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8 @settitle GNAT Reference Manual
13 @dircategory GNU Ada Tools
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24 GNAT Reference Manual , Aug 01, 2019
28 Copyright @copyright{} 2008-2019, 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::
100 * Pragma Acc_Parallel::
102 * Pragma Acc_Kernels::
110 * Pragma Allow_Integer_Address::
113 * Pragma Assert_And_Cut::
114 * Pragma Assertion_Policy::
116 * Pragma Assume_No_Invalid_Values::
117 * Pragma Async_Readers::
118 * Pragma Async_Writers::
119 * Pragma Attribute_Definition::
120 * Pragma C_Pass_By_Copy::
122 * Pragma Check_Float_Overflow::
123 * Pragma Check_Name::
124 * Pragma Check_Policy::
126 * Pragma Common_Object::
127 * Pragma Compile_Time_Error::
128 * Pragma Compile_Time_Warning::
129 * Pragma Compiler_Unit::
130 * Pragma Compiler_Unit_Warning::
131 * Pragma Complete_Representation::
132 * Pragma Complex_Representation::
133 * Pragma Component_Alignment::
134 * Pragma Constant_After_Elaboration::
135 * Pragma Contract_Cases::
136 * Pragma Convention_Identifier::
138 * Pragma CPP_Constructor::
139 * Pragma CPP_Virtual::
140 * Pragma CPP_Vtable::
142 * Pragma Deadline_Floor::
143 * Pragma Default_Initial_Condition::
145 * Pragma Debug_Policy::
146 * Pragma Default_Scalar_Storage_Order::
147 * Pragma Default_Storage_Pool::
149 * Pragma Detect_Blocking::
150 * Pragma Disable_Atomic_Synchronization::
151 * Pragma Dispatching_Domain::
152 * Pragma Effective_Reads::
153 * Pragma Effective_Writes::
154 * Pragma Elaboration_Checks::
156 * Pragma Enable_Atomic_Synchronization::
157 * Pragma Export_Function::
158 * Pragma Export_Object::
159 * Pragma Export_Procedure::
160 * Pragma Export_Value::
161 * Pragma Export_Valued_Procedure::
162 * Pragma Extend_System::
163 * Pragma Extensions_Allowed::
164 * Pragma Extensions_Visible::
166 * Pragma External_Name_Casing::
168 * Pragma Favor_Top_Level::
169 * Pragma Finalize_Storage_Only::
170 * Pragma Float_Representation::
174 * Pragma Ignore_Pragma::
175 * Pragma Implementation_Defined::
176 * Pragma Implemented::
177 * Pragma Implicit_Packing::
178 * Pragma Import_Function::
179 * Pragma Import_Object::
180 * Pragma Import_Procedure::
181 * Pragma Import_Valued_Procedure::
182 * Pragma Independent::
183 * Pragma Independent_Components::
184 * Pragma Initial_Condition::
185 * Pragma Initialize_Scalars::
186 * Pragma Initializes::
187 * Pragma Inline_Always::
188 * Pragma Inline_Generic::
190 * Pragma Interface_Name::
191 * Pragma Interrupt_Handler::
192 * Pragma Interrupt_State::
194 * Pragma Keep_Names::
197 * Pragma Linker_Alias::
198 * Pragma Linker_Constructor::
199 * Pragma Linker_Destructor::
200 * Pragma Linker_Section::
202 * Pragma Loop_Invariant::
203 * Pragma Loop_Optimize::
204 * Pragma Loop_Variant::
205 * Pragma Machine_Attribute::
207 * Pragma Main_Storage::
208 * Pragma Max_Queue_Length::
210 * Pragma No_Caching::
211 * Pragma No_Component_Reordering::
212 * Pragma No_Elaboration_Code_All::
213 * Pragma No_Heap_Finalization::
216 * Pragma No_Run_Time::
217 * Pragma No_Strict_Aliasing::
218 * Pragma No_Tagged_Streams::
219 * Pragma Normalize_Scalars::
220 * Pragma Obsolescent::
221 * Pragma Optimize_Alignment::
223 * Pragma Overflow_Mode::
224 * Pragma Overriding_Renamings::
225 * Pragma Partition_Elaboration_Policy::
228 * Pragma Persistent_BSS::
231 * Pragma Postcondition::
232 * Pragma Post_Class::
233 * Pragma Rename_Pragma::
235 * Pragma Precondition::
237 * Pragma Predicate_Failure::
238 * Pragma Preelaborable_Initialization::
239 * Pragma Prefix_Exception_Messages::
241 * Pragma Priority_Specific_Dispatching::
243 * Pragma Profile_Warnings::
244 * Pragma Propagate_Exceptions::
245 * Pragma Provide_Shift_Operators::
246 * Pragma Psect_Object::
247 * Pragma Pure_Function::
250 * Pragma Refined_Depends::
251 * Pragma Refined_Global::
252 * Pragma Refined_Post::
253 * Pragma Refined_State::
254 * Pragma Relative_Deadline::
255 * Pragma Remote_Access_Type::
256 * Pragma Restricted_Run_Time::
257 * Pragma Restriction_Warnings::
258 * Pragma Reviewable::
259 * Pragma Secondary_Stack_Size::
260 * Pragma Share_Generic::
262 * Pragma Short_Circuit_And_Or::
263 * Pragma Short_Descriptors::
264 * Pragma Simple_Storage_Pool_Type::
265 * Pragma Source_File_Name::
266 * Pragma Source_File_Name_Project::
267 * Pragma Source_Reference::
268 * Pragma SPARK_Mode::
269 * Pragma Static_Elaboration_Desired::
270 * Pragma Stream_Convert::
271 * Pragma Style_Checks::
274 * Pragma Suppress_All::
275 * Pragma Suppress_Debug_Info::
276 * Pragma Suppress_Exception_Locations::
277 * Pragma Suppress_Initialization::
279 * Pragma Task_Storage::
281 * Pragma Thread_Local_Storage::
282 * Pragma Time_Slice::
284 * Pragma Type_Invariant::
285 * Pragma Type_Invariant_Class::
286 * Pragma Unchecked_Union::
287 * Pragma Unevaluated_Use_Of_Old::
288 * Pragma Unimplemented_Unit::
289 * Pragma Universal_Aliasing::
290 * Pragma Universal_Data::
291 * Pragma Unmodified::
292 * Pragma Unreferenced::
293 * Pragma Unreferenced_Objects::
294 * Pragma Unreserve_All_Interrupts::
295 * Pragma Unsuppress::
296 * Pragma Use_VADS_Size::
298 * Pragma Validity_Checks::
300 * Pragma Volatile_Full_Access::
301 * Pragma Volatile_Function::
302 * Pragma Warning_As_Error::
304 * Pragma Weak_External::
305 * Pragma Wide_Character_Encoding::
307 Implementation Defined Aspects
309 * Aspect Abstract_State::
311 * Aspect Async_Readers::
312 * Aspect Async_Writers::
313 * Aspect Constant_After_Elaboration::
314 * Aspect Contract_Cases::
316 * Aspect Default_Initial_Condition::
318 * Aspect Dimension_System::
319 * Aspect Disable_Controlled::
320 * Aspect Effective_Reads::
321 * Aspect Effective_Writes::
322 * Aspect Extensions_Visible::
323 * Aspect Favor_Top_Level::
326 * Aspect Initial_Condition::
327 * Aspect Initializes::
328 * Aspect Inline_Always::
330 * Aspect Invariant'Class::
332 * Aspect Linker_Section::
334 * Aspect Max_Queue_Length::
335 * Aspect No_Caching::
336 * Aspect No_Elaboration_Code_All::
338 * Aspect No_Tagged_Streams::
339 * Aspect Object_Size::
340 * Aspect Obsolescent::
342 * Aspect Persistent_BSS::
344 * Aspect Pure_Function::
345 * Aspect Refined_Depends::
346 * Aspect Refined_Global::
347 * Aspect Refined_Post::
348 * Aspect Refined_State::
349 * Aspect Remote_Access_Type::
350 * Aspect Secondary_Stack_Size::
351 * Aspect Scalar_Storage_Order::
353 * Aspect Simple_Storage_Pool::
354 * Aspect Simple_Storage_Pool_Type::
355 * Aspect SPARK_Mode::
356 * Aspect Suppress_Debug_Info::
357 * Aspect Suppress_Initialization::
359 * Aspect Thread_Local_Storage::
360 * Aspect Universal_Aliasing::
361 * Aspect Universal_Data::
362 * Aspect Unmodified::
363 * Aspect Unreferenced::
364 * Aspect Unreferenced_Objects::
365 * Aspect Value_Size::
366 * Aspect Volatile_Full_Access::
367 * Aspect Volatile_Function::
370 Implementation Defined Attributes
372 * Attribute Abort_Signal::
373 * Attribute Address_Size::
374 * Attribute Asm_Input::
375 * Attribute Asm_Output::
376 * Attribute Atomic_Always_Lock_Free::
378 * Attribute Bit_Position::
379 * Attribute Code_Address::
380 * Attribute Compiler_Version::
381 * Attribute Constrained::
382 * Attribute Default_Bit_Order::
383 * Attribute Default_Scalar_Storage_Order::
385 * Attribute Descriptor_Size::
386 * Attribute Elaborated::
387 * Attribute Elab_Body::
388 * Attribute Elab_Spec::
389 * Attribute Elab_Subp_Body::
391 * Attribute Enabled::
392 * Attribute Enum_Rep::
393 * Attribute Enum_Val::
394 * Attribute Epsilon::
395 * Attribute Fast_Math::
396 * Attribute Finalization_Size::
397 * Attribute Fixed_Value::
398 * Attribute From_Any::
399 * Attribute Has_Access_Values::
400 * Attribute Has_Discriminants::
402 * Attribute Integer_Value::
403 * Attribute Invalid_Value::
404 * Attribute Iterable::
406 * Attribute Library_Level::
407 * Attribute Lock_Free::
408 * Attribute Loop_Entry::
409 * Attribute Machine_Size::
410 * Attribute Mantissa::
411 * Attribute Maximum_Alignment::
412 * Attribute Mechanism_Code::
413 * Attribute Null_Parameter::
414 * Attribute Object_Size::
416 * Attribute Passed_By_Reference::
417 * Attribute Pool_Address::
418 * Attribute Range_Length::
419 * Attribute Restriction_Set::
421 * Attribute Safe_Emax::
422 * Attribute Safe_Large::
423 * Attribute Safe_Small::
424 * Attribute Scalar_Storage_Order::
425 * Attribute Simple_Storage_Pool::
427 * Attribute Storage_Unit::
428 * Attribute Stub_Type::
429 * Attribute System_Allocator_Alignment::
430 * Attribute Target_Name::
431 * Attribute To_Address::
433 * Attribute Type_Class::
434 * Attribute Type_Key::
435 * Attribute TypeCode::
436 * Attribute Unconstrained_Array::
437 * Attribute Universal_Literal_String::
438 * Attribute Unrestricted_Access::
440 * Attribute Valid_Scalars::
441 * Attribute VADS_Size::
442 * Attribute Value_Size::
443 * Attribute Wchar_T_Size::
444 * Attribute Word_Size::
446 Standard and Implementation Defined Restrictions
448 * Partition-Wide Restrictions::
449 * Program Unit Level Restrictions::
451 Partition-Wide Restrictions
453 * Immediate_Reclamation::
454 * Max_Asynchronous_Select_Nesting::
455 * Max_Entry_Queue_Length::
456 * Max_Protected_Entries::
457 * Max_Select_Alternatives::
458 * Max_Storage_At_Blocking::
461 * No_Abort_Statements::
462 * No_Access_Parameter_Allocators::
463 * No_Access_Subprograms::
465 * No_Anonymous_Allocators::
466 * No_Asynchronous_Control::
469 * No_Default_Initialization::
472 * No_Direct_Boolean_Operators::
474 * No_Dispatching_Calls::
475 * No_Dynamic_Attachment::
476 * No_Dynamic_Priorities::
477 * No_Entry_Calls_In_Elaboration_Code::
478 * No_Enumeration_Maps::
479 * No_Exception_Handlers::
480 * No_Exception_Propagation::
481 * No_Exception_Registration::
485 * No_Floating_Point::
486 * No_Implicit_Conditionals::
487 * No_Implicit_Dynamic_Code::
488 * No_Implicit_Heap_Allocations::
489 * No_Implicit_Protected_Object_Allocations::
490 * No_Implicit_Task_Allocations::
491 * No_Initialize_Scalars::
493 * No_Local_Allocators::
494 * No_Local_Protected_Objects::
495 * No_Local_Timing_Events::
496 * No_Long_Long_Integers::
497 * No_Multiple_Elaboration::
498 * No_Nested_Finalization::
499 * No_Protected_Type_Allocators::
500 * No_Protected_Types::
503 * No_Relative_Delay::
504 * No_Requeue_Statements::
505 * No_Secondary_Stack::
506 * No_Select_Statements::
507 * No_Specific_Termination_Handlers::
508 * No_Specification_of_Aspect::
509 * No_Standard_Allocators_After_Elaboration::
510 * No_Standard_Storage_Pools::
511 * No_Stream_Optimizations::
513 * No_Task_Allocators::
514 * No_Task_At_Interrupt_Priority::
515 * No_Task_Attributes_Package::
516 * No_Task_Hierarchy::
517 * No_Task_Termination::
519 * No_Terminate_Alternatives::
520 * No_Unchecked_Access::
521 * No_Unchecked_Conversion::
522 * No_Unchecked_Deallocation::
526 * Static_Priorities::
527 * Static_Storage_Size::
529 Program Unit Level Restrictions
531 * No_Elaboration_Code::
532 * No_Dynamic_Sized_Objects::
534 * No_Implementation_Aspect_Specifications::
535 * No_Implementation_Attributes::
536 * No_Implementation_Identifiers::
537 * No_Implementation_Pragmas::
538 * No_Implementation_Restrictions::
539 * No_Implementation_Units::
540 * No_Implicit_Aliasing::
541 * No_Implicit_Loops::
542 * No_Obsolescent_Features::
543 * No_Wide_Characters::
544 * Static_Dispatch_Tables::
547 Implementation Advice
549 * RM 1.1.3(20); Error Detection: RM 1 1 3 20 Error Detection.
550 * RM 1.1.3(31); Child Units: RM 1 1 3 31 Child Units.
551 * RM 1.1.5(12); Bounded Errors: RM 1 1 5 12 Bounded Errors.
552 * RM 2.8(16); Pragmas: RM 2 8 16 Pragmas.
553 * RM 2.8(17-19); Pragmas: RM 2 8 17-19 Pragmas.
554 * RM 3.5.2(5); Alternative Character Sets: RM 3 5 2 5 Alternative Character Sets.
555 * RM 3.5.4(28); Integer Types: RM 3 5 4 28 Integer Types.
556 * RM 3.5.4(29); Integer Types: RM 3 5 4 29 Integer Types.
557 * RM 3.5.5(8); Enumeration Values: RM 3 5 5 8 Enumeration Values.
558 * RM 3.5.7(17); Float Types: RM 3 5 7 17 Float Types.
559 * RM 3.6.2(11); Multidimensional Arrays: RM 3 6 2 11 Multidimensional Arrays.
560 * RM 9.6(30-31); Duration'Small: RM 9 6 30-31 Duration'Small.
561 * RM 10.2.1(12); Consistent Representation: RM 10 2 1 12 Consistent Representation.
562 * RM 11.4.1(19); Exception Information: RM 11 4 1 19 Exception Information.
563 * RM 11.5(28); Suppression of Checks: RM 11 5 28 Suppression of Checks.
564 * RM 13.1 (21-24); Representation Clauses: RM 13 1 21-24 Representation Clauses.
565 * RM 13.2(6-8); Packed Types: RM 13 2 6-8 Packed Types.
566 * RM 13.3(14-19); Address Clauses: RM 13 3 14-19 Address Clauses.
567 * RM 13.3(29-35); Alignment Clauses: RM 13 3 29-35 Alignment Clauses.
568 * RM 13.3(42-43); Size Clauses: RM 13 3 42-43 Size Clauses.
569 * RM 13.3(50-56); Size Clauses: RM 13 3 50-56 Size Clauses.
570 * RM 13.3(71-73); Component Size Clauses: RM 13 3 71-73 Component Size Clauses.
571 * RM 13.4(9-10); Enumeration Representation Clauses: RM 13 4 9-10 Enumeration Representation Clauses.
572 * RM 13.5.1(17-22); Record Representation Clauses: RM 13 5 1 17-22 Record Representation Clauses.
573 * RM 13.5.2(5); Storage Place Attributes: RM 13 5 2 5 Storage Place Attributes.
574 * RM 13.5.3(7-8); Bit Ordering: RM 13 5 3 7-8 Bit Ordering.
575 * RM 13.7(37); Address as Private: RM 13 7 37 Address as Private.
576 * RM 13.7.1(16); Address Operations: RM 13 7 1 16 Address Operations.
577 * RM 13.9(14-17); Unchecked Conversion: RM 13 9 14-17 Unchecked Conversion.
578 * RM 13.11(23-25); Implicit Heap Usage: RM 13 11 23-25 Implicit Heap Usage.
579 * RM 13.11.2(17); Unchecked Deallocation: RM 13 11 2 17 Unchecked Deallocation.
580 * RM 13.13.2(1.6); Stream Oriented Attributes: RM 13 13 2 1 6 Stream Oriented Attributes.
581 * RM A.1(52); Names of Predefined Numeric Types: RM A 1 52 Names of Predefined Numeric Types.
582 * RM A.3.2(49); Ada.Characters.Handling: RM A 3 2 49 Ada Characters Handling.
583 * RM A.4.4(106); Bounded-Length String Handling: RM A 4 4 106 Bounded-Length String Handling.
584 * RM A.5.2(46-47); Random Number Generation: RM A 5 2 46-47 Random Number Generation.
585 * RM A.10.7(23); Get_Immediate: RM A 10 7 23 Get_Immediate.
586 * RM B.1(39-41); Pragma Export: RM B 1 39-41 Pragma Export.
587 * RM B.2(12-13); Package Interfaces: RM B 2 12-13 Package Interfaces.
588 * RM B.3(63-71); Interfacing with C: RM B 3 63-71 Interfacing with C.
589 * RM B.4(95-98); Interfacing with COBOL: RM B 4 95-98 Interfacing with COBOL.
590 * RM B.5(22-26); Interfacing with Fortran: RM B 5 22-26 Interfacing with Fortran.
591 * RM C.1(3-5); Access to Machine Operations: RM C 1 3-5 Access to Machine Operations.
592 * RM C.1(10-16); Access to Machine Operations: RM C 1 10-16 Access to Machine Operations.
593 * RM C.3(28); Interrupt Support: RM C 3 28 Interrupt Support.
594 * RM C.3.1(20-21); Protected Procedure Handlers: RM C 3 1 20-21 Protected Procedure Handlers.
595 * RM C.3.2(25); Package Interrupts: RM C 3 2 25 Package Interrupts.
596 * RM C.4(14); Pre-elaboration Requirements: RM C 4 14 Pre-elaboration Requirements.
597 * RM C.5(8); Pragma Discard_Names: RM C 5 8 Pragma Discard_Names.
598 * RM C.7.2(30); The Package Task_Attributes: RM C 7 2 30 The Package Task_Attributes.
599 * RM D.3(17); Locking Policies: RM D 3 17 Locking Policies.
600 * RM D.4(16); Entry Queuing Policies: RM D 4 16 Entry Queuing Policies.
601 * RM D.6(9-10); Preemptive Abort: RM D 6 9-10 Preemptive Abort.
602 * RM D.7(21); Tasking Restrictions: RM D 7 21 Tasking Restrictions.
603 * RM D.8(47-49); Monotonic Time: RM D 8 47-49 Monotonic Time.
604 * RM E.5(28-29); Partition Communication Subsystem: RM E 5 28-29 Partition Communication Subsystem.
605 * RM F(7); COBOL Support: RM F 7 COBOL Support.
606 * RM F.1(2); Decimal Radix Support: RM F 1 2 Decimal Radix Support.
607 * RM G; Numerics: RM G Numerics.
608 * RM G.1.1(56-58); Complex Types: RM G 1 1 56-58 Complex Types.
609 * RM G.1.2(49); Complex Elementary Functions: RM G 1 2 49 Complex Elementary Functions.
610 * RM G.2.4(19); Accuracy Requirements: RM G 2 4 19 Accuracy Requirements.
611 * RM G.2.6(15); Complex Arithmetic Accuracy: RM G 2 6 15 Complex Arithmetic Accuracy.
612 * RM H.6(15/2); Pragma Partition_Elaboration_Policy: RM H 6 15/2 Pragma Partition_Elaboration_Policy.
614 Intrinsic Subprograms
616 * Intrinsic Operators::
617 * Compilation_ISO_Date::
621 * Exception_Information::
622 * Exception_Message::
626 * Shifts and Rotates::
629 Representation Clauses and Pragmas
631 * Alignment Clauses::
633 * Storage_Size Clauses::
634 * Size of Variant Record Objects::
635 * Biased Representation::
636 * Value_Size and Object_Size Clauses::
637 * Component_Size Clauses::
638 * Bit_Order Clauses::
639 * Effect of Bit_Order on Byte Ordering::
640 * Pragma Pack for Arrays::
641 * Pragma Pack for Records::
642 * Record Representation Clauses::
643 * Handling of Records with Holes::
644 * Enumeration Clauses::
646 * Use of Address Clauses for Memory-Mapped I/O::
647 * Effect of Convention on Representation::
648 * Conventions and Anonymous Access Types::
649 * Determining the Representations chosen by GNAT::
651 The Implementation of Standard I/O
653 * Standard I/O Packages::
659 * Wide_Wide_Text_IO::
663 * Filenames encoding::
664 * File content encoding::
666 * Operations on C Streams::
667 * Interfacing to C Streams::
671 * Stream Pointer Positioning::
672 * Reading and Writing Non-Regular Files::
674 * Treating Text_IO Files as Streams::
675 * Text_IO Extensions::
676 * Text_IO Facilities for Unbounded Strings::
680 * Stream Pointer Positioning: Stream Pointer Positioning<2>.
681 * Reading and Writing Non-Regular Files: Reading and Writing Non-Regular Files<2>.
685 * Stream Pointer Positioning: Stream Pointer Positioning<3>.
686 * Reading and Writing Non-Regular Files: Reading and Writing Non-Regular Files<3>.
690 * Ada.Characters.Latin_9 (a-chlat9.ads): Ada Characters Latin_9 a-chlat9 ads.
691 * Ada.Characters.Wide_Latin_1 (a-cwila1.ads): Ada Characters Wide_Latin_1 a-cwila1 ads.
692 * Ada.Characters.Wide_Latin_9 (a-cwila1.ads): Ada Characters Wide_Latin_9 a-cwila1 ads.
693 * Ada.Characters.Wide_Wide_Latin_1 (a-chzla1.ads): Ada Characters Wide_Wide_Latin_1 a-chzla1 ads.
694 * Ada.Characters.Wide_Wide_Latin_9 (a-chzla9.ads): Ada Characters Wide_Wide_Latin_9 a-chzla9 ads.
695 * Ada.Containers.Formal_Doubly_Linked_Lists (a-cfdlli.ads): Ada Containers Formal_Doubly_Linked_Lists a-cfdlli ads.
696 * Ada.Containers.Formal_Hashed_Maps (a-cfhama.ads): Ada Containers Formal_Hashed_Maps a-cfhama ads.
697 * Ada.Containers.Formal_Hashed_Sets (a-cfhase.ads): Ada Containers Formal_Hashed_Sets a-cfhase ads.
698 * Ada.Containers.Formal_Ordered_Maps (a-cforma.ads): Ada Containers Formal_Ordered_Maps a-cforma ads.
699 * Ada.Containers.Formal_Ordered_Sets (a-cforse.ads): Ada Containers Formal_Ordered_Sets a-cforse ads.
700 * Ada.Containers.Formal_Vectors (a-cofove.ads): Ada Containers Formal_Vectors a-cofove ads.
701 * Ada.Containers.Formal_Indefinite_Vectors (a-cfinve.ads): Ada Containers Formal_Indefinite_Vectors a-cfinve ads.
702 * Ada.Containers.Functional_Vectors (a-cofuve.ads): Ada Containers Functional_Vectors a-cofuve ads.
703 * Ada.Containers.Functional_Sets (a-cofuse.ads): Ada Containers Functional_Sets a-cofuse ads.
704 * Ada.Containers.Functional_Maps (a-cofuma.ads): Ada Containers Functional_Maps a-cofuma ads.
705 * Ada.Containers.Bounded_Holders (a-coboho.ads): Ada Containers Bounded_Holders a-coboho ads.
706 * Ada.Command_Line.Environment (a-colien.ads): Ada Command_Line Environment a-colien ads.
707 * Ada.Command_Line.Remove (a-colire.ads): Ada Command_Line Remove a-colire ads.
708 * Ada.Command_Line.Response_File (a-clrefi.ads): Ada Command_Line Response_File a-clrefi ads.
709 * Ada.Direct_IO.C_Streams (a-diocst.ads): Ada Direct_IO C_Streams a-diocst ads.
710 * Ada.Exceptions.Is_Null_Occurrence (a-einuoc.ads): Ada Exceptions Is_Null_Occurrence a-einuoc ads.
711 * Ada.Exceptions.Last_Chance_Handler (a-elchha.ads): Ada Exceptions Last_Chance_Handler a-elchha ads.
712 * Ada.Exceptions.Traceback (a-exctra.ads): Ada Exceptions Traceback a-exctra ads.
713 * Ada.Sequential_IO.C_Streams (a-siocst.ads): Ada Sequential_IO C_Streams a-siocst ads.
714 * Ada.Streams.Stream_IO.C_Streams (a-ssicst.ads): Ada Streams Stream_IO C_Streams a-ssicst ads.
715 * Ada.Strings.Unbounded.Text_IO (a-suteio.ads): Ada Strings Unbounded Text_IO a-suteio ads.
716 * Ada.Strings.Wide_Unbounded.Wide_Text_IO (a-swuwti.ads): Ada Strings Wide_Unbounded Wide_Text_IO a-swuwti ads.
717 * Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO (a-szuzti.ads): Ada Strings Wide_Wide_Unbounded Wide_Wide_Text_IO a-szuzti ads.
718 * Ada.Text_IO.C_Streams (a-tiocst.ads): Ada Text_IO C_Streams a-tiocst ads.
719 * Ada.Text_IO.Reset_Standard_Files (a-tirsfi.ads): Ada Text_IO Reset_Standard_Files a-tirsfi ads.
720 * Ada.Wide_Characters.Unicode (a-wichun.ads): Ada Wide_Characters Unicode a-wichun ads.
721 * Ada.Wide_Text_IO.C_Streams (a-wtcstr.ads): Ada Wide_Text_IO C_Streams a-wtcstr ads.
722 * Ada.Wide_Text_IO.Reset_Standard_Files (a-wrstfi.ads): Ada Wide_Text_IO Reset_Standard_Files a-wrstfi ads.
723 * Ada.Wide_Wide_Characters.Unicode (a-zchuni.ads): Ada Wide_Wide_Characters Unicode a-zchuni ads.
724 * Ada.Wide_Wide_Text_IO.C_Streams (a-ztcstr.ads): Ada Wide_Wide_Text_IO C_Streams a-ztcstr ads.
725 * Ada.Wide_Wide_Text_IO.Reset_Standard_Files (a-zrstfi.ads): Ada Wide_Wide_Text_IO Reset_Standard_Files a-zrstfi ads.
726 * GNAT.Altivec (g-altive.ads): GNAT Altivec g-altive ads.
727 * GNAT.Altivec.Conversions (g-altcon.ads): GNAT Altivec Conversions g-altcon ads.
728 * GNAT.Altivec.Vector_Operations (g-alveop.ads): GNAT Altivec Vector_Operations g-alveop ads.
729 * GNAT.Altivec.Vector_Types (g-alvety.ads): GNAT Altivec Vector_Types g-alvety ads.
730 * GNAT.Altivec.Vector_Views (g-alvevi.ads): GNAT Altivec Vector_Views g-alvevi ads.
731 * GNAT.Array_Split (g-arrspl.ads): GNAT Array_Split g-arrspl ads.
732 * GNAT.AWK (g-awk.ads): GNAT AWK g-awk ads.
733 * GNAT.Bind_Environment (g-binenv.ads): GNAT Bind_Environment g-binenv ads.
734 * GNAT.Branch_Prediction (g-brapre.ads): GNAT Branch_Prediction g-brapre ads.
735 * GNAT.Bounded_Buffers (g-boubuf.ads): GNAT Bounded_Buffers g-boubuf ads.
736 * GNAT.Bounded_Mailboxes (g-boumai.ads): GNAT Bounded_Mailboxes g-boumai ads.
737 * GNAT.Bubble_Sort (g-bubsor.ads): GNAT Bubble_Sort g-bubsor ads.
738 * GNAT.Bubble_Sort_A (g-busora.ads): GNAT Bubble_Sort_A g-busora ads.
739 * GNAT.Bubble_Sort_G (g-busorg.ads): GNAT Bubble_Sort_G g-busorg ads.
740 * GNAT.Byte_Order_Mark (g-byorma.ads): GNAT Byte_Order_Mark g-byorma ads.
741 * GNAT.Byte_Swapping (g-bytswa.ads): GNAT Byte_Swapping g-bytswa ads.
742 * GNAT.Calendar (g-calend.ads): GNAT Calendar g-calend ads.
743 * GNAT.Calendar.Time_IO (g-catiio.ads): GNAT Calendar Time_IO g-catiio ads.
744 * GNAT.CRC32 (g-crc32.ads): GNAT CRC32 g-crc32 ads.
745 * GNAT.Case_Util (g-casuti.ads): GNAT Case_Util g-casuti ads.
746 * GNAT.CGI (g-cgi.ads): GNAT CGI g-cgi ads.
747 * GNAT.CGI.Cookie (g-cgicoo.ads): GNAT CGI Cookie g-cgicoo ads.
748 * GNAT.CGI.Debug (g-cgideb.ads): GNAT CGI Debug g-cgideb ads.
749 * GNAT.Command_Line (g-comlin.ads): GNAT Command_Line g-comlin ads.
750 * GNAT.Compiler_Version (g-comver.ads): GNAT Compiler_Version g-comver ads.
751 * GNAT.Ctrl_C (g-ctrl_c.ads): GNAT Ctrl_C g-ctrl_c ads.
752 * GNAT.Current_Exception (g-curexc.ads): GNAT Current_Exception g-curexc ads.
753 * GNAT.Debug_Pools (g-debpoo.ads): GNAT Debug_Pools g-debpoo ads.
754 * GNAT.Debug_Utilities (g-debuti.ads): GNAT Debug_Utilities g-debuti ads.
755 * GNAT.Decode_String (g-decstr.ads): GNAT Decode_String g-decstr ads.
756 * GNAT.Decode_UTF8_String (g-deutst.ads): GNAT Decode_UTF8_String g-deutst ads.
757 * GNAT.Directory_Operations (g-dirope.ads): GNAT Directory_Operations g-dirope ads.
758 * GNAT.Directory_Operations.Iteration (g-diopit.ads): GNAT Directory_Operations Iteration g-diopit ads.
759 * GNAT.Dynamic_HTables (g-dynhta.ads): GNAT Dynamic_HTables g-dynhta ads.
760 * GNAT.Dynamic_Tables (g-dyntab.ads): GNAT Dynamic_Tables g-dyntab ads.
761 * GNAT.Encode_String (g-encstr.ads): GNAT Encode_String g-encstr ads.
762 * GNAT.Encode_UTF8_String (g-enutst.ads): GNAT Encode_UTF8_String g-enutst ads.
763 * GNAT.Exception_Actions (g-excact.ads): GNAT Exception_Actions g-excact ads.
764 * GNAT.Exception_Traces (g-exctra.ads): GNAT Exception_Traces g-exctra ads.
765 * GNAT.Exceptions (g-except.ads): GNAT Exceptions g-except ads.
766 * GNAT.Expect (g-expect.ads): GNAT Expect g-expect ads.
767 * GNAT.Expect.TTY (g-exptty.ads): GNAT Expect TTY g-exptty ads.
768 * GNAT.Float_Control (g-flocon.ads): GNAT Float_Control g-flocon ads.
769 * GNAT.Formatted_String (g-forstr.ads): GNAT Formatted_String g-forstr ads.
770 * GNAT.Heap_Sort (g-heasor.ads): GNAT Heap_Sort g-heasor ads.
771 * GNAT.Heap_Sort_A (g-hesora.ads): GNAT Heap_Sort_A g-hesora ads.
772 * GNAT.Heap_Sort_G (g-hesorg.ads): GNAT Heap_Sort_G g-hesorg ads.
773 * GNAT.HTable (g-htable.ads): GNAT HTable g-htable ads.
774 * GNAT.IO (g-io.ads): GNAT IO g-io ads.
775 * GNAT.IO_Aux (g-io_aux.ads): GNAT IO_Aux g-io_aux ads.
776 * GNAT.Lock_Files (g-locfil.ads): GNAT Lock_Files g-locfil ads.
777 * GNAT.MBBS_Discrete_Random (g-mbdira.ads): GNAT MBBS_Discrete_Random g-mbdira ads.
778 * GNAT.MBBS_Float_Random (g-mbflra.ads): GNAT MBBS_Float_Random g-mbflra ads.
779 * GNAT.MD5 (g-md5.ads): GNAT MD5 g-md5 ads.
780 * GNAT.Memory_Dump (g-memdum.ads): GNAT Memory_Dump g-memdum ads.
781 * GNAT.Most_Recent_Exception (g-moreex.ads): GNAT Most_Recent_Exception g-moreex ads.
782 * GNAT.OS_Lib (g-os_lib.ads): GNAT OS_Lib g-os_lib ads.
783 * GNAT.Perfect_Hash_Generators (g-pehage.ads): GNAT Perfect_Hash_Generators g-pehage ads.
784 * GNAT.Random_Numbers (g-rannum.ads): GNAT Random_Numbers g-rannum ads.
785 * GNAT.Regexp (g-regexp.ads): GNAT Regexp g-regexp ads.
786 * GNAT.Registry (g-regist.ads): GNAT Registry g-regist ads.
787 * GNAT.Regpat (g-regpat.ads): GNAT Regpat g-regpat ads.
788 * GNAT.Rewrite_Data (g-rewdat.ads): GNAT Rewrite_Data g-rewdat ads.
789 * GNAT.Secondary_Stack_Info (g-sestin.ads): GNAT Secondary_Stack_Info g-sestin ads.
790 * GNAT.Semaphores (g-semaph.ads): GNAT Semaphores g-semaph ads.
791 * GNAT.Serial_Communications (g-sercom.ads): GNAT Serial_Communications g-sercom ads.
792 * GNAT.SHA1 (g-sha1.ads): GNAT SHA1 g-sha1 ads.
793 * GNAT.SHA224 (g-sha224.ads): GNAT SHA224 g-sha224 ads.
794 * GNAT.SHA256 (g-sha256.ads): GNAT SHA256 g-sha256 ads.
795 * GNAT.SHA384 (g-sha384.ads): GNAT SHA384 g-sha384 ads.
796 * GNAT.SHA512 (g-sha512.ads): GNAT SHA512 g-sha512 ads.
797 * GNAT.Signals (g-signal.ads): GNAT Signals g-signal ads.
798 * GNAT.Sockets (g-socket.ads): GNAT Sockets g-socket ads.
799 * GNAT.Source_Info (g-souinf.ads): GNAT Source_Info g-souinf ads.
800 * GNAT.Spelling_Checker (g-speche.ads): GNAT Spelling_Checker g-speche ads.
801 * GNAT.Spelling_Checker_Generic (g-spchge.ads): GNAT Spelling_Checker_Generic g-spchge ads.
802 * GNAT.Spitbol.Patterns (g-spipat.ads): GNAT Spitbol Patterns g-spipat ads.
803 * GNAT.Spitbol (g-spitbo.ads): GNAT Spitbol g-spitbo ads.
804 * GNAT.Spitbol.Table_Boolean (g-sptabo.ads): GNAT Spitbol Table_Boolean g-sptabo ads.
805 * GNAT.Spitbol.Table_Integer (g-sptain.ads): GNAT Spitbol Table_Integer g-sptain ads.
806 * GNAT.Spitbol.Table_VString (g-sptavs.ads): GNAT Spitbol Table_VString g-sptavs ads.
807 * GNAT.SSE (g-sse.ads): GNAT SSE g-sse ads.
808 * GNAT.SSE.Vector_Types (g-ssvety.ads): GNAT SSE Vector_Types g-ssvety ads.
809 * GNAT.String_Hash (g-strhas.ads): GNAT String_Hash g-strhas ads.
810 * GNAT.Strings (g-string.ads): GNAT Strings g-string ads.
811 * GNAT.String_Split (g-strspl.ads): GNAT String_Split g-strspl ads.
812 * GNAT.Table (g-table.ads): GNAT Table g-table ads.
813 * GNAT.Task_Lock (g-tasloc.ads): GNAT Task_Lock g-tasloc ads.
814 * GNAT.Time_Stamp (g-timsta.ads): GNAT Time_Stamp g-timsta ads.
815 * GNAT.Threads (g-thread.ads): GNAT Threads g-thread ads.
816 * GNAT.Traceback (g-traceb.ads): GNAT Traceback g-traceb ads.
817 * GNAT.Traceback.Symbolic (g-trasym.ads): GNAT Traceback Symbolic g-trasym ads.
818 * GNAT.UTF_32 (g-table.ads): GNAT UTF_32 g-table ads.
819 * GNAT.Wide_Spelling_Checker (g-u3spch.ads): GNAT Wide_Spelling_Checker g-u3spch ads.
820 * GNAT.Wide_Spelling_Checker (g-wispch.ads): GNAT Wide_Spelling_Checker g-wispch ads.
821 * GNAT.Wide_String_Split (g-wistsp.ads): GNAT Wide_String_Split g-wistsp ads.
822 * GNAT.Wide_Wide_Spelling_Checker (g-zspche.ads): GNAT Wide_Wide_Spelling_Checker g-zspche ads.
823 * GNAT.Wide_Wide_String_Split (g-zistsp.ads): GNAT Wide_Wide_String_Split g-zistsp ads.
824 * Interfaces.C.Extensions (i-cexten.ads): Interfaces C Extensions i-cexten ads.
825 * Interfaces.C.Streams (i-cstrea.ads): Interfaces C Streams i-cstrea ads.
826 * Interfaces.Packed_Decimal (i-pacdec.ads): Interfaces Packed_Decimal i-pacdec ads.
827 * Interfaces.VxWorks (i-vxwork.ads): Interfaces VxWorks i-vxwork ads.
828 * Interfaces.VxWorks.Int_Connection (i-vxinco.ads): Interfaces VxWorks Int_Connection i-vxinco ads.
829 * Interfaces.VxWorks.IO (i-vxwoio.ads): Interfaces VxWorks IO i-vxwoio ads.
830 * System.Address_Image (s-addima.ads): System Address_Image s-addima ads.
831 * System.Assertions (s-assert.ads): System Assertions s-assert ads.
832 * System.Atomic_Counters (s-atocou.ads): System Atomic_Counters s-atocou ads.
833 * System.Memory (s-memory.ads): System Memory s-memory ads.
834 * System.Multiprocessors (s-multip.ads): System Multiprocessors s-multip ads.
835 * System.Multiprocessors.Dispatching_Domains (s-mudido.ads): System Multiprocessors Dispatching_Domains s-mudido ads.
836 * System.Partition_Interface (s-parint.ads): System Partition_Interface s-parint ads.
837 * System.Pool_Global (s-pooglo.ads): System Pool_Global s-pooglo ads.
838 * System.Pool_Local (s-pooloc.ads): System Pool_Local s-pooloc ads.
839 * System.Restrictions (s-restri.ads): System Restrictions s-restri ads.
840 * System.Rident (s-rident.ads): System Rident s-rident ads.
841 * System.Strings.Stream_Ops (s-ststop.ads): System Strings Stream_Ops s-ststop ads.
842 * System.Unsigned_Types (s-unstyp.ads): System Unsigned_Types s-unstyp ads.
843 * System.Wch_Cnv (s-wchcnv.ads): System Wch_Cnv s-wchcnv ads.
844 * System.Wch_Con (s-wchcon.ads): System Wch_Con s-wchcon ads.
846 Interfacing to Other Languages
849 * Interfacing to C++::
850 * Interfacing to COBOL::
851 * Interfacing to Fortran::
852 * Interfacing to non-GNAT Ada code::
854 Implementation of Specific Ada Features
856 * Machine Code Insertions::
857 * GNAT Implementation of Tasking::
858 * GNAT Implementation of Shared Passive Packages::
859 * Code Generation for Array Aggregates::
860 * The Size of Discriminated Records with Default Discriminants::
861 * Strict Conformance to the Ada Reference Manual::
863 GNAT Implementation of Tasking
865 * Mapping Ada Tasks onto the Underlying Kernel Threads::
866 * Ensuring Compliance with the Real-Time Annex::
867 * Support for Locking Policies::
869 Code Generation for Array Aggregates
871 * Static constant aggregates with static bounds::
872 * Constant aggregates with unconstrained nominal types::
873 * Aggregates with static bounds::
874 * Aggregates with nonstatic bounds::
875 * Aggregates in assignment statements::
879 * pragma No_Run_Time::
881 * pragma Restricted_Run_Time::
883 * package System.Task_Info (s-tasinf.ads): package System Task_Info s-tasinf ads.
885 Compatibility and Porting Guide
887 * Writing Portable Fixed-Point Declarations::
888 * Compatibility with Ada 83::
889 * Compatibility between Ada 95 and Ada 2005::
890 * Implementation-dependent characteristics::
891 * Compatibility with Other Ada Systems::
892 * Representation Clauses::
893 * Compatibility with HP Ada 83::
895 Compatibility with Ada 83
897 * Legal Ada 83 programs that are illegal in Ada 95::
898 * More deterministic semantics::
899 * Changed semantics::
900 * Other language compatibility issues::
902 Implementation-dependent characteristics
904 * Implementation-defined pragmas::
905 * Implementation-defined attributes::
907 * Elaboration order::
908 * Target-specific aspects::
913 @node About This Guide,Implementation Defined Pragmas,Top,Top
914 @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}
915 @chapter About This Guide
919 This manual contains useful information in writing programs using the
920 GNAT compiler. It includes information on implementation dependent
921 characteristics of GNAT, including all the information required by
922 Annex M of the Ada language standard.
924 GNAT implements Ada 95, Ada 2005 and Ada 2012, and it may also be
925 invoked in Ada 83 compatibility mode.
926 By default, GNAT assumes Ada 2012,
927 but you can override with a compiler switch
928 to explicitly specify the language version.
929 (Please refer to the @emph{GNAT User's Guide} for details on these switches.)
930 Throughout this manual, references to 'Ada' without a year suffix
931 apply to all the Ada versions of the language.
933 Ada is designed to be highly portable.
934 In general, a program will have the same effect even when compiled by
935 different compilers on different platforms.
936 However, since Ada is designed to be used in a
937 wide variety of applications, it also contains a number of system
938 dependent features to be used in interfacing to the external world.
940 @geindex Implementation-dependent features
944 Note: Any program that makes use of implementation-dependent features
945 may be non-portable. You should follow good programming practice and
946 isolate and clearly document any sections of your program that make use
947 of these features in a non-portable manner.
950 * What This Reference Manual Contains::
952 * Related Information::
956 @node What This Reference Manual Contains,Conventions,,About This Guide
957 @anchor{gnat_rm/about_this_guide what-this-reference-manual-contains}@anchor{6}
958 @section What This Reference Manual Contains
961 This reference manual contains the following chapters:
967 @ref{7,,Implementation Defined Pragmas}, lists GNAT implementation-dependent
968 pragmas, which can be used to extend and enhance the functionality of the
972 @ref{8,,Implementation Defined Attributes}, lists GNAT
973 implementation-dependent attributes, which can be used to extend and
974 enhance the functionality of the compiler.
977 @ref{9,,Standard and Implementation Defined Restrictions}, lists GNAT
978 implementation-dependent restrictions, which can be used to extend and
979 enhance the functionality of the compiler.
982 @ref{a,,Implementation Advice}, provides information on generally
983 desirable behavior which are not requirements that all compilers must
984 follow since it cannot be provided on all systems, or which may be
985 undesirable on some systems.
988 @ref{b,,Implementation Defined Characteristics}, provides a guide to
989 minimizing implementation dependent features.
992 @ref{c,,Intrinsic Subprograms}, describes the intrinsic subprograms
993 implemented by GNAT, and how they can be imported into user
994 application programs.
997 @ref{d,,Representation Clauses and Pragmas}, describes in detail the
998 way that GNAT represents data, and in particular the exact set
999 of representation clauses and pragmas that is accepted.
1002 @ref{e,,Standard Library Routines}, provides a listing of packages and a
1003 brief description of the functionality that is provided by Ada's
1004 extensive set of standard library routines as implemented by GNAT.
1007 @ref{f,,The Implementation of Standard I/O}, details how the GNAT
1008 implementation of the input-output facilities.
1011 @ref{10,,The GNAT Library}, is a catalog of packages that complement
1012 the Ada predefined library.
1015 @ref{11,,Interfacing to Other Languages}, describes how programs
1016 written in Ada using GNAT can be interfaced to other programming
1020 @ref{12,,Specialized Needs Annexes}, describes the GNAT implementation of all
1021 of the specialized needs annexes.
1024 @ref{13,,Implementation of Specific Ada Features}, discusses issues related
1025 to GNAT's implementation of machine code insertions, tasking, and several
1029 @ref{14,,Implementation of Ada 2012 Features}, describes the status of the
1030 GNAT implementation of the Ada 2012 language standard.
1033 @ref{15,,Obsolescent Features} documents implementation dependent features,
1034 including pragmas and attributes, which are considered obsolescent, since
1035 there are other preferred ways of achieving the same results. These
1036 obsolescent forms are retained for backwards compatibility.
1039 @ref{16,,Compatibility and Porting Guide} presents some guidelines for
1040 developing portable Ada code, describes the compatibility issues that
1041 may arise between GNAT and other Ada compilation systems (including those
1042 for Ada 83), and shows how GNAT can expedite porting applications
1043 developed in other Ada environments.
1046 @ref{1,,GNU Free Documentation License} contains the license for this document.
1049 @geindex Ada 95 Language Reference Manual
1051 @geindex Ada 2005 Language Reference Manual
1053 This reference manual assumes a basic familiarity with the Ada 95 language, as
1055 @cite{International Standard ANSI/ISO/IEC-8652:1995}.
1056 It does not require knowledge of the new features introduced by Ada 2005 or
1058 All three reference manuals are included in the GNAT documentation
1061 @node Conventions,Related Information,What This Reference Manual Contains,About This Guide
1062 @anchor{gnat_rm/about_this_guide conventions}@anchor{17}
1063 @section Conventions
1066 @geindex Conventions
1067 @geindex typographical
1069 @geindex Typographical conventions
1071 Following are examples of the typographical and graphic conventions used
1078 @code{Functions}, @code{utility program names}, @code{standard names},
1094 [optional information or parameters]
1097 Examples are described by text
1100 and then shown this way.
1104 Commands that are entered by the user are shown as preceded by a prompt string
1105 comprising the @code{$} character followed by a space.
1108 @node Related Information,,Conventions,About This Guide
1109 @anchor{gnat_rm/about_this_guide related-information}@anchor{18}
1110 @section Related Information
1113 See the following documents for further information on GNAT:
1119 @cite{GNAT User's Guide for Native Platforms},
1120 which provides information on how to use the
1121 GNAT development environment.
1124 @cite{Ada 95 Reference Manual}, the Ada 95 programming language standard.
1127 @cite{Ada 95 Annotated Reference Manual}, which is an annotated version
1128 of the Ada 95 standard. The annotations describe
1129 detailed aspects of the design decision, and in particular contain useful
1130 sections on Ada 83 compatibility.
1133 @cite{Ada 2005 Reference Manual}, the Ada 2005 programming language standard.
1136 @cite{Ada 2005 Annotated Reference Manual}, which is an annotated version
1137 of the Ada 2005 standard. The annotations describe
1138 detailed aspects of the design decision.
1141 @cite{Ada 2012 Reference Manual}, the Ada 2012 programming language standard.
1144 @cite{DEC Ada@comma{} Technical Overview and Comparison on DIGITAL Platforms},
1145 which contains specific information on compatibility between GNAT and
1149 @cite{DEC Ada@comma{} Language Reference Manual}, part number AA-PYZAB-TK, which
1150 describes in detail the pragmas and attributes provided by the DEC Ada 83
1154 @node Implementation Defined Pragmas,Implementation Defined Aspects,About This Guide,Top
1155 @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}
1156 @chapter Implementation Defined Pragmas
1159 Ada defines a set of pragmas that can be used to supply additional
1160 information to the compiler. These language defined pragmas are
1161 implemented in GNAT and work as described in the Ada Reference Manual.
1163 In addition, Ada allows implementations to define additional pragmas
1164 whose meaning is defined by the implementation. GNAT provides a number
1165 of these implementation-defined pragmas, which can be used to extend
1166 and enhance the functionality of the compiler. This section of the GNAT
1167 Reference Manual describes these additional pragmas.
1169 Note that any program using these pragmas might not be portable to other
1170 compilers (although GNAT implements this set of pragmas on all
1171 platforms). Therefore if portability to other compilers is an important
1172 consideration, the use of these pragmas should be minimized.
1175 * Pragma Abort_Defer::
1176 * Pragma Abstract_State::
1177 * Pragma Acc_Parallel::
1179 * Pragma Acc_Kernels::
1187 * Pragma Allow_Integer_Address::
1190 * Pragma Assert_And_Cut::
1191 * Pragma Assertion_Policy::
1193 * Pragma Assume_No_Invalid_Values::
1194 * Pragma Async_Readers::
1195 * Pragma Async_Writers::
1196 * Pragma Attribute_Definition::
1197 * Pragma C_Pass_By_Copy::
1199 * Pragma Check_Float_Overflow::
1200 * Pragma Check_Name::
1201 * Pragma Check_Policy::
1203 * Pragma Common_Object::
1204 * Pragma Compile_Time_Error::
1205 * Pragma Compile_Time_Warning::
1206 * Pragma Compiler_Unit::
1207 * Pragma Compiler_Unit_Warning::
1208 * Pragma Complete_Representation::
1209 * Pragma Complex_Representation::
1210 * Pragma Component_Alignment::
1211 * Pragma Constant_After_Elaboration::
1212 * Pragma Contract_Cases::
1213 * Pragma Convention_Identifier::
1214 * Pragma CPP_Class::
1215 * Pragma CPP_Constructor::
1216 * Pragma CPP_Virtual::
1217 * Pragma CPP_Vtable::
1219 * Pragma Deadline_Floor::
1220 * Pragma Default_Initial_Condition::
1222 * Pragma Debug_Policy::
1223 * Pragma Default_Scalar_Storage_Order::
1224 * Pragma Default_Storage_Pool::
1226 * Pragma Detect_Blocking::
1227 * Pragma Disable_Atomic_Synchronization::
1228 * Pragma Dispatching_Domain::
1229 * Pragma Effective_Reads::
1230 * Pragma Effective_Writes::
1231 * Pragma Elaboration_Checks::
1232 * Pragma Eliminate::
1233 * Pragma Enable_Atomic_Synchronization::
1234 * Pragma Export_Function::
1235 * Pragma Export_Object::
1236 * Pragma Export_Procedure::
1237 * Pragma Export_Value::
1238 * Pragma Export_Valued_Procedure::
1239 * Pragma Extend_System::
1240 * Pragma Extensions_Allowed::
1241 * Pragma Extensions_Visible::
1243 * Pragma External_Name_Casing::
1244 * Pragma Fast_Math::
1245 * Pragma Favor_Top_Level::
1246 * Pragma Finalize_Storage_Only::
1247 * Pragma Float_Representation::
1251 * Pragma Ignore_Pragma::
1252 * Pragma Implementation_Defined::
1253 * Pragma Implemented::
1254 * Pragma Implicit_Packing::
1255 * Pragma Import_Function::
1256 * Pragma Import_Object::
1257 * Pragma Import_Procedure::
1258 * Pragma Import_Valued_Procedure::
1259 * Pragma Independent::
1260 * Pragma Independent_Components::
1261 * Pragma Initial_Condition::
1262 * Pragma Initialize_Scalars::
1263 * Pragma Initializes::
1264 * Pragma Inline_Always::
1265 * Pragma Inline_Generic::
1266 * Pragma Interface::
1267 * Pragma Interface_Name::
1268 * Pragma Interrupt_Handler::
1269 * Pragma Interrupt_State::
1270 * Pragma Invariant::
1271 * Pragma Keep_Names::
1273 * Pragma Link_With::
1274 * Pragma Linker_Alias::
1275 * Pragma Linker_Constructor::
1276 * Pragma Linker_Destructor::
1277 * Pragma Linker_Section::
1278 * Pragma Lock_Free::
1279 * Pragma Loop_Invariant::
1280 * Pragma Loop_Optimize::
1281 * Pragma Loop_Variant::
1282 * Pragma Machine_Attribute::
1284 * Pragma Main_Storage::
1285 * Pragma Max_Queue_Length::
1287 * Pragma No_Caching::
1288 * Pragma No_Component_Reordering::
1289 * Pragma No_Elaboration_Code_All::
1290 * Pragma No_Heap_Finalization::
1291 * Pragma No_Inline::
1292 * Pragma No_Return::
1293 * Pragma No_Run_Time::
1294 * Pragma No_Strict_Aliasing::
1295 * Pragma No_Tagged_Streams::
1296 * Pragma Normalize_Scalars::
1297 * Pragma Obsolescent::
1298 * Pragma Optimize_Alignment::
1300 * Pragma Overflow_Mode::
1301 * Pragma Overriding_Renamings::
1302 * Pragma Partition_Elaboration_Policy::
1305 * Pragma Persistent_BSS::
1308 * Pragma Postcondition::
1309 * Pragma Post_Class::
1310 * Pragma Rename_Pragma::
1312 * Pragma Precondition::
1313 * Pragma Predicate::
1314 * Pragma Predicate_Failure::
1315 * Pragma Preelaborable_Initialization::
1316 * Pragma Prefix_Exception_Messages::
1317 * Pragma Pre_Class::
1318 * Pragma Priority_Specific_Dispatching::
1320 * Pragma Profile_Warnings::
1321 * Pragma Propagate_Exceptions::
1322 * Pragma Provide_Shift_Operators::
1323 * Pragma Psect_Object::
1324 * Pragma Pure_Function::
1326 * Pragma Ravenscar::
1327 * Pragma Refined_Depends::
1328 * Pragma Refined_Global::
1329 * Pragma Refined_Post::
1330 * Pragma Refined_State::
1331 * Pragma Relative_Deadline::
1332 * Pragma Remote_Access_Type::
1333 * Pragma Restricted_Run_Time::
1334 * Pragma Restriction_Warnings::
1335 * Pragma Reviewable::
1336 * Pragma Secondary_Stack_Size::
1337 * Pragma Share_Generic::
1339 * Pragma Short_Circuit_And_Or::
1340 * Pragma Short_Descriptors::
1341 * Pragma Simple_Storage_Pool_Type::
1342 * Pragma Source_File_Name::
1343 * Pragma Source_File_Name_Project::
1344 * Pragma Source_Reference::
1345 * Pragma SPARK_Mode::
1346 * Pragma Static_Elaboration_Desired::
1347 * Pragma Stream_Convert::
1348 * Pragma Style_Checks::
1351 * Pragma Suppress_All::
1352 * Pragma Suppress_Debug_Info::
1353 * Pragma Suppress_Exception_Locations::
1354 * Pragma Suppress_Initialization::
1355 * Pragma Task_Name::
1356 * Pragma Task_Storage::
1357 * Pragma Test_Case::
1358 * Pragma Thread_Local_Storage::
1359 * Pragma Time_Slice::
1361 * Pragma Type_Invariant::
1362 * Pragma Type_Invariant_Class::
1363 * Pragma Unchecked_Union::
1364 * Pragma Unevaluated_Use_Of_Old::
1365 * Pragma Unimplemented_Unit::
1366 * Pragma Universal_Aliasing::
1367 * Pragma Universal_Data::
1368 * Pragma Unmodified::
1369 * Pragma Unreferenced::
1370 * Pragma Unreferenced_Objects::
1371 * Pragma Unreserve_All_Interrupts::
1372 * Pragma Unsuppress::
1373 * Pragma Use_VADS_Size::
1375 * Pragma Validity_Checks::
1377 * Pragma Volatile_Full_Access::
1378 * Pragma Volatile_Function::
1379 * Pragma Warning_As_Error::
1381 * Pragma Weak_External::
1382 * Pragma Wide_Character_Encoding::
1386 @node Pragma Abort_Defer,Pragma Abstract_State,,Implementation Defined Pragmas
1387 @anchor{gnat_rm/implementation_defined_pragmas pragma-abort-defer}@anchor{1b}
1388 @section Pragma Abort_Defer
1391 @geindex Deferring aborts
1399 This pragma must appear at the start of the statement sequence of a
1400 handled sequence of statements (right after the @code{begin}). It has
1401 the effect of deferring aborts for the sequence of statements (but not
1402 for the declarations or handlers, if any, associated with this statement
1405 @node Pragma Abstract_State,Pragma Acc_Parallel,Pragma Abort_Defer,Implementation Defined Pragmas
1406 @anchor{gnat_rm/implementation_defined_pragmas pragma-abstract-state}@anchor{1c}@anchor{gnat_rm/implementation_defined_pragmas id2}@anchor{1d}
1407 @section Pragma Abstract_State
1413 pragma Abstract_State (ABSTRACT_STATE_LIST);
1415 ABSTRACT_STATE_LIST ::=
1417 | STATE_NAME_WITH_OPTIONS
1418 | (STATE_NAME_WITH_OPTIONS @{, STATE_NAME_WITH_OPTIONS@} )
1420 STATE_NAME_WITH_OPTIONS ::=
1422 | (STATE_NAME with OPTION_LIST)
1424 OPTION_LIST ::= OPTION @{, OPTION@}
1430 SIMPLE_OPTION ::= Ghost | Synchronous
1432 NAME_VALUE_OPTION ::=
1433 Part_Of => ABSTRACT_STATE
1434 | External [=> EXTERNAL_PROPERTY_LIST]
1436 EXTERNAL_PROPERTY_LIST ::=
1438 | (EXTERNAL_PROPERTY @{, EXTERNAL_PROPERTY@} )
1440 EXTERNAL_PROPERTY ::=
1441 Async_Readers [=> boolean_EXPRESSION]
1442 | Async_Writers [=> boolean_EXPRESSION]
1443 | Effective_Reads [=> boolean_EXPRESSION]
1444 | Effective_Writes [=> boolean_EXPRESSION]
1445 others => boolean_EXPRESSION
1447 STATE_NAME ::= defining_identifier
1449 ABSTRACT_STATE ::= name
1452 For the semantics of this pragma, see the entry for aspect @code{Abstract_State} in
1453 the SPARK 2014 Reference Manual, section 7.1.4.
1455 @node Pragma Acc_Parallel,Pragma Acc_Loop,Pragma Abstract_State,Implementation Defined Pragmas
1456 @anchor{gnat_rm/implementation_defined_pragmas pragma-acc-parallel}@anchor{1e}
1457 @section Pragma Acc_Parallel
1463 pragma Acc_Parallel [( ACC_PARALLEL_CLAUSE [, ACC_PARALLEL_CLAUSE... ])];
1465 ACC_PARALLEL_CLAUSE ::=
1466 Acc_If => boolean_EXPRESSION
1467 | Acc_Private => IDENTIFIERS
1468 | Async => integer_EXPRESSION
1469 | Copy => IDENTIFIERS
1470 | Copy_In => IDENTIFIERS
1471 | Copy_Out => IDENTIFIERS
1472 | Create => IDENTIFIERS
1474 | Device_Ptr => IDENTIFIERS
1475 | First_Private => IDENTIFIERS
1476 | Num_Gangs => integer_EXPRESSION
1477 | Num_Workers => integer_EXPRESSION
1478 | Present => IDENTIFIERS
1479 | Reduction => (REDUCTION_RECORD)
1480 | Vector_Length => integer_EXPRESSION
1483 REDUCTION_RECORD ::=
1485 | "*" => IDENTIFIERS
1486 | "min" => IDENTIFIERS
1487 | "max" => IDENTIFIERS
1488 | "or" => IDENTIFIERS
1489 | "and" => IDENTIFIERS
1493 | (IDENTIFIER, IDENTIFIERS)
1496 | integer_EXPRESSION
1497 | (integer_EXPRESSION, INTEGERS)
1500 Requires the @code{-fopenacc} flag.
1502 Equivalent to the @code{parallel} directive of the OpenAcc standard. This pragma
1503 should be placed in loops. It offloads the content of the loop to an
1506 For more information about the effect of the clauses, see the OpenAcc
1509 @node Pragma Acc_Loop,Pragma Acc_Kernels,Pragma Acc_Parallel,Implementation Defined Pragmas
1510 @anchor{gnat_rm/implementation_defined_pragmas pragma-acc-loop}@anchor{1f}
1511 @section Pragma Acc_Loop
1517 pragma Acc_Loop [( ACC_LOOP_CLAUSE [, ACC_LOOP_CLAUSE... ])];
1521 | Collapse => INTEGER_LITERAL
1522 | Gang [=> GANG_ARG]
1524 | Private => IDENTIFIERS
1525 | Reduction => (REDUCTION_RECORD)
1527 | Tile => SIZE_EXPRESSION
1528 | Vector [=> integer_EXPRESSION]
1529 | Worker [=> integer_EXPRESSION]
1533 | Static => SIZE_EXPRESSION
1537 | integer_EXPRESSION
1540 Requires the @code{-fopenacc} flag.
1542 Equivalent to the @code{loop} directive of the OpenAcc standard. This pragma
1543 should be placed in for loops after the "Acc_Parallel" pragma. It tells the
1544 compiler how to parallelize the loop.
1546 For more information about the effect of the clauses, see the OpenAcc
1549 @node Pragma Acc_Kernels,Pragma Acc_Data,Pragma Acc_Loop,Implementation Defined Pragmas
1550 @anchor{gnat_rm/implementation_defined_pragmas pragma-acc-kernels}@anchor{20}
1551 @section Pragma Acc_Kernels
1557 pragma Acc_Kernels [( ACC_KERNELS_CLAUSE [, ACC_KERNELS_CLAUSE...])];
1559 ACC_KERNELS_CLAUSE ::=
1560 Acc_If => boolean_EXPRESSION
1561 | Async => integer_EXPRESSION
1562 | Copy => IDENTIFIERS
1563 | Copy_In => IDENTIFIERS
1564 | Copy_Out => IDENTIFIERS
1565 | Create => IDENTIFIERS
1567 | Device_Ptr => IDENTIFIERS
1568 | Num_Gangs => integer_EXPRESSION
1569 | Num_Workers => integer_EXPRESSION
1570 | Present => IDENTIFIERS
1571 | Vector_Length => integer_EXPRESSION
1576 | (IDENTIFIER, IDENTIFIERS)
1579 | integer_EXPRESSION
1580 | (integer_EXPRESSION, INTEGERS)
1583 Requires the @code{-fopenacc} flag.
1585 Equivalent to the kernels directive of the OpenAcc standard. This pragma should
1588 For more information about the effect of the clauses, see the OpenAcc
1591 @node Pragma Acc_Data,Pragma Ada_83,Pragma Acc_Kernels,Implementation Defined Pragmas
1592 @anchor{gnat_rm/implementation_defined_pragmas pragma-acc-data}@anchor{21}
1593 @section Pragma Acc_Data
1599 pragma Acc_Data ([ ACC_DATA_CLAUSE [, ACC_DATA_CLAUSE...]]);
1603 | Copy_In => IDENTIFIERS
1604 | Copy_Out => IDENTIFIERS
1605 | Create => IDENTIFIERS
1606 | Device_Ptr => IDENTIFIERS
1607 | Present => IDENTIFIERS
1610 Requires the @code{-fopenacc} flag.
1612 Equivalent to the @code{data} directive of the OpenAcc standard. This pragma
1613 should be placed in loops.
1615 For more information about the effect of the clauses, see the OpenAcc
1618 @node Pragma Ada_83,Pragma Ada_95,Pragma Acc_Data,Implementation Defined Pragmas
1619 @anchor{gnat_rm/implementation_defined_pragmas pragma-ada-83}@anchor{22}
1620 @section Pragma Ada_83
1629 A configuration pragma that establishes Ada 83 mode for the unit to
1630 which it applies, regardless of the mode set by the command line
1631 switches. In Ada 83 mode, GNAT attempts to be as compatible with
1632 the syntax and semantics of Ada 83, as defined in the original Ada
1633 83 Reference Manual as possible. In particular, the keywords added by Ada 95
1634 and Ada 2005 are not recognized, optional package bodies are allowed,
1635 and generics may name types with unknown discriminants without using
1636 the @code{(<>)} notation. In addition, some but not all of the additional
1637 restrictions of Ada 83 are enforced.
1639 Ada 83 mode is intended for two purposes. Firstly, it allows existing
1640 Ada 83 code to be compiled and adapted to GNAT with less effort.
1641 Secondly, it aids in keeping code backwards compatible with Ada 83.
1642 However, there is no guarantee that code that is processed correctly
1643 by GNAT in Ada 83 mode will in fact compile and execute with an Ada
1644 83 compiler, since GNAT does not enforce all the additional checks
1647 @node Pragma Ada_95,Pragma Ada_05,Pragma Ada_83,Implementation Defined Pragmas
1648 @anchor{gnat_rm/implementation_defined_pragmas pragma-ada-95}@anchor{23}
1649 @section Pragma Ada_95
1658 A configuration pragma that establishes Ada 95 mode for the unit to which
1659 it applies, regardless of the mode set by the command line switches.
1660 This mode is set automatically for the @code{Ada} and @code{System}
1661 packages and their children, so you need not specify it in these
1662 contexts. This pragma is useful when writing a reusable component that
1663 itself uses Ada 95 features, but which is intended to be usable from
1664 either Ada 83 or Ada 95 programs.
1666 @node Pragma Ada_05,Pragma Ada_2005,Pragma Ada_95,Implementation Defined Pragmas
1667 @anchor{gnat_rm/implementation_defined_pragmas pragma-ada-05}@anchor{24}
1668 @section Pragma Ada_05
1675 pragma Ada_05 (local_NAME);
1678 A configuration pragma that establishes Ada 2005 mode for the unit to which
1679 it applies, regardless of the mode set by the command line switches.
1680 This pragma is useful when writing a reusable component that
1681 itself uses Ada 2005 features, but which is intended to be usable from
1682 either Ada 83 or Ada 95 programs.
1684 The one argument form (which is not a configuration pragma)
1685 is used for managing the transition from
1686 Ada 95 to Ada 2005 in the run-time library. If an entity is marked
1687 as Ada_2005 only, then referencing the entity in Ada_83 or Ada_95
1688 mode will generate a warning. In addition, in Ada_83 or Ada_95
1689 mode, a preference rule is established which does not choose
1690 such an entity unless it is unambiguously specified. This avoids
1691 extra subprograms marked this way from generating ambiguities in
1692 otherwise legal pre-Ada_2005 programs. The one argument form is
1693 intended for exclusive use in the GNAT run-time library.
1695 @node Pragma Ada_2005,Pragma Ada_12,Pragma Ada_05,Implementation Defined Pragmas
1696 @anchor{gnat_rm/implementation_defined_pragmas pragma-ada-2005}@anchor{25}
1697 @section Pragma Ada_2005
1706 This configuration pragma is a synonym for pragma Ada_05 and has the
1707 same syntax and effect.
1709 @node Pragma Ada_12,Pragma Ada_2012,Pragma Ada_2005,Implementation Defined Pragmas
1710 @anchor{gnat_rm/implementation_defined_pragmas pragma-ada-12}@anchor{26}
1711 @section Pragma Ada_12
1718 pragma Ada_12 (local_NAME);
1721 A configuration pragma that establishes Ada 2012 mode for the unit to which
1722 it applies, regardless of the mode set by the command line switches.
1723 This mode is set automatically for the @code{Ada} and @code{System}
1724 packages and their children, so you need not specify it in these
1725 contexts. This pragma is useful when writing a reusable component that
1726 itself uses Ada 2012 features, but which is intended to be usable from
1727 Ada 83, Ada 95, or Ada 2005 programs.
1729 The one argument form, which is not a configuration pragma,
1730 is used for managing the transition from Ada
1731 2005 to Ada 2012 in the run-time library. If an entity is marked
1732 as Ada_2012 only, then referencing the entity in any pre-Ada_2012
1733 mode will generate a warning. In addition, in any pre-Ada_2012
1734 mode, a preference rule is established which does not choose
1735 such an entity unless it is unambiguously specified. This avoids
1736 extra subprograms marked this way from generating ambiguities in
1737 otherwise legal pre-Ada_2012 programs. The one argument form is
1738 intended for exclusive use in the GNAT run-time library.
1740 @node Pragma Ada_2012,Pragma Allow_Integer_Address,Pragma Ada_12,Implementation Defined Pragmas
1741 @anchor{gnat_rm/implementation_defined_pragmas pragma-ada-2012}@anchor{27}
1742 @section Pragma Ada_2012
1751 This configuration pragma is a synonym for pragma Ada_12 and has the
1752 same syntax and effect.
1754 @node Pragma Allow_Integer_Address,Pragma Annotate,Pragma Ada_2012,Implementation Defined Pragmas
1755 @anchor{gnat_rm/implementation_defined_pragmas pragma-allow-integer-address}@anchor{28}
1756 @section Pragma Allow_Integer_Address
1762 pragma Allow_Integer_Address;
1765 In almost all versions of GNAT, @code{System.Address} is a private
1766 type in accordance with the implementation advice in the RM. This
1767 means that integer values,
1768 in particular integer literals, are not allowed as address values.
1769 If the configuration pragma
1770 @code{Allow_Integer_Address} is given, then integer expressions may
1771 be used anywhere a value of type @code{System.Address} is required.
1772 The effect is to introduce an implicit unchecked conversion from the
1773 integer value to type @code{System.Address}. The reverse case of using
1774 an address where an integer type is required is handled analogously.
1775 The following example compiles without errors:
1778 pragma Allow_Integer_Address;
1779 with System; use System;
1780 package AddrAsInt is
1783 for X'Address use 16#1240#;
1784 for Y use at 16#3230#;
1785 m : Address := 16#4000#;
1786 n : constant Address := 4000;
1787 p : constant Address := Address (X + Y);
1788 v : Integer := y'Address;
1789 w : constant Integer := Integer (Y'Address);
1790 type R is new integer;
1793 for Z'Address use RR;
1797 Note that pragma @code{Allow_Integer_Address} is ignored if @code{System.Address}
1798 is not a private type. In implementations of @code{GNAT} where
1799 System.Address is a visible integer type,
1800 this pragma serves no purpose but is ignored
1801 rather than rejected to allow common sets of sources to be used
1802 in the two situations.
1804 @node Pragma Annotate,Pragma Assert,Pragma Allow_Integer_Address,Implementation Defined Pragmas
1805 @anchor{gnat_rm/implementation_defined_pragmas pragma-annotate}@anchor{29}@anchor{gnat_rm/implementation_defined_pragmas id3}@anchor{2a}
1806 @section Pragma Annotate
1812 pragma Annotate (IDENTIFIER [, IDENTIFIER @{, ARG@}] [, entity => local_NAME]);
1814 ARG ::= NAME | EXPRESSION
1817 This pragma is used to annotate programs. IDENTIFIER identifies
1818 the type of annotation. GNAT verifies that it is an identifier, but does
1819 not otherwise analyze it. The second optional identifier is also left
1820 unanalyzed, and by convention is used to control the action of the tool to
1821 which the annotation is addressed. The remaining ARG arguments
1822 can be either string literals or more generally expressions.
1823 String literals are assumed to be either of type
1824 @code{Standard.String} or else @code{Wide_String} or @code{Wide_Wide_String}
1825 depending on the character literals they contain.
1826 All other kinds of arguments are analyzed as expressions, and must be
1827 unambiguous. The last argument if present must have the identifier
1828 @code{Entity} and GNAT verifies that a local name is given.
1830 The analyzed pragma is retained in the tree, but not otherwise processed
1831 by any part of the GNAT compiler, except to generate corresponding note
1832 lines in the generated ALI file. For the format of these note lines, see
1833 the compiler source file lib-writ.ads. This pragma is intended for use by
1834 external tools, including ASIS. The use of pragma Annotate does not
1835 affect the compilation process in any way. This pragma may be used as
1836 a configuration pragma.
1838 @node Pragma Assert,Pragma Assert_And_Cut,Pragma Annotate,Implementation Defined Pragmas
1839 @anchor{gnat_rm/implementation_defined_pragmas pragma-assert}@anchor{2b}
1840 @section Pragma Assert
1848 [, string_EXPRESSION]);
1851 The effect of this pragma depends on whether the corresponding command
1852 line switch is set to activate assertions. The pragma expands into code
1853 equivalent to the following:
1856 if assertions-enabled then
1857 if not boolean_EXPRESSION then
1858 System.Assertions.Raise_Assert_Failure
1859 (string_EXPRESSION);
1864 The string argument, if given, is the message that will be associated
1865 with the exception occurrence if the exception is raised. If no second
1866 argument is given, the default message is @code{file}:@code{nnn},
1867 where @code{file} is the name of the source file containing the assert,
1868 and @code{nnn} is the line number of the assert.
1870 Note that, as with the @code{if} statement to which it is equivalent, the
1871 type of the expression is either @code{Standard.Boolean}, or any type derived
1872 from this standard type.
1874 Assert checks can be either checked or ignored. By default they are ignored.
1875 They will be checked if either the command line switch @emph{-gnata} is
1876 used, or if an @code{Assertion_Policy} or @code{Check_Policy} pragma is used
1877 to enable @code{Assert_Checks}.
1879 If assertions are ignored, then there
1880 is no run-time effect (and in particular, any side effects from the
1881 expression will not occur at run time). (The expression is still
1882 analyzed at compile time, and may cause types to be frozen if they are
1883 mentioned here for the first time).
1885 If assertions are checked, then the given expression is tested, and if
1886 it is @code{False} then @code{System.Assertions.Raise_Assert_Failure} is called
1887 which results in the raising of @code{Assert_Failure} with the given message.
1889 You should generally avoid side effects in the expression arguments of
1890 this pragma, because these side effects will turn on and off with the
1891 setting of the assertions mode, resulting in assertions that have an
1892 effect on the program. However, the expressions are analyzed for
1893 semantic correctness whether or not assertions are enabled, so turning
1894 assertions on and off cannot affect the legality of a program.
1896 Note that the implementation defined policy @code{DISABLE}, given in a
1897 pragma @code{Assertion_Policy}, can be used to suppress this semantic analysis.
1899 Note: this is a standard language-defined pragma in versions
1900 of Ada from 2005 on. In GNAT, it is implemented in all versions
1901 of Ada, and the DISABLE policy is an implementation-defined
1904 @node Pragma Assert_And_Cut,Pragma Assertion_Policy,Pragma Assert,Implementation Defined Pragmas
1905 @anchor{gnat_rm/implementation_defined_pragmas pragma-assert-and-cut}@anchor{2c}
1906 @section Pragma Assert_And_Cut
1912 pragma Assert_And_Cut (
1914 [, string_EXPRESSION]);
1917 The effect of this pragma is identical to that of pragma @code{Assert},
1918 except that in an @code{Assertion_Policy} pragma, the identifier
1919 @code{Assert_And_Cut} is used to control whether it is ignored or checked
1922 The intention is that this be used within a subprogram when the
1923 given test expresion sums up all the work done so far in the
1924 subprogram, so that the rest of the subprogram can be verified
1925 (informally or formally) using only the entry preconditions,
1926 and the expression in this pragma. This allows dividing up
1927 a subprogram into sections for the purposes of testing or
1928 formal verification. The pragma also serves as useful
1931 @node Pragma Assertion_Policy,Pragma Assume,Pragma Assert_And_Cut,Implementation Defined Pragmas
1932 @anchor{gnat_rm/implementation_defined_pragmas pragma-assertion-policy}@anchor{2d}
1933 @section Pragma Assertion_Policy
1939 pragma Assertion_Policy (CHECK | DISABLE | IGNORE | SUPPRESSIBLE);
1941 pragma Assertion_Policy (
1942 ASSERTION_KIND => POLICY_IDENTIFIER
1943 @{, ASSERTION_KIND => POLICY_IDENTIFIER@});
1945 ASSERTION_KIND ::= RM_ASSERTION_KIND | ID_ASSERTION_KIND
1947 RM_ASSERTION_KIND ::= Assert |
1955 Type_Invariant'Class
1957 ID_ASSERTION_KIND ::= Assertions |
1971 Statement_Assertions
1973 POLICY_IDENTIFIER ::= Check | Disable | Ignore | Suppressible
1976 This is a standard Ada 2012 pragma that is available as an
1977 implementation-defined pragma in earlier versions of Ada.
1978 The assertion kinds @code{RM_ASSERTION_KIND} are those defined in
1979 the Ada standard. The assertion kinds @code{ID_ASSERTION_KIND}
1980 are implementation defined additions recognized by the GNAT compiler.
1982 The pragma applies in both cases to pragmas and aspects with matching
1983 names, e.g. @code{Pre} applies to the Pre aspect, and @code{Precondition}
1984 applies to both the @code{Precondition} pragma
1985 and the aspect @code{Precondition}. Note that the identifiers for
1986 pragmas Pre_Class and Post_Class are Pre'Class and Post'Class (not
1987 Pre_Class and Post_Class), since these pragmas are intended to be
1988 identical to the corresponding aspects).
1990 If the policy is @code{CHECK}, then assertions are enabled, i.e.
1991 the corresponding pragma or aspect is activated.
1992 If the policy is @code{IGNORE}, then assertions are ignored, i.e.
1993 the corresponding pragma or aspect is deactivated.
1994 This pragma overrides the effect of the @emph{-gnata} switch on the
1996 If the policy is @code{SUPPRESSIBLE}, then assertions are enabled by default,
1997 however, if the @emph{-gnatp} switch is specified all assertions are ignored.
1999 The implementation defined policy @code{DISABLE} is like
2000 @code{IGNORE} except that it completely disables semantic
2001 checking of the corresponding pragma or aspect. This is
2002 useful when the pragma or aspect argument references subprograms
2003 in a with'ed package which is replaced by a dummy package
2004 for the final build.
2006 The implementation defined assertion kind @code{Assertions} applies to all
2007 assertion kinds. The form with no assertion kind given implies this
2008 choice, so it applies to all assertion kinds (RM defined, and
2009 implementation defined).
2011 The implementation defined assertion kind @code{Statement_Assertions}
2012 applies to @code{Assert}, @code{Assert_And_Cut},
2013 @code{Assume}, @code{Loop_Invariant}, and @code{Loop_Variant}.
2015 @node Pragma Assume,Pragma Assume_No_Invalid_Values,Pragma Assertion_Policy,Implementation Defined Pragmas
2016 @anchor{gnat_rm/implementation_defined_pragmas pragma-assume}@anchor{2e}
2017 @section Pragma Assume
2025 [, string_EXPRESSION]);
2028 The effect of this pragma is identical to that of pragma @code{Assert},
2029 except that in an @code{Assertion_Policy} pragma, the identifier
2030 @code{Assume} is used to control whether it is ignored or checked
2033 The intention is that this be used for assumptions about the
2034 external environment. So you cannot expect to verify formally
2035 or informally that the condition is met, this must be
2036 established by examining things outside the program itself.
2037 For example, we may have code that depends on the size of
2038 @code{Long_Long_Integer} being at least 64. So we could write:
2041 pragma Assume (Long_Long_Integer'Size >= 64);
2044 This assumption cannot be proved from the program itself,
2045 but it acts as a useful run-time check that the assumption
2046 is met, and documents the need to ensure that it is met by
2047 reference to information outside the program.
2049 @node Pragma Assume_No_Invalid_Values,Pragma Async_Readers,Pragma Assume,Implementation Defined Pragmas
2050 @anchor{gnat_rm/implementation_defined_pragmas pragma-assume-no-invalid-values}@anchor{2f}
2051 @section Pragma Assume_No_Invalid_Values
2054 @geindex Invalid representations
2056 @geindex Invalid values
2061 pragma Assume_No_Invalid_Values (On | Off);
2064 This is a configuration pragma that controls the assumptions made by the
2065 compiler about the occurrence of invalid representations (invalid values)
2068 The default behavior (corresponding to an Off argument for this pragma), is
2069 to assume that values may in general be invalid unless the compiler can
2070 prove they are valid. Consider the following example:
2073 V1 : Integer range 1 .. 10;
2074 V2 : Integer range 11 .. 20;
2076 for J in V2 .. V1 loop
2081 if V1 and V2 have valid values, then the loop is known at compile
2082 time not to execute since the lower bound must be greater than the
2083 upper bound. However in default mode, no such assumption is made,
2084 and the loop may execute. If @code{Assume_No_Invalid_Values (On)}
2085 is given, the compiler will assume that any occurrence of a variable
2086 other than in an explicit @code{'Valid} test always has a valid
2087 value, and the loop above will be optimized away.
2089 The use of @code{Assume_No_Invalid_Values (On)} is appropriate if
2090 you know your code is free of uninitialized variables and other
2091 possible sources of invalid representations, and may result in
2092 more efficient code. A program that accesses an invalid representation
2093 with this pragma in effect is erroneous, so no guarantees can be made
2096 It is peculiar though permissible to use this pragma in conjunction
2097 with validity checking (-gnatVa). In such cases, accessing invalid
2098 values will generally give an exception, though formally the program
2099 is erroneous so there are no guarantees that this will always be the
2100 case, and it is recommended that these two options not be used together.
2102 @node Pragma Async_Readers,Pragma Async_Writers,Pragma Assume_No_Invalid_Values,Implementation Defined Pragmas
2103 @anchor{gnat_rm/implementation_defined_pragmas pragma-async-readers}@anchor{30}@anchor{gnat_rm/implementation_defined_pragmas id4}@anchor{31}
2104 @section Pragma Async_Readers
2110 pragma Async_Readers [ (boolean_EXPRESSION) ];
2113 For the semantics of this pragma, see the entry for aspect @code{Async_Readers} in
2114 the SPARK 2014 Reference Manual, section 7.1.2.
2116 @node Pragma Async_Writers,Pragma Attribute_Definition,Pragma Async_Readers,Implementation Defined Pragmas
2117 @anchor{gnat_rm/implementation_defined_pragmas id5}@anchor{32}@anchor{gnat_rm/implementation_defined_pragmas pragma-async-writers}@anchor{33}
2118 @section Pragma Async_Writers
2124 pragma Async_Writers [ (boolean_EXPRESSION) ];
2127 For the semantics of this pragma, see the entry for aspect @code{Async_Writers} in
2128 the SPARK 2014 Reference Manual, section 7.1.2.
2130 @node Pragma Attribute_Definition,Pragma C_Pass_By_Copy,Pragma Async_Writers,Implementation Defined Pragmas
2131 @anchor{gnat_rm/implementation_defined_pragmas pragma-attribute-definition}@anchor{34}
2132 @section Pragma Attribute_Definition
2138 pragma Attribute_Definition
2139 ([Attribute =>] ATTRIBUTE_DESIGNATOR,
2140 [Entity =>] LOCAL_NAME,
2141 [Expression =>] EXPRESSION | NAME);
2144 If @code{Attribute} is a known attribute name, this pragma is equivalent to
2145 the attribute definition clause:
2148 for Entity'Attribute use Expression;
2151 If @code{Attribute} is not a recognized attribute name, the pragma is
2152 ignored, and a warning is emitted. This allows source
2153 code to be written that takes advantage of some new attribute, while remaining
2154 compilable with earlier compilers.
2156 @node Pragma C_Pass_By_Copy,Pragma Check,Pragma Attribute_Definition,Implementation Defined Pragmas
2157 @anchor{gnat_rm/implementation_defined_pragmas pragma-c-pass-by-copy}@anchor{35}
2158 @section Pragma C_Pass_By_Copy
2161 @geindex Passing by copy
2166 pragma C_Pass_By_Copy
2167 ([Max_Size =>] static_integer_EXPRESSION);
2170 Normally the default mechanism for passing C convention records to C
2171 convention subprograms is to pass them by reference, as suggested by RM
2172 B.3(69). Use the configuration pragma @code{C_Pass_By_Copy} to change
2173 this default, by requiring that record formal parameters be passed by
2174 copy if all of the following conditions are met:
2180 The size of the record type does not exceed the value specified for
2184 The record type has @code{Convention C}.
2187 The formal parameter has this record type, and the subprogram has a
2188 foreign (non-Ada) convention.
2191 If these conditions are met the argument is passed by copy; i.e., in a
2192 manner consistent with what C expects if the corresponding formal in the
2193 C prototype is a struct (rather than a pointer to a struct).
2195 You can also pass records by copy by specifying the convention
2196 @code{C_Pass_By_Copy} for the record type, or by using the extended
2197 @code{Import} and @code{Export} pragmas, which allow specification of
2198 passing mechanisms on a parameter by parameter basis.
2200 @node Pragma Check,Pragma Check_Float_Overflow,Pragma C_Pass_By_Copy,Implementation Defined Pragmas
2201 @anchor{gnat_rm/implementation_defined_pragmas pragma-check}@anchor{36}
2202 @section Pragma Check
2207 @geindex Named assertions
2213 [Name =>] CHECK_KIND,
2214 [Check =>] Boolean_EXPRESSION
2215 [, [Message =>] string_EXPRESSION] );
2217 CHECK_KIND ::= IDENTIFIER |
2220 Type_Invariant'Class |
2224 This pragma is similar to the predefined pragma @code{Assert} except that an
2225 extra identifier argument is present. In conjunction with pragma
2226 @code{Check_Policy}, this can be used to define groups of assertions that can
2227 be independently controlled. The identifier @code{Assertion} is special, it
2228 refers to the normal set of pragma @code{Assert} statements.
2230 Checks introduced by this pragma are normally deactivated by default. They can
2231 be activated either by the command line option @emph{-gnata}, which turns on
2232 all checks, or individually controlled using pragma @code{Check_Policy}.
2234 The identifiers @code{Assertions} and @code{Statement_Assertions} are not
2235 permitted as check kinds, since this would cause confusion with the use
2236 of these identifiers in @code{Assertion_Policy} and @code{Check_Policy}
2237 pragmas, where they are used to refer to sets of assertions.
2239 @node Pragma Check_Float_Overflow,Pragma Check_Name,Pragma Check,Implementation Defined Pragmas
2240 @anchor{gnat_rm/implementation_defined_pragmas pragma-check-float-overflow}@anchor{37}
2241 @section Pragma Check_Float_Overflow
2244 @geindex Floating-point overflow
2249 pragma Check_Float_Overflow;
2252 In Ada, the predefined floating-point types (@code{Short_Float},
2253 @code{Float}, @code{Long_Float}, @code{Long_Long_Float}) are
2254 defined to be @emph{unconstrained}. This means that even though each
2255 has a well-defined base range, an operation that delivers a result
2256 outside this base range is not required to raise an exception.
2257 This implementation permission accommodates the notion
2258 of infinities in IEEE floating-point, and corresponds to the
2259 efficient execution mode on most machines. GNAT will not raise
2260 overflow exceptions on these machines; instead it will generate
2261 infinities and NaN's as defined in the IEEE standard.
2263 Generating infinities, although efficient, is not always desirable.
2264 Often the preferable approach is to check for overflow, even at the
2265 (perhaps considerable) expense of run-time performance.
2266 This can be accomplished by defining your own constrained floating-point subtypes -- i.e., by supplying explicit
2267 range constraints -- and indeed such a subtype
2268 can have the same base range as its base type. For example:
2271 subtype My_Float is Float range Float'Range;
2274 Here @code{My_Float} has the same range as
2275 @code{Float} but is constrained, so operations on
2276 @code{My_Float} values will be checked for overflow
2279 This style will achieve the desired goal, but
2280 it is often more convenient to be able to simply use
2281 the standard predefined floating-point types as long
2282 as overflow checking could be guaranteed.
2283 The @code{Check_Float_Overflow}
2284 configuration pragma achieves this effect. If a unit is compiled
2285 subject to this configuration pragma, then all operations
2286 on predefined floating-point types including operations on
2287 base types of these floating-point types will be treated as
2288 though those types were constrained, and overflow checks
2289 will be generated. The @code{Constraint_Error}
2290 exception is raised if the result is out of range.
2292 This mode can also be set by use of the compiler
2293 switch @emph{-gnateF}.
2295 @node Pragma Check_Name,Pragma Check_Policy,Pragma Check_Float_Overflow,Implementation Defined Pragmas
2296 @anchor{gnat_rm/implementation_defined_pragmas pragma-check-name}@anchor{38}
2297 @section Pragma Check_Name
2300 @geindex Defining check names
2302 @geindex Check names
2308 pragma Check_Name (check_name_IDENTIFIER);
2311 This is a configuration pragma that defines a new implementation
2312 defined check name (unless IDENTIFIER matches one of the predefined
2313 check names, in which case the pragma has no effect). Check names
2314 are global to a partition, so if two or more configuration pragmas
2315 are present in a partition mentioning the same name, only one new
2316 check name is introduced.
2318 An implementation defined check name introduced with this pragma may
2319 be used in only three contexts: @code{pragma Suppress},
2320 @code{pragma Unsuppress},
2321 and as the prefix of a @code{Check_Name'Enabled} attribute reference. For
2322 any of these three cases, the check name must be visible. A check
2323 name is visible if it is in the configuration pragmas applying to
2324 the current unit, or if it appears at the start of any unit that
2325 is part of the dependency set of the current unit (e.g., units that
2326 are mentioned in @code{with} clauses).
2328 Check names introduced by this pragma are subject to control by compiler
2329 switches (in particular -gnatp) in the usual manner.
2331 @node Pragma Check_Policy,Pragma Comment,Pragma Check_Name,Implementation Defined Pragmas
2332 @anchor{gnat_rm/implementation_defined_pragmas pragma-check-policy}@anchor{39}
2333 @section Pragma Check_Policy
2336 @geindex Controlling assertions
2341 @geindex Check pragma control
2343 @geindex Named assertions
2349 ([Name =>] CHECK_KIND,
2350 [Policy =>] POLICY_IDENTIFIER);
2352 pragma Check_Policy (
2353 CHECK_KIND => POLICY_IDENTIFIER
2354 @{, CHECK_KIND => POLICY_IDENTIFIER@});
2356 ASSERTION_KIND ::= RM_ASSERTION_KIND | ID_ASSERTION_KIND
2358 CHECK_KIND ::= IDENTIFIER |
2361 Type_Invariant'Class |
2364 The identifiers Name and Policy are not allowed as CHECK_KIND values. This
2365 avoids confusion between the two possible syntax forms for this pragma.
2367 POLICY_IDENTIFIER ::= ON | OFF | CHECK | DISABLE | IGNORE
2370 This pragma is used to set the checking policy for assertions (specified
2371 by aspects or pragmas), the @code{Debug} pragma, or additional checks
2372 to be checked using the @code{Check} pragma. It may appear either as
2373 a configuration pragma, or within a declarative part of package. In the
2374 latter case, it applies from the point where it appears to the end of
2375 the declarative region (like pragma @code{Suppress}).
2377 The @code{Check_Policy} pragma is similar to the
2378 predefined @code{Assertion_Policy} pragma,
2379 and if the check kind corresponds to one of the assertion kinds that
2380 are allowed by @code{Assertion_Policy}, then the effect is identical.
2382 If the first argument is Debug, then the policy applies to Debug pragmas,
2383 disabling their effect if the policy is @code{OFF}, @code{DISABLE}, or
2384 @code{IGNORE}, and allowing them to execute with normal semantics if
2385 the policy is @code{ON} or @code{CHECK}. In addition if the policy is
2386 @code{DISABLE}, then the procedure call in @code{Debug} pragmas will
2387 be totally ignored and not analyzed semantically.
2389 Finally the first argument may be some other identifier than the above
2390 possibilities, in which case it controls a set of named assertions
2391 that can be checked using pragma @code{Check}. For example, if the pragma:
2394 pragma Check_Policy (Critical_Error, OFF);
2397 is given, then subsequent @code{Check} pragmas whose first argument is also
2398 @code{Critical_Error} will be disabled.
2400 The check policy is @code{OFF} to turn off corresponding checks, and @code{ON}
2401 to turn on corresponding checks. The default for a set of checks for which no
2402 @code{Check_Policy} is given is @code{OFF} unless the compiler switch
2403 @emph{-gnata} is given, which turns on all checks by default.
2405 The check policy settings @code{CHECK} and @code{IGNORE} are recognized
2406 as synonyms for @code{ON} and @code{OFF}. These synonyms are provided for
2407 compatibility with the standard @code{Assertion_Policy} pragma. The check
2408 policy setting @code{DISABLE} causes the second argument of a corresponding
2409 @code{Check} pragma to be completely ignored and not analyzed.
2411 @node Pragma Comment,Pragma Common_Object,Pragma Check_Policy,Implementation Defined Pragmas
2412 @anchor{gnat_rm/implementation_defined_pragmas pragma-comment}@anchor{3a}
2413 @section Pragma Comment
2419 pragma Comment (static_string_EXPRESSION);
2422 This is almost identical in effect to pragma @code{Ident}. It allows the
2423 placement of a comment into the object file and hence into the
2424 executable file if the operating system permits such usage. The
2425 difference is that @code{Comment}, unlike @code{Ident}, has
2426 no limitations on placement of the pragma (it can be placed
2427 anywhere in the main source unit), and if more than one pragma
2428 is used, all comments are retained.
2430 @node Pragma Common_Object,Pragma Compile_Time_Error,Pragma Comment,Implementation Defined Pragmas
2431 @anchor{gnat_rm/implementation_defined_pragmas pragma-common-object}@anchor{3b}
2432 @section Pragma Common_Object
2438 pragma Common_Object (
2439 [Internal =>] LOCAL_NAME
2440 [, [External =>] EXTERNAL_SYMBOL]
2441 [, [Size =>] EXTERNAL_SYMBOL] );
2445 | static_string_EXPRESSION
2448 This pragma enables the shared use of variables stored in overlaid
2449 linker areas corresponding to the use of @code{COMMON}
2450 in Fortran. The single
2451 object @code{LOCAL_NAME} is assigned to the area designated by
2452 the @code{External} argument.
2453 You may define a record to correspond to a series
2454 of fields. The @code{Size} argument
2455 is syntax checked in GNAT, but otherwise ignored.
2457 @code{Common_Object} is not supported on all platforms. If no
2458 support is available, then the code generator will issue a message
2459 indicating that the necessary attribute for implementation of this
2460 pragma is not available.
2462 @node Pragma Compile_Time_Error,Pragma Compile_Time_Warning,Pragma Common_Object,Implementation Defined Pragmas
2463 @anchor{gnat_rm/implementation_defined_pragmas pragma-compile-time-error}@anchor{3c}
2464 @section Pragma Compile_Time_Error
2470 pragma Compile_Time_Error
2471 (boolean_EXPRESSION, static_string_EXPRESSION);
2474 This pragma can be used to generate additional compile time
2476 is particularly useful in generics, where errors can be issued for
2477 specific problematic instantiations. The first parameter is a boolean
2478 expression. The pragma is effective only if the value of this expression
2479 is known at compile time, and has the value True. The set of expressions
2480 whose values are known at compile time includes all static boolean
2481 expressions, and also other values which the compiler can determine
2482 at compile time (e.g., the size of a record type set by an explicit
2483 size representation clause, or the value of a variable which was
2484 initialized to a constant and is known not to have been modified).
2485 If these conditions are met, an error message is generated using
2486 the value given as the second argument. This string value may contain
2487 embedded ASCII.LF characters to break the message into multiple lines.
2489 @node Pragma Compile_Time_Warning,Pragma Compiler_Unit,Pragma Compile_Time_Error,Implementation Defined Pragmas
2490 @anchor{gnat_rm/implementation_defined_pragmas pragma-compile-time-warning}@anchor{3d}
2491 @section Pragma Compile_Time_Warning
2497 pragma Compile_Time_Warning
2498 (boolean_EXPRESSION, static_string_EXPRESSION);
2501 Same as pragma Compile_Time_Error, except a warning is issued instead
2502 of an error message. Note that if this pragma is used in a package that
2503 is with'ed by a client, the client will get the warning even though it
2504 is issued by a with'ed package (normally warnings in with'ed units are
2505 suppressed, but this is a special exception to that rule).
2507 One typical use is within a generic where compile time known characteristics
2508 of formal parameters are tested, and warnings given appropriately. Another use
2509 with a first parameter of True is to warn a client about use of a package,
2510 for example that it is not fully implemented.
2512 @node Pragma Compiler_Unit,Pragma Compiler_Unit_Warning,Pragma Compile_Time_Warning,Implementation Defined Pragmas
2513 @anchor{gnat_rm/implementation_defined_pragmas pragma-compiler-unit}@anchor{3e}
2514 @section Pragma Compiler_Unit
2520 pragma Compiler_Unit;
2523 This pragma is obsolete. It is equivalent to Compiler_Unit_Warning. It is
2524 retained so that old versions of the GNAT run-time that use this pragma can
2525 be compiled with newer versions of the compiler.
2527 @node Pragma Compiler_Unit_Warning,Pragma Complete_Representation,Pragma Compiler_Unit,Implementation Defined Pragmas
2528 @anchor{gnat_rm/implementation_defined_pragmas pragma-compiler-unit-warning}@anchor{3f}
2529 @section Pragma Compiler_Unit_Warning
2535 pragma Compiler_Unit_Warning;
2538 This pragma is intended only for internal use in the GNAT run-time library.
2539 It indicates that the unit is used as part of the compiler build. The effect
2540 is to generate warnings for the use of constructs (for example, conditional
2541 expressions) that would cause trouble when bootstrapping using an older
2542 version of GNAT. For the exact list of restrictions, see the compiler sources
2543 and references to Check_Compiler_Unit.
2545 @node Pragma Complete_Representation,Pragma Complex_Representation,Pragma Compiler_Unit_Warning,Implementation Defined Pragmas
2546 @anchor{gnat_rm/implementation_defined_pragmas pragma-complete-representation}@anchor{40}
2547 @section Pragma Complete_Representation
2553 pragma Complete_Representation;
2556 This pragma must appear immediately within a record representation
2557 clause. Typical placements are before the first component clause
2558 or after the last component clause. The effect is to give an error
2559 message if any component is missing a component clause. This pragma
2560 may be used to ensure that a record representation clause is
2561 complete, and that this invariant is maintained if fields are
2562 added to the record in the future.
2564 @node Pragma Complex_Representation,Pragma Component_Alignment,Pragma Complete_Representation,Implementation Defined Pragmas
2565 @anchor{gnat_rm/implementation_defined_pragmas pragma-complex-representation}@anchor{41}
2566 @section Pragma Complex_Representation
2572 pragma Complex_Representation
2573 ([Entity =>] LOCAL_NAME);
2576 The @code{Entity} argument must be the name of a record type which has
2577 two fields of the same floating-point type. The effect of this pragma is
2578 to force gcc to use the special internal complex representation form for
2579 this record, which may be more efficient. Note that this may result in
2580 the code for this type not conforming to standard ABI (application
2581 binary interface) requirements for the handling of record types. For
2582 example, in some environments, there is a requirement for passing
2583 records by pointer, and the use of this pragma may result in passing
2584 this type in floating-point registers.
2586 @node Pragma Component_Alignment,Pragma Constant_After_Elaboration,Pragma Complex_Representation,Implementation Defined Pragmas
2587 @anchor{gnat_rm/implementation_defined_pragmas pragma-component-alignment}@anchor{42}
2588 @section Pragma Component_Alignment
2591 @geindex Alignments of components
2593 @geindex Pragma Component_Alignment
2598 pragma Component_Alignment (
2599 [Form =>] ALIGNMENT_CHOICE
2600 [, [Name =>] type_LOCAL_NAME]);
2602 ALIGNMENT_CHOICE ::=
2609 Specifies the alignment of components in array or record types.
2610 The meaning of the @code{Form} argument is as follows:
2614 @geindex Component_Size (in pragma Component_Alignment)
2620 @item @emph{Component_Size}
2622 Aligns scalar components and subcomponents of the array or record type
2623 on boundaries appropriate to their inherent size (naturally
2624 aligned). For example, 1-byte components are aligned on byte boundaries,
2625 2-byte integer components are aligned on 2-byte boundaries, 4-byte
2626 integer components are aligned on 4-byte boundaries and so on. These
2627 alignment rules correspond to the normal rules for C compilers on all
2628 machines except the VAX.
2630 @geindex Component_Size_4 (in pragma Component_Alignment)
2632 @item @emph{Component_Size_4}
2634 Naturally aligns components with a size of four or fewer
2635 bytes. Components that are larger than 4 bytes are placed on the next
2638 @geindex Storage_Unit (in pragma Component_Alignment)
2640 @item @emph{Storage_Unit}
2642 Specifies that array or record components are byte aligned, i.e.,
2643 aligned on boundaries determined by the value of the constant
2644 @code{System.Storage_Unit}.
2646 @geindex Default (in pragma Component_Alignment)
2648 @item @emph{Default}
2650 Specifies that array or record components are aligned on default
2651 boundaries, appropriate to the underlying hardware or operating system or
2652 both. The @code{Default} choice is the same as @code{Component_Size} (natural
2656 If the @code{Name} parameter is present, @code{type_LOCAL_NAME} must
2657 refer to a local record or array type, and the specified alignment
2658 choice applies to the specified type. The use of
2659 @code{Component_Alignment} together with a pragma @code{Pack} causes the
2660 @code{Component_Alignment} pragma to be ignored. The use of
2661 @code{Component_Alignment} together with a record representation clause
2662 is only effective for fields not specified by the representation clause.
2664 If the @code{Name} parameter is absent, the pragma can be used as either
2665 a configuration pragma, in which case it applies to one or more units in
2666 accordance with the normal rules for configuration pragmas, or it can be
2667 used within a declarative part, in which case it applies to types that
2668 are declared within this declarative part, or within any nested scope
2669 within this declarative part. In either case it specifies the alignment
2670 to be applied to any record or array type which has otherwise standard
2673 If the alignment for a record or array type is not specified (using
2674 pragma @code{Pack}, pragma @code{Component_Alignment}, or a record rep
2675 clause), the GNAT uses the default alignment as described previously.
2677 @node Pragma Constant_After_Elaboration,Pragma Contract_Cases,Pragma Component_Alignment,Implementation Defined Pragmas
2678 @anchor{gnat_rm/implementation_defined_pragmas id6}@anchor{43}@anchor{gnat_rm/implementation_defined_pragmas pragma-constant-after-elaboration}@anchor{44}
2679 @section Pragma Constant_After_Elaboration
2685 pragma Constant_After_Elaboration [ (boolean_EXPRESSION) ];
2688 For the semantics of this pragma, see the entry for aspect
2689 @code{Constant_After_Elaboration} in the SPARK 2014 Reference Manual, section 3.3.1.
2691 @node Pragma Contract_Cases,Pragma Convention_Identifier,Pragma Constant_After_Elaboration,Implementation Defined Pragmas
2692 @anchor{gnat_rm/implementation_defined_pragmas id7}@anchor{45}@anchor{gnat_rm/implementation_defined_pragmas pragma-contract-cases}@anchor{46}
2693 @section Pragma Contract_Cases
2696 @geindex Contract cases
2701 pragma Contract_Cases ((CONTRACT_CASE @{, CONTRACT_CASE));
2703 CONTRACT_CASE ::= CASE_GUARD => CONSEQUENCE
2705 CASE_GUARD ::= boolean_EXPRESSION | others
2707 CONSEQUENCE ::= boolean_EXPRESSION
2710 The @code{Contract_Cases} pragma allows defining fine-grain specifications
2711 that can complement or replace the contract given by a precondition and a
2712 postcondition. Additionally, the @code{Contract_Cases} pragma can be used
2713 by testing and formal verification tools. The compiler checks its validity and,
2714 depending on the assertion policy at the point of declaration of the pragma,
2715 it may insert a check in the executable. For code generation, the contract
2719 pragma Contract_Cases (
2727 C1 : constant Boolean := Cond1; -- evaluated at subprogram entry
2728 C2 : constant Boolean := Cond2; -- evaluated at subprogram entry
2729 pragma Precondition ((C1 and not C2) or (C2 and not C1));
2730 pragma Postcondition (if C1 then Pred1);
2731 pragma Postcondition (if C2 then Pred2);
2734 The precondition ensures that one and only one of the case guards is
2735 satisfied on entry to the subprogram.
2736 The postcondition ensures that for the case guard that was True on entry,
2737 the corrresponding consequence is True on exit. Other consequence expressions
2740 A precondition @code{P} and postcondition @code{Q} can also be
2741 expressed as contract cases:
2744 pragma Contract_Cases (P => Q);
2747 The placement and visibility rules for @code{Contract_Cases} pragmas are
2748 identical to those described for preconditions and postconditions.
2750 The compiler checks that boolean expressions given in case guards and
2751 consequences are valid, where the rules for case guards are the same as
2752 the rule for an expression in @code{Precondition} and the rules for
2753 consequences are the same as the rule for an expression in
2754 @code{Postcondition}. In particular, attributes @code{'Old} and
2755 @code{'Result} can only be used within consequence expressions.
2756 The case guard for the last contract case may be @code{others}, to denote
2757 any case not captured by the previous cases. The
2758 following is an example of use within a package spec:
2761 package Math_Functions is
2763 function Sqrt (Arg : Float) return Float;
2764 pragma Contract_Cases (((Arg in 0.0 .. 99.0) => Sqrt'Result < 10.0,
2765 Arg >= 100.0 => Sqrt'Result >= 10.0,
2766 others => Sqrt'Result = 0.0));
2771 The meaning of contract cases is that only one case should apply at each
2772 call, as determined by the corresponding case guard evaluating to True,
2773 and that the consequence for this case should hold when the subprogram
2776 @node Pragma Convention_Identifier,Pragma CPP_Class,Pragma Contract_Cases,Implementation Defined Pragmas
2777 @anchor{gnat_rm/implementation_defined_pragmas pragma-convention-identifier}@anchor{47}
2778 @section Pragma Convention_Identifier
2781 @geindex Conventions
2787 pragma Convention_Identifier (
2788 [Name =>] IDENTIFIER,
2789 [Convention =>] convention_IDENTIFIER);
2792 This pragma provides a mechanism for supplying synonyms for existing
2793 convention identifiers. The @code{Name} identifier can subsequently
2794 be used as a synonym for the given convention in other pragmas (including
2795 for example pragma @code{Import} or another @code{Convention_Identifier}
2796 pragma). As an example of the use of this, suppose you had legacy code
2797 which used Fortran77 as the identifier for Fortran. Then the pragma:
2800 pragma Convention_Identifier (Fortran77, Fortran);
2803 would allow the use of the convention identifier @code{Fortran77} in
2804 subsequent code, avoiding the need to modify the sources. As another
2805 example, you could use this to parameterize convention requirements
2806 according to systems. Suppose you needed to use @code{Stdcall} on
2807 windows systems, and @code{C} on some other system, then you could
2808 define a convention identifier @code{Library} and use a single
2809 @code{Convention_Identifier} pragma to specify which convention
2810 would be used system-wide.
2812 @node Pragma CPP_Class,Pragma CPP_Constructor,Pragma Convention_Identifier,Implementation Defined Pragmas
2813 @anchor{gnat_rm/implementation_defined_pragmas pragma-cpp-class}@anchor{48}
2814 @section Pragma CPP_Class
2817 @geindex Interfacing with C++
2822 pragma CPP_Class ([Entity =>] LOCAL_NAME);
2825 The argument denotes an entity in the current declarative region that is
2826 declared as a record type. It indicates that the type corresponds to an
2827 externally declared C++ class type, and is to be laid out the same way
2828 that C++ would lay out the type. If the C++ class has virtual primitives
2829 then the record must be declared as a tagged record type.
2831 Types for which @code{CPP_Class} is specified do not have assignment or
2832 equality operators defined (such operations can be imported or declared
2833 as subprograms as required). Initialization is allowed only by constructor
2834 functions (see pragma @code{CPP_Constructor}). Such types are implicitly
2835 limited if not explicitly declared as limited or derived from a limited
2836 type, and an error is issued in that case.
2838 See @ref{49,,Interfacing to C++} for related information.
2840 Note: Pragma @code{CPP_Class} is currently obsolete. It is supported
2841 for backward compatibility but its functionality is available
2842 using pragma @code{Import} with @code{Convention} = @code{CPP}.
2844 @node Pragma CPP_Constructor,Pragma CPP_Virtual,Pragma CPP_Class,Implementation Defined Pragmas
2845 @anchor{gnat_rm/implementation_defined_pragmas pragma-cpp-constructor}@anchor{4a}
2846 @section Pragma CPP_Constructor
2849 @geindex Interfacing with C++
2854 pragma CPP_Constructor ([Entity =>] LOCAL_NAME
2855 [, [External_Name =>] static_string_EXPRESSION ]
2856 [, [Link_Name =>] static_string_EXPRESSION ]);
2859 This pragma identifies an imported function (imported in the usual way
2860 with pragma @code{Import}) as corresponding to a C++ constructor. If
2861 @code{External_Name} and @code{Link_Name} are not specified then the
2862 @code{Entity} argument is a name that must have been previously mentioned
2863 in a pragma @code{Import} with @code{Convention} = @code{CPP}. Such name
2864 must be of one of the following forms:
2870 @strong{function} @code{Fname} @strong{return} T`
2873 @strong{function} @code{Fname} @strong{return} T'Class
2876 @strong{function} @code{Fname} (...) @strong{return} T`
2879 @strong{function} @code{Fname} (...) @strong{return} T'Class
2882 where @code{T} is a limited record type imported from C++ with pragma
2883 @code{Import} and @code{Convention} = @code{CPP}.
2885 The first two forms import the default constructor, used when an object
2886 of type @code{T} is created on the Ada side with no explicit constructor.
2887 The latter two forms cover all the non-default constructors of the type.
2888 See the GNAT User's Guide for details.
2890 If no constructors are imported, it is impossible to create any objects
2891 on the Ada side and the type is implicitly declared abstract.
2893 Pragma @code{CPP_Constructor} is intended primarily for automatic generation
2894 using an automatic binding generator tool (such as the @code{-fdump-ada-spec}
2896 See @ref{49,,Interfacing to C++} for more related information.
2898 Note: The use of functions returning class-wide types for constructors is
2899 currently obsolete. They are supported for backward compatibility. The
2900 use of functions returning the type T leave the Ada sources more clear
2901 because the imported C++ constructors always return an object of type T;
2902 that is, they never return an object whose type is a descendant of type T.
2904 @node Pragma CPP_Virtual,Pragma CPP_Vtable,Pragma CPP_Constructor,Implementation Defined Pragmas
2905 @anchor{gnat_rm/implementation_defined_pragmas pragma-cpp-virtual}@anchor{4b}
2906 @section Pragma CPP_Virtual
2909 @geindex Interfacing to C++
2911 This pragma is now obsolete and, other than generating a warning if warnings
2912 on obsolescent features are enabled, is completely ignored.
2913 It is retained for compatibility
2914 purposes. It used to be required to ensure compoatibility with C++, but
2915 is no longer required for that purpose because GNAT generates
2916 the same object layout as the G++ compiler by default.
2918 See @ref{49,,Interfacing to C++} for related information.
2920 @node Pragma CPP_Vtable,Pragma CPU,Pragma CPP_Virtual,Implementation Defined Pragmas
2921 @anchor{gnat_rm/implementation_defined_pragmas pragma-cpp-vtable}@anchor{4c}
2922 @section Pragma CPP_Vtable
2925 @geindex Interfacing with C++
2927 This pragma is now obsolete and, other than generating a warning if warnings
2928 on obsolescent features are enabled, is completely ignored.
2929 It used to be required to ensure compatibility with C++, but
2930 is no longer required for that purpose because GNAT generates
2931 the same object layout as the G++ compiler by default.
2933 See @ref{49,,Interfacing to C++} for related information.
2935 @node Pragma CPU,Pragma Deadline_Floor,Pragma CPP_Vtable,Implementation Defined Pragmas
2936 @anchor{gnat_rm/implementation_defined_pragmas pragma-cpu}@anchor{4d}
2943 pragma CPU (EXPRESSION);
2946 This pragma is standard in Ada 2012, but is available in all earlier
2947 versions of Ada as an implementation-defined pragma.
2948 See Ada 2012 Reference Manual for details.
2950 @node Pragma Deadline_Floor,Pragma Default_Initial_Condition,Pragma CPU,Implementation Defined Pragmas
2951 @anchor{gnat_rm/implementation_defined_pragmas pragma-deadline-floor}@anchor{4e}
2952 @section Pragma Deadline_Floor
2958 pragma Deadline_Floor (time_span_EXPRESSION);
2961 This pragma applies only to protected types and specifies the floor
2962 deadline inherited by a task when the task enters a protected object.
2963 It is effective only when the EDF scheduling policy is used.
2965 @node Pragma Default_Initial_Condition,Pragma Debug,Pragma Deadline_Floor,Implementation Defined Pragmas
2966 @anchor{gnat_rm/implementation_defined_pragmas id8}@anchor{4f}@anchor{gnat_rm/implementation_defined_pragmas pragma-default-initial-condition}@anchor{50}
2967 @section Pragma Default_Initial_Condition
2973 pragma Default_Initial_Condition [ (null | boolean_EXPRESSION) ];
2976 For the semantics of this pragma, see the entry for aspect
2977 @code{Default_Initial_Condition} in the SPARK 2014 Reference Manual, section 7.3.3.
2979 @node Pragma Debug,Pragma Debug_Policy,Pragma Default_Initial_Condition,Implementation Defined Pragmas
2980 @anchor{gnat_rm/implementation_defined_pragmas pragma-debug}@anchor{51}
2981 @section Pragma Debug
2987 pragma Debug ([CONDITION, ]PROCEDURE_CALL_WITHOUT_SEMICOLON);
2989 PROCEDURE_CALL_WITHOUT_SEMICOLON ::=
2991 | PROCEDURE_PREFIX ACTUAL_PARAMETER_PART
2994 The procedure call argument has the syntactic form of an expression, meeting
2995 the syntactic requirements for pragmas.
2997 If debug pragmas are not enabled or if the condition is present and evaluates
2998 to False, this pragma has no effect. If debug pragmas are enabled, the
2999 semantics of the pragma is exactly equivalent to the procedure call statement
3000 corresponding to the argument with a terminating semicolon. Pragmas are
3001 permitted in sequences of declarations, so you can use pragma @code{Debug} to
3002 intersperse calls to debug procedures in the middle of declarations. Debug
3003 pragmas can be enabled either by use of the command line switch @emph{-gnata}
3004 or by use of the pragma @code{Check_Policy} with a first argument of
3007 @node Pragma Debug_Policy,Pragma Default_Scalar_Storage_Order,Pragma Debug,Implementation Defined Pragmas
3008 @anchor{gnat_rm/implementation_defined_pragmas pragma-debug-policy}@anchor{52}
3009 @section Pragma Debug_Policy
3015 pragma Debug_Policy (CHECK | DISABLE | IGNORE | ON | OFF);
3018 This pragma is equivalent to a corresponding @code{Check_Policy} pragma
3019 with a first argument of @code{Debug}. It is retained for historical
3020 compatibility reasons.
3022 @node Pragma Default_Scalar_Storage_Order,Pragma Default_Storage_Pool,Pragma Debug_Policy,Implementation Defined Pragmas
3023 @anchor{gnat_rm/implementation_defined_pragmas pragma-default-scalar-storage-order}@anchor{53}
3024 @section Pragma Default_Scalar_Storage_Order
3027 @geindex Default_Scalar_Storage_Order
3029 @geindex Scalar_Storage_Order
3034 pragma Default_Scalar_Storage_Order (High_Order_First | Low_Order_First);
3037 Normally if no explicit @code{Scalar_Storage_Order} is given for a record
3038 type or array type, then the scalar storage order defaults to the ordinary
3039 default for the target. But this default may be overridden using this pragma.
3040 The pragma may appear as a configuration pragma, or locally within a package
3041 spec or declarative part. In the latter case, it applies to all subsequent
3042 types declared within that package spec or declarative part.
3044 The following example shows the use of this pragma:
3047 pragma Default_Scalar_Storage_Order (High_Order_First);
3048 with System; use System;
3057 for L2'Scalar_Storage_Order use Low_Order_First;
3066 pragma Default_Scalar_Storage_Order (Low_Order_First);
3073 type H4a is new Inner.L4;
3081 In this example record types with names starting with @emph{L} have @cite{Low_Order_First} scalar
3082 storage order, and record types with names starting with @emph{H} have @code{High_Order_First}.
3083 Note that in the case of @code{H4a}, the order is not inherited
3084 from the parent type. Only an explicitly set @code{Scalar_Storage_Order}
3085 gets inherited on type derivation.
3087 If this pragma is used as a configuration pragma which appears within a
3088 configuration pragma file (as opposed to appearing explicitly at the start
3089 of a single unit), then the binder will require that all units in a partition
3090 be compiled in a similar manner, other than run-time units, which are not
3091 affected by this pragma. Note that the use of this form is discouraged because
3092 it may significantly degrade the run-time performance of the software, instead
3093 the default scalar storage order ought to be changed only on a local basis.
3095 @node Pragma Default_Storage_Pool,Pragma Depends,Pragma Default_Scalar_Storage_Order,Implementation Defined Pragmas
3096 @anchor{gnat_rm/implementation_defined_pragmas pragma-default-storage-pool}@anchor{54}
3097 @section Pragma Default_Storage_Pool
3100 @geindex Default_Storage_Pool
3105 pragma Default_Storage_Pool (storage_pool_NAME | null);
3108 This pragma is standard in Ada 2012, but is available in all earlier
3109 versions of Ada as an implementation-defined pragma.
3110 See Ada 2012 Reference Manual for details.
3112 @node Pragma Depends,Pragma Detect_Blocking,Pragma Default_Storage_Pool,Implementation Defined Pragmas
3113 @anchor{gnat_rm/implementation_defined_pragmas pragma-depends}@anchor{55}@anchor{gnat_rm/implementation_defined_pragmas id9}@anchor{56}
3114 @section Pragma Depends
3120 pragma Depends (DEPENDENCY_RELATION);
3122 DEPENDENCY_RELATION ::=
3124 | (DEPENDENCY_CLAUSE @{, DEPENDENCY_CLAUSE@})
3126 DEPENDENCY_CLAUSE ::=
3127 OUTPUT_LIST =>[+] INPUT_LIST
3128 | NULL_DEPENDENCY_CLAUSE
3130 NULL_DEPENDENCY_CLAUSE ::= null => INPUT_LIST
3132 OUTPUT_LIST ::= OUTPUT | (OUTPUT @{, OUTPUT@})
3134 INPUT_LIST ::= null | INPUT | (INPUT @{, INPUT@})
3136 OUTPUT ::= NAME | FUNCTION_RESULT
3139 where FUNCTION_RESULT is a function Result attribute_reference
3142 For the semantics of this pragma, see the entry for aspect @code{Depends} in the
3143 SPARK 2014 Reference Manual, section 6.1.5.
3145 @node Pragma Detect_Blocking,Pragma Disable_Atomic_Synchronization,Pragma Depends,Implementation Defined Pragmas
3146 @anchor{gnat_rm/implementation_defined_pragmas pragma-detect-blocking}@anchor{57}
3147 @section Pragma Detect_Blocking
3153 pragma Detect_Blocking;
3156 This is a standard pragma in Ada 2005, that is available in all earlier
3157 versions of Ada as an implementation-defined pragma.
3159 This is a configuration pragma that forces the detection of potentially
3160 blocking operations within a protected operation, and to raise Program_Error
3163 @node Pragma Disable_Atomic_Synchronization,Pragma Dispatching_Domain,Pragma Detect_Blocking,Implementation Defined Pragmas
3164 @anchor{gnat_rm/implementation_defined_pragmas pragma-disable-atomic-synchronization}@anchor{58}
3165 @section Pragma Disable_Atomic_Synchronization
3168 @geindex Atomic Synchronization
3173 pragma Disable_Atomic_Synchronization [(Entity)];
3176 Ada requires that accesses (reads or writes) of an atomic variable be
3177 regarded as synchronization points in the case of multiple tasks.
3178 Particularly in the case of multi-processors this may require special
3179 handling, e.g. the generation of memory barriers. This capability may
3180 be turned off using this pragma in cases where it is known not to be
3183 The placement and scope rules for this pragma are the same as those
3184 for @code{pragma Suppress}. In particular it can be used as a
3185 configuration pragma, or in a declaration sequence where it applies
3186 till the end of the scope. If an @code{Entity} argument is present,
3187 the action applies only to that entity.
3189 @node Pragma Dispatching_Domain,Pragma Effective_Reads,Pragma Disable_Atomic_Synchronization,Implementation Defined Pragmas
3190 @anchor{gnat_rm/implementation_defined_pragmas pragma-dispatching-domain}@anchor{59}
3191 @section Pragma Dispatching_Domain
3197 pragma Dispatching_Domain (EXPRESSION);
3200 This pragma is standard in Ada 2012, but is available in all earlier
3201 versions of Ada as an implementation-defined pragma.
3202 See Ada 2012 Reference Manual for details.
3204 @node Pragma Effective_Reads,Pragma Effective_Writes,Pragma Dispatching_Domain,Implementation Defined Pragmas
3205 @anchor{gnat_rm/implementation_defined_pragmas id10}@anchor{5a}@anchor{gnat_rm/implementation_defined_pragmas pragma-effective-reads}@anchor{5b}
3206 @section Pragma Effective_Reads
3212 pragma Effective_Reads [ (boolean_EXPRESSION) ];
3215 For the semantics of this pragma, see the entry for aspect @code{Effective_Reads} in
3216 the SPARK 2014 Reference Manual, section 7.1.2.
3218 @node Pragma Effective_Writes,Pragma Elaboration_Checks,Pragma Effective_Reads,Implementation Defined Pragmas
3219 @anchor{gnat_rm/implementation_defined_pragmas id11}@anchor{5c}@anchor{gnat_rm/implementation_defined_pragmas pragma-effective-writes}@anchor{5d}
3220 @section Pragma Effective_Writes
3226 pragma Effective_Writes [ (boolean_EXPRESSION) ];
3229 For the semantics of this pragma, see the entry for aspect @code{Effective_Writes}
3230 in the SPARK 2014 Reference Manual, section 7.1.2.
3232 @node Pragma Elaboration_Checks,Pragma Eliminate,Pragma Effective_Writes,Implementation Defined Pragmas
3233 @anchor{gnat_rm/implementation_defined_pragmas pragma-elaboration-checks}@anchor{5e}
3234 @section Pragma Elaboration_Checks
3237 @geindex Elaboration control
3242 pragma Elaboration_Checks (Dynamic | Static);
3245 This is a configuration pragma which specifies the elaboration model to be
3246 used during compilation. For more information on the elaboration models of
3247 GNAT, consult the chapter on elaboration order handling in the @emph{GNAT User's
3250 The pragma may appear in the following contexts:
3256 Configuration pragmas file
3259 Prior to the context clauses of a compilation unit's initial declaration
3262 Any other placement of the pragma will result in a warning and the effects of
3263 the offending pragma will be ignored.
3265 If the pragma argument is @code{Dynamic}, then the dynamic elaboration model is in
3266 effect. If the pragma argument is @code{Static}, then the static elaboration model
3269 @node Pragma Eliminate,Pragma Enable_Atomic_Synchronization,Pragma Elaboration_Checks,Implementation Defined Pragmas
3270 @anchor{gnat_rm/implementation_defined_pragmas pragma-eliminate}@anchor{5f}
3271 @section Pragma Eliminate
3274 @geindex Elimination of unused subprograms
3280 [ Unit_Name => ] IDENTIFIER | SELECTED_COMPONENT ,
3281 [ Entity => ] IDENTIFIER |
3282 SELECTED_COMPONENT |
3284 [, Source_Location => SOURCE_TRACE ] );
3286 SOURCE_TRACE ::= STRING_LITERAL
3289 This pragma indicates that the given entity is not used in the program to be
3290 compiled and built, thus allowing the compiler to
3291 eliminate the code or data associated with the named entity. Any reference to
3292 an eliminated entity causes a compile-time or link-time error.
3294 The pragma has the following semantics, where @code{U} is the unit specified by
3295 the @code{Unit_Name} argument and @code{E} is the entity specified by the @code{Entity}
3302 @code{E} must be a subprogram that is explicitly declared either:
3304 o Within @code{U}, or
3306 o Within a generic package that is instantiated in @code{U}, or
3308 o As an instance of generic subprogram instantiated in @code{U}.
3310 Otherwise the pragma is ignored.
3313 If @code{E} is overloaded within @code{U} then, in the absence of a
3314 @code{Source_Location} argument, all overloadings are eliminated.
3317 If @code{E} is overloaded within @code{U} and only some overloadings
3318 are to be eliminated, then each overloading to be eliminated
3319 must be specified in a corresponding pragma @code{Eliminate}
3320 with a @code{Source_Location} argument identifying the line where the
3321 declaration appears, as described below.
3324 If @code{E} is declared as the result of a generic instantiation, then
3325 a @code{Source_Location} argument is needed, as described below
3328 Pragma @code{Eliminate} allows a program to be compiled in a system-independent
3329 manner, so that unused entities are eliminated but without
3330 needing to modify the source text. Normally the required set of
3331 @code{Eliminate} pragmas is constructed automatically using the @code{gnatelim} tool.
3333 Any source file change that removes, splits, or
3334 adds lines may make the set of @code{Eliminate} pragmas invalid because their
3335 @code{Source_Location} argument values may get out of date.
3337 Pragma @code{Eliminate} may be used where the referenced entity is a dispatching
3338 operation. In this case all the subprograms to which the given operation can
3339 dispatch are considered to be unused (are never called as a result of a direct
3340 or a dispatching call).
3342 The string literal given for the source location specifies the line number
3343 of the declaration of the entity, using the following syntax for @code{SOURCE_TRACE}:
3346 SOURCE_TRACE ::= SOURCE_REFERENCE [ LBRACKET SOURCE_TRACE RBRACKET ]
3351 SOURCE_REFERENCE ::= FILE_NAME : LINE_NUMBER
3353 LINE_NUMBER ::= DIGIT @{DIGIT@}
3356 Spaces around the colon in a @code{SOURCE_REFERENCE} are optional.
3358 The source trace that is given as the @code{Source_Location} must obey the
3359 following rules (or else the pragma is ignored), where @code{U} is
3360 the unit @code{U} specified by the @code{Unit_Name} argument and @code{E} is the
3361 subprogram specified by the @code{Entity} argument:
3367 @code{FILE_NAME} is the short name (with no directory
3368 information) of the Ada source file for @code{U}, using the required syntax
3369 for the underlying file system (e.g. case is significant if the underlying
3370 operating system is case sensitive).
3371 If @code{U} is a package and @code{E} is a subprogram declared in the package
3372 specification and its full declaration appears in the package body,
3373 then the relevant source file is the one for the package specification;
3374 analogously if @code{U} is a generic package.
3377 If @code{E} is not declared in a generic instantiation (this includes
3378 generic subprogram instances), the source trace includes only one source
3379 line reference. @code{LINE_NUMBER} gives the line number of the occurrence
3380 of the declaration of @code{E} within the source file (as a decimal literal
3381 without an exponent or point).
3384 If @code{E} is declared by a generic instantiation, its source trace
3385 (from left to right) starts with the source location of the
3386 declaration of @code{E} in the generic unit and ends with the source
3387 location of the instantiation, given in square brackets. This approach is
3388 applied recursively with nested instantiations: the rightmost (nested
3389 most deeply in square brackets) element of the source trace is the location
3390 of the outermost instantiation, and the leftmost element (that is, outside
3391 of any square brackets) is the location of the declaration of @code{E} in
3400 pragma Eliminate (Pkg0, Proc);
3401 -- Eliminate (all overloadings of) Proc in Pkg0
3403 pragma Eliminate (Pkg1, Proc,
3404 Source_Location => "pkg1.ads:8");
3405 -- Eliminate overloading of Proc at line 8 in pkg1.ads
3407 -- Assume the following file contents:
3410 -- 2: type T is private;
3411 -- 3: package Gen_Pkg is
3412 -- 4: procedure Proc(N : T);
3418 -- 2: procedure Q is
3419 -- 3: package Inst_Pkg is new Gen_Pkg(Integer);
3420 -- ... -- No calls on Inst_Pkg.Proc
3423 -- The following pragma eliminates Inst_Pkg.Proc from Q
3424 pragma Eliminate (Q, Proc,
3425 Source_Location => "gen_pkg.ads:4[q.adb:3]");
3429 @node Pragma Enable_Atomic_Synchronization,Pragma Export_Function,Pragma Eliminate,Implementation Defined Pragmas
3430 @anchor{gnat_rm/implementation_defined_pragmas pragma-enable-atomic-synchronization}@anchor{60}
3431 @section Pragma Enable_Atomic_Synchronization
3434 @geindex Atomic Synchronization
3439 pragma Enable_Atomic_Synchronization [(Entity)];
3442 Ada requires that accesses (reads or writes) of an atomic variable be
3443 regarded as synchronization points in the case of multiple tasks.
3444 Particularly in the case of multi-processors this may require special
3445 handling, e.g. the generation of memory barriers. This synchronization
3446 is performed by default, but can be turned off using
3447 @code{pragma Disable_Atomic_Synchronization}. The
3448 @code{Enable_Atomic_Synchronization} pragma can be used to turn
3451 The placement and scope rules for this pragma are the same as those
3452 for @code{pragma Unsuppress}. In particular it can be used as a
3453 configuration pragma, or in a declaration sequence where it applies
3454 till the end of the scope. If an @code{Entity} argument is present,
3455 the action applies only to that entity.
3457 @node Pragma Export_Function,Pragma Export_Object,Pragma Enable_Atomic_Synchronization,Implementation Defined Pragmas
3458 @anchor{gnat_rm/implementation_defined_pragmas pragma-export-function}@anchor{61}
3459 @section Pragma Export_Function
3462 @geindex Argument passing mechanisms
3467 pragma Export_Function (
3468 [Internal =>] LOCAL_NAME
3469 [, [External =>] EXTERNAL_SYMBOL]
3470 [, [Parameter_Types =>] PARAMETER_TYPES]
3471 [, [Result_Type =>] result_SUBTYPE_MARK]
3472 [, [Mechanism =>] MECHANISM]
3473 [, [Result_Mechanism =>] MECHANISM_NAME]);
3477 | static_string_EXPRESSION
3482 | TYPE_DESIGNATOR @{, TYPE_DESIGNATOR@}
3486 | subtype_Name ' Access
3490 | (MECHANISM_ASSOCIATION @{, MECHANISM_ASSOCIATION@})
3492 MECHANISM_ASSOCIATION ::=
3493 [formal_parameter_NAME =>] MECHANISM_NAME
3495 MECHANISM_NAME ::= Value | Reference
3498 Use this pragma to make a function externally callable and optionally
3499 provide information on mechanisms to be used for passing parameter and
3500 result values. We recommend, for the purposes of improving portability,
3501 this pragma always be used in conjunction with a separate pragma
3502 @code{Export}, which must precede the pragma @code{Export_Function}.
3503 GNAT does not require a separate pragma @code{Export}, but if none is
3504 present, @code{Convention Ada} is assumed, which is usually
3505 not what is wanted, so it is usually appropriate to use this
3506 pragma in conjunction with a @code{Export} or @code{Convention}
3507 pragma that specifies the desired foreign convention.
3508 Pragma @code{Export_Function}
3509 (and @code{Export}, if present) must appear in the same declarative
3510 region as the function to which they apply.
3512 The @code{internal_name} must uniquely designate the function to which the
3513 pragma applies. If more than one function name exists of this name in
3514 the declarative part you must use the @code{Parameter_Types} and
3515 @code{Result_Type} parameters to achieve the required
3516 unique designation. The @cite{subtype_mark}s in these parameters must
3517 exactly match the subtypes in the corresponding function specification,
3518 using positional notation to match parameters with subtype marks.
3519 The form with an @code{'Access} attribute can be used to match an
3520 anonymous access parameter.
3522 @geindex Suppressing external name
3524 Special treatment is given if the EXTERNAL is an explicit null
3525 string or a static string expressions that evaluates to the null
3526 string. In this case, no external name is generated. This form
3527 still allows the specification of parameter mechanisms.
3529 @node Pragma Export_Object,Pragma Export_Procedure,Pragma Export_Function,Implementation Defined Pragmas
3530 @anchor{gnat_rm/implementation_defined_pragmas pragma-export-object}@anchor{62}
3531 @section Pragma Export_Object
3537 pragma Export_Object
3538 [Internal =>] LOCAL_NAME
3539 [, [External =>] EXTERNAL_SYMBOL]
3540 [, [Size =>] EXTERNAL_SYMBOL]
3544 | static_string_EXPRESSION
3547 This pragma designates an object as exported, and apart from the
3548 extended rules for external symbols, is identical in effect to the use of
3549 the normal @code{Export} pragma applied to an object. You may use a
3550 separate Export pragma (and you probably should from the point of view
3551 of portability), but it is not required. @code{Size} is syntax checked,
3552 but otherwise ignored by GNAT.
3554 @node Pragma Export_Procedure,Pragma Export_Value,Pragma Export_Object,Implementation Defined Pragmas
3555 @anchor{gnat_rm/implementation_defined_pragmas pragma-export-procedure}@anchor{63}
3556 @section Pragma Export_Procedure
3562 pragma Export_Procedure (
3563 [Internal =>] LOCAL_NAME
3564 [, [External =>] EXTERNAL_SYMBOL]
3565 [, [Parameter_Types =>] PARAMETER_TYPES]
3566 [, [Mechanism =>] MECHANISM]);
3570 | static_string_EXPRESSION
3575 | TYPE_DESIGNATOR @{, TYPE_DESIGNATOR@}
3579 | subtype_Name ' Access
3583 | (MECHANISM_ASSOCIATION @{, MECHANISM_ASSOCIATION@})
3585 MECHANISM_ASSOCIATION ::=
3586 [formal_parameter_NAME =>] MECHANISM_NAME
3588 MECHANISM_NAME ::= Value | Reference
3591 This pragma is identical to @code{Export_Function} except that it
3592 applies to a procedure rather than a function and the parameters
3593 @code{Result_Type} and @code{Result_Mechanism} are not permitted.
3594 GNAT does not require a separate pragma @code{Export}, but if none is
3595 present, @code{Convention Ada} is assumed, which is usually
3596 not what is wanted, so it is usually appropriate to use this
3597 pragma in conjunction with a @code{Export} or @code{Convention}
3598 pragma that specifies the desired foreign convention.
3600 @geindex Suppressing external name
3602 Special treatment is given if the EXTERNAL is an explicit null
3603 string or a static string expressions that evaluates to the null
3604 string. In this case, no external name is generated. This form
3605 still allows the specification of parameter mechanisms.
3607 @node Pragma Export_Value,Pragma Export_Valued_Procedure,Pragma Export_Procedure,Implementation Defined Pragmas
3608 @anchor{gnat_rm/implementation_defined_pragmas pragma-export-value}@anchor{64}
3609 @section Pragma Export_Value
3615 pragma Export_Value (
3616 [Value =>] static_integer_EXPRESSION,
3617 [Link_Name =>] static_string_EXPRESSION);
3620 This pragma serves to export a static integer value for external use.
3621 The first argument specifies the value to be exported. The Link_Name
3622 argument specifies the symbolic name to be associated with the integer
3623 value. This pragma is useful for defining a named static value in Ada
3624 that can be referenced in assembly language units to be linked with
3625 the application. This pragma is currently supported only for the
3626 AAMP target and is ignored for other targets.
3628 @node Pragma Export_Valued_Procedure,Pragma Extend_System,Pragma Export_Value,Implementation Defined Pragmas
3629 @anchor{gnat_rm/implementation_defined_pragmas pragma-export-valued-procedure}@anchor{65}
3630 @section Pragma Export_Valued_Procedure
3636 pragma Export_Valued_Procedure (
3637 [Internal =>] LOCAL_NAME
3638 [, [External =>] EXTERNAL_SYMBOL]
3639 [, [Parameter_Types =>] PARAMETER_TYPES]
3640 [, [Mechanism =>] MECHANISM]);
3644 | static_string_EXPRESSION
3649 | TYPE_DESIGNATOR @{, TYPE_DESIGNATOR@}
3653 | subtype_Name ' Access
3657 | (MECHANISM_ASSOCIATION @{, MECHANISM_ASSOCIATION@})
3659 MECHANISM_ASSOCIATION ::=
3660 [formal_parameter_NAME =>] MECHANISM_NAME
3662 MECHANISM_NAME ::= Value | Reference
3665 This pragma is identical to @code{Export_Procedure} except that the
3666 first parameter of @code{LOCAL_NAME}, which must be present, must be of
3667 mode @code{out}, and externally the subprogram is treated as a function
3668 with this parameter as the result of the function. GNAT provides for
3669 this capability to allow the use of @code{out} and @code{in out}
3670 parameters in interfacing to external functions (which are not permitted
3672 GNAT does not require a separate pragma @code{Export}, but if none is
3673 present, @code{Convention Ada} is assumed, which is almost certainly
3674 not what is wanted since the whole point of this pragma is to interface
3675 with foreign language functions, so it is usually appropriate to use this
3676 pragma in conjunction with a @code{Export} or @code{Convention}
3677 pragma that specifies the desired foreign convention.
3679 @geindex Suppressing external name
3681 Special treatment is given if the EXTERNAL is an explicit null
3682 string or a static string expressions that evaluates to the null
3683 string. In this case, no external name is generated. This form
3684 still allows the specification of parameter mechanisms.
3686 @node Pragma Extend_System,Pragma Extensions_Allowed,Pragma Export_Valued_Procedure,Implementation Defined Pragmas
3687 @anchor{gnat_rm/implementation_defined_pragmas pragma-extend-system}@anchor{66}
3688 @section Pragma Extend_System
3699 pragma Extend_System ([Name =>] IDENTIFIER);
3702 This pragma is used to provide backwards compatibility with other
3703 implementations that extend the facilities of package @code{System}. In
3704 GNAT, @code{System} contains only the definitions that are present in
3705 the Ada RM. However, other implementations, notably the DEC Ada 83
3706 implementation, provide many extensions to package @code{System}.
3708 For each such implementation accommodated by this pragma, GNAT provides a
3709 package @code{Aux_@emph{xxx}}, e.g., @code{Aux_DEC} for the DEC Ada 83
3710 implementation, which provides the required additional definitions. You
3711 can use this package in two ways. You can @code{with} it in the normal
3712 way and access entities either by selection or using a @code{use}
3713 clause. In this case no special processing is required.
3715 However, if existing code contains references such as
3716 @code{System.@emph{xxx}} where @emph{xxx} is an entity in the extended
3717 definitions provided in package @code{System}, you may use this pragma
3718 to extend visibility in @code{System} in a non-standard way that
3719 provides greater compatibility with the existing code. Pragma
3720 @code{Extend_System} is a configuration pragma whose single argument is
3721 the name of the package containing the extended definition
3722 (e.g., @code{Aux_DEC} for the DEC Ada case). A unit compiled under
3723 control of this pragma will be processed using special visibility
3724 processing that looks in package @code{System.Aux_@emph{xxx}} where
3725 @code{Aux_@emph{xxx}} is the pragma argument for any entity referenced in
3726 package @code{System}, but not found in package @code{System}.
3728 You can use this pragma either to access a predefined @code{System}
3729 extension supplied with the compiler, for example @code{Aux_DEC} or
3730 you can construct your own extension unit following the above
3731 definition. Note that such a package is a child of @code{System}
3732 and thus is considered part of the implementation.
3733 To compile it you will have to use the @emph{-gnatg} switch
3734 for compiling System units, as explained in the
3737 @node Pragma Extensions_Allowed,Pragma Extensions_Visible,Pragma Extend_System,Implementation Defined Pragmas
3738 @anchor{gnat_rm/implementation_defined_pragmas pragma-extensions-allowed}@anchor{67}
3739 @section Pragma Extensions_Allowed
3742 @geindex Ada Extensions
3744 @geindex GNAT Extensions
3749 pragma Extensions_Allowed (On | Off);
3752 This configuration pragma enables or disables the implementation
3753 extension mode (the use of Off as a parameter cancels the effect
3754 of the @emph{-gnatX} command switch).
3756 In extension mode, the latest version of the Ada language is
3757 implemented (currently Ada 2012), and in addition a small number
3758 of GNAT specific extensions are recognized as follows:
3763 @item @emph{Constrained attribute for generic objects}
3765 The @code{Constrained} attribute is permitted for objects of
3766 generic types. The result indicates if the corresponding actual
3770 @node Pragma Extensions_Visible,Pragma External,Pragma Extensions_Allowed,Implementation Defined Pragmas
3771 @anchor{gnat_rm/implementation_defined_pragmas id12}@anchor{68}@anchor{gnat_rm/implementation_defined_pragmas pragma-extensions-visible}@anchor{69}
3772 @section Pragma Extensions_Visible
3778 pragma Extensions_Visible [ (boolean_EXPRESSION) ];
3781 For the semantics of this pragma, see the entry for aspect @code{Extensions_Visible}
3782 in the SPARK 2014 Reference Manual, section 6.1.7.
3784 @node Pragma External,Pragma External_Name_Casing,Pragma Extensions_Visible,Implementation Defined Pragmas
3785 @anchor{gnat_rm/implementation_defined_pragmas pragma-external}@anchor{6a}
3786 @section Pragma External
3793 [ Convention =>] convention_IDENTIFIER,
3794 [ Entity =>] LOCAL_NAME
3795 [, [External_Name =>] static_string_EXPRESSION ]
3796 [, [Link_Name =>] static_string_EXPRESSION ]);
3799 This pragma is identical in syntax and semantics to pragma
3800 @code{Export} as defined in the Ada Reference Manual. It is
3801 provided for compatibility with some Ada 83 compilers that
3802 used this pragma for exactly the same purposes as pragma
3803 @code{Export} before the latter was standardized.
3805 @node Pragma External_Name_Casing,Pragma Fast_Math,Pragma External,Implementation Defined Pragmas
3806 @anchor{gnat_rm/implementation_defined_pragmas pragma-external-name-casing}@anchor{6b}
3807 @section Pragma External_Name_Casing
3810 @geindex Dec Ada 83 casing compatibility
3812 @geindex External Names
3815 @geindex Casing of External names
3820 pragma External_Name_Casing (
3821 Uppercase | Lowercase
3822 [, Uppercase | Lowercase | As_Is]);
3825 This pragma provides control over the casing of external names associated
3826 with Import and Export pragmas. There are two cases to consider:
3832 Implicit external names
3834 Implicit external names are derived from identifiers. The most common case
3835 arises when a standard Ada Import or Export pragma is used with only two
3839 pragma Import (C, C_Routine);
3842 Since Ada is a case-insensitive language, the spelling of the identifier in
3843 the Ada source program does not provide any information on the desired
3844 casing of the external name, and so a convention is needed. In GNAT the
3845 default treatment is that such names are converted to all lower case
3846 letters. This corresponds to the normal C style in many environments.
3847 The first argument of pragma @code{External_Name_Casing} can be used to
3848 control this treatment. If @code{Uppercase} is specified, then the name
3849 will be forced to all uppercase letters. If @code{Lowercase} is specified,
3850 then the normal default of all lower case letters will be used.
3852 This same implicit treatment is also used in the case of extended DEC Ada 83
3853 compatible Import and Export pragmas where an external name is explicitly
3854 specified using an identifier rather than a string.
3857 Explicit external names
3859 Explicit external names are given as string literals. The most common case
3860 arises when a standard Ada Import or Export pragma is used with three
3864 pragma Import (C, C_Routine, "C_routine");
3867 In this case, the string literal normally provides the exact casing required
3868 for the external name. The second argument of pragma
3869 @code{External_Name_Casing} may be used to modify this behavior.
3870 If @code{Uppercase} is specified, then the name
3871 will be forced to all uppercase letters. If @code{Lowercase} is specified,
3872 then the name will be forced to all lowercase letters. A specification of
3873 @code{As_Is} provides the normal default behavior in which the casing is
3874 taken from the string provided.
3877 This pragma may appear anywhere that a pragma is valid. In particular, it
3878 can be used as a configuration pragma in the @code{gnat.adc} file, in which
3879 case it applies to all subsequent compilations, or it can be used as a program
3880 unit pragma, in which case it only applies to the current unit, or it can
3881 be used more locally to control individual Import/Export pragmas.
3883 It was primarily intended for use with OpenVMS systems, where many
3884 compilers convert all symbols to upper case by default. For interfacing to
3885 such compilers (e.g., the DEC C compiler), it may be convenient to use
3889 pragma External_Name_Casing (Uppercase, Uppercase);
3892 to enforce the upper casing of all external symbols.
3894 @node Pragma Fast_Math,Pragma Favor_Top_Level,Pragma External_Name_Casing,Implementation Defined Pragmas
3895 @anchor{gnat_rm/implementation_defined_pragmas pragma-fast-math}@anchor{6c}
3896 @section Pragma Fast_Math
3905 This is a configuration pragma which activates a mode in which speed is
3906 considered more important for floating-point operations than absolutely
3907 accurate adherence to the requirements of the standard. Currently the
3908 following operations are affected:
3913 @item @emph{Complex Multiplication}
3915 The normal simple formula for complex multiplication can result in intermediate
3916 overflows for numbers near the end of the range. The Ada standard requires that
3917 this situation be detected and corrected by scaling, but in Fast_Math mode such
3918 cases will simply result in overflow. Note that to take advantage of this you
3919 must instantiate your own version of @code{Ada.Numerics.Generic_Complex_Types}
3920 under control of the pragma, rather than use the preinstantiated versions.
3923 @node Pragma Favor_Top_Level,Pragma Finalize_Storage_Only,Pragma Fast_Math,Implementation Defined Pragmas
3924 @anchor{gnat_rm/implementation_defined_pragmas id13}@anchor{6d}@anchor{gnat_rm/implementation_defined_pragmas pragma-favor-top-level}@anchor{6e}
3925 @section Pragma Favor_Top_Level
3931 pragma Favor_Top_Level (type_NAME);
3934 The argument of pragma @code{Favor_Top_Level} must be a named access-to-subprogram
3935 type. This pragma is an efficiency hint to the compiler, regarding the use of
3936 @code{'Access} or @code{'Unrestricted_Access} on nested (non-library-level) subprograms.
3937 The pragma means that nested subprograms are not used with this type, or are
3938 rare, so that the generated code should be efficient in the top-level case.
3939 When this pragma is used, dynamically generated trampolines may be used on some
3940 targets for nested subprograms. See restriction @code{No_Implicit_Dynamic_Code}.
3942 @node Pragma Finalize_Storage_Only,Pragma Float_Representation,Pragma Favor_Top_Level,Implementation Defined Pragmas
3943 @anchor{gnat_rm/implementation_defined_pragmas pragma-finalize-storage-only}@anchor{6f}
3944 @section Pragma Finalize_Storage_Only
3950 pragma Finalize_Storage_Only (first_subtype_LOCAL_NAME);
3953 The argument of pragma @code{Finalize_Storage_Only} must denote a local type which
3954 is derived from @code{Ada.Finalization.Controlled} or @code{Limited_Controlled}. The
3955 pragma suppresses the call to @code{Finalize} for declared library-level objects
3956 of the argument type. This is mostly useful for types where finalization is
3957 only used to deal with storage reclamation since in most environments it is
3958 not necessary to reclaim memory just before terminating execution, hence the
3959 name. Note that this pragma does not suppress Finalize calls for library-level
3960 heap-allocated objects (see pragma @code{No_Heap_Finalization}).
3962 @node Pragma Float_Representation,Pragma Ghost,Pragma Finalize_Storage_Only,Implementation Defined Pragmas
3963 @anchor{gnat_rm/implementation_defined_pragmas pragma-float-representation}@anchor{70}
3964 @section Pragma Float_Representation
3970 pragma Float_Representation (FLOAT_REP[, float_type_LOCAL_NAME]);
3972 FLOAT_REP ::= VAX_Float | IEEE_Float
3975 In the one argument form, this pragma is a configuration pragma which
3976 allows control over the internal representation chosen for the predefined
3977 floating point types declared in the packages @code{Standard} and
3978 @code{System}. This pragma is only provided for compatibility and has no effect.
3980 The two argument form specifies the representation to be used for
3981 the specified floating-point type. The argument must
3982 be @code{IEEE_Float} to specify the use of IEEE format, as follows:
3988 For a digits value of 6, 32-bit IEEE short format will be used.
3991 For a digits value of 15, 64-bit IEEE long format will be used.
3994 No other value of digits is permitted.
3997 @node Pragma Ghost,Pragma Global,Pragma Float_Representation,Implementation Defined Pragmas
3998 @anchor{gnat_rm/implementation_defined_pragmas pragma-ghost}@anchor{71}@anchor{gnat_rm/implementation_defined_pragmas id14}@anchor{72}
3999 @section Pragma Ghost
4005 pragma Ghost [ (boolean_EXPRESSION) ];
4008 For the semantics of this pragma, see the entry for aspect @code{Ghost} in the SPARK
4009 2014 Reference Manual, section 6.9.
4011 @node Pragma Global,Pragma Ident,Pragma Ghost,Implementation Defined Pragmas
4012 @anchor{gnat_rm/implementation_defined_pragmas pragma-global}@anchor{73}@anchor{gnat_rm/implementation_defined_pragmas id15}@anchor{74}
4013 @section Pragma Global
4019 pragma Global (GLOBAL_SPECIFICATION);
4021 GLOBAL_SPECIFICATION ::=
4024 | (MODED_GLOBAL_LIST @{, MODED_GLOBAL_LIST@})
4026 MODED_GLOBAL_LIST ::= MODE_SELECTOR => GLOBAL_LIST
4028 MODE_SELECTOR ::= In_Out | Input | Output | Proof_In
4029 GLOBAL_LIST ::= GLOBAL_ITEM | (GLOBAL_ITEM @{, GLOBAL_ITEM@})
4030 GLOBAL_ITEM ::= NAME
4033 For the semantics of this pragma, see the entry for aspect @code{Global} in the
4034 SPARK 2014 Reference Manual, section 6.1.4.
4036 @node Pragma Ident,Pragma Ignore_Pragma,Pragma Global,Implementation Defined Pragmas
4037 @anchor{gnat_rm/implementation_defined_pragmas pragma-ident}@anchor{75}
4038 @section Pragma Ident
4044 pragma Ident (static_string_EXPRESSION);
4047 This pragma is identical in effect to pragma @code{Comment}. It is provided
4048 for compatibility with other Ada compilers providing this pragma.
4050 @node Pragma Ignore_Pragma,Pragma Implementation_Defined,Pragma Ident,Implementation Defined Pragmas
4051 @anchor{gnat_rm/implementation_defined_pragmas pragma-ignore-pragma}@anchor{76}
4052 @section Pragma Ignore_Pragma
4058 pragma Ignore_Pragma (pragma_IDENTIFIER);
4061 This is a configuration pragma
4062 that takes a single argument that is a simple identifier. Any subsequent
4063 use of a pragma whose pragma identifier matches this argument will be
4064 silently ignored. This may be useful when legacy code or code intended
4065 for compilation with some other compiler contains pragmas that match the
4066 name, but not the exact implementation, of a GNAT pragma. The use of this
4067 pragma allows such pragmas to be ignored, which may be useful in CodePeer
4068 mode, or during porting of legacy code.
4070 @node Pragma Implementation_Defined,Pragma Implemented,Pragma Ignore_Pragma,Implementation Defined Pragmas
4071 @anchor{gnat_rm/implementation_defined_pragmas pragma-implementation-defined}@anchor{77}
4072 @section Pragma Implementation_Defined
4078 pragma Implementation_Defined (local_NAME);
4081 This pragma marks a previously declared entity as implementation-defined.
4082 For an overloaded entity, applies to the most recent homonym.
4085 pragma Implementation_Defined;
4088 The form with no arguments appears anywhere within a scope, most
4089 typically a package spec, and indicates that all entities that are
4090 defined within the package spec are Implementation_Defined.
4092 This pragma is used within the GNAT runtime library to identify
4093 implementation-defined entities introduced in language-defined units,
4094 for the purpose of implementing the No_Implementation_Identifiers
4097 @node Pragma Implemented,Pragma Implicit_Packing,Pragma Implementation_Defined,Implementation Defined Pragmas
4098 @anchor{gnat_rm/implementation_defined_pragmas pragma-implemented}@anchor{78}
4099 @section Pragma Implemented
4105 pragma Implemented (procedure_LOCAL_NAME, implementation_kind);
4107 implementation_kind ::= By_Entry | By_Protected_Procedure | By_Any
4110 This is an Ada 2012 representation pragma which applies to protected, task
4111 and synchronized interface primitives. The use of pragma Implemented provides
4112 a way to impose a static requirement on the overriding operation by adhering
4113 to one of the three implementation kinds: entry, protected procedure or any of
4114 the above. This pragma is available in all earlier versions of Ada as an
4115 implementation-defined pragma.
4118 type Synch_Iface is synchronized interface;
4119 procedure Prim_Op (Obj : in out Iface) is abstract;
4120 pragma Implemented (Prim_Op, By_Protected_Procedure);
4122 protected type Prot_1 is new Synch_Iface with
4123 procedure Prim_Op; -- Legal
4126 protected type Prot_2 is new Synch_Iface with
4127 entry Prim_Op; -- Illegal
4130 task type Task_Typ is new Synch_Iface with
4131 entry Prim_Op; -- Illegal
4135 When applied to the procedure_or_entry_NAME of a requeue statement, pragma
4136 Implemented determines the runtime behavior of the requeue. Implementation kind
4137 By_Entry guarantees that the action of requeueing will proceed from an entry to
4138 another entry. Implementation kind By_Protected_Procedure transforms the
4139 requeue into a dispatching call, thus eliminating the chance of blocking. Kind
4140 By_Any shares the behavior of By_Entry and By_Protected_Procedure depending on
4141 the target's overriding subprogram kind.
4143 @node Pragma Implicit_Packing,Pragma Import_Function,Pragma Implemented,Implementation Defined Pragmas
4144 @anchor{gnat_rm/implementation_defined_pragmas pragma-implicit-packing}@anchor{79}
4145 @section Pragma Implicit_Packing
4148 @geindex Rational Profile
4153 pragma Implicit_Packing;
4156 This is a configuration pragma that requests implicit packing for packed
4157 arrays for which a size clause is given but no explicit pragma Pack or
4158 specification of Component_Size is present. It also applies to records
4159 where no record representation clause is present. Consider this example:
4162 type R is array (0 .. 7) of Boolean;
4166 In accordance with the recommendation in the RM (RM 13.3(53)), a Size clause
4167 does not change the layout of a composite object. So the Size clause in the
4168 above example is normally rejected, since the default layout of the array uses
4169 8-bit components, and thus the array requires a minimum of 64 bits.
4171 If this declaration is compiled in a region of code covered by an occurrence
4172 of the configuration pragma Implicit_Packing, then the Size clause in this
4173 and similar examples will cause implicit packing and thus be accepted. For
4174 this implicit packing to occur, the type in question must be an array of small
4175 components whose size is known at compile time, and the Size clause must
4176 specify the exact size that corresponds to the number of elements in the array
4177 multiplied by the size in bits of the component type (both single and
4178 multi-dimensioned arrays can be controlled with this pragma).
4180 @geindex Array packing
4182 Similarly, the following example shows the use in the record case
4186 a, b, c, d, e, f, g, h : boolean;
4192 Without a pragma Pack, each Boolean field requires 8 bits, so the
4193 minimum size is 72 bits, but with a pragma Pack, 16 bits would be
4194 sufficient. The use of pragma Implicit_Packing allows this record
4195 declaration to compile without an explicit pragma Pack.
4197 @node Pragma Import_Function,Pragma Import_Object,Pragma Implicit_Packing,Implementation Defined Pragmas
4198 @anchor{gnat_rm/implementation_defined_pragmas pragma-import-function}@anchor{7a}
4199 @section Pragma Import_Function
4205 pragma Import_Function (
4206 [Internal =>] LOCAL_NAME,
4207 [, [External =>] EXTERNAL_SYMBOL]
4208 [, [Parameter_Types =>] PARAMETER_TYPES]
4209 [, [Result_Type =>] SUBTYPE_MARK]
4210 [, [Mechanism =>] MECHANISM]
4211 [, [Result_Mechanism =>] MECHANISM_NAME]);
4215 | static_string_EXPRESSION
4219 | TYPE_DESIGNATOR @{, TYPE_DESIGNATOR@}
4223 | subtype_Name ' Access
4227 | (MECHANISM_ASSOCIATION @{, MECHANISM_ASSOCIATION@})
4229 MECHANISM_ASSOCIATION ::=
4230 [formal_parameter_NAME =>] MECHANISM_NAME
4237 This pragma is used in conjunction with a pragma @code{Import} to
4238 specify additional information for an imported function. The pragma
4239 @code{Import} (or equivalent pragma @code{Interface}) must precede the
4240 @code{Import_Function} pragma and both must appear in the same
4241 declarative part as the function specification.
4243 The @code{Internal} argument must uniquely designate
4244 the function to which the
4245 pragma applies. If more than one function name exists of this name in
4246 the declarative part you must use the @code{Parameter_Types} and
4247 @code{Result_Type} parameters to achieve the required unique
4248 designation. Subtype marks in these parameters must exactly match the
4249 subtypes in the corresponding function specification, using positional
4250 notation to match parameters with subtype marks.
4251 The form with an @code{'Access} attribute can be used to match an
4252 anonymous access parameter.
4254 You may optionally use the @code{Mechanism} and @code{Result_Mechanism}
4255 parameters to specify passing mechanisms for the
4256 parameters and result. If you specify a single mechanism name, it
4257 applies to all parameters. Otherwise you may specify a mechanism on a
4258 parameter by parameter basis using either positional or named
4259 notation. If the mechanism is not specified, the default mechanism
4262 @node Pragma Import_Object,Pragma Import_Procedure,Pragma Import_Function,Implementation Defined Pragmas
4263 @anchor{gnat_rm/implementation_defined_pragmas pragma-import-object}@anchor{7b}
4264 @section Pragma Import_Object
4270 pragma Import_Object
4271 [Internal =>] LOCAL_NAME
4272 [, [External =>] EXTERNAL_SYMBOL]
4273 [, [Size =>] EXTERNAL_SYMBOL]);
4277 | static_string_EXPRESSION
4280 This pragma designates an object as imported, and apart from the
4281 extended rules for external symbols, is identical in effect to the use of
4282 the normal @code{Import} pragma applied to an object. Unlike the
4283 subprogram case, you need not use a separate @code{Import} pragma,
4284 although you may do so (and probably should do so from a portability
4285 point of view). @code{size} is syntax checked, but otherwise ignored by
4288 @node Pragma Import_Procedure,Pragma Import_Valued_Procedure,Pragma Import_Object,Implementation Defined Pragmas
4289 @anchor{gnat_rm/implementation_defined_pragmas pragma-import-procedure}@anchor{7c}
4290 @section Pragma Import_Procedure
4296 pragma Import_Procedure (
4297 [Internal =>] LOCAL_NAME
4298 [, [External =>] EXTERNAL_SYMBOL]
4299 [, [Parameter_Types =>] PARAMETER_TYPES]
4300 [, [Mechanism =>] MECHANISM]);
4304 | static_string_EXPRESSION
4308 | TYPE_DESIGNATOR @{, TYPE_DESIGNATOR@}
4312 | subtype_Name ' Access
4316 | (MECHANISM_ASSOCIATION @{, MECHANISM_ASSOCIATION@})
4318 MECHANISM_ASSOCIATION ::=
4319 [formal_parameter_NAME =>] MECHANISM_NAME
4321 MECHANISM_NAME ::= Value | Reference
4324 This pragma is identical to @code{Import_Function} except that it
4325 applies to a procedure rather than a function and the parameters
4326 @code{Result_Type} and @code{Result_Mechanism} are not permitted.
4328 @node Pragma Import_Valued_Procedure,Pragma Independent,Pragma Import_Procedure,Implementation Defined Pragmas
4329 @anchor{gnat_rm/implementation_defined_pragmas pragma-import-valued-procedure}@anchor{7d}
4330 @section Pragma Import_Valued_Procedure
4336 pragma Import_Valued_Procedure (
4337 [Internal =>] LOCAL_NAME
4338 [, [External =>] EXTERNAL_SYMBOL]
4339 [, [Parameter_Types =>] PARAMETER_TYPES]
4340 [, [Mechanism =>] MECHANISM]);
4344 | static_string_EXPRESSION
4348 | TYPE_DESIGNATOR @{, TYPE_DESIGNATOR@}
4352 | subtype_Name ' Access
4356 | (MECHANISM_ASSOCIATION @{, MECHANISM_ASSOCIATION@})
4358 MECHANISM_ASSOCIATION ::=
4359 [formal_parameter_NAME =>] MECHANISM_NAME
4361 MECHANISM_NAME ::= Value | Reference
4364 This pragma is identical to @code{Import_Procedure} except that the
4365 first parameter of @code{LOCAL_NAME}, which must be present, must be of
4366 mode @code{out}, and externally the subprogram is treated as a function
4367 with this parameter as the result of the function. The purpose of this
4368 capability is to allow the use of @code{out} and @code{in out}
4369 parameters in interfacing to external functions (which are not permitted
4370 in Ada functions). You may optionally use the @code{Mechanism}
4371 parameters to specify passing mechanisms for the parameters.
4372 If you specify a single mechanism name, it applies to all parameters.
4373 Otherwise you may specify a mechanism on a parameter by parameter
4374 basis using either positional or named notation. If the mechanism is not
4375 specified, the default mechanism is used.
4377 Note that it is important to use this pragma in conjunction with a separate
4378 pragma Import that specifies the desired convention, since otherwise the
4379 default convention is Ada, which is almost certainly not what is required.
4381 @node Pragma Independent,Pragma Independent_Components,Pragma Import_Valued_Procedure,Implementation Defined Pragmas
4382 @anchor{gnat_rm/implementation_defined_pragmas pragma-independent}@anchor{7e}
4383 @section Pragma Independent
4389 pragma Independent (Local_NAME);
4392 This pragma is standard in Ada 2012 mode (which also provides an aspect
4393 of the same name). It is also available as an implementation-defined
4394 pragma in all earlier versions. It specifies that the
4395 designated object or all objects of the designated type must be
4396 independently addressable. This means that separate tasks can safely
4397 manipulate such objects. For example, if two components of a record are
4398 independent, then two separate tasks may access these two components.
4400 constraints on the representation of the object (for instance prohibiting
4403 @node Pragma Independent_Components,Pragma Initial_Condition,Pragma Independent,Implementation Defined Pragmas
4404 @anchor{gnat_rm/implementation_defined_pragmas pragma-independent-components}@anchor{7f}
4405 @section Pragma Independent_Components
4411 pragma Independent_Components (Local_NAME);
4414 This pragma is standard in Ada 2012 mode (which also provides an aspect
4415 of the same name). It is also available as an implementation-defined
4416 pragma in all earlier versions. It specifies that the components of the
4417 designated object, or the components of each object of the designated
4419 independently addressable. This means that separate tasks can safely
4420 manipulate separate components in the composite object. This may place
4421 constraints on the representation of the object (for instance prohibiting
4424 @node Pragma Initial_Condition,Pragma Initialize_Scalars,Pragma Independent_Components,Implementation Defined Pragmas
4425 @anchor{gnat_rm/implementation_defined_pragmas id16}@anchor{80}@anchor{gnat_rm/implementation_defined_pragmas pragma-initial-condition}@anchor{81}
4426 @section Pragma Initial_Condition
4432 pragma Initial_Condition (boolean_EXPRESSION);
4435 For the semantics of this pragma, see the entry for aspect @code{Initial_Condition}
4436 in the SPARK 2014 Reference Manual, section 7.1.6.
4438 @node Pragma Initialize_Scalars,Pragma Initializes,Pragma Initial_Condition,Implementation Defined Pragmas
4439 @anchor{gnat_rm/implementation_defined_pragmas pragma-initialize-scalars}@anchor{82}
4440 @section Pragma Initialize_Scalars
4443 @geindex debugging with Initialize_Scalars
4448 pragma Initialize_Scalars
4449 [ ( TYPE_VALUE_PAIR @{, TYPE_VALUE_PAIR@} ) ];
4452 SCALAR_TYPE => static_EXPRESSION
4469 This pragma is similar to @code{Normalize_Scalars} conceptually but has two
4470 important differences.
4472 First, there is no requirement for the pragma to be used uniformly in all units
4473 of a partition. In particular, it is fine to use this just for some or all of
4474 the application units of a partition, without needing to recompile the run-time
4475 library. In the case where some units are compiled with the pragma, and some
4476 without, then a declaration of a variable where the type is defined in package
4477 Standard or is locally declared will always be subject to initialization, as
4478 will any declaration of a scalar variable. For composite variables, whether the
4479 variable is initialized may also depend on whether the package in which the
4480 type of the variable is declared is compiled with the pragma.
4482 The other important difference is that the programmer can control the value
4483 used for initializing scalar objects. This effect can be achieved in several
4490 At compile time, the programmer can specify the invalid value for a
4491 particular family of scalar types using the optional arguments of the pragma.
4493 The compile-time approach is intended to optimize the generated code for the
4494 pragma, by possibly using fast operations such as @code{memset}.
4497 At bind time, the programmer has several options:
4503 Initialization with invalid values (similar to Normalize_Scalars, though
4504 for Initialize_Scalars it is not always possible to determine the invalid
4505 values in complex cases like signed component fields with nonstandard
4509 Initialization with high values.
4512 Initialization with low values.
4515 Initialization with a specific bit pattern.
4518 See the GNAT User's Guide for binder options for specifying these cases.
4520 The bind-time approach is intended to provide fast turnaround for testing
4521 with different values, without having to recompile the program.
4524 At execution time, the programmer can speify the invalid values using an
4525 environment variable. See the GNAT User's Guide for details.
4527 The execution-time approach is intended to provide fast turnaround for
4528 testing with different values, without having to recompile and rebind the
4532 Note that pragma @code{Initialize_Scalars} is particularly useful in conjunction
4533 with the enhanced validity checking that is now provided in GNAT, which checks
4534 for invalid values under more conditions. Using this feature (see description
4535 of the @emph{-gnatV} flag in the GNAT User's Guide) in conjunction with pragma
4536 @code{Initialize_Scalars} provides a powerful new tool to assist in the detection
4537 of problems caused by uninitialized variables.
4539 Note: the use of @code{Initialize_Scalars} has a fairly extensive effect on the
4540 generated code. This may cause your code to be substantially larger. It may
4541 also cause an increase in the amount of stack required, so it is probably a
4542 good idea to turn on stack checking (see description of stack checking in the
4543 GNAT User's Guide) when using this pragma.
4545 @node Pragma Initializes,Pragma Inline_Always,Pragma Initialize_Scalars,Implementation Defined Pragmas
4546 @anchor{gnat_rm/implementation_defined_pragmas pragma-initializes}@anchor{83}@anchor{gnat_rm/implementation_defined_pragmas id17}@anchor{84}
4547 @section Pragma Initializes
4553 pragma Initializes (INITIALIZATION_LIST);
4555 INITIALIZATION_LIST ::=
4557 | (INITIALIZATION_ITEM @{, INITIALIZATION_ITEM@})
4559 INITIALIZATION_ITEM ::= name [=> INPUT_LIST]
4564 | (INPUT @{, INPUT@})
4569 For the semantics of this pragma, see the entry for aspect @code{Initializes} in the
4570 SPARK 2014 Reference Manual, section 7.1.5.
4572 @node Pragma Inline_Always,Pragma Inline_Generic,Pragma Initializes,Implementation Defined Pragmas
4573 @anchor{gnat_rm/implementation_defined_pragmas id18}@anchor{85}@anchor{gnat_rm/implementation_defined_pragmas pragma-inline-always}@anchor{86}
4574 @section Pragma Inline_Always
4580 pragma Inline_Always (NAME [, NAME]);
4583 Similar to pragma @code{Inline} except that inlining is unconditional.
4584 Inline_Always instructs the compiler to inline every direct call to the
4585 subprogram or else to emit a compilation error, independently of any
4586 option, in particular @emph{-gnatn} or @emph{-gnatN} or the optimization level.
4587 It is an error to take the address or access of @code{NAME}. It is also an error to
4588 apply this pragma to a primitive operation of a tagged type. Thanks to such
4589 restrictions, the compiler is allowed to remove the out-of-line body of @code{NAME}.
4591 @node Pragma Inline_Generic,Pragma Interface,Pragma Inline_Always,Implementation Defined Pragmas
4592 @anchor{gnat_rm/implementation_defined_pragmas pragma-inline-generic}@anchor{87}
4593 @section Pragma Inline_Generic
4599 pragma Inline_Generic (GNAME @{, GNAME@});
4601 GNAME ::= generic_unit_NAME | generic_instance_NAME
4604 This pragma is provided for compatibility with Dec Ada 83. It has
4605 no effect in GNAT (which always inlines generics), other
4606 than to check that the given names are all names of generic units or
4609 @node Pragma Interface,Pragma Interface_Name,Pragma Inline_Generic,Implementation Defined Pragmas
4610 @anchor{gnat_rm/implementation_defined_pragmas pragma-interface}@anchor{88}
4611 @section Pragma Interface
4618 [Convention =>] convention_identifier,
4619 [Entity =>] local_NAME
4620 [, [External_Name =>] static_string_expression]
4621 [, [Link_Name =>] static_string_expression]);
4624 This pragma is identical in syntax and semantics to
4625 the standard Ada pragma @code{Import}. It is provided for compatibility
4626 with Ada 83. The definition is upwards compatible both with pragma
4627 @code{Interface} as defined in the Ada 83 Reference Manual, and also
4628 with some extended implementations of this pragma in certain Ada 83
4629 implementations. The only difference between pragma @code{Interface}
4630 and pragma @code{Import} is that there is special circuitry to allow
4631 both pragmas to appear for the same subprogram entity (normally it
4632 is illegal to have multiple @code{Import} pragmas. This is useful in
4633 maintaining Ada 83/Ada 95 compatibility and is compatible with other
4636 @node Pragma Interface_Name,Pragma Interrupt_Handler,Pragma Interface,Implementation Defined Pragmas
4637 @anchor{gnat_rm/implementation_defined_pragmas pragma-interface-name}@anchor{89}
4638 @section Pragma Interface_Name
4644 pragma Interface_Name (
4645 [Entity =>] LOCAL_NAME
4646 [, [External_Name =>] static_string_EXPRESSION]
4647 [, [Link_Name =>] static_string_EXPRESSION]);
4650 This pragma provides an alternative way of specifying the interface name
4651 for an interfaced subprogram, and is provided for compatibility with Ada
4652 83 compilers that use the pragma for this purpose. You must provide at
4653 least one of @code{External_Name} or @code{Link_Name}.
4655 @node Pragma Interrupt_Handler,Pragma Interrupt_State,Pragma Interface_Name,Implementation Defined Pragmas
4656 @anchor{gnat_rm/implementation_defined_pragmas pragma-interrupt-handler}@anchor{8a}
4657 @section Pragma Interrupt_Handler
4663 pragma Interrupt_Handler (procedure_LOCAL_NAME);
4666 This program unit pragma is supported for parameterless protected procedures
4667 as described in Annex C of the Ada Reference Manual. On the AAMP target
4668 the pragma can also be specified for nonprotected parameterless procedures
4669 that are declared at the library level (which includes procedures
4670 declared at the top level of a library package). In the case of AAMP,
4671 when this pragma is applied to a nonprotected procedure, the instruction
4672 @code{IERET} is generated for returns from the procedure, enabling
4673 maskable interrupts, in place of the normal return instruction.
4675 @node Pragma Interrupt_State,Pragma Invariant,Pragma Interrupt_Handler,Implementation Defined Pragmas
4676 @anchor{gnat_rm/implementation_defined_pragmas pragma-interrupt-state}@anchor{8b}
4677 @section Pragma Interrupt_State
4683 pragma Interrupt_State
4685 [State =>] SYSTEM | RUNTIME | USER);
4688 Normally certain interrupts are reserved to the implementation. Any attempt
4689 to attach an interrupt causes Program_Error to be raised, as described in
4690 RM C.3.2(22). A typical example is the @code{SIGINT} interrupt used in
4691 many systems for an @code{Ctrl-C} interrupt. Normally this interrupt is
4692 reserved to the implementation, so that @code{Ctrl-C} can be used to
4693 interrupt execution. Additionally, signals such as @code{SIGSEGV},
4694 @code{SIGABRT}, @code{SIGFPE} and @code{SIGILL} are often mapped to specific
4695 Ada exceptions, or used to implement run-time functions such as the
4696 @code{abort} statement and stack overflow checking.
4698 Pragma @code{Interrupt_State} provides a general mechanism for overriding
4699 such uses of interrupts. It subsumes the functionality of pragma
4700 @code{Unreserve_All_Interrupts}. Pragma @code{Interrupt_State} is not
4701 available on Windows or VMS. On all other platforms than VxWorks,
4702 it applies to signals; on VxWorks, it applies to vectored hardware interrupts
4703 and may be used to mark interrupts required by the board support package
4706 Interrupts can be in one of three states:
4714 The interrupt is reserved (no Ada handler can be installed), and the
4715 Ada run-time may not install a handler. As a result you are guaranteed
4716 standard system default action if this interrupt is raised. This also allows
4717 installing a low level handler via C APIs such as sigaction(), outside
4723 The interrupt is reserved (no Ada handler can be installed). The run time
4724 is allowed to install a handler for internal control purposes, but is
4725 not required to do so.
4730 The interrupt is unreserved. The user may install an Ada handler via
4731 Ada.Interrupts and pragma Interrupt_Handler or Attach_Handler to provide
4735 These states are the allowed values of the @code{State} parameter of the
4736 pragma. The @code{Name} parameter is a value of the type
4737 @code{Ada.Interrupts.Interrupt_ID}. Typically, it is a name declared in
4738 @code{Ada.Interrupts.Names}.
4740 This is a configuration pragma, and the binder will check that there
4741 are no inconsistencies between different units in a partition in how a
4742 given interrupt is specified. It may appear anywhere a pragma is legal.
4744 The effect is to move the interrupt to the specified state.
4746 By declaring interrupts to be SYSTEM, you guarantee the standard system
4747 action, such as a core dump.
4749 By declaring interrupts to be USER, you guarantee that you can install
4752 Note that certain signals on many operating systems cannot be caught and
4753 handled by applications. In such cases, the pragma is ignored. See the
4754 operating system documentation, or the value of the array @code{Reserved}
4755 declared in the spec of package @code{System.OS_Interface}.
4757 Overriding the default state of signals used by the Ada runtime may interfere
4758 with an application's runtime behavior in the cases of the synchronous signals,
4759 and in the case of the signal used to implement the @code{abort} statement.
4761 @node Pragma Invariant,Pragma Keep_Names,Pragma Interrupt_State,Implementation Defined Pragmas
4762 @anchor{gnat_rm/implementation_defined_pragmas id19}@anchor{8c}@anchor{gnat_rm/implementation_defined_pragmas pragma-invariant}@anchor{8d}
4763 @section Pragma Invariant
4770 ([Entity =>] private_type_LOCAL_NAME,
4771 [Check =>] EXPRESSION
4772 [,[Message =>] String_Expression]);
4775 This pragma provides exactly the same capabilities as the Type_Invariant aspect
4776 defined in AI05-0146-1, and in the Ada 2012 Reference Manual. The
4777 Type_Invariant aspect is fully implemented in Ada 2012 mode, but since it
4778 requires the use of the aspect syntax, which is not available except in 2012
4779 mode, it is not possible to use the Type_Invariant aspect in earlier versions
4780 of Ada. However the Invariant pragma may be used in any version of Ada. Also
4781 note that the aspect Invariant is a synonym in GNAT for the aspect
4782 Type_Invariant, but there is no pragma Type_Invariant.
4784 The pragma must appear within the visible part of the package specification,
4785 after the type to which its Entity argument appears. As with the Invariant
4786 aspect, the Check expression is not analyzed until the end of the visible
4787 part of the package, so it may contain forward references. The Message
4788 argument, if present, provides the exception message used if the invariant
4789 is violated. If no Message parameter is provided, a default message that
4790 identifies the line on which the pragma appears is used.
4792 It is permissible to have multiple Invariants for the same type entity, in
4793 which case they are and'ed together. It is permissible to use this pragma
4794 in Ada 2012 mode, but you cannot have both an invariant aspect and an
4795 invariant pragma for the same entity.
4797 For further details on the use of this pragma, see the Ada 2012 documentation
4798 of the Type_Invariant aspect.
4800 @node Pragma Keep_Names,Pragma License,Pragma Invariant,Implementation Defined Pragmas
4801 @anchor{gnat_rm/implementation_defined_pragmas pragma-keep-names}@anchor{8e}
4802 @section Pragma Keep_Names
4808 pragma Keep_Names ([On =>] enumeration_first_subtype_LOCAL_NAME);
4811 The @code{LOCAL_NAME} argument
4812 must refer to an enumeration first subtype
4813 in the current declarative part. The effect is to retain the enumeration
4814 literal names for use by @code{Image} and @code{Value} even if a global
4815 @code{Discard_Names} pragma applies. This is useful when you want to
4816 generally suppress enumeration literal names and for example you therefore
4817 use a @code{Discard_Names} pragma in the @code{gnat.adc} file, but you
4818 want to retain the names for specific enumeration types.
4820 @node Pragma License,Pragma Link_With,Pragma Keep_Names,Implementation Defined Pragmas
4821 @anchor{gnat_rm/implementation_defined_pragmas pragma-license}@anchor{8f}
4822 @section Pragma License
4825 @geindex License checking
4830 pragma License (Unrestricted | GPL | Modified_GPL | Restricted);
4833 This pragma is provided to allow automated checking for appropriate license
4834 conditions with respect to the standard and modified GPL. A pragma
4835 @code{License}, which is a configuration pragma that typically appears at
4836 the start of a source file or in a separate @code{gnat.adc} file, specifies
4837 the licensing conditions of a unit as follows:
4844 This is used for a unit that can be freely used with no license restrictions.
4845 Examples of such units are public domain units, and units from the Ada
4850 This is used for a unit that is licensed under the unmodified GPL, and which
4851 therefore cannot be @code{with}ed by a restricted unit.
4855 This is used for a unit licensed under the GNAT modified GPL that includes
4856 a special exception paragraph that specifically permits the inclusion of
4857 the unit in programs without requiring the entire program to be released
4862 This is used for a unit that is restricted in that it is not permitted to
4863 depend on units that are licensed under the GPL. Typical examples are
4864 proprietary code that is to be released under more restrictive license
4865 conditions. Note that restricted units are permitted to @code{with} units
4866 which are licensed under the modified GPL (this is the whole point of the
4870 Normally a unit with no @code{License} pragma is considered to have an
4871 unknown license, and no checking is done. However, standard GNAT headers
4872 are recognized, and license information is derived from them as follows.
4874 A GNAT license header starts with a line containing 78 hyphens. The following
4875 comment text is searched for the appearance of any of the following strings.
4877 If the string 'GNU General Public License' is found, then the unit is assumed
4878 to have GPL license, unless the string 'As a special exception' follows, in
4879 which case the license is assumed to be modified GPL.
4881 If one of the strings
4882 'This specification is adapted from the Ada Semantic Interface' or
4883 'This specification is derived from the Ada Reference Manual' is found
4884 then the unit is assumed to be unrestricted.
4886 These default actions means that a program with a restricted license pragma
4887 will automatically get warnings if a GPL unit is inappropriately
4888 @code{with}ed. For example, the program:
4893 procedure Secret_Stuff is
4898 if compiled with pragma @code{License} (@code{Restricted}) in a
4899 @code{gnat.adc} file will generate the warning:
4904 >>> license of withed unit "Sem_Ch3" is incompatible
4906 2. with GNAT.Sockets;
4907 3. procedure Secret_Stuff is
4910 Here we get a warning on @code{Sem_Ch3} since it is part of the GNAT
4911 compiler and is licensed under the
4912 GPL, but no warning for @code{GNAT.Sockets} which is part of the GNAT
4913 run time, and is therefore licensed under the modified GPL.
4915 @node Pragma Link_With,Pragma Linker_Alias,Pragma License,Implementation Defined Pragmas
4916 @anchor{gnat_rm/implementation_defined_pragmas pragma-link-with}@anchor{90}
4917 @section Pragma Link_With
4923 pragma Link_With (static_string_EXPRESSION @{,static_string_EXPRESSION@});
4926 This pragma is provided for compatibility with certain Ada 83 compilers.
4927 It has exactly the same effect as pragma @code{Linker_Options} except
4928 that spaces occurring within one of the string expressions are treated
4929 as separators. For example, in the following case:
4932 pragma Link_With ("-labc -ldef");
4935 results in passing the strings @code{-labc} and @code{-ldef} as two
4936 separate arguments to the linker. In addition pragma Link_With allows
4937 multiple arguments, with the same effect as successive pragmas.
4939 @node Pragma Linker_Alias,Pragma Linker_Constructor,Pragma Link_With,Implementation Defined Pragmas
4940 @anchor{gnat_rm/implementation_defined_pragmas pragma-linker-alias}@anchor{91}
4941 @section Pragma Linker_Alias
4947 pragma Linker_Alias (
4948 [Entity =>] LOCAL_NAME,
4949 [Target =>] static_string_EXPRESSION);
4952 @code{LOCAL_NAME} must refer to an object that is declared at the library
4953 level. This pragma establishes the given entity as a linker alias for the
4954 given target. It is equivalent to @code{__attribute__((alias))} in GNU C
4955 and causes @code{LOCAL_NAME} to be emitted as an alias for the symbol
4956 @code{static_string_EXPRESSION} in the object file, that is to say no space
4957 is reserved for @code{LOCAL_NAME} by the assembler and it will be resolved
4958 to the same address as @code{static_string_EXPRESSION} by the linker.
4960 The actual linker name for the target must be used (e.g., the fully
4961 encoded name with qualification in Ada, or the mangled name in C++),
4962 or it must be declared using the C convention with @code{pragma Import}
4963 or @code{pragma Export}.
4965 Not all target machines support this pragma. On some of them it is accepted
4966 only if @code{pragma Weak_External} has been applied to @code{LOCAL_NAME}.
4969 -- Example of the use of pragma Linker_Alias
4973 pragma Export (C, i);
4975 new_name_for_i : Integer;
4976 pragma Linker_Alias (new_name_for_i, "i");
4980 @node Pragma Linker_Constructor,Pragma Linker_Destructor,Pragma Linker_Alias,Implementation Defined Pragmas
4981 @anchor{gnat_rm/implementation_defined_pragmas pragma-linker-constructor}@anchor{92}
4982 @section Pragma Linker_Constructor
4988 pragma Linker_Constructor (procedure_LOCAL_NAME);
4991 @code{procedure_LOCAL_NAME} must refer to a parameterless procedure that
4992 is declared at the library level. A procedure to which this pragma is
4993 applied will be treated as an initialization routine by the linker.
4994 It is equivalent to @code{__attribute__((constructor))} in GNU C and
4995 causes @code{procedure_LOCAL_NAME} to be invoked before the entry point
4996 of the executable is called (or immediately after the shared library is
4997 loaded if the procedure is linked in a shared library), in particular
4998 before the Ada run-time environment is set up.
5000 Because of these specific contexts, the set of operations such a procedure
5001 can perform is very limited and the type of objects it can manipulate is
5002 essentially restricted to the elementary types. In particular, it must only
5003 contain code to which pragma Restrictions (No_Elaboration_Code) applies.
5005 This pragma is used by GNAT to implement auto-initialization of shared Stand
5006 Alone Libraries, which provides a related capability without the restrictions
5007 listed above. Where possible, the use of Stand Alone Libraries is preferable
5008 to the use of this pragma.
5010 @node Pragma Linker_Destructor,Pragma Linker_Section,Pragma Linker_Constructor,Implementation Defined Pragmas
5011 @anchor{gnat_rm/implementation_defined_pragmas pragma-linker-destructor}@anchor{93}
5012 @section Pragma Linker_Destructor
5018 pragma Linker_Destructor (procedure_LOCAL_NAME);
5021 @code{procedure_LOCAL_NAME} must refer to a parameterless procedure that
5022 is declared at the library level. A procedure to which this pragma is
5023 applied will be treated as a finalization routine by the linker.
5024 It is equivalent to @code{__attribute__((destructor))} in GNU C and
5025 causes @code{procedure_LOCAL_NAME} to be invoked after the entry point
5026 of the executable has exited (or immediately before the shared library
5027 is unloaded if the procedure is linked in a shared library), in particular
5028 after the Ada run-time environment is shut down.
5030 See @code{pragma Linker_Constructor} for the set of restrictions that apply
5031 because of these specific contexts.
5033 @node Pragma Linker_Section,Pragma Lock_Free,Pragma Linker_Destructor,Implementation Defined Pragmas
5034 @anchor{gnat_rm/implementation_defined_pragmas id20}@anchor{94}@anchor{gnat_rm/implementation_defined_pragmas pragma-linker-section}@anchor{95}
5035 @section Pragma Linker_Section
5041 pragma Linker_Section (
5042 [Entity =>] LOCAL_NAME,
5043 [Section =>] static_string_EXPRESSION);
5046 @code{LOCAL_NAME} must refer to an object, type, or subprogram that is
5047 declared at the library level. This pragma specifies the name of the
5048 linker section for the given entity. It is equivalent to
5049 @code{__attribute__((section))} in GNU C and causes @code{LOCAL_NAME} to
5050 be placed in the @code{static_string_EXPRESSION} section of the
5051 executable (assuming the linker doesn't rename the section).
5052 GNAT also provides an implementation defined aspect of the same name.
5054 In the case of specifying this aspect for a type, the effect is to
5055 specify the corresponding section for all library-level objects of
5056 the type that do not have an explicit linker section set. Note that
5057 this only applies to whole objects, not to components of composite objects.
5059 In the case of a subprogram, the linker section applies to all previously
5060 declared matching overloaded subprograms in the current declarative part
5061 which do not already have a linker section assigned. The linker section
5062 aspect is useful in this case for specifying different linker sections
5063 for different elements of such an overloaded set.
5065 Note that an empty string specifies that no linker section is specified.
5066 This is not quite the same as omitting the pragma or aspect, since it
5067 can be used to specify that one element of an overloaded set of subprograms
5068 has the default linker section, or that one object of a type for which a
5069 linker section is specified should has the default linker section.
5071 The compiler normally places library-level entities in standard sections
5072 depending on the class: procedures and functions generally go in the
5073 @code{.text} section, initialized variables in the @code{.data} section
5074 and uninitialized variables in the @code{.bss} section.
5076 Other, special sections may exist on given target machines to map special
5077 hardware, for example I/O ports or flash memory. This pragma is a means to
5078 defer the final layout of the executable to the linker, thus fully working
5079 at the symbolic level with the compiler.
5081 Some file formats do not support arbitrary sections so not all target
5082 machines support this pragma. The use of this pragma may cause a program
5083 execution to be erroneous if it is used to place an entity into an
5084 inappropriate section (e.g., a modified variable into the @code{.text}
5085 section). See also @code{pragma Persistent_BSS}.
5088 -- Example of the use of pragma Linker_Section
5092 pragma Volatile (Port_A);
5093 pragma Linker_Section (Port_A, ".bss.port_a");
5096 pragma Volatile (Port_B);
5097 pragma Linker_Section (Port_B, ".bss.port_b");
5099 type Port_Type is new Integer with Linker_Section => ".bss";
5100 PA : Port_Type with Linker_Section => ".bss.PA";
5101 PB : Port_Type; -- ends up in linker section ".bss"
5103 procedure Q with Linker_Section => "Qsection";
5107 @node Pragma Lock_Free,Pragma Loop_Invariant,Pragma Linker_Section,Implementation Defined Pragmas
5108 @anchor{gnat_rm/implementation_defined_pragmas id21}@anchor{96}@anchor{gnat_rm/implementation_defined_pragmas pragma-lock-free}@anchor{97}
5109 @section Pragma Lock_Free
5113 This pragma may be specified for protected types or objects. It specifies that
5114 the implementation of protected operations must be implemented without locks.
5115 Compilation fails if the compiler cannot generate lock-free code for the
5118 The current conditions required to support this pragma are:
5124 Protected type declarations may not contain entries
5127 Protected subprogram declarations may not have nonelementary parameters
5130 In addition, each protected subprogram body must satisfy:
5136 May reference only one protected component
5139 May not reference nonconstant entities outside the protected subprogram
5143 May not contain address representation items, allocators, or quantified
5147 May not contain delay, goto, loop, or procedure-call statements.
5150 May not contain exported and imported entities
5153 May not dereferenced access values
5156 Function calls and attribute references must be static
5159 @node Pragma Loop_Invariant,Pragma Loop_Optimize,Pragma Lock_Free,Implementation Defined Pragmas
5160 @anchor{gnat_rm/implementation_defined_pragmas pragma-loop-invariant}@anchor{98}
5161 @section Pragma Loop_Invariant
5167 pragma Loop_Invariant ( boolean_EXPRESSION );
5170 The effect of this pragma is similar to that of pragma @code{Assert},
5171 except that in an @code{Assertion_Policy} pragma, the identifier
5172 @code{Loop_Invariant} is used to control whether it is ignored or checked
5175 @code{Loop_Invariant} can only appear as one of the items in the sequence
5176 of statements of a loop body, or nested inside block statements that
5177 appear in the sequence of statements of a loop body.
5178 The intention is that it be used to
5179 represent a "loop invariant" assertion, i.e. something that is true each
5180 time through the loop, and which can be used to show that the loop is
5181 achieving its purpose.
5183 Multiple @code{Loop_Invariant} and @code{Loop_Variant} pragmas that
5184 apply to the same loop should be grouped in the same sequence of
5187 To aid in writing such invariants, the special attribute @code{Loop_Entry}
5188 may be used to refer to the value of an expression on entry to the loop. This
5189 attribute can only be used within the expression of a @code{Loop_Invariant}
5190 pragma. For full details, see documentation of attribute @code{Loop_Entry}.
5192 @node Pragma Loop_Optimize,Pragma Loop_Variant,Pragma Loop_Invariant,Implementation Defined Pragmas
5193 @anchor{gnat_rm/implementation_defined_pragmas pragma-loop-optimize}@anchor{99}
5194 @section Pragma Loop_Optimize
5200 pragma Loop_Optimize (OPTIMIZATION_HINT @{, OPTIMIZATION_HINT@});
5202 OPTIMIZATION_HINT ::= Ivdep | No_Unroll | Unroll | No_Vector | Vector
5205 This pragma must appear immediately within a loop statement. It allows the
5206 programmer to specify optimization hints for the enclosing loop. The hints
5207 are not mutually exclusive and can be freely mixed, but not all combinations
5208 will yield a sensible outcome.
5210 There are five supported optimization hints for a loop:
5218 The programmer asserts that there are no loop-carried dependencies
5219 which would prevent consecutive iterations of the loop from being
5220 executed simultaneously.
5225 The loop must not be unrolled. This is a strong hint: the compiler will not
5226 unroll a loop marked with this hint.
5231 The loop should be unrolled. This is a weak hint: the compiler will try to
5232 apply unrolling to this loop preferably to other optimizations, notably
5233 vectorization, but there is no guarantee that the loop will be unrolled.
5238 The loop must not be vectorized. This is a strong hint: the compiler will not
5239 vectorize a loop marked with this hint.
5244 The loop should be vectorized. This is a weak hint: the compiler will try to
5245 apply vectorization to this loop preferably to other optimizations, notably
5246 unrolling, but there is no guarantee that the loop will be vectorized.
5249 These hints do not remove the need to pass the appropriate switches to the
5250 compiler in order to enable the relevant optimizations, that is to say
5251 @emph{-funroll-loops} for unrolling and @emph{-ftree-vectorize} for
5254 @node Pragma Loop_Variant,Pragma Machine_Attribute,Pragma Loop_Optimize,Implementation Defined Pragmas
5255 @anchor{gnat_rm/implementation_defined_pragmas pragma-loop-variant}@anchor{9a}
5256 @section Pragma Loop_Variant
5262 pragma Loop_Variant ( LOOP_VARIANT_ITEM @{, LOOP_VARIANT_ITEM @} );
5263 LOOP_VARIANT_ITEM ::= CHANGE_DIRECTION => discrete_EXPRESSION
5264 CHANGE_DIRECTION ::= Increases | Decreases
5267 @code{Loop_Variant} can only appear as one of the items in the sequence
5268 of statements of a loop body, or nested inside block statements that
5269 appear in the sequence of statements of a loop body.
5270 It allows the specification of quantities which must always
5271 decrease or increase in successive iterations of the loop. In its simplest
5272 form, just one expression is specified, whose value must increase or decrease
5273 on each iteration of the loop.
5275 In a more complex form, multiple arguments can be given which are intepreted
5276 in a nesting lexicographic manner. For example:
5279 pragma Loop_Variant (Increases => X, Decreases => Y);
5282 specifies that each time through the loop either X increases, or X stays
5283 the same and Y decreases. A @code{Loop_Variant} pragma ensures that the
5284 loop is making progress. It can be useful in helping to show informally
5285 or prove formally that the loop always terminates.
5287 @code{Loop_Variant} is an assertion whose effect can be controlled using
5288 an @code{Assertion_Policy} with a check name of @code{Loop_Variant}. The
5289 policy can be @code{Check} to enable the loop variant check, @code{Ignore}
5290 to ignore the check (in which case the pragma has no effect on the program),
5291 or @code{Disable} in which case the pragma is not even checked for correct
5294 Multiple @code{Loop_Invariant} and @code{Loop_Variant} pragmas that
5295 apply to the same loop should be grouped in the same sequence of
5298 The @code{Loop_Entry} attribute may be used within the expressions of the
5299 @code{Loop_Variant} pragma to refer to values on entry to the loop.
5301 @node Pragma Machine_Attribute,Pragma Main,Pragma Loop_Variant,Implementation Defined Pragmas
5302 @anchor{gnat_rm/implementation_defined_pragmas pragma-machine-attribute}@anchor{9b}
5303 @section Pragma Machine_Attribute
5309 pragma Machine_Attribute (
5310 [Entity =>] LOCAL_NAME,
5311 [Attribute_Name =>] static_string_EXPRESSION
5312 [, [Info =>] static_EXPRESSION @{, static_EXPRESSION@}] );
5315 Machine-dependent attributes can be specified for types and/or
5316 declarations. This pragma is semantically equivalent to
5317 @code{__attribute__((@emph{attribute_name}))} (if @code{info} is not
5318 specified) or @code{__attribute__((@emph{attribute_name(info})))}
5319 or @code{__attribute__((@emph{attribute_name(info,...})))} in GNU C,
5320 where @emph{attribute_name} is recognized by the compiler middle-end
5321 or the @code{TARGET_ATTRIBUTE_TABLE} machine specific macro. Note
5322 that a string literal for the optional parameter @code{info} or the
5323 following ones is transformed by default into an identifier,
5324 which may make this pragma unusable for some attributes.
5325 For further information see @cite{GNU Compiler Collection (GCC) Internals}.
5327 @node Pragma Main,Pragma Main_Storage,Pragma Machine_Attribute,Implementation Defined Pragmas
5328 @anchor{gnat_rm/implementation_defined_pragmas pragma-main}@anchor{9c}
5329 @section Pragma Main
5336 (MAIN_OPTION [, MAIN_OPTION]);
5339 [Stack_Size =>] static_integer_EXPRESSION
5340 | [Task_Stack_Size_Default =>] static_integer_EXPRESSION
5341 | [Time_Slicing_Enabled =>] static_boolean_EXPRESSION
5344 This pragma is provided for compatibility with OpenVMS VAX Systems. It has
5345 no effect in GNAT, other than being syntax checked.
5347 @node Pragma Main_Storage,Pragma Max_Queue_Length,Pragma Main,Implementation Defined Pragmas
5348 @anchor{gnat_rm/implementation_defined_pragmas pragma-main-storage}@anchor{9d}
5349 @section Pragma Main_Storage
5356 (MAIN_STORAGE_OPTION [, MAIN_STORAGE_OPTION]);
5358 MAIN_STORAGE_OPTION ::=
5359 [WORKING_STORAGE =>] static_SIMPLE_EXPRESSION
5360 | [TOP_GUARD =>] static_SIMPLE_EXPRESSION
5363 This pragma is provided for compatibility with OpenVMS VAX Systems. It has
5364 no effect in GNAT, other than being syntax checked.
5366 @node Pragma Max_Queue_Length,Pragma No_Body,Pragma Main_Storage,Implementation Defined Pragmas
5367 @anchor{gnat_rm/implementation_defined_pragmas id22}@anchor{9e}@anchor{gnat_rm/implementation_defined_pragmas pragma-max-queue-length}@anchor{9f}
5368 @section Pragma Max_Queue_Length
5374 pragma Max_Entry_Queue (static_integer_EXPRESSION);
5377 This pragma is used to specify the maximum callers per entry queue for
5378 individual protected entries and entry families. It accepts a single
5379 positive integer as a parameter and must appear after the declaration
5382 @node Pragma No_Body,Pragma No_Caching,Pragma Max_Queue_Length,Implementation Defined Pragmas
5383 @anchor{gnat_rm/implementation_defined_pragmas pragma-no-body}@anchor{a0}
5384 @section Pragma No_Body
5393 There are a number of cases in which a package spec does not require a body,
5394 and in fact a body is not permitted. GNAT will not permit the spec to be
5395 compiled if there is a body around. The pragma No_Body allows you to provide
5396 a body file, even in a case where no body is allowed. The body file must
5397 contain only comments and a single No_Body pragma. This is recognized by
5398 the compiler as indicating that no body is logically present.
5400 This is particularly useful during maintenance when a package is modified in
5401 such a way that a body needed before is no longer needed. The provision of a
5402 dummy body with a No_Body pragma ensures that there is no interference from
5403 earlier versions of the package body.
5405 @node Pragma No_Caching,Pragma No_Component_Reordering,Pragma No_Body,Implementation Defined Pragmas
5406 @anchor{gnat_rm/implementation_defined_pragmas pragma-no-caching}@anchor{a1}@anchor{gnat_rm/implementation_defined_pragmas id23}@anchor{a2}
5407 @section Pragma No_Caching
5413 pragma No_Caching [ (boolean_EXPRESSION) ];
5416 For the semantics of this pragma, see the entry for aspect @code{No_Caching} in
5417 the SPARK 2014 Reference Manual, section 7.1.2.
5419 @node Pragma No_Component_Reordering,Pragma No_Elaboration_Code_All,Pragma No_Caching,Implementation Defined Pragmas
5420 @anchor{gnat_rm/implementation_defined_pragmas pragma-no-component-reordering}@anchor{a3}
5421 @section Pragma No_Component_Reordering
5427 pragma No_Component_Reordering [([Entity =>] type_LOCAL_NAME)];
5430 @code{type_LOCAL_NAME} must refer to a record type declaration in the current
5431 declarative part. The effect is to preclude any reordering of components
5432 for the layout of the record, i.e. the record is laid out by the compiler
5433 in the order in which the components are declared textually. The form with
5434 no argument is a configuration pragma which applies to all record types
5435 declared in units to which the pragma applies and there is a requirement
5436 that this pragma be used consistently within a partition.
5438 @node Pragma No_Elaboration_Code_All,Pragma No_Heap_Finalization,Pragma No_Component_Reordering,Implementation Defined Pragmas
5439 @anchor{gnat_rm/implementation_defined_pragmas id24}@anchor{a4}@anchor{gnat_rm/implementation_defined_pragmas pragma-no-elaboration-code-all}@anchor{a5}
5440 @section Pragma No_Elaboration_Code_All
5446 pragma No_Elaboration_Code_All [(program_unit_NAME)];
5449 This is a program unit pragma (there is also an equivalent aspect of the
5450 same name) that establishes the restriction @code{No_Elaboration_Code} for
5451 the current unit and any extended main source units (body and subunits).
5452 It also has the effect of enforcing a transitive application of this
5453 aspect, so that if any unit is implicitly or explicitly with'ed by the
5454 current unit, it must also have the No_Elaboration_Code_All aspect set.
5455 It may be applied to package or subprogram specs or their generic versions.
5457 @node Pragma No_Heap_Finalization,Pragma No_Inline,Pragma No_Elaboration_Code_All,Implementation Defined Pragmas
5458 @anchor{gnat_rm/implementation_defined_pragmas pragma-no-heap-finalization}@anchor{a6}
5459 @section Pragma No_Heap_Finalization
5465 pragma No_Heap_Finalization [ (first_subtype_LOCAL_NAME) ];
5468 Pragma @code{No_Heap_Finalization} may be used as a configuration pragma or as a
5469 type-specific pragma.
5471 In its configuration form, the pragma must appear within a configuration file
5472 such as gnat.adc, without an argument. The pragma suppresses the call to
5473 @code{Finalize} for heap-allocated objects created through library-level named
5474 access-to-object types in cases where the designated type requires finalization
5477 In its type-specific form, the argument of the pragma must denote a
5478 library-level named access-to-object type. The pragma suppresses the call to
5479 @code{Finalize} for heap-allocated objects created through the specific access type
5480 in cases where the designated type requires finalization actions.
5482 It is still possible to finalize such heap-allocated objects by explicitly
5485 A library-level named access-to-object type declared within a generic unit will
5486 lose its @code{No_Heap_Finalization} pragma when the corresponding instance does not
5487 appear at the library level.
5489 @node Pragma No_Inline,Pragma No_Return,Pragma No_Heap_Finalization,Implementation Defined Pragmas
5490 @anchor{gnat_rm/implementation_defined_pragmas id25}@anchor{a7}@anchor{gnat_rm/implementation_defined_pragmas pragma-no-inline}@anchor{a8}
5491 @section Pragma No_Inline
5497 pragma No_Inline (NAME @{, NAME@});
5500 This pragma suppresses inlining for the callable entity or the instances of
5501 the generic subprogram designated by @code{NAME}, including inlining that
5502 results from the use of pragma @code{Inline}. This pragma is always active,
5503 in particular it is not subject to the use of option @emph{-gnatn} or
5504 @emph{-gnatN}. It is illegal to specify both pragma @code{No_Inline} and
5505 pragma @code{Inline_Always} for the same @code{NAME}.
5507 @node Pragma No_Return,Pragma No_Run_Time,Pragma No_Inline,Implementation Defined Pragmas
5508 @anchor{gnat_rm/implementation_defined_pragmas pragma-no-return}@anchor{a9}
5509 @section Pragma No_Return
5515 pragma No_Return (procedure_LOCAL_NAME @{, procedure_LOCAL_NAME@});
5518 Each @code{procedure_LOCAL_NAME} argument must refer to one or more procedure
5519 declarations in the current declarative part. A procedure to which this
5520 pragma is applied may not contain any explicit @code{return} statements.
5521 In addition, if the procedure contains any implicit returns from falling
5522 off the end of a statement sequence, then execution of that implicit
5523 return will cause Program_Error to be raised.
5525 One use of this pragma is to identify procedures whose only purpose is to raise
5526 an exception. Another use of this pragma is to suppress incorrect warnings
5527 about missing returns in functions, where the last statement of a function
5528 statement sequence is a call to such a procedure.
5530 Note that in Ada 2005 mode, this pragma is part of the language. It is
5531 available in all earlier versions of Ada as an implementation-defined
5534 @node Pragma No_Run_Time,Pragma No_Strict_Aliasing,Pragma No_Return,Implementation Defined Pragmas
5535 @anchor{gnat_rm/implementation_defined_pragmas pragma-no-run-time}@anchor{aa}
5536 @section Pragma No_Run_Time
5545 This is an obsolete configuration pragma that historically was used to
5546 set up a runtime library with no object code. It is now used only for
5547 internal testing. The pragma has been superseded by the reconfigurable
5548 runtime capability of GNAT.
5550 @node Pragma No_Strict_Aliasing,Pragma No_Tagged_Streams,Pragma No_Run_Time,Implementation Defined Pragmas
5551 @anchor{gnat_rm/implementation_defined_pragmas pragma-no-strict-aliasing}@anchor{ab}
5552 @section Pragma No_Strict_Aliasing
5558 pragma No_Strict_Aliasing [([Entity =>] type_LOCAL_NAME)];
5561 @code{type_LOCAL_NAME} must refer to an access type
5562 declaration in the current declarative part. The effect is to inhibit
5563 strict aliasing optimization for the given type. The form with no
5564 arguments is a configuration pragma which applies to all access types
5565 declared in units to which the pragma applies. For a detailed
5566 description of the strict aliasing optimization, and the situations
5567 in which it must be suppressed, see the section on Optimization and Strict Aliasing
5568 in the @cite{GNAT User's Guide}.
5570 This pragma currently has no effects on access to unconstrained array types.
5572 @node Pragma No_Tagged_Streams,Pragma Normalize_Scalars,Pragma No_Strict_Aliasing,Implementation Defined Pragmas
5573 @anchor{gnat_rm/implementation_defined_pragmas pragma-no-tagged-streams}@anchor{ac}@anchor{gnat_rm/implementation_defined_pragmas id26}@anchor{ad}
5574 @section Pragma No_Tagged_Streams
5580 pragma No_Tagged_Streams [([Entity =>] tagged_type_LOCAL_NAME)];
5583 Normally when a tagged type is introduced using a full type declaration,
5584 part of the processing includes generating stream access routines to be
5585 used by stream attributes referencing the type (or one of its subtypes
5586 or derived types). This can involve the generation of significant amounts
5587 of code which is wasted space if stream routines are not needed for the
5590 The @code{No_Tagged_Streams} pragma causes the generation of these stream
5591 routines to be skipped, and any attempt to use stream operations on
5592 types subject to this pragma will be statically rejected as illegal.
5594 There are two forms of the pragma. The form with no arguments must appear
5595 in a declarative sequence or in the declarations of a package spec. This
5596 pragma affects all subsequent root tagged types declared in the declaration
5597 sequence, and specifies that no stream routines be generated. The form with
5598 an argument (for which there is also a corresponding aspect) specifies a
5599 single root tagged type for which stream routines are not to be generated.
5601 Once the pragma has been given for a particular root tagged type, all subtypes
5602 and derived types of this type inherit the pragma automatically, so the effect
5603 applies to a complete hierarchy (this is necessary to deal with the class-wide
5604 dispatching versions of the stream routines).
5606 When pragmas @code{Discard_Names} and @code{No_Tagged_Streams} are simultaneously
5607 applied to a tagged type its Expanded_Name and External_Tag are initialized
5608 with empty strings. This is useful to avoid exposing entity names at binary
5609 level but has a negative impact on the debuggability of tagged types.
5611 @node Pragma Normalize_Scalars,Pragma Obsolescent,Pragma No_Tagged_Streams,Implementation Defined Pragmas
5612 @anchor{gnat_rm/implementation_defined_pragmas pragma-normalize-scalars}@anchor{ae}
5613 @section Pragma Normalize_Scalars
5619 pragma Normalize_Scalars;
5622 This is a language defined pragma which is fully implemented in GNAT. The
5623 effect is to cause all scalar objects that are not otherwise initialized
5624 to be initialized. The initial values are implementation dependent and
5630 @item @emph{Standard.Character}
5632 Objects whose root type is Standard.Character are initialized to
5633 Character'Last unless the subtype range excludes NUL (in which case
5634 NUL is used). This choice will always generate an invalid value if
5637 @item @emph{Standard.Wide_Character}
5639 Objects whose root type is Standard.Wide_Character are initialized to
5640 Wide_Character'Last unless the subtype range excludes NUL (in which case
5641 NUL is used). This choice will always generate an invalid value if
5644 @item @emph{Standard.Wide_Wide_Character}
5646 Objects whose root type is Standard.Wide_Wide_Character are initialized to
5647 the invalid value 16#FFFF_FFFF# unless the subtype range excludes NUL (in
5648 which case NUL is used). This choice will always generate an invalid value if
5651 @item @emph{Integer types}
5653 Objects of an integer type are treated differently depending on whether
5654 negative values are present in the subtype. If no negative values are
5655 present, then all one bits is used as the initial value except in the
5656 special case where zero is excluded from the subtype, in which case
5657 all zero bits are used. This choice will always generate an invalid
5658 value if one exists.
5660 For subtypes with negative values present, the largest negative number
5661 is used, except in the unusual case where this largest negative number
5662 is in the subtype, and the largest positive number is not, in which case
5663 the largest positive value is used. This choice will always generate
5664 an invalid value if one exists.
5666 @item @emph{Floating-Point Types}
5668 Objects of all floating-point types are initialized to all 1-bits. For
5669 standard IEEE format, this corresponds to a NaN (not a number) which is
5670 indeed an invalid value.
5672 @item @emph{Fixed-Point Types}
5674 Objects of all fixed-point types are treated as described above for integers,
5675 with the rules applying to the underlying integer value used to represent
5676 the fixed-point value.
5678 @item @emph{Modular types}
5680 Objects of a modular type are initialized to all one bits, except in
5681 the special case where zero is excluded from the subtype, in which
5682 case all zero bits are used. This choice will always generate an
5683 invalid value if one exists.
5685 @item @emph{Enumeration types}
5687 Objects of an enumeration type are initialized to all one-bits, i.e., to
5688 the value @code{2 ** typ'Size - 1} unless the subtype excludes the literal
5689 whose Pos value is zero, in which case a code of zero is used. This choice
5690 will always generate an invalid value if one exists.
5693 @node Pragma Obsolescent,Pragma Optimize_Alignment,Pragma Normalize_Scalars,Implementation Defined Pragmas
5694 @anchor{gnat_rm/implementation_defined_pragmas pragma-obsolescent}@anchor{af}@anchor{gnat_rm/implementation_defined_pragmas id27}@anchor{b0}
5695 @section Pragma Obsolescent
5703 pragma Obsolescent (
5704 [Message =>] static_string_EXPRESSION
5705 [,[Version =>] Ada_05]]);
5707 pragma Obsolescent (
5709 [,[Message =>] static_string_EXPRESSION
5710 [,[Version =>] Ada_05]] );
5713 This pragma can occur immediately following a declaration of an entity,
5714 including the case of a record component. If no Entity argument is present,
5715 then this declaration is the one to which the pragma applies. If an Entity
5716 parameter is present, it must either match the name of the entity in this
5717 declaration, or alternatively, the pragma can immediately follow an enumeration
5718 type declaration, where the Entity argument names one of the enumeration
5721 This pragma is used to indicate that the named entity
5722 is considered obsolescent and should not be used. Typically this is
5723 used when an API must be modified by eventually removing or modifying
5724 existing subprograms or other entities. The pragma can be used at an
5725 intermediate stage when the entity is still present, but will be
5728 The effect of this pragma is to output a warning message on a reference to
5729 an entity thus marked that the subprogram is obsolescent if the appropriate
5730 warning option in the compiler is activated. If the @code{Message} parameter is
5731 present, then a second warning message is given containing this text. In
5732 addition, a reference to the entity is considered to be a violation of pragma
5733 @code{Restrictions (No_Obsolescent_Features)}.
5735 This pragma can also be used as a program unit pragma for a package,
5736 in which case the entity name is the name of the package, and the
5737 pragma indicates that the entire package is considered
5738 obsolescent. In this case a client @code{with}ing such a package
5739 violates the restriction, and the @code{with} clause is
5740 flagged with warnings if the warning option is set.
5742 If the @code{Version} parameter is present (which must be exactly
5743 the identifier @code{Ada_05}, no other argument is allowed), then the
5744 indication of obsolescence applies only when compiling in Ada 2005
5745 mode. This is primarily intended for dealing with the situations
5746 in the predefined library where subprograms or packages
5747 have become defined as obsolescent in Ada 2005
5748 (e.g., in @code{Ada.Characters.Handling}), but may be used anywhere.
5750 The following examples show typical uses of this pragma:
5754 pragma Obsolescent (p, Message => "use pp instead of p");
5759 pragma Obsolescent ("use q2new instead");
5761 type R is new integer;
5764 Message => "use RR in Ada 2005",
5774 type E is (a, bc, 'd', quack);
5775 pragma Obsolescent (Entity => bc)
5776 pragma Obsolescent (Entity => 'd')
5779 (a, b : character) return character;
5780 pragma Obsolescent (Entity => "+");
5784 Note that, as for all pragmas, if you use a pragma argument identifier,
5785 then all subsequent parameters must also use a pragma argument identifier.
5786 So if you specify @code{Entity =>} for the @code{Entity} argument, and a @code{Message}
5787 argument is present, it must be preceded by @code{Message =>}.
5789 @node Pragma Optimize_Alignment,Pragma Ordered,Pragma Obsolescent,Implementation Defined Pragmas
5790 @anchor{gnat_rm/implementation_defined_pragmas pragma-optimize-alignment}@anchor{b1}
5791 @section Pragma Optimize_Alignment
5795 @geindex default settings
5800 pragma Optimize_Alignment (TIME | SPACE | OFF);
5803 This is a configuration pragma which affects the choice of default alignments
5804 for types and objects where no alignment is explicitly specified. There is a
5805 time/space trade-off in the selection of these values. Large alignments result
5806 in more efficient code, at the expense of larger data space, since sizes have
5807 to be increased to match these alignments. Smaller alignments save space, but
5808 the access code is slower. The normal choice of default alignments for types
5809 and individual alignment promotions for objects (which is what you get if you
5810 do not use this pragma, or if you use an argument of OFF), tries to balance
5811 these two requirements.
5813 Specifying SPACE causes smaller default alignments to be chosen in two cases.
5814 First any packed record is given an alignment of 1. Second, if a size is given
5815 for the type, then the alignment is chosen to avoid increasing this size. For
5827 In the default mode, this type gets an alignment of 4, so that access to the
5828 Integer field X are efficient. But this means that objects of the type end up
5829 with a size of 8 bytes. This is a valid choice, since sizes of objects are
5830 allowed to be bigger than the size of the type, but it can waste space if for
5831 example fields of type R appear in an enclosing record. If the above type is
5832 compiled in @code{Optimize_Alignment (Space)} mode, the alignment is set to 1.
5834 However, there is one case in which SPACE is ignored. If a variable length
5835 record (that is a discriminated record with a component which is an array
5836 whose length depends on a discriminant), has a pragma Pack, then it is not
5837 in general possible to set the alignment of such a record to one, so the
5838 pragma is ignored in this case (with a warning).
5840 Specifying SPACE also disables alignment promotions for standalone objects,
5841 which occur when the compiler increases the alignment of a specific object
5842 without changing the alignment of its type.
5844 Specifying SPACE also disables component reordering in unpacked record types,
5845 which can result in larger sizes in order to meet alignment requirements.
5847 Specifying TIME causes larger default alignments to be chosen in the case of
5848 small types with sizes that are not a power of 2. For example, consider:
5861 The default alignment for this record is normally 1, but if this type is
5862 compiled in @code{Optimize_Alignment (Time)} mode, then the alignment is set
5863 to 4, which wastes space for objects of the type, since they are now 4 bytes
5864 long, but results in more efficient access when the whole record is referenced.
5866 As noted above, this is a configuration pragma, and there is a requirement
5867 that all units in a partition be compiled with a consistent setting of the
5868 optimization setting. This would normally be achieved by use of a configuration
5869 pragma file containing the appropriate setting. The exception to this rule is
5870 that units with an explicit configuration pragma in the same file as the source
5871 unit are excluded from the consistency check, as are all predefined units. The
5872 latter are compiled by default in pragma Optimize_Alignment (Off) mode if no
5873 pragma appears at the start of the file.
5875 @node Pragma Ordered,Pragma Overflow_Mode,Pragma Optimize_Alignment,Implementation Defined Pragmas
5876 @anchor{gnat_rm/implementation_defined_pragmas pragma-ordered}@anchor{b2}
5877 @section Pragma Ordered
5883 pragma Ordered (enumeration_first_subtype_LOCAL_NAME);
5886 Most enumeration types are from a conceptual point of view unordered.
5887 For example, consider:
5890 type Color is (Red, Blue, Green, Yellow);
5893 By Ada semantics @code{Blue > Red} and @code{Green > Blue},
5894 but really these relations make no sense; the enumeration type merely
5895 specifies a set of possible colors, and the order is unimportant.
5897 For unordered enumeration types, it is generally a good idea if
5898 clients avoid comparisons (other than equality or inequality) and
5899 explicit ranges. (A @emph{client} is a unit where the type is referenced,
5900 other than the unit where the type is declared, its body, and its subunits.)
5901 For example, if code buried in some client says:
5904 if Current_Color < Yellow then ...
5905 if Current_Color in Blue .. Green then ...
5908 then the client code is relying on the order, which is undesirable.
5909 It makes the code hard to read and creates maintenance difficulties if
5910 entries have to be added to the enumeration type. Instead,
5911 the code in the client should list the possibilities, or an
5912 appropriate subtype should be declared in the unit that declares
5913 the original enumeration type. E.g., the following subtype could
5914 be declared along with the type @code{Color}:
5917 subtype RBG is Color range Red .. Green;
5920 and then the client could write:
5923 if Current_Color in RBG then ...
5924 if Current_Color = Blue or Current_Color = Green then ...
5927 However, some enumeration types are legitimately ordered from a conceptual
5928 point of view. For example, if you declare:
5931 type Day is (Mon, Tue, Wed, Thu, Fri, Sat, Sun);
5934 then the ordering imposed by the language is reasonable, and
5935 clients can depend on it, writing for example:
5938 if D in Mon .. Fri then ...
5942 The pragma @emph{Ordered} is provided to mark enumeration types that
5943 are conceptually ordered, alerting the reader that clients may depend
5944 on the ordering. GNAT provides a pragma to mark enumerations as ordered
5945 rather than one to mark them as unordered, since in our experience,
5946 the great majority of enumeration types are conceptually unordered.
5948 The types @code{Boolean}, @code{Character}, @code{Wide_Character},
5949 and @code{Wide_Wide_Character}
5950 are considered to be ordered types, so each is declared with a
5951 pragma @code{Ordered} in package @code{Standard}.
5953 Normally pragma @code{Ordered} serves only as documentation and a guide for
5954 coding standards, but GNAT provides a warning switch @emph{-gnatw.u} that
5955 requests warnings for inappropriate uses (comparisons and explicit
5956 subranges) for unordered types. If this switch is used, then any
5957 enumeration type not marked with pragma @code{Ordered} will be considered
5958 as unordered, and will generate warnings for inappropriate uses.
5960 Note that generic types are not considered ordered or unordered (since the
5961 template can be instantiated for both cases), so we never generate warnings
5962 for the case of generic enumerated types.
5964 For additional information please refer to the description of the
5965 @emph{-gnatw.u} switch in the GNAT User's Guide.
5967 @node Pragma Overflow_Mode,Pragma Overriding_Renamings,Pragma Ordered,Implementation Defined Pragmas
5968 @anchor{gnat_rm/implementation_defined_pragmas pragma-overflow-mode}@anchor{b3}
5969 @section Pragma Overflow_Mode
5975 pragma Overflow_Mode
5977 [,[Assertions =>] MODE]);
5979 MODE ::= STRICT | MINIMIZED | ELIMINATED
5982 This pragma sets the current overflow mode to the given setting. For details
5983 of the meaning of these modes, please refer to the
5984 'Overflow Check Handling in GNAT' appendix in the
5985 GNAT User's Guide. If only the @code{General} parameter is present,
5986 the given mode applies to all expressions. If both parameters are present,
5987 the @code{General} mode applies to expressions outside assertions, and
5988 the @code{Eliminated} mode applies to expressions within assertions.
5990 The case of the @code{MODE} parameter is ignored,
5991 so @code{MINIMIZED}, @code{Minimized} and
5992 @code{minimized} all have the same effect.
5994 The @code{Overflow_Mode} pragma has the same scoping and placement
5995 rules as pragma @code{Suppress}, so it can occur either as a
5996 configuration pragma, specifying a default for the whole
5997 program, or in a declarative scope, where it applies to the
5998 remaining declarations and statements in that scope.
6000 The pragma @code{Suppress (Overflow_Check)} suppresses
6001 overflow checking, but does not affect the overflow mode.
6003 The pragma @code{Unsuppress (Overflow_Check)} unsuppresses (enables)
6004 overflow checking, but does not affect the overflow mode.
6006 @node Pragma Overriding_Renamings,Pragma Partition_Elaboration_Policy,Pragma Overflow_Mode,Implementation Defined Pragmas
6007 @anchor{gnat_rm/implementation_defined_pragmas pragma-overriding-renamings}@anchor{b4}
6008 @section Pragma Overriding_Renamings
6011 @geindex Rational profile
6013 @geindex Rational compatibility
6018 pragma Overriding_Renamings;
6021 This is a GNAT configuration pragma to simplify porting
6022 legacy code accepted by the Rational
6023 Ada compiler. In the presence of this pragma, a renaming declaration that
6024 renames an inherited operation declared in the same scope is legal if selected
6025 notation is used as in:
6028 pragma Overriding_Renamings;
6033 function F (..) renames R.F;
6038 RM 8.3 (15) stipulates that an overridden operation is not visible within the
6039 declaration of the overriding operation.
6041 @node Pragma Partition_Elaboration_Policy,Pragma Part_Of,Pragma Overriding_Renamings,Implementation Defined Pragmas
6042 @anchor{gnat_rm/implementation_defined_pragmas pragma-partition-elaboration-policy}@anchor{b5}
6043 @section Pragma Partition_Elaboration_Policy
6049 pragma Partition_Elaboration_Policy (POLICY_IDENTIFIER);
6051 POLICY_IDENTIFIER ::= Concurrent | Sequential
6054 This pragma is standard in Ada 2005, but is available in all earlier
6055 versions of Ada as an implementation-defined pragma.
6056 See Ada 2012 Reference Manual for details.
6058 @node Pragma Part_Of,Pragma Passive,Pragma Partition_Elaboration_Policy,Implementation Defined Pragmas
6059 @anchor{gnat_rm/implementation_defined_pragmas id28}@anchor{b6}@anchor{gnat_rm/implementation_defined_pragmas pragma-part-of}@anchor{b7}
6060 @section Pragma Part_Of
6066 pragma Part_Of (ABSTRACT_STATE);
6068 ABSTRACT_STATE ::= NAME
6071 For the semantics of this pragma, see the entry for aspect @code{Part_Of} in the
6072 SPARK 2014 Reference Manual, section 7.2.6.
6074 @node Pragma Passive,Pragma Persistent_BSS,Pragma Part_Of,Implementation Defined Pragmas
6075 @anchor{gnat_rm/implementation_defined_pragmas pragma-passive}@anchor{b8}
6076 @section Pragma Passive
6082 pragma Passive [(Semaphore | No)];
6085 Syntax checked, but otherwise ignored by GNAT. This is recognized for
6086 compatibility with DEC Ada 83 implementations, where it is used within a
6087 task definition to request that a task be made passive. If the argument
6088 @code{Semaphore} is present, or the argument is omitted, then DEC Ada 83
6089 treats the pragma as an assertion that the containing task is passive
6090 and that optimization of context switch with this task is permitted and
6091 desired. If the argument @code{No} is present, the task must not be
6092 optimized. GNAT does not attempt to optimize any tasks in this manner
6093 (since protected objects are available in place of passive tasks).
6095 For more information on the subject of passive tasks, see the section
6096 'Passive Task Optimization' in the GNAT Users Guide.
6098 @node Pragma Persistent_BSS,Pragma Polling,Pragma Passive,Implementation Defined Pragmas
6099 @anchor{gnat_rm/implementation_defined_pragmas id29}@anchor{b9}@anchor{gnat_rm/implementation_defined_pragmas pragma-persistent-bss}@anchor{ba}
6100 @section Pragma Persistent_BSS
6106 pragma Persistent_BSS [(LOCAL_NAME)]
6109 This pragma allows selected objects to be placed in the @code{.persistent_bss}
6110 section. On some targets the linker and loader provide for special
6111 treatment of this section, allowing a program to be reloaded without
6112 affecting the contents of this data (hence the name persistent).
6114 There are two forms of usage. If an argument is given, it must be the
6115 local name of a library-level object, with no explicit initialization
6116 and whose type is potentially persistent. If no argument is given, then
6117 the pragma is a configuration pragma, and applies to all library-level
6118 objects with no explicit initialization of potentially persistent types.
6120 A potentially persistent type is a scalar type, or an untagged,
6121 non-discriminated record, all of whose components have no explicit
6122 initialization and are themselves of a potentially persistent type,
6123 or an array, all of whose constraints are static, and whose component
6124 type is potentially persistent.
6126 If this pragma is used on a target where this feature is not supported,
6127 then the pragma will be ignored. See also @code{pragma Linker_Section}.
6129 @node Pragma Polling,Pragma Post,Pragma Persistent_BSS,Implementation Defined Pragmas
6130 @anchor{gnat_rm/implementation_defined_pragmas pragma-polling}@anchor{bb}
6131 @section Pragma Polling
6137 pragma Polling (ON | OFF);
6140 This pragma controls the generation of polling code. This is normally off.
6141 If @code{pragma Polling (ON)} is used then periodic calls are generated to
6142 the routine @code{Ada.Exceptions.Poll}. This routine is a separate unit in the
6143 runtime library, and can be found in file @code{a-excpol.adb}.
6145 Pragma @code{Polling} can appear as a configuration pragma (for example it
6146 can be placed in the @code{gnat.adc} file) to enable polling globally, or it
6147 can be used in the statement or declaration sequence to control polling
6150 A call to the polling routine is generated at the start of every loop and
6151 at the start of every subprogram call. This guarantees that the @code{Poll}
6152 routine is called frequently, and places an upper bound (determined by
6153 the complexity of the code) on the period between two @code{Poll} calls.
6155 The primary purpose of the polling interface is to enable asynchronous
6156 aborts on targets that cannot otherwise support it (for example Windows
6157 NT), but it may be used for any other purpose requiring periodic polling.
6158 The standard version is null, and can be replaced by a user program. This
6159 will require re-compilation of the @code{Ada.Exceptions} package that can
6160 be found in files @code{a-except.ads} and @code{a-except.adb}.
6162 A standard alternative unit (in file @code{4wexcpol.adb} in the standard GNAT
6163 distribution) is used to enable the asynchronous abort capability on
6164 targets that do not normally support the capability. The version of
6165 @code{Poll} in this file makes a call to the appropriate runtime routine
6166 to test for an abort condition.
6168 Note that polling can also be enabled by use of the @emph{-gnatP} switch.
6169 See the section on switches for gcc in the @cite{GNAT User's Guide}.
6171 @node Pragma Post,Pragma Postcondition,Pragma Polling,Implementation Defined Pragmas
6172 @anchor{gnat_rm/implementation_defined_pragmas pragma-post}@anchor{bc}
6173 @section Pragma Post
6179 @geindex postconditions
6184 pragma Post (Boolean_Expression);
6187 The @code{Post} pragma is intended to be an exact replacement for
6188 the language-defined
6189 @code{Post} aspect, and shares its restrictions and semantics.
6190 It must appear either immediately following the corresponding
6191 subprogram declaration (only other pragmas may intervene), or
6192 if there is no separate subprogram declaration, then it can
6193 appear at the start of the declarations in a subprogram body
6194 (preceded only by other pragmas).
6196 @node Pragma Postcondition,Pragma Post_Class,Pragma Post,Implementation Defined Pragmas
6197 @anchor{gnat_rm/implementation_defined_pragmas pragma-postcondition}@anchor{bd}
6198 @section Pragma Postcondition
6201 @geindex Postcondition
6204 @geindex postconditions
6209 pragma Postcondition (
6210 [Check =>] Boolean_Expression
6211 [,[Message =>] String_Expression]);
6214 The @code{Postcondition} pragma allows specification of automatic
6215 postcondition checks for subprograms. These checks are similar to
6216 assertions, but are automatically inserted just prior to the return
6217 statements of the subprogram with which they are associated (including
6218 implicit returns at the end of procedure bodies and associated
6219 exception handlers).
6221 In addition, the boolean expression which is the condition which
6222 must be true may contain references to function'Result in the case
6223 of a function to refer to the returned value.
6225 @code{Postcondition} pragmas may appear either immediately following the
6226 (separate) declaration of a subprogram, or at the start of the
6227 declarations of a subprogram body. Only other pragmas may intervene
6228 (that is appear between the subprogram declaration and its
6229 postconditions, or appear before the postcondition in the
6230 declaration sequence in a subprogram body). In the case of a
6231 postcondition appearing after a subprogram declaration, the
6232 formal arguments of the subprogram are visible, and can be
6233 referenced in the postcondition expressions.
6235 The postconditions are collected and automatically tested just
6236 before any return (implicit or explicit) in the subprogram body.
6237 A postcondition is only recognized if postconditions are active
6238 at the time the pragma is encountered. The compiler switch @emph{gnata}
6239 turns on all postconditions by default, and pragma @code{Check_Policy}
6240 with an identifier of @code{Postcondition} can also be used to
6241 control whether postconditions are active.
6243 The general approach is that postconditions are placed in the spec
6244 if they represent functional aspects which make sense to the client.
6245 For example we might have:
6248 function Direction return Integer;
6249 pragma Postcondition
6250 (Direction'Result = +1
6252 Direction'Result = -1);
6255 which serves to document that the result must be +1 or -1, and
6256 will test that this is the case at run time if postcondition
6259 Postconditions within the subprogram body can be used to
6260 check that some internal aspect of the implementation,
6261 not visible to the client, is operating as expected.
6262 For instance if a square root routine keeps an internal
6263 counter of the number of times it is called, then we
6264 might have the following postcondition:
6267 Sqrt_Calls : Natural := 0;
6269 function Sqrt (Arg : Float) return Float is
6270 pragma Postcondition
6271 (Sqrt_Calls = Sqrt_Calls'Old + 1);
6276 As this example, shows, the use of the @code{Old} attribute
6277 is often useful in postconditions to refer to the state on
6278 entry to the subprogram.
6280 Note that postconditions are only checked on normal returns
6281 from the subprogram. If an abnormal return results from
6282 raising an exception, then the postconditions are not checked.
6284 If a postcondition fails, then the exception
6285 @code{System.Assertions.Assert_Failure} is raised. If
6286 a message argument was supplied, then the given string
6287 will be used as the exception message. If no message
6288 argument was supplied, then the default message has
6289 the form "Postcondition failed at file_name:line". The
6290 exception is raised in the context of the subprogram
6291 body, so it is possible to catch postcondition failures
6292 within the subprogram body itself.
6294 Within a package spec, normal visibility rules
6295 in Ada would prevent forward references within a
6296 postcondition pragma to functions defined later in
6297 the same package. This would introduce undesirable
6298 ordering constraints. To avoid this problem, all
6299 postcondition pragmas are analyzed at the end of
6300 the package spec, allowing forward references.
6302 The following example shows that this even allows
6303 mutually recursive postconditions as in:
6306 package Parity_Functions is
6307 function Odd (X : Natural) return Boolean;
6308 pragma Postcondition
6312 (x /= 0 and then Even (X - 1))));
6314 function Even (X : Natural) return Boolean;
6315 pragma Postcondition
6319 (x /= 1 and then Odd (X - 1))));
6321 end Parity_Functions;
6324 There are no restrictions on the complexity or form of
6325 conditions used within @code{Postcondition} pragmas.
6326 The following example shows that it is even possible
6327 to verify performance behavior.
6332 Performance : constant Float;
6333 -- Performance constant set by implementation
6334 -- to match target architecture behavior.
6336 procedure Treesort (Arg : String);
6337 -- Sorts characters of argument using N*logN sort
6338 pragma Postcondition
6339 (Float (Clock - Clock'Old) <=
6340 Float (Arg'Length) *
6341 log (Float (Arg'Length)) *
6346 Note: postcondition pragmas associated with subprograms that are
6347 marked as Inline_Always, or those marked as Inline with front-end
6348 inlining (-gnatN option set) are accepted and legality-checked
6349 by the compiler, but are ignored at run-time even if postcondition
6350 checking is enabled.
6352 Note that pragma @code{Postcondition} differs from the language-defined
6353 @code{Post} aspect (and corresponding @code{Post} pragma) in allowing
6354 multiple occurrences, allowing occurences in the body even if there
6355 is a separate spec, and allowing a second string parameter, and the
6356 use of the pragma identifier @code{Check}. Historically, pragma
6357 @code{Postcondition} was implemented prior to the development of
6358 Ada 2012, and has been retained in its original form for
6359 compatibility purposes.
6361 @node Pragma Post_Class,Pragma Rename_Pragma,Pragma Postcondition,Implementation Defined Pragmas
6362 @anchor{gnat_rm/implementation_defined_pragmas pragma-post-class}@anchor{be}
6363 @section Pragma Post_Class
6369 @geindex postconditions
6374 pragma Post_Class (Boolean_Expression);
6377 The @code{Post_Class} pragma is intended to be an exact replacement for
6378 the language-defined
6379 @code{Post'Class} aspect, and shares its restrictions and semantics.
6380 It must appear either immediately following the corresponding
6381 subprogram declaration (only other pragmas may intervene), or
6382 if there is no separate subprogram declaration, then it can
6383 appear at the start of the declarations in a subprogram body
6384 (preceded only by other pragmas).
6386 Note: This pragma is called @code{Post_Class} rather than
6387 @code{Post'Class} because the latter would not be strictly
6388 conforming to the allowed syntax for pragmas. The motivation
6389 for provinding pragmas equivalent to the aspects is to allow a program
6390 to be written using the pragmas, and then compiled if necessary
6391 using an Ada compiler that does not recognize the pragmas or
6392 aspects, but is prepared to ignore the pragmas. The assertion
6393 policy that controls this pragma is @code{Post'Class}, not
6396 @node Pragma Rename_Pragma,Pragma Pre,Pragma Post_Class,Implementation Defined Pragmas
6397 @anchor{gnat_rm/implementation_defined_pragmas pragma-rename-pragma}@anchor{bf}
6398 @section Pragma Rename_Pragma
6407 pragma Rename_Pragma (
6408 [New_Name =>] IDENTIFIER,
6409 [Renamed =>] pragma_IDENTIFIER);
6412 This pragma provides a mechanism for supplying new names for existing
6413 pragmas. The @code{New_Name} identifier can subsequently be used as a synonym for
6414 the Renamed pragma. For example, suppose you have code that was originally
6415 developed on a compiler that supports Inline_Only as an implementation defined
6416 pragma. And suppose the semantics of pragma Inline_Only are identical to (or at
6417 least very similar to) the GNAT implementation defined pragma
6418 Inline_Always. You could globally replace Inline_Only with Inline_Always.
6420 However, to avoid that source modification, you could instead add a
6421 configuration pragma:
6424 pragma Rename_Pragma (
6425 New_Name => Inline_Only,
6426 Renamed => Inline_Always);
6429 Then GNAT will treat "pragma Inline_Only ..." as if you had written
6430 "pragma Inline_Always ...".
6432 Pragma Inline_Only will not necessarily mean the same thing as the other Ada
6433 compiler; it's up to you to make sure the semantics are close enough.
6435 @node Pragma Pre,Pragma Precondition,Pragma Rename_Pragma,Implementation Defined Pragmas
6436 @anchor{gnat_rm/implementation_defined_pragmas pragma-pre}@anchor{c0}
6443 @geindex preconditions
6448 pragma Pre (Boolean_Expression);
6451 The @code{Pre} pragma is intended to be an exact replacement for
6452 the language-defined
6453 @code{Pre} aspect, and shares its restrictions and semantics.
6454 It must appear either immediately following the corresponding
6455 subprogram declaration (only other pragmas may intervene), or
6456 if there is no separate subprogram declaration, then it can
6457 appear at the start of the declarations in a subprogram body
6458 (preceded only by other pragmas).
6460 @node Pragma Precondition,Pragma Predicate,Pragma Pre,Implementation Defined Pragmas
6461 @anchor{gnat_rm/implementation_defined_pragmas pragma-precondition}@anchor{c1}
6462 @section Pragma Precondition
6465 @geindex Preconditions
6468 @geindex preconditions
6473 pragma Precondition (
6474 [Check =>] Boolean_Expression
6475 [,[Message =>] String_Expression]);
6478 The @code{Precondition} pragma is similar to @code{Postcondition}
6479 except that the corresponding checks take place immediately upon
6480 entry to the subprogram, and if a precondition fails, the exception
6481 is raised in the context of the caller, and the attribute 'Result
6482 cannot be used within the precondition expression.
6484 Otherwise, the placement and visibility rules are identical to those
6485 described for postconditions. The following is an example of use
6486 within a package spec:
6489 package Math_Functions is
6491 function Sqrt (Arg : Float) return Float;
6492 pragma Precondition (Arg >= 0.0)
6497 @code{Precondition} pragmas may appear either immediately following the
6498 (separate) declaration of a subprogram, or at the start of the
6499 declarations of a subprogram body. Only other pragmas may intervene
6500 (that is appear between the subprogram declaration and its
6501 postconditions, or appear before the postcondition in the
6502 declaration sequence in a subprogram body).
6504 Note: precondition pragmas associated with subprograms that are
6505 marked as Inline_Always, or those marked as Inline with front-end
6506 inlining (-gnatN option set) are accepted and legality-checked
6507 by the compiler, but are ignored at run-time even if precondition
6508 checking is enabled.
6510 Note that pragma @code{Precondition} differs from the language-defined
6511 @code{Pre} aspect (and corresponding @code{Pre} pragma) in allowing
6512 multiple occurrences, allowing occurences in the body even if there
6513 is a separate spec, and allowing a second string parameter, and the
6514 use of the pragma identifier @code{Check}. Historically, pragma
6515 @code{Precondition} was implemented prior to the development of
6516 Ada 2012, and has been retained in its original form for
6517 compatibility purposes.
6519 @node Pragma Predicate,Pragma Predicate_Failure,Pragma Precondition,Implementation Defined Pragmas
6520 @anchor{gnat_rm/implementation_defined_pragmas pragma-predicate}@anchor{c2}@anchor{gnat_rm/implementation_defined_pragmas id30}@anchor{c3}
6521 @section Pragma Predicate
6528 ([Entity =>] type_LOCAL_NAME,
6529 [Check =>] EXPRESSION);
6532 This pragma (available in all versions of Ada in GNAT) encompasses both
6533 the @code{Static_Predicate} and @code{Dynamic_Predicate} aspects in
6534 Ada 2012. A predicate is regarded as static if it has an allowed form
6535 for @code{Static_Predicate} and is otherwise treated as a
6536 @code{Dynamic_Predicate}. Otherwise, predicates specified by this
6537 pragma behave exactly as described in the Ada 2012 reference manual.
6538 For example, if we have
6541 type R is range 1 .. 10;
6543 pragma Predicate (Entity => S, Check => S not in 4 .. 6);
6545 pragma Predicate (Entity => Q, Check => F(Q) or G(Q));
6548 the effect is identical to the following Ada 2012 code:
6551 type R is range 1 .. 10;
6553 Static_Predicate => S not in 4 .. 6;
6555 Dynamic_Predicate => F(Q) or G(Q);
6558 Note that there are no pragmas @code{Dynamic_Predicate}
6559 or @code{Static_Predicate}. That is
6560 because these pragmas would affect legality and semantics of
6561 the program and thus do not have a neutral effect if ignored.
6562 The motivation behind providing pragmas equivalent to
6563 corresponding aspects is to allow a program to be written
6564 using the pragmas, and then compiled with a compiler that
6565 will ignore the pragmas. That doesn't work in the case of
6566 static and dynamic predicates, since if the corresponding
6567 pragmas are ignored, then the behavior of the program is
6568 fundamentally changed (for example a membership test
6569 @code{A in B} would not take into account a predicate
6570 defined for subtype B). When following this approach, the
6571 use of predicates should be avoided.
6573 @node Pragma Predicate_Failure,Pragma Preelaborable_Initialization,Pragma Predicate,Implementation Defined Pragmas
6574 @anchor{gnat_rm/implementation_defined_pragmas pragma-predicate-failure}@anchor{c4}
6575 @section Pragma Predicate_Failure
6581 pragma Predicate_Failure
6582 ([Entity =>] type_LOCAL_NAME,
6583 [Message =>] String_Expression);
6586 The @code{Predicate_Failure} pragma is intended to be an exact replacement for
6587 the language-defined
6588 @code{Predicate_Failure} aspect, and shares its restrictions and semantics.
6590 @node Pragma Preelaborable_Initialization,Pragma Prefix_Exception_Messages,Pragma Predicate_Failure,Implementation Defined Pragmas
6591 @anchor{gnat_rm/implementation_defined_pragmas pragma-preelaborable-initialization}@anchor{c5}
6592 @section Pragma Preelaborable_Initialization
6598 pragma Preelaborable_Initialization (DIRECT_NAME);
6601 This pragma is standard in Ada 2005, but is available in all earlier
6602 versions of Ada as an implementation-defined pragma.
6603 See Ada 2012 Reference Manual for details.
6605 @node Pragma Prefix_Exception_Messages,Pragma Pre_Class,Pragma Preelaborable_Initialization,Implementation Defined Pragmas
6606 @anchor{gnat_rm/implementation_defined_pragmas pragma-prefix-exception-messages}@anchor{c6}
6607 @section Pragma Prefix_Exception_Messages
6610 @geindex Prefix_Exception_Messages
6614 @geindex Exception_Message
6619 pragma Prefix_Exception_Messages;
6622 This is an implementation-defined configuration pragma that affects the
6623 behavior of raise statements with a message given as a static string
6624 constant (typically a string literal). In such cases, the string will
6625 be automatically prefixed by the name of the enclosing entity (giving
6626 the package and subprogram containing the raise statement). This helps
6627 to identify where messages are coming from, and this mode is automatic
6628 for the run-time library.
6630 The pragma has no effect if the message is computed with an expression other
6631 than a static string constant, since the assumption in this case is that
6632 the program computes exactly the string it wants. If you still want the
6633 prefixing in this case, you can always call
6634 @code{GNAT.Source_Info.Enclosing_Entity} and prepend the string manually.
6636 @node Pragma Pre_Class,Pragma Priority_Specific_Dispatching,Pragma Prefix_Exception_Messages,Implementation Defined Pragmas
6637 @anchor{gnat_rm/implementation_defined_pragmas pragma-pre-class}@anchor{c7}
6638 @section Pragma Pre_Class
6644 @geindex preconditions
6649 pragma Pre_Class (Boolean_Expression);
6652 The @code{Pre_Class} pragma is intended to be an exact replacement for
6653 the language-defined
6654 @code{Pre'Class} aspect, and shares its restrictions and semantics.
6655 It must appear either immediately following the corresponding
6656 subprogram declaration (only other pragmas may intervene), or
6657 if there is no separate subprogram declaration, then it can
6658 appear at the start of the declarations in a subprogram body
6659 (preceded only by other pragmas).
6661 Note: This pragma is called @code{Pre_Class} rather than
6662 @code{Pre'Class} because the latter would not be strictly
6663 conforming to the allowed syntax for pragmas. The motivation
6664 for providing pragmas equivalent to the aspects is to allow a program
6665 to be written using the pragmas, and then compiled if necessary
6666 using an Ada compiler that does not recognize the pragmas or
6667 aspects, but is prepared to ignore the pragmas. The assertion
6668 policy that controls this pragma is @code{Pre'Class}, not
6671 @node Pragma Priority_Specific_Dispatching,Pragma Profile,Pragma Pre_Class,Implementation Defined Pragmas
6672 @anchor{gnat_rm/implementation_defined_pragmas pragma-priority-specific-dispatching}@anchor{c8}
6673 @section Pragma Priority_Specific_Dispatching
6679 pragma Priority_Specific_Dispatching (
6681 first_priority_EXPRESSION,
6682 last_priority_EXPRESSION)
6684 POLICY_IDENTIFIER ::=
6685 EDF_Across_Priorities |
6686 FIFO_Within_Priorities |
6687 Non_Preemptive_Within_Priorities |
6688 Round_Robin_Within_Priorities
6691 This pragma is standard in Ada 2005, but is available in all earlier
6692 versions of Ada as an implementation-defined pragma.
6693 See Ada 2012 Reference Manual for details.
6695 @node Pragma Profile,Pragma Profile_Warnings,Pragma Priority_Specific_Dispatching,Implementation Defined Pragmas
6696 @anchor{gnat_rm/implementation_defined_pragmas pragma-profile}@anchor{c9}
6697 @section Pragma Profile
6703 pragma Profile (Ravenscar | Restricted | Rational |
6704 GNAT_Extended_Ravenscar | GNAT_Ravenscar_EDF );
6707 This pragma is standard in Ada 2005, but is available in all earlier
6708 versions of Ada as an implementation-defined pragma. This is a
6709 configuration pragma that establishes a set of configuration pragmas
6710 that depend on the argument. @code{Ravenscar} is standard in Ada 2005.
6711 The other possibilities (@code{Restricted}, @code{Rational},
6712 @code{GNAT_Extended_Ravenscar}, @code{GNAT_Ravenscar_EDF})
6713 are implementation-defined. The set of configuration pragmas
6714 is defined in the following sections.
6720 Pragma Profile (Ravenscar)
6722 The @code{Ravenscar} profile is standard in Ada 2005,
6723 but is available in all earlier
6724 versions of Ada as an implementation-defined pragma. This profile
6725 establishes the following set of configuration pragmas:
6731 @code{Task_Dispatching_Policy (FIFO_Within_Priorities)}
6733 [RM D.2.2] Tasks are dispatched following a preemptive
6734 priority-ordered scheduling policy.
6737 @code{Locking_Policy (Ceiling_Locking)}
6739 [RM D.3] While tasks and interrupts execute a protected action, they inherit
6740 the ceiling priority of the corresponding protected object.
6743 @code{Detect_Blocking}
6745 This pragma forces the detection of potentially blocking operations within a
6746 protected operation, and to raise Program_Error if that happens.
6749 plus the following set of restrictions:
6755 @code{Max_Entry_Queue_Length => 1}
6757 No task can be queued on a protected entry.
6760 @code{Max_Protected_Entries => 1}
6763 @code{Max_Task_Entries => 0}
6765 No rendezvous statements are allowed.
6768 @code{No_Abort_Statements}
6771 @code{No_Dynamic_Attachment}
6774 @code{No_Dynamic_Priorities}
6777 @code{No_Implicit_Heap_Allocations}
6780 @code{No_Local_Protected_Objects}
6783 @code{No_Local_Timing_Events}
6786 @code{No_Protected_Type_Allocators}
6789 @code{No_Relative_Delay}
6792 @code{No_Requeue_Statements}
6795 @code{No_Select_Statements}
6798 @code{No_Specific_Termination_Handlers}
6801 @code{No_Task_Allocators}
6804 @code{No_Task_Hierarchy}
6807 @code{No_Task_Termination}
6810 @code{Simple_Barriers}
6813 The Ravenscar profile also includes the following restrictions that specify
6814 that there are no semantic dependences on the corresponding predefined
6821 @code{No_Dependence => Ada.Asynchronous_Task_Control}
6824 @code{No_Dependence => Ada.Calendar}
6827 @code{No_Dependence => Ada.Execution_Time.Group_Budget}
6830 @code{No_Dependence => Ada.Execution_Time.Timers}
6833 @code{No_Dependence => Ada.Task_Attributes}
6836 @code{No_Dependence => System.Multiprocessors.Dispatching_Domains}
6839 This set of configuration pragmas and restrictions correspond to the
6840 definition of the 'Ravenscar Profile' for limited tasking, devised and
6841 published by the @cite{International Real-Time Ada Workshop@comma{} 1997}.
6842 A description is also available at
6843 @indicateurl{http://www-users.cs.york.ac.uk/~burns/ravenscar.ps}.
6845 The original definition of the profile was revised at subsequent IRTAW
6846 meetings. It has been included in the ISO
6847 @cite{Guide for the Use of the Ada Programming Language in High Integrity Systems},
6848 and was made part of the Ada 2005 standard.
6849 The formal definition given by
6850 the Ada Rapporteur Group (ARG) can be found in two Ada Issues (AI-249 and
6851 AI-305) available at
6852 @indicateurl{http://www.ada-auth.org/cgi-bin/cvsweb.cgi/ais/ai-00249.txt} and
6853 @indicateurl{http://www.ada-auth.org/cgi-bin/cvsweb.cgi/ais/ai-00305.txt}.
6855 The above set is a superset of the restrictions provided by pragma
6856 @code{Profile (Restricted)}, it includes six additional restrictions
6857 (@code{Simple_Barriers}, @code{No_Select_Statements},
6858 @code{No_Calendar}, @code{No_Implicit_Heap_Allocations},
6859 @code{No_Relative_Delay} and @code{No_Task_Termination}). This means
6860 that pragma @code{Profile (Ravenscar)}, like the pragma
6861 @code{Profile (Restricted)},
6862 automatically causes the use of a simplified,
6863 more efficient version of the tasking run-time library.
6866 Pragma Profile (GNAT_Extended_Ravenscar)
6868 This profile corresponds to a GNAT specific extension of the
6869 Ravenscar profile. The profile may change in the future although
6870 only in a compatible way: some restrictions may be removed or
6871 relaxed. It is defined as a variation of the Ravenscar profile.
6873 The @code{No_Implicit_Heap_Allocations} restriction has been replaced
6874 by @code{No_Implicit_Task_Allocations} and
6875 @code{No_Implicit_Protected_Object_Allocations}.
6877 The @code{Simple_Barriers} restriction has been replaced by
6878 @code{Pure_Barriers}.
6880 The @code{Max_Protected_Entries}, @code{Max_Entry_Queue_Length}, and
6881 @code{No_Relative_Delay} restrictions have been removed.
6884 Pragma Profile (GNAT_Ravenscar_EDF)
6886 This profile corresponds to the Ravenscar profile but using
6887 EDF_Across_Priority as the Task_Scheduling_Policy.
6890 Pragma Profile (Restricted)
6892 This profile corresponds to the GNAT restricted run time. It
6893 establishes the following set of restrictions:
6899 @code{No_Abort_Statements}
6902 @code{No_Entry_Queue}
6905 @code{No_Task_Hierarchy}
6908 @code{No_Task_Allocators}
6911 @code{No_Dynamic_Priorities}
6914 @code{No_Terminate_Alternatives}
6917 @code{No_Dynamic_Attachment}
6920 @code{No_Protected_Type_Allocators}
6923 @code{No_Local_Protected_Objects}
6926 @code{No_Requeue_Statements}
6929 @code{No_Task_Attributes_Package}
6932 @code{Max_Asynchronous_Select_Nesting = 0}
6935 @code{Max_Task_Entries = 0}
6938 @code{Max_Protected_Entries = 1}
6941 @code{Max_Select_Alternatives = 0}
6944 This set of restrictions causes the automatic selection of a simplified
6945 version of the run time that provides improved performance for the
6946 limited set of tasking functionality permitted by this set of restrictions.
6949 Pragma Profile (Rational)
6951 The Rational profile is intended to facilitate porting legacy code that
6952 compiles with the Rational APEX compiler, even when the code includes non-
6953 conforming Ada constructs. The profile enables the following three pragmas:
6959 @code{pragma Implicit_Packing}
6962 @code{pragma Overriding_Renamings}
6965 @code{pragma Use_VADS_Size}
6969 @node Pragma Profile_Warnings,Pragma Propagate_Exceptions,Pragma Profile,Implementation Defined Pragmas
6970 @anchor{gnat_rm/implementation_defined_pragmas pragma-profile-warnings}@anchor{ca}
6971 @section Pragma Profile_Warnings
6977 pragma Profile_Warnings (Ravenscar | Restricted | Rational);
6980 This is an implementation-defined pragma that is similar in
6981 effect to @code{pragma Profile} except that instead of
6982 generating @code{Restrictions} pragmas, it generates
6983 @code{Restriction_Warnings} pragmas. The result is that
6984 violations of the profile generate warning messages instead
6987 @node Pragma Propagate_Exceptions,Pragma Provide_Shift_Operators,Pragma Profile_Warnings,Implementation Defined Pragmas
6988 @anchor{gnat_rm/implementation_defined_pragmas pragma-propagate-exceptions}@anchor{cb}
6989 @section Pragma Propagate_Exceptions
6992 @geindex Interfacing to C++
6997 pragma Propagate_Exceptions;
7000 This pragma is now obsolete and, other than generating a warning if warnings
7001 on obsolescent features are enabled, is ignored.
7002 It is retained for compatibility
7003 purposes. It used to be used in connection with optimization of
7004 a now-obsolete mechanism for implementation of exceptions.
7006 @node Pragma Provide_Shift_Operators,Pragma Psect_Object,Pragma Propagate_Exceptions,Implementation Defined Pragmas
7007 @anchor{gnat_rm/implementation_defined_pragmas pragma-provide-shift-operators}@anchor{cc}
7008 @section Pragma Provide_Shift_Operators
7011 @geindex Shift operators
7016 pragma Provide_Shift_Operators (integer_first_subtype_LOCAL_NAME);
7019 This pragma can be applied to a first subtype local name that specifies
7020 either an unsigned or signed type. It has the effect of providing the
7021 five shift operators (Shift_Left, Shift_Right, Shift_Right_Arithmetic,
7022 Rotate_Left and Rotate_Right) for the given type. It is similar to
7023 including the function declarations for these five operators, together
7024 with the pragma Import (Intrinsic, ...) statements.
7026 @node Pragma Psect_Object,Pragma Pure_Function,Pragma Provide_Shift_Operators,Implementation Defined Pragmas
7027 @anchor{gnat_rm/implementation_defined_pragmas pragma-psect-object}@anchor{cd}
7028 @section Pragma Psect_Object
7034 pragma Psect_Object (
7035 [Internal =>] LOCAL_NAME,
7036 [, [External =>] EXTERNAL_SYMBOL]
7037 [, [Size =>] EXTERNAL_SYMBOL]);
7041 | static_string_EXPRESSION
7044 This pragma is identical in effect to pragma @code{Common_Object}.
7046 @node Pragma Pure_Function,Pragma Rational,Pragma Psect_Object,Implementation Defined Pragmas
7047 @anchor{gnat_rm/implementation_defined_pragmas pragma-pure-function}@anchor{ce}@anchor{gnat_rm/implementation_defined_pragmas id31}@anchor{cf}
7048 @section Pragma Pure_Function
7054 pragma Pure_Function ([Entity =>] function_LOCAL_NAME);
7057 This pragma appears in the same declarative part as a function
7058 declaration (or a set of function declarations if more than one
7059 overloaded declaration exists, in which case the pragma applies
7060 to all entities). It specifies that the function @code{Entity} is
7061 to be considered pure for the purposes of code generation. This means
7062 that the compiler can assume that there are no side effects, and
7063 in particular that two calls with identical arguments produce the
7064 same result. It also means that the function can be used in an
7067 Note that, quite deliberately, there are no static checks to try
7068 to ensure that this promise is met, so @code{Pure_Function} can be used
7069 with functions that are conceptually pure, even if they do modify
7070 global variables. For example, a square root function that is
7071 instrumented to count the number of times it is called is still
7072 conceptually pure, and can still be optimized, even though it
7073 modifies a global variable (the count). Memo functions are another
7074 example (where a table of previous calls is kept and consulted to
7075 avoid re-computation).
7077 Note also that the normal rules excluding optimization of subprograms
7078 in pure units (when parameter types are descended from System.Address,
7079 or when the full view of a parameter type is limited), do not apply
7080 for the Pure_Function case. If you explicitly specify Pure_Function,
7081 the compiler may optimize away calls with identical arguments, and
7082 if that results in unexpected behavior, the proper action is not to
7083 use the pragma for subprograms that are not (conceptually) pure.
7085 Note: Most functions in a @code{Pure} package are automatically pure, and
7086 there is no need to use pragma @code{Pure_Function} for such functions. One
7087 exception is any function that has at least one formal of type
7088 @code{System.Address} or a type derived from it. Such functions are not
7089 considered pure by default, since the compiler assumes that the
7090 @code{Address} parameter may be functioning as a pointer and that the
7091 referenced data may change even if the address value does not.
7092 Similarly, imported functions are not considered to be pure by default,
7093 since there is no way of checking that they are in fact pure. The use
7094 of pragma @code{Pure_Function} for such a function will override these default
7095 assumption, and cause the compiler to treat a designated subprogram as pure
7098 Note: If pragma @code{Pure_Function} is applied to a renamed function, it
7099 applies to the underlying renamed function. This can be used to
7100 disambiguate cases of overloading where some but not all functions
7101 in a set of overloaded functions are to be designated as pure.
7103 If pragma @code{Pure_Function} is applied to a library-level function, the
7104 function is also considered pure from an optimization point of view, but the
7105 unit is not a Pure unit in the categorization sense. So for example, a function
7106 thus marked is free to @code{with} non-pure units.
7108 @node Pragma Rational,Pragma Ravenscar,Pragma Pure_Function,Implementation Defined Pragmas
7109 @anchor{gnat_rm/implementation_defined_pragmas pragma-rational}@anchor{d0}
7110 @section Pragma Rational
7119 This pragma is considered obsolescent, but is retained for
7120 compatibility purposes. It is equivalent to:
7123 pragma Profile (Rational);
7126 @node Pragma Ravenscar,Pragma Refined_Depends,Pragma Rational,Implementation Defined Pragmas
7127 @anchor{gnat_rm/implementation_defined_pragmas pragma-ravenscar}@anchor{d1}
7128 @section Pragma Ravenscar
7137 This pragma is considered obsolescent, but is retained for
7138 compatibility purposes. It is equivalent to:
7141 pragma Profile (Ravenscar);
7144 which is the preferred method of setting the @code{Ravenscar} profile.
7146 @node Pragma Refined_Depends,Pragma Refined_Global,Pragma Ravenscar,Implementation Defined Pragmas
7147 @anchor{gnat_rm/implementation_defined_pragmas pragma-refined-depends}@anchor{d2}@anchor{gnat_rm/implementation_defined_pragmas id32}@anchor{d3}
7148 @section Pragma Refined_Depends
7154 pragma Refined_Depends (DEPENDENCY_RELATION);
7156 DEPENDENCY_RELATION ::=
7158 | (DEPENDENCY_CLAUSE @{, DEPENDENCY_CLAUSE@})
7160 DEPENDENCY_CLAUSE ::=
7161 OUTPUT_LIST =>[+] INPUT_LIST
7162 | NULL_DEPENDENCY_CLAUSE
7164 NULL_DEPENDENCY_CLAUSE ::= null => INPUT_LIST
7166 OUTPUT_LIST ::= OUTPUT | (OUTPUT @{, OUTPUT@})
7168 INPUT_LIST ::= null | INPUT | (INPUT @{, INPUT@})
7170 OUTPUT ::= NAME | FUNCTION_RESULT
7173 where FUNCTION_RESULT is a function Result attribute_reference
7176 For the semantics of this pragma, see the entry for aspect @code{Refined_Depends} in
7177 the SPARK 2014 Reference Manual, section 6.1.5.
7179 @node Pragma Refined_Global,Pragma Refined_Post,Pragma Refined_Depends,Implementation Defined Pragmas
7180 @anchor{gnat_rm/implementation_defined_pragmas pragma-refined-global}@anchor{d4}@anchor{gnat_rm/implementation_defined_pragmas id33}@anchor{d5}
7181 @section Pragma Refined_Global
7187 pragma Refined_Global (GLOBAL_SPECIFICATION);
7189 GLOBAL_SPECIFICATION ::=
7192 | (MODED_GLOBAL_LIST @{, MODED_GLOBAL_LIST@})
7194 MODED_GLOBAL_LIST ::= MODE_SELECTOR => GLOBAL_LIST
7196 MODE_SELECTOR ::= In_Out | Input | Output | Proof_In
7197 GLOBAL_LIST ::= GLOBAL_ITEM | (GLOBAL_ITEM @{, GLOBAL_ITEM@})
7198 GLOBAL_ITEM ::= NAME
7201 For the semantics of this pragma, see the entry for aspect @code{Refined_Global} in
7202 the SPARK 2014 Reference Manual, section 6.1.4.
7204 @node Pragma Refined_Post,Pragma Refined_State,Pragma Refined_Global,Implementation Defined Pragmas
7205 @anchor{gnat_rm/implementation_defined_pragmas pragma-refined-post}@anchor{d6}@anchor{gnat_rm/implementation_defined_pragmas id34}@anchor{d7}
7206 @section Pragma Refined_Post
7212 pragma Refined_Post (boolean_EXPRESSION);
7215 For the semantics of this pragma, see the entry for aspect @code{Refined_Post} in
7216 the SPARK 2014 Reference Manual, section 7.2.7.
7218 @node Pragma Refined_State,Pragma Relative_Deadline,Pragma Refined_Post,Implementation Defined Pragmas
7219 @anchor{gnat_rm/implementation_defined_pragmas pragma-refined-state}@anchor{d8}@anchor{gnat_rm/implementation_defined_pragmas id35}@anchor{d9}
7220 @section Pragma Refined_State
7226 pragma Refined_State (REFINEMENT_LIST);
7229 (REFINEMENT_CLAUSE @{, REFINEMENT_CLAUSE@})
7231 REFINEMENT_CLAUSE ::= state_NAME => CONSTITUENT_LIST
7233 CONSTITUENT_LIST ::=
7236 | (CONSTITUENT @{, CONSTITUENT@})
7238 CONSTITUENT ::= object_NAME | state_NAME
7241 For the semantics of this pragma, see the entry for aspect @code{Refined_State} in
7242 the SPARK 2014 Reference Manual, section 7.2.2.
7244 @node Pragma Relative_Deadline,Pragma Remote_Access_Type,Pragma Refined_State,Implementation Defined Pragmas
7245 @anchor{gnat_rm/implementation_defined_pragmas pragma-relative-deadline}@anchor{da}
7246 @section Pragma Relative_Deadline
7252 pragma Relative_Deadline (time_span_EXPRESSION);
7255 This pragma is standard in Ada 2005, but is available in all earlier
7256 versions of Ada as an implementation-defined pragma.
7257 See Ada 2012 Reference Manual for details.
7259 @node Pragma Remote_Access_Type,Pragma Restricted_Run_Time,Pragma Relative_Deadline,Implementation Defined Pragmas
7260 @anchor{gnat_rm/implementation_defined_pragmas id36}@anchor{db}@anchor{gnat_rm/implementation_defined_pragmas pragma-remote-access-type}@anchor{dc}
7261 @section Pragma Remote_Access_Type
7267 pragma Remote_Access_Type ([Entity =>] formal_access_type_LOCAL_NAME);
7270 This pragma appears in the formal part of a generic declaration.
7271 It specifies an exception to the RM rule from E.2.2(17/2), which forbids
7272 the use of a remote access to class-wide type as actual for a formal
7275 When this pragma applies to a formal access type @code{Entity}, that
7276 type is treated as a remote access to class-wide type in the generic.
7277 It must be a formal general access type, and its designated type must
7278 be the class-wide type of a formal tagged limited private type from the
7279 same generic declaration.
7281 In the generic unit, the formal type is subject to all restrictions
7282 pertaining to remote access to class-wide types. At instantiation, the
7283 actual type must be a remote access to class-wide type.
7285 @node Pragma Restricted_Run_Time,Pragma Restriction_Warnings,Pragma Remote_Access_Type,Implementation Defined Pragmas
7286 @anchor{gnat_rm/implementation_defined_pragmas pragma-restricted-run-time}@anchor{dd}
7287 @section Pragma Restricted_Run_Time
7293 pragma Restricted_Run_Time;
7296 This pragma is considered obsolescent, but is retained for
7297 compatibility purposes. It is equivalent to:
7300 pragma Profile (Restricted);
7303 which is the preferred method of setting the restricted run time
7306 @node Pragma Restriction_Warnings,Pragma Reviewable,Pragma Restricted_Run_Time,Implementation Defined Pragmas
7307 @anchor{gnat_rm/implementation_defined_pragmas pragma-restriction-warnings}@anchor{de}
7308 @section Pragma Restriction_Warnings
7314 pragma Restriction_Warnings
7315 (restriction_IDENTIFIER @{, restriction_IDENTIFIER@});
7318 This pragma allows a series of restriction identifiers to be
7319 specified (the list of allowed identifiers is the same as for
7320 pragma @code{Restrictions}). For each of these identifiers
7321 the compiler checks for violations of the restriction, but
7322 generates a warning message rather than an error message
7323 if the restriction is violated.
7325 One use of this is in situations where you want to know
7326 about violations of a restriction, but you want to ignore some of
7327 these violations. Consider this example, where you want to set
7328 Ada_95 mode and enable style checks, but you want to know about
7329 any other use of implementation pragmas:
7332 pragma Restriction_Warnings (No_Implementation_Pragmas);
7333 pragma Warnings (Off, "violation of No_Implementation_Pragmas");
7335 pragma Style_Checks ("2bfhkM160");
7336 pragma Warnings (On, "violation of No_Implementation_Pragmas");
7339 By including the above lines in a configuration pragmas file,
7340 the Ada_95 and Style_Checks pragmas are accepted without
7341 generating a warning, but any other use of implementation
7342 defined pragmas will cause a warning to be generated.
7344 @node Pragma Reviewable,Pragma Secondary_Stack_Size,Pragma Restriction_Warnings,Implementation Defined Pragmas
7345 @anchor{gnat_rm/implementation_defined_pragmas pragma-reviewable}@anchor{df}
7346 @section Pragma Reviewable
7355 This pragma is an RM-defined standard pragma, but has no effect on the
7356 program being compiled, or on the code generated for the program.
7358 To obtain the required output specified in RM H.3.1, the compiler must be
7359 run with various special switches as follows:
7365 @emph{Where compiler-generated run-time checks remain}
7367 The switch @emph{-gnatGL}
7368 may be used to list the expanded code in pseudo-Ada form.
7369 Runtime checks show up in the listing either as explicit
7370 checks or operators marked with @{@} to indicate a check is present.
7373 @emph{An identification of known exceptions at compile time}
7375 If the program is compiled with @emph{-gnatwa},
7376 the compiler warning messages will indicate all cases where the compiler
7377 detects that an exception is certain to occur at run time.
7380 @emph{Possible reads of uninitialized variables}
7382 The compiler warns of many such cases, but its output is incomplete.
7386 A supplemental static analysis tool
7387 may be used to obtain a comprehensive list of all
7388 possible points at which uninitialized data may be read.
7394 @emph{Where run-time support routines are implicitly invoked}
7396 In the output from @emph{-gnatGL},
7397 run-time calls are explicitly listed as calls to the relevant
7401 @emph{Object code listing}
7403 This may be obtained either by using the @emph{-S} switch,
7404 or the objdump utility.
7407 @emph{Constructs known to be erroneous at compile time}
7409 These are identified by warnings issued by the compiler (use @emph{-gnatwa}).
7412 @emph{Stack usage information}
7414 Static stack usage data (maximum per-subprogram) can be obtained via the
7415 @emph{-fstack-usage} switch to the compiler.
7416 Dynamic stack usage data (per task) can be obtained via the @emph{-u} switch
7425 @emph{Object code listing of entire partition}
7427 This can be obtained by compiling the partition with @emph{-S},
7428 or by applying objdump
7429 to all the object files that are part of the partition.
7432 @emph{A description of the run-time model}
7434 The full sources of the run-time are available, and the documentation of
7435 these routines describes how these run-time routines interface to the
7436 underlying operating system facilities.
7439 @emph{Control and data-flow information}
7443 A supplemental static analysis tool
7444 may be used to obtain complete control and data-flow information, as well as
7445 comprehensive messages identifying possible problems based on this
7448 @node Pragma Secondary_Stack_Size,Pragma Share_Generic,Pragma Reviewable,Implementation Defined Pragmas
7449 @anchor{gnat_rm/implementation_defined_pragmas id37}@anchor{e0}@anchor{gnat_rm/implementation_defined_pragmas pragma-secondary-stack-size}@anchor{e1}
7450 @section Pragma Secondary_Stack_Size
7456 pragma Secondary_Stack_Size (integer_EXPRESSION);
7459 This pragma appears within the task definition of a single task declaration
7460 or a task type declaration (like pragma @code{Storage_Size}) and applies to all
7461 task objects of that type. The argument specifies the size of the secondary
7462 stack to be used by these task objects, and must be of an integer type. The
7463 secondary stack is used to handle functions that return a variable-sized
7464 result, for example a function returning an unconstrained String.
7466 Note this pragma only applies to targets using fixed secondary stacks, like
7467 VxWorks 653 and bare board targets, where a fixed block for the
7468 secondary stack is allocated from the primary stack of the task. By default,
7469 these targets assign a percentage of the primary stack for the secondary stack,
7470 as defined by @code{System.Parameter.Sec_Stack_Percentage}. With this pragma,
7471 an @code{integer_EXPRESSION} of bytes is assigned from the primary stack instead.
7473 For most targets, the pragma does not apply as the secondary stack grows on
7474 demand: allocated as a chain of blocks in the heap. The default size of these
7475 blocks can be modified via the @code{-D} binder option as described in
7476 @cite{GNAT User's Guide}.
7478 Note that no check is made to see if the secondary stack can fit inside the
7481 Note the pragma cannot appear when the restriction @code{No_Secondary_Stack}
7484 @node Pragma Share_Generic,Pragma Shared,Pragma Secondary_Stack_Size,Implementation Defined Pragmas
7485 @anchor{gnat_rm/implementation_defined_pragmas pragma-share-generic}@anchor{e2}
7486 @section Pragma Share_Generic
7492 pragma Share_Generic (GNAME @{, GNAME@});
7494 GNAME ::= generic_unit_NAME | generic_instance_NAME
7497 This pragma is provided for compatibility with Dec Ada 83. It has
7498 no effect in GNAT (which does not implement shared generics), other
7499 than to check that the given names are all names of generic units or
7502 @node Pragma Shared,Pragma Short_Circuit_And_Or,Pragma Share_Generic,Implementation Defined Pragmas
7503 @anchor{gnat_rm/implementation_defined_pragmas id38}@anchor{e3}@anchor{gnat_rm/implementation_defined_pragmas pragma-shared}@anchor{e4}
7504 @section Pragma Shared
7507 This pragma is provided for compatibility with Ada 83. The syntax and
7508 semantics are identical to pragma Atomic.
7510 @node Pragma Short_Circuit_And_Or,Pragma Short_Descriptors,Pragma Shared,Implementation Defined Pragmas
7511 @anchor{gnat_rm/implementation_defined_pragmas pragma-short-circuit-and-or}@anchor{e5}
7512 @section Pragma Short_Circuit_And_Or
7518 pragma Short_Circuit_And_Or;
7521 This configuration pragma causes any occurrence of the AND operator applied to
7522 operands of type Standard.Boolean to be short-circuited (i.e. the AND operator
7523 is treated as if it were AND THEN). Or is similarly treated as OR ELSE. This
7524 may be useful in the context of certification protocols requiring the use of
7525 short-circuited logical operators. If this configuration pragma occurs locally
7526 within the file being compiled, it applies only to the file being compiled.
7527 There is no requirement that all units in a partition use this option.
7529 @node Pragma Short_Descriptors,Pragma Simple_Storage_Pool_Type,Pragma Short_Circuit_And_Or,Implementation Defined Pragmas
7530 @anchor{gnat_rm/implementation_defined_pragmas pragma-short-descriptors}@anchor{e6}
7531 @section Pragma Short_Descriptors
7537 pragma Short_Descriptors
7540 This pragma is provided for compatibility with other Ada implementations. It
7541 is recognized but ignored by all current versions of GNAT.
7543 @node Pragma Simple_Storage_Pool_Type,Pragma Source_File_Name,Pragma Short_Descriptors,Implementation Defined Pragmas
7544 @anchor{gnat_rm/implementation_defined_pragmas pragma-simple-storage-pool-type}@anchor{e7}@anchor{gnat_rm/implementation_defined_pragmas id39}@anchor{e8}
7545 @section Pragma Simple_Storage_Pool_Type
7548 @geindex Storage pool
7551 @geindex Simple storage pool
7556 pragma Simple_Storage_Pool_Type (type_LOCAL_NAME);
7559 A type can be established as a 'simple storage pool type' by applying
7560 the representation pragma @code{Simple_Storage_Pool_Type} to the type.
7561 A type named in the pragma must be a library-level immutably limited record
7562 type or limited tagged type declared immediately within a package declaration.
7563 The type can also be a limited private type whose full type is allowed as
7564 a simple storage pool type.
7566 For a simple storage pool type @code{SSP}, nonabstract primitive subprograms
7567 @code{Allocate}, @code{Deallocate}, and @code{Storage_Size} can be declared that
7568 are subtype conformant with the following subprogram declarations:
7573 Storage_Address : out System.Address;
7574 Size_In_Storage_Elements : System.Storage_Elements.Storage_Count;
7575 Alignment : System.Storage_Elements.Storage_Count);
7577 procedure Deallocate
7579 Storage_Address : System.Address;
7580 Size_In_Storage_Elements : System.Storage_Elements.Storage_Count;
7581 Alignment : System.Storage_Elements.Storage_Count);
7583 function Storage_Size (Pool : SSP)
7584 return System.Storage_Elements.Storage_Count;
7587 Procedure @code{Allocate} must be declared, whereas @code{Deallocate} and
7588 @code{Storage_Size} are optional. If @code{Deallocate} is not declared, then
7589 applying an unchecked deallocation has no effect other than to set its actual
7590 parameter to null. If @code{Storage_Size} is not declared, then the
7591 @code{Storage_Size} attribute applied to an access type associated with
7592 a pool object of type SSP returns zero. Additional operations can be declared
7593 for a simple storage pool type (such as for supporting a mark/release
7594 storage-management discipline).
7596 An object of a simple storage pool type can be associated with an access
7597 type by specifying the attribute
7598 @ref{e9,,Simple_Storage_Pool}. For example:
7601 My_Pool : My_Simple_Storage_Pool_Type;
7603 type Acc is access My_Data_Type;
7605 for Acc'Simple_Storage_Pool use My_Pool;
7608 See attribute @ref{e9,,Simple_Storage_Pool}
7609 for further details.
7611 @node Pragma Source_File_Name,Pragma Source_File_Name_Project,Pragma Simple_Storage_Pool_Type,Implementation Defined Pragmas
7612 @anchor{gnat_rm/implementation_defined_pragmas pragma-source-file-name}@anchor{ea}@anchor{gnat_rm/implementation_defined_pragmas id40}@anchor{eb}
7613 @section Pragma Source_File_Name
7619 pragma Source_File_Name (
7620 [Unit_Name =>] unit_NAME,
7621 Spec_File_Name => STRING_LITERAL,
7622 [Index => INTEGER_LITERAL]);
7624 pragma Source_File_Name (
7625 [Unit_Name =>] unit_NAME,
7626 Body_File_Name => STRING_LITERAL,
7627 [Index => INTEGER_LITERAL]);
7630 Use this to override the normal naming convention. It is a configuration
7631 pragma, and so has the usual applicability of configuration pragmas
7632 (i.e., it applies to either an entire partition, or to all units in a
7633 compilation, or to a single unit, depending on how it is used.
7634 @code{unit_name} is mapped to @code{file_name_literal}. The identifier for
7635 the second argument is required, and indicates whether this is the file
7636 name for the spec or for the body.
7638 The optional Index argument should be used when a file contains multiple
7639 units, and when you do not want to use @code{gnatchop} to separate then
7640 into multiple files (which is the recommended procedure to limit the
7641 number of recompilations that are needed when some sources change).
7642 For instance, if the source file @code{source.ada} contains
7656 you could use the following configuration pragmas:
7659 pragma Source_File_Name
7660 (B, Spec_File_Name => "source.ada", Index => 1);
7661 pragma Source_File_Name
7662 (A, Body_File_Name => "source.ada", Index => 2);
7665 Note that the @code{gnatname} utility can also be used to generate those
7666 configuration pragmas.
7668 Another form of the @code{Source_File_Name} pragma allows
7669 the specification of patterns defining alternative file naming schemes
7670 to apply to all files.
7673 pragma Source_File_Name
7674 ( [Spec_File_Name =>] STRING_LITERAL
7675 [,[Casing =>] CASING_SPEC]
7676 [,[Dot_Replacement =>] STRING_LITERAL]);
7678 pragma Source_File_Name
7679 ( [Body_File_Name =>] STRING_LITERAL
7680 [,[Casing =>] CASING_SPEC]
7681 [,[Dot_Replacement =>] STRING_LITERAL]);
7683 pragma Source_File_Name
7684 ( [Subunit_File_Name =>] STRING_LITERAL
7685 [,[Casing =>] CASING_SPEC]
7686 [,[Dot_Replacement =>] STRING_LITERAL]);
7688 CASING_SPEC ::= Lowercase | Uppercase | Mixedcase
7691 The first argument is a pattern that contains a single asterisk indicating
7692 the point at which the unit name is to be inserted in the pattern string
7693 to form the file name. The second argument is optional. If present it
7694 specifies the casing of the unit name in the resulting file name string.
7695 The default is lower case. Finally the third argument allows for systematic
7696 replacement of any dots in the unit name by the specified string literal.
7698 Note that Source_File_Name pragmas should not be used if you are using
7699 project files. The reason for this rule is that the project manager is not
7700 aware of these pragmas, and so other tools that use the projet file would not
7701 be aware of the intended naming conventions. If you are using project files,
7702 file naming is controlled by Source_File_Name_Project pragmas, which are
7703 usually supplied automatically by the project manager. A pragma
7704 Source_File_Name cannot appear after a @ref{ec,,Pragma Source_File_Name_Project}.
7706 For more details on the use of the @code{Source_File_Name} pragma, see the
7707 sections on @code{Using Other File Names} and @cite{Alternative File Naming Schemes' in the :title:`GNAT User's Guide}.
7709 @node Pragma Source_File_Name_Project,Pragma Source_Reference,Pragma Source_File_Name,Implementation Defined Pragmas
7710 @anchor{gnat_rm/implementation_defined_pragmas pragma-source-file-name-project}@anchor{ec}@anchor{gnat_rm/implementation_defined_pragmas id41}@anchor{ed}
7711 @section Pragma Source_File_Name_Project
7714 This pragma has the same syntax and semantics as pragma Source_File_Name.
7715 It is only allowed as a stand-alone configuration pragma.
7716 It cannot appear after a @ref{ea,,Pragma Source_File_Name}, and
7717 most importantly, once pragma Source_File_Name_Project appears,
7718 no further Source_File_Name pragmas are allowed.
7720 The intention is that Source_File_Name_Project pragmas are always
7721 generated by the Project Manager in a manner consistent with the naming
7722 specified in a project file, and when naming is controlled in this manner,
7723 it is not permissible to attempt to modify this naming scheme using
7724 Source_File_Name or Source_File_Name_Project pragmas (which would not be
7725 known to the project manager).
7727 @node Pragma Source_Reference,Pragma SPARK_Mode,Pragma Source_File_Name_Project,Implementation Defined Pragmas
7728 @anchor{gnat_rm/implementation_defined_pragmas pragma-source-reference}@anchor{ee}
7729 @section Pragma Source_Reference
7735 pragma Source_Reference (INTEGER_LITERAL, STRING_LITERAL);
7738 This pragma must appear as the first line of a source file.
7739 @code{integer_literal} is the logical line number of the line following
7740 the pragma line (for use in error messages and debugging
7741 information). @code{string_literal} is a static string constant that
7742 specifies the file name to be used in error messages and debugging
7743 information. This is most notably used for the output of @code{gnatchop}
7744 with the @emph{-r} switch, to make sure that the original unchopped
7745 source file is the one referred to.
7747 The second argument must be a string literal, it cannot be a static
7748 string expression other than a string literal. This is because its value
7749 is needed for error messages issued by all phases of the compiler.
7751 @node Pragma SPARK_Mode,Pragma Static_Elaboration_Desired,Pragma Source_Reference,Implementation Defined Pragmas
7752 @anchor{gnat_rm/implementation_defined_pragmas pragma-spark-mode}@anchor{ef}@anchor{gnat_rm/implementation_defined_pragmas id42}@anchor{f0}
7753 @section Pragma SPARK_Mode
7759 pragma SPARK_Mode [(On | Off)] ;
7762 In general a program can have some parts that are in SPARK 2014 (and
7763 follow all the rules in the SPARK Reference Manual), and some parts
7764 that are full Ada 2012.
7766 The SPARK_Mode pragma is used to identify which parts are in SPARK
7767 2014 (by default programs are in full Ada). The SPARK_Mode pragma can
7768 be used in the following places:
7774 As a configuration pragma, in which case it sets the default mode for
7775 all units compiled with this pragma.
7778 Immediately following a library-level subprogram spec
7781 Immediately within a library-level package body
7784 Immediately following the @code{private} keyword of a library-level
7788 Immediately following the @code{begin} keyword of a library-level
7792 Immediately within a library-level subprogram body
7795 Normally a subprogram or package spec/body inherits the current mode
7796 that is active at the point it is declared. But this can be overridden
7797 by pragma within the spec or body as above.
7799 The basic consistency rule is that you can't turn SPARK_Mode back
7800 @code{On}, once you have explicitly (with a pragma) turned if
7801 @code{Off}. So the following rules apply:
7803 If a subprogram spec has SPARK_Mode @code{Off}, then the body must
7804 also have SPARK_Mode @code{Off}.
7806 For a package, we have four parts:
7812 the package public declarations
7815 the package private part
7818 the body of the package
7821 the elaboration code after @code{begin}
7824 For a package, the rule is that if you explicitly turn SPARK_Mode
7825 @code{Off} for any part, then all the following parts must have
7826 SPARK_Mode @code{Off}. Note that this may require repeating a pragma
7827 SPARK_Mode (@code{Off}) in the body. For example, if we have a
7828 configuration pragma SPARK_Mode (@code{On}) that turns the mode on by
7829 default everywhere, and one particular package spec has pragma
7830 SPARK_Mode (@code{Off}), then that pragma will need to be repeated in
7833 @node Pragma Static_Elaboration_Desired,Pragma Stream_Convert,Pragma SPARK_Mode,Implementation Defined Pragmas
7834 @anchor{gnat_rm/implementation_defined_pragmas pragma-static-elaboration-desired}@anchor{f1}
7835 @section Pragma Static_Elaboration_Desired
7841 pragma Static_Elaboration_Desired;
7844 This pragma is used to indicate that the compiler should attempt to initialize
7845 statically the objects declared in the library unit to which the pragma applies,
7846 when these objects are initialized (explicitly or implicitly) by an aggregate.
7847 In the absence of this pragma, aggregates in object declarations are expanded
7848 into assignments and loops, even when the aggregate components are static
7849 constants. When the aggregate is present the compiler builds a static expression
7850 that requires no run-time code, so that the initialized object can be placed in
7851 read-only data space. If the components are not static, or the aggregate has
7852 more that 100 components, the compiler emits a warning that the pragma cannot
7853 be obeyed. (See also the restriction No_Implicit_Loops, which supports static
7854 construction of larger aggregates with static components that include an others
7857 @node Pragma Stream_Convert,Pragma Style_Checks,Pragma Static_Elaboration_Desired,Implementation Defined Pragmas
7858 @anchor{gnat_rm/implementation_defined_pragmas pragma-stream-convert}@anchor{f2}
7859 @section Pragma Stream_Convert
7865 pragma Stream_Convert (
7866 [Entity =>] type_LOCAL_NAME,
7867 [Read =>] function_NAME,
7868 [Write =>] function_NAME);
7871 This pragma provides an efficient way of providing user-defined stream
7872 attributes. Not only is it simpler to use than specifying the attributes
7873 directly, but more importantly, it allows the specification to be made in such
7874 a way that the predefined unit Ada.Streams is not loaded unless it is actually
7875 needed (i.e. unless the stream attributes are actually used); the use of
7876 the Stream_Convert pragma adds no overhead at all, unless the stream
7877 attributes are actually used on the designated type.
7879 The first argument specifies the type for which stream functions are
7880 provided. The second parameter provides a function used to read values
7881 of this type. It must name a function whose argument type may be any
7882 subtype, and whose returned type must be the type given as the first
7883 argument to the pragma.
7885 The meaning of the @code{Read} parameter is that if a stream attribute directly
7886 or indirectly specifies reading of the type given as the first parameter,
7887 then a value of the type given as the argument to the Read function is
7888 read from the stream, and then the Read function is used to convert this
7889 to the required target type.
7891 Similarly the @code{Write} parameter specifies how to treat write attributes
7892 that directly or indirectly apply to the type given as the first parameter.
7893 It must have an input parameter of the type specified by the first parameter,
7894 and the return type must be the same as the input type of the Read function.
7895 The effect is to first call the Write function to convert to the given stream
7896 type, and then write the result type to the stream.
7898 The Read and Write functions must not be overloaded subprograms. If necessary
7899 renamings can be supplied to meet this requirement.
7900 The usage of this attribute is best illustrated by a simple example, taken
7901 from the GNAT implementation of package Ada.Strings.Unbounded:
7904 function To_Unbounded (S : String) return Unbounded_String
7905 renames To_Unbounded_String;
7907 pragma Stream_Convert
7908 (Unbounded_String, To_Unbounded, To_String);
7911 The specifications of the referenced functions, as given in the Ada
7912 Reference Manual are:
7915 function To_Unbounded_String (Source : String)
7916 return Unbounded_String;
7918 function To_String (Source : Unbounded_String)
7922 The effect is that if the value of an unbounded string is written to a stream,
7923 then the representation of the item in the stream is in the same format that
7924 would be used for @code{Standard.String'Output}, and this same representation
7925 is expected when a value of this type is read from the stream. Note that the
7926 value written always includes the bounds, even for Unbounded_String'Write,
7927 since Unbounded_String is not an array type.
7929 Note that the @code{Stream_Convert} pragma is not effective in the case of
7930 a derived type of a non-limited tagged type. If such a type is specified then
7931 the pragma is silently ignored, and the default implementation of the stream
7932 attributes is used instead.
7934 @node Pragma Style_Checks,Pragma Subtitle,Pragma Stream_Convert,Implementation Defined Pragmas
7935 @anchor{gnat_rm/implementation_defined_pragmas pragma-style-checks}@anchor{f3}
7936 @section Pragma Style_Checks
7942 pragma Style_Checks (string_LITERAL | ALL_CHECKS |
7943 On | Off [, LOCAL_NAME]);
7946 This pragma is used in conjunction with compiler switches to control the
7947 built in style checking provided by GNAT. The compiler switches, if set,
7948 provide an initial setting for the switches, and this pragma may be used
7949 to modify these settings, or the settings may be provided entirely by
7950 the use of the pragma. This pragma can be used anywhere that a pragma
7951 is legal, including use as a configuration pragma (including use in
7952 the @code{gnat.adc} file).
7954 The form with a string literal specifies which style options are to be
7955 activated. These are additive, so they apply in addition to any previously
7956 set style check options. The codes for the options are the same as those
7957 used in the @emph{-gnaty} switch to @emph{gcc} or @emph{gnatmake}.
7958 For example the following two methods can be used to enable
7966 pragma Style_Checks ("l");
7975 The form @code{ALL_CHECKS} activates all standard checks (its use is equivalent
7976 to the use of the @code{gnaty} switch with no options.
7977 See the @cite{GNAT User's Guide} for details.)
7979 Note: the behavior is slightly different in GNAT mode (@code{-gnatg} used).
7980 In this case, @code{ALL_CHECKS} implies the standard set of GNAT mode style check
7981 options (i.e. equivalent to @code{-gnatyg}).
7983 The forms with @code{Off} and @code{On}
7984 can be used to temporarily disable style checks
7985 as shown in the following example:
7988 pragma Style_Checks ("k"); -- requires keywords in lower case
7989 pragma Style_Checks (Off); -- turn off style checks
7990 NULL; -- this will not generate an error message
7991 pragma Style_Checks (On); -- turn style checks back on
7992 NULL; -- this will generate an error message
7995 Finally the two argument form is allowed only if the first argument is
7996 @code{On} or @code{Off}. The effect is to turn of semantic style checks
7997 for the specified entity, as shown in the following example:
8000 pragma Style_Checks ("r"); -- require consistency of identifier casing
8002 Rf1 : Integer := ARG; -- incorrect, wrong case
8003 pragma Style_Checks (Off, Arg);
8004 Rf2 : Integer := ARG; -- OK, no error
8007 @node Pragma Subtitle,Pragma Suppress,Pragma Style_Checks,Implementation Defined Pragmas
8008 @anchor{gnat_rm/implementation_defined_pragmas pragma-subtitle}@anchor{f4}
8009 @section Pragma Subtitle
8015 pragma Subtitle ([Subtitle =>] STRING_LITERAL);
8018 This pragma is recognized for compatibility with other Ada compilers
8019 but is ignored by GNAT.
8021 @node Pragma Suppress,Pragma Suppress_All,Pragma Subtitle,Implementation Defined Pragmas
8022 @anchor{gnat_rm/implementation_defined_pragmas pragma-suppress}@anchor{f5}
8023 @section Pragma Suppress
8029 pragma Suppress (Identifier [, [On =>] Name]);
8032 This is a standard pragma, and supports all the check names required in
8033 the RM. It is included here because GNAT recognizes some additional check
8034 names that are implementation defined (as permitted by the RM):
8040 @code{Alignment_Check} can be used to suppress alignment checks
8041 on addresses used in address clauses. Such checks can also be suppressed
8042 by suppressing range checks, but the specific use of @code{Alignment_Check}
8043 allows suppression of alignment checks without suppressing other range checks.
8044 Note that @code{Alignment_Check} is suppressed by default on machines (such as
8045 the x86) with non-strict alignment.
8048 @code{Atomic_Synchronization} can be used to suppress the special memory
8049 synchronization instructions that are normally generated for access to
8050 @code{Atomic} variables to ensure correct synchronization between tasks
8051 that use such variables for synchronization purposes.
8054 @code{Duplicated_Tag_Check} Can be used to suppress the check that is generated
8055 for a duplicated tag value when a tagged type is declared.
8058 @code{Container_Checks} Can be used to suppress all checks within Ada.Containers
8059 and instances of its children, including Tampering_Check.
8062 @code{Tampering_Check} Can be used to suppress tampering check in the containers.
8065 @code{Predicate_Check} can be used to control whether predicate checks are
8066 active. It is applicable only to predicates for which the policy is
8067 @code{Check}. Unlike @code{Assertion_Policy}, which determines if a given
8068 predicate is ignored or checked for the whole program, the use of
8069 @code{Suppress} and @code{Unsuppress} with this check name allows a given
8070 predicate to be turned on and off at specific points in the program.
8073 @code{Validity_Check} can be used specifically to control validity checks.
8074 If @code{Suppress} is used to suppress validity checks, then no validity
8075 checks are performed, including those specified by the appropriate compiler
8076 switch or the @code{Validity_Checks} pragma.
8079 Additional check names previously introduced by use of the @code{Check_Name}
8080 pragma are also allowed.
8083 Note that pragma Suppress gives the compiler permission to omit
8084 checks, but does not require the compiler to omit checks. The compiler
8085 will generate checks if they are essentially free, even when they are
8086 suppressed. In particular, if the compiler can prove that a certain
8087 check will necessarily fail, it will generate code to do an
8088 unconditional 'raise', even if checks are suppressed. The compiler
8091 Of course, run-time checks are omitted whenever the compiler can prove
8092 that they will not fail, whether or not checks are suppressed.
8094 @node Pragma Suppress_All,Pragma Suppress_Debug_Info,Pragma Suppress,Implementation Defined Pragmas
8095 @anchor{gnat_rm/implementation_defined_pragmas pragma-suppress-all}@anchor{f6}
8096 @section Pragma Suppress_All
8102 pragma Suppress_All;
8105 This pragma can appear anywhere within a unit.
8106 The effect is to apply @code{Suppress (All_Checks)} to the unit
8107 in which it appears. This pragma is implemented for compatibility with DEC
8108 Ada 83 usage where it appears at the end of a unit, and for compatibility
8109 with Rational Ada, where it appears as a program unit pragma.
8110 The use of the standard Ada pragma @code{Suppress (All_Checks)}
8111 as a normal configuration pragma is the preferred usage in GNAT.
8113 @node Pragma Suppress_Debug_Info,Pragma Suppress_Exception_Locations,Pragma Suppress_All,Implementation Defined Pragmas
8114 @anchor{gnat_rm/implementation_defined_pragmas pragma-suppress-debug-info}@anchor{f7}@anchor{gnat_rm/implementation_defined_pragmas id43}@anchor{f8}
8115 @section Pragma Suppress_Debug_Info
8121 pragma Suppress_Debug_Info ([Entity =>] LOCAL_NAME);
8124 This pragma can be used to suppress generation of debug information
8125 for the specified entity. It is intended primarily for use in debugging
8126 the debugger, and navigating around debugger problems.
8128 @node Pragma Suppress_Exception_Locations,Pragma Suppress_Initialization,Pragma Suppress_Debug_Info,Implementation Defined Pragmas
8129 @anchor{gnat_rm/implementation_defined_pragmas pragma-suppress-exception-locations}@anchor{f9}
8130 @section Pragma Suppress_Exception_Locations
8136 pragma Suppress_Exception_Locations;
8139 In normal mode, a raise statement for an exception by default generates
8140 an exception message giving the file name and line number for the location
8141 of the raise. This is useful for debugging and logging purposes, but this
8142 entails extra space for the strings for the messages. The configuration
8143 pragma @code{Suppress_Exception_Locations} can be used to suppress the
8144 generation of these strings, with the result that space is saved, but the
8145 exception message for such raises is null. This configuration pragma may
8146 appear in a global configuration pragma file, or in a specific unit as
8147 usual. It is not required that this pragma be used consistently within
8148 a partition, so it is fine to have some units within a partition compiled
8149 with this pragma and others compiled in normal mode without it.
8151 @node Pragma Suppress_Initialization,Pragma Task_Name,Pragma Suppress_Exception_Locations,Implementation Defined Pragmas
8152 @anchor{gnat_rm/implementation_defined_pragmas id44}@anchor{fa}@anchor{gnat_rm/implementation_defined_pragmas pragma-suppress-initialization}@anchor{fb}
8153 @section Pragma Suppress_Initialization
8156 @geindex Suppressing initialization
8158 @geindex Initialization
8159 @geindex suppression of
8164 pragma Suppress_Initialization ([Entity =>] variable_or_subtype_Name);
8167 Here variable_or_subtype_Name is the name introduced by a type declaration
8168 or subtype declaration or the name of a variable introduced by an
8171 In the case of a type or subtype
8172 this pragma suppresses any implicit or explicit initialization
8173 for all variables of the given type or subtype,
8174 including initialization resulting from the use of pragmas
8175 Normalize_Scalars or Initialize_Scalars.
8177 This is considered a representation item, so it cannot be given after
8178 the type is frozen. It applies to all subsequent object declarations,
8179 and also any allocator that creates objects of the type.
8181 If the pragma is given for the first subtype, then it is considered
8182 to apply to the base type and all its subtypes. If the pragma is given
8183 for other than a first subtype, then it applies only to the given subtype.
8184 The pragma may not be given after the type is frozen.
8186 Note that this includes eliminating initialization of discriminants
8187 for discriminated types, and tags for tagged types. In these cases,
8188 you will have to use some non-portable mechanism (e.g. address
8189 overlays or unchecked conversion) to achieve required initialization
8190 of these fields before accessing any object of the corresponding type.
8192 For the variable case, implicit initialization for the named variable
8193 is suppressed, just as though its subtype had been given in a pragma
8194 Suppress_Initialization, as described above.
8196 @node Pragma Task_Name,Pragma Task_Storage,Pragma Suppress_Initialization,Implementation Defined Pragmas
8197 @anchor{gnat_rm/implementation_defined_pragmas pragma-task-name}@anchor{fc}
8198 @section Pragma Task_Name
8204 pragma Task_Name (string_EXPRESSION);
8207 This pragma appears within a task definition (like pragma
8208 @code{Priority}) and applies to the task in which it appears. The
8209 argument must be of type String, and provides a name to be used for
8210 the task instance when the task is created. Note that this expression
8211 is not required to be static, and in particular, it can contain
8212 references to task discriminants. This facility can be used to
8213 provide different names for different tasks as they are created,
8214 as illustrated in the example below.
8216 The task name is recorded internally in the run-time structures
8217 and is accessible to tools like the debugger. In addition the
8218 routine @code{Ada.Task_Identification.Image} will return this
8219 string, with a unique task address appended.
8222 -- Example of the use of pragma Task_Name
8224 with Ada.Task_Identification;
8225 use Ada.Task_Identification;
8226 with Text_IO; use Text_IO;
8229 type Astring is access String;
8231 task type Task_Typ (Name : access String) is
8232 pragma Task_Name (Name.all);
8235 task body Task_Typ is
8236 Nam : constant String := Image (Current_Task);
8238 Put_Line ("-->" & Nam (1 .. 14) & "<--");
8241 type Ptr_Task is access Task_Typ;
8242 Task_Var : Ptr_Task;
8246 new Task_Typ (new String'("This is task 1"));
8248 new Task_Typ (new String'("This is task 2"));
8252 @node Pragma Task_Storage,Pragma Test_Case,Pragma Task_Name,Implementation Defined Pragmas
8253 @anchor{gnat_rm/implementation_defined_pragmas pragma-task-storage}@anchor{fd}
8254 @section Pragma Task_Storage
8260 pragma Task_Storage (
8261 [Task_Type =>] LOCAL_NAME,
8262 [Top_Guard =>] static_integer_EXPRESSION);
8265 This pragma specifies the length of the guard area for tasks. The guard
8266 area is an additional storage area allocated to a task. A value of zero
8267 means that either no guard area is created or a minimal guard area is
8268 created, depending on the target. This pragma can appear anywhere a
8269 @code{Storage_Size} attribute definition clause is allowed for a task
8272 @node Pragma Test_Case,Pragma Thread_Local_Storage,Pragma Task_Storage,Implementation Defined Pragmas
8273 @anchor{gnat_rm/implementation_defined_pragmas pragma-test-case}@anchor{fe}@anchor{gnat_rm/implementation_defined_pragmas id45}@anchor{ff}
8274 @section Pragma Test_Case
8283 [Name =>] static_string_Expression
8284 ,[Mode =>] (Nominal | Robustness)
8285 [, Requires => Boolean_Expression]
8286 [, Ensures => Boolean_Expression]);
8289 The @code{Test_Case} pragma allows defining fine-grain specifications
8290 for use by testing tools.
8291 The compiler checks the validity of the @code{Test_Case} pragma, but its
8292 presence does not lead to any modification of the code generated by the
8295 @code{Test_Case} pragmas may only appear immediately following the
8296 (separate) declaration of a subprogram in a package declaration, inside
8297 a package spec unit. Only other pragmas may intervene (that is appear
8298 between the subprogram declaration and a test case).
8300 The compiler checks that boolean expressions given in @code{Requires} and
8301 @code{Ensures} are valid, where the rules for @code{Requires} are the
8302 same as the rule for an expression in @code{Precondition} and the rules
8303 for @code{Ensures} are the same as the rule for an expression in
8304 @code{Postcondition}. In particular, attributes @code{'Old} and
8305 @code{'Result} can only be used within the @code{Ensures}
8306 expression. The following is an example of use within a package spec:
8309 package Math_Functions is
8311 function Sqrt (Arg : Float) return Float;
8312 pragma Test_Case (Name => "Test 1",
8314 Requires => Arg < 10000,
8315 Ensures => Sqrt'Result < 10);
8320 The meaning of a test case is that there is at least one context where
8321 @code{Requires} holds such that, if the associated subprogram is executed in
8322 that context, then @code{Ensures} holds when the subprogram returns.
8323 Mode @code{Nominal} indicates that the input context should also satisfy the
8324 precondition of the subprogram, and the output context should also satisfy its
8325 postcondition. Mode @code{Robustness} indicates that the precondition and
8326 postcondition of the subprogram should be ignored for this test case.
8328 @node Pragma Thread_Local_Storage,Pragma Time_Slice,Pragma Test_Case,Implementation Defined Pragmas
8329 @anchor{gnat_rm/implementation_defined_pragmas pragma-thread-local-storage}@anchor{100}@anchor{gnat_rm/implementation_defined_pragmas id46}@anchor{101}
8330 @section Pragma Thread_Local_Storage
8333 @geindex Task specific storage
8335 @geindex TLS (Thread Local Storage)
8337 @geindex Task_Attributes
8342 pragma Thread_Local_Storage ([Entity =>] LOCAL_NAME);
8345 This pragma specifies that the specified entity, which must be
8346 a variable declared in a library-level package, is to be marked as
8347 "Thread Local Storage" (@code{TLS}). On systems supporting this (which
8348 include Windows, Solaris, GNU/Linux, and VxWorks 6), this causes each
8349 thread (and hence each Ada task) to see a distinct copy of the variable.
8351 The variable must not have default initialization, and if there is
8352 an explicit initialization, it must be either @code{null} for an
8353 access variable, a static expression for a scalar variable, or a fully
8354 static aggregate for a composite type, that is to say, an aggregate all
8355 of whose components are static, and which does not include packed or
8356 discriminated components.
8358 This provides a low-level mechanism similar to that provided by
8359 the @code{Ada.Task_Attributes} package, but much more efficient
8360 and is also useful in writing interface code that will interact
8361 with foreign threads.
8363 If this pragma is used on a system where @code{TLS} is not supported,
8364 then an error message will be generated and the program will be rejected.
8366 @node Pragma Time_Slice,Pragma Title,Pragma Thread_Local_Storage,Implementation Defined Pragmas
8367 @anchor{gnat_rm/implementation_defined_pragmas pragma-time-slice}@anchor{102}
8368 @section Pragma Time_Slice
8374 pragma Time_Slice (static_duration_EXPRESSION);
8377 For implementations of GNAT on operating systems where it is possible
8378 to supply a time slice value, this pragma may be used for this purpose.
8379 It is ignored if it is used in a system that does not allow this control,
8380 or if it appears in other than the main program unit.
8382 @node Pragma Title,Pragma Type_Invariant,Pragma Time_Slice,Implementation Defined Pragmas
8383 @anchor{gnat_rm/implementation_defined_pragmas pragma-title}@anchor{103}
8384 @section Pragma Title
8390 pragma Title (TITLING_OPTION [, TITLING OPTION]);
8393 [Title =>] STRING_LITERAL,
8394 | [Subtitle =>] STRING_LITERAL
8397 Syntax checked but otherwise ignored by GNAT. This is a listing control
8398 pragma used in DEC Ada 83 implementations to provide a title and/or
8399 subtitle for the program listing. The program listing generated by GNAT
8400 does not have titles or subtitles.
8402 Unlike other pragmas, the full flexibility of named notation is allowed
8403 for this pragma, i.e., the parameters may be given in any order if named
8404 notation is used, and named and positional notation can be mixed
8405 following the normal rules for procedure calls in Ada.
8407 @node Pragma Type_Invariant,Pragma Type_Invariant_Class,Pragma Title,Implementation Defined Pragmas
8408 @anchor{gnat_rm/implementation_defined_pragmas pragma-type-invariant}@anchor{104}
8409 @section Pragma Type_Invariant
8415 pragma Type_Invariant
8416 ([Entity =>] type_LOCAL_NAME,
8417 [Check =>] EXPRESSION);
8420 The @code{Type_Invariant} pragma is intended to be an exact
8421 replacement for the language-defined @code{Type_Invariant}
8422 aspect, and shares its restrictions and semantics. It differs
8423 from the language defined @code{Invariant} pragma in that it
8424 does not permit a string parameter, and it is
8425 controlled by the assertion identifier @code{Type_Invariant}
8426 rather than @code{Invariant}.
8428 @node Pragma Type_Invariant_Class,Pragma Unchecked_Union,Pragma Type_Invariant,Implementation Defined Pragmas
8429 @anchor{gnat_rm/implementation_defined_pragmas id47}@anchor{105}@anchor{gnat_rm/implementation_defined_pragmas pragma-type-invariant-class}@anchor{106}
8430 @section Pragma Type_Invariant_Class
8436 pragma Type_Invariant_Class
8437 ([Entity =>] type_LOCAL_NAME,
8438 [Check =>] EXPRESSION);
8441 The @code{Type_Invariant_Class} pragma is intended to be an exact
8442 replacement for the language-defined @code{Type_Invariant'Class}
8443 aspect, and shares its restrictions and semantics.
8445 Note: This pragma is called @code{Type_Invariant_Class} rather than
8446 @code{Type_Invariant'Class} because the latter would not be strictly
8447 conforming to the allowed syntax for pragmas. The motivation
8448 for providing pragmas equivalent to the aspects is to allow a program
8449 to be written using the pragmas, and then compiled if necessary
8450 using an Ada compiler that does not recognize the pragmas or
8451 aspects, but is prepared to ignore the pragmas. The assertion
8452 policy that controls this pragma is @code{Type_Invariant'Class},
8453 not @code{Type_Invariant_Class}.
8455 @node Pragma Unchecked_Union,Pragma Unevaluated_Use_Of_Old,Pragma Type_Invariant_Class,Implementation Defined Pragmas
8456 @anchor{gnat_rm/implementation_defined_pragmas pragma-unchecked-union}@anchor{107}
8457 @section Pragma Unchecked_Union
8460 @geindex Unions in C
8465 pragma Unchecked_Union (first_subtype_LOCAL_NAME);
8468 This pragma is used to specify a representation of a record type that is
8469 equivalent to a C union. It was introduced as a GNAT implementation defined
8470 pragma in the GNAT Ada 95 mode. Ada 2005 includes an extended version of this
8471 pragma, making it language defined, and GNAT fully implements this extended
8472 version in all language modes (Ada 83, Ada 95, and Ada 2005). For full
8473 details, consult the Ada 2012 Reference Manual, section B.3.3.
8475 @node Pragma Unevaluated_Use_Of_Old,Pragma Unimplemented_Unit,Pragma Unchecked_Union,Implementation Defined Pragmas
8476 @anchor{gnat_rm/implementation_defined_pragmas pragma-unevaluated-use-of-old}@anchor{108}
8477 @section Pragma Unevaluated_Use_Of_Old
8480 @geindex Attribute Old
8482 @geindex Attribute Loop_Entry
8484 @geindex Unevaluated_Use_Of_Old
8489 pragma Unevaluated_Use_Of_Old (Error | Warn | Allow);
8492 This pragma controls the processing of attributes Old and Loop_Entry.
8493 If either of these attributes is used in a potentially unevaluated
8494 expression (e.g. the then or else parts of an if expression), then
8495 normally this usage is considered illegal if the prefix of the attribute
8496 is other than an entity name. The language requires this
8497 behavior for Old, and GNAT copies the same rule for Loop_Entry.
8499 The reason for this rule is that otherwise, we can have a situation
8500 where we save the Old value, and this results in an exception, even
8501 though we might not evaluate the attribute. Consider this example:
8504 package UnevalOld is
8506 procedure U (A : String; C : Boolean) -- ERROR
8507 with Post => (if C then A(1)'Old = K else True);
8511 If procedure U is called with a string with a lower bound of 2, and
8512 C false, then an exception would be raised trying to evaluate A(1)
8513 on entry even though the value would not be actually used.
8515 Although the rule guarantees against this possibility, it is sometimes
8516 too restrictive. For example if we know that the string has a lower
8517 bound of 1, then we will never raise an exception.
8518 The pragma @code{Unevaluated_Use_Of_Old} can be
8519 used to modify this behavior. If the argument is @code{Error} then an
8520 error is given (this is the default RM behavior). If the argument is
8521 @code{Warn} then the usage is allowed as legal but with a warning
8522 that an exception might be raised. If the argument is @code{Allow}
8523 then the usage is allowed as legal without generating a warning.
8525 This pragma may appear as a configuration pragma, or in a declarative
8526 part or package specification. In the latter case it applies to
8527 uses up to the end of the corresponding statement sequence or
8528 sequence of package declarations.
8530 @node Pragma Unimplemented_Unit,Pragma Universal_Aliasing,Pragma Unevaluated_Use_Of_Old,Implementation Defined Pragmas
8531 @anchor{gnat_rm/implementation_defined_pragmas pragma-unimplemented-unit}@anchor{109}
8532 @section Pragma Unimplemented_Unit
8538 pragma Unimplemented_Unit;
8541 If this pragma occurs in a unit that is processed by the compiler, GNAT
8542 aborts with the message @code{xxx not implemented}, where
8543 @code{xxx} is the name of the current compilation unit. This pragma is
8544 intended to allow the compiler to handle unimplemented library units in
8547 The abort only happens if code is being generated. Thus you can use
8548 specs of unimplemented packages in syntax or semantic checking mode.
8550 @node Pragma Universal_Aliasing,Pragma Universal_Data,Pragma Unimplemented_Unit,Implementation Defined Pragmas
8551 @anchor{gnat_rm/implementation_defined_pragmas pragma-universal-aliasing}@anchor{10a}@anchor{gnat_rm/implementation_defined_pragmas id48}@anchor{10b}
8552 @section Pragma Universal_Aliasing
8558 pragma Universal_Aliasing [([Entity =>] type_LOCAL_NAME)];
8561 @code{type_LOCAL_NAME} must refer to a type declaration in the current
8562 declarative part. The effect is to inhibit strict type-based aliasing
8563 optimization for the given type. In other words, the effect is as though
8564 access types designating this type were subject to pragma No_Strict_Aliasing.
8565 For a detailed description of the strict aliasing optimization, and the
8566 situations in which it must be suppressed, see the section on
8567 @code{Optimization and Strict Aliasing} in the @cite{GNAT User's Guide}.
8569 @node Pragma Universal_Data,Pragma Unmodified,Pragma Universal_Aliasing,Implementation Defined Pragmas
8570 @anchor{gnat_rm/implementation_defined_pragmas pragma-universal-data}@anchor{10c}@anchor{gnat_rm/implementation_defined_pragmas id49}@anchor{10d}
8571 @section Pragma Universal_Data
8577 pragma Universal_Data [(library_unit_Name)];
8580 This pragma is supported only for the AAMP target and is ignored for
8581 other targets. The pragma specifies that all library-level objects
8582 (Counter 0 data) associated with the library unit are to be accessed
8583 and updated using universal addressing (24-bit addresses for AAMP5)
8584 rather than the default of 16-bit Data Environment (DENV) addressing.
8585 Use of this pragma will generally result in less efficient code for
8586 references to global data associated with the library unit, but
8587 allows such data to be located anywhere in memory. This pragma is
8588 a library unit pragma, but can also be used as a configuration pragma
8589 (including use in the @code{gnat.adc} file). The functionality
8590 of this pragma is also available by applying the -univ switch on the
8591 compilations of units where universal addressing of the data is desired.
8593 @node Pragma Unmodified,Pragma Unreferenced,Pragma Universal_Data,Implementation Defined Pragmas
8594 @anchor{gnat_rm/implementation_defined_pragmas id50}@anchor{10e}@anchor{gnat_rm/implementation_defined_pragmas pragma-unmodified}@anchor{10f}
8595 @section Pragma Unmodified
8604 pragma Unmodified (LOCAL_NAME @{, LOCAL_NAME@});
8607 This pragma signals that the assignable entities (variables,
8608 @code{out} parameters, @code{in out} parameters) whose names are listed are
8609 deliberately not assigned in the current source unit. This
8610 suppresses warnings about the
8611 entities being referenced but not assigned, and in addition a warning will be
8612 generated if one of these entities is in fact assigned in the
8613 same unit as the pragma (or in the corresponding body, or one
8616 This is particularly useful for clearly signaling that a particular
8617 parameter is not modified, even though the spec suggests that it might
8620 For the variable case, warnings are never given for unreferenced variables
8621 whose name contains one of the substrings
8622 @code{DISCARD, DUMMY, IGNORE, JUNK, UNUSED} in any casing. Such names
8623 are typically to be used in cases where such warnings are expected.
8624 Thus it is never necessary to use @code{pragma Unmodified} for such
8625 variables, though it is harmless to do so.
8627 @node Pragma Unreferenced,Pragma Unreferenced_Objects,Pragma Unmodified,Implementation Defined Pragmas
8628 @anchor{gnat_rm/implementation_defined_pragmas pragma-unreferenced}@anchor{110}@anchor{gnat_rm/implementation_defined_pragmas id51}@anchor{111}
8629 @section Pragma Unreferenced
8633 @geindex unreferenced
8638 pragma Unreferenced (LOCAL_NAME @{, LOCAL_NAME@});
8639 pragma Unreferenced (library_unit_NAME @{, library_unit_NAME@});
8642 This pragma signals that the entities whose names are listed are
8643 deliberately not referenced in the current source unit after the
8644 occurrence of the pragma. This
8645 suppresses warnings about the
8646 entities being unreferenced, and in addition a warning will be
8647 generated if one of these entities is in fact subsequently referenced in the
8648 same unit as the pragma (or in the corresponding body, or one
8651 This is particularly useful for clearly signaling that a particular
8652 parameter is not referenced in some particular subprogram implementation
8653 and that this is deliberate. It can also be useful in the case of
8654 objects declared only for their initialization or finalization side
8657 If @code{LOCAL_NAME} identifies more than one matching homonym in the
8658 current scope, then the entity most recently declared is the one to which
8659 the pragma applies. Note that in the case of accept formals, the pragma
8660 Unreferenced may appear immediately after the keyword @code{do} which
8661 allows the indication of whether or not accept formals are referenced
8662 or not to be given individually for each accept statement.
8664 The left hand side of an assignment does not count as a reference for the
8665 purpose of this pragma. Thus it is fine to assign to an entity for which
8666 pragma Unreferenced is given.
8668 Note that if a warning is desired for all calls to a given subprogram,
8669 regardless of whether they occur in the same unit as the subprogram
8670 declaration, then this pragma should not be used (calls from another
8671 unit would not be flagged); pragma Obsolescent can be used instead
8672 for this purpose, see @ref{af,,Pragma Obsolescent}.
8674 The second form of pragma @code{Unreferenced} is used within a context
8675 clause. In this case the arguments must be unit names of units previously
8676 mentioned in @code{with} clauses (similar to the usage of pragma
8677 @code{Elaborate_All}. The effect is to suppress warnings about unreferenced
8678 units and unreferenced entities within these units.
8680 For the variable case, warnings are never given for unreferenced variables
8681 whose name contains one of the substrings
8682 @code{DISCARD, DUMMY, IGNORE, JUNK, UNUSED} in any casing. Such names
8683 are typically to be used in cases where such warnings are expected.
8684 Thus it is never necessary to use @code{pragma Unreferenced} for such
8685 variables, though it is harmless to do so.
8687 @node Pragma Unreferenced_Objects,Pragma Unreserve_All_Interrupts,Pragma Unreferenced,Implementation Defined Pragmas
8688 @anchor{gnat_rm/implementation_defined_pragmas pragma-unreferenced-objects}@anchor{112}@anchor{gnat_rm/implementation_defined_pragmas id52}@anchor{113}
8689 @section Pragma Unreferenced_Objects
8693 @geindex unreferenced
8698 pragma Unreferenced_Objects (local_subtype_NAME @{, local_subtype_NAME@});
8701 This pragma signals that for the types or subtypes whose names are
8702 listed, objects which are declared with one of these types or subtypes may
8703 not be referenced, and if no references appear, no warnings are given.
8705 This is particularly useful for objects which are declared solely for their
8706 initialization and finalization effect. Such variables are sometimes referred
8707 to as RAII variables (Resource Acquisition Is Initialization). Using this
8708 pragma on the relevant type (most typically a limited controlled type), the
8709 compiler will automatically suppress unwanted warnings about these variables
8710 not being referenced.
8712 @node Pragma Unreserve_All_Interrupts,Pragma Unsuppress,Pragma Unreferenced_Objects,Implementation Defined Pragmas
8713 @anchor{gnat_rm/implementation_defined_pragmas pragma-unreserve-all-interrupts}@anchor{114}
8714 @section Pragma Unreserve_All_Interrupts
8720 pragma Unreserve_All_Interrupts;
8723 Normally certain interrupts are reserved to the implementation. Any attempt
8724 to attach an interrupt causes Program_Error to be raised, as described in
8725 RM C.3.2(22). A typical example is the @code{SIGINT} interrupt used in
8726 many systems for a @code{Ctrl-C} interrupt. Normally this interrupt is
8727 reserved to the implementation, so that @code{Ctrl-C} can be used to
8728 interrupt execution.
8730 If the pragma @code{Unreserve_All_Interrupts} appears anywhere in any unit in
8731 a program, then all such interrupts are unreserved. This allows the
8732 program to handle these interrupts, but disables their standard
8733 functions. For example, if this pragma is used, then pressing
8734 @code{Ctrl-C} will not automatically interrupt execution. However,
8735 a program can then handle the @code{SIGINT} interrupt as it chooses.
8737 For a full list of the interrupts handled in a specific implementation,
8738 see the source code for the spec of @code{Ada.Interrupts.Names} in
8739 file @code{a-intnam.ads}. This is a target dependent file that contains the
8740 list of interrupts recognized for a given target. The documentation in
8741 this file also specifies what interrupts are affected by the use of
8742 the @code{Unreserve_All_Interrupts} pragma.
8744 For a more general facility for controlling what interrupts can be
8745 handled, see pragma @code{Interrupt_State}, which subsumes the functionality
8746 of the @code{Unreserve_All_Interrupts} pragma.
8748 @node Pragma Unsuppress,Pragma Use_VADS_Size,Pragma Unreserve_All_Interrupts,Implementation Defined Pragmas
8749 @anchor{gnat_rm/implementation_defined_pragmas pragma-unsuppress}@anchor{115}
8750 @section Pragma Unsuppress
8756 pragma Unsuppress (IDENTIFIER [, [On =>] NAME]);
8759 This pragma undoes the effect of a previous pragma @code{Suppress}. If
8760 there is no corresponding pragma @code{Suppress} in effect, it has no
8761 effect. The range of the effect is the same as for pragma
8762 @code{Suppress}. The meaning of the arguments is identical to that used
8763 in pragma @code{Suppress}.
8765 One important application is to ensure that checks are on in cases where
8766 code depends on the checks for its correct functioning, so that the code
8767 will compile correctly even if the compiler switches are set to suppress
8768 checks. For example, in a program that depends on external names of tagged
8769 types and wants to ensure that the duplicated tag check occurs even if all
8770 run-time checks are suppressed by a compiler switch, the following
8771 configuration pragma will ensure this test is not suppressed:
8774 pragma Unsuppress (Duplicated_Tag_Check);
8777 This pragma is standard in Ada 2005. It is available in all earlier versions
8778 of Ada as an implementation-defined pragma.
8780 Note that in addition to the checks defined in the Ada RM, GNAT recogizes a
8781 number of implementation-defined check names. See the description of pragma
8782 @code{Suppress} for full details.
8784 @node Pragma Use_VADS_Size,Pragma Unused,Pragma Unsuppress,Implementation Defined Pragmas
8785 @anchor{gnat_rm/implementation_defined_pragmas pragma-use-vads-size}@anchor{116}
8786 @section Pragma Use_VADS_Size
8790 @geindex VADS compatibility
8792 @geindex Rational profile
8797 pragma Use_VADS_Size;
8800 This is a configuration pragma. In a unit to which it applies, any use
8801 of the 'Size attribute is automatically interpreted as a use of the
8802 'VADS_Size attribute. Note that this may result in incorrect semantic
8803 processing of valid Ada 95 or Ada 2005 programs. This is intended to aid in
8804 the handling of existing code which depends on the interpretation of Size
8805 as implemented in the VADS compiler. See description of the VADS_Size
8806 attribute for further details.
8808 @node Pragma Unused,Pragma Validity_Checks,Pragma Use_VADS_Size,Implementation Defined Pragmas
8809 @anchor{gnat_rm/implementation_defined_pragmas pragma-unused}@anchor{117}@anchor{gnat_rm/implementation_defined_pragmas id53}@anchor{118}
8810 @section Pragma Unused
8819 pragma Unused (LOCAL_NAME @{, LOCAL_NAME@});
8822 This pragma signals that the assignable entities (variables,
8823 @code{out} parameters, and @code{in out} parameters) whose names are listed
8824 deliberately do not get assigned or referenced in the current source unit
8825 after the occurrence of the pragma in the current source unit. This
8826 suppresses warnings about the entities that are unreferenced and/or not
8827 assigned, and, in addition, a warning will be generated if one of these
8828 entities gets assigned or subsequently referenced in the same unit as the
8829 pragma (in the corresponding body or one of its subunits).
8831 This is particularly useful for clearly signaling that a particular
8832 parameter is not modified or referenced, even though the spec suggests
8835 For the variable case, warnings are never given for unreferenced
8836 variables whose name contains one of the substrings
8837 @code{DISCARD, DUMMY, IGNORE, JUNK, UNUSED} in any casing. Such names
8838 are typically to be used in cases where such warnings are expected.
8839 Thus it is never necessary to use @code{pragma Unmodified} for such
8840 variables, though it is harmless to do so.
8842 @node Pragma Validity_Checks,Pragma Volatile,Pragma Unused,Implementation Defined Pragmas
8843 @anchor{gnat_rm/implementation_defined_pragmas pragma-validity-checks}@anchor{119}
8844 @section Pragma Validity_Checks
8850 pragma Validity_Checks (string_LITERAL | ALL_CHECKS | On | Off);
8853 This pragma is used in conjunction with compiler switches to control the
8854 built-in validity checking provided by GNAT. The compiler switches, if set
8855 provide an initial setting for the switches, and this pragma may be used
8856 to modify these settings, or the settings may be provided entirely by
8857 the use of the pragma. This pragma can be used anywhere that a pragma
8858 is legal, including use as a configuration pragma (including use in
8859 the @code{gnat.adc} file).
8861 The form with a string literal specifies which validity options are to be
8862 activated. The validity checks are first set to include only the default
8863 reference manual settings, and then a string of letters in the string
8864 specifies the exact set of options required. The form of this string
8865 is exactly as described for the @emph{-gnatVx} compiler switch (see the
8866 GNAT User's Guide for details). For example the following two
8867 methods can be used to enable validity checking for mode @code{in} and
8868 @code{in out} subprogram parameters:
8875 pragma Validity_Checks ("im");
8880 $ gcc -c -gnatVim ...
8884 The form ALL_CHECKS activates all standard checks (its use is equivalent
8885 to the use of the @code{gnatVa} switch).
8887 The forms with @code{Off} and @code{On} can be used to temporarily disable
8888 validity checks as shown in the following example:
8891 pragma Validity_Checks ("c"); -- validity checks for copies
8892 pragma Validity_Checks (Off); -- turn off validity checks
8893 A := B; -- B will not be validity checked
8894 pragma Validity_Checks (On); -- turn validity checks back on
8895 A := C; -- C will be validity checked
8898 @node Pragma Volatile,Pragma Volatile_Full_Access,Pragma Validity_Checks,Implementation Defined Pragmas
8899 @anchor{gnat_rm/implementation_defined_pragmas id54}@anchor{11a}@anchor{gnat_rm/implementation_defined_pragmas pragma-volatile}@anchor{11b}
8900 @section Pragma Volatile
8906 pragma Volatile (LOCAL_NAME);
8909 This pragma is defined by the Ada Reference Manual, and the GNAT
8910 implementation is fully conformant with this definition. The reason it
8911 is mentioned in this section is that a pragma of the same name was supplied
8912 in some Ada 83 compilers, including DEC Ada 83. The Ada 95 / Ada 2005
8913 implementation of pragma Volatile is upwards compatible with the
8914 implementation in DEC Ada 83.
8916 @node Pragma Volatile_Full_Access,Pragma Volatile_Function,Pragma Volatile,Implementation Defined Pragmas
8917 @anchor{gnat_rm/implementation_defined_pragmas id55}@anchor{11c}@anchor{gnat_rm/implementation_defined_pragmas pragma-volatile-full-access}@anchor{11d}
8918 @section Pragma Volatile_Full_Access
8924 pragma Volatile_Full_Access (LOCAL_NAME);
8927 This is similar in effect to pragma Volatile, except that any reference to the
8928 object is guaranteed to be done only with instructions that read or write all
8929 the bits of the object. Furthermore, if the object is of a composite type,
8930 then any reference to a component of the object is guaranteed to read and/or
8931 write all the bits of the object.
8933 The intention is that this be suitable for use with memory-mapped I/O devices
8934 on some machines. Note that there are two important respects in which this is
8935 different from @code{pragma Atomic}. First a reference to a @code{Volatile_Full_Access}
8936 object is not a sequential action in the RM 9.10 sense and, therefore, does
8937 not create a synchronization point. Second, in the case of @code{pragma Atomic},
8938 there is no guarantee that all the bits will be accessed if the reference
8939 is not to the whole object; the compiler is allowed (and generally will)
8940 access only part of the object in this case.
8942 It is not permissible to specify @code{Atomic} and @code{Volatile_Full_Access} for
8945 It is not permissible to specify @code{Volatile_Full_Access} for a composite
8946 (record or array) type or object that has at least one @code{Aliased} component.
8948 @node Pragma Volatile_Function,Pragma Warning_As_Error,Pragma Volatile_Full_Access,Implementation Defined Pragmas
8949 @anchor{gnat_rm/implementation_defined_pragmas id56}@anchor{11e}@anchor{gnat_rm/implementation_defined_pragmas pragma-volatile-function}@anchor{11f}
8950 @section Pragma Volatile_Function
8956 pragma Volatile_Function [ (boolean_EXPRESSION) ];
8959 For the semantics of this pragma, see the entry for aspect @code{Volatile_Function}
8960 in the SPARK 2014 Reference Manual, section 7.1.2.
8962 @node Pragma Warning_As_Error,Pragma Warnings,Pragma Volatile_Function,Implementation Defined Pragmas
8963 @anchor{gnat_rm/implementation_defined_pragmas pragma-warning-as-error}@anchor{120}
8964 @section Pragma Warning_As_Error
8970 pragma Warning_As_Error (static_string_EXPRESSION);
8973 This configuration pragma allows the programmer to specify a set
8974 of warnings that will be treated as errors. Any warning that
8975 matches the pattern given by the pragma argument will be treated
8976 as an error. This gives more precise control than -gnatwe,
8977 which treats warnings as errors.
8979 This pragma can apply to regular warnings (messages enabled by -gnatw)
8980 and to style warnings (messages that start with "(style)",
8983 The pattern may contain asterisks, which match zero or more characters
8984 in the message. For example, you can use @code{pragma Warning_As_Error
8985 ("bits of*unused")} to treat the warning message @code{warning: 960 bits of
8986 "a" unused} as an error. All characters other than asterisk are treated
8987 as literal characters in the match. The match is case insensitive; for
8988 example XYZ matches xyz.
8990 Note that the pattern matches if it occurs anywhere within the warning
8991 message string (it is not necessary to put an asterisk at the start and
8992 the end of the message, since this is implied).
8994 Another possibility for the static_string_EXPRESSION which works whether
8995 or not error tags are enabled (@emph{-gnatw.d}) is to use the
8996 @emph{-gnatw} tag string, enclosed in brackets,
8997 as shown in the example below, to treat a class of warnings as errors.
8999 The above use of patterns to match the message applies only to warning
9000 messages generated by the front end. This pragma can also be applied to
9001 warnings provided by the back end and mentioned in @ref{121,,Pragma Warnings}.
9002 By using a single full @emph{-Wxxx} switch in the pragma, such warnings
9003 can also be treated as errors.
9005 The pragma can appear either in a global configuration pragma file
9006 (e.g. @code{gnat.adc}), or at the start of a file. Given a global
9007 configuration pragma file containing:
9010 pragma Warning_As_Error ("[-gnatwj]");
9013 which will treat all obsolescent feature warnings as errors, the
9014 following program compiles as shown (compile options here are
9015 @emph{-gnatwa.d -gnatl -gnatj55}).
9018 1. pragma Warning_As_Error ("*never assigned*");
9019 2. function Warnerr return String is
9022 >>> error: variable "X" is never read and
9023 never assigned [-gnatwv] [warning-as-error]
9027 >>> warning: variable "Y" is assigned but
9028 never read [-gnatwu]
9034 >>> error: use of "%" is an obsolescent
9035 feature (RM J.2(4)), use """ instead
9036 [-gnatwj] [warning-as-error]
9040 8 lines: No errors, 3 warnings (2 treated as errors)
9043 Note that this pragma does not affect the set of warnings issued in
9044 any way, it merely changes the effect of a matching warning if one
9045 is produced as a result of other warnings options. As shown in this
9046 example, if the pragma results in a warning being treated as an error,
9047 the tag is changed from "warning:" to "error:" and the string
9048 "[warning-as-error]" is appended to the end of the message.
9050 @node Pragma Warnings,Pragma Weak_External,Pragma Warning_As_Error,Implementation Defined Pragmas
9051 @anchor{gnat_rm/implementation_defined_pragmas id57}@anchor{122}@anchor{gnat_rm/implementation_defined_pragmas pragma-warnings}@anchor{121}
9052 @section Pragma Warnings
9058 pragma Warnings ([TOOL_NAME,] DETAILS [, REASON]);
9060 DETAILS ::= On | Off
9061 DETAILS ::= On | Off, local_NAME
9062 DETAILS ::= static_string_EXPRESSION
9063 DETAILS ::= On | Off, static_string_EXPRESSION
9065 TOOL_NAME ::= GNAT | GNATProve
9067 REASON ::= Reason => STRING_LITERAL @{& STRING_LITERAL@}
9070 Note: in Ada 83 mode, a string literal may be used in place of a static string
9071 expression (which does not exist in Ada 83).
9073 Note if the second argument of @code{DETAILS} is a @code{local_NAME} then the
9074 second form is always understood. If the intention is to use
9075 the fourth form, then you can write @code{NAME & ""} to force the
9076 intepretation as a @emph{static_string_EXPRESSION}.
9078 Note: if the first argument is a valid @code{TOOL_NAME}, it will be interpreted
9079 that way. The use of the @code{TOOL_NAME} argument is relevant only to users
9080 of SPARK and GNATprove, see last part of this section for details.
9082 Normally warnings are enabled, with the output being controlled by
9083 the command line switch. Warnings (@code{Off}) turns off generation of
9084 warnings until a Warnings (@code{On}) is encountered or the end of the
9085 current unit. If generation of warnings is turned off using this
9086 pragma, then some or all of the warning messages are suppressed,
9087 regardless of the setting of the command line switches.
9089 The @code{Reason} parameter may optionally appear as the last argument
9090 in any of the forms of this pragma. It is intended purely for the
9091 purposes of documenting the reason for the @code{Warnings} pragma.
9092 The compiler will check that the argument is a static string but
9093 otherwise ignore this argument. Other tools may provide specialized
9094 processing for this string.
9096 The form with a single argument (or two arguments if Reason present),
9097 where the first argument is @code{ON} or @code{OFF}
9098 may be used as a configuration pragma.
9100 If the @code{LOCAL_NAME} parameter is present, warnings are suppressed for
9101 the specified entity. This suppression is effective from the point where
9102 it occurs till the end of the extended scope of the variable (similar to
9103 the scope of @code{Suppress}). This form cannot be used as a configuration
9106 In the case where the first argument is other than @code{ON} or
9108 the third form with a single static_string_EXPRESSION argument (and possible
9109 reason) provides more precise
9110 control over which warnings are active. The string is a list of letters
9111 specifying which warnings are to be activated and which deactivated. The
9112 code for these letters is the same as the string used in the command
9113 line switch controlling warnings. For a brief summary, use the gnatmake
9114 command with no arguments, which will generate usage information containing
9115 the list of warnings switches supported. For
9116 full details see the section on @code{Warning Message Control} in the
9117 @cite{GNAT User's Guide}.
9118 This form can also be used as a configuration pragma.
9120 The warnings controlled by the @code{-gnatw} switch are generated by the
9121 front end of the compiler. The GCC back end can provide additional warnings
9122 and they are controlled by the @code{-W} switch. Such warnings can be
9123 identified by the appearance of a string of the form @code{[-W@{xxx@}]} in the
9124 message which designates the @code{-W@emph{xxx}} switch that controls the message.
9125 The form with a single @emph{static_string_EXPRESSION} argument also works for these
9126 warnings, but the string must be a single full @code{-W@emph{xxx}} switch in this
9127 case. The above reference lists a few examples of these additional warnings.
9129 The specified warnings will be in effect until the end of the program
9130 or another pragma @code{Warnings} is encountered. The effect of the pragma is
9131 cumulative. Initially the set of warnings is the standard default set
9132 as possibly modified by compiler switches. Then each pragma Warning
9133 modifies this set of warnings as specified. This form of the pragma may
9134 also be used as a configuration pragma.
9136 The fourth form, with an @code{On|Off} parameter and a string, is used to
9137 control individual messages, based on their text. The string argument
9138 is a pattern that is used to match against the text of individual
9139 warning messages (not including the initial "warning: " tag).
9141 The pattern may contain asterisks, which match zero or more characters in
9142 the message. For example, you can use
9143 @code{pragma Warnings (Off, "bits of*unused")} to suppress the warning
9144 message @code{warning: 960 bits of "a" unused}. No other regular
9145 expression notations are permitted. All characters other than asterisk in
9146 these three specific cases are treated as literal characters in the match.
9147 The match is case insensitive, for example XYZ matches xyz.
9149 Note that the pattern matches if it occurs anywhere within the warning
9150 message string (it is not necessary to put an asterisk at the start and
9151 the end of the message, since this is implied).
9153 The above use of patterns to match the message applies only to warning
9154 messages generated by the front end. This form of the pragma with a string
9155 argument can also be used to control warnings provided by the back end and
9156 mentioned above. By using a single full @code{-W@emph{xxx}} switch in the pragma,
9157 such warnings can be turned on and off.
9159 There are two ways to use the pragma in this form. The OFF form can be used
9160 as a configuration pragma. The effect is to suppress all warnings (if any)
9161 that match the pattern string throughout the compilation (or match the
9162 -W switch in the back end case).
9164 The second usage is to suppress a warning locally, and in this case, two
9165 pragmas must appear in sequence:
9168 pragma Warnings (Off, Pattern);
9169 ... code where given warning is to be suppressed
9170 pragma Warnings (On, Pattern);
9173 In this usage, the pattern string must match in the Off and On
9174 pragmas, and (if @emph{-gnatw.w} is given) at least one matching
9175 warning must be suppressed.
9177 Note: if the ON form is not found, then the effect of the OFF form extends
9178 until the end of the file (pragma Warnings is purely textual, so its effect
9179 does not stop at the end of the enclosing scope).
9181 Note: to write a string that will match any warning, use the string
9182 @code{"***"}. It will not work to use a single asterisk or two
9183 asterisks since this looks like an operator name. This form with three
9184 asterisks is similar in effect to specifying @code{pragma Warnings (Off)} except (if @code{-gnatw.w} is given) that a matching
9185 @code{pragma Warnings (On, "***")} will be required. This can be
9186 helpful in avoiding forgetting to turn warnings back on.
9188 Note: the debug flag @code{-gnatd.i} (@code{/NOWARNINGS_PRAGMAS} in VMS) can be
9189 used to cause the compiler to entirely ignore all WARNINGS pragmas. This can
9190 be useful in checking whether obsolete pragmas in existing programs are hiding
9193 Note: pragma Warnings does not affect the processing of style messages. See
9194 separate entry for pragma Style_Checks for control of style messages.
9196 Users of the formal verification tool GNATprove for the SPARK subset of Ada may
9197 use the version of the pragma with a @code{TOOL_NAME} parameter.
9199 If present, @code{TOOL_NAME} is the name of a tool, currently either @code{GNAT} for the
9200 compiler or @code{GNATprove} for the formal verification tool. A given tool only
9201 takes into account pragma Warnings that do not specify a tool name, or that
9202 specify the matching tool name. This makes it possible to disable warnings
9203 selectively for each tool, and as a consequence to detect useless pragma
9204 Warnings with switch @code{-gnatw.w}.
9206 @node Pragma Weak_External,Pragma Wide_Character_Encoding,Pragma Warnings,Implementation Defined Pragmas
9207 @anchor{gnat_rm/implementation_defined_pragmas pragma-weak-external}@anchor{123}
9208 @section Pragma Weak_External
9214 pragma Weak_External ([Entity =>] LOCAL_NAME);
9217 @code{LOCAL_NAME} must refer to an object that is declared at the library
9218 level. This pragma specifies that the given entity should be marked as a
9219 weak symbol for the linker. It is equivalent to @code{__attribute__((weak))}
9220 in GNU C and causes @code{LOCAL_NAME} to be emitted as a weak symbol instead
9221 of a regular symbol, that is to say a symbol that does not have to be
9222 resolved by the linker if used in conjunction with a pragma Import.
9224 When a weak symbol is not resolved by the linker, its address is set to
9225 zero. This is useful in writing interfaces to external modules that may
9226 or may not be linked in the final executable, for example depending on
9227 configuration settings.
9229 If a program references at run time an entity to which this pragma has been
9230 applied, and the corresponding symbol was not resolved at link time, then
9231 the execution of the program is erroneous. It is not erroneous to take the
9232 Address of such an entity, for example to guard potential references,
9233 as shown in the example below.
9235 Some file formats do not support weak symbols so not all target machines
9236 support this pragma.
9239 -- Example of the use of pragma Weak_External
9241 package External_Module is
9243 pragma Import (C, key);
9244 pragma Weak_External (key);
9245 function Present return boolean;
9246 end External_Module;
9248 with System; use System;
9249 package body External_Module is
9250 function Present return boolean is
9252 return key'Address /= System.Null_Address;
9254 end External_Module;
9257 @node Pragma Wide_Character_Encoding,,Pragma Weak_External,Implementation Defined Pragmas
9258 @anchor{gnat_rm/implementation_defined_pragmas pragma-wide-character-encoding}@anchor{124}
9259 @section Pragma Wide_Character_Encoding
9265 pragma Wide_Character_Encoding (IDENTIFIER | CHARACTER_LITERAL);
9268 This pragma specifies the wide character encoding to be used in program
9269 source text appearing subsequently. It is a configuration pragma, but may
9270 also be used at any point that a pragma is allowed, and it is permissible
9271 to have more than one such pragma in a file, allowing multiple encodings
9272 to appear within the same file.
9274 However, note that the pragma cannot immediately precede the relevant
9275 wide character, because then the previous encoding will still be in
9276 effect, causing "illegal character" errors.
9278 The argument can be an identifier or a character literal. In the identifier
9279 case, it is one of @code{HEX}, @code{UPPER}, @code{SHIFT_JIS},
9280 @code{EUC}, @code{UTF8}, or @code{BRACKETS}. In the character literal
9281 case it is correspondingly one of the characters @code{h}, @code{u},
9282 @code{s}, @code{e}, @code{8}, or @code{b}.
9284 Note that when the pragma is used within a file, it affects only the
9285 encoding within that file, and does not affect withed units, specs,
9288 @node Implementation Defined Aspects,Implementation Defined Attributes,Implementation Defined Pragmas,Top
9289 @anchor{gnat_rm/implementation_defined_aspects implementation-defined-aspects}@anchor{125}@anchor{gnat_rm/implementation_defined_aspects doc}@anchor{126}@anchor{gnat_rm/implementation_defined_aspects id1}@anchor{127}
9290 @chapter Implementation Defined Aspects
9293 Ada defines (throughout the Ada 2012 reference manual, summarized
9294 in Annex K) a set of aspects that can be specified for certain entities.
9295 These language defined aspects are implemented in GNAT in Ada 2012 mode
9296 and work as described in the Ada 2012 Reference Manual.
9298 In addition, Ada 2012 allows implementations to define additional aspects
9299 whose meaning is defined by the implementation. GNAT provides
9300 a number of these implementation-defined aspects which can be used
9301 to extend and enhance the functionality of the compiler. This section of
9302 the GNAT reference manual describes these additional aspects.
9304 Note that any program using these aspects may not be portable to
9305 other compilers (although GNAT implements this set of aspects on all
9306 platforms). Therefore if portability to other compilers is an important
9307 consideration, you should minimize the use of these aspects.
9309 Note that for many of these aspects, the effect is essentially similar
9310 to the use of a pragma or attribute specification with the same name
9311 applied to the entity. For example, if we write:
9314 type R is range 1 .. 100
9315 with Value_Size => 10;
9318 then the effect is the same as:
9321 type R is range 1 .. 100;
9322 for R'Value_Size use 10;
9328 type R is new Integer
9329 with Shared => True;
9332 then the effect is the same as:
9335 type R is new Integer;
9339 In the documentation below, such cases are simply marked
9340 as being boolean aspects equivalent to the corresponding pragma
9341 or attribute definition clause.
9344 * Aspect Abstract_State::
9346 * Aspect Async_Readers::
9347 * Aspect Async_Writers::
9348 * Aspect Constant_After_Elaboration::
9349 * Aspect Contract_Cases::
9351 * Aspect Default_Initial_Condition::
9352 * Aspect Dimension::
9353 * Aspect Dimension_System::
9354 * Aspect Disable_Controlled::
9355 * Aspect Effective_Reads::
9356 * Aspect Effective_Writes::
9357 * Aspect Extensions_Visible::
9358 * Aspect Favor_Top_Level::
9361 * Aspect Initial_Condition::
9362 * Aspect Initializes::
9363 * Aspect Inline_Always::
9364 * Aspect Invariant::
9365 * Aspect Invariant'Class::
9367 * Aspect Linker_Section::
9368 * Aspect Lock_Free::
9369 * Aspect Max_Queue_Length::
9370 * Aspect No_Caching::
9371 * Aspect No_Elaboration_Code_All::
9372 * Aspect No_Inline::
9373 * Aspect No_Tagged_Streams::
9374 * Aspect Object_Size::
9375 * Aspect Obsolescent::
9377 * Aspect Persistent_BSS::
9378 * Aspect Predicate::
9379 * Aspect Pure_Function::
9380 * Aspect Refined_Depends::
9381 * Aspect Refined_Global::
9382 * Aspect Refined_Post::
9383 * Aspect Refined_State::
9384 * Aspect Remote_Access_Type::
9385 * Aspect Secondary_Stack_Size::
9386 * Aspect Scalar_Storage_Order::
9388 * Aspect Simple_Storage_Pool::
9389 * Aspect Simple_Storage_Pool_Type::
9390 * Aspect SPARK_Mode::
9391 * Aspect Suppress_Debug_Info::
9392 * Aspect Suppress_Initialization::
9393 * Aspect Test_Case::
9394 * Aspect Thread_Local_Storage::
9395 * Aspect Universal_Aliasing::
9396 * Aspect Universal_Data::
9397 * Aspect Unmodified::
9398 * Aspect Unreferenced::
9399 * Aspect Unreferenced_Objects::
9400 * Aspect Value_Size::
9401 * Aspect Volatile_Full_Access::
9402 * Aspect Volatile_Function::
9407 @node Aspect Abstract_State,Aspect Annotate,,Implementation Defined Aspects
9408 @anchor{gnat_rm/implementation_defined_aspects aspect-abstract-state}@anchor{128}
9409 @section Aspect Abstract_State
9412 @geindex Abstract_State
9414 This aspect is equivalent to @ref{1c,,pragma Abstract_State}.
9416 @node Aspect Annotate,Aspect Async_Readers,Aspect Abstract_State,Implementation Defined Aspects
9417 @anchor{gnat_rm/implementation_defined_aspects aspect-annotate}@anchor{129}
9418 @section Aspect Annotate
9423 There are three forms of this aspect (where ID is an identifier,
9424 and ARG is a general expression),
9425 corresponding to @ref{29,,pragma Annotate}.
9430 @item @emph{Annotate => ID}
9432 Equivalent to @code{pragma Annotate (ID, Entity => Name);}
9434 @item @emph{Annotate => (ID)}
9436 Equivalent to @code{pragma Annotate (ID, Entity => Name);}
9438 @item @emph{Annotate => (ID ,ID @{, ARG@})}
9440 Equivalent to @code{pragma Annotate (ID, ID @{, ARG@}, Entity => Name);}
9443 @node Aspect Async_Readers,Aspect Async_Writers,Aspect Annotate,Implementation Defined Aspects
9444 @anchor{gnat_rm/implementation_defined_aspects aspect-async-readers}@anchor{12a}
9445 @section Aspect Async_Readers
9448 @geindex Async_Readers
9450 This boolean aspect is equivalent to @ref{30,,pragma Async_Readers}.
9452 @node Aspect Async_Writers,Aspect Constant_After_Elaboration,Aspect Async_Readers,Implementation Defined Aspects
9453 @anchor{gnat_rm/implementation_defined_aspects aspect-async-writers}@anchor{12b}
9454 @section Aspect Async_Writers
9457 @geindex Async_Writers
9459 This boolean aspect is equivalent to @ref{33,,pragma Async_Writers}.
9461 @node Aspect Constant_After_Elaboration,Aspect Contract_Cases,Aspect Async_Writers,Implementation Defined Aspects
9462 @anchor{gnat_rm/implementation_defined_aspects aspect-constant-after-elaboration}@anchor{12c}
9463 @section Aspect Constant_After_Elaboration
9466 @geindex Constant_After_Elaboration
9468 This aspect is equivalent to @ref{44,,pragma Constant_After_Elaboration}.
9470 @node Aspect Contract_Cases,Aspect Depends,Aspect Constant_After_Elaboration,Implementation Defined Aspects
9471 @anchor{gnat_rm/implementation_defined_aspects aspect-contract-cases}@anchor{12d}
9472 @section Aspect Contract_Cases
9475 @geindex Contract_Cases
9477 This aspect is equivalent to @ref{46,,pragma Contract_Cases}, the sequence
9478 of clauses being enclosed in parentheses so that syntactically it is an
9481 @node Aspect Depends,Aspect Default_Initial_Condition,Aspect Contract_Cases,Implementation Defined Aspects
9482 @anchor{gnat_rm/implementation_defined_aspects aspect-depends}@anchor{12e}
9483 @section Aspect Depends
9488 This aspect is equivalent to @ref{55,,pragma Depends}.
9490 @node Aspect Default_Initial_Condition,Aspect Dimension,Aspect Depends,Implementation Defined Aspects
9491 @anchor{gnat_rm/implementation_defined_aspects aspect-default-initial-condition}@anchor{12f}
9492 @section Aspect Default_Initial_Condition
9495 @geindex Default_Initial_Condition
9497 This aspect is equivalent to @ref{50,,pragma Default_Initial_Condition}.
9499 @node Aspect Dimension,Aspect Dimension_System,Aspect Default_Initial_Condition,Implementation Defined Aspects
9500 @anchor{gnat_rm/implementation_defined_aspects aspect-dimension}@anchor{130}
9501 @section Aspect Dimension
9506 The @code{Dimension} aspect is used to specify the dimensions of a given
9507 subtype of a dimensioned numeric type. The aspect also specifies a symbol
9508 used when doing formatted output of dimensioned quantities. The syntax is:
9512 ([Symbol =>] SYMBOL, DIMENSION_VALUE @{, DIMENSION_Value@})
9514 SYMBOL ::= STRING_LITERAL | CHARACTER_LITERAL
9518 | others => RATIONAL
9519 | DISCRETE_CHOICE_LIST => RATIONAL
9521 RATIONAL ::= [-] NUMERIC_LITERAL [/ NUMERIC_LITERAL]
9524 This aspect can only be applied to a subtype whose parent type has
9525 a @code{Dimension_System} aspect. The aspect must specify values for
9526 all dimensions of the system. The rational values are the powers of the
9527 corresponding dimensions that are used by the compiler to verify that
9528 physical (numeric) computations are dimensionally consistent. For example,
9529 the computation of a force must result in dimensions (L => 1, M => 1, T => -2).
9530 For further examples of the usage
9531 of this aspect, see package @code{System.Dim.Mks}.
9532 Note that when the dimensioned type is an integer type, then any
9533 dimension value must be an integer literal.
9535 @node Aspect Dimension_System,Aspect Disable_Controlled,Aspect Dimension,Implementation Defined Aspects
9536 @anchor{gnat_rm/implementation_defined_aspects aspect-dimension-system}@anchor{131}
9537 @section Aspect Dimension_System
9540 @geindex Dimension_System
9542 The @code{Dimension_System} aspect is used to define a system of
9543 dimensions that will be used in subsequent subtype declarations with
9544 @code{Dimension} aspects that reference this system. The syntax is:
9547 with Dimension_System => (DIMENSION @{, DIMENSION@});
9549 DIMENSION ::= ([Unit_Name =>] IDENTIFIER,
9550 [Unit_Symbol =>] SYMBOL,
9551 [Dim_Symbol =>] SYMBOL)
9553 SYMBOL ::= CHARACTER_LITERAL | STRING_LITERAL
9556 This aspect is applied to a type, which must be a numeric derived type
9557 (typically a floating-point type), that
9558 will represent values within the dimension system. Each @code{DIMENSION}
9559 corresponds to one particular dimension. A maximum of 7 dimensions may
9560 be specified. @code{Unit_Name} is the name of the dimension (for example
9561 @code{Meter}). @code{Unit_Symbol} is the shorthand used for quantities
9562 of this dimension (for example @code{m} for @code{Meter}).
9563 @code{Dim_Symbol} gives
9564 the identification within the dimension system (typically this is a
9565 single letter, e.g. @code{L} standing for length for unit name @code{Meter}).
9566 The @code{Unit_Symbol} is used in formatted output of dimensioned quantities.
9567 The @code{Dim_Symbol} is used in error messages when numeric operations have
9568 inconsistent dimensions.
9570 GNAT provides the standard definition of the International MKS system in
9571 the run-time package @code{System.Dim.Mks}. You can easily define
9572 similar packages for cgs units or British units, and define conversion factors
9573 between values in different systems. The MKS system is characterized by the
9577 type Mks_Type is new Long_Long_Float with
9578 Dimension_System => (
9579 (Unit_Name => Meter, Unit_Symbol => 'm', Dim_Symbol => 'L'),
9580 (Unit_Name => Kilogram, Unit_Symbol => "kg", Dim_Symbol => 'M'),
9581 (Unit_Name => Second, Unit_Symbol => 's', Dim_Symbol => 'T'),
9582 (Unit_Name => Ampere, Unit_Symbol => 'A', Dim_Symbol => 'I'),
9583 (Unit_Name => Kelvin, Unit_Symbol => 'K', Dim_Symbol => '@@'),
9584 (Unit_Name => Mole, Unit_Symbol => "mol", Dim_Symbol => 'N'),
9585 (Unit_Name => Candela, Unit_Symbol => "cd", Dim_Symbol => 'J'));
9588 Note that in the above type definition, we use the @code{at} symbol (@code{@@}) to
9589 represent a theta character (avoiding the use of extended Latin-1
9590 characters in this context).
9592 See section 'Performing Dimensionality Analysis in GNAT' in the GNAT Users
9593 Guide for detailed examples of use of the dimension system.
9595 @node Aspect Disable_Controlled,Aspect Effective_Reads,Aspect Dimension_System,Implementation Defined Aspects
9596 @anchor{gnat_rm/implementation_defined_aspects aspect-disable-controlled}@anchor{132}
9597 @section Aspect Disable_Controlled
9600 @geindex Disable_Controlled
9602 The aspect @code{Disable_Controlled} is defined for controlled record types. If
9603 active, this aspect causes suppression of all related calls to @code{Initialize},
9604 @code{Adjust}, and @code{Finalize}. The intended use is for conditional compilation,
9605 where for example you might want a record to be controlled or not depending on
9606 whether some run-time check is enabled or suppressed.
9608 @node Aspect Effective_Reads,Aspect Effective_Writes,Aspect Disable_Controlled,Implementation Defined Aspects
9609 @anchor{gnat_rm/implementation_defined_aspects aspect-effective-reads}@anchor{133}
9610 @section Aspect Effective_Reads
9613 @geindex Effective_Reads
9615 This aspect is equivalent to @ref{5b,,pragma Effective_Reads}.
9617 @node Aspect Effective_Writes,Aspect Extensions_Visible,Aspect Effective_Reads,Implementation Defined Aspects
9618 @anchor{gnat_rm/implementation_defined_aspects aspect-effective-writes}@anchor{134}
9619 @section Aspect Effective_Writes
9622 @geindex Effective_Writes
9624 This aspect is equivalent to @ref{5d,,pragma Effective_Writes}.
9626 @node Aspect Extensions_Visible,Aspect Favor_Top_Level,Aspect Effective_Writes,Implementation Defined Aspects
9627 @anchor{gnat_rm/implementation_defined_aspects aspect-extensions-visible}@anchor{135}
9628 @section Aspect Extensions_Visible
9631 @geindex Extensions_Visible
9633 This aspect is equivalent to @ref{69,,pragma Extensions_Visible}.
9635 @node Aspect Favor_Top_Level,Aspect Ghost,Aspect Extensions_Visible,Implementation Defined Aspects
9636 @anchor{gnat_rm/implementation_defined_aspects aspect-favor-top-level}@anchor{136}
9637 @section Aspect Favor_Top_Level
9640 @geindex Favor_Top_Level
9642 This boolean aspect is equivalent to @ref{6e,,pragma Favor_Top_Level}.
9644 @node Aspect Ghost,Aspect Global,Aspect Favor_Top_Level,Implementation Defined Aspects
9645 @anchor{gnat_rm/implementation_defined_aspects aspect-ghost}@anchor{137}
9646 @section Aspect Ghost
9651 This aspect is equivalent to @ref{71,,pragma Ghost}.
9653 @node Aspect Global,Aspect Initial_Condition,Aspect Ghost,Implementation Defined Aspects
9654 @anchor{gnat_rm/implementation_defined_aspects aspect-global}@anchor{138}
9655 @section Aspect Global
9660 This aspect is equivalent to @ref{73,,pragma Global}.
9662 @node Aspect Initial_Condition,Aspect Initializes,Aspect Global,Implementation Defined Aspects
9663 @anchor{gnat_rm/implementation_defined_aspects aspect-initial-condition}@anchor{139}
9664 @section Aspect Initial_Condition
9667 @geindex Initial_Condition
9669 This aspect is equivalent to @ref{81,,pragma Initial_Condition}.
9671 @node Aspect Initializes,Aspect Inline_Always,Aspect Initial_Condition,Implementation Defined Aspects
9672 @anchor{gnat_rm/implementation_defined_aspects aspect-initializes}@anchor{13a}
9673 @section Aspect Initializes
9676 @geindex Initializes
9678 This aspect is equivalent to @ref{83,,pragma Initializes}.
9680 @node Aspect Inline_Always,Aspect Invariant,Aspect Initializes,Implementation Defined Aspects
9681 @anchor{gnat_rm/implementation_defined_aspects aspect-inline-always}@anchor{13b}
9682 @section Aspect Inline_Always
9685 @geindex Inline_Always
9687 This boolean aspect is equivalent to @ref{86,,pragma Inline_Always}.
9689 @node Aspect Invariant,Aspect Invariant'Class,Aspect Inline_Always,Implementation Defined Aspects
9690 @anchor{gnat_rm/implementation_defined_aspects aspect-invariant}@anchor{13c}
9691 @section Aspect Invariant
9696 This aspect is equivalent to @ref{8d,,pragma Invariant}. It is a
9697 synonym for the language defined aspect @code{Type_Invariant} except
9698 that it is separately controllable using pragma @code{Assertion_Policy}.
9700 @node Aspect Invariant'Class,Aspect Iterable,Aspect Invariant,Implementation Defined Aspects
9701 @anchor{gnat_rm/implementation_defined_aspects aspect-invariant-class}@anchor{13d}
9702 @section Aspect Invariant'Class
9705 @geindex Invariant'Class
9707 This aspect is equivalent to @ref{106,,pragma Type_Invariant_Class}. It is a
9708 synonym for the language defined aspect @code{Type_Invariant'Class} except
9709 that it is separately controllable using pragma @code{Assertion_Policy}.
9711 @node Aspect Iterable,Aspect Linker_Section,Aspect Invariant'Class,Implementation Defined Aspects
9712 @anchor{gnat_rm/implementation_defined_aspects aspect-iterable}@anchor{13e}
9713 @section Aspect Iterable
9718 This aspect provides a light-weight mechanism for loops and quantified
9719 expressions over container types, without the overhead imposed by the tampering
9720 checks of standard Ada 2012 iterators. The value of the aspect is an aggregate
9721 with six named components, of which the last three are optional: @code{First},
9722 @code{Next}, @code{Has_Element}, @code{Element}, @code{Last}, and @code{Previous}.
9723 When only the first three components are specified, only the
9724 @code{for .. in} form of iteration over cursors is available. When @code{Element}
9725 is specified, both this form and the @code{for .. of} form of iteration over
9726 elements are available. If the last two components are specified, reverse
9727 iterations over the container can be specified (analogous to what can be done
9728 over predefined containers that support the @code{Reverse_Iterator} interface).
9729 The following is a typical example of use:
9732 type List is private with
9733 Iterable => (First => First_Cursor,
9735 Has_Element => Cursor_Has_Element,
9736 [Element => Get_Element]);
9743 The value denoted by @code{First} must denote a primitive operation of the
9744 container type that returns a @code{Cursor}, which must a be a type declared in
9745 the container package or visible from it. For example:
9749 function First_Cursor (Cont : Container) return Cursor;
9756 The value of @code{Next} is a primitive operation of the container type that takes
9757 both a container and a cursor and yields a cursor. For example:
9761 function Advance (Cont : Container; Position : Cursor) return Cursor;
9768 The value of @code{Has_Element} is a primitive operation of the container type
9769 that takes both a container and a cursor and yields a boolean. For example:
9773 function Cursor_Has_Element (Cont : Container; Position : Cursor) return Boolean;
9780 The value of @code{Element} is a primitive operation of the container type that
9781 takes both a container and a cursor and yields an @code{Element_Type}, which must
9782 be a type declared in the container package or visible from it. For example:
9786 function Get_Element (Cont : Container; Position : Cursor) return Element_Type;
9789 This aspect is used in the GNAT-defined formal container packages.
9791 @node Aspect Linker_Section,Aspect Lock_Free,Aspect Iterable,Implementation Defined Aspects
9792 @anchor{gnat_rm/implementation_defined_aspects aspect-linker-section}@anchor{13f}
9793 @section Aspect Linker_Section
9796 @geindex Linker_Section
9798 This aspect is equivalent to @ref{95,,pragma Linker_Section}.
9800 @node Aspect Lock_Free,Aspect Max_Queue_Length,Aspect Linker_Section,Implementation Defined Aspects
9801 @anchor{gnat_rm/implementation_defined_aspects aspect-lock-free}@anchor{140}
9802 @section Aspect Lock_Free
9807 This boolean aspect is equivalent to @ref{97,,pragma Lock_Free}.
9809 @node Aspect Max_Queue_Length,Aspect No_Caching,Aspect Lock_Free,Implementation Defined Aspects
9810 @anchor{gnat_rm/implementation_defined_aspects aspect-max-queue-length}@anchor{141}
9811 @section Aspect Max_Queue_Length
9814 @geindex Max_Queue_Length
9816 This aspect is equivalent to @ref{9f,,pragma Max_Queue_Length}.
9818 @node Aspect No_Caching,Aspect No_Elaboration_Code_All,Aspect Max_Queue_Length,Implementation Defined Aspects
9819 @anchor{gnat_rm/implementation_defined_aspects aspect-no-caching}@anchor{142}
9820 @section Aspect No_Caching
9825 This boolean aspect is equivalent to @ref{a1,,pragma No_Caching}.
9827 @node Aspect No_Elaboration_Code_All,Aspect No_Inline,Aspect No_Caching,Implementation Defined Aspects
9828 @anchor{gnat_rm/implementation_defined_aspects aspect-no-elaboration-code-all}@anchor{143}
9829 @section Aspect No_Elaboration_Code_All
9832 @geindex No_Elaboration_Code_All
9834 This aspect is equivalent to @ref{a5,,pragma No_Elaboration_Code_All}
9837 @node Aspect No_Inline,Aspect No_Tagged_Streams,Aspect No_Elaboration_Code_All,Implementation Defined Aspects
9838 @anchor{gnat_rm/implementation_defined_aspects aspect-no-inline}@anchor{144}
9839 @section Aspect No_Inline
9844 This boolean aspect is equivalent to @ref{a8,,pragma No_Inline}.
9846 @node Aspect No_Tagged_Streams,Aspect Object_Size,Aspect No_Inline,Implementation Defined Aspects
9847 @anchor{gnat_rm/implementation_defined_aspects aspect-no-tagged-streams}@anchor{145}
9848 @section Aspect No_Tagged_Streams
9851 @geindex No_Tagged_Streams
9853 This aspect is equivalent to @ref{ac,,pragma No_Tagged_Streams} with an
9854 argument specifying a root tagged type (thus this aspect can only be
9855 applied to such a type).
9857 @node Aspect Object_Size,Aspect Obsolescent,Aspect No_Tagged_Streams,Implementation Defined Aspects
9858 @anchor{gnat_rm/implementation_defined_aspects aspect-object-size}@anchor{146}
9859 @section Aspect Object_Size
9862 @geindex Object_Size
9864 This aspect is equivalent to @ref{147,,attribute Object_Size}.
9866 @node Aspect Obsolescent,Aspect Part_Of,Aspect Object_Size,Implementation Defined Aspects
9867 @anchor{gnat_rm/implementation_defined_aspects aspect-obsolescent}@anchor{148}
9868 @section Aspect Obsolescent
9871 @geindex Obsolsecent
9873 This aspect is equivalent to @ref{af,,pragma Obsolescent}. Note that the
9874 evaluation of this aspect happens at the point of occurrence, it is not
9875 delayed until the freeze point.
9877 @node Aspect Part_Of,Aspect Persistent_BSS,Aspect Obsolescent,Implementation Defined Aspects
9878 @anchor{gnat_rm/implementation_defined_aspects aspect-part-of}@anchor{149}
9879 @section Aspect Part_Of
9884 This aspect is equivalent to @ref{b7,,pragma Part_Of}.
9886 @node Aspect Persistent_BSS,Aspect Predicate,Aspect Part_Of,Implementation Defined Aspects
9887 @anchor{gnat_rm/implementation_defined_aspects aspect-persistent-bss}@anchor{14a}
9888 @section Aspect Persistent_BSS
9891 @geindex Persistent_BSS
9893 This boolean aspect is equivalent to @ref{ba,,pragma Persistent_BSS}.
9895 @node Aspect Predicate,Aspect Pure_Function,Aspect Persistent_BSS,Implementation Defined Aspects
9896 @anchor{gnat_rm/implementation_defined_aspects aspect-predicate}@anchor{14b}
9897 @section Aspect Predicate
9902 This aspect is equivalent to @ref{c2,,pragma Predicate}. It is thus
9903 similar to the language defined aspects @code{Dynamic_Predicate}
9904 and @code{Static_Predicate} except that whether the resulting
9905 predicate is static or dynamic is controlled by the form of the
9906 expression. It is also separately controllable using pragma
9907 @code{Assertion_Policy}.
9909 @node Aspect Pure_Function,Aspect Refined_Depends,Aspect Predicate,Implementation Defined Aspects
9910 @anchor{gnat_rm/implementation_defined_aspects aspect-pure-function}@anchor{14c}
9911 @section Aspect Pure_Function
9914 @geindex Pure_Function
9916 This boolean aspect is equivalent to @ref{ce,,pragma Pure_Function}.
9918 @node Aspect Refined_Depends,Aspect Refined_Global,Aspect Pure_Function,Implementation Defined Aspects
9919 @anchor{gnat_rm/implementation_defined_aspects aspect-refined-depends}@anchor{14d}
9920 @section Aspect Refined_Depends
9923 @geindex Refined_Depends
9925 This aspect is equivalent to @ref{d2,,pragma Refined_Depends}.
9927 @node Aspect Refined_Global,Aspect Refined_Post,Aspect Refined_Depends,Implementation Defined Aspects
9928 @anchor{gnat_rm/implementation_defined_aspects aspect-refined-global}@anchor{14e}
9929 @section Aspect Refined_Global
9932 @geindex Refined_Global
9934 This aspect is equivalent to @ref{d4,,pragma Refined_Global}.
9936 @node Aspect Refined_Post,Aspect Refined_State,Aspect Refined_Global,Implementation Defined Aspects
9937 @anchor{gnat_rm/implementation_defined_aspects aspect-refined-post}@anchor{14f}
9938 @section Aspect Refined_Post
9941 @geindex Refined_Post
9943 This aspect is equivalent to @ref{d6,,pragma Refined_Post}.
9945 @node Aspect Refined_State,Aspect Remote_Access_Type,Aspect Refined_Post,Implementation Defined Aspects
9946 @anchor{gnat_rm/implementation_defined_aspects aspect-refined-state}@anchor{150}
9947 @section Aspect Refined_State
9950 @geindex Refined_State
9952 This aspect is equivalent to @ref{d8,,pragma Refined_State}.
9954 @node Aspect Remote_Access_Type,Aspect Secondary_Stack_Size,Aspect Refined_State,Implementation Defined Aspects
9955 @anchor{gnat_rm/implementation_defined_aspects aspect-remote-access-type}@anchor{151}
9956 @section Aspect Remote_Access_Type
9959 @geindex Remote_Access_Type
9961 This aspect is equivalent to @ref{dc,,pragma Remote_Access_Type}.
9963 @node Aspect Secondary_Stack_Size,Aspect Scalar_Storage_Order,Aspect Remote_Access_Type,Implementation Defined Aspects
9964 @anchor{gnat_rm/implementation_defined_aspects aspect-secondary-stack-size}@anchor{152}
9965 @section Aspect Secondary_Stack_Size
9968 @geindex Secondary_Stack_Size
9970 This aspect is equivalent to @ref{e1,,pragma Secondary_Stack_Size}.
9972 @node Aspect Scalar_Storage_Order,Aspect Shared,Aspect Secondary_Stack_Size,Implementation Defined Aspects
9973 @anchor{gnat_rm/implementation_defined_aspects aspect-scalar-storage-order}@anchor{153}
9974 @section Aspect Scalar_Storage_Order
9977 @geindex Scalar_Storage_Order
9979 This aspect is equivalent to a @ref{154,,attribute Scalar_Storage_Order}.
9981 @node Aspect Shared,Aspect Simple_Storage_Pool,Aspect Scalar_Storage_Order,Implementation Defined Aspects
9982 @anchor{gnat_rm/implementation_defined_aspects aspect-shared}@anchor{155}
9983 @section Aspect Shared
9988 This boolean aspect is equivalent to @ref{e4,,pragma Shared}
9989 and is thus a synonym for aspect @code{Atomic}.
9991 @node Aspect Simple_Storage_Pool,Aspect Simple_Storage_Pool_Type,Aspect Shared,Implementation Defined Aspects
9992 @anchor{gnat_rm/implementation_defined_aspects aspect-simple-storage-pool}@anchor{156}
9993 @section Aspect Simple_Storage_Pool
9996 @geindex Simple_Storage_Pool
9998 This aspect is equivalent to @ref{e9,,attribute Simple_Storage_Pool}.
10000 @node Aspect Simple_Storage_Pool_Type,Aspect SPARK_Mode,Aspect Simple_Storage_Pool,Implementation Defined Aspects
10001 @anchor{gnat_rm/implementation_defined_aspects aspect-simple-storage-pool-type}@anchor{157}
10002 @section Aspect Simple_Storage_Pool_Type
10005 @geindex Simple_Storage_Pool_Type
10007 This boolean aspect is equivalent to @ref{e7,,pragma Simple_Storage_Pool_Type}.
10009 @node Aspect SPARK_Mode,Aspect Suppress_Debug_Info,Aspect Simple_Storage_Pool_Type,Implementation Defined Aspects
10010 @anchor{gnat_rm/implementation_defined_aspects aspect-spark-mode}@anchor{158}
10011 @section Aspect SPARK_Mode
10014 @geindex SPARK_Mode
10016 This aspect is equivalent to @ref{ef,,pragma SPARK_Mode} and
10017 may be specified for either or both of the specification and body
10018 of a subprogram or package.
10020 @node Aspect Suppress_Debug_Info,Aspect Suppress_Initialization,Aspect SPARK_Mode,Implementation Defined Aspects
10021 @anchor{gnat_rm/implementation_defined_aspects aspect-suppress-debug-info}@anchor{159}
10022 @section Aspect Suppress_Debug_Info
10025 @geindex Suppress_Debug_Info
10027 This boolean aspect is equivalent to @ref{f7,,pragma Suppress_Debug_Info}.
10029 @node Aspect Suppress_Initialization,Aspect Test_Case,Aspect Suppress_Debug_Info,Implementation Defined Aspects
10030 @anchor{gnat_rm/implementation_defined_aspects aspect-suppress-initialization}@anchor{15a}
10031 @section Aspect Suppress_Initialization
10034 @geindex Suppress_Initialization
10036 This boolean aspect is equivalent to @ref{fb,,pragma Suppress_Initialization}.
10038 @node Aspect Test_Case,Aspect Thread_Local_Storage,Aspect Suppress_Initialization,Implementation Defined Aspects
10039 @anchor{gnat_rm/implementation_defined_aspects aspect-test-case}@anchor{15b}
10040 @section Aspect Test_Case
10045 This aspect is equivalent to @ref{fe,,pragma Test_Case}.
10047 @node Aspect Thread_Local_Storage,Aspect Universal_Aliasing,Aspect Test_Case,Implementation Defined Aspects
10048 @anchor{gnat_rm/implementation_defined_aspects aspect-thread-local-storage}@anchor{15c}
10049 @section Aspect Thread_Local_Storage
10052 @geindex Thread_Local_Storage
10054 This boolean aspect is equivalent to @ref{100,,pragma Thread_Local_Storage}.
10056 @node Aspect Universal_Aliasing,Aspect Universal_Data,Aspect Thread_Local_Storage,Implementation Defined Aspects
10057 @anchor{gnat_rm/implementation_defined_aspects aspect-universal-aliasing}@anchor{15d}
10058 @section Aspect Universal_Aliasing
10061 @geindex Universal_Aliasing
10063 This boolean aspect is equivalent to @ref{10a,,pragma Universal_Aliasing}.
10065 @node Aspect Universal_Data,Aspect Unmodified,Aspect Universal_Aliasing,Implementation Defined Aspects
10066 @anchor{gnat_rm/implementation_defined_aspects aspect-universal-data}@anchor{15e}
10067 @section Aspect Universal_Data
10070 @geindex Universal_Data
10072 This aspect is equivalent to @ref{10c,,pragma Universal_Data}.
10074 @node Aspect Unmodified,Aspect Unreferenced,Aspect Universal_Data,Implementation Defined Aspects
10075 @anchor{gnat_rm/implementation_defined_aspects aspect-unmodified}@anchor{15f}
10076 @section Aspect Unmodified
10079 @geindex Unmodified
10081 This boolean aspect is equivalent to @ref{10f,,pragma Unmodified}.
10083 @node Aspect Unreferenced,Aspect Unreferenced_Objects,Aspect Unmodified,Implementation Defined Aspects
10084 @anchor{gnat_rm/implementation_defined_aspects aspect-unreferenced}@anchor{160}
10085 @section Aspect Unreferenced
10088 @geindex Unreferenced
10090 This boolean aspect is equivalent to @ref{110,,pragma Unreferenced}. Note that
10091 in the case of formal parameters, it is not permitted to have aspects for
10092 a formal parameter, so in this case the pragma form must be used.
10094 @node Aspect Unreferenced_Objects,Aspect Value_Size,Aspect Unreferenced,Implementation Defined Aspects
10095 @anchor{gnat_rm/implementation_defined_aspects aspect-unreferenced-objects}@anchor{161}
10096 @section Aspect Unreferenced_Objects
10099 @geindex Unreferenced_Objects
10101 This boolean aspect is equivalent to @ref{112,,pragma Unreferenced_Objects}.
10103 @node Aspect Value_Size,Aspect Volatile_Full_Access,Aspect Unreferenced_Objects,Implementation Defined Aspects
10104 @anchor{gnat_rm/implementation_defined_aspects aspect-value-size}@anchor{162}
10105 @section Aspect Value_Size
10108 @geindex Value_Size
10110 This aspect is equivalent to @ref{163,,attribute Value_Size}.
10112 @node Aspect Volatile_Full_Access,Aspect Volatile_Function,Aspect Value_Size,Implementation Defined Aspects
10113 @anchor{gnat_rm/implementation_defined_aspects aspect-volatile-full-access}@anchor{164}
10114 @section Aspect Volatile_Full_Access
10117 @geindex Volatile_Full_Access
10119 This boolean aspect is equivalent to @ref{11d,,pragma Volatile_Full_Access}.
10121 @node Aspect Volatile_Function,Aspect Warnings,Aspect Volatile_Full_Access,Implementation Defined Aspects
10122 @anchor{gnat_rm/implementation_defined_aspects aspect-volatile-function}@anchor{165}
10123 @section Aspect Volatile_Function
10126 @geindex Volatile_Function
10128 This boolean aspect is equivalent to @ref{11f,,pragma Volatile_Function}.
10130 @node Aspect Warnings,,Aspect Volatile_Function,Implementation Defined Aspects
10131 @anchor{gnat_rm/implementation_defined_aspects aspect-warnings}@anchor{166}
10132 @section Aspect Warnings
10137 This aspect is equivalent to the two argument form of @ref{121,,pragma Warnings},
10138 where the first argument is @code{ON} or @code{OFF} and the second argument
10141 @node Implementation Defined Attributes,Standard and Implementation Defined Restrictions,Implementation Defined Aspects,Top
10142 @anchor{gnat_rm/implementation_defined_attributes doc}@anchor{167}@anchor{gnat_rm/implementation_defined_attributes implementation-defined-attributes}@anchor{8}@anchor{gnat_rm/implementation_defined_attributes id1}@anchor{168}
10143 @chapter Implementation Defined Attributes
10146 Ada defines (throughout the Ada reference manual,
10147 summarized in Annex K),
10148 a set of attributes that provide useful additional functionality in all
10149 areas of the language. These language defined attributes are implemented
10150 in GNAT and work as described in the Ada Reference Manual.
10152 In addition, Ada allows implementations to define additional
10153 attributes whose meaning is defined by the implementation. GNAT provides
10154 a number of these implementation-dependent attributes which can be used
10155 to extend and enhance the functionality of the compiler. This section of
10156 the GNAT reference manual describes these additional attributes. It also
10157 describes additional implementation-dependent features of standard
10158 language-defined attributes.
10160 Note that any program using these attributes may not be portable to
10161 other compilers (although GNAT implements this set of attributes on all
10162 platforms). Therefore if portability to other compilers is an important
10163 consideration, you should minimize the use of these attributes.
10166 * Attribute Abort_Signal::
10167 * Attribute Address_Size::
10168 * Attribute Asm_Input::
10169 * Attribute Asm_Output::
10170 * Attribute Atomic_Always_Lock_Free::
10172 * Attribute Bit_Position::
10173 * Attribute Code_Address::
10174 * Attribute Compiler_Version::
10175 * Attribute Constrained::
10176 * Attribute Default_Bit_Order::
10177 * Attribute Default_Scalar_Storage_Order::
10178 * Attribute Deref::
10179 * Attribute Descriptor_Size::
10180 * Attribute Elaborated::
10181 * Attribute Elab_Body::
10182 * Attribute Elab_Spec::
10183 * Attribute Elab_Subp_Body::
10185 * Attribute Enabled::
10186 * Attribute Enum_Rep::
10187 * Attribute Enum_Val::
10188 * Attribute Epsilon::
10189 * Attribute Fast_Math::
10190 * Attribute Finalization_Size::
10191 * Attribute Fixed_Value::
10192 * Attribute From_Any::
10193 * Attribute Has_Access_Values::
10194 * Attribute Has_Discriminants::
10196 * Attribute Integer_Value::
10197 * Attribute Invalid_Value::
10198 * Attribute Iterable::
10199 * Attribute Large::
10200 * Attribute Library_Level::
10201 * Attribute Lock_Free::
10202 * Attribute Loop_Entry::
10203 * Attribute Machine_Size::
10204 * Attribute Mantissa::
10205 * Attribute Maximum_Alignment::
10206 * Attribute Mechanism_Code::
10207 * Attribute Null_Parameter::
10208 * Attribute Object_Size::
10210 * Attribute Passed_By_Reference::
10211 * Attribute Pool_Address::
10212 * Attribute Range_Length::
10213 * Attribute Restriction_Set::
10214 * Attribute Result::
10215 * Attribute Safe_Emax::
10216 * Attribute Safe_Large::
10217 * Attribute Safe_Small::
10218 * Attribute Scalar_Storage_Order::
10219 * Attribute Simple_Storage_Pool::
10220 * Attribute Small::
10221 * Attribute Storage_Unit::
10222 * Attribute Stub_Type::
10223 * Attribute System_Allocator_Alignment::
10224 * Attribute Target_Name::
10225 * Attribute To_Address::
10226 * Attribute To_Any::
10227 * Attribute Type_Class::
10228 * Attribute Type_Key::
10229 * Attribute TypeCode::
10230 * Attribute Unconstrained_Array::
10231 * Attribute Universal_Literal_String::
10232 * Attribute Unrestricted_Access::
10233 * Attribute Update::
10234 * Attribute Valid_Scalars::
10235 * Attribute VADS_Size::
10236 * Attribute Value_Size::
10237 * Attribute Wchar_T_Size::
10238 * Attribute Word_Size::
10242 @node Attribute Abort_Signal,Attribute Address_Size,,Implementation Defined Attributes
10243 @anchor{gnat_rm/implementation_defined_attributes attribute-abort-signal}@anchor{169}
10244 @section Attribute Abort_Signal
10247 @geindex Abort_Signal
10249 @code{Standard'Abort_Signal} (@code{Standard} is the only allowed
10250 prefix) provides the entity for the special exception used to signal
10251 task abort or asynchronous transfer of control. Normally this attribute
10252 should only be used in the tasking runtime (it is highly peculiar, and
10253 completely outside the normal semantics of Ada, for a user program to
10254 intercept the abort exception).
10256 @node Attribute Address_Size,Attribute Asm_Input,Attribute Abort_Signal,Implementation Defined Attributes
10257 @anchor{gnat_rm/implementation_defined_attributes attribute-address-size}@anchor{16a}
10258 @section Attribute Address_Size
10261 @geindex Size of `@w{`}Address`@w{`}
10263 @geindex Address_Size
10265 @code{Standard'Address_Size} (@code{Standard} is the only allowed
10266 prefix) is a static constant giving the number of bits in an
10267 @code{Address}. It is the same value as System.Address'Size,
10268 but has the advantage of being static, while a direct
10269 reference to System.Address'Size is nonstatic because Address
10272 @node Attribute Asm_Input,Attribute Asm_Output,Attribute Address_Size,Implementation Defined Attributes
10273 @anchor{gnat_rm/implementation_defined_attributes attribute-asm-input}@anchor{16b}
10274 @section Attribute Asm_Input
10279 The @code{Asm_Input} attribute denotes a function that takes two
10280 parameters. The first is a string, the second is an expression of the
10281 type designated by the prefix. The first (string) argument is required
10282 to be a static expression, and is the constraint for the parameter,
10283 (e.g., what kind of register is required). The second argument is the
10284 value to be used as the input argument. The possible values for the
10285 constant are the same as those used in the RTL, and are dependent on
10286 the configuration file used to built the GCC back end.
10287 @ref{16c,,Machine Code Insertions}
10289 @node Attribute Asm_Output,Attribute Atomic_Always_Lock_Free,Attribute Asm_Input,Implementation Defined Attributes
10290 @anchor{gnat_rm/implementation_defined_attributes attribute-asm-output}@anchor{16d}
10291 @section Attribute Asm_Output
10294 @geindex Asm_Output
10296 The @code{Asm_Output} attribute denotes a function that takes two
10297 parameters. The first is a string, the second is the name of a variable
10298 of the type designated by the attribute prefix. The first (string)
10299 argument is required to be a static expression and designates the
10300 constraint for the parameter (e.g., what kind of register is
10301 required). The second argument is the variable to be updated with the
10302 result. The possible values for constraint are the same as those used in
10303 the RTL, and are dependent on the configuration file used to build the
10304 GCC back end. If there are no output operands, then this argument may
10305 either be omitted, or explicitly given as @code{No_Output_Operands}.
10306 @ref{16c,,Machine Code Insertions}
10308 @node Attribute Atomic_Always_Lock_Free,Attribute Bit,Attribute Asm_Output,Implementation Defined Attributes
10309 @anchor{gnat_rm/implementation_defined_attributes attribute-atomic-always-lock-free}@anchor{16e}
10310 @section Attribute Atomic_Always_Lock_Free
10313 @geindex Atomic_Always_Lock_Free
10315 The prefix of the @code{Atomic_Always_Lock_Free} attribute is a type.
10316 The result is a Boolean value which is True if the type has discriminants,
10317 and False otherwise. The result indicate whether atomic operations are
10318 supported by the target for the given type.
10320 @node Attribute Bit,Attribute Bit_Position,Attribute Atomic_Always_Lock_Free,Implementation Defined Attributes
10321 @anchor{gnat_rm/implementation_defined_attributes attribute-bit}@anchor{16f}
10322 @section Attribute Bit
10327 @code{obj'Bit}, where @code{obj} is any object, yields the bit
10328 offset within the storage unit (byte) that contains the first bit of
10329 storage allocated for the object. The value of this attribute is of the
10330 type @emph{universal_integer}, and is always a non-negative number not
10331 exceeding the value of @code{System.Storage_Unit}.
10333 For an object that is a variable or a constant allocated in a register,
10334 the value is zero. (The use of this attribute does not force the
10335 allocation of a variable to memory).
10337 For an object that is a formal parameter, this attribute applies
10338 to either the matching actual parameter or to a copy of the
10339 matching actual parameter.
10341 For an access object the value is zero. Note that
10342 @code{obj.all'Bit} is subject to an @code{Access_Check} for the
10343 designated object. Similarly for a record component
10344 @code{X.C'Bit} is subject to a discriminant check and
10345 @code{X(I).Bit} and @code{X(I1..I2)'Bit}
10346 are subject to index checks.
10348 This attribute is designed to be compatible with the DEC Ada 83 definition
10349 and implementation of the @code{Bit} attribute.
10351 @node Attribute Bit_Position,Attribute Code_Address,Attribute Bit,Implementation Defined Attributes
10352 @anchor{gnat_rm/implementation_defined_attributes attribute-bit-position}@anchor{170}
10353 @section Attribute Bit_Position
10356 @geindex Bit_Position
10358 @code{R.C'Bit_Position}, where @code{R} is a record object and @code{C} is one
10359 of the fields of the record type, yields the bit
10360 offset within the record contains the first bit of
10361 storage allocated for the object. The value of this attribute is of the
10362 type @emph{universal_integer}. The value depends only on the field
10363 @code{C} and is independent of the alignment of
10364 the containing record @code{R}.
10366 @node Attribute Code_Address,Attribute Compiler_Version,Attribute Bit_Position,Implementation Defined Attributes
10367 @anchor{gnat_rm/implementation_defined_attributes attribute-code-address}@anchor{171}
10368 @section Attribute Code_Address
10371 @geindex Code_Address
10373 @geindex Subprogram address
10375 @geindex Address of subprogram code
10377 The @code{'Address}
10378 attribute may be applied to subprograms in Ada 95 and Ada 2005, but the
10379 intended effect seems to be to provide
10380 an address value which can be used to call the subprogram by means of
10381 an address clause as in the following example:
10387 for L'Address use K'Address;
10388 pragma Import (Ada, L);
10391 A call to @code{L} is then expected to result in a call to @code{K}.
10392 In Ada 83, where there were no access-to-subprogram values, this was
10393 a common work-around for getting the effect of an indirect call.
10394 GNAT implements the above use of @code{Address} and the technique
10395 illustrated by the example code works correctly.
10397 However, for some purposes, it is useful to have the address of the start
10398 of the generated code for the subprogram. On some architectures, this is
10399 not necessarily the same as the @code{Address} value described above.
10400 For example, the @code{Address} value may reference a subprogram
10401 descriptor rather than the subprogram itself.
10403 The @code{'Code_Address} attribute, which can only be applied to
10404 subprogram entities, always returns the address of the start of the
10405 generated code of the specified subprogram, which may or may not be
10406 the same value as is returned by the corresponding @code{'Address}
10409 @node Attribute Compiler_Version,Attribute Constrained,Attribute Code_Address,Implementation Defined Attributes
10410 @anchor{gnat_rm/implementation_defined_attributes attribute-compiler-version}@anchor{172}
10411 @section Attribute Compiler_Version
10414 @geindex Compiler_Version
10416 @code{Standard'Compiler_Version} (@code{Standard} is the only allowed
10417 prefix) yields a static string identifying the version of the compiler
10418 being used to compile the unit containing the attribute reference.
10420 @node Attribute Constrained,Attribute Default_Bit_Order,Attribute Compiler_Version,Implementation Defined Attributes
10421 @anchor{gnat_rm/implementation_defined_attributes attribute-constrained}@anchor{173}
10422 @section Attribute Constrained
10425 @geindex Constrained
10427 In addition to the usage of this attribute in the Ada RM, GNAT
10428 also permits the use of the @code{'Constrained} attribute
10429 in a generic template
10430 for any type, including types without discriminants. The value of this
10431 attribute in the generic instance when applied to a scalar type or a
10432 record type without discriminants is always @code{True}. This usage is
10433 compatible with older Ada compilers, including notably DEC Ada.
10435 @node Attribute Default_Bit_Order,Attribute Default_Scalar_Storage_Order,Attribute Constrained,Implementation Defined Attributes
10436 @anchor{gnat_rm/implementation_defined_attributes attribute-default-bit-order}@anchor{174}
10437 @section Attribute Default_Bit_Order
10440 @geindex Big endian
10442 @geindex Little endian
10444 @geindex Default_Bit_Order
10446 @code{Standard'Default_Bit_Order} (@code{Standard} is the only
10447 permissible prefix), provides the value @code{System.Default_Bit_Order}
10448 as a @code{Pos} value (0 for @code{High_Order_First}, 1 for
10449 @code{Low_Order_First}). This is used to construct the definition of
10450 @code{Default_Bit_Order} in package @code{System}.
10452 @node Attribute Default_Scalar_Storage_Order,Attribute Deref,Attribute Default_Bit_Order,Implementation Defined Attributes
10453 @anchor{gnat_rm/implementation_defined_attributes attribute-default-scalar-storage-order}@anchor{175}
10454 @section Attribute Default_Scalar_Storage_Order
10457 @geindex Big endian
10459 @geindex Little endian
10461 @geindex Default_Scalar_Storage_Order
10463 @code{Standard'Default_Scalar_Storage_Order} (@code{Standard} is the only
10464 permissible prefix), provides the current value of the default scalar storage
10465 order (as specified using pragma @code{Default_Scalar_Storage_Order}, or
10466 equal to @code{Default_Bit_Order} if unspecified) as a
10467 @code{System.Bit_Order} value. This is a static attribute.
10469 @node Attribute Deref,Attribute Descriptor_Size,Attribute Default_Scalar_Storage_Order,Implementation Defined Attributes
10470 @anchor{gnat_rm/implementation_defined_attributes attribute-deref}@anchor{176}
10471 @section Attribute Deref
10476 The attribute @code{typ'Deref(expr)} where @code{expr} is of type @code{System.Address} yields
10477 the variable of type @code{typ} that is located at the given address. It is similar
10478 to @code{(totyp (expr).all)}, where @code{totyp} is an unchecked conversion from address to
10479 a named access-to-@cite{typ} type, except that it yields a variable, so it can be
10480 used on the left side of an assignment.
10482 @node Attribute Descriptor_Size,Attribute Elaborated,Attribute Deref,Implementation Defined Attributes
10483 @anchor{gnat_rm/implementation_defined_attributes attribute-descriptor-size}@anchor{177}
10484 @section Attribute Descriptor_Size
10487 @geindex Descriptor
10489 @geindex Dope vector
10491 @geindex Descriptor_Size
10493 Nonstatic attribute @code{Descriptor_Size} returns the size in bits of the
10494 descriptor allocated for a type. The result is non-zero only for unconstrained
10495 array types and the returned value is of type universal integer. In GNAT, an
10496 array descriptor contains bounds information and is located immediately before
10497 the first element of the array.
10500 type Unconstr_Array is array (Positive range <>) of Boolean;
10501 Put_Line ("Descriptor size = " & Unconstr_Array'Descriptor_Size'Img);
10504 The attribute takes into account any additional padding due to type alignment.
10505 In the example above, the descriptor contains two values of type
10506 @code{Positive} representing the low and high bound. Since @code{Positive} has
10507 a size of 31 bits and an alignment of 4, the descriptor size is @code{2 * Positive'Size + 2} or 64 bits.
10509 @node Attribute Elaborated,Attribute Elab_Body,Attribute Descriptor_Size,Implementation Defined Attributes
10510 @anchor{gnat_rm/implementation_defined_attributes attribute-elaborated}@anchor{178}
10511 @section Attribute Elaborated
10514 @geindex Elaborated
10516 The prefix of the @code{'Elaborated} attribute must be a unit name. The
10517 value is a Boolean which indicates whether or not the given unit has been
10518 elaborated. This attribute is primarily intended for internal use by the
10519 generated code for dynamic elaboration checking, but it can also be used
10520 in user programs. The value will always be True once elaboration of all
10521 units has been completed. An exception is for units which need no
10522 elaboration, the value is always False for such units.
10524 @node Attribute Elab_Body,Attribute Elab_Spec,Attribute Elaborated,Implementation Defined Attributes
10525 @anchor{gnat_rm/implementation_defined_attributes attribute-elab-body}@anchor{179}
10526 @section Attribute Elab_Body
10531 This attribute can only be applied to a program unit name. It returns
10532 the entity for the corresponding elaboration procedure for elaborating
10533 the body of the referenced unit. This is used in the main generated
10534 elaboration procedure by the binder and is not normally used in any
10535 other context. However, there may be specialized situations in which it
10536 is useful to be able to call this elaboration procedure from Ada code,
10537 e.g., if it is necessary to do selective re-elaboration to fix some
10540 @node Attribute Elab_Spec,Attribute Elab_Subp_Body,Attribute Elab_Body,Implementation Defined Attributes
10541 @anchor{gnat_rm/implementation_defined_attributes attribute-elab-spec}@anchor{17a}
10542 @section Attribute Elab_Spec
10547 This attribute can only be applied to a program unit name. It returns
10548 the entity for the corresponding elaboration procedure for elaborating
10549 the spec of the referenced unit. This is used in the main
10550 generated elaboration procedure by the binder and is not normally used
10551 in any other context. However, there may be specialized situations in
10552 which it is useful to be able to call this elaboration procedure from
10553 Ada code, e.g., if it is necessary to do selective re-elaboration to fix
10556 @node Attribute Elab_Subp_Body,Attribute Emax,Attribute Elab_Spec,Implementation Defined Attributes
10557 @anchor{gnat_rm/implementation_defined_attributes attribute-elab-subp-body}@anchor{17b}
10558 @section Attribute Elab_Subp_Body
10561 @geindex Elab_Subp_Body
10563 This attribute can only be applied to a library level subprogram
10564 name and is only allowed in CodePeer mode. It returns the entity
10565 for the corresponding elaboration procedure for elaborating the body
10566 of the referenced subprogram unit. This is used in the main generated
10567 elaboration procedure by the binder in CodePeer mode only and is unrecognized
10570 @node Attribute Emax,Attribute Enabled,Attribute Elab_Subp_Body,Implementation Defined Attributes
10571 @anchor{gnat_rm/implementation_defined_attributes attribute-emax}@anchor{17c}
10572 @section Attribute Emax
10575 @geindex Ada 83 attributes
10579 The @code{Emax} attribute is provided for compatibility with Ada 83. See
10580 the Ada 83 reference manual for an exact description of the semantics of
10583 @node Attribute Enabled,Attribute Enum_Rep,Attribute Emax,Implementation Defined Attributes
10584 @anchor{gnat_rm/implementation_defined_attributes attribute-enabled}@anchor{17d}
10585 @section Attribute Enabled
10590 The @code{Enabled} attribute allows an application program to check at compile
10591 time to see if the designated check is currently enabled. The prefix is a
10592 simple identifier, referencing any predefined check name (other than
10593 @code{All_Checks}) or a check name introduced by pragma Check_Name. If
10594 no argument is given for the attribute, the check is for the general state
10595 of the check, if an argument is given, then it is an entity name, and the
10596 check indicates whether an @code{Suppress} or @code{Unsuppress} has been
10597 given naming the entity (if not, then the argument is ignored).
10599 Note that instantiations inherit the check status at the point of the
10600 instantiation, so a useful idiom is to have a library package that
10601 introduces a check name with @code{pragma Check_Name}, and then contains
10602 generic packages or subprograms which use the @code{Enabled} attribute
10603 to see if the check is enabled. A user of this package can then issue
10604 a @code{pragma Suppress} or @code{pragma Unsuppress} before instantiating
10605 the package or subprogram, controlling whether the check will be present.
10607 @node Attribute Enum_Rep,Attribute Enum_Val,Attribute Enabled,Implementation Defined Attributes
10608 @anchor{gnat_rm/implementation_defined_attributes attribute-enum-rep}@anchor{17e}
10609 @section Attribute Enum_Rep
10612 @geindex Representation of enums
10616 For every enumeration subtype @code{S}, @code{S'Enum_Rep} denotes a
10617 function with the following spec:
10620 function S'Enum_Rep (Arg : S'Base) return <Universal_Integer>;
10623 It is also allowable to apply @code{Enum_Rep} directly to an object of an
10624 enumeration type or to a non-overloaded enumeration
10625 literal. In this case @code{S'Enum_Rep} is equivalent to
10626 @code{typ'Enum_Rep(S)} where @code{typ} is the type of the
10627 enumeration literal or object.
10629 The function returns the representation value for the given enumeration
10630 value. This will be equal to value of the @code{Pos} attribute in the
10631 absence of an enumeration representation clause. This is a static
10632 attribute (i.e.,:the result is static if the argument is static).
10634 @code{S'Enum_Rep} can also be used with integer types and objects,
10635 in which case it simply returns the integer value. The reason for this
10636 is to allow it to be used for @code{(<>)} discrete formal arguments in
10637 a generic unit that can be instantiated with either enumeration types
10638 or integer types. Note that if @code{Enum_Rep} is used on a modular
10639 type whose upper bound exceeds the upper bound of the largest signed
10640 integer type, and the argument is a variable, so that the universal
10641 integer calculation is done at run time, then the call to @code{Enum_Rep}
10642 may raise @code{Constraint_Error}.
10644 @node Attribute Enum_Val,Attribute Epsilon,Attribute Enum_Rep,Implementation Defined Attributes
10645 @anchor{gnat_rm/implementation_defined_attributes attribute-enum-val}@anchor{17f}
10646 @section Attribute Enum_Val
10649 @geindex Representation of enums
10653 For every enumeration subtype @code{S}, @code{S'Enum_Val} denotes a
10654 function with the following spec:
10657 function S'Enum_Val (Arg : <Universal_Integer>) return S'Base;
10660 The function returns the enumeration value whose representation matches the
10661 argument, or raises Constraint_Error if no enumeration literal of the type
10662 has the matching value.
10663 This will be equal to value of the @code{Val} attribute in the
10664 absence of an enumeration representation clause. This is a static
10665 attribute (i.e., the result is static if the argument is static).
10667 @node Attribute Epsilon,Attribute Fast_Math,Attribute Enum_Val,Implementation Defined Attributes
10668 @anchor{gnat_rm/implementation_defined_attributes attribute-epsilon}@anchor{180}
10669 @section Attribute Epsilon
10672 @geindex Ada 83 attributes
10676 The @code{Epsilon} attribute is provided for compatibility with Ada 83. See
10677 the Ada 83 reference manual for an exact description of the semantics of
10680 @node Attribute Fast_Math,Attribute Finalization_Size,Attribute Epsilon,Implementation Defined Attributes
10681 @anchor{gnat_rm/implementation_defined_attributes attribute-fast-math}@anchor{181}
10682 @section Attribute Fast_Math
10687 @code{Standard'Fast_Math} (@code{Standard} is the only allowed
10688 prefix) yields a static Boolean value that is True if pragma
10689 @code{Fast_Math} is active, and False otherwise.
10691 @node Attribute Finalization_Size,Attribute Fixed_Value,Attribute Fast_Math,Implementation Defined Attributes
10692 @anchor{gnat_rm/implementation_defined_attributes attribute-finalization-size}@anchor{182}
10693 @section Attribute Finalization_Size
10696 @geindex Finalization_Size
10698 The prefix of attribute @code{Finalization_Size} must be an object or
10699 a non-class-wide type. This attribute returns the size of any hidden data
10700 reserved by the compiler to handle finalization-related actions. The type of
10701 the attribute is @emph{universal_integer}.
10703 @code{Finalization_Size} yields a value of zero for a type with no controlled
10704 parts, an object whose type has no controlled parts, or an object of a
10705 class-wide type whose tag denotes a type with no controlled parts.
10707 Note that only heap-allocated objects contain finalization data.
10709 @node Attribute Fixed_Value,Attribute From_Any,Attribute Finalization_Size,Implementation Defined Attributes
10710 @anchor{gnat_rm/implementation_defined_attributes attribute-fixed-value}@anchor{183}
10711 @section Attribute Fixed_Value
10714 @geindex Fixed_Value
10716 For every fixed-point type @code{S}, @code{S'Fixed_Value} denotes a
10717 function with the following specification:
10720 function S'Fixed_Value (Arg : <Universal_Integer>) return S;
10723 The value returned is the fixed-point value @code{V} such that:
10729 The effect is thus similar to first converting the argument to the
10730 integer type used to represent @code{S}, and then doing an unchecked
10731 conversion to the fixed-point type. The difference is
10732 that there are full range checks, to ensure that the result is in range.
10733 This attribute is primarily intended for use in implementation of the
10734 input-output functions for fixed-point values.
10736 @node Attribute From_Any,Attribute Has_Access_Values,Attribute Fixed_Value,Implementation Defined Attributes
10737 @anchor{gnat_rm/implementation_defined_attributes attribute-from-any}@anchor{184}
10738 @section Attribute From_Any
10743 This internal attribute is used for the generation of remote subprogram
10744 stubs in the context of the Distributed Systems Annex.
10746 @node Attribute Has_Access_Values,Attribute Has_Discriminants,Attribute From_Any,Implementation Defined Attributes
10747 @anchor{gnat_rm/implementation_defined_attributes attribute-has-access-values}@anchor{185}
10748 @section Attribute Has_Access_Values
10751 @geindex Access values
10752 @geindex testing for
10754 @geindex Has_Access_Values
10756 The prefix of the @code{Has_Access_Values} attribute is a type. The result
10757 is a Boolean value which is True if the is an access type, or is a composite
10758 type with a component (at any nesting depth) that is an access type, and is
10760 The intended use of this attribute is in conjunction with generic
10761 definitions. If the attribute is applied to a generic private type, it
10762 indicates whether or not the corresponding actual type has access values.
10764 @node Attribute Has_Discriminants,Attribute Img,Attribute Has_Access_Values,Implementation Defined Attributes
10765 @anchor{gnat_rm/implementation_defined_attributes attribute-has-discriminants}@anchor{186}
10766 @section Attribute Has_Discriminants
10769 @geindex Discriminants
10770 @geindex testing for
10772 @geindex Has_Discriminants
10774 The prefix of the @code{Has_Discriminants} attribute is a type. The result
10775 is a Boolean value which is True if the type has discriminants, and False
10776 otherwise. The intended use of this attribute is in conjunction with generic
10777 definitions. If the attribute is applied to a generic private type, it
10778 indicates whether or not the corresponding actual type has discriminants.
10780 @node Attribute Img,Attribute Integer_Value,Attribute Has_Discriminants,Implementation Defined Attributes
10781 @anchor{gnat_rm/implementation_defined_attributes attribute-img}@anchor{187}
10782 @section Attribute Img
10787 The @code{Img} attribute differs from @code{Image} in that, while both can be
10788 applied directly to an object, @code{Img} cannot be applied to types.
10790 Example usage of the attribute:
10793 Put_Line ("X = " & X'Img);
10796 which has the same meaning as the more verbose:
10799 Put_Line ("X = " & T'Image (X));
10802 where @code{T} is the (sub)type of the object @code{X}.
10804 Note that technically, in analogy to @code{Image},
10805 @code{X'Img} returns a parameterless function
10806 that returns the appropriate string when called. This means that
10807 @code{X'Img} can be renamed as a function-returning-string, or used
10808 in an instantiation as a function parameter.
10810 @node Attribute Integer_Value,Attribute Invalid_Value,Attribute Img,Implementation Defined Attributes
10811 @anchor{gnat_rm/implementation_defined_attributes attribute-integer-value}@anchor{188}
10812 @section Attribute Integer_Value
10815 @geindex Integer_Value
10817 For every integer type @code{S}, @code{S'Integer_Value} denotes a
10818 function with the following spec:
10821 function S'Integer_Value (Arg : <Universal_Fixed>) return S;
10824 The value returned is the integer value @code{V}, such that:
10830 where @code{T} is the type of @code{Arg}.
10831 The effect is thus similar to first doing an unchecked conversion from
10832 the fixed-point type to its corresponding implementation type, and then
10833 converting the result to the target integer type. The difference is
10834 that there are full range checks, to ensure that the result is in range.
10835 This attribute is primarily intended for use in implementation of the
10836 standard input-output functions for fixed-point values.
10838 @node Attribute Invalid_Value,Attribute Iterable,Attribute Integer_Value,Implementation Defined Attributes
10839 @anchor{gnat_rm/implementation_defined_attributes attribute-invalid-value}@anchor{189}
10840 @section Attribute Invalid_Value
10843 @geindex Invalid_Value
10845 For every scalar type S, S'Invalid_Value returns an undefined value of the
10846 type. If possible this value is an invalid representation for the type. The
10847 value returned is identical to the value used to initialize an otherwise
10848 uninitialized value of the type if pragma Initialize_Scalars is used,
10849 including the ability to modify the value with the binder -Sxx flag and
10850 relevant environment variables at run time.
10852 @node Attribute Iterable,Attribute Large,Attribute Invalid_Value,Implementation Defined Attributes
10853 @anchor{gnat_rm/implementation_defined_attributes attribute-iterable}@anchor{18a}
10854 @section Attribute Iterable
10859 Equivalent to Aspect Iterable.
10861 @node Attribute Large,Attribute Library_Level,Attribute Iterable,Implementation Defined Attributes
10862 @anchor{gnat_rm/implementation_defined_attributes attribute-large}@anchor{18b}
10863 @section Attribute Large
10866 @geindex Ada 83 attributes
10870 The @code{Large} attribute is provided for compatibility with Ada 83. See
10871 the Ada 83 reference manual for an exact description of the semantics of
10874 @node Attribute Library_Level,Attribute Lock_Free,Attribute Large,Implementation Defined Attributes
10875 @anchor{gnat_rm/implementation_defined_attributes attribute-library-level}@anchor{18c}
10876 @section Attribute Library_Level
10879 @geindex Library_Level
10881 @code{P'Library_Level}, where P is an entity name,
10882 returns a Boolean value which is True if the entity is declared
10883 at the library level, and False otherwise. Note that within a
10884 generic instantition, the name of the generic unit denotes the
10885 instance, which means that this attribute can be used to test
10886 if a generic is instantiated at the library level, as shown
10893 pragma Compile_Time_Error
10894 (not Gen'Library_Level,
10895 "Gen can only be instantiated at library level");
10900 @node Attribute Lock_Free,Attribute Loop_Entry,Attribute Library_Level,Implementation Defined Attributes
10901 @anchor{gnat_rm/implementation_defined_attributes attribute-lock-free}@anchor{18d}
10902 @section Attribute Lock_Free
10907 @code{P'Lock_Free}, where P is a protected object, returns True if a
10908 pragma @code{Lock_Free} applies to P.
10910 @node Attribute Loop_Entry,Attribute Machine_Size,Attribute Lock_Free,Implementation Defined Attributes
10911 @anchor{gnat_rm/implementation_defined_attributes attribute-loop-entry}@anchor{18e}
10912 @section Attribute Loop_Entry
10915 @geindex Loop_Entry
10920 X'Loop_Entry [(loop_name)]
10923 The @code{Loop_Entry} attribute is used to refer to the value that an
10924 expression had upon entry to a given loop in much the same way that the
10925 @code{Old} attribute in a subprogram postcondition can be used to refer
10926 to the value an expression had upon entry to the subprogram. The
10927 relevant loop is either identified by the given loop name, or it is the
10928 innermost enclosing loop when no loop name is given.
10930 A @code{Loop_Entry} attribute can only occur within a
10931 @code{Loop_Variant} or @code{Loop_Invariant} pragma. A common use of
10932 @code{Loop_Entry} is to compare the current value of objects with their
10933 initial value at loop entry, in a @code{Loop_Invariant} pragma.
10935 The effect of using @code{X'Loop_Entry} is the same as declaring
10936 a constant initialized with the initial value of @code{X} at loop
10937 entry. This copy is not performed if the loop is not entered, or if the
10938 corresponding pragmas are ignored or disabled.
10940 @node Attribute Machine_Size,Attribute Mantissa,Attribute Loop_Entry,Implementation Defined Attributes
10941 @anchor{gnat_rm/implementation_defined_attributes attribute-machine-size}@anchor{18f}
10942 @section Attribute Machine_Size
10945 @geindex Machine_Size
10947 This attribute is identical to the @code{Object_Size} attribute. It is
10948 provided for compatibility with the DEC Ada 83 attribute of this name.
10950 @node Attribute Mantissa,Attribute Maximum_Alignment,Attribute Machine_Size,Implementation Defined Attributes
10951 @anchor{gnat_rm/implementation_defined_attributes attribute-mantissa}@anchor{190}
10952 @section Attribute Mantissa
10955 @geindex Ada 83 attributes
10959 The @code{Mantissa} attribute is provided for compatibility with Ada 83. See
10960 the Ada 83 reference manual for an exact description of the semantics of
10963 @node Attribute Maximum_Alignment,Attribute Mechanism_Code,Attribute Mantissa,Implementation Defined Attributes
10964 @anchor{gnat_rm/implementation_defined_attributes attribute-maximum-alignment}@anchor{191}@anchor{gnat_rm/implementation_defined_attributes id2}@anchor{192}
10965 @section Attribute Maximum_Alignment
10971 @geindex Maximum_Alignment
10973 @code{Standard'Maximum_Alignment} (@code{Standard} is the only
10974 permissible prefix) provides the maximum useful alignment value for the
10975 target. This is a static value that can be used to specify the alignment
10976 for an object, guaranteeing that it is properly aligned in all
10979 @node Attribute Mechanism_Code,Attribute Null_Parameter,Attribute Maximum_Alignment,Implementation Defined Attributes
10980 @anchor{gnat_rm/implementation_defined_attributes attribute-mechanism-code}@anchor{193}
10981 @section Attribute Mechanism_Code
10984 @geindex Return values
10985 @geindex passing mechanism
10987 @geindex Parameters
10988 @geindex passing mechanism
10990 @geindex Mechanism_Code
10992 @code{func'Mechanism_Code} yields an integer code for the
10993 mechanism used for the result of function @code{func}, and
10994 @code{subprog'Mechanism_Code (n)} yields the mechanism
10995 used for formal parameter number @emph{n} (a static integer value, with 1
10996 meaning the first parameter) of subprogram @code{subprog}. The code returned is:
11010 @node Attribute Null_Parameter,Attribute Object_Size,Attribute Mechanism_Code,Implementation Defined Attributes
11011 @anchor{gnat_rm/implementation_defined_attributes attribute-null-parameter}@anchor{194}
11012 @section Attribute Null_Parameter
11015 @geindex Zero address
11018 @geindex Null_Parameter
11020 A reference @code{T'Null_Parameter} denotes an imaginary object of
11021 type or subtype @code{T} allocated at machine address zero. The attribute
11022 is allowed only as the default expression of a formal parameter, or as
11023 an actual expression of a subprogram call. In either case, the
11024 subprogram must be imported.
11026 The identity of the object is represented by the address zero in the
11027 argument list, independent of the passing mechanism (explicit or
11030 This capability is needed to specify that a zero address should be
11031 passed for a record or other composite object passed by reference.
11032 There is no way of indicating this without the @code{Null_Parameter}
11035 @node Attribute Object_Size,Attribute Old,Attribute Null_Parameter,Implementation Defined Attributes
11036 @anchor{gnat_rm/implementation_defined_attributes attribute-object-size}@anchor{147}@anchor{gnat_rm/implementation_defined_attributes id3}@anchor{195}
11037 @section Attribute Object_Size
11041 @geindex used for objects
11043 @geindex Object_Size
11045 The size of an object is not necessarily the same as the size of the type
11046 of an object. This is because by default object sizes are increased to be
11047 a multiple of the alignment of the object. For example,
11048 @code{Natural'Size} is
11049 31, but by default objects of type @code{Natural} will have a size of 32 bits.
11050 Similarly, a record containing an integer and a character:
11059 will have a size of 40 (that is @code{Rec'Size} will be 40). The
11060 alignment will be 4, because of the
11061 integer field, and so the default size of record objects for this type
11062 will be 64 (8 bytes).
11064 If the alignment of the above record is specified to be 1, then the
11065 object size will be 40 (5 bytes). This is true by default, and also
11066 an object size of 40 can be explicitly specified in this case.
11068 A consequence of this capability is that different object sizes can be
11069 given to subtypes that would otherwise be considered in Ada to be
11070 statically matching. But it makes no sense to consider such subtypes
11071 as statically matching. Consequently, GNAT adds a rule
11072 to the static matching rules that requires object sizes to match.
11073 Consider this example:
11076 1. procedure BadAVConvert is
11077 2. type R is new Integer;
11078 3. subtype R1 is R range 1 .. 10;
11079 4. subtype R2 is R range 1 .. 10;
11080 5. for R1'Object_Size use 8;
11081 6. for R2'Object_Size use 16;
11082 7. type R1P is access all R1;
11083 8. type R2P is access all R2;
11084 9. R1PV : R1P := new R1'(4);
11087 12. R2PV := R2P (R1PV);
11089 >>> target designated subtype not compatible with
11090 type "R1" defined at line 3
11095 In the absence of lines 5 and 6,
11096 types @code{R1} and @code{R2} statically match and
11097 hence the conversion on line 12 is legal. But since lines 5 and 6
11098 cause the object sizes to differ, GNAT considers that types
11099 @code{R1} and @code{R2} are not statically matching, and line 12
11100 generates the diagnostic shown above.
11102 Similar additional checks are performed in other contexts requiring
11103 statically matching subtypes.
11105 @node Attribute Old,Attribute Passed_By_Reference,Attribute Object_Size,Implementation Defined Attributes
11106 @anchor{gnat_rm/implementation_defined_attributes attribute-old}@anchor{196}
11107 @section Attribute Old
11112 In addition to the usage of @code{Old} defined in the Ada 2012 RM (usage
11113 within @code{Post} aspect), GNAT also permits the use of this attribute
11114 in implementation defined pragmas @code{Postcondition},
11115 @code{Contract_Cases} and @code{Test_Case}. Also usages of
11116 @code{Old} which would be illegal according to the Ada 2012 RM
11117 definition are allowed under control of
11118 implementation defined pragma @code{Unevaluated_Use_Of_Old}.
11120 @node Attribute Passed_By_Reference,Attribute Pool_Address,Attribute Old,Implementation Defined Attributes
11121 @anchor{gnat_rm/implementation_defined_attributes attribute-passed-by-reference}@anchor{197}
11122 @section Attribute Passed_By_Reference
11125 @geindex Parameters
11126 @geindex when passed by reference
11128 @geindex Passed_By_Reference
11130 @code{typ'Passed_By_Reference} for any subtype @cite{typ} returns
11131 a value of type @code{Boolean} value that is @code{True} if the type is
11132 normally passed by reference and @code{False} if the type is normally
11133 passed by copy in calls. For scalar types, the result is always @code{False}
11134 and is static. For non-scalar types, the result is nonstatic.
11136 @node Attribute Pool_Address,Attribute Range_Length,Attribute Passed_By_Reference,Implementation Defined Attributes
11137 @anchor{gnat_rm/implementation_defined_attributes attribute-pool-address}@anchor{198}
11138 @section Attribute Pool_Address
11141 @geindex Parameters
11142 @geindex when passed by reference
11144 @geindex Pool_Address
11146 @code{X'Pool_Address} for any object @code{X} returns the address
11147 of X within its storage pool. This is the same as
11148 @code{X'Address}, except that for an unconstrained array whose
11149 bounds are allocated just before the first component,
11150 @code{X'Pool_Address} returns the address of those bounds,
11151 whereas @code{X'Address} returns the address of the first
11154 Here, we are interpreting 'storage pool' broadly to mean
11155 @code{wherever the object is allocated}, which could be a
11156 user-defined storage pool,
11157 the global heap, on the stack, or in a static memory area.
11158 For an object created by @code{new}, @code{Ptr.all'Pool_Address} is
11159 what is passed to @code{Allocate} and returned from @code{Deallocate}.
11161 @node Attribute Range_Length,Attribute Restriction_Set,Attribute Pool_Address,Implementation Defined Attributes
11162 @anchor{gnat_rm/implementation_defined_attributes attribute-range-length}@anchor{199}
11163 @section Attribute Range_Length
11166 @geindex Range_Length
11168 @code{typ'Range_Length} for any discrete type @cite{typ} yields
11169 the number of values represented by the subtype (zero for a null
11170 range). The result is static for static subtypes. @code{Range_Length}
11171 applied to the index subtype of a one dimensional array always gives the
11172 same result as @code{Length} applied to the array itself.
11174 @node Attribute Restriction_Set,Attribute Result,Attribute Range_Length,Implementation Defined Attributes
11175 @anchor{gnat_rm/implementation_defined_attributes attribute-restriction-set}@anchor{19a}
11176 @section Attribute Restriction_Set
11179 @geindex Restriction_Set
11181 @geindex Restrictions
11183 This attribute allows compile time testing of restrictions that
11184 are currently in effect. It is primarily intended for specializing
11185 code in the run-time based on restrictions that are active (e.g.
11186 don't need to save fpt registers if restriction No_Floating_Point
11187 is known to be in effect), but can be used anywhere.
11189 There are two forms:
11192 System'Restriction_Set (partition_boolean_restriction_NAME)
11193 System'Restriction_Set (No_Dependence => library_unit_NAME);
11196 In the case of the first form, the only restriction names
11197 allowed are parameterless restrictions that are checked
11198 for consistency at bind time. For a complete list see the
11199 subtype @code{System.Rident.Partition_Boolean_Restrictions}.
11201 The result returned is True if the restriction is known to
11202 be in effect, and False if the restriction is known not to
11203 be in effect. An important guarantee is that the value of
11204 a Restriction_Set attribute is known to be consistent throughout
11205 all the code of a partition.
11207 This is trivially achieved if the entire partition is compiled
11208 with a consistent set of restriction pragmas. However, the
11209 compilation model does not require this. It is possible to
11210 compile one set of units with one set of pragmas, and another
11211 set of units with another set of pragmas. It is even possible
11212 to compile a spec with one set of pragmas, and then WITH the
11213 same spec with a different set of pragmas. Inconsistencies
11214 in the actual use of the restriction are checked at bind time.
11216 In order to achieve the guarantee of consistency for the
11217 Restriction_Set pragma, we consider that a use of the pragma
11218 that yields False is equivalent to a violation of the
11221 So for example if you write
11224 if System'Restriction_Set (No_Floating_Point) then
11231 And the result is False, so that the else branch is executed,
11232 you can assume that this restriction is not set for any unit
11233 in the partition. This is checked by considering this use of
11234 the restriction pragma to be a violation of the restriction
11235 No_Floating_Point. This means that no other unit can attempt
11236 to set this restriction (if some unit does attempt to set it,
11237 the binder will refuse to bind the partition).
11239 Technical note: The restriction name and the unit name are
11240 intepreted entirely syntactically, as in the corresponding
11241 Restrictions pragma, they are not analyzed semantically,
11242 so they do not have a type.
11244 @node Attribute Result,Attribute Safe_Emax,Attribute Restriction_Set,Implementation Defined Attributes
11245 @anchor{gnat_rm/implementation_defined_attributes attribute-result}@anchor{19b}
11246 @section Attribute Result
11251 @code{function'Result} can only be used with in a Postcondition pragma
11252 for a function. The prefix must be the name of the corresponding function. This
11253 is used to refer to the result of the function in the postcondition expression.
11254 For a further discussion of the use of this attribute and examples of its use,
11255 see the description of pragma Postcondition.
11257 @node Attribute Safe_Emax,Attribute Safe_Large,Attribute Result,Implementation Defined Attributes
11258 @anchor{gnat_rm/implementation_defined_attributes attribute-safe-emax}@anchor{19c}
11259 @section Attribute Safe_Emax
11262 @geindex Ada 83 attributes
11266 The @code{Safe_Emax} attribute is provided for compatibility with Ada 83. See
11267 the Ada 83 reference manual for an exact description of the semantics of
11270 @node Attribute Safe_Large,Attribute Safe_Small,Attribute Safe_Emax,Implementation Defined Attributes
11271 @anchor{gnat_rm/implementation_defined_attributes attribute-safe-large}@anchor{19d}
11272 @section Attribute Safe_Large
11275 @geindex Ada 83 attributes
11277 @geindex Safe_Large
11279 The @code{Safe_Large} attribute is provided for compatibility with Ada 83. See
11280 the Ada 83 reference manual for an exact description of the semantics of
11283 @node Attribute Safe_Small,Attribute Scalar_Storage_Order,Attribute Safe_Large,Implementation Defined Attributes
11284 @anchor{gnat_rm/implementation_defined_attributes attribute-safe-small}@anchor{19e}
11285 @section Attribute Safe_Small
11288 @geindex Ada 83 attributes
11290 @geindex Safe_Small
11292 The @code{Safe_Small} attribute is provided for compatibility with Ada 83. See
11293 the Ada 83 reference manual for an exact description of the semantics of
11296 @node Attribute Scalar_Storage_Order,Attribute Simple_Storage_Pool,Attribute Safe_Small,Implementation Defined Attributes
11297 @anchor{gnat_rm/implementation_defined_attributes id4}@anchor{19f}@anchor{gnat_rm/implementation_defined_attributes attribute-scalar-storage-order}@anchor{154}
11298 @section Attribute Scalar_Storage_Order
11301 @geindex Endianness
11303 @geindex Scalar storage order
11305 @geindex Scalar_Storage_Order
11307 For every array or record type @code{S}, the representation attribute
11308 @code{Scalar_Storage_Order} denotes the order in which storage elements
11309 that make up scalar components are ordered within S. The value given must
11310 be a static expression of type System.Bit_Order. The following is an example
11311 of the use of this feature:
11314 -- Component type definitions
11316 subtype Yr_Type is Natural range 0 .. 127;
11317 subtype Mo_Type is Natural range 1 .. 12;
11318 subtype Da_Type is Natural range 1 .. 31;
11320 -- Record declaration
11322 type Date is record
11323 Years_Since_1980 : Yr_Type;
11325 Day_Of_Month : Da_Type;
11328 -- Record representation clause
11330 for Date use record
11331 Years_Since_1980 at 0 range 0 .. 6;
11332 Month at 0 range 7 .. 10;
11333 Day_Of_Month at 0 range 11 .. 15;
11336 -- Attribute definition clauses
11338 for Date'Bit_Order use System.High_Order_First;
11339 for Date'Scalar_Storage_Order use System.High_Order_First;
11340 -- If Scalar_Storage_Order is specified, it must be consistent with
11341 -- Bit_Order, so it's best to always define the latter explicitly if
11342 -- the former is used.
11345 Other properties are as for the standard representation attribute @code{Bit_Order}
11346 defined by Ada RM 13.5.3(4). The default is @code{System.Default_Bit_Order}.
11348 For a record type @code{T}, if @code{T'Scalar_Storage_Order} is
11349 specified explicitly, it shall be equal to @code{T'Bit_Order}. Note:
11350 this means that if a @code{Scalar_Storage_Order} attribute definition
11351 clause is not confirming, then the type's @code{Bit_Order} shall be
11352 specified explicitly and set to the same value.
11354 Derived types inherit an explicitly set scalar storage order from their parent
11355 types. This may be overridden for the derived type by giving an explicit scalar
11356 storage order for it. However, for a record extension, the derived type must
11357 have the same scalar storage order as the parent type.
11359 A component of a record type that is itself a record or an array and that does
11360 not start and end on a byte boundary must have have the same scalar storage
11361 order as the record type. A component of a bit-packed array type that is itself
11362 a record or an array must have the same scalar storage order as the array type.
11364 No component of a type that has an explicit @code{Scalar_Storage_Order}
11365 attribute definition may be aliased.
11367 A confirming @code{Scalar_Storage_Order} attribute definition clause (i.e.
11368 with a value equal to @code{System.Default_Bit_Order}) has no effect.
11370 If the opposite storage order is specified, then whenever the value of
11371 a scalar component of an object of type @code{S} is read, the storage
11372 elements of the enclosing machine scalar are first reversed (before
11373 retrieving the component value, possibly applying some shift and mask
11374 operatings on the enclosing machine scalar), and the opposite operation
11375 is done for writes.
11377 In that case, the restrictions set forth in 13.5.1(10.3/2) for scalar components
11378 are relaxed. Instead, the following rules apply:
11384 the underlying storage elements are those at positions
11385 @code{(position + first_bit / storage_element_size) .. (position + (last_bit + storage_element_size - 1) / storage_element_size)}
11388 the sequence of underlying storage elements shall have
11389 a size no greater than the largest machine scalar
11392 the enclosing machine scalar is defined as the smallest machine
11393 scalar starting at a position no greater than
11394 @code{position + first_bit / storage_element_size} and covering
11395 storage elements at least up to @code{position + (last_bit + storage_element_size - 1) / storage_element_size`}
11398 the position of the component is interpreted relative to that machine
11402 If no scalar storage order is specified for a type (either directly, or by
11403 inheritance in the case of a derived type), then the default is normally
11404 the native ordering of the target, but this default can be overridden using
11405 pragma @code{Default_Scalar_Storage_Order}.
11407 If a component of @code{T} is itself of a record or array type, the specfied
11408 @code{Scalar_Storage_Order} does @emph{not} apply to that nested type: an explicit
11409 attribute definition clause must be provided for the component type as well
11412 Note that the scalar storage order only affects the in-memory data
11413 representation. It has no effect on the representation used by stream
11416 Note that debuggers may be unable to display the correct value of scalar
11417 components of a type for which the opposite storage order is specified.
11419 @node Attribute Simple_Storage_Pool,Attribute Small,Attribute Scalar_Storage_Order,Implementation Defined Attributes
11420 @anchor{gnat_rm/implementation_defined_attributes attribute-simple-storage-pool}@anchor{e9}@anchor{gnat_rm/implementation_defined_attributes id5}@anchor{1a0}
11421 @section Attribute Simple_Storage_Pool
11424 @geindex Storage pool
11427 @geindex Simple storage pool
11429 @geindex Simple_Storage_Pool
11431 For every nonformal, nonderived access-to-object type @code{Acc}, the
11432 representation attribute @code{Simple_Storage_Pool} may be specified
11433 via an attribute_definition_clause (or by specifying the equivalent aspect):
11436 My_Pool : My_Simple_Storage_Pool_Type;
11438 type Acc is access My_Data_Type;
11440 for Acc'Simple_Storage_Pool use My_Pool;
11443 The name given in an attribute_definition_clause for the
11444 @code{Simple_Storage_Pool} attribute shall denote a variable of
11445 a 'simple storage pool type' (see pragma @cite{Simple_Storage_Pool_Type}).
11447 The use of this attribute is only allowed for a prefix denoting a type
11448 for which it has been specified. The type of the attribute is the type
11449 of the variable specified as the simple storage pool of the access type,
11450 and the attribute denotes that variable.
11452 It is illegal to specify both @code{Storage_Pool} and @code{Simple_Storage_Pool}
11453 for the same access type.
11455 If the @code{Simple_Storage_Pool} attribute has been specified for an access
11456 type, then applying the @code{Storage_Pool} attribute to the type is flagged
11457 with a warning and its evaluation raises the exception @code{Program_Error}.
11459 If the Simple_Storage_Pool attribute has been specified for an access
11460 type @code{S}, then the evaluation of the attribute @code{S'Storage_Size}
11461 returns the result of calling @code{Storage_Size (S'Simple_Storage_Pool)},
11462 which is intended to indicate the number of storage elements reserved for
11463 the simple storage pool. If the Storage_Size function has not been defined
11464 for the simple storage pool type, then this attribute returns zero.
11466 If an access type @code{S} has a specified simple storage pool of type
11467 @code{SSP}, then the evaluation of an allocator for that access type calls
11468 the primitive @code{Allocate} procedure for type @code{SSP}, passing
11469 @code{S'Simple_Storage_Pool} as the pool parameter. The detailed
11470 semantics of such allocators is the same as those defined for allocators
11471 in section 13.11 of the @cite{Ada Reference Manual}, with the term
11472 @emph{simple storage pool} substituted for @emph{storage pool}.
11474 If an access type @code{S} has a specified simple storage pool of type
11475 @code{SSP}, then a call to an instance of the @code{Ada.Unchecked_Deallocation}
11476 for that access type invokes the primitive @code{Deallocate} procedure
11477 for type @code{SSP}, passing @code{S'Simple_Storage_Pool} as the pool
11478 parameter. The detailed semantics of such unchecked deallocations is the same
11479 as defined in section 13.11.2 of the Ada Reference Manual, except that the
11480 term @emph{simple storage pool} is substituted for @emph{storage pool}.
11482 @node Attribute Small,Attribute Storage_Unit,Attribute Simple_Storage_Pool,Implementation Defined Attributes
11483 @anchor{gnat_rm/implementation_defined_attributes attribute-small}@anchor{1a1}
11484 @section Attribute Small
11487 @geindex Ada 83 attributes
11491 The @code{Small} attribute is defined in Ada 95 (and Ada 2005) only for
11493 GNAT also allows this attribute to be applied to floating-point types
11494 for compatibility with Ada 83. See
11495 the Ada 83 reference manual for an exact description of the semantics of
11496 this attribute when applied to floating-point types.
11498 @node Attribute Storage_Unit,Attribute Stub_Type,Attribute Small,Implementation Defined Attributes
11499 @anchor{gnat_rm/implementation_defined_attributes attribute-storage-unit}@anchor{1a2}
11500 @section Attribute Storage_Unit
11503 @geindex Storage_Unit
11505 @code{Standard'Storage_Unit} (@code{Standard} is the only permissible
11506 prefix) provides the same value as @code{System.Storage_Unit}.
11508 @node Attribute Stub_Type,Attribute System_Allocator_Alignment,Attribute Storage_Unit,Implementation Defined Attributes
11509 @anchor{gnat_rm/implementation_defined_attributes attribute-stub-type}@anchor{1a3}
11510 @section Attribute Stub_Type
11515 The GNAT implementation of remote access-to-classwide types is
11516 organized as described in AARM section E.4 (20.t): a value of an RACW type
11517 (designating a remote object) is represented as a normal access
11518 value, pointing to a "stub" object which in turn contains the
11519 necessary information to contact the designated remote object. A
11520 call on any dispatching operation of such a stub object does the
11521 remote call, if necessary, using the information in the stub object
11522 to locate the target partition, etc.
11524 For a prefix @code{T} that denotes a remote access-to-classwide type,
11525 @code{T'Stub_Type} denotes the type of the corresponding stub objects.
11527 By construction, the layout of @code{T'Stub_Type} is identical to that of
11528 type @code{RACW_Stub_Type} declared in the internal implementation-defined
11529 unit @code{System.Partition_Interface}. Use of this attribute will create
11530 an implicit dependency on this unit.
11532 @node Attribute System_Allocator_Alignment,Attribute Target_Name,Attribute Stub_Type,Implementation Defined Attributes
11533 @anchor{gnat_rm/implementation_defined_attributes attribute-system-allocator-alignment}@anchor{1a4}
11534 @section Attribute System_Allocator_Alignment
11540 @geindex System_Allocator_Alignment
11542 @code{Standard'System_Allocator_Alignment} (@code{Standard} is the only
11543 permissible prefix) provides the observable guaranted to be honored by
11544 the system allocator (malloc). This is a static value that can be used
11545 in user storage pools based on malloc either to reject allocation
11546 with alignment too large or to enable a realignment circuitry if the
11547 alignment request is larger than this value.
11549 @node Attribute Target_Name,Attribute To_Address,Attribute System_Allocator_Alignment,Implementation Defined Attributes
11550 @anchor{gnat_rm/implementation_defined_attributes attribute-target-name}@anchor{1a5}
11551 @section Attribute Target_Name
11554 @geindex Target_Name
11556 @code{Standard'Target_Name} (@code{Standard} is the only permissible
11557 prefix) provides a static string value that identifies the target
11558 for the current compilation. For GCC implementations, this is the
11559 standard gcc target name without the terminating slash (for
11560 example, GNAT 5.0 on windows yields "i586-pc-mingw32msv").
11562 @node Attribute To_Address,Attribute To_Any,Attribute Target_Name,Implementation Defined Attributes
11563 @anchor{gnat_rm/implementation_defined_attributes attribute-to-address}@anchor{1a6}
11564 @section Attribute To_Address
11567 @geindex To_Address
11569 The @code{System'To_Address}
11570 (@code{System} is the only permissible prefix)
11571 denotes a function identical to
11572 @code{System.Storage_Elements.To_Address} except that
11573 it is a static attribute. This means that if its argument is
11574 a static expression, then the result of the attribute is a
11575 static expression. This means that such an expression can be
11576 used in contexts (e.g., preelaborable packages) which require a
11577 static expression and where the function call could not be used
11578 (since the function call is always nonstatic, even if its
11579 argument is static). The argument must be in the range
11580 -(2**(m-1)) .. 2**m-1, where m is the memory size
11581 (typically 32 or 64). Negative values are intepreted in a
11582 modular manner (e.g., -1 means the same as 16#FFFF_FFFF# on
11583 a 32 bits machine).
11585 @node Attribute To_Any,Attribute Type_Class,Attribute To_Address,Implementation Defined Attributes
11586 @anchor{gnat_rm/implementation_defined_attributes attribute-to-any}@anchor{1a7}
11587 @section Attribute To_Any
11592 This internal attribute is used for the generation of remote subprogram
11593 stubs in the context of the Distributed Systems Annex.
11595 @node Attribute Type_Class,Attribute Type_Key,Attribute To_Any,Implementation Defined Attributes
11596 @anchor{gnat_rm/implementation_defined_attributes attribute-type-class}@anchor{1a8}
11597 @section Attribute Type_Class
11600 @geindex Type_Class
11602 @code{typ'Type_Class} for any type or subtype @cite{typ} yields
11603 the value of the type class for the full type of @cite{typ}. If
11604 @cite{typ} is a generic formal type, the value is the value for the
11605 corresponding actual subtype. The value of this attribute is of type
11606 @code{System.Aux_DEC.Type_Class}, which has the following definition:
11610 (Type_Class_Enumeration,
11611 Type_Class_Integer,
11612 Type_Class_Fixed_Point,
11613 Type_Class_Floating_Point,
11618 Type_Class_Address);
11621 Protected types yield the value @code{Type_Class_Task}, which thus
11622 applies to all concurrent types. This attribute is designed to
11623 be compatible with the DEC Ada 83 attribute of the same name.
11625 @node Attribute Type_Key,Attribute TypeCode,Attribute Type_Class,Implementation Defined Attributes
11626 @anchor{gnat_rm/implementation_defined_attributes attribute-type-key}@anchor{1a9}
11627 @section Attribute Type_Key
11632 The @code{Type_Key} attribute is applicable to a type or subtype and
11633 yields a value of type Standard.String containing encoded information
11634 about the type or subtype. This provides improved compatibility with
11635 other implementations that support this attribute.
11637 @node Attribute TypeCode,Attribute Unconstrained_Array,Attribute Type_Key,Implementation Defined Attributes
11638 @anchor{gnat_rm/implementation_defined_attributes attribute-typecode}@anchor{1aa}
11639 @section Attribute TypeCode
11644 This internal attribute is used for the generation of remote subprogram
11645 stubs in the context of the Distributed Systems Annex.
11647 @node Attribute Unconstrained_Array,Attribute Universal_Literal_String,Attribute TypeCode,Implementation Defined Attributes
11648 @anchor{gnat_rm/implementation_defined_attributes attribute-unconstrained-array}@anchor{1ab}
11649 @section Attribute Unconstrained_Array
11652 @geindex Unconstrained_Array
11654 The @code{Unconstrained_Array} attribute can be used with a prefix that
11655 denotes any type or subtype. It is a static attribute that yields
11656 @code{True} if the prefix designates an unconstrained array,
11657 and @code{False} otherwise. In a generic instance, the result is
11658 still static, and yields the result of applying this test to the
11661 @node Attribute Universal_Literal_String,Attribute Unrestricted_Access,Attribute Unconstrained_Array,Implementation Defined Attributes
11662 @anchor{gnat_rm/implementation_defined_attributes attribute-universal-literal-string}@anchor{1ac}
11663 @section Attribute Universal_Literal_String
11666 @geindex Named numbers
11667 @geindex representation of
11669 @geindex Universal_Literal_String
11671 The prefix of @code{Universal_Literal_String} must be a named
11672 number. The static result is the string consisting of the characters of
11673 the number as defined in the original source. This allows the user
11674 program to access the actual text of named numbers without intermediate
11675 conversions and without the need to enclose the strings in quotes (which
11676 would preclude their use as numbers).
11678 For example, the following program prints the first 50 digits of pi:
11681 with Text_IO; use Text_IO;
11685 Put (Ada.Numerics.Pi'Universal_Literal_String);
11689 @node Attribute Unrestricted_Access,Attribute Update,Attribute Universal_Literal_String,Implementation Defined Attributes
11690 @anchor{gnat_rm/implementation_defined_attributes attribute-unrestricted-access}@anchor{1ad}
11691 @section Attribute Unrestricted_Access
11695 @geindex unrestricted
11697 @geindex Unrestricted_Access
11699 The @code{Unrestricted_Access} attribute is similar to @code{Access}
11700 except that all accessibility and aliased view checks are omitted. This
11701 is a user-beware attribute.
11703 For objects, it is similar to @code{Address}, for which it is a
11704 desirable replacement where the value desired is an access type.
11705 In other words, its effect is similar to first applying the
11706 @code{Address} attribute and then doing an unchecked conversion to a
11707 desired access type.
11709 For subprograms, @code{P'Unrestricted_Access} may be used where
11710 @code{P'Access} would be illegal, to construct a value of a
11711 less-nested named access type that designates a more-nested
11712 subprogram. This value may be used in indirect calls, so long as the
11713 more-nested subprogram still exists; once the subprogram containing it
11714 has returned, such calls are erroneous. For example:
11719 type Less_Nested is not null access procedure;
11720 Global : Less_Nested;
11728 Local_Var : Integer;
11730 procedure More_Nested is
11735 Global := More_Nested'Unrestricted_Access;
11742 When P1 is called from P2, the call via Global is OK, but if P1 were
11743 called after P2 returns, it would be an erroneous use of a dangling
11746 For objects, it is possible to use @code{Unrestricted_Access} for any
11747 type. However, if the result is of an access-to-unconstrained array
11748 subtype, then the resulting pointer has the same scope as the context
11749 of the attribute, and must not be returned to some enclosing scope.
11750 For instance, if a function uses @code{Unrestricted_Access} to create
11751 an access-to-unconstrained-array and returns that value to the caller,
11752 the result will involve dangling pointers. In addition, it is only
11753 valid to create pointers to unconstrained arrays using this attribute
11754 if the pointer has the normal default 'fat' representation where a
11755 pointer has two components, one points to the array and one points to
11756 the bounds. If a size clause is used to force 'thin' representation
11757 for a pointer to unconstrained where there is only space for a single
11758 pointer, then the resulting pointer is not usable.
11760 In the simple case where a direct use of Unrestricted_Access attempts
11761 to make a thin pointer for a non-aliased object, the compiler will
11762 reject the use as illegal, as shown in the following example:
11765 with System; use System;
11766 procedure SliceUA2 is
11767 type A is access all String;
11768 for A'Size use Standard'Address_Size;
11770 procedure P (Arg : A) is
11775 X : String := "hello world!";
11776 X2 : aliased String := "hello world!";
11778 AV : A := X'Unrestricted_Access; -- ERROR
11780 >>> illegal use of Unrestricted_Access attribute
11781 >>> attempt to generate thin pointer to unaliased object
11784 P (X'Unrestricted_Access); -- ERROR
11786 >>> illegal use of Unrestricted_Access attribute
11787 >>> attempt to generate thin pointer to unaliased object
11789 P (X(7 .. 12)'Unrestricted_Access); -- ERROR
11791 >>> illegal use of Unrestricted_Access attribute
11792 >>> attempt to generate thin pointer to unaliased object
11794 P (X2'Unrestricted_Access); -- OK
11798 but other cases cannot be detected by the compiler, and are
11799 considered to be erroneous. Consider the following example:
11802 with System; use System;
11803 with System; use System;
11804 procedure SliceUA is
11805 type AF is access all String;
11807 type A is access all String;
11808 for A'Size use Standard'Address_Size;
11810 procedure P (Arg : A) is
11812 if Arg'Length /= 6 then
11813 raise Program_Error;
11817 X : String := "hello world!";
11818 Y : AF := X (7 .. 12)'Unrestricted_Access;
11825 A normal unconstrained array value
11826 or a constrained array object marked as aliased has the bounds in memory
11827 just before the array, so a thin pointer can retrieve both the data and
11828 the bounds. But in this case, the non-aliased object @code{X} does not have the
11829 bounds before the string. If the size clause for type @code{A}
11830 were not present, then the pointer
11831 would be a fat pointer, where one component is a pointer to the bounds,
11832 and all would be well. But with the size clause present, the conversion from
11833 fat pointer to thin pointer in the call loses the bounds, and so this
11834 is erroneous, and the program likely raises a @code{Program_Error} exception.
11836 In general, it is advisable to completely
11837 avoid mixing the use of thin pointers and the use of
11838 @code{Unrestricted_Access} where the designated type is an
11839 unconstrained array. The use of thin pointers should be restricted to
11840 cases of porting legacy code that implicitly assumes the size of pointers,
11841 and such code should not in any case be using this attribute.
11843 Another erroneous situation arises if the attribute is
11844 applied to a constant. The resulting pointer can be used to access the
11845 constant, but the effect of trying to modify a constant in this manner
11846 is not well-defined. Consider this example:
11849 P : constant Integer := 4;
11850 type R is access all Integer;
11851 RV : R := P'Unrestricted_Access;
11856 Here we attempt to modify the constant P from 4 to 3, but the compiler may
11857 or may not notice this attempt, and subsequent references to P may yield
11858 either the value 3 or the value 4 or the assignment may blow up if the
11859 compiler decides to put P in read-only memory. One particular case where
11860 @code{Unrestricted_Access} can be used in this way is to modify the
11861 value of an @code{in} parameter:
11864 procedure K (S : in String) is
11865 type R is access all Character;
11866 RV : R := S (3)'Unrestricted_Access;
11872 In general this is a risky approach. It may appear to "work" but such uses of
11873 @code{Unrestricted_Access} are potentially non-portable, even from one version
11874 of GNAT to another, so are best avoided if possible.
11876 @node Attribute Update,Attribute Valid_Scalars,Attribute Unrestricted_Access,Implementation Defined Attributes
11877 @anchor{gnat_rm/implementation_defined_attributes attribute-update}@anchor{1ae}
11878 @section Attribute Update
11883 The @code{Update} attribute creates a copy of an array or record value
11884 with one or more modified components. The syntax is:
11887 PREFIX'Update ( RECORD_COMPONENT_ASSOCIATION_LIST )
11888 PREFIX'Update ( ARRAY_COMPONENT_ASSOCIATION @{, ARRAY_COMPONENT_ASSOCIATION @} )
11889 PREFIX'Update ( MULTIDIMENSIONAL_ARRAY_COMPONENT_ASSOCIATION
11890 @{, MULTIDIMENSIONAL_ARRAY_COMPONENT_ASSOCIATION @} )
11892 MULTIDIMENSIONAL_ARRAY_COMPONENT_ASSOCIATION ::= INDEX_EXPRESSION_LIST_LIST => EXPRESSION
11893 INDEX_EXPRESSION_LIST_LIST ::= INDEX_EXPRESSION_LIST @{| INDEX_EXPRESSION_LIST @}
11894 INDEX_EXPRESSION_LIST ::= ( EXPRESSION @{, EXPRESSION @} )
11897 where @code{PREFIX} is the name of an array or record object, the
11898 association list in parentheses does not contain an @code{others}
11899 choice and the box symbol @code{<>} may not appear in any
11900 expression. The effect is to yield a copy of the array or record value
11901 which is unchanged apart from the components mentioned in the
11902 association list, which are changed to the indicated value. The
11903 original value of the array or record value is not affected. For
11907 type Arr is Array (1 .. 5) of Integer;
11909 Avar1 : Arr := (1,2,3,4,5);
11910 Avar2 : Arr := Avar1'Update (2 => 10, 3 .. 4 => 20);
11913 yields a value for @code{Avar2} of 1,10,20,20,5 with @code{Avar1}
11914 begin unmodified. Similarly:
11917 type Rec is A, B, C : Integer;
11919 Rvar1 : Rec := (A => 1, B => 2, C => 3);
11920 Rvar2 : Rec := Rvar1'Update (B => 20);
11923 yields a value for @code{Rvar2} of (A => 1, B => 20, C => 3),
11924 with @code{Rvar1} being unmodifed.
11925 Note that the value of the attribute reference is computed
11926 completely before it is used. This means that if you write:
11929 Avar1 := Avar1'Update (1 => 10, 2 => Function_Call);
11932 then the value of @code{Avar1} is not modified if @code{Function_Call}
11933 raises an exception, unlike the effect of a series of direct assignments
11934 to elements of @code{Avar1}. In general this requires that
11935 two extra complete copies of the object are required, which should be
11936 kept in mind when considering efficiency.
11938 The @code{Update} attribute cannot be applied to prefixes of a limited
11939 type, and cannot reference discriminants in the case of a record type.
11940 The accessibility level of an Update attribute result object is defined
11941 as for an aggregate.
11943 In the record case, no component can be mentioned more than once. In
11944 the array case, two overlapping ranges can appear in the association list,
11945 in which case the modifications are processed left to right.
11947 Multi-dimensional arrays can be modified, as shown by this example:
11950 A : array (1 .. 10, 1 .. 10) of Integer;
11952 A := A'Update ((1, 2) => 20, (3, 4) => 30);
11955 which changes element (1,2) to 20 and (3,4) to 30.
11957 @node Attribute Valid_Scalars,Attribute VADS_Size,Attribute Update,Implementation Defined Attributes
11958 @anchor{gnat_rm/implementation_defined_attributes attribute-valid-scalars}@anchor{1af}
11959 @section Attribute Valid_Scalars
11962 @geindex Valid_Scalars
11964 The @code{'Valid_Scalars} attribute is intended to make it easier to check the
11965 validity of scalar subcomponents of composite objects. The attribute is defined
11966 for any prefix @code{P} which denotes an object. Prefix @code{P} can be any type
11967 except for tagged private or @code{Unchecked_Union} types. The value of the
11968 attribute is of type @code{Boolean}.
11970 @code{P'Valid_Scalars} yields @code{True} if and only if the evaluation of
11971 @code{C'Valid} yields @code{True} for every scalar subcomponent @code{C} of @code{P}, or if
11972 @code{P} has no scalar subcomponents. Attribute @code{'Valid_Scalars} is equivalent
11973 to attribute @code{'Valid} for scalar types.
11975 It is not specified in what order the subcomponents are checked, nor whether
11976 any more are checked after any one of them is determined to be invalid. If the
11977 prefix @code{P} is of a class-wide type @code{T'Class} (where @code{T} is the associated
11978 specific type), or if the prefix @code{P} is of a specific tagged type @code{T}, then
11979 only the subcomponents of @code{T} are checked; in other words, components of
11980 extensions of @code{T} are not checked even if @code{T'Class (P)'Tag /= T'Tag}.
11982 The compiler will issue a warning if it can be determined at compile time that
11983 the prefix of the attribute has no scalar subcomponents.
11985 Note: @code{Valid_Scalars} can generate a lot of code, especially in the case of
11986 a large variant record. If the attribute is called in many places in the same
11987 program applied to objects of the same type, it can reduce program size to
11988 write a function with a single use of the attribute, and then call that
11989 function from multiple places.
11991 @node Attribute VADS_Size,Attribute Value_Size,Attribute Valid_Scalars,Implementation Defined Attributes
11992 @anchor{gnat_rm/implementation_defined_attributes attribute-vads-size}@anchor{1b0}
11993 @section Attribute VADS_Size
11997 @geindex VADS compatibility
12001 The @code{'VADS_Size} attribute is intended to make it easier to port
12002 legacy code which relies on the semantics of @code{'Size} as implemented
12003 by the VADS Ada 83 compiler. GNAT makes a best effort at duplicating the
12004 same semantic interpretation. In particular, @code{'VADS_Size} applied
12005 to a predefined or other primitive type with no Size clause yields the
12006 Object_Size (for example, @code{Natural'Size} is 32 rather than 31 on
12007 typical machines). In addition @code{'VADS_Size} applied to an object
12008 gives the result that would be obtained by applying the attribute to
12009 the corresponding type.
12011 @node Attribute Value_Size,Attribute Wchar_T_Size,Attribute VADS_Size,Implementation Defined Attributes
12012 @anchor{gnat_rm/implementation_defined_attributes id6}@anchor{1b1}@anchor{gnat_rm/implementation_defined_attributes attribute-value-size}@anchor{163}
12013 @section Attribute Value_Size
12017 @geindex setting for not-first subtype
12019 @geindex Value_Size
12021 @code{type'Value_Size} is the number of bits required to represent
12022 a value of the given subtype. It is the same as @code{type'Size},
12023 but, unlike @code{Size}, may be set for non-first subtypes.
12025 @node Attribute Wchar_T_Size,Attribute Word_Size,Attribute Value_Size,Implementation Defined Attributes
12026 @anchor{gnat_rm/implementation_defined_attributes attribute-wchar-t-size}@anchor{1b2}
12027 @section Attribute Wchar_T_Size
12030 @geindex Wchar_T_Size
12032 @code{Standard'Wchar_T_Size} (@code{Standard} is the only permissible
12033 prefix) provides the size in bits of the C @code{wchar_t} type
12034 primarily for constructing the definition of this type in
12035 package @code{Interfaces.C}. The result is a static constant.
12037 @node Attribute Word_Size,,Attribute Wchar_T_Size,Implementation Defined Attributes
12038 @anchor{gnat_rm/implementation_defined_attributes attribute-word-size}@anchor{1b3}
12039 @section Attribute Word_Size
12044 @code{Standard'Word_Size} (@code{Standard} is the only permissible
12045 prefix) provides the value @code{System.Word_Size}. The result is
12048 @node Standard and Implementation Defined Restrictions,Implementation Advice,Implementation Defined Attributes,Top
12049 @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{1b4}@anchor{gnat_rm/standard_and_implementation_defined_restrictions id1}@anchor{1b5}
12050 @chapter Standard and Implementation Defined Restrictions
12053 All Ada Reference Manual-defined Restriction identifiers are implemented:
12059 language-defined restrictions (see 13.12.1)
12062 tasking restrictions (see D.7)
12065 high integrity restrictions (see H.4)
12068 GNAT implements additional restriction identifiers. All restrictions, whether
12069 language defined or GNAT-specific, are listed in the following.
12072 * Partition-Wide Restrictions::
12073 * Program Unit Level Restrictions::
12077 @node Partition-Wide Restrictions,Program Unit Level Restrictions,,Standard and Implementation Defined Restrictions
12078 @anchor{gnat_rm/standard_and_implementation_defined_restrictions partition-wide-restrictions}@anchor{1b6}@anchor{gnat_rm/standard_and_implementation_defined_restrictions id2}@anchor{1b7}
12079 @section Partition-Wide Restrictions
12082 There are two separate lists of restriction identifiers. The first
12083 set requires consistency throughout a partition (in other words, if the
12084 restriction identifier is used for any compilation unit in the partition,
12085 then all compilation units in the partition must obey the restriction).
12088 * Immediate_Reclamation::
12089 * Max_Asynchronous_Select_Nesting::
12090 * Max_Entry_Queue_Length::
12091 * Max_Protected_Entries::
12092 * Max_Select_Alternatives::
12093 * Max_Storage_At_Blocking::
12094 * Max_Task_Entries::
12096 * No_Abort_Statements::
12097 * No_Access_Parameter_Allocators::
12098 * No_Access_Subprograms::
12100 * No_Anonymous_Allocators::
12101 * No_Asynchronous_Control::
12103 * No_Coextensions::
12104 * No_Default_Initialization::
12107 * No_Direct_Boolean_Operators::
12109 * No_Dispatching_Calls::
12110 * No_Dynamic_Attachment::
12111 * No_Dynamic_Priorities::
12112 * No_Entry_Calls_In_Elaboration_Code::
12113 * No_Enumeration_Maps::
12114 * No_Exception_Handlers::
12115 * No_Exception_Propagation::
12116 * No_Exception_Registration::
12118 * No_Finalization::
12120 * No_Floating_Point::
12121 * No_Implicit_Conditionals::
12122 * No_Implicit_Dynamic_Code::
12123 * No_Implicit_Heap_Allocations::
12124 * No_Implicit_Protected_Object_Allocations::
12125 * No_Implicit_Task_Allocations::
12126 * No_Initialize_Scalars::
12128 * No_Local_Allocators::
12129 * No_Local_Protected_Objects::
12130 * No_Local_Timing_Events::
12131 * No_Long_Long_Integers::
12132 * No_Multiple_Elaboration::
12133 * No_Nested_Finalization::
12134 * No_Protected_Type_Allocators::
12135 * No_Protected_Types::
12138 * No_Relative_Delay::
12139 * No_Requeue_Statements::
12140 * No_Secondary_Stack::
12141 * No_Select_Statements::
12142 * No_Specific_Termination_Handlers::
12143 * No_Specification_of_Aspect::
12144 * No_Standard_Allocators_After_Elaboration::
12145 * No_Standard_Storage_Pools::
12146 * No_Stream_Optimizations::
12148 * No_Task_Allocators::
12149 * No_Task_At_Interrupt_Priority::
12150 * No_Task_Attributes_Package::
12151 * No_Task_Hierarchy::
12152 * No_Task_Termination::
12154 * No_Terminate_Alternatives::
12155 * No_Unchecked_Access::
12156 * No_Unchecked_Conversion::
12157 * No_Unchecked_Deallocation::
12158 * No_Use_Of_Entity::
12160 * Simple_Barriers::
12161 * Static_Priorities::
12162 * Static_Storage_Size::
12166 @node Immediate_Reclamation,Max_Asynchronous_Select_Nesting,,Partition-Wide Restrictions
12167 @anchor{gnat_rm/standard_and_implementation_defined_restrictions immediate-reclamation}@anchor{1b8}
12168 @subsection Immediate_Reclamation
12171 @geindex Immediate_Reclamation
12173 [RM H.4] This restriction ensures that, except for storage occupied by
12174 objects created by allocators and not deallocated via unchecked
12175 deallocation, any storage reserved at run time for an object is
12176 immediately reclaimed when the object no longer exists.
12178 @node Max_Asynchronous_Select_Nesting,Max_Entry_Queue_Length,Immediate_Reclamation,Partition-Wide Restrictions
12179 @anchor{gnat_rm/standard_and_implementation_defined_restrictions max-asynchronous-select-nesting}@anchor{1b9}
12180 @subsection Max_Asynchronous_Select_Nesting
12183 @geindex Max_Asynchronous_Select_Nesting
12185 [RM D.7] Specifies the maximum dynamic nesting level of asynchronous
12186 selects. Violations of this restriction with a value of zero are
12187 detected at compile time. Violations of this restriction with values
12188 other than zero cause Storage_Error to be raised.
12190 @node Max_Entry_Queue_Length,Max_Protected_Entries,Max_Asynchronous_Select_Nesting,Partition-Wide Restrictions
12191 @anchor{gnat_rm/standard_and_implementation_defined_restrictions max-entry-queue-length}@anchor{1ba}
12192 @subsection Max_Entry_Queue_Length
12195 @geindex Max_Entry_Queue_Length
12197 [RM D.7] This restriction is a declaration that any protected entry compiled in
12198 the scope of the restriction has at most the specified number of
12199 tasks waiting on the entry at any one time, and so no queue is required.
12200 Note that this restriction is checked at run time. Violation of this
12201 restriction results in the raising of Program_Error exception at the point of
12204 @geindex Max_Entry_Queue_Depth
12206 The restriction @code{Max_Entry_Queue_Depth} is recognized as a
12207 synonym for @code{Max_Entry_Queue_Length}. This is retained for historical
12208 compatibility purposes (and a warning will be generated for its use if
12209 warnings on obsolescent features are activated).
12211 @node Max_Protected_Entries,Max_Select_Alternatives,Max_Entry_Queue_Length,Partition-Wide Restrictions
12212 @anchor{gnat_rm/standard_and_implementation_defined_restrictions max-protected-entries}@anchor{1bb}
12213 @subsection Max_Protected_Entries
12216 @geindex Max_Protected_Entries
12218 [RM D.7] Specifies the maximum number of entries per protected type. The
12219 bounds of every entry family of a protected unit shall be static, or shall be
12220 defined by a discriminant of a subtype whose corresponding bound is static.
12222 @node Max_Select_Alternatives,Max_Storage_At_Blocking,Max_Protected_Entries,Partition-Wide Restrictions
12223 @anchor{gnat_rm/standard_and_implementation_defined_restrictions max-select-alternatives}@anchor{1bc}
12224 @subsection Max_Select_Alternatives
12227 @geindex Max_Select_Alternatives
12229 [RM D.7] Specifies the maximum number of alternatives in a selective accept.
12231 @node Max_Storage_At_Blocking,Max_Task_Entries,Max_Select_Alternatives,Partition-Wide Restrictions
12232 @anchor{gnat_rm/standard_and_implementation_defined_restrictions max-storage-at-blocking}@anchor{1bd}
12233 @subsection Max_Storage_At_Blocking
12236 @geindex Max_Storage_At_Blocking
12238 [RM D.7] Specifies the maximum portion (in storage elements) of a task's
12239 Storage_Size that can be retained by a blocked task. A violation of this
12240 restriction causes Storage_Error to be raised.
12242 @node Max_Task_Entries,Max_Tasks,Max_Storage_At_Blocking,Partition-Wide Restrictions
12243 @anchor{gnat_rm/standard_and_implementation_defined_restrictions max-task-entries}@anchor{1be}
12244 @subsection Max_Task_Entries
12247 @geindex Max_Task_Entries
12249 [RM D.7] Specifies the maximum number of entries
12250 per task. The bounds of every entry family
12251 of a task unit shall be static, or shall be
12252 defined by a discriminant of a subtype whose
12253 corresponding bound is static.
12255 @node Max_Tasks,No_Abort_Statements,Max_Task_Entries,Partition-Wide Restrictions
12256 @anchor{gnat_rm/standard_and_implementation_defined_restrictions max-tasks}@anchor{1bf}
12257 @subsection Max_Tasks
12262 [RM D.7] Specifies the maximum number of task that may be created, not
12263 counting the creation of the environment task. Violations of this
12264 restriction with a value of zero are detected at compile
12265 time. Violations of this restriction with values other than zero cause
12266 Storage_Error to be raised.
12268 @node No_Abort_Statements,No_Access_Parameter_Allocators,Max_Tasks,Partition-Wide Restrictions
12269 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-abort-statements}@anchor{1c0}
12270 @subsection No_Abort_Statements
12273 @geindex No_Abort_Statements
12275 [RM D.7] There are no abort_statements, and there are
12276 no calls to Task_Identification.Abort_Task.
12278 @node No_Access_Parameter_Allocators,No_Access_Subprograms,No_Abort_Statements,Partition-Wide Restrictions
12279 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-access-parameter-allocators}@anchor{1c1}
12280 @subsection No_Access_Parameter_Allocators
12283 @geindex No_Access_Parameter_Allocators
12285 [RM H.4] This restriction ensures at compile time that there are no
12286 occurrences of an allocator as the actual parameter to an access
12289 @node No_Access_Subprograms,No_Allocators,No_Access_Parameter_Allocators,Partition-Wide Restrictions
12290 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-access-subprograms}@anchor{1c2}
12291 @subsection No_Access_Subprograms
12294 @geindex No_Access_Subprograms
12296 [RM H.4] This restriction ensures at compile time that there are no
12297 declarations of access-to-subprogram types.
12299 @node No_Allocators,No_Anonymous_Allocators,No_Access_Subprograms,Partition-Wide Restrictions
12300 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-allocators}@anchor{1c3}
12301 @subsection No_Allocators
12304 @geindex No_Allocators
12306 [RM H.4] This restriction ensures at compile time that there are no
12307 occurrences of an allocator.
12309 @node No_Anonymous_Allocators,No_Asynchronous_Control,No_Allocators,Partition-Wide Restrictions
12310 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-anonymous-allocators}@anchor{1c4}
12311 @subsection No_Anonymous_Allocators
12314 @geindex No_Anonymous_Allocators
12316 [RM H.4] This restriction ensures at compile time that there are no
12317 occurrences of an allocator of anonymous access type.
12319 @node No_Asynchronous_Control,No_Calendar,No_Anonymous_Allocators,Partition-Wide Restrictions
12320 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-asynchronous-control}@anchor{1c5}
12321 @subsection No_Asynchronous_Control
12324 @geindex No_Asynchronous_Control
12326 [RM J.13] This restriction ensures at compile time that there are no semantic
12327 dependences on the predefined package Asynchronous_Task_Control.
12329 @node No_Calendar,No_Coextensions,No_Asynchronous_Control,Partition-Wide Restrictions
12330 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-calendar}@anchor{1c6}
12331 @subsection No_Calendar
12334 @geindex No_Calendar
12336 [GNAT] This restriction ensures at compile time that there are no semantic
12337 dependences on package Calendar.
12339 @node No_Coextensions,No_Default_Initialization,No_Calendar,Partition-Wide Restrictions
12340 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-coextensions}@anchor{1c7}
12341 @subsection No_Coextensions
12344 @geindex No_Coextensions
12346 [RM H.4] This restriction ensures at compile time that there are no
12347 coextensions. See 3.10.2.
12349 @node No_Default_Initialization,No_Delay,No_Coextensions,Partition-Wide Restrictions
12350 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-default-initialization}@anchor{1c8}
12351 @subsection No_Default_Initialization
12354 @geindex No_Default_Initialization
12356 [GNAT] This restriction prohibits any instance of default initialization
12357 of variables. The binder implements a consistency rule which prevents
12358 any unit compiled without the restriction from with'ing a unit with the
12359 restriction (this allows the generation of initialization procedures to
12360 be skipped, since you can be sure that no call is ever generated to an
12361 initialization procedure in a unit with the restriction active). If used
12362 in conjunction with Initialize_Scalars or Normalize_Scalars, the effect
12363 is to prohibit all cases of variables declared without a specific
12364 initializer (including the case of OUT scalar parameters).
12366 @node No_Delay,No_Dependence,No_Default_Initialization,Partition-Wide Restrictions
12367 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-delay}@anchor{1c9}
12368 @subsection No_Delay
12373 [RM H.4] This restriction ensures at compile time that there are no
12374 delay statements and no semantic dependences on package Calendar.
12376 @node No_Dependence,No_Direct_Boolean_Operators,No_Delay,Partition-Wide Restrictions
12377 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-dependence}@anchor{1ca}
12378 @subsection No_Dependence
12381 @geindex No_Dependence
12383 [RM 13.12.1] This restriction ensures at compile time that there are no
12384 dependences on a library unit.
12386 @node No_Direct_Boolean_Operators,No_Dispatch,No_Dependence,Partition-Wide Restrictions
12387 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-direct-boolean-operators}@anchor{1cb}
12388 @subsection No_Direct_Boolean_Operators
12391 @geindex No_Direct_Boolean_Operators
12393 [GNAT] This restriction ensures that no logical operators (and/or/xor)
12394 are used on operands of type Boolean (or any type derived from Boolean).
12395 This is intended for use in safety critical programs where the certification
12396 protocol requires the use of short-circuit (and then, or else) forms for all
12397 composite boolean operations.
12399 @node No_Dispatch,No_Dispatching_Calls,No_Direct_Boolean_Operators,Partition-Wide Restrictions
12400 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-dispatch}@anchor{1cc}
12401 @subsection No_Dispatch
12404 @geindex No_Dispatch
12406 [RM H.4] This restriction ensures at compile time that there are no
12407 occurrences of @code{T'Class}, for any (tagged) subtype @code{T}.
12409 @node No_Dispatching_Calls,No_Dynamic_Attachment,No_Dispatch,Partition-Wide Restrictions
12410 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-dispatching-calls}@anchor{1cd}
12411 @subsection No_Dispatching_Calls
12414 @geindex No_Dispatching_Calls
12416 [GNAT] This restriction ensures at compile time that the code generated by the
12417 compiler involves no dispatching calls. The use of this restriction allows the
12418 safe use of record extensions, classwide membership tests and other classwide
12419 features not involving implicit dispatching. This restriction ensures that
12420 the code contains no indirect calls through a dispatching mechanism. Note that
12421 this includes internally-generated calls created by the compiler, for example
12422 in the implementation of class-wide objects assignments. The
12423 membership test is allowed in the presence of this restriction, because its
12424 implementation requires no dispatching.
12425 This restriction is comparable to the official Ada restriction
12426 @code{No_Dispatch} except that it is a bit less restrictive in that it allows
12427 all classwide constructs that do not imply dispatching.
12428 The following example indicates constructs that violate this restriction.
12432 type T is tagged record
12435 procedure P (X : T);
12437 type DT is new T with record
12438 More_Data : Natural;
12440 procedure Q (X : DT);
12444 procedure Example is
12445 procedure Test (O : T'Class) is
12446 N : Natural := O'Size;-- Error: Dispatching call
12447 C : T'Class := O; -- Error: implicit Dispatching Call
12449 if O in DT'Class then -- OK : Membership test
12450 Q (DT (O)); -- OK : Type conversion plus direct call
12452 P (O); -- Error: Dispatching call
12458 P (Obj); -- OK : Direct call
12459 P (T (Obj)); -- OK : Type conversion plus direct call
12460 P (T'Class (Obj)); -- Error: Dispatching call
12462 Test (Obj); -- OK : Type conversion
12464 if Obj in T'Class then -- OK : Membership test
12470 @node No_Dynamic_Attachment,No_Dynamic_Priorities,No_Dispatching_Calls,Partition-Wide Restrictions
12471 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-dynamic-attachment}@anchor{1ce}
12472 @subsection No_Dynamic_Attachment
12475 @geindex No_Dynamic_Attachment
12477 [RM D.7] This restriction ensures that there is no call to any of the
12478 operations defined in package Ada.Interrupts
12479 (Is_Reserved, Is_Attached, Current_Handler, Attach_Handler, Exchange_Handler,
12480 Detach_Handler, and Reference).
12482 @geindex No_Dynamic_Interrupts
12484 The restriction @code{No_Dynamic_Interrupts} is recognized as a
12485 synonym for @code{No_Dynamic_Attachment}. This is retained for historical
12486 compatibility purposes (and a warning will be generated for its use if
12487 warnings on obsolescent features are activated).
12489 @node No_Dynamic_Priorities,No_Entry_Calls_In_Elaboration_Code,No_Dynamic_Attachment,Partition-Wide Restrictions
12490 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-dynamic-priorities}@anchor{1cf}
12491 @subsection No_Dynamic_Priorities
12494 @geindex No_Dynamic_Priorities
12496 [RM D.7] There are no semantic dependencies on the package Dynamic_Priorities.
12498 @node No_Entry_Calls_In_Elaboration_Code,No_Enumeration_Maps,No_Dynamic_Priorities,Partition-Wide Restrictions
12499 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-entry-calls-in-elaboration-code}@anchor{1d0}
12500 @subsection No_Entry_Calls_In_Elaboration_Code
12503 @geindex No_Entry_Calls_In_Elaboration_Code
12505 [GNAT] This restriction ensures at compile time that no task or protected entry
12506 calls are made during elaboration code. As a result of the use of this
12507 restriction, the compiler can assume that no code past an accept statement
12508 in a task can be executed at elaboration time.
12510 @node No_Enumeration_Maps,No_Exception_Handlers,No_Entry_Calls_In_Elaboration_Code,Partition-Wide Restrictions
12511 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-enumeration-maps}@anchor{1d1}
12512 @subsection No_Enumeration_Maps
12515 @geindex No_Enumeration_Maps
12517 [GNAT] This restriction ensures at compile time that no operations requiring
12518 enumeration maps are used (that is Image and Value attributes applied
12519 to enumeration types).
12521 @node No_Exception_Handlers,No_Exception_Propagation,No_Enumeration_Maps,Partition-Wide Restrictions
12522 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-exception-handlers}@anchor{1d2}
12523 @subsection No_Exception_Handlers
12526 @geindex No_Exception_Handlers
12528 [GNAT] This restriction ensures at compile time that there are no explicit
12529 exception handlers. It also indicates that no exception propagation will
12530 be provided. In this mode, exceptions may be raised but will result in
12531 an immediate call to the last chance handler, a routine that the user
12532 must define with the following profile:
12535 procedure Last_Chance_Handler
12536 (Source_Location : System.Address; Line : Integer);
12537 pragma Export (C, Last_Chance_Handler,
12538 "__gnat_last_chance_handler");
12541 The parameter is a C null-terminated string representing a message to be
12542 associated with the exception (typically the source location of the raise
12543 statement generated by the compiler). The Line parameter when nonzero
12544 represents the line number in the source program where the raise occurs.
12546 @node No_Exception_Propagation,No_Exception_Registration,No_Exception_Handlers,Partition-Wide Restrictions
12547 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-exception-propagation}@anchor{1d3}
12548 @subsection No_Exception_Propagation
12551 @geindex No_Exception_Propagation
12553 [GNAT] This restriction guarantees that exceptions are never propagated
12554 to an outer subprogram scope. The only case in which an exception may
12555 be raised is when the handler is statically in the same subprogram, so
12556 that the effect of a raise is essentially like a goto statement. Any
12557 other raise statement (implicit or explicit) will be considered
12558 unhandled. Exception handlers are allowed, but may not contain an
12559 exception occurrence identifier (exception choice). In addition, use of
12560 the package GNAT.Current_Exception is not permitted, and reraise
12561 statements (raise with no operand) are not permitted.
12563 @node No_Exception_Registration,No_Exceptions,No_Exception_Propagation,Partition-Wide Restrictions
12564 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-exception-registration}@anchor{1d4}
12565 @subsection No_Exception_Registration
12568 @geindex No_Exception_Registration
12570 [GNAT] This restriction ensures at compile time that no stream operations for
12571 types Exception_Id or Exception_Occurrence are used. This also makes it
12572 impossible to pass exceptions to or from a partition with this restriction
12573 in a distributed environment. If this restriction is active, the generated
12574 code is simplified by omitting the otherwise-required global registration
12575 of exceptions when they are declared.
12577 @node No_Exceptions,No_Finalization,No_Exception_Registration,Partition-Wide Restrictions
12578 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-exceptions}@anchor{1d5}
12579 @subsection No_Exceptions
12582 @geindex No_Exceptions
12584 [RM H.4] This restriction ensures at compile time that there are no
12585 raise statements and no exception handlers and also suppresses the
12586 generation of language-defined run-time checks.
12588 @node No_Finalization,No_Fixed_Point,No_Exceptions,Partition-Wide Restrictions
12589 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-finalization}@anchor{1d6}
12590 @subsection No_Finalization
12593 @geindex No_Finalization
12595 [GNAT] This restriction disables the language features described in
12596 chapter 7.6 of the Ada 2005 RM as well as all form of code generation
12597 performed by the compiler to support these features. The following types
12598 are no longer considered controlled when this restriction is in effect:
12604 @code{Ada.Finalization.Controlled}
12607 @code{Ada.Finalization.Limited_Controlled}
12610 Derivations from @code{Controlled} or @code{Limited_Controlled}
12622 Array and record types with controlled components
12625 The compiler no longer generates code to initialize, finalize or adjust an
12626 object or a nested component, either declared on the stack or on the heap. The
12627 deallocation of a controlled object no longer finalizes its contents.
12629 @node No_Fixed_Point,No_Floating_Point,No_Finalization,Partition-Wide Restrictions
12630 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-fixed-point}@anchor{1d7}
12631 @subsection No_Fixed_Point
12634 @geindex No_Fixed_Point
12636 [RM H.4] This restriction ensures at compile time that there are no
12637 occurrences of fixed point types and operations.
12639 @node No_Floating_Point,No_Implicit_Conditionals,No_Fixed_Point,Partition-Wide Restrictions
12640 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-floating-point}@anchor{1d8}
12641 @subsection No_Floating_Point
12644 @geindex No_Floating_Point
12646 [RM H.4] This restriction ensures at compile time that there are no
12647 occurrences of floating point types and operations.
12649 @node No_Implicit_Conditionals,No_Implicit_Dynamic_Code,No_Floating_Point,Partition-Wide Restrictions
12650 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-conditionals}@anchor{1d9}
12651 @subsection No_Implicit_Conditionals
12654 @geindex No_Implicit_Conditionals
12656 [GNAT] This restriction ensures that the generated code does not contain any
12657 implicit conditionals, either by modifying the generated code where possible,
12658 or by rejecting any construct that would otherwise generate an implicit
12659 conditional. Note that this check does not include run time constraint
12660 checks, which on some targets may generate implicit conditionals as
12661 well. To control the latter, constraint checks can be suppressed in the
12662 normal manner. Constructs generating implicit conditionals include comparisons
12663 of composite objects and the Max/Min attributes.
12665 @node No_Implicit_Dynamic_Code,No_Implicit_Heap_Allocations,No_Implicit_Conditionals,Partition-Wide Restrictions
12666 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-dynamic-code}@anchor{1da}
12667 @subsection No_Implicit_Dynamic_Code
12670 @geindex No_Implicit_Dynamic_Code
12672 @geindex trampoline
12674 [GNAT] This restriction prevents the compiler from building 'trampolines'.
12675 This is a structure that is built on the stack and contains dynamic
12676 code to be executed at run time. On some targets, a trampoline is
12677 built for the following features: @code{Access},
12678 @code{Unrestricted_Access}, or @code{Address} of a nested subprogram;
12679 nested task bodies; primitive operations of nested tagged types.
12680 Trampolines do not work on machines that prevent execution of stack
12681 data. For example, on windows systems, enabling DEP (data execution
12682 protection) will cause trampolines to raise an exception.
12683 Trampolines are also quite slow at run time.
12685 On many targets, trampolines have been largely eliminated. Look at the
12686 version of system.ads for your target --- if it has
12687 Always_Compatible_Rep equal to False, then trampolines are largely
12688 eliminated. In particular, a trampoline is built for the following
12689 features: @code{Address} of a nested subprogram;
12690 @code{Access} or @code{Unrestricted_Access} of a nested subprogram,
12691 but only if pragma Favor_Top_Level applies, or the access type has a
12692 foreign-language convention; primitive operations of nested tagged
12695 @node No_Implicit_Heap_Allocations,No_Implicit_Protected_Object_Allocations,No_Implicit_Dynamic_Code,Partition-Wide Restrictions
12696 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-heap-allocations}@anchor{1db}
12697 @subsection No_Implicit_Heap_Allocations
12700 @geindex No_Implicit_Heap_Allocations
12702 [RM D.7] No constructs are allowed to cause implicit heap allocation.
12704 @node No_Implicit_Protected_Object_Allocations,No_Implicit_Task_Allocations,No_Implicit_Heap_Allocations,Partition-Wide Restrictions
12705 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-protected-object-allocations}@anchor{1dc}
12706 @subsection No_Implicit_Protected_Object_Allocations
12709 @geindex No_Implicit_Protected_Object_Allocations
12711 [GNAT] No constructs are allowed to cause implicit heap allocation of a
12714 @node No_Implicit_Task_Allocations,No_Initialize_Scalars,No_Implicit_Protected_Object_Allocations,Partition-Wide Restrictions
12715 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-task-allocations}@anchor{1dd}
12716 @subsection No_Implicit_Task_Allocations
12719 @geindex No_Implicit_Task_Allocations
12721 [GNAT] No constructs are allowed to cause implicit heap allocation of a task.
12723 @node No_Initialize_Scalars,No_IO,No_Implicit_Task_Allocations,Partition-Wide Restrictions
12724 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-initialize-scalars}@anchor{1de}
12725 @subsection No_Initialize_Scalars
12728 @geindex No_Initialize_Scalars
12730 [GNAT] This restriction ensures that no unit in the partition is compiled with
12731 pragma Initialize_Scalars. This allows the generation of more efficient
12732 code, and in particular eliminates dummy null initialization routines that
12733 are otherwise generated for some record and array types.
12735 @node No_IO,No_Local_Allocators,No_Initialize_Scalars,Partition-Wide Restrictions
12736 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-io}@anchor{1df}
12742 [RM H.4] This restriction ensures at compile time that there are no
12743 dependences on any of the library units Sequential_IO, Direct_IO,
12744 Text_IO, Wide_Text_IO, Wide_Wide_Text_IO, or Stream_IO.
12746 @node No_Local_Allocators,No_Local_Protected_Objects,No_IO,Partition-Wide Restrictions
12747 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-local-allocators}@anchor{1e0}
12748 @subsection No_Local_Allocators
12751 @geindex No_Local_Allocators
12753 [RM H.4] This restriction ensures at compile time that there are no
12754 occurrences of an allocator in subprograms, generic subprograms, tasks,
12757 @node No_Local_Protected_Objects,No_Local_Timing_Events,No_Local_Allocators,Partition-Wide Restrictions
12758 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-local-protected-objects}@anchor{1e1}
12759 @subsection No_Local_Protected_Objects
12762 @geindex No_Local_Protected_Objects
12764 [RM D.7] This restriction ensures at compile time that protected objects are
12765 only declared at the library level.
12767 @node No_Local_Timing_Events,No_Long_Long_Integers,No_Local_Protected_Objects,Partition-Wide Restrictions
12768 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-local-timing-events}@anchor{1e2}
12769 @subsection No_Local_Timing_Events
12772 @geindex No_Local_Timing_Events
12774 [RM D.7] All objects of type Ada.Timing_Events.Timing_Event are
12775 declared at the library level.
12777 @node No_Long_Long_Integers,No_Multiple_Elaboration,No_Local_Timing_Events,Partition-Wide Restrictions
12778 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-long-long-integers}@anchor{1e3}
12779 @subsection No_Long_Long_Integers
12782 @geindex No_Long_Long_Integers
12784 [GNAT] This partition-wide restriction forbids any explicit reference to
12785 type Standard.Long_Long_Integer, and also forbids declaring range types whose
12786 implicit base type is Long_Long_Integer, and modular types whose size exceeds
12789 @node No_Multiple_Elaboration,No_Nested_Finalization,No_Long_Long_Integers,Partition-Wide Restrictions
12790 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-multiple-elaboration}@anchor{1e4}
12791 @subsection No_Multiple_Elaboration
12794 @geindex No_Multiple_Elaboration
12796 [GNAT] When this restriction is active and the static elaboration model is
12797 used, and -fpreserve-control-flow is not used, the compiler is allowed to
12798 suppress the elaboration counter normally associated with the unit, even if
12799 the unit has elaboration code. This counter is typically used to check for
12800 access before elaboration and to control multiple elaboration attempts. If the
12801 restriction is used, then the situations in which multiple elaboration is
12802 possible, including non-Ada main programs and Stand Alone libraries, are not
12803 permitted and will be diagnosed by the binder.
12805 @node No_Nested_Finalization,No_Protected_Type_Allocators,No_Multiple_Elaboration,Partition-Wide Restrictions
12806 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-nested-finalization}@anchor{1e5}
12807 @subsection No_Nested_Finalization
12810 @geindex No_Nested_Finalization
12812 [RM D.7] All objects requiring finalization are declared at the library level.
12814 @node No_Protected_Type_Allocators,No_Protected_Types,No_Nested_Finalization,Partition-Wide Restrictions
12815 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-protected-type-allocators}@anchor{1e6}
12816 @subsection No_Protected_Type_Allocators
12819 @geindex No_Protected_Type_Allocators
12821 [RM D.7] This restriction ensures at compile time that there are no allocator
12822 expressions that attempt to allocate protected objects.
12824 @node No_Protected_Types,No_Recursion,No_Protected_Type_Allocators,Partition-Wide Restrictions
12825 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-protected-types}@anchor{1e7}
12826 @subsection No_Protected_Types
12829 @geindex No_Protected_Types
12831 [RM H.4] This restriction ensures at compile time that there are no
12832 declarations of protected types or protected objects.
12834 @node No_Recursion,No_Reentrancy,No_Protected_Types,Partition-Wide Restrictions
12835 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-recursion}@anchor{1e8}
12836 @subsection No_Recursion
12839 @geindex No_Recursion
12841 [RM H.4] A program execution is erroneous if a subprogram is invoked as
12842 part of its execution.
12844 @node No_Reentrancy,No_Relative_Delay,No_Recursion,Partition-Wide Restrictions
12845 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-reentrancy}@anchor{1e9}
12846 @subsection No_Reentrancy
12849 @geindex No_Reentrancy
12851 [RM H.4] A program execution is erroneous if a subprogram is executed by
12852 two tasks at the same time.
12854 @node No_Relative_Delay,No_Requeue_Statements,No_Reentrancy,Partition-Wide Restrictions
12855 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-relative-delay}@anchor{1ea}
12856 @subsection No_Relative_Delay
12859 @geindex No_Relative_Delay
12861 [RM D.7] This restriction ensures at compile time that there are no delay
12862 relative statements and prevents expressions such as @code{delay 1.23;} from
12863 appearing in source code.
12865 @node No_Requeue_Statements,No_Secondary_Stack,No_Relative_Delay,Partition-Wide Restrictions
12866 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-requeue-statements}@anchor{1eb}
12867 @subsection No_Requeue_Statements
12870 @geindex No_Requeue_Statements
12872 [RM D.7] This restriction ensures at compile time that no requeue statements
12873 are permitted and prevents keyword @code{requeue} from being used in source
12876 @geindex No_Requeue
12878 The restriction @code{No_Requeue} is recognized as a
12879 synonym for @code{No_Requeue_Statements}. This is retained for historical
12880 compatibility purposes (and a warning will be generated for its use if
12881 warnings on oNobsolescent features are activated).
12883 @node No_Secondary_Stack,No_Select_Statements,No_Requeue_Statements,Partition-Wide Restrictions
12884 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-secondary-stack}@anchor{1ec}
12885 @subsection No_Secondary_Stack
12888 @geindex No_Secondary_Stack
12890 [GNAT] This restriction ensures at compile time that the generated code
12891 does not contain any reference to the secondary stack. The secondary
12892 stack is used to implement functions returning unconstrained objects
12893 (arrays or records) on some targets. Suppresses the allocation of
12894 secondary stacks for tasks (excluding the environment task) at run time.
12896 @node No_Select_Statements,No_Specific_Termination_Handlers,No_Secondary_Stack,Partition-Wide Restrictions
12897 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-select-statements}@anchor{1ed}
12898 @subsection No_Select_Statements
12901 @geindex No_Select_Statements
12903 [RM D.7] This restriction ensures at compile time no select statements of any
12904 kind are permitted, that is the keyword @code{select} may not appear.
12906 @node No_Specific_Termination_Handlers,No_Specification_of_Aspect,No_Select_Statements,Partition-Wide Restrictions
12907 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-specific-termination-handlers}@anchor{1ee}
12908 @subsection No_Specific_Termination_Handlers
12911 @geindex No_Specific_Termination_Handlers
12913 [RM D.7] There are no calls to Ada.Task_Termination.Set_Specific_Handler
12914 or to Ada.Task_Termination.Specific_Handler.
12916 @node No_Specification_of_Aspect,No_Standard_Allocators_After_Elaboration,No_Specific_Termination_Handlers,Partition-Wide Restrictions
12917 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-specification-of-aspect}@anchor{1ef}
12918 @subsection No_Specification_of_Aspect
12921 @geindex No_Specification_of_Aspect
12923 [RM 13.12.1] This restriction checks at compile time that no aspect
12924 specification, attribute definition clause, or pragma is given for a
12927 @node No_Standard_Allocators_After_Elaboration,No_Standard_Storage_Pools,No_Specification_of_Aspect,Partition-Wide Restrictions
12928 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-standard-allocators-after-elaboration}@anchor{1f0}
12929 @subsection No_Standard_Allocators_After_Elaboration
12932 @geindex No_Standard_Allocators_After_Elaboration
12934 [RM D.7] Specifies that an allocator using a standard storage pool
12935 should never be evaluated at run time after the elaboration of the
12936 library items of the partition has completed. Otherwise, Storage_Error
12939 @node No_Standard_Storage_Pools,No_Stream_Optimizations,No_Standard_Allocators_After_Elaboration,Partition-Wide Restrictions
12940 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-standard-storage-pools}@anchor{1f1}
12941 @subsection No_Standard_Storage_Pools
12944 @geindex No_Standard_Storage_Pools
12946 [GNAT] This restriction ensures at compile time that no access types
12947 use the standard default storage pool. Any access type declared must
12948 have an explicit Storage_Pool attribute defined specifying a
12949 user-defined storage pool.
12951 @node No_Stream_Optimizations,No_Streams,No_Standard_Storage_Pools,Partition-Wide Restrictions
12952 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-stream-optimizations}@anchor{1f2}
12953 @subsection No_Stream_Optimizations
12956 @geindex No_Stream_Optimizations
12958 [GNAT] This restriction affects the performance of stream operations on types
12959 @code{String}, @code{Wide_String} and @code{Wide_Wide_String}. By default, the
12960 compiler uses block reads and writes when manipulating @code{String} objects
12961 due to their superior performance. When this restriction is in effect, the
12962 compiler performs all IO operations on a per-character basis.
12964 @node No_Streams,No_Task_Allocators,No_Stream_Optimizations,Partition-Wide Restrictions
12965 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-streams}@anchor{1f3}
12966 @subsection No_Streams
12969 @geindex No_Streams
12971 [GNAT] This restriction ensures at compile/bind time that there are no
12972 stream objects created and no use of stream attributes.
12973 This restriction does not forbid dependences on the package
12974 @code{Ada.Streams}. So it is permissible to with
12975 @code{Ada.Streams} (or another package that does so itself)
12976 as long as no actual stream objects are created and no
12977 stream attributes are used.
12979 Note that the use of restriction allows optimization of tagged types,
12980 since they do not need to worry about dispatching stream operations.
12981 To take maximum advantage of this space-saving optimization, any
12982 unit declaring a tagged type should be compiled with the restriction,
12983 though this is not required.
12985 @node No_Task_Allocators,No_Task_At_Interrupt_Priority,No_Streams,Partition-Wide Restrictions
12986 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-task-allocators}@anchor{1f4}
12987 @subsection No_Task_Allocators
12990 @geindex No_Task_Allocators
12992 [RM D.7] There are no allocators for task types
12993 or types containing task subcomponents.
12995 @node No_Task_At_Interrupt_Priority,No_Task_Attributes_Package,No_Task_Allocators,Partition-Wide Restrictions
12996 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-task-at-interrupt-priority}@anchor{1f5}
12997 @subsection No_Task_At_Interrupt_Priority
13000 @geindex No_Task_At_Interrupt_Priority
13002 [GNAT] This restriction ensures at compile time that there is no
13003 Interrupt_Priority aspect or pragma for a task or a task type. As
13004 a consequence, the tasks are always created with a priority below
13005 that an interrupt priority.
13007 @node No_Task_Attributes_Package,No_Task_Hierarchy,No_Task_At_Interrupt_Priority,Partition-Wide Restrictions
13008 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-task-attributes-package}@anchor{1f6}
13009 @subsection No_Task_Attributes_Package
13012 @geindex No_Task_Attributes_Package
13014 [GNAT] This restriction ensures at compile time that there are no implicit or
13015 explicit dependencies on the package @code{Ada.Task_Attributes}.
13017 @geindex No_Task_Attributes
13019 The restriction @code{No_Task_Attributes} is recognized as a synonym
13020 for @code{No_Task_Attributes_Package}. This is retained for historical
13021 compatibility purposes (and a warning will be generated for its use if
13022 warnings on obsolescent features are activated).
13024 @node No_Task_Hierarchy,No_Task_Termination,No_Task_Attributes_Package,Partition-Wide Restrictions
13025 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-task-hierarchy}@anchor{1f7}
13026 @subsection No_Task_Hierarchy
13029 @geindex No_Task_Hierarchy
13031 [RM D.7] All (non-environment) tasks depend
13032 directly on the environment task of the partition.
13034 @node No_Task_Termination,No_Tasking,No_Task_Hierarchy,Partition-Wide Restrictions
13035 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-task-termination}@anchor{1f8}
13036 @subsection No_Task_Termination
13039 @geindex No_Task_Termination
13041 [RM D.7] Tasks that terminate are erroneous.
13043 @node No_Tasking,No_Terminate_Alternatives,No_Task_Termination,Partition-Wide Restrictions
13044 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-tasking}@anchor{1f9}
13045 @subsection No_Tasking
13048 @geindex No_Tasking
13050 [GNAT] This restriction prevents the declaration of tasks or task types
13051 throughout the partition. It is similar in effect to the use of
13052 @code{Max_Tasks => 0} except that violations are caught at compile time
13053 and cause an error message to be output either by the compiler or
13056 @node No_Terminate_Alternatives,No_Unchecked_Access,No_Tasking,Partition-Wide Restrictions
13057 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-terminate-alternatives}@anchor{1fa}
13058 @subsection No_Terminate_Alternatives
13061 @geindex No_Terminate_Alternatives
13063 [RM D.7] There are no selective accepts with terminate alternatives.
13065 @node No_Unchecked_Access,No_Unchecked_Conversion,No_Terminate_Alternatives,Partition-Wide Restrictions
13066 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-unchecked-access}@anchor{1fb}
13067 @subsection No_Unchecked_Access
13070 @geindex No_Unchecked_Access
13072 [RM H.4] This restriction ensures at compile time that there are no
13073 occurrences of the Unchecked_Access attribute.
13075 @node No_Unchecked_Conversion,No_Unchecked_Deallocation,No_Unchecked_Access,Partition-Wide Restrictions
13076 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-unchecked-conversion}@anchor{1fc}
13077 @subsection No_Unchecked_Conversion
13080 @geindex No_Unchecked_Conversion
13082 [RM J.13] This restriction ensures at compile time that there are no semantic
13083 dependences on the predefined generic function Unchecked_Conversion.
13085 @node No_Unchecked_Deallocation,No_Use_Of_Entity,No_Unchecked_Conversion,Partition-Wide Restrictions
13086 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-unchecked-deallocation}@anchor{1fd}
13087 @subsection No_Unchecked_Deallocation
13090 @geindex No_Unchecked_Deallocation
13092 [RM J.13] This restriction ensures at compile time that there are no semantic
13093 dependences on the predefined generic procedure Unchecked_Deallocation.
13095 @node No_Use_Of_Entity,Pure_Barriers,No_Unchecked_Deallocation,Partition-Wide Restrictions
13096 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-use-of-entity}@anchor{1fe}
13097 @subsection No_Use_Of_Entity
13100 @geindex No_Use_Of_Entity
13102 [GNAT] This restriction ensures at compile time that there are no references
13103 to the entity given in the form
13106 No_Use_Of_Entity => Name
13109 where @code{Name} is the fully qualified entity, for example
13112 No_Use_Of_Entity => Ada.Text_IO.Put_Line
13115 @node Pure_Barriers,Simple_Barriers,No_Use_Of_Entity,Partition-Wide Restrictions
13116 @anchor{gnat_rm/standard_and_implementation_defined_restrictions pure-barriers}@anchor{1ff}
13117 @subsection Pure_Barriers
13120 @geindex Pure_Barriers
13122 [GNAT] This restriction ensures at compile time that protected entry
13123 barriers are restricted to:
13129 components of the protected object (excluding selection from dereferences),
13132 constant declarations,
13138 enumeration literals,
13147 character literals,
13150 implicitly defined comparison operators,
13153 uses of the Standard."not" operator,
13156 short-circuit operator,
13159 the Count attribute
13162 This restriction is a relaxation of the Simple_Barriers restriction,
13163 but still ensures absence of side effects, exceptions, and recursion
13164 during the evaluation of the barriers.
13166 @node Simple_Barriers,Static_Priorities,Pure_Barriers,Partition-Wide Restrictions
13167 @anchor{gnat_rm/standard_and_implementation_defined_restrictions simple-barriers}@anchor{200}
13168 @subsection Simple_Barriers
13171 @geindex Simple_Barriers
13173 [RM D.7] This restriction ensures at compile time that barriers in entry
13174 declarations for protected types are restricted to either static boolean
13175 expressions or references to simple boolean variables defined in the private
13176 part of the protected type. No other form of entry barriers is permitted.
13178 @geindex Boolean_Entry_Barriers
13180 The restriction @code{Boolean_Entry_Barriers} is recognized as a
13181 synonym for @code{Simple_Barriers}. This is retained for historical
13182 compatibility purposes (and a warning will be generated for its use if
13183 warnings on obsolescent features are activated).
13185 @node Static_Priorities,Static_Storage_Size,Simple_Barriers,Partition-Wide Restrictions
13186 @anchor{gnat_rm/standard_and_implementation_defined_restrictions static-priorities}@anchor{201}
13187 @subsection Static_Priorities
13190 @geindex Static_Priorities
13192 [GNAT] This restriction ensures at compile time that all priority expressions
13193 are static, and that there are no dependences on the package
13194 @code{Ada.Dynamic_Priorities}.
13196 @node Static_Storage_Size,,Static_Priorities,Partition-Wide Restrictions
13197 @anchor{gnat_rm/standard_and_implementation_defined_restrictions static-storage-size}@anchor{202}
13198 @subsection Static_Storage_Size
13201 @geindex Static_Storage_Size
13203 [GNAT] This restriction ensures at compile time that any expression appearing
13204 in a Storage_Size pragma or attribute definition clause is static.
13206 @node Program Unit Level Restrictions,,Partition-Wide Restrictions,Standard and Implementation Defined Restrictions
13207 @anchor{gnat_rm/standard_and_implementation_defined_restrictions program-unit-level-restrictions}@anchor{203}@anchor{gnat_rm/standard_and_implementation_defined_restrictions id3}@anchor{204}
13208 @section Program Unit Level Restrictions
13211 The second set of restriction identifiers
13212 does not require partition-wide consistency.
13213 The restriction may be enforced for a single
13214 compilation unit without any effect on any of the
13215 other compilation units in the partition.
13218 * No_Elaboration_Code::
13219 * No_Dynamic_Sized_Objects::
13221 * No_Implementation_Aspect_Specifications::
13222 * No_Implementation_Attributes::
13223 * No_Implementation_Identifiers::
13224 * No_Implementation_Pragmas::
13225 * No_Implementation_Restrictions::
13226 * No_Implementation_Units::
13227 * No_Implicit_Aliasing::
13228 * No_Implicit_Loops::
13229 * No_Obsolescent_Features::
13230 * No_Wide_Characters::
13231 * Static_Dispatch_Tables::
13236 @node No_Elaboration_Code,No_Dynamic_Sized_Objects,,Program Unit Level Restrictions
13237 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-elaboration-code}@anchor{205}
13238 @subsection No_Elaboration_Code
13241 @geindex No_Elaboration_Code
13243 [GNAT] This restriction ensures at compile time that no elaboration code is
13244 generated. Note that this is not the same condition as is enforced
13245 by pragma @code{Preelaborate}. There are cases in which pragma
13246 @code{Preelaborate} still permits code to be generated (e.g., code
13247 to initialize a large array to all zeroes), and there are cases of units
13248 which do not meet the requirements for pragma @code{Preelaborate},
13249 but for which no elaboration code is generated. Generally, it is
13250 the case that preelaborable units will meet the restrictions, with
13251 the exception of large aggregates initialized with an others_clause,
13252 and exception declarations (which generate calls to a run-time
13253 registry procedure). This restriction is enforced on
13254 a unit by unit basis, it need not be obeyed consistently
13255 throughout a partition.
13257 In the case of aggregates with others, if the aggregate has a dynamic
13258 size, there is no way to eliminate the elaboration code (such dynamic
13259 bounds would be incompatible with @code{Preelaborate} in any case). If
13260 the bounds are static, then use of this restriction actually modifies
13261 the code choice of the compiler to avoid generating a loop, and instead
13262 generate the aggregate statically if possible, no matter how many times
13263 the data for the others clause must be repeatedly generated.
13265 It is not possible to precisely document
13266 the constructs which are compatible with this restriction, since,
13267 unlike most other restrictions, this is not a restriction on the
13268 source code, but a restriction on the generated object code. For
13269 example, if the source contains a declaration:
13272 Val : constant Integer := X;
13275 where X is not a static constant, it may be possible, depending
13276 on complex optimization circuitry, for the compiler to figure
13277 out the value of X at compile time, in which case this initialization
13278 can be done by the loader, and requires no initialization code. It
13279 is not possible to document the precise conditions under which the
13280 optimizer can figure this out.
13282 Note that this the implementation of this restriction requires full
13283 code generation. If it is used in conjunction with "semantics only"
13284 checking, then some cases of violations may be missed.
13286 When this restriction is active, we are not requesting control-flow
13287 preservation with -fpreserve-control-flow, and the static elaboration model is
13288 used, the compiler is allowed to suppress the elaboration counter normally
13289 associated with the unit. This counter is typically used to check for access
13290 before elaboration and to control multiple elaboration attempts.
13292 @node No_Dynamic_Sized_Objects,No_Entry_Queue,No_Elaboration_Code,Program Unit Level Restrictions
13293 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-dynamic-sized-objects}@anchor{206}
13294 @subsection No_Dynamic_Sized_Objects
13297 @geindex No_Dynamic_Sized_Objects
13299 [GNAT] This restriction disallows certain constructs that might lead to the
13300 creation of dynamic-sized composite objects (or array or discriminated type).
13301 An array subtype indication is illegal if the bounds are not static
13302 or references to discriminants of an enclosing type.
13303 A discriminated subtype indication is illegal if the type has
13304 discriminant-dependent array components or a variant part, and the
13305 discriminants are not static. In addition, array and record aggregates are
13306 illegal in corresponding cases. Note that this restriction does not forbid
13307 access discriminants. It is often a good idea to combine this restriction
13308 with No_Secondary_Stack.
13310 @node No_Entry_Queue,No_Implementation_Aspect_Specifications,No_Dynamic_Sized_Objects,Program Unit Level Restrictions
13311 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-entry-queue}@anchor{207}
13312 @subsection No_Entry_Queue
13315 @geindex No_Entry_Queue
13317 [GNAT] This restriction is a declaration that any protected entry compiled in
13318 the scope of the restriction has at most one task waiting on the entry
13319 at any one time, and so no queue is required. This restriction is not
13320 checked at compile time. A program execution is erroneous if an attempt
13321 is made to queue a second task on such an entry.
13323 @node No_Implementation_Aspect_Specifications,No_Implementation_Attributes,No_Entry_Queue,Program Unit Level Restrictions
13324 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implementation-aspect-specifications}@anchor{208}
13325 @subsection No_Implementation_Aspect_Specifications
13328 @geindex No_Implementation_Aspect_Specifications
13330 [RM 13.12.1] This restriction checks at compile time that no
13331 GNAT-defined aspects are present. With this restriction, the only
13332 aspects that can be used are those defined in the Ada Reference Manual.
13334 @node No_Implementation_Attributes,No_Implementation_Identifiers,No_Implementation_Aspect_Specifications,Program Unit Level Restrictions
13335 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implementation-attributes}@anchor{209}
13336 @subsection No_Implementation_Attributes
13339 @geindex No_Implementation_Attributes
13341 [RM 13.12.1] This restriction checks at compile time that no
13342 GNAT-defined attributes are present. With this restriction, the only
13343 attributes that can be used are those defined in the Ada Reference
13346 @node No_Implementation_Identifiers,No_Implementation_Pragmas,No_Implementation_Attributes,Program Unit Level Restrictions
13347 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implementation-identifiers}@anchor{20a}
13348 @subsection No_Implementation_Identifiers
13351 @geindex No_Implementation_Identifiers
13353 [RM 13.12.1] This restriction checks at compile time that no
13354 implementation-defined identifiers (marked with pragma Implementation_Defined)
13355 occur within language-defined packages.
13357 @node No_Implementation_Pragmas,No_Implementation_Restrictions,No_Implementation_Identifiers,Program Unit Level Restrictions
13358 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implementation-pragmas}@anchor{20b}
13359 @subsection No_Implementation_Pragmas
13362 @geindex No_Implementation_Pragmas
13364 [RM 13.12.1] This restriction checks at compile time that no
13365 GNAT-defined pragmas are present. With this restriction, the only
13366 pragmas that can be used are those defined in the Ada Reference Manual.
13368 @node No_Implementation_Restrictions,No_Implementation_Units,No_Implementation_Pragmas,Program Unit Level Restrictions
13369 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implementation-restrictions}@anchor{20c}
13370 @subsection No_Implementation_Restrictions
13373 @geindex No_Implementation_Restrictions
13375 [GNAT] This restriction checks at compile time that no GNAT-defined restriction
13376 identifiers (other than @code{No_Implementation_Restrictions} itself)
13377 are present. With this restriction, the only other restriction identifiers
13378 that can be used are those defined in the Ada Reference Manual.
13380 @node No_Implementation_Units,No_Implicit_Aliasing,No_Implementation_Restrictions,Program Unit Level Restrictions
13381 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implementation-units}@anchor{20d}
13382 @subsection No_Implementation_Units
13385 @geindex No_Implementation_Units
13387 [RM 13.12.1] This restriction checks at compile time that there is no
13388 mention in the context clause of any implementation-defined descendants
13389 of packages Ada, Interfaces, or System.
13391 @node No_Implicit_Aliasing,No_Implicit_Loops,No_Implementation_Units,Program Unit Level Restrictions
13392 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-aliasing}@anchor{20e}
13393 @subsection No_Implicit_Aliasing
13396 @geindex No_Implicit_Aliasing
13398 [GNAT] This restriction, which is not required to be partition-wide consistent,
13399 requires an explicit aliased keyword for an object to which 'Access,
13400 'Unchecked_Access, or 'Address is applied, and forbids entirely the use of
13401 the 'Unrestricted_Access attribute for objects. Note: the reason that
13402 Unrestricted_Access is forbidden is that it would require the prefix
13403 to be aliased, and in such cases, it can always be replaced by
13404 the standard attribute Unchecked_Access which is preferable.
13406 @node No_Implicit_Loops,No_Obsolescent_Features,No_Implicit_Aliasing,Program Unit Level Restrictions
13407 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-loops}@anchor{20f}
13408 @subsection No_Implicit_Loops
13411 @geindex No_Implicit_Loops
13413 [GNAT] This restriction ensures that the generated code of the unit marked
13414 with this restriction does not contain any implicit @code{for} loops, either by
13415 modifying the generated code where possible, or by rejecting any construct
13416 that would otherwise generate an implicit @code{for} loop. If this restriction is
13417 active, it is possible to build large array aggregates with all static
13418 components without generating an intermediate temporary, and without generating
13419 a loop to initialize individual components. Otherwise, a loop is created for
13420 arrays larger than about 5000 scalar components. Note that if this restriction
13421 is set in the spec of a package, it will not apply to its body.
13423 @node No_Obsolescent_Features,No_Wide_Characters,No_Implicit_Loops,Program Unit Level Restrictions
13424 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-obsolescent-features}@anchor{210}
13425 @subsection No_Obsolescent_Features
13428 @geindex No_Obsolescent_Features
13430 [RM 13.12.1] This restriction checks at compile time that no obsolescent
13431 features are used, as defined in Annex J of the Ada Reference Manual.
13433 @node No_Wide_Characters,Static_Dispatch_Tables,No_Obsolescent_Features,Program Unit Level Restrictions
13434 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-wide-characters}@anchor{211}
13435 @subsection No_Wide_Characters
13438 @geindex No_Wide_Characters
13440 [GNAT] This restriction ensures at compile time that no uses of the types
13441 @code{Wide_Character} or @code{Wide_String} or corresponding wide
13443 appear, and that no wide or wide wide string or character literals
13444 appear in the program (that is literals representing characters not in
13445 type @code{Character}).
13447 @node Static_Dispatch_Tables,SPARK_05,No_Wide_Characters,Program Unit Level Restrictions
13448 @anchor{gnat_rm/standard_and_implementation_defined_restrictions static-dispatch-tables}@anchor{212}
13449 @subsection Static_Dispatch_Tables
13452 @geindex Static_Dispatch_Tables
13454 [GNAT] This restriction checks at compile time that all the artifacts
13455 associated with dispatch tables can be placed in read-only memory.
13457 @node SPARK_05,,Static_Dispatch_Tables,Program Unit Level Restrictions
13458 @anchor{gnat_rm/standard_and_implementation_defined_restrictions spark-05}@anchor{213}
13459 @subsection SPARK_05
13464 [GNAT] This restriction checks at compile time that some constructs forbidden
13465 in SPARK 2005 are not present. Note that SPARK 2005 has been superseded by
13466 SPARK 2014, whose restrictions are checked by the tool GNATprove. To check that
13467 a codebase respects SPARK 2014 restrictions, mark the code with pragma or
13468 aspect @code{SPARK_Mode}, and run the tool GNATprove at Stone assurance level, as
13472 gnatprove -P project.gpr --mode=stone
13478 gnatprove -P project.gpr --mode=check_all
13481 With restriction @code{SPARK_05}, error messages related to SPARK 2005 restriction
13485 violation of restriction "SPARK_05" at <source-location>
13491 The restriction @code{SPARK} is recognized as a synonym for @code{SPARK_05}. This is
13492 retained for historical compatibility purposes (and an unconditional warning
13493 will be generated for its use, advising replacement by @code{SPARK_05}).
13495 This is not a replacement for the semantic checks performed by the
13496 SPARK Examiner tool, as the compiler currently only deals with code,
13497 not SPARK 2005 annotations, and does not guarantee catching all
13498 cases of constructs forbidden by SPARK 2005.
13500 Thus it may well be the case that code which passes the compiler with
13501 the SPARK 2005 restriction is rejected by the SPARK Examiner, e.g. due to
13502 the different visibility rules of the Examiner based on SPARK 2005
13503 @code{inherit} annotations.
13505 This restriction can be useful in providing an initial filter for code
13506 developed using SPARK 2005, or in examining legacy code to see how far
13507 it is from meeting SPARK 2005 restrictions.
13509 The list below summarizes the checks that are performed when this
13510 restriction is in force:
13516 No block statements
13519 No case statements with only an others clause
13522 Exit statements in loops must respect the SPARK 2005 language restrictions
13528 Return can only appear as last statement in function
13531 Function must have return statement
13534 Loop parameter specification must include subtype mark
13537 Prefix of expanded name cannot be a loop statement
13540 Abstract subprogram not allowed
13543 User-defined operators not allowed
13546 Access type parameters not allowed
13549 Default expressions for parameters not allowed
13552 Default expressions for record fields not allowed
13555 No tasking constructs allowed
13558 Label needed at end of subprograms and packages
13561 No mixing of positional and named parameter association
13564 No access types as result type
13567 No unconstrained arrays as result types
13573 Initial and later declarations must be in correct order (declaration can't come after body)
13576 No attributes on private types if full declaration not visible
13579 No package declaration within package specification
13582 No controlled types
13585 No discriminant types
13591 Selector name cannot be operator symbol (i.e. operator symbol cannot be prefixed)
13594 Access attribute not allowed
13597 Allocator not allowed
13600 Result of catenation must be String
13603 Operands of catenation must be string literal, static char or another catenation
13606 No conditional expressions
13609 No explicit dereference
13612 Quantified expression not allowed
13615 Slicing not allowed
13618 No exception renaming
13621 No generic renaming
13630 Aggregates must be qualified
13633 Nonstatic choice in array aggregates not allowed
13636 The only view conversions which are allowed as in-out parameters are conversions of a tagged type to an ancestor type
13639 No mixing of positional and named association in aggregate, no multi choice
13642 AND, OR and XOR for arrays only allowed when operands have same static bounds
13645 Fixed point operands to * or / must be qualified or converted
13648 Comparison operators not allowed for Booleans or arrays (except strings)
13651 Equality not allowed for arrays with non-matching static bounds (except strings)
13654 Conversion / qualification not allowed for arrays with non-matching static bounds
13657 Subprogram declaration only allowed in package spec (unless followed by import)
13660 Access types not allowed
13663 Incomplete type declaration not allowed
13666 Object and subtype declarations must respect SPARK 2005 restrictions
13669 Digits or delta constraint not allowed
13672 Decimal fixed point type not allowed
13675 Aliasing of objects not allowed
13678 Modular type modulus must be power of 2
13681 Base not allowed on subtype mark
13684 Unary operators not allowed on modular types (except not)
13687 Untagged record cannot be null
13690 No class-wide operations
13693 Initialization expressions must respect SPARK 2005 restrictions
13696 Nonstatic ranges not allowed except in iteration schemes
13699 String subtypes must have lower bound of 1
13702 Subtype of Boolean cannot have constraint
13705 At most one tagged type or extension per package
13708 Interface is not allowed
13711 Character literal cannot be prefixed (selector name cannot be character literal)
13714 Record aggregate cannot contain 'others'
13717 Component association in record aggregate must contain a single choice
13720 Ancestor part cannot be a type mark
13723 Attributes 'Image, 'Width and 'Value not allowed
13726 Functions may not update globals
13729 Subprograms may not contain direct calls to themselves (prevents recursion within unit)
13732 Call to subprogram not allowed in same unit before body has been seen (prevents recursion within unit)
13735 The following restrictions are enforced, but note that they are actually more
13736 strict that the latest SPARK 2005 language definition:
13742 No derived types other than tagged type extensions
13745 Subtype of unconstrained array must have constraint
13748 This list summarises the main SPARK 2005 language rules that are not
13749 currently checked by the SPARK_05 restriction:
13755 SPARK 2005 annotations are treated as comments so are not checked at all
13758 Based real literals not allowed
13761 Objects cannot be initialized at declaration by calls to user-defined functions
13764 Objects cannot be initialized at declaration by assignments from variables
13767 Objects cannot be initialized at declaration by assignments from indexed/selected components
13770 Ranges shall not be null
13773 A fixed point delta expression must be a simple expression
13776 Restrictions on where renaming declarations may be placed
13779 Externals of mode 'out' cannot be referenced
13782 Externals of mode 'in' cannot be updated
13785 Loop with no iteration scheme or exits only allowed as last statement in main program or task
13788 Subprogram cannot have parent unit name
13791 SPARK 2005 inherited subprogram must be prefixed with overriding
13794 External variables (or functions that reference them) may not be passed as actual parameters
13797 Globals must be explicitly mentioned in contract
13800 Deferred constants cannot be completed by pragma Import
13803 Package initialization cannot read/write variables from other packages
13806 Prefix not allowed for entities that are directly visible
13809 Identifier declaration can't override inherited package name
13812 Cannot use Standard or other predefined packages as identifiers
13815 After renaming, cannot use the original name
13818 Subprograms can only be renamed to remove package prefix
13821 Pragma import must be immediately after entity it names
13824 No mutual recursion between multiple units (this can be checked with gnatcheck)
13827 Note that if a unit is compiled in Ada 95 mode with the SPARK 2005 restriction,
13828 violations will be reported for constructs forbidden in SPARK 95,
13829 instead of SPARK 2005.
13831 @node Implementation Advice,Implementation Defined Characteristics,Standard and Implementation Defined Restrictions,Top
13832 @anchor{gnat_rm/implementation_advice doc}@anchor{214}@anchor{gnat_rm/implementation_advice implementation-advice}@anchor{a}@anchor{gnat_rm/implementation_advice id1}@anchor{215}
13833 @chapter Implementation Advice
13836 The main text of the Ada Reference Manual describes the required
13837 behavior of all Ada compilers, and the GNAT compiler conforms to
13838 these requirements.
13840 In addition, there are sections throughout the Ada Reference Manual headed
13841 by the phrase 'Implementation advice'. These sections are not normative,
13842 i.e., they do not specify requirements that all compilers must
13843 follow. Rather they provide advice on generally desirable behavior.
13844 They are not requirements, because they describe behavior that cannot
13845 be provided on all systems, or may be undesirable on some systems.
13847 As far as practical, GNAT follows the implementation advice in
13848 the Ada Reference Manual. Each such RM section corresponds to a section
13849 in this chapter whose title specifies the
13850 RM section number and paragraph number and the subject of
13851 the advice. The contents of each section consists of the RM text within
13853 followed by the GNAT interpretation of the advice. Most often, this simply says
13854 'followed', which means that GNAT follows the advice. However, in a
13855 number of cases, GNAT deliberately deviates from this advice, in which
13856 case the text describes what GNAT does and why.
13858 @geindex Error detection
13861 * RM 1.1.3(20); Error Detection: RM 1 1 3 20 Error Detection.
13862 * RM 1.1.3(31); Child Units: RM 1 1 3 31 Child Units.
13863 * RM 1.1.5(12); Bounded Errors: RM 1 1 5 12 Bounded Errors.
13864 * RM 2.8(16); Pragmas: RM 2 8 16 Pragmas.
13865 * RM 2.8(17-19); Pragmas: RM 2 8 17-19 Pragmas.
13866 * RM 3.5.2(5); Alternative Character Sets: RM 3 5 2 5 Alternative Character Sets.
13867 * RM 3.5.4(28); Integer Types: RM 3 5 4 28 Integer Types.
13868 * RM 3.5.4(29); Integer Types: RM 3 5 4 29 Integer Types.
13869 * RM 3.5.5(8); Enumeration Values: RM 3 5 5 8 Enumeration Values.
13870 * RM 3.5.7(17); Float Types: RM 3 5 7 17 Float Types.
13871 * RM 3.6.2(11); Multidimensional Arrays: RM 3 6 2 11 Multidimensional Arrays.
13872 * RM 9.6(30-31); Duration'Small: RM 9 6 30-31 Duration'Small.
13873 * RM 10.2.1(12); Consistent Representation: RM 10 2 1 12 Consistent Representation.
13874 * RM 11.4.1(19); Exception Information: RM 11 4 1 19 Exception Information.
13875 * RM 11.5(28); Suppression of Checks: RM 11 5 28 Suppression of Checks.
13876 * RM 13.1 (21-24); Representation Clauses: RM 13 1 21-24 Representation Clauses.
13877 * RM 13.2(6-8); Packed Types: RM 13 2 6-8 Packed Types.
13878 * RM 13.3(14-19); Address Clauses: RM 13 3 14-19 Address Clauses.
13879 * RM 13.3(29-35); Alignment Clauses: RM 13 3 29-35 Alignment Clauses.
13880 * RM 13.3(42-43); Size Clauses: RM 13 3 42-43 Size Clauses.
13881 * RM 13.3(50-56); Size Clauses: RM 13 3 50-56 Size Clauses.
13882 * RM 13.3(71-73); Component Size Clauses: RM 13 3 71-73 Component Size Clauses.
13883 * RM 13.4(9-10); Enumeration Representation Clauses: RM 13 4 9-10 Enumeration Representation Clauses.
13884 * RM 13.5.1(17-22); Record Representation Clauses: RM 13 5 1 17-22 Record Representation Clauses.
13885 * RM 13.5.2(5); Storage Place Attributes: RM 13 5 2 5 Storage Place Attributes.
13886 * RM 13.5.3(7-8); Bit Ordering: RM 13 5 3 7-8 Bit Ordering.
13887 * RM 13.7(37); Address as Private: RM 13 7 37 Address as Private.
13888 * RM 13.7.1(16); Address Operations: RM 13 7 1 16 Address Operations.
13889 * RM 13.9(14-17); Unchecked Conversion: RM 13 9 14-17 Unchecked Conversion.
13890 * RM 13.11(23-25); Implicit Heap Usage: RM 13 11 23-25 Implicit Heap Usage.
13891 * RM 13.11.2(17); Unchecked Deallocation: RM 13 11 2 17 Unchecked Deallocation.
13892 * RM 13.13.2(1.6); Stream Oriented Attributes: RM 13 13 2 1 6 Stream Oriented Attributes.
13893 * RM A.1(52); Names of Predefined Numeric Types: RM A 1 52 Names of Predefined Numeric Types.
13894 * RM A.3.2(49); Ada.Characters.Handling: RM A 3 2 49 Ada Characters Handling.
13895 * RM A.4.4(106); Bounded-Length String Handling: RM A 4 4 106 Bounded-Length String Handling.
13896 * RM A.5.2(46-47); Random Number Generation: RM A 5 2 46-47 Random Number Generation.
13897 * RM A.10.7(23); Get_Immediate: RM A 10 7 23 Get_Immediate.
13898 * RM B.1(39-41); Pragma Export: RM B 1 39-41 Pragma Export.
13899 * RM B.2(12-13); Package Interfaces: RM B 2 12-13 Package Interfaces.
13900 * RM B.3(63-71); Interfacing with C: RM B 3 63-71 Interfacing with C.
13901 * RM B.4(95-98); Interfacing with COBOL: RM B 4 95-98 Interfacing with COBOL.
13902 * RM B.5(22-26); Interfacing with Fortran: RM B 5 22-26 Interfacing with Fortran.
13903 * RM C.1(3-5); Access to Machine Operations: RM C 1 3-5 Access to Machine Operations.
13904 * RM C.1(10-16); Access to Machine Operations: RM C 1 10-16 Access to Machine Operations.
13905 * RM C.3(28); Interrupt Support: RM C 3 28 Interrupt Support.
13906 * RM C.3.1(20-21); Protected Procedure Handlers: RM C 3 1 20-21 Protected Procedure Handlers.
13907 * RM C.3.2(25); Package Interrupts: RM C 3 2 25 Package Interrupts.
13908 * RM C.4(14); Pre-elaboration Requirements: RM C 4 14 Pre-elaboration Requirements.
13909 * RM C.5(8); Pragma Discard_Names: RM C 5 8 Pragma Discard_Names.
13910 * RM C.7.2(30); The Package Task_Attributes: RM C 7 2 30 The Package Task_Attributes.
13911 * RM D.3(17); Locking Policies: RM D 3 17 Locking Policies.
13912 * RM D.4(16); Entry Queuing Policies: RM D 4 16 Entry Queuing Policies.
13913 * RM D.6(9-10); Preemptive Abort: RM D 6 9-10 Preemptive Abort.
13914 * RM D.7(21); Tasking Restrictions: RM D 7 21 Tasking Restrictions.
13915 * RM D.8(47-49); Monotonic Time: RM D 8 47-49 Monotonic Time.
13916 * RM E.5(28-29); Partition Communication Subsystem: RM E 5 28-29 Partition Communication Subsystem.
13917 * RM F(7); COBOL Support: RM F 7 COBOL Support.
13918 * RM F.1(2); Decimal Radix Support: RM F 1 2 Decimal Radix Support.
13919 * RM G; Numerics: RM G Numerics.
13920 * RM G.1.1(56-58); Complex Types: RM G 1 1 56-58 Complex Types.
13921 * RM G.1.2(49); Complex Elementary Functions: RM G 1 2 49 Complex Elementary Functions.
13922 * RM G.2.4(19); Accuracy Requirements: RM G 2 4 19 Accuracy Requirements.
13923 * RM G.2.6(15); Complex Arithmetic Accuracy: RM G 2 6 15 Complex Arithmetic Accuracy.
13924 * RM H.6(15/2); Pragma Partition_Elaboration_Policy: RM H 6 15/2 Pragma Partition_Elaboration_Policy.
13928 @node RM 1 1 3 20 Error Detection,RM 1 1 3 31 Child Units,,Implementation Advice
13929 @anchor{gnat_rm/implementation_advice rm-1-1-3-20-error-detection}@anchor{216}
13930 @section RM 1.1.3(20): Error Detection
13935 "If an implementation detects the use of an unsupported Specialized Needs
13936 Annex feature at run time, it should raise @code{Program_Error} if
13940 Not relevant. All specialized needs annex features are either supported,
13941 or diagnosed at compile time.
13943 @geindex Child Units
13945 @node RM 1 1 3 31 Child Units,RM 1 1 5 12 Bounded Errors,RM 1 1 3 20 Error Detection,Implementation Advice
13946 @anchor{gnat_rm/implementation_advice rm-1-1-3-31-child-units}@anchor{217}
13947 @section RM 1.1.3(31): Child Units
13952 "If an implementation wishes to provide implementation-defined
13953 extensions to the functionality of a language-defined library unit, it
13954 should normally do so by adding children to the library unit."
13959 @geindex Bounded errors
13961 @node RM 1 1 5 12 Bounded Errors,RM 2 8 16 Pragmas,RM 1 1 3 31 Child Units,Implementation Advice
13962 @anchor{gnat_rm/implementation_advice rm-1-1-5-12-bounded-errors}@anchor{218}
13963 @section RM 1.1.5(12): Bounded Errors
13968 "If an implementation detects a bounded error or erroneous
13969 execution, it should raise @code{Program_Error}."
13972 Followed in all cases in which the implementation detects a bounded
13973 error or erroneous execution. Not all such situations are detected at
13978 @node RM 2 8 16 Pragmas,RM 2 8 17-19 Pragmas,RM 1 1 5 12 Bounded Errors,Implementation Advice
13979 @anchor{gnat_rm/implementation_advice id2}@anchor{219}@anchor{gnat_rm/implementation_advice rm-2-8-16-pragmas}@anchor{21a}
13980 @section RM 2.8(16): Pragmas
13985 "Normally, implementation-defined pragmas should have no semantic effect
13986 for error-free programs; that is, if the implementation-defined pragmas
13987 are removed from a working program, the program should still be legal,
13988 and should still have the same semantics."
13991 The following implementation defined pragmas are exceptions to this
13995 @multitable {xxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxx}
14038 @emph{CPP_Constructor}
14054 @emph{Interface_Name}
14062 @emph{Machine_Attribute}
14070 @emph{Unimplemented_Unit}
14078 @emph{Unchecked_Union}
14087 In each of the above cases, it is essential to the purpose of the pragma
14088 that this advice not be followed. For details see
14089 @ref{7,,Implementation Defined Pragmas}.
14091 @node RM 2 8 17-19 Pragmas,RM 3 5 2 5 Alternative Character Sets,RM 2 8 16 Pragmas,Implementation Advice
14092 @anchor{gnat_rm/implementation_advice rm-2-8-17-19-pragmas}@anchor{21b}
14093 @section RM 2.8(17-19): Pragmas
14098 "Normally, an implementation should not define pragmas that can
14099 make an illegal program legal, except as follows:
14105 A pragma used to complete a declaration, such as a pragma @code{Import};
14108 A pragma used to configure the environment by adding, removing, or
14109 replacing @code{library_items}."
14113 See @ref{21a,,RM 2.8(16); Pragmas}.
14115 @geindex Character Sets
14117 @geindex Alternative Character Sets
14119 @node RM 3 5 2 5 Alternative Character Sets,RM 3 5 4 28 Integer Types,RM 2 8 17-19 Pragmas,Implementation Advice
14120 @anchor{gnat_rm/implementation_advice rm-3-5-2-5-alternative-character-sets}@anchor{21c}
14121 @section RM 3.5.2(5): Alternative Character Sets
14126 "If an implementation supports a mode with alternative interpretations
14127 for @code{Character} and @code{Wide_Character}, the set of graphic
14128 characters of @code{Character} should nevertheless remain a proper
14129 subset of the set of graphic characters of @code{Wide_Character}. Any
14130 character set 'localizations' should be reflected in the results of
14131 the subprograms defined in the language-defined package
14132 @code{Characters.Handling} (see A.3) available in such a mode. In a mode with
14133 an alternative interpretation of @code{Character}, the implementation should
14134 also support a corresponding change in what is a legal
14135 @code{identifier_letter}."
14138 Not all wide character modes follow this advice, in particular the JIS
14139 and IEC modes reflect standard usage in Japan, and in these encoding,
14140 the upper half of the Latin-1 set is not part of the wide-character
14141 subset, since the most significant bit is used for wide character
14142 encoding. However, this only applies to the external forms. Internally
14143 there is no such restriction.
14145 @geindex Integer types
14147 @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
14148 @anchor{gnat_rm/implementation_advice rm-3-5-4-28-integer-types}@anchor{21d}
14149 @section RM 3.5.4(28): Integer Types
14154 "An implementation should support @code{Long_Integer} in addition to
14155 @code{Integer} if the target machine supports 32-bit (or longer)
14156 arithmetic. No other named integer subtypes are recommended for package
14157 @code{Standard}. Instead, appropriate named integer subtypes should be
14158 provided in the library package @code{Interfaces} (see B.2)."
14161 @code{Long_Integer} is supported. Other standard integer types are supported
14162 so this advice is not fully followed. These types
14163 are supported for convenient interface to C, and so that all hardware
14164 types of the machine are easily available.
14166 @node RM 3 5 4 29 Integer Types,RM 3 5 5 8 Enumeration Values,RM 3 5 4 28 Integer Types,Implementation Advice
14167 @anchor{gnat_rm/implementation_advice rm-3-5-4-29-integer-types}@anchor{21e}
14168 @section RM 3.5.4(29): Integer Types
14173 "An implementation for a two's complement machine should support
14174 modular types with a binary modulus up to @code{System.Max_Int*2+2}. An
14175 implementation should support a non-binary modules up to @code{Integer'Last}."
14180 @geindex Enumeration values
14182 @node RM 3 5 5 8 Enumeration Values,RM 3 5 7 17 Float Types,RM 3 5 4 29 Integer Types,Implementation Advice
14183 @anchor{gnat_rm/implementation_advice rm-3-5-5-8-enumeration-values}@anchor{21f}
14184 @section RM 3.5.5(8): Enumeration Values
14189 "For the evaluation of a call on @code{S'Pos} for an enumeration
14190 subtype, if the value of the operand does not correspond to the internal
14191 code for any enumeration literal of its type (perhaps due to an
14192 un-initialized variable), then the implementation should raise
14193 @code{Program_Error}. This is particularly important for enumeration
14194 types with noncontiguous internal codes specified by an
14195 enumeration_representation_clause."
14200 @geindex Float types
14202 @node RM 3 5 7 17 Float Types,RM 3 6 2 11 Multidimensional Arrays,RM 3 5 5 8 Enumeration Values,Implementation Advice
14203 @anchor{gnat_rm/implementation_advice rm-3-5-7-17-float-types}@anchor{220}
14204 @section RM 3.5.7(17): Float Types
14209 "An implementation should support @code{Long_Float} in addition to
14210 @code{Float} if the target machine supports 11 or more digits of
14211 precision. No other named floating point subtypes are recommended for
14212 package @code{Standard}. Instead, appropriate named floating point subtypes
14213 should be provided in the library package @code{Interfaces} (see B.2)."
14216 @code{Short_Float} and @code{Long_Long_Float} are also provided. The
14217 former provides improved compatibility with other implementations
14218 supporting this type. The latter corresponds to the highest precision
14219 floating-point type supported by the hardware. On most machines, this
14220 will be the same as @code{Long_Float}, but on some machines, it will
14221 correspond to the IEEE extended form. The notable case is all ia32
14222 (x86) implementations, where @code{Long_Long_Float} corresponds to
14223 the 80-bit extended precision format supported in hardware on this
14224 processor. Note that the 128-bit format on SPARC is not supported,
14225 since this is a software rather than a hardware format.
14227 @geindex Multidimensional arrays
14230 @geindex multidimensional
14232 @node RM 3 6 2 11 Multidimensional Arrays,RM 9 6 30-31 Duration'Small,RM 3 5 7 17 Float Types,Implementation Advice
14233 @anchor{gnat_rm/implementation_advice rm-3-6-2-11-multidimensional-arrays}@anchor{221}
14234 @section RM 3.6.2(11): Multidimensional Arrays
14239 "An implementation should normally represent multidimensional arrays in
14240 row-major order, consistent with the notation used for multidimensional
14241 array aggregates (see 4.3.3). However, if a pragma @code{Convention}
14242 (@code{Fortran}, ...) applies to a multidimensional array type, then
14243 column-major order should be used instead (see B.5, @emph{Interfacing with Fortran})."
14248 @geindex Duration'Small
14250 @node RM 9 6 30-31 Duration'Small,RM 10 2 1 12 Consistent Representation,RM 3 6 2 11 Multidimensional Arrays,Implementation Advice
14251 @anchor{gnat_rm/implementation_advice rm-9-6-30-31-duration-small}@anchor{222}
14252 @section RM 9.6(30-31): Duration'Small
14257 "Whenever possible in an implementation, the value of @code{Duration'Small}
14258 should be no greater than 100 microseconds."
14261 Followed. (@code{Duration'Small} = 10**(-9)).
14265 "The time base for @code{delay_relative_statements} should be monotonic;
14266 it need not be the same time base as used for @code{Calendar.Clock}."
14271 @node RM 10 2 1 12 Consistent Representation,RM 11 4 1 19 Exception Information,RM 9 6 30-31 Duration'Small,Implementation Advice
14272 @anchor{gnat_rm/implementation_advice rm-10-2-1-12-consistent-representation}@anchor{223}
14273 @section RM 10.2.1(12): Consistent Representation
14278 "In an implementation, a type declared in a pre-elaborated package should
14279 have the same representation in every elaboration of a given version of
14280 the package, whether the elaborations occur in distinct executions of
14281 the same program, or in executions of distinct programs or partitions
14282 that include the given version."
14285 Followed, except in the case of tagged types. Tagged types involve
14286 implicit pointers to a local copy of a dispatch table, and these pointers
14287 have representations which thus depend on a particular elaboration of the
14288 package. It is not easy to see how it would be possible to follow this
14289 advice without severely impacting efficiency of execution.
14291 @geindex Exception information
14293 @node RM 11 4 1 19 Exception Information,RM 11 5 28 Suppression of Checks,RM 10 2 1 12 Consistent Representation,Implementation Advice
14294 @anchor{gnat_rm/implementation_advice rm-11-4-1-19-exception-information}@anchor{224}
14295 @section RM 11.4.1(19): Exception Information
14300 "@code{Exception_Message} by default and @code{Exception_Information}
14301 should produce information useful for
14302 debugging. @code{Exception_Message} should be short, about one
14303 line. @code{Exception_Information} can be long. @code{Exception_Message}
14304 should not include the
14305 @code{Exception_Name}. @code{Exception_Information} should include both
14306 the @code{Exception_Name} and the @code{Exception_Message}."
14309 Followed. For each exception that doesn't have a specified
14310 @code{Exception_Message}, the compiler generates one containing the location
14311 of the raise statement. This location has the form 'file_name:line', where
14312 file_name is the short file name (without path information) and line is the line
14313 number in the file. Note that in the case of the Zero Cost Exception
14314 mechanism, these messages become redundant with the Exception_Information that
14315 contains a full backtrace of the calling sequence, so they are disabled.
14316 To disable explicitly the generation of the source location message, use the
14317 Pragma @code{Discard_Names}.
14319 @geindex Suppression of checks
14322 @geindex suppression of
14324 @node RM 11 5 28 Suppression of Checks,RM 13 1 21-24 Representation Clauses,RM 11 4 1 19 Exception Information,Implementation Advice
14325 @anchor{gnat_rm/implementation_advice rm-11-5-28-suppression-of-checks}@anchor{225}
14326 @section RM 11.5(28): Suppression of Checks
14331 "The implementation should minimize the code executed for checks that
14332 have been suppressed."
14337 @geindex Representation clauses
14339 @node RM 13 1 21-24 Representation Clauses,RM 13 2 6-8 Packed Types,RM 11 5 28 Suppression of Checks,Implementation Advice
14340 @anchor{gnat_rm/implementation_advice rm-13-1-21-24-representation-clauses}@anchor{226}
14341 @section RM 13.1 (21-24): Representation Clauses
14346 "The recommended level of support for all representation items is
14347 qualified as follows:
14349 An implementation need not support representation items containing
14350 nonstatic expressions, except that an implementation should support a
14351 representation item for a given entity if each nonstatic expression in
14352 the representation item is a name that statically denotes a constant
14353 declared before the entity."
14356 Followed. In fact, GNAT goes beyond the recommended level of support
14357 by allowing nonstatic expressions in some representation clauses even
14358 without the need to declare constants initialized with the values of
14365 for Y'Address use X'Address;>>
14368 "An implementation need not support a specification for the `@w{`}Size`@w{`}
14369 for a given composite subtype, nor the size or storage place for an
14370 object (including a component) of a given composite subtype, unless the
14371 constraints on the subtype and its composite subcomponents (if any) are
14372 all static constraints."
14375 Followed. Size Clauses are not permitted on nonstatic components, as
14380 "An aliased component, or a component whose type is by-reference, should
14381 always be allocated at an addressable location."
14386 @geindex Packed types
14388 @node RM 13 2 6-8 Packed Types,RM 13 3 14-19 Address Clauses,RM 13 1 21-24 Representation Clauses,Implementation Advice
14389 @anchor{gnat_rm/implementation_advice rm-13-2-6-8-packed-types}@anchor{227}
14390 @section RM 13.2(6-8): Packed Types
14395 "If a type is packed, then the implementation should try to minimize
14396 storage allocated to objects of the type, possibly at the expense of
14397 speed of accessing components, subject to reasonable complexity in
14398 addressing calculations.
14400 The recommended level of support pragma @code{Pack} is:
14402 For a packed record type, the components should be packed as tightly as
14403 possible subject to the Sizes of the component subtypes, and subject to
14404 any @emph{record_representation_clause} that applies to the type; the
14405 implementation may, but need not, reorder components or cross aligned
14406 word boundaries to improve the packing. A component whose @code{Size} is
14407 greater than the word size may be allocated an integral number of words."
14410 Followed. Tight packing of arrays is supported for all component sizes
14411 up to 64-bits. If the array component size is 1 (that is to say, if
14412 the component is a boolean type or an enumeration type with two values)
14413 then values of the type are implicitly initialized to zero. This
14414 happens both for objects of the packed type, and for objects that have a
14415 subcomponent of the packed type.
14419 "An implementation should support Address clauses for imported
14425 @geindex Address clauses
14427 @node RM 13 3 14-19 Address Clauses,RM 13 3 29-35 Alignment Clauses,RM 13 2 6-8 Packed Types,Implementation Advice
14428 @anchor{gnat_rm/implementation_advice rm-13-3-14-19-address-clauses}@anchor{228}
14429 @section RM 13.3(14-19): Address Clauses
14434 "For an array @code{X}, @code{X'Address} should point at the first
14435 component of the array, and not at the array bounds."
14442 "The recommended level of support for the @code{Address} attribute is:
14444 @code{X'Address} should produce a useful result if @code{X} is an
14445 object that is aliased or of a by-reference type, or is an entity whose
14446 @code{Address} has been specified."
14449 Followed. A valid address will be produced even if none of those
14450 conditions have been met. If necessary, the object is forced into
14451 memory to ensure the address is valid.
14455 "An implementation should support @code{Address} clauses for imported
14463 "Objects (including subcomponents) that are aliased or of a by-reference
14464 type should be allocated on storage element boundaries."
14471 "If the @code{Address} of an object is specified, or it is imported or exported,
14472 then the implementation should not perform optimizations based on
14473 assumptions of no aliases."
14478 @geindex Alignment clauses
14480 @node RM 13 3 29-35 Alignment Clauses,RM 13 3 42-43 Size Clauses,RM 13 3 14-19 Address Clauses,Implementation Advice
14481 @anchor{gnat_rm/implementation_advice rm-13-3-29-35-alignment-clauses}@anchor{229}
14482 @section RM 13.3(29-35): Alignment Clauses
14487 "The recommended level of support for the @code{Alignment} attribute for
14490 An implementation should support specified Alignments that are factors
14491 and multiples of the number of storage elements per word, subject to the
14499 "An implementation need not support specified Alignments for
14500 combinations of Sizes and Alignments that cannot be easily
14501 loaded and stored by available machine instructions."
14508 "An implementation need not support specified Alignments that are
14509 greater than the maximum @code{Alignment} the implementation ever returns by
14517 "The recommended level of support for the @code{Alignment} attribute for
14520 Same as above, for subtypes, but in addition:"
14527 "For stand-alone library-level objects of statically constrained
14528 subtypes, the implementation should support all alignments
14529 supported by the target linker. For example, page alignment is likely to
14530 be supported for such objects, but not for subtypes."
14535 @geindex Size clauses
14537 @node RM 13 3 42-43 Size Clauses,RM 13 3 50-56 Size Clauses,RM 13 3 29-35 Alignment Clauses,Implementation Advice
14538 @anchor{gnat_rm/implementation_advice rm-13-3-42-43-size-clauses}@anchor{22a}
14539 @section RM 13.3(42-43): Size Clauses
14544 "The recommended level of support for the @code{Size} attribute of
14547 A @code{Size} clause should be supported for an object if the specified
14548 @code{Size} is at least as large as its subtype's @code{Size}, and
14549 corresponds to a size in storage elements that is a multiple of the
14550 object's @code{Alignment} (if the @code{Alignment} is nonzero)."
14555 @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
14556 @anchor{gnat_rm/implementation_advice rm-13-3-50-56-size-clauses}@anchor{22b}
14557 @section RM 13.3(50-56): Size Clauses
14562 "If the @code{Size} of a subtype is specified, and allows for efficient
14563 independent addressability (see 9.10) on the target architecture, then
14564 the @code{Size} of the following objects of the subtype should equal the
14565 @code{Size} of the subtype:
14567 Aliased objects (including components)."
14574 "@cite{Size} clause on a composite subtype should not affect the
14575 internal layout of components."
14578 Followed. But note that this can be overridden by use of the implementation
14579 pragma Implicit_Packing in the case of packed arrays.
14583 "The recommended level of support for the @code{Size} attribute of subtypes is:
14585 The @code{Size} (if not specified) of a static discrete or fixed point
14586 subtype should be the number of bits needed to represent each value
14587 belonging to the subtype using an unbiased representation, leaving space
14588 for a sign bit only if the subtype contains negative values. If such a
14589 subtype is a first subtype, then an implementation should support a
14590 specified @code{Size} for it that reflects this representation."
14597 "For a subtype implemented with levels of indirection, the @code{Size}
14598 should include the size of the pointers, but not the size of what they
14604 @geindex Component_Size clauses
14606 @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
14607 @anchor{gnat_rm/implementation_advice rm-13-3-71-73-component-size-clauses}@anchor{22c}
14608 @section RM 13.3(71-73): Component Size Clauses
14613 "The recommended level of support for the @code{Component_Size}
14616 An implementation need not support specified @code{Component_Sizes} that are
14617 less than the @code{Size} of the component subtype."
14624 "An implementation should support specified Component_Sizes that
14625 are factors and multiples of the word size. For such
14626 Component_Sizes, the array should contain no gaps between
14627 components. For other Component_Sizes (if supported), the array
14628 should contain no gaps between components when packing is also
14629 specified; the implementation should forbid this combination in cases
14630 where it cannot support a no-gaps representation."
14635 @geindex Enumeration representation clauses
14637 @geindex Representation clauses
14638 @geindex enumeration
14640 @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
14641 @anchor{gnat_rm/implementation_advice rm-13-4-9-10-enumeration-representation-clauses}@anchor{22d}
14642 @section RM 13.4(9-10): Enumeration Representation Clauses
14647 "The recommended level of support for enumeration representation clauses
14650 An implementation need not support enumeration representation clauses
14651 for boolean types, but should at minimum support the internal codes in
14652 the range @code{System.Min_Int .. System.Max_Int}."
14657 @geindex Record representation clauses
14659 @geindex Representation clauses
14662 @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
14663 @anchor{gnat_rm/implementation_advice rm-13-5-1-17-22-record-representation-clauses}@anchor{22e}
14664 @section RM 13.5.1(17-22): Record Representation Clauses
14669 "The recommended level of support for
14670 @emph{record_representation_clause}s is:
14672 An implementation should support storage places that can be extracted
14673 with a load, mask, shift sequence of machine code, and set with a load,
14674 shift, mask, store sequence, given the available machine instructions
14675 and run-time model."
14682 "A storage place should be supported if its size is equal to the
14683 @code{Size} of the component subtype, and it starts and ends on a
14684 boundary that obeys the @code{Alignment} of the component subtype."
14691 "If the default bit ordering applies to the declaration of a given type,
14692 then for a component whose subtype's @code{Size} is less than the word
14693 size, any storage place that does not cross an aligned word boundary
14694 should be supported."
14701 "An implementation may reserve a storage place for the tag field of a
14702 tagged type, and disallow other components from overlapping that place."
14705 Followed. The storage place for the tag field is the beginning of the tagged
14706 record, and its size is Address'Size. GNAT will reject an explicit component
14707 clause for the tag field.
14711 "An implementation need not support a @emph{component_clause} for a
14712 component of an extension part if the storage place is not after the
14713 storage places of all components of the parent type, whether or not
14714 those storage places had been specified."
14717 Followed. The above advice on record representation clauses is followed,
14718 and all mentioned features are implemented.
14720 @geindex Storage place attributes
14722 @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
14723 @anchor{gnat_rm/implementation_advice rm-13-5-2-5-storage-place-attributes}@anchor{22f}
14724 @section RM 13.5.2(5): Storage Place Attributes
14729 "If a component is represented using some form of pointer (such as an
14730 offset) to the actual data of the component, and this data is contiguous
14731 with the rest of the object, then the storage place attributes should
14732 reflect the place of the actual data, not the pointer. If a component is
14733 allocated discontinuously from the rest of the object, then a warning
14734 should be generated upon reference to one of its storage place
14738 Followed. There are no such components in GNAT.
14740 @geindex Bit ordering
14742 @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
14743 @anchor{gnat_rm/implementation_advice rm-13-5-3-7-8-bit-ordering}@anchor{230}
14744 @section RM 13.5.3(7-8): Bit Ordering
14749 "The recommended level of support for the non-default bit ordering is:
14751 If @code{Word_Size} = @code{Storage_Unit}, then the implementation
14752 should support the non-default bit ordering in addition to the default
14756 Followed. Word size does not equal storage size in this implementation.
14757 Thus non-default bit ordering is not supported.
14760 @geindex as private type
14762 @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
14763 @anchor{gnat_rm/implementation_advice rm-13-7-37-address-as-private}@anchor{231}
14764 @section RM 13.7(37): Address as Private
14769 "@cite{Address} should be of a private type."
14774 @geindex Operations
14775 @geindex on `@w{`}Address`@w{`}
14778 @geindex operations of
14780 @node RM 13 7 1 16 Address Operations,RM 13 9 14-17 Unchecked Conversion,RM 13 7 37 Address as Private,Implementation Advice
14781 @anchor{gnat_rm/implementation_advice rm-13-7-1-16-address-operations}@anchor{232}
14782 @section RM 13.7.1(16): Address Operations
14787 "Operations in @code{System} and its children should reflect the target
14788 environment semantics as closely as is reasonable. For example, on most
14789 machines, it makes sense for address arithmetic to 'wrap around'.
14790 Operations that do not make sense should raise @code{Program_Error}."
14793 Followed. Address arithmetic is modular arithmetic that wraps around. No
14794 operation raises @code{Program_Error}, since all operations make sense.
14796 @geindex Unchecked conversion
14798 @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
14799 @anchor{gnat_rm/implementation_advice rm-13-9-14-17-unchecked-conversion}@anchor{233}
14800 @section RM 13.9(14-17): Unchecked Conversion
14805 "The @code{Size} of an array object should not include its bounds; hence,
14806 the bounds should not be part of the converted data."
14813 "The implementation should not generate unnecessary run-time checks to
14814 ensure that the representation of @code{S} is a representation of the
14815 target type. It should take advantage of the permission to return by
14816 reference when possible. Restrictions on unchecked conversions should be
14817 avoided unless required by the target environment."
14820 Followed. There are no restrictions on unchecked conversion. A warning is
14821 generated if the source and target types do not have the same size since
14822 the semantics in this case may be target dependent.
14826 "The recommended level of support for unchecked conversions is:
14828 Unchecked conversions should be supported and should be reversible in
14829 the cases where this clause defines the result. To enable meaningful use
14830 of unchecked conversion, a contiguous representation should be used for
14831 elementary subtypes, for statically constrained array subtypes whose
14832 component subtype is one of the subtypes described in this paragraph,
14833 and for record subtypes without discriminants whose component subtypes
14834 are described in this paragraph."
14839 @geindex Heap usage
14842 @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
14843 @anchor{gnat_rm/implementation_advice rm-13-11-23-25-implicit-heap-usage}@anchor{234}
14844 @section RM 13.11(23-25): Implicit Heap Usage
14849 "An implementation should document any cases in which it dynamically
14850 allocates heap storage for a purpose other than the evaluation of an
14854 Followed, the only other points at which heap storage is dynamically
14855 allocated are as follows:
14861 At initial elaboration time, to allocate dynamically sized global
14865 To allocate space for a task when a task is created.
14868 To extend the secondary stack dynamically when needed. The secondary
14869 stack is used for returning variable length results.
14875 "A default (implementation-provided) storage pool for an
14876 access-to-constant type should not have overhead to support deallocation of
14877 individual objects."
14884 "A storage pool for an anonymous access type should be created at the
14885 point of an allocator for the type, and be reclaimed when the designated
14886 object becomes inaccessible."
14891 @geindex Unchecked deallocation
14893 @node RM 13 11 2 17 Unchecked Deallocation,RM 13 13 2 1 6 Stream Oriented Attributes,RM 13 11 23-25 Implicit Heap Usage,Implementation Advice
14894 @anchor{gnat_rm/implementation_advice rm-13-11-2-17-unchecked-deallocation}@anchor{235}
14895 @section RM 13.11.2(17): Unchecked Deallocation
14900 "For a standard storage pool, @code{Free} should actually reclaim the
14906 @geindex Stream oriented attributes
14908 @node RM 13 13 2 1 6 Stream Oriented Attributes,RM A 1 52 Names of Predefined Numeric Types,RM 13 11 2 17 Unchecked Deallocation,Implementation Advice
14909 @anchor{gnat_rm/implementation_advice rm-13-13-2-1-6-stream-oriented-attributes}@anchor{236}
14910 @section RM 13.13.2(1.6): Stream Oriented Attributes
14915 "If not specified, the value of Stream_Size for an elementary type
14916 should be the number of bits that corresponds to the minimum number of
14917 stream elements required by the first subtype of the type, rounded up
14918 to the nearest factor or multiple of the word size that is also a
14919 multiple of the stream element size."
14922 Followed, except that the number of stream elements is a power of 2.
14923 The Stream_Size may be used to override the default choice.
14925 However, such an implementation is based on direct binary
14926 representations and is therefore target- and endianness-dependent. To
14927 address this issue, GNAT also supplies an alternate implementation of
14928 the stream attributes @code{Read} and @code{Write}, which uses the
14929 target-independent XDR standard representation for scalar types.
14931 @geindex XDR representation
14933 @geindex Read attribute
14935 @geindex Write attribute
14937 @geindex Stream oriented attributes
14939 The XDR implementation is provided as an alternative body of the
14940 @code{System.Stream_Attributes} package, in the file
14941 @code{s-stratt-xdr.adb} in the GNAT library.
14942 There is no @code{s-stratt-xdr.ads} file.
14943 In order to install the XDR implementation, do the following:
14949 Replace the default implementation of the
14950 @code{System.Stream_Attributes} package with the XDR implementation.
14951 For example on a Unix platform issue the commands:
14954 $ mv s-stratt.adb s-stratt-default.adb
14955 $ mv s-stratt-xdr.adb s-stratt.adb
14959 Rebuild the GNAT run-time library as documented in
14960 the @emph{GNAT and Libraries} section of the @cite{GNAT User's Guide}.
14963 @node RM A 1 52 Names of Predefined Numeric Types,RM A 3 2 49 Ada Characters Handling,RM 13 13 2 1 6 Stream Oriented Attributes,Implementation Advice
14964 @anchor{gnat_rm/implementation_advice rm-a-1-52-names-of-predefined-numeric-types}@anchor{237}
14965 @section RM A.1(52): Names of Predefined Numeric Types
14970 "If an implementation provides additional named predefined integer types,
14971 then the names should end with @code{Integer} as in
14972 @code{Long_Integer}. If an implementation provides additional named
14973 predefined floating point types, then the names should end with
14974 @code{Float} as in @code{Long_Float}."
14979 @geindex Ada.Characters.Handling
14981 @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
14982 @anchor{gnat_rm/implementation_advice rm-a-3-2-49-ada-characters-handling}@anchor{238}
14983 @section RM A.3.2(49): @code{Ada.Characters.Handling}
14988 "If an implementation provides a localized definition of @code{Character}
14989 or @code{Wide_Character}, then the effects of the subprograms in
14990 @code{Characters.Handling} should reflect the localizations.
14994 Followed. GNAT provides no such localized definitions.
14996 @geindex Bounded-length strings
14998 @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
14999 @anchor{gnat_rm/implementation_advice rm-a-4-4-106-bounded-length-string-handling}@anchor{239}
15000 @section RM A.4.4(106): Bounded-Length String Handling
15005 "Bounded string objects should not be implemented by implicit pointers
15006 and dynamic allocation."
15009 Followed. No implicit pointers or dynamic allocation are used.
15011 @geindex Random number generation
15013 @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
15014 @anchor{gnat_rm/implementation_advice rm-a-5-2-46-47-random-number-generation}@anchor{23a}
15015 @section RM A.5.2(46-47): Random Number Generation
15020 "Any storage associated with an object of type @code{Generator} should be
15021 reclaimed on exit from the scope of the object."
15028 "If the generator period is sufficiently long in relation to the number
15029 of distinct initiator values, then each possible value of
15030 @code{Initiator} passed to @code{Reset} should initiate a sequence of
15031 random numbers that does not, in a practical sense, overlap the sequence
15032 initiated by any other value. If this is not possible, then the mapping
15033 between initiator values and generator states should be a rapidly
15034 varying function of the initiator value."
15037 Followed. The generator period is sufficiently long for the first
15038 condition here to hold true.
15040 @geindex Get_Immediate
15042 @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
15043 @anchor{gnat_rm/implementation_advice rm-a-10-7-23-get-immediate}@anchor{23b}
15044 @section RM A.10.7(23): @code{Get_Immediate}
15049 "The @code{Get_Immediate} procedures should be implemented with
15050 unbuffered input. For a device such as a keyboard, input should be
15051 available if a key has already been typed, whereas for a disk
15052 file, input should always be available except at end of file. For a file
15053 associated with a keyboard-like device, any line-editing features of the
15054 underlying operating system should be disabled during the execution of
15055 @code{Get_Immediate}."
15058 Followed on all targets except VxWorks. For VxWorks, there is no way to
15059 provide this functionality that does not result in the input buffer being
15060 flushed before the @code{Get_Immediate} call. A special unit
15061 @code{Interfaces.Vxworks.IO} is provided that contains routines to enable
15062 this functionality.
15066 @node RM B 1 39-41 Pragma Export,RM B 2 12-13 Package Interfaces,RM A 10 7 23 Get_Immediate,Implementation Advice
15067 @anchor{gnat_rm/implementation_advice rm-b-1-39-41-pragma-export}@anchor{23c}
15068 @section RM B.1(39-41): Pragma @code{Export}
15073 "If an implementation supports pragma @code{Export} to a given language,
15074 then it should also allow the main subprogram to be written in that
15075 language. It should support some mechanism for invoking the elaboration
15076 of the Ada library units included in the system, and for invoking the
15077 finalization of the environment task. On typical systems, the
15078 recommended mechanism is to provide two subprograms whose link names are
15079 @code{adainit} and @code{adafinal}. @code{adainit} should contain the
15080 elaboration code for library units. @code{adafinal} should contain the
15081 finalization code. These subprograms should have no effect the second
15082 and subsequent time they are called."
15089 "Automatic elaboration of pre-elaborated packages should be
15090 provided when pragma @code{Export} is supported."
15093 Followed when the main program is in Ada. If the main program is in a
15094 foreign language, then
15095 @code{adainit} must be called to elaborate pre-elaborated
15100 "For each supported convention @emph{L} other than @code{Intrinsic}, an
15101 implementation should support @code{Import} and @code{Export} pragmas
15102 for objects of @emph{L}-compatible types and for subprograms, and pragma
15103 @cite{Convention} for @emph{L}-eligible types and for subprograms,
15104 presuming the other language has corresponding features. Pragma
15105 @code{Convention} need not be supported for scalar types."
15110 @geindex Package Interfaces
15112 @geindex Interfaces
15114 @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
15115 @anchor{gnat_rm/implementation_advice rm-b-2-12-13-package-interfaces}@anchor{23d}
15116 @section RM B.2(12-13): Package @code{Interfaces}
15121 "For each implementation-defined convention identifier, there should be a
15122 child package of package Interfaces with the corresponding name. This
15123 package should contain any declarations that would be useful for
15124 interfacing to the language (implementation) represented by the
15125 convention. Any declarations useful for interfacing to any language on
15126 the given hardware architecture should be provided directly in
15127 @code{Interfaces}."
15134 "An implementation supporting an interface to C, COBOL, or Fortran should
15135 provide the corresponding package or packages described in the following
15139 Followed. GNAT provides all the packages described in this section.
15142 @geindex interfacing with
15144 @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
15145 @anchor{gnat_rm/implementation_advice rm-b-3-63-71-interfacing-with-c}@anchor{23e}
15146 @section RM B.3(63-71): Interfacing with C
15151 "An implementation should support the following interface correspondences
15152 between Ada and C."
15159 "An Ada procedure corresponds to a void-returning C function."
15166 "An Ada function corresponds to a non-void C function."
15173 "An Ada @code{in} scalar parameter is passed as a scalar argument to a C
15181 "An Ada @code{in} parameter of an access-to-object type with designated
15182 type @code{T} is passed as a @code{t*} argument to a C function,
15183 where @code{t} is the C type corresponding to the Ada type @code{T}."
15190 "An Ada access @code{T} parameter, or an Ada @code{out} or @code{in out}
15191 parameter of an elementary type @code{T}, is passed as a @code{t*}
15192 argument to a C function, where @code{t} is the C type corresponding to
15193 the Ada type @code{T}. In the case of an elementary @code{out} or
15194 @code{in out} parameter, a pointer to a temporary copy is used to
15195 preserve by-copy semantics."
15202 "An Ada parameter of a record type @code{T}, of any mode, is passed as a
15203 @code{t*} argument to a C function, where @code{t} is the C
15204 structure corresponding to the Ada type @code{T}."
15207 Followed. This convention may be overridden by the use of the C_Pass_By_Copy
15208 pragma, or Convention, or by explicitly specifying the mechanism for a given
15209 call using an extended import or export pragma.
15213 "An Ada parameter of an array type with component type @code{T}, of any
15214 mode, is passed as a @code{t*} argument to a C function, where
15215 @code{t} is the C type corresponding to the Ada type @code{T}."
15222 "An Ada parameter of an access-to-subprogram type is passed as a pointer
15223 to a C function whose prototype corresponds to the designated
15224 subprogram's specification."
15230 @geindex interfacing with
15232 @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
15233 @anchor{gnat_rm/implementation_advice rm-b-4-95-98-interfacing-with-cobol}@anchor{23f}
15234 @section RM B.4(95-98): Interfacing with COBOL
15239 "An Ada implementation should support the following interface
15240 correspondences between Ada and COBOL."
15247 "An Ada access @code{T} parameter is passed as a @code{BY REFERENCE} data item of
15248 the COBOL type corresponding to @code{T}."
15255 "An Ada in scalar parameter is passed as a @code{BY CONTENT} data item of
15256 the corresponding COBOL type."
15263 "Any other Ada parameter is passed as a @code{BY REFERENCE} data item of the
15264 COBOL type corresponding to the Ada parameter type; for scalars, a local
15265 copy is used if necessary to ensure by-copy semantics."
15271 @geindex interfacing with
15273 @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
15274 @anchor{gnat_rm/implementation_advice rm-b-5-22-26-interfacing-with-fortran}@anchor{240}
15275 @section RM B.5(22-26): Interfacing with Fortran
15280 "An Ada implementation should support the following interface
15281 correspondences between Ada and Fortran:"
15288 "An Ada procedure corresponds to a Fortran subroutine."
15295 "An Ada function corresponds to a Fortran function."
15302 "An Ada parameter of an elementary, array, or record type @code{T} is
15303 passed as a @code{T} argument to a Fortran procedure, where @code{T} is
15304 the Fortran type corresponding to the Ada type @code{T}, and where the
15305 INTENT attribute of the corresponding dummy argument matches the Ada
15306 formal parameter mode; the Fortran implementation's parameter passing
15307 conventions are used. For elementary types, a local copy is used if
15308 necessary to ensure by-copy semantics."
15315 "An Ada parameter of an access-to-subprogram type is passed as a
15316 reference to a Fortran procedure whose interface corresponds to the
15317 designated subprogram's specification."
15322 @geindex Machine operations
15324 @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
15325 @anchor{gnat_rm/implementation_advice rm-c-1-3-5-access-to-machine-operations}@anchor{241}
15326 @section RM C.1(3-5): Access to Machine Operations
15331 "The machine code or intrinsic support should allow access to all
15332 operations normally available to assembly language programmers for the
15333 target environment, including privileged instructions, if any."
15340 "The interfacing pragmas (see Annex B) should support interface to
15341 assembler; the default assembler should be associated with the
15342 convention identifier @code{Assembler}."
15349 "If an entity is exported to assembly language, then the implementation
15350 should allocate it at an addressable location, and should ensure that it
15351 is retained by the linking process, even if not otherwise referenced
15352 from the Ada code. The implementation should assume that any call to a
15353 machine code or assembler subprogram is allowed to read or update every
15354 object that is specified as exported."
15359 @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
15360 @anchor{gnat_rm/implementation_advice rm-c-1-10-16-access-to-machine-operations}@anchor{242}
15361 @section RM C.1(10-16): Access to Machine Operations
15366 "The implementation should ensure that little or no overhead is
15367 associated with calling intrinsic and machine-code subprograms."
15370 Followed for both intrinsics and machine-code subprograms.
15374 "It is recommended that intrinsic subprograms be provided for convenient
15375 access to any machine operations that provide special capabilities or
15376 efficiency and that are not otherwise available through the language
15380 Followed. A full set of machine operation intrinsic subprograms is provided.
15384 "Atomic read-modify-write operations---e.g., test and set, compare and
15385 swap, decrement and test, enqueue/dequeue."
15388 Followed on any target supporting such operations.
15392 "Standard numeric functions---e.g.:, sin, log."
15395 Followed on any target supporting such operations.
15399 "String manipulation operations---e.g.:, translate and test."
15402 Followed on any target supporting such operations.
15406 "Vector operations---e.g.:, compare vector against thresholds."
15409 Followed on any target supporting such operations.
15413 "Direct operations on I/O ports."
15416 Followed on any target supporting such operations.
15418 @geindex Interrupt support
15420 @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
15421 @anchor{gnat_rm/implementation_advice rm-c-3-28-interrupt-support}@anchor{243}
15422 @section RM C.3(28): Interrupt Support
15427 "If the @code{Ceiling_Locking} policy is not in effect, the
15428 implementation should provide means for the application to specify which
15429 interrupts are to be blocked during protected actions, if the underlying
15430 system allows for a finer-grain control of interrupt blocking."
15433 Followed. The underlying system does not allow for finer-grain control
15434 of interrupt blocking.
15436 @geindex Protected procedure handlers
15438 @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
15439 @anchor{gnat_rm/implementation_advice rm-c-3-1-20-21-protected-procedure-handlers}@anchor{244}
15440 @section RM C.3.1(20-21): Protected Procedure Handlers
15445 "Whenever possible, the implementation should allow interrupt handlers to
15446 be called directly by the hardware."
15449 Followed on any target where the underlying operating system permits
15454 "Whenever practical, violations of any
15455 implementation-defined restrictions should be detected before run time."
15458 Followed. Compile time warnings are given when possible.
15460 @geindex Package `@w{`}Interrupts`@w{`}
15462 @geindex Interrupts
15464 @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
15465 @anchor{gnat_rm/implementation_advice rm-c-3-2-25-package-interrupts}@anchor{245}
15466 @section RM C.3.2(25): Package @code{Interrupts}
15471 "If implementation-defined forms of interrupt handler procedures are
15472 supported, such as protected procedures with parameters, then for each
15473 such form of a handler, a type analogous to @code{Parameterless_Handler}
15474 should be specified in a child package of @code{Interrupts}, with the
15475 same operations as in the predefined package Interrupts."
15480 @geindex Pre-elaboration requirements
15482 @node RM C 4 14 Pre-elaboration Requirements,RM C 5 8 Pragma Discard_Names,RM C 3 2 25 Package Interrupts,Implementation Advice
15483 @anchor{gnat_rm/implementation_advice rm-c-4-14-pre-elaboration-requirements}@anchor{246}
15484 @section RM C.4(14): Pre-elaboration Requirements
15489 "It is recommended that pre-elaborated packages be implemented in such a
15490 way that there should be little or no code executed at run time for the
15491 elaboration of entities not already covered by the Implementation
15495 Followed. Executable code is generated in some cases, e.g., loops
15496 to initialize large arrays.
15498 @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
15499 @anchor{gnat_rm/implementation_advice rm-c-5-8-pragma-discard-names}@anchor{247}
15500 @section RM C.5(8): Pragma @code{Discard_Names}
15505 "If the pragma applies to an entity, then the implementation should
15506 reduce the amount of storage used for storing names associated with that
15512 @geindex Package Task_Attributes
15514 @geindex Task_Attributes
15516 @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
15517 @anchor{gnat_rm/implementation_advice rm-c-7-2-30-the-package-task-attributes}@anchor{248}
15518 @section RM C.7.2(30): The Package Task_Attributes
15523 "Some implementations are targeted to domains in which memory use at run
15524 time must be completely deterministic. For such implementations, it is
15525 recommended that the storage for task attributes will be pre-allocated
15526 statically and not from the heap. This can be accomplished by either
15527 placing restrictions on the number and the size of the task's
15528 attributes, or by using the pre-allocated storage for the first @code{N}
15529 attribute objects, and the heap for the others. In the latter case,
15530 @code{N} should be documented."
15533 Not followed. This implementation is not targeted to such a domain.
15535 @geindex Locking Policies
15537 @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
15538 @anchor{gnat_rm/implementation_advice rm-d-3-17-locking-policies}@anchor{249}
15539 @section RM D.3(17): Locking Policies
15544 "The implementation should use names that end with @code{_Locking} for
15545 locking policies defined by the implementation."
15548 Followed. Two implementation-defined locking policies are defined,
15549 whose names (@code{Inheritance_Locking} and
15550 @code{Concurrent_Readers_Locking}) follow this suggestion.
15552 @geindex Entry queuing policies
15554 @node RM D 4 16 Entry Queuing Policies,RM D 6 9-10 Preemptive Abort,RM D 3 17 Locking Policies,Implementation Advice
15555 @anchor{gnat_rm/implementation_advice rm-d-4-16-entry-queuing-policies}@anchor{24a}
15556 @section RM D.4(16): Entry Queuing Policies
15561 "Names that end with @code{_Queuing} should be used
15562 for all implementation-defined queuing policies."
15565 Followed. No such implementation-defined queuing policies exist.
15567 @geindex Preemptive abort
15569 @node RM D 6 9-10 Preemptive Abort,RM D 7 21 Tasking Restrictions,RM D 4 16 Entry Queuing Policies,Implementation Advice
15570 @anchor{gnat_rm/implementation_advice rm-d-6-9-10-preemptive-abort}@anchor{24b}
15571 @section RM D.6(9-10): Preemptive Abort
15576 "Even though the @emph{abort_statement} is included in the list of
15577 potentially blocking operations (see 9.5.1), it is recommended that this
15578 statement be implemented in a way that never requires the task executing
15579 the @emph{abort_statement} to block."
15586 "On a multi-processor, the delay associated with aborting a task on
15587 another processor should be bounded; the implementation should use
15588 periodic polling, if necessary, to achieve this."
15593 @geindex Tasking restrictions
15595 @node RM D 7 21 Tasking Restrictions,RM D 8 47-49 Monotonic Time,RM D 6 9-10 Preemptive Abort,Implementation Advice
15596 @anchor{gnat_rm/implementation_advice rm-d-7-21-tasking-restrictions}@anchor{24c}
15597 @section RM D.7(21): Tasking Restrictions
15602 "When feasible, the implementation should take advantage of the specified
15603 restrictions to produce a more efficient implementation."
15606 GNAT currently takes advantage of these restrictions by providing an optimized
15607 run time when the Ravenscar profile and the GNAT restricted run time set
15608 of restrictions are specified. See pragma @code{Profile (Ravenscar)} and
15609 pragma @code{Profile (Restricted)} for more details.
15614 @node RM D 8 47-49 Monotonic Time,RM E 5 28-29 Partition Communication Subsystem,RM D 7 21 Tasking Restrictions,Implementation Advice
15615 @anchor{gnat_rm/implementation_advice rm-d-8-47-49-monotonic-time}@anchor{24d}
15616 @section RM D.8(47-49): Monotonic Time
15621 "When appropriate, implementations should provide configuration
15622 mechanisms to change the value of @code{Tick}."
15625 Such configuration mechanisms are not appropriate to this implementation
15626 and are thus not supported.
15630 "It is recommended that @code{Calendar.Clock} and @code{Real_Time.Clock}
15631 be implemented as transformations of the same time base."
15638 "It is recommended that the best time base which exists in
15639 the underlying system be available to the application through
15640 @code{Clock}. @cite{Best} may mean highest accuracy or largest range."
15645 @geindex Partition communication subsystem
15649 @node RM E 5 28-29 Partition Communication Subsystem,RM F 7 COBOL Support,RM D 8 47-49 Monotonic Time,Implementation Advice
15650 @anchor{gnat_rm/implementation_advice rm-e-5-28-29-partition-communication-subsystem}@anchor{24e}
15651 @section RM E.5(28-29): Partition Communication Subsystem
15656 "Whenever possible, the PCS on the called partition should allow for
15657 multiple tasks to call the RPC-receiver with different messages and
15658 should allow them to block until the corresponding subprogram body
15662 Followed by GLADE, a separately supplied PCS that can be used with
15667 "The @code{Write} operation on a stream of type @code{Params_Stream_Type}
15668 should raise @code{Storage_Error} if it runs out of space trying to
15669 write the @code{Item} into the stream."
15672 Followed by GLADE, a separately supplied PCS that can be used with
15675 @geindex COBOL support
15677 @node RM F 7 COBOL Support,RM F 1 2 Decimal Radix Support,RM E 5 28-29 Partition Communication Subsystem,Implementation Advice
15678 @anchor{gnat_rm/implementation_advice rm-f-7-cobol-support}@anchor{24f}
15679 @section RM F(7): COBOL Support
15684 "If COBOL (respectively, C) is widely supported in the target
15685 environment, implementations supporting the Information Systems Annex
15686 should provide the child package @code{Interfaces.COBOL} (respectively,
15687 @code{Interfaces.C}) specified in Annex B and should support a
15688 @code{convention_identifier} of COBOL (respectively, C) in the interfacing
15689 pragmas (see Annex B), thus allowing Ada programs to interface with
15690 programs written in that language."
15695 @geindex Decimal radix support
15697 @node RM F 1 2 Decimal Radix Support,RM G Numerics,RM F 7 COBOL Support,Implementation Advice
15698 @anchor{gnat_rm/implementation_advice rm-f-1-2-decimal-radix-support}@anchor{250}
15699 @section RM F.1(2): Decimal Radix Support
15704 "Packed decimal should be used as the internal representation for objects
15705 of subtype @code{S} when @code{S}'Machine_Radix = 10."
15708 Not followed. GNAT ignores @code{S}'Machine_Radix and always uses binary
15713 @node RM G Numerics,RM G 1 1 56-58 Complex Types,RM F 1 2 Decimal Radix Support,Implementation Advice
15714 @anchor{gnat_rm/implementation_advice rm-g-numerics}@anchor{251}
15715 @section RM G: Numerics
15720 "If Fortran (respectively, C) is widely supported in the target
15721 environment, implementations supporting the Numerics Annex
15722 should provide the child package @code{Interfaces.Fortran} (respectively,
15723 @code{Interfaces.C}) specified in Annex B and should support a
15724 @code{convention_identifier} of Fortran (respectively, C) in the interfacing
15725 pragmas (see Annex B), thus allowing Ada programs to interface with
15726 programs written in that language."
15731 @geindex Complex types
15733 @node RM G 1 1 56-58 Complex Types,RM G 1 2 49 Complex Elementary Functions,RM G Numerics,Implementation Advice
15734 @anchor{gnat_rm/implementation_advice rm-g-1-1-56-58-complex-types}@anchor{252}
15735 @section RM G.1.1(56-58): Complex Types
15740 "Because the usual mathematical meaning of multiplication of a complex
15741 operand and a real operand is that of the scaling of both components of
15742 the former by the latter, an implementation should not perform this
15743 operation by first promoting the real operand to complex type and then
15744 performing a full complex multiplication. In systems that, in the
15745 future, support an Ada binding to IEC 559:1989, the latter technique
15746 will not generate the required result when one of the components of the
15747 complex operand is infinite. (Explicit multiplication of the infinite
15748 component by the zero component obtained during promotion yields a NaN
15749 that propagates into the final result.) Analogous advice applies in the
15750 case of multiplication of a complex operand and a pure-imaginary
15751 operand, and in the case of division of a complex operand by a real or
15752 pure-imaginary operand."
15759 "Similarly, because the usual mathematical meaning of addition of a
15760 complex operand and a real operand is that the imaginary operand remains
15761 unchanged, an implementation should not perform this operation by first
15762 promoting the real operand to complex type and then performing a full
15763 complex addition. In implementations in which the @code{Signed_Zeros}
15764 attribute of the component type is @code{True} (and which therefore
15765 conform to IEC 559:1989 in regard to the handling of the sign of zero in
15766 predefined arithmetic operations), the latter technique will not
15767 generate the required result when the imaginary component of the complex
15768 operand is a negatively signed zero. (Explicit addition of the negative
15769 zero to the zero obtained during promotion yields a positive zero.)
15770 Analogous advice applies in the case of addition of a complex operand
15771 and a pure-imaginary operand, and in the case of subtraction of a
15772 complex operand and a real or pure-imaginary operand."
15779 "Implementations in which @code{Real'Signed_Zeros} is @code{True} should
15780 attempt to provide a rational treatment of the signs of zero results and
15781 result components. As one example, the result of the @code{Argument}
15782 function should have the sign of the imaginary component of the
15783 parameter @code{X} when the point represented by that parameter lies on
15784 the positive real axis; as another, the sign of the imaginary component
15785 of the @code{Compose_From_Polar} function should be the same as
15786 (respectively, the opposite of) that of the @code{Argument} parameter when that
15787 parameter has a value of zero and the @code{Modulus} parameter has a
15788 nonnegative (respectively, negative) value."
15793 @geindex Complex elementary functions
15795 @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
15796 @anchor{gnat_rm/implementation_advice rm-g-1-2-49-complex-elementary-functions}@anchor{253}
15797 @section RM G.1.2(49): Complex Elementary Functions
15802 "Implementations in which @code{Complex_Types.Real'Signed_Zeros} is
15803 @code{True} should attempt to provide a rational treatment of the signs
15804 of zero results and result components. For example, many of the complex
15805 elementary functions have components that are odd functions of one of
15806 the parameter components; in these cases, the result component should
15807 have the sign of the parameter component at the origin. Other complex
15808 elementary functions have zero components whose sign is opposite that of
15809 a parameter component at the origin, or is always positive or always
15815 @geindex Accuracy requirements
15817 @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
15818 @anchor{gnat_rm/implementation_advice rm-g-2-4-19-accuracy-requirements}@anchor{254}
15819 @section RM G.2.4(19): Accuracy Requirements
15824 "The versions of the forward trigonometric functions without a
15825 @code{Cycle} parameter should not be implemented by calling the
15826 corresponding version with a @code{Cycle} parameter of
15827 @code{2.0*Numerics.Pi}, since this will not provide the required
15828 accuracy in some portions of the domain. For the same reason, the
15829 version of @code{Log} without a @code{Base} parameter should not be
15830 implemented by calling the corresponding version with a @code{Base}
15831 parameter of @code{Numerics.e}."
15836 @geindex Complex arithmetic accuracy
15839 @geindex complex arithmetic
15841 @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
15842 @anchor{gnat_rm/implementation_advice rm-g-2-6-15-complex-arithmetic-accuracy}@anchor{255}
15843 @section RM G.2.6(15): Complex Arithmetic Accuracy
15848 "The version of the @code{Compose_From_Polar} function without a
15849 @code{Cycle} parameter should not be implemented by calling the
15850 corresponding version with a @code{Cycle} parameter of
15851 @code{2.0*Numerics.Pi}, since this will not provide the required
15852 accuracy in some portions of the domain."
15857 @geindex Sequential elaboration policy
15859 @node RM H 6 15/2 Pragma Partition_Elaboration_Policy,,RM G 2 6 15 Complex Arithmetic Accuracy,Implementation Advice
15860 @anchor{gnat_rm/implementation_advice rm-h-6-15-2-pragma-partition-elaboration-policy}@anchor{256}
15861 @section RM H.6(15/2): Pragma Partition_Elaboration_Policy
15866 "If the partition elaboration policy is @code{Sequential} and the
15867 Environment task becomes permanently blocked during elaboration then the
15868 partition is deadlocked and it is recommended that the partition be
15869 immediately terminated."
15874 @node Implementation Defined Characteristics,Intrinsic Subprograms,Implementation Advice,Top
15875 @anchor{gnat_rm/implementation_defined_characteristics implementation-defined-characteristics}@anchor{b}@anchor{gnat_rm/implementation_defined_characteristics doc}@anchor{257}@anchor{gnat_rm/implementation_defined_characteristics id1}@anchor{258}
15876 @chapter Implementation Defined Characteristics
15879 In addition to the implementation dependent pragmas and attributes, and the
15880 implementation advice, there are a number of other Ada features that are
15881 potentially implementation dependent and are designated as
15882 implementation-defined. These are mentioned throughout the Ada Reference
15883 Manual, and are summarized in Annex M.
15885 A requirement for conforming Ada compilers is that they provide
15886 documentation describing how the implementation deals with each of these
15887 issues. In this chapter you will find each point in Annex M listed,
15888 followed by a description of how GNAT
15889 handles the implementation dependence.
15891 You can use this chapter as a guide to minimizing implementation
15892 dependent features in your programs if portability to other compilers
15893 and other operating systems is an important consideration. The numbers
15894 in each entry below correspond to the paragraph numbers in the Ada
15901 "Whether or not each recommendation given in Implementation
15902 Advice is followed. See 1.1.2(37)."
15905 See @ref{a,,Implementation Advice}.
15911 "Capacity limitations of the implementation. See 1.1.3(3)."
15914 The complexity of programs that can be processed is limited only by the
15915 total amount of available virtual memory, and disk space for the
15916 generated object files.
15922 "Variations from the standard that are impractical to avoid
15923 given the implementation's execution environment. See 1.1.3(6)."
15926 There are no variations from the standard.
15932 "Which code_statements cause external
15933 interactions. See 1.1.3(10)."
15936 Any @emph{code_statement} can potentially cause external interactions.
15942 "The coded representation for the text of an Ada
15943 program. See 2.1(4)."
15946 See separate section on source representation.
15952 "The control functions allowed in comments. See 2.1(14)."
15955 See separate section on source representation.
15961 "The representation for an end of line. See 2.2(2)."
15964 See separate section on source representation.
15970 "Maximum supported line length and lexical element
15971 length. See 2.2(15)."
15974 The maximum line length is 255 characters and the maximum length of
15975 a lexical element is also 255 characters. This is the default setting
15976 if not overridden by the use of compiler switch @emph{-gnaty} (which
15977 sets the maximum to 79) or @emph{-gnatyMnn} which allows the maximum
15978 line length to be specified to be any value up to 32767. The maximum
15979 length of a lexical element is the same as the maximum line length.
15985 "Implementation defined pragmas. See 2.8(14)."
15988 See @ref{7,,Implementation Defined Pragmas}.
15994 "Effect of pragma @code{Optimize}. See 2.8(27)."
15997 Pragma @code{Optimize}, if given with a @code{Time} or @code{Space}
15998 parameter, checks that the optimization flag is set, and aborts if it is
16005 "The sequence of characters of the value returned by
16006 @code{S'Image} when some of the graphic characters of
16007 @code{S'Wide_Image} are not defined in @code{Character}. See
16011 The sequence of characters is as defined by the wide character encoding
16012 method used for the source. See section on source representation for
16019 "The predefined integer types declared in
16020 @code{Standard}. See 3.5.4(25)."
16024 @multitable {xxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
16035 @emph{Short_Short_Integer}
16043 @emph{Short_Integer}
16047 (Short) 16 bit signed
16059 @emph{Long_Integer}
16063 64 bit signed (on most 64 bit targets,
16064 depending on the C definition of long).
16065 32 bit signed (all other targets)
16069 @emph{Long_Long_Integer}
16082 "Any nonstandard integer types and the operators defined
16083 for them. See 3.5.4(26)."
16086 There are no nonstandard integer types.
16092 "Any nonstandard real types and the operators defined for
16093 them. See 3.5.6(8)."
16096 There are no nonstandard real types.
16102 "What combinations of requested decimal precision and range
16103 are supported for floating point types. See 3.5.7(7)."
16106 The precision and range is as defined by the IEEE standard.
16112 "The predefined floating point types declared in
16113 @code{Standard}. See 3.5.7(16)."
16117 @multitable {xxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
16140 (Short) 32 bit IEEE short
16152 @emph{Long_Long_Float}
16156 64 bit IEEE long (80 bit IEEE long on x86 processors)
16165 "The small of an ordinary fixed point type. See 3.5.9(8)."
16168 @code{Fine_Delta} is 2**(-63)
16174 "What combinations of small, range, and digits are
16175 supported for fixed point types. See 3.5.9(10)."
16178 Any combinations are permitted that do not result in a small less than
16179 @code{Fine_Delta} and do not result in a mantissa larger than 63 bits.
16180 If the mantissa is larger than 53 bits on machines where Long_Long_Float
16181 is 64 bits (true of all architectures except ia32), then the output from
16182 Text_IO is accurate to only 53 bits, rather than the full mantissa. This
16183 is because floating-point conversions are used to convert fixed point.
16189 "The result of @code{Tags.Expanded_Name} for types declared
16190 within an unnamed @emph{block_statement}. See 3.9(10)."
16193 Block numbers of the form @code{B@emph{nnn}}, where @emph{nnn} is a
16194 decimal integer are allocated.
16200 "Implementation-defined attributes. See 4.1.4(12)."
16203 See @ref{8,,Implementation Defined Attributes}.
16209 "Any implementation-defined time types. See 9.6(6)."
16212 There are no implementation-defined time types.
16218 "The time base associated with relative delays."
16221 See 9.6(20). The time base used is that provided by the C library
16222 function @code{gettimeofday}.
16228 "The time base of the type @code{Calendar.Time}. See
16232 The time base used is that provided by the C library function
16233 @code{gettimeofday}.
16239 "The time zone used for package @code{Calendar}
16240 operations. See 9.6(24)."
16243 The time zone used by package @code{Calendar} is the current system time zone
16244 setting for local time, as accessed by the C library function
16251 "Any limit on @emph{delay_until_statements} of
16252 @emph{select_statements}. See 9.6(29)."
16255 There are no such limits.
16261 "Whether or not two non-overlapping parts of a composite
16262 object are independently addressable, in the case where packing, record
16263 layout, or @code{Component_Size} is specified for the object. See
16267 Separate components are independently addressable if they do not share
16268 overlapping storage units.
16274 "The representation for a compilation. See 10.1(2)."
16277 A compilation is represented by a sequence of files presented to the
16278 compiler in a single invocation of the @emph{gcc} command.
16284 "Any restrictions on compilations that contain multiple
16285 compilation_units. See 10.1(4)."
16288 No single file can contain more than one compilation unit, but any
16289 sequence of files can be presented to the compiler as a single
16296 "The mechanisms for creating an environment and for adding
16297 and replacing compilation units. See 10.1.4(3)."
16300 See separate section on compilation model.
16306 "The manner of explicitly assigning library units to a
16307 partition. See 10.2(2)."
16310 If a unit contains an Ada main program, then the Ada units for the partition
16311 are determined by recursive application of the rules in the Ada Reference
16312 Manual section 10.2(2-6). In other words, the Ada units will be those that
16313 are needed by the main program, and then this definition of need is applied
16314 recursively to those units, and the partition contains the transitive
16315 closure determined by this relationship. In short, all the necessary units
16316 are included, with no need to explicitly specify the list. If additional
16317 units are required, e.g., by foreign language units, then all units must be
16318 mentioned in the context clause of one of the needed Ada units.
16320 If the partition contains no main program, or if the main program is in
16321 a language other than Ada, then GNAT
16322 provides the binder options @emph{-z} and @emph{-n} respectively, and in
16323 this case a list of units can be explicitly supplied to the binder for
16324 inclusion in the partition (all units needed by these units will also
16325 be included automatically). For full details on the use of these
16326 options, refer to @emph{GNAT Make Program gnatmake} in the
16327 @cite{GNAT User's Guide}.
16333 "The implementation-defined means, if any, of specifying
16334 which compilation units are needed by a given compilation unit. See
16338 The units needed by a given compilation unit are as defined in
16339 the Ada Reference Manual section 10.2(2-6). There are no
16340 implementation-defined pragmas or other implementation-defined
16341 means for specifying needed units.
16347 "The manner of designating the main subprogram of a
16348 partition. See 10.2(7)."
16351 The main program is designated by providing the name of the
16352 corresponding @code{ALI} file as the input parameter to the binder.
16358 "The order of elaboration of @emph{library_items}. See
16362 The first constraint on ordering is that it meets the requirements of
16363 Chapter 10 of the Ada Reference Manual. This still leaves some
16364 implementation dependent choices, which are resolved by first
16365 elaborating bodies as early as possible (i.e., in preference to specs
16366 where there is a choice), and second by evaluating the immediate with
16367 clauses of a unit to determine the probably best choice, and
16368 third by elaborating in alphabetical order of unit names
16369 where a choice still remains.
16375 "Parameter passing and function return for the main
16376 subprogram. See 10.2(21)."
16379 The main program has no parameters. It may be a procedure, or a function
16380 returning an integer type. In the latter case, the returned integer
16381 value is the return code of the program (overriding any value that
16382 may have been set by a call to @code{Ada.Command_Line.Set_Exit_Status}).
16388 "The mechanisms for building and running partitions. See
16392 GNAT itself supports programs with only a single partition. The GNATDIST
16393 tool provided with the GLADE package (which also includes an implementation
16394 of the PCS) provides a completely flexible method for building and running
16395 programs consisting of multiple partitions. See the separate GLADE manual
16402 "The details of program execution, including program
16403 termination. See 10.2(25)."
16406 See separate section on compilation model.
16412 "The semantics of any non-active partitions supported by the
16413 implementation. See 10.2(28)."
16416 Passive partitions are supported on targets where shared memory is
16417 provided by the operating system. See the GLADE reference manual for
16424 "The information returned by @code{Exception_Message}. See
16428 Exception message returns the null string unless a specific message has
16429 been passed by the program.
16435 "The result of @code{Exceptions.Exception_Name} for types
16436 declared within an unnamed @emph{block_statement}. See 11.4.1(12)."
16439 Blocks have implementation defined names of the form @code{B@emph{nnn}}
16440 where @emph{nnn} is an integer.
16446 "The information returned by
16447 @code{Exception_Information}. See 11.4.1(13)."
16450 @code{Exception_Information} returns a string in the following format:
16453 *Exception_Name:* nnnnn
16456 *Load address:* 0xhhhh
16457 *Call stack traceback locations:*
16458 0xhhhh 0xhhhh 0xhhhh ... 0xhhh
16469 @code{nnnn} is the fully qualified name of the exception in all upper
16470 case letters. This line is always present.
16473 @code{mmmm} is the message (this line present only if message is non-null)
16476 @code{ppp} is the Process Id value as a decimal integer (this line is
16477 present only if the Process Id is nonzero). Currently we are
16478 not making use of this field.
16481 The Load address line, the Call stack traceback locations line and the
16482 following values are present only if at least one traceback location was
16483 recorded. The Load address indicates the address at which the main executable
16484 was loaded; this line may not be present if operating system hasn't relocated
16485 the main executable. The values are given in C style format, with lower case
16486 letters for a-f, and only as many digits present as are necessary.
16487 The line terminator sequence at the end of each line, including
16488 the last line is a single @code{LF} character (@code{16#0A#}).
16496 "Implementation-defined check names. See 11.5(27)."
16499 The implementation defined check names include Alignment_Check,
16500 Atomic_Synchronization, Duplicated_Tag_Check, Container_Checks,
16501 Tampering_Check, Predicate_Check, and Validity_Check. In addition, a user
16502 program can add implementation-defined check names by means of the pragma
16503 Check_Name. See the description of pragma @code{Suppress} for full details.
16509 "The interpretation of each aspect of representation. See
16513 See separate section on data representations.
16519 "Any restrictions placed upon representation items. See
16523 See separate section on data representations.
16529 "The meaning of @code{Size} for indefinite subtypes. See
16533 Size for an indefinite subtype is the maximum possible size, except that
16534 for the case of a subprogram parameter, the size of the parameter object
16535 is the actual size.
16541 "The default external representation for a type tag. See
16545 The default external representation for a type tag is the fully expanded
16546 name of the type in upper case letters.
16552 "What determines whether a compilation unit is the same in
16553 two different partitions. See 13.3(76)."
16556 A compilation unit is the same in two different partitions if and only
16557 if it derives from the same source file.
16563 "Implementation-defined components. See 13.5.1(15)."
16566 The only implementation defined component is the tag for a tagged type,
16567 which contains a pointer to the dispatching table.
16573 "If @code{Word_Size} = @code{Storage_Unit}, the default bit
16574 ordering. See 13.5.3(5)."
16577 @code{Word_Size} (32) is not the same as @code{Storage_Unit} (8) for this
16578 implementation, so no non-default bit ordering is supported. The default
16579 bit ordering corresponds to the natural endianness of the target architecture.
16585 "The contents of the visible part of package @code{System}
16586 and its language-defined children. See 13.7(2)."
16589 See the definition of these packages in files @code{system.ads} and
16590 @code{s-stoele.ads}. Note that two declarations are added to package
16594 Max_Priority : constant Positive := Priority'Last;
16595 Max_Interrupt_Priority : constant Positive := Interrupt_Priority'Last;
16602 "The contents of the visible part of package
16603 @code{System.Machine_Code}, and the meaning of
16604 @emph{code_statements}. See 13.8(7)."
16607 See the definition and documentation in file @code{s-maccod.ads}.
16613 "The effect of unchecked conversion. See 13.9(11)."
16616 Unchecked conversion between types of the same size
16617 results in an uninterpreted transmission of the bits from one type
16618 to the other. If the types are of unequal sizes, then in the case of
16619 discrete types, a shorter source is first zero or sign extended as
16620 necessary, and a shorter target is simply truncated on the left.
16621 For all non-discrete types, the source is first copied if necessary
16622 to ensure that the alignment requirements of the target are met, then
16623 a pointer is constructed to the source value, and the result is obtained
16624 by dereferencing this pointer after converting it to be a pointer to the
16625 target type. Unchecked conversions where the target subtype is an
16626 unconstrained array are not permitted. If the target alignment is
16627 greater than the source alignment, then a copy of the result is
16628 made with appropriate alignment
16634 "The semantics of operations on invalid representations.
16635 See 13.9.2(10-11)."
16638 For assignments and other operations where the use of invalid values cannot
16639 result in erroneous behavior, the compiler ignores the possibility of invalid
16640 values. An exception is raised at the point where an invalid value would
16641 result in erroneous behavior. For example executing:
16644 procedure invalidvals is
16646 Y : Natural range 1 .. 10;
16647 for Y'Address use X'Address;
16648 Z : Natural range 1 .. 10;
16649 A : array (Natural range 1 .. 10) of Integer;
16651 Z := Y; -- no exception
16652 A (Z) := 3; -- exception raised;
16656 As indicated, an exception is raised on the array assignment, but not
16657 on the simple assignment of the invalid negative value from Y to Z.
16663 "The manner of choosing a storage pool for an access type
16664 when @code{Storage_Pool} is not specified for the type. See 13.11(17)."
16667 There are 3 different standard pools used by the compiler when
16668 @code{Storage_Pool} is not specified depending whether the type is local
16669 to a subprogram or defined at the library level and whether
16670 @code{Storage_Size`@w{`}is specified or not. See documentation in the runtime
16671 library units `@w{`}System.Pool_Global}, @code{System.Pool_Size} and
16672 @code{System.Pool_Local} in files @code{s-poosiz.ads},
16673 @code{s-pooglo.ads} and @code{s-pooloc.ads} for full details on the
16674 default pools used.
16680 "Whether or not the implementation provides user-accessible
16681 names for the standard pool type(s). See 13.11(17)."
16684 See documentation in the sources of the run time mentioned in the previous
16685 paragraph. All these pools are accessible by means of @cite{with}ing
16692 "The meaning of @code{Storage_Size}. See 13.11(18)."
16695 @code{Storage_Size} is measured in storage units, and refers to the
16696 total space available for an access type collection, or to the primary
16697 stack space for a task.
16703 "Implementation-defined aspects of storage pools. See
16707 See documentation in the sources of the run time mentioned in the
16708 paragraph about standard storage pools above
16709 for details on GNAT-defined aspects of storage pools.
16715 "The set of restrictions allowed in a pragma
16716 @code{Restrictions}. See 13.12(7)."
16719 See @ref{9,,Standard and Implementation Defined Restrictions}.
16725 "The consequences of violating limitations on
16726 @code{Restrictions} pragmas. See 13.12(9)."
16729 Restrictions that can be checked at compile time result in illegalities
16730 if violated. Currently there are no other consequences of violating
16737 "The representation used by the @code{Read} and
16738 @code{Write} attributes of elementary types in terms of stream
16739 elements. See 13.13.2(9)."
16742 The representation is the in-memory representation of the base type of
16743 the type, using the number of bits corresponding to the
16744 @code{type'Size} value, and the natural ordering of the machine.
16750 "The names and characteristics of the numeric subtypes
16751 declared in the visible part of package @code{Standard}. See A.1(3)."
16754 See items describing the integer and floating-point types supported.
16760 "The string returned by @code{Character_Set_Version}.
16764 @code{Ada.Wide_Characters.Handling.Character_Set_Version} returns
16765 the string "Unicode 4.0", referring to version 4.0 of the
16766 Unicode specification.
16772 "The accuracy actually achieved by the elementary
16773 functions. See A.5.1(1)."
16776 The elementary functions correspond to the functions available in the C
16777 library. Only fast math mode is implemented.
16783 "The sign of a zero result from some of the operators or
16784 functions in @code{Numerics.Generic_Elementary_Functions}, when
16785 @code{Float_Type'Signed_Zeros} is @code{True}. See A.5.1(46)."
16788 The sign of zeroes follows the requirements of the IEEE 754 standard on
16796 @code{Numerics.Float_Random.Max_Image_Width}. See A.5.2(27)."
16799 Maximum image width is 6864, see library file @code{s-rannum.ads}.
16806 @code{Numerics.Discrete_Random.Max_Image_Width}. See A.5.2(27)."
16809 Maximum image width is 6864, see library file @code{s-rannum.ads}.
16815 "The algorithms for random number generation. See
16819 The algorithm is the Mersenne Twister, as documented in the source file
16820 @code{s-rannum.adb}. This version of the algorithm has a period of
16827 "The string representation of a random number generator's
16828 state. See A.5.2(38)."
16831 The value returned by the Image function is the concatenation of
16832 the fixed-width decimal representations of the 624 32-bit integers
16833 of the state vector.
16839 "The minimum time interval between calls to the
16840 time-dependent Reset procedure that are guaranteed to initiate different
16841 random number sequences. See A.5.2(45)."
16844 The minimum period between reset calls to guarantee distinct series of
16845 random numbers is one microsecond.
16851 "The values of the @code{Model_Mantissa},
16852 @code{Model_Emin}, @code{Model_Epsilon}, @code{Model},
16853 @code{Safe_First}, and @code{Safe_Last} attributes, if the Numerics
16854 Annex is not supported. See A.5.3(72)."
16857 Run the compiler with @emph{-gnatS} to produce a listing of package
16858 @code{Standard}, has the values of all numeric attributes.
16864 "Any implementation-defined characteristics of the
16865 input-output packages. See A.7(14)."
16868 There are no special implementation defined characteristics for these
16875 "The value of @code{Buffer_Size} in @code{Storage_IO}. See
16879 All type representations are contiguous, and the @code{Buffer_Size} is
16880 the value of @code{type'Size} rounded up to the next storage unit
16887 "External files for standard input, standard output, and
16888 standard error See A.10(5)."
16891 These files are mapped onto the files provided by the C streams
16892 libraries. See source file @code{i-cstrea.ads} for further details.
16898 "The accuracy of the value produced by @code{Put}. See
16902 If more digits are requested in the output than are represented by the
16903 precision of the value, zeroes are output in the corresponding least
16904 significant digit positions.
16910 "The meaning of @code{Argument_Count}, @code{Argument}, and
16911 @code{Command_Name}. See A.15(1)."
16914 These are mapped onto the @code{argv} and @code{argc} parameters of the
16915 main program in the natural manner.
16921 "The interpretation of the @code{Form} parameter in procedure
16922 @code{Create_Directory}. See A.16(56)."
16925 The @code{Form} parameter is not used.
16931 "The interpretation of the @code{Form} parameter in procedure
16932 @code{Create_Path}. See A.16(60)."
16935 The @code{Form} parameter is not used.
16941 "The interpretation of the @code{Form} parameter in procedure
16942 @code{Copy_File}. See A.16(68)."
16945 The @code{Form} parameter is case-insensitive.
16946 Two fields are recognized in the @code{Form} parameter:
16953 <value> starts immediately after the character '=' and ends with the
16954 character immediately preceding the next comma (',') or with the last
16955 character of the parameter.
16957 The only possible values for preserve= are:
16960 @multitable {xxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
16971 @emph{no_attributes}
16975 Do not try to preserve any file attributes. This is the
16976 default if no preserve= is found in Form.
16980 @emph{all_attributes}
16984 Try to preserve all file attributes (timestamps, access rights).
16992 Preserve the timestamp of the copied file, but not the other
16998 The only possible values for mode= are:
17001 @multitable {xxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
17016 Only do the copy if the destination file does not already exist.
17017 If it already exists, Copy_File fails.
17025 Copy the file in all cases. Overwrite an already existing destination file.
17033 Append the original file to the destination file. If the destination file
17034 does not exist, the destination file is a copy of the source file.
17035 When mode=append, the field preserve=, if it exists, is not taken into account.
17040 If the Form parameter includes one or both of the fields and the value or
17041 values are incorrect, Copy_file fails with Use_Error.
17043 Examples of correct Forms:
17046 Form => "preserve=no_attributes,mode=overwrite" (the default)
17047 Form => "mode=append"
17048 Form => "mode=copy, preserve=all_attributes"
17051 Examples of incorrect Forms:
17054 Form => "preserve=junk"
17055 Form => "mode=internal, preserve=timestamps"
17062 "The interpretation of the @code{Pattern} parameter, when not the null string,
17063 in the @code{Start_Search} and @code{Search} procedures.
17064 See A.16(104) and A.16(112)."
17067 When the @code{Pattern} parameter is not the null string, it is interpreted
17068 according to the syntax of regular expressions as defined in the
17069 @code{GNAT.Regexp} package.
17071 See @ref{259,,GNAT.Regexp (g-regexp.ads)}.
17077 "Implementation-defined convention names. See B.1(11)."
17080 The following convention names are supported
17083 @multitable {xxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
17102 @emph{Ada_Pass_By_Copy}
17106 Allowed for any types except by-reference types such as limited
17107 records. Compatible with convention Ada, but causes any parameters
17108 with this convention to be passed by copy.
17112 @emph{Ada_Pass_By_Reference}
17116 Allowed for any types except by-copy types such as scalars.
17117 Compatible with convention Ada, but causes any parameters
17118 with this convention to be passed by reference.
17134 Synonym for Assembler
17142 Synonym for Assembler
17154 @emph{C_Pass_By_Copy}
17158 Allowed only for record types, like C, but also notes that record
17159 is to be passed by copy rather than reference.
17171 @emph{C_Plus_Plus (or CPP)}
17183 Treated the same as C
17191 Treated the same as C
17207 For support of pragma @code{Import} with convention Intrinsic, see
17208 separate section on Intrinsic Subprograms.
17216 Stdcall (used for Windows implementations only). This convention correspond
17217 to the WINAPI (previously called Pascal convention) C/C++ convention under
17218 Windows. A routine with this convention cleans the stack before
17219 exit. This pragma cannot be applied to a dispatching call.
17227 Synonym for Stdcall
17235 Synonym for Stdcall
17243 Stubbed is a special convention used to indicate that the body of the
17244 subprogram will be entirely ignored. Any call to the subprogram
17245 is converted into a raise of the @code{Program_Error} exception. If a
17246 pragma @code{Import} specifies convention @code{stubbed} then no body need
17247 be present at all. This convention is useful during development for the
17248 inclusion of subprograms whose body has not yet been written.
17249 In addition, all otherwise unrecognized convention names are also
17250 treated as being synonymous with convention C. In all implementations
17251 except for VMS, use of such other names results in a warning. In VMS
17252 implementations, these names are accepted silently.
17261 "The meaning of link names. See B.1(36)."
17264 Link names are the actual names used by the linker.
17270 "The manner of choosing link names when neither the link
17271 name nor the address of an imported or exported entity is specified. See
17275 The default linker name is that which would be assigned by the relevant
17276 external language, interpreting the Ada name as being in all lower case
17283 "The effect of pragma @code{Linker_Options}. See B.1(37)."
17286 The string passed to @code{Linker_Options} is presented uninterpreted as
17287 an argument to the link command, unless it contains ASCII.NUL characters.
17288 NUL characters if they appear act as argument separators, so for example
17291 pragma Linker_Options ("-labc" & ASCII.NUL & "-ldef");
17294 causes two separate arguments @code{-labc} and @code{-ldef} to be passed to the
17295 linker. The order of linker options is preserved for a given unit. The final
17296 list of options passed to the linker is in reverse order of the elaboration
17297 order. For example, linker options for a body always appear before the options
17298 from the corresponding package spec.
17304 "The contents of the visible part of package
17305 @code{Interfaces} and its language-defined descendants. See B.2(1)."
17308 See files with prefix @code{i-} in the distributed library.
17314 "Implementation-defined children of package
17315 @code{Interfaces}. The contents of the visible part of package
17316 @code{Interfaces}. See B.2(11)."
17319 See files with prefix @code{i-} in the distributed library.
17325 "The types @code{Floating}, @code{Long_Floating},
17326 @code{Binary}, @code{Long_Binary}, @code{Decimal_ Element}, and
17327 @code{COBOL_Character}; and the initialization of the variables
17328 @code{Ada_To_COBOL} and @code{COBOL_To_Ada}, in
17329 @code{Interfaces.COBOL}. See B.4(50)."
17333 @multitable {xxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
17352 @emph{Long_Floating}
17356 (Floating) Long_Float
17376 @emph{Decimal_Element}
17384 @emph{COBOL_Character}
17393 For initialization, see the file @code{i-cobol.ads} in the distributed library.
17399 "Support for access to machine instructions. See C.1(1)."
17402 See documentation in file @code{s-maccod.ads} in the distributed library.
17408 "Implementation-defined aspects of access to machine
17409 operations. See C.1(9)."
17412 See documentation in file @code{s-maccod.ads} in the distributed library.
17418 "Implementation-defined aspects of interrupts. See C.3(2)."
17421 Interrupts are mapped to signals or conditions as appropriate. See
17423 @code{Ada.Interrupt_Names} in source file @code{a-intnam.ads} for details
17424 on the interrupts supported on a particular target.
17430 "Implementation-defined aspects of pre-elaboration. See
17434 GNAT does not permit a partition to be restarted without reloading,
17435 except under control of the debugger.
17441 "The semantics of pragma @code{Discard_Names}. See C.5(7)."
17444 Pragma @code{Discard_Names} causes names of enumeration literals to
17445 be suppressed. In the presence of this pragma, the Image attribute
17446 provides the image of the Pos of the literal, and Value accepts
17449 For tagged types, when pragmas @code{Discard_Names} and @code{No_Tagged_Streams}
17450 simultaneously apply, their Expanded_Name and External_Tag are initialized
17451 with empty strings. This is useful to avoid exposing entity names at binary
17458 "The result of the @code{Task_Identification.Image}
17459 attribute. See C.7.1(7)."
17462 The result of this attribute is a string that identifies
17463 the object or component that denotes a given task. If a variable @code{Var}
17464 has a task type, the image for this task will have the form @code{Var_@emph{XXXXXXXX}},
17465 where the suffix @emph{XXXXXXXX}
17466 is the hexadecimal representation of the virtual address of the corresponding
17467 task control block. If the variable is an array of tasks, the image of each
17468 task will have the form of an indexed component indicating the position of a
17469 given task in the array, e.g., @code{Group(5)_@emph{XXXXXXX}}. If the task is a
17470 component of a record, the image of the task will have the form of a selected
17471 component. These rules are fully recursive, so that the image of a task that
17472 is a subcomponent of a composite object corresponds to the expression that
17473 designates this task.
17475 If a task is created by an allocator, its image depends on the context. If the
17476 allocator is part of an object declaration, the rules described above are used
17477 to construct its image, and this image is not affected by subsequent
17478 assignments. If the allocator appears within an expression, the image
17479 includes only the name of the task type.
17481 If the configuration pragma Discard_Names is present, or if the restriction
17482 No_Implicit_Heap_Allocation is in effect, the image reduces to
17483 the numeric suffix, that is to say the hexadecimal representation of the
17484 virtual address of the control block of the task.
17490 "The value of @code{Current_Task} when in a protected entry
17491 or interrupt handler. See C.7.1(17)."
17494 Protected entries or interrupt handlers can be executed by any
17495 convenient thread, so the value of @code{Current_Task} is undefined.
17501 "The effect of calling @code{Current_Task} from an entry
17502 body or interrupt handler. See C.7.1(19)."
17505 When GNAT can determine statically that @code{Current_Task} is called directly in
17506 the body of an entry (or barrier) then a warning is emitted and @code{Program_Error}
17507 is raised at run time. Otherwise, the effect of calling @code{Current_Task} from an
17508 entry body or interrupt handler is to return the identification of the task
17509 currently executing the code.
17515 "Implementation-defined aspects of
17516 @code{Task_Attributes}. See C.7.2(19)."
17519 There are no implementation-defined aspects of @code{Task_Attributes}.
17525 "Values of all @code{Metrics}. See D(2)."
17528 The metrics information for GNAT depends on the performance of the
17529 underlying operating system. The sources of the run-time for tasking
17530 implementation, together with the output from @emph{-gnatG} can be
17531 used to determine the exact sequence of operating systems calls made
17532 to implement various tasking constructs. Together with appropriate
17533 information on the performance of the underlying operating system,
17534 on the exact target in use, this information can be used to determine
17535 the required metrics.
17541 "The declarations of @code{Any_Priority} and
17542 @code{Priority}. See D.1(11)."
17545 See declarations in file @code{system.ads}.
17551 "Implementation-defined execution resources. See D.1(15)."
17554 There are no implementation-defined execution resources.
17560 "Whether, on a multiprocessor, a task that is waiting for
17561 access to a protected object keeps its processor busy. See D.2.1(3)."
17564 On a multi-processor, a task that is waiting for access to a protected
17565 object does not keep its processor busy.
17571 "The affect of implementation defined execution resources
17572 on task dispatching. See D.2.1(9)."
17575 Tasks map to threads in the threads package used by GNAT. Where possible
17576 and appropriate, these threads correspond to native threads of the
17577 underlying operating system.
17583 "Implementation-defined @emph{policy_identifiers} allowed
17584 in a pragma @code{Task_Dispatching_Policy}. See D.2.2(3)."
17587 There are no implementation-defined policy-identifiers allowed in this
17594 "Implementation-defined aspects of priority inversion. See
17598 Execution of a task cannot be preempted by the implementation processing
17599 of delay expirations for lower priority tasks.
17605 "Implementation-defined task dispatching. See D.2.2(18)."
17608 The policy is the same as that of the underlying threads implementation.
17614 "Implementation-defined @emph{policy_identifiers} allowed
17615 in a pragma @code{Locking_Policy}. See D.3(4)."
17618 The two implementation defined policies permitted in GNAT are
17619 @code{Inheritance_Locking} and @code{Concurrent_Readers_Locking}. On
17620 targets that support the @code{Inheritance_Locking} policy, locking is
17621 implemented by inheritance, i.e., the task owning the lock operates
17622 at a priority equal to the highest priority of any task currently
17623 requesting the lock. On targets that support the
17624 @code{Concurrent_Readers_Locking} policy, locking is implemented with a
17625 read/write lock allowing multiple protected object functions to enter
17632 "Default ceiling priorities. See D.3(10)."
17635 The ceiling priority of protected objects of the type
17636 @code{System.Interrupt_Priority'Last} as described in the Ada
17637 Reference Manual D.3(10),
17643 "The ceiling of any protected object used internally by
17644 the implementation. See D.3(16)."
17647 The ceiling priority of internal protected objects is
17648 @code{System.Priority'Last}.
17654 "Implementation-defined queuing policies. See D.4(1)."
17657 There are no implementation-defined queuing policies.
17663 "On a multiprocessor, any conditions that cause the
17664 completion of an aborted construct to be delayed later than what is
17665 specified for a single processor. See D.6(3)."
17668 The semantics for abort on a multi-processor is the same as on a single
17669 processor, there are no further delays.
17675 "Any operations that implicitly require heap storage
17676 allocation. See D.7(8)."
17679 The only operation that implicitly requires heap storage allocation is
17686 "What happens when a task terminates in the presence of
17687 pragma @code{No_Task_Termination}. See D.7(15)."
17690 Execution is erroneous in that case.
17696 "Implementation-defined aspects of pragma
17697 @code{Restrictions}. See D.7(20)."
17700 There are no such implementation-defined aspects.
17706 "Implementation-defined aspects of package
17707 @code{Real_Time}. See D.8(17)."
17710 There are no implementation defined aspects of package @code{Real_Time}.
17716 "Implementation-defined aspects of
17717 @emph{delay_statements}. See D.9(8)."
17720 Any difference greater than one microsecond will cause the task to be
17721 delayed (see D.9(7)).
17727 "The upper bound on the duration of interrupt blocking
17728 caused by the implementation. See D.12(5)."
17731 The upper bound is determined by the underlying operating system. In
17732 no cases is it more than 10 milliseconds.
17738 "The means for creating and executing distributed
17739 programs. See E(5)."
17742 The GLADE package provides a utility GNATDIST for creating and executing
17743 distributed programs. See the GLADE reference manual for further details.
17749 "Any events that can result in a partition becoming
17750 inaccessible. See E.1(7)."
17753 See the GLADE reference manual for full details on such events.
17759 "The scheduling policies, treatment of priorities, and
17760 management of shared resources between partitions in certain cases. See
17764 See the GLADE reference manual for full details on these aspects of
17765 multi-partition execution.
17771 "Events that cause the version of a compilation unit to
17772 change. See E.3(5)."
17775 Editing the source file of a compilation unit, or the source files of
17776 any units on which it is dependent in a significant way cause the version
17777 to change. No other actions cause the version number to change. All changes
17778 are significant except those which affect only layout, capitalization or
17785 "Whether the execution of the remote subprogram is
17786 immediately aborted as a result of cancellation. See E.4(13)."
17789 See the GLADE reference manual for details on the effect of abort in
17790 a distributed application.
17796 "Implementation-defined aspects of the PCS. See E.5(25)."
17799 See the GLADE reference manual for a full description of all implementation
17800 defined aspects of the PCS.
17806 "Implementation-defined interfaces in the PCS. See
17810 See the GLADE reference manual for a full description of all
17811 implementation defined interfaces.
17817 "The values of named numbers in the package
17818 @code{Decimal}. See F.2(7)."
17822 @multitable {xxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxx}
17865 @emph{Max_Decimal_Digits}
17878 "The value of @code{Max_Picture_Length} in the package
17879 @code{Text_IO.Editing}. See F.3.3(16)."
17888 "The value of @code{Max_Picture_Length} in the package
17889 @code{Wide_Text_IO.Editing}. See F.3.4(5)."
17898 "The accuracy actually achieved by the complex elementary
17899 functions and by other complex arithmetic operations. See G.1(1)."
17902 Standard library functions are used for the complex arithmetic
17903 operations. Only fast math mode is currently supported.
17909 "The sign of a zero result (or a component thereof) from
17910 any operator or function in @code{Numerics.Generic_Complex_Types}, when
17911 @code{Real'Signed_Zeros} is True. See G.1.1(53)."
17914 The signs of zero values are as recommended by the relevant
17915 implementation advice.
17921 "The sign of a zero result (or a component thereof) from
17922 any operator or function in
17923 @code{Numerics.Generic_Complex_Elementary_Functions}, when
17924 @code{Real'Signed_Zeros} is @code{True}. See G.1.2(45)."
17927 The signs of zero values are as recommended by the relevant
17928 implementation advice.
17934 "Whether the strict mode or the relaxed mode is the
17935 default. See G.2(2)."
17938 The strict mode is the default. There is no separate relaxed mode. GNAT
17939 provides a highly efficient implementation of strict mode.
17945 "The result interval in certain cases of fixed-to-float
17946 conversion. See G.2.1(10)."
17949 For cases where the result interval is implementation dependent, the
17950 accuracy is that provided by performing all operations in 64-bit IEEE
17951 floating-point format.
17957 "The result of a floating point arithmetic operation in
17958 overflow situations, when the @code{Machine_Overflows} attribute of the
17959 result type is @code{False}. See G.2.1(13)."
17962 Infinite and NaN values are produced as dictated by the IEEE
17963 floating-point standard.
17964 Note that on machines that are not fully compliant with the IEEE
17965 floating-point standard, such as Alpha, the @emph{-mieee} compiler flag
17966 must be used for achieving IEEE conforming behavior (although at the cost
17967 of a significant performance penalty), so infinite and NaN values are
17968 properly generated.
17974 "The result interval for division (or exponentiation by a
17975 negative exponent), when the floating point hardware implements division
17976 as multiplication by a reciprocal. See G.2.1(16)."
17979 Not relevant, division is IEEE exact.
17985 "The definition of close result set, which determines the
17986 accuracy of certain fixed point multiplications and divisions. See
17990 Operations in the close result set are performed using IEEE long format
17991 floating-point arithmetic. The input operands are converted to
17992 floating-point, the operation is done in floating-point, and the result
17993 is converted to the target type.
17999 "Conditions on a @emph{universal_real} operand of a fixed
18000 point multiplication or division for which the result shall be in the
18001 perfect result set. See G.2.3(22)."
18004 The result is only defined to be in the perfect result set if the result
18005 can be computed by a single scaling operation involving a scale factor
18006 representable in 64-bits.
18012 "The result of a fixed point arithmetic operation in
18013 overflow situations, when the @code{Machine_Overflows} attribute of the
18014 result type is @code{False}. See G.2.3(27)."
18017 Not relevant, @code{Machine_Overflows} is @code{True} for fixed-point
18024 "The result of an elementary function reference in
18025 overflow situations, when the @code{Machine_Overflows} attribute of the
18026 result type is @code{False}. See G.2.4(4)."
18029 IEEE infinite and Nan values are produced as appropriate.
18035 "The value of the angle threshold, within which certain
18036 elementary functions, complex arithmetic operations, and complex
18037 elementary functions yield results conforming to a maximum relative
18038 error bound. See G.2.4(10)."
18041 Information on this subject is not yet available.
18047 "The accuracy of certain elementary functions for
18048 parameters beyond the angle threshold. See G.2.4(10)."
18051 Information on this subject is not yet available.
18057 "The result of a complex arithmetic operation or complex
18058 elementary function reference in overflow situations, when the
18059 @code{Machine_Overflows} attribute of the corresponding real type is
18060 @code{False}. See G.2.6(5)."
18063 IEEE infinite and Nan values are produced as appropriate.
18069 "The accuracy of certain complex arithmetic operations and
18070 certain complex elementary functions for parameters (or components
18071 thereof) beyond the angle threshold. See G.2.6(8)."
18074 Information on those subjects is not yet available.
18080 "Information regarding bounded errors and erroneous
18081 execution. See H.2(1)."
18084 Information on this subject is not yet available.
18090 "Implementation-defined aspects of pragma
18091 @code{Inspection_Point}. See H.3.2(8)."
18094 Pragma @code{Inspection_Point} ensures that the variable is live and can
18095 be examined by the debugger at the inspection point.
18101 "Implementation-defined aspects of pragma
18102 @code{Restrictions}. See H.4(25)."
18105 There are no implementation-defined aspects of pragma @code{Restrictions}. The
18106 use of pragma @code{Restrictions [No_Exceptions]} has no effect on the
18107 generated code. Checks must suppressed by use of pragma @code{Suppress}.
18113 "Any restrictions on pragma @code{Restrictions}. See
18117 There are no restrictions on pragma @code{Restrictions}.
18119 @node Intrinsic Subprograms,Representation Clauses and Pragmas,Implementation Defined Characteristics,Top
18120 @anchor{gnat_rm/intrinsic_subprograms doc}@anchor{25a}@anchor{gnat_rm/intrinsic_subprograms intrinsic-subprograms}@anchor{c}@anchor{gnat_rm/intrinsic_subprograms id1}@anchor{25b}
18121 @chapter Intrinsic Subprograms
18124 @geindex Intrinsic Subprograms
18126 GNAT allows a user application program to write the declaration:
18129 pragma Import (Intrinsic, name);
18132 providing that the name corresponds to one of the implemented intrinsic
18133 subprograms in GNAT, and that the parameter profile of the referenced
18134 subprogram meets the requirements. This chapter describes the set of
18135 implemented intrinsic subprograms, and the requirements on parameter profiles.
18136 Note that no body is supplied; as with other uses of pragma Import, the
18137 body is supplied elsewhere (in this case by the compiler itself). Note
18138 that any use of this feature is potentially non-portable, since the
18139 Ada standard does not require Ada compilers to implement this feature.
18142 * Intrinsic Operators::
18143 * Compilation_ISO_Date::
18144 * Compilation_Date::
18145 * Compilation_Time::
18146 * Enclosing_Entity::
18147 * Exception_Information::
18148 * Exception_Message::
18152 * Shifts and Rotates::
18153 * Source_Location::
18157 @node Intrinsic Operators,Compilation_ISO_Date,,Intrinsic Subprograms
18158 @anchor{gnat_rm/intrinsic_subprograms id2}@anchor{25c}@anchor{gnat_rm/intrinsic_subprograms intrinsic-operators}@anchor{25d}
18159 @section Intrinsic Operators
18162 @geindex Intrinsic operator
18164 All the predefined numeric operators in package Standard
18165 in @code{pragma Import (Intrinsic,..)}
18166 declarations. In the binary operator case, the operands must have the same
18167 size. The operand or operands must also be appropriate for
18168 the operator. For example, for addition, the operands must
18169 both be floating-point or both be fixed-point, and the
18170 right operand for @code{"**"} must have a root type of
18171 @code{Standard.Integer'Base}.
18172 You can use an intrinsic operator declaration as in the following example:
18175 type Int1 is new Integer;
18176 type Int2 is new Integer;
18178 function "+" (X1 : Int1; X2 : Int2) return Int1;
18179 function "+" (X1 : Int1; X2 : Int2) return Int2;
18180 pragma Import (Intrinsic, "+");
18183 This declaration would permit 'mixed mode' arithmetic on items
18184 of the differing types @code{Int1} and @code{Int2}.
18185 It is also possible to specify such operators for private types, if the
18186 full views are appropriate arithmetic types.
18188 @node Compilation_ISO_Date,Compilation_Date,Intrinsic Operators,Intrinsic Subprograms
18189 @anchor{gnat_rm/intrinsic_subprograms id3}@anchor{25e}@anchor{gnat_rm/intrinsic_subprograms compilation-iso-date}@anchor{25f}
18190 @section Compilation_ISO_Date
18193 @geindex Compilation_ISO_Date
18195 This intrinsic subprogram is used in the implementation of the
18196 library package @code{GNAT.Source_Info}. The only useful use of the
18197 intrinsic import in this case is the one in this unit, so an
18198 application program should simply call the function
18199 @code{GNAT.Source_Info.Compilation_ISO_Date} to obtain the date of
18200 the current compilation (in local time format YYYY-MM-DD).
18202 @node Compilation_Date,Compilation_Time,Compilation_ISO_Date,Intrinsic Subprograms
18203 @anchor{gnat_rm/intrinsic_subprograms compilation-date}@anchor{260}@anchor{gnat_rm/intrinsic_subprograms id4}@anchor{261}
18204 @section Compilation_Date
18207 @geindex Compilation_Date
18209 Same as Compilation_ISO_Date, except the string is in the form
18212 @node Compilation_Time,Enclosing_Entity,Compilation_Date,Intrinsic Subprograms
18213 @anchor{gnat_rm/intrinsic_subprograms compilation-time}@anchor{262}@anchor{gnat_rm/intrinsic_subprograms id5}@anchor{263}
18214 @section Compilation_Time
18217 @geindex Compilation_Time
18219 This intrinsic subprogram is used in the implementation of the
18220 library package @code{GNAT.Source_Info}. The only useful use of the
18221 intrinsic import in this case is the one in this unit, so an
18222 application program should simply call the function
18223 @code{GNAT.Source_Info.Compilation_Time} to obtain the time of
18224 the current compilation (in local time format HH:MM:SS).
18226 @node Enclosing_Entity,Exception_Information,Compilation_Time,Intrinsic Subprograms
18227 @anchor{gnat_rm/intrinsic_subprograms id6}@anchor{264}@anchor{gnat_rm/intrinsic_subprograms enclosing-entity}@anchor{265}
18228 @section Enclosing_Entity
18231 @geindex Enclosing_Entity
18233 This intrinsic subprogram is used in the implementation of the
18234 library package @code{GNAT.Source_Info}. The only useful use of the
18235 intrinsic import in this case is the one in this unit, so an
18236 application program should simply call the function
18237 @code{GNAT.Source_Info.Enclosing_Entity} to obtain the name of
18238 the current subprogram, package, task, entry, or protected subprogram.
18240 @node Exception_Information,Exception_Message,Enclosing_Entity,Intrinsic Subprograms
18241 @anchor{gnat_rm/intrinsic_subprograms id7}@anchor{266}@anchor{gnat_rm/intrinsic_subprograms exception-information}@anchor{267}
18242 @section Exception_Information
18245 @geindex Exception_Information'
18247 This intrinsic subprogram is used in the implementation of the
18248 library package @code{GNAT.Current_Exception}. The only useful
18249 use of the intrinsic import in this case is the one in this unit,
18250 so an application program should simply call the function
18251 @code{GNAT.Current_Exception.Exception_Information} to obtain
18252 the exception information associated with the current exception.
18254 @node Exception_Message,Exception_Name,Exception_Information,Intrinsic Subprograms
18255 @anchor{gnat_rm/intrinsic_subprograms exception-message}@anchor{268}@anchor{gnat_rm/intrinsic_subprograms id8}@anchor{269}
18256 @section Exception_Message
18259 @geindex Exception_Message
18261 This intrinsic subprogram is used in the implementation of the
18262 library package @code{GNAT.Current_Exception}. The only useful
18263 use of the intrinsic import in this case is the one in this unit,
18264 so an application program should simply call the function
18265 @code{GNAT.Current_Exception.Exception_Message} to obtain
18266 the message associated with the current exception.
18268 @node Exception_Name,File,Exception_Message,Intrinsic Subprograms
18269 @anchor{gnat_rm/intrinsic_subprograms exception-name}@anchor{26a}@anchor{gnat_rm/intrinsic_subprograms id9}@anchor{26b}
18270 @section Exception_Name
18273 @geindex Exception_Name
18275 This intrinsic subprogram is used in the implementation of the
18276 library package @code{GNAT.Current_Exception}. The only useful
18277 use of the intrinsic import in this case is the one in this unit,
18278 so an application program should simply call the function
18279 @code{GNAT.Current_Exception.Exception_Name} to obtain
18280 the name of the current exception.
18282 @node File,Line,Exception_Name,Intrinsic Subprograms
18283 @anchor{gnat_rm/intrinsic_subprograms id10}@anchor{26c}@anchor{gnat_rm/intrinsic_subprograms file}@anchor{26d}
18289 This intrinsic subprogram is used in the implementation of the
18290 library package @code{GNAT.Source_Info}. The only useful use of the
18291 intrinsic import in this case is the one in this unit, so an
18292 application program should simply call the function
18293 @code{GNAT.Source_Info.File} to obtain the name of the current
18296 @node Line,Shifts and Rotates,File,Intrinsic Subprograms
18297 @anchor{gnat_rm/intrinsic_subprograms id11}@anchor{26e}@anchor{gnat_rm/intrinsic_subprograms line}@anchor{26f}
18303 This intrinsic subprogram is used in the implementation of the
18304 library package @code{GNAT.Source_Info}. The only useful use of the
18305 intrinsic import in this case is the one in this unit, so an
18306 application program should simply call the function
18307 @code{GNAT.Source_Info.Line} to obtain the number of the current
18310 @node Shifts and Rotates,Source_Location,Line,Intrinsic Subprograms
18311 @anchor{gnat_rm/intrinsic_subprograms shifts-and-rotates}@anchor{270}@anchor{gnat_rm/intrinsic_subprograms id12}@anchor{271}
18312 @section Shifts and Rotates
18315 @geindex Shift_Left
18317 @geindex Shift_Right
18319 @geindex Shift_Right_Arithmetic
18321 @geindex Rotate_Left
18323 @geindex Rotate_Right
18325 In standard Ada, the shift and rotate functions are available only
18326 for the predefined modular types in package @code{Interfaces}. However, in
18327 GNAT it is possible to define these functions for any integer
18328 type (signed or modular), as in this example:
18331 function Shift_Left
18333 Amount : Natural) return T;
18336 The function name must be one of
18337 Shift_Left, Shift_Right, Shift_Right_Arithmetic, Rotate_Left, or
18338 Rotate_Right. T must be an integer type. T'Size must be
18339 8, 16, 32 or 64 bits; if T is modular, the modulus
18340 must be 2**8, 2**16, 2**32 or 2**64.
18341 The result type must be the same as the type of @code{Value}.
18342 The shift amount must be Natural.
18343 The formal parameter names can be anything.
18345 A more convenient way of providing these shift operators is to use
18346 the Provide_Shift_Operators pragma, which provides the function declarations
18347 and corresponding pragma Import's for all five shift functions.
18349 @node Source_Location,,Shifts and Rotates,Intrinsic Subprograms
18350 @anchor{gnat_rm/intrinsic_subprograms source-location}@anchor{272}@anchor{gnat_rm/intrinsic_subprograms id13}@anchor{273}
18351 @section Source_Location
18354 @geindex Source_Location
18356 This intrinsic subprogram is used in the implementation of the
18357 library routine @code{GNAT.Source_Info}. The only useful use of the
18358 intrinsic import in this case is the one in this unit, so an
18359 application program should simply call the function
18360 @code{GNAT.Source_Info.Source_Location} to obtain the current
18361 source file location.
18363 @node Representation Clauses and Pragmas,Standard Library Routines,Intrinsic Subprograms,Top
18364 @anchor{gnat_rm/representation_clauses_and_pragmas representation-clauses-and-pragmas}@anchor{d}@anchor{gnat_rm/representation_clauses_and_pragmas doc}@anchor{274}@anchor{gnat_rm/representation_clauses_and_pragmas id1}@anchor{275}
18365 @chapter Representation Clauses and Pragmas
18368 @geindex Representation Clauses
18370 @geindex Representation Clause
18372 @geindex Representation Pragma
18375 @geindex representation
18377 This section describes the representation clauses accepted by GNAT, and
18378 their effect on the representation of corresponding data objects.
18380 GNAT fully implements Annex C (Systems Programming). This means that all
18381 the implementation advice sections in chapter 13 are fully implemented.
18382 However, these sections only require a minimal level of support for
18383 representation clauses. GNAT provides much more extensive capabilities,
18384 and this section describes the additional capabilities provided.
18387 * Alignment Clauses::
18389 * Storage_Size Clauses::
18390 * Size of Variant Record Objects::
18391 * Biased Representation::
18392 * Value_Size and Object_Size Clauses::
18393 * Component_Size Clauses::
18394 * Bit_Order Clauses::
18395 * Effect of Bit_Order on Byte Ordering::
18396 * Pragma Pack for Arrays::
18397 * Pragma Pack for Records::
18398 * Record Representation Clauses::
18399 * Handling of Records with Holes::
18400 * Enumeration Clauses::
18401 * Address Clauses::
18402 * Use of Address Clauses for Memory-Mapped I/O::
18403 * Effect of Convention on Representation::
18404 * Conventions and Anonymous Access Types::
18405 * Determining the Representations chosen by GNAT::
18409 @node Alignment Clauses,Size Clauses,,Representation Clauses and Pragmas
18410 @anchor{gnat_rm/representation_clauses_and_pragmas id2}@anchor{276}@anchor{gnat_rm/representation_clauses_and_pragmas alignment-clauses}@anchor{277}
18411 @section Alignment Clauses
18414 @geindex Alignment Clause
18416 GNAT requires that all alignment clauses specify 0 or a power of 2, and
18417 all default alignments are always a power of 2. Specifying 0 is the
18418 same as specifying 1.
18420 The default alignment values are as follows:
18426 @emph{Elementary Types}.
18428 For elementary types, the alignment is the minimum of the actual size of
18429 objects of the type divided by @code{Storage_Unit},
18430 and the maximum alignment supported by the target.
18431 (This maximum alignment is given by the GNAT-specific attribute
18432 @code{Standard'Maximum_Alignment}; see @ref{191,,Attribute Maximum_Alignment}.)
18434 @geindex Maximum_Alignment attribute
18436 For example, for type @code{Long_Float}, the object size is 8 bytes, and the
18437 default alignment will be 8 on any target that supports alignments
18438 this large, but on some targets, the maximum alignment may be smaller
18439 than 8, in which case objects of type @code{Long_Float} will be maximally
18445 For arrays, the alignment is equal to the alignment of the component type
18446 for the normal case where no packing or component size is given. If the
18447 array is packed, and the packing is effective (see separate section on
18448 packed arrays), then the alignment will be either 4, 2, or 1 for long packed
18449 arrays or arrays whose length is not known at compile time, depending on
18450 whether the component size is divisible by 4, 2, or is odd. For short packed
18451 arrays, which are handled internally as modular types, the alignment
18452 will be as described for elementary types, e.g. a packed array of length
18453 31 bits will have an object size of four bytes, and an alignment of 4.
18458 For the normal unpacked case, the alignment of a record is equal to
18459 the maximum alignment of any of its components. For tagged records, this
18460 includes the implicit access type used for the tag. If a pragma @code{Pack}
18461 is used and all components are packable (see separate section on pragma
18462 @code{Pack}), then the resulting alignment is 1, unless the layout of the
18463 record makes it profitable to increase it.
18465 A special case is when:
18471 the size of the record is given explicitly, or a
18472 full record representation clause is given, and
18475 the size of the record is 2, 4, or 8 bytes.
18478 In this case, an alignment is chosen to match the
18479 size of the record. For example, if we have:
18482 type Small is record
18485 for Small'Size use 16;
18488 then the default alignment of the record type @code{Small} is 2, not 1. This
18489 leads to more efficient code when the record is treated as a unit, and also
18490 allows the type to specified as @code{Atomic} on architectures requiring
18494 An alignment clause may specify a larger alignment than the default value
18495 up to some maximum value dependent on the target (obtainable by using the
18496 attribute reference @code{Standard'Maximum_Alignment}). It may also specify
18497 a smaller alignment than the default value for enumeration, integer and
18498 fixed point types, as well as for record types, for example
18505 for V'alignment use 1;
18511 The default alignment for the type @code{V} is 4, as a result of the
18512 Integer field in the record, but it is permissible, as shown, to
18513 override the default alignment of the record with a smaller value.
18518 Note that according to the Ada standard, an alignment clause applies only
18519 to the first named subtype. If additional subtypes are declared, then the
18520 compiler is allowed to choose any alignment it likes, and there is no way
18521 to control this choice. Consider:
18524 type R is range 1 .. 10_000;
18525 for R'Alignment use 1;
18526 subtype RS is R range 1 .. 1000;
18529 The alignment clause specifies an alignment of 1 for the first named subtype
18530 @code{R} but this does not necessarily apply to @code{RS}. When writing
18531 portable Ada code, you should avoid writing code that explicitly or
18532 implicitly relies on the alignment of such subtypes.
18534 For the GNAT compiler, if an explicit alignment clause is given, this
18535 value is also used for any subsequent subtypes. So for GNAT, in the
18536 above example, you can count on the alignment of @code{RS} being 1. But this
18537 assumption is non-portable, and other compilers may choose different
18538 alignments for the subtype @code{RS}.
18540 @node Size Clauses,Storage_Size Clauses,Alignment Clauses,Representation Clauses and Pragmas
18541 @anchor{gnat_rm/representation_clauses_and_pragmas id3}@anchor{278}@anchor{gnat_rm/representation_clauses_and_pragmas size-clauses}@anchor{279}
18542 @section Size Clauses
18545 @geindex Size Clause
18547 The default size for a type @code{T} is obtainable through the
18548 language-defined attribute @code{T'Size} and also through the
18549 equivalent GNAT-defined attribute @code{T'Value_Size}.
18550 For objects of type @code{T}, GNAT will generally increase the type size
18551 so that the object size (obtainable through the GNAT-defined attribute
18552 @code{T'Object_Size})
18553 is a multiple of @code{T'Alignment * Storage_Unit}.
18558 type Smallint is range 1 .. 6;
18566 In this example, @code{Smallint'Size} = @code{Smallint'Value_Size} = 3,
18567 as specified by the RM rules,
18568 but objects of this type will have a size of 8
18569 (@code{Smallint'Object_Size} = 8),
18570 since objects by default occupy an integral number
18571 of storage units. On some targets, notably older
18572 versions of the Digital Alpha, the size of stand
18573 alone objects of this type may be 32, reflecting
18574 the inability of the hardware to do byte load/stores.
18576 Similarly, the size of type @code{Rec} is 40 bits
18577 (@code{Rec'Size} = @code{Rec'Value_Size} = 40), but
18578 the alignment is 4, so objects of this type will have
18579 their size increased to 64 bits so that it is a multiple
18580 of the alignment (in bits). This decision is
18581 in accordance with the specific Implementation Advice in RM 13.3(43):
18585 "A @code{Size} clause should be supported for an object if the specified
18586 @code{Size} is at least as large as its subtype's @code{Size}, and corresponds
18587 to a size in storage elements that is a multiple of the object's
18588 @code{Alignment} (if the @code{Alignment} is nonzero)."
18591 An explicit size clause may be used to override the default size by
18592 increasing it. For example, if we have:
18595 type My_Boolean is new Boolean;
18596 for My_Boolean'Size use 32;
18599 then values of this type will always be 32 bits long. In the case of
18600 discrete types, the size can be increased up to 64 bits, with the effect
18601 that the entire specified field is used to hold the value, sign- or
18602 zero-extended as appropriate. If more than 64 bits is specified, then
18603 padding space is allocated after the value, and a warning is issued that
18604 there are unused bits.
18606 Similarly the size of records and arrays may be increased, and the effect
18607 is to add padding bits after the value. This also causes a warning message
18610 The largest Size value permitted in GNAT is 2**31-1. Since this is a
18611 Size in bits, this corresponds to an object of size 256 megabytes (minus
18612 one). This limitation is true on all targets. The reason for this
18613 limitation is that it improves the quality of the code in many cases
18614 if it is known that a Size value can be accommodated in an object of
18617 @node Storage_Size Clauses,Size of Variant Record Objects,Size Clauses,Representation Clauses and Pragmas
18618 @anchor{gnat_rm/representation_clauses_and_pragmas storage-size-clauses}@anchor{27a}@anchor{gnat_rm/representation_clauses_and_pragmas id4}@anchor{27b}
18619 @section Storage_Size Clauses
18622 @geindex Storage_Size Clause
18624 For tasks, the @code{Storage_Size} clause specifies the amount of space
18625 to be allocated for the task stack. This cannot be extended, and if the
18626 stack is exhausted, then @code{Storage_Error} will be raised (if stack
18627 checking is enabled). Use a @code{Storage_Size} attribute definition clause,
18628 or a @code{Storage_Size} pragma in the task definition to set the
18629 appropriate required size. A useful technique is to include in every
18630 task definition a pragma of the form:
18633 pragma Storage_Size (Default_Stack_Size);
18636 Then @code{Default_Stack_Size} can be defined in a global package, and
18637 modified as required. Any tasks requiring stack sizes different from the
18638 default can have an appropriate alternative reference in the pragma.
18640 You can also use the @emph{-d} binder switch to modify the default stack
18643 For access types, the @code{Storage_Size} clause specifies the maximum
18644 space available for allocation of objects of the type. If this space is
18645 exceeded then @code{Storage_Error} will be raised by an allocation attempt.
18646 In the case where the access type is declared local to a subprogram, the
18647 use of a @code{Storage_Size} clause triggers automatic use of a special
18648 predefined storage pool (@code{System.Pool_Size}) that ensures that all
18649 space for the pool is automatically reclaimed on exit from the scope in
18650 which the type is declared.
18652 A special case recognized by the compiler is the specification of a
18653 @code{Storage_Size} of zero for an access type. This means that no
18654 items can be allocated from the pool, and this is recognized at compile
18655 time, and all the overhead normally associated with maintaining a fixed
18656 size storage pool is eliminated. Consider the following example:
18660 type R is array (Natural) of Character;
18661 type P is access all R;
18662 for P'Storage_Size use 0;
18663 -- Above access type intended only for interfacing purposes
18667 procedure g (m : P);
18668 pragma Import (C, g);
18678 As indicated in this example, these dummy storage pools are often useful in
18679 connection with interfacing where no object will ever be allocated. If you
18680 compile the above example, you get the warning:
18683 p.adb:16:09: warning: allocation from empty storage pool
18684 p.adb:16:09: warning: Storage_Error will be raised at run time
18687 Of course in practice, there will not be any explicit allocators in the
18688 case of such an access declaration.
18690 @node Size of Variant Record Objects,Biased Representation,Storage_Size Clauses,Representation Clauses and Pragmas
18691 @anchor{gnat_rm/representation_clauses_and_pragmas id5}@anchor{27c}@anchor{gnat_rm/representation_clauses_and_pragmas size-of-variant-record-objects}@anchor{27d}
18692 @section Size of Variant Record Objects
18696 @geindex variant record objects
18698 @geindex Variant record objects
18701 In the case of variant record objects, there is a question whether Size gives
18702 information about a particular variant, or the maximum size required
18703 for any variant. Consider the following program
18706 with Text_IO; use Text_IO;
18708 type R1 (A : Boolean := False) is record
18710 when True => X : Character;
18711 when False => null;
18719 Put_Line (Integer'Image (V1'Size));
18720 Put_Line (Integer'Image (V2'Size));
18724 Here we are dealing with a variant record, where the True variant
18725 requires 16 bits, and the False variant requires 8 bits.
18726 In the above example, both V1 and V2 contain the False variant,
18727 which is only 8 bits long. However, the result of running the
18735 The reason for the difference here is that the discriminant value of
18736 V1 is fixed, and will always be False. It is not possible to assign
18737 a True variant value to V1, therefore 8 bits is sufficient. On the
18738 other hand, in the case of V2, the initial discriminant value is
18739 False (from the default), but it is possible to assign a True
18740 variant value to V2, therefore 16 bits must be allocated for V2
18741 in the general case, even fewer bits may be needed at any particular
18742 point during the program execution.
18744 As can be seen from the output of this program, the @code{'Size}
18745 attribute applied to such an object in GNAT gives the actual allocated
18746 size of the variable, which is the largest size of any of the variants.
18747 The Ada Reference Manual is not completely clear on what choice should
18748 be made here, but the GNAT behavior seems most consistent with the
18749 language in the RM.
18751 In some cases, it may be desirable to obtain the size of the current
18752 variant, rather than the size of the largest variant. This can be
18753 achieved in GNAT by making use of the fact that in the case of a
18754 subprogram parameter, GNAT does indeed return the size of the current
18755 variant (because a subprogram has no way of knowing how much space
18756 is actually allocated for the actual).
18758 Consider the following modified version of the above program:
18761 with Text_IO; use Text_IO;
18763 type R1 (A : Boolean := False) is record
18765 when True => X : Character;
18766 when False => null;
18772 function Size (V : R1) return Integer is
18778 Put_Line (Integer'Image (V2'Size));
18779 Put_Line (Integer'Image (Size (V2)));
18781 Put_Line (Integer'Image (V2'Size));
18782 Put_Line (Integer'Image (Size (V2)));
18786 The output from this program is
18795 Here we see that while the @code{'Size} attribute always returns
18796 the maximum size, regardless of the current variant value, the
18797 @code{Size} function does indeed return the size of the current
18800 @node Biased Representation,Value_Size and Object_Size Clauses,Size of Variant Record Objects,Representation Clauses and Pragmas
18801 @anchor{gnat_rm/representation_clauses_and_pragmas id6}@anchor{27e}@anchor{gnat_rm/representation_clauses_and_pragmas biased-representation}@anchor{27f}
18802 @section Biased Representation
18805 @geindex Size for biased representation
18807 @geindex Biased representation
18809 In the case of scalars with a range starting at other than zero, it is
18810 possible in some cases to specify a size smaller than the default minimum
18811 value, and in such cases, GNAT uses an unsigned biased representation,
18812 in which zero is used to represent the lower bound, and successive values
18813 represent successive values of the type.
18815 For example, suppose we have the declaration:
18818 type Small is range -7 .. -4;
18819 for Small'Size use 2;
18822 Although the default size of type @code{Small} is 4, the @code{Size}
18823 clause is accepted by GNAT and results in the following representation
18827 -7 is represented as 2#00#
18828 -6 is represented as 2#01#
18829 -5 is represented as 2#10#
18830 -4 is represented as 2#11#
18833 Biased representation is only used if the specified @code{Size} clause
18834 cannot be accepted in any other manner. These reduced sizes that force
18835 biased representation can be used for all discrete types except for
18836 enumeration types for which a representation clause is given.
18838 @node Value_Size and Object_Size Clauses,Component_Size Clauses,Biased Representation,Representation Clauses and Pragmas
18839 @anchor{gnat_rm/representation_clauses_and_pragmas id7}@anchor{280}@anchor{gnat_rm/representation_clauses_and_pragmas value-size-and-object-size-clauses}@anchor{281}
18840 @section Value_Size and Object_Size Clauses
18843 @geindex Value_Size
18845 @geindex Object_Size
18848 @geindex of objects
18850 In Ada 95 and Ada 2005, @code{T'Size} for a type @code{T} is the minimum
18851 number of bits required to hold values of type @code{T}.
18852 Although this interpretation was allowed in Ada 83, it was not required,
18853 and this requirement in practice can cause some significant difficulties.
18854 For example, in most Ada 83 compilers, @code{Natural'Size} was 32.
18855 However, in Ada 95 and Ada 2005,
18856 @code{Natural'Size} is
18857 typically 31. This means that code may change in behavior when moving
18858 from Ada 83 to Ada 95 or Ada 2005. For example, consider:
18861 type Rec is record;
18867 at 0 range 0 .. Natural'Size - 1;
18868 at 0 range Natural'Size .. 2 * Natural'Size - 1;
18872 In the above code, since the typical size of @code{Natural} objects
18873 is 32 bits and @code{Natural'Size} is 31, the above code can cause
18874 unexpected inefficient packing in Ada 95 and Ada 2005, and in general
18875 there are cases where the fact that the object size can exceed the
18876 size of the type causes surprises.
18878 To help get around this problem GNAT provides two implementation
18879 defined attributes, @code{Value_Size} and @code{Object_Size}. When
18880 applied to a type, these attributes yield the size of the type
18881 (corresponding to the RM defined size attribute), and the size of
18882 objects of the type respectively.
18884 The @code{Object_Size} is used for determining the default size of
18885 objects and components. This size value can be referred to using the
18886 @code{Object_Size} attribute. The phrase 'is used' here means that it is
18887 the basis of the determination of the size. The backend is free to
18888 pad this up if necessary for efficiency, e.g., an 8-bit stand-alone
18889 character might be stored in 32 bits on a machine with no efficient
18890 byte access instructions such as the Alpha.
18892 The default rules for the value of @code{Object_Size} for
18893 discrete types are as follows:
18899 The @code{Object_Size} for base subtypes reflect the natural hardware
18900 size in bits (run the compiler with @emph{-gnatS} to find those values
18901 for numeric types). Enumeration types and fixed-point base subtypes have
18902 8, 16, 32, or 64 bits for this size, depending on the range of values
18906 The @code{Object_Size} of a subtype is the same as the
18907 @code{Object_Size} of
18908 the type from which it is obtained.
18911 The @code{Object_Size} of a derived base type is copied from the parent
18912 base type, and the @code{Object_Size} of a derived first subtype is copied
18913 from the parent first subtype.
18916 The @code{Value_Size} attribute
18917 is the (minimum) number of bits required to store a value
18919 This value is used to determine how tightly to pack
18920 records or arrays with components of this type, and also affects
18921 the semantics of unchecked conversion (unchecked conversions where
18922 the @code{Value_Size} values differ generate a warning, and are potentially
18925 The default rules for the value of @code{Value_Size} are as follows:
18931 The @code{Value_Size} for a base subtype is the minimum number of bits
18932 required to store all values of the type (including the sign bit
18933 only if negative values are possible).
18936 If a subtype statically matches the first subtype of a given type, then it has
18937 by default the same @code{Value_Size} as the first subtype. This is a
18938 consequence of RM 13.1(14): "if two subtypes statically match,
18939 then their subtype-specific aspects are the same".)
18942 All other subtypes have a @code{Value_Size} corresponding to the minimum
18943 number of bits required to store all values of the subtype. For
18944 dynamic bounds, it is assumed that the value can range down or up
18945 to the corresponding bound of the ancestor
18948 The RM defined attribute @code{Size} corresponds to the
18949 @code{Value_Size} attribute.
18951 The @code{Size} attribute may be defined for a first-named subtype. This sets
18952 the @code{Value_Size} of
18953 the first-named subtype to the given value, and the
18954 @code{Object_Size} of this first-named subtype to the given value padded up
18955 to an appropriate boundary. It is a consequence of the default rules
18956 above that this @code{Object_Size} will apply to all further subtypes. On the
18957 other hand, @code{Value_Size} is affected only for the first subtype, any
18958 dynamic subtypes obtained from it directly, and any statically matching
18959 subtypes. The @code{Value_Size} of any other static subtypes is not affected.
18961 @code{Value_Size} and
18962 @code{Object_Size} may be explicitly set for any subtype using
18963 an attribute definition clause. Note that the use of these attributes
18964 can cause the RM 13.1(14) rule to be violated. If two access types
18965 reference aliased objects whose subtypes have differing @code{Object_Size}
18966 values as a result of explicit attribute definition clauses, then it
18967 is illegal to convert from one access subtype to the other. For a more
18968 complete description of this additional legality rule, see the
18969 description of the @code{Object_Size} attribute.
18971 To get a feel for the difference, consider the following examples (note
18972 that in each case the base is @code{Short_Short_Integer} with a size of 8):
18975 @multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxx}
18978 Type or subtype declaration
18990 @code{type x1 is range 0 .. 5;}
19002 @code{type x2 is range 0 .. 5;}
19003 @code{for x2'size use 12;}
19015 @code{subtype x3 is x2 range 0 .. 3;}
19027 @code{subtype x4 is x2'base range 0 .. 10;}
19039 @code{dynamic : x2'Base range -64 .. +63;}
19047 @code{subtype x5 is x2 range 0 .. dynamic;}
19059 @code{subtype x6 is x2'base range 0 .. dynamic;}
19072 Note: the entries marked '*' are not actually specified by the Ada
19073 Reference Manual, which has nothing to say about size in the dynamic
19074 case. What GNAT does is to allocate sufficient bits to accomodate any
19075 possible dynamic values for the bounds at run-time.
19077 So far, so good, but GNAT has to obey the RM rules, so the question is
19078 under what conditions must the RM @code{Size} be used.
19079 The following is a list
19080 of the occasions on which the RM @code{Size} must be used:
19086 Component size for packed arrays or records
19089 Value of the attribute @code{Size} for a type
19092 Warning about sizes not matching for unchecked conversion
19095 For record types, the @code{Object_Size} is always a multiple of the
19096 alignment of the type (this is true for all types). In some cases the
19097 @code{Value_Size} can be smaller. Consider:
19106 On a typical 32-bit architecture, the X component will occupy four bytes
19107 and the Y component will occupy one byte, for a total of 5 bytes. As a
19108 result @code{R'Value_Size} will be 40 (bits) since this is the minimum size
19109 required to store a value of this type. For example, it is permissible
19110 to have a component of type R in an array whose component size is
19111 specified to be 40 bits.
19113 However, @code{R'Object_Size} will be 64 (bits). The difference is due to
19114 the alignment requirement for objects of the record type. The X
19115 component will require four-byte alignment because that is what type
19116 Integer requires, whereas the Y component, a Character, will only
19117 require 1-byte alignment. Since the alignment required for X is the
19118 greatest of all the components' alignments, that is the alignment
19119 required for the enclosing record type, i.e., 4 bytes or 32 bits. As
19120 indicated above, the actual object size must be rounded up so that it is
19121 a multiple of the alignment value. Therefore, 40 bits rounded up to the
19122 next multiple of 32 yields 64 bits.
19124 For all other types, the @code{Object_Size}
19125 and @code{Value_Size} are the same (and equivalent to the RM attribute @code{Size}).
19126 Only @code{Size} may be specified for such types.
19128 Note that @code{Value_Size} can be used to force biased representation
19129 for a particular subtype. Consider this example:
19132 type R is (A, B, C, D, E, F);
19133 subtype RAB is R range A .. B;
19134 subtype REF is R range E .. F;
19137 By default, @code{RAB}
19138 has a size of 1 (sufficient to accommodate the representation
19139 of @code{A} and @code{B}, 0 and 1), and @code{REF}
19140 has a size of 3 (sufficient to accommodate the representation
19141 of @code{E} and @code{F}, 4 and 5). But if we add the
19142 following @code{Value_Size} attribute definition clause:
19145 for REF'Value_Size use 1;
19148 then biased representation is forced for @code{REF},
19149 and 0 will represent @code{E} and 1 will represent @code{F}.
19150 A warning is issued when a @code{Value_Size} attribute
19151 definition clause forces biased representation. This
19152 warning can be turned off using @code{-gnatw.B}.
19154 @node Component_Size Clauses,Bit_Order Clauses,Value_Size and Object_Size Clauses,Representation Clauses and Pragmas
19155 @anchor{gnat_rm/representation_clauses_and_pragmas id8}@anchor{282}@anchor{gnat_rm/representation_clauses_and_pragmas component-size-clauses}@anchor{283}
19156 @section Component_Size Clauses
19159 @geindex Component_Size Clause
19161 Normally, the value specified in a component size clause must be consistent
19162 with the subtype of the array component with regard to size and alignment.
19163 In other words, the value specified must be at least equal to the size
19164 of this subtype, and must be a multiple of the alignment value.
19166 In addition, component size clauses are allowed which cause the array
19167 to be packed, by specifying a smaller value. A first case is for
19168 component size values in the range 1 through 63. The value specified
19169 must not be smaller than the Size of the subtype. GNAT will accurately
19170 honor all packing requests in this range. For example, if we have:
19173 type r is array (1 .. 8) of Natural;
19174 for r'Component_Size use 31;
19177 then the resulting array has a length of 31 bytes (248 bits = 8 * 31).
19178 Of course access to the components of such an array is considerably
19179 less efficient than if the natural component size of 32 is used.
19180 A second case is when the subtype of the component is a record type
19181 padded because of its default alignment. For example, if we have:
19190 type a is array (1 .. 8) of r;
19191 for a'Component_Size use 72;
19194 then the resulting array has a length of 72 bytes, instead of 96 bytes
19195 if the alignment of the record (4) was obeyed.
19197 Note that there is no point in giving both a component size clause
19198 and a pragma Pack for the same array type. if such duplicate
19199 clauses are given, the pragma Pack will be ignored.
19201 @node Bit_Order Clauses,Effect of Bit_Order on Byte Ordering,Component_Size Clauses,Representation Clauses and Pragmas
19202 @anchor{gnat_rm/representation_clauses_and_pragmas bit-order-clauses}@anchor{284}@anchor{gnat_rm/representation_clauses_and_pragmas id9}@anchor{285}
19203 @section Bit_Order Clauses
19206 @geindex Bit_Order Clause
19208 @geindex bit ordering
19213 For record subtypes, GNAT permits the specification of the @code{Bit_Order}
19214 attribute. The specification may either correspond to the default bit
19215 order for the target, in which case the specification has no effect and
19216 places no additional restrictions, or it may be for the non-standard
19217 setting (that is the opposite of the default).
19219 In the case where the non-standard value is specified, the effect is
19220 to renumber bits within each byte, but the ordering of bytes is not
19221 affected. There are certain
19222 restrictions placed on component clauses as follows:
19228 Components fitting within a single storage unit.
19230 These are unrestricted, and the effect is merely to renumber bits. For
19231 example if we are on a little-endian machine with @code{Low_Order_First}
19232 being the default, then the following two declarations have exactly
19238 B : Integer range 1 .. 120;
19242 A at 0 range 0 .. 0;
19243 B at 0 range 1 .. 7;
19248 B : Integer range 1 .. 120;
19251 for R2'Bit_Order use High_Order_First;
19254 A at 0 range 7 .. 7;
19255 B at 0 range 0 .. 6;
19259 The useful application here is to write the second declaration with the
19260 @code{Bit_Order} attribute definition clause, and know that it will be treated
19261 the same, regardless of whether the target is little-endian or big-endian.
19264 Components occupying an integral number of bytes.
19266 These are components that exactly fit in two or more bytes. Such component
19267 declarations are allowed, but have no effect, since it is important to realize
19268 that the @code{Bit_Order} specification does not affect the ordering of bytes.
19269 In particular, the following attempt at getting an endian-independent integer
19277 for R2'Bit_Order use High_Order_First;
19280 A at 0 range 0 .. 31;
19284 This declaration will result in a little-endian integer on a
19285 little-endian machine, and a big-endian integer on a big-endian machine.
19286 If byte flipping is required for interoperability between big- and
19287 little-endian machines, this must be explicitly programmed. This capability
19288 is not provided by @code{Bit_Order}.
19291 Components that are positioned across byte boundaries.
19293 but do not occupy an integral number of bytes. Given that bytes are not
19294 reordered, such fields would occupy a non-contiguous sequence of bits
19295 in memory, requiring non-trivial code to reassemble. They are for this
19296 reason not permitted, and any component clause specifying such a layout
19297 will be flagged as illegal by GNAT.
19300 Since the misconception that Bit_Order automatically deals with all
19301 endian-related incompatibilities is a common one, the specification of
19302 a component field that is an integral number of bytes will always
19303 generate a warning. This warning may be suppressed using @code{pragma Warnings (Off)}
19304 if desired. The following section contains additional
19305 details regarding the issue of byte ordering.
19307 @node Effect of Bit_Order on Byte Ordering,Pragma Pack for Arrays,Bit_Order Clauses,Representation Clauses and Pragmas
19308 @anchor{gnat_rm/representation_clauses_and_pragmas id10}@anchor{286}@anchor{gnat_rm/representation_clauses_and_pragmas effect-of-bit-order-on-byte-ordering}@anchor{287}
19309 @section Effect of Bit_Order on Byte Ordering
19312 @geindex byte ordering
19317 In this section we will review the effect of the @code{Bit_Order} attribute
19318 definition clause on byte ordering. Briefly, it has no effect at all, but
19319 a detailed example will be helpful. Before giving this
19320 example, let us review the precise
19321 definition of the effect of defining @code{Bit_Order}. The effect of a
19322 non-standard bit order is described in section 13.5.3 of the Ada
19327 "2 A bit ordering is a method of interpreting the meaning of
19328 the storage place attributes."
19331 To understand the precise definition of storage place attributes in
19332 this context, we visit section 13.5.1 of the manual:
19336 "13 A record_representation_clause (without the mod_clause)
19337 specifies the layout. The storage place attributes (see 13.5.2)
19338 are taken from the values of the position, first_bit, and last_bit
19339 expressions after normalizing those values so that first_bit is
19340 less than Storage_Unit."
19343 The critical point here is that storage places are taken from
19344 the values after normalization, not before. So the @code{Bit_Order}
19345 interpretation applies to normalized values. The interpretation
19346 is described in the later part of the 13.5.3 paragraph:
19350 "2 A bit ordering is a method of interpreting the meaning of
19351 the storage place attributes. High_Order_First (known in the
19352 vernacular as 'big endian') means that the first bit of a
19353 storage element (bit 0) is the most significant bit (interpreting
19354 the sequence of bits that represent a component as an unsigned
19355 integer value). Low_Order_First (known in the vernacular as
19356 'little endian') means the opposite: the first bit is the
19357 least significant."
19360 Note that the numbering is with respect to the bits of a storage
19361 unit. In other words, the specification affects only the numbering
19362 of bits within a single storage unit.
19364 We can make the effect clearer by giving an example.
19366 Suppose that we have an external device which presents two bytes, the first
19367 byte presented, which is the first (low addressed byte) of the two byte
19368 record is called Master, and the second byte is called Slave.
19370 The left most (most significant bit is called Control for each byte, and
19371 the remaining 7 bits are called V1, V2, ... V7, where V7 is the rightmost
19372 (least significant) bit.
19374 On a big-endian machine, we can write the following representation clause
19377 type Data is record
19378 Master_Control : Bit;
19386 Slave_Control : Bit;
19396 for Data use record
19397 Master_Control at 0 range 0 .. 0;
19398 Master_V1 at 0 range 1 .. 1;
19399 Master_V2 at 0 range 2 .. 2;
19400 Master_V3 at 0 range 3 .. 3;
19401 Master_V4 at 0 range 4 .. 4;
19402 Master_V5 at 0 range 5 .. 5;
19403 Master_V6 at 0 range 6 .. 6;
19404 Master_V7 at 0 range 7 .. 7;
19405 Slave_Control at 1 range 0 .. 0;
19406 Slave_V1 at 1 range 1 .. 1;
19407 Slave_V2 at 1 range 2 .. 2;
19408 Slave_V3 at 1 range 3 .. 3;
19409 Slave_V4 at 1 range 4 .. 4;
19410 Slave_V5 at 1 range 5 .. 5;
19411 Slave_V6 at 1 range 6 .. 6;
19412 Slave_V7 at 1 range 7 .. 7;
19416 Now if we move this to a little endian machine, then the bit ordering within
19417 the byte is backwards, so we have to rewrite the record rep clause as:
19420 for Data use record
19421 Master_Control at 0 range 7 .. 7;
19422 Master_V1 at 0 range 6 .. 6;
19423 Master_V2 at 0 range 5 .. 5;
19424 Master_V3 at 0 range 4 .. 4;
19425 Master_V4 at 0 range 3 .. 3;
19426 Master_V5 at 0 range 2 .. 2;
19427 Master_V6 at 0 range 1 .. 1;
19428 Master_V7 at 0 range 0 .. 0;
19429 Slave_Control at 1 range 7 .. 7;
19430 Slave_V1 at 1 range 6 .. 6;
19431 Slave_V2 at 1 range 5 .. 5;
19432 Slave_V3 at 1 range 4 .. 4;
19433 Slave_V4 at 1 range 3 .. 3;
19434 Slave_V5 at 1 range 2 .. 2;
19435 Slave_V6 at 1 range 1 .. 1;
19436 Slave_V7 at 1 range 0 .. 0;
19440 It is a nuisance to have to rewrite the clause, especially if
19441 the code has to be maintained on both machines. However,
19442 this is a case that we can handle with the
19443 @code{Bit_Order} attribute if it is implemented.
19444 Note that the implementation is not required on byte addressed
19445 machines, but it is indeed implemented in GNAT.
19446 This means that we can simply use the
19447 first record clause, together with the declaration
19450 for Data'Bit_Order use High_Order_First;
19453 and the effect is what is desired, namely the layout is exactly the same,
19454 independent of whether the code is compiled on a big-endian or little-endian
19457 The important point to understand is that byte ordering is not affected.
19458 A @code{Bit_Order} attribute definition never affects which byte a field
19459 ends up in, only where it ends up in that byte.
19460 To make this clear, let us rewrite the record rep clause of the previous
19464 for Data'Bit_Order use High_Order_First;
19465 for Data use record
19466 Master_Control at 0 range 0 .. 0;
19467 Master_V1 at 0 range 1 .. 1;
19468 Master_V2 at 0 range 2 .. 2;
19469 Master_V3 at 0 range 3 .. 3;
19470 Master_V4 at 0 range 4 .. 4;
19471 Master_V5 at 0 range 5 .. 5;
19472 Master_V6 at 0 range 6 .. 6;
19473 Master_V7 at 0 range 7 .. 7;
19474 Slave_Control at 0 range 8 .. 8;
19475 Slave_V1 at 0 range 9 .. 9;
19476 Slave_V2 at 0 range 10 .. 10;
19477 Slave_V3 at 0 range 11 .. 11;
19478 Slave_V4 at 0 range 12 .. 12;
19479 Slave_V5 at 0 range 13 .. 13;
19480 Slave_V6 at 0 range 14 .. 14;
19481 Slave_V7 at 0 range 15 .. 15;
19485 This is exactly equivalent to saying (a repeat of the first example):
19488 for Data'Bit_Order use High_Order_First;
19489 for Data use record
19490 Master_Control at 0 range 0 .. 0;
19491 Master_V1 at 0 range 1 .. 1;
19492 Master_V2 at 0 range 2 .. 2;
19493 Master_V3 at 0 range 3 .. 3;
19494 Master_V4 at 0 range 4 .. 4;
19495 Master_V5 at 0 range 5 .. 5;
19496 Master_V6 at 0 range 6 .. 6;
19497 Master_V7 at 0 range 7 .. 7;
19498 Slave_Control at 1 range 0 .. 0;
19499 Slave_V1 at 1 range 1 .. 1;
19500 Slave_V2 at 1 range 2 .. 2;
19501 Slave_V3 at 1 range 3 .. 3;
19502 Slave_V4 at 1 range 4 .. 4;
19503 Slave_V5 at 1 range 5 .. 5;
19504 Slave_V6 at 1 range 6 .. 6;
19505 Slave_V7 at 1 range 7 .. 7;
19509 Why are they equivalent? Well take a specific field, the @code{Slave_V2}
19510 field. The storage place attributes are obtained by normalizing the
19511 values given so that the @code{First_Bit} value is less than 8. After
19512 normalizing the values (0,10,10) we get (1,2,2) which is exactly what
19513 we specified in the other case.
19515 Now one might expect that the @code{Bit_Order} attribute might affect
19516 bit numbering within the entire record component (two bytes in this
19517 case, thus affecting which byte fields end up in), but that is not
19518 the way this feature is defined, it only affects numbering of bits,
19519 not which byte they end up in.
19521 Consequently it never makes sense to specify a starting bit number
19522 greater than 7 (for a byte addressable field) if an attribute
19523 definition for @code{Bit_Order} has been given, and indeed it
19524 may be actively confusing to specify such a value, so the compiler
19525 generates a warning for such usage.
19527 If you do need to control byte ordering then appropriate conditional
19528 values must be used. If in our example, the slave byte came first on
19529 some machines we might write:
19532 Master_Byte_First constant Boolean := ...;
19534 Master_Byte : constant Natural :=
19535 1 - Boolean'Pos (Master_Byte_First);
19536 Slave_Byte : constant Natural :=
19537 Boolean'Pos (Master_Byte_First);
19539 for Data'Bit_Order use High_Order_First;
19540 for Data use record
19541 Master_Control at Master_Byte range 0 .. 0;
19542 Master_V1 at Master_Byte range 1 .. 1;
19543 Master_V2 at Master_Byte range 2 .. 2;
19544 Master_V3 at Master_Byte range 3 .. 3;
19545 Master_V4 at Master_Byte range 4 .. 4;
19546 Master_V5 at Master_Byte range 5 .. 5;
19547 Master_V6 at Master_Byte range 6 .. 6;
19548 Master_V7 at Master_Byte range 7 .. 7;
19549 Slave_Control at Slave_Byte range 0 .. 0;
19550 Slave_V1 at Slave_Byte range 1 .. 1;
19551 Slave_V2 at Slave_Byte range 2 .. 2;
19552 Slave_V3 at Slave_Byte range 3 .. 3;
19553 Slave_V4 at Slave_Byte range 4 .. 4;
19554 Slave_V5 at Slave_Byte range 5 .. 5;
19555 Slave_V6 at Slave_Byte range 6 .. 6;
19556 Slave_V7 at Slave_Byte range 7 .. 7;
19560 Now to switch between machines, all that is necessary is
19561 to set the boolean constant @code{Master_Byte_First} in
19562 an appropriate manner.
19564 @node Pragma Pack for Arrays,Pragma Pack for Records,Effect of Bit_Order on Byte Ordering,Representation Clauses and Pragmas
19565 @anchor{gnat_rm/representation_clauses_and_pragmas pragma-pack-for-arrays}@anchor{288}@anchor{gnat_rm/representation_clauses_and_pragmas id11}@anchor{289}
19566 @section Pragma Pack for Arrays
19569 @geindex Pragma Pack (for arrays)
19571 Pragma @code{Pack} applied to an array has an effect that depends upon whether the
19572 component type is @emph{packable}. For a component type to be @emph{packable}, it must
19573 be one of the following cases:
19579 Any elementary type.
19582 Any small packed array type with a static size.
19585 Any small simple record type with a static size.
19588 For all these cases, if the component subtype size is in the range
19589 1 through 64, then the effect of the pragma @code{Pack} is exactly as though a
19590 component size were specified giving the component subtype size.
19592 All other types are non-packable, they occupy an integral number of storage
19593 units and the only effect of pragma Pack is to remove alignment gaps.
19595 For example if we have:
19598 type r is range 0 .. 17;
19600 type ar is array (1 .. 8) of r;
19604 Then the component size of @code{ar} will be set to 5 (i.e., to @code{r'size},
19605 and the size of the array @code{ar} will be exactly 40 bits).
19607 Note that in some cases this rather fierce approach to packing can produce
19608 unexpected effects. For example, in Ada 95 and Ada 2005,
19609 subtype @code{Natural} typically has a size of 31, meaning that if you
19610 pack an array of @code{Natural}, you get 31-bit
19611 close packing, which saves a few bits, but results in far less efficient
19612 access. Since many other Ada compilers will ignore such a packing request,
19613 GNAT will generate a warning on some uses of pragma @code{Pack} that it guesses
19614 might not be what is intended. You can easily remove this warning by
19615 using an explicit @code{Component_Size} setting instead, which never generates
19616 a warning, since the intention of the programmer is clear in this case.
19618 GNAT treats packed arrays in one of two ways. If the size of the array is
19619 known at compile time and is less than 64 bits, then internally the array
19620 is represented as a single modular type, of exactly the appropriate number
19621 of bits. If the length is greater than 63 bits, or is not known at compile
19622 time, then the packed array is represented as an array of bytes, and the
19623 length is always a multiple of 8 bits.
19625 Note that to represent a packed array as a modular type, the alignment must
19626 be suitable for the modular type involved. For example, on typical machines
19627 a 32-bit packed array will be represented by a 32-bit modular integer with
19628 an alignment of four bytes. If you explicitly override the default alignment
19629 with an alignment clause that is too small, the modular representation
19630 cannot be used. For example, consider the following set of declarations:
19633 type R is range 1 .. 3;
19634 type S is array (1 .. 31) of R;
19635 for S'Component_Size use 2;
19637 for S'Alignment use 1;
19640 If the alignment clause were not present, then a 62-bit modular
19641 representation would be chosen (typically with an alignment of 4 or 8
19642 bytes depending on the target). But the default alignment is overridden
19643 with the explicit alignment clause. This means that the modular
19644 representation cannot be used, and instead the array of bytes
19645 representation must be used, meaning that the length must be a multiple
19646 of 8. Thus the above set of declarations will result in a diagnostic
19647 rejecting the size clause and noting that the minimum size allowed is 64.
19649 @geindex Pragma Pack (for type Natural)
19651 @geindex Pragma Pack warning
19653 One special case that is worth noting occurs when the base type of the
19654 component size is 8/16/32 and the subtype is one bit less. Notably this
19655 occurs with subtype @code{Natural}. Consider:
19658 type Arr is array (1 .. 32) of Natural;
19662 In all commonly used Ada 83 compilers, this pragma Pack would be ignored,
19663 since typically @code{Natural'Size} is 32 in Ada 83, and in any case most
19664 Ada 83 compilers did not attempt 31 bit packing.
19666 In Ada 95 and Ada 2005, @code{Natural'Size} is required to be 31. Furthermore,
19667 GNAT really does pack 31-bit subtype to 31 bits. This may result in a
19668 substantial unintended performance penalty when porting legacy Ada 83 code.
19669 To help prevent this, GNAT generates a warning in such cases. If you really
19670 want 31 bit packing in a case like this, you can set the component size
19674 type Arr is array (1 .. 32) of Natural;
19675 for Arr'Component_Size use 31;
19678 Here 31-bit packing is achieved as required, and no warning is generated,
19679 since in this case the programmer intention is clear.
19681 @node Pragma Pack for Records,Record Representation Clauses,Pragma Pack for Arrays,Representation Clauses and Pragmas
19682 @anchor{gnat_rm/representation_clauses_and_pragmas pragma-pack-for-records}@anchor{28a}@anchor{gnat_rm/representation_clauses_and_pragmas id12}@anchor{28b}
19683 @section Pragma Pack for Records
19686 @geindex Pragma Pack (for records)
19688 Pragma @code{Pack} applied to a record will pack the components to reduce
19689 wasted space from alignment gaps and by reducing the amount of space
19690 taken by components. We distinguish between @emph{packable} components and
19691 @emph{non-packable} components.
19692 Components of the following types are considered packable:
19698 Components of an elementary type are packable unless they are aliased,
19699 independent, or of an atomic type.
19702 Small packed arrays, where the size is statically known, are represented
19703 internally as modular integers, and so they are also packable.
19706 Small simple records, where the size is statically known, are also packable.
19709 For all these cases, if the @code{'Size} value is in the range 1 through 64, the
19710 components occupy the exact number of bits corresponding to this value
19711 and are packed with no padding bits, i.e. they can start on an arbitrary
19714 All other types are non-packable, they occupy an integral number of storage
19715 units and the only effect of pragma @code{Pack} is to remove alignment gaps.
19717 For example, consider the record
19720 type Rb1 is array (1 .. 13) of Boolean;
19723 type Rb2 is array (1 .. 65) of Boolean;
19726 type AF is new Float with Atomic;
19739 The representation for the record @code{X2} is as follows:
19742 for X2'Size use 224;
19744 L1 at 0 range 0 .. 0;
19745 L2 at 0 range 1 .. 64;
19746 L3 at 12 range 0 .. 31;
19747 L4 at 16 range 0 .. 0;
19748 L5 at 16 range 1 .. 13;
19749 L6 at 18 range 0 .. 71;
19753 Studying this example, we see that the packable fields @code{L1}
19755 of length equal to their sizes, and placed at specific bit boundaries (and
19756 not byte boundaries) to
19757 eliminate padding. But @code{L3} is of a non-packable float type (because
19758 it is aliased), so it is on the next appropriate alignment boundary.
19760 The next two fields are fully packable, so @code{L4} and @code{L5} are
19761 minimally packed with no gaps. However, type @code{Rb2} is a packed
19762 array that is longer than 64 bits, so it is itself non-packable. Thus
19763 the @code{L6} field is aligned to the next byte boundary, and takes an
19764 integral number of bytes, i.e., 72 bits.
19766 @node Record Representation Clauses,Handling of Records with Holes,Pragma Pack for Records,Representation Clauses and Pragmas
19767 @anchor{gnat_rm/representation_clauses_and_pragmas id13}@anchor{28c}@anchor{gnat_rm/representation_clauses_and_pragmas record-representation-clauses}@anchor{28d}
19768 @section Record Representation Clauses
19771 @geindex Record Representation Clause
19773 Record representation clauses may be given for all record types, including
19774 types obtained by record extension. Component clauses are allowed for any
19775 static component. The restrictions on component clauses depend on the type
19778 @geindex Component Clause
19780 For all components of an elementary type, the only restriction on component
19781 clauses is that the size must be at least the @code{'Size} value of the type
19782 (actually the Value_Size). There are no restrictions due to alignment,
19783 and such components may freely cross storage boundaries.
19785 Packed arrays with a size up to and including 64 bits are represented
19786 internally using a modular type with the appropriate number of bits, and
19787 thus the same lack of restriction applies. For example, if you declare:
19790 type R is array (1 .. 49) of Boolean;
19795 then a component clause for a component of type @code{R} may start on any
19796 specified bit boundary, and may specify a value of 49 bits or greater.
19798 For packed bit arrays that are longer than 64 bits, there are two
19799 cases. If the component size is a power of 2 (1,2,4,8,16,32 bits),
19800 including the important case of single bits or boolean values, then
19801 there are no limitations on placement of such components, and they
19802 may start and end at arbitrary bit boundaries.
19804 If the component size is not a power of 2 (e.g., 3 or 5), then
19805 an array of this type longer than 64 bits must always be placed on
19806 on a storage unit (byte) boundary and occupy an integral number
19807 of storage units (bytes). Any component clause that does not
19808 meet this requirement will be rejected.
19810 Any aliased component, or component of an aliased type, must
19811 have its normal alignment and size. A component clause that
19812 does not meet this requirement will be rejected.
19814 The tag field of a tagged type always occupies an address sized field at
19815 the start of the record. No component clause may attempt to overlay this
19816 tag. When a tagged type appears as a component, the tag field must have
19819 In the case of a record extension @code{T1}, of a type @code{T}, no component clause applied
19820 to the type @code{T1} can specify a storage location that would overlap the first
19821 @code{T'Size} bytes of the record.
19823 For all other component types, including non-bit-packed arrays,
19824 the component can be placed at an arbitrary bit boundary,
19825 so for example, the following is permitted:
19828 type R is array (1 .. 10) of Boolean;
19837 G at 0 range 0 .. 0;
19838 H at 0 range 1 .. 1;
19839 L at 0 range 2 .. 81;
19840 R at 0 range 82 .. 161;
19844 @node Handling of Records with Holes,Enumeration Clauses,Record Representation Clauses,Representation Clauses and Pragmas
19845 @anchor{gnat_rm/representation_clauses_and_pragmas handling-of-records-with-holes}@anchor{28e}@anchor{gnat_rm/representation_clauses_and_pragmas id14}@anchor{28f}
19846 @section Handling of Records with Holes
19849 @geindex Handling of Records with Holes
19851 As a result of alignment considerations, records may contain "holes"
19853 which do not correspond to the data bits of any of the components.
19854 Record representation clauses can also result in holes in records.
19856 GNAT does not attempt to clear these holes, so in record objects,
19857 they should be considered to hold undefined rubbish. The generated
19858 equality routine just tests components so does not access these
19859 undefined bits, and assignment and copy operations may or may not
19860 preserve the contents of these holes (for assignments, the holes
19861 in the target will in practice contain either the bits that are
19862 present in the holes in the source, or the bits that were present
19863 in the target before the assignment).
19865 If it is necessary to ensure that holes in records have all zero
19866 bits, then record objects for which this initialization is desired
19867 should be explicitly set to all zero values using Unchecked_Conversion
19868 or address overlays. For example
19871 type HRec is record
19877 On typical machines, integers need to be aligned on a four-byte
19878 boundary, resulting in three bytes of undefined rubbish following
19879 the 8-bit field for C. To ensure that the hole in a variable of
19880 type HRec is set to all zero bits,
19881 you could for example do:
19884 type Base is record
19885 Dummy1, Dummy2 : Integer := 0;
19890 for RealVar'Address use BaseVar'Address;
19893 Now the 8-bytes of the value of RealVar start out containing all zero
19894 bits. A safer approach is to just define dummy fields, avoiding the
19898 type HRec is record
19900 Dummy1 : Short_Short_Integer := 0;
19901 Dummy2 : Short_Short_Integer := 0;
19902 Dummy3 : Short_Short_Integer := 0;
19907 And to make absolutely sure that the intent of this is followed, you
19908 can use representation clauses:
19911 for Hrec use record
19912 C at 0 range 0 .. 7;
19913 Dummy1 at 1 range 0 .. 7;
19914 Dummy2 at 2 range 0 .. 7;
19915 Dummy3 at 3 range 0 .. 7;
19916 I at 4 range 0 .. 31;
19918 for Hrec'Size use 64;
19921 @node Enumeration Clauses,Address Clauses,Handling of Records with Holes,Representation Clauses and Pragmas
19922 @anchor{gnat_rm/representation_clauses_and_pragmas enumeration-clauses}@anchor{290}@anchor{gnat_rm/representation_clauses_and_pragmas id15}@anchor{291}
19923 @section Enumeration Clauses
19926 The only restriction on enumeration clauses is that the range of values
19927 must be representable. For the signed case, if one or more of the
19928 representation values are negative, all values must be in the range:
19931 System.Min_Int .. System.Max_Int
19934 For the unsigned case, where all values are nonnegative, the values must
19938 0 .. System.Max_Binary_Modulus;
19941 A @emph{confirming} representation clause is one in which the values range
19942 from 0 in sequence, i.e., a clause that confirms the default representation
19943 for an enumeration type.
19944 Such a confirming representation
19945 is permitted by these rules, and is specially recognized by the compiler so
19946 that no extra overhead results from the use of such a clause.
19948 If an array has an index type which is an enumeration type to which an
19949 enumeration clause has been applied, then the array is stored in a compact
19950 manner. Consider the declarations:
19953 type r is (A, B, C);
19954 for r use (A => 1, B => 5, C => 10);
19955 type t is array (r) of Character;
19958 The array type t corresponds to a vector with exactly three elements and
19959 has a default size equal to @code{3*Character'Size}. This ensures efficient
19960 use of space, but means that accesses to elements of the array will incur
19961 the overhead of converting representation values to the corresponding
19962 positional values, (i.e., the value delivered by the @code{Pos} attribute).
19964 @node Address Clauses,Use of Address Clauses for Memory-Mapped I/O,Enumeration Clauses,Representation Clauses and Pragmas
19965 @anchor{gnat_rm/representation_clauses_and_pragmas id16}@anchor{292}@anchor{gnat_rm/representation_clauses_and_pragmas address-clauses}@anchor{293}
19966 @section Address Clauses
19969 @geindex Address Clause
19971 The reference manual allows a general restriction on representation clauses,
19972 as found in RM 13.1(22):
19976 "An implementation need not support representation
19977 items containing nonstatic expressions, except that
19978 an implementation should support a representation item
19979 for a given entity if each nonstatic expression in the
19980 representation item is a name that statically denotes
19981 a constant declared before the entity."
19984 In practice this is applicable only to address clauses, since this is the
19985 only case in which a nonstatic expression is permitted by the syntax. As
19986 the AARM notes in sections 13.1 (22.a-22.h):
19990 22.a Reason: This is to avoid the following sort of thing:
19992 22.b X : Integer := F(...);
19993 Y : Address := G(...);
19994 for X'Address use Y;
19996 22.c In the above, we have to evaluate the
19997 initialization expression for X before we
19998 know where to put the result. This seems
19999 like an unreasonable implementation burden.
20001 22.d The above code should instead be written
20004 22.e Y : constant Address := G(...);
20005 X : Integer := F(...);
20006 for X'Address use Y;
20008 22.f This allows the expression 'Y' to be safely
20009 evaluated before X is created.
20011 22.g The constant could be a formal parameter of mode in.
20013 22.h An implementation can support other nonstatic
20014 expressions if it wants to. Expressions of type
20015 Address are hardly ever static, but their value
20016 might be known at compile time anyway in many
20020 GNAT does indeed permit many additional cases of nonstatic expressions. In
20021 particular, if the type involved is elementary there are no restrictions
20022 (since in this case, holding a temporary copy of the initialization value,
20023 if one is present, is inexpensive). In addition, if there is no implicit or
20024 explicit initialization, then there are no restrictions. GNAT will reject
20025 only the case where all three of these conditions hold:
20031 The type of the item is non-elementary (e.g., a record or array).
20034 There is explicit or implicit initialization required for the object.
20035 Note that access values are always implicitly initialized.
20038 The address value is nonstatic. Here GNAT is more permissive than the
20039 RM, and allows the address value to be the address of a previously declared
20040 stand-alone variable, as long as it does not itself have an address clause.
20043 Anchor : Some_Initialized_Type;
20044 Overlay : Some_Initialized_Type;
20045 for Overlay'Address use Anchor'Address;
20048 However, the prefix of the address clause cannot be an array component, or
20049 a component of a discriminated record.
20052 As noted above in section 22.h, address values are typically nonstatic. In
20053 particular the To_Address function, even if applied to a literal value, is
20054 a nonstatic function call. To avoid this minor annoyance, GNAT provides
20055 the implementation defined attribute 'To_Address. The following two
20056 expressions have identical values:
20060 @geindex To_Address
20063 To_Address (16#1234_0000#)
20064 System'To_Address (16#1234_0000#);
20067 except that the second form is considered to be a static expression, and
20068 thus when used as an address clause value is always permitted.
20070 Additionally, GNAT treats as static an address clause that is an
20071 unchecked_conversion of a static integer value. This simplifies the porting
20072 of legacy code, and provides a portable equivalent to the GNAT attribute
20075 Another issue with address clauses is the interaction with alignment
20076 requirements. When an address clause is given for an object, the address
20077 value must be consistent with the alignment of the object (which is usually
20078 the same as the alignment of the type of the object). If an address clause
20079 is given that specifies an inappropriately aligned address value, then the
20080 program execution is erroneous.
20082 Since this source of erroneous behavior can have unfortunate effects on
20083 machines with strict alignment requirements, GNAT
20084 checks (at compile time if possible, generating a warning, or at execution
20085 time with a run-time check) that the alignment is appropriate. If the
20086 run-time check fails, then @code{Program_Error} is raised. This run-time
20087 check is suppressed if range checks are suppressed, or if the special GNAT
20088 check Alignment_Check is suppressed, or if
20089 @code{pragma Restrictions (No_Elaboration_Code)} is in effect. It is also
20090 suppressed by default on non-strict alignment machines (such as the x86).
20092 Finally, GNAT does not permit overlaying of objects of class-wide types. In
20093 most cases, the compiler can detect an attempt at such overlays and will
20094 generate a warning at compile time and a Program_Error exception at run time.
20098 An address clause cannot be given for an exported object. More
20099 understandably the real restriction is that objects with an address
20100 clause cannot be exported. This is because such variables are not
20101 defined by the Ada program, so there is no external object to export.
20105 It is permissible to give an address clause and a pragma Import for the
20106 same object. In this case, the variable is not really defined by the
20107 Ada program, so there is no external symbol to be linked. The link name
20108 and the external name are ignored in this case. The reason that we allow this
20109 combination is that it provides a useful idiom to avoid unwanted
20110 initializations on objects with address clauses.
20112 When an address clause is given for an object that has implicit or
20113 explicit initialization, then by default initialization takes place. This
20114 means that the effect of the object declaration is to overwrite the
20115 memory at the specified address. This is almost always not what the
20116 programmer wants, so GNAT will output a warning:
20126 for Ext'Address use System'To_Address (16#1234_1234#);
20128 >>> warning: implicit initialization of "Ext" may
20129 modify overlaid storage
20130 >>> warning: use pragma Import for "Ext" to suppress
20131 initialization (RM B(24))
20136 As indicated by the warning message, the solution is to use a (dummy) pragma
20137 Import to suppress this initialization. The pragma tell the compiler that the
20138 object is declared and initialized elsewhere. The following package compiles
20139 without warnings (and the initialization is suppressed):
20149 for Ext'Address use System'To_Address (16#1234_1234#);
20150 pragma Import (Ada, Ext);
20154 A final issue with address clauses involves their use for overlaying
20155 variables, as in the following example:
20157 @geindex Overlaying of objects
20162 for B'Address use A'Address;
20165 or alternatively, using the form recommended by the RM:
20169 Addr : constant Address := A'Address;
20171 for B'Address use Addr;
20174 In both of these cases, @code{A} and @code{B} become aliased to one another
20175 via the address clause. This use of address clauses to overlay
20176 variables, achieving an effect similar to unchecked conversion
20177 was erroneous in Ada 83, but in Ada 95 and Ada 2005
20178 the effect is implementation defined. Furthermore, the
20179 Ada RM specifically recommends that in a situation
20180 like this, @code{B} should be subject to the following
20181 implementation advice (RM 13.3(19)):
20185 "19 If the Address of an object is specified, or it is imported
20186 or exported, then the implementation should not perform
20187 optimizations based on assumptions of no aliases."
20190 GNAT follows this recommendation, and goes further by also applying
20191 this recommendation to the overlaid variable (@code{A} in the above example)
20192 in this case. This means that the overlay works "as expected", in that
20193 a modification to one of the variables will affect the value of the other.
20195 More generally, GNAT interprets this recommendation conservatively for
20196 address clauses: in the cases other than overlays, it considers that the
20197 object is effectively subject to pragma @code{Volatile} and implements the
20198 associated semantics.
20200 Note that when address clause overlays are used in this way, there is an
20201 issue of unintentional initialization, as shown by this example:
20204 package Overwrite_Record is
20206 A : Character := 'C';
20207 B : Character := 'A';
20209 X : Short_Integer := 3;
20211 for Y'Address use X'Address;
20213 >>> warning: default initialization of "Y" may
20214 modify "X", use pragma Import for "Y" to
20215 suppress initialization (RM B.1(24))
20217 end Overwrite_Record;
20220 Here the default initialization of @code{Y} will clobber the value
20221 of @code{X}, which justifies the warning. The warning notes that
20222 this effect can be eliminated by adding a @code{pragma Import}
20223 which suppresses the initialization:
20226 package Overwrite_Record is
20228 A : Character := 'C';
20229 B : Character := 'A';
20231 X : Short_Integer := 3;
20233 for Y'Address use X'Address;
20234 pragma Import (Ada, Y);
20235 end Overwrite_Record;
20238 Note that the use of @code{pragma Initialize_Scalars} may cause variables to
20239 be initialized when they would not otherwise have been in the absence
20240 of the use of this pragma. This may cause an overlay to have this
20241 unintended clobbering effect. The compiler avoids this for scalar
20242 types, but not for composite objects (where in general the effect
20243 of @code{Initialize_Scalars} is part of the initialization routine
20244 for the composite object:
20247 pragma Initialize_Scalars;
20248 with Ada.Text_IO; use Ada.Text_IO;
20249 procedure Overwrite_Array is
20250 type Arr is array (1 .. 5) of Integer;
20251 X : Arr := (others => 1);
20253 for A'Address use X'Address;
20255 >>> warning: default initialization of "A" may
20256 modify "X", use pragma Import for "A" to
20257 suppress initialization (RM B.1(24))
20260 if X /= Arr'(others => 1) then
20261 Put_Line ("X was clobbered");
20263 Put_Line ("X was not clobbered");
20265 end Overwrite_Array;
20268 The above program generates the warning as shown, and at execution
20269 time, prints @code{X was clobbered}. If the @code{pragma Import} is
20270 added as suggested:
20273 pragma Initialize_Scalars;
20274 with Ada.Text_IO; use Ada.Text_IO;
20275 procedure Overwrite_Array is
20276 type Arr is array (1 .. 5) of Integer;
20277 X : Arr := (others => 1);
20279 for A'Address use X'Address;
20280 pragma Import (Ada, A);
20282 if X /= Arr'(others => 1) then
20283 Put_Line ("X was clobbered");
20285 Put_Line ("X was not clobbered");
20287 end Overwrite_Array;
20290 then the program compiles without the warning and when run will generate
20291 the output @code{X was not clobbered}.
20293 @node Use of Address Clauses for Memory-Mapped I/O,Effect of Convention on Representation,Address Clauses,Representation Clauses and Pragmas
20294 @anchor{gnat_rm/representation_clauses_and_pragmas id17}@anchor{294}@anchor{gnat_rm/representation_clauses_and_pragmas use-of-address-clauses-for-memory-mapped-i-o}@anchor{295}
20295 @section Use of Address Clauses for Memory-Mapped I/O
20298 @geindex Memory-mapped I/O
20300 A common pattern is to use an address clause to map an atomic variable to
20301 a location in memory that corresponds to a memory-mapped I/O operation or
20302 operations, for example:
20305 type Mem_Word is record
20308 pragma Atomic (Mem_Word);
20309 for Mem_Word_Size use 32;
20312 for Mem'Address use some-address;
20319 For a full access (reference or modification) of the variable (Mem) in this
20320 case, as in the above examples, GNAT guarantees that the entire atomic word
20321 will be accessed, in accordance with the RM C.6(15) clause.
20323 A problem arises with a component access such as:
20329 Note that the component A is not declared as atomic. This means that it is
20330 not clear what this assignment means. It could correspond to full word read
20331 and write as given in the first example, or on architectures that supported
20332 such an operation it might be a single byte store instruction. The RM does
20333 not have anything to say in this situation, and GNAT does not make any
20334 guarantee. The code generated may vary from target to target. GNAT will issue
20335 a warning in such a case:
20340 >>> warning: access to non-atomic component of atomic array,
20341 may cause unexpected accesses to atomic object
20344 It is best to be explicit in this situation, by either declaring the
20345 components to be atomic if you want the byte store, or explicitly writing
20346 the full word access sequence if that is what the hardware requires.
20347 Alternatively, if the full word access sequence is required, GNAT also
20348 provides the pragma @code{Volatile_Full_Access} which can be used in lieu of
20349 pragma @code{Atomic} and will give the additional guarantee.
20351 @node Effect of Convention on Representation,Conventions and Anonymous Access Types,Use of Address Clauses for Memory-Mapped I/O,Representation Clauses and Pragmas
20352 @anchor{gnat_rm/representation_clauses_and_pragmas id18}@anchor{296}@anchor{gnat_rm/representation_clauses_and_pragmas effect-of-convention-on-representation}@anchor{297}
20353 @section Effect of Convention on Representation
20356 @geindex Convention
20357 @geindex effect on representation
20359 Normally the specification of a foreign language convention for a type or
20360 an object has no effect on the chosen representation. In particular, the
20361 representation chosen for data in GNAT generally meets the standard system
20362 conventions, and for example records are laid out in a manner that is
20363 consistent with C. This means that specifying convention C (for example)
20366 There are four exceptions to this general rule:
20372 @emph{Convention Fortran and array subtypes}.
20374 If pragma Convention Fortran is specified for an array subtype, then in
20375 accordance with the implementation advice in section 3.6.2(11) of the
20376 Ada Reference Manual, the array will be stored in a Fortran-compatible
20377 column-major manner, instead of the normal default row-major order.
20380 @emph{Convention C and enumeration types}
20382 GNAT normally stores enumeration types in 8, 16, or 32 bits as required
20383 to accommodate all values of the type. For example, for the enumeration
20387 type Color is (Red, Green, Blue);
20390 8 bits is sufficient to store all values of the type, so by default, objects
20391 of type @code{Color} will be represented using 8 bits. However, normal C
20392 convention is to use 32 bits for all enum values in C, since enum values
20393 are essentially of type int. If pragma @code{Convention C} is specified for an
20394 Ada enumeration type, then the size is modified as necessary (usually to
20395 32 bits) to be consistent with the C convention for enum values.
20397 Note that this treatment applies only to types. If Convention C is given for
20398 an enumeration object, where the enumeration type is not Convention C, then
20399 Object_Size bits are allocated. For example, for a normal enumeration type,
20400 with less than 256 elements, only 8 bits will be allocated for the object.
20401 Since this may be a surprise in terms of what C expects, GNAT will issue a
20402 warning in this situation. The warning can be suppressed by giving an explicit
20403 size clause specifying the desired size.
20406 @emph{Convention C/Fortran and Boolean types}
20408 In C, the usual convention for boolean values, that is values used for
20409 conditions, is that zero represents false, and nonzero values represent
20410 true. In Ada, the normal convention is that two specific values, typically
20411 0/1, are used to represent false/true respectively.
20413 Fortran has a similar convention for @code{LOGICAL} values (any nonzero
20414 value represents true).
20416 To accommodate the Fortran and C conventions, if a pragma Convention specifies
20417 C or Fortran convention for a derived Boolean, as in the following example:
20420 type C_Switch is new Boolean;
20421 pragma Convention (C, C_Switch);
20424 then the GNAT generated code will treat any nonzero value as true. For truth
20425 values generated by GNAT, the conventional value 1 will be used for True, but
20426 when one of these values is read, any nonzero value is treated as True.
20429 @node Conventions and Anonymous Access Types,Determining the Representations chosen by GNAT,Effect of Convention on Representation,Representation Clauses and Pragmas
20430 @anchor{gnat_rm/representation_clauses_and_pragmas conventions-and-anonymous-access-types}@anchor{298}@anchor{gnat_rm/representation_clauses_and_pragmas id19}@anchor{299}
20431 @section Conventions and Anonymous Access Types
20434 @geindex Anonymous access types
20436 @geindex Convention for anonymous access types
20438 The RM is not entirely clear on convention handling in a number of cases,
20439 and in particular, it is not clear on the convention to be given to
20440 anonymous access types in general, and in particular what is to be
20441 done for the case of anonymous access-to-subprogram.
20443 In GNAT, we decide that if an explicit Convention is applied
20444 to an object or component, and its type is such an anonymous type,
20445 then the convention will apply to this anonymous type as well. This
20446 seems to make sense since it is anomolous in any case to have a
20447 different convention for an object and its type, and there is clearly
20448 no way to explicitly specify a convention for an anonymous type, since
20449 it doesn't have a name to specify!
20451 Furthermore, we decide that if a convention is applied to a record type,
20452 then this convention is inherited by any of its components that are of an
20453 anonymous access type which do not have an explicitly specified convention.
20455 The following program shows these conventions in action:
20458 package ConvComp is
20459 type Foo is range 1 .. 10;
20461 A : access function (X : Foo) return Integer;
20464 pragma Convention (C, T1);
20467 A : access function (X : Foo) return Integer;
20468 pragma Convention (C, A);
20471 pragma Convention (COBOL, T2);
20474 A : access function (X : Foo) return Integer;
20475 pragma Convention (COBOL, A);
20478 pragma Convention (C, T3);
20481 A : access function (X : Foo) return Integer;
20484 pragma Convention (COBOL, T4);
20486 function F (X : Foo) return Integer;
20487 pragma Convention (C, F);
20489 function F (X : Foo) return Integer is (13);
20491 TV1 : T1 := (F'Access, 12); -- OK
20492 TV2 : T2 := (F'Access, 13); -- OK
20494 TV3 : T3 := (F'Access, 13); -- ERROR
20496 >>> subprogram "F" has wrong convention
20497 >>> does not match access to subprogram declared at line 17
20498 38. TV4 : T4 := (F'Access, 13); -- ERROR
20500 >>> subprogram "F" has wrong convention
20501 >>> does not match access to subprogram declared at line 24
20505 @node Determining the Representations chosen by GNAT,,Conventions and Anonymous Access Types,Representation Clauses and Pragmas
20506 @anchor{gnat_rm/representation_clauses_and_pragmas id20}@anchor{29a}@anchor{gnat_rm/representation_clauses_and_pragmas determining-the-representations-chosen-by-gnat}@anchor{29b}
20507 @section Determining the Representations chosen by GNAT
20510 @geindex Representation
20511 @geindex determination of
20513 @geindex -gnatR (gcc)
20515 Although the descriptions in this section are intended to be complete, it is
20516 often easier to simply experiment to see what GNAT accepts and what the
20517 effect is on the layout of types and objects.
20519 As required by the Ada RM, if a representation clause is not accepted, then
20520 it must be rejected as illegal by the compiler. However, when a
20521 representation clause or pragma is accepted, there can still be questions
20522 of what the compiler actually does. For example, if a partial record
20523 representation clause specifies the location of some components and not
20524 others, then where are the non-specified components placed? Or if pragma
20525 @code{Pack} is used on a record, then exactly where are the resulting
20526 fields placed? The section on pragma @code{Pack} in this chapter can be
20527 used to answer the second question, but it is often easier to just see
20528 what the compiler does.
20530 For this purpose, GNAT provides the option @emph{-gnatR}. If you compile
20531 with this option, then the compiler will output information on the actual
20532 representations chosen, in a format similar to source representation
20533 clauses. For example, if we compile the package:
20537 type r (x : boolean) is tagged record
20539 when True => S : String (1 .. 100);
20540 when False => null;
20544 type r2 is new r (false) with record
20549 y2 at 16 range 0 .. 31;
20556 type x1 is array (1 .. 10) of x;
20557 for x1'component_size use 11;
20559 type ia is access integer;
20561 type Rb1 is array (1 .. 13) of Boolean;
20564 type Rb2 is array (1 .. 65) of Boolean;
20579 using the switch @emph{-gnatR} we obtain the following output:
20582 Representation information for unit q
20583 -------------------------------------
20586 for r'Alignment use 4;
20588 x at 4 range 0 .. 7;
20589 _tag at 0 range 0 .. 31;
20590 s at 5 range 0 .. 799;
20593 for r2'Size use 160;
20594 for r2'Alignment use 4;
20596 x at 4 range 0 .. 7;
20597 _tag at 0 range 0 .. 31;
20598 _parent at 0 range 0 .. 63;
20599 y2 at 16 range 0 .. 31;
20603 for x'Alignment use 1;
20605 y at 0 range 0 .. 7;
20608 for x1'Size use 112;
20609 for x1'Alignment use 1;
20610 for x1'Component_Size use 11;
20612 for rb1'Size use 13;
20613 for rb1'Alignment use 2;
20614 for rb1'Component_Size use 1;
20616 for rb2'Size use 72;
20617 for rb2'Alignment use 1;
20618 for rb2'Component_Size use 1;
20620 for x2'Size use 224;
20621 for x2'Alignment use 4;
20623 l1 at 0 range 0 .. 0;
20624 l2 at 0 range 1 .. 64;
20625 l3 at 12 range 0 .. 31;
20626 l4 at 16 range 0 .. 0;
20627 l5 at 16 range 1 .. 13;
20628 l6 at 18 range 0 .. 71;
20632 The Size values are actually the Object_Size, i.e., the default size that
20633 will be allocated for objects of the type.
20634 The @code{??} size for type r indicates that we have a variant record, and the
20635 actual size of objects will depend on the discriminant value.
20637 The Alignment values show the actual alignment chosen by the compiler
20638 for each record or array type.
20640 The record representation clause for type r shows where all fields
20641 are placed, including the compiler generated tag field (whose location
20642 cannot be controlled by the programmer).
20644 The record representation clause for the type extension r2 shows all the
20645 fields present, including the parent field, which is a copy of the fields
20646 of the parent type of r2, i.e., r1.
20648 The component size and size clauses for types rb1 and rb2 show
20649 the exact effect of pragma @code{Pack} on these arrays, and the record
20650 representation clause for type x2 shows how pragma @cite{Pack} affects
20653 In some cases, it may be useful to cut and paste the representation clauses
20654 generated by the compiler into the original source to fix and guarantee
20655 the actual representation to be used.
20657 @node Standard Library Routines,The Implementation of Standard I/O,Representation Clauses and Pragmas,Top
20658 @anchor{gnat_rm/standard_library_routines standard-library-routines}@anchor{e}@anchor{gnat_rm/standard_library_routines doc}@anchor{29c}@anchor{gnat_rm/standard_library_routines id1}@anchor{29d}
20659 @chapter Standard Library Routines
20662 The Ada Reference Manual contains in Annex A a full description of an
20663 extensive set of standard library routines that can be used in any Ada
20664 program, and which must be provided by all Ada compilers. They are
20665 analogous to the standard C library used by C programs.
20667 GNAT implements all of the facilities described in annex A, and for most
20668 purposes the description in the Ada Reference Manual, or appropriate Ada
20669 text book, will be sufficient for making use of these facilities.
20671 In the case of the input-output facilities,
20672 @ref{f,,The Implementation of Standard I/O},
20673 gives details on exactly how GNAT interfaces to the
20674 file system. For the remaining packages, the Ada Reference Manual
20675 should be sufficient. The following is a list of the packages included,
20676 together with a brief description of the functionality that is provided.
20678 For completeness, references are included to other predefined library
20679 routines defined in other sections of the Ada Reference Manual (these are
20680 cross-indexed from Annex A). For further details see the relevant
20681 package declarations in the run-time library. In particular, a few units
20682 are not implemented, as marked by the presence of pragma Unimplemented_Unit,
20683 and in this case the package declaration contains comments explaining why
20684 the unit is not implemented.
20689 @item @code{Ada} @emph{(A.2)}
20691 This is a parent package for all the standard library packages. It is
20692 usually included implicitly in your program, and itself contains no
20693 useful data or routines.
20695 @item @code{Ada.Assertions} @emph{(11.4.2)}
20697 @code{Assertions} provides the @code{Assert} subprograms, and also
20698 the declaration of the @code{Assertion_Error} exception.
20700 @item @code{Ada.Asynchronous_Task_Control} @emph{(D.11)}
20702 @code{Asynchronous_Task_Control} provides low level facilities for task
20703 synchronization. It is typically not implemented. See package spec for details.
20705 @item @code{Ada.Calendar} @emph{(9.6)}
20707 @code{Calendar} provides time of day access, and routines for
20708 manipulating times and durations.
20710 @item @code{Ada.Calendar.Arithmetic} @emph{(9.6.1)}
20712 This package provides additional arithmetic
20713 operations for @code{Calendar}.
20715 @item @code{Ada.Calendar.Formatting} @emph{(9.6.1)}
20717 This package provides formatting operations for @code{Calendar}.
20719 @item @code{Ada.Calendar.Time_Zones} @emph{(9.6.1)}
20721 This package provides additional @code{Calendar} facilities
20722 for handling time zones.
20724 @item @code{Ada.Characters} @emph{(A.3.1)}
20726 This is a dummy parent package that contains no useful entities
20728 @item @code{Ada.Characters.Conversions} @emph{(A.3.2)}
20730 This package provides character conversion functions.
20732 @item @code{Ada.Characters.Handling} @emph{(A.3.2)}
20734 This package provides some basic character handling capabilities,
20735 including classification functions for classes of characters (e.g., test
20736 for letters, or digits).
20738 @item @code{Ada.Characters.Latin_1} @emph{(A.3.3)}
20740 This package includes a complete set of definitions of the characters
20741 that appear in type CHARACTER. It is useful for writing programs that
20742 will run in international environments. For example, if you want an
20743 upper case E with an acute accent in a string, it is often better to use
20744 the definition of @code{UC_E_Acute} in this package. Then your program
20745 will print in an understandable manner even if your environment does not
20746 support these extended characters.
20748 @item @code{Ada.Command_Line} @emph{(A.15)}
20750 This package provides access to the command line parameters and the name
20751 of the current program (analogous to the use of @code{argc} and @code{argv}
20752 in C), and also allows the exit status for the program to be set in a
20753 system-independent manner.
20755 @item @code{Ada.Complex_Text_IO} @emph{(G.1.3)}
20757 This package provides text input and output of complex numbers.
20759 @item @code{Ada.Containers} @emph{(A.18.1)}
20761 A top level package providing a few basic definitions used by all the
20762 following specific child packages that provide specific kinds of
20766 @code{Ada.Containers.Bounded_Priority_Queues} @emph{(A.18.31)}
20768 @code{Ada.Containers.Bounded_Synchronized_Queues} @emph{(A.18.29)}
20770 @code{Ada.Containers.Doubly_Linked_Lists} @emph{(A.18.3)}
20772 @code{Ada.Containers.Generic_Array_Sort} @emph{(A.18.26)}
20774 @code{Ada.Containers.Generic_Constrained_Array_Sort} @emph{(A.18.26)}
20776 @code{Ada.Containers.Generic_Sort} @emph{(A.18.26)}
20778 @code{Ada.Containers.Hashed_Maps} @emph{(A.18.5)}
20780 @code{Ada.Containers.Hashed_Sets} @emph{(A.18.8)}
20782 @code{Ada.Containers.Indefinite_Doubly_Linked_Lists} @emph{(A.18.12)}
20784 @code{Ada.Containers.Indefinite_Hashed_Maps} @emph{(A.18.13)}
20786 @code{Ada.Containers.Indefinite_Hashed_Sets} @emph{(A.18.15)}
20788 @code{Ada.Containers.Indefinite_Holders} @emph{(A.18.18)}
20790 @code{Ada.Containers.Indefinite_Multiway_Trees} @emph{(A.18.17)}
20792 @code{Ada.Containers.Indefinite_Ordered_Maps} @emph{(A.18.14)}
20794 @code{Ada.Containers.Indefinite_Ordered_Sets} @emph{(A.18.16)}
20796 @code{Ada.Containers.Indefinite_Vectors} @emph{(A.18.11)}
20798 @code{Ada.Containers.Multiway_Trees} @emph{(A.18.10)}
20800 @code{Ada.Containers.Ordered_Maps} @emph{(A.18.6)}
20802 @code{Ada.Containers.Ordered_Sets} @emph{(A.18.9)}
20804 @code{Ada.Containers.Synchronized_Queue_Interfaces} @emph{(A.18.27)}
20806 @code{Ada.Containers.Unbounded_Priority_Queues} @emph{(A.18.30)}
20808 @code{Ada.Containers.Unbounded_Synchronized_Queues} @emph{(A.18.28)}
20810 @code{Ada.Containers.Vectors} @emph{(A.18.2)}
20815 @item @code{Ada.Directories} @emph{(A.16)}
20817 This package provides operations on directories.
20819 @item @code{Ada.Directories.Hierarchical_File_Names} @emph{(A.16.1)}
20821 This package provides additional directory operations handling
20822 hiearchical file names.
20824 @item @code{Ada.Directories.Information} @emph{(A.16)}
20826 This is an implementation defined package for additional directory
20827 operations, which is not implemented in GNAT.
20829 @item @code{Ada.Decimal} @emph{(F.2)}
20831 This package provides constants describing the range of decimal numbers
20832 implemented, and also a decimal divide routine (analogous to the COBOL
20833 verb DIVIDE ... GIVING ... REMAINDER ...)
20835 @item @code{Ada.Direct_IO} @emph{(A.8.4)}
20837 This package provides input-output using a model of a set of records of
20838 fixed-length, containing an arbitrary definite Ada type, indexed by an
20839 integer record number.
20841 @item @code{Ada.Dispatching} @emph{(D.2.1)}
20843 A parent package containing definitions for task dispatching operations.
20845 @item @code{Ada.Dispatching.EDF} @emph{(D.2.6)}
20847 Not implemented in GNAT.
20849 @item @code{Ada.Dispatching.Non_Preemptive} @emph{(D.2.4)}
20851 Not implemented in GNAT.
20853 @item @code{Ada.Dispatching.Round_Robin} @emph{(D.2.5)}
20855 Not implemented in GNAT.
20857 @item @code{Ada.Dynamic_Priorities} @emph{(D.5)}
20859 This package allows the priorities of a task to be adjusted dynamically
20860 as the task is running.
20862 @item @code{Ada.Environment_Variables} @emph{(A.17)}
20864 This package provides facilities for accessing environment variables.
20866 @item @code{Ada.Exceptions} @emph{(11.4.1)}
20868 This package provides additional information on exceptions, and also
20869 contains facilities for treating exceptions as data objects, and raising
20870 exceptions with associated messages.
20872 @item @code{Ada.Execution_Time} @emph{(D.14)}
20874 This package provides CPU clock functionalities. It is not implemented on
20875 all targets (see package spec for details).
20877 @item @code{Ada.Execution_Time.Group_Budgets} @emph{(D.14.2)}
20879 Not implemented in GNAT.
20881 @item @code{Ada.Execution_Time.Timers} @emph{(D.14.1)'}
20883 Not implemented in GNAT.
20885 @item @code{Ada.Finalization} @emph{(7.6)}
20887 This package contains the declarations and subprograms to support the
20888 use of controlled types, providing for automatic initialization and
20889 finalization (analogous to the constructors and destructors of C++).
20891 @item @code{Ada.Float_Text_IO} @emph{(A.10.9)}
20893 A library level instantiation of Text_IO.Float_IO for type Float.
20895 @item @code{Ada.Float_Wide_Text_IO} @emph{(A.10.9)}
20897 A library level instantiation of Wide_Text_IO.Float_IO for type Float.
20899 @item @code{Ada.Float_Wide_Wide_Text_IO} @emph{(A.10.9)}
20901 A library level instantiation of Wide_Wide_Text_IO.Float_IO for type Float.
20903 @item @code{Ada.Integer_Text_IO} @emph{(A.10.9)}
20905 A library level instantiation of Text_IO.Integer_IO for type Integer.
20907 @item @code{Ada.Integer_Wide_Text_IO} @emph{(A.10.9)}
20909 A library level instantiation of Wide_Text_IO.Integer_IO for type Integer.
20911 @item @code{Ada.Integer_Wide_Wide_Text_IO} @emph{(A.10.9)}
20913 A library level instantiation of Wide_Wide_Text_IO.Integer_IO for type Integer.
20915 @item @code{Ada.Interrupts} @emph{(C.3.2)}
20917 This package provides facilities for interfacing to interrupts, which
20918 includes the set of signals or conditions that can be raised and
20919 recognized as interrupts.
20921 @item @code{Ada.Interrupts.Names} @emph{(C.3.2)}
20923 This package provides the set of interrupt names (actually signal
20924 or condition names) that can be handled by GNAT.
20926 @item @code{Ada.IO_Exceptions} @emph{(A.13)}
20928 This package defines the set of exceptions that can be raised by use of
20929 the standard IO packages.
20931 @item @code{Ada.Iterator_Interfaces} @emph{(5.5.1)}
20933 This package provides a generic interface to generalized iterators.
20935 @item @code{Ada.Locales} @emph{(A.19)}
20937 This package provides declarations providing information (Language
20938 and Country) about the current locale.
20940 @item @code{Ada.Numerics}
20942 This package contains some standard constants and exceptions used
20943 throughout the numerics packages. Note that the constants pi and e are
20944 defined here, and it is better to use these definitions than rolling
20947 @item @code{Ada.Numerics.Complex_Arrays} @emph{(G.3.2)}
20949 Provides operations on arrays of complex numbers.
20951 @item @code{Ada.Numerics.Complex_Elementary_Functions}
20953 Provides the implementation of standard elementary functions (such as
20954 log and trigonometric functions) operating on complex numbers using the
20955 standard @code{Float} and the @code{Complex} and @code{Imaginary} types
20956 created by the package @code{Numerics.Complex_Types}.
20958 @item @code{Ada.Numerics.Complex_Types}
20960 This is a predefined instantiation of
20961 @code{Numerics.Generic_Complex_Types} using @code{Standard.Float} to
20962 build the type @code{Complex} and @code{Imaginary}.
20964 @item @code{Ada.Numerics.Discrete_Random}
20966 This generic package provides a random number generator suitable for generating
20967 uniformly distributed values of a specified discrete subtype.
20969 @item @code{Ada.Numerics.Float_Random}
20971 This package provides a random number generator suitable for generating
20972 uniformly distributed floating point values in the unit interval.
20974 @item @code{Ada.Numerics.Generic_Complex_Elementary_Functions}
20976 This is a generic version of the package that provides the
20977 implementation of standard elementary functions (such as log and
20978 trigonometric functions) for an arbitrary complex type.
20980 The following predefined instantiations of this package are provided:
20988 @code{Ada.Numerics.Short_Complex_Elementary_Functions}
20993 @code{Ada.Numerics.Complex_Elementary_Functions}
20998 @code{Ada.Numerics.Long_Complex_Elementary_Functions}
21001 @item @code{Ada.Numerics.Generic_Complex_Types}
21003 This is a generic package that allows the creation of complex types,
21004 with associated complex arithmetic operations.
21006 The following predefined instantiations of this package exist
21014 @code{Ada.Numerics.Short_Complex_Complex_Types}
21019 @code{Ada.Numerics.Complex_Complex_Types}
21024 @code{Ada.Numerics.Long_Complex_Complex_Types}
21027 @item @code{Ada.Numerics.Generic_Elementary_Functions}
21029 This is a generic package that provides the implementation of standard
21030 elementary functions (such as log an trigonometric functions) for an
21031 arbitrary float type.
21033 The following predefined instantiations of this package exist
21041 @code{Ada.Numerics.Short_Elementary_Functions}
21046 @code{Ada.Numerics.Elementary_Functions}
21051 @code{Ada.Numerics.Long_Elementary_Functions}
21054 @item @code{Ada.Numerics.Generic_Real_Arrays} @emph{(G.3.1)}
21056 Generic operations on arrays of reals
21058 @item @code{Ada.Numerics.Real_Arrays} @emph{(G.3.1)}
21060 Preinstantiation of Ada.Numerics.Generic_Real_Arrays (Float).
21062 @item @code{Ada.Real_Time} @emph{(D.8)}
21064 This package provides facilities similar to those of @code{Calendar}, but
21065 operating with a finer clock suitable for real time control. Note that
21066 annex D requires that there be no backward clock jumps, and GNAT generally
21067 guarantees this behavior, but of course if the external clock on which
21068 the GNAT runtime depends is deliberately reset by some external event,
21069 then such a backward jump may occur.
21071 @item @code{Ada.Real_Time.Timing_Events} @emph{(D.15)}
21073 Not implemented in GNAT.
21075 @item @code{Ada.Sequential_IO} @emph{(A.8.1)}
21077 This package provides input-output facilities for sequential files,
21078 which can contain a sequence of values of a single type, which can be
21079 any Ada type, including indefinite (unconstrained) types.
21081 @item @code{Ada.Storage_IO} @emph{(A.9)}
21083 This package provides a facility for mapping arbitrary Ada types to and
21084 from a storage buffer. It is primarily intended for the creation of new
21087 @item @code{Ada.Streams} @emph{(13.13.1)}
21089 This is a generic package that provides the basic support for the
21090 concept of streams as used by the stream attributes (@code{Input},
21091 @code{Output}, @code{Read} and @code{Write}).
21093 @item @code{Ada.Streams.Stream_IO} @emph{(A.12.1)}
21095 This package is a specialization of the type @code{Streams} defined in
21096 package @code{Streams} together with a set of operations providing
21097 Stream_IO capability. The Stream_IO model permits both random and
21098 sequential access to a file which can contain an arbitrary set of values
21099 of one or more Ada types.
21101 @item @code{Ada.Strings} @emph{(A.4.1)}
21103 This package provides some basic constants used by the string handling
21106 @item @code{Ada.Strings.Bounded} @emph{(A.4.4)}
21108 This package provides facilities for handling variable length
21109 strings. The bounded model requires a maximum length. It is thus
21110 somewhat more limited than the unbounded model, but avoids the use of
21111 dynamic allocation or finalization.
21113 @item @code{Ada.Strings.Bounded.Equal_Case_Insensitive} @emph{(A.4.10)}
21115 Provides case-insensitive comparisons of bounded strings
21117 @item @code{Ada.Strings.Bounded.Hash} @emph{(A.4.9)}
21119 This package provides a generic hash function for bounded strings
21121 @item @code{Ada.Strings.Bounded.Hash_Case_Insensitive} @emph{(A.4.9)}
21123 This package provides a generic hash function for bounded strings that
21124 converts the string to be hashed to lower case.
21126 @item @code{Ada.Strings.Bounded.Less_Case_Insensitive} @emph{(A.4.10)}
21128 This package provides a comparison function for bounded strings that works
21129 in a case insensitive manner by converting to lower case before the comparison.
21131 @item @code{Ada.Strings.Fixed} @emph{(A.4.3)}
21133 This package provides facilities for handling fixed length strings.
21135 @item @code{Ada.Strings.Fixed.Equal_Case_Insensitive} @emph{(A.4.10)}
21137 This package provides an equality function for fixed strings that compares
21138 the strings after converting both to lower case.
21140 @item @code{Ada.Strings.Fixed.Hash_Case_Insensitive} @emph{(A.4.9)}
21142 This package provides a case insensitive hash function for fixed strings that
21143 converts the string to lower case before computing the hash.
21145 @item @code{Ada.Strings.Fixed.Less_Case_Insensitive} @emph{(A.4.10)}
21147 This package provides a comparison function for fixed strings that works
21148 in a case insensitive manner by converting to lower case before the comparison.
21150 @item @code{Ada.Strings.Hash} @emph{(A.4.9)}
21152 This package provides a hash function for strings.
21154 @item @code{Ada.Strings.Hash_Case_Insensitive} @emph{(A.4.9)}
21156 This package provides a hash function for strings that is case insensitive.
21157 The string is converted to lower case before computing the hash.
21159 @item @code{Ada.Strings.Less_Case_Insensitive} @emph{(A.4.10)}
21161 This package provides a comparison function for\strings that works
21162 in a case insensitive manner by converting to lower case before the comparison.
21164 @item @code{Ada.Strings.Maps} @emph{(A.4.2)}
21166 This package provides facilities for handling character mappings and
21167 arbitrarily defined subsets of characters. For instance it is useful in
21168 defining specialized translation tables.
21170 @item @code{Ada.Strings.Maps.Constants} @emph{(A.4.6)}
21172 This package provides a standard set of predefined mappings and
21173 predefined character sets. For example, the standard upper to lower case
21174 conversion table is found in this package. Note that upper to lower case
21175 conversion is non-trivial if you want to take the entire set of
21176 characters, including extended characters like E with an acute accent,
21177 into account. You should use the mappings in this package (rather than
21178 adding 32 yourself) to do case mappings.
21180 @item @code{Ada.Strings.Unbounded} @emph{(A.4.5)}
21182 This package provides facilities for handling variable length
21183 strings. The unbounded model allows arbitrary length strings, but
21184 requires the use of dynamic allocation and finalization.
21186 @item @code{Ada.Strings.Unbounded.Equal_Case_Insensitive} @emph{(A.4.10)}
21188 Provides case-insensitive comparisons of unbounded strings
21190 @item @code{Ada.Strings.Unbounded.Hash} @emph{(A.4.9)}
21192 This package provides a generic hash function for unbounded strings
21194 @item @code{Ada.Strings.Unbounded.Hash_Case_Insensitive} @emph{(A.4.9)}
21196 This package provides a generic hash function for unbounded strings that
21197 converts the string to be hashed to lower case.
21199 @item @code{Ada.Strings.Unbounded.Less_Case_Insensitive} @emph{(A.4.10)}
21201 This package provides a comparison function for unbounded strings that works
21202 in a case insensitive manner by converting to lower case before the comparison.
21204 @item @code{Ada.Strings.UTF_Encoding} @emph{(A.4.11)}
21206 This package provides basic definitions for dealing with UTF-encoded strings.
21208 @item @code{Ada.Strings.UTF_Encoding.Conversions} @emph{(A.4.11)}
21210 This package provides conversion functions for UTF-encoded strings.
21213 @code{Ada.Strings.UTF_Encoding.Strings} @emph{(A.4.11)}
21215 @code{Ada.Strings.UTF_Encoding.Wide_Strings} @emph{(A.4.11)}
21220 @item @code{Ada.Strings.UTF_Encoding.Wide_Wide_Strings} @emph{(A.4.11)}
21222 These packages provide facilities for handling UTF encodings for
21223 Strings, Wide_Strings and Wide_Wide_Strings.
21226 @code{Ada.Strings.Wide_Bounded} @emph{(A.4.7)}
21228 @code{Ada.Strings.Wide_Fixed} @emph{(A.4.7)}
21230 @code{Ada.Strings.Wide_Maps} @emph{(A.4.7)}
21235 @item @code{Ada.Strings.Wide_Unbounded} @emph{(A.4.7)}
21237 These packages provide analogous capabilities to the corresponding
21238 packages without @code{Wide_} in the name, but operate with the types
21239 @code{Wide_String} and @code{Wide_Character} instead of @code{String}
21240 and @code{Character}. Versions of all the child packages are available.
21243 @code{Ada.Strings.Wide_Wide_Bounded} @emph{(A.4.7)}
21245 @code{Ada.Strings.Wide_Wide_Fixed} @emph{(A.4.7)}
21247 @code{Ada.Strings.Wide_Wide_Maps} @emph{(A.4.7)}
21252 @item @code{Ada.Strings.Wide_Wide_Unbounded} @emph{(A.4.7)}
21254 These packages provide analogous capabilities to the corresponding
21255 packages without @code{Wide_} in the name, but operate with the types
21256 @code{Wide_Wide_String} and @code{Wide_Wide_Character} instead
21257 of @code{String} and @code{Character}.
21259 @item @code{Ada.Synchronous_Barriers} @emph{(D.10.1)}
21261 This package provides facilities for synchronizing tasks at a low level
21264 @item @code{Ada.Synchronous_Task_Control} @emph{(D.10)}
21266 This package provides some standard facilities for controlling task
21267 communication in a synchronous manner.
21269 @item @code{Ada.Synchronous_Task_Control.EDF} @emph{(D.10)}
21271 Not implemented in GNAT.
21273 @item @code{Ada.Tags}
21275 This package contains definitions for manipulation of the tags of tagged
21278 @item @code{Ada.Tags.Generic_Dispatching_Constructor} @emph{(3.9)}
21280 This package provides a way of constructing tagged class-wide values given
21281 only the tag value.
21283 @item @code{Ada.Task_Attributes} @emph{(C.7.2)}
21285 This package provides the capability of associating arbitrary
21286 task-specific data with separate tasks.
21288 @item @code{Ada.Task_Identifification} @emph{(C.7.1)}
21290 This package provides capabilities for task identification.
21292 @item @code{Ada.Task_Termination} @emph{(C.7.3)}
21294 This package provides control over task termination.
21296 @item @code{Ada.Text_IO}
21298 This package provides basic text input-output capabilities for
21299 character, string and numeric data. The subpackages of this
21300 package are listed next. Note that although these are defined
21301 as subpackages in the RM, they are actually transparently
21302 implemented as child packages in GNAT, meaning that they
21303 are only loaded if needed.
21305 @item @code{Ada.Text_IO.Decimal_IO}
21307 Provides input-output facilities for decimal fixed-point types
21309 @item @code{Ada.Text_IO.Enumeration_IO}
21311 Provides input-output facilities for enumeration types.
21313 @item @code{Ada.Text_IO.Fixed_IO}
21315 Provides input-output facilities for ordinary fixed-point types.
21317 @item @code{Ada.Text_IO.Float_IO}
21319 Provides input-output facilities for float types. The following
21320 predefined instantiations of this generic package are available:
21328 @code{Short_Float_Text_IO}
21333 @code{Float_Text_IO}
21338 @code{Long_Float_Text_IO}
21341 @item @code{Ada.Text_IO.Integer_IO}
21343 Provides input-output facilities for integer types. The following
21344 predefined instantiations of this generic package are available:
21350 @code{Short_Short_Integer}
21352 @code{Ada.Short_Short_Integer_Text_IO}
21355 @code{Short_Integer}
21357 @code{Ada.Short_Integer_Text_IO}
21362 @code{Ada.Integer_Text_IO}
21365 @code{Long_Integer}
21367 @code{Ada.Long_Integer_Text_IO}
21370 @code{Long_Long_Integer}
21372 @code{Ada.Long_Long_Integer_Text_IO}
21375 @item @code{Ada.Text_IO.Modular_IO}
21377 Provides input-output facilities for modular (unsigned) types.
21379 @item @code{Ada.Text_IO.Bounded_IO (A.10.11)}
21381 Provides input-output facilities for bounded strings.
21383 @item @code{Ada.Text_IO.Complex_IO (G.1.3)}
21385 This package provides basic text input-output capabilities for complex
21388 @item @code{Ada.Text_IO.Editing (F.3.3)}
21390 This package contains routines for edited output, analogous to the use
21391 of pictures in COBOL. The picture formats used by this package are a
21392 close copy of the facility in COBOL.
21394 @item @code{Ada.Text_IO.Text_Streams (A.12.2)}
21396 This package provides a facility that allows Text_IO files to be treated
21397 as streams, so that the stream attributes can be used for writing
21398 arbitrary data, including binary data, to Text_IO files.
21400 @item @code{Ada.Text_IO.Unbounded_IO (A.10.12)}
21402 This package provides input-output facilities for unbounded strings.
21404 @item @code{Ada.Unchecked_Conversion (13.9)}
21406 This generic package allows arbitrary conversion from one type to
21407 another of the same size, providing for breaking the type safety in
21408 special circumstances.
21410 If the types have the same Size (more accurately the same Value_Size),
21411 then the effect is simply to transfer the bits from the source to the
21412 target type without any modification. This usage is well defined, and
21413 for simple types whose representation is typically the same across
21414 all implementations, gives a portable method of performing such
21417 If the types do not have the same size, then the result is implementation
21418 defined, and thus may be non-portable. The following describes how GNAT
21419 handles such unchecked conversion cases.
21421 If the types are of different sizes, and are both discrete types, then
21422 the effect is of a normal type conversion without any constraint checking.
21423 In particular if the result type has a larger size, the result will be
21424 zero or sign extended. If the result type has a smaller size, the result
21425 will be truncated by ignoring high order bits.
21427 If the types are of different sizes, and are not both discrete types,
21428 then the conversion works as though pointers were created to the source
21429 and target, and the pointer value is converted. The effect is that bits
21430 are copied from successive low order storage units and bits of the source
21431 up to the length of the target type.
21433 A warning is issued if the lengths differ, since the effect in this
21434 case is implementation dependent, and the above behavior may not match
21435 that of some other compiler.
21437 A pointer to one type may be converted to a pointer to another type using
21438 unchecked conversion. The only case in which the effect is undefined is
21439 when one or both pointers are pointers to unconstrained array types. In
21440 this case, the bounds information may get incorrectly transferred, and in
21441 particular, GNAT uses double size pointers for such types, and it is
21442 meaningless to convert between such pointer types. GNAT will issue a
21443 warning if the alignment of the target designated type is more strict
21444 than the alignment of the source designated type (since the result may
21445 be unaligned in this case).
21447 A pointer other than a pointer to an unconstrained array type may be
21448 converted to and from System.Address. Such usage is common in Ada 83
21449 programs, but note that Ada.Address_To_Access_Conversions is the
21450 preferred method of performing such conversions in Ada 95 and Ada 2005.
21452 unchecked conversion nor Ada.Address_To_Access_Conversions should be
21453 used in conjunction with pointers to unconstrained objects, since
21454 the bounds information cannot be handled correctly in this case.
21456 @item @code{Ada.Unchecked_Deallocation} @emph{(13.11.2)}
21458 This generic package allows explicit freeing of storage previously
21459 allocated by use of an allocator.
21461 @item @code{Ada.Wide_Text_IO} @emph{(A.11)}
21463 This package is similar to @code{Ada.Text_IO}, except that the external
21464 file supports wide character representations, and the internal types are
21465 @code{Wide_Character} and @code{Wide_String} instead of @code{Character}
21466 and @code{String}. The corresponding set of nested packages and child
21467 packages are defined.
21469 @item @code{Ada.Wide_Wide_Text_IO} @emph{(A.11)}
21471 This package is similar to @code{Ada.Text_IO}, except that the external
21472 file supports wide character representations, and the internal types are
21473 @code{Wide_Character} and @code{Wide_String} instead of @code{Character}
21474 and @code{String}. The corresponding set of nested packages and child
21475 packages are defined.
21478 For packages in Interfaces and System, all the RM defined packages are
21479 available in GNAT, see the Ada 2012 RM for full details.
21481 @node The Implementation of Standard I/O,The GNAT Library,Standard Library Routines,Top
21482 @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{29e}@anchor{gnat_rm/the_implementation_of_standard_i_o id1}@anchor{29f}
21483 @chapter The Implementation of Standard I/O
21486 GNAT implements all the required input-output facilities described in
21487 A.6 through A.14. These sections of the Ada Reference Manual describe the
21488 required behavior of these packages from the Ada point of view, and if
21489 you are writing a portable Ada program that does not need to know the
21490 exact manner in which Ada maps to the outside world when it comes to
21491 reading or writing external files, then you do not need to read this
21492 chapter. As long as your files are all regular files (not pipes or
21493 devices), and as long as you write and read the files only from Ada, the
21494 description in the Ada Reference Manual is sufficient.
21496 However, if you want to do input-output to pipes or other devices, such
21497 as the keyboard or screen, or if the files you are dealing with are
21498 either generated by some other language, or to be read by some other
21499 language, then you need to know more about the details of how the GNAT
21500 implementation of these input-output facilities behaves.
21502 In this chapter we give a detailed description of exactly how GNAT
21503 interfaces to the file system. As always, the sources of the system are
21504 available to you for answering questions at an even more detailed level,
21505 but for most purposes the information in this chapter will suffice.
21507 Another reason that you may need to know more about how input-output is
21508 implemented arises when you have a program written in mixed languages
21509 where, for example, files are shared between the C and Ada sections of
21510 the same program. GNAT provides some additional facilities, in the form
21511 of additional child library packages, that facilitate this sharing, and
21512 these additional facilities are also described in this chapter.
21515 * Standard I/O Packages::
21521 * Wide_Wide_Text_IO::
21523 * Text Translation::
21525 * Filenames encoding::
21526 * File content encoding::
21528 * Operations on C Streams::
21529 * Interfacing to C Streams::
21533 @node Standard I/O Packages,FORM Strings,,The Implementation of Standard I/O
21534 @anchor{gnat_rm/the_implementation_of_standard_i_o standard-i-o-packages}@anchor{2a0}@anchor{gnat_rm/the_implementation_of_standard_i_o id2}@anchor{2a1}
21535 @section Standard I/O Packages
21538 The Standard I/O packages described in Annex A for
21547 Ada.Text_IO.Complex_IO
21550 Ada.Text_IO.Text_Streams
21556 Ada.Wide_Text_IO.Complex_IO
21559 Ada.Wide_Text_IO.Text_Streams
21562 Ada.Wide_Wide_Text_IO
21565 Ada.Wide_Wide_Text_IO.Complex_IO
21568 Ada.Wide_Wide_Text_IO.Text_Streams
21580 are implemented using the C
21581 library streams facility; where
21587 All files are opened using @code{fopen}.
21590 All input/output operations use @code{fread}/@cite{fwrite}.
21593 There is no internal buffering of any kind at the Ada library level. The only
21594 buffering is that provided at the system level in the implementation of the
21595 library routines that support streams. This facilitates shared use of these
21596 streams by mixed language programs. Note though that system level buffering is
21597 explicitly enabled at elaboration of the standard I/O packages and that can
21598 have an impact on mixed language programs, in particular those using I/O before
21599 calling the Ada elaboration routine (e.g., adainit). It is recommended to call
21600 the Ada elaboration routine before performing any I/O or when impractical,
21601 flush the common I/O streams and in particular Standard_Output before
21602 elaborating the Ada code.
21604 @node FORM Strings,Direct_IO,Standard I/O Packages,The Implementation of Standard I/O
21605 @anchor{gnat_rm/the_implementation_of_standard_i_o form-strings}@anchor{2a2}@anchor{gnat_rm/the_implementation_of_standard_i_o id3}@anchor{2a3}
21606 @section FORM Strings
21609 The format of a FORM string in GNAT is:
21612 "keyword=value,keyword=value,...,keyword=value"
21615 where letters may be in upper or lower case, and there are no spaces
21616 between values. The order of the entries is not important. Currently
21617 the following keywords defined.
21620 TEXT_TRANSLATION=[YES|NO|TEXT|BINARY|U8TEXT|WTEXT|U16TEXT]
21622 WCEM=[n|h|u|s|e|8|b]
21623 ENCODING=[UTF8|8BITS]
21626 The use of these parameters is described later in this section. If an
21627 unrecognized keyword appears in a form string, it is silently ignored
21628 and not considered invalid.
21630 @node Direct_IO,Sequential_IO,FORM Strings,The Implementation of Standard I/O
21631 @anchor{gnat_rm/the_implementation_of_standard_i_o direct-io}@anchor{2a4}@anchor{gnat_rm/the_implementation_of_standard_i_o id4}@anchor{2a5}
21635 Direct_IO can only be instantiated for definite types. This is a
21636 restriction of the Ada language, which means that the records are fixed
21637 length (the length being determined by @code{type'Size}, rounded
21638 up to the next storage unit boundary if necessary).
21640 The records of a Direct_IO file are simply written to the file in index
21641 sequence, with the first record starting at offset zero, and subsequent
21642 records following. There is no control information of any kind. For
21643 example, if 32-bit integers are being written, each record takes
21644 4-bytes, so the record at index @code{K} starts at offset
21647 There is no limit on the size of Direct_IO files, they are expanded as
21648 necessary to accommodate whatever records are written to the file.
21650 @node Sequential_IO,Text_IO,Direct_IO,The Implementation of Standard I/O
21651 @anchor{gnat_rm/the_implementation_of_standard_i_o sequential-io}@anchor{2a6}@anchor{gnat_rm/the_implementation_of_standard_i_o id5}@anchor{2a7}
21652 @section Sequential_IO
21655 Sequential_IO may be instantiated with either a definite (constrained)
21656 or indefinite (unconstrained) type.
21658 For the definite type case, the elements written to the file are simply
21659 the memory images of the data values with no control information of any
21660 kind. The resulting file should be read using the same type, no validity
21661 checking is performed on input.
21663 For the indefinite type case, the elements written consist of two
21664 parts. First is the size of the data item, written as the memory image
21665 of a @code{Interfaces.C.size_t} value, followed by the memory image of
21666 the data value. The resulting file can only be read using the same
21667 (unconstrained) type. Normal assignment checks are performed on these
21668 read operations, and if these checks fail, @code{Data_Error} is
21669 raised. In particular, in the array case, the lengths must match, and in
21670 the variant record case, if the variable for a particular read operation
21671 is constrained, the discriminants must match.
21673 Note that it is not possible to use Sequential_IO to write variable
21674 length array items, and then read the data back into different length
21675 arrays. For example, the following will raise @code{Data_Error}:
21678 package IO is new Sequential_IO (String);
21683 IO.Write (F, "hello!")
21684 IO.Reset (F, Mode=>In_File);
21689 On some Ada implementations, this will print @code{hell}, but the program is
21690 clearly incorrect, since there is only one element in the file, and that
21691 element is the string @code{hello!}.
21693 In Ada 95 and Ada 2005, this kind of behavior can be legitimately achieved
21694 using Stream_IO, and this is the preferred mechanism. In particular, the
21695 above program fragment rewritten to use Stream_IO will work correctly.
21697 @node Text_IO,Wide_Text_IO,Sequential_IO,The Implementation of Standard I/O
21698 @anchor{gnat_rm/the_implementation_of_standard_i_o id6}@anchor{2a8}@anchor{gnat_rm/the_implementation_of_standard_i_o text-io}@anchor{2a9}
21702 Text_IO files consist of a stream of characters containing the following
21703 special control characters:
21706 LF (line feed, 16#0A#) Line Mark
21707 FF (form feed, 16#0C#) Page Mark
21710 A canonical Text_IO file is defined as one in which the following
21711 conditions are met:
21717 The character @code{LF} is used only as a line mark, i.e., to mark the end
21721 The character @code{FF} is used only as a page mark, i.e., to mark the
21722 end of a page and consequently can appear only immediately following a
21723 @code{LF} (line mark) character.
21726 The file ends with either @code{LF} (line mark) or @code{LF}-@cite{FF}
21727 (line mark, page mark). In the former case, the page mark is implicitly
21728 assumed to be present.
21731 A file written using Text_IO will be in canonical form provided that no
21732 explicit @code{LF} or @code{FF} characters are written using @code{Put}
21733 or @code{Put_Line}. There will be no @code{FF} character at the end of
21734 the file unless an explicit @code{New_Page} operation was performed
21735 before closing the file.
21737 A canonical Text_IO file that is a regular file (i.e., not a device or a
21738 pipe) can be read using any of the routines in Text_IO. The
21739 semantics in this case will be exactly as defined in the Ada Reference
21740 Manual, and all the routines in Text_IO are fully implemented.
21742 A text file that does not meet the requirements for a canonical Text_IO
21743 file has one of the following:
21749 The file contains @code{FF} characters not immediately following a
21750 @code{LF} character.
21753 The file contains @code{LF} or @code{FF} characters written by
21754 @code{Put} or @code{Put_Line}, which are not logically considered to be
21755 line marks or page marks.
21758 The file ends in a character other than @code{LF} or @code{FF},
21759 i.e., there is no explicit line mark or page mark at the end of the file.
21762 Text_IO can be used to read such non-standard text files but subprograms
21763 to do with line or page numbers do not have defined meanings. In
21764 particular, a @code{FF} character that does not follow a @code{LF}
21765 character may or may not be treated as a page mark from the point of
21766 view of page and line numbering. Every @code{LF} character is considered
21767 to end a line, and there is an implied @code{LF} character at the end of
21771 * Stream Pointer Positioning::
21772 * Reading and Writing Non-Regular Files::
21774 * Treating Text_IO Files as Streams::
21775 * Text_IO Extensions::
21776 * Text_IO Facilities for Unbounded Strings::
21780 @node Stream Pointer Positioning,Reading and Writing Non-Regular Files,,Text_IO
21781 @anchor{gnat_rm/the_implementation_of_standard_i_o id7}@anchor{2aa}@anchor{gnat_rm/the_implementation_of_standard_i_o stream-pointer-positioning}@anchor{2ab}
21782 @subsection Stream Pointer Positioning
21785 @code{Ada.Text_IO} has a definition of current position for a file that
21786 is being read. No internal buffering occurs in Text_IO, and usually the
21787 physical position in the stream used to implement the file corresponds
21788 to this logical position defined by Text_IO. There are two exceptions:
21794 After a call to @code{End_Of_Page} that returns @code{True}, the stream
21795 is positioned past the @code{LF} (line mark) that precedes the page
21796 mark. Text_IO maintains an internal flag so that subsequent read
21797 operations properly handle the logical position which is unchanged by
21798 the @code{End_Of_Page} call.
21801 After a call to @code{End_Of_File} that returns @code{True}, if the
21802 Text_IO file was positioned before the line mark at the end of file
21803 before the call, then the logical position is unchanged, but the stream
21804 is physically positioned right at the end of file (past the line mark,
21805 and past a possible page mark following the line mark. Again Text_IO
21806 maintains internal flags so that subsequent read operations properly
21807 handle the logical position.
21810 These discrepancies have no effect on the observable behavior of
21811 Text_IO, but if a single Ada stream is shared between a C program and
21812 Ada program, or shared (using @code{shared=yes} in the form string)
21813 between two Ada files, then the difference may be observable in some
21816 @node Reading and Writing Non-Regular Files,Get_Immediate,Stream Pointer Positioning,Text_IO
21817 @anchor{gnat_rm/the_implementation_of_standard_i_o reading-and-writing-non-regular-files}@anchor{2ac}@anchor{gnat_rm/the_implementation_of_standard_i_o id8}@anchor{2ad}
21818 @subsection Reading and Writing Non-Regular Files
21821 A non-regular file is a device (such as a keyboard), or a pipe. Text_IO
21822 can be used for reading and writing. Writing is not affected and the
21823 sequence of characters output is identical to the normal file case, but
21824 for reading, the behavior of Text_IO is modified to avoid undesirable
21825 look-ahead as follows:
21827 An input file that is not a regular file is considered to have no page
21828 marks. Any @code{Ascii.FF} characters (the character normally used for a
21829 page mark) appearing in the file are considered to be data
21830 characters. In particular:
21836 @code{Get_Line} and @code{Skip_Line} do not test for a page mark
21837 following a line mark. If a page mark appears, it will be treated as a
21841 This avoids the need to wait for an extra character to be typed or
21842 entered from the pipe to complete one of these operations.
21845 @code{End_Of_Page} always returns @code{False}
21848 @code{End_Of_File} will return @code{False} if there is a page mark at
21849 the end of the file.
21852 Output to non-regular files is the same as for regular files. Page marks
21853 may be written to non-regular files using @code{New_Page}, but as noted
21854 above they will not be treated as page marks on input if the output is
21855 piped to another Ada program.
21857 Another important discrepancy when reading non-regular files is that the end
21858 of file indication is not 'sticky'. If an end of file is entered, e.g., by
21859 pressing the @code{EOT} key,
21861 is signaled once (i.e., the test @code{End_Of_File}
21862 will yield @code{True}, or a read will
21863 raise @code{End_Error}), but then reading can resume
21864 to read data past that end of
21865 file indication, until another end of file indication is entered.
21867 @node Get_Immediate,Treating Text_IO Files as Streams,Reading and Writing Non-Regular Files,Text_IO
21868 @anchor{gnat_rm/the_implementation_of_standard_i_o get-immediate}@anchor{2ae}@anchor{gnat_rm/the_implementation_of_standard_i_o id9}@anchor{2af}
21869 @subsection Get_Immediate
21872 @geindex Get_Immediate
21874 Get_Immediate returns the next character (including control characters)
21875 from the input file. In particular, Get_Immediate will return LF or FF
21876 characters used as line marks or page marks. Such operations leave the
21877 file positioned past the control character, and it is thus not treated
21878 as having its normal function. This means that page, line and column
21879 counts after this kind of Get_Immediate call are set as though the mark
21880 did not occur. In the case where a Get_Immediate leaves the file
21881 positioned between the line mark and page mark (which is not normally
21882 possible), it is undefined whether the FF character will be treated as a
21885 @node Treating Text_IO Files as Streams,Text_IO Extensions,Get_Immediate,Text_IO
21886 @anchor{gnat_rm/the_implementation_of_standard_i_o id10}@anchor{2b0}@anchor{gnat_rm/the_implementation_of_standard_i_o treating-text-io-files-as-streams}@anchor{2b1}
21887 @subsection Treating Text_IO Files as Streams
21890 @geindex Stream files
21892 The package @code{Text_IO.Streams} allows a @code{Text_IO} file to be treated
21893 as a stream. Data written to a @code{Text_IO} file in this stream mode is
21894 binary data. If this binary data contains bytes 16#0A# (@code{LF}) or
21895 16#0C# (@code{FF}), the resulting file may have non-standard
21896 format. Similarly if read operations are used to read from a Text_IO
21897 file treated as a stream, then @code{LF} and @code{FF} characters may be
21898 skipped and the effect is similar to that described above for
21899 @code{Get_Immediate}.
21901 @node Text_IO Extensions,Text_IO Facilities for Unbounded Strings,Treating Text_IO Files as Streams,Text_IO
21902 @anchor{gnat_rm/the_implementation_of_standard_i_o id11}@anchor{2b2}@anchor{gnat_rm/the_implementation_of_standard_i_o text-io-extensions}@anchor{2b3}
21903 @subsection Text_IO Extensions
21906 @geindex Text_IO extensions
21908 A package GNAT.IO_Aux in the GNAT library provides some useful extensions
21909 to the standard @code{Text_IO} package:
21915 function File_Exists (Name : String) return Boolean;
21916 Determines if a file of the given name exists.
21919 function Get_Line return String;
21920 Reads a string from the standard input file. The value returned is exactly
21921 the length of the line that was read.
21924 function Get_Line (File : Ada.Text_IO.File_Type) return String;
21925 Similar, except that the parameter File specifies the file from which
21926 the string is to be read.
21929 @node Text_IO Facilities for Unbounded Strings,,Text_IO Extensions,Text_IO
21930 @anchor{gnat_rm/the_implementation_of_standard_i_o text-io-facilities-for-unbounded-strings}@anchor{2b4}@anchor{gnat_rm/the_implementation_of_standard_i_o id12}@anchor{2b5}
21931 @subsection Text_IO Facilities for Unbounded Strings
21934 @geindex Text_IO for unbounded strings
21936 @geindex Unbounded_String
21937 @geindex Text_IO operations
21939 The package @code{Ada.Strings.Unbounded.Text_IO}
21940 in library files @code{a-suteio.ads/adb} contains some GNAT-specific
21941 subprograms useful for Text_IO operations on unbounded strings:
21947 function Get_Line (File : File_Type) return Unbounded_String;
21948 Reads a line from the specified file
21949 and returns the result as an unbounded string.
21952 procedure Put (File : File_Type; U : Unbounded_String);
21953 Writes the value of the given unbounded string to the specified file
21954 Similar to the effect of
21955 @code{Put (To_String (U))} except that an extra copy is avoided.
21958 procedure Put_Line (File : File_Type; U : Unbounded_String);
21959 Writes the value of the given unbounded string to the specified file,
21960 followed by a @code{New_Line}.
21961 Similar to the effect of @code{Put_Line (To_String (U))} except
21962 that an extra copy is avoided.
21965 In the above procedures, @code{File} is of type @code{Ada.Text_IO.File_Type}
21966 and is optional. If the parameter is omitted, then the standard input or
21967 output file is referenced as appropriate.
21969 The package @code{Ada.Strings.Wide_Unbounded.Wide_Text_IO} in library
21970 files @code{a-swuwti.ads} and @code{a-swuwti.adb} provides similar extended
21971 @code{Wide_Text_IO} functionality for unbounded wide strings.
21973 The package @code{Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO} in library
21974 files @code{a-szuzti.ads} and @code{a-szuzti.adb} provides similar extended
21975 @code{Wide_Wide_Text_IO} functionality for unbounded wide wide strings.
21977 @node Wide_Text_IO,Wide_Wide_Text_IO,Text_IO,The Implementation of Standard I/O
21978 @anchor{gnat_rm/the_implementation_of_standard_i_o wide-text-io}@anchor{2b6}@anchor{gnat_rm/the_implementation_of_standard_i_o id13}@anchor{2b7}
21979 @section Wide_Text_IO
21982 @code{Wide_Text_IO} is similar in most respects to Text_IO, except that
21983 both input and output files may contain special sequences that represent
21984 wide character values. The encoding scheme for a given file may be
21985 specified using a FORM parameter:
21991 as part of the FORM string (WCEM = wide character encoding method),
21992 where @code{x} is one of the following characters
21995 @multitable {xxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxx}
22018 Upper half encoding
22055 The encoding methods match those that
22056 can be used in a source
22057 program, but there is no requirement that the encoding method used for
22058 the source program be the same as the encoding method used for files,
22059 and different files may use different encoding methods.
22061 The default encoding method for the standard files, and for opened files
22062 for which no WCEM parameter is given in the FORM string matches the
22063 wide character encoding specified for the main program (the default
22064 being brackets encoding if no coding method was specified with -gnatW).
22069 @item @emph{Hex Coding}
22071 In this encoding, a wide character is represented by a five character
22082 where @code{a}, @code{b}, @code{c}, @code{d} are the four hexadecimal
22083 characters (using upper case letters) of the wide character code. For
22084 example, ESC A345 is used to represent the wide character with code
22085 16#A345#. This scheme is compatible with use of the full
22086 @code{Wide_Character} set.
22092 @item @emph{Upper Half Coding}
22094 The wide character with encoding 16#abcd#, where the upper bit is on
22095 (i.e., a is in the range 8-F) is represented as two bytes 16#ab# and
22096 16#cd#. The second byte may never be a format control character, but is
22097 not required to be in the upper half. This method can be also used for
22098 shift-JIS or EUC where the internal coding matches the external coding.
22100 @item @emph{Shift JIS Coding}
22102 A wide character is represented by a two character sequence 16#ab# and
22103 16#cd#, with the restrictions described for upper half encoding as
22104 described above. The internal character code is the corresponding JIS
22105 character according to the standard algorithm for Shift-JIS
22106 conversion. Only characters defined in the JIS code set table can be
22107 used with this encoding method.
22109 @item @emph{EUC Coding}
22111 A wide character is represented by a two character sequence 16#ab# and
22112 16#cd#, with both characters being in the upper half. The internal
22113 character code is the corresponding JIS character according to the EUC
22114 encoding algorithm. Only characters defined in the JIS code set table
22115 can be used with this encoding method.
22117 @item @emph{UTF-8 Coding}
22119 A wide character is represented using
22120 UCS Transformation Format 8 (UTF-8) as defined in Annex R of ISO
22121 10646-1/Am.2. Depending on the character value, the representation
22122 is a one, two, or three byte sequence:
22126 16#0000#-16#007f#: 2#0xxxxxxx#
22127 16#0080#-16#07ff#: 2#110xxxxx# 2#10xxxxxx#
22128 16#0800#-16#ffff#: 2#1110xxxx# 2#10xxxxxx# 2#10xxxxxx#
22134 where the @code{xxx} bits correspond to the left-padded bits of the
22135 16-bit character value. Note that all lower half ASCII characters
22136 are represented as ASCII bytes and all upper half characters and
22137 other wide characters are represented as sequences of upper-half
22138 (The full UTF-8 scheme allows for encoding 31-bit characters as
22139 6-byte sequences, but in this implementation, all UTF-8 sequences
22140 of four or more bytes length will raise a Constraint_Error, as
22141 will all invalid UTF-8 sequences.)
22147 @item @emph{Brackets Coding}
22149 In this encoding, a wide character is represented by the following eight
22150 character sequence:
22160 where @code{a}, @code{b}, @code{c}, @code{d} are the four hexadecimal
22161 characters (using uppercase letters) of the wide character code. For
22162 example, @code{["A345"]} is used to represent the wide character with code
22164 This scheme is compatible with use of the full Wide_Character set.
22165 On input, brackets coding can also be used for upper half characters,
22166 e.g., @code{["C1"]} for lower case a. However, on output, brackets notation
22167 is only used for wide characters with a code greater than @code{16#FF#}.
22169 Note that brackets coding is not normally used in the context of
22170 Wide_Text_IO or Wide_Wide_Text_IO, since it is really just designed as
22171 a portable way of encoding source files. In the context of Wide_Text_IO
22172 or Wide_Wide_Text_IO, it can only be used if the file does not contain
22173 any instance of the left bracket character other than to encode wide
22174 character values using the brackets encoding method. In practice it is
22175 expected that some standard wide character encoding method such
22176 as UTF-8 will be used for text input output.
22178 If brackets notation is used, then any occurrence of a left bracket
22179 in the input file which is not the start of a valid wide character
22180 sequence will cause Constraint_Error to be raised. It is possible to
22181 encode a left bracket as ["5B"] and Wide_Text_IO and Wide_Wide_Text_IO
22182 input will interpret this as a left bracket.
22184 However, when a left bracket is output, it will be output as a left bracket
22185 and not as ["5B"]. We make this decision because for normal use of
22186 Wide_Text_IO for outputting messages, it is unpleasant to clobber left
22187 brackets. For example, if we write:
22190 Put_Line ("Start of output [first run]");
22193 we really do not want to have the left bracket in this message clobbered so
22194 that the output reads:
22198 Start of output ["5B"]first run]
22204 In practice brackets encoding is reasonably useful for normal Put_Line use
22205 since we won't get confused between left brackets and wide character
22206 sequences in the output. But for input, or when files are written out
22207 and read back in, it really makes better sense to use one of the standard
22208 encoding methods such as UTF-8.
22211 For the coding schemes other than UTF-8, Hex, or Brackets encoding,
22212 not all wide character
22213 values can be represented. An attempt to output a character that cannot
22214 be represented using the encoding scheme for the file causes
22215 Constraint_Error to be raised. An invalid wide character sequence on
22216 input also causes Constraint_Error to be raised.
22219 * Stream Pointer Positioning: Stream Pointer Positioning<2>.
22220 * Reading and Writing Non-Regular Files: Reading and Writing Non-Regular Files<2>.
22224 @node Stream Pointer Positioning<2>,Reading and Writing Non-Regular Files<2>,,Wide_Text_IO
22225 @anchor{gnat_rm/the_implementation_of_standard_i_o stream-pointer-positioning-1}@anchor{2b8}@anchor{gnat_rm/the_implementation_of_standard_i_o id14}@anchor{2b9}
22226 @subsection Stream Pointer Positioning
22229 @code{Ada.Wide_Text_IO} is similar to @code{Ada.Text_IO} in its handling
22230 of stream pointer positioning (@ref{2a9,,Text_IO}). There is one additional
22233 If @code{Ada.Wide_Text_IO.Look_Ahead} reads a character outside the
22234 normal lower ASCII set (i.e., a character in the range:
22237 Wide_Character'Val (16#0080#) .. Wide_Character'Val (16#FFFF#)
22240 then although the logical position of the file pointer is unchanged by
22241 the @code{Look_Ahead} call, the stream is physically positioned past the
22242 wide character sequence. Again this is to avoid the need for buffering
22243 or backup, and all @code{Wide_Text_IO} routines check the internal
22244 indication that this situation has occurred so that this is not visible
22245 to a normal program using @code{Wide_Text_IO}. However, this discrepancy
22246 can be observed if the wide text file shares a stream with another file.
22248 @node Reading and Writing Non-Regular Files<2>,,Stream Pointer Positioning<2>,Wide_Text_IO
22249 @anchor{gnat_rm/the_implementation_of_standard_i_o reading-and-writing-non-regular-files-1}@anchor{2ba}@anchor{gnat_rm/the_implementation_of_standard_i_o id15}@anchor{2bb}
22250 @subsection Reading and Writing Non-Regular Files
22253 As in the case of Text_IO, when a non-regular file is read, it is
22254 assumed that the file contains no page marks (any form characters are
22255 treated as data characters), and @code{End_Of_Page} always returns
22256 @code{False}. Similarly, the end of file indication is not sticky, so
22257 it is possible to read beyond an end of file.
22259 @node Wide_Wide_Text_IO,Stream_IO,Wide_Text_IO,The Implementation of Standard I/O
22260 @anchor{gnat_rm/the_implementation_of_standard_i_o id16}@anchor{2bc}@anchor{gnat_rm/the_implementation_of_standard_i_o wide-wide-text-io}@anchor{2bd}
22261 @section Wide_Wide_Text_IO
22264 @code{Wide_Wide_Text_IO} is similar in most respects to Text_IO, except that
22265 both input and output files may contain special sequences that represent
22266 wide wide character values. The encoding scheme for a given file may be
22267 specified using a FORM parameter:
22273 as part of the FORM string (WCEM = wide character encoding method),
22274 where @code{x} is one of the following characters
22277 @multitable {xxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxx}
22300 Upper half encoding
22337 The encoding methods match those that
22338 can be used in a source
22339 program, but there is no requirement that the encoding method used for
22340 the source program be the same as the encoding method used for files,
22341 and different files may use different encoding methods.
22343 The default encoding method for the standard files, and for opened files
22344 for which no WCEM parameter is given in the FORM string matches the
22345 wide character encoding specified for the main program (the default
22346 being brackets encoding if no coding method was specified with -gnatW).
22351 @item @emph{UTF-8 Coding}
22353 A wide character is represented using
22354 UCS Transformation Format 8 (UTF-8) as defined in Annex R of ISO
22355 10646-1/Am.2. Depending on the character value, the representation
22356 is a one, two, three, or four byte sequence:
22360 16#000000#-16#00007f#: 2#0xxxxxxx#
22361 16#000080#-16#0007ff#: 2#110xxxxx# 2#10xxxxxx#
22362 16#000800#-16#00ffff#: 2#1110xxxx# 2#10xxxxxx# 2#10xxxxxx#
22363 16#010000#-16#10ffff#: 2#11110xxx# 2#10xxxxxx# 2#10xxxxxx# 2#10xxxxxx#
22369 where the @code{xxx} bits correspond to the left-padded bits of the
22370 21-bit character value. Note that all lower half ASCII characters
22371 are represented as ASCII bytes and all upper half characters and
22372 other wide characters are represented as sequences of upper-half
22379 @item @emph{Brackets Coding}
22381 In this encoding, a wide wide character is represented by the following eight
22382 character sequence if is in wide character range
22392 and by the following ten character sequence if not
22396 [ " a b c d e f " ]
22402 where @code{a}, @code{b}, @code{c}, @code{d}, @code{e}, and @code{f}
22403 are the four or six hexadecimal
22404 characters (using uppercase letters) of the wide wide character code. For
22405 example, @code{["01A345"]} is used to represent the wide wide character
22406 with code @code{16#01A345#}.
22408 This scheme is compatible with use of the full Wide_Wide_Character set.
22409 On input, brackets coding can also be used for upper half characters,
22410 e.g., @code{["C1"]} for lower case a. However, on output, brackets notation
22411 is only used for wide characters with a code greater than @code{16#FF#}.
22414 If is also possible to use the other Wide_Character encoding methods,
22415 such as Shift-JIS, but the other schemes cannot support the full range
22416 of wide wide characters.
22417 An attempt to output a character that cannot
22418 be represented using the encoding scheme for the file causes
22419 Constraint_Error to be raised. An invalid wide character sequence on
22420 input also causes Constraint_Error to be raised.
22423 * Stream Pointer Positioning: Stream Pointer Positioning<3>.
22424 * Reading and Writing Non-Regular Files: Reading and Writing Non-Regular Files<3>.
22428 @node Stream Pointer Positioning<3>,Reading and Writing Non-Regular Files<3>,,Wide_Wide_Text_IO
22429 @anchor{gnat_rm/the_implementation_of_standard_i_o stream-pointer-positioning-2}@anchor{2be}@anchor{gnat_rm/the_implementation_of_standard_i_o id17}@anchor{2bf}
22430 @subsection Stream Pointer Positioning
22433 @code{Ada.Wide_Wide_Text_IO} is similar to @code{Ada.Text_IO} in its handling
22434 of stream pointer positioning (@ref{2a9,,Text_IO}). There is one additional
22437 If @code{Ada.Wide_Wide_Text_IO.Look_Ahead} reads a character outside the
22438 normal lower ASCII set (i.e., a character in the range:
22441 Wide_Wide_Character'Val (16#0080#) .. Wide_Wide_Character'Val (16#10FFFF#)
22444 then although the logical position of the file pointer is unchanged by
22445 the @code{Look_Ahead} call, the stream is physically positioned past the
22446 wide character sequence. Again this is to avoid the need for buffering
22447 or backup, and all @code{Wide_Wide_Text_IO} routines check the internal
22448 indication that this situation has occurred so that this is not visible
22449 to a normal program using @code{Wide_Wide_Text_IO}. However, this discrepancy
22450 can be observed if the wide text file shares a stream with another file.
22452 @node Reading and Writing Non-Regular Files<3>,,Stream Pointer Positioning<3>,Wide_Wide_Text_IO
22453 @anchor{gnat_rm/the_implementation_of_standard_i_o id18}@anchor{2c0}@anchor{gnat_rm/the_implementation_of_standard_i_o reading-and-writing-non-regular-files-2}@anchor{2c1}
22454 @subsection Reading and Writing Non-Regular Files
22457 As in the case of Text_IO, when a non-regular file is read, it is
22458 assumed that the file contains no page marks (any form characters are
22459 treated as data characters), and @code{End_Of_Page} always returns
22460 @code{False}. Similarly, the end of file indication is not sticky, so
22461 it is possible to read beyond an end of file.
22463 @node Stream_IO,Text Translation,Wide_Wide_Text_IO,The Implementation of Standard I/O
22464 @anchor{gnat_rm/the_implementation_of_standard_i_o id19}@anchor{2c2}@anchor{gnat_rm/the_implementation_of_standard_i_o stream-io}@anchor{2c3}
22468 A stream file is a sequence of bytes, where individual elements are
22469 written to the file as described in the Ada Reference Manual. The type
22470 @code{Stream_Element} is simply a byte. There are two ways to read or
22471 write a stream file.
22477 The operations @code{Read} and @code{Write} directly read or write a
22478 sequence of stream elements with no control information.
22481 The stream attributes applied to a stream file transfer data in the
22482 manner described for stream attributes.
22485 @node Text Translation,Shared Files,Stream_IO,The Implementation of Standard I/O
22486 @anchor{gnat_rm/the_implementation_of_standard_i_o id20}@anchor{2c4}@anchor{gnat_rm/the_implementation_of_standard_i_o text-translation}@anchor{2c5}
22487 @section Text Translation
22490 @code{Text_Translation=xxx} may be used as the Form parameter
22491 passed to Text_IO.Create and Text_IO.Open. @code{Text_Translation=xxx}
22492 has no effect on Unix systems. Possible values are:
22498 @code{Yes} or @code{Text} is the default, which means to
22499 translate LF to/from CR/LF on Windows systems.
22501 @code{No} disables this translation; i.e. it
22502 uses binary mode. For output files, @code{Text_Translation=No}
22503 may be used to create Unix-style files on
22507 @code{wtext} translation enabled in Unicode mode.
22508 (corresponds to _O_WTEXT).
22511 @code{u8text} translation enabled in Unicode UTF-8 mode.
22512 (corresponds to O_U8TEXT).
22515 @code{u16text} translation enabled in Unicode UTF-16
22516 mode. (corresponds to_O_U16TEXT).
22519 @node Shared Files,Filenames encoding,Text Translation,The Implementation of Standard I/O
22520 @anchor{gnat_rm/the_implementation_of_standard_i_o id21}@anchor{2c6}@anchor{gnat_rm/the_implementation_of_standard_i_o shared-files}@anchor{2c7}
22521 @section Shared Files
22524 Section A.14 of the Ada Reference Manual allows implementations to
22525 provide a wide variety of behavior if an attempt is made to access the
22526 same external file with two or more internal files.
22528 To provide a full range of functionality, while at the same time
22529 minimizing the problems of portability caused by this implementation
22530 dependence, GNAT handles file sharing as follows:
22536 In the absence of a @code{shared=xxx} form parameter, an attempt
22537 to open two or more files with the same full name is considered an error
22538 and is not supported. The exception @code{Use_Error} will be
22539 raised. Note that a file that is not explicitly closed by the program
22540 remains open until the program terminates.
22543 If the form parameter @code{shared=no} appears in the form string, the
22544 file can be opened or created with its own separate stream identifier,
22545 regardless of whether other files sharing the same external file are
22546 opened. The exact effect depends on how the C stream routines handle
22547 multiple accesses to the same external files using separate streams.
22550 If the form parameter @code{shared=yes} appears in the form string for
22551 each of two or more files opened using the same full name, the same
22552 stream is shared between these files, and the semantics are as described
22553 in Ada Reference Manual, Section A.14.
22556 When a program that opens multiple files with the same name is ported
22557 from another Ada compiler to GNAT, the effect will be that
22558 @code{Use_Error} is raised.
22560 The documentation of the original compiler and the documentation of the
22561 program should then be examined to determine if file sharing was
22562 expected, and @code{shared=xxx} parameters added to @code{Open}
22563 and @code{Create} calls as required.
22565 When a program is ported from GNAT to some other Ada compiler, no
22566 special attention is required unless the @code{shared=xxx} form
22567 parameter is used in the program. In this case, you must examine the
22568 documentation of the new compiler to see if it supports the required
22569 file sharing semantics, and form strings modified appropriately. Of
22570 course it may be the case that the program cannot be ported if the
22571 target compiler does not support the required functionality. The best
22572 approach in writing portable code is to avoid file sharing (and hence
22573 the use of the @code{shared=xxx} parameter in the form string)
22576 One common use of file sharing in Ada 83 is the use of instantiations of
22577 Sequential_IO on the same file with different types, to achieve
22578 heterogeneous input-output. Although this approach will work in GNAT if
22579 @code{shared=yes} is specified, it is preferable in Ada to use Stream_IO
22580 for this purpose (using the stream attributes)
22582 @node Filenames encoding,File content encoding,Shared Files,The Implementation of Standard I/O
22583 @anchor{gnat_rm/the_implementation_of_standard_i_o filenames-encoding}@anchor{2c8}@anchor{gnat_rm/the_implementation_of_standard_i_o id22}@anchor{2c9}
22584 @section Filenames encoding
22587 An encoding form parameter can be used to specify the filename
22588 encoding @code{encoding=xxx}.
22594 If the form parameter @code{encoding=utf8} appears in the form string, the
22595 filename must be encoded in UTF-8.
22598 If the form parameter @code{encoding=8bits} appears in the form
22599 string, the filename must be a standard 8bits string.
22602 In the absence of a @code{encoding=xxx} form parameter, the
22603 encoding is controlled by the @code{GNAT_CODE_PAGE} environment
22604 variable. And if not set @code{utf8} is assumed.
22609 @item @emph{CP_ACP}
22611 The current system Windows ANSI code page.
22613 @item @emph{CP_UTF8}
22618 This encoding form parameter is only supported on the Windows
22619 platform. On the other Operating Systems the run-time is supporting
22622 @node File content encoding,Open Modes,Filenames encoding,The Implementation of Standard I/O
22623 @anchor{gnat_rm/the_implementation_of_standard_i_o file-content-encoding}@anchor{2ca}@anchor{gnat_rm/the_implementation_of_standard_i_o id23}@anchor{2cb}
22624 @section File content encoding
22627 For text files it is possible to specify the encoding to use. This is
22628 controlled by the by the @code{GNAT_CCS_ENCODING} environment
22629 variable. And if not set @code{TEXT} is assumed.
22631 The possible values are those supported on Windows:
22638 Translated text mode
22642 Translated unicode encoding
22644 @item @emph{U16TEXT}
22646 Unicode 16-bit encoding
22648 @item @emph{U8TEXT}
22650 Unicode 8-bit encoding
22653 This encoding is only supported on the Windows platform.
22655 @node Open Modes,Operations on C Streams,File content encoding,The Implementation of Standard I/O
22656 @anchor{gnat_rm/the_implementation_of_standard_i_o open-modes}@anchor{2cc}@anchor{gnat_rm/the_implementation_of_standard_i_o id24}@anchor{2cd}
22657 @section Open Modes
22660 @code{Open} and @code{Create} calls result in a call to @code{fopen}
22661 using the mode shown in the following table:
22664 @multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxx}
22667 @code{Open} and @code{Create} Call Modes
22709 Out_File (Direct_IO)
22721 Out_File (all other cases)
22746 If text file translation is required, then either @code{b} or @code{t}
22747 is added to the mode, depending on the setting of Text. Text file
22748 translation refers to the mapping of CR/LF sequences in an external file
22749 to LF characters internally. This mapping only occurs in DOS and
22750 DOS-like systems, and is not relevant to other systems.
22752 A special case occurs with Stream_IO. As shown in the above table, the
22753 file is initially opened in @code{r} or @code{w} mode for the
22754 @code{In_File} and @code{Out_File} cases. If a @code{Set_Mode} operation
22755 subsequently requires switching from reading to writing or vice-versa,
22756 then the file is reopened in @code{r+} mode to permit the required operation.
22758 @node Operations on C Streams,Interfacing to C Streams,Open Modes,The Implementation of Standard I/O
22759 @anchor{gnat_rm/the_implementation_of_standard_i_o operations-on-c-streams}@anchor{2ce}@anchor{gnat_rm/the_implementation_of_standard_i_o id25}@anchor{2cf}
22760 @section Operations on C Streams
22763 The package @code{Interfaces.C_Streams} provides an Ada program with direct
22764 access to the C library functions for operations on C streams:
22767 package Interfaces.C_Streams is
22768 -- Note: the reason we do not use the types that are in
22769 -- Interfaces.C is that we want to avoid dragging in the
22770 -- code in this unit if possible.
22771 subtype chars is System.Address;
22772 -- Pointer to null-terminated array of characters
22773 subtype FILEs is System.Address;
22774 -- Corresponds to the C type FILE*
22775 subtype voids is System.Address;
22776 -- Corresponds to the C type void*
22777 subtype int is Integer;
22778 subtype long is Long_Integer;
22779 -- Note: the above types are subtypes deliberately, and it
22780 -- is part of this spec that the above correspondences are
22781 -- guaranteed. This means that it is legitimate to, for
22782 -- example, use Integer instead of int. We provide these
22783 -- synonyms for clarity, but in some cases it may be
22784 -- convenient to use the underlying types (for example to
22785 -- avoid an unnecessary dependency of a spec on the spec
22787 type size_t is mod 2 ** Standard'Address_Size;
22788 NULL_Stream : constant FILEs;
22789 -- Value returned (NULL in C) to indicate an
22790 -- fdopen/fopen/tmpfile error
22791 ----------------------------------
22792 -- Constants Defined in stdio.h --
22793 ----------------------------------
22794 EOF : constant int;
22795 -- Used by a number of routines to indicate error or
22797 IOFBF : constant int;
22798 IOLBF : constant int;
22799 IONBF : constant int;
22800 -- Used to indicate buffering mode for setvbuf call
22801 SEEK_CUR : constant int;
22802 SEEK_END : constant int;
22803 SEEK_SET : constant int;
22804 -- Used to indicate origin for fseek call
22805 function stdin return FILEs;
22806 function stdout return FILEs;
22807 function stderr return FILEs;
22808 -- Streams associated with standard files
22809 --------------------------
22810 -- Standard C functions --
22811 --------------------------
22812 -- The functions selected below are ones that are
22813 -- available in UNIX (but not necessarily in ANSI C).
22814 -- These are very thin interfaces
22815 -- which copy exactly the C headers. For more
22816 -- documentation on these functions, see the Microsoft C
22817 -- "Run-Time Library Reference" (Microsoft Press, 1990,
22818 -- ISBN 1-55615-225-6), which includes useful information
22819 -- on system compatibility.
22820 procedure clearerr (stream : FILEs);
22821 function fclose (stream : FILEs) return int;
22822 function fdopen (handle : int; mode : chars) return FILEs;
22823 function feof (stream : FILEs) return int;
22824 function ferror (stream : FILEs) return int;
22825 function fflush (stream : FILEs) return int;
22826 function fgetc (stream : FILEs) return int;
22827 function fgets (strng : chars; n : int; stream : FILEs)
22829 function fileno (stream : FILEs) return int;
22830 function fopen (filename : chars; Mode : chars)
22832 -- Note: to maintain target independence, use
22833 -- text_translation_required, a boolean variable defined in
22834 -- a-sysdep.c to deal with the target dependent text
22835 -- translation requirement. If this variable is set,
22836 -- then b/t should be appended to the standard mode
22837 -- argument to set the text translation mode off or on
22839 function fputc (C : int; stream : FILEs) return int;
22840 function fputs (Strng : chars; Stream : FILEs) return int;
22857 function ftell (stream : FILEs) return long;
22864 function isatty (handle : int) return int;
22865 procedure mktemp (template : chars);
22866 -- The return value (which is just a pointer to template)
22868 procedure rewind (stream : FILEs);
22869 function rmtmp return int;
22877 function tmpfile return FILEs;
22878 function ungetc (c : int; stream : FILEs) return int;
22879 function unlink (filename : chars) return int;
22880 ---------------------
22881 -- Extra functions --
22882 ---------------------
22883 -- These functions supply slightly thicker bindings than
22884 -- those above. They are derived from functions in the
22885 -- C Run-Time Library, but may do a bit more work than
22886 -- just directly calling one of the Library functions.
22887 function is_regular_file (handle : int) return int;
22888 -- Tests if given handle is for a regular file (result 1)
22889 -- or for a non-regular file (pipe or device, result 0).
22890 ---------------------------------
22891 -- Control of Text/Binary Mode --
22892 ---------------------------------
22893 -- If text_translation_required is true, then the following
22894 -- functions may be used to dynamically switch a file from
22895 -- binary to text mode or vice versa. These functions have
22896 -- no effect if text_translation_required is false (i.e., in
22897 -- normal UNIX mode). Use fileno to get a stream handle.
22898 procedure set_binary_mode (handle : int);
22899 procedure set_text_mode (handle : int);
22900 ----------------------------
22901 -- Full Path Name support --
22902 ----------------------------
22903 procedure full_name (nam : chars; buffer : chars);
22904 -- Given a NUL terminated string representing a file
22905 -- name, returns in buffer a NUL terminated string
22906 -- representing the full path name for the file name.
22907 -- On systems where it is relevant the drive is also
22908 -- part of the full path name. It is the responsibility
22909 -- of the caller to pass an actual parameter for buffer
22910 -- that is big enough for any full path name. Use
22911 -- max_path_len given below as the size of buffer.
22912 max_path_len : integer;
22913 -- Maximum length of an allowable full path name on the
22914 -- system, including a terminating NUL character.
22915 end Interfaces.C_Streams;
22918 @node Interfacing to C Streams,,Operations on C Streams,The Implementation of Standard I/O
22919 @anchor{gnat_rm/the_implementation_of_standard_i_o interfacing-to-c-streams}@anchor{2d0}@anchor{gnat_rm/the_implementation_of_standard_i_o id26}@anchor{2d1}
22920 @section Interfacing to C Streams
22923 The packages in this section permit interfacing Ada files to C Stream
22927 with Interfaces.C_Streams;
22928 package Ada.Sequential_IO.C_Streams is
22929 function C_Stream (F : File_Type)
22930 return Interfaces.C_Streams.FILEs;
22932 (File : in out File_Type;
22933 Mode : in File_Mode;
22934 C_Stream : in Interfaces.C_Streams.FILEs;
22935 Form : in String := "");
22936 end Ada.Sequential_IO.C_Streams;
22938 with Interfaces.C_Streams;
22939 package Ada.Direct_IO.C_Streams is
22940 function C_Stream (F : File_Type)
22941 return Interfaces.C_Streams.FILEs;
22943 (File : in out File_Type;
22944 Mode : in File_Mode;
22945 C_Stream : in Interfaces.C_Streams.FILEs;
22946 Form : in String := "");
22947 end Ada.Direct_IO.C_Streams;
22949 with Interfaces.C_Streams;
22950 package Ada.Text_IO.C_Streams is
22951 function C_Stream (F : File_Type)
22952 return Interfaces.C_Streams.FILEs;
22954 (File : in out File_Type;
22955 Mode : in File_Mode;
22956 C_Stream : in Interfaces.C_Streams.FILEs;
22957 Form : in String := "");
22958 end Ada.Text_IO.C_Streams;
22960 with Interfaces.C_Streams;
22961 package Ada.Wide_Text_IO.C_Streams is
22962 function C_Stream (F : File_Type)
22963 return Interfaces.C_Streams.FILEs;
22965 (File : in out File_Type;
22966 Mode : in File_Mode;
22967 C_Stream : in Interfaces.C_Streams.FILEs;
22968 Form : in String := "");
22969 end Ada.Wide_Text_IO.C_Streams;
22971 with Interfaces.C_Streams;
22972 package Ada.Wide_Wide_Text_IO.C_Streams is
22973 function C_Stream (F : File_Type)
22974 return Interfaces.C_Streams.FILEs;
22976 (File : in out File_Type;
22977 Mode : in File_Mode;
22978 C_Stream : in Interfaces.C_Streams.FILEs;
22979 Form : in String := "");
22980 end Ada.Wide_Wide_Text_IO.C_Streams;
22982 with Interfaces.C_Streams;
22983 package Ada.Stream_IO.C_Streams is
22984 function C_Stream (F : File_Type)
22985 return Interfaces.C_Streams.FILEs;
22987 (File : in out File_Type;
22988 Mode : in File_Mode;
22989 C_Stream : in Interfaces.C_Streams.FILEs;
22990 Form : in String := "");
22991 end Ada.Stream_IO.C_Streams;
22994 In each of these six packages, the @code{C_Stream} function obtains the
22995 @code{FILE} pointer from a currently opened Ada file. It is then
22996 possible to use the @code{Interfaces.C_Streams} package to operate on
22997 this stream, or the stream can be passed to a C program which can
22998 operate on it directly. Of course the program is responsible for
22999 ensuring that only appropriate sequences of operations are executed.
23001 One particular use of relevance to an Ada program is that the
23002 @code{setvbuf} function can be used to control the buffering of the
23003 stream used by an Ada file. In the absence of such a call the standard
23004 default buffering is used.
23006 The @code{Open} procedures in these packages open a file giving an
23007 existing C Stream instead of a file name. Typically this stream is
23008 imported from a C program, allowing an Ada file to operate on an
23011 @node The GNAT Library,Interfacing to Other Languages,The Implementation of Standard I/O,Top
23012 @anchor{gnat_rm/the_gnat_library the-gnat-library}@anchor{10}@anchor{gnat_rm/the_gnat_library doc}@anchor{2d2}@anchor{gnat_rm/the_gnat_library id1}@anchor{2d3}
23013 @chapter The GNAT Library
23016 The GNAT library contains a number of general and special purpose packages.
23017 It represents functionality that the GNAT developers have found useful, and
23018 which is made available to GNAT users. The packages described here are fully
23019 supported, and upwards compatibility will be maintained in future releases,
23020 so you can use these facilities with the confidence that the same functionality
23021 will be available in future releases.
23023 The chapter here simply gives a brief summary of the facilities available.
23024 The full documentation is found in the spec file for the package. The full
23025 sources of these library packages, including both spec and body, are provided
23026 with all GNAT releases. For example, to find out the full specifications of
23027 the SPITBOL pattern matching capability, including a full tutorial and
23028 extensive examples, look in the @code{g-spipat.ads} file in the library.
23030 For each entry here, the package name (as it would appear in a @code{with}
23031 clause) is given, followed by the name of the corresponding spec file in
23032 parentheses. The packages are children in four hierarchies, @code{Ada},
23033 @code{Interfaces}, @code{System}, and @code{GNAT}, the latter being a
23034 GNAT-specific hierarchy.
23036 Note that an application program should only use packages in one of these
23037 four hierarchies if the package is defined in the Ada Reference Manual,
23038 or is listed in this section of the GNAT Programmers Reference Manual.
23039 All other units should be considered internal implementation units and
23040 should not be directly @code{with}ed by application code. The use of
23041 a @code{with} clause that references one of these internal implementation
23042 units makes an application potentially dependent on changes in versions
23043 of GNAT, and will generate a warning message.
23046 * Ada.Characters.Latin_9 (a-chlat9.ads): Ada Characters Latin_9 a-chlat9 ads.
23047 * Ada.Characters.Wide_Latin_1 (a-cwila1.ads): Ada Characters Wide_Latin_1 a-cwila1 ads.
23048 * Ada.Characters.Wide_Latin_9 (a-cwila1.ads): Ada Characters Wide_Latin_9 a-cwila1 ads.
23049 * Ada.Characters.Wide_Wide_Latin_1 (a-chzla1.ads): Ada Characters Wide_Wide_Latin_1 a-chzla1 ads.
23050 * Ada.Characters.Wide_Wide_Latin_9 (a-chzla9.ads): Ada Characters Wide_Wide_Latin_9 a-chzla9 ads.
23051 * Ada.Containers.Formal_Doubly_Linked_Lists (a-cfdlli.ads): Ada Containers Formal_Doubly_Linked_Lists a-cfdlli ads.
23052 * Ada.Containers.Formal_Hashed_Maps (a-cfhama.ads): Ada Containers Formal_Hashed_Maps a-cfhama ads.
23053 * Ada.Containers.Formal_Hashed_Sets (a-cfhase.ads): Ada Containers Formal_Hashed_Sets a-cfhase ads.
23054 * Ada.Containers.Formal_Ordered_Maps (a-cforma.ads): Ada Containers Formal_Ordered_Maps a-cforma ads.
23055 * Ada.Containers.Formal_Ordered_Sets (a-cforse.ads): Ada Containers Formal_Ordered_Sets a-cforse ads.
23056 * Ada.Containers.Formal_Vectors (a-cofove.ads): Ada Containers Formal_Vectors a-cofove ads.
23057 * Ada.Containers.Formal_Indefinite_Vectors (a-cfinve.ads): Ada Containers Formal_Indefinite_Vectors a-cfinve ads.
23058 * Ada.Containers.Functional_Vectors (a-cofuve.ads): Ada Containers Functional_Vectors a-cofuve ads.
23059 * Ada.Containers.Functional_Sets (a-cofuse.ads): Ada Containers Functional_Sets a-cofuse ads.
23060 * Ada.Containers.Functional_Maps (a-cofuma.ads): Ada Containers Functional_Maps a-cofuma ads.
23061 * Ada.Containers.Bounded_Holders (a-coboho.ads): Ada Containers Bounded_Holders a-coboho ads.
23062 * Ada.Command_Line.Environment (a-colien.ads): Ada Command_Line Environment a-colien ads.
23063 * Ada.Command_Line.Remove (a-colire.ads): Ada Command_Line Remove a-colire ads.
23064 * Ada.Command_Line.Response_File (a-clrefi.ads): Ada Command_Line Response_File a-clrefi ads.
23065 * Ada.Direct_IO.C_Streams (a-diocst.ads): Ada Direct_IO C_Streams a-diocst ads.
23066 * Ada.Exceptions.Is_Null_Occurrence (a-einuoc.ads): Ada Exceptions Is_Null_Occurrence a-einuoc ads.
23067 * Ada.Exceptions.Last_Chance_Handler (a-elchha.ads): Ada Exceptions Last_Chance_Handler a-elchha ads.
23068 * Ada.Exceptions.Traceback (a-exctra.ads): Ada Exceptions Traceback a-exctra ads.
23069 * Ada.Sequential_IO.C_Streams (a-siocst.ads): Ada Sequential_IO C_Streams a-siocst ads.
23070 * Ada.Streams.Stream_IO.C_Streams (a-ssicst.ads): Ada Streams Stream_IO C_Streams a-ssicst ads.
23071 * Ada.Strings.Unbounded.Text_IO (a-suteio.ads): Ada Strings Unbounded Text_IO a-suteio ads.
23072 * Ada.Strings.Wide_Unbounded.Wide_Text_IO (a-swuwti.ads): Ada Strings Wide_Unbounded Wide_Text_IO a-swuwti ads.
23073 * Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO (a-szuzti.ads): Ada Strings Wide_Wide_Unbounded Wide_Wide_Text_IO a-szuzti ads.
23074 * Ada.Text_IO.C_Streams (a-tiocst.ads): Ada Text_IO C_Streams a-tiocst ads.
23075 * Ada.Text_IO.Reset_Standard_Files (a-tirsfi.ads): Ada Text_IO Reset_Standard_Files a-tirsfi ads.
23076 * Ada.Wide_Characters.Unicode (a-wichun.ads): Ada Wide_Characters Unicode a-wichun ads.
23077 * Ada.Wide_Text_IO.C_Streams (a-wtcstr.ads): Ada Wide_Text_IO C_Streams a-wtcstr ads.
23078 * Ada.Wide_Text_IO.Reset_Standard_Files (a-wrstfi.ads): Ada Wide_Text_IO Reset_Standard_Files a-wrstfi ads.
23079 * Ada.Wide_Wide_Characters.Unicode (a-zchuni.ads): Ada Wide_Wide_Characters Unicode a-zchuni ads.
23080 * Ada.Wide_Wide_Text_IO.C_Streams (a-ztcstr.ads): Ada Wide_Wide_Text_IO C_Streams a-ztcstr ads.
23081 * Ada.Wide_Wide_Text_IO.Reset_Standard_Files (a-zrstfi.ads): Ada Wide_Wide_Text_IO Reset_Standard_Files a-zrstfi ads.
23082 * GNAT.Altivec (g-altive.ads): GNAT Altivec g-altive ads.
23083 * GNAT.Altivec.Conversions (g-altcon.ads): GNAT Altivec Conversions g-altcon ads.
23084 * GNAT.Altivec.Vector_Operations (g-alveop.ads): GNAT Altivec Vector_Operations g-alveop ads.
23085 * GNAT.Altivec.Vector_Types (g-alvety.ads): GNAT Altivec Vector_Types g-alvety ads.
23086 * GNAT.Altivec.Vector_Views (g-alvevi.ads): GNAT Altivec Vector_Views g-alvevi ads.
23087 * GNAT.Array_Split (g-arrspl.ads): GNAT Array_Split g-arrspl ads.
23088 * GNAT.AWK (g-awk.ads): GNAT AWK g-awk ads.
23089 * GNAT.Bind_Environment (g-binenv.ads): GNAT Bind_Environment g-binenv ads.
23090 * GNAT.Branch_Prediction (g-brapre.ads): GNAT Branch_Prediction g-brapre ads.
23091 * GNAT.Bounded_Buffers (g-boubuf.ads): GNAT Bounded_Buffers g-boubuf ads.
23092 * GNAT.Bounded_Mailboxes (g-boumai.ads): GNAT Bounded_Mailboxes g-boumai ads.
23093 * GNAT.Bubble_Sort (g-bubsor.ads): GNAT Bubble_Sort g-bubsor ads.
23094 * GNAT.Bubble_Sort_A (g-busora.ads): GNAT Bubble_Sort_A g-busora ads.
23095 * GNAT.Bubble_Sort_G (g-busorg.ads): GNAT Bubble_Sort_G g-busorg ads.
23096 * GNAT.Byte_Order_Mark (g-byorma.ads): GNAT Byte_Order_Mark g-byorma ads.
23097 * GNAT.Byte_Swapping (g-bytswa.ads): GNAT Byte_Swapping g-bytswa ads.
23098 * GNAT.Calendar (g-calend.ads): GNAT Calendar g-calend ads.
23099 * GNAT.Calendar.Time_IO (g-catiio.ads): GNAT Calendar Time_IO g-catiio ads.
23100 * GNAT.CRC32 (g-crc32.ads): GNAT CRC32 g-crc32 ads.
23101 * GNAT.Case_Util (g-casuti.ads): GNAT Case_Util g-casuti ads.
23102 * GNAT.CGI (g-cgi.ads): GNAT CGI g-cgi ads.
23103 * GNAT.CGI.Cookie (g-cgicoo.ads): GNAT CGI Cookie g-cgicoo ads.
23104 * GNAT.CGI.Debug (g-cgideb.ads): GNAT CGI Debug g-cgideb ads.
23105 * GNAT.Command_Line (g-comlin.ads): GNAT Command_Line g-comlin ads.
23106 * GNAT.Compiler_Version (g-comver.ads): GNAT Compiler_Version g-comver ads.
23107 * GNAT.Ctrl_C (g-ctrl_c.ads): GNAT Ctrl_C g-ctrl_c ads.
23108 * GNAT.Current_Exception (g-curexc.ads): GNAT Current_Exception g-curexc ads.
23109 * GNAT.Debug_Pools (g-debpoo.ads): GNAT Debug_Pools g-debpoo ads.
23110 * GNAT.Debug_Utilities (g-debuti.ads): GNAT Debug_Utilities g-debuti ads.
23111 * GNAT.Decode_String (g-decstr.ads): GNAT Decode_String g-decstr ads.
23112 * GNAT.Decode_UTF8_String (g-deutst.ads): GNAT Decode_UTF8_String g-deutst ads.
23113 * GNAT.Directory_Operations (g-dirope.ads): GNAT Directory_Operations g-dirope ads.
23114 * GNAT.Directory_Operations.Iteration (g-diopit.ads): GNAT Directory_Operations Iteration g-diopit ads.
23115 * GNAT.Dynamic_HTables (g-dynhta.ads): GNAT Dynamic_HTables g-dynhta ads.
23116 * GNAT.Dynamic_Tables (g-dyntab.ads): GNAT Dynamic_Tables g-dyntab ads.
23117 * GNAT.Encode_String (g-encstr.ads): GNAT Encode_String g-encstr ads.
23118 * GNAT.Encode_UTF8_String (g-enutst.ads): GNAT Encode_UTF8_String g-enutst ads.
23119 * GNAT.Exception_Actions (g-excact.ads): GNAT Exception_Actions g-excact ads.
23120 * GNAT.Exception_Traces (g-exctra.ads): GNAT Exception_Traces g-exctra ads.
23121 * GNAT.Exceptions (g-except.ads): GNAT Exceptions g-except ads.
23122 * GNAT.Expect (g-expect.ads): GNAT Expect g-expect ads.
23123 * GNAT.Expect.TTY (g-exptty.ads): GNAT Expect TTY g-exptty ads.
23124 * GNAT.Float_Control (g-flocon.ads): GNAT Float_Control g-flocon ads.
23125 * GNAT.Formatted_String (g-forstr.ads): GNAT Formatted_String g-forstr ads.
23126 * GNAT.Heap_Sort (g-heasor.ads): GNAT Heap_Sort g-heasor ads.
23127 * GNAT.Heap_Sort_A (g-hesora.ads): GNAT Heap_Sort_A g-hesora ads.
23128 * GNAT.Heap_Sort_G (g-hesorg.ads): GNAT Heap_Sort_G g-hesorg ads.
23129 * GNAT.HTable (g-htable.ads): GNAT HTable g-htable ads.
23130 * GNAT.IO (g-io.ads): GNAT IO g-io ads.
23131 * GNAT.IO_Aux (g-io_aux.ads): GNAT IO_Aux g-io_aux ads.
23132 * GNAT.Lock_Files (g-locfil.ads): GNAT Lock_Files g-locfil ads.
23133 * GNAT.MBBS_Discrete_Random (g-mbdira.ads): GNAT MBBS_Discrete_Random g-mbdira ads.
23134 * GNAT.MBBS_Float_Random (g-mbflra.ads): GNAT MBBS_Float_Random g-mbflra ads.
23135 * GNAT.MD5 (g-md5.ads): GNAT MD5 g-md5 ads.
23136 * GNAT.Memory_Dump (g-memdum.ads): GNAT Memory_Dump g-memdum ads.
23137 * GNAT.Most_Recent_Exception (g-moreex.ads): GNAT Most_Recent_Exception g-moreex ads.
23138 * GNAT.OS_Lib (g-os_lib.ads): GNAT OS_Lib g-os_lib ads.
23139 * GNAT.Perfect_Hash_Generators (g-pehage.ads): GNAT Perfect_Hash_Generators g-pehage ads.
23140 * GNAT.Random_Numbers (g-rannum.ads): GNAT Random_Numbers g-rannum ads.
23141 * GNAT.Regexp (g-regexp.ads): GNAT Regexp g-regexp ads.
23142 * GNAT.Registry (g-regist.ads): GNAT Registry g-regist ads.
23143 * GNAT.Regpat (g-regpat.ads): GNAT Regpat g-regpat ads.
23144 * GNAT.Rewrite_Data (g-rewdat.ads): GNAT Rewrite_Data g-rewdat ads.
23145 * GNAT.Secondary_Stack_Info (g-sestin.ads): GNAT Secondary_Stack_Info g-sestin ads.
23146 * GNAT.Semaphores (g-semaph.ads): GNAT Semaphores g-semaph ads.
23147 * GNAT.Serial_Communications (g-sercom.ads): GNAT Serial_Communications g-sercom ads.
23148 * GNAT.SHA1 (g-sha1.ads): GNAT SHA1 g-sha1 ads.
23149 * GNAT.SHA224 (g-sha224.ads): GNAT SHA224 g-sha224 ads.
23150 * GNAT.SHA256 (g-sha256.ads): GNAT SHA256 g-sha256 ads.
23151 * GNAT.SHA384 (g-sha384.ads): GNAT SHA384 g-sha384 ads.
23152 * GNAT.SHA512 (g-sha512.ads): GNAT SHA512 g-sha512 ads.
23153 * GNAT.Signals (g-signal.ads): GNAT Signals g-signal ads.
23154 * GNAT.Sockets (g-socket.ads): GNAT Sockets g-socket ads.
23155 * GNAT.Source_Info (g-souinf.ads): GNAT Source_Info g-souinf ads.
23156 * GNAT.Spelling_Checker (g-speche.ads): GNAT Spelling_Checker g-speche ads.
23157 * GNAT.Spelling_Checker_Generic (g-spchge.ads): GNAT Spelling_Checker_Generic g-spchge ads.
23158 * GNAT.Spitbol.Patterns (g-spipat.ads): GNAT Spitbol Patterns g-spipat ads.
23159 * GNAT.Spitbol (g-spitbo.ads): GNAT Spitbol g-spitbo ads.
23160 * GNAT.Spitbol.Table_Boolean (g-sptabo.ads): GNAT Spitbol Table_Boolean g-sptabo ads.
23161 * GNAT.Spitbol.Table_Integer (g-sptain.ads): GNAT Spitbol Table_Integer g-sptain ads.
23162 * GNAT.Spitbol.Table_VString (g-sptavs.ads): GNAT Spitbol Table_VString g-sptavs ads.
23163 * GNAT.SSE (g-sse.ads): GNAT SSE g-sse ads.
23164 * GNAT.SSE.Vector_Types (g-ssvety.ads): GNAT SSE Vector_Types g-ssvety ads.
23165 * GNAT.String_Hash (g-strhas.ads): GNAT String_Hash g-strhas ads.
23166 * GNAT.Strings (g-string.ads): GNAT Strings g-string ads.
23167 * GNAT.String_Split (g-strspl.ads): GNAT String_Split g-strspl ads.
23168 * GNAT.Table (g-table.ads): GNAT Table g-table ads.
23169 * GNAT.Task_Lock (g-tasloc.ads): GNAT Task_Lock g-tasloc ads.
23170 * GNAT.Time_Stamp (g-timsta.ads): GNAT Time_Stamp g-timsta ads.
23171 * GNAT.Threads (g-thread.ads): GNAT Threads g-thread ads.
23172 * GNAT.Traceback (g-traceb.ads): GNAT Traceback g-traceb ads.
23173 * GNAT.Traceback.Symbolic (g-trasym.ads): GNAT Traceback Symbolic g-trasym ads.
23174 * GNAT.UTF_32 (g-table.ads): GNAT UTF_32 g-table ads.
23175 * GNAT.Wide_Spelling_Checker (g-u3spch.ads): GNAT Wide_Spelling_Checker g-u3spch ads.
23176 * GNAT.Wide_Spelling_Checker (g-wispch.ads): GNAT Wide_Spelling_Checker g-wispch ads.
23177 * GNAT.Wide_String_Split (g-wistsp.ads): GNAT Wide_String_Split g-wistsp ads.
23178 * GNAT.Wide_Wide_Spelling_Checker (g-zspche.ads): GNAT Wide_Wide_Spelling_Checker g-zspche ads.
23179 * GNAT.Wide_Wide_String_Split (g-zistsp.ads): GNAT Wide_Wide_String_Split g-zistsp ads.
23180 * Interfaces.C.Extensions (i-cexten.ads): Interfaces C Extensions i-cexten ads.
23181 * Interfaces.C.Streams (i-cstrea.ads): Interfaces C Streams i-cstrea ads.
23182 * Interfaces.Packed_Decimal (i-pacdec.ads): Interfaces Packed_Decimal i-pacdec ads.
23183 * Interfaces.VxWorks (i-vxwork.ads): Interfaces VxWorks i-vxwork ads.
23184 * Interfaces.VxWorks.Int_Connection (i-vxinco.ads): Interfaces VxWorks Int_Connection i-vxinco ads.
23185 * Interfaces.VxWorks.IO (i-vxwoio.ads): Interfaces VxWorks IO i-vxwoio ads.
23186 * System.Address_Image (s-addima.ads): System Address_Image s-addima ads.
23187 * System.Assertions (s-assert.ads): System Assertions s-assert ads.
23188 * System.Atomic_Counters (s-atocou.ads): System Atomic_Counters s-atocou ads.
23189 * System.Memory (s-memory.ads): System Memory s-memory ads.
23190 * System.Multiprocessors (s-multip.ads): System Multiprocessors s-multip ads.
23191 * System.Multiprocessors.Dispatching_Domains (s-mudido.ads): System Multiprocessors Dispatching_Domains s-mudido ads.
23192 * System.Partition_Interface (s-parint.ads): System Partition_Interface s-parint ads.
23193 * System.Pool_Global (s-pooglo.ads): System Pool_Global s-pooglo ads.
23194 * System.Pool_Local (s-pooloc.ads): System Pool_Local s-pooloc ads.
23195 * System.Restrictions (s-restri.ads): System Restrictions s-restri ads.
23196 * System.Rident (s-rident.ads): System Rident s-rident ads.
23197 * System.Strings.Stream_Ops (s-ststop.ads): System Strings Stream_Ops s-ststop ads.
23198 * System.Unsigned_Types (s-unstyp.ads): System Unsigned_Types s-unstyp ads.
23199 * System.Wch_Cnv (s-wchcnv.ads): System Wch_Cnv s-wchcnv ads.
23200 * System.Wch_Con (s-wchcon.ads): System Wch_Con s-wchcon ads.
23204 @node Ada Characters Latin_9 a-chlat9 ads,Ada Characters Wide_Latin_1 a-cwila1 ads,,The GNAT Library
23205 @anchor{gnat_rm/the_gnat_library id2}@anchor{2d4}@anchor{gnat_rm/the_gnat_library ada-characters-latin-9-a-chlat9-ads}@anchor{2d5}
23206 @section @code{Ada.Characters.Latin_9} (@code{a-chlat9.ads})
23209 @geindex Ada.Characters.Latin_9 (a-chlat9.ads)
23211 @geindex Latin_9 constants for Character
23213 This child of @code{Ada.Characters}
23214 provides a set of definitions corresponding to those in the
23215 RM-defined package @code{Ada.Characters.Latin_1} but with the
23216 few modifications required for @code{Latin-9}
23217 The provision of such a package
23218 is specifically authorized by the Ada Reference Manual
23221 @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
23222 @anchor{gnat_rm/the_gnat_library ada-characters-wide-latin-1-a-cwila1-ads}@anchor{2d6}@anchor{gnat_rm/the_gnat_library id3}@anchor{2d7}
23223 @section @code{Ada.Characters.Wide_Latin_1} (@code{a-cwila1.ads})
23226 @geindex Ada.Characters.Wide_Latin_1 (a-cwila1.ads)
23228 @geindex Latin_1 constants for Wide_Character
23230 This child of @code{Ada.Characters}
23231 provides a set of definitions corresponding to those in the
23232 RM-defined package @code{Ada.Characters.Latin_1} but with the
23233 types of the constants being @code{Wide_Character}
23234 instead of @code{Character}. The provision of such a package
23235 is specifically authorized by the Ada Reference Manual
23238 @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
23239 @anchor{gnat_rm/the_gnat_library id4}@anchor{2d8}@anchor{gnat_rm/the_gnat_library ada-characters-wide-latin-9-a-cwila1-ads}@anchor{2d9}
23240 @section @code{Ada.Characters.Wide_Latin_9} (@code{a-cwila1.ads})
23243 @geindex Ada.Characters.Wide_Latin_9 (a-cwila1.ads)
23245 @geindex Latin_9 constants for Wide_Character
23247 This child of @code{Ada.Characters}
23248 provides a set of definitions corresponding to those in the
23249 GNAT defined package @code{Ada.Characters.Latin_9} but with the
23250 types of the constants being @code{Wide_Character}
23251 instead of @code{Character}. The provision of such a package
23252 is specifically authorized by the Ada Reference Manual
23255 @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
23256 @anchor{gnat_rm/the_gnat_library ada-characters-wide-wide-latin-1-a-chzla1-ads}@anchor{2da}@anchor{gnat_rm/the_gnat_library id5}@anchor{2db}
23257 @section @code{Ada.Characters.Wide_Wide_Latin_1} (@code{a-chzla1.ads})
23260 @geindex Ada.Characters.Wide_Wide_Latin_1 (a-chzla1.ads)
23262 @geindex Latin_1 constants for Wide_Wide_Character
23264 This child of @code{Ada.Characters}
23265 provides a set of definitions corresponding to those in the
23266 RM-defined package @code{Ada.Characters.Latin_1} but with the
23267 types of the constants being @code{Wide_Wide_Character}
23268 instead of @code{Character}. The provision of such a package
23269 is specifically authorized by the Ada Reference Manual
23272 @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
23273 @anchor{gnat_rm/the_gnat_library ada-characters-wide-wide-latin-9-a-chzla9-ads}@anchor{2dc}@anchor{gnat_rm/the_gnat_library id6}@anchor{2dd}
23274 @section @code{Ada.Characters.Wide_Wide_Latin_9} (@code{a-chzla9.ads})
23277 @geindex Ada.Characters.Wide_Wide_Latin_9 (a-chzla9.ads)
23279 @geindex Latin_9 constants for Wide_Wide_Character
23281 This child of @code{Ada.Characters}
23282 provides a set of definitions corresponding to those in the
23283 GNAT defined package @code{Ada.Characters.Latin_9} but with the
23284 types of the constants being @code{Wide_Wide_Character}
23285 instead of @code{Character}. The provision of such a package
23286 is specifically authorized by the Ada Reference Manual
23289 @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
23290 @anchor{gnat_rm/the_gnat_library id7}@anchor{2de}@anchor{gnat_rm/the_gnat_library ada-containers-formal-doubly-linked-lists-a-cfdlli-ads}@anchor{2df}
23291 @section @code{Ada.Containers.Formal_Doubly_Linked_Lists} (@code{a-cfdlli.ads})
23294 @geindex Ada.Containers.Formal_Doubly_Linked_Lists (a-cfdlli.ads)
23296 @geindex Formal container for doubly linked lists
23298 This child of @code{Ada.Containers} defines a modified version of the
23299 Ada 2005 container for doubly linked lists, meant to facilitate formal
23300 verification of code using such containers. The specification of this
23301 unit is compatible with SPARK 2014.
23303 Note that although this container was designed with formal verification
23304 in mind, it may well be generally useful in that it is a simplified more
23305 efficient version than the one defined in the standard. In particular it
23306 does not have the complex overhead required to detect cursor tampering.
23308 @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
23309 @anchor{gnat_rm/the_gnat_library id8}@anchor{2e0}@anchor{gnat_rm/the_gnat_library ada-containers-formal-hashed-maps-a-cfhama-ads}@anchor{2e1}
23310 @section @code{Ada.Containers.Formal_Hashed_Maps} (@code{a-cfhama.ads})
23313 @geindex Ada.Containers.Formal_Hashed_Maps (a-cfhama.ads)
23315 @geindex Formal container for hashed maps
23317 This child of @code{Ada.Containers} defines a modified version of the
23318 Ada 2005 container for hashed maps, meant to facilitate formal
23319 verification of code using such containers. The specification of this
23320 unit is compatible with SPARK 2014.
23322 Note that although this container was designed with formal verification
23323 in mind, it may well be generally useful in that it is a simplified more
23324 efficient version than the one defined in the standard. In particular it
23325 does not have the complex overhead required to detect cursor tampering.
23327 @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
23328 @anchor{gnat_rm/the_gnat_library id9}@anchor{2e2}@anchor{gnat_rm/the_gnat_library ada-containers-formal-hashed-sets-a-cfhase-ads}@anchor{2e3}
23329 @section @code{Ada.Containers.Formal_Hashed_Sets} (@code{a-cfhase.ads})
23332 @geindex Ada.Containers.Formal_Hashed_Sets (a-cfhase.ads)
23334 @geindex Formal container for hashed sets
23336 This child of @code{Ada.Containers} defines a modified version of the
23337 Ada 2005 container for hashed sets, meant to facilitate formal
23338 verification of code using such containers. The specification of this
23339 unit is compatible with SPARK 2014.
23341 Note that although this container was designed with formal verification
23342 in mind, it may well be generally useful in that it is a simplified more
23343 efficient version than the one defined in the standard. In particular it
23344 does not have the complex overhead required to detect cursor tampering.
23346 @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
23347 @anchor{gnat_rm/the_gnat_library id10}@anchor{2e4}@anchor{gnat_rm/the_gnat_library ada-containers-formal-ordered-maps-a-cforma-ads}@anchor{2e5}
23348 @section @code{Ada.Containers.Formal_Ordered_Maps} (@code{a-cforma.ads})
23351 @geindex Ada.Containers.Formal_Ordered_Maps (a-cforma.ads)
23353 @geindex Formal container for ordered maps
23355 This child of @code{Ada.Containers} defines a modified version of the
23356 Ada 2005 container for ordered maps, meant to facilitate formal
23357 verification of code using such containers. The specification of this
23358 unit is compatible with SPARK 2014.
23360 Note that although this container was designed with formal verification
23361 in mind, it may well be generally useful in that it is a simplified more
23362 efficient version than the one defined in the standard. In particular it
23363 does not have the complex overhead required to detect cursor tampering.
23365 @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
23366 @anchor{gnat_rm/the_gnat_library ada-containers-formal-ordered-sets-a-cforse-ads}@anchor{2e6}@anchor{gnat_rm/the_gnat_library id11}@anchor{2e7}
23367 @section @code{Ada.Containers.Formal_Ordered_Sets} (@code{a-cforse.ads})
23370 @geindex Ada.Containers.Formal_Ordered_Sets (a-cforse.ads)
23372 @geindex Formal container for ordered sets
23374 This child of @code{Ada.Containers} defines a modified version of the
23375 Ada 2005 container for ordered sets, meant to facilitate formal
23376 verification of code using such containers. The specification of this
23377 unit is compatible with SPARK 2014.
23379 Note that although this container was designed with formal verification
23380 in mind, it may well be generally useful in that it is a simplified more
23381 efficient version than the one defined in the standard. In particular it
23382 does not have the complex overhead required to detect cursor tampering.
23384 @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
23385 @anchor{gnat_rm/the_gnat_library id12}@anchor{2e8}@anchor{gnat_rm/the_gnat_library ada-containers-formal-vectors-a-cofove-ads}@anchor{2e9}
23386 @section @code{Ada.Containers.Formal_Vectors} (@code{a-cofove.ads})
23389 @geindex Ada.Containers.Formal_Vectors (a-cofove.ads)
23391 @geindex Formal container for vectors
23393 This child of @code{Ada.Containers} defines a modified version of the
23394 Ada 2005 container for vectors, meant to facilitate formal
23395 verification of code using such containers. The specification of this
23396 unit is compatible with SPARK 2014.
23398 Note that although this container was designed with formal verification
23399 in mind, it may well be generally useful in that it is a simplified more
23400 efficient version than the one defined in the standard. In particular it
23401 does not have the complex overhead required to detect cursor tampering.
23403 @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
23404 @anchor{gnat_rm/the_gnat_library id13}@anchor{2ea}@anchor{gnat_rm/the_gnat_library ada-containers-formal-indefinite-vectors-a-cfinve-ads}@anchor{2eb}
23405 @section @code{Ada.Containers.Formal_Indefinite_Vectors} (@code{a-cfinve.ads})
23408 @geindex Ada.Containers.Formal_Indefinite_Vectors (a-cfinve.ads)
23410 @geindex Formal container for vectors
23412 This child of @code{Ada.Containers} defines a modified version of the
23413 Ada 2005 container for vectors of indefinite elements, meant to
23414 facilitate formal verification of code using such containers. The
23415 specification of this unit is compatible with SPARK 2014.
23417 Note that although this container was designed with formal verification
23418 in mind, it may well be generally useful in that it is a simplified more
23419 efficient version than the one defined in the standard. In particular it
23420 does not have the complex overhead required to detect cursor tampering.
23422 @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
23423 @anchor{gnat_rm/the_gnat_library id14}@anchor{2ec}@anchor{gnat_rm/the_gnat_library ada-containers-functional-vectors-a-cofuve-ads}@anchor{2ed}
23424 @section @code{Ada.Containers.Functional_Vectors} (@code{a-cofuve.ads})
23427 @geindex Ada.Containers.Functional_Vectors (a-cofuve.ads)
23429 @geindex Functional vectors
23431 This child of @code{Ada.Containers} defines immutable vectors. These
23432 containers are unbounded and may contain indefinite elements. Furthermore, to
23433 be usable in every context, they are neither controlled nor limited. As they
23434 are functional, that is, no primitives are provided which would allow modifying
23435 an existing container, these containers can still be used safely.
23437 Their API features functions creating new containers from existing ones.
23438 As a consequence, these containers are highly inefficient. They are also
23439 memory consuming, as the allocated memory is not reclaimed when the container
23440 is no longer referenced. Thus, they should in general be used in ghost code
23441 and annotations, so that they can be removed from the final executable. The
23442 specification of this unit is compatible with SPARK 2014.
23444 @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
23445 @anchor{gnat_rm/the_gnat_library ada-containers-functional-sets-a-cofuse-ads}@anchor{2ee}@anchor{gnat_rm/the_gnat_library id15}@anchor{2ef}
23446 @section @code{Ada.Containers.Functional_Sets} (@code{a-cofuse.ads})
23449 @geindex Ada.Containers.Functional_Sets (a-cofuse.ads)
23451 @geindex Functional sets
23453 This child of @code{Ada.Containers} defines immutable sets. These containers are
23454 unbounded and may contain indefinite elements. Furthermore, to be usable in
23455 every context, they are neither controlled nor limited. As they are functional,
23456 that is, no primitives are provided which would allow modifying an existing
23457 container, these containers can still be used safely.
23459 Their API features functions creating new containers from existing ones.
23460 As a consequence, these containers are highly inefficient. They are also
23461 memory consuming, as the allocated memory is not reclaimed when the container
23462 is no longer referenced. Thus, they should in general be used in ghost code
23463 and annotations, so that they can be removed from the final executable. The
23464 specification of this unit is compatible with SPARK 2014.
23466 @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
23467 @anchor{gnat_rm/the_gnat_library id16}@anchor{2f0}@anchor{gnat_rm/the_gnat_library ada-containers-functional-maps-a-cofuma-ads}@anchor{2f1}
23468 @section @code{Ada.Containers.Functional_Maps} (@code{a-cofuma.ads})
23471 @geindex Ada.Containers.Functional_Maps (a-cofuma.ads)
23473 @geindex Functional maps
23475 This child of @code{Ada.Containers} defines immutable maps. These containers are
23476 unbounded and may contain indefinite elements. Furthermore, to be usable in
23477 every context, they are neither controlled nor limited. As they are functional,
23478 that is, no primitives are provided which would allow modifying an existing
23479 container, these containers can still be used safely.
23481 Their API features functions creating new containers from existing ones.
23482 As a consequence, these containers are highly inefficient. They are also
23483 memory consuming, as the allocated memory is not reclaimed when the container
23484 is no longer referenced. Thus, they should in general be used in ghost code
23485 and annotations, so that they can be removed from the final executable. The
23486 specification of this unit is compatible with SPARK 2014.
23488 @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
23489 @anchor{gnat_rm/the_gnat_library ada-containers-bounded-holders-a-coboho-ads}@anchor{2f2}@anchor{gnat_rm/the_gnat_library id17}@anchor{2f3}
23490 @section @code{Ada.Containers.Bounded_Holders} (@code{a-coboho.ads})
23493 @geindex Ada.Containers.Bounded_Holders (a-coboho.ads)
23495 @geindex Formal container for vectors
23497 This child of @code{Ada.Containers} defines a modified version of
23498 Indefinite_Holders that avoids heap allocation.
23500 @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
23501 @anchor{gnat_rm/the_gnat_library ada-command-line-environment-a-colien-ads}@anchor{2f4}@anchor{gnat_rm/the_gnat_library id18}@anchor{2f5}
23502 @section @code{Ada.Command_Line.Environment} (@code{a-colien.ads})
23505 @geindex Ada.Command_Line.Environment (a-colien.ads)
23507 @geindex Environment entries
23509 This child of @code{Ada.Command_Line}
23510 provides a mechanism for obtaining environment values on systems
23511 where this concept makes sense.
23513 @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
23514 @anchor{gnat_rm/the_gnat_library id19}@anchor{2f6}@anchor{gnat_rm/the_gnat_library ada-command-line-remove-a-colire-ads}@anchor{2f7}
23515 @section @code{Ada.Command_Line.Remove} (@code{a-colire.ads})
23518 @geindex Ada.Command_Line.Remove (a-colire.ads)
23520 @geindex Removing command line arguments
23522 @geindex Command line
23523 @geindex argument removal
23525 This child of @code{Ada.Command_Line}
23526 provides a mechanism for logically removing
23527 arguments from the argument list. Once removed, an argument is not visible
23528 to further calls on the subprograms in @code{Ada.Command_Line} will not
23529 see the removed argument.
23531 @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
23532 @anchor{gnat_rm/the_gnat_library id20}@anchor{2f8}@anchor{gnat_rm/the_gnat_library ada-command-line-response-file-a-clrefi-ads}@anchor{2f9}
23533 @section @code{Ada.Command_Line.Response_File} (@code{a-clrefi.ads})
23536 @geindex Ada.Command_Line.Response_File (a-clrefi.ads)
23538 @geindex Response file for command line
23540 @geindex Command line
23541 @geindex response file
23543 @geindex Command line
23544 @geindex handling long command lines
23546 This child of @code{Ada.Command_Line} provides a mechanism facilities for
23547 getting command line arguments from a text file, called a "response file".
23548 Using a response file allow passing a set of arguments to an executable longer
23549 than the maximum allowed by the system on the command line.
23551 @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
23552 @anchor{gnat_rm/the_gnat_library id21}@anchor{2fa}@anchor{gnat_rm/the_gnat_library ada-direct-io-c-streams-a-diocst-ads}@anchor{2fb}
23553 @section @code{Ada.Direct_IO.C_Streams} (@code{a-diocst.ads})
23556 @geindex Ada.Direct_IO.C_Streams (a-diocst.ads)
23559 @geindex Interfacing with Direct_IO
23561 This package provides subprograms that allow interfacing between
23562 C streams and @code{Direct_IO}. The stream identifier can be
23563 extracted from a file opened on the Ada side, and an Ada file
23564 can be constructed from a stream opened on the C side.
23566 @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
23567 @anchor{gnat_rm/the_gnat_library id22}@anchor{2fc}@anchor{gnat_rm/the_gnat_library ada-exceptions-is-null-occurrence-a-einuoc-ads}@anchor{2fd}
23568 @section @code{Ada.Exceptions.Is_Null_Occurrence} (@code{a-einuoc.ads})
23571 @geindex Ada.Exceptions.Is_Null_Occurrence (a-einuoc.ads)
23573 @geindex Null_Occurrence
23574 @geindex testing for
23576 This child subprogram provides a way of testing for the null
23577 exception occurrence (@code{Null_Occurrence}) without raising
23580 @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
23581 @anchor{gnat_rm/the_gnat_library id23}@anchor{2fe}@anchor{gnat_rm/the_gnat_library ada-exceptions-last-chance-handler-a-elchha-ads}@anchor{2ff}
23582 @section @code{Ada.Exceptions.Last_Chance_Handler} (@code{a-elchha.ads})
23585 @geindex Ada.Exceptions.Last_Chance_Handler (a-elchha.ads)
23587 @geindex Null_Occurrence
23588 @geindex testing for
23590 This child subprogram is used for handling otherwise unhandled
23591 exceptions (hence the name last chance), and perform clean ups before
23592 terminating the program. Note that this subprogram never returns.
23594 @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
23595 @anchor{gnat_rm/the_gnat_library ada-exceptions-traceback-a-exctra-ads}@anchor{300}@anchor{gnat_rm/the_gnat_library id24}@anchor{301}
23596 @section @code{Ada.Exceptions.Traceback} (@code{a-exctra.ads})
23599 @geindex Ada.Exceptions.Traceback (a-exctra.ads)
23601 @geindex Traceback for Exception Occurrence
23603 This child package provides the subprogram (@code{Tracebacks}) to
23604 give a traceback array of addresses based on an exception
23607 @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
23608 @anchor{gnat_rm/the_gnat_library ada-sequential-io-c-streams-a-siocst-ads}@anchor{302}@anchor{gnat_rm/the_gnat_library id25}@anchor{303}
23609 @section @code{Ada.Sequential_IO.C_Streams} (@code{a-siocst.ads})
23612 @geindex Ada.Sequential_IO.C_Streams (a-siocst.ads)
23615 @geindex Interfacing with Sequential_IO
23617 This package provides subprograms that allow interfacing between
23618 C streams and @code{Sequential_IO}. The stream identifier can be
23619 extracted from a file opened on the Ada side, and an Ada file
23620 can be constructed from a stream opened on the C side.
23622 @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
23623 @anchor{gnat_rm/the_gnat_library id26}@anchor{304}@anchor{gnat_rm/the_gnat_library ada-streams-stream-io-c-streams-a-ssicst-ads}@anchor{305}
23624 @section @code{Ada.Streams.Stream_IO.C_Streams} (@code{a-ssicst.ads})
23627 @geindex Ada.Streams.Stream_IO.C_Streams (a-ssicst.ads)
23630 @geindex Interfacing with Stream_IO
23632 This package provides subprograms that allow interfacing between
23633 C streams and @code{Stream_IO}. The stream identifier can be
23634 extracted from a file opened on the Ada side, and an Ada file
23635 can be constructed from a stream opened on the C side.
23637 @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
23638 @anchor{gnat_rm/the_gnat_library ada-strings-unbounded-text-io-a-suteio-ads}@anchor{306}@anchor{gnat_rm/the_gnat_library id27}@anchor{307}
23639 @section @code{Ada.Strings.Unbounded.Text_IO} (@code{a-suteio.ads})
23642 @geindex Ada.Strings.Unbounded.Text_IO (a-suteio.ads)
23644 @geindex Unbounded_String
23645 @geindex IO support
23648 @geindex extensions for unbounded strings
23650 This package provides subprograms for Text_IO for unbounded
23651 strings, avoiding the necessity for an intermediate operation
23652 with ordinary strings.
23654 @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
23655 @anchor{gnat_rm/the_gnat_library id28}@anchor{308}@anchor{gnat_rm/the_gnat_library ada-strings-wide-unbounded-wide-text-io-a-swuwti-ads}@anchor{309}
23656 @section @code{Ada.Strings.Wide_Unbounded.Wide_Text_IO} (@code{a-swuwti.ads})
23659 @geindex Ada.Strings.Wide_Unbounded.Wide_Text_IO (a-swuwti.ads)
23661 @geindex Unbounded_Wide_String
23662 @geindex IO support
23665 @geindex extensions for unbounded wide strings
23667 This package provides subprograms for Text_IO for unbounded
23668 wide strings, avoiding the necessity for an intermediate operation
23669 with ordinary wide strings.
23671 @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
23672 @anchor{gnat_rm/the_gnat_library id29}@anchor{30a}@anchor{gnat_rm/the_gnat_library ada-strings-wide-wide-unbounded-wide-wide-text-io-a-szuzti-ads}@anchor{30b}
23673 @section @code{Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO} (@code{a-szuzti.ads})
23676 @geindex Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO (a-szuzti.ads)
23678 @geindex Unbounded_Wide_Wide_String
23679 @geindex IO support
23682 @geindex extensions for unbounded wide wide strings
23684 This package provides subprograms for Text_IO for unbounded
23685 wide wide strings, avoiding the necessity for an intermediate operation
23686 with ordinary wide wide strings.
23688 @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
23689 @anchor{gnat_rm/the_gnat_library ada-text-io-c-streams-a-tiocst-ads}@anchor{30c}@anchor{gnat_rm/the_gnat_library id30}@anchor{30d}
23690 @section @code{Ada.Text_IO.C_Streams} (@code{a-tiocst.ads})
23693 @geindex Ada.Text_IO.C_Streams (a-tiocst.ads)
23696 @geindex Interfacing with `@w{`}Text_IO`@w{`}
23698 This package provides subprograms that allow interfacing between
23699 C streams and @code{Text_IO}. The stream identifier can be
23700 extracted from a file opened on the Ada side, and an Ada file
23701 can be constructed from a stream opened on the C side.
23703 @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
23704 @anchor{gnat_rm/the_gnat_library ada-text-io-reset-standard-files-a-tirsfi-ads}@anchor{30e}@anchor{gnat_rm/the_gnat_library id31}@anchor{30f}
23705 @section @code{Ada.Text_IO.Reset_Standard_Files} (@code{a-tirsfi.ads})
23708 @geindex Ada.Text_IO.Reset_Standard_Files (a-tirsfi.ads)
23710 @geindex Text_IO resetting standard files
23712 This procedure is used to reset the status of the standard files used
23713 by Ada.Text_IO. This is useful in a situation (such as a restart in an
23714 embedded application) where the status of the files may change during
23715 execution (for example a standard input file may be redefined to be
23718 @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
23719 @anchor{gnat_rm/the_gnat_library id32}@anchor{310}@anchor{gnat_rm/the_gnat_library ada-wide-characters-unicode-a-wichun-ads}@anchor{311}
23720 @section @code{Ada.Wide_Characters.Unicode} (@code{a-wichun.ads})
23723 @geindex Ada.Wide_Characters.Unicode (a-wichun.ads)
23725 @geindex Unicode categorization
23726 @geindex Wide_Character
23728 This package provides subprograms that allow categorization of
23729 Wide_Character values according to Unicode categories.
23731 @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
23732 @anchor{gnat_rm/the_gnat_library ada-wide-text-io-c-streams-a-wtcstr-ads}@anchor{312}@anchor{gnat_rm/the_gnat_library id33}@anchor{313}
23733 @section @code{Ada.Wide_Text_IO.C_Streams} (@code{a-wtcstr.ads})
23736 @geindex Ada.Wide_Text_IO.C_Streams (a-wtcstr.ads)
23739 @geindex Interfacing with `@w{`}Wide_Text_IO`@w{`}
23741 This package provides subprograms that allow interfacing between
23742 C streams and @code{Wide_Text_IO}. The stream identifier can be
23743 extracted from a file opened on the Ada side, and an Ada file
23744 can be constructed from a stream opened on the C side.
23746 @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
23747 @anchor{gnat_rm/the_gnat_library ada-wide-text-io-reset-standard-files-a-wrstfi-ads}@anchor{314}@anchor{gnat_rm/the_gnat_library id34}@anchor{315}
23748 @section @code{Ada.Wide_Text_IO.Reset_Standard_Files} (@code{a-wrstfi.ads})
23751 @geindex Ada.Wide_Text_IO.Reset_Standard_Files (a-wrstfi.ads)
23753 @geindex Wide_Text_IO resetting standard files
23755 This procedure is used to reset the status of the standard files used
23756 by Ada.Wide_Text_IO. This is useful in a situation (such as a restart in an
23757 embedded application) where the status of the files may change during
23758 execution (for example a standard input file may be redefined to be
23761 @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
23762 @anchor{gnat_rm/the_gnat_library id35}@anchor{316}@anchor{gnat_rm/the_gnat_library ada-wide-wide-characters-unicode-a-zchuni-ads}@anchor{317}
23763 @section @code{Ada.Wide_Wide_Characters.Unicode} (@code{a-zchuni.ads})
23766 @geindex Ada.Wide_Wide_Characters.Unicode (a-zchuni.ads)
23768 @geindex Unicode categorization
23769 @geindex Wide_Wide_Character
23771 This package provides subprograms that allow categorization of
23772 Wide_Wide_Character values according to Unicode categories.
23774 @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
23775 @anchor{gnat_rm/the_gnat_library id36}@anchor{318}@anchor{gnat_rm/the_gnat_library ada-wide-wide-text-io-c-streams-a-ztcstr-ads}@anchor{319}
23776 @section @code{Ada.Wide_Wide_Text_IO.C_Streams} (@code{a-ztcstr.ads})
23779 @geindex Ada.Wide_Wide_Text_IO.C_Streams (a-ztcstr.ads)
23782 @geindex Interfacing with `@w{`}Wide_Wide_Text_IO`@w{`}
23784 This package provides subprograms that allow interfacing between
23785 C streams and @code{Wide_Wide_Text_IO}. The stream identifier can be
23786 extracted from a file opened on the Ada side, and an Ada file
23787 can be constructed from a stream opened on the C side.
23789 @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
23790 @anchor{gnat_rm/the_gnat_library id37}@anchor{31a}@anchor{gnat_rm/the_gnat_library ada-wide-wide-text-io-reset-standard-files-a-zrstfi-ads}@anchor{31b}
23791 @section @code{Ada.Wide_Wide_Text_IO.Reset_Standard_Files} (@code{a-zrstfi.ads})
23794 @geindex Ada.Wide_Wide_Text_IO.Reset_Standard_Files (a-zrstfi.ads)
23796 @geindex Wide_Wide_Text_IO resetting standard files
23798 This procedure is used to reset the status of the standard files used
23799 by Ada.Wide_Wide_Text_IO. This is useful in a situation (such as a
23800 restart in an embedded application) where the status of the files may
23801 change during execution (for example a standard input file may be
23802 redefined to be interactive).
23804 @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
23805 @anchor{gnat_rm/the_gnat_library gnat-altivec-g-altive-ads}@anchor{31c}@anchor{gnat_rm/the_gnat_library id38}@anchor{31d}
23806 @section @code{GNAT.Altivec} (@code{g-altive.ads})
23809 @geindex GNAT.Altivec (g-altive.ads)
23813 This is the root package of the GNAT AltiVec binding. It provides
23814 definitions of constants and types common to all the versions of the
23817 @node GNAT Altivec Conversions g-altcon ads,GNAT Altivec Vector_Operations g-alveop ads,GNAT Altivec g-altive ads,The GNAT Library
23818 @anchor{gnat_rm/the_gnat_library gnat-altivec-conversions-g-altcon-ads}@anchor{31e}@anchor{gnat_rm/the_gnat_library id39}@anchor{31f}
23819 @section @code{GNAT.Altivec.Conversions} (@code{g-altcon.ads})
23822 @geindex GNAT.Altivec.Conversions (g-altcon.ads)
23826 This package provides the Vector/View conversion routines.
23828 @node GNAT Altivec Vector_Operations g-alveop ads,GNAT Altivec Vector_Types g-alvety ads,GNAT Altivec Conversions g-altcon ads,The GNAT Library
23829 @anchor{gnat_rm/the_gnat_library gnat-altivec-vector-operations-g-alveop-ads}@anchor{320}@anchor{gnat_rm/the_gnat_library id40}@anchor{321}
23830 @section @code{GNAT.Altivec.Vector_Operations} (@code{g-alveop.ads})
23833 @geindex GNAT.Altivec.Vector_Operations (g-alveop.ads)
23837 This package exposes the Ada interface to the AltiVec operations on
23838 vector objects. A soft emulation is included by default in the GNAT
23839 library. The hard binding is provided as a separate package. This unit
23840 is common to both bindings.
23842 @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
23843 @anchor{gnat_rm/the_gnat_library gnat-altivec-vector-types-g-alvety-ads}@anchor{322}@anchor{gnat_rm/the_gnat_library id41}@anchor{323}
23844 @section @code{GNAT.Altivec.Vector_Types} (@code{g-alvety.ads})
23847 @geindex GNAT.Altivec.Vector_Types (g-alvety.ads)
23851 This package exposes the various vector types part of the Ada binding
23852 to AltiVec facilities.
23854 @node GNAT Altivec Vector_Views g-alvevi ads,GNAT Array_Split g-arrspl ads,GNAT Altivec Vector_Types g-alvety ads,The GNAT Library
23855 @anchor{gnat_rm/the_gnat_library gnat-altivec-vector-views-g-alvevi-ads}@anchor{324}@anchor{gnat_rm/the_gnat_library id42}@anchor{325}
23856 @section @code{GNAT.Altivec.Vector_Views} (@code{g-alvevi.ads})
23859 @geindex GNAT.Altivec.Vector_Views (g-alvevi.ads)
23863 This package provides public 'View' data types from/to which private
23864 vector representations can be converted via
23865 GNAT.Altivec.Conversions. This allows convenient access to individual
23866 vector elements and provides a simple way to initialize vector
23869 @node GNAT Array_Split g-arrspl ads,GNAT AWK g-awk ads,GNAT Altivec Vector_Views g-alvevi ads,The GNAT Library
23870 @anchor{gnat_rm/the_gnat_library gnat-array-split-g-arrspl-ads}@anchor{326}@anchor{gnat_rm/the_gnat_library id43}@anchor{327}
23871 @section @code{GNAT.Array_Split} (@code{g-arrspl.ads})
23874 @geindex GNAT.Array_Split (g-arrspl.ads)
23876 @geindex Array splitter
23878 Useful array-manipulation routines: given a set of separators, split
23879 an array wherever the separators appear, and provide direct access
23880 to the resulting slices.
23882 @node GNAT AWK g-awk ads,GNAT Bind_Environment g-binenv ads,GNAT Array_Split g-arrspl ads,The GNAT Library
23883 @anchor{gnat_rm/the_gnat_library id44}@anchor{328}@anchor{gnat_rm/the_gnat_library gnat-awk-g-awk-ads}@anchor{329}
23884 @section @code{GNAT.AWK} (@code{g-awk.ads})
23887 @geindex GNAT.AWK (g-awk.ads)
23893 Provides AWK-like parsing functions, with an easy interface for parsing one
23894 or more files containing formatted data. The file is viewed as a database
23895 where each record is a line and a field is a data element in this line.
23897 @node GNAT Bind_Environment g-binenv ads,GNAT Branch_Prediction g-brapre ads,GNAT AWK g-awk ads,The GNAT Library
23898 @anchor{gnat_rm/the_gnat_library gnat-bind-environment-g-binenv-ads}@anchor{32a}@anchor{gnat_rm/the_gnat_library id45}@anchor{32b}
23899 @section @code{GNAT.Bind_Environment} (@code{g-binenv.ads})
23902 @geindex GNAT.Bind_Environment (g-binenv.ads)
23904 @geindex Bind environment
23906 Provides access to key=value associations captured at bind time.
23907 These associations can be specified using the @code{-V} binder command
23910 @node GNAT Branch_Prediction g-brapre ads,GNAT Bounded_Buffers g-boubuf ads,GNAT Bind_Environment g-binenv ads,The GNAT Library
23911 @anchor{gnat_rm/the_gnat_library id46}@anchor{32c}@anchor{gnat_rm/the_gnat_library gnat-branch-prediction-g-brapre-ads}@anchor{32d}
23912 @section @code{GNAT.Branch_Prediction} (@code{g-brapre.ads})
23915 @geindex GNAT.Branch_Prediction (g-brapre.ads)
23917 @geindex Branch Prediction
23919 Provides routines giving hints to the branch predictor of the code generator.
23921 @node GNAT Bounded_Buffers g-boubuf ads,GNAT Bounded_Mailboxes g-boumai ads,GNAT Branch_Prediction g-brapre ads,The GNAT Library
23922 @anchor{gnat_rm/the_gnat_library id47}@anchor{32e}@anchor{gnat_rm/the_gnat_library gnat-bounded-buffers-g-boubuf-ads}@anchor{32f}
23923 @section @code{GNAT.Bounded_Buffers} (@code{g-boubuf.ads})
23926 @geindex GNAT.Bounded_Buffers (g-boubuf.ads)
23930 @geindex Bounded Buffers
23932 Provides a concurrent generic bounded buffer abstraction. Instances are
23933 useful directly or as parts of the implementations of other abstractions,
23936 @node GNAT Bounded_Mailboxes g-boumai ads,GNAT Bubble_Sort g-bubsor ads,GNAT Bounded_Buffers g-boubuf ads,The GNAT Library
23937 @anchor{gnat_rm/the_gnat_library gnat-bounded-mailboxes-g-boumai-ads}@anchor{330}@anchor{gnat_rm/the_gnat_library id48}@anchor{331}
23938 @section @code{GNAT.Bounded_Mailboxes} (@code{g-boumai.ads})
23941 @geindex GNAT.Bounded_Mailboxes (g-boumai.ads)
23947 Provides a thread-safe asynchronous intertask mailbox communication facility.
23949 @node GNAT Bubble_Sort g-bubsor ads,GNAT Bubble_Sort_A g-busora ads,GNAT Bounded_Mailboxes g-boumai ads,The GNAT Library
23950 @anchor{gnat_rm/the_gnat_library gnat-bubble-sort-g-bubsor-ads}@anchor{332}@anchor{gnat_rm/the_gnat_library id49}@anchor{333}
23951 @section @code{GNAT.Bubble_Sort} (@code{g-bubsor.ads})
23954 @geindex GNAT.Bubble_Sort (g-bubsor.ads)
23958 @geindex Bubble sort
23960 Provides a general implementation of bubble sort usable for sorting arbitrary
23961 data items. Exchange and comparison procedures are provided by passing
23962 access-to-procedure values.
23964 @node GNAT Bubble_Sort_A g-busora ads,GNAT Bubble_Sort_G g-busorg ads,GNAT Bubble_Sort g-bubsor ads,The GNAT Library
23965 @anchor{gnat_rm/the_gnat_library id50}@anchor{334}@anchor{gnat_rm/the_gnat_library gnat-bubble-sort-a-g-busora-ads}@anchor{335}
23966 @section @code{GNAT.Bubble_Sort_A} (@code{g-busora.ads})
23969 @geindex GNAT.Bubble_Sort_A (g-busora.ads)
23973 @geindex Bubble sort
23975 Provides a general implementation of bubble sort usable for sorting arbitrary
23976 data items. Move and comparison procedures are provided by passing
23977 access-to-procedure values. This is an older version, retained for
23978 compatibility. Usually @code{GNAT.Bubble_Sort} will be preferable.
23980 @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
23981 @anchor{gnat_rm/the_gnat_library gnat-bubble-sort-g-g-busorg-ads}@anchor{336}@anchor{gnat_rm/the_gnat_library id51}@anchor{337}
23982 @section @code{GNAT.Bubble_Sort_G} (@code{g-busorg.ads})
23985 @geindex GNAT.Bubble_Sort_G (g-busorg.ads)
23989 @geindex Bubble sort
23991 Similar to @code{Bubble_Sort_A} except that the move and sorting procedures
23992 are provided as generic parameters, this improves efficiency, especially
23993 if the procedures can be inlined, at the expense of duplicating code for
23994 multiple instantiations.
23996 @node GNAT Byte_Order_Mark g-byorma ads,GNAT Byte_Swapping g-bytswa ads,GNAT Bubble_Sort_G g-busorg ads,The GNAT Library
23997 @anchor{gnat_rm/the_gnat_library gnat-byte-order-mark-g-byorma-ads}@anchor{338}@anchor{gnat_rm/the_gnat_library id52}@anchor{339}
23998 @section @code{GNAT.Byte_Order_Mark} (@code{g-byorma.ads})
24001 @geindex GNAT.Byte_Order_Mark (g-byorma.ads)
24003 @geindex UTF-8 representation
24005 @geindex Wide characte representations
24007 Provides a routine which given a string, reads the start of the string to
24008 see whether it is one of the standard byte order marks (BOM's) which signal
24009 the encoding of the string. The routine includes detection of special XML
24010 sequences for various UCS input formats.
24012 @node GNAT Byte_Swapping g-bytswa ads,GNAT Calendar g-calend ads,GNAT Byte_Order_Mark g-byorma ads,The GNAT Library
24013 @anchor{gnat_rm/the_gnat_library gnat-byte-swapping-g-bytswa-ads}@anchor{33a}@anchor{gnat_rm/the_gnat_library id53}@anchor{33b}
24014 @section @code{GNAT.Byte_Swapping} (@code{g-bytswa.ads})
24017 @geindex GNAT.Byte_Swapping (g-bytswa.ads)
24019 @geindex Byte swapping
24021 @geindex Endianness
24023 General routines for swapping the bytes in 2-, 4-, and 8-byte quantities.
24024 Machine-specific implementations are available in some cases.
24026 @node GNAT Calendar g-calend ads,GNAT Calendar Time_IO g-catiio ads,GNAT Byte_Swapping g-bytswa ads,The GNAT Library
24027 @anchor{gnat_rm/the_gnat_library id54}@anchor{33c}@anchor{gnat_rm/the_gnat_library gnat-calendar-g-calend-ads}@anchor{33d}
24028 @section @code{GNAT.Calendar} (@code{g-calend.ads})
24031 @geindex GNAT.Calendar (g-calend.ads)
24035 Extends the facilities provided by @code{Ada.Calendar} to include handling
24036 of days of the week, an extended @code{Split} and @code{Time_Of} capability.
24037 Also provides conversion of @code{Ada.Calendar.Time} values to and from the
24038 C @code{timeval} format.
24040 @node GNAT Calendar Time_IO g-catiio ads,GNAT CRC32 g-crc32 ads,GNAT Calendar g-calend ads,The GNAT Library
24041 @anchor{gnat_rm/the_gnat_library id55}@anchor{33e}@anchor{gnat_rm/the_gnat_library gnat-calendar-time-io-g-catiio-ads}@anchor{33f}
24042 @section @code{GNAT.Calendar.Time_IO} (@code{g-catiio.ads})
24049 @geindex GNAT.Calendar.Time_IO (g-catiio.ads)
24051 @node GNAT CRC32 g-crc32 ads,GNAT Case_Util g-casuti ads,GNAT Calendar Time_IO g-catiio ads,The GNAT Library
24052 @anchor{gnat_rm/the_gnat_library id56}@anchor{340}@anchor{gnat_rm/the_gnat_library gnat-crc32-g-crc32-ads}@anchor{341}
24053 @section @code{GNAT.CRC32} (@code{g-crc32.ads})
24056 @geindex GNAT.CRC32 (g-crc32.ads)
24060 @geindex Cyclic Redundancy Check
24062 This package implements the CRC-32 algorithm. For a full description
24063 of this algorithm see
24064 @emph{Computation of Cyclic Redundancy Checks via Table Look-Up},
24065 @cite{Communications of the ACM}, Vol. 31 No. 8, pp. 1008-1013,
24066 Aug. 1988. Sarwate, D.V.
24068 @node GNAT Case_Util g-casuti ads,GNAT CGI g-cgi ads,GNAT CRC32 g-crc32 ads,The GNAT Library
24069 @anchor{gnat_rm/the_gnat_library id57}@anchor{342}@anchor{gnat_rm/the_gnat_library gnat-case-util-g-casuti-ads}@anchor{343}
24070 @section @code{GNAT.Case_Util} (@code{g-casuti.ads})
24073 @geindex GNAT.Case_Util (g-casuti.ads)
24075 @geindex Casing utilities
24077 @geindex Character handling (`@w{`}GNAT.Case_Util`@w{`})
24079 A set of simple routines for handling upper and lower casing of strings
24080 without the overhead of the full casing tables
24081 in @code{Ada.Characters.Handling}.
24083 @node GNAT CGI g-cgi ads,GNAT CGI Cookie g-cgicoo ads,GNAT Case_Util g-casuti ads,The GNAT Library
24084 @anchor{gnat_rm/the_gnat_library id58}@anchor{344}@anchor{gnat_rm/the_gnat_library gnat-cgi-g-cgi-ads}@anchor{345}
24085 @section @code{GNAT.CGI} (@code{g-cgi.ads})
24088 @geindex GNAT.CGI (g-cgi.ads)
24090 @geindex CGI (Common Gateway Interface)
24092 This is a package for interfacing a GNAT program with a Web server via the
24093 Common Gateway Interface (CGI). Basically this package parses the CGI
24094 parameters, which are a set of key/value pairs sent by the Web server. It
24095 builds a table whose index is the key and provides some services to deal
24098 @node GNAT CGI Cookie g-cgicoo ads,GNAT CGI Debug g-cgideb ads,GNAT CGI g-cgi ads,The GNAT Library
24099 @anchor{gnat_rm/the_gnat_library gnat-cgi-cookie-g-cgicoo-ads}@anchor{346}@anchor{gnat_rm/the_gnat_library id59}@anchor{347}
24100 @section @code{GNAT.CGI.Cookie} (@code{g-cgicoo.ads})
24103 @geindex GNAT.CGI.Cookie (g-cgicoo.ads)
24105 @geindex CGI (Common Gateway Interface) cookie support
24107 @geindex Cookie support in CGI
24109 This is a package to interface a GNAT program with a Web server via the
24110 Common Gateway Interface (CGI). It exports services to deal with Web
24111 cookies (piece of information kept in the Web client software).
24113 @node GNAT CGI Debug g-cgideb ads,GNAT Command_Line g-comlin ads,GNAT CGI Cookie g-cgicoo ads,The GNAT Library
24114 @anchor{gnat_rm/the_gnat_library gnat-cgi-debug-g-cgideb-ads}@anchor{348}@anchor{gnat_rm/the_gnat_library id60}@anchor{349}
24115 @section @code{GNAT.CGI.Debug} (@code{g-cgideb.ads})
24118 @geindex GNAT.CGI.Debug (g-cgideb.ads)
24120 @geindex CGI (Common Gateway Interface) debugging
24122 This is a package to help debugging CGI (Common Gateway Interface)
24123 programs written in Ada.
24125 @node GNAT Command_Line g-comlin ads,GNAT Compiler_Version g-comver ads,GNAT CGI Debug g-cgideb ads,The GNAT Library
24126 @anchor{gnat_rm/the_gnat_library id61}@anchor{34a}@anchor{gnat_rm/the_gnat_library gnat-command-line-g-comlin-ads}@anchor{34b}
24127 @section @code{GNAT.Command_Line} (@code{g-comlin.ads})
24130 @geindex GNAT.Command_Line (g-comlin.ads)
24132 @geindex Command line
24134 Provides a high level interface to @code{Ada.Command_Line} facilities,
24135 including the ability to scan for named switches with optional parameters
24136 and expand file names using wildcard notations.
24138 @node GNAT Compiler_Version g-comver ads,GNAT Ctrl_C g-ctrl_c ads,GNAT Command_Line g-comlin ads,The GNAT Library
24139 @anchor{gnat_rm/the_gnat_library gnat-compiler-version-g-comver-ads}@anchor{34c}@anchor{gnat_rm/the_gnat_library id62}@anchor{34d}
24140 @section @code{GNAT.Compiler_Version} (@code{g-comver.ads})
24143 @geindex GNAT.Compiler_Version (g-comver.ads)
24145 @geindex Compiler Version
24148 @geindex of compiler
24150 Provides a routine for obtaining the version of the compiler used to
24151 compile the program. More accurately this is the version of the binder
24152 used to bind the program (this will normally be the same as the version
24153 of the compiler if a consistent tool set is used to compile all units
24156 @node GNAT Ctrl_C g-ctrl_c ads,GNAT Current_Exception g-curexc ads,GNAT Compiler_Version g-comver ads,The GNAT Library
24157 @anchor{gnat_rm/the_gnat_library gnat-ctrl-c-g-ctrl-c-ads}@anchor{34e}@anchor{gnat_rm/the_gnat_library id63}@anchor{34f}
24158 @section @code{GNAT.Ctrl_C} (@code{g-ctrl_c.ads})
24161 @geindex GNAT.Ctrl_C (g-ctrl_c.ads)
24165 Provides a simple interface to handle Ctrl-C keyboard events.
24167 @node GNAT Current_Exception g-curexc ads,GNAT Debug_Pools g-debpoo ads,GNAT Ctrl_C g-ctrl_c ads,The GNAT Library
24168 @anchor{gnat_rm/the_gnat_library id64}@anchor{350}@anchor{gnat_rm/the_gnat_library gnat-current-exception-g-curexc-ads}@anchor{351}
24169 @section @code{GNAT.Current_Exception} (@code{g-curexc.ads})
24172 @geindex GNAT.Current_Exception (g-curexc.ads)
24174 @geindex Current exception
24176 @geindex Exception retrieval
24178 Provides access to information on the current exception that has been raised
24179 without the need for using the Ada 95 / Ada 2005 exception choice parameter
24180 specification syntax.
24181 This is particularly useful in simulating typical facilities for
24182 obtaining information about exceptions provided by Ada 83 compilers.
24184 @node GNAT Debug_Pools g-debpoo ads,GNAT Debug_Utilities g-debuti ads,GNAT Current_Exception g-curexc ads,The GNAT Library
24185 @anchor{gnat_rm/the_gnat_library gnat-debug-pools-g-debpoo-ads}@anchor{352}@anchor{gnat_rm/the_gnat_library id65}@anchor{353}
24186 @section @code{GNAT.Debug_Pools} (@code{g-debpoo.ads})
24189 @geindex GNAT.Debug_Pools (g-debpoo.ads)
24193 @geindex Debug pools
24195 @geindex Memory corruption debugging
24197 Provide a debugging storage pools that helps tracking memory corruption
24199 See @code{The GNAT Debug_Pool Facility} section in the @cite{GNAT User's Guide}.
24201 @node GNAT Debug_Utilities g-debuti ads,GNAT Decode_String g-decstr ads,GNAT Debug_Pools g-debpoo ads,The GNAT Library
24202 @anchor{gnat_rm/the_gnat_library gnat-debug-utilities-g-debuti-ads}@anchor{354}@anchor{gnat_rm/the_gnat_library id66}@anchor{355}
24203 @section @code{GNAT.Debug_Utilities} (@code{g-debuti.ads})
24206 @geindex GNAT.Debug_Utilities (g-debuti.ads)
24210 Provides a few useful utilities for debugging purposes, including conversion
24211 to and from string images of address values. Supports both C and Ada formats
24212 for hexadecimal literals.
24214 @node GNAT Decode_String g-decstr ads,GNAT Decode_UTF8_String g-deutst ads,GNAT Debug_Utilities g-debuti ads,The GNAT Library
24215 @anchor{gnat_rm/the_gnat_library id67}@anchor{356}@anchor{gnat_rm/the_gnat_library gnat-decode-string-g-decstr-ads}@anchor{357}
24216 @section @code{GNAT.Decode_String} (@code{g-decstr.ads})
24219 @geindex GNAT.Decode_String (g-decstr.ads)
24221 @geindex Decoding strings
24223 @geindex String decoding
24225 @geindex Wide character encoding
24231 A generic package providing routines for decoding wide character and wide wide
24232 character strings encoded as sequences of 8-bit characters using a specified
24233 encoding method. Includes validation routines, and also routines for stepping
24234 to next or previous encoded character in an encoded string.
24235 Useful in conjunction with Unicode character coding. Note there is a
24236 preinstantiation for UTF-8. See next entry.
24238 @node GNAT Decode_UTF8_String g-deutst ads,GNAT Directory_Operations g-dirope ads,GNAT Decode_String g-decstr ads,The GNAT Library
24239 @anchor{gnat_rm/the_gnat_library gnat-decode-utf8-string-g-deutst-ads}@anchor{358}@anchor{gnat_rm/the_gnat_library id68}@anchor{359}
24240 @section @code{GNAT.Decode_UTF8_String} (@code{g-deutst.ads})
24243 @geindex GNAT.Decode_UTF8_String (g-deutst.ads)
24245 @geindex Decoding strings
24247 @geindex Decoding UTF-8 strings
24249 @geindex UTF-8 string decoding
24251 @geindex Wide character decoding
24257 A preinstantiation of GNAT.Decode_Strings for UTF-8 encoding.
24259 @node GNAT Directory_Operations g-dirope ads,GNAT Directory_Operations Iteration g-diopit ads,GNAT Decode_UTF8_String g-deutst ads,The GNAT Library
24260 @anchor{gnat_rm/the_gnat_library id69}@anchor{35a}@anchor{gnat_rm/the_gnat_library gnat-directory-operations-g-dirope-ads}@anchor{35b}
24261 @section @code{GNAT.Directory_Operations} (@code{g-dirope.ads})
24264 @geindex GNAT.Directory_Operations (g-dirope.ads)
24266 @geindex Directory operations
24268 Provides a set of routines for manipulating directories, including changing
24269 the current directory, making new directories, and scanning the files in a
24272 @node GNAT Directory_Operations Iteration g-diopit ads,GNAT Dynamic_HTables g-dynhta ads,GNAT Directory_Operations g-dirope ads,The GNAT Library
24273 @anchor{gnat_rm/the_gnat_library id70}@anchor{35c}@anchor{gnat_rm/the_gnat_library gnat-directory-operations-iteration-g-diopit-ads}@anchor{35d}
24274 @section @code{GNAT.Directory_Operations.Iteration} (@code{g-diopit.ads})
24277 @geindex GNAT.Directory_Operations.Iteration (g-diopit.ads)
24279 @geindex Directory operations iteration
24281 A child unit of GNAT.Directory_Operations providing additional operations
24282 for iterating through directories.
24284 @node GNAT Dynamic_HTables g-dynhta ads,GNAT Dynamic_Tables g-dyntab ads,GNAT Directory_Operations Iteration g-diopit ads,The GNAT Library
24285 @anchor{gnat_rm/the_gnat_library id71}@anchor{35e}@anchor{gnat_rm/the_gnat_library gnat-dynamic-htables-g-dynhta-ads}@anchor{35f}
24286 @section @code{GNAT.Dynamic_HTables} (@code{g-dynhta.ads})
24289 @geindex GNAT.Dynamic_HTables (g-dynhta.ads)
24291 @geindex Hash tables
24293 A generic implementation of hash tables that can be used to hash arbitrary
24294 data. Provided in two forms, a simple form with built in hash functions,
24295 and a more complex form in which the hash function is supplied.
24297 This package provides a facility similar to that of @code{GNAT.HTable},
24298 except that this package declares a type that can be used to define
24299 dynamic instances of the hash table, while an instantiation of
24300 @code{GNAT.HTable} creates a single instance of the hash table.
24302 @node GNAT Dynamic_Tables g-dyntab ads,GNAT Encode_String g-encstr ads,GNAT Dynamic_HTables g-dynhta ads,The GNAT Library
24303 @anchor{gnat_rm/the_gnat_library gnat-dynamic-tables-g-dyntab-ads}@anchor{360}@anchor{gnat_rm/the_gnat_library id72}@anchor{361}
24304 @section @code{GNAT.Dynamic_Tables} (@code{g-dyntab.ads})
24307 @geindex GNAT.Dynamic_Tables (g-dyntab.ads)
24309 @geindex Table implementation
24312 @geindex extendable
24314 A generic package providing a single dimension array abstraction where the
24315 length of the array can be dynamically modified.
24317 This package provides a facility similar to that of @code{GNAT.Table},
24318 except that this package declares a type that can be used to define
24319 dynamic instances of the table, while an instantiation of
24320 @code{GNAT.Table} creates a single instance of the table type.
24322 @node GNAT Encode_String g-encstr ads,GNAT Encode_UTF8_String g-enutst ads,GNAT Dynamic_Tables g-dyntab ads,The GNAT Library
24323 @anchor{gnat_rm/the_gnat_library id73}@anchor{362}@anchor{gnat_rm/the_gnat_library gnat-encode-string-g-encstr-ads}@anchor{363}
24324 @section @code{GNAT.Encode_String} (@code{g-encstr.ads})
24327 @geindex GNAT.Encode_String (g-encstr.ads)
24329 @geindex Encoding strings
24331 @geindex String encoding
24333 @geindex Wide character encoding
24339 A generic package providing routines for encoding wide character and wide
24340 wide character strings as sequences of 8-bit characters using a specified
24341 encoding method. Useful in conjunction with Unicode character coding.
24342 Note there is a preinstantiation for UTF-8. See next entry.
24344 @node GNAT Encode_UTF8_String g-enutst ads,GNAT Exception_Actions g-excact ads,GNAT Encode_String g-encstr ads,The GNAT Library
24345 @anchor{gnat_rm/the_gnat_library gnat-encode-utf8-string-g-enutst-ads}@anchor{364}@anchor{gnat_rm/the_gnat_library id74}@anchor{365}
24346 @section @code{GNAT.Encode_UTF8_String} (@code{g-enutst.ads})
24349 @geindex GNAT.Encode_UTF8_String (g-enutst.ads)
24351 @geindex Encoding strings
24353 @geindex Encoding UTF-8 strings
24355 @geindex UTF-8 string encoding
24357 @geindex Wide character encoding
24363 A preinstantiation of GNAT.Encode_Strings for UTF-8 encoding.
24365 @node GNAT Exception_Actions g-excact ads,GNAT Exception_Traces g-exctra ads,GNAT Encode_UTF8_String g-enutst ads,The GNAT Library
24366 @anchor{gnat_rm/the_gnat_library gnat-exception-actions-g-excact-ads}@anchor{366}@anchor{gnat_rm/the_gnat_library id75}@anchor{367}
24367 @section @code{GNAT.Exception_Actions} (@code{g-excact.ads})
24370 @geindex GNAT.Exception_Actions (g-excact.ads)
24372 @geindex Exception actions
24374 Provides callbacks when an exception is raised. Callbacks can be registered
24375 for specific exceptions, or when any exception is raised. This
24376 can be used for instance to force a core dump to ease debugging.
24378 @node GNAT Exception_Traces g-exctra ads,GNAT Exceptions g-except ads,GNAT Exception_Actions g-excact ads,The GNAT Library
24379 @anchor{gnat_rm/the_gnat_library gnat-exception-traces-g-exctra-ads}@anchor{368}@anchor{gnat_rm/the_gnat_library id76}@anchor{369}
24380 @section @code{GNAT.Exception_Traces} (@code{g-exctra.ads})
24383 @geindex GNAT.Exception_Traces (g-exctra.ads)
24385 @geindex Exception traces
24389 Provides an interface allowing to control automatic output upon exception
24392 @node GNAT Exceptions g-except ads,GNAT Expect g-expect ads,GNAT Exception_Traces g-exctra ads,The GNAT Library
24393 @anchor{gnat_rm/the_gnat_library id77}@anchor{36a}@anchor{gnat_rm/the_gnat_library gnat-exceptions-g-except-ads}@anchor{36b}
24394 @section @code{GNAT.Exceptions} (@code{g-except.ads})
24397 @geindex GNAT.Exceptions (g-except.ads)
24399 @geindex Exceptions
24402 @geindex Pure packages
24403 @geindex exceptions
24405 Normally it is not possible to raise an exception with
24406 a message from a subprogram in a pure package, since the
24407 necessary types and subprograms are in @code{Ada.Exceptions}
24408 which is not a pure unit. @code{GNAT.Exceptions} provides a
24409 facility for getting around this limitation for a few
24410 predefined exceptions, and for example allow raising
24411 @code{Constraint_Error} with a message from a pure subprogram.
24413 @node GNAT Expect g-expect ads,GNAT Expect TTY g-exptty ads,GNAT Exceptions g-except ads,The GNAT Library
24414 @anchor{gnat_rm/the_gnat_library id78}@anchor{36c}@anchor{gnat_rm/the_gnat_library gnat-expect-g-expect-ads}@anchor{36d}
24415 @section @code{GNAT.Expect} (@code{g-expect.ads})
24418 @geindex GNAT.Expect (g-expect.ads)
24420 Provides a set of subprograms similar to what is available
24421 with the standard Tcl Expect tool.
24422 It allows you to easily spawn and communicate with an external process.
24423 You can send commands or inputs to the process, and compare the output
24424 with some expected regular expression. Currently @code{GNAT.Expect}
24425 is implemented on all native GNAT ports.
24426 It is not implemented for cross ports, and in particular is not
24427 implemented for VxWorks or LynxOS.
24429 @node GNAT Expect TTY g-exptty ads,GNAT Float_Control g-flocon ads,GNAT Expect g-expect ads,The GNAT Library
24430 @anchor{gnat_rm/the_gnat_library id79}@anchor{36e}@anchor{gnat_rm/the_gnat_library gnat-expect-tty-g-exptty-ads}@anchor{36f}
24431 @section @code{GNAT.Expect.TTY} (@code{g-exptty.ads})
24434 @geindex GNAT.Expect.TTY (g-exptty.ads)
24436 As GNAT.Expect but using pseudo-terminal.
24437 Currently @code{GNAT.Expect.TTY} is implemented on all native GNAT
24438 ports. It is not implemented for cross ports, and
24439 in particular is not implemented for VxWorks or LynxOS.
24441 @node GNAT Float_Control g-flocon ads,GNAT Formatted_String g-forstr ads,GNAT Expect TTY g-exptty ads,The GNAT Library
24442 @anchor{gnat_rm/the_gnat_library id80}@anchor{370}@anchor{gnat_rm/the_gnat_library gnat-float-control-g-flocon-ads}@anchor{371}
24443 @section @code{GNAT.Float_Control} (@code{g-flocon.ads})
24446 @geindex GNAT.Float_Control (g-flocon.ads)
24448 @geindex Floating-Point Processor
24450 Provides an interface for resetting the floating-point processor into the
24451 mode required for correct semantic operation in Ada. Some third party
24452 library calls may cause this mode to be modified, and the Reset procedure
24453 in this package can be used to reestablish the required mode.
24455 @node GNAT Formatted_String g-forstr ads,GNAT Heap_Sort g-heasor ads,GNAT Float_Control g-flocon ads,The GNAT Library
24456 @anchor{gnat_rm/the_gnat_library id81}@anchor{372}@anchor{gnat_rm/the_gnat_library gnat-formatted-string-g-forstr-ads}@anchor{373}
24457 @section @code{GNAT.Formatted_String} (@code{g-forstr.ads})
24460 @geindex GNAT.Formatted_String (g-forstr.ads)
24462 @geindex Formatted String
24464 Provides support for C/C++ printf() formatted strings. The format is
24465 copied from the printf() routine and should therefore gives identical
24466 output. Some generic routines are provided to be able to use types
24467 derived from Integer, Float or enumerations as values for the
24470 @node GNAT Heap_Sort g-heasor ads,GNAT Heap_Sort_A g-hesora ads,GNAT Formatted_String g-forstr ads,The GNAT Library
24471 @anchor{gnat_rm/the_gnat_library gnat-heap-sort-g-heasor-ads}@anchor{374}@anchor{gnat_rm/the_gnat_library id82}@anchor{375}
24472 @section @code{GNAT.Heap_Sort} (@code{g-heasor.ads})
24475 @geindex GNAT.Heap_Sort (g-heasor.ads)
24479 Provides a general implementation of heap sort usable for sorting arbitrary
24480 data items. Exchange and comparison procedures are provided by passing
24481 access-to-procedure values. The algorithm used is a modified heap sort
24482 that performs approximately N*log(N) comparisons in the worst case.
24484 @node GNAT Heap_Sort_A g-hesora ads,GNAT Heap_Sort_G g-hesorg ads,GNAT Heap_Sort g-heasor ads,The GNAT Library
24485 @anchor{gnat_rm/the_gnat_library id83}@anchor{376}@anchor{gnat_rm/the_gnat_library gnat-heap-sort-a-g-hesora-ads}@anchor{377}
24486 @section @code{GNAT.Heap_Sort_A} (@code{g-hesora.ads})
24489 @geindex GNAT.Heap_Sort_A (g-hesora.ads)
24493 Provides a general implementation of heap sort usable for sorting arbitrary
24494 data items. Move and comparison procedures are provided by passing
24495 access-to-procedure values. The algorithm used is a modified heap sort
24496 that performs approximately N*log(N) comparisons in the worst case.
24497 This differs from @code{GNAT.Heap_Sort} in having a less convenient
24498 interface, but may be slightly more efficient.
24500 @node GNAT Heap_Sort_G g-hesorg ads,GNAT HTable g-htable ads,GNAT Heap_Sort_A g-hesora ads,The GNAT Library
24501 @anchor{gnat_rm/the_gnat_library id84}@anchor{378}@anchor{gnat_rm/the_gnat_library gnat-heap-sort-g-g-hesorg-ads}@anchor{379}
24502 @section @code{GNAT.Heap_Sort_G} (@code{g-hesorg.ads})
24505 @geindex GNAT.Heap_Sort_G (g-hesorg.ads)
24509 Similar to @code{Heap_Sort_A} except that the move and sorting procedures
24510 are provided as generic parameters, this improves efficiency, especially
24511 if the procedures can be inlined, at the expense of duplicating code for
24512 multiple instantiations.
24514 @node GNAT HTable g-htable ads,GNAT IO g-io ads,GNAT Heap_Sort_G g-hesorg ads,The GNAT Library
24515 @anchor{gnat_rm/the_gnat_library id85}@anchor{37a}@anchor{gnat_rm/the_gnat_library gnat-htable-g-htable-ads}@anchor{37b}
24516 @section @code{GNAT.HTable} (@code{g-htable.ads})
24519 @geindex GNAT.HTable (g-htable.ads)
24521 @geindex Hash tables
24523 A generic implementation of hash tables that can be used to hash arbitrary
24524 data. Provides two approaches, one a simple static approach, and the other
24525 allowing arbitrary dynamic hash tables.
24527 @node GNAT IO g-io ads,GNAT IO_Aux g-io_aux ads,GNAT HTable g-htable ads,The GNAT Library
24528 @anchor{gnat_rm/the_gnat_library id86}@anchor{37c}@anchor{gnat_rm/the_gnat_library gnat-io-g-io-ads}@anchor{37d}
24529 @section @code{GNAT.IO} (@code{g-io.ads})
24532 @geindex GNAT.IO (g-io.ads)
24534 @geindex Simple I/O
24536 @geindex Input/Output facilities
24538 A simple preelaborable input-output package that provides a subset of
24539 simple Text_IO functions for reading characters and strings from
24540 Standard_Input, and writing characters, strings and integers to either
24541 Standard_Output or Standard_Error.
24543 @node GNAT IO_Aux g-io_aux ads,GNAT Lock_Files g-locfil ads,GNAT IO g-io ads,The GNAT Library
24544 @anchor{gnat_rm/the_gnat_library id87}@anchor{37e}@anchor{gnat_rm/the_gnat_library gnat-io-aux-g-io-aux-ads}@anchor{37f}
24545 @section @code{GNAT.IO_Aux} (@code{g-io_aux.ads})
24548 @geindex GNAT.IO_Aux (g-io_aux.ads)
24552 @geindex Input/Output facilities
24554 Provides some auxiliary functions for use with Text_IO, including a test
24555 for whether a file exists, and functions for reading a line of text.
24557 @node GNAT Lock_Files g-locfil ads,GNAT MBBS_Discrete_Random g-mbdira ads,GNAT IO_Aux g-io_aux ads,The GNAT Library
24558 @anchor{gnat_rm/the_gnat_library id88}@anchor{380}@anchor{gnat_rm/the_gnat_library gnat-lock-files-g-locfil-ads}@anchor{381}
24559 @section @code{GNAT.Lock_Files} (@code{g-locfil.ads})
24562 @geindex GNAT.Lock_Files (g-locfil.ads)
24564 @geindex File locking
24566 @geindex Locking using files
24568 Provides a general interface for using files as locks. Can be used for
24569 providing program level synchronization.
24571 @node GNAT MBBS_Discrete_Random g-mbdira ads,GNAT MBBS_Float_Random g-mbflra ads,GNAT Lock_Files g-locfil ads,The GNAT Library
24572 @anchor{gnat_rm/the_gnat_library id89}@anchor{382}@anchor{gnat_rm/the_gnat_library gnat-mbbs-discrete-random-g-mbdira-ads}@anchor{383}
24573 @section @code{GNAT.MBBS_Discrete_Random} (@code{g-mbdira.ads})
24576 @geindex GNAT.MBBS_Discrete_Random (g-mbdira.ads)
24578 @geindex Random number generation
24580 The original implementation of @code{Ada.Numerics.Discrete_Random}. Uses
24581 a modified version of the Blum-Blum-Shub generator.
24583 @node GNAT MBBS_Float_Random g-mbflra ads,GNAT MD5 g-md5 ads,GNAT MBBS_Discrete_Random g-mbdira ads,The GNAT Library
24584 @anchor{gnat_rm/the_gnat_library id90}@anchor{384}@anchor{gnat_rm/the_gnat_library gnat-mbbs-float-random-g-mbflra-ads}@anchor{385}
24585 @section @code{GNAT.MBBS_Float_Random} (@code{g-mbflra.ads})
24588 @geindex GNAT.MBBS_Float_Random (g-mbflra.ads)
24590 @geindex Random number generation
24592 The original implementation of @code{Ada.Numerics.Float_Random}. Uses
24593 a modified version of the Blum-Blum-Shub generator.
24595 @node GNAT MD5 g-md5 ads,GNAT Memory_Dump g-memdum ads,GNAT MBBS_Float_Random g-mbflra ads,The GNAT Library
24596 @anchor{gnat_rm/the_gnat_library id91}@anchor{386}@anchor{gnat_rm/the_gnat_library gnat-md5-g-md5-ads}@anchor{387}
24597 @section @code{GNAT.MD5} (@code{g-md5.ads})
24600 @geindex GNAT.MD5 (g-md5.ads)
24602 @geindex Message Digest MD5
24604 Implements the MD5 Message-Digest Algorithm as described in RFC 1321, and
24605 the HMAC-MD5 message authentication function as described in RFC 2104 and
24608 @node GNAT Memory_Dump g-memdum ads,GNAT Most_Recent_Exception g-moreex ads,GNAT MD5 g-md5 ads,The GNAT Library
24609 @anchor{gnat_rm/the_gnat_library id92}@anchor{388}@anchor{gnat_rm/the_gnat_library gnat-memory-dump-g-memdum-ads}@anchor{389}
24610 @section @code{GNAT.Memory_Dump} (@code{g-memdum.ads})
24613 @geindex GNAT.Memory_Dump (g-memdum.ads)
24615 @geindex Dump Memory
24617 Provides a convenient routine for dumping raw memory to either the
24618 standard output or standard error files. Uses GNAT.IO for actual
24621 @node GNAT Most_Recent_Exception g-moreex ads,GNAT OS_Lib g-os_lib ads,GNAT Memory_Dump g-memdum ads,The GNAT Library
24622 @anchor{gnat_rm/the_gnat_library gnat-most-recent-exception-g-moreex-ads}@anchor{38a}@anchor{gnat_rm/the_gnat_library id93}@anchor{38b}
24623 @section @code{GNAT.Most_Recent_Exception} (@code{g-moreex.ads})
24626 @geindex GNAT.Most_Recent_Exception (g-moreex.ads)
24629 @geindex obtaining most recent
24631 Provides access to the most recently raised exception. Can be used for
24632 various logging purposes, including duplicating functionality of some
24633 Ada 83 implementation dependent extensions.
24635 @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
24636 @anchor{gnat_rm/the_gnat_library gnat-os-lib-g-os-lib-ads}@anchor{38c}@anchor{gnat_rm/the_gnat_library id94}@anchor{38d}
24637 @section @code{GNAT.OS_Lib} (@code{g-os_lib.ads})
24640 @geindex GNAT.OS_Lib (g-os_lib.ads)
24642 @geindex Operating System interface
24644 @geindex Spawn capability
24646 Provides a range of target independent operating system interface functions,
24647 including time/date management, file operations, subprocess management,
24648 including a portable spawn procedure, and access to environment variables
24649 and error return codes.
24651 @node GNAT Perfect_Hash_Generators g-pehage ads,GNAT Random_Numbers g-rannum ads,GNAT OS_Lib g-os_lib ads,The GNAT Library
24652 @anchor{gnat_rm/the_gnat_library gnat-perfect-hash-generators-g-pehage-ads}@anchor{38e}@anchor{gnat_rm/the_gnat_library id95}@anchor{38f}
24653 @section @code{GNAT.Perfect_Hash_Generators} (@code{g-pehage.ads})
24656 @geindex GNAT.Perfect_Hash_Generators (g-pehage.ads)
24658 @geindex Hash functions
24660 Provides a generator of static minimal perfect hash functions. No
24661 collisions occur and each item can be retrieved from the table in one
24662 probe (perfect property). The hash table size corresponds to the exact
24663 size of the key set and no larger (minimal property). The key set has to
24664 be know in advance (static property). The hash functions are also order
24665 preserving. If w2 is inserted after w1 in the generator, their
24666 hashcode are in the same order. These hashing functions are very
24667 convenient for use with realtime applications.
24669 @node GNAT Random_Numbers g-rannum ads,GNAT Regexp g-regexp ads,GNAT Perfect_Hash_Generators g-pehage ads,The GNAT Library
24670 @anchor{gnat_rm/the_gnat_library gnat-random-numbers-g-rannum-ads}@anchor{390}@anchor{gnat_rm/the_gnat_library id96}@anchor{391}
24671 @section @code{GNAT.Random_Numbers} (@code{g-rannum.ads})
24674 @geindex GNAT.Random_Numbers (g-rannum.ads)
24676 @geindex Random number generation
24678 Provides random number capabilities which extend those available in the
24679 standard Ada library and are more convenient to use.
24681 @node GNAT Regexp g-regexp ads,GNAT Registry g-regist ads,GNAT Random_Numbers g-rannum ads,The GNAT Library
24682 @anchor{gnat_rm/the_gnat_library gnat-regexp-g-regexp-ads}@anchor{259}@anchor{gnat_rm/the_gnat_library id97}@anchor{392}
24683 @section @code{GNAT.Regexp} (@code{g-regexp.ads})
24686 @geindex GNAT.Regexp (g-regexp.ads)
24688 @geindex Regular expressions
24690 @geindex Pattern matching
24692 A simple implementation of regular expressions, using a subset of regular
24693 expression syntax copied from familiar Unix style utilities. This is the
24694 simplest of the three pattern matching packages provided, and is particularly
24695 suitable for 'file globbing' applications.
24697 @node GNAT Registry g-regist ads,GNAT Regpat g-regpat ads,GNAT Regexp g-regexp ads,The GNAT Library
24698 @anchor{gnat_rm/the_gnat_library id98}@anchor{393}@anchor{gnat_rm/the_gnat_library gnat-registry-g-regist-ads}@anchor{394}
24699 @section @code{GNAT.Registry} (@code{g-regist.ads})
24702 @geindex GNAT.Registry (g-regist.ads)
24704 @geindex Windows Registry
24706 This is a high level binding to the Windows registry. It is possible to
24707 do simple things like reading a key value, creating a new key. For full
24708 registry API, but at a lower level of abstraction, refer to the Win32.Winreg
24709 package provided with the Win32Ada binding
24711 @node GNAT Regpat g-regpat ads,GNAT Rewrite_Data g-rewdat ads,GNAT Registry g-regist ads,The GNAT Library
24712 @anchor{gnat_rm/the_gnat_library id99}@anchor{395}@anchor{gnat_rm/the_gnat_library gnat-regpat-g-regpat-ads}@anchor{396}
24713 @section @code{GNAT.Regpat} (@code{g-regpat.ads})
24716 @geindex GNAT.Regpat (g-regpat.ads)
24718 @geindex Regular expressions
24720 @geindex Pattern matching
24722 A complete implementation of Unix-style regular expression matching, copied
24723 from the original V7 style regular expression library written in C by
24724 Henry Spencer (and binary compatible with this C library).
24726 @node GNAT Rewrite_Data g-rewdat ads,GNAT Secondary_Stack_Info g-sestin ads,GNAT Regpat g-regpat ads,The GNAT Library
24727 @anchor{gnat_rm/the_gnat_library id100}@anchor{397}@anchor{gnat_rm/the_gnat_library gnat-rewrite-data-g-rewdat-ads}@anchor{398}
24728 @section @code{GNAT.Rewrite_Data} (@code{g-rewdat.ads})
24731 @geindex GNAT.Rewrite_Data (g-rewdat.ads)
24733 @geindex Rewrite data
24735 A unit to rewrite on-the-fly string occurrences in a stream of
24736 data. The implementation has a very minimal memory footprint as the
24737 full content to be processed is not loaded into memory all at once. This makes
24738 this interface usable for large files or socket streams.
24740 @node GNAT Secondary_Stack_Info g-sestin ads,GNAT Semaphores g-semaph ads,GNAT Rewrite_Data g-rewdat ads,The GNAT Library
24741 @anchor{gnat_rm/the_gnat_library id101}@anchor{399}@anchor{gnat_rm/the_gnat_library gnat-secondary-stack-info-g-sestin-ads}@anchor{39a}
24742 @section @code{GNAT.Secondary_Stack_Info} (@code{g-sestin.ads})
24745 @geindex GNAT.Secondary_Stack_Info (g-sestin.ads)
24747 @geindex Secondary Stack Info
24749 Provide the capability to query the high water mark of the current task's
24752 @node GNAT Semaphores g-semaph ads,GNAT Serial_Communications g-sercom ads,GNAT Secondary_Stack_Info g-sestin ads,The GNAT Library
24753 @anchor{gnat_rm/the_gnat_library id102}@anchor{39b}@anchor{gnat_rm/the_gnat_library gnat-semaphores-g-semaph-ads}@anchor{39c}
24754 @section @code{GNAT.Semaphores} (@code{g-semaph.ads})
24757 @geindex GNAT.Semaphores (g-semaph.ads)
24759 @geindex Semaphores
24761 Provides classic counting and binary semaphores using protected types.
24763 @node GNAT Serial_Communications g-sercom ads,GNAT SHA1 g-sha1 ads,GNAT Semaphores g-semaph ads,The GNAT Library
24764 @anchor{gnat_rm/the_gnat_library gnat-serial-communications-g-sercom-ads}@anchor{39d}@anchor{gnat_rm/the_gnat_library id103}@anchor{39e}
24765 @section @code{GNAT.Serial_Communications} (@code{g-sercom.ads})
24768 @geindex GNAT.Serial_Communications (g-sercom.ads)
24770 @geindex Serial_Communications
24772 Provides a simple interface to send and receive data over a serial
24773 port. This is only supported on GNU/Linux and Windows.
24775 @node GNAT SHA1 g-sha1 ads,GNAT SHA224 g-sha224 ads,GNAT Serial_Communications g-sercom ads,The GNAT Library
24776 @anchor{gnat_rm/the_gnat_library gnat-sha1-g-sha1-ads}@anchor{39f}@anchor{gnat_rm/the_gnat_library id104}@anchor{3a0}
24777 @section @code{GNAT.SHA1} (@code{g-sha1.ads})
24780 @geindex GNAT.SHA1 (g-sha1.ads)
24782 @geindex Secure Hash Algorithm SHA-1
24784 Implements the SHA-1 Secure Hash Algorithm as described in FIPS PUB 180-3
24785 and RFC 3174, and the HMAC-SHA1 message authentication function as described
24786 in RFC 2104 and FIPS PUB 198.
24788 @node GNAT SHA224 g-sha224 ads,GNAT SHA256 g-sha256 ads,GNAT SHA1 g-sha1 ads,The GNAT Library
24789 @anchor{gnat_rm/the_gnat_library gnat-sha224-g-sha224-ads}@anchor{3a1}@anchor{gnat_rm/the_gnat_library id105}@anchor{3a2}
24790 @section @code{GNAT.SHA224} (@code{g-sha224.ads})
24793 @geindex GNAT.SHA224 (g-sha224.ads)
24795 @geindex Secure Hash Algorithm SHA-224
24797 Implements the SHA-224 Secure Hash Algorithm as described in FIPS PUB 180-3,
24798 and the HMAC-SHA224 message authentication function as described
24799 in RFC 2104 and FIPS PUB 198.
24801 @node GNAT SHA256 g-sha256 ads,GNAT SHA384 g-sha384 ads,GNAT SHA224 g-sha224 ads,The GNAT Library
24802 @anchor{gnat_rm/the_gnat_library gnat-sha256-g-sha256-ads}@anchor{3a3}@anchor{gnat_rm/the_gnat_library id106}@anchor{3a4}
24803 @section @code{GNAT.SHA256} (@code{g-sha256.ads})
24806 @geindex GNAT.SHA256 (g-sha256.ads)
24808 @geindex Secure Hash Algorithm SHA-256
24810 Implements the SHA-256 Secure Hash Algorithm as described in FIPS PUB 180-3,
24811 and the HMAC-SHA256 message authentication function as described
24812 in RFC 2104 and FIPS PUB 198.
24814 @node GNAT SHA384 g-sha384 ads,GNAT SHA512 g-sha512 ads,GNAT SHA256 g-sha256 ads,The GNAT Library
24815 @anchor{gnat_rm/the_gnat_library gnat-sha384-g-sha384-ads}@anchor{3a5}@anchor{gnat_rm/the_gnat_library id107}@anchor{3a6}
24816 @section @code{GNAT.SHA384} (@code{g-sha384.ads})
24819 @geindex GNAT.SHA384 (g-sha384.ads)
24821 @geindex Secure Hash Algorithm SHA-384
24823 Implements the SHA-384 Secure Hash Algorithm as described in FIPS PUB 180-3,
24824 and the HMAC-SHA384 message authentication function as described
24825 in RFC 2104 and FIPS PUB 198.
24827 @node GNAT SHA512 g-sha512 ads,GNAT Signals g-signal ads,GNAT SHA384 g-sha384 ads,The GNAT Library
24828 @anchor{gnat_rm/the_gnat_library id108}@anchor{3a7}@anchor{gnat_rm/the_gnat_library gnat-sha512-g-sha512-ads}@anchor{3a8}
24829 @section @code{GNAT.SHA512} (@code{g-sha512.ads})
24832 @geindex GNAT.SHA512 (g-sha512.ads)
24834 @geindex Secure Hash Algorithm SHA-512
24836 Implements the SHA-512 Secure Hash Algorithm as described in FIPS PUB 180-3,
24837 and the HMAC-SHA512 message authentication function as described
24838 in RFC 2104 and FIPS PUB 198.
24840 @node GNAT Signals g-signal ads,GNAT Sockets g-socket ads,GNAT SHA512 g-sha512 ads,The GNAT Library
24841 @anchor{gnat_rm/the_gnat_library id109}@anchor{3a9}@anchor{gnat_rm/the_gnat_library gnat-signals-g-signal-ads}@anchor{3aa}
24842 @section @code{GNAT.Signals} (@code{g-signal.ads})
24845 @geindex GNAT.Signals (g-signal.ads)
24849 Provides the ability to manipulate the blocked status of signals on supported
24852 @node GNAT Sockets g-socket ads,GNAT Source_Info g-souinf ads,GNAT Signals g-signal ads,The GNAT Library
24853 @anchor{gnat_rm/the_gnat_library gnat-sockets-g-socket-ads}@anchor{3ab}@anchor{gnat_rm/the_gnat_library id110}@anchor{3ac}
24854 @section @code{GNAT.Sockets} (@code{g-socket.ads})
24857 @geindex GNAT.Sockets (g-socket.ads)
24861 A high level and portable interface to develop sockets based applications.
24862 This package is based on the sockets thin binding found in
24863 @code{GNAT.Sockets.Thin}. Currently @code{GNAT.Sockets} is implemented
24864 on all native GNAT ports and on VxWorks cross prots. It is not implemented for
24865 the LynxOS cross port.
24867 @node GNAT Source_Info g-souinf ads,GNAT Spelling_Checker g-speche ads,GNAT Sockets g-socket ads,The GNAT Library
24868 @anchor{gnat_rm/the_gnat_library gnat-source-info-g-souinf-ads}@anchor{3ad}@anchor{gnat_rm/the_gnat_library id111}@anchor{3ae}
24869 @section @code{GNAT.Source_Info} (@code{g-souinf.ads})
24872 @geindex GNAT.Source_Info (g-souinf.ads)
24874 @geindex Source Information
24876 Provides subprograms that give access to source code information known at
24877 compile time, such as the current file name and line number. Also provides
24878 subprograms yielding the date and time of the current compilation (like the
24879 C macros @code{__DATE__} and @code{__TIME__})
24881 @node GNAT Spelling_Checker g-speche ads,GNAT Spelling_Checker_Generic g-spchge ads,GNAT Source_Info g-souinf ads,The GNAT Library
24882 @anchor{gnat_rm/the_gnat_library id112}@anchor{3af}@anchor{gnat_rm/the_gnat_library gnat-spelling-checker-g-speche-ads}@anchor{3b0}
24883 @section @code{GNAT.Spelling_Checker} (@code{g-speche.ads})
24886 @geindex GNAT.Spelling_Checker (g-speche.ads)
24888 @geindex Spell checking
24890 Provides a function for determining whether one string is a plausible
24891 near misspelling of another string.
24893 @node GNAT Spelling_Checker_Generic g-spchge ads,GNAT Spitbol Patterns g-spipat ads,GNAT Spelling_Checker g-speche ads,The GNAT Library
24894 @anchor{gnat_rm/the_gnat_library gnat-spelling-checker-generic-g-spchge-ads}@anchor{3b1}@anchor{gnat_rm/the_gnat_library id113}@anchor{3b2}
24895 @section @code{GNAT.Spelling_Checker_Generic} (@code{g-spchge.ads})
24898 @geindex GNAT.Spelling_Checker_Generic (g-spchge.ads)
24900 @geindex Spell checking
24902 Provides a generic function that can be instantiated with a string type for
24903 determining whether one string is a plausible near misspelling of another
24906 @node GNAT Spitbol Patterns g-spipat ads,GNAT Spitbol g-spitbo ads,GNAT Spelling_Checker_Generic g-spchge ads,The GNAT Library
24907 @anchor{gnat_rm/the_gnat_library gnat-spitbol-patterns-g-spipat-ads}@anchor{3b3}@anchor{gnat_rm/the_gnat_library id114}@anchor{3b4}
24908 @section @code{GNAT.Spitbol.Patterns} (@code{g-spipat.ads})
24911 @geindex GNAT.Spitbol.Patterns (g-spipat.ads)
24913 @geindex SPITBOL pattern matching
24915 @geindex Pattern matching
24917 A complete implementation of SNOBOL4 style pattern matching. This is the
24918 most elaborate of the pattern matching packages provided. It fully duplicates
24919 the SNOBOL4 dynamic pattern construction and matching capabilities, using the
24920 efficient algorithm developed by Robert Dewar for the SPITBOL system.
24922 @node GNAT Spitbol g-spitbo ads,GNAT Spitbol Table_Boolean g-sptabo ads,GNAT Spitbol Patterns g-spipat ads,The GNAT Library
24923 @anchor{gnat_rm/the_gnat_library gnat-spitbol-g-spitbo-ads}@anchor{3b5}@anchor{gnat_rm/the_gnat_library id115}@anchor{3b6}
24924 @section @code{GNAT.Spitbol} (@code{g-spitbo.ads})
24927 @geindex GNAT.Spitbol (g-spitbo.ads)
24929 @geindex SPITBOL interface
24931 The top level package of the collection of SPITBOL-style functionality, this
24932 package provides basic SNOBOL4 string manipulation functions, such as
24933 Pad, Reverse, Trim, Substr capability, as well as a generic table function
24934 useful for constructing arbitrary mappings from strings in the style of
24935 the SNOBOL4 TABLE function.
24937 @node GNAT Spitbol Table_Boolean g-sptabo ads,GNAT Spitbol Table_Integer g-sptain ads,GNAT Spitbol g-spitbo ads,The GNAT Library
24938 @anchor{gnat_rm/the_gnat_library id116}@anchor{3b7}@anchor{gnat_rm/the_gnat_library gnat-spitbol-table-boolean-g-sptabo-ads}@anchor{3b8}
24939 @section @code{GNAT.Spitbol.Table_Boolean} (@code{g-sptabo.ads})
24942 @geindex GNAT.Spitbol.Table_Boolean (g-sptabo.ads)
24944 @geindex Sets of strings
24946 @geindex SPITBOL Tables
24948 A library level of instantiation of @code{GNAT.Spitbol.Patterns.Table}
24949 for type @code{Standard.Boolean}, giving an implementation of sets of
24952 @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
24953 @anchor{gnat_rm/the_gnat_library gnat-spitbol-table-integer-g-sptain-ads}@anchor{3b9}@anchor{gnat_rm/the_gnat_library id117}@anchor{3ba}
24954 @section @code{GNAT.Spitbol.Table_Integer} (@code{g-sptain.ads})
24957 @geindex GNAT.Spitbol.Table_Integer (g-sptain.ads)
24959 @geindex Integer maps
24963 @geindex SPITBOL Tables
24965 A library level of instantiation of @code{GNAT.Spitbol.Patterns.Table}
24966 for type @code{Standard.Integer}, giving an implementation of maps
24967 from string to integer values.
24969 @node GNAT Spitbol Table_VString g-sptavs ads,GNAT SSE g-sse ads,GNAT Spitbol Table_Integer g-sptain ads,The GNAT Library
24970 @anchor{gnat_rm/the_gnat_library id118}@anchor{3bb}@anchor{gnat_rm/the_gnat_library gnat-spitbol-table-vstring-g-sptavs-ads}@anchor{3bc}
24971 @section @code{GNAT.Spitbol.Table_VString} (@code{g-sptavs.ads})
24974 @geindex GNAT.Spitbol.Table_VString (g-sptavs.ads)
24976 @geindex String maps
24980 @geindex SPITBOL Tables
24982 A library level of instantiation of @code{GNAT.Spitbol.Patterns.Table} for
24983 a variable length string type, giving an implementation of general
24984 maps from strings to strings.
24986 @node GNAT SSE g-sse ads,GNAT SSE Vector_Types g-ssvety ads,GNAT Spitbol Table_VString g-sptavs ads,The GNAT Library
24987 @anchor{gnat_rm/the_gnat_library id119}@anchor{3bd}@anchor{gnat_rm/the_gnat_library gnat-sse-g-sse-ads}@anchor{3be}
24988 @section @code{GNAT.SSE} (@code{g-sse.ads})
24991 @geindex GNAT.SSE (g-sse.ads)
24993 Root of a set of units aimed at offering Ada bindings to a subset of
24994 the Intel(r) Streaming SIMD Extensions with GNAT on the x86 family of
24995 targets. It exposes vector component types together with a general
24996 introduction to the binding contents and use.
24998 @node GNAT SSE Vector_Types g-ssvety ads,GNAT String_Hash g-strhas ads,GNAT SSE g-sse ads,The GNAT Library
24999 @anchor{gnat_rm/the_gnat_library gnat-sse-vector-types-g-ssvety-ads}@anchor{3bf}@anchor{gnat_rm/the_gnat_library id120}@anchor{3c0}
25000 @section @code{GNAT.SSE.Vector_Types} (@code{g-ssvety.ads})
25003 @geindex GNAT.SSE.Vector_Types (g-ssvety.ads)
25005 SSE vector types for use with SSE related intrinsics.
25007 @node GNAT String_Hash g-strhas ads,GNAT Strings g-string ads,GNAT SSE Vector_Types g-ssvety ads,The GNAT Library
25008 @anchor{gnat_rm/the_gnat_library gnat-string-hash-g-strhas-ads}@anchor{3c1}@anchor{gnat_rm/the_gnat_library id121}@anchor{3c2}
25009 @section @code{GNAT.String_Hash} (@code{g-strhas.ads})
25012 @geindex GNAT.String_Hash (g-strhas.ads)
25014 @geindex Hash functions
25016 Provides a generic hash function working on arrays of scalars. Both the scalar
25017 type and the hash result type are parameters.
25019 @node GNAT Strings g-string ads,GNAT String_Split g-strspl ads,GNAT String_Hash g-strhas ads,The GNAT Library
25020 @anchor{gnat_rm/the_gnat_library gnat-strings-g-string-ads}@anchor{3c3}@anchor{gnat_rm/the_gnat_library id122}@anchor{3c4}
25021 @section @code{GNAT.Strings} (@code{g-string.ads})
25024 @geindex GNAT.Strings (g-string.ads)
25026 Common String access types and related subprograms. Basically it
25027 defines a string access and an array of string access types.
25029 @node GNAT String_Split g-strspl ads,GNAT Table g-table ads,GNAT Strings g-string ads,The GNAT Library
25030 @anchor{gnat_rm/the_gnat_library gnat-string-split-g-strspl-ads}@anchor{3c5}@anchor{gnat_rm/the_gnat_library id123}@anchor{3c6}
25031 @section @code{GNAT.String_Split} (@code{g-strspl.ads})
25034 @geindex GNAT.String_Split (g-strspl.ads)
25036 @geindex String splitter
25038 Useful string manipulation routines: given a set of separators, split
25039 a string wherever the separators appear, and provide direct access
25040 to the resulting slices. This package is instantiated from
25041 @code{GNAT.Array_Split}.
25043 @node GNAT Table g-table ads,GNAT Task_Lock g-tasloc ads,GNAT String_Split g-strspl ads,The GNAT Library
25044 @anchor{gnat_rm/the_gnat_library id124}@anchor{3c7}@anchor{gnat_rm/the_gnat_library gnat-table-g-table-ads}@anchor{3c8}
25045 @section @code{GNAT.Table} (@code{g-table.ads})
25048 @geindex GNAT.Table (g-table.ads)
25050 @geindex Table implementation
25053 @geindex extendable
25055 A generic package providing a single dimension array abstraction where the
25056 length of the array can be dynamically modified.
25058 This package provides a facility similar to that of @code{GNAT.Dynamic_Tables},
25059 except that this package declares a single instance of the table type,
25060 while an instantiation of @code{GNAT.Dynamic_Tables} creates a type that can be
25061 used to define dynamic instances of the table.
25063 @node GNAT Task_Lock g-tasloc ads,GNAT Time_Stamp g-timsta ads,GNAT Table g-table ads,The GNAT Library
25064 @anchor{gnat_rm/the_gnat_library id125}@anchor{3c9}@anchor{gnat_rm/the_gnat_library gnat-task-lock-g-tasloc-ads}@anchor{3ca}
25065 @section @code{GNAT.Task_Lock} (@code{g-tasloc.ads})
25068 @geindex GNAT.Task_Lock (g-tasloc.ads)
25070 @geindex Task synchronization
25072 @geindex Task locking
25076 A very simple facility for locking and unlocking sections of code using a
25077 single global task lock. Appropriate for use in situations where contention
25078 between tasks is very rarely expected.
25080 @node GNAT Time_Stamp g-timsta ads,GNAT Threads g-thread ads,GNAT Task_Lock g-tasloc ads,The GNAT Library
25081 @anchor{gnat_rm/the_gnat_library id126}@anchor{3cb}@anchor{gnat_rm/the_gnat_library gnat-time-stamp-g-timsta-ads}@anchor{3cc}
25082 @section @code{GNAT.Time_Stamp} (@code{g-timsta.ads})
25085 @geindex GNAT.Time_Stamp (g-timsta.ads)
25087 @geindex Time stamp
25089 @geindex Current time
25091 Provides a simple function that returns a string YYYY-MM-DD HH:MM:SS.SS that
25092 represents the current date and time in ISO 8601 format. This is a very simple
25093 routine with minimal code and there are no dependencies on any other unit.
25095 @node GNAT Threads g-thread ads,GNAT Traceback g-traceb ads,GNAT Time_Stamp g-timsta ads,The GNAT Library
25096 @anchor{gnat_rm/the_gnat_library id127}@anchor{3cd}@anchor{gnat_rm/the_gnat_library gnat-threads-g-thread-ads}@anchor{3ce}
25097 @section @code{GNAT.Threads} (@code{g-thread.ads})
25100 @geindex GNAT.Threads (g-thread.ads)
25102 @geindex Foreign threads
25107 Provides facilities for dealing with foreign threads which need to be known
25108 by the GNAT run-time system. Consult the documentation of this package for
25109 further details if your program has threads that are created by a non-Ada
25110 environment which then accesses Ada code.
25112 @node GNAT Traceback g-traceb ads,GNAT Traceback Symbolic g-trasym ads,GNAT Threads g-thread ads,The GNAT Library
25113 @anchor{gnat_rm/the_gnat_library id128}@anchor{3cf}@anchor{gnat_rm/the_gnat_library gnat-traceback-g-traceb-ads}@anchor{3d0}
25114 @section @code{GNAT.Traceback} (@code{g-traceb.ads})
25117 @geindex GNAT.Traceback (g-traceb.ads)
25119 @geindex Trace back facilities
25121 Provides a facility for obtaining non-symbolic traceback information, useful
25122 in various debugging situations.
25124 @node GNAT Traceback Symbolic g-trasym ads,GNAT UTF_32 g-table ads,GNAT Traceback g-traceb ads,The GNAT Library
25125 @anchor{gnat_rm/the_gnat_library gnat-traceback-symbolic-g-trasym-ads}@anchor{3d1}@anchor{gnat_rm/the_gnat_library id129}@anchor{3d2}
25126 @section @code{GNAT.Traceback.Symbolic} (@code{g-trasym.ads})
25129 @geindex GNAT.Traceback.Symbolic (g-trasym.ads)
25131 @geindex Trace back facilities
25133 @node GNAT UTF_32 g-table ads,GNAT Wide_Spelling_Checker g-u3spch ads,GNAT Traceback Symbolic g-trasym ads,The GNAT Library
25134 @anchor{gnat_rm/the_gnat_library id130}@anchor{3d3}@anchor{gnat_rm/the_gnat_library gnat-utf-32-g-table-ads}@anchor{3d4}
25135 @section @code{GNAT.UTF_32} (@code{g-table.ads})
25138 @geindex GNAT.UTF_32 (g-table.ads)
25140 @geindex Wide character codes
25142 This is a package intended to be used in conjunction with the
25143 @code{Wide_Character} type in Ada 95 and the
25144 @code{Wide_Wide_Character} type in Ada 2005 (available
25145 in @code{GNAT} in Ada 2005 mode). This package contains
25146 Unicode categorization routines, as well as lexical
25147 categorization routines corresponding to the Ada 2005
25148 lexical rules for identifiers and strings, and also a
25149 lower case to upper case fold routine corresponding to
25150 the Ada 2005 rules for identifier equivalence.
25152 @node GNAT Wide_Spelling_Checker g-u3spch ads,GNAT Wide_Spelling_Checker g-wispch ads,GNAT UTF_32 g-table ads,The GNAT Library
25153 @anchor{gnat_rm/the_gnat_library gnat-wide-spelling-checker-g-u3spch-ads}@anchor{3d5}@anchor{gnat_rm/the_gnat_library id131}@anchor{3d6}
25154 @section @code{GNAT.Wide_Spelling_Checker} (@code{g-u3spch.ads})
25157 @geindex GNAT.Wide_Spelling_Checker (g-u3spch.ads)
25159 @geindex Spell checking
25161 Provides a function for determining whether one wide wide string is a plausible
25162 near misspelling of another wide wide string, where the strings are represented
25163 using the UTF_32_String type defined in System.Wch_Cnv.
25165 @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
25166 @anchor{gnat_rm/the_gnat_library gnat-wide-spelling-checker-g-wispch-ads}@anchor{3d7}@anchor{gnat_rm/the_gnat_library id132}@anchor{3d8}
25167 @section @code{GNAT.Wide_Spelling_Checker} (@code{g-wispch.ads})
25170 @geindex GNAT.Wide_Spelling_Checker (g-wispch.ads)
25172 @geindex Spell checking
25174 Provides a function for determining whether one wide string is a plausible
25175 near misspelling of another wide string.
25177 @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
25178 @anchor{gnat_rm/the_gnat_library id133}@anchor{3d9}@anchor{gnat_rm/the_gnat_library gnat-wide-string-split-g-wistsp-ads}@anchor{3da}
25179 @section @code{GNAT.Wide_String_Split} (@code{g-wistsp.ads})
25182 @geindex GNAT.Wide_String_Split (g-wistsp.ads)
25184 @geindex Wide_String splitter
25186 Useful wide string manipulation routines: given a set of separators, split
25187 a wide string wherever the separators appear, and provide direct access
25188 to the resulting slices. This package is instantiated from
25189 @code{GNAT.Array_Split}.
25191 @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
25192 @anchor{gnat_rm/the_gnat_library gnat-wide-wide-spelling-checker-g-zspche-ads}@anchor{3db}@anchor{gnat_rm/the_gnat_library id134}@anchor{3dc}
25193 @section @code{GNAT.Wide_Wide_Spelling_Checker} (@code{g-zspche.ads})
25196 @geindex GNAT.Wide_Wide_Spelling_Checker (g-zspche.ads)
25198 @geindex Spell checking
25200 Provides a function for determining whether one wide wide string is a plausible
25201 near misspelling of another wide wide string.
25203 @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
25204 @anchor{gnat_rm/the_gnat_library gnat-wide-wide-string-split-g-zistsp-ads}@anchor{3dd}@anchor{gnat_rm/the_gnat_library id135}@anchor{3de}
25205 @section @code{GNAT.Wide_Wide_String_Split} (@code{g-zistsp.ads})
25208 @geindex GNAT.Wide_Wide_String_Split (g-zistsp.ads)
25210 @geindex Wide_Wide_String splitter
25212 Useful wide wide string manipulation routines: given a set of separators, split
25213 a wide wide string wherever the separators appear, and provide direct access
25214 to the resulting slices. This package is instantiated from
25215 @code{GNAT.Array_Split}.
25217 @node Interfaces C Extensions i-cexten ads,Interfaces C Streams i-cstrea ads,GNAT Wide_Wide_String_Split g-zistsp ads,The GNAT Library
25218 @anchor{gnat_rm/the_gnat_library interfaces-c-extensions-i-cexten-ads}@anchor{3df}@anchor{gnat_rm/the_gnat_library id136}@anchor{3e0}
25219 @section @code{Interfaces.C.Extensions} (@code{i-cexten.ads})
25222 @geindex Interfaces.C.Extensions (i-cexten.ads)
25224 This package contains additional C-related definitions, intended
25225 for use with either manually or automatically generated bindings
25228 @node Interfaces C Streams i-cstrea ads,Interfaces Packed_Decimal i-pacdec ads,Interfaces C Extensions i-cexten ads,The GNAT Library
25229 @anchor{gnat_rm/the_gnat_library interfaces-c-streams-i-cstrea-ads}@anchor{3e1}@anchor{gnat_rm/the_gnat_library id137}@anchor{3e2}
25230 @section @code{Interfaces.C.Streams} (@code{i-cstrea.ads})
25233 @geindex Interfaces.C.Streams (i-cstrea.ads)
25236 @geindex interfacing
25238 This package is a binding for the most commonly used operations
25241 @node Interfaces Packed_Decimal i-pacdec ads,Interfaces VxWorks i-vxwork ads,Interfaces C Streams i-cstrea ads,The GNAT Library
25242 @anchor{gnat_rm/the_gnat_library id138}@anchor{3e3}@anchor{gnat_rm/the_gnat_library interfaces-packed-decimal-i-pacdec-ads}@anchor{3e4}
25243 @section @code{Interfaces.Packed_Decimal} (@code{i-pacdec.ads})
25246 @geindex Interfaces.Packed_Decimal (i-pacdec.ads)
25248 @geindex IBM Packed Format
25250 @geindex Packed Decimal
25252 This package provides a set of routines for conversions to and
25253 from a packed decimal format compatible with that used on IBM
25256 @node Interfaces VxWorks i-vxwork ads,Interfaces VxWorks Int_Connection i-vxinco ads,Interfaces Packed_Decimal i-pacdec ads,The GNAT Library
25257 @anchor{gnat_rm/the_gnat_library id139}@anchor{3e5}@anchor{gnat_rm/the_gnat_library interfaces-vxworks-i-vxwork-ads}@anchor{3e6}
25258 @section @code{Interfaces.VxWorks} (@code{i-vxwork.ads})
25261 @geindex Interfaces.VxWorks (i-vxwork.ads)
25263 @geindex Interfacing to VxWorks
25266 @geindex interfacing
25268 This package provides a limited binding to the VxWorks API.
25269 In particular, it interfaces with the
25270 VxWorks hardware interrupt facilities.
25272 @node Interfaces VxWorks Int_Connection i-vxinco ads,Interfaces VxWorks IO i-vxwoio ads,Interfaces VxWorks i-vxwork ads,The GNAT Library
25273 @anchor{gnat_rm/the_gnat_library interfaces-vxworks-int-connection-i-vxinco-ads}@anchor{3e7}@anchor{gnat_rm/the_gnat_library id140}@anchor{3e8}
25274 @section @code{Interfaces.VxWorks.Int_Connection} (@code{i-vxinco.ads})
25277 @geindex Interfaces.VxWorks.Int_Connection (i-vxinco.ads)
25279 @geindex Interfacing to VxWorks
25282 @geindex interfacing
25284 This package provides a way for users to replace the use of
25285 intConnect() with a custom routine for installing interrupt
25288 @node Interfaces VxWorks IO i-vxwoio ads,System Address_Image s-addima ads,Interfaces VxWorks Int_Connection i-vxinco ads,The GNAT Library
25289 @anchor{gnat_rm/the_gnat_library interfaces-vxworks-io-i-vxwoio-ads}@anchor{3e9}@anchor{gnat_rm/the_gnat_library id141}@anchor{3ea}
25290 @section @code{Interfaces.VxWorks.IO} (@code{i-vxwoio.ads})
25293 @geindex Interfaces.VxWorks.IO (i-vxwoio.ads)
25295 @geindex Interfacing to VxWorks' I/O
25298 @geindex I/O interfacing
25301 @geindex Get_Immediate
25303 @geindex Get_Immediate
25306 This package provides a binding to the ioctl (IO/Control)
25307 function of VxWorks, defining a set of option values and
25308 function codes. A particular use of this package is
25309 to enable the use of Get_Immediate under VxWorks.
25311 @node System Address_Image s-addima ads,System Assertions s-assert ads,Interfaces VxWorks IO i-vxwoio ads,The GNAT Library
25312 @anchor{gnat_rm/the_gnat_library system-address-image-s-addima-ads}@anchor{3eb}@anchor{gnat_rm/the_gnat_library id142}@anchor{3ec}
25313 @section @code{System.Address_Image} (@code{s-addima.ads})
25316 @geindex System.Address_Image (s-addima.ads)
25318 @geindex Address image
25321 @geindex of an address
25323 This function provides a useful debugging
25324 function that gives an (implementation dependent)
25325 string which identifies an address.
25327 @node System Assertions s-assert ads,System Atomic_Counters s-atocou ads,System Address_Image s-addima ads,The GNAT Library
25328 @anchor{gnat_rm/the_gnat_library system-assertions-s-assert-ads}@anchor{3ed}@anchor{gnat_rm/the_gnat_library id143}@anchor{3ee}
25329 @section @code{System.Assertions} (@code{s-assert.ads})
25332 @geindex System.Assertions (s-assert.ads)
25334 @geindex Assertions
25336 @geindex Assert_Failure
25339 This package provides the declaration of the exception raised
25340 by an run-time assertion failure, as well as the routine that
25341 is used internally to raise this assertion.
25343 @node System Atomic_Counters s-atocou ads,System Memory s-memory ads,System Assertions s-assert ads,The GNAT Library
25344 @anchor{gnat_rm/the_gnat_library id144}@anchor{3ef}@anchor{gnat_rm/the_gnat_library system-atomic-counters-s-atocou-ads}@anchor{3f0}
25345 @section @code{System.Atomic_Counters} (@code{s-atocou.ads})
25348 @geindex System.Atomic_Counters (s-atocou.ads)
25350 This package provides the declaration of an atomic counter type,
25351 together with efficient routines (using hardware
25352 synchronization primitives) for incrementing, decrementing,
25353 and testing of these counters. This package is implemented
25354 on most targets, including all Alpha, ia64, PowerPC, SPARC V9,
25355 x86, and x86_64 platforms.
25357 @node System Memory s-memory ads,System Multiprocessors s-multip ads,System Atomic_Counters s-atocou ads,The GNAT Library
25358 @anchor{gnat_rm/the_gnat_library system-memory-s-memory-ads}@anchor{3f1}@anchor{gnat_rm/the_gnat_library id145}@anchor{3f2}
25359 @section @code{System.Memory} (@code{s-memory.ads})
25362 @geindex System.Memory (s-memory.ads)
25364 @geindex Memory allocation
25366 This package provides the interface to the low level routines used
25367 by the generated code for allocation and freeing storage for the
25368 default storage pool (analogous to the C routines malloc and free.
25369 It also provides a reallocation interface analogous to the C routine
25370 realloc. The body of this unit may be modified to provide alternative
25371 allocation mechanisms for the default pool, and in addition, direct
25372 calls to this unit may be made for low level allocation uses (for
25373 example see the body of @code{GNAT.Tables}).
25375 @node System Multiprocessors s-multip ads,System Multiprocessors Dispatching_Domains s-mudido ads,System Memory s-memory ads,The GNAT Library
25376 @anchor{gnat_rm/the_gnat_library id146}@anchor{3f3}@anchor{gnat_rm/the_gnat_library system-multiprocessors-s-multip-ads}@anchor{3f4}
25377 @section @code{System.Multiprocessors} (@code{s-multip.ads})
25380 @geindex System.Multiprocessors (s-multip.ads)
25382 @geindex Multiprocessor interface
25384 This is an Ada 2012 unit defined in the Ada 2012 Reference Manual, but
25385 in GNAT we also make it available in Ada 95 and Ada 2005 (where it is
25386 technically an implementation-defined addition).
25388 @node System Multiprocessors Dispatching_Domains s-mudido ads,System Partition_Interface s-parint ads,System Multiprocessors s-multip ads,The GNAT Library
25389 @anchor{gnat_rm/the_gnat_library system-multiprocessors-dispatching-domains-s-mudido-ads}@anchor{3f5}@anchor{gnat_rm/the_gnat_library id147}@anchor{3f6}
25390 @section @code{System.Multiprocessors.Dispatching_Domains} (@code{s-mudido.ads})
25393 @geindex System.Multiprocessors.Dispatching_Domains (s-mudido.ads)
25395 @geindex Multiprocessor interface
25397 This is an Ada 2012 unit defined in the Ada 2012 Reference Manual, but
25398 in GNAT we also make it available in Ada 95 and Ada 2005 (where it is
25399 technically an implementation-defined addition).
25401 @node System Partition_Interface s-parint ads,System Pool_Global s-pooglo ads,System Multiprocessors Dispatching_Domains s-mudido ads,The GNAT Library
25402 @anchor{gnat_rm/the_gnat_library id148}@anchor{3f7}@anchor{gnat_rm/the_gnat_library system-partition-interface-s-parint-ads}@anchor{3f8}
25403 @section @code{System.Partition_Interface} (@code{s-parint.ads})
25406 @geindex System.Partition_Interface (s-parint.ads)
25408 @geindex Partition interfacing functions
25410 This package provides facilities for partition interfacing. It
25411 is used primarily in a distribution context when using Annex E
25414 @node System Pool_Global s-pooglo ads,System Pool_Local s-pooloc ads,System Partition_Interface s-parint ads,The GNAT Library
25415 @anchor{gnat_rm/the_gnat_library id149}@anchor{3f9}@anchor{gnat_rm/the_gnat_library system-pool-global-s-pooglo-ads}@anchor{3fa}
25416 @section @code{System.Pool_Global} (@code{s-pooglo.ads})
25419 @geindex System.Pool_Global (s-pooglo.ads)
25421 @geindex Storage pool
25424 @geindex Global storage pool
25426 This package provides a storage pool that is equivalent to the default
25427 storage pool used for access types for which no pool is specifically
25428 declared. It uses malloc/free to allocate/free and does not attempt to
25429 do any automatic reclamation.
25431 @node System Pool_Local s-pooloc ads,System Restrictions s-restri ads,System Pool_Global s-pooglo ads,The GNAT Library
25432 @anchor{gnat_rm/the_gnat_library system-pool-local-s-pooloc-ads}@anchor{3fb}@anchor{gnat_rm/the_gnat_library id150}@anchor{3fc}
25433 @section @code{System.Pool_Local} (@code{s-pooloc.ads})
25436 @geindex System.Pool_Local (s-pooloc.ads)
25438 @geindex Storage pool
25441 @geindex Local storage pool
25443 This package provides a storage pool that is intended for use with locally
25444 defined access types. It uses malloc/free for allocate/free, and maintains
25445 a list of allocated blocks, so that all storage allocated for the pool can
25446 be freed automatically when the pool is finalized.
25448 @node System Restrictions s-restri ads,System Rident s-rident ads,System Pool_Local s-pooloc ads,The GNAT Library
25449 @anchor{gnat_rm/the_gnat_library system-restrictions-s-restri-ads}@anchor{3fd}@anchor{gnat_rm/the_gnat_library id151}@anchor{3fe}
25450 @section @code{System.Restrictions} (@code{s-restri.ads})
25453 @geindex System.Restrictions (s-restri.ads)
25455 @geindex Run-time restrictions access
25457 This package provides facilities for accessing at run time
25458 the status of restrictions specified at compile time for
25459 the partition. Information is available both with regard
25460 to actual restrictions specified, and with regard to
25461 compiler determined information on which restrictions
25462 are violated by one or more packages in the partition.
25464 @node System Rident s-rident ads,System Strings Stream_Ops s-ststop ads,System Restrictions s-restri ads,The GNAT Library
25465 @anchor{gnat_rm/the_gnat_library system-rident-s-rident-ads}@anchor{3ff}@anchor{gnat_rm/the_gnat_library id152}@anchor{400}
25466 @section @code{System.Rident} (@code{s-rident.ads})
25469 @geindex System.Rident (s-rident.ads)
25471 @geindex Restrictions definitions
25473 This package provides definitions of the restrictions
25474 identifiers supported by GNAT, and also the format of
25475 the restrictions provided in package System.Restrictions.
25476 It is not normally necessary to @code{with} this generic package
25477 since the necessary instantiation is included in
25478 package System.Restrictions.
25480 @node System Strings Stream_Ops s-ststop ads,System Unsigned_Types s-unstyp ads,System Rident s-rident ads,The GNAT Library
25481 @anchor{gnat_rm/the_gnat_library id153}@anchor{401}@anchor{gnat_rm/the_gnat_library system-strings-stream-ops-s-ststop-ads}@anchor{402}
25482 @section @code{System.Strings.Stream_Ops} (@code{s-ststop.ads})
25485 @geindex System.Strings.Stream_Ops (s-ststop.ads)
25487 @geindex Stream operations
25489 @geindex String stream operations
25491 This package provides a set of stream subprograms for standard string types.
25492 It is intended primarily to support implicit use of such subprograms when
25493 stream attributes are applied to string types, but the subprograms in this
25494 package can be used directly by application programs.
25496 @node System Unsigned_Types s-unstyp ads,System Wch_Cnv s-wchcnv ads,System Strings Stream_Ops s-ststop ads,The GNAT Library
25497 @anchor{gnat_rm/the_gnat_library system-unsigned-types-s-unstyp-ads}@anchor{403}@anchor{gnat_rm/the_gnat_library id154}@anchor{404}
25498 @section @code{System.Unsigned_Types} (@code{s-unstyp.ads})
25501 @geindex System.Unsigned_Types (s-unstyp.ads)
25503 This package contains definitions of standard unsigned types that
25504 correspond in size to the standard signed types declared in Standard,
25505 and (unlike the types in Interfaces) have corresponding names. It
25506 also contains some related definitions for other specialized types
25507 used by the compiler in connection with packed array types.
25509 @node System Wch_Cnv s-wchcnv ads,System Wch_Con s-wchcon ads,System Unsigned_Types s-unstyp ads,The GNAT Library
25510 @anchor{gnat_rm/the_gnat_library system-wch-cnv-s-wchcnv-ads}@anchor{405}@anchor{gnat_rm/the_gnat_library id155}@anchor{406}
25511 @section @code{System.Wch_Cnv} (@code{s-wchcnv.ads})
25514 @geindex System.Wch_Cnv (s-wchcnv.ads)
25516 @geindex Wide Character
25517 @geindex Representation
25519 @geindex Wide String
25520 @geindex Conversion
25522 @geindex Representation of wide characters
25524 This package provides routines for converting between
25525 wide and wide wide characters and a representation as a value of type
25526 @code{Standard.String}, using a specified wide character
25527 encoding method. It uses definitions in
25528 package @code{System.Wch_Con}.
25530 @node System Wch_Con s-wchcon ads,,System Wch_Cnv s-wchcnv ads,The GNAT Library
25531 @anchor{gnat_rm/the_gnat_library id156}@anchor{407}@anchor{gnat_rm/the_gnat_library system-wch-con-s-wchcon-ads}@anchor{408}
25532 @section @code{System.Wch_Con} (@code{s-wchcon.ads})
25535 @geindex System.Wch_Con (s-wchcon.ads)
25537 This package provides definitions and descriptions of
25538 the various methods used for encoding wide characters
25539 in ordinary strings. These definitions are used by
25540 the package @code{System.Wch_Cnv}.
25542 @node Interfacing to Other Languages,Specialized Needs Annexes,The GNAT Library,Top
25543 @anchor{gnat_rm/interfacing_to_other_languages interfacing-to-other-languages}@anchor{11}@anchor{gnat_rm/interfacing_to_other_languages doc}@anchor{409}@anchor{gnat_rm/interfacing_to_other_languages id1}@anchor{40a}
25544 @chapter Interfacing to Other Languages
25547 The facilities in Annex B of the Ada Reference Manual are fully
25548 implemented in GNAT, and in addition, a full interface to C++ is
25552 * Interfacing to C::
25553 * Interfacing to C++::
25554 * Interfacing to COBOL::
25555 * Interfacing to Fortran::
25556 * Interfacing to non-GNAT Ada code::
25560 @node Interfacing to C,Interfacing to C++,,Interfacing to Other Languages
25561 @anchor{gnat_rm/interfacing_to_other_languages interfacing-to-c}@anchor{40b}@anchor{gnat_rm/interfacing_to_other_languages id2}@anchor{40c}
25562 @section Interfacing to C
25565 Interfacing to C with GNAT can use one of two approaches:
25571 The types in the package @code{Interfaces.C} may be used.
25574 Standard Ada types may be used directly. This may be less portable to
25575 other compilers, but will work on all GNAT compilers, which guarantee
25576 correspondence between the C and Ada types.
25579 Pragma @code{Convention C} may be applied to Ada types, but mostly has no
25580 effect, since this is the default. The following table shows the
25581 correspondence between Ada scalar types and the corresponding C types.
25584 @multitable {xxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
25603 @code{Short_Integer}
25611 @code{Short_Short_Integer}
25619 @code{Long_Integer}
25627 @code{Long_Long_Integer}
25659 @code{Long_Long_Float}
25663 This is the longest floating-point type supported by the hardware.
25668 Additionally, there are the following general correspondences between Ada
25675 Ada enumeration types map to C enumeration types directly if pragma
25676 @code{Convention C} is specified, which causes them to have a length of
25677 32 bits, except for boolean types which map to C99 @code{bool} and for
25678 which the length is 8 bits.
25679 Without pragma @code{Convention C}, Ada enumeration types map to
25680 8, 16, or 32 bits (i.e., C types @code{signed char}, @code{short},
25681 @code{int}, respectively) depending on the number of values passed.
25682 This is the only case in which pragma @code{Convention C} affects the
25683 representation of an Ada type.
25686 Ada access types map to C pointers, except for the case of pointers to
25687 unconstrained types in Ada, which have no direct C equivalent.
25690 Ada arrays map directly to C arrays.
25693 Ada records map directly to C structures.
25696 Packed Ada records map to C structures where all members are bit fields
25697 of the length corresponding to the @code{type'Size} value in Ada.
25700 @node Interfacing to C++,Interfacing to COBOL,Interfacing to C,Interfacing to Other Languages
25701 @anchor{gnat_rm/interfacing_to_other_languages id4}@anchor{40d}@anchor{gnat_rm/interfacing_to_other_languages id3}@anchor{49}
25702 @section Interfacing to C++
25705 The interface to C++ makes use of the following pragmas, which are
25706 primarily intended to be constructed automatically using a binding generator
25707 tool, although it is possible to construct them by hand.
25709 Using these pragmas it is possible to achieve complete
25710 inter-operability between Ada tagged types and C++ class definitions.
25711 See @ref{7,,Implementation Defined Pragmas}, for more details.
25716 @item @code{pragma CPP_Class ([Entity =>] @emph{LOCAL_NAME})}
25718 The argument denotes an entity in the current declarative region that is
25719 declared as a tagged or untagged record type. It indicates that the type
25720 corresponds to an externally declared C++ class type, and is to be laid
25721 out the same way that C++ would lay out the type.
25723 Note: Pragma @code{CPP_Class} is currently obsolete. It is supported
25724 for backward compatibility but its functionality is available
25725 using pragma @code{Import} with @code{Convention} = @code{CPP}.
25727 @item @code{pragma CPP_Constructor ([Entity =>] @emph{LOCAL_NAME})}
25729 This pragma identifies an imported function (imported in the usual way
25730 with pragma @code{Import}) as corresponding to a C++ constructor.
25733 A few restrictions are placed on the use of the @code{Access} attribute
25734 in conjunction with subprograms subject to convention @code{CPP}: the
25735 attribute may be used neither on primitive operations of a tagged
25736 record type with convention @code{CPP}, imported or not, nor on
25737 subprograms imported with pragma @code{CPP_Constructor}.
25739 In addition, C++ exceptions are propagated and can be handled in an
25740 @code{others} choice of an exception handler. The corresponding Ada
25741 occurrence has no message, and the simple name of the exception identity
25742 contains @code{Foreign_Exception}. Finalization and awaiting dependent
25743 tasks works properly when such foreign exceptions are propagated.
25745 It is also possible to import a C++ exception using the following syntax:
25748 LOCAL_NAME : exception;
25749 pragma Import (Cpp,
25750 [Entity =>] LOCAL_NAME,
25751 [External_Name =>] static_string_EXPRESSION);
25754 The @code{External_Name} is the name of the C++ RTTI symbol. You can then
25755 cover a specific C++ exception in an exception handler.
25757 @node Interfacing to COBOL,Interfacing to Fortran,Interfacing to C++,Interfacing to Other Languages
25758 @anchor{gnat_rm/interfacing_to_other_languages id5}@anchor{40e}@anchor{gnat_rm/interfacing_to_other_languages interfacing-to-cobol}@anchor{40f}
25759 @section Interfacing to COBOL
25762 Interfacing to COBOL is achieved as described in section B.4 of
25763 the Ada Reference Manual.
25765 @node Interfacing to Fortran,Interfacing to non-GNAT Ada code,Interfacing to COBOL,Interfacing to Other Languages
25766 @anchor{gnat_rm/interfacing_to_other_languages id6}@anchor{410}@anchor{gnat_rm/interfacing_to_other_languages interfacing-to-fortran}@anchor{411}
25767 @section Interfacing to Fortran
25770 Interfacing to Fortran is achieved as described in section B.5 of the
25771 Ada Reference Manual. The pragma @code{Convention Fortran}, applied to a
25772 multi-dimensional array causes the array to be stored in column-major
25773 order as required for convenient interface to Fortran.
25775 @node Interfacing to non-GNAT Ada code,,Interfacing to Fortran,Interfacing to Other Languages
25776 @anchor{gnat_rm/interfacing_to_other_languages interfacing-to-non-gnat-ada-code}@anchor{412}@anchor{gnat_rm/interfacing_to_other_languages id7}@anchor{413}
25777 @section Interfacing to non-GNAT Ada code
25780 It is possible to specify the convention @code{Ada} in a pragma
25781 @code{Import} or pragma @code{Export}. However this refers to
25782 the calling conventions used by GNAT, which may or may not be
25783 similar enough to those used by some other Ada 83 / Ada 95 / Ada 2005
25784 compiler to allow interoperation.
25786 If arguments types are kept simple, and if the foreign compiler generally
25787 follows system calling conventions, then it may be possible to integrate
25788 files compiled by other Ada compilers, provided that the elaboration
25789 issues are adequately addressed (for example by eliminating the
25790 need for any load time elaboration).
25792 In particular, GNAT running on VMS is designed to
25793 be highly compatible with the DEC Ada 83 compiler, so this is one
25794 case in which it is possible to import foreign units of this type,
25795 provided that the data items passed are restricted to simple scalar
25796 values or simple record types without variants, or simple array
25797 types with fixed bounds.
25799 @node Specialized Needs Annexes,Implementation of Specific Ada Features,Interfacing to Other Languages,Top
25800 @anchor{gnat_rm/specialized_needs_annexes specialized-needs-annexes}@anchor{12}@anchor{gnat_rm/specialized_needs_annexes doc}@anchor{414}@anchor{gnat_rm/specialized_needs_annexes id1}@anchor{415}
25801 @chapter Specialized Needs Annexes
25804 Ada 95, Ada 2005, and Ada 2012 define a number of Specialized Needs Annexes, which are not
25805 required in all implementations. However, as described in this chapter,
25806 GNAT implements all of these annexes:
25811 @item @emph{Systems Programming (Annex C)}
25813 The Systems Programming Annex is fully implemented.
25815 @item @emph{Real-Time Systems (Annex D)}
25817 The Real-Time Systems Annex is fully implemented.
25819 @item @emph{Distributed Systems (Annex E)}
25821 Stub generation is fully implemented in the GNAT compiler. In addition,
25822 a complete compatible PCS is available as part of the GLADE system,
25823 a separate product. When the two
25824 products are used in conjunction, this annex is fully implemented.
25826 @item @emph{Information Systems (Annex F)}
25828 The Information Systems annex is fully implemented.
25830 @item @emph{Numerics (Annex G)}
25832 The Numerics Annex is fully implemented.
25834 @item @emph{Safety and Security / High-Integrity Systems (Annex H)}
25836 The Safety and Security Annex (termed the High-Integrity Systems Annex
25837 in Ada 2005) is fully implemented.
25840 @node Implementation of Specific Ada Features,Implementation of Ada 2012 Features,Specialized Needs Annexes,Top
25841 @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{416}@anchor{gnat_rm/implementation_of_specific_ada_features id1}@anchor{417}
25842 @chapter Implementation of Specific Ada Features
25845 This chapter describes the GNAT implementation of several Ada language
25849 * Machine Code Insertions::
25850 * GNAT Implementation of Tasking::
25851 * GNAT Implementation of Shared Passive Packages::
25852 * Code Generation for Array Aggregates::
25853 * The Size of Discriminated Records with Default Discriminants::
25854 * Strict Conformance to the Ada Reference Manual::
25858 @node Machine Code Insertions,GNAT Implementation of Tasking,,Implementation of Specific Ada Features
25859 @anchor{gnat_rm/implementation_of_specific_ada_features machine-code-insertions}@anchor{16c}@anchor{gnat_rm/implementation_of_specific_ada_features id2}@anchor{418}
25860 @section Machine Code Insertions
25863 @geindex Machine Code insertions
25865 Package @code{Machine_Code} provides machine code support as described
25866 in the Ada Reference Manual in two separate forms:
25872 Machine code statements, consisting of qualified expressions that
25873 fit the requirements of RM section 13.8.
25876 An intrinsic callable procedure, providing an alternative mechanism of
25877 including machine instructions in a subprogram.
25880 The two features are similar, and both are closely related to the mechanism
25881 provided by the asm instruction in the GNU C compiler. Full understanding
25882 and use of the facilities in this package requires understanding the asm
25883 instruction, see the section on Extended Asm in
25884 @cite{Using_the_GNU_Compiler_Collection_(GCC)}.
25886 Calls to the function @code{Asm} and the procedure @code{Asm} have identical
25887 semantic restrictions and effects as described below. Both are provided so
25888 that the procedure call can be used as a statement, and the function call
25889 can be used to form a code_statement.
25891 Consider this C @code{asm} instruction:
25894 asm ("fsinx %1 %0" : "=f" (result) : "f" (angle));
25897 The equivalent can be written for GNAT as:
25900 Asm ("fsinx %1 %0",
25901 My_Float'Asm_Output ("=f", result),
25902 My_Float'Asm_Input ("f", angle));
25905 The first argument to @code{Asm} is the assembler template, and is
25906 identical to what is used in GNU C. This string must be a static
25907 expression. The second argument is the output operand list. It is
25908 either a single @code{Asm_Output} attribute reference, or a list of such
25909 references enclosed in parentheses (technically an array aggregate of
25912 The @code{Asm_Output} attribute denotes a function that takes two
25913 parameters. The first is a string, the second is the name of a variable
25914 of the type designated by the attribute prefix. The first (string)
25915 argument is required to be a static expression and designates the
25916 constraint (see the section on Constraints in
25917 @cite{Using_the_GNU_Compiler_Collection_(GCC)})
25918 for the parameter; e.g., what kind of register is required. The second
25919 argument is the variable to be written or updated with the
25920 result. The possible values for constraint are the same as those used in
25921 the RTL, and are dependent on the configuration file used to build the
25922 GCC back end. If there are no output operands, then this argument may
25923 either be omitted, or explicitly given as @code{No_Output_Operands}.
25924 No support is provided for GNU C's symbolic names for output parameters.
25926 The second argument of @code{my_float'Asm_Output} functions as
25927 though it were an @code{out} parameter, which is a little curious, but
25928 all names have the form of expressions, so there is no syntactic
25929 irregularity, even though normally functions would not be permitted
25930 @code{out} parameters. The third argument is the list of input
25931 operands. It is either a single @code{Asm_Input} attribute reference, or
25932 a list of such references enclosed in parentheses (technically an array
25933 aggregate of such references).
25935 The @code{Asm_Input} attribute denotes a function that takes two
25936 parameters. The first is a string, the second is an expression of the
25937 type designated by the prefix. The first (string) argument is required
25938 to be a static expression, and is the constraint for the parameter,
25939 (e.g., what kind of register is required). The second argument is the
25940 value to be used as the input argument. The possible values for the
25941 constraint are the same as those used in the RTL, and are dependent on
25942 the configuration file used to built the GCC back end.
25943 No support is provided for GNU C's symbolic names for input parameters.
25945 If there are no input operands, this argument may either be omitted, or
25946 explicitly given as @code{No_Input_Operands}. The fourth argument, not
25947 present in the above example, is a list of register names, called the
25948 @emph{clobber} argument. This argument, if given, must be a static string
25949 expression, and is a space or comma separated list of names of registers
25950 that must be considered destroyed as a result of the @code{Asm} call. If
25951 this argument is the null string (the default value), then the code
25952 generator assumes that no additional registers are destroyed.
25953 In addition to registers, the special clobbers @code{memory} and
25954 @code{cc} as described in the GNU C docs are both supported.
25956 The fifth argument, not present in the above example, called the
25957 @emph{volatile} argument, is by default @code{False}. It can be set to
25958 the literal value @code{True} to indicate to the code generator that all
25959 optimizations with respect to the instruction specified should be
25960 suppressed, and in particular an instruction that has outputs
25961 will still be generated, even if none of the outputs are
25962 used. See @cite{Using_the_GNU_Compiler_Collection_(GCC)}
25963 for the full description.
25964 Generally it is strongly advisable to use Volatile for any ASM statement
25965 that is missing either input or output operands or to avoid unwanted
25966 optimizations. A warning is generated if this advice is not followed.
25968 No support is provided for GNU C's @code{asm goto} feature.
25970 The @code{Asm} subprograms may be used in two ways. First the procedure
25971 forms can be used anywhere a procedure call would be valid, and
25972 correspond to what the RM calls 'intrinsic' routines. Such calls can
25973 be used to intersperse machine instructions with other Ada statements.
25974 Second, the function forms, which return a dummy value of the limited
25975 private type @code{Asm_Insn}, can be used in code statements, and indeed
25976 this is the only context where such calls are allowed. Code statements
25977 appear as aggregates of the form:
25980 Asm_Insn'(Asm (...));
25981 Asm_Insn'(Asm_Volatile (...));
25984 In accordance with RM rules, such code statements are allowed only
25985 within subprograms whose entire body consists of such statements. It is
25986 not permissible to intermix such statements with other Ada statements.
25988 Typically the form using intrinsic procedure calls is more convenient
25989 and more flexible. The code statement form is provided to meet the RM
25990 suggestion that such a facility should be made available. The following
25991 is the exact syntax of the call to @code{Asm}. As usual, if named notation
25992 is used, the arguments may be given in arbitrary order, following the
25993 normal rules for use of positional and named arguments:
25997 [Template =>] static_string_EXPRESSION
25998 [,[Outputs =>] OUTPUT_OPERAND_LIST ]
25999 [,[Inputs =>] INPUT_OPERAND_LIST ]
26000 [,[Clobber =>] static_string_EXPRESSION ]
26001 [,[Volatile =>] static_boolean_EXPRESSION] )
26003 OUTPUT_OPERAND_LIST ::=
26004 [PREFIX.]No_Output_Operands
26005 | OUTPUT_OPERAND_ATTRIBUTE
26006 | (OUTPUT_OPERAND_ATTRIBUTE @{,OUTPUT_OPERAND_ATTRIBUTE@})
26008 OUTPUT_OPERAND_ATTRIBUTE ::=
26009 SUBTYPE_MARK'Asm_Output (static_string_EXPRESSION, NAME)
26011 INPUT_OPERAND_LIST ::=
26012 [PREFIX.]No_Input_Operands
26013 | INPUT_OPERAND_ATTRIBUTE
26014 | (INPUT_OPERAND_ATTRIBUTE @{,INPUT_OPERAND_ATTRIBUTE@})
26016 INPUT_OPERAND_ATTRIBUTE ::=
26017 SUBTYPE_MARK'Asm_Input (static_string_EXPRESSION, EXPRESSION)
26020 The identifiers @code{No_Input_Operands} and @code{No_Output_Operands}
26021 are declared in the package @code{Machine_Code} and must be referenced
26022 according to normal visibility rules. In particular if there is no
26023 @code{use} clause for this package, then appropriate package name
26024 qualification is required.
26026 @node GNAT Implementation of Tasking,GNAT Implementation of Shared Passive Packages,Machine Code Insertions,Implementation of Specific Ada Features
26027 @anchor{gnat_rm/implementation_of_specific_ada_features id3}@anchor{419}@anchor{gnat_rm/implementation_of_specific_ada_features gnat-implementation-of-tasking}@anchor{41a}
26028 @section GNAT Implementation of Tasking
26031 This chapter outlines the basic GNAT approach to tasking (in particular,
26032 a multi-layered library for portability) and discusses issues related
26033 to compliance with the Real-Time Systems Annex.
26036 * Mapping Ada Tasks onto the Underlying Kernel Threads::
26037 * Ensuring Compliance with the Real-Time Annex::
26038 * Support for Locking Policies::
26042 @node Mapping Ada Tasks onto the Underlying Kernel Threads,Ensuring Compliance with the Real-Time Annex,,GNAT Implementation of Tasking
26043 @anchor{gnat_rm/implementation_of_specific_ada_features mapping-ada-tasks-onto-the-underlying-kernel-threads}@anchor{41b}@anchor{gnat_rm/implementation_of_specific_ada_features id4}@anchor{41c}
26044 @subsection Mapping Ada Tasks onto the Underlying Kernel Threads
26047 GNAT's run-time support comprises two layers:
26053 GNARL (GNAT Run-time Layer)
26056 GNULL (GNAT Low-level Library)
26059 In GNAT, Ada's tasking services rely on a platform and OS independent
26060 layer known as GNARL. This code is responsible for implementing the
26061 correct semantics of Ada's task creation, rendezvous, protected
26064 GNARL decomposes Ada's tasking semantics into simpler lower level
26065 operations such as create a thread, set the priority of a thread,
26066 yield, create a lock, lock/unlock, etc. The spec for these low-level
26067 operations constitutes GNULLI, the GNULL Interface. This interface is
26068 directly inspired from the POSIX real-time API.
26070 If the underlying executive or OS implements the POSIX standard
26071 faithfully, the GNULL Interface maps as is to the services offered by
26072 the underlying kernel. Otherwise, some target dependent glue code maps
26073 the services offered by the underlying kernel to the semantics expected
26076 Whatever the underlying OS (VxWorks, UNIX, Windows, etc.) the
26077 key point is that each Ada task is mapped on a thread in the underlying
26078 kernel. For example, in the case of VxWorks, one Ada task = one VxWorks task.
26080 In addition Ada task priorities map onto the underlying thread priorities.
26081 Mapping Ada tasks onto the underlying kernel threads has several advantages:
26087 The underlying scheduler is used to schedule the Ada tasks. This
26088 makes Ada tasks as efficient as kernel threads from a scheduling
26092 Interaction with code written in C containing threads is eased
26093 since at the lowest level Ada tasks and C threads map onto the same
26094 underlying kernel concept.
26097 When an Ada task is blocked during I/O the remaining Ada tasks are
26101 On multiprocessor systems Ada tasks can execute in parallel.
26104 Some threads libraries offer a mechanism to fork a new process, with the
26105 child process duplicating the threads from the parent.
26107 support this functionality when the parent contains more than one task.
26109 @geindex Forking a new process
26111 @node Ensuring Compliance with the Real-Time Annex,Support for Locking Policies,Mapping Ada Tasks onto the Underlying Kernel Threads,GNAT Implementation of Tasking
26112 @anchor{gnat_rm/implementation_of_specific_ada_features id5}@anchor{41d}@anchor{gnat_rm/implementation_of_specific_ada_features ensuring-compliance-with-the-real-time-annex}@anchor{41e}
26113 @subsection Ensuring Compliance with the Real-Time Annex
26116 @geindex Real-Time Systems Annex compliance
26118 Although mapping Ada tasks onto
26119 the underlying threads has significant advantages, it does create some
26120 complications when it comes to respecting the scheduling semantics
26121 specified in the real-time annex (Annex D).
26123 For instance the Annex D requirement for the @code{FIFO_Within_Priorities}
26124 scheduling policy states:
26128 @emph{When the active priority of a ready task that is not running
26129 changes, or the setting of its base priority takes effect, the
26130 task is removed from the ready queue for its old active priority
26131 and is added at the tail of the ready queue for its new active
26132 priority, except in the case where the active priority is lowered
26133 due to the loss of inherited priority, in which case the task is
26134 added at the head of the ready queue for its new active priority.}
26137 While most kernels do put tasks at the end of the priority queue when
26138 a task changes its priority, (which respects the main
26139 FIFO_Within_Priorities requirement), almost none keep a thread at the
26140 beginning of its priority queue when its priority drops from the loss
26141 of inherited priority.
26143 As a result most vendors have provided incomplete Annex D implementations.
26145 The GNAT run-time, has a nice cooperative solution to this problem
26146 which ensures that accurate FIFO_Within_Priorities semantics are
26149 The principle is as follows. When an Ada task T is about to start
26150 running, it checks whether some other Ada task R with the same
26151 priority as T has been suspended due to the loss of priority
26152 inheritance. If this is the case, T yields and is placed at the end of
26153 its priority queue. When R arrives at the front of the queue it
26156 Note that this simple scheme preserves the relative order of the tasks
26157 that were ready to execute in the priority queue where R has been
26160 @c Support_for_Locking_Policies
26162 @node Support for Locking Policies,,Ensuring Compliance with the Real-Time Annex,GNAT Implementation of Tasking
26163 @anchor{gnat_rm/implementation_of_specific_ada_features support-for-locking-policies}@anchor{41f}
26164 @subsection Support for Locking Policies
26167 This section specifies which policies specified by pragma Locking_Policy
26168 are supported on which platforms.
26170 GNAT supports the standard @code{Ceiling_Locking} policy, and the
26171 implementation defined @code{Inheritance_Locking} and
26172 @code{Concurrent_Readers_Locking} policies.
26174 @code{Ceiling_Locking} is supported on all platforms if the operating system
26175 supports it. In particular, @code{Ceiling_Locking} is not supported on
26177 @code{Inheritance_Locking} is supported on
26182 @code{Concurrent_Readers_Locking} is supported on Linux.
26184 Notes about @code{Ceiling_Locking} on Linux:
26185 If the process is running as 'root', ceiling locking is used.
26186 If the capabilities facility is installed
26187 ("sudo apt-get --assume-yes install libcap-dev" on Ubuntu,
26189 and the program is linked against that library
26191 and the executable file has the cap_sys_nice capability
26192 ("sudo /sbin/setcap cap_sys_nice=ep executable_file_name"),
26193 then ceiling locking is used.
26194 Otherwise, the @code{Ceiling_Locking} policy is ignored.
26196 @node GNAT Implementation of Shared Passive Packages,Code Generation for Array Aggregates,GNAT Implementation of Tasking,Implementation of Specific Ada Features
26197 @anchor{gnat_rm/implementation_of_specific_ada_features id6}@anchor{420}@anchor{gnat_rm/implementation_of_specific_ada_features gnat-implementation-of-shared-passive-packages}@anchor{421}
26198 @section GNAT Implementation of Shared Passive Packages
26201 @geindex Shared passive packages
26203 GNAT fully implements the
26204 @geindex pragma Shared_Passive
26206 @code{Shared_Passive} for
26207 the purpose of designating shared passive packages.
26208 This allows the use of passive partitions in the
26209 context described in the Ada Reference Manual; i.e., for communication
26210 between separate partitions of a distributed application using the
26211 features in Annex E.
26215 @geindex Distribution Systems Annex
26217 However, the implementation approach used by GNAT provides for more
26218 extensive usage as follows:
26223 @item @emph{Communication between separate programs}
26225 This allows separate programs to access the data in passive
26226 partitions, using protected objects for synchronization where
26227 needed. The only requirement is that the two programs have a
26228 common shared file system. It is even possible for programs
26229 running on different machines with different architectures
26230 (e.g., different endianness) to communicate via the data in
26231 a passive partition.
26233 @item @emph{Persistence between program runs}
26235 The data in a passive package can persist from one run of a
26236 program to another, so that a later program sees the final
26237 values stored by a previous run of the same program.
26240 The implementation approach used is to store the data in files. A
26241 separate stream file is created for each object in the package, and
26242 an access to an object causes the corresponding file to be read or
26245 @geindex SHARED_MEMORY_DIRECTORY environment variable
26247 The environment variable @code{SHARED_MEMORY_DIRECTORY} should be
26248 set to the directory to be used for these files.
26249 The files in this directory
26250 have names that correspond to their fully qualified names. For
26251 example, if we have the package
26255 pragma Shared_Passive (X);
26261 and the environment variable is set to @code{/stemp/}, then the files created
26262 will have the names:
26269 These files are created when a value is initially written to the object, and
26270 the files are retained until manually deleted. This provides the persistence
26271 semantics. If no file exists, it means that no partition has assigned a value
26272 to the variable; in this case the initial value declared in the package
26273 will be used. This model ensures that there are no issues in synchronizing
26274 the elaboration process, since elaboration of passive packages elaborates the
26275 initial values, but does not create the files.
26277 The files are written using normal @code{Stream_IO} access.
26278 If you want to be able
26279 to communicate between programs or partitions running on different
26280 architectures, then you should use the XDR versions of the stream attribute
26281 routines, since these are architecture independent.
26283 If active synchronization is required for access to the variables in the
26284 shared passive package, then as described in the Ada Reference Manual, the
26285 package may contain protected objects used for this purpose. In this case
26286 a lock file (whose name is @code{___lock} (three underscores)
26287 is created in the shared memory directory.
26289 @geindex ___lock file (for shared passive packages)
26291 This is used to provide the required locking
26292 semantics for proper protected object synchronization.
26294 GNAT supports shared passive packages on all platforms
26295 except for OpenVMS.
26297 @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
26298 @anchor{gnat_rm/implementation_of_specific_ada_features code-generation-for-array-aggregates}@anchor{422}@anchor{gnat_rm/implementation_of_specific_ada_features id7}@anchor{423}
26299 @section Code Generation for Array Aggregates
26302 Aggregates have a rich syntax and allow the user to specify the values of
26303 complex data structures by means of a single construct. As a result, the
26304 code generated for aggregates can be quite complex and involve loops, case
26305 statements and multiple assignments. In the simplest cases, however, the
26306 compiler will recognize aggregates whose components and constraints are
26307 fully static, and in those cases the compiler will generate little or no
26308 executable code. The following is an outline of the code that GNAT generates
26309 for various aggregate constructs. For further details, you will find it
26310 useful to examine the output produced by the -gnatG flag to see the expanded
26311 source that is input to the code generator. You may also want to examine
26312 the assembly code generated at various levels of optimization.
26314 The code generated for aggregates depends on the context, the component values,
26315 and the type. In the context of an object declaration the code generated is
26316 generally simpler than in the case of an assignment. As a general rule, static
26317 component values and static subtypes also lead to simpler code.
26320 * Static constant aggregates with static bounds::
26321 * Constant aggregates with unconstrained nominal types::
26322 * Aggregates with static bounds::
26323 * Aggregates with nonstatic bounds::
26324 * Aggregates in assignment statements::
26328 @node Static constant aggregates with static bounds,Constant aggregates with unconstrained nominal types,,Code Generation for Array Aggregates
26329 @anchor{gnat_rm/implementation_of_specific_ada_features static-constant-aggregates-with-static-bounds}@anchor{424}@anchor{gnat_rm/implementation_of_specific_ada_features id8}@anchor{425}
26330 @subsection Static constant aggregates with static bounds
26333 For the declarations:
26336 type One_Dim is array (1..10) of integer;
26337 ar0 : constant One_Dim := (1, 2, 3, 4, 5, 6, 7, 8, 9, 0);
26340 GNAT generates no executable code: the constant ar0 is placed in static memory.
26341 The same is true for constant aggregates with named associations:
26344 Cr1 : constant One_Dim := (4 => 16, 2 => 4, 3 => 9, 1 => 1, 5 .. 10 => 0);
26345 Cr3 : constant One_Dim := (others => 7777);
26348 The same is true for multidimensional constant arrays such as:
26351 type two_dim is array (1..3, 1..3) of integer;
26352 Unit : constant two_dim := ( (1,0,0), (0,1,0), (0,0,1));
26355 The same is true for arrays of one-dimensional arrays: the following are
26359 type ar1b is array (1..3) of boolean;
26360 type ar_ar is array (1..3) of ar1b;
26361 None : constant ar1b := (others => false); -- fully static
26362 None2 : constant ar_ar := (1..3 => None); -- fully static
26365 However, for multidimensional aggregates with named associations, GNAT will
26366 generate assignments and loops, even if all associations are static. The
26367 following two declarations generate a loop for the first dimension, and
26368 individual component assignments for the second dimension:
26371 Zero1: constant two_dim := (1..3 => (1..3 => 0));
26372 Zero2: constant two_dim := (others => (others => 0));
26375 @node Constant aggregates with unconstrained nominal types,Aggregates with static bounds,Static constant aggregates with static bounds,Code Generation for Array Aggregates
26376 @anchor{gnat_rm/implementation_of_specific_ada_features constant-aggregates-with-unconstrained-nominal-types}@anchor{426}@anchor{gnat_rm/implementation_of_specific_ada_features id9}@anchor{427}
26377 @subsection Constant aggregates with unconstrained nominal types
26380 In such cases the aggregate itself establishes the subtype, so that
26381 associations with @code{others} cannot be used. GNAT determines the
26382 bounds for the actual subtype of the aggregate, and allocates the
26383 aggregate statically as well. No code is generated for the following:
26386 type One_Unc is array (natural range <>) of integer;
26387 Cr_Unc : constant One_Unc := (12,24,36);
26390 @node Aggregates with static bounds,Aggregates with nonstatic bounds,Constant aggregates with unconstrained nominal types,Code Generation for Array Aggregates
26391 @anchor{gnat_rm/implementation_of_specific_ada_features id10}@anchor{428}@anchor{gnat_rm/implementation_of_specific_ada_features aggregates-with-static-bounds}@anchor{429}
26392 @subsection Aggregates with static bounds
26395 In all previous examples the aggregate was the initial (and immutable) value
26396 of a constant. If the aggregate initializes a variable, then code is generated
26397 for it as a combination of individual assignments and loops over the target
26398 object. The declarations
26401 Cr_Var1 : One_Dim := (2, 5, 7, 11, 0, 0, 0, 0, 0, 0);
26402 Cr_Var2 : One_Dim := (others > -1);
26405 generate the equivalent of
26413 for I in Cr_Var2'range loop
26418 @node Aggregates with nonstatic bounds,Aggregates in assignment statements,Aggregates with static bounds,Code Generation for Array Aggregates
26419 @anchor{gnat_rm/implementation_of_specific_ada_features id11}@anchor{42a}@anchor{gnat_rm/implementation_of_specific_ada_features aggregates-with-nonstatic-bounds}@anchor{42b}
26420 @subsection Aggregates with nonstatic bounds
26423 If the bounds of the aggregate are not statically compatible with the bounds
26424 of the nominal subtype of the target, then constraint checks have to be
26425 generated on the bounds. For a multidimensional array, constraint checks may
26426 have to be applied to sub-arrays individually, if they do not have statically
26427 compatible subtypes.
26429 @node Aggregates in assignment statements,,Aggregates with nonstatic bounds,Code Generation for Array Aggregates
26430 @anchor{gnat_rm/implementation_of_specific_ada_features id12}@anchor{42c}@anchor{gnat_rm/implementation_of_specific_ada_features aggregates-in-assignment-statements}@anchor{42d}
26431 @subsection Aggregates in assignment statements
26434 In general, aggregate assignment requires the construction of a temporary,
26435 and a copy from the temporary to the target of the assignment. This is because
26436 it is not always possible to convert the assignment into a series of individual
26437 component assignments. For example, consider the simple case:
26443 This cannot be converted into:
26450 So the aggregate has to be built first in a separate location, and then
26451 copied into the target. GNAT recognizes simple cases where this intermediate
26452 step is not required, and the assignments can be performed in place, directly
26453 into the target. The following sufficient criteria are applied:
26459 The bounds of the aggregate are static, and the associations are static.
26462 The components of the aggregate are static constants, names of
26463 simple variables that are not renamings, or expressions not involving
26464 indexed components whose operands obey these rules.
26467 If any of these conditions are violated, the aggregate will be built in
26468 a temporary (created either by the front-end or the code generator) and then
26469 that temporary will be copied onto the target.
26471 @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
26472 @anchor{gnat_rm/implementation_of_specific_ada_features id13}@anchor{42e}@anchor{gnat_rm/implementation_of_specific_ada_features the-size-of-discriminated-records-with-default-discriminants}@anchor{42f}
26473 @section The Size of Discriminated Records with Default Discriminants
26476 If a discriminated type @code{T} has discriminants with default values, it is
26477 possible to declare an object of this type without providing an explicit
26481 type Size is range 1..100;
26483 type Rec (D : Size := 15) is record
26484 Name : String (1..D);
26490 Such an object is said to be @emph{unconstrained}.
26491 The discriminant of the object
26492 can be modified by a full assignment to the object, as long as it preserves the
26493 relation between the value of the discriminant, and the value of the components
26497 Word := (3, "yes");
26499 Word := (5, "maybe");
26501 Word := (5, "no"); -- raises Constraint_Error
26504 In order to support this behavior efficiently, an unconstrained object is
26505 given the maximum size that any value of the type requires. In the case
26506 above, @code{Word} has storage for the discriminant and for
26507 a @code{String} of length 100.
26508 It is important to note that unconstrained objects do not require dynamic
26509 allocation. It would be an improper implementation to place on the heap those
26510 components whose size depends on discriminants. (This improper implementation
26511 was used by some Ada83 compilers, where the @code{Name} component above
26513 been stored as a pointer to a dynamic string). Following the principle that
26514 dynamic storage management should never be introduced implicitly,
26515 an Ada compiler should reserve the full size for an unconstrained declared
26516 object, and place it on the stack.
26518 This maximum size approach
26519 has been a source of surprise to some users, who expect the default
26520 values of the discriminants to determine the size reserved for an
26521 unconstrained object: "If the default is 15, why should the object occupy
26523 The answer, of course, is that the discriminant may be later modified,
26524 and its full range of values must be taken into account. This is why the
26528 type Rec (D : Positive := 15) is record
26529 Name : String (1..D);
26535 is flagged by the compiler with a warning:
26536 an attempt to create @code{Too_Large} will raise @code{Storage_Error},
26537 because the required size includes @code{Positive'Last}
26538 bytes. As the first example indicates, the proper approach is to declare an
26539 index type of 'reasonable' range so that unconstrained objects are not too
26542 One final wrinkle: if the object is declared to be @code{aliased}, or if it is
26543 created in the heap by means of an allocator, then it is @emph{not}
26545 it is constrained by the default values of the discriminants, and those values
26546 cannot be modified by full assignment. This is because in the presence of
26547 aliasing all views of the object (which may be manipulated by different tasks,
26548 say) must be consistent, so it is imperative that the object, once created,
26551 @node Strict Conformance to the Ada Reference Manual,,The Size of Discriminated Records with Default Discriminants,Implementation of Specific Ada Features
26552 @anchor{gnat_rm/implementation_of_specific_ada_features strict-conformance-to-the-ada-reference-manual}@anchor{430}@anchor{gnat_rm/implementation_of_specific_ada_features id14}@anchor{431}
26553 @section Strict Conformance to the Ada Reference Manual
26556 The dynamic semantics defined by the Ada Reference Manual impose a set of
26557 run-time checks to be generated. By default, the GNAT compiler will insert many
26558 run-time checks into the compiled code, including most of those required by the
26559 Ada Reference Manual. However, there are two checks that are not enabled in
26560 the default mode for efficiency reasons: checks for access before elaboration
26561 on subprogram calls, and stack overflow checking (most operating systems do not
26562 perform this check by default).
26564 Strict conformance to the Ada Reference Manual can be achieved by adding two
26565 compiler options for dynamic checks for access-before-elaboration on subprogram
26566 calls and generic instantiations (@emph{-gnatE}), and stack overflow checking
26567 (@emph{-fstack-check}).
26569 Note that the result of a floating point arithmetic operation in overflow and
26570 invalid situations, when the @code{Machine_Overflows} attribute of the result
26571 type is @code{False}, is to generate IEEE NaN and infinite values. This is the
26572 case for machines compliant with the IEEE floating-point standard, but on
26573 machines that are not fully compliant with this standard, such as Alpha, the
26574 @emph{-mieee} compiler flag must be used for achieving IEEE confirming
26575 behavior (although at the cost of a significant performance penalty), so
26576 infinite and NaN values are properly generated.
26578 @node Implementation of Ada 2012 Features,Obsolescent Features,Implementation of Specific Ada Features,Top
26579 @anchor{gnat_rm/implementation_of_ada_2012_features doc}@anchor{432}@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{433}
26580 @chapter Implementation of Ada 2012 Features
26583 @geindex Ada 2012 implementation status
26585 @geindex -gnat12 option (gcc)
26587 @geindex pragma Ada_2012
26589 @geindex configuration pragma Ada_2012
26591 @geindex Ada_2012 configuration pragma
26593 This chapter contains a complete list of Ada 2012 features that have been
26595 Generally, these features are only
26596 available if the @emph{-gnat12} (Ada 2012 features enabled) option is set,
26597 which is the default behavior,
26598 or if the configuration pragma @code{Ada_2012} is used.
26600 However, new pragmas, attributes, and restrictions are
26601 unconditionally available, since the Ada 95 standard allows the addition of
26602 new pragmas, attributes, and restrictions (there are exceptions, which are
26603 documented in the individual descriptions), and also certain packages
26604 were made available in earlier versions of Ada.
26606 An ISO date (YYYY-MM-DD) appears in parentheses on the description line.
26607 This date shows the implementation date of the feature. Any wavefront
26608 subsequent to this date will contain the indicated feature, as will any
26609 subsequent releases. A date of 0000-00-00 means that GNAT has always
26610 implemented the feature, or implemented it as soon as it appeared as a
26611 binding interpretation.
26613 Each feature corresponds to an Ada Issue ('AI') approved by the Ada
26614 standardization group (ISO/IEC JTC1/SC22/WG9) for inclusion in Ada 2012.
26615 The features are ordered based on the relevant sections of the Ada
26616 Reference Manual ("RM"). When a given AI relates to multiple points
26617 in the RM, the earliest is used.
26619 A complete description of the AIs may be found in
26620 @indicateurl{http://www.ada-auth.org/ai05-summary.html}.
26622 @geindex AI-0176 (Ada 2012 feature)
26628 @emph{AI-0176 Quantified expressions (2010-09-29)}
26630 Both universally and existentially quantified expressions are implemented.
26631 They use the new syntax for iterators proposed in AI05-139-2, as well as
26632 the standard Ada loop syntax.
26634 RM References: 1.01.04 (12) 2.09 (2/2) 4.04 (7) 4.05.09 (0)
26637 @geindex AI-0079 (Ada 2012 feature)
26643 @emph{AI-0079 Allow other_format characters in source (2010-07-10)}
26645 Wide characters in the unicode category @emph{other_format} are now allowed in
26646 source programs between tokens, but not within a token such as an identifier.
26648 RM References: 2.01 (4/2) 2.02 (7)
26651 @geindex AI-0091 (Ada 2012 feature)
26657 @emph{AI-0091 Do not allow other_format in identifiers (0000-00-00)}
26659 Wide characters in the unicode category @emph{other_format} are not permitted
26660 within an identifier, since this can be a security problem. The error
26661 message for this case has been improved to be more specific, but GNAT has
26662 never allowed such characters to appear in identifiers.
26664 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)
26667 @geindex AI-0100 (Ada 2012 feature)
26673 @emph{AI-0100 Placement of pragmas (2010-07-01)}
26675 This AI is an earlier version of AI-163. It simplifies the rules
26676 for legal placement of pragmas. In the case of lists that allow pragmas, if
26677 the list may have no elements, then the list may consist solely of pragmas.
26679 RM References: 2.08 (7)
26682 @geindex AI-0163 (Ada 2012 feature)
26688 @emph{AI-0163 Pragmas in place of null (2010-07-01)}
26690 A statement sequence may be composed entirely of pragmas. It is no longer
26691 necessary to add a dummy @code{null} statement to make the sequence legal.
26693 RM References: 2.08 (7) 2.08 (16)
26696 @geindex AI-0080 (Ada 2012 feature)
26702 @emph{AI-0080 'View of' not needed if clear from context (0000-00-00)}
26704 This is an editorial change only, described as non-testable in the AI.
26706 RM References: 3.01 (7)
26709 @geindex AI-0183 (Ada 2012 feature)
26715 @emph{AI-0183 Aspect specifications (2010-08-16)}
26717 Aspect specifications have been fully implemented except for pre and post-
26718 conditions, and type invariants, which have their own separate AI's. All
26719 forms of declarations listed in the AI are supported. The following is a
26720 list of the aspects supported (with GNAT implementation aspects marked)
26724 @multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxx}
26769 @code{Atomic_Components}
26781 @code{Component_Size}
26787 @code{Contract_Cases}
26795 @code{Discard_Names}
26801 @code{External_Tag}
26807 @code{Favor_Top_Level}
26821 @code{Inline_Always}
26837 @code{Machine_Radix}
26863 @code{Persistent_BSS}
26889 @code{Preelaborable_Initialization}
26895 @code{Pure_Function}
26903 @code{Remote_Access_Type}
26925 @code{Storage_Pool}
26931 @code{Storage_Size}
26949 @code{Suppress_Debug_Info}
26965 @code{Thread_Local_Storage}
26973 @code{Type_Invariant}
26979 @code{Unchecked_Union}
26985 @code{Universal_Aliasing}
27001 @code{Unreferenced}
27009 @code{Unreferenced_Objects}
27037 @code{Volatile_Components}
27054 Note that for aspects with an expression, e.g. @code{Size}, the expression is
27055 treated like a default expression (visibility is analyzed at the point of
27056 occurrence of the aspect, but evaluation of the expression occurs at the
27057 freeze point of the entity involved).
27059 RM References: 3.02.01 (3) 3.02.02 (2) 3.03.01 (2/2) 3.08 (6)
27060 3.09.03 (1.1/2) 6.01 (2/2) 6.07 (2/2) 9.05.02 (2/2) 7.01 (3) 7.03
27061 (2) 7.03 (3) 9.01 (2/2) 9.01 (3/2) 9.04 (2/2) 9.04 (3/2)
27062 9.05.02 (2/2) 11.01 (2) 12.01 (3) 12.03 (2/2) 12.04 (2/2) 12.05 (2)
27063 12.06 (2.1/2) 12.06 (2.2/2) 12.07 (2) 13.01 (0.1/2) 13.03 (5/1)
27067 @geindex AI-0128 (Ada 2012 feature)
27073 @emph{AI-0128 Inequality is a primitive operation (0000-00-00)}
27075 If an equality operator ("=") is declared for a type, then the implicitly
27076 declared inequality operator ("/=") is a primitive operation of the type.
27077 This is the only reasonable interpretation, and is the one always implemented
27078 by GNAT, but the RM was not entirely clear in making this point.
27080 RM References: 3.02.03 (6) 6.06 (6)
27083 @geindex AI-0003 (Ada 2012 feature)
27089 @emph{AI-0003 Qualified expressions as names (2010-07-11)}
27091 In Ada 2012, a qualified expression is considered to be syntactically a name,
27092 meaning that constructs such as @code{A'(F(X)).B} are now legal. This is
27093 useful in disambiguating some cases of overloading.
27095 RM References: 3.03 (11) 3.03 (21) 4.01 (2) 4.04 (7) 4.07 (3)
27099 @geindex AI-0120 (Ada 2012 feature)
27105 @emph{AI-0120 Constant instance of protected object (0000-00-00)}
27107 This is an RM editorial change only. The section that lists objects that are
27108 constant failed to include the current instance of a protected object
27109 within a protected function. This has always been treated as a constant
27112 RM References: 3.03 (21)
27115 @geindex AI-0008 (Ada 2012 feature)
27121 @emph{AI-0008 General access to constrained objects (0000-00-00)}
27123 The wording in the RM implied that if you have a general access to a
27124 constrained object, it could be used to modify the discriminants. This was
27125 obviously not intended. @code{Constraint_Error} should be raised, and GNAT
27126 has always done so in this situation.
27128 RM References: 3.03 (23) 3.10.02 (26/2) 4.01 (9) 6.04.01 (17) 8.05.01 (5/2)
27131 @geindex AI-0093 (Ada 2012 feature)
27137 @emph{AI-0093 Additional rules use immutably limited (0000-00-00)}
27139 This is an editorial change only, to make more widespread use of the Ada 2012
27140 'immutably limited'.
27142 RM References: 3.03 (23.4/3)
27145 @geindex AI-0096 (Ada 2012 feature)
27151 @emph{AI-0096 Deriving from formal private types (2010-07-20)}
27153 In general it is illegal for a type derived from a formal limited type to be
27154 nonlimited. This AI makes an exception to this rule: derivation is legal
27155 if it appears in the private part of the generic, and the formal type is not
27156 tagged. If the type is tagged, the legality check must be applied to the
27157 private part of the package.
27159 RM References: 3.04 (5.1/2) 6.02 (7)
27162 @geindex AI-0181 (Ada 2012 feature)
27168 @emph{AI-0181 Soft hyphen is a non-graphic character (2010-07-23)}
27170 From Ada 2005 on, soft hyphen is considered a non-graphic character, which
27171 means that it has a special name (@code{SOFT_HYPHEN}) in conjunction with the
27172 @code{Image} and @code{Value} attributes for the character types. Strictly
27173 speaking this is an inconsistency with Ada 95, but in practice the use of
27174 these attributes is so obscure that it will not cause problems.
27176 RM References: 3.05.02 (2/2) A.01 (35/2) A.03.03 (21)
27179 @geindex AI-0182 (Ada 2012 feature)
27185 @emph{AI-0182 Additional forms for} @code{Character'Value} @emph{(0000-00-00)}
27187 This AI allows @code{Character'Value} to accept the string @code{'?'} where
27188 @code{?} is any character including non-graphic control characters. GNAT has
27189 always accepted such strings. It also allows strings such as
27190 @code{HEX_00000041} to be accepted, but GNAT does not take advantage of this
27191 permission and raises @code{Constraint_Error}, as is certainly still
27194 RM References: 3.05 (56/2)
27197 @geindex AI-0214 (Ada 2012 feature)
27203 @emph{AI-0214 Defaulted discriminants for limited tagged (2010-10-01)}
27205 Ada 2012 relaxes the restriction that forbids discriminants of tagged types
27206 to have default expressions by allowing them when the type is limited. It
27207 is often useful to define a default value for a discriminant even though
27208 it can't be changed by assignment.
27210 RM References: 3.07 (9.1/2) 3.07.02 (3)
27213 @geindex AI-0102 (Ada 2012 feature)
27219 @emph{AI-0102 Some implicit conversions are illegal (0000-00-00)}
27221 It is illegal to assign an anonymous access constant to an anonymous access
27222 variable. The RM did not have a clear rule to prevent this, but GNAT has
27223 always generated an error for this usage.
27225 RM References: 3.07 (16) 3.07.01 (9) 6.04.01 (6) 8.06 (27/2)
27228 @geindex AI-0158 (Ada 2012 feature)
27234 @emph{AI-0158 Generalizing membership tests (2010-09-16)}
27236 This AI extends the syntax of membership tests to simplify complex conditions
27237 that can be expressed as membership in a subset of values of any type. It
27238 introduces syntax for a list of expressions that may be used in loop contexts
27241 RM References: 3.08.01 (5) 4.04 (3) 4.05.02 (3) 4.05.02 (5) 4.05.02 (27)
27244 @geindex AI-0173 (Ada 2012 feature)
27250 @emph{AI-0173 Testing if tags represent abstract types (2010-07-03)}
27252 The function @code{Ada.Tags.Type_Is_Abstract} returns @code{True} if invoked
27253 with the tag of an abstract type, and @code{False} otherwise.
27255 RM References: 3.09 (7.4/2) 3.09 (12.4/2)
27258 @geindex AI-0076 (Ada 2012 feature)
27264 @emph{AI-0076 function with controlling result (0000-00-00)}
27266 This is an editorial change only. The RM defines calls with controlling
27267 results, but uses the term 'function with controlling result' without an
27268 explicit definition.
27270 RM References: 3.09.02 (2/2)
27273 @geindex AI-0126 (Ada 2012 feature)
27279 @emph{AI-0126 Dispatching with no declared operation (0000-00-00)}
27281 This AI clarifies dispatching rules, and simply confirms that dispatching
27282 executes the operation of the parent type when there is no explicitly or
27283 implicitly declared operation for the descendant type. This has always been
27284 the case in all versions of GNAT.
27286 RM References: 3.09.02 (20/2) 3.09.02 (20.1/2) 3.09.02 (20.2/2)
27289 @geindex AI-0097 (Ada 2012 feature)
27295 @emph{AI-0097 Treatment of abstract null extension (2010-07-19)}
27297 The RM as written implied that in some cases it was possible to create an
27298 object of an abstract type, by having an abstract extension inherit a non-
27299 abstract constructor from its parent type. This mistake has been corrected
27300 in GNAT and in the RM, and this construct is now illegal.
27302 RM References: 3.09.03 (4/2)
27305 @geindex AI-0203 (Ada 2012 feature)
27311 @emph{AI-0203 Extended return cannot be abstract (0000-00-00)}
27313 A return_subtype_indication cannot denote an abstract subtype. GNAT has never
27314 permitted such usage.
27316 RM References: 3.09.03 (8/3)
27319 @geindex AI-0198 (Ada 2012 feature)
27325 @emph{AI-0198 Inheriting abstract operators (0000-00-00)}
27327 This AI resolves a conflict between two rules involving inherited abstract
27328 operations and predefined operators. If a derived numeric type inherits
27329 an abstract operator, it overrides the predefined one. This interpretation
27330 was always the one implemented in GNAT.
27332 RM References: 3.09.03 (4/3)
27335 @geindex AI-0073 (Ada 2012 feature)
27341 @emph{AI-0073 Functions returning abstract types (2010-07-10)}
27343 This AI covers a number of issues regarding returning abstract types. In
27344 particular generic functions cannot have abstract result types or access
27345 result types designated an abstract type. There are some other cases which
27346 are detailed in the AI. Note that this binding interpretation has not been
27347 retrofitted to operate before Ada 2012 mode, since it caused a significant
27348 number of regressions.
27350 RM References: 3.09.03 (8) 3.09.03 (10) 6.05 (8/2)
27353 @geindex AI-0070 (Ada 2012 feature)
27359 @emph{AI-0070 Elaboration of interface types (0000-00-00)}
27361 This is an editorial change only, there are no testable consequences short of
27362 checking for the absence of generated code for an interface declaration.
27364 RM References: 3.09.04 (18/2)
27367 @geindex AI-0208 (Ada 2012 feature)
27373 @emph{AI-0208 Characteristics of incomplete views (0000-00-00)}
27375 The wording in the Ada 2005 RM concerning characteristics of incomplete views
27376 was incorrect and implied that some programs intended to be legal were now
27377 illegal. GNAT had never considered such programs illegal, so it has always
27378 implemented the intent of this AI.
27380 RM References: 3.10.01 (2.4/2) 3.10.01 (2.6/2)
27383 @geindex AI-0162 (Ada 2012 feature)
27389 @emph{AI-0162 Incomplete type completed by partial view (2010-09-15)}
27391 Incomplete types are made more useful by allowing them to be completed by
27392 private types and private extensions.
27394 RM References: 3.10.01 (2.5/2) 3.10.01 (2.6/2) 3.10.01 (3) 3.10.01 (4/2)
27397 @geindex AI-0098 (Ada 2012 feature)
27403 @emph{AI-0098 Anonymous subprogram access restrictions (0000-00-00)}
27405 An unintentional omission in the RM implied some inconsistent restrictions on
27406 the use of anonymous access to subprogram values. These restrictions were not
27407 intentional, and have never been enforced by GNAT.
27409 RM References: 3.10.01 (6) 3.10.01 (9.2/2)
27412 @geindex AI-0199 (Ada 2012 feature)
27418 @emph{AI-0199 Aggregate with anonymous access components (2010-07-14)}
27420 A choice list in a record aggregate can include several components of
27421 (distinct) anonymous access types as long as they have matching designated
27424 RM References: 4.03.01 (16)
27427 @geindex AI-0220 (Ada 2012 feature)
27433 @emph{AI-0220 Needed components for aggregates (0000-00-00)}
27435 This AI addresses a wording problem in the RM that appears to permit some
27436 complex cases of aggregates with nonstatic discriminants. GNAT has always
27437 implemented the intended semantics.
27439 RM References: 4.03.01 (17)
27442 @geindex AI-0147 (Ada 2012 feature)
27448 @emph{AI-0147 Conditional expressions (2009-03-29)}
27450 Conditional expressions are permitted. The form of such an expression is:
27453 (if expr then expr @{elsif expr then expr@} [else expr])
27456 The parentheses can be omitted in contexts where parentheses are present
27457 anyway, such as subprogram arguments and pragma arguments. If the @strong{else}
27458 clause is omitted, @strong{else} @emph{True} is assumed;
27459 thus @code{(if A then B)} is a way to conveniently represent
27460 @emph{(A implies B)} in standard logic.
27462 RM References: 4.03.03 (15) 4.04 (1) 4.04 (7) 4.05.07 (0) 4.07 (2)
27463 4.07 (3) 4.09 (12) 4.09 (33) 5.03 (3) 5.03 (4) 7.05 (2.1/2)
27466 @geindex AI-0037 (Ada 2012 feature)
27472 @emph{AI-0037 Out-of-range box associations in aggregate (0000-00-00)}
27474 This AI confirms that an association of the form @code{Indx => <>} in an
27475 array aggregate must raise @code{Constraint_Error} if @code{Indx}
27476 is out of range. The RM specified a range check on other associations, but
27477 not when the value of the association was defaulted. GNAT has always inserted
27478 a constraint check on the index value.
27480 RM References: 4.03.03 (29)
27483 @geindex AI-0123 (Ada 2012 feature)
27489 @emph{AI-0123 Composability of equality (2010-04-13)}
27491 Equality of untagged record composes, so that the predefined equality for a
27492 composite type that includes a component of some untagged record type
27493 @code{R} uses the equality operation of @code{R} (which may be user-defined
27494 or predefined). This makes the behavior of untagged records identical to that
27495 of tagged types in this respect.
27497 This change is an incompatibility with previous versions of Ada, but it
27498 corrects a non-uniformity that was often a source of confusion. Analysis of
27499 a large number of industrial programs indicates that in those rare cases
27500 where a composite type had an untagged record component with a user-defined
27501 equality, either there was no use of the composite equality, or else the code
27502 expected the same composability as for tagged types, and thus had a bug that
27503 would be fixed by this change.
27505 RM References: 4.05.02 (9.7/2) 4.05.02 (14) 4.05.02 (15) 4.05.02 (24)
27509 @geindex AI-0088 (Ada 2012 feature)
27515 @emph{AI-0088 The value of exponentiation (0000-00-00)}
27517 This AI clarifies the equivalence rule given for the dynamic semantics of
27518 exponentiation: the value of the operation can be obtained by repeated
27519 multiplication, but the operation can be implemented otherwise (for example
27520 using the familiar divide-by-two-and-square algorithm, even if this is less
27521 accurate), and does not imply repeated reads of a volatile base.
27523 RM References: 4.05.06 (11)
27526 @geindex AI-0188 (Ada 2012 feature)
27532 @emph{AI-0188 Case expressions (2010-01-09)}
27534 Case expressions are permitted. This allows use of constructs such as:
27537 X := (case Y is when 1 => 2, when 2 => 3, when others => 31)
27540 RM References: 4.05.07 (0) 4.05.08 (0) 4.09 (12) 4.09 (33)
27543 @geindex AI-0104 (Ada 2012 feature)
27549 @emph{AI-0104 Null exclusion and uninitialized allocator (2010-07-15)}
27551 The assignment @code{Ptr := new not null Some_Ptr;} will raise
27552 @code{Constraint_Error} because the default value of the allocated object is
27553 @strong{null}. This useless construct is illegal in Ada 2012.
27555 RM References: 4.08 (2)
27558 @geindex AI-0157 (Ada 2012 feature)
27564 @emph{AI-0157 Allocation/Deallocation from empty pool (2010-07-11)}
27566 Allocation and Deallocation from an empty storage pool (i.e. allocation or
27567 deallocation of a pointer for which a static storage size clause of zero
27568 has been given) is now illegal and is detected as such. GNAT
27569 previously gave a warning but not an error.
27571 RM References: 4.08 (5.3/2) 13.11.02 (4) 13.11.02 (17)
27574 @geindex AI-0179 (Ada 2012 feature)
27580 @emph{AI-0179 Statement not required after label (2010-04-10)}
27582 It is not necessary to have a statement following a label, so a label
27583 can appear at the end of a statement sequence without the need for putting a
27584 null statement afterwards, but it is not allowable to have only labels and
27585 no real statements in a statement sequence.
27587 RM References: 5.01 (2)
27590 @geindex AI-0139-2 (Ada 2012 feature)
27596 @emph{AI-0139-2 Syntactic sugar for iterators (2010-09-29)}
27598 The new syntax for iterating over arrays and containers is now implemented.
27599 Iteration over containers is for now limited to read-only iterators. Only
27600 default iterators are supported, with the syntax: @code{for Elem of C}.
27602 RM References: 5.05
27605 @geindex AI-0134 (Ada 2012 feature)
27611 @emph{AI-0134 Profiles must match for full conformance (0000-00-00)}
27613 For full conformance, the profiles of anonymous-access-to-subprogram
27614 parameters must match. GNAT has always enforced this rule.
27616 RM References: 6.03.01 (18)
27619 @geindex AI-0207 (Ada 2012 feature)
27625 @emph{AI-0207 Mode conformance and access constant (0000-00-00)}
27627 This AI confirms that access_to_constant indication must match for mode
27628 conformance. This was implemented in GNAT when the qualifier was originally
27629 introduced in Ada 2005.
27631 RM References: 6.03.01 (16/2)
27634 @geindex AI-0046 (Ada 2012 feature)
27640 @emph{AI-0046 Null exclusion match for full conformance (2010-07-17)}
27642 For full conformance, in the case of access parameters, the null exclusion
27643 must match (either both or neither must have @code{not null}).
27645 RM References: 6.03.02 (18)
27648 @geindex AI-0118 (Ada 2012 feature)
27654 @emph{AI-0118 The association of parameter associations (0000-00-00)}
27656 This AI clarifies the rules for named associations in subprogram calls and
27657 generic instantiations. The rules have been in place since Ada 83.
27659 RM References: 6.04.01 (2) 12.03 (9)
27662 @geindex AI-0196 (Ada 2012 feature)
27668 @emph{AI-0196 Null exclusion tests for out parameters (0000-00-00)}
27670 Null exclusion checks are not made for @code{out} parameters when
27671 evaluating the actual parameters. GNAT has never generated these checks.
27673 RM References: 6.04.01 (13)
27676 @geindex AI-0015 (Ada 2012 feature)
27682 @emph{AI-0015 Constant return objects (0000-00-00)}
27684 The return object declared in an @emph{extended_return_statement} may be
27685 declared constant. This was always intended, and GNAT has always allowed it.
27687 RM References: 6.05 (2.1/2) 3.03 (10/2) 3.03 (21) 6.05 (5/2)
27691 @geindex AI-0032 (Ada 2012 feature)
27697 @emph{AI-0032 Extended return for class-wide functions (0000-00-00)}
27699 If a function returns a class-wide type, the object of an extended return
27700 statement can be declared with a specific type that is covered by the class-
27701 wide type. This has been implemented in GNAT since the introduction of
27702 extended returns. Note AI-0103 complements this AI by imposing matching
27703 rules for constrained return types.
27705 RM References: 6.05 (5.2/2) 6.05 (5.3/2) 6.05 (5.6/2) 6.05 (5.8/2)
27709 @geindex AI-0103 (Ada 2012 feature)
27715 @emph{AI-0103 Static matching for extended return (2010-07-23)}
27717 If the return subtype of a function is an elementary type or a constrained
27718 type, the subtype indication in an extended return statement must match
27719 statically this return subtype.
27721 RM References: 6.05 (5.2/2)
27724 @geindex AI-0058 (Ada 2012 feature)
27730 @emph{AI-0058 Abnormal completion of an extended return (0000-00-00)}
27732 The RM had some incorrect wording implying wrong treatment of abnormal
27733 completion in an extended return. GNAT has always implemented the intended
27734 correct semantics as described by this AI.
27736 RM References: 6.05 (22/2)
27739 @geindex AI-0050 (Ada 2012 feature)
27745 @emph{AI-0050 Raising Constraint_Error early for function call (0000-00-00)}
27747 The implementation permissions for raising @code{Constraint_Error} early on a function call
27748 when it was clear an exception would be raised were over-permissive and allowed
27749 mishandling of discriminants in some cases. GNAT did
27750 not take advantage of these incorrect permissions in any case.
27752 RM References: 6.05 (24/2)
27755 @geindex AI-0125 (Ada 2012 feature)
27761 @emph{AI-0125 Nonoverridable operations of an ancestor (2010-09-28)}
27763 In Ada 2012, the declaration of a primitive operation of a type extension
27764 or private extension can also override an inherited primitive that is not
27765 visible at the point of this declaration.
27767 RM References: 7.03.01 (6) 8.03 (23) 8.03.01 (5/2) 8.03.01 (6/2)
27770 @geindex AI-0062 (Ada 2012 feature)
27776 @emph{AI-0062 Null exclusions and deferred constants (0000-00-00)}
27778 A full constant may have a null exclusion even if its associated deferred
27779 constant does not. GNAT has always allowed this.
27781 RM References: 7.04 (6/2) 7.04 (7.1/2)
27784 @geindex AI-0178 (Ada 2012 feature)
27790 @emph{AI-0178 Incomplete views are limited (0000-00-00)}
27792 This AI clarifies the role of incomplete views and plugs an omission in the
27793 RM. GNAT always correctly restricted the use of incomplete views and types.
27795 RM References: 7.05 (3/2) 7.05 (6/2)
27798 @geindex AI-0087 (Ada 2012 feature)
27804 @emph{AI-0087 Actual for formal nonlimited derived type (2010-07-15)}
27806 The actual for a formal nonlimited derived type cannot be limited. In
27807 particular, a formal derived type that extends a limited interface but which
27808 is not explicitly limited cannot be instantiated with a limited type.
27810 RM References: 7.05 (5/2) 12.05.01 (5.1/2)
27813 @geindex AI-0099 (Ada 2012 feature)
27819 @emph{AI-0099 Tag determines whether finalization needed (0000-00-00)}
27821 This AI clarifies that 'needs finalization' is part of dynamic semantics,
27822 and therefore depends on the run-time characteristics of an object (i.e. its
27823 tag) and not on its nominal type. As the AI indicates: "we do not expect
27824 this to affect any implementation'@w{'}.
27826 RM References: 7.06.01 (6) 7.06.01 (7) 7.06.01 (8) 7.06.01 (9/2)
27829 @geindex AI-0064 (Ada 2012 feature)
27835 @emph{AI-0064 Redundant finalization rule (0000-00-00)}
27837 This is an editorial change only. The intended behavior is already checked
27838 by an existing ACATS test, which GNAT has always executed correctly.
27840 RM References: 7.06.01 (17.1/1)
27843 @geindex AI-0026 (Ada 2012 feature)
27849 @emph{AI-0026 Missing rules for Unchecked_Union (2010-07-07)}
27851 Record representation clauses concerning Unchecked_Union types cannot mention
27852 the discriminant of the type. The type of a component declared in the variant
27853 part of an Unchecked_Union cannot be controlled, have controlled components,
27854 nor have protected or task parts. If an Unchecked_Union type is declared
27855 within the body of a generic unit or its descendants, then the type of a
27856 component declared in the variant part cannot be a formal private type or a
27857 formal private extension declared within the same generic unit.
27859 RM References: 7.06 (9.4/2) B.03.03 (9/2) B.03.03 (10/2)
27862 @geindex AI-0205 (Ada 2012 feature)
27868 @emph{AI-0205 Extended return declares visible name (0000-00-00)}
27870 This AI corrects a simple omission in the RM. Return objects have always
27871 been visible within an extended return statement.
27873 RM References: 8.03 (17)
27876 @geindex AI-0042 (Ada 2012 feature)
27882 @emph{AI-0042 Overriding versus implemented-by (0000-00-00)}
27884 This AI fixes a wording gap in the RM. An operation of a synchronized
27885 interface can be implemented by a protected or task entry, but the abstract
27886 operation is not being overridden in the usual sense, and it must be stated
27887 separately that this implementation is legal. This has always been the case
27890 RM References: 9.01 (9.2/2) 9.04 (11.1/2)
27893 @geindex AI-0030 (Ada 2012 feature)
27899 @emph{AI-0030 Requeue on synchronized interfaces (2010-07-19)}
27901 Requeue is permitted to a protected, synchronized or task interface primitive
27902 providing it is known that the overriding operation is an entry. Otherwise
27903 the requeue statement has the same effect as a procedure call. Use of pragma
27904 @code{Implemented} provides a way to impose a static requirement on the
27905 overriding operation by adhering to one of the implementation kinds: entry,
27906 protected procedure or any of the above.
27908 RM References: 9.05 (9) 9.05.04 (2) 9.05.04 (3) 9.05.04 (5)
27909 9.05.04 (6) 9.05.04 (7) 9.05.04 (12)
27912 @geindex AI-0201 (Ada 2012 feature)
27918 @emph{AI-0201 Independence of atomic object components (2010-07-22)}
27920 If an Atomic object has a pragma @code{Pack} or a @code{Component_Size}
27921 attribute, then individual components may not be addressable by independent
27922 tasks. However, if the representation clause has no effect (is confirming),
27923 then independence is not compromised. Furthermore, in GNAT, specification of
27924 other appropriately addressable component sizes (e.g. 16 for 8-bit
27925 characters) also preserves independence. GNAT now gives very clear warnings
27926 both for the declaration of such a type, and for any assignment to its components.
27928 RM References: 9.10 (1/3) C.06 (22/2) C.06 (23/2)
27931 @geindex AI-0009 (Ada 2012 feature)
27937 @emph{AI-0009 Pragma Independent[_Components] (2010-07-23)}
27939 This AI introduces the new pragmas @code{Independent} and
27940 @code{Independent_Components},
27941 which control guaranteeing independence of access to objects and components.
27942 The AI also requires independence not unaffected by confirming rep clauses.
27944 RM References: 9.10 (1) 13.01 (15/1) 13.02 (9) 13.03 (13) C.06 (2)
27945 C.06 (4) C.06 (6) C.06 (9) C.06 (13) C.06 (14)
27948 @geindex AI-0072 (Ada 2012 feature)
27954 @emph{AI-0072 Task signalling using 'Terminated (0000-00-00)}
27956 This AI clarifies that task signalling for reading @code{'Terminated} only
27957 occurs if the result is True. GNAT semantics has always been consistent with
27958 this notion of task signalling.
27960 RM References: 9.10 (6.1/1)
27963 @geindex AI-0108 (Ada 2012 feature)
27969 @emph{AI-0108 Limited incomplete view and discriminants (0000-00-00)}
27971 This AI confirms that an incomplete type from a limited view does not have
27972 discriminants. This has always been the case in GNAT.
27974 RM References: 10.01.01 (12.3/2)
27977 @geindex AI-0129 (Ada 2012 feature)
27983 @emph{AI-0129 Limited views and incomplete types (0000-00-00)}
27985 This AI clarifies the description of limited views: a limited view of a
27986 package includes only one view of a type that has an incomplete declaration
27987 and a full declaration (there is no possible ambiguity in a client package).
27988 This AI also fixes an omission: a nested package in the private part has no
27989 limited view. GNAT always implemented this correctly.
27991 RM References: 10.01.01 (12.2/2) 10.01.01 (12.3/2)
27994 @geindex AI-0077 (Ada 2012 feature)
28000 @emph{AI-0077 Limited withs and scope of declarations (0000-00-00)}
28002 This AI clarifies that a declaration does not include a context clause,
28003 and confirms that it is illegal to have a context in which both a limited
28004 and a nonlimited view of a package are accessible. Such double visibility
28005 was always rejected by GNAT.
28007 RM References: 10.01.02 (12/2) 10.01.02 (21/2) 10.01.02 (22/2)
28010 @geindex AI-0122 (Ada 2012 feature)
28016 @emph{AI-0122 Private with and children of generics (0000-00-00)}
28018 This AI clarifies the visibility of private children of generic units within
28019 instantiations of a parent. GNAT has always handled this correctly.
28021 RM References: 10.01.02 (12/2)
28024 @geindex AI-0040 (Ada 2012 feature)
28030 @emph{AI-0040 Limited with clauses on descendant (0000-00-00)}
28032 This AI confirms that a limited with clause in a child unit cannot name
28033 an ancestor of the unit. This has always been checked in GNAT.
28035 RM References: 10.01.02 (20/2)
28038 @geindex AI-0132 (Ada 2012 feature)
28044 @emph{AI-0132 Placement of library unit pragmas (0000-00-00)}
28046 This AI fills a gap in the description of library unit pragmas. The pragma
28047 clearly must apply to a library unit, even if it does not carry the name
28048 of the enclosing unit. GNAT has always enforced the required check.
28050 RM References: 10.01.05 (7)
28053 @geindex AI-0034 (Ada 2012 feature)
28059 @emph{AI-0034 Categorization of limited views (0000-00-00)}
28061 The RM makes certain limited with clauses illegal because of categorization
28062 considerations, when the corresponding normal with would be legal. This is
28063 not intended, and GNAT has always implemented the recommended behavior.
28065 RM References: 10.02.01 (11/1) 10.02.01 (17/2)
28068 @geindex AI-0035 (Ada 2012 feature)
28074 @emph{AI-0035 Inconsistencies with Pure units (0000-00-00)}
28076 This AI remedies some inconsistencies in the legality rules for Pure units.
28077 Derived access types are legal in a pure unit (on the assumption that the
28078 rule for a zero storage pool size has been enforced on the ancestor type).
28079 The rules are enforced in generic instances and in subunits. GNAT has always
28080 implemented the recommended behavior.
28082 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)
28085 @geindex AI-0219 (Ada 2012 feature)
28091 @emph{AI-0219 Pure permissions and limited parameters (2010-05-25)}
28093 This AI refines the rules for the cases with limited parameters which do not
28094 allow the implementations to omit 'redundant'. GNAT now properly conforms
28095 to the requirements of this binding interpretation.
28097 RM References: 10.02.01 (18/2)
28100 @geindex AI-0043 (Ada 2012 feature)
28106 @emph{AI-0043 Rules about raising exceptions (0000-00-00)}
28108 This AI covers various omissions in the RM regarding the raising of
28109 exceptions. GNAT has always implemented the intended semantics.
28111 RM References: 11.04.01 (10.1/2) 11 (2)
28114 @geindex AI-0200 (Ada 2012 feature)
28120 @emph{AI-0200 Mismatches in formal package declarations (0000-00-00)}
28122 This AI plugs a gap in the RM which appeared to allow some obviously intended
28123 illegal instantiations. GNAT has never allowed these instantiations.
28125 RM References: 12.07 (16)
28128 @geindex AI-0112 (Ada 2012 feature)
28134 @emph{AI-0112 Detection of duplicate pragmas (2010-07-24)}
28136 This AI concerns giving names to various representation aspects, but the
28137 practical effect is simply to make the use of duplicate
28138 @code{Atomic[_Components]},
28139 @code{Volatile[_Components]}, and
28140 @code{Independent[_Components]} pragmas illegal, and GNAT
28141 now performs this required check.
28143 RM References: 13.01 (8)
28146 @geindex AI-0106 (Ada 2012 feature)
28152 @emph{AI-0106 No representation pragmas on generic formals (0000-00-00)}
28154 The RM appeared to allow representation pragmas on generic formal parameters,
28155 but this was not intended, and GNAT has never permitted this usage.
28157 RM References: 13.01 (9.1/1)
28160 @geindex AI-0012 (Ada 2012 feature)
28166 @emph{AI-0012 Pack/Component_Size for aliased/atomic (2010-07-15)}
28168 It is now illegal to give an inappropriate component size or a pragma
28169 @code{Pack} that attempts to change the component size in the case of atomic
28170 or aliased components. Previously GNAT ignored such an attempt with a
28173 RM References: 13.02 (6.1/2) 13.02 (7) C.06 (10) C.06 (11) C.06 (21)
28176 @geindex AI-0039 (Ada 2012 feature)
28182 @emph{AI-0039 Stream attributes cannot be dynamic (0000-00-00)}
28184 The RM permitted the use of dynamic expressions (such as @code{ptr.all})`
28185 for stream attributes, but these were never useful and are now illegal. GNAT
28186 has always regarded such expressions as illegal.
28188 RM References: 13.03 (4) 13.03 (6) 13.13.02 (38/2)
28191 @geindex AI-0095 (Ada 2012 feature)
28197 @emph{AI-0095 Address of intrinsic subprograms (0000-00-00)}
28199 The prefix of @code{'Address} cannot statically denote a subprogram with
28200 convention @code{Intrinsic}. The use of the @code{Address} attribute raises
28201 @code{Program_Error} if the prefix denotes a subprogram with convention
28204 RM References: 13.03 (11/1)
28207 @geindex AI-0116 (Ada 2012 feature)
28213 @emph{AI-0116 Alignment of class-wide objects (0000-00-00)}
28215 This AI requires that the alignment of a class-wide object be no greater
28216 than the alignment of any type in the class. GNAT has always followed this
28219 RM References: 13.03 (29) 13.11 (16)
28222 @geindex AI-0146 (Ada 2012 feature)
28228 @emph{AI-0146 Type invariants (2009-09-21)}
28230 Type invariants may be specified for private types using the aspect notation.
28231 Aspect @code{Type_Invariant} may be specified for any private type,
28232 @code{Type_Invariant'Class} can
28233 only be specified for tagged types, and is inherited by any descendent of the
28234 tagged types. The invariant is a boolean expression that is tested for being
28235 true in the following situations: conversions to the private type, object
28236 declarations for the private type that are default initialized, and
28237 [@strong{in}] @strong{out}
28238 parameters and returned result on return from any primitive operation for
28239 the type that is visible to a client.
28240 GNAT defines the synonyms @code{Invariant} for @code{Type_Invariant} and
28241 @code{Invariant'Class} for @code{Type_Invariant'Class}.
28243 RM References: 13.03.03 (00)
28246 @geindex AI-0078 (Ada 2012 feature)
28252 @emph{AI-0078 Relax Unchecked_Conversion alignment rules (0000-00-00)}
28254 In Ada 2012, compilers are required to support unchecked conversion where the
28255 target alignment is a multiple of the source alignment. GNAT always supported
28256 this case (and indeed all cases of differing alignments, doing copies where
28257 required if the alignment was reduced).
28259 RM References: 13.09 (7)
28262 @geindex AI-0195 (Ada 2012 feature)
28268 @emph{AI-0195 Invalid value handling is implementation defined (2010-07-03)}
28270 The handling of invalid values is now designated to be implementation
28271 defined. This is a documentation change only, requiring Annex M in the GNAT
28272 Reference Manual to document this handling.
28273 In GNAT, checks for invalid values are made
28274 only when necessary to avoid erroneous behavior. Operations like assignments
28275 which cannot cause erroneous behavior ignore the possibility of invalid
28276 values and do not do a check. The date given above applies only to the
28277 documentation change, this behavior has always been implemented by GNAT.
28279 RM References: 13.09.01 (10)
28282 @geindex AI-0193 (Ada 2012 feature)
28288 @emph{AI-0193 Alignment of allocators (2010-09-16)}
28290 This AI introduces a new attribute @code{Max_Alignment_For_Allocation},
28291 analogous to @code{Max_Size_In_Storage_Elements}, but for alignment instead
28294 RM References: 13.11 (16) 13.11 (21) 13.11.01 (0) 13.11.01 (1)
28295 13.11.01 (2) 13.11.01 (3)
28298 @geindex AI-0177 (Ada 2012 feature)
28304 @emph{AI-0177 Parameterized expressions (2010-07-10)}
28306 The new Ada 2012 notion of parameterized expressions is implemented. The form
28310 function-specification is (expression)
28313 This is exactly equivalent to the
28314 corresponding function body that returns the expression, but it can appear
28315 in a package spec. Note that the expression must be parenthesized.
28317 RM References: 13.11.01 (3/2)
28320 @geindex AI-0033 (Ada 2012 feature)
28326 @emph{AI-0033 Attach/Interrupt_Handler in generic (2010-07-24)}
28328 Neither of these two pragmas may appear within a generic template, because
28329 the generic might be instantiated at other than the library level.
28331 RM References: 13.11.02 (16) C.03.01 (7/2) C.03.01 (8/2)
28334 @geindex AI-0161 (Ada 2012 feature)
28340 @emph{AI-0161 Restriction No_Default_Stream_Attributes (2010-09-11)}
28342 A new restriction @code{No_Default_Stream_Attributes} prevents the use of any
28343 of the default stream attributes for elementary types. If this restriction is
28344 in force, then it is necessary to provide explicit subprograms for any
28345 stream attributes used.
28347 RM References: 13.12.01 (4/2) 13.13.02 (40/2) 13.13.02 (52/2)
28350 @geindex AI-0194 (Ada 2012 feature)
28356 @emph{AI-0194 Value of Stream_Size attribute (0000-00-00)}
28358 The @code{Stream_Size} attribute returns the default number of bits in the
28359 stream representation of the given type.
28360 This value is not affected by the presence
28361 of stream subprogram attributes for the type. GNAT has always implemented
28362 this interpretation.
28364 RM References: 13.13.02 (1.2/2)
28367 @geindex AI-0109 (Ada 2012 feature)
28373 @emph{AI-0109 Redundant check in S'Class'Input (0000-00-00)}
28375 This AI is an editorial change only. It removes the need for a tag check
28376 that can never fail.
28378 RM References: 13.13.02 (34/2)
28381 @geindex AI-0007 (Ada 2012 feature)
28387 @emph{AI-0007 Stream read and private scalar types (0000-00-00)}
28389 The RM as written appeared to limit the possibilities of declaring read
28390 attribute procedures for private scalar types. This limitation was not
28391 intended, and has never been enforced by GNAT.
28393 RM References: 13.13.02 (50/2) 13.13.02 (51/2)
28396 @geindex AI-0065 (Ada 2012 feature)
28402 @emph{AI-0065 Remote access types and external streaming (0000-00-00)}
28404 This AI clarifies the fact that all remote access types support external
28405 streaming. This fixes an obvious oversight in the definition of the
28406 language, and GNAT always implemented the intended correct rules.
28408 RM References: 13.13.02 (52/2)
28411 @geindex AI-0019 (Ada 2012 feature)
28417 @emph{AI-0019 Freezing of primitives for tagged types (0000-00-00)}
28419 The RM suggests that primitive subprograms of a specific tagged type are
28420 frozen when the tagged type is frozen. This would be an incompatible change
28421 and is not intended. GNAT has never attempted this kind of freezing and its
28422 behavior is consistent with the recommendation of this AI.
28424 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)
28427 @geindex AI-0017 (Ada 2012 feature)
28433 @emph{AI-0017 Freezing and incomplete types (0000-00-00)}
28435 So-called 'Taft-amendment types' (i.e., types that are completed in package
28436 bodies) are not frozen by the occurrence of bodies in the
28437 enclosing declarative part. GNAT always implemented this properly.
28439 RM References: 13.14 (3/1)
28442 @geindex AI-0060 (Ada 2012 feature)
28448 @emph{AI-0060 Extended definition of remote access types (0000-00-00)}
28450 This AI extends the definition of remote access types to include access
28451 to limited, synchronized, protected or task class-wide interface types.
28452 GNAT already implemented this extension.
28454 RM References: A (4) E.02.02 (9/1) E.02.02 (9.2/1) E.02.02 (14/2) E.02.02 (18)
28457 @geindex AI-0114 (Ada 2012 feature)
28463 @emph{AI-0114 Classification of letters (0000-00-00)}
28465 The code points 170 (@code{FEMININE ORDINAL INDICATOR}),
28466 181 (@code{MICRO SIGN}), and
28467 186 (@code{MASCULINE ORDINAL INDICATOR}) are technically considered
28468 lower case letters by Unicode.
28469 However, they are not allowed in identifiers, and they
28470 return @code{False} to @code{Ada.Characters.Handling.Is_Letter/Is_Lower}.
28471 This behavior is consistent with that defined in Ada 95.
28473 RM References: A.03.02 (59) A.04.06 (7)
28476 @geindex AI-0185 (Ada 2012 feature)
28482 @emph{AI-0185 Ada.Wide_[Wide_]Characters.Handling (2010-07-06)}
28484 Two new packages @code{Ada.Wide_[Wide_]Characters.Handling} provide
28485 classification functions for @code{Wide_Character} and
28486 @code{Wide_Wide_Character}, as well as providing
28487 case folding routines for @code{Wide_[Wide_]Character} and
28488 @code{Wide_[Wide_]String}.
28490 RM References: A.03.05 (0) A.03.06 (0)
28493 @geindex AI-0031 (Ada 2012 feature)
28499 @emph{AI-0031 Add From parameter to Find_Token (2010-07-25)}
28501 A new version of @code{Find_Token} is added to all relevant string packages,
28502 with an extra parameter @code{From}. Instead of starting at the first
28503 character of the string, the search for a matching Token starts at the
28504 character indexed by the value of @code{From}.
28505 These procedures are available in all versions of Ada
28506 but if used in versions earlier than Ada 2012 they will generate a warning
28507 that an Ada 2012 subprogram is being used.
28509 RM References: A.04.03 (16) A.04.03 (67) A.04.03 (68/1) A.04.04 (51)
28513 @geindex AI-0056 (Ada 2012 feature)
28519 @emph{AI-0056 Index on null string returns zero (0000-00-00)}
28521 The wording in the Ada 2005 RM implied an incompatible handling of the
28522 @code{Index} functions, resulting in raising an exception instead of
28523 returning zero in some situations.
28524 This was not intended and has been corrected.
28525 GNAT always returned zero, and is thus consistent with this AI.
28527 RM References: A.04.03 (56.2/2) A.04.03 (58.5/2)
28530 @geindex AI-0137 (Ada 2012 feature)
28536 @emph{AI-0137 String encoding package (2010-03-25)}
28538 The packages @code{Ada.Strings.UTF_Encoding}, together with its child
28539 packages, @code{Conversions}, @code{Strings}, @code{Wide_Strings},
28540 and @code{Wide_Wide_Strings} have been
28541 implemented. These packages (whose documentation can be found in the spec
28542 files @code{a-stuten.ads}, @code{a-suenco.ads}, @code{a-suenst.ads},
28543 @code{a-suewst.ads}, @code{a-suezst.ads}) allow encoding and decoding of
28544 @code{String}, @code{Wide_String}, and @code{Wide_Wide_String}
28545 values using UTF coding schemes (including UTF-8, UTF-16LE, UTF-16BE, and
28546 UTF-16), as well as conversions between the different UTF encodings. With
28547 the exception of @code{Wide_Wide_Strings}, these packages are available in
28548 Ada 95 and Ada 2005 mode as well as Ada 2012 mode.
28549 The @code{Wide_Wide_Strings} package
28550 is available in Ada 2005 mode as well as Ada 2012 mode (but not in Ada 95
28551 mode since it uses @code{Wide_Wide_Character}).
28553 RM References: A.04.11
28556 @geindex AI-0038 (Ada 2012 feature)
28562 @emph{AI-0038 Minor errors in Text_IO (0000-00-00)}
28564 These are minor errors in the description on three points. The intent on
28565 all these points has always been clear, and GNAT has always implemented the
28566 correct intended semantics.
28568 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)
28571 @geindex AI-0044 (Ada 2012 feature)
28577 @emph{AI-0044 Restrictions on container instantiations (0000-00-00)}
28579 This AI places restrictions on allowed instantiations of generic containers.
28580 These restrictions are not checked by the compiler, so there is nothing to
28581 change in the implementation. This affects only the RM documentation.
28583 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)
28586 @geindex AI-0127 (Ada 2012 feature)
28592 @emph{AI-0127 Adding Locale Capabilities (2010-09-29)}
28594 This package provides an interface for identifying the current locale.
28596 RM References: A.19 A.19.01 A.19.02 A.19.03 A.19.05 A.19.06
28597 A.19.07 A.19.08 A.19.09 A.19.10 A.19.11 A.19.12 A.19.13
28600 @geindex AI-0002 (Ada 2012 feature)
28606 @emph{AI-0002 Export C with unconstrained arrays (0000-00-00)}
28608 The compiler is not required to support exporting an Ada subprogram with
28609 convention C if there are parameters or a return type of an unconstrained
28610 array type (such as @code{String}). GNAT allows such declarations but
28611 generates warnings. It is possible, but complicated, to write the
28612 corresponding C code and certainly such code would be specific to GNAT and
28615 RM References: B.01 (17) B.03 (62) B.03 (71.1/2)
28618 @geindex AI05-0216 (Ada 2012 feature)
28624 @emph{AI-0216 No_Task_Hierarchy forbids local tasks (0000-00-00)}
28626 It is clearly the intention that @code{No_Task_Hierarchy} is intended to
28627 forbid tasks declared locally within subprograms, or functions returning task
28628 objects, and that is the implementation that GNAT has always provided.
28629 However the language in the RM was not sufficiently clear on this point.
28630 Thus this is a documentation change in the RM only.
28632 RM References: D.07 (3/3)
28635 @geindex AI-0211 (Ada 2012 feature)
28641 @emph{AI-0211 No_Relative_Delays forbids Set_Handler use (2010-07-09)}
28643 The restriction @code{No_Relative_Delays} forbids any calls to the subprogram
28644 @code{Ada.Real_Time.Timing_Events.Set_Handler}.
28646 RM References: D.07 (5) D.07 (10/2) D.07 (10.4/2) D.07 (10.7/2)
28649 @geindex AI-0190 (Ada 2012 feature)
28655 @emph{AI-0190 pragma Default_Storage_Pool (2010-09-15)}
28657 This AI introduces a new pragma @code{Default_Storage_Pool}, which can be
28658 used to control storage pools globally.
28659 In particular, you can force every access
28660 type that is used for allocation (@strong{new}) to have an explicit storage pool,
28661 or you can declare a pool globally to be used for all access types that lack
28664 RM References: D.07 (8)
28667 @geindex AI-0189 (Ada 2012 feature)
28673 @emph{AI-0189 No_Allocators_After_Elaboration (2010-01-23)}
28675 This AI introduces a new restriction @code{No_Allocators_After_Elaboration},
28676 which says that no dynamic allocation will occur once elaboration is
28678 In general this requires a run-time check, which is not required, and which
28679 GNAT does not attempt. But the static cases of allocators in a task body or
28680 in the body of the main program are detected and flagged at compile or bind
28683 RM References: D.07 (19.1/2) H.04 (23.3/2)
28686 @geindex AI-0171 (Ada 2012 feature)
28692 @emph{AI-0171 Pragma CPU and Ravenscar Profile (2010-09-24)}
28694 A new package @code{System.Multiprocessors} is added, together with the
28695 definition of pragma @code{CPU} for controlling task affinity. A new no
28696 dependence restriction, on @code{System.Multiprocessors.Dispatching_Domains},
28697 is added to the Ravenscar profile.
28699 RM References: D.13.01 (4/2) D.16
28702 @geindex AI-0210 (Ada 2012 feature)
28708 @emph{AI-0210 Correct Timing_Events metric (0000-00-00)}
28710 This is a documentation only issue regarding wording of metric requirements,
28711 that does not affect the implementation of the compiler.
28713 RM References: D.15 (24/2)
28716 @geindex AI-0206 (Ada 2012 feature)
28722 @emph{AI-0206 Remote types packages and preelaborate (2010-07-24)}
28724 Remote types packages are now allowed to depend on preelaborated packages.
28725 This was formerly considered illegal.
28727 RM References: E.02.02 (6)
28730 @geindex AI-0152 (Ada 2012 feature)
28736 @emph{AI-0152 Restriction No_Anonymous_Allocators (2010-09-08)}
28738 Restriction @code{No_Anonymous_Allocators} prevents the use of allocators
28739 where the type of the returned value is an anonymous access type.
28741 RM References: H.04 (8/1)
28744 @node Obsolescent Features,Compatibility and Porting Guide,Implementation of Ada 2012 Features,Top
28745 @anchor{gnat_rm/obsolescent_features id1}@anchor{434}@anchor{gnat_rm/obsolescent_features doc}@anchor{435}@anchor{gnat_rm/obsolescent_features obsolescent-features}@anchor{15}
28746 @chapter Obsolescent Features
28749 This chapter describes features that are provided by GNAT, but are
28750 considered obsolescent since there are preferred ways of achieving
28751 the same effect. These features are provided solely for historical
28752 compatibility purposes.
28755 * pragma No_Run_Time::
28756 * pragma Ravenscar::
28757 * pragma Restricted_Run_Time::
28758 * pragma Task_Info::
28759 * package System.Task_Info (s-tasinf.ads): package System Task_Info s-tasinf ads.
28763 @node pragma No_Run_Time,pragma Ravenscar,,Obsolescent Features
28764 @anchor{gnat_rm/obsolescent_features id2}@anchor{436}@anchor{gnat_rm/obsolescent_features pragma-no-run-time}@anchor{437}
28765 @section pragma No_Run_Time
28768 The pragma @code{No_Run_Time} is used to achieve an affect similar
28769 to the use of the "Zero Foot Print" configurable run time, but without
28770 requiring a specially configured run time. The result of using this
28771 pragma, which must be used for all units in a partition, is to restrict
28772 the use of any language features requiring run-time support code. The
28773 preferred usage is to use an appropriately configured run-time that
28774 includes just those features that are to be made accessible.
28776 @node pragma Ravenscar,pragma Restricted_Run_Time,pragma No_Run_Time,Obsolescent Features
28777 @anchor{gnat_rm/obsolescent_features id3}@anchor{438}@anchor{gnat_rm/obsolescent_features pragma-ravenscar}@anchor{439}
28778 @section pragma Ravenscar
28781 The pragma @code{Ravenscar} has exactly the same effect as pragma
28782 @code{Profile (Ravenscar)}. The latter usage is preferred since it
28783 is part of the new Ada 2005 standard.
28785 @node pragma Restricted_Run_Time,pragma Task_Info,pragma Ravenscar,Obsolescent Features
28786 @anchor{gnat_rm/obsolescent_features pragma-restricted-run-time}@anchor{43a}@anchor{gnat_rm/obsolescent_features id4}@anchor{43b}
28787 @section pragma Restricted_Run_Time
28790 The pragma @code{Restricted_Run_Time} has exactly the same effect as
28791 pragma @code{Profile (Restricted)}. The latter usage is
28792 preferred since the Ada 2005 pragma @code{Profile} is intended for
28793 this kind of implementation dependent addition.
28795 @node pragma Task_Info,package System Task_Info s-tasinf ads,pragma Restricted_Run_Time,Obsolescent Features
28796 @anchor{gnat_rm/obsolescent_features pragma-task-info}@anchor{43c}@anchor{gnat_rm/obsolescent_features id5}@anchor{43d}
28797 @section pragma Task_Info
28800 The functionality provided by pragma @code{Task_Info} is now part of the
28801 Ada language. The @code{CPU} aspect and the package
28802 @code{System.Multiprocessors} offer a less system-dependent way to specify
28803 task affinity or to query the number of processsors.
28808 pragma Task_Info (EXPRESSION);
28811 This pragma appears within a task definition (like pragma
28812 @code{Priority}) and applies to the task in which it appears. The
28813 argument must be of type @code{System.Task_Info.Task_Info_Type}.
28814 The @code{Task_Info} pragma provides system dependent control over
28815 aspects of tasking implementation, for example, the ability to map
28816 tasks to specific processors. For details on the facilities available
28817 for the version of GNAT that you are using, see the documentation
28818 in the spec of package System.Task_Info in the runtime
28821 @node package System Task_Info s-tasinf ads,,pragma Task_Info,Obsolescent Features
28822 @anchor{gnat_rm/obsolescent_features package-system-task-info}@anchor{43e}@anchor{gnat_rm/obsolescent_features package-system-task-info-s-tasinf-ads}@anchor{43f}
28823 @section package System.Task_Info (@code{s-tasinf.ads})
28826 This package provides target dependent functionality that is used
28827 to support the @code{Task_Info} pragma. The predefined Ada package
28828 @code{System.Multiprocessors} and the @code{CPU} aspect now provide a
28829 standard replacement for GNAT's @code{Task_Info} functionality.
28831 @node Compatibility and Porting Guide,GNU Free Documentation License,Obsolescent Features,Top
28832 @anchor{gnat_rm/compatibility_and_porting_guide compatibility-and-porting-guide}@anchor{16}@anchor{gnat_rm/compatibility_and_porting_guide doc}@anchor{440}@anchor{gnat_rm/compatibility_and_porting_guide id1}@anchor{441}
28833 @chapter Compatibility and Porting Guide
28836 This chapter presents some guidelines for developing portable Ada code,
28837 describes the compatibility issues that may arise between
28838 GNAT and other Ada compilation systems (including those for Ada 83),
28839 and shows how GNAT can expedite porting
28840 applications developed in other Ada environments.
28843 * Writing Portable Fixed-Point Declarations::
28844 * Compatibility with Ada 83::
28845 * Compatibility between Ada 95 and Ada 2005::
28846 * Implementation-dependent characteristics::
28847 * Compatibility with Other Ada Systems::
28848 * Representation Clauses::
28849 * Compatibility with HP Ada 83::
28853 @node Writing Portable Fixed-Point Declarations,Compatibility with Ada 83,,Compatibility and Porting Guide
28854 @anchor{gnat_rm/compatibility_and_porting_guide id2}@anchor{442}@anchor{gnat_rm/compatibility_and_porting_guide writing-portable-fixed-point-declarations}@anchor{443}
28855 @section Writing Portable Fixed-Point Declarations
28858 The Ada Reference Manual gives an implementation freedom to choose bounds
28859 that are narrower by @code{Small} from the given bounds.
28860 For example, if we write
28863 type F1 is delta 1.0 range -128.0 .. +128.0;
28866 then the implementation is allowed to choose -128.0 .. +127.0 if it
28867 likes, but is not required to do so.
28869 This leads to possible portability problems, so let's have a closer
28870 look at this, and figure out how to avoid these problems.
28872 First, why does this freedom exist, and why would an implementation
28873 take advantage of it? To answer this, take a closer look at the type
28874 declaration for @code{F1} above. If the compiler uses the given bounds,
28875 it would need 9 bits to hold the largest positive value (and typically
28876 that means 16 bits on all machines). But if the implementation chooses
28877 the +127.0 bound then it can fit values of the type in 8 bits.
28879 Why not make the user write +127.0 if that's what is wanted?
28880 The rationale is that if you are thinking of fixed point
28881 as a kind of 'poor man's floating-point', then you don't want
28882 to be thinking about the scaled integers that are used in its
28883 representation. Let's take another example:
28886 type F2 is delta 2.0**(-15) range -1.0 .. +1.0;
28889 Looking at this declaration, it seems casually as though
28890 it should fit in 16 bits, but again that extra positive value
28891 +1.0 has the scaled integer equivalent of 2**15 which is one too
28892 big for signed 16 bits. The implementation can treat this as:
28895 type F2 is delta 2.0**(-15) range -1.0 .. +1.0-(2.0**(-15));
28898 and the Ada language design team felt that this was too annoying
28899 to require. We don't need to debate this decision at this point,
28900 since it is well established (the rule about narrowing the ranges
28903 But the important point is that an implementation is not required
28904 to do this narrowing, so we have a potential portability problem.
28905 We could imagine three types of implementation:
28911 those that narrow the range automatically if they can figure
28912 out that the narrower range will allow storage in a smaller machine unit,
28915 those that will narrow only if forced to by a @code{'Size} clause, and
28918 those that will never narrow.
28921 Now if we are language theoreticians, we can imagine a fourth
28922 approach: to narrow all the time, e.g. to treat
28925 type F3 is delta 1.0 range -10.0 .. +23.0;
28928 as though it had been written:
28931 type F3 is delta 1.0 range -9.0 .. +22.0;
28934 But although technically allowed, such a behavior would be hostile and silly,
28935 and no real compiler would do this. All real compilers will fall into one of
28936 the categories (a), (b) or (c) above.
28938 So, how do you get the compiler to do what you want? The answer is give the
28939 actual bounds you want, and then use a @code{'Small} clause and a
28940 @code{'Size} clause to absolutely pin down what the compiler does.
28941 E.g., for @code{F2} above, we will write:
28944 My_Small : constant := 2.0**(-15);
28945 My_First : constant := -1.0;
28946 My_Last : constant := +1.0 - My_Small;
28948 type F2 is delta My_Small range My_First .. My_Last;
28954 for F2'Small use my_Small;
28955 for F2'Size use 16;
28958 In practice all compilers will do the same thing here and will give you
28959 what you want, so the above declarations are fully portable. If you really
28960 want to play language lawyer and guard against ludicrous behavior by the
28961 compiler you could add
28964 Test1 : constant := 1 / Boolean'Pos (F2'First = My_First);
28965 Test2 : constant := 1 / Boolean'Pos (F2'Last = My_Last);
28968 One or other or both are allowed to be illegal if the compiler is
28969 behaving in a silly manner, but at least the silly compiler will not
28970 get away with silently messing with your (very clear) intentions.
28972 If you follow this scheme you will be guaranteed that your fixed-point
28973 types will be portable.
28975 @node Compatibility with Ada 83,Compatibility between Ada 95 and Ada 2005,Writing Portable Fixed-Point Declarations,Compatibility and Porting Guide
28976 @anchor{gnat_rm/compatibility_and_porting_guide compatibility-with-ada-83}@anchor{444}@anchor{gnat_rm/compatibility_and_porting_guide id3}@anchor{445}
28977 @section Compatibility with Ada 83
28980 @geindex Compatibility (between Ada 83 and Ada 95 / Ada 2005 / Ada 2012)
28982 Ada 95 and the subsequent revisions Ada 2005 and Ada 2012
28983 are highly upwards compatible with Ada 83. In
28984 particular, the design intention was that the difficulties associated
28985 with moving from Ada 83 to later versions of the standard should be no greater
28986 than those that occur when moving from one Ada 83 system to another.
28988 However, there are a number of points at which there are minor
28989 incompatibilities. The @cite{Ada 95 Annotated Reference Manual} contains
28990 full details of these issues as they relate to Ada 95,
28991 and should be consulted for a complete treatment.
28993 following subsections treat the most likely issues to be encountered.
28996 * Legal Ada 83 programs that are illegal in Ada 95::
28997 * More deterministic semantics::
28998 * Changed semantics::
28999 * Other language compatibility issues::
29003 @node Legal Ada 83 programs that are illegal in Ada 95,More deterministic semantics,,Compatibility with Ada 83
29004 @anchor{gnat_rm/compatibility_and_porting_guide id4}@anchor{446}@anchor{gnat_rm/compatibility_and_porting_guide legal-ada-83-programs-that-are-illegal-in-ada-95}@anchor{447}
29005 @subsection Legal Ada 83 programs that are illegal in Ada 95
29008 Some legal Ada 83 programs are illegal (i.e., they will fail to compile) in
29009 Ada 95 and later versions of the standard:
29015 @emph{Character literals}
29017 Some uses of character literals are ambiguous. Since Ada 95 has introduced
29018 @code{Wide_Character} as a new predefined character type, some uses of
29019 character literals that were legal in Ada 83 are illegal in Ada 95.
29023 for Char in 'A' .. 'Z' loop ... end loop;
29026 The problem is that 'A' and 'Z' could be from either
29027 @code{Character} or @code{Wide_Character}. The simplest correction
29028 is to make the type explicit; e.g.:
29031 for Char in Character range 'A' .. 'Z' loop ... end loop;
29035 @emph{New reserved words}
29037 The identifiers @code{abstract}, @code{aliased}, @code{protected},
29038 @code{requeue}, @code{tagged}, and @code{until} are reserved in Ada 95.
29039 Existing Ada 83 code using any of these identifiers must be edited to
29040 use some alternative name.
29043 @emph{Freezing rules}
29045 The rules in Ada 95 are slightly different with regard to the point at
29046 which entities are frozen, and representation pragmas and clauses are
29047 not permitted past the freeze point. This shows up most typically in
29048 the form of an error message complaining that a representation item
29049 appears too late, and the appropriate corrective action is to move
29050 the item nearer to the declaration of the entity to which it refers.
29052 A particular case is that representation pragmas
29053 cannot be applied to a subprogram body. If necessary, a separate subprogram
29054 declaration must be introduced to which the pragma can be applied.
29057 @emph{Optional bodies for library packages}
29059 In Ada 83, a package that did not require a package body was nevertheless
29060 allowed to have one. This lead to certain surprises in compiling large
29061 systems (situations in which the body could be unexpectedly ignored by the
29062 binder). In Ada 95, if a package does not require a body then it is not
29063 permitted to have a body. To fix this problem, simply remove a redundant
29064 body if it is empty, or, if it is non-empty, introduce a dummy declaration
29065 into the spec that makes the body required. One approach is to add a private
29066 part to the package declaration (if necessary), and define a parameterless
29067 procedure called @code{Requires_Body}, which must then be given a dummy
29068 procedure body in the package body, which then becomes required.
29069 Another approach (assuming that this does not introduce elaboration
29070 circularities) is to add an @code{Elaborate_Body} pragma to the package spec,
29071 since one effect of this pragma is to require the presence of a package body.
29074 @emph{Numeric_Error is the same exception as Constraint_Error}
29076 In Ada 95, the exception @code{Numeric_Error} is a renaming of @code{Constraint_Error}.
29077 This means that it is illegal to have separate exception handlers for
29078 the two exceptions. The fix is simply to remove the handler for the
29079 @code{Numeric_Error} case (since even in Ada 83, a compiler was free to raise
29080 @code{Constraint_Error} in place of @code{Numeric_Error} in all cases).
29083 @emph{Indefinite subtypes in generics}
29085 In Ada 83, it was permissible to pass an indefinite type (e.g, @code{String})
29086 as the actual for a generic formal private type, but then the instantiation
29087 would be illegal if there were any instances of declarations of variables
29088 of this type in the generic body. In Ada 95, to avoid this clear violation
29089 of the methodological principle known as the 'contract model',
29090 the generic declaration explicitly indicates whether
29091 or not such instantiations are permitted. If a generic formal parameter
29092 has explicit unknown discriminants, indicated by using @code{(<>)} after the
29093 subtype name, then it can be instantiated with indefinite types, but no
29094 stand-alone variables can be declared of this type. Any attempt to declare
29095 such a variable will result in an illegality at the time the generic is
29096 declared. If the @code{(<>)} notation is not used, then it is illegal
29097 to instantiate the generic with an indefinite type.
29098 This is the potential incompatibility issue when porting Ada 83 code to Ada 95.
29099 It will show up as a compile time error, and
29100 the fix is usually simply to add the @code{(<>)} to the generic declaration.
29103 @node More deterministic semantics,Changed semantics,Legal Ada 83 programs that are illegal in Ada 95,Compatibility with Ada 83
29104 @anchor{gnat_rm/compatibility_and_porting_guide more-deterministic-semantics}@anchor{448}@anchor{gnat_rm/compatibility_and_porting_guide id5}@anchor{449}
29105 @subsection More deterministic semantics
29114 Conversions from real types to integer types round away from 0. In Ada 83
29115 the conversion Integer(2.5) could deliver either 2 or 3 as its value. This
29116 implementation freedom was intended to support unbiased rounding in
29117 statistical applications, but in practice it interfered with portability.
29118 In Ada 95 the conversion semantics are unambiguous, and rounding away from 0
29119 is required. Numeric code may be affected by this change in semantics.
29120 Note, though, that this issue is no worse than already existed in Ada 83
29121 when porting code from one vendor to another.
29126 The Real-Time Annex introduces a set of policies that define the behavior of
29127 features that were implementation dependent in Ada 83, such as the order in
29128 which open select branches are executed.
29131 @node Changed semantics,Other language compatibility issues,More deterministic semantics,Compatibility with Ada 83
29132 @anchor{gnat_rm/compatibility_and_porting_guide id6}@anchor{44a}@anchor{gnat_rm/compatibility_and_porting_guide changed-semantics}@anchor{44b}
29133 @subsection Changed semantics
29136 The worst kind of incompatibility is one where a program that is legal in
29137 Ada 83 is also legal in Ada 95 but can have an effect in Ada 95 that was not
29138 possible in Ada 83. Fortunately this is extremely rare, but the one
29139 situation that you should be alert to is the change in the predefined type
29140 @code{Character} from 7-bit ASCII to 8-bit Latin-1.
29151 @emph{Range of type `@w{`}Character`@w{`}}
29153 The range of @code{Standard.Character} is now the full 256 characters
29154 of Latin-1, whereas in most Ada 83 implementations it was restricted
29155 to 128 characters. Although some of the effects of
29156 this change will be manifest in compile-time rejection of legal
29157 Ada 83 programs it is possible for a working Ada 83 program to have
29158 a different effect in Ada 95, one that was not permitted in Ada 83.
29159 As an example, the expression
29160 @code{Character'Pos(Character'Last)} returned @code{127} in Ada 83 and now
29161 delivers @code{255} as its value.
29162 In general, you should look at the logic of any
29163 character-processing Ada 83 program and see whether it needs to be adapted
29164 to work correctly with Latin-1. Note that the predefined Ada 95 API has a
29165 character handling package that may be relevant if code needs to be adapted
29166 to account for the additional Latin-1 elements.
29167 The desirable fix is to
29168 modify the program to accommodate the full character set, but in some cases
29169 it may be convenient to define a subtype or derived type of Character that
29170 covers only the restricted range.
29173 @node Other language compatibility issues,,Changed semantics,Compatibility with Ada 83
29174 @anchor{gnat_rm/compatibility_and_porting_guide other-language-compatibility-issues}@anchor{44c}@anchor{gnat_rm/compatibility_and_porting_guide id7}@anchor{44d}
29175 @subsection Other language compatibility issues
29182 @emph{-gnat83} switch
29184 All implementations of GNAT provide a switch that causes GNAT to operate
29185 in Ada 83 mode. In this mode, some but not all compatibility problems
29186 of the type described above are handled automatically. For example, the
29187 new reserved words introduced in Ada 95 and Ada 2005 are treated simply
29188 as identifiers as in Ada 83. However,
29189 in practice, it is usually advisable to make the necessary modifications
29190 to the program to remove the need for using this switch.
29191 See the @code{Compiling Different Versions of Ada} section in
29192 the @cite{GNAT User's Guide}.
29195 Support for removed Ada 83 pragmas and attributes
29197 A number of pragmas and attributes from Ada 83 were removed from Ada 95,
29198 generally because they were replaced by other mechanisms. Ada 95 and Ada 2005
29199 compilers are allowed, but not required, to implement these missing
29200 elements. In contrast with some other compilers, GNAT implements all
29201 such pragmas and attributes, eliminating this compatibility concern. These
29202 include @code{pragma Interface} and the floating point type attributes
29203 (@code{Emax}, @code{Mantissa}, etc.), among other items.
29206 @node Compatibility between Ada 95 and Ada 2005,Implementation-dependent characteristics,Compatibility with Ada 83,Compatibility and Porting Guide
29207 @anchor{gnat_rm/compatibility_and_porting_guide compatibility-between-ada-95-and-ada-2005}@anchor{44e}@anchor{gnat_rm/compatibility_and_porting_guide id8}@anchor{44f}
29208 @section Compatibility between Ada 95 and Ada 2005
29211 @geindex Compatibility between Ada 95 and Ada 2005
29213 Although Ada 2005 was designed to be upwards compatible with Ada 95, there are
29214 a number of incompatibilities. Several are enumerated below;
29215 for a complete description please see the
29216 @cite{Annotated Ada 2005 Reference Manual}, or section 9.1.1 in
29217 @cite{Rationale for Ada 2005}.
29223 @emph{New reserved words.}
29225 The words @code{interface}, @code{overriding} and @code{synchronized} are
29226 reserved in Ada 2005.
29227 A pre-Ada 2005 program that uses any of these as an identifier will be
29231 @emph{New declarations in predefined packages.}
29233 A number of packages in the predefined environment contain new declarations:
29234 @code{Ada.Exceptions}, @code{Ada.Real_Time}, @code{Ada.Strings},
29235 @code{Ada.Strings.Fixed}, @code{Ada.Strings.Bounded},
29236 @code{Ada.Strings.Unbounded}, @code{Ada.Strings.Wide_Fixed},
29237 @code{Ada.Strings.Wide_Bounded}, @code{Ada.Strings.Wide_Unbounded},
29238 @code{Ada.Tags}, @code{Ada.Text_IO}, and @code{Interfaces.C}.
29239 If an Ada 95 program does a @code{with} and @code{use} of any of these
29240 packages, the new declarations may cause name clashes.
29243 @emph{Access parameters.}
29245 A nondispatching subprogram with an access parameter cannot be renamed
29246 as a dispatching operation. This was permitted in Ada 95.
29249 @emph{Access types, discriminants, and constraints.}
29251 Rule changes in this area have led to some incompatibilities; for example,
29252 constrained subtypes of some access types are not permitted in Ada 2005.
29255 @emph{Aggregates for limited types.}
29257 The allowance of aggregates for limited types in Ada 2005 raises the
29258 possibility of ambiguities in legal Ada 95 programs, since additional types
29259 now need to be considered in expression resolution.
29262 @emph{Fixed-point multiplication and division.}
29264 Certain expressions involving '*' or '/' for a fixed-point type, which
29265 were legal in Ada 95 and invoked the predefined versions of these operations,
29267 The ambiguity may be resolved either by applying a type conversion to the
29268 expression, or by explicitly invoking the operation from package
29272 @emph{Return-by-reference types.}
29274 The Ada 95 return-by-reference mechanism has been removed. Instead, the user
29275 can declare a function returning a value from an anonymous access type.
29278 @node Implementation-dependent characteristics,Compatibility with Other Ada Systems,Compatibility between Ada 95 and Ada 2005,Compatibility and Porting Guide
29279 @anchor{gnat_rm/compatibility_and_porting_guide implementation-dependent-characteristics}@anchor{450}@anchor{gnat_rm/compatibility_and_porting_guide id9}@anchor{451}
29280 @section Implementation-dependent characteristics
29283 Although the Ada language defines the semantics of each construct as
29284 precisely as practical, in some situations (for example for reasons of
29285 efficiency, or where the effect is heavily dependent on the host or target
29286 platform) the implementation is allowed some freedom. In porting Ada 83
29287 code to GNAT, you need to be aware of whether / how the existing code
29288 exercised such implementation dependencies. Such characteristics fall into
29289 several categories, and GNAT offers specific support in assisting the
29290 transition from certain Ada 83 compilers.
29293 * Implementation-defined pragmas::
29294 * Implementation-defined attributes::
29296 * Elaboration order::
29297 * Target-specific aspects::
29301 @node Implementation-defined pragmas,Implementation-defined attributes,,Implementation-dependent characteristics
29302 @anchor{gnat_rm/compatibility_and_porting_guide implementation-defined-pragmas}@anchor{452}@anchor{gnat_rm/compatibility_and_porting_guide id10}@anchor{453}
29303 @subsection Implementation-defined pragmas
29306 Ada compilers are allowed to supplement the language-defined pragmas, and
29307 these are a potential source of non-portability. All GNAT-defined pragmas
29308 are described in @ref{7,,Implementation Defined Pragmas},
29309 and these include several that are specifically
29310 intended to correspond to other vendors' Ada 83 pragmas.
29311 For migrating from VADS, the pragma @code{Use_VADS_Size} may be useful.
29312 For compatibility with HP Ada 83, GNAT supplies the pragmas
29313 @code{Extend_System}, @code{Ident}, @code{Inline_Generic},
29314 @code{Interface_Name}, @code{Passive}, @code{Suppress_All},
29315 and @code{Volatile}.
29316 Other relevant pragmas include @code{External} and @code{Link_With}.
29317 Some vendor-specific
29318 Ada 83 pragmas (@code{Share_Generic}, @code{Subtitle}, and @code{Title}) are
29320 avoiding compiler rejection of units that contain such pragmas; they are not
29321 relevant in a GNAT context and hence are not otherwise implemented.
29323 @node Implementation-defined attributes,Libraries,Implementation-defined pragmas,Implementation-dependent characteristics
29324 @anchor{gnat_rm/compatibility_and_porting_guide id11}@anchor{454}@anchor{gnat_rm/compatibility_and_porting_guide implementation-defined-attributes}@anchor{455}
29325 @subsection Implementation-defined attributes
29328 Analogous to pragmas, the set of attributes may be extended by an
29329 implementation. All GNAT-defined attributes are described in
29330 @ref{8,,Implementation Defined Attributes},
29331 and these include several that are specifically intended
29332 to correspond to other vendors' Ada 83 attributes. For migrating from VADS,
29333 the attribute @code{VADS_Size} may be useful. For compatibility with HP
29334 Ada 83, GNAT supplies the attributes @code{Bit}, @code{Machine_Size} and
29337 @node Libraries,Elaboration order,Implementation-defined attributes,Implementation-dependent characteristics
29338 @anchor{gnat_rm/compatibility_and_porting_guide libraries}@anchor{456}@anchor{gnat_rm/compatibility_and_porting_guide id12}@anchor{457}
29339 @subsection Libraries
29342 Vendors may supply libraries to supplement the standard Ada API. If Ada 83
29343 code uses vendor-specific libraries then there are several ways to manage
29344 this in Ada 95 and later versions of the standard:
29350 If the source code for the libraries (specs and bodies) are
29351 available, then the libraries can be migrated in the same way as the
29355 If the source code for the specs but not the bodies are
29356 available, then you can reimplement the bodies.
29359 Some features introduced by Ada 95 obviate the need for library support. For
29360 example most Ada 83 vendors supplied a package for unsigned integers. The
29361 Ada 95 modular type feature is the preferred way to handle this need, so
29362 instead of migrating or reimplementing the unsigned integer package it may
29363 be preferable to retrofit the application using modular types.
29366 @node Elaboration order,Target-specific aspects,Libraries,Implementation-dependent characteristics
29367 @anchor{gnat_rm/compatibility_and_porting_guide elaboration-order}@anchor{458}@anchor{gnat_rm/compatibility_and_porting_guide id13}@anchor{459}
29368 @subsection Elaboration order
29371 The implementation can choose any elaboration order consistent with the unit
29372 dependency relationship. This freedom means that some orders can result in
29373 Program_Error being raised due to an 'Access Before Elaboration': an attempt
29374 to invoke a subprogram before its body has been elaborated, or to instantiate
29375 a generic before the generic body has been elaborated. By default GNAT
29376 attempts to choose a safe order (one that will not encounter access before
29377 elaboration problems) by implicitly inserting @code{Elaborate} or
29378 @code{Elaborate_All} pragmas where
29379 needed. However, this can lead to the creation of elaboration circularities
29380 and a resulting rejection of the program by gnatbind. This issue is
29381 thoroughly described in the @emph{Elaboration Order Handling in GNAT} appendix
29382 in the @cite{GNAT User's Guide}.
29383 In brief, there are several
29384 ways to deal with this situation:
29390 Modify the program to eliminate the circularities, e.g., by moving
29391 elaboration-time code into explicitly-invoked procedures
29394 Constrain the elaboration order by including explicit @code{Elaborate_Body} or
29395 @code{Elaborate} pragmas, and then inhibit the generation of implicit
29396 @code{Elaborate_All}
29397 pragmas either globally (as an effect of the @emph{-gnatE} switch) or locally
29398 (by selectively suppressing elaboration checks via pragma
29399 @code{Suppress(Elaboration_Check)} when it is safe to do so).
29402 @node Target-specific aspects,,Elaboration order,Implementation-dependent characteristics
29403 @anchor{gnat_rm/compatibility_and_porting_guide target-specific-aspects}@anchor{45a}@anchor{gnat_rm/compatibility_and_porting_guide id14}@anchor{45b}
29404 @subsection Target-specific aspects
29407 Low-level applications need to deal with machine addresses, data
29408 representations, interfacing with assembler code, and similar issues. If
29409 such an Ada 83 application is being ported to different target hardware (for
29410 example where the byte endianness has changed) then you will need to
29411 carefully examine the program logic; the porting effort will heavily depend
29412 on the robustness of the original design. Moreover, Ada 95 (and thus
29413 Ada 2005 and Ada 2012) are sometimes
29414 incompatible with typical Ada 83 compiler practices regarding implicit
29415 packing, the meaning of the Size attribute, and the size of access values.
29416 GNAT's approach to these issues is described in @ref{45c,,Representation Clauses}.
29418 @node Compatibility with Other Ada Systems,Representation Clauses,Implementation-dependent characteristics,Compatibility and Porting Guide
29419 @anchor{gnat_rm/compatibility_and_porting_guide id15}@anchor{45d}@anchor{gnat_rm/compatibility_and_porting_guide compatibility-with-other-ada-systems}@anchor{45e}
29420 @section Compatibility with Other Ada Systems
29423 If programs avoid the use of implementation dependent and
29424 implementation defined features, as documented in the
29425 @cite{Ada Reference Manual}, there should be a high degree of portability between
29426 GNAT and other Ada systems. The following are specific items which
29427 have proved troublesome in moving Ada 95 programs from GNAT to other Ada 95
29428 compilers, but do not affect porting code to GNAT.
29429 (As of January 2007, GNAT is the only compiler available for Ada 2005;
29430 the following issues may or may not arise for Ada 2005 programs
29431 when other compilers appear.)
29437 @emph{Ada 83 Pragmas and Attributes}
29439 Ada 95 compilers are allowed, but not required, to implement the missing
29440 Ada 83 pragmas and attributes that are no longer defined in Ada 95.
29441 GNAT implements all such pragmas and attributes, eliminating this as
29442 a compatibility concern, but some other Ada 95 compilers reject these
29443 pragmas and attributes.
29446 @emph{Specialized Needs Annexes}
29448 GNAT implements the full set of special needs annexes. At the
29449 current time, it is the only Ada 95 compiler to do so. This means that
29450 programs making use of these features may not be portable to other Ada
29451 95 compilation systems.
29454 @emph{Representation Clauses}
29456 Some other Ada 95 compilers implement only the minimal set of
29457 representation clauses required by the Ada 95 reference manual. GNAT goes
29458 far beyond this minimal set, as described in the next section.
29461 @node Representation Clauses,Compatibility with HP Ada 83,Compatibility with Other Ada Systems,Compatibility and Porting Guide
29462 @anchor{gnat_rm/compatibility_and_porting_guide representation-clauses}@anchor{45c}@anchor{gnat_rm/compatibility_and_porting_guide id16}@anchor{45f}
29463 @section Representation Clauses
29466 The Ada 83 reference manual was quite vague in describing both the minimal
29467 required implementation of representation clauses, and also their precise
29468 effects. Ada 95 (and thus also Ada 2005) are much more explicit, but the
29469 minimal set of capabilities required is still quite limited.
29471 GNAT implements the full required set of capabilities in
29472 Ada 95 and Ada 2005, but also goes much further, and in particular
29473 an effort has been made to be compatible with existing Ada 83 usage to the
29474 greatest extent possible.
29476 A few cases exist in which Ada 83 compiler behavior is incompatible with
29477 the requirements in Ada 95 (and thus also Ada 2005). These are instances of
29478 intentional or accidental dependence on specific implementation dependent
29479 characteristics of these Ada 83 compilers. The following is a list of
29480 the cases most likely to arise in existing Ada 83 code.
29486 @emph{Implicit Packing}
29488 Some Ada 83 compilers allowed a Size specification to cause implicit
29489 packing of an array or record. This could cause expensive implicit
29490 conversions for change of representation in the presence of derived
29491 types, and the Ada design intends to avoid this possibility.
29492 Subsequent AI's were issued to make it clear that such implicit
29493 change of representation in response to a Size clause is inadvisable,
29494 and this recommendation is represented explicitly in the Ada 95 (and Ada 2005)
29495 Reference Manuals as implementation advice that is followed by GNAT.
29496 The problem will show up as an error
29497 message rejecting the size clause. The fix is simply to provide
29498 the explicit pragma @code{Pack}, or for more fine tuned control, provide
29499 a Component_Size clause.
29502 @emph{Meaning of Size Attribute}
29504 The Size attribute in Ada 95 (and Ada 2005) for discrete types is defined as
29505 the minimal number of bits required to hold values of the type. For example,
29506 on a 32-bit machine, the size of @code{Natural} will typically be 31 and not
29507 32 (since no sign bit is required). Some Ada 83 compilers gave 31, and
29508 some 32 in this situation. This problem will usually show up as a compile
29509 time error, but not always. It is a good idea to check all uses of the
29510 'Size attribute when porting Ada 83 code. The GNAT specific attribute
29511 Object_Size can provide a useful way of duplicating the behavior of
29512 some Ada 83 compiler systems.
29515 @emph{Size of Access Types}
29517 A common assumption in Ada 83 code is that an access type is in fact a pointer,
29518 and that therefore it will be the same size as a System.Address value. This
29519 assumption is true for GNAT in most cases with one exception. For the case of
29520 a pointer to an unconstrained array type (where the bounds may vary from one
29521 value of the access type to another), the default is to use a 'fat pointer',
29522 which is represented as two separate pointers, one to the bounds, and one to
29523 the array. This representation has a number of advantages, including improved
29524 efficiency. However, it may cause some difficulties in porting existing Ada 83
29525 code which makes the assumption that, for example, pointers fit in 32 bits on
29526 a machine with 32-bit addressing.
29528 To get around this problem, GNAT also permits the use of 'thin pointers' for
29529 access types in this case (where the designated type is an unconstrained array
29530 type). These thin pointers are indeed the same size as a System.Address value.
29531 To specify a thin pointer, use a size clause for the type, for example:
29534 type X is access all String;
29535 for X'Size use Standard'Address_Size;
29538 which will cause the type X to be represented using a single pointer.
29539 When using this representation, the bounds are right behind the array.
29540 This representation is slightly less efficient, and does not allow quite
29541 such flexibility in the use of foreign pointers or in using the
29542 Unrestricted_Access attribute to create pointers to non-aliased objects.
29543 But for any standard portable use of the access type it will work in
29544 a functionally correct manner and allow porting of existing code.
29545 Note that another way of forcing a thin pointer representation
29546 is to use a component size clause for the element size in an array,
29547 or a record representation clause for an access field in a record.
29549 See the documentation of Unrestricted_Access in the GNAT RM for a
29550 full discussion of possible problems using this attribute in conjunction
29551 with thin pointers.
29554 @node Compatibility with HP Ada 83,,Representation Clauses,Compatibility and Porting Guide
29555 @anchor{gnat_rm/compatibility_and_porting_guide compatibility-with-hp-ada-83}@anchor{460}@anchor{gnat_rm/compatibility_and_porting_guide id17}@anchor{461}
29556 @section Compatibility with HP Ada 83
29559 All the HP Ada 83 pragmas and attributes are recognized, although only a subset
29560 of them can sensibly be implemented. The description of pragmas in
29561 @ref{7,,Implementation Defined Pragmas} indicates whether or not they are
29562 applicable to GNAT.
29568 @emph{Default floating-point representation}
29570 In GNAT, the default floating-point format is IEEE, whereas in HP Ada 83,
29576 the package System in GNAT exactly corresponds to the definition in the
29577 Ada 95 reference manual, which means that it excludes many of the
29578 HP Ada 83 extensions. However, a separate package Aux_DEC is provided
29579 that contains the additional definitions, and a special pragma,
29580 Extend_System allows this package to be treated transparently as an
29581 extension of package System.
29584 @node GNU Free Documentation License,Index,Compatibility and Porting Guide,Top
29585 @anchor{share/gnu_free_documentation_license gnu-fdl}@anchor{1}@anchor{share/gnu_free_documentation_license doc}@anchor{462}@anchor{share/gnu_free_documentation_license gnu-free-documentation-license}@anchor{463}
29586 @chapter GNU Free Documentation License
29589 Version 1.3, 3 November 2008
29591 Copyright 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc
29592 @indicateurl{http://fsf.org/}
29594 Everyone is permitted to copy and distribute verbatim copies of this
29595 license document, but changing it is not allowed.
29599 The purpose of this License is to make a manual, textbook, or other
29600 functional and useful document "free" in the sense of freedom: to
29601 assure everyone the effective freedom to copy and redistribute it,
29602 with or without modifying it, either commercially or noncommercially.
29603 Secondarily, this License preserves for the author and publisher a way
29604 to get credit for their work, while not being considered responsible
29605 for modifications made by others.
29607 This License is a kind of "copyleft", which means that derivative
29608 works of the document must themselves be free in the same sense. It
29609 complements the GNU General Public License, which is a copyleft
29610 license designed for free software.
29612 We have designed this License in order to use it for manuals for free
29613 software, because free software needs free documentation: a free
29614 program should come with manuals providing the same freedoms that the
29615 software does. But this License is not limited to software manuals;
29616 it can be used for any textual work, regardless of subject matter or
29617 whether it is published as a printed book. We recommend this License
29618 principally for works whose purpose is instruction or reference.
29620 @strong{1. APPLICABILITY AND DEFINITIONS}
29622 This License applies to any manual or other work, in any medium, that
29623 contains a notice placed by the copyright holder saying it can be
29624 distributed under the terms of this License. Such a notice grants a
29625 world-wide, royalty-free license, unlimited in duration, to use that
29626 work under the conditions stated herein. The @strong{Document}, below,
29627 refers to any such manual or work. Any member of the public is a
29628 licensee, and is addressed as "@strong{you}". You accept the license if you
29629 copy, modify or distribute the work in a way requiring permission
29630 under copyright law.
29632 A "@strong{Modified Version}" of the Document means any work containing the
29633 Document or a portion of it, either copied verbatim, or with
29634 modifications and/or translated into another language.
29636 A "@strong{Secondary Section}" is a named appendix or a front-matter section of
29637 the Document that deals exclusively with the relationship of the
29638 publishers or authors of the Document to the Document's overall subject
29639 (or to related matters) and contains nothing that could fall directly
29640 within that overall subject. (Thus, if the Document is in part a
29641 textbook of mathematics, a Secondary Section may not explain any
29642 mathematics.) The relationship could be a matter of historical
29643 connection with the subject or with related matters, or of legal,
29644 commercial, philosophical, ethical or political position regarding
29647 The "@strong{Invariant Sections}" are certain Secondary Sections whose titles
29648 are designated, as being those of Invariant Sections, in the notice
29649 that says that the Document is released under this License. If a
29650 section does not fit the above definition of Secondary then it is not
29651 allowed to be designated as Invariant. The Document may contain zero
29652 Invariant Sections. If the Document does not identify any Invariant
29653 Sections then there are none.
29655 The "@strong{Cover Texts}" are certain short passages of text that are listed,
29656 as Front-Cover Texts or Back-Cover Texts, in the notice that says that
29657 the Document is released under this License. A Front-Cover Text may
29658 be at most 5 words, and a Back-Cover Text may be at most 25 words.
29660 A "@strong{Transparent}" copy of the Document means a machine-readable copy,
29661 represented in a format whose specification is available to the
29662 general public, that is suitable for revising the document
29663 straightforwardly with generic text editors or (for images composed of
29664 pixels) generic paint programs or (for drawings) some widely available
29665 drawing editor, and that is suitable for input to text formatters or
29666 for automatic translation to a variety of formats suitable for input
29667 to text formatters. A copy made in an otherwise Transparent file
29668 format whose markup, or absence of markup, has been arranged to thwart
29669 or discourage subsequent modification by readers is not Transparent.
29670 An image format is not Transparent if used for any substantial amount
29671 of text. A copy that is not "Transparent" is called @strong{Opaque}.
29673 Examples of suitable formats for Transparent copies include plain
29674 ASCII without markup, Texinfo input format, LaTeX input format, SGML
29675 or XML using a publicly available DTD, and standard-conforming simple
29676 HTML, PostScript or PDF designed for human modification. Examples of
29677 transparent image formats include PNG, XCF and JPG. Opaque formats
29678 include proprietary formats that can be read and edited only by
29679 proprietary word processors, SGML or XML for which the DTD and/or
29680 processing tools are not generally available, and the
29681 machine-generated HTML, PostScript or PDF produced by some word
29682 processors for output purposes only.
29684 The "@strong{Title Page}" means, for a printed book, the title page itself,
29685 plus such following pages as are needed to hold, legibly, the material
29686 this License requires to appear in the title page. For works in
29687 formats which do not have any title page as such, "Title Page" means
29688 the text near the most prominent appearance of the work's title,
29689 preceding the beginning of the body of the text.
29691 The "@strong{publisher}" means any person or entity that distributes
29692 copies of the Document to the public.
29694 A section "@strong{Entitled XYZ}" means a named subunit of the Document whose
29695 title either is precisely XYZ or contains XYZ in parentheses following
29696 text that translates XYZ in another language. (Here XYZ stands for a
29697 specific section name mentioned below, such as "@strong{Acknowledgements}",
29698 "@strong{Dedications}", "@strong{Endorsements}", or "@strong{History}".)
29699 To "@strong{Preserve the Title}"
29700 of such a section when you modify the Document means that it remains a
29701 section "Entitled XYZ" according to this definition.
29703 The Document may include Warranty Disclaimers next to the notice which
29704 states that this License applies to the Document. These Warranty
29705 Disclaimers are considered to be included by reference in this
29706 License, but only as regards disclaiming warranties: any other
29707 implication that these Warranty Disclaimers may have is void and has
29708 no effect on the meaning of this License.
29710 @strong{2. VERBATIM COPYING}
29712 You may copy and distribute the Document in any medium, either
29713 commercially or noncommercially, provided that this License, the
29714 copyright notices, and the license notice saying this License applies
29715 to the Document are reproduced in all copies, and that you add no other
29716 conditions whatsoever to those of this License. You may not use
29717 technical measures to obstruct or control the reading or further
29718 copying of the copies you make or distribute. However, you may accept
29719 compensation in exchange for copies. If you distribute a large enough
29720 number of copies you must also follow the conditions in section 3.
29722 You may also lend copies, under the same conditions stated above, and
29723 you may publicly display copies.
29725 @strong{3. COPYING IN QUANTITY}
29727 If you publish printed copies (or copies in media that commonly have
29728 printed covers) of the Document, numbering more than 100, and the
29729 Document's license notice requires Cover Texts, you must enclose the
29730 copies in covers that carry, clearly and legibly, all these Cover
29731 Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on
29732 the back cover. Both covers must also clearly and legibly identify
29733 you as the publisher of these copies. The front cover must present
29734 the full title with all words of the title equally prominent and
29735 visible. You may add other material on the covers in addition.
29736 Copying with changes limited to the covers, as long as they preserve
29737 the title of the Document and satisfy these conditions, can be treated
29738 as verbatim copying in other respects.
29740 If the required texts for either cover are too voluminous to fit
29741 legibly, you should put the first ones listed (as many as fit
29742 reasonably) on the actual cover, and continue the rest onto adjacent
29745 If you publish or distribute Opaque copies of the Document numbering
29746 more than 100, you must either include a machine-readable Transparent
29747 copy along with each Opaque copy, or state in or with each Opaque copy
29748 a computer-network location from which the general network-using
29749 public has access to download using public-standard network protocols
29750 a complete Transparent copy of the Document, free of added material.
29751 If you use the latter option, you must take reasonably prudent steps,
29752 when you begin distribution of Opaque copies in quantity, to ensure
29753 that this Transparent copy will remain thus accessible at the stated
29754 location until at least one year after the last time you distribute an
29755 Opaque copy (directly or through your agents or retailers) of that
29756 edition to the public.
29758 It is requested, but not required, that you contact the authors of the
29759 Document well before redistributing any large number of copies, to give
29760 them a chance to provide you with an updated version of the Document.
29762 @strong{4. MODIFICATIONS}
29764 You may copy and distribute a Modified Version of the Document under
29765 the conditions of sections 2 and 3 above, provided that you release
29766 the Modified Version under precisely this License, with the Modified
29767 Version filling the role of the Document, thus licensing distribution
29768 and modification of the Modified Version to whoever possesses a copy
29769 of it. In addition, you must do these things in the Modified Version:
29775 Use in the Title Page (and on the covers, if any) a title distinct
29776 from that of the Document, and from those of previous versions
29777 (which should, if there were any, be listed in the History section
29778 of the Document). You may use the same title as a previous version
29779 if the original publisher of that version gives permission.
29782 List on the Title Page, as authors, one or more persons or entities
29783 responsible for authorship of the modifications in the Modified
29784 Version, together with at least five of the principal authors of the
29785 Document (all of its principal authors, if it has fewer than five),
29786 unless they release you from this requirement.
29789 State on the Title page the name of the publisher of the
29790 Modified Version, as the publisher.
29793 Preserve all the copyright notices of the Document.
29796 Add an appropriate copyright notice for your modifications
29797 adjacent to the other copyright notices.
29800 Include, immediately after the copyright notices, a license notice
29801 giving the public permission to use the Modified Version under the
29802 terms of this License, in the form shown in the Addendum below.
29805 Preserve in that license notice the full lists of Invariant Sections
29806 and required Cover Texts given in the Document's license notice.
29809 Include an unaltered copy of this License.
29812 Preserve the section Entitled "History", Preserve its Title, and add
29813 to it an item stating at least the title, year, new authors, and
29814 publisher of the Modified Version as given on the Title Page. If
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29817 given on its Title Page, then add an item describing the Modified
29818 Version as stated in the previous sentence.
29821 Preserve the network location, if any, given in the Document for
29822 public access to a Transparent copy of the Document, and likewise
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29824 it was based on. These may be placed in the "History" section.
29825 You may omit a network location for a work that was published at
29826 least four years before the Document itself, or if the original
29827 publisher of the version it refers to gives permission.
29830 For any section Entitled "Acknowledgements" or "Dedications",
29831 Preserve the Title of the section, and preserve in the section all
29832 the substance and tone of each of the contributor acknowledgements
29833 and/or dedications given therein.
29836 Preserve all the Invariant Sections of the Document,
29837 unaltered in their text and in their titles. Section numbers
29838 or the equivalent are not considered part of the section titles.
29841 Delete any section Entitled "Endorsements". Such a section
29842 may not be included in the Modified Version.
29845 Do not retitle any existing section to be Entitled "Endorsements"
29846 or to conflict in title with any Invariant Section.
29849 Preserve any Warranty Disclaimers.
29852 If the Modified Version includes new front-matter sections or
29853 appendices that qualify as Secondary Sections and contain no material
29854 copied from the Document, you may at your option designate some or all
29855 of these sections as invariant. To do this, add their titles to the
29856 list of Invariant Sections in the Modified Version's license notice.
29857 These titles must be distinct from any other section titles.
29859 You may add a section Entitled "Endorsements", provided it contains
29860 nothing but endorsements of your Modified Version by various
29861 parties---for example, statements of peer review or that the text has
29862 been approved by an organization as the authoritative definition of a
29865 You may add a passage of up to five words as a Front-Cover Text, and a
29866 passage of up to 25 words as a Back-Cover Text, to the end of the list
29867 of Cover Texts in the Modified Version. Only one passage of
29868 Front-Cover Text and one of Back-Cover Text may be added by (or
29869 through arrangements made by) any one entity. If the Document already
29870 includes a cover text for the same cover, previously added by you or
29871 by arrangement made by the same entity you are acting on behalf of,
29872 you may not add another; but you may replace the old one, on explicit
29873 permission from the previous publisher that added the old one.
29875 The author(s) and publisher(s) of the Document do not by this License
29876 give permission to use their names for publicity for or to assert or
29877 imply endorsement of any Modified Version.
29879 @strong{5. COMBINING DOCUMENTS}
29881 You may combine the Document with other documents released under this
29882 License, under the terms defined in section 4 above for modified
29883 versions, provided that you include in the combination all of the
29884 Invariant Sections of all of the original documents, unmodified, and
29885 list them all as Invariant Sections of your combined work in its
29886 license notice, and that you preserve all their Warranty Disclaimers.
29888 The combined work need only contain one copy of this License, and
29889 multiple identical Invariant Sections may be replaced with a single
29890 copy. If there are multiple Invariant Sections with the same name but
29891 different contents, make the title of each such section unique by
29892 adding at the end of it, in parentheses, the name of the original
29893 author or publisher of that section if known, or else a unique number.
29894 Make the same adjustment to the section titles in the list of
29895 Invariant Sections in the license notice of the combined work.
29897 In the combination, you must combine any sections Entitled "History"
29898 in the various original documents, forming one section Entitled
29899 "History"; likewise combine any sections Entitled "Acknowledgements",
29900 and any sections Entitled "Dedications". You must delete all sections
29901 Entitled "Endorsements".
29903 @strong{6. COLLECTIONS OF DOCUMENTS}
29905 You may make a collection consisting of the Document and other documents
29906 released under this License, and replace the individual copies of this
29907 License in the various documents with a single copy that is included in
29908 the collection, provided that you follow the rules of this License for
29909 verbatim copying of each of the documents in all other respects.
29911 You may extract a single document from such a collection, and distribute
29912 it individually under this License, provided you insert a copy of this
29913 License into the extracted document, and follow this License in all
29914 other respects regarding verbatim copying of that document.
29916 @strong{7. AGGREGATION WITH INDEPENDENT WORKS}
29918 A compilation of the Document or its derivatives with other separate
29919 and independent documents or works, in or on a volume of a storage or
29920 distribution medium, is called an "aggregate" if the copyright
29921 resulting from the compilation is not used to limit the legal rights
29922 of the compilation's users beyond what the individual works permit.
29923 When the Document is included in an aggregate, this License does not
29924 apply to the other works in the aggregate which are not themselves
29925 derivative works of the Document.
29927 If the Cover Text requirement of section 3 is applicable to these
29928 copies of the Document, then if the Document is less than one half of
29929 the entire aggregate, the Document's Cover Texts may be placed on
29930 covers that bracket the Document within the aggregate, or the
29931 electronic equivalent of covers if the Document is in electronic form.
29932 Otherwise they must appear on printed covers that bracket the whole
29935 @strong{8. TRANSLATION}
29937 Translation is considered a kind of modification, so you may
29938 distribute translations of the Document under the terms of section 4.
29939 Replacing Invariant Sections with translations requires special
29940 permission from their copyright holders, but you may include
29941 translations of some or all Invariant Sections in addition to the
29942 original versions of these Invariant Sections. You may include a
29943 translation of this License, and all the license notices in the
29944 Document, and any Warranty Disclaimers, provided that you also include
29945 the original English version of this License and the original versions
29946 of those notices and disclaimers. In case of a disagreement between
29947 the translation and the original version of this License or a notice
29948 or disclaimer, the original version will prevail.
29950 If a section in the Document is Entitled "Acknowledgements",
29951 "Dedications", or "History", the requirement (section 4) to Preserve
29952 its Title (section 1) will typically require changing the actual
29955 @strong{9. TERMINATION}
29957 You may not copy, modify, sublicense, or distribute the Document
29958 except as expressly provided under this License. Any attempt
29959 otherwise to copy, modify, sublicense, or distribute it is void, and
29960 will automatically terminate your rights under this License.
29962 However, if you cease all violation of this License, then your license
29963 from a particular copyright holder is reinstated (a) provisionally,
29964 unless and until the copyright holder explicitly and finally
29965 terminates your license, and (b) permanently, if the copyright holder
29966 fails to notify you of the violation by some reasonable means prior to
29967 60 days after the cessation.
29969 Moreover, your license from a particular copyright holder is
29970 reinstated permanently if the copyright holder notifies you of the
29971 violation by some reasonable means, this is the first time you have
29972 received notice of violation of this License (for any work) from that
29973 copyright holder, and you cure the violation prior to 30 days after
29974 your receipt of the notice.
29976 Termination of your rights under this section does not terminate the
29977 licenses of parties who have received copies or rights from you under
29978 this License. If your rights have been terminated and not permanently
29979 reinstated, receipt of a copy of some or all of the same material does
29980 not give you any rights to use it.
29982 @strong{10. FUTURE REVISIONS OF THIS LICENSE}
29984 The Free Software Foundation may publish new, revised versions
29985 of the GNU Free Documentation License from time to time. Such new
29986 versions will be similar in spirit to the present version, but may
29987 differ in detail to address new problems or concerns. See
29988 @indicateurl{http://www.gnu.org/copyleft/}.
29990 Each version of the License is given a distinguishing version number.
29991 If the Document specifies that a particular numbered version of this
29992 License "or any later version" applies to it, you have the option of
29993 following the terms and conditions either of that specified version or
29994 of any later version that has been published (not as a draft) by the
29995 Free Software Foundation. If the Document does not specify a version
29996 number of this License, you may choose any version ever published (not
29997 as a draft) by the Free Software Foundation. If the Document
29998 specifies that a proxy can decide which future versions of this
29999 License can be used, that proxy's public statement of acceptance of a
30000 version permanently authorizes you to choose that version for the
30003 @strong{11. RELICENSING}
30005 "Massive Multiauthor Collaboration Site" (or "MMC Site") means any
30006 World Wide Web server that publishes copyrightable works and also
30007 provides prominent facilities for anybody to edit those works. A
30008 public wiki that anybody can edit is an example of such a server. A
30009 "Massive Multiauthor Collaboration" (or "MMC") contained in the
30010 site means any set of copyrightable works thus published on the MMC
30013 "CC-BY-SA" means the Creative Commons Attribution-Share Alike 3.0
30014 license published by Creative Commons Corporation, a not-for-profit
30015 corporation with a principal place of business in San Francisco,
30016 California, as well as future copyleft versions of that license
30017 published by that same organization.
30019 "Incorporate" means to publish or republish a Document, in whole or
30020 in part, as part of another Document.
30022 An MMC is "eligible for relicensing" if it is licensed under this
30023 License, and if all works that were first published under this License
30024 somewhere other than this MMC, and subsequently incorporated in whole
30025 or in part into the MMC, (1) had no cover texts or invariant sections,
30026 and (2) were thus incorporated prior to November 1, 2008.
30028 The operator of an MMC Site may republish an MMC contained in the site
30029 under CC-BY-SA on the same site at any time before August 1, 2009,
30030 provided the MMC is eligible for relicensing.
30032 @strong{ADDENDUM: How to use this License for your documents}
30034 To use this License in a document you have written, include a copy of
30035 the License in the document and put the following copyright and
30036 license notices just after the title page:
30040 Copyright © YEAR YOUR NAME.
30041 Permission is granted to copy, distribute and/or modify this document
30042 under the terms of the GNU Free Documentation License, Version 1.3
30043 or any later version published by the Free Software Foundation;
30044 with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
30045 A copy of the license is included in the section entitled "GNU
30046 Free Documentation License".
30049 If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts,
30050 replace the "with ... Texts." line with this:
30054 with the Invariant Sections being LIST THEIR TITLES, with the
30055 Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST.
30058 If you have Invariant Sections without Cover Texts, or some other
30059 combination of the three, merge those two alternatives to suit the
30062 If your document contains nontrivial examples of program code, we
30063 recommend releasing these examples in parallel under your choice of
30064 free software license, such as the GNU General Public License,
30065 to permit their use in free software.
30067 @node Index,,GNU Free Documentation License,Top