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8 @settitle GNAT Reference Manual
13 @dircategory GNU Ada Tools
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24 GNAT Reference Manual , Dec 10, 2019
28 Copyright @copyright{} 2008-2020, 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 Aggregate_Individually_Assign::
111 * Pragma Allow_Integer_Address::
114 * Pragma Assert_And_Cut::
115 * Pragma Assertion_Policy::
117 * Pragma Assume_No_Invalid_Values::
118 * Pragma Async_Readers::
119 * Pragma Async_Writers::
120 * Pragma Attribute_Definition::
121 * Pragma C_Pass_By_Copy::
123 * Pragma Check_Float_Overflow::
124 * Pragma Check_Name::
125 * Pragma Check_Policy::
127 * Pragma Common_Object::
128 * Pragma Compile_Time_Error::
129 * Pragma Compile_Time_Warning::
130 * Pragma Compiler_Unit::
131 * Pragma Compiler_Unit_Warning::
132 * Pragma Complete_Representation::
133 * Pragma Complex_Representation::
134 * Pragma Component_Alignment::
135 * Pragma Constant_After_Elaboration::
136 * Pragma Contract_Cases::
137 * Pragma Convention_Identifier::
139 * Pragma CPP_Constructor::
140 * Pragma CPP_Virtual::
141 * Pragma CPP_Vtable::
143 * Pragma Deadline_Floor::
144 * Pragma Default_Initial_Condition::
146 * Pragma Debug_Policy::
147 * Pragma Default_Scalar_Storage_Order::
148 * Pragma Default_Storage_Pool::
150 * Pragma Detect_Blocking::
151 * Pragma Disable_Atomic_Synchronization::
152 * Pragma Dispatching_Domain::
153 * Pragma Effective_Reads::
154 * Pragma Effective_Writes::
155 * Pragma Elaboration_Checks::
157 * Pragma Enable_Atomic_Synchronization::
158 * Pragma Export_Function::
159 * Pragma Export_Object::
160 * Pragma Export_Procedure::
161 * Pragma Export_Value::
162 * Pragma Export_Valued_Procedure::
163 * Pragma Extend_System::
164 * Pragma Extensions_Allowed::
165 * Pragma Extensions_Visible::
167 * Pragma External_Name_Casing::
169 * Pragma Favor_Top_Level::
170 * Pragma Finalize_Storage_Only::
171 * Pragma Float_Representation::
175 * Pragma Ignore_Pragma::
176 * Pragma Implementation_Defined::
177 * Pragma Implemented::
178 * Pragma Implicit_Packing::
179 * Pragma Import_Function::
180 * Pragma Import_Object::
181 * Pragma Import_Procedure::
182 * Pragma Import_Valued_Procedure::
183 * Pragma Independent::
184 * Pragma Independent_Components::
185 * Pragma Initial_Condition::
186 * Pragma Initialize_Scalars::
187 * Pragma Initializes::
188 * Pragma Inline_Always::
189 * Pragma Inline_Generic::
191 * Pragma Interface_Name::
192 * Pragma Interrupt_Handler::
193 * Pragma Interrupt_State::
195 * Pragma Keep_Names::
198 * Pragma Linker_Alias::
199 * Pragma Linker_Constructor::
200 * Pragma Linker_Destructor::
201 * Pragma Linker_Section::
203 * Pragma Loop_Invariant::
204 * Pragma Loop_Optimize::
205 * Pragma Loop_Variant::
206 * Pragma Machine_Attribute::
208 * Pragma Main_Storage::
209 * Pragma Max_Queue_Length::
211 * Pragma No_Caching::
212 * Pragma No_Component_Reordering::
213 * Pragma No_Elaboration_Code_All::
214 * Pragma No_Heap_Finalization::
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 Aggregate_Individually_Assign::
1188 * Pragma Allow_Integer_Address::
1191 * Pragma Assert_And_Cut::
1192 * Pragma Assertion_Policy::
1194 * Pragma Assume_No_Invalid_Values::
1195 * Pragma Async_Readers::
1196 * Pragma Async_Writers::
1197 * Pragma Attribute_Definition::
1198 * Pragma C_Pass_By_Copy::
1200 * Pragma Check_Float_Overflow::
1201 * Pragma Check_Name::
1202 * Pragma Check_Policy::
1204 * Pragma Common_Object::
1205 * Pragma Compile_Time_Error::
1206 * Pragma Compile_Time_Warning::
1207 * Pragma Compiler_Unit::
1208 * Pragma Compiler_Unit_Warning::
1209 * Pragma Complete_Representation::
1210 * Pragma Complex_Representation::
1211 * Pragma Component_Alignment::
1212 * Pragma Constant_After_Elaboration::
1213 * Pragma Contract_Cases::
1214 * Pragma Convention_Identifier::
1215 * Pragma CPP_Class::
1216 * Pragma CPP_Constructor::
1217 * Pragma CPP_Virtual::
1218 * Pragma CPP_Vtable::
1220 * Pragma Deadline_Floor::
1221 * Pragma Default_Initial_Condition::
1223 * Pragma Debug_Policy::
1224 * Pragma Default_Scalar_Storage_Order::
1225 * Pragma Default_Storage_Pool::
1227 * Pragma Detect_Blocking::
1228 * Pragma Disable_Atomic_Synchronization::
1229 * Pragma Dispatching_Domain::
1230 * Pragma Effective_Reads::
1231 * Pragma Effective_Writes::
1232 * Pragma Elaboration_Checks::
1233 * Pragma Eliminate::
1234 * Pragma Enable_Atomic_Synchronization::
1235 * Pragma Export_Function::
1236 * Pragma Export_Object::
1237 * Pragma Export_Procedure::
1238 * Pragma Export_Value::
1239 * Pragma Export_Valued_Procedure::
1240 * Pragma Extend_System::
1241 * Pragma Extensions_Allowed::
1242 * Pragma Extensions_Visible::
1244 * Pragma External_Name_Casing::
1245 * Pragma Fast_Math::
1246 * Pragma Favor_Top_Level::
1247 * Pragma Finalize_Storage_Only::
1248 * Pragma Float_Representation::
1252 * Pragma Ignore_Pragma::
1253 * Pragma Implementation_Defined::
1254 * Pragma Implemented::
1255 * Pragma Implicit_Packing::
1256 * Pragma Import_Function::
1257 * Pragma Import_Object::
1258 * Pragma Import_Procedure::
1259 * Pragma Import_Valued_Procedure::
1260 * Pragma Independent::
1261 * Pragma Independent_Components::
1262 * Pragma Initial_Condition::
1263 * Pragma Initialize_Scalars::
1264 * Pragma Initializes::
1265 * Pragma Inline_Always::
1266 * Pragma Inline_Generic::
1267 * Pragma Interface::
1268 * Pragma Interface_Name::
1269 * Pragma Interrupt_Handler::
1270 * Pragma Interrupt_State::
1271 * Pragma Invariant::
1272 * Pragma Keep_Names::
1274 * Pragma Link_With::
1275 * Pragma Linker_Alias::
1276 * Pragma Linker_Constructor::
1277 * Pragma Linker_Destructor::
1278 * Pragma Linker_Section::
1279 * Pragma Lock_Free::
1280 * Pragma Loop_Invariant::
1281 * Pragma Loop_Optimize::
1282 * Pragma Loop_Variant::
1283 * Pragma Machine_Attribute::
1285 * Pragma Main_Storage::
1286 * Pragma Max_Queue_Length::
1288 * Pragma No_Caching::
1289 * Pragma No_Component_Reordering::
1290 * Pragma No_Elaboration_Code_All::
1291 * Pragma No_Heap_Finalization::
1292 * Pragma No_Inline::
1293 * Pragma No_Return::
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 Aggregate_Individually_Assign,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 Aggregate_Individually_Assign,Pragma Allow_Integer_Address,Pragma Ada_2012,Implementation Defined Pragmas
1755 @anchor{gnat_rm/implementation_defined_pragmas pragma-aggregate-individually-assign}@anchor{28}
1756 @section Pragma Aggregate_Individually_Assign
1762 pragma Aggregate_Individually_Assign;
1765 Where possible, GNAT will store the binary representation of a record aggregate
1766 in memory for space and performance reasons. This configuration pragma changes
1767 this behavior so that record aggregates are instead always converted into
1768 individual assignment statements.
1770 @node Pragma Allow_Integer_Address,Pragma Annotate,Pragma Aggregate_Individually_Assign,Implementation Defined Pragmas
1771 @anchor{gnat_rm/implementation_defined_pragmas pragma-allow-integer-address}@anchor{29}
1772 @section Pragma Allow_Integer_Address
1778 pragma Allow_Integer_Address;
1781 In almost all versions of GNAT, @code{System.Address} is a private
1782 type in accordance with the implementation advice in the RM. This
1783 means that integer values,
1784 in particular integer literals, are not allowed as address values.
1785 If the configuration pragma
1786 @code{Allow_Integer_Address} is given, then integer expressions may
1787 be used anywhere a value of type @code{System.Address} is required.
1788 The effect is to introduce an implicit unchecked conversion from the
1789 integer value to type @code{System.Address}. The reverse case of using
1790 an address where an integer type is required is handled analogously.
1791 The following example compiles without errors:
1794 pragma Allow_Integer_Address;
1795 with System; use System;
1796 package AddrAsInt is
1799 for X'Address use 16#1240#;
1800 for Y use at 16#3230#;
1801 m : Address := 16#4000#;
1802 n : constant Address := 4000;
1803 p : constant Address := Address (X + Y);
1804 v : Integer := y'Address;
1805 w : constant Integer := Integer (Y'Address);
1806 type R is new integer;
1809 for Z'Address use RR;
1813 Note that pragma @code{Allow_Integer_Address} is ignored if @code{System.Address}
1814 is not a private type. In implementations of @code{GNAT} where
1815 System.Address is a visible integer type,
1816 this pragma serves no purpose but is ignored
1817 rather than rejected to allow common sets of sources to be used
1818 in the two situations.
1820 @node Pragma Annotate,Pragma Assert,Pragma Allow_Integer_Address,Implementation Defined Pragmas
1821 @anchor{gnat_rm/implementation_defined_pragmas pragma-annotate}@anchor{2a}@anchor{gnat_rm/implementation_defined_pragmas id3}@anchor{2b}
1822 @section Pragma Annotate
1828 pragma Annotate (IDENTIFIER [, IDENTIFIER @{, ARG@}] [, entity => local_NAME]);
1830 ARG ::= NAME | EXPRESSION
1833 This pragma is used to annotate programs. IDENTIFIER identifies
1834 the type of annotation. GNAT verifies that it is an identifier, but does
1835 not otherwise analyze it. The second optional identifier is also left
1836 unanalyzed, and by convention is used to control the action of the tool to
1837 which the annotation is addressed. The remaining ARG arguments
1838 can be either string literals or more generally expressions.
1839 String literals (and concatenations of string literals) are assumed to be
1841 @code{Standard.String} or else @code{Wide_String} or @code{Wide_Wide_String}
1842 depending on the character literals they contain.
1843 All other kinds of arguments are analyzed as expressions, and must be
1844 unambiguous. The last argument if present must have the identifier
1845 @code{Entity} and GNAT verifies that a local name is given.
1847 The analyzed pragma is retained in the tree, but not otherwise processed
1848 by any part of the GNAT compiler, except to generate corresponding note
1849 lines in the generated ALI file. For the format of these note lines, see
1850 the compiler source file lib-writ.ads. This pragma is intended for use by
1851 external tools, including ASIS. The use of pragma Annotate does not
1852 affect the compilation process in any way. This pragma may be used as
1853 a configuration pragma.
1855 @node Pragma Assert,Pragma Assert_And_Cut,Pragma Annotate,Implementation Defined Pragmas
1856 @anchor{gnat_rm/implementation_defined_pragmas pragma-assert}@anchor{2c}
1857 @section Pragma Assert
1865 [, string_EXPRESSION]);
1868 The effect of this pragma depends on whether the corresponding command
1869 line switch is set to activate assertions. The pragma expands into code
1870 equivalent to the following:
1873 if assertions-enabled then
1874 if not boolean_EXPRESSION then
1875 System.Assertions.Raise_Assert_Failure
1876 (string_EXPRESSION);
1881 The string argument, if given, is the message that will be associated
1882 with the exception occurrence if the exception is raised. If no second
1883 argument is given, the default message is @code{file}:@code{nnn},
1884 where @code{file} is the name of the source file containing the assert,
1885 and @code{nnn} is the line number of the assert.
1887 Note that, as with the @code{if} statement to which it is equivalent, the
1888 type of the expression is either @code{Standard.Boolean}, or any type derived
1889 from this standard type.
1891 Assert checks can be either checked or ignored. By default they are ignored.
1892 They will be checked if either the command line switch @emph{-gnata} is
1893 used, or if an @code{Assertion_Policy} or @code{Check_Policy} pragma is used
1894 to enable @code{Assert_Checks}.
1896 If assertions are ignored, then there
1897 is no run-time effect (and in particular, any side effects from the
1898 expression will not occur at run time). (The expression is still
1899 analyzed at compile time, and may cause types to be frozen if they are
1900 mentioned here for the first time).
1902 If assertions are checked, then the given expression is tested, and if
1903 it is @code{False} then @code{System.Assertions.Raise_Assert_Failure} is called
1904 which results in the raising of @code{Assert_Failure} with the given message.
1906 You should generally avoid side effects in the expression arguments of
1907 this pragma, because these side effects will turn on and off with the
1908 setting of the assertions mode, resulting in assertions that have an
1909 effect on the program. However, the expressions are analyzed for
1910 semantic correctness whether or not assertions are enabled, so turning
1911 assertions on and off cannot affect the legality of a program.
1913 Note that the implementation defined policy @code{DISABLE}, given in a
1914 pragma @code{Assertion_Policy}, can be used to suppress this semantic analysis.
1916 Note: this is a standard language-defined pragma in versions
1917 of Ada from 2005 on. In GNAT, it is implemented in all versions
1918 of Ada, and the DISABLE policy is an implementation-defined
1921 @node Pragma Assert_And_Cut,Pragma Assertion_Policy,Pragma Assert,Implementation Defined Pragmas
1922 @anchor{gnat_rm/implementation_defined_pragmas pragma-assert-and-cut}@anchor{2d}
1923 @section Pragma Assert_And_Cut
1929 pragma Assert_And_Cut (
1931 [, string_EXPRESSION]);
1934 The effect of this pragma is identical to that of pragma @code{Assert},
1935 except that in an @code{Assertion_Policy} pragma, the identifier
1936 @code{Assert_And_Cut} is used to control whether it is ignored or checked
1939 The intention is that this be used within a subprogram when the
1940 given test expresion sums up all the work done so far in the
1941 subprogram, so that the rest of the subprogram can be verified
1942 (informally or formally) using only the entry preconditions,
1943 and the expression in this pragma. This allows dividing up
1944 a subprogram into sections for the purposes of testing or
1945 formal verification. The pragma also serves as useful
1948 @node Pragma Assertion_Policy,Pragma Assume,Pragma Assert_And_Cut,Implementation Defined Pragmas
1949 @anchor{gnat_rm/implementation_defined_pragmas pragma-assertion-policy}@anchor{2e}
1950 @section Pragma Assertion_Policy
1956 pragma Assertion_Policy (CHECK | DISABLE | IGNORE | SUPPRESSIBLE);
1958 pragma Assertion_Policy (
1959 ASSERTION_KIND => POLICY_IDENTIFIER
1960 @{, ASSERTION_KIND => POLICY_IDENTIFIER@});
1962 ASSERTION_KIND ::= RM_ASSERTION_KIND | ID_ASSERTION_KIND
1964 RM_ASSERTION_KIND ::= Assert |
1972 Type_Invariant'Class
1974 ID_ASSERTION_KIND ::= Assertions |
1988 Statement_Assertions
1990 POLICY_IDENTIFIER ::= Check | Disable | Ignore | Suppressible
1993 This is a standard Ada 2012 pragma that is available as an
1994 implementation-defined pragma in earlier versions of Ada.
1995 The assertion kinds @code{RM_ASSERTION_KIND} are those defined in
1996 the Ada standard. The assertion kinds @code{ID_ASSERTION_KIND}
1997 are implementation defined additions recognized by the GNAT compiler.
1999 The pragma applies in both cases to pragmas and aspects with matching
2000 names, e.g. @code{Pre} applies to the Pre aspect, and @code{Precondition}
2001 applies to both the @code{Precondition} pragma
2002 and the aspect @code{Precondition}. Note that the identifiers for
2003 pragmas Pre_Class and Post_Class are Pre'Class and Post'Class (not
2004 Pre_Class and Post_Class), since these pragmas are intended to be
2005 identical to the corresponding aspects).
2007 If the policy is @code{CHECK}, then assertions are enabled, i.e.
2008 the corresponding pragma or aspect is activated.
2009 If the policy is @code{IGNORE}, then assertions are ignored, i.e.
2010 the corresponding pragma or aspect is deactivated.
2011 This pragma overrides the effect of the @emph{-gnata} switch on the
2013 If the policy is @code{SUPPRESSIBLE}, then assertions are enabled by default,
2014 however, if the @emph{-gnatp} switch is specified all assertions are ignored.
2016 The implementation defined policy @code{DISABLE} is like
2017 @code{IGNORE} except that it completely disables semantic
2018 checking of the corresponding pragma or aspect. This is
2019 useful when the pragma or aspect argument references subprograms
2020 in a with'ed package which is replaced by a dummy package
2021 for the final build.
2023 The implementation defined assertion kind @code{Assertions} applies to all
2024 assertion kinds. The form with no assertion kind given implies this
2025 choice, so it applies to all assertion kinds (RM defined, and
2026 implementation defined).
2028 The implementation defined assertion kind @code{Statement_Assertions}
2029 applies to @code{Assert}, @code{Assert_And_Cut},
2030 @code{Assume}, @code{Loop_Invariant}, and @code{Loop_Variant}.
2032 @node Pragma Assume,Pragma Assume_No_Invalid_Values,Pragma Assertion_Policy,Implementation Defined Pragmas
2033 @anchor{gnat_rm/implementation_defined_pragmas pragma-assume}@anchor{2f}
2034 @section Pragma Assume
2042 [, string_EXPRESSION]);
2045 The effect of this pragma is identical to that of pragma @code{Assert},
2046 except that in an @code{Assertion_Policy} pragma, the identifier
2047 @code{Assume} is used to control whether it is ignored or checked
2050 The intention is that this be used for assumptions about the
2051 external environment. So you cannot expect to verify formally
2052 or informally that the condition is met, this must be
2053 established by examining things outside the program itself.
2054 For example, we may have code that depends on the size of
2055 @code{Long_Long_Integer} being at least 64. So we could write:
2058 pragma Assume (Long_Long_Integer'Size >= 64);
2061 This assumption cannot be proved from the program itself,
2062 but it acts as a useful run-time check that the assumption
2063 is met, and documents the need to ensure that it is met by
2064 reference to information outside the program.
2066 @node Pragma Assume_No_Invalid_Values,Pragma Async_Readers,Pragma Assume,Implementation Defined Pragmas
2067 @anchor{gnat_rm/implementation_defined_pragmas pragma-assume-no-invalid-values}@anchor{30}
2068 @section Pragma Assume_No_Invalid_Values
2071 @geindex Invalid representations
2073 @geindex Invalid values
2078 pragma Assume_No_Invalid_Values (On | Off);
2081 This is a configuration pragma that controls the assumptions made by the
2082 compiler about the occurrence of invalid representations (invalid values)
2085 The default behavior (corresponding to an Off argument for this pragma), is
2086 to assume that values may in general be invalid unless the compiler can
2087 prove they are valid. Consider the following example:
2090 V1 : Integer range 1 .. 10;
2091 V2 : Integer range 11 .. 20;
2093 for J in V2 .. V1 loop
2098 if V1 and V2 have valid values, then the loop is known at compile
2099 time not to execute since the lower bound must be greater than the
2100 upper bound. However in default mode, no such assumption is made,
2101 and the loop may execute. If @code{Assume_No_Invalid_Values (On)}
2102 is given, the compiler will assume that any occurrence of a variable
2103 other than in an explicit @code{'Valid} test always has a valid
2104 value, and the loop above will be optimized away.
2106 The use of @code{Assume_No_Invalid_Values (On)} is appropriate if
2107 you know your code is free of uninitialized variables and other
2108 possible sources of invalid representations, and may result in
2109 more efficient code. A program that accesses an invalid representation
2110 with this pragma in effect is erroneous, so no guarantees can be made
2113 It is peculiar though permissible to use this pragma in conjunction
2114 with validity checking (-gnatVa). In such cases, accessing invalid
2115 values will generally give an exception, though formally the program
2116 is erroneous so there are no guarantees that this will always be the
2117 case, and it is recommended that these two options not be used together.
2119 @node Pragma Async_Readers,Pragma Async_Writers,Pragma Assume_No_Invalid_Values,Implementation Defined Pragmas
2120 @anchor{gnat_rm/implementation_defined_pragmas pragma-async-readers}@anchor{31}@anchor{gnat_rm/implementation_defined_pragmas id4}@anchor{32}
2121 @section Pragma Async_Readers
2127 pragma Async_Readers [ (boolean_EXPRESSION) ];
2130 For the semantics of this pragma, see the entry for aspect @code{Async_Readers} in
2131 the SPARK 2014 Reference Manual, section 7.1.2.
2133 @node Pragma Async_Writers,Pragma Attribute_Definition,Pragma Async_Readers,Implementation Defined Pragmas
2134 @anchor{gnat_rm/implementation_defined_pragmas id5}@anchor{33}@anchor{gnat_rm/implementation_defined_pragmas pragma-async-writers}@anchor{34}
2135 @section Pragma Async_Writers
2141 pragma Async_Writers [ (boolean_EXPRESSION) ];
2144 For the semantics of this pragma, see the entry for aspect @code{Async_Writers} in
2145 the SPARK 2014 Reference Manual, section 7.1.2.
2147 @node Pragma Attribute_Definition,Pragma C_Pass_By_Copy,Pragma Async_Writers,Implementation Defined Pragmas
2148 @anchor{gnat_rm/implementation_defined_pragmas pragma-attribute-definition}@anchor{35}
2149 @section Pragma Attribute_Definition
2155 pragma Attribute_Definition
2156 ([Attribute =>] ATTRIBUTE_DESIGNATOR,
2157 [Entity =>] LOCAL_NAME,
2158 [Expression =>] EXPRESSION | NAME);
2161 If @code{Attribute} is a known attribute name, this pragma is equivalent to
2162 the attribute definition clause:
2165 for Entity'Attribute use Expression;
2168 If @code{Attribute} is not a recognized attribute name, the pragma is
2169 ignored, and a warning is emitted. This allows source
2170 code to be written that takes advantage of some new attribute, while remaining
2171 compilable with earlier compilers.
2173 @node Pragma C_Pass_By_Copy,Pragma Check,Pragma Attribute_Definition,Implementation Defined Pragmas
2174 @anchor{gnat_rm/implementation_defined_pragmas pragma-c-pass-by-copy}@anchor{36}
2175 @section Pragma C_Pass_By_Copy
2178 @geindex Passing by copy
2183 pragma C_Pass_By_Copy
2184 ([Max_Size =>] static_integer_EXPRESSION);
2187 Normally the default mechanism for passing C convention records to C
2188 convention subprograms is to pass them by reference, as suggested by RM
2189 B.3(69). Use the configuration pragma @code{C_Pass_By_Copy} to change
2190 this default, by requiring that record formal parameters be passed by
2191 copy if all of the following conditions are met:
2197 The size of the record type does not exceed the value specified for
2201 The record type has @code{Convention C}.
2204 The formal parameter has this record type, and the subprogram has a
2205 foreign (non-Ada) convention.
2208 If these conditions are met the argument is passed by copy; i.e., in a
2209 manner consistent with what C expects if the corresponding formal in the
2210 C prototype is a struct (rather than a pointer to a struct).
2212 You can also pass records by copy by specifying the convention
2213 @code{C_Pass_By_Copy} for the record type, or by using the extended
2214 @code{Import} and @code{Export} pragmas, which allow specification of
2215 passing mechanisms on a parameter by parameter basis.
2217 @node Pragma Check,Pragma Check_Float_Overflow,Pragma C_Pass_By_Copy,Implementation Defined Pragmas
2218 @anchor{gnat_rm/implementation_defined_pragmas pragma-check}@anchor{37}
2219 @section Pragma Check
2224 @geindex Named assertions
2230 [Name =>] CHECK_KIND,
2231 [Check =>] Boolean_EXPRESSION
2232 [, [Message =>] string_EXPRESSION] );
2234 CHECK_KIND ::= IDENTIFIER |
2237 Type_Invariant'Class |
2241 This pragma is similar to the predefined pragma @code{Assert} except that an
2242 extra identifier argument is present. In conjunction with pragma
2243 @code{Check_Policy}, this can be used to define groups of assertions that can
2244 be independently controlled. The identifier @code{Assertion} is special, it
2245 refers to the normal set of pragma @code{Assert} statements.
2247 Checks introduced by this pragma are normally deactivated by default. They can
2248 be activated either by the command line option @emph{-gnata}, which turns on
2249 all checks, or individually controlled using pragma @code{Check_Policy}.
2251 The identifiers @code{Assertions} and @code{Statement_Assertions} are not
2252 permitted as check kinds, since this would cause confusion with the use
2253 of these identifiers in @code{Assertion_Policy} and @code{Check_Policy}
2254 pragmas, where they are used to refer to sets of assertions.
2256 @node Pragma Check_Float_Overflow,Pragma Check_Name,Pragma Check,Implementation Defined Pragmas
2257 @anchor{gnat_rm/implementation_defined_pragmas pragma-check-float-overflow}@anchor{38}
2258 @section Pragma Check_Float_Overflow
2261 @geindex Floating-point overflow
2266 pragma Check_Float_Overflow;
2269 In Ada, the predefined floating-point types (@code{Short_Float},
2270 @code{Float}, @code{Long_Float}, @code{Long_Long_Float}) are
2271 defined to be @emph{unconstrained}. This means that even though each
2272 has a well-defined base range, an operation that delivers a result
2273 outside this base range is not required to raise an exception.
2274 This implementation permission accommodates the notion
2275 of infinities in IEEE floating-point, and corresponds to the
2276 efficient execution mode on most machines. GNAT will not raise
2277 overflow exceptions on these machines; instead it will generate
2278 infinities and NaN's as defined in the IEEE standard.
2280 Generating infinities, although efficient, is not always desirable.
2281 Often the preferable approach is to check for overflow, even at the
2282 (perhaps considerable) expense of run-time performance.
2283 This can be accomplished by defining your own constrained floating-point subtypes -- i.e., by supplying explicit
2284 range constraints -- and indeed such a subtype
2285 can have the same base range as its base type. For example:
2288 subtype My_Float is Float range Float'Range;
2291 Here @code{My_Float} has the same range as
2292 @code{Float} but is constrained, so operations on
2293 @code{My_Float} values will be checked for overflow
2296 This style will achieve the desired goal, but
2297 it is often more convenient to be able to simply use
2298 the standard predefined floating-point types as long
2299 as overflow checking could be guaranteed.
2300 The @code{Check_Float_Overflow}
2301 configuration pragma achieves this effect. If a unit is compiled
2302 subject to this configuration pragma, then all operations
2303 on predefined floating-point types including operations on
2304 base types of these floating-point types will be treated as
2305 though those types were constrained, and overflow checks
2306 will be generated. The @code{Constraint_Error}
2307 exception is raised if the result is out of range.
2309 This mode can also be set by use of the compiler
2310 switch @emph{-gnateF}.
2312 @node Pragma Check_Name,Pragma Check_Policy,Pragma Check_Float_Overflow,Implementation Defined Pragmas
2313 @anchor{gnat_rm/implementation_defined_pragmas pragma-check-name}@anchor{39}
2314 @section Pragma Check_Name
2317 @geindex Defining check names
2319 @geindex Check names
2325 pragma Check_Name (check_name_IDENTIFIER);
2328 This is a configuration pragma that defines a new implementation
2329 defined check name (unless IDENTIFIER matches one of the predefined
2330 check names, in which case the pragma has no effect). Check names
2331 are global to a partition, so if two or more configuration pragmas
2332 are present in a partition mentioning the same name, only one new
2333 check name is introduced.
2335 An implementation defined check name introduced with this pragma may
2336 be used in only three contexts: @code{pragma Suppress},
2337 @code{pragma Unsuppress},
2338 and as the prefix of a @code{Check_Name'Enabled} attribute reference. For
2339 any of these three cases, the check name must be visible. A check
2340 name is visible if it is in the configuration pragmas applying to
2341 the current unit, or if it appears at the start of any unit that
2342 is part of the dependency set of the current unit (e.g., units that
2343 are mentioned in @code{with} clauses).
2345 Check names introduced by this pragma are subject to control by compiler
2346 switches (in particular -gnatp) in the usual manner.
2348 @node Pragma Check_Policy,Pragma Comment,Pragma Check_Name,Implementation Defined Pragmas
2349 @anchor{gnat_rm/implementation_defined_pragmas pragma-check-policy}@anchor{3a}
2350 @section Pragma Check_Policy
2353 @geindex Controlling assertions
2358 @geindex Check pragma control
2360 @geindex Named assertions
2366 ([Name =>] CHECK_KIND,
2367 [Policy =>] POLICY_IDENTIFIER);
2369 pragma Check_Policy (
2370 CHECK_KIND => POLICY_IDENTIFIER
2371 @{, CHECK_KIND => POLICY_IDENTIFIER@});
2373 ASSERTION_KIND ::= RM_ASSERTION_KIND | ID_ASSERTION_KIND
2375 CHECK_KIND ::= IDENTIFIER |
2378 Type_Invariant'Class |
2381 The identifiers Name and Policy are not allowed as CHECK_KIND values. This
2382 avoids confusion between the two possible syntax forms for this pragma.
2384 POLICY_IDENTIFIER ::= ON | OFF | CHECK | DISABLE | IGNORE
2387 This pragma is used to set the checking policy for assertions (specified
2388 by aspects or pragmas), the @code{Debug} pragma, or additional checks
2389 to be checked using the @code{Check} pragma. It may appear either as
2390 a configuration pragma, or within a declarative part of package. In the
2391 latter case, it applies from the point where it appears to the end of
2392 the declarative region (like pragma @code{Suppress}).
2394 The @code{Check_Policy} pragma is similar to the
2395 predefined @code{Assertion_Policy} pragma,
2396 and if the check kind corresponds to one of the assertion kinds that
2397 are allowed by @code{Assertion_Policy}, then the effect is identical.
2399 If the first argument is Debug, then the policy applies to Debug pragmas,
2400 disabling their effect if the policy is @code{OFF}, @code{DISABLE}, or
2401 @code{IGNORE}, and allowing them to execute with normal semantics if
2402 the policy is @code{ON} or @code{CHECK}. In addition if the policy is
2403 @code{DISABLE}, then the procedure call in @code{Debug} pragmas will
2404 be totally ignored and not analyzed semantically.
2406 Finally the first argument may be some other identifier than the above
2407 possibilities, in which case it controls a set of named assertions
2408 that can be checked using pragma @code{Check}. For example, if the pragma:
2411 pragma Check_Policy (Critical_Error, OFF);
2414 is given, then subsequent @code{Check} pragmas whose first argument is also
2415 @code{Critical_Error} will be disabled.
2417 The check policy is @code{OFF} to turn off corresponding checks, and @code{ON}
2418 to turn on corresponding checks. The default for a set of checks for which no
2419 @code{Check_Policy} is given is @code{OFF} unless the compiler switch
2420 @emph{-gnata} is given, which turns on all checks by default.
2422 The check policy settings @code{CHECK} and @code{IGNORE} are recognized
2423 as synonyms for @code{ON} and @code{OFF}. These synonyms are provided for
2424 compatibility with the standard @code{Assertion_Policy} pragma. The check
2425 policy setting @code{DISABLE} causes the second argument of a corresponding
2426 @code{Check} pragma to be completely ignored and not analyzed.
2428 @node Pragma Comment,Pragma Common_Object,Pragma Check_Policy,Implementation Defined Pragmas
2429 @anchor{gnat_rm/implementation_defined_pragmas pragma-comment}@anchor{3b}
2430 @section Pragma Comment
2436 pragma Comment (static_string_EXPRESSION);
2439 This is almost identical in effect to pragma @code{Ident}. It allows the
2440 placement of a comment into the object file and hence into the
2441 executable file if the operating system permits such usage. The
2442 difference is that @code{Comment}, unlike @code{Ident}, has
2443 no limitations on placement of the pragma (it can be placed
2444 anywhere in the main source unit), and if more than one pragma
2445 is used, all comments are retained.
2447 @node Pragma Common_Object,Pragma Compile_Time_Error,Pragma Comment,Implementation Defined Pragmas
2448 @anchor{gnat_rm/implementation_defined_pragmas pragma-common-object}@anchor{3c}
2449 @section Pragma Common_Object
2455 pragma Common_Object (
2456 [Internal =>] LOCAL_NAME
2457 [, [External =>] EXTERNAL_SYMBOL]
2458 [, [Size =>] EXTERNAL_SYMBOL] );
2462 | static_string_EXPRESSION
2465 This pragma enables the shared use of variables stored in overlaid
2466 linker areas corresponding to the use of @code{COMMON}
2467 in Fortran. The single
2468 object @code{LOCAL_NAME} is assigned to the area designated by
2469 the @code{External} argument.
2470 You may define a record to correspond to a series
2471 of fields. The @code{Size} argument
2472 is syntax checked in GNAT, but otherwise ignored.
2474 @code{Common_Object} is not supported on all platforms. If no
2475 support is available, then the code generator will issue a message
2476 indicating that the necessary attribute for implementation of this
2477 pragma is not available.
2479 @node Pragma Compile_Time_Error,Pragma Compile_Time_Warning,Pragma Common_Object,Implementation Defined Pragmas
2480 @anchor{gnat_rm/implementation_defined_pragmas pragma-compile-time-error}@anchor{3d}
2481 @section Pragma Compile_Time_Error
2487 pragma Compile_Time_Error
2488 (boolean_EXPRESSION, static_string_EXPRESSION);
2491 This pragma can be used to generate additional compile time
2493 is particularly useful in generics, where errors can be issued for
2494 specific problematic instantiations. The first parameter is a boolean
2495 expression. The pragma is effective only if the value of this expression
2496 is known at compile time, and has the value True. The set of expressions
2497 whose values are known at compile time includes all static boolean
2498 expressions, and also other values which the compiler can determine
2499 at compile time (e.g., the size of a record type set by an explicit
2500 size representation clause, or the value of a variable which was
2501 initialized to a constant and is known not to have been modified).
2502 If these conditions are met, an error message is generated using
2503 the value given as the second argument. This string value may contain
2504 embedded ASCII.LF characters to break the message into multiple lines.
2506 @node Pragma Compile_Time_Warning,Pragma Compiler_Unit,Pragma Compile_Time_Error,Implementation Defined Pragmas
2507 @anchor{gnat_rm/implementation_defined_pragmas pragma-compile-time-warning}@anchor{3e}
2508 @section Pragma Compile_Time_Warning
2514 pragma Compile_Time_Warning
2515 (boolean_EXPRESSION, static_string_EXPRESSION);
2518 Same as pragma Compile_Time_Error, except a warning is issued instead
2519 of an error message. Note that if this pragma is used in a package that
2520 is with'ed by a client, the client will get the warning even though it
2521 is issued by a with'ed package (normally warnings in with'ed units are
2522 suppressed, but this is a special exception to that rule).
2524 One typical use is within a generic where compile time known characteristics
2525 of formal parameters are tested, and warnings given appropriately. Another use
2526 with a first parameter of True is to warn a client about use of a package,
2527 for example that it is not fully implemented.
2529 @node Pragma Compiler_Unit,Pragma Compiler_Unit_Warning,Pragma Compile_Time_Warning,Implementation Defined Pragmas
2530 @anchor{gnat_rm/implementation_defined_pragmas pragma-compiler-unit}@anchor{3f}
2531 @section Pragma Compiler_Unit
2537 pragma Compiler_Unit;
2540 This pragma is obsolete. It is equivalent to Compiler_Unit_Warning. It is
2541 retained so that old versions of the GNAT run-time that use this pragma can
2542 be compiled with newer versions of the compiler.
2544 @node Pragma Compiler_Unit_Warning,Pragma Complete_Representation,Pragma Compiler_Unit,Implementation Defined Pragmas
2545 @anchor{gnat_rm/implementation_defined_pragmas pragma-compiler-unit-warning}@anchor{40}
2546 @section Pragma Compiler_Unit_Warning
2552 pragma Compiler_Unit_Warning;
2555 This pragma is intended only for internal use in the GNAT run-time library.
2556 It indicates that the unit is used as part of the compiler build. The effect
2557 is to generate warnings for the use of constructs (for example, conditional
2558 expressions) that would cause trouble when bootstrapping using an older
2559 version of GNAT. For the exact list of restrictions, see the compiler sources
2560 and references to Check_Compiler_Unit.
2562 @node Pragma Complete_Representation,Pragma Complex_Representation,Pragma Compiler_Unit_Warning,Implementation Defined Pragmas
2563 @anchor{gnat_rm/implementation_defined_pragmas pragma-complete-representation}@anchor{41}
2564 @section Pragma Complete_Representation
2570 pragma Complete_Representation;
2573 This pragma must appear immediately within a record representation
2574 clause. Typical placements are before the first component clause
2575 or after the last component clause. The effect is to give an error
2576 message if any component is missing a component clause. This pragma
2577 may be used to ensure that a record representation clause is
2578 complete, and that this invariant is maintained if fields are
2579 added to the record in the future.
2581 @node Pragma Complex_Representation,Pragma Component_Alignment,Pragma Complete_Representation,Implementation Defined Pragmas
2582 @anchor{gnat_rm/implementation_defined_pragmas pragma-complex-representation}@anchor{42}
2583 @section Pragma Complex_Representation
2589 pragma Complex_Representation
2590 ([Entity =>] LOCAL_NAME);
2593 The @code{Entity} argument must be the name of a record type which has
2594 two fields of the same floating-point type. The effect of this pragma is
2595 to force gcc to use the special internal complex representation form for
2596 this record, which may be more efficient. Note that this may result in
2597 the code for this type not conforming to standard ABI (application
2598 binary interface) requirements for the handling of record types. For
2599 example, in some environments, there is a requirement for passing
2600 records by pointer, and the use of this pragma may result in passing
2601 this type in floating-point registers.
2603 @node Pragma Component_Alignment,Pragma Constant_After_Elaboration,Pragma Complex_Representation,Implementation Defined Pragmas
2604 @anchor{gnat_rm/implementation_defined_pragmas pragma-component-alignment}@anchor{43}
2605 @section Pragma Component_Alignment
2608 @geindex Alignments of components
2610 @geindex Pragma Component_Alignment
2615 pragma Component_Alignment (
2616 [Form =>] ALIGNMENT_CHOICE
2617 [, [Name =>] type_LOCAL_NAME]);
2619 ALIGNMENT_CHOICE ::=
2626 Specifies the alignment of components in array or record types.
2627 The meaning of the @code{Form} argument is as follows:
2631 @geindex Component_Size (in pragma Component_Alignment)
2637 @item @emph{Component_Size}
2639 Aligns scalar components and subcomponents of the array or record type
2640 on boundaries appropriate to their inherent size (naturally
2641 aligned). For example, 1-byte components are aligned on byte boundaries,
2642 2-byte integer components are aligned on 2-byte boundaries, 4-byte
2643 integer components are aligned on 4-byte boundaries and so on. These
2644 alignment rules correspond to the normal rules for C compilers on all
2645 machines except the VAX.
2647 @geindex Component_Size_4 (in pragma Component_Alignment)
2649 @item @emph{Component_Size_4}
2651 Naturally aligns components with a size of four or fewer
2652 bytes. Components that are larger than 4 bytes are placed on the next
2655 @geindex Storage_Unit (in pragma Component_Alignment)
2657 @item @emph{Storage_Unit}
2659 Specifies that array or record components are byte aligned, i.e.,
2660 aligned on boundaries determined by the value of the constant
2661 @code{System.Storage_Unit}.
2663 @geindex Default (in pragma Component_Alignment)
2665 @item @emph{Default}
2667 Specifies that array or record components are aligned on default
2668 boundaries, appropriate to the underlying hardware or operating system or
2669 both. The @code{Default} choice is the same as @code{Component_Size} (natural
2673 If the @code{Name} parameter is present, @code{type_LOCAL_NAME} must
2674 refer to a local record or array type, and the specified alignment
2675 choice applies to the specified type. The use of
2676 @code{Component_Alignment} together with a pragma @code{Pack} causes the
2677 @code{Component_Alignment} pragma to be ignored. The use of
2678 @code{Component_Alignment} together with a record representation clause
2679 is only effective for fields not specified by the representation clause.
2681 If the @code{Name} parameter is absent, the pragma can be used as either
2682 a configuration pragma, in which case it applies to one or more units in
2683 accordance with the normal rules for configuration pragmas, or it can be
2684 used within a declarative part, in which case it applies to types that
2685 are declared within this declarative part, or within any nested scope
2686 within this declarative part. In either case it specifies the alignment
2687 to be applied to any record or array type which has otherwise standard
2690 If the alignment for a record or array type is not specified (using
2691 pragma @code{Pack}, pragma @code{Component_Alignment}, or a record rep
2692 clause), the GNAT uses the default alignment as described previously.
2694 @node Pragma Constant_After_Elaboration,Pragma Contract_Cases,Pragma Component_Alignment,Implementation Defined Pragmas
2695 @anchor{gnat_rm/implementation_defined_pragmas id6}@anchor{44}@anchor{gnat_rm/implementation_defined_pragmas pragma-constant-after-elaboration}@anchor{45}
2696 @section Pragma Constant_After_Elaboration
2702 pragma Constant_After_Elaboration [ (boolean_EXPRESSION) ];
2705 For the semantics of this pragma, see the entry for aspect
2706 @code{Constant_After_Elaboration} in the SPARK 2014 Reference Manual, section 3.3.1.
2708 @node Pragma Contract_Cases,Pragma Convention_Identifier,Pragma Constant_After_Elaboration,Implementation Defined Pragmas
2709 @anchor{gnat_rm/implementation_defined_pragmas id7}@anchor{46}@anchor{gnat_rm/implementation_defined_pragmas pragma-contract-cases}@anchor{47}
2710 @section Pragma Contract_Cases
2713 @geindex Contract cases
2718 pragma Contract_Cases ((CONTRACT_CASE @{, CONTRACT_CASE));
2720 CONTRACT_CASE ::= CASE_GUARD => CONSEQUENCE
2722 CASE_GUARD ::= boolean_EXPRESSION | others
2724 CONSEQUENCE ::= boolean_EXPRESSION
2727 The @code{Contract_Cases} pragma allows defining fine-grain specifications
2728 that can complement or replace the contract given by a precondition and a
2729 postcondition. Additionally, the @code{Contract_Cases} pragma can be used
2730 by testing and formal verification tools. The compiler checks its validity and,
2731 depending on the assertion policy at the point of declaration of the pragma,
2732 it may insert a check in the executable. For code generation, the contract
2736 pragma Contract_Cases (
2744 C1 : constant Boolean := Cond1; -- evaluated at subprogram entry
2745 C2 : constant Boolean := Cond2; -- evaluated at subprogram entry
2746 pragma Precondition ((C1 and not C2) or (C2 and not C1));
2747 pragma Postcondition (if C1 then Pred1);
2748 pragma Postcondition (if C2 then Pred2);
2751 The precondition ensures that one and only one of the case guards is
2752 satisfied on entry to the subprogram.
2753 The postcondition ensures that for the case guard that was True on entry,
2754 the corresponding consequence is True on exit. Other consequence expressions
2757 A precondition @code{P} and postcondition @code{Q} can also be
2758 expressed as contract cases:
2761 pragma Contract_Cases (P => Q);
2764 The placement and visibility rules for @code{Contract_Cases} pragmas are
2765 identical to those described for preconditions and postconditions.
2767 The compiler checks that boolean expressions given in case guards and
2768 consequences are valid, where the rules for case guards are the same as
2769 the rule for an expression in @code{Precondition} and the rules for
2770 consequences are the same as the rule for an expression in
2771 @code{Postcondition}. In particular, attributes @code{'Old} and
2772 @code{'Result} can only be used within consequence expressions.
2773 The case guard for the last contract case may be @code{others}, to denote
2774 any case not captured by the previous cases. The
2775 following is an example of use within a package spec:
2778 package Math_Functions is
2780 function Sqrt (Arg : Float) return Float;
2781 pragma Contract_Cases (((Arg in 0.0 .. 99.0) => Sqrt'Result < 10.0,
2782 Arg >= 100.0 => Sqrt'Result >= 10.0,
2783 others => Sqrt'Result = 0.0));
2788 The meaning of contract cases is that only one case should apply at each
2789 call, as determined by the corresponding case guard evaluating to True,
2790 and that the consequence for this case should hold when the subprogram
2793 @node Pragma Convention_Identifier,Pragma CPP_Class,Pragma Contract_Cases,Implementation Defined Pragmas
2794 @anchor{gnat_rm/implementation_defined_pragmas pragma-convention-identifier}@anchor{48}
2795 @section Pragma Convention_Identifier
2798 @geindex Conventions
2804 pragma Convention_Identifier (
2805 [Name =>] IDENTIFIER,
2806 [Convention =>] convention_IDENTIFIER);
2809 This pragma provides a mechanism for supplying synonyms for existing
2810 convention identifiers. The @code{Name} identifier can subsequently
2811 be used as a synonym for the given convention in other pragmas (including
2812 for example pragma @code{Import} or another @code{Convention_Identifier}
2813 pragma). As an example of the use of this, suppose you had legacy code
2814 which used Fortran77 as the identifier for Fortran. Then the pragma:
2817 pragma Convention_Identifier (Fortran77, Fortran);
2820 would allow the use of the convention identifier @code{Fortran77} in
2821 subsequent code, avoiding the need to modify the sources. As another
2822 example, you could use this to parameterize convention requirements
2823 according to systems. Suppose you needed to use @code{Stdcall} on
2824 windows systems, and @code{C} on some other system, then you could
2825 define a convention identifier @code{Library} and use a single
2826 @code{Convention_Identifier} pragma to specify which convention
2827 would be used system-wide.
2829 @node Pragma CPP_Class,Pragma CPP_Constructor,Pragma Convention_Identifier,Implementation Defined Pragmas
2830 @anchor{gnat_rm/implementation_defined_pragmas pragma-cpp-class}@anchor{49}
2831 @section Pragma CPP_Class
2834 @geindex Interfacing with C++
2839 pragma CPP_Class ([Entity =>] LOCAL_NAME);
2842 The argument denotes an entity in the current declarative region that is
2843 declared as a record type. It indicates that the type corresponds to an
2844 externally declared C++ class type, and is to be laid out the same way
2845 that C++ would lay out the type. If the C++ class has virtual primitives
2846 then the record must be declared as a tagged record type.
2848 Types for which @code{CPP_Class} is specified do not have assignment or
2849 equality operators defined (such operations can be imported or declared
2850 as subprograms as required). Initialization is allowed only by constructor
2851 functions (see pragma @code{CPP_Constructor}). Such types are implicitly
2852 limited if not explicitly declared as limited or derived from a limited
2853 type, and an error is issued in that case.
2855 See @ref{4a,,Interfacing to C++} for related information.
2857 Note: Pragma @code{CPP_Class} is currently obsolete. It is supported
2858 for backward compatibility but its functionality is available
2859 using pragma @code{Import} with @code{Convention} = @code{CPP}.
2861 @node Pragma CPP_Constructor,Pragma CPP_Virtual,Pragma CPP_Class,Implementation Defined Pragmas
2862 @anchor{gnat_rm/implementation_defined_pragmas pragma-cpp-constructor}@anchor{4b}
2863 @section Pragma CPP_Constructor
2866 @geindex Interfacing with C++
2871 pragma CPP_Constructor ([Entity =>] LOCAL_NAME
2872 [, [External_Name =>] static_string_EXPRESSION ]
2873 [, [Link_Name =>] static_string_EXPRESSION ]);
2876 This pragma identifies an imported function (imported in the usual way
2877 with pragma @code{Import}) as corresponding to a C++ constructor. If
2878 @code{External_Name} and @code{Link_Name} are not specified then the
2879 @code{Entity} argument is a name that must have been previously mentioned
2880 in a pragma @code{Import} with @code{Convention} = @code{CPP}. Such name
2881 must be of one of the following forms:
2887 @strong{function} @code{Fname} @strong{return} T`
2890 @strong{function} @code{Fname} @strong{return} T'Class
2893 @strong{function} @code{Fname} (...) @strong{return} T`
2896 @strong{function} @code{Fname} (...) @strong{return} T'Class
2899 where @code{T} is a limited record type imported from C++ with pragma
2900 @code{Import} and @code{Convention} = @code{CPP}.
2902 The first two forms import the default constructor, used when an object
2903 of type @code{T} is created on the Ada side with no explicit constructor.
2904 The latter two forms cover all the non-default constructors of the type.
2905 See the GNAT User's Guide for details.
2907 If no constructors are imported, it is impossible to create any objects
2908 on the Ada side and the type is implicitly declared abstract.
2910 Pragma @code{CPP_Constructor} is intended primarily for automatic generation
2911 using an automatic binding generator tool (such as the @code{-fdump-ada-spec}
2913 See @ref{4a,,Interfacing to C++} for more related information.
2915 Note: The use of functions returning class-wide types for constructors is
2916 currently obsolete. They are supported for backward compatibility. The
2917 use of functions returning the type T leave the Ada sources more clear
2918 because the imported C++ constructors always return an object of type T;
2919 that is, they never return an object whose type is a descendant of type T.
2921 @node Pragma CPP_Virtual,Pragma CPP_Vtable,Pragma CPP_Constructor,Implementation Defined Pragmas
2922 @anchor{gnat_rm/implementation_defined_pragmas pragma-cpp-virtual}@anchor{4c}
2923 @section Pragma CPP_Virtual
2926 @geindex Interfacing to C++
2928 This pragma is now obsolete and, other than generating a warning if warnings
2929 on obsolescent features are enabled, is completely ignored.
2930 It is retained for compatibility
2931 purposes. It used to be required to ensure compoatibility with C++, but
2932 is no longer required for that purpose because GNAT generates
2933 the same object layout as the G++ compiler by default.
2935 See @ref{4a,,Interfacing to C++} for related information.
2937 @node Pragma CPP_Vtable,Pragma CPU,Pragma CPP_Virtual,Implementation Defined Pragmas
2938 @anchor{gnat_rm/implementation_defined_pragmas pragma-cpp-vtable}@anchor{4d}
2939 @section Pragma CPP_Vtable
2942 @geindex Interfacing with C++
2944 This pragma is now obsolete and, other than generating a warning if warnings
2945 on obsolescent features are enabled, is completely ignored.
2946 It used to be required to ensure compatibility with C++, but
2947 is no longer required for that purpose because GNAT generates
2948 the same object layout as the G++ compiler by default.
2950 See @ref{4a,,Interfacing to C++} for related information.
2952 @node Pragma CPU,Pragma Deadline_Floor,Pragma CPP_Vtable,Implementation Defined Pragmas
2953 @anchor{gnat_rm/implementation_defined_pragmas pragma-cpu}@anchor{4e}
2960 pragma CPU (EXPRESSION);
2963 This pragma is standard in Ada 2012, but is available in all earlier
2964 versions of Ada as an implementation-defined pragma.
2965 See Ada 2012 Reference Manual for details.
2967 @node Pragma Deadline_Floor,Pragma Default_Initial_Condition,Pragma CPU,Implementation Defined Pragmas
2968 @anchor{gnat_rm/implementation_defined_pragmas pragma-deadline-floor}@anchor{4f}
2969 @section Pragma Deadline_Floor
2975 pragma Deadline_Floor (time_span_EXPRESSION);
2978 This pragma applies only to protected types and specifies the floor
2979 deadline inherited by a task when the task enters a protected object.
2980 It is effective only when the EDF scheduling policy is used.
2982 @node Pragma Default_Initial_Condition,Pragma Debug,Pragma Deadline_Floor,Implementation Defined Pragmas
2983 @anchor{gnat_rm/implementation_defined_pragmas id8}@anchor{50}@anchor{gnat_rm/implementation_defined_pragmas pragma-default-initial-condition}@anchor{51}
2984 @section Pragma Default_Initial_Condition
2990 pragma Default_Initial_Condition [ (null | boolean_EXPRESSION) ];
2993 For the semantics of this pragma, see the entry for aspect
2994 @code{Default_Initial_Condition} in the SPARK 2014 Reference Manual, section 7.3.3.
2996 @node Pragma Debug,Pragma Debug_Policy,Pragma Default_Initial_Condition,Implementation Defined Pragmas
2997 @anchor{gnat_rm/implementation_defined_pragmas pragma-debug}@anchor{52}
2998 @section Pragma Debug
3004 pragma Debug ([CONDITION, ]PROCEDURE_CALL_WITHOUT_SEMICOLON);
3006 PROCEDURE_CALL_WITHOUT_SEMICOLON ::=
3008 | PROCEDURE_PREFIX ACTUAL_PARAMETER_PART
3011 The procedure call argument has the syntactic form of an expression, meeting
3012 the syntactic requirements for pragmas.
3014 If debug pragmas are not enabled or if the condition is present and evaluates
3015 to False, this pragma has no effect. If debug pragmas are enabled, the
3016 semantics of the pragma is exactly equivalent to the procedure call statement
3017 corresponding to the argument with a terminating semicolon. Pragmas are
3018 permitted in sequences of declarations, so you can use pragma @code{Debug} to
3019 intersperse calls to debug procedures in the middle of declarations. Debug
3020 pragmas can be enabled either by use of the command line switch @emph{-gnata}
3021 or by use of the pragma @code{Check_Policy} with a first argument of
3024 @node Pragma Debug_Policy,Pragma Default_Scalar_Storage_Order,Pragma Debug,Implementation Defined Pragmas
3025 @anchor{gnat_rm/implementation_defined_pragmas pragma-debug-policy}@anchor{53}
3026 @section Pragma Debug_Policy
3032 pragma Debug_Policy (CHECK | DISABLE | IGNORE | ON | OFF);
3035 This pragma is equivalent to a corresponding @code{Check_Policy} pragma
3036 with a first argument of @code{Debug}. It is retained for historical
3037 compatibility reasons.
3039 @node Pragma Default_Scalar_Storage_Order,Pragma Default_Storage_Pool,Pragma Debug_Policy,Implementation Defined Pragmas
3040 @anchor{gnat_rm/implementation_defined_pragmas pragma-default-scalar-storage-order}@anchor{54}
3041 @section Pragma Default_Scalar_Storage_Order
3044 @geindex Default_Scalar_Storage_Order
3046 @geindex Scalar_Storage_Order
3051 pragma Default_Scalar_Storage_Order (High_Order_First | Low_Order_First);
3054 Normally if no explicit @code{Scalar_Storage_Order} is given for a record
3055 type or array type, then the scalar storage order defaults to the ordinary
3056 default for the target. But this default may be overridden using this pragma.
3057 The pragma may appear as a configuration pragma, or locally within a package
3058 spec or declarative part. In the latter case, it applies to all subsequent
3059 types declared within that package spec or declarative part.
3061 The following example shows the use of this pragma:
3064 pragma Default_Scalar_Storage_Order (High_Order_First);
3065 with System; use System;
3074 for L2'Scalar_Storage_Order use Low_Order_First;
3083 pragma Default_Scalar_Storage_Order (Low_Order_First);
3090 type H4a is new Inner.L4;
3098 In this example record types with names starting with @emph{L} have @cite{Low_Order_First} scalar
3099 storage order, and record types with names starting with @emph{H} have @code{High_Order_First}.
3100 Note that in the case of @code{H4a}, the order is not inherited
3101 from the parent type. Only an explicitly set @code{Scalar_Storage_Order}
3102 gets inherited on type derivation.
3104 If this pragma is used as a configuration pragma which appears within a
3105 configuration pragma file (as opposed to appearing explicitly at the start
3106 of a single unit), then the binder will require that all units in a partition
3107 be compiled in a similar manner, other than run-time units, which are not
3108 affected by this pragma. Note that the use of this form is discouraged because
3109 it may significantly degrade the run-time performance of the software, instead
3110 the default scalar storage order ought to be changed only on a local basis.
3112 @node Pragma Default_Storage_Pool,Pragma Depends,Pragma Default_Scalar_Storage_Order,Implementation Defined Pragmas
3113 @anchor{gnat_rm/implementation_defined_pragmas pragma-default-storage-pool}@anchor{55}
3114 @section Pragma Default_Storage_Pool
3117 @geindex Default_Storage_Pool
3122 pragma Default_Storage_Pool (storage_pool_NAME | null);
3125 This pragma is standard in Ada 2012, but is available in all earlier
3126 versions of Ada as an implementation-defined pragma.
3127 See Ada 2012 Reference Manual for details.
3129 @node Pragma Depends,Pragma Detect_Blocking,Pragma Default_Storage_Pool,Implementation Defined Pragmas
3130 @anchor{gnat_rm/implementation_defined_pragmas pragma-depends}@anchor{56}@anchor{gnat_rm/implementation_defined_pragmas id9}@anchor{57}
3131 @section Pragma Depends
3137 pragma Depends (DEPENDENCY_RELATION);
3139 DEPENDENCY_RELATION ::=
3141 | (DEPENDENCY_CLAUSE @{, DEPENDENCY_CLAUSE@})
3143 DEPENDENCY_CLAUSE ::=
3144 OUTPUT_LIST =>[+] INPUT_LIST
3145 | NULL_DEPENDENCY_CLAUSE
3147 NULL_DEPENDENCY_CLAUSE ::= null => INPUT_LIST
3149 OUTPUT_LIST ::= OUTPUT | (OUTPUT @{, OUTPUT@})
3151 INPUT_LIST ::= null | INPUT | (INPUT @{, INPUT@})
3153 OUTPUT ::= NAME | FUNCTION_RESULT
3156 where FUNCTION_RESULT is a function Result attribute_reference
3159 For the semantics of this pragma, see the entry for aspect @code{Depends} in the
3160 SPARK 2014 Reference Manual, section 6.1.5.
3162 @node Pragma Detect_Blocking,Pragma Disable_Atomic_Synchronization,Pragma Depends,Implementation Defined Pragmas
3163 @anchor{gnat_rm/implementation_defined_pragmas pragma-detect-blocking}@anchor{58}
3164 @section Pragma Detect_Blocking
3170 pragma Detect_Blocking;
3173 This is a standard pragma in Ada 2005, that is available in all earlier
3174 versions of Ada as an implementation-defined pragma.
3176 This is a configuration pragma that forces the detection of potentially
3177 blocking operations within a protected operation, and to raise Program_Error
3180 @node Pragma Disable_Atomic_Synchronization,Pragma Dispatching_Domain,Pragma Detect_Blocking,Implementation Defined Pragmas
3181 @anchor{gnat_rm/implementation_defined_pragmas pragma-disable-atomic-synchronization}@anchor{59}
3182 @section Pragma Disable_Atomic_Synchronization
3185 @geindex Atomic Synchronization
3190 pragma Disable_Atomic_Synchronization [(Entity)];
3193 Ada requires that accesses (reads or writes) of an atomic variable be
3194 regarded as synchronization points in the case of multiple tasks.
3195 Particularly in the case of multi-processors this may require special
3196 handling, e.g. the generation of memory barriers. This capability may
3197 be turned off using this pragma in cases where it is known not to be
3200 The placement and scope rules for this pragma are the same as those
3201 for @code{pragma Suppress}. In particular it can be used as a
3202 configuration pragma, or in a declaration sequence where it applies
3203 till the end of the scope. If an @code{Entity} argument is present,
3204 the action applies only to that entity.
3206 @node Pragma Dispatching_Domain,Pragma Effective_Reads,Pragma Disable_Atomic_Synchronization,Implementation Defined Pragmas
3207 @anchor{gnat_rm/implementation_defined_pragmas pragma-dispatching-domain}@anchor{5a}
3208 @section Pragma Dispatching_Domain
3214 pragma Dispatching_Domain (EXPRESSION);
3217 This pragma is standard in Ada 2012, but is available in all earlier
3218 versions of Ada as an implementation-defined pragma.
3219 See Ada 2012 Reference Manual for details.
3221 @node Pragma Effective_Reads,Pragma Effective_Writes,Pragma Dispatching_Domain,Implementation Defined Pragmas
3222 @anchor{gnat_rm/implementation_defined_pragmas id10}@anchor{5b}@anchor{gnat_rm/implementation_defined_pragmas pragma-effective-reads}@anchor{5c}
3223 @section Pragma Effective_Reads
3229 pragma Effective_Reads [ (boolean_EXPRESSION) ];
3232 For the semantics of this pragma, see the entry for aspect @code{Effective_Reads} in
3233 the SPARK 2014 Reference Manual, section 7.1.2.
3235 @node Pragma Effective_Writes,Pragma Elaboration_Checks,Pragma Effective_Reads,Implementation Defined Pragmas
3236 @anchor{gnat_rm/implementation_defined_pragmas id11}@anchor{5d}@anchor{gnat_rm/implementation_defined_pragmas pragma-effective-writes}@anchor{5e}
3237 @section Pragma Effective_Writes
3243 pragma Effective_Writes [ (boolean_EXPRESSION) ];
3246 For the semantics of this pragma, see the entry for aspect @code{Effective_Writes}
3247 in the SPARK 2014 Reference Manual, section 7.1.2.
3249 @node Pragma Elaboration_Checks,Pragma Eliminate,Pragma Effective_Writes,Implementation Defined Pragmas
3250 @anchor{gnat_rm/implementation_defined_pragmas pragma-elaboration-checks}@anchor{5f}
3251 @section Pragma Elaboration_Checks
3254 @geindex Elaboration control
3259 pragma Elaboration_Checks (Dynamic | Static);
3262 This is a configuration pragma which specifies the elaboration model to be
3263 used during compilation. For more information on the elaboration models of
3264 GNAT, consult the chapter on elaboration order handling in the @emph{GNAT User's
3267 The pragma may appear in the following contexts:
3273 Configuration pragmas file
3276 Prior to the context clauses of a compilation unit's initial declaration
3279 Any other placement of the pragma will result in a warning and the effects of
3280 the offending pragma will be ignored.
3282 If the pragma argument is @code{Dynamic}, then the dynamic elaboration model is in
3283 effect. If the pragma argument is @code{Static}, then the static elaboration model
3286 @node Pragma Eliminate,Pragma Enable_Atomic_Synchronization,Pragma Elaboration_Checks,Implementation Defined Pragmas
3287 @anchor{gnat_rm/implementation_defined_pragmas pragma-eliminate}@anchor{60}
3288 @section Pragma Eliminate
3291 @geindex Elimination of unused subprograms
3297 [ Unit_Name => ] IDENTIFIER | SELECTED_COMPONENT ,
3298 [ Entity => ] IDENTIFIER |
3299 SELECTED_COMPONENT |
3301 [, Source_Location => SOURCE_TRACE ] );
3303 SOURCE_TRACE ::= STRING_LITERAL
3306 This pragma indicates that the given entity is not used in the program to be
3307 compiled and built, thus allowing the compiler to
3308 eliminate the code or data associated with the named entity. Any reference to
3309 an eliminated entity causes a compile-time or link-time error.
3311 The pragma has the following semantics, where @code{U} is the unit specified by
3312 the @code{Unit_Name} argument and @code{E} is the entity specified by the @code{Entity}
3319 @code{E} must be a subprogram that is explicitly declared either:
3321 o Within @code{U}, or
3323 o Within a generic package that is instantiated in @code{U}, or
3325 o As an instance of generic subprogram instantiated in @code{U}.
3327 Otherwise the pragma is ignored.
3330 If @code{E} is overloaded within @code{U} then, in the absence of a
3331 @code{Source_Location} argument, all overloadings are eliminated.
3334 If @code{E} is overloaded within @code{U} and only some overloadings
3335 are to be eliminated, then each overloading to be eliminated
3336 must be specified in a corresponding pragma @code{Eliminate}
3337 with a @code{Source_Location} argument identifying the line where the
3338 declaration appears, as described below.
3341 If @code{E} is declared as the result of a generic instantiation, then
3342 a @code{Source_Location} argument is needed, as described below
3345 Pragma @code{Eliminate} allows a program to be compiled in a system-independent
3346 manner, so that unused entities are eliminated but without
3347 needing to modify the source text. Normally the required set of
3348 @code{Eliminate} pragmas is constructed automatically using the @code{gnatelim} tool.
3350 Any source file change that removes, splits, or
3351 adds lines may make the set of @code{Eliminate} pragmas invalid because their
3352 @code{Source_Location} argument values may get out of date.
3354 Pragma @code{Eliminate} may be used where the referenced entity is a dispatching
3355 operation. In this case all the subprograms to which the given operation can
3356 dispatch are considered to be unused (are never called as a result of a direct
3357 or a dispatching call).
3359 The string literal given for the source location specifies the line number
3360 of the declaration of the entity, using the following syntax for @code{SOURCE_TRACE}:
3363 SOURCE_TRACE ::= SOURCE_REFERENCE [ LBRACKET SOURCE_TRACE RBRACKET ]
3368 SOURCE_REFERENCE ::= FILE_NAME : LINE_NUMBER
3370 LINE_NUMBER ::= DIGIT @{DIGIT@}
3373 Spaces around the colon in a @code{SOURCE_REFERENCE} are optional.
3375 The source trace that is given as the @code{Source_Location} must obey the
3376 following rules (or else the pragma is ignored), where @code{U} is
3377 the unit @code{U} specified by the @code{Unit_Name} argument and @code{E} is the
3378 subprogram specified by the @code{Entity} argument:
3384 @code{FILE_NAME} is the short name (with no directory
3385 information) of the Ada source file for @code{U}, using the required syntax
3386 for the underlying file system (e.g. case is significant if the underlying
3387 operating system is case sensitive).
3388 If @code{U} is a package and @code{E} is a subprogram declared in the package
3389 specification and its full declaration appears in the package body,
3390 then the relevant source file is the one for the package specification;
3391 analogously if @code{U} is a generic package.
3394 If @code{E} is not declared in a generic instantiation (this includes
3395 generic subprogram instances), the source trace includes only one source
3396 line reference. @code{LINE_NUMBER} gives the line number of the occurrence
3397 of the declaration of @code{E} within the source file (as a decimal literal
3398 without an exponent or point).
3401 If @code{E} is declared by a generic instantiation, its source trace
3402 (from left to right) starts with the source location of the
3403 declaration of @code{E} in the generic unit and ends with the source
3404 location of the instantiation, given in square brackets. This approach is
3405 applied recursively with nested instantiations: the rightmost (nested
3406 most deeply in square brackets) element of the source trace is the location
3407 of the outermost instantiation, and the leftmost element (that is, outside
3408 of any square brackets) is the location of the declaration of @code{E} in
3417 pragma Eliminate (Pkg0, Proc);
3418 -- Eliminate (all overloadings of) Proc in Pkg0
3420 pragma Eliminate (Pkg1, Proc,
3421 Source_Location => "pkg1.ads:8");
3422 -- Eliminate overloading of Proc at line 8 in pkg1.ads
3424 -- Assume the following file contents:
3427 -- 2: type T is private;
3428 -- 3: package Gen_Pkg is
3429 -- 4: procedure Proc(N : T);
3435 -- 2: procedure Q is
3436 -- 3: package Inst_Pkg is new Gen_Pkg(Integer);
3437 -- ... -- No calls on Inst_Pkg.Proc
3440 -- The following pragma eliminates Inst_Pkg.Proc from Q
3441 pragma Eliminate (Q, Proc,
3442 Source_Location => "gen_pkg.ads:4[q.adb:3]");
3446 @node Pragma Enable_Atomic_Synchronization,Pragma Export_Function,Pragma Eliminate,Implementation Defined Pragmas
3447 @anchor{gnat_rm/implementation_defined_pragmas pragma-enable-atomic-synchronization}@anchor{61}
3448 @section Pragma Enable_Atomic_Synchronization
3451 @geindex Atomic Synchronization
3456 pragma Enable_Atomic_Synchronization [(Entity)];
3459 Ada requires that accesses (reads or writes) of an atomic variable be
3460 regarded as synchronization points in the case of multiple tasks.
3461 Particularly in the case of multi-processors this may require special
3462 handling, e.g. the generation of memory barriers. This synchronization
3463 is performed by default, but can be turned off using
3464 @code{pragma Disable_Atomic_Synchronization}. The
3465 @code{Enable_Atomic_Synchronization} pragma can be used to turn
3468 The placement and scope rules for this pragma are the same as those
3469 for @code{pragma Unsuppress}. In particular it can be used as a
3470 configuration pragma, or in a declaration sequence where it applies
3471 till the end of the scope. If an @code{Entity} argument is present,
3472 the action applies only to that entity.
3474 @node Pragma Export_Function,Pragma Export_Object,Pragma Enable_Atomic_Synchronization,Implementation Defined Pragmas
3475 @anchor{gnat_rm/implementation_defined_pragmas pragma-export-function}@anchor{62}
3476 @section Pragma Export_Function
3479 @geindex Argument passing mechanisms
3484 pragma Export_Function (
3485 [Internal =>] LOCAL_NAME
3486 [, [External =>] EXTERNAL_SYMBOL]
3487 [, [Parameter_Types =>] PARAMETER_TYPES]
3488 [, [Result_Type =>] result_SUBTYPE_MARK]
3489 [, [Mechanism =>] MECHANISM]
3490 [, [Result_Mechanism =>] MECHANISM_NAME]);
3494 | static_string_EXPRESSION
3499 | TYPE_DESIGNATOR @{, TYPE_DESIGNATOR@}
3503 | subtype_Name ' Access
3507 | (MECHANISM_ASSOCIATION @{, MECHANISM_ASSOCIATION@})
3509 MECHANISM_ASSOCIATION ::=
3510 [formal_parameter_NAME =>] MECHANISM_NAME
3512 MECHANISM_NAME ::= Value | Reference
3515 Use this pragma to make a function externally callable and optionally
3516 provide information on mechanisms to be used for passing parameter and
3517 result values. We recommend, for the purposes of improving portability,
3518 this pragma always be used in conjunction with a separate pragma
3519 @code{Export}, which must precede the pragma @code{Export_Function}.
3520 GNAT does not require a separate pragma @code{Export}, but if none is
3521 present, @code{Convention Ada} is assumed, which is usually
3522 not what is wanted, so it is usually appropriate to use this
3523 pragma in conjunction with a @code{Export} or @code{Convention}
3524 pragma that specifies the desired foreign convention.
3525 Pragma @code{Export_Function}
3526 (and @code{Export}, if present) must appear in the same declarative
3527 region as the function to which they apply.
3529 The @code{internal_name} must uniquely designate the function to which the
3530 pragma applies. If more than one function name exists of this name in
3531 the declarative part you must use the @code{Parameter_Types} and
3532 @code{Result_Type} parameters to achieve the required
3533 unique designation. The @cite{subtype_mark}s in these parameters must
3534 exactly match the subtypes in the corresponding function specification,
3535 using positional notation to match parameters with subtype marks.
3536 The form with an @code{'Access} attribute can be used to match an
3537 anonymous access parameter.
3539 @geindex Suppressing external name
3541 Special treatment is given if the EXTERNAL is an explicit null
3542 string or a static string expressions that evaluates to the null
3543 string. In this case, no external name is generated. This form
3544 still allows the specification of parameter mechanisms.
3546 @node Pragma Export_Object,Pragma Export_Procedure,Pragma Export_Function,Implementation Defined Pragmas
3547 @anchor{gnat_rm/implementation_defined_pragmas pragma-export-object}@anchor{63}
3548 @section Pragma Export_Object
3554 pragma Export_Object
3555 [Internal =>] LOCAL_NAME
3556 [, [External =>] EXTERNAL_SYMBOL]
3557 [, [Size =>] EXTERNAL_SYMBOL]
3561 | static_string_EXPRESSION
3564 This pragma designates an object as exported, and apart from the
3565 extended rules for external symbols, is identical in effect to the use of
3566 the normal @code{Export} pragma applied to an object. You may use a
3567 separate Export pragma (and you probably should from the point of view
3568 of portability), but it is not required. @code{Size} is syntax checked,
3569 but otherwise ignored by GNAT.
3571 @node Pragma Export_Procedure,Pragma Export_Value,Pragma Export_Object,Implementation Defined Pragmas
3572 @anchor{gnat_rm/implementation_defined_pragmas pragma-export-procedure}@anchor{64}
3573 @section Pragma Export_Procedure
3579 pragma Export_Procedure (
3580 [Internal =>] LOCAL_NAME
3581 [, [External =>] EXTERNAL_SYMBOL]
3582 [, [Parameter_Types =>] PARAMETER_TYPES]
3583 [, [Mechanism =>] MECHANISM]);
3587 | static_string_EXPRESSION
3592 | TYPE_DESIGNATOR @{, TYPE_DESIGNATOR@}
3596 | subtype_Name ' Access
3600 | (MECHANISM_ASSOCIATION @{, MECHANISM_ASSOCIATION@})
3602 MECHANISM_ASSOCIATION ::=
3603 [formal_parameter_NAME =>] MECHANISM_NAME
3605 MECHANISM_NAME ::= Value | Reference
3608 This pragma is identical to @code{Export_Function} except that it
3609 applies to a procedure rather than a function and the parameters
3610 @code{Result_Type} and @code{Result_Mechanism} are not permitted.
3611 GNAT does not require a separate pragma @code{Export}, but if none is
3612 present, @code{Convention Ada} is assumed, which is usually
3613 not what is wanted, so it is usually appropriate to use this
3614 pragma in conjunction with a @code{Export} or @code{Convention}
3615 pragma that specifies the desired foreign convention.
3617 @geindex Suppressing external name
3619 Special treatment is given if the EXTERNAL is an explicit null
3620 string or a static string expressions that evaluates to the null
3621 string. In this case, no external name is generated. This form
3622 still allows the specification of parameter mechanisms.
3624 @node Pragma Export_Value,Pragma Export_Valued_Procedure,Pragma Export_Procedure,Implementation Defined Pragmas
3625 @anchor{gnat_rm/implementation_defined_pragmas pragma-export-value}@anchor{65}
3626 @section Pragma Export_Value
3632 pragma Export_Value (
3633 [Value =>] static_integer_EXPRESSION,
3634 [Link_Name =>] static_string_EXPRESSION);
3637 This pragma serves to export a static integer value for external use.
3638 The first argument specifies the value to be exported. The Link_Name
3639 argument specifies the symbolic name to be associated with the integer
3640 value. This pragma is useful for defining a named static value in Ada
3641 that can be referenced in assembly language units to be linked with
3642 the application. This pragma is currently supported only for the
3643 AAMP target and is ignored for other targets.
3645 @node Pragma Export_Valued_Procedure,Pragma Extend_System,Pragma Export_Value,Implementation Defined Pragmas
3646 @anchor{gnat_rm/implementation_defined_pragmas pragma-export-valued-procedure}@anchor{66}
3647 @section Pragma Export_Valued_Procedure
3653 pragma Export_Valued_Procedure (
3654 [Internal =>] LOCAL_NAME
3655 [, [External =>] EXTERNAL_SYMBOL]
3656 [, [Parameter_Types =>] PARAMETER_TYPES]
3657 [, [Mechanism =>] MECHANISM]);
3661 | static_string_EXPRESSION
3666 | TYPE_DESIGNATOR @{, TYPE_DESIGNATOR@}
3670 | subtype_Name ' Access
3674 | (MECHANISM_ASSOCIATION @{, MECHANISM_ASSOCIATION@})
3676 MECHANISM_ASSOCIATION ::=
3677 [formal_parameter_NAME =>] MECHANISM_NAME
3679 MECHANISM_NAME ::= Value | Reference
3682 This pragma is identical to @code{Export_Procedure} except that the
3683 first parameter of @code{LOCAL_NAME}, which must be present, must be of
3684 mode @code{out}, and externally the subprogram is treated as a function
3685 with this parameter as the result of the function. GNAT provides for
3686 this capability to allow the use of @code{out} and @code{in out}
3687 parameters in interfacing to external functions (which are not permitted
3689 GNAT does not require a separate pragma @code{Export}, but if none is
3690 present, @code{Convention Ada} is assumed, which is almost certainly
3691 not what is wanted since the whole point of this pragma is to interface
3692 with foreign language functions, so it is usually appropriate to use this
3693 pragma in conjunction with a @code{Export} or @code{Convention}
3694 pragma that specifies the desired foreign convention.
3696 @geindex Suppressing external name
3698 Special treatment is given if the EXTERNAL is an explicit null
3699 string or a static string expressions that evaluates to the null
3700 string. In this case, no external name is generated. This form
3701 still allows the specification of parameter mechanisms.
3703 @node Pragma Extend_System,Pragma Extensions_Allowed,Pragma Export_Valued_Procedure,Implementation Defined Pragmas
3704 @anchor{gnat_rm/implementation_defined_pragmas pragma-extend-system}@anchor{67}
3705 @section Pragma Extend_System
3716 pragma Extend_System ([Name =>] IDENTIFIER);
3719 This pragma is used to provide backwards compatibility with other
3720 implementations that extend the facilities of package @code{System}. In
3721 GNAT, @code{System} contains only the definitions that are present in
3722 the Ada RM. However, other implementations, notably the DEC Ada 83
3723 implementation, provide many extensions to package @code{System}.
3725 For each such implementation accommodated by this pragma, GNAT provides a
3726 package @code{Aux_@emph{xxx}}, e.g., @code{Aux_DEC} for the DEC Ada 83
3727 implementation, which provides the required additional definitions. You
3728 can use this package in two ways. You can @code{with} it in the normal
3729 way and access entities either by selection or using a @code{use}
3730 clause. In this case no special processing is required.
3732 However, if existing code contains references such as
3733 @code{System.@emph{xxx}} where @emph{xxx} is an entity in the extended
3734 definitions provided in package @code{System}, you may use this pragma
3735 to extend visibility in @code{System} in a non-standard way that
3736 provides greater compatibility with the existing code. Pragma
3737 @code{Extend_System} is a configuration pragma whose single argument is
3738 the name of the package containing the extended definition
3739 (e.g., @code{Aux_DEC} for the DEC Ada case). A unit compiled under
3740 control of this pragma will be processed using special visibility
3741 processing that looks in package @code{System.Aux_@emph{xxx}} where
3742 @code{Aux_@emph{xxx}} is the pragma argument for any entity referenced in
3743 package @code{System}, but not found in package @code{System}.
3745 You can use this pragma either to access a predefined @code{System}
3746 extension supplied with the compiler, for example @code{Aux_DEC} or
3747 you can construct your own extension unit following the above
3748 definition. Note that such a package is a child of @code{System}
3749 and thus is considered part of the implementation.
3750 To compile it you will have to use the @emph{-gnatg} switch
3751 for compiling System units, as explained in the
3754 @node Pragma Extensions_Allowed,Pragma Extensions_Visible,Pragma Extend_System,Implementation Defined Pragmas
3755 @anchor{gnat_rm/implementation_defined_pragmas pragma-extensions-allowed}@anchor{68}
3756 @section Pragma Extensions_Allowed
3759 @geindex Ada Extensions
3761 @geindex GNAT Extensions
3766 pragma Extensions_Allowed (On | Off);
3769 This configuration pragma enables or disables the implementation
3770 extension mode (the use of Off as a parameter cancels the effect
3771 of the @emph{-gnatX} command switch).
3773 In extension mode, the latest version of the Ada language is
3774 implemented (currently Ada 2012), and in addition a small number
3775 of GNAT specific extensions are recognized as follows:
3780 @item @emph{Constrained attribute for generic objects}
3782 The @code{Constrained} attribute is permitted for objects of
3783 generic types. The result indicates if the corresponding actual
3787 @node Pragma Extensions_Visible,Pragma External,Pragma Extensions_Allowed,Implementation Defined Pragmas
3788 @anchor{gnat_rm/implementation_defined_pragmas id12}@anchor{69}@anchor{gnat_rm/implementation_defined_pragmas pragma-extensions-visible}@anchor{6a}
3789 @section Pragma Extensions_Visible
3795 pragma Extensions_Visible [ (boolean_EXPRESSION) ];
3798 For the semantics of this pragma, see the entry for aspect @code{Extensions_Visible}
3799 in the SPARK 2014 Reference Manual, section 6.1.7.
3801 @node Pragma External,Pragma External_Name_Casing,Pragma Extensions_Visible,Implementation Defined Pragmas
3802 @anchor{gnat_rm/implementation_defined_pragmas pragma-external}@anchor{6b}
3803 @section Pragma External
3810 [ Convention =>] convention_IDENTIFIER,
3811 [ Entity =>] LOCAL_NAME
3812 [, [External_Name =>] static_string_EXPRESSION ]
3813 [, [Link_Name =>] static_string_EXPRESSION ]);
3816 This pragma is identical in syntax and semantics to pragma
3817 @code{Export} as defined in the Ada Reference Manual. It is
3818 provided for compatibility with some Ada 83 compilers that
3819 used this pragma for exactly the same purposes as pragma
3820 @code{Export} before the latter was standardized.
3822 @node Pragma External_Name_Casing,Pragma Fast_Math,Pragma External,Implementation Defined Pragmas
3823 @anchor{gnat_rm/implementation_defined_pragmas pragma-external-name-casing}@anchor{6c}
3824 @section Pragma External_Name_Casing
3827 @geindex Dec Ada 83 casing compatibility
3829 @geindex External Names
3832 @geindex Casing of External names
3837 pragma External_Name_Casing (
3838 Uppercase | Lowercase
3839 [, Uppercase | Lowercase | As_Is]);
3842 This pragma provides control over the casing of external names associated
3843 with Import and Export pragmas. There are two cases to consider:
3849 Implicit external names
3851 Implicit external names are derived from identifiers. The most common case
3852 arises when a standard Ada Import or Export pragma is used with only two
3856 pragma Import (C, C_Routine);
3859 Since Ada is a case-insensitive language, the spelling of the identifier in
3860 the Ada source program does not provide any information on the desired
3861 casing of the external name, and so a convention is needed. In GNAT the
3862 default treatment is that such names are converted to all lower case
3863 letters. This corresponds to the normal C style in many environments.
3864 The first argument of pragma @code{External_Name_Casing} can be used to
3865 control this treatment. If @code{Uppercase} is specified, then the name
3866 will be forced to all uppercase letters. If @code{Lowercase} is specified,
3867 then the normal default of all lower case letters will be used.
3869 This same implicit treatment is also used in the case of extended DEC Ada 83
3870 compatible Import and Export pragmas where an external name is explicitly
3871 specified using an identifier rather than a string.
3874 Explicit external names
3876 Explicit external names are given as string literals. The most common case
3877 arises when a standard Ada Import or Export pragma is used with three
3881 pragma Import (C, C_Routine, "C_routine");
3884 In this case, the string literal normally provides the exact casing required
3885 for the external name. The second argument of pragma
3886 @code{External_Name_Casing} may be used to modify this behavior.
3887 If @code{Uppercase} is specified, then the name
3888 will be forced to all uppercase letters. If @code{Lowercase} is specified,
3889 then the name will be forced to all lowercase letters. A specification of
3890 @code{As_Is} provides the normal default behavior in which the casing is
3891 taken from the string provided.
3894 This pragma may appear anywhere that a pragma is valid. In particular, it
3895 can be used as a configuration pragma in the @code{gnat.adc} file, in which
3896 case it applies to all subsequent compilations, or it can be used as a program
3897 unit pragma, in which case it only applies to the current unit, or it can
3898 be used more locally to control individual Import/Export pragmas.
3900 It was primarily intended for use with OpenVMS systems, where many
3901 compilers convert all symbols to upper case by default. For interfacing to
3902 such compilers (e.g., the DEC C compiler), it may be convenient to use
3906 pragma External_Name_Casing (Uppercase, Uppercase);
3909 to enforce the upper casing of all external symbols.
3911 @node Pragma Fast_Math,Pragma Favor_Top_Level,Pragma External_Name_Casing,Implementation Defined Pragmas
3912 @anchor{gnat_rm/implementation_defined_pragmas pragma-fast-math}@anchor{6d}
3913 @section Pragma Fast_Math
3922 This is a configuration pragma which activates a mode in which speed is
3923 considered more important for floating-point operations than absolutely
3924 accurate adherence to the requirements of the standard. Currently the
3925 following operations are affected:
3930 @item @emph{Complex Multiplication}
3932 The normal simple formula for complex multiplication can result in intermediate
3933 overflows for numbers near the end of the range. The Ada standard requires that
3934 this situation be detected and corrected by scaling, but in Fast_Math mode such
3935 cases will simply result in overflow. Note that to take advantage of this you
3936 must instantiate your own version of @code{Ada.Numerics.Generic_Complex_Types}
3937 under control of the pragma, rather than use the preinstantiated versions.
3940 @node Pragma Favor_Top_Level,Pragma Finalize_Storage_Only,Pragma Fast_Math,Implementation Defined Pragmas
3941 @anchor{gnat_rm/implementation_defined_pragmas id13}@anchor{6e}@anchor{gnat_rm/implementation_defined_pragmas pragma-favor-top-level}@anchor{6f}
3942 @section Pragma Favor_Top_Level
3948 pragma Favor_Top_Level (type_NAME);
3951 The argument of pragma @code{Favor_Top_Level} must be a named access-to-subprogram
3952 type. This pragma is an efficiency hint to the compiler, regarding the use of
3953 @code{'Access} or @code{'Unrestricted_Access} on nested (non-library-level) subprograms.
3954 The pragma means that nested subprograms are not used with this type, or are
3955 rare, so that the generated code should be efficient in the top-level case.
3956 When this pragma is used, dynamically generated trampolines may be used on some
3957 targets for nested subprograms. See restriction @code{No_Implicit_Dynamic_Code}.
3959 @node Pragma Finalize_Storage_Only,Pragma Float_Representation,Pragma Favor_Top_Level,Implementation Defined Pragmas
3960 @anchor{gnat_rm/implementation_defined_pragmas pragma-finalize-storage-only}@anchor{70}
3961 @section Pragma Finalize_Storage_Only
3967 pragma Finalize_Storage_Only (first_subtype_LOCAL_NAME);
3970 The argument of pragma @code{Finalize_Storage_Only} must denote a local type which
3971 is derived from @code{Ada.Finalization.Controlled} or @code{Limited_Controlled}. The
3972 pragma suppresses the call to @code{Finalize} for declared library-level objects
3973 of the argument type. This is mostly useful for types where finalization is
3974 only used to deal with storage reclamation since in most environments it is
3975 not necessary to reclaim memory just before terminating execution, hence the
3976 name. Note that this pragma does not suppress Finalize calls for library-level
3977 heap-allocated objects (see pragma @code{No_Heap_Finalization}).
3979 @node Pragma Float_Representation,Pragma Ghost,Pragma Finalize_Storage_Only,Implementation Defined Pragmas
3980 @anchor{gnat_rm/implementation_defined_pragmas pragma-float-representation}@anchor{71}
3981 @section Pragma Float_Representation
3987 pragma Float_Representation (FLOAT_REP[, float_type_LOCAL_NAME]);
3989 FLOAT_REP ::= VAX_Float | IEEE_Float
3992 In the one argument form, this pragma is a configuration pragma which
3993 allows control over the internal representation chosen for the predefined
3994 floating point types declared in the packages @code{Standard} and
3995 @code{System}. This pragma is only provided for compatibility and has no effect.
3997 The two argument form specifies the representation to be used for
3998 the specified floating-point type. The argument must
3999 be @code{IEEE_Float} to specify the use of IEEE format, as follows:
4005 For a digits value of 6, 32-bit IEEE short format will be used.
4008 For a digits value of 15, 64-bit IEEE long format will be used.
4011 No other value of digits is permitted.
4014 @node Pragma Ghost,Pragma Global,Pragma Float_Representation,Implementation Defined Pragmas
4015 @anchor{gnat_rm/implementation_defined_pragmas pragma-ghost}@anchor{72}@anchor{gnat_rm/implementation_defined_pragmas id14}@anchor{73}
4016 @section Pragma Ghost
4022 pragma Ghost [ (boolean_EXPRESSION) ];
4025 For the semantics of this pragma, see the entry for aspect @code{Ghost} in the SPARK
4026 2014 Reference Manual, section 6.9.
4028 @node Pragma Global,Pragma Ident,Pragma Ghost,Implementation Defined Pragmas
4029 @anchor{gnat_rm/implementation_defined_pragmas pragma-global}@anchor{74}@anchor{gnat_rm/implementation_defined_pragmas id15}@anchor{75}
4030 @section Pragma Global
4036 pragma Global (GLOBAL_SPECIFICATION);
4038 GLOBAL_SPECIFICATION ::=
4041 | (MODED_GLOBAL_LIST @{, MODED_GLOBAL_LIST@})
4043 MODED_GLOBAL_LIST ::= MODE_SELECTOR => GLOBAL_LIST
4045 MODE_SELECTOR ::= In_Out | Input | Output | Proof_In
4046 GLOBAL_LIST ::= GLOBAL_ITEM | (GLOBAL_ITEM @{, GLOBAL_ITEM@})
4047 GLOBAL_ITEM ::= NAME
4050 For the semantics of this pragma, see the entry for aspect @code{Global} in the
4051 SPARK 2014 Reference Manual, section 6.1.4.
4053 @node Pragma Ident,Pragma Ignore_Pragma,Pragma Global,Implementation Defined Pragmas
4054 @anchor{gnat_rm/implementation_defined_pragmas pragma-ident}@anchor{76}
4055 @section Pragma Ident
4061 pragma Ident (static_string_EXPRESSION);
4064 This pragma is identical in effect to pragma @code{Comment}. It is provided
4065 for compatibility with other Ada compilers providing this pragma.
4067 @node Pragma Ignore_Pragma,Pragma Implementation_Defined,Pragma Ident,Implementation Defined Pragmas
4068 @anchor{gnat_rm/implementation_defined_pragmas pragma-ignore-pragma}@anchor{77}
4069 @section Pragma Ignore_Pragma
4075 pragma Ignore_Pragma (pragma_IDENTIFIER);
4078 This is a configuration pragma
4079 that takes a single argument that is a simple identifier. Any subsequent
4080 use of a pragma whose pragma identifier matches this argument will be
4081 silently ignored. This may be useful when legacy code or code intended
4082 for compilation with some other compiler contains pragmas that match the
4083 name, but not the exact implementation, of a GNAT pragma. The use of this
4084 pragma allows such pragmas to be ignored, which may be useful in CodePeer
4085 mode, or during porting of legacy code.
4087 @node Pragma Implementation_Defined,Pragma Implemented,Pragma Ignore_Pragma,Implementation Defined Pragmas
4088 @anchor{gnat_rm/implementation_defined_pragmas pragma-implementation-defined}@anchor{78}
4089 @section Pragma Implementation_Defined
4095 pragma Implementation_Defined (local_NAME);
4098 This pragma marks a previously declared entity as implementation-defined.
4099 For an overloaded entity, applies to the most recent homonym.
4102 pragma Implementation_Defined;
4105 The form with no arguments appears anywhere within a scope, most
4106 typically a package spec, and indicates that all entities that are
4107 defined within the package spec are Implementation_Defined.
4109 This pragma is used within the GNAT runtime library to identify
4110 implementation-defined entities introduced in language-defined units,
4111 for the purpose of implementing the No_Implementation_Identifiers
4114 @node Pragma Implemented,Pragma Implicit_Packing,Pragma Implementation_Defined,Implementation Defined Pragmas
4115 @anchor{gnat_rm/implementation_defined_pragmas pragma-implemented}@anchor{79}
4116 @section Pragma Implemented
4122 pragma Implemented (procedure_LOCAL_NAME, implementation_kind);
4124 implementation_kind ::= By_Entry | By_Protected_Procedure | By_Any
4127 This is an Ada 2012 representation pragma which applies to protected, task
4128 and synchronized interface primitives. The use of pragma Implemented provides
4129 a way to impose a static requirement on the overriding operation by adhering
4130 to one of the three implementation kinds: entry, protected procedure or any of
4131 the above. This pragma is available in all earlier versions of Ada as an
4132 implementation-defined pragma.
4135 type Synch_Iface is synchronized interface;
4136 procedure Prim_Op (Obj : in out Iface) is abstract;
4137 pragma Implemented (Prim_Op, By_Protected_Procedure);
4139 protected type Prot_1 is new Synch_Iface with
4140 procedure Prim_Op; -- Legal
4143 protected type Prot_2 is new Synch_Iface with
4144 entry Prim_Op; -- Illegal
4147 task type Task_Typ is new Synch_Iface with
4148 entry Prim_Op; -- Illegal
4152 When applied to the procedure_or_entry_NAME of a requeue statement, pragma
4153 Implemented determines the runtime behavior of the requeue. Implementation kind
4154 By_Entry guarantees that the action of requeueing will proceed from an entry to
4155 another entry. Implementation kind By_Protected_Procedure transforms the
4156 requeue into a dispatching call, thus eliminating the chance of blocking. Kind
4157 By_Any shares the behavior of By_Entry and By_Protected_Procedure depending on
4158 the target's overriding subprogram kind.
4160 @node Pragma Implicit_Packing,Pragma Import_Function,Pragma Implemented,Implementation Defined Pragmas
4161 @anchor{gnat_rm/implementation_defined_pragmas pragma-implicit-packing}@anchor{7a}
4162 @section Pragma Implicit_Packing
4165 @geindex Rational Profile
4170 pragma Implicit_Packing;
4173 This is a configuration pragma that requests implicit packing for packed
4174 arrays for which a size clause is given but no explicit pragma Pack or
4175 specification of Component_Size is present. It also applies to records
4176 where no record representation clause is present. Consider this example:
4179 type R is array (0 .. 7) of Boolean;
4183 In accordance with the recommendation in the RM (RM 13.3(53)), a Size clause
4184 does not change the layout of a composite object. So the Size clause in the
4185 above example is normally rejected, since the default layout of the array uses
4186 8-bit components, and thus the array requires a minimum of 64 bits.
4188 If this declaration is compiled in a region of code covered by an occurrence
4189 of the configuration pragma Implicit_Packing, then the Size clause in this
4190 and similar examples will cause implicit packing and thus be accepted. For
4191 this implicit packing to occur, the type in question must be an array of small
4192 components whose size is known at compile time, and the Size clause must
4193 specify the exact size that corresponds to the number of elements in the array
4194 multiplied by the size in bits of the component type (both single and
4195 multi-dimensioned arrays can be controlled with this pragma).
4197 @geindex Array packing
4199 Similarly, the following example shows the use in the record case
4203 a, b, c, d, e, f, g, h : boolean;
4209 Without a pragma Pack, each Boolean field requires 8 bits, so the
4210 minimum size is 72 bits, but with a pragma Pack, 16 bits would be
4211 sufficient. The use of pragma Implicit_Packing allows this record
4212 declaration to compile without an explicit pragma Pack.
4214 @node Pragma Import_Function,Pragma Import_Object,Pragma Implicit_Packing,Implementation Defined Pragmas
4215 @anchor{gnat_rm/implementation_defined_pragmas pragma-import-function}@anchor{7b}
4216 @section Pragma Import_Function
4222 pragma Import_Function (
4223 [Internal =>] LOCAL_NAME,
4224 [, [External =>] EXTERNAL_SYMBOL]
4225 [, [Parameter_Types =>] PARAMETER_TYPES]
4226 [, [Result_Type =>] SUBTYPE_MARK]
4227 [, [Mechanism =>] MECHANISM]
4228 [, [Result_Mechanism =>] MECHANISM_NAME]);
4232 | static_string_EXPRESSION
4236 | TYPE_DESIGNATOR @{, TYPE_DESIGNATOR@}
4240 | subtype_Name ' Access
4244 | (MECHANISM_ASSOCIATION @{, MECHANISM_ASSOCIATION@})
4246 MECHANISM_ASSOCIATION ::=
4247 [formal_parameter_NAME =>] MECHANISM_NAME
4254 This pragma is used in conjunction with a pragma @code{Import} to
4255 specify additional information for an imported function. The pragma
4256 @code{Import} (or equivalent pragma @code{Interface}) must precede the
4257 @code{Import_Function} pragma and both must appear in the same
4258 declarative part as the function specification.
4260 The @code{Internal} argument must uniquely designate
4261 the function to which the
4262 pragma applies. If more than one function name exists of this name in
4263 the declarative part you must use the @code{Parameter_Types} and
4264 @code{Result_Type} parameters to achieve the required unique
4265 designation. Subtype marks in these parameters must exactly match the
4266 subtypes in the corresponding function specification, using positional
4267 notation to match parameters with subtype marks.
4268 The form with an @code{'Access} attribute can be used to match an
4269 anonymous access parameter.
4271 You may optionally use the @code{Mechanism} and @code{Result_Mechanism}
4272 parameters to specify passing mechanisms for the
4273 parameters and result. If you specify a single mechanism name, it
4274 applies to all parameters. Otherwise you may specify a mechanism on a
4275 parameter by parameter basis using either positional or named
4276 notation. If the mechanism is not specified, the default mechanism
4279 @node Pragma Import_Object,Pragma Import_Procedure,Pragma Import_Function,Implementation Defined Pragmas
4280 @anchor{gnat_rm/implementation_defined_pragmas pragma-import-object}@anchor{7c}
4281 @section Pragma Import_Object
4287 pragma Import_Object
4288 [Internal =>] LOCAL_NAME
4289 [, [External =>] EXTERNAL_SYMBOL]
4290 [, [Size =>] EXTERNAL_SYMBOL]);
4294 | static_string_EXPRESSION
4297 This pragma designates an object as imported, and apart from the
4298 extended rules for external symbols, is identical in effect to the use of
4299 the normal @code{Import} pragma applied to an object. Unlike the
4300 subprogram case, you need not use a separate @code{Import} pragma,
4301 although you may do so (and probably should do so from a portability
4302 point of view). @code{size} is syntax checked, but otherwise ignored by
4305 @node Pragma Import_Procedure,Pragma Import_Valued_Procedure,Pragma Import_Object,Implementation Defined Pragmas
4306 @anchor{gnat_rm/implementation_defined_pragmas pragma-import-procedure}@anchor{7d}
4307 @section Pragma Import_Procedure
4313 pragma Import_Procedure (
4314 [Internal =>] LOCAL_NAME
4315 [, [External =>] EXTERNAL_SYMBOL]
4316 [, [Parameter_Types =>] PARAMETER_TYPES]
4317 [, [Mechanism =>] MECHANISM]);
4321 | static_string_EXPRESSION
4325 | TYPE_DESIGNATOR @{, TYPE_DESIGNATOR@}
4329 | subtype_Name ' Access
4333 | (MECHANISM_ASSOCIATION @{, MECHANISM_ASSOCIATION@})
4335 MECHANISM_ASSOCIATION ::=
4336 [formal_parameter_NAME =>] MECHANISM_NAME
4338 MECHANISM_NAME ::= Value | Reference
4341 This pragma is identical to @code{Import_Function} except that it
4342 applies to a procedure rather than a function and the parameters
4343 @code{Result_Type} and @code{Result_Mechanism} are not permitted.
4345 @node Pragma Import_Valued_Procedure,Pragma Independent,Pragma Import_Procedure,Implementation Defined Pragmas
4346 @anchor{gnat_rm/implementation_defined_pragmas pragma-import-valued-procedure}@anchor{7e}
4347 @section Pragma Import_Valued_Procedure
4353 pragma Import_Valued_Procedure (
4354 [Internal =>] LOCAL_NAME
4355 [, [External =>] EXTERNAL_SYMBOL]
4356 [, [Parameter_Types =>] PARAMETER_TYPES]
4357 [, [Mechanism =>] MECHANISM]);
4361 | static_string_EXPRESSION
4365 | TYPE_DESIGNATOR @{, TYPE_DESIGNATOR@}
4369 | subtype_Name ' Access
4373 | (MECHANISM_ASSOCIATION @{, MECHANISM_ASSOCIATION@})
4375 MECHANISM_ASSOCIATION ::=
4376 [formal_parameter_NAME =>] MECHANISM_NAME
4378 MECHANISM_NAME ::= Value | Reference
4381 This pragma is identical to @code{Import_Procedure} except that the
4382 first parameter of @code{LOCAL_NAME}, which must be present, must be of
4383 mode @code{out}, and externally the subprogram is treated as a function
4384 with this parameter as the result of the function. The purpose of this
4385 capability is to allow the use of @code{out} and @code{in out}
4386 parameters in interfacing to external functions (which are not permitted
4387 in Ada functions). You may optionally use the @code{Mechanism}
4388 parameters to specify passing mechanisms for the parameters.
4389 If you specify a single mechanism name, it applies to all parameters.
4390 Otherwise you may specify a mechanism on a parameter by parameter
4391 basis using either positional or named notation. If the mechanism is not
4392 specified, the default mechanism is used.
4394 Note that it is important to use this pragma in conjunction with a separate
4395 pragma Import that specifies the desired convention, since otherwise the
4396 default convention is Ada, which is almost certainly not what is required.
4398 @node Pragma Independent,Pragma Independent_Components,Pragma Import_Valued_Procedure,Implementation Defined Pragmas
4399 @anchor{gnat_rm/implementation_defined_pragmas pragma-independent}@anchor{7f}
4400 @section Pragma Independent
4406 pragma Independent (Local_NAME);
4409 This pragma is standard in Ada 2012 mode (which also provides an aspect
4410 of the same name). It is also available as an implementation-defined
4411 pragma in all earlier versions. It specifies that the
4412 designated object or all objects of the designated type must be
4413 independently addressable. This means that separate tasks can safely
4414 manipulate such objects. For example, if two components of a record are
4415 independent, then two separate tasks may access these two components.
4417 constraints on the representation of the object (for instance prohibiting
4420 @node Pragma Independent_Components,Pragma Initial_Condition,Pragma Independent,Implementation Defined Pragmas
4421 @anchor{gnat_rm/implementation_defined_pragmas pragma-independent-components}@anchor{80}
4422 @section Pragma Independent_Components
4428 pragma Independent_Components (Local_NAME);
4431 This pragma is standard in Ada 2012 mode (which also provides an aspect
4432 of the same name). It is also available as an implementation-defined
4433 pragma in all earlier versions. It specifies that the components of the
4434 designated object, or the components of each object of the designated
4436 independently addressable. This means that separate tasks can safely
4437 manipulate separate components in the composite object. This may place
4438 constraints on the representation of the object (for instance prohibiting
4441 @node Pragma Initial_Condition,Pragma Initialize_Scalars,Pragma Independent_Components,Implementation Defined Pragmas
4442 @anchor{gnat_rm/implementation_defined_pragmas id16}@anchor{81}@anchor{gnat_rm/implementation_defined_pragmas pragma-initial-condition}@anchor{82}
4443 @section Pragma Initial_Condition
4449 pragma Initial_Condition (boolean_EXPRESSION);
4452 For the semantics of this pragma, see the entry for aspect @code{Initial_Condition}
4453 in the SPARK 2014 Reference Manual, section 7.1.6.
4455 @node Pragma Initialize_Scalars,Pragma Initializes,Pragma Initial_Condition,Implementation Defined Pragmas
4456 @anchor{gnat_rm/implementation_defined_pragmas pragma-initialize-scalars}@anchor{83}
4457 @section Pragma Initialize_Scalars
4460 @geindex debugging with Initialize_Scalars
4465 pragma Initialize_Scalars
4466 [ ( TYPE_VALUE_PAIR @{, TYPE_VALUE_PAIR@} ) ];
4469 SCALAR_TYPE => static_EXPRESSION
4486 This pragma is similar to @code{Normalize_Scalars} conceptually but has two
4487 important differences.
4489 First, there is no requirement for the pragma to be used uniformly in all units
4490 of a partition. In particular, it is fine to use this just for some or all of
4491 the application units of a partition, without needing to recompile the run-time
4492 library. In the case where some units are compiled with the pragma, and some
4493 without, then a declaration of a variable where the type is defined in package
4494 Standard or is locally declared will always be subject to initialization, as
4495 will any declaration of a scalar variable. For composite variables, whether the
4496 variable is initialized may also depend on whether the package in which the
4497 type of the variable is declared is compiled with the pragma.
4499 The other important difference is that the programmer can control the value
4500 used for initializing scalar objects. This effect can be achieved in several
4507 At compile time, the programmer can specify the invalid value for a
4508 particular family of scalar types using the optional arguments of the pragma.
4510 The compile-time approach is intended to optimize the generated code for the
4511 pragma, by possibly using fast operations such as @code{memset}. Note that such
4512 optimizations require using values where the bytes all have the same binary
4516 At bind time, the programmer has several options:
4522 Initialization with invalid values (similar to Normalize_Scalars, though
4523 for Initialize_Scalars it is not always possible to determine the invalid
4524 values in complex cases like signed component fields with nonstandard
4528 Initialization with high values.
4531 Initialization with low values.
4534 Initialization with a specific bit pattern.
4537 See the GNAT User's Guide for binder options for specifying these cases.
4539 The bind-time approach is intended to provide fast turnaround for testing
4540 with different values, without having to recompile the program.
4543 At execution time, the programmer can specify the invalid values using an
4544 environment variable. See the GNAT User's Guide for details.
4546 The execution-time approach is intended to provide fast turnaround for
4547 testing with different values, without having to recompile and rebind the
4551 Note that pragma @code{Initialize_Scalars} is particularly useful in conjunction
4552 with the enhanced validity checking that is now provided in GNAT, which checks
4553 for invalid values under more conditions. Using this feature (see description
4554 of the @emph{-gnatV} flag in the GNAT User's Guide) in conjunction with pragma
4555 @code{Initialize_Scalars} provides a powerful new tool to assist in the detection
4556 of problems caused by uninitialized variables.
4558 Note: the use of @code{Initialize_Scalars} has a fairly extensive effect on the
4559 generated code. This may cause your code to be substantially larger. It may
4560 also cause an increase in the amount of stack required, so it is probably a
4561 good idea to turn on stack checking (see description of stack checking in the
4562 GNAT User's Guide) when using this pragma.
4564 @node Pragma Initializes,Pragma Inline_Always,Pragma Initialize_Scalars,Implementation Defined Pragmas
4565 @anchor{gnat_rm/implementation_defined_pragmas pragma-initializes}@anchor{84}@anchor{gnat_rm/implementation_defined_pragmas id17}@anchor{85}
4566 @section Pragma Initializes
4572 pragma Initializes (INITIALIZATION_LIST);
4574 INITIALIZATION_LIST ::=
4576 | (INITIALIZATION_ITEM @{, INITIALIZATION_ITEM@})
4578 INITIALIZATION_ITEM ::= name [=> INPUT_LIST]
4583 | (INPUT @{, INPUT@})
4588 For the semantics of this pragma, see the entry for aspect @code{Initializes} in the
4589 SPARK 2014 Reference Manual, section 7.1.5.
4591 @node Pragma Inline_Always,Pragma Inline_Generic,Pragma Initializes,Implementation Defined Pragmas
4592 @anchor{gnat_rm/implementation_defined_pragmas id18}@anchor{86}@anchor{gnat_rm/implementation_defined_pragmas pragma-inline-always}@anchor{87}
4593 @section Pragma Inline_Always
4599 pragma Inline_Always (NAME [, NAME]);
4602 Similar to pragma @code{Inline} except that inlining is unconditional.
4603 Inline_Always instructs the compiler to inline every direct call to the
4604 subprogram or else to emit a compilation error, independently of any
4605 option, in particular @emph{-gnatn} or @emph{-gnatN} or the optimization level.
4606 It is an error to take the address or access of @code{NAME}. It is also an error to
4607 apply this pragma to a primitive operation of a tagged type. Thanks to such
4608 restrictions, the compiler is allowed to remove the out-of-line body of @code{NAME}.
4610 @node Pragma Inline_Generic,Pragma Interface,Pragma Inline_Always,Implementation Defined Pragmas
4611 @anchor{gnat_rm/implementation_defined_pragmas pragma-inline-generic}@anchor{88}
4612 @section Pragma Inline_Generic
4618 pragma Inline_Generic (GNAME @{, GNAME@});
4620 GNAME ::= generic_unit_NAME | generic_instance_NAME
4623 This pragma is provided for compatibility with Dec Ada 83. It has
4624 no effect in GNAT (which always inlines generics), other
4625 than to check that the given names are all names of generic units or
4628 @node Pragma Interface,Pragma Interface_Name,Pragma Inline_Generic,Implementation Defined Pragmas
4629 @anchor{gnat_rm/implementation_defined_pragmas pragma-interface}@anchor{89}
4630 @section Pragma Interface
4637 [Convention =>] convention_identifier,
4638 [Entity =>] local_NAME
4639 [, [External_Name =>] static_string_expression]
4640 [, [Link_Name =>] static_string_expression]);
4643 This pragma is identical in syntax and semantics to
4644 the standard Ada pragma @code{Import}. It is provided for compatibility
4645 with Ada 83. The definition is upwards compatible both with pragma
4646 @code{Interface} as defined in the Ada 83 Reference Manual, and also
4647 with some extended implementations of this pragma in certain Ada 83
4648 implementations. The only difference between pragma @code{Interface}
4649 and pragma @code{Import} is that there is special circuitry to allow
4650 both pragmas to appear for the same subprogram entity (normally it
4651 is illegal to have multiple @code{Import} pragmas. This is useful in
4652 maintaining Ada 83/Ada 95 compatibility and is compatible with other
4655 @node Pragma Interface_Name,Pragma Interrupt_Handler,Pragma Interface,Implementation Defined Pragmas
4656 @anchor{gnat_rm/implementation_defined_pragmas pragma-interface-name}@anchor{8a}
4657 @section Pragma Interface_Name
4663 pragma Interface_Name (
4664 [Entity =>] LOCAL_NAME
4665 [, [External_Name =>] static_string_EXPRESSION]
4666 [, [Link_Name =>] static_string_EXPRESSION]);
4669 This pragma provides an alternative way of specifying the interface name
4670 for an interfaced subprogram, and is provided for compatibility with Ada
4671 83 compilers that use the pragma for this purpose. You must provide at
4672 least one of @code{External_Name} or @code{Link_Name}.
4674 @node Pragma Interrupt_Handler,Pragma Interrupt_State,Pragma Interface_Name,Implementation Defined Pragmas
4675 @anchor{gnat_rm/implementation_defined_pragmas pragma-interrupt-handler}@anchor{8b}
4676 @section Pragma Interrupt_Handler
4682 pragma Interrupt_Handler (procedure_LOCAL_NAME);
4685 This program unit pragma is supported for parameterless protected procedures
4686 as described in Annex C of the Ada Reference Manual. On the AAMP target
4687 the pragma can also be specified for nonprotected parameterless procedures
4688 that are declared at the library level (which includes procedures
4689 declared at the top level of a library package). In the case of AAMP,
4690 when this pragma is applied to a nonprotected procedure, the instruction
4691 @code{IERET} is generated for returns from the procedure, enabling
4692 maskable interrupts, in place of the normal return instruction.
4694 @node Pragma Interrupt_State,Pragma Invariant,Pragma Interrupt_Handler,Implementation Defined Pragmas
4695 @anchor{gnat_rm/implementation_defined_pragmas pragma-interrupt-state}@anchor{8c}
4696 @section Pragma Interrupt_State
4702 pragma Interrupt_State
4704 [State =>] SYSTEM | RUNTIME | USER);
4707 Normally certain interrupts are reserved to the implementation. Any attempt
4708 to attach an interrupt causes Program_Error to be raised, as described in
4709 RM C.3.2(22). A typical example is the @code{SIGINT} interrupt used in
4710 many systems for an @code{Ctrl-C} interrupt. Normally this interrupt is
4711 reserved to the implementation, so that @code{Ctrl-C} can be used to
4712 interrupt execution. Additionally, signals such as @code{SIGSEGV},
4713 @code{SIGABRT}, @code{SIGFPE} and @code{SIGILL} are often mapped to specific
4714 Ada exceptions, or used to implement run-time functions such as the
4715 @code{abort} statement and stack overflow checking.
4717 Pragma @code{Interrupt_State} provides a general mechanism for overriding
4718 such uses of interrupts. It subsumes the functionality of pragma
4719 @code{Unreserve_All_Interrupts}. Pragma @code{Interrupt_State} is not
4720 available on Windows. On all other platforms than VxWorks,
4721 it applies to signals; on VxWorks, it applies to vectored hardware interrupts
4722 and may be used to mark interrupts required by the board support package
4725 Interrupts can be in one of three states:
4733 The interrupt is reserved (no Ada handler can be installed), and the
4734 Ada run-time may not install a handler. As a result you are guaranteed
4735 standard system default action if this interrupt is raised. This also allows
4736 installing a low level handler via C APIs such as sigaction(), outside
4742 The interrupt is reserved (no Ada handler can be installed). The run time
4743 is allowed to install a handler for internal control purposes, but is
4744 not required to do so.
4749 The interrupt is unreserved. The user may install an Ada handler via
4750 Ada.Interrupts and pragma Interrupt_Handler or Attach_Handler to provide
4754 These states are the allowed values of the @code{State} parameter of the
4755 pragma. The @code{Name} parameter is a value of the type
4756 @code{Ada.Interrupts.Interrupt_ID}. Typically, it is a name declared in
4757 @code{Ada.Interrupts.Names}.
4759 This is a configuration pragma, and the binder will check that there
4760 are no inconsistencies between different units in a partition in how a
4761 given interrupt is specified. It may appear anywhere a pragma is legal.
4763 The effect is to move the interrupt to the specified state.
4765 By declaring interrupts to be SYSTEM, you guarantee the standard system
4766 action, such as a core dump.
4768 By declaring interrupts to be USER, you guarantee that you can install
4771 Note that certain signals on many operating systems cannot be caught and
4772 handled by applications. In such cases, the pragma is ignored. See the
4773 operating system documentation, or the value of the array @code{Reserved}
4774 declared in the spec of package @code{System.OS_Interface}.
4776 Overriding the default state of signals used by the Ada runtime may interfere
4777 with an application's runtime behavior in the cases of the synchronous signals,
4778 and in the case of the signal used to implement the @code{abort} statement.
4780 @node Pragma Invariant,Pragma Keep_Names,Pragma Interrupt_State,Implementation Defined Pragmas
4781 @anchor{gnat_rm/implementation_defined_pragmas id19}@anchor{8d}@anchor{gnat_rm/implementation_defined_pragmas pragma-invariant}@anchor{8e}
4782 @section Pragma Invariant
4789 ([Entity =>] private_type_LOCAL_NAME,
4790 [Check =>] EXPRESSION
4791 [,[Message =>] String_Expression]);
4794 This pragma provides exactly the same capabilities as the Type_Invariant aspect
4795 defined in AI05-0146-1, and in the Ada 2012 Reference Manual. The
4796 Type_Invariant aspect is fully implemented in Ada 2012 mode, but since it
4797 requires the use of the aspect syntax, which is not available except in 2012
4798 mode, it is not possible to use the Type_Invariant aspect in earlier versions
4799 of Ada. However the Invariant pragma may be used in any version of Ada. Also
4800 note that the aspect Invariant is a synonym in GNAT for the aspect
4801 Type_Invariant, but there is no pragma Type_Invariant.
4803 The pragma must appear within the visible part of the package specification,
4804 after the type to which its Entity argument appears. As with the Invariant
4805 aspect, the Check expression is not analyzed until the end of the visible
4806 part of the package, so it may contain forward references. The Message
4807 argument, if present, provides the exception message used if the invariant
4808 is violated. If no Message parameter is provided, a default message that
4809 identifies the line on which the pragma appears is used.
4811 It is permissible to have multiple Invariants for the same type entity, in
4812 which case they are and'ed together. It is permissible to use this pragma
4813 in Ada 2012 mode, but you cannot have both an invariant aspect and an
4814 invariant pragma for the same entity.
4816 For further details on the use of this pragma, see the Ada 2012 documentation
4817 of the Type_Invariant aspect.
4819 @node Pragma Keep_Names,Pragma License,Pragma Invariant,Implementation Defined Pragmas
4820 @anchor{gnat_rm/implementation_defined_pragmas pragma-keep-names}@anchor{8f}
4821 @section Pragma Keep_Names
4827 pragma Keep_Names ([On =>] enumeration_first_subtype_LOCAL_NAME);
4830 The @code{LOCAL_NAME} argument
4831 must refer to an enumeration first subtype
4832 in the current declarative part. The effect is to retain the enumeration
4833 literal names for use by @code{Image} and @code{Value} even if a global
4834 @code{Discard_Names} pragma applies. This is useful when you want to
4835 generally suppress enumeration literal names and for example you therefore
4836 use a @code{Discard_Names} pragma in the @code{gnat.adc} file, but you
4837 want to retain the names for specific enumeration types.
4839 @node Pragma License,Pragma Link_With,Pragma Keep_Names,Implementation Defined Pragmas
4840 @anchor{gnat_rm/implementation_defined_pragmas pragma-license}@anchor{90}
4841 @section Pragma License
4844 @geindex License checking
4849 pragma License (Unrestricted | GPL | Modified_GPL | Restricted);
4852 This pragma is provided to allow automated checking for appropriate license
4853 conditions with respect to the standard and modified GPL. A pragma
4854 @code{License}, which is a configuration pragma that typically appears at
4855 the start of a source file or in a separate @code{gnat.adc} file, specifies
4856 the licensing conditions of a unit as follows:
4863 This is used for a unit that can be freely used with no license restrictions.
4864 Examples of such units are public domain units, and units from the Ada
4869 This is used for a unit that is licensed under the unmodified GPL, and which
4870 therefore cannot be @code{with}ed by a restricted unit.
4874 This is used for a unit licensed under the GNAT modified GPL that includes
4875 a special exception paragraph that specifically permits the inclusion of
4876 the unit in programs without requiring the entire program to be released
4881 This is used for a unit that is restricted in that it is not permitted to
4882 depend on units that are licensed under the GPL. Typical examples are
4883 proprietary code that is to be released under more restrictive license
4884 conditions. Note that restricted units are permitted to @code{with} units
4885 which are licensed under the modified GPL (this is the whole point of the
4889 Normally a unit with no @code{License} pragma is considered to have an
4890 unknown license, and no checking is done. However, standard GNAT headers
4891 are recognized, and license information is derived from them as follows.
4893 A GNAT license header starts with a line containing 78 hyphens. The following
4894 comment text is searched for the appearance of any of the following strings.
4896 If the string 'GNU General Public License' is found, then the unit is assumed
4897 to have GPL license, unless the string 'As a special exception' follows, in
4898 which case the license is assumed to be modified GPL.
4900 If one of the strings
4901 'This specification is adapted from the Ada Semantic Interface' or
4902 'This specification is derived from the Ada Reference Manual' is found
4903 then the unit is assumed to be unrestricted.
4905 These default actions means that a program with a restricted license pragma
4906 will automatically get warnings if a GPL unit is inappropriately
4907 @code{with}ed. For example, the program:
4912 procedure Secret_Stuff is
4917 if compiled with pragma @code{License} (@code{Restricted}) in a
4918 @code{gnat.adc} file will generate the warning:
4923 >>> license of withed unit "Sem_Ch3" is incompatible
4925 2. with GNAT.Sockets;
4926 3. procedure Secret_Stuff is
4929 Here we get a warning on @code{Sem_Ch3} since it is part of the GNAT
4930 compiler and is licensed under the
4931 GPL, but no warning for @code{GNAT.Sockets} which is part of the GNAT
4932 run time, and is therefore licensed under the modified GPL.
4934 @node Pragma Link_With,Pragma Linker_Alias,Pragma License,Implementation Defined Pragmas
4935 @anchor{gnat_rm/implementation_defined_pragmas pragma-link-with}@anchor{91}
4936 @section Pragma Link_With
4942 pragma Link_With (static_string_EXPRESSION @{,static_string_EXPRESSION@});
4945 This pragma is provided for compatibility with certain Ada 83 compilers.
4946 It has exactly the same effect as pragma @code{Linker_Options} except
4947 that spaces occurring within one of the string expressions are treated
4948 as separators. For example, in the following case:
4951 pragma Link_With ("-labc -ldef");
4954 results in passing the strings @code{-labc} and @code{-ldef} as two
4955 separate arguments to the linker. In addition pragma Link_With allows
4956 multiple arguments, with the same effect as successive pragmas.
4958 @node Pragma Linker_Alias,Pragma Linker_Constructor,Pragma Link_With,Implementation Defined Pragmas
4959 @anchor{gnat_rm/implementation_defined_pragmas pragma-linker-alias}@anchor{92}
4960 @section Pragma Linker_Alias
4966 pragma Linker_Alias (
4967 [Entity =>] LOCAL_NAME,
4968 [Target =>] static_string_EXPRESSION);
4971 @code{LOCAL_NAME} must refer to an object that is declared at the library
4972 level. This pragma establishes the given entity as a linker alias for the
4973 given target. It is equivalent to @code{__attribute__((alias))} in GNU C
4974 and causes @code{LOCAL_NAME} to be emitted as an alias for the symbol
4975 @code{static_string_EXPRESSION} in the object file, that is to say no space
4976 is reserved for @code{LOCAL_NAME} by the assembler and it will be resolved
4977 to the same address as @code{static_string_EXPRESSION} by the linker.
4979 The actual linker name for the target must be used (e.g., the fully
4980 encoded name with qualification in Ada, or the mangled name in C++),
4981 or it must be declared using the C convention with @code{pragma Import}
4982 or @code{pragma Export}.
4984 Not all target machines support this pragma. On some of them it is accepted
4985 only if @code{pragma Weak_External} has been applied to @code{LOCAL_NAME}.
4988 -- Example of the use of pragma Linker_Alias
4992 pragma Export (C, i);
4994 new_name_for_i : Integer;
4995 pragma Linker_Alias (new_name_for_i, "i");
4999 @node Pragma Linker_Constructor,Pragma Linker_Destructor,Pragma Linker_Alias,Implementation Defined Pragmas
5000 @anchor{gnat_rm/implementation_defined_pragmas pragma-linker-constructor}@anchor{93}
5001 @section Pragma Linker_Constructor
5007 pragma Linker_Constructor (procedure_LOCAL_NAME);
5010 @code{procedure_LOCAL_NAME} must refer to a parameterless procedure that
5011 is declared at the library level. A procedure to which this pragma is
5012 applied will be treated as an initialization routine by the linker.
5013 It is equivalent to @code{__attribute__((constructor))} in GNU C and
5014 causes @code{procedure_LOCAL_NAME} to be invoked before the entry point
5015 of the executable is called (or immediately after the shared library is
5016 loaded if the procedure is linked in a shared library), in particular
5017 before the Ada run-time environment is set up.
5019 Because of these specific contexts, the set of operations such a procedure
5020 can perform is very limited and the type of objects it can manipulate is
5021 essentially restricted to the elementary types. In particular, it must only
5022 contain code to which pragma Restrictions (No_Elaboration_Code) applies.
5024 This pragma is used by GNAT to implement auto-initialization of shared Stand
5025 Alone Libraries, which provides a related capability without the restrictions
5026 listed above. Where possible, the use of Stand Alone Libraries is preferable
5027 to the use of this pragma.
5029 @node Pragma Linker_Destructor,Pragma Linker_Section,Pragma Linker_Constructor,Implementation Defined Pragmas
5030 @anchor{gnat_rm/implementation_defined_pragmas pragma-linker-destructor}@anchor{94}
5031 @section Pragma Linker_Destructor
5037 pragma Linker_Destructor (procedure_LOCAL_NAME);
5040 @code{procedure_LOCAL_NAME} must refer to a parameterless procedure that
5041 is declared at the library level. A procedure to which this pragma is
5042 applied will be treated as a finalization routine by the linker.
5043 It is equivalent to @code{__attribute__((destructor))} in GNU C and
5044 causes @code{procedure_LOCAL_NAME} to be invoked after the entry point
5045 of the executable has exited (or immediately before the shared library
5046 is unloaded if the procedure is linked in a shared library), in particular
5047 after the Ada run-time environment is shut down.
5049 See @code{pragma Linker_Constructor} for the set of restrictions that apply
5050 because of these specific contexts.
5052 @node Pragma Linker_Section,Pragma Lock_Free,Pragma Linker_Destructor,Implementation Defined Pragmas
5053 @anchor{gnat_rm/implementation_defined_pragmas id20}@anchor{95}@anchor{gnat_rm/implementation_defined_pragmas pragma-linker-section}@anchor{96}
5054 @section Pragma Linker_Section
5060 pragma Linker_Section (
5061 [Entity =>] LOCAL_NAME,
5062 [Section =>] static_string_EXPRESSION);
5065 @code{LOCAL_NAME} must refer to an object, type, or subprogram that is
5066 declared at the library level. This pragma specifies the name of the
5067 linker section for the given entity. It is equivalent to
5068 @code{__attribute__((section))} in GNU C and causes @code{LOCAL_NAME} to
5069 be placed in the @code{static_string_EXPRESSION} section of the
5070 executable (assuming the linker doesn't rename the section).
5071 GNAT also provides an implementation defined aspect of the same name.
5073 In the case of specifying this aspect for a type, the effect is to
5074 specify the corresponding section for all library-level objects of
5075 the type that do not have an explicit linker section set. Note that
5076 this only applies to whole objects, not to components of composite objects.
5078 In the case of a subprogram, the linker section applies to all previously
5079 declared matching overloaded subprograms in the current declarative part
5080 which do not already have a linker section assigned. The linker section
5081 aspect is useful in this case for specifying different linker sections
5082 for different elements of such an overloaded set.
5084 Note that an empty string specifies that no linker section is specified.
5085 This is not quite the same as omitting the pragma or aspect, since it
5086 can be used to specify that one element of an overloaded set of subprograms
5087 has the default linker section, or that one object of a type for which a
5088 linker section is specified should has the default linker section.
5090 The compiler normally places library-level entities in standard sections
5091 depending on the class: procedures and functions generally go in the
5092 @code{.text} section, initialized variables in the @code{.data} section
5093 and uninitialized variables in the @code{.bss} section.
5095 Other, special sections may exist on given target machines to map special
5096 hardware, for example I/O ports or flash memory. This pragma is a means to
5097 defer the final layout of the executable to the linker, thus fully working
5098 at the symbolic level with the compiler.
5100 Some file formats do not support arbitrary sections so not all target
5101 machines support this pragma. The use of this pragma may cause a program
5102 execution to be erroneous if it is used to place an entity into an
5103 inappropriate section (e.g., a modified variable into the @code{.text}
5104 section). See also @code{pragma Persistent_BSS}.
5107 -- Example of the use of pragma Linker_Section
5111 pragma Volatile (Port_A);
5112 pragma Linker_Section (Port_A, ".bss.port_a");
5115 pragma Volatile (Port_B);
5116 pragma Linker_Section (Port_B, ".bss.port_b");
5118 type Port_Type is new Integer with Linker_Section => ".bss";
5119 PA : Port_Type with Linker_Section => ".bss.PA";
5120 PB : Port_Type; -- ends up in linker section ".bss"
5122 procedure Q with Linker_Section => "Qsection";
5126 @node Pragma Lock_Free,Pragma Loop_Invariant,Pragma Linker_Section,Implementation Defined Pragmas
5127 @anchor{gnat_rm/implementation_defined_pragmas id21}@anchor{97}@anchor{gnat_rm/implementation_defined_pragmas pragma-lock-free}@anchor{98}
5128 @section Pragma Lock_Free
5132 This pragma may be specified for protected types or objects. It specifies that
5133 the implementation of protected operations must be implemented without locks.
5134 Compilation fails if the compiler cannot generate lock-free code for the
5137 The current conditions required to support this pragma are:
5143 Protected type declarations may not contain entries
5146 Protected subprogram declarations may not have nonelementary parameters
5149 In addition, each protected subprogram body must satisfy:
5155 May reference only one protected component
5158 May not reference nonconstant entities outside the protected subprogram
5162 May not contain address representation items, allocators, or quantified
5166 May not contain delay, goto, loop, or procedure-call statements.
5169 May not contain exported and imported entities
5172 May not dereferenced access values
5175 Function calls and attribute references must be static
5178 @node Pragma Loop_Invariant,Pragma Loop_Optimize,Pragma Lock_Free,Implementation Defined Pragmas
5179 @anchor{gnat_rm/implementation_defined_pragmas pragma-loop-invariant}@anchor{99}
5180 @section Pragma Loop_Invariant
5186 pragma Loop_Invariant ( boolean_EXPRESSION );
5189 The effect of this pragma is similar to that of pragma @code{Assert},
5190 except that in an @code{Assertion_Policy} pragma, the identifier
5191 @code{Loop_Invariant} is used to control whether it is ignored or checked
5194 @code{Loop_Invariant} can only appear as one of the items in the sequence
5195 of statements of a loop body, or nested inside block statements that
5196 appear in the sequence of statements of a loop body.
5197 The intention is that it be used to
5198 represent a "loop invariant" assertion, i.e. something that is true each
5199 time through the loop, and which can be used to show that the loop is
5200 achieving its purpose.
5202 Multiple @code{Loop_Invariant} and @code{Loop_Variant} pragmas that
5203 apply to the same loop should be grouped in the same sequence of
5206 To aid in writing such invariants, the special attribute @code{Loop_Entry}
5207 may be used to refer to the value of an expression on entry to the loop. This
5208 attribute can only be used within the expression of a @code{Loop_Invariant}
5209 pragma. For full details, see documentation of attribute @code{Loop_Entry}.
5211 @node Pragma Loop_Optimize,Pragma Loop_Variant,Pragma Loop_Invariant,Implementation Defined Pragmas
5212 @anchor{gnat_rm/implementation_defined_pragmas pragma-loop-optimize}@anchor{9a}
5213 @section Pragma Loop_Optimize
5219 pragma Loop_Optimize (OPTIMIZATION_HINT @{, OPTIMIZATION_HINT@});
5221 OPTIMIZATION_HINT ::= Ivdep | No_Unroll | Unroll | No_Vector | Vector
5224 This pragma must appear immediately within a loop statement. It allows the
5225 programmer to specify optimization hints for the enclosing loop. The hints
5226 are not mutually exclusive and can be freely mixed, but not all combinations
5227 will yield a sensible outcome.
5229 There are five supported optimization hints for a loop:
5237 The programmer asserts that there are no loop-carried dependencies
5238 which would prevent consecutive iterations of the loop from being
5239 executed simultaneously.
5244 The loop must not be unrolled. This is a strong hint: the compiler will not
5245 unroll a loop marked with this hint.
5250 The loop should be unrolled. This is a weak hint: the compiler will try to
5251 apply unrolling to this loop preferably to other optimizations, notably
5252 vectorization, but there is no guarantee that the loop will be unrolled.
5257 The loop must not be vectorized. This is a strong hint: the compiler will not
5258 vectorize a loop marked with this hint.
5263 The loop should be vectorized. This is a weak hint: the compiler will try to
5264 apply vectorization to this loop preferably to other optimizations, notably
5265 unrolling, but there is no guarantee that the loop will be vectorized.
5268 These hints do not remove the need to pass the appropriate switches to the
5269 compiler in order to enable the relevant optimizations, that is to say
5270 @emph{-funroll-loops} for unrolling and @emph{-ftree-vectorize} for
5273 @node Pragma Loop_Variant,Pragma Machine_Attribute,Pragma Loop_Optimize,Implementation Defined Pragmas
5274 @anchor{gnat_rm/implementation_defined_pragmas pragma-loop-variant}@anchor{9b}
5275 @section Pragma Loop_Variant
5281 pragma Loop_Variant ( LOOP_VARIANT_ITEM @{, LOOP_VARIANT_ITEM @} );
5282 LOOP_VARIANT_ITEM ::= CHANGE_DIRECTION => discrete_EXPRESSION
5283 CHANGE_DIRECTION ::= Increases | Decreases
5286 @code{Loop_Variant} can only appear as one of the items in the sequence
5287 of statements of a loop body, or nested inside block statements that
5288 appear in the sequence of statements of a loop body.
5289 It allows the specification of quantities which must always
5290 decrease or increase in successive iterations of the loop. In its simplest
5291 form, just one expression is specified, whose value must increase or decrease
5292 on each iteration of the loop.
5294 In a more complex form, multiple arguments can be given which are intepreted
5295 in a nesting lexicographic manner. For example:
5298 pragma Loop_Variant (Increases => X, Decreases => Y);
5301 specifies that each time through the loop either X increases, or X stays
5302 the same and Y decreases. A @code{Loop_Variant} pragma ensures that the
5303 loop is making progress. It can be useful in helping to show informally
5304 or prove formally that the loop always terminates.
5306 @code{Loop_Variant} is an assertion whose effect can be controlled using
5307 an @code{Assertion_Policy} with a check name of @code{Loop_Variant}. The
5308 policy can be @code{Check} to enable the loop variant check, @code{Ignore}
5309 to ignore the check (in which case the pragma has no effect on the program),
5310 or @code{Disable} in which case the pragma is not even checked for correct
5313 Multiple @code{Loop_Invariant} and @code{Loop_Variant} pragmas that
5314 apply to the same loop should be grouped in the same sequence of
5317 The @code{Loop_Entry} attribute may be used within the expressions of the
5318 @code{Loop_Variant} pragma to refer to values on entry to the loop.
5320 @node Pragma Machine_Attribute,Pragma Main,Pragma Loop_Variant,Implementation Defined Pragmas
5321 @anchor{gnat_rm/implementation_defined_pragmas pragma-machine-attribute}@anchor{9c}
5322 @section Pragma Machine_Attribute
5328 pragma Machine_Attribute (
5329 [Entity =>] LOCAL_NAME,
5330 [Attribute_Name =>] static_string_EXPRESSION
5331 [, [Info =>] static_EXPRESSION @{, static_EXPRESSION@}] );
5334 Machine-dependent attributes can be specified for types and/or
5335 declarations. This pragma is semantically equivalent to
5336 @code{__attribute__((@emph{attribute_name}))} (if @code{info} is not
5337 specified) or @code{__attribute__((@emph{attribute_name(info})))}
5338 or @code{__attribute__((@emph{attribute_name(info,...})))} in GNU C,
5339 where @emph{attribute_name} is recognized by the compiler middle-end
5340 or the @code{TARGET_ATTRIBUTE_TABLE} machine specific macro. Note
5341 that a string literal for the optional parameter @code{info} or the
5342 following ones is transformed by default into an identifier,
5343 which may make this pragma unusable for some attributes.
5344 For further information see @cite{GNU Compiler Collection (GCC) Internals}.
5346 @node Pragma Main,Pragma Main_Storage,Pragma Machine_Attribute,Implementation Defined Pragmas
5347 @anchor{gnat_rm/implementation_defined_pragmas pragma-main}@anchor{9d}
5348 @section Pragma Main
5355 (MAIN_OPTION [, MAIN_OPTION]);
5358 [Stack_Size =>] static_integer_EXPRESSION
5359 | [Task_Stack_Size_Default =>] static_integer_EXPRESSION
5360 | [Time_Slicing_Enabled =>] static_boolean_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 Main_Storage,Pragma Max_Queue_Length,Pragma Main,Implementation Defined Pragmas
5367 @anchor{gnat_rm/implementation_defined_pragmas pragma-main-storage}@anchor{9e}
5368 @section Pragma Main_Storage
5375 (MAIN_STORAGE_OPTION [, MAIN_STORAGE_OPTION]);
5377 MAIN_STORAGE_OPTION ::=
5378 [WORKING_STORAGE =>] static_SIMPLE_EXPRESSION
5379 | [TOP_GUARD =>] static_SIMPLE_EXPRESSION
5382 This pragma is provided for compatibility with OpenVMS VAX Systems. It has
5383 no effect in GNAT, other than being syntax checked.
5385 @node Pragma Max_Queue_Length,Pragma No_Body,Pragma Main_Storage,Implementation Defined Pragmas
5386 @anchor{gnat_rm/implementation_defined_pragmas id22}@anchor{9f}@anchor{gnat_rm/implementation_defined_pragmas pragma-max-queue-length}@anchor{a0}
5387 @section Pragma Max_Queue_Length
5393 pragma Max_Entry_Queue (static_integer_EXPRESSION);
5396 This pragma is used to specify the maximum callers per entry queue for
5397 individual protected entries and entry families. It accepts a single
5398 integer (-1 or more) as a parameter and must appear after the declaration of an
5401 A value of -1 represents no additional restriction on queue length.
5403 @node Pragma No_Body,Pragma No_Caching,Pragma Max_Queue_Length,Implementation Defined Pragmas
5404 @anchor{gnat_rm/implementation_defined_pragmas pragma-no-body}@anchor{a1}
5405 @section Pragma No_Body
5414 There are a number of cases in which a package spec does not require a body,
5415 and in fact a body is not permitted. GNAT will not permit the spec to be
5416 compiled if there is a body around. The pragma No_Body allows you to provide
5417 a body file, even in a case where no body is allowed. The body file must
5418 contain only comments and a single No_Body pragma. This is recognized by
5419 the compiler as indicating that no body is logically present.
5421 This is particularly useful during maintenance when a package is modified in
5422 such a way that a body needed before is no longer needed. The provision of a
5423 dummy body with a No_Body pragma ensures that there is no interference from
5424 earlier versions of the package body.
5426 @node Pragma No_Caching,Pragma No_Component_Reordering,Pragma No_Body,Implementation Defined Pragmas
5427 @anchor{gnat_rm/implementation_defined_pragmas pragma-no-caching}@anchor{a2}@anchor{gnat_rm/implementation_defined_pragmas id23}@anchor{a3}
5428 @section Pragma No_Caching
5434 pragma No_Caching [ (boolean_EXPRESSION) ];
5437 For the semantics of this pragma, see the entry for aspect @code{No_Caching} in
5438 the SPARK 2014 Reference Manual, section 7.1.2.
5440 @node Pragma No_Component_Reordering,Pragma No_Elaboration_Code_All,Pragma No_Caching,Implementation Defined Pragmas
5441 @anchor{gnat_rm/implementation_defined_pragmas pragma-no-component-reordering}@anchor{a4}
5442 @section Pragma No_Component_Reordering
5448 pragma No_Component_Reordering [([Entity =>] type_LOCAL_NAME)];
5451 @code{type_LOCAL_NAME} must refer to a record type declaration in the current
5452 declarative part. The effect is to preclude any reordering of components
5453 for the layout of the record, i.e. the record is laid out by the compiler
5454 in the order in which the components are declared textually. The form with
5455 no argument is a configuration pragma which applies to all record types
5456 declared in units to which the pragma applies and there is a requirement
5457 that this pragma be used consistently within a partition.
5459 @node Pragma No_Elaboration_Code_All,Pragma No_Heap_Finalization,Pragma No_Component_Reordering,Implementation Defined Pragmas
5460 @anchor{gnat_rm/implementation_defined_pragmas id24}@anchor{a5}@anchor{gnat_rm/implementation_defined_pragmas pragma-no-elaboration-code-all}@anchor{a6}
5461 @section Pragma No_Elaboration_Code_All
5467 pragma No_Elaboration_Code_All [(program_unit_NAME)];
5470 This is a program unit pragma (there is also an equivalent aspect of the
5471 same name) that establishes the restriction @code{No_Elaboration_Code} for
5472 the current unit and any extended main source units (body and subunits).
5473 It also has the effect of enforcing a transitive application of this
5474 aspect, so that if any unit is implicitly or explicitly with'ed by the
5475 current unit, it must also have the No_Elaboration_Code_All aspect set.
5476 It may be applied to package or subprogram specs or their generic versions.
5478 @node Pragma No_Heap_Finalization,Pragma No_Inline,Pragma No_Elaboration_Code_All,Implementation Defined Pragmas
5479 @anchor{gnat_rm/implementation_defined_pragmas pragma-no-heap-finalization}@anchor{a7}
5480 @section Pragma No_Heap_Finalization
5486 pragma No_Heap_Finalization [ (first_subtype_LOCAL_NAME) ];
5489 Pragma @code{No_Heap_Finalization} may be used as a configuration pragma or as a
5490 type-specific pragma.
5492 In its configuration form, the pragma must appear within a configuration file
5493 such as gnat.adc, without an argument. The pragma suppresses the call to
5494 @code{Finalize} for heap-allocated objects created through library-level named
5495 access-to-object types in cases where the designated type requires finalization
5498 In its type-specific form, the argument of the pragma must denote a
5499 library-level named access-to-object type. The pragma suppresses the call to
5500 @code{Finalize} for heap-allocated objects created through the specific access type
5501 in cases where the designated type requires finalization actions.
5503 It is still possible to finalize such heap-allocated objects by explicitly
5506 A library-level named access-to-object type declared within a generic unit will
5507 lose its @code{No_Heap_Finalization} pragma when the corresponding instance does not
5508 appear at the library level.
5510 @node Pragma No_Inline,Pragma No_Return,Pragma No_Heap_Finalization,Implementation Defined Pragmas
5511 @anchor{gnat_rm/implementation_defined_pragmas id25}@anchor{a8}@anchor{gnat_rm/implementation_defined_pragmas pragma-no-inline}@anchor{a9}
5512 @section Pragma No_Inline
5518 pragma No_Inline (NAME @{, NAME@});
5521 This pragma suppresses inlining for the callable entity or the instances of
5522 the generic subprogram designated by @code{NAME}, including inlining that
5523 results from the use of pragma @code{Inline}. This pragma is always active,
5524 in particular it is not subject to the use of option @emph{-gnatn} or
5525 @emph{-gnatN}. It is illegal to specify both pragma @code{No_Inline} and
5526 pragma @code{Inline_Always} for the same @code{NAME}.
5528 @node Pragma No_Return,Pragma No_Strict_Aliasing,Pragma No_Inline,Implementation Defined Pragmas
5529 @anchor{gnat_rm/implementation_defined_pragmas pragma-no-return}@anchor{aa}
5530 @section Pragma No_Return
5536 pragma No_Return (procedure_LOCAL_NAME @{, procedure_LOCAL_NAME@});
5539 Each @code{procedure_LOCAL_NAME} argument must refer to one or more procedure
5540 declarations in the current declarative part. A procedure to which this
5541 pragma is applied may not contain any explicit @code{return} statements.
5542 In addition, if the procedure contains any implicit returns from falling
5543 off the end of a statement sequence, then execution of that implicit
5544 return will cause Program_Error to be raised.
5546 One use of this pragma is to identify procedures whose only purpose is to raise
5547 an exception. Another use of this pragma is to suppress incorrect warnings
5548 about missing returns in functions, where the last statement of a function
5549 statement sequence is a call to such a procedure.
5551 Note that in Ada 2005 mode, this pragma is part of the language. It is
5552 available in all earlier versions of Ada as an implementation-defined
5555 @node Pragma No_Strict_Aliasing,Pragma No_Tagged_Streams,Pragma No_Return,Implementation Defined Pragmas
5556 @anchor{gnat_rm/implementation_defined_pragmas pragma-no-strict-aliasing}@anchor{ab}
5557 @section Pragma No_Strict_Aliasing
5563 pragma No_Strict_Aliasing [([Entity =>] type_LOCAL_NAME)];
5566 @code{type_LOCAL_NAME} must refer to an access type
5567 declaration in the current declarative part. The effect is to inhibit
5568 strict aliasing optimization for the given type. The form with no
5569 arguments is a configuration pragma which applies to all access types
5570 declared in units to which the pragma applies. For a detailed
5571 description of the strict aliasing optimization, and the situations
5572 in which it must be suppressed, see the section on Optimization and Strict Aliasing
5573 in the @cite{GNAT User's Guide}.
5575 This pragma currently has no effects on access to unconstrained array types.
5577 @node Pragma No_Tagged_Streams,Pragma Normalize_Scalars,Pragma No_Strict_Aliasing,Implementation Defined Pragmas
5578 @anchor{gnat_rm/implementation_defined_pragmas pragma-no-tagged-streams}@anchor{ac}@anchor{gnat_rm/implementation_defined_pragmas id26}@anchor{ad}
5579 @section Pragma No_Tagged_Streams
5585 pragma No_Tagged_Streams [([Entity =>] tagged_type_LOCAL_NAME)];
5588 Normally when a tagged type is introduced using a full type declaration,
5589 part of the processing includes generating stream access routines to be
5590 used by stream attributes referencing the type (or one of its subtypes
5591 or derived types). This can involve the generation of significant amounts
5592 of code which is wasted space if stream routines are not needed for the
5595 The @code{No_Tagged_Streams} pragma causes the generation of these stream
5596 routines to be skipped, and any attempt to use stream operations on
5597 types subject to this pragma will be statically rejected as illegal.
5599 There are two forms of the pragma. The form with no arguments must appear
5600 in a declarative sequence or in the declarations of a package spec. This
5601 pragma affects all subsequent root tagged types declared in the declaration
5602 sequence, and specifies that no stream routines be generated. The form with
5603 an argument (for which there is also a corresponding aspect) specifies a
5604 single root tagged type for which stream routines are not to be generated.
5606 Once the pragma has been given for a particular root tagged type, all subtypes
5607 and derived types of this type inherit the pragma automatically, so the effect
5608 applies to a complete hierarchy (this is necessary to deal with the class-wide
5609 dispatching versions of the stream routines).
5611 When pragmas @code{Discard_Names} and @code{No_Tagged_Streams} are simultaneously
5612 applied to a tagged type its Expanded_Name and External_Tag are initialized
5613 with empty strings. This is useful to avoid exposing entity names at binary
5614 level but has a negative impact on the debuggability of tagged types.
5616 @node Pragma Normalize_Scalars,Pragma Obsolescent,Pragma No_Tagged_Streams,Implementation Defined Pragmas
5617 @anchor{gnat_rm/implementation_defined_pragmas pragma-normalize-scalars}@anchor{ae}
5618 @section Pragma Normalize_Scalars
5624 pragma Normalize_Scalars;
5627 This is a language defined pragma which is fully implemented in GNAT. The
5628 effect is to cause all scalar objects that are not otherwise initialized
5629 to be initialized. The initial values are implementation dependent and
5635 @item @emph{Standard.Character}
5637 Objects whose root type is Standard.Character are initialized to
5638 Character'Last unless the subtype range excludes NUL (in which case
5639 NUL is used). This choice will always generate an invalid value if
5642 @item @emph{Standard.Wide_Character}
5644 Objects whose root type is Standard.Wide_Character are initialized to
5645 Wide_Character'Last unless the subtype range excludes NUL (in which case
5646 NUL is used). This choice will always generate an invalid value if
5649 @item @emph{Standard.Wide_Wide_Character}
5651 Objects whose root type is Standard.Wide_Wide_Character are initialized to
5652 the invalid value 16#FFFF_FFFF# unless the subtype range excludes NUL (in
5653 which case NUL is used). This choice will always generate an invalid value if
5656 @item @emph{Integer types}
5658 Objects of an integer type are treated differently depending on whether
5659 negative values are present in the subtype. If no negative values are
5660 present, then all one bits is used as the initial value except in the
5661 special case where zero is excluded from the subtype, in which case
5662 all zero bits are used. This choice will always generate an invalid
5663 value if one exists.
5665 For subtypes with negative values present, the largest negative number
5666 is used, except in the unusual case where this largest negative number
5667 is in the subtype, and the largest positive number is not, in which case
5668 the largest positive value is used. This choice will always generate
5669 an invalid value if one exists.
5671 @item @emph{Floating-Point Types}
5673 Objects of all floating-point types are initialized to all 1-bits. For
5674 standard IEEE format, this corresponds to a NaN (not a number) which is
5675 indeed an invalid value.
5677 @item @emph{Fixed-Point Types}
5679 Objects of all fixed-point types are treated as described above for integers,
5680 with the rules applying to the underlying integer value used to represent
5681 the fixed-point value.
5683 @item @emph{Modular types}
5685 Objects of a modular type are initialized to all one bits, except in
5686 the special case where zero is excluded from the subtype, in which
5687 case all zero bits are used. This choice will always generate an
5688 invalid value if one exists.
5690 @item @emph{Enumeration types}
5692 Objects of an enumeration type are initialized to all one-bits, i.e., to
5693 the value @code{2 ** typ'Size - 1} unless the subtype excludes the literal
5694 whose Pos value is zero, in which case a code of zero is used. This choice
5695 will always generate an invalid value if one exists.
5698 @node Pragma Obsolescent,Pragma Optimize_Alignment,Pragma Normalize_Scalars,Implementation Defined Pragmas
5699 @anchor{gnat_rm/implementation_defined_pragmas pragma-obsolescent}@anchor{af}@anchor{gnat_rm/implementation_defined_pragmas id27}@anchor{b0}
5700 @section Pragma Obsolescent
5708 pragma Obsolescent (
5709 [Message =>] static_string_EXPRESSION
5710 [,[Version =>] Ada_05]]);
5712 pragma Obsolescent (
5714 [,[Message =>] static_string_EXPRESSION
5715 [,[Version =>] Ada_05]] );
5718 This pragma can occur immediately following a declaration of an entity,
5719 including the case of a record component. If no Entity argument is present,
5720 then this declaration is the one to which the pragma applies. If an Entity
5721 parameter is present, it must either match the name of the entity in this
5722 declaration, or alternatively, the pragma can immediately follow an enumeration
5723 type declaration, where the Entity argument names one of the enumeration
5726 This pragma is used to indicate that the named entity
5727 is considered obsolescent and should not be used. Typically this is
5728 used when an API must be modified by eventually removing or modifying
5729 existing subprograms or other entities. The pragma can be used at an
5730 intermediate stage when the entity is still present, but will be
5733 The effect of this pragma is to output a warning message on a reference to
5734 an entity thus marked that the subprogram is obsolescent if the appropriate
5735 warning option in the compiler is activated. If the @code{Message} parameter is
5736 present, then a second warning message is given containing this text. In
5737 addition, a reference to the entity is considered to be a violation of pragma
5738 @code{Restrictions (No_Obsolescent_Features)}.
5740 This pragma can also be used as a program unit pragma for a package,
5741 in which case the entity name is the name of the package, and the
5742 pragma indicates that the entire package is considered
5743 obsolescent. In this case a client @code{with}ing such a package
5744 violates the restriction, and the @code{with} clause is
5745 flagged with warnings if the warning option is set.
5747 If the @code{Version} parameter is present (which must be exactly
5748 the identifier @code{Ada_05}, no other argument is allowed), then the
5749 indication of obsolescence applies only when compiling in Ada 2005
5750 mode. This is primarily intended for dealing with the situations
5751 in the predefined library where subprograms or packages
5752 have become defined as obsolescent in Ada 2005
5753 (e.g., in @code{Ada.Characters.Handling}), but may be used anywhere.
5755 The following examples show typical uses of this pragma:
5759 pragma Obsolescent (p, Message => "use pp instead of p");
5764 pragma Obsolescent ("use q2new instead");
5766 type R is new integer;
5769 Message => "use RR in Ada 2005",
5779 type E is (a, bc, 'd', quack);
5780 pragma Obsolescent (Entity => bc)
5781 pragma Obsolescent (Entity => 'd')
5784 (a, b : character) return character;
5785 pragma Obsolescent (Entity => "+");
5789 Note that, as for all pragmas, if you use a pragma argument identifier,
5790 then all subsequent parameters must also use a pragma argument identifier.
5791 So if you specify @code{Entity =>} for the @code{Entity} argument, and a @code{Message}
5792 argument is present, it must be preceded by @code{Message =>}.
5794 @node Pragma Optimize_Alignment,Pragma Ordered,Pragma Obsolescent,Implementation Defined Pragmas
5795 @anchor{gnat_rm/implementation_defined_pragmas pragma-optimize-alignment}@anchor{b1}
5796 @section Pragma Optimize_Alignment
5800 @geindex default settings
5805 pragma Optimize_Alignment (TIME | SPACE | OFF);
5808 This is a configuration pragma which affects the choice of default alignments
5809 for types and objects where no alignment is explicitly specified. There is a
5810 time/space trade-off in the selection of these values. Large alignments result
5811 in more efficient code, at the expense of larger data space, since sizes have
5812 to be increased to match these alignments. Smaller alignments save space, but
5813 the access code is slower. The normal choice of default alignments for types
5814 and individual alignment promotions for objects (which is what you get if you
5815 do not use this pragma, or if you use an argument of OFF), tries to balance
5816 these two requirements.
5818 Specifying SPACE causes smaller default alignments to be chosen in two cases.
5819 First any packed record is given an alignment of 1. Second, if a size is given
5820 for the type, then the alignment is chosen to avoid increasing this size. For
5832 In the default mode, this type gets an alignment of 4, so that access to the
5833 Integer field X are efficient. But this means that objects of the type end up
5834 with a size of 8 bytes. This is a valid choice, since sizes of objects are
5835 allowed to be bigger than the size of the type, but it can waste space if for
5836 example fields of type R appear in an enclosing record. If the above type is
5837 compiled in @code{Optimize_Alignment (Space)} mode, the alignment is set to 1.
5839 However, there is one case in which SPACE is ignored. If a variable length
5840 record (that is a discriminated record with a component which is an array
5841 whose length depends on a discriminant), has a pragma Pack, then it is not
5842 in general possible to set the alignment of such a record to one, so the
5843 pragma is ignored in this case (with a warning).
5845 Specifying SPACE also disables alignment promotions for standalone objects,
5846 which occur when the compiler increases the alignment of a specific object
5847 without changing the alignment of its type.
5849 Specifying SPACE also disables component reordering in unpacked record types,
5850 which can result in larger sizes in order to meet alignment requirements.
5852 Specifying TIME causes larger default alignments to be chosen in the case of
5853 small types with sizes that are not a power of 2. For example, consider:
5866 The default alignment for this record is normally 1, but if this type is
5867 compiled in @code{Optimize_Alignment (Time)} mode, then the alignment is set
5868 to 4, which wastes space for objects of the type, since they are now 4 bytes
5869 long, but results in more efficient access when the whole record is referenced.
5871 As noted above, this is a configuration pragma, and there is a requirement
5872 that all units in a partition be compiled with a consistent setting of the
5873 optimization setting. This would normally be achieved by use of a configuration
5874 pragma file containing the appropriate setting. The exception to this rule is
5875 that units with an explicit configuration pragma in the same file as the source
5876 unit are excluded from the consistency check, as are all predefined units. The
5877 latter are compiled by default in pragma Optimize_Alignment (Off) mode if no
5878 pragma appears at the start of the file.
5880 @node Pragma Ordered,Pragma Overflow_Mode,Pragma Optimize_Alignment,Implementation Defined Pragmas
5881 @anchor{gnat_rm/implementation_defined_pragmas pragma-ordered}@anchor{b2}
5882 @section Pragma Ordered
5888 pragma Ordered (enumeration_first_subtype_LOCAL_NAME);
5891 Most enumeration types are from a conceptual point of view unordered.
5892 For example, consider:
5895 type Color is (Red, Blue, Green, Yellow);
5898 By Ada semantics @code{Blue > Red} and @code{Green > Blue},
5899 but really these relations make no sense; the enumeration type merely
5900 specifies a set of possible colors, and the order is unimportant.
5902 For unordered enumeration types, it is generally a good idea if
5903 clients avoid comparisons (other than equality or inequality) and
5904 explicit ranges. (A @emph{client} is a unit where the type is referenced,
5905 other than the unit where the type is declared, its body, and its subunits.)
5906 For example, if code buried in some client says:
5909 if Current_Color < Yellow then ...
5910 if Current_Color in Blue .. Green then ...
5913 then the client code is relying on the order, which is undesirable.
5914 It makes the code hard to read and creates maintenance difficulties if
5915 entries have to be added to the enumeration type. Instead,
5916 the code in the client should list the possibilities, or an
5917 appropriate subtype should be declared in the unit that declares
5918 the original enumeration type. E.g., the following subtype could
5919 be declared along with the type @code{Color}:
5922 subtype RBG is Color range Red .. Green;
5925 and then the client could write:
5928 if Current_Color in RBG then ...
5929 if Current_Color = Blue or Current_Color = Green then ...
5932 However, some enumeration types are legitimately ordered from a conceptual
5933 point of view. For example, if you declare:
5936 type Day is (Mon, Tue, Wed, Thu, Fri, Sat, Sun);
5939 then the ordering imposed by the language is reasonable, and
5940 clients can depend on it, writing for example:
5943 if D in Mon .. Fri then ...
5947 The pragma @emph{Ordered} is provided to mark enumeration types that
5948 are conceptually ordered, alerting the reader that clients may depend
5949 on the ordering. GNAT provides a pragma to mark enumerations as ordered
5950 rather than one to mark them as unordered, since in our experience,
5951 the great majority of enumeration types are conceptually unordered.
5953 The types @code{Boolean}, @code{Character}, @code{Wide_Character},
5954 and @code{Wide_Wide_Character}
5955 are considered to be ordered types, so each is declared with a
5956 pragma @code{Ordered} in package @code{Standard}.
5958 Normally pragma @code{Ordered} serves only as documentation and a guide for
5959 coding standards, but GNAT provides a warning switch @emph{-gnatw.u} that
5960 requests warnings for inappropriate uses (comparisons and explicit
5961 subranges) for unordered types. If this switch is used, then any
5962 enumeration type not marked with pragma @code{Ordered} will be considered
5963 as unordered, and will generate warnings for inappropriate uses.
5965 Note that generic types are not considered ordered or unordered (since the
5966 template can be instantiated for both cases), so we never generate warnings
5967 for the case of generic enumerated types.
5969 For additional information please refer to the description of the
5970 @emph{-gnatw.u} switch in the GNAT User's Guide.
5972 @node Pragma Overflow_Mode,Pragma Overriding_Renamings,Pragma Ordered,Implementation Defined Pragmas
5973 @anchor{gnat_rm/implementation_defined_pragmas pragma-overflow-mode}@anchor{b3}
5974 @section Pragma Overflow_Mode
5980 pragma Overflow_Mode
5982 [,[Assertions =>] MODE]);
5984 MODE ::= STRICT | MINIMIZED | ELIMINATED
5987 This pragma sets the current overflow mode to the given setting. For details
5988 of the meaning of these modes, please refer to the
5989 'Overflow Check Handling in GNAT' appendix in the
5990 GNAT User's Guide. If only the @code{General} parameter is present,
5991 the given mode applies to all expressions. If both parameters are present,
5992 the @code{General} mode applies to expressions outside assertions, and
5993 the @code{Eliminated} mode applies to expressions within assertions.
5995 The case of the @code{MODE} parameter is ignored,
5996 so @code{MINIMIZED}, @code{Minimized} and
5997 @code{minimized} all have the same effect.
5999 The @code{Overflow_Mode} pragma has the same scoping and placement
6000 rules as pragma @code{Suppress}, so it can occur either as a
6001 configuration pragma, specifying a default for the whole
6002 program, or in a declarative scope, where it applies to the
6003 remaining declarations and statements in that scope.
6005 The pragma @code{Suppress (Overflow_Check)} suppresses
6006 overflow checking, but does not affect the overflow mode.
6008 The pragma @code{Unsuppress (Overflow_Check)} unsuppresses (enables)
6009 overflow checking, but does not affect the overflow mode.
6011 @node Pragma Overriding_Renamings,Pragma Partition_Elaboration_Policy,Pragma Overflow_Mode,Implementation Defined Pragmas
6012 @anchor{gnat_rm/implementation_defined_pragmas pragma-overriding-renamings}@anchor{b4}
6013 @section Pragma Overriding_Renamings
6016 @geindex Rational profile
6018 @geindex Rational compatibility
6023 pragma Overriding_Renamings;
6026 This is a GNAT configuration pragma to simplify porting
6027 legacy code accepted by the Rational
6028 Ada compiler. In the presence of this pragma, a renaming declaration that
6029 renames an inherited operation declared in the same scope is legal if selected
6030 notation is used as in:
6033 pragma Overriding_Renamings;
6038 function F (..) renames R.F;
6043 RM 8.3 (15) stipulates that an overridden operation is not visible within the
6044 declaration of the overriding operation.
6046 @node Pragma Partition_Elaboration_Policy,Pragma Part_Of,Pragma Overriding_Renamings,Implementation Defined Pragmas
6047 @anchor{gnat_rm/implementation_defined_pragmas pragma-partition-elaboration-policy}@anchor{b5}
6048 @section Pragma Partition_Elaboration_Policy
6054 pragma Partition_Elaboration_Policy (POLICY_IDENTIFIER);
6056 POLICY_IDENTIFIER ::= Concurrent | Sequential
6059 This pragma is standard in Ada 2005, but is available in all earlier
6060 versions of Ada as an implementation-defined pragma.
6061 See Ada 2012 Reference Manual for details.
6063 @node Pragma Part_Of,Pragma Passive,Pragma Partition_Elaboration_Policy,Implementation Defined Pragmas
6064 @anchor{gnat_rm/implementation_defined_pragmas id28}@anchor{b6}@anchor{gnat_rm/implementation_defined_pragmas pragma-part-of}@anchor{b7}
6065 @section Pragma Part_Of
6071 pragma Part_Of (ABSTRACT_STATE);
6073 ABSTRACT_STATE ::= NAME
6076 For the semantics of this pragma, see the entry for aspect @code{Part_Of} in the
6077 SPARK 2014 Reference Manual, section 7.2.6.
6079 @node Pragma Passive,Pragma Persistent_BSS,Pragma Part_Of,Implementation Defined Pragmas
6080 @anchor{gnat_rm/implementation_defined_pragmas pragma-passive}@anchor{b8}
6081 @section Pragma Passive
6087 pragma Passive [(Semaphore | No)];
6090 Syntax checked, but otherwise ignored by GNAT. This is recognized for
6091 compatibility with DEC Ada 83 implementations, where it is used within a
6092 task definition to request that a task be made passive. If the argument
6093 @code{Semaphore} is present, or the argument is omitted, then DEC Ada 83
6094 treats the pragma as an assertion that the containing task is passive
6095 and that optimization of context switch with this task is permitted and
6096 desired. If the argument @code{No} is present, the task must not be
6097 optimized. GNAT does not attempt to optimize any tasks in this manner
6098 (since protected objects are available in place of passive tasks).
6100 For more information on the subject of passive tasks, see the section
6101 'Passive Task Optimization' in the GNAT Users Guide.
6103 @node Pragma Persistent_BSS,Pragma Polling,Pragma Passive,Implementation Defined Pragmas
6104 @anchor{gnat_rm/implementation_defined_pragmas id29}@anchor{b9}@anchor{gnat_rm/implementation_defined_pragmas pragma-persistent-bss}@anchor{ba}
6105 @section Pragma Persistent_BSS
6111 pragma Persistent_BSS [(LOCAL_NAME)]
6114 This pragma allows selected objects to be placed in the @code{.persistent_bss}
6115 section. On some targets the linker and loader provide for special
6116 treatment of this section, allowing a program to be reloaded without
6117 affecting the contents of this data (hence the name persistent).
6119 There are two forms of usage. If an argument is given, it must be the
6120 local name of a library-level object, with no explicit initialization
6121 and whose type is potentially persistent. If no argument is given, then
6122 the pragma is a configuration pragma, and applies to all library-level
6123 objects with no explicit initialization of potentially persistent types.
6125 A potentially persistent type is a scalar type, or an untagged,
6126 non-discriminated record, all of whose components have no explicit
6127 initialization and are themselves of a potentially persistent type,
6128 or an array, all of whose constraints are static, and whose component
6129 type is potentially persistent.
6131 If this pragma is used on a target where this feature is not supported,
6132 then the pragma will be ignored. See also @code{pragma Linker_Section}.
6134 @node Pragma Polling,Pragma Post,Pragma Persistent_BSS,Implementation Defined Pragmas
6135 @anchor{gnat_rm/implementation_defined_pragmas pragma-polling}@anchor{bb}
6136 @section Pragma Polling
6142 pragma Polling (ON | OFF);
6145 This pragma controls the generation of polling code. This is normally off.
6146 If @code{pragma Polling (ON)} is used then periodic calls are generated to
6147 the routine @code{Ada.Exceptions.Poll}. This routine is a separate unit in the
6148 runtime library, and can be found in file @code{a-excpol.adb}.
6150 Pragma @code{Polling} can appear as a configuration pragma (for example it
6151 can be placed in the @code{gnat.adc} file) to enable polling globally, or it
6152 can be used in the statement or declaration sequence to control polling
6155 A call to the polling routine is generated at the start of every loop and
6156 at the start of every subprogram call. This guarantees that the @code{Poll}
6157 routine is called frequently, and places an upper bound (determined by
6158 the complexity of the code) on the period between two @code{Poll} calls.
6160 The primary purpose of the polling interface is to enable asynchronous
6161 aborts on targets that cannot otherwise support it (for example Windows
6162 NT), but it may be used for any other purpose requiring periodic polling.
6163 The standard version is null, and can be replaced by a user program. This
6164 will require re-compilation of the @code{Ada.Exceptions} package that can
6165 be found in files @code{a-except.ads} and @code{a-except.adb}.
6167 A standard alternative unit (in file @code{4wexcpol.adb} in the standard GNAT
6168 distribution) is used to enable the asynchronous abort capability on
6169 targets that do not normally support the capability. The version of
6170 @code{Poll} in this file makes a call to the appropriate runtime routine
6171 to test for an abort condition.
6173 Note that polling can also be enabled by use of the @emph{-gnatP} switch.
6174 See the section on switches for gcc in the @cite{GNAT User's Guide}.
6176 @node Pragma Post,Pragma Postcondition,Pragma Polling,Implementation Defined Pragmas
6177 @anchor{gnat_rm/implementation_defined_pragmas pragma-post}@anchor{bc}
6178 @section Pragma Post
6184 @geindex postconditions
6189 pragma Post (Boolean_Expression);
6192 The @code{Post} pragma is intended to be an exact replacement for
6193 the language-defined
6194 @code{Post} aspect, and shares its restrictions and semantics.
6195 It must appear either immediately following the corresponding
6196 subprogram declaration (only other pragmas may intervene), or
6197 if there is no separate subprogram declaration, then it can
6198 appear at the start of the declarations in a subprogram body
6199 (preceded only by other pragmas).
6201 @node Pragma Postcondition,Pragma Post_Class,Pragma Post,Implementation Defined Pragmas
6202 @anchor{gnat_rm/implementation_defined_pragmas pragma-postcondition}@anchor{bd}
6203 @section Pragma Postcondition
6206 @geindex Postcondition
6209 @geindex postconditions
6214 pragma Postcondition (
6215 [Check =>] Boolean_Expression
6216 [,[Message =>] String_Expression]);
6219 The @code{Postcondition} pragma allows specification of automatic
6220 postcondition checks for subprograms. These checks are similar to
6221 assertions, but are automatically inserted just prior to the return
6222 statements of the subprogram with which they are associated (including
6223 implicit returns at the end of procedure bodies and associated
6224 exception handlers).
6226 In addition, the boolean expression which is the condition which
6227 must be true may contain references to function'Result in the case
6228 of a function to refer to the returned value.
6230 @code{Postcondition} pragmas may appear either immediately following the
6231 (separate) declaration of a subprogram, or at the start of the
6232 declarations of a subprogram body. Only other pragmas may intervene
6233 (that is appear between the subprogram declaration and its
6234 postconditions, or appear before the postcondition in the
6235 declaration sequence in a subprogram body). In the case of a
6236 postcondition appearing after a subprogram declaration, the
6237 formal arguments of the subprogram are visible, and can be
6238 referenced in the postcondition expressions.
6240 The postconditions are collected and automatically tested just
6241 before any return (implicit or explicit) in the subprogram body.
6242 A postcondition is only recognized if postconditions are active
6243 at the time the pragma is encountered. The compiler switch @emph{gnata}
6244 turns on all postconditions by default, and pragma @code{Check_Policy}
6245 with an identifier of @code{Postcondition} can also be used to
6246 control whether postconditions are active.
6248 The general approach is that postconditions are placed in the spec
6249 if they represent functional aspects which make sense to the client.
6250 For example we might have:
6253 function Direction return Integer;
6254 pragma Postcondition
6255 (Direction'Result = +1
6257 Direction'Result = -1);
6260 which serves to document that the result must be +1 or -1, and
6261 will test that this is the case at run time if postcondition
6264 Postconditions within the subprogram body can be used to
6265 check that some internal aspect of the implementation,
6266 not visible to the client, is operating as expected.
6267 For instance if a square root routine keeps an internal
6268 counter of the number of times it is called, then we
6269 might have the following postcondition:
6272 Sqrt_Calls : Natural := 0;
6274 function Sqrt (Arg : Float) return Float is
6275 pragma Postcondition
6276 (Sqrt_Calls = Sqrt_Calls'Old + 1);
6281 As this example, shows, the use of the @code{Old} attribute
6282 is often useful in postconditions to refer to the state on
6283 entry to the subprogram.
6285 Note that postconditions are only checked on normal returns
6286 from the subprogram. If an abnormal return results from
6287 raising an exception, then the postconditions are not checked.
6289 If a postcondition fails, then the exception
6290 @code{System.Assertions.Assert_Failure} is raised. If
6291 a message argument was supplied, then the given string
6292 will be used as the exception message. If no message
6293 argument was supplied, then the default message has
6294 the form "Postcondition failed at file_name:line". The
6295 exception is raised in the context of the subprogram
6296 body, so it is possible to catch postcondition failures
6297 within the subprogram body itself.
6299 Within a package spec, normal visibility rules
6300 in Ada would prevent forward references within a
6301 postcondition pragma to functions defined later in
6302 the same package. This would introduce undesirable
6303 ordering constraints. To avoid this problem, all
6304 postcondition pragmas are analyzed at the end of
6305 the package spec, allowing forward references.
6307 The following example shows that this even allows
6308 mutually recursive postconditions as in:
6311 package Parity_Functions is
6312 function Odd (X : Natural) return Boolean;
6313 pragma Postcondition
6317 (x /= 0 and then Even (X - 1))));
6319 function Even (X : Natural) return Boolean;
6320 pragma Postcondition
6324 (x /= 1 and then Odd (X - 1))));
6326 end Parity_Functions;
6329 There are no restrictions on the complexity or form of
6330 conditions used within @code{Postcondition} pragmas.
6331 The following example shows that it is even possible
6332 to verify performance behavior.
6337 Performance : constant Float;
6338 -- Performance constant set by implementation
6339 -- to match target architecture behavior.
6341 procedure Treesort (Arg : String);
6342 -- Sorts characters of argument using N*logN sort
6343 pragma Postcondition
6344 (Float (Clock - Clock'Old) <=
6345 Float (Arg'Length) *
6346 log (Float (Arg'Length)) *
6351 Note: postcondition pragmas associated with subprograms that are
6352 marked as Inline_Always, or those marked as Inline with front-end
6353 inlining (-gnatN option set) are accepted and legality-checked
6354 by the compiler, but are ignored at run-time even if postcondition
6355 checking is enabled.
6357 Note that pragma @code{Postcondition} differs from the language-defined
6358 @code{Post} aspect (and corresponding @code{Post} pragma) in allowing
6359 multiple occurrences, allowing occurences in the body even if there
6360 is a separate spec, and allowing a second string parameter, and the
6361 use of the pragma identifier @code{Check}. Historically, pragma
6362 @code{Postcondition} was implemented prior to the development of
6363 Ada 2012, and has been retained in its original form for
6364 compatibility purposes.
6366 @node Pragma Post_Class,Pragma Rename_Pragma,Pragma Postcondition,Implementation Defined Pragmas
6367 @anchor{gnat_rm/implementation_defined_pragmas pragma-post-class}@anchor{be}
6368 @section Pragma Post_Class
6374 @geindex postconditions
6379 pragma Post_Class (Boolean_Expression);
6382 The @code{Post_Class} pragma is intended to be an exact replacement for
6383 the language-defined
6384 @code{Post'Class} aspect, and shares its restrictions and semantics.
6385 It must appear either immediately following the corresponding
6386 subprogram declaration (only other pragmas may intervene), or
6387 if there is no separate subprogram declaration, then it can
6388 appear at the start of the declarations in a subprogram body
6389 (preceded only by other pragmas).
6391 Note: This pragma is called @code{Post_Class} rather than
6392 @code{Post'Class} because the latter would not be strictly
6393 conforming to the allowed syntax for pragmas. The motivation
6394 for provinding pragmas equivalent to the aspects is to allow a program
6395 to be written using the pragmas, and then compiled if necessary
6396 using an Ada compiler that does not recognize the pragmas or
6397 aspects, but is prepared to ignore the pragmas. The assertion
6398 policy that controls this pragma is @code{Post'Class}, not
6401 @node Pragma Rename_Pragma,Pragma Pre,Pragma Post_Class,Implementation Defined Pragmas
6402 @anchor{gnat_rm/implementation_defined_pragmas pragma-rename-pragma}@anchor{bf}
6403 @section Pragma Rename_Pragma
6412 pragma Rename_Pragma (
6413 [New_Name =>] IDENTIFIER,
6414 [Renamed =>] pragma_IDENTIFIER);
6417 This pragma provides a mechanism for supplying new names for existing
6418 pragmas. The @code{New_Name} identifier can subsequently be used as a synonym for
6419 the Renamed pragma. For example, suppose you have code that was originally
6420 developed on a compiler that supports Inline_Only as an implementation defined
6421 pragma. And suppose the semantics of pragma Inline_Only are identical to (or at
6422 least very similar to) the GNAT implementation defined pragma
6423 Inline_Always. You could globally replace Inline_Only with Inline_Always.
6425 However, to avoid that source modification, you could instead add a
6426 configuration pragma:
6429 pragma Rename_Pragma (
6430 New_Name => Inline_Only,
6431 Renamed => Inline_Always);
6434 Then GNAT will treat "pragma Inline_Only ..." as if you had written
6435 "pragma Inline_Always ...".
6437 Pragma Inline_Only will not necessarily mean the same thing as the other Ada
6438 compiler; it's up to you to make sure the semantics are close enough.
6440 @node Pragma Pre,Pragma Precondition,Pragma Rename_Pragma,Implementation Defined Pragmas
6441 @anchor{gnat_rm/implementation_defined_pragmas pragma-pre}@anchor{c0}
6448 @geindex preconditions
6453 pragma Pre (Boolean_Expression);
6456 The @code{Pre} pragma is intended to be an exact replacement for
6457 the language-defined
6458 @code{Pre} aspect, and shares its restrictions and semantics.
6459 It must appear either immediately following the corresponding
6460 subprogram declaration (only other pragmas may intervene), or
6461 if there is no separate subprogram declaration, then it can
6462 appear at the start of the declarations in a subprogram body
6463 (preceded only by other pragmas).
6465 @node Pragma Precondition,Pragma Predicate,Pragma Pre,Implementation Defined Pragmas
6466 @anchor{gnat_rm/implementation_defined_pragmas pragma-precondition}@anchor{c1}
6467 @section Pragma Precondition
6470 @geindex Preconditions
6473 @geindex preconditions
6478 pragma Precondition (
6479 [Check =>] Boolean_Expression
6480 [,[Message =>] String_Expression]);
6483 The @code{Precondition} pragma is similar to @code{Postcondition}
6484 except that the corresponding checks take place immediately upon
6485 entry to the subprogram, and if a precondition fails, the exception
6486 is raised in the context of the caller, and the attribute 'Result
6487 cannot be used within the precondition expression.
6489 Otherwise, the placement and visibility rules are identical to those
6490 described for postconditions. The following is an example of use
6491 within a package spec:
6494 package Math_Functions is
6496 function Sqrt (Arg : Float) return Float;
6497 pragma Precondition (Arg >= 0.0)
6502 @code{Precondition} pragmas may appear either immediately following the
6503 (separate) declaration of a subprogram, or at the start of the
6504 declarations of a subprogram body. Only other pragmas may intervene
6505 (that is appear between the subprogram declaration and its
6506 postconditions, or appear before the postcondition in the
6507 declaration sequence in a subprogram body).
6509 Note: precondition pragmas associated with subprograms that are
6510 marked as Inline_Always, or those marked as Inline with front-end
6511 inlining (-gnatN option set) are accepted and legality-checked
6512 by the compiler, but are ignored at run-time even if precondition
6513 checking is enabled.
6515 Note that pragma @code{Precondition} differs from the language-defined
6516 @code{Pre} aspect (and corresponding @code{Pre} pragma) in allowing
6517 multiple occurrences, allowing occurences in the body even if there
6518 is a separate spec, and allowing a second string parameter, and the
6519 use of the pragma identifier @code{Check}. Historically, pragma
6520 @code{Precondition} was implemented prior to the development of
6521 Ada 2012, and has been retained in its original form for
6522 compatibility purposes.
6524 @node Pragma Predicate,Pragma Predicate_Failure,Pragma Precondition,Implementation Defined Pragmas
6525 @anchor{gnat_rm/implementation_defined_pragmas pragma-predicate}@anchor{c2}@anchor{gnat_rm/implementation_defined_pragmas id30}@anchor{c3}
6526 @section Pragma Predicate
6533 ([Entity =>] type_LOCAL_NAME,
6534 [Check =>] EXPRESSION);
6537 This pragma (available in all versions of Ada in GNAT) encompasses both
6538 the @code{Static_Predicate} and @code{Dynamic_Predicate} aspects in
6539 Ada 2012. A predicate is regarded as static if it has an allowed form
6540 for @code{Static_Predicate} and is otherwise treated as a
6541 @code{Dynamic_Predicate}. Otherwise, predicates specified by this
6542 pragma behave exactly as described in the Ada 2012 reference manual.
6543 For example, if we have
6546 type R is range 1 .. 10;
6548 pragma Predicate (Entity => S, Check => S not in 4 .. 6);
6550 pragma Predicate (Entity => Q, Check => F(Q) or G(Q));
6553 the effect is identical to the following Ada 2012 code:
6556 type R is range 1 .. 10;
6558 Static_Predicate => S not in 4 .. 6;
6560 Dynamic_Predicate => F(Q) or G(Q);
6563 Note that there are no pragmas @code{Dynamic_Predicate}
6564 or @code{Static_Predicate}. That is
6565 because these pragmas would affect legality and semantics of
6566 the program and thus do not have a neutral effect if ignored.
6567 The motivation behind providing pragmas equivalent to
6568 corresponding aspects is to allow a program to be written
6569 using the pragmas, and then compiled with a compiler that
6570 will ignore the pragmas. That doesn't work in the case of
6571 static and dynamic predicates, since if the corresponding
6572 pragmas are ignored, then the behavior of the program is
6573 fundamentally changed (for example a membership test
6574 @code{A in B} would not take into account a predicate
6575 defined for subtype B). When following this approach, the
6576 use of predicates should be avoided.
6578 @node Pragma Predicate_Failure,Pragma Preelaborable_Initialization,Pragma Predicate,Implementation Defined Pragmas
6579 @anchor{gnat_rm/implementation_defined_pragmas pragma-predicate-failure}@anchor{c4}
6580 @section Pragma Predicate_Failure
6586 pragma Predicate_Failure
6587 ([Entity =>] type_LOCAL_NAME,
6588 [Message =>] String_Expression);
6591 The @code{Predicate_Failure} pragma is intended to be an exact replacement for
6592 the language-defined
6593 @code{Predicate_Failure} aspect, and shares its restrictions and semantics.
6595 @node Pragma Preelaborable_Initialization,Pragma Prefix_Exception_Messages,Pragma Predicate_Failure,Implementation Defined Pragmas
6596 @anchor{gnat_rm/implementation_defined_pragmas pragma-preelaborable-initialization}@anchor{c5}
6597 @section Pragma Preelaborable_Initialization
6603 pragma Preelaborable_Initialization (DIRECT_NAME);
6606 This pragma is standard in Ada 2005, but is available in all earlier
6607 versions of Ada as an implementation-defined pragma.
6608 See Ada 2012 Reference Manual for details.
6610 @node Pragma Prefix_Exception_Messages,Pragma Pre_Class,Pragma Preelaborable_Initialization,Implementation Defined Pragmas
6611 @anchor{gnat_rm/implementation_defined_pragmas pragma-prefix-exception-messages}@anchor{c6}
6612 @section Pragma Prefix_Exception_Messages
6615 @geindex Prefix_Exception_Messages
6619 @geindex Exception_Message
6624 pragma Prefix_Exception_Messages;
6627 This is an implementation-defined configuration pragma that affects the
6628 behavior of raise statements with a message given as a static string
6629 constant (typically a string literal). In such cases, the string will
6630 be automatically prefixed by the name of the enclosing entity (giving
6631 the package and subprogram containing the raise statement). This helps
6632 to identify where messages are coming from, and this mode is automatic
6633 for the run-time library.
6635 The pragma has no effect if the message is computed with an expression other
6636 than a static string constant, since the assumption in this case is that
6637 the program computes exactly the string it wants. If you still want the
6638 prefixing in this case, you can always call
6639 @code{GNAT.Source_Info.Enclosing_Entity} and prepend the string manually.
6641 @node Pragma Pre_Class,Pragma Priority_Specific_Dispatching,Pragma Prefix_Exception_Messages,Implementation Defined Pragmas
6642 @anchor{gnat_rm/implementation_defined_pragmas pragma-pre-class}@anchor{c7}
6643 @section Pragma Pre_Class
6649 @geindex preconditions
6654 pragma Pre_Class (Boolean_Expression);
6657 The @code{Pre_Class} pragma is intended to be an exact replacement for
6658 the language-defined
6659 @code{Pre'Class} aspect, and shares its restrictions and semantics.
6660 It must appear either immediately following the corresponding
6661 subprogram declaration (only other pragmas may intervene), or
6662 if there is no separate subprogram declaration, then it can
6663 appear at the start of the declarations in a subprogram body
6664 (preceded only by other pragmas).
6666 Note: This pragma is called @code{Pre_Class} rather than
6667 @code{Pre'Class} because the latter would not be strictly
6668 conforming to the allowed syntax for pragmas. The motivation
6669 for providing pragmas equivalent to the aspects is to allow a program
6670 to be written using the pragmas, and then compiled if necessary
6671 using an Ada compiler that does not recognize the pragmas or
6672 aspects, but is prepared to ignore the pragmas. The assertion
6673 policy that controls this pragma is @code{Pre'Class}, not
6676 @node Pragma Priority_Specific_Dispatching,Pragma Profile,Pragma Pre_Class,Implementation Defined Pragmas
6677 @anchor{gnat_rm/implementation_defined_pragmas pragma-priority-specific-dispatching}@anchor{c8}
6678 @section Pragma Priority_Specific_Dispatching
6684 pragma Priority_Specific_Dispatching (
6686 first_priority_EXPRESSION,
6687 last_priority_EXPRESSION)
6689 POLICY_IDENTIFIER ::=
6690 EDF_Across_Priorities |
6691 FIFO_Within_Priorities |
6692 Non_Preemptive_Within_Priorities |
6693 Round_Robin_Within_Priorities
6696 This pragma is standard in Ada 2005, but is available in all earlier
6697 versions of Ada as an implementation-defined pragma.
6698 See Ada 2012 Reference Manual for details.
6700 @node Pragma Profile,Pragma Profile_Warnings,Pragma Priority_Specific_Dispatching,Implementation Defined Pragmas
6701 @anchor{gnat_rm/implementation_defined_pragmas pragma-profile}@anchor{c9}
6702 @section Pragma Profile
6708 pragma Profile (Ravenscar | Restricted | Rational |
6709 GNAT_Extended_Ravenscar | GNAT_Ravenscar_EDF );
6712 This pragma is standard in Ada 2005, but is available in all earlier
6713 versions of Ada as an implementation-defined pragma. This is a
6714 configuration pragma that establishes a set of configuration pragmas
6715 that depend on the argument. @code{Ravenscar} is standard in Ada 2005.
6716 The other possibilities (@code{Restricted}, @code{Rational},
6717 @code{GNAT_Extended_Ravenscar}, @code{GNAT_Ravenscar_EDF})
6718 are implementation-defined. The set of configuration pragmas
6719 is defined in the following sections.
6725 Pragma Profile (Ravenscar)
6727 The @code{Ravenscar} profile is standard in Ada 2005,
6728 but is available in all earlier
6729 versions of Ada as an implementation-defined pragma. This profile
6730 establishes the following set of configuration pragmas:
6736 @code{Task_Dispatching_Policy (FIFO_Within_Priorities)}
6738 [RM D.2.2] Tasks are dispatched following a preemptive
6739 priority-ordered scheduling policy.
6742 @code{Locking_Policy (Ceiling_Locking)}
6744 [RM D.3] While tasks and interrupts execute a protected action, they inherit
6745 the ceiling priority of the corresponding protected object.
6748 @code{Detect_Blocking}
6750 This pragma forces the detection of potentially blocking operations within a
6751 protected operation, and to raise Program_Error if that happens.
6754 plus the following set of restrictions:
6760 @code{Max_Entry_Queue_Length => 1}
6762 No task can be queued on a protected entry.
6765 @code{Max_Protected_Entries => 1}
6768 @code{Max_Task_Entries => 0}
6770 No rendezvous statements are allowed.
6773 @code{No_Abort_Statements}
6776 @code{No_Dynamic_Attachment}
6779 @code{No_Dynamic_Priorities}
6782 @code{No_Implicit_Heap_Allocations}
6785 @code{No_Local_Protected_Objects}
6788 @code{No_Local_Timing_Events}
6791 @code{No_Protected_Type_Allocators}
6794 @code{No_Relative_Delay}
6797 @code{No_Requeue_Statements}
6800 @code{No_Select_Statements}
6803 @code{No_Specific_Termination_Handlers}
6806 @code{No_Task_Allocators}
6809 @code{No_Task_Hierarchy}
6812 @code{No_Task_Termination}
6815 @code{Simple_Barriers}
6818 The Ravenscar profile also includes the following restrictions that specify
6819 that there are no semantic dependences on the corresponding predefined
6826 @code{No_Dependence => Ada.Asynchronous_Task_Control}
6829 @code{No_Dependence => Ada.Calendar}
6832 @code{No_Dependence => Ada.Execution_Time.Group_Budget}
6835 @code{No_Dependence => Ada.Execution_Time.Timers}
6838 @code{No_Dependence => Ada.Task_Attributes}
6841 @code{No_Dependence => System.Multiprocessors.Dispatching_Domains}
6844 This set of configuration pragmas and restrictions correspond to the
6845 definition of the 'Ravenscar Profile' for limited tasking, devised and
6846 published by the @cite{International Real-Time Ada Workshop@comma{} 1997}.
6847 A description is also available at
6848 @indicateurl{http://www-users.cs.york.ac.uk/~burns/ravenscar.ps}.
6850 The original definition of the profile was revised at subsequent IRTAW
6851 meetings. It has been included in the ISO
6852 @cite{Guide for the Use of the Ada Programming Language in High Integrity Systems},
6853 and was made part of the Ada 2005 standard.
6854 The formal definition given by
6855 the Ada Rapporteur Group (ARG) can be found in two Ada Issues (AI-249 and
6856 AI-305) available at
6857 @indicateurl{http://www.ada-auth.org/cgi-bin/cvsweb.cgi/ais/ai-00249.txt} and
6858 @indicateurl{http://www.ada-auth.org/cgi-bin/cvsweb.cgi/ais/ai-00305.txt}.
6860 The above set is a superset of the restrictions provided by pragma
6861 @code{Profile (Restricted)}, it includes six additional restrictions
6862 (@code{Simple_Barriers}, @code{No_Select_Statements},
6863 @code{No_Calendar}, @code{No_Implicit_Heap_Allocations},
6864 @code{No_Relative_Delay} and @code{No_Task_Termination}). This means
6865 that pragma @code{Profile (Ravenscar)}, like the pragma
6866 @code{Profile (Restricted)},
6867 automatically causes the use of a simplified,
6868 more efficient version of the tasking run-time library.
6871 Pragma Profile (GNAT_Extended_Ravenscar)
6873 This profile corresponds to a GNAT specific extension of the
6874 Ravenscar profile. The profile may change in the future although
6875 only in a compatible way: some restrictions may be removed or
6876 relaxed. It is defined as a variation of the Ravenscar profile.
6878 The @code{No_Implicit_Heap_Allocations} restriction has been replaced
6879 by @code{No_Implicit_Task_Allocations} and
6880 @code{No_Implicit_Protected_Object_Allocations}.
6882 The @code{Simple_Barriers} restriction has been replaced by
6883 @code{Pure_Barriers}.
6885 The @code{Max_Protected_Entries}, @code{Max_Entry_Queue_Length}, and
6886 @code{No_Relative_Delay} restrictions have been removed.
6889 Pragma Profile (GNAT_Ravenscar_EDF)
6891 This profile corresponds to the Ravenscar profile but using
6892 EDF_Across_Priority as the Task_Scheduling_Policy.
6895 Pragma Profile (Restricted)
6897 This profile corresponds to the GNAT restricted run time. It
6898 establishes the following set of restrictions:
6904 @code{No_Abort_Statements}
6907 @code{No_Entry_Queue}
6910 @code{No_Task_Hierarchy}
6913 @code{No_Task_Allocators}
6916 @code{No_Dynamic_Priorities}
6919 @code{No_Terminate_Alternatives}
6922 @code{No_Dynamic_Attachment}
6925 @code{No_Protected_Type_Allocators}
6928 @code{No_Local_Protected_Objects}
6931 @code{No_Requeue_Statements}
6934 @code{No_Task_Attributes_Package}
6937 @code{Max_Asynchronous_Select_Nesting = 0}
6940 @code{Max_Task_Entries = 0}
6943 @code{Max_Protected_Entries = 1}
6946 @code{Max_Select_Alternatives = 0}
6949 This set of restrictions causes the automatic selection of a simplified
6950 version of the run time that provides improved performance for the
6951 limited set of tasking functionality permitted by this set of restrictions.
6954 Pragma Profile (Rational)
6956 The Rational profile is intended to facilitate porting legacy code that
6957 compiles with the Rational APEX compiler, even when the code includes non-
6958 conforming Ada constructs. The profile enables the following three pragmas:
6964 @code{pragma Implicit_Packing}
6967 @code{pragma Overriding_Renamings}
6970 @code{pragma Use_VADS_Size}
6974 @node Pragma Profile_Warnings,Pragma Propagate_Exceptions,Pragma Profile,Implementation Defined Pragmas
6975 @anchor{gnat_rm/implementation_defined_pragmas pragma-profile-warnings}@anchor{ca}
6976 @section Pragma Profile_Warnings
6982 pragma Profile_Warnings (Ravenscar | Restricted | Rational);
6985 This is an implementation-defined pragma that is similar in
6986 effect to @code{pragma Profile} except that instead of
6987 generating @code{Restrictions} pragmas, it generates
6988 @code{Restriction_Warnings} pragmas. The result is that
6989 violations of the profile generate warning messages instead
6992 @node Pragma Propagate_Exceptions,Pragma Provide_Shift_Operators,Pragma Profile_Warnings,Implementation Defined Pragmas
6993 @anchor{gnat_rm/implementation_defined_pragmas pragma-propagate-exceptions}@anchor{cb}
6994 @section Pragma Propagate_Exceptions
6997 @geindex Interfacing to C++
7002 pragma Propagate_Exceptions;
7005 This pragma is now obsolete and, other than generating a warning if warnings
7006 on obsolescent features are enabled, is ignored.
7007 It is retained for compatibility
7008 purposes. It used to be used in connection with optimization of
7009 a now-obsolete mechanism for implementation of exceptions.
7011 @node Pragma Provide_Shift_Operators,Pragma Psect_Object,Pragma Propagate_Exceptions,Implementation Defined Pragmas
7012 @anchor{gnat_rm/implementation_defined_pragmas pragma-provide-shift-operators}@anchor{cc}
7013 @section Pragma Provide_Shift_Operators
7016 @geindex Shift operators
7021 pragma Provide_Shift_Operators (integer_first_subtype_LOCAL_NAME);
7024 This pragma can be applied to a first subtype local name that specifies
7025 either an unsigned or signed type. It has the effect of providing the
7026 five shift operators (Shift_Left, Shift_Right, Shift_Right_Arithmetic,
7027 Rotate_Left and Rotate_Right) for the given type. It is similar to
7028 including the function declarations for these five operators, together
7029 with the pragma Import (Intrinsic, ...) statements.
7031 @node Pragma Psect_Object,Pragma Pure_Function,Pragma Provide_Shift_Operators,Implementation Defined Pragmas
7032 @anchor{gnat_rm/implementation_defined_pragmas pragma-psect-object}@anchor{cd}
7033 @section Pragma Psect_Object
7039 pragma Psect_Object (
7040 [Internal =>] LOCAL_NAME,
7041 [, [External =>] EXTERNAL_SYMBOL]
7042 [, [Size =>] EXTERNAL_SYMBOL]);
7046 | static_string_EXPRESSION
7049 This pragma is identical in effect to pragma @code{Common_Object}.
7051 @node Pragma Pure_Function,Pragma Rational,Pragma Psect_Object,Implementation Defined Pragmas
7052 @anchor{gnat_rm/implementation_defined_pragmas pragma-pure-function}@anchor{ce}@anchor{gnat_rm/implementation_defined_pragmas id31}@anchor{cf}
7053 @section Pragma Pure_Function
7059 pragma Pure_Function ([Entity =>] function_LOCAL_NAME);
7062 This pragma appears in the same declarative part as a function
7063 declaration (or a set of function declarations if more than one
7064 overloaded declaration exists, in which case the pragma applies
7065 to all entities). It specifies that the function @code{Entity} is
7066 to be considered pure for the purposes of code generation. This means
7067 that the compiler can assume that there are no side effects, and
7068 in particular that two calls with identical arguments produce the
7069 same result. It also means that the function can be used in an
7072 Note that, quite deliberately, there are no static checks to try
7073 to ensure that this promise is met, so @code{Pure_Function} can be used
7074 with functions that are conceptually pure, even if they do modify
7075 global variables. For example, a square root function that is
7076 instrumented to count the number of times it is called is still
7077 conceptually pure, and can still be optimized, even though it
7078 modifies a global variable (the count). Memo functions are another
7079 example (where a table of previous calls is kept and consulted to
7080 avoid re-computation).
7082 Note also that the normal rules excluding optimization of subprograms
7083 in pure units (when parameter types are descended from System.Address,
7084 or when the full view of a parameter type is limited), do not apply
7085 for the Pure_Function case. If you explicitly specify Pure_Function,
7086 the compiler may optimize away calls with identical arguments, and
7087 if that results in unexpected behavior, the proper action is not to
7088 use the pragma for subprograms that are not (conceptually) pure.
7090 Note: Most functions in a @code{Pure} package are automatically pure, and
7091 there is no need to use pragma @code{Pure_Function} for such functions. One
7092 exception is any function that has at least one formal of type
7093 @code{System.Address} or a type derived from it. Such functions are not
7094 considered pure by default, since the compiler assumes that the
7095 @code{Address} parameter may be functioning as a pointer and that the
7096 referenced data may change even if the address value does not.
7097 Similarly, imported functions are not considered to be pure by default,
7098 since there is no way of checking that they are in fact pure. The use
7099 of pragma @code{Pure_Function} for such a function will override these default
7100 assumption, and cause the compiler to treat a designated subprogram as pure
7103 Note: If pragma @code{Pure_Function} is applied to a renamed function, it
7104 applies to the underlying renamed function. This can be used to
7105 disambiguate cases of overloading where some but not all functions
7106 in a set of overloaded functions are to be designated as pure.
7108 If pragma @code{Pure_Function} is applied to a library-level function, the
7109 function is also considered pure from an optimization point of view, but the
7110 unit is not a Pure unit in the categorization sense. So for example, a function
7111 thus marked is free to @code{with} non-pure units.
7113 @node Pragma Rational,Pragma Ravenscar,Pragma Pure_Function,Implementation Defined Pragmas
7114 @anchor{gnat_rm/implementation_defined_pragmas pragma-rational}@anchor{d0}
7115 @section Pragma Rational
7124 This pragma is considered obsolescent, but is retained for
7125 compatibility purposes. It is equivalent to:
7128 pragma Profile (Rational);
7131 @node Pragma Ravenscar,Pragma Refined_Depends,Pragma Rational,Implementation Defined Pragmas
7132 @anchor{gnat_rm/implementation_defined_pragmas pragma-ravenscar}@anchor{d1}
7133 @section Pragma Ravenscar
7142 This pragma is considered obsolescent, but is retained for
7143 compatibility purposes. It is equivalent to:
7146 pragma Profile (Ravenscar);
7149 which is the preferred method of setting the @code{Ravenscar} profile.
7151 @node Pragma Refined_Depends,Pragma Refined_Global,Pragma Ravenscar,Implementation Defined Pragmas
7152 @anchor{gnat_rm/implementation_defined_pragmas pragma-refined-depends}@anchor{d2}@anchor{gnat_rm/implementation_defined_pragmas id32}@anchor{d3}
7153 @section Pragma Refined_Depends
7159 pragma Refined_Depends (DEPENDENCY_RELATION);
7161 DEPENDENCY_RELATION ::=
7163 | (DEPENDENCY_CLAUSE @{, DEPENDENCY_CLAUSE@})
7165 DEPENDENCY_CLAUSE ::=
7166 OUTPUT_LIST =>[+] INPUT_LIST
7167 | NULL_DEPENDENCY_CLAUSE
7169 NULL_DEPENDENCY_CLAUSE ::= null => INPUT_LIST
7171 OUTPUT_LIST ::= OUTPUT | (OUTPUT @{, OUTPUT@})
7173 INPUT_LIST ::= null | INPUT | (INPUT @{, INPUT@})
7175 OUTPUT ::= NAME | FUNCTION_RESULT
7178 where FUNCTION_RESULT is a function Result attribute_reference
7181 For the semantics of this pragma, see the entry for aspect @code{Refined_Depends} in
7182 the SPARK 2014 Reference Manual, section 6.1.5.
7184 @node Pragma Refined_Global,Pragma Refined_Post,Pragma Refined_Depends,Implementation Defined Pragmas
7185 @anchor{gnat_rm/implementation_defined_pragmas pragma-refined-global}@anchor{d4}@anchor{gnat_rm/implementation_defined_pragmas id33}@anchor{d5}
7186 @section Pragma Refined_Global
7192 pragma Refined_Global (GLOBAL_SPECIFICATION);
7194 GLOBAL_SPECIFICATION ::=
7197 | (MODED_GLOBAL_LIST @{, MODED_GLOBAL_LIST@})
7199 MODED_GLOBAL_LIST ::= MODE_SELECTOR => GLOBAL_LIST
7201 MODE_SELECTOR ::= In_Out | Input | Output | Proof_In
7202 GLOBAL_LIST ::= GLOBAL_ITEM | (GLOBAL_ITEM @{, GLOBAL_ITEM@})
7203 GLOBAL_ITEM ::= NAME
7206 For the semantics of this pragma, see the entry for aspect @code{Refined_Global} in
7207 the SPARK 2014 Reference Manual, section 6.1.4.
7209 @node Pragma Refined_Post,Pragma Refined_State,Pragma Refined_Global,Implementation Defined Pragmas
7210 @anchor{gnat_rm/implementation_defined_pragmas pragma-refined-post}@anchor{d6}@anchor{gnat_rm/implementation_defined_pragmas id34}@anchor{d7}
7211 @section Pragma Refined_Post
7217 pragma Refined_Post (boolean_EXPRESSION);
7220 For the semantics of this pragma, see the entry for aspect @code{Refined_Post} in
7221 the SPARK 2014 Reference Manual, section 7.2.7.
7223 @node Pragma Refined_State,Pragma Relative_Deadline,Pragma Refined_Post,Implementation Defined Pragmas
7224 @anchor{gnat_rm/implementation_defined_pragmas pragma-refined-state}@anchor{d8}@anchor{gnat_rm/implementation_defined_pragmas id35}@anchor{d9}
7225 @section Pragma Refined_State
7231 pragma Refined_State (REFINEMENT_LIST);
7234 (REFINEMENT_CLAUSE @{, REFINEMENT_CLAUSE@})
7236 REFINEMENT_CLAUSE ::= state_NAME => CONSTITUENT_LIST
7238 CONSTITUENT_LIST ::=
7241 | (CONSTITUENT @{, CONSTITUENT@})
7243 CONSTITUENT ::= object_NAME | state_NAME
7246 For the semantics of this pragma, see the entry for aspect @code{Refined_State} in
7247 the SPARK 2014 Reference Manual, section 7.2.2.
7249 @node Pragma Relative_Deadline,Pragma Remote_Access_Type,Pragma Refined_State,Implementation Defined Pragmas
7250 @anchor{gnat_rm/implementation_defined_pragmas pragma-relative-deadline}@anchor{da}
7251 @section Pragma Relative_Deadline
7257 pragma Relative_Deadline (time_span_EXPRESSION);
7260 This pragma is standard in Ada 2005, but is available in all earlier
7261 versions of Ada as an implementation-defined pragma.
7262 See Ada 2012 Reference Manual for details.
7264 @node Pragma Remote_Access_Type,Pragma Restricted_Run_Time,Pragma Relative_Deadline,Implementation Defined Pragmas
7265 @anchor{gnat_rm/implementation_defined_pragmas id36}@anchor{db}@anchor{gnat_rm/implementation_defined_pragmas pragma-remote-access-type}@anchor{dc}
7266 @section Pragma Remote_Access_Type
7272 pragma Remote_Access_Type ([Entity =>] formal_access_type_LOCAL_NAME);
7275 This pragma appears in the formal part of a generic declaration.
7276 It specifies an exception to the RM rule from E.2.2(17/2), which forbids
7277 the use of a remote access to class-wide type as actual for a formal
7280 When this pragma applies to a formal access type @code{Entity}, that
7281 type is treated as a remote access to class-wide type in the generic.
7282 It must be a formal general access type, and its designated type must
7283 be the class-wide type of a formal tagged limited private type from the
7284 same generic declaration.
7286 In the generic unit, the formal type is subject to all restrictions
7287 pertaining to remote access to class-wide types. At instantiation, the
7288 actual type must be a remote access to class-wide type.
7290 @node Pragma Restricted_Run_Time,Pragma Restriction_Warnings,Pragma Remote_Access_Type,Implementation Defined Pragmas
7291 @anchor{gnat_rm/implementation_defined_pragmas pragma-restricted-run-time}@anchor{dd}
7292 @section Pragma Restricted_Run_Time
7298 pragma Restricted_Run_Time;
7301 This pragma is considered obsolescent, but is retained for
7302 compatibility purposes. It is equivalent to:
7305 pragma Profile (Restricted);
7308 which is the preferred method of setting the restricted run time
7311 @node Pragma Restriction_Warnings,Pragma Reviewable,Pragma Restricted_Run_Time,Implementation Defined Pragmas
7312 @anchor{gnat_rm/implementation_defined_pragmas pragma-restriction-warnings}@anchor{de}
7313 @section Pragma Restriction_Warnings
7319 pragma Restriction_Warnings
7320 (restriction_IDENTIFIER @{, restriction_IDENTIFIER@});
7323 This pragma allows a series of restriction identifiers to be
7324 specified (the list of allowed identifiers is the same as for
7325 pragma @code{Restrictions}). For each of these identifiers
7326 the compiler checks for violations of the restriction, but
7327 generates a warning message rather than an error message
7328 if the restriction is violated.
7330 One use of this is in situations where you want to know
7331 about violations of a restriction, but you want to ignore some of
7332 these violations. Consider this example, where you want to set
7333 Ada_95 mode and enable style checks, but you want to know about
7334 any other use of implementation pragmas:
7337 pragma Restriction_Warnings (No_Implementation_Pragmas);
7338 pragma Warnings (Off, "violation of No_Implementation_Pragmas");
7340 pragma Style_Checks ("2bfhkM160");
7341 pragma Warnings (On, "violation of No_Implementation_Pragmas");
7344 By including the above lines in a configuration pragmas file,
7345 the Ada_95 and Style_Checks pragmas are accepted without
7346 generating a warning, but any other use of implementation
7347 defined pragmas will cause a warning to be generated.
7349 @node Pragma Reviewable,Pragma Secondary_Stack_Size,Pragma Restriction_Warnings,Implementation Defined Pragmas
7350 @anchor{gnat_rm/implementation_defined_pragmas pragma-reviewable}@anchor{df}
7351 @section Pragma Reviewable
7360 This pragma is an RM-defined standard pragma, but has no effect on the
7361 program being compiled, or on the code generated for the program.
7363 To obtain the required output specified in RM H.3.1, the compiler must be
7364 run with various special switches as follows:
7370 @emph{Where compiler-generated run-time checks remain}
7372 The switch @emph{-gnatGL}
7373 may be used to list the expanded code in pseudo-Ada form.
7374 Runtime checks show up in the listing either as explicit
7375 checks or operators marked with @{@} to indicate a check is present.
7378 @emph{An identification of known exceptions at compile time}
7380 If the program is compiled with @emph{-gnatwa},
7381 the compiler warning messages will indicate all cases where the compiler
7382 detects that an exception is certain to occur at run time.
7385 @emph{Possible reads of uninitialized variables}
7387 The compiler warns of many such cases, but its output is incomplete.
7391 A supplemental static analysis tool
7392 may be used to obtain a comprehensive list of all
7393 possible points at which uninitialized data may be read.
7399 @emph{Where run-time support routines are implicitly invoked}
7401 In the output from @emph{-gnatGL},
7402 run-time calls are explicitly listed as calls to the relevant
7406 @emph{Object code listing}
7408 This may be obtained either by using the @emph{-S} switch,
7409 or the objdump utility.
7412 @emph{Constructs known to be erroneous at compile time}
7414 These are identified by warnings issued by the compiler (use @emph{-gnatwa}).
7417 @emph{Stack usage information}
7419 Static stack usage data (maximum per-subprogram) can be obtained via the
7420 @emph{-fstack-usage} switch to the compiler.
7421 Dynamic stack usage data (per task) can be obtained via the @emph{-u} switch
7430 @emph{Object code listing of entire partition}
7432 This can be obtained by compiling the partition with @emph{-S},
7433 or by applying objdump
7434 to all the object files that are part of the partition.
7437 @emph{A description of the run-time model}
7439 The full sources of the run-time are available, and the documentation of
7440 these routines describes how these run-time routines interface to the
7441 underlying operating system facilities.
7444 @emph{Control and data-flow information}
7448 A supplemental static analysis tool
7449 may be used to obtain complete control and data-flow information, as well as
7450 comprehensive messages identifying possible problems based on this
7453 @node Pragma Secondary_Stack_Size,Pragma Share_Generic,Pragma Reviewable,Implementation Defined Pragmas
7454 @anchor{gnat_rm/implementation_defined_pragmas id37}@anchor{e0}@anchor{gnat_rm/implementation_defined_pragmas pragma-secondary-stack-size}@anchor{e1}
7455 @section Pragma Secondary_Stack_Size
7461 pragma Secondary_Stack_Size (integer_EXPRESSION);
7464 This pragma appears within the task definition of a single task declaration
7465 or a task type declaration (like pragma @code{Storage_Size}) and applies to all
7466 task objects of that type. The argument specifies the size of the secondary
7467 stack to be used by these task objects, and must be of an integer type. The
7468 secondary stack is used to handle functions that return a variable-sized
7469 result, for example a function returning an unconstrained String.
7471 Note this pragma only applies to targets using fixed secondary stacks, like
7472 VxWorks 653 and bare board targets, where a fixed block for the
7473 secondary stack is allocated from the primary stack of the task. By default,
7474 these targets assign a percentage of the primary stack for the secondary stack,
7475 as defined by @code{System.Parameter.Sec_Stack_Percentage}. With this pragma,
7476 an @code{integer_EXPRESSION} of bytes is assigned from the primary stack instead.
7478 For most targets, the pragma does not apply as the secondary stack grows on
7479 demand: allocated as a chain of blocks in the heap. The default size of these
7480 blocks can be modified via the @code{-D} binder option as described in
7481 @cite{GNAT User's Guide}.
7483 Note that no check is made to see if the secondary stack can fit inside the
7486 Note the pragma cannot appear when the restriction @code{No_Secondary_Stack}
7489 @node Pragma Share_Generic,Pragma Shared,Pragma Secondary_Stack_Size,Implementation Defined Pragmas
7490 @anchor{gnat_rm/implementation_defined_pragmas pragma-share-generic}@anchor{e2}
7491 @section Pragma Share_Generic
7497 pragma Share_Generic (GNAME @{, GNAME@});
7499 GNAME ::= generic_unit_NAME | generic_instance_NAME
7502 This pragma is provided for compatibility with Dec Ada 83. It has
7503 no effect in GNAT (which does not implement shared generics), other
7504 than to check that the given names are all names of generic units or
7507 @node Pragma Shared,Pragma Short_Circuit_And_Or,Pragma Share_Generic,Implementation Defined Pragmas
7508 @anchor{gnat_rm/implementation_defined_pragmas id38}@anchor{e3}@anchor{gnat_rm/implementation_defined_pragmas pragma-shared}@anchor{e4}
7509 @section Pragma Shared
7512 This pragma is provided for compatibility with Ada 83. The syntax and
7513 semantics are identical to pragma Atomic.
7515 @node Pragma Short_Circuit_And_Or,Pragma Short_Descriptors,Pragma Shared,Implementation Defined Pragmas
7516 @anchor{gnat_rm/implementation_defined_pragmas pragma-short-circuit-and-or}@anchor{e5}
7517 @section Pragma Short_Circuit_And_Or
7523 pragma Short_Circuit_And_Or;
7526 This configuration pragma causes any occurrence of the AND operator applied to
7527 operands of type Standard.Boolean to be short-circuited (i.e. the AND operator
7528 is treated as if it were AND THEN). Or is similarly treated as OR ELSE. This
7529 may be useful in the context of certification protocols requiring the use of
7530 short-circuited logical operators. If this configuration pragma occurs locally
7531 within the file being compiled, it applies only to the file being compiled.
7532 There is no requirement that all units in a partition use this option.
7534 @node Pragma Short_Descriptors,Pragma Simple_Storage_Pool_Type,Pragma Short_Circuit_And_Or,Implementation Defined Pragmas
7535 @anchor{gnat_rm/implementation_defined_pragmas pragma-short-descriptors}@anchor{e6}
7536 @section Pragma Short_Descriptors
7542 pragma Short_Descriptors
7545 This pragma is provided for compatibility with other Ada implementations. It
7546 is recognized but ignored by all current versions of GNAT.
7548 @node Pragma Simple_Storage_Pool_Type,Pragma Source_File_Name,Pragma Short_Descriptors,Implementation Defined Pragmas
7549 @anchor{gnat_rm/implementation_defined_pragmas pragma-simple-storage-pool-type}@anchor{e7}@anchor{gnat_rm/implementation_defined_pragmas id39}@anchor{e8}
7550 @section Pragma Simple_Storage_Pool_Type
7553 @geindex Storage pool
7556 @geindex Simple storage pool
7561 pragma Simple_Storage_Pool_Type (type_LOCAL_NAME);
7564 A type can be established as a 'simple storage pool type' by applying
7565 the representation pragma @code{Simple_Storage_Pool_Type} to the type.
7566 A type named in the pragma must be a library-level immutably limited record
7567 type or limited tagged type declared immediately within a package declaration.
7568 The type can also be a limited private type whose full type is allowed as
7569 a simple storage pool type.
7571 For a simple storage pool type @code{SSP}, nonabstract primitive subprograms
7572 @code{Allocate}, @code{Deallocate}, and @code{Storage_Size} can be declared that
7573 are subtype conformant with the following subprogram declarations:
7578 Storage_Address : out System.Address;
7579 Size_In_Storage_Elements : System.Storage_Elements.Storage_Count;
7580 Alignment : System.Storage_Elements.Storage_Count);
7582 procedure Deallocate
7584 Storage_Address : System.Address;
7585 Size_In_Storage_Elements : System.Storage_Elements.Storage_Count;
7586 Alignment : System.Storage_Elements.Storage_Count);
7588 function Storage_Size (Pool : SSP)
7589 return System.Storage_Elements.Storage_Count;
7592 Procedure @code{Allocate} must be declared, whereas @code{Deallocate} and
7593 @code{Storage_Size} are optional. If @code{Deallocate} is not declared, then
7594 applying an unchecked deallocation has no effect other than to set its actual
7595 parameter to null. If @code{Storage_Size} is not declared, then the
7596 @code{Storage_Size} attribute applied to an access type associated with
7597 a pool object of type SSP returns zero. Additional operations can be declared
7598 for a simple storage pool type (such as for supporting a mark/release
7599 storage-management discipline).
7601 An object of a simple storage pool type can be associated with an access
7602 type by specifying the attribute
7603 @ref{e9,,Simple_Storage_Pool}. For example:
7606 My_Pool : My_Simple_Storage_Pool_Type;
7608 type Acc is access My_Data_Type;
7610 for Acc'Simple_Storage_Pool use My_Pool;
7613 See attribute @ref{e9,,Simple_Storage_Pool}
7614 for further details.
7616 @node Pragma Source_File_Name,Pragma Source_File_Name_Project,Pragma Simple_Storage_Pool_Type,Implementation Defined Pragmas
7617 @anchor{gnat_rm/implementation_defined_pragmas pragma-source-file-name}@anchor{ea}@anchor{gnat_rm/implementation_defined_pragmas id40}@anchor{eb}
7618 @section Pragma Source_File_Name
7624 pragma Source_File_Name (
7625 [Unit_Name =>] unit_NAME,
7626 Spec_File_Name => STRING_LITERAL,
7627 [Index => INTEGER_LITERAL]);
7629 pragma Source_File_Name (
7630 [Unit_Name =>] unit_NAME,
7631 Body_File_Name => STRING_LITERAL,
7632 [Index => INTEGER_LITERAL]);
7635 Use this to override the normal naming convention. It is a configuration
7636 pragma, and so has the usual applicability of configuration pragmas
7637 (i.e., it applies to either an entire partition, or to all units in a
7638 compilation, or to a single unit, depending on how it is used.
7639 @code{unit_name} is mapped to @code{file_name_literal}. The identifier for
7640 the second argument is required, and indicates whether this is the file
7641 name for the spec or for the body.
7643 The optional Index argument should be used when a file contains multiple
7644 units, and when you do not want to use @code{gnatchop} to separate then
7645 into multiple files (which is the recommended procedure to limit the
7646 number of recompilations that are needed when some sources change).
7647 For instance, if the source file @code{source.ada} contains
7661 you could use the following configuration pragmas:
7664 pragma Source_File_Name
7665 (B, Spec_File_Name => "source.ada", Index => 1);
7666 pragma Source_File_Name
7667 (A, Body_File_Name => "source.ada", Index => 2);
7670 Note that the @code{gnatname} utility can also be used to generate those
7671 configuration pragmas.
7673 Another form of the @code{Source_File_Name} pragma allows
7674 the specification of patterns defining alternative file naming schemes
7675 to apply to all files.
7678 pragma Source_File_Name
7679 ( [Spec_File_Name =>] STRING_LITERAL
7680 [,[Casing =>] CASING_SPEC]
7681 [,[Dot_Replacement =>] STRING_LITERAL]);
7683 pragma Source_File_Name
7684 ( [Body_File_Name =>] STRING_LITERAL
7685 [,[Casing =>] CASING_SPEC]
7686 [,[Dot_Replacement =>] STRING_LITERAL]);
7688 pragma Source_File_Name
7689 ( [Subunit_File_Name =>] STRING_LITERAL
7690 [,[Casing =>] CASING_SPEC]
7691 [,[Dot_Replacement =>] STRING_LITERAL]);
7693 CASING_SPEC ::= Lowercase | Uppercase | Mixedcase
7696 The first argument is a pattern that contains a single asterisk indicating
7697 the point at which the unit name is to be inserted in the pattern string
7698 to form the file name. The second argument is optional. If present it
7699 specifies the casing of the unit name in the resulting file name string.
7700 The default is lower case. Finally the third argument allows for systematic
7701 replacement of any dots in the unit name by the specified string literal.
7703 Note that Source_File_Name pragmas should not be used if you are using
7704 project files. The reason for this rule is that the project manager is not
7705 aware of these pragmas, and so other tools that use the projet file would not
7706 be aware of the intended naming conventions. If you are using project files,
7707 file naming is controlled by Source_File_Name_Project pragmas, which are
7708 usually supplied automatically by the project manager. A pragma
7709 Source_File_Name cannot appear after a @ref{ec,,Pragma Source_File_Name_Project}.
7711 For more details on the use of the @code{Source_File_Name} pragma, see the
7712 sections on @cite{Using Other File Names} and @cite{Alternative File Naming Schemes}
7713 in the @cite{GNAT User's Guide}.
7715 @node Pragma Source_File_Name_Project,Pragma Source_Reference,Pragma Source_File_Name,Implementation Defined Pragmas
7716 @anchor{gnat_rm/implementation_defined_pragmas pragma-source-file-name-project}@anchor{ec}@anchor{gnat_rm/implementation_defined_pragmas id41}@anchor{ed}
7717 @section Pragma Source_File_Name_Project
7720 This pragma has the same syntax and semantics as pragma Source_File_Name.
7721 It is only allowed as a stand-alone configuration pragma.
7722 It cannot appear after a @ref{ea,,Pragma Source_File_Name}, and
7723 most importantly, once pragma Source_File_Name_Project appears,
7724 no further Source_File_Name pragmas are allowed.
7726 The intention is that Source_File_Name_Project pragmas are always
7727 generated by the Project Manager in a manner consistent with the naming
7728 specified in a project file, and when naming is controlled in this manner,
7729 it is not permissible to attempt to modify this naming scheme using
7730 Source_File_Name or Source_File_Name_Project pragmas (which would not be
7731 known to the project manager).
7733 @node Pragma Source_Reference,Pragma SPARK_Mode,Pragma Source_File_Name_Project,Implementation Defined Pragmas
7734 @anchor{gnat_rm/implementation_defined_pragmas pragma-source-reference}@anchor{ee}
7735 @section Pragma Source_Reference
7741 pragma Source_Reference (INTEGER_LITERAL, STRING_LITERAL);
7744 This pragma must appear as the first line of a source file.
7745 @code{integer_literal} is the logical line number of the line following
7746 the pragma line (for use in error messages and debugging
7747 information). @code{string_literal} is a static string constant that
7748 specifies the file name to be used in error messages and debugging
7749 information. This is most notably used for the output of @code{gnatchop}
7750 with the @emph{-r} switch, to make sure that the original unchopped
7751 source file is the one referred to.
7753 The second argument must be a string literal, it cannot be a static
7754 string expression other than a string literal. This is because its value
7755 is needed for error messages issued by all phases of the compiler.
7757 @node Pragma SPARK_Mode,Pragma Static_Elaboration_Desired,Pragma Source_Reference,Implementation Defined Pragmas
7758 @anchor{gnat_rm/implementation_defined_pragmas pragma-spark-mode}@anchor{ef}@anchor{gnat_rm/implementation_defined_pragmas id42}@anchor{f0}
7759 @section Pragma SPARK_Mode
7765 pragma SPARK_Mode [(On | Off)] ;
7768 In general a program can have some parts that are in SPARK 2014 (and
7769 follow all the rules in the SPARK Reference Manual), and some parts
7770 that are full Ada 2012.
7772 The SPARK_Mode pragma is used to identify which parts are in SPARK
7773 2014 (by default programs are in full Ada). The SPARK_Mode pragma can
7774 be used in the following places:
7780 As a configuration pragma, in which case it sets the default mode for
7781 all units compiled with this pragma.
7784 Immediately following a library-level subprogram spec
7787 Immediately within a library-level package body
7790 Immediately following the @code{private} keyword of a library-level
7794 Immediately following the @code{begin} keyword of a library-level
7798 Immediately within a library-level subprogram body
7801 Normally a subprogram or package spec/body inherits the current mode
7802 that is active at the point it is declared. But this can be overridden
7803 by pragma within the spec or body as above.
7805 The basic consistency rule is that you can't turn SPARK_Mode back
7806 @code{On}, once you have explicitly (with a pragma) turned if
7807 @code{Off}. So the following rules apply:
7809 If a subprogram spec has SPARK_Mode @code{Off}, then the body must
7810 also have SPARK_Mode @code{Off}.
7812 For a package, we have four parts:
7818 the package public declarations
7821 the package private part
7824 the body of the package
7827 the elaboration code after @code{begin}
7830 For a package, the rule is that if you explicitly turn SPARK_Mode
7831 @code{Off} for any part, then all the following parts must have
7832 SPARK_Mode @code{Off}. Note that this may require repeating a pragma
7833 SPARK_Mode (@code{Off}) in the body. For example, if we have a
7834 configuration pragma SPARK_Mode (@code{On}) that turns the mode on by
7835 default everywhere, and one particular package spec has pragma
7836 SPARK_Mode (@code{Off}), then that pragma will need to be repeated in
7839 @node Pragma Static_Elaboration_Desired,Pragma Stream_Convert,Pragma SPARK_Mode,Implementation Defined Pragmas
7840 @anchor{gnat_rm/implementation_defined_pragmas pragma-static-elaboration-desired}@anchor{f1}
7841 @section Pragma Static_Elaboration_Desired
7847 pragma Static_Elaboration_Desired;
7850 This pragma is used to indicate that the compiler should attempt to initialize
7851 statically the objects declared in the library unit to which the pragma applies,
7852 when these objects are initialized (explicitly or implicitly) by an aggregate.
7853 In the absence of this pragma, aggregates in object declarations are expanded
7854 into assignments and loops, even when the aggregate components are static
7855 constants. When the aggregate is present the compiler builds a static expression
7856 that requires no run-time code, so that the initialized object can be placed in
7857 read-only data space. If the components are not static, or the aggregate has
7858 more that 100 components, the compiler emits a warning that the pragma cannot
7859 be obeyed. (See also the restriction No_Implicit_Loops, which supports static
7860 construction of larger aggregates with static components that include an others
7863 @node Pragma Stream_Convert,Pragma Style_Checks,Pragma Static_Elaboration_Desired,Implementation Defined Pragmas
7864 @anchor{gnat_rm/implementation_defined_pragmas pragma-stream-convert}@anchor{f2}
7865 @section Pragma Stream_Convert
7871 pragma Stream_Convert (
7872 [Entity =>] type_LOCAL_NAME,
7873 [Read =>] function_NAME,
7874 [Write =>] function_NAME);
7877 This pragma provides an efficient way of providing user-defined stream
7878 attributes. Not only is it simpler to use than specifying the attributes
7879 directly, but more importantly, it allows the specification to be made in such
7880 a way that the predefined unit Ada.Streams is not loaded unless it is actually
7881 needed (i.e. unless the stream attributes are actually used); the use of
7882 the Stream_Convert pragma adds no overhead at all, unless the stream
7883 attributes are actually used on the designated type.
7885 The first argument specifies the type for which stream functions are
7886 provided. The second parameter provides a function used to read values
7887 of this type. It must name a function whose argument type may be any
7888 subtype, and whose returned type must be the type given as the first
7889 argument to the pragma.
7891 The meaning of the @code{Read} parameter is that if a stream attribute directly
7892 or indirectly specifies reading of the type given as the first parameter,
7893 then a value of the type given as the argument to the Read function is
7894 read from the stream, and then the Read function is used to convert this
7895 to the required target type.
7897 Similarly the @code{Write} parameter specifies how to treat write attributes
7898 that directly or indirectly apply to the type given as the first parameter.
7899 It must have an input parameter of the type specified by the first parameter,
7900 and the return type must be the same as the input type of the Read function.
7901 The effect is to first call the Write function to convert to the given stream
7902 type, and then write the result type to the stream.
7904 The Read and Write functions must not be overloaded subprograms. If necessary
7905 renamings can be supplied to meet this requirement.
7906 The usage of this attribute is best illustrated by a simple example, taken
7907 from the GNAT implementation of package Ada.Strings.Unbounded:
7910 function To_Unbounded (S : String) return Unbounded_String
7911 renames To_Unbounded_String;
7913 pragma Stream_Convert
7914 (Unbounded_String, To_Unbounded, To_String);
7917 The specifications of the referenced functions, as given in the Ada
7918 Reference Manual are:
7921 function To_Unbounded_String (Source : String)
7922 return Unbounded_String;
7924 function To_String (Source : Unbounded_String)
7928 The effect is that if the value of an unbounded string is written to a stream,
7929 then the representation of the item in the stream is in the same format that
7930 would be used for @code{Standard.String'Output}, and this same representation
7931 is expected when a value of this type is read from the stream. Note that the
7932 value written always includes the bounds, even for Unbounded_String'Write,
7933 since Unbounded_String is not an array type.
7935 Note that the @code{Stream_Convert} pragma is not effective in the case of
7936 a derived type of a non-limited tagged type. If such a type is specified then
7937 the pragma is silently ignored, and the default implementation of the stream
7938 attributes is used instead.
7940 @node Pragma Style_Checks,Pragma Subtitle,Pragma Stream_Convert,Implementation Defined Pragmas
7941 @anchor{gnat_rm/implementation_defined_pragmas pragma-style-checks}@anchor{f3}
7942 @section Pragma Style_Checks
7948 pragma Style_Checks (string_LITERAL | ALL_CHECKS |
7949 On | Off [, LOCAL_NAME]);
7952 This pragma is used in conjunction with compiler switches to control the
7953 built in style checking provided by GNAT. The compiler switches, if set,
7954 provide an initial setting for the switches, and this pragma may be used
7955 to modify these settings, or the settings may be provided entirely by
7956 the use of the pragma. This pragma can be used anywhere that a pragma
7957 is legal, including use as a configuration pragma (including use in
7958 the @code{gnat.adc} file).
7960 The form with a string literal specifies which style options are to be
7961 activated. These are additive, so they apply in addition to any previously
7962 set style check options. The codes for the options are the same as those
7963 used in the @emph{-gnaty} switch to @emph{gcc} or @emph{gnatmake}.
7964 For example the following two methods can be used to enable
7972 pragma Style_Checks ("l");
7981 The form @code{ALL_CHECKS} activates all standard checks (its use is equivalent
7982 to the use of the @code{gnaty} switch with no options.
7983 See the @cite{GNAT User's Guide} for details.)
7985 Note: the behavior is slightly different in GNAT mode (@code{-gnatg} used).
7986 In this case, @code{ALL_CHECKS} implies the standard set of GNAT mode style check
7987 options (i.e. equivalent to @code{-gnatyg}).
7989 The forms with @code{Off} and @code{On}
7990 can be used to temporarily disable style checks
7991 as shown in the following example:
7994 pragma Style_Checks ("k"); -- requires keywords in lower case
7995 pragma Style_Checks (Off); -- turn off style checks
7996 NULL; -- this will not generate an error message
7997 pragma Style_Checks (On); -- turn style checks back on
7998 NULL; -- this will generate an error message
8001 Finally the two argument form is allowed only if the first argument is
8002 @code{On} or @code{Off}. The effect is to turn of semantic style checks
8003 for the specified entity, as shown in the following example:
8006 pragma Style_Checks ("r"); -- require consistency of identifier casing
8008 Rf1 : Integer := ARG; -- incorrect, wrong case
8009 pragma Style_Checks (Off, Arg);
8010 Rf2 : Integer := ARG; -- OK, no error
8013 @node Pragma Subtitle,Pragma Suppress,Pragma Style_Checks,Implementation Defined Pragmas
8014 @anchor{gnat_rm/implementation_defined_pragmas pragma-subtitle}@anchor{f4}
8015 @section Pragma Subtitle
8021 pragma Subtitle ([Subtitle =>] STRING_LITERAL);
8024 This pragma is recognized for compatibility with other Ada compilers
8025 but is ignored by GNAT.
8027 @node Pragma Suppress,Pragma Suppress_All,Pragma Subtitle,Implementation Defined Pragmas
8028 @anchor{gnat_rm/implementation_defined_pragmas pragma-suppress}@anchor{f5}
8029 @section Pragma Suppress
8035 pragma Suppress (Identifier [, [On =>] Name]);
8038 This is a standard pragma, and supports all the check names required in
8039 the RM. It is included here because GNAT recognizes some additional check
8040 names that are implementation defined (as permitted by the RM):
8046 @code{Alignment_Check} can be used to suppress alignment checks
8047 on addresses used in address clauses. Such checks can also be suppressed
8048 by suppressing range checks, but the specific use of @code{Alignment_Check}
8049 allows suppression of alignment checks without suppressing other range checks.
8050 Note that @code{Alignment_Check} is suppressed by default on machines (such as
8051 the x86) with non-strict alignment.
8054 @code{Atomic_Synchronization} can be used to suppress the special memory
8055 synchronization instructions that are normally generated for access to
8056 @code{Atomic} variables to ensure correct synchronization between tasks
8057 that use such variables for synchronization purposes.
8060 @code{Duplicated_Tag_Check} Can be used to suppress the check that is generated
8061 for a duplicated tag value when a tagged type is declared.
8064 @code{Container_Checks} Can be used to suppress all checks within Ada.Containers
8065 and instances of its children, including Tampering_Check.
8068 @code{Tampering_Check} Can be used to suppress tampering check in the containers.
8071 @code{Predicate_Check} can be used to control whether predicate checks are
8072 active. It is applicable only to predicates for which the policy is
8073 @code{Check}. Unlike @code{Assertion_Policy}, which determines if a given
8074 predicate is ignored or checked for the whole program, the use of
8075 @code{Suppress} and @code{Unsuppress} with this check name allows a given
8076 predicate to be turned on and off at specific points in the program.
8079 @code{Validity_Check} can be used specifically to control validity checks.
8080 If @code{Suppress} is used to suppress validity checks, then no validity
8081 checks are performed, including those specified by the appropriate compiler
8082 switch or the @code{Validity_Checks} pragma.
8085 Additional check names previously introduced by use of the @code{Check_Name}
8086 pragma are also allowed.
8089 Note that pragma Suppress gives the compiler permission to omit
8090 checks, but does not require the compiler to omit checks. The compiler
8091 will generate checks if they are essentially free, even when they are
8092 suppressed. In particular, if the compiler can prove that a certain
8093 check will necessarily fail, it will generate code to do an
8094 unconditional 'raise', even if checks are suppressed. The compiler
8097 Of course, run-time checks are omitted whenever the compiler can prove
8098 that they will not fail, whether or not checks are suppressed.
8100 @node Pragma Suppress_All,Pragma Suppress_Debug_Info,Pragma Suppress,Implementation Defined Pragmas
8101 @anchor{gnat_rm/implementation_defined_pragmas pragma-suppress-all}@anchor{f6}
8102 @section Pragma Suppress_All
8108 pragma Suppress_All;
8111 This pragma can appear anywhere within a unit.
8112 The effect is to apply @code{Suppress (All_Checks)} to the unit
8113 in which it appears. This pragma is implemented for compatibility with DEC
8114 Ada 83 usage where it appears at the end of a unit, and for compatibility
8115 with Rational Ada, where it appears as a program unit pragma.
8116 The use of the standard Ada pragma @code{Suppress (All_Checks)}
8117 as a normal configuration pragma is the preferred usage in GNAT.
8119 @node Pragma Suppress_Debug_Info,Pragma Suppress_Exception_Locations,Pragma Suppress_All,Implementation Defined Pragmas
8120 @anchor{gnat_rm/implementation_defined_pragmas pragma-suppress-debug-info}@anchor{f7}@anchor{gnat_rm/implementation_defined_pragmas id43}@anchor{f8}
8121 @section Pragma Suppress_Debug_Info
8127 pragma Suppress_Debug_Info ([Entity =>] LOCAL_NAME);
8130 This pragma can be used to suppress generation of debug information
8131 for the specified entity. It is intended primarily for use in debugging
8132 the debugger, and navigating around debugger problems.
8134 @node Pragma Suppress_Exception_Locations,Pragma Suppress_Initialization,Pragma Suppress_Debug_Info,Implementation Defined Pragmas
8135 @anchor{gnat_rm/implementation_defined_pragmas pragma-suppress-exception-locations}@anchor{f9}
8136 @section Pragma Suppress_Exception_Locations
8142 pragma Suppress_Exception_Locations;
8145 In normal mode, a raise statement for an exception by default generates
8146 an exception message giving the file name and line number for the location
8147 of the raise. This is useful for debugging and logging purposes, but this
8148 entails extra space for the strings for the messages. The configuration
8149 pragma @code{Suppress_Exception_Locations} can be used to suppress the
8150 generation of these strings, with the result that space is saved, but the
8151 exception message for such raises is null. This configuration pragma may
8152 appear in a global configuration pragma file, or in a specific unit as
8153 usual. It is not required that this pragma be used consistently within
8154 a partition, so it is fine to have some units within a partition compiled
8155 with this pragma and others compiled in normal mode without it.
8157 @node Pragma Suppress_Initialization,Pragma Task_Name,Pragma Suppress_Exception_Locations,Implementation Defined Pragmas
8158 @anchor{gnat_rm/implementation_defined_pragmas id44}@anchor{fa}@anchor{gnat_rm/implementation_defined_pragmas pragma-suppress-initialization}@anchor{fb}
8159 @section Pragma Suppress_Initialization
8162 @geindex Suppressing initialization
8164 @geindex Initialization
8165 @geindex suppression of
8170 pragma Suppress_Initialization ([Entity =>] variable_or_subtype_Name);
8173 Here variable_or_subtype_Name is the name introduced by a type declaration
8174 or subtype declaration or the name of a variable introduced by an
8177 In the case of a type or subtype
8178 this pragma suppresses any implicit or explicit initialization
8179 for all variables of the given type or subtype,
8180 including initialization resulting from the use of pragmas
8181 Normalize_Scalars or Initialize_Scalars.
8183 This is considered a representation item, so it cannot be given after
8184 the type is frozen. It applies to all subsequent object declarations,
8185 and also any allocator that creates objects of the type.
8187 If the pragma is given for the first subtype, then it is considered
8188 to apply to the base type and all its subtypes. If the pragma is given
8189 for other than a first subtype, then it applies only to the given subtype.
8190 The pragma may not be given after the type is frozen.
8192 Note that this includes eliminating initialization of discriminants
8193 for discriminated types, and tags for tagged types. In these cases,
8194 you will have to use some non-portable mechanism (e.g. address
8195 overlays or unchecked conversion) to achieve required initialization
8196 of these fields before accessing any object of the corresponding type.
8198 For the variable case, implicit initialization for the named variable
8199 is suppressed, just as though its subtype had been given in a pragma
8200 Suppress_Initialization, as described above.
8202 @node Pragma Task_Name,Pragma Task_Storage,Pragma Suppress_Initialization,Implementation Defined Pragmas
8203 @anchor{gnat_rm/implementation_defined_pragmas pragma-task-name}@anchor{fc}
8204 @section Pragma Task_Name
8210 pragma Task_Name (string_EXPRESSION);
8213 This pragma appears within a task definition (like pragma
8214 @code{Priority}) and applies to the task in which it appears. The
8215 argument must be of type String, and provides a name to be used for
8216 the task instance when the task is created. Note that this expression
8217 is not required to be static, and in particular, it can contain
8218 references to task discriminants. This facility can be used to
8219 provide different names for different tasks as they are created,
8220 as illustrated in the example below.
8222 The task name is recorded internally in the run-time structures
8223 and is accessible to tools like the debugger. In addition the
8224 routine @code{Ada.Task_Identification.Image} will return this
8225 string, with a unique task address appended.
8228 -- Example of the use of pragma Task_Name
8230 with Ada.Task_Identification;
8231 use Ada.Task_Identification;
8232 with Text_IO; use Text_IO;
8235 type Astring is access String;
8237 task type Task_Typ (Name : access String) is
8238 pragma Task_Name (Name.all);
8241 task body Task_Typ is
8242 Nam : constant String := Image (Current_Task);
8244 Put_Line ("-->" & Nam (1 .. 14) & "<--");
8247 type Ptr_Task is access Task_Typ;
8248 Task_Var : Ptr_Task;
8252 new Task_Typ (new String'("This is task 1"));
8254 new Task_Typ (new String'("This is task 2"));
8258 @node Pragma Task_Storage,Pragma Test_Case,Pragma Task_Name,Implementation Defined Pragmas
8259 @anchor{gnat_rm/implementation_defined_pragmas pragma-task-storage}@anchor{fd}
8260 @section Pragma Task_Storage
8266 pragma Task_Storage (
8267 [Task_Type =>] LOCAL_NAME,
8268 [Top_Guard =>] static_integer_EXPRESSION);
8271 This pragma specifies the length of the guard area for tasks. The guard
8272 area is an additional storage area allocated to a task. A value of zero
8273 means that either no guard area is created or a minimal guard area is
8274 created, depending on the target. This pragma can appear anywhere a
8275 @code{Storage_Size} attribute definition clause is allowed for a task
8278 @node Pragma Test_Case,Pragma Thread_Local_Storage,Pragma Task_Storage,Implementation Defined Pragmas
8279 @anchor{gnat_rm/implementation_defined_pragmas pragma-test-case}@anchor{fe}@anchor{gnat_rm/implementation_defined_pragmas id45}@anchor{ff}
8280 @section Pragma Test_Case
8289 [Name =>] static_string_Expression
8290 ,[Mode =>] (Nominal | Robustness)
8291 [, Requires => Boolean_Expression]
8292 [, Ensures => Boolean_Expression]);
8295 The @code{Test_Case} pragma allows defining fine-grain specifications
8296 for use by testing tools.
8297 The compiler checks the validity of the @code{Test_Case} pragma, but its
8298 presence does not lead to any modification of the code generated by the
8301 @code{Test_Case} pragmas may only appear immediately following the
8302 (separate) declaration of a subprogram in a package declaration, inside
8303 a package spec unit. Only other pragmas may intervene (that is appear
8304 between the subprogram declaration and a test case).
8306 The compiler checks that boolean expressions given in @code{Requires} and
8307 @code{Ensures} are valid, where the rules for @code{Requires} are the
8308 same as the rule for an expression in @code{Precondition} and the rules
8309 for @code{Ensures} are the same as the rule for an expression in
8310 @code{Postcondition}. In particular, attributes @code{'Old} and
8311 @code{'Result} can only be used within the @code{Ensures}
8312 expression. The following is an example of use within a package spec:
8315 package Math_Functions is
8317 function Sqrt (Arg : Float) return Float;
8318 pragma Test_Case (Name => "Test 1",
8320 Requires => Arg < 10000,
8321 Ensures => Sqrt'Result < 10);
8326 The meaning of a test case is that there is at least one context where
8327 @code{Requires} holds such that, if the associated subprogram is executed in
8328 that context, then @code{Ensures} holds when the subprogram returns.
8329 Mode @code{Nominal} indicates that the input context should also satisfy the
8330 precondition of the subprogram, and the output context should also satisfy its
8331 postcondition. Mode @code{Robustness} indicates that the precondition and
8332 postcondition of the subprogram should be ignored for this test case.
8334 @node Pragma Thread_Local_Storage,Pragma Time_Slice,Pragma Test_Case,Implementation Defined Pragmas
8335 @anchor{gnat_rm/implementation_defined_pragmas pragma-thread-local-storage}@anchor{100}@anchor{gnat_rm/implementation_defined_pragmas id46}@anchor{101}
8336 @section Pragma Thread_Local_Storage
8339 @geindex Task specific storage
8341 @geindex TLS (Thread Local Storage)
8343 @geindex Task_Attributes
8348 pragma Thread_Local_Storage ([Entity =>] LOCAL_NAME);
8351 This pragma specifies that the specified entity, which must be
8352 a variable declared in a library-level package, is to be marked as
8353 "Thread Local Storage" (@code{TLS}). On systems supporting this (which
8354 include Windows, Solaris, GNU/Linux, and VxWorks 6), this causes each
8355 thread (and hence each Ada task) to see a distinct copy of the variable.
8357 The variable must not have default initialization, and if there is
8358 an explicit initialization, it must be either @code{null} for an
8359 access variable, a static expression for a scalar variable, or a fully
8360 static aggregate for a composite type, that is to say, an aggregate all
8361 of whose components are static, and which does not include packed or
8362 discriminated components.
8364 This provides a low-level mechanism similar to that provided by
8365 the @code{Ada.Task_Attributes} package, but much more efficient
8366 and is also useful in writing interface code that will interact
8367 with foreign threads.
8369 If this pragma is used on a system where @code{TLS} is not supported,
8370 then an error message will be generated and the program will be rejected.
8372 @node Pragma Time_Slice,Pragma Title,Pragma Thread_Local_Storage,Implementation Defined Pragmas
8373 @anchor{gnat_rm/implementation_defined_pragmas pragma-time-slice}@anchor{102}
8374 @section Pragma Time_Slice
8380 pragma Time_Slice (static_duration_EXPRESSION);
8383 For implementations of GNAT on operating systems where it is possible
8384 to supply a time slice value, this pragma may be used for this purpose.
8385 It is ignored if it is used in a system that does not allow this control,
8386 or if it appears in other than the main program unit.
8388 @node Pragma Title,Pragma Type_Invariant,Pragma Time_Slice,Implementation Defined Pragmas
8389 @anchor{gnat_rm/implementation_defined_pragmas pragma-title}@anchor{103}
8390 @section Pragma Title
8396 pragma Title (TITLING_OPTION [, TITLING OPTION]);
8399 [Title =>] STRING_LITERAL,
8400 | [Subtitle =>] STRING_LITERAL
8403 Syntax checked but otherwise ignored by GNAT. This is a listing control
8404 pragma used in DEC Ada 83 implementations to provide a title and/or
8405 subtitle for the program listing. The program listing generated by GNAT
8406 does not have titles or subtitles.
8408 Unlike other pragmas, the full flexibility of named notation is allowed
8409 for this pragma, i.e., the parameters may be given in any order if named
8410 notation is used, and named and positional notation can be mixed
8411 following the normal rules for procedure calls in Ada.
8413 @node Pragma Type_Invariant,Pragma Type_Invariant_Class,Pragma Title,Implementation Defined Pragmas
8414 @anchor{gnat_rm/implementation_defined_pragmas pragma-type-invariant}@anchor{104}
8415 @section Pragma Type_Invariant
8421 pragma Type_Invariant
8422 ([Entity =>] type_LOCAL_NAME,
8423 [Check =>] EXPRESSION);
8426 The @code{Type_Invariant} pragma is intended to be an exact
8427 replacement for the language-defined @code{Type_Invariant}
8428 aspect, and shares its restrictions and semantics. It differs
8429 from the language defined @code{Invariant} pragma in that it
8430 does not permit a string parameter, and it is
8431 controlled by the assertion identifier @code{Type_Invariant}
8432 rather than @code{Invariant}.
8434 @node Pragma Type_Invariant_Class,Pragma Unchecked_Union,Pragma Type_Invariant,Implementation Defined Pragmas
8435 @anchor{gnat_rm/implementation_defined_pragmas id47}@anchor{105}@anchor{gnat_rm/implementation_defined_pragmas pragma-type-invariant-class}@anchor{106}
8436 @section Pragma Type_Invariant_Class
8442 pragma Type_Invariant_Class
8443 ([Entity =>] type_LOCAL_NAME,
8444 [Check =>] EXPRESSION);
8447 The @code{Type_Invariant_Class} pragma is intended to be an exact
8448 replacement for the language-defined @code{Type_Invariant'Class}
8449 aspect, and shares its restrictions and semantics.
8451 Note: This pragma is called @code{Type_Invariant_Class} rather than
8452 @code{Type_Invariant'Class} because the latter would not be strictly
8453 conforming to the allowed syntax for pragmas. The motivation
8454 for providing pragmas equivalent to the aspects is to allow a program
8455 to be written using the pragmas, and then compiled if necessary
8456 using an Ada compiler that does not recognize the pragmas or
8457 aspects, but is prepared to ignore the pragmas. The assertion
8458 policy that controls this pragma is @code{Type_Invariant'Class},
8459 not @code{Type_Invariant_Class}.
8461 @node Pragma Unchecked_Union,Pragma Unevaluated_Use_Of_Old,Pragma Type_Invariant_Class,Implementation Defined Pragmas
8462 @anchor{gnat_rm/implementation_defined_pragmas pragma-unchecked-union}@anchor{107}
8463 @section Pragma Unchecked_Union
8466 @geindex Unions in C
8471 pragma Unchecked_Union (first_subtype_LOCAL_NAME);
8474 This pragma is used to specify a representation of a record type that is
8475 equivalent to a C union. It was introduced as a GNAT implementation defined
8476 pragma in the GNAT Ada 95 mode. Ada 2005 includes an extended version of this
8477 pragma, making it language defined, and GNAT fully implements this extended
8478 version in all language modes (Ada 83, Ada 95, and Ada 2005). For full
8479 details, consult the Ada 2012 Reference Manual, section B.3.3.
8481 @node Pragma Unevaluated_Use_Of_Old,Pragma Unimplemented_Unit,Pragma Unchecked_Union,Implementation Defined Pragmas
8482 @anchor{gnat_rm/implementation_defined_pragmas pragma-unevaluated-use-of-old}@anchor{108}
8483 @section Pragma Unevaluated_Use_Of_Old
8486 @geindex Attribute Old
8488 @geindex Attribute Loop_Entry
8490 @geindex Unevaluated_Use_Of_Old
8495 pragma Unevaluated_Use_Of_Old (Error | Warn | Allow);
8498 This pragma controls the processing of attributes Old and Loop_Entry.
8499 If either of these attributes is used in a potentially unevaluated
8500 expression (e.g. the then or else parts of an if expression), then
8501 normally this usage is considered illegal if the prefix of the attribute
8502 is other than an entity name. The language requires this
8503 behavior for Old, and GNAT copies the same rule for Loop_Entry.
8505 The reason for this rule is that otherwise, we can have a situation
8506 where we save the Old value, and this results in an exception, even
8507 though we might not evaluate the attribute. Consider this example:
8510 package UnevalOld is
8512 procedure U (A : String; C : Boolean) -- ERROR
8513 with Post => (if C then A(1)'Old = K else True);
8517 If procedure U is called with a string with a lower bound of 2, and
8518 C false, then an exception would be raised trying to evaluate A(1)
8519 on entry even though the value would not be actually used.
8521 Although the rule guarantees against this possibility, it is sometimes
8522 too restrictive. For example if we know that the string has a lower
8523 bound of 1, then we will never raise an exception.
8524 The pragma @code{Unevaluated_Use_Of_Old} can be
8525 used to modify this behavior. If the argument is @code{Error} then an
8526 error is given (this is the default RM behavior). If the argument is
8527 @code{Warn} then the usage is allowed as legal but with a warning
8528 that an exception might be raised. If the argument is @code{Allow}
8529 then the usage is allowed as legal without generating a warning.
8531 This pragma may appear as a configuration pragma, or in a declarative
8532 part or package specification. In the latter case it applies to
8533 uses up to the end of the corresponding statement sequence or
8534 sequence of package declarations.
8536 @node Pragma Unimplemented_Unit,Pragma Universal_Aliasing,Pragma Unevaluated_Use_Of_Old,Implementation Defined Pragmas
8537 @anchor{gnat_rm/implementation_defined_pragmas pragma-unimplemented-unit}@anchor{109}
8538 @section Pragma Unimplemented_Unit
8544 pragma Unimplemented_Unit;
8547 If this pragma occurs in a unit that is processed by the compiler, GNAT
8548 aborts with the message @code{xxx not implemented}, where
8549 @code{xxx} is the name of the current compilation unit. This pragma is
8550 intended to allow the compiler to handle unimplemented library units in
8553 The abort only happens if code is being generated. Thus you can use
8554 specs of unimplemented packages in syntax or semantic checking mode.
8556 @node Pragma Universal_Aliasing,Pragma Universal_Data,Pragma Unimplemented_Unit,Implementation Defined Pragmas
8557 @anchor{gnat_rm/implementation_defined_pragmas pragma-universal-aliasing}@anchor{10a}@anchor{gnat_rm/implementation_defined_pragmas id48}@anchor{10b}
8558 @section Pragma Universal_Aliasing
8564 pragma Universal_Aliasing [([Entity =>] type_LOCAL_NAME)];
8567 @code{type_LOCAL_NAME} must refer to a type declaration in the current
8568 declarative part. The effect is to inhibit strict type-based aliasing
8569 optimization for the given type. In other words, the effect is as though
8570 access types designating this type were subject to pragma No_Strict_Aliasing.
8571 For a detailed description of the strict aliasing optimization, and the
8572 situations in which it must be suppressed, see the section on
8573 @code{Optimization and Strict Aliasing} in the @cite{GNAT User's Guide}.
8575 @node Pragma Universal_Data,Pragma Unmodified,Pragma Universal_Aliasing,Implementation Defined Pragmas
8576 @anchor{gnat_rm/implementation_defined_pragmas pragma-universal-data}@anchor{10c}@anchor{gnat_rm/implementation_defined_pragmas id49}@anchor{10d}
8577 @section Pragma Universal_Data
8583 pragma Universal_Data [(library_unit_Name)];
8586 This pragma is supported only for the AAMP target and is ignored for
8587 other targets. The pragma specifies that all library-level objects
8588 (Counter 0 data) associated with the library unit are to be accessed
8589 and updated using universal addressing (24-bit addresses for AAMP5)
8590 rather than the default of 16-bit Data Environment (DENV) addressing.
8591 Use of this pragma will generally result in less efficient code for
8592 references to global data associated with the library unit, but
8593 allows such data to be located anywhere in memory. This pragma is
8594 a library unit pragma, but can also be used as a configuration pragma
8595 (including use in the @code{gnat.adc} file). The functionality
8596 of this pragma is also available by applying the -univ switch on the
8597 compilations of units where universal addressing of the data is desired.
8599 @node Pragma Unmodified,Pragma Unreferenced,Pragma Universal_Data,Implementation Defined Pragmas
8600 @anchor{gnat_rm/implementation_defined_pragmas id50}@anchor{10e}@anchor{gnat_rm/implementation_defined_pragmas pragma-unmodified}@anchor{10f}
8601 @section Pragma Unmodified
8610 pragma Unmodified (LOCAL_NAME @{, LOCAL_NAME@});
8613 This pragma signals that the assignable entities (variables,
8614 @code{out} parameters, @code{in out} parameters) whose names are listed are
8615 deliberately not assigned in the current source unit. This
8616 suppresses warnings about the
8617 entities being referenced but not assigned, and in addition a warning will be
8618 generated if one of these entities is in fact assigned in the
8619 same unit as the pragma (or in the corresponding body, or one
8622 This is particularly useful for clearly signaling that a particular
8623 parameter is not modified, even though the spec suggests that it might
8626 For the variable case, warnings are never given for unreferenced variables
8627 whose name contains one of the substrings
8628 @code{DISCARD, DUMMY, IGNORE, JUNK, UNUSED} in any casing. Such names
8629 are typically to be used in cases where such warnings are expected.
8630 Thus it is never necessary to use @code{pragma Unmodified} for such
8631 variables, though it is harmless to do so.
8633 @node Pragma Unreferenced,Pragma Unreferenced_Objects,Pragma Unmodified,Implementation Defined Pragmas
8634 @anchor{gnat_rm/implementation_defined_pragmas pragma-unreferenced}@anchor{110}@anchor{gnat_rm/implementation_defined_pragmas id51}@anchor{111}
8635 @section Pragma Unreferenced
8639 @geindex unreferenced
8644 pragma Unreferenced (LOCAL_NAME @{, LOCAL_NAME@});
8645 pragma Unreferenced (library_unit_NAME @{, library_unit_NAME@});
8648 This pragma signals that the entities whose names are listed are
8649 deliberately not referenced in the current source unit after the
8650 occurrence of the pragma. This
8651 suppresses warnings about the
8652 entities being unreferenced, and in addition a warning will be
8653 generated if one of these entities is in fact subsequently referenced in the
8654 same unit as the pragma (or in the corresponding body, or one
8657 This is particularly useful for clearly signaling that a particular
8658 parameter is not referenced in some particular subprogram implementation
8659 and that this is deliberate. It can also be useful in the case of
8660 objects declared only for their initialization or finalization side
8663 If @code{LOCAL_NAME} identifies more than one matching homonym in the
8664 current scope, then the entity most recently declared is the one to which
8665 the pragma applies. Note that in the case of accept formals, the pragma
8666 Unreferenced may appear immediately after the keyword @code{do} which
8667 allows the indication of whether or not accept formals are referenced
8668 or not to be given individually for each accept statement.
8670 The left hand side of an assignment does not count as a reference for the
8671 purpose of this pragma. Thus it is fine to assign to an entity for which
8672 pragma Unreferenced is given.
8674 Note that if a warning is desired for all calls to a given subprogram,
8675 regardless of whether they occur in the same unit as the subprogram
8676 declaration, then this pragma should not be used (calls from another
8677 unit would not be flagged); pragma Obsolescent can be used instead
8678 for this purpose, see @ref{af,,Pragma Obsolescent}.
8680 The second form of pragma @code{Unreferenced} is used within a context
8681 clause. In this case the arguments must be unit names of units previously
8682 mentioned in @code{with} clauses (similar to the usage of pragma
8683 @code{Elaborate_All}. The effect is to suppress warnings about unreferenced
8684 units and unreferenced entities within these units.
8686 For the variable case, warnings are never given for unreferenced variables
8687 whose name contains one of the substrings
8688 @code{DISCARD, DUMMY, IGNORE, JUNK, UNUSED} in any casing. Such names
8689 are typically to be used in cases where such warnings are expected.
8690 Thus it is never necessary to use @code{pragma Unreferenced} for such
8691 variables, though it is harmless to do so.
8693 @node Pragma Unreferenced_Objects,Pragma Unreserve_All_Interrupts,Pragma Unreferenced,Implementation Defined Pragmas
8694 @anchor{gnat_rm/implementation_defined_pragmas pragma-unreferenced-objects}@anchor{112}@anchor{gnat_rm/implementation_defined_pragmas id52}@anchor{113}
8695 @section Pragma Unreferenced_Objects
8699 @geindex unreferenced
8704 pragma Unreferenced_Objects (local_subtype_NAME @{, local_subtype_NAME@});
8707 This pragma signals that for the types or subtypes whose names are
8708 listed, objects which are declared with one of these types or subtypes may
8709 not be referenced, and if no references appear, no warnings are given.
8711 This is particularly useful for objects which are declared solely for their
8712 initialization and finalization effect. Such variables are sometimes referred
8713 to as RAII variables (Resource Acquisition Is Initialization). Using this
8714 pragma on the relevant type (most typically a limited controlled type), the
8715 compiler will automatically suppress unwanted warnings about these variables
8716 not being referenced.
8718 @node Pragma Unreserve_All_Interrupts,Pragma Unsuppress,Pragma Unreferenced_Objects,Implementation Defined Pragmas
8719 @anchor{gnat_rm/implementation_defined_pragmas pragma-unreserve-all-interrupts}@anchor{114}
8720 @section Pragma Unreserve_All_Interrupts
8726 pragma Unreserve_All_Interrupts;
8729 Normally certain interrupts are reserved to the implementation. Any attempt
8730 to attach an interrupt causes Program_Error to be raised, as described in
8731 RM C.3.2(22). A typical example is the @code{SIGINT} interrupt used in
8732 many systems for a @code{Ctrl-C} interrupt. Normally this interrupt is
8733 reserved to the implementation, so that @code{Ctrl-C} can be used to
8734 interrupt execution.
8736 If the pragma @code{Unreserve_All_Interrupts} appears anywhere in any unit in
8737 a program, then all such interrupts are unreserved. This allows the
8738 program to handle these interrupts, but disables their standard
8739 functions. For example, if this pragma is used, then pressing
8740 @code{Ctrl-C} will not automatically interrupt execution. However,
8741 a program can then handle the @code{SIGINT} interrupt as it chooses.
8743 For a full list of the interrupts handled in a specific implementation,
8744 see the source code for the spec of @code{Ada.Interrupts.Names} in
8745 file @code{a-intnam.ads}. This is a target dependent file that contains the
8746 list of interrupts recognized for a given target. The documentation in
8747 this file also specifies what interrupts are affected by the use of
8748 the @code{Unreserve_All_Interrupts} pragma.
8750 For a more general facility for controlling what interrupts can be
8751 handled, see pragma @code{Interrupt_State}, which subsumes the functionality
8752 of the @code{Unreserve_All_Interrupts} pragma.
8754 @node Pragma Unsuppress,Pragma Use_VADS_Size,Pragma Unreserve_All_Interrupts,Implementation Defined Pragmas
8755 @anchor{gnat_rm/implementation_defined_pragmas pragma-unsuppress}@anchor{115}
8756 @section Pragma Unsuppress
8762 pragma Unsuppress (IDENTIFIER [, [On =>] NAME]);
8765 This pragma undoes the effect of a previous pragma @code{Suppress}. If
8766 there is no corresponding pragma @code{Suppress} in effect, it has no
8767 effect. The range of the effect is the same as for pragma
8768 @code{Suppress}. The meaning of the arguments is identical to that used
8769 in pragma @code{Suppress}.
8771 One important application is to ensure that checks are on in cases where
8772 code depends on the checks for its correct functioning, so that the code
8773 will compile correctly even if the compiler switches are set to suppress
8774 checks. For example, in a program that depends on external names of tagged
8775 types and wants to ensure that the duplicated tag check occurs even if all
8776 run-time checks are suppressed by a compiler switch, the following
8777 configuration pragma will ensure this test is not suppressed:
8780 pragma Unsuppress (Duplicated_Tag_Check);
8783 This pragma is standard in Ada 2005. It is available in all earlier versions
8784 of Ada as an implementation-defined pragma.
8786 Note that in addition to the checks defined in the Ada RM, GNAT recogizes a
8787 number of implementation-defined check names. See the description of pragma
8788 @code{Suppress} for full details.
8790 @node Pragma Use_VADS_Size,Pragma Unused,Pragma Unsuppress,Implementation Defined Pragmas
8791 @anchor{gnat_rm/implementation_defined_pragmas pragma-use-vads-size}@anchor{116}
8792 @section Pragma Use_VADS_Size
8796 @geindex VADS compatibility
8798 @geindex Rational profile
8803 pragma Use_VADS_Size;
8806 This is a configuration pragma. In a unit to which it applies, any use
8807 of the 'Size attribute is automatically interpreted as a use of the
8808 'VADS_Size attribute. Note that this may result in incorrect semantic
8809 processing of valid Ada 95 or Ada 2005 programs. This is intended to aid in
8810 the handling of existing code which depends on the interpretation of Size
8811 as implemented in the VADS compiler. See description of the VADS_Size
8812 attribute for further details.
8814 @node Pragma Unused,Pragma Validity_Checks,Pragma Use_VADS_Size,Implementation Defined Pragmas
8815 @anchor{gnat_rm/implementation_defined_pragmas pragma-unused}@anchor{117}@anchor{gnat_rm/implementation_defined_pragmas id53}@anchor{118}
8816 @section Pragma Unused
8825 pragma Unused (LOCAL_NAME @{, LOCAL_NAME@});
8828 This pragma signals that the assignable entities (variables,
8829 @code{out} parameters, and @code{in out} parameters) whose names are listed
8830 deliberately do not get assigned or referenced in the current source unit
8831 after the occurrence of the pragma in the current source unit. This
8832 suppresses warnings about the entities that are unreferenced and/or not
8833 assigned, and, in addition, a warning will be generated if one of these
8834 entities gets assigned or subsequently referenced in the same unit as the
8835 pragma (in the corresponding body or one of its subunits).
8837 This is particularly useful for clearly signaling that a particular
8838 parameter is not modified or referenced, even though the spec suggests
8841 For the variable case, warnings are never given for unreferenced
8842 variables whose name contains one of the substrings
8843 @code{DISCARD, DUMMY, IGNORE, JUNK, UNUSED} in any casing. Such names
8844 are typically to be used in cases where such warnings are expected.
8845 Thus it is never necessary to use @code{pragma Unmodified} for such
8846 variables, though it is harmless to do so.
8848 @node Pragma Validity_Checks,Pragma Volatile,Pragma Unused,Implementation Defined Pragmas
8849 @anchor{gnat_rm/implementation_defined_pragmas pragma-validity-checks}@anchor{119}
8850 @section Pragma Validity_Checks
8856 pragma Validity_Checks (string_LITERAL | ALL_CHECKS | On | Off);
8859 This pragma is used in conjunction with compiler switches to control the
8860 built-in validity checking provided by GNAT. The compiler switches, if set
8861 provide an initial setting for the switches, and this pragma may be used
8862 to modify these settings, or the settings may be provided entirely by
8863 the use of the pragma. This pragma can be used anywhere that a pragma
8864 is legal, including use as a configuration pragma (including use in
8865 the @code{gnat.adc} file).
8867 The form with a string literal specifies which validity options are to be
8868 activated. The validity checks are first set to include only the default
8869 reference manual settings, and then a string of letters in the string
8870 specifies the exact set of options required. The form of this string
8871 is exactly as described for the @emph{-gnatVx} compiler switch (see the
8872 GNAT User's Guide for details). For example the following two
8873 methods can be used to enable validity checking for mode @code{in} and
8874 @code{in out} subprogram parameters:
8881 pragma Validity_Checks ("im");
8886 $ gcc -c -gnatVim ...
8890 The form ALL_CHECKS activates all standard checks (its use is equivalent
8891 to the use of the @code{gnatVa} switch).
8893 The forms with @code{Off} and @code{On} can be used to temporarily disable
8894 validity checks as shown in the following example:
8897 pragma Validity_Checks ("c"); -- validity checks for copies
8898 pragma Validity_Checks (Off); -- turn off validity checks
8899 A := B; -- B will not be validity checked
8900 pragma Validity_Checks (On); -- turn validity checks back on
8901 A := C; -- C will be validity checked
8904 @node Pragma Volatile,Pragma Volatile_Full_Access,Pragma Validity_Checks,Implementation Defined Pragmas
8905 @anchor{gnat_rm/implementation_defined_pragmas id54}@anchor{11a}@anchor{gnat_rm/implementation_defined_pragmas pragma-volatile}@anchor{11b}
8906 @section Pragma Volatile
8912 pragma Volatile (LOCAL_NAME);
8915 This pragma is defined by the Ada Reference Manual, and the GNAT
8916 implementation is fully conformant with this definition. The reason it
8917 is mentioned in this section is that a pragma of the same name was supplied
8918 in some Ada 83 compilers, including DEC Ada 83. The Ada 95 / Ada 2005
8919 implementation of pragma Volatile is upwards compatible with the
8920 implementation in DEC Ada 83.
8922 @node Pragma Volatile_Full_Access,Pragma Volatile_Function,Pragma Volatile,Implementation Defined Pragmas
8923 @anchor{gnat_rm/implementation_defined_pragmas id55}@anchor{11c}@anchor{gnat_rm/implementation_defined_pragmas pragma-volatile-full-access}@anchor{11d}
8924 @section Pragma Volatile_Full_Access
8930 pragma Volatile_Full_Access (LOCAL_NAME);
8933 This is similar in effect to pragma Volatile, except that any reference to the
8934 object is guaranteed to be done only with instructions that read or write all
8935 the bits of the object. Furthermore, if the object is of a composite type,
8936 then any reference to a subcomponent of the object is guaranteed to read
8937 and/or write all the bits of the object.
8939 The intention is that this be suitable for use with memory-mapped I/O devices
8940 on some machines. Note that there are two important respects in which this is
8941 different from @code{pragma Atomic}. First a reference to a @code{Volatile_Full_Access}
8942 object is not a sequential action in the RM 9.10 sense and, therefore, does
8943 not create a synchronization point. Second, in the case of @code{pragma Atomic},
8944 there is no guarantee that all the bits will be accessed if the reference
8945 is not to the whole object; the compiler is allowed (and generally will)
8946 access only part of the object in this case.
8948 It is not permissible to specify @code{Atomic} and @code{Volatile_Full_Access} for
8949 the same type or object.
8951 It is not permissible to specify @code{Volatile_Full_Access} for a composite
8952 (record or array) type or object that has an @code{Aliased} subcomponent.
8954 @node Pragma Volatile_Function,Pragma Warning_As_Error,Pragma Volatile_Full_Access,Implementation Defined Pragmas
8955 @anchor{gnat_rm/implementation_defined_pragmas id56}@anchor{11e}@anchor{gnat_rm/implementation_defined_pragmas pragma-volatile-function}@anchor{11f}
8956 @section Pragma Volatile_Function
8962 pragma Volatile_Function [ (boolean_EXPRESSION) ];
8965 For the semantics of this pragma, see the entry for aspect @code{Volatile_Function}
8966 in the SPARK 2014 Reference Manual, section 7.1.2.
8968 @node Pragma Warning_As_Error,Pragma Warnings,Pragma Volatile_Function,Implementation Defined Pragmas
8969 @anchor{gnat_rm/implementation_defined_pragmas pragma-warning-as-error}@anchor{120}
8970 @section Pragma Warning_As_Error
8976 pragma Warning_As_Error (static_string_EXPRESSION);
8979 This configuration pragma allows the programmer to specify a set
8980 of warnings that will be treated as errors. Any warning that
8981 matches the pattern given by the pragma argument will be treated
8982 as an error. This gives more precise control than -gnatwe,
8983 which treats warnings as errors.
8985 This pragma can apply to regular warnings (messages enabled by -gnatw)
8986 and to style warnings (messages that start with "(style)",
8989 The pattern may contain asterisks, which match zero or more characters
8990 in the message. For example, you can use @code{pragma Warning_As_Error
8991 ("bits of*unused")} to treat the warning message @code{warning: 960 bits of
8992 "a" unused} as an error. All characters other than asterisk are treated
8993 as literal characters in the match. The match is case insensitive; for
8994 example XYZ matches xyz.
8996 Note that the pattern matches if it occurs anywhere within the warning
8997 message string (it is not necessary to put an asterisk at the start and
8998 the end of the message, since this is implied).
9000 Another possibility for the static_string_EXPRESSION which works whether
9001 or not error tags are enabled (@emph{-gnatw.d}) is to use a single
9002 @emph{-gnatw} tag string, enclosed in brackets,
9003 as shown in the example below, to treat one category of warnings as errors.
9004 Note that if you want to treat multiple categories of warnings as errors,
9005 you can use multiple pragma Warning_As_Error.
9007 The above use of patterns to match the message applies only to warning
9008 messages generated by the front end. This pragma can also be applied to
9009 warnings provided by the back end and mentioned in @ref{121,,Pragma Warnings}.
9010 By using a single full @emph{-Wxxx} switch in the pragma, such warnings
9011 can also be treated as errors.
9013 The pragma can appear either in a global configuration pragma file
9014 (e.g. @code{gnat.adc}), or at the start of a file. Given a global
9015 configuration pragma file containing:
9018 pragma Warning_As_Error ("[-gnatwj]");
9021 which will treat all obsolescent feature warnings as errors, the
9022 following program compiles as shown (compile options here are
9023 @emph{-gnatwa.d -gnatl -gnatj55}).
9026 1. pragma Warning_As_Error ("*never assigned*");
9027 2. function Warnerr return String is
9030 >>> error: variable "X" is never read and
9031 never assigned [-gnatwv] [warning-as-error]
9035 >>> warning: variable "Y" is assigned but
9036 never read [-gnatwu]
9042 >>> error: use of "%" is an obsolescent
9043 feature (RM J.2(4)), use """ instead
9044 [-gnatwj] [warning-as-error]
9048 8 lines: No errors, 3 warnings (2 treated as errors)
9051 Note that this pragma does not affect the set of warnings issued in
9052 any way, it merely changes the effect of a matching warning if one
9053 is produced as a result of other warnings options. As shown in this
9054 example, if the pragma results in a warning being treated as an error,
9055 the tag is changed from "warning:" to "error:" and the string
9056 "[warning-as-error]" is appended to the end of the message.
9058 @node Pragma Warnings,Pragma Weak_External,Pragma Warning_As_Error,Implementation Defined Pragmas
9059 @anchor{gnat_rm/implementation_defined_pragmas id57}@anchor{122}@anchor{gnat_rm/implementation_defined_pragmas pragma-warnings}@anchor{121}
9060 @section Pragma Warnings
9066 pragma Warnings ([TOOL_NAME,] DETAILS [, REASON]);
9068 DETAILS ::= On | Off
9069 DETAILS ::= On | Off, local_NAME
9070 DETAILS ::= static_string_EXPRESSION
9071 DETAILS ::= On | Off, static_string_EXPRESSION
9073 TOOL_NAME ::= GNAT | GNATProve
9075 REASON ::= Reason => STRING_LITERAL @{& STRING_LITERAL@}
9078 Note: in Ada 83 mode, a string literal may be used in place of a static string
9079 expression (which does not exist in Ada 83).
9081 Note if the second argument of @code{DETAILS} is a @code{local_NAME} then the
9082 second form is always understood. If the intention is to use
9083 the fourth form, then you can write @code{NAME & ""} to force the
9084 intepretation as a @emph{static_string_EXPRESSION}.
9086 Note: if the first argument is a valid @code{TOOL_NAME}, it will be interpreted
9087 that way. The use of the @code{TOOL_NAME} argument is relevant only to users
9088 of SPARK and GNATprove, see last part of this section for details.
9090 Normally warnings are enabled, with the output being controlled by
9091 the command line switch. Warnings (@code{Off}) turns off generation of
9092 warnings until a Warnings (@code{On}) is encountered or the end of the
9093 current unit. If generation of warnings is turned off using this
9094 pragma, then some or all of the warning messages are suppressed,
9095 regardless of the setting of the command line switches.
9097 The @code{Reason} parameter may optionally appear as the last argument
9098 in any of the forms of this pragma. It is intended purely for the
9099 purposes of documenting the reason for the @code{Warnings} pragma.
9100 The compiler will check that the argument is a static string but
9101 otherwise ignore this argument. Other tools may provide specialized
9102 processing for this string.
9104 The form with a single argument (or two arguments if Reason present),
9105 where the first argument is @code{ON} or @code{OFF}
9106 may be used as a configuration pragma.
9108 If the @code{LOCAL_NAME} parameter is present, warnings are suppressed for
9109 the specified entity. This suppression is effective from the point where
9110 it occurs till the end of the extended scope of the variable (similar to
9111 the scope of @code{Suppress}). This form cannot be used as a configuration
9114 In the case where the first argument is other than @code{ON} or
9116 the third form with a single static_string_EXPRESSION argument (and possible
9117 reason) provides more precise
9118 control over which warnings are active. The string is a list of letters
9119 specifying which warnings are to be activated and which deactivated. The
9120 code for these letters is the same as the string used in the command
9121 line switch controlling warnings. For a brief summary, use the gnatmake
9122 command with no arguments, which will generate usage information containing
9123 the list of warnings switches supported. For
9124 full details see the section on @code{Warning Message Control} in the
9125 @cite{GNAT User's Guide}.
9126 This form can also be used as a configuration pragma.
9128 The warnings controlled by the @code{-gnatw} switch are generated by the
9129 front end of the compiler. The GCC back end can provide additional warnings
9130 and they are controlled by the @code{-W} switch. Such warnings can be
9131 identified by the appearance of a string of the form @code{[-W@{xxx@}]} in the
9132 message which designates the @code{-W@emph{xxx}} switch that controls the message.
9133 The form with a single @emph{static_string_EXPRESSION} argument also works for these
9134 warnings, but the string must be a single full @code{-W@emph{xxx}} switch in this
9135 case. The above reference lists a few examples of these additional warnings.
9137 The specified warnings will be in effect until the end of the program
9138 or another pragma @code{Warnings} is encountered. The effect of the pragma is
9139 cumulative. Initially the set of warnings is the standard default set
9140 as possibly modified by compiler switches. Then each pragma Warning
9141 modifies this set of warnings as specified. This form of the pragma may
9142 also be used as a configuration pragma.
9144 The fourth form, with an @code{On|Off} parameter and a string, is used to
9145 control individual messages, based on their text. The string argument
9146 is a pattern that is used to match against the text of individual
9147 warning messages (not including the initial "warning: " tag).
9149 The pattern may contain asterisks, which match zero or more characters in
9150 the message. For example, you can use
9151 @code{pragma Warnings (Off, "bits of*unused")} to suppress the warning
9152 message @code{warning: 960 bits of "a" unused}. No other regular
9153 expression notations are permitted. All characters other than asterisk in
9154 these three specific cases are treated as literal characters in the match.
9155 The match is case insensitive, for example XYZ matches xyz.
9157 Note that the pattern matches if it occurs anywhere within the warning
9158 message string (it is not necessary to put an asterisk at the start and
9159 the end of the message, since this is implied).
9161 The above use of patterns to match the message applies only to warning
9162 messages generated by the front end. This form of the pragma with a string
9163 argument can also be used to control warnings provided by the back end and
9164 mentioned above. By using a single full @code{-W@emph{xxx}} switch in the pragma,
9165 such warnings can be turned on and off.
9167 There are two ways to use the pragma in this form. The OFF form can be used
9168 as a configuration pragma. The effect is to suppress all warnings (if any)
9169 that match the pattern string throughout the compilation (or match the
9170 -W switch in the back end case).
9172 The second usage is to suppress a warning locally, and in this case, two
9173 pragmas must appear in sequence:
9176 pragma Warnings (Off, Pattern);
9177 ... code where given warning is to be suppressed
9178 pragma Warnings (On, Pattern);
9181 In this usage, the pattern string must match in the Off and On
9182 pragmas, and (if @emph{-gnatw.w} is given) at least one matching
9183 warning must be suppressed.
9185 Note: if the ON form is not found, then the effect of the OFF form extends
9186 until the end of the file (pragma Warnings is purely textual, so its effect
9187 does not stop at the end of the enclosing scope).
9189 Note: to write a string that will match any warning, use the string
9190 @code{"***"}. It will not work to use a single asterisk or two
9191 asterisks since this looks like an operator name. This form with three
9192 asterisks is similar in effect to specifying @code{pragma Warnings (Off)} except (if @code{-gnatw.w} is given) that a matching
9193 @code{pragma Warnings (On, "***")} will be required. This can be
9194 helpful in avoiding forgetting to turn warnings back on.
9196 Note: the debug flag @code{-gnatd.i} can be
9197 used to cause the compiler to entirely ignore all WARNINGS pragmas. This can
9198 be useful in checking whether obsolete pragmas in existing programs are hiding
9201 Note: pragma Warnings does not affect the processing of style messages. See
9202 separate entry for pragma Style_Checks for control of style messages.
9204 Users of the formal verification tool GNATprove for the SPARK subset of Ada may
9205 use the version of the pragma with a @code{TOOL_NAME} parameter.
9207 If present, @code{TOOL_NAME} is the name of a tool, currently either @code{GNAT} for the
9208 compiler or @code{GNATprove} for the formal verification tool. A given tool only
9209 takes into account pragma Warnings that do not specify a tool name, or that
9210 specify the matching tool name. This makes it possible to disable warnings
9211 selectively for each tool, and as a consequence to detect useless pragma
9212 Warnings with switch @code{-gnatw.w}.
9214 @node Pragma Weak_External,Pragma Wide_Character_Encoding,Pragma Warnings,Implementation Defined Pragmas
9215 @anchor{gnat_rm/implementation_defined_pragmas pragma-weak-external}@anchor{123}
9216 @section Pragma Weak_External
9222 pragma Weak_External ([Entity =>] LOCAL_NAME);
9225 @code{LOCAL_NAME} must refer to an object that is declared at the library
9226 level. This pragma specifies that the given entity should be marked as a
9227 weak symbol for the linker. It is equivalent to @code{__attribute__((weak))}
9228 in GNU C and causes @code{LOCAL_NAME} to be emitted as a weak symbol instead
9229 of a regular symbol, that is to say a symbol that does not have to be
9230 resolved by the linker if used in conjunction with a pragma Import.
9232 When a weak symbol is not resolved by the linker, its address is set to
9233 zero. This is useful in writing interfaces to external modules that may
9234 or may not be linked in the final executable, for example depending on
9235 configuration settings.
9237 If a program references at run time an entity to which this pragma has been
9238 applied, and the corresponding symbol was not resolved at link time, then
9239 the execution of the program is erroneous. It is not erroneous to take the
9240 Address of such an entity, for example to guard potential references,
9241 as shown in the example below.
9243 Some file formats do not support weak symbols so not all target machines
9244 support this pragma.
9247 -- Example of the use of pragma Weak_External
9249 package External_Module is
9251 pragma Import (C, key);
9252 pragma Weak_External (key);
9253 function Present return boolean;
9254 end External_Module;
9256 with System; use System;
9257 package body External_Module is
9258 function Present return boolean is
9260 return key'Address /= System.Null_Address;
9262 end External_Module;
9265 @node Pragma Wide_Character_Encoding,,Pragma Weak_External,Implementation Defined Pragmas
9266 @anchor{gnat_rm/implementation_defined_pragmas pragma-wide-character-encoding}@anchor{124}
9267 @section Pragma Wide_Character_Encoding
9273 pragma Wide_Character_Encoding (IDENTIFIER | CHARACTER_LITERAL);
9276 This pragma specifies the wide character encoding to be used in program
9277 source text appearing subsequently. It is a configuration pragma, but may
9278 also be used at any point that a pragma is allowed, and it is permissible
9279 to have more than one such pragma in a file, allowing multiple encodings
9280 to appear within the same file.
9282 However, note that the pragma cannot immediately precede the relevant
9283 wide character, because then the previous encoding will still be in
9284 effect, causing "illegal character" errors.
9286 The argument can be an identifier or a character literal. In the identifier
9287 case, it is one of @code{HEX}, @code{UPPER}, @code{SHIFT_JIS},
9288 @code{EUC}, @code{UTF8}, or @code{BRACKETS}. In the character literal
9289 case it is correspondingly one of the characters @code{h}, @code{u},
9290 @code{s}, @code{e}, @code{8}, or @code{b}.
9292 Note that when the pragma is used within a file, it affects only the
9293 encoding within that file, and does not affect withed units, specs,
9296 @node Implementation Defined Aspects,Implementation Defined Attributes,Implementation Defined Pragmas,Top
9297 @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}
9298 @chapter Implementation Defined Aspects
9301 Ada defines (throughout the Ada 2012 reference manual, summarized
9302 in Annex K) a set of aspects that can be specified for certain entities.
9303 These language defined aspects are implemented in GNAT in Ada 2012 mode
9304 and work as described in the Ada 2012 Reference Manual.
9306 In addition, Ada 2012 allows implementations to define additional aspects
9307 whose meaning is defined by the implementation. GNAT provides
9308 a number of these implementation-defined aspects which can be used
9309 to extend and enhance the functionality of the compiler. This section of
9310 the GNAT reference manual describes these additional aspects.
9312 Note that any program using these aspects may not be portable to
9313 other compilers (although GNAT implements this set of aspects on all
9314 platforms). Therefore if portability to other compilers is an important
9315 consideration, you should minimize the use of these aspects.
9317 Note that for many of these aspects, the effect is essentially similar
9318 to the use of a pragma or attribute specification with the same name
9319 applied to the entity. For example, if we write:
9322 type R is range 1 .. 100
9323 with Value_Size => 10;
9326 then the effect is the same as:
9329 type R is range 1 .. 100;
9330 for R'Value_Size use 10;
9336 type R is new Integer
9337 with Shared => True;
9340 then the effect is the same as:
9343 type R is new Integer;
9347 In the documentation below, such cases are simply marked
9348 as being boolean aspects equivalent to the corresponding pragma
9349 or attribute definition clause.
9352 * Aspect Abstract_State::
9354 * Aspect Async_Readers::
9355 * Aspect Async_Writers::
9356 * Aspect Constant_After_Elaboration::
9357 * Aspect Contract_Cases::
9359 * Aspect Default_Initial_Condition::
9360 * Aspect Dimension::
9361 * Aspect Dimension_System::
9362 * Aspect Disable_Controlled::
9363 * Aspect Effective_Reads::
9364 * Aspect Effective_Writes::
9365 * Aspect Extensions_Visible::
9366 * Aspect Favor_Top_Level::
9369 * Aspect Initial_Condition::
9370 * Aspect Initializes::
9371 * Aspect Inline_Always::
9372 * Aspect Invariant::
9373 * Aspect Invariant'Class::
9375 * Aspect Linker_Section::
9376 * Aspect Lock_Free::
9377 * Aspect Max_Queue_Length::
9378 * Aspect No_Caching::
9379 * Aspect No_Elaboration_Code_All::
9380 * Aspect No_Inline::
9381 * Aspect No_Tagged_Streams::
9382 * Aspect Object_Size::
9383 * Aspect Obsolescent::
9385 * Aspect Persistent_BSS::
9386 * Aspect Predicate::
9387 * Aspect Pure_Function::
9388 * Aspect Refined_Depends::
9389 * Aspect Refined_Global::
9390 * Aspect Refined_Post::
9391 * Aspect Refined_State::
9392 * Aspect Remote_Access_Type::
9393 * Aspect Secondary_Stack_Size::
9394 * Aspect Scalar_Storage_Order::
9396 * Aspect Simple_Storage_Pool::
9397 * Aspect Simple_Storage_Pool_Type::
9398 * Aspect SPARK_Mode::
9399 * Aspect Suppress_Debug_Info::
9400 * Aspect Suppress_Initialization::
9401 * Aspect Test_Case::
9402 * Aspect Thread_Local_Storage::
9403 * Aspect Universal_Aliasing::
9404 * Aspect Universal_Data::
9405 * Aspect Unmodified::
9406 * Aspect Unreferenced::
9407 * Aspect Unreferenced_Objects::
9408 * Aspect Value_Size::
9409 * Aspect Volatile_Full_Access::
9410 * Aspect Volatile_Function::
9415 @node Aspect Abstract_State,Aspect Annotate,,Implementation Defined Aspects
9416 @anchor{gnat_rm/implementation_defined_aspects aspect-abstract-state}@anchor{128}
9417 @section Aspect Abstract_State
9420 @geindex Abstract_State
9422 This aspect is equivalent to @ref{1c,,pragma Abstract_State}.
9424 @node Aspect Annotate,Aspect Async_Readers,Aspect Abstract_State,Implementation Defined Aspects
9425 @anchor{gnat_rm/implementation_defined_aspects aspect-annotate}@anchor{129}
9426 @section Aspect Annotate
9431 There are three forms of this aspect (where ID is an identifier,
9432 and ARG is a general expression),
9433 corresponding to @ref{2a,,pragma Annotate}.
9438 @item @emph{Annotate => ID}
9440 Equivalent to @code{pragma Annotate (ID, Entity => Name);}
9442 @item @emph{Annotate => (ID)}
9444 Equivalent to @code{pragma Annotate (ID, Entity => Name);}
9446 @item @emph{Annotate => (ID ,ID @{, ARG@})}
9448 Equivalent to @code{pragma Annotate (ID, ID @{, ARG@}, Entity => Name);}
9451 @node Aspect Async_Readers,Aspect Async_Writers,Aspect Annotate,Implementation Defined Aspects
9452 @anchor{gnat_rm/implementation_defined_aspects aspect-async-readers}@anchor{12a}
9453 @section Aspect Async_Readers
9456 @geindex Async_Readers
9458 This boolean aspect is equivalent to @ref{31,,pragma Async_Readers}.
9460 @node Aspect Async_Writers,Aspect Constant_After_Elaboration,Aspect Async_Readers,Implementation Defined Aspects
9461 @anchor{gnat_rm/implementation_defined_aspects aspect-async-writers}@anchor{12b}
9462 @section Aspect Async_Writers
9465 @geindex Async_Writers
9467 This boolean aspect is equivalent to @ref{34,,pragma Async_Writers}.
9469 @node Aspect Constant_After_Elaboration,Aspect Contract_Cases,Aspect Async_Writers,Implementation Defined Aspects
9470 @anchor{gnat_rm/implementation_defined_aspects aspect-constant-after-elaboration}@anchor{12c}
9471 @section Aspect Constant_After_Elaboration
9474 @geindex Constant_After_Elaboration
9476 This aspect is equivalent to @ref{45,,pragma Constant_After_Elaboration}.
9478 @node Aspect Contract_Cases,Aspect Depends,Aspect Constant_After_Elaboration,Implementation Defined Aspects
9479 @anchor{gnat_rm/implementation_defined_aspects aspect-contract-cases}@anchor{12d}
9480 @section Aspect Contract_Cases
9483 @geindex Contract_Cases
9485 This aspect is equivalent to @ref{47,,pragma Contract_Cases}, the sequence
9486 of clauses being enclosed in parentheses so that syntactically it is an
9489 @node Aspect Depends,Aspect Default_Initial_Condition,Aspect Contract_Cases,Implementation Defined Aspects
9490 @anchor{gnat_rm/implementation_defined_aspects aspect-depends}@anchor{12e}
9491 @section Aspect Depends
9496 This aspect is equivalent to @ref{56,,pragma Depends}.
9498 @node Aspect Default_Initial_Condition,Aspect Dimension,Aspect Depends,Implementation Defined Aspects
9499 @anchor{gnat_rm/implementation_defined_aspects aspect-default-initial-condition}@anchor{12f}
9500 @section Aspect Default_Initial_Condition
9503 @geindex Default_Initial_Condition
9505 This aspect is equivalent to @ref{51,,pragma Default_Initial_Condition}.
9507 @node Aspect Dimension,Aspect Dimension_System,Aspect Default_Initial_Condition,Implementation Defined Aspects
9508 @anchor{gnat_rm/implementation_defined_aspects aspect-dimension}@anchor{130}
9509 @section Aspect Dimension
9514 The @code{Dimension} aspect is used to specify the dimensions of a given
9515 subtype of a dimensioned numeric type. The aspect also specifies a symbol
9516 used when doing formatted output of dimensioned quantities. The syntax is:
9520 ([Symbol =>] SYMBOL, DIMENSION_VALUE @{, DIMENSION_Value@})
9522 SYMBOL ::= STRING_LITERAL | CHARACTER_LITERAL
9526 | others => RATIONAL
9527 | DISCRETE_CHOICE_LIST => RATIONAL
9529 RATIONAL ::= [-] NUMERIC_LITERAL [/ NUMERIC_LITERAL]
9532 This aspect can only be applied to a subtype whose parent type has
9533 a @code{Dimension_System} aspect. The aspect must specify values for
9534 all dimensions of the system. The rational values are the powers of the
9535 corresponding dimensions that are used by the compiler to verify that
9536 physical (numeric) computations are dimensionally consistent. For example,
9537 the computation of a force must result in dimensions (L => 1, M => 1, T => -2).
9538 For further examples of the usage
9539 of this aspect, see package @code{System.Dim.Mks}.
9540 Note that when the dimensioned type is an integer type, then any
9541 dimension value must be an integer literal.
9543 @node Aspect Dimension_System,Aspect Disable_Controlled,Aspect Dimension,Implementation Defined Aspects
9544 @anchor{gnat_rm/implementation_defined_aspects aspect-dimension-system}@anchor{131}
9545 @section Aspect Dimension_System
9548 @geindex Dimension_System
9550 The @code{Dimension_System} aspect is used to define a system of
9551 dimensions that will be used in subsequent subtype declarations with
9552 @code{Dimension} aspects that reference this system. The syntax is:
9555 with Dimension_System => (DIMENSION @{, DIMENSION@});
9557 DIMENSION ::= ([Unit_Name =>] IDENTIFIER,
9558 [Unit_Symbol =>] SYMBOL,
9559 [Dim_Symbol =>] SYMBOL)
9561 SYMBOL ::= CHARACTER_LITERAL | STRING_LITERAL
9564 This aspect is applied to a type, which must be a numeric derived type
9565 (typically a floating-point type), that
9566 will represent values within the dimension system. Each @code{DIMENSION}
9567 corresponds to one particular dimension. A maximum of 7 dimensions may
9568 be specified. @code{Unit_Name} is the name of the dimension (for example
9569 @code{Meter}). @code{Unit_Symbol} is the shorthand used for quantities
9570 of this dimension (for example @code{m} for @code{Meter}).
9571 @code{Dim_Symbol} gives
9572 the identification within the dimension system (typically this is a
9573 single letter, e.g. @code{L} standing for length for unit name @code{Meter}).
9574 The @code{Unit_Symbol} is used in formatted output of dimensioned quantities.
9575 The @code{Dim_Symbol} is used in error messages when numeric operations have
9576 inconsistent dimensions.
9578 GNAT provides the standard definition of the International MKS system in
9579 the run-time package @code{System.Dim.Mks}. You can easily define
9580 similar packages for cgs units or British units, and define conversion factors
9581 between values in different systems. The MKS system is characterized by the
9585 type Mks_Type is new Long_Long_Float with
9586 Dimension_System => (
9587 (Unit_Name => Meter, Unit_Symbol => 'm', Dim_Symbol => 'L'),
9588 (Unit_Name => Kilogram, Unit_Symbol => "kg", Dim_Symbol => 'M'),
9589 (Unit_Name => Second, Unit_Symbol => 's', Dim_Symbol => 'T'),
9590 (Unit_Name => Ampere, Unit_Symbol => 'A', Dim_Symbol => 'I'),
9591 (Unit_Name => Kelvin, Unit_Symbol => 'K', Dim_Symbol => '@@'),
9592 (Unit_Name => Mole, Unit_Symbol => "mol", Dim_Symbol => 'N'),
9593 (Unit_Name => Candela, Unit_Symbol => "cd", Dim_Symbol => 'J'));
9596 Note that in the above type definition, we use the @code{at} symbol (@code{@@}) to
9597 represent a theta character (avoiding the use of extended Latin-1
9598 characters in this context).
9600 See section 'Performing Dimensionality Analysis in GNAT' in the GNAT Users
9601 Guide for detailed examples of use of the dimension system.
9603 @node Aspect Disable_Controlled,Aspect Effective_Reads,Aspect Dimension_System,Implementation Defined Aspects
9604 @anchor{gnat_rm/implementation_defined_aspects aspect-disable-controlled}@anchor{132}
9605 @section Aspect Disable_Controlled
9608 @geindex Disable_Controlled
9610 The aspect @code{Disable_Controlled} is defined for controlled record types. If
9611 active, this aspect causes suppression of all related calls to @code{Initialize},
9612 @code{Adjust}, and @code{Finalize}. The intended use is for conditional compilation,
9613 where for example you might want a record to be controlled or not depending on
9614 whether some run-time check is enabled or suppressed.
9616 @node Aspect Effective_Reads,Aspect Effective_Writes,Aspect Disable_Controlled,Implementation Defined Aspects
9617 @anchor{gnat_rm/implementation_defined_aspects aspect-effective-reads}@anchor{133}
9618 @section Aspect Effective_Reads
9621 @geindex Effective_Reads
9623 This aspect is equivalent to @ref{5c,,pragma Effective_Reads}.
9625 @node Aspect Effective_Writes,Aspect Extensions_Visible,Aspect Effective_Reads,Implementation Defined Aspects
9626 @anchor{gnat_rm/implementation_defined_aspects aspect-effective-writes}@anchor{134}
9627 @section Aspect Effective_Writes
9630 @geindex Effective_Writes
9632 This aspect is equivalent to @ref{5e,,pragma Effective_Writes}.
9634 @node Aspect Extensions_Visible,Aspect Favor_Top_Level,Aspect Effective_Writes,Implementation Defined Aspects
9635 @anchor{gnat_rm/implementation_defined_aspects aspect-extensions-visible}@anchor{135}
9636 @section Aspect Extensions_Visible
9639 @geindex Extensions_Visible
9641 This aspect is equivalent to @ref{6a,,pragma Extensions_Visible}.
9643 @node Aspect Favor_Top_Level,Aspect Ghost,Aspect Extensions_Visible,Implementation Defined Aspects
9644 @anchor{gnat_rm/implementation_defined_aspects aspect-favor-top-level}@anchor{136}
9645 @section Aspect Favor_Top_Level
9648 @geindex Favor_Top_Level
9650 This boolean aspect is equivalent to @ref{6f,,pragma Favor_Top_Level}.
9652 @node Aspect Ghost,Aspect Global,Aspect Favor_Top_Level,Implementation Defined Aspects
9653 @anchor{gnat_rm/implementation_defined_aspects aspect-ghost}@anchor{137}
9654 @section Aspect Ghost
9659 This aspect is equivalent to @ref{72,,pragma Ghost}.
9661 @node Aspect Global,Aspect Initial_Condition,Aspect Ghost,Implementation Defined Aspects
9662 @anchor{gnat_rm/implementation_defined_aspects aspect-global}@anchor{138}
9663 @section Aspect Global
9668 This aspect is equivalent to @ref{74,,pragma Global}.
9670 @node Aspect Initial_Condition,Aspect Initializes,Aspect Global,Implementation Defined Aspects
9671 @anchor{gnat_rm/implementation_defined_aspects aspect-initial-condition}@anchor{139}
9672 @section Aspect Initial_Condition
9675 @geindex Initial_Condition
9677 This aspect is equivalent to @ref{82,,pragma Initial_Condition}.
9679 @node Aspect Initializes,Aspect Inline_Always,Aspect Initial_Condition,Implementation Defined Aspects
9680 @anchor{gnat_rm/implementation_defined_aspects aspect-initializes}@anchor{13a}
9681 @section Aspect Initializes
9684 @geindex Initializes
9686 This aspect is equivalent to @ref{84,,pragma Initializes}.
9688 @node Aspect Inline_Always,Aspect Invariant,Aspect Initializes,Implementation Defined Aspects
9689 @anchor{gnat_rm/implementation_defined_aspects aspect-inline-always}@anchor{13b}
9690 @section Aspect Inline_Always
9693 @geindex Inline_Always
9695 This boolean aspect is equivalent to @ref{87,,pragma Inline_Always}.
9697 @node Aspect Invariant,Aspect Invariant'Class,Aspect Inline_Always,Implementation Defined Aspects
9698 @anchor{gnat_rm/implementation_defined_aspects aspect-invariant}@anchor{13c}
9699 @section Aspect Invariant
9704 This aspect is equivalent to @ref{8e,,pragma Invariant}. It is a
9705 synonym for the language defined aspect @code{Type_Invariant} except
9706 that it is separately controllable using pragma @code{Assertion_Policy}.
9708 @node Aspect Invariant'Class,Aspect Iterable,Aspect Invariant,Implementation Defined Aspects
9709 @anchor{gnat_rm/implementation_defined_aspects aspect-invariant-class}@anchor{13d}
9710 @section Aspect Invariant'Class
9713 @geindex Invariant'Class
9715 This aspect is equivalent to @ref{106,,pragma Type_Invariant_Class}. It is a
9716 synonym for the language defined aspect @code{Type_Invariant'Class} except
9717 that it is separately controllable using pragma @code{Assertion_Policy}.
9719 @node Aspect Iterable,Aspect Linker_Section,Aspect Invariant'Class,Implementation Defined Aspects
9720 @anchor{gnat_rm/implementation_defined_aspects aspect-iterable}@anchor{13e}
9721 @section Aspect Iterable
9726 This aspect provides a light-weight mechanism for loops and quantified
9727 expressions over container types, without the overhead imposed by the tampering
9728 checks of standard Ada 2012 iterators. The value of the aspect is an aggregate
9729 with six named components, of which the last three are optional: @code{First},
9730 @code{Next}, @code{Has_Element}, @code{Element}, @code{Last}, and @code{Previous}.
9731 When only the first three components are specified, only the
9732 @code{for .. in} form of iteration over cursors is available. When @code{Element}
9733 is specified, both this form and the @code{for .. of} form of iteration over
9734 elements are available. If the last two components are specified, reverse
9735 iterations over the container can be specified (analogous to what can be done
9736 over predefined containers that support the @code{Reverse_Iterator} interface).
9737 The following is a typical example of use:
9740 type List is private with
9741 Iterable => (First => First_Cursor,
9743 Has_Element => Cursor_Has_Element,
9744 [Element => Get_Element]);
9751 The value denoted by @code{First} must denote a primitive operation of the
9752 container type that returns a @code{Cursor}, which must a be a type declared in
9753 the container package or visible from it. For example:
9757 function First_Cursor (Cont : Container) return Cursor;
9764 The value of @code{Next} is a primitive operation of the container type that takes
9765 both a container and a cursor and yields a cursor. For example:
9769 function Advance (Cont : Container; Position : Cursor) return Cursor;
9776 The value of @code{Has_Element} is a primitive operation of the container type
9777 that takes both a container and a cursor and yields a boolean. For example:
9781 function Cursor_Has_Element (Cont : Container; Position : Cursor) return Boolean;
9788 The value of @code{Element} is a primitive operation of the container type that
9789 takes both a container and a cursor and yields an @code{Element_Type}, which must
9790 be a type declared in the container package or visible from it. For example:
9794 function Get_Element (Cont : Container; Position : Cursor) return Element_Type;
9797 This aspect is used in the GNAT-defined formal container packages.
9799 @node Aspect Linker_Section,Aspect Lock_Free,Aspect Iterable,Implementation Defined Aspects
9800 @anchor{gnat_rm/implementation_defined_aspects aspect-linker-section}@anchor{13f}
9801 @section Aspect Linker_Section
9804 @geindex Linker_Section
9806 This aspect is equivalent to @ref{96,,pragma Linker_Section}.
9808 @node Aspect Lock_Free,Aspect Max_Queue_Length,Aspect Linker_Section,Implementation Defined Aspects
9809 @anchor{gnat_rm/implementation_defined_aspects aspect-lock-free}@anchor{140}
9810 @section Aspect Lock_Free
9815 This boolean aspect is equivalent to @ref{98,,pragma Lock_Free}.
9817 @node Aspect Max_Queue_Length,Aspect No_Caching,Aspect Lock_Free,Implementation Defined Aspects
9818 @anchor{gnat_rm/implementation_defined_aspects aspect-max-queue-length}@anchor{141}
9819 @section Aspect Max_Queue_Length
9822 @geindex Max_Queue_Length
9824 This aspect is equivalent to @ref{a0,,pragma Max_Queue_Length}.
9826 @node Aspect No_Caching,Aspect No_Elaboration_Code_All,Aspect Max_Queue_Length,Implementation Defined Aspects
9827 @anchor{gnat_rm/implementation_defined_aspects aspect-no-caching}@anchor{142}
9828 @section Aspect No_Caching
9833 This boolean aspect is equivalent to @ref{a2,,pragma No_Caching}.
9835 @node Aspect No_Elaboration_Code_All,Aspect No_Inline,Aspect No_Caching,Implementation Defined Aspects
9836 @anchor{gnat_rm/implementation_defined_aspects aspect-no-elaboration-code-all}@anchor{143}
9837 @section Aspect No_Elaboration_Code_All
9840 @geindex No_Elaboration_Code_All
9842 This aspect is equivalent to @ref{a6,,pragma No_Elaboration_Code_All}
9845 @node Aspect No_Inline,Aspect No_Tagged_Streams,Aspect No_Elaboration_Code_All,Implementation Defined Aspects
9846 @anchor{gnat_rm/implementation_defined_aspects aspect-no-inline}@anchor{144}
9847 @section Aspect No_Inline
9852 This boolean aspect is equivalent to @ref{a9,,pragma No_Inline}.
9854 @node Aspect No_Tagged_Streams,Aspect Object_Size,Aspect No_Inline,Implementation Defined Aspects
9855 @anchor{gnat_rm/implementation_defined_aspects aspect-no-tagged-streams}@anchor{145}
9856 @section Aspect No_Tagged_Streams
9859 @geindex No_Tagged_Streams
9861 This aspect is equivalent to @ref{ac,,pragma No_Tagged_Streams} with an
9862 argument specifying a root tagged type (thus this aspect can only be
9863 applied to such a type).
9865 @node Aspect Object_Size,Aspect Obsolescent,Aspect No_Tagged_Streams,Implementation Defined Aspects
9866 @anchor{gnat_rm/implementation_defined_aspects aspect-object-size}@anchor{146}
9867 @section Aspect Object_Size
9870 @geindex Object_Size
9872 This aspect is equivalent to @ref{147,,attribute Object_Size}.
9874 @node Aspect Obsolescent,Aspect Part_Of,Aspect Object_Size,Implementation Defined Aspects
9875 @anchor{gnat_rm/implementation_defined_aspects aspect-obsolescent}@anchor{148}
9876 @section Aspect Obsolescent
9879 @geindex Obsolsecent
9881 This aspect is equivalent to @ref{af,,pragma Obsolescent}. Note that the
9882 evaluation of this aspect happens at the point of occurrence, it is not
9883 delayed until the freeze point.
9885 @node Aspect Part_Of,Aspect Persistent_BSS,Aspect Obsolescent,Implementation Defined Aspects
9886 @anchor{gnat_rm/implementation_defined_aspects aspect-part-of}@anchor{149}
9887 @section Aspect Part_Of
9892 This aspect is equivalent to @ref{b7,,pragma Part_Of}.
9894 @node Aspect Persistent_BSS,Aspect Predicate,Aspect Part_Of,Implementation Defined Aspects
9895 @anchor{gnat_rm/implementation_defined_aspects aspect-persistent-bss}@anchor{14a}
9896 @section Aspect Persistent_BSS
9899 @geindex Persistent_BSS
9901 This boolean aspect is equivalent to @ref{ba,,pragma Persistent_BSS}.
9903 @node Aspect Predicate,Aspect Pure_Function,Aspect Persistent_BSS,Implementation Defined Aspects
9904 @anchor{gnat_rm/implementation_defined_aspects aspect-predicate}@anchor{14b}
9905 @section Aspect Predicate
9910 This aspect is equivalent to @ref{c2,,pragma Predicate}. It is thus
9911 similar to the language defined aspects @code{Dynamic_Predicate}
9912 and @code{Static_Predicate} except that whether the resulting
9913 predicate is static or dynamic is controlled by the form of the
9914 expression. It is also separately controllable using pragma
9915 @code{Assertion_Policy}.
9917 @node Aspect Pure_Function,Aspect Refined_Depends,Aspect Predicate,Implementation Defined Aspects
9918 @anchor{gnat_rm/implementation_defined_aspects aspect-pure-function}@anchor{14c}
9919 @section Aspect Pure_Function
9922 @geindex Pure_Function
9924 This boolean aspect is equivalent to @ref{ce,,pragma Pure_Function}.
9926 @node Aspect Refined_Depends,Aspect Refined_Global,Aspect Pure_Function,Implementation Defined Aspects
9927 @anchor{gnat_rm/implementation_defined_aspects aspect-refined-depends}@anchor{14d}
9928 @section Aspect Refined_Depends
9931 @geindex Refined_Depends
9933 This aspect is equivalent to @ref{d2,,pragma Refined_Depends}.
9935 @node Aspect Refined_Global,Aspect Refined_Post,Aspect Refined_Depends,Implementation Defined Aspects
9936 @anchor{gnat_rm/implementation_defined_aspects aspect-refined-global}@anchor{14e}
9937 @section Aspect Refined_Global
9940 @geindex Refined_Global
9942 This aspect is equivalent to @ref{d4,,pragma Refined_Global}.
9944 @node Aspect Refined_Post,Aspect Refined_State,Aspect Refined_Global,Implementation Defined Aspects
9945 @anchor{gnat_rm/implementation_defined_aspects aspect-refined-post}@anchor{14f}
9946 @section Aspect Refined_Post
9949 @geindex Refined_Post
9951 This aspect is equivalent to @ref{d6,,pragma Refined_Post}.
9953 @node Aspect Refined_State,Aspect Remote_Access_Type,Aspect Refined_Post,Implementation Defined Aspects
9954 @anchor{gnat_rm/implementation_defined_aspects aspect-refined-state}@anchor{150}
9955 @section Aspect Refined_State
9958 @geindex Refined_State
9960 This aspect is equivalent to @ref{d8,,pragma Refined_State}.
9962 @node Aspect Remote_Access_Type,Aspect Secondary_Stack_Size,Aspect Refined_State,Implementation Defined Aspects
9963 @anchor{gnat_rm/implementation_defined_aspects aspect-remote-access-type}@anchor{151}
9964 @section Aspect Remote_Access_Type
9967 @geindex Remote_Access_Type
9969 This aspect is equivalent to @ref{dc,,pragma Remote_Access_Type}.
9971 @node Aspect Secondary_Stack_Size,Aspect Scalar_Storage_Order,Aspect Remote_Access_Type,Implementation Defined Aspects
9972 @anchor{gnat_rm/implementation_defined_aspects aspect-secondary-stack-size}@anchor{152}
9973 @section Aspect Secondary_Stack_Size
9976 @geindex Secondary_Stack_Size
9978 This aspect is equivalent to @ref{e1,,pragma Secondary_Stack_Size}.
9980 @node Aspect Scalar_Storage_Order,Aspect Shared,Aspect Secondary_Stack_Size,Implementation Defined Aspects
9981 @anchor{gnat_rm/implementation_defined_aspects aspect-scalar-storage-order}@anchor{153}
9982 @section Aspect Scalar_Storage_Order
9985 @geindex Scalar_Storage_Order
9987 This aspect is equivalent to a @ref{154,,attribute Scalar_Storage_Order}.
9989 @node Aspect Shared,Aspect Simple_Storage_Pool,Aspect Scalar_Storage_Order,Implementation Defined Aspects
9990 @anchor{gnat_rm/implementation_defined_aspects aspect-shared}@anchor{155}
9991 @section Aspect Shared
9996 This boolean aspect is equivalent to @ref{e4,,pragma Shared}
9997 and is thus a synonym for aspect @code{Atomic}.
9999 @node Aspect Simple_Storage_Pool,Aspect Simple_Storage_Pool_Type,Aspect Shared,Implementation Defined Aspects
10000 @anchor{gnat_rm/implementation_defined_aspects aspect-simple-storage-pool}@anchor{156}
10001 @section Aspect Simple_Storage_Pool
10004 @geindex Simple_Storage_Pool
10006 This aspect is equivalent to @ref{e9,,attribute Simple_Storage_Pool}.
10008 @node Aspect Simple_Storage_Pool_Type,Aspect SPARK_Mode,Aspect Simple_Storage_Pool,Implementation Defined Aspects
10009 @anchor{gnat_rm/implementation_defined_aspects aspect-simple-storage-pool-type}@anchor{157}
10010 @section Aspect Simple_Storage_Pool_Type
10013 @geindex Simple_Storage_Pool_Type
10015 This boolean aspect is equivalent to @ref{e7,,pragma Simple_Storage_Pool_Type}.
10017 @node Aspect SPARK_Mode,Aspect Suppress_Debug_Info,Aspect Simple_Storage_Pool_Type,Implementation Defined Aspects
10018 @anchor{gnat_rm/implementation_defined_aspects aspect-spark-mode}@anchor{158}
10019 @section Aspect SPARK_Mode
10022 @geindex SPARK_Mode
10024 This aspect is equivalent to @ref{ef,,pragma SPARK_Mode} and
10025 may be specified for either or both of the specification and body
10026 of a subprogram or package.
10028 @node Aspect Suppress_Debug_Info,Aspect Suppress_Initialization,Aspect SPARK_Mode,Implementation Defined Aspects
10029 @anchor{gnat_rm/implementation_defined_aspects aspect-suppress-debug-info}@anchor{159}
10030 @section Aspect Suppress_Debug_Info
10033 @geindex Suppress_Debug_Info
10035 This boolean aspect is equivalent to @ref{f7,,pragma Suppress_Debug_Info}.
10037 @node Aspect Suppress_Initialization,Aspect Test_Case,Aspect Suppress_Debug_Info,Implementation Defined Aspects
10038 @anchor{gnat_rm/implementation_defined_aspects aspect-suppress-initialization}@anchor{15a}
10039 @section Aspect Suppress_Initialization
10042 @geindex Suppress_Initialization
10044 This boolean aspect is equivalent to @ref{fb,,pragma Suppress_Initialization}.
10046 @node Aspect Test_Case,Aspect Thread_Local_Storage,Aspect Suppress_Initialization,Implementation Defined Aspects
10047 @anchor{gnat_rm/implementation_defined_aspects aspect-test-case}@anchor{15b}
10048 @section Aspect Test_Case
10053 This aspect is equivalent to @ref{fe,,pragma Test_Case}.
10055 @node Aspect Thread_Local_Storage,Aspect Universal_Aliasing,Aspect Test_Case,Implementation Defined Aspects
10056 @anchor{gnat_rm/implementation_defined_aspects aspect-thread-local-storage}@anchor{15c}
10057 @section Aspect Thread_Local_Storage
10060 @geindex Thread_Local_Storage
10062 This boolean aspect is equivalent to @ref{100,,pragma Thread_Local_Storage}.
10064 @node Aspect Universal_Aliasing,Aspect Universal_Data,Aspect Thread_Local_Storage,Implementation Defined Aspects
10065 @anchor{gnat_rm/implementation_defined_aspects aspect-universal-aliasing}@anchor{15d}
10066 @section Aspect Universal_Aliasing
10069 @geindex Universal_Aliasing
10071 This boolean aspect is equivalent to @ref{10a,,pragma Universal_Aliasing}.
10073 @node Aspect Universal_Data,Aspect Unmodified,Aspect Universal_Aliasing,Implementation Defined Aspects
10074 @anchor{gnat_rm/implementation_defined_aspects aspect-universal-data}@anchor{15e}
10075 @section Aspect Universal_Data
10078 @geindex Universal_Data
10080 This aspect is equivalent to @ref{10c,,pragma Universal_Data}.
10082 @node Aspect Unmodified,Aspect Unreferenced,Aspect Universal_Data,Implementation Defined Aspects
10083 @anchor{gnat_rm/implementation_defined_aspects aspect-unmodified}@anchor{15f}
10084 @section Aspect Unmodified
10087 @geindex Unmodified
10089 This boolean aspect is equivalent to @ref{10f,,pragma Unmodified}.
10091 @node Aspect Unreferenced,Aspect Unreferenced_Objects,Aspect Unmodified,Implementation Defined Aspects
10092 @anchor{gnat_rm/implementation_defined_aspects aspect-unreferenced}@anchor{160}
10093 @section Aspect Unreferenced
10096 @geindex Unreferenced
10098 This boolean aspect is equivalent to @ref{110,,pragma Unreferenced}. Note that
10099 in the case of formal parameters, it is not permitted to have aspects for
10100 a formal parameter, so in this case the pragma form must be used.
10102 @node Aspect Unreferenced_Objects,Aspect Value_Size,Aspect Unreferenced,Implementation Defined Aspects
10103 @anchor{gnat_rm/implementation_defined_aspects aspect-unreferenced-objects}@anchor{161}
10104 @section Aspect Unreferenced_Objects
10107 @geindex Unreferenced_Objects
10109 This boolean aspect is equivalent to @ref{112,,pragma Unreferenced_Objects}.
10111 @node Aspect Value_Size,Aspect Volatile_Full_Access,Aspect Unreferenced_Objects,Implementation Defined Aspects
10112 @anchor{gnat_rm/implementation_defined_aspects aspect-value-size}@anchor{162}
10113 @section Aspect Value_Size
10116 @geindex Value_Size
10118 This aspect is equivalent to @ref{163,,attribute Value_Size}.
10120 @node Aspect Volatile_Full_Access,Aspect Volatile_Function,Aspect Value_Size,Implementation Defined Aspects
10121 @anchor{gnat_rm/implementation_defined_aspects aspect-volatile-full-access}@anchor{164}
10122 @section Aspect Volatile_Full_Access
10125 @geindex Volatile_Full_Access
10127 This boolean aspect is equivalent to @ref{11d,,pragma Volatile_Full_Access}.
10129 @node Aspect Volatile_Function,Aspect Warnings,Aspect Volatile_Full_Access,Implementation Defined Aspects
10130 @anchor{gnat_rm/implementation_defined_aspects aspect-volatile-function}@anchor{165}
10131 @section Aspect Volatile_Function
10134 @geindex Volatile_Function
10136 This boolean aspect is equivalent to @ref{11f,,pragma Volatile_Function}.
10138 @node Aspect Warnings,,Aspect Volatile_Function,Implementation Defined Aspects
10139 @anchor{gnat_rm/implementation_defined_aspects aspect-warnings}@anchor{166}
10140 @section Aspect Warnings
10145 This aspect is equivalent to the two argument form of @ref{121,,pragma Warnings},
10146 where the first argument is @code{ON} or @code{OFF} and the second argument
10149 @node Implementation Defined Attributes,Standard and Implementation Defined Restrictions,Implementation Defined Aspects,Top
10150 @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}
10151 @chapter Implementation Defined Attributes
10154 Ada defines (throughout the Ada reference manual,
10155 summarized in Annex K),
10156 a set of attributes that provide useful additional functionality in all
10157 areas of the language. These language defined attributes are implemented
10158 in GNAT and work as described in the Ada Reference Manual.
10160 In addition, Ada allows implementations to define additional
10161 attributes whose meaning is defined by the implementation. GNAT provides
10162 a number of these implementation-dependent attributes which can be used
10163 to extend and enhance the functionality of the compiler. This section of
10164 the GNAT reference manual describes these additional attributes. It also
10165 describes additional implementation-dependent features of standard
10166 language-defined attributes.
10168 Note that any program using these attributes may not be portable to
10169 other compilers (although GNAT implements this set of attributes on all
10170 platforms). Therefore if portability to other compilers is an important
10171 consideration, you should minimize the use of these attributes.
10174 * Attribute Abort_Signal::
10175 * Attribute Address_Size::
10176 * Attribute Asm_Input::
10177 * Attribute Asm_Output::
10178 * Attribute Atomic_Always_Lock_Free::
10180 * Attribute Bit_Position::
10181 * Attribute Code_Address::
10182 * Attribute Compiler_Version::
10183 * Attribute Constrained::
10184 * Attribute Default_Bit_Order::
10185 * Attribute Default_Scalar_Storage_Order::
10186 * Attribute Deref::
10187 * Attribute Descriptor_Size::
10188 * Attribute Elaborated::
10189 * Attribute Elab_Body::
10190 * Attribute Elab_Spec::
10191 * Attribute Elab_Subp_Body::
10193 * Attribute Enabled::
10194 * Attribute Enum_Rep::
10195 * Attribute Enum_Val::
10196 * Attribute Epsilon::
10197 * Attribute Fast_Math::
10198 * Attribute Finalization_Size::
10199 * Attribute Fixed_Value::
10200 * Attribute From_Any::
10201 * Attribute Has_Access_Values::
10202 * Attribute Has_Discriminants::
10204 * Attribute Integer_Value::
10205 * Attribute Invalid_Value::
10206 * Attribute Iterable::
10207 * Attribute Large::
10208 * Attribute Library_Level::
10209 * Attribute Lock_Free::
10210 * Attribute Loop_Entry::
10211 * Attribute Machine_Size::
10212 * Attribute Mantissa::
10213 * Attribute Maximum_Alignment::
10214 * Attribute Mechanism_Code::
10215 * Attribute Null_Parameter::
10216 * Attribute Object_Size::
10218 * Attribute Passed_By_Reference::
10219 * Attribute Pool_Address::
10220 * Attribute Range_Length::
10221 * Attribute Restriction_Set::
10222 * Attribute Result::
10223 * Attribute Safe_Emax::
10224 * Attribute Safe_Large::
10225 * Attribute Safe_Small::
10226 * Attribute Scalar_Storage_Order::
10227 * Attribute Simple_Storage_Pool::
10228 * Attribute Small::
10229 * Attribute Storage_Unit::
10230 * Attribute Stub_Type::
10231 * Attribute System_Allocator_Alignment::
10232 * Attribute Target_Name::
10233 * Attribute To_Address::
10234 * Attribute To_Any::
10235 * Attribute Type_Class::
10236 * Attribute Type_Key::
10237 * Attribute TypeCode::
10238 * Attribute Unconstrained_Array::
10239 * Attribute Universal_Literal_String::
10240 * Attribute Unrestricted_Access::
10241 * Attribute Update::
10242 * Attribute Valid_Scalars::
10243 * Attribute VADS_Size::
10244 * Attribute Value_Size::
10245 * Attribute Wchar_T_Size::
10246 * Attribute Word_Size::
10250 @node Attribute Abort_Signal,Attribute Address_Size,,Implementation Defined Attributes
10251 @anchor{gnat_rm/implementation_defined_attributes attribute-abort-signal}@anchor{169}
10252 @section Attribute Abort_Signal
10255 @geindex Abort_Signal
10257 @code{Standard'Abort_Signal} (@code{Standard} is the only allowed
10258 prefix) provides the entity for the special exception used to signal
10259 task abort or asynchronous transfer of control. Normally this attribute
10260 should only be used in the tasking runtime (it is highly peculiar, and
10261 completely outside the normal semantics of Ada, for a user program to
10262 intercept the abort exception).
10264 @node Attribute Address_Size,Attribute Asm_Input,Attribute Abort_Signal,Implementation Defined Attributes
10265 @anchor{gnat_rm/implementation_defined_attributes attribute-address-size}@anchor{16a}
10266 @section Attribute Address_Size
10269 @geindex Size of `@w{`}Address`@w{`}
10271 @geindex Address_Size
10273 @code{Standard'Address_Size} (@code{Standard} is the only allowed
10274 prefix) is a static constant giving the number of bits in an
10275 @code{Address}. It is the same value as System.Address'Size,
10276 but has the advantage of being static, while a direct
10277 reference to System.Address'Size is nonstatic because Address
10280 @node Attribute Asm_Input,Attribute Asm_Output,Attribute Address_Size,Implementation Defined Attributes
10281 @anchor{gnat_rm/implementation_defined_attributes attribute-asm-input}@anchor{16b}
10282 @section Attribute Asm_Input
10287 The @code{Asm_Input} attribute denotes a function that takes two
10288 parameters. The first is a string, the second is an expression of the
10289 type designated by the prefix. The first (string) argument is required
10290 to be a static expression, and is the constraint for the parameter,
10291 (e.g., what kind of register is required). The second argument is the
10292 value to be used as the input argument. The possible values for the
10293 constant are the same as those used in the RTL, and are dependent on
10294 the configuration file used to built the GCC back end.
10295 @ref{16c,,Machine Code Insertions}
10297 @node Attribute Asm_Output,Attribute Atomic_Always_Lock_Free,Attribute Asm_Input,Implementation Defined Attributes
10298 @anchor{gnat_rm/implementation_defined_attributes attribute-asm-output}@anchor{16d}
10299 @section Attribute Asm_Output
10302 @geindex Asm_Output
10304 The @code{Asm_Output} attribute denotes a function that takes two
10305 parameters. The first is a string, the second is the name of a variable
10306 of the type designated by the attribute prefix. The first (string)
10307 argument is required to be a static expression and designates the
10308 constraint for the parameter (e.g., what kind of register is
10309 required). The second argument is the variable to be updated with the
10310 result. The possible values for constraint are the same as those used in
10311 the RTL, and are dependent on the configuration file used to build the
10312 GCC back end. If there are no output operands, then this argument may
10313 either be omitted, or explicitly given as @code{No_Output_Operands}.
10314 @ref{16c,,Machine Code Insertions}
10316 @node Attribute Atomic_Always_Lock_Free,Attribute Bit,Attribute Asm_Output,Implementation Defined Attributes
10317 @anchor{gnat_rm/implementation_defined_attributes attribute-atomic-always-lock-free}@anchor{16e}
10318 @section Attribute Atomic_Always_Lock_Free
10321 @geindex Atomic_Always_Lock_Free
10323 The prefix of the @code{Atomic_Always_Lock_Free} attribute is a type.
10324 The result is a Boolean value which is True if the type has discriminants,
10325 and False otherwise. The result indicate whether atomic operations are
10326 supported by the target for the given type.
10328 @node Attribute Bit,Attribute Bit_Position,Attribute Atomic_Always_Lock_Free,Implementation Defined Attributes
10329 @anchor{gnat_rm/implementation_defined_attributes attribute-bit}@anchor{16f}
10330 @section Attribute Bit
10335 @code{obj'Bit}, where @code{obj} is any object, yields the bit
10336 offset within the storage unit (byte) that contains the first bit of
10337 storage allocated for the object. The value of this attribute is of the
10338 type @emph{universal_integer}, and is always a non-negative number not
10339 exceeding the value of @code{System.Storage_Unit}.
10341 For an object that is a variable or a constant allocated in a register,
10342 the value is zero. (The use of this attribute does not force the
10343 allocation of a variable to memory).
10345 For an object that is a formal parameter, this attribute applies
10346 to either the matching actual parameter or to a copy of the
10347 matching actual parameter.
10349 For an access object the value is zero. Note that
10350 @code{obj.all'Bit} is subject to an @code{Access_Check} for the
10351 designated object. Similarly for a record component
10352 @code{X.C'Bit} is subject to a discriminant check and
10353 @code{X(I).Bit} and @code{X(I1..I2)'Bit}
10354 are subject to index checks.
10356 This attribute is designed to be compatible with the DEC Ada 83 definition
10357 and implementation of the @code{Bit} attribute.
10359 @node Attribute Bit_Position,Attribute Code_Address,Attribute Bit,Implementation Defined Attributes
10360 @anchor{gnat_rm/implementation_defined_attributes attribute-bit-position}@anchor{170}
10361 @section Attribute Bit_Position
10364 @geindex Bit_Position
10366 @code{R.C'Bit_Position}, where @code{R} is a record object and @code{C} is one
10367 of the fields of the record type, yields the bit
10368 offset within the record contains the first bit of
10369 storage allocated for the object. The value of this attribute is of the
10370 type @emph{universal_integer}. The value depends only on the field
10371 @code{C} and is independent of the alignment of
10372 the containing record @code{R}.
10374 @node Attribute Code_Address,Attribute Compiler_Version,Attribute Bit_Position,Implementation Defined Attributes
10375 @anchor{gnat_rm/implementation_defined_attributes attribute-code-address}@anchor{171}
10376 @section Attribute Code_Address
10379 @geindex Code_Address
10381 @geindex Subprogram address
10383 @geindex Address of subprogram code
10385 The @code{'Address}
10386 attribute may be applied to subprograms in Ada 95 and Ada 2005, but the
10387 intended effect seems to be to provide
10388 an address value which can be used to call the subprogram by means of
10389 an address clause as in the following example:
10395 for L'Address use K'Address;
10396 pragma Import (Ada, L);
10399 A call to @code{L} is then expected to result in a call to @code{K}.
10400 In Ada 83, where there were no access-to-subprogram values, this was
10401 a common work-around for getting the effect of an indirect call.
10402 GNAT implements the above use of @code{Address} and the technique
10403 illustrated by the example code works correctly.
10405 However, for some purposes, it is useful to have the address of the start
10406 of the generated code for the subprogram. On some architectures, this is
10407 not necessarily the same as the @code{Address} value described above.
10408 For example, the @code{Address} value may reference a subprogram
10409 descriptor rather than the subprogram itself.
10411 The @code{'Code_Address} attribute, which can only be applied to
10412 subprogram entities, always returns the address of the start of the
10413 generated code of the specified subprogram, which may or may not be
10414 the same value as is returned by the corresponding @code{'Address}
10417 @node Attribute Compiler_Version,Attribute Constrained,Attribute Code_Address,Implementation Defined Attributes
10418 @anchor{gnat_rm/implementation_defined_attributes attribute-compiler-version}@anchor{172}
10419 @section Attribute Compiler_Version
10422 @geindex Compiler_Version
10424 @code{Standard'Compiler_Version} (@code{Standard} is the only allowed
10425 prefix) yields a static string identifying the version of the compiler
10426 being used to compile the unit containing the attribute reference.
10428 @node Attribute Constrained,Attribute Default_Bit_Order,Attribute Compiler_Version,Implementation Defined Attributes
10429 @anchor{gnat_rm/implementation_defined_attributes attribute-constrained}@anchor{173}
10430 @section Attribute Constrained
10433 @geindex Constrained
10435 In addition to the usage of this attribute in the Ada RM, GNAT
10436 also permits the use of the @code{'Constrained} attribute
10437 in a generic template
10438 for any type, including types without discriminants. The value of this
10439 attribute in the generic instance when applied to a scalar type or a
10440 record type without discriminants is always @code{True}. This usage is
10441 compatible with older Ada compilers, including notably DEC Ada.
10443 @node Attribute Default_Bit_Order,Attribute Default_Scalar_Storage_Order,Attribute Constrained,Implementation Defined Attributes
10444 @anchor{gnat_rm/implementation_defined_attributes attribute-default-bit-order}@anchor{174}
10445 @section Attribute Default_Bit_Order
10448 @geindex Big endian
10450 @geindex Little endian
10452 @geindex Default_Bit_Order
10454 @code{Standard'Default_Bit_Order} (@code{Standard} is the only
10455 permissible prefix), provides the value @code{System.Default_Bit_Order}
10456 as a @code{Pos} value (0 for @code{High_Order_First}, 1 for
10457 @code{Low_Order_First}). This is used to construct the definition of
10458 @code{Default_Bit_Order} in package @code{System}.
10460 @node Attribute Default_Scalar_Storage_Order,Attribute Deref,Attribute Default_Bit_Order,Implementation Defined Attributes
10461 @anchor{gnat_rm/implementation_defined_attributes attribute-default-scalar-storage-order}@anchor{175}
10462 @section Attribute Default_Scalar_Storage_Order
10465 @geindex Big endian
10467 @geindex Little endian
10469 @geindex Default_Scalar_Storage_Order
10471 @code{Standard'Default_Scalar_Storage_Order} (@code{Standard} is the only
10472 permissible prefix), provides the current value of the default scalar storage
10473 order (as specified using pragma @code{Default_Scalar_Storage_Order}, or
10474 equal to @code{Default_Bit_Order} if unspecified) as a
10475 @code{System.Bit_Order} value. This is a static attribute.
10477 @node Attribute Deref,Attribute Descriptor_Size,Attribute Default_Scalar_Storage_Order,Implementation Defined Attributes
10478 @anchor{gnat_rm/implementation_defined_attributes attribute-deref}@anchor{176}
10479 @section Attribute Deref
10484 The attribute @code{typ'Deref(expr)} where @code{expr} is of type @code{System.Address} yields
10485 the variable of type @code{typ} that is located at the given address. It is similar
10486 to @code{(totyp (expr).all)}, where @code{totyp} is an unchecked conversion from address to
10487 a named access-to-@cite{typ} type, except that it yields a variable, so it can be
10488 used on the left side of an assignment.
10490 @node Attribute Descriptor_Size,Attribute Elaborated,Attribute Deref,Implementation Defined Attributes
10491 @anchor{gnat_rm/implementation_defined_attributes attribute-descriptor-size}@anchor{177}
10492 @section Attribute Descriptor_Size
10495 @geindex Descriptor
10497 @geindex Dope vector
10499 @geindex Descriptor_Size
10501 Nonstatic attribute @code{Descriptor_Size} returns the size in bits of the
10502 descriptor allocated for a type. The result is non-zero only for unconstrained
10503 array types and the returned value is of type universal integer. In GNAT, an
10504 array descriptor contains bounds information and is located immediately before
10505 the first element of the array.
10508 type Unconstr_Array is array (Positive range <>) of Boolean;
10509 Put_Line ("Descriptor size = " & Unconstr_Array'Descriptor_Size'Img);
10512 The attribute takes into account any additional padding due to type alignment.
10513 In the example above, the descriptor contains two values of type
10514 @code{Positive} representing the low and high bound. Since @code{Positive} has
10515 a size of 31 bits and an alignment of 4, the descriptor size is @code{2 * Positive'Size + 2} or 64 bits.
10517 @node Attribute Elaborated,Attribute Elab_Body,Attribute Descriptor_Size,Implementation Defined Attributes
10518 @anchor{gnat_rm/implementation_defined_attributes attribute-elaborated}@anchor{178}
10519 @section Attribute Elaborated
10522 @geindex Elaborated
10524 The prefix of the @code{'Elaborated} attribute must be a unit name. The
10525 value is a Boolean which indicates whether or not the given unit has been
10526 elaborated. This attribute is primarily intended for internal use by the
10527 generated code for dynamic elaboration checking, but it can also be used
10528 in user programs. The value will always be True once elaboration of all
10529 units has been completed. An exception is for units which need no
10530 elaboration, the value is always False for such units.
10532 @node Attribute Elab_Body,Attribute Elab_Spec,Attribute Elaborated,Implementation Defined Attributes
10533 @anchor{gnat_rm/implementation_defined_attributes attribute-elab-body}@anchor{179}
10534 @section Attribute Elab_Body
10539 This attribute can only be applied to a program unit name. It returns
10540 the entity for the corresponding elaboration procedure for elaborating
10541 the body of the referenced unit. This is used in the main generated
10542 elaboration procedure by the binder and is not normally used in any
10543 other context. However, there may be specialized situations in which it
10544 is useful to be able to call this elaboration procedure from Ada code,
10545 e.g., if it is necessary to do selective re-elaboration to fix some
10548 @node Attribute Elab_Spec,Attribute Elab_Subp_Body,Attribute Elab_Body,Implementation Defined Attributes
10549 @anchor{gnat_rm/implementation_defined_attributes attribute-elab-spec}@anchor{17a}
10550 @section Attribute Elab_Spec
10555 This attribute can only be applied to a program unit name. It returns
10556 the entity for the corresponding elaboration procedure for elaborating
10557 the spec of the referenced unit. This is used in the main
10558 generated elaboration procedure by the binder and is not normally used
10559 in any other context. However, there may be specialized situations in
10560 which it is useful to be able to call this elaboration procedure from
10561 Ada code, e.g., if it is necessary to do selective re-elaboration to fix
10564 @node Attribute Elab_Subp_Body,Attribute Emax,Attribute Elab_Spec,Implementation Defined Attributes
10565 @anchor{gnat_rm/implementation_defined_attributes attribute-elab-subp-body}@anchor{17b}
10566 @section Attribute Elab_Subp_Body
10569 @geindex Elab_Subp_Body
10571 This attribute can only be applied to a library level subprogram
10572 name and is only allowed in CodePeer mode. It returns the entity
10573 for the corresponding elaboration procedure for elaborating the body
10574 of the referenced subprogram unit. This is used in the main generated
10575 elaboration procedure by the binder in CodePeer mode only and is unrecognized
10578 @node Attribute Emax,Attribute Enabled,Attribute Elab_Subp_Body,Implementation Defined Attributes
10579 @anchor{gnat_rm/implementation_defined_attributes attribute-emax}@anchor{17c}
10580 @section Attribute Emax
10583 @geindex Ada 83 attributes
10587 The @code{Emax} attribute is provided for compatibility with Ada 83. See
10588 the Ada 83 reference manual for an exact description of the semantics of
10591 @node Attribute Enabled,Attribute Enum_Rep,Attribute Emax,Implementation Defined Attributes
10592 @anchor{gnat_rm/implementation_defined_attributes attribute-enabled}@anchor{17d}
10593 @section Attribute Enabled
10598 The @code{Enabled} attribute allows an application program to check at compile
10599 time to see if the designated check is currently enabled. The prefix is a
10600 simple identifier, referencing any predefined check name (other than
10601 @code{All_Checks}) or a check name introduced by pragma Check_Name. If
10602 no argument is given for the attribute, the check is for the general state
10603 of the check, if an argument is given, then it is an entity name, and the
10604 check indicates whether an @code{Suppress} or @code{Unsuppress} has been
10605 given naming the entity (if not, then the argument is ignored).
10607 Note that instantiations inherit the check status at the point of the
10608 instantiation, so a useful idiom is to have a library package that
10609 introduces a check name with @code{pragma Check_Name}, and then contains
10610 generic packages or subprograms which use the @code{Enabled} attribute
10611 to see if the check is enabled. A user of this package can then issue
10612 a @code{pragma Suppress} or @code{pragma Unsuppress} before instantiating
10613 the package or subprogram, controlling whether the check will be present.
10615 @node Attribute Enum_Rep,Attribute Enum_Val,Attribute Enabled,Implementation Defined Attributes
10616 @anchor{gnat_rm/implementation_defined_attributes attribute-enum-rep}@anchor{17e}
10617 @section Attribute Enum_Rep
10620 @geindex Representation of enums
10624 For every enumeration subtype @code{S}, @code{S'Enum_Rep} denotes a
10625 function with the following spec:
10628 function S'Enum_Rep (Arg : S'Base) return <Universal_Integer>;
10631 It is also allowable to apply @code{Enum_Rep} directly to an object of an
10632 enumeration type or to a non-overloaded enumeration
10633 literal. In this case @code{S'Enum_Rep} is equivalent to
10634 @code{typ'Enum_Rep(S)} where @code{typ} is the type of the
10635 enumeration literal or object.
10637 The function returns the representation value for the given enumeration
10638 value. This will be equal to value of the @code{Pos} attribute in the
10639 absence of an enumeration representation clause. This is a static
10640 attribute (i.e.,:the result is static if the argument is static).
10642 @code{S'Enum_Rep} can also be used with integer types and objects,
10643 in which case it simply returns the integer value. The reason for this
10644 is to allow it to be used for @code{(<>)} discrete formal arguments in
10645 a generic unit that can be instantiated with either enumeration types
10646 or integer types. Note that if @code{Enum_Rep} is used on a modular
10647 type whose upper bound exceeds the upper bound of the largest signed
10648 integer type, and the argument is a variable, so that the universal
10649 integer calculation is done at run time, then the call to @code{Enum_Rep}
10650 may raise @code{Constraint_Error}.
10652 @node Attribute Enum_Val,Attribute Epsilon,Attribute Enum_Rep,Implementation Defined Attributes
10653 @anchor{gnat_rm/implementation_defined_attributes attribute-enum-val}@anchor{17f}
10654 @section Attribute Enum_Val
10657 @geindex Representation of enums
10661 For every enumeration subtype @code{S}, @code{S'Enum_Val} denotes a
10662 function with the following spec:
10665 function S'Enum_Val (Arg : <Universal_Integer>) return S'Base;
10668 The function returns the enumeration value whose representation matches the
10669 argument, or raises Constraint_Error if no enumeration literal of the type
10670 has the matching value.
10671 This will be equal to value of the @code{Val} attribute in the
10672 absence of an enumeration representation clause. This is a static
10673 attribute (i.e., the result is static if the argument is static).
10675 @node Attribute Epsilon,Attribute Fast_Math,Attribute Enum_Val,Implementation Defined Attributes
10676 @anchor{gnat_rm/implementation_defined_attributes attribute-epsilon}@anchor{180}
10677 @section Attribute Epsilon
10680 @geindex Ada 83 attributes
10684 The @code{Epsilon} attribute is provided for compatibility with Ada 83. See
10685 the Ada 83 reference manual for an exact description of the semantics of
10688 @node Attribute Fast_Math,Attribute Finalization_Size,Attribute Epsilon,Implementation Defined Attributes
10689 @anchor{gnat_rm/implementation_defined_attributes attribute-fast-math}@anchor{181}
10690 @section Attribute Fast_Math
10695 @code{Standard'Fast_Math} (@code{Standard} is the only allowed
10696 prefix) yields a static Boolean value that is True if pragma
10697 @code{Fast_Math} is active, and False otherwise.
10699 @node Attribute Finalization_Size,Attribute Fixed_Value,Attribute Fast_Math,Implementation Defined Attributes
10700 @anchor{gnat_rm/implementation_defined_attributes attribute-finalization-size}@anchor{182}
10701 @section Attribute Finalization_Size
10704 @geindex Finalization_Size
10706 The prefix of attribute @code{Finalization_Size} must be an object or
10707 a non-class-wide type. This attribute returns the size of any hidden data
10708 reserved by the compiler to handle finalization-related actions. The type of
10709 the attribute is @emph{universal_integer}.
10711 @code{Finalization_Size} yields a value of zero for a type with no controlled
10712 parts, an object whose type has no controlled parts, or an object of a
10713 class-wide type whose tag denotes a type with no controlled parts.
10715 Note that only heap-allocated objects contain finalization data.
10717 @node Attribute Fixed_Value,Attribute From_Any,Attribute Finalization_Size,Implementation Defined Attributes
10718 @anchor{gnat_rm/implementation_defined_attributes attribute-fixed-value}@anchor{183}
10719 @section Attribute Fixed_Value
10722 @geindex Fixed_Value
10724 For every fixed-point type @code{S}, @code{S'Fixed_Value} denotes a
10725 function with the following specification:
10728 function S'Fixed_Value (Arg : <Universal_Integer>) return S;
10731 The value returned is the fixed-point value @code{V} such that:
10737 The effect is thus similar to first converting the argument to the
10738 integer type used to represent @code{S}, and then doing an unchecked
10739 conversion to the fixed-point type. The difference is
10740 that there are full range checks, to ensure that the result is in range.
10741 This attribute is primarily intended for use in implementation of the
10742 input-output functions for fixed-point values.
10744 @node Attribute From_Any,Attribute Has_Access_Values,Attribute Fixed_Value,Implementation Defined Attributes
10745 @anchor{gnat_rm/implementation_defined_attributes attribute-from-any}@anchor{184}
10746 @section Attribute From_Any
10751 This internal attribute is used for the generation of remote subprogram
10752 stubs in the context of the Distributed Systems Annex.
10754 @node Attribute Has_Access_Values,Attribute Has_Discriminants,Attribute From_Any,Implementation Defined Attributes
10755 @anchor{gnat_rm/implementation_defined_attributes attribute-has-access-values}@anchor{185}
10756 @section Attribute Has_Access_Values
10759 @geindex Access values
10760 @geindex testing for
10762 @geindex Has_Access_Values
10764 The prefix of the @code{Has_Access_Values} attribute is a type. The result
10765 is a Boolean value which is True if the is an access type, or is a composite
10766 type with a component (at any nesting depth) that is an access type, and is
10768 The intended use of this attribute is in conjunction with generic
10769 definitions. If the attribute is applied to a generic private type, it
10770 indicates whether or not the corresponding actual type has access values.
10772 @node Attribute Has_Discriminants,Attribute Img,Attribute Has_Access_Values,Implementation Defined Attributes
10773 @anchor{gnat_rm/implementation_defined_attributes attribute-has-discriminants}@anchor{186}
10774 @section Attribute Has_Discriminants
10777 @geindex Discriminants
10778 @geindex testing for
10780 @geindex Has_Discriminants
10782 The prefix of the @code{Has_Discriminants} attribute is a type. The result
10783 is a Boolean value which is True if the type has discriminants, and False
10784 otherwise. The intended use of this attribute is in conjunction with generic
10785 definitions. If the attribute is applied to a generic private type, it
10786 indicates whether or not the corresponding actual type has discriminants.
10788 @node Attribute Img,Attribute Integer_Value,Attribute Has_Discriminants,Implementation Defined Attributes
10789 @anchor{gnat_rm/implementation_defined_attributes attribute-img}@anchor{187}
10790 @section Attribute Img
10795 The @code{Img} attribute differs from @code{Image} in that, while both can be
10796 applied directly to an object, @code{Img} cannot be applied to types.
10798 Example usage of the attribute:
10801 Put_Line ("X = " & X'Img);
10804 which has the same meaning as the more verbose:
10807 Put_Line ("X = " & T'Image (X));
10810 where @code{T} is the (sub)type of the object @code{X}.
10812 Note that technically, in analogy to @code{Image},
10813 @code{X'Img} returns a parameterless function
10814 that returns the appropriate string when called. This means that
10815 @code{X'Img} can be renamed as a function-returning-string, or used
10816 in an instantiation as a function parameter.
10818 @node Attribute Integer_Value,Attribute Invalid_Value,Attribute Img,Implementation Defined Attributes
10819 @anchor{gnat_rm/implementation_defined_attributes attribute-integer-value}@anchor{188}
10820 @section Attribute Integer_Value
10823 @geindex Integer_Value
10825 For every integer type @code{S}, @code{S'Integer_Value} denotes a
10826 function with the following spec:
10829 function S'Integer_Value (Arg : <Universal_Fixed>) return S;
10832 The value returned is the integer value @code{V}, such that:
10838 where @code{T} is the type of @code{Arg}.
10839 The effect is thus similar to first doing an unchecked conversion from
10840 the fixed-point type to its corresponding implementation type, and then
10841 converting the result to the target integer type. The difference is
10842 that there are full range checks, to ensure that the result is in range.
10843 This attribute is primarily intended for use in implementation of the
10844 standard input-output functions for fixed-point values.
10846 @node Attribute Invalid_Value,Attribute Iterable,Attribute Integer_Value,Implementation Defined Attributes
10847 @anchor{gnat_rm/implementation_defined_attributes attribute-invalid-value}@anchor{189}
10848 @section Attribute Invalid_Value
10851 @geindex Invalid_Value
10853 For every scalar type S, S'Invalid_Value returns an undefined value of the
10854 type. If possible this value is an invalid representation for the type. The
10855 value returned is identical to the value used to initialize an otherwise
10856 uninitialized value of the type if pragma Initialize_Scalars is used,
10857 including the ability to modify the value with the binder -Sxx flag and
10858 relevant environment variables at run time.
10860 @node Attribute Iterable,Attribute Large,Attribute Invalid_Value,Implementation Defined Attributes
10861 @anchor{gnat_rm/implementation_defined_attributes attribute-iterable}@anchor{18a}
10862 @section Attribute Iterable
10867 Equivalent to Aspect Iterable.
10869 @node Attribute Large,Attribute Library_Level,Attribute Iterable,Implementation Defined Attributes
10870 @anchor{gnat_rm/implementation_defined_attributes attribute-large}@anchor{18b}
10871 @section Attribute Large
10874 @geindex Ada 83 attributes
10878 The @code{Large} attribute is provided for compatibility with Ada 83. See
10879 the Ada 83 reference manual for an exact description of the semantics of
10882 @node Attribute Library_Level,Attribute Lock_Free,Attribute Large,Implementation Defined Attributes
10883 @anchor{gnat_rm/implementation_defined_attributes attribute-library-level}@anchor{18c}
10884 @section Attribute Library_Level
10887 @geindex Library_Level
10889 @code{P'Library_Level}, where P is an entity name,
10890 returns a Boolean value which is True if the entity is declared
10891 at the library level, and False otherwise. Note that within a
10892 generic instantition, the name of the generic unit denotes the
10893 instance, which means that this attribute can be used to test
10894 if a generic is instantiated at the library level, as shown
10901 pragma Compile_Time_Error
10902 (not Gen'Library_Level,
10903 "Gen can only be instantiated at library level");
10908 @node Attribute Lock_Free,Attribute Loop_Entry,Attribute Library_Level,Implementation Defined Attributes
10909 @anchor{gnat_rm/implementation_defined_attributes attribute-lock-free}@anchor{18d}
10910 @section Attribute Lock_Free
10915 @code{P'Lock_Free}, where P is a protected object, returns True if a
10916 pragma @code{Lock_Free} applies to P.
10918 @node Attribute Loop_Entry,Attribute Machine_Size,Attribute Lock_Free,Implementation Defined Attributes
10919 @anchor{gnat_rm/implementation_defined_attributes attribute-loop-entry}@anchor{18e}
10920 @section Attribute Loop_Entry
10923 @geindex Loop_Entry
10928 X'Loop_Entry [(loop_name)]
10931 The @code{Loop_Entry} attribute is used to refer to the value that an
10932 expression had upon entry to a given loop in much the same way that the
10933 @code{Old} attribute in a subprogram postcondition can be used to refer
10934 to the value an expression had upon entry to the subprogram. The
10935 relevant loop is either identified by the given loop name, or it is the
10936 innermost enclosing loop when no loop name is given.
10938 A @code{Loop_Entry} attribute can only occur within a
10939 @code{Loop_Variant} or @code{Loop_Invariant} pragma. A common use of
10940 @code{Loop_Entry} is to compare the current value of objects with their
10941 initial value at loop entry, in a @code{Loop_Invariant} pragma.
10943 The effect of using @code{X'Loop_Entry} is the same as declaring
10944 a constant initialized with the initial value of @code{X} at loop
10945 entry. This copy is not performed if the loop is not entered, or if the
10946 corresponding pragmas are ignored or disabled.
10948 @node Attribute Machine_Size,Attribute Mantissa,Attribute Loop_Entry,Implementation Defined Attributes
10949 @anchor{gnat_rm/implementation_defined_attributes attribute-machine-size}@anchor{18f}
10950 @section Attribute Machine_Size
10953 @geindex Machine_Size
10955 This attribute is identical to the @code{Object_Size} attribute. It is
10956 provided for compatibility with the DEC Ada 83 attribute of this name.
10958 @node Attribute Mantissa,Attribute Maximum_Alignment,Attribute Machine_Size,Implementation Defined Attributes
10959 @anchor{gnat_rm/implementation_defined_attributes attribute-mantissa}@anchor{190}
10960 @section Attribute Mantissa
10963 @geindex Ada 83 attributes
10967 The @code{Mantissa} attribute is provided for compatibility with Ada 83. See
10968 the Ada 83 reference manual for an exact description of the semantics of
10971 @node Attribute Maximum_Alignment,Attribute Mechanism_Code,Attribute Mantissa,Implementation Defined Attributes
10972 @anchor{gnat_rm/implementation_defined_attributes attribute-maximum-alignment}@anchor{191}@anchor{gnat_rm/implementation_defined_attributes id2}@anchor{192}
10973 @section Attribute Maximum_Alignment
10979 @geindex Maximum_Alignment
10981 @code{Standard'Maximum_Alignment} (@code{Standard} is the only
10982 permissible prefix) provides the maximum useful alignment value for the
10983 target. This is a static value that can be used to specify the alignment
10984 for an object, guaranteeing that it is properly aligned in all
10987 @node Attribute Mechanism_Code,Attribute Null_Parameter,Attribute Maximum_Alignment,Implementation Defined Attributes
10988 @anchor{gnat_rm/implementation_defined_attributes attribute-mechanism-code}@anchor{193}
10989 @section Attribute Mechanism_Code
10992 @geindex Return values
10993 @geindex passing mechanism
10995 @geindex Parameters
10996 @geindex passing mechanism
10998 @geindex Mechanism_Code
11000 @code{func'Mechanism_Code} yields an integer code for the
11001 mechanism used for the result of function @code{func}, and
11002 @code{subprog'Mechanism_Code (n)} yields the mechanism
11003 used for formal parameter number @emph{n} (a static integer value, with 1
11004 meaning the first parameter) of subprogram @code{subprog}. The code returned is:
11018 @node Attribute Null_Parameter,Attribute Object_Size,Attribute Mechanism_Code,Implementation Defined Attributes
11019 @anchor{gnat_rm/implementation_defined_attributes attribute-null-parameter}@anchor{194}
11020 @section Attribute Null_Parameter
11023 @geindex Zero address
11026 @geindex Null_Parameter
11028 A reference @code{T'Null_Parameter} denotes an imaginary object of
11029 type or subtype @code{T} allocated at machine address zero. The attribute
11030 is allowed only as the default expression of a formal parameter, or as
11031 an actual expression of a subprogram call. In either case, the
11032 subprogram must be imported.
11034 The identity of the object is represented by the address zero in the
11035 argument list, independent of the passing mechanism (explicit or
11038 This capability is needed to specify that a zero address should be
11039 passed for a record or other composite object passed by reference.
11040 There is no way of indicating this without the @code{Null_Parameter}
11043 @node Attribute Object_Size,Attribute Old,Attribute Null_Parameter,Implementation Defined Attributes
11044 @anchor{gnat_rm/implementation_defined_attributes attribute-object-size}@anchor{147}@anchor{gnat_rm/implementation_defined_attributes id3}@anchor{195}
11045 @section Attribute Object_Size
11049 @geindex used for objects
11051 @geindex Object_Size
11053 The size of an object is not necessarily the same as the size of the type
11054 of an object. This is because by default object sizes are increased to be
11055 a multiple of the alignment of the object. For example,
11056 @code{Natural'Size} is
11057 31, but by default objects of type @code{Natural} will have a size of 32 bits.
11058 Similarly, a record containing an integer and a character:
11067 will have a size of 40 (that is @code{Rec'Size} will be 40). The
11068 alignment will be 4, because of the
11069 integer field, and so the default size of record objects for this type
11070 will be 64 (8 bytes).
11072 If the alignment of the above record is specified to be 1, then the
11073 object size will be 40 (5 bytes). This is true by default, and also
11074 an object size of 40 can be explicitly specified in this case.
11076 A consequence of this capability is that different object sizes can be
11077 given to subtypes that would otherwise be considered in Ada to be
11078 statically matching. But it makes no sense to consider such subtypes
11079 as statically matching. Consequently, GNAT adds a rule
11080 to the static matching rules that requires object sizes to match.
11081 Consider this example:
11084 1. procedure BadAVConvert is
11085 2. type R is new Integer;
11086 3. subtype R1 is R range 1 .. 10;
11087 4. subtype R2 is R range 1 .. 10;
11088 5. for R1'Object_Size use 8;
11089 6. for R2'Object_Size use 16;
11090 7. type R1P is access all R1;
11091 8. type R2P is access all R2;
11092 9. R1PV : R1P := new R1'(4);
11095 12. R2PV := R2P (R1PV);
11097 >>> target designated subtype not compatible with
11098 type "R1" defined at line 3
11103 In the absence of lines 5 and 6,
11104 types @code{R1} and @code{R2} statically match and
11105 hence the conversion on line 12 is legal. But since lines 5 and 6
11106 cause the object sizes to differ, GNAT considers that types
11107 @code{R1} and @code{R2} are not statically matching, and line 12
11108 generates the diagnostic shown above.
11110 Similar additional checks are performed in other contexts requiring
11111 statically matching subtypes.
11113 @node Attribute Old,Attribute Passed_By_Reference,Attribute Object_Size,Implementation Defined Attributes
11114 @anchor{gnat_rm/implementation_defined_attributes attribute-old}@anchor{196}
11115 @section Attribute Old
11120 In addition to the usage of @code{Old} defined in the Ada 2012 RM (usage
11121 within @code{Post} aspect), GNAT also permits the use of this attribute
11122 in implementation defined pragmas @code{Postcondition},
11123 @code{Contract_Cases} and @code{Test_Case}. Also usages of
11124 @code{Old} which would be illegal according to the Ada 2012 RM
11125 definition are allowed under control of
11126 implementation defined pragma @code{Unevaluated_Use_Of_Old}.
11128 @node Attribute Passed_By_Reference,Attribute Pool_Address,Attribute Old,Implementation Defined Attributes
11129 @anchor{gnat_rm/implementation_defined_attributes attribute-passed-by-reference}@anchor{197}
11130 @section Attribute Passed_By_Reference
11133 @geindex Parameters
11134 @geindex when passed by reference
11136 @geindex Passed_By_Reference
11138 @code{typ'Passed_By_Reference} for any subtype @cite{typ} returns
11139 a value of type @code{Boolean} value that is @code{True} if the type is
11140 normally passed by reference and @code{False} if the type is normally
11141 passed by copy in calls. For scalar types, the result is always @code{False}
11142 and is static. For non-scalar types, the result is nonstatic.
11144 @node Attribute Pool_Address,Attribute Range_Length,Attribute Passed_By_Reference,Implementation Defined Attributes
11145 @anchor{gnat_rm/implementation_defined_attributes attribute-pool-address}@anchor{198}
11146 @section Attribute Pool_Address
11149 @geindex Parameters
11150 @geindex when passed by reference
11152 @geindex Pool_Address
11154 @code{X'Pool_Address} for any object @code{X} returns the address
11155 of X within its storage pool. This is the same as
11156 @code{X'Address}, except that for an unconstrained array whose
11157 bounds are allocated just before the first component,
11158 @code{X'Pool_Address} returns the address of those bounds,
11159 whereas @code{X'Address} returns the address of the first
11162 Here, we are interpreting 'storage pool' broadly to mean
11163 @code{wherever the object is allocated}, which could be a
11164 user-defined storage pool,
11165 the global heap, on the stack, or in a static memory area.
11166 For an object created by @code{new}, @code{Ptr.all'Pool_Address} is
11167 what is passed to @code{Allocate} and returned from @code{Deallocate}.
11169 @node Attribute Range_Length,Attribute Restriction_Set,Attribute Pool_Address,Implementation Defined Attributes
11170 @anchor{gnat_rm/implementation_defined_attributes attribute-range-length}@anchor{199}
11171 @section Attribute Range_Length
11174 @geindex Range_Length
11176 @code{typ'Range_Length} for any discrete type @cite{typ} yields
11177 the number of values represented by the subtype (zero for a null
11178 range). The result is static for static subtypes. @code{Range_Length}
11179 applied to the index subtype of a one dimensional array always gives the
11180 same result as @code{Length} applied to the array itself.
11182 @node Attribute Restriction_Set,Attribute Result,Attribute Range_Length,Implementation Defined Attributes
11183 @anchor{gnat_rm/implementation_defined_attributes attribute-restriction-set}@anchor{19a}
11184 @section Attribute Restriction_Set
11187 @geindex Restriction_Set
11189 @geindex Restrictions
11191 This attribute allows compile time testing of restrictions that
11192 are currently in effect. It is primarily intended for specializing
11193 code in the run-time based on restrictions that are active (e.g.
11194 don't need to save fpt registers if restriction No_Floating_Point
11195 is known to be in effect), but can be used anywhere.
11197 There are two forms:
11200 System'Restriction_Set (partition_boolean_restriction_NAME)
11201 System'Restriction_Set (No_Dependence => library_unit_NAME);
11204 In the case of the first form, the only restriction names
11205 allowed are parameterless restrictions that are checked
11206 for consistency at bind time. For a complete list see the
11207 subtype @code{System.Rident.Partition_Boolean_Restrictions}.
11209 The result returned is True if the restriction is known to
11210 be in effect, and False if the restriction is known not to
11211 be in effect. An important guarantee is that the value of
11212 a Restriction_Set attribute is known to be consistent throughout
11213 all the code of a partition.
11215 This is trivially achieved if the entire partition is compiled
11216 with a consistent set of restriction pragmas. However, the
11217 compilation model does not require this. It is possible to
11218 compile one set of units with one set of pragmas, and another
11219 set of units with another set of pragmas. It is even possible
11220 to compile a spec with one set of pragmas, and then WITH the
11221 same spec with a different set of pragmas. Inconsistencies
11222 in the actual use of the restriction are checked at bind time.
11224 In order to achieve the guarantee of consistency for the
11225 Restriction_Set pragma, we consider that a use of the pragma
11226 that yields False is equivalent to a violation of the
11229 So for example if you write
11232 if System'Restriction_Set (No_Floating_Point) then
11239 And the result is False, so that the else branch is executed,
11240 you can assume that this restriction is not set for any unit
11241 in the partition. This is checked by considering this use of
11242 the restriction pragma to be a violation of the restriction
11243 No_Floating_Point. This means that no other unit can attempt
11244 to set this restriction (if some unit does attempt to set it,
11245 the binder will refuse to bind the partition).
11247 Technical note: The restriction name and the unit name are
11248 intepreted entirely syntactically, as in the corresponding
11249 Restrictions pragma, they are not analyzed semantically,
11250 so they do not have a type.
11252 @node Attribute Result,Attribute Safe_Emax,Attribute Restriction_Set,Implementation Defined Attributes
11253 @anchor{gnat_rm/implementation_defined_attributes attribute-result}@anchor{19b}
11254 @section Attribute Result
11259 @code{function'Result} can only be used with in a Postcondition pragma
11260 for a function. The prefix must be the name of the corresponding function. This
11261 is used to refer to the result of the function in the postcondition expression.
11262 For a further discussion of the use of this attribute and examples of its use,
11263 see the description of pragma Postcondition.
11265 @node Attribute Safe_Emax,Attribute Safe_Large,Attribute Result,Implementation Defined Attributes
11266 @anchor{gnat_rm/implementation_defined_attributes attribute-safe-emax}@anchor{19c}
11267 @section Attribute Safe_Emax
11270 @geindex Ada 83 attributes
11274 The @code{Safe_Emax} attribute is provided for compatibility with Ada 83. See
11275 the Ada 83 reference manual for an exact description of the semantics of
11278 @node Attribute Safe_Large,Attribute Safe_Small,Attribute Safe_Emax,Implementation Defined Attributes
11279 @anchor{gnat_rm/implementation_defined_attributes attribute-safe-large}@anchor{19d}
11280 @section Attribute Safe_Large
11283 @geindex Ada 83 attributes
11285 @geindex Safe_Large
11287 The @code{Safe_Large} attribute is provided for compatibility with Ada 83. See
11288 the Ada 83 reference manual for an exact description of the semantics of
11291 @node Attribute Safe_Small,Attribute Scalar_Storage_Order,Attribute Safe_Large,Implementation Defined Attributes
11292 @anchor{gnat_rm/implementation_defined_attributes attribute-safe-small}@anchor{19e}
11293 @section Attribute Safe_Small
11296 @geindex Ada 83 attributes
11298 @geindex Safe_Small
11300 The @code{Safe_Small} attribute is provided for compatibility with Ada 83. See
11301 the Ada 83 reference manual for an exact description of the semantics of
11304 @node Attribute Scalar_Storage_Order,Attribute Simple_Storage_Pool,Attribute Safe_Small,Implementation Defined Attributes
11305 @anchor{gnat_rm/implementation_defined_attributes id4}@anchor{19f}@anchor{gnat_rm/implementation_defined_attributes attribute-scalar-storage-order}@anchor{154}
11306 @section Attribute Scalar_Storage_Order
11309 @geindex Endianness
11311 @geindex Scalar storage order
11313 @geindex Scalar_Storage_Order
11315 For every array or record type @code{S}, the representation attribute
11316 @code{Scalar_Storage_Order} denotes the order in which storage elements
11317 that make up scalar components are ordered within S. The value given must
11318 be a static expression of type System.Bit_Order. The following is an example
11319 of the use of this feature:
11322 -- Component type definitions
11324 subtype Yr_Type is Natural range 0 .. 127;
11325 subtype Mo_Type is Natural range 1 .. 12;
11326 subtype Da_Type is Natural range 1 .. 31;
11328 -- Record declaration
11330 type Date is record
11331 Years_Since_1980 : Yr_Type;
11333 Day_Of_Month : Da_Type;
11336 -- Record representation clause
11338 for Date use record
11339 Years_Since_1980 at 0 range 0 .. 6;
11340 Month at 0 range 7 .. 10;
11341 Day_Of_Month at 0 range 11 .. 15;
11344 -- Attribute definition clauses
11346 for Date'Bit_Order use System.High_Order_First;
11347 for Date'Scalar_Storage_Order use System.High_Order_First;
11348 -- If Scalar_Storage_Order is specified, it must be consistent with
11349 -- Bit_Order, so it's best to always define the latter explicitly if
11350 -- the former is used.
11353 Other properties are as for the standard representation attribute @code{Bit_Order}
11354 defined by Ada RM 13.5.3(4). The default is @code{System.Default_Bit_Order}.
11356 For a record type @code{T}, if @code{T'Scalar_Storage_Order} is
11357 specified explicitly, it shall be equal to @code{T'Bit_Order}. Note:
11358 this means that if a @code{Scalar_Storage_Order} attribute definition
11359 clause is not confirming, then the type's @code{Bit_Order} shall be
11360 specified explicitly and set to the same value.
11362 Derived types inherit an explicitly set scalar storage order from their parent
11363 types. This may be overridden for the derived type by giving an explicit scalar
11364 storage order for it. However, for a record extension, the derived type must
11365 have the same scalar storage order as the parent type.
11367 A component of a record type that is itself a record or an array and that does
11368 not start and end on a byte boundary must have have the same scalar storage
11369 order as the record type. A component of a bit-packed array type that is itself
11370 a record or an array must have the same scalar storage order as the array type.
11372 No component of a type that has an explicit @code{Scalar_Storage_Order}
11373 attribute definition may be aliased.
11375 A confirming @code{Scalar_Storage_Order} attribute definition clause (i.e.
11376 with a value equal to @code{System.Default_Bit_Order}) has no effect.
11378 If the opposite storage order is specified, then whenever the value of
11379 a scalar component of an object of type @code{S} is read, the storage
11380 elements of the enclosing machine scalar are first reversed (before
11381 retrieving the component value, possibly applying some shift and mask
11382 operatings on the enclosing machine scalar), and the opposite operation
11383 is done for writes.
11385 In that case, the restrictions set forth in 13.5.1(10.3/2) for scalar components
11386 are relaxed. Instead, the following rules apply:
11392 the underlying storage elements are those at positions
11393 @code{(position + first_bit / storage_element_size) .. (position + (last_bit + storage_element_size - 1) / storage_element_size)}
11396 the sequence of underlying storage elements shall have
11397 a size no greater than the largest machine scalar
11400 the enclosing machine scalar is defined as the smallest machine
11401 scalar starting at a position no greater than
11402 @code{position + first_bit / storage_element_size} and covering
11403 storage elements at least up to @code{position + (last_bit + storage_element_size - 1) / storage_element_size`}
11406 the position of the component is interpreted relative to that machine
11410 If no scalar storage order is specified for a type (either directly, or by
11411 inheritance in the case of a derived type), then the default is normally
11412 the native ordering of the target, but this default can be overridden using
11413 pragma @code{Default_Scalar_Storage_Order}.
11415 If a component of @code{T} is itself of a record or array type, the specfied
11416 @code{Scalar_Storage_Order} does @emph{not} apply to that nested type: an explicit
11417 attribute definition clause must be provided for the component type as well
11420 Note that the scalar storage order only affects the in-memory data
11421 representation. It has no effect on the representation used by stream
11424 Note that debuggers may be unable to display the correct value of scalar
11425 components of a type for which the opposite storage order is specified.
11427 @node Attribute Simple_Storage_Pool,Attribute Small,Attribute Scalar_Storage_Order,Implementation Defined Attributes
11428 @anchor{gnat_rm/implementation_defined_attributes attribute-simple-storage-pool}@anchor{e9}@anchor{gnat_rm/implementation_defined_attributes id5}@anchor{1a0}
11429 @section Attribute Simple_Storage_Pool
11432 @geindex Storage pool
11435 @geindex Simple storage pool
11437 @geindex Simple_Storage_Pool
11439 For every nonformal, nonderived access-to-object type @code{Acc}, the
11440 representation attribute @code{Simple_Storage_Pool} may be specified
11441 via an attribute_definition_clause (or by specifying the equivalent aspect):
11444 My_Pool : My_Simple_Storage_Pool_Type;
11446 type Acc is access My_Data_Type;
11448 for Acc'Simple_Storage_Pool use My_Pool;
11451 The name given in an attribute_definition_clause for the
11452 @code{Simple_Storage_Pool} attribute shall denote a variable of
11453 a 'simple storage pool type' (see pragma @cite{Simple_Storage_Pool_Type}).
11455 The use of this attribute is only allowed for a prefix denoting a type
11456 for which it has been specified. The type of the attribute is the type
11457 of the variable specified as the simple storage pool of the access type,
11458 and the attribute denotes that variable.
11460 It is illegal to specify both @code{Storage_Pool} and @code{Simple_Storage_Pool}
11461 for the same access type.
11463 If the @code{Simple_Storage_Pool} attribute has been specified for an access
11464 type, then applying the @code{Storage_Pool} attribute to the type is flagged
11465 with a warning and its evaluation raises the exception @code{Program_Error}.
11467 If the Simple_Storage_Pool attribute has been specified for an access
11468 type @code{S}, then the evaluation of the attribute @code{S'Storage_Size}
11469 returns the result of calling @code{Storage_Size (S'Simple_Storage_Pool)},
11470 which is intended to indicate the number of storage elements reserved for
11471 the simple storage pool. If the Storage_Size function has not been defined
11472 for the simple storage pool type, then this attribute returns zero.
11474 If an access type @code{S} has a specified simple storage pool of type
11475 @code{SSP}, then the evaluation of an allocator for that access type calls
11476 the primitive @code{Allocate} procedure for type @code{SSP}, passing
11477 @code{S'Simple_Storage_Pool} as the pool parameter. The detailed
11478 semantics of such allocators is the same as those defined for allocators
11479 in section 13.11 of the @cite{Ada Reference Manual}, with the term
11480 @emph{simple storage pool} substituted for @emph{storage pool}.
11482 If an access type @code{S} has a specified simple storage pool of type
11483 @code{SSP}, then a call to an instance of the @code{Ada.Unchecked_Deallocation}
11484 for that access type invokes the primitive @code{Deallocate} procedure
11485 for type @code{SSP}, passing @code{S'Simple_Storage_Pool} as the pool
11486 parameter. The detailed semantics of such unchecked deallocations is the same
11487 as defined in section 13.11.2 of the Ada Reference Manual, except that the
11488 term @emph{simple storage pool} is substituted for @emph{storage pool}.
11490 @node Attribute Small,Attribute Storage_Unit,Attribute Simple_Storage_Pool,Implementation Defined Attributes
11491 @anchor{gnat_rm/implementation_defined_attributes attribute-small}@anchor{1a1}
11492 @section Attribute Small
11495 @geindex Ada 83 attributes
11499 The @code{Small} attribute is defined in Ada 95 (and Ada 2005) only for
11501 GNAT also allows this attribute to be applied to floating-point types
11502 for compatibility with Ada 83. See
11503 the Ada 83 reference manual for an exact description of the semantics of
11504 this attribute when applied to floating-point types.
11506 @node Attribute Storage_Unit,Attribute Stub_Type,Attribute Small,Implementation Defined Attributes
11507 @anchor{gnat_rm/implementation_defined_attributes attribute-storage-unit}@anchor{1a2}
11508 @section Attribute Storage_Unit
11511 @geindex Storage_Unit
11513 @code{Standard'Storage_Unit} (@code{Standard} is the only permissible
11514 prefix) provides the same value as @code{System.Storage_Unit}.
11516 @node Attribute Stub_Type,Attribute System_Allocator_Alignment,Attribute Storage_Unit,Implementation Defined Attributes
11517 @anchor{gnat_rm/implementation_defined_attributes attribute-stub-type}@anchor{1a3}
11518 @section Attribute Stub_Type
11523 The GNAT implementation of remote access-to-classwide types is
11524 organized as described in AARM section E.4 (20.t): a value of an RACW type
11525 (designating a remote object) is represented as a normal access
11526 value, pointing to a "stub" object which in turn contains the
11527 necessary information to contact the designated remote object. A
11528 call on any dispatching operation of such a stub object does the
11529 remote call, if necessary, using the information in the stub object
11530 to locate the target partition, etc.
11532 For a prefix @code{T} that denotes a remote access-to-classwide type,
11533 @code{T'Stub_Type} denotes the type of the corresponding stub objects.
11535 By construction, the layout of @code{T'Stub_Type} is identical to that of
11536 type @code{RACW_Stub_Type} declared in the internal implementation-defined
11537 unit @code{System.Partition_Interface}. Use of this attribute will create
11538 an implicit dependency on this unit.
11540 @node Attribute System_Allocator_Alignment,Attribute Target_Name,Attribute Stub_Type,Implementation Defined Attributes
11541 @anchor{gnat_rm/implementation_defined_attributes attribute-system-allocator-alignment}@anchor{1a4}
11542 @section Attribute System_Allocator_Alignment
11548 @geindex System_Allocator_Alignment
11550 @code{Standard'System_Allocator_Alignment} (@code{Standard} is the only
11551 permissible prefix) provides the observable guaranted to be honored by
11552 the system allocator (malloc). This is a static value that can be used
11553 in user storage pools based on malloc either to reject allocation
11554 with alignment too large or to enable a realignment circuitry if the
11555 alignment request is larger than this value.
11557 @node Attribute Target_Name,Attribute To_Address,Attribute System_Allocator_Alignment,Implementation Defined Attributes
11558 @anchor{gnat_rm/implementation_defined_attributes attribute-target-name}@anchor{1a5}
11559 @section Attribute Target_Name
11562 @geindex Target_Name
11564 @code{Standard'Target_Name} (@code{Standard} is the only permissible
11565 prefix) provides a static string value that identifies the target
11566 for the current compilation. For GCC implementations, this is the
11567 standard gcc target name without the terminating slash (for
11568 example, GNAT 5.0 on windows yields "i586-pc-mingw32msv").
11570 @node Attribute To_Address,Attribute To_Any,Attribute Target_Name,Implementation Defined Attributes
11571 @anchor{gnat_rm/implementation_defined_attributes attribute-to-address}@anchor{1a6}
11572 @section Attribute To_Address
11575 @geindex To_Address
11577 The @code{System'To_Address}
11578 (@code{System} is the only permissible prefix)
11579 denotes a function identical to
11580 @code{System.Storage_Elements.To_Address} except that
11581 it is a static attribute. This means that if its argument is
11582 a static expression, then the result of the attribute is a
11583 static expression. This means that such an expression can be
11584 used in contexts (e.g., preelaborable packages) which require a
11585 static expression and where the function call could not be used
11586 (since the function call is always nonstatic, even if its
11587 argument is static). The argument must be in the range
11588 -(2**(m-1)) .. 2**m-1, where m is the memory size
11589 (typically 32 or 64). Negative values are intepreted in a
11590 modular manner (e.g., -1 means the same as 16#FFFF_FFFF# on
11591 a 32 bits machine).
11593 @node Attribute To_Any,Attribute Type_Class,Attribute To_Address,Implementation Defined Attributes
11594 @anchor{gnat_rm/implementation_defined_attributes attribute-to-any}@anchor{1a7}
11595 @section Attribute To_Any
11600 This internal attribute is used for the generation of remote subprogram
11601 stubs in the context of the Distributed Systems Annex.
11603 @node Attribute Type_Class,Attribute Type_Key,Attribute To_Any,Implementation Defined Attributes
11604 @anchor{gnat_rm/implementation_defined_attributes attribute-type-class}@anchor{1a8}
11605 @section Attribute Type_Class
11608 @geindex Type_Class
11610 @code{typ'Type_Class} for any type or subtype @cite{typ} yields
11611 the value of the type class for the full type of @cite{typ}. If
11612 @cite{typ} is a generic formal type, the value is the value for the
11613 corresponding actual subtype. The value of this attribute is of type
11614 @code{System.Aux_DEC.Type_Class}, which has the following definition:
11618 (Type_Class_Enumeration,
11619 Type_Class_Integer,
11620 Type_Class_Fixed_Point,
11621 Type_Class_Floating_Point,
11626 Type_Class_Address);
11629 Protected types yield the value @code{Type_Class_Task}, which thus
11630 applies to all concurrent types. This attribute is designed to
11631 be compatible with the DEC Ada 83 attribute of the same name.
11633 @node Attribute Type_Key,Attribute TypeCode,Attribute Type_Class,Implementation Defined Attributes
11634 @anchor{gnat_rm/implementation_defined_attributes attribute-type-key}@anchor{1a9}
11635 @section Attribute Type_Key
11640 The @code{Type_Key} attribute is applicable to a type or subtype and
11641 yields a value of type Standard.String containing encoded information
11642 about the type or subtype. This provides improved compatibility with
11643 other implementations that support this attribute.
11645 @node Attribute TypeCode,Attribute Unconstrained_Array,Attribute Type_Key,Implementation Defined Attributes
11646 @anchor{gnat_rm/implementation_defined_attributes attribute-typecode}@anchor{1aa}
11647 @section Attribute TypeCode
11652 This internal attribute is used for the generation of remote subprogram
11653 stubs in the context of the Distributed Systems Annex.
11655 @node Attribute Unconstrained_Array,Attribute Universal_Literal_String,Attribute TypeCode,Implementation Defined Attributes
11656 @anchor{gnat_rm/implementation_defined_attributes attribute-unconstrained-array}@anchor{1ab}
11657 @section Attribute Unconstrained_Array
11660 @geindex Unconstrained_Array
11662 The @code{Unconstrained_Array} attribute can be used with a prefix that
11663 denotes any type or subtype. It is a static attribute that yields
11664 @code{True} if the prefix designates an unconstrained array,
11665 and @code{False} otherwise. In a generic instance, the result is
11666 still static, and yields the result of applying this test to the
11669 @node Attribute Universal_Literal_String,Attribute Unrestricted_Access,Attribute Unconstrained_Array,Implementation Defined Attributes
11670 @anchor{gnat_rm/implementation_defined_attributes attribute-universal-literal-string}@anchor{1ac}
11671 @section Attribute Universal_Literal_String
11674 @geindex Named numbers
11675 @geindex representation of
11677 @geindex Universal_Literal_String
11679 The prefix of @code{Universal_Literal_String} must be a named
11680 number. The static result is the string consisting of the characters of
11681 the number as defined in the original source. This allows the user
11682 program to access the actual text of named numbers without intermediate
11683 conversions and without the need to enclose the strings in quotes (which
11684 would preclude their use as numbers).
11686 For example, the following program prints the first 50 digits of pi:
11689 with Text_IO; use Text_IO;
11693 Put (Ada.Numerics.Pi'Universal_Literal_String);
11697 @node Attribute Unrestricted_Access,Attribute Update,Attribute Universal_Literal_String,Implementation Defined Attributes
11698 @anchor{gnat_rm/implementation_defined_attributes attribute-unrestricted-access}@anchor{1ad}
11699 @section Attribute Unrestricted_Access
11703 @geindex unrestricted
11705 @geindex Unrestricted_Access
11707 The @code{Unrestricted_Access} attribute is similar to @code{Access}
11708 except that all accessibility and aliased view checks are omitted. This
11709 is a user-beware attribute.
11711 For objects, it is similar to @code{Address}, for which it is a
11712 desirable replacement where the value desired is an access type.
11713 In other words, its effect is similar to first applying the
11714 @code{Address} attribute and then doing an unchecked conversion to a
11715 desired access type.
11717 For subprograms, @code{P'Unrestricted_Access} may be used where
11718 @code{P'Access} would be illegal, to construct a value of a
11719 less-nested named access type that designates a more-nested
11720 subprogram. This value may be used in indirect calls, so long as the
11721 more-nested subprogram still exists; once the subprogram containing it
11722 has returned, such calls are erroneous. For example:
11727 type Less_Nested is not null access procedure;
11728 Global : Less_Nested;
11736 Local_Var : Integer;
11738 procedure More_Nested is
11743 Global := More_Nested'Unrestricted_Access;
11750 When P1 is called from P2, the call via Global is OK, but if P1 were
11751 called after P2 returns, it would be an erroneous use of a dangling
11754 For objects, it is possible to use @code{Unrestricted_Access} for any
11755 type. However, if the result is of an access-to-unconstrained array
11756 subtype, then the resulting pointer has the same scope as the context
11757 of the attribute, and must not be returned to some enclosing scope.
11758 For instance, if a function uses @code{Unrestricted_Access} to create
11759 an access-to-unconstrained-array and returns that value to the caller,
11760 the result will involve dangling pointers. In addition, it is only
11761 valid to create pointers to unconstrained arrays using this attribute
11762 if the pointer has the normal default 'fat' representation where a
11763 pointer has two components, one points to the array and one points to
11764 the bounds. If a size clause is used to force 'thin' representation
11765 for a pointer to unconstrained where there is only space for a single
11766 pointer, then the resulting pointer is not usable.
11768 In the simple case where a direct use of Unrestricted_Access attempts
11769 to make a thin pointer for a non-aliased object, the compiler will
11770 reject the use as illegal, as shown in the following example:
11773 with System; use System;
11774 procedure SliceUA2 is
11775 type A is access all String;
11776 for A'Size use Standard'Address_Size;
11778 procedure P (Arg : A) is
11783 X : String := "hello world!";
11784 X2 : aliased String := "hello world!";
11786 AV : A := X'Unrestricted_Access; -- ERROR
11788 >>> illegal use of Unrestricted_Access attribute
11789 >>> attempt to generate thin pointer to unaliased object
11792 P (X'Unrestricted_Access); -- ERROR
11794 >>> illegal use of Unrestricted_Access attribute
11795 >>> attempt to generate thin pointer to unaliased object
11797 P (X(7 .. 12)'Unrestricted_Access); -- ERROR
11799 >>> illegal use of Unrestricted_Access attribute
11800 >>> attempt to generate thin pointer to unaliased object
11802 P (X2'Unrestricted_Access); -- OK
11806 but other cases cannot be detected by the compiler, and are
11807 considered to be erroneous. Consider the following example:
11810 with System; use System;
11811 with System; use System;
11812 procedure SliceUA is
11813 type AF is access all String;
11815 type A is access all String;
11816 for A'Size use Standard'Address_Size;
11818 procedure P (Arg : A) is
11820 if Arg'Length /= 6 then
11821 raise Program_Error;
11825 X : String := "hello world!";
11826 Y : AF := X (7 .. 12)'Unrestricted_Access;
11833 A normal unconstrained array value
11834 or a constrained array object marked as aliased has the bounds in memory
11835 just before the array, so a thin pointer can retrieve both the data and
11836 the bounds. But in this case, the non-aliased object @code{X} does not have the
11837 bounds before the string. If the size clause for type @code{A}
11838 were not present, then the pointer
11839 would be a fat pointer, where one component is a pointer to the bounds,
11840 and all would be well. But with the size clause present, the conversion from
11841 fat pointer to thin pointer in the call loses the bounds, and so this
11842 is erroneous, and the program likely raises a @code{Program_Error} exception.
11844 In general, it is advisable to completely
11845 avoid mixing the use of thin pointers and the use of
11846 @code{Unrestricted_Access} where the designated type is an
11847 unconstrained array. The use of thin pointers should be restricted to
11848 cases of porting legacy code that implicitly assumes the size of pointers,
11849 and such code should not in any case be using this attribute.
11851 Another erroneous situation arises if the attribute is
11852 applied to a constant. The resulting pointer can be used to access the
11853 constant, but the effect of trying to modify a constant in this manner
11854 is not well-defined. Consider this example:
11857 P : constant Integer := 4;
11858 type R is access all Integer;
11859 RV : R := P'Unrestricted_Access;
11864 Here we attempt to modify the constant P from 4 to 3, but the compiler may
11865 or may not notice this attempt, and subsequent references to P may yield
11866 either the value 3 or the value 4 or the assignment may blow up if the
11867 compiler decides to put P in read-only memory. One particular case where
11868 @code{Unrestricted_Access} can be used in this way is to modify the
11869 value of an @code{in} parameter:
11872 procedure K (S : in String) is
11873 type R is access all Character;
11874 RV : R := S (3)'Unrestricted_Access;
11880 In general this is a risky approach. It may appear to "work" but such uses of
11881 @code{Unrestricted_Access} are potentially non-portable, even from one version
11882 of GNAT to another, so are best avoided if possible.
11884 @node Attribute Update,Attribute Valid_Scalars,Attribute Unrestricted_Access,Implementation Defined Attributes
11885 @anchor{gnat_rm/implementation_defined_attributes attribute-update}@anchor{1ae}
11886 @section Attribute Update
11891 The @code{Update} attribute creates a copy of an array or record value
11892 with one or more modified components. The syntax is:
11895 PREFIX'Update ( RECORD_COMPONENT_ASSOCIATION_LIST )
11896 PREFIX'Update ( ARRAY_COMPONENT_ASSOCIATION @{, ARRAY_COMPONENT_ASSOCIATION @} )
11897 PREFIX'Update ( MULTIDIMENSIONAL_ARRAY_COMPONENT_ASSOCIATION
11898 @{, MULTIDIMENSIONAL_ARRAY_COMPONENT_ASSOCIATION @} )
11900 MULTIDIMENSIONAL_ARRAY_COMPONENT_ASSOCIATION ::= INDEX_EXPRESSION_LIST_LIST => EXPRESSION
11901 INDEX_EXPRESSION_LIST_LIST ::= INDEX_EXPRESSION_LIST @{| INDEX_EXPRESSION_LIST @}
11902 INDEX_EXPRESSION_LIST ::= ( EXPRESSION @{, EXPRESSION @} )
11905 where @code{PREFIX} is the name of an array or record object, the
11906 association list in parentheses does not contain an @code{others}
11907 choice and the box symbol @code{<>} may not appear in any
11908 expression. The effect is to yield a copy of the array or record value
11909 which is unchanged apart from the components mentioned in the
11910 association list, which are changed to the indicated value. The
11911 original value of the array or record value is not affected. For
11915 type Arr is Array (1 .. 5) of Integer;
11917 Avar1 : Arr := (1,2,3,4,5);
11918 Avar2 : Arr := Avar1'Update (2 => 10, 3 .. 4 => 20);
11921 yields a value for @code{Avar2} of 1,10,20,20,5 with @code{Avar1}
11922 begin unmodified. Similarly:
11925 type Rec is A, B, C : Integer;
11927 Rvar1 : Rec := (A => 1, B => 2, C => 3);
11928 Rvar2 : Rec := Rvar1'Update (B => 20);
11931 yields a value for @code{Rvar2} of (A => 1, B => 20, C => 3),
11932 with @code{Rvar1} being unmodifed.
11933 Note that the value of the attribute reference is computed
11934 completely before it is used. This means that if you write:
11937 Avar1 := Avar1'Update (1 => 10, 2 => Function_Call);
11940 then the value of @code{Avar1} is not modified if @code{Function_Call}
11941 raises an exception, unlike the effect of a series of direct assignments
11942 to elements of @code{Avar1}. In general this requires that
11943 two extra complete copies of the object are required, which should be
11944 kept in mind when considering efficiency.
11946 The @code{Update} attribute cannot be applied to prefixes of a limited
11947 type, and cannot reference discriminants in the case of a record type.
11948 The accessibility level of an Update attribute result object is defined
11949 as for an aggregate.
11951 In the record case, no component can be mentioned more than once. In
11952 the array case, two overlapping ranges can appear in the association list,
11953 in which case the modifications are processed left to right.
11955 Multi-dimensional arrays can be modified, as shown by this example:
11958 A : array (1 .. 10, 1 .. 10) of Integer;
11960 A := A'Update ((1, 2) => 20, (3, 4) => 30);
11963 which changes element (1,2) to 20 and (3,4) to 30.
11965 @node Attribute Valid_Scalars,Attribute VADS_Size,Attribute Update,Implementation Defined Attributes
11966 @anchor{gnat_rm/implementation_defined_attributes attribute-valid-scalars}@anchor{1af}
11967 @section Attribute Valid_Scalars
11970 @geindex Valid_Scalars
11972 The @code{'Valid_Scalars} attribute is intended to make it easier to check the
11973 validity of scalar subcomponents of composite objects. The attribute is defined
11974 for any prefix @code{P} which denotes an object. Prefix @code{P} can be any type
11975 except for tagged private or @code{Unchecked_Union} types. The value of the
11976 attribute is of type @code{Boolean}.
11978 @code{P'Valid_Scalars} yields @code{True} if and only if the evaluation of
11979 @code{C'Valid} yields @code{True} for every scalar subcomponent @code{C} of @code{P}, or if
11980 @code{P} has no scalar subcomponents. Attribute @code{'Valid_Scalars} is equivalent
11981 to attribute @code{'Valid} for scalar types.
11983 It is not specified in what order the subcomponents are checked, nor whether
11984 any more are checked after any one of them is determined to be invalid. If the
11985 prefix @code{P} is of a class-wide type @code{T'Class} (where @code{T} is the associated
11986 specific type), or if the prefix @code{P} is of a specific tagged type @code{T}, then
11987 only the subcomponents of @code{T} are checked; in other words, components of
11988 extensions of @code{T} are not checked even if @code{T'Class (P)'Tag /= T'Tag}.
11990 The compiler will issue a warning if it can be determined at compile time that
11991 the prefix of the attribute has no scalar subcomponents.
11993 Note: @code{Valid_Scalars} can generate a lot of code, especially in the case of
11994 a large variant record. If the attribute is called in many places in the same
11995 program applied to objects of the same type, it can reduce program size to
11996 write a function with a single use of the attribute, and then call that
11997 function from multiple places.
11999 @node Attribute VADS_Size,Attribute Value_Size,Attribute Valid_Scalars,Implementation Defined Attributes
12000 @anchor{gnat_rm/implementation_defined_attributes attribute-vads-size}@anchor{1b0}
12001 @section Attribute VADS_Size
12005 @geindex VADS compatibility
12009 The @code{'VADS_Size} attribute is intended to make it easier to port
12010 legacy code which relies on the semantics of @code{'Size} as implemented
12011 by the VADS Ada 83 compiler. GNAT makes a best effort at duplicating the
12012 same semantic interpretation. In particular, @code{'VADS_Size} applied
12013 to a predefined or other primitive type with no Size clause yields the
12014 Object_Size (for example, @code{Natural'Size} is 32 rather than 31 on
12015 typical machines). In addition @code{'VADS_Size} applied to an object
12016 gives the result that would be obtained by applying the attribute to
12017 the corresponding type.
12019 @node Attribute Value_Size,Attribute Wchar_T_Size,Attribute VADS_Size,Implementation Defined Attributes
12020 @anchor{gnat_rm/implementation_defined_attributes id6}@anchor{1b1}@anchor{gnat_rm/implementation_defined_attributes attribute-value-size}@anchor{163}
12021 @section Attribute Value_Size
12025 @geindex setting for not-first subtype
12027 @geindex Value_Size
12029 @code{type'Value_Size} is the number of bits required to represent
12030 a value of the given subtype. It is the same as @code{type'Size},
12031 but, unlike @code{Size}, may be set for non-first subtypes.
12033 @node Attribute Wchar_T_Size,Attribute Word_Size,Attribute Value_Size,Implementation Defined Attributes
12034 @anchor{gnat_rm/implementation_defined_attributes attribute-wchar-t-size}@anchor{1b2}
12035 @section Attribute Wchar_T_Size
12038 @geindex Wchar_T_Size
12040 @code{Standard'Wchar_T_Size} (@code{Standard} is the only permissible
12041 prefix) provides the size in bits of the C @code{wchar_t} type
12042 primarily for constructing the definition of this type in
12043 package @code{Interfaces.C}. The result is a static constant.
12045 @node Attribute Word_Size,,Attribute Wchar_T_Size,Implementation Defined Attributes
12046 @anchor{gnat_rm/implementation_defined_attributes attribute-word-size}@anchor{1b3}
12047 @section Attribute Word_Size
12052 @code{Standard'Word_Size} (@code{Standard} is the only permissible
12053 prefix) provides the value @code{System.Word_Size}. The result is
12056 @node Standard and Implementation Defined Restrictions,Implementation Advice,Implementation Defined Attributes,Top
12057 @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}
12058 @chapter Standard and Implementation Defined Restrictions
12061 All Ada Reference Manual-defined Restriction identifiers are implemented:
12067 language-defined restrictions (see 13.12.1)
12070 tasking restrictions (see D.7)
12073 high integrity restrictions (see H.4)
12076 GNAT implements additional restriction identifiers. All restrictions, whether
12077 language defined or GNAT-specific, are listed in the following.
12080 * Partition-Wide Restrictions::
12081 * Program Unit Level Restrictions::
12085 @node Partition-Wide Restrictions,Program Unit Level Restrictions,,Standard and Implementation Defined Restrictions
12086 @anchor{gnat_rm/standard_and_implementation_defined_restrictions partition-wide-restrictions}@anchor{1b6}@anchor{gnat_rm/standard_and_implementation_defined_restrictions id2}@anchor{1b7}
12087 @section Partition-Wide Restrictions
12090 There are two separate lists of restriction identifiers. The first
12091 set requires consistency throughout a partition (in other words, if the
12092 restriction identifier is used for any compilation unit in the partition,
12093 then all compilation units in the partition must obey the restriction).
12096 * Immediate_Reclamation::
12097 * Max_Asynchronous_Select_Nesting::
12098 * Max_Entry_Queue_Length::
12099 * Max_Protected_Entries::
12100 * Max_Select_Alternatives::
12101 * Max_Storage_At_Blocking::
12102 * Max_Task_Entries::
12104 * No_Abort_Statements::
12105 * No_Access_Parameter_Allocators::
12106 * No_Access_Subprograms::
12108 * No_Anonymous_Allocators::
12109 * No_Asynchronous_Control::
12111 * No_Coextensions::
12112 * No_Default_Initialization::
12115 * No_Direct_Boolean_Operators::
12117 * No_Dispatching_Calls::
12118 * No_Dynamic_Attachment::
12119 * No_Dynamic_Priorities::
12120 * No_Entry_Calls_In_Elaboration_Code::
12121 * No_Enumeration_Maps::
12122 * No_Exception_Handlers::
12123 * No_Exception_Propagation::
12124 * No_Exception_Registration::
12126 * No_Finalization::
12128 * No_Floating_Point::
12129 * No_Implicit_Conditionals::
12130 * No_Implicit_Dynamic_Code::
12131 * No_Implicit_Heap_Allocations::
12132 * No_Implicit_Protected_Object_Allocations::
12133 * No_Implicit_Task_Allocations::
12134 * No_Initialize_Scalars::
12136 * No_Local_Allocators::
12137 * No_Local_Protected_Objects::
12138 * No_Local_Timing_Events::
12139 * No_Long_Long_Integers::
12140 * No_Multiple_Elaboration::
12141 * No_Nested_Finalization::
12142 * No_Protected_Type_Allocators::
12143 * No_Protected_Types::
12146 * No_Relative_Delay::
12147 * No_Requeue_Statements::
12148 * No_Secondary_Stack::
12149 * No_Select_Statements::
12150 * No_Specific_Termination_Handlers::
12151 * No_Specification_of_Aspect::
12152 * No_Standard_Allocators_After_Elaboration::
12153 * No_Standard_Storage_Pools::
12154 * No_Stream_Optimizations::
12156 * No_Task_Allocators::
12157 * No_Task_At_Interrupt_Priority::
12158 * No_Task_Attributes_Package::
12159 * No_Task_Hierarchy::
12160 * No_Task_Termination::
12162 * No_Terminate_Alternatives::
12163 * No_Unchecked_Access::
12164 * No_Unchecked_Conversion::
12165 * No_Unchecked_Deallocation::
12166 * No_Use_Of_Entity::
12168 * Simple_Barriers::
12169 * Static_Priorities::
12170 * Static_Storage_Size::
12174 @node Immediate_Reclamation,Max_Asynchronous_Select_Nesting,,Partition-Wide Restrictions
12175 @anchor{gnat_rm/standard_and_implementation_defined_restrictions immediate-reclamation}@anchor{1b8}
12176 @subsection Immediate_Reclamation
12179 @geindex Immediate_Reclamation
12181 [RM H.4] This restriction ensures that, except for storage occupied by
12182 objects created by allocators and not deallocated via unchecked
12183 deallocation, any storage reserved at run time for an object is
12184 immediately reclaimed when the object no longer exists.
12186 @node Max_Asynchronous_Select_Nesting,Max_Entry_Queue_Length,Immediate_Reclamation,Partition-Wide Restrictions
12187 @anchor{gnat_rm/standard_and_implementation_defined_restrictions max-asynchronous-select-nesting}@anchor{1b9}
12188 @subsection Max_Asynchronous_Select_Nesting
12191 @geindex Max_Asynchronous_Select_Nesting
12193 [RM D.7] Specifies the maximum dynamic nesting level of asynchronous
12194 selects. Violations of this restriction with a value of zero are
12195 detected at compile time. Violations of this restriction with values
12196 other than zero cause Storage_Error to be raised.
12198 @node Max_Entry_Queue_Length,Max_Protected_Entries,Max_Asynchronous_Select_Nesting,Partition-Wide Restrictions
12199 @anchor{gnat_rm/standard_and_implementation_defined_restrictions max-entry-queue-length}@anchor{1ba}
12200 @subsection Max_Entry_Queue_Length
12203 @geindex Max_Entry_Queue_Length
12205 [RM D.7] This restriction is a declaration that any protected entry compiled in
12206 the scope of the restriction has at most the specified number of
12207 tasks waiting on the entry at any one time, and so no queue is required.
12208 Note that this restriction is checked at run time. Violation of this
12209 restriction results in the raising of Program_Error exception at the point of
12212 @geindex Max_Entry_Queue_Depth
12214 The restriction @code{Max_Entry_Queue_Depth} is recognized as a
12215 synonym for @code{Max_Entry_Queue_Length}. This is retained for historical
12216 compatibility purposes (and a warning will be generated for its use if
12217 warnings on obsolescent features are activated).
12219 @node Max_Protected_Entries,Max_Select_Alternatives,Max_Entry_Queue_Length,Partition-Wide Restrictions
12220 @anchor{gnat_rm/standard_and_implementation_defined_restrictions max-protected-entries}@anchor{1bb}
12221 @subsection Max_Protected_Entries
12224 @geindex Max_Protected_Entries
12226 [RM D.7] Specifies the maximum number of entries per protected type. The
12227 bounds of every entry family of a protected unit shall be static, or shall be
12228 defined by a discriminant of a subtype whose corresponding bound is static.
12230 @node Max_Select_Alternatives,Max_Storage_At_Blocking,Max_Protected_Entries,Partition-Wide Restrictions
12231 @anchor{gnat_rm/standard_and_implementation_defined_restrictions max-select-alternatives}@anchor{1bc}
12232 @subsection Max_Select_Alternatives
12235 @geindex Max_Select_Alternatives
12237 [RM D.7] Specifies the maximum number of alternatives in a selective accept.
12239 @node Max_Storage_At_Blocking,Max_Task_Entries,Max_Select_Alternatives,Partition-Wide Restrictions
12240 @anchor{gnat_rm/standard_and_implementation_defined_restrictions max-storage-at-blocking}@anchor{1bd}
12241 @subsection Max_Storage_At_Blocking
12244 @geindex Max_Storage_At_Blocking
12246 [RM D.7] Specifies the maximum portion (in storage elements) of a task's
12247 Storage_Size that can be retained by a blocked task. A violation of this
12248 restriction causes Storage_Error to be raised.
12250 @node Max_Task_Entries,Max_Tasks,Max_Storage_At_Blocking,Partition-Wide Restrictions
12251 @anchor{gnat_rm/standard_and_implementation_defined_restrictions max-task-entries}@anchor{1be}
12252 @subsection Max_Task_Entries
12255 @geindex Max_Task_Entries
12257 [RM D.7] Specifies the maximum number of entries
12258 per task. The bounds of every entry family
12259 of a task unit shall be static, or shall be
12260 defined by a discriminant of a subtype whose
12261 corresponding bound is static.
12263 @node Max_Tasks,No_Abort_Statements,Max_Task_Entries,Partition-Wide Restrictions
12264 @anchor{gnat_rm/standard_and_implementation_defined_restrictions max-tasks}@anchor{1bf}
12265 @subsection Max_Tasks
12270 [RM D.7] Specifies the maximum number of task that may be created, not
12271 counting the creation of the environment task. Violations of this
12272 restriction with a value of zero are detected at compile
12273 time. Violations of this restriction with values other than zero cause
12274 Storage_Error to be raised.
12276 @node No_Abort_Statements,No_Access_Parameter_Allocators,Max_Tasks,Partition-Wide Restrictions
12277 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-abort-statements}@anchor{1c0}
12278 @subsection No_Abort_Statements
12281 @geindex No_Abort_Statements
12283 [RM D.7] There are no abort_statements, and there are
12284 no calls to Task_Identification.Abort_Task.
12286 @node No_Access_Parameter_Allocators,No_Access_Subprograms,No_Abort_Statements,Partition-Wide Restrictions
12287 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-access-parameter-allocators}@anchor{1c1}
12288 @subsection No_Access_Parameter_Allocators
12291 @geindex No_Access_Parameter_Allocators
12293 [RM H.4] This restriction ensures at compile time that there are no
12294 occurrences of an allocator as the actual parameter to an access
12297 @node No_Access_Subprograms,No_Allocators,No_Access_Parameter_Allocators,Partition-Wide Restrictions
12298 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-access-subprograms}@anchor{1c2}
12299 @subsection No_Access_Subprograms
12302 @geindex No_Access_Subprograms
12304 [RM H.4] This restriction ensures at compile time that there are no
12305 declarations of access-to-subprogram types.
12307 @node No_Allocators,No_Anonymous_Allocators,No_Access_Subprograms,Partition-Wide Restrictions
12308 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-allocators}@anchor{1c3}
12309 @subsection No_Allocators
12312 @geindex No_Allocators
12314 [RM H.4] This restriction ensures at compile time that there are no
12315 occurrences of an allocator.
12317 @node No_Anonymous_Allocators,No_Asynchronous_Control,No_Allocators,Partition-Wide Restrictions
12318 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-anonymous-allocators}@anchor{1c4}
12319 @subsection No_Anonymous_Allocators
12322 @geindex No_Anonymous_Allocators
12324 [RM H.4] This restriction ensures at compile time that there are no
12325 occurrences of an allocator of anonymous access type.
12327 @node No_Asynchronous_Control,No_Calendar,No_Anonymous_Allocators,Partition-Wide Restrictions
12328 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-asynchronous-control}@anchor{1c5}
12329 @subsection No_Asynchronous_Control
12332 @geindex No_Asynchronous_Control
12334 [RM J.13] This restriction ensures at compile time that there are no semantic
12335 dependences on the predefined package Asynchronous_Task_Control.
12337 @node No_Calendar,No_Coextensions,No_Asynchronous_Control,Partition-Wide Restrictions
12338 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-calendar}@anchor{1c6}
12339 @subsection No_Calendar
12342 @geindex No_Calendar
12344 [GNAT] This restriction ensures at compile time that there are no semantic
12345 dependences on package Calendar.
12347 @node No_Coextensions,No_Default_Initialization,No_Calendar,Partition-Wide Restrictions
12348 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-coextensions}@anchor{1c7}
12349 @subsection No_Coextensions
12352 @geindex No_Coextensions
12354 [RM H.4] This restriction ensures at compile time that there are no
12355 coextensions. See 3.10.2.
12357 @node No_Default_Initialization,No_Delay,No_Coextensions,Partition-Wide Restrictions
12358 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-default-initialization}@anchor{1c8}
12359 @subsection No_Default_Initialization
12362 @geindex No_Default_Initialization
12364 [GNAT] This restriction prohibits any instance of default initialization
12365 of variables. The binder implements a consistency rule which prevents
12366 any unit compiled without the restriction from with'ing a unit with the
12367 restriction (this allows the generation of initialization procedures to
12368 be skipped, since you can be sure that no call is ever generated to an
12369 initialization procedure in a unit with the restriction active). If used
12370 in conjunction with Initialize_Scalars or Normalize_Scalars, the effect
12371 is to prohibit all cases of variables declared without a specific
12372 initializer (including the case of OUT scalar parameters).
12374 @node No_Delay,No_Dependence,No_Default_Initialization,Partition-Wide Restrictions
12375 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-delay}@anchor{1c9}
12376 @subsection No_Delay
12381 [RM H.4] This restriction ensures at compile time that there are no
12382 delay statements and no semantic dependences on package Calendar.
12384 @node No_Dependence,No_Direct_Boolean_Operators,No_Delay,Partition-Wide Restrictions
12385 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-dependence}@anchor{1ca}
12386 @subsection No_Dependence
12389 @geindex No_Dependence
12391 [RM 13.12.1] This restriction ensures at compile time that there are no
12392 dependences on a library unit.
12394 @node No_Direct_Boolean_Operators,No_Dispatch,No_Dependence,Partition-Wide Restrictions
12395 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-direct-boolean-operators}@anchor{1cb}
12396 @subsection No_Direct_Boolean_Operators
12399 @geindex No_Direct_Boolean_Operators
12401 [GNAT] This restriction ensures that no logical operators (and/or/xor)
12402 are used on operands of type Boolean (or any type derived from Boolean).
12403 This is intended for use in safety critical programs where the certification
12404 protocol requires the use of short-circuit (and then, or else) forms for all
12405 composite boolean operations.
12407 @node No_Dispatch,No_Dispatching_Calls,No_Direct_Boolean_Operators,Partition-Wide Restrictions
12408 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-dispatch}@anchor{1cc}
12409 @subsection No_Dispatch
12412 @geindex No_Dispatch
12414 [RM H.4] This restriction ensures at compile time that there are no
12415 occurrences of @code{T'Class}, for any (tagged) subtype @code{T}.
12417 @node No_Dispatching_Calls,No_Dynamic_Attachment,No_Dispatch,Partition-Wide Restrictions
12418 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-dispatching-calls}@anchor{1cd}
12419 @subsection No_Dispatching_Calls
12422 @geindex No_Dispatching_Calls
12424 [GNAT] This restriction ensures at compile time that the code generated by the
12425 compiler involves no dispatching calls. The use of this restriction allows the
12426 safe use of record extensions, classwide membership tests and other classwide
12427 features not involving implicit dispatching. This restriction ensures that
12428 the code contains no indirect calls through a dispatching mechanism. Note that
12429 this includes internally-generated calls created by the compiler, for example
12430 in the implementation of class-wide objects assignments. The
12431 membership test is allowed in the presence of this restriction, because its
12432 implementation requires no dispatching.
12433 This restriction is comparable to the official Ada restriction
12434 @code{No_Dispatch} except that it is a bit less restrictive in that it allows
12435 all classwide constructs that do not imply dispatching.
12436 The following example indicates constructs that violate this restriction.
12440 type T is tagged record
12443 procedure P (X : T);
12445 type DT is new T with record
12446 More_Data : Natural;
12448 procedure Q (X : DT);
12452 procedure Example is
12453 procedure Test (O : T'Class) is
12454 N : Natural := O'Size;-- Error: Dispatching call
12455 C : T'Class := O; -- Error: implicit Dispatching Call
12457 if O in DT'Class then -- OK : Membership test
12458 Q (DT (O)); -- OK : Type conversion plus direct call
12460 P (O); -- Error: Dispatching call
12466 P (Obj); -- OK : Direct call
12467 P (T (Obj)); -- OK : Type conversion plus direct call
12468 P (T'Class (Obj)); -- Error: Dispatching call
12470 Test (Obj); -- OK : Type conversion
12472 if Obj in T'Class then -- OK : Membership test
12478 @node No_Dynamic_Attachment,No_Dynamic_Priorities,No_Dispatching_Calls,Partition-Wide Restrictions
12479 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-dynamic-attachment}@anchor{1ce}
12480 @subsection No_Dynamic_Attachment
12483 @geindex No_Dynamic_Attachment
12485 [RM D.7] This restriction ensures that there is no call to any of the
12486 operations defined in package Ada.Interrupts
12487 (Is_Reserved, Is_Attached, Current_Handler, Attach_Handler, Exchange_Handler,
12488 Detach_Handler, and Reference).
12490 @geindex No_Dynamic_Interrupts
12492 The restriction @code{No_Dynamic_Interrupts} is recognized as a
12493 synonym for @code{No_Dynamic_Attachment}. This is retained for historical
12494 compatibility purposes (and a warning will be generated for its use if
12495 warnings on obsolescent features are activated).
12497 @node No_Dynamic_Priorities,No_Entry_Calls_In_Elaboration_Code,No_Dynamic_Attachment,Partition-Wide Restrictions
12498 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-dynamic-priorities}@anchor{1cf}
12499 @subsection No_Dynamic_Priorities
12502 @geindex No_Dynamic_Priorities
12504 [RM D.7] There are no semantic dependencies on the package Dynamic_Priorities.
12506 @node No_Entry_Calls_In_Elaboration_Code,No_Enumeration_Maps,No_Dynamic_Priorities,Partition-Wide Restrictions
12507 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-entry-calls-in-elaboration-code}@anchor{1d0}
12508 @subsection No_Entry_Calls_In_Elaboration_Code
12511 @geindex No_Entry_Calls_In_Elaboration_Code
12513 [GNAT] This restriction ensures at compile time that no task or protected entry
12514 calls are made during elaboration code. As a result of the use of this
12515 restriction, the compiler can assume that no code past an accept statement
12516 in a task can be executed at elaboration time.
12518 @node No_Enumeration_Maps,No_Exception_Handlers,No_Entry_Calls_In_Elaboration_Code,Partition-Wide Restrictions
12519 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-enumeration-maps}@anchor{1d1}
12520 @subsection No_Enumeration_Maps
12523 @geindex No_Enumeration_Maps
12525 [GNAT] This restriction ensures at compile time that no operations requiring
12526 enumeration maps are used (that is Image and Value attributes applied
12527 to enumeration types).
12529 @node No_Exception_Handlers,No_Exception_Propagation,No_Enumeration_Maps,Partition-Wide Restrictions
12530 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-exception-handlers}@anchor{1d2}
12531 @subsection No_Exception_Handlers
12534 @geindex No_Exception_Handlers
12536 [GNAT] This restriction ensures at compile time that there are no explicit
12537 exception handlers. It also indicates that no exception propagation will
12538 be provided. In this mode, exceptions may be raised but will result in
12539 an immediate call to the last chance handler, a routine that the user
12540 must define with the following profile:
12543 procedure Last_Chance_Handler
12544 (Source_Location : System.Address; Line : Integer);
12545 pragma Export (C, Last_Chance_Handler,
12546 "__gnat_last_chance_handler");
12549 The parameter is a C null-terminated string representing a message to be
12550 associated with the exception (typically the source location of the raise
12551 statement generated by the compiler). The Line parameter when nonzero
12552 represents the line number in the source program where the raise occurs.
12554 @node No_Exception_Propagation,No_Exception_Registration,No_Exception_Handlers,Partition-Wide Restrictions
12555 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-exception-propagation}@anchor{1d3}
12556 @subsection No_Exception_Propagation
12559 @geindex No_Exception_Propagation
12561 [GNAT] This restriction guarantees that exceptions are never propagated
12562 to an outer subprogram scope. The only case in which an exception may
12563 be raised is when the handler is statically in the same subprogram, so
12564 that the effect of a raise is essentially like a goto statement. Any
12565 other raise statement (implicit or explicit) will be considered
12566 unhandled. Exception handlers are allowed, but may not contain an
12567 exception occurrence identifier (exception choice). In addition, use of
12568 the package GNAT.Current_Exception is not permitted, and reraise
12569 statements (raise with no operand) are not permitted.
12571 @node No_Exception_Registration,No_Exceptions,No_Exception_Propagation,Partition-Wide Restrictions
12572 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-exception-registration}@anchor{1d4}
12573 @subsection No_Exception_Registration
12576 @geindex No_Exception_Registration
12578 [GNAT] This restriction ensures at compile time that no stream operations for
12579 types Exception_Id or Exception_Occurrence are used. This also makes it
12580 impossible to pass exceptions to or from a partition with this restriction
12581 in a distributed environment. If this restriction is active, the generated
12582 code is simplified by omitting the otherwise-required global registration
12583 of exceptions when they are declared.
12585 @node No_Exceptions,No_Finalization,No_Exception_Registration,Partition-Wide Restrictions
12586 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-exceptions}@anchor{1d5}
12587 @subsection No_Exceptions
12590 @geindex No_Exceptions
12592 [RM H.4] This restriction ensures at compile time that there are no
12593 raise statements and no exception handlers and also suppresses the
12594 generation of language-defined run-time checks.
12596 @node No_Finalization,No_Fixed_Point,No_Exceptions,Partition-Wide Restrictions
12597 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-finalization}@anchor{1d6}
12598 @subsection No_Finalization
12601 @geindex No_Finalization
12603 [GNAT] This restriction disables the language features described in
12604 chapter 7.6 of the Ada 2005 RM as well as all form of code generation
12605 performed by the compiler to support these features. The following types
12606 are no longer considered controlled when this restriction is in effect:
12612 @code{Ada.Finalization.Controlled}
12615 @code{Ada.Finalization.Limited_Controlled}
12618 Derivations from @code{Controlled} or @code{Limited_Controlled}
12630 Array and record types with controlled components
12633 The compiler no longer generates code to initialize, finalize or adjust an
12634 object or a nested component, either declared on the stack or on the heap. The
12635 deallocation of a controlled object no longer finalizes its contents.
12637 @node No_Fixed_Point,No_Floating_Point,No_Finalization,Partition-Wide Restrictions
12638 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-fixed-point}@anchor{1d7}
12639 @subsection No_Fixed_Point
12642 @geindex No_Fixed_Point
12644 [RM H.4] This restriction ensures at compile time that there are no
12645 occurrences of fixed point types and operations.
12647 @node No_Floating_Point,No_Implicit_Conditionals,No_Fixed_Point,Partition-Wide Restrictions
12648 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-floating-point}@anchor{1d8}
12649 @subsection No_Floating_Point
12652 @geindex No_Floating_Point
12654 [RM H.4] This restriction ensures at compile time that there are no
12655 occurrences of floating point types and operations.
12657 @node No_Implicit_Conditionals,No_Implicit_Dynamic_Code,No_Floating_Point,Partition-Wide Restrictions
12658 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-conditionals}@anchor{1d9}
12659 @subsection No_Implicit_Conditionals
12662 @geindex No_Implicit_Conditionals
12664 [GNAT] This restriction ensures that the generated code does not contain any
12665 implicit conditionals, either by modifying the generated code where possible,
12666 or by rejecting any construct that would otherwise generate an implicit
12667 conditional. Note that this check does not include run time constraint
12668 checks, which on some targets may generate implicit conditionals as
12669 well. To control the latter, constraint checks can be suppressed in the
12670 normal manner. Constructs generating implicit conditionals include comparisons
12671 of composite objects and the Max/Min attributes.
12673 @node No_Implicit_Dynamic_Code,No_Implicit_Heap_Allocations,No_Implicit_Conditionals,Partition-Wide Restrictions
12674 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-dynamic-code}@anchor{1da}
12675 @subsection No_Implicit_Dynamic_Code
12678 @geindex No_Implicit_Dynamic_Code
12680 @geindex trampoline
12682 [GNAT] This restriction prevents the compiler from building 'trampolines'.
12683 This is a structure that is built on the stack and contains dynamic
12684 code to be executed at run time. On some targets, a trampoline is
12685 built for the following features: @code{Access},
12686 @code{Unrestricted_Access}, or @code{Address} of a nested subprogram;
12687 nested task bodies; primitive operations of nested tagged types.
12688 Trampolines do not work on machines that prevent execution of stack
12689 data. For example, on windows systems, enabling DEP (data execution
12690 protection) will cause trampolines to raise an exception.
12691 Trampolines are also quite slow at run time.
12693 On many targets, trampolines have been largely eliminated. Look at the
12694 version of system.ads for your target --- if it has
12695 Always_Compatible_Rep equal to False, then trampolines are largely
12696 eliminated. In particular, a trampoline is built for the following
12697 features: @code{Address} of a nested subprogram;
12698 @code{Access} or @code{Unrestricted_Access} of a nested subprogram,
12699 but only if pragma Favor_Top_Level applies, or the access type has a
12700 foreign-language convention; primitive operations of nested tagged
12703 @node No_Implicit_Heap_Allocations,No_Implicit_Protected_Object_Allocations,No_Implicit_Dynamic_Code,Partition-Wide Restrictions
12704 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-heap-allocations}@anchor{1db}
12705 @subsection No_Implicit_Heap_Allocations
12708 @geindex No_Implicit_Heap_Allocations
12710 [RM D.7] No constructs are allowed to cause implicit heap allocation.
12712 @node No_Implicit_Protected_Object_Allocations,No_Implicit_Task_Allocations,No_Implicit_Heap_Allocations,Partition-Wide Restrictions
12713 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-protected-object-allocations}@anchor{1dc}
12714 @subsection No_Implicit_Protected_Object_Allocations
12717 @geindex No_Implicit_Protected_Object_Allocations
12719 [GNAT] No constructs are allowed to cause implicit heap allocation of a
12722 @node No_Implicit_Task_Allocations,No_Initialize_Scalars,No_Implicit_Protected_Object_Allocations,Partition-Wide Restrictions
12723 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-task-allocations}@anchor{1dd}
12724 @subsection No_Implicit_Task_Allocations
12727 @geindex No_Implicit_Task_Allocations
12729 [GNAT] No constructs are allowed to cause implicit heap allocation of a task.
12731 @node No_Initialize_Scalars,No_IO,No_Implicit_Task_Allocations,Partition-Wide Restrictions
12732 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-initialize-scalars}@anchor{1de}
12733 @subsection No_Initialize_Scalars
12736 @geindex No_Initialize_Scalars
12738 [GNAT] This restriction ensures that no unit in the partition is compiled with
12739 pragma Initialize_Scalars. This allows the generation of more efficient
12740 code, and in particular eliminates dummy null initialization routines that
12741 are otherwise generated for some record and array types.
12743 @node No_IO,No_Local_Allocators,No_Initialize_Scalars,Partition-Wide Restrictions
12744 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-io}@anchor{1df}
12750 [RM H.4] This restriction ensures at compile time that there are no
12751 dependences on any of the library units Sequential_IO, Direct_IO,
12752 Text_IO, Wide_Text_IO, Wide_Wide_Text_IO, or Stream_IO.
12754 @node No_Local_Allocators,No_Local_Protected_Objects,No_IO,Partition-Wide Restrictions
12755 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-local-allocators}@anchor{1e0}
12756 @subsection No_Local_Allocators
12759 @geindex No_Local_Allocators
12761 [RM H.4] This restriction ensures at compile time that there are no
12762 occurrences of an allocator in subprograms, generic subprograms, tasks,
12765 @node No_Local_Protected_Objects,No_Local_Timing_Events,No_Local_Allocators,Partition-Wide Restrictions
12766 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-local-protected-objects}@anchor{1e1}
12767 @subsection No_Local_Protected_Objects
12770 @geindex No_Local_Protected_Objects
12772 [RM D.7] This restriction ensures at compile time that protected objects are
12773 only declared at the library level.
12775 @node No_Local_Timing_Events,No_Long_Long_Integers,No_Local_Protected_Objects,Partition-Wide Restrictions
12776 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-local-timing-events}@anchor{1e2}
12777 @subsection No_Local_Timing_Events
12780 @geindex No_Local_Timing_Events
12782 [RM D.7] All objects of type Ada.Timing_Events.Timing_Event are
12783 declared at the library level.
12785 @node No_Long_Long_Integers,No_Multiple_Elaboration,No_Local_Timing_Events,Partition-Wide Restrictions
12786 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-long-long-integers}@anchor{1e3}
12787 @subsection No_Long_Long_Integers
12790 @geindex No_Long_Long_Integers
12792 [GNAT] This partition-wide restriction forbids any explicit reference to
12793 type Standard.Long_Long_Integer, and also forbids declaring range types whose
12794 implicit base type is Long_Long_Integer, and modular types whose size exceeds
12797 @node No_Multiple_Elaboration,No_Nested_Finalization,No_Long_Long_Integers,Partition-Wide Restrictions
12798 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-multiple-elaboration}@anchor{1e4}
12799 @subsection No_Multiple_Elaboration
12802 @geindex No_Multiple_Elaboration
12804 [GNAT] When this restriction is active and the static elaboration model is
12805 used, and -fpreserve-control-flow is not used, the compiler is allowed to
12806 suppress the elaboration counter normally associated with the unit, even if
12807 the unit has elaboration code. This counter is typically used to check for
12808 access before elaboration and to control multiple elaboration attempts. If the
12809 restriction is used, then the situations in which multiple elaboration is
12810 possible, including non-Ada main programs and Stand Alone libraries, are not
12811 permitted and will be diagnosed by the binder.
12813 @node No_Nested_Finalization,No_Protected_Type_Allocators,No_Multiple_Elaboration,Partition-Wide Restrictions
12814 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-nested-finalization}@anchor{1e5}
12815 @subsection No_Nested_Finalization
12818 @geindex No_Nested_Finalization
12820 [RM D.7] All objects requiring finalization are declared at the library level.
12822 @node No_Protected_Type_Allocators,No_Protected_Types,No_Nested_Finalization,Partition-Wide Restrictions
12823 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-protected-type-allocators}@anchor{1e6}
12824 @subsection No_Protected_Type_Allocators
12827 @geindex No_Protected_Type_Allocators
12829 [RM D.7] This restriction ensures at compile time that there are no allocator
12830 expressions that attempt to allocate protected objects.
12832 @node No_Protected_Types,No_Recursion,No_Protected_Type_Allocators,Partition-Wide Restrictions
12833 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-protected-types}@anchor{1e7}
12834 @subsection No_Protected_Types
12837 @geindex No_Protected_Types
12839 [RM H.4] This restriction ensures at compile time that there are no
12840 declarations of protected types or protected objects.
12842 @node No_Recursion,No_Reentrancy,No_Protected_Types,Partition-Wide Restrictions
12843 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-recursion}@anchor{1e8}
12844 @subsection No_Recursion
12847 @geindex No_Recursion
12849 [RM H.4] A program execution is erroneous if a subprogram is invoked as
12850 part of its execution.
12852 @node No_Reentrancy,No_Relative_Delay,No_Recursion,Partition-Wide Restrictions
12853 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-reentrancy}@anchor{1e9}
12854 @subsection No_Reentrancy
12857 @geindex No_Reentrancy
12859 [RM H.4] A program execution is erroneous if a subprogram is executed by
12860 two tasks at the same time.
12862 @node No_Relative_Delay,No_Requeue_Statements,No_Reentrancy,Partition-Wide Restrictions
12863 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-relative-delay}@anchor{1ea}
12864 @subsection No_Relative_Delay
12867 @geindex No_Relative_Delay
12869 [RM D.7] This restriction ensures at compile time that there are no delay
12870 relative statements and prevents expressions such as @code{delay 1.23;} from
12871 appearing in source code.
12873 @node No_Requeue_Statements,No_Secondary_Stack,No_Relative_Delay,Partition-Wide Restrictions
12874 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-requeue-statements}@anchor{1eb}
12875 @subsection No_Requeue_Statements
12878 @geindex No_Requeue_Statements
12880 [RM D.7] This restriction ensures at compile time that no requeue statements
12881 are permitted and prevents keyword @code{requeue} from being used in source
12884 @geindex No_Requeue
12886 The restriction @code{No_Requeue} is recognized as a
12887 synonym for @code{No_Requeue_Statements}. This is retained for historical
12888 compatibility purposes (and a warning will be generated for its use if
12889 warnings on oNobsolescent features are activated).
12891 @node No_Secondary_Stack,No_Select_Statements,No_Requeue_Statements,Partition-Wide Restrictions
12892 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-secondary-stack}@anchor{1ec}
12893 @subsection No_Secondary_Stack
12896 @geindex No_Secondary_Stack
12898 [GNAT] This restriction ensures at compile time that the generated code
12899 does not contain any reference to the secondary stack. The secondary
12900 stack is used to implement functions returning unconstrained objects
12901 (arrays or records) on some targets. Suppresses the allocation of
12902 secondary stacks for tasks (excluding the environment task) at run time.
12904 @node No_Select_Statements,No_Specific_Termination_Handlers,No_Secondary_Stack,Partition-Wide Restrictions
12905 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-select-statements}@anchor{1ed}
12906 @subsection No_Select_Statements
12909 @geindex No_Select_Statements
12911 [RM D.7] This restriction ensures at compile time no select statements of any
12912 kind are permitted, that is the keyword @code{select} may not appear.
12914 @node No_Specific_Termination_Handlers,No_Specification_of_Aspect,No_Select_Statements,Partition-Wide Restrictions
12915 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-specific-termination-handlers}@anchor{1ee}
12916 @subsection No_Specific_Termination_Handlers
12919 @geindex No_Specific_Termination_Handlers
12921 [RM D.7] There are no calls to Ada.Task_Termination.Set_Specific_Handler
12922 or to Ada.Task_Termination.Specific_Handler.
12924 @node No_Specification_of_Aspect,No_Standard_Allocators_After_Elaboration,No_Specific_Termination_Handlers,Partition-Wide Restrictions
12925 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-specification-of-aspect}@anchor{1ef}
12926 @subsection No_Specification_of_Aspect
12929 @geindex No_Specification_of_Aspect
12931 [RM 13.12.1] This restriction checks at compile time that no aspect
12932 specification, attribute definition clause, or pragma is given for a
12935 @node No_Standard_Allocators_After_Elaboration,No_Standard_Storage_Pools,No_Specification_of_Aspect,Partition-Wide Restrictions
12936 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-standard-allocators-after-elaboration}@anchor{1f0}
12937 @subsection No_Standard_Allocators_After_Elaboration
12940 @geindex No_Standard_Allocators_After_Elaboration
12942 [RM D.7] Specifies that an allocator using a standard storage pool
12943 should never be evaluated at run time after the elaboration of the
12944 library items of the partition has completed. Otherwise, Storage_Error
12947 @node No_Standard_Storage_Pools,No_Stream_Optimizations,No_Standard_Allocators_After_Elaboration,Partition-Wide Restrictions
12948 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-standard-storage-pools}@anchor{1f1}
12949 @subsection No_Standard_Storage_Pools
12952 @geindex No_Standard_Storage_Pools
12954 [GNAT] This restriction ensures at compile time that no access types
12955 use the standard default storage pool. Any access type declared must
12956 have an explicit Storage_Pool attribute defined specifying a
12957 user-defined storage pool.
12959 @node No_Stream_Optimizations,No_Streams,No_Standard_Storage_Pools,Partition-Wide Restrictions
12960 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-stream-optimizations}@anchor{1f2}
12961 @subsection No_Stream_Optimizations
12964 @geindex No_Stream_Optimizations
12966 [GNAT] This restriction affects the performance of stream operations on types
12967 @code{String}, @code{Wide_String} and @code{Wide_Wide_String}. By default, the
12968 compiler uses block reads and writes when manipulating @code{String} objects
12969 due to their superior performance. When this restriction is in effect, the
12970 compiler performs all IO operations on a per-character basis.
12972 @node No_Streams,No_Task_Allocators,No_Stream_Optimizations,Partition-Wide Restrictions
12973 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-streams}@anchor{1f3}
12974 @subsection No_Streams
12977 @geindex No_Streams
12979 [GNAT] This restriction ensures at compile/bind time that there are no
12980 stream objects created and no use of stream attributes.
12981 This restriction does not forbid dependences on the package
12982 @code{Ada.Streams}. So it is permissible to with
12983 @code{Ada.Streams} (or another package that does so itself)
12984 as long as no actual stream objects are created and no
12985 stream attributes are used.
12987 Note that the use of restriction allows optimization of tagged types,
12988 since they do not need to worry about dispatching stream operations.
12989 To take maximum advantage of this space-saving optimization, any
12990 unit declaring a tagged type should be compiled with the restriction,
12991 though this is not required.
12993 @node No_Task_Allocators,No_Task_At_Interrupt_Priority,No_Streams,Partition-Wide Restrictions
12994 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-task-allocators}@anchor{1f4}
12995 @subsection No_Task_Allocators
12998 @geindex No_Task_Allocators
13000 [RM D.7] There are no allocators for task types
13001 or types containing task subcomponents.
13003 @node No_Task_At_Interrupt_Priority,No_Task_Attributes_Package,No_Task_Allocators,Partition-Wide Restrictions
13004 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-task-at-interrupt-priority}@anchor{1f5}
13005 @subsection No_Task_At_Interrupt_Priority
13008 @geindex No_Task_At_Interrupt_Priority
13010 [GNAT] This restriction ensures at compile time that there is no
13011 Interrupt_Priority aspect or pragma for a task or a task type. As
13012 a consequence, the tasks are always created with a priority below
13013 that an interrupt priority.
13015 @node No_Task_Attributes_Package,No_Task_Hierarchy,No_Task_At_Interrupt_Priority,Partition-Wide Restrictions
13016 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-task-attributes-package}@anchor{1f6}
13017 @subsection No_Task_Attributes_Package
13020 @geindex No_Task_Attributes_Package
13022 [GNAT] This restriction ensures at compile time that there are no implicit or
13023 explicit dependencies on the package @code{Ada.Task_Attributes}.
13025 @geindex No_Task_Attributes
13027 The restriction @code{No_Task_Attributes} is recognized as a synonym
13028 for @code{No_Task_Attributes_Package}. This is retained for historical
13029 compatibility purposes (and a warning will be generated for its use if
13030 warnings on obsolescent features are activated).
13032 @node No_Task_Hierarchy,No_Task_Termination,No_Task_Attributes_Package,Partition-Wide Restrictions
13033 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-task-hierarchy}@anchor{1f7}
13034 @subsection No_Task_Hierarchy
13037 @geindex No_Task_Hierarchy
13039 [RM D.7] All (non-environment) tasks depend
13040 directly on the environment task of the partition.
13042 @node No_Task_Termination,No_Tasking,No_Task_Hierarchy,Partition-Wide Restrictions
13043 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-task-termination}@anchor{1f8}
13044 @subsection No_Task_Termination
13047 @geindex No_Task_Termination
13049 [RM D.7] Tasks that terminate are erroneous.
13051 @node No_Tasking,No_Terminate_Alternatives,No_Task_Termination,Partition-Wide Restrictions
13052 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-tasking}@anchor{1f9}
13053 @subsection No_Tasking
13056 @geindex No_Tasking
13058 [GNAT] This restriction prevents the declaration of tasks or task types
13059 throughout the partition. It is similar in effect to the use of
13060 @code{Max_Tasks => 0} except that violations are caught at compile time
13061 and cause an error message to be output either by the compiler or
13064 @node No_Terminate_Alternatives,No_Unchecked_Access,No_Tasking,Partition-Wide Restrictions
13065 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-terminate-alternatives}@anchor{1fa}
13066 @subsection No_Terminate_Alternatives
13069 @geindex No_Terminate_Alternatives
13071 [RM D.7] There are no selective accepts with terminate alternatives.
13073 @node No_Unchecked_Access,No_Unchecked_Conversion,No_Terminate_Alternatives,Partition-Wide Restrictions
13074 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-unchecked-access}@anchor{1fb}
13075 @subsection No_Unchecked_Access
13078 @geindex No_Unchecked_Access
13080 [RM H.4] This restriction ensures at compile time that there are no
13081 occurrences of the Unchecked_Access attribute.
13083 @node No_Unchecked_Conversion,No_Unchecked_Deallocation,No_Unchecked_Access,Partition-Wide Restrictions
13084 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-unchecked-conversion}@anchor{1fc}
13085 @subsection No_Unchecked_Conversion
13088 @geindex No_Unchecked_Conversion
13090 [RM J.13] This restriction ensures at compile time that there are no semantic
13091 dependences on the predefined generic function Unchecked_Conversion.
13093 @node No_Unchecked_Deallocation,No_Use_Of_Entity,No_Unchecked_Conversion,Partition-Wide Restrictions
13094 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-unchecked-deallocation}@anchor{1fd}
13095 @subsection No_Unchecked_Deallocation
13098 @geindex No_Unchecked_Deallocation
13100 [RM J.13] This restriction ensures at compile time that there are no semantic
13101 dependences on the predefined generic procedure Unchecked_Deallocation.
13103 @node No_Use_Of_Entity,Pure_Barriers,No_Unchecked_Deallocation,Partition-Wide Restrictions
13104 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-use-of-entity}@anchor{1fe}
13105 @subsection No_Use_Of_Entity
13108 @geindex No_Use_Of_Entity
13110 [GNAT] This restriction ensures at compile time that there are no references
13111 to the entity given in the form
13114 No_Use_Of_Entity => Name
13117 where @code{Name} is the fully qualified entity, for example
13120 No_Use_Of_Entity => Ada.Text_IO.Put_Line
13123 @node Pure_Barriers,Simple_Barriers,No_Use_Of_Entity,Partition-Wide Restrictions
13124 @anchor{gnat_rm/standard_and_implementation_defined_restrictions pure-barriers}@anchor{1ff}
13125 @subsection Pure_Barriers
13128 @geindex Pure_Barriers
13130 [GNAT] This restriction ensures at compile time that protected entry
13131 barriers are restricted to:
13137 components of the protected object (excluding selection from dereferences),
13140 constant declarations,
13146 enumeration literals,
13155 character literals,
13158 implicitly defined comparison operators,
13161 uses of the Standard."not" operator,
13164 short-circuit operator,
13167 the Count attribute
13170 This restriction is a relaxation of the Simple_Barriers restriction,
13171 but still ensures absence of side effects, exceptions, and recursion
13172 during the evaluation of the barriers.
13174 @node Simple_Barriers,Static_Priorities,Pure_Barriers,Partition-Wide Restrictions
13175 @anchor{gnat_rm/standard_and_implementation_defined_restrictions simple-barriers}@anchor{200}
13176 @subsection Simple_Barriers
13179 @geindex Simple_Barriers
13181 [RM D.7] This restriction ensures at compile time that barriers in entry
13182 declarations for protected types are restricted to either static boolean
13183 expressions or references to simple boolean variables defined in the private
13184 part of the protected type. No other form of entry barriers is permitted.
13186 @geindex Boolean_Entry_Barriers
13188 The restriction @code{Boolean_Entry_Barriers} is recognized as a
13189 synonym for @code{Simple_Barriers}. This is retained for historical
13190 compatibility purposes (and a warning will be generated for its use if
13191 warnings on obsolescent features are activated).
13193 @node Static_Priorities,Static_Storage_Size,Simple_Barriers,Partition-Wide Restrictions
13194 @anchor{gnat_rm/standard_and_implementation_defined_restrictions static-priorities}@anchor{201}
13195 @subsection Static_Priorities
13198 @geindex Static_Priorities
13200 [GNAT] This restriction ensures at compile time that all priority expressions
13201 are static, and that there are no dependences on the package
13202 @code{Ada.Dynamic_Priorities}.
13204 @node Static_Storage_Size,,Static_Priorities,Partition-Wide Restrictions
13205 @anchor{gnat_rm/standard_and_implementation_defined_restrictions static-storage-size}@anchor{202}
13206 @subsection Static_Storage_Size
13209 @geindex Static_Storage_Size
13211 [GNAT] This restriction ensures at compile time that any expression appearing
13212 in a Storage_Size pragma or attribute definition clause is static.
13214 @node Program Unit Level Restrictions,,Partition-Wide Restrictions,Standard and Implementation Defined Restrictions
13215 @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}
13216 @section Program Unit Level Restrictions
13219 The second set of restriction identifiers
13220 does not require partition-wide consistency.
13221 The restriction may be enforced for a single
13222 compilation unit without any effect on any of the
13223 other compilation units in the partition.
13226 * No_Elaboration_Code::
13227 * No_Dynamic_Sized_Objects::
13229 * No_Implementation_Aspect_Specifications::
13230 * No_Implementation_Attributes::
13231 * No_Implementation_Identifiers::
13232 * No_Implementation_Pragmas::
13233 * No_Implementation_Restrictions::
13234 * No_Implementation_Units::
13235 * No_Implicit_Aliasing::
13236 * No_Implicit_Loops::
13237 * No_Obsolescent_Features::
13238 * No_Wide_Characters::
13239 * Static_Dispatch_Tables::
13244 @node No_Elaboration_Code,No_Dynamic_Sized_Objects,,Program Unit Level Restrictions
13245 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-elaboration-code}@anchor{205}
13246 @subsection No_Elaboration_Code
13249 @geindex No_Elaboration_Code
13251 [GNAT] This restriction ensures at compile time that no elaboration code is
13252 generated. Note that this is not the same condition as is enforced
13253 by pragma @code{Preelaborate}. There are cases in which pragma
13254 @code{Preelaborate} still permits code to be generated (e.g., code
13255 to initialize a large array to all zeroes), and there are cases of units
13256 which do not meet the requirements for pragma @code{Preelaborate},
13257 but for which no elaboration code is generated. Generally, it is
13258 the case that preelaborable units will meet the restrictions, with
13259 the exception of large aggregates initialized with an others_clause,
13260 and exception declarations (which generate calls to a run-time
13261 registry procedure). This restriction is enforced on
13262 a unit by unit basis, it need not be obeyed consistently
13263 throughout a partition.
13265 In the case of aggregates with others, if the aggregate has a dynamic
13266 size, there is no way to eliminate the elaboration code (such dynamic
13267 bounds would be incompatible with @code{Preelaborate} in any case). If
13268 the bounds are static, then use of this restriction actually modifies
13269 the code choice of the compiler to avoid generating a loop, and instead
13270 generate the aggregate statically if possible, no matter how many times
13271 the data for the others clause must be repeatedly generated.
13273 It is not possible to precisely document
13274 the constructs which are compatible with this restriction, since,
13275 unlike most other restrictions, this is not a restriction on the
13276 source code, but a restriction on the generated object code. For
13277 example, if the source contains a declaration:
13280 Val : constant Integer := X;
13283 where X is not a static constant, it may be possible, depending
13284 on complex optimization circuitry, for the compiler to figure
13285 out the value of X at compile time, in which case this initialization
13286 can be done by the loader, and requires no initialization code. It
13287 is not possible to document the precise conditions under which the
13288 optimizer can figure this out.
13290 Note that this the implementation of this restriction requires full
13291 code generation. If it is used in conjunction with "semantics only"
13292 checking, then some cases of violations may be missed.
13294 When this restriction is active, we are not requesting control-flow
13295 preservation with -fpreserve-control-flow, and the static elaboration model is
13296 used, the compiler is allowed to suppress the elaboration counter normally
13297 associated with the unit. This counter is typically used to check for access
13298 before elaboration and to control multiple elaboration attempts.
13300 @node No_Dynamic_Sized_Objects,No_Entry_Queue,No_Elaboration_Code,Program Unit Level Restrictions
13301 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-dynamic-sized-objects}@anchor{206}
13302 @subsection No_Dynamic_Sized_Objects
13305 @geindex No_Dynamic_Sized_Objects
13307 [GNAT] This restriction disallows certain constructs that might lead to the
13308 creation of dynamic-sized composite objects (or array or discriminated type).
13309 An array subtype indication is illegal if the bounds are not static
13310 or references to discriminants of an enclosing type.
13311 A discriminated subtype indication is illegal if the type has
13312 discriminant-dependent array components or a variant part, and the
13313 discriminants are not static. In addition, array and record aggregates are
13314 illegal in corresponding cases. Note that this restriction does not forbid
13315 access discriminants. It is often a good idea to combine this restriction
13316 with No_Secondary_Stack.
13318 @node No_Entry_Queue,No_Implementation_Aspect_Specifications,No_Dynamic_Sized_Objects,Program Unit Level Restrictions
13319 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-entry-queue}@anchor{207}
13320 @subsection No_Entry_Queue
13323 @geindex No_Entry_Queue
13325 [GNAT] This restriction is a declaration that any protected entry compiled in
13326 the scope of the restriction has at most one task waiting on the entry
13327 at any one time, and so no queue is required. This restriction is not
13328 checked at compile time. A program execution is erroneous if an attempt
13329 is made to queue a second task on such an entry.
13331 @node No_Implementation_Aspect_Specifications,No_Implementation_Attributes,No_Entry_Queue,Program Unit Level Restrictions
13332 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implementation-aspect-specifications}@anchor{208}
13333 @subsection No_Implementation_Aspect_Specifications
13336 @geindex No_Implementation_Aspect_Specifications
13338 [RM 13.12.1] This restriction checks at compile time that no
13339 GNAT-defined aspects are present. With this restriction, the only
13340 aspects that can be used are those defined in the Ada Reference Manual.
13342 @node No_Implementation_Attributes,No_Implementation_Identifiers,No_Implementation_Aspect_Specifications,Program Unit Level Restrictions
13343 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implementation-attributes}@anchor{209}
13344 @subsection No_Implementation_Attributes
13347 @geindex No_Implementation_Attributes
13349 [RM 13.12.1] This restriction checks at compile time that no
13350 GNAT-defined attributes are present. With this restriction, the only
13351 attributes that can be used are those defined in the Ada Reference
13354 @node No_Implementation_Identifiers,No_Implementation_Pragmas,No_Implementation_Attributes,Program Unit Level Restrictions
13355 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implementation-identifiers}@anchor{20a}
13356 @subsection No_Implementation_Identifiers
13359 @geindex No_Implementation_Identifiers
13361 [RM 13.12.1] This restriction checks at compile time that no
13362 implementation-defined identifiers (marked with pragma Implementation_Defined)
13363 occur within language-defined packages.
13365 @node No_Implementation_Pragmas,No_Implementation_Restrictions,No_Implementation_Identifiers,Program Unit Level Restrictions
13366 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implementation-pragmas}@anchor{20b}
13367 @subsection No_Implementation_Pragmas
13370 @geindex No_Implementation_Pragmas
13372 [RM 13.12.1] This restriction checks at compile time that no
13373 GNAT-defined pragmas are present. With this restriction, the only
13374 pragmas that can be used are those defined in the Ada Reference Manual.
13376 @node No_Implementation_Restrictions,No_Implementation_Units,No_Implementation_Pragmas,Program Unit Level Restrictions
13377 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implementation-restrictions}@anchor{20c}
13378 @subsection No_Implementation_Restrictions
13381 @geindex No_Implementation_Restrictions
13383 [GNAT] This restriction checks at compile time that no GNAT-defined restriction
13384 identifiers (other than @code{No_Implementation_Restrictions} itself)
13385 are present. With this restriction, the only other restriction identifiers
13386 that can be used are those defined in the Ada Reference Manual.
13388 @node No_Implementation_Units,No_Implicit_Aliasing,No_Implementation_Restrictions,Program Unit Level Restrictions
13389 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implementation-units}@anchor{20d}
13390 @subsection No_Implementation_Units
13393 @geindex No_Implementation_Units
13395 [RM 13.12.1] This restriction checks at compile time that there is no
13396 mention in the context clause of any implementation-defined descendants
13397 of packages Ada, Interfaces, or System.
13399 @node No_Implicit_Aliasing,No_Implicit_Loops,No_Implementation_Units,Program Unit Level Restrictions
13400 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-aliasing}@anchor{20e}
13401 @subsection No_Implicit_Aliasing
13404 @geindex No_Implicit_Aliasing
13406 [GNAT] This restriction, which is not required to be partition-wide consistent,
13407 requires an explicit aliased keyword for an object to which 'Access,
13408 'Unchecked_Access, or 'Address is applied, and forbids entirely the use of
13409 the 'Unrestricted_Access attribute for objects. Note: the reason that
13410 Unrestricted_Access is forbidden is that it would require the prefix
13411 to be aliased, and in such cases, it can always be replaced by
13412 the standard attribute Unchecked_Access which is preferable.
13414 @node No_Implicit_Loops,No_Obsolescent_Features,No_Implicit_Aliasing,Program Unit Level Restrictions
13415 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-loops}@anchor{20f}
13416 @subsection No_Implicit_Loops
13419 @geindex No_Implicit_Loops
13421 [GNAT] This restriction ensures that the generated code of the unit marked
13422 with this restriction does not contain any implicit @code{for} loops, either by
13423 modifying the generated code where possible, or by rejecting any construct
13424 that would otherwise generate an implicit @code{for} loop. If this restriction is
13425 active, it is possible to build large array aggregates with all static
13426 components without generating an intermediate temporary, and without generating
13427 a loop to initialize individual components. Otherwise, a loop is created for
13428 arrays larger than about 5000 scalar components. Note that if this restriction
13429 is set in the spec of a package, it will not apply to its body.
13431 @node No_Obsolescent_Features,No_Wide_Characters,No_Implicit_Loops,Program Unit Level Restrictions
13432 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-obsolescent-features}@anchor{210}
13433 @subsection No_Obsolescent_Features
13436 @geindex No_Obsolescent_Features
13438 [RM 13.12.1] This restriction checks at compile time that no obsolescent
13439 features are used, as defined in Annex J of the Ada Reference Manual.
13441 @node No_Wide_Characters,Static_Dispatch_Tables,No_Obsolescent_Features,Program Unit Level Restrictions
13442 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-wide-characters}@anchor{211}
13443 @subsection No_Wide_Characters
13446 @geindex No_Wide_Characters
13448 [GNAT] This restriction ensures at compile time that no uses of the types
13449 @code{Wide_Character} or @code{Wide_String} or corresponding wide
13451 appear, and that no wide or wide wide string or character literals
13452 appear in the program (that is literals representing characters not in
13453 type @code{Character}).
13455 @node Static_Dispatch_Tables,SPARK_05,No_Wide_Characters,Program Unit Level Restrictions
13456 @anchor{gnat_rm/standard_and_implementation_defined_restrictions static-dispatch-tables}@anchor{212}
13457 @subsection Static_Dispatch_Tables
13460 @geindex Static_Dispatch_Tables
13462 [GNAT] This restriction checks at compile time that all the artifacts
13463 associated with dispatch tables can be placed in read-only memory.
13465 @node SPARK_05,,Static_Dispatch_Tables,Program Unit Level Restrictions
13466 @anchor{gnat_rm/standard_and_implementation_defined_restrictions spark-05}@anchor{213}
13467 @subsection SPARK_05
13472 [GNAT] This restriction checks at compile time that some constructs forbidden
13473 in SPARK 2005 are not present. Note that SPARK 2005 has been superseded by
13474 SPARK 2014, whose restrictions are checked by the tool GNATprove. To check that
13475 a codebase respects SPARK 2014 restrictions, mark the code with pragma or
13476 aspect @code{SPARK_Mode}, and run the tool GNATprove at Stone assurance level, as
13480 gnatprove -P project.gpr --mode=stone
13486 gnatprove -P project.gpr --mode=check_all
13489 With restriction @code{SPARK_05}, error messages related to SPARK 2005 restriction
13493 violation of restriction "SPARK_05" at <source-location>
13499 The restriction @code{SPARK} is recognized as a synonym for @code{SPARK_05}. This is
13500 retained for historical compatibility purposes (and an unconditional warning
13501 will be generated for its use, advising replacement by @code{SPARK_05}).
13503 This is not a replacement for the semantic checks performed by the
13504 SPARK Examiner tool, as the compiler currently only deals with code,
13505 not SPARK 2005 annotations, and does not guarantee catching all
13506 cases of constructs forbidden by SPARK 2005.
13508 Thus it may well be the case that code which passes the compiler with
13509 the SPARK 2005 restriction is rejected by the SPARK Examiner, e.g. due to
13510 the different visibility rules of the Examiner based on SPARK 2005
13511 @code{inherit} annotations.
13513 This restriction can be useful in providing an initial filter for code
13514 developed using SPARK 2005, or in examining legacy code to see how far
13515 it is from meeting SPARK 2005 restrictions.
13517 The list below summarizes the checks that are performed when this
13518 restriction is in force:
13524 No block statements
13527 No case statements with only an others clause
13530 Exit statements in loops must respect the SPARK 2005 language restrictions
13536 Return can only appear as last statement in function
13539 Function must have return statement
13542 Loop parameter specification must include subtype mark
13545 Prefix of expanded name cannot be a loop statement
13548 Abstract subprogram not allowed
13551 User-defined operators not allowed
13554 Access type parameters not allowed
13557 Default expressions for parameters not allowed
13560 Default expressions for record fields not allowed
13563 No tasking constructs allowed
13566 Label needed at end of subprograms and packages
13569 No mixing of positional and named parameter association
13572 No access types as result type
13575 No unconstrained arrays as result types
13581 Initial and later declarations must be in correct order (declaration can't come after body)
13584 No attributes on private types if full declaration not visible
13587 No package declaration within package specification
13590 No controlled types
13593 No discriminant types
13599 Selector name cannot be operator symbol (i.e. operator symbol cannot be prefixed)
13602 Access attribute not allowed
13605 Allocator not allowed
13608 Result of catenation must be String
13611 Operands of catenation must be string literal, static char or another catenation
13614 No conditional expressions
13617 No explicit dereference
13620 Quantified expression not allowed
13623 Slicing not allowed
13626 No exception renaming
13629 No generic renaming
13638 Aggregates must be qualified
13641 Nonstatic choice in array aggregates not allowed
13644 The only view conversions which are allowed as in-out parameters are conversions of a tagged type to an ancestor type
13647 No mixing of positional and named association in aggregate, no multi choice
13650 AND, OR and XOR for arrays only allowed when operands have same static bounds
13653 Fixed point operands to * or / must be qualified or converted
13656 Comparison operators not allowed for Booleans or arrays (except strings)
13659 Equality not allowed for arrays with non-matching static bounds (except strings)
13662 Conversion / qualification not allowed for arrays with non-matching static bounds
13665 Subprogram declaration only allowed in package spec (unless followed by import)
13668 Access types not allowed
13671 Incomplete type declaration not allowed
13674 Object and subtype declarations must respect SPARK 2005 restrictions
13677 Digits or delta constraint not allowed
13680 Decimal fixed point type not allowed
13683 Aliasing of objects not allowed
13686 Modular type modulus must be power of 2
13689 Base not allowed on subtype mark
13692 Unary operators not allowed on modular types (except not)
13695 Untagged record cannot be null
13698 No class-wide operations
13701 Initialization expressions must respect SPARK 2005 restrictions
13704 Nonstatic ranges not allowed except in iteration schemes
13707 String subtypes must have lower bound of 1
13710 Subtype of Boolean cannot have constraint
13713 At most one tagged type or extension per package
13716 Interface is not allowed
13719 Character literal cannot be prefixed (selector name cannot be character literal)
13722 Record aggregate cannot contain 'others'
13725 Component association in record aggregate must contain a single choice
13728 Ancestor part cannot be a type mark
13731 Attributes 'Image, 'Width and 'Value not allowed
13734 Functions may not update globals
13737 Subprograms may not contain direct calls to themselves (prevents recursion within unit)
13740 Call to subprogram not allowed in same unit before body has been seen (prevents recursion within unit)
13743 The following restrictions are enforced, but note that they are actually more
13744 strict that the latest SPARK 2005 language definition:
13750 No derived types other than tagged type extensions
13753 Subtype of unconstrained array must have constraint
13756 This list summarises the main SPARK 2005 language rules that are not
13757 currently checked by the SPARK_05 restriction:
13763 SPARK 2005 annotations are treated as comments so are not checked at all
13766 Based real literals not allowed
13769 Objects cannot be initialized at declaration by calls to user-defined functions
13772 Objects cannot be initialized at declaration by assignments from variables
13775 Objects cannot be initialized at declaration by assignments from indexed/selected components
13778 Ranges shall not be null
13781 A fixed point delta expression must be a simple expression
13784 Restrictions on where renaming declarations may be placed
13787 Externals of mode 'out' cannot be referenced
13790 Externals of mode 'in' cannot be updated
13793 Loop with no iteration scheme or exits only allowed as last statement in main program or task
13796 Subprogram cannot have parent unit name
13799 SPARK 2005 inherited subprogram must be prefixed with overriding
13802 External variables (or functions that reference them) may not be passed as actual parameters
13805 Globals must be explicitly mentioned in contract
13808 Deferred constants cannot be completed by pragma Import
13811 Package initialization cannot read/write variables from other packages
13814 Prefix not allowed for entities that are directly visible
13817 Identifier declaration can't override inherited package name
13820 Cannot use Standard or other predefined packages as identifiers
13823 After renaming, cannot use the original name
13826 Subprograms can only be renamed to remove package prefix
13829 Pragma import must be immediately after entity it names
13832 No mutual recursion between multiple units (this can be checked with gnatcheck)
13835 Note that if a unit is compiled in Ada 95 mode with the SPARK 2005 restriction,
13836 violations will be reported for constructs forbidden in SPARK 95,
13837 instead of SPARK 2005.
13839 @node Implementation Advice,Implementation Defined Characteristics,Standard and Implementation Defined Restrictions,Top
13840 @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}
13841 @chapter Implementation Advice
13844 The main text of the Ada Reference Manual describes the required
13845 behavior of all Ada compilers, and the GNAT compiler conforms to
13846 these requirements.
13848 In addition, there are sections throughout the Ada Reference Manual headed
13849 by the phrase 'Implementation advice'. These sections are not normative,
13850 i.e., they do not specify requirements that all compilers must
13851 follow. Rather they provide advice on generally desirable behavior.
13852 They are not requirements, because they describe behavior that cannot
13853 be provided on all systems, or may be undesirable on some systems.
13855 As far as practical, GNAT follows the implementation advice in
13856 the Ada Reference Manual. Each such RM section corresponds to a section
13857 in this chapter whose title specifies the
13858 RM section number and paragraph number and the subject of
13859 the advice. The contents of each section consists of the RM text within
13861 followed by the GNAT interpretation of the advice. Most often, this simply says
13862 'followed', which means that GNAT follows the advice. However, in a
13863 number of cases, GNAT deliberately deviates from this advice, in which
13864 case the text describes what GNAT does and why.
13866 @geindex Error detection
13869 * RM 1.1.3(20); Error Detection: RM 1 1 3 20 Error Detection.
13870 * RM 1.1.3(31); Child Units: RM 1 1 3 31 Child Units.
13871 * RM 1.1.5(12); Bounded Errors: RM 1 1 5 12 Bounded Errors.
13872 * RM 2.8(16); Pragmas: RM 2 8 16 Pragmas.
13873 * RM 2.8(17-19); Pragmas: RM 2 8 17-19 Pragmas.
13874 * RM 3.5.2(5); Alternative Character Sets: RM 3 5 2 5 Alternative Character Sets.
13875 * RM 3.5.4(28); Integer Types: RM 3 5 4 28 Integer Types.
13876 * RM 3.5.4(29); Integer Types: RM 3 5 4 29 Integer Types.
13877 * RM 3.5.5(8); Enumeration Values: RM 3 5 5 8 Enumeration Values.
13878 * RM 3.5.7(17); Float Types: RM 3 5 7 17 Float Types.
13879 * RM 3.6.2(11); Multidimensional Arrays: RM 3 6 2 11 Multidimensional Arrays.
13880 * RM 9.6(30-31); Duration'Small: RM 9 6 30-31 Duration'Small.
13881 * RM 10.2.1(12); Consistent Representation: RM 10 2 1 12 Consistent Representation.
13882 * RM 11.4.1(19); Exception Information: RM 11 4 1 19 Exception Information.
13883 * RM 11.5(28); Suppression of Checks: RM 11 5 28 Suppression of Checks.
13884 * RM 13.1 (21-24); Representation Clauses: RM 13 1 21-24 Representation Clauses.
13885 * RM 13.2(6-8); Packed Types: RM 13 2 6-8 Packed Types.
13886 * RM 13.3(14-19); Address Clauses: RM 13 3 14-19 Address Clauses.
13887 * RM 13.3(29-35); Alignment Clauses: RM 13 3 29-35 Alignment Clauses.
13888 * RM 13.3(42-43); Size Clauses: RM 13 3 42-43 Size Clauses.
13889 * RM 13.3(50-56); Size Clauses: RM 13 3 50-56 Size Clauses.
13890 * RM 13.3(71-73); Component Size Clauses: RM 13 3 71-73 Component Size Clauses.
13891 * RM 13.4(9-10); Enumeration Representation Clauses: RM 13 4 9-10 Enumeration Representation Clauses.
13892 * RM 13.5.1(17-22); Record Representation Clauses: RM 13 5 1 17-22 Record Representation Clauses.
13893 * RM 13.5.2(5); Storage Place Attributes: RM 13 5 2 5 Storage Place Attributes.
13894 * RM 13.5.3(7-8); Bit Ordering: RM 13 5 3 7-8 Bit Ordering.
13895 * RM 13.7(37); Address as Private: RM 13 7 37 Address as Private.
13896 * RM 13.7.1(16); Address Operations: RM 13 7 1 16 Address Operations.
13897 * RM 13.9(14-17); Unchecked Conversion: RM 13 9 14-17 Unchecked Conversion.
13898 * RM 13.11(23-25); Implicit Heap Usage: RM 13 11 23-25 Implicit Heap Usage.
13899 * RM 13.11.2(17); Unchecked Deallocation: RM 13 11 2 17 Unchecked Deallocation.
13900 * RM 13.13.2(1.6); Stream Oriented Attributes: RM 13 13 2 1 6 Stream Oriented Attributes.
13901 * RM A.1(52); Names of Predefined Numeric Types: RM A 1 52 Names of Predefined Numeric Types.
13902 * RM A.3.2(49); Ada.Characters.Handling: RM A 3 2 49 Ada Characters Handling.
13903 * RM A.4.4(106); Bounded-Length String Handling: RM A 4 4 106 Bounded-Length String Handling.
13904 * RM A.5.2(46-47); Random Number Generation: RM A 5 2 46-47 Random Number Generation.
13905 * RM A.10.7(23); Get_Immediate: RM A 10 7 23 Get_Immediate.
13906 * RM B.1(39-41); Pragma Export: RM B 1 39-41 Pragma Export.
13907 * RM B.2(12-13); Package Interfaces: RM B 2 12-13 Package Interfaces.
13908 * RM B.3(63-71); Interfacing with C: RM B 3 63-71 Interfacing with C.
13909 * RM B.4(95-98); Interfacing with COBOL: RM B 4 95-98 Interfacing with COBOL.
13910 * RM B.5(22-26); Interfacing with Fortran: RM B 5 22-26 Interfacing with Fortran.
13911 * RM C.1(3-5); Access to Machine Operations: RM C 1 3-5 Access to Machine Operations.
13912 * RM C.1(10-16); Access to Machine Operations: RM C 1 10-16 Access to Machine Operations.
13913 * RM C.3(28); Interrupt Support: RM C 3 28 Interrupt Support.
13914 * RM C.3.1(20-21); Protected Procedure Handlers: RM C 3 1 20-21 Protected Procedure Handlers.
13915 * RM C.3.2(25); Package Interrupts: RM C 3 2 25 Package Interrupts.
13916 * RM C.4(14); Pre-elaboration Requirements: RM C 4 14 Pre-elaboration Requirements.
13917 * RM C.5(8); Pragma Discard_Names: RM C 5 8 Pragma Discard_Names.
13918 * RM C.7.2(30); The Package Task_Attributes: RM C 7 2 30 The Package Task_Attributes.
13919 * RM D.3(17); Locking Policies: RM D 3 17 Locking Policies.
13920 * RM D.4(16); Entry Queuing Policies: RM D 4 16 Entry Queuing Policies.
13921 * RM D.6(9-10); Preemptive Abort: RM D 6 9-10 Preemptive Abort.
13922 * RM D.7(21); Tasking Restrictions: RM D 7 21 Tasking Restrictions.
13923 * RM D.8(47-49); Monotonic Time: RM D 8 47-49 Monotonic Time.
13924 * RM E.5(28-29); Partition Communication Subsystem: RM E 5 28-29 Partition Communication Subsystem.
13925 * RM F(7); COBOL Support: RM F 7 COBOL Support.
13926 * RM F.1(2); Decimal Radix Support: RM F 1 2 Decimal Radix Support.
13927 * RM G; Numerics: RM G Numerics.
13928 * RM G.1.1(56-58); Complex Types: RM G 1 1 56-58 Complex Types.
13929 * RM G.1.2(49); Complex Elementary Functions: RM G 1 2 49 Complex Elementary Functions.
13930 * RM G.2.4(19); Accuracy Requirements: RM G 2 4 19 Accuracy Requirements.
13931 * RM G.2.6(15); Complex Arithmetic Accuracy: RM G 2 6 15 Complex Arithmetic Accuracy.
13932 * RM H.6(15/2); Pragma Partition_Elaboration_Policy: RM H 6 15/2 Pragma Partition_Elaboration_Policy.
13936 @node RM 1 1 3 20 Error Detection,RM 1 1 3 31 Child Units,,Implementation Advice
13937 @anchor{gnat_rm/implementation_advice rm-1-1-3-20-error-detection}@anchor{216}
13938 @section RM 1.1.3(20): Error Detection
13943 "If an implementation detects the use of an unsupported Specialized Needs
13944 Annex feature at run time, it should raise @code{Program_Error} if
13948 Not relevant. All specialized needs annex features are either supported,
13949 or diagnosed at compile time.
13951 @geindex Child Units
13953 @node RM 1 1 3 31 Child Units,RM 1 1 5 12 Bounded Errors,RM 1 1 3 20 Error Detection,Implementation Advice
13954 @anchor{gnat_rm/implementation_advice rm-1-1-3-31-child-units}@anchor{217}
13955 @section RM 1.1.3(31): Child Units
13960 "If an implementation wishes to provide implementation-defined
13961 extensions to the functionality of a language-defined library unit, it
13962 should normally do so by adding children to the library unit."
13967 @geindex Bounded errors
13969 @node RM 1 1 5 12 Bounded Errors,RM 2 8 16 Pragmas,RM 1 1 3 31 Child Units,Implementation Advice
13970 @anchor{gnat_rm/implementation_advice rm-1-1-5-12-bounded-errors}@anchor{218}
13971 @section RM 1.1.5(12): Bounded Errors
13976 "If an implementation detects a bounded error or erroneous
13977 execution, it should raise @code{Program_Error}."
13980 Followed in all cases in which the implementation detects a bounded
13981 error or erroneous execution. Not all such situations are detected at
13986 @node RM 2 8 16 Pragmas,RM 2 8 17-19 Pragmas,RM 1 1 5 12 Bounded Errors,Implementation Advice
13987 @anchor{gnat_rm/implementation_advice id2}@anchor{219}@anchor{gnat_rm/implementation_advice rm-2-8-16-pragmas}@anchor{21a}
13988 @section RM 2.8(16): Pragmas
13993 "Normally, implementation-defined pragmas should have no semantic effect
13994 for error-free programs; that is, if the implementation-defined pragmas
13995 are removed from a working program, the program should still be legal,
13996 and should still have the same semantics."
13999 The following implementation defined pragmas are exceptions to this
14003 @multitable {xxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxx}
14046 @emph{CPP_Constructor}
14062 @emph{Interface_Name}
14070 @emph{Machine_Attribute}
14078 @emph{Unimplemented_Unit}
14086 @emph{Unchecked_Union}
14095 In each of the above cases, it is essential to the purpose of the pragma
14096 that this advice not be followed. For details see
14097 @ref{7,,Implementation Defined Pragmas}.
14099 @node RM 2 8 17-19 Pragmas,RM 3 5 2 5 Alternative Character Sets,RM 2 8 16 Pragmas,Implementation Advice
14100 @anchor{gnat_rm/implementation_advice rm-2-8-17-19-pragmas}@anchor{21b}
14101 @section RM 2.8(17-19): Pragmas
14106 "Normally, an implementation should not define pragmas that can
14107 make an illegal program legal, except as follows:
14113 A pragma used to complete a declaration, such as a pragma @code{Import};
14116 A pragma used to configure the environment by adding, removing, or
14117 replacing @code{library_items}."
14121 See @ref{21a,,RM 2.8(16); Pragmas}.
14123 @geindex Character Sets
14125 @geindex Alternative Character Sets
14127 @node RM 3 5 2 5 Alternative Character Sets,RM 3 5 4 28 Integer Types,RM 2 8 17-19 Pragmas,Implementation Advice
14128 @anchor{gnat_rm/implementation_advice rm-3-5-2-5-alternative-character-sets}@anchor{21c}
14129 @section RM 3.5.2(5): Alternative Character Sets
14134 "If an implementation supports a mode with alternative interpretations
14135 for @code{Character} and @code{Wide_Character}, the set of graphic
14136 characters of @code{Character} should nevertheless remain a proper
14137 subset of the set of graphic characters of @code{Wide_Character}. Any
14138 character set 'localizations' should be reflected in the results of
14139 the subprograms defined in the language-defined package
14140 @code{Characters.Handling} (see A.3) available in such a mode. In a mode with
14141 an alternative interpretation of @code{Character}, the implementation should
14142 also support a corresponding change in what is a legal
14143 @code{identifier_letter}."
14146 Not all wide character modes follow this advice, in particular the JIS
14147 and IEC modes reflect standard usage in Japan, and in these encoding,
14148 the upper half of the Latin-1 set is not part of the wide-character
14149 subset, since the most significant bit is used for wide character
14150 encoding. However, this only applies to the external forms. Internally
14151 there is no such restriction.
14153 @geindex Integer types
14155 @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
14156 @anchor{gnat_rm/implementation_advice rm-3-5-4-28-integer-types}@anchor{21d}
14157 @section RM 3.5.4(28): Integer Types
14162 "An implementation should support @code{Long_Integer} in addition to
14163 @code{Integer} if the target machine supports 32-bit (or longer)
14164 arithmetic. No other named integer subtypes are recommended for package
14165 @code{Standard}. Instead, appropriate named integer subtypes should be
14166 provided in the library package @code{Interfaces} (see B.2)."
14169 @code{Long_Integer} is supported. Other standard integer types are supported
14170 so this advice is not fully followed. These types
14171 are supported for convenient interface to C, and so that all hardware
14172 types of the machine are easily available.
14174 @node RM 3 5 4 29 Integer Types,RM 3 5 5 8 Enumeration Values,RM 3 5 4 28 Integer Types,Implementation Advice
14175 @anchor{gnat_rm/implementation_advice rm-3-5-4-29-integer-types}@anchor{21e}
14176 @section RM 3.5.4(29): Integer Types
14181 "An implementation for a two's complement machine should support
14182 modular types with a binary modulus up to @code{System.Max_Int*2+2}. An
14183 implementation should support a non-binary modules up to @code{Integer'Last}."
14188 @geindex Enumeration values
14190 @node RM 3 5 5 8 Enumeration Values,RM 3 5 7 17 Float Types,RM 3 5 4 29 Integer Types,Implementation Advice
14191 @anchor{gnat_rm/implementation_advice rm-3-5-5-8-enumeration-values}@anchor{21f}
14192 @section RM 3.5.5(8): Enumeration Values
14197 "For the evaluation of a call on @code{S'Pos} for an enumeration
14198 subtype, if the value of the operand does not correspond to the internal
14199 code for any enumeration literal of its type (perhaps due to an
14200 un-initialized variable), then the implementation should raise
14201 @code{Program_Error}. This is particularly important for enumeration
14202 types with noncontiguous internal codes specified by an
14203 enumeration_representation_clause."
14208 @geindex Float types
14210 @node RM 3 5 7 17 Float Types,RM 3 6 2 11 Multidimensional Arrays,RM 3 5 5 8 Enumeration Values,Implementation Advice
14211 @anchor{gnat_rm/implementation_advice rm-3-5-7-17-float-types}@anchor{220}
14212 @section RM 3.5.7(17): Float Types
14217 "An implementation should support @code{Long_Float} in addition to
14218 @code{Float} if the target machine supports 11 or more digits of
14219 precision. No other named floating point subtypes are recommended for
14220 package @code{Standard}. Instead, appropriate named floating point subtypes
14221 should be provided in the library package @code{Interfaces} (see B.2)."
14224 @code{Short_Float} and @code{Long_Long_Float} are also provided. The
14225 former provides improved compatibility with other implementations
14226 supporting this type. The latter corresponds to the highest precision
14227 floating-point type supported by the hardware. On most machines, this
14228 will be the same as @code{Long_Float}, but on some machines, it will
14229 correspond to the IEEE extended form. The notable case is all ia32
14230 (x86) implementations, where @code{Long_Long_Float} corresponds to
14231 the 80-bit extended precision format supported in hardware on this
14232 processor. Note that the 128-bit format on SPARC is not supported,
14233 since this is a software rather than a hardware format.
14235 @geindex Multidimensional arrays
14238 @geindex multidimensional
14240 @node RM 3 6 2 11 Multidimensional Arrays,RM 9 6 30-31 Duration'Small,RM 3 5 7 17 Float Types,Implementation Advice
14241 @anchor{gnat_rm/implementation_advice rm-3-6-2-11-multidimensional-arrays}@anchor{221}
14242 @section RM 3.6.2(11): Multidimensional Arrays
14247 "An implementation should normally represent multidimensional arrays in
14248 row-major order, consistent with the notation used for multidimensional
14249 array aggregates (see 4.3.3). However, if a pragma @code{Convention}
14250 (@code{Fortran}, ...) applies to a multidimensional array type, then
14251 column-major order should be used instead (see B.5, @emph{Interfacing with Fortran})."
14256 @geindex Duration'Small
14258 @node RM 9 6 30-31 Duration'Small,RM 10 2 1 12 Consistent Representation,RM 3 6 2 11 Multidimensional Arrays,Implementation Advice
14259 @anchor{gnat_rm/implementation_advice rm-9-6-30-31-duration-small}@anchor{222}
14260 @section RM 9.6(30-31): Duration'Small
14265 "Whenever possible in an implementation, the value of @code{Duration'Small}
14266 should be no greater than 100 microseconds."
14269 Followed. (@code{Duration'Small} = 10**(-9)).
14273 "The time base for @code{delay_relative_statements} should be monotonic;
14274 it need not be the same time base as used for @code{Calendar.Clock}."
14279 @node RM 10 2 1 12 Consistent Representation,RM 11 4 1 19 Exception Information,RM 9 6 30-31 Duration'Small,Implementation Advice
14280 @anchor{gnat_rm/implementation_advice rm-10-2-1-12-consistent-representation}@anchor{223}
14281 @section RM 10.2.1(12): Consistent Representation
14286 "In an implementation, a type declared in a pre-elaborated package should
14287 have the same representation in every elaboration of a given version of
14288 the package, whether the elaborations occur in distinct executions of
14289 the same program, or in executions of distinct programs or partitions
14290 that include the given version."
14293 Followed, except in the case of tagged types. Tagged types involve
14294 implicit pointers to a local copy of a dispatch table, and these pointers
14295 have representations which thus depend on a particular elaboration of the
14296 package. It is not easy to see how it would be possible to follow this
14297 advice without severely impacting efficiency of execution.
14299 @geindex Exception information
14301 @node RM 11 4 1 19 Exception Information,RM 11 5 28 Suppression of Checks,RM 10 2 1 12 Consistent Representation,Implementation Advice
14302 @anchor{gnat_rm/implementation_advice rm-11-4-1-19-exception-information}@anchor{224}
14303 @section RM 11.4.1(19): Exception Information
14308 "@code{Exception_Message} by default and @code{Exception_Information}
14309 should produce information useful for
14310 debugging. @code{Exception_Message} should be short, about one
14311 line. @code{Exception_Information} can be long. @code{Exception_Message}
14312 should not include the
14313 @code{Exception_Name}. @code{Exception_Information} should include both
14314 the @code{Exception_Name} and the @code{Exception_Message}."
14317 Followed. For each exception that doesn't have a specified
14318 @code{Exception_Message}, the compiler generates one containing the location
14319 of the raise statement. This location has the form 'file_name:line', where
14320 file_name is the short file name (without path information) and line is the line
14321 number in the file. Note that in the case of the Zero Cost Exception
14322 mechanism, these messages become redundant with the Exception_Information that
14323 contains a full backtrace of the calling sequence, so they are disabled.
14324 To disable explicitly the generation of the source location message, use the
14325 Pragma @code{Discard_Names}.
14327 @geindex Suppression of checks
14330 @geindex suppression of
14332 @node RM 11 5 28 Suppression of Checks,RM 13 1 21-24 Representation Clauses,RM 11 4 1 19 Exception Information,Implementation Advice
14333 @anchor{gnat_rm/implementation_advice rm-11-5-28-suppression-of-checks}@anchor{225}
14334 @section RM 11.5(28): Suppression of Checks
14339 "The implementation should minimize the code executed for checks that
14340 have been suppressed."
14345 @geindex Representation clauses
14347 @node RM 13 1 21-24 Representation Clauses,RM 13 2 6-8 Packed Types,RM 11 5 28 Suppression of Checks,Implementation Advice
14348 @anchor{gnat_rm/implementation_advice rm-13-1-21-24-representation-clauses}@anchor{226}
14349 @section RM 13.1 (21-24): Representation Clauses
14354 "The recommended level of support for all representation items is
14355 qualified as follows:
14357 An implementation need not support representation items containing
14358 nonstatic expressions, except that an implementation should support a
14359 representation item for a given entity if each nonstatic expression in
14360 the representation item is a name that statically denotes a constant
14361 declared before the entity."
14364 Followed. In fact, GNAT goes beyond the recommended level of support
14365 by allowing nonstatic expressions in some representation clauses even
14366 without the need to declare constants initialized with the values of
14373 for Y'Address use X'Address;>>
14376 "An implementation need not support a specification for the `@w{`}Size`@w{`}
14377 for a given composite subtype, nor the size or storage place for an
14378 object (including a component) of a given composite subtype, unless the
14379 constraints on the subtype and its composite subcomponents (if any) are
14380 all static constraints."
14383 Followed. Size Clauses are not permitted on nonstatic components, as
14388 "An aliased component, or a component whose type is by-reference, should
14389 always be allocated at an addressable location."
14394 @geindex Packed types
14396 @node RM 13 2 6-8 Packed Types,RM 13 3 14-19 Address Clauses,RM 13 1 21-24 Representation Clauses,Implementation Advice
14397 @anchor{gnat_rm/implementation_advice rm-13-2-6-8-packed-types}@anchor{227}
14398 @section RM 13.2(6-8): Packed Types
14403 "If a type is packed, then the implementation should try to minimize
14404 storage allocated to objects of the type, possibly at the expense of
14405 speed of accessing components, subject to reasonable complexity in
14406 addressing calculations.
14408 The recommended level of support pragma @code{Pack} is:
14410 For a packed record type, the components should be packed as tightly as
14411 possible subject to the Sizes of the component subtypes, and subject to
14412 any @emph{record_representation_clause} that applies to the type; the
14413 implementation may, but need not, reorder components or cross aligned
14414 word boundaries to improve the packing. A component whose @code{Size} is
14415 greater than the word size may be allocated an integral number of words."
14418 Followed. Tight packing of arrays is supported for all component sizes
14419 up to 64-bits. If the array component size is 1 (that is to say, if
14420 the component is a boolean type or an enumeration type with two values)
14421 then values of the type are implicitly initialized to zero. This
14422 happens both for objects of the packed type, and for objects that have a
14423 subcomponent of the packed type.
14427 "An implementation should support Address clauses for imported
14433 @geindex Address clauses
14435 @node RM 13 3 14-19 Address Clauses,RM 13 3 29-35 Alignment Clauses,RM 13 2 6-8 Packed Types,Implementation Advice
14436 @anchor{gnat_rm/implementation_advice rm-13-3-14-19-address-clauses}@anchor{228}
14437 @section RM 13.3(14-19): Address Clauses
14442 "For an array @code{X}, @code{X'Address} should point at the first
14443 component of the array, and not at the array bounds."
14450 "The recommended level of support for the @code{Address} attribute is:
14452 @code{X'Address} should produce a useful result if @code{X} is an
14453 object that is aliased or of a by-reference type, or is an entity whose
14454 @code{Address} has been specified."
14457 Followed. A valid address will be produced even if none of those
14458 conditions have been met. If necessary, the object is forced into
14459 memory to ensure the address is valid.
14463 "An implementation should support @code{Address} clauses for imported
14471 "Objects (including subcomponents) that are aliased or of a by-reference
14472 type should be allocated on storage element boundaries."
14479 "If the @code{Address} of an object is specified, or it is imported or exported,
14480 then the implementation should not perform optimizations based on
14481 assumptions of no aliases."
14486 @geindex Alignment clauses
14488 @node RM 13 3 29-35 Alignment Clauses,RM 13 3 42-43 Size Clauses,RM 13 3 14-19 Address Clauses,Implementation Advice
14489 @anchor{gnat_rm/implementation_advice rm-13-3-29-35-alignment-clauses}@anchor{229}
14490 @section RM 13.3(29-35): Alignment Clauses
14495 "The recommended level of support for the @code{Alignment} attribute for
14498 An implementation should support specified Alignments that are factors
14499 and multiples of the number of storage elements per word, subject to the
14507 "An implementation need not support specified Alignments for
14508 combinations of Sizes and Alignments that cannot be easily
14509 loaded and stored by available machine instructions."
14516 "An implementation need not support specified Alignments that are
14517 greater than the maximum @code{Alignment} the implementation ever returns by
14525 "The recommended level of support for the @code{Alignment} attribute for
14528 Same as above, for subtypes, but in addition:"
14535 "For stand-alone library-level objects of statically constrained
14536 subtypes, the implementation should support all alignments
14537 supported by the target linker. For example, page alignment is likely to
14538 be supported for such objects, but not for subtypes."
14543 @geindex Size clauses
14545 @node RM 13 3 42-43 Size Clauses,RM 13 3 50-56 Size Clauses,RM 13 3 29-35 Alignment Clauses,Implementation Advice
14546 @anchor{gnat_rm/implementation_advice rm-13-3-42-43-size-clauses}@anchor{22a}
14547 @section RM 13.3(42-43): Size Clauses
14552 "The recommended level of support for the @code{Size} attribute of
14555 A @code{Size} clause should be supported for an object if the specified
14556 @code{Size} is at least as large as its subtype's @code{Size}, and
14557 corresponds to a size in storage elements that is a multiple of the
14558 object's @code{Alignment} (if the @code{Alignment} is nonzero)."
14563 @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
14564 @anchor{gnat_rm/implementation_advice rm-13-3-50-56-size-clauses}@anchor{22b}
14565 @section RM 13.3(50-56): Size Clauses
14570 "If the @code{Size} of a subtype is specified, and allows for efficient
14571 independent addressability (see 9.10) on the target architecture, then
14572 the @code{Size} of the following objects of the subtype should equal the
14573 @code{Size} of the subtype:
14575 Aliased objects (including components)."
14582 "@cite{Size} clause on a composite subtype should not affect the
14583 internal layout of components."
14586 Followed. But note that this can be overridden by use of the implementation
14587 pragma Implicit_Packing in the case of packed arrays.
14591 "The recommended level of support for the @code{Size} attribute of subtypes is:
14593 The @code{Size} (if not specified) of a static discrete or fixed point
14594 subtype should be the number of bits needed to represent each value
14595 belonging to the subtype using an unbiased representation, leaving space
14596 for a sign bit only if the subtype contains negative values. If such a
14597 subtype is a first subtype, then an implementation should support a
14598 specified @code{Size} for it that reflects this representation."
14605 "For a subtype implemented with levels of indirection, the @code{Size}
14606 should include the size of the pointers, but not the size of what they
14612 @geindex Component_Size clauses
14614 @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
14615 @anchor{gnat_rm/implementation_advice rm-13-3-71-73-component-size-clauses}@anchor{22c}
14616 @section RM 13.3(71-73): Component Size Clauses
14621 "The recommended level of support for the @code{Component_Size}
14624 An implementation need not support specified @code{Component_Sizes} that are
14625 less than the @code{Size} of the component subtype."
14632 "An implementation should support specified Component_Sizes that
14633 are factors and multiples of the word size. For such
14634 Component_Sizes, the array should contain no gaps between
14635 components. For other Component_Sizes (if supported), the array
14636 should contain no gaps between components when packing is also
14637 specified; the implementation should forbid this combination in cases
14638 where it cannot support a no-gaps representation."
14643 @geindex Enumeration representation clauses
14645 @geindex Representation clauses
14646 @geindex enumeration
14648 @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
14649 @anchor{gnat_rm/implementation_advice rm-13-4-9-10-enumeration-representation-clauses}@anchor{22d}
14650 @section RM 13.4(9-10): Enumeration Representation Clauses
14655 "The recommended level of support for enumeration representation clauses
14658 An implementation need not support enumeration representation clauses
14659 for boolean types, but should at minimum support the internal codes in
14660 the range @code{System.Min_Int .. System.Max_Int}."
14665 @geindex Record representation clauses
14667 @geindex Representation clauses
14670 @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
14671 @anchor{gnat_rm/implementation_advice rm-13-5-1-17-22-record-representation-clauses}@anchor{22e}
14672 @section RM 13.5.1(17-22): Record Representation Clauses
14677 "The recommended level of support for
14678 @emph{record_representation_clause}s is:
14680 An implementation should support storage places that can be extracted
14681 with a load, mask, shift sequence of machine code, and set with a load,
14682 shift, mask, store sequence, given the available machine instructions
14683 and run-time model."
14690 "A storage place should be supported if its size is equal to the
14691 @code{Size} of the component subtype, and it starts and ends on a
14692 boundary that obeys the @code{Alignment} of the component subtype."
14699 "If the default bit ordering applies to the declaration of a given type,
14700 then for a component whose subtype's @code{Size} is less than the word
14701 size, any storage place that does not cross an aligned word boundary
14702 should be supported."
14709 "An implementation may reserve a storage place for the tag field of a
14710 tagged type, and disallow other components from overlapping that place."
14713 Followed. The storage place for the tag field is the beginning of the tagged
14714 record, and its size is Address'Size. GNAT will reject an explicit component
14715 clause for the tag field.
14719 "An implementation need not support a @emph{component_clause} for a
14720 component of an extension part if the storage place is not after the
14721 storage places of all components of the parent type, whether or not
14722 those storage places had been specified."
14725 Followed. The above advice on record representation clauses is followed,
14726 and all mentioned features are implemented.
14728 @geindex Storage place attributes
14730 @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
14731 @anchor{gnat_rm/implementation_advice rm-13-5-2-5-storage-place-attributes}@anchor{22f}
14732 @section RM 13.5.2(5): Storage Place Attributes
14737 "If a component is represented using some form of pointer (such as an
14738 offset) to the actual data of the component, and this data is contiguous
14739 with the rest of the object, then the storage place attributes should
14740 reflect the place of the actual data, not the pointer. If a component is
14741 allocated discontinuously from the rest of the object, then a warning
14742 should be generated upon reference to one of its storage place
14746 Followed. There are no such components in GNAT.
14748 @geindex Bit ordering
14750 @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
14751 @anchor{gnat_rm/implementation_advice rm-13-5-3-7-8-bit-ordering}@anchor{230}
14752 @section RM 13.5.3(7-8): Bit Ordering
14757 "The recommended level of support for the non-default bit ordering is:
14759 If @code{Word_Size} = @code{Storage_Unit}, then the implementation
14760 should support the non-default bit ordering in addition to the default
14764 Followed. Word size does not equal storage size in this implementation.
14765 Thus non-default bit ordering is not supported.
14768 @geindex as private type
14770 @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
14771 @anchor{gnat_rm/implementation_advice rm-13-7-37-address-as-private}@anchor{231}
14772 @section RM 13.7(37): Address as Private
14777 "@cite{Address} should be of a private type."
14782 @geindex Operations
14783 @geindex on `@w{`}Address`@w{`}
14786 @geindex operations of
14788 @node RM 13 7 1 16 Address Operations,RM 13 9 14-17 Unchecked Conversion,RM 13 7 37 Address as Private,Implementation Advice
14789 @anchor{gnat_rm/implementation_advice rm-13-7-1-16-address-operations}@anchor{232}
14790 @section RM 13.7.1(16): Address Operations
14795 "Operations in @code{System} and its children should reflect the target
14796 environment semantics as closely as is reasonable. For example, on most
14797 machines, it makes sense for address arithmetic to 'wrap around'.
14798 Operations that do not make sense should raise @code{Program_Error}."
14801 Followed. Address arithmetic is modular arithmetic that wraps around. No
14802 operation raises @code{Program_Error}, since all operations make sense.
14804 @geindex Unchecked conversion
14806 @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
14807 @anchor{gnat_rm/implementation_advice rm-13-9-14-17-unchecked-conversion}@anchor{233}
14808 @section RM 13.9(14-17): Unchecked Conversion
14813 "The @code{Size} of an array object should not include its bounds; hence,
14814 the bounds should not be part of the converted data."
14821 "The implementation should not generate unnecessary run-time checks to
14822 ensure that the representation of @code{S} is a representation of the
14823 target type. It should take advantage of the permission to return by
14824 reference when possible. Restrictions on unchecked conversions should be
14825 avoided unless required by the target environment."
14828 Followed. There are no restrictions on unchecked conversion. A warning is
14829 generated if the source and target types do not have the same size since
14830 the semantics in this case may be target dependent.
14834 "The recommended level of support for unchecked conversions is:
14836 Unchecked conversions should be supported and should be reversible in
14837 the cases where this clause defines the result. To enable meaningful use
14838 of unchecked conversion, a contiguous representation should be used for
14839 elementary subtypes, for statically constrained array subtypes whose
14840 component subtype is one of the subtypes described in this paragraph,
14841 and for record subtypes without discriminants whose component subtypes
14842 are described in this paragraph."
14847 @geindex Heap usage
14850 @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
14851 @anchor{gnat_rm/implementation_advice rm-13-11-23-25-implicit-heap-usage}@anchor{234}
14852 @section RM 13.11(23-25): Implicit Heap Usage
14857 "An implementation should document any cases in which it dynamically
14858 allocates heap storage for a purpose other than the evaluation of an
14862 Followed, the only other points at which heap storage is dynamically
14863 allocated are as follows:
14869 At initial elaboration time, to allocate dynamically sized global
14873 To allocate space for a task when a task is created.
14876 To extend the secondary stack dynamically when needed. The secondary
14877 stack is used for returning variable length results.
14883 "A default (implementation-provided) storage pool for an
14884 access-to-constant type should not have overhead to support deallocation of
14885 individual objects."
14892 "A storage pool for an anonymous access type should be created at the
14893 point of an allocator for the type, and be reclaimed when the designated
14894 object becomes inaccessible."
14899 @geindex Unchecked deallocation
14901 @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
14902 @anchor{gnat_rm/implementation_advice rm-13-11-2-17-unchecked-deallocation}@anchor{235}
14903 @section RM 13.11.2(17): Unchecked Deallocation
14908 "For a standard storage pool, @code{Free} should actually reclaim the
14914 @geindex Stream oriented attributes
14916 @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
14917 @anchor{gnat_rm/implementation_advice rm-13-13-2-1-6-stream-oriented-attributes}@anchor{236}
14918 @section RM 13.13.2(1.6): Stream Oriented Attributes
14923 "If not specified, the value of Stream_Size for an elementary type
14924 should be the number of bits that corresponds to the minimum number of
14925 stream elements required by the first subtype of the type, rounded up
14926 to the nearest factor or multiple of the word size that is also a
14927 multiple of the stream element size."
14930 Followed, except that the number of stream elements is a power of 2.
14931 The Stream_Size may be used to override the default choice.
14933 However, such an implementation is based on direct binary
14934 representations and is therefore target- and endianness-dependent. To
14935 address this issue, GNAT also supplies an alternate implementation of
14936 the stream attributes @code{Read} and @code{Write}, which uses the
14937 target-independent XDR standard representation for scalar types.
14939 @geindex XDR representation
14941 @geindex Read attribute
14943 @geindex Write attribute
14945 @geindex Stream oriented attributes
14947 The XDR implementation is provided as an alternative body of the
14948 @code{System.Stream_Attributes} package, in the file
14949 @code{s-stratt-xdr.adb} in the GNAT library.
14950 There is no @code{s-stratt-xdr.ads} file.
14951 In order to install the XDR implementation, do the following:
14957 Replace the default implementation of the
14958 @code{System.Stream_Attributes} package with the XDR implementation.
14959 For example on a Unix platform issue the commands:
14962 $ mv s-stratt.adb s-stratt-default.adb
14963 $ mv s-stratt-xdr.adb s-stratt.adb
14967 Rebuild the GNAT run-time library as documented in
14968 the @emph{GNAT and Libraries} section of the @cite{GNAT User's Guide}.
14971 @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
14972 @anchor{gnat_rm/implementation_advice rm-a-1-52-names-of-predefined-numeric-types}@anchor{237}
14973 @section RM A.1(52): Names of Predefined Numeric Types
14978 "If an implementation provides additional named predefined integer types,
14979 then the names should end with @code{Integer} as in
14980 @code{Long_Integer}. If an implementation provides additional named
14981 predefined floating point types, then the names should end with
14982 @code{Float} as in @code{Long_Float}."
14987 @geindex Ada.Characters.Handling
14989 @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
14990 @anchor{gnat_rm/implementation_advice rm-a-3-2-49-ada-characters-handling}@anchor{238}
14991 @section RM A.3.2(49): @code{Ada.Characters.Handling}
14996 "If an implementation provides a localized definition of @code{Character}
14997 or @code{Wide_Character}, then the effects of the subprograms in
14998 @code{Characters.Handling} should reflect the localizations.
15002 Followed. GNAT provides no such localized definitions.
15004 @geindex Bounded-length strings
15006 @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
15007 @anchor{gnat_rm/implementation_advice rm-a-4-4-106-bounded-length-string-handling}@anchor{239}
15008 @section RM A.4.4(106): Bounded-Length String Handling
15013 "Bounded string objects should not be implemented by implicit pointers
15014 and dynamic allocation."
15017 Followed. No implicit pointers or dynamic allocation are used.
15019 @geindex Random number generation
15021 @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
15022 @anchor{gnat_rm/implementation_advice rm-a-5-2-46-47-random-number-generation}@anchor{23a}
15023 @section RM A.5.2(46-47): Random Number Generation
15028 "Any storage associated with an object of type @code{Generator} should be
15029 reclaimed on exit from the scope of the object."
15036 "If the generator period is sufficiently long in relation to the number
15037 of distinct initiator values, then each possible value of
15038 @code{Initiator} passed to @code{Reset} should initiate a sequence of
15039 random numbers that does not, in a practical sense, overlap the sequence
15040 initiated by any other value. If this is not possible, then the mapping
15041 between initiator values and generator states should be a rapidly
15042 varying function of the initiator value."
15045 Followed. The generator period is sufficiently long for the first
15046 condition here to hold true.
15048 @geindex Get_Immediate
15050 @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
15051 @anchor{gnat_rm/implementation_advice rm-a-10-7-23-get-immediate}@anchor{23b}
15052 @section RM A.10.7(23): @code{Get_Immediate}
15057 "The @code{Get_Immediate} procedures should be implemented with
15058 unbuffered input. For a device such as a keyboard, input should be
15059 available if a key has already been typed, whereas for a disk
15060 file, input should always be available except at end of file. For a file
15061 associated with a keyboard-like device, any line-editing features of the
15062 underlying operating system should be disabled during the execution of
15063 @code{Get_Immediate}."
15066 Followed on all targets except VxWorks. For VxWorks, there is no way to
15067 provide this functionality that does not result in the input buffer being
15068 flushed before the @code{Get_Immediate} call. A special unit
15069 @code{Interfaces.Vxworks.IO} is provided that contains routines to enable
15070 this functionality.
15074 @node RM B 1 39-41 Pragma Export,RM B 2 12-13 Package Interfaces,RM A 10 7 23 Get_Immediate,Implementation Advice
15075 @anchor{gnat_rm/implementation_advice rm-b-1-39-41-pragma-export}@anchor{23c}
15076 @section RM B.1(39-41): Pragma @code{Export}
15081 "If an implementation supports pragma @code{Export} to a given language,
15082 then it should also allow the main subprogram to be written in that
15083 language. It should support some mechanism for invoking the elaboration
15084 of the Ada library units included in the system, and for invoking the
15085 finalization of the environment task. On typical systems, the
15086 recommended mechanism is to provide two subprograms whose link names are
15087 @code{adainit} and @code{adafinal}. @code{adainit} should contain the
15088 elaboration code for library units. @code{adafinal} should contain the
15089 finalization code. These subprograms should have no effect the second
15090 and subsequent time they are called."
15097 "Automatic elaboration of pre-elaborated packages should be
15098 provided when pragma @code{Export} is supported."
15101 Followed when the main program is in Ada. If the main program is in a
15102 foreign language, then
15103 @code{adainit} must be called to elaborate pre-elaborated
15108 "For each supported convention @emph{L} other than @code{Intrinsic}, an
15109 implementation should support @code{Import} and @code{Export} pragmas
15110 for objects of @emph{L}-compatible types and for subprograms, and pragma
15111 @cite{Convention} for @emph{L}-eligible types and for subprograms,
15112 presuming the other language has corresponding features. Pragma
15113 @code{Convention} need not be supported for scalar types."
15118 @geindex Package Interfaces
15120 @geindex Interfaces
15122 @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
15123 @anchor{gnat_rm/implementation_advice rm-b-2-12-13-package-interfaces}@anchor{23d}
15124 @section RM B.2(12-13): Package @code{Interfaces}
15129 "For each implementation-defined convention identifier, there should be a
15130 child package of package Interfaces with the corresponding name. This
15131 package should contain any declarations that would be useful for
15132 interfacing to the language (implementation) represented by the
15133 convention. Any declarations useful for interfacing to any language on
15134 the given hardware architecture should be provided directly in
15135 @code{Interfaces}."
15142 "An implementation supporting an interface to C, COBOL, or Fortran should
15143 provide the corresponding package or packages described in the following
15147 Followed. GNAT provides all the packages described in this section.
15150 @geindex interfacing with
15152 @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
15153 @anchor{gnat_rm/implementation_advice rm-b-3-63-71-interfacing-with-c}@anchor{23e}
15154 @section RM B.3(63-71): Interfacing with C
15159 "An implementation should support the following interface correspondences
15160 between Ada and C."
15167 "An Ada procedure corresponds to a void-returning C function."
15174 "An Ada function corresponds to a non-void C function."
15181 "An Ada @code{in} scalar parameter is passed as a scalar argument to a C
15189 "An Ada @code{in} parameter of an access-to-object type with designated
15190 type @code{T} is passed as a @code{t*} argument to a C function,
15191 where @code{t} is the C type corresponding to the Ada type @code{T}."
15198 "An Ada access @code{T} parameter, or an Ada @code{out} or @code{in out}
15199 parameter of an elementary type @code{T}, is passed as a @code{t*}
15200 argument to a C function, where @code{t} is the C type corresponding to
15201 the Ada type @code{T}. In the case of an elementary @code{out} or
15202 @code{in out} parameter, a pointer to a temporary copy is used to
15203 preserve by-copy semantics."
15210 "An Ada parameter of a record type @code{T}, of any mode, is passed as a
15211 @code{t*} argument to a C function, where @code{t} is the C
15212 structure corresponding to the Ada type @code{T}."
15215 Followed. This convention may be overridden by the use of the C_Pass_By_Copy
15216 pragma, or Convention, or by explicitly specifying the mechanism for a given
15217 call using an extended import or export pragma.
15221 "An Ada parameter of an array type with component type @code{T}, of any
15222 mode, is passed as a @code{t*} argument to a C function, where
15223 @code{t} is the C type corresponding to the Ada type @code{T}."
15230 "An Ada parameter of an access-to-subprogram type is passed as a pointer
15231 to a C function whose prototype corresponds to the designated
15232 subprogram's specification."
15238 @geindex interfacing with
15240 @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
15241 @anchor{gnat_rm/implementation_advice rm-b-4-95-98-interfacing-with-cobol}@anchor{23f}
15242 @section RM B.4(95-98): Interfacing with COBOL
15247 "An Ada implementation should support the following interface
15248 correspondences between Ada and COBOL."
15255 "An Ada access @code{T} parameter is passed as a @code{BY REFERENCE} data item of
15256 the COBOL type corresponding to @code{T}."
15263 "An Ada in scalar parameter is passed as a @code{BY CONTENT} data item of
15264 the corresponding COBOL type."
15271 "Any other Ada parameter is passed as a @code{BY REFERENCE} data item of the
15272 COBOL type corresponding to the Ada parameter type; for scalars, a local
15273 copy is used if necessary to ensure by-copy semantics."
15279 @geindex interfacing with
15281 @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
15282 @anchor{gnat_rm/implementation_advice rm-b-5-22-26-interfacing-with-fortran}@anchor{240}
15283 @section RM B.5(22-26): Interfacing with Fortran
15288 "An Ada implementation should support the following interface
15289 correspondences between Ada and Fortran:"
15296 "An Ada procedure corresponds to a Fortran subroutine."
15303 "An Ada function corresponds to a Fortran function."
15310 "An Ada parameter of an elementary, array, or record type @code{T} is
15311 passed as a @code{T} argument to a Fortran procedure, where @code{T} is
15312 the Fortran type corresponding to the Ada type @code{T}, and where the
15313 INTENT attribute of the corresponding dummy argument matches the Ada
15314 formal parameter mode; the Fortran implementation's parameter passing
15315 conventions are used. For elementary types, a local copy is used if
15316 necessary to ensure by-copy semantics."
15323 "An Ada parameter of an access-to-subprogram type is passed as a
15324 reference to a Fortran procedure whose interface corresponds to the
15325 designated subprogram's specification."
15330 @geindex Machine operations
15332 @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
15333 @anchor{gnat_rm/implementation_advice rm-c-1-3-5-access-to-machine-operations}@anchor{241}
15334 @section RM C.1(3-5): Access to Machine Operations
15339 "The machine code or intrinsic support should allow access to all
15340 operations normally available to assembly language programmers for the
15341 target environment, including privileged instructions, if any."
15348 "The interfacing pragmas (see Annex B) should support interface to
15349 assembler; the default assembler should be associated with the
15350 convention identifier @code{Assembler}."
15357 "If an entity is exported to assembly language, then the implementation
15358 should allocate it at an addressable location, and should ensure that it
15359 is retained by the linking process, even if not otherwise referenced
15360 from the Ada code. The implementation should assume that any call to a
15361 machine code or assembler subprogram is allowed to read or update every
15362 object that is specified as exported."
15367 @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
15368 @anchor{gnat_rm/implementation_advice rm-c-1-10-16-access-to-machine-operations}@anchor{242}
15369 @section RM C.1(10-16): Access to Machine Operations
15374 "The implementation should ensure that little or no overhead is
15375 associated with calling intrinsic and machine-code subprograms."
15378 Followed for both intrinsics and machine-code subprograms.
15382 "It is recommended that intrinsic subprograms be provided for convenient
15383 access to any machine operations that provide special capabilities or
15384 efficiency and that are not otherwise available through the language
15388 Followed. A full set of machine operation intrinsic subprograms is provided.
15392 "Atomic read-modify-write operations---e.g., test and set, compare and
15393 swap, decrement and test, enqueue/dequeue."
15396 Followed on any target supporting such operations.
15400 "Standard numeric functions---e.g.:, sin, log."
15403 Followed on any target supporting such operations.
15407 "String manipulation operations---e.g.:, translate and test."
15410 Followed on any target supporting such operations.
15414 "Vector operations---e.g.:, compare vector against thresholds."
15417 Followed on any target supporting such operations.
15421 "Direct operations on I/O ports."
15424 Followed on any target supporting such operations.
15426 @geindex Interrupt support
15428 @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
15429 @anchor{gnat_rm/implementation_advice rm-c-3-28-interrupt-support}@anchor{243}
15430 @section RM C.3(28): Interrupt Support
15435 "If the @code{Ceiling_Locking} policy is not in effect, the
15436 implementation should provide means for the application to specify which
15437 interrupts are to be blocked during protected actions, if the underlying
15438 system allows for a finer-grain control of interrupt blocking."
15441 Followed. The underlying system does not allow for finer-grain control
15442 of interrupt blocking.
15444 @geindex Protected procedure handlers
15446 @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
15447 @anchor{gnat_rm/implementation_advice rm-c-3-1-20-21-protected-procedure-handlers}@anchor{244}
15448 @section RM C.3.1(20-21): Protected Procedure Handlers
15453 "Whenever possible, the implementation should allow interrupt handlers to
15454 be called directly by the hardware."
15457 Followed on any target where the underlying operating system permits
15462 "Whenever practical, violations of any
15463 implementation-defined restrictions should be detected before run time."
15466 Followed. Compile time warnings are given when possible.
15468 @geindex Package `@w{`}Interrupts`@w{`}
15470 @geindex Interrupts
15472 @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
15473 @anchor{gnat_rm/implementation_advice rm-c-3-2-25-package-interrupts}@anchor{245}
15474 @section RM C.3.2(25): Package @code{Interrupts}
15479 "If implementation-defined forms of interrupt handler procedures are
15480 supported, such as protected procedures with parameters, then for each
15481 such form of a handler, a type analogous to @code{Parameterless_Handler}
15482 should be specified in a child package of @code{Interrupts}, with the
15483 same operations as in the predefined package Interrupts."
15488 @geindex Pre-elaboration requirements
15490 @node RM C 4 14 Pre-elaboration Requirements,RM C 5 8 Pragma Discard_Names,RM C 3 2 25 Package Interrupts,Implementation Advice
15491 @anchor{gnat_rm/implementation_advice rm-c-4-14-pre-elaboration-requirements}@anchor{246}
15492 @section RM C.4(14): Pre-elaboration Requirements
15497 "It is recommended that pre-elaborated packages be implemented in such a
15498 way that there should be little or no code executed at run time for the
15499 elaboration of entities not already covered by the Implementation
15503 Followed. Executable code is generated in some cases, e.g., loops
15504 to initialize large arrays.
15506 @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
15507 @anchor{gnat_rm/implementation_advice rm-c-5-8-pragma-discard-names}@anchor{247}
15508 @section RM C.5(8): Pragma @code{Discard_Names}
15513 "If the pragma applies to an entity, then the implementation should
15514 reduce the amount of storage used for storing names associated with that
15520 @geindex Package Task_Attributes
15522 @geindex Task_Attributes
15524 @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
15525 @anchor{gnat_rm/implementation_advice rm-c-7-2-30-the-package-task-attributes}@anchor{248}
15526 @section RM C.7.2(30): The Package Task_Attributes
15531 "Some implementations are targeted to domains in which memory use at run
15532 time must be completely deterministic. For such implementations, it is
15533 recommended that the storage for task attributes will be pre-allocated
15534 statically and not from the heap. This can be accomplished by either
15535 placing restrictions on the number and the size of the task's
15536 attributes, or by using the pre-allocated storage for the first @code{N}
15537 attribute objects, and the heap for the others. In the latter case,
15538 @code{N} should be documented."
15541 Not followed. This implementation is not targeted to such a domain.
15543 @geindex Locking Policies
15545 @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
15546 @anchor{gnat_rm/implementation_advice rm-d-3-17-locking-policies}@anchor{249}
15547 @section RM D.3(17): Locking Policies
15552 "The implementation should use names that end with @code{_Locking} for
15553 locking policies defined by the implementation."
15556 Followed. Two implementation-defined locking policies are defined,
15557 whose names (@code{Inheritance_Locking} and
15558 @code{Concurrent_Readers_Locking}) follow this suggestion.
15560 @geindex Entry queuing policies
15562 @node RM D 4 16 Entry Queuing Policies,RM D 6 9-10 Preemptive Abort,RM D 3 17 Locking Policies,Implementation Advice
15563 @anchor{gnat_rm/implementation_advice rm-d-4-16-entry-queuing-policies}@anchor{24a}
15564 @section RM D.4(16): Entry Queuing Policies
15569 "Names that end with @code{_Queuing} should be used
15570 for all implementation-defined queuing policies."
15573 Followed. No such implementation-defined queuing policies exist.
15575 @geindex Preemptive abort
15577 @node RM D 6 9-10 Preemptive Abort,RM D 7 21 Tasking Restrictions,RM D 4 16 Entry Queuing Policies,Implementation Advice
15578 @anchor{gnat_rm/implementation_advice rm-d-6-9-10-preemptive-abort}@anchor{24b}
15579 @section RM D.6(9-10): Preemptive Abort
15584 "Even though the @emph{abort_statement} is included in the list of
15585 potentially blocking operations (see 9.5.1), it is recommended that this
15586 statement be implemented in a way that never requires the task executing
15587 the @emph{abort_statement} to block."
15594 "On a multi-processor, the delay associated with aborting a task on
15595 another processor should be bounded; the implementation should use
15596 periodic polling, if necessary, to achieve this."
15601 @geindex Tasking restrictions
15603 @node RM D 7 21 Tasking Restrictions,RM D 8 47-49 Monotonic Time,RM D 6 9-10 Preemptive Abort,Implementation Advice
15604 @anchor{gnat_rm/implementation_advice rm-d-7-21-tasking-restrictions}@anchor{24c}
15605 @section RM D.7(21): Tasking Restrictions
15610 "When feasible, the implementation should take advantage of the specified
15611 restrictions to produce a more efficient implementation."
15614 GNAT currently takes advantage of these restrictions by providing an optimized
15615 run time when the Ravenscar profile and the GNAT restricted run time set
15616 of restrictions are specified. See pragma @code{Profile (Ravenscar)} and
15617 pragma @code{Profile (Restricted)} for more details.
15622 @node RM D 8 47-49 Monotonic Time,RM E 5 28-29 Partition Communication Subsystem,RM D 7 21 Tasking Restrictions,Implementation Advice
15623 @anchor{gnat_rm/implementation_advice rm-d-8-47-49-monotonic-time}@anchor{24d}
15624 @section RM D.8(47-49): Monotonic Time
15629 "When appropriate, implementations should provide configuration
15630 mechanisms to change the value of @code{Tick}."
15633 Such configuration mechanisms are not appropriate to this implementation
15634 and are thus not supported.
15638 "It is recommended that @code{Calendar.Clock} and @code{Real_Time.Clock}
15639 be implemented as transformations of the same time base."
15646 "It is recommended that the best time base which exists in
15647 the underlying system be available to the application through
15648 @code{Clock}. @cite{Best} may mean highest accuracy or largest range."
15653 @geindex Partition communication subsystem
15657 @node RM E 5 28-29 Partition Communication Subsystem,RM F 7 COBOL Support,RM D 8 47-49 Monotonic Time,Implementation Advice
15658 @anchor{gnat_rm/implementation_advice rm-e-5-28-29-partition-communication-subsystem}@anchor{24e}
15659 @section RM E.5(28-29): Partition Communication Subsystem
15664 "Whenever possible, the PCS on the called partition should allow for
15665 multiple tasks to call the RPC-receiver with different messages and
15666 should allow them to block until the corresponding subprogram body
15670 Followed by GLADE, a separately supplied PCS that can be used with
15675 "The @code{Write} operation on a stream of type @code{Params_Stream_Type}
15676 should raise @code{Storage_Error} if it runs out of space trying to
15677 write the @code{Item} into the stream."
15680 Followed by GLADE, a separately supplied PCS that can be used with
15683 @geindex COBOL support
15685 @node RM F 7 COBOL Support,RM F 1 2 Decimal Radix Support,RM E 5 28-29 Partition Communication Subsystem,Implementation Advice
15686 @anchor{gnat_rm/implementation_advice rm-f-7-cobol-support}@anchor{24f}
15687 @section RM F(7): COBOL Support
15692 "If COBOL (respectively, C) is widely supported in the target
15693 environment, implementations supporting the Information Systems Annex
15694 should provide the child package @code{Interfaces.COBOL} (respectively,
15695 @code{Interfaces.C}) specified in Annex B and should support a
15696 @code{convention_identifier} of COBOL (respectively, C) in the interfacing
15697 pragmas (see Annex B), thus allowing Ada programs to interface with
15698 programs written in that language."
15703 @geindex Decimal radix support
15705 @node RM F 1 2 Decimal Radix Support,RM G Numerics,RM F 7 COBOL Support,Implementation Advice
15706 @anchor{gnat_rm/implementation_advice rm-f-1-2-decimal-radix-support}@anchor{250}
15707 @section RM F.1(2): Decimal Radix Support
15712 "Packed decimal should be used as the internal representation for objects
15713 of subtype @code{S} when @code{S}'Machine_Radix = 10."
15716 Not followed. GNAT ignores @code{S}'Machine_Radix and always uses binary
15721 @node RM G Numerics,RM G 1 1 56-58 Complex Types,RM F 1 2 Decimal Radix Support,Implementation Advice
15722 @anchor{gnat_rm/implementation_advice rm-g-numerics}@anchor{251}
15723 @section RM G: Numerics
15728 "If Fortran (respectively, C) is widely supported in the target
15729 environment, implementations supporting the Numerics Annex
15730 should provide the child package @code{Interfaces.Fortran} (respectively,
15731 @code{Interfaces.C}) specified in Annex B and should support a
15732 @code{convention_identifier} of Fortran (respectively, C) in the interfacing
15733 pragmas (see Annex B), thus allowing Ada programs to interface with
15734 programs written in that language."
15739 @geindex Complex types
15741 @node RM G 1 1 56-58 Complex Types,RM G 1 2 49 Complex Elementary Functions,RM G Numerics,Implementation Advice
15742 @anchor{gnat_rm/implementation_advice rm-g-1-1-56-58-complex-types}@anchor{252}
15743 @section RM G.1.1(56-58): Complex Types
15748 "Because the usual mathematical meaning of multiplication of a complex
15749 operand and a real operand is that of the scaling of both components of
15750 the former by the latter, an implementation should not perform this
15751 operation by first promoting the real operand to complex type and then
15752 performing a full complex multiplication. In systems that, in the
15753 future, support an Ada binding to IEC 559:1989, the latter technique
15754 will not generate the required result when one of the components of the
15755 complex operand is infinite. (Explicit multiplication of the infinite
15756 component by the zero component obtained during promotion yields a NaN
15757 that propagates into the final result.) Analogous advice applies in the
15758 case of multiplication of a complex operand and a pure-imaginary
15759 operand, and in the case of division of a complex operand by a real or
15760 pure-imaginary operand."
15767 "Similarly, because the usual mathematical meaning of addition of a
15768 complex operand and a real operand is that the imaginary operand remains
15769 unchanged, an implementation should not perform this operation by first
15770 promoting the real operand to complex type and then performing a full
15771 complex addition. In implementations in which the @code{Signed_Zeros}
15772 attribute of the component type is @code{True} (and which therefore
15773 conform to IEC 559:1989 in regard to the handling of the sign of zero in
15774 predefined arithmetic operations), the latter technique will not
15775 generate the required result when the imaginary component of the complex
15776 operand is a negatively signed zero. (Explicit addition of the negative
15777 zero to the zero obtained during promotion yields a positive zero.)
15778 Analogous advice applies in the case of addition of a complex operand
15779 and a pure-imaginary operand, and in the case of subtraction of a
15780 complex operand and a real or pure-imaginary operand."
15787 "Implementations in which @code{Real'Signed_Zeros} is @code{True} should
15788 attempt to provide a rational treatment of the signs of zero results and
15789 result components. As one example, the result of the @code{Argument}
15790 function should have the sign of the imaginary component of the
15791 parameter @code{X} when the point represented by that parameter lies on
15792 the positive real axis; as another, the sign of the imaginary component
15793 of the @code{Compose_From_Polar} function should be the same as
15794 (respectively, the opposite of) that of the @code{Argument} parameter when that
15795 parameter has a value of zero and the @code{Modulus} parameter has a
15796 nonnegative (respectively, negative) value."
15801 @geindex Complex elementary functions
15803 @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
15804 @anchor{gnat_rm/implementation_advice rm-g-1-2-49-complex-elementary-functions}@anchor{253}
15805 @section RM G.1.2(49): Complex Elementary Functions
15810 "Implementations in which @code{Complex_Types.Real'Signed_Zeros} is
15811 @code{True} should attempt to provide a rational treatment of the signs
15812 of zero results and result components. For example, many of the complex
15813 elementary functions have components that are odd functions of one of
15814 the parameter components; in these cases, the result component should
15815 have the sign of the parameter component at the origin. Other complex
15816 elementary functions have zero components whose sign is opposite that of
15817 a parameter component at the origin, or is always positive or always
15823 @geindex Accuracy requirements
15825 @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
15826 @anchor{gnat_rm/implementation_advice rm-g-2-4-19-accuracy-requirements}@anchor{254}
15827 @section RM G.2.4(19): Accuracy Requirements
15832 "The versions of the forward trigonometric functions without a
15833 @code{Cycle} parameter should not be implemented by calling the
15834 corresponding version with a @code{Cycle} parameter of
15835 @code{2.0*Numerics.Pi}, since this will not provide the required
15836 accuracy in some portions of the domain. For the same reason, the
15837 version of @code{Log} without a @code{Base} parameter should not be
15838 implemented by calling the corresponding version with a @code{Base}
15839 parameter of @code{Numerics.e}."
15844 @geindex Complex arithmetic accuracy
15847 @geindex complex arithmetic
15849 @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
15850 @anchor{gnat_rm/implementation_advice rm-g-2-6-15-complex-arithmetic-accuracy}@anchor{255}
15851 @section RM G.2.6(15): Complex Arithmetic Accuracy
15856 "The version of the @code{Compose_From_Polar} function without a
15857 @code{Cycle} parameter should not be implemented by calling the
15858 corresponding version with a @code{Cycle} parameter of
15859 @code{2.0*Numerics.Pi}, since this will not provide the required
15860 accuracy in some portions of the domain."
15865 @geindex Sequential elaboration policy
15867 @node RM H 6 15/2 Pragma Partition_Elaboration_Policy,,RM G 2 6 15 Complex Arithmetic Accuracy,Implementation Advice
15868 @anchor{gnat_rm/implementation_advice rm-h-6-15-2-pragma-partition-elaboration-policy}@anchor{256}
15869 @section RM H.6(15/2): Pragma Partition_Elaboration_Policy
15874 "If the partition elaboration policy is @code{Sequential} and the
15875 Environment task becomes permanently blocked during elaboration then the
15876 partition is deadlocked and it is recommended that the partition be
15877 immediately terminated."
15882 @node Implementation Defined Characteristics,Intrinsic Subprograms,Implementation Advice,Top
15883 @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}
15884 @chapter Implementation Defined Characteristics
15887 In addition to the implementation dependent pragmas and attributes, and the
15888 implementation advice, there are a number of other Ada features that are
15889 potentially implementation dependent and are designated as
15890 implementation-defined. These are mentioned throughout the Ada Reference
15891 Manual, and are summarized in Annex M.
15893 A requirement for conforming Ada compilers is that they provide
15894 documentation describing how the implementation deals with each of these
15895 issues. In this chapter you will find each point in Annex M listed,
15896 followed by a description of how GNAT
15897 handles the implementation dependence.
15899 You can use this chapter as a guide to minimizing implementation
15900 dependent features in your programs if portability to other compilers
15901 and other operating systems is an important consideration. The numbers
15902 in each entry below correspond to the paragraph numbers in the Ada
15909 "Whether or not each recommendation given in Implementation
15910 Advice is followed. See 1.1.2(37)."
15913 See @ref{a,,Implementation Advice}.
15919 "Capacity limitations of the implementation. See 1.1.3(3)."
15922 The complexity of programs that can be processed is limited only by the
15923 total amount of available virtual memory, and disk space for the
15924 generated object files.
15930 "Variations from the standard that are impractical to avoid
15931 given the implementation's execution environment. See 1.1.3(6)."
15934 There are no variations from the standard.
15940 "Which code_statements cause external
15941 interactions. See 1.1.3(10)."
15944 Any @emph{code_statement} can potentially cause external interactions.
15950 "The coded representation for the text of an Ada
15951 program. See 2.1(4)."
15954 See separate section on source representation.
15960 "The control functions allowed in comments. See 2.1(14)."
15963 See separate section on source representation.
15969 "The representation for an end of line. See 2.2(2)."
15972 See separate section on source representation.
15978 "Maximum supported line length and lexical element
15979 length. See 2.2(15)."
15982 The maximum line length is 255 characters and the maximum length of
15983 a lexical element is also 255 characters. This is the default setting
15984 if not overridden by the use of compiler switch @emph{-gnaty} (which
15985 sets the maximum to 79) or @emph{-gnatyMnn} which allows the maximum
15986 line length to be specified to be any value up to 32767. The maximum
15987 length of a lexical element is the same as the maximum line length.
15993 "Implementation defined pragmas. See 2.8(14)."
15996 See @ref{7,,Implementation Defined Pragmas}.
16002 "Effect of pragma @code{Optimize}. See 2.8(27)."
16005 Pragma @code{Optimize}, if given with a @code{Time} or @code{Space}
16006 parameter, checks that the optimization flag is set, and aborts if it is
16013 "The sequence of characters of the value returned by
16014 @code{S'Image} when some of the graphic characters of
16015 @code{S'Wide_Image} are not defined in @code{Character}. See
16019 The sequence of characters is as defined by the wide character encoding
16020 method used for the source. See section on source representation for
16027 "The predefined integer types declared in
16028 @code{Standard}. See 3.5.4(25)."
16032 @multitable {xxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
16043 @emph{Short_Short_Integer}
16051 @emph{Short_Integer}
16055 (Short) 16 bit signed
16067 @emph{Long_Integer}
16071 64 bit signed (on most 64 bit targets,
16072 depending on the C definition of long).
16073 32 bit signed (all other targets)
16077 @emph{Long_Long_Integer}
16090 "Any nonstandard integer types and the operators defined
16091 for them. See 3.5.4(26)."
16094 There are no nonstandard integer types.
16100 "Any nonstandard real types and the operators defined for
16101 them. See 3.5.6(8)."
16104 There are no nonstandard real types.
16110 "What combinations of requested decimal precision and range
16111 are supported for floating point types. See 3.5.7(7)."
16114 The precision and range is as defined by the IEEE standard.
16120 "The predefined floating point types declared in
16121 @code{Standard}. See 3.5.7(16)."
16125 @multitable {xxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
16148 (Short) 32 bit IEEE short
16160 @emph{Long_Long_Float}
16164 64 bit IEEE long (80 bit IEEE long on x86 processors)
16173 "The small of an ordinary fixed point type. See 3.5.9(8)."
16176 @code{Fine_Delta} is 2**(-63)
16182 "What combinations of small, range, and digits are
16183 supported for fixed point types. See 3.5.9(10)."
16186 Any combinations are permitted that do not result in a small less than
16187 @code{Fine_Delta} and do not result in a mantissa larger than 63 bits.
16188 If the mantissa is larger than 53 bits on machines where Long_Long_Float
16189 is 64 bits (true of all architectures except ia32), then the output from
16190 Text_IO is accurate to only 53 bits, rather than the full mantissa. This
16191 is because floating-point conversions are used to convert fixed point.
16197 "The result of @code{Tags.Expanded_Name} for types declared
16198 within an unnamed @emph{block_statement}. See 3.9(10)."
16201 Block numbers of the form @code{B@emph{nnn}}, where @emph{nnn} is a
16202 decimal integer are allocated.
16208 "Implementation-defined attributes. See 4.1.4(12)."
16211 See @ref{8,,Implementation Defined Attributes}.
16217 "Any implementation-defined time types. See 9.6(6)."
16220 There are no implementation-defined time types.
16226 "The time base associated with relative delays."
16229 See 9.6(20). The time base used is that provided by the C library
16230 function @code{gettimeofday}.
16236 "The time base of the type @code{Calendar.Time}. See
16240 The time base used is that provided by the C library function
16241 @code{gettimeofday}.
16247 "The time zone used for package @code{Calendar}
16248 operations. See 9.6(24)."
16251 The time zone used by package @code{Calendar} is the current system time zone
16252 setting for local time, as accessed by the C library function
16259 "Any limit on @emph{delay_until_statements} of
16260 @emph{select_statements}. See 9.6(29)."
16263 There are no such limits.
16269 "Whether or not two non-overlapping parts of a composite
16270 object are independently addressable, in the case where packing, record
16271 layout, or @code{Component_Size} is specified for the object. See
16275 Separate components are independently addressable if they do not share
16276 overlapping storage units.
16282 "The representation for a compilation. See 10.1(2)."
16285 A compilation is represented by a sequence of files presented to the
16286 compiler in a single invocation of the @emph{gcc} command.
16292 "Any restrictions on compilations that contain multiple
16293 compilation_units. See 10.1(4)."
16296 No single file can contain more than one compilation unit, but any
16297 sequence of files can be presented to the compiler as a single
16304 "The mechanisms for creating an environment and for adding
16305 and replacing compilation units. See 10.1.4(3)."
16308 See separate section on compilation model.
16314 "The manner of explicitly assigning library units to a
16315 partition. See 10.2(2)."
16318 If a unit contains an Ada main program, then the Ada units for the partition
16319 are determined by recursive application of the rules in the Ada Reference
16320 Manual section 10.2(2-6). In other words, the Ada units will be those that
16321 are needed by the main program, and then this definition of need is applied
16322 recursively to those units, and the partition contains the transitive
16323 closure determined by this relationship. In short, all the necessary units
16324 are included, with no need to explicitly specify the list. If additional
16325 units are required, e.g., by foreign language units, then all units must be
16326 mentioned in the context clause of one of the needed Ada units.
16328 If the partition contains no main program, or if the main program is in
16329 a language other than Ada, then GNAT
16330 provides the binder options @emph{-z} and @emph{-n} respectively, and in
16331 this case a list of units can be explicitly supplied to the binder for
16332 inclusion in the partition (all units needed by these units will also
16333 be included automatically). For full details on the use of these
16334 options, refer to @emph{GNAT Make Program gnatmake} in the
16335 @cite{GNAT User's Guide}.
16341 "The implementation-defined means, if any, of specifying
16342 which compilation units are needed by a given compilation unit. See
16346 The units needed by a given compilation unit are as defined in
16347 the Ada Reference Manual section 10.2(2-6). There are no
16348 implementation-defined pragmas or other implementation-defined
16349 means for specifying needed units.
16355 "The manner of designating the main subprogram of a
16356 partition. See 10.2(7)."
16359 The main program is designated by providing the name of the
16360 corresponding @code{ALI} file as the input parameter to the binder.
16366 "The order of elaboration of @emph{library_items}. See
16370 The first constraint on ordering is that it meets the requirements of
16371 Chapter 10 of the Ada Reference Manual. This still leaves some
16372 implementation dependent choices, which are resolved by first
16373 elaborating bodies as early as possible (i.e., in preference to specs
16374 where there is a choice), and second by evaluating the immediate with
16375 clauses of a unit to determine the probably best choice, and
16376 third by elaborating in alphabetical order of unit names
16377 where a choice still remains.
16383 "Parameter passing and function return for the main
16384 subprogram. See 10.2(21)."
16387 The main program has no parameters. It may be a procedure, or a function
16388 returning an integer type. In the latter case, the returned integer
16389 value is the return code of the program (overriding any value that
16390 may have been set by a call to @code{Ada.Command_Line.Set_Exit_Status}).
16396 "The mechanisms for building and running partitions. See
16400 GNAT itself supports programs with only a single partition. The GNATDIST
16401 tool provided with the GLADE package (which also includes an implementation
16402 of the PCS) provides a completely flexible method for building and running
16403 programs consisting of multiple partitions. See the separate GLADE manual
16410 "The details of program execution, including program
16411 termination. See 10.2(25)."
16414 See separate section on compilation model.
16420 "The semantics of any non-active partitions supported by the
16421 implementation. See 10.2(28)."
16424 Passive partitions are supported on targets where shared memory is
16425 provided by the operating system. See the GLADE reference manual for
16432 "The information returned by @code{Exception_Message}. See
16436 Exception message returns the null string unless a specific message has
16437 been passed by the program.
16443 "The result of @code{Exceptions.Exception_Name} for types
16444 declared within an unnamed @emph{block_statement}. See 11.4.1(12)."
16447 Blocks have implementation defined names of the form @code{B@emph{nnn}}
16448 where @emph{nnn} is an integer.
16454 "The information returned by
16455 @code{Exception_Information}. See 11.4.1(13)."
16458 @code{Exception_Information} returns a string in the following format:
16461 *Exception_Name:* nnnnn
16464 *Load address:* 0xhhhh
16465 *Call stack traceback locations:*
16466 0xhhhh 0xhhhh 0xhhhh ... 0xhhh
16477 @code{nnnn} is the fully qualified name of the exception in all upper
16478 case letters. This line is always present.
16481 @code{mmmm} is the message (this line present only if message is non-null)
16484 @code{ppp} is the Process Id value as a decimal integer (this line is
16485 present only if the Process Id is nonzero). Currently we are
16486 not making use of this field.
16489 The Load address line, the Call stack traceback locations line and the
16490 following values are present only if at least one traceback location was
16491 recorded. The Load address indicates the address at which the main executable
16492 was loaded; this line may not be present if operating system hasn't relocated
16493 the main executable. The values are given in C style format, with lower case
16494 letters for a-f, and only as many digits present as are necessary.
16495 The line terminator sequence at the end of each line, including
16496 the last line is a single @code{LF} character (@code{16#0A#}).
16504 "Implementation-defined check names. See 11.5(27)."
16507 The implementation defined check names include Alignment_Check,
16508 Atomic_Synchronization, Duplicated_Tag_Check, Container_Checks,
16509 Tampering_Check, Predicate_Check, and Validity_Check. In addition, a user
16510 program can add implementation-defined check names by means of the pragma
16511 Check_Name. See the description of pragma @code{Suppress} for full details.
16517 "The interpretation of each aspect of representation. See
16521 See separate section on data representations.
16527 "Any restrictions placed upon representation items. See
16531 See separate section on data representations.
16537 "The meaning of @code{Size} for indefinite subtypes. See
16541 Size for an indefinite subtype is the maximum possible size, except that
16542 for the case of a subprogram parameter, the size of the parameter object
16543 is the actual size.
16549 "The default external representation for a type tag. See
16553 The default external representation for a type tag is the fully expanded
16554 name of the type in upper case letters.
16560 "What determines whether a compilation unit is the same in
16561 two different partitions. See 13.3(76)."
16564 A compilation unit is the same in two different partitions if and only
16565 if it derives from the same source file.
16571 "Implementation-defined components. See 13.5.1(15)."
16574 The only implementation defined component is the tag for a tagged type,
16575 which contains a pointer to the dispatching table.
16581 "If @code{Word_Size} = @code{Storage_Unit}, the default bit
16582 ordering. See 13.5.3(5)."
16585 @code{Word_Size} (32) is not the same as @code{Storage_Unit} (8) for this
16586 implementation, so no non-default bit ordering is supported. The default
16587 bit ordering corresponds to the natural endianness of the target architecture.
16593 "The contents of the visible part of package @code{System}
16594 and its language-defined children. See 13.7(2)."
16597 See the definition of these packages in files @code{system.ads} and
16598 @code{s-stoele.ads}. Note that two declarations are added to package
16602 Max_Priority : constant Positive := Priority'Last;
16603 Max_Interrupt_Priority : constant Positive := Interrupt_Priority'Last;
16610 "The contents of the visible part of package
16611 @code{System.Machine_Code}, and the meaning of
16612 @emph{code_statements}. See 13.8(7)."
16615 See the definition and documentation in file @code{s-maccod.ads}.
16621 "The effect of unchecked conversion. See 13.9(11)."
16624 Unchecked conversion between types of the same size
16625 results in an uninterpreted transmission of the bits from one type
16626 to the other. If the types are of unequal sizes, then in the case of
16627 discrete types, a shorter source is first zero or sign extended as
16628 necessary, and a shorter target is simply truncated on the left.
16629 For all non-discrete types, the source is first copied if necessary
16630 to ensure that the alignment requirements of the target are met, then
16631 a pointer is constructed to the source value, and the result is obtained
16632 by dereferencing this pointer after converting it to be a pointer to the
16633 target type. Unchecked conversions where the target subtype is an
16634 unconstrained array are not permitted. If the target alignment is
16635 greater than the source alignment, then a copy of the result is
16636 made with appropriate alignment
16642 "The semantics of operations on invalid representations.
16643 See 13.9.2(10-11)."
16646 For assignments and other operations where the use of invalid values cannot
16647 result in erroneous behavior, the compiler ignores the possibility of invalid
16648 values. An exception is raised at the point where an invalid value would
16649 result in erroneous behavior. For example executing:
16652 procedure invalidvals is
16654 Y : Natural range 1 .. 10;
16655 for Y'Address use X'Address;
16656 Z : Natural range 1 .. 10;
16657 A : array (Natural range 1 .. 10) of Integer;
16659 Z := Y; -- no exception
16660 A (Z) := 3; -- exception raised;
16664 As indicated, an exception is raised on the array assignment, but not
16665 on the simple assignment of the invalid negative value from Y to Z.
16671 "The manner of choosing a storage pool for an access type
16672 when @code{Storage_Pool} is not specified for the type. See 13.11(17)."
16675 There are 3 different standard pools used by the compiler when
16676 @code{Storage_Pool} is not specified depending whether the type is local
16677 to a subprogram or defined at the library level and whether
16678 @code{Storage_Size`@w{`}is specified or not. See documentation in the runtime
16679 library units `@w{`}System.Pool_Global}, @code{System.Pool_Size} and
16680 @code{System.Pool_Local} in files @code{s-poosiz.ads},
16681 @code{s-pooglo.ads} and @code{s-pooloc.ads} for full details on the
16682 default pools used.
16688 "Whether or not the implementation provides user-accessible
16689 names for the standard pool type(s). See 13.11(17)."
16692 See documentation in the sources of the run time mentioned in the previous
16693 paragraph. All these pools are accessible by means of @cite{with}ing
16700 "The meaning of @code{Storage_Size}. See 13.11(18)."
16703 @code{Storage_Size} is measured in storage units, and refers to the
16704 total space available for an access type collection, or to the primary
16705 stack space for a task.
16711 "Implementation-defined aspects of storage pools. See
16715 See documentation in the sources of the run time mentioned in the
16716 paragraph about standard storage pools above
16717 for details on GNAT-defined aspects of storage pools.
16723 "The set of restrictions allowed in a pragma
16724 @code{Restrictions}. See 13.12(7)."
16727 See @ref{9,,Standard and Implementation Defined Restrictions}.
16733 "The consequences of violating limitations on
16734 @code{Restrictions} pragmas. See 13.12(9)."
16737 Restrictions that can be checked at compile time result in illegalities
16738 if violated. Currently there are no other consequences of violating
16745 "The representation used by the @code{Read} and
16746 @code{Write} attributes of elementary types in terms of stream
16747 elements. See 13.13.2(9)."
16750 The representation is the in-memory representation of the base type of
16751 the type, using the number of bits corresponding to the
16752 @code{type'Size} value, and the natural ordering of the machine.
16758 "The names and characteristics of the numeric subtypes
16759 declared in the visible part of package @code{Standard}. See A.1(3)."
16762 See items describing the integer and floating-point types supported.
16768 "The string returned by @code{Character_Set_Version}.
16772 @code{Ada.Wide_Characters.Handling.Character_Set_Version} returns
16773 the string "Unicode 4.0", referring to version 4.0 of the
16774 Unicode specification.
16780 "The accuracy actually achieved by the elementary
16781 functions. See A.5.1(1)."
16784 The elementary functions correspond to the functions available in the C
16785 library. Only fast math mode is implemented.
16791 "The sign of a zero result from some of the operators or
16792 functions in @code{Numerics.Generic_Elementary_Functions}, when
16793 @code{Float_Type'Signed_Zeros} is @code{True}. See A.5.1(46)."
16796 The sign of zeroes follows the requirements of the IEEE 754 standard on
16804 @code{Numerics.Float_Random.Max_Image_Width}. See A.5.2(27)."
16807 Maximum image width is 6864, see library file @code{s-rannum.ads}.
16814 @code{Numerics.Discrete_Random.Max_Image_Width}. See A.5.2(27)."
16817 Maximum image width is 6864, see library file @code{s-rannum.ads}.
16823 "The algorithms for random number generation. See
16827 The algorithm is the Mersenne Twister, as documented in the source file
16828 @code{s-rannum.adb}. This version of the algorithm has a period of
16835 "The string representation of a random number generator's
16836 state. See A.5.2(38)."
16839 The value returned by the Image function is the concatenation of
16840 the fixed-width decimal representations of the 624 32-bit integers
16841 of the state vector.
16847 "The minimum time interval between calls to the
16848 time-dependent Reset procedure that are guaranteed to initiate different
16849 random number sequences. See A.5.2(45)."
16852 The minimum period between reset calls to guarantee distinct series of
16853 random numbers is one microsecond.
16859 "The values of the @code{Model_Mantissa},
16860 @code{Model_Emin}, @code{Model_Epsilon}, @code{Model},
16861 @code{Safe_First}, and @code{Safe_Last} attributes, if the Numerics
16862 Annex is not supported. See A.5.3(72)."
16865 Run the compiler with @emph{-gnatS} to produce a listing of package
16866 @code{Standard}, has the values of all numeric attributes.
16872 "Any implementation-defined characteristics of the
16873 input-output packages. See A.7(14)."
16876 There are no special implementation defined characteristics for these
16883 "The value of @code{Buffer_Size} in @code{Storage_IO}. See
16887 All type representations are contiguous, and the @code{Buffer_Size} is
16888 the value of @code{type'Size} rounded up to the next storage unit
16895 "External files for standard input, standard output, and
16896 standard error See A.10(5)."
16899 These files are mapped onto the files provided by the C streams
16900 libraries. See source file @code{i-cstrea.ads} for further details.
16906 "The accuracy of the value produced by @code{Put}. See
16910 If more digits are requested in the output than are represented by the
16911 precision of the value, zeroes are output in the corresponding least
16912 significant digit positions.
16918 "The meaning of @code{Argument_Count}, @code{Argument}, and
16919 @code{Command_Name}. See A.15(1)."
16922 These are mapped onto the @code{argv} and @code{argc} parameters of the
16923 main program in the natural manner.
16929 "The interpretation of the @code{Form} parameter in procedure
16930 @code{Create_Directory}. See A.16(56)."
16933 The @code{Form} parameter is not used.
16939 "The interpretation of the @code{Form} parameter in procedure
16940 @code{Create_Path}. See A.16(60)."
16943 The @code{Form} parameter is not used.
16949 "The interpretation of the @code{Form} parameter in procedure
16950 @code{Copy_File}. See A.16(68)."
16953 The @code{Form} parameter is case-insensitive.
16954 Two fields are recognized in the @code{Form} parameter:
16961 <value> starts immediately after the character '=' and ends with the
16962 character immediately preceding the next comma (',') or with the last
16963 character of the parameter.
16965 The only possible values for preserve= are:
16968 @multitable {xxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
16979 @emph{no_attributes}
16983 Do not try to preserve any file attributes. This is the
16984 default if no preserve= is found in Form.
16988 @emph{all_attributes}
16992 Try to preserve all file attributes (timestamps, access rights).
17000 Preserve the timestamp of the copied file, but not the other
17006 The only possible values for mode= are:
17009 @multitable {xxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
17024 Only do the copy if the destination file does not already exist.
17025 If it already exists, Copy_File fails.
17033 Copy the file in all cases. Overwrite an already existing destination file.
17041 Append the original file to the destination file. If the destination file
17042 does not exist, the destination file is a copy of the source file.
17043 When mode=append, the field preserve=, if it exists, is not taken into account.
17048 If the Form parameter includes one or both of the fields and the value or
17049 values are incorrect, Copy_file fails with Use_Error.
17051 Examples of correct Forms:
17054 Form => "preserve=no_attributes,mode=overwrite" (the default)
17055 Form => "mode=append"
17056 Form => "mode=copy, preserve=all_attributes"
17059 Examples of incorrect Forms:
17062 Form => "preserve=junk"
17063 Form => "mode=internal, preserve=timestamps"
17070 "The interpretation of the @code{Pattern} parameter, when not the null string,
17071 in the @code{Start_Search} and @code{Search} procedures.
17072 See A.16(104) and A.16(112)."
17075 When the @code{Pattern} parameter is not the null string, it is interpreted
17076 according to the syntax of regular expressions as defined in the
17077 @code{GNAT.Regexp} package.
17079 See @ref{259,,GNAT.Regexp (g-regexp.ads)}.
17085 "Implementation-defined convention names. See B.1(11)."
17088 The following convention names are supported
17091 @multitable {xxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
17110 @emph{Ada_Pass_By_Copy}
17114 Allowed for any types except by-reference types such as limited
17115 records. Compatible with convention Ada, but causes any parameters
17116 with this convention to be passed by copy.
17120 @emph{Ada_Pass_By_Reference}
17124 Allowed for any types except by-copy types such as scalars.
17125 Compatible with convention Ada, but causes any parameters
17126 with this convention to be passed by reference.
17142 Synonym for Assembler
17150 Synonym for Assembler
17162 @emph{C_Pass_By_Copy}
17166 Allowed only for record types, like C, but also notes that record
17167 is to be passed by copy rather than reference.
17179 @emph{C_Plus_Plus (or CPP)}
17191 Treated the same as C
17199 Treated the same as C
17215 For support of pragma @code{Import} with convention Intrinsic, see
17216 separate section on Intrinsic Subprograms.
17224 Stdcall (used for Windows implementations only). This convention correspond
17225 to the WINAPI (previously called Pascal convention) C/C++ convention under
17226 Windows. A routine with this convention cleans the stack before
17227 exit. This pragma cannot be applied to a dispatching call.
17235 Synonym for Stdcall
17243 Synonym for Stdcall
17251 Stubbed is a special convention used to indicate that the body of the
17252 subprogram will be entirely ignored. Any call to the subprogram
17253 is converted into a raise of the @code{Program_Error} exception. If a
17254 pragma @code{Import} specifies convention @code{stubbed} then no body need
17255 be present at all. This convention is useful during development for the
17256 inclusion of subprograms whose body has not yet been written.
17257 In addition, all otherwise unrecognized convention names are also
17258 treated as being synonymous with convention C. In all implementations,
17259 use of such other names results in a warning.
17268 "The meaning of link names. See B.1(36)."
17271 Link names are the actual names used by the linker.
17277 "The manner of choosing link names when neither the link
17278 name nor the address of an imported or exported entity is specified. See
17282 The default linker name is that which would be assigned by the relevant
17283 external language, interpreting the Ada name as being in all lower case
17290 "The effect of pragma @code{Linker_Options}. See B.1(37)."
17293 The string passed to @code{Linker_Options} is presented uninterpreted as
17294 an argument to the link command, unless it contains ASCII.NUL characters.
17295 NUL characters if they appear act as argument separators, so for example
17298 pragma Linker_Options ("-labc" & ASCII.NUL & "-ldef");
17301 causes two separate arguments @code{-labc} and @code{-ldef} to be passed to the
17302 linker. The order of linker options is preserved for a given unit. The final
17303 list of options passed to the linker is in reverse order of the elaboration
17304 order. For example, linker options for a body always appear before the options
17305 from the corresponding package spec.
17311 "The contents of the visible part of package
17312 @code{Interfaces} and its language-defined descendants. See B.2(1)."
17315 See files with prefix @code{i-} in the distributed library.
17321 "Implementation-defined children of package
17322 @code{Interfaces}. The contents of the visible part of package
17323 @code{Interfaces}. See B.2(11)."
17326 See files with prefix @code{i-} in the distributed library.
17332 "The types @code{Floating}, @code{Long_Floating},
17333 @code{Binary}, @code{Long_Binary}, @code{Decimal_ Element}, and
17334 @code{COBOL_Character}; and the initialization of the variables
17335 @code{Ada_To_COBOL} and @code{COBOL_To_Ada}, in
17336 @code{Interfaces.COBOL}. See B.4(50)."
17340 @multitable {xxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
17359 @emph{Long_Floating}
17363 (Floating) Long_Float
17383 @emph{Decimal_Element}
17391 @emph{COBOL_Character}
17400 For initialization, see the file @code{i-cobol.ads} in the distributed library.
17406 "Support for access to machine instructions. See C.1(1)."
17409 See documentation in file @code{s-maccod.ads} in the distributed library.
17415 "Implementation-defined aspects of access to machine
17416 operations. See C.1(9)."
17419 See documentation in file @code{s-maccod.ads} in the distributed library.
17425 "Implementation-defined aspects of interrupts. See C.3(2)."
17428 Interrupts are mapped to signals or conditions as appropriate. See
17430 @code{Ada.Interrupt_Names} in source file @code{a-intnam.ads} for details
17431 on the interrupts supported on a particular target.
17437 "Implementation-defined aspects of pre-elaboration. See
17441 GNAT does not permit a partition to be restarted without reloading,
17442 except under control of the debugger.
17448 "The semantics of pragma @code{Discard_Names}. See C.5(7)."
17451 Pragma @code{Discard_Names} causes names of enumeration literals to
17452 be suppressed. In the presence of this pragma, the Image attribute
17453 provides the image of the Pos of the literal, and Value accepts
17456 For tagged types, when pragmas @code{Discard_Names} and @code{No_Tagged_Streams}
17457 simultaneously apply, their Expanded_Name and External_Tag are initialized
17458 with empty strings. This is useful to avoid exposing entity names at binary
17465 "The result of the @code{Task_Identification.Image}
17466 attribute. See C.7.1(7)."
17469 The result of this attribute is a string that identifies
17470 the object or component that denotes a given task. If a variable @code{Var}
17471 has a task type, the image for this task will have the form @code{Var_@emph{XXXXXXXX}},
17472 where the suffix @emph{XXXXXXXX}
17473 is the hexadecimal representation of the virtual address of the corresponding
17474 task control block. If the variable is an array of tasks, the image of each
17475 task will have the form of an indexed component indicating the position of a
17476 given task in the array, e.g., @code{Group(5)_@emph{XXXXXXX}}. If the task is a
17477 component of a record, the image of the task will have the form of a selected
17478 component. These rules are fully recursive, so that the image of a task that
17479 is a subcomponent of a composite object corresponds to the expression that
17480 designates this task.
17482 If a task is created by an allocator, its image depends on the context. If the
17483 allocator is part of an object declaration, the rules described above are used
17484 to construct its image, and this image is not affected by subsequent
17485 assignments. If the allocator appears within an expression, the image
17486 includes only the name of the task type.
17488 If the configuration pragma Discard_Names is present, or if the restriction
17489 No_Implicit_Heap_Allocation is in effect, the image reduces to
17490 the numeric suffix, that is to say the hexadecimal representation of the
17491 virtual address of the control block of the task.
17497 "The value of @code{Current_Task} when in a protected entry
17498 or interrupt handler. See C.7.1(17)."
17501 Protected entries or interrupt handlers can be executed by any
17502 convenient thread, so the value of @code{Current_Task} is undefined.
17508 "The effect of calling @code{Current_Task} from an entry
17509 body or interrupt handler. See C.7.1(19)."
17512 When GNAT can determine statically that @code{Current_Task} is called directly in
17513 the body of an entry (or barrier) then a warning is emitted and @code{Program_Error}
17514 is raised at run time. Otherwise, the effect of calling @code{Current_Task} from an
17515 entry body or interrupt handler is to return the identification of the task
17516 currently executing the code.
17522 "Implementation-defined aspects of
17523 @code{Task_Attributes}. See C.7.2(19)."
17526 There are no implementation-defined aspects of @code{Task_Attributes}.
17532 "Values of all @code{Metrics}. See D(2)."
17535 The metrics information for GNAT depends on the performance of the
17536 underlying operating system. The sources of the run-time for tasking
17537 implementation, together with the output from @emph{-gnatG} can be
17538 used to determine the exact sequence of operating systems calls made
17539 to implement various tasking constructs. Together with appropriate
17540 information on the performance of the underlying operating system,
17541 on the exact target in use, this information can be used to determine
17542 the required metrics.
17548 "The declarations of @code{Any_Priority} and
17549 @code{Priority}. See D.1(11)."
17552 See declarations in file @code{system.ads}.
17558 "Implementation-defined execution resources. See D.1(15)."
17561 There are no implementation-defined execution resources.
17567 "Whether, on a multiprocessor, a task that is waiting for
17568 access to a protected object keeps its processor busy. See D.2.1(3)."
17571 On a multi-processor, a task that is waiting for access to a protected
17572 object does not keep its processor busy.
17578 "The affect of implementation defined execution resources
17579 on task dispatching. See D.2.1(9)."
17582 Tasks map to threads in the threads package used by GNAT. Where possible
17583 and appropriate, these threads correspond to native threads of the
17584 underlying operating system.
17590 "Implementation-defined @emph{policy_identifiers} allowed
17591 in a pragma @code{Task_Dispatching_Policy}. See D.2.2(3)."
17594 There are no implementation-defined policy-identifiers allowed in this
17601 "Implementation-defined aspects of priority inversion. See
17605 Execution of a task cannot be preempted by the implementation processing
17606 of delay expirations for lower priority tasks.
17612 "Implementation-defined task dispatching. See D.2.2(18)."
17615 The policy is the same as that of the underlying threads implementation.
17621 "Implementation-defined @emph{policy_identifiers} allowed
17622 in a pragma @code{Locking_Policy}. See D.3(4)."
17625 The two implementation defined policies permitted in GNAT are
17626 @code{Inheritance_Locking} and @code{Concurrent_Readers_Locking}. On
17627 targets that support the @code{Inheritance_Locking} policy, locking is
17628 implemented by inheritance, i.e., the task owning the lock operates
17629 at a priority equal to the highest priority of any task currently
17630 requesting the lock. On targets that support the
17631 @code{Concurrent_Readers_Locking} policy, locking is implemented with a
17632 read/write lock allowing multiple protected object functions to enter
17639 "Default ceiling priorities. See D.3(10)."
17642 The ceiling priority of protected objects of the type
17643 @code{System.Interrupt_Priority'Last} as described in the Ada
17644 Reference Manual D.3(10),
17650 "The ceiling of any protected object used internally by
17651 the implementation. See D.3(16)."
17654 The ceiling priority of internal protected objects is
17655 @code{System.Priority'Last}.
17661 "Implementation-defined queuing policies. See D.4(1)."
17664 There are no implementation-defined queuing policies.
17670 "On a multiprocessor, any conditions that cause the
17671 completion of an aborted construct to be delayed later than what is
17672 specified for a single processor. See D.6(3)."
17675 The semantics for abort on a multi-processor is the same as on a single
17676 processor, there are no further delays.
17682 "Any operations that implicitly require heap storage
17683 allocation. See D.7(8)."
17686 The only operation that implicitly requires heap storage allocation is
17693 "What happens when a task terminates in the presence of
17694 pragma @code{No_Task_Termination}. See D.7(15)."
17697 Execution is erroneous in that case.
17703 "Implementation-defined aspects of pragma
17704 @code{Restrictions}. See D.7(20)."
17707 There are no such implementation-defined aspects.
17713 "Implementation-defined aspects of package
17714 @code{Real_Time}. See D.8(17)."
17717 There are no implementation defined aspects of package @code{Real_Time}.
17723 "Implementation-defined aspects of
17724 @emph{delay_statements}. See D.9(8)."
17727 Any difference greater than one microsecond will cause the task to be
17728 delayed (see D.9(7)).
17734 "The upper bound on the duration of interrupt blocking
17735 caused by the implementation. See D.12(5)."
17738 The upper bound is determined by the underlying operating system. In
17739 no cases is it more than 10 milliseconds.
17745 "The means for creating and executing distributed
17746 programs. See E(5)."
17749 The GLADE package provides a utility GNATDIST for creating and executing
17750 distributed programs. See the GLADE reference manual for further details.
17756 "Any events that can result in a partition becoming
17757 inaccessible. See E.1(7)."
17760 See the GLADE reference manual for full details on such events.
17766 "The scheduling policies, treatment of priorities, and
17767 management of shared resources between partitions in certain cases. See
17771 See the GLADE reference manual for full details on these aspects of
17772 multi-partition execution.
17778 "Events that cause the version of a compilation unit to
17779 change. See E.3(5)."
17782 Editing the source file of a compilation unit, or the source files of
17783 any units on which it is dependent in a significant way cause the version
17784 to change. No other actions cause the version number to change. All changes
17785 are significant except those which affect only layout, capitalization or
17792 "Whether the execution of the remote subprogram is
17793 immediately aborted as a result of cancellation. See E.4(13)."
17796 See the GLADE reference manual for details on the effect of abort in
17797 a distributed application.
17803 "Implementation-defined aspects of the PCS. See E.5(25)."
17806 See the GLADE reference manual for a full description of all implementation
17807 defined aspects of the PCS.
17813 "Implementation-defined interfaces in the PCS. See
17817 See the GLADE reference manual for a full description of all
17818 implementation defined interfaces.
17824 "The values of named numbers in the package
17825 @code{Decimal}. See F.2(7)."
17829 @multitable {xxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxx}
17872 @emph{Max_Decimal_Digits}
17885 "The value of @code{Max_Picture_Length} in the package
17886 @code{Text_IO.Editing}. See F.3.3(16)."
17895 "The value of @code{Max_Picture_Length} in the package
17896 @code{Wide_Text_IO.Editing}. See F.3.4(5)."
17905 "The accuracy actually achieved by the complex elementary
17906 functions and by other complex arithmetic operations. See G.1(1)."
17909 Standard library functions are used for the complex arithmetic
17910 operations. Only fast math mode is currently supported.
17916 "The sign of a zero result (or a component thereof) from
17917 any operator or function in @code{Numerics.Generic_Complex_Types}, when
17918 @code{Real'Signed_Zeros} is True. See G.1.1(53)."
17921 The signs of zero values are as recommended by the relevant
17922 implementation advice.
17928 "The sign of a zero result (or a component thereof) from
17929 any operator or function in
17930 @code{Numerics.Generic_Complex_Elementary_Functions}, when
17931 @code{Real'Signed_Zeros} is @code{True}. See G.1.2(45)."
17934 The signs of zero values are as recommended by the relevant
17935 implementation advice.
17941 "Whether the strict mode or the relaxed mode is the
17942 default. See G.2(2)."
17945 The strict mode is the default. There is no separate relaxed mode. GNAT
17946 provides a highly efficient implementation of strict mode.
17952 "The result interval in certain cases of fixed-to-float
17953 conversion. See G.2.1(10)."
17956 For cases where the result interval is implementation dependent, the
17957 accuracy is that provided by performing all operations in 64-bit IEEE
17958 floating-point format.
17964 "The result of a floating point arithmetic operation in
17965 overflow situations, when the @code{Machine_Overflows} attribute of the
17966 result type is @code{False}. See G.2.1(13)."
17969 Infinite and NaN values are produced as dictated by the IEEE
17970 floating-point standard.
17971 Note that on machines that are not fully compliant with the IEEE
17972 floating-point standard, such as Alpha, the @emph{-mieee} compiler flag
17973 must be used for achieving IEEE conforming behavior (although at the cost
17974 of a significant performance penalty), so infinite and NaN values are
17975 properly generated.
17981 "The result interval for division (or exponentiation by a
17982 negative exponent), when the floating point hardware implements division
17983 as multiplication by a reciprocal. See G.2.1(16)."
17986 Not relevant, division is IEEE exact.
17992 "The definition of close result set, which determines the
17993 accuracy of certain fixed point multiplications and divisions. See
17997 Operations in the close result set are performed using IEEE long format
17998 floating-point arithmetic. The input operands are converted to
17999 floating-point, the operation is done in floating-point, and the result
18000 is converted to the target type.
18006 "Conditions on a @emph{universal_real} operand of a fixed
18007 point multiplication or division for which the result shall be in the
18008 perfect result set. See G.2.3(22)."
18011 The result is only defined to be in the perfect result set if the result
18012 can be computed by a single scaling operation involving a scale factor
18013 representable in 64-bits.
18019 "The result of a fixed point arithmetic operation in
18020 overflow situations, when the @code{Machine_Overflows} attribute of the
18021 result type is @code{False}. See G.2.3(27)."
18024 Not relevant, @code{Machine_Overflows} is @code{True} for fixed-point
18031 "The result of an elementary function reference in
18032 overflow situations, when the @code{Machine_Overflows} attribute of the
18033 result type is @code{False}. See G.2.4(4)."
18036 IEEE infinite and Nan values are produced as appropriate.
18042 "The value of the angle threshold, within which certain
18043 elementary functions, complex arithmetic operations, and complex
18044 elementary functions yield results conforming to a maximum relative
18045 error bound. See G.2.4(10)."
18048 Information on this subject is not yet available.
18054 "The accuracy of certain elementary functions for
18055 parameters beyond the angle threshold. See G.2.4(10)."
18058 Information on this subject is not yet available.
18064 "The result of a complex arithmetic operation or complex
18065 elementary function reference in overflow situations, when the
18066 @code{Machine_Overflows} attribute of the corresponding real type is
18067 @code{False}. See G.2.6(5)."
18070 IEEE infinite and Nan values are produced as appropriate.
18076 "The accuracy of certain complex arithmetic operations and
18077 certain complex elementary functions for parameters (or components
18078 thereof) beyond the angle threshold. See G.2.6(8)."
18081 Information on those subjects is not yet available.
18087 "Information regarding bounded errors and erroneous
18088 execution. See H.2(1)."
18091 Information on this subject is not yet available.
18097 "Implementation-defined aspects of pragma
18098 @code{Inspection_Point}. See H.3.2(8)."
18101 Pragma @code{Inspection_Point} ensures that the variable is live and can
18102 be examined by the debugger at the inspection point.
18108 "Implementation-defined aspects of pragma
18109 @code{Restrictions}. See H.4(25)."
18112 There are no implementation-defined aspects of pragma @code{Restrictions}. The
18113 use of pragma @code{Restrictions [No_Exceptions]} has no effect on the
18114 generated code. Checks must suppressed by use of pragma @code{Suppress}.
18120 "Any restrictions on pragma @code{Restrictions}. See
18124 There are no restrictions on pragma @code{Restrictions}.
18126 @node Intrinsic Subprograms,Representation Clauses and Pragmas,Implementation Defined Characteristics,Top
18127 @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}
18128 @chapter Intrinsic Subprograms
18131 @geindex Intrinsic Subprograms
18133 GNAT allows a user application program to write the declaration:
18136 pragma Import (Intrinsic, name);
18139 providing that the name corresponds to one of the implemented intrinsic
18140 subprograms in GNAT, and that the parameter profile of the referenced
18141 subprogram meets the requirements. This chapter describes the set of
18142 implemented intrinsic subprograms, and the requirements on parameter profiles.
18143 Note that no body is supplied; as with other uses of pragma Import, the
18144 body is supplied elsewhere (in this case by the compiler itself). Note
18145 that any use of this feature is potentially non-portable, since the
18146 Ada standard does not require Ada compilers to implement this feature.
18149 * Intrinsic Operators::
18150 * Compilation_ISO_Date::
18151 * Compilation_Date::
18152 * Compilation_Time::
18153 * Enclosing_Entity::
18154 * Exception_Information::
18155 * Exception_Message::
18159 * Shifts and Rotates::
18160 * Source_Location::
18164 @node Intrinsic Operators,Compilation_ISO_Date,,Intrinsic Subprograms
18165 @anchor{gnat_rm/intrinsic_subprograms id2}@anchor{25c}@anchor{gnat_rm/intrinsic_subprograms intrinsic-operators}@anchor{25d}
18166 @section Intrinsic Operators
18169 @geindex Intrinsic operator
18171 All the predefined numeric operators in package Standard
18172 in @code{pragma Import (Intrinsic,..)}
18173 declarations. In the binary operator case, the operands must have the same
18174 size. The operand or operands must also be appropriate for
18175 the operator. For example, for addition, the operands must
18176 both be floating-point or both be fixed-point, and the
18177 right operand for @code{"**"} must have a root type of
18178 @code{Standard.Integer'Base}.
18179 You can use an intrinsic operator declaration as in the following example:
18182 type Int1 is new Integer;
18183 type Int2 is new Integer;
18185 function "+" (X1 : Int1; X2 : Int2) return Int1;
18186 function "+" (X1 : Int1; X2 : Int2) return Int2;
18187 pragma Import (Intrinsic, "+");
18190 This declaration would permit 'mixed mode' arithmetic on items
18191 of the differing types @code{Int1} and @code{Int2}.
18192 It is also possible to specify such operators for private types, if the
18193 full views are appropriate arithmetic types.
18195 @node Compilation_ISO_Date,Compilation_Date,Intrinsic Operators,Intrinsic Subprograms
18196 @anchor{gnat_rm/intrinsic_subprograms id3}@anchor{25e}@anchor{gnat_rm/intrinsic_subprograms compilation-iso-date}@anchor{25f}
18197 @section Compilation_ISO_Date
18200 @geindex Compilation_ISO_Date
18202 This intrinsic subprogram is used in the implementation of the
18203 library package @code{GNAT.Source_Info}. The only useful use of the
18204 intrinsic import in this case is the one in this unit, so an
18205 application program should simply call the function
18206 @code{GNAT.Source_Info.Compilation_ISO_Date} to obtain the date of
18207 the current compilation (in local time format YYYY-MM-DD).
18209 @node Compilation_Date,Compilation_Time,Compilation_ISO_Date,Intrinsic Subprograms
18210 @anchor{gnat_rm/intrinsic_subprograms compilation-date}@anchor{260}@anchor{gnat_rm/intrinsic_subprograms id4}@anchor{261}
18211 @section Compilation_Date
18214 @geindex Compilation_Date
18216 Same as Compilation_ISO_Date, except the string is in the form
18219 @node Compilation_Time,Enclosing_Entity,Compilation_Date,Intrinsic Subprograms
18220 @anchor{gnat_rm/intrinsic_subprograms compilation-time}@anchor{262}@anchor{gnat_rm/intrinsic_subprograms id5}@anchor{263}
18221 @section Compilation_Time
18224 @geindex Compilation_Time
18226 This intrinsic subprogram is used in the implementation of the
18227 library package @code{GNAT.Source_Info}. The only useful use of the
18228 intrinsic import in this case is the one in this unit, so an
18229 application program should simply call the function
18230 @code{GNAT.Source_Info.Compilation_Time} to obtain the time of
18231 the current compilation (in local time format HH:MM:SS).
18233 @node Enclosing_Entity,Exception_Information,Compilation_Time,Intrinsic Subprograms
18234 @anchor{gnat_rm/intrinsic_subprograms id6}@anchor{264}@anchor{gnat_rm/intrinsic_subprograms enclosing-entity}@anchor{265}
18235 @section Enclosing_Entity
18238 @geindex Enclosing_Entity
18240 This intrinsic subprogram is used in the implementation of the
18241 library package @code{GNAT.Source_Info}. The only useful use of the
18242 intrinsic import in this case is the one in this unit, so an
18243 application program should simply call the function
18244 @code{GNAT.Source_Info.Enclosing_Entity} to obtain the name of
18245 the current subprogram, package, task, entry, or protected subprogram.
18247 @node Exception_Information,Exception_Message,Enclosing_Entity,Intrinsic Subprograms
18248 @anchor{gnat_rm/intrinsic_subprograms id7}@anchor{266}@anchor{gnat_rm/intrinsic_subprograms exception-information}@anchor{267}
18249 @section Exception_Information
18252 @geindex Exception_Information'
18254 This intrinsic subprogram is used in the implementation of the
18255 library package @code{GNAT.Current_Exception}. The only useful
18256 use of the intrinsic import in this case is the one in this unit,
18257 so an application program should simply call the function
18258 @code{GNAT.Current_Exception.Exception_Information} to obtain
18259 the exception information associated with the current exception.
18261 @node Exception_Message,Exception_Name,Exception_Information,Intrinsic Subprograms
18262 @anchor{gnat_rm/intrinsic_subprograms exception-message}@anchor{268}@anchor{gnat_rm/intrinsic_subprograms id8}@anchor{269}
18263 @section Exception_Message
18266 @geindex Exception_Message
18268 This intrinsic subprogram is used in the implementation of the
18269 library package @code{GNAT.Current_Exception}. The only useful
18270 use of the intrinsic import in this case is the one in this unit,
18271 so an application program should simply call the function
18272 @code{GNAT.Current_Exception.Exception_Message} to obtain
18273 the message associated with the current exception.
18275 @node Exception_Name,File,Exception_Message,Intrinsic Subprograms
18276 @anchor{gnat_rm/intrinsic_subprograms exception-name}@anchor{26a}@anchor{gnat_rm/intrinsic_subprograms id9}@anchor{26b}
18277 @section Exception_Name
18280 @geindex Exception_Name
18282 This intrinsic subprogram is used in the implementation of the
18283 library package @code{GNAT.Current_Exception}. The only useful
18284 use of the intrinsic import in this case is the one in this unit,
18285 so an application program should simply call the function
18286 @code{GNAT.Current_Exception.Exception_Name} to obtain
18287 the name of the current exception.
18289 @node File,Line,Exception_Name,Intrinsic Subprograms
18290 @anchor{gnat_rm/intrinsic_subprograms id10}@anchor{26c}@anchor{gnat_rm/intrinsic_subprograms file}@anchor{26d}
18296 This intrinsic subprogram is used in the implementation of the
18297 library package @code{GNAT.Source_Info}. The only useful use of the
18298 intrinsic import in this case is the one in this unit, so an
18299 application program should simply call the function
18300 @code{GNAT.Source_Info.File} to obtain the name of the current
18303 @node Line,Shifts and Rotates,File,Intrinsic Subprograms
18304 @anchor{gnat_rm/intrinsic_subprograms id11}@anchor{26e}@anchor{gnat_rm/intrinsic_subprograms line}@anchor{26f}
18310 This intrinsic subprogram is used in the implementation of the
18311 library package @code{GNAT.Source_Info}. The only useful use of the
18312 intrinsic import in this case is the one in this unit, so an
18313 application program should simply call the function
18314 @code{GNAT.Source_Info.Line} to obtain the number of the current
18317 @node Shifts and Rotates,Source_Location,Line,Intrinsic Subprograms
18318 @anchor{gnat_rm/intrinsic_subprograms shifts-and-rotates}@anchor{270}@anchor{gnat_rm/intrinsic_subprograms id12}@anchor{271}
18319 @section Shifts and Rotates
18322 @geindex Shift_Left
18324 @geindex Shift_Right
18326 @geindex Shift_Right_Arithmetic
18328 @geindex Rotate_Left
18330 @geindex Rotate_Right
18332 In standard Ada, the shift and rotate functions are available only
18333 for the predefined modular types in package @code{Interfaces}. However, in
18334 GNAT it is possible to define these functions for any integer
18335 type (signed or modular), as in this example:
18338 function Shift_Left
18340 Amount : Natural) return T;
18343 The function name must be one of
18344 Shift_Left, Shift_Right, Shift_Right_Arithmetic, Rotate_Left, or
18345 Rotate_Right. T must be an integer type. T'Size must be
18346 8, 16, 32 or 64 bits; if T is modular, the modulus
18347 must be 2**8, 2**16, 2**32 or 2**64.
18348 The result type must be the same as the type of @code{Value}.
18349 The shift amount must be Natural.
18350 The formal parameter names can be anything.
18352 A more convenient way of providing these shift operators is to use
18353 the Provide_Shift_Operators pragma, which provides the function declarations
18354 and corresponding pragma Import's for all five shift functions.
18356 @node Source_Location,,Shifts and Rotates,Intrinsic Subprograms
18357 @anchor{gnat_rm/intrinsic_subprograms source-location}@anchor{272}@anchor{gnat_rm/intrinsic_subprograms id13}@anchor{273}
18358 @section Source_Location
18361 @geindex Source_Location
18363 This intrinsic subprogram is used in the implementation of the
18364 library routine @code{GNAT.Source_Info}. The only useful use of the
18365 intrinsic import in this case is the one in this unit, so an
18366 application program should simply call the function
18367 @code{GNAT.Source_Info.Source_Location} to obtain the current
18368 source file location.
18370 @node Representation Clauses and Pragmas,Standard Library Routines,Intrinsic Subprograms,Top
18371 @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}
18372 @chapter Representation Clauses and Pragmas
18375 @geindex Representation Clauses
18377 @geindex Representation Clause
18379 @geindex Representation Pragma
18382 @geindex representation
18384 This section describes the representation clauses accepted by GNAT, and
18385 their effect on the representation of corresponding data objects.
18387 GNAT fully implements Annex C (Systems Programming). This means that all
18388 the implementation advice sections in chapter 13 are fully implemented.
18389 However, these sections only require a minimal level of support for
18390 representation clauses. GNAT provides much more extensive capabilities,
18391 and this section describes the additional capabilities provided.
18394 * Alignment Clauses::
18396 * Storage_Size Clauses::
18397 * Size of Variant Record Objects::
18398 * Biased Representation::
18399 * Value_Size and Object_Size Clauses::
18400 * Component_Size Clauses::
18401 * Bit_Order Clauses::
18402 * Effect of Bit_Order on Byte Ordering::
18403 * Pragma Pack for Arrays::
18404 * Pragma Pack for Records::
18405 * Record Representation Clauses::
18406 * Handling of Records with Holes::
18407 * Enumeration Clauses::
18408 * Address Clauses::
18409 * Use of Address Clauses for Memory-Mapped I/O::
18410 * Effect of Convention on Representation::
18411 * Conventions and Anonymous Access Types::
18412 * Determining the Representations chosen by GNAT::
18416 @node Alignment Clauses,Size Clauses,,Representation Clauses and Pragmas
18417 @anchor{gnat_rm/representation_clauses_and_pragmas id2}@anchor{276}@anchor{gnat_rm/representation_clauses_and_pragmas alignment-clauses}@anchor{277}
18418 @section Alignment Clauses
18421 @geindex Alignment Clause
18423 GNAT requires that all alignment clauses specify 0 or a power of 2, and
18424 all default alignments are always a power of 2. Specifying 0 is the
18425 same as specifying 1.
18427 The default alignment values are as follows:
18433 @emph{Elementary Types}.
18435 For elementary types, the alignment is the minimum of the actual size of
18436 objects of the type divided by @code{Storage_Unit},
18437 and the maximum alignment supported by the target.
18438 (This maximum alignment is given by the GNAT-specific attribute
18439 @code{Standard'Maximum_Alignment}; see @ref{191,,Attribute Maximum_Alignment}.)
18441 @geindex Maximum_Alignment attribute
18443 For example, for type @code{Long_Float}, the object size is 8 bytes, and the
18444 default alignment will be 8 on any target that supports alignments
18445 this large, but on some targets, the maximum alignment may be smaller
18446 than 8, in which case objects of type @code{Long_Float} will be maximally
18452 For arrays, the alignment is equal to the alignment of the component type
18453 for the normal case where no packing or component size is given. If the
18454 array is packed, and the packing is effective (see separate section on
18455 packed arrays), then the alignment will be either 4, 2, or 1 for long packed
18456 arrays or arrays whose length is not known at compile time, depending on
18457 whether the component size is divisible by 4, 2, or is odd. For short packed
18458 arrays, which are handled internally as modular types, the alignment
18459 will be as described for elementary types, e.g. a packed array of length
18460 31 bits will have an object size of four bytes, and an alignment of 4.
18465 For the normal unpacked case, the alignment of a record is equal to
18466 the maximum alignment of any of its components. For tagged records, this
18467 includes the implicit access type used for the tag. If a pragma @code{Pack}
18468 is used and all components are packable (see separate section on pragma
18469 @code{Pack}), then the resulting alignment is 1, unless the layout of the
18470 record makes it profitable to increase it.
18472 A special case is when:
18478 the size of the record is given explicitly, or a
18479 full record representation clause is given, and
18482 the size of the record is 2, 4, or 8 bytes.
18485 In this case, an alignment is chosen to match the
18486 size of the record. For example, if we have:
18489 type Small is record
18492 for Small'Size use 16;
18495 then the default alignment of the record type @code{Small} is 2, not 1. This
18496 leads to more efficient code when the record is treated as a unit, and also
18497 allows the type to specified as @code{Atomic} on architectures requiring
18501 An alignment clause may specify a larger alignment than the default value
18502 up to some maximum value dependent on the target (obtainable by using the
18503 attribute reference @code{Standard'Maximum_Alignment}). It may also specify
18504 a smaller alignment than the default value for enumeration, integer and
18505 fixed point types, as well as for record types, for example
18512 for V'alignment use 1;
18518 The default alignment for the type @code{V} is 4, as a result of the
18519 Integer field in the record, but it is permissible, as shown, to
18520 override the default alignment of the record with a smaller value.
18525 Note that according to the Ada standard, an alignment clause applies only
18526 to the first named subtype. If additional subtypes are declared, then the
18527 compiler is allowed to choose any alignment it likes, and there is no way
18528 to control this choice. Consider:
18531 type R is range 1 .. 10_000;
18532 for R'Alignment use 1;
18533 subtype RS is R range 1 .. 1000;
18536 The alignment clause specifies an alignment of 1 for the first named subtype
18537 @code{R} but this does not necessarily apply to @code{RS}. When writing
18538 portable Ada code, you should avoid writing code that explicitly or
18539 implicitly relies on the alignment of such subtypes.
18541 For the GNAT compiler, if an explicit alignment clause is given, this
18542 value is also used for any subsequent subtypes. So for GNAT, in the
18543 above example, you can count on the alignment of @code{RS} being 1. But this
18544 assumption is non-portable, and other compilers may choose different
18545 alignments for the subtype @code{RS}.
18547 @node Size Clauses,Storage_Size Clauses,Alignment Clauses,Representation Clauses and Pragmas
18548 @anchor{gnat_rm/representation_clauses_and_pragmas id3}@anchor{278}@anchor{gnat_rm/representation_clauses_and_pragmas size-clauses}@anchor{279}
18549 @section Size Clauses
18552 @geindex Size Clause
18554 The default size for a type @code{T} is obtainable through the
18555 language-defined attribute @code{T'Size} and also through the
18556 equivalent GNAT-defined attribute @code{T'Value_Size}.
18557 For objects of type @code{T}, GNAT will generally increase the type size
18558 so that the object size (obtainable through the GNAT-defined attribute
18559 @code{T'Object_Size})
18560 is a multiple of @code{T'Alignment * Storage_Unit}.
18565 type Smallint is range 1 .. 6;
18573 In this example, @code{Smallint'Size} = @code{Smallint'Value_Size} = 3,
18574 as specified by the RM rules,
18575 but objects of this type will have a size of 8
18576 (@code{Smallint'Object_Size} = 8),
18577 since objects by default occupy an integral number
18578 of storage units. On some targets, notably older
18579 versions of the Digital Alpha, the size of stand
18580 alone objects of this type may be 32, reflecting
18581 the inability of the hardware to do byte load/stores.
18583 Similarly, the size of type @code{Rec} is 40 bits
18584 (@code{Rec'Size} = @code{Rec'Value_Size} = 40), but
18585 the alignment is 4, so objects of this type will have
18586 their size increased to 64 bits so that it is a multiple
18587 of the alignment (in bits). This decision is
18588 in accordance with the specific Implementation Advice in RM 13.3(43):
18592 "A @code{Size} clause should be supported for an object if the specified
18593 @code{Size} is at least as large as its subtype's @code{Size}, and corresponds
18594 to a size in storage elements that is a multiple of the object's
18595 @code{Alignment} (if the @code{Alignment} is nonzero)."
18598 An explicit size clause may be used to override the default size by
18599 increasing it. For example, if we have:
18602 type My_Boolean is new Boolean;
18603 for My_Boolean'Size use 32;
18606 then values of this type will always be 32 bits long. In the case of
18607 discrete types, the size can be increased up to 64 bits, with the effect
18608 that the entire specified field is used to hold the value, sign- or
18609 zero-extended as appropriate. If more than 64 bits is specified, then
18610 padding space is allocated after the value, and a warning is issued that
18611 there are unused bits.
18613 Similarly the size of records and arrays may be increased, and the effect
18614 is to add padding bits after the value. This also causes a warning message
18617 The largest Size value permitted in GNAT is 2**31-1. Since this is a
18618 Size in bits, this corresponds to an object of size 256 megabytes (minus
18619 one). This limitation is true on all targets. The reason for this
18620 limitation is that it improves the quality of the code in many cases
18621 if it is known that a Size value can be accommodated in an object of
18624 @node Storage_Size Clauses,Size of Variant Record Objects,Size Clauses,Representation Clauses and Pragmas
18625 @anchor{gnat_rm/representation_clauses_and_pragmas storage-size-clauses}@anchor{27a}@anchor{gnat_rm/representation_clauses_and_pragmas id4}@anchor{27b}
18626 @section Storage_Size Clauses
18629 @geindex Storage_Size Clause
18631 For tasks, the @code{Storage_Size} clause specifies the amount of space
18632 to be allocated for the task stack. This cannot be extended, and if the
18633 stack is exhausted, then @code{Storage_Error} will be raised (if stack
18634 checking is enabled). Use a @code{Storage_Size} attribute definition clause,
18635 or a @code{Storage_Size} pragma in the task definition to set the
18636 appropriate required size. A useful technique is to include in every
18637 task definition a pragma of the form:
18640 pragma Storage_Size (Default_Stack_Size);
18643 Then @code{Default_Stack_Size} can be defined in a global package, and
18644 modified as required. Any tasks requiring stack sizes different from the
18645 default can have an appropriate alternative reference in the pragma.
18647 You can also use the @emph{-d} binder switch to modify the default stack
18650 For access types, the @code{Storage_Size} clause specifies the maximum
18651 space available for allocation of objects of the type. If this space is
18652 exceeded then @code{Storage_Error} will be raised by an allocation attempt.
18653 In the case where the access type is declared local to a subprogram, the
18654 use of a @code{Storage_Size} clause triggers automatic use of a special
18655 predefined storage pool (@code{System.Pool_Size}) that ensures that all
18656 space for the pool is automatically reclaimed on exit from the scope in
18657 which the type is declared.
18659 A special case recognized by the compiler is the specification of a
18660 @code{Storage_Size} of zero for an access type. This means that no
18661 items can be allocated from the pool, and this is recognized at compile
18662 time, and all the overhead normally associated with maintaining a fixed
18663 size storage pool is eliminated. Consider the following example:
18667 type R is array (Natural) of Character;
18668 type P is access all R;
18669 for P'Storage_Size use 0;
18670 -- Above access type intended only for interfacing purposes
18674 procedure g (m : P);
18675 pragma Import (C, g);
18685 As indicated in this example, these dummy storage pools are often useful in
18686 connection with interfacing where no object will ever be allocated. If you
18687 compile the above example, you get the warning:
18690 p.adb:16:09: warning: allocation from empty storage pool
18691 p.adb:16:09: warning: Storage_Error will be raised at run time
18694 Of course in practice, there will not be any explicit allocators in the
18695 case of such an access declaration.
18697 @node Size of Variant Record Objects,Biased Representation,Storage_Size Clauses,Representation Clauses and Pragmas
18698 @anchor{gnat_rm/representation_clauses_and_pragmas id5}@anchor{27c}@anchor{gnat_rm/representation_clauses_and_pragmas size-of-variant-record-objects}@anchor{27d}
18699 @section Size of Variant Record Objects
18703 @geindex variant record objects
18705 @geindex Variant record objects
18708 In the case of variant record objects, there is a question whether Size gives
18709 information about a particular variant, or the maximum size required
18710 for any variant. Consider the following program
18713 with Text_IO; use Text_IO;
18715 type R1 (A : Boolean := False) is record
18717 when True => X : Character;
18718 when False => null;
18726 Put_Line (Integer'Image (V1'Size));
18727 Put_Line (Integer'Image (V2'Size));
18731 Here we are dealing with a variant record, where the True variant
18732 requires 16 bits, and the False variant requires 8 bits.
18733 In the above example, both V1 and V2 contain the False variant,
18734 which is only 8 bits long. However, the result of running the
18742 The reason for the difference here is that the discriminant value of
18743 V1 is fixed, and will always be False. It is not possible to assign
18744 a True variant value to V1, therefore 8 bits is sufficient. On the
18745 other hand, in the case of V2, the initial discriminant value is
18746 False (from the default), but it is possible to assign a True
18747 variant value to V2, therefore 16 bits must be allocated for V2
18748 in the general case, even fewer bits may be needed at any particular
18749 point during the program execution.
18751 As can be seen from the output of this program, the @code{'Size}
18752 attribute applied to such an object in GNAT gives the actual allocated
18753 size of the variable, which is the largest size of any of the variants.
18754 The Ada Reference Manual is not completely clear on what choice should
18755 be made here, but the GNAT behavior seems most consistent with the
18756 language in the RM.
18758 In some cases, it may be desirable to obtain the size of the current
18759 variant, rather than the size of the largest variant. This can be
18760 achieved in GNAT by making use of the fact that in the case of a
18761 subprogram parameter, GNAT does indeed return the size of the current
18762 variant (because a subprogram has no way of knowing how much space
18763 is actually allocated for the actual).
18765 Consider the following modified version of the above program:
18768 with Text_IO; use Text_IO;
18770 type R1 (A : Boolean := False) is record
18772 when True => X : Character;
18773 when False => null;
18779 function Size (V : R1) return Integer is
18785 Put_Line (Integer'Image (V2'Size));
18786 Put_Line (Integer'Image (Size (V2)));
18788 Put_Line (Integer'Image (V2'Size));
18789 Put_Line (Integer'Image (Size (V2)));
18793 The output from this program is
18802 Here we see that while the @code{'Size} attribute always returns
18803 the maximum size, regardless of the current variant value, the
18804 @code{Size} function does indeed return the size of the current
18807 @node Biased Representation,Value_Size and Object_Size Clauses,Size of Variant Record Objects,Representation Clauses and Pragmas
18808 @anchor{gnat_rm/representation_clauses_and_pragmas id6}@anchor{27e}@anchor{gnat_rm/representation_clauses_and_pragmas biased-representation}@anchor{27f}
18809 @section Biased Representation
18812 @geindex Size for biased representation
18814 @geindex Biased representation
18816 In the case of scalars with a range starting at other than zero, it is
18817 possible in some cases to specify a size smaller than the default minimum
18818 value, and in such cases, GNAT uses an unsigned biased representation,
18819 in which zero is used to represent the lower bound, and successive values
18820 represent successive values of the type.
18822 For example, suppose we have the declaration:
18825 type Small is range -7 .. -4;
18826 for Small'Size use 2;
18829 Although the default size of type @code{Small} is 4, the @code{Size}
18830 clause is accepted by GNAT and results in the following representation
18834 -7 is represented as 2#00#
18835 -6 is represented as 2#01#
18836 -5 is represented as 2#10#
18837 -4 is represented as 2#11#
18840 Biased representation is only used if the specified @code{Size} clause
18841 cannot be accepted in any other manner. These reduced sizes that force
18842 biased representation can be used for all discrete types except for
18843 enumeration types for which a representation clause is given.
18845 @node Value_Size and Object_Size Clauses,Component_Size Clauses,Biased Representation,Representation Clauses and Pragmas
18846 @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}
18847 @section Value_Size and Object_Size Clauses
18850 @geindex Value_Size
18852 @geindex Object_Size
18855 @geindex of objects
18857 In Ada 95 and Ada 2005, @code{T'Size} for a type @code{T} is the minimum
18858 number of bits required to hold values of type @code{T}.
18859 Although this interpretation was allowed in Ada 83, it was not required,
18860 and this requirement in practice can cause some significant difficulties.
18861 For example, in most Ada 83 compilers, @code{Natural'Size} was 32.
18862 However, in Ada 95 and Ada 2005,
18863 @code{Natural'Size} is
18864 typically 31. This means that code may change in behavior when moving
18865 from Ada 83 to Ada 95 or Ada 2005. For example, consider:
18868 type Rec is record;
18874 at 0 range 0 .. Natural'Size - 1;
18875 at 0 range Natural'Size .. 2 * Natural'Size - 1;
18879 In the above code, since the typical size of @code{Natural} objects
18880 is 32 bits and @code{Natural'Size} is 31, the above code can cause
18881 unexpected inefficient packing in Ada 95 and Ada 2005, and in general
18882 there are cases where the fact that the object size can exceed the
18883 size of the type causes surprises.
18885 To help get around this problem GNAT provides two implementation
18886 defined attributes, @code{Value_Size} and @code{Object_Size}. When
18887 applied to a type, these attributes yield the size of the type
18888 (corresponding to the RM defined size attribute), and the size of
18889 objects of the type respectively.
18891 The @code{Object_Size} is used for determining the default size of
18892 objects and components. This size value can be referred to using the
18893 @code{Object_Size} attribute. The phrase 'is used' here means that it is
18894 the basis of the determination of the size. The backend is free to
18895 pad this up if necessary for efficiency, e.g., an 8-bit stand-alone
18896 character might be stored in 32 bits on a machine with no efficient
18897 byte access instructions such as the Alpha.
18899 The default rules for the value of @code{Object_Size} for
18900 discrete types are as follows:
18906 The @code{Object_Size} for base subtypes reflect the natural hardware
18907 size in bits (run the compiler with @emph{-gnatS} to find those values
18908 for numeric types). Enumeration types and fixed-point base subtypes have
18909 8, 16, 32, or 64 bits for this size, depending on the range of values
18913 The @code{Object_Size} of a subtype is the same as the
18914 @code{Object_Size} of
18915 the type from which it is obtained.
18918 The @code{Object_Size} of a derived base type is copied from the parent
18919 base type, and the @code{Object_Size} of a derived first subtype is copied
18920 from the parent first subtype.
18923 The @code{Value_Size} attribute
18924 is the (minimum) number of bits required to store a value
18926 This value is used to determine how tightly to pack
18927 records or arrays with components of this type, and also affects
18928 the semantics of unchecked conversion (unchecked conversions where
18929 the @code{Value_Size} values differ generate a warning, and are potentially
18932 The default rules for the value of @code{Value_Size} are as follows:
18938 The @code{Value_Size} for a base subtype is the minimum number of bits
18939 required to store all values of the type (including the sign bit
18940 only if negative values are possible).
18943 If a subtype statically matches the first subtype of a given type, then it has
18944 by default the same @code{Value_Size} as the first subtype. This is a
18945 consequence of RM 13.1(14): "if two subtypes statically match,
18946 then their subtype-specific aspects are the same".)
18949 All other subtypes have a @code{Value_Size} corresponding to the minimum
18950 number of bits required to store all values of the subtype. For
18951 dynamic bounds, it is assumed that the value can range down or up
18952 to the corresponding bound of the ancestor
18955 The RM defined attribute @code{Size} corresponds to the
18956 @code{Value_Size} attribute.
18958 The @code{Size} attribute may be defined for a first-named subtype. This sets
18959 the @code{Value_Size} of
18960 the first-named subtype to the given value, and the
18961 @code{Object_Size} of this first-named subtype to the given value padded up
18962 to an appropriate boundary. It is a consequence of the default rules
18963 above that this @code{Object_Size} will apply to all further subtypes. On the
18964 other hand, @code{Value_Size} is affected only for the first subtype, any
18965 dynamic subtypes obtained from it directly, and any statically matching
18966 subtypes. The @code{Value_Size} of any other static subtypes is not affected.
18968 @code{Value_Size} and
18969 @code{Object_Size} may be explicitly set for any subtype using
18970 an attribute definition clause. Note that the use of these attributes
18971 can cause the RM 13.1(14) rule to be violated. If two access types
18972 reference aliased objects whose subtypes have differing @code{Object_Size}
18973 values as a result of explicit attribute definition clauses, then it
18974 is illegal to convert from one access subtype to the other. For a more
18975 complete description of this additional legality rule, see the
18976 description of the @code{Object_Size} attribute.
18978 To get a feel for the difference, consider the following examples (note
18979 that in each case the base is @code{Short_Short_Integer} with a size of 8):
18982 @multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxx}
18985 Type or subtype declaration
18997 @code{type x1 is range 0 .. 5;}
19009 @code{type x2 is range 0 .. 5;}
19010 @code{for x2'size use 12;}
19022 @code{subtype x3 is x2 range 0 .. 3;}
19034 @code{subtype x4 is x2'base range 0 .. 10;}
19046 @code{dynamic : x2'Base range -64 .. +63;}
19054 @code{subtype x5 is x2 range 0 .. dynamic;}
19066 @code{subtype x6 is x2'base range 0 .. dynamic;}
19079 Note: the entries marked '*' are not actually specified by the Ada
19080 Reference Manual, which has nothing to say about size in the dynamic
19081 case. What GNAT does is to allocate sufficient bits to accomodate any
19082 possible dynamic values for the bounds at run-time.
19084 So far, so good, but GNAT has to obey the RM rules, so the question is
19085 under what conditions must the RM @code{Size} be used.
19086 The following is a list
19087 of the occasions on which the RM @code{Size} must be used:
19093 Component size for packed arrays or records
19096 Value of the attribute @code{Size} for a type
19099 Warning about sizes not matching for unchecked conversion
19102 For record types, the @code{Object_Size} is always a multiple of the
19103 alignment of the type (this is true for all types). In some cases the
19104 @code{Value_Size} can be smaller. Consider:
19113 On a typical 32-bit architecture, the X component will occupy four bytes
19114 and the Y component will occupy one byte, for a total of 5 bytes. As a
19115 result @code{R'Value_Size} will be 40 (bits) since this is the minimum size
19116 required to store a value of this type. For example, it is permissible
19117 to have a component of type R in an array whose component size is
19118 specified to be 40 bits.
19120 However, @code{R'Object_Size} will be 64 (bits). The difference is due to
19121 the alignment requirement for objects of the record type. The X
19122 component will require four-byte alignment because that is what type
19123 Integer requires, whereas the Y component, a Character, will only
19124 require 1-byte alignment. Since the alignment required for X is the
19125 greatest of all the components' alignments, that is the alignment
19126 required for the enclosing record type, i.e., 4 bytes or 32 bits. As
19127 indicated above, the actual object size must be rounded up so that it is
19128 a multiple of the alignment value. Therefore, 40 bits rounded up to the
19129 next multiple of 32 yields 64 bits.
19131 For all other types, the @code{Object_Size}
19132 and @code{Value_Size} are the same (and equivalent to the RM attribute @code{Size}).
19133 Only @code{Size} may be specified for such types.
19135 Note that @code{Value_Size} can be used to force biased representation
19136 for a particular subtype. Consider this example:
19139 type R is (A, B, C, D, E, F);
19140 subtype RAB is R range A .. B;
19141 subtype REF is R range E .. F;
19144 By default, @code{RAB}
19145 has a size of 1 (sufficient to accommodate the representation
19146 of @code{A} and @code{B}, 0 and 1), and @code{REF}
19147 has a size of 3 (sufficient to accommodate the representation
19148 of @code{E} and @code{F}, 4 and 5). But if we add the
19149 following @code{Value_Size} attribute definition clause:
19152 for REF'Value_Size use 1;
19155 then biased representation is forced for @code{REF},
19156 and 0 will represent @code{E} and 1 will represent @code{F}.
19157 A warning is issued when a @code{Value_Size} attribute
19158 definition clause forces biased representation. This
19159 warning can be turned off using @code{-gnatw.B}.
19161 @node Component_Size Clauses,Bit_Order Clauses,Value_Size and Object_Size Clauses,Representation Clauses and Pragmas
19162 @anchor{gnat_rm/representation_clauses_and_pragmas id8}@anchor{282}@anchor{gnat_rm/representation_clauses_and_pragmas component-size-clauses}@anchor{283}
19163 @section Component_Size Clauses
19166 @geindex Component_Size Clause
19168 Normally, the value specified in a component size clause must be consistent
19169 with the subtype of the array component with regard to size and alignment.
19170 In other words, the value specified must be at least equal to the size
19171 of this subtype, and must be a multiple of the alignment value.
19173 In addition, component size clauses are allowed which cause the array
19174 to be packed, by specifying a smaller value. A first case is for
19175 component size values in the range 1 through 63. The value specified
19176 must not be smaller than the Size of the subtype. GNAT will accurately
19177 honor all packing requests in this range. For example, if we have:
19180 type r is array (1 .. 8) of Natural;
19181 for r'Component_Size use 31;
19184 then the resulting array has a length of 31 bytes (248 bits = 8 * 31).
19185 Of course access to the components of such an array is considerably
19186 less efficient than if the natural component size of 32 is used.
19187 A second case is when the subtype of the component is a record type
19188 padded because of its default alignment. For example, if we have:
19197 type a is array (1 .. 8) of r;
19198 for a'Component_Size use 72;
19201 then the resulting array has a length of 72 bytes, instead of 96 bytes
19202 if the alignment of the record (4) was obeyed.
19204 Note that there is no point in giving both a component size clause
19205 and a pragma Pack for the same array type. if such duplicate
19206 clauses are given, the pragma Pack will be ignored.
19208 @node Bit_Order Clauses,Effect of Bit_Order on Byte Ordering,Component_Size Clauses,Representation Clauses and Pragmas
19209 @anchor{gnat_rm/representation_clauses_and_pragmas bit-order-clauses}@anchor{284}@anchor{gnat_rm/representation_clauses_and_pragmas id9}@anchor{285}
19210 @section Bit_Order Clauses
19213 @geindex Bit_Order Clause
19215 @geindex bit ordering
19220 For record subtypes, GNAT permits the specification of the @code{Bit_Order}
19221 attribute. The specification may either correspond to the default bit
19222 order for the target, in which case the specification has no effect and
19223 places no additional restrictions, or it may be for the non-standard
19224 setting (that is the opposite of the default).
19226 In the case where the non-standard value is specified, the effect is
19227 to renumber bits within each byte, but the ordering of bytes is not
19228 affected. There are certain
19229 restrictions placed on component clauses as follows:
19235 Components fitting within a single storage unit.
19237 These are unrestricted, and the effect is merely to renumber bits. For
19238 example if we are on a little-endian machine with @code{Low_Order_First}
19239 being the default, then the following two declarations have exactly
19245 B : Integer range 1 .. 120;
19249 A at 0 range 0 .. 0;
19250 B at 0 range 1 .. 7;
19255 B : Integer range 1 .. 120;
19258 for R2'Bit_Order use High_Order_First;
19261 A at 0 range 7 .. 7;
19262 B at 0 range 0 .. 6;
19266 The useful application here is to write the second declaration with the
19267 @code{Bit_Order} attribute definition clause, and know that it will be treated
19268 the same, regardless of whether the target is little-endian or big-endian.
19271 Components occupying an integral number of bytes.
19273 These are components that exactly fit in two or more bytes. Such component
19274 declarations are allowed, but have no effect, since it is important to realize
19275 that the @code{Bit_Order} specification does not affect the ordering of bytes.
19276 In particular, the following attempt at getting an endian-independent integer
19284 for R2'Bit_Order use High_Order_First;
19287 A at 0 range 0 .. 31;
19291 This declaration will result in a little-endian integer on a
19292 little-endian machine, and a big-endian integer on a big-endian machine.
19293 If byte flipping is required for interoperability between big- and
19294 little-endian machines, this must be explicitly programmed. This capability
19295 is not provided by @code{Bit_Order}.
19298 Components that are positioned across byte boundaries.
19300 but do not occupy an integral number of bytes. Given that bytes are not
19301 reordered, such fields would occupy a non-contiguous sequence of bits
19302 in memory, requiring non-trivial code to reassemble. They are for this
19303 reason not permitted, and any component clause specifying such a layout
19304 will be flagged as illegal by GNAT.
19307 Since the misconception that Bit_Order automatically deals with all
19308 endian-related incompatibilities is a common one, the specification of
19309 a component field that is an integral number of bytes will always
19310 generate a warning. This warning may be suppressed using @code{pragma Warnings (Off)}
19311 if desired. The following section contains additional
19312 details regarding the issue of byte ordering.
19314 @node Effect of Bit_Order on Byte Ordering,Pragma Pack for Arrays,Bit_Order Clauses,Representation Clauses and Pragmas
19315 @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}
19316 @section Effect of Bit_Order on Byte Ordering
19319 @geindex byte ordering
19324 In this section we will review the effect of the @code{Bit_Order} attribute
19325 definition clause on byte ordering. Briefly, it has no effect at all, but
19326 a detailed example will be helpful. Before giving this
19327 example, let us review the precise
19328 definition of the effect of defining @code{Bit_Order}. The effect of a
19329 non-standard bit order is described in section 13.5.3 of the Ada
19334 "2 A bit ordering is a method of interpreting the meaning of
19335 the storage place attributes."
19338 To understand the precise definition of storage place attributes in
19339 this context, we visit section 13.5.1 of the manual:
19343 "13 A record_representation_clause (without the mod_clause)
19344 specifies the layout. The storage place attributes (see 13.5.2)
19345 are taken from the values of the position, first_bit, and last_bit
19346 expressions after normalizing those values so that first_bit is
19347 less than Storage_Unit."
19350 The critical point here is that storage places are taken from
19351 the values after normalization, not before. So the @code{Bit_Order}
19352 interpretation applies to normalized values. The interpretation
19353 is described in the later part of the 13.5.3 paragraph:
19357 "2 A bit ordering is a method of interpreting the meaning of
19358 the storage place attributes. High_Order_First (known in the
19359 vernacular as 'big endian') means that the first bit of a
19360 storage element (bit 0) is the most significant bit (interpreting
19361 the sequence of bits that represent a component as an unsigned
19362 integer value). Low_Order_First (known in the vernacular as
19363 'little endian') means the opposite: the first bit is the
19364 least significant."
19367 Note that the numbering is with respect to the bits of a storage
19368 unit. In other words, the specification affects only the numbering
19369 of bits within a single storage unit.
19371 We can make the effect clearer by giving an example.
19373 Suppose that we have an external device which presents two bytes, the first
19374 byte presented, which is the first (low addressed byte) of the two byte
19375 record is called Master, and the second byte is called Slave.
19377 The left most (most significant bit is called Control for each byte, and
19378 the remaining 7 bits are called V1, V2, ... V7, where V7 is the rightmost
19379 (least significant) bit.
19381 On a big-endian machine, we can write the following representation clause
19384 type Data is record
19385 Master_Control : Bit;
19393 Slave_Control : Bit;
19403 for Data use record
19404 Master_Control at 0 range 0 .. 0;
19405 Master_V1 at 0 range 1 .. 1;
19406 Master_V2 at 0 range 2 .. 2;
19407 Master_V3 at 0 range 3 .. 3;
19408 Master_V4 at 0 range 4 .. 4;
19409 Master_V5 at 0 range 5 .. 5;
19410 Master_V6 at 0 range 6 .. 6;
19411 Master_V7 at 0 range 7 .. 7;
19412 Slave_Control at 1 range 0 .. 0;
19413 Slave_V1 at 1 range 1 .. 1;
19414 Slave_V2 at 1 range 2 .. 2;
19415 Slave_V3 at 1 range 3 .. 3;
19416 Slave_V4 at 1 range 4 .. 4;
19417 Slave_V5 at 1 range 5 .. 5;
19418 Slave_V6 at 1 range 6 .. 6;
19419 Slave_V7 at 1 range 7 .. 7;
19423 Now if we move this to a little endian machine, then the bit ordering within
19424 the byte is backwards, so we have to rewrite the record rep clause as:
19427 for Data use record
19428 Master_Control at 0 range 7 .. 7;
19429 Master_V1 at 0 range 6 .. 6;
19430 Master_V2 at 0 range 5 .. 5;
19431 Master_V3 at 0 range 4 .. 4;
19432 Master_V4 at 0 range 3 .. 3;
19433 Master_V5 at 0 range 2 .. 2;
19434 Master_V6 at 0 range 1 .. 1;
19435 Master_V7 at 0 range 0 .. 0;
19436 Slave_Control at 1 range 7 .. 7;
19437 Slave_V1 at 1 range 6 .. 6;
19438 Slave_V2 at 1 range 5 .. 5;
19439 Slave_V3 at 1 range 4 .. 4;
19440 Slave_V4 at 1 range 3 .. 3;
19441 Slave_V5 at 1 range 2 .. 2;
19442 Slave_V6 at 1 range 1 .. 1;
19443 Slave_V7 at 1 range 0 .. 0;
19447 It is a nuisance to have to rewrite the clause, especially if
19448 the code has to be maintained on both machines. However,
19449 this is a case that we can handle with the
19450 @code{Bit_Order} attribute if it is implemented.
19451 Note that the implementation is not required on byte addressed
19452 machines, but it is indeed implemented in GNAT.
19453 This means that we can simply use the
19454 first record clause, together with the declaration
19457 for Data'Bit_Order use High_Order_First;
19460 and the effect is what is desired, namely the layout is exactly the same,
19461 independent of whether the code is compiled on a big-endian or little-endian
19464 The important point to understand is that byte ordering is not affected.
19465 A @code{Bit_Order} attribute definition never affects which byte a field
19466 ends up in, only where it ends up in that byte.
19467 To make this clear, let us rewrite the record rep clause of the previous
19471 for Data'Bit_Order use High_Order_First;
19472 for Data use record
19473 Master_Control at 0 range 0 .. 0;
19474 Master_V1 at 0 range 1 .. 1;
19475 Master_V2 at 0 range 2 .. 2;
19476 Master_V3 at 0 range 3 .. 3;
19477 Master_V4 at 0 range 4 .. 4;
19478 Master_V5 at 0 range 5 .. 5;
19479 Master_V6 at 0 range 6 .. 6;
19480 Master_V7 at 0 range 7 .. 7;
19481 Slave_Control at 0 range 8 .. 8;
19482 Slave_V1 at 0 range 9 .. 9;
19483 Slave_V2 at 0 range 10 .. 10;
19484 Slave_V3 at 0 range 11 .. 11;
19485 Slave_V4 at 0 range 12 .. 12;
19486 Slave_V5 at 0 range 13 .. 13;
19487 Slave_V6 at 0 range 14 .. 14;
19488 Slave_V7 at 0 range 15 .. 15;
19492 This is exactly equivalent to saying (a repeat of the first example):
19495 for Data'Bit_Order use High_Order_First;
19496 for Data use record
19497 Master_Control at 0 range 0 .. 0;
19498 Master_V1 at 0 range 1 .. 1;
19499 Master_V2 at 0 range 2 .. 2;
19500 Master_V3 at 0 range 3 .. 3;
19501 Master_V4 at 0 range 4 .. 4;
19502 Master_V5 at 0 range 5 .. 5;
19503 Master_V6 at 0 range 6 .. 6;
19504 Master_V7 at 0 range 7 .. 7;
19505 Slave_Control at 1 range 0 .. 0;
19506 Slave_V1 at 1 range 1 .. 1;
19507 Slave_V2 at 1 range 2 .. 2;
19508 Slave_V3 at 1 range 3 .. 3;
19509 Slave_V4 at 1 range 4 .. 4;
19510 Slave_V5 at 1 range 5 .. 5;
19511 Slave_V6 at 1 range 6 .. 6;
19512 Slave_V7 at 1 range 7 .. 7;
19516 Why are they equivalent? Well take a specific field, the @code{Slave_V2}
19517 field. The storage place attributes are obtained by normalizing the
19518 values given so that the @code{First_Bit} value is less than 8. After
19519 normalizing the values (0,10,10) we get (1,2,2) which is exactly what
19520 we specified in the other case.
19522 Now one might expect that the @code{Bit_Order} attribute might affect
19523 bit numbering within the entire record component (two bytes in this
19524 case, thus affecting which byte fields end up in), but that is not
19525 the way this feature is defined, it only affects numbering of bits,
19526 not which byte they end up in.
19528 Consequently it never makes sense to specify a starting bit number
19529 greater than 7 (for a byte addressable field) if an attribute
19530 definition for @code{Bit_Order} has been given, and indeed it
19531 may be actively confusing to specify such a value, so the compiler
19532 generates a warning for such usage.
19534 If you do need to control byte ordering then appropriate conditional
19535 values must be used. If in our example, the slave byte came first on
19536 some machines we might write:
19539 Master_Byte_First constant Boolean := ...;
19541 Master_Byte : constant Natural :=
19542 1 - Boolean'Pos (Master_Byte_First);
19543 Slave_Byte : constant Natural :=
19544 Boolean'Pos (Master_Byte_First);
19546 for Data'Bit_Order use High_Order_First;
19547 for Data use record
19548 Master_Control at Master_Byte range 0 .. 0;
19549 Master_V1 at Master_Byte range 1 .. 1;
19550 Master_V2 at Master_Byte range 2 .. 2;
19551 Master_V3 at Master_Byte range 3 .. 3;
19552 Master_V4 at Master_Byte range 4 .. 4;
19553 Master_V5 at Master_Byte range 5 .. 5;
19554 Master_V6 at Master_Byte range 6 .. 6;
19555 Master_V7 at Master_Byte range 7 .. 7;
19556 Slave_Control at Slave_Byte range 0 .. 0;
19557 Slave_V1 at Slave_Byte range 1 .. 1;
19558 Slave_V2 at Slave_Byte range 2 .. 2;
19559 Slave_V3 at Slave_Byte range 3 .. 3;
19560 Slave_V4 at Slave_Byte range 4 .. 4;
19561 Slave_V5 at Slave_Byte range 5 .. 5;
19562 Slave_V6 at Slave_Byte range 6 .. 6;
19563 Slave_V7 at Slave_Byte range 7 .. 7;
19567 Now to switch between machines, all that is necessary is
19568 to set the boolean constant @code{Master_Byte_First} in
19569 an appropriate manner.
19571 @node Pragma Pack for Arrays,Pragma Pack for Records,Effect of Bit_Order on Byte Ordering,Representation Clauses and Pragmas
19572 @anchor{gnat_rm/representation_clauses_and_pragmas pragma-pack-for-arrays}@anchor{288}@anchor{gnat_rm/representation_clauses_and_pragmas id11}@anchor{289}
19573 @section Pragma Pack for Arrays
19576 @geindex Pragma Pack (for arrays)
19578 Pragma @code{Pack} applied to an array has an effect that depends upon whether the
19579 component type is @emph{packable}. For a component type to be @emph{packable}, it must
19580 be one of the following cases:
19586 Any elementary type.
19589 Any small packed array type with a static size.
19592 Any small simple record type with a static size.
19595 For all these cases, if the component subtype size is in the range
19596 1 through 64, then the effect of the pragma @code{Pack} is exactly as though a
19597 component size were specified giving the component subtype size.
19599 All other types are non-packable, they occupy an integral number of storage
19600 units and the only effect of pragma Pack is to remove alignment gaps.
19602 For example if we have:
19605 type r is range 0 .. 17;
19607 type ar is array (1 .. 8) of r;
19611 Then the component size of @code{ar} will be set to 5 (i.e., to @code{r'size},
19612 and the size of the array @code{ar} will be exactly 40 bits).
19614 Note that in some cases this rather fierce approach to packing can produce
19615 unexpected effects. For example, in Ada 95 and Ada 2005,
19616 subtype @code{Natural} typically has a size of 31, meaning that if you
19617 pack an array of @code{Natural}, you get 31-bit
19618 close packing, which saves a few bits, but results in far less efficient
19619 access. Since many other Ada compilers will ignore such a packing request,
19620 GNAT will generate a warning on some uses of pragma @code{Pack} that it guesses
19621 might not be what is intended. You can easily remove this warning by
19622 using an explicit @code{Component_Size} setting instead, which never generates
19623 a warning, since the intention of the programmer is clear in this case.
19625 GNAT treats packed arrays in one of two ways. If the size of the array is
19626 known at compile time and is less than 64 bits, then internally the array
19627 is represented as a single modular type, of exactly the appropriate number
19628 of bits. If the length is greater than 63 bits, or is not known at compile
19629 time, then the packed array is represented as an array of bytes, and the
19630 length is always a multiple of 8 bits.
19632 Note that to represent a packed array as a modular type, the alignment must
19633 be suitable for the modular type involved. For example, on typical machines
19634 a 32-bit packed array will be represented by a 32-bit modular integer with
19635 an alignment of four bytes. If you explicitly override the default alignment
19636 with an alignment clause that is too small, the modular representation
19637 cannot be used. For example, consider the following set of declarations:
19640 type R is range 1 .. 3;
19641 type S is array (1 .. 31) of R;
19642 for S'Component_Size use 2;
19644 for S'Alignment use 1;
19647 If the alignment clause were not present, then a 62-bit modular
19648 representation would be chosen (typically with an alignment of 4 or 8
19649 bytes depending on the target). But the default alignment is overridden
19650 with the explicit alignment clause. This means that the modular
19651 representation cannot be used, and instead the array of bytes
19652 representation must be used, meaning that the length must be a multiple
19653 of 8. Thus the above set of declarations will result in a diagnostic
19654 rejecting the size clause and noting that the minimum size allowed is 64.
19656 @geindex Pragma Pack (for type Natural)
19658 @geindex Pragma Pack warning
19660 One special case that is worth noting occurs when the base type of the
19661 component size is 8/16/32 and the subtype is one bit less. Notably this
19662 occurs with subtype @code{Natural}. Consider:
19665 type Arr is array (1 .. 32) of Natural;
19669 In all commonly used Ada 83 compilers, this pragma Pack would be ignored,
19670 since typically @code{Natural'Size} is 32 in Ada 83, and in any case most
19671 Ada 83 compilers did not attempt 31 bit packing.
19673 In Ada 95 and Ada 2005, @code{Natural'Size} is required to be 31. Furthermore,
19674 GNAT really does pack 31-bit subtype to 31 bits. This may result in a
19675 substantial unintended performance penalty when porting legacy Ada 83 code.
19676 To help prevent this, GNAT generates a warning in such cases. If you really
19677 want 31 bit packing in a case like this, you can set the component size
19681 type Arr is array (1 .. 32) of Natural;
19682 for Arr'Component_Size use 31;
19685 Here 31-bit packing is achieved as required, and no warning is generated,
19686 since in this case the programmer intention is clear.
19688 @node Pragma Pack for Records,Record Representation Clauses,Pragma Pack for Arrays,Representation Clauses and Pragmas
19689 @anchor{gnat_rm/representation_clauses_and_pragmas pragma-pack-for-records}@anchor{28a}@anchor{gnat_rm/representation_clauses_and_pragmas id12}@anchor{28b}
19690 @section Pragma Pack for Records
19693 @geindex Pragma Pack (for records)
19695 Pragma @code{Pack} applied to a record will pack the components to reduce
19696 wasted space from alignment gaps and by reducing the amount of space
19697 taken by components. We distinguish between @emph{packable} components and
19698 @emph{non-packable} components.
19699 Components of the following types are considered packable:
19705 Components of an elementary type are packable unless they are aliased,
19706 independent, or of an atomic type.
19709 Small packed arrays, where the size is statically known, are represented
19710 internally as modular integers, and so they are also packable.
19713 Small simple records, where the size is statically known, are also packable.
19716 For all these cases, if the @code{'Size} value is in the range 1 through 64, the
19717 components occupy the exact number of bits corresponding to this value
19718 and are packed with no padding bits, i.e. they can start on an arbitrary
19721 All other types are non-packable, they occupy an integral number of storage
19722 units and the only effect of pragma @code{Pack} is to remove alignment gaps.
19724 For example, consider the record
19727 type Rb1 is array (1 .. 13) of Boolean;
19730 type Rb2 is array (1 .. 65) of Boolean;
19733 type AF is new Float with Atomic;
19746 The representation for the record @code{X2} is as follows:
19749 for X2'Size use 224;
19751 L1 at 0 range 0 .. 0;
19752 L2 at 0 range 1 .. 64;
19753 L3 at 12 range 0 .. 31;
19754 L4 at 16 range 0 .. 0;
19755 L5 at 16 range 1 .. 13;
19756 L6 at 18 range 0 .. 71;
19760 Studying this example, we see that the packable fields @code{L1}
19762 of length equal to their sizes, and placed at specific bit boundaries (and
19763 not byte boundaries) to
19764 eliminate padding. But @code{L3} is of a non-packable float type (because
19765 it is aliased), so it is on the next appropriate alignment boundary.
19767 The next two fields are fully packable, so @code{L4} and @code{L5} are
19768 minimally packed with no gaps. However, type @code{Rb2} is a packed
19769 array that is longer than 64 bits, so it is itself non-packable. Thus
19770 the @code{L6} field is aligned to the next byte boundary, and takes an
19771 integral number of bytes, i.e., 72 bits.
19773 @node Record Representation Clauses,Handling of Records with Holes,Pragma Pack for Records,Representation Clauses and Pragmas
19774 @anchor{gnat_rm/representation_clauses_and_pragmas id13}@anchor{28c}@anchor{gnat_rm/representation_clauses_and_pragmas record-representation-clauses}@anchor{28d}
19775 @section Record Representation Clauses
19778 @geindex Record Representation Clause
19780 Record representation clauses may be given for all record types, including
19781 types obtained by record extension. Component clauses are allowed for any
19782 static component. The restrictions on component clauses depend on the type
19785 @geindex Component Clause
19787 For all components of an elementary type, the only restriction on component
19788 clauses is that the size must be at least the @code{'Size} value of the type
19789 (actually the Value_Size). There are no restrictions due to alignment,
19790 and such components may freely cross storage boundaries.
19792 Packed arrays with a size up to and including 64 bits are represented
19793 internally using a modular type with the appropriate number of bits, and
19794 thus the same lack of restriction applies. For example, if you declare:
19797 type R is array (1 .. 49) of Boolean;
19802 then a component clause for a component of type @code{R} may start on any
19803 specified bit boundary, and may specify a value of 49 bits or greater.
19805 For packed bit arrays that are longer than 64 bits, there are two
19806 cases. If the component size is a power of 2 (1,2,4,8,16,32 bits),
19807 including the important case of single bits or boolean values, then
19808 there are no limitations on placement of such components, and they
19809 may start and end at arbitrary bit boundaries.
19811 If the component size is not a power of 2 (e.g., 3 or 5), then
19812 an array of this type longer than 64 bits must always be placed on
19813 on a storage unit (byte) boundary and occupy an integral number
19814 of storage units (bytes). Any component clause that does not
19815 meet this requirement will be rejected.
19817 Any aliased component, or component of an aliased type, must
19818 have its normal alignment and size. A component clause that
19819 does not meet this requirement will be rejected.
19821 The tag field of a tagged type always occupies an address sized field at
19822 the start of the record. No component clause may attempt to overlay this
19823 tag. When a tagged type appears as a component, the tag field must have
19826 In the case of a record extension @code{T1}, of a type @code{T}, no component clause applied
19827 to the type @code{T1} can specify a storage location that would overlap the first
19828 @code{T'Size} bytes of the record.
19830 For all other component types, including non-bit-packed arrays,
19831 the component can be placed at an arbitrary bit boundary,
19832 so for example, the following is permitted:
19835 type R is array (1 .. 10) of Boolean;
19844 G at 0 range 0 .. 0;
19845 H at 0 range 1 .. 1;
19846 L at 0 range 2 .. 81;
19847 R at 0 range 82 .. 161;
19851 @node Handling of Records with Holes,Enumeration Clauses,Record Representation Clauses,Representation Clauses and Pragmas
19852 @anchor{gnat_rm/representation_clauses_and_pragmas handling-of-records-with-holes}@anchor{28e}@anchor{gnat_rm/representation_clauses_and_pragmas id14}@anchor{28f}
19853 @section Handling of Records with Holes
19856 @geindex Handling of Records with Holes
19858 As a result of alignment considerations, records may contain "holes"
19860 which do not correspond to the data bits of any of the components.
19861 Record representation clauses can also result in holes in records.
19863 GNAT does not attempt to clear these holes, so in record objects,
19864 they should be considered to hold undefined rubbish. The generated
19865 equality routine just tests components so does not access these
19866 undefined bits, and assignment and copy operations may or may not
19867 preserve the contents of these holes (for assignments, the holes
19868 in the target will in practice contain either the bits that are
19869 present in the holes in the source, or the bits that were present
19870 in the target before the assignment).
19872 If it is necessary to ensure that holes in records have all zero
19873 bits, then record objects for which this initialization is desired
19874 should be explicitly set to all zero values using Unchecked_Conversion
19875 or address overlays. For example
19878 type HRec is record
19884 On typical machines, integers need to be aligned on a four-byte
19885 boundary, resulting in three bytes of undefined rubbish following
19886 the 8-bit field for C. To ensure that the hole in a variable of
19887 type HRec is set to all zero bits,
19888 you could for example do:
19891 type Base is record
19892 Dummy1, Dummy2 : Integer := 0;
19897 for RealVar'Address use BaseVar'Address;
19900 Now the 8-bytes of the value of RealVar start out containing all zero
19901 bits. A safer approach is to just define dummy fields, avoiding the
19905 type HRec is record
19907 Dummy1 : Short_Short_Integer := 0;
19908 Dummy2 : Short_Short_Integer := 0;
19909 Dummy3 : Short_Short_Integer := 0;
19914 And to make absolutely sure that the intent of this is followed, you
19915 can use representation clauses:
19918 for Hrec use record
19919 C at 0 range 0 .. 7;
19920 Dummy1 at 1 range 0 .. 7;
19921 Dummy2 at 2 range 0 .. 7;
19922 Dummy3 at 3 range 0 .. 7;
19923 I at 4 range 0 .. 31;
19925 for Hrec'Size use 64;
19928 @node Enumeration Clauses,Address Clauses,Handling of Records with Holes,Representation Clauses and Pragmas
19929 @anchor{gnat_rm/representation_clauses_and_pragmas enumeration-clauses}@anchor{290}@anchor{gnat_rm/representation_clauses_and_pragmas id15}@anchor{291}
19930 @section Enumeration Clauses
19933 The only restriction on enumeration clauses is that the range of values
19934 must be representable. For the signed case, if one or more of the
19935 representation values are negative, all values must be in the range:
19938 System.Min_Int .. System.Max_Int
19941 For the unsigned case, where all values are nonnegative, the values must
19945 0 .. System.Max_Binary_Modulus;
19948 A @emph{confirming} representation clause is one in which the values range
19949 from 0 in sequence, i.e., a clause that confirms the default representation
19950 for an enumeration type.
19951 Such a confirming representation
19952 is permitted by these rules, and is specially recognized by the compiler so
19953 that no extra overhead results from the use of such a clause.
19955 If an array has an index type which is an enumeration type to which an
19956 enumeration clause has been applied, then the array is stored in a compact
19957 manner. Consider the declarations:
19960 type r is (A, B, C);
19961 for r use (A => 1, B => 5, C => 10);
19962 type t is array (r) of Character;
19965 The array type t corresponds to a vector with exactly three elements and
19966 has a default size equal to @code{3*Character'Size}. This ensures efficient
19967 use of space, but means that accesses to elements of the array will incur
19968 the overhead of converting representation values to the corresponding
19969 positional values, (i.e., the value delivered by the @code{Pos} attribute).
19971 @node Address Clauses,Use of Address Clauses for Memory-Mapped I/O,Enumeration Clauses,Representation Clauses and Pragmas
19972 @anchor{gnat_rm/representation_clauses_and_pragmas id16}@anchor{292}@anchor{gnat_rm/representation_clauses_and_pragmas address-clauses}@anchor{293}
19973 @section Address Clauses
19976 @geindex Address Clause
19978 The reference manual allows a general restriction on representation clauses,
19979 as found in RM 13.1(22):
19983 "An implementation need not support representation
19984 items containing nonstatic expressions, except that
19985 an implementation should support a representation item
19986 for a given entity if each nonstatic expression in the
19987 representation item is a name that statically denotes
19988 a constant declared before the entity."
19991 In practice this is applicable only to address clauses, since this is the
19992 only case in which a nonstatic expression is permitted by the syntax. As
19993 the AARM notes in sections 13.1 (22.a-22.h):
19997 22.a Reason: This is to avoid the following sort of thing:
19999 22.b X : Integer := F(...);
20000 Y : Address := G(...);
20001 for X'Address use Y;
20003 22.c In the above, we have to evaluate the
20004 initialization expression for X before we
20005 know where to put the result. This seems
20006 like an unreasonable implementation burden.
20008 22.d The above code should instead be written
20011 22.e Y : constant Address := G(...);
20012 X : Integer := F(...);
20013 for X'Address use Y;
20015 22.f This allows the expression 'Y' to be safely
20016 evaluated before X is created.
20018 22.g The constant could be a formal parameter of mode in.
20020 22.h An implementation can support other nonstatic
20021 expressions if it wants to. Expressions of type
20022 Address are hardly ever static, but their value
20023 might be known at compile time anyway in many
20027 GNAT does indeed permit many additional cases of nonstatic expressions. In
20028 particular, if the type involved is elementary there are no restrictions
20029 (since in this case, holding a temporary copy of the initialization value,
20030 if one is present, is inexpensive). In addition, if there is no implicit or
20031 explicit initialization, then there are no restrictions. GNAT will reject
20032 only the case where all three of these conditions hold:
20038 The type of the item is non-elementary (e.g., a record or array).
20041 There is explicit or implicit initialization required for the object.
20042 Note that access values are always implicitly initialized.
20045 The address value is nonstatic. Here GNAT is more permissive than the
20046 RM, and allows the address value to be the address of a previously declared
20047 stand-alone variable, as long as it does not itself have an address clause.
20050 Anchor : Some_Initialized_Type;
20051 Overlay : Some_Initialized_Type;
20052 for Overlay'Address use Anchor'Address;
20055 However, the prefix of the address clause cannot be an array component, or
20056 a component of a discriminated record.
20059 As noted above in section 22.h, address values are typically nonstatic. In
20060 particular the To_Address function, even if applied to a literal value, is
20061 a nonstatic function call. To avoid this minor annoyance, GNAT provides
20062 the implementation defined attribute 'To_Address. The following two
20063 expressions have identical values:
20067 @geindex To_Address
20070 To_Address (16#1234_0000#)
20071 System'To_Address (16#1234_0000#);
20074 except that the second form is considered to be a static expression, and
20075 thus when used as an address clause value is always permitted.
20077 Additionally, GNAT treats as static an address clause that is an
20078 unchecked_conversion of a static integer value. This simplifies the porting
20079 of legacy code, and provides a portable equivalent to the GNAT attribute
20082 Another issue with address clauses is the interaction with alignment
20083 requirements. When an address clause is given for an object, the address
20084 value must be consistent with the alignment of the object (which is usually
20085 the same as the alignment of the type of the object). If an address clause
20086 is given that specifies an inappropriately aligned address value, then the
20087 program execution is erroneous.
20089 Since this source of erroneous behavior can have unfortunate effects on
20090 machines with strict alignment requirements, GNAT
20091 checks (at compile time if possible, generating a warning, or at execution
20092 time with a run-time check) that the alignment is appropriate. If the
20093 run-time check fails, then @code{Program_Error} is raised. This run-time
20094 check is suppressed if range checks are suppressed, or if the special GNAT
20095 check Alignment_Check is suppressed, or if
20096 @code{pragma Restrictions (No_Elaboration_Code)} is in effect. It is also
20097 suppressed by default on non-strict alignment machines (such as the x86).
20099 Finally, GNAT does not permit overlaying of objects of class-wide types. In
20100 most cases, the compiler can detect an attempt at such overlays and will
20101 generate a warning at compile time and a Program_Error exception at run time.
20105 An address clause cannot be given for an exported object. More
20106 understandably the real restriction is that objects with an address
20107 clause cannot be exported. This is because such variables are not
20108 defined by the Ada program, so there is no external object to export.
20112 It is permissible to give an address clause and a pragma Import for the
20113 same object. In this case, the variable is not really defined by the
20114 Ada program, so there is no external symbol to be linked. The link name
20115 and the external name are ignored in this case. The reason that we allow this
20116 combination is that it provides a useful idiom to avoid unwanted
20117 initializations on objects with address clauses.
20119 When an address clause is given for an object that has implicit or
20120 explicit initialization, then by default initialization takes place. This
20121 means that the effect of the object declaration is to overwrite the
20122 memory at the specified address. This is almost always not what the
20123 programmer wants, so GNAT will output a warning:
20133 for Ext'Address use System'To_Address (16#1234_1234#);
20135 >>> warning: implicit initialization of "Ext" may
20136 modify overlaid storage
20137 >>> warning: use pragma Import for "Ext" to suppress
20138 initialization (RM B(24))
20143 As indicated by the warning message, the solution is to use a (dummy) pragma
20144 Import to suppress this initialization. The pragma tell the compiler that the
20145 object is declared and initialized elsewhere. The following package compiles
20146 without warnings (and the initialization is suppressed):
20156 for Ext'Address use System'To_Address (16#1234_1234#);
20157 pragma Import (Ada, Ext);
20161 A final issue with address clauses involves their use for overlaying
20162 variables, as in the following example:
20164 @geindex Overlaying of objects
20169 for B'Address use A'Address;
20172 or alternatively, using the form recommended by the RM:
20176 Addr : constant Address := A'Address;
20178 for B'Address use Addr;
20181 In both of these cases, @code{A} and @code{B} become aliased to one another
20182 via the address clause. This use of address clauses to overlay
20183 variables, achieving an effect similar to unchecked conversion
20184 was erroneous in Ada 83, but in Ada 95 and Ada 2005
20185 the effect is implementation defined. Furthermore, the
20186 Ada RM specifically recommends that in a situation
20187 like this, @code{B} should be subject to the following
20188 implementation advice (RM 13.3(19)):
20192 "19 If the Address of an object is specified, or it is imported
20193 or exported, then the implementation should not perform
20194 optimizations based on assumptions of no aliases."
20197 GNAT follows this recommendation, and goes further by also applying
20198 this recommendation to the overlaid variable (@code{A} in the above example)
20199 in this case. This means that the overlay works "as expected", in that
20200 a modification to one of the variables will affect the value of the other.
20202 More generally, GNAT interprets this recommendation conservatively for
20203 address clauses: in the cases other than overlays, it considers that the
20204 object is effectively subject to pragma @code{Volatile} and implements the
20205 associated semantics.
20207 Note that when address clause overlays are used in this way, there is an
20208 issue of unintentional initialization, as shown by this example:
20211 package Overwrite_Record is
20213 A : Character := 'C';
20214 B : Character := 'A';
20216 X : Short_Integer := 3;
20218 for Y'Address use X'Address;
20220 >>> warning: default initialization of "Y" may
20221 modify "X", use pragma Import for "Y" to
20222 suppress initialization (RM B.1(24))
20224 end Overwrite_Record;
20227 Here the default initialization of @code{Y} will clobber the value
20228 of @code{X}, which justifies the warning. The warning notes that
20229 this effect can be eliminated by adding a @code{pragma Import}
20230 which suppresses the initialization:
20233 package Overwrite_Record is
20235 A : Character := 'C';
20236 B : Character := 'A';
20238 X : Short_Integer := 3;
20240 for Y'Address use X'Address;
20241 pragma Import (Ada, Y);
20242 end Overwrite_Record;
20245 Note that the use of @code{pragma Initialize_Scalars} may cause variables to
20246 be initialized when they would not otherwise have been in the absence
20247 of the use of this pragma. This may cause an overlay to have this
20248 unintended clobbering effect. The compiler avoids this for scalar
20249 types, but not for composite objects (where in general the effect
20250 of @code{Initialize_Scalars} is part of the initialization routine
20251 for the composite object:
20254 pragma Initialize_Scalars;
20255 with Ada.Text_IO; use Ada.Text_IO;
20256 procedure Overwrite_Array is
20257 type Arr is array (1 .. 5) of Integer;
20258 X : Arr := (others => 1);
20260 for A'Address use X'Address;
20262 >>> warning: default initialization of "A" may
20263 modify "X", use pragma Import for "A" to
20264 suppress initialization (RM B.1(24))
20267 if X /= Arr'(others => 1) then
20268 Put_Line ("X was clobbered");
20270 Put_Line ("X was not clobbered");
20272 end Overwrite_Array;
20275 The above program generates the warning as shown, and at execution
20276 time, prints @code{X was clobbered}. If the @code{pragma Import} is
20277 added as suggested:
20280 pragma Initialize_Scalars;
20281 with Ada.Text_IO; use Ada.Text_IO;
20282 procedure Overwrite_Array is
20283 type Arr is array (1 .. 5) of Integer;
20284 X : Arr := (others => 1);
20286 for A'Address use X'Address;
20287 pragma Import (Ada, A);
20289 if X /= Arr'(others => 1) then
20290 Put_Line ("X was clobbered");
20292 Put_Line ("X was not clobbered");
20294 end Overwrite_Array;
20297 then the program compiles without the warning and when run will generate
20298 the output @code{X was not clobbered}.
20300 @node Use of Address Clauses for Memory-Mapped I/O,Effect of Convention on Representation,Address Clauses,Representation Clauses and Pragmas
20301 @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}
20302 @section Use of Address Clauses for Memory-Mapped I/O
20305 @geindex Memory-mapped I/O
20307 A common pattern is to use an address clause to map an atomic variable to
20308 a location in memory that corresponds to a memory-mapped I/O operation or
20309 operations, for example:
20312 type Mem_Word is record
20315 pragma Atomic (Mem_Word);
20316 for Mem_Word_Size use 32;
20319 for Mem'Address use some-address;
20326 For a full access (reference or modification) of the variable (Mem) in this
20327 case, as in the above examples, GNAT guarantees that the entire atomic word
20328 will be accessed, in accordance with the RM C.6(15) clause.
20330 A problem arises with a component access such as:
20336 Note that the component A is not declared as atomic. This means that it is
20337 not clear what this assignment means. It could correspond to full word read
20338 and write as given in the first example, or on architectures that supported
20339 such an operation it might be a single byte store instruction. The RM does
20340 not have anything to say in this situation, and GNAT does not make any
20341 guarantee. The code generated may vary from target to target. GNAT will issue
20342 a warning in such a case:
20347 >>> warning: access to non-atomic component of atomic array,
20348 may cause unexpected accesses to atomic object
20351 It is best to be explicit in this situation, by either declaring the
20352 components to be atomic if you want the byte store, or explicitly writing
20353 the full word access sequence if that is what the hardware requires.
20354 Alternatively, if the full word access sequence is required, GNAT also
20355 provides the pragma @code{Volatile_Full_Access} which can be used in lieu of
20356 pragma @code{Atomic} and will give the additional guarantee.
20358 @node Effect of Convention on Representation,Conventions and Anonymous Access Types,Use of Address Clauses for Memory-Mapped I/O,Representation Clauses and Pragmas
20359 @anchor{gnat_rm/representation_clauses_and_pragmas id18}@anchor{296}@anchor{gnat_rm/representation_clauses_and_pragmas effect-of-convention-on-representation}@anchor{297}
20360 @section Effect of Convention on Representation
20363 @geindex Convention
20364 @geindex effect on representation
20366 Normally the specification of a foreign language convention for a type or
20367 an object has no effect on the chosen representation. In particular, the
20368 representation chosen for data in GNAT generally meets the standard system
20369 conventions, and for example records are laid out in a manner that is
20370 consistent with C. This means that specifying convention C (for example)
20373 There are four exceptions to this general rule:
20379 @emph{Convention Fortran and array subtypes}.
20381 If pragma Convention Fortran is specified for an array subtype, then in
20382 accordance with the implementation advice in section 3.6.2(11) of the
20383 Ada Reference Manual, the array will be stored in a Fortran-compatible
20384 column-major manner, instead of the normal default row-major order.
20387 @emph{Convention C and enumeration types}
20389 GNAT normally stores enumeration types in 8, 16, or 32 bits as required
20390 to accommodate all values of the type. For example, for the enumeration
20394 type Color is (Red, Green, Blue);
20397 8 bits is sufficient to store all values of the type, so by default, objects
20398 of type @code{Color} will be represented using 8 bits. However, normal C
20399 convention is to use 32 bits for all enum values in C, since enum values
20400 are essentially of type int. If pragma @code{Convention C} is specified for an
20401 Ada enumeration type, then the size is modified as necessary (usually to
20402 32 bits) to be consistent with the C convention for enum values.
20404 Note that this treatment applies only to types. If Convention C is given for
20405 an enumeration object, where the enumeration type is not Convention C, then
20406 Object_Size bits are allocated. For example, for a normal enumeration type,
20407 with less than 256 elements, only 8 bits will be allocated for the object.
20408 Since this may be a surprise in terms of what C expects, GNAT will issue a
20409 warning in this situation. The warning can be suppressed by giving an explicit
20410 size clause specifying the desired size.
20413 @emph{Convention C/Fortran and Boolean types}
20415 In C, the usual convention for boolean values, that is values used for
20416 conditions, is that zero represents false, and nonzero values represent
20417 true. In Ada, the normal convention is that two specific values, typically
20418 0/1, are used to represent false/true respectively.
20420 Fortran has a similar convention for @code{LOGICAL} values (any nonzero
20421 value represents true).
20423 To accommodate the Fortran and C conventions, if a pragma Convention specifies
20424 C or Fortran convention for a derived Boolean, as in the following example:
20427 type C_Switch is new Boolean;
20428 pragma Convention (C, C_Switch);
20431 then the GNAT generated code will treat any nonzero value as true. For truth
20432 values generated by GNAT, the conventional value 1 will be used for True, but
20433 when one of these values is read, any nonzero value is treated as True.
20436 @node Conventions and Anonymous Access Types,Determining the Representations chosen by GNAT,Effect of Convention on Representation,Representation Clauses and Pragmas
20437 @anchor{gnat_rm/representation_clauses_and_pragmas conventions-and-anonymous-access-types}@anchor{298}@anchor{gnat_rm/representation_clauses_and_pragmas id19}@anchor{299}
20438 @section Conventions and Anonymous Access Types
20441 @geindex Anonymous access types
20443 @geindex Convention for anonymous access types
20445 The RM is not entirely clear on convention handling in a number of cases,
20446 and in particular, it is not clear on the convention to be given to
20447 anonymous access types in general, and in particular what is to be
20448 done for the case of anonymous access-to-subprogram.
20450 In GNAT, we decide that if an explicit Convention is applied
20451 to an object or component, and its type is such an anonymous type,
20452 then the convention will apply to this anonymous type as well. This
20453 seems to make sense since it is anomolous in any case to have a
20454 different convention for an object and its type, and there is clearly
20455 no way to explicitly specify a convention for an anonymous type, since
20456 it doesn't have a name to specify!
20458 Furthermore, we decide that if a convention is applied to a record type,
20459 then this convention is inherited by any of its components that are of an
20460 anonymous access type which do not have an explicitly specified convention.
20462 The following program shows these conventions in action:
20465 package ConvComp is
20466 type Foo is range 1 .. 10;
20468 A : access function (X : Foo) return Integer;
20471 pragma Convention (C, T1);
20474 A : access function (X : Foo) return Integer;
20475 pragma Convention (C, A);
20478 pragma Convention (COBOL, T2);
20481 A : access function (X : Foo) return Integer;
20482 pragma Convention (COBOL, A);
20485 pragma Convention (C, T3);
20488 A : access function (X : Foo) return Integer;
20491 pragma Convention (COBOL, T4);
20493 function F (X : Foo) return Integer;
20494 pragma Convention (C, F);
20496 function F (X : Foo) return Integer is (13);
20498 TV1 : T1 := (F'Access, 12); -- OK
20499 TV2 : T2 := (F'Access, 13); -- OK
20501 TV3 : T3 := (F'Access, 13); -- ERROR
20503 >>> subprogram "F" has wrong convention
20504 >>> does not match access to subprogram declared at line 17
20505 38. TV4 : T4 := (F'Access, 13); -- ERROR
20507 >>> subprogram "F" has wrong convention
20508 >>> does not match access to subprogram declared at line 24
20512 @node Determining the Representations chosen by GNAT,,Conventions and Anonymous Access Types,Representation Clauses and Pragmas
20513 @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}
20514 @section Determining the Representations chosen by GNAT
20517 @geindex Representation
20518 @geindex determination of
20520 @geindex -gnatR (gcc)
20522 Although the descriptions in this section are intended to be complete, it is
20523 often easier to simply experiment to see what GNAT accepts and what the
20524 effect is on the layout of types and objects.
20526 As required by the Ada RM, if a representation clause is not accepted, then
20527 it must be rejected as illegal by the compiler. However, when a
20528 representation clause or pragma is accepted, there can still be questions
20529 of what the compiler actually does. For example, if a partial record
20530 representation clause specifies the location of some components and not
20531 others, then where are the non-specified components placed? Or if pragma
20532 @code{Pack} is used on a record, then exactly where are the resulting
20533 fields placed? The section on pragma @code{Pack} in this chapter can be
20534 used to answer the second question, but it is often easier to just see
20535 what the compiler does.
20537 For this purpose, GNAT provides the option @emph{-gnatR}. If you compile
20538 with this option, then the compiler will output information on the actual
20539 representations chosen, in a format similar to source representation
20540 clauses. For example, if we compile the package:
20544 type r (x : boolean) is tagged record
20546 when True => S : String (1 .. 100);
20547 when False => null;
20551 type r2 is new r (false) with record
20556 y2 at 16 range 0 .. 31;
20563 type x1 is array (1 .. 10) of x;
20564 for x1'component_size use 11;
20566 type ia is access integer;
20568 type Rb1 is array (1 .. 13) of Boolean;
20571 type Rb2 is array (1 .. 65) of Boolean;
20586 using the switch @emph{-gnatR} we obtain the following output:
20589 Representation information for unit q
20590 -------------------------------------
20593 for r'Alignment use 4;
20595 x at 4 range 0 .. 7;
20596 _tag at 0 range 0 .. 31;
20597 s at 5 range 0 .. 799;
20600 for r2'Size use 160;
20601 for r2'Alignment use 4;
20603 x at 4 range 0 .. 7;
20604 _tag at 0 range 0 .. 31;
20605 _parent at 0 range 0 .. 63;
20606 y2 at 16 range 0 .. 31;
20610 for x'Alignment use 1;
20612 y at 0 range 0 .. 7;
20615 for x1'Size use 112;
20616 for x1'Alignment use 1;
20617 for x1'Component_Size use 11;
20619 for rb1'Size use 13;
20620 for rb1'Alignment use 2;
20621 for rb1'Component_Size use 1;
20623 for rb2'Size use 72;
20624 for rb2'Alignment use 1;
20625 for rb2'Component_Size use 1;
20627 for x2'Size use 224;
20628 for x2'Alignment use 4;
20630 l1 at 0 range 0 .. 0;
20631 l2 at 0 range 1 .. 64;
20632 l3 at 12 range 0 .. 31;
20633 l4 at 16 range 0 .. 0;
20634 l5 at 16 range 1 .. 13;
20635 l6 at 18 range 0 .. 71;
20639 The Size values are actually the Object_Size, i.e., the default size that
20640 will be allocated for objects of the type.
20641 The @code{??} size for type r indicates that we have a variant record, and the
20642 actual size of objects will depend on the discriminant value.
20644 The Alignment values show the actual alignment chosen by the compiler
20645 for each record or array type.
20647 The record representation clause for type r shows where all fields
20648 are placed, including the compiler generated tag field (whose location
20649 cannot be controlled by the programmer).
20651 The record representation clause for the type extension r2 shows all the
20652 fields present, including the parent field, which is a copy of the fields
20653 of the parent type of r2, i.e., r1.
20655 The component size and size clauses for types rb1 and rb2 show
20656 the exact effect of pragma @code{Pack} on these arrays, and the record
20657 representation clause for type x2 shows how pragma @cite{Pack} affects
20660 In some cases, it may be useful to cut and paste the representation clauses
20661 generated by the compiler into the original source to fix and guarantee
20662 the actual representation to be used.
20664 @node Standard Library Routines,The Implementation of Standard I/O,Representation Clauses and Pragmas,Top
20665 @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}
20666 @chapter Standard Library Routines
20669 The Ada Reference Manual contains in Annex A a full description of an
20670 extensive set of standard library routines that can be used in any Ada
20671 program, and which must be provided by all Ada compilers. They are
20672 analogous to the standard C library used by C programs.
20674 GNAT implements all of the facilities described in annex A, and for most
20675 purposes the description in the Ada Reference Manual, or appropriate Ada
20676 text book, will be sufficient for making use of these facilities.
20678 In the case of the input-output facilities,
20679 @ref{f,,The Implementation of Standard I/O},
20680 gives details on exactly how GNAT interfaces to the
20681 file system. For the remaining packages, the Ada Reference Manual
20682 should be sufficient. The following is a list of the packages included,
20683 together with a brief description of the functionality that is provided.
20685 For completeness, references are included to other predefined library
20686 routines defined in other sections of the Ada Reference Manual (these are
20687 cross-indexed from Annex A). For further details see the relevant
20688 package declarations in the run-time library. In particular, a few units
20689 are not implemented, as marked by the presence of pragma Unimplemented_Unit,
20690 and in this case the package declaration contains comments explaining why
20691 the unit is not implemented.
20696 @item @code{Ada} @emph{(A.2)}
20698 This is a parent package for all the standard library packages. It is
20699 usually included implicitly in your program, and itself contains no
20700 useful data or routines.
20702 @item @code{Ada.Assertions} @emph{(11.4.2)}
20704 @code{Assertions} provides the @code{Assert} subprograms, and also
20705 the declaration of the @code{Assertion_Error} exception.
20707 @item @code{Ada.Asynchronous_Task_Control} @emph{(D.11)}
20709 @code{Asynchronous_Task_Control} provides low level facilities for task
20710 synchronization. It is typically not implemented. See package spec for details.
20712 @item @code{Ada.Calendar} @emph{(9.6)}
20714 @code{Calendar} provides time of day access, and routines for
20715 manipulating times and durations.
20717 @item @code{Ada.Calendar.Arithmetic} @emph{(9.6.1)}
20719 This package provides additional arithmetic
20720 operations for @code{Calendar}.
20722 @item @code{Ada.Calendar.Formatting} @emph{(9.6.1)}
20724 This package provides formatting operations for @code{Calendar}.
20726 @item @code{Ada.Calendar.Time_Zones} @emph{(9.6.1)}
20728 This package provides additional @code{Calendar} facilities
20729 for handling time zones.
20731 @item @code{Ada.Characters} @emph{(A.3.1)}
20733 This is a dummy parent package that contains no useful entities
20735 @item @code{Ada.Characters.Conversions} @emph{(A.3.2)}
20737 This package provides character conversion functions.
20739 @item @code{Ada.Characters.Handling} @emph{(A.3.2)}
20741 This package provides some basic character handling capabilities,
20742 including classification functions for classes of characters (e.g., test
20743 for letters, or digits).
20745 @item @code{Ada.Characters.Latin_1} @emph{(A.3.3)}
20747 This package includes a complete set of definitions of the characters
20748 that appear in type CHARACTER. It is useful for writing programs that
20749 will run in international environments. For example, if you want an
20750 upper case E with an acute accent in a string, it is often better to use
20751 the definition of @code{UC_E_Acute} in this package. Then your program
20752 will print in an understandable manner even if your environment does not
20753 support these extended characters.
20755 @item @code{Ada.Command_Line} @emph{(A.15)}
20757 This package provides access to the command line parameters and the name
20758 of the current program (analogous to the use of @code{argc} and @code{argv}
20759 in C), and also allows the exit status for the program to be set in a
20760 system-independent manner.
20762 @item @code{Ada.Complex_Text_IO} @emph{(G.1.3)}
20764 This package provides text input and output of complex numbers.
20766 @item @code{Ada.Containers} @emph{(A.18.1)}
20768 A top level package providing a few basic definitions used by all the
20769 following specific child packages that provide specific kinds of
20773 @code{Ada.Containers.Bounded_Priority_Queues} @emph{(A.18.31)}
20775 @code{Ada.Containers.Bounded_Synchronized_Queues} @emph{(A.18.29)}
20777 @code{Ada.Containers.Doubly_Linked_Lists} @emph{(A.18.3)}
20779 @code{Ada.Containers.Generic_Array_Sort} @emph{(A.18.26)}
20781 @code{Ada.Containers.Generic_Constrained_Array_Sort} @emph{(A.18.26)}
20783 @code{Ada.Containers.Generic_Sort} @emph{(A.18.26)}
20785 @code{Ada.Containers.Hashed_Maps} @emph{(A.18.5)}
20787 @code{Ada.Containers.Hashed_Sets} @emph{(A.18.8)}
20789 @code{Ada.Containers.Indefinite_Doubly_Linked_Lists} @emph{(A.18.12)}
20791 @code{Ada.Containers.Indefinite_Hashed_Maps} @emph{(A.18.13)}
20793 @code{Ada.Containers.Indefinite_Hashed_Sets} @emph{(A.18.15)}
20795 @code{Ada.Containers.Indefinite_Holders} @emph{(A.18.18)}
20797 @code{Ada.Containers.Indefinite_Multiway_Trees} @emph{(A.18.17)}
20799 @code{Ada.Containers.Indefinite_Ordered_Maps} @emph{(A.18.14)}
20801 @code{Ada.Containers.Indefinite_Ordered_Sets} @emph{(A.18.16)}
20803 @code{Ada.Containers.Indefinite_Vectors} @emph{(A.18.11)}
20805 @code{Ada.Containers.Multiway_Trees} @emph{(A.18.10)}
20807 @code{Ada.Containers.Ordered_Maps} @emph{(A.18.6)}
20809 @code{Ada.Containers.Ordered_Sets} @emph{(A.18.9)}
20811 @code{Ada.Containers.Synchronized_Queue_Interfaces} @emph{(A.18.27)}
20813 @code{Ada.Containers.Unbounded_Priority_Queues} @emph{(A.18.30)}
20815 @code{Ada.Containers.Unbounded_Synchronized_Queues} @emph{(A.18.28)}
20817 @code{Ada.Containers.Vectors} @emph{(A.18.2)}
20822 @item @code{Ada.Directories} @emph{(A.16)}
20824 This package provides operations on directories.
20826 @item @code{Ada.Directories.Hierarchical_File_Names} @emph{(A.16.1)}
20828 This package provides additional directory operations handling
20829 hiearchical file names.
20831 @item @code{Ada.Directories.Information} @emph{(A.16)}
20833 This is an implementation defined package for additional directory
20834 operations, which is not implemented in GNAT.
20836 @item @code{Ada.Decimal} @emph{(F.2)}
20838 This package provides constants describing the range of decimal numbers
20839 implemented, and also a decimal divide routine (analogous to the COBOL
20840 verb DIVIDE ... GIVING ... REMAINDER ...)
20842 @item @code{Ada.Direct_IO} @emph{(A.8.4)}
20844 This package provides input-output using a model of a set of records of
20845 fixed-length, containing an arbitrary definite Ada type, indexed by an
20846 integer record number.
20848 @item @code{Ada.Dispatching} @emph{(D.2.1)}
20850 A parent package containing definitions for task dispatching operations.
20852 @item @code{Ada.Dispatching.EDF} @emph{(D.2.6)}
20854 Not implemented in GNAT.
20856 @item @code{Ada.Dispatching.Non_Preemptive} @emph{(D.2.4)}
20858 Not implemented in GNAT.
20860 @item @code{Ada.Dispatching.Round_Robin} @emph{(D.2.5)}
20862 Not implemented in GNAT.
20864 @item @code{Ada.Dynamic_Priorities} @emph{(D.5)}
20866 This package allows the priorities of a task to be adjusted dynamically
20867 as the task is running.
20869 @item @code{Ada.Environment_Variables} @emph{(A.17)}
20871 This package provides facilities for accessing environment variables.
20873 @item @code{Ada.Exceptions} @emph{(11.4.1)}
20875 This package provides additional information on exceptions, and also
20876 contains facilities for treating exceptions as data objects, and raising
20877 exceptions with associated messages.
20879 @item @code{Ada.Execution_Time} @emph{(D.14)}
20881 This package provides CPU clock functionalities. It is not implemented on
20882 all targets (see package spec for details).
20884 @item @code{Ada.Execution_Time.Group_Budgets} @emph{(D.14.2)}
20886 Not implemented in GNAT.
20888 @item @code{Ada.Execution_Time.Timers} @emph{(D.14.1)'}
20890 Not implemented in GNAT.
20892 @item @code{Ada.Finalization} @emph{(7.6)}
20894 This package contains the declarations and subprograms to support the
20895 use of controlled types, providing for automatic initialization and
20896 finalization (analogous to the constructors and destructors of C++).
20898 @item @code{Ada.Float_Text_IO} @emph{(A.10.9)}
20900 A library level instantiation of Text_IO.Float_IO for type Float.
20902 @item @code{Ada.Float_Wide_Text_IO} @emph{(A.10.9)}
20904 A library level instantiation of Wide_Text_IO.Float_IO for type Float.
20906 @item @code{Ada.Float_Wide_Wide_Text_IO} @emph{(A.10.9)}
20908 A library level instantiation of Wide_Wide_Text_IO.Float_IO for type Float.
20910 @item @code{Ada.Integer_Text_IO} @emph{(A.10.9)}
20912 A library level instantiation of Text_IO.Integer_IO for type Integer.
20914 @item @code{Ada.Integer_Wide_Text_IO} @emph{(A.10.9)}
20916 A library level instantiation of Wide_Text_IO.Integer_IO for type Integer.
20918 @item @code{Ada.Integer_Wide_Wide_Text_IO} @emph{(A.10.9)}
20920 A library level instantiation of Wide_Wide_Text_IO.Integer_IO for type Integer.
20922 @item @code{Ada.Interrupts} @emph{(C.3.2)}
20924 This package provides facilities for interfacing to interrupts, which
20925 includes the set of signals or conditions that can be raised and
20926 recognized as interrupts.
20928 @item @code{Ada.Interrupts.Names} @emph{(C.3.2)}
20930 This package provides the set of interrupt names (actually signal
20931 or condition names) that can be handled by GNAT.
20933 @item @code{Ada.IO_Exceptions} @emph{(A.13)}
20935 This package defines the set of exceptions that can be raised by use of
20936 the standard IO packages.
20938 @item @code{Ada.Iterator_Interfaces} @emph{(5.5.1)}
20940 This package provides a generic interface to generalized iterators.
20942 @item @code{Ada.Locales} @emph{(A.19)}
20944 This package provides declarations providing information (Language
20945 and Country) about the current locale.
20947 @item @code{Ada.Numerics}
20949 This package contains some standard constants and exceptions used
20950 throughout the numerics packages. Note that the constants pi and e are
20951 defined here, and it is better to use these definitions than rolling
20954 @item @code{Ada.Numerics.Complex_Arrays} @emph{(G.3.2)}
20956 Provides operations on arrays of complex numbers.
20958 @item @code{Ada.Numerics.Complex_Elementary_Functions}
20960 Provides the implementation of standard elementary functions (such as
20961 log and trigonometric functions) operating on complex numbers using the
20962 standard @code{Float} and the @code{Complex} and @code{Imaginary} types
20963 created by the package @code{Numerics.Complex_Types}.
20965 @item @code{Ada.Numerics.Complex_Types}
20967 This is a predefined instantiation of
20968 @code{Numerics.Generic_Complex_Types} using @code{Standard.Float} to
20969 build the type @code{Complex} and @code{Imaginary}.
20971 @item @code{Ada.Numerics.Discrete_Random}
20973 This generic package provides a random number generator suitable for generating
20974 uniformly distributed values of a specified discrete subtype.
20976 @item @code{Ada.Numerics.Float_Random}
20978 This package provides a random number generator suitable for generating
20979 uniformly distributed floating point values in the unit interval.
20981 @item @code{Ada.Numerics.Generic_Complex_Elementary_Functions}
20983 This is a generic version of the package that provides the
20984 implementation of standard elementary functions (such as log and
20985 trigonometric functions) for an arbitrary complex type.
20987 The following predefined instantiations of this package are provided:
20995 @code{Ada.Numerics.Short_Complex_Elementary_Functions}
21000 @code{Ada.Numerics.Complex_Elementary_Functions}
21005 @code{Ada.Numerics.Long_Complex_Elementary_Functions}
21008 @item @code{Ada.Numerics.Generic_Complex_Types}
21010 This is a generic package that allows the creation of complex types,
21011 with associated complex arithmetic operations.
21013 The following predefined instantiations of this package exist
21021 @code{Ada.Numerics.Short_Complex_Complex_Types}
21026 @code{Ada.Numerics.Complex_Complex_Types}
21031 @code{Ada.Numerics.Long_Complex_Complex_Types}
21034 @item @code{Ada.Numerics.Generic_Elementary_Functions}
21036 This is a generic package that provides the implementation of standard
21037 elementary functions (such as log an trigonometric functions) for an
21038 arbitrary float type.
21040 The following predefined instantiations of this package exist
21048 @code{Ada.Numerics.Short_Elementary_Functions}
21053 @code{Ada.Numerics.Elementary_Functions}
21058 @code{Ada.Numerics.Long_Elementary_Functions}
21061 @item @code{Ada.Numerics.Generic_Real_Arrays} @emph{(G.3.1)}
21063 Generic operations on arrays of reals
21065 @item @code{Ada.Numerics.Real_Arrays} @emph{(G.3.1)}
21067 Preinstantiation of Ada.Numerics.Generic_Real_Arrays (Float).
21069 @item @code{Ada.Real_Time} @emph{(D.8)}
21071 This package provides facilities similar to those of @code{Calendar}, but
21072 operating with a finer clock suitable for real time control. Note that
21073 annex D requires that there be no backward clock jumps, and GNAT generally
21074 guarantees this behavior, but of course if the external clock on which
21075 the GNAT runtime depends is deliberately reset by some external event,
21076 then such a backward jump may occur.
21078 @item @code{Ada.Real_Time.Timing_Events} @emph{(D.15)}
21080 Not implemented in GNAT.
21082 @item @code{Ada.Sequential_IO} @emph{(A.8.1)}
21084 This package provides input-output facilities for sequential files,
21085 which can contain a sequence of values of a single type, which can be
21086 any Ada type, including indefinite (unconstrained) types.
21088 @item @code{Ada.Storage_IO} @emph{(A.9)}
21090 This package provides a facility for mapping arbitrary Ada types to and
21091 from a storage buffer. It is primarily intended for the creation of new
21094 @item @code{Ada.Streams} @emph{(13.13.1)}
21096 This is a generic package that provides the basic support for the
21097 concept of streams as used by the stream attributes (@code{Input},
21098 @code{Output}, @code{Read} and @code{Write}).
21100 @item @code{Ada.Streams.Stream_IO} @emph{(A.12.1)}
21102 This package is a specialization of the type @code{Streams} defined in
21103 package @code{Streams} together with a set of operations providing
21104 Stream_IO capability. The Stream_IO model permits both random and
21105 sequential access to a file which can contain an arbitrary set of values
21106 of one or more Ada types.
21108 @item @code{Ada.Strings} @emph{(A.4.1)}
21110 This package provides some basic constants used by the string handling
21113 @item @code{Ada.Strings.Bounded} @emph{(A.4.4)}
21115 This package provides facilities for handling variable length
21116 strings. The bounded model requires a maximum length. It is thus
21117 somewhat more limited than the unbounded model, but avoids the use of
21118 dynamic allocation or finalization.
21120 @item @code{Ada.Strings.Bounded.Equal_Case_Insensitive} @emph{(A.4.10)}
21122 Provides case-insensitive comparisons of bounded strings
21124 @item @code{Ada.Strings.Bounded.Hash} @emph{(A.4.9)}
21126 This package provides a generic hash function for bounded strings
21128 @item @code{Ada.Strings.Bounded.Hash_Case_Insensitive} @emph{(A.4.9)}
21130 This package provides a generic hash function for bounded strings that
21131 converts the string to be hashed to lower case.
21133 @item @code{Ada.Strings.Bounded.Less_Case_Insensitive} @emph{(A.4.10)}
21135 This package provides a comparison function for bounded strings that works
21136 in a case insensitive manner by converting to lower case before the comparison.
21138 @item @code{Ada.Strings.Fixed} @emph{(A.4.3)}
21140 This package provides facilities for handling fixed length strings.
21142 @item @code{Ada.Strings.Fixed.Equal_Case_Insensitive} @emph{(A.4.10)}
21144 This package provides an equality function for fixed strings that compares
21145 the strings after converting both to lower case.
21147 @item @code{Ada.Strings.Fixed.Hash_Case_Insensitive} @emph{(A.4.9)}
21149 This package provides a case insensitive hash function for fixed strings that
21150 converts the string to lower case before computing the hash.
21152 @item @code{Ada.Strings.Fixed.Less_Case_Insensitive} @emph{(A.4.10)}
21154 This package provides a comparison function for fixed strings that works
21155 in a case insensitive manner by converting to lower case before the comparison.
21157 @item @code{Ada.Strings.Hash} @emph{(A.4.9)}
21159 This package provides a hash function for strings.
21161 @item @code{Ada.Strings.Hash_Case_Insensitive} @emph{(A.4.9)}
21163 This package provides a hash function for strings that is case insensitive.
21164 The string is converted to lower case before computing the hash.
21166 @item @code{Ada.Strings.Less_Case_Insensitive} @emph{(A.4.10)}
21168 This package provides a comparison function for\strings that works
21169 in a case insensitive manner by converting to lower case before the comparison.
21171 @item @code{Ada.Strings.Maps} @emph{(A.4.2)}
21173 This package provides facilities for handling character mappings and
21174 arbitrarily defined subsets of characters. For instance it is useful in
21175 defining specialized translation tables.
21177 @item @code{Ada.Strings.Maps.Constants} @emph{(A.4.6)}
21179 This package provides a standard set of predefined mappings and
21180 predefined character sets. For example, the standard upper to lower case
21181 conversion table is found in this package. Note that upper to lower case
21182 conversion is non-trivial if you want to take the entire set of
21183 characters, including extended characters like E with an acute accent,
21184 into account. You should use the mappings in this package (rather than
21185 adding 32 yourself) to do case mappings.
21187 @item @code{Ada.Strings.Unbounded} @emph{(A.4.5)}
21189 This package provides facilities for handling variable length
21190 strings. The unbounded model allows arbitrary length strings, but
21191 requires the use of dynamic allocation and finalization.
21193 @item @code{Ada.Strings.Unbounded.Equal_Case_Insensitive} @emph{(A.4.10)}
21195 Provides case-insensitive comparisons of unbounded strings
21197 @item @code{Ada.Strings.Unbounded.Hash} @emph{(A.4.9)}
21199 This package provides a generic hash function for unbounded strings
21201 @item @code{Ada.Strings.Unbounded.Hash_Case_Insensitive} @emph{(A.4.9)}
21203 This package provides a generic hash function for unbounded strings that
21204 converts the string to be hashed to lower case.
21206 @item @code{Ada.Strings.Unbounded.Less_Case_Insensitive} @emph{(A.4.10)}
21208 This package provides a comparison function for unbounded strings that works
21209 in a case insensitive manner by converting to lower case before the comparison.
21211 @item @code{Ada.Strings.UTF_Encoding} @emph{(A.4.11)}
21213 This package provides basic definitions for dealing with UTF-encoded strings.
21215 @item @code{Ada.Strings.UTF_Encoding.Conversions} @emph{(A.4.11)}
21217 This package provides conversion functions for UTF-encoded strings.
21220 @code{Ada.Strings.UTF_Encoding.Strings} @emph{(A.4.11)}
21222 @code{Ada.Strings.UTF_Encoding.Wide_Strings} @emph{(A.4.11)}
21227 @item @code{Ada.Strings.UTF_Encoding.Wide_Wide_Strings} @emph{(A.4.11)}
21229 These packages provide facilities for handling UTF encodings for
21230 Strings, Wide_Strings and Wide_Wide_Strings.
21233 @code{Ada.Strings.Wide_Bounded} @emph{(A.4.7)}
21235 @code{Ada.Strings.Wide_Fixed} @emph{(A.4.7)}
21237 @code{Ada.Strings.Wide_Maps} @emph{(A.4.7)}
21242 @item @code{Ada.Strings.Wide_Unbounded} @emph{(A.4.7)}
21244 These packages provide analogous capabilities to the corresponding
21245 packages without @code{Wide_} in the name, but operate with the types
21246 @code{Wide_String} and @code{Wide_Character} instead of @code{String}
21247 and @code{Character}. Versions of all the child packages are available.
21250 @code{Ada.Strings.Wide_Wide_Bounded} @emph{(A.4.7)}
21252 @code{Ada.Strings.Wide_Wide_Fixed} @emph{(A.4.7)}
21254 @code{Ada.Strings.Wide_Wide_Maps} @emph{(A.4.7)}
21259 @item @code{Ada.Strings.Wide_Wide_Unbounded} @emph{(A.4.7)}
21261 These packages provide analogous capabilities to the corresponding
21262 packages without @code{Wide_} in the name, but operate with the types
21263 @code{Wide_Wide_String} and @code{Wide_Wide_Character} instead
21264 of @code{String} and @code{Character}.
21266 @item @code{Ada.Synchronous_Barriers} @emph{(D.10.1)}
21268 This package provides facilities for synchronizing tasks at a low level
21271 @item @code{Ada.Synchronous_Task_Control} @emph{(D.10)}
21273 This package provides some standard facilities for controlling task
21274 communication in a synchronous manner.
21276 @item @code{Ada.Synchronous_Task_Control.EDF} @emph{(D.10)}
21278 Not implemented in GNAT.
21280 @item @code{Ada.Tags}
21282 This package contains definitions for manipulation of the tags of tagged
21285 @item @code{Ada.Tags.Generic_Dispatching_Constructor} @emph{(3.9)}
21287 This package provides a way of constructing tagged class-wide values given
21288 only the tag value.
21290 @item @code{Ada.Task_Attributes} @emph{(C.7.2)}
21292 This package provides the capability of associating arbitrary
21293 task-specific data with separate tasks.
21295 @item @code{Ada.Task_Identifification} @emph{(C.7.1)}
21297 This package provides capabilities for task identification.
21299 @item @code{Ada.Task_Termination} @emph{(C.7.3)}
21301 This package provides control over task termination.
21303 @item @code{Ada.Text_IO}
21305 This package provides basic text input-output capabilities for
21306 character, string and numeric data. The subpackages of this
21307 package are listed next. Note that although these are defined
21308 as subpackages in the RM, they are actually transparently
21309 implemented as child packages in GNAT, meaning that they
21310 are only loaded if needed.
21312 @item @code{Ada.Text_IO.Decimal_IO}
21314 Provides input-output facilities for decimal fixed-point types
21316 @item @code{Ada.Text_IO.Enumeration_IO}
21318 Provides input-output facilities for enumeration types.
21320 @item @code{Ada.Text_IO.Fixed_IO}
21322 Provides input-output facilities for ordinary fixed-point types.
21324 @item @code{Ada.Text_IO.Float_IO}
21326 Provides input-output facilities for float types. The following
21327 predefined instantiations of this generic package are available:
21335 @code{Short_Float_Text_IO}
21340 @code{Float_Text_IO}
21345 @code{Long_Float_Text_IO}
21348 @item @code{Ada.Text_IO.Integer_IO}
21350 Provides input-output facilities for integer types. The following
21351 predefined instantiations of this generic package are available:
21357 @code{Short_Short_Integer}
21359 @code{Ada.Short_Short_Integer_Text_IO}
21362 @code{Short_Integer}
21364 @code{Ada.Short_Integer_Text_IO}
21369 @code{Ada.Integer_Text_IO}
21372 @code{Long_Integer}
21374 @code{Ada.Long_Integer_Text_IO}
21377 @code{Long_Long_Integer}
21379 @code{Ada.Long_Long_Integer_Text_IO}
21382 @item @code{Ada.Text_IO.Modular_IO}
21384 Provides input-output facilities for modular (unsigned) types.
21386 @item @code{Ada.Text_IO.Bounded_IO (A.10.11)}
21388 Provides input-output facilities for bounded strings.
21390 @item @code{Ada.Text_IO.Complex_IO (G.1.3)}
21392 This package provides basic text input-output capabilities for complex
21395 @item @code{Ada.Text_IO.Editing (F.3.3)}
21397 This package contains routines for edited output, analogous to the use
21398 of pictures in COBOL. The picture formats used by this package are a
21399 close copy of the facility in COBOL.
21401 @item @code{Ada.Text_IO.Text_Streams (A.12.2)}
21403 This package provides a facility that allows Text_IO files to be treated
21404 as streams, so that the stream attributes can be used for writing
21405 arbitrary data, including binary data, to Text_IO files.
21407 @item @code{Ada.Text_IO.Unbounded_IO (A.10.12)}
21409 This package provides input-output facilities for unbounded strings.
21411 @item @code{Ada.Unchecked_Conversion (13.9)}
21413 This generic package allows arbitrary conversion from one type to
21414 another of the same size, providing for breaking the type safety in
21415 special circumstances.
21417 If the types have the same Size (more accurately the same Value_Size),
21418 then the effect is simply to transfer the bits from the source to the
21419 target type without any modification. This usage is well defined, and
21420 for simple types whose representation is typically the same across
21421 all implementations, gives a portable method of performing such
21424 If the types do not have the same size, then the result is implementation
21425 defined, and thus may be non-portable. The following describes how GNAT
21426 handles such unchecked conversion cases.
21428 If the types are of different sizes, and are both discrete types, then
21429 the effect is of a normal type conversion without any constraint checking.
21430 In particular if the result type has a larger size, the result will be
21431 zero or sign extended. If the result type has a smaller size, the result
21432 will be truncated by ignoring high order bits.
21434 If the types are of different sizes, and are not both discrete types,
21435 then the conversion works as though pointers were created to the source
21436 and target, and the pointer value is converted. The effect is that bits
21437 are copied from successive low order storage units and bits of the source
21438 up to the length of the target type.
21440 A warning is issued if the lengths differ, since the effect in this
21441 case is implementation dependent, and the above behavior may not match
21442 that of some other compiler.
21444 A pointer to one type may be converted to a pointer to another type using
21445 unchecked conversion. The only case in which the effect is undefined is
21446 when one or both pointers are pointers to unconstrained array types. In
21447 this case, the bounds information may get incorrectly transferred, and in
21448 particular, GNAT uses double size pointers for such types, and it is
21449 meaningless to convert between such pointer types. GNAT will issue a
21450 warning if the alignment of the target designated type is more strict
21451 than the alignment of the source designated type (since the result may
21452 be unaligned in this case).
21454 A pointer other than a pointer to an unconstrained array type may be
21455 converted to and from System.Address. Such usage is common in Ada 83
21456 programs, but note that Ada.Address_To_Access_Conversions is the
21457 preferred method of performing such conversions in Ada 95 and Ada 2005.
21459 unchecked conversion nor Ada.Address_To_Access_Conversions should be
21460 used in conjunction with pointers to unconstrained objects, since
21461 the bounds information cannot be handled correctly in this case.
21463 @item @code{Ada.Unchecked_Deallocation} @emph{(13.11.2)}
21465 This generic package allows explicit freeing of storage previously
21466 allocated by use of an allocator.
21468 @item @code{Ada.Wide_Text_IO} @emph{(A.11)}
21470 This package is similar to @code{Ada.Text_IO}, except that the external
21471 file supports wide character representations, and the internal types are
21472 @code{Wide_Character} and @code{Wide_String} instead of @code{Character}
21473 and @code{String}. The corresponding set of nested packages and child
21474 packages are defined.
21476 @item @code{Ada.Wide_Wide_Text_IO} @emph{(A.11)}
21478 This package is similar to @code{Ada.Text_IO}, except that the external
21479 file supports wide character representations, and the internal types are
21480 @code{Wide_Character} and @code{Wide_String} instead of @code{Character}
21481 and @code{String}. The corresponding set of nested packages and child
21482 packages are defined.
21485 For packages in Interfaces and System, all the RM defined packages are
21486 available in GNAT, see the Ada 2012 RM for full details.
21488 @node The Implementation of Standard I/O,The GNAT Library,Standard Library Routines,Top
21489 @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}
21490 @chapter The Implementation of Standard I/O
21493 GNAT implements all the required input-output facilities described in
21494 A.6 through A.14. These sections of the Ada Reference Manual describe the
21495 required behavior of these packages from the Ada point of view, and if
21496 you are writing a portable Ada program that does not need to know the
21497 exact manner in which Ada maps to the outside world when it comes to
21498 reading or writing external files, then you do not need to read this
21499 chapter. As long as your files are all regular files (not pipes or
21500 devices), and as long as you write and read the files only from Ada, the
21501 description in the Ada Reference Manual is sufficient.
21503 However, if you want to do input-output to pipes or other devices, such
21504 as the keyboard or screen, or if the files you are dealing with are
21505 either generated by some other language, or to be read by some other
21506 language, then you need to know more about the details of how the GNAT
21507 implementation of these input-output facilities behaves.
21509 In this chapter we give a detailed description of exactly how GNAT
21510 interfaces to the file system. As always, the sources of the system are
21511 available to you for answering questions at an even more detailed level,
21512 but for most purposes the information in this chapter will suffice.
21514 Another reason that you may need to know more about how input-output is
21515 implemented arises when you have a program written in mixed languages
21516 where, for example, files are shared between the C and Ada sections of
21517 the same program. GNAT provides some additional facilities, in the form
21518 of additional child library packages, that facilitate this sharing, and
21519 these additional facilities are also described in this chapter.
21522 * Standard I/O Packages::
21528 * Wide_Wide_Text_IO::
21530 * Text Translation::
21532 * Filenames encoding::
21533 * File content encoding::
21535 * Operations on C Streams::
21536 * Interfacing to C Streams::
21540 @node Standard I/O Packages,FORM Strings,,The Implementation of Standard I/O
21541 @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}
21542 @section Standard I/O Packages
21545 The Standard I/O packages described in Annex A for
21554 Ada.Text_IO.Complex_IO
21557 Ada.Text_IO.Text_Streams
21563 Ada.Wide_Text_IO.Complex_IO
21566 Ada.Wide_Text_IO.Text_Streams
21569 Ada.Wide_Wide_Text_IO
21572 Ada.Wide_Wide_Text_IO.Complex_IO
21575 Ada.Wide_Wide_Text_IO.Text_Streams
21587 are implemented using the C
21588 library streams facility; where
21594 All files are opened using @code{fopen}.
21597 All input/output operations use @code{fread}/@cite{fwrite}.
21600 There is no internal buffering of any kind at the Ada library level. The only
21601 buffering is that provided at the system level in the implementation of the
21602 library routines that support streams. This facilitates shared use of these
21603 streams by mixed language programs. Note though that system level buffering is
21604 explicitly enabled at elaboration of the standard I/O packages and that can
21605 have an impact on mixed language programs, in particular those using I/O before
21606 calling the Ada elaboration routine (e.g., adainit). It is recommended to call
21607 the Ada elaboration routine before performing any I/O or when impractical,
21608 flush the common I/O streams and in particular Standard_Output before
21609 elaborating the Ada code.
21611 @node FORM Strings,Direct_IO,Standard I/O Packages,The Implementation of Standard I/O
21612 @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}
21613 @section FORM Strings
21616 The format of a FORM string in GNAT is:
21619 "keyword=value,keyword=value,...,keyword=value"
21622 where letters may be in upper or lower case, and there are no spaces
21623 between values. The order of the entries is not important. Currently
21624 the following keywords defined.
21627 TEXT_TRANSLATION=[YES|NO|TEXT|BINARY|U8TEXT|WTEXT|U16TEXT]
21629 WCEM=[n|h|u|s|e|8|b]
21630 ENCODING=[UTF8|8BITS]
21633 The use of these parameters is described later in this section. If an
21634 unrecognized keyword appears in a form string, it is silently ignored
21635 and not considered invalid.
21637 @node Direct_IO,Sequential_IO,FORM Strings,The Implementation of Standard I/O
21638 @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}
21642 Direct_IO can only be instantiated for definite types. This is a
21643 restriction of the Ada language, which means that the records are fixed
21644 length (the length being determined by @code{type'Size}, rounded
21645 up to the next storage unit boundary if necessary).
21647 The records of a Direct_IO file are simply written to the file in index
21648 sequence, with the first record starting at offset zero, and subsequent
21649 records following. There is no control information of any kind. For
21650 example, if 32-bit integers are being written, each record takes
21651 4-bytes, so the record at index @code{K} starts at offset
21654 There is no limit on the size of Direct_IO files, they are expanded as
21655 necessary to accommodate whatever records are written to the file.
21657 @node Sequential_IO,Text_IO,Direct_IO,The Implementation of Standard I/O
21658 @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}
21659 @section Sequential_IO
21662 Sequential_IO may be instantiated with either a definite (constrained)
21663 or indefinite (unconstrained) type.
21665 For the definite type case, the elements written to the file are simply
21666 the memory images of the data values with no control information of any
21667 kind. The resulting file should be read using the same type, no validity
21668 checking is performed on input.
21670 For the indefinite type case, the elements written consist of two
21671 parts. First is the size of the data item, written as the memory image
21672 of a @code{Interfaces.C.size_t} value, followed by the memory image of
21673 the data value. The resulting file can only be read using the same
21674 (unconstrained) type. Normal assignment checks are performed on these
21675 read operations, and if these checks fail, @code{Data_Error} is
21676 raised. In particular, in the array case, the lengths must match, and in
21677 the variant record case, if the variable for a particular read operation
21678 is constrained, the discriminants must match.
21680 Note that it is not possible to use Sequential_IO to write variable
21681 length array items, and then read the data back into different length
21682 arrays. For example, the following will raise @code{Data_Error}:
21685 package IO is new Sequential_IO (String);
21690 IO.Write (F, "hello!")
21691 IO.Reset (F, Mode=>In_File);
21696 On some Ada implementations, this will print @code{hell}, but the program is
21697 clearly incorrect, since there is only one element in the file, and that
21698 element is the string @code{hello!}.
21700 In Ada 95 and Ada 2005, this kind of behavior can be legitimately achieved
21701 using Stream_IO, and this is the preferred mechanism. In particular, the
21702 above program fragment rewritten to use Stream_IO will work correctly.
21704 @node Text_IO,Wide_Text_IO,Sequential_IO,The Implementation of Standard I/O
21705 @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}
21709 Text_IO files consist of a stream of characters containing the following
21710 special control characters:
21713 LF (line feed, 16#0A#) Line Mark
21714 FF (form feed, 16#0C#) Page Mark
21717 A canonical Text_IO file is defined as one in which the following
21718 conditions are met:
21724 The character @code{LF} is used only as a line mark, i.e., to mark the end
21728 The character @code{FF} is used only as a page mark, i.e., to mark the
21729 end of a page and consequently can appear only immediately following a
21730 @code{LF} (line mark) character.
21733 The file ends with either @code{LF} (line mark) or @code{LF}-@cite{FF}
21734 (line mark, page mark). In the former case, the page mark is implicitly
21735 assumed to be present.
21738 A file written using Text_IO will be in canonical form provided that no
21739 explicit @code{LF} or @code{FF} characters are written using @code{Put}
21740 or @code{Put_Line}. There will be no @code{FF} character at the end of
21741 the file unless an explicit @code{New_Page} operation was performed
21742 before closing the file.
21744 A canonical Text_IO file that is a regular file (i.e., not a device or a
21745 pipe) can be read using any of the routines in Text_IO. The
21746 semantics in this case will be exactly as defined in the Ada Reference
21747 Manual, and all the routines in Text_IO are fully implemented.
21749 A text file that does not meet the requirements for a canonical Text_IO
21750 file has one of the following:
21756 The file contains @code{FF} characters not immediately following a
21757 @code{LF} character.
21760 The file contains @code{LF} or @code{FF} characters written by
21761 @code{Put} or @code{Put_Line}, which are not logically considered to be
21762 line marks or page marks.
21765 The file ends in a character other than @code{LF} or @code{FF},
21766 i.e., there is no explicit line mark or page mark at the end of the file.
21769 Text_IO can be used to read such non-standard text files but subprograms
21770 to do with line or page numbers do not have defined meanings. In
21771 particular, a @code{FF} character that does not follow a @code{LF}
21772 character may or may not be treated as a page mark from the point of
21773 view of page and line numbering. Every @code{LF} character is considered
21774 to end a line, and there is an implied @code{LF} character at the end of
21778 * Stream Pointer Positioning::
21779 * Reading and Writing Non-Regular Files::
21781 * Treating Text_IO Files as Streams::
21782 * Text_IO Extensions::
21783 * Text_IO Facilities for Unbounded Strings::
21787 @node Stream Pointer Positioning,Reading and Writing Non-Regular Files,,Text_IO
21788 @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}
21789 @subsection Stream Pointer Positioning
21792 @code{Ada.Text_IO} has a definition of current position for a file that
21793 is being read. No internal buffering occurs in Text_IO, and usually the
21794 physical position in the stream used to implement the file corresponds
21795 to this logical position defined by Text_IO. There are two exceptions:
21801 After a call to @code{End_Of_Page} that returns @code{True}, the stream
21802 is positioned past the @code{LF} (line mark) that precedes the page
21803 mark. Text_IO maintains an internal flag so that subsequent read
21804 operations properly handle the logical position which is unchanged by
21805 the @code{End_Of_Page} call.
21808 After a call to @code{End_Of_File} that returns @code{True}, if the
21809 Text_IO file was positioned before the line mark at the end of file
21810 before the call, then the logical position is unchanged, but the stream
21811 is physically positioned right at the end of file (past the line mark,
21812 and past a possible page mark following the line mark. Again Text_IO
21813 maintains internal flags so that subsequent read operations properly
21814 handle the logical position.
21817 These discrepancies have no effect on the observable behavior of
21818 Text_IO, but if a single Ada stream is shared between a C program and
21819 Ada program, or shared (using @code{shared=yes} in the form string)
21820 between two Ada files, then the difference may be observable in some
21823 @node Reading and Writing Non-Regular Files,Get_Immediate,Stream Pointer Positioning,Text_IO
21824 @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}
21825 @subsection Reading and Writing Non-Regular Files
21828 A non-regular file is a device (such as a keyboard), or a pipe. Text_IO
21829 can be used for reading and writing. Writing is not affected and the
21830 sequence of characters output is identical to the normal file case, but
21831 for reading, the behavior of Text_IO is modified to avoid undesirable
21832 look-ahead as follows:
21834 An input file that is not a regular file is considered to have no page
21835 marks. Any @code{Ascii.FF} characters (the character normally used for a
21836 page mark) appearing in the file are considered to be data
21837 characters. In particular:
21843 @code{Get_Line} and @code{Skip_Line} do not test for a page mark
21844 following a line mark. If a page mark appears, it will be treated as a
21848 This avoids the need to wait for an extra character to be typed or
21849 entered from the pipe to complete one of these operations.
21852 @code{End_Of_Page} always returns @code{False}
21855 @code{End_Of_File} will return @code{False} if there is a page mark at
21856 the end of the file.
21859 Output to non-regular files is the same as for regular files. Page marks
21860 may be written to non-regular files using @code{New_Page}, but as noted
21861 above they will not be treated as page marks on input if the output is
21862 piped to another Ada program.
21864 Another important discrepancy when reading non-regular files is that the end
21865 of file indication is not 'sticky'. If an end of file is entered, e.g., by
21866 pressing the @code{EOT} key,
21868 is signaled once (i.e., the test @code{End_Of_File}
21869 will yield @code{True}, or a read will
21870 raise @code{End_Error}), but then reading can resume
21871 to read data past that end of
21872 file indication, until another end of file indication is entered.
21874 @node Get_Immediate,Treating Text_IO Files as Streams,Reading and Writing Non-Regular Files,Text_IO
21875 @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}
21876 @subsection Get_Immediate
21879 @geindex Get_Immediate
21881 Get_Immediate returns the next character (including control characters)
21882 from the input file. In particular, Get_Immediate will return LF or FF
21883 characters used as line marks or page marks. Such operations leave the
21884 file positioned past the control character, and it is thus not treated
21885 as having its normal function. This means that page, line and column
21886 counts after this kind of Get_Immediate call are set as though the mark
21887 did not occur. In the case where a Get_Immediate leaves the file
21888 positioned between the line mark and page mark (which is not normally
21889 possible), it is undefined whether the FF character will be treated as a
21892 @node Treating Text_IO Files as Streams,Text_IO Extensions,Get_Immediate,Text_IO
21893 @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}
21894 @subsection Treating Text_IO Files as Streams
21897 @geindex Stream files
21899 The package @code{Text_IO.Streams} allows a @code{Text_IO} file to be treated
21900 as a stream. Data written to a @code{Text_IO} file in this stream mode is
21901 binary data. If this binary data contains bytes 16#0A# (@code{LF}) or
21902 16#0C# (@code{FF}), the resulting file may have non-standard
21903 format. Similarly if read operations are used to read from a Text_IO
21904 file treated as a stream, then @code{LF} and @code{FF} characters may be
21905 skipped and the effect is similar to that described above for
21906 @code{Get_Immediate}.
21908 @node Text_IO Extensions,Text_IO Facilities for Unbounded Strings,Treating Text_IO Files as Streams,Text_IO
21909 @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}
21910 @subsection Text_IO Extensions
21913 @geindex Text_IO extensions
21915 A package GNAT.IO_Aux in the GNAT library provides some useful extensions
21916 to the standard @code{Text_IO} package:
21922 function File_Exists (Name : String) return Boolean;
21923 Determines if a file of the given name exists.
21926 function Get_Line return String;
21927 Reads a string from the standard input file. The value returned is exactly
21928 the length of the line that was read.
21931 function Get_Line (File : Ada.Text_IO.File_Type) return String;
21932 Similar, except that the parameter File specifies the file from which
21933 the string is to be read.
21936 @node Text_IO Facilities for Unbounded Strings,,Text_IO Extensions,Text_IO
21937 @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}
21938 @subsection Text_IO Facilities for Unbounded Strings
21941 @geindex Text_IO for unbounded strings
21943 @geindex Unbounded_String
21944 @geindex Text_IO operations
21946 The package @code{Ada.Strings.Unbounded.Text_IO}
21947 in library files @code{a-suteio.ads/adb} contains some GNAT-specific
21948 subprograms useful for Text_IO operations on unbounded strings:
21954 function Get_Line (File : File_Type) return Unbounded_String;
21955 Reads a line from the specified file
21956 and returns the result as an unbounded string.
21959 procedure Put (File : File_Type; U : Unbounded_String);
21960 Writes the value of the given unbounded string to the specified file
21961 Similar to the effect of
21962 @code{Put (To_String (U))} except that an extra copy is avoided.
21965 procedure Put_Line (File : File_Type; U : Unbounded_String);
21966 Writes the value of the given unbounded string to the specified file,
21967 followed by a @code{New_Line}.
21968 Similar to the effect of @code{Put_Line (To_String (U))} except
21969 that an extra copy is avoided.
21972 In the above procedures, @code{File} is of type @code{Ada.Text_IO.File_Type}
21973 and is optional. If the parameter is omitted, then the standard input or
21974 output file is referenced as appropriate.
21976 The package @code{Ada.Strings.Wide_Unbounded.Wide_Text_IO} in library
21977 files @code{a-swuwti.ads} and @code{a-swuwti.adb} provides similar extended
21978 @code{Wide_Text_IO} functionality for unbounded wide strings.
21980 The package @code{Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO} in library
21981 files @code{a-szuzti.ads} and @code{a-szuzti.adb} provides similar extended
21982 @code{Wide_Wide_Text_IO} functionality for unbounded wide wide strings.
21984 @node Wide_Text_IO,Wide_Wide_Text_IO,Text_IO,The Implementation of Standard I/O
21985 @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}
21986 @section Wide_Text_IO
21989 @code{Wide_Text_IO} is similar in most respects to Text_IO, except that
21990 both input and output files may contain special sequences that represent
21991 wide character values. The encoding scheme for a given file may be
21992 specified using a FORM parameter:
21998 as part of the FORM string (WCEM = wide character encoding method),
21999 where @code{x} is one of the following characters
22002 @multitable {xxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxx}
22025 Upper half encoding
22062 The encoding methods match those that
22063 can be used in a source
22064 program, but there is no requirement that the encoding method used for
22065 the source program be the same as the encoding method used for files,
22066 and different files may use different encoding methods.
22068 The default encoding method for the standard files, and for opened files
22069 for which no WCEM parameter is given in the FORM string matches the
22070 wide character encoding specified for the main program (the default
22071 being brackets encoding if no coding method was specified with -gnatW).
22076 @item @emph{Hex Coding}
22078 In this encoding, a wide character is represented by a five character
22089 where @code{a}, @code{b}, @code{c}, @code{d} are the four hexadecimal
22090 characters (using upper case letters) of the wide character code. For
22091 example, ESC A345 is used to represent the wide character with code
22092 16#A345#. This scheme is compatible with use of the full
22093 @code{Wide_Character} set.
22099 @item @emph{Upper Half Coding}
22101 The wide character with encoding 16#abcd#, where the upper bit is on
22102 (i.e., a is in the range 8-F) is represented as two bytes 16#ab# and
22103 16#cd#. The second byte may never be a format control character, but is
22104 not required to be in the upper half. This method can be also used for
22105 shift-JIS or EUC where the internal coding matches the external coding.
22107 @item @emph{Shift JIS Coding}
22109 A wide character is represented by a two character sequence 16#ab# and
22110 16#cd#, with the restrictions described for upper half encoding as
22111 described above. The internal character code is the corresponding JIS
22112 character according to the standard algorithm for Shift-JIS
22113 conversion. Only characters defined in the JIS code set table can be
22114 used with this encoding method.
22116 @item @emph{EUC Coding}
22118 A wide character is represented by a two character sequence 16#ab# and
22119 16#cd#, with both characters being in the upper half. The internal
22120 character code is the corresponding JIS character according to the EUC
22121 encoding algorithm. Only characters defined in the JIS code set table
22122 can be used with this encoding method.
22124 @item @emph{UTF-8 Coding}
22126 A wide character is represented using
22127 UCS Transformation Format 8 (UTF-8) as defined in Annex R of ISO
22128 10646-1/Am.2. Depending on the character value, the representation
22129 is a one, two, or three byte sequence:
22133 16#0000#-16#007f#: 2#0xxxxxxx#
22134 16#0080#-16#07ff#: 2#110xxxxx# 2#10xxxxxx#
22135 16#0800#-16#ffff#: 2#1110xxxx# 2#10xxxxxx# 2#10xxxxxx#
22141 where the @code{xxx} bits correspond to the left-padded bits of the
22142 16-bit character value. Note that all lower half ASCII characters
22143 are represented as ASCII bytes and all upper half characters and
22144 other wide characters are represented as sequences of upper-half
22145 (The full UTF-8 scheme allows for encoding 31-bit characters as
22146 6-byte sequences, but in this implementation, all UTF-8 sequences
22147 of four or more bytes length will raise a Constraint_Error, as
22148 will all invalid UTF-8 sequences.)
22154 @item @emph{Brackets Coding}
22156 In this encoding, a wide character is represented by the following eight
22157 character sequence:
22167 where @code{a}, @code{b}, @code{c}, @code{d} are the four hexadecimal
22168 characters (using uppercase letters) of the wide character code. For
22169 example, @code{["A345"]} is used to represent the wide character with code
22171 This scheme is compatible with use of the full Wide_Character set.
22172 On input, brackets coding can also be used for upper half characters,
22173 e.g., @code{["C1"]} for lower case a. However, on output, brackets notation
22174 is only used for wide characters with a code greater than @code{16#FF#}.
22176 Note that brackets coding is not normally used in the context of
22177 Wide_Text_IO or Wide_Wide_Text_IO, since it is really just designed as
22178 a portable way of encoding source files. In the context of Wide_Text_IO
22179 or Wide_Wide_Text_IO, it can only be used if the file does not contain
22180 any instance of the left bracket character other than to encode wide
22181 character values using the brackets encoding method. In practice it is
22182 expected that some standard wide character encoding method such
22183 as UTF-8 will be used for text input output.
22185 If brackets notation is used, then any occurrence of a left bracket
22186 in the input file which is not the start of a valid wide character
22187 sequence will cause Constraint_Error to be raised. It is possible to
22188 encode a left bracket as ["5B"] and Wide_Text_IO and Wide_Wide_Text_IO
22189 input will interpret this as a left bracket.
22191 However, when a left bracket is output, it will be output as a left bracket
22192 and not as ["5B"]. We make this decision because for normal use of
22193 Wide_Text_IO for outputting messages, it is unpleasant to clobber left
22194 brackets. For example, if we write:
22197 Put_Line ("Start of output [first run]");
22200 we really do not want to have the left bracket in this message clobbered so
22201 that the output reads:
22205 Start of output ["5B"]first run]
22211 In practice brackets encoding is reasonably useful for normal Put_Line use
22212 since we won't get confused between left brackets and wide character
22213 sequences in the output. But for input, or when files are written out
22214 and read back in, it really makes better sense to use one of the standard
22215 encoding methods such as UTF-8.
22218 For the coding schemes other than UTF-8, Hex, or Brackets encoding,
22219 not all wide character
22220 values can be represented. An attempt to output a character that cannot
22221 be represented using the encoding scheme for the file causes
22222 Constraint_Error to be raised. An invalid wide character sequence on
22223 input also causes Constraint_Error to be raised.
22226 * Stream Pointer Positioning: Stream Pointer Positioning<2>.
22227 * Reading and Writing Non-Regular Files: Reading and Writing Non-Regular Files<2>.
22231 @node Stream Pointer Positioning<2>,Reading and Writing Non-Regular Files<2>,,Wide_Text_IO
22232 @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}
22233 @subsection Stream Pointer Positioning
22236 @code{Ada.Wide_Text_IO} is similar to @code{Ada.Text_IO} in its handling
22237 of stream pointer positioning (@ref{2a9,,Text_IO}). There is one additional
22240 If @code{Ada.Wide_Text_IO.Look_Ahead} reads a character outside the
22241 normal lower ASCII set (i.e., a character in the range:
22244 Wide_Character'Val (16#0080#) .. Wide_Character'Val (16#FFFF#)
22247 then although the logical position of the file pointer is unchanged by
22248 the @code{Look_Ahead} call, the stream is physically positioned past the
22249 wide character sequence. Again this is to avoid the need for buffering
22250 or backup, and all @code{Wide_Text_IO} routines check the internal
22251 indication that this situation has occurred so that this is not visible
22252 to a normal program using @code{Wide_Text_IO}. However, this discrepancy
22253 can be observed if the wide text file shares a stream with another file.
22255 @node Reading and Writing Non-Regular Files<2>,,Stream Pointer Positioning<2>,Wide_Text_IO
22256 @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}
22257 @subsection Reading and Writing Non-Regular Files
22260 As in the case of Text_IO, when a non-regular file is read, it is
22261 assumed that the file contains no page marks (any form characters are
22262 treated as data characters), and @code{End_Of_Page} always returns
22263 @code{False}. Similarly, the end of file indication is not sticky, so
22264 it is possible to read beyond an end of file.
22266 @node Wide_Wide_Text_IO,Stream_IO,Wide_Text_IO,The Implementation of Standard I/O
22267 @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}
22268 @section Wide_Wide_Text_IO
22271 @code{Wide_Wide_Text_IO} is similar in most respects to Text_IO, except that
22272 both input and output files may contain special sequences that represent
22273 wide wide character values. The encoding scheme for a given file may be
22274 specified using a FORM parameter:
22280 as part of the FORM string (WCEM = wide character encoding method),
22281 where @code{x} is one of the following characters
22284 @multitable {xxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxx}
22307 Upper half encoding
22344 The encoding methods match those that
22345 can be used in a source
22346 program, but there is no requirement that the encoding method used for
22347 the source program be the same as the encoding method used for files,
22348 and different files may use different encoding methods.
22350 The default encoding method for the standard files, and for opened files
22351 for which no WCEM parameter is given in the FORM string matches the
22352 wide character encoding specified for the main program (the default
22353 being brackets encoding if no coding method was specified with -gnatW).
22358 @item @emph{UTF-8 Coding}
22360 A wide character is represented using
22361 UCS Transformation Format 8 (UTF-8) as defined in Annex R of ISO
22362 10646-1/Am.2. Depending on the character value, the representation
22363 is a one, two, three, or four byte sequence:
22367 16#000000#-16#00007f#: 2#0xxxxxxx#
22368 16#000080#-16#0007ff#: 2#110xxxxx# 2#10xxxxxx#
22369 16#000800#-16#00ffff#: 2#1110xxxx# 2#10xxxxxx# 2#10xxxxxx#
22370 16#010000#-16#10ffff#: 2#11110xxx# 2#10xxxxxx# 2#10xxxxxx# 2#10xxxxxx#
22376 where the @code{xxx} bits correspond to the left-padded bits of the
22377 21-bit character value. Note that all lower half ASCII characters
22378 are represented as ASCII bytes and all upper half characters and
22379 other wide characters are represented as sequences of upper-half
22386 @item @emph{Brackets Coding}
22388 In this encoding, a wide wide character is represented by the following eight
22389 character sequence if is in wide character range
22399 and by the following ten character sequence if not
22403 [ " a b c d e f " ]
22409 where @code{a}, @code{b}, @code{c}, @code{d}, @code{e}, and @code{f}
22410 are the four or six hexadecimal
22411 characters (using uppercase letters) of the wide wide character code. For
22412 example, @code{["01A345"]} is used to represent the wide wide character
22413 with code @code{16#01A345#}.
22415 This scheme is compatible with use of the full Wide_Wide_Character set.
22416 On input, brackets coding can also be used for upper half characters,
22417 e.g., @code{["C1"]} for lower case a. However, on output, brackets notation
22418 is only used for wide characters with a code greater than @code{16#FF#}.
22421 If is also possible to use the other Wide_Character encoding methods,
22422 such as Shift-JIS, but the other schemes cannot support the full range
22423 of wide wide characters.
22424 An attempt to output a character that cannot
22425 be represented using the encoding scheme for the file causes
22426 Constraint_Error to be raised. An invalid wide character sequence on
22427 input also causes Constraint_Error to be raised.
22430 * Stream Pointer Positioning: Stream Pointer Positioning<3>.
22431 * Reading and Writing Non-Regular Files: Reading and Writing Non-Regular Files<3>.
22435 @node Stream Pointer Positioning<3>,Reading and Writing Non-Regular Files<3>,,Wide_Wide_Text_IO
22436 @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}
22437 @subsection Stream Pointer Positioning
22440 @code{Ada.Wide_Wide_Text_IO} is similar to @code{Ada.Text_IO} in its handling
22441 of stream pointer positioning (@ref{2a9,,Text_IO}). There is one additional
22444 If @code{Ada.Wide_Wide_Text_IO.Look_Ahead} reads a character outside the
22445 normal lower ASCII set (i.e., a character in the range:
22448 Wide_Wide_Character'Val (16#0080#) .. Wide_Wide_Character'Val (16#10FFFF#)
22451 then although the logical position of the file pointer is unchanged by
22452 the @code{Look_Ahead} call, the stream is physically positioned past the
22453 wide character sequence. Again this is to avoid the need for buffering
22454 or backup, and all @code{Wide_Wide_Text_IO} routines check the internal
22455 indication that this situation has occurred so that this is not visible
22456 to a normal program using @code{Wide_Wide_Text_IO}. However, this discrepancy
22457 can be observed if the wide text file shares a stream with another file.
22459 @node Reading and Writing Non-Regular Files<3>,,Stream Pointer Positioning<3>,Wide_Wide_Text_IO
22460 @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}
22461 @subsection Reading and Writing Non-Regular Files
22464 As in the case of Text_IO, when a non-regular file is read, it is
22465 assumed that the file contains no page marks (any form characters are
22466 treated as data characters), and @code{End_Of_Page} always returns
22467 @code{False}. Similarly, the end of file indication is not sticky, so
22468 it is possible to read beyond an end of file.
22470 @node Stream_IO,Text Translation,Wide_Wide_Text_IO,The Implementation of Standard I/O
22471 @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}
22475 A stream file is a sequence of bytes, where individual elements are
22476 written to the file as described in the Ada Reference Manual. The type
22477 @code{Stream_Element} is simply a byte. There are two ways to read or
22478 write a stream file.
22484 The operations @code{Read} and @code{Write} directly read or write a
22485 sequence of stream elements with no control information.
22488 The stream attributes applied to a stream file transfer data in the
22489 manner described for stream attributes.
22492 @node Text Translation,Shared Files,Stream_IO,The Implementation of Standard I/O
22493 @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}
22494 @section Text Translation
22497 @code{Text_Translation=xxx} may be used as the Form parameter
22498 passed to Text_IO.Create and Text_IO.Open. @code{Text_Translation=xxx}
22499 has no effect on Unix systems. Possible values are:
22505 @code{Yes} or @code{Text} is the default, which means to
22506 translate LF to/from CR/LF on Windows systems.
22508 @code{No} disables this translation; i.e. it
22509 uses binary mode. For output files, @code{Text_Translation=No}
22510 may be used to create Unix-style files on
22514 @code{wtext} translation enabled in Unicode mode.
22515 (corresponds to _O_WTEXT).
22518 @code{u8text} translation enabled in Unicode UTF-8 mode.
22519 (corresponds to O_U8TEXT).
22522 @code{u16text} translation enabled in Unicode UTF-16
22523 mode. (corresponds to_O_U16TEXT).
22526 @node Shared Files,Filenames encoding,Text Translation,The Implementation of Standard I/O
22527 @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}
22528 @section Shared Files
22531 Section A.14 of the Ada Reference Manual allows implementations to
22532 provide a wide variety of behavior if an attempt is made to access the
22533 same external file with two or more internal files.
22535 To provide a full range of functionality, while at the same time
22536 minimizing the problems of portability caused by this implementation
22537 dependence, GNAT handles file sharing as follows:
22543 In the absence of a @code{shared=xxx} form parameter, an attempt
22544 to open two or more files with the same full name is considered an error
22545 and is not supported. The exception @code{Use_Error} will be
22546 raised. Note that a file that is not explicitly closed by the program
22547 remains open until the program terminates.
22550 If the form parameter @code{shared=no} appears in the form string, the
22551 file can be opened or created with its own separate stream identifier,
22552 regardless of whether other files sharing the same external file are
22553 opened. The exact effect depends on how the C stream routines handle
22554 multiple accesses to the same external files using separate streams.
22557 If the form parameter @code{shared=yes} appears in the form string for
22558 each of two or more files opened using the same full name, the same
22559 stream is shared between these files, and the semantics are as described
22560 in Ada Reference Manual, Section A.14.
22563 When a program that opens multiple files with the same name is ported
22564 from another Ada compiler to GNAT, the effect will be that
22565 @code{Use_Error} is raised.
22567 The documentation of the original compiler and the documentation of the
22568 program should then be examined to determine if file sharing was
22569 expected, and @code{shared=xxx} parameters added to @code{Open}
22570 and @code{Create} calls as required.
22572 When a program is ported from GNAT to some other Ada compiler, no
22573 special attention is required unless the @code{shared=xxx} form
22574 parameter is used in the program. In this case, you must examine the
22575 documentation of the new compiler to see if it supports the required
22576 file sharing semantics, and form strings modified appropriately. Of
22577 course it may be the case that the program cannot be ported if the
22578 target compiler does not support the required functionality. The best
22579 approach in writing portable code is to avoid file sharing (and hence
22580 the use of the @code{shared=xxx} parameter in the form string)
22583 One common use of file sharing in Ada 83 is the use of instantiations of
22584 Sequential_IO on the same file with different types, to achieve
22585 heterogeneous input-output. Although this approach will work in GNAT if
22586 @code{shared=yes} is specified, it is preferable in Ada to use Stream_IO
22587 for this purpose (using the stream attributes)
22589 @node Filenames encoding,File content encoding,Shared Files,The Implementation of Standard I/O
22590 @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}
22591 @section Filenames encoding
22594 An encoding form parameter can be used to specify the filename
22595 encoding @code{encoding=xxx}.
22601 If the form parameter @code{encoding=utf8} appears in the form string, the
22602 filename must be encoded in UTF-8.
22605 If the form parameter @code{encoding=8bits} appears in the form
22606 string, the filename must be a standard 8bits string.
22609 In the absence of a @code{encoding=xxx} form parameter, the
22610 encoding is controlled by the @code{GNAT_CODE_PAGE} environment
22611 variable. And if not set @code{utf8} is assumed.
22616 @item @emph{CP_ACP}
22618 The current system Windows ANSI code page.
22620 @item @emph{CP_UTF8}
22625 This encoding form parameter is only supported on the Windows
22626 platform. On the other Operating Systems the run-time is supporting
22629 @node File content encoding,Open Modes,Filenames encoding,The Implementation of Standard I/O
22630 @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}
22631 @section File content encoding
22634 For text files it is possible to specify the encoding to use. This is
22635 controlled by the by the @code{GNAT_CCS_ENCODING} environment
22636 variable. And if not set @code{TEXT} is assumed.
22638 The possible values are those supported on Windows:
22645 Translated text mode
22649 Translated unicode encoding
22651 @item @emph{U16TEXT}
22653 Unicode 16-bit encoding
22655 @item @emph{U8TEXT}
22657 Unicode 8-bit encoding
22660 This encoding is only supported on the Windows platform.
22662 @node Open Modes,Operations on C Streams,File content encoding,The Implementation of Standard I/O
22663 @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}
22664 @section Open Modes
22667 @code{Open} and @code{Create} calls result in a call to @code{fopen}
22668 using the mode shown in the following table:
22671 @multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxx}
22674 @code{Open} and @code{Create} Call Modes
22716 Out_File (Direct_IO)
22728 Out_File (all other cases)
22753 If text file translation is required, then either @code{b} or @code{t}
22754 is added to the mode, depending on the setting of Text. Text file
22755 translation refers to the mapping of CR/LF sequences in an external file
22756 to LF characters internally. This mapping only occurs in DOS and
22757 DOS-like systems, and is not relevant to other systems.
22759 A special case occurs with Stream_IO. As shown in the above table, the
22760 file is initially opened in @code{r} or @code{w} mode for the
22761 @code{In_File} and @code{Out_File} cases. If a @code{Set_Mode} operation
22762 subsequently requires switching from reading to writing or vice-versa,
22763 then the file is reopened in @code{r+} mode to permit the required operation.
22765 @node Operations on C Streams,Interfacing to C Streams,Open Modes,The Implementation of Standard I/O
22766 @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}
22767 @section Operations on C Streams
22770 The package @code{Interfaces.C_Streams} provides an Ada program with direct
22771 access to the C library functions for operations on C streams:
22774 package Interfaces.C_Streams is
22775 -- Note: the reason we do not use the types that are in
22776 -- Interfaces.C is that we want to avoid dragging in the
22777 -- code in this unit if possible.
22778 subtype chars is System.Address;
22779 -- Pointer to null-terminated array of characters
22780 subtype FILEs is System.Address;
22781 -- Corresponds to the C type FILE*
22782 subtype voids is System.Address;
22783 -- Corresponds to the C type void*
22784 subtype int is Integer;
22785 subtype long is Long_Integer;
22786 -- Note: the above types are subtypes deliberately, and it
22787 -- is part of this spec that the above correspondences are
22788 -- guaranteed. This means that it is legitimate to, for
22789 -- example, use Integer instead of int. We provide these
22790 -- synonyms for clarity, but in some cases it may be
22791 -- convenient to use the underlying types (for example to
22792 -- avoid an unnecessary dependency of a spec on the spec
22794 type size_t is mod 2 ** Standard'Address_Size;
22795 NULL_Stream : constant FILEs;
22796 -- Value returned (NULL in C) to indicate an
22797 -- fdopen/fopen/tmpfile error
22798 ----------------------------------
22799 -- Constants Defined in stdio.h --
22800 ----------------------------------
22801 EOF : constant int;
22802 -- Used by a number of routines to indicate error or
22804 IOFBF : constant int;
22805 IOLBF : constant int;
22806 IONBF : constant int;
22807 -- Used to indicate buffering mode for setvbuf call
22808 SEEK_CUR : constant int;
22809 SEEK_END : constant int;
22810 SEEK_SET : constant int;
22811 -- Used to indicate origin for fseek call
22812 function stdin return FILEs;
22813 function stdout return FILEs;
22814 function stderr return FILEs;
22815 -- Streams associated with standard files
22816 --------------------------
22817 -- Standard C functions --
22818 --------------------------
22819 -- The functions selected below are ones that are
22820 -- available in UNIX (but not necessarily in ANSI C).
22821 -- These are very thin interfaces
22822 -- which copy exactly the C headers. For more
22823 -- documentation on these functions, see the Microsoft C
22824 -- "Run-Time Library Reference" (Microsoft Press, 1990,
22825 -- ISBN 1-55615-225-6), which includes useful information
22826 -- on system compatibility.
22827 procedure clearerr (stream : FILEs);
22828 function fclose (stream : FILEs) return int;
22829 function fdopen (handle : int; mode : chars) return FILEs;
22830 function feof (stream : FILEs) return int;
22831 function ferror (stream : FILEs) return int;
22832 function fflush (stream : FILEs) return int;
22833 function fgetc (stream : FILEs) return int;
22834 function fgets (strng : chars; n : int; stream : FILEs)
22836 function fileno (stream : FILEs) return int;
22837 function fopen (filename : chars; Mode : chars)
22839 -- Note: to maintain target independence, use
22840 -- text_translation_required, a boolean variable defined in
22841 -- a-sysdep.c to deal with the target dependent text
22842 -- translation requirement. If this variable is set,
22843 -- then b/t should be appended to the standard mode
22844 -- argument to set the text translation mode off or on
22846 function fputc (C : int; stream : FILEs) return int;
22847 function fputs (Strng : chars; Stream : FILEs) return int;
22864 function ftell (stream : FILEs) return long;
22871 function isatty (handle : int) return int;
22872 procedure mktemp (template : chars);
22873 -- The return value (which is just a pointer to template)
22875 procedure rewind (stream : FILEs);
22876 function rmtmp return int;
22884 function tmpfile return FILEs;
22885 function ungetc (c : int; stream : FILEs) return int;
22886 function unlink (filename : chars) return int;
22887 ---------------------
22888 -- Extra functions --
22889 ---------------------
22890 -- These functions supply slightly thicker bindings than
22891 -- those above. They are derived from functions in the
22892 -- C Run-Time Library, but may do a bit more work than
22893 -- just directly calling one of the Library functions.
22894 function is_regular_file (handle : int) return int;
22895 -- Tests if given handle is for a regular file (result 1)
22896 -- or for a non-regular file (pipe or device, result 0).
22897 ---------------------------------
22898 -- Control of Text/Binary Mode --
22899 ---------------------------------
22900 -- If text_translation_required is true, then the following
22901 -- functions may be used to dynamically switch a file from
22902 -- binary to text mode or vice versa. These functions have
22903 -- no effect if text_translation_required is false (i.e., in
22904 -- normal UNIX mode). Use fileno to get a stream handle.
22905 procedure set_binary_mode (handle : int);
22906 procedure set_text_mode (handle : int);
22907 ----------------------------
22908 -- Full Path Name support --
22909 ----------------------------
22910 procedure full_name (nam : chars; buffer : chars);
22911 -- Given a NUL terminated string representing a file
22912 -- name, returns in buffer a NUL terminated string
22913 -- representing the full path name for the file name.
22914 -- On systems where it is relevant the drive is also
22915 -- part of the full path name. It is the responsibility
22916 -- of the caller to pass an actual parameter for buffer
22917 -- that is big enough for any full path name. Use
22918 -- max_path_len given below as the size of buffer.
22919 max_path_len : integer;
22920 -- Maximum length of an allowable full path name on the
22921 -- system, including a terminating NUL character.
22922 end Interfaces.C_Streams;
22925 @node Interfacing to C Streams,,Operations on C Streams,The Implementation of Standard I/O
22926 @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}
22927 @section Interfacing to C Streams
22930 The packages in this section permit interfacing Ada files to C Stream
22934 with Interfaces.C_Streams;
22935 package Ada.Sequential_IO.C_Streams is
22936 function C_Stream (F : File_Type)
22937 return Interfaces.C_Streams.FILEs;
22939 (File : in out File_Type;
22940 Mode : in File_Mode;
22941 C_Stream : in Interfaces.C_Streams.FILEs;
22942 Form : in String := "");
22943 end Ada.Sequential_IO.C_Streams;
22945 with Interfaces.C_Streams;
22946 package Ada.Direct_IO.C_Streams is
22947 function C_Stream (F : File_Type)
22948 return Interfaces.C_Streams.FILEs;
22950 (File : in out File_Type;
22951 Mode : in File_Mode;
22952 C_Stream : in Interfaces.C_Streams.FILEs;
22953 Form : in String := "");
22954 end Ada.Direct_IO.C_Streams;
22956 with Interfaces.C_Streams;
22957 package Ada.Text_IO.C_Streams is
22958 function C_Stream (F : File_Type)
22959 return Interfaces.C_Streams.FILEs;
22961 (File : in out File_Type;
22962 Mode : in File_Mode;
22963 C_Stream : in Interfaces.C_Streams.FILEs;
22964 Form : in String := "");
22965 end Ada.Text_IO.C_Streams;
22967 with Interfaces.C_Streams;
22968 package Ada.Wide_Text_IO.C_Streams is
22969 function C_Stream (F : File_Type)
22970 return Interfaces.C_Streams.FILEs;
22972 (File : in out File_Type;
22973 Mode : in File_Mode;
22974 C_Stream : in Interfaces.C_Streams.FILEs;
22975 Form : in String := "");
22976 end Ada.Wide_Text_IO.C_Streams;
22978 with Interfaces.C_Streams;
22979 package Ada.Wide_Wide_Text_IO.C_Streams is
22980 function C_Stream (F : File_Type)
22981 return Interfaces.C_Streams.FILEs;
22983 (File : in out File_Type;
22984 Mode : in File_Mode;
22985 C_Stream : in Interfaces.C_Streams.FILEs;
22986 Form : in String := "");
22987 end Ada.Wide_Wide_Text_IO.C_Streams;
22989 with Interfaces.C_Streams;
22990 package Ada.Stream_IO.C_Streams is
22991 function C_Stream (F : File_Type)
22992 return Interfaces.C_Streams.FILEs;
22994 (File : in out File_Type;
22995 Mode : in File_Mode;
22996 C_Stream : in Interfaces.C_Streams.FILEs;
22997 Form : in String := "");
22998 end Ada.Stream_IO.C_Streams;
23001 In each of these six packages, the @code{C_Stream} function obtains the
23002 @code{FILE} pointer from a currently opened Ada file. It is then
23003 possible to use the @code{Interfaces.C_Streams} package to operate on
23004 this stream, or the stream can be passed to a C program which can
23005 operate on it directly. Of course the program is responsible for
23006 ensuring that only appropriate sequences of operations are executed.
23008 One particular use of relevance to an Ada program is that the
23009 @code{setvbuf} function can be used to control the buffering of the
23010 stream used by an Ada file. In the absence of such a call the standard
23011 default buffering is used.
23013 The @code{Open} procedures in these packages open a file giving an
23014 existing C Stream instead of a file name. Typically this stream is
23015 imported from a C program, allowing an Ada file to operate on an
23018 @node The GNAT Library,Interfacing to Other Languages,The Implementation of Standard I/O,Top
23019 @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}
23020 @chapter The GNAT Library
23023 The GNAT library contains a number of general and special purpose packages.
23024 It represents functionality that the GNAT developers have found useful, and
23025 which is made available to GNAT users. The packages described here are fully
23026 supported, and upwards compatibility will be maintained in future releases,
23027 so you can use these facilities with the confidence that the same functionality
23028 will be available in future releases.
23030 The chapter here simply gives a brief summary of the facilities available.
23031 The full documentation is found in the spec file for the package. The full
23032 sources of these library packages, including both spec and body, are provided
23033 with all GNAT releases. For example, to find out the full specifications of
23034 the SPITBOL pattern matching capability, including a full tutorial and
23035 extensive examples, look in the @code{g-spipat.ads} file in the library.
23037 For each entry here, the package name (as it would appear in a @code{with}
23038 clause) is given, followed by the name of the corresponding spec file in
23039 parentheses. The packages are children in four hierarchies, @code{Ada},
23040 @code{Interfaces}, @code{System}, and @code{GNAT}, the latter being a
23041 GNAT-specific hierarchy.
23043 Note that an application program should only use packages in one of these
23044 four hierarchies if the package is defined in the Ada Reference Manual,
23045 or is listed in this section of the GNAT Programmers Reference Manual.
23046 All other units should be considered internal implementation units and
23047 should not be directly @code{with}ed by application code. The use of
23048 a @code{with} clause that references one of these internal implementation
23049 units makes an application potentially dependent on changes in versions
23050 of GNAT, and will generate a warning message.
23053 * Ada.Characters.Latin_9 (a-chlat9.ads): Ada Characters Latin_9 a-chlat9 ads.
23054 * Ada.Characters.Wide_Latin_1 (a-cwila1.ads): Ada Characters Wide_Latin_1 a-cwila1 ads.
23055 * Ada.Characters.Wide_Latin_9 (a-cwila1.ads): Ada Characters Wide_Latin_9 a-cwila1 ads.
23056 * Ada.Characters.Wide_Wide_Latin_1 (a-chzla1.ads): Ada Characters Wide_Wide_Latin_1 a-chzla1 ads.
23057 * Ada.Characters.Wide_Wide_Latin_9 (a-chzla9.ads): Ada Characters Wide_Wide_Latin_9 a-chzla9 ads.
23058 * Ada.Containers.Formal_Doubly_Linked_Lists (a-cfdlli.ads): Ada Containers Formal_Doubly_Linked_Lists a-cfdlli ads.
23059 * Ada.Containers.Formal_Hashed_Maps (a-cfhama.ads): Ada Containers Formal_Hashed_Maps a-cfhama ads.
23060 * Ada.Containers.Formal_Hashed_Sets (a-cfhase.ads): Ada Containers Formal_Hashed_Sets a-cfhase ads.
23061 * Ada.Containers.Formal_Ordered_Maps (a-cforma.ads): Ada Containers Formal_Ordered_Maps a-cforma ads.
23062 * Ada.Containers.Formal_Ordered_Sets (a-cforse.ads): Ada Containers Formal_Ordered_Sets a-cforse ads.
23063 * Ada.Containers.Formal_Vectors (a-cofove.ads): Ada Containers Formal_Vectors a-cofove ads.
23064 * Ada.Containers.Formal_Indefinite_Vectors (a-cfinve.ads): Ada Containers Formal_Indefinite_Vectors a-cfinve ads.
23065 * Ada.Containers.Functional_Vectors (a-cofuve.ads): Ada Containers Functional_Vectors a-cofuve ads.
23066 * Ada.Containers.Functional_Sets (a-cofuse.ads): Ada Containers Functional_Sets a-cofuse ads.
23067 * Ada.Containers.Functional_Maps (a-cofuma.ads): Ada Containers Functional_Maps a-cofuma ads.
23068 * Ada.Containers.Bounded_Holders (a-coboho.ads): Ada Containers Bounded_Holders a-coboho ads.
23069 * Ada.Command_Line.Environment (a-colien.ads): Ada Command_Line Environment a-colien ads.
23070 * Ada.Command_Line.Remove (a-colire.ads): Ada Command_Line Remove a-colire ads.
23071 * Ada.Command_Line.Response_File (a-clrefi.ads): Ada Command_Line Response_File a-clrefi ads.
23072 * Ada.Direct_IO.C_Streams (a-diocst.ads): Ada Direct_IO C_Streams a-diocst ads.
23073 * Ada.Exceptions.Is_Null_Occurrence (a-einuoc.ads): Ada Exceptions Is_Null_Occurrence a-einuoc ads.
23074 * Ada.Exceptions.Last_Chance_Handler (a-elchha.ads): Ada Exceptions Last_Chance_Handler a-elchha ads.
23075 * Ada.Exceptions.Traceback (a-exctra.ads): Ada Exceptions Traceback a-exctra ads.
23076 * Ada.Sequential_IO.C_Streams (a-siocst.ads): Ada Sequential_IO C_Streams a-siocst ads.
23077 * Ada.Streams.Stream_IO.C_Streams (a-ssicst.ads): Ada Streams Stream_IO C_Streams a-ssicst ads.
23078 * Ada.Strings.Unbounded.Text_IO (a-suteio.ads): Ada Strings Unbounded Text_IO a-suteio ads.
23079 * Ada.Strings.Wide_Unbounded.Wide_Text_IO (a-swuwti.ads): Ada Strings Wide_Unbounded Wide_Text_IO a-swuwti ads.
23080 * Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO (a-szuzti.ads): Ada Strings Wide_Wide_Unbounded Wide_Wide_Text_IO a-szuzti ads.
23081 * Ada.Text_IO.C_Streams (a-tiocst.ads): Ada Text_IO C_Streams a-tiocst ads.
23082 * Ada.Text_IO.Reset_Standard_Files (a-tirsfi.ads): Ada Text_IO Reset_Standard_Files a-tirsfi ads.
23083 * Ada.Wide_Characters.Unicode (a-wichun.ads): Ada Wide_Characters Unicode a-wichun ads.
23084 * Ada.Wide_Text_IO.C_Streams (a-wtcstr.ads): Ada Wide_Text_IO C_Streams a-wtcstr ads.
23085 * Ada.Wide_Text_IO.Reset_Standard_Files (a-wrstfi.ads): Ada Wide_Text_IO Reset_Standard_Files a-wrstfi ads.
23086 * Ada.Wide_Wide_Characters.Unicode (a-zchuni.ads): Ada Wide_Wide_Characters Unicode a-zchuni ads.
23087 * Ada.Wide_Wide_Text_IO.C_Streams (a-ztcstr.ads): Ada Wide_Wide_Text_IO C_Streams a-ztcstr ads.
23088 * Ada.Wide_Wide_Text_IO.Reset_Standard_Files (a-zrstfi.ads): Ada Wide_Wide_Text_IO Reset_Standard_Files a-zrstfi ads.
23089 * GNAT.Altivec (g-altive.ads): GNAT Altivec g-altive ads.
23090 * GNAT.Altivec.Conversions (g-altcon.ads): GNAT Altivec Conversions g-altcon ads.
23091 * GNAT.Altivec.Vector_Operations (g-alveop.ads): GNAT Altivec Vector_Operations g-alveop ads.
23092 * GNAT.Altivec.Vector_Types (g-alvety.ads): GNAT Altivec Vector_Types g-alvety ads.
23093 * GNAT.Altivec.Vector_Views (g-alvevi.ads): GNAT Altivec Vector_Views g-alvevi ads.
23094 * GNAT.Array_Split (g-arrspl.ads): GNAT Array_Split g-arrspl ads.
23095 * GNAT.AWK (g-awk.ads): GNAT AWK g-awk ads.
23096 * GNAT.Bind_Environment (g-binenv.ads): GNAT Bind_Environment g-binenv ads.
23097 * GNAT.Branch_Prediction (g-brapre.ads): GNAT Branch_Prediction g-brapre ads.
23098 * GNAT.Bounded_Buffers (g-boubuf.ads): GNAT Bounded_Buffers g-boubuf ads.
23099 * GNAT.Bounded_Mailboxes (g-boumai.ads): GNAT Bounded_Mailboxes g-boumai ads.
23100 * GNAT.Bubble_Sort (g-bubsor.ads): GNAT Bubble_Sort g-bubsor ads.
23101 * GNAT.Bubble_Sort_A (g-busora.ads): GNAT Bubble_Sort_A g-busora ads.
23102 * GNAT.Bubble_Sort_G (g-busorg.ads): GNAT Bubble_Sort_G g-busorg ads.
23103 * GNAT.Byte_Order_Mark (g-byorma.ads): GNAT Byte_Order_Mark g-byorma ads.
23104 * GNAT.Byte_Swapping (g-bytswa.ads): GNAT Byte_Swapping g-bytswa ads.
23105 * GNAT.Calendar (g-calend.ads): GNAT Calendar g-calend ads.
23106 * GNAT.Calendar.Time_IO (g-catiio.ads): GNAT Calendar Time_IO g-catiio ads.
23107 * GNAT.CRC32 (g-crc32.ads): GNAT CRC32 g-crc32 ads.
23108 * GNAT.Case_Util (g-casuti.ads): GNAT Case_Util g-casuti ads.
23109 * GNAT.CGI (g-cgi.ads): GNAT CGI g-cgi ads.
23110 * GNAT.CGI.Cookie (g-cgicoo.ads): GNAT CGI Cookie g-cgicoo ads.
23111 * GNAT.CGI.Debug (g-cgideb.ads): GNAT CGI Debug g-cgideb ads.
23112 * GNAT.Command_Line (g-comlin.ads): GNAT Command_Line g-comlin ads.
23113 * GNAT.Compiler_Version (g-comver.ads): GNAT Compiler_Version g-comver ads.
23114 * GNAT.Ctrl_C (g-ctrl_c.ads): GNAT Ctrl_C g-ctrl_c ads.
23115 * GNAT.Current_Exception (g-curexc.ads): GNAT Current_Exception g-curexc ads.
23116 * GNAT.Debug_Pools (g-debpoo.ads): GNAT Debug_Pools g-debpoo ads.
23117 * GNAT.Debug_Utilities (g-debuti.ads): GNAT Debug_Utilities g-debuti ads.
23118 * GNAT.Decode_String (g-decstr.ads): GNAT Decode_String g-decstr ads.
23119 * GNAT.Decode_UTF8_String (g-deutst.ads): GNAT Decode_UTF8_String g-deutst ads.
23120 * GNAT.Directory_Operations (g-dirope.ads): GNAT Directory_Operations g-dirope ads.
23121 * GNAT.Directory_Operations.Iteration (g-diopit.ads): GNAT Directory_Operations Iteration g-diopit ads.
23122 * GNAT.Dynamic_HTables (g-dynhta.ads): GNAT Dynamic_HTables g-dynhta ads.
23123 * GNAT.Dynamic_Tables (g-dyntab.ads): GNAT Dynamic_Tables g-dyntab ads.
23124 * GNAT.Encode_String (g-encstr.ads): GNAT Encode_String g-encstr ads.
23125 * GNAT.Encode_UTF8_String (g-enutst.ads): GNAT Encode_UTF8_String g-enutst ads.
23126 * GNAT.Exception_Actions (g-excact.ads): GNAT Exception_Actions g-excact ads.
23127 * GNAT.Exception_Traces (g-exctra.ads): GNAT Exception_Traces g-exctra ads.
23128 * GNAT.Exceptions (g-except.ads): GNAT Exceptions g-except ads.
23129 * GNAT.Expect (g-expect.ads): GNAT Expect g-expect ads.
23130 * GNAT.Expect.TTY (g-exptty.ads): GNAT Expect TTY g-exptty ads.
23131 * GNAT.Float_Control (g-flocon.ads): GNAT Float_Control g-flocon ads.
23132 * GNAT.Formatted_String (g-forstr.ads): GNAT Formatted_String g-forstr ads.
23133 * GNAT.Heap_Sort (g-heasor.ads): GNAT Heap_Sort g-heasor ads.
23134 * GNAT.Heap_Sort_A (g-hesora.ads): GNAT Heap_Sort_A g-hesora ads.
23135 * GNAT.Heap_Sort_G (g-hesorg.ads): GNAT Heap_Sort_G g-hesorg ads.
23136 * GNAT.HTable (g-htable.ads): GNAT HTable g-htable ads.
23137 * GNAT.IO (g-io.ads): GNAT IO g-io ads.
23138 * GNAT.IO_Aux (g-io_aux.ads): GNAT IO_Aux g-io_aux ads.
23139 * GNAT.Lock_Files (g-locfil.ads): GNAT Lock_Files g-locfil ads.
23140 * GNAT.MBBS_Discrete_Random (g-mbdira.ads): GNAT MBBS_Discrete_Random g-mbdira ads.
23141 * GNAT.MBBS_Float_Random (g-mbflra.ads): GNAT MBBS_Float_Random g-mbflra ads.
23142 * GNAT.MD5 (g-md5.ads): GNAT MD5 g-md5 ads.
23143 * GNAT.Memory_Dump (g-memdum.ads): GNAT Memory_Dump g-memdum ads.
23144 * GNAT.Most_Recent_Exception (g-moreex.ads): GNAT Most_Recent_Exception g-moreex ads.
23145 * GNAT.OS_Lib (g-os_lib.ads): GNAT OS_Lib g-os_lib ads.
23146 * GNAT.Perfect_Hash_Generators (g-pehage.ads): GNAT Perfect_Hash_Generators g-pehage ads.
23147 * GNAT.Random_Numbers (g-rannum.ads): GNAT Random_Numbers g-rannum ads.
23148 * GNAT.Regexp (g-regexp.ads): GNAT Regexp g-regexp ads.
23149 * GNAT.Registry (g-regist.ads): GNAT Registry g-regist ads.
23150 * GNAT.Regpat (g-regpat.ads): GNAT Regpat g-regpat ads.
23151 * GNAT.Rewrite_Data (g-rewdat.ads): GNAT Rewrite_Data g-rewdat ads.
23152 * GNAT.Secondary_Stack_Info (g-sestin.ads): GNAT Secondary_Stack_Info g-sestin ads.
23153 * GNAT.Semaphores (g-semaph.ads): GNAT Semaphores g-semaph ads.
23154 * GNAT.Serial_Communications (g-sercom.ads): GNAT Serial_Communications g-sercom ads.
23155 * GNAT.SHA1 (g-sha1.ads): GNAT SHA1 g-sha1 ads.
23156 * GNAT.SHA224 (g-sha224.ads): GNAT SHA224 g-sha224 ads.
23157 * GNAT.SHA256 (g-sha256.ads): GNAT SHA256 g-sha256 ads.
23158 * GNAT.SHA384 (g-sha384.ads): GNAT SHA384 g-sha384 ads.
23159 * GNAT.SHA512 (g-sha512.ads): GNAT SHA512 g-sha512 ads.
23160 * GNAT.Signals (g-signal.ads): GNAT Signals g-signal ads.
23161 * GNAT.Sockets (g-socket.ads): GNAT Sockets g-socket ads.
23162 * GNAT.Source_Info (g-souinf.ads): GNAT Source_Info g-souinf ads.
23163 * GNAT.Spelling_Checker (g-speche.ads): GNAT Spelling_Checker g-speche ads.
23164 * GNAT.Spelling_Checker_Generic (g-spchge.ads): GNAT Spelling_Checker_Generic g-spchge ads.
23165 * GNAT.Spitbol.Patterns (g-spipat.ads): GNAT Spitbol Patterns g-spipat ads.
23166 * GNAT.Spitbol (g-spitbo.ads): GNAT Spitbol g-spitbo ads.
23167 * GNAT.Spitbol.Table_Boolean (g-sptabo.ads): GNAT Spitbol Table_Boolean g-sptabo ads.
23168 * GNAT.Spitbol.Table_Integer (g-sptain.ads): GNAT Spitbol Table_Integer g-sptain ads.
23169 * GNAT.Spitbol.Table_VString (g-sptavs.ads): GNAT Spitbol Table_VString g-sptavs ads.
23170 * GNAT.SSE (g-sse.ads): GNAT SSE g-sse ads.
23171 * GNAT.SSE.Vector_Types (g-ssvety.ads): GNAT SSE Vector_Types g-ssvety ads.
23172 * GNAT.String_Hash (g-strhas.ads): GNAT String_Hash g-strhas ads.
23173 * GNAT.Strings (g-string.ads): GNAT Strings g-string ads.
23174 * GNAT.String_Split (g-strspl.ads): GNAT String_Split g-strspl ads.
23175 * GNAT.Table (g-table.ads): GNAT Table g-table ads.
23176 * GNAT.Task_Lock (g-tasloc.ads): GNAT Task_Lock g-tasloc ads.
23177 * GNAT.Time_Stamp (g-timsta.ads): GNAT Time_Stamp g-timsta ads.
23178 * GNAT.Threads (g-thread.ads): GNAT Threads g-thread ads.
23179 * GNAT.Traceback (g-traceb.ads): GNAT Traceback g-traceb ads.
23180 * GNAT.Traceback.Symbolic (g-trasym.ads): GNAT Traceback Symbolic g-trasym ads.
23181 * GNAT.UTF_32 (g-table.ads): GNAT UTF_32 g-table ads.
23182 * GNAT.Wide_Spelling_Checker (g-u3spch.ads): GNAT Wide_Spelling_Checker g-u3spch ads.
23183 * GNAT.Wide_Spelling_Checker (g-wispch.ads): GNAT Wide_Spelling_Checker g-wispch ads.
23184 * GNAT.Wide_String_Split (g-wistsp.ads): GNAT Wide_String_Split g-wistsp ads.
23185 * GNAT.Wide_Wide_Spelling_Checker (g-zspche.ads): GNAT Wide_Wide_Spelling_Checker g-zspche ads.
23186 * GNAT.Wide_Wide_String_Split (g-zistsp.ads): GNAT Wide_Wide_String_Split g-zistsp ads.
23187 * Interfaces.C.Extensions (i-cexten.ads): Interfaces C Extensions i-cexten ads.
23188 * Interfaces.C.Streams (i-cstrea.ads): Interfaces C Streams i-cstrea ads.
23189 * Interfaces.Packed_Decimal (i-pacdec.ads): Interfaces Packed_Decimal i-pacdec ads.
23190 * Interfaces.VxWorks (i-vxwork.ads): Interfaces VxWorks i-vxwork ads.
23191 * Interfaces.VxWorks.Int_Connection (i-vxinco.ads): Interfaces VxWorks Int_Connection i-vxinco ads.
23192 * Interfaces.VxWorks.IO (i-vxwoio.ads): Interfaces VxWorks IO i-vxwoio ads.
23193 * System.Address_Image (s-addima.ads): System Address_Image s-addima ads.
23194 * System.Assertions (s-assert.ads): System Assertions s-assert ads.
23195 * System.Atomic_Counters (s-atocou.ads): System Atomic_Counters s-atocou ads.
23196 * System.Memory (s-memory.ads): System Memory s-memory ads.
23197 * System.Multiprocessors (s-multip.ads): System Multiprocessors s-multip ads.
23198 * System.Multiprocessors.Dispatching_Domains (s-mudido.ads): System Multiprocessors Dispatching_Domains s-mudido ads.
23199 * System.Partition_Interface (s-parint.ads): System Partition_Interface s-parint ads.
23200 * System.Pool_Global (s-pooglo.ads): System Pool_Global s-pooglo ads.
23201 * System.Pool_Local (s-pooloc.ads): System Pool_Local s-pooloc ads.
23202 * System.Restrictions (s-restri.ads): System Restrictions s-restri ads.
23203 * System.Rident (s-rident.ads): System Rident s-rident ads.
23204 * System.Strings.Stream_Ops (s-ststop.ads): System Strings Stream_Ops s-ststop ads.
23205 * System.Unsigned_Types (s-unstyp.ads): System Unsigned_Types s-unstyp ads.
23206 * System.Wch_Cnv (s-wchcnv.ads): System Wch_Cnv s-wchcnv ads.
23207 * System.Wch_Con (s-wchcon.ads): System Wch_Con s-wchcon ads.
23211 @node Ada Characters Latin_9 a-chlat9 ads,Ada Characters Wide_Latin_1 a-cwila1 ads,,The GNAT Library
23212 @anchor{gnat_rm/the_gnat_library id2}@anchor{2d4}@anchor{gnat_rm/the_gnat_library ada-characters-latin-9-a-chlat9-ads}@anchor{2d5}
23213 @section @code{Ada.Characters.Latin_9} (@code{a-chlat9.ads})
23216 @geindex Ada.Characters.Latin_9 (a-chlat9.ads)
23218 @geindex Latin_9 constants for Character
23220 This child of @code{Ada.Characters}
23221 provides a set of definitions corresponding to those in the
23222 RM-defined package @code{Ada.Characters.Latin_1} but with the
23223 few modifications required for @code{Latin-9}
23224 The provision of such a package
23225 is specifically authorized by the Ada Reference Manual
23228 @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
23229 @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}
23230 @section @code{Ada.Characters.Wide_Latin_1} (@code{a-cwila1.ads})
23233 @geindex Ada.Characters.Wide_Latin_1 (a-cwila1.ads)
23235 @geindex Latin_1 constants for Wide_Character
23237 This child of @code{Ada.Characters}
23238 provides a set of definitions corresponding to those in the
23239 RM-defined package @code{Ada.Characters.Latin_1} but with the
23240 types of the constants being @code{Wide_Character}
23241 instead of @code{Character}. The provision of such a package
23242 is specifically authorized by the Ada Reference Manual
23245 @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
23246 @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}
23247 @section @code{Ada.Characters.Wide_Latin_9} (@code{a-cwila1.ads})
23250 @geindex Ada.Characters.Wide_Latin_9 (a-cwila1.ads)
23252 @geindex Latin_9 constants for Wide_Character
23254 This child of @code{Ada.Characters}
23255 provides a set of definitions corresponding to those in the
23256 GNAT defined package @code{Ada.Characters.Latin_9} but with the
23257 types of the constants being @code{Wide_Character}
23258 instead of @code{Character}. The provision of such a package
23259 is specifically authorized by the Ada Reference Manual
23262 @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
23263 @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}
23264 @section @code{Ada.Characters.Wide_Wide_Latin_1} (@code{a-chzla1.ads})
23267 @geindex Ada.Characters.Wide_Wide_Latin_1 (a-chzla1.ads)
23269 @geindex Latin_1 constants for Wide_Wide_Character
23271 This child of @code{Ada.Characters}
23272 provides a set of definitions corresponding to those in the
23273 RM-defined package @code{Ada.Characters.Latin_1} but with the
23274 types of the constants being @code{Wide_Wide_Character}
23275 instead of @code{Character}. The provision of such a package
23276 is specifically authorized by the Ada Reference Manual
23279 @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
23280 @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}
23281 @section @code{Ada.Characters.Wide_Wide_Latin_9} (@code{a-chzla9.ads})
23284 @geindex Ada.Characters.Wide_Wide_Latin_9 (a-chzla9.ads)
23286 @geindex Latin_9 constants for Wide_Wide_Character
23288 This child of @code{Ada.Characters}
23289 provides a set of definitions corresponding to those in the
23290 GNAT defined package @code{Ada.Characters.Latin_9} but with the
23291 types of the constants being @code{Wide_Wide_Character}
23292 instead of @code{Character}. The provision of such a package
23293 is specifically authorized by the Ada Reference Manual
23296 @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
23297 @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}
23298 @section @code{Ada.Containers.Formal_Doubly_Linked_Lists} (@code{a-cfdlli.ads})
23301 @geindex Ada.Containers.Formal_Doubly_Linked_Lists (a-cfdlli.ads)
23303 @geindex Formal container for doubly linked lists
23305 This child of @code{Ada.Containers} defines a modified version of the
23306 Ada 2005 container for doubly linked lists, meant to facilitate formal
23307 verification of code using such containers. The specification of this
23308 unit is compatible with SPARK 2014.
23310 Note that although this container was designed with formal verification
23311 in mind, it may well be generally useful in that it is a simplified more
23312 efficient version than the one defined in the standard. In particular it
23313 does not have the complex overhead required to detect cursor tampering.
23315 @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
23316 @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}
23317 @section @code{Ada.Containers.Formal_Hashed_Maps} (@code{a-cfhama.ads})
23320 @geindex Ada.Containers.Formal_Hashed_Maps (a-cfhama.ads)
23322 @geindex Formal container for hashed maps
23324 This child of @code{Ada.Containers} defines a modified version of the
23325 Ada 2005 container for hashed maps, meant to facilitate formal
23326 verification of code using such containers. The specification of this
23327 unit is compatible with SPARK 2014.
23329 Note that although this container was designed with formal verification
23330 in mind, it may well be generally useful in that it is a simplified more
23331 efficient version than the one defined in the standard. In particular it
23332 does not have the complex overhead required to detect cursor tampering.
23334 @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
23335 @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}
23336 @section @code{Ada.Containers.Formal_Hashed_Sets} (@code{a-cfhase.ads})
23339 @geindex Ada.Containers.Formal_Hashed_Sets (a-cfhase.ads)
23341 @geindex Formal container for hashed sets
23343 This child of @code{Ada.Containers} defines a modified version of the
23344 Ada 2005 container for hashed sets, meant to facilitate formal
23345 verification of code using such containers. The specification of this
23346 unit is compatible with SPARK 2014.
23348 Note that although this container was designed with formal verification
23349 in mind, it may well be generally useful in that it is a simplified more
23350 efficient version than the one defined in the standard. In particular it
23351 does not have the complex overhead required to detect cursor tampering.
23353 @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
23354 @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}
23355 @section @code{Ada.Containers.Formal_Ordered_Maps} (@code{a-cforma.ads})
23358 @geindex Ada.Containers.Formal_Ordered_Maps (a-cforma.ads)
23360 @geindex Formal container for ordered maps
23362 This child of @code{Ada.Containers} defines a modified version of the
23363 Ada 2005 container for ordered maps, meant to facilitate formal
23364 verification of code using such containers. The specification of this
23365 unit is compatible with SPARK 2014.
23367 Note that although this container was designed with formal verification
23368 in mind, it may well be generally useful in that it is a simplified more
23369 efficient version than the one defined in the standard. In particular it
23370 does not have the complex overhead required to detect cursor tampering.
23372 @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
23373 @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}
23374 @section @code{Ada.Containers.Formal_Ordered_Sets} (@code{a-cforse.ads})
23377 @geindex Ada.Containers.Formal_Ordered_Sets (a-cforse.ads)
23379 @geindex Formal container for ordered sets
23381 This child of @code{Ada.Containers} defines a modified version of the
23382 Ada 2005 container for ordered sets, meant to facilitate formal
23383 verification of code using such containers. The specification of this
23384 unit is compatible with SPARK 2014.
23386 Note that although this container was designed with formal verification
23387 in mind, it may well be generally useful in that it is a simplified more
23388 efficient version than the one defined in the standard. In particular it
23389 does not have the complex overhead required to detect cursor tampering.
23391 @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
23392 @anchor{gnat_rm/the_gnat_library id12}@anchor{2e8}@anchor{gnat_rm/the_gnat_library ada-containers-formal-vectors-a-cofove-ads}@anchor{2e9}
23393 @section @code{Ada.Containers.Formal_Vectors} (@code{a-cofove.ads})
23396 @geindex Ada.Containers.Formal_Vectors (a-cofove.ads)
23398 @geindex Formal container for vectors
23400 This child of @code{Ada.Containers} defines a modified version of the
23401 Ada 2005 container for vectors, meant to facilitate formal
23402 verification of code using such containers. The specification of this
23403 unit is compatible with SPARK 2014.
23405 Note that although this container was designed with formal verification
23406 in mind, it may well be generally useful in that it is a simplified more
23407 efficient version than the one defined in the standard. In particular it
23408 does not have the complex overhead required to detect cursor tampering.
23410 @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
23411 @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}
23412 @section @code{Ada.Containers.Formal_Indefinite_Vectors} (@code{a-cfinve.ads})
23415 @geindex Ada.Containers.Formal_Indefinite_Vectors (a-cfinve.ads)
23417 @geindex Formal container for vectors
23419 This child of @code{Ada.Containers} defines a modified version of the
23420 Ada 2005 container for vectors of indefinite elements, meant to
23421 facilitate formal verification of code using such containers. The
23422 specification of this unit is compatible with SPARK 2014.
23424 Note that although this container was designed with formal verification
23425 in mind, it may well be generally useful in that it is a simplified more
23426 efficient version than the one defined in the standard. In particular it
23427 does not have the complex overhead required to detect cursor tampering.
23429 @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
23430 @anchor{gnat_rm/the_gnat_library id14}@anchor{2ec}@anchor{gnat_rm/the_gnat_library ada-containers-functional-vectors-a-cofuve-ads}@anchor{2ed}
23431 @section @code{Ada.Containers.Functional_Vectors} (@code{a-cofuve.ads})
23434 @geindex Ada.Containers.Functional_Vectors (a-cofuve.ads)
23436 @geindex Functional vectors
23438 This child of @code{Ada.Containers} defines immutable vectors. These
23439 containers are unbounded and may contain indefinite elements. Furthermore, to
23440 be usable in every context, they are neither controlled nor limited. As they
23441 are functional, that is, no primitives are provided which would allow modifying
23442 an existing container, these containers can still be used safely.
23444 Their API features functions creating new containers from existing ones.
23445 As a consequence, these containers are highly inefficient. They are also
23446 memory consuming, as the allocated memory is not reclaimed when the container
23447 is no longer referenced. Thus, they should in general be used in ghost code
23448 and annotations, so that they can be removed from the final executable. The
23449 specification of this unit is compatible with SPARK 2014.
23451 @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
23452 @anchor{gnat_rm/the_gnat_library ada-containers-functional-sets-a-cofuse-ads}@anchor{2ee}@anchor{gnat_rm/the_gnat_library id15}@anchor{2ef}
23453 @section @code{Ada.Containers.Functional_Sets} (@code{a-cofuse.ads})
23456 @geindex Ada.Containers.Functional_Sets (a-cofuse.ads)
23458 @geindex Functional sets
23460 This child of @code{Ada.Containers} defines immutable sets. These containers are
23461 unbounded and may contain indefinite elements. Furthermore, to be usable in
23462 every context, they are neither controlled nor limited. As they are functional,
23463 that is, no primitives are provided which would allow modifying an existing
23464 container, these containers can still be used safely.
23466 Their API features functions creating new containers from existing ones.
23467 As a consequence, these containers are highly inefficient. They are also
23468 memory consuming, as the allocated memory is not reclaimed when the container
23469 is no longer referenced. Thus, they should in general be used in ghost code
23470 and annotations, so that they can be removed from the final executable. The
23471 specification of this unit is compatible with SPARK 2014.
23473 @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
23474 @anchor{gnat_rm/the_gnat_library id16}@anchor{2f0}@anchor{gnat_rm/the_gnat_library ada-containers-functional-maps-a-cofuma-ads}@anchor{2f1}
23475 @section @code{Ada.Containers.Functional_Maps} (@code{a-cofuma.ads})
23478 @geindex Ada.Containers.Functional_Maps (a-cofuma.ads)
23480 @geindex Functional maps
23482 This child of @code{Ada.Containers} defines immutable maps. These containers are
23483 unbounded and may contain indefinite elements. Furthermore, to be usable in
23484 every context, they are neither controlled nor limited. As they are functional,
23485 that is, no primitives are provided which would allow modifying an existing
23486 container, these containers can still be used safely.
23488 Their API features functions creating new containers from existing ones.
23489 As a consequence, these containers are highly inefficient. They are also
23490 memory consuming, as the allocated memory is not reclaimed when the container
23491 is no longer referenced. Thus, they should in general be used in ghost code
23492 and annotations, so that they can be removed from the final executable. The
23493 specification of this unit is compatible with SPARK 2014.
23495 @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
23496 @anchor{gnat_rm/the_gnat_library ada-containers-bounded-holders-a-coboho-ads}@anchor{2f2}@anchor{gnat_rm/the_gnat_library id17}@anchor{2f3}
23497 @section @code{Ada.Containers.Bounded_Holders} (@code{a-coboho.ads})
23500 @geindex Ada.Containers.Bounded_Holders (a-coboho.ads)
23502 @geindex Formal container for vectors
23504 This child of @code{Ada.Containers} defines a modified version of
23505 Indefinite_Holders that avoids heap allocation.
23507 @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
23508 @anchor{gnat_rm/the_gnat_library ada-command-line-environment-a-colien-ads}@anchor{2f4}@anchor{gnat_rm/the_gnat_library id18}@anchor{2f5}
23509 @section @code{Ada.Command_Line.Environment} (@code{a-colien.ads})
23512 @geindex Ada.Command_Line.Environment (a-colien.ads)
23514 @geindex Environment entries
23516 This child of @code{Ada.Command_Line}
23517 provides a mechanism for obtaining environment values on systems
23518 where this concept makes sense.
23520 @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
23521 @anchor{gnat_rm/the_gnat_library id19}@anchor{2f6}@anchor{gnat_rm/the_gnat_library ada-command-line-remove-a-colire-ads}@anchor{2f7}
23522 @section @code{Ada.Command_Line.Remove} (@code{a-colire.ads})
23525 @geindex Ada.Command_Line.Remove (a-colire.ads)
23527 @geindex Removing command line arguments
23529 @geindex Command line
23530 @geindex argument removal
23532 This child of @code{Ada.Command_Line}
23533 provides a mechanism for logically removing
23534 arguments from the argument list. Once removed, an argument is not visible
23535 to further calls on the subprograms in @code{Ada.Command_Line} will not
23536 see the removed argument.
23538 @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
23539 @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}
23540 @section @code{Ada.Command_Line.Response_File} (@code{a-clrefi.ads})
23543 @geindex Ada.Command_Line.Response_File (a-clrefi.ads)
23545 @geindex Response file for command line
23547 @geindex Command line
23548 @geindex response file
23550 @geindex Command line
23551 @geindex handling long command lines
23553 This child of @code{Ada.Command_Line} provides a mechanism facilities for
23554 getting command line arguments from a text file, called a "response file".
23555 Using a response file allow passing a set of arguments to an executable longer
23556 than the maximum allowed by the system on the command line.
23558 @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
23559 @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}
23560 @section @code{Ada.Direct_IO.C_Streams} (@code{a-diocst.ads})
23563 @geindex Ada.Direct_IO.C_Streams (a-diocst.ads)
23566 @geindex Interfacing with Direct_IO
23568 This package provides subprograms that allow interfacing between
23569 C streams and @code{Direct_IO}. The stream identifier can be
23570 extracted from a file opened on the Ada side, and an Ada file
23571 can be constructed from a stream opened on the C side.
23573 @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
23574 @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}
23575 @section @code{Ada.Exceptions.Is_Null_Occurrence} (@code{a-einuoc.ads})
23578 @geindex Ada.Exceptions.Is_Null_Occurrence (a-einuoc.ads)
23580 @geindex Null_Occurrence
23581 @geindex testing for
23583 This child subprogram provides a way of testing for the null
23584 exception occurrence (@code{Null_Occurrence}) without raising
23587 @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
23588 @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}
23589 @section @code{Ada.Exceptions.Last_Chance_Handler} (@code{a-elchha.ads})
23592 @geindex Ada.Exceptions.Last_Chance_Handler (a-elchha.ads)
23594 @geindex Null_Occurrence
23595 @geindex testing for
23597 This child subprogram is used for handling otherwise unhandled
23598 exceptions (hence the name last chance), and perform clean ups before
23599 terminating the program. Note that this subprogram never returns.
23601 @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
23602 @anchor{gnat_rm/the_gnat_library ada-exceptions-traceback-a-exctra-ads}@anchor{300}@anchor{gnat_rm/the_gnat_library id24}@anchor{301}
23603 @section @code{Ada.Exceptions.Traceback} (@code{a-exctra.ads})
23606 @geindex Ada.Exceptions.Traceback (a-exctra.ads)
23608 @geindex Traceback for Exception Occurrence
23610 This child package provides the subprogram (@code{Tracebacks}) to
23611 give a traceback array of addresses based on an exception
23614 @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
23615 @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}
23616 @section @code{Ada.Sequential_IO.C_Streams} (@code{a-siocst.ads})
23619 @geindex Ada.Sequential_IO.C_Streams (a-siocst.ads)
23622 @geindex Interfacing with Sequential_IO
23624 This package provides subprograms that allow interfacing between
23625 C streams and @code{Sequential_IO}. The stream identifier can be
23626 extracted from a file opened on the Ada side, and an Ada file
23627 can be constructed from a stream opened on the C side.
23629 @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
23630 @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}
23631 @section @code{Ada.Streams.Stream_IO.C_Streams} (@code{a-ssicst.ads})
23634 @geindex Ada.Streams.Stream_IO.C_Streams (a-ssicst.ads)
23637 @geindex Interfacing with Stream_IO
23639 This package provides subprograms that allow interfacing between
23640 C streams and @code{Stream_IO}. The stream identifier can be
23641 extracted from a file opened on the Ada side, and an Ada file
23642 can be constructed from a stream opened on the C side.
23644 @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
23645 @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}
23646 @section @code{Ada.Strings.Unbounded.Text_IO} (@code{a-suteio.ads})
23649 @geindex Ada.Strings.Unbounded.Text_IO (a-suteio.ads)
23651 @geindex Unbounded_String
23652 @geindex IO support
23655 @geindex extensions for unbounded strings
23657 This package provides subprograms for Text_IO for unbounded
23658 strings, avoiding the necessity for an intermediate operation
23659 with ordinary strings.
23661 @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
23662 @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}
23663 @section @code{Ada.Strings.Wide_Unbounded.Wide_Text_IO} (@code{a-swuwti.ads})
23666 @geindex Ada.Strings.Wide_Unbounded.Wide_Text_IO (a-swuwti.ads)
23668 @geindex Unbounded_Wide_String
23669 @geindex IO support
23672 @geindex extensions for unbounded wide strings
23674 This package provides subprograms for Text_IO for unbounded
23675 wide strings, avoiding the necessity for an intermediate operation
23676 with ordinary wide strings.
23678 @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
23679 @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}
23680 @section @code{Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO} (@code{a-szuzti.ads})
23683 @geindex Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO (a-szuzti.ads)
23685 @geindex Unbounded_Wide_Wide_String
23686 @geindex IO support
23689 @geindex extensions for unbounded wide wide strings
23691 This package provides subprograms for Text_IO for unbounded
23692 wide wide strings, avoiding the necessity for an intermediate operation
23693 with ordinary wide wide strings.
23695 @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
23696 @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}
23697 @section @code{Ada.Text_IO.C_Streams} (@code{a-tiocst.ads})
23700 @geindex Ada.Text_IO.C_Streams (a-tiocst.ads)
23703 @geindex Interfacing with `@w{`}Text_IO`@w{`}
23705 This package provides subprograms that allow interfacing between
23706 C streams and @code{Text_IO}. The stream identifier can be
23707 extracted from a file opened on the Ada side, and an Ada file
23708 can be constructed from a stream opened on the C side.
23710 @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
23711 @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}
23712 @section @code{Ada.Text_IO.Reset_Standard_Files} (@code{a-tirsfi.ads})
23715 @geindex Ada.Text_IO.Reset_Standard_Files (a-tirsfi.ads)
23717 @geindex Text_IO resetting standard files
23719 This procedure is used to reset the status of the standard files used
23720 by Ada.Text_IO. This is useful in a situation (such as a restart in an
23721 embedded application) where the status of the files may change during
23722 execution (for example a standard input file may be redefined to be
23725 @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
23726 @anchor{gnat_rm/the_gnat_library id32}@anchor{310}@anchor{gnat_rm/the_gnat_library ada-wide-characters-unicode-a-wichun-ads}@anchor{311}
23727 @section @code{Ada.Wide_Characters.Unicode} (@code{a-wichun.ads})
23730 @geindex Ada.Wide_Characters.Unicode (a-wichun.ads)
23732 @geindex Unicode categorization
23733 @geindex Wide_Character
23735 This package provides subprograms that allow categorization of
23736 Wide_Character values according to Unicode categories.
23738 @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
23739 @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}
23740 @section @code{Ada.Wide_Text_IO.C_Streams} (@code{a-wtcstr.ads})
23743 @geindex Ada.Wide_Text_IO.C_Streams (a-wtcstr.ads)
23746 @geindex Interfacing with `@w{`}Wide_Text_IO`@w{`}
23748 This package provides subprograms that allow interfacing between
23749 C streams and @code{Wide_Text_IO}. The stream identifier can be
23750 extracted from a file opened on the Ada side, and an Ada file
23751 can be constructed from a stream opened on the C side.
23753 @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
23754 @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}
23755 @section @code{Ada.Wide_Text_IO.Reset_Standard_Files} (@code{a-wrstfi.ads})
23758 @geindex Ada.Wide_Text_IO.Reset_Standard_Files (a-wrstfi.ads)
23760 @geindex Wide_Text_IO resetting standard files
23762 This procedure is used to reset the status of the standard files used
23763 by Ada.Wide_Text_IO. This is useful in a situation (such as a restart in an
23764 embedded application) where the status of the files may change during
23765 execution (for example a standard input file may be redefined to be
23768 @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
23769 @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}
23770 @section @code{Ada.Wide_Wide_Characters.Unicode} (@code{a-zchuni.ads})
23773 @geindex Ada.Wide_Wide_Characters.Unicode (a-zchuni.ads)
23775 @geindex Unicode categorization
23776 @geindex Wide_Wide_Character
23778 This package provides subprograms that allow categorization of
23779 Wide_Wide_Character values according to Unicode categories.
23781 @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
23782 @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}
23783 @section @code{Ada.Wide_Wide_Text_IO.C_Streams} (@code{a-ztcstr.ads})
23786 @geindex Ada.Wide_Wide_Text_IO.C_Streams (a-ztcstr.ads)
23789 @geindex Interfacing with `@w{`}Wide_Wide_Text_IO`@w{`}
23791 This package provides subprograms that allow interfacing between
23792 C streams and @code{Wide_Wide_Text_IO}. The stream identifier can be
23793 extracted from a file opened on the Ada side, and an Ada file
23794 can be constructed from a stream opened on the C side.
23796 @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
23797 @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}
23798 @section @code{Ada.Wide_Wide_Text_IO.Reset_Standard_Files} (@code{a-zrstfi.ads})
23801 @geindex Ada.Wide_Wide_Text_IO.Reset_Standard_Files (a-zrstfi.ads)
23803 @geindex Wide_Wide_Text_IO resetting standard files
23805 This procedure is used to reset the status of the standard files used
23806 by Ada.Wide_Wide_Text_IO. This is useful in a situation (such as a
23807 restart in an embedded application) where the status of the files may
23808 change during execution (for example a standard input file may be
23809 redefined to be interactive).
23811 @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
23812 @anchor{gnat_rm/the_gnat_library gnat-altivec-g-altive-ads}@anchor{31c}@anchor{gnat_rm/the_gnat_library id38}@anchor{31d}
23813 @section @code{GNAT.Altivec} (@code{g-altive.ads})
23816 @geindex GNAT.Altivec (g-altive.ads)
23820 This is the root package of the GNAT AltiVec binding. It provides
23821 definitions of constants and types common to all the versions of the
23824 @node GNAT Altivec Conversions g-altcon ads,GNAT Altivec Vector_Operations g-alveop ads,GNAT Altivec g-altive ads,The GNAT Library
23825 @anchor{gnat_rm/the_gnat_library gnat-altivec-conversions-g-altcon-ads}@anchor{31e}@anchor{gnat_rm/the_gnat_library id39}@anchor{31f}
23826 @section @code{GNAT.Altivec.Conversions} (@code{g-altcon.ads})
23829 @geindex GNAT.Altivec.Conversions (g-altcon.ads)
23833 This package provides the Vector/View conversion routines.
23835 @node GNAT Altivec Vector_Operations g-alveop ads,GNAT Altivec Vector_Types g-alvety ads,GNAT Altivec Conversions g-altcon ads,The GNAT Library
23836 @anchor{gnat_rm/the_gnat_library gnat-altivec-vector-operations-g-alveop-ads}@anchor{320}@anchor{gnat_rm/the_gnat_library id40}@anchor{321}
23837 @section @code{GNAT.Altivec.Vector_Operations} (@code{g-alveop.ads})
23840 @geindex GNAT.Altivec.Vector_Operations (g-alveop.ads)
23844 This package exposes the Ada interface to the AltiVec operations on
23845 vector objects. A soft emulation is included by default in the GNAT
23846 library. The hard binding is provided as a separate package. This unit
23847 is common to both bindings.
23849 @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
23850 @anchor{gnat_rm/the_gnat_library gnat-altivec-vector-types-g-alvety-ads}@anchor{322}@anchor{gnat_rm/the_gnat_library id41}@anchor{323}
23851 @section @code{GNAT.Altivec.Vector_Types} (@code{g-alvety.ads})
23854 @geindex GNAT.Altivec.Vector_Types (g-alvety.ads)
23858 This package exposes the various vector types part of the Ada binding
23859 to AltiVec facilities.
23861 @node GNAT Altivec Vector_Views g-alvevi ads,GNAT Array_Split g-arrspl ads,GNAT Altivec Vector_Types g-alvety ads,The GNAT Library
23862 @anchor{gnat_rm/the_gnat_library gnat-altivec-vector-views-g-alvevi-ads}@anchor{324}@anchor{gnat_rm/the_gnat_library id42}@anchor{325}
23863 @section @code{GNAT.Altivec.Vector_Views} (@code{g-alvevi.ads})
23866 @geindex GNAT.Altivec.Vector_Views (g-alvevi.ads)
23870 This package provides public 'View' data types from/to which private
23871 vector representations can be converted via
23872 GNAT.Altivec.Conversions. This allows convenient access to individual
23873 vector elements and provides a simple way to initialize vector
23876 @node GNAT Array_Split g-arrspl ads,GNAT AWK g-awk ads,GNAT Altivec Vector_Views g-alvevi ads,The GNAT Library
23877 @anchor{gnat_rm/the_gnat_library gnat-array-split-g-arrspl-ads}@anchor{326}@anchor{gnat_rm/the_gnat_library id43}@anchor{327}
23878 @section @code{GNAT.Array_Split} (@code{g-arrspl.ads})
23881 @geindex GNAT.Array_Split (g-arrspl.ads)
23883 @geindex Array splitter
23885 Useful array-manipulation routines: given a set of separators, split
23886 an array wherever the separators appear, and provide direct access
23887 to the resulting slices.
23889 @node GNAT AWK g-awk ads,GNAT Bind_Environment g-binenv ads,GNAT Array_Split g-arrspl ads,The GNAT Library
23890 @anchor{gnat_rm/the_gnat_library id44}@anchor{328}@anchor{gnat_rm/the_gnat_library gnat-awk-g-awk-ads}@anchor{329}
23891 @section @code{GNAT.AWK} (@code{g-awk.ads})
23894 @geindex GNAT.AWK (g-awk.ads)
23900 Provides AWK-like parsing functions, with an easy interface for parsing one
23901 or more files containing formatted data. The file is viewed as a database
23902 where each record is a line and a field is a data element in this line.
23904 @node GNAT Bind_Environment g-binenv ads,GNAT Branch_Prediction g-brapre ads,GNAT AWK g-awk ads,The GNAT Library
23905 @anchor{gnat_rm/the_gnat_library gnat-bind-environment-g-binenv-ads}@anchor{32a}@anchor{gnat_rm/the_gnat_library id45}@anchor{32b}
23906 @section @code{GNAT.Bind_Environment} (@code{g-binenv.ads})
23909 @geindex GNAT.Bind_Environment (g-binenv.ads)
23911 @geindex Bind environment
23913 Provides access to key=value associations captured at bind time.
23914 These associations can be specified using the @code{-V} binder command
23917 @node GNAT Branch_Prediction g-brapre ads,GNAT Bounded_Buffers g-boubuf ads,GNAT Bind_Environment g-binenv ads,The GNAT Library
23918 @anchor{gnat_rm/the_gnat_library id46}@anchor{32c}@anchor{gnat_rm/the_gnat_library gnat-branch-prediction-g-brapre-ads}@anchor{32d}
23919 @section @code{GNAT.Branch_Prediction} (@code{g-brapre.ads})
23922 @geindex GNAT.Branch_Prediction (g-brapre.ads)
23924 @geindex Branch Prediction
23926 Provides routines giving hints to the branch predictor of the code generator.
23928 @node GNAT Bounded_Buffers g-boubuf ads,GNAT Bounded_Mailboxes g-boumai ads,GNAT Branch_Prediction g-brapre ads,The GNAT Library
23929 @anchor{gnat_rm/the_gnat_library id47}@anchor{32e}@anchor{gnat_rm/the_gnat_library gnat-bounded-buffers-g-boubuf-ads}@anchor{32f}
23930 @section @code{GNAT.Bounded_Buffers} (@code{g-boubuf.ads})
23933 @geindex GNAT.Bounded_Buffers (g-boubuf.ads)
23937 @geindex Bounded Buffers
23939 Provides a concurrent generic bounded buffer abstraction. Instances are
23940 useful directly or as parts of the implementations of other abstractions,
23943 @node GNAT Bounded_Mailboxes g-boumai ads,GNAT Bubble_Sort g-bubsor ads,GNAT Bounded_Buffers g-boubuf ads,The GNAT Library
23944 @anchor{gnat_rm/the_gnat_library gnat-bounded-mailboxes-g-boumai-ads}@anchor{330}@anchor{gnat_rm/the_gnat_library id48}@anchor{331}
23945 @section @code{GNAT.Bounded_Mailboxes} (@code{g-boumai.ads})
23948 @geindex GNAT.Bounded_Mailboxes (g-boumai.ads)
23954 Provides a thread-safe asynchronous intertask mailbox communication facility.
23956 @node GNAT Bubble_Sort g-bubsor ads,GNAT Bubble_Sort_A g-busora ads,GNAT Bounded_Mailboxes g-boumai ads,The GNAT Library
23957 @anchor{gnat_rm/the_gnat_library gnat-bubble-sort-g-bubsor-ads}@anchor{332}@anchor{gnat_rm/the_gnat_library id49}@anchor{333}
23958 @section @code{GNAT.Bubble_Sort} (@code{g-bubsor.ads})
23961 @geindex GNAT.Bubble_Sort (g-bubsor.ads)
23965 @geindex Bubble sort
23967 Provides a general implementation of bubble sort usable for sorting arbitrary
23968 data items. Exchange and comparison procedures are provided by passing
23969 access-to-procedure values.
23971 @node GNAT Bubble_Sort_A g-busora ads,GNAT Bubble_Sort_G g-busorg ads,GNAT Bubble_Sort g-bubsor ads,The GNAT Library
23972 @anchor{gnat_rm/the_gnat_library id50}@anchor{334}@anchor{gnat_rm/the_gnat_library gnat-bubble-sort-a-g-busora-ads}@anchor{335}
23973 @section @code{GNAT.Bubble_Sort_A} (@code{g-busora.ads})
23976 @geindex GNAT.Bubble_Sort_A (g-busora.ads)
23980 @geindex Bubble sort
23982 Provides a general implementation of bubble sort usable for sorting arbitrary
23983 data items. Move and comparison procedures are provided by passing
23984 access-to-procedure values. This is an older version, retained for
23985 compatibility. Usually @code{GNAT.Bubble_Sort} will be preferable.
23987 @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
23988 @anchor{gnat_rm/the_gnat_library gnat-bubble-sort-g-g-busorg-ads}@anchor{336}@anchor{gnat_rm/the_gnat_library id51}@anchor{337}
23989 @section @code{GNAT.Bubble_Sort_G} (@code{g-busorg.ads})
23992 @geindex GNAT.Bubble_Sort_G (g-busorg.ads)
23996 @geindex Bubble sort
23998 Similar to @code{Bubble_Sort_A} except that the move and sorting procedures
23999 are provided as generic parameters, this improves efficiency, especially
24000 if the procedures can be inlined, at the expense of duplicating code for
24001 multiple instantiations.
24003 @node GNAT Byte_Order_Mark g-byorma ads,GNAT Byte_Swapping g-bytswa ads,GNAT Bubble_Sort_G g-busorg ads,The GNAT Library
24004 @anchor{gnat_rm/the_gnat_library gnat-byte-order-mark-g-byorma-ads}@anchor{338}@anchor{gnat_rm/the_gnat_library id52}@anchor{339}
24005 @section @code{GNAT.Byte_Order_Mark} (@code{g-byorma.ads})
24008 @geindex GNAT.Byte_Order_Mark (g-byorma.ads)
24010 @geindex UTF-8 representation
24012 @geindex Wide characte representations
24014 Provides a routine which given a string, reads the start of the string to
24015 see whether it is one of the standard byte order marks (BOM's) which signal
24016 the encoding of the string. The routine includes detection of special XML
24017 sequences for various UCS input formats.
24019 @node GNAT Byte_Swapping g-bytswa ads,GNAT Calendar g-calend ads,GNAT Byte_Order_Mark g-byorma ads,The GNAT Library
24020 @anchor{gnat_rm/the_gnat_library gnat-byte-swapping-g-bytswa-ads}@anchor{33a}@anchor{gnat_rm/the_gnat_library id53}@anchor{33b}
24021 @section @code{GNAT.Byte_Swapping} (@code{g-bytswa.ads})
24024 @geindex GNAT.Byte_Swapping (g-bytswa.ads)
24026 @geindex Byte swapping
24028 @geindex Endianness
24030 General routines for swapping the bytes in 2-, 4-, and 8-byte quantities.
24031 Machine-specific implementations are available in some cases.
24033 @node GNAT Calendar g-calend ads,GNAT Calendar Time_IO g-catiio ads,GNAT Byte_Swapping g-bytswa ads,The GNAT Library
24034 @anchor{gnat_rm/the_gnat_library id54}@anchor{33c}@anchor{gnat_rm/the_gnat_library gnat-calendar-g-calend-ads}@anchor{33d}
24035 @section @code{GNAT.Calendar} (@code{g-calend.ads})
24038 @geindex GNAT.Calendar (g-calend.ads)
24042 Extends the facilities provided by @code{Ada.Calendar} to include handling
24043 of days of the week, an extended @code{Split} and @code{Time_Of} capability.
24044 Also provides conversion of @code{Ada.Calendar.Time} values to and from the
24045 C @code{timeval} format.
24047 @node GNAT Calendar Time_IO g-catiio ads,GNAT CRC32 g-crc32 ads,GNAT Calendar g-calend ads,The GNAT Library
24048 @anchor{gnat_rm/the_gnat_library id55}@anchor{33e}@anchor{gnat_rm/the_gnat_library gnat-calendar-time-io-g-catiio-ads}@anchor{33f}
24049 @section @code{GNAT.Calendar.Time_IO} (@code{g-catiio.ads})
24056 @geindex GNAT.Calendar.Time_IO (g-catiio.ads)
24058 @node GNAT CRC32 g-crc32 ads,GNAT Case_Util g-casuti ads,GNAT Calendar Time_IO g-catiio ads,The GNAT Library
24059 @anchor{gnat_rm/the_gnat_library id56}@anchor{340}@anchor{gnat_rm/the_gnat_library gnat-crc32-g-crc32-ads}@anchor{341}
24060 @section @code{GNAT.CRC32} (@code{g-crc32.ads})
24063 @geindex GNAT.CRC32 (g-crc32.ads)
24067 @geindex Cyclic Redundancy Check
24069 This package implements the CRC-32 algorithm. For a full description
24070 of this algorithm see
24071 @emph{Computation of Cyclic Redundancy Checks via Table Look-Up},
24072 @cite{Communications of the ACM}, Vol. 31 No. 8, pp. 1008-1013,
24073 Aug. 1988. Sarwate, D.V.
24075 @node GNAT Case_Util g-casuti ads,GNAT CGI g-cgi ads,GNAT CRC32 g-crc32 ads,The GNAT Library
24076 @anchor{gnat_rm/the_gnat_library id57}@anchor{342}@anchor{gnat_rm/the_gnat_library gnat-case-util-g-casuti-ads}@anchor{343}
24077 @section @code{GNAT.Case_Util} (@code{g-casuti.ads})
24080 @geindex GNAT.Case_Util (g-casuti.ads)
24082 @geindex Casing utilities
24084 @geindex Character handling (`@w{`}GNAT.Case_Util`@w{`})
24086 A set of simple routines for handling upper and lower casing of strings
24087 without the overhead of the full casing tables
24088 in @code{Ada.Characters.Handling}.
24090 @node GNAT CGI g-cgi ads,GNAT CGI Cookie g-cgicoo ads,GNAT Case_Util g-casuti ads,The GNAT Library
24091 @anchor{gnat_rm/the_gnat_library id58}@anchor{344}@anchor{gnat_rm/the_gnat_library gnat-cgi-g-cgi-ads}@anchor{345}
24092 @section @code{GNAT.CGI} (@code{g-cgi.ads})
24095 @geindex GNAT.CGI (g-cgi.ads)
24097 @geindex CGI (Common Gateway Interface)
24099 This is a package for interfacing a GNAT program with a Web server via the
24100 Common Gateway Interface (CGI). Basically this package parses the CGI
24101 parameters, which are a set of key/value pairs sent by the Web server. It
24102 builds a table whose index is the key and provides some services to deal
24105 @node GNAT CGI Cookie g-cgicoo ads,GNAT CGI Debug g-cgideb ads,GNAT CGI g-cgi ads,The GNAT Library
24106 @anchor{gnat_rm/the_gnat_library gnat-cgi-cookie-g-cgicoo-ads}@anchor{346}@anchor{gnat_rm/the_gnat_library id59}@anchor{347}
24107 @section @code{GNAT.CGI.Cookie} (@code{g-cgicoo.ads})
24110 @geindex GNAT.CGI.Cookie (g-cgicoo.ads)
24112 @geindex CGI (Common Gateway Interface) cookie support
24114 @geindex Cookie support in CGI
24116 This is a package to interface a GNAT program with a Web server via the
24117 Common Gateway Interface (CGI). It exports services to deal with Web
24118 cookies (piece of information kept in the Web client software).
24120 @node GNAT CGI Debug g-cgideb ads,GNAT Command_Line g-comlin ads,GNAT CGI Cookie g-cgicoo ads,The GNAT Library
24121 @anchor{gnat_rm/the_gnat_library gnat-cgi-debug-g-cgideb-ads}@anchor{348}@anchor{gnat_rm/the_gnat_library id60}@anchor{349}
24122 @section @code{GNAT.CGI.Debug} (@code{g-cgideb.ads})
24125 @geindex GNAT.CGI.Debug (g-cgideb.ads)
24127 @geindex CGI (Common Gateway Interface) debugging
24129 This is a package to help debugging CGI (Common Gateway Interface)
24130 programs written in Ada.
24132 @node GNAT Command_Line g-comlin ads,GNAT Compiler_Version g-comver ads,GNAT CGI Debug g-cgideb ads,The GNAT Library
24133 @anchor{gnat_rm/the_gnat_library id61}@anchor{34a}@anchor{gnat_rm/the_gnat_library gnat-command-line-g-comlin-ads}@anchor{34b}
24134 @section @code{GNAT.Command_Line} (@code{g-comlin.ads})
24137 @geindex GNAT.Command_Line (g-comlin.ads)
24139 @geindex Command line
24141 Provides a high level interface to @code{Ada.Command_Line} facilities,
24142 including the ability to scan for named switches with optional parameters
24143 and expand file names using wildcard notations.
24145 @node GNAT Compiler_Version g-comver ads,GNAT Ctrl_C g-ctrl_c ads,GNAT Command_Line g-comlin ads,The GNAT Library
24146 @anchor{gnat_rm/the_gnat_library gnat-compiler-version-g-comver-ads}@anchor{34c}@anchor{gnat_rm/the_gnat_library id62}@anchor{34d}
24147 @section @code{GNAT.Compiler_Version} (@code{g-comver.ads})
24150 @geindex GNAT.Compiler_Version (g-comver.ads)
24152 @geindex Compiler Version
24155 @geindex of compiler
24157 Provides a routine for obtaining the version of the compiler used to
24158 compile the program. More accurately this is the version of the binder
24159 used to bind the program (this will normally be the same as the version
24160 of the compiler if a consistent tool set is used to compile all units
24163 @node GNAT Ctrl_C g-ctrl_c ads,GNAT Current_Exception g-curexc ads,GNAT Compiler_Version g-comver ads,The GNAT Library
24164 @anchor{gnat_rm/the_gnat_library gnat-ctrl-c-g-ctrl-c-ads}@anchor{34e}@anchor{gnat_rm/the_gnat_library id63}@anchor{34f}
24165 @section @code{GNAT.Ctrl_C} (@code{g-ctrl_c.ads})
24168 @geindex GNAT.Ctrl_C (g-ctrl_c.ads)
24172 Provides a simple interface to handle Ctrl-C keyboard events.
24174 @node GNAT Current_Exception g-curexc ads,GNAT Debug_Pools g-debpoo ads,GNAT Ctrl_C g-ctrl_c ads,The GNAT Library
24175 @anchor{gnat_rm/the_gnat_library id64}@anchor{350}@anchor{gnat_rm/the_gnat_library gnat-current-exception-g-curexc-ads}@anchor{351}
24176 @section @code{GNAT.Current_Exception} (@code{g-curexc.ads})
24179 @geindex GNAT.Current_Exception (g-curexc.ads)
24181 @geindex Current exception
24183 @geindex Exception retrieval
24185 Provides access to information on the current exception that has been raised
24186 without the need for using the Ada 95 / Ada 2005 exception choice parameter
24187 specification syntax.
24188 This is particularly useful in simulating typical facilities for
24189 obtaining information about exceptions provided by Ada 83 compilers.
24191 @node GNAT Debug_Pools g-debpoo ads,GNAT Debug_Utilities g-debuti ads,GNAT Current_Exception g-curexc ads,The GNAT Library
24192 @anchor{gnat_rm/the_gnat_library gnat-debug-pools-g-debpoo-ads}@anchor{352}@anchor{gnat_rm/the_gnat_library id65}@anchor{353}
24193 @section @code{GNAT.Debug_Pools} (@code{g-debpoo.ads})
24196 @geindex GNAT.Debug_Pools (g-debpoo.ads)
24200 @geindex Debug pools
24202 @geindex Memory corruption debugging
24204 Provide a debugging storage pools that helps tracking memory corruption
24206 See @code{The GNAT Debug_Pool Facility} section in the @cite{GNAT User's Guide}.
24208 @node GNAT Debug_Utilities g-debuti ads,GNAT Decode_String g-decstr ads,GNAT Debug_Pools g-debpoo ads,The GNAT Library
24209 @anchor{gnat_rm/the_gnat_library gnat-debug-utilities-g-debuti-ads}@anchor{354}@anchor{gnat_rm/the_gnat_library id66}@anchor{355}
24210 @section @code{GNAT.Debug_Utilities} (@code{g-debuti.ads})
24213 @geindex GNAT.Debug_Utilities (g-debuti.ads)
24217 Provides a few useful utilities for debugging purposes, including conversion
24218 to and from string images of address values. Supports both C and Ada formats
24219 for hexadecimal literals.
24221 @node GNAT Decode_String g-decstr ads,GNAT Decode_UTF8_String g-deutst ads,GNAT Debug_Utilities g-debuti ads,The GNAT Library
24222 @anchor{gnat_rm/the_gnat_library id67}@anchor{356}@anchor{gnat_rm/the_gnat_library gnat-decode-string-g-decstr-ads}@anchor{357}
24223 @section @code{GNAT.Decode_String} (@code{g-decstr.ads})
24226 @geindex GNAT.Decode_String (g-decstr.ads)
24228 @geindex Decoding strings
24230 @geindex String decoding
24232 @geindex Wide character encoding
24238 A generic package providing routines for decoding wide character and wide wide
24239 character strings encoded as sequences of 8-bit characters using a specified
24240 encoding method. Includes validation routines, and also routines for stepping
24241 to next or previous encoded character in an encoded string.
24242 Useful in conjunction with Unicode character coding. Note there is a
24243 preinstantiation for UTF-8. See next entry.
24245 @node GNAT Decode_UTF8_String g-deutst ads,GNAT Directory_Operations g-dirope ads,GNAT Decode_String g-decstr ads,The GNAT Library
24246 @anchor{gnat_rm/the_gnat_library gnat-decode-utf8-string-g-deutst-ads}@anchor{358}@anchor{gnat_rm/the_gnat_library id68}@anchor{359}
24247 @section @code{GNAT.Decode_UTF8_String} (@code{g-deutst.ads})
24250 @geindex GNAT.Decode_UTF8_String (g-deutst.ads)
24252 @geindex Decoding strings
24254 @geindex Decoding UTF-8 strings
24256 @geindex UTF-8 string decoding
24258 @geindex Wide character decoding
24264 A preinstantiation of GNAT.Decode_Strings for UTF-8 encoding.
24266 @node GNAT Directory_Operations g-dirope ads,GNAT Directory_Operations Iteration g-diopit ads,GNAT Decode_UTF8_String g-deutst ads,The GNAT Library
24267 @anchor{gnat_rm/the_gnat_library id69}@anchor{35a}@anchor{gnat_rm/the_gnat_library gnat-directory-operations-g-dirope-ads}@anchor{35b}
24268 @section @code{GNAT.Directory_Operations} (@code{g-dirope.ads})
24271 @geindex GNAT.Directory_Operations (g-dirope.ads)
24273 @geindex Directory operations
24275 Provides a set of routines for manipulating directories, including changing
24276 the current directory, making new directories, and scanning the files in a
24279 @node GNAT Directory_Operations Iteration g-diopit ads,GNAT Dynamic_HTables g-dynhta ads,GNAT Directory_Operations g-dirope ads,The GNAT Library
24280 @anchor{gnat_rm/the_gnat_library id70}@anchor{35c}@anchor{gnat_rm/the_gnat_library gnat-directory-operations-iteration-g-diopit-ads}@anchor{35d}
24281 @section @code{GNAT.Directory_Operations.Iteration} (@code{g-diopit.ads})
24284 @geindex GNAT.Directory_Operations.Iteration (g-diopit.ads)
24286 @geindex Directory operations iteration
24288 A child unit of GNAT.Directory_Operations providing additional operations
24289 for iterating through directories.
24291 @node GNAT Dynamic_HTables g-dynhta ads,GNAT Dynamic_Tables g-dyntab ads,GNAT Directory_Operations Iteration g-diopit ads,The GNAT Library
24292 @anchor{gnat_rm/the_gnat_library id71}@anchor{35e}@anchor{gnat_rm/the_gnat_library gnat-dynamic-htables-g-dynhta-ads}@anchor{35f}
24293 @section @code{GNAT.Dynamic_HTables} (@code{g-dynhta.ads})
24296 @geindex GNAT.Dynamic_HTables (g-dynhta.ads)
24298 @geindex Hash tables
24300 A generic implementation of hash tables that can be used to hash arbitrary
24301 data. Provided in two forms, a simple form with built in hash functions,
24302 and a more complex form in which the hash function is supplied.
24304 This package provides a facility similar to that of @code{GNAT.HTable},
24305 except that this package declares a type that can be used to define
24306 dynamic instances of the hash table, while an instantiation of
24307 @code{GNAT.HTable} creates a single instance of the hash table.
24309 @node GNAT Dynamic_Tables g-dyntab ads,GNAT Encode_String g-encstr ads,GNAT Dynamic_HTables g-dynhta ads,The GNAT Library
24310 @anchor{gnat_rm/the_gnat_library gnat-dynamic-tables-g-dyntab-ads}@anchor{360}@anchor{gnat_rm/the_gnat_library id72}@anchor{361}
24311 @section @code{GNAT.Dynamic_Tables} (@code{g-dyntab.ads})
24314 @geindex GNAT.Dynamic_Tables (g-dyntab.ads)
24316 @geindex Table implementation
24319 @geindex extendable
24321 A generic package providing a single dimension array abstraction where the
24322 length of the array can be dynamically modified.
24324 This package provides a facility similar to that of @code{GNAT.Table},
24325 except that this package declares a type that can be used to define
24326 dynamic instances of the table, while an instantiation of
24327 @code{GNAT.Table} creates a single instance of the table type.
24329 @node GNAT Encode_String g-encstr ads,GNAT Encode_UTF8_String g-enutst ads,GNAT Dynamic_Tables g-dyntab ads,The GNAT Library
24330 @anchor{gnat_rm/the_gnat_library id73}@anchor{362}@anchor{gnat_rm/the_gnat_library gnat-encode-string-g-encstr-ads}@anchor{363}
24331 @section @code{GNAT.Encode_String} (@code{g-encstr.ads})
24334 @geindex GNAT.Encode_String (g-encstr.ads)
24336 @geindex Encoding strings
24338 @geindex String encoding
24340 @geindex Wide character encoding
24346 A generic package providing routines for encoding wide character and wide
24347 wide character strings as sequences of 8-bit characters using a specified
24348 encoding method. Useful in conjunction with Unicode character coding.
24349 Note there is a preinstantiation for UTF-8. See next entry.
24351 @node GNAT Encode_UTF8_String g-enutst ads,GNAT Exception_Actions g-excact ads,GNAT Encode_String g-encstr ads,The GNAT Library
24352 @anchor{gnat_rm/the_gnat_library gnat-encode-utf8-string-g-enutst-ads}@anchor{364}@anchor{gnat_rm/the_gnat_library id74}@anchor{365}
24353 @section @code{GNAT.Encode_UTF8_String} (@code{g-enutst.ads})
24356 @geindex GNAT.Encode_UTF8_String (g-enutst.ads)
24358 @geindex Encoding strings
24360 @geindex Encoding UTF-8 strings
24362 @geindex UTF-8 string encoding
24364 @geindex Wide character encoding
24370 A preinstantiation of GNAT.Encode_Strings for UTF-8 encoding.
24372 @node GNAT Exception_Actions g-excact ads,GNAT Exception_Traces g-exctra ads,GNAT Encode_UTF8_String g-enutst ads,The GNAT Library
24373 @anchor{gnat_rm/the_gnat_library gnat-exception-actions-g-excact-ads}@anchor{366}@anchor{gnat_rm/the_gnat_library id75}@anchor{367}
24374 @section @code{GNAT.Exception_Actions} (@code{g-excact.ads})
24377 @geindex GNAT.Exception_Actions (g-excact.ads)
24379 @geindex Exception actions
24381 Provides callbacks when an exception is raised. Callbacks can be registered
24382 for specific exceptions, or when any exception is raised. This
24383 can be used for instance to force a core dump to ease debugging.
24385 @node GNAT Exception_Traces g-exctra ads,GNAT Exceptions g-except ads,GNAT Exception_Actions g-excact ads,The GNAT Library
24386 @anchor{gnat_rm/the_gnat_library gnat-exception-traces-g-exctra-ads}@anchor{368}@anchor{gnat_rm/the_gnat_library id76}@anchor{369}
24387 @section @code{GNAT.Exception_Traces} (@code{g-exctra.ads})
24390 @geindex GNAT.Exception_Traces (g-exctra.ads)
24392 @geindex Exception traces
24396 Provides an interface allowing to control automatic output upon exception
24399 @node GNAT Exceptions g-except ads,GNAT Expect g-expect ads,GNAT Exception_Traces g-exctra ads,The GNAT Library
24400 @anchor{gnat_rm/the_gnat_library id77}@anchor{36a}@anchor{gnat_rm/the_gnat_library gnat-exceptions-g-except-ads}@anchor{36b}
24401 @section @code{GNAT.Exceptions} (@code{g-except.ads})
24404 @geindex GNAT.Exceptions (g-except.ads)
24406 @geindex Exceptions
24409 @geindex Pure packages
24410 @geindex exceptions
24412 Normally it is not possible to raise an exception with
24413 a message from a subprogram in a pure package, since the
24414 necessary types and subprograms are in @code{Ada.Exceptions}
24415 which is not a pure unit. @code{GNAT.Exceptions} provides a
24416 facility for getting around this limitation for a few
24417 predefined exceptions, and for example allow raising
24418 @code{Constraint_Error} with a message from a pure subprogram.
24420 @node GNAT Expect g-expect ads,GNAT Expect TTY g-exptty ads,GNAT Exceptions g-except ads,The GNAT Library
24421 @anchor{gnat_rm/the_gnat_library id78}@anchor{36c}@anchor{gnat_rm/the_gnat_library gnat-expect-g-expect-ads}@anchor{36d}
24422 @section @code{GNAT.Expect} (@code{g-expect.ads})
24425 @geindex GNAT.Expect (g-expect.ads)
24427 Provides a set of subprograms similar to what is available
24428 with the standard Tcl Expect tool.
24429 It allows you to easily spawn and communicate with an external process.
24430 You can send commands or inputs to the process, and compare the output
24431 with some expected regular expression. Currently @code{GNAT.Expect}
24432 is implemented on all native GNAT ports.
24433 It is not implemented for cross ports, and in particular is not
24434 implemented for VxWorks or LynxOS.
24436 @node GNAT Expect TTY g-exptty ads,GNAT Float_Control g-flocon ads,GNAT Expect g-expect ads,The GNAT Library
24437 @anchor{gnat_rm/the_gnat_library id79}@anchor{36e}@anchor{gnat_rm/the_gnat_library gnat-expect-tty-g-exptty-ads}@anchor{36f}
24438 @section @code{GNAT.Expect.TTY} (@code{g-exptty.ads})
24441 @geindex GNAT.Expect.TTY (g-exptty.ads)
24443 As GNAT.Expect but using pseudo-terminal.
24444 Currently @code{GNAT.Expect.TTY} is implemented on all native GNAT
24445 ports. It is not implemented for cross ports, and
24446 in particular is not implemented for VxWorks or LynxOS.
24448 @node GNAT Float_Control g-flocon ads,GNAT Formatted_String g-forstr ads,GNAT Expect TTY g-exptty ads,The GNAT Library
24449 @anchor{gnat_rm/the_gnat_library id80}@anchor{370}@anchor{gnat_rm/the_gnat_library gnat-float-control-g-flocon-ads}@anchor{371}
24450 @section @code{GNAT.Float_Control} (@code{g-flocon.ads})
24453 @geindex GNAT.Float_Control (g-flocon.ads)
24455 @geindex Floating-Point Processor
24457 Provides an interface for resetting the floating-point processor into the
24458 mode required for correct semantic operation in Ada. Some third party
24459 library calls may cause this mode to be modified, and the Reset procedure
24460 in this package can be used to reestablish the required mode.
24462 @node GNAT Formatted_String g-forstr ads,GNAT Heap_Sort g-heasor ads,GNAT Float_Control g-flocon ads,The GNAT Library
24463 @anchor{gnat_rm/the_gnat_library id81}@anchor{372}@anchor{gnat_rm/the_gnat_library gnat-formatted-string-g-forstr-ads}@anchor{373}
24464 @section @code{GNAT.Formatted_String} (@code{g-forstr.ads})
24467 @geindex GNAT.Formatted_String (g-forstr.ads)
24469 @geindex Formatted String
24471 Provides support for C/C++ printf() formatted strings. The format is
24472 copied from the printf() routine and should therefore gives identical
24473 output. Some generic routines are provided to be able to use types
24474 derived from Integer, Float or enumerations as values for the
24477 @node GNAT Heap_Sort g-heasor ads,GNAT Heap_Sort_A g-hesora ads,GNAT Formatted_String g-forstr ads,The GNAT Library
24478 @anchor{gnat_rm/the_gnat_library gnat-heap-sort-g-heasor-ads}@anchor{374}@anchor{gnat_rm/the_gnat_library id82}@anchor{375}
24479 @section @code{GNAT.Heap_Sort} (@code{g-heasor.ads})
24482 @geindex GNAT.Heap_Sort (g-heasor.ads)
24486 Provides a general implementation of heap sort usable for sorting arbitrary
24487 data items. Exchange and comparison procedures are provided by passing
24488 access-to-procedure values. The algorithm used is a modified heap sort
24489 that performs approximately N*log(N) comparisons in the worst case.
24491 @node GNAT Heap_Sort_A g-hesora ads,GNAT Heap_Sort_G g-hesorg ads,GNAT Heap_Sort g-heasor ads,The GNAT Library
24492 @anchor{gnat_rm/the_gnat_library id83}@anchor{376}@anchor{gnat_rm/the_gnat_library gnat-heap-sort-a-g-hesora-ads}@anchor{377}
24493 @section @code{GNAT.Heap_Sort_A} (@code{g-hesora.ads})
24496 @geindex GNAT.Heap_Sort_A (g-hesora.ads)
24500 Provides a general implementation of heap sort usable for sorting arbitrary
24501 data items. Move and comparison procedures are provided by passing
24502 access-to-procedure values. The algorithm used is a modified heap sort
24503 that performs approximately N*log(N) comparisons in the worst case.
24504 This differs from @code{GNAT.Heap_Sort} in having a less convenient
24505 interface, but may be slightly more efficient.
24507 @node GNAT Heap_Sort_G g-hesorg ads,GNAT HTable g-htable ads,GNAT Heap_Sort_A g-hesora ads,The GNAT Library
24508 @anchor{gnat_rm/the_gnat_library id84}@anchor{378}@anchor{gnat_rm/the_gnat_library gnat-heap-sort-g-g-hesorg-ads}@anchor{379}
24509 @section @code{GNAT.Heap_Sort_G} (@code{g-hesorg.ads})
24512 @geindex GNAT.Heap_Sort_G (g-hesorg.ads)
24516 Similar to @code{Heap_Sort_A} except that the move and sorting procedures
24517 are provided as generic parameters, this improves efficiency, especially
24518 if the procedures can be inlined, at the expense of duplicating code for
24519 multiple instantiations.
24521 @node GNAT HTable g-htable ads,GNAT IO g-io ads,GNAT Heap_Sort_G g-hesorg ads,The GNAT Library
24522 @anchor{gnat_rm/the_gnat_library id85}@anchor{37a}@anchor{gnat_rm/the_gnat_library gnat-htable-g-htable-ads}@anchor{37b}
24523 @section @code{GNAT.HTable} (@code{g-htable.ads})
24526 @geindex GNAT.HTable (g-htable.ads)
24528 @geindex Hash tables
24530 A generic implementation of hash tables that can be used to hash arbitrary
24531 data. Provides two approaches, one a simple static approach, and the other
24532 allowing arbitrary dynamic hash tables.
24534 @node GNAT IO g-io ads,GNAT IO_Aux g-io_aux ads,GNAT HTable g-htable ads,The GNAT Library
24535 @anchor{gnat_rm/the_gnat_library id86}@anchor{37c}@anchor{gnat_rm/the_gnat_library gnat-io-g-io-ads}@anchor{37d}
24536 @section @code{GNAT.IO} (@code{g-io.ads})
24539 @geindex GNAT.IO (g-io.ads)
24541 @geindex Simple I/O
24543 @geindex Input/Output facilities
24545 A simple preelaborable input-output package that provides a subset of
24546 simple Text_IO functions for reading characters and strings from
24547 Standard_Input, and writing characters, strings and integers to either
24548 Standard_Output or Standard_Error.
24550 @node GNAT IO_Aux g-io_aux ads,GNAT Lock_Files g-locfil ads,GNAT IO g-io ads,The GNAT Library
24551 @anchor{gnat_rm/the_gnat_library id87}@anchor{37e}@anchor{gnat_rm/the_gnat_library gnat-io-aux-g-io-aux-ads}@anchor{37f}
24552 @section @code{GNAT.IO_Aux} (@code{g-io_aux.ads})
24555 @geindex GNAT.IO_Aux (g-io_aux.ads)
24559 @geindex Input/Output facilities
24561 Provides some auxiliary functions for use with Text_IO, including a test
24562 for whether a file exists, and functions for reading a line of text.
24564 @node GNAT Lock_Files g-locfil ads,GNAT MBBS_Discrete_Random g-mbdira ads,GNAT IO_Aux g-io_aux ads,The GNAT Library
24565 @anchor{gnat_rm/the_gnat_library id88}@anchor{380}@anchor{gnat_rm/the_gnat_library gnat-lock-files-g-locfil-ads}@anchor{381}
24566 @section @code{GNAT.Lock_Files} (@code{g-locfil.ads})
24569 @geindex GNAT.Lock_Files (g-locfil.ads)
24571 @geindex File locking
24573 @geindex Locking using files
24575 Provides a general interface for using files as locks. Can be used for
24576 providing program level synchronization.
24578 @node GNAT MBBS_Discrete_Random g-mbdira ads,GNAT MBBS_Float_Random g-mbflra ads,GNAT Lock_Files g-locfil ads,The GNAT Library
24579 @anchor{gnat_rm/the_gnat_library id89}@anchor{382}@anchor{gnat_rm/the_gnat_library gnat-mbbs-discrete-random-g-mbdira-ads}@anchor{383}
24580 @section @code{GNAT.MBBS_Discrete_Random} (@code{g-mbdira.ads})
24583 @geindex GNAT.MBBS_Discrete_Random (g-mbdira.ads)
24585 @geindex Random number generation
24587 The original implementation of @code{Ada.Numerics.Discrete_Random}. Uses
24588 a modified version of the Blum-Blum-Shub generator.
24590 @node GNAT MBBS_Float_Random g-mbflra ads,GNAT MD5 g-md5 ads,GNAT MBBS_Discrete_Random g-mbdira ads,The GNAT Library
24591 @anchor{gnat_rm/the_gnat_library id90}@anchor{384}@anchor{gnat_rm/the_gnat_library gnat-mbbs-float-random-g-mbflra-ads}@anchor{385}
24592 @section @code{GNAT.MBBS_Float_Random} (@code{g-mbflra.ads})
24595 @geindex GNAT.MBBS_Float_Random (g-mbflra.ads)
24597 @geindex Random number generation
24599 The original implementation of @code{Ada.Numerics.Float_Random}. Uses
24600 a modified version of the Blum-Blum-Shub generator.
24602 @node GNAT MD5 g-md5 ads,GNAT Memory_Dump g-memdum ads,GNAT MBBS_Float_Random g-mbflra ads,The GNAT Library
24603 @anchor{gnat_rm/the_gnat_library id91}@anchor{386}@anchor{gnat_rm/the_gnat_library gnat-md5-g-md5-ads}@anchor{387}
24604 @section @code{GNAT.MD5} (@code{g-md5.ads})
24607 @geindex GNAT.MD5 (g-md5.ads)
24609 @geindex Message Digest MD5
24611 Implements the MD5 Message-Digest Algorithm as described in RFC 1321, and
24612 the HMAC-MD5 message authentication function as described in RFC 2104 and
24615 @node GNAT Memory_Dump g-memdum ads,GNAT Most_Recent_Exception g-moreex ads,GNAT MD5 g-md5 ads,The GNAT Library
24616 @anchor{gnat_rm/the_gnat_library id92}@anchor{388}@anchor{gnat_rm/the_gnat_library gnat-memory-dump-g-memdum-ads}@anchor{389}
24617 @section @code{GNAT.Memory_Dump} (@code{g-memdum.ads})
24620 @geindex GNAT.Memory_Dump (g-memdum.ads)
24622 @geindex Dump Memory
24624 Provides a convenient routine for dumping raw memory to either the
24625 standard output or standard error files. Uses GNAT.IO for actual
24628 @node GNAT Most_Recent_Exception g-moreex ads,GNAT OS_Lib g-os_lib ads,GNAT Memory_Dump g-memdum ads,The GNAT Library
24629 @anchor{gnat_rm/the_gnat_library gnat-most-recent-exception-g-moreex-ads}@anchor{38a}@anchor{gnat_rm/the_gnat_library id93}@anchor{38b}
24630 @section @code{GNAT.Most_Recent_Exception} (@code{g-moreex.ads})
24633 @geindex GNAT.Most_Recent_Exception (g-moreex.ads)
24636 @geindex obtaining most recent
24638 Provides access to the most recently raised exception. Can be used for
24639 various logging purposes, including duplicating functionality of some
24640 Ada 83 implementation dependent extensions.
24642 @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
24643 @anchor{gnat_rm/the_gnat_library gnat-os-lib-g-os-lib-ads}@anchor{38c}@anchor{gnat_rm/the_gnat_library id94}@anchor{38d}
24644 @section @code{GNAT.OS_Lib} (@code{g-os_lib.ads})
24647 @geindex GNAT.OS_Lib (g-os_lib.ads)
24649 @geindex Operating System interface
24651 @geindex Spawn capability
24653 Provides a range of target independent operating system interface functions,
24654 including time/date management, file operations, subprocess management,
24655 including a portable spawn procedure, and access to environment variables
24656 and error return codes.
24658 @node GNAT Perfect_Hash_Generators g-pehage ads,GNAT Random_Numbers g-rannum ads,GNAT OS_Lib g-os_lib ads,The GNAT Library
24659 @anchor{gnat_rm/the_gnat_library gnat-perfect-hash-generators-g-pehage-ads}@anchor{38e}@anchor{gnat_rm/the_gnat_library id95}@anchor{38f}
24660 @section @code{GNAT.Perfect_Hash_Generators} (@code{g-pehage.ads})
24663 @geindex GNAT.Perfect_Hash_Generators (g-pehage.ads)
24665 @geindex Hash functions
24667 Provides a generator of static minimal perfect hash functions. No
24668 collisions occur and each item can be retrieved from the table in one
24669 probe (perfect property). The hash table size corresponds to the exact
24670 size of the key set and no larger (minimal property). The key set has to
24671 be know in advance (static property). The hash functions are also order
24672 preserving. If w2 is inserted after w1 in the generator, their
24673 hashcode are in the same order. These hashing functions are very
24674 convenient for use with realtime applications.
24676 @node GNAT Random_Numbers g-rannum ads,GNAT Regexp g-regexp ads,GNAT Perfect_Hash_Generators g-pehage ads,The GNAT Library
24677 @anchor{gnat_rm/the_gnat_library gnat-random-numbers-g-rannum-ads}@anchor{390}@anchor{gnat_rm/the_gnat_library id96}@anchor{391}
24678 @section @code{GNAT.Random_Numbers} (@code{g-rannum.ads})
24681 @geindex GNAT.Random_Numbers (g-rannum.ads)
24683 @geindex Random number generation
24685 Provides random number capabilities which extend those available in the
24686 standard Ada library and are more convenient to use.
24688 @node GNAT Regexp g-regexp ads,GNAT Registry g-regist ads,GNAT Random_Numbers g-rannum ads,The GNAT Library
24689 @anchor{gnat_rm/the_gnat_library gnat-regexp-g-regexp-ads}@anchor{259}@anchor{gnat_rm/the_gnat_library id97}@anchor{392}
24690 @section @code{GNAT.Regexp} (@code{g-regexp.ads})
24693 @geindex GNAT.Regexp (g-regexp.ads)
24695 @geindex Regular expressions
24697 @geindex Pattern matching
24699 A simple implementation of regular expressions, using a subset of regular
24700 expression syntax copied from familiar Unix style utilities. This is the
24701 simplest of the three pattern matching packages provided, and is particularly
24702 suitable for 'file globbing' applications.
24704 @node GNAT Registry g-regist ads,GNAT Regpat g-regpat ads,GNAT Regexp g-regexp ads,The GNAT Library
24705 @anchor{gnat_rm/the_gnat_library id98}@anchor{393}@anchor{gnat_rm/the_gnat_library gnat-registry-g-regist-ads}@anchor{394}
24706 @section @code{GNAT.Registry} (@code{g-regist.ads})
24709 @geindex GNAT.Registry (g-regist.ads)
24711 @geindex Windows Registry
24713 This is a high level binding to the Windows registry. It is possible to
24714 do simple things like reading a key value, creating a new key. For full
24715 registry API, but at a lower level of abstraction, refer to the Win32.Winreg
24716 package provided with the Win32Ada binding
24718 @node GNAT Regpat g-regpat ads,GNAT Rewrite_Data g-rewdat ads,GNAT Registry g-regist ads,The GNAT Library
24719 @anchor{gnat_rm/the_gnat_library id99}@anchor{395}@anchor{gnat_rm/the_gnat_library gnat-regpat-g-regpat-ads}@anchor{396}
24720 @section @code{GNAT.Regpat} (@code{g-regpat.ads})
24723 @geindex GNAT.Regpat (g-regpat.ads)
24725 @geindex Regular expressions
24727 @geindex Pattern matching
24729 A complete implementation of Unix-style regular expression matching, copied
24730 from the original V7 style regular expression library written in C by
24731 Henry Spencer (and binary compatible with this C library).
24733 @node GNAT Rewrite_Data g-rewdat ads,GNAT Secondary_Stack_Info g-sestin ads,GNAT Regpat g-regpat ads,The GNAT Library
24734 @anchor{gnat_rm/the_gnat_library id100}@anchor{397}@anchor{gnat_rm/the_gnat_library gnat-rewrite-data-g-rewdat-ads}@anchor{398}
24735 @section @code{GNAT.Rewrite_Data} (@code{g-rewdat.ads})
24738 @geindex GNAT.Rewrite_Data (g-rewdat.ads)
24740 @geindex Rewrite data
24742 A unit to rewrite on-the-fly string occurrences in a stream of
24743 data. The implementation has a very minimal memory footprint as the
24744 full content to be processed is not loaded into memory all at once. This makes
24745 this interface usable for large files or socket streams.
24747 @node GNAT Secondary_Stack_Info g-sestin ads,GNAT Semaphores g-semaph ads,GNAT Rewrite_Data g-rewdat ads,The GNAT Library
24748 @anchor{gnat_rm/the_gnat_library id101}@anchor{399}@anchor{gnat_rm/the_gnat_library gnat-secondary-stack-info-g-sestin-ads}@anchor{39a}
24749 @section @code{GNAT.Secondary_Stack_Info} (@code{g-sestin.ads})
24752 @geindex GNAT.Secondary_Stack_Info (g-sestin.ads)
24754 @geindex Secondary Stack Info
24756 Provide the capability to query the high water mark of the current task's
24759 @node GNAT Semaphores g-semaph ads,GNAT Serial_Communications g-sercom ads,GNAT Secondary_Stack_Info g-sestin ads,The GNAT Library
24760 @anchor{gnat_rm/the_gnat_library id102}@anchor{39b}@anchor{gnat_rm/the_gnat_library gnat-semaphores-g-semaph-ads}@anchor{39c}
24761 @section @code{GNAT.Semaphores} (@code{g-semaph.ads})
24764 @geindex GNAT.Semaphores (g-semaph.ads)
24766 @geindex Semaphores
24768 Provides classic counting and binary semaphores using protected types.
24770 @node GNAT Serial_Communications g-sercom ads,GNAT SHA1 g-sha1 ads,GNAT Semaphores g-semaph ads,The GNAT Library
24771 @anchor{gnat_rm/the_gnat_library gnat-serial-communications-g-sercom-ads}@anchor{39d}@anchor{gnat_rm/the_gnat_library id103}@anchor{39e}
24772 @section @code{GNAT.Serial_Communications} (@code{g-sercom.ads})
24775 @geindex GNAT.Serial_Communications (g-sercom.ads)
24777 @geindex Serial_Communications
24779 Provides a simple interface to send and receive data over a serial
24780 port. This is only supported on GNU/Linux and Windows.
24782 @node GNAT SHA1 g-sha1 ads,GNAT SHA224 g-sha224 ads,GNAT Serial_Communications g-sercom ads,The GNAT Library
24783 @anchor{gnat_rm/the_gnat_library gnat-sha1-g-sha1-ads}@anchor{39f}@anchor{gnat_rm/the_gnat_library id104}@anchor{3a0}
24784 @section @code{GNAT.SHA1} (@code{g-sha1.ads})
24787 @geindex GNAT.SHA1 (g-sha1.ads)
24789 @geindex Secure Hash Algorithm SHA-1
24791 Implements the SHA-1 Secure Hash Algorithm as described in FIPS PUB 180-3
24792 and RFC 3174, and the HMAC-SHA1 message authentication function as described
24793 in RFC 2104 and FIPS PUB 198.
24795 @node GNAT SHA224 g-sha224 ads,GNAT SHA256 g-sha256 ads,GNAT SHA1 g-sha1 ads,The GNAT Library
24796 @anchor{gnat_rm/the_gnat_library gnat-sha224-g-sha224-ads}@anchor{3a1}@anchor{gnat_rm/the_gnat_library id105}@anchor{3a2}
24797 @section @code{GNAT.SHA224} (@code{g-sha224.ads})
24800 @geindex GNAT.SHA224 (g-sha224.ads)
24802 @geindex Secure Hash Algorithm SHA-224
24804 Implements the SHA-224 Secure Hash Algorithm as described in FIPS PUB 180-3,
24805 and the HMAC-SHA224 message authentication function as described
24806 in RFC 2104 and FIPS PUB 198.
24808 @node GNAT SHA256 g-sha256 ads,GNAT SHA384 g-sha384 ads,GNAT SHA224 g-sha224 ads,The GNAT Library
24809 @anchor{gnat_rm/the_gnat_library gnat-sha256-g-sha256-ads}@anchor{3a3}@anchor{gnat_rm/the_gnat_library id106}@anchor{3a4}
24810 @section @code{GNAT.SHA256} (@code{g-sha256.ads})
24813 @geindex GNAT.SHA256 (g-sha256.ads)
24815 @geindex Secure Hash Algorithm SHA-256
24817 Implements the SHA-256 Secure Hash Algorithm as described in FIPS PUB 180-3,
24818 and the HMAC-SHA256 message authentication function as described
24819 in RFC 2104 and FIPS PUB 198.
24821 @node GNAT SHA384 g-sha384 ads,GNAT SHA512 g-sha512 ads,GNAT SHA256 g-sha256 ads,The GNAT Library
24822 @anchor{gnat_rm/the_gnat_library gnat-sha384-g-sha384-ads}@anchor{3a5}@anchor{gnat_rm/the_gnat_library id107}@anchor{3a6}
24823 @section @code{GNAT.SHA384} (@code{g-sha384.ads})
24826 @geindex GNAT.SHA384 (g-sha384.ads)
24828 @geindex Secure Hash Algorithm SHA-384
24830 Implements the SHA-384 Secure Hash Algorithm as described in FIPS PUB 180-3,
24831 and the HMAC-SHA384 message authentication function as described
24832 in RFC 2104 and FIPS PUB 198.
24834 @node GNAT SHA512 g-sha512 ads,GNAT Signals g-signal ads,GNAT SHA384 g-sha384 ads,The GNAT Library
24835 @anchor{gnat_rm/the_gnat_library id108}@anchor{3a7}@anchor{gnat_rm/the_gnat_library gnat-sha512-g-sha512-ads}@anchor{3a8}
24836 @section @code{GNAT.SHA512} (@code{g-sha512.ads})
24839 @geindex GNAT.SHA512 (g-sha512.ads)
24841 @geindex Secure Hash Algorithm SHA-512
24843 Implements the SHA-512 Secure Hash Algorithm as described in FIPS PUB 180-3,
24844 and the HMAC-SHA512 message authentication function as described
24845 in RFC 2104 and FIPS PUB 198.
24847 @node GNAT Signals g-signal ads,GNAT Sockets g-socket ads,GNAT SHA512 g-sha512 ads,The GNAT Library
24848 @anchor{gnat_rm/the_gnat_library id109}@anchor{3a9}@anchor{gnat_rm/the_gnat_library gnat-signals-g-signal-ads}@anchor{3aa}
24849 @section @code{GNAT.Signals} (@code{g-signal.ads})
24852 @geindex GNAT.Signals (g-signal.ads)
24856 Provides the ability to manipulate the blocked status of signals on supported
24859 @node GNAT Sockets g-socket ads,GNAT Source_Info g-souinf ads,GNAT Signals g-signal ads,The GNAT Library
24860 @anchor{gnat_rm/the_gnat_library gnat-sockets-g-socket-ads}@anchor{3ab}@anchor{gnat_rm/the_gnat_library id110}@anchor{3ac}
24861 @section @code{GNAT.Sockets} (@code{g-socket.ads})
24864 @geindex GNAT.Sockets (g-socket.ads)
24868 A high level and portable interface to develop sockets based applications.
24869 This package is based on the sockets thin binding found in
24870 @code{GNAT.Sockets.Thin}. Currently @code{GNAT.Sockets} is implemented
24871 on all native GNAT ports and on VxWorks cross prots. It is not implemented for
24872 the LynxOS cross port.
24874 @node GNAT Source_Info g-souinf ads,GNAT Spelling_Checker g-speche ads,GNAT Sockets g-socket ads,The GNAT Library
24875 @anchor{gnat_rm/the_gnat_library gnat-source-info-g-souinf-ads}@anchor{3ad}@anchor{gnat_rm/the_gnat_library id111}@anchor{3ae}
24876 @section @code{GNAT.Source_Info} (@code{g-souinf.ads})
24879 @geindex GNAT.Source_Info (g-souinf.ads)
24881 @geindex Source Information
24883 Provides subprograms that give access to source code information known at
24884 compile time, such as the current file name and line number. Also provides
24885 subprograms yielding the date and time of the current compilation (like the
24886 C macros @code{__DATE__} and @code{__TIME__})
24888 @node GNAT Spelling_Checker g-speche ads,GNAT Spelling_Checker_Generic g-spchge ads,GNAT Source_Info g-souinf ads,The GNAT Library
24889 @anchor{gnat_rm/the_gnat_library id112}@anchor{3af}@anchor{gnat_rm/the_gnat_library gnat-spelling-checker-g-speche-ads}@anchor{3b0}
24890 @section @code{GNAT.Spelling_Checker} (@code{g-speche.ads})
24893 @geindex GNAT.Spelling_Checker (g-speche.ads)
24895 @geindex Spell checking
24897 Provides a function for determining whether one string is a plausible
24898 near misspelling of another string.
24900 @node GNAT Spelling_Checker_Generic g-spchge ads,GNAT Spitbol Patterns g-spipat ads,GNAT Spelling_Checker g-speche ads,The GNAT Library
24901 @anchor{gnat_rm/the_gnat_library gnat-spelling-checker-generic-g-spchge-ads}@anchor{3b1}@anchor{gnat_rm/the_gnat_library id113}@anchor{3b2}
24902 @section @code{GNAT.Spelling_Checker_Generic} (@code{g-spchge.ads})
24905 @geindex GNAT.Spelling_Checker_Generic (g-spchge.ads)
24907 @geindex Spell checking
24909 Provides a generic function that can be instantiated with a string type for
24910 determining whether one string is a plausible near misspelling of another
24913 @node GNAT Spitbol Patterns g-spipat ads,GNAT Spitbol g-spitbo ads,GNAT Spelling_Checker_Generic g-spchge ads,The GNAT Library
24914 @anchor{gnat_rm/the_gnat_library gnat-spitbol-patterns-g-spipat-ads}@anchor{3b3}@anchor{gnat_rm/the_gnat_library id114}@anchor{3b4}
24915 @section @code{GNAT.Spitbol.Patterns} (@code{g-spipat.ads})
24918 @geindex GNAT.Spitbol.Patterns (g-spipat.ads)
24920 @geindex SPITBOL pattern matching
24922 @geindex Pattern matching
24924 A complete implementation of SNOBOL4 style pattern matching. This is the
24925 most elaborate of the pattern matching packages provided. It fully duplicates
24926 the SNOBOL4 dynamic pattern construction and matching capabilities, using the
24927 efficient algorithm developed by Robert Dewar for the SPITBOL system.
24929 @node GNAT Spitbol g-spitbo ads,GNAT Spitbol Table_Boolean g-sptabo ads,GNAT Spitbol Patterns g-spipat ads,The GNAT Library
24930 @anchor{gnat_rm/the_gnat_library gnat-spitbol-g-spitbo-ads}@anchor{3b5}@anchor{gnat_rm/the_gnat_library id115}@anchor{3b6}
24931 @section @code{GNAT.Spitbol} (@code{g-spitbo.ads})
24934 @geindex GNAT.Spitbol (g-spitbo.ads)
24936 @geindex SPITBOL interface
24938 The top level package of the collection of SPITBOL-style functionality, this
24939 package provides basic SNOBOL4 string manipulation functions, such as
24940 Pad, Reverse, Trim, Substr capability, as well as a generic table function
24941 useful for constructing arbitrary mappings from strings in the style of
24942 the SNOBOL4 TABLE function.
24944 @node GNAT Spitbol Table_Boolean g-sptabo ads,GNAT Spitbol Table_Integer g-sptain ads,GNAT Spitbol g-spitbo ads,The GNAT Library
24945 @anchor{gnat_rm/the_gnat_library id116}@anchor{3b7}@anchor{gnat_rm/the_gnat_library gnat-spitbol-table-boolean-g-sptabo-ads}@anchor{3b8}
24946 @section @code{GNAT.Spitbol.Table_Boolean} (@code{g-sptabo.ads})
24949 @geindex GNAT.Spitbol.Table_Boolean (g-sptabo.ads)
24951 @geindex Sets of strings
24953 @geindex SPITBOL Tables
24955 A library level of instantiation of @code{GNAT.Spitbol.Patterns.Table}
24956 for type @code{Standard.Boolean}, giving an implementation of sets of
24959 @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
24960 @anchor{gnat_rm/the_gnat_library gnat-spitbol-table-integer-g-sptain-ads}@anchor{3b9}@anchor{gnat_rm/the_gnat_library id117}@anchor{3ba}
24961 @section @code{GNAT.Spitbol.Table_Integer} (@code{g-sptain.ads})
24964 @geindex GNAT.Spitbol.Table_Integer (g-sptain.ads)
24966 @geindex Integer maps
24970 @geindex SPITBOL Tables
24972 A library level of instantiation of @code{GNAT.Spitbol.Patterns.Table}
24973 for type @code{Standard.Integer}, giving an implementation of maps
24974 from string to integer values.
24976 @node GNAT Spitbol Table_VString g-sptavs ads,GNAT SSE g-sse ads,GNAT Spitbol Table_Integer g-sptain ads,The GNAT Library
24977 @anchor{gnat_rm/the_gnat_library id118}@anchor{3bb}@anchor{gnat_rm/the_gnat_library gnat-spitbol-table-vstring-g-sptavs-ads}@anchor{3bc}
24978 @section @code{GNAT.Spitbol.Table_VString} (@code{g-sptavs.ads})
24981 @geindex GNAT.Spitbol.Table_VString (g-sptavs.ads)
24983 @geindex String maps
24987 @geindex SPITBOL Tables
24989 A library level of instantiation of @code{GNAT.Spitbol.Patterns.Table} for
24990 a variable length string type, giving an implementation of general
24991 maps from strings to strings.
24993 @node GNAT SSE g-sse ads,GNAT SSE Vector_Types g-ssvety ads,GNAT Spitbol Table_VString g-sptavs ads,The GNAT Library
24994 @anchor{gnat_rm/the_gnat_library id119}@anchor{3bd}@anchor{gnat_rm/the_gnat_library gnat-sse-g-sse-ads}@anchor{3be}
24995 @section @code{GNAT.SSE} (@code{g-sse.ads})
24998 @geindex GNAT.SSE (g-sse.ads)
25000 Root of a set of units aimed at offering Ada bindings to a subset of
25001 the Intel(r) Streaming SIMD Extensions with GNAT on the x86 family of
25002 targets. It exposes vector component types together with a general
25003 introduction to the binding contents and use.
25005 @node GNAT SSE Vector_Types g-ssvety ads,GNAT String_Hash g-strhas ads,GNAT SSE g-sse ads,The GNAT Library
25006 @anchor{gnat_rm/the_gnat_library gnat-sse-vector-types-g-ssvety-ads}@anchor{3bf}@anchor{gnat_rm/the_gnat_library id120}@anchor{3c0}
25007 @section @code{GNAT.SSE.Vector_Types} (@code{g-ssvety.ads})
25010 @geindex GNAT.SSE.Vector_Types (g-ssvety.ads)
25012 SSE vector types for use with SSE related intrinsics.
25014 @node GNAT String_Hash g-strhas ads,GNAT Strings g-string ads,GNAT SSE Vector_Types g-ssvety ads,The GNAT Library
25015 @anchor{gnat_rm/the_gnat_library gnat-string-hash-g-strhas-ads}@anchor{3c1}@anchor{gnat_rm/the_gnat_library id121}@anchor{3c2}
25016 @section @code{GNAT.String_Hash} (@code{g-strhas.ads})
25019 @geindex GNAT.String_Hash (g-strhas.ads)
25021 @geindex Hash functions
25023 Provides a generic hash function working on arrays of scalars. Both the scalar
25024 type and the hash result type are parameters.
25026 @node GNAT Strings g-string ads,GNAT String_Split g-strspl ads,GNAT String_Hash g-strhas ads,The GNAT Library
25027 @anchor{gnat_rm/the_gnat_library gnat-strings-g-string-ads}@anchor{3c3}@anchor{gnat_rm/the_gnat_library id122}@anchor{3c4}
25028 @section @code{GNAT.Strings} (@code{g-string.ads})
25031 @geindex GNAT.Strings (g-string.ads)
25033 Common String access types and related subprograms. Basically it
25034 defines a string access and an array of string access types.
25036 @node GNAT String_Split g-strspl ads,GNAT Table g-table ads,GNAT Strings g-string ads,The GNAT Library
25037 @anchor{gnat_rm/the_gnat_library gnat-string-split-g-strspl-ads}@anchor{3c5}@anchor{gnat_rm/the_gnat_library id123}@anchor{3c6}
25038 @section @code{GNAT.String_Split} (@code{g-strspl.ads})
25041 @geindex GNAT.String_Split (g-strspl.ads)
25043 @geindex String splitter
25045 Useful string manipulation routines: given a set of separators, split
25046 a string wherever the separators appear, and provide direct access
25047 to the resulting slices. This package is instantiated from
25048 @code{GNAT.Array_Split}.
25050 @node GNAT Table g-table ads,GNAT Task_Lock g-tasloc ads,GNAT String_Split g-strspl ads,The GNAT Library
25051 @anchor{gnat_rm/the_gnat_library id124}@anchor{3c7}@anchor{gnat_rm/the_gnat_library gnat-table-g-table-ads}@anchor{3c8}
25052 @section @code{GNAT.Table} (@code{g-table.ads})
25055 @geindex GNAT.Table (g-table.ads)
25057 @geindex Table implementation
25060 @geindex extendable
25062 A generic package providing a single dimension array abstraction where the
25063 length of the array can be dynamically modified.
25065 This package provides a facility similar to that of @code{GNAT.Dynamic_Tables},
25066 except that this package declares a single instance of the table type,
25067 while an instantiation of @code{GNAT.Dynamic_Tables} creates a type that can be
25068 used to define dynamic instances of the table.
25070 @node GNAT Task_Lock g-tasloc ads,GNAT Time_Stamp g-timsta ads,GNAT Table g-table ads,The GNAT Library
25071 @anchor{gnat_rm/the_gnat_library id125}@anchor{3c9}@anchor{gnat_rm/the_gnat_library gnat-task-lock-g-tasloc-ads}@anchor{3ca}
25072 @section @code{GNAT.Task_Lock} (@code{g-tasloc.ads})
25075 @geindex GNAT.Task_Lock (g-tasloc.ads)
25077 @geindex Task synchronization
25079 @geindex Task locking
25083 A very simple facility for locking and unlocking sections of code using a
25084 single global task lock. Appropriate for use in situations where contention
25085 between tasks is very rarely expected.
25087 @node GNAT Time_Stamp g-timsta ads,GNAT Threads g-thread ads,GNAT Task_Lock g-tasloc ads,The GNAT Library
25088 @anchor{gnat_rm/the_gnat_library id126}@anchor{3cb}@anchor{gnat_rm/the_gnat_library gnat-time-stamp-g-timsta-ads}@anchor{3cc}
25089 @section @code{GNAT.Time_Stamp} (@code{g-timsta.ads})
25092 @geindex GNAT.Time_Stamp (g-timsta.ads)
25094 @geindex Time stamp
25096 @geindex Current time
25098 Provides a simple function that returns a string YYYY-MM-DD HH:MM:SS.SS that
25099 represents the current date and time in ISO 8601 format. This is a very simple
25100 routine with minimal code and there are no dependencies on any other unit.
25102 @node GNAT Threads g-thread ads,GNAT Traceback g-traceb ads,GNAT Time_Stamp g-timsta ads,The GNAT Library
25103 @anchor{gnat_rm/the_gnat_library id127}@anchor{3cd}@anchor{gnat_rm/the_gnat_library gnat-threads-g-thread-ads}@anchor{3ce}
25104 @section @code{GNAT.Threads} (@code{g-thread.ads})
25107 @geindex GNAT.Threads (g-thread.ads)
25109 @geindex Foreign threads
25114 Provides facilities for dealing with foreign threads which need to be known
25115 by the GNAT run-time system. Consult the documentation of this package for
25116 further details if your program has threads that are created by a non-Ada
25117 environment which then accesses Ada code.
25119 @node GNAT Traceback g-traceb ads,GNAT Traceback Symbolic g-trasym ads,GNAT Threads g-thread ads,The GNAT Library
25120 @anchor{gnat_rm/the_gnat_library id128}@anchor{3cf}@anchor{gnat_rm/the_gnat_library gnat-traceback-g-traceb-ads}@anchor{3d0}
25121 @section @code{GNAT.Traceback} (@code{g-traceb.ads})
25124 @geindex GNAT.Traceback (g-traceb.ads)
25126 @geindex Trace back facilities
25128 Provides a facility for obtaining non-symbolic traceback information, useful
25129 in various debugging situations.
25131 @node GNAT Traceback Symbolic g-trasym ads,GNAT UTF_32 g-table ads,GNAT Traceback g-traceb ads,The GNAT Library
25132 @anchor{gnat_rm/the_gnat_library gnat-traceback-symbolic-g-trasym-ads}@anchor{3d1}@anchor{gnat_rm/the_gnat_library id129}@anchor{3d2}
25133 @section @code{GNAT.Traceback.Symbolic} (@code{g-trasym.ads})
25136 @geindex GNAT.Traceback.Symbolic (g-trasym.ads)
25138 @geindex Trace back facilities
25140 @node GNAT UTF_32 g-table ads,GNAT Wide_Spelling_Checker g-u3spch ads,GNAT Traceback Symbolic g-trasym ads,The GNAT Library
25141 @anchor{gnat_rm/the_gnat_library id130}@anchor{3d3}@anchor{gnat_rm/the_gnat_library gnat-utf-32-g-table-ads}@anchor{3d4}
25142 @section @code{GNAT.UTF_32} (@code{g-table.ads})
25145 @geindex GNAT.UTF_32 (g-table.ads)
25147 @geindex Wide character codes
25149 This is a package intended to be used in conjunction with the
25150 @code{Wide_Character} type in Ada 95 and the
25151 @code{Wide_Wide_Character} type in Ada 2005 (available
25152 in @code{GNAT} in Ada 2005 mode). This package contains
25153 Unicode categorization routines, as well as lexical
25154 categorization routines corresponding to the Ada 2005
25155 lexical rules for identifiers and strings, and also a
25156 lower case to upper case fold routine corresponding to
25157 the Ada 2005 rules for identifier equivalence.
25159 @node GNAT Wide_Spelling_Checker g-u3spch ads,GNAT Wide_Spelling_Checker g-wispch ads,GNAT UTF_32 g-table ads,The GNAT Library
25160 @anchor{gnat_rm/the_gnat_library gnat-wide-spelling-checker-g-u3spch-ads}@anchor{3d5}@anchor{gnat_rm/the_gnat_library id131}@anchor{3d6}
25161 @section @code{GNAT.Wide_Spelling_Checker} (@code{g-u3spch.ads})
25164 @geindex GNAT.Wide_Spelling_Checker (g-u3spch.ads)
25166 @geindex Spell checking
25168 Provides a function for determining whether one wide wide string is a plausible
25169 near misspelling of another wide wide string, where the strings are represented
25170 using the UTF_32_String type defined in System.Wch_Cnv.
25172 @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
25173 @anchor{gnat_rm/the_gnat_library gnat-wide-spelling-checker-g-wispch-ads}@anchor{3d7}@anchor{gnat_rm/the_gnat_library id132}@anchor{3d8}
25174 @section @code{GNAT.Wide_Spelling_Checker} (@code{g-wispch.ads})
25177 @geindex GNAT.Wide_Spelling_Checker (g-wispch.ads)
25179 @geindex Spell checking
25181 Provides a function for determining whether one wide string is a plausible
25182 near misspelling of another wide string.
25184 @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
25185 @anchor{gnat_rm/the_gnat_library id133}@anchor{3d9}@anchor{gnat_rm/the_gnat_library gnat-wide-string-split-g-wistsp-ads}@anchor{3da}
25186 @section @code{GNAT.Wide_String_Split} (@code{g-wistsp.ads})
25189 @geindex GNAT.Wide_String_Split (g-wistsp.ads)
25191 @geindex Wide_String splitter
25193 Useful wide string manipulation routines: given a set of separators, split
25194 a wide string wherever the separators appear, and provide direct access
25195 to the resulting slices. This package is instantiated from
25196 @code{GNAT.Array_Split}.
25198 @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
25199 @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}
25200 @section @code{GNAT.Wide_Wide_Spelling_Checker} (@code{g-zspche.ads})
25203 @geindex GNAT.Wide_Wide_Spelling_Checker (g-zspche.ads)
25205 @geindex Spell checking
25207 Provides a function for determining whether one wide wide string is a plausible
25208 near misspelling of another wide wide string.
25210 @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
25211 @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}
25212 @section @code{GNAT.Wide_Wide_String_Split} (@code{g-zistsp.ads})
25215 @geindex GNAT.Wide_Wide_String_Split (g-zistsp.ads)
25217 @geindex Wide_Wide_String splitter
25219 Useful wide wide string manipulation routines: given a set of separators, split
25220 a wide wide string wherever the separators appear, and provide direct access
25221 to the resulting slices. This package is instantiated from
25222 @code{GNAT.Array_Split}.
25224 @node Interfaces C Extensions i-cexten ads,Interfaces C Streams i-cstrea ads,GNAT Wide_Wide_String_Split g-zistsp ads,The GNAT Library
25225 @anchor{gnat_rm/the_gnat_library interfaces-c-extensions-i-cexten-ads}@anchor{3df}@anchor{gnat_rm/the_gnat_library id136}@anchor{3e0}
25226 @section @code{Interfaces.C.Extensions} (@code{i-cexten.ads})
25229 @geindex Interfaces.C.Extensions (i-cexten.ads)
25231 This package contains additional C-related definitions, intended
25232 for use with either manually or automatically generated bindings
25235 @node Interfaces C Streams i-cstrea ads,Interfaces Packed_Decimal i-pacdec ads,Interfaces C Extensions i-cexten ads,The GNAT Library
25236 @anchor{gnat_rm/the_gnat_library interfaces-c-streams-i-cstrea-ads}@anchor{3e1}@anchor{gnat_rm/the_gnat_library id137}@anchor{3e2}
25237 @section @code{Interfaces.C.Streams} (@code{i-cstrea.ads})
25240 @geindex Interfaces.C.Streams (i-cstrea.ads)
25243 @geindex interfacing
25245 This package is a binding for the most commonly used operations
25248 @node Interfaces Packed_Decimal i-pacdec ads,Interfaces VxWorks i-vxwork ads,Interfaces C Streams i-cstrea ads,The GNAT Library
25249 @anchor{gnat_rm/the_gnat_library id138}@anchor{3e3}@anchor{gnat_rm/the_gnat_library interfaces-packed-decimal-i-pacdec-ads}@anchor{3e4}
25250 @section @code{Interfaces.Packed_Decimal} (@code{i-pacdec.ads})
25253 @geindex Interfaces.Packed_Decimal (i-pacdec.ads)
25255 @geindex IBM Packed Format
25257 @geindex Packed Decimal
25259 This package provides a set of routines for conversions to and
25260 from a packed decimal format compatible with that used on IBM
25263 @node Interfaces VxWorks i-vxwork ads,Interfaces VxWorks Int_Connection i-vxinco ads,Interfaces Packed_Decimal i-pacdec ads,The GNAT Library
25264 @anchor{gnat_rm/the_gnat_library id139}@anchor{3e5}@anchor{gnat_rm/the_gnat_library interfaces-vxworks-i-vxwork-ads}@anchor{3e6}
25265 @section @code{Interfaces.VxWorks} (@code{i-vxwork.ads})
25268 @geindex Interfaces.VxWorks (i-vxwork.ads)
25270 @geindex Interfacing to VxWorks
25273 @geindex interfacing
25275 This package provides a limited binding to the VxWorks API.
25276 In particular, it interfaces with the
25277 VxWorks hardware interrupt facilities.
25279 @node Interfaces VxWorks Int_Connection i-vxinco ads,Interfaces VxWorks IO i-vxwoio ads,Interfaces VxWorks i-vxwork ads,The GNAT Library
25280 @anchor{gnat_rm/the_gnat_library interfaces-vxworks-int-connection-i-vxinco-ads}@anchor{3e7}@anchor{gnat_rm/the_gnat_library id140}@anchor{3e8}
25281 @section @code{Interfaces.VxWorks.Int_Connection} (@code{i-vxinco.ads})
25284 @geindex Interfaces.VxWorks.Int_Connection (i-vxinco.ads)
25286 @geindex Interfacing to VxWorks
25289 @geindex interfacing
25291 This package provides a way for users to replace the use of
25292 intConnect() with a custom routine for installing interrupt
25295 @node Interfaces VxWorks IO i-vxwoio ads,System Address_Image s-addima ads,Interfaces VxWorks Int_Connection i-vxinco ads,The GNAT Library
25296 @anchor{gnat_rm/the_gnat_library interfaces-vxworks-io-i-vxwoio-ads}@anchor{3e9}@anchor{gnat_rm/the_gnat_library id141}@anchor{3ea}
25297 @section @code{Interfaces.VxWorks.IO} (@code{i-vxwoio.ads})
25300 @geindex Interfaces.VxWorks.IO (i-vxwoio.ads)
25302 @geindex Interfacing to VxWorks' I/O
25305 @geindex I/O interfacing
25308 @geindex Get_Immediate
25310 @geindex Get_Immediate
25313 This package provides a binding to the ioctl (IO/Control)
25314 function of VxWorks, defining a set of option values and
25315 function codes. A particular use of this package is
25316 to enable the use of Get_Immediate under VxWorks.
25318 @node System Address_Image s-addima ads,System Assertions s-assert ads,Interfaces VxWorks IO i-vxwoio ads,The GNAT Library
25319 @anchor{gnat_rm/the_gnat_library system-address-image-s-addima-ads}@anchor{3eb}@anchor{gnat_rm/the_gnat_library id142}@anchor{3ec}
25320 @section @code{System.Address_Image} (@code{s-addima.ads})
25323 @geindex System.Address_Image (s-addima.ads)
25325 @geindex Address image
25328 @geindex of an address
25330 This function provides a useful debugging
25331 function that gives an (implementation dependent)
25332 string which identifies an address.
25334 @node System Assertions s-assert ads,System Atomic_Counters s-atocou ads,System Address_Image s-addima ads,The GNAT Library
25335 @anchor{gnat_rm/the_gnat_library system-assertions-s-assert-ads}@anchor{3ed}@anchor{gnat_rm/the_gnat_library id143}@anchor{3ee}
25336 @section @code{System.Assertions} (@code{s-assert.ads})
25339 @geindex System.Assertions (s-assert.ads)
25341 @geindex Assertions
25343 @geindex Assert_Failure
25346 This package provides the declaration of the exception raised
25347 by an run-time assertion failure, as well as the routine that
25348 is used internally to raise this assertion.
25350 @node System Atomic_Counters s-atocou ads,System Memory s-memory ads,System Assertions s-assert ads,The GNAT Library
25351 @anchor{gnat_rm/the_gnat_library id144}@anchor{3ef}@anchor{gnat_rm/the_gnat_library system-atomic-counters-s-atocou-ads}@anchor{3f0}
25352 @section @code{System.Atomic_Counters} (@code{s-atocou.ads})
25355 @geindex System.Atomic_Counters (s-atocou.ads)
25357 This package provides the declaration of an atomic counter type,
25358 together with efficient routines (using hardware
25359 synchronization primitives) for incrementing, decrementing,
25360 and testing of these counters. This package is implemented
25361 on most targets, including all Alpha, ia64, PowerPC, SPARC V9,
25362 x86, and x86_64 platforms.
25364 @node System Memory s-memory ads,System Multiprocessors s-multip ads,System Atomic_Counters s-atocou ads,The GNAT Library
25365 @anchor{gnat_rm/the_gnat_library system-memory-s-memory-ads}@anchor{3f1}@anchor{gnat_rm/the_gnat_library id145}@anchor{3f2}
25366 @section @code{System.Memory} (@code{s-memory.ads})
25369 @geindex System.Memory (s-memory.ads)
25371 @geindex Memory allocation
25373 This package provides the interface to the low level routines used
25374 by the generated code for allocation and freeing storage for the
25375 default storage pool (analogous to the C routines malloc and free.
25376 It also provides a reallocation interface analogous to the C routine
25377 realloc. The body of this unit may be modified to provide alternative
25378 allocation mechanisms for the default pool, and in addition, direct
25379 calls to this unit may be made for low level allocation uses (for
25380 example see the body of @code{GNAT.Tables}).
25382 @node System Multiprocessors s-multip ads,System Multiprocessors Dispatching_Domains s-mudido ads,System Memory s-memory ads,The GNAT Library
25383 @anchor{gnat_rm/the_gnat_library id146}@anchor{3f3}@anchor{gnat_rm/the_gnat_library system-multiprocessors-s-multip-ads}@anchor{3f4}
25384 @section @code{System.Multiprocessors} (@code{s-multip.ads})
25387 @geindex System.Multiprocessors (s-multip.ads)
25389 @geindex Multiprocessor interface
25391 This is an Ada 2012 unit defined in the Ada 2012 Reference Manual, but
25392 in GNAT we also make it available in Ada 95 and Ada 2005 (where it is
25393 technically an implementation-defined addition).
25395 @node System Multiprocessors Dispatching_Domains s-mudido ads,System Partition_Interface s-parint ads,System Multiprocessors s-multip ads,The GNAT Library
25396 @anchor{gnat_rm/the_gnat_library system-multiprocessors-dispatching-domains-s-mudido-ads}@anchor{3f5}@anchor{gnat_rm/the_gnat_library id147}@anchor{3f6}
25397 @section @code{System.Multiprocessors.Dispatching_Domains} (@code{s-mudido.ads})
25400 @geindex System.Multiprocessors.Dispatching_Domains (s-mudido.ads)
25402 @geindex Multiprocessor interface
25404 This is an Ada 2012 unit defined in the Ada 2012 Reference Manual, but
25405 in GNAT we also make it available in Ada 95 and Ada 2005 (where it is
25406 technically an implementation-defined addition).
25408 @node System Partition_Interface s-parint ads,System Pool_Global s-pooglo ads,System Multiprocessors Dispatching_Domains s-mudido ads,The GNAT Library
25409 @anchor{gnat_rm/the_gnat_library id148}@anchor{3f7}@anchor{gnat_rm/the_gnat_library system-partition-interface-s-parint-ads}@anchor{3f8}
25410 @section @code{System.Partition_Interface} (@code{s-parint.ads})
25413 @geindex System.Partition_Interface (s-parint.ads)
25415 @geindex Partition interfacing functions
25417 This package provides facilities for partition interfacing. It
25418 is used primarily in a distribution context when using Annex E
25421 @node System Pool_Global s-pooglo ads,System Pool_Local s-pooloc ads,System Partition_Interface s-parint ads,The GNAT Library
25422 @anchor{gnat_rm/the_gnat_library id149}@anchor{3f9}@anchor{gnat_rm/the_gnat_library system-pool-global-s-pooglo-ads}@anchor{3fa}
25423 @section @code{System.Pool_Global} (@code{s-pooglo.ads})
25426 @geindex System.Pool_Global (s-pooglo.ads)
25428 @geindex Storage pool
25431 @geindex Global storage pool
25433 This package provides a storage pool that is equivalent to the default
25434 storage pool used for access types for which no pool is specifically
25435 declared. It uses malloc/free to allocate/free and does not attempt to
25436 do any automatic reclamation.
25438 @node System Pool_Local s-pooloc ads,System Restrictions s-restri ads,System Pool_Global s-pooglo ads,The GNAT Library
25439 @anchor{gnat_rm/the_gnat_library system-pool-local-s-pooloc-ads}@anchor{3fb}@anchor{gnat_rm/the_gnat_library id150}@anchor{3fc}
25440 @section @code{System.Pool_Local} (@code{s-pooloc.ads})
25443 @geindex System.Pool_Local (s-pooloc.ads)
25445 @geindex Storage pool
25448 @geindex Local storage pool
25450 This package provides a storage pool that is intended for use with locally
25451 defined access types. It uses malloc/free for allocate/free, and maintains
25452 a list of allocated blocks, so that all storage allocated for the pool can
25453 be freed automatically when the pool is finalized.
25455 @node System Restrictions s-restri ads,System Rident s-rident ads,System Pool_Local s-pooloc ads,The GNAT Library
25456 @anchor{gnat_rm/the_gnat_library system-restrictions-s-restri-ads}@anchor{3fd}@anchor{gnat_rm/the_gnat_library id151}@anchor{3fe}
25457 @section @code{System.Restrictions} (@code{s-restri.ads})
25460 @geindex System.Restrictions (s-restri.ads)
25462 @geindex Run-time restrictions access
25464 This package provides facilities for accessing at run time
25465 the status of restrictions specified at compile time for
25466 the partition. Information is available both with regard
25467 to actual restrictions specified, and with regard to
25468 compiler determined information on which restrictions
25469 are violated by one or more packages in the partition.
25471 @node System Rident s-rident ads,System Strings Stream_Ops s-ststop ads,System Restrictions s-restri ads,The GNAT Library
25472 @anchor{gnat_rm/the_gnat_library system-rident-s-rident-ads}@anchor{3ff}@anchor{gnat_rm/the_gnat_library id152}@anchor{400}
25473 @section @code{System.Rident} (@code{s-rident.ads})
25476 @geindex System.Rident (s-rident.ads)
25478 @geindex Restrictions definitions
25480 This package provides definitions of the restrictions
25481 identifiers supported by GNAT, and also the format of
25482 the restrictions provided in package System.Restrictions.
25483 It is not normally necessary to @code{with} this generic package
25484 since the necessary instantiation is included in
25485 package System.Restrictions.
25487 @node System Strings Stream_Ops s-ststop ads,System Unsigned_Types s-unstyp ads,System Rident s-rident ads,The GNAT Library
25488 @anchor{gnat_rm/the_gnat_library id153}@anchor{401}@anchor{gnat_rm/the_gnat_library system-strings-stream-ops-s-ststop-ads}@anchor{402}
25489 @section @code{System.Strings.Stream_Ops} (@code{s-ststop.ads})
25492 @geindex System.Strings.Stream_Ops (s-ststop.ads)
25494 @geindex Stream operations
25496 @geindex String stream operations
25498 This package provides a set of stream subprograms for standard string types.
25499 It is intended primarily to support implicit use of such subprograms when
25500 stream attributes are applied to string types, but the subprograms in this
25501 package can be used directly by application programs.
25503 @node System Unsigned_Types s-unstyp ads,System Wch_Cnv s-wchcnv ads,System Strings Stream_Ops s-ststop ads,The GNAT Library
25504 @anchor{gnat_rm/the_gnat_library system-unsigned-types-s-unstyp-ads}@anchor{403}@anchor{gnat_rm/the_gnat_library id154}@anchor{404}
25505 @section @code{System.Unsigned_Types} (@code{s-unstyp.ads})
25508 @geindex System.Unsigned_Types (s-unstyp.ads)
25510 This package contains definitions of standard unsigned types that
25511 correspond in size to the standard signed types declared in Standard,
25512 and (unlike the types in Interfaces) have corresponding names. It
25513 also contains some related definitions for other specialized types
25514 used by the compiler in connection with packed array types.
25516 @node System Wch_Cnv s-wchcnv ads,System Wch_Con s-wchcon ads,System Unsigned_Types s-unstyp ads,The GNAT Library
25517 @anchor{gnat_rm/the_gnat_library system-wch-cnv-s-wchcnv-ads}@anchor{405}@anchor{gnat_rm/the_gnat_library id155}@anchor{406}
25518 @section @code{System.Wch_Cnv} (@code{s-wchcnv.ads})
25521 @geindex System.Wch_Cnv (s-wchcnv.ads)
25523 @geindex Wide Character
25524 @geindex Representation
25526 @geindex Wide String
25527 @geindex Conversion
25529 @geindex Representation of wide characters
25531 This package provides routines for converting between
25532 wide and wide wide characters and a representation as a value of type
25533 @code{Standard.String}, using a specified wide character
25534 encoding method. It uses definitions in
25535 package @code{System.Wch_Con}.
25537 @node System Wch_Con s-wchcon ads,,System Wch_Cnv s-wchcnv ads,The GNAT Library
25538 @anchor{gnat_rm/the_gnat_library id156}@anchor{407}@anchor{gnat_rm/the_gnat_library system-wch-con-s-wchcon-ads}@anchor{408}
25539 @section @code{System.Wch_Con} (@code{s-wchcon.ads})
25542 @geindex System.Wch_Con (s-wchcon.ads)
25544 This package provides definitions and descriptions of
25545 the various methods used for encoding wide characters
25546 in ordinary strings. These definitions are used by
25547 the package @code{System.Wch_Cnv}.
25549 @node Interfacing to Other Languages,Specialized Needs Annexes,The GNAT Library,Top
25550 @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}
25551 @chapter Interfacing to Other Languages
25554 The facilities in Annex B of the Ada Reference Manual are fully
25555 implemented in GNAT, and in addition, a full interface to C++ is
25559 * Interfacing to C::
25560 * Interfacing to C++::
25561 * Interfacing to COBOL::
25562 * Interfacing to Fortran::
25563 * Interfacing to non-GNAT Ada code::
25567 @node Interfacing to C,Interfacing to C++,,Interfacing to Other Languages
25568 @anchor{gnat_rm/interfacing_to_other_languages interfacing-to-c}@anchor{40b}@anchor{gnat_rm/interfacing_to_other_languages id2}@anchor{40c}
25569 @section Interfacing to C
25572 Interfacing to C with GNAT can use one of two approaches:
25578 The types in the package @code{Interfaces.C} may be used.
25581 Standard Ada types may be used directly. This may be less portable to
25582 other compilers, but will work on all GNAT compilers, which guarantee
25583 correspondence between the C and Ada types.
25586 Pragma @code{Convention C} may be applied to Ada types, but mostly has no
25587 effect, since this is the default. The following table shows the
25588 correspondence between Ada scalar types and the corresponding C types.
25591 @multitable {xxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
25610 @code{Short_Integer}
25618 @code{Short_Short_Integer}
25626 @code{Long_Integer}
25634 @code{Long_Long_Integer}
25666 @code{Long_Long_Float}
25670 This is the longest floating-point type supported by the hardware.
25675 Additionally, there are the following general correspondences between Ada
25682 Ada enumeration types map to C enumeration types directly if pragma
25683 @code{Convention C} is specified, which causes them to have a length of
25684 32 bits, except for boolean types which map to C99 @code{bool} and for
25685 which the length is 8 bits.
25686 Without pragma @code{Convention C}, Ada enumeration types map to
25687 8, 16, or 32 bits (i.e., C types @code{signed char}, @code{short},
25688 @code{int}, respectively) depending on the number of values passed.
25689 This is the only case in which pragma @code{Convention C} affects the
25690 representation of an Ada type.
25693 Ada access types map to C pointers, except for the case of pointers to
25694 unconstrained types in Ada, which have no direct C equivalent.
25697 Ada arrays map directly to C arrays.
25700 Ada records map directly to C structures.
25703 Packed Ada records map to C structures where all members are bit fields
25704 of the length corresponding to the @code{type'Size} value in Ada.
25707 @node Interfacing to C++,Interfacing to COBOL,Interfacing to C,Interfacing to Other Languages
25708 @anchor{gnat_rm/interfacing_to_other_languages id4}@anchor{40d}@anchor{gnat_rm/interfacing_to_other_languages id3}@anchor{4a}
25709 @section Interfacing to C++
25712 The interface to C++ makes use of the following pragmas, which are
25713 primarily intended to be constructed automatically using a binding generator
25714 tool, although it is possible to construct them by hand.
25716 Using these pragmas it is possible to achieve complete
25717 inter-operability between Ada tagged types and C++ class definitions.
25718 See @ref{7,,Implementation Defined Pragmas}, for more details.
25723 @item @code{pragma CPP_Class ([Entity =>] @emph{LOCAL_NAME})}
25725 The argument denotes an entity in the current declarative region that is
25726 declared as a tagged or untagged record type. It indicates that the type
25727 corresponds to an externally declared C++ class type, and is to be laid
25728 out the same way that C++ would lay out the type.
25730 Note: Pragma @code{CPP_Class} is currently obsolete. It is supported
25731 for backward compatibility but its functionality is available
25732 using pragma @code{Import} with @code{Convention} = @code{CPP}.
25734 @item @code{pragma CPP_Constructor ([Entity =>] @emph{LOCAL_NAME})}
25736 This pragma identifies an imported function (imported in the usual way
25737 with pragma @code{Import}) as corresponding to a C++ constructor.
25740 A few restrictions are placed on the use of the @code{Access} attribute
25741 in conjunction with subprograms subject to convention @code{CPP}: the
25742 attribute may be used neither on primitive operations of a tagged
25743 record type with convention @code{CPP}, imported or not, nor on
25744 subprograms imported with pragma @code{CPP_Constructor}.
25746 In addition, C++ exceptions are propagated and can be handled in an
25747 @code{others} choice of an exception handler. The corresponding Ada
25748 occurrence has no message, and the simple name of the exception identity
25749 contains @code{Foreign_Exception}. Finalization and awaiting dependent
25750 tasks works properly when such foreign exceptions are propagated.
25752 It is also possible to import a C++ exception using the following syntax:
25755 LOCAL_NAME : exception;
25756 pragma Import (Cpp,
25757 [Entity =>] LOCAL_NAME,
25758 [External_Name =>] static_string_EXPRESSION);
25761 The @code{External_Name} is the name of the C++ RTTI symbol. You can then
25762 cover a specific C++ exception in an exception handler.
25764 @node Interfacing to COBOL,Interfacing to Fortran,Interfacing to C++,Interfacing to Other Languages
25765 @anchor{gnat_rm/interfacing_to_other_languages id5}@anchor{40e}@anchor{gnat_rm/interfacing_to_other_languages interfacing-to-cobol}@anchor{40f}
25766 @section Interfacing to COBOL
25769 Interfacing to COBOL is achieved as described in section B.4 of
25770 the Ada Reference Manual.
25772 @node Interfacing to Fortran,Interfacing to non-GNAT Ada code,Interfacing to COBOL,Interfacing to Other Languages
25773 @anchor{gnat_rm/interfacing_to_other_languages id6}@anchor{410}@anchor{gnat_rm/interfacing_to_other_languages interfacing-to-fortran}@anchor{411}
25774 @section Interfacing to Fortran
25777 Interfacing to Fortran is achieved as described in section B.5 of the
25778 Ada Reference Manual. The pragma @code{Convention Fortran}, applied to a
25779 multi-dimensional array causes the array to be stored in column-major
25780 order as required for convenient interface to Fortran.
25782 @node Interfacing to non-GNAT Ada code,,Interfacing to Fortran,Interfacing to Other Languages
25783 @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}
25784 @section Interfacing to non-GNAT Ada code
25787 It is possible to specify the convention @code{Ada} in a pragma
25788 @code{Import} or pragma @code{Export}. However this refers to
25789 the calling conventions used by GNAT, which may or may not be
25790 similar enough to those used by some other Ada 83 / Ada 95 / Ada 2005
25791 compiler to allow interoperation.
25793 If arguments types are kept simple, and if the foreign compiler generally
25794 follows system calling conventions, then it may be possible to integrate
25795 files compiled by other Ada compilers, provided that the elaboration
25796 issues are adequately addressed (for example by eliminating the
25797 need for any load time elaboration).
25799 In particular, GNAT running on VMS is designed to
25800 be highly compatible with the DEC Ada 83 compiler, so this is one
25801 case in which it is possible to import foreign units of this type,
25802 provided that the data items passed are restricted to simple scalar
25803 values or simple record types without variants, or simple array
25804 types with fixed bounds.
25806 @node Specialized Needs Annexes,Implementation of Specific Ada Features,Interfacing to Other Languages,Top
25807 @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}
25808 @chapter Specialized Needs Annexes
25811 Ada 95, Ada 2005, and Ada 2012 define a number of Specialized Needs Annexes, which are not
25812 required in all implementations. However, as described in this chapter,
25813 GNAT implements all of these annexes:
25818 @item @emph{Systems Programming (Annex C)}
25820 The Systems Programming Annex is fully implemented.
25822 @item @emph{Real-Time Systems (Annex D)}
25824 The Real-Time Systems Annex is fully implemented.
25826 @item @emph{Distributed Systems (Annex E)}
25828 Stub generation is fully implemented in the GNAT compiler. In addition,
25829 a complete compatible PCS is available as part of the GLADE system,
25830 a separate product. When the two
25831 products are used in conjunction, this annex is fully implemented.
25833 @item @emph{Information Systems (Annex F)}
25835 The Information Systems annex is fully implemented.
25837 @item @emph{Numerics (Annex G)}
25839 The Numerics Annex is fully implemented.
25841 @item @emph{Safety and Security / High-Integrity Systems (Annex H)}
25843 The Safety and Security Annex (termed the High-Integrity Systems Annex
25844 in Ada 2005) is fully implemented.
25847 @node Implementation of Specific Ada Features,Implementation of Ada 2012 Features,Specialized Needs Annexes,Top
25848 @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}
25849 @chapter Implementation of Specific Ada Features
25852 This chapter describes the GNAT implementation of several Ada language
25856 * Machine Code Insertions::
25857 * GNAT Implementation of Tasking::
25858 * GNAT Implementation of Shared Passive Packages::
25859 * Code Generation for Array Aggregates::
25860 * The Size of Discriminated Records with Default Discriminants::
25861 * Strict Conformance to the Ada Reference Manual::
25865 @node Machine Code Insertions,GNAT Implementation of Tasking,,Implementation of Specific Ada Features
25866 @anchor{gnat_rm/implementation_of_specific_ada_features machine-code-insertions}@anchor{16c}@anchor{gnat_rm/implementation_of_specific_ada_features id2}@anchor{418}
25867 @section Machine Code Insertions
25870 @geindex Machine Code insertions
25872 Package @code{Machine_Code} provides machine code support as described
25873 in the Ada Reference Manual in two separate forms:
25879 Machine code statements, consisting of qualified expressions that
25880 fit the requirements of RM section 13.8.
25883 An intrinsic callable procedure, providing an alternative mechanism of
25884 including machine instructions in a subprogram.
25887 The two features are similar, and both are closely related to the mechanism
25888 provided by the asm instruction in the GNU C compiler. Full understanding
25889 and use of the facilities in this package requires understanding the asm
25890 instruction, see the section on Extended Asm in
25891 @cite{Using_the_GNU_Compiler_Collection_(GCC)}.
25893 Calls to the function @code{Asm} and the procedure @code{Asm} have identical
25894 semantic restrictions and effects as described below. Both are provided so
25895 that the procedure call can be used as a statement, and the function call
25896 can be used to form a code_statement.
25898 Consider this C @code{asm} instruction:
25901 asm ("fsinx %1 %0" : "=f" (result) : "f" (angle));
25904 The equivalent can be written for GNAT as:
25907 Asm ("fsinx %1 %0",
25908 My_Float'Asm_Output ("=f", result),
25909 My_Float'Asm_Input ("f", angle));
25912 The first argument to @code{Asm} is the assembler template, and is
25913 identical to what is used in GNU C. This string must be a static
25914 expression. The second argument is the output operand list. It is
25915 either a single @code{Asm_Output} attribute reference, or a list of such
25916 references enclosed in parentheses (technically an array aggregate of
25919 The @code{Asm_Output} attribute denotes a function that takes two
25920 parameters. The first is a string, the second is the name of a variable
25921 of the type designated by the attribute prefix. The first (string)
25922 argument is required to be a static expression and designates the
25923 constraint (see the section on Constraints in
25924 @cite{Using_the_GNU_Compiler_Collection_(GCC)})
25925 for the parameter; e.g., what kind of register is required. The second
25926 argument is the variable to be written or updated with the
25927 result. The possible values for constraint are the same as those used in
25928 the RTL, and are dependent on the configuration file used to build the
25929 GCC back end. If there are no output operands, then this argument may
25930 either be omitted, or explicitly given as @code{No_Output_Operands}.
25931 No support is provided for GNU C's symbolic names for output parameters.
25933 The second argument of @code{my_float'Asm_Output} functions as
25934 though it were an @code{out} parameter, which is a little curious, but
25935 all names have the form of expressions, so there is no syntactic
25936 irregularity, even though normally functions would not be permitted
25937 @code{out} parameters. The third argument is the list of input
25938 operands. It is either a single @code{Asm_Input} attribute reference, or
25939 a list of such references enclosed in parentheses (technically an array
25940 aggregate of such references).
25942 The @code{Asm_Input} attribute denotes a function that takes two
25943 parameters. The first is a string, the second is an expression of the
25944 type designated by the prefix. The first (string) argument is required
25945 to be a static expression, and is the constraint for the parameter,
25946 (e.g., what kind of register is required). The second argument is the
25947 value to be used as the input argument. The possible values for the
25948 constraint are the same as those used in the RTL, and are dependent on
25949 the configuration file used to built the GCC back end.
25950 No support is provided for GNU C's symbolic names for input parameters.
25952 If there are no input operands, this argument may either be omitted, or
25953 explicitly given as @code{No_Input_Operands}. The fourth argument, not
25954 present in the above example, is a list of register names, called the
25955 @emph{clobber} argument. This argument, if given, must be a static string
25956 expression, and is a space or comma separated list of names of registers
25957 that must be considered destroyed as a result of the @code{Asm} call. If
25958 this argument is the null string (the default value), then the code
25959 generator assumes that no additional registers are destroyed.
25960 In addition to registers, the special clobbers @code{memory} and
25961 @code{cc} as described in the GNU C docs are both supported.
25963 The fifth argument, not present in the above example, called the
25964 @emph{volatile} argument, is by default @code{False}. It can be set to
25965 the literal value @code{True} to indicate to the code generator that all
25966 optimizations with respect to the instruction specified should be
25967 suppressed, and in particular an instruction that has outputs
25968 will still be generated, even if none of the outputs are
25969 used. See @cite{Using_the_GNU_Compiler_Collection_(GCC)}
25970 for the full description.
25971 Generally it is strongly advisable to use Volatile for any ASM statement
25972 that is missing either input or output operands or to avoid unwanted
25973 optimizations. A warning is generated if this advice is not followed.
25975 No support is provided for GNU C's @code{asm goto} feature.
25977 The @code{Asm} subprograms may be used in two ways. First the procedure
25978 forms can be used anywhere a procedure call would be valid, and
25979 correspond to what the RM calls 'intrinsic' routines. Such calls can
25980 be used to intersperse machine instructions with other Ada statements.
25981 Second, the function forms, which return a dummy value of the limited
25982 private type @code{Asm_Insn}, can be used in code statements, and indeed
25983 this is the only context where such calls are allowed. Code statements
25984 appear as aggregates of the form:
25987 Asm_Insn'(Asm (...));
25988 Asm_Insn'(Asm_Volatile (...));
25991 In accordance with RM rules, such code statements are allowed only
25992 within subprograms whose entire body consists of such statements. It is
25993 not permissible to intermix such statements with other Ada statements.
25995 Typically the form using intrinsic procedure calls is more convenient
25996 and more flexible. The code statement form is provided to meet the RM
25997 suggestion that such a facility should be made available. The following
25998 is the exact syntax of the call to @code{Asm}. As usual, if named notation
25999 is used, the arguments may be given in arbitrary order, following the
26000 normal rules for use of positional and named arguments:
26004 [Template =>] static_string_EXPRESSION
26005 [,[Outputs =>] OUTPUT_OPERAND_LIST ]
26006 [,[Inputs =>] INPUT_OPERAND_LIST ]
26007 [,[Clobber =>] static_string_EXPRESSION ]
26008 [,[Volatile =>] static_boolean_EXPRESSION] )
26010 OUTPUT_OPERAND_LIST ::=
26011 [PREFIX.]No_Output_Operands
26012 | OUTPUT_OPERAND_ATTRIBUTE
26013 | (OUTPUT_OPERAND_ATTRIBUTE @{,OUTPUT_OPERAND_ATTRIBUTE@})
26015 OUTPUT_OPERAND_ATTRIBUTE ::=
26016 SUBTYPE_MARK'Asm_Output (static_string_EXPRESSION, NAME)
26018 INPUT_OPERAND_LIST ::=
26019 [PREFIX.]No_Input_Operands
26020 | INPUT_OPERAND_ATTRIBUTE
26021 | (INPUT_OPERAND_ATTRIBUTE @{,INPUT_OPERAND_ATTRIBUTE@})
26023 INPUT_OPERAND_ATTRIBUTE ::=
26024 SUBTYPE_MARK'Asm_Input (static_string_EXPRESSION, EXPRESSION)
26027 The identifiers @code{No_Input_Operands} and @code{No_Output_Operands}
26028 are declared in the package @code{Machine_Code} and must be referenced
26029 according to normal visibility rules. In particular if there is no
26030 @code{use} clause for this package, then appropriate package name
26031 qualification is required.
26033 @node GNAT Implementation of Tasking,GNAT Implementation of Shared Passive Packages,Machine Code Insertions,Implementation of Specific Ada Features
26034 @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}
26035 @section GNAT Implementation of Tasking
26038 This chapter outlines the basic GNAT approach to tasking (in particular,
26039 a multi-layered library for portability) and discusses issues related
26040 to compliance with the Real-Time Systems Annex.
26043 * Mapping Ada Tasks onto the Underlying Kernel Threads::
26044 * Ensuring Compliance with the Real-Time Annex::
26045 * Support for Locking Policies::
26049 @node Mapping Ada Tasks onto the Underlying Kernel Threads,Ensuring Compliance with the Real-Time Annex,,GNAT Implementation of Tasking
26050 @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}
26051 @subsection Mapping Ada Tasks onto the Underlying Kernel Threads
26054 GNAT's run-time support comprises two layers:
26060 GNARL (GNAT Run-time Layer)
26063 GNULL (GNAT Low-level Library)
26066 In GNAT, Ada's tasking services rely on a platform and OS independent
26067 layer known as GNARL. This code is responsible for implementing the
26068 correct semantics of Ada's task creation, rendezvous, protected
26071 GNARL decomposes Ada's tasking semantics into simpler lower level
26072 operations such as create a thread, set the priority of a thread,
26073 yield, create a lock, lock/unlock, etc. The spec for these low-level
26074 operations constitutes GNULLI, the GNULL Interface. This interface is
26075 directly inspired from the POSIX real-time API.
26077 If the underlying executive or OS implements the POSIX standard
26078 faithfully, the GNULL Interface maps as is to the services offered by
26079 the underlying kernel. Otherwise, some target dependent glue code maps
26080 the services offered by the underlying kernel to the semantics expected
26083 Whatever the underlying OS (VxWorks, UNIX, Windows, etc.) the
26084 key point is that each Ada task is mapped on a thread in the underlying
26085 kernel. For example, in the case of VxWorks, one Ada task = one VxWorks task.
26087 In addition Ada task priorities map onto the underlying thread priorities.
26088 Mapping Ada tasks onto the underlying kernel threads has several advantages:
26094 The underlying scheduler is used to schedule the Ada tasks. This
26095 makes Ada tasks as efficient as kernel threads from a scheduling
26099 Interaction with code written in C containing threads is eased
26100 since at the lowest level Ada tasks and C threads map onto the same
26101 underlying kernel concept.
26104 When an Ada task is blocked during I/O the remaining Ada tasks are
26108 On multiprocessor systems Ada tasks can execute in parallel.
26111 Some threads libraries offer a mechanism to fork a new process, with the
26112 child process duplicating the threads from the parent.
26114 support this functionality when the parent contains more than one task.
26116 @geindex Forking a new process
26118 @node Ensuring Compliance with the Real-Time Annex,Support for Locking Policies,Mapping Ada Tasks onto the Underlying Kernel Threads,GNAT Implementation of Tasking
26119 @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}
26120 @subsection Ensuring Compliance with the Real-Time Annex
26123 @geindex Real-Time Systems Annex compliance
26125 Although mapping Ada tasks onto
26126 the underlying threads has significant advantages, it does create some
26127 complications when it comes to respecting the scheduling semantics
26128 specified in the real-time annex (Annex D).
26130 For instance the Annex D requirement for the @code{FIFO_Within_Priorities}
26131 scheduling policy states:
26135 @emph{When the active priority of a ready task that is not running
26136 changes, or the setting of its base priority takes effect, the
26137 task is removed from the ready queue for its old active priority
26138 and is added at the tail of the ready queue for its new active
26139 priority, except in the case where the active priority is lowered
26140 due to the loss of inherited priority, in which case the task is
26141 added at the head of the ready queue for its new active priority.}
26144 While most kernels do put tasks at the end of the priority queue when
26145 a task changes its priority, (which respects the main
26146 FIFO_Within_Priorities requirement), almost none keep a thread at the
26147 beginning of its priority queue when its priority drops from the loss
26148 of inherited priority.
26150 As a result most vendors have provided incomplete Annex D implementations.
26152 The GNAT run-time, has a nice cooperative solution to this problem
26153 which ensures that accurate FIFO_Within_Priorities semantics are
26156 The principle is as follows. When an Ada task T is about to start
26157 running, it checks whether some other Ada task R with the same
26158 priority as T has been suspended due to the loss of priority
26159 inheritance. If this is the case, T yields and is placed at the end of
26160 its priority queue. When R arrives at the front of the queue it
26163 Note that this simple scheme preserves the relative order of the tasks
26164 that were ready to execute in the priority queue where R has been
26167 @c Support_for_Locking_Policies
26169 @node Support for Locking Policies,,Ensuring Compliance with the Real-Time Annex,GNAT Implementation of Tasking
26170 @anchor{gnat_rm/implementation_of_specific_ada_features support-for-locking-policies}@anchor{41f}
26171 @subsection Support for Locking Policies
26174 This section specifies which policies specified by pragma Locking_Policy
26175 are supported on which platforms.
26177 GNAT supports the standard @code{Ceiling_Locking} policy, and the
26178 implementation defined @code{Inheritance_Locking} and
26179 @code{Concurrent_Readers_Locking} policies.
26181 @code{Ceiling_Locking} is supported on all platforms if the operating system
26182 supports it. In particular, @code{Ceiling_Locking} is not supported on
26184 @code{Inheritance_Locking} is supported on
26189 @code{Concurrent_Readers_Locking} is supported on Linux.
26191 Notes about @code{Ceiling_Locking} on Linux:
26192 If the process is running as 'root', ceiling locking is used.
26193 If the capabilities facility is installed
26194 ("sudo apt-get --assume-yes install libcap-dev" on Ubuntu,
26196 and the program is linked against that library
26198 and the executable file has the cap_sys_nice capability
26199 ("sudo /sbin/setcap cap_sys_nice=ep executable_file_name"),
26200 then ceiling locking is used.
26201 Otherwise, the @code{Ceiling_Locking} policy is ignored.
26203 @node GNAT Implementation of Shared Passive Packages,Code Generation for Array Aggregates,GNAT Implementation of Tasking,Implementation of Specific Ada Features
26204 @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}
26205 @section GNAT Implementation of Shared Passive Packages
26208 @geindex Shared passive packages
26210 GNAT fully implements the
26211 @geindex pragma Shared_Passive
26213 @code{Shared_Passive} for
26214 the purpose of designating shared passive packages.
26215 This allows the use of passive partitions in the
26216 context described in the Ada Reference Manual; i.e., for communication
26217 between separate partitions of a distributed application using the
26218 features in Annex E.
26222 @geindex Distribution Systems Annex
26224 However, the implementation approach used by GNAT provides for more
26225 extensive usage as follows:
26230 @item @emph{Communication between separate programs}
26232 This allows separate programs to access the data in passive
26233 partitions, using protected objects for synchronization where
26234 needed. The only requirement is that the two programs have a
26235 common shared file system. It is even possible for programs
26236 running on different machines with different architectures
26237 (e.g., different endianness) to communicate via the data in
26238 a passive partition.
26240 @item @emph{Persistence between program runs}
26242 The data in a passive package can persist from one run of a
26243 program to another, so that a later program sees the final
26244 values stored by a previous run of the same program.
26247 The implementation approach used is to store the data in files. A
26248 separate stream file is created for each object in the package, and
26249 an access to an object causes the corresponding file to be read or
26252 @geindex SHARED_MEMORY_DIRECTORY environment variable
26254 The environment variable @code{SHARED_MEMORY_DIRECTORY} should be
26255 set to the directory to be used for these files.
26256 The files in this directory
26257 have names that correspond to their fully qualified names. For
26258 example, if we have the package
26262 pragma Shared_Passive (X);
26268 and the environment variable is set to @code{/stemp/}, then the files created
26269 will have the names:
26276 These files are created when a value is initially written to the object, and
26277 the files are retained until manually deleted. This provides the persistence
26278 semantics. If no file exists, it means that no partition has assigned a value
26279 to the variable; in this case the initial value declared in the package
26280 will be used. This model ensures that there are no issues in synchronizing
26281 the elaboration process, since elaboration of passive packages elaborates the
26282 initial values, but does not create the files.
26284 The files are written using normal @code{Stream_IO} access.
26285 If you want to be able
26286 to communicate between programs or partitions running on different
26287 architectures, then you should use the XDR versions of the stream attribute
26288 routines, since these are architecture independent.
26290 If active synchronization is required for access to the variables in the
26291 shared passive package, then as described in the Ada Reference Manual, the
26292 package may contain protected objects used for this purpose. In this case
26293 a lock file (whose name is @code{___lock} (three underscores)
26294 is created in the shared memory directory.
26296 @geindex ___lock file (for shared passive packages)
26298 This is used to provide the required locking
26299 semantics for proper protected object synchronization.
26301 @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
26302 @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}
26303 @section Code Generation for Array Aggregates
26306 Aggregates have a rich syntax and allow the user to specify the values of
26307 complex data structures by means of a single construct. As a result, the
26308 code generated for aggregates can be quite complex and involve loops, case
26309 statements and multiple assignments. In the simplest cases, however, the
26310 compiler will recognize aggregates whose components and constraints are
26311 fully static, and in those cases the compiler will generate little or no
26312 executable code. The following is an outline of the code that GNAT generates
26313 for various aggregate constructs. For further details, you will find it
26314 useful to examine the output produced by the -gnatG flag to see the expanded
26315 source that is input to the code generator. You may also want to examine
26316 the assembly code generated at various levels of optimization.
26318 The code generated for aggregates depends on the context, the component values,
26319 and the type. In the context of an object declaration the code generated is
26320 generally simpler than in the case of an assignment. As a general rule, static
26321 component values and static subtypes also lead to simpler code.
26324 * Static constant aggregates with static bounds::
26325 * Constant aggregates with unconstrained nominal types::
26326 * Aggregates with static bounds::
26327 * Aggregates with nonstatic bounds::
26328 * Aggregates in assignment statements::
26332 @node Static constant aggregates with static bounds,Constant aggregates with unconstrained nominal types,,Code Generation for Array Aggregates
26333 @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}
26334 @subsection Static constant aggregates with static bounds
26337 For the declarations:
26340 type One_Dim is array (1..10) of integer;
26341 ar0 : constant One_Dim := (1, 2, 3, 4, 5, 6, 7, 8, 9, 0);
26344 GNAT generates no executable code: the constant ar0 is placed in static memory.
26345 The same is true for constant aggregates with named associations:
26348 Cr1 : constant One_Dim := (4 => 16, 2 => 4, 3 => 9, 1 => 1, 5 .. 10 => 0);
26349 Cr3 : constant One_Dim := (others => 7777);
26352 The same is true for multidimensional constant arrays such as:
26355 type two_dim is array (1..3, 1..3) of integer;
26356 Unit : constant two_dim := ( (1,0,0), (0,1,0), (0,0,1));
26359 The same is true for arrays of one-dimensional arrays: the following are
26363 type ar1b is array (1..3) of boolean;
26364 type ar_ar is array (1..3) of ar1b;
26365 None : constant ar1b := (others => false); -- fully static
26366 None2 : constant ar_ar := (1..3 => None); -- fully static
26369 However, for multidimensional aggregates with named associations, GNAT will
26370 generate assignments and loops, even if all associations are static. The
26371 following two declarations generate a loop for the first dimension, and
26372 individual component assignments for the second dimension:
26375 Zero1: constant two_dim := (1..3 => (1..3 => 0));
26376 Zero2: constant two_dim := (others => (others => 0));
26379 @node Constant aggregates with unconstrained nominal types,Aggregates with static bounds,Static constant aggregates with static bounds,Code Generation for Array Aggregates
26380 @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}
26381 @subsection Constant aggregates with unconstrained nominal types
26384 In such cases the aggregate itself establishes the subtype, so that
26385 associations with @code{others} cannot be used. GNAT determines the
26386 bounds for the actual subtype of the aggregate, and allocates the
26387 aggregate statically as well. No code is generated for the following:
26390 type One_Unc is array (natural range <>) of integer;
26391 Cr_Unc : constant One_Unc := (12,24,36);
26394 @node Aggregates with static bounds,Aggregates with nonstatic bounds,Constant aggregates with unconstrained nominal types,Code Generation for Array Aggregates
26395 @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}
26396 @subsection Aggregates with static bounds
26399 In all previous examples the aggregate was the initial (and immutable) value
26400 of a constant. If the aggregate initializes a variable, then code is generated
26401 for it as a combination of individual assignments and loops over the target
26402 object. The declarations
26405 Cr_Var1 : One_Dim := (2, 5, 7, 11, 0, 0, 0, 0, 0, 0);
26406 Cr_Var2 : One_Dim := (others > -1);
26409 generate the equivalent of
26417 for I in Cr_Var2'range loop
26422 @node Aggregates with nonstatic bounds,Aggregates in assignment statements,Aggregates with static bounds,Code Generation for Array Aggregates
26423 @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}
26424 @subsection Aggregates with nonstatic bounds
26427 If the bounds of the aggregate are not statically compatible with the bounds
26428 of the nominal subtype of the target, then constraint checks have to be
26429 generated on the bounds. For a multidimensional array, constraint checks may
26430 have to be applied to sub-arrays individually, if they do not have statically
26431 compatible subtypes.
26433 @node Aggregates in assignment statements,,Aggregates with nonstatic bounds,Code Generation for Array Aggregates
26434 @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}
26435 @subsection Aggregates in assignment statements
26438 In general, aggregate assignment requires the construction of a temporary,
26439 and a copy from the temporary to the target of the assignment. This is because
26440 it is not always possible to convert the assignment into a series of individual
26441 component assignments. For example, consider the simple case:
26447 This cannot be converted into:
26454 So the aggregate has to be built first in a separate location, and then
26455 copied into the target. GNAT recognizes simple cases where this intermediate
26456 step is not required, and the assignments can be performed in place, directly
26457 into the target. The following sufficient criteria are applied:
26463 The bounds of the aggregate are static, and the associations are static.
26466 The components of the aggregate are static constants, names of
26467 simple variables that are not renamings, or expressions not involving
26468 indexed components whose operands obey these rules.
26471 If any of these conditions are violated, the aggregate will be built in
26472 a temporary (created either by the front-end or the code generator) and then
26473 that temporary will be copied onto the target.
26475 @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
26476 @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}
26477 @section The Size of Discriminated Records with Default Discriminants
26480 If a discriminated type @code{T} has discriminants with default values, it is
26481 possible to declare an object of this type without providing an explicit
26485 type Size is range 1..100;
26487 type Rec (D : Size := 15) is record
26488 Name : String (1..D);
26494 Such an object is said to be @emph{unconstrained}.
26495 The discriminant of the object
26496 can be modified by a full assignment to the object, as long as it preserves the
26497 relation between the value of the discriminant, and the value of the components
26501 Word := (3, "yes");
26503 Word := (5, "maybe");
26505 Word := (5, "no"); -- raises Constraint_Error
26508 In order to support this behavior efficiently, an unconstrained object is
26509 given the maximum size that any value of the type requires. In the case
26510 above, @code{Word} has storage for the discriminant and for
26511 a @code{String} of length 100.
26512 It is important to note that unconstrained objects do not require dynamic
26513 allocation. It would be an improper implementation to place on the heap those
26514 components whose size depends on discriminants. (This improper implementation
26515 was used by some Ada83 compilers, where the @code{Name} component above
26517 been stored as a pointer to a dynamic string). Following the principle that
26518 dynamic storage management should never be introduced implicitly,
26519 an Ada compiler should reserve the full size for an unconstrained declared
26520 object, and place it on the stack.
26522 This maximum size approach
26523 has been a source of surprise to some users, who expect the default
26524 values of the discriminants to determine the size reserved for an
26525 unconstrained object: "If the default is 15, why should the object occupy
26527 The answer, of course, is that the discriminant may be later modified,
26528 and its full range of values must be taken into account. This is why the
26532 type Rec (D : Positive := 15) is record
26533 Name : String (1..D);
26539 is flagged by the compiler with a warning:
26540 an attempt to create @code{Too_Large} will raise @code{Storage_Error},
26541 because the required size includes @code{Positive'Last}
26542 bytes. As the first example indicates, the proper approach is to declare an
26543 index type of 'reasonable' range so that unconstrained objects are not too
26546 One final wrinkle: if the object is declared to be @code{aliased}, or if it is
26547 created in the heap by means of an allocator, then it is @emph{not}
26549 it is constrained by the default values of the discriminants, and those values
26550 cannot be modified by full assignment. This is because in the presence of
26551 aliasing all views of the object (which may be manipulated by different tasks,
26552 say) must be consistent, so it is imperative that the object, once created,
26555 @node Strict Conformance to the Ada Reference Manual,,The Size of Discriminated Records with Default Discriminants,Implementation of Specific Ada Features
26556 @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}
26557 @section Strict Conformance to the Ada Reference Manual
26560 The dynamic semantics defined by the Ada Reference Manual impose a set of
26561 run-time checks to be generated. By default, the GNAT compiler will insert many
26562 run-time checks into the compiled code, including most of those required by the
26563 Ada Reference Manual. However, there are two checks that are not enabled in
26564 the default mode for efficiency reasons: checks for access before elaboration
26565 on subprogram calls, and stack overflow checking (most operating systems do not
26566 perform this check by default).
26568 Strict conformance to the Ada Reference Manual can be achieved by adding two
26569 compiler options for dynamic checks for access-before-elaboration on subprogram
26570 calls and generic instantiations (@emph{-gnatE}), and stack overflow checking
26571 (@emph{-fstack-check}).
26573 Note that the result of a floating point arithmetic operation in overflow and
26574 invalid situations, when the @code{Machine_Overflows} attribute of the result
26575 type is @code{False}, is to generate IEEE NaN and infinite values. This is the
26576 case for machines compliant with the IEEE floating-point standard, but on
26577 machines that are not fully compliant with this standard, such as Alpha, the
26578 @emph{-mieee} compiler flag must be used for achieving IEEE confirming
26579 behavior (although at the cost of a significant performance penalty), so
26580 infinite and NaN values are properly generated.
26582 @node Implementation of Ada 2012 Features,Obsolescent Features,Implementation of Specific Ada Features,Top
26583 @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}
26584 @chapter Implementation of Ada 2012 Features
26587 @geindex Ada 2012 implementation status
26589 @geindex -gnat12 option (gcc)
26591 @geindex pragma Ada_2012
26593 @geindex configuration pragma Ada_2012
26595 @geindex Ada_2012 configuration pragma
26597 This chapter contains a complete list of Ada 2012 features that have been
26599 Generally, these features are only
26600 available if the @emph{-gnat12} (Ada 2012 features enabled) option is set,
26601 which is the default behavior,
26602 or if the configuration pragma @code{Ada_2012} is used.
26604 However, new pragmas, attributes, and restrictions are
26605 unconditionally available, since the Ada 95 standard allows the addition of
26606 new pragmas, attributes, and restrictions (there are exceptions, which are
26607 documented in the individual descriptions), and also certain packages
26608 were made available in earlier versions of Ada.
26610 An ISO date (YYYY-MM-DD) appears in parentheses on the description line.
26611 This date shows the implementation date of the feature. Any wavefront
26612 subsequent to this date will contain the indicated feature, as will any
26613 subsequent releases. A date of 0000-00-00 means that GNAT has always
26614 implemented the feature, or implemented it as soon as it appeared as a
26615 binding interpretation.
26617 Each feature corresponds to an Ada Issue ('AI') approved by the Ada
26618 standardization group (ISO/IEC JTC1/SC22/WG9) for inclusion in Ada 2012.
26619 The features are ordered based on the relevant sections of the Ada
26620 Reference Manual ("RM"). When a given AI relates to multiple points
26621 in the RM, the earliest is used.
26623 A complete description of the AIs may be found in
26624 @indicateurl{http://www.ada-auth.org/ai05-summary.html}.
26626 @geindex AI-0176 (Ada 2012 feature)
26632 @emph{AI-0176 Quantified expressions (2010-09-29)}
26634 Both universally and existentially quantified expressions are implemented.
26635 They use the new syntax for iterators proposed in AI05-139-2, as well as
26636 the standard Ada loop syntax.
26638 RM References: 1.01.04 (12) 2.09 (2/2) 4.04 (7) 4.05.09 (0)
26641 @geindex AI-0079 (Ada 2012 feature)
26647 @emph{AI-0079 Allow other_format characters in source (2010-07-10)}
26649 Wide characters in the unicode category @emph{other_format} are now allowed in
26650 source programs between tokens, but not within a token such as an identifier.
26652 RM References: 2.01 (4/2) 2.02 (7)
26655 @geindex AI-0091 (Ada 2012 feature)
26661 @emph{AI-0091 Do not allow other_format in identifiers (0000-00-00)}
26663 Wide characters in the unicode category @emph{other_format} are not permitted
26664 within an identifier, since this can be a security problem. The error
26665 message for this case has been improved to be more specific, but GNAT has
26666 never allowed such characters to appear in identifiers.
26668 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)
26671 @geindex AI-0100 (Ada 2012 feature)
26677 @emph{AI-0100 Placement of pragmas (2010-07-01)}
26679 This AI is an earlier version of AI-163. It simplifies the rules
26680 for legal placement of pragmas. In the case of lists that allow pragmas, if
26681 the list may have no elements, then the list may consist solely of pragmas.
26683 RM References: 2.08 (7)
26686 @geindex AI-0163 (Ada 2012 feature)
26692 @emph{AI-0163 Pragmas in place of null (2010-07-01)}
26694 A statement sequence may be composed entirely of pragmas. It is no longer
26695 necessary to add a dummy @code{null} statement to make the sequence legal.
26697 RM References: 2.08 (7) 2.08 (16)
26700 @geindex AI-0080 (Ada 2012 feature)
26706 @emph{AI-0080 'View of' not needed if clear from context (0000-00-00)}
26708 This is an editorial change only, described as non-testable in the AI.
26710 RM References: 3.01 (7)
26713 @geindex AI-0183 (Ada 2012 feature)
26719 @emph{AI-0183 Aspect specifications (2010-08-16)}
26721 Aspect specifications have been fully implemented except for pre and post-
26722 conditions, and type invariants, which have their own separate AI's. All
26723 forms of declarations listed in the AI are supported. The following is a
26724 list of the aspects supported (with GNAT implementation aspects marked)
26728 @multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxx}
26773 @code{Atomic_Components}
26785 @code{Component_Size}
26791 @code{Contract_Cases}
26799 @code{Discard_Names}
26805 @code{External_Tag}
26811 @code{Favor_Top_Level}
26825 @code{Inline_Always}
26841 @code{Machine_Radix}
26867 @code{Persistent_BSS}
26893 @code{Preelaborable_Initialization}
26899 @code{Pure_Function}
26907 @code{Remote_Access_Type}
26929 @code{Storage_Pool}
26935 @code{Storage_Size}
26953 @code{Suppress_Debug_Info}
26969 @code{Thread_Local_Storage}
26977 @code{Type_Invariant}
26983 @code{Unchecked_Union}
26989 @code{Universal_Aliasing}
27005 @code{Unreferenced}
27013 @code{Unreferenced_Objects}
27041 @code{Volatile_Components}
27058 Note that for aspects with an expression, e.g. @code{Size}, the expression is
27059 treated like a default expression (visibility is analyzed at the point of
27060 occurrence of the aspect, but evaluation of the expression occurs at the
27061 freeze point of the entity involved).
27063 RM References: 3.02.01 (3) 3.02.02 (2) 3.03.01 (2/2) 3.08 (6)
27064 3.09.03 (1.1/2) 6.01 (2/2) 6.07 (2/2) 9.05.02 (2/2) 7.01 (3) 7.03
27065 (2) 7.03 (3) 9.01 (2/2) 9.01 (3/2) 9.04 (2/2) 9.04 (3/2)
27066 9.05.02 (2/2) 11.01 (2) 12.01 (3) 12.03 (2/2) 12.04 (2/2) 12.05 (2)
27067 12.06 (2.1/2) 12.06 (2.2/2) 12.07 (2) 13.01 (0.1/2) 13.03 (5/1)
27071 @geindex AI-0128 (Ada 2012 feature)
27077 @emph{AI-0128 Inequality is a primitive operation (0000-00-00)}
27079 If an equality operator ("=") is declared for a type, then the implicitly
27080 declared inequality operator ("/=") is a primitive operation of the type.
27081 This is the only reasonable interpretation, and is the one always implemented
27082 by GNAT, but the RM was not entirely clear in making this point.
27084 RM References: 3.02.03 (6) 6.06 (6)
27087 @geindex AI-0003 (Ada 2012 feature)
27093 @emph{AI-0003 Qualified expressions as names (2010-07-11)}
27095 In Ada 2012, a qualified expression is considered to be syntactically a name,
27096 meaning that constructs such as @code{A'(F(X)).B} are now legal. This is
27097 useful in disambiguating some cases of overloading.
27099 RM References: 3.03 (11) 3.03 (21) 4.01 (2) 4.04 (7) 4.07 (3)
27103 @geindex AI-0120 (Ada 2012 feature)
27109 @emph{AI-0120 Constant instance of protected object (0000-00-00)}
27111 This is an RM editorial change only. The section that lists objects that are
27112 constant failed to include the current instance of a protected object
27113 within a protected function. This has always been treated as a constant
27116 RM References: 3.03 (21)
27119 @geindex AI-0008 (Ada 2012 feature)
27125 @emph{AI-0008 General access to constrained objects (0000-00-00)}
27127 The wording in the RM implied that if you have a general access to a
27128 constrained object, it could be used to modify the discriminants. This was
27129 obviously not intended. @code{Constraint_Error} should be raised, and GNAT
27130 has always done so in this situation.
27132 RM References: 3.03 (23) 3.10.02 (26/2) 4.01 (9) 6.04.01 (17) 8.05.01 (5/2)
27135 @geindex AI-0093 (Ada 2012 feature)
27141 @emph{AI-0093 Additional rules use immutably limited (0000-00-00)}
27143 This is an editorial change only, to make more widespread use of the Ada 2012
27144 'immutably limited'.
27146 RM References: 3.03 (23.4/3)
27149 @geindex AI-0096 (Ada 2012 feature)
27155 @emph{AI-0096 Deriving from formal private types (2010-07-20)}
27157 In general it is illegal for a type derived from a formal limited type to be
27158 nonlimited. This AI makes an exception to this rule: derivation is legal
27159 if it appears in the private part of the generic, and the formal type is not
27160 tagged. If the type is tagged, the legality check must be applied to the
27161 private part of the package.
27163 RM References: 3.04 (5.1/2) 6.02 (7)
27166 @geindex AI-0181 (Ada 2012 feature)
27172 @emph{AI-0181 Soft hyphen is a non-graphic character (2010-07-23)}
27174 From Ada 2005 on, soft hyphen is considered a non-graphic character, which
27175 means that it has a special name (@code{SOFT_HYPHEN}) in conjunction with the
27176 @code{Image} and @code{Value} attributes for the character types. Strictly
27177 speaking this is an inconsistency with Ada 95, but in practice the use of
27178 these attributes is so obscure that it will not cause problems.
27180 RM References: 3.05.02 (2/2) A.01 (35/2) A.03.03 (21)
27183 @geindex AI-0182 (Ada 2012 feature)
27189 @emph{AI-0182 Additional forms for} @code{Character'Value} @emph{(0000-00-00)}
27191 This AI allows @code{Character'Value} to accept the string @code{'?'} where
27192 @code{?} is any character including non-graphic control characters. GNAT has
27193 always accepted such strings. It also allows strings such as
27194 @code{HEX_00000041} to be accepted, but GNAT does not take advantage of this
27195 permission and raises @code{Constraint_Error}, as is certainly still
27198 RM References: 3.05 (56/2)
27201 @geindex AI-0214 (Ada 2012 feature)
27207 @emph{AI-0214 Defaulted discriminants for limited tagged (2010-10-01)}
27209 Ada 2012 relaxes the restriction that forbids discriminants of tagged types
27210 to have default expressions by allowing them when the type is limited. It
27211 is often useful to define a default value for a discriminant even though
27212 it can't be changed by assignment.
27214 RM References: 3.07 (9.1/2) 3.07.02 (3)
27217 @geindex AI-0102 (Ada 2012 feature)
27223 @emph{AI-0102 Some implicit conversions are illegal (0000-00-00)}
27225 It is illegal to assign an anonymous access constant to an anonymous access
27226 variable. The RM did not have a clear rule to prevent this, but GNAT has
27227 always generated an error for this usage.
27229 RM References: 3.07 (16) 3.07.01 (9) 6.04.01 (6) 8.06 (27/2)
27232 @geindex AI-0158 (Ada 2012 feature)
27238 @emph{AI-0158 Generalizing membership tests (2010-09-16)}
27240 This AI extends the syntax of membership tests to simplify complex conditions
27241 that can be expressed as membership in a subset of values of any type. It
27242 introduces syntax for a list of expressions that may be used in loop contexts
27245 RM References: 3.08.01 (5) 4.04 (3) 4.05.02 (3) 4.05.02 (5) 4.05.02 (27)
27248 @geindex AI-0173 (Ada 2012 feature)
27254 @emph{AI-0173 Testing if tags represent abstract types (2010-07-03)}
27256 The function @code{Ada.Tags.Type_Is_Abstract} returns @code{True} if invoked
27257 with the tag of an abstract type, and @code{False} otherwise.
27259 RM References: 3.09 (7.4/2) 3.09 (12.4/2)
27262 @geindex AI-0076 (Ada 2012 feature)
27268 @emph{AI-0076 function with controlling result (0000-00-00)}
27270 This is an editorial change only. The RM defines calls with controlling
27271 results, but uses the term 'function with controlling result' without an
27272 explicit definition.
27274 RM References: 3.09.02 (2/2)
27277 @geindex AI-0126 (Ada 2012 feature)
27283 @emph{AI-0126 Dispatching with no declared operation (0000-00-00)}
27285 This AI clarifies dispatching rules, and simply confirms that dispatching
27286 executes the operation of the parent type when there is no explicitly or
27287 implicitly declared operation for the descendant type. This has always been
27288 the case in all versions of GNAT.
27290 RM References: 3.09.02 (20/2) 3.09.02 (20.1/2) 3.09.02 (20.2/2)
27293 @geindex AI-0097 (Ada 2012 feature)
27299 @emph{AI-0097 Treatment of abstract null extension (2010-07-19)}
27301 The RM as written implied that in some cases it was possible to create an
27302 object of an abstract type, by having an abstract extension inherit a non-
27303 abstract constructor from its parent type. This mistake has been corrected
27304 in GNAT and in the RM, and this construct is now illegal.
27306 RM References: 3.09.03 (4/2)
27309 @geindex AI-0203 (Ada 2012 feature)
27315 @emph{AI-0203 Extended return cannot be abstract (0000-00-00)}
27317 A return_subtype_indication cannot denote an abstract subtype. GNAT has never
27318 permitted such usage.
27320 RM References: 3.09.03 (8/3)
27323 @geindex AI-0198 (Ada 2012 feature)
27329 @emph{AI-0198 Inheriting abstract operators (0000-00-00)}
27331 This AI resolves a conflict between two rules involving inherited abstract
27332 operations and predefined operators. If a derived numeric type inherits
27333 an abstract operator, it overrides the predefined one. This interpretation
27334 was always the one implemented in GNAT.
27336 RM References: 3.09.03 (4/3)
27339 @geindex AI-0073 (Ada 2012 feature)
27345 @emph{AI-0073 Functions returning abstract types (2010-07-10)}
27347 This AI covers a number of issues regarding returning abstract types. In
27348 particular generic functions cannot have abstract result types or access
27349 result types designated an abstract type. There are some other cases which
27350 are detailed in the AI. Note that this binding interpretation has not been
27351 retrofitted to operate before Ada 2012 mode, since it caused a significant
27352 number of regressions.
27354 RM References: 3.09.03 (8) 3.09.03 (10) 6.05 (8/2)
27357 @geindex AI-0070 (Ada 2012 feature)
27363 @emph{AI-0070 Elaboration of interface types (0000-00-00)}
27365 This is an editorial change only, there are no testable consequences short of
27366 checking for the absence of generated code for an interface declaration.
27368 RM References: 3.09.04 (18/2)
27371 @geindex AI-0208 (Ada 2012 feature)
27377 @emph{AI-0208 Characteristics of incomplete views (0000-00-00)}
27379 The wording in the Ada 2005 RM concerning characteristics of incomplete views
27380 was incorrect and implied that some programs intended to be legal were now
27381 illegal. GNAT had never considered such programs illegal, so it has always
27382 implemented the intent of this AI.
27384 RM References: 3.10.01 (2.4/2) 3.10.01 (2.6/2)
27387 @geindex AI-0162 (Ada 2012 feature)
27393 @emph{AI-0162 Incomplete type completed by partial view (2010-09-15)}
27395 Incomplete types are made more useful by allowing them to be completed by
27396 private types and private extensions.
27398 RM References: 3.10.01 (2.5/2) 3.10.01 (2.6/2) 3.10.01 (3) 3.10.01 (4/2)
27401 @geindex AI-0098 (Ada 2012 feature)
27407 @emph{AI-0098 Anonymous subprogram access restrictions (0000-00-00)}
27409 An unintentional omission in the RM implied some inconsistent restrictions on
27410 the use of anonymous access to subprogram values. These restrictions were not
27411 intentional, and have never been enforced by GNAT.
27413 RM References: 3.10.01 (6) 3.10.01 (9.2/2)
27416 @geindex AI-0199 (Ada 2012 feature)
27422 @emph{AI-0199 Aggregate with anonymous access components (2010-07-14)}
27424 A choice list in a record aggregate can include several components of
27425 (distinct) anonymous access types as long as they have matching designated
27428 RM References: 4.03.01 (16)
27431 @geindex AI-0220 (Ada 2012 feature)
27437 @emph{AI-0220 Needed components for aggregates (0000-00-00)}
27439 This AI addresses a wording problem in the RM that appears to permit some
27440 complex cases of aggregates with nonstatic discriminants. GNAT has always
27441 implemented the intended semantics.
27443 RM References: 4.03.01 (17)
27446 @geindex AI-0147 (Ada 2012 feature)
27452 @emph{AI-0147 Conditional expressions (2009-03-29)}
27454 Conditional expressions are permitted. The form of such an expression is:
27457 (if expr then expr @{elsif expr then expr@} [else expr])
27460 The parentheses can be omitted in contexts where parentheses are present
27461 anyway, such as subprogram arguments and pragma arguments. If the @strong{else}
27462 clause is omitted, @strong{else} @emph{True} is assumed;
27463 thus @code{(if A then B)} is a way to conveniently represent
27464 @emph{(A implies B)} in standard logic.
27466 RM References: 4.03.03 (15) 4.04 (1) 4.04 (7) 4.05.07 (0) 4.07 (2)
27467 4.07 (3) 4.09 (12) 4.09 (33) 5.03 (3) 5.03 (4) 7.05 (2.1/2)
27470 @geindex AI-0037 (Ada 2012 feature)
27476 @emph{AI-0037 Out-of-range box associations in aggregate (0000-00-00)}
27478 This AI confirms that an association of the form @code{Indx => <>} in an
27479 array aggregate must raise @code{Constraint_Error} if @code{Indx}
27480 is out of range. The RM specified a range check on other associations, but
27481 not when the value of the association was defaulted. GNAT has always inserted
27482 a constraint check on the index value.
27484 RM References: 4.03.03 (29)
27487 @geindex AI-0123 (Ada 2012 feature)
27493 @emph{AI-0123 Composability of equality (2010-04-13)}
27495 Equality of untagged record composes, so that the predefined equality for a
27496 composite type that includes a component of some untagged record type
27497 @code{R} uses the equality operation of @code{R} (which may be user-defined
27498 or predefined). This makes the behavior of untagged records identical to that
27499 of tagged types in this respect.
27501 This change is an incompatibility with previous versions of Ada, but it
27502 corrects a non-uniformity that was often a source of confusion. Analysis of
27503 a large number of industrial programs indicates that in those rare cases
27504 where a composite type had an untagged record component with a user-defined
27505 equality, either there was no use of the composite equality, or else the code
27506 expected the same composability as for tagged types, and thus had a bug that
27507 would be fixed by this change.
27509 RM References: 4.05.02 (9.7/2) 4.05.02 (14) 4.05.02 (15) 4.05.02 (24)
27513 @geindex AI-0088 (Ada 2012 feature)
27519 @emph{AI-0088 The value of exponentiation (0000-00-00)}
27521 This AI clarifies the equivalence rule given for the dynamic semantics of
27522 exponentiation: the value of the operation can be obtained by repeated
27523 multiplication, but the operation can be implemented otherwise (for example
27524 using the familiar divide-by-two-and-square algorithm, even if this is less
27525 accurate), and does not imply repeated reads of a volatile base.
27527 RM References: 4.05.06 (11)
27530 @geindex AI-0188 (Ada 2012 feature)
27536 @emph{AI-0188 Case expressions (2010-01-09)}
27538 Case expressions are permitted. This allows use of constructs such as:
27541 X := (case Y is when 1 => 2, when 2 => 3, when others => 31)
27544 RM References: 4.05.07 (0) 4.05.08 (0) 4.09 (12) 4.09 (33)
27547 @geindex AI-0104 (Ada 2012 feature)
27553 @emph{AI-0104 Null exclusion and uninitialized allocator (2010-07-15)}
27555 The assignment @code{Ptr := new not null Some_Ptr;} will raise
27556 @code{Constraint_Error} because the default value of the allocated object is
27557 @strong{null}. This useless construct is illegal in Ada 2012.
27559 RM References: 4.08 (2)
27562 @geindex AI-0157 (Ada 2012 feature)
27568 @emph{AI-0157 Allocation/Deallocation from empty pool (2010-07-11)}
27570 Allocation and Deallocation from an empty storage pool (i.e. allocation or
27571 deallocation of a pointer for which a static storage size clause of zero
27572 has been given) is now illegal and is detected as such. GNAT
27573 previously gave a warning but not an error.
27575 RM References: 4.08 (5.3/2) 13.11.02 (4) 13.11.02 (17)
27578 @geindex AI-0179 (Ada 2012 feature)
27584 @emph{AI-0179 Statement not required after label (2010-04-10)}
27586 It is not necessary to have a statement following a label, so a label
27587 can appear at the end of a statement sequence without the need for putting a
27588 null statement afterwards, but it is not allowable to have only labels and
27589 no real statements in a statement sequence.
27591 RM References: 5.01 (2)
27594 @geindex AI-0139-2 (Ada 2012 feature)
27600 @emph{AI-0139-2 Syntactic sugar for iterators (2010-09-29)}
27602 The new syntax for iterating over arrays and containers is now implemented.
27603 Iteration over containers is for now limited to read-only iterators. Only
27604 default iterators are supported, with the syntax: @code{for Elem of C}.
27606 RM References: 5.05
27609 @geindex AI-0134 (Ada 2012 feature)
27615 @emph{AI-0134 Profiles must match for full conformance (0000-00-00)}
27617 For full conformance, the profiles of anonymous-access-to-subprogram
27618 parameters must match. GNAT has always enforced this rule.
27620 RM References: 6.03.01 (18)
27623 @geindex AI-0207 (Ada 2012 feature)
27629 @emph{AI-0207 Mode conformance and access constant (0000-00-00)}
27631 This AI confirms that access_to_constant indication must match for mode
27632 conformance. This was implemented in GNAT when the qualifier was originally
27633 introduced in Ada 2005.
27635 RM References: 6.03.01 (16/2)
27638 @geindex AI-0046 (Ada 2012 feature)
27644 @emph{AI-0046 Null exclusion match for full conformance (2010-07-17)}
27646 For full conformance, in the case of access parameters, the null exclusion
27647 must match (either both or neither must have @code{not null}).
27649 RM References: 6.03.02 (18)
27652 @geindex AI-0118 (Ada 2012 feature)
27658 @emph{AI-0118 The association of parameter associations (0000-00-00)}
27660 This AI clarifies the rules for named associations in subprogram calls and
27661 generic instantiations. The rules have been in place since Ada 83.
27663 RM References: 6.04.01 (2) 12.03 (9)
27666 @geindex AI-0196 (Ada 2012 feature)
27672 @emph{AI-0196 Null exclusion tests for out parameters (0000-00-00)}
27674 Null exclusion checks are not made for @code{out} parameters when
27675 evaluating the actual parameters. GNAT has never generated these checks.
27677 RM References: 6.04.01 (13)
27680 @geindex AI-0015 (Ada 2012 feature)
27686 @emph{AI-0015 Constant return objects (0000-00-00)}
27688 The return object declared in an @emph{extended_return_statement} may be
27689 declared constant. This was always intended, and GNAT has always allowed it.
27691 RM References: 6.05 (2.1/2) 3.03 (10/2) 3.03 (21) 6.05 (5/2)
27695 @geindex AI-0032 (Ada 2012 feature)
27701 @emph{AI-0032 Extended return for class-wide functions (0000-00-00)}
27703 If a function returns a class-wide type, the object of an extended return
27704 statement can be declared with a specific type that is covered by the class-
27705 wide type. This has been implemented in GNAT since the introduction of
27706 extended returns. Note AI-0103 complements this AI by imposing matching
27707 rules for constrained return types.
27709 RM References: 6.05 (5.2/2) 6.05 (5.3/2) 6.05 (5.6/2) 6.05 (5.8/2)
27713 @geindex AI-0103 (Ada 2012 feature)
27719 @emph{AI-0103 Static matching for extended return (2010-07-23)}
27721 If the return subtype of a function is an elementary type or a constrained
27722 type, the subtype indication in an extended return statement must match
27723 statically this return subtype.
27725 RM References: 6.05 (5.2/2)
27728 @geindex AI-0058 (Ada 2012 feature)
27734 @emph{AI-0058 Abnormal completion of an extended return (0000-00-00)}
27736 The RM had some incorrect wording implying wrong treatment of abnormal
27737 completion in an extended return. GNAT has always implemented the intended
27738 correct semantics as described by this AI.
27740 RM References: 6.05 (22/2)
27743 @geindex AI-0050 (Ada 2012 feature)
27749 @emph{AI-0050 Raising Constraint_Error early for function call (0000-00-00)}
27751 The implementation permissions for raising @code{Constraint_Error} early on a function call
27752 when it was clear an exception would be raised were over-permissive and allowed
27753 mishandling of discriminants in some cases. GNAT did
27754 not take advantage of these incorrect permissions in any case.
27756 RM References: 6.05 (24/2)
27759 @geindex AI-0125 (Ada 2012 feature)
27765 @emph{AI-0125 Nonoverridable operations of an ancestor (2010-09-28)}
27767 In Ada 2012, the declaration of a primitive operation of a type extension
27768 or private extension can also override an inherited primitive that is not
27769 visible at the point of this declaration.
27771 RM References: 7.03.01 (6) 8.03 (23) 8.03.01 (5/2) 8.03.01 (6/2)
27774 @geindex AI-0062 (Ada 2012 feature)
27780 @emph{AI-0062 Null exclusions and deferred constants (0000-00-00)}
27782 A full constant may have a null exclusion even if its associated deferred
27783 constant does not. GNAT has always allowed this.
27785 RM References: 7.04 (6/2) 7.04 (7.1/2)
27788 @geindex AI-0178 (Ada 2012 feature)
27794 @emph{AI-0178 Incomplete views are limited (0000-00-00)}
27796 This AI clarifies the role of incomplete views and plugs an omission in the
27797 RM. GNAT always correctly restricted the use of incomplete views and types.
27799 RM References: 7.05 (3/2) 7.05 (6/2)
27802 @geindex AI-0087 (Ada 2012 feature)
27808 @emph{AI-0087 Actual for formal nonlimited derived type (2010-07-15)}
27810 The actual for a formal nonlimited derived type cannot be limited. In
27811 particular, a formal derived type that extends a limited interface but which
27812 is not explicitly limited cannot be instantiated with a limited type.
27814 RM References: 7.05 (5/2) 12.05.01 (5.1/2)
27817 @geindex AI-0099 (Ada 2012 feature)
27823 @emph{AI-0099 Tag determines whether finalization needed (0000-00-00)}
27825 This AI clarifies that 'needs finalization' is part of dynamic semantics,
27826 and therefore depends on the run-time characteristics of an object (i.e. its
27827 tag) and not on its nominal type. As the AI indicates: "we do not expect
27828 this to affect any implementation'@w{'}.
27830 RM References: 7.06.01 (6) 7.06.01 (7) 7.06.01 (8) 7.06.01 (9/2)
27833 @geindex AI-0064 (Ada 2012 feature)
27839 @emph{AI-0064 Redundant finalization rule (0000-00-00)}
27841 This is an editorial change only. The intended behavior is already checked
27842 by an existing ACATS test, which GNAT has always executed correctly.
27844 RM References: 7.06.01 (17.1/1)
27847 @geindex AI-0026 (Ada 2012 feature)
27853 @emph{AI-0026 Missing rules for Unchecked_Union (2010-07-07)}
27855 Record representation clauses concerning Unchecked_Union types cannot mention
27856 the discriminant of the type. The type of a component declared in the variant
27857 part of an Unchecked_Union cannot be controlled, have controlled components,
27858 nor have protected or task parts. If an Unchecked_Union type is declared
27859 within the body of a generic unit or its descendants, then the type of a
27860 component declared in the variant part cannot be a formal private type or a
27861 formal private extension declared within the same generic unit.
27863 RM References: 7.06 (9.4/2) B.03.03 (9/2) B.03.03 (10/2)
27866 @geindex AI-0205 (Ada 2012 feature)
27872 @emph{AI-0205 Extended return declares visible name (0000-00-00)}
27874 This AI corrects a simple omission in the RM. Return objects have always
27875 been visible within an extended return statement.
27877 RM References: 8.03 (17)
27880 @geindex AI-0042 (Ada 2012 feature)
27886 @emph{AI-0042 Overriding versus implemented-by (0000-00-00)}
27888 This AI fixes a wording gap in the RM. An operation of a synchronized
27889 interface can be implemented by a protected or task entry, but the abstract
27890 operation is not being overridden in the usual sense, and it must be stated
27891 separately that this implementation is legal. This has always been the case
27894 RM References: 9.01 (9.2/2) 9.04 (11.1/2)
27897 @geindex AI-0030 (Ada 2012 feature)
27903 @emph{AI-0030 Requeue on synchronized interfaces (2010-07-19)}
27905 Requeue is permitted to a protected, synchronized or task interface primitive
27906 providing it is known that the overriding operation is an entry. Otherwise
27907 the requeue statement has the same effect as a procedure call. Use of pragma
27908 @code{Implemented} provides a way to impose a static requirement on the
27909 overriding operation by adhering to one of the implementation kinds: entry,
27910 protected procedure or any of the above.
27912 RM References: 9.05 (9) 9.05.04 (2) 9.05.04 (3) 9.05.04 (5)
27913 9.05.04 (6) 9.05.04 (7) 9.05.04 (12)
27916 @geindex AI-0201 (Ada 2012 feature)
27922 @emph{AI-0201 Independence of atomic object components (2010-07-22)}
27924 If an Atomic object has a pragma @code{Pack} or a @code{Component_Size}
27925 attribute, then individual components may not be addressable by independent
27926 tasks. However, if the representation clause has no effect (is confirming),
27927 then independence is not compromised. Furthermore, in GNAT, specification of
27928 other appropriately addressable component sizes (e.g. 16 for 8-bit
27929 characters) also preserves independence. GNAT now gives very clear warnings
27930 both for the declaration of such a type, and for any assignment to its components.
27932 RM References: 9.10 (1/3) C.06 (22/2) C.06 (23/2)
27935 @geindex AI-0009 (Ada 2012 feature)
27941 @emph{AI-0009 Pragma Independent[_Components] (2010-07-23)}
27943 This AI introduces the new pragmas @code{Independent} and
27944 @code{Independent_Components},
27945 which control guaranteeing independence of access to objects and components.
27946 The AI also requires independence not unaffected by confirming rep clauses.
27948 RM References: 9.10 (1) 13.01 (15/1) 13.02 (9) 13.03 (13) C.06 (2)
27949 C.06 (4) C.06 (6) C.06 (9) C.06 (13) C.06 (14)
27952 @geindex AI-0072 (Ada 2012 feature)
27958 @emph{AI-0072 Task signalling using 'Terminated (0000-00-00)}
27960 This AI clarifies that task signalling for reading @code{'Terminated} only
27961 occurs if the result is True. GNAT semantics has always been consistent with
27962 this notion of task signalling.
27964 RM References: 9.10 (6.1/1)
27967 @geindex AI-0108 (Ada 2012 feature)
27973 @emph{AI-0108 Limited incomplete view and discriminants (0000-00-00)}
27975 This AI confirms that an incomplete type from a limited view does not have
27976 discriminants. This has always been the case in GNAT.
27978 RM References: 10.01.01 (12.3/2)
27981 @geindex AI-0129 (Ada 2012 feature)
27987 @emph{AI-0129 Limited views and incomplete types (0000-00-00)}
27989 This AI clarifies the description of limited views: a limited view of a
27990 package includes only one view of a type that has an incomplete declaration
27991 and a full declaration (there is no possible ambiguity in a client package).
27992 This AI also fixes an omission: a nested package in the private part has no
27993 limited view. GNAT always implemented this correctly.
27995 RM References: 10.01.01 (12.2/2) 10.01.01 (12.3/2)
27998 @geindex AI-0077 (Ada 2012 feature)
28004 @emph{AI-0077 Limited withs and scope of declarations (0000-00-00)}
28006 This AI clarifies that a declaration does not include a context clause,
28007 and confirms that it is illegal to have a context in which both a limited
28008 and a nonlimited view of a package are accessible. Such double visibility
28009 was always rejected by GNAT.
28011 RM References: 10.01.02 (12/2) 10.01.02 (21/2) 10.01.02 (22/2)
28014 @geindex AI-0122 (Ada 2012 feature)
28020 @emph{AI-0122 Private with and children of generics (0000-00-00)}
28022 This AI clarifies the visibility of private children of generic units within
28023 instantiations of a parent. GNAT has always handled this correctly.
28025 RM References: 10.01.02 (12/2)
28028 @geindex AI-0040 (Ada 2012 feature)
28034 @emph{AI-0040 Limited with clauses on descendant (0000-00-00)}
28036 This AI confirms that a limited with clause in a child unit cannot name
28037 an ancestor of the unit. This has always been checked in GNAT.
28039 RM References: 10.01.02 (20/2)
28042 @geindex AI-0132 (Ada 2012 feature)
28048 @emph{AI-0132 Placement of library unit pragmas (0000-00-00)}
28050 This AI fills a gap in the description of library unit pragmas. The pragma
28051 clearly must apply to a library unit, even if it does not carry the name
28052 of the enclosing unit. GNAT has always enforced the required check.
28054 RM References: 10.01.05 (7)
28057 @geindex AI-0034 (Ada 2012 feature)
28063 @emph{AI-0034 Categorization of limited views (0000-00-00)}
28065 The RM makes certain limited with clauses illegal because of categorization
28066 considerations, when the corresponding normal with would be legal. This is
28067 not intended, and GNAT has always implemented the recommended behavior.
28069 RM References: 10.02.01 (11/1) 10.02.01 (17/2)
28072 @geindex AI-0035 (Ada 2012 feature)
28078 @emph{AI-0035 Inconsistencies with Pure units (0000-00-00)}
28080 This AI remedies some inconsistencies in the legality rules for Pure units.
28081 Derived access types are legal in a pure unit (on the assumption that the
28082 rule for a zero storage pool size has been enforced on the ancestor type).
28083 The rules are enforced in generic instances and in subunits. GNAT has always
28084 implemented the recommended behavior.
28086 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)
28089 @geindex AI-0219 (Ada 2012 feature)
28095 @emph{AI-0219 Pure permissions and limited parameters (2010-05-25)}
28097 This AI refines the rules for the cases with limited parameters which do not
28098 allow the implementations to omit 'redundant'. GNAT now properly conforms
28099 to the requirements of this binding interpretation.
28101 RM References: 10.02.01 (18/2)
28104 @geindex AI-0043 (Ada 2012 feature)
28110 @emph{AI-0043 Rules about raising exceptions (0000-00-00)}
28112 This AI covers various omissions in the RM regarding the raising of
28113 exceptions. GNAT has always implemented the intended semantics.
28115 RM References: 11.04.01 (10.1/2) 11 (2)
28118 @geindex AI-0200 (Ada 2012 feature)
28124 @emph{AI-0200 Mismatches in formal package declarations (0000-00-00)}
28126 This AI plugs a gap in the RM which appeared to allow some obviously intended
28127 illegal instantiations. GNAT has never allowed these instantiations.
28129 RM References: 12.07 (16)
28132 @geindex AI-0112 (Ada 2012 feature)
28138 @emph{AI-0112 Detection of duplicate pragmas (2010-07-24)}
28140 This AI concerns giving names to various representation aspects, but the
28141 practical effect is simply to make the use of duplicate
28142 @code{Atomic[_Components]},
28143 @code{Volatile[_Components]}, and
28144 @code{Independent[_Components]} pragmas illegal, and GNAT
28145 now performs this required check.
28147 RM References: 13.01 (8)
28150 @geindex AI-0106 (Ada 2012 feature)
28156 @emph{AI-0106 No representation pragmas on generic formals (0000-00-00)}
28158 The RM appeared to allow representation pragmas on generic formal parameters,
28159 but this was not intended, and GNAT has never permitted this usage.
28161 RM References: 13.01 (9.1/1)
28164 @geindex AI-0012 (Ada 2012 feature)
28170 @emph{AI-0012 Pack/Component_Size for aliased/atomic (2010-07-15)}
28172 It is now illegal to give an inappropriate component size or a pragma
28173 @code{Pack} that attempts to change the component size in the case of atomic
28174 or aliased components. Previously GNAT ignored such an attempt with a
28177 RM References: 13.02 (6.1/2) 13.02 (7) C.06 (10) C.06 (11) C.06 (21)
28180 @geindex AI-0039 (Ada 2012 feature)
28186 @emph{AI-0039 Stream attributes cannot be dynamic (0000-00-00)}
28188 The RM permitted the use of dynamic expressions (such as @code{ptr.all})`
28189 for stream attributes, but these were never useful and are now illegal. GNAT
28190 has always regarded such expressions as illegal.
28192 RM References: 13.03 (4) 13.03 (6) 13.13.02 (38/2)
28195 @geindex AI-0095 (Ada 2012 feature)
28201 @emph{AI-0095 Address of intrinsic subprograms (0000-00-00)}
28203 The prefix of @code{'Address} cannot statically denote a subprogram with
28204 convention @code{Intrinsic}. The use of the @code{Address} attribute raises
28205 @code{Program_Error} if the prefix denotes a subprogram with convention
28208 RM References: 13.03 (11/1)
28211 @geindex AI-0116 (Ada 2012 feature)
28217 @emph{AI-0116 Alignment of class-wide objects (0000-00-00)}
28219 This AI requires that the alignment of a class-wide object be no greater
28220 than the alignment of any type in the class. GNAT has always followed this
28223 RM References: 13.03 (29) 13.11 (16)
28226 @geindex AI-0146 (Ada 2012 feature)
28232 @emph{AI-0146 Type invariants (2009-09-21)}
28234 Type invariants may be specified for private types using the aspect notation.
28235 Aspect @code{Type_Invariant} may be specified for any private type,
28236 @code{Type_Invariant'Class} can
28237 only be specified for tagged types, and is inherited by any descendent of the
28238 tagged types. The invariant is a boolean expression that is tested for being
28239 true in the following situations: conversions to the private type, object
28240 declarations for the private type that are default initialized, and
28241 [@strong{in}] @strong{out}
28242 parameters and returned result on return from any primitive operation for
28243 the type that is visible to a client.
28244 GNAT defines the synonyms @code{Invariant} for @code{Type_Invariant} and
28245 @code{Invariant'Class} for @code{Type_Invariant'Class}.
28247 RM References: 13.03.03 (00)
28250 @geindex AI-0078 (Ada 2012 feature)
28256 @emph{AI-0078 Relax Unchecked_Conversion alignment rules (0000-00-00)}
28258 In Ada 2012, compilers are required to support unchecked conversion where the
28259 target alignment is a multiple of the source alignment. GNAT always supported
28260 this case (and indeed all cases of differing alignments, doing copies where
28261 required if the alignment was reduced).
28263 RM References: 13.09 (7)
28266 @geindex AI-0195 (Ada 2012 feature)
28272 @emph{AI-0195 Invalid value handling is implementation defined (2010-07-03)}
28274 The handling of invalid values is now designated to be implementation
28275 defined. This is a documentation change only, requiring Annex M in the GNAT
28276 Reference Manual to document this handling.
28277 In GNAT, checks for invalid values are made
28278 only when necessary to avoid erroneous behavior. Operations like assignments
28279 which cannot cause erroneous behavior ignore the possibility of invalid
28280 values and do not do a check. The date given above applies only to the
28281 documentation change, this behavior has always been implemented by GNAT.
28283 RM References: 13.09.01 (10)
28286 @geindex AI-0193 (Ada 2012 feature)
28292 @emph{AI-0193 Alignment of allocators (2010-09-16)}
28294 This AI introduces a new attribute @code{Max_Alignment_For_Allocation},
28295 analogous to @code{Max_Size_In_Storage_Elements}, but for alignment instead
28298 RM References: 13.11 (16) 13.11 (21) 13.11.01 (0) 13.11.01 (1)
28299 13.11.01 (2) 13.11.01 (3)
28302 @geindex AI-0177 (Ada 2012 feature)
28308 @emph{AI-0177 Parameterized expressions (2010-07-10)}
28310 The new Ada 2012 notion of parameterized expressions is implemented. The form
28314 function-specification is (expression)
28317 This is exactly equivalent to the
28318 corresponding function body that returns the expression, but it can appear
28319 in a package spec. Note that the expression must be parenthesized.
28321 RM References: 13.11.01 (3/2)
28324 @geindex AI-0033 (Ada 2012 feature)
28330 @emph{AI-0033 Attach/Interrupt_Handler in generic (2010-07-24)}
28332 Neither of these two pragmas may appear within a generic template, because
28333 the generic might be instantiated at other than the library level.
28335 RM References: 13.11.02 (16) C.03.01 (7/2) C.03.01 (8/2)
28338 @geindex AI-0161 (Ada 2012 feature)
28344 @emph{AI-0161 Restriction No_Default_Stream_Attributes (2010-09-11)}
28346 A new restriction @code{No_Default_Stream_Attributes} prevents the use of any
28347 of the default stream attributes for elementary types. If this restriction is
28348 in force, then it is necessary to provide explicit subprograms for any
28349 stream attributes used.
28351 RM References: 13.12.01 (4/2) 13.13.02 (40/2) 13.13.02 (52/2)
28354 @geindex AI-0194 (Ada 2012 feature)
28360 @emph{AI-0194 Value of Stream_Size attribute (0000-00-00)}
28362 The @code{Stream_Size} attribute returns the default number of bits in the
28363 stream representation of the given type.
28364 This value is not affected by the presence
28365 of stream subprogram attributes for the type. GNAT has always implemented
28366 this interpretation.
28368 RM References: 13.13.02 (1.2/2)
28371 @geindex AI-0109 (Ada 2012 feature)
28377 @emph{AI-0109 Redundant check in S'Class'Input (0000-00-00)}
28379 This AI is an editorial change only. It removes the need for a tag check
28380 that can never fail.
28382 RM References: 13.13.02 (34/2)
28385 @geindex AI-0007 (Ada 2012 feature)
28391 @emph{AI-0007 Stream read and private scalar types (0000-00-00)}
28393 The RM as written appeared to limit the possibilities of declaring read
28394 attribute procedures for private scalar types. This limitation was not
28395 intended, and has never been enforced by GNAT.
28397 RM References: 13.13.02 (50/2) 13.13.02 (51/2)
28400 @geindex AI-0065 (Ada 2012 feature)
28406 @emph{AI-0065 Remote access types and external streaming (0000-00-00)}
28408 This AI clarifies the fact that all remote access types support external
28409 streaming. This fixes an obvious oversight in the definition of the
28410 language, and GNAT always implemented the intended correct rules.
28412 RM References: 13.13.02 (52/2)
28415 @geindex AI-0019 (Ada 2012 feature)
28421 @emph{AI-0019 Freezing of primitives for tagged types (0000-00-00)}
28423 The RM suggests that primitive subprograms of a specific tagged type are
28424 frozen when the tagged type is frozen. This would be an incompatible change
28425 and is not intended. GNAT has never attempted this kind of freezing and its
28426 behavior is consistent with the recommendation of this AI.
28428 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)
28431 @geindex AI-0017 (Ada 2012 feature)
28437 @emph{AI-0017 Freezing and incomplete types (0000-00-00)}
28439 So-called 'Taft-amendment types' (i.e., types that are completed in package
28440 bodies) are not frozen by the occurrence of bodies in the
28441 enclosing declarative part. GNAT always implemented this properly.
28443 RM References: 13.14 (3/1)
28446 @geindex AI-0060 (Ada 2012 feature)
28452 @emph{AI-0060 Extended definition of remote access types (0000-00-00)}
28454 This AI extends the definition of remote access types to include access
28455 to limited, synchronized, protected or task class-wide interface types.
28456 GNAT already implemented this extension.
28458 RM References: A (4) E.02.02 (9/1) E.02.02 (9.2/1) E.02.02 (14/2) E.02.02 (18)
28461 @geindex AI-0114 (Ada 2012 feature)
28467 @emph{AI-0114 Classification of letters (0000-00-00)}
28469 The code points 170 (@code{FEMININE ORDINAL INDICATOR}),
28470 181 (@code{MICRO SIGN}), and
28471 186 (@code{MASCULINE ORDINAL INDICATOR}) are technically considered
28472 lower case letters by Unicode.
28473 However, they are not allowed in identifiers, and they
28474 return @code{False} to @code{Ada.Characters.Handling.Is_Letter/Is_Lower}.
28475 This behavior is consistent with that defined in Ada 95.
28477 RM References: A.03.02 (59) A.04.06 (7)
28480 @geindex AI-0185 (Ada 2012 feature)
28486 @emph{AI-0185 Ada.Wide_[Wide_]Characters.Handling (2010-07-06)}
28488 Two new packages @code{Ada.Wide_[Wide_]Characters.Handling} provide
28489 classification functions for @code{Wide_Character} and
28490 @code{Wide_Wide_Character}, as well as providing
28491 case folding routines for @code{Wide_[Wide_]Character} and
28492 @code{Wide_[Wide_]String}.
28494 RM References: A.03.05 (0) A.03.06 (0)
28497 @geindex AI-0031 (Ada 2012 feature)
28503 @emph{AI-0031 Add From parameter to Find_Token (2010-07-25)}
28505 A new version of @code{Find_Token} is added to all relevant string packages,
28506 with an extra parameter @code{From}. Instead of starting at the first
28507 character of the string, the search for a matching Token starts at the
28508 character indexed by the value of @code{From}.
28509 These procedures are available in all versions of Ada
28510 but if used in versions earlier than Ada 2012 they will generate a warning
28511 that an Ada 2012 subprogram is being used.
28513 RM References: A.04.03 (16) A.04.03 (67) A.04.03 (68/1) A.04.04 (51)
28517 @geindex AI-0056 (Ada 2012 feature)
28523 @emph{AI-0056 Index on null string returns zero (0000-00-00)}
28525 The wording in the Ada 2005 RM implied an incompatible handling of the
28526 @code{Index} functions, resulting in raising an exception instead of
28527 returning zero in some situations.
28528 This was not intended and has been corrected.
28529 GNAT always returned zero, and is thus consistent with this AI.
28531 RM References: A.04.03 (56.2/2) A.04.03 (58.5/2)
28534 @geindex AI-0137 (Ada 2012 feature)
28540 @emph{AI-0137 String encoding package (2010-03-25)}
28542 The packages @code{Ada.Strings.UTF_Encoding}, together with its child
28543 packages, @code{Conversions}, @code{Strings}, @code{Wide_Strings},
28544 and @code{Wide_Wide_Strings} have been
28545 implemented. These packages (whose documentation can be found in the spec
28546 files @code{a-stuten.ads}, @code{a-suenco.ads}, @code{a-suenst.ads},
28547 @code{a-suewst.ads}, @code{a-suezst.ads}) allow encoding and decoding of
28548 @code{String}, @code{Wide_String}, and @code{Wide_Wide_String}
28549 values using UTF coding schemes (including UTF-8, UTF-16LE, UTF-16BE, and
28550 UTF-16), as well as conversions between the different UTF encodings. With
28551 the exception of @code{Wide_Wide_Strings}, these packages are available in
28552 Ada 95 and Ada 2005 mode as well as Ada 2012 mode.
28553 The @code{Wide_Wide_Strings} package
28554 is available in Ada 2005 mode as well as Ada 2012 mode (but not in Ada 95
28555 mode since it uses @code{Wide_Wide_Character}).
28557 RM References: A.04.11
28560 @geindex AI-0038 (Ada 2012 feature)
28566 @emph{AI-0038 Minor errors in Text_IO (0000-00-00)}
28568 These are minor errors in the description on three points. The intent on
28569 all these points has always been clear, and GNAT has always implemented the
28570 correct intended semantics.
28572 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)
28575 @geindex AI-0044 (Ada 2012 feature)
28581 @emph{AI-0044 Restrictions on container instantiations (0000-00-00)}
28583 This AI places restrictions on allowed instantiations of generic containers.
28584 These restrictions are not checked by the compiler, so there is nothing to
28585 change in the implementation. This affects only the RM documentation.
28587 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)
28590 @geindex AI-0127 (Ada 2012 feature)
28596 @emph{AI-0127 Adding Locale Capabilities (2010-09-29)}
28598 This package provides an interface for identifying the current locale.
28600 RM References: A.19 A.19.01 A.19.02 A.19.03 A.19.05 A.19.06
28601 A.19.07 A.19.08 A.19.09 A.19.10 A.19.11 A.19.12 A.19.13
28604 @geindex AI-0002 (Ada 2012 feature)
28610 @emph{AI-0002 Export C with unconstrained arrays (0000-00-00)}
28612 The compiler is not required to support exporting an Ada subprogram with
28613 convention C if there are parameters or a return type of an unconstrained
28614 array type (such as @code{String}). GNAT allows such declarations but
28615 generates warnings. It is possible, but complicated, to write the
28616 corresponding C code and certainly such code would be specific to GNAT and
28619 RM References: B.01 (17) B.03 (62) B.03 (71.1/2)
28622 @geindex AI05-0216 (Ada 2012 feature)
28628 @emph{AI-0216 No_Task_Hierarchy forbids local tasks (0000-00-00)}
28630 It is clearly the intention that @code{No_Task_Hierarchy} is intended to
28631 forbid tasks declared locally within subprograms, or functions returning task
28632 objects, and that is the implementation that GNAT has always provided.
28633 However the language in the RM was not sufficiently clear on this point.
28634 Thus this is a documentation change in the RM only.
28636 RM References: D.07 (3/3)
28639 @geindex AI-0211 (Ada 2012 feature)
28645 @emph{AI-0211 No_Relative_Delays forbids Set_Handler use (2010-07-09)}
28647 The restriction @code{No_Relative_Delays} forbids any calls to the subprogram
28648 @code{Ada.Real_Time.Timing_Events.Set_Handler}.
28650 RM References: D.07 (5) D.07 (10/2) D.07 (10.4/2) D.07 (10.7/2)
28653 @geindex AI-0190 (Ada 2012 feature)
28659 @emph{AI-0190 pragma Default_Storage_Pool (2010-09-15)}
28661 This AI introduces a new pragma @code{Default_Storage_Pool}, which can be
28662 used to control storage pools globally.
28663 In particular, you can force every access
28664 type that is used for allocation (@strong{new}) to have an explicit storage pool,
28665 or you can declare a pool globally to be used for all access types that lack
28668 RM References: D.07 (8)
28671 @geindex AI-0189 (Ada 2012 feature)
28677 @emph{AI-0189 No_Allocators_After_Elaboration (2010-01-23)}
28679 This AI introduces a new restriction @code{No_Allocators_After_Elaboration},
28680 which says that no dynamic allocation will occur once elaboration is
28682 In general this requires a run-time check, which is not required, and which
28683 GNAT does not attempt. But the static cases of allocators in a task body or
28684 in the body of the main program are detected and flagged at compile or bind
28687 RM References: D.07 (19.1/2) H.04 (23.3/2)
28690 @geindex AI-0171 (Ada 2012 feature)
28696 @emph{AI-0171 Pragma CPU and Ravenscar Profile (2010-09-24)}
28698 A new package @code{System.Multiprocessors} is added, together with the
28699 definition of pragma @code{CPU} for controlling task affinity. A new no
28700 dependence restriction, on @code{System.Multiprocessors.Dispatching_Domains},
28701 is added to the Ravenscar profile.
28703 RM References: D.13.01 (4/2) D.16
28706 @geindex AI-0210 (Ada 2012 feature)
28712 @emph{AI-0210 Correct Timing_Events metric (0000-00-00)}
28714 This is a documentation only issue regarding wording of metric requirements,
28715 that does not affect the implementation of the compiler.
28717 RM References: D.15 (24/2)
28720 @geindex AI-0206 (Ada 2012 feature)
28726 @emph{AI-0206 Remote types packages and preelaborate (2010-07-24)}
28728 Remote types packages are now allowed to depend on preelaborated packages.
28729 This was formerly considered illegal.
28731 RM References: E.02.02 (6)
28734 @geindex AI-0152 (Ada 2012 feature)
28740 @emph{AI-0152 Restriction No_Anonymous_Allocators (2010-09-08)}
28742 Restriction @code{No_Anonymous_Allocators} prevents the use of allocators
28743 where the type of the returned value is an anonymous access type.
28745 RM References: H.04 (8/1)
28748 @node Obsolescent Features,Compatibility and Porting Guide,Implementation of Ada 2012 Features,Top
28749 @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}
28750 @chapter Obsolescent Features
28753 This chapter describes features that are provided by GNAT, but are
28754 considered obsolescent since there are preferred ways of achieving
28755 the same effect. These features are provided solely for historical
28756 compatibility purposes.
28759 * pragma No_Run_Time::
28760 * pragma Ravenscar::
28761 * pragma Restricted_Run_Time::
28762 * pragma Task_Info::
28763 * package System.Task_Info (s-tasinf.ads): package System Task_Info s-tasinf ads.
28767 @node pragma No_Run_Time,pragma Ravenscar,,Obsolescent Features
28768 @anchor{gnat_rm/obsolescent_features id2}@anchor{436}@anchor{gnat_rm/obsolescent_features pragma-no-run-time}@anchor{437}
28769 @section pragma No_Run_Time
28772 The pragma @code{No_Run_Time} is used to achieve an affect similar
28773 to the use of the "Zero Foot Print" configurable run time, but without
28774 requiring a specially configured run time. The result of using this
28775 pragma, which must be used for all units in a partition, is to restrict
28776 the use of any language features requiring run-time support code. The
28777 preferred usage is to use an appropriately configured run-time that
28778 includes just those features that are to be made accessible.
28780 @node pragma Ravenscar,pragma Restricted_Run_Time,pragma No_Run_Time,Obsolescent Features
28781 @anchor{gnat_rm/obsolescent_features id3}@anchor{438}@anchor{gnat_rm/obsolescent_features pragma-ravenscar}@anchor{439}
28782 @section pragma Ravenscar
28785 The pragma @code{Ravenscar} has exactly the same effect as pragma
28786 @code{Profile (Ravenscar)}. The latter usage is preferred since it
28787 is part of the new Ada 2005 standard.
28789 @node pragma Restricted_Run_Time,pragma Task_Info,pragma Ravenscar,Obsolescent Features
28790 @anchor{gnat_rm/obsolescent_features pragma-restricted-run-time}@anchor{43a}@anchor{gnat_rm/obsolescent_features id4}@anchor{43b}
28791 @section pragma Restricted_Run_Time
28794 The pragma @code{Restricted_Run_Time} has exactly the same effect as
28795 pragma @code{Profile (Restricted)}. The latter usage is
28796 preferred since the Ada 2005 pragma @code{Profile} is intended for
28797 this kind of implementation dependent addition.
28799 @node pragma Task_Info,package System Task_Info s-tasinf ads,pragma Restricted_Run_Time,Obsolescent Features
28800 @anchor{gnat_rm/obsolescent_features pragma-task-info}@anchor{43c}@anchor{gnat_rm/obsolescent_features id5}@anchor{43d}
28801 @section pragma Task_Info
28804 The functionality provided by pragma @code{Task_Info} is now part of the
28805 Ada language. The @code{CPU} aspect and the package
28806 @code{System.Multiprocessors} offer a less system-dependent way to specify
28807 task affinity or to query the number of processors.
28812 pragma Task_Info (EXPRESSION);
28815 This pragma appears within a task definition (like pragma
28816 @code{Priority}) and applies to the task in which it appears. The
28817 argument must be of type @code{System.Task_Info.Task_Info_Type}.
28818 The @code{Task_Info} pragma provides system dependent control over
28819 aspects of tasking implementation, for example, the ability to map
28820 tasks to specific processors. For details on the facilities available
28821 for the version of GNAT that you are using, see the documentation
28822 in the spec of package System.Task_Info in the runtime
28825 @node package System Task_Info s-tasinf ads,,pragma Task_Info,Obsolescent Features
28826 @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}
28827 @section package System.Task_Info (@code{s-tasinf.ads})
28830 This package provides target dependent functionality that is used
28831 to support the @code{Task_Info} pragma. The predefined Ada package
28832 @code{System.Multiprocessors} and the @code{CPU} aspect now provide a
28833 standard replacement for GNAT's @code{Task_Info} functionality.
28835 @node Compatibility and Porting Guide,GNU Free Documentation License,Obsolescent Features,Top
28836 @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}
28837 @chapter Compatibility and Porting Guide
28840 This chapter presents some guidelines for developing portable Ada code,
28841 describes the compatibility issues that may arise between
28842 GNAT and other Ada compilation systems (including those for Ada 83),
28843 and shows how GNAT can expedite porting
28844 applications developed in other Ada environments.
28847 * Writing Portable Fixed-Point Declarations::
28848 * Compatibility with Ada 83::
28849 * Compatibility between Ada 95 and Ada 2005::
28850 * Implementation-dependent characteristics::
28851 * Compatibility with Other Ada Systems::
28852 * Representation Clauses::
28853 * Compatibility with HP Ada 83::
28857 @node Writing Portable Fixed-Point Declarations,Compatibility with Ada 83,,Compatibility and Porting Guide
28858 @anchor{gnat_rm/compatibility_and_porting_guide id2}@anchor{442}@anchor{gnat_rm/compatibility_and_porting_guide writing-portable-fixed-point-declarations}@anchor{443}
28859 @section Writing Portable Fixed-Point Declarations
28862 The Ada Reference Manual gives an implementation freedom to choose bounds
28863 that are narrower by @code{Small} from the given bounds.
28864 For example, if we write
28867 type F1 is delta 1.0 range -128.0 .. +128.0;
28870 then the implementation is allowed to choose -128.0 .. +127.0 if it
28871 likes, but is not required to do so.
28873 This leads to possible portability problems, so let's have a closer
28874 look at this, and figure out how to avoid these problems.
28876 First, why does this freedom exist, and why would an implementation
28877 take advantage of it? To answer this, take a closer look at the type
28878 declaration for @code{F1} above. If the compiler uses the given bounds,
28879 it would need 9 bits to hold the largest positive value (and typically
28880 that means 16 bits on all machines). But if the implementation chooses
28881 the +127.0 bound then it can fit values of the type in 8 bits.
28883 Why not make the user write +127.0 if that's what is wanted?
28884 The rationale is that if you are thinking of fixed point
28885 as a kind of 'poor man's floating-point', then you don't want
28886 to be thinking about the scaled integers that are used in its
28887 representation. Let's take another example:
28890 type F2 is delta 2.0**(-15) range -1.0 .. +1.0;
28893 Looking at this declaration, it seems casually as though
28894 it should fit in 16 bits, but again that extra positive value
28895 +1.0 has the scaled integer equivalent of 2**15 which is one too
28896 big for signed 16 bits. The implementation can treat this as:
28899 type F2 is delta 2.0**(-15) range -1.0 .. +1.0-(2.0**(-15));
28902 and the Ada language design team felt that this was too annoying
28903 to require. We don't need to debate this decision at this point,
28904 since it is well established (the rule about narrowing the ranges
28907 But the important point is that an implementation is not required
28908 to do this narrowing, so we have a potential portability problem.
28909 We could imagine three types of implementation:
28915 those that narrow the range automatically if they can figure
28916 out that the narrower range will allow storage in a smaller machine unit,
28919 those that will narrow only if forced to by a @code{'Size} clause, and
28922 those that will never narrow.
28925 Now if we are language theoreticians, we can imagine a fourth
28926 approach: to narrow all the time, e.g. to treat
28929 type F3 is delta 1.0 range -10.0 .. +23.0;
28932 as though it had been written:
28935 type F3 is delta 1.0 range -9.0 .. +22.0;
28938 But although technically allowed, such a behavior would be hostile and silly,
28939 and no real compiler would do this. All real compilers will fall into one of
28940 the categories (a), (b) or (c) above.
28942 So, how do you get the compiler to do what you want? The answer is give the
28943 actual bounds you want, and then use a @code{'Small} clause and a
28944 @code{'Size} clause to absolutely pin down what the compiler does.
28945 E.g., for @code{F2} above, we will write:
28948 My_Small : constant := 2.0**(-15);
28949 My_First : constant := -1.0;
28950 My_Last : constant := +1.0 - My_Small;
28952 type F2 is delta My_Small range My_First .. My_Last;
28958 for F2'Small use my_Small;
28959 for F2'Size use 16;
28962 In practice all compilers will do the same thing here and will give you
28963 what you want, so the above declarations are fully portable. If you really
28964 want to play language lawyer and guard against ludicrous behavior by the
28965 compiler you could add
28968 Test1 : constant := 1 / Boolean'Pos (F2'First = My_First);
28969 Test2 : constant := 1 / Boolean'Pos (F2'Last = My_Last);
28972 One or other or both are allowed to be illegal if the compiler is
28973 behaving in a silly manner, but at least the silly compiler will not
28974 get away with silently messing with your (very clear) intentions.
28976 If you follow this scheme you will be guaranteed that your fixed-point
28977 types will be portable.
28979 @node Compatibility with Ada 83,Compatibility between Ada 95 and Ada 2005,Writing Portable Fixed-Point Declarations,Compatibility and Porting Guide
28980 @anchor{gnat_rm/compatibility_and_porting_guide compatibility-with-ada-83}@anchor{444}@anchor{gnat_rm/compatibility_and_porting_guide id3}@anchor{445}
28981 @section Compatibility with Ada 83
28984 @geindex Compatibility (between Ada 83 and Ada 95 / Ada 2005 / Ada 2012)
28986 Ada 95 and the subsequent revisions Ada 2005 and Ada 2012
28987 are highly upwards compatible with Ada 83. In
28988 particular, the design intention was that the difficulties associated
28989 with moving from Ada 83 to later versions of the standard should be no greater
28990 than those that occur when moving from one Ada 83 system to another.
28992 However, there are a number of points at which there are minor
28993 incompatibilities. The @cite{Ada 95 Annotated Reference Manual} contains
28994 full details of these issues as they relate to Ada 95,
28995 and should be consulted for a complete treatment.
28997 following subsections treat the most likely issues to be encountered.
29000 * Legal Ada 83 programs that are illegal in Ada 95::
29001 * More deterministic semantics::
29002 * Changed semantics::
29003 * Other language compatibility issues::
29007 @node Legal Ada 83 programs that are illegal in Ada 95,More deterministic semantics,,Compatibility with Ada 83
29008 @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}
29009 @subsection Legal Ada 83 programs that are illegal in Ada 95
29012 Some legal Ada 83 programs are illegal (i.e., they will fail to compile) in
29013 Ada 95 and later versions of the standard:
29019 @emph{Character literals}
29021 Some uses of character literals are ambiguous. Since Ada 95 has introduced
29022 @code{Wide_Character} as a new predefined character type, some uses of
29023 character literals that were legal in Ada 83 are illegal in Ada 95.
29027 for Char in 'A' .. 'Z' loop ... end loop;
29030 The problem is that 'A' and 'Z' could be from either
29031 @code{Character} or @code{Wide_Character}. The simplest correction
29032 is to make the type explicit; e.g.:
29035 for Char in Character range 'A' .. 'Z' loop ... end loop;
29039 @emph{New reserved words}
29041 The identifiers @code{abstract}, @code{aliased}, @code{protected},
29042 @code{requeue}, @code{tagged}, and @code{until} are reserved in Ada 95.
29043 Existing Ada 83 code using any of these identifiers must be edited to
29044 use some alternative name.
29047 @emph{Freezing rules}
29049 The rules in Ada 95 are slightly different with regard to the point at
29050 which entities are frozen, and representation pragmas and clauses are
29051 not permitted past the freeze point. This shows up most typically in
29052 the form of an error message complaining that a representation item
29053 appears too late, and the appropriate corrective action is to move
29054 the item nearer to the declaration of the entity to which it refers.
29056 A particular case is that representation pragmas
29057 cannot be applied to a subprogram body. If necessary, a separate subprogram
29058 declaration must be introduced to which the pragma can be applied.
29061 @emph{Optional bodies for library packages}
29063 In Ada 83, a package that did not require a package body was nevertheless
29064 allowed to have one. This lead to certain surprises in compiling large
29065 systems (situations in which the body could be unexpectedly ignored by the
29066 binder). In Ada 95, if a package does not require a body then it is not
29067 permitted to have a body. To fix this problem, simply remove a redundant
29068 body if it is empty, or, if it is non-empty, introduce a dummy declaration
29069 into the spec that makes the body required. One approach is to add a private
29070 part to the package declaration (if necessary), and define a parameterless
29071 procedure called @code{Requires_Body}, which must then be given a dummy
29072 procedure body in the package body, which then becomes required.
29073 Another approach (assuming that this does not introduce elaboration
29074 circularities) is to add an @code{Elaborate_Body} pragma to the package spec,
29075 since one effect of this pragma is to require the presence of a package body.
29078 @emph{Numeric_Error is the same exception as Constraint_Error}
29080 In Ada 95, the exception @code{Numeric_Error} is a renaming of @code{Constraint_Error}.
29081 This means that it is illegal to have separate exception handlers for
29082 the two exceptions. The fix is simply to remove the handler for the
29083 @code{Numeric_Error} case (since even in Ada 83, a compiler was free to raise
29084 @code{Constraint_Error} in place of @code{Numeric_Error} in all cases).
29087 @emph{Indefinite subtypes in generics}
29089 In Ada 83, it was permissible to pass an indefinite type (e.g, @code{String})
29090 as the actual for a generic formal private type, but then the instantiation
29091 would be illegal if there were any instances of declarations of variables
29092 of this type in the generic body. In Ada 95, to avoid this clear violation
29093 of the methodological principle known as the 'contract model',
29094 the generic declaration explicitly indicates whether
29095 or not such instantiations are permitted. If a generic formal parameter
29096 has explicit unknown discriminants, indicated by using @code{(<>)} after the
29097 subtype name, then it can be instantiated with indefinite types, but no
29098 stand-alone variables can be declared of this type. Any attempt to declare
29099 such a variable will result in an illegality at the time the generic is
29100 declared. If the @code{(<>)} notation is not used, then it is illegal
29101 to instantiate the generic with an indefinite type.
29102 This is the potential incompatibility issue when porting Ada 83 code to Ada 95.
29103 It will show up as a compile time error, and
29104 the fix is usually simply to add the @code{(<>)} to the generic declaration.
29107 @node More deterministic semantics,Changed semantics,Legal Ada 83 programs that are illegal in Ada 95,Compatibility with Ada 83
29108 @anchor{gnat_rm/compatibility_and_porting_guide more-deterministic-semantics}@anchor{448}@anchor{gnat_rm/compatibility_and_porting_guide id5}@anchor{449}
29109 @subsection More deterministic semantics
29118 Conversions from real types to integer types round away from 0. In Ada 83
29119 the conversion Integer(2.5) could deliver either 2 or 3 as its value. This
29120 implementation freedom was intended to support unbiased rounding in
29121 statistical applications, but in practice it interfered with portability.
29122 In Ada 95 the conversion semantics are unambiguous, and rounding away from 0
29123 is required. Numeric code may be affected by this change in semantics.
29124 Note, though, that this issue is no worse than already existed in Ada 83
29125 when porting code from one vendor to another.
29130 The Real-Time Annex introduces a set of policies that define the behavior of
29131 features that were implementation dependent in Ada 83, such as the order in
29132 which open select branches are executed.
29135 @node Changed semantics,Other language compatibility issues,More deterministic semantics,Compatibility with Ada 83
29136 @anchor{gnat_rm/compatibility_and_porting_guide id6}@anchor{44a}@anchor{gnat_rm/compatibility_and_porting_guide changed-semantics}@anchor{44b}
29137 @subsection Changed semantics
29140 The worst kind of incompatibility is one where a program that is legal in
29141 Ada 83 is also legal in Ada 95 but can have an effect in Ada 95 that was not
29142 possible in Ada 83. Fortunately this is extremely rare, but the one
29143 situation that you should be alert to is the change in the predefined type
29144 @code{Character} from 7-bit ASCII to 8-bit Latin-1.
29155 @emph{Range of type `@w{`}Character`@w{`}}
29157 The range of @code{Standard.Character} is now the full 256 characters
29158 of Latin-1, whereas in most Ada 83 implementations it was restricted
29159 to 128 characters. Although some of the effects of
29160 this change will be manifest in compile-time rejection of legal
29161 Ada 83 programs it is possible for a working Ada 83 program to have
29162 a different effect in Ada 95, one that was not permitted in Ada 83.
29163 As an example, the expression
29164 @code{Character'Pos(Character'Last)} returned @code{127} in Ada 83 and now
29165 delivers @code{255} as its value.
29166 In general, you should look at the logic of any
29167 character-processing Ada 83 program and see whether it needs to be adapted
29168 to work correctly with Latin-1. Note that the predefined Ada 95 API has a
29169 character handling package that may be relevant if code needs to be adapted
29170 to account for the additional Latin-1 elements.
29171 The desirable fix is to
29172 modify the program to accommodate the full character set, but in some cases
29173 it may be convenient to define a subtype or derived type of Character that
29174 covers only the restricted range.
29177 @node Other language compatibility issues,,Changed semantics,Compatibility with Ada 83
29178 @anchor{gnat_rm/compatibility_and_porting_guide other-language-compatibility-issues}@anchor{44c}@anchor{gnat_rm/compatibility_and_porting_guide id7}@anchor{44d}
29179 @subsection Other language compatibility issues
29186 @emph{-gnat83} switch
29188 All implementations of GNAT provide a switch that causes GNAT to operate
29189 in Ada 83 mode. In this mode, some but not all compatibility problems
29190 of the type described above are handled automatically. For example, the
29191 new reserved words introduced in Ada 95 and Ada 2005 are treated simply
29192 as identifiers as in Ada 83. However,
29193 in practice, it is usually advisable to make the necessary modifications
29194 to the program to remove the need for using this switch.
29195 See the @code{Compiling Different Versions of Ada} section in
29196 the @cite{GNAT User's Guide}.
29199 Support for removed Ada 83 pragmas and attributes
29201 A number of pragmas and attributes from Ada 83 were removed from Ada 95,
29202 generally because they were replaced by other mechanisms. Ada 95 and Ada 2005
29203 compilers are allowed, but not required, to implement these missing
29204 elements. In contrast with some other compilers, GNAT implements all
29205 such pragmas and attributes, eliminating this compatibility concern. These
29206 include @code{pragma Interface} and the floating point type attributes
29207 (@code{Emax}, @code{Mantissa}, etc.), among other items.
29210 @node Compatibility between Ada 95 and Ada 2005,Implementation-dependent characteristics,Compatibility with Ada 83,Compatibility and Porting Guide
29211 @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}
29212 @section Compatibility between Ada 95 and Ada 2005
29215 @geindex Compatibility between Ada 95 and Ada 2005
29217 Although Ada 2005 was designed to be upwards compatible with Ada 95, there are
29218 a number of incompatibilities. Several are enumerated below;
29219 for a complete description please see the
29220 @cite{Annotated Ada 2005 Reference Manual}, or section 9.1.1 in
29221 @cite{Rationale for Ada 2005}.
29227 @emph{New reserved words.}
29229 The words @code{interface}, @code{overriding} and @code{synchronized} are
29230 reserved in Ada 2005.
29231 A pre-Ada 2005 program that uses any of these as an identifier will be
29235 @emph{New declarations in predefined packages.}
29237 A number of packages in the predefined environment contain new declarations:
29238 @code{Ada.Exceptions}, @code{Ada.Real_Time}, @code{Ada.Strings},
29239 @code{Ada.Strings.Fixed}, @code{Ada.Strings.Bounded},
29240 @code{Ada.Strings.Unbounded}, @code{Ada.Strings.Wide_Fixed},
29241 @code{Ada.Strings.Wide_Bounded}, @code{Ada.Strings.Wide_Unbounded},
29242 @code{Ada.Tags}, @code{Ada.Text_IO}, and @code{Interfaces.C}.
29243 If an Ada 95 program does a @code{with} and @code{use} of any of these
29244 packages, the new declarations may cause name clashes.
29247 @emph{Access parameters.}
29249 A nondispatching subprogram with an access parameter cannot be renamed
29250 as a dispatching operation. This was permitted in Ada 95.
29253 @emph{Access types, discriminants, and constraints.}
29255 Rule changes in this area have led to some incompatibilities; for example,
29256 constrained subtypes of some access types are not permitted in Ada 2005.
29259 @emph{Aggregates for limited types.}
29261 The allowance of aggregates for limited types in Ada 2005 raises the
29262 possibility of ambiguities in legal Ada 95 programs, since additional types
29263 now need to be considered in expression resolution.
29266 @emph{Fixed-point multiplication and division.}
29268 Certain expressions involving '*' or '/' for a fixed-point type, which
29269 were legal in Ada 95 and invoked the predefined versions of these operations,
29271 The ambiguity may be resolved either by applying a type conversion to the
29272 expression, or by explicitly invoking the operation from package
29276 @emph{Return-by-reference types.}
29278 The Ada 95 return-by-reference mechanism has been removed. Instead, the user
29279 can declare a function returning a value from an anonymous access type.
29282 @node Implementation-dependent characteristics,Compatibility with Other Ada Systems,Compatibility between Ada 95 and Ada 2005,Compatibility and Porting Guide
29283 @anchor{gnat_rm/compatibility_and_porting_guide implementation-dependent-characteristics}@anchor{450}@anchor{gnat_rm/compatibility_and_porting_guide id9}@anchor{451}
29284 @section Implementation-dependent characteristics
29287 Although the Ada language defines the semantics of each construct as
29288 precisely as practical, in some situations (for example for reasons of
29289 efficiency, or where the effect is heavily dependent on the host or target
29290 platform) the implementation is allowed some freedom. In porting Ada 83
29291 code to GNAT, you need to be aware of whether / how the existing code
29292 exercised such implementation dependencies. Such characteristics fall into
29293 several categories, and GNAT offers specific support in assisting the
29294 transition from certain Ada 83 compilers.
29297 * Implementation-defined pragmas::
29298 * Implementation-defined attributes::
29300 * Elaboration order::
29301 * Target-specific aspects::
29305 @node Implementation-defined pragmas,Implementation-defined attributes,,Implementation-dependent characteristics
29306 @anchor{gnat_rm/compatibility_and_porting_guide implementation-defined-pragmas}@anchor{452}@anchor{gnat_rm/compatibility_and_porting_guide id10}@anchor{453}
29307 @subsection Implementation-defined pragmas
29310 Ada compilers are allowed to supplement the language-defined pragmas, and
29311 these are a potential source of non-portability. All GNAT-defined pragmas
29312 are described in @ref{7,,Implementation Defined Pragmas},
29313 and these include several that are specifically
29314 intended to correspond to other vendors' Ada 83 pragmas.
29315 For migrating from VADS, the pragma @code{Use_VADS_Size} may be useful.
29316 For compatibility with HP Ada 83, GNAT supplies the pragmas
29317 @code{Extend_System}, @code{Ident}, @code{Inline_Generic},
29318 @code{Interface_Name}, @code{Passive}, @code{Suppress_All},
29319 and @code{Volatile}.
29320 Other relevant pragmas include @code{External} and @code{Link_With}.
29321 Some vendor-specific
29322 Ada 83 pragmas (@code{Share_Generic}, @code{Subtitle}, and @code{Title}) are
29324 avoiding compiler rejection of units that contain such pragmas; they are not
29325 relevant in a GNAT context and hence are not otherwise implemented.
29327 @node Implementation-defined attributes,Libraries,Implementation-defined pragmas,Implementation-dependent characteristics
29328 @anchor{gnat_rm/compatibility_and_porting_guide id11}@anchor{454}@anchor{gnat_rm/compatibility_and_porting_guide implementation-defined-attributes}@anchor{455}
29329 @subsection Implementation-defined attributes
29332 Analogous to pragmas, the set of attributes may be extended by an
29333 implementation. All GNAT-defined attributes are described in
29334 @ref{8,,Implementation Defined Attributes},
29335 and these include several that are specifically intended
29336 to correspond to other vendors' Ada 83 attributes. For migrating from VADS,
29337 the attribute @code{VADS_Size} may be useful. For compatibility with HP
29338 Ada 83, GNAT supplies the attributes @code{Bit}, @code{Machine_Size} and
29341 @node Libraries,Elaboration order,Implementation-defined attributes,Implementation-dependent characteristics
29342 @anchor{gnat_rm/compatibility_and_porting_guide libraries}@anchor{456}@anchor{gnat_rm/compatibility_and_porting_guide id12}@anchor{457}
29343 @subsection Libraries
29346 Vendors may supply libraries to supplement the standard Ada API. If Ada 83
29347 code uses vendor-specific libraries then there are several ways to manage
29348 this in Ada 95 and later versions of the standard:
29354 If the source code for the libraries (specs and bodies) are
29355 available, then the libraries can be migrated in the same way as the
29359 If the source code for the specs but not the bodies are
29360 available, then you can reimplement the bodies.
29363 Some features introduced by Ada 95 obviate the need for library support. For
29364 example most Ada 83 vendors supplied a package for unsigned integers. The
29365 Ada 95 modular type feature is the preferred way to handle this need, so
29366 instead of migrating or reimplementing the unsigned integer package it may
29367 be preferable to retrofit the application using modular types.
29370 @node Elaboration order,Target-specific aspects,Libraries,Implementation-dependent characteristics
29371 @anchor{gnat_rm/compatibility_and_porting_guide elaboration-order}@anchor{458}@anchor{gnat_rm/compatibility_and_porting_guide id13}@anchor{459}
29372 @subsection Elaboration order
29375 The implementation can choose any elaboration order consistent with the unit
29376 dependency relationship. This freedom means that some orders can result in
29377 Program_Error being raised due to an 'Access Before Elaboration': an attempt
29378 to invoke a subprogram before its body has been elaborated, or to instantiate
29379 a generic before the generic body has been elaborated. By default GNAT
29380 attempts to choose a safe order (one that will not encounter access before
29381 elaboration problems) by implicitly inserting @code{Elaborate} or
29382 @code{Elaborate_All} pragmas where
29383 needed. However, this can lead to the creation of elaboration circularities
29384 and a resulting rejection of the program by gnatbind. This issue is
29385 thoroughly described in the @emph{Elaboration Order Handling in GNAT} appendix
29386 in the @cite{GNAT User's Guide}.
29387 In brief, there are several
29388 ways to deal with this situation:
29394 Modify the program to eliminate the circularities, e.g., by moving
29395 elaboration-time code into explicitly-invoked procedures
29398 Constrain the elaboration order by including explicit @code{Elaborate_Body} or
29399 @code{Elaborate} pragmas, and then inhibit the generation of implicit
29400 @code{Elaborate_All}
29401 pragmas either globally (as an effect of the @emph{-gnatE} switch) or locally
29402 (by selectively suppressing elaboration checks via pragma
29403 @code{Suppress(Elaboration_Check)} when it is safe to do so).
29406 @node Target-specific aspects,,Elaboration order,Implementation-dependent characteristics
29407 @anchor{gnat_rm/compatibility_and_porting_guide target-specific-aspects}@anchor{45a}@anchor{gnat_rm/compatibility_and_porting_guide id14}@anchor{45b}
29408 @subsection Target-specific aspects
29411 Low-level applications need to deal with machine addresses, data
29412 representations, interfacing with assembler code, and similar issues. If
29413 such an Ada 83 application is being ported to different target hardware (for
29414 example where the byte endianness has changed) then you will need to
29415 carefully examine the program logic; the porting effort will heavily depend
29416 on the robustness of the original design. Moreover, Ada 95 (and thus
29417 Ada 2005 and Ada 2012) are sometimes
29418 incompatible with typical Ada 83 compiler practices regarding implicit
29419 packing, the meaning of the Size attribute, and the size of access values.
29420 GNAT's approach to these issues is described in @ref{45c,,Representation Clauses}.
29422 @node Compatibility with Other Ada Systems,Representation Clauses,Implementation-dependent characteristics,Compatibility and Porting Guide
29423 @anchor{gnat_rm/compatibility_and_porting_guide id15}@anchor{45d}@anchor{gnat_rm/compatibility_and_porting_guide compatibility-with-other-ada-systems}@anchor{45e}
29424 @section Compatibility with Other Ada Systems
29427 If programs avoid the use of implementation dependent and
29428 implementation defined features, as documented in the
29429 @cite{Ada Reference Manual}, there should be a high degree of portability between
29430 GNAT and other Ada systems. The following are specific items which
29431 have proved troublesome in moving Ada 95 programs from GNAT to other Ada 95
29432 compilers, but do not affect porting code to GNAT.
29433 (As of January 2007, GNAT is the only compiler available for Ada 2005;
29434 the following issues may or may not arise for Ada 2005 programs
29435 when other compilers appear.)
29441 @emph{Ada 83 Pragmas and Attributes}
29443 Ada 95 compilers are allowed, but not required, to implement the missing
29444 Ada 83 pragmas and attributes that are no longer defined in Ada 95.
29445 GNAT implements all such pragmas and attributes, eliminating this as
29446 a compatibility concern, but some other Ada 95 compilers reject these
29447 pragmas and attributes.
29450 @emph{Specialized Needs Annexes}
29452 GNAT implements the full set of special needs annexes. At the
29453 current time, it is the only Ada 95 compiler to do so. This means that
29454 programs making use of these features may not be portable to other Ada
29455 95 compilation systems.
29458 @emph{Representation Clauses}
29460 Some other Ada 95 compilers implement only the minimal set of
29461 representation clauses required by the Ada 95 reference manual. GNAT goes
29462 far beyond this minimal set, as described in the next section.
29465 @node Representation Clauses,Compatibility with HP Ada 83,Compatibility with Other Ada Systems,Compatibility and Porting Guide
29466 @anchor{gnat_rm/compatibility_and_porting_guide representation-clauses}@anchor{45c}@anchor{gnat_rm/compatibility_and_porting_guide id16}@anchor{45f}
29467 @section Representation Clauses
29470 The Ada 83 reference manual was quite vague in describing both the minimal
29471 required implementation of representation clauses, and also their precise
29472 effects. Ada 95 (and thus also Ada 2005) are much more explicit, but the
29473 minimal set of capabilities required is still quite limited.
29475 GNAT implements the full required set of capabilities in
29476 Ada 95 and Ada 2005, but also goes much further, and in particular
29477 an effort has been made to be compatible with existing Ada 83 usage to the
29478 greatest extent possible.
29480 A few cases exist in which Ada 83 compiler behavior is incompatible with
29481 the requirements in Ada 95 (and thus also Ada 2005). These are instances of
29482 intentional or accidental dependence on specific implementation dependent
29483 characteristics of these Ada 83 compilers. The following is a list of
29484 the cases most likely to arise in existing Ada 83 code.
29490 @emph{Implicit Packing}
29492 Some Ada 83 compilers allowed a Size specification to cause implicit
29493 packing of an array or record. This could cause expensive implicit
29494 conversions for change of representation in the presence of derived
29495 types, and the Ada design intends to avoid this possibility.
29496 Subsequent AI's were issued to make it clear that such implicit
29497 change of representation in response to a Size clause is inadvisable,
29498 and this recommendation is represented explicitly in the Ada 95 (and Ada 2005)
29499 Reference Manuals as implementation advice that is followed by GNAT.
29500 The problem will show up as an error
29501 message rejecting the size clause. The fix is simply to provide
29502 the explicit pragma @code{Pack}, or for more fine tuned control, provide
29503 a Component_Size clause.
29506 @emph{Meaning of Size Attribute}
29508 The Size attribute in Ada 95 (and Ada 2005) for discrete types is defined as
29509 the minimal number of bits required to hold values of the type. For example,
29510 on a 32-bit machine, the size of @code{Natural} will typically be 31 and not
29511 32 (since no sign bit is required). Some Ada 83 compilers gave 31, and
29512 some 32 in this situation. This problem will usually show up as a compile
29513 time error, but not always. It is a good idea to check all uses of the
29514 'Size attribute when porting Ada 83 code. The GNAT specific attribute
29515 Object_Size can provide a useful way of duplicating the behavior of
29516 some Ada 83 compiler systems.
29519 @emph{Size of Access Types}
29521 A common assumption in Ada 83 code is that an access type is in fact a pointer,
29522 and that therefore it will be the same size as a System.Address value. This
29523 assumption is true for GNAT in most cases with one exception. For the case of
29524 a pointer to an unconstrained array type (where the bounds may vary from one
29525 value of the access type to another), the default is to use a 'fat pointer',
29526 which is represented as two separate pointers, one to the bounds, and one to
29527 the array. This representation has a number of advantages, including improved
29528 efficiency. However, it may cause some difficulties in porting existing Ada 83
29529 code which makes the assumption that, for example, pointers fit in 32 bits on
29530 a machine with 32-bit addressing.
29532 To get around this problem, GNAT also permits the use of 'thin pointers' for
29533 access types in this case (where the designated type is an unconstrained array
29534 type). These thin pointers are indeed the same size as a System.Address value.
29535 To specify a thin pointer, use a size clause for the type, for example:
29538 type X is access all String;
29539 for X'Size use Standard'Address_Size;
29542 which will cause the type X to be represented using a single pointer.
29543 When using this representation, the bounds are right behind the array.
29544 This representation is slightly less efficient, and does not allow quite
29545 such flexibility in the use of foreign pointers or in using the
29546 Unrestricted_Access attribute to create pointers to non-aliased objects.
29547 But for any standard portable use of the access type it will work in
29548 a functionally correct manner and allow porting of existing code.
29549 Note that another way of forcing a thin pointer representation
29550 is to use a component size clause for the element size in an array,
29551 or a record representation clause for an access field in a record.
29553 See the documentation of Unrestricted_Access in the GNAT RM for a
29554 full discussion of possible problems using this attribute in conjunction
29555 with thin pointers.
29558 @node Compatibility with HP Ada 83,,Representation Clauses,Compatibility and Porting Guide
29559 @anchor{gnat_rm/compatibility_and_porting_guide compatibility-with-hp-ada-83}@anchor{460}@anchor{gnat_rm/compatibility_and_porting_guide id17}@anchor{461}
29560 @section Compatibility with HP Ada 83
29563 All the HP Ada 83 pragmas and attributes are recognized, although only a subset
29564 of them can sensibly be implemented. The description of pragmas in
29565 @ref{7,,Implementation Defined Pragmas} indicates whether or not they are
29566 applicable to GNAT.
29572 @emph{Default floating-point representation}
29574 In GNAT, the default floating-point format is IEEE, whereas in HP Ada 83,
29580 the package System in GNAT exactly corresponds to the definition in the
29581 Ada 95 reference manual, which means that it excludes many of the
29582 HP Ada 83 extensions. However, a separate package Aux_DEC is provided
29583 that contains the additional definitions, and a special pragma,
29584 Extend_System allows this package to be treated transparently as an
29585 extension of package System.
29588 @node GNU Free Documentation License,Index,Compatibility and Porting Guide,Top
29589 @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}
29590 @chapter GNU Free Documentation License
29593 Version 1.3, 3 November 2008
29595 Copyright 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc
29596 @indicateurl{http://fsf.org/}
29598 Everyone is permitted to copy and distribute verbatim copies of this
29599 license document, but changing it is not allowed.
29603 The purpose of this License is to make a manual, textbook, or other
29604 functional and useful document "free" in the sense of freedom: to
29605 assure everyone the effective freedom to copy and redistribute it,
29606 with or without modifying it, either commercially or noncommercially.
29607 Secondarily, this License preserves for the author and publisher a way
29608 to get credit for their work, while not being considered responsible
29609 for modifications made by others.
29611 This License is a kind of "copyleft", which means that derivative
29612 works of the document must themselves be free in the same sense. It
29613 complements the GNU General Public License, which is a copyleft
29614 license designed for free software.
29616 We have designed this License in order to use it for manuals for free
29617 software, because free software needs free documentation: a free
29618 program should come with manuals providing the same freedoms that the
29619 software does. But this License is not limited to software manuals;
29620 it can be used for any textual work, regardless of subject matter or
29621 whether it is published as a printed book. We recommend this License
29622 principally for works whose purpose is instruction or reference.
29624 @strong{1. APPLICABILITY AND DEFINITIONS}
29626 This License applies to any manual or other work, in any medium, that
29627 contains a notice placed by the copyright holder saying it can be
29628 distributed under the terms of this License. Such a notice grants a
29629 world-wide, royalty-free license, unlimited in duration, to use that
29630 work under the conditions stated herein. The @strong{Document}, below,
29631 refers to any such manual or work. Any member of the public is a
29632 licensee, and is addressed as "@strong{you}". You accept the license if you
29633 copy, modify or distribute the work in a way requiring permission
29634 under copyright law.
29636 A "@strong{Modified Version}" of the Document means any work containing the
29637 Document or a portion of it, either copied verbatim, or with
29638 modifications and/or translated into another language.
29640 A "@strong{Secondary Section}" is a named appendix or a front-matter section of
29641 the Document that deals exclusively with the relationship of the
29642 publishers or authors of the Document to the Document's overall subject
29643 (or to related matters) and contains nothing that could fall directly
29644 within that overall subject. (Thus, if the Document is in part a
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29646 mathematics.) The relationship could be a matter of historical
29647 connection with the subject or with related matters, or of legal,
29648 commercial, philosophical, ethical or political position regarding
29651 The "@strong{Invariant Sections}" are certain Secondary Sections whose titles
29652 are designated, as being those of Invariant Sections, in the notice
29653 that says that the Document is released under this License. If a
29654 section does not fit the above definition of Secondary then it is not
29655 allowed to be designated as Invariant. The Document may contain zero
29656 Invariant Sections. If the Document does not identify any Invariant
29657 Sections then there are none.
29659 The "@strong{Cover Texts}" are certain short passages of text that are listed,
29660 as Front-Cover Texts or Back-Cover Texts, in the notice that says that
29661 the Document is released under this License. A Front-Cover Text may
29662 be at most 5 words, and a Back-Cover Text may be at most 25 words.
29664 A "@strong{Transparent}" copy of the Document means a machine-readable copy,
29665 represented in a format whose specification is available to the
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29669 drawing editor, and that is suitable for input to text formatters or
29670 for automatic translation to a variety of formats suitable for input
29671 to text formatters. A copy made in an otherwise Transparent file
29672 format whose markup, or absence of markup, has been arranged to thwart
29673 or discourage subsequent modification by readers is not Transparent.
29674 An image format is not Transparent if used for any substantial amount
29675 of text. A copy that is not "Transparent" is called @strong{Opaque}.
29677 Examples of suitable formats for Transparent copies include plain
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29679 or XML using a publicly available DTD, and standard-conforming simple
29680 HTML, PostScript or PDF designed for human modification. Examples of
29681 transparent image formats include PNG, XCF and JPG. Opaque formats
29682 include proprietary formats that can be read and edited only by
29683 proprietary word processors, SGML or XML for which the DTD and/or
29684 processing tools are not generally available, and the
29685 machine-generated HTML, PostScript or PDF produced by some word
29686 processors for output purposes only.
29688 The "@strong{Title Page}" means, for a printed book, the title page itself,
29689 plus such following pages as are needed to hold, legibly, the material
29690 this License requires to appear in the title page. For works in
29691 formats which do not have any title page as such, "Title Page" means
29692 the text near the most prominent appearance of the work's title,
29693 preceding the beginning of the body of the text.
29695 The "@strong{publisher}" means any person or entity that distributes
29696 copies of the Document to the public.
29698 A section "@strong{Entitled XYZ}" means a named subunit of the Document whose
29699 title either is precisely XYZ or contains XYZ in parentheses following
29700 text that translates XYZ in another language. (Here XYZ stands for a
29701 specific section name mentioned below, such as "@strong{Acknowledgements}",
29702 "@strong{Dedications}", "@strong{Endorsements}", or "@strong{History}".)
29703 To "@strong{Preserve the Title}"
29704 of such a section when you modify the Document means that it remains a
29705 section "Entitled XYZ" according to this definition.
29707 The Document may include Warranty Disclaimers next to the notice which
29708 states that this License applies to the Document. These Warranty
29709 Disclaimers are considered to be included by reference in this
29710 License, but only as regards disclaiming warranties: any other
29711 implication that these Warranty Disclaimers may have is void and has
29712 no effect on the meaning of this License.
29714 @strong{2. VERBATIM COPYING}
29716 You may copy and distribute the Document in any medium, either
29717 commercially or noncommercially, provided that this License, the
29718 copyright notices, and the license notice saying this License applies
29719 to the Document are reproduced in all copies, and that you add no other
29720 conditions whatsoever to those of this License. You may not use
29721 technical measures to obstruct or control the reading or further
29722 copying of the copies you make or distribute. However, you may accept
29723 compensation in exchange for copies. If you distribute a large enough
29724 number of copies you must also follow the conditions in section 3.
29726 You may also lend copies, under the same conditions stated above, and
29727 you may publicly display copies.
29729 @strong{3. COPYING IN QUANTITY}
29731 If you publish printed copies (or copies in media that commonly have
29732 printed covers) of the Document, numbering more than 100, and the
29733 Document's license notice requires Cover Texts, you must enclose the
29734 copies in covers that carry, clearly and legibly, all these Cover
29735 Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on
29736 the back cover. Both covers must also clearly and legibly identify
29737 you as the publisher of these copies. The front cover must present
29738 the full title with all words of the title equally prominent and
29739 visible. You may add other material on the covers in addition.
29740 Copying with changes limited to the covers, as long as they preserve
29741 the title of the Document and satisfy these conditions, can be treated
29742 as verbatim copying in other respects.
29744 If the required texts for either cover are too voluminous to fit
29745 legibly, you should put the first ones listed (as many as fit
29746 reasonably) on the actual cover, and continue the rest onto adjacent
29749 If you publish or distribute Opaque copies of the Document numbering
29750 more than 100, you must either include a machine-readable Transparent
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29752 a computer-network location from which the general network-using
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29756 when you begin distribution of Opaque copies in quantity, to ensure
29757 that this Transparent copy will remain thus accessible at the stated
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29759 Opaque copy (directly or through your agents or retailers) of that
29760 edition to the public.
29762 It is requested, but not required, that you contact the authors of the
29763 Document well before redistributing any large number of copies, to give
29764 them a chance to provide you with an updated version of the Document.
29766 @strong{4. MODIFICATIONS}
29768 You may copy and distribute a Modified Version of the Document under
29769 the conditions of sections 2 and 3 above, provided that you release
29770 the Modified Version under precisely this License, with the Modified
29771 Version filling the role of the Document, thus licensing distribution
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29773 of it. In addition, you must do these things in the Modified Version:
29779 Use in the Title Page (and on the covers, if any) a title distinct
29780 from that of the Document, and from those of previous versions
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29782 of the Document). You may use the same title as a previous version
29783 if the original publisher of that version gives permission.
29786 List on the Title Page, as authors, one or more persons or entities
29787 responsible for authorship of the modifications in the Modified
29788 Version, together with at least five of the principal authors of the
29789 Document (all of its principal authors, if it has fewer than five),
29790 unless they release you from this requirement.
29793 State on the Title page the name of the publisher of the
29794 Modified Version, as the publisher.
29797 Preserve all the copyright notices of the Document.
29800 Add an appropriate copyright notice for your modifications
29801 adjacent to the other copyright notices.
29804 Include, immediately after the copyright notices, a license notice
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29810 and required Cover Texts given in the Document's license notice.
29813 Include an unaltered copy of this License.
29816 Preserve the section Entitled "History", Preserve its Title, and add
29817 to it an item stating at least the title, year, new authors, and
29818 publisher of the Modified Version as given on the Title Page. If
29819 there is no section Entitled "History" in the Document, create one
29820 stating the title, year, authors, and publisher of the Document as
29821 given on its Title Page, then add an item describing the Modified
29822 Version as stated in the previous sentence.
29825 Preserve the network location, if any, given in the Document for
29826 public access to a Transparent copy of the Document, and likewise
29827 the network locations given in the Document for previous versions
29828 it was based on. These may be placed in the "History" section.
29829 You may omit a network location for a work that was published at
29830 least four years before the Document itself, or if the original
29831 publisher of the version it refers to gives permission.
29834 For any section Entitled "Acknowledgements" or "Dedications",
29835 Preserve the Title of the section, and preserve in the section all
29836 the substance and tone of each of the contributor acknowledgements
29837 and/or dedications given therein.
29840 Preserve all the Invariant Sections of the Document,
29841 unaltered in their text and in their titles. Section numbers
29842 or the equivalent are not considered part of the section titles.
29845 Delete any section Entitled "Endorsements". Such a section
29846 may not be included in the Modified Version.
29849 Do not retitle any existing section to be Entitled "Endorsements"
29850 or to conflict in title with any Invariant Section.
29853 Preserve any Warranty Disclaimers.
29856 If the Modified Version includes new front-matter sections or
29857 appendices that qualify as Secondary Sections and contain no material
29858 copied from the Document, you may at your option designate some or all
29859 of these sections as invariant. To do this, add their titles to the
29860 list of Invariant Sections in the Modified Version's license notice.
29861 These titles must be distinct from any other section titles.
29863 You may add a section Entitled "Endorsements", provided it contains
29864 nothing but endorsements of your Modified Version by various
29865 parties---for example, statements of peer review or that the text has
29866 been approved by an organization as the authoritative definition of a
29869 You may add a passage of up to five words as a Front-Cover Text, and a
29870 passage of up to 25 words as a Back-Cover Text, to the end of the list
29871 of Cover Texts in the Modified Version. Only one passage of
29872 Front-Cover Text and one of Back-Cover Text may be added by (or
29873 through arrangements made by) any one entity. If the Document already
29874 includes a cover text for the same cover, previously added by you or
29875 by arrangement made by the same entity you are acting on behalf of,
29876 you may not add another; but you may replace the old one, on explicit
29877 permission from the previous publisher that added the old one.
29879 The author(s) and publisher(s) of the Document do not by this License
29880 give permission to use their names for publicity for or to assert or
29881 imply endorsement of any Modified Version.
29883 @strong{5. COMBINING DOCUMENTS}
29885 You may combine the Document with other documents released under this
29886 License, under the terms defined in section 4 above for modified
29887 versions, provided that you include in the combination all of the
29888 Invariant Sections of all of the original documents, unmodified, and
29889 list them all as Invariant Sections of your combined work in its
29890 license notice, and that you preserve all their Warranty Disclaimers.
29892 The combined work need only contain one copy of this License, and
29893 multiple identical Invariant Sections may be replaced with a single
29894 copy. If there are multiple Invariant Sections with the same name but
29895 different contents, make the title of each such section unique by
29896 adding at the end of it, in parentheses, the name of the original
29897 author or publisher of that section if known, or else a unique number.
29898 Make the same adjustment to the section titles in the list of
29899 Invariant Sections in the license notice of the combined work.
29901 In the combination, you must combine any sections Entitled "History"
29902 in the various original documents, forming one section Entitled
29903 "History"; likewise combine any sections Entitled "Acknowledgements",
29904 and any sections Entitled "Dedications". You must delete all sections
29905 Entitled "Endorsements".
29907 @strong{6. COLLECTIONS OF DOCUMENTS}
29909 You may make a collection consisting of the Document and other documents
29910 released under this License, and replace the individual copies of this
29911 License in the various documents with a single copy that is included in
29912 the collection, provided that you follow the rules of this License for
29913 verbatim copying of each of the documents in all other respects.
29915 You may extract a single document from such a collection, and distribute
29916 it individually under this License, provided you insert a copy of this
29917 License into the extracted document, and follow this License in all
29918 other respects regarding verbatim copying of that document.
29920 @strong{7. AGGREGATION WITH INDEPENDENT WORKS}
29922 A compilation of the Document or its derivatives with other separate
29923 and independent documents or works, in or on a volume of a storage or
29924 distribution medium, is called an "aggregate" if the copyright
29925 resulting from the compilation is not used to limit the legal rights
29926 of the compilation's users beyond what the individual works permit.
29927 When the Document is included in an aggregate, this License does not
29928 apply to the other works in the aggregate which are not themselves
29929 derivative works of the Document.
29931 If the Cover Text requirement of section 3 is applicable to these
29932 copies of the Document, then if the Document is less than one half of
29933 the entire aggregate, the Document's Cover Texts may be placed on
29934 covers that bracket the Document within the aggregate, or the
29935 electronic equivalent of covers if the Document is in electronic form.
29936 Otherwise they must appear on printed covers that bracket the whole
29939 @strong{8. TRANSLATION}
29941 Translation is considered a kind of modification, so you may
29942 distribute translations of the Document under the terms of section 4.
29943 Replacing Invariant Sections with translations requires special
29944 permission from their copyright holders, but you may include
29945 translations of some or all Invariant Sections in addition to the
29946 original versions of these Invariant Sections. You may include a
29947 translation of this License, and all the license notices in the
29948 Document, and any Warranty Disclaimers, provided that you also include
29949 the original English version of this License and the original versions
29950 of those notices and disclaimers. In case of a disagreement between
29951 the translation and the original version of this License or a notice
29952 or disclaimer, the original version will prevail.
29954 If a section in the Document is Entitled "Acknowledgements",
29955 "Dedications", or "History", the requirement (section 4) to Preserve
29956 its Title (section 1) will typically require changing the actual
29959 @strong{9. TERMINATION}
29961 You may not copy, modify, sublicense, or distribute the Document
29962 except as expressly provided under this License. Any attempt
29963 otherwise to copy, modify, sublicense, or distribute it is void, and
29964 will automatically terminate your rights under this License.
29966 However, if you cease all violation of this License, then your license
29967 from a particular copyright holder is reinstated (a) provisionally,
29968 unless and until the copyright holder explicitly and finally
29969 terminates your license, and (b) permanently, if the copyright holder
29970 fails to notify you of the violation by some reasonable means prior to
29971 60 days after the cessation.
29973 Moreover, your license from a particular copyright holder is
29974 reinstated permanently if the copyright holder notifies you of the
29975 violation by some reasonable means, this is the first time you have
29976 received notice of violation of this License (for any work) from that
29977 copyright holder, and you cure the violation prior to 30 days after
29978 your receipt of the notice.
29980 Termination of your rights under this section does not terminate the
29981 licenses of parties who have received copies or rights from you under
29982 this License. If your rights have been terminated and not permanently
29983 reinstated, receipt of a copy of some or all of the same material does
29984 not give you any rights to use it.
29986 @strong{10. FUTURE REVISIONS OF THIS LICENSE}
29988 The Free Software Foundation may publish new, revised versions
29989 of the GNU Free Documentation License from time to time. Such new
29990 versions will be similar in spirit to the present version, but may
29991 differ in detail to address new problems or concerns. See
29992 @indicateurl{http://www.gnu.org/copyleft/}.
29994 Each version of the License is given a distinguishing version number.
29995 If the Document specifies that a particular numbered version of this
29996 License "or any later version" applies to it, you have the option of
29997 following the terms and conditions either of that specified version or
29998 of any later version that has been published (not as a draft) by the
29999 Free Software Foundation. If the Document does not specify a version
30000 number of this License, you may choose any version ever published (not
30001 as a draft) by the Free Software Foundation. If the Document
30002 specifies that a proxy can decide which future versions of this
30003 License can be used, that proxy's public statement of acceptance of a
30004 version permanently authorizes you to choose that version for the
30007 @strong{11. RELICENSING}
30009 "Massive Multiauthor Collaboration Site" (or "MMC Site") means any
30010 World Wide Web server that publishes copyrightable works and also
30011 provides prominent facilities for anybody to edit those works. A
30012 public wiki that anybody can edit is an example of such a server. A
30013 "Massive Multiauthor Collaboration" (or "MMC") contained in the
30014 site means any set of copyrightable works thus published on the MMC
30017 "CC-BY-SA" means the Creative Commons Attribution-Share Alike 3.0
30018 license published by Creative Commons Corporation, a not-for-profit
30019 corporation with a principal place of business in San Francisco,
30020 California, as well as future copyleft versions of that license
30021 published by that same organization.
30023 "Incorporate" means to publish or republish a Document, in whole or
30024 in part, as part of another Document.
30026 An MMC is "eligible for relicensing" if it is licensed under this
30027 License, and if all works that were first published under this License
30028 somewhere other than this MMC, and subsequently incorporated in whole
30029 or in part into the MMC, (1) had no cover texts or invariant sections,
30030 and (2) were thus incorporated prior to November 1, 2008.
30032 The operator of an MMC Site may republish an MMC contained in the site
30033 under CC-BY-SA on the same site at any time before August 1, 2009,
30034 provided the MMC is eligible for relicensing.
30036 @strong{ADDENDUM: How to use this License for your documents}
30038 To use this License in a document you have written, include a copy of
30039 the License in the document and put the following copyright and
30040 license notices just after the title page:
30044 Copyright © YEAR YOUR NAME.
30045 Permission is granted to copy, distribute and/or modify this document
30046 under the terms of the GNU Free Documentation License, Version 1.3
30047 or any later version published by the Free Software Foundation;
30048 with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
30049 A copy of the license is included in the section entitled "GNU
30050 Free Documentation License".
30053 If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts,
30054 replace the "with ... Texts." line with this:
30058 with the Invariant Sections being LIST THEIR TITLES, with the
30059 Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST.
30062 If you have Invariant Sections without Cover Texts, or some other
30063 combination of the three, merge those two alternatives to suit the
30066 If your document contains nontrivial examples of program code, we
30067 recommend releasing these examples in parallel under your choice of
30068 free software license, such as the GNU General Public License,
30069 to permit their use in free software.
30071 @node Index,,GNU Free Documentation License,Top