GNAT, and
18012 their effect on the representation of corresponding data objects.
18014 GNAT fully implements Annex C (Systems Programming). This means that all
18015 the implementation advice sections in chapter 13 are fully implemented.
18016 However, these sections only require a minimal level of support for
18017 representation clauses. GNAT provides much more extensive capabilities,
18018 and this section describes the additional capabilities provided.
18021 * Alignment Clauses::
18023 * Storage_Size Clauses::
18024 * Size of Variant Record Objects::
18025 * Biased Representation::
18026 * Value_Size and Object_Size Clauses::
18027 * Component_Size Clauses::
18028 * Bit_Order Clauses::
18029 * Effect of Bit_Order on Byte Ordering::
18030 * Pragma Pack for Arrays::
18031 * Pragma Pack for Records::
18032 * Record Representation Clauses::
18033 * Handling of Records with Holes::
18034 * Enumeration Clauses::
18035 * Address Clauses::
18036 * Use of Address Clauses for Memory-Mapped I/O::
18037 * Effect of Convention on Representation::
18038 * Conventions and Anonymous Access Types::
18039 * Determining the Representations chosen by GNAT::
18043 @node Alignment Clauses,Size Clauses,,Representation Clauses and Pragmas
18044 @anchor{gnat_rm/representation_clauses_and_pragmas id2}@anchor{26b}@anchor{gnat_rm/representation_clauses_and_pragmas alignment-clauses}@anchor{26c}
18045 @section Alignment Clauses
18048 @geindex Alignment Clause
18050 GNAT requires that all alignment clauses specify a power of 2, and all
18051 default alignments are always a power of 2. The default alignment
18052 values are as follows:
18058 @emph{Elementary Types}.
18060 For elementary types, the alignment is the minimum of the actual size of
18061 objects of the type divided by @code{Storage_Unit},
18062 and the maximum alignment supported by the target.
18063 (This maximum alignment is given by the GNAT-specific attribute
18064 @code{Standard'Maximum_Alignment}; see @ref{189,,Attribute Maximum_Alignment}.)
18066 @geindex Maximum_Alignment attribute
18068 For example, for type @code{Long_Float}, the object size is 8 bytes, and the
18069 default alignment will be 8 on any target that supports alignments
18070 this large, but on some targets, the maximum alignment may be smaller
18071 than 8, in which case objects of type @code{Long_Float} will be maximally
18077 For arrays, the alignment is equal to the alignment of the component type
18078 for the normal case where no packing or component size is given. If the
18079 array is packed, and the packing is effective (see separate section on
18080 packed arrays), then the alignment will be either 4, 2, or 1 for long packed
18081 arrays or arrays whose length is not known at compile time, depending on
18082 whether the component size is divisible by 4, 2, or is odd. For short packed
18083 arrays, which are handled internally as modular types, the alignment
18084 will be as described for elementary types, e.g. a packed array of length
18085 31 bits will have an object size of four bytes, and an alignment of 4.
18090 For the normal non-packed case, the alignment of a record is equal to
18091 the maximum alignment of any of its components. For tagged records, this
18092 includes the implicit access type used for the tag. If a pragma @code{Pack}
18093 is used and all components are packable (see separate section on pragma
18094 @code{Pack}), then the resulting alignment is 1, unless the layout of the
18095 record makes it profitable to increase it.
18097 A special case is when:
18103 the size of the record is given explicitly, or a
18104 full record representation clause is given, and
18107 the size of the record is 2, 4, or 8 bytes.
18110 In this case, an alignment is chosen to match the
18111 size of the record. For example, if we have:
18114 type Small is record
18117 for Small'Size use 16;
18120 then the default alignment of the record type @code{Small} is 2, not 1. This
18121 leads to more efficient code when the record is treated as a unit, and also
18122 allows the type to specified as @code{Atomic} on architectures requiring
18126 An alignment clause may specify a larger alignment than the default value
18127 up to some maximum value dependent on the target (obtainable by using the
18128 attribute reference @code{Standard'Maximum_Alignment}). It may also specify
18129 a smaller alignment than the default value for enumeration, integer and
18130 fixed point types, as well as for record types, for example
18137 for V'alignment use 1;
18143 The default alignment for the type @code{V} is 4, as a result of the
18144 Integer field in the record, but it is permissible, as shown, to
18145 override the default alignment of the record with a smaller value.
18150 Note that according to the Ada standard, an alignment clause applies only
18151 to the first named subtype. If additional subtypes are declared, then the
18152 compiler is allowed to choose any alignment it likes, and there is no way
18153 to control this choice. Consider:
18156 type R is range 1 .. 10_000;
18157 for R'Alignment use 1;
18158 subtype RS is R range 1 .. 1000;
18161 The alignment clause specifies an alignment of 1 for the first named subtype
18162 @code{R} but this does not necessarily apply to @code{RS}. When writing
18163 portable Ada code, you should avoid writing code that explicitly or
18164 implicitly relies on the alignment of such subtypes.
18166 For the GNAT compiler, if an explicit alignment clause is given, this
18167 value is also used for any subsequent subtypes. So for GNAT, in the
18168 above example, you can count on the alignment of @code{RS} being 1. But this
18169 assumption is non-portable, and other compilers may choose different
18170 alignments for the subtype @code{RS}.
18172 @node Size Clauses,Storage_Size Clauses,Alignment Clauses,Representation Clauses and Pragmas
18173 @anchor{gnat_rm/representation_clauses_and_pragmas id3}@anchor{26d}@anchor{gnat_rm/representation_clauses_and_pragmas size-clauses}@anchor{26e}
18174 @section Size Clauses
18177 @geindex Size Clause
18179 The default size for a type @code{T} is obtainable through the
18180 language-defined attribute @code{T'Size} and also through the
18181 equivalent GNAT-defined attribute @code{T'Value_Size}.
18182 For objects of type @code{T}, GNAT will generally increase the type size
18183 so that the object size (obtainable through the GNAT-defined attribute
18184 @code{T'Object_Size})
18185 is a multiple of @code{T'Alignment * Storage_Unit}.
18190 type Smallint is range 1 .. 6;
18198 In this example, @code{Smallint'Size} = @code{Smallint'Value_Size} = 3,
18199 as specified by the RM rules,
18200 but objects of this type will have a size of 8
18201 (@code{Smallint'Object_Size} = 8),
18202 since objects by default occupy an integral number
18203 of storage units. On some targets, notably older
18204 versions of the Digital Alpha, the size of stand
18205 alone objects of this type may be 32, reflecting
18206 the inability of the hardware to do byte load/stores.
18208 Similarly, the size of type @code{Rec} is 40 bits
18209 (@code{Rec'Size} = @code{Rec'Value_Size} = 40), but
18210 the alignment is 4, so objects of this type will have
18211 their size increased to 64 bits so that it is a multiple
18212 of the alignment (in bits). This decision is
18213 in accordance with the specific Implementation Advice in RM 13.3(43):
18217 "A @code{Size} clause should be supported for an object if the specified
18218 @code{Size} is at least as large as its subtype's @code{Size}, and corresponds
18219 to a size in storage elements that is a multiple of the object's
18220 @code{Alignment} (if the @code{Alignment} is nonzero)."
18223 An explicit size clause may be used to override the default size by
18224 increasing it. For example, if we have:
18227 type My_Boolean is new Boolean;
18228 for My_Boolean'Size use 32;
18231 then values of this type will always be 32 bits long. In the case of
18232 discrete types, the size can be increased up to 64 bits, with the effect
18233 that the entire specified field is used to hold the value, sign- or
18234 zero-extended as appropriate. If more than 64 bits is specified, then
18235 padding space is allocated after the value, and a warning is issued that
18236 there are unused bits.
18238 Similarly the size of records and arrays may be increased, and the effect
18239 is to add padding bits after the value. This also causes a warning message
18242 The largest Size value permitted in GNAT is 2**31-1. Since this is a
18243 Size in bits, this corresponds to an object of size 256 megabytes (minus
18244 one). This limitation is true on all targets. The reason for this
18245 limitation is that it improves the quality of the code in many cases
18246 if it is known that a Size value can be accommodated in an object of
18249 @node Storage_Size Clauses,Size of Variant Record Objects,Size Clauses,Representation Clauses and Pragmas
18250 @anchor{gnat_rm/representation_clauses_and_pragmas storage-size-clauses}@anchor{26f}@anchor{gnat_rm/representation_clauses_and_pragmas id4}@anchor{270}
18251 @section Storage_Size Clauses
18254 @geindex Storage_Size Clause
18256 For tasks, the @code{Storage_Size} clause specifies the amount of space
18257 to be allocated for the task stack. This cannot be extended, and if the
18258 stack is exhausted, then @code{Storage_Error} will be raised (if stack
18259 checking is enabled). Use a @code{Storage_Size} attribute definition clause,
18260 or a @code{Storage_Size} pragma in the task definition to set the
18261 appropriate required size. A useful technique is to include in every
18262 task definition a pragma of the form:
18265 pragma Storage_Size (Default_Stack_Size);
18268 Then @code{Default_Stack_Size} can be defined in a global package, and
18269 modified as required. Any tasks requiring stack sizes different from the
18270 default can have an appropriate alternative reference in the pragma.
18272 You can also use the @emph{-d} binder switch to modify the default stack
18275 For access types, the @code{Storage_Size} clause specifies the maximum
18276 space available for allocation of objects of the type. If this space is
18277 exceeded then @code{Storage_Error} will be raised by an allocation attempt.
18278 In the case where the access type is declared local to a subprogram, the
18279 use of a @code{Storage_Size} clause triggers automatic use of a special
18280 predefined storage pool (@code{System.Pool_Size}) that ensures that all
18281 space for the pool is automatically reclaimed on exit from the scope in
18282 which the type is declared.
18284 A special case recognized by the compiler is the specification of a
18285 @code{Storage_Size} of zero for an access type. This means that no
18286 items can be allocated from the pool, and this is recognized at compile
18287 time, and all the overhead normally associated with maintaining a fixed
18288 size storage pool is eliminated. Consider the following example:
18292 type R is array (Natural) of Character;
18293 type P is access all R;
18294 for P'Storage_Size use 0;
18295 -- Above access type intended only for interfacing purposes
18299 procedure g (m : P);
18300 pragma Import (C, g);
18310 As indicated in this example, these dummy storage pools are often useful in
18311 connection with interfacing where no object will ever be allocated. If you
18312 compile the above example, you get the warning:
18315 p.adb:16:09: warning: allocation from empty storage pool
18316 p.adb:16:09: warning: Storage_Error will be raised at run time
18319 Of course in practice, there will not be any explicit allocators in the
18320 case of such an access declaration.
18322 @node Size of Variant Record Objects,Biased Representation,Storage_Size Clauses,Representation Clauses and Pragmas
18323 @anchor{gnat_rm/representation_clauses_and_pragmas id5}@anchor{271}@anchor{gnat_rm/representation_clauses_and_pragmas size-of-variant-record-objects}@anchor{272}
18324 @section Size of Variant Record Objects
18328 @geindex variant record objects
18330 @geindex Variant record objects
18333 In the case of variant record objects, there is a question whether Size gives
18334 information about a particular variant, or the maximum size required
18335 for any variant. Consider the following program
18338 with Text_IO; use Text_IO;
18340 type R1 (A : Boolean := False) is record
18342 when True => X : Character;
18343 when False => null;
18351 Put_Line (Integer'Image (V1'Size));
18352 Put_Line (Integer'Image (V2'Size));
18356 Here we are dealing with a variant record, where the True variant
18357 requires 16 bits, and the False variant requires 8 bits.
18358 In the above example, both V1 and V2 contain the False variant,
18359 which is only 8 bits long. However, the result of running the
18367 The reason for the difference here is that the discriminant value of
18368 V1 is fixed, and will always be False. It is not possible to assign
18369 a True variant value to V1, therefore 8 bits is sufficient. On the
18370 other hand, in the case of V2, the initial discriminant value is
18371 False (from the default), but it is possible to assign a True
18372 variant value to V2, therefore 16 bits must be allocated for V2
18373 in the general case, even fewer bits may be needed at any particular
18374 point during the program execution.
18376 As can be seen from the output of this program, the @code{'Size}
18377 attribute applied to such an object in GNAT gives the actual allocated
18378 size of the variable, which is the largest size of any of the variants.
18379 The Ada Reference Manual is not completely clear on what choice should
18380 be made here, but the GNAT behavior seems most consistent with the
18381 language in the RM.
18383 In some cases, it may be desirable to obtain the size of the current
18384 variant, rather than the size of the largest variant. This can be
18385 achieved in GNAT by making use of the fact that in the case of a
18386 subprogram parameter, GNAT does indeed return the size of the current
18387 variant (because a subprogram has no way of knowing how much space
18388 is actually allocated for the actual).
18390 Consider the following modified version of the above program:
18393 with Text_IO; use Text_IO;
18395 type R1 (A : Boolean := False) is record
18397 when True => X : Character;
18398 when False => null;
18404 function Size (V : R1) return Integer is
18410 Put_Line (Integer'Image (V2'Size));
18411 Put_Line (Integer'Image (Size (V2)));
18413 Put_Line (Integer'Image (V2'Size));
18414 Put_Line (Integer'Image (Size (V2)));
18418 The output from this program is
18427 Here we see that while the @code{'Size} attribute always returns
18428 the maximum size, regardless of the current variant value, the
18429 @code{Size} function does indeed return the size of the current
18432 @node Biased Representation,Value_Size and Object_Size Clauses,Size of Variant Record Objects,Representation Clauses and Pragmas
18433 @anchor{gnat_rm/representation_clauses_and_pragmas id6}@anchor{273}@anchor{gnat_rm/representation_clauses_and_pragmas biased-representation}@anchor{274}
18434 @section Biased Representation
18437 @geindex Size for biased representation
18439 @geindex Biased representation
18441 In the case of scalars with a range starting at other than zero, it is
18442 possible in some cases to specify a size smaller than the default minimum
18443 value, and in such cases, GNAT uses an unsigned biased representation,
18444 in which zero is used to represent the lower bound, and successive values
18445 represent successive values of the type.
18447 For example, suppose we have the declaration:
18450 type Small is range -7 .. -4;
18451 for Small'Size use 2;
18454 Although the default size of type @code{Small} is 4, the @code{Size}
18455 clause is accepted by GNAT and results in the following representation
18459 -7 is represented as 2#00#
18460 -6 is represented as 2#01#
18461 -5 is represented as 2#10#
18462 -4 is represented as 2#11#
18465 Biased representation is only used if the specified @code{Size} clause
18466 cannot be accepted in any other manner. These reduced sizes that force
18467 biased representation can be used for all discrete types except for
18468 enumeration types for which a representation clause is given.
18470 @node Value_Size and Object_Size Clauses,Component_Size Clauses,Biased Representation,Representation Clauses and Pragmas
18471 @anchor{gnat_rm/representation_clauses_and_pragmas id7}@anchor{275}@anchor{gnat_rm/representation_clauses_and_pragmas value-size-and-object-size-clauses}@anchor{276}
18472 @section Value_Size and Object_Size Clauses
18475 @geindex Value_Size
18477 @geindex Object_Size
18480 @geindex of objects
18482 In Ada 95 and Ada 2005, @code{T'Size} for a type @code{T} is the minimum
18483 number of bits required to hold values of type @code{T}.
18484 Although this interpretation was allowed in Ada 83, it was not required,
18485 and this requirement in practice can cause some significant difficulties.
18486 For example, in most Ada 83 compilers, @code{Natural'Size} was 32.
18487 However, in Ada 95 and Ada 2005,
18488 @code{Natural'Size} is
18489 typically 31. This means that code may change in behavior when moving
18490 from Ada 83 to Ada 95 or Ada 2005. For example, consider:
18493 type Rec is record;
18499 at 0 range 0 .. Natural'Size - 1;
18500 at 0 range Natural'Size .. 2 * Natural'Size - 1;
18504 In the above code, since the typical size of @code{Natural} objects
18505 is 32 bits and @code{Natural'Size} is 31, the above code can cause
18506 unexpected inefficient packing in Ada 95 and Ada 2005, and in general
18507 there are cases where the fact that the object size can exceed the
18508 size of the type causes surprises.
18510 To help get around this problem GNAT provides two implementation
18511 defined attributes, @code{Value_Size} and @code{Object_Size}. When
18512 applied to a type, these attributes yield the size of the type
18513 (corresponding to the RM defined size attribute), and the size of
18514 objects of the type respectively.
18516 The @code{Object_Size} is used for determining the default size of
18517 objects and components. This size value can be referred to using the
18518 @code{Object_Size} attribute. The phrase 'is used' here means that it is
18519 the basis of the determination of the size. The backend is free to
18520 pad this up if necessary for efficiency, e.g., an 8-bit stand-alone
18521 character might be stored in 32 bits on a machine with no efficient
18522 byte access instructions such as the Alpha.
18524 The default rules for the value of @code{Object_Size} for
18525 discrete types are as follows:
18531 The @code{Object_Size} for base subtypes reflect the natural hardware
18532 size in bits (run the compiler with @emph{-gnatS} to find those values
18533 for numeric types). Enumeration types and fixed-point base subtypes have
18534 8, 16, 32, or 64 bits for this size, depending on the range of values
18538 The @code{Object_Size} of a subtype is the same as the
18539 @code{Object_Size} of
18540 the type from which it is obtained.
18543 The @code{Object_Size} of a derived base type is copied from the parent
18544 base type, and the @code{Object_Size} of a derived first subtype is copied
18545 from the parent first subtype.
18548 The @code{Value_Size} attribute
18549 is the (minimum) number of bits required to store a value
18551 This value is used to determine how tightly to pack
18552 records or arrays with components of this type, and also affects
18553 the semantics of unchecked conversion (unchecked conversions where
18554 the @code{Value_Size} values differ generate a warning, and are potentially
18557 The default rules for the value of @code{Value_Size} are as follows:
18563 The @code{Value_Size} for a base subtype is the minimum number of bits
18564 required to store all values of the type (including the sign bit
18565 only if negative values are possible).
18568 If a subtype statically matches the first subtype of a given type, then it has
18569 by default the same @code{Value_Size} as the first subtype. This is a
18570 consequence of RM 13.1(14): "if two subtypes statically match,
18571 then their subtype-specific aspects are the same".)
18574 All other subtypes have a @code{Value_Size} corresponding to the minimum
18575 number of bits required to store all values of the subtype. For
18576 dynamic bounds, it is assumed that the value can range down or up
18577 to the corresponding bound of the ancestor
18580 The RM defined attribute @code{Size} corresponds to the
18581 @code{Value_Size} attribute.
18583 The @code{Size} attribute may be defined for a first-named subtype. This sets
18584 the @code{Value_Size} of
18585 the first-named subtype to the given value, and the
18586 @code{Object_Size} of this first-named subtype to the given value padded up
18587 to an appropriate boundary. It is a consequence of the default rules
18588 above that this @code{Object_Size} will apply to all further subtypes. On the
18589 other hand, @code{Value_Size} is affected only for the first subtype, any
18590 dynamic subtypes obtained from it directly, and any statically matching
18591 subtypes. The @code{Value_Size} of any other static subtypes is not affected.
18593 @code{Value_Size} and
18594 @code{Object_Size} may be explicitly set for any subtype using
18595 an attribute definition clause. Note that the use of these attributes
18596 can cause the RM 13.1(14) rule to be violated. If two access types
18597 reference aliased objects whose subtypes have differing @code{Object_Size}
18598 values as a result of explicit attribute definition clauses, then it
18599 is illegal to convert from one access subtype to the other. For a more
18600 complete description of this additional legality rule, see the
18601 description of the @code{Object_Size} attribute.
18603 To get a feel for the difference, consider the following examples (note
18604 that in each case the base is @code{Short_Short_Integer} with a size of 8):
18607 @multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxx}
18610 Type or subtype declaration
18622 @code{type x1 is range 0 .. 5;}
18634 @code{type x2 is range 0 .. 5;}
18635 @code{for x2'size use 12;}
18647 @code{subtype x3 is x2 range 0 .. 3;}
18659 @code{subtype x4 is x2'base range 0 .. 10;}
18671 @code{dynamic : x2'Base range -64 .. +63;}
18679 @code{subtype x5 is x2 range 0 .. dynamic;}
18691 @code{subtype x6 is x2'base range 0 .. dynamic;}
18704 Note: the entries marked '*' are not actually specified by the Ada
18705 Reference Manual, which has nothing to say about size in the dynamic
18706 case. What GNAT does is to allocate sufficient bits to accomodate any
18707 possible dynamic values for the bounds at run-time.
18709 So far, so good, but GNAT has to obey the RM rules, so the question is
18710 under what conditions must the RM @code{Size} be used.
18711 The following is a list
18712 of the occasions on which the RM @code{Size} must be used:
18718 Component size for packed arrays or records
18721 Value of the attribute @code{Size} for a type
18724 Warning about sizes not matching for unchecked conversion
18727 For record types, the @code{Object_Size} is always a multiple of the
18728 alignment of the type (this is true for all types). In some cases the
18729 @code{Value_Size} can be smaller. Consider:
18738 On a typical 32-bit architecture, the X component will be four bytes, and
18739 require four-byte alignment, and the Y component will be one byte. In this
18740 case @code{R'Value_Size} will be 40 (bits) since this is the minimum size
18741 required to store a value of this type, and for example, it is permissible
18742 to have a component of type R in an outer array whose component size is
18743 specified to be 48 bits. However, @code{R'Object_Size} will be 64 (bits),
18744 since it must be rounded up so that this value is a multiple of the
18745 alignment (4 bytes = 32 bits).
18747 For all other types, the @code{Object_Size}
18748 and @code{Value_Size} are the same (and equivalent to the RM attribute @code{Size}).
18749 Only @code{Size} may be specified for such types.
18751 Note that @code{Value_Size} can be used to force biased representation
18752 for a particular subtype. Consider this example:
18755 type R is (A, B, C, D, E, F);
18756 subtype RAB is R range A .. B;
18757 subtype REF is R range E .. F;
18760 By default, @code{RAB}
18761 has a size of 1 (sufficient to accommodate the representation
18762 of @code{A} and @code{B}, 0 and 1), and @code{REF}
18763 has a size of 3 (sufficient to accommodate the representation
18764 of @code{E} and @code{F}, 4 and 5). But if we add the
18765 following @code{Value_Size} attribute definition clause:
18768 for REF'Value_Size use 1;
18771 then biased representation is forced for @code{REF},
18772 and 0 will represent @code{E} and 1 will represent @code{F}.
18773 A warning is issued when a @code{Value_Size} attribute
18774 definition clause forces biased representation. This
18775 warning can be turned off using @code{-gnatw.B}.
18777 @node Component_Size Clauses,Bit_Order Clauses,Value_Size and Object_Size Clauses,Representation Clauses and Pragmas
18778 @anchor{gnat_rm/representation_clauses_and_pragmas id8}@anchor{277}@anchor{gnat_rm/representation_clauses_and_pragmas component-size-clauses}@anchor{278}
18779 @section Component_Size Clauses
18782 @geindex Component_Size Clause
18784 Normally, the value specified in a component size clause must be consistent
18785 with the subtype of the array component with regard to size and alignment.
18786 In other words, the value specified must be at least equal to the size
18787 of this subtype, and must be a multiple of the alignment value.
18789 In addition, component size clauses are allowed which cause the array
18790 to be packed, by specifying a smaller value. A first case is for
18791 component size values in the range 1 through 63. The value specified
18792 must not be smaller than the Size of the subtype. GNAT will accurately
18793 honor all packing requests in this range. For example, if we have:
18796 type r is array (1 .. 8) of Natural;
18797 for r'Component_Size use 31;
18800 then the resulting array has a length of 31 bytes (248 bits = 8 * 31).
18801 Of course access to the components of such an array is considerably
18802 less efficient than if the natural component size of 32 is used.
18803 A second case is when the subtype of the component is a record type
18804 padded because of its default alignment. For example, if we have:
18813 type a is array (1 .. 8) of r;
18814 for a'Component_Size use 72;
18817 then the resulting array has a length of 72 bytes, instead of 96 bytes
18818 if the alignment of the record (4) was obeyed.
18820 Note that there is no point in giving both a component size clause
18821 and a pragma Pack for the same array type. if such duplicate
18822 clauses are given, the pragma Pack will be ignored.
18824 @node Bit_Order Clauses,Effect of Bit_Order on Byte Ordering,Component_Size Clauses,Representation Clauses and Pragmas
18825 @anchor{gnat_rm/representation_clauses_and_pragmas bit-order-clauses}@anchor{279}@anchor{gnat_rm/representation_clauses_and_pragmas id9}@anchor{27a}
18826 @section Bit_Order Clauses
18829 @geindex Bit_Order Clause
18831 @geindex bit ordering
18836 For record subtypes, GNAT permits the specification of the @code{Bit_Order}
18837 attribute. The specification may either correspond to the default bit
18838 order for the target, in which case the specification has no effect and
18839 places no additional restrictions, or it may be for the non-standard
18840 setting (that is the opposite of the default).
18842 In the case where the non-standard value is specified, the effect is
18843 to renumber bits within each byte, but the ordering of bytes is not
18844 affected. There are certain
18845 restrictions placed on component clauses as follows:
18851 Components fitting within a single storage unit.
18853 These are unrestricted, and the effect is merely to renumber bits. For
18854 example if we are on a little-endian machine with @code{Low_Order_First}
18855 being the default, then the following two declarations have exactly
18861 B : Integer range 1 .. 120;
18865 A at 0 range 0 .. 0;
18866 B at 0 range 1 .. 7;
18871 B : Integer range 1 .. 120;
18874 for R2'Bit_Order use High_Order_First;
18877 A at 0 range 7 .. 7;
18878 B at 0 range 0 .. 6;
18882 The useful application here is to write the second declaration with the
18883 @code{Bit_Order} attribute definition clause, and know that it will be treated
18884 the same, regardless of whether the target is little-endian or big-endian.
18887 Components occupying an integral number of bytes.
18889 These are components that exactly fit in two or more bytes. Such component
18890 declarations are allowed, but have no effect, since it is important to realize
18891 that the @code{Bit_Order} specification does not affect the ordering of bytes.
18892 In particular, the following attempt at getting an endian-independent integer
18900 for R2'Bit_Order use High_Order_First;
18903 A at 0 range 0 .. 31;
18907 This declaration will result in a little-endian integer on a
18908 little-endian machine, and a big-endian integer on a big-endian machine.
18909 If byte flipping is required for interoperability between big- and
18910 little-endian machines, this must be explicitly programmed. This capability
18911 is not provided by @code{Bit_Order}.
18914 Components that are positioned across byte boundaries.
18916 but do not occupy an integral number of bytes. Given that bytes are not
18917 reordered, such fields would occupy a non-contiguous sequence of bits
18918 in memory, requiring non-trivial code to reassemble. They are for this
18919 reason not permitted, and any component clause specifying such a layout
18920 will be flagged as illegal by GNAT.
18923 Since the misconception that Bit_Order automatically deals with all
18924 endian-related incompatibilities is a common one, the specification of
18925 a component field that is an integral number of bytes will always
18926 generate a warning. This warning may be suppressed using @code{pragma Warnings (Off)}
18927 if desired. The following section contains additional
18928 details regarding the issue of byte ordering.
18930 @node Effect of Bit_Order on Byte Ordering,Pragma Pack for Arrays,Bit_Order Clauses,Representation Clauses and Pragmas
18931 @anchor{gnat_rm/representation_clauses_and_pragmas id10}@anchor{27b}@anchor{gnat_rm/representation_clauses_and_pragmas effect-of-bit-order-on-byte-ordering}@anchor{27c}
18932 @section Effect of Bit_Order on Byte Ordering
18935 @geindex byte ordering
18940 In this section we will review the effect of the @code{Bit_Order} attribute
18941 definition clause on byte ordering. Briefly, it has no effect at all, but
18942 a detailed example will be helpful. Before giving this
18943 example, let us review the precise
18944 definition of the effect of defining @code{Bit_Order}. The effect of a
18945 non-standard bit order is described in section 13.5.3 of the Ada
18950 "2 A bit ordering is a method of interpreting the meaning of
18951 the storage place attributes."
18954 To understand the precise definition of storage place attributes in
18955 this context, we visit section 13.5.1 of the manual:
18959 "13 A record_representation_clause (without the mod_clause)
18960 specifies the layout. The storage place attributes (see 13.5.2)
18961 are taken from the values of the position, first_bit, and last_bit
18962 expressions after normalizing those values so that first_bit is
18963 less than Storage_Unit."
18966 The critical point here is that storage places are taken from
18967 the values after normalization, not before. So the @code{Bit_Order}
18968 interpretation applies to normalized values. The interpretation
18969 is described in the later part of the 13.5.3 paragraph:
18973 "2 A bit ordering is a method of interpreting the meaning of
18974 the storage place attributes. High_Order_First (known in the
18975 vernacular as 'big endian') means that the first bit of a
18976 storage element (bit 0) is the most significant bit (interpreting
18977 the sequence of bits that represent a component as an unsigned
18978 integer value). Low_Order_First (known in the vernacular as
18979 'little endian') means the opposite: the first bit is the
18980 least significant."
18983 Note that the numbering is with respect to the bits of a storage
18984 unit. In other words, the specification affects only the numbering
18985 of bits within a single storage unit.
18987 We can make the effect clearer by giving an example.
18989 Suppose that we have an external device which presents two bytes, the first
18990 byte presented, which is the first (low addressed byte) of the two byte
18991 record is called Master, and the second byte is called Slave.
18993 The left most (most significant bit is called Control for each byte, and
18994 the remaining 7 bits are called V1, V2, ... V7, where V7 is the rightmost
18995 (least significant) bit.
18997 On a big-endian machine, we can write the following representation clause
19000 type Data is record
19001 Master_Control : Bit;
19009 Slave_Control : Bit;
19019 for Data use record
19020 Master_Control at 0 range 0 .. 0;
19021 Master_V1 at 0 range 1 .. 1;
19022 Master_V2 at 0 range 2 .. 2;
19023 Master_V3 at 0 range 3 .. 3;
19024 Master_V4 at 0 range 4 .. 4;
19025 Master_V5 at 0 range 5 .. 5;
19026 Master_V6 at 0 range 6 .. 6;
19027 Master_V7 at 0 range 7 .. 7;
19028 Slave_Control at 1 range 0 .. 0;
19029 Slave_V1 at 1 range 1 .. 1;
19030 Slave_V2 at 1 range 2 .. 2;
19031 Slave_V3 at 1 range 3 .. 3;
19032 Slave_V4 at 1 range 4 .. 4;
19033 Slave_V5 at 1 range 5 .. 5;
19034 Slave_V6 at 1 range 6 .. 6;
19035 Slave_V7 at 1 range 7 .. 7;
19039 Now if we move this to a little endian machine, then the bit ordering within
19040 the byte is backwards, so we have to rewrite the record rep clause as:
19043 for Data use record
19044 Master_Control at 0 range 7 .. 7;
19045 Master_V1 at 0 range 6 .. 6;
19046 Master_V2 at 0 range 5 .. 5;
19047 Master_V3 at 0 range 4 .. 4;
19048 Master_V4 at 0 range 3 .. 3;
19049 Master_V5 at 0 range 2 .. 2;
19050 Master_V6 at 0 range 1 .. 1;
19051 Master_V7 at 0 range 0 .. 0;
19052 Slave_Control at 1 range 7 .. 7;
19053 Slave_V1 at 1 range 6 .. 6;
19054 Slave_V2 at 1 range 5 .. 5;
19055 Slave_V3 at 1 range 4 .. 4;
19056 Slave_V4 at 1 range 3 .. 3;
19057 Slave_V5 at 1 range 2 .. 2;
19058 Slave_V6 at 1 range 1 .. 1;
19059 Slave_V7 at 1 range 0 .. 0;
19063 It is a nuisance to have to rewrite the clause, especially if
19064 the code has to be maintained on both machines. However,
19065 this is a case that we can handle with the
19066 @code{Bit_Order} attribute if it is implemented.
19067 Note that the implementation is not required on byte addressed
19068 machines, but it is indeed implemented in GNAT.
19069 This means that we can simply use the
19070 first record clause, together with the declaration
19073 for Data'Bit_Order use High_Order_First;
19076 and the effect is what is desired, namely the layout is exactly the same,
19077 independent of whether the code is compiled on a big-endian or little-endian
19080 The important point to understand is that byte ordering is not affected.
19081 A @code{Bit_Order} attribute definition never affects which byte a field
19082 ends up in, only where it ends up in that byte.
19083 To make this clear, let us rewrite the record rep clause of the previous
19087 for Data'Bit_Order use High_Order_First;
19088 for Data use record
19089 Master_Control at 0 range 0 .. 0;
19090 Master_V1 at 0 range 1 .. 1;
19091 Master_V2 at 0 range 2 .. 2;
19092 Master_V3 at 0 range 3 .. 3;
19093 Master_V4 at 0 range 4 .. 4;
19094 Master_V5 at 0 range 5 .. 5;
19095 Master_V6 at 0 range 6 .. 6;
19096 Master_V7 at 0 range 7 .. 7;
19097 Slave_Control at 0 range 8 .. 8;
19098 Slave_V1 at 0 range 9 .. 9;
19099 Slave_V2 at 0 range 10 .. 10;
19100 Slave_V3 at 0 range 11 .. 11;
19101 Slave_V4 at 0 range 12 .. 12;
19102 Slave_V5 at 0 range 13 .. 13;
19103 Slave_V6 at 0 range 14 .. 14;
19104 Slave_V7 at 0 range 15 .. 15;
19108 This is exactly equivalent to saying (a repeat of the first example):
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 1 range 0 .. 0;
19122 Slave_V1 at 1 range 1 .. 1;
19123 Slave_V2 at 1 range 2 .. 2;
19124 Slave_V3 at 1 range 3 .. 3;
19125 Slave_V4 at 1 range 4 .. 4;
19126 Slave_V5 at 1 range 5 .. 5;
19127 Slave_V6 at 1 range 6 .. 6;
19128 Slave_V7 at 1 range 7 .. 7;
19132 Why are they equivalent? Well take a specific field, the @code{Slave_V2}
19133 field. The storage place attributes are obtained by normalizing the
19134 values given so that the @code{First_Bit} value is less than 8. After
19135 normalizing the values (0,10,10) we get (1,2,2) which is exactly what
19136 we specified in the other case.
19138 Now one might expect that the @code{Bit_Order} attribute might affect
19139 bit numbering within the entire record component (two bytes in this
19140 case, thus affecting which byte fields end up in), but that is not
19141 the way this feature is defined, it only affects numbering of bits,
19142 not which byte they end up in.
19144 Consequently it never makes sense to specify a starting bit number
19145 greater than 7 (for a byte addressable field) if an attribute
19146 definition for @code{Bit_Order} has been given, and indeed it
19147 may be actively confusing to specify such a value, so the compiler
19148 generates a warning for such usage.
19150 If you do need to control byte ordering then appropriate conditional
19151 values must be used. If in our example, the slave byte came first on
19152 some machines we might write:
19155 Master_Byte_First constant Boolean := ...;
19157 Master_Byte : constant Natural :=
19158 1 - Boolean'Pos (Master_Byte_First);
19159 Slave_Byte : constant Natural :=
19160 Boolean'Pos (Master_Byte_First);
19162 for Data'Bit_Order use High_Order_First;
19163 for Data use record
19164 Master_Control at Master_Byte range 0 .. 0;
19165 Master_V1 at Master_Byte range 1 .. 1;
19166 Master_V2 at Master_Byte range 2 .. 2;
19167 Master_V3 at Master_Byte range 3 .. 3;
19168 Master_V4 at Master_Byte range 4 .. 4;
19169 Master_V5 at Master_Byte range 5 .. 5;
19170 Master_V6 at Master_Byte range 6 .. 6;
19171 Master_V7 at Master_Byte range 7 .. 7;
19172 Slave_Control at Slave_Byte range 0 .. 0;
19173 Slave_V1 at Slave_Byte range 1 .. 1;
19174 Slave_V2 at Slave_Byte range 2 .. 2;
19175 Slave_V3 at Slave_Byte range 3 .. 3;
19176 Slave_V4 at Slave_Byte range 4 .. 4;
19177 Slave_V5 at Slave_Byte range 5 .. 5;
19178 Slave_V6 at Slave_Byte range 6 .. 6;
19179 Slave_V7 at Slave_Byte range 7 .. 7;
19183 Now to switch between machines, all that is necessary is
19184 to set the boolean constant @code{Master_Byte_First} in
19185 an appropriate manner.
19187 @node Pragma Pack for Arrays,Pragma Pack for Records,Effect of Bit_Order on Byte Ordering,Representation Clauses and Pragmas
19188 @anchor{gnat_rm/representation_clauses_and_pragmas pragma-pack-for-arrays}@anchor{27d}@anchor{gnat_rm/representation_clauses_and_pragmas id11}@anchor{27e}
19189 @section Pragma Pack for Arrays
19192 @geindex Pragma Pack (for arrays)
19194 Pragma @code{Pack} applied to an array has an effect that depends upon whether the
19195 component type is @emph{packable}. For a component type to be @emph{packable}, it must
19196 be one of the following cases:
19202 Any elementary type.
19205 Any small packed array type with a static size.
19208 Any small simple record type with a static size.
19211 For all these cases, if the component subtype size is in the range
19212 1 through 64, then the effect of the pragma @code{Pack} is exactly as though a
19213 component size were specified giving the component subtype size.
19215 All other types are non-packable, they occupy an integral number of storage
19216 units and the only effect of pragma Pack is to remove alignment gaps.
19218 For example if we have:
19221 type r is range 0 .. 17;
19223 type ar is array (1 .. 8) of r;
19227 Then the component size of @code{ar} will be set to 5 (i.e., to @code{r'size},
19228 and the size of the array @code{ar} will be exactly 40 bits).
19230 Note that in some cases this rather fierce approach to packing can produce
19231 unexpected effects. For example, in Ada 95 and Ada 2005,
19232 subtype @code{Natural} typically has a size of 31, meaning that if you
19233 pack an array of @code{Natural}, you get 31-bit
19234 close packing, which saves a few bits, but results in far less efficient
19235 access. Since many other Ada compilers will ignore such a packing request,
19236 GNAT will generate a warning on some uses of pragma @code{Pack} that it guesses
19237 might not be what is intended. You can easily remove this warning by
19238 using an explicit @code{Component_Size} setting instead, which never generates
19239 a warning, since the intention of the programmer is clear in this case.
19241 GNAT treats packed arrays in one of two ways. If the size of the array is
19242 known at compile time and is less than 64 bits, then internally the array
19243 is represented as a single modular type, of exactly the appropriate number
19244 of bits. If the length is greater than 63 bits, or is not known at compile
19245 time, then the packed array is represented as an array of bytes, and the
19246 length is always a multiple of 8 bits.
19248 Note that to represent a packed array as a modular type, the alignment must
19249 be suitable for the modular type involved. For example, on typical machines
19250 a 32-bit packed array will be represented by a 32-bit modular integer with
19251 an alignment of four bytes. If you explicitly override the default alignment
19252 with an alignment clause that is too small, the modular representation
19253 cannot be used. For example, consider the following set of declarations:
19256 type R is range 1 .. 3;
19257 type S is array (1 .. 31) of R;
19258 for S'Component_Size use 2;
19260 for S'Alignment use 1;
19263 If the alignment clause were not present, then a 62-bit modular
19264 representation would be chosen (typically with an alignment of 4 or 8
19265 bytes depending on the target). But the default alignment is overridden
19266 with the explicit alignment clause. This means that the modular
19267 representation cannot be used, and instead the array of bytes
19268 representation must be used, meaning that the length must be a multiple
19269 of 8. Thus the above set of declarations will result in a diagnostic
19270 rejecting the size clause and noting that the minimum size allowed is 64.
19272 @geindex Pragma Pack (for type Natural)
19274 @geindex Pragma Pack warning
19276 One special case that is worth noting occurs when the base type of the
19277 component size is 8/16/32 and the subtype is one bit less. Notably this
19278 occurs with subtype @code{Natural}. Consider:
19281 type Arr is array (1 .. 32) of Natural;
19285 In all commonly used Ada 83 compilers, this pragma Pack would be ignored,
19286 since typically @code{Natural'Size} is 32 in Ada 83, and in any case most
19287 Ada 83 compilers did not attempt 31 bit packing.
19289 In Ada 95 and Ada 2005, @code{Natural'Size} is required to be 31. Furthermore,
19290 GNAT really does pack 31-bit subtype to 31 bits. This may result in a
19291 substantial unintended performance penalty when porting legacy Ada 83 code.
19292 To help prevent this, GNAT generates a warning in such cases. If you really
19293 want 31 bit packing in a case like this, you can set the component size
19297 type Arr is array (1 .. 32) of Natural;
19298 for Arr'Component_Size use 31;
19301 Here 31-bit packing is achieved as required, and no warning is generated,
19302 since in this case the programmer intention is clear.
19304 @node Pragma Pack for Records,Record Representation Clauses,Pragma Pack for Arrays,Representation Clauses and Pragmas
19305 @anchor{gnat_rm/representation_clauses_and_pragmas pragma-pack-for-records}@anchor{27f}@anchor{gnat_rm/representation_clauses_and_pragmas id12}@anchor{280}
19306 @section Pragma Pack for Records
19309 @geindex Pragma Pack (for records)
19311 Pragma @code{Pack} applied to a record will pack the components to reduce
19312 wasted space from alignment gaps and by reducing the amount of space
19313 taken by components. We distinguish between @emph{packable} components and
19314 @emph{non-packable} components.
19315 Components of the following types are considered packable:
19321 Components of an elementary type are packable unless they are aliased,
19322 independent, or of an atomic type.
19325 Small packed arrays, where the size is statically known, are represented
19326 internally as modular integers, and so they are also packable.
19329 Small simple records, where the size is statically known, are also packable.
19332 For all these cases, if the @code{'Size} value is in the range 1 through 64, the
19333 components occupy the exact number of bits corresponding to this value
19334 and are packed with no padding bits, i.e. they can start on an arbitrary
19337 All other types are non-packable, they occupy an integral number of storage
19338 units and the only effect of pragma @code{Pack} is to remove alignment gaps.
19340 For example, consider the record
19343 type Rb1 is array (1 .. 13) of Boolean;
19346 type Rb2 is array (1 .. 65) of Boolean;
19349 type AF is new Float with Atomic;
19362 The representation for the record @code{X2} is as follows:
19365 for X2'Size use 224;
19367 L1 at 0 range 0 .. 0;
19368 L2 at 0 range 1 .. 64;
19369 L3 at 12 range 0 .. 31;
19370 L4 at 16 range 0 .. 0;
19371 L5 at 16 range 1 .. 13;
19372 L6 at 18 range 0 .. 71;
19376 Studying this example, we see that the packable fields @code{L1}
19378 of length equal to their sizes, and placed at specific bit boundaries (and
19379 not byte boundaries) to
19380 eliminate padding. But @code{L3} is of a non-packable float type (because
19381 it is aliased), so it is on the next appropriate alignment boundary.
19383 The next two fields are fully packable, so @code{L4} and @code{L5} are
19384 minimally packed with no gaps. However, type @code{Rb2} is a packed
19385 array that is longer than 64 bits, so it is itself non-packable. Thus
19386 the @code{L6} field is aligned to the next byte boundary, and takes an
19387 integral number of bytes, i.e., 72 bits.
19389 @node Record Representation Clauses,Handling of Records with Holes,Pragma Pack for Records,Representation Clauses and Pragmas
19390 @anchor{gnat_rm/representation_clauses_and_pragmas id13}@anchor{281}@anchor{gnat_rm/representation_clauses_and_pragmas record-representation-clauses}@anchor{282}
19391 @section Record Representation Clauses
19394 @geindex Record Representation Clause
19396 Record representation clauses may be given for all record types, including
19397 types obtained by record extension. Component clauses are allowed for any
19398 static component. The restrictions on component clauses depend on the type
19401 @geindex Component Clause
19403 For all components of an elementary type, the only restriction on component
19404 clauses is that the size must be at least the @code{'Size} value of the type
19405 (actually the Value_Size). There are no restrictions due to alignment,
19406 and such components may freely cross storage boundaries.
19408 Packed arrays with a size up to and including 64 bits are represented
19409 internally using a modular type with the appropriate number of bits, and
19410 thus the same lack of restriction applies. For example, if you declare:
19413 type R is array (1 .. 49) of Boolean;
19418 then a component clause for a component of type @code{R} may start on any
19419 specified bit boundary, and may specify a value of 49 bits or greater.
19421 For packed bit arrays that are longer than 64 bits, there are two
19422 cases. If the component size is a power of 2 (1,2,4,8,16,32 bits),
19423 including the important case of single bits or boolean values, then
19424 there are no limitations on placement of such components, and they
19425 may start and end at arbitrary bit boundaries.
19427 If the component size is not a power of 2 (e.g., 3 or 5), then
19428 an array of this type longer than 64 bits must always be placed on
19429 on a storage unit (byte) boundary and occupy an integral number
19430 of storage units (bytes). Any component clause that does not
19431 meet this requirement will be rejected.
19433 Any aliased component, or component of an aliased type, must
19434 have its normal alignment and size. A component clause that
19435 does not meet this requirement will be rejected.
19437 The tag field of a tagged type always occupies an address sized field at
19438 the start of the record. No component clause may attempt to overlay this
19439 tag. When a tagged type appears as a component, the tag field must have
19442 In the case of a record extension @code{T1}, of a type @code{T}, no component clause applied
19443 to the type @code{T1} can specify a storage location that would overlap the first
19444 @code{T'Size} bytes of the record.
19446 For all other component types, including non-bit-packed arrays,
19447 the component can be placed at an arbitrary bit boundary,
19448 so for example, the following is permitted:
19451 type R is array (1 .. 10) of Boolean;
19460 G at 0 range 0 .. 0;
19461 H at 0 range 1 .. 1;
19462 L at 0 range 2 .. 81;
19463 R at 0 range 82 .. 161;
19467 @node Handling of Records with Holes,Enumeration Clauses,Record Representation Clauses,Representation Clauses and Pragmas
19468 @anchor{gnat_rm/representation_clauses_and_pragmas handling-of-records-with-holes}@anchor{283}@anchor{gnat_rm/representation_clauses_and_pragmas id14}@anchor{284}
19469 @section Handling of Records with Holes
19472 @geindex Handling of Records with Holes
19474 As a result of alignment considerations, records may contain "holes"
19476 which do not correspond to the data bits of any of the components.
19477 Record representation clauses can also result in holes in records.
19479 GNAT does not attempt to clear these holes, so in record objects,
19480 they should be considered to hold undefined rubbish. The generated
19481 equality routine just tests components so does not access these
19482 undefined bits, and assignment and copy operations may or may not
19483 preserve the contents of these holes (for assignments, the holes
19484 in the target will in practice contain either the bits that are
19485 present in the holes in the source, or the bits that were present
19486 in the target before the assignment).
19488 If it is necessary to ensure that holes in records have all zero
19489 bits, then record objects for which this initialization is desired
19490 should be explicitly set to all zero values using Unchecked_Conversion
19491 or address overlays. For example
19494 type HRec is record
19500 On typical machines, integers need to be aligned on a four-byte
19501 boundary, resulting in three bytes of undefined rubbish following
19502 the 8-bit field for C. To ensure that the hole in a variable of
19503 type HRec is set to all zero bits,
19504 you could for example do:
19507 type Base is record
19508 Dummy1, Dummy2 : Integer := 0;
19513 for RealVar'Address use BaseVar'Address;
19516 Now the 8-bytes of the value of RealVar start out containing all zero
19517 bits. A safer approach is to just define dummy fields, avoiding the
19521 type HRec is record
19523 Dummy1 : Short_Short_Integer := 0;
19524 Dummy2 : Short_Short_Integer := 0;
19525 Dummy3 : Short_Short_Integer := 0;
19530 And to make absolutely sure that the intent of this is followed, you
19531 can use representation clauses:
19534 for Hrec use record
19535 C at 0 range 0 .. 7;
19536 Dummy1 at 1 range 0 .. 7;
19537 Dummy2 at 2 range 0 .. 7;
19538 Dummy3 at 3 range 0 .. 7;
19539 I at 4 range 0 .. 31;
19541 for Hrec'Size use 64;
19544 @node Enumeration Clauses,Address Clauses,Handling of Records with Holes,Representation Clauses and Pragmas
19545 @anchor{gnat_rm/representation_clauses_and_pragmas enumeration-clauses}@anchor{285}@anchor{gnat_rm/representation_clauses_and_pragmas id15}@anchor{286}
19546 @section Enumeration Clauses
19549 The only restriction on enumeration clauses is that the range of values
19550 must be representable. For the signed case, if one or more of the
19551 representation values are negative, all values must be in the range:
19554 System.Min_Int .. System.Max_Int
19557 For the unsigned case, where all values are nonnegative, the values must
19561 0 .. System.Max_Binary_Modulus;
19564 A @emph{confirming} representation clause is one in which the values range
19565 from 0 in sequence, i.e., a clause that confirms the default representation
19566 for an enumeration type.
19567 Such a confirming representation
19568 is permitted by these rules, and is specially recognized by the compiler so
19569 that no extra overhead results from the use of such a clause.
19571 If an array has an index type which is an enumeration type to which an
19572 enumeration clause has been applied, then the array is stored in a compact
19573 manner. Consider the declarations:
19576 type r is (A, B, C);
19577 for r use (A => 1, B => 5, C => 10);
19578 type t is array (r) of Character;
19581 The array type t corresponds to a vector with exactly three elements and
19582 has a default size equal to @code{3*Character'Size}. This ensures efficient
19583 use of space, but means that accesses to elements of the array will incur
19584 the overhead of converting representation values to the corresponding
19585 positional values, (i.e., the value delivered by the @code{Pos} attribute).
19587 @node Address Clauses,Use of Address Clauses for Memory-Mapped I/O,Enumeration Clauses,Representation Clauses and Pragmas
19588 @anchor{gnat_rm/representation_clauses_and_pragmas id16}@anchor{287}@anchor{gnat_rm/representation_clauses_and_pragmas address-clauses}@anchor{288}
19589 @section Address Clauses
19592 @geindex Address Clause
19594 The reference manual allows a general restriction on representation clauses,
19595 as found in RM 13.1(22):
19599 "An implementation need not support representation
19600 items containing nonstatic expressions, except that
19601 an implementation should support a representation item
19602 for a given entity if each nonstatic expression in the
19603 representation item is a name that statically denotes
19604 a constant declared before the entity."
19607 In practice this is applicable only to address clauses, since this is the
19608 only case in which a nonstatic expression is permitted by the syntax. As
19609 the AARM notes in sections 13.1 (22.a-22.h):
19613 22.a Reason: This is to avoid the following sort of thing:
19615 22.b X : Integer := F(...);
19616 Y : Address := G(...);
19617 for X'Address use Y;
19619 22.c In the above, we have to evaluate the
19620 initialization expression for X before we
19621 know where to put the result. This seems
19622 like an unreasonable implementation burden.
19624 22.d The above code should instead be written
19627 22.e Y : constant Address := G(...);
19628 X : Integer := F(...);
19629 for X'Address use Y;
19631 22.f This allows the expression 'Y' to be safely
19632 evaluated before X is created.
19634 22.g The constant could be a formal parameter of mode in.
19636 22.h An implementation can support other nonstatic
19637 expressions if it wants to. Expressions of type
19638 Address are hardly ever static, but their value
19639 might be known at compile time anyway in many
19643 GNAT does indeed permit many additional cases of nonstatic expressions. In
19644 particular, if the type involved is elementary there are no restrictions
19645 (since in this case, holding a temporary copy of the initialization value,
19646 if one is present, is inexpensive). In addition, if there is no implicit or
19647 explicit initialization, then there are no restrictions. GNAT will reject
19648 only the case where all three of these conditions hold:
19654 The type of the item is non-elementary (e.g., a record or array).
19657 There is explicit or implicit initialization required for the object.
19658 Note that access values are always implicitly initialized.
19661 The address value is nonstatic. Here GNAT is more permissive than the
19662 RM, and allows the address value to be the address of a previously declared
19663 stand-alone variable, as long as it does not itself have an address clause.
19666 Anchor : Some_Initialized_Type;
19667 Overlay : Some_Initialized_Type;
19668 for Overlay'Address use Anchor'Address;
19671 However, the prefix of the address clause cannot be an array component, or
19672 a component of a discriminated record.
19675 As noted above in section 22.h, address values are typically nonstatic. In
19676 particular the To_Address function, even if applied to a literal value, is
19677 a nonstatic function call. To avoid this minor annoyance, GNAT provides
19678 the implementation defined attribute 'To_Address. The following two
19679 expressions have identical values:
19683 @geindex To_Address
19686 To_Address (16#1234_0000#)
19687 System'To_Address (16#1234_0000#);
19690 except that the second form is considered to be a static expression, and
19691 thus when used as an address clause value is always permitted.
19693 Additionally, GNAT treats as static an address clause that is an
19694 unchecked_conversion of a static integer value. This simplifies the porting
19695 of legacy code, and provides a portable equivalent to the GNAT attribute
19698 Another issue with address clauses is the interaction with alignment
19699 requirements. When an address clause is given for an object, the address
19700 value must be consistent with the alignment of the object (which is usually
19701 the same as the alignment of the type of the object). If an address clause
19702 is given that specifies an inappropriately aligned address value, then the
19703 program execution is erroneous.
19705 Since this source of erroneous behavior can have unfortunate effects on
19706 machines with strict alignment requirements, GNAT
19707 checks (at compile time if possible, generating a warning, or at execution
19708 time with a run-time check) that the alignment is appropriate. If the
19709 run-time check fails, then @code{Program_Error} is raised. This run-time
19710 check is suppressed if range checks are suppressed, or if the special GNAT
19711 check Alignment_Check is suppressed, or if
19712 @code{pragma Restrictions (No_Elaboration_Code)} is in effect. It is also
19713 suppressed by default on non-strict alignment machines (such as the x86).
19715 Finally, GNAT does not permit overlaying of objects of class-wide types. In
19716 most cases, the compiler can detect an attempt at such overlays and will
19717 generate a warning at compile time and a Program_Error exception at run time.
19721 An address clause cannot be given for an exported object. More
19722 understandably the real restriction is that objects with an address
19723 clause cannot be exported. This is because such variables are not
19724 defined by the Ada program, so there is no external object to export.
19728 It is permissible to give an address clause and a pragma Import for the
19729 same object. In this case, the variable is not really defined by the
19730 Ada program, so there is no external symbol to be linked. The link name
19731 and the external name are ignored in this case. The reason that we allow this
19732 combination is that it provides a useful idiom to avoid unwanted
19733 initializations on objects with address clauses.
19735 When an address clause is given for an object that has implicit or
19736 explicit initialization, then by default initialization takes place. This
19737 means that the effect of the object declaration is to overwrite the
19738 memory at the specified address. This is almost always not what the
19739 programmer wants, so GNAT will output a warning:
19749 for Ext'Address use System'To_Address (16#1234_1234#);
19751 >>> warning: implicit initialization of "Ext" may
19752 modify overlaid storage
19753 >>> warning: use pragma Import for "Ext" to suppress
19754 initialization (RM B(24))
19759 As indicated by the warning message, the solution is to use a (dummy) pragma
19760 Import to suppress this initialization. The pragma tell the compiler that the
19761 object is declared and initialized elsewhere. The following package compiles
19762 without warnings (and the initialization is suppressed):
19772 for Ext'Address use System'To_Address (16#1234_1234#);
19773 pragma Import (Ada, Ext);
19777 A final issue with address clauses involves their use for overlaying
19778 variables, as in the following example:
19780 @geindex Overlaying of objects
19785 for B'Address use A'Address;
19788 or alternatively, using the form recommended by the RM:
19792 Addr : constant Address := A'Address;
19794 for B'Address use Addr;
19797 In both of these cases, @code{A} and @code{B} become aliased to one another
19798 via the address clause. This use of address clauses to overlay
19799 variables, achieving an effect similar to unchecked conversion
19800 was erroneous in Ada 83, but in Ada 95 and Ada 2005
19801 the effect is implementation defined. Furthermore, the
19802 Ada RM specifically recommends that in a situation
19803 like this, @code{B} should be subject to the following
19804 implementation advice (RM 13.3(19)):
19808 "19 If the Address of an object is specified, or it is imported
19809 or exported, then the implementation should not perform
19810 optimizations based on assumptions of no aliases."
19813 GNAT follows this recommendation, and goes further by also applying
19814 this recommendation to the overlaid variable (@code{A} in the above example)
19815 in this case. This means that the overlay works "as expected", in that
19816 a modification to one of the variables will affect the value of the other.
19818 More generally, GNAT interprets this recommendation conservatively for
19819 address clauses: in the cases other than overlays, it considers that the
19820 object is effectively subject to pragma @code{Volatile} and implements the
19821 associated semantics.
19823 Note that when address clause overlays are used in this way, there is an
19824 issue of unintentional initialization, as shown by this example:
19827 package Overwrite_Record is
19829 A : Character := 'C';
19830 B : Character := 'A';
19832 X : Short_Integer := 3;
19834 for Y'Address use X'Address;
19836 >>> warning: default initialization of "Y" may
19837 modify "X", use pragma Import for "Y" to
19838 suppress initialization (RM B.1(24))
19840 end Overwrite_Record;
19843 Here the default initialization of @code{Y} will clobber the value
19844 of @code{X}, which justifies the warning. The warning notes that
19845 this effect can be eliminated by adding a @code{pragma Import}
19846 which suppresses the initialization:
19849 package Overwrite_Record is
19851 A : Character := 'C';
19852 B : Character := 'A';
19854 X : Short_Integer := 3;
19856 for Y'Address use X'Address;
19857 pragma Import (Ada, Y);
19858 end Overwrite_Record;
19861 Note that the use of @code{pragma Initialize_Scalars} may cause variables to
19862 be initialized when they would not otherwise have been in the absence
19863 of the use of this pragma. This may cause an overlay to have this
19864 unintended clobbering effect. The compiler avoids this for scalar
19865 types, but not for composite objects (where in general the effect
19866 of @code{Initialize_Scalars} is part of the initialization routine
19867 for the composite object:
19870 pragma Initialize_Scalars;
19871 with Ada.Text_IO; use Ada.Text_IO;
19872 procedure Overwrite_Array is
19873 type Arr is array (1 .. 5) of Integer;
19874 X : Arr := (others => 1);
19876 for A'Address use X'Address;
19878 >>> warning: default initialization of "A" may
19879 modify "X", use pragma Import for "A" to
19880 suppress initialization (RM B.1(24))
19883 if X /= Arr'(others => 1) then
19884 Put_Line ("X was clobbered");
19886 Put_Line ("X was not clobbered");
19888 end Overwrite_Array;
19891 The above program generates the warning as shown, and at execution
19892 time, prints @code{X was clobbered}. If the @code{pragma Import} is
19893 added as suggested:
19896 pragma Initialize_Scalars;
19897 with Ada.Text_IO; use Ada.Text_IO;
19898 procedure Overwrite_Array is
19899 type Arr is array (1 .. 5) of Integer;
19900 X : Arr := (others => 1);
19902 for A'Address use X'Address;
19903 pragma Import (Ada, A);
19905 if X /= Arr'(others => 1) then
19906 Put_Line ("X was clobbered");
19908 Put_Line ("X was not clobbered");
19910 end Overwrite_Array;
19913 then the program compiles without the warning and when run will generate
19914 the output @code{X was not clobbered}.
19916 @node Use of Address Clauses for Memory-Mapped I/O,Effect of Convention on Representation,Address Clauses,Representation Clauses and Pragmas
19917 @anchor{gnat_rm/representation_clauses_and_pragmas id17}@anchor{289}@anchor{gnat_rm/representation_clauses_and_pragmas use-of-address-clauses-for-memory-mapped-i-o}@anchor{28a}
19918 @section Use of Address Clauses for Memory-Mapped I/O
19921 @geindex Memory-mapped I/O
19923 A common pattern is to use an address clause to map an atomic variable to
19924 a location in memory that corresponds to a memory-mapped I/O operation or
19925 operations, for example:
19928 type Mem_Word is record
19931 pragma Atomic (Mem_Word);
19932 for Mem_Word_Size use 32;
19935 for Mem'Address use some-address;
19942 For a full access (reference or modification) of the variable (Mem) in this
19943 case, as in the above examples, GNAT guarantees that the entire atomic word
19944 will be accessed, in accordance with the RM C.6(15) clause.
19946 A problem arises with a component access such as:
19952 Note that the component A is not declared as atomic. This means that it is
19953 not clear what this assignment means. It could correspond to full word read
19954 and write as given in the first example, or on architectures that supported
19955 such an operation it might be a single byte store instruction. The RM does
19956 not have anything to say in this situation, and GNAT does not make any
19957 guarantee. The code generated may vary from target to target. GNAT will issue
19958 a warning in such a case:
19963 >>> warning: access to non-atomic component of atomic array,
19964 may cause unexpected accesses to atomic object
19967 It is best to be explicit in this situation, by either declaring the
19968 components to be atomic if you want the byte store, or explicitly writing
19969 the full word access sequence if that is what the hardware requires.
19970 Alternatively, if the full word access sequence is required, GNAT also
19971 provides the pragma @code{Volatile_Full_Access} which can be used in lieu of
19972 pragma @code{Atomic} and will give the additional guarantee.
19974 @node Effect of Convention on Representation,Conventions and Anonymous Access Types,Use of Address Clauses for Memory-Mapped I/O,Representation Clauses and Pragmas
19975 @anchor{gnat_rm/representation_clauses_and_pragmas id18}@anchor{28b}@anchor{gnat_rm/representation_clauses_and_pragmas effect-of-convention-on-representation}@anchor{28c}
19976 @section Effect of Convention on Representation
19979 @geindex Convention
19980 @geindex effect on representation
19982 Normally the specification of a foreign language convention for a type or
19983 an object has no effect on the chosen representation. In particular, the
19984 representation chosen for data in GNAT generally meets the standard system
19985 conventions, and for example records are laid out in a manner that is
19986 consistent with C. This means that specifying convention C (for example)
19989 There are four exceptions to this general rule:
19995 @emph{Convention Fortran and array subtypes}.
19997 If pragma Convention Fortran is specified for an array subtype, then in
19998 accordance with the implementation advice in section 3.6.2(11) of the
19999 Ada Reference Manual, the array will be stored in a Fortran-compatible
20000 column-major manner, instead of the normal default row-major order.
20003 @emph{Convention C and enumeration types}
20005 GNAT normally stores enumeration types in 8, 16, or 32 bits as required
20006 to accommodate all values of the type. For example, for the enumeration
20010 type Color is (Red, Green, Blue);
20013 8 bits is sufficient to store all values of the type, so by default, objects
20014 of type @code{Color} will be represented using 8 bits. However, normal C
20015 convention is to use 32 bits for all enum values in C, since enum values
20016 are essentially of type int. If pragma @code{Convention C} is specified for an
20017 Ada enumeration type, then the size is modified as necessary (usually to
20018 32 bits) to be consistent with the C convention for enum values.
20020 Note that this treatment applies only to types. If Convention C is given for
20021 an enumeration object, where the enumeration type is not Convention C, then
20022 Object_Size bits are allocated. For example, for a normal enumeration type,
20023 with less than 256 elements, only 8 bits will be allocated for the object.
20024 Since this may be a surprise in terms of what C expects, GNAT will issue a
20025 warning in this situation. The warning can be suppressed by giving an explicit
20026 size clause specifying the desired size.
20029 @emph{Convention C/Fortran and Boolean types}
20031 In C, the usual convention for boolean values, that is values used for
20032 conditions, is that zero represents false, and nonzero values represent
20033 true. In Ada, the normal convention is that two specific values, typically
20034 0/1, are used to represent false/true respectively.
20036 Fortran has a similar convention for @code{LOGICAL} values (any nonzero
20037 value represents true).
20039 To accommodate the Fortran and C conventions, if a pragma Convention specifies
20040 C or Fortran convention for a derived Boolean, as in the following example:
20043 type C_Switch is new Boolean;
20044 pragma Convention (C, C_Switch);
20047 then the GNAT generated code will treat any nonzero value as true. For truth
20048 values generated by GNAT, the conventional value 1 will be used for True, but
20049 when one of these values is read, any nonzero value is treated as True.
20052 @node Conventions and Anonymous Access Types,Determining the Representations chosen by GNAT,Effect of Convention on Representation,Representation Clauses and Pragmas
20053 @anchor{gnat_rm/representation_clauses_and_pragmas conventions-and-anonymous-access-types}@anchor{28d}@anchor{gnat_rm/representation_clauses_and_pragmas id19}@anchor{28e}
20054 @section Conventions and Anonymous Access Types
20057 @geindex Anonymous access types
20059 @geindex Convention for anonymous access types
20061 The RM is not entirely clear on convention handling in a number of cases,
20062 and in particular, it is not clear on the convention to be given to
20063 anonymous access types in general, and in particular what is to be
20064 done for the case of anonymous access-to-subprogram.
20066 In GNAT, we decide that if an explicit Convention is applied
20067 to an object or component, and its type is such an anonymous type,
20068 then the convention will apply to this anonymous type as well. This
20069 seems to make sense since it is anomolous in any case to have a
20070 different convention for an object and its type, and there is clearly
20071 no way to explicitly specify a convention for an anonymous type, since
20072 it doesn't have a name to specify!
20074 Furthermore, we decide that if a convention is applied to a record type,
20075 then this convention is inherited by any of its components that are of an
20076 anonymous access type which do not have an explicitly specified convention.
20078 The following program shows these conventions in action:
20081 package ConvComp is
20082 type Foo is range 1 .. 10;
20084 A : access function (X : Foo) return Integer;
20087 pragma Convention (C, T1);
20090 A : access function (X : Foo) return Integer;
20091 pragma Convention (C, A);
20094 pragma Convention (COBOL, T2);
20097 A : access function (X : Foo) return Integer;
20098 pragma Convention (COBOL, A);
20101 pragma Convention (C, T3);
20104 A : access function (X : Foo) return Integer;
20107 pragma Convention (COBOL, T4);
20109 function F (X : Foo) return Integer;
20110 pragma Convention (C, F);
20112 function F (X : Foo) return Integer is (13);
20114 TV1 : T1 := (F'Access, 12); -- OK
20115 TV2 : T2 := (F'Access, 13); -- OK
20117 TV3 : T3 := (F'Access, 13); -- ERROR
20119 >>> subprogram "F" has wrong convention
20120 >>> does not match access to subprogram declared at line 17
20121 38. TV4 : T4 := (F'Access, 13); -- ERROR
20123 >>> subprogram "F" has wrong convention
20124 >>> does not match access to subprogram declared at line 24
20128 @node Determining the Representations chosen by GNAT,,Conventions and Anonymous Access Types,Representation Clauses and Pragmas
20129 @anchor{gnat_rm/representation_clauses_and_pragmas id20}@anchor{28f}@anchor{gnat_rm/representation_clauses_and_pragmas determining-the-representations-chosen-by-gnat}@anchor{290}
20130 @section Determining the Representations chosen by GNAT
20133 @geindex Representation
20134 @geindex determination of
20136 @geindex -gnatR (gcc)
20138 Although the descriptions in this section are intended to be complete, it is
20139 often easier to simply experiment to see what GNAT accepts and what the
20140 effect is on the layout of types and objects.
20142 As required by the Ada RM, if a representation clause is not accepted, then
20143 it must be rejected as illegal by the compiler. However, when a
20144 representation clause or pragma is accepted, there can still be questions
20145 of what the compiler actually does. For example, if a partial record
20146 representation clause specifies the location of some components and not
20147 others, then where are the non-specified components placed? Or if pragma
20148 @code{Pack} is used on a record, then exactly where are the resulting
20149 fields placed? The section on pragma @code{Pack} in this chapter can be
20150 used to answer the second question, but it is often easier to just see
20151 what the compiler does.
20153 For this purpose, GNAT provides the option @emph{-gnatR}. If you compile
20154 with this option, then the compiler will output information on the actual
20155 representations chosen, in a format similar to source representation
20156 clauses. For example, if we compile the package:
20160 type r (x : boolean) is tagged record
20162 when True => S : String (1 .. 100);
20163 when False => null;
20167 type r2 is new r (false) with record
20172 y2 at 16 range 0 .. 31;
20179 type x1 is array (1 .. 10) of x;
20180 for x1'component_size use 11;
20182 type ia is access integer;
20184 type Rb1 is array (1 .. 13) of Boolean;
20187 type Rb2 is array (1 .. 65) of Boolean;
20202 using the switch @emph{-gnatR} we obtain the following output:
20205 Representation information for unit q
20206 -------------------------------------
20209 for r'Alignment use 4;
20211 x at 4 range 0 .. 7;
20212 _tag at 0 range 0 .. 31;
20213 s at 5 range 0 .. 799;
20216 for r2'Size use 160;
20217 for r2'Alignment use 4;
20219 x at 4 range 0 .. 7;
20220 _tag at 0 range 0 .. 31;
20221 _parent at 0 range 0 .. 63;
20222 y2 at 16 range 0 .. 31;
20226 for x'Alignment use 1;
20228 y at 0 range 0 .. 7;
20231 for x1'Size use 112;
20232 for x1'Alignment use 1;
20233 for x1'Component_Size use 11;
20235 for rb1'Size use 13;
20236 for rb1'Alignment use 2;
20237 for rb1'Component_Size use 1;
20239 for rb2'Size use 72;
20240 for rb2'Alignment use 1;
20241 for rb2'Component_Size use 1;
20243 for x2'Size use 224;
20244 for x2'Alignment use 4;
20246 l1 at 0 range 0 .. 0;
20247 l2 at 0 range 1 .. 64;
20248 l3 at 12 range 0 .. 31;
20249 l4 at 16 range 0 .. 0;
20250 l5 at 16 range 1 .. 13;
20251 l6 at 18 range 0 .. 71;
20255 The Size values are actually the Object_Size, i.e., the default size that
20256 will be allocated for objects of the type.
20257 The @code{??} size for type r indicates that we have a variant record, and the
20258 actual size of objects will depend on the discriminant value.
20260 The Alignment values show the actual alignment chosen by the compiler
20261 for each record or array type.
20263 The record representation clause for type r shows where all fields
20264 are placed, including the compiler generated tag field (whose location
20265 cannot be controlled by the programmer).
20267 The record representation clause for the type extension r2 shows all the
20268 fields present, including the parent field, which is a copy of the fields
20269 of the parent type of r2, i.e., r1.
20271 The component size and size clauses for types rb1 and rb2 show
20272 the exact effect of pragma @code{Pack} on these arrays, and the record
20273 representation clause for type x2 shows how pragma @cite{Pack} affects
20276 In some cases, it may be useful to cut and paste the representation clauses
20277 generated by the compiler into the original source to fix and guarantee
20278 the actual representation to be used.
20280 @node Standard Library Routines,The Implementation of Standard I/O,Representation Clauses and Pragmas,Top
20281 @anchor{gnat_rm/standard_library_routines standard-library-routines}@anchor{e}@anchor{gnat_rm/standard_library_routines doc}@anchor{291}@anchor{gnat_rm/standard_library_routines id1}@anchor{292}
20282 @chapter Standard Library Routines
20285 The Ada Reference Manual contains in Annex A a full description of an
20286 extensive set of standard library routines that can be used in any Ada
20287 program, and which must be provided by all Ada compilers. They are
20288 analogous to the standard C library used by C programs.
20290 GNAT implements all of the facilities described in annex A, and for most
20291 purposes the description in the Ada Reference Manual, or appropriate Ada
20292 text book, will be sufficient for making use of these facilities.
20294 In the case of the input-output facilities,
20295 @ref{f,,The Implementation of Standard I/O},
20296 gives details on exactly how GNAT interfaces to the
20297 file system. For the remaining packages, the Ada Reference Manual
20298 should be sufficient. The following is a list of the packages included,
20299 together with a brief description of the functionality that is provided.
20301 For completeness, references are included to other predefined library
20302 routines defined in other sections of the Ada Reference Manual (these are
20303 cross-indexed from Annex A). For further details see the relevant
20304 package declarations in the run-time library. In particular, a few units
20305 are not implemented, as marked by the presence of pragma Unimplemented_Unit,
20306 and in this case the package declaration contains comments explaining why
20307 the unit is not implemented.
20312 @item @code{Ada} @emph{(A.2)}
20314 This is a parent package for all the standard library packages. It is
20315 usually included implicitly in your program, and itself contains no
20316 useful data or routines.
20318 @item @code{Ada.Assertions} @emph{(11.4.2)}
20320 @code{Assertions} provides the @code{Assert} subprograms, and also
20321 the declaration of the @code{Assertion_Error} exception.
20323 @item @code{Ada.Asynchronous_Task_Control} @emph{(D.11)}
20325 @code{Asynchronous_Task_Control} provides low level facilities for task
20326 synchronization. It is typically not implemented. See package spec for details.
20328 @item @code{Ada.Calendar} @emph{(9.6)}
20330 @code{Calendar} provides time of day access, and routines for
20331 manipulating times and durations.
20333 @item @code{Ada.Calendar.Arithmetic} @emph{(9.6.1)}
20335 This package provides additional arithmetic
20336 operations for @code{Calendar}.
20338 @item @code{Ada.Calendar.Formatting} @emph{(9.6.1)}
20340 This package provides formatting operations for @code{Calendar}.
20342 @item @code{Ada.Calendar.Time_Zones} @emph{(9.6.1)}
20344 This package provides additional @code{Calendar} facilities
20345 for handling time zones.
20347 @item @code{Ada.Characters} @emph{(A.3.1)}
20349 This is a dummy parent package that contains no useful entities
20351 @item @code{Ada.Characters.Conversions} @emph{(A.3.2)}
20353 This package provides character conversion functions.
20355 @item @code{Ada.Characters.Handling} @emph{(A.3.2)}
20357 This package provides some basic character handling capabilities,
20358 including classification functions for classes of characters (e.g., test
20359 for letters, or digits).
20361 @item @code{Ada.Characters.Latin_1} @emph{(A.3.3)}
20363 This package includes a complete set of definitions of the characters
20364 that appear in type CHARACTER. It is useful for writing programs that
20365 will run in international environments. For example, if you want an
20366 upper case E with an acute accent in a string, it is often better to use
20367 the definition of @code{UC_E_Acute} in this package. Then your program
20368 will print in an understandable manner even if your environment does not
20369 support these extended characters.
20371 @item @code{Ada.Command_Line} @emph{(A.15)}
20373 This package provides access to the command line parameters and the name
20374 of the current program (analogous to the use of @code{argc} and @code{argv}
20375 in C), and also allows the exit status for the program to be set in a
20376 system-independent manner.
20378 @item @code{Ada.Complex_Text_IO} @emph{(G.1.3)}
20380 This package provides text input and output of complex numbers.
20382 @item @code{Ada.Containers} @emph{(A.18.1)}
20384 A top level package providing a few basic definitions used by all the
20385 following specific child packages that provide specific kinds of
20389 @code{Ada.Containers.Bounded_Priority_Queues} @emph{(A.18.31)}
20391 @code{Ada.Containers.Bounded_Synchronized_Queues} @emph{(A.18.29)}
20393 @code{Ada.Containers.Doubly_Linked_Lists} @emph{(A.18.3)}
20395 @code{Ada.Containers.Generic_Array_Sort} @emph{(A.18.26)}
20397 @code{Ada.Containers.Generic_Constrained_Array_Sort} @emph{(A.18.26)}
20399 @code{Ada.Containers.Generic_Sort} @emph{(A.18.26)}
20401 @code{Ada.Containers.Hashed_Maps} @emph{(A.18.5)}
20403 @code{Ada.Containers.Hashed_Sets} @emph{(A.18.8)}
20405 @code{Ada.Containers.Indefinite_Doubly_Linked_Lists} @emph{(A.18.12)}
20407 @code{Ada.Containers.Indefinite_Hashed_Maps} @emph{(A.18.13)}
20409 @code{Ada.Containers.Indefinite_Hashed_Sets} @emph{(A.18.15)}
20411 @code{Ada.Containers.Indefinite_Holders} @emph{(A.18.18)}
20413 @code{Ada.Containers.Indefinite_Multiway_Trees} @emph{(A.18.17)}
20415 @code{Ada.Containers.Indefinite_Ordered_Maps} @emph{(A.18.14)}
20417 @code{Ada.Containers.Indefinite_Ordered_Sets} @emph{(A.18.16)}
20419 @code{Ada.Containers.Indefinite_Vectors} @emph{(A.18.11)}
20421 @code{Ada.Containers.Multiway_Trees} @emph{(A.18.10)}
20423 @code{Ada.Containers.Ordered_Maps} @emph{(A.18.6)}
20425 @code{Ada.Containers.Ordered_Sets} @emph{(A.18.9)}
20427 @code{Ada.Containers.Synchronized_Queue_Interfaces} @emph{(A.18.27)}
20429 @code{Ada.Containers.Unbounded_Priority_Queues} @emph{(A.18.30)}
20431 @code{Ada.Containers.Unbounded_Synchronized_Queues} @emph{(A.18.28)}
20433 @code{Ada.Containers.Vectors} @emph{(A.18.2)}
20438 @item @code{Ada.Directories} @emph{(A.16)}
20440 This package provides operations on directories.
20442 @item @code{Ada.Directories.Hierarchical_File_Names} @emph{(A.16.1)}
20444 This package provides additional directory operations handling
20445 hiearchical file names.
20447 @item @code{Ada.Directories.Information} @emph{(A.16)}
20449 This is an implementation defined package for additional directory
20450 operations, which is not implemented in GNAT.
20452 @item @code{Ada.Decimal} @emph{(F.2)}
20454 This package provides constants describing the range of decimal numbers
20455 implemented, and also a decimal divide routine (analogous to the COBOL
20456 verb DIVIDE ... GIVING ... REMAINDER ...)
20458 @item @code{Ada.Direct_IO} @emph{(A.8.4)}
20460 This package provides input-output using a model of a set of records of
20461 fixed-length, containing an arbitrary definite Ada type, indexed by an
20462 integer record number.
20464 @item @code{Ada.Dispatching} @emph{(D.2.1)}
20466 A parent package containing definitions for task dispatching operations.
20468 @item @code{Ada.Dispatching.EDF} @emph{(D.2.6)}
20470 Not implemented in GNAT.
20472 @item @code{Ada.Dispatching.Non_Preemptive} @emph{(D.2.4)}
20474 Not implemented in GNAT.
20476 @item @code{Ada.Dispatching.Round_Robin} @emph{(D.2.5)}
20478 Not implemented in GNAT.
20480 @item @code{Ada.Dynamic_Priorities} @emph{(D.5)}
20482 This package allows the priorities of a task to be adjusted dynamically
20483 as the task is running.
20485 @item @code{Ada.Environment_Variables} @emph{(A.17)}
20487 This package provides facilities for accessing environment variables.
20489 @item @code{Ada.Exceptions} @emph{(11.4.1)}
20491 This package provides additional information on exceptions, and also
20492 contains facilities for treating exceptions as data objects, and raising
20493 exceptions with associated messages.
20495 @item @code{Ada.Execution_Time} @emph{(D.14)}
20497 Not implemented in GNAT.
20499 @item @code{Ada.Execution_Time.Group_Budgets} @emph{(D.14.2)}
20501 Not implemented in GNAT.
20503 @item @code{Ada.Execution_Time.Timers} @emph{(D.14.1)'}
20505 Not implemented in GNAT.
20507 @item @code{Ada.Finalization} @emph{(7.6)}
20509 This package contains the declarations and subprograms to support the
20510 use of controlled types, providing for automatic initialization and
20511 finalization (analogous to the constructors and destructors of C++).
20513 @item @code{Ada.Float_Text_IO} @emph{(A.10.9)}
20515 A library level instantiation of Text_IO.Float_IO for type Float.
20517 @item @code{Ada.Float_Wide_Text_IO} @emph{(A.10.9)}
20519 A library level instantiation of Wide_Text_IO.Float_IO for type Float.
20521 @item @code{Ada.Float_Wide_Wide_Text_IO} @emph{(A.10.9)}
20523 A library level instantiation of Wide_Wide_Text_IO.Float_IO for type Float.
20525 @item @code{Ada.Integer_Text_IO} @emph{(A.10.9)}
20527 A library level instantiation of Text_IO.Integer_IO for type Integer.
20529 @item @code{Ada.Integer_Wide_Text_IO} @emph{(A.10.9)}
20531 A library level instantiation of Wide_Text_IO.Integer_IO for type Integer.
20533 @item @code{Ada.Integer_Wide_Wide_Text_IO} @emph{(A.10.9)}
20535 A library level instantiation of Wide_Wide_Text_IO.Integer_IO for type Integer.
20537 @item @code{Ada.Interrupts} @emph{(C.3.2)}
20539 This package provides facilities for interfacing to interrupts, which
20540 includes the set of signals or conditions that can be raised and
20541 recognized as interrupts.
20543 @item @code{Ada.Interrupts.Names} @emph{(C.3.2)}
20545 This package provides the set of interrupt names (actually signal
20546 or condition names) that can be handled by GNAT.
20548 @item @code{Ada.IO_Exceptions} @emph{(A.13)}
20550 This package defines the set of exceptions that can be raised by use of
20551 the standard IO packages.
20553 @item @code{Ada.Iterator_Interfaces} @emph{(5.5.1)}
20555 This package provides a generic interface to generalized iterators.
20557 @item @code{Ada.Locales} @emph{(A.19)}
20559 This package provides declarations providing information (Language
20560 and Country) about the current locale. This package is currently not
20561 implemented other than by providing stubs which will always return
20562 Language_Unknown/Country_Unknown.
20564 @item @code{Ada.Numerics}
20566 This package contains some standard constants and exceptions used
20567 throughout the numerics packages. Note that the constants pi and e are
20568 defined here, and it is better to use these definitions than rolling
20571 @item @code{Ada.Numerics.Complex_Arrays} @emph{(G.3.2)}
20573 Provides operations on arrays of complex numbers.
20575 @item @code{Ada.Numerics.Complex_Elementary_Functions}
20577 Provides the implementation of standard elementary functions (such as
20578 log and trigonometric functions) operating on complex numbers using the
20579 standard @code{Float} and the @code{Complex} and @code{Imaginary} types
20580 created by the package @code{Numerics.Complex_Types}.
20582 @item @code{Ada.Numerics.Complex_Types}
20584 This is a predefined instantiation of
20585 @code{Numerics.Generic_Complex_Types} using @code{Standard.Float} to
20586 build the type @code{Complex} and @code{Imaginary}.
20588 @item @code{Ada.Numerics.Discrete_Random}
20590 This generic package provides a random number generator suitable for generating
20591 uniformly distributed values of a specified discrete subtype.
20593 @item @code{Ada.Numerics.Float_Random}
20595 This package provides a random number generator suitable for generating
20596 uniformly distributed floating point values in the unit interval.
20598 @item @code{Ada.Numerics.Generic_Complex_Elementary_Functions}
20600 This is a generic version of the package that provides the
20601 implementation of standard elementary functions (such as log and
20602 trigonometric functions) for an arbitrary complex type.
20604 The following predefined instantiations of this package are provided:
20612 @code{Ada.Numerics.Short_Complex_Elementary_Functions}
20617 @code{Ada.Numerics.Complex_Elementary_Functions}
20622 @code{Ada.Numerics.Long_Complex_Elementary_Functions}
20625 @item @code{Ada.Numerics.Generic_Complex_Types}
20627 This is a generic package that allows the creation of complex types,
20628 with associated complex arithmetic operations.
20630 The following predefined instantiations of this package exist
20638 @code{Ada.Numerics.Short_Complex_Complex_Types}
20643 @code{Ada.Numerics.Complex_Complex_Types}
20648 @code{Ada.Numerics.Long_Complex_Complex_Types}
20651 @item @code{Ada.Numerics.Generic_Elementary_Functions}
20653 This is a generic package that provides the implementation of standard
20654 elementary functions (such as log an trigonometric functions) for an
20655 arbitrary float type.
20657 The following predefined instantiations of this package exist
20665 @code{Ada.Numerics.Short_Elementary_Functions}
20670 @code{Ada.Numerics.Elementary_Functions}
20675 @code{Ada.Numerics.Long_Elementary_Functions}
20678 @item @code{Ada.Numerics.Generic_Real_Arrays} @emph{(G.3.1)}
20680 Generic operations on arrays of reals
20682 @item @code{Ada.Numerics.Real_Arrays} @emph{(G.3.1)}
20684 Preinstantiation of Ada.Numerics.Generic_Real_Arrays (Float).
20686 @item @code{Ada.Real_Time} @emph{(D.8)}
20688 This package provides facilities similar to those of @code{Calendar}, but
20689 operating with a finer clock suitable for real time control. Note that
20690 annex D requires that there be no backward clock jumps, and GNAT generally
20691 guarantees this behavior, but of course if the external clock on which
20692 the GNAT runtime depends is deliberately reset by some external event,
20693 then such a backward jump may occur.
20695 @item @code{Ada.Real_Time.Timing_Events} @emph{(D.15)}
20697 Not implemented in GNAT.
20699 @item @code{Ada.Sequential_IO} @emph{(A.8.1)}
20701 This package provides input-output facilities for sequential files,
20702 which can contain a sequence of values of a single type, which can be
20703 any Ada type, including indefinite (unconstrained) types.
20705 @item @code{Ada.Storage_IO} @emph{(A.9)}
20707 This package provides a facility for mapping arbitrary Ada types to and
20708 from a storage buffer. It is primarily intended for the creation of new
20711 @item @code{Ada.Streams} @emph{(13.13.1)}
20713 This is a generic package that provides the basic support for the
20714 concept of streams as used by the stream attributes (@code{Input},
20715 @code{Output}, @code{Read} and @code{Write}).
20717 @item @code{Ada.Streams.Stream_IO} @emph{(A.12.1)}
20719 This package is a specialization of the type @code{Streams} defined in
20720 package @code{Streams} together with a set of operations providing
20721 Stream_IO capability. The Stream_IO model permits both random and
20722 sequential access to a file which can contain an arbitrary set of values
20723 of one or more Ada types.
20725 @item @code{Ada.Strings} @emph{(A.4.1)}
20727 This package provides some basic constants used by the string handling
20730 @item @code{Ada.Strings.Bounded} @emph{(A.4.4)}
20732 This package provides facilities for handling variable length
20733 strings. The bounded model requires a maximum length. It is thus
20734 somewhat more limited than the unbounded model, but avoids the use of
20735 dynamic allocation or finalization.
20737 @item @code{Ada.Strings.Bounded.Equal_Case_Insensitive} @emph{(A.4.10)}
20739 Provides case-insensitive comparisons of bounded strings
20741 @item @code{Ada.Strings.Bounded.Hash} @emph{(A.4.9)}
20743 This package provides a generic hash function for bounded strings
20745 @item @code{Ada.Strings.Bounded.Hash_Case_Insensitive} @emph{(A.4.9)}
20747 This package provides a generic hash function for bounded strings that
20748 converts the string to be hashed to lower case.
20750 @item @code{Ada.Strings.Bounded.Less_Case_Insensitive} @emph{(A.4.10)}
20752 This package provides a comparison function for bounded strings that works
20753 in a case insensitive manner by converting to lower case before the comparison.
20755 @item @code{Ada.Strings.Fixed} @emph{(A.4.3)}
20757 This package provides facilities for handling fixed length strings.
20759 @item @code{Ada.Strings.Fixed.Equal_Case_Insensitive} @emph{(A.4.10)}
20761 This package provides an equality function for fixed strings that compares
20762 the strings after converting both to lower case.
20764 @item @code{Ada.Strings.Fixed.Hash_Case_Insensitive} @emph{(A.4.9)}
20766 This package provides a case insensitive hash function for fixed strings that
20767 converts the string to lower case before computing the hash.
20769 @item @code{Ada.Strings.Fixed.Less_Case_Insensitive} @emph{(A.4.10)}
20771 This package provides a comparison function for fixed strings that works
20772 in a case insensitive manner by converting to lower case before the comparison.
20774 @item @code{Ada.Strings.Hash} @emph{(A.4.9)}
20776 This package provides a hash function for strings.
20778 @item @code{Ada.Strings.Hash_Case_Insensitive} @emph{(A.4.9)}
20780 This package provides a hash function for strings that is case insensitive.
20781 The string is converted to lower case before computing the hash.
20783 @item @code{Ada.Strings.Less_Case_Insensitive} @emph{(A.4.10)}
20785 This package provides a comparison function for\strings that works
20786 in a case insensitive manner by converting to lower case before the comparison.
20788 @item @code{Ada.Strings.Maps} @emph{(A.4.2)}
20790 This package provides facilities for handling character mappings and
20791 arbitrarily defined subsets of characters. For instance it is useful in
20792 defining specialized translation tables.
20794 @item @code{Ada.Strings.Maps.Constants} @emph{(A.4.6)}
20796 This package provides a standard set of predefined mappings and
20797 predefined character sets. For example, the standard upper to lower case
20798 conversion table is found in this package. Note that upper to lower case
20799 conversion is non-trivial if you want to take the entire set of
20800 characters, including extended characters like E with an acute accent,
20801 into account. You should use the mappings in this package (rather than
20802 adding 32 yourself) to do case mappings.
20804 @item @code{Ada.Strings.Unbounded} @emph{(A.4.5)}
20806 This package provides facilities for handling variable length
20807 strings. The unbounded model allows arbitrary length strings, but
20808 requires the use of dynamic allocation and finalization.
20810 @item @code{Ada.Strings.Unbounded.Equal_Case_Insensitive} @emph{(A.4.10)}
20812 Provides case-insensitive comparisons of unbounded strings
20814 @item @code{Ada.Strings.Unbounded.Hash} @emph{(A.4.9)}
20816 This package provides a generic hash function for unbounded strings
20818 @item @code{Ada.Strings.Unbounded.Hash_Case_Insensitive} @emph{(A.4.9)}
20820 This package provides a generic hash function for unbounded strings that
20821 converts the string to be hashed to lower case.
20823 @item @code{Ada.Strings.Unbounded.Less_Case_Insensitive} @emph{(A.4.10)}
20825 This package provides a comparison function for unbounded strings that works
20826 in a case insensitive manner by converting to lower case before the comparison.
20828 @item @code{Ada.Strings.UTF_Encoding} @emph{(A.4.11)}
20830 This package provides basic definitions for dealing with UTF-encoded strings.
20832 @item @code{Ada.Strings.UTF_Encoding.Conversions} @emph{(A.4.11)}
20834 This package provides conversion functions for UTF-encoded strings.
20837 @code{Ada.Strings.UTF_Encoding.Strings} @emph{(A.4.11)}
20839 @code{Ada.Strings.UTF_Encoding.Wide_Strings} @emph{(A.4.11)}
20844 @item @code{Ada.Strings.UTF_Encoding.Wide_Wide_Strings} @emph{(A.4.11)}
20846 These packages provide facilities for handling UTF encodings for
20847 Strings, Wide_Strings and Wide_Wide_Strings.
20850 @code{Ada.Strings.Wide_Bounded} @emph{(A.4.7)}
20852 @code{Ada.Strings.Wide_Fixed} @emph{(A.4.7)}
20854 @code{Ada.Strings.Wide_Maps} @emph{(A.4.7)}
20859 @item @code{Ada.Strings.Wide_Unbounded} @emph{(A.4.7)}
20861 These packages provide analogous capabilities to the corresponding
20862 packages without @code{Wide_} in the name, but operate with the types
20863 @code{Wide_String} and @code{Wide_Character} instead of @code{String}
20864 and @code{Character}. Versions of all the child packages are available.
20867 @code{Ada.Strings.Wide_Wide_Bounded} @emph{(A.4.7)}
20869 @code{Ada.Strings.Wide_Wide_Fixed} @emph{(A.4.7)}
20871 @code{Ada.Strings.Wide_Wide_Maps} @emph{(A.4.7)}
20876 @item @code{Ada.Strings.Wide_Wide_Unbounded} @emph{(A.4.7)}
20878 These packages provide analogous capabilities to the corresponding
20879 packages without @code{Wide_} in the name, but operate with the types
20880 @code{Wide_Wide_String} and @code{Wide_Wide_Character} instead
20881 of @code{String} and @code{Character}.
20883 @item @code{Ada.Synchronous_Barriers} @emph{(D.10.1)}
20885 This package provides facilities for synchronizing tasks at a low level
20888 @item @code{Ada.Synchronous_Task_Control} @emph{(D.10)}
20890 This package provides some standard facilities for controlling task
20891 communication in a synchronous manner.
20893 @item @code{Ada.Synchronous_Task_Control.EDF} @emph{(D.10)}
20895 Not implemented in GNAT.
20897 @item @code{Ada.Tags}
20899 This package contains definitions for manipulation of the tags of tagged
20902 @item @code{Ada.Tags.Generic_Dispatching_Constructor} @emph{(3.9)}
20904 This package provides a way of constructing tagged class-wide values given
20905 only the tag value.
20907 @item @code{Ada.Task_Attributes} @emph{(C.7.2)}
20909 This package provides the capability of associating arbitrary
20910 task-specific data with separate tasks.
20912 @item @code{Ada.Task_Identifification} @emph{(C.7.1)}
20914 This package provides capabilities for task identification.
20916 @item @code{Ada.Task_Termination} @emph{(C.7.3)}
20918 This package provides control over task termination.
20920 @item @code{Ada.Text_IO}
20922 This package provides basic text input-output capabilities for
20923 character, string and numeric data. The subpackages of this
20924 package are listed next. Note that although these are defined
20925 as subpackages in the RM, they are actually transparently
20926 implemented as child packages in GNAT, meaning that they
20927 are only loaded if needed.
20929 @item @code{Ada.Text_IO.Decimal_IO}
20931 Provides input-output facilities for decimal fixed-point types
20933 @item @code{Ada.Text_IO.Enumeration_IO}
20935 Provides input-output facilities for enumeration types.
20937 @item @code{Ada.Text_IO.Fixed_IO}
20939 Provides input-output facilities for ordinary fixed-point types.
20941 @item @code{Ada.Text_IO.Float_IO}
20943 Provides input-output facilities for float types. The following
20944 predefined instantiations of this generic package are available:
20952 @code{Short_Float_Text_IO}
20957 @code{Float_Text_IO}
20962 @code{Long_Float_Text_IO}
20965 @item @code{Ada.Text_IO.Integer_IO}
20967 Provides input-output facilities for integer types. The following
20968 predefined instantiations of this generic package are available:
20974 @code{Short_Short_Integer}
20976 @code{Ada.Short_Short_Integer_Text_IO}
20979 @code{Short_Integer}
20981 @code{Ada.Short_Integer_Text_IO}
20986 @code{Ada.Integer_Text_IO}
20989 @code{Long_Integer}
20991 @code{Ada.Long_Integer_Text_IO}
20994 @code{Long_Long_Integer}
20996 @code{Ada.Long_Long_Integer_Text_IO}
20999 @item @code{Ada.Text_IO.Modular_IO}
21001 Provides input-output facilities for modular (unsigned) types.
21003 @item @code{Ada.Text_IO.Bounded_IO (A.10.11)}
21005 Provides input-output facilities for bounded strings.
21007 @item @code{Ada.Text_IO.Complex_IO (G.1.3)}
21009 This package provides basic text input-output capabilities for complex
21012 @item @code{Ada.Text_IO.Editing (F.3.3)}
21014 This package contains routines for edited output, analogous to the use
21015 of pictures in COBOL. The picture formats used by this package are a
21016 close copy of the facility in COBOL.
21018 @item @code{Ada.Text_IO.Text_Streams (A.12.2)}
21020 This package provides a facility that allows Text_IO files to be treated
21021 as streams, so that the stream attributes can be used for writing
21022 arbitrary data, including binary data, to Text_IO files.
21024 @item @code{Ada.Text_IO.Unbounded_IO (A.10.12)}
21026 This package provides input-output facilities for unbounded strings.
21028 @item @code{Ada.Unchecked_Conversion (13.9)}
21030 This generic package allows arbitrary conversion from one type to
21031 another of the same size, providing for breaking the type safety in
21032 special circumstances.
21034 If the types have the same Size (more accurately the same Value_Size),
21035 then the effect is simply to transfer the bits from the source to the
21036 target type without any modification. This usage is well defined, and
21037 for simple types whose representation is typically the same across
21038 all implementations, gives a portable method of performing such
21041 If the types do not have the same size, then the result is implementation
21042 defined, and thus may be non-portable. The following describes how GNAT
21043 handles such unchecked conversion cases.
21045 If the types are of different sizes, and are both discrete types, then
21046 the effect is of a normal type conversion without any constraint checking.
21047 In particular if the result type has a larger size, the result will be
21048 zero or sign extended. If the result type has a smaller size, the result
21049 will be truncated by ignoring high order bits.
21051 If the types are of different sizes, and are not both discrete types,
21052 then the conversion works as though pointers were created to the source
21053 and target, and the pointer value is converted. The effect is that bits
21054 are copied from successive low order storage units and bits of the source
21055 up to the length of the target type.
21057 A warning is issued if the lengths differ, since the effect in this
21058 case is implementation dependent, and the above behavior may not match
21059 that of some other compiler.
21061 A pointer to one type may be converted to a pointer to another type using
21062 unchecked conversion. The only case in which the effect is undefined is
21063 when one or both pointers are pointers to unconstrained array types. In
21064 this case, the bounds information may get incorrectly transferred, and in
21065 particular, GNAT uses double size pointers for such types, and it is
21066 meaningless to convert between such pointer types. GNAT will issue a
21067 warning if the alignment of the target designated type is more strict
21068 than the alignment of the source designated type (since the result may
21069 be unaligned in this case).
21071 A pointer other than a pointer to an unconstrained array type may be
21072 converted to and from System.Address. Such usage is common in Ada 83
21073 programs, but note that Ada.Address_To_Access_Conversions is the
21074 preferred method of performing such conversions in Ada 95 and Ada 2005.
21076 unchecked conversion nor Ada.Address_To_Access_Conversions should be
21077 used in conjunction with pointers to unconstrained objects, since
21078 the bounds information cannot be handled correctly in this case.
21080 @item @code{Ada.Unchecked_Deallocation} @emph{(13.11.2)}
21082 This generic package allows explicit freeing of storage previously
21083 allocated by use of an allocator.
21085 @item @code{Ada.Wide_Text_IO} @emph{(A.11)}
21087 This package is similar to @code{Ada.Text_IO}, except that the external
21088 file supports wide character representations, and the internal types are
21089 @code{Wide_Character} and @code{Wide_String} instead of @code{Character}
21090 and @code{String}. The corresponding set of nested packages and child
21091 packages are defined.
21093 @item @code{Ada.Wide_Wide_Text_IO} @emph{(A.11)}
21095 This package is similar to @code{Ada.Text_IO}, except that the external
21096 file supports wide character representations, and the internal types are
21097 @code{Wide_Character} and @code{Wide_String} instead of @code{Character}
21098 and @code{String}. The corresponding set of nested packages and child
21099 packages are defined.
21102 For packages in Interfaces and System, all the RM defined packages are
21103 available in GNAT, see the Ada 2012 RM for full details.
21105 @node The Implementation of Standard I/O,The GNAT Library,Standard Library Routines,Top
21106 @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{293}@anchor{gnat_rm/the_implementation_of_standard_i_o id1}@anchor{294}
21107 @chapter The Implementation of Standard I/O
21110 GNAT implements all the required input-output facilities described in
21111 A.6 through A.14. These sections of the Ada Reference Manual describe the
21112 required behavior of these packages from the Ada point of view, and if
21113 you are writing a portable Ada program that does not need to know the
21114 exact manner in which Ada maps to the outside world when it comes to
21115 reading or writing external files, then you do not need to read this
21116 chapter. As long as your files are all regular files (not pipes or
21117 devices), and as long as you write and read the files only from Ada, the
21118 description in the Ada Reference Manual is sufficient.
21120 However, if you want to do input-output to pipes or other devices, such
21121 as the keyboard or screen, or if the files you are dealing with are
21122 either generated by some other language, or to be read by some other
21123 language, then you need to know more about the details of how the GNAT
21124 implementation of these input-output facilities behaves.
21126 In this chapter we give a detailed description of exactly how GNAT
21127 interfaces to the file system. As always, the sources of the system are
21128 available to you for answering questions at an even more detailed level,
21129 but for most purposes the information in this chapter will suffice.
21131 Another reason that you may need to know more about how input-output is
21132 implemented arises when you have a program written in mixed languages
21133 where, for example, files are shared between the C and Ada sections of
21134 the same program. GNAT provides some additional facilities, in the form
21135 of additional child library packages, that facilitate this sharing, and
21136 these additional facilities are also described in this chapter.
21139 * Standard I/O Packages::
21145 * Wide_Wide_Text_IO::
21147 * Text Translation::
21149 * Filenames encoding::
21150 * File content encoding::
21152 * Operations on C Streams::
21153 * Interfacing to C Streams::
21157 @node Standard I/O Packages,FORM Strings,,The Implementation of Standard I/O
21158 @anchor{gnat_rm/the_implementation_of_standard_i_o standard-i-o-packages}@anchor{295}@anchor{gnat_rm/the_implementation_of_standard_i_o id2}@anchor{296}
21159 @section Standard I/O Packages
21162 The Standard I/O packages described in Annex A for
21171 Ada.Text_IO.Complex_IO
21174 Ada.Text_IO.Text_Streams
21180 Ada.Wide_Text_IO.Complex_IO
21183 Ada.Wide_Text_IO.Text_Streams
21186 Ada.Wide_Wide_Text_IO
21189 Ada.Wide_Wide_Text_IO.Complex_IO
21192 Ada.Wide_Wide_Text_IO.Text_Streams
21204 are implemented using the C
21205 library streams facility; where
21211 All files are opened using @code{fopen}.
21214 All input/output operations use @code{fread}/@cite{fwrite}.
21217 There is no internal buffering of any kind at the Ada library level. The only
21218 buffering is that provided at the system level in the implementation of the
21219 library routines that support streams. This facilitates shared use of these
21220 streams by mixed language programs. Note though that system level buffering is
21221 explicitly enabled at elaboration of the standard I/O packages and that can
21222 have an impact on mixed language programs, in particular those using I/O before
21223 calling the Ada elaboration routine (e.g., adainit). It is recommended to call
21224 the Ada elaboration routine before performing any I/O or when impractical,
21225 flush the common I/O streams and in particular Standard_Output before
21226 elaborating the Ada code.
21228 @node FORM Strings,Direct_IO,Standard I/O Packages,The Implementation of Standard I/O
21229 @anchor{gnat_rm/the_implementation_of_standard_i_o form-strings}@anchor{297}@anchor{gnat_rm/the_implementation_of_standard_i_o id3}@anchor{298}
21230 @section FORM Strings
21233 The format of a FORM string in GNAT is:
21236 "keyword=value,keyword=value,...,keyword=value"
21239 where letters may be in upper or lower case, and there are no spaces
21240 between values. The order of the entries is not important. Currently
21241 the following keywords defined.
21244 TEXT_TRANSLATION=[YES|NO|TEXT|BINARY|U8TEXT|WTEXT|U16TEXT]
21246 WCEM=[n|h|u|s|e|8|b]
21247 ENCODING=[UTF8|8BITS]
21250 The use of these parameters is described later in this section. If an
21251 unrecognized keyword appears in a form string, it is silently ignored
21252 and not considered invalid.
21254 @node Direct_IO,Sequential_IO,FORM Strings,The Implementation of Standard I/O
21255 @anchor{gnat_rm/the_implementation_of_standard_i_o direct-io}@anchor{299}@anchor{gnat_rm/the_implementation_of_standard_i_o id4}@anchor{29a}
21259 Direct_IO can only be instantiated for definite types. This is a
21260 restriction of the Ada language, which means that the records are fixed
21261 length (the length being determined by @code{type'Size}, rounded
21262 up to the next storage unit boundary if necessary).
21264 The records of a Direct_IO file are simply written to the file in index
21265 sequence, with the first record starting at offset zero, and subsequent
21266 records following. There is no control information of any kind. For
21267 example, if 32-bit integers are being written, each record takes
21268 4-bytes, so the record at index @code{K} starts at offset
21271 There is no limit on the size of Direct_IO files, they are expanded as
21272 necessary to accommodate whatever records are written to the file.
21274 @node Sequential_IO,Text_IO,Direct_IO,The Implementation of Standard I/O
21275 @anchor{gnat_rm/the_implementation_of_standard_i_o sequential-io}@anchor{29b}@anchor{gnat_rm/the_implementation_of_standard_i_o id5}@anchor{29c}
21276 @section Sequential_IO
21279 Sequential_IO may be instantiated with either a definite (constrained)
21280 or indefinite (unconstrained) type.
21282 For the definite type case, the elements written to the file are simply
21283 the memory images of the data values with no control information of any
21284 kind. The resulting file should be read using the same type, no validity
21285 checking is performed on input.
21287 For the indefinite type case, the elements written consist of two
21288 parts. First is the size of the data item, written as the memory image
21289 of a @code{Interfaces.C.size_t} value, followed by the memory image of
21290 the data value. The resulting file can only be read using the same
21291 (unconstrained) type. Normal assignment checks are performed on these
21292 read operations, and if these checks fail, @code{Data_Error} is
21293 raised. In particular, in the array case, the lengths must match, and in
21294 the variant record case, if the variable for a particular read operation
21295 is constrained, the discriminants must match.
21297 Note that it is not possible to use Sequential_IO to write variable
21298 length array items, and then read the data back into different length
21299 arrays. For example, the following will raise @code{Data_Error}:
21302 package IO is new Sequential_IO (String);
21307 IO.Write (F, "hello!")
21308 IO.Reset (F, Mode=>In_File);
21313 On some Ada implementations, this will print @code{hell}, but the program is
21314 clearly incorrect, since there is only one element in the file, and that
21315 element is the string @code{hello!}.
21317 In Ada 95 and Ada 2005, this kind of behavior can be legitimately achieved
21318 using Stream_IO, and this is the preferred mechanism. In particular, the
21319 above program fragment rewritten to use Stream_IO will work correctly.
21321 @node Text_IO,Wide_Text_IO,Sequential_IO,The Implementation of Standard I/O
21322 @anchor{gnat_rm/the_implementation_of_standard_i_o id6}@anchor{29d}@anchor{gnat_rm/the_implementation_of_standard_i_o text-io}@anchor{29e}
21326 Text_IO files consist of a stream of characters containing the following
21327 special control characters:
21330 LF (line feed, 16#0A#) Line Mark
21331 FF (form feed, 16#0C#) Page Mark
21334 A canonical Text_IO file is defined as one in which the following
21335 conditions are met:
21341 The character @code{LF} is used only as a line mark, i.e., to mark the end
21345 The character @code{FF} is used only as a page mark, i.e., to mark the
21346 end of a page and consequently can appear only immediately following a
21347 @code{LF} (line mark) character.
21350 The file ends with either @code{LF} (line mark) or @code{LF}-@cite{FF}
21351 (line mark, page mark). In the former case, the page mark is implicitly
21352 assumed to be present.
21355 A file written using Text_IO will be in canonical form provided that no
21356 explicit @code{LF} or @code{FF} characters are written using @code{Put}
21357 or @code{Put_Line}. There will be no @code{FF} character at the end of
21358 the file unless an explicit @code{New_Page} operation was performed
21359 before closing the file.
21361 A canonical Text_IO file that is a regular file (i.e., not a device or a
21362 pipe) can be read using any of the routines in Text_IO. The
21363 semantics in this case will be exactly as defined in the Ada Reference
21364 Manual, and all the routines in Text_IO are fully implemented.
21366 A text file that does not meet the requirements for a canonical Text_IO
21367 file has one of the following:
21373 The file contains @code{FF} characters not immediately following a
21374 @code{LF} character.
21377 The file contains @code{LF} or @code{FF} characters written by
21378 @code{Put} or @code{Put_Line}, which are not logically considered to be
21379 line marks or page marks.
21382 The file ends in a character other than @code{LF} or @code{FF},
21383 i.e., there is no explicit line mark or page mark at the end of the file.
21386 Text_IO can be used to read such non-standard text files but subprograms
21387 to do with line or page numbers do not have defined meanings. In
21388 particular, a @code{FF} character that does not follow a @code{LF}
21389 character may or may not be treated as a page mark from the point of
21390 view of page and line numbering. Every @code{LF} character is considered
21391 to end a line, and there is an implied @code{LF} character at the end of
21395 * Stream Pointer Positioning::
21396 * Reading and Writing Non-Regular Files::
21398 * Treating Text_IO Files as Streams::
21399 * Text_IO Extensions::
21400 * Text_IO Facilities for Unbounded Strings::
21404 @node Stream Pointer Positioning,Reading and Writing Non-Regular Files,,Text_IO
21405 @anchor{gnat_rm/the_implementation_of_standard_i_o id7}@anchor{29f}@anchor{gnat_rm/the_implementation_of_standard_i_o stream-pointer-positioning}@anchor{2a0}
21406 @subsection Stream Pointer Positioning
21409 @code{Ada.Text_IO} has a definition of current position for a file that
21410 is being read. No internal buffering occurs in Text_IO, and usually the
21411 physical position in the stream used to implement the file corresponds
21412 to this logical position defined by Text_IO. There are two exceptions:
21418 After a call to @code{End_Of_Page} that returns @code{True}, the stream
21419 is positioned past the @code{LF} (line mark) that precedes the page
21420 mark. Text_IO maintains an internal flag so that subsequent read
21421 operations properly handle the logical position which is unchanged by
21422 the @code{End_Of_Page} call.
21425 After a call to @code{End_Of_File} that returns @code{True}, if the
21426 Text_IO file was positioned before the line mark at the end of file
21427 before the call, then the logical position is unchanged, but the stream
21428 is physically positioned right at the end of file (past the line mark,
21429 and past a possible page mark following the line mark. Again Text_IO
21430 maintains internal flags so that subsequent read operations properly
21431 handle the logical position.
21434 These discrepancies have no effect on the observable behavior of
21435 Text_IO, but if a single Ada stream is shared between a C program and
21436 Ada program, or shared (using @code{shared=yes} in the form string)
21437 between two Ada files, then the difference may be observable in some
21440 @node Reading and Writing Non-Regular Files,Get_Immediate,Stream Pointer Positioning,Text_IO
21441 @anchor{gnat_rm/the_implementation_of_standard_i_o reading-and-writing-non-regular-files}@anchor{2a1}@anchor{gnat_rm/the_implementation_of_standard_i_o id8}@anchor{2a2}
21442 @subsection Reading and Writing Non-Regular Files
21445 A non-regular file is a device (such as a keyboard), or a pipe. Text_IO
21446 can be used for reading and writing. Writing is not affected and the
21447 sequence of characters output is identical to the normal file case, but
21448 for reading, the behavior of Text_IO is modified to avoid undesirable
21449 look-ahead as follows:
21451 An input file that is not a regular file is considered to have no page
21452 marks. Any @code{Ascii.FF} characters (the character normally used for a
21453 page mark) appearing in the file are considered to be data
21454 characters. In particular:
21460 @code{Get_Line} and @code{Skip_Line} do not test for a page mark
21461 following a line mark. If a page mark appears, it will be treated as a
21465 This avoids the need to wait for an extra character to be typed or
21466 entered from the pipe to complete one of these operations.
21469 @code{End_Of_Page} always returns @code{False}
21472 @code{End_Of_File} will return @code{False} if there is a page mark at
21473 the end of the file.
21476 Output to non-regular files is the same as for regular files. Page marks
21477 may be written to non-regular files using @code{New_Page}, but as noted
21478 above they will not be treated as page marks on input if the output is
21479 piped to another Ada program.
21481 Another important discrepancy when reading non-regular files is that the end
21482 of file indication is not 'sticky'. If an end of file is entered, e.g., by
21483 pressing the @code{EOT} key,
21485 is signaled once (i.e., the test @code{End_Of_File}
21486 will yield @code{True}, or a read will
21487 raise @code{End_Error}), but then reading can resume
21488 to read data past that end of
21489 file indication, until another end of file indication is entered.
21491 @node Get_Immediate,Treating Text_IO Files as Streams,Reading and Writing Non-Regular Files,Text_IO
21492 @anchor{gnat_rm/the_implementation_of_standard_i_o get-immediate}@anchor{2a3}@anchor{gnat_rm/the_implementation_of_standard_i_o id9}@anchor{2a4}
21493 @subsection Get_Immediate
21496 @geindex Get_Immediate
21498 Get_Immediate returns the next character (including control characters)
21499 from the input file. In particular, Get_Immediate will return LF or FF
21500 characters used as line marks or page marks. Such operations leave the
21501 file positioned past the control character, and it is thus not treated
21502 as having its normal function. This means that page, line and column
21503 counts after this kind of Get_Immediate call are set as though the mark
21504 did not occur. In the case where a Get_Immediate leaves the file
21505 positioned between the line mark and page mark (which is not normally
21506 possible), it is undefined whether the FF character will be treated as a
21509 @node Treating Text_IO Files as Streams,Text_IO Extensions,Get_Immediate,Text_IO
21510 @anchor{gnat_rm/the_implementation_of_standard_i_o id10}@anchor{2a5}@anchor{gnat_rm/the_implementation_of_standard_i_o treating-text-io-files-as-streams}@anchor{2a6}
21511 @subsection Treating Text_IO Files as Streams
21514 @geindex Stream files
21516 The package @code{Text_IO.Streams} allows a @code{Text_IO} file to be treated
21517 as a stream. Data written to a @code{Text_IO} file in this stream mode is
21518 binary data. If this binary data contains bytes 16#0A# (@code{LF}) or
21519 16#0C# (@code{FF}), the resulting file may have non-standard
21520 format. Similarly if read operations are used to read from a Text_IO
21521 file treated as a stream, then @code{LF} and @code{FF} characters may be
21522 skipped and the effect is similar to that described above for
21523 @code{Get_Immediate}.
21525 @node Text_IO Extensions,Text_IO Facilities for Unbounded Strings,Treating Text_IO Files as Streams,Text_IO
21526 @anchor{gnat_rm/the_implementation_of_standard_i_o id11}@anchor{2a7}@anchor{gnat_rm/the_implementation_of_standard_i_o text-io-extensions}@anchor{2a8}
21527 @subsection Text_IO Extensions
21530 @geindex Text_IO extensions
21532 A package GNAT.IO_Aux in the GNAT library provides some useful extensions
21533 to the standard @code{Text_IO} package:
21539 function File_Exists (Name : String) return Boolean;
21540 Determines if a file of the given name exists.
21543 function Get_Line return String;
21544 Reads a string from the standard input file. The value returned is exactly
21545 the length of the line that was read.
21548 function Get_Line (File : Ada.Text_IO.File_Type) return String;
21549 Similar, except that the parameter File specifies the file from which
21550 the string is to be read.
21553 @node Text_IO Facilities for Unbounded Strings,,Text_IO Extensions,Text_IO
21554 @anchor{gnat_rm/the_implementation_of_standard_i_o text-io-facilities-for-unbounded-strings}@anchor{2a9}@anchor{gnat_rm/the_implementation_of_standard_i_o id12}@anchor{2aa}
21555 @subsection Text_IO Facilities for Unbounded Strings
21558 @geindex Text_IO for unbounded strings
21560 @geindex Unbounded_String
21561 @geindex Text_IO operations
21563 The package @code{Ada.Strings.Unbounded.Text_IO}
21564 in library files @code{a-suteio.ads/adb} contains some GNAT-specific
21565 subprograms useful for Text_IO operations on unbounded strings:
21571 function Get_Line (File : File_Type) return Unbounded_String;
21572 Reads a line from the specified file
21573 and returns the result as an unbounded string.
21576 procedure Put (File : File_Type; U : Unbounded_String);
21577 Writes the value of the given unbounded string to the specified file
21578 Similar to the effect of
21579 @code{Put (To_String (U))} except that an extra copy is avoided.
21582 procedure Put_Line (File : File_Type; U : Unbounded_String);
21583 Writes the value of the given unbounded string to the specified file,
21584 followed by a @code{New_Line}.
21585 Similar to the effect of @code{Put_Line (To_String (U))} except
21586 that an extra copy is avoided.
21589 In the above procedures, @code{File} is of type @code{Ada.Text_IO.File_Type}
21590 and is optional. If the parameter is omitted, then the standard input or
21591 output file is referenced as appropriate.
21593 The package @code{Ada.Strings.Wide_Unbounded.Wide_Text_IO} in library
21594 files @code{a-swuwti.ads} and @code{a-swuwti.adb} provides similar extended
21595 @code{Wide_Text_IO} functionality for unbounded wide strings.
21597 The package @code{Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO} in library
21598 files @code{a-szuzti.ads} and @code{a-szuzti.adb} provides similar extended
21599 @code{Wide_Wide_Text_IO} functionality for unbounded wide wide strings.
21601 @node Wide_Text_IO,Wide_Wide_Text_IO,Text_IO,The Implementation of Standard I/O
21602 @anchor{gnat_rm/the_implementation_of_standard_i_o wide-text-io}@anchor{2ab}@anchor{gnat_rm/the_implementation_of_standard_i_o id13}@anchor{2ac}
21603 @section Wide_Text_IO
21606 @code{Wide_Text_IO} is similar in most respects to Text_IO, except that
21607 both input and output files may contain special sequences that represent
21608 wide character values. The encoding scheme for a given file may be
21609 specified using a FORM parameter:
21615 as part of the FORM string (WCEM = wide character encoding method),
21616 where @code{x} is one of the following characters
21619 @multitable {xxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxx}
21642 Upper half encoding
21679 The encoding methods match those that
21680 can be used in a source
21681 program, but there is no requirement that the encoding method used for
21682 the source program be the same as the encoding method used for files,
21683 and different files may use different encoding methods.
21685 The default encoding method for the standard files, and for opened files
21686 for which no WCEM parameter is given in the FORM string matches the
21687 wide character encoding specified for the main program (the default
21688 being brackets encoding if no coding method was specified with -gnatW).
21693 @item @emph{Hex Coding}
21695 In this encoding, a wide character is represented by a five character
21706 where @code{a}, @code{b}, @code{c}, @code{d} are the four hexadecimal
21707 characters (using upper case letters) of the wide character code. For
21708 example, ESC A345 is used to represent the wide character with code
21709 16#A345#. This scheme is compatible with use of the full
21710 @code{Wide_Character} set.
21716 @item @emph{Upper Half Coding}
21718 The wide character with encoding 16#abcd#, where the upper bit is on
21719 (i.e., a is in the range 8-F) is represented as two bytes 16#ab# and
21720 16#cd#. The second byte may never be a format control character, but is
21721 not required to be in the upper half. This method can be also used for
21722 shift-JIS or EUC where the internal coding matches the external coding.
21724 @item @emph{Shift JIS Coding}
21726 A wide character is represented by a two character sequence 16#ab# and
21727 16#cd#, with the restrictions described for upper half encoding as
21728 described above. The internal character code is the corresponding JIS
21729 character according to the standard algorithm for Shift-JIS
21730 conversion. Only characters defined in the JIS code set table can be
21731 used with this encoding method.
21733 @item @emph{EUC Coding}
21735 A wide character is represented by a two character sequence 16#ab# and
21736 16#cd#, with both characters being in the upper half. The internal
21737 character code is the corresponding JIS character according to the EUC
21738 encoding algorithm. Only characters defined in the JIS code set table
21739 can be used with this encoding method.
21741 @item @emph{UTF-8 Coding}
21743 A wide character is represented using
21744 UCS Transformation Format 8 (UTF-8) as defined in Annex R of ISO
21745 10646-1/Am.2. Depending on the character value, the representation
21746 is a one, two, or three byte sequence:
21750 16#0000#-16#007f#: 2#0xxxxxxx#
21751 16#0080#-16#07ff#: 2#110xxxxx# 2#10xxxxxx#
21752 16#0800#-16#ffff#: 2#1110xxxx# 2#10xxxxxx# 2#10xxxxxx#
21758 where the @code{xxx} bits correspond to the left-padded bits of the
21759 16-bit character value. Note that all lower half ASCII characters
21760 are represented as ASCII bytes and all upper half characters and
21761 other wide characters are represented as sequences of upper-half
21762 (The full UTF-8 scheme allows for encoding 31-bit characters as
21763 6-byte sequences, but in this implementation, all UTF-8 sequences
21764 of four or more bytes length will raise a Constraint_Error, as
21765 will all invalid UTF-8 sequences.)
21771 @item @emph{Brackets Coding}
21773 In this encoding, a wide character is represented by the following eight
21774 character sequence:
21784 where @code{a}, @code{b}, @code{c}, @code{d} are the four hexadecimal
21785 characters (using uppercase letters) of the wide character code. For
21786 example, @code{["A345"]} is used to represent the wide character with code
21788 This scheme is compatible with use of the full Wide_Character set.
21789 On input, brackets coding can also be used for upper half characters,
21790 e.g., @code{["C1"]} for lower case a. However, on output, brackets notation
21791 is only used for wide characters with a code greater than @code{16#FF#}.
21793 Note that brackets coding is not normally used in the context of
21794 Wide_Text_IO or Wide_Wide_Text_IO, since it is really just designed as
21795 a portable way of encoding source files. In the context of Wide_Text_IO
21796 or Wide_Wide_Text_IO, it can only be used if the file does not contain
21797 any instance of the left bracket character other than to encode wide
21798 character values using the brackets encoding method. In practice it is
21799 expected that some standard wide character encoding method such
21800 as UTF-8 will be used for text input output.
21802 If brackets notation is used, then any occurrence of a left bracket
21803 in the input file which is not the start of a valid wide character
21804 sequence will cause Constraint_Error to be raised. It is possible to
21805 encode a left bracket as ["5B"] and Wide_Text_IO and Wide_Wide_Text_IO
21806 input will interpret this as a left bracket.
21808 However, when a left bracket is output, it will be output as a left bracket
21809 and not as ["5B"]. We make this decision because for normal use of
21810 Wide_Text_IO for outputting messages, it is unpleasant to clobber left
21811 brackets. For example, if we write:
21814 Put_Line ("Start of output [first run]");
21817 we really do not want to have the left bracket in this message clobbered so
21818 that the output reads:
21822 Start of output ["5B"]first run]
21828 In practice brackets encoding is reasonably useful for normal Put_Line use
21829 since we won't get confused between left brackets and wide character
21830 sequences in the output. But for input, or when files are written out
21831 and read back in, it really makes better sense to use one of the standard
21832 encoding methods such as UTF-8.
21835 For the coding schemes other than UTF-8, Hex, or Brackets encoding,
21836 not all wide character
21837 values can be represented. An attempt to output a character that cannot
21838 be represented using the encoding scheme for the file causes
21839 Constraint_Error to be raised. An invalid wide character sequence on
21840 input also causes Constraint_Error to be raised.
21843 * Stream Pointer Positioning: Stream Pointer Positioning<2>.
21844 * Reading and Writing Non-Regular Files: Reading and Writing Non-Regular Files<2>.
21848 @node Stream Pointer Positioning<2>,Reading and Writing Non-Regular Files<2>,,Wide_Text_IO
21849 @anchor{gnat_rm/the_implementation_of_standard_i_o stream-pointer-positioning-1}@anchor{2ad}@anchor{gnat_rm/the_implementation_of_standard_i_o id14}@anchor{2ae}
21850 @subsection Stream Pointer Positioning
21853 @code{Ada.Wide_Text_IO} is similar to @code{Ada.Text_IO} in its handling
21854 of stream pointer positioning (@ref{29e,,Text_IO}). There is one additional
21857 If @code{Ada.Wide_Text_IO.Look_Ahead} reads a character outside the
21858 normal lower ASCII set (i.e., a character in the range:
21861 Wide_Character'Val (16#0080#) .. Wide_Character'Val (16#FFFF#)
21864 then although the logical position of the file pointer is unchanged by
21865 the @code{Look_Ahead} call, the stream is physically positioned past the
21866 wide character sequence. Again this is to avoid the need for buffering
21867 or backup, and all @code{Wide_Text_IO} routines check the internal
21868 indication that this situation has occurred so that this is not visible
21869 to a normal program using @code{Wide_Text_IO}. However, this discrepancy
21870 can be observed if the wide text file shares a stream with another file.
21872 @node Reading and Writing Non-Regular Files<2>,,Stream Pointer Positioning<2>,Wide_Text_IO
21873 @anchor{gnat_rm/the_implementation_of_standard_i_o reading-and-writing-non-regular-files-1}@anchor{2af}@anchor{gnat_rm/the_implementation_of_standard_i_o id15}@anchor{2b0}
21874 @subsection Reading and Writing Non-Regular Files
21877 As in the case of Text_IO, when a non-regular file is read, it is
21878 assumed that the file contains no page marks (any form characters are
21879 treated as data characters), and @code{End_Of_Page} always returns
21880 @code{False}. Similarly, the end of file indication is not sticky, so
21881 it is possible to read beyond an end of file.
21883 @node Wide_Wide_Text_IO,Stream_IO,Wide_Text_IO,The Implementation of Standard I/O
21884 @anchor{gnat_rm/the_implementation_of_standard_i_o id16}@anchor{2b1}@anchor{gnat_rm/the_implementation_of_standard_i_o wide-wide-text-io}@anchor{2b2}
21885 @section Wide_Wide_Text_IO
21888 @code{Wide_Wide_Text_IO} is similar in most respects to Text_IO, except that
21889 both input and output files may contain special sequences that represent
21890 wide wide character values. The encoding scheme for a given file may be
21891 specified using a FORM parameter:
21897 as part of the FORM string (WCEM = wide character encoding method),
21898 where @code{x} is one of the following characters
21901 @multitable {xxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxx}
21924 Upper half encoding
21961 The encoding methods match those that
21962 can be used in a source
21963 program, but there is no requirement that the encoding method used for
21964 the source program be the same as the encoding method used for files,
21965 and different files may use different encoding methods.
21967 The default encoding method for the standard files, and for opened files
21968 for which no WCEM parameter is given in the FORM string matches the
21969 wide character encoding specified for the main program (the default
21970 being brackets encoding if no coding method was specified with -gnatW).
21975 @item @emph{UTF-8 Coding}
21977 A wide character is represented using
21978 UCS Transformation Format 8 (UTF-8) as defined in Annex R of ISO
21979 10646-1/Am.2. Depending on the character value, the representation
21980 is a one, two, three, or four byte sequence:
21984 16#000000#-16#00007f#: 2#0xxxxxxx#
21985 16#000080#-16#0007ff#: 2#110xxxxx# 2#10xxxxxx#
21986 16#000800#-16#00ffff#: 2#1110xxxx# 2#10xxxxxx# 2#10xxxxxx#
21987 16#010000#-16#10ffff#: 2#11110xxx# 2#10xxxxxx# 2#10xxxxxx# 2#10xxxxxx#
21993 where the @code{xxx} bits correspond to the left-padded bits of the
21994 21-bit character value. Note that all lower half ASCII characters
21995 are represented as ASCII bytes and all upper half characters and
21996 other wide characters are represented as sequences of upper-half
22003 @item @emph{Brackets Coding}
22005 In this encoding, a wide wide character is represented by the following eight
22006 character sequence if is in wide character range
22016 and by the following ten character sequence if not
22020 [ " a b c d e f " ]
22026 where @code{a}, @code{b}, @code{c}, @code{d}, @code{e}, and @code{f}
22027 are the four or six hexadecimal
22028 characters (using uppercase letters) of the wide wide character code. For
22029 example, @code{["01A345"]} is used to represent the wide wide character
22030 with code @code{16#01A345#}.
22032 This scheme is compatible with use of the full Wide_Wide_Character set.
22033 On input, brackets coding can also be used for upper half characters,
22034 e.g., @code{["C1"]} for lower case a. However, on output, brackets notation
22035 is only used for wide characters with a code greater than @code{16#FF#}.
22038 If is also possible to use the other Wide_Character encoding methods,
22039 such as Shift-JIS, but the other schemes cannot support the full range
22040 of wide wide characters.
22041 An attempt to output a character that cannot
22042 be represented using the encoding scheme for the file causes
22043 Constraint_Error to be raised. An invalid wide character sequence on
22044 input also causes Constraint_Error to be raised.
22047 * Stream Pointer Positioning: Stream Pointer Positioning<3>.
22048 * Reading and Writing Non-Regular Files: Reading and Writing Non-Regular Files<3>.
22052 @node Stream Pointer Positioning<3>,Reading and Writing Non-Regular Files<3>,,Wide_Wide_Text_IO
22053 @anchor{gnat_rm/the_implementation_of_standard_i_o stream-pointer-positioning-2}@anchor{2b3}@anchor{gnat_rm/the_implementation_of_standard_i_o id17}@anchor{2b4}
22054 @subsection Stream Pointer Positioning
22057 @code{Ada.Wide_Wide_Text_IO} is similar to @code{Ada.Text_IO} in its handling
22058 of stream pointer positioning (@ref{29e,,Text_IO}). There is one additional
22061 If @code{Ada.Wide_Wide_Text_IO.Look_Ahead} reads a character outside the
22062 normal lower ASCII set (i.e., a character in the range:
22065 Wide_Wide_Character'Val (16#0080#) .. Wide_Wide_Character'Val (16#10FFFF#)
22068 then although the logical position of the file pointer is unchanged by
22069 the @code{Look_Ahead} call, the stream is physically positioned past the
22070 wide character sequence. Again this is to avoid the need for buffering
22071 or backup, and all @code{Wide_Wide_Text_IO} routines check the internal
22072 indication that this situation has occurred so that this is not visible
22073 to a normal program using @code{Wide_Wide_Text_IO}. However, this discrepancy
22074 can be observed if the wide text file shares a stream with another file.
22076 @node Reading and Writing Non-Regular Files<3>,,Stream Pointer Positioning<3>,Wide_Wide_Text_IO
22077 @anchor{gnat_rm/the_implementation_of_standard_i_o id18}@anchor{2b5}@anchor{gnat_rm/the_implementation_of_standard_i_o reading-and-writing-non-regular-files-2}@anchor{2b6}
22078 @subsection Reading and Writing Non-Regular Files
22081 As in the case of Text_IO, when a non-regular file is read, it is
22082 assumed that the file contains no page marks (any form characters are
22083 treated as data characters), and @code{End_Of_Page} always returns
22084 @code{False}. Similarly, the end of file indication is not sticky, so
22085 it is possible to read beyond an end of file.
22087 @node Stream_IO,Text Translation,Wide_Wide_Text_IO,The Implementation of Standard I/O
22088 @anchor{gnat_rm/the_implementation_of_standard_i_o id19}@anchor{2b7}@anchor{gnat_rm/the_implementation_of_standard_i_o stream-io}@anchor{2b8}
22092 A stream file is a sequence of bytes, where individual elements are
22093 written to the file as described in the Ada Reference Manual. The type
22094 @code{Stream_Element} is simply a byte. There are two ways to read or
22095 write a stream file.
22101 The operations @code{Read} and @code{Write} directly read or write a
22102 sequence of stream elements with no control information.
22105 The stream attributes applied to a stream file transfer data in the
22106 manner described for stream attributes.
22109 @node Text Translation,Shared Files,Stream_IO,The Implementation of Standard I/O
22110 @anchor{gnat_rm/the_implementation_of_standard_i_o id20}@anchor{2b9}@anchor{gnat_rm/the_implementation_of_standard_i_o text-translation}@anchor{2ba}
22111 @section Text Translation
22114 @code{Text_Translation=xxx} may be used as the Form parameter
22115 passed to Text_IO.Create and Text_IO.Open. @code{Text_Translation=xxx}
22116 has no effect on Unix systems. Possible values are:
22122 @code{Yes} or @code{Text} is the default, which means to
22123 translate LF to/from CR/LF on Windows systems.
22125 @code{No} disables this translation; i.e. it
22126 uses binary mode. For output files, @code{Text_Translation=No}
22127 may be used to create Unix-style files on
22131 @code{wtext} translation enabled in Unicode mode.
22132 (corresponds to _O_WTEXT).
22135 @code{u8text} translation enabled in Unicode UTF-8 mode.
22136 (corresponds to O_U8TEXT).
22139 @code{u16text} translation enabled in Unicode UTF-16
22140 mode. (corresponds to_O_U16TEXT).
22143 @node Shared Files,Filenames encoding,Text Translation,The Implementation of Standard I/O
22144 @anchor{gnat_rm/the_implementation_of_standard_i_o id21}@anchor{2bb}@anchor{gnat_rm/the_implementation_of_standard_i_o shared-files}@anchor{2bc}
22145 @section Shared Files
22148 Section A.14 of the Ada Reference Manual allows implementations to
22149 provide a wide variety of behavior if an attempt is made to access the
22150 same external file with two or more internal files.
22152 To provide a full range of functionality, while at the same time
22153 minimizing the problems of portability caused by this implementation
22154 dependence, GNAT handles file sharing as follows:
22160 In the absence of a @code{shared=xxx} form parameter, an attempt
22161 to open two or more files with the same full name is considered an error
22162 and is not supported. The exception @code{Use_Error} will be
22163 raised. Note that a file that is not explicitly closed by the program
22164 remains open until the program terminates.
22167 If the form parameter @code{shared=no} appears in the form string, the
22168 file can be opened or created with its own separate stream identifier,
22169 regardless of whether other files sharing the same external file are
22170 opened. The exact effect depends on how the C stream routines handle
22171 multiple accesses to the same external files using separate streams.
22174 If the form parameter @code{shared=yes} appears in the form string for
22175 each of two or more files opened using the same full name, the same
22176 stream is shared between these files, and the semantics are as described
22177 in Ada Reference Manual, Section A.14.
22180 When a program that opens multiple files with the same name is ported
22181 from another Ada compiler to GNAT, the effect will be that
22182 @code{Use_Error} is raised.
22184 The documentation of the original compiler and the documentation of the
22185 program should then be examined to determine if file sharing was
22186 expected, and @code{shared=xxx} parameters added to @code{Open}
22187 and @code{Create} calls as required.
22189 When a program is ported from GNAT to some other Ada compiler, no
22190 special attention is required unless the @code{shared=xxx} form
22191 parameter is used in the program. In this case, you must examine the
22192 documentation of the new compiler to see if it supports the required
22193 file sharing semantics, and form strings modified appropriately. Of
22194 course it may be the case that the program cannot be ported if the
22195 target compiler does not support the required functionality. The best
22196 approach in writing portable code is to avoid file sharing (and hence
22197 the use of the @code{shared=xxx} parameter in the form string)
22200 One common use of file sharing in Ada 83 is the use of instantiations of
22201 Sequential_IO on the same file with different types, to achieve
22202 heterogeneous input-output. Although this approach will work in GNAT if
22203 @code{shared=yes} is specified, it is preferable in Ada to use Stream_IO
22204 for this purpose (using the stream attributes)
22206 @node Filenames encoding,File content encoding,Shared Files,The Implementation of Standard I/O
22207 @anchor{gnat_rm/the_implementation_of_standard_i_o filenames-encoding}@anchor{2bd}@anchor{gnat_rm/the_implementation_of_standard_i_o id22}@anchor{2be}
22208 @section Filenames encoding
22211 An encoding form parameter can be used to specify the filename
22212 encoding @code{encoding=xxx}.
22218 If the form parameter @code{encoding=utf8} appears in the form string, the
22219 filename must be encoded in UTF-8.
22222 If the form parameter @code{encoding=8bits} appears in the form
22223 string, the filename must be a standard 8bits string.
22226 In the absence of a @code{encoding=xxx} form parameter, the
22227 encoding is controlled by the @code{GNAT_CODE_PAGE} environment
22228 variable. And if not set @code{utf8} is assumed.
22233 @item @emph{CP_ACP}
22235 The current system Windows ANSI code page.
22237 @item @emph{CP_UTF8}
22242 This encoding form parameter is only supported on the Windows
22243 platform. On the other Operating Systems the run-time is supporting
22246 @node File content encoding,Open Modes,Filenames encoding,The Implementation of Standard I/O
22247 @anchor{gnat_rm/the_implementation_of_standard_i_o file-content-encoding}@anchor{2bf}@anchor{gnat_rm/the_implementation_of_standard_i_o id23}@anchor{2c0}
22248 @section File content encoding
22251 For text files it is possible to specify the encoding to use. This is
22252 controlled by the by the @code{GNAT_CCS_ENCODING} environment
22253 variable. And if not set @code{TEXT} is assumed.
22255 The possible values are those supported on Windows:
22262 Translated text mode
22266 Translated unicode encoding
22268 @item @emph{U16TEXT}
22270 Unicode 16-bit encoding
22272 @item @emph{U8TEXT}
22274 Unicode 8-bit encoding
22277 This encoding is only supported on the Windows platform.
22279 @node Open Modes,Operations on C Streams,File content encoding,The Implementation of Standard I/O
22280 @anchor{gnat_rm/the_implementation_of_standard_i_o open-modes}@anchor{2c1}@anchor{gnat_rm/the_implementation_of_standard_i_o id24}@anchor{2c2}
22281 @section Open Modes
22284 @code{Open} and @code{Create} calls result in a call to @code{fopen}
22285 using the mode shown in the following table:
22288 @multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxx}
22291 @code{Open} and @code{Create} Call Modes
22333 Out_File (Direct_IO)
22345 Out_File (all other cases)
22370 If text file translation is required, then either @code{b} or @code{t}
22371 is added to the mode, depending on the setting of Text. Text file
22372 translation refers to the mapping of CR/LF sequences in an external file
22373 to LF characters internally. This mapping only occurs in DOS and
22374 DOS-like systems, and is not relevant to other systems.
22376 A special case occurs with Stream_IO. As shown in the above table, the
22377 file is initially opened in @code{r} or @code{w} mode for the
22378 @code{In_File} and @code{Out_File} cases. If a @code{Set_Mode} operation
22379 subsequently requires switching from reading to writing or vice-versa,
22380 then the file is reopened in @code{r+} mode to permit the required operation.
22382 @node Operations on C Streams,Interfacing to C Streams,Open Modes,The Implementation of Standard I/O
22383 @anchor{gnat_rm/the_implementation_of_standard_i_o operations-on-c-streams}@anchor{2c3}@anchor{gnat_rm/the_implementation_of_standard_i_o id25}@anchor{2c4}
22384 @section Operations on C Streams
22387 The package @code{Interfaces.C_Streams} provides an Ada program with direct
22388 access to the C library functions for operations on C streams:
22391 package Interfaces.C_Streams is
22392 -- Note: the reason we do not use the types that are in
22393 -- Interfaces.C is that we want to avoid dragging in the
22394 -- code in this unit if possible.
22395 subtype chars is System.Address;
22396 -- Pointer to null-terminated array of characters
22397 subtype FILEs is System.Address;
22398 -- Corresponds to the C type FILE*
22399 subtype voids is System.Address;
22400 -- Corresponds to the C type void*
22401 subtype int is Integer;
22402 subtype long is Long_Integer;
22403 -- Note: the above types are subtypes deliberately, and it
22404 -- is part of this spec that the above correspondences are
22405 -- guaranteed. This means that it is legitimate to, for
22406 -- example, use Integer instead of int. We provide these
22407 -- synonyms for clarity, but in some cases it may be
22408 -- convenient to use the underlying types (for example to
22409 -- avoid an unnecessary dependency of a spec on the spec
22411 type size_t is mod 2 ** Standard'Address_Size;
22412 NULL_Stream : constant FILEs;
22413 -- Value returned (NULL in C) to indicate an
22414 -- fdopen/fopen/tmpfile error
22415 ----------------------------------
22416 -- Constants Defined in stdio.h --
22417 ----------------------------------
22418 EOF : constant int;
22419 -- Used by a number of routines to indicate error or
22421 IOFBF : constant int;
22422 IOLBF : constant int;
22423 IONBF : constant int;
22424 -- Used to indicate buffering mode for setvbuf call
22425 SEEK_CUR : constant int;
22426 SEEK_END : constant int;
22427 SEEK_SET : constant int;
22428 -- Used to indicate origin for fseek call
22429 function stdin return FILEs;
22430 function stdout return FILEs;
22431 function stderr return FILEs;
22432 -- Streams associated with standard files
22433 --------------------------
22434 -- Standard C functions --
22435 --------------------------
22436 -- The functions selected below are ones that are
22437 -- available in UNIX (but not necessarily in ANSI C).
22438 -- These are very thin interfaces
22439 -- which copy exactly the C headers. For more
22440 -- documentation on these functions, see the Microsoft C
22441 -- "Run-Time Library Reference" (Microsoft Press, 1990,
22442 -- ISBN 1-55615-225-6), which includes useful information
22443 -- on system compatibility.
22444 procedure clearerr (stream : FILEs);
22445 function fclose (stream : FILEs) return int;
22446 function fdopen (handle : int; mode : chars) return FILEs;
22447 function feof (stream : FILEs) return int;
22448 function ferror (stream : FILEs) return int;
22449 function fflush (stream : FILEs) return int;
22450 function fgetc (stream : FILEs) return int;
22451 function fgets (strng : chars; n : int; stream : FILEs)
22453 function fileno (stream : FILEs) return int;
22454 function fopen (filename : chars; Mode : chars)
22456 -- Note: to maintain target independence, use
22457 -- text_translation_required, a boolean variable defined in
22458 -- a-sysdep.c to deal with the target dependent text
22459 -- translation requirement. If this variable is set,
22460 -- then b/t should be appended to the standard mode
22461 -- argument to set the text translation mode off or on
22463 function fputc (C : int; stream : FILEs) return int;
22464 function fputs (Strng : chars; Stream : FILEs) return int;
22481 function ftell (stream : FILEs) return long;
22488 function isatty (handle : int) return int;
22489 procedure mktemp (template : chars);
22490 -- The return value (which is just a pointer to template)
22492 procedure rewind (stream : FILEs);
22493 function rmtmp return int;
22501 function tmpfile return FILEs;
22502 function ungetc (c : int; stream : FILEs) return int;
22503 function unlink (filename : chars) return int;
22504 ---------------------
22505 -- Extra functions --
22506 ---------------------
22507 -- These functions supply slightly thicker bindings than
22508 -- those above. They are derived from functions in the
22509 -- C Run-Time Library, but may do a bit more work than
22510 -- just directly calling one of the Library functions.
22511 function is_regular_file (handle : int) return int;
22512 -- Tests if given handle is for a regular file (result 1)
22513 -- or for a non-regular file (pipe or device, result 0).
22514 ---------------------------------
22515 -- Control of Text/Binary Mode --
22516 ---------------------------------
22517 -- If text_translation_required is true, then the following
22518 -- functions may be used to dynamically switch a file from
22519 -- binary to text mode or vice versa. These functions have
22520 -- no effect if text_translation_required is false (i.e., in
22521 -- normal UNIX mode). Use fileno to get a stream handle.
22522 procedure set_binary_mode (handle : int);
22523 procedure set_text_mode (handle : int);
22524 ----------------------------
22525 -- Full Path Name support --
22526 ----------------------------
22527 procedure full_name (nam : chars; buffer : chars);
22528 -- Given a NUL terminated string representing a file
22529 -- name, returns in buffer a NUL terminated string
22530 -- representing the full path name for the file name.
22531 -- On systems where it is relevant the drive is also
22532 -- part of the full path name. It is the responsibility
22533 -- of the caller to pass an actual parameter for buffer
22534 -- that is big enough for any full path name. Use
22535 -- max_path_len given below as the size of buffer.
22536 max_path_len : integer;
22537 -- Maximum length of an allowable full path name on the
22538 -- system, including a terminating NUL character.
22539 end Interfaces.C_Streams;
22542 @node Interfacing to C Streams,,Operations on C Streams,The Implementation of Standard I/O
22543 @anchor{gnat_rm/the_implementation_of_standard_i_o interfacing-to-c-streams}@anchor{2c5}@anchor{gnat_rm/the_implementation_of_standard_i_o id26}@anchor{2c6}
22544 @section Interfacing to C Streams
22547 The packages in this section permit interfacing Ada files to C Stream
22551 with Interfaces.C_Streams;
22552 package Ada.Sequential_IO.C_Streams is
22553 function C_Stream (F : File_Type)
22554 return Interfaces.C_Streams.FILEs;
22556 (File : in out File_Type;
22557 Mode : in File_Mode;
22558 C_Stream : in Interfaces.C_Streams.FILEs;
22559 Form : in String := "");
22560 end Ada.Sequential_IO.C_Streams;
22562 with Interfaces.C_Streams;
22563 package Ada.Direct_IO.C_Streams is
22564 function C_Stream (F : File_Type)
22565 return Interfaces.C_Streams.FILEs;
22567 (File : in out File_Type;
22568 Mode : in File_Mode;
22569 C_Stream : in Interfaces.C_Streams.FILEs;
22570 Form : in String := "");
22571 end Ada.Direct_IO.C_Streams;
22573 with Interfaces.C_Streams;
22574 package Ada.Text_IO.C_Streams is
22575 function C_Stream (F : File_Type)
22576 return Interfaces.C_Streams.FILEs;
22578 (File : in out File_Type;
22579 Mode : in File_Mode;
22580 C_Stream : in Interfaces.C_Streams.FILEs;
22581 Form : in String := "");
22582 end Ada.Text_IO.C_Streams;
22584 with Interfaces.C_Streams;
22585 package Ada.Wide_Text_IO.C_Streams is
22586 function C_Stream (F : File_Type)
22587 return Interfaces.C_Streams.FILEs;
22589 (File : in out File_Type;
22590 Mode : in File_Mode;
22591 C_Stream : in Interfaces.C_Streams.FILEs;
22592 Form : in String := "");
22593 end Ada.Wide_Text_IO.C_Streams;
22595 with Interfaces.C_Streams;
22596 package Ada.Wide_Wide_Text_IO.C_Streams is
22597 function C_Stream (F : File_Type)
22598 return Interfaces.C_Streams.FILEs;
22600 (File : in out File_Type;
22601 Mode : in File_Mode;
22602 C_Stream : in Interfaces.C_Streams.FILEs;
22603 Form : in String := "");
22604 end Ada.Wide_Wide_Text_IO.C_Streams;
22606 with Interfaces.C_Streams;
22607 package Ada.Stream_IO.C_Streams is
22608 function C_Stream (F : File_Type)
22609 return Interfaces.C_Streams.FILEs;
22611 (File : in out File_Type;
22612 Mode : in File_Mode;
22613 C_Stream : in Interfaces.C_Streams.FILEs;
22614 Form : in String := "");
22615 end Ada.Stream_IO.C_Streams;
22618 In each of these six packages, the @code{C_Stream} function obtains the
22619 @code{FILE} pointer from a currently opened Ada file. It is then
22620 possible to use the @code{Interfaces.C_Streams} package to operate on
22621 this stream, or the stream can be passed to a C program which can
22622 operate on it directly. Of course the program is responsible for
22623 ensuring that only appropriate sequences of operations are executed.
22625 One particular use of relevance to an Ada program is that the
22626 @code{setvbuf} function can be used to control the buffering of the
22627 stream used by an Ada file. In the absence of such a call the standard
22628 default buffering is used.
22630 The @code{Open} procedures in these packages open a file giving an
22631 existing C Stream instead of a file name. Typically this stream is
22632 imported from a C program, allowing an Ada file to operate on an
22635 @node The GNAT Library,Interfacing to Other Languages,The Implementation of Standard I/O,Top
22636 @anchor{gnat_rm/the_gnat_library the-gnat-library}@anchor{10}@anchor{gnat_rm/the_gnat_library doc}@anchor{2c7}@anchor{gnat_rm/the_gnat_library id1}@anchor{2c8}
22637 @chapter The GNAT Library
22640 The GNAT library contains a number of general and special purpose packages.
22641 It represents functionality that the GNAT developers have found useful, and
22642 which is made available to GNAT users. The packages described here are fully
22643 supported, and upwards compatibility will be maintained in future releases,
22644 so you can use these facilities with the confidence that the same functionality
22645 will be available in future releases.
22647 The chapter here simply gives a brief summary of the facilities available.
22648 The full documentation is found in the spec file for the package. The full
22649 sources of these library packages, including both spec and body, are provided
22650 with all GNAT releases. For example, to find out the full specifications of
22651 the SPITBOL pattern matching capability, including a full tutorial and
22652 extensive examples, look in the @code{g-spipat.ads} file in the library.
22654 For each entry here, the package name (as it would appear in a @code{with}
22655 clause) is given, followed by the name of the corresponding spec file in
22656 parentheses. The packages are children in four hierarchies, @code{Ada},
22657 @code{Interfaces}, @code{System}, and @code{GNAT}, the latter being a
22658 GNAT-specific hierarchy.
22660 Note that an application program should only use packages in one of these
22661 four hierarchies if the package is defined in the Ada Reference Manual,
22662 or is listed in this section of the GNAT Programmers Reference Manual.
22663 All other units should be considered internal implementation units and
22664 should not be directly @code{with}ed by application code. The use of
22665 a @code{with} clause that references one of these internal implementation
22666 units makes an application potentially dependent on changes in versions
22667 of GNAT, and will generate a warning message.
22670 * Ada.Characters.Latin_9 (a-chlat9.ads): Ada Characters Latin_9 a-chlat9 ads.
22671 * Ada.Characters.Wide_Latin_1 (a-cwila1.ads): Ada Characters Wide_Latin_1 a-cwila1 ads.
22672 * Ada.Characters.Wide_Latin_9 (a-cwila1.ads): Ada Characters Wide_Latin_9 a-cwila1 ads.
22673 * Ada.Characters.Wide_Wide_Latin_1 (a-chzla1.ads): Ada Characters Wide_Wide_Latin_1 a-chzla1 ads.
22674 * Ada.Characters.Wide_Wide_Latin_9 (a-chzla9.ads): Ada Characters Wide_Wide_Latin_9 a-chzla9 ads.
22675 * Ada.Containers.Formal_Doubly_Linked_Lists (a-cfdlli.ads): Ada Containers Formal_Doubly_Linked_Lists a-cfdlli ads.
22676 * Ada.Containers.Formal_Hashed_Maps (a-cfhama.ads): Ada Containers Formal_Hashed_Maps a-cfhama ads.
22677 * Ada.Containers.Formal_Hashed_Sets (a-cfhase.ads): Ada Containers Formal_Hashed_Sets a-cfhase ads.
22678 * Ada.Containers.Formal_Ordered_Maps (a-cforma.ads): Ada Containers Formal_Ordered_Maps a-cforma ads.
22679 * Ada.Containers.Formal_Ordered_Sets (a-cforse.ads): Ada Containers Formal_Ordered_Sets a-cforse ads.
22680 * Ada.Containers.Formal_Vectors (a-cofove.ads): Ada Containers Formal_Vectors a-cofove ads.
22681 * Ada.Containers.Formal_Indefinite_Vectors (a-cfinve.ads): Ada Containers Formal_Indefinite_Vectors a-cfinve ads.
22682 * Ada.Containers.Functional_Vectors (a-cofuve.ads): Ada Containers Functional_Vectors a-cofuve ads.
22683 * Ada.Containers.Functional_Sets (a-cofuse.ads): Ada Containers Functional_Sets a-cofuse ads.
22684 * Ada.Containers.Functional_Maps (a-cofuma.ads): Ada Containers Functional_Maps a-cofuma ads.
22685 * Ada.Containers.Bounded_Holders (a-coboho.ads): Ada Containers Bounded_Holders a-coboho ads.
22686 * Ada.Command_Line.Environment (a-colien.ads): Ada Command_Line Environment a-colien ads.
22687 * Ada.Command_Line.Remove (a-colire.ads): Ada Command_Line Remove a-colire ads.
22688 * Ada.Command_Line.Response_File (a-clrefi.ads): Ada Command_Line Response_File a-clrefi ads.
22689 * Ada.Direct_IO.C_Streams (a-diocst.ads): Ada Direct_IO C_Streams a-diocst ads.
22690 * Ada.Exceptions.Is_Null_Occurrence (a-einuoc.ads): Ada Exceptions Is_Null_Occurrence a-einuoc ads.
22691 * Ada.Exceptions.Last_Chance_Handler (a-elchha.ads): Ada Exceptions Last_Chance_Handler a-elchha ads.
22692 * Ada.Exceptions.Traceback (a-exctra.ads): Ada Exceptions Traceback a-exctra ads.
22693 * Ada.Sequential_IO.C_Streams (a-siocst.ads): Ada Sequential_IO C_Streams a-siocst ads.
22694 * Ada.Streams.Stream_IO.C_Streams (a-ssicst.ads): Ada Streams Stream_IO C_Streams a-ssicst ads.
22695 * Ada.Strings.Unbounded.Text_IO (a-suteio.ads): Ada Strings Unbounded Text_IO a-suteio ads.
22696 * Ada.Strings.Wide_Unbounded.Wide_Text_IO (a-swuwti.ads): Ada Strings Wide_Unbounded Wide_Text_IO a-swuwti ads.
22697 * Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO (a-szuzti.ads): Ada Strings Wide_Wide_Unbounded Wide_Wide_Text_IO a-szuzti ads.
22698 * Ada.Text_IO.C_Streams (a-tiocst.ads): Ada Text_IO C_Streams a-tiocst ads.
22699 * Ada.Text_IO.Reset_Standard_Files (a-tirsfi.ads): Ada Text_IO Reset_Standard_Files a-tirsfi ads.
22700 * Ada.Wide_Characters.Unicode (a-wichun.ads): Ada Wide_Characters Unicode a-wichun ads.
22701 * Ada.Wide_Text_IO.C_Streams (a-wtcstr.ads): Ada Wide_Text_IO C_Streams a-wtcstr ads.
22702 * Ada.Wide_Text_IO.Reset_Standard_Files (a-wrstfi.ads): Ada Wide_Text_IO Reset_Standard_Files a-wrstfi ads.
22703 * Ada.Wide_Wide_Characters.Unicode (a-zchuni.ads): Ada Wide_Wide_Characters Unicode a-zchuni ads.
22704 * Ada.Wide_Wide_Text_IO.C_Streams (a-ztcstr.ads): Ada Wide_Wide_Text_IO C_Streams a-ztcstr ads.
22705 * Ada.Wide_Wide_Text_IO.Reset_Standard_Files (a-zrstfi.ads): Ada Wide_Wide_Text_IO Reset_Standard_Files a-zrstfi ads.
22706 * GNAT.Altivec (g-altive.ads): GNAT Altivec g-altive ads.
22707 * GNAT.Altivec.Conversions (g-altcon.ads): GNAT Altivec Conversions g-altcon ads.
22708 * GNAT.Altivec.Vector_Operations (g-alveop.ads): GNAT Altivec Vector_Operations g-alveop ads.
22709 * GNAT.Altivec.Vector_Types (g-alvety.ads): GNAT Altivec Vector_Types g-alvety ads.
22710 * GNAT.Altivec.Vector_Views (g-alvevi.ads): GNAT Altivec Vector_Views g-alvevi ads.
22711 * GNAT.Array_Split (g-arrspl.ads): GNAT Array_Split g-arrspl ads.
22712 * GNAT.AWK (g-awk.ads): GNAT AWK g-awk ads.
22713 * GNAT.Bind_Environment (g-binenv.ads): GNAT Bind_Environment g-binenv ads.
22714 * GNAT.Bounded_Buffers (g-boubuf.ads): GNAT Bounded_Buffers g-boubuf ads.
22715 * GNAT.Bounded_Mailboxes (g-boumai.ads): GNAT Bounded_Mailboxes g-boumai ads.
22716 * GNAT.Bubble_Sort (g-bubsor.ads): GNAT Bubble_Sort g-bubsor ads.
22717 * GNAT.Bubble_Sort_A (g-busora.ads): GNAT Bubble_Sort_A g-busora ads.
22718 * GNAT.Bubble_Sort_G (g-busorg.ads): GNAT Bubble_Sort_G g-busorg ads.
22719 * GNAT.Byte_Order_Mark (g-byorma.ads): GNAT Byte_Order_Mark g-byorma ads.
22720 * GNAT.Byte_Swapping (g-bytswa.ads): GNAT Byte_Swapping g-bytswa ads.
22721 * GNAT.Calendar (g-calend.ads): GNAT Calendar g-calend ads.
22722 * GNAT.Calendar.Time_IO (g-catiio.ads): GNAT Calendar Time_IO g-catiio ads.
22723 * GNAT.CRC32 (g-crc32.ads): GNAT CRC32 g-crc32 ads.
22724 * GNAT.Case_Util (g-casuti.ads): GNAT Case_Util g-casuti ads.
22725 * GNAT.CGI (g-cgi.ads): GNAT CGI g-cgi ads.
22726 * GNAT.CGI.Cookie (g-cgicoo.ads): GNAT CGI Cookie g-cgicoo ads.
22727 * GNAT.CGI.Debug (g-cgideb.ads): GNAT CGI Debug g-cgideb ads.
22728 * GNAT.Command_Line (g-comlin.ads): GNAT Command_Line g-comlin ads.
22729 * GNAT.Compiler_Version (g-comver.ads): GNAT Compiler_Version g-comver ads.
22730 * GNAT.Ctrl_C (g-ctrl_c.ads): GNAT Ctrl_C g-ctrl_c ads.
22731 * GNAT.Current_Exception (g-curexc.ads): GNAT Current_Exception g-curexc ads.
22732 * GNAT.Debug_Pools (g-debpoo.ads): GNAT Debug_Pools g-debpoo ads.
22733 * GNAT.Debug_Utilities (g-debuti.ads): GNAT Debug_Utilities g-debuti ads.
22734 * GNAT.Decode_String (g-decstr.ads): GNAT Decode_String g-decstr ads.
22735 * GNAT.Decode_UTF8_String (g-deutst.ads): GNAT Decode_UTF8_String g-deutst ads.
22736 * GNAT.Directory_Operations (g-dirope.ads): GNAT Directory_Operations g-dirope ads.
22737 * GNAT.Directory_Operations.Iteration (g-diopit.ads): GNAT Directory_Operations Iteration g-diopit ads.
22738 * GNAT.Dynamic_HTables (g-dynhta.ads): GNAT Dynamic_HTables g-dynhta ads.
22739 * GNAT.Dynamic_Tables (g-dyntab.ads): GNAT Dynamic_Tables g-dyntab ads.
22740 * GNAT.Encode_String (g-encstr.ads): GNAT Encode_String g-encstr ads.
22741 * GNAT.Encode_UTF8_String (g-enutst.ads): GNAT Encode_UTF8_String g-enutst ads.
22742 * GNAT.Exception_Actions (g-excact.ads): GNAT Exception_Actions g-excact ads.
22743 * GNAT.Exception_Traces (g-exctra.ads): GNAT Exception_Traces g-exctra ads.
22744 * GNAT.Exceptions (g-expect.ads): GNAT Exceptions g-expect ads.
22745 * GNAT.Expect (g-expect.ads): GNAT Expect g-expect ads.
22746 * GNAT.Expect.TTY (g-exptty.ads): GNAT Expect TTY g-exptty ads.
22747 * GNAT.Float_Control (g-flocon.ads): GNAT Float_Control g-flocon ads.
22748 * GNAT.Formatted_String (g-forstr.ads): GNAT Formatted_String g-forstr ads.
22749 * GNAT.Heap_Sort (g-heasor.ads): GNAT Heap_Sort g-heasor ads.
22750 * GNAT.Heap_Sort_A (g-hesora.ads): GNAT Heap_Sort_A g-hesora ads.
22751 * GNAT.Heap_Sort_G (g-hesorg.ads): GNAT Heap_Sort_G g-hesorg ads.
22752 * GNAT.HTable (g-htable.ads): GNAT HTable g-htable ads.
22753 * GNAT.IO (g-io.ads): GNAT IO g-io ads.
22754 * GNAT.IO_Aux (g-io_aux.ads): GNAT IO_Aux g-io_aux ads.
22755 * GNAT.Lock_Files (g-locfil.ads): GNAT Lock_Files g-locfil ads.
22756 * GNAT.MBBS_Discrete_Random (g-mbdira.ads): GNAT MBBS_Discrete_Random g-mbdira ads.
22757 * GNAT.MBBS_Float_Random (g-mbflra.ads): GNAT MBBS_Float_Random g-mbflra ads.
22758 * GNAT.MD5 (g-md5.ads): GNAT MD5 g-md5 ads.
22759 * GNAT.Memory_Dump (g-memdum.ads): GNAT Memory_Dump g-memdum ads.
22760 * GNAT.Most_Recent_Exception (g-moreex.ads): GNAT Most_Recent_Exception g-moreex ads.
22761 * GNAT.OS_Lib (g-os_lib.ads): GNAT OS_Lib g-os_lib ads.
22762 * GNAT.Perfect_Hash_Generators (g-pehage.ads): GNAT Perfect_Hash_Generators g-pehage ads.
22763 * GNAT.Random_Numbers (g-rannum.ads): GNAT Random_Numbers g-rannum ads.
22764 * GNAT.Regexp (g-regexp.ads): GNAT Regexp g-regexp ads.
22765 * GNAT.Registry (g-regist.ads): GNAT Registry g-regist ads.
22766 * GNAT.Regpat (g-regpat.ads): GNAT Regpat g-regpat ads.
22767 * GNAT.Rewrite_Data (g-rewdat.ads): GNAT Rewrite_Data g-rewdat ads.
22768 * GNAT.Secondary_Stack_Info (g-sestin.ads): GNAT Secondary_Stack_Info g-sestin ads.
22769 * GNAT.Semaphores (g-semaph.ads): GNAT Semaphores g-semaph ads.
22770 * GNAT.Serial_Communications (g-sercom.ads): GNAT Serial_Communications g-sercom ads.
22771 * GNAT.SHA1 (g-sha1.ads): GNAT SHA1 g-sha1 ads.
22772 * GNAT.SHA224 (g-sha224.ads): GNAT SHA224 g-sha224 ads.
22773 * GNAT.SHA256 (g-sha256.ads): GNAT SHA256 g-sha256 ads.
22774 * GNAT.SHA384 (g-sha384.ads): GNAT SHA384 g-sha384 ads.
22775 * GNAT.SHA512 (g-sha512.ads): GNAT SHA512 g-sha512 ads.
22776 * GNAT.Signals (g-signal.ads): GNAT Signals g-signal ads.
22777 * GNAT.Sockets (g-socket.ads): GNAT Sockets g-socket ads.
22778 * GNAT.Source_Info (g-souinf.ads): GNAT Source_Info g-souinf ads.
22779 * GNAT.Spelling_Checker (g-speche.ads): GNAT Spelling_Checker g-speche ads.
22780 * GNAT.Spelling_Checker_Generic (g-spchge.ads): GNAT Spelling_Checker_Generic g-spchge ads.
22781 * GNAT.Spitbol.Patterns (g-spipat.ads): GNAT Spitbol Patterns g-spipat ads.
22782 * GNAT.Spitbol (g-spitbo.ads): GNAT Spitbol g-spitbo ads.
22783 * GNAT.Spitbol.Table_Boolean (g-sptabo.ads): GNAT Spitbol Table_Boolean g-sptabo ads.
22784 * GNAT.Spitbol.Table_Integer (g-sptain.ads): GNAT Spitbol Table_Integer g-sptain ads.
22785 * GNAT.Spitbol.Table_VString (g-sptavs.ads): GNAT Spitbol Table_VString g-sptavs ads.
22786 * GNAT.SSE (g-sse.ads): GNAT SSE g-sse ads.
22787 * GNAT.SSE.Vector_Types (g-ssvety.ads): GNAT SSE Vector_Types g-ssvety ads.
22788 * GNAT.String_Hash (g-strhas.ads): GNAT String_Hash g-strhas ads.
22789 * GNAT.Strings (g-string.ads): GNAT Strings g-string ads.
22790 * GNAT.String_Split (g-strspl.ads): GNAT String_Split g-strspl ads.
22791 * GNAT.Table (g-table.ads): GNAT Table g-table ads.
22792 * GNAT.Task_Lock (g-tasloc.ads): GNAT Task_Lock g-tasloc ads.
22793 * GNAT.Time_Stamp (g-timsta.ads): GNAT Time_Stamp g-timsta ads.
22794 * GNAT.Threads (g-thread.ads): GNAT Threads g-thread ads.
22795 * GNAT.Traceback (g-traceb.ads): GNAT Traceback g-traceb ads.
22796 * GNAT.Traceback.Symbolic (g-trasym.ads): GNAT Traceback Symbolic g-trasym ads.
22797 * GNAT.UTF_32 (g-table.ads): GNAT UTF_32 g-table ads.
22798 * GNAT.Wide_Spelling_Checker (g-u3spch.ads): GNAT Wide_Spelling_Checker g-u3spch ads.
22799 * GNAT.Wide_Spelling_Checker (g-wispch.ads): GNAT Wide_Spelling_Checker g-wispch ads.
22800 * GNAT.Wide_String_Split (g-wistsp.ads): GNAT Wide_String_Split g-wistsp ads.
22801 * GNAT.Wide_Wide_Spelling_Checker (g-zspche.ads): GNAT Wide_Wide_Spelling_Checker g-zspche ads.
22802 * GNAT.Wide_Wide_String_Split (g-zistsp.ads): GNAT Wide_Wide_String_Split g-zistsp ads.
22803 * Interfaces.C.Extensions (i-cexten.ads): Interfaces C Extensions i-cexten ads.
22804 * Interfaces.C.Streams (i-cstrea.ads): Interfaces C Streams i-cstrea ads.
22805 * Interfaces.Packed_Decimal (i-pacdec.ads): Interfaces Packed_Decimal i-pacdec ads.
22806 * Interfaces.VxWorks (i-vxwork.ads): Interfaces VxWorks i-vxwork ads.
22807 * Interfaces.VxWorks.Int_Connection (i-vxinco.ads): Interfaces VxWorks Int_Connection i-vxinco ads.
22808 * Interfaces.VxWorks.IO (i-vxwoio.ads): Interfaces VxWorks IO i-vxwoio ads.
22809 * System.Address_Image (s-addima.ads): System Address_Image s-addima ads.
22810 * System.Assertions (s-assert.ads): System Assertions s-assert ads.
22811 * System.Atomic_Counters (s-atocou.ads): System Atomic_Counters s-atocou ads.
22812 * System.Memory (s-memory.ads): System Memory s-memory ads.
22813 * System.Multiprocessors (s-multip.ads): System Multiprocessors s-multip ads.
22814 * System.Multiprocessors.Dispatching_Domains (s-mudido.ads): System Multiprocessors Dispatching_Domains s-mudido ads.
22815 * System.Partition_Interface (s-parint.ads): System Partition_Interface s-parint ads.
22816 * System.Pool_Global (s-pooglo.ads): System Pool_Global s-pooglo ads.
22817 * System.Pool_Local (s-pooloc.ads): System Pool_Local s-pooloc ads.
22818 * System.Restrictions (s-restri.ads): System Restrictions s-restri ads.
22819 * System.Rident (s-rident.ads): System Rident s-rident ads.
22820 * System.Strings.Stream_Ops (s-ststop.ads): System Strings Stream_Ops s-ststop ads.
22821 * System.Unsigned_Types (s-unstyp.ads): System Unsigned_Types s-unstyp ads.
22822 * System.Wch_Cnv (s-wchcnv.ads): System Wch_Cnv s-wchcnv ads.
22823 * System.Wch_Con (s-wchcon.ads): System Wch_Con s-wchcon ads.
22827 @node Ada Characters Latin_9 a-chlat9 ads,Ada Characters Wide_Latin_1 a-cwila1 ads,,The GNAT Library
22828 @anchor{gnat_rm/the_gnat_library id2}@anchor{2c9}@anchor{gnat_rm/the_gnat_library ada-characters-latin-9-a-chlat9-ads}@anchor{2ca}
22829 @section @code{Ada.Characters.Latin_9} (@code{a-chlat9.ads})
22832 @geindex Ada.Characters.Latin_9 (a-chlat9.ads)
22834 @geindex Latin_9 constants for Character
22836 This child of @code{Ada.Characters}
22837 provides a set of definitions corresponding to those in the
22838 RM-defined package @code{Ada.Characters.Latin_1} but with the
22839 few modifications required for @code{Latin-9}
22840 The provision of such a package
22841 is specifically authorized by the Ada Reference Manual
22844 @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
22845 @anchor{gnat_rm/the_gnat_library ada-characters-wide-latin-1-a-cwila1-ads}@anchor{2cb}@anchor{gnat_rm/the_gnat_library id3}@anchor{2cc}
22846 @section @code{Ada.Characters.Wide_Latin_1} (@code{a-cwila1.ads})
22849 @geindex Ada.Characters.Wide_Latin_1 (a-cwila1.ads)
22851 @geindex Latin_1 constants for Wide_Character
22853 This child of @code{Ada.Characters}
22854 provides a set of definitions corresponding to those in the
22855 RM-defined package @code{Ada.Characters.Latin_1} but with the
22856 types of the constants being @code{Wide_Character}
22857 instead of @code{Character}. The provision of such a package
22858 is specifically authorized by the Ada Reference Manual
22861 @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
22862 @anchor{gnat_rm/the_gnat_library id4}@anchor{2cd}@anchor{gnat_rm/the_gnat_library ada-characters-wide-latin-9-a-cwila1-ads}@anchor{2ce}
22863 @section @code{Ada.Characters.Wide_Latin_9} (@code{a-cwila1.ads})
22866 @geindex Ada.Characters.Wide_Latin_9 (a-cwila1.ads)
22868 @geindex Latin_9 constants for Wide_Character
22870 This child of @code{Ada.Characters}
22871 provides a set of definitions corresponding to those in the
22872 GNAT defined package @code{Ada.Characters.Latin_9} but with the
22873 types of the constants being @code{Wide_Character}
22874 instead of @code{Character}. The provision of such a package
22875 is specifically authorized by the Ada Reference Manual
22878 @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
22879 @anchor{gnat_rm/the_gnat_library ada-characters-wide-wide-latin-1-a-chzla1-ads}@anchor{2cf}@anchor{gnat_rm/the_gnat_library id5}@anchor{2d0}
22880 @section @code{Ada.Characters.Wide_Wide_Latin_1} (@code{a-chzla1.ads})
22883 @geindex Ada.Characters.Wide_Wide_Latin_1 (a-chzla1.ads)
22885 @geindex Latin_1 constants for Wide_Wide_Character
22887 This child of @code{Ada.Characters}
22888 provides a set of definitions corresponding to those in the
22889 RM-defined package @code{Ada.Characters.Latin_1} but with the
22890 types of the constants being @code{Wide_Wide_Character}
22891 instead of @code{Character}. The provision of such a package
22892 is specifically authorized by the Ada Reference Manual
22895 @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
22896 @anchor{gnat_rm/the_gnat_library ada-characters-wide-wide-latin-9-a-chzla9-ads}@anchor{2d1}@anchor{gnat_rm/the_gnat_library id6}@anchor{2d2}
22897 @section @code{Ada.Characters.Wide_Wide_Latin_9} (@code{a-chzla9.ads})
22900 @geindex Ada.Characters.Wide_Wide_Latin_9 (a-chzla9.ads)
22902 @geindex Latin_9 constants for Wide_Wide_Character
22904 This child of @code{Ada.Characters}
22905 provides a set of definitions corresponding to those in the
22906 GNAT defined package @code{Ada.Characters.Latin_9} but with the
22907 types of the constants being @code{Wide_Wide_Character}
22908 instead of @code{Character}. The provision of such a package
22909 is specifically authorized by the Ada Reference Manual
22912 @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
22913 @anchor{gnat_rm/the_gnat_library id7}@anchor{2d3}@anchor{gnat_rm/the_gnat_library ada-containers-formal-doubly-linked-lists-a-cfdlli-ads}@anchor{2d4}
22914 @section @code{Ada.Containers.Formal_Doubly_Linked_Lists} (@code{a-cfdlli.ads})
22917 @geindex Ada.Containers.Formal_Doubly_Linked_Lists (a-cfdlli.ads)
22919 @geindex Formal container for doubly linked lists
22921 This child of @code{Ada.Containers} defines a modified version of the
22922 Ada 2005 container for doubly linked lists, meant to facilitate formal
22923 verification of code using such containers. The specification of this
22924 unit is compatible with SPARK 2014.
22926 Note that although this container was designed with formal verification
22927 in mind, it may well be generally useful in that it is a simplified more
22928 efficient version than the one defined in the standard. In particular it
22929 does not have the complex overhead required to detect cursor tampering.
22931 @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
22932 @anchor{gnat_rm/the_gnat_library id8}@anchor{2d5}@anchor{gnat_rm/the_gnat_library ada-containers-formal-hashed-maps-a-cfhama-ads}@anchor{2d6}
22933 @section @code{Ada.Containers.Formal_Hashed_Maps} (@code{a-cfhama.ads})
22936 @geindex Ada.Containers.Formal_Hashed_Maps (a-cfhama.ads)
22938 @geindex Formal container for hashed maps
22940 This child of @code{Ada.Containers} defines a modified version of the
22941 Ada 2005 container for hashed maps, meant to facilitate formal
22942 verification of code using such containers. The specification of this
22943 unit is compatible with SPARK 2014.
22945 Note that although this container was designed with formal verification
22946 in mind, it may well be generally useful in that it is a simplified more
22947 efficient version than the one defined in the standard. In particular it
22948 does not have the complex overhead required to detect cursor tampering.
22950 @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
22951 @anchor{gnat_rm/the_gnat_library id9}@anchor{2d7}@anchor{gnat_rm/the_gnat_library ada-containers-formal-hashed-sets-a-cfhase-ads}@anchor{2d8}
22952 @section @code{Ada.Containers.Formal_Hashed_Sets} (@code{a-cfhase.ads})
22955 @geindex Ada.Containers.Formal_Hashed_Sets (a-cfhase.ads)
22957 @geindex Formal container for hashed sets
22959 This child of @code{Ada.Containers} defines a modified version of the
22960 Ada 2005 container for hashed sets, meant to facilitate formal
22961 verification of code using such containers. The specification of this
22962 unit is compatible with SPARK 2014.
22964 Note that although this container was designed with formal verification
22965 in mind, it may well be generally useful in that it is a simplified more
22966 efficient version than the one defined in the standard. In particular it
22967 does not have the complex overhead required to detect cursor tampering.
22969 @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
22970 @anchor{gnat_rm/the_gnat_library id10}@anchor{2d9}@anchor{gnat_rm/the_gnat_library ada-containers-formal-ordered-maps-a-cforma-ads}@anchor{2da}
22971 @section @code{Ada.Containers.Formal_Ordered_Maps} (@code{a-cforma.ads})
22974 @geindex Ada.Containers.Formal_Ordered_Maps (a-cforma.ads)
22976 @geindex Formal container for ordered maps
22978 This child of @code{Ada.Containers} defines a modified version of the
22979 Ada 2005 container for ordered maps, meant to facilitate formal
22980 verification of code using such containers. The specification of this
22981 unit is compatible with SPARK 2014.
22983 Note that although this container was designed with formal verification
22984 in mind, it may well be generally useful in that it is a simplified more
22985 efficient version than the one defined in the standard. In particular it
22986 does not have the complex overhead required to detect cursor tampering.
22988 @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
22989 @anchor{gnat_rm/the_gnat_library ada-containers-formal-ordered-sets-a-cforse-ads}@anchor{2db}@anchor{gnat_rm/the_gnat_library id11}@anchor{2dc}
22990 @section @code{Ada.Containers.Formal_Ordered_Sets} (@code{a-cforse.ads})
22993 @geindex Ada.Containers.Formal_Ordered_Sets (a-cforse.ads)
22995 @geindex Formal container for ordered sets
22997 This child of @code{Ada.Containers} defines a modified version of the
22998 Ada 2005 container for ordered sets, meant to facilitate formal
22999 verification of code using such containers. The specification of this
23000 unit is compatible with SPARK 2014.
23002 Note that although this container was designed with formal verification
23003 in mind, it may well be generally useful in that it is a simplified more
23004 efficient version than the one defined in the standard. In particular it
23005 does not have the complex overhead required to detect cursor tampering.
23007 @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
23008 @anchor{gnat_rm/the_gnat_library id12}@anchor{2dd}@anchor{gnat_rm/the_gnat_library ada-containers-formal-vectors-a-cofove-ads}@anchor{2de}
23009 @section @code{Ada.Containers.Formal_Vectors} (@code{a-cofove.ads})
23012 @geindex Ada.Containers.Formal_Vectors (a-cofove.ads)
23014 @geindex Formal container for vectors
23016 This child of @code{Ada.Containers} defines a modified version of the
23017 Ada 2005 container for vectors, meant to facilitate formal
23018 verification of code using such containers. The specification of this
23019 unit is compatible with SPARK 2014.
23021 Note that although this container was designed with formal verification
23022 in mind, it may well be generally useful in that it is a simplified more
23023 efficient version than the one defined in the standard. In particular it
23024 does not have the complex overhead required to detect cursor tampering.
23026 @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
23027 @anchor{gnat_rm/the_gnat_library id13}@anchor{2df}@anchor{gnat_rm/the_gnat_library ada-containers-formal-indefinite-vectors-a-cfinve-ads}@anchor{2e0}
23028 @section @code{Ada.Containers.Formal_Indefinite_Vectors} (@code{a-cfinve.ads})
23031 @geindex Ada.Containers.Formal_Indefinite_Vectors (a-cfinve.ads)
23033 @geindex Formal container for vectors
23035 This child of @code{Ada.Containers} defines a modified version of the
23036 Ada 2005 container for vectors of indefinite elements, meant to
23037 facilitate formal verification of code using such containers. The
23038 specification of this unit is compatible with SPARK 2014.
23040 Note that although this container was designed with formal verification
23041 in mind, it may well be generally useful in that it is a simplified more
23042 efficient version than the one defined in the standard. In particular it
23043 does not have the complex overhead required to detect cursor tampering.
23045 @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
23046 @anchor{gnat_rm/the_gnat_library id14}@anchor{2e1}@anchor{gnat_rm/the_gnat_library ada-containers-functional-vectors-a-cofuve-ads}@anchor{2e2}
23047 @section @code{Ada.Containers.Functional_Vectors} (@code{a-cofuve.ads})
23050 @geindex Ada.Containers.Functional_Vectors (a-cofuve.ads)
23052 @geindex Functional vectors
23054 This child of @code{Ada.Containers} defines immutable vectors. These
23055 containers are unbounded and may contain indefinite elements. Furthermore, to
23056 be usable in every context, they are neither controlled nor limited. As they
23057 are functional, that is, no primitives are provided which would allow modifying
23058 an existing container, these containers can still be used safely.
23060 Their API features functions creating new containers from existing ones.
23061 As a consequence, these containers are highly inefficient. They are also
23062 memory consuming, as the allocated memory is not reclaimed when the container
23063 is no longer referenced. Thus, they should in general be used in ghost code
23064 and annotations, so that they can be removed from the final executable. The
23065 specification of this unit is compatible with SPARK 2014.
23067 @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
23068 @anchor{gnat_rm/the_gnat_library ada-containers-functional-sets-a-cofuse-ads}@anchor{2e3}@anchor{gnat_rm/the_gnat_library id15}@anchor{2e4}
23069 @section @code{Ada.Containers.Functional_Sets} (@code{a-cofuse.ads})
23072 @geindex Ada.Containers.Functional_Sets (a-cofuse.ads)
23074 @geindex Functional sets
23076 This child of @code{Ada.Containers} defines immutable sets. These containers are
23077 unbounded and may contain indefinite elements. Furthermore, to be usable in
23078 every context, they are neither controlled nor limited. As they are functional,
23079 that is, no primitives are provided which would allow modifying an existing
23080 container, these containers can still be used safely.
23082 Their API features functions creating new containers from existing ones.
23083 As a consequence, these containers are highly inefficient. They are also
23084 memory consuming, as the allocated memory is not reclaimed when the container
23085 is no longer referenced. Thus, they should in general be used in ghost code
23086 and annotations, so that they can be removed from the final executable. The
23087 specification of this unit is compatible with SPARK 2014.
23089 @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
23090 @anchor{gnat_rm/the_gnat_library id16}@anchor{2e5}@anchor{gnat_rm/the_gnat_library ada-containers-functional-maps-a-cofuma-ads}@anchor{2e6}
23091 @section @code{Ada.Containers.Functional_Maps} (@code{a-cofuma.ads})
23094 @geindex Ada.Containers.Functional_Maps (a-cofuma.ads)
23096 @geindex Functional maps
23098 This child of @code{Ada.Containers} defines immutable maps. These containers are
23099 unbounded and may contain indefinite elements. Furthermore, to be usable in
23100 every context, they are neither controlled nor limited. As they are functional,
23101 that is, no primitives are provided which would allow modifying an existing
23102 container, these containers can still be used safely.
23104 Their API features functions creating new containers from existing ones.
23105 As a consequence, these containers are highly inefficient. They are also
23106 memory consuming, as the allocated memory is not reclaimed when the container
23107 is no longer referenced. Thus, they should in general be used in ghost code
23108 and annotations, so that they can be removed from the final executable. The
23109 specification of this unit is compatible with SPARK 2014.
23111 @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
23112 @anchor{gnat_rm/the_gnat_library ada-containers-bounded-holders-a-coboho-ads}@anchor{2e7}@anchor{gnat_rm/the_gnat_library id17}@anchor{2e8}
23113 @section @code{Ada.Containers.Bounded_Holders} (@code{a-coboho.ads})
23116 @geindex Ada.Containers.Bounded_Holders (a-coboho.ads)
23118 @geindex Formal container for vectors
23120 This child of @code{Ada.Containers} defines a modified version of
23121 Indefinite_Holders that avoids heap allocation.
23123 @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
23124 @anchor{gnat_rm/the_gnat_library ada-command-line-environment-a-colien-ads}@anchor{2e9}@anchor{gnat_rm/the_gnat_library id18}@anchor{2ea}
23125 @section @code{Ada.Command_Line.Environment} (@code{a-colien.ads})
23128 @geindex Ada.Command_Line.Environment (a-colien.ads)
23130 @geindex Environment entries
23132 This child of @code{Ada.Command_Line}
23133 provides a mechanism for obtaining environment values on systems
23134 where this concept makes sense.
23136 @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
23137 @anchor{gnat_rm/the_gnat_library id19}@anchor{2eb}@anchor{gnat_rm/the_gnat_library ada-command-line-remove-a-colire-ads}@anchor{2ec}
23138 @section @code{Ada.Command_Line.Remove} (@code{a-colire.ads})
23141 @geindex Ada.Command_Line.Remove (a-colire.ads)
23143 @geindex Removing command line arguments
23145 @geindex Command line
23146 @geindex argument removal
23148 This child of @code{Ada.Command_Line}
23149 provides a mechanism for logically removing
23150 arguments from the argument list. Once removed, an argument is not visible
23151 to further calls on the subprograms in @code{Ada.Command_Line} will not
23152 see the removed argument.
23154 @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
23155 @anchor{gnat_rm/the_gnat_library id20}@anchor{2ed}@anchor{gnat_rm/the_gnat_library ada-command-line-response-file-a-clrefi-ads}@anchor{2ee}
23156 @section @code{Ada.Command_Line.Response_File} (@code{a-clrefi.ads})
23159 @geindex Ada.Command_Line.Response_File (a-clrefi.ads)
23161 @geindex Response file for command line
23163 @geindex Command line
23164 @geindex response file
23166 @geindex Command line
23167 @geindex handling long command lines
23169 This child of @code{Ada.Command_Line} provides a mechanism facilities for
23170 getting command line arguments from a text file, called a "response file".
23171 Using a response file allow passing a set of arguments to an executable longer
23172 than the maximum allowed by the system on the command line.
23174 @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
23175 @anchor{gnat_rm/the_gnat_library id21}@anchor{2ef}@anchor{gnat_rm/the_gnat_library ada-direct-io-c-streams-a-diocst-ads}@anchor{2f0}
23176 @section @code{Ada.Direct_IO.C_Streams} (@code{a-diocst.ads})
23179 @geindex Ada.Direct_IO.C_Streams (a-diocst.ads)
23182 @geindex Interfacing with Direct_IO
23184 This package provides subprograms that allow interfacing between
23185 C streams and @code{Direct_IO}. The stream identifier can be
23186 extracted from a file opened on the Ada side, and an Ada file
23187 can be constructed from a stream opened on the C side.
23189 @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
23190 @anchor{gnat_rm/the_gnat_library id22}@anchor{2f1}@anchor{gnat_rm/the_gnat_library ada-exceptions-is-null-occurrence-a-einuoc-ads}@anchor{2f2}
23191 @section @code{Ada.Exceptions.Is_Null_Occurrence} (@code{a-einuoc.ads})
23194 @geindex Ada.Exceptions.Is_Null_Occurrence (a-einuoc.ads)
23196 @geindex Null_Occurrence
23197 @geindex testing for
23199 This child subprogram provides a way of testing for the null
23200 exception occurrence (@code{Null_Occurrence}) without raising
23203 @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
23204 @anchor{gnat_rm/the_gnat_library id23}@anchor{2f3}@anchor{gnat_rm/the_gnat_library ada-exceptions-last-chance-handler-a-elchha-ads}@anchor{2f4}
23205 @section @code{Ada.Exceptions.Last_Chance_Handler} (@code{a-elchha.ads})
23208 @geindex Ada.Exceptions.Last_Chance_Handler (a-elchha.ads)
23210 @geindex Null_Occurrence
23211 @geindex testing for
23213 This child subprogram is used for handling otherwise unhandled
23214 exceptions (hence the name last chance), and perform clean ups before
23215 terminating the program. Note that this subprogram never returns.
23217 @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
23218 @anchor{gnat_rm/the_gnat_library ada-exceptions-traceback-a-exctra-ads}@anchor{2f5}@anchor{gnat_rm/the_gnat_library id24}@anchor{2f6}
23219 @section @code{Ada.Exceptions.Traceback} (@code{a-exctra.ads})
23222 @geindex Ada.Exceptions.Traceback (a-exctra.ads)
23224 @geindex Traceback for Exception Occurrence
23226 This child package provides the subprogram (@code{Tracebacks}) to
23227 give a traceback array of addresses based on an exception
23230 @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
23231 @anchor{gnat_rm/the_gnat_library ada-sequential-io-c-streams-a-siocst-ads}@anchor{2f7}@anchor{gnat_rm/the_gnat_library id25}@anchor{2f8}
23232 @section @code{Ada.Sequential_IO.C_Streams} (@code{a-siocst.ads})
23235 @geindex Ada.Sequential_IO.C_Streams (a-siocst.ads)
23238 @geindex Interfacing with Sequential_IO
23240 This package provides subprograms that allow interfacing between
23241 C streams and @code{Sequential_IO}. The stream identifier can be
23242 extracted from a file opened on the Ada side, and an Ada file
23243 can be constructed from a stream opened on the C side.
23245 @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
23246 @anchor{gnat_rm/the_gnat_library id26}@anchor{2f9}@anchor{gnat_rm/the_gnat_library ada-streams-stream-io-c-streams-a-ssicst-ads}@anchor{2fa}
23247 @section @code{Ada.Streams.Stream_IO.C_Streams} (@code{a-ssicst.ads})
23250 @geindex Ada.Streams.Stream_IO.C_Streams (a-ssicst.ads)
23253 @geindex Interfacing with Stream_IO
23255 This package provides subprograms that allow interfacing between
23256 C streams and @code{Stream_IO}. The stream identifier can be
23257 extracted from a file opened on the Ada side, and an Ada file
23258 can be constructed from a stream opened on the C side.
23260 @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
23261 @anchor{gnat_rm/the_gnat_library ada-strings-unbounded-text-io-a-suteio-ads}@anchor{2fb}@anchor{gnat_rm/the_gnat_library id27}@anchor{2fc}
23262 @section @code{Ada.Strings.Unbounded.Text_IO} (@code{a-suteio.ads})
23265 @geindex Ada.Strings.Unbounded.Text_IO (a-suteio.ads)
23267 @geindex Unbounded_String
23268 @geindex IO support
23271 @geindex extensions for unbounded strings
23273 This package provides subprograms for Text_IO for unbounded
23274 strings, avoiding the necessity for an intermediate operation
23275 with ordinary strings.
23277 @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
23278 @anchor{gnat_rm/the_gnat_library id28}@anchor{2fd}@anchor{gnat_rm/the_gnat_library ada-strings-wide-unbounded-wide-text-io-a-swuwti-ads}@anchor{2fe}
23279 @section @code{Ada.Strings.Wide_Unbounded.Wide_Text_IO} (@code{a-swuwti.ads})
23282 @geindex Ada.Strings.Wide_Unbounded.Wide_Text_IO (a-swuwti.ads)
23284 @geindex Unbounded_Wide_String
23285 @geindex IO support
23288 @geindex extensions for unbounded wide strings
23290 This package provides subprograms for Text_IO for unbounded
23291 wide strings, avoiding the necessity for an intermediate operation
23292 with ordinary wide strings.
23294 @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
23295 @anchor{gnat_rm/the_gnat_library id29}@anchor{2ff}@anchor{gnat_rm/the_gnat_library ada-strings-wide-wide-unbounded-wide-wide-text-io-a-szuzti-ads}@anchor{300}
23296 @section @code{Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO} (@code{a-szuzti.ads})
23299 @geindex Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO (a-szuzti.ads)
23301 @geindex Unbounded_Wide_Wide_String
23302 @geindex IO support
23305 @geindex extensions for unbounded wide wide strings
23307 This package provides subprograms for Text_IO for unbounded
23308 wide wide strings, avoiding the necessity for an intermediate operation
23309 with ordinary wide wide strings.
23311 @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
23312 @anchor{gnat_rm/the_gnat_library ada-text-io-c-streams-a-tiocst-ads}@anchor{301}@anchor{gnat_rm/the_gnat_library id30}@anchor{302}
23313 @section @code{Ada.Text_IO.C_Streams} (@code{a-tiocst.ads})
23316 @geindex Ada.Text_IO.C_Streams (a-tiocst.ads)
23319 @geindex Interfacing with `@w{`}Text_IO`@w{`}
23321 This package provides subprograms that allow interfacing between
23322 C streams and @code{Text_IO}. The stream identifier can be
23323 extracted from a file opened on the Ada side, and an Ada file
23324 can be constructed from a stream opened on the C side.
23326 @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
23327 @anchor{gnat_rm/the_gnat_library ada-text-io-reset-standard-files-a-tirsfi-ads}@anchor{303}@anchor{gnat_rm/the_gnat_library id31}@anchor{304}
23328 @section @code{Ada.Text_IO.Reset_Standard_Files} (@code{a-tirsfi.ads})
23331 @geindex Ada.Text_IO.Reset_Standard_Files (a-tirsfi.ads)
23333 @geindex Text_IO resetting standard files
23335 This procedure is used to reset the status of the standard files used
23336 by Ada.Text_IO. This is useful in a situation (such as a restart in an
23337 embedded application) where the status of the files may change during
23338 execution (for example a standard input file may be redefined to be
23341 @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
23342 @anchor{gnat_rm/the_gnat_library id32}@anchor{305}@anchor{gnat_rm/the_gnat_library ada-wide-characters-unicode-a-wichun-ads}@anchor{306}
23343 @section @code{Ada.Wide_Characters.Unicode} (@code{a-wichun.ads})
23346 @geindex Ada.Wide_Characters.Unicode (a-wichun.ads)
23348 @geindex Unicode categorization
23349 @geindex Wide_Character
23351 This package provides subprograms that allow categorization of
23352 Wide_Character values according to Unicode categories.
23354 @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
23355 @anchor{gnat_rm/the_gnat_library ada-wide-text-io-c-streams-a-wtcstr-ads}@anchor{307}@anchor{gnat_rm/the_gnat_library id33}@anchor{308}
23356 @section @code{Ada.Wide_Text_IO.C_Streams} (@code{a-wtcstr.ads})
23359 @geindex Ada.Wide_Text_IO.C_Streams (a-wtcstr.ads)
23362 @geindex Interfacing with `@w{`}Wide_Text_IO`@w{`}
23364 This package provides subprograms that allow interfacing between
23365 C streams and @code{Wide_Text_IO}. The stream identifier can be
23366 extracted from a file opened on the Ada side, and an Ada file
23367 can be constructed from a stream opened on the C side.
23369 @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
23370 @anchor{gnat_rm/the_gnat_library ada-wide-text-io-reset-standard-files-a-wrstfi-ads}@anchor{309}@anchor{gnat_rm/the_gnat_library id34}@anchor{30a}
23371 @section @code{Ada.Wide_Text_IO.Reset_Standard_Files} (@code{a-wrstfi.ads})
23374 @geindex Ada.Wide_Text_IO.Reset_Standard_Files (a-wrstfi.ads)
23376 @geindex Wide_Text_IO resetting standard files
23378 This procedure is used to reset the status of the standard files used
23379 by Ada.Wide_Text_IO. This is useful in a situation (such as a restart in an
23380 embedded application) where the status of the files may change during
23381 execution (for example a standard input file may be redefined to be
23384 @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
23385 @anchor{gnat_rm/the_gnat_library id35}@anchor{30b}@anchor{gnat_rm/the_gnat_library ada-wide-wide-characters-unicode-a-zchuni-ads}@anchor{30c}
23386 @section @code{Ada.Wide_Wide_Characters.Unicode} (@code{a-zchuni.ads})
23389 @geindex Ada.Wide_Wide_Characters.Unicode (a-zchuni.ads)
23391 @geindex Unicode categorization
23392 @geindex Wide_Wide_Character
23394 This package provides subprograms that allow categorization of
23395 Wide_Wide_Character values according to Unicode categories.
23397 @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
23398 @anchor{gnat_rm/the_gnat_library id36}@anchor{30d}@anchor{gnat_rm/the_gnat_library ada-wide-wide-text-io-c-streams-a-ztcstr-ads}@anchor{30e}
23399 @section @code{Ada.Wide_Wide_Text_IO.C_Streams} (@code{a-ztcstr.ads})
23402 @geindex Ada.Wide_Wide_Text_IO.C_Streams (a-ztcstr.ads)
23405 @geindex Interfacing with `@w{`}Wide_Wide_Text_IO`@w{`}
23407 This package provides subprograms that allow interfacing between
23408 C streams and @code{Wide_Wide_Text_IO}. The stream identifier can be
23409 extracted from a file opened on the Ada side, and an Ada file
23410 can be constructed from a stream opened on the C side.
23412 @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
23413 @anchor{gnat_rm/the_gnat_library id37}@anchor{30f}@anchor{gnat_rm/the_gnat_library ada-wide-wide-text-io-reset-standard-files-a-zrstfi-ads}@anchor{310}
23414 @section @code{Ada.Wide_Wide_Text_IO.Reset_Standard_Files} (@code{a-zrstfi.ads})
23417 @geindex Ada.Wide_Wide_Text_IO.Reset_Standard_Files (a-zrstfi.ads)
23419 @geindex Wide_Wide_Text_IO resetting standard files
23421 This procedure is used to reset the status of the standard files used
23422 by Ada.Wide_Wide_Text_IO. This is useful in a situation (such as a
23423 restart in an embedded application) where the status of the files may
23424 change during execution (for example a standard input file may be
23425 redefined to be interactive).
23427 @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
23428 @anchor{gnat_rm/the_gnat_library gnat-altivec-g-altive-ads}@anchor{311}@anchor{gnat_rm/the_gnat_library id38}@anchor{312}
23429 @section @code{GNAT.Altivec} (@code{g-altive.ads})
23432 @geindex GNAT.Altivec (g-altive.ads)
23436 This is the root package of the GNAT AltiVec binding. It provides
23437 definitions of constants and types common to all the versions of the
23440 @node GNAT Altivec Conversions g-altcon ads,GNAT Altivec Vector_Operations g-alveop ads,GNAT Altivec g-altive ads,The GNAT Library
23441 @anchor{gnat_rm/the_gnat_library gnat-altivec-conversions-g-altcon-ads}@anchor{313}@anchor{gnat_rm/the_gnat_library id39}@anchor{314}
23442 @section @code{GNAT.Altivec.Conversions} (@code{g-altcon.ads})
23445 @geindex GNAT.Altivec.Conversions (g-altcon.ads)
23449 This package provides the Vector/View conversion routines.
23451 @node GNAT Altivec Vector_Operations g-alveop ads,GNAT Altivec Vector_Types g-alvety ads,GNAT Altivec Conversions g-altcon ads,The GNAT Library
23452 @anchor{gnat_rm/the_gnat_library gnat-altivec-vector-operations-g-alveop-ads}@anchor{315}@anchor{gnat_rm/the_gnat_library id40}@anchor{316}
23453 @section @code{GNAT.Altivec.Vector_Operations} (@code{g-alveop.ads})
23456 @geindex GNAT.Altivec.Vector_Operations (g-alveop.ads)
23460 This package exposes the Ada interface to the AltiVec operations on
23461 vector objects. A soft emulation is included by default in the GNAT
23462 library. The hard binding is provided as a separate package. This unit
23463 is common to both bindings.
23465 @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
23466 @anchor{gnat_rm/the_gnat_library gnat-altivec-vector-types-g-alvety-ads}@anchor{317}@anchor{gnat_rm/the_gnat_library id41}@anchor{318}
23467 @section @code{GNAT.Altivec.Vector_Types} (@code{g-alvety.ads})
23470 @geindex GNAT.Altivec.Vector_Types (g-alvety.ads)
23474 This package exposes the various vector types part of the Ada binding
23475 to AltiVec facilities.
23477 @node GNAT Altivec Vector_Views g-alvevi ads,GNAT Array_Split g-arrspl ads,GNAT Altivec Vector_Types g-alvety ads,The GNAT Library
23478 @anchor{gnat_rm/the_gnat_library gnat-altivec-vector-views-g-alvevi-ads}@anchor{319}@anchor{gnat_rm/the_gnat_library id42}@anchor{31a}
23479 @section @code{GNAT.Altivec.Vector_Views} (@code{g-alvevi.ads})
23482 @geindex GNAT.Altivec.Vector_Views (g-alvevi.ads)
23486 This package provides public 'View' data types from/to which private
23487 vector representations can be converted via
23488 GNAT.Altivec.Conversions. This allows convenient access to individual
23489 vector elements and provides a simple way to initialize vector
23492 @node GNAT Array_Split g-arrspl ads,GNAT AWK g-awk ads,GNAT Altivec Vector_Views g-alvevi ads,The GNAT Library
23493 @anchor{gnat_rm/the_gnat_library gnat-array-split-g-arrspl-ads}@anchor{31b}@anchor{gnat_rm/the_gnat_library id43}@anchor{31c}
23494 @section @code{GNAT.Array_Split} (@code{g-arrspl.ads})
23497 @geindex GNAT.Array_Split (g-arrspl.ads)
23499 @geindex Array splitter
23501 Useful array-manipulation routines: given a set of separators, split
23502 an array wherever the separators appear, and provide direct access
23503 to the resulting slices.
23505 @node GNAT AWK g-awk ads,GNAT Bind_Environment g-binenv ads,GNAT Array_Split g-arrspl ads,The GNAT Library
23506 @anchor{gnat_rm/the_gnat_library id44}@anchor{31d}@anchor{gnat_rm/the_gnat_library gnat-awk-g-awk-ads}@anchor{31e}
23507 @section @code{GNAT.AWK} (@code{g-awk.ads})
23510 @geindex GNAT.AWK (g-awk.ads)
23516 Provides AWK-like parsing functions, with an easy interface for parsing one
23517 or more files containing formatted data. The file is viewed as a database
23518 where each record is a line and a field is a data element in this line.
23520 @node GNAT Bind_Environment g-binenv ads,GNAT Bounded_Buffers g-boubuf ads,GNAT AWK g-awk ads,The GNAT Library
23521 @anchor{gnat_rm/the_gnat_library gnat-bind-environment-g-binenv-ads}@anchor{31f}@anchor{gnat_rm/the_gnat_library id45}@anchor{320}
23522 @section @code{GNAT.Bind_Environment} (@code{g-binenv.ads})
23525 @geindex GNAT.Bind_Environment (g-binenv.ads)
23527 @geindex Bind environment
23529 Provides access to key=value associations captured at bind time.
23530 These associations can be specified using the @code{-V} binder command
23533 @node GNAT Bounded_Buffers g-boubuf ads,GNAT Bounded_Mailboxes g-boumai ads,GNAT Bind_Environment g-binenv ads,The GNAT Library
23534 @anchor{gnat_rm/the_gnat_library id46}@anchor{321}@anchor{gnat_rm/the_gnat_library gnat-bounded-buffers-g-boubuf-ads}@anchor{322}
23535 @section @code{GNAT.Bounded_Buffers} (@code{g-boubuf.ads})
23538 @geindex GNAT.Bounded_Buffers (g-boubuf.ads)
23542 @geindex Bounded Buffers
23544 Provides a concurrent generic bounded buffer abstraction. Instances are
23545 useful directly or as parts of the implementations of other abstractions,
23548 @node GNAT Bounded_Mailboxes g-boumai ads,GNAT Bubble_Sort g-bubsor ads,GNAT Bounded_Buffers g-boubuf ads,The GNAT Library
23549 @anchor{gnat_rm/the_gnat_library id47}@anchor{323}@anchor{gnat_rm/the_gnat_library gnat-bounded-mailboxes-g-boumai-ads}@anchor{324}
23550 @section @code{GNAT.Bounded_Mailboxes} (@code{g-boumai.ads})
23553 @geindex GNAT.Bounded_Mailboxes (g-boumai.ads)
23559 Provides a thread-safe asynchronous intertask mailbox communication facility.
23561 @node GNAT Bubble_Sort g-bubsor ads,GNAT Bubble_Sort_A g-busora ads,GNAT Bounded_Mailboxes g-boumai ads,The GNAT Library
23562 @anchor{gnat_rm/the_gnat_library gnat-bubble-sort-g-bubsor-ads}@anchor{325}@anchor{gnat_rm/the_gnat_library id48}@anchor{326}
23563 @section @code{GNAT.Bubble_Sort} (@code{g-bubsor.ads})
23566 @geindex GNAT.Bubble_Sort (g-bubsor.ads)
23570 @geindex Bubble sort
23572 Provides a general implementation of bubble sort usable for sorting arbitrary
23573 data items. Exchange and comparison procedures are provided by passing
23574 access-to-procedure values.
23576 @node GNAT Bubble_Sort_A g-busora ads,GNAT Bubble_Sort_G g-busorg ads,GNAT Bubble_Sort g-bubsor ads,The GNAT Library
23577 @anchor{gnat_rm/the_gnat_library id49}@anchor{327}@anchor{gnat_rm/the_gnat_library gnat-bubble-sort-a-g-busora-ads}@anchor{328}
23578 @section @code{GNAT.Bubble_Sort_A} (@code{g-busora.ads})
23581 @geindex GNAT.Bubble_Sort_A (g-busora.ads)
23585 @geindex Bubble sort
23587 Provides a general implementation of bubble sort usable for sorting arbitrary
23588 data items. Move and comparison procedures are provided by passing
23589 access-to-procedure values. This is an older version, retained for
23590 compatibility. Usually @code{GNAT.Bubble_Sort} will be preferable.
23592 @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
23593 @anchor{gnat_rm/the_gnat_library gnat-bubble-sort-g-g-busorg-ads}@anchor{329}@anchor{gnat_rm/the_gnat_library id50}@anchor{32a}
23594 @section @code{GNAT.Bubble_Sort_G} (@code{g-busorg.ads})
23597 @geindex GNAT.Bubble_Sort_G (g-busorg.ads)
23601 @geindex Bubble sort
23603 Similar to @code{Bubble_Sort_A} except that the move and sorting procedures
23604 are provided as generic parameters, this improves efficiency, especially
23605 if the procedures can be inlined, at the expense of duplicating code for
23606 multiple instantiations.
23608 @node GNAT Byte_Order_Mark g-byorma ads,GNAT Byte_Swapping g-bytswa ads,GNAT Bubble_Sort_G g-busorg ads,The GNAT Library
23609 @anchor{gnat_rm/the_gnat_library gnat-byte-order-mark-g-byorma-ads}@anchor{32b}@anchor{gnat_rm/the_gnat_library id51}@anchor{32c}
23610 @section @code{GNAT.Byte_Order_Mark} (@code{g-byorma.ads})
23613 @geindex GNAT.Byte_Order_Mark (g-byorma.ads)
23615 @geindex UTF-8 representation
23617 @geindex Wide characte representations
23619 Provides a routine which given a string, reads the start of the string to
23620 see whether it is one of the standard byte order marks (BOM's) which signal
23621 the encoding of the string. The routine includes detection of special XML
23622 sequences for various UCS input formats.
23624 @node GNAT Byte_Swapping g-bytswa ads,GNAT Calendar g-calend ads,GNAT Byte_Order_Mark g-byorma ads,The GNAT Library
23625 @anchor{gnat_rm/the_gnat_library gnat-byte-swapping-g-bytswa-ads}@anchor{32d}@anchor{gnat_rm/the_gnat_library id52}@anchor{32e}
23626 @section @code{GNAT.Byte_Swapping} (@code{g-bytswa.ads})
23629 @geindex GNAT.Byte_Swapping (g-bytswa.ads)
23631 @geindex Byte swapping
23633 @geindex Endianness
23635 General routines for swapping the bytes in 2-, 4-, and 8-byte quantities.
23636 Machine-specific implementations are available in some cases.
23638 @node GNAT Calendar g-calend ads,GNAT Calendar Time_IO g-catiio ads,GNAT Byte_Swapping g-bytswa ads,The GNAT Library
23639 @anchor{gnat_rm/the_gnat_library gnat-calendar-g-calend-ads}@anchor{32f}@anchor{gnat_rm/the_gnat_library id53}@anchor{330}
23640 @section @code{GNAT.Calendar} (@code{g-calend.ads})
23643 @geindex GNAT.Calendar (g-calend.ads)
23647 Extends the facilities provided by @code{Ada.Calendar} to include handling
23648 of days of the week, an extended @code{Split} and @code{Time_Of} capability.
23649 Also provides conversion of @code{Ada.Calendar.Time} values to and from the
23650 C @code{timeval} format.
23652 @node GNAT Calendar Time_IO g-catiio ads,GNAT CRC32 g-crc32 ads,GNAT Calendar g-calend ads,The GNAT Library
23653 @anchor{gnat_rm/the_gnat_library id54}@anchor{331}@anchor{gnat_rm/the_gnat_library gnat-calendar-time-io-g-catiio-ads}@anchor{332}
23654 @section @code{GNAT.Calendar.Time_IO} (@code{g-catiio.ads})
23661 @geindex GNAT.Calendar.Time_IO (g-catiio.ads)
23663 @node GNAT CRC32 g-crc32 ads,GNAT Case_Util g-casuti ads,GNAT Calendar Time_IO g-catiio ads,The GNAT Library
23664 @anchor{gnat_rm/the_gnat_library id55}@anchor{333}@anchor{gnat_rm/the_gnat_library gnat-crc32-g-crc32-ads}@anchor{334}
23665 @section @code{GNAT.CRC32} (@code{g-crc32.ads})
23668 @geindex GNAT.CRC32 (g-crc32.ads)
23672 @geindex Cyclic Redundancy Check
23674 This package implements the CRC-32 algorithm. For a full description
23675 of this algorithm see
23676 @emph{Computation of Cyclic Redundancy Checks via Table Look-Up},
23677 @cite{Communications of the ACM}, Vol. 31 No. 8, pp. 1008-1013,
23678 Aug. 1988. Sarwate, D.V.
23680 @node GNAT Case_Util g-casuti ads,GNAT CGI g-cgi ads,GNAT CRC32 g-crc32 ads,The GNAT Library
23681 @anchor{gnat_rm/the_gnat_library id56}@anchor{335}@anchor{gnat_rm/the_gnat_library gnat-case-util-g-casuti-ads}@anchor{336}
23682 @section @code{GNAT.Case_Util} (@code{g-casuti.ads})
23685 @geindex GNAT.Case_Util (g-casuti.ads)
23687 @geindex Casing utilities
23689 @geindex Character handling (`@w{`}GNAT.Case_Util`@w{`})
23691 A set of simple routines for handling upper and lower casing of strings
23692 without the overhead of the full casing tables
23693 in @code{Ada.Characters.Handling}.
23695 @node GNAT CGI g-cgi ads,GNAT CGI Cookie g-cgicoo ads,GNAT Case_Util g-casuti ads,The GNAT Library
23696 @anchor{gnat_rm/the_gnat_library id57}@anchor{337}@anchor{gnat_rm/the_gnat_library gnat-cgi-g-cgi-ads}@anchor{338}
23697 @section @code{GNAT.CGI} (@code{g-cgi.ads})
23700 @geindex GNAT.CGI (g-cgi.ads)
23702 @geindex CGI (Common Gateway Interface)
23704 This is a package for interfacing a GNAT program with a Web server via the
23705 Common Gateway Interface (CGI). Basically this package parses the CGI
23706 parameters, which are a set of key/value pairs sent by the Web server. It
23707 builds a table whose index is the key and provides some services to deal
23710 @node GNAT CGI Cookie g-cgicoo ads,GNAT CGI Debug g-cgideb ads,GNAT CGI g-cgi ads,The GNAT Library
23711 @anchor{gnat_rm/the_gnat_library gnat-cgi-cookie-g-cgicoo-ads}@anchor{339}@anchor{gnat_rm/the_gnat_library id58}@anchor{33a}
23712 @section @code{GNAT.CGI.Cookie} (@code{g-cgicoo.ads})
23715 @geindex GNAT.CGI.Cookie (g-cgicoo.ads)
23717 @geindex CGI (Common Gateway Interface) cookie support
23719 @geindex Cookie support in CGI
23721 This is a package to interface a GNAT program with a Web server via the
23722 Common Gateway Interface (CGI). It exports services to deal with Web
23723 cookies (piece of information kept in the Web client software).
23725 @node GNAT CGI Debug g-cgideb ads,GNAT Command_Line g-comlin ads,GNAT CGI Cookie g-cgicoo ads,The GNAT Library
23726 @anchor{gnat_rm/the_gnat_library gnat-cgi-debug-g-cgideb-ads}@anchor{33b}@anchor{gnat_rm/the_gnat_library id59}@anchor{33c}
23727 @section @code{GNAT.CGI.Debug} (@code{g-cgideb.ads})
23730 @geindex GNAT.CGI.Debug (g-cgideb.ads)
23732 @geindex CGI (Common Gateway Interface) debugging
23734 This is a package to help debugging CGI (Common Gateway Interface)
23735 programs written in Ada.
23737 @node GNAT Command_Line g-comlin ads,GNAT Compiler_Version g-comver ads,GNAT CGI Debug g-cgideb ads,The GNAT Library
23738 @anchor{gnat_rm/the_gnat_library id60}@anchor{33d}@anchor{gnat_rm/the_gnat_library gnat-command-line-g-comlin-ads}@anchor{33e}
23739 @section @code{GNAT.Command_Line} (@code{g-comlin.ads})
23742 @geindex GNAT.Command_Line (g-comlin.ads)
23744 @geindex Command line
23746 Provides a high level interface to @code{Ada.Command_Line} facilities,
23747 including the ability to scan for named switches with optional parameters
23748 and expand file names using wild card notations.
23750 @node GNAT Compiler_Version g-comver ads,GNAT Ctrl_C g-ctrl_c ads,GNAT Command_Line g-comlin ads,The GNAT Library
23751 @anchor{gnat_rm/the_gnat_library gnat-compiler-version-g-comver-ads}@anchor{33f}@anchor{gnat_rm/the_gnat_library id61}@anchor{340}
23752 @section @code{GNAT.Compiler_Version} (@code{g-comver.ads})
23755 @geindex GNAT.Compiler_Version (g-comver.ads)
23757 @geindex Compiler Version
23760 @geindex of compiler
23762 Provides a routine for obtaining the version of the compiler used to
23763 compile the program. More accurately this is the version of the binder
23764 used to bind the program (this will normally be the same as the version
23765 of the compiler if a consistent tool set is used to compile all units
23768 @node GNAT Ctrl_C g-ctrl_c ads,GNAT Current_Exception g-curexc ads,GNAT Compiler_Version g-comver ads,The GNAT Library
23769 @anchor{gnat_rm/the_gnat_library gnat-ctrl-c-g-ctrl-c-ads}@anchor{341}@anchor{gnat_rm/the_gnat_library id62}@anchor{342}
23770 @section @code{GNAT.Ctrl_C} (@code{g-ctrl_c.ads})
23773 @geindex GNAT.Ctrl_C (g-ctrl_c.ads)
23777 Provides a simple interface to handle Ctrl-C keyboard events.
23779 @node GNAT Current_Exception g-curexc ads,GNAT Debug_Pools g-debpoo ads,GNAT Ctrl_C g-ctrl_c ads,The GNAT Library
23780 @anchor{gnat_rm/the_gnat_library id63}@anchor{343}@anchor{gnat_rm/the_gnat_library gnat-current-exception-g-curexc-ads}@anchor{344}
23781 @section @code{GNAT.Current_Exception} (@code{g-curexc.ads})
23784 @geindex GNAT.Current_Exception (g-curexc.ads)
23786 @geindex Current exception
23788 @geindex Exception retrieval
23790 Provides access to information on the current exception that has been raised
23791 without the need for using the Ada 95 / Ada 2005 exception choice parameter
23792 specification syntax.
23793 This is particularly useful in simulating typical facilities for
23794 obtaining information about exceptions provided by Ada 83 compilers.
23796 @node GNAT Debug_Pools g-debpoo ads,GNAT Debug_Utilities g-debuti ads,GNAT Current_Exception g-curexc ads,The GNAT Library
23797 @anchor{gnat_rm/the_gnat_library gnat-debug-pools-g-debpoo-ads}@anchor{345}@anchor{gnat_rm/the_gnat_library id64}@anchor{346}
23798 @section @code{GNAT.Debug_Pools} (@code{g-debpoo.ads})
23801 @geindex GNAT.Debug_Pools (g-debpoo.ads)
23805 @geindex Debug pools
23807 @geindex Memory corruption debugging
23809 Provide a debugging storage pools that helps tracking memory corruption
23811 See @code{The GNAT Debug_Pool Facility} section in the @cite{GNAT User's Guide}.
23813 @node GNAT Debug_Utilities g-debuti ads,GNAT Decode_String g-decstr ads,GNAT Debug_Pools g-debpoo ads,The GNAT Library
23814 @anchor{gnat_rm/the_gnat_library id65}@anchor{347}@anchor{gnat_rm/the_gnat_library gnat-debug-utilities-g-debuti-ads}@anchor{348}
23815 @section @code{GNAT.Debug_Utilities} (@code{g-debuti.ads})
23818 @geindex GNAT.Debug_Utilities (g-debuti.ads)
23822 Provides a few useful utilities for debugging purposes, including conversion
23823 to and from string images of address values. Supports both C and Ada formats
23824 for hexadecimal literals.
23826 @node GNAT Decode_String g-decstr ads,GNAT Decode_UTF8_String g-deutst ads,GNAT Debug_Utilities g-debuti ads,The GNAT Library
23827 @anchor{gnat_rm/the_gnat_library gnat-decode-string-g-decstr-ads}@anchor{349}@anchor{gnat_rm/the_gnat_library id66}@anchor{34a}
23828 @section @code{GNAT.Decode_String} (@code{g-decstr.ads})
23831 @geindex GNAT.Decode_String (g-decstr.ads)
23833 @geindex Decoding strings
23835 @geindex String decoding
23837 @geindex Wide character encoding
23843 A generic package providing routines for decoding wide character and wide wide
23844 character strings encoded as sequences of 8-bit characters using a specified
23845 encoding method. Includes validation routines, and also routines for stepping
23846 to next or previous encoded character in an encoded string.
23847 Useful in conjunction with Unicode character coding. Note there is a
23848 preinstantiation for UTF-8. See next entry.
23850 @node GNAT Decode_UTF8_String g-deutst ads,GNAT Directory_Operations g-dirope ads,GNAT Decode_String g-decstr ads,The GNAT Library
23851 @anchor{gnat_rm/the_gnat_library gnat-decode-utf8-string-g-deutst-ads}@anchor{34b}@anchor{gnat_rm/the_gnat_library id67}@anchor{34c}
23852 @section @code{GNAT.Decode_UTF8_String} (@code{g-deutst.ads})
23855 @geindex GNAT.Decode_UTF8_String (g-deutst.ads)
23857 @geindex Decoding strings
23859 @geindex Decoding UTF-8 strings
23861 @geindex UTF-8 string decoding
23863 @geindex Wide character decoding
23869 A preinstantiation of GNAT.Decode_Strings for UTF-8 encoding.
23871 @node GNAT Directory_Operations g-dirope ads,GNAT Directory_Operations Iteration g-diopit ads,GNAT Decode_UTF8_String g-deutst ads,The GNAT Library
23872 @anchor{gnat_rm/the_gnat_library gnat-directory-operations-g-dirope-ads}@anchor{34d}@anchor{gnat_rm/the_gnat_library id68}@anchor{34e}
23873 @section @code{GNAT.Directory_Operations} (@code{g-dirope.ads})
23876 @geindex GNAT.Directory_Operations (g-dirope.ads)
23878 @geindex Directory operations
23880 Provides a set of routines for manipulating directories, including changing
23881 the current directory, making new directories, and scanning the files in a
23884 @node GNAT Directory_Operations Iteration g-diopit ads,GNAT Dynamic_HTables g-dynhta ads,GNAT Directory_Operations g-dirope ads,The GNAT Library
23885 @anchor{gnat_rm/the_gnat_library id69}@anchor{34f}@anchor{gnat_rm/the_gnat_library gnat-directory-operations-iteration-g-diopit-ads}@anchor{350}
23886 @section @code{GNAT.Directory_Operations.Iteration} (@code{g-diopit.ads})
23889 @geindex GNAT.Directory_Operations.Iteration (g-diopit.ads)
23891 @geindex Directory operations iteration
23893 A child unit of GNAT.Directory_Operations providing additional operations
23894 for iterating through directories.
23896 @node GNAT Dynamic_HTables g-dynhta ads,GNAT Dynamic_Tables g-dyntab ads,GNAT Directory_Operations Iteration g-diopit ads,The GNAT Library
23897 @anchor{gnat_rm/the_gnat_library id70}@anchor{351}@anchor{gnat_rm/the_gnat_library gnat-dynamic-htables-g-dynhta-ads}@anchor{352}
23898 @section @code{GNAT.Dynamic_HTables} (@code{g-dynhta.ads})
23901 @geindex GNAT.Dynamic_HTables (g-dynhta.ads)
23903 @geindex Hash tables
23905 A generic implementation of hash tables that can be used to hash arbitrary
23906 data. Provided in two forms, a simple form with built in hash functions,
23907 and a more complex form in which the hash function is supplied.
23909 This package provides a facility similar to that of @code{GNAT.HTable},
23910 except that this package declares a type that can be used to define
23911 dynamic instances of the hash table, while an instantiation of
23912 @code{GNAT.HTable} creates a single instance of the hash table.
23914 @node GNAT Dynamic_Tables g-dyntab ads,GNAT Encode_String g-encstr ads,GNAT Dynamic_HTables g-dynhta ads,The GNAT Library
23915 @anchor{gnat_rm/the_gnat_library gnat-dynamic-tables-g-dyntab-ads}@anchor{353}@anchor{gnat_rm/the_gnat_library id71}@anchor{354}
23916 @section @code{GNAT.Dynamic_Tables} (@code{g-dyntab.ads})
23919 @geindex GNAT.Dynamic_Tables (g-dyntab.ads)
23921 @geindex Table implementation
23924 @geindex extendable
23926 A generic package providing a single dimension array abstraction where the
23927 length of the array can be dynamically modified.
23929 This package provides a facility similar to that of @code{GNAT.Table},
23930 except that this package declares a type that can be used to define
23931 dynamic instances of the table, while an instantiation of
23932 @code{GNAT.Table} creates a single instance of the table type.
23934 @node GNAT Encode_String g-encstr ads,GNAT Encode_UTF8_String g-enutst ads,GNAT Dynamic_Tables g-dyntab ads,The GNAT Library
23935 @anchor{gnat_rm/the_gnat_library id72}@anchor{355}@anchor{gnat_rm/the_gnat_library gnat-encode-string-g-encstr-ads}@anchor{356}
23936 @section @code{GNAT.Encode_String} (@code{g-encstr.ads})
23939 @geindex GNAT.Encode_String (g-encstr.ads)
23941 @geindex Encoding strings
23943 @geindex String encoding
23945 @geindex Wide character encoding
23951 A generic package providing routines for encoding wide character and wide
23952 wide character strings as sequences of 8-bit characters using a specified
23953 encoding method. Useful in conjunction with Unicode character coding.
23954 Note there is a preinstantiation for UTF-8. See next entry.
23956 @node GNAT Encode_UTF8_String g-enutst ads,GNAT Exception_Actions g-excact ads,GNAT Encode_String g-encstr ads,The GNAT Library
23957 @anchor{gnat_rm/the_gnat_library gnat-encode-utf8-string-g-enutst-ads}@anchor{357}@anchor{gnat_rm/the_gnat_library id73}@anchor{358}
23958 @section @code{GNAT.Encode_UTF8_String} (@code{g-enutst.ads})
23961 @geindex GNAT.Encode_UTF8_String (g-enutst.ads)
23963 @geindex Encoding strings
23965 @geindex Encoding UTF-8 strings
23967 @geindex UTF-8 string encoding
23969 @geindex Wide character encoding
23975 A preinstantiation of GNAT.Encode_Strings for UTF-8 encoding.
23977 @node GNAT Exception_Actions g-excact ads,GNAT Exception_Traces g-exctra ads,GNAT Encode_UTF8_String g-enutst ads,The GNAT Library
23978 @anchor{gnat_rm/the_gnat_library gnat-exception-actions-g-excact-ads}@anchor{359}@anchor{gnat_rm/the_gnat_library id74}@anchor{35a}
23979 @section @code{GNAT.Exception_Actions} (@code{g-excact.ads})
23982 @geindex GNAT.Exception_Actions (g-excact.ads)
23984 @geindex Exception actions
23986 Provides callbacks when an exception is raised. Callbacks can be registered
23987 for specific exceptions, or when any exception is raised. This
23988 can be used for instance to force a core dump to ease debugging.
23990 @node GNAT Exception_Traces g-exctra ads,GNAT Exceptions g-expect ads,GNAT Exception_Actions g-excact ads,The GNAT Library
23991 @anchor{gnat_rm/the_gnat_library gnat-exception-traces-g-exctra-ads}@anchor{35b}@anchor{gnat_rm/the_gnat_library id75}@anchor{35c}
23992 @section @code{GNAT.Exception_Traces} (@code{g-exctra.ads})
23995 @geindex GNAT.Exception_Traces (g-exctra.ads)
23997 @geindex Exception traces
24001 Provides an interface allowing to control automatic output upon exception
24004 @node GNAT Exceptions g-expect ads,GNAT Expect g-expect ads,GNAT Exception_Traces g-exctra ads,The GNAT Library
24005 @anchor{gnat_rm/the_gnat_library id76}@anchor{35d}@anchor{gnat_rm/the_gnat_library gnat-exceptions-g-expect-ads}@anchor{35e}
24006 @section @code{GNAT.Exceptions} (@code{g-expect.ads})
24009 @geindex GNAT.Exceptions (g-expect.ads)
24011 @geindex Exceptions
24014 @geindex Pure packages
24015 @geindex exceptions
24017 Normally it is not possible to raise an exception with
24018 a message from a subprogram in a pure package, since the
24019 necessary types and subprograms are in @code{Ada.Exceptions}
24020 which is not a pure unit. @code{GNAT.Exceptions} provides a
24021 facility for getting around this limitation for a few
24022 predefined exceptions, and for example allow raising
24023 @code{Constraint_Error} with a message from a pure subprogram.
24025 @node GNAT Expect g-expect ads,GNAT Expect TTY g-exptty ads,GNAT Exceptions g-expect ads,The GNAT Library
24026 @anchor{gnat_rm/the_gnat_library gnat-expect-g-expect-ads}@anchor{35f}@anchor{gnat_rm/the_gnat_library id77}@anchor{360}
24027 @section @code{GNAT.Expect} (@code{g-expect.ads})
24030 @geindex GNAT.Expect (g-expect.ads)
24032 Provides a set of subprograms similar to what is available
24033 with the standard Tcl Expect tool.
24034 It allows you to easily spawn and communicate with an external process.
24035 You can send commands or inputs to the process, and compare the output
24036 with some expected regular expression. Currently @code{GNAT.Expect}
24037 is implemented on all native GNAT ports.
24038 It is not implemented for cross ports, and in particular is not
24039 implemented for VxWorks or LynxOS.
24041 @node GNAT Expect TTY g-exptty ads,GNAT Float_Control g-flocon ads,GNAT Expect g-expect ads,The GNAT Library
24042 @anchor{gnat_rm/the_gnat_library id78}@anchor{361}@anchor{gnat_rm/the_gnat_library gnat-expect-tty-g-exptty-ads}@anchor{362}
24043 @section @code{GNAT.Expect.TTY} (@code{g-exptty.ads})
24046 @geindex GNAT.Expect.TTY (g-exptty.ads)
24048 As GNAT.Expect but using pseudo-terminal.
24049 Currently @code{GNAT.Expect.TTY} is implemented on all native GNAT
24050 ports. It is not implemented for cross ports, and
24051 in particular is not implemented for VxWorks or LynxOS.
24053 @node GNAT Float_Control g-flocon ads,GNAT Formatted_String g-forstr ads,GNAT Expect TTY g-exptty ads,The GNAT Library
24054 @anchor{gnat_rm/the_gnat_library id79}@anchor{363}@anchor{gnat_rm/the_gnat_library gnat-float-control-g-flocon-ads}@anchor{364}
24055 @section @code{GNAT.Float_Control} (@code{g-flocon.ads})
24058 @geindex GNAT.Float_Control (g-flocon.ads)
24060 @geindex Floating-Point Processor
24062 Provides an interface for resetting the floating-point processor into the
24063 mode required for correct semantic operation in Ada. Some third party
24064 library calls may cause this mode to be modified, and the Reset procedure
24065 in this package can be used to reestablish the required mode.
24067 @node GNAT Formatted_String g-forstr ads,GNAT Heap_Sort g-heasor ads,GNAT Float_Control g-flocon ads,The GNAT Library
24068 @anchor{gnat_rm/the_gnat_library id80}@anchor{365}@anchor{gnat_rm/the_gnat_library gnat-formatted-string-g-forstr-ads}@anchor{366}
24069 @section @code{GNAT.Formatted_String} (@code{g-forstr.ads})
24072 @geindex GNAT.Formatted_String (g-forstr.ads)
24074 @geindex Formatted String
24076 Provides support for C/C++ printf() formatted strings. The format is
24077 copied from the printf() routine and should therefore gives identical
24078 output. Some generic routines are provided to be able to use types
24079 derived from Integer, Float or enumerations as values for the
24082 @node GNAT Heap_Sort g-heasor ads,GNAT Heap_Sort_A g-hesora ads,GNAT Formatted_String g-forstr ads,The GNAT Library
24083 @anchor{gnat_rm/the_gnat_library gnat-heap-sort-g-heasor-ads}@anchor{367}@anchor{gnat_rm/the_gnat_library id81}@anchor{368}
24084 @section @code{GNAT.Heap_Sort} (@code{g-heasor.ads})
24087 @geindex GNAT.Heap_Sort (g-heasor.ads)
24091 Provides a general implementation of heap sort usable for sorting arbitrary
24092 data items. Exchange and comparison procedures are provided by passing
24093 access-to-procedure values. The algorithm used is a modified heap sort
24094 that performs approximately N*log(N) comparisons in the worst case.
24096 @node GNAT Heap_Sort_A g-hesora ads,GNAT Heap_Sort_G g-hesorg ads,GNAT Heap_Sort g-heasor ads,The GNAT Library
24097 @anchor{gnat_rm/the_gnat_library id82}@anchor{369}@anchor{gnat_rm/the_gnat_library gnat-heap-sort-a-g-hesora-ads}@anchor{36a}
24098 @section @code{GNAT.Heap_Sort_A} (@code{g-hesora.ads})
24101 @geindex GNAT.Heap_Sort_A (g-hesora.ads)
24105 Provides a general implementation of heap sort usable for sorting arbitrary
24106 data items. Move and comparison procedures are provided by passing
24107 access-to-procedure values. The algorithm used is a modified heap sort
24108 that performs approximately N*log(N) comparisons in the worst case.
24109 This differs from @code{GNAT.Heap_Sort} in having a less convenient
24110 interface, but may be slightly more efficient.
24112 @node GNAT Heap_Sort_G g-hesorg ads,GNAT HTable g-htable ads,GNAT Heap_Sort_A g-hesora ads,The GNAT Library
24113 @anchor{gnat_rm/the_gnat_library id83}@anchor{36b}@anchor{gnat_rm/the_gnat_library gnat-heap-sort-g-g-hesorg-ads}@anchor{36c}
24114 @section @code{GNAT.Heap_Sort_G} (@code{g-hesorg.ads})
24117 @geindex GNAT.Heap_Sort_G (g-hesorg.ads)
24121 Similar to @code{Heap_Sort_A} except that the move and sorting procedures
24122 are provided as generic parameters, this improves efficiency, especially
24123 if the procedures can be inlined, at the expense of duplicating code for
24124 multiple instantiations.
24126 @node GNAT HTable g-htable ads,GNAT IO g-io ads,GNAT Heap_Sort_G g-hesorg ads,The GNAT Library
24127 @anchor{gnat_rm/the_gnat_library id84}@anchor{36d}@anchor{gnat_rm/the_gnat_library gnat-htable-g-htable-ads}@anchor{36e}
24128 @section @code{GNAT.HTable} (@code{g-htable.ads})
24131 @geindex GNAT.HTable (g-htable.ads)
24133 @geindex Hash tables
24135 A generic implementation of hash tables that can be used to hash arbitrary
24136 data. Provides two approaches, one a simple static approach, and the other
24137 allowing arbitrary dynamic hash tables.
24139 @node GNAT IO g-io ads,GNAT IO_Aux g-io_aux ads,GNAT HTable g-htable ads,The GNAT Library
24140 @anchor{gnat_rm/the_gnat_library id85}@anchor{36f}@anchor{gnat_rm/the_gnat_library gnat-io-g-io-ads}@anchor{370}
24141 @section @code{GNAT.IO} (@code{g-io.ads})
24144 @geindex GNAT.IO (g-io.ads)
24146 @geindex Simple I/O
24148 @geindex Input/Output facilities
24150 A simple preelaborable input-output package that provides a subset of
24151 simple Text_IO functions for reading characters and strings from
24152 Standard_Input, and writing characters, strings and integers to either
24153 Standard_Output or Standard_Error.
24155 @node GNAT IO_Aux g-io_aux ads,GNAT Lock_Files g-locfil ads,GNAT IO g-io ads,The GNAT Library
24156 @anchor{gnat_rm/the_gnat_library gnat-io-aux-g-io-aux-ads}@anchor{371}@anchor{gnat_rm/the_gnat_library id86}@anchor{372}
24157 @section @code{GNAT.IO_Aux} (@code{g-io_aux.ads})
24160 @geindex GNAT.IO_Aux (g-io_aux.ads)
24164 @geindex Input/Output facilities
24166 Provides some auxiliary functions for use with Text_IO, including a test
24167 for whether a file exists, and functions for reading a line of text.
24169 @node GNAT Lock_Files g-locfil ads,GNAT MBBS_Discrete_Random g-mbdira ads,GNAT IO_Aux g-io_aux ads,The GNAT Library
24170 @anchor{gnat_rm/the_gnat_library id87}@anchor{373}@anchor{gnat_rm/the_gnat_library gnat-lock-files-g-locfil-ads}@anchor{374}
24171 @section @code{GNAT.Lock_Files} (@code{g-locfil.ads})
24174 @geindex GNAT.Lock_Files (g-locfil.ads)
24176 @geindex File locking
24178 @geindex Locking using files
24180 Provides a general interface for using files as locks. Can be used for
24181 providing program level synchronization.
24183 @node GNAT MBBS_Discrete_Random g-mbdira ads,GNAT MBBS_Float_Random g-mbflra ads,GNAT Lock_Files g-locfil ads,The GNAT Library
24184 @anchor{gnat_rm/the_gnat_library id88}@anchor{375}@anchor{gnat_rm/the_gnat_library gnat-mbbs-discrete-random-g-mbdira-ads}@anchor{376}
24185 @section @code{GNAT.MBBS_Discrete_Random} (@code{g-mbdira.ads})
24188 @geindex GNAT.MBBS_Discrete_Random (g-mbdira.ads)
24190 @geindex Random number generation
24192 The original implementation of @code{Ada.Numerics.Discrete_Random}. Uses
24193 a modified version of the Blum-Blum-Shub generator.
24195 @node GNAT MBBS_Float_Random g-mbflra ads,GNAT MD5 g-md5 ads,GNAT MBBS_Discrete_Random g-mbdira ads,The GNAT Library
24196 @anchor{gnat_rm/the_gnat_library id89}@anchor{377}@anchor{gnat_rm/the_gnat_library gnat-mbbs-float-random-g-mbflra-ads}@anchor{378}
24197 @section @code{GNAT.MBBS_Float_Random} (@code{g-mbflra.ads})
24200 @geindex GNAT.MBBS_Float_Random (g-mbflra.ads)
24202 @geindex Random number generation
24204 The original implementation of @code{Ada.Numerics.Float_Random}. Uses
24205 a modified version of the Blum-Blum-Shub generator.
24207 @node GNAT MD5 g-md5 ads,GNAT Memory_Dump g-memdum ads,GNAT MBBS_Float_Random g-mbflra ads,The GNAT Library
24208 @anchor{gnat_rm/the_gnat_library id90}@anchor{379}@anchor{gnat_rm/the_gnat_library gnat-md5-g-md5-ads}@anchor{37a}
24209 @section @code{GNAT.MD5} (@code{g-md5.ads})
24212 @geindex GNAT.MD5 (g-md5.ads)
24214 @geindex Message Digest MD5
24216 Implements the MD5 Message-Digest Algorithm as described in RFC 1321, and
24217 the HMAC-MD5 message authentication function as described in RFC 2104 and
24220 @node GNAT Memory_Dump g-memdum ads,GNAT Most_Recent_Exception g-moreex ads,GNAT MD5 g-md5 ads,The GNAT Library
24221 @anchor{gnat_rm/the_gnat_library id91}@anchor{37b}@anchor{gnat_rm/the_gnat_library gnat-memory-dump-g-memdum-ads}@anchor{37c}
24222 @section @code{GNAT.Memory_Dump} (@code{g-memdum.ads})
24225 @geindex GNAT.Memory_Dump (g-memdum.ads)
24227 @geindex Dump Memory
24229 Provides a convenient routine for dumping raw memory to either the
24230 standard output or standard error files. Uses GNAT.IO for actual
24233 @node GNAT Most_Recent_Exception g-moreex ads,GNAT OS_Lib g-os_lib ads,GNAT Memory_Dump g-memdum ads,The GNAT Library
24234 @anchor{gnat_rm/the_gnat_library id92}@anchor{37d}@anchor{gnat_rm/the_gnat_library gnat-most-recent-exception-g-moreex-ads}@anchor{37e}
24235 @section @code{GNAT.Most_Recent_Exception} (@code{g-moreex.ads})
24238 @geindex GNAT.Most_Recent_Exception (g-moreex.ads)
24241 @geindex obtaining most recent
24243 Provides access to the most recently raised exception. Can be used for
24244 various logging purposes, including duplicating functionality of some
24245 Ada 83 implementation dependent extensions.
24247 @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
24248 @anchor{gnat_rm/the_gnat_library gnat-os-lib-g-os-lib-ads}@anchor{37f}@anchor{gnat_rm/the_gnat_library id93}@anchor{380}
24249 @section @code{GNAT.OS_Lib} (@code{g-os_lib.ads})
24252 @geindex GNAT.OS_Lib (g-os_lib.ads)
24254 @geindex Operating System interface
24256 @geindex Spawn capability
24258 Provides a range of target independent operating system interface functions,
24259 including time/date management, file operations, subprocess management,
24260 including a portable spawn procedure, and access to environment variables
24261 and error return codes.
24263 @node GNAT Perfect_Hash_Generators g-pehage ads,GNAT Random_Numbers g-rannum ads,GNAT OS_Lib g-os_lib ads,The GNAT Library
24264 @anchor{gnat_rm/the_gnat_library gnat-perfect-hash-generators-g-pehage-ads}@anchor{381}@anchor{gnat_rm/the_gnat_library id94}@anchor{382}
24265 @section @code{GNAT.Perfect_Hash_Generators} (@code{g-pehage.ads})
24268 @geindex GNAT.Perfect_Hash_Generators (g-pehage.ads)
24270 @geindex Hash functions
24272 Provides a generator of static minimal perfect hash functions. No
24273 collisions occur and each item can be retrieved from the table in one
24274 probe (perfect property). The hash table size corresponds to the exact
24275 size of the key set and no larger (minimal property). The key set has to
24276 be know in advance (static property). The hash functions are also order
24277 preserving. If w2 is inserted after w1 in the generator, their
24278 hashcode are in the same order. These hashing functions are very
24279 convenient for use with realtime applications.
24281 @node GNAT Random_Numbers g-rannum ads,GNAT Regexp g-regexp ads,GNAT Perfect_Hash_Generators g-pehage ads,The GNAT Library
24282 @anchor{gnat_rm/the_gnat_library gnat-random-numbers-g-rannum-ads}@anchor{383}@anchor{gnat_rm/the_gnat_library id95}@anchor{384}
24283 @section @code{GNAT.Random_Numbers} (@code{g-rannum.ads})
24286 @geindex GNAT.Random_Numbers (g-rannum.ads)
24288 @geindex Random number generation
24290 Provides random number capabilities which extend those available in the
24291 standard Ada library and are more convenient to use.
24293 @node GNAT Regexp g-regexp ads,GNAT Registry g-regist ads,GNAT Random_Numbers g-rannum ads,The GNAT Library
24294 @anchor{gnat_rm/the_gnat_library gnat-regexp-g-regexp-ads}@anchor{250}@anchor{gnat_rm/the_gnat_library id96}@anchor{385}
24295 @section @code{GNAT.Regexp} (@code{g-regexp.ads})
24298 @geindex GNAT.Regexp (g-regexp.ads)
24300 @geindex Regular expressions
24302 @geindex Pattern matching
24304 A simple implementation of regular expressions, using a subset of regular
24305 expression syntax copied from familiar Unix style utilities. This is the
24306 simplest of the three pattern matching packages provided, and is particularly
24307 suitable for 'file globbing' applications.
24309 @node GNAT Registry g-regist ads,GNAT Regpat g-regpat ads,GNAT Regexp g-regexp ads,The GNAT Library
24310 @anchor{gnat_rm/the_gnat_library gnat-registry-g-regist-ads}@anchor{386}@anchor{gnat_rm/the_gnat_library id97}@anchor{387}
24311 @section @code{GNAT.Registry} (@code{g-regist.ads})
24314 @geindex GNAT.Registry (g-regist.ads)
24316 @geindex Windows Registry
24318 This is a high level binding to the Windows registry. It is possible to
24319 do simple things like reading a key value, creating a new key. For full
24320 registry API, but at a lower level of abstraction, refer to the Win32.Winreg
24321 package provided with the Win32Ada binding
24323 @node GNAT Regpat g-regpat ads,GNAT Rewrite_Data g-rewdat ads,GNAT Registry g-regist ads,The GNAT Library
24324 @anchor{gnat_rm/the_gnat_library id98}@anchor{388}@anchor{gnat_rm/the_gnat_library gnat-regpat-g-regpat-ads}@anchor{389}
24325 @section @code{GNAT.Regpat} (@code{g-regpat.ads})
24328 @geindex GNAT.Regpat (g-regpat.ads)
24330 @geindex Regular expressions
24332 @geindex Pattern matching
24334 A complete implementation of Unix-style regular expression matching, copied
24335 from the original V7 style regular expression library written in C by
24336 Henry Spencer (and binary compatible with this C library).
24338 @node GNAT Rewrite_Data g-rewdat ads,GNAT Secondary_Stack_Info g-sestin ads,GNAT Regpat g-regpat ads,The GNAT Library
24339 @anchor{gnat_rm/the_gnat_library id99}@anchor{38a}@anchor{gnat_rm/the_gnat_library gnat-rewrite-data-g-rewdat-ads}@anchor{38b}
24340 @section @code{GNAT.Rewrite_Data} (@code{g-rewdat.ads})
24343 @geindex GNAT.Rewrite_Data (g-rewdat.ads)
24345 @geindex Rewrite data
24347 A unit to rewrite on-the-fly string occurrences in a stream of
24348 data. The implementation has a very minimal memory footprint as the
24349 full content to be processed is not loaded into memory all at once. This makes
24350 this interface usable for large files or socket streams.
24352 @node GNAT Secondary_Stack_Info g-sestin ads,GNAT Semaphores g-semaph ads,GNAT Rewrite_Data g-rewdat ads,The GNAT Library
24353 @anchor{gnat_rm/the_gnat_library id100}@anchor{38c}@anchor{gnat_rm/the_gnat_library gnat-secondary-stack-info-g-sestin-ads}@anchor{38d}
24354 @section @code{GNAT.Secondary_Stack_Info} (@code{g-sestin.ads})
24357 @geindex GNAT.Secondary_Stack_Info (g-sestin.ads)
24359 @geindex Secondary Stack Info
24361 Provide the capability to query the high water mark of the current task's
24364 @node GNAT Semaphores g-semaph ads,GNAT Serial_Communications g-sercom ads,GNAT Secondary_Stack_Info g-sestin ads,The GNAT Library
24365 @anchor{gnat_rm/the_gnat_library id101}@anchor{38e}@anchor{gnat_rm/the_gnat_library gnat-semaphores-g-semaph-ads}@anchor{38f}
24366 @section @code{GNAT.Semaphores} (@code{g-semaph.ads})
24369 @geindex GNAT.Semaphores (g-semaph.ads)
24371 @geindex Semaphores
24373 Provides classic counting and binary semaphores using protected types.
24375 @node GNAT Serial_Communications g-sercom ads,GNAT SHA1 g-sha1 ads,GNAT Semaphores g-semaph ads,The GNAT Library
24376 @anchor{gnat_rm/the_gnat_library gnat-serial-communications-g-sercom-ads}@anchor{390}@anchor{gnat_rm/the_gnat_library id102}@anchor{391}
24377 @section @code{GNAT.Serial_Communications} (@code{g-sercom.ads})
24380 @geindex GNAT.Serial_Communications (g-sercom.ads)
24382 @geindex Serial_Communications
24384 Provides a simple interface to send and receive data over a serial
24385 port. This is only supported on GNU/Linux and Windows.
24387 @node GNAT SHA1 g-sha1 ads,GNAT SHA224 g-sha224 ads,GNAT Serial_Communications g-sercom ads,The GNAT Library
24388 @anchor{gnat_rm/the_gnat_library gnat-sha1-g-sha1-ads}@anchor{392}@anchor{gnat_rm/the_gnat_library id103}@anchor{393}
24389 @section @code{GNAT.SHA1} (@code{g-sha1.ads})
24392 @geindex GNAT.SHA1 (g-sha1.ads)
24394 @geindex Secure Hash Algorithm SHA-1
24396 Implements the SHA-1 Secure Hash Algorithm as described in FIPS PUB 180-3
24397 and RFC 3174, and the HMAC-SHA1 message authentication function as described
24398 in RFC 2104 and FIPS PUB 198.
24400 @node GNAT SHA224 g-sha224 ads,GNAT SHA256 g-sha256 ads,GNAT SHA1 g-sha1 ads,The GNAT Library
24401 @anchor{gnat_rm/the_gnat_library gnat-sha224-g-sha224-ads}@anchor{394}@anchor{gnat_rm/the_gnat_library id104}@anchor{395}
24402 @section @code{GNAT.SHA224} (@code{g-sha224.ads})
24405 @geindex GNAT.SHA224 (g-sha224.ads)
24407 @geindex Secure Hash Algorithm SHA-224
24409 Implements the SHA-224 Secure Hash Algorithm as described in FIPS PUB 180-3,
24410 and the HMAC-SHA224 message authentication function as described
24411 in RFC 2104 and FIPS PUB 198.
24413 @node GNAT SHA256 g-sha256 ads,GNAT SHA384 g-sha384 ads,GNAT SHA224 g-sha224 ads,The GNAT Library
24414 @anchor{gnat_rm/the_gnat_library id105}@anchor{396}@anchor{gnat_rm/the_gnat_library gnat-sha256-g-sha256-ads}@anchor{397}
24415 @section @code{GNAT.SHA256} (@code{g-sha256.ads})
24418 @geindex GNAT.SHA256 (g-sha256.ads)
24420 @geindex Secure Hash Algorithm SHA-256
24422 Implements the SHA-256 Secure Hash Algorithm as described in FIPS PUB 180-3,
24423 and the HMAC-SHA256 message authentication function as described
24424 in RFC 2104 and FIPS PUB 198.
24426 @node GNAT SHA384 g-sha384 ads,GNAT SHA512 g-sha512 ads,GNAT SHA256 g-sha256 ads,The GNAT Library
24427 @anchor{gnat_rm/the_gnat_library gnat-sha384-g-sha384-ads}@anchor{398}@anchor{gnat_rm/the_gnat_library id106}@anchor{399}
24428 @section @code{GNAT.SHA384} (@code{g-sha384.ads})
24431 @geindex GNAT.SHA384 (g-sha384.ads)
24433 @geindex Secure Hash Algorithm SHA-384
24435 Implements the SHA-384 Secure Hash Algorithm as described in FIPS PUB 180-3,
24436 and the HMAC-SHA384 message authentication function as described
24437 in RFC 2104 and FIPS PUB 198.
24439 @node GNAT SHA512 g-sha512 ads,GNAT Signals g-signal ads,GNAT SHA384 g-sha384 ads,The GNAT Library
24440 @anchor{gnat_rm/the_gnat_library gnat-sha512-g-sha512-ads}@anchor{39a}@anchor{gnat_rm/the_gnat_library id107}@anchor{39b}
24441 @section @code{GNAT.SHA512} (@code{g-sha512.ads})
24444 @geindex GNAT.SHA512 (g-sha512.ads)
24446 @geindex Secure Hash Algorithm SHA-512
24448 Implements the SHA-512 Secure Hash Algorithm as described in FIPS PUB 180-3,
24449 and the HMAC-SHA512 message authentication function as described
24450 in RFC 2104 and FIPS PUB 198.
24452 @node GNAT Signals g-signal ads,GNAT Sockets g-socket ads,GNAT SHA512 g-sha512 ads,The GNAT Library
24453 @anchor{gnat_rm/the_gnat_library gnat-signals-g-signal-ads}@anchor{39c}@anchor{gnat_rm/the_gnat_library id108}@anchor{39d}
24454 @section @code{GNAT.Signals} (@code{g-signal.ads})
24457 @geindex GNAT.Signals (g-signal.ads)
24461 Provides the ability to manipulate the blocked status of signals on supported
24464 @node GNAT Sockets g-socket ads,GNAT Source_Info g-souinf ads,GNAT Signals g-signal ads,The GNAT Library
24465 @anchor{gnat_rm/the_gnat_library id109}@anchor{39e}@anchor{gnat_rm/the_gnat_library gnat-sockets-g-socket-ads}@anchor{39f}
24466 @section @code{GNAT.Sockets} (@code{g-socket.ads})
24469 @geindex GNAT.Sockets (g-socket.ads)
24473 A high level and portable interface to develop sockets based applications.
24474 This package is based on the sockets thin binding found in
24475 @code{GNAT.Sockets.Thin}. Currently @code{GNAT.Sockets} is implemented
24476 on all native GNAT ports and on VxWorks cross prots. It is not implemented for
24477 the LynxOS cross port.
24479 @node GNAT Source_Info g-souinf ads,GNAT Spelling_Checker g-speche ads,GNAT Sockets g-socket ads,The GNAT Library
24480 @anchor{gnat_rm/the_gnat_library gnat-source-info-g-souinf-ads}@anchor{3a0}@anchor{gnat_rm/the_gnat_library id110}@anchor{3a1}
24481 @section @code{GNAT.Source_Info} (@code{g-souinf.ads})
24484 @geindex GNAT.Source_Info (g-souinf.ads)
24486 @geindex Source Information
24488 Provides subprograms that give access to source code information known at
24489 compile time, such as the current file name and line number. Also provides
24490 subprograms yielding the date and time of the current compilation (like the
24491 C macros @code{__DATE__} and @code{__TIME__})
24493 @node GNAT Spelling_Checker g-speche ads,GNAT Spelling_Checker_Generic g-spchge ads,GNAT Source_Info g-souinf ads,The GNAT Library
24494 @anchor{gnat_rm/the_gnat_library gnat-spelling-checker-g-speche-ads}@anchor{3a2}@anchor{gnat_rm/the_gnat_library id111}@anchor{3a3}
24495 @section @code{GNAT.Spelling_Checker} (@code{g-speche.ads})
24498 @geindex GNAT.Spelling_Checker (g-speche.ads)
24500 @geindex Spell checking
24502 Provides a function for determining whether one string is a plausible
24503 near misspelling of another string.
24505 @node GNAT Spelling_Checker_Generic g-spchge ads,GNAT Spitbol Patterns g-spipat ads,GNAT Spelling_Checker g-speche ads,The GNAT Library
24506 @anchor{gnat_rm/the_gnat_library id112}@anchor{3a4}@anchor{gnat_rm/the_gnat_library gnat-spelling-checker-generic-g-spchge-ads}@anchor{3a5}
24507 @section @code{GNAT.Spelling_Checker_Generic} (@code{g-spchge.ads})
24510 @geindex GNAT.Spelling_Checker_Generic (g-spchge.ads)
24512 @geindex Spell checking
24514 Provides a generic function that can be instantiated with a string type for
24515 determining whether one string is a plausible near misspelling of another
24518 @node GNAT Spitbol Patterns g-spipat ads,GNAT Spitbol g-spitbo ads,GNAT Spelling_Checker_Generic g-spchge ads,The GNAT Library
24519 @anchor{gnat_rm/the_gnat_library id113}@anchor{3a6}@anchor{gnat_rm/the_gnat_library gnat-spitbol-patterns-g-spipat-ads}@anchor{3a7}
24520 @section @code{GNAT.Spitbol.Patterns} (@code{g-spipat.ads})
24523 @geindex GNAT.Spitbol.Patterns (g-spipat.ads)
24525 @geindex SPITBOL pattern matching
24527 @geindex Pattern matching
24529 A complete implementation of SNOBOL4 style pattern matching. This is the
24530 most elaborate of the pattern matching packages provided. It fully duplicates
24531 the SNOBOL4 dynamic pattern construction and matching capabilities, using the
24532 efficient algorithm developed by Robert Dewar for the SPITBOL system.
24534 @node GNAT Spitbol g-spitbo ads,GNAT Spitbol Table_Boolean g-sptabo ads,GNAT Spitbol Patterns g-spipat ads,The GNAT Library
24535 @anchor{gnat_rm/the_gnat_library gnat-spitbol-g-spitbo-ads}@anchor{3a8}@anchor{gnat_rm/the_gnat_library id114}@anchor{3a9}
24536 @section @code{GNAT.Spitbol} (@code{g-spitbo.ads})
24539 @geindex GNAT.Spitbol (g-spitbo.ads)
24541 @geindex SPITBOL interface
24543 The top level package of the collection of SPITBOL-style functionality, this
24544 package provides basic SNOBOL4 string manipulation functions, such as
24545 Pad, Reverse, Trim, Substr capability, as well as a generic table function
24546 useful for constructing arbitrary mappings from strings in the style of
24547 the SNOBOL4 TABLE function.
24549 @node GNAT Spitbol Table_Boolean g-sptabo ads,GNAT Spitbol Table_Integer g-sptain ads,GNAT Spitbol g-spitbo ads,The GNAT Library
24550 @anchor{gnat_rm/the_gnat_library gnat-spitbol-table-boolean-g-sptabo-ads}@anchor{3aa}@anchor{gnat_rm/the_gnat_library id115}@anchor{3ab}
24551 @section @code{GNAT.Spitbol.Table_Boolean} (@code{g-sptabo.ads})
24554 @geindex GNAT.Spitbol.Table_Boolean (g-sptabo.ads)
24556 @geindex Sets of strings
24558 @geindex SPITBOL Tables
24560 A library level of instantiation of @code{GNAT.Spitbol.Patterns.Table}
24561 for type @code{Standard.Boolean}, giving an implementation of sets of
24564 @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
24565 @anchor{gnat_rm/the_gnat_library gnat-spitbol-table-integer-g-sptain-ads}@anchor{3ac}@anchor{gnat_rm/the_gnat_library id116}@anchor{3ad}
24566 @section @code{GNAT.Spitbol.Table_Integer} (@code{g-sptain.ads})
24569 @geindex GNAT.Spitbol.Table_Integer (g-sptain.ads)
24571 @geindex Integer maps
24575 @geindex SPITBOL Tables
24577 A library level of instantiation of @code{GNAT.Spitbol.Patterns.Table}
24578 for type @code{Standard.Integer}, giving an implementation of maps
24579 from string to integer values.
24581 @node GNAT Spitbol Table_VString g-sptavs ads,GNAT SSE g-sse ads,GNAT Spitbol Table_Integer g-sptain ads,The GNAT Library
24582 @anchor{gnat_rm/the_gnat_library id117}@anchor{3ae}@anchor{gnat_rm/the_gnat_library gnat-spitbol-table-vstring-g-sptavs-ads}@anchor{3af}
24583 @section @code{GNAT.Spitbol.Table_VString} (@code{g-sptavs.ads})
24586 @geindex GNAT.Spitbol.Table_VString (g-sptavs.ads)
24588 @geindex String maps
24592 @geindex SPITBOL Tables
24594 A library level of instantiation of @code{GNAT.Spitbol.Patterns.Table} for
24595 a variable length string type, giving an implementation of general
24596 maps from strings to strings.
24598 @node GNAT SSE g-sse ads,GNAT SSE Vector_Types g-ssvety ads,GNAT Spitbol Table_VString g-sptavs ads,The GNAT Library
24599 @anchor{gnat_rm/the_gnat_library id118}@anchor{3b0}@anchor{gnat_rm/the_gnat_library gnat-sse-g-sse-ads}@anchor{3b1}
24600 @section @code{GNAT.SSE} (@code{g-sse.ads})
24603 @geindex GNAT.SSE (g-sse.ads)
24605 Root of a set of units aimed at offering Ada bindings to a subset of
24606 the Intel(r) Streaming SIMD Extensions with GNAT on the x86 family of
24607 targets. It exposes vector component types together with a general
24608 introduction to the binding contents and use.
24610 @node GNAT SSE Vector_Types g-ssvety ads,GNAT String_Hash g-strhas ads,GNAT SSE g-sse ads,The GNAT Library
24611 @anchor{gnat_rm/the_gnat_library gnat-sse-vector-types-g-ssvety-ads}@anchor{3b2}@anchor{gnat_rm/the_gnat_library id119}@anchor{3b3}
24612 @section @code{GNAT.SSE.Vector_Types} (@code{g-ssvety.ads})
24615 @geindex GNAT.SSE.Vector_Types (g-ssvety.ads)
24617 SSE vector types for use with SSE related intrinsics.
24619 @node GNAT String_Hash g-strhas ads,GNAT Strings g-string ads,GNAT SSE Vector_Types g-ssvety ads,The GNAT Library
24620 @anchor{gnat_rm/the_gnat_library gnat-string-hash-g-strhas-ads}@anchor{3b4}@anchor{gnat_rm/the_gnat_library id120}@anchor{3b5}
24621 @section @code{GNAT.String_Hash} (@code{g-strhas.ads})
24624 @geindex GNAT.String_Hash (g-strhas.ads)
24626 @geindex Hash functions
24628 Provides a generic hash function working on arrays of scalars. Both the scalar
24629 type and the hash result type are parameters.
24631 @node GNAT Strings g-string ads,GNAT String_Split g-strspl ads,GNAT String_Hash g-strhas ads,The GNAT Library
24632 @anchor{gnat_rm/the_gnat_library gnat-strings-g-string-ads}@anchor{3b6}@anchor{gnat_rm/the_gnat_library id121}@anchor{3b7}
24633 @section @code{GNAT.Strings} (@code{g-string.ads})
24636 @geindex GNAT.Strings (g-string.ads)
24638 Common String access types and related subprograms. Basically it
24639 defines a string access and an array of string access types.
24641 @node GNAT String_Split g-strspl ads,GNAT Table g-table ads,GNAT Strings g-string ads,The GNAT Library
24642 @anchor{gnat_rm/the_gnat_library gnat-string-split-g-strspl-ads}@anchor{3b8}@anchor{gnat_rm/the_gnat_library id122}@anchor{3b9}
24643 @section @code{GNAT.String_Split} (@code{g-strspl.ads})
24646 @geindex GNAT.String_Split (g-strspl.ads)
24648 @geindex String splitter
24650 Useful string manipulation routines: given a set of separators, split
24651 a string wherever the separators appear, and provide direct access
24652 to the resulting slices. This package is instantiated from
24653 @code{GNAT.Array_Split}.
24655 @node GNAT Table g-table ads,GNAT Task_Lock g-tasloc ads,GNAT String_Split g-strspl ads,The GNAT Library
24656 @anchor{gnat_rm/the_gnat_library gnat-table-g-table-ads}@anchor{3ba}@anchor{gnat_rm/the_gnat_library id123}@anchor{3bb}
24657 @section @code{GNAT.Table} (@code{g-table.ads})
24660 @geindex GNAT.Table (g-table.ads)
24662 @geindex Table implementation
24665 @geindex extendable
24667 A generic package providing a single dimension array abstraction where the
24668 length of the array can be dynamically modified.
24670 This package provides a facility similar to that of @code{GNAT.Dynamic_Tables},
24671 except that this package declares a single instance of the table type,
24672 while an instantiation of @code{GNAT.Dynamic_Tables} creates a type that can be
24673 used to define dynamic instances of the table.
24675 @node GNAT Task_Lock g-tasloc ads,GNAT Time_Stamp g-timsta ads,GNAT Table g-table ads,The GNAT Library
24676 @anchor{gnat_rm/the_gnat_library id124}@anchor{3bc}@anchor{gnat_rm/the_gnat_library gnat-task-lock-g-tasloc-ads}@anchor{3bd}
24677 @section @code{GNAT.Task_Lock} (@code{g-tasloc.ads})
24680 @geindex GNAT.Task_Lock (g-tasloc.ads)
24682 @geindex Task synchronization
24684 @geindex Task locking
24688 A very simple facility for locking and unlocking sections of code using a
24689 single global task lock. Appropriate for use in situations where contention
24690 between tasks is very rarely expected.
24692 @node GNAT Time_Stamp g-timsta ads,GNAT Threads g-thread ads,GNAT Task_Lock g-tasloc ads,The GNAT Library
24693 @anchor{gnat_rm/the_gnat_library id125}@anchor{3be}@anchor{gnat_rm/the_gnat_library gnat-time-stamp-g-timsta-ads}@anchor{3bf}
24694 @section @code{GNAT.Time_Stamp} (@code{g-timsta.ads})
24697 @geindex GNAT.Time_Stamp (g-timsta.ads)
24699 @geindex Time stamp
24701 @geindex Current time
24703 Provides a simple function that returns a string YYYY-MM-DD HH:MM:SS.SS that
24704 represents the current date and time in ISO 8601 format. This is a very simple
24705 routine with minimal code and there are no dependencies on any other unit.
24707 @node GNAT Threads g-thread ads,GNAT Traceback g-traceb ads,GNAT Time_Stamp g-timsta ads,The GNAT Library
24708 @anchor{gnat_rm/the_gnat_library gnat-threads-g-thread-ads}@anchor{3c0}@anchor{gnat_rm/the_gnat_library id126}@anchor{3c1}
24709 @section @code{GNAT.Threads} (@code{g-thread.ads})
24712 @geindex GNAT.Threads (g-thread.ads)
24714 @geindex Foreign threads
24719 Provides facilities for dealing with foreign threads which need to be known
24720 by the GNAT run-time system. Consult the documentation of this package for
24721 further details if your program has threads that are created by a non-Ada
24722 environment which then accesses Ada code.
24724 @node GNAT Traceback g-traceb ads,GNAT Traceback Symbolic g-trasym ads,GNAT Threads g-thread ads,The GNAT Library
24725 @anchor{gnat_rm/the_gnat_library id127}@anchor{3c2}@anchor{gnat_rm/the_gnat_library gnat-traceback-g-traceb-ads}@anchor{3c3}
24726 @section @code{GNAT.Traceback} (@code{g-traceb.ads})
24729 @geindex GNAT.Traceback (g-traceb.ads)
24731 @geindex Trace back facilities
24733 Provides a facility for obtaining non-symbolic traceback information, useful
24734 in various debugging situations.
24736 @node GNAT Traceback Symbolic g-trasym ads,GNAT UTF_32 g-table ads,GNAT Traceback g-traceb ads,The GNAT Library
24737 @anchor{gnat_rm/the_gnat_library gnat-traceback-symbolic-g-trasym-ads}@anchor{3c4}@anchor{gnat_rm/the_gnat_library id128}@anchor{3c5}
24738 @section @code{GNAT.Traceback.Symbolic} (@code{g-trasym.ads})
24741 @geindex GNAT.Traceback.Symbolic (g-trasym.ads)
24743 @geindex Trace back facilities
24745 @node GNAT UTF_32 g-table ads,GNAT Wide_Spelling_Checker g-u3spch ads,GNAT Traceback Symbolic g-trasym ads,The GNAT Library
24746 @anchor{gnat_rm/the_gnat_library id129}@anchor{3c6}@anchor{gnat_rm/the_gnat_library gnat-utf-32-g-table-ads}@anchor{3c7}
24747 @section @code{GNAT.UTF_32} (@code{g-table.ads})
24750 @geindex GNAT.UTF_32 (g-table.ads)
24752 @geindex Wide character codes
24754 This is a package intended to be used in conjunction with the
24755 @code{Wide_Character} type in Ada 95 and the
24756 @code{Wide_Wide_Character} type in Ada 2005 (available
24757 in @code{GNAT} in Ada 2005 mode). This package contains
24758 Unicode categorization routines, as well as lexical
24759 categorization routines corresponding to the Ada 2005
24760 lexical rules for identifiers and strings, and also a
24761 lower case to upper case fold routine corresponding to
24762 the Ada 2005 rules for identifier equivalence.
24764 @node GNAT Wide_Spelling_Checker g-u3spch ads,GNAT Wide_Spelling_Checker g-wispch ads,GNAT UTF_32 g-table ads,The GNAT Library
24765 @anchor{gnat_rm/the_gnat_library gnat-wide-spelling-checker-g-u3spch-ads}@anchor{3c8}@anchor{gnat_rm/the_gnat_library id130}@anchor{3c9}
24766 @section @code{GNAT.Wide_Spelling_Checker} (@code{g-u3spch.ads})
24769 @geindex GNAT.Wide_Spelling_Checker (g-u3spch.ads)
24771 @geindex Spell checking
24773 Provides a function for determining whether one wide wide string is a plausible
24774 near misspelling of another wide wide string, where the strings are represented
24775 using the UTF_32_String type defined in System.Wch_Cnv.
24777 @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
24778 @anchor{gnat_rm/the_gnat_library gnat-wide-spelling-checker-g-wispch-ads}@anchor{3ca}@anchor{gnat_rm/the_gnat_library id131}@anchor{3cb}
24779 @section @code{GNAT.Wide_Spelling_Checker} (@code{g-wispch.ads})
24782 @geindex GNAT.Wide_Spelling_Checker (g-wispch.ads)
24784 @geindex Spell checking
24786 Provides a function for determining whether one wide string is a plausible
24787 near misspelling of another wide string.
24789 @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
24790 @anchor{gnat_rm/the_gnat_library id132}@anchor{3cc}@anchor{gnat_rm/the_gnat_library gnat-wide-string-split-g-wistsp-ads}@anchor{3cd}
24791 @section @code{GNAT.Wide_String_Split} (@code{g-wistsp.ads})
24794 @geindex GNAT.Wide_String_Split (g-wistsp.ads)
24796 @geindex Wide_String splitter
24798 Useful wide string manipulation routines: given a set of separators, split
24799 a wide string wherever the separators appear, and provide direct access
24800 to the resulting slices. This package is instantiated from
24801 @code{GNAT.Array_Split}.
24803 @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
24804 @anchor{gnat_rm/the_gnat_library gnat-wide-wide-spelling-checker-g-zspche-ads}@anchor{3ce}@anchor{gnat_rm/the_gnat_library id133}@anchor{3cf}
24805 @section @code{GNAT.Wide_Wide_Spelling_Checker} (@code{g-zspche.ads})
24808 @geindex GNAT.Wide_Wide_Spelling_Checker (g-zspche.ads)
24810 @geindex Spell checking
24812 Provides a function for determining whether one wide wide string is a plausible
24813 near misspelling of another wide wide string.
24815 @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
24816 @anchor{gnat_rm/the_gnat_library gnat-wide-wide-string-split-g-zistsp-ads}@anchor{3d0}@anchor{gnat_rm/the_gnat_library id134}@anchor{3d1}
24817 @section @code{GNAT.Wide_Wide_String_Split} (@code{g-zistsp.ads})
24820 @geindex GNAT.Wide_Wide_String_Split (g-zistsp.ads)
24822 @geindex Wide_Wide_String splitter
24824 Useful wide wide string manipulation routines: given a set of separators, split
24825 a wide wide string wherever the separators appear, and provide direct access
24826 to the resulting slices. This package is instantiated from
24827 @code{GNAT.Array_Split}.
24829 @node Interfaces C Extensions i-cexten ads,Interfaces C Streams i-cstrea ads,GNAT Wide_Wide_String_Split g-zistsp ads,The GNAT Library
24830 @anchor{gnat_rm/the_gnat_library interfaces-c-extensions-i-cexten-ads}@anchor{3d2}@anchor{gnat_rm/the_gnat_library id135}@anchor{3d3}
24831 @section @code{Interfaces.C.Extensions} (@code{i-cexten.ads})
24834 @geindex Interfaces.C.Extensions (i-cexten.ads)
24836 This package contains additional C-related definitions, intended
24837 for use with either manually or automatically generated bindings
24840 @node Interfaces C Streams i-cstrea ads,Interfaces Packed_Decimal i-pacdec ads,Interfaces C Extensions i-cexten ads,The GNAT Library
24841 @anchor{gnat_rm/the_gnat_library interfaces-c-streams-i-cstrea-ads}@anchor{3d4}@anchor{gnat_rm/the_gnat_library id136}@anchor{3d5}
24842 @section @code{Interfaces.C.Streams} (@code{i-cstrea.ads})
24845 @geindex Interfaces.C.Streams (i-cstrea.ads)
24848 @geindex interfacing
24850 This package is a binding for the most commonly used operations
24853 @node Interfaces Packed_Decimal i-pacdec ads,Interfaces VxWorks i-vxwork ads,Interfaces C Streams i-cstrea ads,The GNAT Library
24854 @anchor{gnat_rm/the_gnat_library interfaces-packed-decimal-i-pacdec-ads}@anchor{3d6}@anchor{gnat_rm/the_gnat_library id137}@anchor{3d7}
24855 @section @code{Interfaces.Packed_Decimal} (@code{i-pacdec.ads})
24858 @geindex Interfaces.Packed_Decimal (i-pacdec.ads)
24860 @geindex IBM Packed Format
24862 @geindex Packed Decimal
24864 This package provides a set of routines for conversions to and
24865 from a packed decimal format compatible with that used on IBM
24868 @node Interfaces VxWorks i-vxwork ads,Interfaces VxWorks Int_Connection i-vxinco ads,Interfaces Packed_Decimal i-pacdec ads,The GNAT Library
24869 @anchor{gnat_rm/the_gnat_library id138}@anchor{3d8}@anchor{gnat_rm/the_gnat_library interfaces-vxworks-i-vxwork-ads}@anchor{3d9}
24870 @section @code{Interfaces.VxWorks} (@code{i-vxwork.ads})
24873 @geindex Interfaces.VxWorks (i-vxwork.ads)
24875 @geindex Interfacing to VxWorks
24878 @geindex interfacing
24880 This package provides a limited binding to the VxWorks API.
24881 In particular, it interfaces with the
24882 VxWorks hardware interrupt facilities.
24884 @node Interfaces VxWorks Int_Connection i-vxinco ads,Interfaces VxWorks IO i-vxwoio ads,Interfaces VxWorks i-vxwork ads,The GNAT Library
24885 @anchor{gnat_rm/the_gnat_library interfaces-vxworks-int-connection-i-vxinco-ads}@anchor{3da}@anchor{gnat_rm/the_gnat_library id139}@anchor{3db}
24886 @section @code{Interfaces.VxWorks.Int_Connection} (@code{i-vxinco.ads})
24889 @geindex Interfaces.VxWorks.Int_Connection (i-vxinco.ads)
24891 @geindex Interfacing to VxWorks
24894 @geindex interfacing
24896 This package provides a way for users to replace the use of
24897 intConnect() with a custom routine for installing interrupt
24900 @node Interfaces VxWorks IO i-vxwoio ads,System Address_Image s-addima ads,Interfaces VxWorks Int_Connection i-vxinco ads,The GNAT Library
24901 @anchor{gnat_rm/the_gnat_library interfaces-vxworks-io-i-vxwoio-ads}@anchor{3dc}@anchor{gnat_rm/the_gnat_library id140}@anchor{3dd}
24902 @section @code{Interfaces.VxWorks.IO} (@code{i-vxwoio.ads})
24905 @geindex Interfaces.VxWorks.IO (i-vxwoio.ads)
24907 @geindex Interfacing to VxWorks' I/O
24910 @geindex I/O interfacing
24913 @geindex Get_Immediate
24915 @geindex Get_Immediate
24918 This package provides a binding to the ioctl (IO/Control)
24919 function of VxWorks, defining a set of option values and
24920 function codes. A particular use of this package is
24921 to enable the use of Get_Immediate under VxWorks.
24923 @node System Address_Image s-addima ads,System Assertions s-assert ads,Interfaces VxWorks IO i-vxwoio ads,The GNAT Library
24924 @anchor{gnat_rm/the_gnat_library id141}@anchor{3de}@anchor{gnat_rm/the_gnat_library system-address-image-s-addima-ads}@anchor{3df}
24925 @section @code{System.Address_Image} (@code{s-addima.ads})
24928 @geindex System.Address_Image (s-addima.ads)
24930 @geindex Address image
24933 @geindex of an address
24935 This function provides a useful debugging
24936 function that gives an (implementation dependent)
24937 string which identifies an address.
24939 @node System Assertions s-assert ads,System Atomic_Counters s-atocou ads,System Address_Image s-addima ads,The GNAT Library
24940 @anchor{gnat_rm/the_gnat_library system-assertions-s-assert-ads}@anchor{3e0}@anchor{gnat_rm/the_gnat_library id142}@anchor{3e1}
24941 @section @code{System.Assertions} (@code{s-assert.ads})
24944 @geindex System.Assertions (s-assert.ads)
24946 @geindex Assertions
24948 @geindex Assert_Failure
24951 This package provides the declaration of the exception raised
24952 by an run-time assertion failure, as well as the routine that
24953 is used internally to raise this assertion.
24955 @node System Atomic_Counters s-atocou ads,System Memory s-memory ads,System Assertions s-assert ads,The GNAT Library
24956 @anchor{gnat_rm/the_gnat_library id143}@anchor{3e2}@anchor{gnat_rm/the_gnat_library system-atomic-counters-s-atocou-ads}@anchor{3e3}
24957 @section @code{System.Atomic_Counters} (@code{s-atocou.ads})
24960 @geindex System.Atomic_Counters (s-atocou.ads)
24962 This package provides the declaration of an atomic counter type,
24963 together with efficient routines (using hardware
24964 synchronization primitives) for incrementing, decrementing,
24965 and testing of these counters. This package is implemented
24966 on most targets, including all Alpha, ia64, PowerPC, SPARC V9,
24967 x86, and x86_64 platforms.
24969 @node System Memory s-memory ads,System Multiprocessors s-multip ads,System Atomic_Counters s-atocou ads,The GNAT Library
24970 @anchor{gnat_rm/the_gnat_library system-memory-s-memory-ads}@anchor{3e4}@anchor{gnat_rm/the_gnat_library id144}@anchor{3e5}
24971 @section @code{System.Memory} (@code{s-memory.ads})
24974 @geindex System.Memory (s-memory.ads)
24976 @geindex Memory allocation
24978 This package provides the interface to the low level routines used
24979 by the generated code for allocation and freeing storage for the
24980 default storage pool (analogous to the C routines malloc and free.
24981 It also provides a reallocation interface analogous to the C routine
24982 realloc. The body of this unit may be modified to provide alternative
24983 allocation mechanisms for the default pool, and in addition, direct
24984 calls to this unit may be made for low level allocation uses (for
24985 example see the body of @code{GNAT.Tables}).
24987 @node System Multiprocessors s-multip ads,System Multiprocessors Dispatching_Domains s-mudido ads,System Memory s-memory ads,The GNAT Library
24988 @anchor{gnat_rm/the_gnat_library id145}@anchor{3e6}@anchor{gnat_rm/the_gnat_library system-multiprocessors-s-multip-ads}@anchor{3e7}
24989 @section @code{System.Multiprocessors} (@code{s-multip.ads})
24992 @geindex System.Multiprocessors (s-multip.ads)
24994 @geindex Multiprocessor interface
24996 This is an Ada 2012 unit defined in the Ada 2012 Reference Manual, but
24997 in GNAT we also make it available in Ada 95 and Ada 2005 (where it is
24998 technically an implementation-defined addition).
25000 @node System Multiprocessors Dispatching_Domains s-mudido ads,System Partition_Interface s-parint ads,System Multiprocessors s-multip ads,The GNAT Library
25001 @anchor{gnat_rm/the_gnat_library system-multiprocessors-dispatching-domains-s-mudido-ads}@anchor{3e8}@anchor{gnat_rm/the_gnat_library id146}@anchor{3e9}
25002 @section @code{System.Multiprocessors.Dispatching_Domains} (@code{s-mudido.ads})
25005 @geindex System.Multiprocessors.Dispatching_Domains (s-mudido.ads)
25007 @geindex Multiprocessor interface
25009 This is an Ada 2012 unit defined in the Ada 2012 Reference Manual, but
25010 in GNAT we also make it available in Ada 95 and Ada 2005 (where it is
25011 technically an implementation-defined addition).
25013 @node System Partition_Interface s-parint ads,System Pool_Global s-pooglo ads,System Multiprocessors Dispatching_Domains s-mudido ads,The GNAT Library
25014 @anchor{gnat_rm/the_gnat_library id147}@anchor{3ea}@anchor{gnat_rm/the_gnat_library system-partition-interface-s-parint-ads}@anchor{3eb}
25015 @section @code{System.Partition_Interface} (@code{s-parint.ads})
25018 @geindex System.Partition_Interface (s-parint.ads)
25020 @geindex Partition interfacing functions
25022 This package provides facilities for partition interfacing. It
25023 is used primarily in a distribution context when using Annex E
25026 @node System Pool_Global s-pooglo ads,System Pool_Local s-pooloc ads,System Partition_Interface s-parint ads,The GNAT Library
25027 @anchor{gnat_rm/the_gnat_library id148}@anchor{3ec}@anchor{gnat_rm/the_gnat_library system-pool-global-s-pooglo-ads}@anchor{3ed}
25028 @section @code{System.Pool_Global} (@code{s-pooglo.ads})
25031 @geindex System.Pool_Global (s-pooglo.ads)
25033 @geindex Storage pool
25036 @geindex Global storage pool
25038 This package provides a storage pool that is equivalent to the default
25039 storage pool used for access types for which no pool is specifically
25040 declared. It uses malloc/free to allocate/free and does not attempt to
25041 do any automatic reclamation.
25043 @node System Pool_Local s-pooloc ads,System Restrictions s-restri ads,System Pool_Global s-pooglo ads,The GNAT Library
25044 @anchor{gnat_rm/the_gnat_library system-pool-local-s-pooloc-ads}@anchor{3ee}@anchor{gnat_rm/the_gnat_library id149}@anchor{3ef}
25045 @section @code{System.Pool_Local} (@code{s-pooloc.ads})
25048 @geindex System.Pool_Local (s-pooloc.ads)
25050 @geindex Storage pool
25053 @geindex Local storage pool
25055 This package provides a storage pool that is intended for use with locally
25056 defined access types. It uses malloc/free for allocate/free, and maintains
25057 a list of allocated blocks, so that all storage allocated for the pool can
25058 be freed automatically when the pool is finalized.
25060 @node System Restrictions s-restri ads,System Rident s-rident ads,System Pool_Local s-pooloc ads,The GNAT Library
25061 @anchor{gnat_rm/the_gnat_library id150}@anchor{3f0}@anchor{gnat_rm/the_gnat_library system-restrictions-s-restri-ads}@anchor{3f1}
25062 @section @code{System.Restrictions} (@code{s-restri.ads})
25065 @geindex System.Restrictions (s-restri.ads)
25067 @geindex Run-time restrictions access
25069 This package provides facilities for accessing at run time
25070 the status of restrictions specified at compile time for
25071 the partition. Information is available both with regard
25072 to actual restrictions specified, and with regard to
25073 compiler determined information on which restrictions
25074 are violated by one or more packages in the partition.
25076 @node System Rident s-rident ads,System Strings Stream_Ops s-ststop ads,System Restrictions s-restri ads,The GNAT Library
25077 @anchor{gnat_rm/the_gnat_library system-rident-s-rident-ads}@anchor{3f2}@anchor{gnat_rm/the_gnat_library id151}@anchor{3f3}
25078 @section @code{System.Rident} (@code{s-rident.ads})
25081 @geindex System.Rident (s-rident.ads)
25083 @geindex Restrictions definitions
25085 This package provides definitions of the restrictions
25086 identifiers supported by GNAT, and also the format of
25087 the restrictions provided in package System.Restrictions.
25088 It is not normally necessary to @code{with} this generic package
25089 since the necessary instantiation is included in
25090 package System.Restrictions.
25092 @node System Strings Stream_Ops s-ststop ads,System Unsigned_Types s-unstyp ads,System Rident s-rident ads,The GNAT Library
25093 @anchor{gnat_rm/the_gnat_library id152}@anchor{3f4}@anchor{gnat_rm/the_gnat_library system-strings-stream-ops-s-ststop-ads}@anchor{3f5}
25094 @section @code{System.Strings.Stream_Ops} (@code{s-ststop.ads})
25097 @geindex System.Strings.Stream_Ops (s-ststop.ads)
25099 @geindex Stream operations
25101 @geindex String stream operations
25103 This package provides a set of stream subprograms for standard string types.
25104 It is intended primarily to support implicit use of such subprograms when
25105 stream attributes are applied to string types, but the subprograms in this
25106 package can be used directly by application programs.
25108 @node System Unsigned_Types s-unstyp ads,System Wch_Cnv s-wchcnv ads,System Strings Stream_Ops s-ststop ads,The GNAT Library
25109 @anchor{gnat_rm/the_gnat_library system-unsigned-types-s-unstyp-ads}@anchor{3f6}@anchor{gnat_rm/the_gnat_library id153}@anchor{3f7}
25110 @section @code{System.Unsigned_Types} (@code{s-unstyp.ads})
25113 @geindex System.Unsigned_Types (s-unstyp.ads)
25115 This package contains definitions of standard unsigned types that
25116 correspond in size to the standard signed types declared in Standard,
25117 and (unlike the types in Interfaces) have corresponding names. It
25118 also contains some related definitions for other specialized types
25119 used by the compiler in connection with packed array types.
25121 @node System Wch_Cnv s-wchcnv ads,System Wch_Con s-wchcon ads,System Unsigned_Types s-unstyp ads,The GNAT Library
25122 @anchor{gnat_rm/the_gnat_library system-wch-cnv-s-wchcnv-ads}@anchor{3f8}@anchor{gnat_rm/the_gnat_library id154}@anchor{3f9}
25123 @section @code{System.Wch_Cnv} (@code{s-wchcnv.ads})
25126 @geindex System.Wch_Cnv (s-wchcnv.ads)
25128 @geindex Wide Character
25129 @geindex Representation
25131 @geindex Wide String
25132 @geindex Conversion
25134 @geindex Representation of wide characters
25136 This package provides routines for converting between
25137 wide and wide wide characters and a representation as a value of type
25138 @code{Standard.String}, using a specified wide character
25139 encoding method. It uses definitions in
25140 package @code{System.Wch_Con}.
25142 @node System Wch_Con s-wchcon ads,,System Wch_Cnv s-wchcnv ads,The GNAT Library
25143 @anchor{gnat_rm/the_gnat_library system-wch-con-s-wchcon-ads}@anchor{3fa}@anchor{gnat_rm/the_gnat_library id155}@anchor{3fb}
25144 @section @code{System.Wch_Con} (@code{s-wchcon.ads})
25147 @geindex System.Wch_Con (s-wchcon.ads)
25149 This package provides definitions and descriptions of
25150 the various methods used for encoding wide characters
25151 in ordinary strings. These definitions are used by
25152 the package @code{System.Wch_Cnv}.
25154 @node Interfacing to Other Languages,Specialized Needs Annexes,The GNAT Library,Top
25155 @anchor{gnat_rm/interfacing_to_other_languages interfacing-to-other-languages}@anchor{11}@anchor{gnat_rm/interfacing_to_other_languages doc}@anchor{3fc}@anchor{gnat_rm/interfacing_to_other_languages id1}@anchor{3fd}
25156 @chapter Interfacing to Other Languages
25159 The facilities in Annex B of the Ada Reference Manual are fully
25160 implemented in GNAT, and in addition, a full interface to C++ is
25164 * Interfacing to C::
25165 * Interfacing to C++::
25166 * Interfacing to COBOL::
25167 * Interfacing to Fortran::
25168 * Interfacing to non-GNAT Ada code::
25172 @node Interfacing to C,Interfacing to C++,,Interfacing to Other Languages
25173 @anchor{gnat_rm/interfacing_to_other_languages interfacing-to-c}@anchor{3fe}@anchor{gnat_rm/interfacing_to_other_languages id2}@anchor{3ff}
25174 @section Interfacing to C
25177 Interfacing to C with GNAT can use one of two approaches:
25183 The types in the package @code{Interfaces.C} may be used.
25186 Standard Ada types may be used directly. This may be less portable to
25187 other compilers, but will work on all GNAT compilers, which guarantee
25188 correspondence between the C and Ada types.
25191 Pragma @code{Convention C} may be applied to Ada types, but mostly has no
25192 effect, since this is the default. The following table shows the
25193 correspondence between Ada scalar types and the corresponding C types.
25196 @multitable {xxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
25215 @code{Short_Integer}
25223 @code{Short_Short_Integer}
25231 @code{Long_Integer}
25239 @code{Long_Long_Integer}
25271 @code{Long_Long_Float}
25275 This is the longest floating-point type supported by the hardware.
25280 Additionally, there are the following general correspondences between Ada
25287 Ada enumeration types map to C enumeration types directly if pragma
25288 @code{Convention C} is specified, which causes them to have int
25289 length. Without pragma @code{Convention C}, Ada enumeration types map to
25290 8, 16, or 32 bits (i.e., C types @code{signed char}, @code{short},
25291 @code{int}, respectively) depending on the number of values passed.
25292 This is the only case in which pragma @code{Convention C} affects the
25293 representation of an Ada type.
25296 Ada access types map to C pointers, except for the case of pointers to
25297 unconstrained types in Ada, which have no direct C equivalent.
25300 Ada arrays map directly to C arrays.
25303 Ada records map directly to C structures.
25306 Packed Ada records map to C structures where all members are bit fields
25307 of the length corresponding to the @code{type'Size} value in Ada.
25310 @node Interfacing to C++,Interfacing to COBOL,Interfacing to C,Interfacing to Other Languages
25311 @anchor{gnat_rm/interfacing_to_other_languages id4}@anchor{400}@anchor{gnat_rm/interfacing_to_other_languages id3}@anchor{45}
25312 @section Interfacing to C++
25315 The interface to C++ makes use of the following pragmas, which are
25316 primarily intended to be constructed automatically using a binding generator
25317 tool, although it is possible to construct them by hand.
25319 Using these pragmas it is possible to achieve complete
25320 inter-operability between Ada tagged types and C++ class definitions.
25321 See @ref{7,,Implementation Defined Pragmas}, for more details.
25326 @item @code{pragma CPP_Class ([Entity =>] @emph{LOCAL_NAME})}
25328 The argument denotes an entity in the current declarative region that is
25329 declared as a tagged or untagged record type. It indicates that the type
25330 corresponds to an externally declared C++ class type, and is to be laid
25331 out the same way that C++ would lay out the type.
25333 Note: Pragma @code{CPP_Class} is currently obsolete. It is supported
25334 for backward compatibility but its functionality is available
25335 using pragma @code{Import} with @code{Convention} = @code{CPP}.
25337 @item @code{pragma CPP_Constructor ([Entity =>] @emph{LOCAL_NAME})}
25339 This pragma identifies an imported function (imported in the usual way
25340 with pragma @code{Import}) as corresponding to a C++ constructor.
25343 A few restrictions are placed on the use of the @code{Access} attribute
25344 in conjunction with subprograms subject to convention @code{CPP}: the
25345 attribute may be used neither on primitive operations of a tagged
25346 record type with convention @code{CPP}, imported or not, nor on
25347 subprograms imported with pragma @code{CPP_Constructor}.
25349 In addition, C++ exceptions are propagated and can be handled in an
25350 @code{others} choice of an exception handler. The corresponding Ada
25351 occurrence has no message, and the simple name of the exception identity
25352 contains @code{Foreign_Exception}. Finalization and awaiting dependent
25353 tasks works properly when such foreign exceptions are propagated.
25355 It is also possible to import a C++ exception using the following syntax:
25358 LOCAL_NAME : exception;
25359 pragma Import (Cpp,
25360 [Entity =>] LOCAL_NAME,
25361 [External_Name =>] static_string_EXPRESSION);
25364 The @code{External_Name} is the name of the C++ RTTI symbol. You can then
25365 cover a specific C++ exception in an exception handler.
25367 @node Interfacing to COBOL,Interfacing to Fortran,Interfacing to C++,Interfacing to Other Languages
25368 @anchor{gnat_rm/interfacing_to_other_languages id5}@anchor{401}@anchor{gnat_rm/interfacing_to_other_languages interfacing-to-cobol}@anchor{402}
25369 @section Interfacing to COBOL
25372 Interfacing to COBOL is achieved as described in section B.4 of
25373 the Ada Reference Manual.
25375 @node Interfacing to Fortran,Interfacing to non-GNAT Ada code,Interfacing to COBOL,Interfacing to Other Languages
25376 @anchor{gnat_rm/interfacing_to_other_languages id6}@anchor{403}@anchor{gnat_rm/interfacing_to_other_languages interfacing-to-fortran}@anchor{404}
25377 @section Interfacing to Fortran
25380 Interfacing to Fortran is achieved as described in section B.5 of the
25381 Ada Reference Manual. The pragma @code{Convention Fortran}, applied to a
25382 multi-dimensional array causes the array to be stored in column-major
25383 order as required for convenient interface to Fortran.
25385 @node Interfacing to non-GNAT Ada code,,Interfacing to Fortran,Interfacing to Other Languages
25386 @anchor{gnat_rm/interfacing_to_other_languages interfacing-to-non-gnat-ada-code}@anchor{405}@anchor{gnat_rm/interfacing_to_other_languages id7}@anchor{406}
25387 @section Interfacing to non-GNAT Ada code
25390 It is possible to specify the convention @code{Ada} in a pragma
25391 @code{Import} or pragma @code{Export}. However this refers to
25392 the calling conventions used by GNAT, which may or may not be
25393 similar enough to those used by some other Ada 83 / Ada 95 / Ada 2005
25394 compiler to allow interoperation.
25396 If arguments types are kept simple, and if the foreign compiler generally
25397 follows system calling conventions, then it may be possible to integrate
25398 files compiled by other Ada compilers, provided that the elaboration
25399 issues are adequately addressed (for example by eliminating the
25400 need for any load time elaboration).
25402 In particular, GNAT running on VMS is designed to
25403 be highly compatible with the DEC Ada 83 compiler, so this is one
25404 case in which it is possible to import foreign units of this type,
25405 provided that the data items passed are restricted to simple scalar
25406 values or simple record types without variants, or simple array
25407 types with fixed bounds.
25409 @node Specialized Needs Annexes,Implementation of Specific Ada Features,Interfacing to Other Languages,Top
25410 @anchor{gnat_rm/specialized_needs_annexes specialized-needs-annexes}@anchor{12}@anchor{gnat_rm/specialized_needs_annexes doc}@anchor{407}@anchor{gnat_rm/specialized_needs_annexes id1}@anchor{408}
25411 @chapter Specialized Needs Annexes
25414 Ada 95, Ada 2005, and Ada 2012 define a number of Specialized Needs Annexes, which are not
25415 required in all implementations. However, as described in this chapter,
25416 GNAT implements all of these annexes:
25421 @item @emph{Systems Programming (Annex C)}
25423 The Systems Programming Annex is fully implemented.
25425 @item @emph{Real-Time Systems (Annex D)}
25427 The Real-Time Systems Annex is fully implemented.
25429 @item @emph{Distributed Systems (Annex E)}
25431 Stub generation is fully implemented in the GNAT compiler. In addition,
25432 a complete compatible PCS is available as part of the GLADE system,
25433 a separate product. When the two
25434 products are used in conjunction, this annex is fully implemented.
25436 @item @emph{Information Systems (Annex F)}
25438 The Information Systems annex is fully implemented.
25440 @item @emph{Numerics (Annex G)}
25442 The Numerics Annex is fully implemented.
25444 @item @emph{Safety and Security / High-Integrity Systems (Annex H)}
25446 The Safety and Security Annex (termed the High-Integrity Systems Annex
25447 in Ada 2005) is fully implemented.
25450 @node Implementation of Specific Ada Features,Implementation of Ada 2012 Features,Specialized Needs Annexes,Top
25451 @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{409}@anchor{gnat_rm/implementation_of_specific_ada_features id1}@anchor{40a}
25452 @chapter Implementation of Specific Ada Features
25455 This chapter describes the GNAT implementation of several Ada language
25459 * Machine Code Insertions::
25460 * GNAT Implementation of Tasking::
25461 * GNAT Implementation of Shared Passive Packages::
25462 * Code Generation for Array Aggregates::
25463 * The Size of Discriminated Records with Default Discriminants::
25464 * Strict Conformance to the Ada Reference Manual::
25468 @node Machine Code Insertions,GNAT Implementation of Tasking,,Implementation of Specific Ada Features
25469 @anchor{gnat_rm/implementation_of_specific_ada_features machine-code-insertions}@anchor{164}@anchor{gnat_rm/implementation_of_specific_ada_features id2}@anchor{40b}
25470 @section Machine Code Insertions
25473 @geindex Machine Code insertions
25475 Package @code{Machine_Code} provides machine code support as described
25476 in the Ada Reference Manual in two separate forms:
25482 Machine code statements, consisting of qualified expressions that
25483 fit the requirements of RM section 13.8.
25486 An intrinsic callable procedure, providing an alternative mechanism of
25487 including machine instructions in a subprogram.
25490 The two features are similar, and both are closely related to the mechanism
25491 provided by the asm instruction in the GNU C compiler. Full understanding
25492 and use of the facilities in this package requires understanding the asm
25493 instruction, see the section on Extended Asm in
25494 @cite{Using_the_GNU_Compiler_Collection_(GCC)}.
25496 Calls to the function @code{Asm} and the procedure @code{Asm} have identical
25497 semantic restrictions and effects as described below. Both are provided so
25498 that the procedure call can be used as a statement, and the function call
25499 can be used to form a code_statement.
25501 Consider this C @code{asm} instruction:
25504 asm ("fsinx %1 %0" : "=f" (result) : "f" (angle));
25507 The equivalent can be written for GNAT as:
25510 Asm ("fsinx %1 %0",
25511 My_Float'Asm_Output ("=f", result),
25512 My_Float'Asm_Input ("f", angle));
25515 The first argument to @code{Asm} is the assembler template, and is
25516 identical to what is used in GNU C. This string must be a static
25517 expression. The second argument is the output operand list. It is
25518 either a single @code{Asm_Output} attribute reference, or a list of such
25519 references enclosed in parentheses (technically an array aggregate of
25522 The @code{Asm_Output} attribute denotes a function that takes two
25523 parameters. The first is a string, the second is the name of a variable
25524 of the type designated by the attribute prefix. The first (string)
25525 argument is required to be a static expression and designates the
25526 constraint (see the section on Constraints in
25527 @cite{Using_the_GNU_Compiler_Collection_(GCC)})
25528 for the parameter; e.g., what kind of register is required. The second
25529 argument is the variable to be written or updated with the
25530 result. The possible values for constraint are the same as those used in
25531 the RTL, and are dependent on the configuration file used to build the
25532 GCC back end. If there are no output operands, then this argument may
25533 either be omitted, or explicitly given as @code{No_Output_Operands}.
25534 No support is provided for GNU C's symbolic names for output parameters.
25536 The second argument of @code{my_float'Asm_Output} functions as
25537 though it were an @code{out} parameter, which is a little curious, but
25538 all names have the form of expressions, so there is no syntactic
25539 irregularity, even though normally functions would not be permitted
25540 @code{out} parameters. The third argument is the list of input
25541 operands. It is either a single @code{Asm_Input} attribute reference, or
25542 a list of such references enclosed in parentheses (technically an array
25543 aggregate of such references).
25545 The @code{Asm_Input} attribute denotes a function that takes two
25546 parameters. The first is a string, the second is an expression of the
25547 type designated by the prefix. The first (string) argument is required
25548 to be a static expression, and is the constraint for the parameter,
25549 (e.g., what kind of register is required). The second argument is the
25550 value to be used as the input argument. The possible values for the
25551 constraint are the same as those used in the RTL, and are dependent on
25552 the configuration file used to built the GCC back end.
25553 No support is provided for GNU C's symbolic names for input parameters.
25555 If there are no input operands, this argument may either be omitted, or
25556 explicitly given as @code{No_Input_Operands}. The fourth argument, not
25557 present in the above example, is a list of register names, called the
25558 @emph{clobber} argument. This argument, if given, must be a static string
25559 expression, and is a space or comma separated list of names of registers
25560 that must be considered destroyed as a result of the @code{Asm} call. If
25561 this argument is the null string (the default value), then the code
25562 generator assumes that no additional registers are destroyed.
25563 In addition to registers, the special clobbers @code{memory} and
25564 @code{cc} as described in the GNU C docs are both supported.
25566 The fifth argument, not present in the above example, called the
25567 @emph{volatile} argument, is by default @code{False}. It can be set to
25568 the literal value @code{True} to indicate to the code generator that all
25569 optimizations with respect to the instruction specified should be
25570 suppressed, and in particular an instruction that has outputs
25571 will still be generated, even if none of the outputs are
25572 used. See @cite{Using_the_GNU_Compiler_Collection_(GCC)}
25573 for the full description.
25574 Generally it is strongly advisable to use Volatile for any ASM statement
25575 that is missing either input or output operands or to avoid unwanted
25576 optimizations. A warning is generated if this advice is not followed.
25578 No support is provided for GNU C's @code{asm goto} feature.
25580 The @code{Asm} subprograms may be used in two ways. First the procedure
25581 forms can be used anywhere a procedure call would be valid, and
25582 correspond to what the RM calls 'intrinsic' routines. Such calls can
25583 be used to intersperse machine instructions with other Ada statements.
25584 Second, the function forms, which return a dummy value of the limited
25585 private type @code{Asm_Insn}, can be used in code statements, and indeed
25586 this is the only context where such calls are allowed. Code statements
25587 appear as aggregates of the form:
25590 Asm_Insn'(Asm (...));
25591 Asm_Insn'(Asm_Volatile (...));
25594 In accordance with RM rules, such code statements are allowed only
25595 within subprograms whose entire body consists of such statements. It is
25596 not permissible to intermix such statements with other Ada statements.
25598 Typically the form using intrinsic procedure calls is more convenient
25599 and more flexible. The code statement form is provided to meet the RM
25600 suggestion that such a facility should be made available. The following
25601 is the exact syntax of the call to @code{Asm}. As usual, if named notation
25602 is used, the arguments may be given in arbitrary order, following the
25603 normal rules for use of positional and named arguments:
25607 [Template =>] static_string_EXPRESSION
25608 [,[Outputs =>] OUTPUT_OPERAND_LIST ]
25609 [,[Inputs =>] INPUT_OPERAND_LIST ]
25610 [,[Clobber =>] static_string_EXPRESSION ]
25611 [,[Volatile =>] static_boolean_EXPRESSION] )
25613 OUTPUT_OPERAND_LIST ::=
25614 [PREFIX.]No_Output_Operands
25615 | OUTPUT_OPERAND_ATTRIBUTE
25616 | (OUTPUT_OPERAND_ATTRIBUTE @{,OUTPUT_OPERAND_ATTRIBUTE@})
25618 OUTPUT_OPERAND_ATTRIBUTE ::=
25619 SUBTYPE_MARK'Asm_Output (static_string_EXPRESSION, NAME)
25621 INPUT_OPERAND_LIST ::=
25622 [PREFIX.]No_Input_Operands
25623 | INPUT_OPERAND_ATTRIBUTE
25624 | (INPUT_OPERAND_ATTRIBUTE @{,INPUT_OPERAND_ATTRIBUTE@})
25626 INPUT_OPERAND_ATTRIBUTE ::=
25627 SUBTYPE_MARK'Asm_Input (static_string_EXPRESSION, EXPRESSION)
25630 The identifiers @code{No_Input_Operands} and @code{No_Output_Operands}
25631 are declared in the package @code{Machine_Code} and must be referenced
25632 according to normal visibility rules. In particular if there is no
25633 @code{use} clause for this package, then appropriate package name
25634 qualification is required.
25636 @node GNAT Implementation of Tasking,GNAT Implementation of Shared Passive Packages,Machine Code Insertions,Implementation of Specific Ada Features
25637 @anchor{gnat_rm/implementation_of_specific_ada_features id3}@anchor{40c}@anchor{gnat_rm/implementation_of_specific_ada_features gnat-implementation-of-tasking}@anchor{40d}
25638 @section GNAT Implementation of Tasking
25641 This chapter outlines the basic GNAT approach to tasking (in particular,
25642 a multi-layered library for portability) and discusses issues related
25643 to compliance with the Real-Time Systems Annex.
25646 * Mapping Ada Tasks onto the Underlying Kernel Threads::
25647 * Ensuring Compliance with the Real-Time Annex::
25648 * Support for Locking Policies::
25652 @node Mapping Ada Tasks onto the Underlying Kernel Threads,Ensuring Compliance with the Real-Time Annex,,GNAT Implementation of Tasking
25653 @anchor{gnat_rm/implementation_of_specific_ada_features mapping-ada-tasks-onto-the-underlying-kernel-threads}@anchor{40e}@anchor{gnat_rm/implementation_of_specific_ada_features id4}@anchor{40f}
25654 @subsection Mapping Ada Tasks onto the Underlying Kernel Threads
25657 GNAT's run-time support comprises two layers:
25663 GNARL (GNAT Run-time Layer)
25666 GNULL (GNAT Low-level Library)
25669 In GNAT, Ada's tasking services rely on a platform and OS independent
25670 layer known as GNARL. This code is responsible for implementing the
25671 correct semantics of Ada's task creation, rendezvous, protected
25674 GNARL decomposes Ada's tasking semantics into simpler lower level
25675 operations such as create a thread, set the priority of a thread,
25676 yield, create a lock, lock/unlock, etc. The spec for these low-level
25677 operations constitutes GNULLI, the GNULL Interface. This interface is
25678 directly inspired from the POSIX real-time API.
25680 If the underlying executive or OS implements the POSIX standard
25681 faithfully, the GNULL Interface maps as is to the services offered by
25682 the underlying kernel. Otherwise, some target dependent glue code maps
25683 the services offered by the underlying kernel to the semantics expected
25686 Whatever the underlying OS (VxWorks, UNIX, Windows, etc.) the
25687 key point is that each Ada task is mapped on a thread in the underlying
25688 kernel. For example, in the case of VxWorks, one Ada task = one VxWorks task.
25690 In addition Ada task priorities map onto the underlying thread priorities.
25691 Mapping Ada tasks onto the underlying kernel threads has several advantages:
25697 The underlying scheduler is used to schedule the Ada tasks. This
25698 makes Ada tasks as efficient as kernel threads from a scheduling
25702 Interaction with code written in C containing threads is eased
25703 since at the lowest level Ada tasks and C threads map onto the same
25704 underlying kernel concept.
25707 When an Ada task is blocked during I/O the remaining Ada tasks are
25711 On multiprocessor systems Ada tasks can execute in parallel.
25714 Some threads libraries offer a mechanism to fork a new process, with the
25715 child process duplicating the threads from the parent.
25717 support this functionality when the parent contains more than one task.
25719 @geindex Forking a new process
25721 @node Ensuring Compliance with the Real-Time Annex,Support for Locking Policies,Mapping Ada Tasks onto the Underlying Kernel Threads,GNAT Implementation of Tasking
25722 @anchor{gnat_rm/implementation_of_specific_ada_features id5}@anchor{410}@anchor{gnat_rm/implementation_of_specific_ada_features ensuring-compliance-with-the-real-time-annex}@anchor{411}
25723 @subsection Ensuring Compliance with the Real-Time Annex
25726 @geindex Real-Time Systems Annex compliance
25728 Although mapping Ada tasks onto
25729 the underlying threads has significant advantages, it does create some
25730 complications when it comes to respecting the scheduling semantics
25731 specified in the real-time annex (Annex D).
25733 For instance the Annex D requirement for the @code{FIFO_Within_Priorities}
25734 scheduling policy states:
25738 @emph{When the active priority of a ready task that is not running
25739 changes, or the setting of its base priority takes effect, the
25740 task is removed from the ready queue for its old active priority
25741 and is added at the tail of the ready queue for its new active
25742 priority, except in the case where the active priority is lowered
25743 due to the loss of inherited priority, in which case the task is
25744 added at the head of the ready queue for its new active priority.}
25747 While most kernels do put tasks at the end of the priority queue when
25748 a task changes its priority, (which respects the main
25749 FIFO_Within_Priorities requirement), almost none keep a thread at the
25750 beginning of its priority queue when its priority drops from the loss
25751 of inherited priority.
25753 As a result most vendors have provided incomplete Annex D implementations.
25755 The GNAT run-time, has a nice cooperative solution to this problem
25756 which ensures that accurate FIFO_Within_Priorities semantics are
25759 The principle is as follows. When an Ada task T is about to start
25760 running, it checks whether some other Ada task R with the same
25761 priority as T has been suspended due to the loss of priority
25762 inheritance. If this is the case, T yields and is placed at the end of
25763 its priority queue. When R arrives at the front of the queue it
25766 Note that this simple scheme preserves the relative order of the tasks
25767 that were ready to execute in the priority queue where R has been
25770 @c Support_for_Locking_Policies
25772 @node Support for Locking Policies,,Ensuring Compliance with the Real-Time Annex,GNAT Implementation of Tasking
25773 @anchor{gnat_rm/implementation_of_specific_ada_features support-for-locking-policies}@anchor{412}
25774 @subsection Support for Locking Policies
25777 This section specifies which policies specified by pragma Locking_Policy
25778 are supported on which platforms.
25780 GNAT supports the standard @code{Ceiling_Locking} policy, and the
25781 implementation defined @code{Inheritance_Locking} and
25782 @code{Concurrent_Readers_Locking} policies.
25784 @code{Ceiling_Locking} is supported on all platforms if the operating system
25785 supports it. In particular, @code{Ceiling_Locking} is not supported on
25787 @code{Inheritance_Locking} is supported on
25792 @code{Concurrent_Readers_Locking} is supported on Linux.
25794 Notes about @code{Ceiling_Locking} on Linux:
25795 If the process is running as 'root', ceiling locking is used.
25796 If the capabilities facility is installed
25797 ("sudo apt-get --assume-yes install libcap-dev" on Ubuntu,
25799 and the program is linked against that library
25801 and the executable file has the cap_sys_nice capability
25802 ("sudo /sbin/setcap cap_sys_nice=ep executable_file_name"),
25803 then ceiling locking is used.
25804 Otherwise, the @code{Ceiling_Locking} policy is ignored.
25806 @node GNAT Implementation of Shared Passive Packages,Code Generation for Array Aggregates,GNAT Implementation of Tasking,Implementation of Specific Ada Features
25807 @anchor{gnat_rm/implementation_of_specific_ada_features id6}@anchor{413}@anchor{gnat_rm/implementation_of_specific_ada_features gnat-implementation-of-shared-passive-packages}@anchor{414}
25808 @section GNAT Implementation of Shared Passive Packages
25811 @geindex Shared passive packages
25813 GNAT fully implements the
25814 @geindex pragma Shared_Passive
25816 @code{Shared_Passive} for
25817 the purpose of designating shared passive packages.
25818 This allows the use of passive partitions in the
25819 context described in the Ada Reference Manual; i.e., for communication
25820 between separate partitions of a distributed application using the
25821 features in Annex E.
25825 @geindex Distribution Systems Annex
25827 However, the implementation approach used by GNAT provides for more
25828 extensive usage as follows:
25833 @item @emph{Communication between separate programs}
25835 This allows separate programs to access the data in passive
25836 partitions, using protected objects for synchronization where
25837 needed. The only requirement is that the two programs have a
25838 common shared file system. It is even possible for programs
25839 running on different machines with different architectures
25840 (e.g., different endianness) to communicate via the data in
25841 a passive partition.
25843 @item @emph{Persistence between program runs}
25845 The data in a passive package can persist from one run of a
25846 program to another, so that a later program sees the final
25847 values stored by a previous run of the same program.
25850 The implementation approach used is to store the data in files. A
25851 separate stream file is created for each object in the package, and
25852 an access to an object causes the corresponding file to be read or
25855 @geindex SHARED_MEMORY_DIRECTORY environment variable
25857 The environment variable @code{SHARED_MEMORY_DIRECTORY} should be
25858 set to the directory to be used for these files.
25859 The files in this directory
25860 have names that correspond to their fully qualified names. For
25861 example, if we have the package
25865 pragma Shared_Passive (X);
25871 and the environment variable is set to @code{/stemp/}, then the files created
25872 will have the names:
25879 These files are created when a value is initially written to the object, and
25880 the files are retained until manually deleted. This provides the persistence
25881 semantics. If no file exists, it means that no partition has assigned a value
25882 to the variable; in this case the initial value declared in the package
25883 will be used. This model ensures that there are no issues in synchronizing
25884 the elaboration process, since elaboration of passive packages elaborates the
25885 initial values, but does not create the files.
25887 The files are written using normal @code{Stream_IO} access.
25888 If you want to be able
25889 to communicate between programs or partitions running on different
25890 architectures, then you should use the XDR versions of the stream attribute
25891 routines, since these are architecture independent.
25893 If active synchronization is required for access to the variables in the
25894 shared passive package, then as described in the Ada Reference Manual, the
25895 package may contain protected objects used for this purpose. In this case
25896 a lock file (whose name is @code{___lock} (three underscores)
25897 is created in the shared memory directory.
25899 @geindex ___lock file (for shared passive packages)
25901 This is used to provide the required locking
25902 semantics for proper protected object synchronization.
25904 GNAT supports shared passive packages on all platforms
25905 except for OpenVMS.
25907 @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
25908 @anchor{gnat_rm/implementation_of_specific_ada_features code-generation-for-array-aggregates}@anchor{415}@anchor{gnat_rm/implementation_of_specific_ada_features id7}@anchor{416}
25909 @section Code Generation for Array Aggregates
25912 Aggregates have a rich syntax and allow the user to specify the values of
25913 complex data structures by means of a single construct. As a result, the
25914 code generated for aggregates can be quite complex and involve loops, case
25915 statements and multiple assignments. In the simplest cases, however, the
25916 compiler will recognize aggregates whose components and constraints are
25917 fully static, and in those cases the compiler will generate little or no
25918 executable code. The following is an outline of the code that GNAT generates
25919 for various aggregate constructs. For further details, you will find it
25920 useful to examine the output produced by the -gnatG flag to see the expanded
25921 source that is input to the code generator. You may also want to examine
25922 the assembly code generated at various levels of optimization.
25924 The code generated for aggregates depends on the context, the component values,
25925 and the type. In the context of an object declaration the code generated is
25926 generally simpler than in the case of an assignment. As a general rule, static
25927 component values and static subtypes also lead to simpler code.
25930 * Static constant aggregates with static bounds::
25931 * Constant aggregates with unconstrained nominal types::
25932 * Aggregates with static bounds::
25933 * Aggregates with nonstatic bounds::
25934 * Aggregates in assignment statements::
25938 @node Static constant aggregates with static bounds,Constant aggregates with unconstrained nominal types,,Code Generation for Array Aggregates
25939 @anchor{gnat_rm/implementation_of_specific_ada_features static-constant-aggregates-with-static-bounds}@anchor{417}@anchor{gnat_rm/implementation_of_specific_ada_features id8}@anchor{418}
25940 @subsection Static constant aggregates with static bounds
25943 For the declarations:
25946 type One_Dim is array (1..10) of integer;
25947 ar0 : constant One_Dim := (1, 2, 3, 4, 5, 6, 7, 8, 9, 0);
25950 GNAT generates no executable code: the constant ar0 is placed in static memory.
25951 The same is true for constant aggregates with named associations:
25954 Cr1 : constant One_Dim := (4 => 16, 2 => 4, 3 => 9, 1 => 1, 5 .. 10 => 0);
25955 Cr3 : constant One_Dim := (others => 7777);
25958 The same is true for multidimensional constant arrays such as:
25961 type two_dim is array (1..3, 1..3) of integer;
25962 Unit : constant two_dim := ( (1,0,0), (0,1,0), (0,0,1));
25965 The same is true for arrays of one-dimensional arrays: the following are
25969 type ar1b is array (1..3) of boolean;
25970 type ar_ar is array (1..3) of ar1b;
25971 None : constant ar1b := (others => false); -- fully static
25972 None2 : constant ar_ar := (1..3 => None); -- fully static
25975 However, for multidimensional aggregates with named associations, GNAT will
25976 generate assignments and loops, even if all associations are static. The
25977 following two declarations generate a loop for the first dimension, and
25978 individual component assignments for the second dimension:
25981 Zero1: constant two_dim := (1..3 => (1..3 => 0));
25982 Zero2: constant two_dim := (others => (others => 0));
25985 @node Constant aggregates with unconstrained nominal types,Aggregates with static bounds,Static constant aggregates with static bounds,Code Generation for Array Aggregates
25986 @anchor{gnat_rm/implementation_of_specific_ada_features constant-aggregates-with-unconstrained-nominal-types}@anchor{419}@anchor{gnat_rm/implementation_of_specific_ada_features id9}@anchor{41a}
25987 @subsection Constant aggregates with unconstrained nominal types
25990 In such cases the aggregate itself establishes the subtype, so that
25991 associations with @code{others} cannot be used. GNAT determines the
25992 bounds for the actual subtype of the aggregate, and allocates the
25993 aggregate statically as well. No code is generated for the following:
25996 type One_Unc is array (natural range <>) of integer;
25997 Cr_Unc : constant One_Unc := (12,24,36);
26000 @node Aggregates with static bounds,Aggregates with nonstatic bounds,Constant aggregates with unconstrained nominal types,Code Generation for Array Aggregates
26001 @anchor{gnat_rm/implementation_of_specific_ada_features id10}@anchor{41b}@anchor{gnat_rm/implementation_of_specific_ada_features aggregates-with-static-bounds}@anchor{41c}
26002 @subsection Aggregates with static bounds
26005 In all previous examples the aggregate was the initial (and immutable) value
26006 of a constant. If the aggregate initializes a variable, then code is generated
26007 for it as a combination of individual assignments and loops over the target
26008 object. The declarations
26011 Cr_Var1 : One_Dim := (2, 5, 7, 11, 0, 0, 0, 0, 0, 0);
26012 Cr_Var2 : One_Dim := (others > -1);
26015 generate the equivalent of
26023 for I in Cr_Var2'range loop
26028 @node Aggregates with nonstatic bounds,Aggregates in assignment statements,Aggregates with static bounds,Code Generation for Array Aggregates
26029 @anchor{gnat_rm/implementation_of_specific_ada_features id11}@anchor{41d}@anchor{gnat_rm/implementation_of_specific_ada_features aggregates-with-nonstatic-bounds}@anchor{41e}
26030 @subsection Aggregates with nonstatic bounds
26033 If the bounds of the aggregate are not statically compatible with the bounds
26034 of the nominal subtype of the target, then constraint checks have to be
26035 generated on the bounds. For a multidimensional array, constraint checks may
26036 have to be applied to sub-arrays individually, if they do not have statically
26037 compatible subtypes.
26039 @node Aggregates in assignment statements,,Aggregates with nonstatic bounds,Code Generation for Array Aggregates
26040 @anchor{gnat_rm/implementation_of_specific_ada_features id12}@anchor{41f}@anchor{gnat_rm/implementation_of_specific_ada_features aggregates-in-assignment-statements}@anchor{420}
26041 @subsection Aggregates in assignment statements
26044 In general, aggregate assignment requires the construction of a temporary,
26045 and a copy from the temporary to the target of the assignment. This is because
26046 it is not always possible to convert the assignment into a series of individual
26047 component assignments. For example, consider the simple case:
26053 This cannot be converted into:
26060 So the aggregate has to be built first in a separate location, and then
26061 copied into the target. GNAT recognizes simple cases where this intermediate
26062 step is not required, and the assignments can be performed in place, directly
26063 into the target. The following sufficient criteria are applied:
26069 The bounds of the aggregate are static, and the associations are static.
26072 The components of the aggregate are static constants, names of
26073 simple variables that are not renamings, or expressions not involving
26074 indexed components whose operands obey these rules.
26077 If any of these conditions are violated, the aggregate will be built in
26078 a temporary (created either by the front-end or the code generator) and then
26079 that temporary will be copied onto the target.
26081 @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
26082 @anchor{gnat_rm/implementation_of_specific_ada_features id13}@anchor{421}@anchor{gnat_rm/implementation_of_specific_ada_features the-size-of-discriminated-records-with-default-discriminants}@anchor{422}
26083 @section The Size of Discriminated Records with Default Discriminants
26086 If a discriminated type @code{T} has discriminants with default values, it is
26087 possible to declare an object of this type without providing an explicit
26091 type Size is range 1..100;
26093 type Rec (D : Size := 15) is record
26094 Name : String (1..D);
26100 Such an object is said to be @emph{unconstrained}.
26101 The discriminant of the object
26102 can be modified by a full assignment to the object, as long as it preserves the
26103 relation between the value of the discriminant, and the value of the components
26107 Word := (3, "yes");
26109 Word := (5, "maybe");
26111 Word := (5, "no"); -- raises Constraint_Error
26114 In order to support this behavior efficiently, an unconstrained object is
26115 given the maximum size that any value of the type requires. In the case
26116 above, @code{Word} has storage for the discriminant and for
26117 a @code{String} of length 100.
26118 It is important to note that unconstrained objects do not require dynamic
26119 allocation. It would be an improper implementation to place on the heap those
26120 components whose size depends on discriminants. (This improper implementation
26121 was used by some Ada83 compilers, where the @code{Name} component above
26123 been stored as a pointer to a dynamic string). Following the principle that
26124 dynamic storage management should never be introduced implicitly,
26125 an Ada compiler should reserve the full size for an unconstrained declared
26126 object, and place it on the stack.
26128 This maximum size approach
26129 has been a source of surprise to some users, who expect the default
26130 values of the discriminants to determine the size reserved for an
26131 unconstrained object: "If the default is 15, why should the object occupy
26133 The answer, of course, is that the discriminant may be later modified,
26134 and its full range of values must be taken into account. This is why the
26138 type Rec (D : Positive := 15) is record
26139 Name : String (1..D);
26145 is flagged by the compiler with a warning:
26146 an attempt to create @code{Too_Large} will raise @code{Storage_Error},
26147 because the required size includes @code{Positive'Last}
26148 bytes. As the first example indicates, the proper approach is to declare an
26149 index type of 'reasonable' range so that unconstrained objects are not too
26152 One final wrinkle: if the object is declared to be @code{aliased}, or if it is
26153 created in the heap by means of an allocator, then it is @emph{not}
26155 it is constrained by the default values of the discriminants, and those values
26156 cannot be modified by full assignment. This is because in the presence of
26157 aliasing all views of the object (which may be manipulated by different tasks,
26158 say) must be consistent, so it is imperative that the object, once created,
26161 @node Strict Conformance to the Ada Reference Manual,,The Size of Discriminated Records with Default Discriminants,Implementation of Specific Ada Features
26162 @anchor{gnat_rm/implementation_of_specific_ada_features strict-conformance-to-the-ada-reference-manual}@anchor{423}@anchor{gnat_rm/implementation_of_specific_ada_features id14}@anchor{424}
26163 @section Strict Conformance to the Ada Reference Manual
26166 The dynamic semantics defined by the Ada Reference Manual impose a set of
26167 run-time checks to be generated. By default, the GNAT compiler will insert many
26168 run-time checks into the compiled code, including most of those required by the
26169 Ada Reference Manual. However, there are two checks that are not enabled in
26170 the default mode for efficiency reasons: checks for access before elaboration
26171 on subprogram calls, and stack overflow checking (most operating systems do not
26172 perform this check by default).
26174 Strict conformance to the Ada Reference Manual can be achieved by adding two
26175 compiler options for dynamic checks for access-before-elaboration on subprogram
26176 calls and generic instantiations (@emph{-gnatE}), and stack overflow checking
26177 (@emph{-fstack-check}).
26179 Note that the result of a floating point arithmetic operation in overflow and
26180 invalid situations, when the @code{Machine_Overflows} attribute of the result
26181 type is @code{False}, is to generate IEEE NaN and infinite values. This is the
26182 case for machines compliant with the IEEE floating-point standard, but on
26183 machines that are not fully compliant with this standard, such as Alpha, the
26184 @emph{-mieee} compiler flag must be used for achieving IEEE confirming
26185 behavior (although at the cost of a significant performance penalty), so
26186 infinite and NaN values are properly generated.
26188 @node Implementation of Ada 2012 Features,Obsolescent Features,Implementation of Specific Ada Features,Top
26189 @anchor{gnat_rm/implementation_of_ada_2012_features doc}@anchor{425}@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{426}
26190 @chapter Implementation of Ada 2012 Features
26193 @geindex Ada 2012 implementation status
26195 @geindex -gnat12 option (gcc)
26197 @geindex pragma Ada_2012
26199 @geindex configuration pragma Ada_2012
26201 @geindex Ada_2012 configuration pragma
26203 This chapter contains a complete list of Ada 2012 features that have been
26205 Generally, these features are only
26206 available if the @emph{-gnat12} (Ada 2012 features enabled) option is set,
26207 which is the default behavior,
26208 or if the configuration pragma @code{Ada_2012} is used.
26210 However, new pragmas, attributes, and restrictions are
26211 unconditionally available, since the Ada 95 standard allows the addition of
26212 new pragmas, attributes, and restrictions (there are exceptions, which are
26213 documented in the individual descriptions), and also certain packages
26214 were made available in earlier versions of Ada.
26216 An ISO date (YYYY-MM-DD) appears in parentheses on the description line.
26217 This date shows the implementation date of the feature. Any wavefront
26218 subsequent to this date will contain the indicated feature, as will any
26219 subsequent releases. A date of 0000-00-00 means that GNAT has always
26220 implemented the feature, or implemented it as soon as it appeared as a
26221 binding interpretation.
26223 Each feature corresponds to an Ada Issue ('AI') approved by the Ada
26224 standardization group (ISO/IEC JTC1/SC22/WG9) for inclusion in Ada 2012.
26225 The features are ordered based on the relevant sections of the Ada
26226 Reference Manual ("RM"). When a given AI relates to multiple points
26227 in the RM, the earliest is used.
26229 A complete description of the AIs may be found in
26230 @indicateurl{http://www.ada-auth.org/ai05-summary.html}.
26232 @geindex AI-0176 (Ada 2012 feature)
26238 @emph{AI-0176 Quantified expressions (2010-09-29)}
26240 Both universally and existentially quantified expressions are implemented.
26241 They use the new syntax for iterators proposed in AI05-139-2, as well as
26242 the standard Ada loop syntax.
26244 RM References: 1.01.04 (12) 2.09 (2/2) 4.04 (7) 4.05.09 (0)
26247 @geindex AI-0079 (Ada 2012 feature)
26253 @emph{AI-0079 Allow other_format characters in source (2010-07-10)}
26255 Wide characters in the unicode category @emph{other_format} are now allowed in
26256 source programs between tokens, but not within a token such as an identifier.
26258 RM References: 2.01 (4/2) 2.02 (7)
26261 @geindex AI-0091 (Ada 2012 feature)
26267 @emph{AI-0091 Do not allow other_format in identifiers (0000-00-00)}
26269 Wide characters in the unicode category @emph{other_format} are not permitted
26270 within an identifier, since this can be a security problem. The error
26271 message for this case has been improved to be more specific, but GNAT has
26272 never allowed such characters to appear in identifiers.
26274 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)
26277 @geindex AI-0100 (Ada 2012 feature)
26283 @emph{AI-0100 Placement of pragmas (2010-07-01)}
26285 This AI is an earlier version of AI-163. It simplifies the rules
26286 for legal placement of pragmas. In the case of lists that allow pragmas, if
26287 the list may have no elements, then the list may consist solely of pragmas.
26289 RM References: 2.08 (7)
26292 @geindex AI-0163 (Ada 2012 feature)
26298 @emph{AI-0163 Pragmas in place of null (2010-07-01)}
26300 A statement sequence may be composed entirely of pragmas. It is no longer
26301 necessary to add a dummy @code{null} statement to make the sequence legal.
26303 RM References: 2.08 (7) 2.08 (16)
26306 @geindex AI-0080 (Ada 2012 feature)
26312 @emph{AI-0080 'View of' not needed if clear from context (0000-00-00)}
26314 This is an editorial change only, described as non-testable in the AI.
26316 RM References: 3.01 (7)
26319 @geindex AI-0183 (Ada 2012 feature)
26325 @emph{AI-0183 Aspect specifications (2010-08-16)}
26327 Aspect specifications have been fully implemented except for pre and post-
26328 conditions, and type invariants, which have their own separate AI's. All
26329 forms of declarations listed in the AI are supported. The following is a
26330 list of the aspects supported (with GNAT implementation aspects marked)
26334 @multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxx}
26379 @code{Atomic_Components}
26391 @code{Component_Size}
26397 @code{Contract_Cases}
26405 @code{Discard_Names}
26411 @code{External_Tag}
26417 @code{Favor_Top_Level}
26431 @code{Inline_Always}
26447 @code{Machine_Radix}
26473 @code{Persistent_BSS}
26499 @code{Preelaborable_Initialization}
26505 @code{Pure_Function}
26513 @code{Remote_Access_Type}
26535 @code{Storage_Pool}
26541 @code{Storage_Size}
26559 @code{Suppress_Debug_Info}
26575 @code{Thread_Local_Storage}
26583 @code{Type_Invariant}
26589 @code{Unchecked_Union}
26595 @code{Universal_Aliasing}
26611 @code{Unreferenced}
26619 @code{Unreferenced_Objects}
26647 @code{Volatile_Components}
26664 Note that for aspects with an expression, e.g. @code{Size}, the expression is
26665 treated like a default expression (visibility is analyzed at the point of
26666 occurrence of the aspect, but evaluation of the expression occurs at the
26667 freeze point of the entity involved).
26669 RM References: 3.02.01 (3) 3.02.02 (2) 3.03.01 (2/2) 3.08 (6)
26670 3.09.03 (1.1/2) 6.01 (2/2) 6.07 (2/2) 9.05.02 (2/2) 7.01 (3) 7.03
26671 (2) 7.03 (3) 9.01 (2/2) 9.01 (3/2) 9.04 (2/2) 9.04 (3/2)
26672 9.05.02 (2/2) 11.01 (2) 12.01 (3) 12.03 (2/2) 12.04 (2/2) 12.05 (2)
26673 12.06 (2.1/2) 12.06 (2.2/2) 12.07 (2) 13.01 (0.1/2) 13.03 (5/1)
26677 @geindex AI-0128 (Ada 2012 feature)
26683 @emph{AI-0128 Inequality is a primitive operation (0000-00-00)}
26685 If an equality operator ("=") is declared for a type, then the implicitly
26686 declared inequality operator ("/=") is a primitive operation of the type.
26687 This is the only reasonable interpretation, and is the one always implemented
26688 by GNAT, but the RM was not entirely clear in making this point.
26690 RM References: 3.02.03 (6) 6.06 (6)
26693 @geindex AI-0003 (Ada 2012 feature)
26699 @emph{AI-0003 Qualified expressions as names (2010-07-11)}
26701 In Ada 2012, a qualified expression is considered to be syntactically a name,
26702 meaning that constructs such as @code{A'(F(X)).B} are now legal. This is
26703 useful in disambiguating some cases of overloading.
26705 RM References: 3.03 (11) 3.03 (21) 4.01 (2) 4.04 (7) 4.07 (3)
26709 @geindex AI-0120 (Ada 2012 feature)
26715 @emph{AI-0120 Constant instance of protected object (0000-00-00)}
26717 This is an RM editorial change only. The section that lists objects that are
26718 constant failed to include the current instance of a protected object
26719 within a protected function. This has always been treated as a constant
26722 RM References: 3.03 (21)
26725 @geindex AI-0008 (Ada 2012 feature)
26731 @emph{AI-0008 General access to constrained objects (0000-00-00)}
26733 The wording in the RM implied that if you have a general access to a
26734 constrained object, it could be used to modify the discriminants. This was
26735 obviously not intended. @code{Constraint_Error} should be raised, and GNAT
26736 has always done so in this situation.
26738 RM References: 3.03 (23) 3.10.02 (26/2) 4.01 (9) 6.04.01 (17) 8.05.01 (5/2)
26741 @geindex AI-0093 (Ada 2012 feature)
26747 @emph{AI-0093 Additional rules use immutably limited (0000-00-00)}
26749 This is an editorial change only, to make more widespread use of the Ada 2012
26750 'immutably limited'.
26752 RM References: 3.03 (23.4/3)
26755 @geindex AI-0096 (Ada 2012 feature)
26761 @emph{AI-0096 Deriving from formal private types (2010-07-20)}
26763 In general it is illegal for a type derived from a formal limited type to be
26764 nonlimited. This AI makes an exception to this rule: derivation is legal
26765 if it appears in the private part of the generic, and the formal type is not
26766 tagged. If the type is tagged, the legality check must be applied to the
26767 private part of the package.
26769 RM References: 3.04 (5.1/2) 6.02 (7)
26772 @geindex AI-0181 (Ada 2012 feature)
26778 @emph{AI-0181 Soft hyphen is a non-graphic character (2010-07-23)}
26780 From Ada 2005 on, soft hyphen is considered a non-graphic character, which
26781 means that it has a special name (@code{SOFT_HYPHEN}) in conjunction with the
26782 @code{Image} and @code{Value} attributes for the character types. Strictly
26783 speaking this is an inconsistency with Ada 95, but in practice the use of
26784 these attributes is so obscure that it will not cause problems.
26786 RM References: 3.05.02 (2/2) A.01 (35/2) A.03.03 (21)
26789 @geindex AI-0182 (Ada 2012 feature)
26795 @emph{AI-0182 Additional forms for} @code{Character'Value} @emph{(0000-00-00)}
26797 This AI allows @code{Character'Value} to accept the string @code{'?'} where
26798 @code{?} is any character including non-graphic control characters. GNAT has
26799 always accepted such strings. It also allows strings such as
26800 @code{HEX_00000041} to be accepted, but GNAT does not take advantage of this
26801 permission and raises @code{Constraint_Error}, as is certainly still
26804 RM References: 3.05 (56/2)
26807 @geindex AI-0214 (Ada 2012 feature)
26813 @emph{AI-0214 Defaulted discriminants for limited tagged (2010-10-01)}
26815 Ada 2012 relaxes the restriction that forbids discriminants of tagged types
26816 to have default expressions by allowing them when the type is limited. It
26817 is often useful to define a default value for a discriminant even though
26818 it can't be changed by assignment.
26820 RM References: 3.07 (9.1/2) 3.07.02 (3)
26823 @geindex AI-0102 (Ada 2012 feature)
26829 @emph{AI-0102 Some implicit conversions are illegal (0000-00-00)}
26831 It is illegal to assign an anonymous access constant to an anonymous access
26832 variable. The RM did not have a clear rule to prevent this, but GNAT has
26833 always generated an error for this usage.
26835 RM References: 3.07 (16) 3.07.01 (9) 6.04.01 (6) 8.06 (27/2)
26838 @geindex AI-0158 (Ada 2012 feature)
26844 @emph{AI-0158 Generalizing membership tests (2010-09-16)}
26846 This AI extends the syntax of membership tests to simplify complex conditions
26847 that can be expressed as membership in a subset of values of any type. It
26848 introduces syntax for a list of expressions that may be used in loop contexts
26851 RM References: 3.08.01 (5) 4.04 (3) 4.05.02 (3) 4.05.02 (5) 4.05.02 (27)
26854 @geindex AI-0173 (Ada 2012 feature)
26860 @emph{AI-0173 Testing if tags represent abstract types (2010-07-03)}
26862 The function @code{Ada.Tags.Type_Is_Abstract} returns @code{True} if invoked
26863 with the tag of an abstract type, and @code{False} otherwise.
26865 RM References: 3.09 (7.4/2) 3.09 (12.4/2)
26868 @geindex AI-0076 (Ada 2012 feature)
26874 @emph{AI-0076 function with controlling result (0000-00-00)}
26876 This is an editorial change only. The RM defines calls with controlling
26877 results, but uses the term 'function with controlling result' without an
26878 explicit definition.
26880 RM References: 3.09.02 (2/2)
26883 @geindex AI-0126 (Ada 2012 feature)
26889 @emph{AI-0126 Dispatching with no declared operation (0000-00-00)}
26891 This AI clarifies dispatching rules, and simply confirms that dispatching
26892 executes the operation of the parent type when there is no explicitly or
26893 implicitly declared operation for the descendant type. This has always been
26894 the case in all versions of GNAT.
26896 RM References: 3.09.02 (20/2) 3.09.02 (20.1/2) 3.09.02 (20.2/2)
26899 @geindex AI-0097 (Ada 2012 feature)
26905 @emph{AI-0097 Treatment of abstract null extension (2010-07-19)}
26907 The RM as written implied that in some cases it was possible to create an
26908 object of an abstract type, by having an abstract extension inherit a non-
26909 abstract constructor from its parent type. This mistake has been corrected
26910 in GNAT and in the RM, and this construct is now illegal.
26912 RM References: 3.09.03 (4/2)
26915 @geindex AI-0203 (Ada 2012 feature)
26921 @emph{AI-0203 Extended return cannot be abstract (0000-00-00)}
26923 A return_subtype_indication cannot denote an abstract subtype. GNAT has never
26924 permitted such usage.
26926 RM References: 3.09.03 (8/3)
26929 @geindex AI-0198 (Ada 2012 feature)
26935 @emph{AI-0198 Inheriting abstract operators (0000-00-00)}
26937 This AI resolves a conflict between two rules involving inherited abstract
26938 operations and predefined operators. If a derived numeric type inherits
26939 an abstract operator, it overrides the predefined one. This interpretation
26940 was always the one implemented in GNAT.
26942 RM References: 3.09.03 (4/3)
26945 @geindex AI-0073 (Ada 2012 feature)
26951 @emph{AI-0073 Functions returning abstract types (2010-07-10)}
26953 This AI covers a number of issues regarding returning abstract types. In
26954 particular generic functions cannot have abstract result types or access
26955 result types designated an abstract type. There are some other cases which
26956 are detailed in the AI. Note that this binding interpretation has not been
26957 retrofitted to operate before Ada 2012 mode, since it caused a significant
26958 number of regressions.
26960 RM References: 3.09.03 (8) 3.09.03 (10) 6.05 (8/2)
26963 @geindex AI-0070 (Ada 2012 feature)
26969 @emph{AI-0070 Elaboration of interface types (0000-00-00)}
26971 This is an editorial change only, there are no testable consequences short of
26972 checking for the absence of generated code for an interface declaration.
26974 RM References: 3.09.04 (18/2)
26977 @geindex AI-0208 (Ada 2012 feature)
26983 @emph{AI-0208 Characteristics of incomplete views (0000-00-00)}
26985 The wording in the Ada 2005 RM concerning characteristics of incomplete views
26986 was incorrect and implied that some programs intended to be legal were now
26987 illegal. GNAT had never considered such programs illegal, so it has always
26988 implemented the intent of this AI.
26990 RM References: 3.10.01 (2.4/2) 3.10.01 (2.6/2)
26993 @geindex AI-0162 (Ada 2012 feature)
26999 @emph{AI-0162 Incomplete type completed by partial view (2010-09-15)}
27001 Incomplete types are made more useful by allowing them to be completed by
27002 private types and private extensions.
27004 RM References: 3.10.01 (2.5/2) 3.10.01 (2.6/2) 3.10.01 (3) 3.10.01 (4/2)
27007 @geindex AI-0098 (Ada 2012 feature)
27013 @emph{AI-0098 Anonymous subprogram access restrictions (0000-00-00)}
27015 An unintentional omission in the RM implied some inconsistent restrictions on
27016 the use of anonymous access to subprogram values. These restrictions were not
27017 intentional, and have never been enforced by GNAT.
27019 RM References: 3.10.01 (6) 3.10.01 (9.2/2)
27022 @geindex AI-0199 (Ada 2012 feature)
27028 @emph{AI-0199 Aggregate with anonymous access components (2010-07-14)}
27030 A choice list in a record aggregate can include several components of
27031 (distinct) anonymous access types as long as they have matching designated
27034 RM References: 4.03.01 (16)
27037 @geindex AI-0220 (Ada 2012 feature)
27043 @emph{AI-0220 Needed components for aggregates (0000-00-00)}
27045 This AI addresses a wording problem in the RM that appears to permit some
27046 complex cases of aggregates with nonstatic discriminants. GNAT has always
27047 implemented the intended semantics.
27049 RM References: 4.03.01 (17)
27052 @geindex AI-0147 (Ada 2012 feature)
27058 @emph{AI-0147 Conditional expressions (2009-03-29)}
27060 Conditional expressions are permitted. The form of such an expression is:
27063 (if expr then expr @{elsif expr then expr@} [else expr])
27066 The parentheses can be omitted in contexts where parentheses are present
27067 anyway, such as subprogram arguments and pragma arguments. If the @strong{else}
27068 clause is omitted, @strong{else} @emph{True} is assumed;
27069 thus @code{(if A then B)} is a way to conveniently represent
27070 @emph{(A implies B)} in standard logic.
27072 RM References: 4.03.03 (15) 4.04 (1) 4.04 (7) 4.05.07 (0) 4.07 (2)
27073 4.07 (3) 4.09 (12) 4.09 (33) 5.03 (3) 5.03 (4) 7.05 (2.1/2)
27076 @geindex AI-0037 (Ada 2012 feature)
27082 @emph{AI-0037 Out-of-range box associations in aggregate (0000-00-00)}
27084 This AI confirms that an association of the form @code{Indx => <>} in an
27085 array aggregate must raise @code{Constraint_Error} if @code{Indx}
27086 is out of range. The RM specified a range check on other associations, but
27087 not when the value of the association was defaulted. GNAT has always inserted
27088 a constraint check on the index value.
27090 RM References: 4.03.03 (29)
27093 @geindex AI-0123 (Ada 2012 feature)
27099 @emph{AI-0123 Composability of equality (2010-04-13)}
27101 Equality of untagged record composes, so that the predefined equality for a
27102 composite type that includes a component of some untagged record type
27103 @code{R} uses the equality operation of @code{R} (which may be user-defined
27104 or predefined). This makes the behavior of untagged records identical to that
27105 of tagged types in this respect.
27107 This change is an incompatibility with previous versions of Ada, but it
27108 corrects a non-uniformity that was often a source of confusion. Analysis of
27109 a large number of industrial programs indicates that in those rare cases
27110 where a composite type had an untagged record component with a user-defined
27111 equality, either there was no use of the composite equality, or else the code
27112 expected the same composability as for tagged types, and thus had a bug that
27113 would be fixed by this change.
27115 RM References: 4.05.02 (9.7/2) 4.05.02 (14) 4.05.02 (15) 4.05.02 (24)
27119 @geindex AI-0088 (Ada 2012 feature)
27125 @emph{AI-0088 The value of exponentiation (0000-00-00)}
27127 This AI clarifies the equivalence rule given for the dynamic semantics of
27128 exponentiation: the value of the operation can be obtained by repeated
27129 multiplication, but the operation can be implemented otherwise (for example
27130 using the familiar divide-by-two-and-square algorithm, even if this is less
27131 accurate), and does not imply repeated reads of a volatile base.
27133 RM References: 4.05.06 (11)
27136 @geindex AI-0188 (Ada 2012 feature)
27142 @emph{AI-0188 Case expressions (2010-01-09)}
27144 Case expressions are permitted. This allows use of constructs such as:
27147 X := (case Y is when 1 => 2, when 2 => 3, when others => 31)
27150 RM References: 4.05.07 (0) 4.05.08 (0) 4.09 (12) 4.09 (33)
27153 @geindex AI-0104 (Ada 2012 feature)
27159 @emph{AI-0104 Null exclusion and uninitialized allocator (2010-07-15)}
27161 The assignment @code{Ptr := new not null Some_Ptr;} will raise
27162 @code{Constraint_Error} because the default value of the allocated object is
27163 @strong{null}. This useless construct is illegal in Ada 2012.
27165 RM References: 4.08 (2)
27168 @geindex AI-0157 (Ada 2012 feature)
27174 @emph{AI-0157 Allocation/Deallocation from empty pool (2010-07-11)}
27176 Allocation and Deallocation from an empty storage pool (i.e. allocation or
27177 deallocation of a pointer for which a static storage size clause of zero
27178 has been given) is now illegal and is detected as such. GNAT
27179 previously gave a warning but not an error.
27181 RM References: 4.08 (5.3/2) 13.11.02 (4) 13.11.02 (17)
27184 @geindex AI-0179 (Ada 2012 feature)
27190 @emph{AI-0179 Statement not required after label (2010-04-10)}
27192 It is not necessary to have a statement following a label, so a label
27193 can appear at the end of a statement sequence without the need for putting a
27194 null statement afterwards, but it is not allowable to have only labels and
27195 no real statements in a statement sequence.
27197 RM References: 5.01 (2)
27200 @geindex AI-0139-2 (Ada 2012 feature)
27206 @emph{AI-0139-2 Syntactic sugar for iterators (2010-09-29)}
27208 The new syntax for iterating over arrays and containers is now implemented.
27209 Iteration over containers is for now limited to read-only iterators. Only
27210 default iterators are supported, with the syntax: @code{for Elem of C}.
27212 RM References: 5.05
27215 @geindex AI-0134 (Ada 2012 feature)
27221 @emph{AI-0134 Profiles must match for full conformance (0000-00-00)}
27223 For full conformance, the profiles of anonymous-access-to-subprogram
27224 parameters must match. GNAT has always enforced this rule.
27226 RM References: 6.03.01 (18)
27229 @geindex AI-0207 (Ada 2012 feature)
27235 @emph{AI-0207 Mode conformance and access constant (0000-00-00)}
27237 This AI confirms that access_to_constant indication must match for mode
27238 conformance. This was implemented in GNAT when the qualifier was originally
27239 introduced in Ada 2005.
27241 RM References: 6.03.01 (16/2)
27244 @geindex AI-0046 (Ada 2012 feature)
27250 @emph{AI-0046 Null exclusion match for full conformance (2010-07-17)}
27252 For full conformance, in the case of access parameters, the null exclusion
27253 must match (either both or neither must have @code{not null}).
27255 RM References: 6.03.02 (18)
27258 @geindex AI-0118 (Ada 2012 feature)
27264 @emph{AI-0118 The association of parameter associations (0000-00-00)}
27266 This AI clarifies the rules for named associations in subprogram calls and
27267 generic instantiations. The rules have been in place since Ada 83.
27269 RM References: 6.04.01 (2) 12.03 (9)
27272 @geindex AI-0196 (Ada 2012 feature)
27278 @emph{AI-0196 Null exclusion tests for out parameters (0000-00-00)}
27280 Null exclusion checks are not made for @code{out} parameters when
27281 evaluating the actual parameters. GNAT has never generated these checks.
27283 RM References: 6.04.01 (13)
27286 @geindex AI-0015 (Ada 2012 feature)
27292 @emph{AI-0015 Constant return objects (0000-00-00)}
27294 The return object declared in an @emph{extended_return_statement} may be
27295 declared constant. This was always intended, and GNAT has always allowed it.
27297 RM References: 6.05 (2.1/2) 3.03 (10/2) 3.03 (21) 6.05 (5/2)
27301 @geindex AI-0032 (Ada 2012 feature)
27307 @emph{AI-0032 Extended return for class-wide functions (0000-00-00)}
27309 If a function returns a class-wide type, the object of an extended return
27310 statement can be declared with a specific type that is covered by the class-
27311 wide type. This has been implemented in GNAT since the introduction of
27312 extended returns. Note AI-0103 complements this AI by imposing matching
27313 rules for constrained return types.
27315 RM References: 6.05 (5.2/2) 6.05 (5.3/2) 6.05 (5.6/2) 6.05 (5.8/2)
27319 @geindex AI-0103 (Ada 2012 feature)
27325 @emph{AI-0103 Static matching for extended return (2010-07-23)}
27327 If the return subtype of a function is an elementary type or a constrained
27328 type, the subtype indication in an extended return statement must match
27329 statically this return subtype.
27331 RM References: 6.05 (5.2/2)
27334 @geindex AI-0058 (Ada 2012 feature)
27340 @emph{AI-0058 Abnormal completion of an extended return (0000-00-00)}
27342 The RM had some incorrect wording implying wrong treatment of abnormal
27343 completion in an extended return. GNAT has always implemented the intended
27344 correct semantics as described by this AI.
27346 RM References: 6.05 (22/2)
27349 @geindex AI-0050 (Ada 2012 feature)
27355 @emph{AI-0050 Raising Constraint_Error early for function call (0000-00-00)}
27357 The implementation permissions for raising @code{Constraint_Error} early on a function call
27358 when it was clear an exception would be raised were over-permissive and allowed
27359 mishandling of discriminants in some cases. GNAT did
27360 not take advantage of these incorrect permissions in any case.
27362 RM References: 6.05 (24/2)
27365 @geindex AI-0125 (Ada 2012 feature)
27371 @emph{AI-0125 Nonoverridable operations of an ancestor (2010-09-28)}
27373 In Ada 2012, the declaration of a primitive operation of a type extension
27374 or private extension can also override an inherited primitive that is not
27375 visible at the point of this declaration.
27377 RM References: 7.03.01 (6) 8.03 (23) 8.03.01 (5/2) 8.03.01 (6/2)
27380 @geindex AI-0062 (Ada 2012 feature)
27386 @emph{AI-0062 Null exclusions and deferred constants (0000-00-00)}
27388 A full constant may have a null exclusion even if its associated deferred
27389 constant does not. GNAT has always allowed this.
27391 RM References: 7.04 (6/2) 7.04 (7.1/2)
27394 @geindex AI-0178 (Ada 2012 feature)
27400 @emph{AI-0178 Incomplete views are limited (0000-00-00)}
27402 This AI clarifies the role of incomplete views and plugs an omission in the
27403 RM. GNAT always correctly restricted the use of incomplete views and types.
27405 RM References: 7.05 (3/2) 7.05 (6/2)
27408 @geindex AI-0087 (Ada 2012 feature)
27414 @emph{AI-0087 Actual for formal nonlimited derived type (2010-07-15)}
27416 The actual for a formal nonlimited derived type cannot be limited. In
27417 particular, a formal derived type that extends a limited interface but which
27418 is not explicitly limited cannot be instantiated with a limited type.
27420 RM References: 7.05 (5/2) 12.05.01 (5.1/2)
27423 @geindex AI-0099 (Ada 2012 feature)
27429 @emph{AI-0099 Tag determines whether finalization needed (0000-00-00)}
27431 This AI clarifies that 'needs finalization' is part of dynamic semantics,
27432 and therefore depends on the run-time characteristics of an object (i.e. its
27433 tag) and not on its nominal type. As the AI indicates: "we do not expect
27434 this to affect any implementation'@w{'}.
27436 RM References: 7.06.01 (6) 7.06.01 (7) 7.06.01 (8) 7.06.01 (9/2)
27439 @geindex AI-0064 (Ada 2012 feature)
27445 @emph{AI-0064 Redundant finalization rule (0000-00-00)}
27447 This is an editorial change only. The intended behavior is already checked
27448 by an existing ACATS test, which GNAT has always executed correctly.
27450 RM References: 7.06.01 (17.1/1)
27453 @geindex AI-0026 (Ada 2012 feature)
27459 @emph{AI-0026 Missing rules for Unchecked_Union (2010-07-07)}
27461 Record representation clauses concerning Unchecked_Union types cannot mention
27462 the discriminant of the type. The type of a component declared in the variant
27463 part of an Unchecked_Union cannot be controlled, have controlled components,
27464 nor have protected or task parts. If an Unchecked_Union type is declared
27465 within the body of a generic unit or its descendants, then the type of a
27466 component declared in the variant part cannot be a formal private type or a
27467 formal private extension declared within the same generic unit.
27469 RM References: 7.06 (9.4/2) B.03.03 (9/2) B.03.03 (10/2)
27472 @geindex AI-0205 (Ada 2012 feature)
27478 @emph{AI-0205 Extended return declares visible name (0000-00-00)}
27480 This AI corrects a simple omission in the RM. Return objects have always
27481 been visible within an extended return statement.
27483 RM References: 8.03 (17)
27486 @geindex AI-0042 (Ada 2012 feature)
27492 @emph{AI-0042 Overriding versus implemented-by (0000-00-00)}
27494 This AI fixes a wording gap in the RM. An operation of a synchronized
27495 interface can be implemented by a protected or task entry, but the abstract
27496 operation is not being overridden in the usual sense, and it must be stated
27497 separately that this implementation is legal. This has always been the case
27500 RM References: 9.01 (9.2/2) 9.04 (11.1/2)
27503 @geindex AI-0030 (Ada 2012 feature)
27509 @emph{AI-0030 Requeue on synchronized interfaces (2010-07-19)}
27511 Requeue is permitted to a protected, synchronized or task interface primitive
27512 providing it is known that the overriding operation is an entry. Otherwise
27513 the requeue statement has the same effect as a procedure call. Use of pragma
27514 @code{Implemented} provides a way to impose a static requirement on the
27515 overriding operation by adhering to one of the implementation kinds: entry,
27516 protected procedure or any of the above.
27518 RM References: 9.05 (9) 9.05.04 (2) 9.05.04 (3) 9.05.04 (5)
27519 9.05.04 (6) 9.05.04 (7) 9.05.04 (12)
27522 @geindex AI-0201 (Ada 2012 feature)
27528 @emph{AI-0201 Independence of atomic object components (2010-07-22)}
27530 If an Atomic object has a pragma @code{Pack} or a @code{Component_Size}
27531 attribute, then individual components may not be addressable by independent
27532 tasks. However, if the representation clause has no effect (is confirming),
27533 then independence is not compromised. Furthermore, in GNAT, specification of
27534 other appropriately addressable component sizes (e.g. 16 for 8-bit
27535 characters) also preserves independence. GNAT now gives very clear warnings
27536 both for the declaration of such a type, and for any assignment to its components.
27538 RM References: 9.10 (1/3) C.06 (22/2) C.06 (23/2)
27541 @geindex AI-0009 (Ada 2012 feature)
27547 @emph{AI-0009 Pragma Independent[_Components] (2010-07-23)}
27549 This AI introduces the new pragmas @code{Independent} and
27550 @code{Independent_Components},
27551 which control guaranteeing independence of access to objects and components.
27552 The AI also requires independence not unaffected by confirming rep clauses.
27554 RM References: 9.10 (1) 13.01 (15/1) 13.02 (9) 13.03 (13) C.06 (2)
27555 C.06 (4) C.06 (6) C.06 (9) C.06 (13) C.06 (14)
27558 @geindex AI-0072 (Ada 2012 feature)
27564 @emph{AI-0072 Task signalling using 'Terminated (0000-00-00)}
27566 This AI clarifies that task signalling for reading @code{'Terminated} only
27567 occurs if the result is True. GNAT semantics has always been consistent with
27568 this notion of task signalling.
27570 RM References: 9.10 (6.1/1)
27573 @geindex AI-0108 (Ada 2012 feature)
27579 @emph{AI-0108 Limited incomplete view and discriminants (0000-00-00)}
27581 This AI confirms that an incomplete type from a limited view does not have
27582 discriminants. This has always been the case in GNAT.
27584 RM References: 10.01.01 (12.3/2)
27587 @geindex AI-0129 (Ada 2012 feature)
27593 @emph{AI-0129 Limited views and incomplete types (0000-00-00)}
27595 This AI clarifies the description of limited views: a limited view of a
27596 package includes only one view of a type that has an incomplete declaration
27597 and a full declaration (there is no possible ambiguity in a client package).
27598 This AI also fixes an omission: a nested package in the private part has no
27599 limited view. GNAT always implemented this correctly.
27601 RM References: 10.01.01 (12.2/2) 10.01.01 (12.3/2)
27604 @geindex AI-0077 (Ada 2012 feature)
27610 @emph{AI-0077 Limited withs and scope of declarations (0000-00-00)}
27612 This AI clarifies that a declaration does not include a context clause,
27613 and confirms that it is illegal to have a context in which both a limited
27614 and a nonlimited view of a package are accessible. Such double visibility
27615 was always rejected by GNAT.
27617 RM References: 10.01.02 (12/2) 10.01.02 (21/2) 10.01.02 (22/2)
27620 @geindex AI-0122 (Ada 2012 feature)
27626 @emph{AI-0122 Private with and children of generics (0000-00-00)}
27628 This AI clarifies the visibility of private children of generic units within
27629 instantiations of a parent. GNAT has always handled this correctly.
27631 RM References: 10.01.02 (12/2)
27634 @geindex AI-0040 (Ada 2012 feature)
27640 @emph{AI-0040 Limited with clauses on descendant (0000-00-00)}
27642 This AI confirms that a limited with clause in a child unit cannot name
27643 an ancestor of the unit. This has always been checked in GNAT.
27645 RM References: 10.01.02 (20/2)
27648 @geindex AI-0132 (Ada 2012 feature)
27654 @emph{AI-0132 Placement of library unit pragmas (0000-00-00)}
27656 This AI fills a gap in the description of library unit pragmas. The pragma
27657 clearly must apply to a library unit, even if it does not carry the name
27658 of the enclosing unit. GNAT has always enforced the required check.
27660 RM References: 10.01.05 (7)
27663 @geindex AI-0034 (Ada 2012 feature)
27669 @emph{AI-0034 Categorization of limited views (0000-00-00)}
27671 The RM makes certain limited with clauses illegal because of categorization
27672 considerations, when the corresponding normal with would be legal. This is
27673 not intended, and GNAT has always implemented the recommended behavior.
27675 RM References: 10.02.01 (11/1) 10.02.01 (17/2)
27678 @geindex AI-0035 (Ada 2012 feature)
27684 @emph{AI-0035 Inconsistencies with Pure units (0000-00-00)}
27686 This AI remedies some inconsistencies in the legality rules for Pure units.
27687 Derived access types are legal in a pure unit (on the assumption that the
27688 rule for a zero storage pool size has been enforced on the ancestor type).
27689 The rules are enforced in generic instances and in subunits. GNAT has always
27690 implemented the recommended behavior.
27692 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)
27695 @geindex AI-0219 (Ada 2012 feature)
27701 @emph{AI-0219 Pure permissions and limited parameters (2010-05-25)}
27703 This AI refines the rules for the cases with limited parameters which do not
27704 allow the implementations to omit 'redundant'. GNAT now properly conforms
27705 to the requirements of this binding interpretation.
27707 RM References: 10.02.01 (18/2)
27710 @geindex AI-0043 (Ada 2012 feature)
27716 @emph{AI-0043 Rules about raising exceptions (0000-00-00)}
27718 This AI covers various omissions in the RM regarding the raising of
27719 exceptions. GNAT has always implemented the intended semantics.
27721 RM References: 11.04.01 (10.1/2) 11 (2)
27724 @geindex AI-0200 (Ada 2012 feature)
27730 @emph{AI-0200 Mismatches in formal package declarations (0000-00-00)}
27732 This AI plugs a gap in the RM which appeared to allow some obviously intended
27733 illegal instantiations. GNAT has never allowed these instantiations.
27735 RM References: 12.07 (16)
27738 @geindex AI-0112 (Ada 2012 feature)
27744 @emph{AI-0112 Detection of duplicate pragmas (2010-07-24)}
27746 This AI concerns giving names to various representation aspects, but the
27747 practical effect is simply to make the use of duplicate
27748 @code{Atomic[_Components]},
27749 @code{Volatile[_Components]}, and
27750 @code{Independent[_Components]} pragmas illegal, and GNAT
27751 now performs this required check.
27753 RM References: 13.01 (8)
27756 @geindex AI-0106 (Ada 2012 feature)
27762 @emph{AI-0106 No representation pragmas on generic formals (0000-00-00)}
27764 The RM appeared to allow representation pragmas on generic formal parameters,
27765 but this was not intended, and GNAT has never permitted this usage.
27767 RM References: 13.01 (9.1/1)
27770 @geindex AI-0012 (Ada 2012 feature)
27776 @emph{AI-0012 Pack/Component_Size for aliased/atomic (2010-07-15)}
27778 It is now illegal to give an inappropriate component size or a pragma
27779 @code{Pack} that attempts to change the component size in the case of atomic
27780 or aliased components. Previously GNAT ignored such an attempt with a
27783 RM References: 13.02 (6.1/2) 13.02 (7) C.06 (10) C.06 (11) C.06 (21)
27786 @geindex AI-0039 (Ada 2012 feature)
27792 @emph{AI-0039 Stream attributes cannot be dynamic (0000-00-00)}
27794 The RM permitted the use of dynamic expressions (such as @code{ptr.all})`
27795 for stream attributes, but these were never useful and are now illegal. GNAT
27796 has always regarded such expressions as illegal.
27798 RM References: 13.03 (4) 13.03 (6) 13.13.02 (38/2)
27801 @geindex AI-0095 (Ada 2012 feature)
27807 @emph{AI-0095 Address of intrinsic subprograms (0000-00-00)}
27809 The prefix of @code{'Address} cannot statically denote a subprogram with
27810 convention @code{Intrinsic}. The use of the @code{Address} attribute raises
27811 @code{Program_Error} if the prefix denotes a subprogram with convention
27814 RM References: 13.03 (11/1)
27817 @geindex AI-0116 (Ada 2012 feature)
27823 @emph{AI-0116 Alignment of class-wide objects (0000-00-00)}
27825 This AI requires that the alignment of a class-wide object be no greater
27826 than the alignment of any type in the class. GNAT has always followed this
27829 RM References: 13.03 (29) 13.11 (16)
27832 @geindex AI-0146 (Ada 2012 feature)
27838 @emph{AI-0146 Type invariants (2009-09-21)}
27840 Type invariants may be specified for private types using the aspect notation.
27841 Aspect @code{Type_Invariant} may be specified for any private type,
27842 @code{Type_Invariant'Class} can
27843 only be specified for tagged types, and is inherited by any descendent of the
27844 tagged types. The invariant is a boolean expression that is tested for being
27845 true in the following situations: conversions to the private type, object
27846 declarations for the private type that are default initialized, and
27847 [@strong{in}] @strong{out}
27848 parameters and returned result on return from any primitive operation for
27849 the type that is visible to a client.
27850 GNAT defines the synonyms @code{Invariant} for @code{Type_Invariant} and
27851 @code{Invariant'Class} for @code{Type_Invariant'Class}.
27853 RM References: 13.03.03 (00)
27856 @geindex AI-0078 (Ada 2012 feature)
27862 @emph{AI-0078 Relax Unchecked_Conversion alignment rules (0000-00-00)}
27864 In Ada 2012, compilers are required to support unchecked conversion where the
27865 target alignment is a multiple of the source alignment. GNAT always supported
27866 this case (and indeed all cases of differing alignments, doing copies where
27867 required if the alignment was reduced).
27869 RM References: 13.09 (7)
27872 @geindex AI-0195 (Ada 2012 feature)
27878 @emph{AI-0195 Invalid value handling is implementation defined (2010-07-03)}
27880 The handling of invalid values is now designated to be implementation
27881 defined. This is a documentation change only, requiring Annex M in the GNAT
27882 Reference Manual to document this handling.
27883 In GNAT, checks for invalid values are made
27884 only when necessary to avoid erroneous behavior. Operations like assignments
27885 which cannot cause erroneous behavior ignore the possibility of invalid
27886 values and do not do a check. The date given above applies only to the
27887 documentation change, this behavior has always been implemented by GNAT.
27889 RM References: 13.09.01 (10)
27892 @geindex AI-0193 (Ada 2012 feature)
27898 @emph{AI-0193 Alignment of allocators (2010-09-16)}
27900 This AI introduces a new attribute @code{Max_Alignment_For_Allocation},
27901 analogous to @code{Max_Size_In_Storage_Elements}, but for alignment instead
27904 RM References: 13.11 (16) 13.11 (21) 13.11.01 (0) 13.11.01 (1)
27905 13.11.01 (2) 13.11.01 (3)
27908 @geindex AI-0177 (Ada 2012 feature)
27914 @emph{AI-0177 Parameterized expressions (2010-07-10)}
27916 The new Ada 2012 notion of parameterized expressions is implemented. The form
27920 function-specification is (expression)
27923 This is exactly equivalent to the
27924 corresponding function body that returns the expression, but it can appear
27925 in a package spec. Note that the expression must be parenthesized.
27927 RM References: 13.11.01 (3/2)
27930 @geindex AI-0033 (Ada 2012 feature)
27936 @emph{AI-0033 Attach/Interrupt_Handler in generic (2010-07-24)}
27938 Neither of these two pragmas may appear within a generic template, because
27939 the generic might be instantiated at other than the library level.
27941 RM References: 13.11.02 (16) C.03.01 (7/2) C.03.01 (8/2)
27944 @geindex AI-0161 (Ada 2012 feature)
27950 @emph{AI-0161 Restriction No_Default_Stream_Attributes (2010-09-11)}
27952 A new restriction @code{No_Default_Stream_Attributes} prevents the use of any
27953 of the default stream attributes for elementary types. If this restriction is
27954 in force, then it is necessary to provide explicit subprograms for any
27955 stream attributes used.
27957 RM References: 13.12.01 (4/2) 13.13.02 (40/2) 13.13.02 (52/2)
27960 @geindex AI-0194 (Ada 2012 feature)
27966 @emph{AI-0194 Value of Stream_Size attribute (0000-00-00)}
27968 The @code{Stream_Size} attribute returns the default number of bits in the
27969 stream representation of the given type.
27970 This value is not affected by the presence
27971 of stream subprogram attributes for the type. GNAT has always implemented
27972 this interpretation.
27974 RM References: 13.13.02 (1.2/2)
27977 @geindex AI-0109 (Ada 2012 feature)
27983 @emph{AI-0109 Redundant check in S'Class'Input (0000-00-00)}
27985 This AI is an editorial change only. It removes the need for a tag check
27986 that can never fail.
27988 RM References: 13.13.02 (34/2)
27991 @geindex AI-0007 (Ada 2012 feature)
27997 @emph{AI-0007 Stream read and private scalar types (0000-00-00)}
27999 The RM as written appeared to limit the possibilities of declaring read
28000 attribute procedures for private scalar types. This limitation was not
28001 intended, and has never been enforced by GNAT.
28003 RM References: 13.13.02 (50/2) 13.13.02 (51/2)
28006 @geindex AI-0065 (Ada 2012 feature)
28012 @emph{AI-0065 Remote access types and external streaming (0000-00-00)}
28014 This AI clarifies the fact that all remote access types support external
28015 streaming. This fixes an obvious oversight in the definition of the
28016 language, and GNAT always implemented the intended correct rules.
28018 RM References: 13.13.02 (52/2)
28021 @geindex AI-0019 (Ada 2012 feature)
28027 @emph{AI-0019 Freezing of primitives for tagged types (0000-00-00)}
28029 The RM suggests that primitive subprograms of a specific tagged type are
28030 frozen when the tagged type is frozen. This would be an incompatible change
28031 and is not intended. GNAT has never attempted this kind of freezing and its
28032 behavior is consistent with the recommendation of this AI.
28034 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)
28037 @geindex AI-0017 (Ada 2012 feature)
28043 @emph{AI-0017 Freezing and incomplete types (0000-00-00)}
28045 So-called 'Taft-amendment types' (i.e., types that are completed in package
28046 bodies) are not frozen by the occurrence of bodies in the
28047 enclosing declarative part. GNAT always implemented this properly.
28049 RM References: 13.14 (3/1)
28052 @geindex AI-0060 (Ada 2012 feature)
28058 @emph{AI-0060 Extended definition of remote access types (0000-00-00)}
28060 This AI extends the definition of remote access types to include access
28061 to limited, synchronized, protected or task class-wide interface types.
28062 GNAT already implemented this extension.
28064 RM References: A (4) E.02.02 (9/1) E.02.02 (9.2/1) E.02.02 (14/2) E.02.02 (18)
28067 @geindex AI-0114 (Ada 2012 feature)
28073 @emph{AI-0114 Classification of letters (0000-00-00)}
28075 The code points 170 (@code{FEMININE ORDINAL INDICATOR}),
28076 181 (@code{MICRO SIGN}), and
28077 186 (@code{MASCULINE ORDINAL INDICATOR}) are technically considered
28078 lower case letters by Unicode.
28079 However, they are not allowed in identifiers, and they
28080 return @code{False} to @code{Ada.Characters.Handling.Is_Letter/Is_Lower}.
28081 This behavior is consistent with that defined in Ada 95.
28083 RM References: A.03.02 (59) A.04.06 (7)
28086 @geindex AI-0185 (Ada 2012 feature)
28092 @emph{AI-0185 Ada.Wide_[Wide_]Characters.Handling (2010-07-06)}
28094 Two new packages @code{Ada.Wide_[Wide_]Characters.Handling} provide
28095 classification functions for @code{Wide_Character} and
28096 @code{Wide_Wide_Character}, as well as providing
28097 case folding routines for @code{Wide_[Wide_]Character} and
28098 @code{Wide_[Wide_]String}.
28100 RM References: A.03.05 (0) A.03.06 (0)
28103 @geindex AI-0031 (Ada 2012 feature)
28109 @emph{AI-0031 Add From parameter to Find_Token (2010-07-25)}
28111 A new version of @code{Find_Token} is added to all relevant string packages,
28112 with an extra parameter @code{From}. Instead of starting at the first
28113 character of the string, the search for a matching Token starts at the
28114 character indexed by the value of @code{From}.
28115 These procedures are available in all versions of Ada
28116 but if used in versions earlier than Ada 2012 they will generate a warning
28117 that an Ada 2012 subprogram is being used.
28119 RM References: A.04.03 (16) A.04.03 (67) A.04.03 (68/1) A.04.04 (51)
28123 @geindex AI-0056 (Ada 2012 feature)
28129 @emph{AI-0056 Index on null string returns zero (0000-00-00)}
28131 The wording in the Ada 2005 RM implied an incompatible handling of the
28132 @code{Index} functions, resulting in raising an exception instead of
28133 returning zero in some situations.
28134 This was not intended and has been corrected.
28135 GNAT always returned zero, and is thus consistent with this AI.
28137 RM References: A.04.03 (56.2/2) A.04.03 (58.5/2)
28140 @geindex AI-0137 (Ada 2012 feature)
28146 @emph{AI-0137 String encoding package (2010-03-25)}
28148 The packages @code{Ada.Strings.UTF_Encoding}, together with its child
28149 packages, @code{Conversions}, @code{Strings}, @code{Wide_Strings},
28150 and @code{Wide_Wide_Strings} have been
28151 implemented. These packages (whose documentation can be found in the spec
28152 files @code{a-stuten.ads}, @code{a-suenco.ads}, @code{a-suenst.ads},
28153 @code{a-suewst.ads}, @code{a-suezst.ads}) allow encoding and decoding of
28154 @code{String}, @code{Wide_String}, and @code{Wide_Wide_String}
28155 values using UTF coding schemes (including UTF-8, UTF-16LE, UTF-16BE, and
28156 UTF-16), as well as conversions between the different UTF encodings. With
28157 the exception of @code{Wide_Wide_Strings}, these packages are available in
28158 Ada 95 and Ada 2005 mode as well as Ada 2012 mode.
28159 The @code{Wide_Wide_Strings} package
28160 is available in Ada 2005 mode as well as Ada 2012 mode (but not in Ada 95
28161 mode since it uses @code{Wide_Wide_Character}).
28163 RM References: A.04.11
28166 @geindex AI-0038 (Ada 2012 feature)
28172 @emph{AI-0038 Minor errors in Text_IO (0000-00-00)}
28174 These are minor errors in the description on three points. The intent on
28175 all these points has always been clear, and GNAT has always implemented the
28176 correct intended semantics.
28178 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)
28181 @geindex AI-0044 (Ada 2012 feature)
28187 @emph{AI-0044 Restrictions on container instantiations (0000-00-00)}
28189 This AI places restrictions on allowed instantiations of generic containers.
28190 These restrictions are not checked by the compiler, so there is nothing to
28191 change in the implementation. This affects only the RM documentation.
28193 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)
28196 @geindex AI-0127 (Ada 2012 feature)
28202 @emph{AI-0127 Adding Locale Capabilities (2010-09-29)}
28204 This package provides an interface for identifying the current locale.
28206 RM References: A.19 A.19.01 A.19.02 A.19.03 A.19.05 A.19.06
28207 A.19.07 A.19.08 A.19.09 A.19.10 A.19.11 A.19.12 A.19.13
28210 @geindex AI-0002 (Ada 2012 feature)
28216 @emph{AI-0002 Export C with unconstrained arrays (0000-00-00)}
28218 The compiler is not required to support exporting an Ada subprogram with
28219 convention C if there are parameters or a return type of an unconstrained
28220 array type (such as @code{String}). GNAT allows such declarations but
28221 generates warnings. It is possible, but complicated, to write the
28222 corresponding C code and certainly such code would be specific to GNAT and
28225 RM References: B.01 (17) B.03 (62) B.03 (71.1/2)
28228 @geindex AI05-0216 (Ada 2012 feature)
28234 @emph{AI-0216 No_Task_Hierarchy forbids local tasks (0000-00-00)}
28236 It is clearly the intention that @code{No_Task_Hierarchy} is intended to
28237 forbid tasks declared locally within subprograms, or functions returning task
28238 objects, and that is the implementation that GNAT has always provided.
28239 However the language in the RM was not sufficiently clear on this point.
28240 Thus this is a documentation change in the RM only.
28242 RM References: D.07 (3/3)
28245 @geindex AI-0211 (Ada 2012 feature)
28251 @emph{AI-0211 No_Relative_Delays forbids Set_Handler use (2010-07-09)}
28253 The restriction @code{No_Relative_Delays} forbids any calls to the subprogram
28254 @code{Ada.Real_Time.Timing_Events.Set_Handler}.
28256 RM References: D.07 (5) D.07 (10/2) D.07 (10.4/2) D.07 (10.7/2)
28259 @geindex AI-0190 (Ada 2012 feature)
28265 @emph{AI-0190 pragma Default_Storage_Pool (2010-09-15)}
28267 This AI introduces a new pragma @code{Default_Storage_Pool}, which can be
28268 used to control storage pools globally.
28269 In particular, you can force every access
28270 type that is used for allocation (@strong{new}) to have an explicit storage pool,
28271 or you can declare a pool globally to be used for all access types that lack
28274 RM References: D.07 (8)
28277 @geindex AI-0189 (Ada 2012 feature)
28283 @emph{AI-0189 No_Allocators_After_Elaboration (2010-01-23)}
28285 This AI introduces a new restriction @code{No_Allocators_After_Elaboration},
28286 which says that no dynamic allocation will occur once elaboration is
28288 In general this requires a run-time check, which is not required, and which
28289 GNAT does not attempt. But the static cases of allocators in a task body or
28290 in the body of the main program are detected and flagged at compile or bind
28293 RM References: D.07 (19.1/2) H.04 (23.3/2)
28296 @geindex AI-0171 (Ada 2012 feature)
28302 @emph{AI-0171 Pragma CPU and Ravenscar Profile (2010-09-24)}
28304 A new package @code{System.Multiprocessors} is added, together with the
28305 definition of pragma @code{CPU} for controlling task affinity. A new no
28306 dependence restriction, on @code{System.Multiprocessors.Dispatching_Domains},
28307 is added to the Ravenscar profile.
28309 RM References: D.13.01 (4/2) D.16
28312 @geindex AI-0210 (Ada 2012 feature)
28318 @emph{AI-0210 Correct Timing_Events metric (0000-00-00)}
28320 This is a documentation only issue regarding wording of metric requirements,
28321 that does not affect the implementation of the compiler.
28323 RM References: D.15 (24/2)
28326 @geindex AI-0206 (Ada 2012 feature)
28332 @emph{AI-0206 Remote types packages and preelaborate (2010-07-24)}
28334 Remote types packages are now allowed to depend on preelaborated packages.
28335 This was formerly considered illegal.
28337 RM References: E.02.02 (6)
28340 @geindex AI-0152 (Ada 2012 feature)
28346 @emph{AI-0152 Restriction No_Anonymous_Allocators (2010-09-08)}
28348 Restriction @code{No_Anonymous_Allocators} prevents the use of allocators
28349 where the type of the returned value is an anonymous access type.
28351 RM References: H.04 (8/1)
28354 @node Obsolescent Features,Compatibility and Porting Guide,Implementation of Ada 2012 Features,Top
28355 @anchor{gnat_rm/obsolescent_features id1}@anchor{427}@anchor{gnat_rm/obsolescent_features doc}@anchor{428}@anchor{gnat_rm/obsolescent_features obsolescent-features}@anchor{15}
28356 @chapter Obsolescent Features
28359 This chapter describes features that are provided by GNAT, but are
28360 considered obsolescent since there are preferred ways of achieving
28361 the same effect. These features are provided solely for historical
28362 compatibility purposes.
28365 * pragma No_Run_Time::
28366 * pragma Ravenscar::
28367 * pragma Restricted_Run_Time::
28368 * pragma Task_Info::
28369 * package System.Task_Info (s-tasinf.ads): package System Task_Info s-tasinf ads.
28373 @node pragma No_Run_Time,pragma Ravenscar,,Obsolescent Features
28374 @anchor{gnat_rm/obsolescent_features id2}@anchor{429}@anchor{gnat_rm/obsolescent_features pragma-no-run-time}@anchor{42a}
28375 @section pragma No_Run_Time
28378 The pragma @code{No_Run_Time} is used to achieve an affect similar
28379 to the use of the "Zero Foot Print" configurable run time, but without
28380 requiring a specially configured run time. The result of using this
28381 pragma, which must be used for all units in a partition, is to restrict
28382 the use of any language features requiring run-time support code. The
28383 preferred usage is to use an appropriately configured run-time that
28384 includes just those features that are to be made accessible.
28386 @node pragma Ravenscar,pragma Restricted_Run_Time,pragma No_Run_Time,Obsolescent Features
28387 @anchor{gnat_rm/obsolescent_features id3}@anchor{42b}@anchor{gnat_rm/obsolescent_features pragma-ravenscar}@anchor{42c}
28388 @section pragma Ravenscar
28391 The pragma @code{Ravenscar} has exactly the same effect as pragma
28392 @code{Profile (Ravenscar)}. The latter usage is preferred since it
28393 is part of the new Ada 2005 standard.
28395 @node pragma Restricted_Run_Time,pragma Task_Info,pragma Ravenscar,Obsolescent Features
28396 @anchor{gnat_rm/obsolescent_features pragma-restricted-run-time}@anchor{42d}@anchor{gnat_rm/obsolescent_features id4}@anchor{42e}
28397 @section pragma Restricted_Run_Time
28400 The pragma @code{Restricted_Run_Time} has exactly the same effect as
28401 pragma @code{Profile (Restricted)}. The latter usage is
28402 preferred since the Ada 2005 pragma @code{Profile} is intended for
28403 this kind of implementation dependent addition.
28405 @node pragma Task_Info,package System Task_Info s-tasinf ads,pragma Restricted_Run_Time,Obsolescent Features
28406 @anchor{gnat_rm/obsolescent_features pragma-task-info}@anchor{42f}@anchor{gnat_rm/obsolescent_features id5}@anchor{430}
28407 @section pragma Task_Info
28410 The functionality provided by pragma @code{Task_Info} is now part of the
28411 Ada language. The @code{CPU} aspect and the package
28412 @code{System.Multiprocessors} offer a less system-dependent way to specify
28413 task affinity or to query the number of processsors.
28418 pragma Task_Info (EXPRESSION);
28421 This pragma appears within a task definition (like pragma
28422 @code{Priority}) and applies to the task in which it appears. The
28423 argument must be of type @code{System.Task_Info.Task_Info_Type}.
28424 The @code{Task_Info} pragma provides system dependent control over
28425 aspects of tasking implementation, for example, the ability to map
28426 tasks to specific processors. For details on the facilities available
28427 for the version of GNAT that you are using, see the documentation
28428 in the spec of package System.Task_Info in the runtime
28431 @node package System Task_Info s-tasinf ads,,pragma Task_Info,Obsolescent Features
28432 @anchor{gnat_rm/obsolescent_features package-system-task-info}@anchor{431}@anchor{gnat_rm/obsolescent_features package-system-task-info-s-tasinf-ads}@anchor{432}
28433 @section package System.Task_Info (@code{s-tasinf.ads})
28436 This package provides target dependent functionality that is used
28437 to support the @code{Task_Info} pragma. The predefined Ada package
28438 @code{System.Multiprocessors} and the @code{CPU} aspect now provide a
28439 standard replacement for GNAT's @code{Task_Info} functionality.
28441 @node Compatibility and Porting Guide,GNU Free Documentation License,Obsolescent Features,Top
28442 @anchor{gnat_rm/compatibility_and_porting_guide compatibility-and-porting-guide}@anchor{16}@anchor{gnat_rm/compatibility_and_porting_guide doc}@anchor{433}@anchor{gnat_rm/compatibility_and_porting_guide id1}@anchor{434}
28443 @chapter Compatibility and Porting Guide
28446 This chapter presents some guidelines for developing portable Ada code,
28447 describes the compatibility issues that may arise between
28448 GNAT and other Ada compilation systems (including those for Ada 83),
28449 and shows how GNAT can expedite porting
28450 applications developed in other Ada environments.
28453 * Writing Portable Fixed-Point Declarations::
28454 * Compatibility with Ada 83::
28455 * Compatibility between Ada 95 and Ada 2005::
28456 * Implementation-dependent characteristics::
28457 * Compatibility with Other Ada Systems::
28458 * Representation Clauses::
28459 * Compatibility with HP Ada 83::
28463 @node Writing Portable Fixed-Point Declarations,Compatibility with Ada 83,,Compatibility and Porting Guide
28464 @anchor{gnat_rm/compatibility_and_porting_guide id2}@anchor{435}@anchor{gnat_rm/compatibility_and_porting_guide writing-portable-fixed-point-declarations}@anchor{436}
28465 @section Writing Portable Fixed-Point Declarations
28468 The Ada Reference Manual gives an implementation freedom to choose bounds
28469 that are narrower by @code{Small} from the given bounds.
28470 For example, if we write
28473 type F1 is delta 1.0 range -128.0 .. +128.0;
28476 then the implementation is allowed to choose -128.0 .. +127.0 if it
28477 likes, but is not required to do so.
28479 This leads to possible portability problems, so let's have a closer
28480 look at this, and figure out how to avoid these problems.
28482 First, why does this freedom exist, and why would an implementation
28483 take advantage of it? To answer this, take a closer look at the type
28484 declaration for @code{F1} above. If the compiler uses the given bounds,
28485 it would need 9 bits to hold the largest positive value (and typically
28486 that means 16 bits on all machines). But if the implementation chooses
28487 the +127.0 bound then it can fit values of the type in 8 bits.
28489 Why not make the user write +127.0 if that's what is wanted?
28490 The rationale is that if you are thinking of fixed point
28491 as a kind of 'poor man's floating-point', then you don't want
28492 to be thinking about the scaled integers that are used in its
28493 representation. Let's take another example:
28496 type F2 is delta 2.0**(-15) range -1.0 .. +1.0;
28499 Looking at this declaration, it seems casually as though
28500 it should fit in 16 bits, but again that extra positive value
28501 +1.0 has the scaled integer equivalent of 2**15 which is one too
28502 big for signed 16 bits. The implementation can treat this as:
28505 type F2 is delta 2.0**(-15) range -1.0 .. +1.0-(2.0**(-15));
28508 and the Ada language design team felt that this was too annoying
28509 to require. We don't need to debate this decision at this point,
28510 since it is well established (the rule about narrowing the ranges
28513 But the important point is that an implementation is not required
28514 to do this narrowing, so we have a potential portability problem.
28515 We could imagine three types of implementation:
28521 those that narrow the range automatically if they can figure
28522 out that the narrower range will allow storage in a smaller machine unit,
28525 those that will narrow only if forced to by a @code{'Size} clause, and
28528 those that will never narrow.
28531 Now if we are language theoreticians, we can imagine a fourth
28532 approach: to narrow all the time, e.g. to treat
28535 type F3 is delta 1.0 range -10.0 .. +23.0;
28538 as though it had been written:
28541 type F3 is delta 1.0 range -9.0 .. +22.0;
28544 But although technically allowed, such a behavior would be hostile and silly,
28545 and no real compiler would do this. All real compilers will fall into one of
28546 the categories (a), (b) or (c) above.
28548 So, how do you get the compiler to do what you want? The answer is give the
28549 actual bounds you want, and then use a @code{'Small} clause and a
28550 @code{'Size} clause to absolutely pin down what the compiler does.
28551 E.g., for @code{F2} above, we will write:
28554 My_Small : constant := 2.0**(-15);
28555 My_First : constant := -1.0;
28556 My_Last : constant := +1.0 - My_Small;
28558 type F2 is delta My_Small range My_First .. My_Last;
28564 for F2'Small use my_Small;
28565 for F2'Size use 16;
28568 In practice all compilers will do the same thing here and will give you
28569 what you want, so the above declarations are fully portable. If you really
28570 want to play language lawyer and guard against ludicrous behavior by the
28571 compiler you could add
28574 Test1 : constant := 1 / Boolean'Pos (F2'First = My_First);
28575 Test2 : constant := 1 / Boolean'Pos (F2'Last = My_Last);
28578 One or other or both are allowed to be illegal if the compiler is
28579 behaving in a silly manner, but at least the silly compiler will not
28580 get away with silently messing with your (very clear) intentions.
28582 If you follow this scheme you will be guaranteed that your fixed-point
28583 types will be portable.
28585 @node Compatibility with Ada 83,Compatibility between Ada 95 and Ada 2005,Writing Portable Fixed-Point Declarations,Compatibility and Porting Guide
28586 @anchor{gnat_rm/compatibility_and_porting_guide compatibility-with-ada-83}@anchor{437}@anchor{gnat_rm/compatibility_and_porting_guide id3}@anchor{438}
28587 @section Compatibility with Ada 83
28590 @geindex Compatibility (between Ada 83 and Ada 95 / Ada 2005 / Ada 2012)
28592 Ada 95 and the subsequent revisions Ada 2005 and Ada 2012
28593 are highly upwards compatible with Ada 83. In
28594 particular, the design intention was that the difficulties associated
28595 with moving from Ada 83 to later versions of the standard should be no greater
28596 than those that occur when moving from one Ada 83 system to another.
28598 However, there are a number of points at which there are minor
28599 incompatibilities. The @cite{Ada 95 Annotated Reference Manual} contains
28600 full details of these issues as they relate to Ada 95,
28601 and should be consulted for a complete treatment.
28603 following subsections treat the most likely issues to be encountered.
28606 * Legal Ada 83 programs that are illegal in Ada 95::
28607 * More deterministic semantics::
28608 * Changed semantics::
28609 * Other language compatibility issues::
28613 @node Legal Ada 83 programs that are illegal in Ada 95,More deterministic semantics,,Compatibility with Ada 83
28614 @anchor{gnat_rm/compatibility_and_porting_guide id4}@anchor{439}@anchor{gnat_rm/compatibility_and_porting_guide legal-ada-83-programs-that-are-illegal-in-ada-95}@anchor{43a}
28615 @subsection Legal Ada 83 programs that are illegal in Ada 95
28618 Some legal Ada 83 programs are illegal (i.e., they will fail to compile) in
28619 Ada 95 and later versions of the standard:
28625 @emph{Character literals}
28627 Some uses of character literals are ambiguous. Since Ada 95 has introduced
28628 @code{Wide_Character} as a new predefined character type, some uses of
28629 character literals that were legal in Ada 83 are illegal in Ada 95.
28633 for Char in 'A' .. 'Z' loop ... end loop;
28636 The problem is that 'A' and 'Z' could be from either
28637 @code{Character} or @code{Wide_Character}. The simplest correction
28638 is to make the type explicit; e.g.:
28641 for Char in Character range 'A' .. 'Z' loop ... end loop;
28645 @emph{New reserved words}
28647 The identifiers @code{abstract}, @code{aliased}, @code{protected},
28648 @code{requeue}, @code{tagged}, and @code{until} are reserved in Ada 95.
28649 Existing Ada 83 code using any of these identifiers must be edited to
28650 use some alternative name.
28653 @emph{Freezing rules}
28655 The rules in Ada 95 are slightly different with regard to the point at
28656 which entities are frozen, and representation pragmas and clauses are
28657 not permitted past the freeze point. This shows up most typically in
28658 the form of an error message complaining that a representation item
28659 appears too late, and the appropriate corrective action is to move
28660 the item nearer to the declaration of the entity to which it refers.
28662 A particular case is that representation pragmas
28663 cannot be applied to a subprogram body. If necessary, a separate subprogram
28664 declaration must be introduced to which the pragma can be applied.
28667 @emph{Optional bodies for library packages}
28669 In Ada 83, a package that did not require a package body was nevertheless
28670 allowed to have one. This lead to certain surprises in compiling large
28671 systems (situations in which the body could be unexpectedly ignored by the
28672 binder). In Ada 95, if a package does not require a body then it is not
28673 permitted to have a body. To fix this problem, simply remove a redundant
28674 body if it is empty, or, if it is non-empty, introduce a dummy declaration
28675 into the spec that makes the body required. One approach is to add a private
28676 part to the package declaration (if necessary), and define a parameterless
28677 procedure called @code{Requires_Body}, which must then be given a dummy
28678 procedure body in the package body, which then becomes required.
28679 Another approach (assuming that this does not introduce elaboration
28680 circularities) is to add an @code{Elaborate_Body} pragma to the package spec,
28681 since one effect of this pragma is to require the presence of a package body.
28684 @emph{Numeric_Error is the same exception as Constraint_Error}
28686 In Ada 95, the exception @code{Numeric_Error} is a renaming of @code{Constraint_Error}.
28687 This means that it is illegal to have separate exception handlers for
28688 the two exceptions. The fix is simply to remove the handler for the
28689 @code{Numeric_Error} case (since even in Ada 83, a compiler was free to raise
28690 @code{Constraint_Error} in place of @code{Numeric_Error} in all cases).
28693 @emph{Indefinite subtypes in generics}
28695 In Ada 83, it was permissible to pass an indefinite type (e.g, @code{String})
28696 as the actual for a generic formal private type, but then the instantiation
28697 would be illegal if there were any instances of declarations of variables
28698 of this type in the generic body. In Ada 95, to avoid this clear violation
28699 of the methodological principle known as the 'contract model',
28700 the generic declaration explicitly indicates whether
28701 or not such instantiations are permitted. If a generic formal parameter
28702 has explicit unknown discriminants, indicated by using @code{(<>)} after the
28703 subtype name, then it can be instantiated with indefinite types, but no
28704 stand-alone variables can be declared of this type. Any attempt to declare
28705 such a variable will result in an illegality at the time the generic is
28706 declared. If the @code{(<>)} notation is not used, then it is illegal
28707 to instantiate the generic with an indefinite type.
28708 This is the potential incompatibility issue when porting Ada 83 code to Ada 95.
28709 It will show up as a compile time error, and
28710 the fix is usually simply to add the @code{(<>)} to the generic declaration.
28713 @node More deterministic semantics,Changed semantics,Legal Ada 83 programs that are illegal in Ada 95,Compatibility with Ada 83
28714 @anchor{gnat_rm/compatibility_and_porting_guide more-deterministic-semantics}@anchor{43b}@anchor{gnat_rm/compatibility_and_porting_guide id5}@anchor{43c}
28715 @subsection More deterministic semantics
28724 Conversions from real types to integer types round away from 0. In Ada 83
28725 the conversion Integer(2.5) could deliver either 2 or 3 as its value. This
28726 implementation freedom was intended to support unbiased rounding in
28727 statistical applications, but in practice it interfered with portability.
28728 In Ada 95 the conversion semantics are unambiguous, and rounding away from 0
28729 is required. Numeric code may be affected by this change in semantics.
28730 Note, though, that this issue is no worse than already existed in Ada 83
28731 when porting code from one vendor to another.
28736 The Real-Time Annex introduces a set of policies that define the behavior of
28737 features that were implementation dependent in Ada 83, such as the order in
28738 which open select branches are executed.
28741 @node Changed semantics,Other language compatibility issues,More deterministic semantics,Compatibility with Ada 83
28742 @anchor{gnat_rm/compatibility_and_porting_guide id6}@anchor{43d}@anchor{gnat_rm/compatibility_and_porting_guide changed-semantics}@anchor{43e}
28743 @subsection Changed semantics
28746 The worst kind of incompatibility is one where a program that is legal in
28747 Ada 83 is also legal in Ada 95 but can have an effect in Ada 95 that was not
28748 possible in Ada 83. Fortunately this is extremely rare, but the one
28749 situation that you should be alert to is the change in the predefined type
28750 @code{Character} from 7-bit ASCII to 8-bit Latin-1.
28761 @emph{Range of type `@w{`}Character`@w{`}}
28763 The range of @code{Standard.Character} is now the full 256 characters
28764 of Latin-1, whereas in most Ada 83 implementations it was restricted
28765 to 128 characters. Although some of the effects of
28766 this change will be manifest in compile-time rejection of legal
28767 Ada 83 programs it is possible for a working Ada 83 program to have
28768 a different effect in Ada 95, one that was not permitted in Ada 83.
28769 As an example, the expression
28770 @code{Character'Pos(Character'Last)} returned @code{127} in Ada 83 and now
28771 delivers @code{255} as its value.
28772 In general, you should look at the logic of any
28773 character-processing Ada 83 program and see whether it needs to be adapted
28774 to work correctly with Latin-1. Note that the predefined Ada 95 API has a
28775 character handling package that may be relevant if code needs to be adapted
28776 to account for the additional Latin-1 elements.
28777 The desirable fix is to
28778 modify the program to accommodate the full character set, but in some cases
28779 it may be convenient to define a subtype or derived type of Character that
28780 covers only the restricted range.
28783 @node Other language compatibility issues,,Changed semantics,Compatibility with Ada 83
28784 @anchor{gnat_rm/compatibility_and_porting_guide other-language-compatibility-issues}@anchor{43f}@anchor{gnat_rm/compatibility_and_porting_guide id7}@anchor{440}
28785 @subsection Other language compatibility issues
28792 @emph{-gnat83} switch
28794 All implementations of GNAT provide a switch that causes GNAT to operate
28795 in Ada 83 mode. In this mode, some but not all compatibility problems
28796 of the type described above are handled automatically. For example, the
28797 new reserved words introduced in Ada 95 and Ada 2005 are treated simply
28798 as identifiers as in Ada 83. However,
28799 in practice, it is usually advisable to make the necessary modifications
28800 to the program to remove the need for using this switch.
28801 See the @code{Compiling Different Versions of Ada} section in
28802 the @cite{GNAT User's Guide}.
28805 Support for removed Ada 83 pragmas and attributes
28807 A number of pragmas and attributes from Ada 83 were removed from Ada 95,
28808 generally because they were replaced by other mechanisms. Ada 95 and Ada 2005
28809 compilers are allowed, but not required, to implement these missing
28810 elements. In contrast with some other compilers, GNAT implements all
28811 such pragmas and attributes, eliminating this compatibility concern. These
28812 include @code{pragma Interface} and the floating point type attributes
28813 (@code{Emax}, @code{Mantissa}, etc.), among other items.
28816 @node Compatibility between Ada 95 and Ada 2005,Implementation-dependent characteristics,Compatibility with Ada 83,Compatibility and Porting Guide
28817 @anchor{gnat_rm/compatibility_and_porting_guide compatibility-between-ada-95-and-ada-2005}@anchor{441}@anchor{gnat_rm/compatibility_and_porting_guide id8}@anchor{442}
28818 @section Compatibility between Ada 95 and Ada 2005
28821 @geindex Compatibility between Ada 95 and Ada 2005
28823 Although Ada 2005 was designed to be upwards compatible with Ada 95, there are
28824 a number of incompatibilities. Several are enumerated below;
28825 for a complete description please see the
28826 @cite{Annotated Ada 2005 Reference Manual}, or section 9.1.1 in
28827 @cite{Rationale for Ada 2005}.
28833 @emph{New reserved words.}
28835 The words @code{interface}, @code{overriding} and @code{synchronized} are
28836 reserved in Ada 2005.
28837 A pre-Ada 2005 program that uses any of these as an identifier will be
28841 @emph{New declarations in predefined packages.}
28843 A number of packages in the predefined environment contain new declarations:
28844 @code{Ada.Exceptions}, @code{Ada.Real_Time}, @code{Ada.Strings},
28845 @code{Ada.Strings.Fixed}, @code{Ada.Strings.Bounded},
28846 @code{Ada.Strings.Unbounded}, @code{Ada.Strings.Wide_Fixed},
28847 @code{Ada.Strings.Wide_Bounded}, @code{Ada.Strings.Wide_Unbounded},
28848 @code{Ada.Tags}, @code{Ada.Text_IO}, and @code{Interfaces.C}.
28849 If an Ada 95 program does a @code{with} and @code{use} of any of these
28850 packages, the new declarations may cause name clashes.
28853 @emph{Access parameters.}
28855 A nondispatching subprogram with an access parameter cannot be renamed
28856 as a dispatching operation. This was permitted in Ada 95.
28859 @emph{Access types, discriminants, and constraints.}
28861 Rule changes in this area have led to some incompatibilities; for example,
28862 constrained subtypes of some access types are not permitted in Ada 2005.
28865 @emph{Aggregates for limited types.}
28867 The allowance of aggregates for limited types in Ada 2005 raises the
28868 possibility of ambiguities in legal Ada 95 programs, since additional types
28869 now need to be considered in expression resolution.
28872 @emph{Fixed-point multiplication and division.}
28874 Certain expressions involving '*' or '/' for a fixed-point type, which
28875 were legal in Ada 95 and invoked the predefined versions of these operations,
28877 The ambiguity may be resolved either by applying a type conversion to the
28878 expression, or by explicitly invoking the operation from package
28882 @emph{Return-by-reference types.}
28884 The Ada 95 return-by-reference mechanism has been removed. Instead, the user
28885 can declare a function returning a value from an anonymous access type.
28888 @node Implementation-dependent characteristics,Compatibility with Other Ada Systems,Compatibility between Ada 95 and Ada 2005,Compatibility and Porting Guide
28889 @anchor{gnat_rm/compatibility_and_porting_guide implementation-dependent-characteristics}@anchor{443}@anchor{gnat_rm/compatibility_and_porting_guide id9}@anchor{444}
28890 @section Implementation-dependent characteristics
28893 Although the Ada language defines the semantics of each construct as
28894 precisely as practical, in some situations (for example for reasons of
28895 efficiency, or where the effect is heavily dependent on the host or target
28896 platform) the implementation is allowed some freedom. In porting Ada 83
28897 code to GNAT, you need to be aware of whether / how the existing code
28898 exercised such implementation dependencies. Such characteristics fall into
28899 several categories, and GNAT offers specific support in assisting the
28900 transition from certain Ada 83 compilers.
28903 * Implementation-defined pragmas::
28904 * Implementation-defined attributes::
28906 * Elaboration order::
28907 * Target-specific aspects::
28911 @node Implementation-defined pragmas,Implementation-defined attributes,,Implementation-dependent characteristics
28912 @anchor{gnat_rm/compatibility_and_porting_guide implementation-defined-pragmas}@anchor{445}@anchor{gnat_rm/compatibility_and_porting_guide id10}@anchor{446}
28913 @subsection Implementation-defined pragmas
28916 Ada compilers are allowed to supplement the language-defined pragmas, and
28917 these are a potential source of non-portability. All GNAT-defined pragmas
28918 are described in @ref{7,,Implementation Defined Pragmas},
28919 and these include several that are specifically
28920 intended to correspond to other vendors' Ada 83 pragmas.
28921 For migrating from VADS, the pragma @code{Use_VADS_Size} may be useful.
28922 For compatibility with HP Ada 83, GNAT supplies the pragmas
28923 @code{Extend_System}, @code{Ident}, @code{Inline_Generic},
28924 @code{Interface_Name}, @code{Passive}, @code{Suppress_All},
28925 and @code{Volatile}.
28926 Other relevant pragmas include @code{External} and @code{Link_With}.
28927 Some vendor-specific
28928 Ada 83 pragmas (@code{Share_Generic}, @code{Subtitle}, and @code{Title}) are
28930 avoiding compiler rejection of units that contain such pragmas; they are not
28931 relevant in a GNAT context and hence are not otherwise implemented.
28933 @node Implementation-defined attributes,Libraries,Implementation-defined pragmas,Implementation-dependent characteristics
28934 @anchor{gnat_rm/compatibility_and_porting_guide id11}@anchor{447}@anchor{gnat_rm/compatibility_and_porting_guide implementation-defined-attributes}@anchor{448}
28935 @subsection Implementation-defined attributes
28938 Analogous to pragmas, the set of attributes may be extended by an
28939 implementation. All GNAT-defined attributes are described in
28940 @ref{8,,Implementation Defined Attributes},
28941 and these include several that are specifically intended
28942 to correspond to other vendors' Ada 83 attributes. For migrating from VADS,
28943 the attribute @code{VADS_Size} may be useful. For compatibility with HP
28944 Ada 83, GNAT supplies the attributes @code{Bit}, @code{Machine_Size} and
28947 @node Libraries,Elaboration order,Implementation-defined attributes,Implementation-dependent characteristics
28948 @anchor{gnat_rm/compatibility_and_porting_guide libraries}@anchor{449}@anchor{gnat_rm/compatibility_and_porting_guide id12}@anchor{44a}
28949 @subsection Libraries
28952 Vendors may supply libraries to supplement the standard Ada API. If Ada 83
28953 code uses vendor-specific libraries then there are several ways to manage
28954 this in Ada 95 and later versions of the standard:
28960 If the source code for the libraries (specs and bodies) are
28961 available, then the libraries can be migrated in the same way as the
28965 If the source code for the specs but not the bodies are
28966 available, then you can reimplement the bodies.
28969 Some features introduced by Ada 95 obviate the need for library support. For
28970 example most Ada 83 vendors supplied a package for unsigned integers. The
28971 Ada 95 modular type feature is the preferred way to handle this need, so
28972 instead of migrating or reimplementing the unsigned integer package it may
28973 be preferable to retrofit the application using modular types.
28976 @node Elaboration order,Target-specific aspects,Libraries,Implementation-dependent characteristics
28977 @anchor{gnat_rm/compatibility_and_porting_guide elaboration-order}@anchor{44b}@anchor{gnat_rm/compatibility_and_porting_guide id13}@anchor{44c}
28978 @subsection Elaboration order
28981 The implementation can choose any elaboration order consistent with the unit
28982 dependency relationship. This freedom means that some orders can result in
28983 Program_Error being raised due to an 'Access Before Elaboration': an attempt
28984 to invoke a subprogram before its body has been elaborated, or to instantiate
28985 a generic before the generic body has been elaborated. By default GNAT
28986 attempts to choose a safe order (one that will not encounter access before
28987 elaboration problems) by implicitly inserting @code{Elaborate} or
28988 @code{Elaborate_All} pragmas where
28989 needed. However, this can lead to the creation of elaboration circularities
28990 and a resulting rejection of the program by gnatbind. This issue is
28991 thoroughly described in the @emph{Elaboration Order Handling in GNAT} appendix
28992 in the @cite{GNAT User's Guide}.
28993 In brief, there are several
28994 ways to deal with this situation:
29000 Modify the program to eliminate the circularities, e.g., by moving
29001 elaboration-time code into explicitly-invoked procedures
29004 Constrain the elaboration order by including explicit @code{Elaborate_Body} or
29005 @code{Elaborate} pragmas, and then inhibit the generation of implicit
29006 @code{Elaborate_All}
29007 pragmas either globally (as an effect of the @emph{-gnatE} switch) or locally
29008 (by selectively suppressing elaboration checks via pragma
29009 @code{Suppress(Elaboration_Check)} when it is safe to do so).
29012 @node Target-specific aspects,,Elaboration order,Implementation-dependent characteristics
29013 @anchor{gnat_rm/compatibility_and_porting_guide target-specific-aspects}@anchor{44d}@anchor{gnat_rm/compatibility_and_porting_guide id14}@anchor{44e}
29014 @subsection Target-specific aspects
29017 Low-level applications need to deal with machine addresses, data
29018 representations, interfacing with assembler code, and similar issues. If
29019 such an Ada 83 application is being ported to different target hardware (for
29020 example where the byte endianness has changed) then you will need to
29021 carefully examine the program logic; the porting effort will heavily depend
29022 on the robustness of the original design. Moreover, Ada 95 (and thus
29023 Ada 2005 and Ada 2012) are sometimes
29024 incompatible with typical Ada 83 compiler practices regarding implicit
29025 packing, the meaning of the Size attribute, and the size of access values.
29026 GNAT's approach to these issues is described in @ref{44f,,Representation Clauses}.
29028 @node Compatibility with Other Ada Systems,Representation Clauses,Implementation-dependent characteristics,Compatibility and Porting Guide
29029 @anchor{gnat_rm/compatibility_and_porting_guide id15}@anchor{450}@anchor{gnat_rm/compatibility_and_porting_guide compatibility-with-other-ada-systems}@anchor{451}
29030 @section Compatibility with Other Ada Systems
29033 If programs avoid the use of implementation dependent and
29034 implementation defined features, as documented in the
29035 @cite{Ada Reference Manual}, there should be a high degree of portability between
29036 GNAT and other Ada systems. The following are specific items which
29037 have proved troublesome in moving Ada 95 programs from GNAT to other Ada 95
29038 compilers, but do not affect porting code to GNAT.
29039 (As of January 2007, GNAT is the only compiler available for Ada 2005;
29040 the following issues may or may not arise for Ada 2005 programs
29041 when other compilers appear.)
29047 @emph{Ada 83 Pragmas and Attributes}
29049 Ada 95 compilers are allowed, but not required, to implement the missing
29050 Ada 83 pragmas and attributes that are no longer defined in Ada 95.
29051 GNAT implements all such pragmas and attributes, eliminating this as
29052 a compatibility concern, but some other Ada 95 compilers reject these
29053 pragmas and attributes.
29056 @emph{Specialized Needs Annexes}
29058 GNAT implements the full set of special needs annexes. At the
29059 current time, it is the only Ada 95 compiler to do so. This means that
29060 programs making use of these features may not be portable to other Ada
29061 95 compilation systems.
29064 @emph{Representation Clauses}
29066 Some other Ada 95 compilers implement only the minimal set of
29067 representation clauses required by the Ada 95 reference manual. GNAT goes
29068 far beyond this minimal set, as described in the next section.
29071 @node Representation Clauses,Compatibility with HP Ada 83,Compatibility with Other Ada Systems,Compatibility and Porting Guide
29072 @anchor{gnat_rm/compatibility_and_porting_guide representation-clauses}@anchor{44f}@anchor{gnat_rm/compatibility_and_porting_guide id16}@anchor{452}
29073 @section Representation Clauses
29076 The Ada 83 reference manual was quite vague in describing both the minimal
29077 required implementation of representation clauses, and also their precise
29078 effects. Ada 95 (and thus also Ada 2005) are much more explicit, but the
29079 minimal set of capabilities required is still quite limited.
29081 GNAT implements the full required set of capabilities in
29082 Ada 95 and Ada 2005, but also goes much further, and in particular
29083 an effort has been made to be compatible with existing Ada 83 usage to the
29084 greatest extent possible.
29086 A few cases exist in which Ada 83 compiler behavior is incompatible with
29087 the requirements in Ada 95 (and thus also Ada 2005). These are instances of
29088 intentional or accidental dependence on specific implementation dependent
29089 characteristics of these Ada 83 compilers. The following is a list of
29090 the cases most likely to arise in existing Ada 83 code.
29096 @emph{Implicit Packing}
29098 Some Ada 83 compilers allowed a Size specification to cause implicit
29099 packing of an array or record. This could cause expensive implicit
29100 conversions for change of representation in the presence of derived
29101 types, and the Ada design intends to avoid this possibility.
29102 Subsequent AI's were issued to make it clear that such implicit
29103 change of representation in response to a Size clause is inadvisable,
29104 and this recommendation is represented explicitly in the Ada 95 (and Ada 2005)
29105 Reference Manuals as implementation advice that is followed by GNAT.
29106 The problem will show up as an error
29107 message rejecting the size clause. The fix is simply to provide
29108 the explicit pragma @code{Pack}, or for more fine tuned control, provide
29109 a Component_Size clause.
29112 @emph{Meaning of Size Attribute}
29114 The Size attribute in Ada 95 (and Ada 2005) for discrete types is defined as
29115 the minimal number of bits required to hold values of the type. For example,
29116 on a 32-bit machine, the size of @code{Natural} will typically be 31 and not
29117 32 (since no sign bit is required). Some Ada 83 compilers gave 31, and
29118 some 32 in this situation. This problem will usually show up as a compile
29119 time error, but not always. It is a good idea to check all uses of the
29120 'Size attribute when porting Ada 83 code. The GNAT specific attribute
29121 Object_Size can provide a useful way of duplicating the behavior of
29122 some Ada 83 compiler systems.
29125 @emph{Size of Access Types}
29127 A common assumption in Ada 83 code is that an access type is in fact a pointer,
29128 and that therefore it will be the same size as a System.Address value. This
29129 assumption is true for GNAT in most cases with one exception. For the case of
29130 a pointer to an unconstrained array type (where the bounds may vary from one
29131 value of the access type to another), the default is to use a 'fat pointer',
29132 which is represented as two separate pointers, one to the bounds, and one to
29133 the array. This representation has a number of advantages, including improved
29134 efficiency. However, it may cause some difficulties in porting existing Ada 83
29135 code which makes the assumption that, for example, pointers fit in 32 bits on
29136 a machine with 32-bit addressing.
29138 To get around this problem, GNAT also permits the use of 'thin pointers' for
29139 access types in this case (where the designated type is an unconstrained array
29140 type). These thin pointers are indeed the same size as a System.Address value.
29141 To specify a thin pointer, use a size clause for the type, for example:
29144 type X is access all String;
29145 for X'Size use Standard'Address_Size;
29148 which will cause the type X to be represented using a single pointer.
29149 When using this representation, the bounds are right behind the array.
29150 This representation is slightly less efficient, and does not allow quite
29151 such flexibility in the use of foreign pointers or in using the
29152 Unrestricted_Access attribute to create pointers to non-aliased objects.
29153 But for any standard portable use of the access type it will work in
29154 a functionally correct manner and allow porting of existing code.
29155 Note that another way of forcing a thin pointer representation
29156 is to use a component size clause for the element size in an array,
29157 or a record representation clause for an access field in a record.
29159 See the documentation of Unrestricted_Access in the GNAT RM for a
29160 full discussion of possible problems using this attribute in conjunction
29161 with thin pointers.
29164 @node Compatibility with HP Ada 83,,Representation Clauses,Compatibility and Porting Guide
29165 @anchor{gnat_rm/compatibility_and_porting_guide compatibility-with-hp-ada-83}@anchor{453}@anchor{gnat_rm/compatibility_and_porting_guide id17}@anchor{454}
29166 @section Compatibility with HP Ada 83
29169 All the HP Ada 83 pragmas and attributes are recognized, although only a subset
29170 of them can sensibly be implemented. The description of pragmas in
29171 @ref{7,,Implementation Defined Pragmas} indicates whether or not they are
29172 applicable to GNAT.
29178 @emph{Default floating-point representation}
29180 In GNAT, the default floating-point format is IEEE, whereas in HP Ada 83,
29186 the package System in GNAT exactly corresponds to the definition in the
29187 Ada 95 reference manual, which means that it excludes many of the
29188 HP Ada 83 extensions. However, a separate package Aux_DEC is provided
29189 that contains the additional definitions, and a special pragma,
29190 Extend_System allows this package to be treated transparently as an
29191 extension of package System.
29194 @node GNU Free Documentation License,Index,Compatibility and Porting Guide,Top
29195 @anchor{share/gnu_free_documentation_license gnu-fdl}@anchor{1}@anchor{share/gnu_free_documentation_license doc}@anchor{455}@anchor{share/gnu_free_documentation_license gnu-free-documentation-license}@anchor{456}
29196 @chapter GNU Free Documentation License
29199 Version 1.3, 3 November 2008
29201 Copyright 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc
29202 @indicateurl{http://fsf.org/}
29204 Everyone is permitted to copy and distribute verbatim copies of this
29205 license document, but changing it is not allowed.
29209 The purpose of this License is to make a manual, textbook, or other
29210 functional and useful document "free" in the sense of freedom: to
29211 assure everyone the effective freedom to copy and redistribute it,
29212 with or without modifying it, either commercially or noncommercially.
29213 Secondarily, this License preserves for the author and publisher a way
29214 to get credit for their work, while not being considered responsible
29215 for modifications made by others.
29217 This License is a kind of "copyleft", which means that derivative
29218 works of the document must themselves be free in the same sense. It
29219 complements the GNU General Public License, which is a copyleft
29220 license designed for free software.
29222 We have designed this License in order to use it for manuals for free
29223 software, because free software needs free documentation: a free
29224 program should come with manuals providing the same freedoms that the
29225 software does. But this License is not limited to software manuals;
29226 it can be used for any textual work, regardless of subject matter or
29227 whether it is published as a printed book. We recommend this License
29228 principally for works whose purpose is instruction or reference.
29230 @strong{1. APPLICABILITY AND DEFINITIONS}
29232 This License applies to any manual or other work, in any medium, that
29233 contains a notice placed by the copyright holder saying it can be
29234 distributed under the terms of this License. Such a notice grants a
29235 world-wide, royalty-free license, unlimited in duration, to use that
29236 work under the conditions stated herein. The @strong{Document}, below,
29237 refers to any such manual or work. Any member of the public is a
29238 licensee, and is addressed as "@strong{you}". You accept the license if you
29239 copy, modify or distribute the work in a way requiring permission
29240 under copyright law.
29242 A "@strong{Modified Version}" of the Document means any work containing the
29243 Document or a portion of it, either copied verbatim, or with
29244 modifications and/or translated into another language.
29246 A "@strong{Secondary Section}" is a named appendix or a front-matter section of
29247 the Document that deals exclusively with the relationship of the
29248 publishers or authors of the Document to the Document's overall subject
29249 (or to related matters) and contains nothing that could fall directly
29250 within that overall subject. (Thus, if the Document is in part a
29251 textbook of mathematics, a Secondary Section may not explain any
29252 mathematics.) The relationship could be a matter of historical
29253 connection with the subject or with related matters, or of legal,
29254 commercial, philosophical, ethical or political position regarding
29257 The "@strong{Invariant Sections}" are certain Secondary Sections whose titles
29258 are designated, as being those of Invariant Sections, in the notice
29259 that says that the Document is released under this License. If a
29260 section does not fit the above definition of Secondary then it is not
29261 allowed to be designated as Invariant. The Document may contain zero
29262 Invariant Sections. If the Document does not identify any Invariant
29263 Sections then there are none.
29265 The "@strong{Cover Texts}" are certain short passages of text that are listed,
29266 as Front-Cover Texts or Back-Cover Texts, in the notice that says that
29267 the Document is released under this License. A Front-Cover Text may
29268 be at most 5 words, and a Back-Cover Text may be at most 25 words.
29270 A "@strong{Transparent}" copy of the Document means a machine-readable copy,
29271 represented in a format whose specification is available to the
29272 general public, that is suitable for revising the document
29273 straightforwardly with generic text editors or (for images composed of
29274 pixels) generic paint programs or (for drawings) some widely available
29275 drawing editor, and that is suitable for input to text formatters or
29276 for automatic translation to a variety of formats suitable for input
29277 to text formatters. A copy made in an otherwise Transparent file
29278 format whose markup, or absence of markup, has been arranged to thwart
29279 or discourage subsequent modification by readers is not Transparent.
29280 An image format is not Transparent if used for any substantial amount
29281 of text. A copy that is not "Transparent" is called @strong{Opaque}.
29283 Examples of suitable formats for Transparent copies include plain
29284 ASCII without markup, Texinfo input format, LaTeX input format, SGML
29285 or XML using a publicly available DTD, and standard-conforming simple
29286 HTML, PostScript or PDF designed for human modification. Examples of
29287 transparent image formats include PNG, XCF and JPG. Opaque formats
29288 include proprietary formats that can be read and edited only by
29289 proprietary word processors, SGML or XML for which the DTD and/or
29290 processing tools are not generally available, and the
29291 machine-generated HTML, PostScript or PDF produced by some word
29292 processors for output purposes only.
29294 The "@strong{Title Page}" means, for a printed book, the title page itself,
29295 plus such following pages as are needed to hold, legibly, the material
29296 this License requires to appear in the title page. For works in
29297 formats which do not have any title page as such, "Title Page" means
29298 the text near the most prominent appearance of the work's title,
29299 preceding the beginning of the body of the text.
29301 The "@strong{publisher}" means any person or entity that distributes
29302 copies of the Document to the public.
29304 A section "@strong{Entitled XYZ}" means a named subunit of the Document whose
29305 title either is precisely XYZ or contains XYZ in parentheses following
29306 text that translates XYZ in another language. (Here XYZ stands for a
29307 specific section name mentioned below, such as "@strong{Acknowledgements}",
29308 "@strong{Dedications}", "@strong{Endorsements}", or "@strong{History}".)
29309 To "@strong{Preserve the Title}"
29310 of such a section when you modify the Document means that it remains a
29311 section "Entitled XYZ" according to this definition.
29313 The Document may include Warranty Disclaimers next to the notice which
29314 states that this License applies to the Document. These Warranty
29315 Disclaimers are considered to be included by reference in this
29316 License, but only as regards disclaiming warranties: any other
29317 implication that these Warranty Disclaimers may have is void and has
29318 no effect on the meaning of this License.
29320 @strong{2. VERBATIM COPYING}
29322 You may copy and distribute the Document in any medium, either
29323 commercially or noncommercially, provided that this License, the
29324 copyright notices, and the license notice saying this License applies
29325 to the Document are reproduced in all copies, and that you add no other
29326 conditions whatsoever to those of this License. You may not use
29327 technical measures to obstruct or control the reading or further
29328 copying of the copies you make or distribute. However, you may accept
29329 compensation in exchange for copies. If you distribute a large enough
29330 number of copies you must also follow the conditions in section 3.
29332 You may also lend copies, under the same conditions stated above, and
29333 you may publicly display copies.
29335 @strong{3. COPYING IN QUANTITY}
29337 If you publish printed copies (or copies in media that commonly have
29338 printed covers) of the Document, numbering more than 100, and the
29339 Document's license notice requires Cover Texts, you must enclose the
29340 copies in covers that carry, clearly and legibly, all these Cover
29341 Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on
29342 the back cover. Both covers must also clearly and legibly identify
29343 you as the publisher of these copies. The front cover must present
29344 the full title with all words of the title equally prominent and
29345 visible. You may add other material on the covers in addition.
29346 Copying with changes limited to the covers, as long as they preserve
29347 the title of the Document and satisfy these conditions, can be treated
29348 as verbatim copying in other respects.
29350 If the required texts for either cover are too voluminous to fit
29351 legibly, you should put the first ones listed (as many as fit
29352 reasonably) on the actual cover, and continue the rest onto adjacent
29355 If you publish or distribute Opaque copies of the Document numbering
29356 more than 100, you must either include a machine-readable Transparent
29357 copy along with each Opaque copy, or state in or with each Opaque copy
29358 a computer-network location from which the general network-using
29359 public has access to download using public-standard network protocols
29360 a complete Transparent copy of the Document, free of added material.
29361 If you use the latter option, you must take reasonably prudent steps,
29362 when you begin distribution of Opaque copies in quantity, to ensure
29363 that this Transparent copy will remain thus accessible at the stated
29364 location until at least one year after the last time you distribute an
29365 Opaque copy (directly or through your agents or retailers) of that
29366 edition to the public.
29368 It is requested, but not required, that you contact the authors of the
29369 Document well before redistributing any large number of copies, to give
29370 them a chance to provide you with an updated version of the Document.
29372 @strong{4. MODIFICATIONS}
29374 You may copy and distribute a Modified Version of the Document under
29375 the conditions of sections 2 and 3 above, provided that you release
29376 the Modified Version under precisely this License, with the Modified
29377 Version filling the role of the Document, thus licensing distribution
29378 and modification of the Modified Version to whoever possesses a copy
29379 of it. In addition, you must do these things in the Modified Version:
29385 Use in the Title Page (and on the covers, if any) a title distinct
29386 from that of the Document, and from those of previous versions
29387 (which should, if there were any, be listed in the History section
29388 of the Document). You may use the same title as a previous version
29389 if the original publisher of that version gives permission.
29392 List on the Title Page, as authors, one or more persons or entities
29393 responsible for authorship of the modifications in the Modified
29394 Version, together with at least five of the principal authors of the
29395 Document (all of its principal authors, if it has fewer than five),
29396 unless they release you from this requirement.
29399 State on the Title page the name of the publisher of the
29400 Modified Version, as the publisher.
29403 Preserve all the copyright notices of the Document.
29406 Add an appropriate copyright notice for your modifications
29407 adjacent to the other copyright notices.
29410 Include, immediately after the copyright notices, a license notice
29411 giving the public permission to use the Modified Version under the
29412 terms of this License, in the form shown in the Addendum below.
29415 Preserve in that license notice the full lists of Invariant Sections
29416 and required Cover Texts given in the Document's license notice.
29419 Include an unaltered copy of this License.
29422 Preserve the section Entitled "History", Preserve its Title, and add
29423 to it an item stating at least the title, year, new authors, and
29424 publisher of the Modified Version as given on the Title Page. If
29425 there is no section Entitled "History" in the Document, create one
29426 stating the title, year, authors, and publisher of the Document as
29427 given on its Title Page, then add an item describing the Modified
29428 Version as stated in the previous sentence.
29431 Preserve the network location, if any, given in the Document for
29432 public access to a Transparent copy of the Document, and likewise
29433 the network locations given in the Document for previous versions
29434 it was based on. These may be placed in the "History" section.
29435 You may omit a network location for a work that was published at
29436 least four years before the Document itself, or if the original
29437 publisher of the version it refers to gives permission.
29440 For any section Entitled "Acknowledgements" or "Dedications",
29441 Preserve the Title of the section, and preserve in the section all
29442 the substance and tone of each of the contributor acknowledgements
29443 and/or dedications given therein.
29446 Preserve all the Invariant Sections of the Document,
29447 unaltered in their text and in their titles. Section numbers
29448 or the equivalent are not considered part of the section titles.
29451 Delete any section Entitled "Endorsements". Such a section
29452 may not be included in the Modified Version.
29455 Do not retitle any existing section to be Entitled "Endorsements"
29456 or to conflict in title with any Invariant Section.
29459 Preserve any Warranty Disclaimers.
29462 If the Modified Version includes new front-matter sections or
29463 appendices that qualify as Secondary Sections and contain no material
29464 copied from the Document, you may at your option designate some or all
29465 of these sections as invariant. To do this, add their titles to the
29466 list of Invariant Sections in the Modified Version's license notice.
29467 These titles must be distinct from any other section titles.
29469 You may add a section Entitled "Endorsements", provided it contains
29470 nothing but endorsements of your Modified Version by various
29471 parties---for example, statements of peer review or that the text has
29472 been approved by an organization as the authoritative definition of a
29475 You may add a passage of up to five words as a Front-Cover Text, and a
29476 passage of up to 25 words as a Back-Cover Text, to the end of the list
29477 of Cover Texts in the Modified Version. Only one passage of
29478 Front-Cover Text and one of Back-Cover Text may be added by (or
29479 through arrangements made by) any one entity. If the Document already
29480 includes a cover text for the same cover, previously added by you or
29481 by arrangement made by the same entity you are acting on behalf of,
29482 you may not add another; but you may replace the old one, on explicit
29483 permission from the previous publisher that added the old one.
29485 The author(s) and publisher(s) of the Document do not by this License
29486 give permission to use their names for publicity for or to assert or
29487 imply endorsement of any Modified Version.
29489 @strong{5. COMBINING DOCUMENTS}
29491 You may combine the Document with other documents released under this
29492 License, under the terms defined in section 4 above for modified
29493 versions, provided that you include in the combination all of the
29494 Invariant Sections of all of the original documents, unmodified, and
29495 list them all as Invariant Sections of your combined work in its
29496 license notice, and that you preserve all their Warranty Disclaimers.
29498 The combined work need only contain one copy of this License, and
29499 multiple identical Invariant Sections may be replaced with a single
29500 copy. If there are multiple Invariant Sections with the same name but
29501 different contents, make the title of each such section unique by
29502 adding at the end of it, in parentheses, the name of the original
29503 author or publisher of that section if known, or else a unique number.
29504 Make the same adjustment to the section titles in the list of
29505 Invariant Sections in the license notice of the combined work.
29507 In the combination, you must combine any sections Entitled "History"
29508 in the various original documents, forming one section Entitled
29509 "History"; likewise combine any sections Entitled "Acknowledgements",
29510 and any sections Entitled "Dedications". You must delete all sections
29511 Entitled "Endorsements".
29513 @strong{6. COLLECTIONS OF DOCUMENTS}
29515 You may make a collection consisting of the Document and other documents
29516 released under this License, and replace the individual copies of this
29517 License in the various documents with a single copy that is included in
29518 the collection, provided that you follow the rules of this License for
29519 verbatim copying of each of the documents in all other respects.
29521 You may extract a single document from such a collection, and distribute
29522 it individually under this License, provided you insert a copy of this
29523 License into the extracted document, and follow this License in all
29524 other respects regarding verbatim copying of that document.
29526 @strong{7. AGGREGATION WITH INDEPENDENT WORKS}
29528 A compilation of the Document or its derivatives with other separate
29529 and independent documents or works, in or on a volume of a storage or
29530 distribution medium, is called an "aggregate" if the copyright
29531 resulting from the compilation is not used to limit the legal rights
29532 of the compilation's users beyond what the individual works permit.
29533 When the Document is included in an aggregate, this License does not
29534 apply to the other works in the aggregate which are not themselves
29535 derivative works of the Document.
29537 If the Cover Text requirement of section 3 is applicable to these
29538 copies of the Document, then if the Document is less than one half of
29539 the entire aggregate, the Document's Cover Texts may be placed on
29540 covers that bracket the Document within the aggregate, or the
29541 electronic equivalent of covers if the Document is in electronic form.
29542 Otherwise they must appear on printed covers that bracket the whole
29545 @strong{8. TRANSLATION}
29547 Translation is considered a kind of modification, so you may
29548 distribute translations of the Document under the terms of section 4.
29549 Replacing Invariant Sections with translations requires special
29550 permission from their copyright holders, but you may include
29551 translations of some or all Invariant Sections in addition to the
29552 original versions of these Invariant Sections. You may include a
29553 translation of this License, and all the license notices in the
29554 Document, and any Warranty Disclaimers, provided that you also include
29555 the original English version of this License and the original versions
29556 of those notices and disclaimers. In case of a disagreement between
29557 the translation and the original version of this License or a notice
29558 or disclaimer, the original version will prevail.
29560 If a section in the Document is Entitled "Acknowledgements",
29561 "Dedications", or "History", the requirement (section 4) to Preserve
29562 its Title (section 1) will typically require changing the actual
29565 @strong{9. TERMINATION}
29567 You may not copy, modify, sublicense, or distribute the Document
29568 except as expressly provided under this License. Any attempt
29569 otherwise to copy, modify, sublicense, or distribute it is void, and
29570 will automatically terminate your rights under this License.
29572 However, if you cease all violation of this License, then your license
29573 from a particular copyright holder is reinstated (a) provisionally,
29574 unless and until the copyright holder explicitly and finally
29575 terminates your license, and (b) permanently, if the copyright holder
29576 fails to notify you of the violation by some reasonable means prior to
29577 60 days after the cessation.
29579 Moreover, your license from a particular copyright holder is
29580 reinstated permanently if the copyright holder notifies you of the
29581 violation by some reasonable means, this is the first time you have
29582 received notice of violation of this License (for any work) from that
29583 copyright holder, and you cure the violation prior to 30 days after
29584 your receipt of the notice.
29586 Termination of your rights under this section does not terminate the
29587 licenses of parties who have received copies or rights from you under
29588 this License. If your rights have been terminated and not permanently
29589 reinstated, receipt of a copy of some or all of the same material does
29590 not give you any rights to use it.
29592 @strong{10. FUTURE REVISIONS OF THIS LICENSE}
29594 The Free Software Foundation may publish new, revised versions
29595 of the GNU Free Documentation License from time to time. Such new
29596 versions will be similar in spirit to the present version, but may
29597 differ in detail to address new problems or concerns. See
29598 @indicateurl{http://www.gnu.org/copyleft/}.
29600 Each version of the License is given a distinguishing version number.
29601 If the Document specifies that a particular numbered version of this
29602 License "or any later version" applies to it, you have the option of
29603 following the terms and conditions either of that specified version or
29604 of any later version that has been published (not as a draft) by the
29605 Free Software Foundation. If the Document does not specify a version
29606 number of this License, you may choose any version ever published (not
29607 as a draft) by the Free Software Foundation. If the Document
29608 specifies that a proxy can decide which future versions of this
29609 License can be used, that proxy's public statement of acceptance of a
29610 version permanently authorizes you to choose that version for the
29613 @strong{11. RELICENSING}
29615 "Massive Multiauthor Collaboration Site" (or "MMC Site") means any
29616 World Wide Web server that publishes copyrightable works and also
29617 provides prominent facilities for anybody to edit those works. A
29618 public wiki that anybody can edit is an example of such a server. A
29619 "Massive Multiauthor Collaboration" (or "MMC") contained in the
29620 site means any set of copyrightable works thus published on the MMC
29623 "CC-BY-SA" means the Creative Commons Attribution-Share Alike 3.0
29624 license published by Creative Commons Corporation, a not-for-profit
29625 corporation with a principal place of business in San Francisco,
29626 California, as well as future copyleft versions of that license
29627 published by that same organization.
29629 "Incorporate" means to publish or republish a Document, in whole or
29630 in part, as part of another Document.
29632 An MMC is "eligible for relicensing" if it is licensed under this
29633 License, and if all works that were first published under this License
29634 somewhere other than this MMC, and subsequently incorporated in whole
29635 or in part into the MMC, (1) had no cover texts or invariant sections,
29636 and (2) were thus incorporated prior to November 1, 2008.
29638 The operator of an MMC Site may republish an MMC contained in the site
29639 under CC-BY-SA on the same site at any time before August 1, 2009,
29640 provided the MMC is eligible for relicensing.
29642 @strong{ADDENDUM: How to use this License for your documents}
29644 To use this License in a document you have written, include a copy of
29645 the License in the document and put the following copyright and
29646 license notices just after the title page:
29650 Copyright © YEAR YOUR NAME.
29651 Permission is granted to copy, distribute and/or modify this document
29652 under the terms of the GNU Free Documentation License, Version 1.3
29653 or any later version published by the Free Software Foundation;
29654 with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
29655 A copy of the license is included in the section entitled "GNU
29656 Free Documentation License".
29659 If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts,
29660 replace the "with ... Texts." line with this:
29664 with the Invariant Sections being LIST THEIR TITLES, with the
29665 Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST.
29668 If you have Invariant Sections without Cover Texts, or some other
29669 combination of the three, merge those two alternatives to suit the
29672 If your document contains nontrivial examples of program code, we
29673 recommend releasing these examples in parallel under your choice of
29674 free software license, such as the GNU General Public License,
29675 to permit their use in free software.
29677 @node Index,,GNU Free Documentation License,Top