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8 @settitle GNAT Reference Manual
13 @dircategory GNU Ada Tools
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24 GNAT Reference Manual , Sep 29, 2020
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::
106 * Pragma Aggregate_Individually_Assign::
107 * Pragma Allow_Integer_Address::
110 * Pragma Assert_And_Cut::
111 * Pragma Assertion_Policy::
113 * Pragma Assume_No_Invalid_Values::
114 * Pragma Async_Readers::
115 * Pragma Async_Writers::
116 * Pragma Attribute_Definition::
117 * Pragma C_Pass_By_Copy::
119 * Pragma Check_Float_Overflow::
120 * Pragma Check_Name::
121 * Pragma Check_Policy::
123 * Pragma Common_Object::
124 * Pragma Compile_Time_Error::
125 * Pragma Compile_Time_Warning::
126 * Pragma Compiler_Unit::
127 * Pragma Compiler_Unit_Warning::
128 * Pragma Complete_Representation::
129 * Pragma Complex_Representation::
130 * Pragma Component_Alignment::
131 * Pragma Constant_After_Elaboration::
132 * Pragma Contract_Cases::
133 * Pragma Convention_Identifier::
135 * Pragma CPP_Constructor::
136 * Pragma CPP_Virtual::
137 * Pragma CPP_Vtable::
139 * Pragma Deadline_Floor::
140 * Pragma Default_Initial_Condition::
142 * Pragma Debug_Policy::
143 * Pragma Default_Scalar_Storage_Order::
144 * Pragma Default_Storage_Pool::
146 * Pragma Detect_Blocking::
147 * Pragma Disable_Atomic_Synchronization::
148 * Pragma Dispatching_Domain::
149 * Pragma Effective_Reads::
150 * Pragma Effective_Writes::
151 * Pragma Elaboration_Checks::
153 * Pragma Enable_Atomic_Synchronization::
154 * Pragma Export_Function::
155 * Pragma Export_Object::
156 * Pragma Export_Procedure::
157 * Pragma Export_Value::
158 * Pragma Export_Valued_Procedure::
159 * Pragma Extend_System::
160 * Pragma Extensions_Allowed::
161 * Pragma Extensions_Visible::
163 * Pragma External_Name_Casing::
165 * Pragma Favor_Top_Level::
166 * Pragma Finalize_Storage_Only::
167 * Pragma Float_Representation::
171 * Pragma Ignore_Pragma::
172 * Pragma Implementation_Defined::
173 * Pragma Implemented::
174 * Pragma Implicit_Packing::
175 * Pragma Import_Function::
176 * Pragma Import_Object::
177 * Pragma Import_Procedure::
178 * Pragma Import_Valued_Procedure::
179 * Pragma Independent::
180 * Pragma Independent_Components::
181 * Pragma Initial_Condition::
182 * Pragma Initialize_Scalars::
183 * Pragma Initializes::
184 * Pragma Inline_Always::
185 * Pragma Inline_Generic::
187 * Pragma Interface_Name::
188 * Pragma Interrupt_Handler::
189 * Pragma Interrupt_State::
191 * Pragma Keep_Names::
194 * Pragma Linker_Alias::
195 * Pragma Linker_Constructor::
196 * Pragma Linker_Destructor::
197 * Pragma Linker_Section::
199 * Pragma Loop_Invariant::
200 * Pragma Loop_Optimize::
201 * Pragma Loop_Variant::
202 * Pragma Machine_Attribute::
204 * Pragma Main_Storage::
205 * Pragma Max_Queue_Length::
207 * Pragma No_Caching::
208 * Pragma No_Component_Reordering::
209 * Pragma No_Elaboration_Code_All::
210 * Pragma No_Heap_Finalization::
213 * Pragma No_Strict_Aliasing::
214 * Pragma No_Tagged_Streams::
215 * Pragma Normalize_Scalars::
216 * Pragma Obsolescent::
217 * Pragma Optimize_Alignment::
219 * Pragma Overflow_Mode::
220 * Pragma Overriding_Renamings::
221 * Pragma Partition_Elaboration_Policy::
224 * Pragma Persistent_BSS::
226 * Pragma Postcondition::
227 * Pragma Post_Class::
228 * Pragma Rename_Pragma::
230 * Pragma Precondition::
232 * Pragma Predicate_Failure::
233 * Pragma Preelaborable_Initialization::
234 * Pragma Prefix_Exception_Messages::
236 * Pragma Priority_Specific_Dispatching::
238 * Pragma Profile_Warnings::
239 * Pragma Propagate_Exceptions::
240 * Pragma Provide_Shift_Operators::
241 * Pragma Psect_Object::
242 * Pragma Pure_Function::
245 * Pragma Refined_Depends::
246 * Pragma Refined_Global::
247 * Pragma Refined_Post::
248 * Pragma Refined_State::
249 * Pragma Relative_Deadline::
250 * Pragma Remote_Access_Type::
251 * Pragma Restricted_Run_Time::
252 * Pragma Restriction_Warnings::
253 * Pragma Reviewable::
254 * Pragma Secondary_Stack_Size::
255 * Pragma Share_Generic::
257 * Pragma Short_Circuit_And_Or::
258 * Pragma Short_Descriptors::
259 * Pragma Simple_Storage_Pool_Type::
260 * Pragma Source_File_Name::
261 * Pragma Source_File_Name_Project::
262 * Pragma Source_Reference::
263 * Pragma SPARK_Mode::
264 * Pragma Static_Elaboration_Desired::
265 * Pragma Stream_Convert::
266 * Pragma Style_Checks::
269 * Pragma Suppress_All::
270 * Pragma Suppress_Debug_Info::
271 * Pragma Suppress_Exception_Locations::
272 * Pragma Suppress_Initialization::
274 * Pragma Task_Storage::
276 * Pragma Thread_Local_Storage::
277 * Pragma Time_Slice::
279 * Pragma Type_Invariant::
280 * Pragma Type_Invariant_Class::
281 * Pragma Unchecked_Union::
282 * Pragma Unevaluated_Use_Of_Old::
283 * Pragma Unimplemented_Unit::
284 * Pragma Universal_Aliasing::
285 * Pragma Universal_Data::
286 * Pragma Unmodified::
287 * Pragma Unreferenced::
288 * Pragma Unreferenced_Objects::
289 * Pragma Unreserve_All_Interrupts::
290 * Pragma Unsuppress::
291 * Pragma Use_VADS_Size::
293 * Pragma Validity_Checks::
295 * Pragma Volatile_Full_Access::
296 * Pragma Volatile_Function::
297 * Pragma Warning_As_Error::
299 * Pragma Weak_External::
300 * Pragma Wide_Character_Encoding::
302 Implementation Defined Aspects
304 * Aspect Abstract_State::
306 * Aspect Async_Readers::
307 * Aspect Async_Writers::
308 * Aspect Constant_After_Elaboration::
309 * Aspect Contract_Cases::
311 * Aspect Default_Initial_Condition::
313 * Aspect Dimension_System::
314 * Aspect Disable_Controlled::
315 * Aspect Effective_Reads::
316 * Aspect Effective_Writes::
317 * Aspect Extensions_Visible::
318 * Aspect Favor_Top_Level::
321 * Aspect Initial_Condition::
322 * Aspect Initializes::
323 * Aspect Inline_Always::
325 * Aspect Invariant'Class::
327 * Aspect Linker_Section::
329 * Aspect Max_Queue_Length::
330 * Aspect No_Caching::
331 * Aspect No_Elaboration_Code_All::
333 * Aspect No_Tagged_Streams::
334 * Aspect Object_Size::
335 * Aspect Obsolescent::
337 * Aspect Persistent_BSS::
339 * Aspect Pure_Function::
340 * Aspect Refined_Depends::
341 * Aspect Refined_Global::
342 * Aspect Refined_Post::
343 * Aspect Refined_State::
344 * Aspect Relaxed_Initialization::
345 * Aspect Remote_Access_Type::
346 * Aspect Secondary_Stack_Size::
347 * Aspect Scalar_Storage_Order::
349 * Aspect Simple_Storage_Pool::
350 * Aspect Simple_Storage_Pool_Type::
351 * Aspect SPARK_Mode::
352 * Aspect Suppress_Debug_Info::
353 * Aspect Suppress_Initialization::
355 * Aspect Thread_Local_Storage::
356 * Aspect Universal_Aliasing::
357 * Aspect Universal_Data::
358 * Aspect Unmodified::
359 * Aspect Unreferenced::
360 * Aspect Unreferenced_Objects::
361 * Aspect Value_Size::
362 * Aspect Volatile_Full_Access::
363 * Aspect Volatile_Function::
366 Implementation Defined Attributes
368 * Attribute Abort_Signal::
369 * Attribute Address_Size::
370 * Attribute Asm_Input::
371 * Attribute Asm_Output::
372 * Attribute Atomic_Always_Lock_Free::
374 * Attribute Bit_Position::
375 * Attribute Code_Address::
376 * Attribute Compiler_Version::
377 * Attribute Constrained::
378 * Attribute Default_Bit_Order::
379 * Attribute Default_Scalar_Storage_Order::
381 * Attribute Descriptor_Size::
382 * Attribute Elaborated::
383 * Attribute Elab_Body::
384 * Attribute Elab_Spec::
385 * Attribute Elab_Subp_Body::
387 * Attribute Enabled::
388 * Attribute Enum_Rep::
389 * Attribute Enum_Val::
390 * Attribute Epsilon::
391 * Attribute Fast_Math::
392 * Attribute Finalization_Size::
393 * Attribute Fixed_Value::
394 * Attribute From_Any::
395 * Attribute Has_Access_Values::
396 * Attribute Has_Discriminants::
398 * Attribute Initialized::
399 * Attribute Integer_Value::
400 * Attribute Invalid_Value::
401 * Attribute Iterable::
403 * Attribute Library_Level::
404 * Attribute Lock_Free::
405 * Attribute Loop_Entry::
406 * Attribute Machine_Size::
407 * Attribute Mantissa::
408 * Attribute Maximum_Alignment::
409 * Attribute Max_Integer_Size::
410 * Attribute Mechanism_Code::
411 * Attribute Null_Parameter::
412 * Attribute Object_Size::
414 * Attribute Passed_By_Reference::
415 * Attribute Pool_Address::
416 * Attribute Range_Length::
417 * Attribute Restriction_Set::
419 * Attribute Safe_Emax::
420 * Attribute Safe_Large::
421 * Attribute Safe_Small::
422 * Attribute Scalar_Storage_Order::
423 * Attribute Simple_Storage_Pool::
425 * Attribute Storage_Unit::
426 * Attribute Stub_Type::
427 * Attribute System_Allocator_Alignment::
428 * Attribute Target_Name::
429 * Attribute To_Address::
431 * Attribute Type_Class::
432 * Attribute Type_Key::
433 * Attribute TypeCode::
434 * Attribute Unconstrained_Array::
435 * Attribute Universal_Literal_String::
436 * Attribute Unrestricted_Access::
438 * Attribute Valid_Scalars::
439 * Attribute VADS_Size::
440 * Attribute Value_Size::
441 * Attribute Wchar_T_Size::
442 * Attribute Word_Size::
444 Standard and Implementation Defined Restrictions
446 * Partition-Wide Restrictions::
447 * Program Unit Level Restrictions::
449 Partition-Wide Restrictions
451 * Immediate_Reclamation::
452 * Max_Asynchronous_Select_Nesting::
453 * Max_Entry_Queue_Length::
454 * Max_Protected_Entries::
455 * Max_Select_Alternatives::
456 * Max_Storage_At_Blocking::
459 * No_Abort_Statements::
460 * No_Access_Parameter_Allocators::
461 * No_Access_Subprograms::
463 * No_Anonymous_Allocators::
464 * No_Asynchronous_Control::
467 * No_Default_Initialization::
470 * No_Direct_Boolean_Operators::
472 * No_Dispatching_Calls::
473 * No_Dynamic_Attachment::
474 * No_Dynamic_Priorities::
475 * No_Entry_Calls_In_Elaboration_Code::
476 * No_Enumeration_Maps::
477 * No_Exception_Handlers::
478 * No_Exception_Propagation::
479 * No_Exception_Registration::
483 * No_Floating_Point::
484 * No_Implicit_Conditionals::
485 * No_Implicit_Dynamic_Code::
486 * No_Implicit_Heap_Allocations::
487 * No_Implicit_Protected_Object_Allocations::
488 * No_Implicit_Task_Allocations::
489 * No_Initialize_Scalars::
491 * No_Local_Allocators::
492 * No_Local_Protected_Objects::
493 * No_Local_Timing_Events::
494 * No_Long_Long_Integers::
495 * No_Multiple_Elaboration::
496 * No_Nested_Finalization::
497 * No_Protected_Type_Allocators::
498 * No_Protected_Types::
501 * No_Relative_Delay::
502 * No_Requeue_Statements::
503 * No_Secondary_Stack::
504 * No_Select_Statements::
505 * No_Specific_Termination_Handlers::
506 * No_Specification_of_Aspect::
507 * No_Standard_Allocators_After_Elaboration::
508 * No_Standard_Storage_Pools::
509 * No_Stream_Optimizations::
511 * No_Task_Allocators::
512 * No_Task_At_Interrupt_Priority::
513 * No_Task_Attributes_Package::
514 * No_Task_Hierarchy::
515 * No_Task_Termination::
517 * No_Terminate_Alternatives::
518 * No_Unchecked_Access::
519 * No_Unchecked_Conversion::
520 * No_Unchecked_Deallocation::
524 * Static_Priorities::
525 * Static_Storage_Size::
527 Program Unit Level Restrictions
529 * No_Elaboration_Code::
530 * No_Dynamic_Sized_Objects::
532 * No_Implementation_Aspect_Specifications::
533 * No_Implementation_Attributes::
534 * No_Implementation_Identifiers::
535 * No_Implementation_Pragmas::
536 * No_Implementation_Restrictions::
537 * No_Implementation_Units::
538 * No_Implicit_Aliasing::
539 * No_Implicit_Loops::
540 * No_Obsolescent_Features::
541 * No_Wide_Characters::
542 * Static_Dispatch_Tables::
545 Implementation Advice
547 * RM 1.1.3(20); Error Detection: RM 1 1 3 20 Error Detection.
548 * RM 1.1.3(31); Child Units: RM 1 1 3 31 Child Units.
549 * RM 1.1.5(12); Bounded Errors: RM 1 1 5 12 Bounded Errors.
550 * RM 2.8(16); Pragmas: RM 2 8 16 Pragmas.
551 * RM 2.8(17-19); Pragmas: RM 2 8 17-19 Pragmas.
552 * RM 3.5.2(5); Alternative Character Sets: RM 3 5 2 5 Alternative Character Sets.
553 * RM 3.5.4(28); Integer Types: RM 3 5 4 28 Integer Types.
554 * RM 3.5.4(29); Integer Types: RM 3 5 4 29 Integer Types.
555 * RM 3.5.5(8); Enumeration Values: RM 3 5 5 8 Enumeration Values.
556 * RM 3.5.7(17); Float Types: RM 3 5 7 17 Float Types.
557 * RM 3.6.2(11); Multidimensional Arrays: RM 3 6 2 11 Multidimensional Arrays.
558 * RM 9.6(30-31); Duration'Small: RM 9 6 30-31 Duration'Small.
559 * RM 10.2.1(12); Consistent Representation: RM 10 2 1 12 Consistent Representation.
560 * RM 11.4.1(19); Exception Information: RM 11 4 1 19 Exception Information.
561 * RM 11.5(28); Suppression of Checks: RM 11 5 28 Suppression of Checks.
562 * RM 13.1 (21-24); Representation Clauses: RM 13 1 21-24 Representation Clauses.
563 * RM 13.2(6-8); Packed Types: RM 13 2 6-8 Packed Types.
564 * RM 13.3(14-19); Address Clauses: RM 13 3 14-19 Address Clauses.
565 * RM 13.3(29-35); Alignment Clauses: RM 13 3 29-35 Alignment Clauses.
566 * RM 13.3(42-43); Size Clauses: RM 13 3 42-43 Size Clauses.
567 * RM 13.3(50-56); Size Clauses: RM 13 3 50-56 Size Clauses.
568 * RM 13.3(71-73); Component Size Clauses: RM 13 3 71-73 Component Size Clauses.
569 * RM 13.4(9-10); Enumeration Representation Clauses: RM 13 4 9-10 Enumeration Representation Clauses.
570 * RM 13.5.1(17-22); Record Representation Clauses: RM 13 5 1 17-22 Record Representation Clauses.
571 * RM 13.5.2(5); Storage Place Attributes: RM 13 5 2 5 Storage Place Attributes.
572 * RM 13.5.3(7-8); Bit Ordering: RM 13 5 3 7-8 Bit Ordering.
573 * RM 13.7(37); Address as Private: RM 13 7 37 Address as Private.
574 * RM 13.7.1(16); Address Operations: RM 13 7 1 16 Address Operations.
575 * RM 13.9(14-17); Unchecked Conversion: RM 13 9 14-17 Unchecked Conversion.
576 * RM 13.11(23-25); Implicit Heap Usage: RM 13 11 23-25 Implicit Heap Usage.
577 * RM 13.11.2(17); Unchecked Deallocation: RM 13 11 2 17 Unchecked Deallocation.
578 * RM 13.13.2(1.6); Stream Oriented Attributes: RM 13 13 2 1 6 Stream Oriented Attributes.
579 * RM A.1(52); Names of Predefined Numeric Types: RM A 1 52 Names of Predefined Numeric Types.
580 * RM A.3.2(49); Ada.Characters.Handling: RM A 3 2 49 Ada Characters Handling.
581 * RM A.4.4(106); Bounded-Length String Handling: RM A 4 4 106 Bounded-Length String Handling.
582 * RM A.5.2(46-47); Random Number Generation: RM A 5 2 46-47 Random Number Generation.
583 * RM A.10.7(23); Get_Immediate: RM A 10 7 23 Get_Immediate.
584 * RM B.1(39-41); Pragma Export: RM B 1 39-41 Pragma Export.
585 * RM B.2(12-13); Package Interfaces: RM B 2 12-13 Package Interfaces.
586 * RM B.3(63-71); Interfacing with C: RM B 3 63-71 Interfacing with C.
587 * RM B.4(95-98); Interfacing with COBOL: RM B 4 95-98 Interfacing with COBOL.
588 * RM B.5(22-26); Interfacing with Fortran: RM B 5 22-26 Interfacing with Fortran.
589 * RM C.1(3-5); Access to Machine Operations: RM C 1 3-5 Access to Machine Operations.
590 * RM C.1(10-16); Access to Machine Operations: RM C 1 10-16 Access to Machine Operations.
591 * RM C.3(28); Interrupt Support: RM C 3 28 Interrupt Support.
592 * RM C.3.1(20-21); Protected Procedure Handlers: RM C 3 1 20-21 Protected Procedure Handlers.
593 * RM C.3.2(25); Package Interrupts: RM C 3 2 25 Package Interrupts.
594 * RM C.4(14); Pre-elaboration Requirements: RM C 4 14 Pre-elaboration Requirements.
595 * RM C.5(8); Pragma Discard_Names: RM C 5 8 Pragma Discard_Names.
596 * RM C.7.2(30); The Package Task_Attributes: RM C 7 2 30 The Package Task_Attributes.
597 * RM D.3(17); Locking Policies: RM D 3 17 Locking Policies.
598 * RM D.4(16); Entry Queuing Policies: RM D 4 16 Entry Queuing Policies.
599 * RM D.6(9-10); Preemptive Abort: RM D 6 9-10 Preemptive Abort.
600 * RM D.7(21); Tasking Restrictions: RM D 7 21 Tasking Restrictions.
601 * RM D.8(47-49); Monotonic Time: RM D 8 47-49 Monotonic Time.
602 * RM E.5(28-29); Partition Communication Subsystem: RM E 5 28-29 Partition Communication Subsystem.
603 * RM F(7); COBOL Support: RM F 7 COBOL Support.
604 * RM F.1(2); Decimal Radix Support: RM F 1 2 Decimal Radix Support.
605 * RM G; Numerics: RM G Numerics.
606 * RM G.1.1(56-58); Complex Types: RM G 1 1 56-58 Complex Types.
607 * RM G.1.2(49); Complex Elementary Functions: RM G 1 2 49 Complex Elementary Functions.
608 * RM G.2.4(19); Accuracy Requirements: RM G 2 4 19 Accuracy Requirements.
609 * RM G.2.6(15); Complex Arithmetic Accuracy: RM G 2 6 15 Complex Arithmetic Accuracy.
610 * RM H.6(15/2); Pragma Partition_Elaboration_Policy: RM H 6 15/2 Pragma Partition_Elaboration_Policy.
612 Intrinsic Subprograms
614 * Intrinsic Operators::
615 * Compilation_ISO_Date::
619 * Exception_Information::
620 * Exception_Message::
624 * Shifts and Rotates::
627 Representation Clauses and Pragmas
629 * Alignment Clauses::
631 * Storage_Size Clauses::
632 * Size of Variant Record Objects::
633 * Biased Representation::
634 * Value_Size and Object_Size Clauses::
635 * Component_Size Clauses::
636 * Bit_Order Clauses::
637 * Effect of Bit_Order on Byte Ordering::
638 * Pragma Pack for Arrays::
639 * Pragma Pack for Records::
640 * Record Representation Clauses::
641 * Handling of Records with Holes::
642 * Enumeration Clauses::
644 * Use of Address Clauses for Memory-Mapped I/O::
645 * Effect of Convention on Representation::
646 * Conventions and Anonymous Access Types::
647 * Determining the Representations chosen by GNAT::
649 The Implementation of Standard I/O
651 * Standard I/O Packages::
657 * Wide_Wide_Text_IO::
661 * Filenames encoding::
662 * File content encoding::
664 * Operations on C Streams::
665 * Interfacing to C Streams::
669 * Stream Pointer Positioning::
670 * Reading and Writing Non-Regular Files::
672 * Treating Text_IO Files as Streams::
673 * Text_IO Extensions::
674 * Text_IO Facilities for Unbounded Strings::
678 * Stream Pointer Positioning: Stream Pointer Positioning<2>.
679 * Reading and Writing Non-Regular Files: Reading and Writing Non-Regular Files<2>.
683 * Stream Pointer Positioning: Stream Pointer Positioning<3>.
684 * Reading and Writing Non-Regular Files: Reading and Writing Non-Regular Files<3>.
688 * Ada.Characters.Latin_9 (a-chlat9.ads): Ada Characters Latin_9 a-chlat9 ads.
689 * Ada.Characters.Wide_Latin_1 (a-cwila1.ads): Ada Characters Wide_Latin_1 a-cwila1 ads.
690 * Ada.Characters.Wide_Latin_9 (a-cwila1.ads): Ada Characters Wide_Latin_9 a-cwila1 ads.
691 * Ada.Characters.Wide_Wide_Latin_1 (a-chzla1.ads): Ada Characters Wide_Wide_Latin_1 a-chzla1 ads.
692 * Ada.Characters.Wide_Wide_Latin_9 (a-chzla9.ads): Ada Characters Wide_Wide_Latin_9 a-chzla9 ads.
693 * Ada.Containers.Formal_Doubly_Linked_Lists (a-cfdlli.ads): Ada Containers Formal_Doubly_Linked_Lists a-cfdlli ads.
694 * Ada.Containers.Formal_Hashed_Maps (a-cfhama.ads): Ada Containers Formal_Hashed_Maps a-cfhama ads.
695 * Ada.Containers.Formal_Hashed_Sets (a-cfhase.ads): Ada Containers Formal_Hashed_Sets a-cfhase ads.
696 * Ada.Containers.Formal_Ordered_Maps (a-cforma.ads): Ada Containers Formal_Ordered_Maps a-cforma ads.
697 * Ada.Containers.Formal_Ordered_Sets (a-cforse.ads): Ada Containers Formal_Ordered_Sets a-cforse ads.
698 * Ada.Containers.Formal_Vectors (a-cofove.ads): Ada Containers Formal_Vectors a-cofove ads.
699 * Ada.Containers.Formal_Indefinite_Vectors (a-cfinve.ads): Ada Containers Formal_Indefinite_Vectors a-cfinve ads.
700 * Ada.Containers.Functional_Vectors (a-cofuve.ads): Ada Containers Functional_Vectors a-cofuve ads.
701 * Ada.Containers.Functional_Sets (a-cofuse.ads): Ada Containers Functional_Sets a-cofuse ads.
702 * Ada.Containers.Functional_Maps (a-cofuma.ads): Ada Containers Functional_Maps a-cofuma ads.
703 * Ada.Containers.Bounded_Holders (a-coboho.ads): Ada Containers Bounded_Holders a-coboho ads.
704 * Ada.Command_Line.Environment (a-colien.ads): Ada Command_Line Environment a-colien ads.
705 * Ada.Command_Line.Remove (a-colire.ads): Ada Command_Line Remove a-colire ads.
706 * Ada.Command_Line.Response_File (a-clrefi.ads): Ada Command_Line Response_File a-clrefi ads.
707 * Ada.Direct_IO.C_Streams (a-diocst.ads): Ada Direct_IO C_Streams a-diocst ads.
708 * Ada.Exceptions.Is_Null_Occurrence (a-einuoc.ads): Ada Exceptions Is_Null_Occurrence a-einuoc ads.
709 * Ada.Exceptions.Last_Chance_Handler (a-elchha.ads): Ada Exceptions Last_Chance_Handler a-elchha ads.
710 * Ada.Exceptions.Traceback (a-exctra.ads): Ada Exceptions Traceback a-exctra ads.
711 * Ada.Sequential_IO.C_Streams (a-siocst.ads): Ada Sequential_IO C_Streams a-siocst ads.
712 * Ada.Streams.Stream_IO.C_Streams (a-ssicst.ads): Ada Streams Stream_IO C_Streams a-ssicst ads.
713 * Ada.Strings.Unbounded.Text_IO (a-suteio.ads): Ada Strings Unbounded Text_IO a-suteio ads.
714 * Ada.Strings.Wide_Unbounded.Wide_Text_IO (a-swuwti.ads): Ada Strings Wide_Unbounded Wide_Text_IO a-swuwti ads.
715 * Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO (a-szuzti.ads): Ada Strings Wide_Wide_Unbounded Wide_Wide_Text_IO a-szuzti ads.
716 * Ada.Task_Initialization (a-tasini.ads): Ada Task_Initialization a-tasini ads.
717 * Ada.Text_IO.C_Streams (a-tiocst.ads): Ada Text_IO C_Streams a-tiocst ads.
718 * Ada.Text_IO.Reset_Standard_Files (a-tirsfi.ads): Ada Text_IO Reset_Standard_Files a-tirsfi ads.
719 * Ada.Wide_Characters.Unicode (a-wichun.ads): Ada Wide_Characters Unicode a-wichun ads.
720 * Ada.Wide_Text_IO.C_Streams (a-wtcstr.ads): Ada Wide_Text_IO C_Streams a-wtcstr ads.
721 * Ada.Wide_Text_IO.Reset_Standard_Files (a-wrstfi.ads): Ada Wide_Text_IO Reset_Standard_Files a-wrstfi ads.
722 * Ada.Wide_Wide_Characters.Unicode (a-zchuni.ads): Ada Wide_Wide_Characters Unicode a-zchuni ads.
723 * Ada.Wide_Wide_Text_IO.C_Streams (a-ztcstr.ads): Ada Wide_Wide_Text_IO C_Streams a-ztcstr ads.
724 * Ada.Wide_Wide_Text_IO.Reset_Standard_Files (a-zrstfi.ads): Ada Wide_Wide_Text_IO Reset_Standard_Files a-zrstfi ads.
725 * GNAT.Altivec (g-altive.ads): GNAT Altivec g-altive ads.
726 * GNAT.Altivec.Conversions (g-altcon.ads): GNAT Altivec Conversions g-altcon ads.
727 * GNAT.Altivec.Vector_Operations (g-alveop.ads): GNAT Altivec Vector_Operations g-alveop ads.
728 * GNAT.Altivec.Vector_Types (g-alvety.ads): GNAT Altivec Vector_Types g-alvety ads.
729 * GNAT.Altivec.Vector_Views (g-alvevi.ads): GNAT Altivec Vector_Views g-alvevi ads.
730 * GNAT.Array_Split (g-arrspl.ads): GNAT Array_Split g-arrspl ads.
731 * GNAT.AWK (g-awk.ads): GNAT AWK g-awk ads.
732 * GNAT.Bind_Environment (g-binenv.ads): GNAT Bind_Environment g-binenv ads.
733 * GNAT.Branch_Prediction (g-brapre.ads): GNAT Branch_Prediction g-brapre ads.
734 * GNAT.Bounded_Buffers (g-boubuf.ads): GNAT Bounded_Buffers g-boubuf ads.
735 * GNAT.Bounded_Mailboxes (g-boumai.ads): GNAT Bounded_Mailboxes g-boumai ads.
736 * GNAT.Bubble_Sort (g-bubsor.ads): GNAT Bubble_Sort g-bubsor ads.
737 * GNAT.Bubble_Sort_A (g-busora.ads): GNAT Bubble_Sort_A g-busora ads.
738 * GNAT.Bubble_Sort_G (g-busorg.ads): GNAT Bubble_Sort_G g-busorg ads.
739 * GNAT.Byte_Order_Mark (g-byorma.ads): GNAT Byte_Order_Mark g-byorma ads.
740 * GNAT.Byte_Swapping (g-bytswa.ads): GNAT Byte_Swapping g-bytswa ads.
741 * GNAT.Calendar (g-calend.ads): GNAT Calendar g-calend ads.
742 * GNAT.Calendar.Time_IO (g-catiio.ads): GNAT Calendar Time_IO g-catiio ads.
743 * GNAT.CRC32 (g-crc32.ads): GNAT CRC32 g-crc32 ads.
744 * GNAT.Case_Util (g-casuti.ads): GNAT Case_Util g-casuti ads.
745 * GNAT.CGI (g-cgi.ads): GNAT CGI g-cgi ads.
746 * GNAT.CGI.Cookie (g-cgicoo.ads): GNAT CGI Cookie g-cgicoo ads.
747 * GNAT.CGI.Debug (g-cgideb.ads): GNAT CGI Debug g-cgideb ads.
748 * GNAT.Command_Line (g-comlin.ads): GNAT Command_Line g-comlin ads.
749 * GNAT.Compiler_Version (g-comver.ads): GNAT Compiler_Version g-comver ads.
750 * GNAT.Ctrl_C (g-ctrl_c.ads): GNAT Ctrl_C g-ctrl_c ads.
751 * GNAT.Current_Exception (g-curexc.ads): GNAT Current_Exception g-curexc ads.
752 * GNAT.Debug_Pools (g-debpoo.ads): GNAT Debug_Pools g-debpoo ads.
753 * GNAT.Debug_Utilities (g-debuti.ads): GNAT Debug_Utilities g-debuti ads.
754 * GNAT.Decode_String (g-decstr.ads): GNAT Decode_String g-decstr ads.
755 * GNAT.Decode_UTF8_String (g-deutst.ads): GNAT Decode_UTF8_String g-deutst ads.
756 * GNAT.Directory_Operations (g-dirope.ads): GNAT Directory_Operations g-dirope ads.
757 * GNAT.Directory_Operations.Iteration (g-diopit.ads): GNAT Directory_Operations Iteration g-diopit ads.
758 * GNAT.Dynamic_HTables (g-dynhta.ads): GNAT Dynamic_HTables g-dynhta ads.
759 * GNAT.Dynamic_Tables (g-dyntab.ads): GNAT Dynamic_Tables g-dyntab ads.
760 * GNAT.Encode_String (g-encstr.ads): GNAT Encode_String g-encstr ads.
761 * GNAT.Encode_UTF8_String (g-enutst.ads): GNAT Encode_UTF8_String g-enutst ads.
762 * GNAT.Exception_Actions (g-excact.ads): GNAT Exception_Actions g-excact ads.
763 * GNAT.Exception_Traces (g-exctra.ads): GNAT Exception_Traces g-exctra ads.
764 * GNAT.Exceptions (g-except.ads): GNAT Exceptions g-except ads.
765 * GNAT.Expect (g-expect.ads): GNAT Expect g-expect ads.
766 * GNAT.Expect.TTY (g-exptty.ads): GNAT Expect TTY g-exptty ads.
767 * GNAT.Float_Control (g-flocon.ads): GNAT Float_Control g-flocon ads.
768 * GNAT.Formatted_String (g-forstr.ads): GNAT Formatted_String g-forstr ads.
769 * GNAT.Heap_Sort (g-heasor.ads): GNAT Heap_Sort g-heasor ads.
770 * GNAT.Heap_Sort_A (g-hesora.ads): GNAT Heap_Sort_A g-hesora ads.
771 * GNAT.Heap_Sort_G (g-hesorg.ads): GNAT Heap_Sort_G g-hesorg ads.
772 * GNAT.HTable (g-htable.ads): GNAT HTable g-htable ads.
773 * GNAT.IO (g-io.ads): GNAT IO g-io ads.
774 * GNAT.IO_Aux (g-io_aux.ads): GNAT IO_Aux g-io_aux ads.
775 * GNAT.Lock_Files (g-locfil.ads): GNAT Lock_Files g-locfil ads.
776 * GNAT.MBBS_Discrete_Random (g-mbdira.ads): GNAT MBBS_Discrete_Random g-mbdira ads.
777 * GNAT.MBBS_Float_Random (g-mbflra.ads): GNAT MBBS_Float_Random g-mbflra ads.
778 * GNAT.MD5 (g-md5.ads): GNAT MD5 g-md5 ads.
779 * GNAT.Memory_Dump (g-memdum.ads): GNAT Memory_Dump g-memdum ads.
780 * GNAT.Most_Recent_Exception (g-moreex.ads): GNAT Most_Recent_Exception g-moreex ads.
781 * GNAT.OS_Lib (g-os_lib.ads): GNAT OS_Lib g-os_lib ads.
782 * GNAT.Perfect_Hash_Generators (g-pehage.ads): GNAT Perfect_Hash_Generators g-pehage ads.
783 * GNAT.Random_Numbers (g-rannum.ads): GNAT Random_Numbers g-rannum ads.
784 * GNAT.Regexp (g-regexp.ads): GNAT Regexp g-regexp ads.
785 * GNAT.Registry (g-regist.ads): GNAT Registry g-regist ads.
786 * GNAT.Regpat (g-regpat.ads): GNAT Regpat g-regpat ads.
787 * GNAT.Rewrite_Data (g-rewdat.ads): GNAT Rewrite_Data g-rewdat ads.
788 * GNAT.Secondary_Stack_Info (g-sestin.ads): GNAT Secondary_Stack_Info g-sestin ads.
789 * GNAT.Semaphores (g-semaph.ads): GNAT Semaphores g-semaph ads.
790 * GNAT.Serial_Communications (g-sercom.ads): GNAT Serial_Communications g-sercom ads.
791 * GNAT.SHA1 (g-sha1.ads): GNAT SHA1 g-sha1 ads.
792 * GNAT.SHA224 (g-sha224.ads): GNAT SHA224 g-sha224 ads.
793 * GNAT.SHA256 (g-sha256.ads): GNAT SHA256 g-sha256 ads.
794 * GNAT.SHA384 (g-sha384.ads): GNAT SHA384 g-sha384 ads.
795 * GNAT.SHA512 (g-sha512.ads): GNAT SHA512 g-sha512 ads.
796 * GNAT.Signals (g-signal.ads): GNAT Signals g-signal ads.
797 * GNAT.Sockets (g-socket.ads): GNAT Sockets g-socket ads.
798 * GNAT.Source_Info (g-souinf.ads): GNAT Source_Info g-souinf ads.
799 * GNAT.Spelling_Checker (g-speche.ads): GNAT Spelling_Checker g-speche ads.
800 * GNAT.Spelling_Checker_Generic (g-spchge.ads): GNAT Spelling_Checker_Generic g-spchge ads.
801 * GNAT.Spitbol.Patterns (g-spipat.ads): GNAT Spitbol Patterns g-spipat ads.
802 * GNAT.Spitbol (g-spitbo.ads): GNAT Spitbol g-spitbo ads.
803 * GNAT.Spitbol.Table_Boolean (g-sptabo.ads): GNAT Spitbol Table_Boolean g-sptabo ads.
804 * GNAT.Spitbol.Table_Integer (g-sptain.ads): GNAT Spitbol Table_Integer g-sptain ads.
805 * GNAT.Spitbol.Table_VString (g-sptavs.ads): GNAT Spitbol Table_VString g-sptavs ads.
806 * GNAT.SSE (g-sse.ads): GNAT SSE g-sse ads.
807 * GNAT.SSE.Vector_Types (g-ssvety.ads): GNAT SSE Vector_Types g-ssvety ads.
808 * GNAT.String_Hash (g-strhas.ads): GNAT String_Hash g-strhas ads.
809 * GNAT.Strings (g-string.ads): GNAT Strings g-string ads.
810 * GNAT.String_Split (g-strspl.ads): GNAT String_Split g-strspl ads.
811 * GNAT.Table (g-table.ads): GNAT Table g-table ads.
812 * GNAT.Task_Lock (g-tasloc.ads): GNAT Task_Lock g-tasloc ads.
813 * GNAT.Time_Stamp (g-timsta.ads): GNAT Time_Stamp g-timsta ads.
814 * GNAT.Threads (g-thread.ads): GNAT Threads g-thread ads.
815 * GNAT.Traceback (g-traceb.ads): GNAT Traceback g-traceb ads.
816 * GNAT.Traceback.Symbolic (g-trasym.ads): GNAT Traceback Symbolic g-trasym ads.
817 * GNAT.UTF_32 (g-table.ads): GNAT UTF_32 g-table ads.
818 * GNAT.Wide_Spelling_Checker (g-u3spch.ads): GNAT Wide_Spelling_Checker g-u3spch ads.
819 * GNAT.Wide_Spelling_Checker (g-wispch.ads): GNAT Wide_Spelling_Checker g-wispch ads.
820 * GNAT.Wide_String_Split (g-wistsp.ads): GNAT Wide_String_Split g-wistsp ads.
821 * GNAT.Wide_Wide_Spelling_Checker (g-zspche.ads): GNAT Wide_Wide_Spelling_Checker g-zspche ads.
822 * GNAT.Wide_Wide_String_Split (g-zistsp.ads): GNAT Wide_Wide_String_Split g-zistsp ads.
823 * Interfaces.C.Extensions (i-cexten.ads): Interfaces C Extensions i-cexten ads.
824 * Interfaces.C.Streams (i-cstrea.ads): Interfaces C Streams i-cstrea ads.
825 * Interfaces.Packed_Decimal (i-pacdec.ads): Interfaces Packed_Decimal i-pacdec ads.
826 * Interfaces.VxWorks (i-vxwork.ads): Interfaces VxWorks i-vxwork ads.
827 * Interfaces.VxWorks.Int_Connection (i-vxinco.ads): Interfaces VxWorks Int_Connection i-vxinco ads.
828 * Interfaces.VxWorks.IO (i-vxwoio.ads): Interfaces VxWorks IO i-vxwoio ads.
829 * System.Address_Image (s-addima.ads): System Address_Image s-addima ads.
830 * System.Assertions (s-assert.ads): System Assertions s-assert ads.
831 * System.Atomic_Counters (s-atocou.ads): System Atomic_Counters s-atocou ads.
832 * System.Memory (s-memory.ads): System Memory s-memory ads.
833 * System.Multiprocessors (s-multip.ads): System Multiprocessors s-multip ads.
834 * System.Multiprocessors.Dispatching_Domains (s-mudido.ads): System Multiprocessors Dispatching_Domains s-mudido ads.
835 * System.Partition_Interface (s-parint.ads): System Partition_Interface s-parint ads.
836 * System.Pool_Global (s-pooglo.ads): System Pool_Global s-pooglo ads.
837 * System.Pool_Local (s-pooloc.ads): System Pool_Local s-pooloc ads.
838 * System.Restrictions (s-restri.ads): System Restrictions s-restri ads.
839 * System.Rident (s-rident.ads): System Rident s-rident ads.
840 * System.Strings.Stream_Ops (s-ststop.ads): System Strings Stream_Ops s-ststop ads.
841 * System.Unsigned_Types (s-unstyp.ads): System Unsigned_Types s-unstyp ads.
842 * System.Wch_Cnv (s-wchcnv.ads): System Wch_Cnv s-wchcnv ads.
843 * System.Wch_Con (s-wchcon.ads): System Wch_Con s-wchcon ads.
845 Interfacing to Other Languages
848 * Interfacing to C++::
849 * Interfacing to COBOL::
850 * Interfacing to Fortran::
851 * Interfacing to non-GNAT Ada code::
853 Implementation of Specific Ada Features
855 * Machine Code Insertions::
856 * GNAT Implementation of Tasking::
857 * GNAT Implementation of Shared Passive Packages::
858 * Code Generation for Array Aggregates::
859 * The Size of Discriminated Records with Default Discriminants::
860 * Strict Conformance to the Ada Reference Manual::
862 GNAT Implementation of Tasking
864 * Mapping Ada Tasks onto the Underlying Kernel Threads::
865 * Ensuring Compliance with the Real-Time Annex::
866 * Support for Locking Policies::
868 Code Generation for Array Aggregates
870 * Static constant aggregates with static bounds::
871 * Constant aggregates with unconstrained nominal types::
872 * Aggregates with static bounds::
873 * Aggregates with nonstatic bounds::
874 * Aggregates in assignment statements::
878 * pragma No_Run_Time::
880 * pragma Restricted_Run_Time::
882 * package System.Task_Info (s-tasinf.ads): package System Task_Info s-tasinf ads.
884 Compatibility and Porting Guide
886 * Writing Portable Fixed-Point Declarations::
887 * Compatibility with Ada 83::
888 * Compatibility between Ada 95 and Ada 2005::
889 * Implementation-dependent characteristics::
890 * Compatibility with Other Ada Systems::
891 * Representation Clauses::
892 * Compatibility with HP Ada 83::
894 Compatibility with Ada 83
896 * Legal Ada 83 programs that are illegal in Ada 95::
897 * More deterministic semantics::
898 * Changed semantics::
899 * Other language compatibility issues::
901 Implementation-dependent characteristics
903 * Implementation-defined pragmas::
904 * Implementation-defined attributes::
906 * Elaboration order::
907 * Target-specific aspects::
912 @node About This Guide,Implementation Defined Pragmas,Top,Top
913 @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}
914 @chapter About This Guide
918 This manual contains useful information in writing programs using the
919 GNAT compiler. It includes information on implementation dependent
920 characteristics of GNAT, including all the information required by
921 Annex M of the Ada language standard.
923 GNAT implements Ada 95, Ada 2005 and Ada 2012, and it may also be
924 invoked in Ada 83 compatibility mode.
925 By default, GNAT assumes Ada 2012,
926 but you can override with a compiler switch
927 to explicitly specify the language version.
928 (Please refer to the @emph{GNAT User's Guide} for details on these switches.)
929 Throughout this manual, references to 'Ada' without a year suffix
930 apply to all the Ada versions of the language.
932 Ada is designed to be highly portable.
933 In general, a program will have the same effect even when compiled by
934 different compilers on different platforms.
935 However, since Ada is designed to be used in a
936 wide variety of applications, it also contains a number of system
937 dependent features to be used in interfacing to the external world.
939 @geindex Implementation-dependent features
943 Note: Any program that makes use of implementation-dependent features
944 may be non-portable. You should follow good programming practice and
945 isolate and clearly document any sections of your program that make use
946 of these features in a non-portable manner.
949 * What This Reference Manual Contains::
951 * Related Information::
955 @node What This Reference Manual Contains,Conventions,,About This Guide
956 @anchor{gnat_rm/about_this_guide what-this-reference-manual-contains}@anchor{6}
957 @section What This Reference Manual Contains
960 This reference manual contains the following chapters:
966 @ref{7,,Implementation Defined Pragmas}, lists GNAT implementation-dependent
967 pragmas, which can be used to extend and enhance the functionality of the
971 @ref{8,,Implementation Defined Attributes}, lists GNAT
972 implementation-dependent attributes, which can be used to extend and
973 enhance the functionality of the compiler.
976 @ref{9,,Standard and Implementation Defined Restrictions}, lists GNAT
977 implementation-dependent restrictions, which can be used to extend and
978 enhance the functionality of the compiler.
981 @ref{a,,Implementation Advice}, provides information on generally
982 desirable behavior which are not requirements that all compilers must
983 follow since it cannot be provided on all systems, or which may be
984 undesirable on some systems.
987 @ref{b,,Implementation Defined Characteristics}, provides a guide to
988 minimizing implementation dependent features.
991 @ref{c,,Intrinsic Subprograms}, describes the intrinsic subprograms
992 implemented by GNAT, and how they can be imported into user
993 application programs.
996 @ref{d,,Representation Clauses and Pragmas}, describes in detail the
997 way that GNAT represents data, and in particular the exact set
998 of representation clauses and pragmas that is accepted.
1001 @ref{e,,Standard Library Routines}, provides a listing of packages and a
1002 brief description of the functionality that is provided by Ada's
1003 extensive set of standard library routines as implemented by GNAT.
1006 @ref{f,,The Implementation of Standard I/O}, details how the GNAT
1007 implementation of the input-output facilities.
1010 @ref{10,,The GNAT Library}, is a catalog of packages that complement
1011 the Ada predefined library.
1014 @ref{11,,Interfacing to Other Languages}, describes how programs
1015 written in Ada using GNAT can be interfaced to other programming
1019 @ref{12,,Specialized Needs Annexes}, describes the GNAT implementation of all
1020 of the specialized needs annexes.
1023 @ref{13,,Implementation of Specific Ada Features}, discusses issues related
1024 to GNAT's implementation of machine code insertions, tasking, and several
1028 @ref{14,,Implementation of Ada 2012 Features}, describes the status of the
1029 GNAT implementation of the Ada 2012 language standard.
1032 @ref{15,,Obsolescent Features} documents implementation dependent features,
1033 including pragmas and attributes, which are considered obsolescent, since
1034 there are other preferred ways of achieving the same results. These
1035 obsolescent forms are retained for backwards compatibility.
1038 @ref{16,,Compatibility and Porting Guide} presents some guidelines for
1039 developing portable Ada code, describes the compatibility issues that
1040 may arise between GNAT and other Ada compilation systems (including those
1041 for Ada 83), and shows how GNAT can expedite porting applications
1042 developed in other Ada environments.
1045 @ref{1,,GNU Free Documentation License} contains the license for this document.
1048 @geindex Ada 95 Language Reference Manual
1050 @geindex Ada 2005 Language Reference Manual
1052 This reference manual assumes a basic familiarity with the Ada 95 language, as
1054 @cite{International Standard ANSI/ISO/IEC-8652:1995}.
1055 It does not require knowledge of the new features introduced by Ada 2005 or
1057 All three reference manuals are included in the GNAT documentation
1060 @node Conventions,Related Information,What This Reference Manual Contains,About This Guide
1061 @anchor{gnat_rm/about_this_guide conventions}@anchor{17}
1062 @section Conventions
1065 @geindex Conventions
1066 @geindex typographical
1068 @geindex Typographical conventions
1070 Following are examples of the typographical and graphic conventions used
1077 @code{Functions}, @code{utility program names}, @code{standard names},
1093 [optional information or parameters]
1096 Examples are described by text
1099 and then shown this way.
1103 Commands that are entered by the user are shown as preceded by a prompt string
1104 comprising the @code{$} character followed by a space.
1107 @node Related Information,,Conventions,About This Guide
1108 @anchor{gnat_rm/about_this_guide related-information}@anchor{18}
1109 @section Related Information
1112 See the following documents for further information on GNAT:
1118 @cite{GNAT User's Guide for Native Platforms},
1119 which provides information on how to use the
1120 GNAT development environment.
1123 @cite{Ada 95 Reference Manual}, the Ada 95 programming language standard.
1126 @cite{Ada 95 Annotated Reference Manual}, which is an annotated version
1127 of the Ada 95 standard. The annotations describe
1128 detailed aspects of the design decision, and in particular contain useful
1129 sections on Ada 83 compatibility.
1132 @cite{Ada 2005 Reference Manual}, the Ada 2005 programming language standard.
1135 @cite{Ada 2005 Annotated Reference Manual}, which is an annotated version
1136 of the Ada 2005 standard. The annotations describe
1137 detailed aspects of the design decision.
1140 @cite{Ada 2012 Reference Manual}, the Ada 2012 programming language standard.
1143 @cite{DEC Ada@comma{} Technical Overview and Comparison on DIGITAL Platforms},
1144 which contains specific information on compatibility between GNAT and
1148 @cite{DEC Ada@comma{} Language Reference Manual}, part number AA-PYZAB-TK, which
1149 describes in detail the pragmas and attributes provided by the DEC Ada 83
1153 @node Implementation Defined Pragmas,Implementation Defined Aspects,About This Guide,Top
1154 @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}
1155 @chapter Implementation Defined Pragmas
1158 Ada defines a set of pragmas that can be used to supply additional
1159 information to the compiler. These language defined pragmas are
1160 implemented in GNAT and work as described in the Ada Reference Manual.
1162 In addition, Ada allows implementations to define additional pragmas
1163 whose meaning is defined by the implementation. GNAT provides a number
1164 of these implementation-defined pragmas, which can be used to extend
1165 and enhance the functionality of the compiler. This section of the GNAT
1166 Reference Manual describes these additional pragmas.
1168 Note that any program using these pragmas might not be portable to other
1169 compilers (although GNAT implements this set of pragmas on all
1170 platforms). Therefore if portability to other compilers is an important
1171 consideration, the use of these pragmas should be minimized.
1174 * Pragma Abort_Defer::
1175 * Pragma Abstract_State::
1182 * Pragma Aggregate_Individually_Assign::
1183 * Pragma Allow_Integer_Address::
1186 * Pragma Assert_And_Cut::
1187 * Pragma Assertion_Policy::
1189 * Pragma Assume_No_Invalid_Values::
1190 * Pragma Async_Readers::
1191 * Pragma Async_Writers::
1192 * Pragma Attribute_Definition::
1193 * Pragma C_Pass_By_Copy::
1195 * Pragma Check_Float_Overflow::
1196 * Pragma Check_Name::
1197 * Pragma Check_Policy::
1199 * Pragma Common_Object::
1200 * Pragma Compile_Time_Error::
1201 * Pragma Compile_Time_Warning::
1202 * Pragma Compiler_Unit::
1203 * Pragma Compiler_Unit_Warning::
1204 * Pragma Complete_Representation::
1205 * Pragma Complex_Representation::
1206 * Pragma Component_Alignment::
1207 * Pragma Constant_After_Elaboration::
1208 * Pragma Contract_Cases::
1209 * Pragma Convention_Identifier::
1210 * Pragma CPP_Class::
1211 * Pragma CPP_Constructor::
1212 * Pragma CPP_Virtual::
1213 * Pragma CPP_Vtable::
1215 * Pragma Deadline_Floor::
1216 * Pragma Default_Initial_Condition::
1218 * Pragma Debug_Policy::
1219 * Pragma Default_Scalar_Storage_Order::
1220 * Pragma Default_Storage_Pool::
1222 * Pragma Detect_Blocking::
1223 * Pragma Disable_Atomic_Synchronization::
1224 * Pragma Dispatching_Domain::
1225 * Pragma Effective_Reads::
1226 * Pragma Effective_Writes::
1227 * Pragma Elaboration_Checks::
1228 * Pragma Eliminate::
1229 * Pragma Enable_Atomic_Synchronization::
1230 * Pragma Export_Function::
1231 * Pragma Export_Object::
1232 * Pragma Export_Procedure::
1233 * Pragma Export_Value::
1234 * Pragma Export_Valued_Procedure::
1235 * Pragma Extend_System::
1236 * Pragma Extensions_Allowed::
1237 * Pragma Extensions_Visible::
1239 * Pragma External_Name_Casing::
1240 * Pragma Fast_Math::
1241 * Pragma Favor_Top_Level::
1242 * Pragma Finalize_Storage_Only::
1243 * Pragma Float_Representation::
1247 * Pragma Ignore_Pragma::
1248 * Pragma Implementation_Defined::
1249 * Pragma Implemented::
1250 * Pragma Implicit_Packing::
1251 * Pragma Import_Function::
1252 * Pragma Import_Object::
1253 * Pragma Import_Procedure::
1254 * Pragma Import_Valued_Procedure::
1255 * Pragma Independent::
1256 * Pragma Independent_Components::
1257 * Pragma Initial_Condition::
1258 * Pragma Initialize_Scalars::
1259 * Pragma Initializes::
1260 * Pragma Inline_Always::
1261 * Pragma Inline_Generic::
1262 * Pragma Interface::
1263 * Pragma Interface_Name::
1264 * Pragma Interrupt_Handler::
1265 * Pragma Interrupt_State::
1266 * Pragma Invariant::
1267 * Pragma Keep_Names::
1269 * Pragma Link_With::
1270 * Pragma Linker_Alias::
1271 * Pragma Linker_Constructor::
1272 * Pragma Linker_Destructor::
1273 * Pragma Linker_Section::
1274 * Pragma Lock_Free::
1275 * Pragma Loop_Invariant::
1276 * Pragma Loop_Optimize::
1277 * Pragma Loop_Variant::
1278 * Pragma Machine_Attribute::
1280 * Pragma Main_Storage::
1281 * Pragma Max_Queue_Length::
1283 * Pragma No_Caching::
1284 * Pragma No_Component_Reordering::
1285 * Pragma No_Elaboration_Code_All::
1286 * Pragma No_Heap_Finalization::
1287 * Pragma No_Inline::
1288 * Pragma No_Return::
1289 * Pragma No_Strict_Aliasing::
1290 * Pragma No_Tagged_Streams::
1291 * Pragma Normalize_Scalars::
1292 * Pragma Obsolescent::
1293 * Pragma Optimize_Alignment::
1295 * Pragma Overflow_Mode::
1296 * Pragma Overriding_Renamings::
1297 * Pragma Partition_Elaboration_Policy::
1300 * Pragma Persistent_BSS::
1302 * Pragma Postcondition::
1303 * Pragma Post_Class::
1304 * Pragma Rename_Pragma::
1306 * Pragma Precondition::
1307 * Pragma Predicate::
1308 * Pragma Predicate_Failure::
1309 * Pragma Preelaborable_Initialization::
1310 * Pragma Prefix_Exception_Messages::
1311 * Pragma Pre_Class::
1312 * Pragma Priority_Specific_Dispatching::
1314 * Pragma Profile_Warnings::
1315 * Pragma Propagate_Exceptions::
1316 * Pragma Provide_Shift_Operators::
1317 * Pragma Psect_Object::
1318 * Pragma Pure_Function::
1320 * Pragma Ravenscar::
1321 * Pragma Refined_Depends::
1322 * Pragma Refined_Global::
1323 * Pragma Refined_Post::
1324 * Pragma Refined_State::
1325 * Pragma Relative_Deadline::
1326 * Pragma Remote_Access_Type::
1327 * Pragma Restricted_Run_Time::
1328 * Pragma Restriction_Warnings::
1329 * Pragma Reviewable::
1330 * Pragma Secondary_Stack_Size::
1331 * Pragma Share_Generic::
1333 * Pragma Short_Circuit_And_Or::
1334 * Pragma Short_Descriptors::
1335 * Pragma Simple_Storage_Pool_Type::
1336 * Pragma Source_File_Name::
1337 * Pragma Source_File_Name_Project::
1338 * Pragma Source_Reference::
1339 * Pragma SPARK_Mode::
1340 * Pragma Static_Elaboration_Desired::
1341 * Pragma Stream_Convert::
1342 * Pragma Style_Checks::
1345 * Pragma Suppress_All::
1346 * Pragma Suppress_Debug_Info::
1347 * Pragma Suppress_Exception_Locations::
1348 * Pragma Suppress_Initialization::
1349 * Pragma Task_Name::
1350 * Pragma Task_Storage::
1351 * Pragma Test_Case::
1352 * Pragma Thread_Local_Storage::
1353 * Pragma Time_Slice::
1355 * Pragma Type_Invariant::
1356 * Pragma Type_Invariant_Class::
1357 * Pragma Unchecked_Union::
1358 * Pragma Unevaluated_Use_Of_Old::
1359 * Pragma Unimplemented_Unit::
1360 * Pragma Universal_Aliasing::
1361 * Pragma Universal_Data::
1362 * Pragma Unmodified::
1363 * Pragma Unreferenced::
1364 * Pragma Unreferenced_Objects::
1365 * Pragma Unreserve_All_Interrupts::
1366 * Pragma Unsuppress::
1367 * Pragma Use_VADS_Size::
1369 * Pragma Validity_Checks::
1371 * Pragma Volatile_Full_Access::
1372 * Pragma Volatile_Function::
1373 * Pragma Warning_As_Error::
1375 * Pragma Weak_External::
1376 * Pragma Wide_Character_Encoding::
1380 @node Pragma Abort_Defer,Pragma Abstract_State,,Implementation Defined Pragmas
1381 @anchor{gnat_rm/implementation_defined_pragmas pragma-abort-defer}@anchor{1b}
1382 @section Pragma Abort_Defer
1385 @geindex Deferring aborts
1393 This pragma must appear at the start of the statement sequence of a
1394 handled sequence of statements (right after the @code{begin}). It has
1395 the effect of deferring aborts for the sequence of statements (but not
1396 for the declarations or handlers, if any, associated with this statement
1399 @node Pragma Abstract_State,Pragma Ada_83,Pragma Abort_Defer,Implementation Defined Pragmas
1400 @anchor{gnat_rm/implementation_defined_pragmas pragma-abstract-state}@anchor{1c}@anchor{gnat_rm/implementation_defined_pragmas id2}@anchor{1d}
1401 @section Pragma Abstract_State
1407 pragma Abstract_State (ABSTRACT_STATE_LIST);
1409 ABSTRACT_STATE_LIST ::=
1411 | STATE_NAME_WITH_OPTIONS
1412 | (STATE_NAME_WITH_OPTIONS @{, STATE_NAME_WITH_OPTIONS@} )
1414 STATE_NAME_WITH_OPTIONS ::=
1416 | (STATE_NAME with OPTION_LIST)
1418 OPTION_LIST ::= OPTION @{, OPTION@}
1424 SIMPLE_OPTION ::= Ghost | Synchronous
1426 NAME_VALUE_OPTION ::=
1427 Part_Of => ABSTRACT_STATE
1428 | External [=> EXTERNAL_PROPERTY_LIST]
1430 EXTERNAL_PROPERTY_LIST ::=
1432 | (EXTERNAL_PROPERTY @{, EXTERNAL_PROPERTY@} )
1434 EXTERNAL_PROPERTY ::=
1435 Async_Readers [=> boolean_EXPRESSION]
1436 | Async_Writers [=> boolean_EXPRESSION]
1437 | Effective_Reads [=> boolean_EXPRESSION]
1438 | Effective_Writes [=> boolean_EXPRESSION]
1439 others => boolean_EXPRESSION
1441 STATE_NAME ::= defining_identifier
1443 ABSTRACT_STATE ::= name
1446 For the semantics of this pragma, see the entry for aspect @code{Abstract_State} in
1447 the SPARK 2014 Reference Manual, section 7.1.4.
1449 @node Pragma Ada_83,Pragma Ada_95,Pragma Abstract_State,Implementation Defined Pragmas
1450 @anchor{gnat_rm/implementation_defined_pragmas pragma-ada-83}@anchor{1e}
1451 @section Pragma Ada_83
1460 A configuration pragma that establishes Ada 83 mode for the unit to
1461 which it applies, regardless of the mode set by the command line
1462 switches. In Ada 83 mode, GNAT attempts to be as compatible with
1463 the syntax and semantics of Ada 83, as defined in the original Ada
1464 83 Reference Manual as possible. In particular, the keywords added by Ada 95
1465 and Ada 2005 are not recognized, optional package bodies are allowed,
1466 and generics may name types with unknown discriminants without using
1467 the @code{(<>)} notation. In addition, some but not all of the additional
1468 restrictions of Ada 83 are enforced.
1470 Ada 83 mode is intended for two purposes. Firstly, it allows existing
1471 Ada 83 code to be compiled and adapted to GNAT with less effort.
1472 Secondly, it aids in keeping code backwards compatible with Ada 83.
1473 However, there is no guarantee that code that is processed correctly
1474 by GNAT in Ada 83 mode will in fact compile and execute with an Ada
1475 83 compiler, since GNAT does not enforce all the additional checks
1478 @node Pragma Ada_95,Pragma Ada_05,Pragma Ada_83,Implementation Defined Pragmas
1479 @anchor{gnat_rm/implementation_defined_pragmas pragma-ada-95}@anchor{1f}
1480 @section Pragma Ada_95
1489 A configuration pragma that establishes Ada 95 mode for the unit to which
1490 it applies, regardless of the mode set by the command line switches.
1491 This mode is set automatically for the @code{Ada} and @code{System}
1492 packages and their children, so you need not specify it in these
1493 contexts. This pragma is useful when writing a reusable component that
1494 itself uses Ada 95 features, but which is intended to be usable from
1495 either Ada 83 or Ada 95 programs.
1497 @node Pragma Ada_05,Pragma Ada_2005,Pragma Ada_95,Implementation Defined Pragmas
1498 @anchor{gnat_rm/implementation_defined_pragmas pragma-ada-05}@anchor{20}
1499 @section Pragma Ada_05
1506 pragma Ada_05 (local_NAME);
1509 A configuration pragma that establishes Ada 2005 mode for the unit to which
1510 it applies, regardless of the mode set by the command line switches.
1511 This pragma is useful when writing a reusable component that
1512 itself uses Ada 2005 features, but which is intended to be usable from
1513 either Ada 83 or Ada 95 programs.
1515 The one argument form (which is not a configuration pragma)
1516 is used for managing the transition from
1517 Ada 95 to Ada 2005 in the run-time library. If an entity is marked
1518 as Ada_2005 only, then referencing the entity in Ada_83 or Ada_95
1519 mode will generate a warning. In addition, in Ada_83 or Ada_95
1520 mode, a preference rule is established which does not choose
1521 such an entity unless it is unambiguously specified. This avoids
1522 extra subprograms marked this way from generating ambiguities in
1523 otherwise legal pre-Ada_2005 programs. The one argument form is
1524 intended for exclusive use in the GNAT run-time library.
1526 @node Pragma Ada_2005,Pragma Ada_12,Pragma Ada_05,Implementation Defined Pragmas
1527 @anchor{gnat_rm/implementation_defined_pragmas pragma-ada-2005}@anchor{21}
1528 @section Pragma Ada_2005
1537 This configuration pragma is a synonym for pragma Ada_05 and has the
1538 same syntax and effect.
1540 @node Pragma Ada_12,Pragma Ada_2012,Pragma Ada_2005,Implementation Defined Pragmas
1541 @anchor{gnat_rm/implementation_defined_pragmas pragma-ada-12}@anchor{22}
1542 @section Pragma Ada_12
1549 pragma Ada_12 (local_NAME);
1552 A configuration pragma that establishes Ada 2012 mode for the unit to which
1553 it applies, regardless of the mode set by the command line switches.
1554 This mode is set automatically for the @code{Ada} and @code{System}
1555 packages and their children, so you need not specify it in these
1556 contexts. This pragma is useful when writing a reusable component that
1557 itself uses Ada 2012 features, but which is intended to be usable from
1558 Ada 83, Ada 95, or Ada 2005 programs.
1560 The one argument form, which is not a configuration pragma,
1561 is used for managing the transition from Ada
1562 2005 to Ada 2012 in the run-time library. If an entity is marked
1563 as Ada_2012 only, then referencing the entity in any pre-Ada_2012
1564 mode will generate a warning. In addition, in any pre-Ada_2012
1565 mode, a preference rule is established which does not choose
1566 such an entity unless it is unambiguously specified. This avoids
1567 extra subprograms marked this way from generating ambiguities in
1568 otherwise legal pre-Ada_2012 programs. The one argument form is
1569 intended for exclusive use in the GNAT run-time library.
1571 @node Pragma Ada_2012,Pragma Aggregate_Individually_Assign,Pragma Ada_12,Implementation Defined Pragmas
1572 @anchor{gnat_rm/implementation_defined_pragmas pragma-ada-2012}@anchor{23}
1573 @section Pragma Ada_2012
1582 This configuration pragma is a synonym for pragma Ada_12 and has the
1583 same syntax and effect.
1585 @node Pragma Aggregate_Individually_Assign,Pragma Allow_Integer_Address,Pragma Ada_2012,Implementation Defined Pragmas
1586 @anchor{gnat_rm/implementation_defined_pragmas pragma-aggregate-individually-assign}@anchor{24}
1587 @section Pragma Aggregate_Individually_Assign
1593 pragma Aggregate_Individually_Assign;
1596 Where possible, GNAT will store the binary representation of a record aggregate
1597 in memory for space and performance reasons. This configuration pragma changes
1598 this behavior so that record aggregates are instead always converted into
1599 individual assignment statements.
1601 @node Pragma Allow_Integer_Address,Pragma Annotate,Pragma Aggregate_Individually_Assign,Implementation Defined Pragmas
1602 @anchor{gnat_rm/implementation_defined_pragmas pragma-allow-integer-address}@anchor{25}
1603 @section Pragma Allow_Integer_Address
1609 pragma Allow_Integer_Address;
1612 In almost all versions of GNAT, @code{System.Address} is a private
1613 type in accordance with the implementation advice in the RM. This
1614 means that integer values,
1615 in particular integer literals, are not allowed as address values.
1616 If the configuration pragma
1617 @code{Allow_Integer_Address} is given, then integer expressions may
1618 be used anywhere a value of type @code{System.Address} is required.
1619 The effect is to introduce an implicit unchecked conversion from the
1620 integer value to type @code{System.Address}. The reverse case of using
1621 an address where an integer type is required is handled analogously.
1622 The following example compiles without errors:
1625 pragma Allow_Integer_Address;
1626 with System; use System;
1627 package AddrAsInt is
1630 for X'Address use 16#1240#;
1631 for Y use at 16#3230#;
1632 m : Address := 16#4000#;
1633 n : constant Address := 4000;
1634 p : constant Address := Address (X + Y);
1635 v : Integer := y'Address;
1636 w : constant Integer := Integer (Y'Address);
1637 type R is new integer;
1640 for Z'Address use RR;
1644 Note that pragma @code{Allow_Integer_Address} is ignored if @code{System.Address}
1645 is not a private type. In implementations of @code{GNAT} where
1646 System.Address is a visible integer type,
1647 this pragma serves no purpose but is ignored
1648 rather than rejected to allow common sets of sources to be used
1649 in the two situations.
1651 @node Pragma Annotate,Pragma Assert,Pragma Allow_Integer_Address,Implementation Defined Pragmas
1652 @anchor{gnat_rm/implementation_defined_pragmas pragma-annotate}@anchor{26}@anchor{gnat_rm/implementation_defined_pragmas id3}@anchor{27}
1653 @section Pragma Annotate
1659 pragma Annotate (IDENTIFIER [, IDENTIFIER @{, ARG@}] [, entity => local_NAME]);
1661 ARG ::= NAME | EXPRESSION
1664 This pragma is used to annotate programs. IDENTIFIER identifies
1665 the type of annotation. GNAT verifies that it is an identifier, but does
1666 not otherwise analyze it. The second optional identifier is also left
1667 unanalyzed, and by convention is used to control the action of the tool to
1668 which the annotation is addressed. The remaining ARG arguments
1669 can be either string literals or more generally expressions.
1670 String literals (and concatenations of string literals) are assumed to be
1672 @code{Standard.String} or else @code{Wide_String} or @code{Wide_Wide_String}
1673 depending on the character literals they contain.
1674 All other kinds of arguments are analyzed as expressions, and must be
1675 unambiguous. The last argument if present must have the identifier
1676 @code{Entity} and GNAT verifies that a local name is given.
1678 The analyzed pragma is retained in the tree, but not otherwise processed
1679 by any part of the GNAT compiler, except to generate corresponding note
1680 lines in the generated ALI file. For the format of these note lines, see
1681 the compiler source file lib-writ.ads. This pragma is intended for use by
1682 external tools, including ASIS. The use of pragma Annotate does not
1683 affect the compilation process in any way. This pragma may be used as
1684 a configuration pragma.
1686 @node Pragma Assert,Pragma Assert_And_Cut,Pragma Annotate,Implementation Defined Pragmas
1687 @anchor{gnat_rm/implementation_defined_pragmas pragma-assert}@anchor{28}
1688 @section Pragma Assert
1696 [, string_EXPRESSION]);
1699 The effect of this pragma depends on whether the corresponding command
1700 line switch is set to activate assertions. The pragma expands into code
1701 equivalent to the following:
1704 if assertions-enabled then
1705 if not boolean_EXPRESSION then
1706 System.Assertions.Raise_Assert_Failure
1707 (string_EXPRESSION);
1712 The string argument, if given, is the message that will be associated
1713 with the exception occurrence if the exception is raised. If no second
1714 argument is given, the default message is @code{file}:@code{nnn},
1715 where @code{file} is the name of the source file containing the assert,
1716 and @code{nnn} is the line number of the assert.
1718 Note that, as with the @code{if} statement to which it is equivalent, the
1719 type of the expression is either @code{Standard.Boolean}, or any type derived
1720 from this standard type.
1722 Assert checks can be either checked or ignored. By default they are ignored.
1723 They will be checked if either the command line switch @emph{-gnata} is
1724 used, or if an @code{Assertion_Policy} or @code{Check_Policy} pragma is used
1725 to enable @code{Assert_Checks}.
1727 If assertions are ignored, then there
1728 is no run-time effect (and in particular, any side effects from the
1729 expression will not occur at run time). (The expression is still
1730 analyzed at compile time, and may cause types to be frozen if they are
1731 mentioned here for the first time).
1733 If assertions are checked, then the given expression is tested, and if
1734 it is @code{False} then @code{System.Assertions.Raise_Assert_Failure} is called
1735 which results in the raising of @code{Assert_Failure} with the given message.
1737 You should generally avoid side effects in the expression arguments of
1738 this pragma, because these side effects will turn on and off with the
1739 setting of the assertions mode, resulting in assertions that have an
1740 effect on the program. However, the expressions are analyzed for
1741 semantic correctness whether or not assertions are enabled, so turning
1742 assertions on and off cannot affect the legality of a program.
1744 Note that the implementation defined policy @code{DISABLE}, given in a
1745 pragma @code{Assertion_Policy}, can be used to suppress this semantic analysis.
1747 Note: this is a standard language-defined pragma in versions
1748 of Ada from 2005 on. In GNAT, it is implemented in all versions
1749 of Ada, and the DISABLE policy is an implementation-defined
1752 @node Pragma Assert_And_Cut,Pragma Assertion_Policy,Pragma Assert,Implementation Defined Pragmas
1753 @anchor{gnat_rm/implementation_defined_pragmas pragma-assert-and-cut}@anchor{29}
1754 @section Pragma Assert_And_Cut
1760 pragma Assert_And_Cut (
1762 [, string_EXPRESSION]);
1765 The effect of this pragma is identical to that of pragma @code{Assert},
1766 except that in an @code{Assertion_Policy} pragma, the identifier
1767 @code{Assert_And_Cut} is used to control whether it is ignored or checked
1770 The intention is that this be used within a subprogram when the
1771 given test expresion sums up all the work done so far in the
1772 subprogram, so that the rest of the subprogram can be verified
1773 (informally or formally) using only the entry preconditions,
1774 and the expression in this pragma. This allows dividing up
1775 a subprogram into sections for the purposes of testing or
1776 formal verification. The pragma also serves as useful
1779 @node Pragma Assertion_Policy,Pragma Assume,Pragma Assert_And_Cut,Implementation Defined Pragmas
1780 @anchor{gnat_rm/implementation_defined_pragmas pragma-assertion-policy}@anchor{2a}
1781 @section Pragma Assertion_Policy
1787 pragma Assertion_Policy (CHECK | DISABLE | IGNORE | SUPPRESSIBLE);
1789 pragma Assertion_Policy (
1790 ASSERTION_KIND => POLICY_IDENTIFIER
1791 @{, ASSERTION_KIND => POLICY_IDENTIFIER@});
1793 ASSERTION_KIND ::= RM_ASSERTION_KIND | ID_ASSERTION_KIND
1795 RM_ASSERTION_KIND ::= Assert |
1803 Type_Invariant'Class
1805 ID_ASSERTION_KIND ::= Assertions |
1819 Statement_Assertions
1821 POLICY_IDENTIFIER ::= Check | Disable | Ignore | Suppressible
1824 This is a standard Ada 2012 pragma that is available as an
1825 implementation-defined pragma in earlier versions of Ada.
1826 The assertion kinds @code{RM_ASSERTION_KIND} are those defined in
1827 the Ada standard. The assertion kinds @code{ID_ASSERTION_KIND}
1828 are implementation defined additions recognized by the GNAT compiler.
1830 The pragma applies in both cases to pragmas and aspects with matching
1831 names, e.g. @code{Pre} applies to the Pre aspect, and @code{Precondition}
1832 applies to both the @code{Precondition} pragma
1833 and the aspect @code{Precondition}. Note that the identifiers for
1834 pragmas Pre_Class and Post_Class are Pre'Class and Post'Class (not
1835 Pre_Class and Post_Class), since these pragmas are intended to be
1836 identical to the corresponding aspects).
1838 If the policy is @code{CHECK}, then assertions are enabled, i.e.
1839 the corresponding pragma or aspect is activated.
1840 If the policy is @code{IGNORE}, then assertions are ignored, i.e.
1841 the corresponding pragma or aspect is deactivated.
1842 This pragma overrides the effect of the @emph{-gnata} switch on the
1844 If the policy is @code{SUPPRESSIBLE}, then assertions are enabled by default,
1845 however, if the @emph{-gnatp} switch is specified all assertions are ignored.
1847 The implementation defined policy @code{DISABLE} is like
1848 @code{IGNORE} except that it completely disables semantic
1849 checking of the corresponding pragma or aspect. This is
1850 useful when the pragma or aspect argument references subprograms
1851 in a with'ed package which is replaced by a dummy package
1852 for the final build.
1854 The implementation defined assertion kind @code{Assertions} applies to all
1855 assertion kinds. The form with no assertion kind given implies this
1856 choice, so it applies to all assertion kinds (RM defined, and
1857 implementation defined).
1859 The implementation defined assertion kind @code{Statement_Assertions}
1860 applies to @code{Assert}, @code{Assert_And_Cut},
1861 @code{Assume}, @code{Loop_Invariant}, and @code{Loop_Variant}.
1863 @node Pragma Assume,Pragma Assume_No_Invalid_Values,Pragma Assertion_Policy,Implementation Defined Pragmas
1864 @anchor{gnat_rm/implementation_defined_pragmas pragma-assume}@anchor{2b}
1865 @section Pragma Assume
1873 [, string_EXPRESSION]);
1876 The effect of this pragma is identical to that of pragma @code{Assert},
1877 except that in an @code{Assertion_Policy} pragma, the identifier
1878 @code{Assume} is used to control whether it is ignored or checked
1881 The intention is that this be used for assumptions about the
1882 external environment. So you cannot expect to verify formally
1883 or informally that the condition is met, this must be
1884 established by examining things outside the program itself.
1885 For example, we may have code that depends on the size of
1886 @code{Long_Long_Integer} being at least 64. So we could write:
1889 pragma Assume (Long_Long_Integer'Size >= 64);
1892 This assumption cannot be proved from the program itself,
1893 but it acts as a useful run-time check that the assumption
1894 is met, and documents the need to ensure that it is met by
1895 reference to information outside the program.
1897 @node Pragma Assume_No_Invalid_Values,Pragma Async_Readers,Pragma Assume,Implementation Defined Pragmas
1898 @anchor{gnat_rm/implementation_defined_pragmas pragma-assume-no-invalid-values}@anchor{2c}
1899 @section Pragma Assume_No_Invalid_Values
1902 @geindex Invalid representations
1904 @geindex Invalid values
1909 pragma Assume_No_Invalid_Values (On | Off);
1912 This is a configuration pragma that controls the assumptions made by the
1913 compiler about the occurrence of invalid representations (invalid values)
1916 The default behavior (corresponding to an Off argument for this pragma), is
1917 to assume that values may in general be invalid unless the compiler can
1918 prove they are valid. Consider the following example:
1921 V1 : Integer range 1 .. 10;
1922 V2 : Integer range 11 .. 20;
1924 for J in V2 .. V1 loop
1929 if V1 and V2 have valid values, then the loop is known at compile
1930 time not to execute since the lower bound must be greater than the
1931 upper bound. However in default mode, no such assumption is made,
1932 and the loop may execute. If @code{Assume_No_Invalid_Values (On)}
1933 is given, the compiler will assume that any occurrence of a variable
1934 other than in an explicit @code{'Valid} test always has a valid
1935 value, and the loop above will be optimized away.
1937 The use of @code{Assume_No_Invalid_Values (On)} is appropriate if
1938 you know your code is free of uninitialized variables and other
1939 possible sources of invalid representations, and may result in
1940 more efficient code. A program that accesses an invalid representation
1941 with this pragma in effect is erroneous, so no guarantees can be made
1944 It is peculiar though permissible to use this pragma in conjunction
1945 with validity checking (-gnatVa). In such cases, accessing invalid
1946 values will generally give an exception, though formally the program
1947 is erroneous so there are no guarantees that this will always be the
1948 case, and it is recommended that these two options not be used together.
1950 @node Pragma Async_Readers,Pragma Async_Writers,Pragma Assume_No_Invalid_Values,Implementation Defined Pragmas
1951 @anchor{gnat_rm/implementation_defined_pragmas pragma-async-readers}@anchor{2d}@anchor{gnat_rm/implementation_defined_pragmas id4}@anchor{2e}
1952 @section Pragma Async_Readers
1958 pragma Async_Readers [ (boolean_EXPRESSION) ];
1961 For the semantics of this pragma, see the entry for aspect @code{Async_Readers} in
1962 the SPARK 2014 Reference Manual, section 7.1.2.
1964 @node Pragma Async_Writers,Pragma Attribute_Definition,Pragma Async_Readers,Implementation Defined Pragmas
1965 @anchor{gnat_rm/implementation_defined_pragmas id5}@anchor{2f}@anchor{gnat_rm/implementation_defined_pragmas pragma-async-writers}@anchor{30}
1966 @section Pragma Async_Writers
1972 pragma Async_Writers [ (boolean_EXPRESSION) ];
1975 For the semantics of this pragma, see the entry for aspect @code{Async_Writers} in
1976 the SPARK 2014 Reference Manual, section 7.1.2.
1978 @node Pragma Attribute_Definition,Pragma C_Pass_By_Copy,Pragma Async_Writers,Implementation Defined Pragmas
1979 @anchor{gnat_rm/implementation_defined_pragmas pragma-attribute-definition}@anchor{31}
1980 @section Pragma Attribute_Definition
1986 pragma Attribute_Definition
1987 ([Attribute =>] ATTRIBUTE_DESIGNATOR,
1988 [Entity =>] LOCAL_NAME,
1989 [Expression =>] EXPRESSION | NAME);
1992 If @code{Attribute} is a known attribute name, this pragma is equivalent to
1993 the attribute definition clause:
1996 for Entity'Attribute use Expression;
1999 If @code{Attribute} is not a recognized attribute name, the pragma is
2000 ignored, and a warning is emitted. This allows source
2001 code to be written that takes advantage of some new attribute, while remaining
2002 compilable with earlier compilers.
2004 @node Pragma C_Pass_By_Copy,Pragma Check,Pragma Attribute_Definition,Implementation Defined Pragmas
2005 @anchor{gnat_rm/implementation_defined_pragmas pragma-c-pass-by-copy}@anchor{32}
2006 @section Pragma C_Pass_By_Copy
2009 @geindex Passing by copy
2014 pragma C_Pass_By_Copy
2015 ([Max_Size =>] static_integer_EXPRESSION);
2018 Normally the default mechanism for passing C convention records to C
2019 convention subprograms is to pass them by reference, as suggested by RM
2020 B.3(69). Use the configuration pragma @code{C_Pass_By_Copy} to change
2021 this default, by requiring that record formal parameters be passed by
2022 copy if all of the following conditions are met:
2028 The size of the record type does not exceed the value specified for
2032 The record type has @code{Convention C}.
2035 The formal parameter has this record type, and the subprogram has a
2036 foreign (non-Ada) convention.
2039 If these conditions are met the argument is passed by copy; i.e., in a
2040 manner consistent with what C expects if the corresponding formal in the
2041 C prototype is a struct (rather than a pointer to a struct).
2043 You can also pass records by copy by specifying the convention
2044 @code{C_Pass_By_Copy} for the record type, or by using the extended
2045 @code{Import} and @code{Export} pragmas, which allow specification of
2046 passing mechanisms on a parameter by parameter basis.
2048 @node Pragma Check,Pragma Check_Float_Overflow,Pragma C_Pass_By_Copy,Implementation Defined Pragmas
2049 @anchor{gnat_rm/implementation_defined_pragmas pragma-check}@anchor{33}
2050 @section Pragma Check
2055 @geindex Named assertions
2061 [Name =>] CHECK_KIND,
2062 [Check =>] Boolean_EXPRESSION
2063 [, [Message =>] string_EXPRESSION] );
2065 CHECK_KIND ::= IDENTIFIER |
2068 Type_Invariant'Class |
2072 This pragma is similar to the predefined pragma @code{Assert} except that an
2073 extra identifier argument is present. In conjunction with pragma
2074 @code{Check_Policy}, this can be used to define groups of assertions that can
2075 be independently controlled. The identifier @code{Assertion} is special, it
2076 refers to the normal set of pragma @code{Assert} statements.
2078 Checks introduced by this pragma are normally deactivated by default. They can
2079 be activated either by the command line option @emph{-gnata}, which turns on
2080 all checks, or individually controlled using pragma @code{Check_Policy}.
2082 The identifiers @code{Assertions} and @code{Statement_Assertions} are not
2083 permitted as check kinds, since this would cause confusion with the use
2084 of these identifiers in @code{Assertion_Policy} and @code{Check_Policy}
2085 pragmas, where they are used to refer to sets of assertions.
2087 @node Pragma Check_Float_Overflow,Pragma Check_Name,Pragma Check,Implementation Defined Pragmas
2088 @anchor{gnat_rm/implementation_defined_pragmas pragma-check-float-overflow}@anchor{34}
2089 @section Pragma Check_Float_Overflow
2092 @geindex Floating-point overflow
2097 pragma Check_Float_Overflow;
2100 In Ada, the predefined floating-point types (@code{Short_Float},
2101 @code{Float}, @code{Long_Float}, @code{Long_Long_Float}) are
2102 defined to be @emph{unconstrained}. This means that even though each
2103 has a well-defined base range, an operation that delivers a result
2104 outside this base range is not required to raise an exception.
2105 This implementation permission accommodates the notion
2106 of infinities in IEEE floating-point, and corresponds to the
2107 efficient execution mode on most machines. GNAT will not raise
2108 overflow exceptions on these machines; instead it will generate
2109 infinities and NaN's as defined in the IEEE standard.
2111 Generating infinities, although efficient, is not always desirable.
2112 Often the preferable approach is to check for overflow, even at the
2113 (perhaps considerable) expense of run-time performance.
2114 This can be accomplished by defining your own constrained floating-point subtypes -- i.e., by supplying explicit
2115 range constraints -- and indeed such a subtype
2116 can have the same base range as its base type. For example:
2119 subtype My_Float is Float range Float'Range;
2122 Here @code{My_Float} has the same range as
2123 @code{Float} but is constrained, so operations on
2124 @code{My_Float} values will be checked for overflow
2127 This style will achieve the desired goal, but
2128 it is often more convenient to be able to simply use
2129 the standard predefined floating-point types as long
2130 as overflow checking could be guaranteed.
2131 The @code{Check_Float_Overflow}
2132 configuration pragma achieves this effect. If a unit is compiled
2133 subject to this configuration pragma, then all operations
2134 on predefined floating-point types including operations on
2135 base types of these floating-point types will be treated as
2136 though those types were constrained, and overflow checks
2137 will be generated. The @code{Constraint_Error}
2138 exception is raised if the result is out of range.
2140 This mode can also be set by use of the compiler
2141 switch @emph{-gnateF}.
2143 @node Pragma Check_Name,Pragma Check_Policy,Pragma Check_Float_Overflow,Implementation Defined Pragmas
2144 @anchor{gnat_rm/implementation_defined_pragmas pragma-check-name}@anchor{35}
2145 @section Pragma Check_Name
2148 @geindex Defining check names
2150 @geindex Check names
2156 pragma Check_Name (check_name_IDENTIFIER);
2159 This is a configuration pragma that defines a new implementation
2160 defined check name (unless IDENTIFIER matches one of the predefined
2161 check names, in which case the pragma has no effect). Check names
2162 are global to a partition, so if two or more configuration pragmas
2163 are present in a partition mentioning the same name, only one new
2164 check name is introduced.
2166 An implementation defined check name introduced with this pragma may
2167 be used in only three contexts: @code{pragma Suppress},
2168 @code{pragma Unsuppress},
2169 and as the prefix of a @code{Check_Name'Enabled} attribute reference. For
2170 any of these three cases, the check name must be visible. A check
2171 name is visible if it is in the configuration pragmas applying to
2172 the current unit, or if it appears at the start of any unit that
2173 is part of the dependency set of the current unit (e.g., units that
2174 are mentioned in @code{with} clauses).
2176 Check names introduced by this pragma are subject to control by compiler
2177 switches (in particular -gnatp) in the usual manner.
2179 @node Pragma Check_Policy,Pragma Comment,Pragma Check_Name,Implementation Defined Pragmas
2180 @anchor{gnat_rm/implementation_defined_pragmas pragma-check-policy}@anchor{36}
2181 @section Pragma Check_Policy
2184 @geindex Controlling assertions
2189 @geindex Check pragma control
2191 @geindex Named assertions
2197 ([Name =>] CHECK_KIND,
2198 [Policy =>] POLICY_IDENTIFIER);
2200 pragma Check_Policy (
2201 CHECK_KIND => POLICY_IDENTIFIER
2202 @{, CHECK_KIND => POLICY_IDENTIFIER@});
2204 ASSERTION_KIND ::= RM_ASSERTION_KIND | ID_ASSERTION_KIND
2206 CHECK_KIND ::= IDENTIFIER |
2209 Type_Invariant'Class |
2212 The identifiers Name and Policy are not allowed as CHECK_KIND values. This
2213 avoids confusion between the two possible syntax forms for this pragma.
2215 POLICY_IDENTIFIER ::= ON | OFF | CHECK | DISABLE | IGNORE
2218 This pragma is used to set the checking policy for assertions (specified
2219 by aspects or pragmas), the @code{Debug} pragma, or additional checks
2220 to be checked using the @code{Check} pragma. It may appear either as
2221 a configuration pragma, or within a declarative part of package. In the
2222 latter case, it applies from the point where it appears to the end of
2223 the declarative region (like pragma @code{Suppress}).
2225 The @code{Check_Policy} pragma is similar to the
2226 predefined @code{Assertion_Policy} pragma,
2227 and if the check kind corresponds to one of the assertion kinds that
2228 are allowed by @code{Assertion_Policy}, then the effect is identical.
2230 If the first argument is Debug, then the policy applies to Debug pragmas,
2231 disabling their effect if the policy is @code{OFF}, @code{DISABLE}, or
2232 @code{IGNORE}, and allowing them to execute with normal semantics if
2233 the policy is @code{ON} or @code{CHECK}. In addition if the policy is
2234 @code{DISABLE}, then the procedure call in @code{Debug} pragmas will
2235 be totally ignored and not analyzed semantically.
2237 Finally the first argument may be some other identifier than the above
2238 possibilities, in which case it controls a set of named assertions
2239 that can be checked using pragma @code{Check}. For example, if the pragma:
2242 pragma Check_Policy (Critical_Error, OFF);
2245 is given, then subsequent @code{Check} pragmas whose first argument is also
2246 @code{Critical_Error} will be disabled.
2248 The check policy is @code{OFF} to turn off corresponding checks, and @code{ON}
2249 to turn on corresponding checks. The default for a set of checks for which no
2250 @code{Check_Policy} is given is @code{OFF} unless the compiler switch
2251 @emph{-gnata} is given, which turns on all checks by default.
2253 The check policy settings @code{CHECK} and @code{IGNORE} are recognized
2254 as synonyms for @code{ON} and @code{OFF}. These synonyms are provided for
2255 compatibility with the standard @code{Assertion_Policy} pragma. The check
2256 policy setting @code{DISABLE} causes the second argument of a corresponding
2257 @code{Check} pragma to be completely ignored and not analyzed.
2259 @node Pragma Comment,Pragma Common_Object,Pragma Check_Policy,Implementation Defined Pragmas
2260 @anchor{gnat_rm/implementation_defined_pragmas pragma-comment}@anchor{37}
2261 @section Pragma Comment
2267 pragma Comment (static_string_EXPRESSION);
2270 This is almost identical in effect to pragma @code{Ident}. It allows the
2271 placement of a comment into the object file and hence into the
2272 executable file if the operating system permits such usage. The
2273 difference is that @code{Comment}, unlike @code{Ident}, has
2274 no limitations on placement of the pragma (it can be placed
2275 anywhere in the main source unit), and if more than one pragma
2276 is used, all comments are retained.
2278 @node Pragma Common_Object,Pragma Compile_Time_Error,Pragma Comment,Implementation Defined Pragmas
2279 @anchor{gnat_rm/implementation_defined_pragmas pragma-common-object}@anchor{38}
2280 @section Pragma Common_Object
2286 pragma Common_Object (
2287 [Internal =>] LOCAL_NAME
2288 [, [External =>] EXTERNAL_SYMBOL]
2289 [, [Size =>] EXTERNAL_SYMBOL] );
2293 | static_string_EXPRESSION
2296 This pragma enables the shared use of variables stored in overlaid
2297 linker areas corresponding to the use of @code{COMMON}
2298 in Fortran. The single
2299 object @code{LOCAL_NAME} is assigned to the area designated by
2300 the @code{External} argument.
2301 You may define a record to correspond to a series
2302 of fields. The @code{Size} argument
2303 is syntax checked in GNAT, but otherwise ignored.
2305 @code{Common_Object} is not supported on all platforms. If no
2306 support is available, then the code generator will issue a message
2307 indicating that the necessary attribute for implementation of this
2308 pragma is not available.
2310 @node Pragma Compile_Time_Error,Pragma Compile_Time_Warning,Pragma Common_Object,Implementation Defined Pragmas
2311 @anchor{gnat_rm/implementation_defined_pragmas pragma-compile-time-error}@anchor{39}@anchor{gnat_rm/implementation_defined_pragmas compile-time-error}@anchor{3a}
2312 @section Pragma Compile_Time_Error
2318 pragma Compile_Time_Error
2319 (boolean_EXPRESSION, static_string_EXPRESSION);
2322 This pragma can be used to generate additional compile time
2324 is particularly useful in generics, where errors can be issued for
2325 specific problematic instantiations. The first parameter is a boolean
2326 expression. The pragma ensures that the value of an expression
2327 is known at compile time, and has the value False. The set of expressions
2328 whose values are known at compile time includes all static boolean
2329 expressions, and also other values which the compiler can determine
2330 at compile time (e.g., the size of a record type set by an explicit
2331 size representation clause, or the value of a variable which was
2332 initialized to a constant and is known not to have been modified).
2333 If these conditions are not met, an error message is generated using
2334 the value given as the second argument. This string value may contain
2335 embedded ASCII.LF characters to break the message into multiple lines.
2337 @node Pragma Compile_Time_Warning,Pragma Compiler_Unit,Pragma Compile_Time_Error,Implementation Defined Pragmas
2338 @anchor{gnat_rm/implementation_defined_pragmas pragma-compile-time-warning}@anchor{3b}
2339 @section Pragma Compile_Time_Warning
2345 pragma Compile_Time_Warning
2346 (boolean_EXPRESSION, static_string_EXPRESSION);
2349 Same as pragma Compile_Time_Error, except a warning is issued instead
2350 of an error message. If switch @emph{-gnatw_C} is used, a warning is only issued
2351 if the value of the expression is known to be True at compile time, not when
2352 the value of the expression is not known at compile time.
2353 Note that if this pragma is used in a package that
2354 is with'ed by a client, the client will get the warning even though it
2355 is issued by a with'ed package (normally warnings in with'ed units are
2356 suppressed, but this is a special exception to that rule).
2358 One typical use is within a generic where compile time known characteristics
2359 of formal parameters are tested, and warnings given appropriately. Another use
2360 with a first parameter of True is to warn a client about use of a package,
2361 for example that it is not fully implemented.
2363 In previous versions of the compiler, combining @emph{-gnatwe} with
2364 Compile_Time_Warning resulted in a fatal error. Now the compiler always emits
2365 a warning. You can use @ref{3a,,Pragma Compile_Time_Error} to force the generation of
2368 @node Pragma Compiler_Unit,Pragma Compiler_Unit_Warning,Pragma Compile_Time_Warning,Implementation Defined Pragmas
2369 @anchor{gnat_rm/implementation_defined_pragmas pragma-compiler-unit}@anchor{3c}
2370 @section Pragma Compiler_Unit
2376 pragma Compiler_Unit;
2379 This pragma is obsolete. It is equivalent to Compiler_Unit_Warning. It is
2380 retained so that old versions of the GNAT run-time that use this pragma can
2381 be compiled with newer versions of the compiler.
2383 @node Pragma Compiler_Unit_Warning,Pragma Complete_Representation,Pragma Compiler_Unit,Implementation Defined Pragmas
2384 @anchor{gnat_rm/implementation_defined_pragmas pragma-compiler-unit-warning}@anchor{3d}
2385 @section Pragma Compiler_Unit_Warning
2391 pragma Compiler_Unit_Warning;
2394 This pragma is intended only for internal use in the GNAT run-time library.
2395 It indicates that the unit is used as part of the compiler build. The effect
2396 is to generate warnings for the use of constructs (for example, conditional
2397 expressions) that would cause trouble when bootstrapping using an older
2398 version of GNAT. For the exact list of restrictions, see the compiler sources
2399 and references to Check_Compiler_Unit.
2401 @node Pragma Complete_Representation,Pragma Complex_Representation,Pragma Compiler_Unit_Warning,Implementation Defined Pragmas
2402 @anchor{gnat_rm/implementation_defined_pragmas pragma-complete-representation}@anchor{3e}
2403 @section Pragma Complete_Representation
2409 pragma Complete_Representation;
2412 This pragma must appear immediately within a record representation
2413 clause. Typical placements are before the first component clause
2414 or after the last component clause. The effect is to give an error
2415 message if any component is missing a component clause. This pragma
2416 may be used to ensure that a record representation clause is
2417 complete, and that this invariant is maintained if fields are
2418 added to the record in the future.
2420 @node Pragma Complex_Representation,Pragma Component_Alignment,Pragma Complete_Representation,Implementation Defined Pragmas
2421 @anchor{gnat_rm/implementation_defined_pragmas pragma-complex-representation}@anchor{3f}
2422 @section Pragma Complex_Representation
2428 pragma Complex_Representation
2429 ([Entity =>] LOCAL_NAME);
2432 The @code{Entity} argument must be the name of a record type which has
2433 two fields of the same floating-point type. The effect of this pragma is
2434 to force gcc to use the special internal complex representation form for
2435 this record, which may be more efficient. Note that this may result in
2436 the code for this type not conforming to standard ABI (application
2437 binary interface) requirements for the handling of record types. For
2438 example, in some environments, there is a requirement for passing
2439 records by pointer, and the use of this pragma may result in passing
2440 this type in floating-point registers.
2442 @node Pragma Component_Alignment,Pragma Constant_After_Elaboration,Pragma Complex_Representation,Implementation Defined Pragmas
2443 @anchor{gnat_rm/implementation_defined_pragmas pragma-component-alignment}@anchor{40}
2444 @section Pragma Component_Alignment
2447 @geindex Alignments of components
2449 @geindex Pragma Component_Alignment
2454 pragma Component_Alignment (
2455 [Form =>] ALIGNMENT_CHOICE
2456 [, [Name =>] type_LOCAL_NAME]);
2458 ALIGNMENT_CHOICE ::=
2465 Specifies the alignment of components in array or record types.
2466 The meaning of the @code{Form} argument is as follows:
2470 @geindex Component_Size (in pragma Component_Alignment)
2476 @item @emph{Component_Size}
2478 Aligns scalar components and subcomponents of the array or record type
2479 on boundaries appropriate to their inherent size (naturally
2480 aligned). For example, 1-byte components are aligned on byte boundaries,
2481 2-byte integer components are aligned on 2-byte boundaries, 4-byte
2482 integer components are aligned on 4-byte boundaries and so on. These
2483 alignment rules correspond to the normal rules for C compilers on all
2484 machines except the VAX.
2486 @geindex Component_Size_4 (in pragma Component_Alignment)
2488 @item @emph{Component_Size_4}
2490 Naturally aligns components with a size of four or fewer
2491 bytes. Components that are larger than 4 bytes are placed on the next
2494 @geindex Storage_Unit (in pragma Component_Alignment)
2496 @item @emph{Storage_Unit}
2498 Specifies that array or record components are byte aligned, i.e.,
2499 aligned on boundaries determined by the value of the constant
2500 @code{System.Storage_Unit}.
2502 @geindex Default (in pragma Component_Alignment)
2504 @item @emph{Default}
2506 Specifies that array or record components are aligned on default
2507 boundaries, appropriate to the underlying hardware or operating system or
2508 both. The @code{Default} choice is the same as @code{Component_Size} (natural
2512 If the @code{Name} parameter is present, @code{type_LOCAL_NAME} must
2513 refer to a local record or array type, and the specified alignment
2514 choice applies to the specified type. The use of
2515 @code{Component_Alignment} together with a pragma @code{Pack} causes the
2516 @code{Component_Alignment} pragma to be ignored. The use of
2517 @code{Component_Alignment} together with a record representation clause
2518 is only effective for fields not specified by the representation clause.
2520 If the @code{Name} parameter is absent, the pragma can be used as either
2521 a configuration pragma, in which case it applies to one or more units in
2522 accordance with the normal rules for configuration pragmas, or it can be
2523 used within a declarative part, in which case it applies to types that
2524 are declared within this declarative part, or within any nested scope
2525 within this declarative part. In either case it specifies the alignment
2526 to be applied to any record or array type which has otherwise standard
2529 If the alignment for a record or array type is not specified (using
2530 pragma @code{Pack}, pragma @code{Component_Alignment}, or a record rep
2531 clause), the GNAT uses the default alignment as described previously.
2533 @node Pragma Constant_After_Elaboration,Pragma Contract_Cases,Pragma Component_Alignment,Implementation Defined Pragmas
2534 @anchor{gnat_rm/implementation_defined_pragmas id6}@anchor{41}@anchor{gnat_rm/implementation_defined_pragmas pragma-constant-after-elaboration}@anchor{42}
2535 @section Pragma Constant_After_Elaboration
2541 pragma Constant_After_Elaboration [ (boolean_EXPRESSION) ];
2544 For the semantics of this pragma, see the entry for aspect
2545 @code{Constant_After_Elaboration} in the SPARK 2014 Reference Manual, section 3.3.1.
2547 @node Pragma Contract_Cases,Pragma Convention_Identifier,Pragma Constant_After_Elaboration,Implementation Defined Pragmas
2548 @anchor{gnat_rm/implementation_defined_pragmas id7}@anchor{43}@anchor{gnat_rm/implementation_defined_pragmas pragma-contract-cases}@anchor{44}
2549 @section Pragma Contract_Cases
2552 @geindex Contract cases
2557 pragma Contract_Cases ((CONTRACT_CASE @{, CONTRACT_CASE));
2559 CONTRACT_CASE ::= CASE_GUARD => CONSEQUENCE
2561 CASE_GUARD ::= boolean_EXPRESSION | others
2563 CONSEQUENCE ::= boolean_EXPRESSION
2566 The @code{Contract_Cases} pragma allows defining fine-grain specifications
2567 that can complement or replace the contract given by a precondition and a
2568 postcondition. Additionally, the @code{Contract_Cases} pragma can be used
2569 by testing and formal verification tools. The compiler checks its validity and,
2570 depending on the assertion policy at the point of declaration of the pragma,
2571 it may insert a check in the executable. For code generation, the contract
2575 pragma Contract_Cases (
2583 C1 : constant Boolean := Cond1; -- evaluated at subprogram entry
2584 C2 : constant Boolean := Cond2; -- evaluated at subprogram entry
2585 pragma Precondition ((C1 and not C2) or (C2 and not C1));
2586 pragma Postcondition (if C1 then Pred1);
2587 pragma Postcondition (if C2 then Pred2);
2590 The precondition ensures that one and only one of the case guards is
2591 satisfied on entry to the subprogram.
2592 The postcondition ensures that for the case guard that was True on entry,
2593 the corresponding consequence is True on exit. Other consequence expressions
2596 A precondition @code{P} and postcondition @code{Q} can also be
2597 expressed as contract cases:
2600 pragma Contract_Cases (P => Q);
2603 The placement and visibility rules for @code{Contract_Cases} pragmas are
2604 identical to those described for preconditions and postconditions.
2606 The compiler checks that boolean expressions given in case guards and
2607 consequences are valid, where the rules for case guards are the same as
2608 the rule for an expression in @code{Precondition} and the rules for
2609 consequences are the same as the rule for an expression in
2610 @code{Postcondition}. In particular, attributes @code{'Old} and
2611 @code{'Result} can only be used within consequence expressions.
2612 The case guard for the last contract case may be @code{others}, to denote
2613 any case not captured by the previous cases. The
2614 following is an example of use within a package spec:
2617 package Math_Functions is
2619 function Sqrt (Arg : Float) return Float;
2620 pragma Contract_Cases (((Arg in 0.0 .. 99.0) => Sqrt'Result < 10.0,
2621 Arg >= 100.0 => Sqrt'Result >= 10.0,
2622 others => Sqrt'Result = 0.0));
2627 The meaning of contract cases is that only one case should apply at each
2628 call, as determined by the corresponding case guard evaluating to True,
2629 and that the consequence for this case should hold when the subprogram
2632 @node Pragma Convention_Identifier,Pragma CPP_Class,Pragma Contract_Cases,Implementation Defined Pragmas
2633 @anchor{gnat_rm/implementation_defined_pragmas pragma-convention-identifier}@anchor{45}
2634 @section Pragma Convention_Identifier
2637 @geindex Conventions
2643 pragma Convention_Identifier (
2644 [Name =>] IDENTIFIER,
2645 [Convention =>] convention_IDENTIFIER);
2648 This pragma provides a mechanism for supplying synonyms for existing
2649 convention identifiers. The @code{Name} identifier can subsequently
2650 be used as a synonym for the given convention in other pragmas (including
2651 for example pragma @code{Import} or another @code{Convention_Identifier}
2652 pragma). As an example of the use of this, suppose you had legacy code
2653 which used Fortran77 as the identifier for Fortran. Then the pragma:
2656 pragma Convention_Identifier (Fortran77, Fortran);
2659 would allow the use of the convention identifier @code{Fortran77} in
2660 subsequent code, avoiding the need to modify the sources. As another
2661 example, you could use this to parameterize convention requirements
2662 according to systems. Suppose you needed to use @code{Stdcall} on
2663 windows systems, and @code{C} on some other system, then you could
2664 define a convention identifier @code{Library} and use a single
2665 @code{Convention_Identifier} pragma to specify which convention
2666 would be used system-wide.
2668 @node Pragma CPP_Class,Pragma CPP_Constructor,Pragma Convention_Identifier,Implementation Defined Pragmas
2669 @anchor{gnat_rm/implementation_defined_pragmas pragma-cpp-class}@anchor{46}
2670 @section Pragma CPP_Class
2673 @geindex Interfacing with C++
2678 pragma CPP_Class ([Entity =>] LOCAL_NAME);
2681 The argument denotes an entity in the current declarative region that is
2682 declared as a record type. It indicates that the type corresponds to an
2683 externally declared C++ class type, and is to be laid out the same way
2684 that C++ would lay out the type. If the C++ class has virtual primitives
2685 then the record must be declared as a tagged record type.
2687 Types for which @code{CPP_Class} is specified do not have assignment or
2688 equality operators defined (such operations can be imported or declared
2689 as subprograms as required). Initialization is allowed only by constructor
2690 functions (see pragma @code{CPP_Constructor}). Such types are implicitly
2691 limited if not explicitly declared as limited or derived from a limited
2692 type, and an error is issued in that case.
2694 See @ref{47,,Interfacing to C++} for related information.
2696 Note: Pragma @code{CPP_Class} is currently obsolete. It is supported
2697 for backward compatibility but its functionality is available
2698 using pragma @code{Import} with @code{Convention} = @code{CPP}.
2700 @node Pragma CPP_Constructor,Pragma CPP_Virtual,Pragma CPP_Class,Implementation Defined Pragmas
2701 @anchor{gnat_rm/implementation_defined_pragmas pragma-cpp-constructor}@anchor{48}
2702 @section Pragma CPP_Constructor
2705 @geindex Interfacing with C++
2710 pragma CPP_Constructor ([Entity =>] LOCAL_NAME
2711 [, [External_Name =>] static_string_EXPRESSION ]
2712 [, [Link_Name =>] static_string_EXPRESSION ]);
2715 This pragma identifies an imported function (imported in the usual way
2716 with pragma @code{Import}) as corresponding to a C++ constructor. If
2717 @code{External_Name} and @code{Link_Name} are not specified then the
2718 @code{Entity} argument is a name that must have been previously mentioned
2719 in a pragma @code{Import} with @code{Convention} = @code{CPP}. Such name
2720 must be of one of the following forms:
2726 @strong{function} @code{Fname} @strong{return} T`
2729 @strong{function} @code{Fname} @strong{return} T'Class
2732 @strong{function} @code{Fname} (...) @strong{return} T`
2735 @strong{function} @code{Fname} (...) @strong{return} T'Class
2738 where @code{T} is a limited record type imported from C++ with pragma
2739 @code{Import} and @code{Convention} = @code{CPP}.
2741 The first two forms import the default constructor, used when an object
2742 of type @code{T} is created on the Ada side with no explicit constructor.
2743 The latter two forms cover all the non-default constructors of the type.
2744 See the GNAT User's Guide for details.
2746 If no constructors are imported, it is impossible to create any objects
2747 on the Ada side and the type is implicitly declared abstract.
2749 Pragma @code{CPP_Constructor} is intended primarily for automatic generation
2750 using an automatic binding generator tool (such as the @code{-fdump-ada-spec}
2752 See @ref{47,,Interfacing to C++} for more related information.
2754 Note: The use of functions returning class-wide types for constructors is
2755 currently obsolete. They are supported for backward compatibility. The
2756 use of functions returning the type T leave the Ada sources more clear
2757 because the imported C++ constructors always return an object of type T;
2758 that is, they never return an object whose type is a descendant of type T.
2760 @node Pragma CPP_Virtual,Pragma CPP_Vtable,Pragma CPP_Constructor,Implementation Defined Pragmas
2761 @anchor{gnat_rm/implementation_defined_pragmas pragma-cpp-virtual}@anchor{49}
2762 @section Pragma CPP_Virtual
2765 @geindex Interfacing to C++
2767 This pragma is now obsolete and, other than generating a warning if warnings
2768 on obsolescent features are enabled, is completely ignored.
2769 It is retained for compatibility
2770 purposes. It used to be required to ensure compoatibility with C++, but
2771 is no longer required for that purpose because GNAT generates
2772 the same object layout as the G++ compiler by default.
2774 See @ref{47,,Interfacing to C++} for related information.
2776 @node Pragma CPP_Vtable,Pragma CPU,Pragma CPP_Virtual,Implementation Defined Pragmas
2777 @anchor{gnat_rm/implementation_defined_pragmas pragma-cpp-vtable}@anchor{4a}
2778 @section Pragma CPP_Vtable
2781 @geindex Interfacing with C++
2783 This pragma is now obsolete and, other than generating a warning if warnings
2784 on obsolescent features are enabled, is completely ignored.
2785 It used to be required to ensure compatibility with C++, but
2786 is no longer required for that purpose because GNAT generates
2787 the same object layout as the G++ compiler by default.
2789 See @ref{47,,Interfacing to C++} for related information.
2791 @node Pragma CPU,Pragma Deadline_Floor,Pragma CPP_Vtable,Implementation Defined Pragmas
2792 @anchor{gnat_rm/implementation_defined_pragmas pragma-cpu}@anchor{4b}
2799 pragma CPU (EXPRESSION);
2802 This pragma is standard in Ada 2012, but is available in all earlier
2803 versions of Ada as an implementation-defined pragma.
2804 See Ada 2012 Reference Manual for details.
2806 @node Pragma Deadline_Floor,Pragma Default_Initial_Condition,Pragma CPU,Implementation Defined Pragmas
2807 @anchor{gnat_rm/implementation_defined_pragmas pragma-deadline-floor}@anchor{4c}
2808 @section Pragma Deadline_Floor
2814 pragma Deadline_Floor (time_span_EXPRESSION);
2817 This pragma applies only to protected types and specifies the floor
2818 deadline inherited by a task when the task enters a protected object.
2819 It is effective only when the EDF scheduling policy is used.
2821 @node Pragma Default_Initial_Condition,Pragma Debug,Pragma Deadline_Floor,Implementation Defined Pragmas
2822 @anchor{gnat_rm/implementation_defined_pragmas id8}@anchor{4d}@anchor{gnat_rm/implementation_defined_pragmas pragma-default-initial-condition}@anchor{4e}
2823 @section Pragma Default_Initial_Condition
2829 pragma Default_Initial_Condition [ (null | boolean_EXPRESSION) ];
2832 For the semantics of this pragma, see the entry for aspect
2833 @code{Default_Initial_Condition} in the SPARK 2014 Reference Manual, section 7.3.3.
2835 @node Pragma Debug,Pragma Debug_Policy,Pragma Default_Initial_Condition,Implementation Defined Pragmas
2836 @anchor{gnat_rm/implementation_defined_pragmas pragma-debug}@anchor{4f}
2837 @section Pragma Debug
2843 pragma Debug ([CONDITION, ]PROCEDURE_CALL_WITHOUT_SEMICOLON);
2845 PROCEDURE_CALL_WITHOUT_SEMICOLON ::=
2847 | PROCEDURE_PREFIX ACTUAL_PARAMETER_PART
2850 The procedure call argument has the syntactic form of an expression, meeting
2851 the syntactic requirements for pragmas.
2853 If debug pragmas are not enabled or if the condition is present and evaluates
2854 to False, this pragma has no effect. If debug pragmas are enabled, the
2855 semantics of the pragma is exactly equivalent to the procedure call statement
2856 corresponding to the argument with a terminating semicolon. Pragmas are
2857 permitted in sequences of declarations, so you can use pragma @code{Debug} to
2858 intersperse calls to debug procedures in the middle of declarations. Debug
2859 pragmas can be enabled either by use of the command line switch @emph{-gnata}
2860 or by use of the pragma @code{Check_Policy} with a first argument of
2863 @node Pragma Debug_Policy,Pragma Default_Scalar_Storage_Order,Pragma Debug,Implementation Defined Pragmas
2864 @anchor{gnat_rm/implementation_defined_pragmas pragma-debug-policy}@anchor{50}
2865 @section Pragma Debug_Policy
2871 pragma Debug_Policy (CHECK | DISABLE | IGNORE | ON | OFF);
2874 This pragma is equivalent to a corresponding @code{Check_Policy} pragma
2875 with a first argument of @code{Debug}. It is retained for historical
2876 compatibility reasons.
2878 @node Pragma Default_Scalar_Storage_Order,Pragma Default_Storage_Pool,Pragma Debug_Policy,Implementation Defined Pragmas
2879 @anchor{gnat_rm/implementation_defined_pragmas pragma-default-scalar-storage-order}@anchor{51}
2880 @section Pragma Default_Scalar_Storage_Order
2883 @geindex Default_Scalar_Storage_Order
2885 @geindex Scalar_Storage_Order
2890 pragma Default_Scalar_Storage_Order (High_Order_First | Low_Order_First);
2893 Normally if no explicit @code{Scalar_Storage_Order} is given for a record
2894 type or array type, then the scalar storage order defaults to the ordinary
2895 default for the target. But this default may be overridden using this pragma.
2896 The pragma may appear as a configuration pragma, or locally within a package
2897 spec or declarative part. In the latter case, it applies to all subsequent
2898 types declared within that package spec or declarative part.
2900 The following example shows the use of this pragma:
2903 pragma Default_Scalar_Storage_Order (High_Order_First);
2904 with System; use System;
2913 for L2'Scalar_Storage_Order use Low_Order_First;
2922 pragma Default_Scalar_Storage_Order (Low_Order_First);
2929 type H4a is new Inner.L4;
2937 In this example record types with names starting with @emph{L} have @cite{Low_Order_First} scalar
2938 storage order, and record types with names starting with @emph{H} have @code{High_Order_First}.
2939 Note that in the case of @code{H4a}, the order is not inherited
2940 from the parent type. Only an explicitly set @code{Scalar_Storage_Order}
2941 gets inherited on type derivation.
2943 If this pragma is used as a configuration pragma which appears within a
2944 configuration pragma file (as opposed to appearing explicitly at the start
2945 of a single unit), then the binder will require that all units in a partition
2946 be compiled in a similar manner, other than run-time units, which are not
2947 affected by this pragma. Note that the use of this form is discouraged because
2948 it may significantly degrade the run-time performance of the software, instead
2949 the default scalar storage order ought to be changed only on a local basis.
2951 @node Pragma Default_Storage_Pool,Pragma Depends,Pragma Default_Scalar_Storage_Order,Implementation Defined Pragmas
2952 @anchor{gnat_rm/implementation_defined_pragmas pragma-default-storage-pool}@anchor{52}
2953 @section Pragma Default_Storage_Pool
2956 @geindex Default_Storage_Pool
2961 pragma Default_Storage_Pool (storage_pool_NAME | null);
2964 This pragma is standard in Ada 2012, but is available in all earlier
2965 versions of Ada as an implementation-defined pragma.
2966 See Ada 2012 Reference Manual for details.
2968 @node Pragma Depends,Pragma Detect_Blocking,Pragma Default_Storage_Pool,Implementation Defined Pragmas
2969 @anchor{gnat_rm/implementation_defined_pragmas pragma-depends}@anchor{53}@anchor{gnat_rm/implementation_defined_pragmas id9}@anchor{54}
2970 @section Pragma Depends
2976 pragma Depends (DEPENDENCY_RELATION);
2978 DEPENDENCY_RELATION ::=
2980 | (DEPENDENCY_CLAUSE @{, DEPENDENCY_CLAUSE@})
2982 DEPENDENCY_CLAUSE ::=
2983 OUTPUT_LIST =>[+] INPUT_LIST
2984 | NULL_DEPENDENCY_CLAUSE
2986 NULL_DEPENDENCY_CLAUSE ::= null => INPUT_LIST
2988 OUTPUT_LIST ::= OUTPUT | (OUTPUT @{, OUTPUT@})
2990 INPUT_LIST ::= null | INPUT | (INPUT @{, INPUT@})
2992 OUTPUT ::= NAME | FUNCTION_RESULT
2995 where FUNCTION_RESULT is a function Result attribute_reference
2998 For the semantics of this pragma, see the entry for aspect @code{Depends} in the
2999 SPARK 2014 Reference Manual, section 6.1.5.
3001 @node Pragma Detect_Blocking,Pragma Disable_Atomic_Synchronization,Pragma Depends,Implementation Defined Pragmas
3002 @anchor{gnat_rm/implementation_defined_pragmas pragma-detect-blocking}@anchor{55}
3003 @section Pragma Detect_Blocking
3009 pragma Detect_Blocking;
3012 This is a standard pragma in Ada 2005, that is available in all earlier
3013 versions of Ada as an implementation-defined pragma.
3015 This is a configuration pragma that forces the detection of potentially
3016 blocking operations within a protected operation, and to raise Program_Error
3019 @node Pragma Disable_Atomic_Synchronization,Pragma Dispatching_Domain,Pragma Detect_Blocking,Implementation Defined Pragmas
3020 @anchor{gnat_rm/implementation_defined_pragmas pragma-disable-atomic-synchronization}@anchor{56}
3021 @section Pragma Disable_Atomic_Synchronization
3024 @geindex Atomic Synchronization
3029 pragma Disable_Atomic_Synchronization [(Entity)];
3032 Ada requires that accesses (reads or writes) of an atomic variable be
3033 regarded as synchronization points in the case of multiple tasks.
3034 Particularly in the case of multi-processors this may require special
3035 handling, e.g. the generation of memory barriers. This capability may
3036 be turned off using this pragma in cases where it is known not to be
3039 The placement and scope rules for this pragma are the same as those
3040 for @code{pragma Suppress}. In particular it can be used as a
3041 configuration pragma, or in a declaration sequence where it applies
3042 till the end of the scope. If an @code{Entity} argument is present,
3043 the action applies only to that entity.
3045 @node Pragma Dispatching_Domain,Pragma Effective_Reads,Pragma Disable_Atomic_Synchronization,Implementation Defined Pragmas
3046 @anchor{gnat_rm/implementation_defined_pragmas pragma-dispatching-domain}@anchor{57}
3047 @section Pragma Dispatching_Domain
3053 pragma Dispatching_Domain (EXPRESSION);
3056 This pragma is standard in Ada 2012, but is available in all earlier
3057 versions of Ada as an implementation-defined pragma.
3058 See Ada 2012 Reference Manual for details.
3060 @node Pragma Effective_Reads,Pragma Effective_Writes,Pragma Dispatching_Domain,Implementation Defined Pragmas
3061 @anchor{gnat_rm/implementation_defined_pragmas id10}@anchor{58}@anchor{gnat_rm/implementation_defined_pragmas pragma-effective-reads}@anchor{59}
3062 @section Pragma Effective_Reads
3068 pragma Effective_Reads [ (boolean_EXPRESSION) ];
3071 For the semantics of this pragma, see the entry for aspect @code{Effective_Reads} in
3072 the SPARK 2014 Reference Manual, section 7.1.2.
3074 @node Pragma Effective_Writes,Pragma Elaboration_Checks,Pragma Effective_Reads,Implementation Defined Pragmas
3075 @anchor{gnat_rm/implementation_defined_pragmas id11}@anchor{5a}@anchor{gnat_rm/implementation_defined_pragmas pragma-effective-writes}@anchor{5b}
3076 @section Pragma Effective_Writes
3082 pragma Effective_Writes [ (boolean_EXPRESSION) ];
3085 For the semantics of this pragma, see the entry for aspect @code{Effective_Writes}
3086 in the SPARK 2014 Reference Manual, section 7.1.2.
3088 @node Pragma Elaboration_Checks,Pragma Eliminate,Pragma Effective_Writes,Implementation Defined Pragmas
3089 @anchor{gnat_rm/implementation_defined_pragmas pragma-elaboration-checks}@anchor{5c}
3090 @section Pragma Elaboration_Checks
3093 @geindex Elaboration control
3098 pragma Elaboration_Checks (Dynamic | Static);
3101 This is a configuration pragma which specifies the elaboration model to be
3102 used during compilation. For more information on the elaboration models of
3103 GNAT, consult the chapter on elaboration order handling in the @emph{GNAT User's
3106 The pragma may appear in the following contexts:
3112 Configuration pragmas file
3115 Prior to the context clauses of a compilation unit's initial declaration
3118 Any other placement of the pragma will result in a warning and the effects of
3119 the offending pragma will be ignored.
3121 If the pragma argument is @code{Dynamic}, then the dynamic elaboration model is in
3122 effect. If the pragma argument is @code{Static}, then the static elaboration model
3125 @node Pragma Eliminate,Pragma Enable_Atomic_Synchronization,Pragma Elaboration_Checks,Implementation Defined Pragmas
3126 @anchor{gnat_rm/implementation_defined_pragmas pragma-eliminate}@anchor{5d}
3127 @section Pragma Eliminate
3130 @geindex Elimination of unused subprograms
3136 [ Unit_Name => ] IDENTIFIER | SELECTED_COMPONENT ,
3137 [ Entity => ] IDENTIFIER |
3138 SELECTED_COMPONENT |
3140 [, Source_Location => SOURCE_TRACE ] );
3142 SOURCE_TRACE ::= STRING_LITERAL
3145 This pragma indicates that the given entity is not used in the program to be
3146 compiled and built, thus allowing the compiler to
3147 eliminate the code or data associated with the named entity. Any reference to
3148 an eliminated entity causes a compile-time or link-time error.
3150 The pragma has the following semantics, where @code{U} is the unit specified by
3151 the @code{Unit_Name} argument and @code{E} is the entity specified by the @code{Entity}
3158 @code{E} must be a subprogram that is explicitly declared either:
3160 o Within @code{U}, or
3162 o Within a generic package that is instantiated in @code{U}, or
3164 o As an instance of generic subprogram instantiated in @code{U}.
3166 Otherwise the pragma is ignored.
3169 If @code{E} is overloaded within @code{U} then, in the absence of a
3170 @code{Source_Location} argument, all overloadings are eliminated.
3173 If @code{E} is overloaded within @code{U} and only some overloadings
3174 are to be eliminated, then each overloading to be eliminated
3175 must be specified in a corresponding pragma @code{Eliminate}
3176 with a @code{Source_Location} argument identifying the line where the
3177 declaration appears, as described below.
3180 If @code{E} is declared as the result of a generic instantiation, then
3181 a @code{Source_Location} argument is needed, as described below
3184 Pragma @code{Eliminate} allows a program to be compiled in a system-independent
3185 manner, so that unused entities are eliminated but without
3186 needing to modify the source text. Normally the required set of
3187 @code{Eliminate} pragmas is constructed automatically using the @code{gnatelim} tool.
3189 Any source file change that removes, splits, or
3190 adds lines may make the set of @code{Eliminate} pragmas invalid because their
3191 @code{Source_Location} argument values may get out of date.
3193 Pragma @code{Eliminate} may be used where the referenced entity is a dispatching
3194 operation. In this case all the subprograms to which the given operation can
3195 dispatch are considered to be unused (are never called as a result of a direct
3196 or a dispatching call).
3198 The string literal given for the source location specifies the line number
3199 of the declaration of the entity, using the following syntax for @code{SOURCE_TRACE}:
3202 SOURCE_TRACE ::= SOURCE_REFERENCE [ LBRACKET SOURCE_TRACE RBRACKET ]
3207 SOURCE_REFERENCE ::= FILE_NAME : LINE_NUMBER
3209 LINE_NUMBER ::= DIGIT @{DIGIT@}
3212 Spaces around the colon in a @code{SOURCE_REFERENCE} are optional.
3214 The source trace that is given as the @code{Source_Location} must obey the
3215 following rules (or else the pragma is ignored), where @code{U} is
3216 the unit @code{U} specified by the @code{Unit_Name} argument and @code{E} is the
3217 subprogram specified by the @code{Entity} argument:
3223 @code{FILE_NAME} is the short name (with no directory
3224 information) of the Ada source file for @code{U}, using the required syntax
3225 for the underlying file system (e.g. case is significant if the underlying
3226 operating system is case sensitive).
3227 If @code{U} is a package and @code{E} is a subprogram declared in the package
3228 specification and its full declaration appears in the package body,
3229 then the relevant source file is the one for the package specification;
3230 analogously if @code{U} is a generic package.
3233 If @code{E} is not declared in a generic instantiation (this includes
3234 generic subprogram instances), the source trace includes only one source
3235 line reference. @code{LINE_NUMBER} gives the line number of the occurrence
3236 of the declaration of @code{E} within the source file (as a decimal literal
3237 without an exponent or point).
3240 If @code{E} is declared by a generic instantiation, its source trace
3241 (from left to right) starts with the source location of the
3242 declaration of @code{E} in the generic unit and ends with the source
3243 location of the instantiation, given in square brackets. This approach is
3244 applied recursively with nested instantiations: the rightmost (nested
3245 most deeply in square brackets) element of the source trace is the location
3246 of the outermost instantiation, and the leftmost element (that is, outside
3247 of any square brackets) is the location of the declaration of @code{E} in
3256 pragma Eliminate (Pkg0, Proc);
3257 -- Eliminate (all overloadings of) Proc in Pkg0
3259 pragma Eliminate (Pkg1, Proc,
3260 Source_Location => "pkg1.ads:8");
3261 -- Eliminate overloading of Proc at line 8 in pkg1.ads
3263 -- Assume the following file contents:
3266 -- 2: type T is private;
3267 -- 3: package Gen_Pkg is
3268 -- 4: procedure Proc(N : T);
3274 -- 2: procedure Q is
3275 -- 3: package Inst_Pkg is new Gen_Pkg(Integer);
3276 -- ... -- No calls on Inst_Pkg.Proc
3279 -- The following pragma eliminates Inst_Pkg.Proc from Q
3280 pragma Eliminate (Q, Proc,
3281 Source_Location => "gen_pkg.ads:4[q.adb:3]");
3285 @node Pragma Enable_Atomic_Synchronization,Pragma Export_Function,Pragma Eliminate,Implementation Defined Pragmas
3286 @anchor{gnat_rm/implementation_defined_pragmas pragma-enable-atomic-synchronization}@anchor{5e}
3287 @section Pragma Enable_Atomic_Synchronization
3290 @geindex Atomic Synchronization
3295 pragma Enable_Atomic_Synchronization [(Entity)];
3298 Ada requires that accesses (reads or writes) of an atomic variable be
3299 regarded as synchronization points in the case of multiple tasks.
3300 Particularly in the case of multi-processors this may require special
3301 handling, e.g. the generation of memory barriers. This synchronization
3302 is performed by default, but can be turned off using
3303 @code{pragma Disable_Atomic_Synchronization}. The
3304 @code{Enable_Atomic_Synchronization} pragma can be used to turn
3307 The placement and scope rules for this pragma are the same as those
3308 for @code{pragma Unsuppress}. In particular it can be used as a
3309 configuration pragma, or in a declaration sequence where it applies
3310 till the end of the scope. If an @code{Entity} argument is present,
3311 the action applies only to that entity.
3313 @node Pragma Export_Function,Pragma Export_Object,Pragma Enable_Atomic_Synchronization,Implementation Defined Pragmas
3314 @anchor{gnat_rm/implementation_defined_pragmas pragma-export-function}@anchor{5f}
3315 @section Pragma Export_Function
3318 @geindex Argument passing mechanisms
3323 pragma Export_Function (
3324 [Internal =>] LOCAL_NAME
3325 [, [External =>] EXTERNAL_SYMBOL]
3326 [, [Parameter_Types =>] PARAMETER_TYPES]
3327 [, [Result_Type =>] result_SUBTYPE_MARK]
3328 [, [Mechanism =>] MECHANISM]
3329 [, [Result_Mechanism =>] MECHANISM_NAME]);
3333 | static_string_EXPRESSION
3338 | TYPE_DESIGNATOR @{, TYPE_DESIGNATOR@}
3342 | subtype_Name ' Access
3346 | (MECHANISM_ASSOCIATION @{, MECHANISM_ASSOCIATION@})
3348 MECHANISM_ASSOCIATION ::=
3349 [formal_parameter_NAME =>] MECHANISM_NAME
3351 MECHANISM_NAME ::= Value | Reference
3354 Use this pragma to make a function externally callable and optionally
3355 provide information on mechanisms to be used for passing parameter and
3356 result values. We recommend, for the purposes of improving portability,
3357 this pragma always be used in conjunction with a separate pragma
3358 @code{Export}, which must precede the pragma @code{Export_Function}.
3359 GNAT does not require a separate pragma @code{Export}, but if none is
3360 present, @code{Convention Ada} is assumed, which is usually
3361 not what is wanted, so it is usually appropriate to use this
3362 pragma in conjunction with a @code{Export} or @code{Convention}
3363 pragma that specifies the desired foreign convention.
3364 Pragma @code{Export_Function}
3365 (and @code{Export}, if present) must appear in the same declarative
3366 region as the function to which they apply.
3368 The @code{internal_name} must uniquely designate the function to which the
3369 pragma applies. If more than one function name exists of this name in
3370 the declarative part you must use the @code{Parameter_Types} and
3371 @code{Result_Type} parameters to achieve the required
3372 unique designation. The @cite{subtype_mark}s in these parameters must
3373 exactly match the subtypes in the corresponding function specification,
3374 using positional notation to match parameters with subtype marks.
3375 The form with an @code{'Access} attribute can be used to match an
3376 anonymous access parameter.
3378 @geindex Suppressing external name
3380 Special treatment is given if the EXTERNAL is an explicit null
3381 string or a static string expressions that evaluates to the null
3382 string. In this case, no external name is generated. This form
3383 still allows the specification of parameter mechanisms.
3385 @node Pragma Export_Object,Pragma Export_Procedure,Pragma Export_Function,Implementation Defined Pragmas
3386 @anchor{gnat_rm/implementation_defined_pragmas pragma-export-object}@anchor{60}
3387 @section Pragma Export_Object
3393 pragma Export_Object
3394 [Internal =>] LOCAL_NAME
3395 [, [External =>] EXTERNAL_SYMBOL]
3396 [, [Size =>] EXTERNAL_SYMBOL]
3400 | static_string_EXPRESSION
3403 This pragma designates an object as exported, and apart from the
3404 extended rules for external symbols, is identical in effect to the use of
3405 the normal @code{Export} pragma applied to an object. You may use a
3406 separate Export pragma (and you probably should from the point of view
3407 of portability), but it is not required. @code{Size} is syntax checked,
3408 but otherwise ignored by GNAT.
3410 @node Pragma Export_Procedure,Pragma Export_Value,Pragma Export_Object,Implementation Defined Pragmas
3411 @anchor{gnat_rm/implementation_defined_pragmas pragma-export-procedure}@anchor{61}
3412 @section Pragma Export_Procedure
3418 pragma Export_Procedure (
3419 [Internal =>] LOCAL_NAME
3420 [, [External =>] EXTERNAL_SYMBOL]
3421 [, [Parameter_Types =>] PARAMETER_TYPES]
3422 [, [Mechanism =>] MECHANISM]);
3426 | static_string_EXPRESSION
3431 | TYPE_DESIGNATOR @{, TYPE_DESIGNATOR@}
3435 | subtype_Name ' Access
3439 | (MECHANISM_ASSOCIATION @{, MECHANISM_ASSOCIATION@})
3441 MECHANISM_ASSOCIATION ::=
3442 [formal_parameter_NAME =>] MECHANISM_NAME
3444 MECHANISM_NAME ::= Value | Reference
3447 This pragma is identical to @code{Export_Function} except that it
3448 applies to a procedure rather than a function and the parameters
3449 @code{Result_Type} and @code{Result_Mechanism} are not permitted.
3450 GNAT does not require a separate pragma @code{Export}, but if none is
3451 present, @code{Convention Ada} is assumed, which is usually
3452 not what is wanted, so it is usually appropriate to use this
3453 pragma in conjunction with a @code{Export} or @code{Convention}
3454 pragma that specifies the desired foreign convention.
3456 @geindex Suppressing external name
3458 Special treatment is given if the EXTERNAL is an explicit null
3459 string or a static string expressions that evaluates to the null
3460 string. In this case, no external name is generated. This form
3461 still allows the specification of parameter mechanisms.
3463 @node Pragma Export_Value,Pragma Export_Valued_Procedure,Pragma Export_Procedure,Implementation Defined Pragmas
3464 @anchor{gnat_rm/implementation_defined_pragmas pragma-export-value}@anchor{62}
3465 @section Pragma Export_Value
3471 pragma Export_Value (
3472 [Value =>] static_integer_EXPRESSION,
3473 [Link_Name =>] static_string_EXPRESSION);
3476 This pragma serves to export a static integer value for external use.
3477 The first argument specifies the value to be exported. The Link_Name
3478 argument specifies the symbolic name to be associated with the integer
3479 value. This pragma is useful for defining a named static value in Ada
3480 that can be referenced in assembly language units to be linked with
3481 the application. This pragma is currently supported only for the
3482 AAMP target and is ignored for other targets.
3484 @node Pragma Export_Valued_Procedure,Pragma Extend_System,Pragma Export_Value,Implementation Defined Pragmas
3485 @anchor{gnat_rm/implementation_defined_pragmas pragma-export-valued-procedure}@anchor{63}
3486 @section Pragma Export_Valued_Procedure
3492 pragma Export_Valued_Procedure (
3493 [Internal =>] LOCAL_NAME
3494 [, [External =>] EXTERNAL_SYMBOL]
3495 [, [Parameter_Types =>] PARAMETER_TYPES]
3496 [, [Mechanism =>] MECHANISM]);
3500 | static_string_EXPRESSION
3505 | TYPE_DESIGNATOR @{, TYPE_DESIGNATOR@}
3509 | subtype_Name ' Access
3513 | (MECHANISM_ASSOCIATION @{, MECHANISM_ASSOCIATION@})
3515 MECHANISM_ASSOCIATION ::=
3516 [formal_parameter_NAME =>] MECHANISM_NAME
3518 MECHANISM_NAME ::= Value | Reference
3521 This pragma is identical to @code{Export_Procedure} except that the
3522 first parameter of @code{LOCAL_NAME}, which must be present, must be of
3523 mode @code{out}, and externally the subprogram is treated as a function
3524 with this parameter as the result of the function. GNAT provides for
3525 this capability to allow the use of @code{out} and @code{in out}
3526 parameters in interfacing to external functions (which are not permitted
3528 GNAT does not require a separate pragma @code{Export}, but if none is
3529 present, @code{Convention Ada} is assumed, which is almost certainly
3530 not what is wanted since the whole point of this pragma is to interface
3531 with foreign language functions, so it is usually appropriate to use this
3532 pragma in conjunction with a @code{Export} or @code{Convention}
3533 pragma that specifies the desired foreign convention.
3535 @geindex Suppressing external name
3537 Special treatment is given if the EXTERNAL is an explicit null
3538 string or a static string expressions that evaluates to the null
3539 string. In this case, no external name is generated. This form
3540 still allows the specification of parameter mechanisms.
3542 @node Pragma Extend_System,Pragma Extensions_Allowed,Pragma Export_Valued_Procedure,Implementation Defined Pragmas
3543 @anchor{gnat_rm/implementation_defined_pragmas pragma-extend-system}@anchor{64}
3544 @section Pragma Extend_System
3555 pragma Extend_System ([Name =>] IDENTIFIER);
3558 This pragma is used to provide backwards compatibility with other
3559 implementations that extend the facilities of package @code{System}. In
3560 GNAT, @code{System} contains only the definitions that are present in
3561 the Ada RM. However, other implementations, notably the DEC Ada 83
3562 implementation, provide many extensions to package @code{System}.
3564 For each such implementation accommodated by this pragma, GNAT provides a
3565 package @code{Aux_@emph{xxx}}, e.g., @code{Aux_DEC} for the DEC Ada 83
3566 implementation, which provides the required additional definitions. You
3567 can use this package in two ways. You can @code{with} it in the normal
3568 way and access entities either by selection or using a @code{use}
3569 clause. In this case no special processing is required.
3571 However, if existing code contains references such as
3572 @code{System.@emph{xxx}} where @emph{xxx} is an entity in the extended
3573 definitions provided in package @code{System}, you may use this pragma
3574 to extend visibility in @code{System} in a non-standard way that
3575 provides greater compatibility with the existing code. Pragma
3576 @code{Extend_System} is a configuration pragma whose single argument is
3577 the name of the package containing the extended definition
3578 (e.g., @code{Aux_DEC} for the DEC Ada case). A unit compiled under
3579 control of this pragma will be processed using special visibility
3580 processing that looks in package @code{System.Aux_@emph{xxx}} where
3581 @code{Aux_@emph{xxx}} is the pragma argument for any entity referenced in
3582 package @code{System}, but not found in package @code{System}.
3584 You can use this pragma either to access a predefined @code{System}
3585 extension supplied with the compiler, for example @code{Aux_DEC} or
3586 you can construct your own extension unit following the above
3587 definition. Note that such a package is a child of @code{System}
3588 and thus is considered part of the implementation.
3589 To compile it you will have to use the @emph{-gnatg} switch
3590 for compiling System units, as explained in the
3593 @node Pragma Extensions_Allowed,Pragma Extensions_Visible,Pragma Extend_System,Implementation Defined Pragmas
3594 @anchor{gnat_rm/implementation_defined_pragmas pragma-extensions-allowed}@anchor{65}
3595 @section Pragma Extensions_Allowed
3598 @geindex Ada Extensions
3600 @geindex GNAT Extensions
3605 pragma Extensions_Allowed (On | Off);
3608 This configuration pragma enables or disables the implementation
3609 extension mode (the use of Off as a parameter cancels the effect
3610 of the @emph{-gnatX} command switch).
3612 In extension mode, the latest version of the Ada language is
3613 implemented (currently Ada 202x), and in addition a small number
3614 of GNAT specific extensions are recognized as follows:
3620 Constrained attribute for generic objects
3622 The @code{Constrained} attribute is permitted for objects of
3623 generic types. The result indicates if the corresponding actual
3627 @code{Static} aspect on intrinsic functions
3629 The Ada 202x @code{Static} aspect can be specified on Intrinsic imported
3630 functions and the compiler will evaluate some of these intrinsic statically,
3631 in particular the @code{Shift_Left} and @code{Shift_Right} intrinsics.
3634 @code{'Reduce} attribute
3636 This attribute part of the Ada 202x language definition is provided for
3637 now under -gnatX to confirm and potentially refine its usage and syntax.
3640 @code{[]} aggregates
3642 This new aggregate syntax for arrays and containers is provided under -gnatX
3643 to experiment and confirm this new language syntax.
3646 @node Pragma Extensions_Visible,Pragma External,Pragma Extensions_Allowed,Implementation Defined Pragmas
3647 @anchor{gnat_rm/implementation_defined_pragmas id12}@anchor{66}@anchor{gnat_rm/implementation_defined_pragmas pragma-extensions-visible}@anchor{67}
3648 @section Pragma Extensions_Visible
3654 pragma Extensions_Visible [ (boolean_EXPRESSION) ];
3657 For the semantics of this pragma, see the entry for aspect @code{Extensions_Visible}
3658 in the SPARK 2014 Reference Manual, section 6.1.7.
3660 @node Pragma External,Pragma External_Name_Casing,Pragma Extensions_Visible,Implementation Defined Pragmas
3661 @anchor{gnat_rm/implementation_defined_pragmas pragma-external}@anchor{68}
3662 @section Pragma External
3669 [ Convention =>] convention_IDENTIFIER,
3670 [ Entity =>] LOCAL_NAME
3671 [, [External_Name =>] static_string_EXPRESSION ]
3672 [, [Link_Name =>] static_string_EXPRESSION ]);
3675 This pragma is identical in syntax and semantics to pragma
3676 @code{Export} as defined in the Ada Reference Manual. It is
3677 provided for compatibility with some Ada 83 compilers that
3678 used this pragma for exactly the same purposes as pragma
3679 @code{Export} before the latter was standardized.
3681 @node Pragma External_Name_Casing,Pragma Fast_Math,Pragma External,Implementation Defined Pragmas
3682 @anchor{gnat_rm/implementation_defined_pragmas pragma-external-name-casing}@anchor{69}
3683 @section Pragma External_Name_Casing
3686 @geindex Dec Ada 83 casing compatibility
3688 @geindex External Names
3691 @geindex Casing of External names
3696 pragma External_Name_Casing (
3697 Uppercase | Lowercase
3698 [, Uppercase | Lowercase | As_Is]);
3701 This pragma provides control over the casing of external names associated
3702 with Import and Export pragmas. There are two cases to consider:
3708 Implicit external names
3710 Implicit external names are derived from identifiers. The most common case
3711 arises when a standard Ada Import or Export pragma is used with only two
3715 pragma Import (C, C_Routine);
3718 Since Ada is a case-insensitive language, the spelling of the identifier in
3719 the Ada source program does not provide any information on the desired
3720 casing of the external name, and so a convention is needed. In GNAT the
3721 default treatment is that such names are converted to all lower case
3722 letters. This corresponds to the normal C style in many environments.
3723 The first argument of pragma @code{External_Name_Casing} can be used to
3724 control this treatment. If @code{Uppercase} is specified, then the name
3725 will be forced to all uppercase letters. If @code{Lowercase} is specified,
3726 then the normal default of all lower case letters will be used.
3728 This same implicit treatment is also used in the case of extended DEC Ada 83
3729 compatible Import and Export pragmas where an external name is explicitly
3730 specified using an identifier rather than a string.
3733 Explicit external names
3735 Explicit external names are given as string literals. The most common case
3736 arises when a standard Ada Import or Export pragma is used with three
3740 pragma Import (C, C_Routine, "C_routine");
3743 In this case, the string literal normally provides the exact casing required
3744 for the external name. The second argument of pragma
3745 @code{External_Name_Casing} may be used to modify this behavior.
3746 If @code{Uppercase} is specified, then the name
3747 will be forced to all uppercase letters. If @code{Lowercase} is specified,
3748 then the name will be forced to all lowercase letters. A specification of
3749 @code{As_Is} provides the normal default behavior in which the casing is
3750 taken from the string provided.
3753 This pragma may appear anywhere that a pragma is valid. In particular, it
3754 can be used as a configuration pragma in the @code{gnat.adc} file, in which
3755 case it applies to all subsequent compilations, or it can be used as a program
3756 unit pragma, in which case it only applies to the current unit, or it can
3757 be used more locally to control individual Import/Export pragmas.
3759 It was primarily intended for use with OpenVMS systems, where many
3760 compilers convert all symbols to upper case by default. For interfacing to
3761 such compilers (e.g., the DEC C compiler), it may be convenient to use
3765 pragma External_Name_Casing (Uppercase, Uppercase);
3768 to enforce the upper casing of all external symbols.
3770 @node Pragma Fast_Math,Pragma Favor_Top_Level,Pragma External_Name_Casing,Implementation Defined Pragmas
3771 @anchor{gnat_rm/implementation_defined_pragmas pragma-fast-math}@anchor{6a}
3772 @section Pragma Fast_Math
3781 This is a configuration pragma which activates a mode in which speed is
3782 considered more important for floating-point operations than absolutely
3783 accurate adherence to the requirements of the standard. Currently the
3784 following operations are affected:
3789 @item @emph{Complex Multiplication}
3791 The normal simple formula for complex multiplication can result in intermediate
3792 overflows for numbers near the end of the range. The Ada standard requires that
3793 this situation be detected and corrected by scaling, but in Fast_Math mode such
3794 cases will simply result in overflow. Note that to take advantage of this you
3795 must instantiate your own version of @code{Ada.Numerics.Generic_Complex_Types}
3796 under control of the pragma, rather than use the preinstantiated versions.
3799 @node Pragma Favor_Top_Level,Pragma Finalize_Storage_Only,Pragma Fast_Math,Implementation Defined Pragmas
3800 @anchor{gnat_rm/implementation_defined_pragmas id13}@anchor{6b}@anchor{gnat_rm/implementation_defined_pragmas pragma-favor-top-level}@anchor{6c}
3801 @section Pragma Favor_Top_Level
3807 pragma Favor_Top_Level (type_NAME);
3810 The argument of pragma @code{Favor_Top_Level} must be a named access-to-subprogram
3811 type. This pragma is an efficiency hint to the compiler, regarding the use of
3812 @code{'Access} or @code{'Unrestricted_Access} on nested (non-library-level) subprograms.
3813 The pragma means that nested subprograms are not used with this type, or are
3814 rare, so that the generated code should be efficient in the top-level case.
3815 When this pragma is used, dynamically generated trampolines may be used on some
3816 targets for nested subprograms. See restriction @code{No_Implicit_Dynamic_Code}.
3818 @node Pragma Finalize_Storage_Only,Pragma Float_Representation,Pragma Favor_Top_Level,Implementation Defined Pragmas
3819 @anchor{gnat_rm/implementation_defined_pragmas pragma-finalize-storage-only}@anchor{6d}
3820 @section Pragma Finalize_Storage_Only
3826 pragma Finalize_Storage_Only (first_subtype_LOCAL_NAME);
3829 The argument of pragma @code{Finalize_Storage_Only} must denote a local type which
3830 is derived from @code{Ada.Finalization.Controlled} or @code{Limited_Controlled}. The
3831 pragma suppresses the call to @code{Finalize} for declared library-level objects
3832 of the argument type. This is mostly useful for types where finalization is
3833 only used to deal with storage reclamation since in most environments it is
3834 not necessary to reclaim memory just before terminating execution, hence the
3835 name. Note that this pragma does not suppress Finalize calls for library-level
3836 heap-allocated objects (see pragma @code{No_Heap_Finalization}).
3838 @node Pragma Float_Representation,Pragma Ghost,Pragma Finalize_Storage_Only,Implementation Defined Pragmas
3839 @anchor{gnat_rm/implementation_defined_pragmas pragma-float-representation}@anchor{6e}
3840 @section Pragma Float_Representation
3846 pragma Float_Representation (FLOAT_REP[, float_type_LOCAL_NAME]);
3848 FLOAT_REP ::= VAX_Float | IEEE_Float
3851 In the one argument form, this pragma is a configuration pragma which
3852 allows control over the internal representation chosen for the predefined
3853 floating point types declared in the packages @code{Standard} and
3854 @code{System}. This pragma is only provided for compatibility and has no effect.
3856 The two argument form specifies the representation to be used for
3857 the specified floating-point type. The argument must
3858 be @code{IEEE_Float} to specify the use of IEEE format, as follows:
3864 For a digits value of 6, 32-bit IEEE short format will be used.
3867 For a digits value of 15, 64-bit IEEE long format will be used.
3870 No other value of digits is permitted.
3873 @node Pragma Ghost,Pragma Global,Pragma Float_Representation,Implementation Defined Pragmas
3874 @anchor{gnat_rm/implementation_defined_pragmas pragma-ghost}@anchor{6f}@anchor{gnat_rm/implementation_defined_pragmas id14}@anchor{70}
3875 @section Pragma Ghost
3881 pragma Ghost [ (boolean_EXPRESSION) ];
3884 For the semantics of this pragma, see the entry for aspect @code{Ghost} in the SPARK
3885 2014 Reference Manual, section 6.9.
3887 @node Pragma Global,Pragma Ident,Pragma Ghost,Implementation Defined Pragmas
3888 @anchor{gnat_rm/implementation_defined_pragmas pragma-global}@anchor{71}@anchor{gnat_rm/implementation_defined_pragmas id15}@anchor{72}
3889 @section Pragma Global
3895 pragma Global (GLOBAL_SPECIFICATION);
3897 GLOBAL_SPECIFICATION ::=
3900 | (MODED_GLOBAL_LIST @{, MODED_GLOBAL_LIST@})
3902 MODED_GLOBAL_LIST ::= MODE_SELECTOR => GLOBAL_LIST
3904 MODE_SELECTOR ::= In_Out | Input | Output | Proof_In
3905 GLOBAL_LIST ::= GLOBAL_ITEM | (GLOBAL_ITEM @{, GLOBAL_ITEM@})
3906 GLOBAL_ITEM ::= NAME
3909 For the semantics of this pragma, see the entry for aspect @code{Global} in the
3910 SPARK 2014 Reference Manual, section 6.1.4.
3912 @node Pragma Ident,Pragma Ignore_Pragma,Pragma Global,Implementation Defined Pragmas
3913 @anchor{gnat_rm/implementation_defined_pragmas pragma-ident}@anchor{73}
3914 @section Pragma Ident
3920 pragma Ident (static_string_EXPRESSION);
3923 This pragma is identical in effect to pragma @code{Comment}. It is provided
3924 for compatibility with other Ada compilers providing this pragma.
3926 @node Pragma Ignore_Pragma,Pragma Implementation_Defined,Pragma Ident,Implementation Defined Pragmas
3927 @anchor{gnat_rm/implementation_defined_pragmas pragma-ignore-pragma}@anchor{74}
3928 @section Pragma Ignore_Pragma
3934 pragma Ignore_Pragma (pragma_IDENTIFIER);
3937 This is a configuration pragma
3938 that takes a single argument that is a simple identifier. Any subsequent
3939 use of a pragma whose pragma identifier matches this argument will be
3940 silently ignored. This may be useful when legacy code or code intended
3941 for compilation with some other compiler contains pragmas that match the
3942 name, but not the exact implementation, of a GNAT pragma. The use of this
3943 pragma allows such pragmas to be ignored, which may be useful in CodePeer
3944 mode, or during porting of legacy code.
3946 @node Pragma Implementation_Defined,Pragma Implemented,Pragma Ignore_Pragma,Implementation Defined Pragmas
3947 @anchor{gnat_rm/implementation_defined_pragmas pragma-implementation-defined}@anchor{75}
3948 @section Pragma Implementation_Defined
3954 pragma Implementation_Defined (local_NAME);
3957 This pragma marks a previously declared entity as implementation-defined.
3958 For an overloaded entity, applies to the most recent homonym.
3961 pragma Implementation_Defined;
3964 The form with no arguments appears anywhere within a scope, most
3965 typically a package spec, and indicates that all entities that are
3966 defined within the package spec are Implementation_Defined.
3968 This pragma is used within the GNAT runtime library to identify
3969 implementation-defined entities introduced in language-defined units,
3970 for the purpose of implementing the No_Implementation_Identifiers
3973 @node Pragma Implemented,Pragma Implicit_Packing,Pragma Implementation_Defined,Implementation Defined Pragmas
3974 @anchor{gnat_rm/implementation_defined_pragmas pragma-implemented}@anchor{76}
3975 @section Pragma Implemented
3981 pragma Implemented (procedure_LOCAL_NAME, implementation_kind);
3983 implementation_kind ::= By_Entry | By_Protected_Procedure | By_Any
3986 This is an Ada 2012 representation pragma which applies to protected, task
3987 and synchronized interface primitives. The use of pragma Implemented provides
3988 a way to impose a static requirement on the overriding operation by adhering
3989 to one of the three implementation kinds: entry, protected procedure or any of
3990 the above. This pragma is available in all earlier versions of Ada as an
3991 implementation-defined pragma.
3994 type Synch_Iface is synchronized interface;
3995 procedure Prim_Op (Obj : in out Iface) is abstract;
3996 pragma Implemented (Prim_Op, By_Protected_Procedure);
3998 protected type Prot_1 is new Synch_Iface with
3999 procedure Prim_Op; -- Legal
4002 protected type Prot_2 is new Synch_Iface with
4003 entry Prim_Op; -- Illegal
4006 task type Task_Typ is new Synch_Iface with
4007 entry Prim_Op; -- Illegal
4011 When applied to the procedure_or_entry_NAME of a requeue statement, pragma
4012 Implemented determines the runtime behavior of the requeue. Implementation kind
4013 By_Entry guarantees that the action of requeueing will proceed from an entry to
4014 another entry. Implementation kind By_Protected_Procedure transforms the
4015 requeue into a dispatching call, thus eliminating the chance of blocking. Kind
4016 By_Any shares the behavior of By_Entry and By_Protected_Procedure depending on
4017 the target's overriding subprogram kind.
4019 @node Pragma Implicit_Packing,Pragma Import_Function,Pragma Implemented,Implementation Defined Pragmas
4020 @anchor{gnat_rm/implementation_defined_pragmas pragma-implicit-packing}@anchor{77}
4021 @section Pragma Implicit_Packing
4024 @geindex Rational Profile
4029 pragma Implicit_Packing;
4032 This is a configuration pragma that requests implicit packing for packed
4033 arrays for which a size clause is given but no explicit pragma Pack or
4034 specification of Component_Size is present. It also applies to records
4035 where no record representation clause is present. Consider this example:
4038 type R is array (0 .. 7) of Boolean;
4042 In accordance with the recommendation in the RM (RM 13.3(53)), a Size clause
4043 does not change the layout of a composite object. So the Size clause in the
4044 above example is normally rejected, since the default layout of the array uses
4045 8-bit components, and thus the array requires a minimum of 64 bits.
4047 If this declaration is compiled in a region of code covered by an occurrence
4048 of the configuration pragma Implicit_Packing, then the Size clause in this
4049 and similar examples will cause implicit packing and thus be accepted. For
4050 this implicit packing to occur, the type in question must be an array of small
4051 components whose size is known at compile time, and the Size clause must
4052 specify the exact size that corresponds to the number of elements in the array
4053 multiplied by the size in bits of the component type (both single and
4054 multi-dimensioned arrays can be controlled with this pragma).
4056 @geindex Array packing
4058 Similarly, the following example shows the use in the record case
4062 a, b, c, d, e, f, g, h : boolean;
4068 Without a pragma Pack, each Boolean field requires 8 bits, so the
4069 minimum size is 72 bits, but with a pragma Pack, 16 bits would be
4070 sufficient. The use of pragma Implicit_Packing allows this record
4071 declaration to compile without an explicit pragma Pack.
4073 @node Pragma Import_Function,Pragma Import_Object,Pragma Implicit_Packing,Implementation Defined Pragmas
4074 @anchor{gnat_rm/implementation_defined_pragmas pragma-import-function}@anchor{78}
4075 @section Pragma Import_Function
4081 pragma Import_Function (
4082 [Internal =>] LOCAL_NAME,
4083 [, [External =>] EXTERNAL_SYMBOL]
4084 [, [Parameter_Types =>] PARAMETER_TYPES]
4085 [, [Result_Type =>] SUBTYPE_MARK]
4086 [, [Mechanism =>] MECHANISM]
4087 [, [Result_Mechanism =>] MECHANISM_NAME]);
4091 | static_string_EXPRESSION
4095 | TYPE_DESIGNATOR @{, TYPE_DESIGNATOR@}
4099 | subtype_Name ' Access
4103 | (MECHANISM_ASSOCIATION @{, MECHANISM_ASSOCIATION@})
4105 MECHANISM_ASSOCIATION ::=
4106 [formal_parameter_NAME =>] MECHANISM_NAME
4113 This pragma is used in conjunction with a pragma @code{Import} to
4114 specify additional information for an imported function. The pragma
4115 @code{Import} (or equivalent pragma @code{Interface}) must precede the
4116 @code{Import_Function} pragma and both must appear in the same
4117 declarative part as the function specification.
4119 The @code{Internal} argument must uniquely designate
4120 the function to which the
4121 pragma applies. If more than one function name exists of this name in
4122 the declarative part you must use the @code{Parameter_Types} and
4123 @code{Result_Type} parameters to achieve the required unique
4124 designation. Subtype marks in these parameters must exactly match the
4125 subtypes in the corresponding function specification, using positional
4126 notation to match parameters with subtype marks.
4127 The form with an @code{'Access} attribute can be used to match an
4128 anonymous access parameter.
4130 You may optionally use the @code{Mechanism} and @code{Result_Mechanism}
4131 parameters to specify passing mechanisms for the
4132 parameters and result. If you specify a single mechanism name, it
4133 applies to all parameters. Otherwise you may specify a mechanism on a
4134 parameter by parameter basis using either positional or named
4135 notation. If the mechanism is not specified, the default mechanism
4138 @node Pragma Import_Object,Pragma Import_Procedure,Pragma Import_Function,Implementation Defined Pragmas
4139 @anchor{gnat_rm/implementation_defined_pragmas pragma-import-object}@anchor{79}
4140 @section Pragma Import_Object
4146 pragma Import_Object
4147 [Internal =>] LOCAL_NAME
4148 [, [External =>] EXTERNAL_SYMBOL]
4149 [, [Size =>] EXTERNAL_SYMBOL]);
4153 | static_string_EXPRESSION
4156 This pragma designates an object as imported, and apart from the
4157 extended rules for external symbols, is identical in effect to the use of
4158 the normal @code{Import} pragma applied to an object. Unlike the
4159 subprogram case, you need not use a separate @code{Import} pragma,
4160 although you may do so (and probably should do so from a portability
4161 point of view). @code{size} is syntax checked, but otherwise ignored by
4164 @node Pragma Import_Procedure,Pragma Import_Valued_Procedure,Pragma Import_Object,Implementation Defined Pragmas
4165 @anchor{gnat_rm/implementation_defined_pragmas pragma-import-procedure}@anchor{7a}
4166 @section Pragma Import_Procedure
4172 pragma Import_Procedure (
4173 [Internal =>] LOCAL_NAME
4174 [, [External =>] EXTERNAL_SYMBOL]
4175 [, [Parameter_Types =>] PARAMETER_TYPES]
4176 [, [Mechanism =>] MECHANISM]);
4180 | static_string_EXPRESSION
4184 | TYPE_DESIGNATOR @{, TYPE_DESIGNATOR@}
4188 | subtype_Name ' Access
4192 | (MECHANISM_ASSOCIATION @{, MECHANISM_ASSOCIATION@})
4194 MECHANISM_ASSOCIATION ::=
4195 [formal_parameter_NAME =>] MECHANISM_NAME
4197 MECHANISM_NAME ::= Value | Reference
4200 This pragma is identical to @code{Import_Function} except that it
4201 applies to a procedure rather than a function and the parameters
4202 @code{Result_Type} and @code{Result_Mechanism} are not permitted.
4204 @node Pragma Import_Valued_Procedure,Pragma Independent,Pragma Import_Procedure,Implementation Defined Pragmas
4205 @anchor{gnat_rm/implementation_defined_pragmas pragma-import-valued-procedure}@anchor{7b}
4206 @section Pragma Import_Valued_Procedure
4212 pragma Import_Valued_Procedure (
4213 [Internal =>] LOCAL_NAME
4214 [, [External =>] EXTERNAL_SYMBOL]
4215 [, [Parameter_Types =>] PARAMETER_TYPES]
4216 [, [Mechanism =>] MECHANISM]);
4220 | static_string_EXPRESSION
4224 | TYPE_DESIGNATOR @{, TYPE_DESIGNATOR@}
4228 | subtype_Name ' Access
4232 | (MECHANISM_ASSOCIATION @{, MECHANISM_ASSOCIATION@})
4234 MECHANISM_ASSOCIATION ::=
4235 [formal_parameter_NAME =>] MECHANISM_NAME
4237 MECHANISM_NAME ::= Value | Reference
4240 This pragma is identical to @code{Import_Procedure} except that the
4241 first parameter of @code{LOCAL_NAME}, which must be present, must be of
4242 mode @code{out}, and externally the subprogram is treated as a function
4243 with this parameter as the result of the function. The purpose of this
4244 capability is to allow the use of @code{out} and @code{in out}
4245 parameters in interfacing to external functions (which are not permitted
4246 in Ada functions). You may optionally use the @code{Mechanism}
4247 parameters to specify passing mechanisms for the parameters.
4248 If you specify a single mechanism name, it applies to all parameters.
4249 Otherwise you may specify a mechanism on a parameter by parameter
4250 basis using either positional or named notation. If the mechanism is not
4251 specified, the default mechanism is used.
4253 Note that it is important to use this pragma in conjunction with a separate
4254 pragma Import that specifies the desired convention, since otherwise the
4255 default convention is Ada, which is almost certainly not what is required.
4257 @node Pragma Independent,Pragma Independent_Components,Pragma Import_Valued_Procedure,Implementation Defined Pragmas
4258 @anchor{gnat_rm/implementation_defined_pragmas pragma-independent}@anchor{7c}
4259 @section Pragma Independent
4265 pragma Independent (Local_NAME);
4268 This pragma is standard in Ada 2012 mode (which also provides an aspect
4269 of the same name). It is also available as an implementation-defined
4270 pragma in all earlier versions. It specifies that the
4271 designated object or all objects of the designated type must be
4272 independently addressable. This means that separate tasks can safely
4273 manipulate such objects. For example, if two components of a record are
4274 independent, then two separate tasks may access these two components.
4276 constraints on the representation of the object (for instance prohibiting
4279 @node Pragma Independent_Components,Pragma Initial_Condition,Pragma Independent,Implementation Defined Pragmas
4280 @anchor{gnat_rm/implementation_defined_pragmas pragma-independent-components}@anchor{7d}
4281 @section Pragma Independent_Components
4287 pragma Independent_Components (Local_NAME);
4290 This pragma is standard in Ada 2012 mode (which also provides an aspect
4291 of the same name). It is also available as an implementation-defined
4292 pragma in all earlier versions. It specifies that the components of the
4293 designated object, or the components of each object of the designated
4295 independently addressable. This means that separate tasks can safely
4296 manipulate separate components in the composite object. This may place
4297 constraints on the representation of the object (for instance prohibiting
4300 @node Pragma Initial_Condition,Pragma Initialize_Scalars,Pragma Independent_Components,Implementation Defined Pragmas
4301 @anchor{gnat_rm/implementation_defined_pragmas id16}@anchor{7e}@anchor{gnat_rm/implementation_defined_pragmas pragma-initial-condition}@anchor{7f}
4302 @section Pragma Initial_Condition
4308 pragma Initial_Condition (boolean_EXPRESSION);
4311 For the semantics of this pragma, see the entry for aspect @code{Initial_Condition}
4312 in the SPARK 2014 Reference Manual, section 7.1.6.
4314 @node Pragma Initialize_Scalars,Pragma Initializes,Pragma Initial_Condition,Implementation Defined Pragmas
4315 @anchor{gnat_rm/implementation_defined_pragmas pragma-initialize-scalars}@anchor{80}
4316 @section Pragma Initialize_Scalars
4319 @geindex debugging with Initialize_Scalars
4324 pragma Initialize_Scalars
4325 [ ( TYPE_VALUE_PAIR @{, TYPE_VALUE_PAIR@} ) ];
4328 SCALAR_TYPE => static_EXPRESSION
4345 This pragma is similar to @code{Normalize_Scalars} conceptually but has two
4346 important differences.
4348 First, there is no requirement for the pragma to be used uniformly in all units
4349 of a partition. In particular, it is fine to use this just for some or all of
4350 the application units of a partition, without needing to recompile the run-time
4351 library. In the case where some units are compiled with the pragma, and some
4352 without, then a declaration of a variable where the type is defined in package
4353 Standard or is locally declared will always be subject to initialization, as
4354 will any declaration of a scalar variable. For composite variables, whether the
4355 variable is initialized may also depend on whether the package in which the
4356 type of the variable is declared is compiled with the pragma.
4358 The other important difference is that the programmer can control the value
4359 used for initializing scalar objects. This effect can be achieved in several
4366 At compile time, the programmer can specify the invalid value for a
4367 particular family of scalar types using the optional arguments of the pragma.
4369 The compile-time approach is intended to optimize the generated code for the
4370 pragma, by possibly using fast operations such as @code{memset}. Note that such
4371 optimizations require using values where the bytes all have the same binary
4375 At bind time, the programmer has several options:
4381 Initialization with invalid values (similar to Normalize_Scalars, though
4382 for Initialize_Scalars it is not always possible to determine the invalid
4383 values in complex cases like signed component fields with nonstandard
4387 Initialization with high values.
4390 Initialization with low values.
4393 Initialization with a specific bit pattern.
4396 See the GNAT User's Guide for binder options for specifying these cases.
4398 The bind-time approach is intended to provide fast turnaround for testing
4399 with different values, without having to recompile the program.
4402 At execution time, the programmer can specify the invalid values using an
4403 environment variable. See the GNAT User's Guide for details.
4405 The execution-time approach is intended to provide fast turnaround for
4406 testing with different values, without having to recompile and rebind the
4410 Note that pragma @code{Initialize_Scalars} is particularly useful in conjunction
4411 with the enhanced validity checking that is now provided in GNAT, which checks
4412 for invalid values under more conditions. Using this feature (see description
4413 of the @emph{-gnatV} flag in the GNAT User's Guide) in conjunction with pragma
4414 @code{Initialize_Scalars} provides a powerful new tool to assist in the detection
4415 of problems caused by uninitialized variables.
4417 Note: the use of @code{Initialize_Scalars} has a fairly extensive effect on the
4418 generated code. This may cause your code to be substantially larger. It may
4419 also cause an increase in the amount of stack required, so it is probably a
4420 good idea to turn on stack checking (see description of stack checking in the
4421 GNAT User's Guide) when using this pragma.
4423 @node Pragma Initializes,Pragma Inline_Always,Pragma Initialize_Scalars,Implementation Defined Pragmas
4424 @anchor{gnat_rm/implementation_defined_pragmas pragma-initializes}@anchor{81}@anchor{gnat_rm/implementation_defined_pragmas id17}@anchor{82}
4425 @section Pragma Initializes
4431 pragma Initializes (INITIALIZATION_LIST);
4433 INITIALIZATION_LIST ::=
4435 | (INITIALIZATION_ITEM @{, INITIALIZATION_ITEM@})
4437 INITIALIZATION_ITEM ::= name [=> INPUT_LIST]
4442 | (INPUT @{, INPUT@})
4447 For the semantics of this pragma, see the entry for aspect @code{Initializes} in the
4448 SPARK 2014 Reference Manual, section 7.1.5.
4450 @node Pragma Inline_Always,Pragma Inline_Generic,Pragma Initializes,Implementation Defined Pragmas
4451 @anchor{gnat_rm/implementation_defined_pragmas id18}@anchor{83}@anchor{gnat_rm/implementation_defined_pragmas pragma-inline-always}@anchor{84}
4452 @section Pragma Inline_Always
4458 pragma Inline_Always (NAME [, NAME]);
4461 Similar to pragma @code{Inline} except that inlining is unconditional.
4462 Inline_Always instructs the compiler to inline every direct call to the
4463 subprogram or else to emit a compilation error, independently of any
4464 option, in particular @emph{-gnatn} or @emph{-gnatN} or the optimization level.
4465 It is an error to take the address or access of @code{NAME}. It is also an error to
4466 apply this pragma to a primitive operation of a tagged type. Thanks to such
4467 restrictions, the compiler is allowed to remove the out-of-line body of @code{NAME}.
4469 @node Pragma Inline_Generic,Pragma Interface,Pragma Inline_Always,Implementation Defined Pragmas
4470 @anchor{gnat_rm/implementation_defined_pragmas pragma-inline-generic}@anchor{85}
4471 @section Pragma Inline_Generic
4477 pragma Inline_Generic (GNAME @{, GNAME@});
4479 GNAME ::= generic_unit_NAME | generic_instance_NAME
4482 This pragma is provided for compatibility with Dec Ada 83. It has
4483 no effect in GNAT (which always inlines generics), other
4484 than to check that the given names are all names of generic units or
4487 @node Pragma Interface,Pragma Interface_Name,Pragma Inline_Generic,Implementation Defined Pragmas
4488 @anchor{gnat_rm/implementation_defined_pragmas pragma-interface}@anchor{86}
4489 @section Pragma Interface
4496 [Convention =>] convention_identifier,
4497 [Entity =>] local_NAME
4498 [, [External_Name =>] static_string_expression]
4499 [, [Link_Name =>] static_string_expression]);
4502 This pragma is identical in syntax and semantics to
4503 the standard Ada pragma @code{Import}. It is provided for compatibility
4504 with Ada 83. The definition is upwards compatible both with pragma
4505 @code{Interface} as defined in the Ada 83 Reference Manual, and also
4506 with some extended implementations of this pragma in certain Ada 83
4507 implementations. The only difference between pragma @code{Interface}
4508 and pragma @code{Import} is that there is special circuitry to allow
4509 both pragmas to appear for the same subprogram entity (normally it
4510 is illegal to have multiple @code{Import} pragmas. This is useful in
4511 maintaining Ada 83/Ada 95 compatibility and is compatible with other
4514 @node Pragma Interface_Name,Pragma Interrupt_Handler,Pragma Interface,Implementation Defined Pragmas
4515 @anchor{gnat_rm/implementation_defined_pragmas pragma-interface-name}@anchor{87}
4516 @section Pragma Interface_Name
4522 pragma Interface_Name (
4523 [Entity =>] LOCAL_NAME
4524 [, [External_Name =>] static_string_EXPRESSION]
4525 [, [Link_Name =>] static_string_EXPRESSION]);
4528 This pragma provides an alternative way of specifying the interface name
4529 for an interfaced subprogram, and is provided for compatibility with Ada
4530 83 compilers that use the pragma for this purpose. You must provide at
4531 least one of @code{External_Name} or @code{Link_Name}.
4533 @node Pragma Interrupt_Handler,Pragma Interrupt_State,Pragma Interface_Name,Implementation Defined Pragmas
4534 @anchor{gnat_rm/implementation_defined_pragmas pragma-interrupt-handler}@anchor{88}
4535 @section Pragma Interrupt_Handler
4541 pragma Interrupt_Handler (procedure_LOCAL_NAME);
4544 This program unit pragma is supported for parameterless protected procedures
4545 as described in Annex C of the Ada Reference Manual. On the AAMP target
4546 the pragma can also be specified for nonprotected parameterless procedures
4547 that are declared at the library level (which includes procedures
4548 declared at the top level of a library package). In the case of AAMP,
4549 when this pragma is applied to a nonprotected procedure, the instruction
4550 @code{IERET} is generated for returns from the procedure, enabling
4551 maskable interrupts, in place of the normal return instruction.
4553 @node Pragma Interrupt_State,Pragma Invariant,Pragma Interrupt_Handler,Implementation Defined Pragmas
4554 @anchor{gnat_rm/implementation_defined_pragmas pragma-interrupt-state}@anchor{89}
4555 @section Pragma Interrupt_State
4561 pragma Interrupt_State
4563 [State =>] SYSTEM | RUNTIME | USER);
4566 Normally certain interrupts are reserved to the implementation. Any attempt
4567 to attach an interrupt causes Program_Error to be raised, as described in
4568 RM C.3.2(22). A typical example is the @code{SIGINT} interrupt used in
4569 many systems for an @code{Ctrl-C} interrupt. Normally this interrupt is
4570 reserved to the implementation, so that @code{Ctrl-C} can be used to
4571 interrupt execution. Additionally, signals such as @code{SIGSEGV},
4572 @code{SIGABRT}, @code{SIGFPE} and @code{SIGILL} are often mapped to specific
4573 Ada exceptions, or used to implement run-time functions such as the
4574 @code{abort} statement and stack overflow checking.
4576 Pragma @code{Interrupt_State} provides a general mechanism for overriding
4577 such uses of interrupts. It subsumes the functionality of pragma
4578 @code{Unreserve_All_Interrupts}. Pragma @code{Interrupt_State} is not
4579 available on Windows. On all other platforms than VxWorks,
4580 it applies to signals; on VxWorks, it applies to vectored hardware interrupts
4581 and may be used to mark interrupts required by the board support package
4584 Interrupts can be in one of three states:
4592 The interrupt is reserved (no Ada handler can be installed), and the
4593 Ada run-time may not install a handler. As a result you are guaranteed
4594 standard system default action if this interrupt is raised. This also allows
4595 installing a low level handler via C APIs such as sigaction(), outside
4601 The interrupt is reserved (no Ada handler can be installed). The run time
4602 is allowed to install a handler for internal control purposes, but is
4603 not required to do so.
4608 The interrupt is unreserved. The user may install an Ada handler via
4609 Ada.Interrupts and pragma Interrupt_Handler or Attach_Handler to provide
4613 These states are the allowed values of the @code{State} parameter of the
4614 pragma. The @code{Name} parameter is a value of the type
4615 @code{Ada.Interrupts.Interrupt_ID}. Typically, it is a name declared in
4616 @code{Ada.Interrupts.Names}.
4618 This is a configuration pragma, and the binder will check that there
4619 are no inconsistencies between different units in a partition in how a
4620 given interrupt is specified. It may appear anywhere a pragma is legal.
4622 The effect is to move the interrupt to the specified state.
4624 By declaring interrupts to be SYSTEM, you guarantee the standard system
4625 action, such as a core dump.
4627 By declaring interrupts to be USER, you guarantee that you can install
4630 Note that certain signals on many operating systems cannot be caught and
4631 handled by applications. In such cases, the pragma is ignored. See the
4632 operating system documentation, or the value of the array @code{Reserved}
4633 declared in the spec of package @code{System.OS_Interface}.
4635 Overriding the default state of signals used by the Ada runtime may interfere
4636 with an application's runtime behavior in the cases of the synchronous signals,
4637 and in the case of the signal used to implement the @code{abort} statement.
4639 @node Pragma Invariant,Pragma Keep_Names,Pragma Interrupt_State,Implementation Defined Pragmas
4640 @anchor{gnat_rm/implementation_defined_pragmas id19}@anchor{8a}@anchor{gnat_rm/implementation_defined_pragmas pragma-invariant}@anchor{8b}
4641 @section Pragma Invariant
4648 ([Entity =>] private_type_LOCAL_NAME,
4649 [Check =>] EXPRESSION
4650 [,[Message =>] String_Expression]);
4653 This pragma provides exactly the same capabilities as the Type_Invariant aspect
4654 defined in AI05-0146-1, and in the Ada 2012 Reference Manual. The
4655 Type_Invariant aspect is fully implemented in Ada 2012 mode, but since it
4656 requires the use of the aspect syntax, which is not available except in 2012
4657 mode, it is not possible to use the Type_Invariant aspect in earlier versions
4658 of Ada. However the Invariant pragma may be used in any version of Ada. Also
4659 note that the aspect Invariant is a synonym in GNAT for the aspect
4660 Type_Invariant, but there is no pragma Type_Invariant.
4662 The pragma must appear within the visible part of the package specification,
4663 after the type to which its Entity argument appears. As with the Invariant
4664 aspect, the Check expression is not analyzed until the end of the visible
4665 part of the package, so it may contain forward references. The Message
4666 argument, if present, provides the exception message used if the invariant
4667 is violated. If no Message parameter is provided, a default message that
4668 identifies the line on which the pragma appears is used.
4670 It is permissible to have multiple Invariants for the same type entity, in
4671 which case they are and'ed together. It is permissible to use this pragma
4672 in Ada 2012 mode, but you cannot have both an invariant aspect and an
4673 invariant pragma for the same entity.
4675 For further details on the use of this pragma, see the Ada 2012 documentation
4676 of the Type_Invariant aspect.
4678 @node Pragma Keep_Names,Pragma License,Pragma Invariant,Implementation Defined Pragmas
4679 @anchor{gnat_rm/implementation_defined_pragmas pragma-keep-names}@anchor{8c}
4680 @section Pragma Keep_Names
4686 pragma Keep_Names ([On =>] enumeration_first_subtype_LOCAL_NAME);
4689 The @code{LOCAL_NAME} argument
4690 must refer to an enumeration first subtype
4691 in the current declarative part. The effect is to retain the enumeration
4692 literal names for use by @code{Image} and @code{Value} even if a global
4693 @code{Discard_Names} pragma applies. This is useful when you want to
4694 generally suppress enumeration literal names and for example you therefore
4695 use a @code{Discard_Names} pragma in the @code{gnat.adc} file, but you
4696 want to retain the names for specific enumeration types.
4698 @node Pragma License,Pragma Link_With,Pragma Keep_Names,Implementation Defined Pragmas
4699 @anchor{gnat_rm/implementation_defined_pragmas pragma-license}@anchor{8d}
4700 @section Pragma License
4703 @geindex License checking
4708 pragma License (Unrestricted | GPL | Modified_GPL | Restricted);
4711 This pragma is provided to allow automated checking for appropriate license
4712 conditions with respect to the standard and modified GPL. A pragma
4713 @code{License}, which is a configuration pragma that typically appears at
4714 the start of a source file or in a separate @code{gnat.adc} file, specifies
4715 the licensing conditions of a unit as follows:
4722 This is used for a unit that can be freely used with no license restrictions.
4723 Examples of such units are public domain units, and units from the Ada
4728 This is used for a unit that is licensed under the unmodified GPL, and which
4729 therefore cannot be @code{with}ed by a restricted unit.
4733 This is used for a unit licensed under the GNAT modified GPL that includes
4734 a special exception paragraph that specifically permits the inclusion of
4735 the unit in programs without requiring the entire program to be released
4740 This is used for a unit that is restricted in that it is not permitted to
4741 depend on units that are licensed under the GPL. Typical examples are
4742 proprietary code that is to be released under more restrictive license
4743 conditions. Note that restricted units are permitted to @code{with} units
4744 which are licensed under the modified GPL (this is the whole point of the
4748 Normally a unit with no @code{License} pragma is considered to have an
4749 unknown license, and no checking is done. However, standard GNAT headers
4750 are recognized, and license information is derived from them as follows.
4752 A GNAT license header starts with a line containing 78 hyphens. The following
4753 comment text is searched for the appearance of any of the following strings.
4755 If the string 'GNU General Public License' is found, then the unit is assumed
4756 to have GPL license, unless the string 'As a special exception' follows, in
4757 which case the license is assumed to be modified GPL.
4759 If one of the strings
4760 'This specification is adapted from the Ada Semantic Interface' or
4761 'This specification is derived from the Ada Reference Manual' is found
4762 then the unit is assumed to be unrestricted.
4764 These default actions means that a program with a restricted license pragma
4765 will automatically get warnings if a GPL unit is inappropriately
4766 @code{with}ed. For example, the program:
4771 procedure Secret_Stuff is
4776 if compiled with pragma @code{License} (@code{Restricted}) in a
4777 @code{gnat.adc} file will generate the warning:
4782 >>> license of withed unit "Sem_Ch3" is incompatible
4784 2. with GNAT.Sockets;
4785 3. procedure Secret_Stuff is
4788 Here we get a warning on @code{Sem_Ch3} since it is part of the GNAT
4789 compiler and is licensed under the
4790 GPL, but no warning for @code{GNAT.Sockets} which is part of the GNAT
4791 run time, and is therefore licensed under the modified GPL.
4793 @node Pragma Link_With,Pragma Linker_Alias,Pragma License,Implementation Defined Pragmas
4794 @anchor{gnat_rm/implementation_defined_pragmas pragma-link-with}@anchor{8e}
4795 @section Pragma Link_With
4801 pragma Link_With (static_string_EXPRESSION @{,static_string_EXPRESSION@});
4804 This pragma is provided for compatibility with certain Ada 83 compilers.
4805 It has exactly the same effect as pragma @code{Linker_Options} except
4806 that spaces occurring within one of the string expressions are treated
4807 as separators. For example, in the following case:
4810 pragma Link_With ("-labc -ldef");
4813 results in passing the strings @code{-labc} and @code{-ldef} as two
4814 separate arguments to the linker. In addition pragma Link_With allows
4815 multiple arguments, with the same effect as successive pragmas.
4817 @node Pragma Linker_Alias,Pragma Linker_Constructor,Pragma Link_With,Implementation Defined Pragmas
4818 @anchor{gnat_rm/implementation_defined_pragmas pragma-linker-alias}@anchor{8f}
4819 @section Pragma Linker_Alias
4825 pragma Linker_Alias (
4826 [Entity =>] LOCAL_NAME,
4827 [Target =>] static_string_EXPRESSION);
4830 @code{LOCAL_NAME} must refer to an object that is declared at the library
4831 level. This pragma establishes the given entity as a linker alias for the
4832 given target. It is equivalent to @code{__attribute__((alias))} in GNU C
4833 and causes @code{LOCAL_NAME} to be emitted as an alias for the symbol
4834 @code{static_string_EXPRESSION} in the object file, that is to say no space
4835 is reserved for @code{LOCAL_NAME} by the assembler and it will be resolved
4836 to the same address as @code{static_string_EXPRESSION} by the linker.
4838 The actual linker name for the target must be used (e.g., the fully
4839 encoded name with qualification in Ada, or the mangled name in C++),
4840 or it must be declared using the C convention with @code{pragma Import}
4841 or @code{pragma Export}.
4843 Not all target machines support this pragma. On some of them it is accepted
4844 only if @code{pragma Weak_External} has been applied to @code{LOCAL_NAME}.
4847 -- Example of the use of pragma Linker_Alias
4851 pragma Export (C, i);
4853 new_name_for_i : Integer;
4854 pragma Linker_Alias (new_name_for_i, "i");
4858 @node Pragma Linker_Constructor,Pragma Linker_Destructor,Pragma Linker_Alias,Implementation Defined Pragmas
4859 @anchor{gnat_rm/implementation_defined_pragmas pragma-linker-constructor}@anchor{90}
4860 @section Pragma Linker_Constructor
4866 pragma Linker_Constructor (procedure_LOCAL_NAME);
4869 @code{procedure_LOCAL_NAME} must refer to a parameterless procedure that
4870 is declared at the library level. A procedure to which this pragma is
4871 applied will be treated as an initialization routine by the linker.
4872 It is equivalent to @code{__attribute__((constructor))} in GNU C and
4873 causes @code{procedure_LOCAL_NAME} to be invoked before the entry point
4874 of the executable is called (or immediately after the shared library is
4875 loaded if the procedure is linked in a shared library), in particular
4876 before the Ada run-time environment is set up.
4878 Because of these specific contexts, the set of operations such a procedure
4879 can perform is very limited and the type of objects it can manipulate is
4880 essentially restricted to the elementary types. In particular, it must only
4881 contain code to which pragma Restrictions (No_Elaboration_Code) applies.
4883 This pragma is used by GNAT to implement auto-initialization of shared Stand
4884 Alone Libraries, which provides a related capability without the restrictions
4885 listed above. Where possible, the use of Stand Alone Libraries is preferable
4886 to the use of this pragma.
4888 @node Pragma Linker_Destructor,Pragma Linker_Section,Pragma Linker_Constructor,Implementation Defined Pragmas
4889 @anchor{gnat_rm/implementation_defined_pragmas pragma-linker-destructor}@anchor{91}
4890 @section Pragma Linker_Destructor
4896 pragma Linker_Destructor (procedure_LOCAL_NAME);
4899 @code{procedure_LOCAL_NAME} must refer to a parameterless procedure that
4900 is declared at the library level. A procedure to which this pragma is
4901 applied will be treated as a finalization routine by the linker.
4902 It is equivalent to @code{__attribute__((destructor))} in GNU C and
4903 causes @code{procedure_LOCAL_NAME} to be invoked after the entry point
4904 of the executable has exited (or immediately before the shared library
4905 is unloaded if the procedure is linked in a shared library), in particular
4906 after the Ada run-time environment is shut down.
4908 See @code{pragma Linker_Constructor} for the set of restrictions that apply
4909 because of these specific contexts.
4911 @node Pragma Linker_Section,Pragma Lock_Free,Pragma Linker_Destructor,Implementation Defined Pragmas
4912 @anchor{gnat_rm/implementation_defined_pragmas id20}@anchor{92}@anchor{gnat_rm/implementation_defined_pragmas pragma-linker-section}@anchor{93}
4913 @section Pragma Linker_Section
4919 pragma Linker_Section (
4920 [Entity =>] LOCAL_NAME,
4921 [Section =>] static_string_EXPRESSION);
4924 @code{LOCAL_NAME} must refer to an object, type, or subprogram that is
4925 declared at the library level. This pragma specifies the name of the
4926 linker section for the given entity. It is equivalent to
4927 @code{__attribute__((section))} in GNU C and causes @code{LOCAL_NAME} to
4928 be placed in the @code{static_string_EXPRESSION} section of the
4929 executable (assuming the linker doesn't rename the section).
4930 GNAT also provides an implementation defined aspect of the same name.
4932 In the case of specifying this aspect for a type, the effect is to
4933 specify the corresponding section for all library-level objects of
4934 the type that do not have an explicit linker section set. Note that
4935 this only applies to whole objects, not to components of composite objects.
4937 In the case of a subprogram, the linker section applies to all previously
4938 declared matching overloaded subprograms in the current declarative part
4939 which do not already have a linker section assigned. The linker section
4940 aspect is useful in this case for specifying different linker sections
4941 for different elements of such an overloaded set.
4943 Note that an empty string specifies that no linker section is specified.
4944 This is not quite the same as omitting the pragma or aspect, since it
4945 can be used to specify that one element of an overloaded set of subprograms
4946 has the default linker section, or that one object of a type for which a
4947 linker section is specified should has the default linker section.
4949 The compiler normally places library-level entities in standard sections
4950 depending on the class: procedures and functions generally go in the
4951 @code{.text} section, initialized variables in the @code{.data} section
4952 and uninitialized variables in the @code{.bss} section.
4954 Other, special sections may exist on given target machines to map special
4955 hardware, for example I/O ports or flash memory. This pragma is a means to
4956 defer the final layout of the executable to the linker, thus fully working
4957 at the symbolic level with the compiler.
4959 Some file formats do not support arbitrary sections so not all target
4960 machines support this pragma. The use of this pragma may cause a program
4961 execution to be erroneous if it is used to place an entity into an
4962 inappropriate section (e.g., a modified variable into the @code{.text}
4963 section). See also @code{pragma Persistent_BSS}.
4966 -- Example of the use of pragma Linker_Section
4970 pragma Volatile (Port_A);
4971 pragma Linker_Section (Port_A, ".bss.port_a");
4974 pragma Volatile (Port_B);
4975 pragma Linker_Section (Port_B, ".bss.port_b");
4977 type Port_Type is new Integer with Linker_Section => ".bss";
4978 PA : Port_Type with Linker_Section => ".bss.PA";
4979 PB : Port_Type; -- ends up in linker section ".bss"
4981 procedure Q with Linker_Section => "Qsection";
4985 @node Pragma Lock_Free,Pragma Loop_Invariant,Pragma Linker_Section,Implementation Defined Pragmas
4986 @anchor{gnat_rm/implementation_defined_pragmas id21}@anchor{94}@anchor{gnat_rm/implementation_defined_pragmas pragma-lock-free}@anchor{95}
4987 @section Pragma Lock_Free
4991 This pragma may be specified for protected types or objects. It specifies that
4992 the implementation of protected operations must be implemented without locks.
4993 Compilation fails if the compiler cannot generate lock-free code for the
4996 The current conditions required to support this pragma are:
5002 Protected type declarations may not contain entries
5005 Protected subprogram declarations may not have nonelementary parameters
5008 In addition, each protected subprogram body must satisfy:
5014 May reference only one protected component
5017 May not reference nonconstant entities outside the protected subprogram
5021 May not contain address representation items, allocators, or quantified
5025 May not contain delay, goto, loop, or procedure-call statements.
5028 May not contain exported and imported entities
5031 May not dereferenced access values
5034 Function calls and attribute references must be static
5037 @node Pragma Loop_Invariant,Pragma Loop_Optimize,Pragma Lock_Free,Implementation Defined Pragmas
5038 @anchor{gnat_rm/implementation_defined_pragmas pragma-loop-invariant}@anchor{96}
5039 @section Pragma Loop_Invariant
5045 pragma Loop_Invariant ( boolean_EXPRESSION );
5048 The effect of this pragma is similar to that of pragma @code{Assert},
5049 except that in an @code{Assertion_Policy} pragma, the identifier
5050 @code{Loop_Invariant} is used to control whether it is ignored or checked
5053 @code{Loop_Invariant} can only appear as one of the items in the sequence
5054 of statements of a loop body, or nested inside block statements that
5055 appear in the sequence of statements of a loop body.
5056 The intention is that it be used to
5057 represent a "loop invariant" assertion, i.e. something that is true each
5058 time through the loop, and which can be used to show that the loop is
5059 achieving its purpose.
5061 Multiple @code{Loop_Invariant} and @code{Loop_Variant} pragmas that
5062 apply to the same loop should be grouped in the same sequence of
5065 To aid in writing such invariants, the special attribute @code{Loop_Entry}
5066 may be used to refer to the value of an expression on entry to the loop. This
5067 attribute can only be used within the expression of a @code{Loop_Invariant}
5068 pragma. For full details, see documentation of attribute @code{Loop_Entry}.
5070 @node Pragma Loop_Optimize,Pragma Loop_Variant,Pragma Loop_Invariant,Implementation Defined Pragmas
5071 @anchor{gnat_rm/implementation_defined_pragmas pragma-loop-optimize}@anchor{97}
5072 @section Pragma Loop_Optimize
5078 pragma Loop_Optimize (OPTIMIZATION_HINT @{, OPTIMIZATION_HINT@});
5080 OPTIMIZATION_HINT ::= Ivdep | No_Unroll | Unroll | No_Vector | Vector
5083 This pragma must appear immediately within a loop statement. It allows the
5084 programmer to specify optimization hints for the enclosing loop. The hints
5085 are not mutually exclusive and can be freely mixed, but not all combinations
5086 will yield a sensible outcome.
5088 There are five supported optimization hints for a loop:
5096 The programmer asserts that there are no loop-carried dependencies
5097 which would prevent consecutive iterations of the loop from being
5098 executed simultaneously.
5103 The loop must not be unrolled. This is a strong hint: the compiler will not
5104 unroll a loop marked with this hint.
5109 The loop should be unrolled. This is a weak hint: the compiler will try to
5110 apply unrolling to this loop preferably to other optimizations, notably
5111 vectorization, but there is no guarantee that the loop will be unrolled.
5116 The loop must not be vectorized. This is a strong hint: the compiler will not
5117 vectorize a loop marked with this hint.
5122 The loop should be vectorized. This is a weak hint: the compiler will try to
5123 apply vectorization to this loop preferably to other optimizations, notably
5124 unrolling, but there is no guarantee that the loop will be vectorized.
5127 These hints do not remove the need to pass the appropriate switches to the
5128 compiler in order to enable the relevant optimizations, that is to say
5129 @emph{-funroll-loops} for unrolling and @emph{-ftree-vectorize} for
5132 @node Pragma Loop_Variant,Pragma Machine_Attribute,Pragma Loop_Optimize,Implementation Defined Pragmas
5133 @anchor{gnat_rm/implementation_defined_pragmas pragma-loop-variant}@anchor{98}
5134 @section Pragma Loop_Variant
5140 pragma Loop_Variant ( LOOP_VARIANT_ITEM @{, LOOP_VARIANT_ITEM @} );
5141 LOOP_VARIANT_ITEM ::= CHANGE_DIRECTION => discrete_EXPRESSION
5142 CHANGE_DIRECTION ::= Increases | Decreases
5145 @code{Loop_Variant} can only appear as one of the items in the sequence
5146 of statements of a loop body, or nested inside block statements that
5147 appear in the sequence of statements of a loop body.
5148 It allows the specification of quantities which must always
5149 decrease or increase in successive iterations of the loop. In its simplest
5150 form, just one expression is specified, whose value must increase or decrease
5151 on each iteration of the loop.
5153 In a more complex form, multiple arguments can be given which are intepreted
5154 in a nesting lexicographic manner. For example:
5157 pragma Loop_Variant (Increases => X, Decreases => Y);
5160 specifies that each time through the loop either X increases, or X stays
5161 the same and Y decreases. A @code{Loop_Variant} pragma ensures that the
5162 loop is making progress. It can be useful in helping to show informally
5163 or prove formally that the loop always terminates.
5165 @code{Loop_Variant} is an assertion whose effect can be controlled using
5166 an @code{Assertion_Policy} with a check name of @code{Loop_Variant}. The
5167 policy can be @code{Check} to enable the loop variant check, @code{Ignore}
5168 to ignore the check (in which case the pragma has no effect on the program),
5169 or @code{Disable} in which case the pragma is not even checked for correct
5172 Multiple @code{Loop_Invariant} and @code{Loop_Variant} pragmas that
5173 apply to the same loop should be grouped in the same sequence of
5176 The @code{Loop_Entry} attribute may be used within the expressions of the
5177 @code{Loop_Variant} pragma to refer to values on entry to the loop.
5179 @node Pragma Machine_Attribute,Pragma Main,Pragma Loop_Variant,Implementation Defined Pragmas
5180 @anchor{gnat_rm/implementation_defined_pragmas pragma-machine-attribute}@anchor{99}
5181 @section Pragma Machine_Attribute
5187 pragma Machine_Attribute (
5188 [Entity =>] LOCAL_NAME,
5189 [Attribute_Name =>] static_string_EXPRESSION
5190 [, [Info =>] static_EXPRESSION @{, static_EXPRESSION@}] );
5193 Machine-dependent attributes can be specified for types and/or
5194 declarations. This pragma is semantically equivalent to
5195 @code{__attribute__((@emph{attribute_name}))} (if @code{info} is not
5196 specified) or @code{__attribute__((@emph{attribute_name(info})))}
5197 or @code{__attribute__((@emph{attribute_name(info,...})))} in GNU C,
5198 where @emph{attribute_name} is recognized by the compiler middle-end
5199 or the @code{TARGET_ATTRIBUTE_TABLE} machine specific macro. Note
5200 that a string literal for the optional parameter @code{info} or the
5201 following ones is transformed by default into an identifier,
5202 which may make this pragma unusable for some attributes.
5203 For further information see @cite{GNU Compiler Collection (GCC) Internals}.
5205 @node Pragma Main,Pragma Main_Storage,Pragma Machine_Attribute,Implementation Defined Pragmas
5206 @anchor{gnat_rm/implementation_defined_pragmas pragma-main}@anchor{9a}
5207 @section Pragma Main
5214 (MAIN_OPTION [, MAIN_OPTION]);
5217 [Stack_Size =>] static_integer_EXPRESSION
5218 | [Task_Stack_Size_Default =>] static_integer_EXPRESSION
5219 | [Time_Slicing_Enabled =>] static_boolean_EXPRESSION
5222 This pragma is provided for compatibility with OpenVMS VAX Systems. It has
5223 no effect in GNAT, other than being syntax checked.
5225 @node Pragma Main_Storage,Pragma Max_Queue_Length,Pragma Main,Implementation Defined Pragmas
5226 @anchor{gnat_rm/implementation_defined_pragmas pragma-main-storage}@anchor{9b}
5227 @section Pragma Main_Storage
5234 (MAIN_STORAGE_OPTION [, MAIN_STORAGE_OPTION]);
5236 MAIN_STORAGE_OPTION ::=
5237 [WORKING_STORAGE =>] static_SIMPLE_EXPRESSION
5238 | [TOP_GUARD =>] static_SIMPLE_EXPRESSION
5241 This pragma is provided for compatibility with OpenVMS VAX Systems. It has
5242 no effect in GNAT, other than being syntax checked.
5244 @node Pragma Max_Queue_Length,Pragma No_Body,Pragma Main_Storage,Implementation Defined Pragmas
5245 @anchor{gnat_rm/implementation_defined_pragmas id22}@anchor{9c}@anchor{gnat_rm/implementation_defined_pragmas pragma-max-queue-length}@anchor{9d}
5246 @section Pragma Max_Queue_Length
5252 pragma Max_Entry_Queue (static_integer_EXPRESSION);
5255 This pragma is used to specify the maximum callers per entry queue for
5256 individual protected entries and entry families. It accepts a single
5257 integer (-1 or more) as a parameter and must appear after the declaration of an
5260 A value of -1 represents no additional restriction on queue length.
5262 @node Pragma No_Body,Pragma No_Caching,Pragma Max_Queue_Length,Implementation Defined Pragmas
5263 @anchor{gnat_rm/implementation_defined_pragmas pragma-no-body}@anchor{9e}
5264 @section Pragma No_Body
5273 There are a number of cases in which a package spec does not require a body,
5274 and in fact a body is not permitted. GNAT will not permit the spec to be
5275 compiled if there is a body around. The pragma No_Body allows you to provide
5276 a body file, even in a case where no body is allowed. The body file must
5277 contain only comments and a single No_Body pragma. This is recognized by
5278 the compiler as indicating that no body is logically present.
5280 This is particularly useful during maintenance when a package is modified in
5281 such a way that a body needed before is no longer needed. The provision of a
5282 dummy body with a No_Body pragma ensures that there is no interference from
5283 earlier versions of the package body.
5285 @node Pragma No_Caching,Pragma No_Component_Reordering,Pragma No_Body,Implementation Defined Pragmas
5286 @anchor{gnat_rm/implementation_defined_pragmas pragma-no-caching}@anchor{9f}@anchor{gnat_rm/implementation_defined_pragmas id23}@anchor{a0}
5287 @section Pragma No_Caching
5293 pragma No_Caching [ (boolean_EXPRESSION) ];
5296 For the semantics of this pragma, see the entry for aspect @code{No_Caching} in
5297 the SPARK 2014 Reference Manual, section 7.1.2.
5299 @node Pragma No_Component_Reordering,Pragma No_Elaboration_Code_All,Pragma No_Caching,Implementation Defined Pragmas
5300 @anchor{gnat_rm/implementation_defined_pragmas pragma-no-component-reordering}@anchor{a1}
5301 @section Pragma No_Component_Reordering
5307 pragma No_Component_Reordering [([Entity =>] type_LOCAL_NAME)];
5310 @code{type_LOCAL_NAME} must refer to a record type declaration in the current
5311 declarative part. The effect is to preclude any reordering of components
5312 for the layout of the record, i.e. the record is laid out by the compiler
5313 in the order in which the components are declared textually. The form with
5314 no argument is a configuration pragma which applies to all record types
5315 declared in units to which the pragma applies and there is a requirement
5316 that this pragma be used consistently within a partition.
5318 @node Pragma No_Elaboration_Code_All,Pragma No_Heap_Finalization,Pragma No_Component_Reordering,Implementation Defined Pragmas
5319 @anchor{gnat_rm/implementation_defined_pragmas id24}@anchor{a2}@anchor{gnat_rm/implementation_defined_pragmas pragma-no-elaboration-code-all}@anchor{a3}
5320 @section Pragma No_Elaboration_Code_All
5326 pragma No_Elaboration_Code_All [(program_unit_NAME)];
5329 This is a program unit pragma (there is also an equivalent aspect of the
5330 same name) that establishes the restriction @code{No_Elaboration_Code} for
5331 the current unit and any extended main source units (body and subunits).
5332 It also has the effect of enforcing a transitive application of this
5333 aspect, so that if any unit is implicitly or explicitly with'ed by the
5334 current unit, it must also have the No_Elaboration_Code_All aspect set.
5335 It may be applied to package or subprogram specs or their generic versions.
5337 @node Pragma No_Heap_Finalization,Pragma No_Inline,Pragma No_Elaboration_Code_All,Implementation Defined Pragmas
5338 @anchor{gnat_rm/implementation_defined_pragmas pragma-no-heap-finalization}@anchor{a4}
5339 @section Pragma No_Heap_Finalization
5345 pragma No_Heap_Finalization [ (first_subtype_LOCAL_NAME) ];
5348 Pragma @code{No_Heap_Finalization} may be used as a configuration pragma or as a
5349 type-specific pragma.
5351 In its configuration form, the pragma must appear within a configuration file
5352 such as gnat.adc, without an argument. The pragma suppresses the call to
5353 @code{Finalize} for heap-allocated objects created through library-level named
5354 access-to-object types in cases where the designated type requires finalization
5357 In its type-specific form, the argument of the pragma must denote a
5358 library-level named access-to-object type. The pragma suppresses the call to
5359 @code{Finalize} for heap-allocated objects created through the specific access type
5360 in cases where the designated type requires finalization actions.
5362 It is still possible to finalize such heap-allocated objects by explicitly
5365 A library-level named access-to-object type declared within a generic unit will
5366 lose its @code{No_Heap_Finalization} pragma when the corresponding instance does not
5367 appear at the library level.
5369 @node Pragma No_Inline,Pragma No_Return,Pragma No_Heap_Finalization,Implementation Defined Pragmas
5370 @anchor{gnat_rm/implementation_defined_pragmas id25}@anchor{a5}@anchor{gnat_rm/implementation_defined_pragmas pragma-no-inline}@anchor{a6}
5371 @section Pragma No_Inline
5377 pragma No_Inline (NAME @{, NAME@});
5380 This pragma suppresses inlining for the callable entity or the instances of
5381 the generic subprogram designated by @code{NAME}, including inlining that
5382 results from the use of pragma @code{Inline}. This pragma is always active,
5383 in particular it is not subject to the use of option @emph{-gnatn} or
5384 @emph{-gnatN}. It is illegal to specify both pragma @code{No_Inline} and
5385 pragma @code{Inline_Always} for the same @code{NAME}.
5387 @node Pragma No_Return,Pragma No_Strict_Aliasing,Pragma No_Inline,Implementation Defined Pragmas
5388 @anchor{gnat_rm/implementation_defined_pragmas pragma-no-return}@anchor{a7}
5389 @section Pragma No_Return
5395 pragma No_Return (procedure_LOCAL_NAME @{, procedure_LOCAL_NAME@});
5398 Each @code{procedure_LOCAL_NAME} argument must refer to one or more procedure
5399 declarations in the current declarative part. A procedure to which this
5400 pragma is applied may not contain any explicit @code{return} statements.
5401 In addition, if the procedure contains any implicit returns from falling
5402 off the end of a statement sequence, then execution of that implicit
5403 return will cause Program_Error to be raised.
5405 One use of this pragma is to identify procedures whose only purpose is to raise
5406 an exception. Another use of this pragma is to suppress incorrect warnings
5407 about missing returns in functions, where the last statement of a function
5408 statement sequence is a call to such a procedure.
5410 Note that in Ada 2005 mode, this pragma is part of the language. It is
5411 available in all earlier versions of Ada as an implementation-defined
5414 @node Pragma No_Strict_Aliasing,Pragma No_Tagged_Streams,Pragma No_Return,Implementation Defined Pragmas
5415 @anchor{gnat_rm/implementation_defined_pragmas pragma-no-strict-aliasing}@anchor{a8}
5416 @section Pragma No_Strict_Aliasing
5422 pragma No_Strict_Aliasing [([Entity =>] type_LOCAL_NAME)];
5425 @code{type_LOCAL_NAME} must refer to an access type
5426 declaration in the current declarative part. The effect is to inhibit
5427 strict aliasing optimization for the given type. The form with no
5428 arguments is a configuration pragma which applies to all access types
5429 declared in units to which the pragma applies. For a detailed
5430 description of the strict aliasing optimization, and the situations
5431 in which it must be suppressed, see the section on Optimization and Strict Aliasing
5432 in the @cite{GNAT User's Guide}.
5434 This pragma currently has no effects on access to unconstrained array types.
5436 @node Pragma No_Tagged_Streams,Pragma Normalize_Scalars,Pragma No_Strict_Aliasing,Implementation Defined Pragmas
5437 @anchor{gnat_rm/implementation_defined_pragmas pragma-no-tagged-streams}@anchor{a9}@anchor{gnat_rm/implementation_defined_pragmas id26}@anchor{aa}
5438 @section Pragma No_Tagged_Streams
5444 pragma No_Tagged_Streams [([Entity =>] tagged_type_LOCAL_NAME)];
5447 Normally when a tagged type is introduced using a full type declaration,
5448 part of the processing includes generating stream access routines to be
5449 used by stream attributes referencing the type (or one of its subtypes
5450 or derived types). This can involve the generation of significant amounts
5451 of code which is wasted space if stream routines are not needed for the
5454 The @code{No_Tagged_Streams} pragma causes the generation of these stream
5455 routines to be skipped, and any attempt to use stream operations on
5456 types subject to this pragma will be statically rejected as illegal.
5458 There are two forms of the pragma. The form with no arguments must appear
5459 in a declarative sequence or in the declarations of a package spec. This
5460 pragma affects all subsequent root tagged types declared in the declaration
5461 sequence, and specifies that no stream routines be generated. The form with
5462 an argument (for which there is also a corresponding aspect) specifies a
5463 single root tagged type for which stream routines are not to be generated.
5465 Once the pragma has been given for a particular root tagged type, all subtypes
5466 and derived types of this type inherit the pragma automatically, so the effect
5467 applies to a complete hierarchy (this is necessary to deal with the class-wide
5468 dispatching versions of the stream routines).
5470 When pragmas @code{Discard_Names} and @code{No_Tagged_Streams} are simultaneously
5471 applied to a tagged type its Expanded_Name and External_Tag are initialized
5472 with empty strings. This is useful to avoid exposing entity names at binary
5473 level but has a negative impact on the debuggability of tagged types.
5475 @node Pragma Normalize_Scalars,Pragma Obsolescent,Pragma No_Tagged_Streams,Implementation Defined Pragmas
5476 @anchor{gnat_rm/implementation_defined_pragmas pragma-normalize-scalars}@anchor{ab}
5477 @section Pragma Normalize_Scalars
5483 pragma Normalize_Scalars;
5486 This is a language defined pragma which is fully implemented in GNAT. The
5487 effect is to cause all scalar objects that are not otherwise initialized
5488 to be initialized. The initial values are implementation dependent and
5494 @item @emph{Standard.Character}
5496 Objects whose root type is Standard.Character are initialized to
5497 Character'Last unless the subtype range excludes NUL (in which case
5498 NUL is used). This choice will always generate an invalid value if
5501 @item @emph{Standard.Wide_Character}
5503 Objects whose root type is Standard.Wide_Character are initialized to
5504 Wide_Character'Last unless the subtype range excludes NUL (in which case
5505 NUL is used). This choice will always generate an invalid value if
5508 @item @emph{Standard.Wide_Wide_Character}
5510 Objects whose root type is Standard.Wide_Wide_Character are initialized to
5511 the invalid value 16#FFFF_FFFF# unless the subtype range excludes NUL (in
5512 which case NUL is used). This choice will always generate an invalid value if
5515 @item @emph{Integer types}
5517 Objects of an integer type are treated differently depending on whether
5518 negative values are present in the subtype. If no negative values are
5519 present, then all one bits is used as the initial value except in the
5520 special case where zero is excluded from the subtype, in which case
5521 all zero bits are used. This choice will always generate an invalid
5522 value if one exists.
5524 For subtypes with negative values present, the largest negative number
5525 is used, except in the unusual case where this largest negative number
5526 is in the subtype, and the largest positive number is not, in which case
5527 the largest positive value is used. This choice will always generate
5528 an invalid value if one exists.
5530 @item @emph{Floating-Point Types}
5532 Objects of all floating-point types are initialized to all 1-bits. For
5533 standard IEEE format, this corresponds to a NaN (not a number) which is
5534 indeed an invalid value.
5536 @item @emph{Fixed-Point Types}
5538 Objects of all fixed-point types are treated as described above for integers,
5539 with the rules applying to the underlying integer value used to represent
5540 the fixed-point value.
5542 @item @emph{Modular types}
5544 Objects of a modular type are initialized to all one bits, except in
5545 the special case where zero is excluded from the subtype, in which
5546 case all zero bits are used. This choice will always generate an
5547 invalid value if one exists.
5549 @item @emph{Enumeration types}
5551 Objects of an enumeration type are initialized to all one-bits, i.e., to
5552 the value @code{2 ** typ'Size - 1} unless the subtype excludes the literal
5553 whose Pos value is zero, in which case a code of zero is used. This choice
5554 will always generate an invalid value if one exists.
5557 @node Pragma Obsolescent,Pragma Optimize_Alignment,Pragma Normalize_Scalars,Implementation Defined Pragmas
5558 @anchor{gnat_rm/implementation_defined_pragmas pragma-obsolescent}@anchor{ac}@anchor{gnat_rm/implementation_defined_pragmas id27}@anchor{ad}
5559 @section Pragma Obsolescent
5567 pragma Obsolescent (
5568 [Message =>] static_string_EXPRESSION
5569 [,[Version =>] Ada_05]]);
5571 pragma Obsolescent (
5573 [,[Message =>] static_string_EXPRESSION
5574 [,[Version =>] Ada_05]] );
5577 This pragma can occur immediately following a declaration of an entity,
5578 including the case of a record component. If no Entity argument is present,
5579 then this declaration is the one to which the pragma applies. If an Entity
5580 parameter is present, it must either match the name of the entity in this
5581 declaration, or alternatively, the pragma can immediately follow an enumeration
5582 type declaration, where the Entity argument names one of the enumeration
5585 This pragma is used to indicate that the named entity
5586 is considered obsolescent and should not be used. Typically this is
5587 used when an API must be modified by eventually removing or modifying
5588 existing subprograms or other entities. The pragma can be used at an
5589 intermediate stage when the entity is still present, but will be
5592 The effect of this pragma is to output a warning message on a reference to
5593 an entity thus marked that the subprogram is obsolescent if the appropriate
5594 warning option in the compiler is activated. If the @code{Message} parameter is
5595 present, then a second warning message is given containing this text. In
5596 addition, a reference to the entity is considered to be a violation of pragma
5597 @code{Restrictions (No_Obsolescent_Features)}.
5599 This pragma can also be used as a program unit pragma for a package,
5600 in which case the entity name is the name of the package, and the
5601 pragma indicates that the entire package is considered
5602 obsolescent. In this case a client @code{with}ing such a package
5603 violates the restriction, and the @code{with} clause is
5604 flagged with warnings if the warning option is set.
5606 If the @code{Version} parameter is present (which must be exactly
5607 the identifier @code{Ada_05}, no other argument is allowed), then the
5608 indication of obsolescence applies only when compiling in Ada 2005
5609 mode. This is primarily intended for dealing with the situations
5610 in the predefined library where subprograms or packages
5611 have become defined as obsolescent in Ada 2005
5612 (e.g., in @code{Ada.Characters.Handling}), but may be used anywhere.
5614 The following examples show typical uses of this pragma:
5618 pragma Obsolescent (p, Message => "use pp instead of p");
5623 pragma Obsolescent ("use q2new instead");
5625 type R is new integer;
5628 Message => "use RR in Ada 2005",
5638 type E is (a, bc, 'd', quack);
5639 pragma Obsolescent (Entity => bc)
5640 pragma Obsolescent (Entity => 'd')
5643 (a, b : character) return character;
5644 pragma Obsolescent (Entity => "+");
5648 Note that, as for all pragmas, if you use a pragma argument identifier,
5649 then all subsequent parameters must also use a pragma argument identifier.
5650 So if you specify @code{Entity =>} for the @code{Entity} argument, and a @code{Message}
5651 argument is present, it must be preceded by @code{Message =>}.
5653 @node Pragma Optimize_Alignment,Pragma Ordered,Pragma Obsolescent,Implementation Defined Pragmas
5654 @anchor{gnat_rm/implementation_defined_pragmas pragma-optimize-alignment}@anchor{ae}
5655 @section Pragma Optimize_Alignment
5659 @geindex default settings
5664 pragma Optimize_Alignment (TIME | SPACE | OFF);
5667 This is a configuration pragma which affects the choice of default alignments
5668 for types and objects where no alignment is explicitly specified. There is a
5669 time/space trade-off in the selection of these values. Large alignments result
5670 in more efficient code, at the expense of larger data space, since sizes have
5671 to be increased to match these alignments. Smaller alignments save space, but
5672 the access code is slower. The normal choice of default alignments for types
5673 and individual alignment promotions for objects (which is what you get if you
5674 do not use this pragma, or if you use an argument of OFF), tries to balance
5675 these two requirements.
5677 Specifying SPACE causes smaller default alignments to be chosen in two cases.
5678 First any packed record is given an alignment of 1. Second, if a size is given
5679 for the type, then the alignment is chosen to avoid increasing this size. For
5691 In the default mode, this type gets an alignment of 4, so that access to the
5692 Integer field X are efficient. But this means that objects of the type end up
5693 with a size of 8 bytes. This is a valid choice, since sizes of objects are
5694 allowed to be bigger than the size of the type, but it can waste space if for
5695 example fields of type R appear in an enclosing record. If the above type is
5696 compiled in @code{Optimize_Alignment (Space)} mode, the alignment is set to 1.
5698 However, there is one case in which SPACE is ignored. If a variable length
5699 record (that is a discriminated record with a component which is an array
5700 whose length depends on a discriminant), has a pragma Pack, then it is not
5701 in general possible to set the alignment of such a record to one, so the
5702 pragma is ignored in this case (with a warning).
5704 Specifying SPACE also disables alignment promotions for standalone objects,
5705 which occur when the compiler increases the alignment of a specific object
5706 without changing the alignment of its type.
5708 Specifying SPACE also disables component reordering in unpacked record types,
5709 which can result in larger sizes in order to meet alignment requirements.
5711 Specifying TIME causes larger default alignments to be chosen in the case of
5712 small types with sizes that are not a power of 2. For example, consider:
5725 The default alignment for this record is normally 1, but if this type is
5726 compiled in @code{Optimize_Alignment (Time)} mode, then the alignment is set
5727 to 4, which wastes space for objects of the type, since they are now 4 bytes
5728 long, but results in more efficient access when the whole record is referenced.
5730 As noted above, this is a configuration pragma, and there is a requirement
5731 that all units in a partition be compiled with a consistent setting of the
5732 optimization setting. This would normally be achieved by use of a configuration
5733 pragma file containing the appropriate setting. The exception to this rule is
5734 that units with an explicit configuration pragma in the same file as the source
5735 unit are excluded from the consistency check, as are all predefined units. The
5736 latter are compiled by default in pragma Optimize_Alignment (Off) mode if no
5737 pragma appears at the start of the file.
5739 @node Pragma Ordered,Pragma Overflow_Mode,Pragma Optimize_Alignment,Implementation Defined Pragmas
5740 @anchor{gnat_rm/implementation_defined_pragmas pragma-ordered}@anchor{af}
5741 @section Pragma Ordered
5747 pragma Ordered (enumeration_first_subtype_LOCAL_NAME);
5750 Most enumeration types are from a conceptual point of view unordered.
5751 For example, consider:
5754 type Color is (Red, Blue, Green, Yellow);
5757 By Ada semantics @code{Blue > Red} and @code{Green > Blue},
5758 but really these relations make no sense; the enumeration type merely
5759 specifies a set of possible colors, and the order is unimportant.
5761 For unordered enumeration types, it is generally a good idea if
5762 clients avoid comparisons (other than equality or inequality) and
5763 explicit ranges. (A @emph{client} is a unit where the type is referenced,
5764 other than the unit where the type is declared, its body, and its subunits.)
5765 For example, if code buried in some client says:
5768 if Current_Color < Yellow then ...
5769 if Current_Color in Blue .. Green then ...
5772 then the client code is relying on the order, which is undesirable.
5773 It makes the code hard to read and creates maintenance difficulties if
5774 entries have to be added to the enumeration type. Instead,
5775 the code in the client should list the possibilities, or an
5776 appropriate subtype should be declared in the unit that declares
5777 the original enumeration type. E.g., the following subtype could
5778 be declared along with the type @code{Color}:
5781 subtype RBG is Color range Red .. Green;
5784 and then the client could write:
5787 if Current_Color in RBG then ...
5788 if Current_Color = Blue or Current_Color = Green then ...
5791 However, some enumeration types are legitimately ordered from a conceptual
5792 point of view. For example, if you declare:
5795 type Day is (Mon, Tue, Wed, Thu, Fri, Sat, Sun);
5798 then the ordering imposed by the language is reasonable, and
5799 clients can depend on it, writing for example:
5802 if D in Mon .. Fri then ...
5806 The pragma @emph{Ordered} is provided to mark enumeration types that
5807 are conceptually ordered, alerting the reader that clients may depend
5808 on the ordering. GNAT provides a pragma to mark enumerations as ordered
5809 rather than one to mark them as unordered, since in our experience,
5810 the great majority of enumeration types are conceptually unordered.
5812 The types @code{Boolean}, @code{Character}, @code{Wide_Character},
5813 and @code{Wide_Wide_Character}
5814 are considered to be ordered types, so each is declared with a
5815 pragma @code{Ordered} in package @code{Standard}.
5817 Normally pragma @code{Ordered} serves only as documentation and a guide for
5818 coding standards, but GNAT provides a warning switch @emph{-gnatw.u} that
5819 requests warnings for inappropriate uses (comparisons and explicit
5820 subranges) for unordered types. If this switch is used, then any
5821 enumeration type not marked with pragma @code{Ordered} will be considered
5822 as unordered, and will generate warnings for inappropriate uses.
5824 Note that generic types are not considered ordered or unordered (since the
5825 template can be instantiated for both cases), so we never generate warnings
5826 for the case of generic enumerated types.
5828 For additional information please refer to the description of the
5829 @emph{-gnatw.u} switch in the GNAT User's Guide.
5831 @node Pragma Overflow_Mode,Pragma Overriding_Renamings,Pragma Ordered,Implementation Defined Pragmas
5832 @anchor{gnat_rm/implementation_defined_pragmas pragma-overflow-mode}@anchor{b0}
5833 @section Pragma Overflow_Mode
5839 pragma Overflow_Mode
5841 [,[Assertions =>] MODE]);
5843 MODE ::= STRICT | MINIMIZED | ELIMINATED
5846 This pragma sets the current overflow mode to the given setting. For details
5847 of the meaning of these modes, please refer to the
5848 'Overflow Check Handling in GNAT' appendix in the
5849 GNAT User's Guide. If only the @code{General} parameter is present,
5850 the given mode applies to all expressions. If both parameters are present,
5851 the @code{General} mode applies to expressions outside assertions, and
5852 the @code{Eliminated} mode applies to expressions within assertions.
5854 The case of the @code{MODE} parameter is ignored,
5855 so @code{MINIMIZED}, @code{Minimized} and
5856 @code{minimized} all have the same effect.
5858 The @code{Overflow_Mode} pragma has the same scoping and placement
5859 rules as pragma @code{Suppress}, so it can occur either as a
5860 configuration pragma, specifying a default for the whole
5861 program, or in a declarative scope, where it applies to the
5862 remaining declarations and statements in that scope.
5864 The pragma @code{Suppress (Overflow_Check)} suppresses
5865 overflow checking, but does not affect the overflow mode.
5867 The pragma @code{Unsuppress (Overflow_Check)} unsuppresses (enables)
5868 overflow checking, but does not affect the overflow mode.
5870 @node Pragma Overriding_Renamings,Pragma Partition_Elaboration_Policy,Pragma Overflow_Mode,Implementation Defined Pragmas
5871 @anchor{gnat_rm/implementation_defined_pragmas pragma-overriding-renamings}@anchor{b1}
5872 @section Pragma Overriding_Renamings
5875 @geindex Rational profile
5877 @geindex Rational compatibility
5882 pragma Overriding_Renamings;
5885 This is a GNAT configuration pragma to simplify porting
5886 legacy code accepted by the Rational
5887 Ada compiler. In the presence of this pragma, a renaming declaration that
5888 renames an inherited operation declared in the same scope is legal if selected
5889 notation is used as in:
5892 pragma Overriding_Renamings;
5897 function F (..) renames R.F;
5902 RM 8.3 (15) stipulates that an overridden operation is not visible within the
5903 declaration of the overriding operation.
5905 @node Pragma Partition_Elaboration_Policy,Pragma Part_Of,Pragma Overriding_Renamings,Implementation Defined Pragmas
5906 @anchor{gnat_rm/implementation_defined_pragmas pragma-partition-elaboration-policy}@anchor{b2}
5907 @section Pragma Partition_Elaboration_Policy
5913 pragma Partition_Elaboration_Policy (POLICY_IDENTIFIER);
5915 POLICY_IDENTIFIER ::= Concurrent | Sequential
5918 This pragma is standard in Ada 2005, but is available in all earlier
5919 versions of Ada as an implementation-defined pragma.
5920 See Ada 2012 Reference Manual for details.
5922 @node Pragma Part_Of,Pragma Passive,Pragma Partition_Elaboration_Policy,Implementation Defined Pragmas
5923 @anchor{gnat_rm/implementation_defined_pragmas id28}@anchor{b3}@anchor{gnat_rm/implementation_defined_pragmas pragma-part-of}@anchor{b4}
5924 @section Pragma Part_Of
5930 pragma Part_Of (ABSTRACT_STATE);
5932 ABSTRACT_STATE ::= NAME
5935 For the semantics of this pragma, see the entry for aspect @code{Part_Of} in the
5936 SPARK 2014 Reference Manual, section 7.2.6.
5938 @node Pragma Passive,Pragma Persistent_BSS,Pragma Part_Of,Implementation Defined Pragmas
5939 @anchor{gnat_rm/implementation_defined_pragmas pragma-passive}@anchor{b5}
5940 @section Pragma Passive
5946 pragma Passive [(Semaphore | No)];
5949 Syntax checked, but otherwise ignored by GNAT. This is recognized for
5950 compatibility with DEC Ada 83 implementations, where it is used within a
5951 task definition to request that a task be made passive. If the argument
5952 @code{Semaphore} is present, or the argument is omitted, then DEC Ada 83
5953 treats the pragma as an assertion that the containing task is passive
5954 and that optimization of context switch with this task is permitted and
5955 desired. If the argument @code{No} is present, the task must not be
5956 optimized. GNAT does not attempt to optimize any tasks in this manner
5957 (since protected objects are available in place of passive tasks).
5959 For more information on the subject of passive tasks, see the section
5960 'Passive Task Optimization' in the GNAT Users Guide.
5962 @node Pragma Persistent_BSS,Pragma Post,Pragma Passive,Implementation Defined Pragmas
5963 @anchor{gnat_rm/implementation_defined_pragmas id29}@anchor{b6}@anchor{gnat_rm/implementation_defined_pragmas pragma-persistent-bss}@anchor{b7}
5964 @section Pragma Persistent_BSS
5970 pragma Persistent_BSS [(LOCAL_NAME)]
5973 This pragma allows selected objects to be placed in the @code{.persistent_bss}
5974 section. On some targets the linker and loader provide for special
5975 treatment of this section, allowing a program to be reloaded without
5976 affecting the contents of this data (hence the name persistent).
5978 There are two forms of usage. If an argument is given, it must be the
5979 local name of a library-level object, with no explicit initialization
5980 and whose type is potentially persistent. If no argument is given, then
5981 the pragma is a configuration pragma, and applies to all library-level
5982 objects with no explicit initialization of potentially persistent types.
5984 A potentially persistent type is a scalar type, or an untagged,
5985 non-discriminated record, all of whose components have no explicit
5986 initialization and are themselves of a potentially persistent type,
5987 or an array, all of whose constraints are static, and whose component
5988 type is potentially persistent.
5990 If this pragma is used on a target where this feature is not supported,
5991 then the pragma will be ignored. See also @code{pragma Linker_Section}.
5993 @node Pragma Post,Pragma Postcondition,Pragma Persistent_BSS,Implementation Defined Pragmas
5994 @anchor{gnat_rm/implementation_defined_pragmas pragma-post}@anchor{b8}
5995 @section Pragma Post
6001 @geindex postconditions
6006 pragma Post (Boolean_Expression);
6009 The @code{Post} pragma is intended to be an exact replacement for
6010 the language-defined
6011 @code{Post} aspect, and shares its restrictions and semantics.
6012 It must appear either immediately following the corresponding
6013 subprogram declaration (only other pragmas may intervene), or
6014 if there is no separate subprogram declaration, then it can
6015 appear at the start of the declarations in a subprogram body
6016 (preceded only by other pragmas).
6018 @node Pragma Postcondition,Pragma Post_Class,Pragma Post,Implementation Defined Pragmas
6019 @anchor{gnat_rm/implementation_defined_pragmas pragma-postcondition}@anchor{b9}
6020 @section Pragma Postcondition
6023 @geindex Postcondition
6026 @geindex postconditions
6031 pragma Postcondition (
6032 [Check =>] Boolean_Expression
6033 [,[Message =>] String_Expression]);
6036 The @code{Postcondition} pragma allows specification of automatic
6037 postcondition checks for subprograms. These checks are similar to
6038 assertions, but are automatically inserted just prior to the return
6039 statements of the subprogram with which they are associated (including
6040 implicit returns at the end of procedure bodies and associated
6041 exception handlers).
6043 In addition, the boolean expression which is the condition which
6044 must be true may contain references to function'Result in the case
6045 of a function to refer to the returned value.
6047 @code{Postcondition} pragmas may appear either immediately following the
6048 (separate) declaration of a subprogram, or at the start of the
6049 declarations of a subprogram body. Only other pragmas may intervene
6050 (that is appear between the subprogram declaration and its
6051 postconditions, or appear before the postcondition in the
6052 declaration sequence in a subprogram body). In the case of a
6053 postcondition appearing after a subprogram declaration, the
6054 formal arguments of the subprogram are visible, and can be
6055 referenced in the postcondition expressions.
6057 The postconditions are collected and automatically tested just
6058 before any return (implicit or explicit) in the subprogram body.
6059 A postcondition is only recognized if postconditions are active
6060 at the time the pragma is encountered. The compiler switch @emph{gnata}
6061 turns on all postconditions by default, and pragma @code{Check_Policy}
6062 with an identifier of @code{Postcondition} can also be used to
6063 control whether postconditions are active.
6065 The general approach is that postconditions are placed in the spec
6066 if they represent functional aspects which make sense to the client.
6067 For example we might have:
6070 function Direction return Integer;
6071 pragma Postcondition
6072 (Direction'Result = +1
6074 Direction'Result = -1);
6077 which serves to document that the result must be +1 or -1, and
6078 will test that this is the case at run time if postcondition
6081 Postconditions within the subprogram body can be used to
6082 check that some internal aspect of the implementation,
6083 not visible to the client, is operating as expected.
6084 For instance if a square root routine keeps an internal
6085 counter of the number of times it is called, then we
6086 might have the following postcondition:
6089 Sqrt_Calls : Natural := 0;
6091 function Sqrt (Arg : Float) return Float is
6092 pragma Postcondition
6093 (Sqrt_Calls = Sqrt_Calls'Old + 1);
6098 As this example, shows, the use of the @code{Old} attribute
6099 is often useful in postconditions to refer to the state on
6100 entry to the subprogram.
6102 Note that postconditions are only checked on normal returns
6103 from the subprogram. If an abnormal return results from
6104 raising an exception, then the postconditions are not checked.
6106 If a postcondition fails, then the exception
6107 @code{System.Assertions.Assert_Failure} is raised. If
6108 a message argument was supplied, then the given string
6109 will be used as the exception message. If no message
6110 argument was supplied, then the default message has
6111 the form "Postcondition failed at file_name:line". The
6112 exception is raised in the context of the subprogram
6113 body, so it is possible to catch postcondition failures
6114 within the subprogram body itself.
6116 Within a package spec, normal visibility rules
6117 in Ada would prevent forward references within a
6118 postcondition pragma to functions defined later in
6119 the same package. This would introduce undesirable
6120 ordering constraints. To avoid this problem, all
6121 postcondition pragmas are analyzed at the end of
6122 the package spec, allowing forward references.
6124 The following example shows that this even allows
6125 mutually recursive postconditions as in:
6128 package Parity_Functions is
6129 function Odd (X : Natural) return Boolean;
6130 pragma Postcondition
6134 (x /= 0 and then Even (X - 1))));
6136 function Even (X : Natural) return Boolean;
6137 pragma Postcondition
6141 (x /= 1 and then Odd (X - 1))));
6143 end Parity_Functions;
6146 There are no restrictions on the complexity or form of
6147 conditions used within @code{Postcondition} pragmas.
6148 The following example shows that it is even possible
6149 to verify performance behavior.
6154 Performance : constant Float;
6155 -- Performance constant set by implementation
6156 -- to match target architecture behavior.
6158 procedure Treesort (Arg : String);
6159 -- Sorts characters of argument using N*logN sort
6160 pragma Postcondition
6161 (Float (Clock - Clock'Old) <=
6162 Float (Arg'Length) *
6163 log (Float (Arg'Length)) *
6168 Note: postcondition pragmas associated with subprograms that are
6169 marked as Inline_Always, or those marked as Inline with front-end
6170 inlining (-gnatN option set) are accepted and legality-checked
6171 by the compiler, but are ignored at run-time even if postcondition
6172 checking is enabled.
6174 Note that pragma @code{Postcondition} differs from the language-defined
6175 @code{Post} aspect (and corresponding @code{Post} pragma) in allowing
6176 multiple occurrences, allowing occurences in the body even if there
6177 is a separate spec, and allowing a second string parameter, and the
6178 use of the pragma identifier @code{Check}. Historically, pragma
6179 @code{Postcondition} was implemented prior to the development of
6180 Ada 2012, and has been retained in its original form for
6181 compatibility purposes.
6183 @node Pragma Post_Class,Pragma Rename_Pragma,Pragma Postcondition,Implementation Defined Pragmas
6184 @anchor{gnat_rm/implementation_defined_pragmas pragma-post-class}@anchor{ba}
6185 @section Pragma Post_Class
6191 @geindex postconditions
6196 pragma Post_Class (Boolean_Expression);
6199 The @code{Post_Class} pragma is intended to be an exact replacement for
6200 the language-defined
6201 @code{Post'Class} aspect, and shares its restrictions and semantics.
6202 It must appear either immediately following the corresponding
6203 subprogram declaration (only other pragmas may intervene), or
6204 if there is no separate subprogram declaration, then it can
6205 appear at the start of the declarations in a subprogram body
6206 (preceded only by other pragmas).
6208 Note: This pragma is called @code{Post_Class} rather than
6209 @code{Post'Class} because the latter would not be strictly
6210 conforming to the allowed syntax for pragmas. The motivation
6211 for provinding pragmas equivalent to the aspects is to allow a program
6212 to be written using the pragmas, and then compiled if necessary
6213 using an Ada compiler that does not recognize the pragmas or
6214 aspects, but is prepared to ignore the pragmas. The assertion
6215 policy that controls this pragma is @code{Post'Class}, not
6218 @node Pragma Rename_Pragma,Pragma Pre,Pragma Post_Class,Implementation Defined Pragmas
6219 @anchor{gnat_rm/implementation_defined_pragmas pragma-rename-pragma}@anchor{bb}
6220 @section Pragma Rename_Pragma
6229 pragma Rename_Pragma (
6230 [New_Name =>] IDENTIFIER,
6231 [Renamed =>] pragma_IDENTIFIER);
6234 This pragma provides a mechanism for supplying new names for existing
6235 pragmas. The @code{New_Name} identifier can subsequently be used as a synonym for
6236 the Renamed pragma. For example, suppose you have code that was originally
6237 developed on a compiler that supports Inline_Only as an implementation defined
6238 pragma. And suppose the semantics of pragma Inline_Only are identical to (or at
6239 least very similar to) the GNAT implementation defined pragma
6240 Inline_Always. You could globally replace Inline_Only with Inline_Always.
6242 However, to avoid that source modification, you could instead add a
6243 configuration pragma:
6246 pragma Rename_Pragma (
6247 New_Name => Inline_Only,
6248 Renamed => Inline_Always);
6251 Then GNAT will treat "pragma Inline_Only ..." as if you had written
6252 "pragma Inline_Always ...".
6254 Pragma Inline_Only will not necessarily mean the same thing as the other Ada
6255 compiler; it's up to you to make sure the semantics are close enough.
6257 @node Pragma Pre,Pragma Precondition,Pragma Rename_Pragma,Implementation Defined Pragmas
6258 @anchor{gnat_rm/implementation_defined_pragmas pragma-pre}@anchor{bc}
6265 @geindex preconditions
6270 pragma Pre (Boolean_Expression);
6273 The @code{Pre} pragma is intended to be an exact replacement for
6274 the language-defined
6275 @code{Pre} aspect, and shares its restrictions and semantics.
6276 It must appear either immediately following the corresponding
6277 subprogram declaration (only other pragmas may intervene), or
6278 if there is no separate subprogram declaration, then it can
6279 appear at the start of the declarations in a subprogram body
6280 (preceded only by other pragmas).
6282 @node Pragma Precondition,Pragma Predicate,Pragma Pre,Implementation Defined Pragmas
6283 @anchor{gnat_rm/implementation_defined_pragmas pragma-precondition}@anchor{bd}
6284 @section Pragma Precondition
6287 @geindex Preconditions
6290 @geindex preconditions
6295 pragma Precondition (
6296 [Check =>] Boolean_Expression
6297 [,[Message =>] String_Expression]);
6300 The @code{Precondition} pragma is similar to @code{Postcondition}
6301 except that the corresponding checks take place immediately upon
6302 entry to the subprogram, and if a precondition fails, the exception
6303 is raised in the context of the caller, and the attribute 'Result
6304 cannot be used within the precondition expression.
6306 Otherwise, the placement and visibility rules are identical to those
6307 described for postconditions. The following is an example of use
6308 within a package spec:
6311 package Math_Functions is
6313 function Sqrt (Arg : Float) return Float;
6314 pragma Precondition (Arg >= 0.0)
6319 @code{Precondition} pragmas may appear either immediately following the
6320 (separate) declaration of a subprogram, or at the start of the
6321 declarations of a subprogram body. Only other pragmas may intervene
6322 (that is appear between the subprogram declaration and its
6323 postconditions, or appear before the postcondition in the
6324 declaration sequence in a subprogram body).
6326 Note: precondition pragmas associated with subprograms that are
6327 marked as Inline_Always, or those marked as Inline with front-end
6328 inlining (-gnatN option set) are accepted and legality-checked
6329 by the compiler, but are ignored at run-time even if precondition
6330 checking is enabled.
6332 Note that pragma @code{Precondition} differs from the language-defined
6333 @code{Pre} aspect (and corresponding @code{Pre} pragma) in allowing
6334 multiple occurrences, allowing occurences in the body even if there
6335 is a separate spec, and allowing a second string parameter, and the
6336 use of the pragma identifier @code{Check}. Historically, pragma
6337 @code{Precondition} was implemented prior to the development of
6338 Ada 2012, and has been retained in its original form for
6339 compatibility purposes.
6341 @node Pragma Predicate,Pragma Predicate_Failure,Pragma Precondition,Implementation Defined Pragmas
6342 @anchor{gnat_rm/implementation_defined_pragmas pragma-predicate}@anchor{be}@anchor{gnat_rm/implementation_defined_pragmas id30}@anchor{bf}
6343 @section Pragma Predicate
6350 ([Entity =>] type_LOCAL_NAME,
6351 [Check =>] EXPRESSION);
6354 This pragma (available in all versions of Ada in GNAT) encompasses both
6355 the @code{Static_Predicate} and @code{Dynamic_Predicate} aspects in
6356 Ada 2012. A predicate is regarded as static if it has an allowed form
6357 for @code{Static_Predicate} and is otherwise treated as a
6358 @code{Dynamic_Predicate}. Otherwise, predicates specified by this
6359 pragma behave exactly as described in the Ada 2012 reference manual.
6360 For example, if we have
6363 type R is range 1 .. 10;
6365 pragma Predicate (Entity => S, Check => S not in 4 .. 6);
6367 pragma Predicate (Entity => Q, Check => F(Q) or G(Q));
6370 the effect is identical to the following Ada 2012 code:
6373 type R is range 1 .. 10;
6375 Static_Predicate => S not in 4 .. 6;
6377 Dynamic_Predicate => F(Q) or G(Q);
6380 Note that there are no pragmas @code{Dynamic_Predicate}
6381 or @code{Static_Predicate}. That is
6382 because these pragmas would affect legality and semantics of
6383 the program and thus do not have a neutral effect if ignored.
6384 The motivation behind providing pragmas equivalent to
6385 corresponding aspects is to allow a program to be written
6386 using the pragmas, and then compiled with a compiler that
6387 will ignore the pragmas. That doesn't work in the case of
6388 static and dynamic predicates, since if the corresponding
6389 pragmas are ignored, then the behavior of the program is
6390 fundamentally changed (for example a membership test
6391 @code{A in B} would not take into account a predicate
6392 defined for subtype B). When following this approach, the
6393 use of predicates should be avoided.
6395 @node Pragma Predicate_Failure,Pragma Preelaborable_Initialization,Pragma Predicate,Implementation Defined Pragmas
6396 @anchor{gnat_rm/implementation_defined_pragmas pragma-predicate-failure}@anchor{c0}
6397 @section Pragma Predicate_Failure
6403 pragma Predicate_Failure
6404 ([Entity =>] type_LOCAL_NAME,
6405 [Message =>] String_Expression);
6408 The @code{Predicate_Failure} pragma is intended to be an exact replacement for
6409 the language-defined
6410 @code{Predicate_Failure} aspect, and shares its restrictions and semantics.
6412 @node Pragma Preelaborable_Initialization,Pragma Prefix_Exception_Messages,Pragma Predicate_Failure,Implementation Defined Pragmas
6413 @anchor{gnat_rm/implementation_defined_pragmas pragma-preelaborable-initialization}@anchor{c1}
6414 @section Pragma Preelaborable_Initialization
6420 pragma Preelaborable_Initialization (DIRECT_NAME);
6423 This pragma is standard in Ada 2005, but is available in all earlier
6424 versions of Ada as an implementation-defined pragma.
6425 See Ada 2012 Reference Manual for details.
6427 @node Pragma Prefix_Exception_Messages,Pragma Pre_Class,Pragma Preelaborable_Initialization,Implementation Defined Pragmas
6428 @anchor{gnat_rm/implementation_defined_pragmas pragma-prefix-exception-messages}@anchor{c2}
6429 @section Pragma Prefix_Exception_Messages
6432 @geindex Prefix_Exception_Messages
6436 @geindex Exception_Message
6441 pragma Prefix_Exception_Messages;
6444 This is an implementation-defined configuration pragma that affects the
6445 behavior of raise statements with a message given as a static string
6446 constant (typically a string literal). In such cases, the string will
6447 be automatically prefixed by the name of the enclosing entity (giving
6448 the package and subprogram containing the raise statement). This helps
6449 to identify where messages are coming from, and this mode is automatic
6450 for the run-time library.
6452 The pragma has no effect if the message is computed with an expression other
6453 than a static string constant, since the assumption in this case is that
6454 the program computes exactly the string it wants. If you still want the
6455 prefixing in this case, you can always call
6456 @code{GNAT.Source_Info.Enclosing_Entity} and prepend the string manually.
6458 @node Pragma Pre_Class,Pragma Priority_Specific_Dispatching,Pragma Prefix_Exception_Messages,Implementation Defined Pragmas
6459 @anchor{gnat_rm/implementation_defined_pragmas pragma-pre-class}@anchor{c3}
6460 @section Pragma Pre_Class
6466 @geindex preconditions
6471 pragma Pre_Class (Boolean_Expression);
6474 The @code{Pre_Class} pragma is intended to be an exact replacement for
6475 the language-defined
6476 @code{Pre'Class} aspect, and shares its restrictions and semantics.
6477 It must appear either immediately following the corresponding
6478 subprogram declaration (only other pragmas may intervene), or
6479 if there is no separate subprogram declaration, then it can
6480 appear at the start of the declarations in a subprogram body
6481 (preceded only by other pragmas).
6483 Note: This pragma is called @code{Pre_Class} rather than
6484 @code{Pre'Class} because the latter would not be strictly
6485 conforming to the allowed syntax for pragmas. The motivation
6486 for providing pragmas equivalent to the aspects is to allow a program
6487 to be written using the pragmas, and then compiled if necessary
6488 using an Ada compiler that does not recognize the pragmas or
6489 aspects, but is prepared to ignore the pragmas. The assertion
6490 policy that controls this pragma is @code{Pre'Class}, not
6493 @node Pragma Priority_Specific_Dispatching,Pragma Profile,Pragma Pre_Class,Implementation Defined Pragmas
6494 @anchor{gnat_rm/implementation_defined_pragmas pragma-priority-specific-dispatching}@anchor{c4}
6495 @section Pragma Priority_Specific_Dispatching
6501 pragma Priority_Specific_Dispatching (
6503 first_priority_EXPRESSION,
6504 last_priority_EXPRESSION)
6506 POLICY_IDENTIFIER ::=
6507 EDF_Across_Priorities |
6508 FIFO_Within_Priorities |
6509 Non_Preemptive_Within_Priorities |
6510 Round_Robin_Within_Priorities
6513 This pragma is standard in Ada 2005, but is available in all earlier
6514 versions of Ada as an implementation-defined pragma.
6515 See Ada 2012 Reference Manual for details.
6517 @node Pragma Profile,Pragma Profile_Warnings,Pragma Priority_Specific_Dispatching,Implementation Defined Pragmas
6518 @anchor{gnat_rm/implementation_defined_pragmas pragma-profile}@anchor{c5}
6519 @section Pragma Profile
6525 pragma Profile (Ravenscar | Restricted | Rational |
6526 GNAT_Extended_Ravenscar | GNAT_Ravenscar_EDF );
6529 This pragma is standard in Ada 2005, but is available in all earlier
6530 versions of Ada as an implementation-defined pragma. This is a
6531 configuration pragma that establishes a set of configuration pragmas
6532 that depend on the argument. @code{Ravenscar} is standard in Ada 2005.
6533 The other possibilities (@code{Restricted}, @code{Rational},
6534 @code{GNAT_Extended_Ravenscar}, @code{GNAT_Ravenscar_EDF})
6535 are implementation-defined. The set of configuration pragmas
6536 is defined in the following sections.
6542 Pragma Profile (Ravenscar)
6544 The @code{Ravenscar} profile is standard in Ada 2005,
6545 but is available in all earlier
6546 versions of Ada as an implementation-defined pragma. This profile
6547 establishes the following set of configuration pragmas:
6553 @code{Task_Dispatching_Policy (FIFO_Within_Priorities)}
6555 [RM D.2.2] Tasks are dispatched following a preemptive
6556 priority-ordered scheduling policy.
6559 @code{Locking_Policy (Ceiling_Locking)}
6561 [RM D.3] While tasks and interrupts execute a protected action, they inherit
6562 the ceiling priority of the corresponding protected object.
6565 @code{Detect_Blocking}
6567 This pragma forces the detection of potentially blocking operations within a
6568 protected operation, and to raise Program_Error if that happens.
6571 plus the following set of restrictions:
6577 @code{Max_Entry_Queue_Length => 1}
6579 No task can be queued on a protected entry.
6582 @code{Max_Protected_Entries => 1}
6585 @code{Max_Task_Entries => 0}
6587 No rendezvous statements are allowed.
6590 @code{No_Abort_Statements}
6593 @code{No_Dynamic_Attachment}
6596 @code{No_Dynamic_Priorities}
6599 @code{No_Implicit_Heap_Allocations}
6602 @code{No_Local_Protected_Objects}
6605 @code{No_Local_Timing_Events}
6608 @code{No_Protected_Type_Allocators}
6611 @code{No_Relative_Delay}
6614 @code{No_Requeue_Statements}
6617 @code{No_Select_Statements}
6620 @code{No_Specific_Termination_Handlers}
6623 @code{No_Task_Allocators}
6626 @code{No_Task_Hierarchy}
6629 @code{No_Task_Termination}
6632 @code{Simple_Barriers}
6635 The Ravenscar profile also includes the following restrictions that specify
6636 that there are no semantic dependences on the corresponding predefined
6643 @code{No_Dependence => Ada.Asynchronous_Task_Control}
6646 @code{No_Dependence => Ada.Calendar}
6649 @code{No_Dependence => Ada.Execution_Time.Group_Budget}
6652 @code{No_Dependence => Ada.Execution_Time.Timers}
6655 @code{No_Dependence => Ada.Task_Attributes}
6658 @code{No_Dependence => System.Multiprocessors.Dispatching_Domains}
6661 This set of configuration pragmas and restrictions correspond to the
6662 definition of the 'Ravenscar Profile' for limited tasking, devised and
6663 published by the @cite{International Real-Time Ada Workshop@comma{} 1997}.
6664 A description is also available at
6665 @indicateurl{http://www-users.cs.york.ac.uk/~burns/ravenscar.ps}.
6667 The original definition of the profile was revised at subsequent IRTAW
6668 meetings. It has been included in the ISO
6669 @cite{Guide for the Use of the Ada Programming Language in High Integrity Systems},
6670 and was made part of the Ada 2005 standard.
6671 The formal definition given by
6672 the Ada Rapporteur Group (ARG) can be found in two Ada Issues (AI-249 and
6673 AI-305) available at
6674 @indicateurl{http://www.ada-auth.org/cgi-bin/cvsweb.cgi/ais/ai-00249.txt} and
6675 @indicateurl{http://www.ada-auth.org/cgi-bin/cvsweb.cgi/ais/ai-00305.txt}.
6677 The above set is a superset of the restrictions provided by pragma
6678 @code{Profile (Restricted)}, it includes six additional restrictions
6679 (@code{Simple_Barriers}, @code{No_Select_Statements},
6680 @code{No_Calendar}, @code{No_Implicit_Heap_Allocations},
6681 @code{No_Relative_Delay} and @code{No_Task_Termination}). This means
6682 that pragma @code{Profile (Ravenscar)}, like the pragma
6683 @code{Profile (Restricted)},
6684 automatically causes the use of a simplified,
6685 more efficient version of the tasking run-time library.
6688 Pragma Profile (GNAT_Extended_Ravenscar)
6690 This profile corresponds to a GNAT specific extension of the
6691 Ravenscar profile. The profile may change in the future although
6692 only in a compatible way: some restrictions may be removed or
6693 relaxed. It is defined as a variation of the Ravenscar profile.
6695 The @code{No_Implicit_Heap_Allocations} restriction has been replaced
6696 by @code{No_Implicit_Task_Allocations} and
6697 @code{No_Implicit_Protected_Object_Allocations}.
6699 The @code{Simple_Barriers} restriction has been replaced by
6700 @code{Pure_Barriers}.
6702 The @code{Max_Protected_Entries}, @code{Max_Entry_Queue_Length}, and
6703 @code{No_Relative_Delay} restrictions have been removed.
6706 Pragma Profile (GNAT_Ravenscar_EDF)
6708 This profile corresponds to the Ravenscar profile but using
6709 EDF_Across_Priority as the Task_Scheduling_Policy.
6712 Pragma Profile (Restricted)
6714 This profile corresponds to the GNAT restricted run time. It
6715 establishes the following set of restrictions:
6721 @code{No_Abort_Statements}
6724 @code{No_Entry_Queue}
6727 @code{No_Task_Hierarchy}
6730 @code{No_Task_Allocators}
6733 @code{No_Dynamic_Priorities}
6736 @code{No_Terminate_Alternatives}
6739 @code{No_Dynamic_Attachment}
6742 @code{No_Protected_Type_Allocators}
6745 @code{No_Local_Protected_Objects}
6748 @code{No_Requeue_Statements}
6751 @code{No_Task_Attributes_Package}
6754 @code{Max_Asynchronous_Select_Nesting = 0}
6757 @code{Max_Task_Entries = 0}
6760 @code{Max_Protected_Entries = 1}
6763 @code{Max_Select_Alternatives = 0}
6766 This set of restrictions causes the automatic selection of a simplified
6767 version of the run time that provides improved performance for the
6768 limited set of tasking functionality permitted by this set of restrictions.
6771 Pragma Profile (Rational)
6773 The Rational profile is intended to facilitate porting legacy code that
6774 compiles with the Rational APEX compiler, even when the code includes non-
6775 conforming Ada constructs. The profile enables the following three pragmas:
6781 @code{pragma Implicit_Packing}
6784 @code{pragma Overriding_Renamings}
6787 @code{pragma Use_VADS_Size}
6791 @node Pragma Profile_Warnings,Pragma Propagate_Exceptions,Pragma Profile,Implementation Defined Pragmas
6792 @anchor{gnat_rm/implementation_defined_pragmas pragma-profile-warnings}@anchor{c6}
6793 @section Pragma Profile_Warnings
6799 pragma Profile_Warnings (Ravenscar | Restricted | Rational);
6802 This is an implementation-defined pragma that is similar in
6803 effect to @code{pragma Profile} except that instead of
6804 generating @code{Restrictions} pragmas, it generates
6805 @code{Restriction_Warnings} pragmas. The result is that
6806 violations of the profile generate warning messages instead
6809 @node Pragma Propagate_Exceptions,Pragma Provide_Shift_Operators,Pragma Profile_Warnings,Implementation Defined Pragmas
6810 @anchor{gnat_rm/implementation_defined_pragmas pragma-propagate-exceptions}@anchor{c7}
6811 @section Pragma Propagate_Exceptions
6814 @geindex Interfacing to C++
6819 pragma Propagate_Exceptions;
6822 This pragma is now obsolete and, other than generating a warning if warnings
6823 on obsolescent features are enabled, is ignored.
6824 It is retained for compatibility
6825 purposes. It used to be used in connection with optimization of
6826 a now-obsolete mechanism for implementation of exceptions.
6828 @node Pragma Provide_Shift_Operators,Pragma Psect_Object,Pragma Propagate_Exceptions,Implementation Defined Pragmas
6829 @anchor{gnat_rm/implementation_defined_pragmas pragma-provide-shift-operators}@anchor{c8}
6830 @section Pragma Provide_Shift_Operators
6833 @geindex Shift operators
6838 pragma Provide_Shift_Operators (integer_first_subtype_LOCAL_NAME);
6841 This pragma can be applied to a first subtype local name that specifies
6842 either an unsigned or signed type. It has the effect of providing the
6843 five shift operators (Shift_Left, Shift_Right, Shift_Right_Arithmetic,
6844 Rotate_Left and Rotate_Right) for the given type. It is similar to
6845 including the function declarations for these five operators, together
6846 with the pragma Import (Intrinsic, ...) statements.
6848 @node Pragma Psect_Object,Pragma Pure_Function,Pragma Provide_Shift_Operators,Implementation Defined Pragmas
6849 @anchor{gnat_rm/implementation_defined_pragmas pragma-psect-object}@anchor{c9}
6850 @section Pragma Psect_Object
6856 pragma Psect_Object (
6857 [Internal =>] LOCAL_NAME,
6858 [, [External =>] EXTERNAL_SYMBOL]
6859 [, [Size =>] EXTERNAL_SYMBOL]);
6863 | static_string_EXPRESSION
6866 This pragma is identical in effect to pragma @code{Common_Object}.
6868 @node Pragma Pure_Function,Pragma Rational,Pragma Psect_Object,Implementation Defined Pragmas
6869 @anchor{gnat_rm/implementation_defined_pragmas pragma-pure-function}@anchor{ca}@anchor{gnat_rm/implementation_defined_pragmas id31}@anchor{cb}
6870 @section Pragma Pure_Function
6876 pragma Pure_Function ([Entity =>] function_LOCAL_NAME);
6879 This pragma appears in the same declarative part as a function
6880 declaration (or a set of function declarations if more than one
6881 overloaded declaration exists, in which case the pragma applies
6882 to all entities). It specifies that the function @code{Entity} is
6883 to be considered pure for the purposes of code generation. This means
6884 that the compiler can assume that there are no side effects, and
6885 in particular that two calls with identical arguments produce the
6886 same result. It also means that the function can be used in an
6889 Note that, quite deliberately, there are no static checks to try
6890 to ensure that this promise is met, so @code{Pure_Function} can be used
6891 with functions that are conceptually pure, even if they do modify
6892 global variables. For example, a square root function that is
6893 instrumented to count the number of times it is called is still
6894 conceptually pure, and can still be optimized, even though it
6895 modifies a global variable (the count). Memo functions are another
6896 example (where a table of previous calls is kept and consulted to
6897 avoid re-computation).
6899 Note also that the normal rules excluding optimization of subprograms
6900 in pure units (when parameter types are descended from System.Address,
6901 or when the full view of a parameter type is limited), do not apply
6902 for the Pure_Function case. If you explicitly specify Pure_Function,
6903 the compiler may optimize away calls with identical arguments, and
6904 if that results in unexpected behavior, the proper action is not to
6905 use the pragma for subprograms that are not (conceptually) pure.
6907 Note: Most functions in a @code{Pure} package are automatically pure, and
6908 there is no need to use pragma @code{Pure_Function} for such functions. One
6909 exception is any function that has at least one formal of type
6910 @code{System.Address} or a type derived from it. Such functions are not
6911 considered pure by default, since the compiler assumes that the
6912 @code{Address} parameter may be functioning as a pointer and that the
6913 referenced data may change even if the address value does not.
6914 Similarly, imported functions are not considered to be pure by default,
6915 since there is no way of checking that they are in fact pure. The use
6916 of pragma @code{Pure_Function} for such a function will override these default
6917 assumption, and cause the compiler to treat a designated subprogram as pure
6920 Note: If pragma @code{Pure_Function} is applied to a renamed function, it
6921 applies to the underlying renamed function. This can be used to
6922 disambiguate cases of overloading where some but not all functions
6923 in a set of overloaded functions are to be designated as pure.
6925 If pragma @code{Pure_Function} is applied to a library-level function, the
6926 function is also considered pure from an optimization point of view, but the
6927 unit is not a Pure unit in the categorization sense. So for example, a function
6928 thus marked is free to @code{with} non-pure units.
6930 @node Pragma Rational,Pragma Ravenscar,Pragma Pure_Function,Implementation Defined Pragmas
6931 @anchor{gnat_rm/implementation_defined_pragmas pragma-rational}@anchor{cc}
6932 @section Pragma Rational
6941 This pragma is considered obsolescent, but is retained for
6942 compatibility purposes. It is equivalent to:
6945 pragma Profile (Rational);
6948 @node Pragma Ravenscar,Pragma Refined_Depends,Pragma Rational,Implementation Defined Pragmas
6949 @anchor{gnat_rm/implementation_defined_pragmas pragma-ravenscar}@anchor{cd}
6950 @section Pragma Ravenscar
6959 This pragma is considered obsolescent, but is retained for
6960 compatibility purposes. It is equivalent to:
6963 pragma Profile (Ravenscar);
6966 which is the preferred method of setting the @code{Ravenscar} profile.
6968 @node Pragma Refined_Depends,Pragma Refined_Global,Pragma Ravenscar,Implementation Defined Pragmas
6969 @anchor{gnat_rm/implementation_defined_pragmas pragma-refined-depends}@anchor{ce}@anchor{gnat_rm/implementation_defined_pragmas id32}@anchor{cf}
6970 @section Pragma Refined_Depends
6976 pragma Refined_Depends (DEPENDENCY_RELATION);
6978 DEPENDENCY_RELATION ::=
6980 | (DEPENDENCY_CLAUSE @{, DEPENDENCY_CLAUSE@})
6982 DEPENDENCY_CLAUSE ::=
6983 OUTPUT_LIST =>[+] INPUT_LIST
6984 | NULL_DEPENDENCY_CLAUSE
6986 NULL_DEPENDENCY_CLAUSE ::= null => INPUT_LIST
6988 OUTPUT_LIST ::= OUTPUT | (OUTPUT @{, OUTPUT@})
6990 INPUT_LIST ::= null | INPUT | (INPUT @{, INPUT@})
6992 OUTPUT ::= NAME | FUNCTION_RESULT
6995 where FUNCTION_RESULT is a function Result attribute_reference
6998 For the semantics of this pragma, see the entry for aspect @code{Refined_Depends} in
6999 the SPARK 2014 Reference Manual, section 6.1.5.
7001 @node Pragma Refined_Global,Pragma Refined_Post,Pragma Refined_Depends,Implementation Defined Pragmas
7002 @anchor{gnat_rm/implementation_defined_pragmas pragma-refined-global}@anchor{d0}@anchor{gnat_rm/implementation_defined_pragmas id33}@anchor{d1}
7003 @section Pragma Refined_Global
7009 pragma Refined_Global (GLOBAL_SPECIFICATION);
7011 GLOBAL_SPECIFICATION ::=
7014 | (MODED_GLOBAL_LIST @{, MODED_GLOBAL_LIST@})
7016 MODED_GLOBAL_LIST ::= MODE_SELECTOR => GLOBAL_LIST
7018 MODE_SELECTOR ::= In_Out | Input | Output | Proof_In
7019 GLOBAL_LIST ::= GLOBAL_ITEM | (GLOBAL_ITEM @{, GLOBAL_ITEM@})
7020 GLOBAL_ITEM ::= NAME
7023 For the semantics of this pragma, see the entry for aspect @code{Refined_Global} in
7024 the SPARK 2014 Reference Manual, section 6.1.4.
7026 @node Pragma Refined_Post,Pragma Refined_State,Pragma Refined_Global,Implementation Defined Pragmas
7027 @anchor{gnat_rm/implementation_defined_pragmas pragma-refined-post}@anchor{d2}@anchor{gnat_rm/implementation_defined_pragmas id34}@anchor{d3}
7028 @section Pragma Refined_Post
7034 pragma Refined_Post (boolean_EXPRESSION);
7037 For the semantics of this pragma, see the entry for aspect @code{Refined_Post} in
7038 the SPARK 2014 Reference Manual, section 7.2.7.
7040 @node Pragma Refined_State,Pragma Relative_Deadline,Pragma Refined_Post,Implementation Defined Pragmas
7041 @anchor{gnat_rm/implementation_defined_pragmas pragma-refined-state}@anchor{d4}@anchor{gnat_rm/implementation_defined_pragmas id35}@anchor{d5}
7042 @section Pragma Refined_State
7048 pragma Refined_State (REFINEMENT_LIST);
7051 (REFINEMENT_CLAUSE @{, REFINEMENT_CLAUSE@})
7053 REFINEMENT_CLAUSE ::= state_NAME => CONSTITUENT_LIST
7055 CONSTITUENT_LIST ::=
7058 | (CONSTITUENT @{, CONSTITUENT@})
7060 CONSTITUENT ::= object_NAME | state_NAME
7063 For the semantics of this pragma, see the entry for aspect @code{Refined_State} in
7064 the SPARK 2014 Reference Manual, section 7.2.2.
7066 @node Pragma Relative_Deadline,Pragma Remote_Access_Type,Pragma Refined_State,Implementation Defined Pragmas
7067 @anchor{gnat_rm/implementation_defined_pragmas pragma-relative-deadline}@anchor{d6}
7068 @section Pragma Relative_Deadline
7074 pragma Relative_Deadline (time_span_EXPRESSION);
7077 This pragma is standard in Ada 2005, but is available in all earlier
7078 versions of Ada as an implementation-defined pragma.
7079 See Ada 2012 Reference Manual for details.
7081 @node Pragma Remote_Access_Type,Pragma Restricted_Run_Time,Pragma Relative_Deadline,Implementation Defined Pragmas
7082 @anchor{gnat_rm/implementation_defined_pragmas id36}@anchor{d7}@anchor{gnat_rm/implementation_defined_pragmas pragma-remote-access-type}@anchor{d8}
7083 @section Pragma Remote_Access_Type
7089 pragma Remote_Access_Type ([Entity =>] formal_access_type_LOCAL_NAME);
7092 This pragma appears in the formal part of a generic declaration.
7093 It specifies an exception to the RM rule from E.2.2(17/2), which forbids
7094 the use of a remote access to class-wide type as actual for a formal
7097 When this pragma applies to a formal access type @code{Entity}, that
7098 type is treated as a remote access to class-wide type in the generic.
7099 It must be a formal general access type, and its designated type must
7100 be the class-wide type of a formal tagged limited private type from the
7101 same generic declaration.
7103 In the generic unit, the formal type is subject to all restrictions
7104 pertaining to remote access to class-wide types. At instantiation, the
7105 actual type must be a remote access to class-wide type.
7107 @node Pragma Restricted_Run_Time,Pragma Restriction_Warnings,Pragma Remote_Access_Type,Implementation Defined Pragmas
7108 @anchor{gnat_rm/implementation_defined_pragmas pragma-restricted-run-time}@anchor{d9}
7109 @section Pragma Restricted_Run_Time
7115 pragma Restricted_Run_Time;
7118 This pragma is considered obsolescent, but is retained for
7119 compatibility purposes. It is equivalent to:
7122 pragma Profile (Restricted);
7125 which is the preferred method of setting the restricted run time
7128 @node Pragma Restriction_Warnings,Pragma Reviewable,Pragma Restricted_Run_Time,Implementation Defined Pragmas
7129 @anchor{gnat_rm/implementation_defined_pragmas pragma-restriction-warnings}@anchor{da}
7130 @section Pragma Restriction_Warnings
7136 pragma Restriction_Warnings
7137 (restriction_IDENTIFIER @{, restriction_IDENTIFIER@});
7140 This pragma allows a series of restriction identifiers to be
7141 specified (the list of allowed identifiers is the same as for
7142 pragma @code{Restrictions}). For each of these identifiers
7143 the compiler checks for violations of the restriction, but
7144 generates a warning message rather than an error message
7145 if the restriction is violated.
7147 One use of this is in situations where you want to know
7148 about violations of a restriction, but you want to ignore some of
7149 these violations. Consider this example, where you want to set
7150 Ada_95 mode and enable style checks, but you want to know about
7151 any other use of implementation pragmas:
7154 pragma Restriction_Warnings (No_Implementation_Pragmas);
7155 pragma Warnings (Off, "violation of No_Implementation_Pragmas");
7157 pragma Style_Checks ("2bfhkM160");
7158 pragma Warnings (On, "violation of No_Implementation_Pragmas");
7161 By including the above lines in a configuration pragmas file,
7162 the Ada_95 and Style_Checks pragmas are accepted without
7163 generating a warning, but any other use of implementation
7164 defined pragmas will cause a warning to be generated.
7166 @node Pragma Reviewable,Pragma Secondary_Stack_Size,Pragma Restriction_Warnings,Implementation Defined Pragmas
7167 @anchor{gnat_rm/implementation_defined_pragmas pragma-reviewable}@anchor{db}
7168 @section Pragma Reviewable
7177 This pragma is an RM-defined standard pragma, but has no effect on the
7178 program being compiled, or on the code generated for the program.
7180 To obtain the required output specified in RM H.3.1, the compiler must be
7181 run with various special switches as follows:
7187 @emph{Where compiler-generated run-time checks remain}
7189 The switch @emph{-gnatGL}
7190 may be used to list the expanded code in pseudo-Ada form.
7191 Runtime checks show up in the listing either as explicit
7192 checks or operators marked with @{@} to indicate a check is present.
7195 @emph{An identification of known exceptions at compile time}
7197 If the program is compiled with @emph{-gnatwa},
7198 the compiler warning messages will indicate all cases where the compiler
7199 detects that an exception is certain to occur at run time.
7202 @emph{Possible reads of uninitialized variables}
7204 The compiler warns of many such cases, but its output is incomplete.
7208 A supplemental static analysis tool
7209 may be used to obtain a comprehensive list of all
7210 possible points at which uninitialized data may be read.
7216 @emph{Where run-time support routines are implicitly invoked}
7218 In the output from @emph{-gnatGL},
7219 run-time calls are explicitly listed as calls to the relevant
7223 @emph{Object code listing}
7225 This may be obtained either by using the @emph{-S} switch,
7226 or the objdump utility.
7229 @emph{Constructs known to be erroneous at compile time}
7231 These are identified by warnings issued by the compiler (use @emph{-gnatwa}).
7234 @emph{Stack usage information}
7236 Static stack usage data (maximum per-subprogram) can be obtained via the
7237 @emph{-fstack-usage} switch to the compiler.
7238 Dynamic stack usage data (per task) can be obtained via the @emph{-u} switch
7247 @emph{Object code listing of entire partition}
7249 This can be obtained by compiling the partition with @emph{-S},
7250 or by applying objdump
7251 to all the object files that are part of the partition.
7254 @emph{A description of the run-time model}
7256 The full sources of the run-time are available, and the documentation of
7257 these routines describes how these run-time routines interface to the
7258 underlying operating system facilities.
7261 @emph{Control and data-flow information}
7265 A supplemental static analysis tool
7266 may be used to obtain complete control and data-flow information, as well as
7267 comprehensive messages identifying possible problems based on this
7270 @node Pragma Secondary_Stack_Size,Pragma Share_Generic,Pragma Reviewable,Implementation Defined Pragmas
7271 @anchor{gnat_rm/implementation_defined_pragmas id37}@anchor{dc}@anchor{gnat_rm/implementation_defined_pragmas pragma-secondary-stack-size}@anchor{dd}
7272 @section Pragma Secondary_Stack_Size
7278 pragma Secondary_Stack_Size (integer_EXPRESSION);
7281 This pragma appears within the task definition of a single task declaration
7282 or a task type declaration (like pragma @code{Storage_Size}) and applies to all
7283 task objects of that type. The argument specifies the size of the secondary
7284 stack to be used by these task objects, and must be of an integer type. The
7285 secondary stack is used to handle functions that return a variable-sized
7286 result, for example a function returning an unconstrained String.
7288 Note this pragma only applies to targets using fixed secondary stacks, like
7289 VxWorks 653 and bare board targets, where a fixed block for the
7290 secondary stack is allocated from the primary stack of the task. By default,
7291 these targets assign a percentage of the primary stack for the secondary stack,
7292 as defined by @code{System.Parameter.Sec_Stack_Percentage}. With this pragma,
7293 an @code{integer_EXPRESSION} of bytes is assigned from the primary stack instead.
7295 For most targets, the pragma does not apply as the secondary stack grows on
7296 demand: allocated as a chain of blocks in the heap. The default size of these
7297 blocks can be modified via the @code{-D} binder option as described in
7298 @cite{GNAT User's Guide}.
7300 Note that no check is made to see if the secondary stack can fit inside the
7303 Note the pragma cannot appear when the restriction @code{No_Secondary_Stack}
7306 @node Pragma Share_Generic,Pragma Shared,Pragma Secondary_Stack_Size,Implementation Defined Pragmas
7307 @anchor{gnat_rm/implementation_defined_pragmas pragma-share-generic}@anchor{de}
7308 @section Pragma Share_Generic
7314 pragma Share_Generic (GNAME @{, GNAME@});
7316 GNAME ::= generic_unit_NAME | generic_instance_NAME
7319 This pragma is provided for compatibility with Dec Ada 83. It has
7320 no effect in GNAT (which does not implement shared generics), other
7321 than to check that the given names are all names of generic units or
7324 @node Pragma Shared,Pragma Short_Circuit_And_Or,Pragma Share_Generic,Implementation Defined Pragmas
7325 @anchor{gnat_rm/implementation_defined_pragmas id38}@anchor{df}@anchor{gnat_rm/implementation_defined_pragmas pragma-shared}@anchor{e0}
7326 @section Pragma Shared
7329 This pragma is provided for compatibility with Ada 83. The syntax and
7330 semantics are identical to pragma Atomic.
7332 @node Pragma Short_Circuit_And_Or,Pragma Short_Descriptors,Pragma Shared,Implementation Defined Pragmas
7333 @anchor{gnat_rm/implementation_defined_pragmas pragma-short-circuit-and-or}@anchor{e1}
7334 @section Pragma Short_Circuit_And_Or
7340 pragma Short_Circuit_And_Or;
7343 This configuration pragma causes any occurrence of the AND operator applied to
7344 operands of type Standard.Boolean to be short-circuited (i.e. the AND operator
7345 is treated as if it were AND THEN). Or is similarly treated as OR ELSE. This
7346 may be useful in the context of certification protocols requiring the use of
7347 short-circuited logical operators. If this configuration pragma occurs locally
7348 within the file being compiled, it applies only to the file being compiled.
7349 There is no requirement that all units in a partition use this option.
7351 @node Pragma Short_Descriptors,Pragma Simple_Storage_Pool_Type,Pragma Short_Circuit_And_Or,Implementation Defined Pragmas
7352 @anchor{gnat_rm/implementation_defined_pragmas pragma-short-descriptors}@anchor{e2}
7353 @section Pragma Short_Descriptors
7359 pragma Short_Descriptors
7362 This pragma is provided for compatibility with other Ada implementations. It
7363 is recognized but ignored by all current versions of GNAT.
7365 @node Pragma Simple_Storage_Pool_Type,Pragma Source_File_Name,Pragma Short_Descriptors,Implementation Defined Pragmas
7366 @anchor{gnat_rm/implementation_defined_pragmas pragma-simple-storage-pool-type}@anchor{e3}@anchor{gnat_rm/implementation_defined_pragmas id39}@anchor{e4}
7367 @section Pragma Simple_Storage_Pool_Type
7370 @geindex Storage pool
7373 @geindex Simple storage pool
7378 pragma Simple_Storage_Pool_Type (type_LOCAL_NAME);
7381 A type can be established as a 'simple storage pool type' by applying
7382 the representation pragma @code{Simple_Storage_Pool_Type} to the type.
7383 A type named in the pragma must be a library-level immutably limited record
7384 type or limited tagged type declared immediately within a package declaration.
7385 The type can also be a limited private type whose full type is allowed as
7386 a simple storage pool type.
7388 For a simple storage pool type @code{SSP}, nonabstract primitive subprograms
7389 @code{Allocate}, @code{Deallocate}, and @code{Storage_Size} can be declared that
7390 are subtype conformant with the following subprogram declarations:
7395 Storage_Address : out System.Address;
7396 Size_In_Storage_Elements : System.Storage_Elements.Storage_Count;
7397 Alignment : System.Storage_Elements.Storage_Count);
7399 procedure Deallocate
7401 Storage_Address : System.Address;
7402 Size_In_Storage_Elements : System.Storage_Elements.Storage_Count;
7403 Alignment : System.Storage_Elements.Storage_Count);
7405 function Storage_Size (Pool : SSP)
7406 return System.Storage_Elements.Storage_Count;
7409 Procedure @code{Allocate} must be declared, whereas @code{Deallocate} and
7410 @code{Storage_Size} are optional. If @code{Deallocate} is not declared, then
7411 applying an unchecked deallocation has no effect other than to set its actual
7412 parameter to null. If @code{Storage_Size} is not declared, then the
7413 @code{Storage_Size} attribute applied to an access type associated with
7414 a pool object of type SSP returns zero. Additional operations can be declared
7415 for a simple storage pool type (such as for supporting a mark/release
7416 storage-management discipline).
7418 An object of a simple storage pool type can be associated with an access
7419 type by specifying the attribute
7420 @ref{e5,,Simple_Storage_Pool}. For example:
7423 My_Pool : My_Simple_Storage_Pool_Type;
7425 type Acc is access My_Data_Type;
7427 for Acc'Simple_Storage_Pool use My_Pool;
7430 See attribute @ref{e5,,Simple_Storage_Pool}
7431 for further details.
7433 @node Pragma Source_File_Name,Pragma Source_File_Name_Project,Pragma Simple_Storage_Pool_Type,Implementation Defined Pragmas
7434 @anchor{gnat_rm/implementation_defined_pragmas pragma-source-file-name}@anchor{e6}@anchor{gnat_rm/implementation_defined_pragmas id40}@anchor{e7}
7435 @section Pragma Source_File_Name
7441 pragma Source_File_Name (
7442 [Unit_Name =>] unit_NAME,
7443 Spec_File_Name => STRING_LITERAL,
7444 [Index => INTEGER_LITERAL]);
7446 pragma Source_File_Name (
7447 [Unit_Name =>] unit_NAME,
7448 Body_File_Name => STRING_LITERAL,
7449 [Index => INTEGER_LITERAL]);
7452 Use this to override the normal naming convention. It is a configuration
7453 pragma, and so has the usual applicability of configuration pragmas
7454 (i.e., it applies to either an entire partition, or to all units in a
7455 compilation, or to a single unit, depending on how it is used.
7456 @code{unit_name} is mapped to @code{file_name_literal}. The identifier for
7457 the second argument is required, and indicates whether this is the file
7458 name for the spec or for the body.
7460 The optional Index argument should be used when a file contains multiple
7461 units, and when you do not want to use @code{gnatchop} to separate then
7462 into multiple files (which is the recommended procedure to limit the
7463 number of recompilations that are needed when some sources change).
7464 For instance, if the source file @code{source.ada} contains
7478 you could use the following configuration pragmas:
7481 pragma Source_File_Name
7482 (B, Spec_File_Name => "source.ada", Index => 1);
7483 pragma Source_File_Name
7484 (A, Body_File_Name => "source.ada", Index => 2);
7487 Note that the @code{gnatname} utility can also be used to generate those
7488 configuration pragmas.
7490 Another form of the @code{Source_File_Name} pragma allows
7491 the specification of patterns defining alternative file naming schemes
7492 to apply to all files.
7495 pragma Source_File_Name
7496 ( [Spec_File_Name =>] STRING_LITERAL
7497 [,[Casing =>] CASING_SPEC]
7498 [,[Dot_Replacement =>] STRING_LITERAL]);
7500 pragma Source_File_Name
7501 ( [Body_File_Name =>] STRING_LITERAL
7502 [,[Casing =>] CASING_SPEC]
7503 [,[Dot_Replacement =>] STRING_LITERAL]);
7505 pragma Source_File_Name
7506 ( [Subunit_File_Name =>] STRING_LITERAL
7507 [,[Casing =>] CASING_SPEC]
7508 [,[Dot_Replacement =>] STRING_LITERAL]);
7510 CASING_SPEC ::= Lowercase | Uppercase | Mixedcase
7513 The first argument is a pattern that contains a single asterisk indicating
7514 the point at which the unit name is to be inserted in the pattern string
7515 to form the file name. The second argument is optional. If present it
7516 specifies the casing of the unit name in the resulting file name string.
7517 The default is lower case. Finally the third argument allows for systematic
7518 replacement of any dots in the unit name by the specified string literal.
7520 Note that Source_File_Name pragmas should not be used if you are using
7521 project files. The reason for this rule is that the project manager is not
7522 aware of these pragmas, and so other tools that use the projet file would not
7523 be aware of the intended naming conventions. If you are using project files,
7524 file naming is controlled by Source_File_Name_Project pragmas, which are
7525 usually supplied automatically by the project manager. A pragma
7526 Source_File_Name cannot appear after a @ref{e8,,Pragma Source_File_Name_Project}.
7528 For more details on the use of the @code{Source_File_Name} pragma, see the
7529 sections on @cite{Using Other File Names} and @cite{Alternative File Naming Schemes}
7530 in the @cite{GNAT User's Guide}.
7532 @node Pragma Source_File_Name_Project,Pragma Source_Reference,Pragma Source_File_Name,Implementation Defined Pragmas
7533 @anchor{gnat_rm/implementation_defined_pragmas pragma-source-file-name-project}@anchor{e8}@anchor{gnat_rm/implementation_defined_pragmas id41}@anchor{e9}
7534 @section Pragma Source_File_Name_Project
7537 This pragma has the same syntax and semantics as pragma Source_File_Name.
7538 It is only allowed as a stand-alone configuration pragma.
7539 It cannot appear after a @ref{e6,,Pragma Source_File_Name}, and
7540 most importantly, once pragma Source_File_Name_Project appears,
7541 no further Source_File_Name pragmas are allowed.
7543 The intention is that Source_File_Name_Project pragmas are always
7544 generated by the Project Manager in a manner consistent with the naming
7545 specified in a project file, and when naming is controlled in this manner,
7546 it is not permissible to attempt to modify this naming scheme using
7547 Source_File_Name or Source_File_Name_Project pragmas (which would not be
7548 known to the project manager).
7550 @node Pragma Source_Reference,Pragma SPARK_Mode,Pragma Source_File_Name_Project,Implementation Defined Pragmas
7551 @anchor{gnat_rm/implementation_defined_pragmas pragma-source-reference}@anchor{ea}
7552 @section Pragma Source_Reference
7558 pragma Source_Reference (INTEGER_LITERAL, STRING_LITERAL);
7561 This pragma must appear as the first line of a source file.
7562 @code{integer_literal} is the logical line number of the line following
7563 the pragma line (for use in error messages and debugging
7564 information). @code{string_literal} is a static string constant that
7565 specifies the file name to be used in error messages and debugging
7566 information. This is most notably used for the output of @code{gnatchop}
7567 with the @emph{-r} switch, to make sure that the original unchopped
7568 source file is the one referred to.
7570 The second argument must be a string literal, it cannot be a static
7571 string expression other than a string literal. This is because its value
7572 is needed for error messages issued by all phases of the compiler.
7574 @node Pragma SPARK_Mode,Pragma Static_Elaboration_Desired,Pragma Source_Reference,Implementation Defined Pragmas
7575 @anchor{gnat_rm/implementation_defined_pragmas pragma-spark-mode}@anchor{eb}@anchor{gnat_rm/implementation_defined_pragmas id42}@anchor{ec}
7576 @section Pragma SPARK_Mode
7582 pragma SPARK_Mode [(On | Off)] ;
7585 In general a program can have some parts that are in SPARK 2014 (and
7586 follow all the rules in the SPARK Reference Manual), and some parts
7587 that are full Ada 2012.
7589 The SPARK_Mode pragma is used to identify which parts are in SPARK
7590 2014 (by default programs are in full Ada). The SPARK_Mode pragma can
7591 be used in the following places:
7597 As a configuration pragma, in which case it sets the default mode for
7598 all units compiled with this pragma.
7601 Immediately following a library-level subprogram spec
7604 Immediately within a library-level package body
7607 Immediately following the @code{private} keyword of a library-level
7611 Immediately following the @code{begin} keyword of a library-level
7615 Immediately within a library-level subprogram body
7618 Normally a subprogram or package spec/body inherits the current mode
7619 that is active at the point it is declared. But this can be overridden
7620 by pragma within the spec or body as above.
7622 The basic consistency rule is that you can't turn SPARK_Mode back
7623 @code{On}, once you have explicitly (with a pragma) turned if
7624 @code{Off}. So the following rules apply:
7626 If a subprogram spec has SPARK_Mode @code{Off}, then the body must
7627 also have SPARK_Mode @code{Off}.
7629 For a package, we have four parts:
7635 the package public declarations
7638 the package private part
7641 the body of the package
7644 the elaboration code after @code{begin}
7647 For a package, the rule is that if you explicitly turn SPARK_Mode
7648 @code{Off} for any part, then all the following parts must have
7649 SPARK_Mode @code{Off}. Note that this may require repeating a pragma
7650 SPARK_Mode (@code{Off}) in the body. For example, if we have a
7651 configuration pragma SPARK_Mode (@code{On}) that turns the mode on by
7652 default everywhere, and one particular package spec has pragma
7653 SPARK_Mode (@code{Off}), then that pragma will need to be repeated in
7656 @node Pragma Static_Elaboration_Desired,Pragma Stream_Convert,Pragma SPARK_Mode,Implementation Defined Pragmas
7657 @anchor{gnat_rm/implementation_defined_pragmas pragma-static-elaboration-desired}@anchor{ed}
7658 @section Pragma Static_Elaboration_Desired
7664 pragma Static_Elaboration_Desired;
7667 This pragma is used to indicate that the compiler should attempt to initialize
7668 statically the objects declared in the library unit to which the pragma applies,
7669 when these objects are initialized (explicitly or implicitly) by an aggregate.
7670 In the absence of this pragma, aggregates in object declarations are expanded
7671 into assignments and loops, even when the aggregate components are static
7672 constants. When the aggregate is present the compiler builds a static expression
7673 that requires no run-time code, so that the initialized object can be placed in
7674 read-only data space. If the components are not static, or the aggregate has
7675 more that 100 components, the compiler emits a warning that the pragma cannot
7676 be obeyed. (See also the restriction No_Implicit_Loops, which supports static
7677 construction of larger aggregates with static components that include an others
7680 @node Pragma Stream_Convert,Pragma Style_Checks,Pragma Static_Elaboration_Desired,Implementation Defined Pragmas
7681 @anchor{gnat_rm/implementation_defined_pragmas pragma-stream-convert}@anchor{ee}
7682 @section Pragma Stream_Convert
7688 pragma Stream_Convert (
7689 [Entity =>] type_LOCAL_NAME,
7690 [Read =>] function_NAME,
7691 [Write =>] function_NAME);
7694 This pragma provides an efficient way of providing user-defined stream
7695 attributes. Not only is it simpler to use than specifying the attributes
7696 directly, but more importantly, it allows the specification to be made in such
7697 a way that the predefined unit Ada.Streams is not loaded unless it is actually
7698 needed (i.e. unless the stream attributes are actually used); the use of
7699 the Stream_Convert pragma adds no overhead at all, unless the stream
7700 attributes are actually used on the designated type.
7702 The first argument specifies the type for which stream functions are
7703 provided. The second parameter provides a function used to read values
7704 of this type. It must name a function whose argument type may be any
7705 subtype, and whose returned type must be the type given as the first
7706 argument to the pragma.
7708 The meaning of the @code{Read} parameter is that if a stream attribute directly
7709 or indirectly specifies reading of the type given as the first parameter,
7710 then a value of the type given as the argument to the Read function is
7711 read from the stream, and then the Read function is used to convert this
7712 to the required target type.
7714 Similarly the @code{Write} parameter specifies how to treat write attributes
7715 that directly or indirectly apply to the type given as the first parameter.
7716 It must have an input parameter of the type specified by the first parameter,
7717 and the return type must be the same as the input type of the Read function.
7718 The effect is to first call the Write function to convert to the given stream
7719 type, and then write the result type to the stream.
7721 The Read and Write functions must not be overloaded subprograms. If necessary
7722 renamings can be supplied to meet this requirement.
7723 The usage of this attribute is best illustrated by a simple example, taken
7724 from the GNAT implementation of package Ada.Strings.Unbounded:
7727 function To_Unbounded (S : String) return Unbounded_String
7728 renames To_Unbounded_String;
7730 pragma Stream_Convert
7731 (Unbounded_String, To_Unbounded, To_String);
7734 The specifications of the referenced functions, as given in the Ada
7735 Reference Manual are:
7738 function To_Unbounded_String (Source : String)
7739 return Unbounded_String;
7741 function To_String (Source : Unbounded_String)
7745 The effect is that if the value of an unbounded string is written to a stream,
7746 then the representation of the item in the stream is in the same format that
7747 would be used for @code{Standard.String'Output}, and this same representation
7748 is expected when a value of this type is read from the stream. Note that the
7749 value written always includes the bounds, even for Unbounded_String'Write,
7750 since Unbounded_String is not an array type.
7752 Note that the @code{Stream_Convert} pragma is not effective in the case of
7753 a derived type of a non-limited tagged type. If such a type is specified then
7754 the pragma is silently ignored, and the default implementation of the stream
7755 attributes is used instead.
7757 @node Pragma Style_Checks,Pragma Subtitle,Pragma Stream_Convert,Implementation Defined Pragmas
7758 @anchor{gnat_rm/implementation_defined_pragmas pragma-style-checks}@anchor{ef}
7759 @section Pragma Style_Checks
7765 pragma Style_Checks (string_LITERAL | ALL_CHECKS |
7766 On | Off [, LOCAL_NAME]);
7769 This pragma is used in conjunction with compiler switches to control the
7770 built in style checking provided by GNAT. The compiler switches, if set,
7771 provide an initial setting for the switches, and this pragma may be used
7772 to modify these settings, or the settings may be provided entirely by
7773 the use of the pragma. This pragma can be used anywhere that a pragma
7774 is legal, including use as a configuration pragma (including use in
7775 the @code{gnat.adc} file).
7777 The form with a string literal specifies which style options are to be
7778 activated. These are additive, so they apply in addition to any previously
7779 set style check options. The codes for the options are the same as those
7780 used in the @emph{-gnaty} switch to @emph{gcc} or @emph{gnatmake}.
7781 For example the following two methods can be used to enable
7789 pragma Style_Checks ("l");
7798 The form @code{ALL_CHECKS} activates all standard checks (its use is equivalent
7799 to the use of the @code{gnaty} switch with no options.
7800 See the @cite{GNAT User's Guide} for details.)
7802 Note: the behavior is slightly different in GNAT mode (@code{-gnatg} used).
7803 In this case, @code{ALL_CHECKS} implies the standard set of GNAT mode style check
7804 options (i.e. equivalent to @code{-gnatyg}).
7806 The forms with @code{Off} and @code{On}
7807 can be used to temporarily disable style checks
7808 as shown in the following example:
7811 pragma Style_Checks ("k"); -- requires keywords in lower case
7812 pragma Style_Checks (Off); -- turn off style checks
7813 NULL; -- this will not generate an error message
7814 pragma Style_Checks (On); -- turn style checks back on
7815 NULL; -- this will generate an error message
7818 Finally the two argument form is allowed only if the first argument is
7819 @code{On} or @code{Off}. The effect is to turn of semantic style checks
7820 for the specified entity, as shown in the following example:
7823 pragma Style_Checks ("r"); -- require consistency of identifier casing
7825 Rf1 : Integer := ARG; -- incorrect, wrong case
7826 pragma Style_Checks (Off, Arg);
7827 Rf2 : Integer := ARG; -- OK, no error
7830 @node Pragma Subtitle,Pragma Suppress,Pragma Style_Checks,Implementation Defined Pragmas
7831 @anchor{gnat_rm/implementation_defined_pragmas pragma-subtitle}@anchor{f0}
7832 @section Pragma Subtitle
7838 pragma Subtitle ([Subtitle =>] STRING_LITERAL);
7841 This pragma is recognized for compatibility with other Ada compilers
7842 but is ignored by GNAT.
7844 @node Pragma Suppress,Pragma Suppress_All,Pragma Subtitle,Implementation Defined Pragmas
7845 @anchor{gnat_rm/implementation_defined_pragmas pragma-suppress}@anchor{f1}
7846 @section Pragma Suppress
7852 pragma Suppress (Identifier [, [On =>] Name]);
7855 This is a standard pragma, and supports all the check names required in
7856 the RM. It is included here because GNAT recognizes some additional check
7857 names that are implementation defined (as permitted by the RM):
7863 @code{Alignment_Check} can be used to suppress alignment checks
7864 on addresses used in address clauses. Such checks can also be suppressed
7865 by suppressing range checks, but the specific use of @code{Alignment_Check}
7866 allows suppression of alignment checks without suppressing other range checks.
7867 Note that @code{Alignment_Check} is suppressed by default on machines (such as
7868 the x86) with non-strict alignment.
7871 @code{Atomic_Synchronization} can be used to suppress the special memory
7872 synchronization instructions that are normally generated for access to
7873 @code{Atomic} variables to ensure correct synchronization between tasks
7874 that use such variables for synchronization purposes.
7877 @code{Duplicated_Tag_Check} Can be used to suppress the check that is generated
7878 for a duplicated tag value when a tagged type is declared.
7881 @code{Container_Checks} Can be used to suppress all checks within Ada.Containers
7882 and instances of its children, including Tampering_Check.
7885 @code{Tampering_Check} Can be used to suppress tampering check in the containers.
7888 @code{Predicate_Check} can be used to control whether predicate checks are
7889 active. It is applicable only to predicates for which the policy is
7890 @code{Check}. Unlike @code{Assertion_Policy}, which determines if a given
7891 predicate is ignored or checked for the whole program, the use of
7892 @code{Suppress} and @code{Unsuppress} with this check name allows a given
7893 predicate to be turned on and off at specific points in the program.
7896 @code{Validity_Check} can be used specifically to control validity checks.
7897 If @code{Suppress} is used to suppress validity checks, then no validity
7898 checks are performed, including those specified by the appropriate compiler
7899 switch or the @code{Validity_Checks} pragma.
7902 Additional check names previously introduced by use of the @code{Check_Name}
7903 pragma are also allowed.
7906 Note that pragma Suppress gives the compiler permission to omit
7907 checks, but does not require the compiler to omit checks. The compiler
7908 will generate checks if they are essentially free, even when they are
7909 suppressed. In particular, if the compiler can prove that a certain
7910 check will necessarily fail, it will generate code to do an
7911 unconditional 'raise', even if checks are suppressed. The compiler
7914 Of course, run-time checks are omitted whenever the compiler can prove
7915 that they will not fail, whether or not checks are suppressed.
7917 @node Pragma Suppress_All,Pragma Suppress_Debug_Info,Pragma Suppress,Implementation Defined Pragmas
7918 @anchor{gnat_rm/implementation_defined_pragmas pragma-suppress-all}@anchor{f2}
7919 @section Pragma Suppress_All
7925 pragma Suppress_All;
7928 This pragma can appear anywhere within a unit.
7929 The effect is to apply @code{Suppress (All_Checks)} to the unit
7930 in which it appears. This pragma is implemented for compatibility with DEC
7931 Ada 83 usage where it appears at the end of a unit, and for compatibility
7932 with Rational Ada, where it appears as a program unit pragma.
7933 The use of the standard Ada pragma @code{Suppress (All_Checks)}
7934 as a normal configuration pragma is the preferred usage in GNAT.
7936 @node Pragma Suppress_Debug_Info,Pragma Suppress_Exception_Locations,Pragma Suppress_All,Implementation Defined Pragmas
7937 @anchor{gnat_rm/implementation_defined_pragmas pragma-suppress-debug-info}@anchor{f3}@anchor{gnat_rm/implementation_defined_pragmas id43}@anchor{f4}
7938 @section Pragma Suppress_Debug_Info
7944 pragma Suppress_Debug_Info ([Entity =>] LOCAL_NAME);
7947 This pragma can be used to suppress generation of debug information
7948 for the specified entity. It is intended primarily for use in debugging
7949 the debugger, and navigating around debugger problems.
7951 @node Pragma Suppress_Exception_Locations,Pragma Suppress_Initialization,Pragma Suppress_Debug_Info,Implementation Defined Pragmas
7952 @anchor{gnat_rm/implementation_defined_pragmas pragma-suppress-exception-locations}@anchor{f5}
7953 @section Pragma Suppress_Exception_Locations
7959 pragma Suppress_Exception_Locations;
7962 In normal mode, a raise statement for an exception by default generates
7963 an exception message giving the file name and line number for the location
7964 of the raise. This is useful for debugging and logging purposes, but this
7965 entails extra space for the strings for the messages. The configuration
7966 pragma @code{Suppress_Exception_Locations} can be used to suppress the
7967 generation of these strings, with the result that space is saved, but the
7968 exception message for such raises is null. This configuration pragma may
7969 appear in a global configuration pragma file, or in a specific unit as
7970 usual. It is not required that this pragma be used consistently within
7971 a partition, so it is fine to have some units within a partition compiled
7972 with this pragma and others compiled in normal mode without it.
7974 @node Pragma Suppress_Initialization,Pragma Task_Name,Pragma Suppress_Exception_Locations,Implementation Defined Pragmas
7975 @anchor{gnat_rm/implementation_defined_pragmas id44}@anchor{f6}@anchor{gnat_rm/implementation_defined_pragmas pragma-suppress-initialization}@anchor{f7}
7976 @section Pragma Suppress_Initialization
7979 @geindex Suppressing initialization
7981 @geindex Initialization
7982 @geindex suppression of
7987 pragma Suppress_Initialization ([Entity =>] variable_or_subtype_Name);
7990 Here variable_or_subtype_Name is the name introduced by a type declaration
7991 or subtype declaration or the name of a variable introduced by an
7994 In the case of a type or subtype
7995 this pragma suppresses any implicit or explicit initialization
7996 for all variables of the given type or subtype,
7997 including initialization resulting from the use of pragmas
7998 Normalize_Scalars or Initialize_Scalars.
8000 This is considered a representation item, so it cannot be given after
8001 the type is frozen. It applies to all subsequent object declarations,
8002 and also any allocator that creates objects of the type.
8004 If the pragma is given for the first subtype, then it is considered
8005 to apply to the base type and all its subtypes. If the pragma is given
8006 for other than a first subtype, then it applies only to the given subtype.
8007 The pragma may not be given after the type is frozen.
8009 Note that this includes eliminating initialization of discriminants
8010 for discriminated types, and tags for tagged types. In these cases,
8011 you will have to use some non-portable mechanism (e.g. address
8012 overlays or unchecked conversion) to achieve required initialization
8013 of these fields before accessing any object of the corresponding type.
8015 For the variable case, implicit initialization for the named variable
8016 is suppressed, just as though its subtype had been given in a pragma
8017 Suppress_Initialization, as described above.
8019 @node Pragma Task_Name,Pragma Task_Storage,Pragma Suppress_Initialization,Implementation Defined Pragmas
8020 @anchor{gnat_rm/implementation_defined_pragmas pragma-task-name}@anchor{f8}
8021 @section Pragma Task_Name
8027 pragma Task_Name (string_EXPRESSION);
8030 This pragma appears within a task definition (like pragma
8031 @code{Priority}) and applies to the task in which it appears. The
8032 argument must be of type String, and provides a name to be used for
8033 the task instance when the task is created. Note that this expression
8034 is not required to be static, and in particular, it can contain
8035 references to task discriminants. This facility can be used to
8036 provide different names for different tasks as they are created,
8037 as illustrated in the example below.
8039 The task name is recorded internally in the run-time structures
8040 and is accessible to tools like the debugger. In addition the
8041 routine @code{Ada.Task_Identification.Image} will return this
8042 string, with a unique task address appended.
8045 -- Example of the use of pragma Task_Name
8047 with Ada.Task_Identification;
8048 use Ada.Task_Identification;
8049 with Text_IO; use Text_IO;
8052 type Astring is access String;
8054 task type Task_Typ (Name : access String) is
8055 pragma Task_Name (Name.all);
8058 task body Task_Typ is
8059 Nam : constant String := Image (Current_Task);
8061 Put_Line ("-->" & Nam (1 .. 14) & "<--");
8064 type Ptr_Task is access Task_Typ;
8065 Task_Var : Ptr_Task;
8069 new Task_Typ (new String'("This is task 1"));
8071 new Task_Typ (new String'("This is task 2"));
8075 @node Pragma Task_Storage,Pragma Test_Case,Pragma Task_Name,Implementation Defined Pragmas
8076 @anchor{gnat_rm/implementation_defined_pragmas pragma-task-storage}@anchor{f9}
8077 @section Pragma Task_Storage
8083 pragma Task_Storage (
8084 [Task_Type =>] LOCAL_NAME,
8085 [Top_Guard =>] static_integer_EXPRESSION);
8088 This pragma specifies the length of the guard area for tasks. The guard
8089 area is an additional storage area allocated to a task. A value of zero
8090 means that either no guard area is created or a minimal guard area is
8091 created, depending on the target. This pragma can appear anywhere a
8092 @code{Storage_Size} attribute definition clause is allowed for a task
8095 @node Pragma Test_Case,Pragma Thread_Local_Storage,Pragma Task_Storage,Implementation Defined Pragmas
8096 @anchor{gnat_rm/implementation_defined_pragmas pragma-test-case}@anchor{fa}@anchor{gnat_rm/implementation_defined_pragmas id45}@anchor{fb}
8097 @section Pragma Test_Case
8106 [Name =>] static_string_Expression
8107 ,[Mode =>] (Nominal | Robustness)
8108 [, Requires => Boolean_Expression]
8109 [, Ensures => Boolean_Expression]);
8112 The @code{Test_Case} pragma allows defining fine-grain specifications
8113 for use by testing tools.
8114 The compiler checks the validity of the @code{Test_Case} pragma, but its
8115 presence does not lead to any modification of the code generated by the
8118 @code{Test_Case} pragmas may only appear immediately following the
8119 (separate) declaration of a subprogram in a package declaration, inside
8120 a package spec unit. Only other pragmas may intervene (that is appear
8121 between the subprogram declaration and a test case).
8123 The compiler checks that boolean expressions given in @code{Requires} and
8124 @code{Ensures} are valid, where the rules for @code{Requires} are the
8125 same as the rule for an expression in @code{Precondition} and the rules
8126 for @code{Ensures} are the same as the rule for an expression in
8127 @code{Postcondition}. In particular, attributes @code{'Old} and
8128 @code{'Result} can only be used within the @code{Ensures}
8129 expression. The following is an example of use within a package spec:
8132 package Math_Functions is
8134 function Sqrt (Arg : Float) return Float;
8135 pragma Test_Case (Name => "Test 1",
8137 Requires => Arg < 10000,
8138 Ensures => Sqrt'Result < 10);
8143 The meaning of a test case is that there is at least one context where
8144 @code{Requires} holds such that, if the associated subprogram is executed in
8145 that context, then @code{Ensures} holds when the subprogram returns.
8146 Mode @code{Nominal} indicates that the input context should also satisfy the
8147 precondition of the subprogram, and the output context should also satisfy its
8148 postcondition. Mode @code{Robustness} indicates that the precondition and
8149 postcondition of the subprogram should be ignored for this test case.
8151 @node Pragma Thread_Local_Storage,Pragma Time_Slice,Pragma Test_Case,Implementation Defined Pragmas
8152 @anchor{gnat_rm/implementation_defined_pragmas pragma-thread-local-storage}@anchor{fc}@anchor{gnat_rm/implementation_defined_pragmas id46}@anchor{fd}
8153 @section Pragma Thread_Local_Storage
8156 @geindex Task specific storage
8158 @geindex TLS (Thread Local Storage)
8160 @geindex Task_Attributes
8165 pragma Thread_Local_Storage ([Entity =>] LOCAL_NAME);
8168 This pragma specifies that the specified entity, which must be
8169 a variable declared in a library-level package, is to be marked as
8170 "Thread Local Storage" (@code{TLS}). On systems supporting this (which
8171 include Windows, Solaris, GNU/Linux, and VxWorks 6), this causes each
8172 thread (and hence each Ada task) to see a distinct copy of the variable.
8174 The variable must not have default initialization, and if there is
8175 an explicit initialization, it must be either @code{null} for an
8176 access variable, a static expression for a scalar variable, or a fully
8177 static aggregate for a composite type, that is to say, an aggregate all
8178 of whose components are static, and which does not include packed or
8179 discriminated components.
8181 This provides a low-level mechanism similar to that provided by
8182 the @code{Ada.Task_Attributes} package, but much more efficient
8183 and is also useful in writing interface code that will interact
8184 with foreign threads.
8186 If this pragma is used on a system where @code{TLS} is not supported,
8187 then an error message will be generated and the program will be rejected.
8189 @node Pragma Time_Slice,Pragma Title,Pragma Thread_Local_Storage,Implementation Defined Pragmas
8190 @anchor{gnat_rm/implementation_defined_pragmas pragma-time-slice}@anchor{fe}
8191 @section Pragma Time_Slice
8197 pragma Time_Slice (static_duration_EXPRESSION);
8200 For implementations of GNAT on operating systems where it is possible
8201 to supply a time slice value, this pragma may be used for this purpose.
8202 It is ignored if it is used in a system that does not allow this control,
8203 or if it appears in other than the main program unit.
8205 @node Pragma Title,Pragma Type_Invariant,Pragma Time_Slice,Implementation Defined Pragmas
8206 @anchor{gnat_rm/implementation_defined_pragmas pragma-title}@anchor{ff}
8207 @section Pragma Title
8213 pragma Title (TITLING_OPTION [, TITLING OPTION]);
8216 [Title =>] STRING_LITERAL,
8217 | [Subtitle =>] STRING_LITERAL
8220 Syntax checked but otherwise ignored by GNAT. This is a listing control
8221 pragma used in DEC Ada 83 implementations to provide a title and/or
8222 subtitle for the program listing. The program listing generated by GNAT
8223 does not have titles or subtitles.
8225 Unlike other pragmas, the full flexibility of named notation is allowed
8226 for this pragma, i.e., the parameters may be given in any order if named
8227 notation is used, and named and positional notation can be mixed
8228 following the normal rules for procedure calls in Ada.
8230 @node Pragma Type_Invariant,Pragma Type_Invariant_Class,Pragma Title,Implementation Defined Pragmas
8231 @anchor{gnat_rm/implementation_defined_pragmas pragma-type-invariant}@anchor{100}
8232 @section Pragma Type_Invariant
8238 pragma Type_Invariant
8239 ([Entity =>] type_LOCAL_NAME,
8240 [Check =>] EXPRESSION);
8243 The @code{Type_Invariant} pragma is intended to be an exact
8244 replacement for the language-defined @code{Type_Invariant}
8245 aspect, and shares its restrictions and semantics. It differs
8246 from the language defined @code{Invariant} pragma in that it
8247 does not permit a string parameter, and it is
8248 controlled by the assertion identifier @code{Type_Invariant}
8249 rather than @code{Invariant}.
8251 @node Pragma Type_Invariant_Class,Pragma Unchecked_Union,Pragma Type_Invariant,Implementation Defined Pragmas
8252 @anchor{gnat_rm/implementation_defined_pragmas id47}@anchor{101}@anchor{gnat_rm/implementation_defined_pragmas pragma-type-invariant-class}@anchor{102}
8253 @section Pragma Type_Invariant_Class
8259 pragma Type_Invariant_Class
8260 ([Entity =>] type_LOCAL_NAME,
8261 [Check =>] EXPRESSION);
8264 The @code{Type_Invariant_Class} pragma is intended to be an exact
8265 replacement for the language-defined @code{Type_Invariant'Class}
8266 aspect, and shares its restrictions and semantics.
8268 Note: This pragma is called @code{Type_Invariant_Class} rather than
8269 @code{Type_Invariant'Class} because the latter would not be strictly
8270 conforming to the allowed syntax for pragmas. The motivation
8271 for providing pragmas equivalent to the aspects is to allow a program
8272 to be written using the pragmas, and then compiled if necessary
8273 using an Ada compiler that does not recognize the pragmas or
8274 aspects, but is prepared to ignore the pragmas. The assertion
8275 policy that controls this pragma is @code{Type_Invariant'Class},
8276 not @code{Type_Invariant_Class}.
8278 @node Pragma Unchecked_Union,Pragma Unevaluated_Use_Of_Old,Pragma Type_Invariant_Class,Implementation Defined Pragmas
8279 @anchor{gnat_rm/implementation_defined_pragmas pragma-unchecked-union}@anchor{103}
8280 @section Pragma Unchecked_Union
8283 @geindex Unions in C
8288 pragma Unchecked_Union (first_subtype_LOCAL_NAME);
8291 This pragma is used to specify a representation of a record type that is
8292 equivalent to a C union. It was introduced as a GNAT implementation defined
8293 pragma in the GNAT Ada 95 mode. Ada 2005 includes an extended version of this
8294 pragma, making it language defined, and GNAT fully implements this extended
8295 version in all language modes (Ada 83, Ada 95, and Ada 2005). For full
8296 details, consult the Ada 2012 Reference Manual, section B.3.3.
8298 @node Pragma Unevaluated_Use_Of_Old,Pragma Unimplemented_Unit,Pragma Unchecked_Union,Implementation Defined Pragmas
8299 @anchor{gnat_rm/implementation_defined_pragmas pragma-unevaluated-use-of-old}@anchor{104}
8300 @section Pragma Unevaluated_Use_Of_Old
8303 @geindex Attribute Old
8305 @geindex Attribute Loop_Entry
8307 @geindex Unevaluated_Use_Of_Old
8312 pragma Unevaluated_Use_Of_Old (Error | Warn | Allow);
8315 This pragma controls the processing of attributes Old and Loop_Entry.
8316 If either of these attributes is used in a potentially unevaluated
8317 expression (e.g. the then or else parts of an if expression), then
8318 normally this usage is considered illegal if the prefix of the attribute
8319 is other than an entity name. The language requires this
8320 behavior for Old, and GNAT copies the same rule for Loop_Entry.
8322 The reason for this rule is that otherwise, we can have a situation
8323 where we save the Old value, and this results in an exception, even
8324 though we might not evaluate the attribute. Consider this example:
8327 package UnevalOld is
8329 procedure U (A : String; C : Boolean) -- ERROR
8330 with Post => (if C then A(1)'Old = K else True);
8334 If procedure U is called with a string with a lower bound of 2, and
8335 C false, then an exception would be raised trying to evaluate A(1)
8336 on entry even though the value would not be actually used.
8338 Although the rule guarantees against this possibility, it is sometimes
8339 too restrictive. For example if we know that the string has a lower
8340 bound of 1, then we will never raise an exception.
8341 The pragma @code{Unevaluated_Use_Of_Old} can be
8342 used to modify this behavior. If the argument is @code{Error} then an
8343 error is given (this is the default RM behavior). If the argument is
8344 @code{Warn} then the usage is allowed as legal but with a warning
8345 that an exception might be raised. If the argument is @code{Allow}
8346 then the usage is allowed as legal without generating a warning.
8348 This pragma may appear as a configuration pragma, or in a declarative
8349 part or package specification. In the latter case it applies to
8350 uses up to the end of the corresponding statement sequence or
8351 sequence of package declarations.
8353 @node Pragma Unimplemented_Unit,Pragma Universal_Aliasing,Pragma Unevaluated_Use_Of_Old,Implementation Defined Pragmas
8354 @anchor{gnat_rm/implementation_defined_pragmas pragma-unimplemented-unit}@anchor{105}
8355 @section Pragma Unimplemented_Unit
8361 pragma Unimplemented_Unit;
8364 If this pragma occurs in a unit that is processed by the compiler, GNAT
8365 aborts with the message @code{xxx not implemented}, where
8366 @code{xxx} is the name of the current compilation unit. This pragma is
8367 intended to allow the compiler to handle unimplemented library units in
8370 The abort only happens if code is being generated. Thus you can use
8371 specs of unimplemented packages in syntax or semantic checking mode.
8373 @node Pragma Universal_Aliasing,Pragma Universal_Data,Pragma Unimplemented_Unit,Implementation Defined Pragmas
8374 @anchor{gnat_rm/implementation_defined_pragmas pragma-universal-aliasing}@anchor{106}@anchor{gnat_rm/implementation_defined_pragmas id48}@anchor{107}
8375 @section Pragma Universal_Aliasing
8381 pragma Universal_Aliasing [([Entity =>] type_LOCAL_NAME)];
8384 @code{type_LOCAL_NAME} must refer to a type declaration in the current
8385 declarative part. The effect is to inhibit strict type-based aliasing
8386 optimization for the given type. In other words, the effect is as though
8387 access types designating this type were subject to pragma No_Strict_Aliasing.
8388 For a detailed description of the strict aliasing optimization, and the
8389 situations in which it must be suppressed, see the section on
8390 @code{Optimization and Strict Aliasing} in the @cite{GNAT User's Guide}.
8392 @node Pragma Universal_Data,Pragma Unmodified,Pragma Universal_Aliasing,Implementation Defined Pragmas
8393 @anchor{gnat_rm/implementation_defined_pragmas pragma-universal-data}@anchor{108}@anchor{gnat_rm/implementation_defined_pragmas id49}@anchor{109}
8394 @section Pragma Universal_Data
8400 pragma Universal_Data [(library_unit_Name)];
8403 This pragma is supported only for the AAMP target and is ignored for
8404 other targets. The pragma specifies that all library-level objects
8405 (Counter 0 data) associated with the library unit are to be accessed
8406 and updated using universal addressing (24-bit addresses for AAMP5)
8407 rather than the default of 16-bit Data Environment (DENV) addressing.
8408 Use of this pragma will generally result in less efficient code for
8409 references to global data associated with the library unit, but
8410 allows such data to be located anywhere in memory. This pragma is
8411 a library unit pragma, but can also be used as a configuration pragma
8412 (including use in the @code{gnat.adc} file). The functionality
8413 of this pragma is also available by applying the -univ switch on the
8414 compilations of units where universal addressing of the data is desired.
8416 @node Pragma Unmodified,Pragma Unreferenced,Pragma Universal_Data,Implementation Defined Pragmas
8417 @anchor{gnat_rm/implementation_defined_pragmas id50}@anchor{10a}@anchor{gnat_rm/implementation_defined_pragmas pragma-unmodified}@anchor{10b}
8418 @section Pragma Unmodified
8427 pragma Unmodified (LOCAL_NAME @{, LOCAL_NAME@});
8430 This pragma signals that the assignable entities (variables,
8431 @code{out} parameters, @code{in out} parameters) whose names are listed are
8432 deliberately not assigned in the current source unit. This
8433 suppresses warnings about the
8434 entities being referenced but not assigned, and in addition a warning will be
8435 generated if one of these entities is in fact assigned in the
8436 same unit as the pragma (or in the corresponding body, or one
8439 This is particularly useful for clearly signaling that a particular
8440 parameter is not modified, even though the spec suggests that it might
8443 For the variable case, warnings are never given for unreferenced variables
8444 whose name contains one of the substrings
8445 @code{DISCARD, DUMMY, IGNORE, JUNK, UNUSED} in any casing. Such names
8446 are typically to be used in cases where such warnings are expected.
8447 Thus it is never necessary to use @code{pragma Unmodified} for such
8448 variables, though it is harmless to do so.
8450 @node Pragma Unreferenced,Pragma Unreferenced_Objects,Pragma Unmodified,Implementation Defined Pragmas
8451 @anchor{gnat_rm/implementation_defined_pragmas pragma-unreferenced}@anchor{10c}@anchor{gnat_rm/implementation_defined_pragmas id51}@anchor{10d}
8452 @section Pragma Unreferenced
8456 @geindex unreferenced
8461 pragma Unreferenced (LOCAL_NAME @{, LOCAL_NAME@});
8462 pragma Unreferenced (library_unit_NAME @{, library_unit_NAME@});
8465 This pragma signals that the entities whose names are listed are
8466 deliberately not referenced in the current source unit after the
8467 occurrence of the pragma. This
8468 suppresses warnings about the
8469 entities being unreferenced, and in addition a warning will be
8470 generated if one of these entities is in fact subsequently referenced in the
8471 same unit as the pragma (or in the corresponding body, or one
8474 This is particularly useful for clearly signaling that a particular
8475 parameter is not referenced in some particular subprogram implementation
8476 and that this is deliberate. It can also be useful in the case of
8477 objects declared only for their initialization or finalization side
8480 If @code{LOCAL_NAME} identifies more than one matching homonym in the
8481 current scope, then the entity most recently declared is the one to which
8482 the pragma applies. Note that in the case of accept formals, the pragma
8483 Unreferenced may appear immediately after the keyword @code{do} which
8484 allows the indication of whether or not accept formals are referenced
8485 or not to be given individually for each accept statement.
8487 The left hand side of an assignment does not count as a reference for the
8488 purpose of this pragma. Thus it is fine to assign to an entity for which
8489 pragma Unreferenced is given.
8491 Note that if a warning is desired for all calls to a given subprogram,
8492 regardless of whether they occur in the same unit as the subprogram
8493 declaration, then this pragma should not be used (calls from another
8494 unit would not be flagged); pragma Obsolescent can be used instead
8495 for this purpose, see @ref{ac,,Pragma Obsolescent}.
8497 The second form of pragma @code{Unreferenced} is used within a context
8498 clause. In this case the arguments must be unit names of units previously
8499 mentioned in @code{with} clauses (similar to the usage of pragma
8500 @code{Elaborate_All}. The effect is to suppress warnings about unreferenced
8501 units and unreferenced entities within these units.
8503 For the variable case, warnings are never given for unreferenced variables
8504 whose name contains one of the substrings
8505 @code{DISCARD, DUMMY, IGNORE, JUNK, UNUSED} in any casing. Such names
8506 are typically to be used in cases where such warnings are expected.
8507 Thus it is never necessary to use @code{pragma Unreferenced} for such
8508 variables, though it is harmless to do so.
8510 @node Pragma Unreferenced_Objects,Pragma Unreserve_All_Interrupts,Pragma Unreferenced,Implementation Defined Pragmas
8511 @anchor{gnat_rm/implementation_defined_pragmas pragma-unreferenced-objects}@anchor{10e}@anchor{gnat_rm/implementation_defined_pragmas id52}@anchor{10f}
8512 @section Pragma Unreferenced_Objects
8516 @geindex unreferenced
8521 pragma Unreferenced_Objects (local_subtype_NAME @{, local_subtype_NAME@});
8524 This pragma signals that for the types or subtypes whose names are
8525 listed, objects which are declared with one of these types or subtypes may
8526 not be referenced, and if no references appear, no warnings are given.
8528 This is particularly useful for objects which are declared solely for their
8529 initialization and finalization effect. Such variables are sometimes referred
8530 to as RAII variables (Resource Acquisition Is Initialization). Using this
8531 pragma on the relevant type (most typically a limited controlled type), the
8532 compiler will automatically suppress unwanted warnings about these variables
8533 not being referenced.
8535 @node Pragma Unreserve_All_Interrupts,Pragma Unsuppress,Pragma Unreferenced_Objects,Implementation Defined Pragmas
8536 @anchor{gnat_rm/implementation_defined_pragmas pragma-unreserve-all-interrupts}@anchor{110}
8537 @section Pragma Unreserve_All_Interrupts
8543 pragma Unreserve_All_Interrupts;
8546 Normally certain interrupts are reserved to the implementation. Any attempt
8547 to attach an interrupt causes Program_Error to be raised, as described in
8548 RM C.3.2(22). A typical example is the @code{SIGINT} interrupt used in
8549 many systems for a @code{Ctrl-C} interrupt. Normally this interrupt is
8550 reserved to the implementation, so that @code{Ctrl-C} can be used to
8551 interrupt execution.
8553 If the pragma @code{Unreserve_All_Interrupts} appears anywhere in any unit in
8554 a program, then all such interrupts are unreserved. This allows the
8555 program to handle these interrupts, but disables their standard
8556 functions. For example, if this pragma is used, then pressing
8557 @code{Ctrl-C} will not automatically interrupt execution. However,
8558 a program can then handle the @code{SIGINT} interrupt as it chooses.
8560 For a full list of the interrupts handled in a specific implementation,
8561 see the source code for the spec of @code{Ada.Interrupts.Names} in
8562 file @code{a-intnam.ads}. This is a target dependent file that contains the
8563 list of interrupts recognized for a given target. The documentation in
8564 this file also specifies what interrupts are affected by the use of
8565 the @code{Unreserve_All_Interrupts} pragma.
8567 For a more general facility for controlling what interrupts can be
8568 handled, see pragma @code{Interrupt_State}, which subsumes the functionality
8569 of the @code{Unreserve_All_Interrupts} pragma.
8571 @node Pragma Unsuppress,Pragma Use_VADS_Size,Pragma Unreserve_All_Interrupts,Implementation Defined Pragmas
8572 @anchor{gnat_rm/implementation_defined_pragmas pragma-unsuppress}@anchor{111}
8573 @section Pragma Unsuppress
8579 pragma Unsuppress (IDENTIFIER [, [On =>] NAME]);
8582 This pragma undoes the effect of a previous pragma @code{Suppress}. If
8583 there is no corresponding pragma @code{Suppress} in effect, it has no
8584 effect. The range of the effect is the same as for pragma
8585 @code{Suppress}. The meaning of the arguments is identical to that used
8586 in pragma @code{Suppress}.
8588 One important application is to ensure that checks are on in cases where
8589 code depends on the checks for its correct functioning, so that the code
8590 will compile correctly even if the compiler switches are set to suppress
8591 checks. For example, in a program that depends on external names of tagged
8592 types and wants to ensure that the duplicated tag check occurs even if all
8593 run-time checks are suppressed by a compiler switch, the following
8594 configuration pragma will ensure this test is not suppressed:
8597 pragma Unsuppress (Duplicated_Tag_Check);
8600 This pragma is standard in Ada 2005. It is available in all earlier versions
8601 of Ada as an implementation-defined pragma.
8603 Note that in addition to the checks defined in the Ada RM, GNAT recogizes a
8604 number of implementation-defined check names. See the description of pragma
8605 @code{Suppress} for full details.
8607 @node Pragma Use_VADS_Size,Pragma Unused,Pragma Unsuppress,Implementation Defined Pragmas
8608 @anchor{gnat_rm/implementation_defined_pragmas pragma-use-vads-size}@anchor{112}
8609 @section Pragma Use_VADS_Size
8613 @geindex VADS compatibility
8615 @geindex Rational profile
8620 pragma Use_VADS_Size;
8623 This is a configuration pragma. In a unit to which it applies, any use
8624 of the 'Size attribute is automatically interpreted as a use of the
8625 'VADS_Size attribute. Note that this may result in incorrect semantic
8626 processing of valid Ada 95 or Ada 2005 programs. This is intended to aid in
8627 the handling of existing code which depends on the interpretation of Size
8628 as implemented in the VADS compiler. See description of the VADS_Size
8629 attribute for further details.
8631 @node Pragma Unused,Pragma Validity_Checks,Pragma Use_VADS_Size,Implementation Defined Pragmas
8632 @anchor{gnat_rm/implementation_defined_pragmas pragma-unused}@anchor{113}@anchor{gnat_rm/implementation_defined_pragmas id53}@anchor{114}
8633 @section Pragma Unused
8642 pragma Unused (LOCAL_NAME @{, LOCAL_NAME@});
8645 This pragma signals that the assignable entities (variables,
8646 @code{out} parameters, and @code{in out} parameters) whose names are listed
8647 deliberately do not get assigned or referenced in the current source unit
8648 after the occurrence of the pragma in the current source unit. This
8649 suppresses warnings about the entities that are unreferenced and/or not
8650 assigned, and, in addition, a warning will be generated if one of these
8651 entities gets assigned or subsequently referenced in the same unit as the
8652 pragma (in the corresponding body or one of its subunits).
8654 This is particularly useful for clearly signaling that a particular
8655 parameter is not modified or referenced, even though the spec suggests
8658 For the variable case, warnings are never given for unreferenced
8659 variables whose name contains one of the substrings
8660 @code{DISCARD, DUMMY, IGNORE, JUNK, UNUSED} in any casing. Such names
8661 are typically to be used in cases where such warnings are expected.
8662 Thus it is never necessary to use @code{pragma Unmodified} for such
8663 variables, though it is harmless to do so.
8665 @node Pragma Validity_Checks,Pragma Volatile,Pragma Unused,Implementation Defined Pragmas
8666 @anchor{gnat_rm/implementation_defined_pragmas pragma-validity-checks}@anchor{115}
8667 @section Pragma Validity_Checks
8673 pragma Validity_Checks (string_LITERAL | ALL_CHECKS | On | Off);
8676 This pragma is used in conjunction with compiler switches to control the
8677 built-in validity checking provided by GNAT. The compiler switches, if set
8678 provide an initial setting for the switches, and this pragma may be used
8679 to modify these settings, or the settings may be provided entirely by
8680 the use of the pragma. This pragma can be used anywhere that a pragma
8681 is legal, including use as a configuration pragma (including use in
8682 the @code{gnat.adc} file).
8684 The form with a string literal specifies which validity options are to be
8685 activated. The validity checks are first set to include only the default
8686 reference manual settings, and then a string of letters in the string
8687 specifies the exact set of options required. The form of this string
8688 is exactly as described for the @emph{-gnatVx} compiler switch (see the
8689 GNAT User's Guide for details). For example the following two
8690 methods can be used to enable validity checking for mode @code{in} and
8691 @code{in out} subprogram parameters:
8698 pragma Validity_Checks ("im");
8703 $ gcc -c -gnatVim ...
8707 The form ALL_CHECKS activates all standard checks (its use is equivalent
8708 to the use of the @code{gnatVa} switch).
8710 The forms with @code{Off} and @code{On} can be used to temporarily disable
8711 validity checks as shown in the following example:
8714 pragma Validity_Checks ("c"); -- validity checks for copies
8715 pragma Validity_Checks (Off); -- turn off validity checks
8716 A := B; -- B will not be validity checked
8717 pragma Validity_Checks (On); -- turn validity checks back on
8718 A := C; -- C will be validity checked
8721 @node Pragma Volatile,Pragma Volatile_Full_Access,Pragma Validity_Checks,Implementation Defined Pragmas
8722 @anchor{gnat_rm/implementation_defined_pragmas id54}@anchor{116}@anchor{gnat_rm/implementation_defined_pragmas pragma-volatile}@anchor{117}
8723 @section Pragma Volatile
8729 pragma Volatile (LOCAL_NAME);
8732 This pragma is defined by the Ada Reference Manual, and the GNAT
8733 implementation is fully conformant with this definition. The reason it
8734 is mentioned in this section is that a pragma of the same name was supplied
8735 in some Ada 83 compilers, including DEC Ada 83. The Ada 95 / Ada 2005
8736 implementation of pragma Volatile is upwards compatible with the
8737 implementation in DEC Ada 83.
8739 @node Pragma Volatile_Full_Access,Pragma Volatile_Function,Pragma Volatile,Implementation Defined Pragmas
8740 @anchor{gnat_rm/implementation_defined_pragmas id55}@anchor{118}@anchor{gnat_rm/implementation_defined_pragmas pragma-volatile-full-access}@anchor{119}
8741 @section Pragma Volatile_Full_Access
8747 pragma Volatile_Full_Access (LOCAL_NAME);
8750 This is similar in effect to pragma Volatile, except that any reference to the
8751 object is guaranteed to be done only with instructions that read or write all
8752 the bits of the object. Furthermore, if the object is of a composite type,
8753 then any reference to a subcomponent of the object is guaranteed to read
8754 and/or write all the bits of the object.
8756 The intention is that this be suitable for use with memory-mapped I/O devices
8757 on some machines. Note that there are two important respects in which this is
8758 different from @code{pragma Atomic}. First a reference to a @code{Volatile_Full_Access}
8759 object is not a sequential action in the RM 9.10 sense and, therefore, does
8760 not create a synchronization point. Second, in the case of @code{pragma Atomic},
8761 there is no guarantee that all the bits will be accessed if the reference
8762 is not to the whole object; the compiler is allowed (and generally will)
8763 access only part of the object in this case.
8765 It is not permissible to specify @code{Atomic} and @code{Volatile_Full_Access} for
8766 the same type or object.
8768 It is not permissible to specify @code{Volatile_Full_Access} for a composite
8769 (record or array) type or object that has an @code{Aliased} subcomponent.
8771 @node Pragma Volatile_Function,Pragma Warning_As_Error,Pragma Volatile_Full_Access,Implementation Defined Pragmas
8772 @anchor{gnat_rm/implementation_defined_pragmas id56}@anchor{11a}@anchor{gnat_rm/implementation_defined_pragmas pragma-volatile-function}@anchor{11b}
8773 @section Pragma Volatile_Function
8779 pragma Volatile_Function [ (boolean_EXPRESSION) ];
8782 For the semantics of this pragma, see the entry for aspect @code{Volatile_Function}
8783 in the SPARK 2014 Reference Manual, section 7.1.2.
8785 @node Pragma Warning_As_Error,Pragma Warnings,Pragma Volatile_Function,Implementation Defined Pragmas
8786 @anchor{gnat_rm/implementation_defined_pragmas pragma-warning-as-error}@anchor{11c}
8787 @section Pragma Warning_As_Error
8793 pragma Warning_As_Error (static_string_EXPRESSION);
8796 This configuration pragma allows the programmer to specify a set
8797 of warnings that will be treated as errors. Any warning that
8798 matches the pattern given by the pragma argument will be treated
8799 as an error. This gives more precise control than -gnatwe,
8800 which treats warnings as errors.
8802 This pragma can apply to regular warnings (messages enabled by -gnatw)
8803 and to style warnings (messages that start with "(style)",
8806 The pattern may contain asterisks, which match zero or more characters
8807 in the message. For example, you can use @code{pragma Warning_As_Error
8808 ("bits of*unused")} to treat the warning message @code{warning: 960 bits of
8809 "a" unused} as an error. All characters other than asterisk are treated
8810 as literal characters in the match. The match is case insensitive; for
8811 example XYZ matches xyz.
8813 Note that the pattern matches if it occurs anywhere within the warning
8814 message string (it is not necessary to put an asterisk at the start and
8815 the end of the message, since this is implied).
8817 Another possibility for the static_string_EXPRESSION which works whether
8818 or not error tags are enabled (@emph{-gnatw.d}) is to use a single
8819 @emph{-gnatw} tag string, enclosed in brackets,
8820 as shown in the example below, to treat one category of warnings as errors.
8821 Note that if you want to treat multiple categories of warnings as errors,
8822 you can use multiple pragma Warning_As_Error.
8824 The above use of patterns to match the message applies only to warning
8825 messages generated by the front end. This pragma can also be applied to
8826 warnings provided by the back end and mentioned in @ref{11d,,Pragma Warnings}.
8827 By using a single full @emph{-Wxxx} switch in the pragma, such warnings
8828 can also be treated as errors.
8830 The pragma can appear either in a global configuration pragma file
8831 (e.g. @code{gnat.adc}), or at the start of a file. Given a global
8832 configuration pragma file containing:
8835 pragma Warning_As_Error ("[-gnatwj]");
8838 which will treat all obsolescent feature warnings as errors, the
8839 following program compiles as shown (compile options here are
8840 @emph{-gnatwa.d -gnatl -gnatj55}).
8843 1. pragma Warning_As_Error ("*never assigned*");
8844 2. function Warnerr return String is
8847 >>> error: variable "X" is never read and
8848 never assigned [-gnatwv] [warning-as-error]
8852 >>> warning: variable "Y" is assigned but
8853 never read [-gnatwu]
8859 >>> error: use of "%" is an obsolescent
8860 feature (RM J.2(4)), use """ instead
8861 [-gnatwj] [warning-as-error]
8865 8 lines: No errors, 3 warnings (2 treated as errors)
8868 Note that this pragma does not affect the set of warnings issued in
8869 any way, it merely changes the effect of a matching warning if one
8870 is produced as a result of other warnings options. As shown in this
8871 example, if the pragma results in a warning being treated as an error,
8872 the tag is changed from "warning:" to "error:" and the string
8873 "[warning-as-error]" is appended to the end of the message.
8875 @node Pragma Warnings,Pragma Weak_External,Pragma Warning_As_Error,Implementation Defined Pragmas
8876 @anchor{gnat_rm/implementation_defined_pragmas id57}@anchor{11e}@anchor{gnat_rm/implementation_defined_pragmas pragma-warnings}@anchor{11d}
8877 @section Pragma Warnings
8883 pragma Warnings ([TOOL_NAME,] DETAILS [, REASON]);
8885 DETAILS ::= On | Off
8886 DETAILS ::= On | Off, local_NAME
8887 DETAILS ::= static_string_EXPRESSION
8888 DETAILS ::= On | Off, static_string_EXPRESSION
8890 TOOL_NAME ::= GNAT | GNATprove
8892 REASON ::= Reason => STRING_LITERAL @{& STRING_LITERAL@}
8895 Note: in Ada 83 mode, a string literal may be used in place of a static string
8896 expression (which does not exist in Ada 83).
8898 Note if the second argument of @code{DETAILS} is a @code{local_NAME} then the
8899 second form is always understood. If the intention is to use
8900 the fourth form, then you can write @code{NAME & ""} to force the
8901 intepretation as a @emph{static_string_EXPRESSION}.
8903 Note: if the first argument is a valid @code{TOOL_NAME}, it will be interpreted
8904 that way. The use of the @code{TOOL_NAME} argument is relevant only to users
8905 of SPARK and GNATprove, see last part of this section for details.
8907 Normally warnings are enabled, with the output being controlled by
8908 the command line switch. Warnings (@code{Off}) turns off generation of
8909 warnings until a Warnings (@code{On}) is encountered or the end of the
8910 current unit. If generation of warnings is turned off using this
8911 pragma, then some or all of the warning messages are suppressed,
8912 regardless of the setting of the command line switches.
8914 The @code{Reason} parameter may optionally appear as the last argument
8915 in any of the forms of this pragma. It is intended purely for the
8916 purposes of documenting the reason for the @code{Warnings} pragma.
8917 The compiler will check that the argument is a static string but
8918 otherwise ignore this argument. Other tools may provide specialized
8919 processing for this string.
8921 The form with a single argument (or two arguments if Reason present),
8922 where the first argument is @code{ON} or @code{OFF}
8923 may be used as a configuration pragma.
8925 If the @code{LOCAL_NAME} parameter is present, warnings are suppressed for
8926 the specified entity. This suppression is effective from the point where
8927 it occurs till the end of the extended scope of the variable (similar to
8928 the scope of @code{Suppress}). This form cannot be used as a configuration
8931 In the case where the first argument is other than @code{ON} or
8933 the third form with a single static_string_EXPRESSION argument (and possible
8934 reason) provides more precise
8935 control over which warnings are active. The string is a list of letters
8936 specifying which warnings are to be activated and which deactivated. The
8937 code for these letters is the same as the string used in the command
8938 line switch controlling warnings. For a brief summary, use the gnatmake
8939 command with no arguments, which will generate usage information containing
8940 the list of warnings switches supported. For
8941 full details see the section on @code{Warning Message Control} in the
8942 @cite{GNAT User's Guide}.
8943 This form can also be used as a configuration pragma.
8945 The warnings controlled by the @code{-gnatw} switch are generated by the
8946 front end of the compiler. The GCC back end can provide additional warnings
8947 and they are controlled by the @code{-W} switch. Such warnings can be
8948 identified by the appearance of a string of the form @code{[-W@{xxx@}]} in the
8949 message which designates the @code{-W@emph{xxx}} switch that controls the message.
8950 The form with a single @emph{static_string_EXPRESSION} argument also works for these
8951 warnings, but the string must be a single full @code{-W@emph{xxx}} switch in this
8952 case. The above reference lists a few examples of these additional warnings.
8954 The specified warnings will be in effect until the end of the program
8955 or another pragma @code{Warnings} is encountered. The effect of the pragma is
8956 cumulative. Initially the set of warnings is the standard default set
8957 as possibly modified by compiler switches. Then each pragma Warning
8958 modifies this set of warnings as specified. This form of the pragma may
8959 also be used as a configuration pragma.
8961 The fourth form, with an @code{On|Off} parameter and a string, is used to
8962 control individual messages, based on their text. The string argument
8963 is a pattern that is used to match against the text of individual
8964 warning messages (not including the initial "warning: " tag).
8966 The pattern may contain asterisks, which match zero or more characters in
8967 the message. For example, you can use
8968 @code{pragma Warnings (Off, "bits of*unused")} to suppress the warning
8969 message @code{warning: 960 bits of "a" unused}. No other regular
8970 expression notations are permitted. All characters other than asterisk in
8971 these three specific cases are treated as literal characters in the match.
8972 The match is case insensitive, for example XYZ matches xyz.
8974 Note that the pattern matches if it occurs anywhere within the warning
8975 message string (it is not necessary to put an asterisk at the start and
8976 the end of the message, since this is implied).
8978 The above use of patterns to match the message applies only to warning
8979 messages generated by the front end. This form of the pragma with a string
8980 argument can also be used to control warnings provided by the back end and
8981 mentioned above. By using a single full @code{-W@emph{xxx}} switch in the pragma,
8982 such warnings can be turned on and off.
8984 There are two ways to use the pragma in this form. The OFF form can be used
8985 as a configuration pragma. The effect is to suppress all warnings (if any)
8986 that match the pattern string throughout the compilation (or match the
8987 -W switch in the back end case).
8989 The second usage is to suppress a warning locally, and in this case, two
8990 pragmas must appear in sequence:
8993 pragma Warnings (Off, Pattern);
8994 ... code where given warning is to be suppressed
8995 pragma Warnings (On, Pattern);
8998 In this usage, the pattern string must match in the Off and On
8999 pragmas, and (if @emph{-gnatw.w} is given) at least one matching
9000 warning must be suppressed.
9002 Note: if the ON form is not found, then the effect of the OFF form extends
9003 until the end of the file (pragma Warnings is purely textual, so its effect
9004 does not stop at the end of the enclosing scope).
9006 Note: to write a string that will match any warning, use the string
9007 @code{"***"}. It will not work to use a single asterisk or two
9008 asterisks since this looks like an operator name. This form with three
9009 asterisks is similar in effect to specifying @code{pragma Warnings (Off)} except (if @code{-gnatw.w} is given) that a matching
9010 @code{pragma Warnings (On, "***")} will be required. This can be
9011 helpful in avoiding forgetting to turn warnings back on.
9013 Note: the debug flag @code{-gnatd.i} can be
9014 used to cause the compiler to entirely ignore all WARNINGS pragmas. This can
9015 be useful in checking whether obsolete pragmas in existing programs are hiding
9018 Note: pragma Warnings does not affect the processing of style messages. See
9019 separate entry for pragma Style_Checks for control of style messages.
9021 Users of the formal verification tool GNATprove for the SPARK subset of Ada may
9022 use the version of the pragma with a @code{TOOL_NAME} parameter.
9024 If present, @code{TOOL_NAME} is the name of a tool, currently either @code{GNAT} for the
9025 compiler or @code{GNATprove} for the formal verification tool. A given tool only
9026 takes into account pragma Warnings that do not specify a tool name, or that
9027 specify the matching tool name. This makes it possible to disable warnings
9028 selectively for each tool, and as a consequence to detect useless pragma
9029 Warnings with switch @code{-gnatw.w}.
9031 @node Pragma Weak_External,Pragma Wide_Character_Encoding,Pragma Warnings,Implementation Defined Pragmas
9032 @anchor{gnat_rm/implementation_defined_pragmas pragma-weak-external}@anchor{11f}
9033 @section Pragma Weak_External
9039 pragma Weak_External ([Entity =>] LOCAL_NAME);
9042 @code{LOCAL_NAME} must refer to an object that is declared at the library
9043 level. This pragma specifies that the given entity should be marked as a
9044 weak symbol for the linker. It is equivalent to @code{__attribute__((weak))}
9045 in GNU C and causes @code{LOCAL_NAME} to be emitted as a weak symbol instead
9046 of a regular symbol, that is to say a symbol that does not have to be
9047 resolved by the linker if used in conjunction with a pragma Import.
9049 When a weak symbol is not resolved by the linker, its address is set to
9050 zero. This is useful in writing interfaces to external modules that may
9051 or may not be linked in the final executable, for example depending on
9052 configuration settings.
9054 If a program references at run time an entity to which this pragma has been
9055 applied, and the corresponding symbol was not resolved at link time, then
9056 the execution of the program is erroneous. It is not erroneous to take the
9057 Address of such an entity, for example to guard potential references,
9058 as shown in the example below.
9060 Some file formats do not support weak symbols so not all target machines
9061 support this pragma.
9064 -- Example of the use of pragma Weak_External
9066 package External_Module is
9068 pragma Import (C, key);
9069 pragma Weak_External (key);
9070 function Present return boolean;
9071 end External_Module;
9073 with System; use System;
9074 package body External_Module is
9075 function Present return boolean is
9077 return key'Address /= System.Null_Address;
9079 end External_Module;
9082 @node Pragma Wide_Character_Encoding,,Pragma Weak_External,Implementation Defined Pragmas
9083 @anchor{gnat_rm/implementation_defined_pragmas pragma-wide-character-encoding}@anchor{120}
9084 @section Pragma Wide_Character_Encoding
9090 pragma Wide_Character_Encoding (IDENTIFIER | CHARACTER_LITERAL);
9093 This pragma specifies the wide character encoding to be used in program
9094 source text appearing subsequently. It is a configuration pragma, but may
9095 also be used at any point that a pragma is allowed, and it is permissible
9096 to have more than one such pragma in a file, allowing multiple encodings
9097 to appear within the same file.
9099 However, note that the pragma cannot immediately precede the relevant
9100 wide character, because then the previous encoding will still be in
9101 effect, causing "illegal character" errors.
9103 The argument can be an identifier or a character literal. In the identifier
9104 case, it is one of @code{HEX}, @code{UPPER}, @code{SHIFT_JIS},
9105 @code{EUC}, @code{UTF8}, or @code{BRACKETS}. In the character literal
9106 case it is correspondingly one of the characters @code{h}, @code{u},
9107 @code{s}, @code{e}, @code{8}, or @code{b}.
9109 Note that when the pragma is used within a file, it affects only the
9110 encoding within that file, and does not affect withed units, specs,
9113 @node Implementation Defined Aspects,Implementation Defined Attributes,Implementation Defined Pragmas,Top
9114 @anchor{gnat_rm/implementation_defined_aspects implementation-defined-aspects}@anchor{121}@anchor{gnat_rm/implementation_defined_aspects doc}@anchor{122}@anchor{gnat_rm/implementation_defined_aspects id1}@anchor{123}
9115 @chapter Implementation Defined Aspects
9118 Ada defines (throughout the Ada 2012 reference manual, summarized
9119 in Annex K) a set of aspects that can be specified for certain entities.
9120 These language defined aspects are implemented in GNAT in Ada 2012 mode
9121 and work as described in the Ada 2012 Reference Manual.
9123 In addition, Ada 2012 allows implementations to define additional aspects
9124 whose meaning is defined by the implementation. GNAT provides
9125 a number of these implementation-defined aspects which can be used
9126 to extend and enhance the functionality of the compiler. This section of
9127 the GNAT reference manual describes these additional aspects.
9129 Note that any program using these aspects may not be portable to
9130 other compilers (although GNAT implements this set of aspects on all
9131 platforms). Therefore if portability to other compilers is an important
9132 consideration, you should minimize the use of these aspects.
9134 Note that for many of these aspects, the effect is essentially similar
9135 to the use of a pragma or attribute specification with the same name
9136 applied to the entity. For example, if we write:
9139 type R is range 1 .. 100
9140 with Value_Size => 10;
9143 then the effect is the same as:
9146 type R is range 1 .. 100;
9147 for R'Value_Size use 10;
9153 type R is new Integer
9154 with Shared => True;
9157 then the effect is the same as:
9160 type R is new Integer;
9164 In the documentation below, such cases are simply marked
9165 as being boolean aspects equivalent to the corresponding pragma
9166 or attribute definition clause.
9169 * Aspect Abstract_State::
9171 * Aspect Async_Readers::
9172 * Aspect Async_Writers::
9173 * Aspect Constant_After_Elaboration::
9174 * Aspect Contract_Cases::
9176 * Aspect Default_Initial_Condition::
9177 * Aspect Dimension::
9178 * Aspect Dimension_System::
9179 * Aspect Disable_Controlled::
9180 * Aspect Effective_Reads::
9181 * Aspect Effective_Writes::
9182 * Aspect Extensions_Visible::
9183 * Aspect Favor_Top_Level::
9186 * Aspect Initial_Condition::
9187 * Aspect Initializes::
9188 * Aspect Inline_Always::
9189 * Aspect Invariant::
9190 * Aspect Invariant'Class::
9192 * Aspect Linker_Section::
9193 * Aspect Lock_Free::
9194 * Aspect Max_Queue_Length::
9195 * Aspect No_Caching::
9196 * Aspect No_Elaboration_Code_All::
9197 * Aspect No_Inline::
9198 * Aspect No_Tagged_Streams::
9199 * Aspect Object_Size::
9200 * Aspect Obsolescent::
9202 * Aspect Persistent_BSS::
9203 * Aspect Predicate::
9204 * Aspect Pure_Function::
9205 * Aspect Refined_Depends::
9206 * Aspect Refined_Global::
9207 * Aspect Refined_Post::
9208 * Aspect Refined_State::
9209 * Aspect Relaxed_Initialization::
9210 * Aspect Remote_Access_Type::
9211 * Aspect Secondary_Stack_Size::
9212 * Aspect Scalar_Storage_Order::
9214 * Aspect Simple_Storage_Pool::
9215 * Aspect Simple_Storage_Pool_Type::
9216 * Aspect SPARK_Mode::
9217 * Aspect Suppress_Debug_Info::
9218 * Aspect Suppress_Initialization::
9219 * Aspect Test_Case::
9220 * Aspect Thread_Local_Storage::
9221 * Aspect Universal_Aliasing::
9222 * Aspect Universal_Data::
9223 * Aspect Unmodified::
9224 * Aspect Unreferenced::
9225 * Aspect Unreferenced_Objects::
9226 * Aspect Value_Size::
9227 * Aspect Volatile_Full_Access::
9228 * Aspect Volatile_Function::
9233 @node Aspect Abstract_State,Aspect Annotate,,Implementation Defined Aspects
9234 @anchor{gnat_rm/implementation_defined_aspects aspect-abstract-state}@anchor{124}
9235 @section Aspect Abstract_State
9238 @geindex Abstract_State
9240 This aspect is equivalent to @ref{1c,,pragma Abstract_State}.
9242 @node Aspect Annotate,Aspect Async_Readers,Aspect Abstract_State,Implementation Defined Aspects
9243 @anchor{gnat_rm/implementation_defined_aspects aspect-annotate}@anchor{125}
9244 @section Aspect Annotate
9249 There are three forms of this aspect (where ID is an identifier,
9250 and ARG is a general expression),
9251 corresponding to @ref{26,,pragma Annotate}.
9256 @item @emph{Annotate => ID}
9258 Equivalent to @code{pragma Annotate (ID, Entity => Name);}
9260 @item @emph{Annotate => (ID)}
9262 Equivalent to @code{pragma Annotate (ID, Entity => Name);}
9264 @item @emph{Annotate => (ID ,ID @{, ARG@})}
9266 Equivalent to @code{pragma Annotate (ID, ID @{, ARG@}, Entity => Name);}
9269 @node Aspect Async_Readers,Aspect Async_Writers,Aspect Annotate,Implementation Defined Aspects
9270 @anchor{gnat_rm/implementation_defined_aspects aspect-async-readers}@anchor{126}
9271 @section Aspect Async_Readers
9274 @geindex Async_Readers
9276 This boolean aspect is equivalent to @ref{2d,,pragma Async_Readers}.
9278 @node Aspect Async_Writers,Aspect Constant_After_Elaboration,Aspect Async_Readers,Implementation Defined Aspects
9279 @anchor{gnat_rm/implementation_defined_aspects aspect-async-writers}@anchor{127}
9280 @section Aspect Async_Writers
9283 @geindex Async_Writers
9285 This boolean aspect is equivalent to @ref{30,,pragma Async_Writers}.
9287 @node Aspect Constant_After_Elaboration,Aspect Contract_Cases,Aspect Async_Writers,Implementation Defined Aspects
9288 @anchor{gnat_rm/implementation_defined_aspects aspect-constant-after-elaboration}@anchor{128}
9289 @section Aspect Constant_After_Elaboration
9292 @geindex Constant_After_Elaboration
9294 This aspect is equivalent to @ref{42,,pragma Constant_After_Elaboration}.
9296 @node Aspect Contract_Cases,Aspect Depends,Aspect Constant_After_Elaboration,Implementation Defined Aspects
9297 @anchor{gnat_rm/implementation_defined_aspects aspect-contract-cases}@anchor{129}
9298 @section Aspect Contract_Cases
9301 @geindex Contract_Cases
9303 This aspect is equivalent to @ref{44,,pragma Contract_Cases}, the sequence
9304 of clauses being enclosed in parentheses so that syntactically it is an
9307 @node Aspect Depends,Aspect Default_Initial_Condition,Aspect Contract_Cases,Implementation Defined Aspects
9308 @anchor{gnat_rm/implementation_defined_aspects aspect-depends}@anchor{12a}
9309 @section Aspect Depends
9314 This aspect is equivalent to @ref{53,,pragma Depends}.
9316 @node Aspect Default_Initial_Condition,Aspect Dimension,Aspect Depends,Implementation Defined Aspects
9317 @anchor{gnat_rm/implementation_defined_aspects aspect-default-initial-condition}@anchor{12b}
9318 @section Aspect Default_Initial_Condition
9321 @geindex Default_Initial_Condition
9323 This aspect is equivalent to @ref{4e,,pragma Default_Initial_Condition}.
9325 @node Aspect Dimension,Aspect Dimension_System,Aspect Default_Initial_Condition,Implementation Defined Aspects
9326 @anchor{gnat_rm/implementation_defined_aspects aspect-dimension}@anchor{12c}
9327 @section Aspect Dimension
9332 The @code{Dimension} aspect is used to specify the dimensions of a given
9333 subtype of a dimensioned numeric type. The aspect also specifies a symbol
9334 used when doing formatted output of dimensioned quantities. The syntax is:
9338 ([Symbol =>] SYMBOL, DIMENSION_VALUE @{, DIMENSION_Value@})
9340 SYMBOL ::= STRING_LITERAL | CHARACTER_LITERAL
9344 | others => RATIONAL
9345 | DISCRETE_CHOICE_LIST => RATIONAL
9347 RATIONAL ::= [-] NUMERIC_LITERAL [/ NUMERIC_LITERAL]
9350 This aspect can only be applied to a subtype whose parent type has
9351 a @code{Dimension_System} aspect. The aspect must specify values for
9352 all dimensions of the system. The rational values are the powers of the
9353 corresponding dimensions that are used by the compiler to verify that
9354 physical (numeric) computations are dimensionally consistent. For example,
9355 the computation of a force must result in dimensions (L => 1, M => 1, T => -2).
9356 For further examples of the usage
9357 of this aspect, see package @code{System.Dim.Mks}.
9358 Note that when the dimensioned type is an integer type, then any
9359 dimension value must be an integer literal.
9361 @node Aspect Dimension_System,Aspect Disable_Controlled,Aspect Dimension,Implementation Defined Aspects
9362 @anchor{gnat_rm/implementation_defined_aspects aspect-dimension-system}@anchor{12d}
9363 @section Aspect Dimension_System
9366 @geindex Dimension_System
9368 The @code{Dimension_System} aspect is used to define a system of
9369 dimensions that will be used in subsequent subtype declarations with
9370 @code{Dimension} aspects that reference this system. The syntax is:
9373 with Dimension_System => (DIMENSION @{, DIMENSION@});
9375 DIMENSION ::= ([Unit_Name =>] IDENTIFIER,
9376 [Unit_Symbol =>] SYMBOL,
9377 [Dim_Symbol =>] SYMBOL)
9379 SYMBOL ::= CHARACTER_LITERAL | STRING_LITERAL
9382 This aspect is applied to a type, which must be a numeric derived type
9383 (typically a floating-point type), that
9384 will represent values within the dimension system. Each @code{DIMENSION}
9385 corresponds to one particular dimension. A maximum of 7 dimensions may
9386 be specified. @code{Unit_Name} is the name of the dimension (for example
9387 @code{Meter}). @code{Unit_Symbol} is the shorthand used for quantities
9388 of this dimension (for example @code{m} for @code{Meter}).
9389 @code{Dim_Symbol} gives
9390 the identification within the dimension system (typically this is a
9391 single letter, e.g. @code{L} standing for length for unit name @code{Meter}).
9392 The @code{Unit_Symbol} is used in formatted output of dimensioned quantities.
9393 The @code{Dim_Symbol} is used in error messages when numeric operations have
9394 inconsistent dimensions.
9396 GNAT provides the standard definition of the International MKS system in
9397 the run-time package @code{System.Dim.Mks}. You can easily define
9398 similar packages for cgs units or British units, and define conversion factors
9399 between values in different systems. The MKS system is characterized by the
9403 type Mks_Type is new Long_Long_Float with
9404 Dimension_System => (
9405 (Unit_Name => Meter, Unit_Symbol => 'm', Dim_Symbol => 'L'),
9406 (Unit_Name => Kilogram, Unit_Symbol => "kg", Dim_Symbol => 'M'),
9407 (Unit_Name => Second, Unit_Symbol => 's', Dim_Symbol => 'T'),
9408 (Unit_Name => Ampere, Unit_Symbol => 'A', Dim_Symbol => 'I'),
9409 (Unit_Name => Kelvin, Unit_Symbol => 'K', Dim_Symbol => '@@'),
9410 (Unit_Name => Mole, Unit_Symbol => "mol", Dim_Symbol => 'N'),
9411 (Unit_Name => Candela, Unit_Symbol => "cd", Dim_Symbol => 'J'));
9414 Note that in the above type definition, we use the @code{at} symbol (@code{@@}) to
9415 represent a theta character (avoiding the use of extended Latin-1
9416 characters in this context).
9418 See section 'Performing Dimensionality Analysis in GNAT' in the GNAT Users
9419 Guide for detailed examples of use of the dimension system.
9421 @node Aspect Disable_Controlled,Aspect Effective_Reads,Aspect Dimension_System,Implementation Defined Aspects
9422 @anchor{gnat_rm/implementation_defined_aspects aspect-disable-controlled}@anchor{12e}
9423 @section Aspect Disable_Controlled
9426 @geindex Disable_Controlled
9428 The aspect @code{Disable_Controlled} is defined for controlled record types. If
9429 active, this aspect causes suppression of all related calls to @code{Initialize},
9430 @code{Adjust}, and @code{Finalize}. The intended use is for conditional compilation,
9431 where for example you might want a record to be controlled or not depending on
9432 whether some run-time check is enabled or suppressed.
9434 @node Aspect Effective_Reads,Aspect Effective_Writes,Aspect Disable_Controlled,Implementation Defined Aspects
9435 @anchor{gnat_rm/implementation_defined_aspects aspect-effective-reads}@anchor{12f}
9436 @section Aspect Effective_Reads
9439 @geindex Effective_Reads
9441 This aspect is equivalent to @ref{59,,pragma Effective_Reads}.
9443 @node Aspect Effective_Writes,Aspect Extensions_Visible,Aspect Effective_Reads,Implementation Defined Aspects
9444 @anchor{gnat_rm/implementation_defined_aspects aspect-effective-writes}@anchor{130}
9445 @section Aspect Effective_Writes
9448 @geindex Effective_Writes
9450 This aspect is equivalent to @ref{5b,,pragma Effective_Writes}.
9452 @node Aspect Extensions_Visible,Aspect Favor_Top_Level,Aspect Effective_Writes,Implementation Defined Aspects
9453 @anchor{gnat_rm/implementation_defined_aspects aspect-extensions-visible}@anchor{131}
9454 @section Aspect Extensions_Visible
9457 @geindex Extensions_Visible
9459 This aspect is equivalent to @ref{67,,pragma Extensions_Visible}.
9461 @node Aspect Favor_Top_Level,Aspect Ghost,Aspect Extensions_Visible,Implementation Defined Aspects
9462 @anchor{gnat_rm/implementation_defined_aspects aspect-favor-top-level}@anchor{132}
9463 @section Aspect Favor_Top_Level
9466 @geindex Favor_Top_Level
9468 This boolean aspect is equivalent to @ref{6c,,pragma Favor_Top_Level}.
9470 @node Aspect Ghost,Aspect Global,Aspect Favor_Top_Level,Implementation Defined Aspects
9471 @anchor{gnat_rm/implementation_defined_aspects aspect-ghost}@anchor{133}
9472 @section Aspect Ghost
9477 This aspect is equivalent to @ref{6f,,pragma Ghost}.
9479 @node Aspect Global,Aspect Initial_Condition,Aspect Ghost,Implementation Defined Aspects
9480 @anchor{gnat_rm/implementation_defined_aspects aspect-global}@anchor{134}
9481 @section Aspect Global
9486 This aspect is equivalent to @ref{71,,pragma Global}.
9488 @node Aspect Initial_Condition,Aspect Initializes,Aspect Global,Implementation Defined Aspects
9489 @anchor{gnat_rm/implementation_defined_aspects aspect-initial-condition}@anchor{135}
9490 @section Aspect Initial_Condition
9493 @geindex Initial_Condition
9495 This aspect is equivalent to @ref{7f,,pragma Initial_Condition}.
9497 @node Aspect Initializes,Aspect Inline_Always,Aspect Initial_Condition,Implementation Defined Aspects
9498 @anchor{gnat_rm/implementation_defined_aspects aspect-initializes}@anchor{136}
9499 @section Aspect Initializes
9502 @geindex Initializes
9504 This aspect is equivalent to @ref{81,,pragma Initializes}.
9506 @node Aspect Inline_Always,Aspect Invariant,Aspect Initializes,Implementation Defined Aspects
9507 @anchor{gnat_rm/implementation_defined_aspects aspect-inline-always}@anchor{137}
9508 @section Aspect Inline_Always
9511 @geindex Inline_Always
9513 This boolean aspect is equivalent to @ref{84,,pragma Inline_Always}.
9515 @node Aspect Invariant,Aspect Invariant'Class,Aspect Inline_Always,Implementation Defined Aspects
9516 @anchor{gnat_rm/implementation_defined_aspects aspect-invariant}@anchor{138}
9517 @section Aspect Invariant
9522 This aspect is equivalent to @ref{8b,,pragma Invariant}. It is a
9523 synonym for the language defined aspect @code{Type_Invariant} except
9524 that it is separately controllable using pragma @code{Assertion_Policy}.
9526 @node Aspect Invariant'Class,Aspect Iterable,Aspect Invariant,Implementation Defined Aspects
9527 @anchor{gnat_rm/implementation_defined_aspects aspect-invariant-class}@anchor{139}
9528 @section Aspect Invariant'Class
9531 @geindex Invariant'Class
9533 This aspect is equivalent to @ref{102,,pragma Type_Invariant_Class}. It is a
9534 synonym for the language defined aspect @code{Type_Invariant'Class} except
9535 that it is separately controllable using pragma @code{Assertion_Policy}.
9537 @node Aspect Iterable,Aspect Linker_Section,Aspect Invariant'Class,Implementation Defined Aspects
9538 @anchor{gnat_rm/implementation_defined_aspects aspect-iterable}@anchor{13a}
9539 @section Aspect Iterable
9544 This aspect provides a light-weight mechanism for loops and quantified
9545 expressions over container types, without the overhead imposed by the tampering
9546 checks of standard Ada 2012 iterators. The value of the aspect is an aggregate
9547 with six named components, of which the last three are optional: @code{First},
9548 @code{Next}, @code{Has_Element}, @code{Element}, @code{Last}, and @code{Previous}.
9549 When only the first three components are specified, only the
9550 @code{for .. in} form of iteration over cursors is available. When @code{Element}
9551 is specified, both this form and the @code{for .. of} form of iteration over
9552 elements are available. If the last two components are specified, reverse
9553 iterations over the container can be specified (analogous to what can be done
9554 over predefined containers that support the @code{Reverse_Iterator} interface).
9555 The following is a typical example of use:
9558 type List is private with
9559 Iterable => (First => First_Cursor,
9561 Has_Element => Cursor_Has_Element,
9562 [Element => Get_Element]);
9569 The value denoted by @code{First} must denote a primitive operation of the
9570 container type that returns a @code{Cursor}, which must a be a type declared in
9571 the container package or visible from it. For example:
9575 function First_Cursor (Cont : Container) return Cursor;
9582 The value of @code{Next} is a primitive operation of the container type that takes
9583 both a container and a cursor and yields a cursor. For example:
9587 function Advance (Cont : Container; Position : Cursor) return Cursor;
9594 The value of @code{Has_Element} is a primitive operation of the container type
9595 that takes both a container and a cursor and yields a boolean. For example:
9599 function Cursor_Has_Element (Cont : Container; Position : Cursor) return Boolean;
9606 The value of @code{Element} is a primitive operation of the container type that
9607 takes both a container and a cursor and yields an @code{Element_Type}, which must
9608 be a type declared in the container package or visible from it. For example:
9612 function Get_Element (Cont : Container; Position : Cursor) return Element_Type;
9615 This aspect is used in the GNAT-defined formal container packages.
9617 @node Aspect Linker_Section,Aspect Lock_Free,Aspect Iterable,Implementation Defined Aspects
9618 @anchor{gnat_rm/implementation_defined_aspects aspect-linker-section}@anchor{13b}
9619 @section Aspect Linker_Section
9622 @geindex Linker_Section
9624 This aspect is equivalent to @ref{93,,pragma Linker_Section}.
9626 @node Aspect Lock_Free,Aspect Max_Queue_Length,Aspect Linker_Section,Implementation Defined Aspects
9627 @anchor{gnat_rm/implementation_defined_aspects aspect-lock-free}@anchor{13c}
9628 @section Aspect Lock_Free
9633 This boolean aspect is equivalent to @ref{95,,pragma Lock_Free}.
9635 @node Aspect Max_Queue_Length,Aspect No_Caching,Aspect Lock_Free,Implementation Defined Aspects
9636 @anchor{gnat_rm/implementation_defined_aspects aspect-max-queue-length}@anchor{13d}
9637 @section Aspect Max_Queue_Length
9640 @geindex Max_Queue_Length
9642 This aspect is equivalent to @ref{9d,,pragma Max_Queue_Length}.
9644 @node Aspect No_Caching,Aspect No_Elaboration_Code_All,Aspect Max_Queue_Length,Implementation Defined Aspects
9645 @anchor{gnat_rm/implementation_defined_aspects aspect-no-caching}@anchor{13e}
9646 @section Aspect No_Caching
9651 This boolean aspect is equivalent to @ref{9f,,pragma No_Caching}.
9653 @node Aspect No_Elaboration_Code_All,Aspect No_Inline,Aspect No_Caching,Implementation Defined Aspects
9654 @anchor{gnat_rm/implementation_defined_aspects aspect-no-elaboration-code-all}@anchor{13f}
9655 @section Aspect No_Elaboration_Code_All
9658 @geindex No_Elaboration_Code_All
9660 This aspect is equivalent to @ref{a3,,pragma No_Elaboration_Code_All}
9663 @node Aspect No_Inline,Aspect No_Tagged_Streams,Aspect No_Elaboration_Code_All,Implementation Defined Aspects
9664 @anchor{gnat_rm/implementation_defined_aspects aspect-no-inline}@anchor{140}
9665 @section Aspect No_Inline
9670 This boolean aspect is equivalent to @ref{a6,,pragma No_Inline}.
9672 @node Aspect No_Tagged_Streams,Aspect Object_Size,Aspect No_Inline,Implementation Defined Aspects
9673 @anchor{gnat_rm/implementation_defined_aspects aspect-no-tagged-streams}@anchor{141}
9674 @section Aspect No_Tagged_Streams
9677 @geindex No_Tagged_Streams
9679 This aspect is equivalent to @ref{a9,,pragma No_Tagged_Streams} with an
9680 argument specifying a root tagged type (thus this aspect can only be
9681 applied to such a type).
9683 @node Aspect Object_Size,Aspect Obsolescent,Aspect No_Tagged_Streams,Implementation Defined Aspects
9684 @anchor{gnat_rm/implementation_defined_aspects aspect-object-size}@anchor{142}
9685 @section Aspect Object_Size
9688 @geindex Object_Size
9690 This aspect is equivalent to @ref{143,,attribute Object_Size}.
9692 @node Aspect Obsolescent,Aspect Part_Of,Aspect Object_Size,Implementation Defined Aspects
9693 @anchor{gnat_rm/implementation_defined_aspects aspect-obsolescent}@anchor{144}
9694 @section Aspect Obsolescent
9697 @geindex Obsolsecent
9699 This aspect is equivalent to @ref{ac,,pragma Obsolescent}. Note that the
9700 evaluation of this aspect happens at the point of occurrence, it is not
9701 delayed until the freeze point.
9703 @node Aspect Part_Of,Aspect Persistent_BSS,Aspect Obsolescent,Implementation Defined Aspects
9704 @anchor{gnat_rm/implementation_defined_aspects aspect-part-of}@anchor{145}
9705 @section Aspect Part_Of
9710 This aspect is equivalent to @ref{b4,,pragma Part_Of}.
9712 @node Aspect Persistent_BSS,Aspect Predicate,Aspect Part_Of,Implementation Defined Aspects
9713 @anchor{gnat_rm/implementation_defined_aspects aspect-persistent-bss}@anchor{146}
9714 @section Aspect Persistent_BSS
9717 @geindex Persistent_BSS
9719 This boolean aspect is equivalent to @ref{b7,,pragma Persistent_BSS}.
9721 @node Aspect Predicate,Aspect Pure_Function,Aspect Persistent_BSS,Implementation Defined Aspects
9722 @anchor{gnat_rm/implementation_defined_aspects aspect-predicate}@anchor{147}
9723 @section Aspect Predicate
9728 This aspect is equivalent to @ref{be,,pragma Predicate}. It is thus
9729 similar to the language defined aspects @code{Dynamic_Predicate}
9730 and @code{Static_Predicate} except that whether the resulting
9731 predicate is static or dynamic is controlled by the form of the
9732 expression. It is also separately controllable using pragma
9733 @code{Assertion_Policy}.
9735 @node Aspect Pure_Function,Aspect Refined_Depends,Aspect Predicate,Implementation Defined Aspects
9736 @anchor{gnat_rm/implementation_defined_aspects aspect-pure-function}@anchor{148}
9737 @section Aspect Pure_Function
9740 @geindex Pure_Function
9742 This boolean aspect is equivalent to @ref{ca,,pragma Pure_Function}.
9744 @node Aspect Refined_Depends,Aspect Refined_Global,Aspect Pure_Function,Implementation Defined Aspects
9745 @anchor{gnat_rm/implementation_defined_aspects aspect-refined-depends}@anchor{149}
9746 @section Aspect Refined_Depends
9749 @geindex Refined_Depends
9751 This aspect is equivalent to @ref{ce,,pragma Refined_Depends}.
9753 @node Aspect Refined_Global,Aspect Refined_Post,Aspect Refined_Depends,Implementation Defined Aspects
9754 @anchor{gnat_rm/implementation_defined_aspects aspect-refined-global}@anchor{14a}
9755 @section Aspect Refined_Global
9758 @geindex Refined_Global
9760 This aspect is equivalent to @ref{d0,,pragma Refined_Global}.
9762 @node Aspect Refined_Post,Aspect Refined_State,Aspect Refined_Global,Implementation Defined Aspects
9763 @anchor{gnat_rm/implementation_defined_aspects aspect-refined-post}@anchor{14b}
9764 @section Aspect Refined_Post
9767 @geindex Refined_Post
9769 This aspect is equivalent to @ref{d2,,pragma Refined_Post}.
9771 @node Aspect Refined_State,Aspect Relaxed_Initialization,Aspect Refined_Post,Implementation Defined Aspects
9772 @anchor{gnat_rm/implementation_defined_aspects aspect-refined-state}@anchor{14c}
9773 @section Aspect Refined_State
9776 @geindex Refined_State
9778 This aspect is equivalent to @ref{d4,,pragma Refined_State}.
9780 @node Aspect Relaxed_Initialization,Aspect Remote_Access_Type,Aspect Refined_State,Implementation Defined Aspects
9781 @anchor{gnat_rm/implementation_defined_aspects aspect-relaxed-initialization}@anchor{14d}
9782 @section Aspect Relaxed_Initialization
9785 @geindex Refined_Initialization
9787 For the syntax and semantics of this aspect, see the SPARK 2014 Reference
9788 Manual, section 6.10.
9790 @node Aspect Remote_Access_Type,Aspect Secondary_Stack_Size,Aspect Relaxed_Initialization,Implementation Defined Aspects
9791 @anchor{gnat_rm/implementation_defined_aspects aspect-remote-access-type}@anchor{14e}
9792 @section Aspect Remote_Access_Type
9795 @geindex Remote_Access_Type
9797 This aspect is equivalent to @ref{d8,,pragma Remote_Access_Type}.
9799 @node Aspect Secondary_Stack_Size,Aspect Scalar_Storage_Order,Aspect Remote_Access_Type,Implementation Defined Aspects
9800 @anchor{gnat_rm/implementation_defined_aspects aspect-secondary-stack-size}@anchor{14f}
9801 @section Aspect Secondary_Stack_Size
9804 @geindex Secondary_Stack_Size
9806 This aspect is equivalent to @ref{dd,,pragma Secondary_Stack_Size}.
9808 @node Aspect Scalar_Storage_Order,Aspect Shared,Aspect Secondary_Stack_Size,Implementation Defined Aspects
9809 @anchor{gnat_rm/implementation_defined_aspects aspect-scalar-storage-order}@anchor{150}
9810 @section Aspect Scalar_Storage_Order
9813 @geindex Scalar_Storage_Order
9815 This aspect is equivalent to a @ref{151,,attribute Scalar_Storage_Order}.
9817 @node Aspect Shared,Aspect Simple_Storage_Pool,Aspect Scalar_Storage_Order,Implementation Defined Aspects
9818 @anchor{gnat_rm/implementation_defined_aspects aspect-shared}@anchor{152}
9819 @section Aspect Shared
9824 This boolean aspect is equivalent to @ref{e0,,pragma Shared}
9825 and is thus a synonym for aspect @code{Atomic}.
9827 @node Aspect Simple_Storage_Pool,Aspect Simple_Storage_Pool_Type,Aspect Shared,Implementation Defined Aspects
9828 @anchor{gnat_rm/implementation_defined_aspects aspect-simple-storage-pool}@anchor{153}
9829 @section Aspect Simple_Storage_Pool
9832 @geindex Simple_Storage_Pool
9834 This aspect is equivalent to @ref{e5,,attribute Simple_Storage_Pool}.
9836 @node Aspect Simple_Storage_Pool_Type,Aspect SPARK_Mode,Aspect Simple_Storage_Pool,Implementation Defined Aspects
9837 @anchor{gnat_rm/implementation_defined_aspects aspect-simple-storage-pool-type}@anchor{154}
9838 @section Aspect Simple_Storage_Pool_Type
9841 @geindex Simple_Storage_Pool_Type
9843 This boolean aspect is equivalent to @ref{e3,,pragma Simple_Storage_Pool_Type}.
9845 @node Aspect SPARK_Mode,Aspect Suppress_Debug_Info,Aspect Simple_Storage_Pool_Type,Implementation Defined Aspects
9846 @anchor{gnat_rm/implementation_defined_aspects aspect-spark-mode}@anchor{155}
9847 @section Aspect SPARK_Mode
9852 This aspect is equivalent to @ref{eb,,pragma SPARK_Mode} and
9853 may be specified for either or both of the specification and body
9854 of a subprogram or package.
9856 @node Aspect Suppress_Debug_Info,Aspect Suppress_Initialization,Aspect SPARK_Mode,Implementation Defined Aspects
9857 @anchor{gnat_rm/implementation_defined_aspects aspect-suppress-debug-info}@anchor{156}
9858 @section Aspect Suppress_Debug_Info
9861 @geindex Suppress_Debug_Info
9863 This boolean aspect is equivalent to @ref{f3,,pragma Suppress_Debug_Info}.
9865 @node Aspect Suppress_Initialization,Aspect Test_Case,Aspect Suppress_Debug_Info,Implementation Defined Aspects
9866 @anchor{gnat_rm/implementation_defined_aspects aspect-suppress-initialization}@anchor{157}
9867 @section Aspect Suppress_Initialization
9870 @geindex Suppress_Initialization
9872 This boolean aspect is equivalent to @ref{f7,,pragma Suppress_Initialization}.
9874 @node Aspect Test_Case,Aspect Thread_Local_Storage,Aspect Suppress_Initialization,Implementation Defined Aspects
9875 @anchor{gnat_rm/implementation_defined_aspects aspect-test-case}@anchor{158}
9876 @section Aspect Test_Case
9881 This aspect is equivalent to @ref{fa,,pragma Test_Case}.
9883 @node Aspect Thread_Local_Storage,Aspect Universal_Aliasing,Aspect Test_Case,Implementation Defined Aspects
9884 @anchor{gnat_rm/implementation_defined_aspects aspect-thread-local-storage}@anchor{159}
9885 @section Aspect Thread_Local_Storage
9888 @geindex Thread_Local_Storage
9890 This boolean aspect is equivalent to @ref{fc,,pragma Thread_Local_Storage}.
9892 @node Aspect Universal_Aliasing,Aspect Universal_Data,Aspect Thread_Local_Storage,Implementation Defined Aspects
9893 @anchor{gnat_rm/implementation_defined_aspects aspect-universal-aliasing}@anchor{15a}
9894 @section Aspect Universal_Aliasing
9897 @geindex Universal_Aliasing
9899 This boolean aspect is equivalent to @ref{106,,pragma Universal_Aliasing}.
9901 @node Aspect Universal_Data,Aspect Unmodified,Aspect Universal_Aliasing,Implementation Defined Aspects
9902 @anchor{gnat_rm/implementation_defined_aspects aspect-universal-data}@anchor{15b}
9903 @section Aspect Universal_Data
9906 @geindex Universal_Data
9908 This aspect is equivalent to @ref{108,,pragma Universal_Data}.
9910 @node Aspect Unmodified,Aspect Unreferenced,Aspect Universal_Data,Implementation Defined Aspects
9911 @anchor{gnat_rm/implementation_defined_aspects aspect-unmodified}@anchor{15c}
9912 @section Aspect Unmodified
9917 This boolean aspect is equivalent to @ref{10b,,pragma Unmodified}.
9919 @node Aspect Unreferenced,Aspect Unreferenced_Objects,Aspect Unmodified,Implementation Defined Aspects
9920 @anchor{gnat_rm/implementation_defined_aspects aspect-unreferenced}@anchor{15d}
9921 @section Aspect Unreferenced
9924 @geindex Unreferenced
9926 This boolean aspect is equivalent to @ref{10c,,pragma Unreferenced}.
9928 When using the @code{-gnatX} switch, this aspect is also supported on formal
9929 parameters, which is in particular the only form possible for expression
9932 @node Aspect Unreferenced_Objects,Aspect Value_Size,Aspect Unreferenced,Implementation Defined Aspects
9933 @anchor{gnat_rm/implementation_defined_aspects aspect-unreferenced-objects}@anchor{15e}
9934 @section Aspect Unreferenced_Objects
9937 @geindex Unreferenced_Objects
9939 This boolean aspect is equivalent to @ref{10e,,pragma Unreferenced_Objects}.
9941 @node Aspect Value_Size,Aspect Volatile_Full_Access,Aspect Unreferenced_Objects,Implementation Defined Aspects
9942 @anchor{gnat_rm/implementation_defined_aspects aspect-value-size}@anchor{15f}
9943 @section Aspect Value_Size
9948 This aspect is equivalent to @ref{160,,attribute Value_Size}.
9950 @node Aspect Volatile_Full_Access,Aspect Volatile_Function,Aspect Value_Size,Implementation Defined Aspects
9951 @anchor{gnat_rm/implementation_defined_aspects aspect-volatile-full-access}@anchor{161}
9952 @section Aspect Volatile_Full_Access
9955 @geindex Volatile_Full_Access
9957 This boolean aspect is equivalent to @ref{119,,pragma Volatile_Full_Access}.
9959 @node Aspect Volatile_Function,Aspect Warnings,Aspect Volatile_Full_Access,Implementation Defined Aspects
9960 @anchor{gnat_rm/implementation_defined_aspects aspect-volatile-function}@anchor{162}
9961 @section Aspect Volatile_Function
9964 @geindex Volatile_Function
9966 This boolean aspect is equivalent to @ref{11b,,pragma Volatile_Function}.
9968 @node Aspect Warnings,,Aspect Volatile_Function,Implementation Defined Aspects
9969 @anchor{gnat_rm/implementation_defined_aspects aspect-warnings}@anchor{163}
9970 @section Aspect Warnings
9975 This aspect is equivalent to the two argument form of @ref{11d,,pragma Warnings},
9976 where the first argument is @code{ON} or @code{OFF} and the second argument
9979 @node Implementation Defined Attributes,Standard and Implementation Defined Restrictions,Implementation Defined Aspects,Top
9980 @anchor{gnat_rm/implementation_defined_attributes doc}@anchor{164}@anchor{gnat_rm/implementation_defined_attributes implementation-defined-attributes}@anchor{8}@anchor{gnat_rm/implementation_defined_attributes id1}@anchor{165}
9981 @chapter Implementation Defined Attributes
9984 Ada defines (throughout the Ada reference manual,
9985 summarized in Annex K),
9986 a set of attributes that provide useful additional functionality in all
9987 areas of the language. These language defined attributes are implemented
9988 in GNAT and work as described in the Ada Reference Manual.
9990 In addition, Ada allows implementations to define additional
9991 attributes whose meaning is defined by the implementation. GNAT provides
9992 a number of these implementation-dependent attributes which can be used
9993 to extend and enhance the functionality of the compiler. This section of
9994 the GNAT reference manual describes these additional attributes. It also
9995 describes additional implementation-dependent features of standard
9996 language-defined attributes.
9998 Note that any program using these attributes may not be portable to
9999 other compilers (although GNAT implements this set of attributes on all
10000 platforms). Therefore if portability to other compilers is an important
10001 consideration, you should minimize the use of these attributes.
10004 * Attribute Abort_Signal::
10005 * Attribute Address_Size::
10006 * Attribute Asm_Input::
10007 * Attribute Asm_Output::
10008 * Attribute Atomic_Always_Lock_Free::
10010 * Attribute Bit_Position::
10011 * Attribute Code_Address::
10012 * Attribute Compiler_Version::
10013 * Attribute Constrained::
10014 * Attribute Default_Bit_Order::
10015 * Attribute Default_Scalar_Storage_Order::
10016 * Attribute Deref::
10017 * Attribute Descriptor_Size::
10018 * Attribute Elaborated::
10019 * Attribute Elab_Body::
10020 * Attribute Elab_Spec::
10021 * Attribute Elab_Subp_Body::
10023 * Attribute Enabled::
10024 * Attribute Enum_Rep::
10025 * Attribute Enum_Val::
10026 * Attribute Epsilon::
10027 * Attribute Fast_Math::
10028 * Attribute Finalization_Size::
10029 * Attribute Fixed_Value::
10030 * Attribute From_Any::
10031 * Attribute Has_Access_Values::
10032 * Attribute Has_Discriminants::
10034 * Attribute Initialized::
10035 * Attribute Integer_Value::
10036 * Attribute Invalid_Value::
10037 * Attribute Iterable::
10038 * Attribute Large::
10039 * Attribute Library_Level::
10040 * Attribute Lock_Free::
10041 * Attribute Loop_Entry::
10042 * Attribute Machine_Size::
10043 * Attribute Mantissa::
10044 * Attribute Maximum_Alignment::
10045 * Attribute Max_Integer_Size::
10046 * Attribute Mechanism_Code::
10047 * Attribute Null_Parameter::
10048 * Attribute Object_Size::
10050 * Attribute Passed_By_Reference::
10051 * Attribute Pool_Address::
10052 * Attribute Range_Length::
10053 * Attribute Restriction_Set::
10054 * Attribute Result::
10055 * Attribute Safe_Emax::
10056 * Attribute Safe_Large::
10057 * Attribute Safe_Small::
10058 * Attribute Scalar_Storage_Order::
10059 * Attribute Simple_Storage_Pool::
10060 * Attribute Small::
10061 * Attribute Storage_Unit::
10062 * Attribute Stub_Type::
10063 * Attribute System_Allocator_Alignment::
10064 * Attribute Target_Name::
10065 * Attribute To_Address::
10066 * Attribute To_Any::
10067 * Attribute Type_Class::
10068 * Attribute Type_Key::
10069 * Attribute TypeCode::
10070 * Attribute Unconstrained_Array::
10071 * Attribute Universal_Literal_String::
10072 * Attribute Unrestricted_Access::
10073 * Attribute Update::
10074 * Attribute Valid_Scalars::
10075 * Attribute VADS_Size::
10076 * Attribute Value_Size::
10077 * Attribute Wchar_T_Size::
10078 * Attribute Word_Size::
10082 @node Attribute Abort_Signal,Attribute Address_Size,,Implementation Defined Attributes
10083 @anchor{gnat_rm/implementation_defined_attributes attribute-abort-signal}@anchor{166}
10084 @section Attribute Abort_Signal
10087 @geindex Abort_Signal
10089 @code{Standard'Abort_Signal} (@code{Standard} is the only allowed
10090 prefix) provides the entity for the special exception used to signal
10091 task abort or asynchronous transfer of control. Normally this attribute
10092 should only be used in the tasking runtime (it is highly peculiar, and
10093 completely outside the normal semantics of Ada, for a user program to
10094 intercept the abort exception).
10096 @node Attribute Address_Size,Attribute Asm_Input,Attribute Abort_Signal,Implementation Defined Attributes
10097 @anchor{gnat_rm/implementation_defined_attributes attribute-address-size}@anchor{167}
10098 @section Attribute Address_Size
10101 @geindex Size of `@w{`}Address`@w{`}
10103 @geindex Address_Size
10105 @code{Standard'Address_Size} (@code{Standard} is the only allowed
10106 prefix) is a static constant giving the number of bits in an
10107 @code{Address}. It is the same value as System.Address'Size,
10108 but has the advantage of being static, while a direct
10109 reference to System.Address'Size is nonstatic because Address
10112 @node Attribute Asm_Input,Attribute Asm_Output,Attribute Address_Size,Implementation Defined Attributes
10113 @anchor{gnat_rm/implementation_defined_attributes attribute-asm-input}@anchor{168}
10114 @section Attribute Asm_Input
10119 The @code{Asm_Input} attribute denotes a function that takes two
10120 parameters. The first is a string, the second is an expression of the
10121 type designated by the prefix. The first (string) argument is required
10122 to be a static expression, and is the constraint for the parameter,
10123 (e.g., what kind of register is required). The second argument is the
10124 value to be used as the input argument. The possible values for the
10125 constant are the same as those used in the RTL, and are dependent on
10126 the configuration file used to built the GCC back end.
10127 @ref{169,,Machine Code Insertions}
10129 @node Attribute Asm_Output,Attribute Atomic_Always_Lock_Free,Attribute Asm_Input,Implementation Defined Attributes
10130 @anchor{gnat_rm/implementation_defined_attributes attribute-asm-output}@anchor{16a}
10131 @section Attribute Asm_Output
10134 @geindex Asm_Output
10136 The @code{Asm_Output} attribute denotes a function that takes two
10137 parameters. The first is a string, the second is the name of a variable
10138 of the type designated by the attribute prefix. The first (string)
10139 argument is required to be a static expression and designates the
10140 constraint for the parameter (e.g., what kind of register is
10141 required). The second argument is the variable to be updated with the
10142 result. The possible values for constraint are the same as those used in
10143 the RTL, and are dependent on the configuration file used to build the
10144 GCC back end. If there are no output operands, then this argument may
10145 either be omitted, or explicitly given as @code{No_Output_Operands}.
10146 @ref{169,,Machine Code Insertions}
10148 @node Attribute Atomic_Always_Lock_Free,Attribute Bit,Attribute Asm_Output,Implementation Defined Attributes
10149 @anchor{gnat_rm/implementation_defined_attributes attribute-atomic-always-lock-free}@anchor{16b}
10150 @section Attribute Atomic_Always_Lock_Free
10153 @geindex Atomic_Always_Lock_Free
10155 The prefix of the @code{Atomic_Always_Lock_Free} attribute is a type.
10156 The result is a Boolean value which is True if the type has discriminants,
10157 and False otherwise. The result indicate whether atomic operations are
10158 supported by the target for the given type.
10160 @node Attribute Bit,Attribute Bit_Position,Attribute Atomic_Always_Lock_Free,Implementation Defined Attributes
10161 @anchor{gnat_rm/implementation_defined_attributes attribute-bit}@anchor{16c}
10162 @section Attribute Bit
10167 @code{obj'Bit}, where @code{obj} is any object, yields the bit
10168 offset within the storage unit (byte) that contains the first bit of
10169 storage allocated for the object. The value of this attribute is of the
10170 type @emph{universal_integer} and is always a nonnegative number smaller
10171 than @code{System.Storage_Unit}.
10173 For an object that is a variable or a constant allocated in a register,
10174 the value is zero. (The use of this attribute does not force the
10175 allocation of a variable to memory).
10177 For an object that is a formal parameter, this attribute applies
10178 to either the matching actual parameter or to a copy of the
10179 matching actual parameter.
10181 For an access object the value is zero. Note that
10182 @code{obj.all'Bit} is subject to an @code{Access_Check} for the
10183 designated object. Similarly for a record component
10184 @code{X.C'Bit} is subject to a discriminant check and
10185 @code{X(I).Bit} and @code{X(I1..I2)'Bit}
10186 are subject to index checks.
10188 This attribute is designed to be compatible with the DEC Ada 83 definition
10189 and implementation of the @code{Bit} attribute.
10191 @node Attribute Bit_Position,Attribute Code_Address,Attribute Bit,Implementation Defined Attributes
10192 @anchor{gnat_rm/implementation_defined_attributes attribute-bit-position}@anchor{16d}
10193 @section Attribute Bit_Position
10196 @geindex Bit_Position
10198 @code{R.C'Bit_Position}, where @code{R} is a record object and @code{C} is one
10199 of the fields of the record type, yields the bit
10200 offset within the record contains the first bit of
10201 storage allocated for the object. The value of this attribute is of the
10202 type @emph{universal_integer}. The value depends only on the field
10203 @code{C} and is independent of the alignment of
10204 the containing record @code{R}.
10206 @node Attribute Code_Address,Attribute Compiler_Version,Attribute Bit_Position,Implementation Defined Attributes
10207 @anchor{gnat_rm/implementation_defined_attributes attribute-code-address}@anchor{16e}
10208 @section Attribute Code_Address
10211 @geindex Code_Address
10213 @geindex Subprogram address
10215 @geindex Address of subprogram code
10217 The @code{'Address}
10218 attribute may be applied to subprograms in Ada 95 and Ada 2005, but the
10219 intended effect seems to be to provide
10220 an address value which can be used to call the subprogram by means of
10221 an address clause as in the following example:
10227 for L'Address use K'Address;
10228 pragma Import (Ada, L);
10231 A call to @code{L} is then expected to result in a call to @code{K}.
10232 In Ada 83, where there were no access-to-subprogram values, this was
10233 a common work-around for getting the effect of an indirect call.
10234 GNAT implements the above use of @code{Address} and the technique
10235 illustrated by the example code works correctly.
10237 However, for some purposes, it is useful to have the address of the start
10238 of the generated code for the subprogram. On some architectures, this is
10239 not necessarily the same as the @code{Address} value described above.
10240 For example, the @code{Address} value may reference a subprogram
10241 descriptor rather than the subprogram itself.
10243 The @code{'Code_Address} attribute, which can only be applied to
10244 subprogram entities, always returns the address of the start of the
10245 generated code of the specified subprogram, which may or may not be
10246 the same value as is returned by the corresponding @code{'Address}
10249 @node Attribute Compiler_Version,Attribute Constrained,Attribute Code_Address,Implementation Defined Attributes
10250 @anchor{gnat_rm/implementation_defined_attributes attribute-compiler-version}@anchor{16f}
10251 @section Attribute Compiler_Version
10254 @geindex Compiler_Version
10256 @code{Standard'Compiler_Version} (@code{Standard} is the only allowed
10257 prefix) yields a static string identifying the version of the compiler
10258 being used to compile the unit containing the attribute reference.
10260 @node Attribute Constrained,Attribute Default_Bit_Order,Attribute Compiler_Version,Implementation Defined Attributes
10261 @anchor{gnat_rm/implementation_defined_attributes attribute-constrained}@anchor{170}
10262 @section Attribute Constrained
10265 @geindex Constrained
10267 In addition to the usage of this attribute in the Ada RM, GNAT
10268 also permits the use of the @code{'Constrained} attribute
10269 in a generic template
10270 for any type, including types without discriminants. The value of this
10271 attribute in the generic instance when applied to a scalar type or a
10272 record type without discriminants is always @code{True}. This usage is
10273 compatible with older Ada compilers, including notably DEC Ada.
10275 @node Attribute Default_Bit_Order,Attribute Default_Scalar_Storage_Order,Attribute Constrained,Implementation Defined Attributes
10276 @anchor{gnat_rm/implementation_defined_attributes attribute-default-bit-order}@anchor{171}
10277 @section Attribute Default_Bit_Order
10280 @geindex Big endian
10282 @geindex Little endian
10284 @geindex Default_Bit_Order
10286 @code{Standard'Default_Bit_Order} (@code{Standard} is the only
10287 permissible prefix), provides the value @code{System.Default_Bit_Order}
10288 as a @code{Pos} value (0 for @code{High_Order_First}, 1 for
10289 @code{Low_Order_First}). This is used to construct the definition of
10290 @code{Default_Bit_Order} in package @code{System}.
10292 @node Attribute Default_Scalar_Storage_Order,Attribute Deref,Attribute Default_Bit_Order,Implementation Defined Attributes
10293 @anchor{gnat_rm/implementation_defined_attributes attribute-default-scalar-storage-order}@anchor{172}
10294 @section Attribute Default_Scalar_Storage_Order
10297 @geindex Big endian
10299 @geindex Little endian
10301 @geindex Default_Scalar_Storage_Order
10303 @code{Standard'Default_Scalar_Storage_Order} (@code{Standard} is the only
10304 permissible prefix), provides the current value of the default scalar storage
10305 order (as specified using pragma @code{Default_Scalar_Storage_Order}, or
10306 equal to @code{Default_Bit_Order} if unspecified) as a
10307 @code{System.Bit_Order} value. This is a static attribute.
10309 @node Attribute Deref,Attribute Descriptor_Size,Attribute Default_Scalar_Storage_Order,Implementation Defined Attributes
10310 @anchor{gnat_rm/implementation_defined_attributes attribute-deref}@anchor{173}
10311 @section Attribute Deref
10316 The attribute @code{typ'Deref(expr)} where @code{expr} is of type @code{System.Address} yields
10317 the variable of type @code{typ} that is located at the given address. It is similar
10318 to @code{(totyp (expr).all)}, where @code{totyp} is an unchecked conversion from address to
10319 a named access-to-@cite{typ} type, except that it yields a variable, so it can be
10320 used on the left side of an assignment.
10322 @node Attribute Descriptor_Size,Attribute Elaborated,Attribute Deref,Implementation Defined Attributes
10323 @anchor{gnat_rm/implementation_defined_attributes attribute-descriptor-size}@anchor{174}
10324 @section Attribute Descriptor_Size
10327 @geindex Descriptor
10329 @geindex Dope vector
10331 @geindex Descriptor_Size
10333 Nonstatic attribute @code{Descriptor_Size} returns the size in bits of the
10334 descriptor allocated for a type. The result is non-zero only for unconstrained
10335 array types and the returned value is of type universal integer. In GNAT, an
10336 array descriptor contains bounds information and is located immediately before
10337 the first element of the array.
10340 type Unconstr_Array is array (Short_Short_Integer range <>) of Positive;
10341 Put_Line ("Descriptor size = " & Unconstr_Array'Descriptor_Size'Img);
10344 The attribute takes into account any padding due to the alignment of the
10345 component type. In the example above, the descriptor contains two values
10346 of type @code{Short_Short_Integer} representing the low and high bound. But,
10347 since @code{Positive} has an alignment of 4, the size of the descriptor is
10348 @code{2 * Short_Short_Integer'Size} rounded up to the next multiple of 32,
10349 which yields a size of 32 bits, i.e. including 16 bits of padding.
10351 @node Attribute Elaborated,Attribute Elab_Body,Attribute Descriptor_Size,Implementation Defined Attributes
10352 @anchor{gnat_rm/implementation_defined_attributes attribute-elaborated}@anchor{175}
10353 @section Attribute Elaborated
10356 @geindex Elaborated
10358 The prefix of the @code{'Elaborated} attribute must be a unit name. The
10359 value is a Boolean which indicates whether or not the given unit has been
10360 elaborated. This attribute is primarily intended for internal use by the
10361 generated code for dynamic elaboration checking, but it can also be used
10362 in user programs. The value will always be True once elaboration of all
10363 units has been completed. An exception is for units which need no
10364 elaboration, the value is always False for such units.
10366 @node Attribute Elab_Body,Attribute Elab_Spec,Attribute Elaborated,Implementation Defined Attributes
10367 @anchor{gnat_rm/implementation_defined_attributes attribute-elab-body}@anchor{176}
10368 @section Attribute Elab_Body
10373 This attribute can only be applied to a program unit name. It returns
10374 the entity for the corresponding elaboration procedure for elaborating
10375 the body of the referenced unit. This is used in the main generated
10376 elaboration procedure by the binder and is not normally used in any
10377 other context. However, there may be specialized situations in which it
10378 is useful to be able to call this elaboration procedure from Ada code,
10379 e.g., if it is necessary to do selective re-elaboration to fix some
10382 @node Attribute Elab_Spec,Attribute Elab_Subp_Body,Attribute Elab_Body,Implementation Defined Attributes
10383 @anchor{gnat_rm/implementation_defined_attributes attribute-elab-spec}@anchor{177}
10384 @section Attribute Elab_Spec
10389 This attribute can only be applied to a program unit name. It returns
10390 the entity for the corresponding elaboration procedure for elaborating
10391 the spec of the referenced unit. This is used in the main
10392 generated elaboration procedure by the binder and is not normally used
10393 in any other context. However, there may be specialized situations in
10394 which it is useful to be able to call this elaboration procedure from
10395 Ada code, e.g., if it is necessary to do selective re-elaboration to fix
10398 @node Attribute Elab_Subp_Body,Attribute Emax,Attribute Elab_Spec,Implementation Defined Attributes
10399 @anchor{gnat_rm/implementation_defined_attributes attribute-elab-subp-body}@anchor{178}
10400 @section Attribute Elab_Subp_Body
10403 @geindex Elab_Subp_Body
10405 This attribute can only be applied to a library level subprogram
10406 name and is only allowed in CodePeer mode. It returns the entity
10407 for the corresponding elaboration procedure for elaborating the body
10408 of the referenced subprogram unit. This is used in the main generated
10409 elaboration procedure by the binder in CodePeer mode only and is unrecognized
10412 @node Attribute Emax,Attribute Enabled,Attribute Elab_Subp_Body,Implementation Defined Attributes
10413 @anchor{gnat_rm/implementation_defined_attributes attribute-emax}@anchor{179}
10414 @section Attribute Emax
10417 @geindex Ada 83 attributes
10421 The @code{Emax} attribute is provided for compatibility with Ada 83. See
10422 the Ada 83 reference manual for an exact description of the semantics of
10425 @node Attribute Enabled,Attribute Enum_Rep,Attribute Emax,Implementation Defined Attributes
10426 @anchor{gnat_rm/implementation_defined_attributes attribute-enabled}@anchor{17a}
10427 @section Attribute Enabled
10432 The @code{Enabled} attribute allows an application program to check at compile
10433 time to see if the designated check is currently enabled. The prefix is a
10434 simple identifier, referencing any predefined check name (other than
10435 @code{All_Checks}) or a check name introduced by pragma Check_Name. If
10436 no argument is given for the attribute, the check is for the general state
10437 of the check, if an argument is given, then it is an entity name, and the
10438 check indicates whether an @code{Suppress} or @code{Unsuppress} has been
10439 given naming the entity (if not, then the argument is ignored).
10441 Note that instantiations inherit the check status at the point of the
10442 instantiation, so a useful idiom is to have a library package that
10443 introduces a check name with @code{pragma Check_Name}, and then contains
10444 generic packages or subprograms which use the @code{Enabled} attribute
10445 to see if the check is enabled. A user of this package can then issue
10446 a @code{pragma Suppress} or @code{pragma Unsuppress} before instantiating
10447 the package or subprogram, controlling whether the check will be present.
10449 @node Attribute Enum_Rep,Attribute Enum_Val,Attribute Enabled,Implementation Defined Attributes
10450 @anchor{gnat_rm/implementation_defined_attributes attribute-enum-rep}@anchor{17b}
10451 @section Attribute Enum_Rep
10454 @geindex Representation of enums
10458 Note that this attribute is now standard in Ada 202x and is available
10459 as an implementation defined attribute for earlier Ada versions.
10461 For every enumeration subtype @code{S}, @code{S'Enum_Rep} denotes a
10462 function with the following spec:
10465 function S'Enum_Rep (Arg : S'Base) return <Universal_Integer>;
10468 It is also allowable to apply @code{Enum_Rep} directly to an object of an
10469 enumeration type or to a non-overloaded enumeration
10470 literal. In this case @code{S'Enum_Rep} is equivalent to
10471 @code{typ'Enum_Rep(S)} where @code{typ} is the type of the
10472 enumeration literal or object.
10474 The function returns the representation value for the given enumeration
10475 value. This will be equal to value of the @code{Pos} attribute in the
10476 absence of an enumeration representation clause. This is a static
10477 attribute (i.e., the result is static if the argument is static).
10479 @code{S'Enum_Rep} can also be used with integer types and objects,
10480 in which case it simply returns the integer value. The reason for this
10481 is to allow it to be used for @code{(<>)} discrete formal arguments in
10482 a generic unit that can be instantiated with either enumeration types
10483 or integer types. Note that if @code{Enum_Rep} is used on a modular
10484 type whose upper bound exceeds the upper bound of the largest signed
10485 integer type, and the argument is a variable, so that the universal
10486 integer calculation is done at run time, then the call to @code{Enum_Rep}
10487 may raise @code{Constraint_Error}.
10489 @node Attribute Enum_Val,Attribute Epsilon,Attribute Enum_Rep,Implementation Defined Attributes
10490 @anchor{gnat_rm/implementation_defined_attributes attribute-enum-val}@anchor{17c}
10491 @section Attribute Enum_Val
10494 @geindex Representation of enums
10498 Note that this attribute is now standard in Ada 202x and is available
10499 as an implementation defined attribute for earlier Ada versions.
10501 For every enumeration subtype @code{S}, @code{S'Enum_Val} denotes a
10502 function with the following spec:
10505 function S'Enum_Val (Arg : <Universal_Integer>) return S'Base;
10508 The function returns the enumeration value whose representation matches the
10509 argument, or raises Constraint_Error if no enumeration literal of the type
10510 has the matching value.
10511 This will be equal to value of the @code{Val} attribute in the
10512 absence of an enumeration representation clause. This is a static
10513 attribute (i.e., the result is static if the argument is static).
10515 @node Attribute Epsilon,Attribute Fast_Math,Attribute Enum_Val,Implementation Defined Attributes
10516 @anchor{gnat_rm/implementation_defined_attributes attribute-epsilon}@anchor{17d}
10517 @section Attribute Epsilon
10520 @geindex Ada 83 attributes
10524 The @code{Epsilon} attribute is provided for compatibility with Ada 83. See
10525 the Ada 83 reference manual for an exact description of the semantics of
10528 @node Attribute Fast_Math,Attribute Finalization_Size,Attribute Epsilon,Implementation Defined Attributes
10529 @anchor{gnat_rm/implementation_defined_attributes attribute-fast-math}@anchor{17e}
10530 @section Attribute Fast_Math
10535 @code{Standard'Fast_Math} (@code{Standard} is the only allowed
10536 prefix) yields a static Boolean value that is True if pragma
10537 @code{Fast_Math} is active, and False otherwise.
10539 @node Attribute Finalization_Size,Attribute Fixed_Value,Attribute Fast_Math,Implementation Defined Attributes
10540 @anchor{gnat_rm/implementation_defined_attributes attribute-finalization-size}@anchor{17f}
10541 @section Attribute Finalization_Size
10544 @geindex Finalization_Size
10546 The prefix of attribute @code{Finalization_Size} must be an object or
10547 a non-class-wide type. This attribute returns the size of any hidden data
10548 reserved by the compiler to handle finalization-related actions. The type of
10549 the attribute is @emph{universal_integer}.
10551 @code{Finalization_Size} yields a value of zero for a type with no controlled
10552 parts, an object whose type has no controlled parts, or an object of a
10553 class-wide type whose tag denotes a type with no controlled parts.
10555 Note that only heap-allocated objects contain finalization data.
10557 @node Attribute Fixed_Value,Attribute From_Any,Attribute Finalization_Size,Implementation Defined Attributes
10558 @anchor{gnat_rm/implementation_defined_attributes attribute-fixed-value}@anchor{180}
10559 @section Attribute Fixed_Value
10562 @geindex Fixed_Value
10564 For every fixed-point type @code{S}, @code{S'Fixed_Value} denotes a
10565 function with the following specification:
10568 function S'Fixed_Value (Arg : <Universal_Integer>) return S;
10571 The value returned is the fixed-point value @code{V} such that:
10577 The effect is thus similar to first converting the argument to the
10578 integer type used to represent @code{S}, and then doing an unchecked
10579 conversion to the fixed-point type. The difference is
10580 that there are full range checks, to ensure that the result is in range.
10581 This attribute is primarily intended for use in implementation of the
10582 input-output functions for fixed-point values.
10584 @node Attribute From_Any,Attribute Has_Access_Values,Attribute Fixed_Value,Implementation Defined Attributes
10585 @anchor{gnat_rm/implementation_defined_attributes attribute-from-any}@anchor{181}
10586 @section Attribute From_Any
10591 This internal attribute is used for the generation of remote subprogram
10592 stubs in the context of the Distributed Systems Annex.
10594 @node Attribute Has_Access_Values,Attribute Has_Discriminants,Attribute From_Any,Implementation Defined Attributes
10595 @anchor{gnat_rm/implementation_defined_attributes attribute-has-access-values}@anchor{182}
10596 @section Attribute Has_Access_Values
10599 @geindex Access values
10600 @geindex testing for
10602 @geindex Has_Access_Values
10604 The prefix of the @code{Has_Access_Values} attribute is a type. The result
10605 is a Boolean value which is True if the is an access type, or is a composite
10606 type with a component (at any nesting depth) that is an access type, and is
10608 The intended use of this attribute is in conjunction with generic
10609 definitions. If the attribute is applied to a generic private type, it
10610 indicates whether or not the corresponding actual type has access values.
10612 @node Attribute Has_Discriminants,Attribute Img,Attribute Has_Access_Values,Implementation Defined Attributes
10613 @anchor{gnat_rm/implementation_defined_attributes attribute-has-discriminants}@anchor{183}
10614 @section Attribute Has_Discriminants
10617 @geindex Discriminants
10618 @geindex testing for
10620 @geindex Has_Discriminants
10622 The prefix of the @code{Has_Discriminants} attribute is a type. The result
10623 is a Boolean value which is True if the type has discriminants, and False
10624 otherwise. The intended use of this attribute is in conjunction with generic
10625 definitions. If the attribute is applied to a generic private type, it
10626 indicates whether or not the corresponding actual type has discriminants.
10628 @node Attribute Img,Attribute Initialized,Attribute Has_Discriminants,Implementation Defined Attributes
10629 @anchor{gnat_rm/implementation_defined_attributes attribute-img}@anchor{184}
10630 @section Attribute Img
10635 The @code{Img} attribute differs from @code{Image} in that, while both can be
10636 applied directly to an object, @code{Img} cannot be applied to types.
10638 Example usage of the attribute:
10641 Put_Line ("X = " & X'Img);
10644 which has the same meaning as the more verbose:
10647 Put_Line ("X = " & T'Image (X));
10650 where @code{T} is the (sub)type of the object @code{X}.
10652 Note that technically, in analogy to @code{Image},
10653 @code{X'Img} returns a parameterless function
10654 that returns the appropriate string when called. This means that
10655 @code{X'Img} can be renamed as a function-returning-string, or used
10656 in an instantiation as a function parameter.
10658 @node Attribute Initialized,Attribute Integer_Value,Attribute Img,Implementation Defined Attributes
10659 @anchor{gnat_rm/implementation_defined_attributes attribute-initialized}@anchor{185}
10660 @section Attribute Initialized
10663 @geindex Initialized
10665 For the syntax and semantics of this attribute, see the SPARK 2014 Reference
10666 Manual, section 6.10.
10668 @node Attribute Integer_Value,Attribute Invalid_Value,Attribute Initialized,Implementation Defined Attributes
10669 @anchor{gnat_rm/implementation_defined_attributes attribute-integer-value}@anchor{186}
10670 @section Attribute Integer_Value
10673 @geindex Integer_Value
10675 For every integer type @code{S}, @code{S'Integer_Value} denotes a
10676 function with the following spec:
10679 function S'Integer_Value (Arg : <Universal_Fixed>) return S;
10682 The value returned is the integer value @code{V}, such that:
10688 where @code{T} is the type of @code{Arg}.
10689 The effect is thus similar to first doing an unchecked conversion from
10690 the fixed-point type to its corresponding implementation type, and then
10691 converting the result to the target integer type. The difference is
10692 that there are full range checks, to ensure that the result is in range.
10693 This attribute is primarily intended for use in implementation of the
10694 standard input-output functions for fixed-point values.
10696 @node Attribute Invalid_Value,Attribute Iterable,Attribute Integer_Value,Implementation Defined Attributes
10697 @anchor{gnat_rm/implementation_defined_attributes attribute-invalid-value}@anchor{187}
10698 @section Attribute Invalid_Value
10701 @geindex Invalid_Value
10703 For every scalar type S, S'Invalid_Value returns an undefined value of the
10704 type. If possible this value is an invalid representation for the type. The
10705 value returned is identical to the value used to initialize an otherwise
10706 uninitialized value of the type if pragma Initialize_Scalars is used,
10707 including the ability to modify the value with the binder -Sxx flag and
10708 relevant environment variables at run time.
10710 @node Attribute Iterable,Attribute Large,Attribute Invalid_Value,Implementation Defined Attributes
10711 @anchor{gnat_rm/implementation_defined_attributes attribute-iterable}@anchor{188}
10712 @section Attribute Iterable
10717 Equivalent to Aspect Iterable.
10719 @node Attribute Large,Attribute Library_Level,Attribute Iterable,Implementation Defined Attributes
10720 @anchor{gnat_rm/implementation_defined_attributes attribute-large}@anchor{189}
10721 @section Attribute Large
10724 @geindex Ada 83 attributes
10728 The @code{Large} attribute is provided for compatibility with Ada 83. See
10729 the Ada 83 reference manual for an exact description of the semantics of
10732 @node Attribute Library_Level,Attribute Lock_Free,Attribute Large,Implementation Defined Attributes
10733 @anchor{gnat_rm/implementation_defined_attributes attribute-library-level}@anchor{18a}
10734 @section Attribute Library_Level
10737 @geindex Library_Level
10739 @code{P'Library_Level}, where P is an entity name,
10740 returns a Boolean value which is True if the entity is declared
10741 at the library level, and False otherwise. Note that within a
10742 generic instantition, the name of the generic unit denotes the
10743 instance, which means that this attribute can be used to test
10744 if a generic is instantiated at the library level, as shown
10751 pragma Compile_Time_Error
10752 (not Gen'Library_Level,
10753 "Gen can only be instantiated at library level");
10758 @node Attribute Lock_Free,Attribute Loop_Entry,Attribute Library_Level,Implementation Defined Attributes
10759 @anchor{gnat_rm/implementation_defined_attributes attribute-lock-free}@anchor{18b}
10760 @section Attribute Lock_Free
10765 @code{P'Lock_Free}, where P is a protected object, returns True if a
10766 pragma @code{Lock_Free} applies to P.
10768 @node Attribute Loop_Entry,Attribute Machine_Size,Attribute Lock_Free,Implementation Defined Attributes
10769 @anchor{gnat_rm/implementation_defined_attributes attribute-loop-entry}@anchor{18c}
10770 @section Attribute Loop_Entry
10773 @geindex Loop_Entry
10778 X'Loop_Entry [(loop_name)]
10781 The @code{Loop_Entry} attribute is used to refer to the value that an
10782 expression had upon entry to a given loop in much the same way that the
10783 @code{Old} attribute in a subprogram postcondition can be used to refer
10784 to the value an expression had upon entry to the subprogram. The
10785 relevant loop is either identified by the given loop name, or it is the
10786 innermost enclosing loop when no loop name is given.
10788 A @code{Loop_Entry} attribute can only occur within a
10789 @code{Loop_Variant} or @code{Loop_Invariant} pragma. A common use of
10790 @code{Loop_Entry} is to compare the current value of objects with their
10791 initial value at loop entry, in a @code{Loop_Invariant} pragma.
10793 The effect of using @code{X'Loop_Entry} is the same as declaring
10794 a constant initialized with the initial value of @code{X} at loop
10795 entry. This copy is not performed if the loop is not entered, or if the
10796 corresponding pragmas are ignored or disabled.
10798 @node Attribute Machine_Size,Attribute Mantissa,Attribute Loop_Entry,Implementation Defined Attributes
10799 @anchor{gnat_rm/implementation_defined_attributes attribute-machine-size}@anchor{18d}
10800 @section Attribute Machine_Size
10803 @geindex Machine_Size
10805 This attribute is identical to the @code{Object_Size} attribute. It is
10806 provided for compatibility with the DEC Ada 83 attribute of this name.
10808 @node Attribute Mantissa,Attribute Maximum_Alignment,Attribute Machine_Size,Implementation Defined Attributes
10809 @anchor{gnat_rm/implementation_defined_attributes attribute-mantissa}@anchor{18e}
10810 @section Attribute Mantissa
10813 @geindex Ada 83 attributes
10817 The @code{Mantissa} attribute is provided for compatibility with Ada 83. See
10818 the Ada 83 reference manual for an exact description of the semantics of
10821 @node Attribute Maximum_Alignment,Attribute Max_Integer_Size,Attribute Mantissa,Implementation Defined Attributes
10822 @anchor{gnat_rm/implementation_defined_attributes attribute-maximum-alignment}@anchor{18f}@anchor{gnat_rm/implementation_defined_attributes id2}@anchor{190}
10823 @section Attribute Maximum_Alignment
10829 @geindex Maximum_Alignment
10831 @code{Standard'Maximum_Alignment} (@code{Standard} is the only
10832 permissible prefix) provides the maximum useful alignment value for the
10833 target. This is a static value that can be used to specify the alignment
10834 for an object, guaranteeing that it is properly aligned in all
10837 @node Attribute Max_Integer_Size,Attribute Mechanism_Code,Attribute Maximum_Alignment,Implementation Defined Attributes
10838 @anchor{gnat_rm/implementation_defined_attributes attribute-max-integer-size}@anchor{191}
10839 @section Attribute Max_Integer_Size
10842 @geindex Max_Integer_Size
10844 @code{Standard'Max_Integer_Size} (@code{Standard} is the only permissible
10845 prefix) provides the size of the largest supported integer type for
10846 the target. The result is a static constant.
10848 @node Attribute Mechanism_Code,Attribute Null_Parameter,Attribute Max_Integer_Size,Implementation Defined Attributes
10849 @anchor{gnat_rm/implementation_defined_attributes attribute-mechanism-code}@anchor{192}
10850 @section Attribute Mechanism_Code
10853 @geindex Return values
10854 @geindex passing mechanism
10856 @geindex Parameters
10857 @geindex passing mechanism
10859 @geindex Mechanism_Code
10861 @code{func'Mechanism_Code} yields an integer code for the
10862 mechanism used for the result of function @code{func}, and
10863 @code{subprog'Mechanism_Code (n)} yields the mechanism
10864 used for formal parameter number @emph{n} (a static integer value, with 1
10865 meaning the first parameter) of subprogram @code{subprog}. The code returned is:
10879 @node Attribute Null_Parameter,Attribute Object_Size,Attribute Mechanism_Code,Implementation Defined Attributes
10880 @anchor{gnat_rm/implementation_defined_attributes attribute-null-parameter}@anchor{193}
10881 @section Attribute Null_Parameter
10884 @geindex Zero address
10887 @geindex Null_Parameter
10889 A reference @code{T'Null_Parameter} denotes an imaginary object of
10890 type or subtype @code{T} allocated at machine address zero. The attribute
10891 is allowed only as the default expression of a formal parameter, or as
10892 an actual expression of a subprogram call. In either case, the
10893 subprogram must be imported.
10895 The identity of the object is represented by the address zero in the
10896 argument list, independent of the passing mechanism (explicit or
10899 This capability is needed to specify that a zero address should be
10900 passed for a record or other composite object passed by reference.
10901 There is no way of indicating this without the @code{Null_Parameter}
10904 @node Attribute Object_Size,Attribute Old,Attribute Null_Parameter,Implementation Defined Attributes
10905 @anchor{gnat_rm/implementation_defined_attributes attribute-object-size}@anchor{143}@anchor{gnat_rm/implementation_defined_attributes id3}@anchor{194}
10906 @section Attribute Object_Size
10910 @geindex used for objects
10912 @geindex Object_Size
10914 The size of an object is not necessarily the same as the size of the type
10915 of an object. This is because by default object sizes are increased to be
10916 a multiple of the alignment of the object. For example,
10917 @code{Natural'Size} is
10918 31, but by default objects of type @code{Natural} will have a size of 32 bits.
10919 Similarly, a record containing an integer and a character:
10928 will have a size of 40 (that is @code{Rec'Size} will be 40). The
10929 alignment will be 4, because of the
10930 integer field, and so the default size of record objects for this type
10931 will be 64 (8 bytes).
10933 If the alignment of the above record is specified to be 1, then the
10934 object size will be 40 (5 bytes). This is true by default, and also
10935 an object size of 40 can be explicitly specified in this case.
10937 A consequence of this capability is that different object sizes can be
10938 given to subtypes that would otherwise be considered in Ada to be
10939 statically matching. But it makes no sense to consider such subtypes
10940 as statically matching. Consequently, GNAT adds a rule
10941 to the static matching rules that requires object sizes to match.
10942 Consider this example:
10945 1. procedure BadAVConvert is
10946 2. type R is new Integer;
10947 3. subtype R1 is R range 1 .. 10;
10948 4. subtype R2 is R range 1 .. 10;
10949 5. for R1'Object_Size use 8;
10950 6. for R2'Object_Size use 16;
10951 7. type R1P is access all R1;
10952 8. type R2P is access all R2;
10953 9. R1PV : R1P := new R1'(4);
10956 12. R2PV := R2P (R1PV);
10958 >>> target designated subtype not compatible with
10959 type "R1" defined at line 3
10964 In the absence of lines 5 and 6,
10965 types @code{R1} and @code{R2} statically match and
10966 hence the conversion on line 12 is legal. But since lines 5 and 6
10967 cause the object sizes to differ, GNAT considers that types
10968 @code{R1} and @code{R2} are not statically matching, and line 12
10969 generates the diagnostic shown above.
10971 Similar additional checks are performed in other contexts requiring
10972 statically matching subtypes.
10974 @node Attribute Old,Attribute Passed_By_Reference,Attribute Object_Size,Implementation Defined Attributes
10975 @anchor{gnat_rm/implementation_defined_attributes attribute-old}@anchor{195}
10976 @section Attribute Old
10981 In addition to the usage of @code{Old} defined in the Ada 2012 RM (usage
10982 within @code{Post} aspect), GNAT also permits the use of this attribute
10983 in implementation defined pragmas @code{Postcondition},
10984 @code{Contract_Cases} and @code{Test_Case}. Also usages of
10985 @code{Old} which would be illegal according to the Ada 2012 RM
10986 definition are allowed under control of
10987 implementation defined pragma @code{Unevaluated_Use_Of_Old}.
10989 @node Attribute Passed_By_Reference,Attribute Pool_Address,Attribute Old,Implementation Defined Attributes
10990 @anchor{gnat_rm/implementation_defined_attributes attribute-passed-by-reference}@anchor{196}
10991 @section Attribute Passed_By_Reference
10994 @geindex Parameters
10995 @geindex when passed by reference
10997 @geindex Passed_By_Reference
10999 @code{typ'Passed_By_Reference} for any subtype @cite{typ} returns
11000 a value of type @code{Boolean} value that is @code{True} if the type is
11001 normally passed by reference and @code{False} if the type is normally
11002 passed by copy in calls. For scalar types, the result is always @code{False}
11003 and is static. For non-scalar types, the result is nonstatic.
11005 @node Attribute Pool_Address,Attribute Range_Length,Attribute Passed_By_Reference,Implementation Defined Attributes
11006 @anchor{gnat_rm/implementation_defined_attributes attribute-pool-address}@anchor{197}
11007 @section Attribute Pool_Address
11010 @geindex Parameters
11011 @geindex when passed by reference
11013 @geindex Pool_Address
11015 @code{X'Pool_Address} for any object @code{X} returns the address
11016 of X within its storage pool. This is the same as
11017 @code{X'Address}, except that for an unconstrained array whose
11018 bounds are allocated just before the first component,
11019 @code{X'Pool_Address} returns the address of those bounds,
11020 whereas @code{X'Address} returns the address of the first
11023 Here, we are interpreting 'storage pool' broadly to mean
11024 @code{wherever the object is allocated}, which could be a
11025 user-defined storage pool,
11026 the global heap, on the stack, or in a static memory area.
11027 For an object created by @code{new}, @code{Ptr.all'Pool_Address} is
11028 what is passed to @code{Allocate} and returned from @code{Deallocate}.
11030 @node Attribute Range_Length,Attribute Restriction_Set,Attribute Pool_Address,Implementation Defined Attributes
11031 @anchor{gnat_rm/implementation_defined_attributes attribute-range-length}@anchor{198}
11032 @section Attribute Range_Length
11035 @geindex Range_Length
11037 @code{typ'Range_Length} for any discrete type @cite{typ} yields
11038 the number of values represented by the subtype (zero for a null
11039 range). The result is static for static subtypes. @code{Range_Length}
11040 applied to the index subtype of a one dimensional array always gives the
11041 same result as @code{Length} applied to the array itself.
11043 @node Attribute Restriction_Set,Attribute Result,Attribute Range_Length,Implementation Defined Attributes
11044 @anchor{gnat_rm/implementation_defined_attributes attribute-restriction-set}@anchor{199}
11045 @section Attribute Restriction_Set
11048 @geindex Restriction_Set
11050 @geindex Restrictions
11052 This attribute allows compile time testing of restrictions that
11053 are currently in effect. It is primarily intended for specializing
11054 code in the run-time based on restrictions that are active (e.g.
11055 don't need to save fpt registers if restriction No_Floating_Point
11056 is known to be in effect), but can be used anywhere.
11058 There are two forms:
11061 System'Restriction_Set (partition_boolean_restriction_NAME)
11062 System'Restriction_Set (No_Dependence => library_unit_NAME);
11065 In the case of the first form, the only restriction names
11066 allowed are parameterless restrictions that are checked
11067 for consistency at bind time. For a complete list see the
11068 subtype @code{System.Rident.Partition_Boolean_Restrictions}.
11070 The result returned is True if the restriction is known to
11071 be in effect, and False if the restriction is known not to
11072 be in effect. An important guarantee is that the value of
11073 a Restriction_Set attribute is known to be consistent throughout
11074 all the code of a partition.
11076 This is trivially achieved if the entire partition is compiled
11077 with a consistent set of restriction pragmas. However, the
11078 compilation model does not require this. It is possible to
11079 compile one set of units with one set of pragmas, and another
11080 set of units with another set of pragmas. It is even possible
11081 to compile a spec with one set of pragmas, and then WITH the
11082 same spec with a different set of pragmas. Inconsistencies
11083 in the actual use of the restriction are checked at bind time.
11085 In order to achieve the guarantee of consistency for the
11086 Restriction_Set pragma, we consider that a use of the pragma
11087 that yields False is equivalent to a violation of the
11090 So for example if you write
11093 if System'Restriction_Set (No_Floating_Point) then
11100 And the result is False, so that the else branch is executed,
11101 you can assume that this restriction is not set for any unit
11102 in the partition. This is checked by considering this use of
11103 the restriction pragma to be a violation of the restriction
11104 No_Floating_Point. This means that no other unit can attempt
11105 to set this restriction (if some unit does attempt to set it,
11106 the binder will refuse to bind the partition).
11108 Technical note: The restriction name and the unit name are
11109 intepreted entirely syntactically, as in the corresponding
11110 Restrictions pragma, they are not analyzed semantically,
11111 so they do not have a type.
11113 @node Attribute Result,Attribute Safe_Emax,Attribute Restriction_Set,Implementation Defined Attributes
11114 @anchor{gnat_rm/implementation_defined_attributes attribute-result}@anchor{19a}
11115 @section Attribute Result
11120 @code{function'Result} can only be used with in a Postcondition pragma
11121 for a function. The prefix must be the name of the corresponding function. This
11122 is used to refer to the result of the function in the postcondition expression.
11123 For a further discussion of the use of this attribute and examples of its use,
11124 see the description of pragma Postcondition.
11126 @node Attribute Safe_Emax,Attribute Safe_Large,Attribute Result,Implementation Defined Attributes
11127 @anchor{gnat_rm/implementation_defined_attributes attribute-safe-emax}@anchor{19b}
11128 @section Attribute Safe_Emax
11131 @geindex Ada 83 attributes
11135 The @code{Safe_Emax} attribute is provided for compatibility with Ada 83. See
11136 the Ada 83 reference manual for an exact description of the semantics of
11139 @node Attribute Safe_Large,Attribute Safe_Small,Attribute Safe_Emax,Implementation Defined Attributes
11140 @anchor{gnat_rm/implementation_defined_attributes attribute-safe-large}@anchor{19c}
11141 @section Attribute Safe_Large
11144 @geindex Ada 83 attributes
11146 @geindex Safe_Large
11148 The @code{Safe_Large} attribute is provided for compatibility with Ada 83. See
11149 the Ada 83 reference manual for an exact description of the semantics of
11152 @node Attribute Safe_Small,Attribute Scalar_Storage_Order,Attribute Safe_Large,Implementation Defined Attributes
11153 @anchor{gnat_rm/implementation_defined_attributes attribute-safe-small}@anchor{19d}
11154 @section Attribute Safe_Small
11157 @geindex Ada 83 attributes
11159 @geindex Safe_Small
11161 The @code{Safe_Small} attribute is provided for compatibility with Ada 83. See
11162 the Ada 83 reference manual for an exact description of the semantics of
11165 @node Attribute Scalar_Storage_Order,Attribute Simple_Storage_Pool,Attribute Safe_Small,Implementation Defined Attributes
11166 @anchor{gnat_rm/implementation_defined_attributes id4}@anchor{19e}@anchor{gnat_rm/implementation_defined_attributes attribute-scalar-storage-order}@anchor{151}
11167 @section Attribute Scalar_Storage_Order
11170 @geindex Endianness
11172 @geindex Scalar storage order
11174 @geindex Scalar_Storage_Order
11176 For every array or record type @code{S}, the representation attribute
11177 @code{Scalar_Storage_Order} denotes the order in which storage elements
11178 that make up scalar components are ordered within S. The value given must
11179 be a static expression of type System.Bit_Order. The following is an example
11180 of the use of this feature:
11183 -- Component type definitions
11185 subtype Yr_Type is Natural range 0 .. 127;
11186 subtype Mo_Type is Natural range 1 .. 12;
11187 subtype Da_Type is Natural range 1 .. 31;
11189 -- Record declaration
11191 type Date is record
11192 Years_Since_1980 : Yr_Type;
11194 Day_Of_Month : Da_Type;
11197 -- Record representation clause
11199 for Date use record
11200 Years_Since_1980 at 0 range 0 .. 6;
11201 Month at 0 range 7 .. 10;
11202 Day_Of_Month at 0 range 11 .. 15;
11205 -- Attribute definition clauses
11207 for Date'Bit_Order use System.High_Order_First;
11208 for Date'Scalar_Storage_Order use System.High_Order_First;
11209 -- If Scalar_Storage_Order is specified, it must be consistent with
11210 -- Bit_Order, so it's best to always define the latter explicitly if
11211 -- the former is used.
11214 Other properties are as for the standard representation attribute @code{Bit_Order}
11215 defined by Ada RM 13.5.3(4). The default is @code{System.Default_Bit_Order}.
11217 For a record type @code{T}, if @code{T'Scalar_Storage_Order} is
11218 specified explicitly, it shall be equal to @code{T'Bit_Order}. Note:
11219 this means that if a @code{Scalar_Storage_Order} attribute definition
11220 clause is not confirming, then the type's @code{Bit_Order} shall be
11221 specified explicitly and set to the same value.
11223 Derived types inherit an explicitly set scalar storage order from their parent
11224 types. This may be overridden for the derived type by giving an explicit scalar
11225 storage order for it. However, for a record extension, the derived type must
11226 have the same scalar storage order as the parent type.
11228 A component of a record type that is itself a record or an array and that does
11229 not start and end on a byte boundary must have have the same scalar storage
11230 order as the record type. A component of a bit-packed array type that is itself
11231 a record or an array must have the same scalar storage order as the array type.
11233 No component of a type that has an explicit @code{Scalar_Storage_Order}
11234 attribute definition may be aliased.
11236 A confirming @code{Scalar_Storage_Order} attribute definition clause (i.e.
11237 with a value equal to @code{System.Default_Bit_Order}) has no effect.
11239 If the opposite storage order is specified, then whenever the value of
11240 a scalar component of an object of type @code{S} is read, the storage
11241 elements of the enclosing machine scalar are first reversed (before
11242 retrieving the component value, possibly applying some shift and mask
11243 operatings on the enclosing machine scalar), and the opposite operation
11244 is done for writes.
11246 In that case, the restrictions set forth in 13.5.1(10.3/2) for scalar components
11247 are relaxed. Instead, the following rules apply:
11253 the underlying storage elements are those at positions
11254 @code{(position + first_bit / storage_element_size) .. (position + (last_bit + storage_element_size - 1) / storage_element_size)}
11257 the sequence of underlying storage elements shall have
11258 a size no greater than the largest machine scalar
11261 the enclosing machine scalar is defined as the smallest machine
11262 scalar starting at a position no greater than
11263 @code{position + first_bit / storage_element_size} and covering
11264 storage elements at least up to @code{position + (last_bit + storage_element_size - 1) / storage_element_size`}
11267 the position of the component is interpreted relative to that machine
11271 If no scalar storage order is specified for a type (either directly, or by
11272 inheritance in the case of a derived type), then the default is normally
11273 the native ordering of the target, but this default can be overridden using
11274 pragma @code{Default_Scalar_Storage_Order}.
11276 If a component of @code{T} is itself of a record or array type, the specfied
11277 @code{Scalar_Storage_Order} does @emph{not} apply to that nested type: an explicit
11278 attribute definition clause must be provided for the component type as well
11281 Note that the scalar storage order only affects the in-memory data
11282 representation. It has no effect on the representation used by stream
11285 Note that debuggers may be unable to display the correct value of scalar
11286 components of a type for which the opposite storage order is specified.
11288 @node Attribute Simple_Storage_Pool,Attribute Small,Attribute Scalar_Storage_Order,Implementation Defined Attributes
11289 @anchor{gnat_rm/implementation_defined_attributes attribute-simple-storage-pool}@anchor{e5}@anchor{gnat_rm/implementation_defined_attributes id5}@anchor{19f}
11290 @section Attribute Simple_Storage_Pool
11293 @geindex Storage pool
11296 @geindex Simple storage pool
11298 @geindex Simple_Storage_Pool
11300 For every nonformal, nonderived access-to-object type @code{Acc}, the
11301 representation attribute @code{Simple_Storage_Pool} may be specified
11302 via an attribute_definition_clause (or by specifying the equivalent aspect):
11305 My_Pool : My_Simple_Storage_Pool_Type;
11307 type Acc is access My_Data_Type;
11309 for Acc'Simple_Storage_Pool use My_Pool;
11312 The name given in an attribute_definition_clause for the
11313 @code{Simple_Storage_Pool} attribute shall denote a variable of
11314 a 'simple storage pool type' (see pragma @cite{Simple_Storage_Pool_Type}).
11316 The use of this attribute is only allowed for a prefix denoting a type
11317 for which it has been specified. The type of the attribute is the type
11318 of the variable specified as the simple storage pool of the access type,
11319 and the attribute denotes that variable.
11321 It is illegal to specify both @code{Storage_Pool} and @code{Simple_Storage_Pool}
11322 for the same access type.
11324 If the @code{Simple_Storage_Pool} attribute has been specified for an access
11325 type, then applying the @code{Storage_Pool} attribute to the type is flagged
11326 with a warning and its evaluation raises the exception @code{Program_Error}.
11328 If the Simple_Storage_Pool attribute has been specified for an access
11329 type @code{S}, then the evaluation of the attribute @code{S'Storage_Size}
11330 returns the result of calling @code{Storage_Size (S'Simple_Storage_Pool)},
11331 which is intended to indicate the number of storage elements reserved for
11332 the simple storage pool. If the Storage_Size function has not been defined
11333 for the simple storage pool type, then this attribute returns zero.
11335 If an access type @code{S} has a specified simple storage pool of type
11336 @code{SSP}, then the evaluation of an allocator for that access type calls
11337 the primitive @code{Allocate} procedure for type @code{SSP}, passing
11338 @code{S'Simple_Storage_Pool} as the pool parameter. The detailed
11339 semantics of such allocators is the same as those defined for allocators
11340 in section 13.11 of the @cite{Ada Reference Manual}, with the term
11341 @emph{simple storage pool} substituted for @emph{storage pool}.
11343 If an access type @code{S} has a specified simple storage pool of type
11344 @code{SSP}, then a call to an instance of the @code{Ada.Unchecked_Deallocation}
11345 for that access type invokes the primitive @code{Deallocate} procedure
11346 for type @code{SSP}, passing @code{S'Simple_Storage_Pool} as the pool
11347 parameter. The detailed semantics of such unchecked deallocations is the same
11348 as defined in section 13.11.2 of the Ada Reference Manual, except that the
11349 term @emph{simple storage pool} is substituted for @emph{storage pool}.
11351 @node Attribute Small,Attribute Storage_Unit,Attribute Simple_Storage_Pool,Implementation Defined Attributes
11352 @anchor{gnat_rm/implementation_defined_attributes attribute-small}@anchor{1a0}
11353 @section Attribute Small
11356 @geindex Ada 83 attributes
11360 The @code{Small} attribute is defined in Ada 95 (and Ada 2005) only for
11362 GNAT also allows this attribute to be applied to floating-point types
11363 for compatibility with Ada 83. See
11364 the Ada 83 reference manual for an exact description of the semantics of
11365 this attribute when applied to floating-point types.
11367 @node Attribute Storage_Unit,Attribute Stub_Type,Attribute Small,Implementation Defined Attributes
11368 @anchor{gnat_rm/implementation_defined_attributes attribute-storage-unit}@anchor{1a1}
11369 @section Attribute Storage_Unit
11372 @geindex Storage_Unit
11374 @code{Standard'Storage_Unit} (@code{Standard} is the only permissible
11375 prefix) provides the same value as @code{System.Storage_Unit}.
11377 @node Attribute Stub_Type,Attribute System_Allocator_Alignment,Attribute Storage_Unit,Implementation Defined Attributes
11378 @anchor{gnat_rm/implementation_defined_attributes attribute-stub-type}@anchor{1a2}
11379 @section Attribute Stub_Type
11384 The GNAT implementation of remote access-to-classwide types is
11385 organized as described in AARM section E.4 (20.t): a value of an RACW type
11386 (designating a remote object) is represented as a normal access
11387 value, pointing to a "stub" object which in turn contains the
11388 necessary information to contact the designated remote object. A
11389 call on any dispatching operation of such a stub object does the
11390 remote call, if necessary, using the information in the stub object
11391 to locate the target partition, etc.
11393 For a prefix @code{T} that denotes a remote access-to-classwide type,
11394 @code{T'Stub_Type} denotes the type of the corresponding stub objects.
11396 By construction, the layout of @code{T'Stub_Type} is identical to that of
11397 type @code{RACW_Stub_Type} declared in the internal implementation-defined
11398 unit @code{System.Partition_Interface}. Use of this attribute will create
11399 an implicit dependency on this unit.
11401 @node Attribute System_Allocator_Alignment,Attribute Target_Name,Attribute Stub_Type,Implementation Defined Attributes
11402 @anchor{gnat_rm/implementation_defined_attributes attribute-system-allocator-alignment}@anchor{1a3}
11403 @section Attribute System_Allocator_Alignment
11409 @geindex System_Allocator_Alignment
11411 @code{Standard'System_Allocator_Alignment} (@code{Standard} is the only
11412 permissible prefix) provides the observable guaranted to be honored by
11413 the system allocator (malloc). This is a static value that can be used
11414 in user storage pools based on malloc either to reject allocation
11415 with alignment too large or to enable a realignment circuitry if the
11416 alignment request is larger than this value.
11418 @node Attribute Target_Name,Attribute To_Address,Attribute System_Allocator_Alignment,Implementation Defined Attributes
11419 @anchor{gnat_rm/implementation_defined_attributes attribute-target-name}@anchor{1a4}
11420 @section Attribute Target_Name
11423 @geindex Target_Name
11425 @code{Standard'Target_Name} (@code{Standard} is the only permissible
11426 prefix) provides a static string value that identifies the target
11427 for the current compilation. For GCC implementations, this is the
11428 standard gcc target name without the terminating slash (for
11429 example, GNAT 5.0 on windows yields "i586-pc-mingw32msv").
11431 @node Attribute To_Address,Attribute To_Any,Attribute Target_Name,Implementation Defined Attributes
11432 @anchor{gnat_rm/implementation_defined_attributes attribute-to-address}@anchor{1a5}
11433 @section Attribute To_Address
11436 @geindex To_Address
11438 The @code{System'To_Address}
11439 (@code{System} is the only permissible prefix)
11440 denotes a function identical to
11441 @code{System.Storage_Elements.To_Address} except that
11442 it is a static attribute. This means that if its argument is
11443 a static expression, then the result of the attribute is a
11444 static expression. This means that such an expression can be
11445 used in contexts (e.g., preelaborable packages) which require a
11446 static expression and where the function call could not be used
11447 (since the function call is always nonstatic, even if its
11448 argument is static). The argument must be in the range
11449 -(2**(m-1)) .. 2**m-1, where m is the memory size
11450 (typically 32 or 64). Negative values are intepreted in a
11451 modular manner (e.g., -1 means the same as 16#FFFF_FFFF# on
11452 a 32 bits machine).
11454 @node Attribute To_Any,Attribute Type_Class,Attribute To_Address,Implementation Defined Attributes
11455 @anchor{gnat_rm/implementation_defined_attributes attribute-to-any}@anchor{1a6}
11456 @section Attribute To_Any
11461 This internal attribute is used for the generation of remote subprogram
11462 stubs in the context of the Distributed Systems Annex.
11464 @node Attribute Type_Class,Attribute Type_Key,Attribute To_Any,Implementation Defined Attributes
11465 @anchor{gnat_rm/implementation_defined_attributes attribute-type-class}@anchor{1a7}
11466 @section Attribute Type_Class
11469 @geindex Type_Class
11471 @code{typ'Type_Class} for any type or subtype @cite{typ} yields
11472 the value of the type class for the full type of @cite{typ}. If
11473 @cite{typ} is a generic formal type, the value is the value for the
11474 corresponding actual subtype. The value of this attribute is of type
11475 @code{System.Aux_DEC.Type_Class}, which has the following definition:
11479 (Type_Class_Enumeration,
11480 Type_Class_Integer,
11481 Type_Class_Fixed_Point,
11482 Type_Class_Floating_Point,
11487 Type_Class_Address);
11490 Protected types yield the value @code{Type_Class_Task}, which thus
11491 applies to all concurrent types. This attribute is designed to
11492 be compatible with the DEC Ada 83 attribute of the same name.
11494 @node Attribute Type_Key,Attribute TypeCode,Attribute Type_Class,Implementation Defined Attributes
11495 @anchor{gnat_rm/implementation_defined_attributes attribute-type-key}@anchor{1a8}
11496 @section Attribute Type_Key
11501 The @code{Type_Key} attribute is applicable to a type or subtype and
11502 yields a value of type Standard.String containing encoded information
11503 about the type or subtype. This provides improved compatibility with
11504 other implementations that support this attribute.
11506 @node Attribute TypeCode,Attribute Unconstrained_Array,Attribute Type_Key,Implementation Defined Attributes
11507 @anchor{gnat_rm/implementation_defined_attributes attribute-typecode}@anchor{1a9}
11508 @section Attribute TypeCode
11513 This internal attribute is used for the generation of remote subprogram
11514 stubs in the context of the Distributed Systems Annex.
11516 @node Attribute Unconstrained_Array,Attribute Universal_Literal_String,Attribute TypeCode,Implementation Defined Attributes
11517 @anchor{gnat_rm/implementation_defined_attributes attribute-unconstrained-array}@anchor{1aa}
11518 @section Attribute Unconstrained_Array
11521 @geindex Unconstrained_Array
11523 The @code{Unconstrained_Array} attribute can be used with a prefix that
11524 denotes any type or subtype. It is a static attribute that yields
11525 @code{True} if the prefix designates an unconstrained array,
11526 and @code{False} otherwise. In a generic instance, the result is
11527 still static, and yields the result of applying this test to the
11530 @node Attribute Universal_Literal_String,Attribute Unrestricted_Access,Attribute Unconstrained_Array,Implementation Defined Attributes
11531 @anchor{gnat_rm/implementation_defined_attributes attribute-universal-literal-string}@anchor{1ab}
11532 @section Attribute Universal_Literal_String
11535 @geindex Named numbers
11536 @geindex representation of
11538 @geindex Universal_Literal_String
11540 The prefix of @code{Universal_Literal_String} must be a named
11541 number. The static result is the string consisting of the characters of
11542 the number as defined in the original source. This allows the user
11543 program to access the actual text of named numbers without intermediate
11544 conversions and without the need to enclose the strings in quotes (which
11545 would preclude their use as numbers).
11547 For example, the following program prints the first 50 digits of pi:
11550 with Text_IO; use Text_IO;
11554 Put (Ada.Numerics.Pi'Universal_Literal_String);
11558 @node Attribute Unrestricted_Access,Attribute Update,Attribute Universal_Literal_String,Implementation Defined Attributes
11559 @anchor{gnat_rm/implementation_defined_attributes attribute-unrestricted-access}@anchor{1ac}
11560 @section Attribute Unrestricted_Access
11564 @geindex unrestricted
11566 @geindex Unrestricted_Access
11568 The @code{Unrestricted_Access} attribute is similar to @code{Access}
11569 except that all accessibility and aliased view checks are omitted. This
11570 is a user-beware attribute.
11572 For objects, it is similar to @code{Address}, for which it is a
11573 desirable replacement where the value desired is an access type.
11574 In other words, its effect is similar to first applying the
11575 @code{Address} attribute and then doing an unchecked conversion to a
11576 desired access type.
11578 For subprograms, @code{P'Unrestricted_Access} may be used where
11579 @code{P'Access} would be illegal, to construct a value of a
11580 less-nested named access type that designates a more-nested
11581 subprogram. This value may be used in indirect calls, so long as the
11582 more-nested subprogram still exists; once the subprogram containing it
11583 has returned, such calls are erroneous. For example:
11588 type Less_Nested is not null access procedure;
11589 Global : Less_Nested;
11597 Local_Var : Integer;
11599 procedure More_Nested is
11604 Global := More_Nested'Unrestricted_Access;
11611 When P1 is called from P2, the call via Global is OK, but if P1 were
11612 called after P2 returns, it would be an erroneous use of a dangling
11615 For objects, it is possible to use @code{Unrestricted_Access} for any
11616 type. However, if the result is of an access-to-unconstrained array
11617 subtype, then the resulting pointer has the same scope as the context
11618 of the attribute, and must not be returned to some enclosing scope.
11619 For instance, if a function uses @code{Unrestricted_Access} to create
11620 an access-to-unconstrained-array and returns that value to the caller,
11621 the result will involve dangling pointers. In addition, it is only
11622 valid to create pointers to unconstrained arrays using this attribute
11623 if the pointer has the normal default 'fat' representation where a
11624 pointer has two components, one points to the array and one points to
11625 the bounds. If a size clause is used to force 'thin' representation
11626 for a pointer to unconstrained where there is only space for a single
11627 pointer, then the resulting pointer is not usable.
11629 In the simple case where a direct use of Unrestricted_Access attempts
11630 to make a thin pointer for a non-aliased object, the compiler will
11631 reject the use as illegal, as shown in the following example:
11634 with System; use System;
11635 procedure SliceUA2 is
11636 type A is access all String;
11637 for A'Size use Standard'Address_Size;
11639 procedure P (Arg : A) is
11644 X : String := "hello world!";
11645 X2 : aliased String := "hello world!";
11647 AV : A := X'Unrestricted_Access; -- ERROR
11649 >>> illegal use of Unrestricted_Access attribute
11650 >>> attempt to generate thin pointer to unaliased object
11653 P (X'Unrestricted_Access); -- ERROR
11655 >>> illegal use of Unrestricted_Access attribute
11656 >>> attempt to generate thin pointer to unaliased object
11658 P (X(7 .. 12)'Unrestricted_Access); -- ERROR
11660 >>> illegal use of Unrestricted_Access attribute
11661 >>> attempt to generate thin pointer to unaliased object
11663 P (X2'Unrestricted_Access); -- OK
11667 but other cases cannot be detected by the compiler, and are
11668 considered to be erroneous. Consider the following example:
11671 with System; use System;
11672 with System; use System;
11673 procedure SliceUA is
11674 type AF is access all String;
11676 type A is access all String;
11677 for A'Size use Standard'Address_Size;
11679 procedure P (Arg : A) is
11681 if Arg'Length /= 6 then
11682 raise Program_Error;
11686 X : String := "hello world!";
11687 Y : AF := X (7 .. 12)'Unrestricted_Access;
11694 A normal unconstrained array value
11695 or a constrained array object marked as aliased has the bounds in memory
11696 just before the array, so a thin pointer can retrieve both the data and
11697 the bounds. But in this case, the non-aliased object @code{X} does not have the
11698 bounds before the string. If the size clause for type @code{A}
11699 were not present, then the pointer
11700 would be a fat pointer, where one component is a pointer to the bounds,
11701 and all would be well. But with the size clause present, the conversion from
11702 fat pointer to thin pointer in the call loses the bounds, and so this
11703 is erroneous, and the program likely raises a @code{Program_Error} exception.
11705 In general, it is advisable to completely
11706 avoid mixing the use of thin pointers and the use of
11707 @code{Unrestricted_Access} where the designated type is an
11708 unconstrained array. The use of thin pointers should be restricted to
11709 cases of porting legacy code that implicitly assumes the size of pointers,
11710 and such code should not in any case be using this attribute.
11712 Another erroneous situation arises if the attribute is
11713 applied to a constant. The resulting pointer can be used to access the
11714 constant, but the effect of trying to modify a constant in this manner
11715 is not well-defined. Consider this example:
11718 P : constant Integer := 4;
11719 type R is access all Integer;
11720 RV : R := P'Unrestricted_Access;
11725 Here we attempt to modify the constant P from 4 to 3, but the compiler may
11726 or may not notice this attempt, and subsequent references to P may yield
11727 either the value 3 or the value 4 or the assignment may blow up if the
11728 compiler decides to put P in read-only memory. One particular case where
11729 @code{Unrestricted_Access} can be used in this way is to modify the
11730 value of an @code{in} parameter:
11733 procedure K (S : in String) is
11734 type R is access all Character;
11735 RV : R := S (3)'Unrestricted_Access;
11741 In general this is a risky approach. It may appear to "work" but such uses of
11742 @code{Unrestricted_Access} are potentially non-portable, even from one version
11743 of GNAT to another, so are best avoided if possible.
11745 @node Attribute Update,Attribute Valid_Scalars,Attribute Unrestricted_Access,Implementation Defined Attributes
11746 @anchor{gnat_rm/implementation_defined_attributes attribute-update}@anchor{1ad}
11747 @section Attribute Update
11752 The @code{Update} attribute creates a copy of an array or record value
11753 with one or more modified components. The syntax is:
11756 PREFIX'Update ( RECORD_COMPONENT_ASSOCIATION_LIST )
11757 PREFIX'Update ( ARRAY_COMPONENT_ASSOCIATION @{, ARRAY_COMPONENT_ASSOCIATION @} )
11758 PREFIX'Update ( MULTIDIMENSIONAL_ARRAY_COMPONENT_ASSOCIATION
11759 @{, MULTIDIMENSIONAL_ARRAY_COMPONENT_ASSOCIATION @} )
11761 MULTIDIMENSIONAL_ARRAY_COMPONENT_ASSOCIATION ::= INDEX_EXPRESSION_LIST_LIST => EXPRESSION
11762 INDEX_EXPRESSION_LIST_LIST ::= INDEX_EXPRESSION_LIST @{| INDEX_EXPRESSION_LIST @}
11763 INDEX_EXPRESSION_LIST ::= ( EXPRESSION @{, EXPRESSION @} )
11766 where @code{PREFIX} is the name of an array or record object, the
11767 association list in parentheses does not contain an @code{others}
11768 choice and the box symbol @code{<>} may not appear in any
11769 expression. The effect is to yield a copy of the array or record value
11770 which is unchanged apart from the components mentioned in the
11771 association list, which are changed to the indicated value. The
11772 original value of the array or record value is not affected. For
11776 type Arr is Array (1 .. 5) of Integer;
11778 Avar1 : Arr := (1,2,3,4,5);
11779 Avar2 : Arr := Avar1'Update (2 => 10, 3 .. 4 => 20);
11782 yields a value for @code{Avar2} of 1,10,20,20,5 with @code{Avar1}
11783 begin unmodified. Similarly:
11786 type Rec is A, B, C : Integer;
11788 Rvar1 : Rec := (A => 1, B => 2, C => 3);
11789 Rvar2 : Rec := Rvar1'Update (B => 20);
11792 yields a value for @code{Rvar2} of (A => 1, B => 20, C => 3),
11793 with @code{Rvar1} being unmodifed.
11794 Note that the value of the attribute reference is computed
11795 completely before it is used. This means that if you write:
11798 Avar1 := Avar1'Update (1 => 10, 2 => Function_Call);
11801 then the value of @code{Avar1} is not modified if @code{Function_Call}
11802 raises an exception, unlike the effect of a series of direct assignments
11803 to elements of @code{Avar1}. In general this requires that
11804 two extra complete copies of the object are required, which should be
11805 kept in mind when considering efficiency.
11807 The @code{Update} attribute cannot be applied to prefixes of a limited
11808 type, and cannot reference discriminants in the case of a record type.
11809 The accessibility level of an Update attribute result object is defined
11810 as for an aggregate.
11812 In the record case, no component can be mentioned more than once. In
11813 the array case, two overlapping ranges can appear in the association list,
11814 in which case the modifications are processed left to right.
11816 Multi-dimensional arrays can be modified, as shown by this example:
11819 A : array (1 .. 10, 1 .. 10) of Integer;
11821 A := A'Update ((1, 2) => 20, (3, 4) => 30);
11824 which changes element (1,2) to 20 and (3,4) to 30.
11826 @node Attribute Valid_Scalars,Attribute VADS_Size,Attribute Update,Implementation Defined Attributes
11827 @anchor{gnat_rm/implementation_defined_attributes attribute-valid-scalars}@anchor{1ae}
11828 @section Attribute Valid_Scalars
11831 @geindex Valid_Scalars
11833 The @code{'Valid_Scalars} attribute is intended to make it easier to check the
11834 validity of scalar subcomponents of composite objects. The attribute is defined
11835 for any prefix @code{P} which denotes an object. Prefix @code{P} can be any type
11836 except for tagged private or @code{Unchecked_Union} types. The value of the
11837 attribute is of type @code{Boolean}.
11839 @code{P'Valid_Scalars} yields @code{True} if and only if the evaluation of
11840 @code{C'Valid} yields @code{True} for every scalar subcomponent @code{C} of @code{P}, or if
11841 @code{P} has no scalar subcomponents. Attribute @code{'Valid_Scalars} is equivalent
11842 to attribute @code{'Valid} for scalar types.
11844 It is not specified in what order the subcomponents are checked, nor whether
11845 any more are checked after any one of them is determined to be invalid. If the
11846 prefix @code{P} is of a class-wide type @code{T'Class} (where @code{T} is the associated
11847 specific type), or if the prefix @code{P} is of a specific tagged type @code{T}, then
11848 only the subcomponents of @code{T} are checked; in other words, components of
11849 extensions of @code{T} are not checked even if @code{T'Class (P)'Tag /= T'Tag}.
11851 The compiler will issue a warning if it can be determined at compile time that
11852 the prefix of the attribute has no scalar subcomponents.
11854 Note: @code{Valid_Scalars} can generate a lot of code, especially in the case of
11855 a large variant record. If the attribute is called in many places in the same
11856 program applied to objects of the same type, it can reduce program size to
11857 write a function with a single use of the attribute, and then call that
11858 function from multiple places.
11860 @node Attribute VADS_Size,Attribute Value_Size,Attribute Valid_Scalars,Implementation Defined Attributes
11861 @anchor{gnat_rm/implementation_defined_attributes attribute-vads-size}@anchor{1af}
11862 @section Attribute VADS_Size
11866 @geindex VADS compatibility
11870 The @code{'VADS_Size} attribute is intended to make it easier to port
11871 legacy code which relies on the semantics of @code{'Size} as implemented
11872 by the VADS Ada 83 compiler. GNAT makes a best effort at duplicating the
11873 same semantic interpretation. In particular, @code{'VADS_Size} applied
11874 to a predefined or other primitive type with no Size clause yields the
11875 Object_Size (for example, @code{Natural'Size} is 32 rather than 31 on
11876 typical machines). In addition @code{'VADS_Size} applied to an object
11877 gives the result that would be obtained by applying the attribute to
11878 the corresponding type.
11880 @node Attribute Value_Size,Attribute Wchar_T_Size,Attribute VADS_Size,Implementation Defined Attributes
11881 @anchor{gnat_rm/implementation_defined_attributes id6}@anchor{1b0}@anchor{gnat_rm/implementation_defined_attributes attribute-value-size}@anchor{160}
11882 @section Attribute Value_Size
11886 @geindex setting for not-first subtype
11888 @geindex Value_Size
11890 @code{type'Value_Size} is the number of bits required to represent
11891 a value of the given subtype. It is the same as @code{type'Size},
11892 but, unlike @code{Size}, may be set for non-first subtypes.
11894 @node Attribute Wchar_T_Size,Attribute Word_Size,Attribute Value_Size,Implementation Defined Attributes
11895 @anchor{gnat_rm/implementation_defined_attributes attribute-wchar-t-size}@anchor{1b1}
11896 @section Attribute Wchar_T_Size
11899 @geindex Wchar_T_Size
11901 @code{Standard'Wchar_T_Size} (@code{Standard} is the only permissible
11902 prefix) provides the size in bits of the C @code{wchar_t} type
11903 primarily for constructing the definition of this type in
11904 package @code{Interfaces.C}. The result is a static constant.
11906 @node Attribute Word_Size,,Attribute Wchar_T_Size,Implementation Defined Attributes
11907 @anchor{gnat_rm/implementation_defined_attributes attribute-word-size}@anchor{1b2}
11908 @section Attribute Word_Size
11913 @code{Standard'Word_Size} (@code{Standard} is the only permissible
11914 prefix) provides the value @code{System.Word_Size}. The result is
11917 @node Standard and Implementation Defined Restrictions,Implementation Advice,Implementation Defined Attributes,Top
11918 @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{1b3}@anchor{gnat_rm/standard_and_implementation_defined_restrictions id1}@anchor{1b4}
11919 @chapter Standard and Implementation Defined Restrictions
11922 All Ada Reference Manual-defined Restriction identifiers are implemented:
11928 language-defined restrictions (see 13.12.1)
11931 tasking restrictions (see D.7)
11934 high integrity restrictions (see H.4)
11937 GNAT implements additional restriction identifiers. All restrictions, whether
11938 language defined or GNAT-specific, are listed in the following.
11941 * Partition-Wide Restrictions::
11942 * Program Unit Level Restrictions::
11946 @node Partition-Wide Restrictions,Program Unit Level Restrictions,,Standard and Implementation Defined Restrictions
11947 @anchor{gnat_rm/standard_and_implementation_defined_restrictions partition-wide-restrictions}@anchor{1b5}@anchor{gnat_rm/standard_and_implementation_defined_restrictions id2}@anchor{1b6}
11948 @section Partition-Wide Restrictions
11951 There are two separate lists of restriction identifiers. The first
11952 set requires consistency throughout a partition (in other words, if the
11953 restriction identifier is used for any compilation unit in the partition,
11954 then all compilation units in the partition must obey the restriction).
11957 * Immediate_Reclamation::
11958 * Max_Asynchronous_Select_Nesting::
11959 * Max_Entry_Queue_Length::
11960 * Max_Protected_Entries::
11961 * Max_Select_Alternatives::
11962 * Max_Storage_At_Blocking::
11963 * Max_Task_Entries::
11965 * No_Abort_Statements::
11966 * No_Access_Parameter_Allocators::
11967 * No_Access_Subprograms::
11969 * No_Anonymous_Allocators::
11970 * No_Asynchronous_Control::
11972 * No_Coextensions::
11973 * No_Default_Initialization::
11976 * No_Direct_Boolean_Operators::
11978 * No_Dispatching_Calls::
11979 * No_Dynamic_Attachment::
11980 * No_Dynamic_Priorities::
11981 * No_Entry_Calls_In_Elaboration_Code::
11982 * No_Enumeration_Maps::
11983 * No_Exception_Handlers::
11984 * No_Exception_Propagation::
11985 * No_Exception_Registration::
11987 * No_Finalization::
11989 * No_Floating_Point::
11990 * No_Implicit_Conditionals::
11991 * No_Implicit_Dynamic_Code::
11992 * No_Implicit_Heap_Allocations::
11993 * No_Implicit_Protected_Object_Allocations::
11994 * No_Implicit_Task_Allocations::
11995 * No_Initialize_Scalars::
11997 * No_Local_Allocators::
11998 * No_Local_Protected_Objects::
11999 * No_Local_Timing_Events::
12000 * No_Long_Long_Integers::
12001 * No_Multiple_Elaboration::
12002 * No_Nested_Finalization::
12003 * No_Protected_Type_Allocators::
12004 * No_Protected_Types::
12007 * No_Relative_Delay::
12008 * No_Requeue_Statements::
12009 * No_Secondary_Stack::
12010 * No_Select_Statements::
12011 * No_Specific_Termination_Handlers::
12012 * No_Specification_of_Aspect::
12013 * No_Standard_Allocators_After_Elaboration::
12014 * No_Standard_Storage_Pools::
12015 * No_Stream_Optimizations::
12017 * No_Task_Allocators::
12018 * No_Task_At_Interrupt_Priority::
12019 * No_Task_Attributes_Package::
12020 * No_Task_Hierarchy::
12021 * No_Task_Termination::
12023 * No_Terminate_Alternatives::
12024 * No_Unchecked_Access::
12025 * No_Unchecked_Conversion::
12026 * No_Unchecked_Deallocation::
12027 * No_Use_Of_Entity::
12029 * Simple_Barriers::
12030 * Static_Priorities::
12031 * Static_Storage_Size::
12035 @node Immediate_Reclamation,Max_Asynchronous_Select_Nesting,,Partition-Wide Restrictions
12036 @anchor{gnat_rm/standard_and_implementation_defined_restrictions immediate-reclamation}@anchor{1b7}
12037 @subsection Immediate_Reclamation
12040 @geindex Immediate_Reclamation
12042 [RM H.4] This restriction ensures that, except for storage occupied by
12043 objects created by allocators and not deallocated via unchecked
12044 deallocation, any storage reserved at run time for an object is
12045 immediately reclaimed when the object no longer exists.
12047 @node Max_Asynchronous_Select_Nesting,Max_Entry_Queue_Length,Immediate_Reclamation,Partition-Wide Restrictions
12048 @anchor{gnat_rm/standard_and_implementation_defined_restrictions max-asynchronous-select-nesting}@anchor{1b8}
12049 @subsection Max_Asynchronous_Select_Nesting
12052 @geindex Max_Asynchronous_Select_Nesting
12054 [RM D.7] Specifies the maximum dynamic nesting level of asynchronous
12055 selects. Violations of this restriction with a value of zero are
12056 detected at compile time. Violations of this restriction with values
12057 other than zero cause Storage_Error to be raised.
12059 @node Max_Entry_Queue_Length,Max_Protected_Entries,Max_Asynchronous_Select_Nesting,Partition-Wide Restrictions
12060 @anchor{gnat_rm/standard_and_implementation_defined_restrictions max-entry-queue-length}@anchor{1b9}
12061 @subsection Max_Entry_Queue_Length
12064 @geindex Max_Entry_Queue_Length
12066 [RM D.7] This restriction is a declaration that any protected entry compiled in
12067 the scope of the restriction has at most the specified number of
12068 tasks waiting on the entry at any one time, and so no queue is required.
12069 Note that this restriction is checked at run time. Violation of this
12070 restriction results in the raising of Program_Error exception at the point of
12073 @geindex Max_Entry_Queue_Depth
12075 The restriction @code{Max_Entry_Queue_Depth} is recognized as a
12076 synonym for @code{Max_Entry_Queue_Length}. This is retained for historical
12077 compatibility purposes (and a warning will be generated for its use if
12078 warnings on obsolescent features are activated).
12080 @node Max_Protected_Entries,Max_Select_Alternatives,Max_Entry_Queue_Length,Partition-Wide Restrictions
12081 @anchor{gnat_rm/standard_and_implementation_defined_restrictions max-protected-entries}@anchor{1ba}
12082 @subsection Max_Protected_Entries
12085 @geindex Max_Protected_Entries
12087 [RM D.7] Specifies the maximum number of entries per protected type. The
12088 bounds of every entry family of a protected unit shall be static, or shall be
12089 defined by a discriminant of a subtype whose corresponding bound is static.
12091 @node Max_Select_Alternatives,Max_Storage_At_Blocking,Max_Protected_Entries,Partition-Wide Restrictions
12092 @anchor{gnat_rm/standard_and_implementation_defined_restrictions max-select-alternatives}@anchor{1bb}
12093 @subsection Max_Select_Alternatives
12096 @geindex Max_Select_Alternatives
12098 [RM D.7] Specifies the maximum number of alternatives in a selective accept.
12100 @node Max_Storage_At_Blocking,Max_Task_Entries,Max_Select_Alternatives,Partition-Wide Restrictions
12101 @anchor{gnat_rm/standard_and_implementation_defined_restrictions max-storage-at-blocking}@anchor{1bc}
12102 @subsection Max_Storage_At_Blocking
12105 @geindex Max_Storage_At_Blocking
12107 [RM D.7] Specifies the maximum portion (in storage elements) of a task's
12108 Storage_Size that can be retained by a blocked task. A violation of this
12109 restriction causes Storage_Error to be raised.
12111 @node Max_Task_Entries,Max_Tasks,Max_Storage_At_Blocking,Partition-Wide Restrictions
12112 @anchor{gnat_rm/standard_and_implementation_defined_restrictions max-task-entries}@anchor{1bd}
12113 @subsection Max_Task_Entries
12116 @geindex Max_Task_Entries
12118 [RM D.7] Specifies the maximum number of entries
12119 per task. The bounds of every entry family
12120 of a task unit shall be static, or shall be
12121 defined by a discriminant of a subtype whose
12122 corresponding bound is static.
12124 @node Max_Tasks,No_Abort_Statements,Max_Task_Entries,Partition-Wide Restrictions
12125 @anchor{gnat_rm/standard_and_implementation_defined_restrictions max-tasks}@anchor{1be}
12126 @subsection Max_Tasks
12131 [RM D.7] Specifies the maximum number of task that may be created, not
12132 counting the creation of the environment task. Violations of this
12133 restriction with a value of zero are detected at compile
12134 time. Violations of this restriction with values other than zero cause
12135 Storage_Error to be raised.
12137 @node No_Abort_Statements,No_Access_Parameter_Allocators,Max_Tasks,Partition-Wide Restrictions
12138 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-abort-statements}@anchor{1bf}
12139 @subsection No_Abort_Statements
12142 @geindex No_Abort_Statements
12144 [RM D.7] There are no abort_statements, and there are
12145 no calls to Task_Identification.Abort_Task.
12147 @node No_Access_Parameter_Allocators,No_Access_Subprograms,No_Abort_Statements,Partition-Wide Restrictions
12148 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-access-parameter-allocators}@anchor{1c0}
12149 @subsection No_Access_Parameter_Allocators
12152 @geindex No_Access_Parameter_Allocators
12154 [RM H.4] This restriction ensures at compile time that there are no
12155 occurrences of an allocator as the actual parameter to an access
12158 @node No_Access_Subprograms,No_Allocators,No_Access_Parameter_Allocators,Partition-Wide Restrictions
12159 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-access-subprograms}@anchor{1c1}
12160 @subsection No_Access_Subprograms
12163 @geindex No_Access_Subprograms
12165 [RM H.4] This restriction ensures at compile time that there are no
12166 declarations of access-to-subprogram types.
12168 @node No_Allocators,No_Anonymous_Allocators,No_Access_Subprograms,Partition-Wide Restrictions
12169 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-allocators}@anchor{1c2}
12170 @subsection No_Allocators
12173 @geindex No_Allocators
12175 [RM H.4] This restriction ensures at compile time that there are no
12176 occurrences of an allocator.
12178 @node No_Anonymous_Allocators,No_Asynchronous_Control,No_Allocators,Partition-Wide Restrictions
12179 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-anonymous-allocators}@anchor{1c3}
12180 @subsection No_Anonymous_Allocators
12183 @geindex No_Anonymous_Allocators
12185 [RM H.4] This restriction ensures at compile time that there are no
12186 occurrences of an allocator of anonymous access type.
12188 @node No_Asynchronous_Control,No_Calendar,No_Anonymous_Allocators,Partition-Wide Restrictions
12189 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-asynchronous-control}@anchor{1c4}
12190 @subsection No_Asynchronous_Control
12193 @geindex No_Asynchronous_Control
12195 [RM J.13] This restriction ensures at compile time that there are no semantic
12196 dependences on the predefined package Asynchronous_Task_Control.
12198 @node No_Calendar,No_Coextensions,No_Asynchronous_Control,Partition-Wide Restrictions
12199 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-calendar}@anchor{1c5}
12200 @subsection No_Calendar
12203 @geindex No_Calendar
12205 [GNAT] This restriction ensures at compile time that there are no semantic
12206 dependences on package Calendar.
12208 @node No_Coextensions,No_Default_Initialization,No_Calendar,Partition-Wide Restrictions
12209 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-coextensions}@anchor{1c6}
12210 @subsection No_Coextensions
12213 @geindex No_Coextensions
12215 [RM H.4] This restriction ensures at compile time that there are no
12216 coextensions. See 3.10.2.
12218 @node No_Default_Initialization,No_Delay,No_Coextensions,Partition-Wide Restrictions
12219 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-default-initialization}@anchor{1c7}
12220 @subsection No_Default_Initialization
12223 @geindex No_Default_Initialization
12225 [GNAT] This restriction prohibits any instance of default initialization
12226 of variables. The binder implements a consistency rule which prevents
12227 any unit compiled without the restriction from with'ing a unit with the
12228 restriction (this allows the generation of initialization procedures to
12229 be skipped, since you can be sure that no call is ever generated to an
12230 initialization procedure in a unit with the restriction active). If used
12231 in conjunction with Initialize_Scalars or Normalize_Scalars, the effect
12232 is to prohibit all cases of variables declared without a specific
12233 initializer (including the case of OUT scalar parameters).
12235 @node No_Delay,No_Dependence,No_Default_Initialization,Partition-Wide Restrictions
12236 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-delay}@anchor{1c8}
12237 @subsection No_Delay
12242 [RM H.4] This restriction ensures at compile time that there are no
12243 delay statements and no semantic dependences on package Calendar.
12245 @node No_Dependence,No_Direct_Boolean_Operators,No_Delay,Partition-Wide Restrictions
12246 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-dependence}@anchor{1c9}
12247 @subsection No_Dependence
12250 @geindex No_Dependence
12252 [RM 13.12.1] This restriction ensures at compile time that there are no
12253 dependences on a library unit.
12255 @node No_Direct_Boolean_Operators,No_Dispatch,No_Dependence,Partition-Wide Restrictions
12256 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-direct-boolean-operators}@anchor{1ca}
12257 @subsection No_Direct_Boolean_Operators
12260 @geindex No_Direct_Boolean_Operators
12262 [GNAT] This restriction ensures that no logical operators (and/or/xor)
12263 are used on operands of type Boolean (or any type derived from Boolean).
12264 This is intended for use in safety critical programs where the certification
12265 protocol requires the use of short-circuit (and then, or else) forms for all
12266 composite boolean operations.
12268 @node No_Dispatch,No_Dispatching_Calls,No_Direct_Boolean_Operators,Partition-Wide Restrictions
12269 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-dispatch}@anchor{1cb}
12270 @subsection No_Dispatch
12273 @geindex No_Dispatch
12275 [RM H.4] This restriction ensures at compile time that there are no
12276 occurrences of @code{T'Class}, for any (tagged) subtype @code{T}.
12278 @node No_Dispatching_Calls,No_Dynamic_Attachment,No_Dispatch,Partition-Wide Restrictions
12279 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-dispatching-calls}@anchor{1cc}
12280 @subsection No_Dispatching_Calls
12283 @geindex No_Dispatching_Calls
12285 [GNAT] This restriction ensures at compile time that the code generated by the
12286 compiler involves no dispatching calls. The use of this restriction allows the
12287 safe use of record extensions, classwide membership tests and other classwide
12288 features not involving implicit dispatching. This restriction ensures that
12289 the code contains no indirect calls through a dispatching mechanism. Note that
12290 this includes internally-generated calls created by the compiler, for example
12291 in the implementation of class-wide objects assignments. The
12292 membership test is allowed in the presence of this restriction, because its
12293 implementation requires no dispatching.
12294 This restriction is comparable to the official Ada restriction
12295 @code{No_Dispatch} except that it is a bit less restrictive in that it allows
12296 all classwide constructs that do not imply dispatching.
12297 The following example indicates constructs that violate this restriction.
12301 type T is tagged record
12304 procedure P (X : T);
12306 type DT is new T with record
12307 More_Data : Natural;
12309 procedure Q (X : DT);
12313 procedure Example is
12314 procedure Test (O : T'Class) is
12315 N : Natural := O'Size;-- Error: Dispatching call
12316 C : T'Class := O; -- Error: implicit Dispatching Call
12318 if O in DT'Class then -- OK : Membership test
12319 Q (DT (O)); -- OK : Type conversion plus direct call
12321 P (O); -- Error: Dispatching call
12327 P (Obj); -- OK : Direct call
12328 P (T (Obj)); -- OK : Type conversion plus direct call
12329 P (T'Class (Obj)); -- Error: Dispatching call
12331 Test (Obj); -- OK : Type conversion
12333 if Obj in T'Class then -- OK : Membership test
12339 @node No_Dynamic_Attachment,No_Dynamic_Priorities,No_Dispatching_Calls,Partition-Wide Restrictions
12340 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-dynamic-attachment}@anchor{1cd}
12341 @subsection No_Dynamic_Attachment
12344 @geindex No_Dynamic_Attachment
12346 [RM D.7] This restriction ensures that there is no call to any of the
12347 operations defined in package Ada.Interrupts
12348 (Is_Reserved, Is_Attached, Current_Handler, Attach_Handler, Exchange_Handler,
12349 Detach_Handler, and Reference).
12351 @geindex No_Dynamic_Interrupts
12353 The restriction @code{No_Dynamic_Interrupts} is recognized as a
12354 synonym for @code{No_Dynamic_Attachment}. This is retained for historical
12355 compatibility purposes (and a warning will be generated for its use if
12356 warnings on obsolescent features are activated).
12358 @node No_Dynamic_Priorities,No_Entry_Calls_In_Elaboration_Code,No_Dynamic_Attachment,Partition-Wide Restrictions
12359 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-dynamic-priorities}@anchor{1ce}
12360 @subsection No_Dynamic_Priorities
12363 @geindex No_Dynamic_Priorities
12365 [RM D.7] There are no semantic dependencies on the package Dynamic_Priorities.
12367 @node No_Entry_Calls_In_Elaboration_Code,No_Enumeration_Maps,No_Dynamic_Priorities,Partition-Wide Restrictions
12368 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-entry-calls-in-elaboration-code}@anchor{1cf}
12369 @subsection No_Entry_Calls_In_Elaboration_Code
12372 @geindex No_Entry_Calls_In_Elaboration_Code
12374 [GNAT] This restriction ensures at compile time that no task or protected entry
12375 calls are made during elaboration code. As a result of the use of this
12376 restriction, the compiler can assume that no code past an accept statement
12377 in a task can be executed at elaboration time.
12379 @node No_Enumeration_Maps,No_Exception_Handlers,No_Entry_Calls_In_Elaboration_Code,Partition-Wide Restrictions
12380 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-enumeration-maps}@anchor{1d0}
12381 @subsection No_Enumeration_Maps
12384 @geindex No_Enumeration_Maps
12386 [GNAT] This restriction ensures at compile time that no operations requiring
12387 enumeration maps are used (that is Image and Value attributes applied
12388 to enumeration types).
12390 @node No_Exception_Handlers,No_Exception_Propagation,No_Enumeration_Maps,Partition-Wide Restrictions
12391 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-exception-handlers}@anchor{1d1}
12392 @subsection No_Exception_Handlers
12395 @geindex No_Exception_Handlers
12397 [GNAT] This restriction ensures at compile time that there are no explicit
12398 exception handlers. It also indicates that no exception propagation will
12399 be provided. In this mode, exceptions may be raised but will result in
12400 an immediate call to the last chance handler, a routine that the user
12401 must define with the following profile:
12404 procedure Last_Chance_Handler
12405 (Source_Location : System.Address; Line : Integer);
12406 pragma Export (C, Last_Chance_Handler,
12407 "__gnat_last_chance_handler");
12410 The parameter is a C null-terminated string representing a message to be
12411 associated with the exception (typically the source location of the raise
12412 statement generated by the compiler). The Line parameter when nonzero
12413 represents the line number in the source program where the raise occurs.
12415 @node No_Exception_Propagation,No_Exception_Registration,No_Exception_Handlers,Partition-Wide Restrictions
12416 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-exception-propagation}@anchor{1d2}
12417 @subsection No_Exception_Propagation
12420 @geindex No_Exception_Propagation
12422 [GNAT] This restriction guarantees that exceptions are never propagated
12423 to an outer subprogram scope. The only case in which an exception may
12424 be raised is when the handler is statically in the same subprogram, so
12425 that the effect of a raise is essentially like a goto statement. Any
12426 other raise statement (implicit or explicit) will be considered
12427 unhandled. Exception handlers are allowed, but may not contain an
12428 exception occurrence identifier (exception choice). In addition, use of
12429 the package GNAT.Current_Exception is not permitted, and reraise
12430 statements (raise with no operand) are not permitted.
12432 @node No_Exception_Registration,No_Exceptions,No_Exception_Propagation,Partition-Wide Restrictions
12433 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-exception-registration}@anchor{1d3}
12434 @subsection No_Exception_Registration
12437 @geindex No_Exception_Registration
12439 [GNAT] This restriction ensures at compile time that no stream operations for
12440 types Exception_Id or Exception_Occurrence are used. This also makes it
12441 impossible to pass exceptions to or from a partition with this restriction
12442 in a distributed environment. If this restriction is active, the generated
12443 code is simplified by omitting the otherwise-required global registration
12444 of exceptions when they are declared.
12446 @node No_Exceptions,No_Finalization,No_Exception_Registration,Partition-Wide Restrictions
12447 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-exceptions}@anchor{1d4}
12448 @subsection No_Exceptions
12451 @geindex No_Exceptions
12453 [RM H.4] This restriction ensures at compile time that there are no
12454 raise statements and no exception handlers and also suppresses the
12455 generation of language-defined run-time checks.
12457 @node No_Finalization,No_Fixed_Point,No_Exceptions,Partition-Wide Restrictions
12458 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-finalization}@anchor{1d5}
12459 @subsection No_Finalization
12462 @geindex No_Finalization
12464 [GNAT] This restriction disables the language features described in
12465 chapter 7.6 of the Ada 2005 RM as well as all form of code generation
12466 performed by the compiler to support these features. The following types
12467 are no longer considered controlled when this restriction is in effect:
12473 @code{Ada.Finalization.Controlled}
12476 @code{Ada.Finalization.Limited_Controlled}
12479 Derivations from @code{Controlled} or @code{Limited_Controlled}
12491 Array and record types with controlled components
12494 The compiler no longer generates code to initialize, finalize or adjust an
12495 object or a nested component, either declared on the stack or on the heap. The
12496 deallocation of a controlled object no longer finalizes its contents.
12498 @node No_Fixed_Point,No_Floating_Point,No_Finalization,Partition-Wide Restrictions
12499 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-fixed-point}@anchor{1d6}
12500 @subsection No_Fixed_Point
12503 @geindex No_Fixed_Point
12505 [RM H.4] This restriction ensures at compile time that there are no
12506 occurrences of fixed point types and operations.
12508 @node No_Floating_Point,No_Implicit_Conditionals,No_Fixed_Point,Partition-Wide Restrictions
12509 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-floating-point}@anchor{1d7}
12510 @subsection No_Floating_Point
12513 @geindex No_Floating_Point
12515 [RM H.4] This restriction ensures at compile time that there are no
12516 occurrences of floating point types and operations.
12518 @node No_Implicit_Conditionals,No_Implicit_Dynamic_Code,No_Floating_Point,Partition-Wide Restrictions
12519 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-conditionals}@anchor{1d8}
12520 @subsection No_Implicit_Conditionals
12523 @geindex No_Implicit_Conditionals
12525 [GNAT] This restriction ensures that the generated code does not contain any
12526 implicit conditionals, either by modifying the generated code where possible,
12527 or by rejecting any construct that would otherwise generate an implicit
12528 conditional. Note that this check does not include run time constraint
12529 checks, which on some targets may generate implicit conditionals as
12530 well. To control the latter, constraint checks can be suppressed in the
12531 normal manner. Constructs generating implicit conditionals include comparisons
12532 of composite objects and the Max/Min attributes.
12534 @node No_Implicit_Dynamic_Code,No_Implicit_Heap_Allocations,No_Implicit_Conditionals,Partition-Wide Restrictions
12535 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-dynamic-code}@anchor{1d9}
12536 @subsection No_Implicit_Dynamic_Code
12539 @geindex No_Implicit_Dynamic_Code
12541 @geindex trampoline
12543 [GNAT] This restriction prevents the compiler from building 'trampolines'.
12544 This is a structure that is built on the stack and contains dynamic
12545 code to be executed at run time. On some targets, a trampoline is
12546 built for the following features: @code{Access},
12547 @code{Unrestricted_Access}, or @code{Address} of a nested subprogram;
12548 nested task bodies; primitive operations of nested tagged types.
12549 Trampolines do not work on machines that prevent execution of stack
12550 data. For example, on windows systems, enabling DEP (data execution
12551 protection) will cause trampolines to raise an exception.
12552 Trampolines are also quite slow at run time.
12554 On many targets, trampolines have been largely eliminated. Look at the
12555 version of system.ads for your target --- if it has
12556 Always_Compatible_Rep equal to False, then trampolines are largely
12557 eliminated. In particular, a trampoline is built for the following
12558 features: @code{Address} of a nested subprogram;
12559 @code{Access} or @code{Unrestricted_Access} of a nested subprogram,
12560 but only if pragma Favor_Top_Level applies, or the access type has a
12561 foreign-language convention; primitive operations of nested tagged
12564 @node No_Implicit_Heap_Allocations,No_Implicit_Protected_Object_Allocations,No_Implicit_Dynamic_Code,Partition-Wide Restrictions
12565 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-heap-allocations}@anchor{1da}
12566 @subsection No_Implicit_Heap_Allocations
12569 @geindex No_Implicit_Heap_Allocations
12571 [RM D.7] No constructs are allowed to cause implicit heap allocation.
12573 @node No_Implicit_Protected_Object_Allocations,No_Implicit_Task_Allocations,No_Implicit_Heap_Allocations,Partition-Wide Restrictions
12574 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-protected-object-allocations}@anchor{1db}
12575 @subsection No_Implicit_Protected_Object_Allocations
12578 @geindex No_Implicit_Protected_Object_Allocations
12580 [GNAT] No constructs are allowed to cause implicit heap allocation of a
12583 @node No_Implicit_Task_Allocations,No_Initialize_Scalars,No_Implicit_Protected_Object_Allocations,Partition-Wide Restrictions
12584 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-task-allocations}@anchor{1dc}
12585 @subsection No_Implicit_Task_Allocations
12588 @geindex No_Implicit_Task_Allocations
12590 [GNAT] No constructs are allowed to cause implicit heap allocation of a task.
12592 @node No_Initialize_Scalars,No_IO,No_Implicit_Task_Allocations,Partition-Wide Restrictions
12593 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-initialize-scalars}@anchor{1dd}
12594 @subsection No_Initialize_Scalars
12597 @geindex No_Initialize_Scalars
12599 [GNAT] This restriction ensures that no unit in the partition is compiled with
12600 pragma Initialize_Scalars. This allows the generation of more efficient
12601 code, and in particular eliminates dummy null initialization routines that
12602 are otherwise generated for some record and array types.
12604 @node No_IO,No_Local_Allocators,No_Initialize_Scalars,Partition-Wide Restrictions
12605 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-io}@anchor{1de}
12611 [RM H.4] This restriction ensures at compile time that there are no
12612 dependences on any of the library units Sequential_IO, Direct_IO,
12613 Text_IO, Wide_Text_IO, Wide_Wide_Text_IO, or Stream_IO.
12615 @node No_Local_Allocators,No_Local_Protected_Objects,No_IO,Partition-Wide Restrictions
12616 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-local-allocators}@anchor{1df}
12617 @subsection No_Local_Allocators
12620 @geindex No_Local_Allocators
12622 [RM H.4] This restriction ensures at compile time that there are no
12623 occurrences of an allocator in subprograms, generic subprograms, tasks,
12626 @node No_Local_Protected_Objects,No_Local_Timing_Events,No_Local_Allocators,Partition-Wide Restrictions
12627 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-local-protected-objects}@anchor{1e0}
12628 @subsection No_Local_Protected_Objects
12631 @geindex No_Local_Protected_Objects
12633 [RM D.7] This restriction ensures at compile time that protected objects are
12634 only declared at the library level.
12636 @node No_Local_Timing_Events,No_Long_Long_Integers,No_Local_Protected_Objects,Partition-Wide Restrictions
12637 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-local-timing-events}@anchor{1e1}
12638 @subsection No_Local_Timing_Events
12641 @geindex No_Local_Timing_Events
12643 [RM D.7] All objects of type Ada.Real_Time.Timing_Events.Timing_Event are
12644 declared at the library level.
12646 @node No_Long_Long_Integers,No_Multiple_Elaboration,No_Local_Timing_Events,Partition-Wide Restrictions
12647 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-long-long-integers}@anchor{1e2}
12648 @subsection No_Long_Long_Integers
12651 @geindex No_Long_Long_Integers
12653 [GNAT] This partition-wide restriction forbids any explicit reference to
12654 type Standard.Long_Long_Integer, and also forbids declaring range types whose
12655 implicit base type is Long_Long_Integer, and modular types whose size exceeds
12658 @node No_Multiple_Elaboration,No_Nested_Finalization,No_Long_Long_Integers,Partition-Wide Restrictions
12659 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-multiple-elaboration}@anchor{1e3}
12660 @subsection No_Multiple_Elaboration
12663 @geindex No_Multiple_Elaboration
12665 [GNAT] When this restriction is active and the static elaboration model is
12666 used, and -fpreserve-control-flow is not used, the compiler is allowed to
12667 suppress the elaboration counter normally associated with the unit, even if
12668 the unit has elaboration code. This counter is typically used to check for
12669 access before elaboration and to control multiple elaboration attempts. If the
12670 restriction is used, then the situations in which multiple elaboration is
12671 possible, including non-Ada main programs and Stand Alone libraries, are not
12672 permitted and will be diagnosed by the binder.
12674 @node No_Nested_Finalization,No_Protected_Type_Allocators,No_Multiple_Elaboration,Partition-Wide Restrictions
12675 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-nested-finalization}@anchor{1e4}
12676 @subsection No_Nested_Finalization
12679 @geindex No_Nested_Finalization
12681 [RM D.7] All objects requiring finalization are declared at the library level.
12683 @node No_Protected_Type_Allocators,No_Protected_Types,No_Nested_Finalization,Partition-Wide Restrictions
12684 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-protected-type-allocators}@anchor{1e5}
12685 @subsection No_Protected_Type_Allocators
12688 @geindex No_Protected_Type_Allocators
12690 [RM D.7] This restriction ensures at compile time that there are no allocator
12691 expressions that attempt to allocate protected objects.
12693 @node No_Protected_Types,No_Recursion,No_Protected_Type_Allocators,Partition-Wide Restrictions
12694 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-protected-types}@anchor{1e6}
12695 @subsection No_Protected_Types
12698 @geindex No_Protected_Types
12700 [RM H.4] This restriction ensures at compile time that there are no
12701 declarations of protected types or protected objects.
12703 @node No_Recursion,No_Reentrancy,No_Protected_Types,Partition-Wide Restrictions
12704 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-recursion}@anchor{1e7}
12705 @subsection No_Recursion
12708 @geindex No_Recursion
12710 [RM H.4] A program execution is erroneous if a subprogram is invoked as
12711 part of its execution.
12713 @node No_Reentrancy,No_Relative_Delay,No_Recursion,Partition-Wide Restrictions
12714 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-reentrancy}@anchor{1e8}
12715 @subsection No_Reentrancy
12718 @geindex No_Reentrancy
12720 [RM H.4] A program execution is erroneous if a subprogram is executed by
12721 two tasks at the same time.
12723 @node No_Relative_Delay,No_Requeue_Statements,No_Reentrancy,Partition-Wide Restrictions
12724 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-relative-delay}@anchor{1e9}
12725 @subsection No_Relative_Delay
12728 @geindex No_Relative_Delay
12730 [RM D.7] This restriction ensures at compile time that there are no delay
12731 relative statements and prevents expressions such as @code{delay 1.23;} from
12732 appearing in source code.
12734 @node No_Requeue_Statements,No_Secondary_Stack,No_Relative_Delay,Partition-Wide Restrictions
12735 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-requeue-statements}@anchor{1ea}
12736 @subsection No_Requeue_Statements
12739 @geindex No_Requeue_Statements
12741 [RM D.7] This restriction ensures at compile time that no requeue statements
12742 are permitted and prevents keyword @code{requeue} from being used in source
12745 @geindex No_Requeue
12747 The restriction @code{No_Requeue} is recognized as a
12748 synonym for @code{No_Requeue_Statements}. This is retained for historical
12749 compatibility purposes (and a warning will be generated for its use if
12750 warnings on oNobsolescent features are activated).
12752 @node No_Secondary_Stack,No_Select_Statements,No_Requeue_Statements,Partition-Wide Restrictions
12753 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-secondary-stack}@anchor{1eb}
12754 @subsection No_Secondary_Stack
12757 @geindex No_Secondary_Stack
12759 [GNAT] This restriction ensures at compile time that the generated code
12760 does not contain any reference to the secondary stack. The secondary
12761 stack is used to implement functions returning unconstrained objects
12762 (arrays or records) on some targets. Suppresses the allocation of
12763 secondary stacks for tasks (excluding the environment task) at run time.
12765 @node No_Select_Statements,No_Specific_Termination_Handlers,No_Secondary_Stack,Partition-Wide Restrictions
12766 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-select-statements}@anchor{1ec}
12767 @subsection No_Select_Statements
12770 @geindex No_Select_Statements
12772 [RM D.7] This restriction ensures at compile time no select statements of any
12773 kind are permitted, that is the keyword @code{select} may not appear.
12775 @node No_Specific_Termination_Handlers,No_Specification_of_Aspect,No_Select_Statements,Partition-Wide Restrictions
12776 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-specific-termination-handlers}@anchor{1ed}
12777 @subsection No_Specific_Termination_Handlers
12780 @geindex No_Specific_Termination_Handlers
12782 [RM D.7] There are no calls to Ada.Task_Termination.Set_Specific_Handler
12783 or to Ada.Task_Termination.Specific_Handler.
12785 @node No_Specification_of_Aspect,No_Standard_Allocators_After_Elaboration,No_Specific_Termination_Handlers,Partition-Wide Restrictions
12786 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-specification-of-aspect}@anchor{1ee}
12787 @subsection No_Specification_of_Aspect
12790 @geindex No_Specification_of_Aspect
12792 [RM 13.12.1] This restriction checks at compile time that no aspect
12793 specification, attribute definition clause, or pragma is given for a
12796 @node No_Standard_Allocators_After_Elaboration,No_Standard_Storage_Pools,No_Specification_of_Aspect,Partition-Wide Restrictions
12797 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-standard-allocators-after-elaboration}@anchor{1ef}
12798 @subsection No_Standard_Allocators_After_Elaboration
12801 @geindex No_Standard_Allocators_After_Elaboration
12803 [RM D.7] Specifies that an allocator using a standard storage pool
12804 should never be evaluated at run time after the elaboration of the
12805 library items of the partition has completed. Otherwise, Storage_Error
12808 @node No_Standard_Storage_Pools,No_Stream_Optimizations,No_Standard_Allocators_After_Elaboration,Partition-Wide Restrictions
12809 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-standard-storage-pools}@anchor{1f0}
12810 @subsection No_Standard_Storage_Pools
12813 @geindex No_Standard_Storage_Pools
12815 [GNAT] This restriction ensures at compile time that no access types
12816 use the standard default storage pool. Any access type declared must
12817 have an explicit Storage_Pool attribute defined specifying a
12818 user-defined storage pool.
12820 @node No_Stream_Optimizations,No_Streams,No_Standard_Storage_Pools,Partition-Wide Restrictions
12821 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-stream-optimizations}@anchor{1f1}
12822 @subsection No_Stream_Optimizations
12825 @geindex No_Stream_Optimizations
12827 [GNAT] This restriction affects the performance of stream operations on types
12828 @code{String}, @code{Wide_String} and @code{Wide_Wide_String}. By default, the
12829 compiler uses block reads and writes when manipulating @code{String} objects
12830 due to their superior performance. When this restriction is in effect, the
12831 compiler performs all IO operations on a per-character basis.
12833 @node No_Streams,No_Task_Allocators,No_Stream_Optimizations,Partition-Wide Restrictions
12834 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-streams}@anchor{1f2}
12835 @subsection No_Streams
12838 @geindex No_Streams
12840 [GNAT] This restriction ensures at compile/bind time that there are no
12841 stream objects created and no use of stream attributes.
12842 This restriction does not forbid dependences on the package
12843 @code{Ada.Streams}. So it is permissible to with
12844 @code{Ada.Streams} (or another package that does so itself)
12845 as long as no actual stream objects are created and no
12846 stream attributes are used.
12848 Note that the use of restriction allows optimization of tagged types,
12849 since they do not need to worry about dispatching stream operations.
12850 To take maximum advantage of this space-saving optimization, any
12851 unit declaring a tagged type should be compiled with the restriction,
12852 though this is not required.
12854 @node No_Task_Allocators,No_Task_At_Interrupt_Priority,No_Streams,Partition-Wide Restrictions
12855 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-task-allocators}@anchor{1f3}
12856 @subsection No_Task_Allocators
12859 @geindex No_Task_Allocators
12861 [RM D.7] There are no allocators for task types
12862 or types containing task subcomponents.
12864 @node No_Task_At_Interrupt_Priority,No_Task_Attributes_Package,No_Task_Allocators,Partition-Wide Restrictions
12865 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-task-at-interrupt-priority}@anchor{1f4}
12866 @subsection No_Task_At_Interrupt_Priority
12869 @geindex No_Task_At_Interrupt_Priority
12871 [GNAT] This restriction ensures at compile time that there is no
12872 Interrupt_Priority aspect or pragma for a task or a task type. As
12873 a consequence, the tasks are always created with a priority below
12874 that an interrupt priority.
12876 @node No_Task_Attributes_Package,No_Task_Hierarchy,No_Task_At_Interrupt_Priority,Partition-Wide Restrictions
12877 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-task-attributes-package}@anchor{1f5}
12878 @subsection No_Task_Attributes_Package
12881 @geindex No_Task_Attributes_Package
12883 [GNAT] This restriction ensures at compile time that there are no implicit or
12884 explicit dependencies on the package @code{Ada.Task_Attributes}.
12886 @geindex No_Task_Attributes
12888 The restriction @code{No_Task_Attributes} is recognized as a synonym
12889 for @code{No_Task_Attributes_Package}. This is retained for historical
12890 compatibility purposes (and a warning will be generated for its use if
12891 warnings on obsolescent features are activated).
12893 @node No_Task_Hierarchy,No_Task_Termination,No_Task_Attributes_Package,Partition-Wide Restrictions
12894 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-task-hierarchy}@anchor{1f6}
12895 @subsection No_Task_Hierarchy
12898 @geindex No_Task_Hierarchy
12900 [RM D.7] All (non-environment) tasks depend
12901 directly on the environment task of the partition.
12903 @node No_Task_Termination,No_Tasking,No_Task_Hierarchy,Partition-Wide Restrictions
12904 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-task-termination}@anchor{1f7}
12905 @subsection No_Task_Termination
12908 @geindex No_Task_Termination
12910 [RM D.7] Tasks that terminate are erroneous.
12912 @node No_Tasking,No_Terminate_Alternatives,No_Task_Termination,Partition-Wide Restrictions
12913 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-tasking}@anchor{1f8}
12914 @subsection No_Tasking
12917 @geindex No_Tasking
12919 [GNAT] This restriction prevents the declaration of tasks or task types
12920 throughout the partition. It is similar in effect to the use of
12921 @code{Max_Tasks => 0} except that violations are caught at compile time
12922 and cause an error message to be output either by the compiler or
12925 @node No_Terminate_Alternatives,No_Unchecked_Access,No_Tasking,Partition-Wide Restrictions
12926 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-terminate-alternatives}@anchor{1f9}
12927 @subsection No_Terminate_Alternatives
12930 @geindex No_Terminate_Alternatives
12932 [RM D.7] There are no selective accepts with terminate alternatives.
12934 @node No_Unchecked_Access,No_Unchecked_Conversion,No_Terminate_Alternatives,Partition-Wide Restrictions
12935 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-unchecked-access}@anchor{1fa}
12936 @subsection No_Unchecked_Access
12939 @geindex No_Unchecked_Access
12941 [RM H.4] This restriction ensures at compile time that there are no
12942 occurrences of the Unchecked_Access attribute.
12944 @node No_Unchecked_Conversion,No_Unchecked_Deallocation,No_Unchecked_Access,Partition-Wide Restrictions
12945 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-unchecked-conversion}@anchor{1fb}
12946 @subsection No_Unchecked_Conversion
12949 @geindex No_Unchecked_Conversion
12951 [RM J.13] This restriction ensures at compile time that there are no semantic
12952 dependences on the predefined generic function Unchecked_Conversion.
12954 @node No_Unchecked_Deallocation,No_Use_Of_Entity,No_Unchecked_Conversion,Partition-Wide Restrictions
12955 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-unchecked-deallocation}@anchor{1fc}
12956 @subsection No_Unchecked_Deallocation
12959 @geindex No_Unchecked_Deallocation
12961 [RM J.13] This restriction ensures at compile time that there are no semantic
12962 dependences on the predefined generic procedure Unchecked_Deallocation.
12964 @node No_Use_Of_Entity,Pure_Barriers,No_Unchecked_Deallocation,Partition-Wide Restrictions
12965 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-use-of-entity}@anchor{1fd}
12966 @subsection No_Use_Of_Entity
12969 @geindex No_Use_Of_Entity
12971 [GNAT] This restriction ensures at compile time that there are no references
12972 to the entity given in the form
12975 No_Use_Of_Entity => Name
12978 where @code{Name} is the fully qualified entity, for example
12981 No_Use_Of_Entity => Ada.Text_IO.Put_Line
12984 @node Pure_Barriers,Simple_Barriers,No_Use_Of_Entity,Partition-Wide Restrictions
12985 @anchor{gnat_rm/standard_and_implementation_defined_restrictions pure-barriers}@anchor{1fe}
12986 @subsection Pure_Barriers
12989 @geindex Pure_Barriers
12991 [GNAT] This restriction ensures at compile time that protected entry
12992 barriers are restricted to:
12998 components of the protected object (excluding selection from dereferences),
13001 constant declarations,
13007 enumeration literals,
13016 character literals,
13019 implicitly defined comparison operators,
13022 uses of the Standard."not" operator,
13025 short-circuit operator,
13028 the Count attribute
13031 This restriction is a relaxation of the Simple_Barriers restriction,
13032 but still ensures absence of side effects, exceptions, and recursion
13033 during the evaluation of the barriers.
13035 @node Simple_Barriers,Static_Priorities,Pure_Barriers,Partition-Wide Restrictions
13036 @anchor{gnat_rm/standard_and_implementation_defined_restrictions simple-barriers}@anchor{1ff}
13037 @subsection Simple_Barriers
13040 @geindex Simple_Barriers
13042 [RM D.7] This restriction ensures at compile time that barriers in entry
13043 declarations for protected types are restricted to either static boolean
13044 expressions or references to simple boolean variables defined in the private
13045 part of the protected type. No other form of entry barriers is permitted.
13047 @geindex Boolean_Entry_Barriers
13049 The restriction @code{Boolean_Entry_Barriers} is recognized as a
13050 synonym for @code{Simple_Barriers}. This is retained for historical
13051 compatibility purposes (and a warning will be generated for its use if
13052 warnings on obsolescent features are activated).
13054 @node Static_Priorities,Static_Storage_Size,Simple_Barriers,Partition-Wide Restrictions
13055 @anchor{gnat_rm/standard_and_implementation_defined_restrictions static-priorities}@anchor{200}
13056 @subsection Static_Priorities
13059 @geindex Static_Priorities
13061 [GNAT] This restriction ensures at compile time that all priority expressions
13062 are static, and that there are no dependences on the package
13063 @code{Ada.Dynamic_Priorities}.
13065 @node Static_Storage_Size,,Static_Priorities,Partition-Wide Restrictions
13066 @anchor{gnat_rm/standard_and_implementation_defined_restrictions static-storage-size}@anchor{201}
13067 @subsection Static_Storage_Size
13070 @geindex Static_Storage_Size
13072 [GNAT] This restriction ensures at compile time that any expression appearing
13073 in a Storage_Size pragma or attribute definition clause is static.
13075 @node Program Unit Level Restrictions,,Partition-Wide Restrictions,Standard and Implementation Defined Restrictions
13076 @anchor{gnat_rm/standard_and_implementation_defined_restrictions program-unit-level-restrictions}@anchor{202}@anchor{gnat_rm/standard_and_implementation_defined_restrictions id3}@anchor{203}
13077 @section Program Unit Level Restrictions
13080 The second set of restriction identifiers
13081 does not require partition-wide consistency.
13082 The restriction may be enforced for a single
13083 compilation unit without any effect on any of the
13084 other compilation units in the partition.
13087 * No_Elaboration_Code::
13088 * No_Dynamic_Sized_Objects::
13090 * No_Implementation_Aspect_Specifications::
13091 * No_Implementation_Attributes::
13092 * No_Implementation_Identifiers::
13093 * No_Implementation_Pragmas::
13094 * No_Implementation_Restrictions::
13095 * No_Implementation_Units::
13096 * No_Implicit_Aliasing::
13097 * No_Implicit_Loops::
13098 * No_Obsolescent_Features::
13099 * No_Wide_Characters::
13100 * Static_Dispatch_Tables::
13105 @node No_Elaboration_Code,No_Dynamic_Sized_Objects,,Program Unit Level Restrictions
13106 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-elaboration-code}@anchor{204}
13107 @subsection No_Elaboration_Code
13110 @geindex No_Elaboration_Code
13112 [GNAT] This restriction ensures at compile time that no elaboration code is
13113 generated. Note that this is not the same condition as is enforced
13114 by pragma @code{Preelaborate}. There are cases in which pragma
13115 @code{Preelaborate} still permits code to be generated (e.g., code
13116 to initialize a large array to all zeroes), and there are cases of units
13117 which do not meet the requirements for pragma @code{Preelaborate},
13118 but for which no elaboration code is generated. Generally, it is
13119 the case that preelaborable units will meet the restrictions, with
13120 the exception of large aggregates initialized with an others_clause,
13121 and exception declarations (which generate calls to a run-time
13122 registry procedure). This restriction is enforced on
13123 a unit by unit basis, it need not be obeyed consistently
13124 throughout a partition.
13126 In the case of aggregates with others, if the aggregate has a dynamic
13127 size, there is no way to eliminate the elaboration code (such dynamic
13128 bounds would be incompatible with @code{Preelaborate} in any case). If
13129 the bounds are static, then use of this restriction actually modifies
13130 the code choice of the compiler to avoid generating a loop, and instead
13131 generate the aggregate statically if possible, no matter how many times
13132 the data for the others clause must be repeatedly generated.
13134 It is not possible to precisely document
13135 the constructs which are compatible with this restriction, since,
13136 unlike most other restrictions, this is not a restriction on the
13137 source code, but a restriction on the generated object code. For
13138 example, if the source contains a declaration:
13141 Val : constant Integer := X;
13144 where X is not a static constant, it may be possible, depending
13145 on complex optimization circuitry, for the compiler to figure
13146 out the value of X at compile time, in which case this initialization
13147 can be done by the loader, and requires no initialization code. It
13148 is not possible to document the precise conditions under which the
13149 optimizer can figure this out.
13151 Note that this the implementation of this restriction requires full
13152 code generation. If it is used in conjunction with "semantics only"
13153 checking, then some cases of violations may be missed.
13155 When this restriction is active, we are not requesting control-flow
13156 preservation with -fpreserve-control-flow, and the static elaboration model is
13157 used, the compiler is allowed to suppress the elaboration counter normally
13158 associated with the unit. This counter is typically used to check for access
13159 before elaboration and to control multiple elaboration attempts.
13161 @node No_Dynamic_Sized_Objects,No_Entry_Queue,No_Elaboration_Code,Program Unit Level Restrictions
13162 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-dynamic-sized-objects}@anchor{205}
13163 @subsection No_Dynamic_Sized_Objects
13166 @geindex No_Dynamic_Sized_Objects
13168 [GNAT] This restriction disallows certain constructs that might lead to the
13169 creation of dynamic-sized composite objects (or array or discriminated type).
13170 An array subtype indication is illegal if the bounds are not static
13171 or references to discriminants of an enclosing type.
13172 A discriminated subtype indication is illegal if the type has
13173 discriminant-dependent array components or a variant part, and the
13174 discriminants are not static. In addition, array and record aggregates are
13175 illegal in corresponding cases. Note that this restriction does not forbid
13176 access discriminants. It is often a good idea to combine this restriction
13177 with No_Secondary_Stack.
13179 @node No_Entry_Queue,No_Implementation_Aspect_Specifications,No_Dynamic_Sized_Objects,Program Unit Level Restrictions
13180 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-entry-queue}@anchor{206}
13181 @subsection No_Entry_Queue
13184 @geindex No_Entry_Queue
13186 [GNAT] This restriction is a declaration that any protected entry compiled in
13187 the scope of the restriction has at most one task waiting on the entry
13188 at any one time, and so no queue is required. This restriction is not
13189 checked at compile time. A program execution is erroneous if an attempt
13190 is made to queue a second task on such an entry.
13192 @node No_Implementation_Aspect_Specifications,No_Implementation_Attributes,No_Entry_Queue,Program Unit Level Restrictions
13193 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implementation-aspect-specifications}@anchor{207}
13194 @subsection No_Implementation_Aspect_Specifications
13197 @geindex No_Implementation_Aspect_Specifications
13199 [RM 13.12.1] This restriction checks at compile time that no
13200 GNAT-defined aspects are present. With this restriction, the only
13201 aspects that can be used are those defined in the Ada Reference Manual.
13203 @node No_Implementation_Attributes,No_Implementation_Identifiers,No_Implementation_Aspect_Specifications,Program Unit Level Restrictions
13204 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implementation-attributes}@anchor{208}
13205 @subsection No_Implementation_Attributes
13208 @geindex No_Implementation_Attributes
13210 [RM 13.12.1] This restriction checks at compile time that no
13211 GNAT-defined attributes are present. With this restriction, the only
13212 attributes that can be used are those defined in the Ada Reference
13215 @node No_Implementation_Identifiers,No_Implementation_Pragmas,No_Implementation_Attributes,Program Unit Level Restrictions
13216 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implementation-identifiers}@anchor{209}
13217 @subsection No_Implementation_Identifiers
13220 @geindex No_Implementation_Identifiers
13222 [RM 13.12.1] This restriction checks at compile time that no
13223 implementation-defined identifiers (marked with pragma Implementation_Defined)
13224 occur within language-defined packages.
13226 @node No_Implementation_Pragmas,No_Implementation_Restrictions,No_Implementation_Identifiers,Program Unit Level Restrictions
13227 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implementation-pragmas}@anchor{20a}
13228 @subsection No_Implementation_Pragmas
13231 @geindex No_Implementation_Pragmas
13233 [RM 13.12.1] This restriction checks at compile time that no
13234 GNAT-defined pragmas are present. With this restriction, the only
13235 pragmas that can be used are those defined in the Ada Reference Manual.
13237 @node No_Implementation_Restrictions,No_Implementation_Units,No_Implementation_Pragmas,Program Unit Level Restrictions
13238 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implementation-restrictions}@anchor{20b}
13239 @subsection No_Implementation_Restrictions
13242 @geindex No_Implementation_Restrictions
13244 [GNAT] This restriction checks at compile time that no GNAT-defined restriction
13245 identifiers (other than @code{No_Implementation_Restrictions} itself)
13246 are present. With this restriction, the only other restriction identifiers
13247 that can be used are those defined in the Ada Reference Manual.
13249 @node No_Implementation_Units,No_Implicit_Aliasing,No_Implementation_Restrictions,Program Unit Level Restrictions
13250 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implementation-units}@anchor{20c}
13251 @subsection No_Implementation_Units
13254 @geindex No_Implementation_Units
13256 [RM 13.12.1] This restriction checks at compile time that there is no
13257 mention in the context clause of any implementation-defined descendants
13258 of packages Ada, Interfaces, or System.
13260 @node No_Implicit_Aliasing,No_Implicit_Loops,No_Implementation_Units,Program Unit Level Restrictions
13261 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-aliasing}@anchor{20d}
13262 @subsection No_Implicit_Aliasing
13265 @geindex No_Implicit_Aliasing
13267 [GNAT] This restriction, which is not required to be partition-wide consistent,
13268 requires an explicit aliased keyword for an object to which 'Access,
13269 'Unchecked_Access, or 'Address is applied, and forbids entirely the use of
13270 the 'Unrestricted_Access attribute for objects. Note: the reason that
13271 Unrestricted_Access is forbidden is that it would require the prefix
13272 to be aliased, and in such cases, it can always be replaced by
13273 the standard attribute Unchecked_Access which is preferable.
13275 @node No_Implicit_Loops,No_Obsolescent_Features,No_Implicit_Aliasing,Program Unit Level Restrictions
13276 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-loops}@anchor{20e}
13277 @subsection No_Implicit_Loops
13280 @geindex No_Implicit_Loops
13282 [GNAT] This restriction ensures that the generated code of the unit marked
13283 with this restriction does not contain any implicit @code{for} loops, either by
13284 modifying the generated code where possible, or by rejecting any construct
13285 that would otherwise generate an implicit @code{for} loop. If this restriction is
13286 active, it is possible to build large array aggregates with all static
13287 components without generating an intermediate temporary, and without generating
13288 a loop to initialize individual components. Otherwise, a loop is created for
13289 arrays larger than about 5000 scalar components. Note that if this restriction
13290 is set in the spec of a package, it will not apply to its body.
13292 @node No_Obsolescent_Features,No_Wide_Characters,No_Implicit_Loops,Program Unit Level Restrictions
13293 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-obsolescent-features}@anchor{20f}
13294 @subsection No_Obsolescent_Features
13297 @geindex No_Obsolescent_Features
13299 [RM 13.12.1] This restriction checks at compile time that no obsolescent
13300 features are used, as defined in Annex J of the Ada Reference Manual.
13302 @node No_Wide_Characters,Static_Dispatch_Tables,No_Obsolescent_Features,Program Unit Level Restrictions
13303 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-wide-characters}@anchor{210}
13304 @subsection No_Wide_Characters
13307 @geindex No_Wide_Characters
13309 [GNAT] This restriction ensures at compile time that no uses of the types
13310 @code{Wide_Character} or @code{Wide_String} or corresponding wide
13312 appear, and that no wide or wide wide string or character literals
13313 appear in the program (that is literals representing characters not in
13314 type @code{Character}).
13316 @node Static_Dispatch_Tables,SPARK_05,No_Wide_Characters,Program Unit Level Restrictions
13317 @anchor{gnat_rm/standard_and_implementation_defined_restrictions static-dispatch-tables}@anchor{211}
13318 @subsection Static_Dispatch_Tables
13321 @geindex Static_Dispatch_Tables
13323 [GNAT] This restriction checks at compile time that all the artifacts
13324 associated with dispatch tables can be placed in read-only memory.
13326 @node SPARK_05,,Static_Dispatch_Tables,Program Unit Level Restrictions
13327 @anchor{gnat_rm/standard_and_implementation_defined_restrictions spark-05}@anchor{212}
13328 @subsection SPARK_05
13333 [GNAT] This restriction no longer has any effect and is superseded by
13334 SPARK 2014, whose restrictions are checked by the tool GNATprove. To check that
13335 a codebase respects SPARK 2014 restrictions, mark the code with pragma or
13336 aspect @code{SPARK_Mode}, and run the tool GNATprove at Stone assurance level, as
13340 gnatprove -P project.gpr --mode=stone
13346 gnatprove -P project.gpr --mode=check_all
13349 @node Implementation Advice,Implementation Defined Characteristics,Standard and Implementation Defined Restrictions,Top
13350 @anchor{gnat_rm/implementation_advice doc}@anchor{213}@anchor{gnat_rm/implementation_advice implementation-advice}@anchor{a}@anchor{gnat_rm/implementation_advice id1}@anchor{214}
13351 @chapter Implementation Advice
13354 The main text of the Ada Reference Manual describes the required
13355 behavior of all Ada compilers, and the GNAT compiler conforms to
13356 these requirements.
13358 In addition, there are sections throughout the Ada Reference Manual headed
13359 by the phrase 'Implementation advice'. These sections are not normative,
13360 i.e., they do not specify requirements that all compilers must
13361 follow. Rather they provide advice on generally desirable behavior.
13362 They are not requirements, because they describe behavior that cannot
13363 be provided on all systems, or may be undesirable on some systems.
13365 As far as practical, GNAT follows the implementation advice in
13366 the Ada Reference Manual. Each such RM section corresponds to a section
13367 in this chapter whose title specifies the
13368 RM section number and paragraph number and the subject of
13369 the advice. The contents of each section consists of the RM text within
13371 followed by the GNAT interpretation of the advice. Most often, this simply says
13372 'followed', which means that GNAT follows the advice. However, in a
13373 number of cases, GNAT deliberately deviates from this advice, in which
13374 case the text describes what GNAT does and why.
13376 @geindex Error detection
13379 * RM 1.1.3(20); Error Detection: RM 1 1 3 20 Error Detection.
13380 * RM 1.1.3(31); Child Units: RM 1 1 3 31 Child Units.
13381 * RM 1.1.5(12); Bounded Errors: RM 1 1 5 12 Bounded Errors.
13382 * RM 2.8(16); Pragmas: RM 2 8 16 Pragmas.
13383 * RM 2.8(17-19); Pragmas: RM 2 8 17-19 Pragmas.
13384 * RM 3.5.2(5); Alternative Character Sets: RM 3 5 2 5 Alternative Character Sets.
13385 * RM 3.5.4(28); Integer Types: RM 3 5 4 28 Integer Types.
13386 * RM 3.5.4(29); Integer Types: RM 3 5 4 29 Integer Types.
13387 * RM 3.5.5(8); Enumeration Values: RM 3 5 5 8 Enumeration Values.
13388 * RM 3.5.7(17); Float Types: RM 3 5 7 17 Float Types.
13389 * RM 3.6.2(11); Multidimensional Arrays: RM 3 6 2 11 Multidimensional Arrays.
13390 * RM 9.6(30-31); Duration'Small: RM 9 6 30-31 Duration'Small.
13391 * RM 10.2.1(12); Consistent Representation: RM 10 2 1 12 Consistent Representation.
13392 * RM 11.4.1(19); Exception Information: RM 11 4 1 19 Exception Information.
13393 * RM 11.5(28); Suppression of Checks: RM 11 5 28 Suppression of Checks.
13394 * RM 13.1 (21-24); Representation Clauses: RM 13 1 21-24 Representation Clauses.
13395 * RM 13.2(6-8); Packed Types: RM 13 2 6-8 Packed Types.
13396 * RM 13.3(14-19); Address Clauses: RM 13 3 14-19 Address Clauses.
13397 * RM 13.3(29-35); Alignment Clauses: RM 13 3 29-35 Alignment Clauses.
13398 * RM 13.3(42-43); Size Clauses: RM 13 3 42-43 Size Clauses.
13399 * RM 13.3(50-56); Size Clauses: RM 13 3 50-56 Size Clauses.
13400 * RM 13.3(71-73); Component Size Clauses: RM 13 3 71-73 Component Size Clauses.
13401 * RM 13.4(9-10); Enumeration Representation Clauses: RM 13 4 9-10 Enumeration Representation Clauses.
13402 * RM 13.5.1(17-22); Record Representation Clauses: RM 13 5 1 17-22 Record Representation Clauses.
13403 * RM 13.5.2(5); Storage Place Attributes: RM 13 5 2 5 Storage Place Attributes.
13404 * RM 13.5.3(7-8); Bit Ordering: RM 13 5 3 7-8 Bit Ordering.
13405 * RM 13.7(37); Address as Private: RM 13 7 37 Address as Private.
13406 * RM 13.7.1(16); Address Operations: RM 13 7 1 16 Address Operations.
13407 * RM 13.9(14-17); Unchecked Conversion: RM 13 9 14-17 Unchecked Conversion.
13408 * RM 13.11(23-25); Implicit Heap Usage: RM 13 11 23-25 Implicit Heap Usage.
13409 * RM 13.11.2(17); Unchecked Deallocation: RM 13 11 2 17 Unchecked Deallocation.
13410 * RM 13.13.2(1.6); Stream Oriented Attributes: RM 13 13 2 1 6 Stream Oriented Attributes.
13411 * RM A.1(52); Names of Predefined Numeric Types: RM A 1 52 Names of Predefined Numeric Types.
13412 * RM A.3.2(49); Ada.Characters.Handling: RM A 3 2 49 Ada Characters Handling.
13413 * RM A.4.4(106); Bounded-Length String Handling: RM A 4 4 106 Bounded-Length String Handling.
13414 * RM A.5.2(46-47); Random Number Generation: RM A 5 2 46-47 Random Number Generation.
13415 * RM A.10.7(23); Get_Immediate: RM A 10 7 23 Get_Immediate.
13416 * RM B.1(39-41); Pragma Export: RM B 1 39-41 Pragma Export.
13417 * RM B.2(12-13); Package Interfaces: RM B 2 12-13 Package Interfaces.
13418 * RM B.3(63-71); Interfacing with C: RM B 3 63-71 Interfacing with C.
13419 * RM B.4(95-98); Interfacing with COBOL: RM B 4 95-98 Interfacing with COBOL.
13420 * RM B.5(22-26); Interfacing with Fortran: RM B 5 22-26 Interfacing with Fortran.
13421 * RM C.1(3-5); Access to Machine Operations: RM C 1 3-5 Access to Machine Operations.
13422 * RM C.1(10-16); Access to Machine Operations: RM C 1 10-16 Access to Machine Operations.
13423 * RM C.3(28); Interrupt Support: RM C 3 28 Interrupt Support.
13424 * RM C.3.1(20-21); Protected Procedure Handlers: RM C 3 1 20-21 Protected Procedure Handlers.
13425 * RM C.3.2(25); Package Interrupts: RM C 3 2 25 Package Interrupts.
13426 * RM C.4(14); Pre-elaboration Requirements: RM C 4 14 Pre-elaboration Requirements.
13427 * RM C.5(8); Pragma Discard_Names: RM C 5 8 Pragma Discard_Names.
13428 * RM C.7.2(30); The Package Task_Attributes: RM C 7 2 30 The Package Task_Attributes.
13429 * RM D.3(17); Locking Policies: RM D 3 17 Locking Policies.
13430 * RM D.4(16); Entry Queuing Policies: RM D 4 16 Entry Queuing Policies.
13431 * RM D.6(9-10); Preemptive Abort: RM D 6 9-10 Preemptive Abort.
13432 * RM D.7(21); Tasking Restrictions: RM D 7 21 Tasking Restrictions.
13433 * RM D.8(47-49); Monotonic Time: RM D 8 47-49 Monotonic Time.
13434 * RM E.5(28-29); Partition Communication Subsystem: RM E 5 28-29 Partition Communication Subsystem.
13435 * RM F(7); COBOL Support: RM F 7 COBOL Support.
13436 * RM F.1(2); Decimal Radix Support: RM F 1 2 Decimal Radix Support.
13437 * RM G; Numerics: RM G Numerics.
13438 * RM G.1.1(56-58); Complex Types: RM G 1 1 56-58 Complex Types.
13439 * RM G.1.2(49); Complex Elementary Functions: RM G 1 2 49 Complex Elementary Functions.
13440 * RM G.2.4(19); Accuracy Requirements: RM G 2 4 19 Accuracy Requirements.
13441 * RM G.2.6(15); Complex Arithmetic Accuracy: RM G 2 6 15 Complex Arithmetic Accuracy.
13442 * RM H.6(15/2); Pragma Partition_Elaboration_Policy: RM H 6 15/2 Pragma Partition_Elaboration_Policy.
13446 @node RM 1 1 3 20 Error Detection,RM 1 1 3 31 Child Units,,Implementation Advice
13447 @anchor{gnat_rm/implementation_advice rm-1-1-3-20-error-detection}@anchor{215}
13448 @section RM 1.1.3(20): Error Detection
13453 "If an implementation detects the use of an unsupported Specialized Needs
13454 Annex feature at run time, it should raise @code{Program_Error} if
13458 Not relevant. All specialized needs annex features are either supported,
13459 or diagnosed at compile time.
13461 @geindex Child Units
13463 @node RM 1 1 3 31 Child Units,RM 1 1 5 12 Bounded Errors,RM 1 1 3 20 Error Detection,Implementation Advice
13464 @anchor{gnat_rm/implementation_advice rm-1-1-3-31-child-units}@anchor{216}
13465 @section RM 1.1.3(31): Child Units
13470 "If an implementation wishes to provide implementation-defined
13471 extensions to the functionality of a language-defined library unit, it
13472 should normally do so by adding children to the library unit."
13477 @geindex Bounded errors
13479 @node RM 1 1 5 12 Bounded Errors,RM 2 8 16 Pragmas,RM 1 1 3 31 Child Units,Implementation Advice
13480 @anchor{gnat_rm/implementation_advice rm-1-1-5-12-bounded-errors}@anchor{217}
13481 @section RM 1.1.5(12): Bounded Errors
13486 "If an implementation detects a bounded error or erroneous
13487 execution, it should raise @code{Program_Error}."
13490 Followed in all cases in which the implementation detects a bounded
13491 error or erroneous execution. Not all such situations are detected at
13496 @node RM 2 8 16 Pragmas,RM 2 8 17-19 Pragmas,RM 1 1 5 12 Bounded Errors,Implementation Advice
13497 @anchor{gnat_rm/implementation_advice id2}@anchor{218}@anchor{gnat_rm/implementation_advice rm-2-8-16-pragmas}@anchor{219}
13498 @section RM 2.8(16): Pragmas
13503 "Normally, implementation-defined pragmas should have no semantic effect
13504 for error-free programs; that is, if the implementation-defined pragmas
13505 are removed from a working program, the program should still be legal,
13506 and should still have the same semantics."
13509 The following implementation defined pragmas are exceptions to this
13513 @multitable {xxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxx}
13556 @emph{CPP_Constructor}
13572 @emph{Interface_Name}
13580 @emph{Machine_Attribute}
13588 @emph{Unimplemented_Unit}
13596 @emph{Unchecked_Union}
13605 In each of the above cases, it is essential to the purpose of the pragma
13606 that this advice not be followed. For details see
13607 @ref{7,,Implementation Defined Pragmas}.
13609 @node RM 2 8 17-19 Pragmas,RM 3 5 2 5 Alternative Character Sets,RM 2 8 16 Pragmas,Implementation Advice
13610 @anchor{gnat_rm/implementation_advice rm-2-8-17-19-pragmas}@anchor{21a}
13611 @section RM 2.8(17-19): Pragmas
13616 "Normally, an implementation should not define pragmas that can
13617 make an illegal program legal, except as follows:
13623 A pragma used to complete a declaration, such as a pragma @code{Import};
13626 A pragma used to configure the environment by adding, removing, or
13627 replacing @code{library_items}."
13631 See @ref{219,,RM 2.8(16); Pragmas}.
13633 @geindex Character Sets
13635 @geindex Alternative Character Sets
13637 @node RM 3 5 2 5 Alternative Character Sets,RM 3 5 4 28 Integer Types,RM 2 8 17-19 Pragmas,Implementation Advice
13638 @anchor{gnat_rm/implementation_advice rm-3-5-2-5-alternative-character-sets}@anchor{21b}
13639 @section RM 3.5.2(5): Alternative Character Sets
13644 "If an implementation supports a mode with alternative interpretations
13645 for @code{Character} and @code{Wide_Character}, the set of graphic
13646 characters of @code{Character} should nevertheless remain a proper
13647 subset of the set of graphic characters of @code{Wide_Character}. Any
13648 character set 'localizations' should be reflected in the results of
13649 the subprograms defined in the language-defined package
13650 @code{Characters.Handling} (see A.3) available in such a mode. In a mode with
13651 an alternative interpretation of @code{Character}, the implementation should
13652 also support a corresponding change in what is a legal
13653 @code{identifier_letter}."
13656 Not all wide character modes follow this advice, in particular the JIS
13657 and IEC modes reflect standard usage in Japan, and in these encoding,
13658 the upper half of the Latin-1 set is not part of the wide-character
13659 subset, since the most significant bit is used for wide character
13660 encoding. However, this only applies to the external forms. Internally
13661 there is no such restriction.
13663 @geindex Integer types
13665 @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
13666 @anchor{gnat_rm/implementation_advice rm-3-5-4-28-integer-types}@anchor{21c}
13667 @section RM 3.5.4(28): Integer Types
13672 "An implementation should support @code{Long_Integer} in addition to
13673 @code{Integer} if the target machine supports 32-bit (or longer)
13674 arithmetic. No other named integer subtypes are recommended for package
13675 @code{Standard}. Instead, appropriate named integer subtypes should be
13676 provided in the library package @code{Interfaces} (see B.2)."
13679 @code{Long_Integer} is supported. Other standard integer types are supported
13680 so this advice is not fully followed. These types
13681 are supported for convenient interface to C, and so that all hardware
13682 types of the machine are easily available.
13684 @node RM 3 5 4 29 Integer Types,RM 3 5 5 8 Enumeration Values,RM 3 5 4 28 Integer Types,Implementation Advice
13685 @anchor{gnat_rm/implementation_advice rm-3-5-4-29-integer-types}@anchor{21d}
13686 @section RM 3.5.4(29): Integer Types
13691 "An implementation for a two's complement machine should support
13692 modular types with a binary modulus up to @code{System.Max_Int*2+2}. An
13693 implementation should support a non-binary modules up to @code{Integer'Last}."
13698 @geindex Enumeration values
13700 @node RM 3 5 5 8 Enumeration Values,RM 3 5 7 17 Float Types,RM 3 5 4 29 Integer Types,Implementation Advice
13701 @anchor{gnat_rm/implementation_advice rm-3-5-5-8-enumeration-values}@anchor{21e}
13702 @section RM 3.5.5(8): Enumeration Values
13707 "For the evaluation of a call on @code{S'Pos} for an enumeration
13708 subtype, if the value of the operand does not correspond to the internal
13709 code for any enumeration literal of its type (perhaps due to an
13710 un-initialized variable), then the implementation should raise
13711 @code{Program_Error}. This is particularly important for enumeration
13712 types with noncontiguous internal codes specified by an
13713 enumeration_representation_clause."
13718 @geindex Float types
13720 @node RM 3 5 7 17 Float Types,RM 3 6 2 11 Multidimensional Arrays,RM 3 5 5 8 Enumeration Values,Implementation Advice
13721 @anchor{gnat_rm/implementation_advice rm-3-5-7-17-float-types}@anchor{21f}
13722 @section RM 3.5.7(17): Float Types
13727 "An implementation should support @code{Long_Float} in addition to
13728 @code{Float} if the target machine supports 11 or more digits of
13729 precision. No other named floating point subtypes are recommended for
13730 package @code{Standard}. Instead, appropriate named floating point subtypes
13731 should be provided in the library package @code{Interfaces} (see B.2)."
13734 @code{Short_Float} and @code{Long_Long_Float} are also provided. The
13735 former provides improved compatibility with other implementations
13736 supporting this type. The latter corresponds to the highest precision
13737 floating-point type supported by the hardware. On most machines, this
13738 will be the same as @code{Long_Float}, but on some machines, it will
13739 correspond to the IEEE extended form. The notable case is all ia32
13740 (x86) implementations, where @code{Long_Long_Float} corresponds to
13741 the 80-bit extended precision format supported in hardware on this
13742 processor. Note that the 128-bit format on SPARC is not supported,
13743 since this is a software rather than a hardware format.
13745 @geindex Multidimensional arrays
13748 @geindex multidimensional
13750 @node RM 3 6 2 11 Multidimensional Arrays,RM 9 6 30-31 Duration'Small,RM 3 5 7 17 Float Types,Implementation Advice
13751 @anchor{gnat_rm/implementation_advice rm-3-6-2-11-multidimensional-arrays}@anchor{220}
13752 @section RM 3.6.2(11): Multidimensional Arrays
13757 "An implementation should normally represent multidimensional arrays in
13758 row-major order, consistent with the notation used for multidimensional
13759 array aggregates (see 4.3.3). However, if a pragma @code{Convention}
13760 (@code{Fortran}, ...) applies to a multidimensional array type, then
13761 column-major order should be used instead (see B.5, @emph{Interfacing with Fortran})."
13766 @geindex Duration'Small
13768 @node RM 9 6 30-31 Duration'Small,RM 10 2 1 12 Consistent Representation,RM 3 6 2 11 Multidimensional Arrays,Implementation Advice
13769 @anchor{gnat_rm/implementation_advice rm-9-6-30-31-duration-small}@anchor{221}
13770 @section RM 9.6(30-31): Duration'Small
13775 "Whenever possible in an implementation, the value of @code{Duration'Small}
13776 should be no greater than 100 microseconds."
13779 Followed. (@code{Duration'Small} = 10**(-9)).
13783 "The time base for @code{delay_relative_statements} should be monotonic;
13784 it need not be the same time base as used for @code{Calendar.Clock}."
13789 @node RM 10 2 1 12 Consistent Representation,RM 11 4 1 19 Exception Information,RM 9 6 30-31 Duration'Small,Implementation Advice
13790 @anchor{gnat_rm/implementation_advice rm-10-2-1-12-consistent-representation}@anchor{222}
13791 @section RM 10.2.1(12): Consistent Representation
13796 "In an implementation, a type declared in a pre-elaborated package should
13797 have the same representation in every elaboration of a given version of
13798 the package, whether the elaborations occur in distinct executions of
13799 the same program, or in executions of distinct programs or partitions
13800 that include the given version."
13803 Followed, except in the case of tagged types. Tagged types involve
13804 implicit pointers to a local copy of a dispatch table, and these pointers
13805 have representations which thus depend on a particular elaboration of the
13806 package. It is not easy to see how it would be possible to follow this
13807 advice without severely impacting efficiency of execution.
13809 @geindex Exception information
13811 @node RM 11 4 1 19 Exception Information,RM 11 5 28 Suppression of Checks,RM 10 2 1 12 Consistent Representation,Implementation Advice
13812 @anchor{gnat_rm/implementation_advice rm-11-4-1-19-exception-information}@anchor{223}
13813 @section RM 11.4.1(19): Exception Information
13818 "@code{Exception_Message} by default and @code{Exception_Information}
13819 should produce information useful for
13820 debugging. @code{Exception_Message} should be short, about one
13821 line. @code{Exception_Information} can be long. @code{Exception_Message}
13822 should not include the
13823 @code{Exception_Name}. @code{Exception_Information} should include both
13824 the @code{Exception_Name} and the @code{Exception_Message}."
13827 Followed. For each exception that doesn't have a specified
13828 @code{Exception_Message}, the compiler generates one containing the location
13829 of the raise statement. This location has the form 'file_name:line', where
13830 file_name is the short file name (without path information) and line is the line
13831 number in the file. Note that in the case of the Zero Cost Exception
13832 mechanism, these messages become redundant with the Exception_Information that
13833 contains a full backtrace of the calling sequence, so they are disabled.
13834 To disable explicitly the generation of the source location message, use the
13835 Pragma @code{Discard_Names}.
13837 @geindex Suppression of checks
13840 @geindex suppression of
13842 @node RM 11 5 28 Suppression of Checks,RM 13 1 21-24 Representation Clauses,RM 11 4 1 19 Exception Information,Implementation Advice
13843 @anchor{gnat_rm/implementation_advice rm-11-5-28-suppression-of-checks}@anchor{224}
13844 @section RM 11.5(28): Suppression of Checks
13849 "The implementation should minimize the code executed for checks that
13850 have been suppressed."
13855 @geindex Representation clauses
13857 @node RM 13 1 21-24 Representation Clauses,RM 13 2 6-8 Packed Types,RM 11 5 28 Suppression of Checks,Implementation Advice
13858 @anchor{gnat_rm/implementation_advice rm-13-1-21-24-representation-clauses}@anchor{225}
13859 @section RM 13.1 (21-24): Representation Clauses
13864 "The recommended level of support for all representation items is
13865 qualified as follows:
13867 An implementation need not support representation items containing
13868 nonstatic expressions, except that an implementation should support a
13869 representation item for a given entity if each nonstatic expression in
13870 the representation item is a name that statically denotes a constant
13871 declared before the entity."
13874 Followed. In fact, GNAT goes beyond the recommended level of support
13875 by allowing nonstatic expressions in some representation clauses even
13876 without the need to declare constants initialized with the values of
13883 for Y'Address use X'Address;>>
13886 "An implementation need not support a specification for the `@w{`}Size`@w{`}
13887 for a given composite subtype, nor the size or storage place for an
13888 object (including a component) of a given composite subtype, unless the
13889 constraints on the subtype and its composite subcomponents (if any) are
13890 all static constraints."
13893 Followed. Size Clauses are not permitted on nonstatic components, as
13898 "An aliased component, or a component whose type is by-reference, should
13899 always be allocated at an addressable location."
13904 @geindex Packed types
13906 @node RM 13 2 6-8 Packed Types,RM 13 3 14-19 Address Clauses,RM 13 1 21-24 Representation Clauses,Implementation Advice
13907 @anchor{gnat_rm/implementation_advice rm-13-2-6-8-packed-types}@anchor{226}
13908 @section RM 13.2(6-8): Packed Types
13913 "If a type is packed, then the implementation should try to minimize
13914 storage allocated to objects of the type, possibly at the expense of
13915 speed of accessing components, subject to reasonable complexity in
13916 addressing calculations.
13918 The recommended level of support pragma @code{Pack} is:
13920 For a packed record type, the components should be packed as tightly as
13921 possible subject to the Sizes of the component subtypes, and subject to
13922 any @emph{record_representation_clause} that applies to the type; the
13923 implementation may, but need not, reorder components or cross aligned
13924 word boundaries to improve the packing. A component whose @code{Size} is
13925 greater than the word size may be allocated an integral number of words."
13928 Followed. Tight packing of arrays is supported for all component sizes
13929 up to 64-bits. If the array component size is 1 (that is to say, if
13930 the component is a boolean type or an enumeration type with two values)
13931 then values of the type are implicitly initialized to zero. This
13932 happens both for objects of the packed type, and for objects that have a
13933 subcomponent of the packed type.
13937 "An implementation should support Address clauses for imported
13943 @geindex Address clauses
13945 @node RM 13 3 14-19 Address Clauses,RM 13 3 29-35 Alignment Clauses,RM 13 2 6-8 Packed Types,Implementation Advice
13946 @anchor{gnat_rm/implementation_advice rm-13-3-14-19-address-clauses}@anchor{227}
13947 @section RM 13.3(14-19): Address Clauses
13952 "For an array @code{X}, @code{X'Address} should point at the first
13953 component of the array, and not at the array bounds."
13960 "The recommended level of support for the @code{Address} attribute is:
13962 @code{X'Address} should produce a useful result if @code{X} is an
13963 object that is aliased or of a by-reference type, or is an entity whose
13964 @code{Address} has been specified."
13967 Followed. A valid address will be produced even if none of those
13968 conditions have been met. If necessary, the object is forced into
13969 memory to ensure the address is valid.
13973 "An implementation should support @code{Address} clauses for imported
13981 "Objects (including subcomponents) that are aliased or of a by-reference
13982 type should be allocated on storage element boundaries."
13989 "If the @code{Address} of an object is specified, or it is imported or exported,
13990 then the implementation should not perform optimizations based on
13991 assumptions of no aliases."
13996 @geindex Alignment clauses
13998 @node RM 13 3 29-35 Alignment Clauses,RM 13 3 42-43 Size Clauses,RM 13 3 14-19 Address Clauses,Implementation Advice
13999 @anchor{gnat_rm/implementation_advice rm-13-3-29-35-alignment-clauses}@anchor{228}
14000 @section RM 13.3(29-35): Alignment Clauses
14005 "The recommended level of support for the @code{Alignment} attribute for
14008 An implementation should support specified Alignments that are factors
14009 and multiples of the number of storage elements per word, subject to the
14017 "An implementation need not support specified Alignments for
14018 combinations of Sizes and Alignments that cannot be easily
14019 loaded and stored by available machine instructions."
14026 "An implementation need not support specified Alignments that are
14027 greater than the maximum @code{Alignment} the implementation ever returns by
14035 "The recommended level of support for the @code{Alignment} attribute for
14038 Same as above, for subtypes, but in addition:"
14045 "For stand-alone library-level objects of statically constrained
14046 subtypes, the implementation should support all alignments
14047 supported by the target linker. For example, page alignment is likely to
14048 be supported for such objects, but not for subtypes."
14053 @geindex Size clauses
14055 @node RM 13 3 42-43 Size Clauses,RM 13 3 50-56 Size Clauses,RM 13 3 29-35 Alignment Clauses,Implementation Advice
14056 @anchor{gnat_rm/implementation_advice rm-13-3-42-43-size-clauses}@anchor{229}
14057 @section RM 13.3(42-43): Size Clauses
14062 "The recommended level of support for the @code{Size} attribute of
14065 A @code{Size} clause should be supported for an object if the specified
14066 @code{Size} is at least as large as its subtype's @code{Size}, and
14067 corresponds to a size in storage elements that is a multiple of the
14068 object's @code{Alignment} (if the @code{Alignment} is nonzero)."
14073 @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
14074 @anchor{gnat_rm/implementation_advice rm-13-3-50-56-size-clauses}@anchor{22a}
14075 @section RM 13.3(50-56): Size Clauses
14080 "If the @code{Size} of a subtype is specified, and allows for efficient
14081 independent addressability (see 9.10) on the target architecture, then
14082 the @code{Size} of the following objects of the subtype should equal the
14083 @code{Size} of the subtype:
14085 Aliased objects (including components)."
14092 "@cite{Size} clause on a composite subtype should not affect the
14093 internal layout of components."
14096 Followed. But note that this can be overridden by use of the implementation
14097 pragma Implicit_Packing in the case of packed arrays.
14101 "The recommended level of support for the @code{Size} attribute of subtypes is:
14103 The @code{Size} (if not specified) of a static discrete or fixed point
14104 subtype should be the number of bits needed to represent each value
14105 belonging to the subtype using an unbiased representation, leaving space
14106 for a sign bit only if the subtype contains negative values. If such a
14107 subtype is a first subtype, then an implementation should support a
14108 specified @code{Size} for it that reflects this representation."
14115 "For a subtype implemented with levels of indirection, the @code{Size}
14116 should include the size of the pointers, but not the size of what they
14122 @geindex Component_Size clauses
14124 @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
14125 @anchor{gnat_rm/implementation_advice rm-13-3-71-73-component-size-clauses}@anchor{22b}
14126 @section RM 13.3(71-73): Component Size Clauses
14131 "The recommended level of support for the @code{Component_Size}
14134 An implementation need not support specified @code{Component_Sizes} that are
14135 less than the @code{Size} of the component subtype."
14142 "An implementation should support specified Component_Sizes that
14143 are factors and multiples of the word size. For such
14144 Component_Sizes, the array should contain no gaps between
14145 components. For other Component_Sizes (if supported), the array
14146 should contain no gaps between components when packing is also
14147 specified; the implementation should forbid this combination in cases
14148 where it cannot support a no-gaps representation."
14153 @geindex Enumeration representation clauses
14155 @geindex Representation clauses
14156 @geindex enumeration
14158 @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
14159 @anchor{gnat_rm/implementation_advice rm-13-4-9-10-enumeration-representation-clauses}@anchor{22c}
14160 @section RM 13.4(9-10): Enumeration Representation Clauses
14165 "The recommended level of support for enumeration representation clauses
14168 An implementation need not support enumeration representation clauses
14169 for boolean types, but should at minimum support the internal codes in
14170 the range @code{System.Min_Int .. System.Max_Int}."
14175 @geindex Record representation clauses
14177 @geindex Representation clauses
14180 @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
14181 @anchor{gnat_rm/implementation_advice rm-13-5-1-17-22-record-representation-clauses}@anchor{22d}
14182 @section RM 13.5.1(17-22): Record Representation Clauses
14187 "The recommended level of support for
14188 @emph{record_representation_clause}s is:
14190 An implementation should support storage places that can be extracted
14191 with a load, mask, shift sequence of machine code, and set with a load,
14192 shift, mask, store sequence, given the available machine instructions
14193 and run-time model."
14200 "A storage place should be supported if its size is equal to the
14201 @code{Size} of the component subtype, and it starts and ends on a
14202 boundary that obeys the @code{Alignment} of the component subtype."
14209 "If the default bit ordering applies to the declaration of a given type,
14210 then for a component whose subtype's @code{Size} is less than the word
14211 size, any storage place that does not cross an aligned word boundary
14212 should be supported."
14219 "An implementation may reserve a storage place for the tag field of a
14220 tagged type, and disallow other components from overlapping that place."
14223 Followed. The storage place for the tag field is the beginning of the tagged
14224 record, and its size is Address'Size. GNAT will reject an explicit component
14225 clause for the tag field.
14229 "An implementation need not support a @emph{component_clause} for a
14230 component of an extension part if the storage place is not after the
14231 storage places of all components of the parent type, whether or not
14232 those storage places had been specified."
14235 Followed. The above advice on record representation clauses is followed,
14236 and all mentioned features are implemented.
14238 @geindex Storage place attributes
14240 @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
14241 @anchor{gnat_rm/implementation_advice rm-13-5-2-5-storage-place-attributes}@anchor{22e}
14242 @section RM 13.5.2(5): Storage Place Attributes
14247 "If a component is represented using some form of pointer (such as an
14248 offset) to the actual data of the component, and this data is contiguous
14249 with the rest of the object, then the storage place attributes should
14250 reflect the place of the actual data, not the pointer. If a component is
14251 allocated discontinuously from the rest of the object, then a warning
14252 should be generated upon reference to one of its storage place
14256 Followed. There are no such components in GNAT.
14258 @geindex Bit ordering
14260 @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
14261 @anchor{gnat_rm/implementation_advice rm-13-5-3-7-8-bit-ordering}@anchor{22f}
14262 @section RM 13.5.3(7-8): Bit Ordering
14267 "The recommended level of support for the non-default bit ordering is:
14269 If @code{Word_Size} = @code{Storage_Unit}, then the implementation
14270 should support the non-default bit ordering in addition to the default
14274 Followed. Word size does not equal storage size in this implementation.
14275 Thus non-default bit ordering is not supported.
14278 @geindex as private type
14280 @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
14281 @anchor{gnat_rm/implementation_advice rm-13-7-37-address-as-private}@anchor{230}
14282 @section RM 13.7(37): Address as Private
14287 "@cite{Address} should be of a private type."
14292 @geindex Operations
14293 @geindex on `@w{`}Address`@w{`}
14296 @geindex operations of
14298 @node RM 13 7 1 16 Address Operations,RM 13 9 14-17 Unchecked Conversion,RM 13 7 37 Address as Private,Implementation Advice
14299 @anchor{gnat_rm/implementation_advice rm-13-7-1-16-address-operations}@anchor{231}
14300 @section RM 13.7.1(16): Address Operations
14305 "Operations in @code{System} and its children should reflect the target
14306 environment semantics as closely as is reasonable. For example, on most
14307 machines, it makes sense for address arithmetic to 'wrap around'.
14308 Operations that do not make sense should raise @code{Program_Error}."
14311 Followed. Address arithmetic is modular arithmetic that wraps around. No
14312 operation raises @code{Program_Error}, since all operations make sense.
14314 @geindex Unchecked conversion
14316 @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
14317 @anchor{gnat_rm/implementation_advice rm-13-9-14-17-unchecked-conversion}@anchor{232}
14318 @section RM 13.9(14-17): Unchecked Conversion
14323 "The @code{Size} of an array object should not include its bounds; hence,
14324 the bounds should not be part of the converted data."
14331 "The implementation should not generate unnecessary run-time checks to
14332 ensure that the representation of @code{S} is a representation of the
14333 target type. It should take advantage of the permission to return by
14334 reference when possible. Restrictions on unchecked conversions should be
14335 avoided unless required by the target environment."
14338 Followed. There are no restrictions on unchecked conversion. A warning is
14339 generated if the source and target types do not have the same size since
14340 the semantics in this case may be target dependent.
14344 "The recommended level of support for unchecked conversions is:
14346 Unchecked conversions should be supported and should be reversible in
14347 the cases where this clause defines the result. To enable meaningful use
14348 of unchecked conversion, a contiguous representation should be used for
14349 elementary subtypes, for statically constrained array subtypes whose
14350 component subtype is one of the subtypes described in this paragraph,
14351 and for record subtypes without discriminants whose component subtypes
14352 are described in this paragraph."
14357 @geindex Heap usage
14360 @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
14361 @anchor{gnat_rm/implementation_advice rm-13-11-23-25-implicit-heap-usage}@anchor{233}
14362 @section RM 13.11(23-25): Implicit Heap Usage
14367 "An implementation should document any cases in which it dynamically
14368 allocates heap storage for a purpose other than the evaluation of an
14372 Followed, the only other points at which heap storage is dynamically
14373 allocated are as follows:
14379 At initial elaboration time, to allocate dynamically sized global
14383 To allocate space for a task when a task is created.
14386 To extend the secondary stack dynamically when needed. The secondary
14387 stack is used for returning variable length results.
14393 "A default (implementation-provided) storage pool for an
14394 access-to-constant type should not have overhead to support deallocation of
14395 individual objects."
14402 "A storage pool for an anonymous access type should be created at the
14403 point of an allocator for the type, and be reclaimed when the designated
14404 object becomes inaccessible."
14409 @geindex Unchecked deallocation
14411 @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
14412 @anchor{gnat_rm/implementation_advice rm-13-11-2-17-unchecked-deallocation}@anchor{234}
14413 @section RM 13.11.2(17): Unchecked Deallocation
14418 "For a standard storage pool, @code{Free} should actually reclaim the
14424 @geindex Stream oriented attributes
14426 @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
14427 @anchor{gnat_rm/implementation_advice rm-13-13-2-1-6-stream-oriented-attributes}@anchor{235}
14428 @section RM 13.13.2(1.6): Stream Oriented Attributes
14433 "If not specified, the value of Stream_Size for an elementary type
14434 should be the number of bits that corresponds to the minimum number of
14435 stream elements required by the first subtype of the type, rounded up
14436 to the nearest factor or multiple of the word size that is also a
14437 multiple of the stream element size."
14440 Followed, except that the number of stream elements is 1, 2, 3, 4 or 8.
14441 The Stream_Size may be used to override the default choice.
14443 The default implementation is based on direct binary representations and is
14444 therefore target- and endianness-dependent. To address this issue, GNAT also
14445 supplies an alternate implementation of the stream attributes @code{Read} and
14446 @code{Write}, which uses the target-independent XDR standard representation for
14447 scalar types. This XDR alternative can be enabled via the binder switch -xdr.
14449 @geindex XDR representation
14451 @geindex Read attribute
14453 @geindex Write attribute
14455 @geindex Stream oriented attributes
14457 @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
14458 @anchor{gnat_rm/implementation_advice rm-a-1-52-names-of-predefined-numeric-types}@anchor{236}
14459 @section RM A.1(52): Names of Predefined Numeric Types
14464 "If an implementation provides additional named predefined integer types,
14465 then the names should end with @code{Integer} as in
14466 @code{Long_Integer}. If an implementation provides additional named
14467 predefined floating point types, then the names should end with
14468 @code{Float} as in @code{Long_Float}."
14473 @geindex Ada.Characters.Handling
14475 @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
14476 @anchor{gnat_rm/implementation_advice rm-a-3-2-49-ada-characters-handling}@anchor{237}
14477 @section RM A.3.2(49): @code{Ada.Characters.Handling}
14482 "If an implementation provides a localized definition of @code{Character}
14483 or @code{Wide_Character}, then the effects of the subprograms in
14484 @code{Characters.Handling} should reflect the localizations.
14488 Followed. GNAT provides no such localized definitions.
14490 @geindex Bounded-length strings
14492 @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
14493 @anchor{gnat_rm/implementation_advice rm-a-4-4-106-bounded-length-string-handling}@anchor{238}
14494 @section RM A.4.4(106): Bounded-Length String Handling
14499 "Bounded string objects should not be implemented by implicit pointers
14500 and dynamic allocation."
14503 Followed. No implicit pointers or dynamic allocation are used.
14505 @geindex Random number generation
14507 @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
14508 @anchor{gnat_rm/implementation_advice rm-a-5-2-46-47-random-number-generation}@anchor{239}
14509 @section RM A.5.2(46-47): Random Number Generation
14514 "Any storage associated with an object of type @code{Generator} should be
14515 reclaimed on exit from the scope of the object."
14522 "If the generator period is sufficiently long in relation to the number
14523 of distinct initiator values, then each possible value of
14524 @code{Initiator} passed to @code{Reset} should initiate a sequence of
14525 random numbers that does not, in a practical sense, overlap the sequence
14526 initiated by any other value. If this is not possible, then the mapping
14527 between initiator values and generator states should be a rapidly
14528 varying function of the initiator value."
14531 Followed. The generator period is sufficiently long for the first
14532 condition here to hold true.
14534 @geindex Get_Immediate
14536 @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
14537 @anchor{gnat_rm/implementation_advice rm-a-10-7-23-get-immediate}@anchor{23a}
14538 @section RM A.10.7(23): @code{Get_Immediate}
14543 "The @code{Get_Immediate} procedures should be implemented with
14544 unbuffered input. For a device such as a keyboard, input should be
14545 available if a key has already been typed, whereas for a disk
14546 file, input should always be available except at end of file. For a file
14547 associated with a keyboard-like device, any line-editing features of the
14548 underlying operating system should be disabled during the execution of
14549 @code{Get_Immediate}."
14552 Followed on all targets except VxWorks. For VxWorks, there is no way to
14553 provide this functionality that does not result in the input buffer being
14554 flushed before the @code{Get_Immediate} call. A special unit
14555 @code{Interfaces.Vxworks.IO} is provided that contains routines to enable
14556 this functionality.
14560 @node RM B 1 39-41 Pragma Export,RM B 2 12-13 Package Interfaces,RM A 10 7 23 Get_Immediate,Implementation Advice
14561 @anchor{gnat_rm/implementation_advice rm-b-1-39-41-pragma-export}@anchor{23b}
14562 @section RM B.1(39-41): Pragma @code{Export}
14567 "If an implementation supports pragma @code{Export} to a given language,
14568 then it should also allow the main subprogram to be written in that
14569 language. It should support some mechanism for invoking the elaboration
14570 of the Ada library units included in the system, and for invoking the
14571 finalization of the environment task. On typical systems, the
14572 recommended mechanism is to provide two subprograms whose link names are
14573 @code{adainit} and @code{adafinal}. @code{adainit} should contain the
14574 elaboration code for library units. @code{adafinal} should contain the
14575 finalization code. These subprograms should have no effect the second
14576 and subsequent time they are called."
14583 "Automatic elaboration of pre-elaborated packages should be
14584 provided when pragma @code{Export} is supported."
14587 Followed when the main program is in Ada. If the main program is in a
14588 foreign language, then
14589 @code{adainit} must be called to elaborate pre-elaborated
14594 "For each supported convention @emph{L} other than @code{Intrinsic}, an
14595 implementation should support @code{Import} and @code{Export} pragmas
14596 for objects of @emph{L}-compatible types and for subprograms, and pragma
14597 @cite{Convention} for @emph{L}-eligible types and for subprograms,
14598 presuming the other language has corresponding features. Pragma
14599 @code{Convention} need not be supported for scalar types."
14604 @geindex Package Interfaces
14606 @geindex Interfaces
14608 @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
14609 @anchor{gnat_rm/implementation_advice rm-b-2-12-13-package-interfaces}@anchor{23c}
14610 @section RM B.2(12-13): Package @code{Interfaces}
14615 "For each implementation-defined convention identifier, there should be a
14616 child package of package Interfaces with the corresponding name. This
14617 package should contain any declarations that would be useful for
14618 interfacing to the language (implementation) represented by the
14619 convention. Any declarations useful for interfacing to any language on
14620 the given hardware architecture should be provided directly in
14621 @code{Interfaces}."
14628 "An implementation supporting an interface to C, COBOL, or Fortran should
14629 provide the corresponding package or packages described in the following
14633 Followed. GNAT provides all the packages described in this section.
14636 @geindex interfacing with
14638 @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
14639 @anchor{gnat_rm/implementation_advice rm-b-3-63-71-interfacing-with-c}@anchor{23d}
14640 @section RM B.3(63-71): Interfacing with C
14645 "An implementation should support the following interface correspondences
14646 between Ada and C."
14653 "An Ada procedure corresponds to a void-returning C function."
14660 "An Ada function corresponds to a non-void C function."
14667 "An Ada @code{in} scalar parameter is passed as a scalar argument to a C
14675 "An Ada @code{in} parameter of an access-to-object type with designated
14676 type @code{T} is passed as a @code{t*} argument to a C function,
14677 where @code{t} is the C type corresponding to the Ada type @code{T}."
14684 "An Ada access @code{T} parameter, or an Ada @code{out} or @code{in out}
14685 parameter of an elementary type @code{T}, is passed as a @code{t*}
14686 argument to a C function, where @code{t} is the C type corresponding to
14687 the Ada type @code{T}. In the case of an elementary @code{out} or
14688 @code{in out} parameter, a pointer to a temporary copy is used to
14689 preserve by-copy semantics."
14696 "An Ada parameter of a record type @code{T}, of any mode, is passed as a
14697 @code{t*} argument to a C function, where @code{t} is the C
14698 structure corresponding to the Ada type @code{T}."
14701 Followed. This convention may be overridden by the use of the C_Pass_By_Copy
14702 pragma, or Convention, or by explicitly specifying the mechanism for a given
14703 call using an extended import or export pragma.
14707 "An Ada parameter of an array type with component type @code{T}, of any
14708 mode, is passed as a @code{t*} argument to a C function, where
14709 @code{t} is the C type corresponding to the Ada type @code{T}."
14716 "An Ada parameter of an access-to-subprogram type is passed as a pointer
14717 to a C function whose prototype corresponds to the designated
14718 subprogram's specification."
14724 @geindex interfacing with
14726 @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
14727 @anchor{gnat_rm/implementation_advice rm-b-4-95-98-interfacing-with-cobol}@anchor{23e}
14728 @section RM B.4(95-98): Interfacing with COBOL
14733 "An Ada implementation should support the following interface
14734 correspondences between Ada and COBOL."
14741 "An Ada access @code{T} parameter is passed as a @code{BY REFERENCE} data item of
14742 the COBOL type corresponding to @code{T}."
14749 "An Ada in scalar parameter is passed as a @code{BY CONTENT} data item of
14750 the corresponding COBOL type."
14757 "Any other Ada parameter is passed as a @code{BY REFERENCE} data item of the
14758 COBOL type corresponding to the Ada parameter type; for scalars, a local
14759 copy is used if necessary to ensure by-copy semantics."
14765 @geindex interfacing with
14767 @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
14768 @anchor{gnat_rm/implementation_advice rm-b-5-22-26-interfacing-with-fortran}@anchor{23f}
14769 @section RM B.5(22-26): Interfacing with Fortran
14774 "An Ada implementation should support the following interface
14775 correspondences between Ada and Fortran:"
14782 "An Ada procedure corresponds to a Fortran subroutine."
14789 "An Ada function corresponds to a Fortran function."
14796 "An Ada parameter of an elementary, array, or record type @code{T} is
14797 passed as a @code{T} argument to a Fortran procedure, where @code{T} is
14798 the Fortran type corresponding to the Ada type @code{T}, and where the
14799 INTENT attribute of the corresponding dummy argument matches the Ada
14800 formal parameter mode; the Fortran implementation's parameter passing
14801 conventions are used. For elementary types, a local copy is used if
14802 necessary to ensure by-copy semantics."
14809 "An Ada parameter of an access-to-subprogram type is passed as a
14810 reference to a Fortran procedure whose interface corresponds to the
14811 designated subprogram's specification."
14816 @geindex Machine operations
14818 @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
14819 @anchor{gnat_rm/implementation_advice rm-c-1-3-5-access-to-machine-operations}@anchor{240}
14820 @section RM C.1(3-5): Access to Machine Operations
14825 "The machine code or intrinsic support should allow access to all
14826 operations normally available to assembly language programmers for the
14827 target environment, including privileged instructions, if any."
14834 "The interfacing pragmas (see Annex B) should support interface to
14835 assembler; the default assembler should be associated with the
14836 convention identifier @code{Assembler}."
14843 "If an entity is exported to assembly language, then the implementation
14844 should allocate it at an addressable location, and should ensure that it
14845 is retained by the linking process, even if not otherwise referenced
14846 from the Ada code. The implementation should assume that any call to a
14847 machine code or assembler subprogram is allowed to read or update every
14848 object that is specified as exported."
14853 @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
14854 @anchor{gnat_rm/implementation_advice rm-c-1-10-16-access-to-machine-operations}@anchor{241}
14855 @section RM C.1(10-16): Access to Machine Operations
14860 "The implementation should ensure that little or no overhead is
14861 associated with calling intrinsic and machine-code subprograms."
14864 Followed for both intrinsics and machine-code subprograms.
14868 "It is recommended that intrinsic subprograms be provided for convenient
14869 access to any machine operations that provide special capabilities or
14870 efficiency and that are not otherwise available through the language
14874 Followed. A full set of machine operation intrinsic subprograms is provided.
14878 "Atomic read-modify-write operations---e.g., test and set, compare and
14879 swap, decrement and test, enqueue/dequeue."
14882 Followed on any target supporting such operations.
14886 "Standard numeric functions---e.g.:, sin, log."
14889 Followed on any target supporting such operations.
14893 "String manipulation operations---e.g.:, translate and test."
14896 Followed on any target supporting such operations.
14900 "Vector operations---e.g.:, compare vector against thresholds."
14903 Followed on any target supporting such operations.
14907 "Direct operations on I/O ports."
14910 Followed on any target supporting such operations.
14912 @geindex Interrupt support
14914 @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
14915 @anchor{gnat_rm/implementation_advice rm-c-3-28-interrupt-support}@anchor{242}
14916 @section RM C.3(28): Interrupt Support
14921 "If the @code{Ceiling_Locking} policy is not in effect, the
14922 implementation should provide means for the application to specify which
14923 interrupts are to be blocked during protected actions, if the underlying
14924 system allows for a finer-grain control of interrupt blocking."
14927 Followed. The underlying system does not allow for finer-grain control
14928 of interrupt blocking.
14930 @geindex Protected procedure handlers
14932 @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
14933 @anchor{gnat_rm/implementation_advice rm-c-3-1-20-21-protected-procedure-handlers}@anchor{243}
14934 @section RM C.3.1(20-21): Protected Procedure Handlers
14939 "Whenever possible, the implementation should allow interrupt handlers to
14940 be called directly by the hardware."
14943 Followed on any target where the underlying operating system permits
14948 "Whenever practical, violations of any
14949 implementation-defined restrictions should be detected before run time."
14952 Followed. Compile time warnings are given when possible.
14954 @geindex Package `@w{`}Interrupts`@w{`}
14956 @geindex Interrupts
14958 @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
14959 @anchor{gnat_rm/implementation_advice rm-c-3-2-25-package-interrupts}@anchor{244}
14960 @section RM C.3.2(25): Package @code{Interrupts}
14965 "If implementation-defined forms of interrupt handler procedures are
14966 supported, such as protected procedures with parameters, then for each
14967 such form of a handler, a type analogous to @code{Parameterless_Handler}
14968 should be specified in a child package of @code{Interrupts}, with the
14969 same operations as in the predefined package Interrupts."
14974 @geindex Pre-elaboration requirements
14976 @node RM C 4 14 Pre-elaboration Requirements,RM C 5 8 Pragma Discard_Names,RM C 3 2 25 Package Interrupts,Implementation Advice
14977 @anchor{gnat_rm/implementation_advice rm-c-4-14-pre-elaboration-requirements}@anchor{245}
14978 @section RM C.4(14): Pre-elaboration Requirements
14983 "It is recommended that pre-elaborated packages be implemented in such a
14984 way that there should be little or no code executed at run time for the
14985 elaboration of entities not already covered by the Implementation
14989 Followed. Executable code is generated in some cases, e.g., loops
14990 to initialize large arrays.
14992 @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
14993 @anchor{gnat_rm/implementation_advice rm-c-5-8-pragma-discard-names}@anchor{246}
14994 @section RM C.5(8): Pragma @code{Discard_Names}
14999 "If the pragma applies to an entity, then the implementation should
15000 reduce the amount of storage used for storing names associated with that
15006 @geindex Package Task_Attributes
15008 @geindex Task_Attributes
15010 @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
15011 @anchor{gnat_rm/implementation_advice rm-c-7-2-30-the-package-task-attributes}@anchor{247}
15012 @section RM C.7.2(30): The Package Task_Attributes
15017 "Some implementations are targeted to domains in which memory use at run
15018 time must be completely deterministic. For such implementations, it is
15019 recommended that the storage for task attributes will be pre-allocated
15020 statically and not from the heap. This can be accomplished by either
15021 placing restrictions on the number and the size of the task's
15022 attributes, or by using the pre-allocated storage for the first @code{N}
15023 attribute objects, and the heap for the others. In the latter case,
15024 @code{N} should be documented."
15027 Not followed. This implementation is not targeted to such a domain.
15029 @geindex Locking Policies
15031 @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
15032 @anchor{gnat_rm/implementation_advice rm-d-3-17-locking-policies}@anchor{248}
15033 @section RM D.3(17): Locking Policies
15038 "The implementation should use names that end with @code{_Locking} for
15039 locking policies defined by the implementation."
15042 Followed. Two implementation-defined locking policies are defined,
15043 whose names (@code{Inheritance_Locking} and
15044 @code{Concurrent_Readers_Locking}) follow this suggestion.
15046 @geindex Entry queuing policies
15048 @node RM D 4 16 Entry Queuing Policies,RM D 6 9-10 Preemptive Abort,RM D 3 17 Locking Policies,Implementation Advice
15049 @anchor{gnat_rm/implementation_advice rm-d-4-16-entry-queuing-policies}@anchor{249}
15050 @section RM D.4(16): Entry Queuing Policies
15055 "Names that end with @code{_Queuing} should be used
15056 for all implementation-defined queuing policies."
15059 Followed. No such implementation-defined queuing policies exist.
15061 @geindex Preemptive abort
15063 @node RM D 6 9-10 Preemptive Abort,RM D 7 21 Tasking Restrictions,RM D 4 16 Entry Queuing Policies,Implementation Advice
15064 @anchor{gnat_rm/implementation_advice rm-d-6-9-10-preemptive-abort}@anchor{24a}
15065 @section RM D.6(9-10): Preemptive Abort
15070 "Even though the @emph{abort_statement} is included in the list of
15071 potentially blocking operations (see 9.5.1), it is recommended that this
15072 statement be implemented in a way that never requires the task executing
15073 the @emph{abort_statement} to block."
15080 "On a multi-processor, the delay associated with aborting a task on
15081 another processor should be bounded; the implementation should use
15082 periodic polling, if necessary, to achieve this."
15087 @geindex Tasking restrictions
15089 @node RM D 7 21 Tasking Restrictions,RM D 8 47-49 Monotonic Time,RM D 6 9-10 Preemptive Abort,Implementation Advice
15090 @anchor{gnat_rm/implementation_advice rm-d-7-21-tasking-restrictions}@anchor{24b}
15091 @section RM D.7(21): Tasking Restrictions
15096 "When feasible, the implementation should take advantage of the specified
15097 restrictions to produce a more efficient implementation."
15100 GNAT currently takes advantage of these restrictions by providing an optimized
15101 run time when the Ravenscar profile and the GNAT restricted run time set
15102 of restrictions are specified. See pragma @code{Profile (Ravenscar)} and
15103 pragma @code{Profile (Restricted)} for more details.
15108 @node RM D 8 47-49 Monotonic Time,RM E 5 28-29 Partition Communication Subsystem,RM D 7 21 Tasking Restrictions,Implementation Advice
15109 @anchor{gnat_rm/implementation_advice rm-d-8-47-49-monotonic-time}@anchor{24c}
15110 @section RM D.8(47-49): Monotonic Time
15115 "When appropriate, implementations should provide configuration
15116 mechanisms to change the value of @code{Tick}."
15119 Such configuration mechanisms are not appropriate to this implementation
15120 and are thus not supported.
15124 "It is recommended that @code{Calendar.Clock} and @code{Real_Time.Clock}
15125 be implemented as transformations of the same time base."
15132 "It is recommended that the best time base which exists in
15133 the underlying system be available to the application through
15134 @code{Clock}. @cite{Best} may mean highest accuracy or largest range."
15139 @geindex Partition communication subsystem
15143 @node RM E 5 28-29 Partition Communication Subsystem,RM F 7 COBOL Support,RM D 8 47-49 Monotonic Time,Implementation Advice
15144 @anchor{gnat_rm/implementation_advice rm-e-5-28-29-partition-communication-subsystem}@anchor{24d}
15145 @section RM E.5(28-29): Partition Communication Subsystem
15150 "Whenever possible, the PCS on the called partition should allow for
15151 multiple tasks to call the RPC-receiver with different messages and
15152 should allow them to block until the corresponding subprogram body
15156 Followed by GLADE, a separately supplied PCS that can be used with
15161 "The @code{Write} operation on a stream of type @code{Params_Stream_Type}
15162 should raise @code{Storage_Error} if it runs out of space trying to
15163 write the @code{Item} into the stream."
15166 Followed by GLADE, a separately supplied PCS that can be used with
15169 @geindex COBOL support
15171 @node RM F 7 COBOL Support,RM F 1 2 Decimal Radix Support,RM E 5 28-29 Partition Communication Subsystem,Implementation Advice
15172 @anchor{gnat_rm/implementation_advice rm-f-7-cobol-support}@anchor{24e}
15173 @section RM F(7): COBOL Support
15178 "If COBOL (respectively, C) is widely supported in the target
15179 environment, implementations supporting the Information Systems Annex
15180 should provide the child package @code{Interfaces.COBOL} (respectively,
15181 @code{Interfaces.C}) specified in Annex B and should support a
15182 @code{convention_identifier} of COBOL (respectively, C) in the interfacing
15183 pragmas (see Annex B), thus allowing Ada programs to interface with
15184 programs written in that language."
15189 @geindex Decimal radix support
15191 @node RM F 1 2 Decimal Radix Support,RM G Numerics,RM F 7 COBOL Support,Implementation Advice
15192 @anchor{gnat_rm/implementation_advice rm-f-1-2-decimal-radix-support}@anchor{24f}
15193 @section RM F.1(2): Decimal Radix Support
15198 "Packed decimal should be used as the internal representation for objects
15199 of subtype @code{S} when @code{S}'Machine_Radix = 10."
15202 Not followed. GNAT ignores @code{S}'Machine_Radix and always uses binary
15207 @node RM G Numerics,RM G 1 1 56-58 Complex Types,RM F 1 2 Decimal Radix Support,Implementation Advice
15208 @anchor{gnat_rm/implementation_advice rm-g-numerics}@anchor{250}
15209 @section RM G: Numerics
15214 "If Fortran (respectively, C) is widely supported in the target
15215 environment, implementations supporting the Numerics Annex
15216 should provide the child package @code{Interfaces.Fortran} (respectively,
15217 @code{Interfaces.C}) specified in Annex B and should support a
15218 @code{convention_identifier} of Fortran (respectively, C) in the interfacing
15219 pragmas (see Annex B), thus allowing Ada programs to interface with
15220 programs written in that language."
15225 @geindex Complex types
15227 @node RM G 1 1 56-58 Complex Types,RM G 1 2 49 Complex Elementary Functions,RM G Numerics,Implementation Advice
15228 @anchor{gnat_rm/implementation_advice rm-g-1-1-56-58-complex-types}@anchor{251}
15229 @section RM G.1.1(56-58): Complex Types
15234 "Because the usual mathematical meaning of multiplication of a complex
15235 operand and a real operand is that of the scaling of both components of
15236 the former by the latter, an implementation should not perform this
15237 operation by first promoting the real operand to complex type and then
15238 performing a full complex multiplication. In systems that, in the
15239 future, support an Ada binding to IEC 559:1989, the latter technique
15240 will not generate the required result when one of the components of the
15241 complex operand is infinite. (Explicit multiplication of the infinite
15242 component by the zero component obtained during promotion yields a NaN
15243 that propagates into the final result.) Analogous advice applies in the
15244 case of multiplication of a complex operand and a pure-imaginary
15245 operand, and in the case of division of a complex operand by a real or
15246 pure-imaginary operand."
15253 "Similarly, because the usual mathematical meaning of addition of a
15254 complex operand and a real operand is that the imaginary operand remains
15255 unchanged, an implementation should not perform this operation by first
15256 promoting the real operand to complex type and then performing a full
15257 complex addition. In implementations in which the @code{Signed_Zeros}
15258 attribute of the component type is @code{True} (and which therefore
15259 conform to IEC 559:1989 in regard to the handling of the sign of zero in
15260 predefined arithmetic operations), the latter technique will not
15261 generate the required result when the imaginary component of the complex
15262 operand is a negatively signed zero. (Explicit addition of the negative
15263 zero to the zero obtained during promotion yields a positive zero.)
15264 Analogous advice applies in the case of addition of a complex operand
15265 and a pure-imaginary operand, and in the case of subtraction of a
15266 complex operand and a real or pure-imaginary operand."
15273 "Implementations in which @code{Real'Signed_Zeros} is @code{True} should
15274 attempt to provide a rational treatment of the signs of zero results and
15275 result components. As one example, the result of the @code{Argument}
15276 function should have the sign of the imaginary component of the
15277 parameter @code{X} when the point represented by that parameter lies on
15278 the positive real axis; as another, the sign of the imaginary component
15279 of the @code{Compose_From_Polar} function should be the same as
15280 (respectively, the opposite of) that of the @code{Argument} parameter when that
15281 parameter has a value of zero and the @code{Modulus} parameter has a
15282 nonnegative (respectively, negative) value."
15287 @geindex Complex elementary functions
15289 @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
15290 @anchor{gnat_rm/implementation_advice rm-g-1-2-49-complex-elementary-functions}@anchor{252}
15291 @section RM G.1.2(49): Complex Elementary Functions
15296 "Implementations in which @code{Complex_Types.Real'Signed_Zeros} is
15297 @code{True} should attempt to provide a rational treatment of the signs
15298 of zero results and result components. For example, many of the complex
15299 elementary functions have components that are odd functions of one of
15300 the parameter components; in these cases, the result component should
15301 have the sign of the parameter component at the origin. Other complex
15302 elementary functions have zero components whose sign is opposite that of
15303 a parameter component at the origin, or is always positive or always
15309 @geindex Accuracy requirements
15311 @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
15312 @anchor{gnat_rm/implementation_advice rm-g-2-4-19-accuracy-requirements}@anchor{253}
15313 @section RM G.2.4(19): Accuracy Requirements
15318 "The versions of the forward trigonometric functions without a
15319 @code{Cycle} parameter should not be implemented by calling the
15320 corresponding version with a @code{Cycle} parameter of
15321 @code{2.0*Numerics.Pi}, since this will not provide the required
15322 accuracy in some portions of the domain. For the same reason, the
15323 version of @code{Log} without a @code{Base} parameter should not be
15324 implemented by calling the corresponding version with a @code{Base}
15325 parameter of @code{Numerics.e}."
15330 @geindex Complex arithmetic accuracy
15333 @geindex complex arithmetic
15335 @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
15336 @anchor{gnat_rm/implementation_advice rm-g-2-6-15-complex-arithmetic-accuracy}@anchor{254}
15337 @section RM G.2.6(15): Complex Arithmetic Accuracy
15342 "The version of the @code{Compose_From_Polar} function without a
15343 @code{Cycle} parameter should not be implemented by calling the
15344 corresponding version with a @code{Cycle} parameter of
15345 @code{2.0*Numerics.Pi}, since this will not provide the required
15346 accuracy in some portions of the domain."
15351 @geindex Sequential elaboration policy
15353 @node RM H 6 15/2 Pragma Partition_Elaboration_Policy,,RM G 2 6 15 Complex Arithmetic Accuracy,Implementation Advice
15354 @anchor{gnat_rm/implementation_advice rm-h-6-15-2-pragma-partition-elaboration-policy}@anchor{255}
15355 @section RM H.6(15/2): Pragma Partition_Elaboration_Policy
15360 "If the partition elaboration policy is @code{Sequential} and the
15361 Environment task becomes permanently blocked during elaboration then the
15362 partition is deadlocked and it is recommended that the partition be
15363 immediately terminated."
15368 @node Implementation Defined Characteristics,Intrinsic Subprograms,Implementation Advice,Top
15369 @anchor{gnat_rm/implementation_defined_characteristics implementation-defined-characteristics}@anchor{b}@anchor{gnat_rm/implementation_defined_characteristics doc}@anchor{256}@anchor{gnat_rm/implementation_defined_characteristics id1}@anchor{257}
15370 @chapter Implementation Defined Characteristics
15373 In addition to the implementation dependent pragmas and attributes, and the
15374 implementation advice, there are a number of other Ada features that are
15375 potentially implementation dependent and are designated as
15376 implementation-defined. These are mentioned throughout the Ada Reference
15377 Manual, and are summarized in Annex M.
15379 A requirement for conforming Ada compilers is that they provide
15380 documentation describing how the implementation deals with each of these
15381 issues. In this chapter you will find each point in Annex M listed,
15382 followed by a description of how GNAT handles the implementation dependence.
15384 You can use this chapter as a guide to minimizing implementation
15385 dependent features in your programs if portability to other compilers
15386 and other operating systems is an important consideration. The numbers
15387 in each entry below correspond to the paragraph numbers in the Ada
15394 "Whether or not each recommendation given in Implementation
15395 Advice is followed. See 1.1.2(37)."
15398 See @ref{a,,Implementation Advice}.
15404 "Capacity limitations of the implementation. See 1.1.3(3)."
15407 The complexity of programs that can be processed is limited only by the
15408 total amount of available virtual memory, and disk space for the
15409 generated object files.
15415 "Variations from the standard that are impractical to avoid
15416 given the implementation's execution environment. See 1.1.3(6)."
15419 There are no variations from the standard.
15425 "Which code_statements cause external
15426 interactions. See 1.1.3(10)."
15429 Any @emph{code_statement} can potentially cause external interactions.
15435 "The coded representation for the text of an Ada
15436 program. See 2.1(4)."
15439 See separate section on source representation.
15445 "The control functions allowed in comments. See 2.1(14)."
15448 See separate section on source representation.
15454 "The representation for an end of line. See 2.2(2)."
15457 See separate section on source representation.
15463 "Maximum supported line length and lexical element
15464 length. See 2.2(15)."
15467 The maximum line length is 255 characters and the maximum length of
15468 a lexical element is also 255 characters. This is the default setting
15469 if not overridden by the use of compiler switch @emph{-gnaty} (which
15470 sets the maximum to 79) or @emph{-gnatyMnn} which allows the maximum
15471 line length to be specified to be any value up to 32767. The maximum
15472 length of a lexical element is the same as the maximum line length.
15478 "Implementation defined pragmas. See 2.8(14)."
15481 See @ref{7,,Implementation Defined Pragmas}.
15487 "Effect of pragma @code{Optimize}. See 2.8(27)."
15490 Pragma @code{Optimize}, if given with a @code{Time} or @code{Space}
15491 parameter, checks that the optimization flag is set, and aborts if it is
15498 "The sequence of characters of the value returned by
15499 @code{S'Image} when some of the graphic characters of
15500 @code{S'Wide_Image} are not defined in @code{Character}. See
15504 The sequence of characters is as defined by the wide character encoding
15505 method used for the source. See section on source representation for
15512 "The predefined integer types declared in
15513 @code{Standard}. See 3.5.4(25)."
15517 @multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
15528 @emph{Short_Short_Integer}
15536 @emph{Short_Integer}
15552 @emph{Long_Integer}
15556 64-bit signed (on most 64-bit targets,
15557 depending on the C definition of long)
15558 32-bit signed (on all other targets)
15562 @emph{Long_Long_Integer}
15570 @emph{Long_Long_Long_Integer}
15574 128-bit signed (on 64-bit targets)
15575 64-bit signed (on 32-bit targets)
15584 "Any nonstandard integer types and the operators defined
15585 for them. See 3.5.4(26)."
15588 There are no nonstandard integer types.
15594 "Any nonstandard real types and the operators defined for
15595 them. See 3.5.6(8)."
15598 There are no nonstandard real types.
15604 "What combinations of requested decimal precision and range
15605 are supported for floating point types. See 3.5.7(7)."
15608 The precision and range is as defined by the IEEE standard.
15614 "The predefined floating point types declared in
15615 @code{Standard}. See 3.5.7(16)."
15619 @multitable {xxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
15642 (Short) 32 bit IEEE short
15654 @emph{Long_Long_Float}
15658 64 bit IEEE long (80 bit IEEE long on x86 processors)
15667 "The small of an ordinary fixed point type. See 3.5.9(8)."
15670 @code{Fine_Delta} is 2**(-63)
15676 "What combinations of small, range, and digits are
15677 supported for fixed point types. See 3.5.9(10)."
15680 Any combinations are permitted that do not result in a small less than
15681 @code{Fine_Delta} and do not result in a mantissa larger than 63 bits.
15682 If the mantissa is larger than 53 bits on machines where Long_Long_Float
15683 is 64 bits (true of all architectures except x86), then the output from
15684 Text_IO is accurate to only 53 bits, rather than the full mantissa. This
15685 is because floating-point conversions are used to convert fixed point.
15691 "The result of @code{Tags.Expanded_Name} for types declared
15692 within an unnamed @emph{block_statement}. See 3.9(10)."
15695 Block numbers of the form @code{B@emph{nnn}}, where @emph{nnn} is a
15696 decimal integer are allocated.
15702 "Implementation-defined attributes. See 4.1.4(12)."
15705 See @ref{8,,Implementation Defined Attributes}.
15711 "Any implementation-defined time types. See 9.6(6)."
15714 There are no implementation-defined time types.
15720 "The time base associated with relative delays."
15723 See 9.6(20). The time base used is that provided by the C library
15724 function @code{gettimeofday}.
15730 "The time base of the type @code{Calendar.Time}. See
15734 The time base used is that provided by the C library function
15735 @code{gettimeofday}.
15741 "The time zone used for package @code{Calendar}
15742 operations. See 9.6(24)."
15745 The time zone used by package @code{Calendar} is the current system time zone
15746 setting for local time, as accessed by the C library function
15753 "Any limit on @emph{delay_until_statements} of
15754 @emph{select_statements}. See 9.6(29)."
15757 There are no such limits.
15763 "Whether or not two non-overlapping parts of a composite
15764 object are independently addressable, in the case where packing, record
15765 layout, or @code{Component_Size} is specified for the object. See
15769 Separate components are independently addressable if they do not share
15770 overlapping storage units.
15776 "The representation for a compilation. See 10.1(2)."
15779 A compilation is represented by a sequence of files presented to the
15780 compiler in a single invocation of the @emph{gcc} command.
15786 "Any restrictions on compilations that contain multiple
15787 compilation_units. See 10.1(4)."
15790 No single file can contain more than one compilation unit, but any
15791 sequence of files can be presented to the compiler as a single
15798 "The mechanisms for creating an environment and for adding
15799 and replacing compilation units. See 10.1.4(3)."
15802 See separate section on compilation model.
15808 "The manner of explicitly assigning library units to a
15809 partition. See 10.2(2)."
15812 If a unit contains an Ada main program, then the Ada units for the partition
15813 are determined by recursive application of the rules in the Ada Reference
15814 Manual section 10.2(2-6). In other words, the Ada units will be those that
15815 are needed by the main program, and then this definition of need is applied
15816 recursively to those units, and the partition contains the transitive
15817 closure determined by this relationship. In short, all the necessary units
15818 are included, with no need to explicitly specify the list. If additional
15819 units are required, e.g., by foreign language units, then all units must be
15820 mentioned in the context clause of one of the needed Ada units.
15822 If the partition contains no main program, or if the main program is in
15823 a language other than Ada, then GNAT
15824 provides the binder options @emph{-z} and @emph{-n} respectively, and in
15825 this case a list of units can be explicitly supplied to the binder for
15826 inclusion in the partition (all units needed by these units will also
15827 be included automatically). For full details on the use of these
15828 options, refer to @emph{GNAT Make Program gnatmake} in the
15829 @cite{GNAT User's Guide}.
15835 "The implementation-defined means, if any, of specifying
15836 which compilation units are needed by a given compilation unit. See
15840 The units needed by a given compilation unit are as defined in
15841 the Ada Reference Manual section 10.2(2-6). There are no
15842 implementation-defined pragmas or other implementation-defined
15843 means for specifying needed units.
15849 "The manner of designating the main subprogram of a
15850 partition. See 10.2(7)."
15853 The main program is designated by providing the name of the
15854 corresponding @code{ALI} file as the input parameter to the binder.
15860 "The order of elaboration of @emph{library_items}. See
15864 The first constraint on ordering is that it meets the requirements of
15865 Chapter 10 of the Ada Reference Manual. This still leaves some
15866 implementation dependent choices, which are resolved by first
15867 elaborating bodies as early as possible (i.e., in preference to specs
15868 where there is a choice), and second by evaluating the immediate with
15869 clauses of a unit to determine the probably best choice, and
15870 third by elaborating in alphabetical order of unit names
15871 where a choice still remains.
15877 "Parameter passing and function return for the main
15878 subprogram. See 10.2(21)."
15881 The main program has no parameters. It may be a procedure, or a function
15882 returning an integer type. In the latter case, the returned integer
15883 value is the return code of the program (overriding any value that
15884 may have been set by a call to @code{Ada.Command_Line.Set_Exit_Status}).
15890 "The mechanisms for building and running partitions. See
15894 GNAT itself supports programs with only a single partition. The GNATDIST
15895 tool provided with the GLADE package (which also includes an implementation
15896 of the PCS) provides a completely flexible method for building and running
15897 programs consisting of multiple partitions. See the separate GLADE manual
15904 "The details of program execution, including program
15905 termination. See 10.2(25)."
15908 See separate section on compilation model.
15914 "The semantics of any non-active partitions supported by the
15915 implementation. See 10.2(28)."
15918 Passive partitions are supported on targets where shared memory is
15919 provided by the operating system. See the GLADE reference manual for
15926 "The information returned by @code{Exception_Message}. See
15930 Exception message returns the null string unless a specific message has
15931 been passed by the program.
15937 "The result of @code{Exceptions.Exception_Name} for types
15938 declared within an unnamed @emph{block_statement}. See 11.4.1(12)."
15941 Blocks have implementation defined names of the form @code{B@emph{nnn}}
15942 where @emph{nnn} is an integer.
15948 "The information returned by
15949 @code{Exception_Information}. See 11.4.1(13)."
15952 @code{Exception_Information} returns a string in the following format:
15955 *Exception_Name:* nnnnn
15958 *Load address:* 0xhhhh
15959 *Call stack traceback locations:*
15960 0xhhhh 0xhhhh 0xhhhh ... 0xhhh
15971 @code{nnnn} is the fully qualified name of the exception in all upper
15972 case letters. This line is always present.
15975 @code{mmmm} is the message (this line present only if message is non-null)
15978 @code{ppp} is the Process Id value as a decimal integer (this line is
15979 present only if the Process Id is nonzero). Currently we are
15980 not making use of this field.
15983 The Load address line, the Call stack traceback locations line and the
15984 following values are present only if at least one traceback location was
15985 recorded. The Load address indicates the address at which the main executable
15986 was loaded; this line may not be present if operating system hasn't relocated
15987 the main executable. The values are given in C style format, with lower case
15988 letters for a-f, and only as many digits present as are necessary.
15989 The line terminator sequence at the end of each line, including
15990 the last line is a single @code{LF} character (@code{16#0A#}).
15998 "Implementation-defined check names. See 11.5(27)."
16001 The implementation defined check names include Alignment_Check,
16002 Atomic_Synchronization, Duplicated_Tag_Check, Container_Checks,
16003 Tampering_Check, Predicate_Check, and Validity_Check. In addition, a user
16004 program can add implementation-defined check names by means of the pragma
16005 Check_Name. See the description of pragma @code{Suppress} for full details.
16011 "The interpretation of each aspect of representation. See
16015 See separate section on data representations.
16021 "Any restrictions placed upon representation items. See
16025 See separate section on data representations.
16031 "The meaning of @code{Size} for indefinite subtypes. See
16035 Size for an indefinite subtype is the maximum possible size, except that
16036 for the case of a subprogram parameter, the size of the parameter object
16037 is the actual size.
16043 "The default external representation for a type tag. See
16047 The default external representation for a type tag is the fully expanded
16048 name of the type in upper case letters.
16054 "What determines whether a compilation unit is the same in
16055 two different partitions. See 13.3(76)."
16058 A compilation unit is the same in two different partitions if and only
16059 if it derives from the same source file.
16065 "Implementation-defined components. See 13.5.1(15)."
16068 The only implementation defined component is the tag for a tagged type,
16069 which contains a pointer to the dispatching table.
16075 "If @code{Word_Size} = @code{Storage_Unit}, the default bit
16076 ordering. See 13.5.3(5)."
16079 @code{Word_Size} (32) is not the same as @code{Storage_Unit} (8) for this
16080 implementation, so no non-default bit ordering is supported. The default
16081 bit ordering corresponds to the natural endianness of the target architecture.
16087 "The contents of the visible part of package @code{System}
16088 and its language-defined children. See 13.7(2)."
16091 See the definition of these packages in files @code{system.ads} and
16092 @code{s-stoele.ads}. Note that two declarations are added to package
16096 Max_Priority : constant Positive := Priority'Last;
16097 Max_Interrupt_Priority : constant Positive := Interrupt_Priority'Last;
16104 "The contents of the visible part of package
16105 @code{System.Machine_Code}, and the meaning of
16106 @emph{code_statements}. See 13.8(7)."
16109 See the definition and documentation in file @code{s-maccod.ads}.
16115 "The effect of unchecked conversion. See 13.9(11)."
16118 Unchecked conversion between types of the same size
16119 results in an uninterpreted transmission of the bits from one type
16120 to the other. If the types are of unequal sizes, then in the case of
16121 discrete types, a shorter source is first zero or sign extended as
16122 necessary, and a shorter target is simply truncated on the left.
16123 For all non-discrete types, the source is first copied if necessary
16124 to ensure that the alignment requirements of the target are met, then
16125 a pointer is constructed to the source value, and the result is obtained
16126 by dereferencing this pointer after converting it to be a pointer to the
16127 target type. Unchecked conversions where the target subtype is an
16128 unconstrained array are not permitted. If the target alignment is
16129 greater than the source alignment, then a copy of the result is
16130 made with appropriate alignment
16136 "The semantics of operations on invalid representations.
16137 See 13.9.2(10-11)."
16140 For assignments and other operations where the use of invalid values cannot
16141 result in erroneous behavior, the compiler ignores the possibility of invalid
16142 values. An exception is raised at the point where an invalid value would
16143 result in erroneous behavior. For example executing:
16146 procedure invalidvals is
16148 Y : Natural range 1 .. 10;
16149 for Y'Address use X'Address;
16150 Z : Natural range 1 .. 10;
16151 A : array (Natural range 1 .. 10) of Integer;
16153 Z := Y; -- no exception
16154 A (Z) := 3; -- exception raised;
16158 As indicated, an exception is raised on the array assignment, but not
16159 on the simple assignment of the invalid negative value from Y to Z.
16165 "The manner of choosing a storage pool for an access type
16166 when @code{Storage_Pool} is not specified for the type. See 13.11(17)."
16169 There are 3 different standard pools used by the compiler when
16170 @code{Storage_Pool} is not specified depending whether the type is local
16171 to a subprogram or defined at the library level and whether
16172 @code{Storage_Size`@w{`}is specified or not. See documentation in the runtime
16173 library units `@w{`}System.Pool_Global}, @code{System.Pool_Size} and
16174 @code{System.Pool_Local} in files @code{s-poosiz.ads},
16175 @code{s-pooglo.ads} and @code{s-pooloc.ads} for full details on the
16176 default pools used.
16182 "Whether or not the implementation provides user-accessible
16183 names for the standard pool type(s). See 13.11(17)."
16186 See documentation in the sources of the run time mentioned in the previous
16187 paragraph. All these pools are accessible by means of @cite{with}ing
16194 "The meaning of @code{Storage_Size}. See 13.11(18)."
16197 @code{Storage_Size} is measured in storage units, and refers to the
16198 total space available for an access type collection, or to the primary
16199 stack space for a task.
16205 "Implementation-defined aspects of storage pools. See
16209 See documentation in the sources of the run time mentioned in the
16210 paragraph about standard storage pools above
16211 for details on GNAT-defined aspects of storage pools.
16217 "The set of restrictions allowed in a pragma
16218 @code{Restrictions}. See 13.12(7)."
16221 See @ref{9,,Standard and Implementation Defined Restrictions}.
16227 "The consequences of violating limitations on
16228 @code{Restrictions} pragmas. See 13.12(9)."
16231 Restrictions that can be checked at compile time result in illegalities
16232 if violated. Currently there are no other consequences of violating
16239 "The representation used by the @code{Read} and
16240 @code{Write} attributes of elementary types in terms of stream
16241 elements. See 13.13.2(9)."
16244 The representation is the in-memory representation of the base type of
16245 the type, using the number of bits corresponding to the
16246 @code{type'Size} value, and the natural ordering of the machine.
16252 "The names and characteristics of the numeric subtypes
16253 declared in the visible part of package @code{Standard}. See A.1(3)."
16256 See items describing the integer and floating-point types supported.
16262 "The string returned by @code{Character_Set_Version}.
16266 @code{Ada.Wide_Characters.Handling.Character_Set_Version} returns
16267 the string "Unicode 4.0", referring to version 4.0 of the
16268 Unicode specification.
16274 "The accuracy actually achieved by the elementary
16275 functions. See A.5.1(1)."
16278 The elementary functions correspond to the functions available in the C
16279 library. Only fast math mode is implemented.
16285 "The sign of a zero result from some of the operators or
16286 functions in @code{Numerics.Generic_Elementary_Functions}, when
16287 @code{Float_Type'Signed_Zeros} is @code{True}. See A.5.1(46)."
16290 The sign of zeroes follows the requirements of the IEEE 754 standard on
16298 @code{Numerics.Float_Random.Max_Image_Width}. See A.5.2(27)."
16301 Maximum image width is 6864, see library file @code{s-rannum.ads}.
16308 @code{Numerics.Discrete_Random.Max_Image_Width}. See A.5.2(27)."
16311 Maximum image width is 6864, see library file @code{s-rannum.ads}.
16317 "The algorithms for random number generation. See
16321 The algorithm is the Mersenne Twister, as documented in the source file
16322 @code{s-rannum.adb}. This version of the algorithm has a period of
16329 "The string representation of a random number generator's
16330 state. See A.5.2(38)."
16333 The value returned by the Image function is the concatenation of
16334 the fixed-width decimal representations of the 624 32-bit integers
16335 of the state vector.
16341 "The minimum time interval between calls to the
16342 time-dependent Reset procedure that are guaranteed to initiate different
16343 random number sequences. See A.5.2(45)."
16346 The minimum period between reset calls to guarantee distinct series of
16347 random numbers is one microsecond.
16353 "The values of the @code{Model_Mantissa},
16354 @code{Model_Emin}, @code{Model_Epsilon}, @code{Model},
16355 @code{Safe_First}, and @code{Safe_Last} attributes, if the Numerics
16356 Annex is not supported. See A.5.3(72)."
16359 Run the compiler with @emph{-gnatS} to produce a listing of package
16360 @code{Standard}, has the values of all numeric attributes.
16366 "Any implementation-defined characteristics of the
16367 input-output packages. See A.7(14)."
16370 There are no special implementation defined characteristics for these
16377 "The value of @code{Buffer_Size} in @code{Storage_IO}. See
16381 All type representations are contiguous, and the @code{Buffer_Size} is
16382 the value of @code{type'Size} rounded up to the next storage unit
16389 "External files for standard input, standard output, and
16390 standard error See A.10(5)."
16393 These files are mapped onto the files provided by the C streams
16394 libraries. See source file @code{i-cstrea.ads} for further details.
16400 "The accuracy of the value produced by @code{Put}. See
16404 If more digits are requested in the output than are represented by the
16405 precision of the value, zeroes are output in the corresponding least
16406 significant digit positions.
16412 "The meaning of @code{Argument_Count}, @code{Argument}, and
16413 @code{Command_Name}. See A.15(1)."
16416 These are mapped onto the @code{argv} and @code{argc} parameters of the
16417 main program in the natural manner.
16423 "The interpretation of the @code{Form} parameter in procedure
16424 @code{Create_Directory}. See A.16(56)."
16427 The @code{Form} parameter is not used.
16433 "The interpretation of the @code{Form} parameter in procedure
16434 @code{Create_Path}. See A.16(60)."
16437 The @code{Form} parameter is not used.
16443 "The interpretation of the @code{Form} parameter in procedure
16444 @code{Copy_File}. See A.16(68)."
16447 The @code{Form} parameter is case-insensitive.
16448 Two fields are recognized in the @code{Form} parameter:
16455 <value> starts immediately after the character '=' and ends with the
16456 character immediately preceding the next comma (',') or with the last
16457 character of the parameter.
16459 The only possible values for preserve= are:
16462 @multitable {xxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
16473 @emph{no_attributes}
16477 Do not try to preserve any file attributes. This is the
16478 default if no preserve= is found in Form.
16482 @emph{all_attributes}
16486 Try to preserve all file attributes (timestamps, access rights).
16494 Preserve the timestamp of the copied file, but not the other
16500 The only possible values for mode= are:
16503 @multitable {xxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
16518 Only do the copy if the destination file does not already exist.
16519 If it already exists, Copy_File fails.
16527 Copy the file in all cases. Overwrite an already existing destination file.
16535 Append the original file to the destination file. If the destination file
16536 does not exist, the destination file is a copy of the source file.
16537 When mode=append, the field preserve=, if it exists, is not taken into account.
16542 If the Form parameter includes one or both of the fields and the value or
16543 values are incorrect, Copy_file fails with Use_Error.
16545 Examples of correct Forms:
16548 Form => "preserve=no_attributes,mode=overwrite" (the default)
16549 Form => "mode=append"
16550 Form => "mode=copy, preserve=all_attributes"
16553 Examples of incorrect Forms:
16556 Form => "preserve=junk"
16557 Form => "mode=internal, preserve=timestamps"
16564 "The interpretation of the @code{Pattern} parameter, when not the null string,
16565 in the @code{Start_Search} and @code{Search} procedures.
16566 See A.16(104) and A.16(112)."
16569 When the @code{Pattern} parameter is not the null string, it is interpreted
16570 according to the syntax of regular expressions as defined in the
16571 @code{GNAT.Regexp} package.
16573 See @ref{258,,GNAT.Regexp (g-regexp.ads)}.
16579 "Implementation-defined convention names. See B.1(11)."
16582 The following convention names are supported
16585 @multitable {xxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
16604 @emph{Ada_Pass_By_Copy}
16608 Allowed for any types except by-reference types such as limited
16609 records. Compatible with convention Ada, but causes any parameters
16610 with this convention to be passed by copy.
16614 @emph{Ada_Pass_By_Reference}
16618 Allowed for any types except by-copy types such as scalars.
16619 Compatible with convention Ada, but causes any parameters
16620 with this convention to be passed by reference.
16636 Synonym for Assembler
16644 Synonym for Assembler
16656 @emph{C_Pass_By_Copy}
16660 Allowed only for record types, like C, but also notes that record
16661 is to be passed by copy rather than reference.
16673 @emph{C_Plus_Plus (or CPP)}
16685 Treated the same as C
16693 Treated the same as C
16709 For support of pragma @code{Import} with convention Intrinsic, see
16710 separate section on Intrinsic Subprograms.
16718 Stdcall (used for Windows implementations only). This convention correspond
16719 to the WINAPI (previously called Pascal convention) C/C++ convention under
16720 Windows. A routine with this convention cleans the stack before
16721 exit. This pragma cannot be applied to a dispatching call.
16729 Synonym for Stdcall
16737 Synonym for Stdcall
16745 Stubbed is a special convention used to indicate that the body of the
16746 subprogram will be entirely ignored. Any call to the subprogram
16747 is converted into a raise of the @code{Program_Error} exception. If a
16748 pragma @code{Import} specifies convention @code{stubbed} then no body need
16749 be present at all. This convention is useful during development for the
16750 inclusion of subprograms whose body has not yet been written.
16751 In addition, all otherwise unrecognized convention names are also
16752 treated as being synonymous with convention C. In all implementations,
16753 use of such other names results in a warning.
16762 "The meaning of link names. See B.1(36)."
16765 Link names are the actual names used by the linker.
16771 "The manner of choosing link names when neither the link
16772 name nor the address of an imported or exported entity is specified. See
16776 The default linker name is that which would be assigned by the relevant
16777 external language, interpreting the Ada name as being in all lower case
16784 "The effect of pragma @code{Linker_Options}. See B.1(37)."
16787 The string passed to @code{Linker_Options} is presented uninterpreted as
16788 an argument to the link command, unless it contains ASCII.NUL characters.
16789 NUL characters if they appear act as argument separators, so for example
16792 pragma Linker_Options ("-labc" & ASCII.NUL & "-ldef");
16795 causes two separate arguments @code{-labc} and @code{-ldef} to be passed to the
16796 linker. The order of linker options is preserved for a given unit. The final
16797 list of options passed to the linker is in reverse order of the elaboration
16798 order. For example, linker options for a body always appear before the options
16799 from the corresponding package spec.
16805 "The contents of the visible part of package
16806 @code{Interfaces} and its language-defined descendants. See B.2(1)."
16809 See files with prefix @code{i-} in the distributed library.
16815 "Implementation-defined children of package
16816 @code{Interfaces}. The contents of the visible part of package
16817 @code{Interfaces}. See B.2(11)."
16820 See files with prefix @code{i-} in the distributed library.
16826 "The types @code{Floating}, @code{Long_Floating},
16827 @code{Binary}, @code{Long_Binary}, @code{Decimal_ Element}, and
16828 @code{COBOL_Character}; and the initialization of the variables
16829 @code{Ada_To_COBOL} and @code{COBOL_To_Ada}, in
16830 @code{Interfaces.COBOL}. See B.4(50)."
16834 @multitable {xxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
16853 @emph{Long_Floating}
16857 (Floating) Long_Float
16877 @emph{Decimal_Element}
16885 @emph{COBOL_Character}
16894 For initialization, see the file @code{i-cobol.ads} in the distributed library.
16900 "Support for access to machine instructions. See C.1(1)."
16903 See documentation in file @code{s-maccod.ads} in the distributed library.
16909 "Implementation-defined aspects of access to machine
16910 operations. See C.1(9)."
16913 See documentation in file @code{s-maccod.ads} in the distributed library.
16919 "Implementation-defined aspects of interrupts. See C.3(2)."
16922 Interrupts are mapped to signals or conditions as appropriate. See
16924 @code{Ada.Interrupt_Names} in source file @code{a-intnam.ads} for details
16925 on the interrupts supported on a particular target.
16931 "Implementation-defined aspects of pre-elaboration. See
16935 GNAT does not permit a partition to be restarted without reloading,
16936 except under control of the debugger.
16942 "The semantics of pragma @code{Discard_Names}. See C.5(7)."
16945 Pragma @code{Discard_Names} causes names of enumeration literals to
16946 be suppressed. In the presence of this pragma, the Image attribute
16947 provides the image of the Pos of the literal, and Value accepts
16950 For tagged types, when pragmas @code{Discard_Names} and @code{No_Tagged_Streams}
16951 simultaneously apply, their Expanded_Name and External_Tag are initialized
16952 with empty strings. This is useful to avoid exposing entity names at binary
16959 "The result of the @code{Task_Identification.Image}
16960 attribute. See C.7.1(7)."
16963 The result of this attribute is a string that identifies
16964 the object or component that denotes a given task. If a variable @code{Var}
16965 has a task type, the image for this task will have the form @code{Var_@emph{XXXXXXXX}},
16966 where the suffix @emph{XXXXXXXX}
16967 is the hexadecimal representation of the virtual address of the corresponding
16968 task control block. If the variable is an array of tasks, the image of each
16969 task will have the form of an indexed component indicating the position of a
16970 given task in the array, e.g., @code{Group(5)_@emph{XXXXXXX}}. If the task is a
16971 component of a record, the image of the task will have the form of a selected
16972 component. These rules are fully recursive, so that the image of a task that
16973 is a subcomponent of a composite object corresponds to the expression that
16974 designates this task.
16976 If a task is created by an allocator, its image depends on the context. If the
16977 allocator is part of an object declaration, the rules described above are used
16978 to construct its image, and this image is not affected by subsequent
16979 assignments. If the allocator appears within an expression, the image
16980 includes only the name of the task type.
16982 If the configuration pragma Discard_Names is present, or if the restriction
16983 No_Implicit_Heap_Allocation is in effect, the image reduces to
16984 the numeric suffix, that is to say the hexadecimal representation of the
16985 virtual address of the control block of the task.
16991 "The value of @code{Current_Task} when in a protected entry
16992 or interrupt handler. See C.7.1(17)."
16995 Protected entries or interrupt handlers can be executed by any
16996 convenient thread, so the value of @code{Current_Task} is undefined.
17002 "The effect of calling @code{Current_Task} from an entry
17003 body or interrupt handler. See C.7.1(19)."
17006 When GNAT can determine statically that @code{Current_Task} is called directly in
17007 the body of an entry (or barrier) then a warning is emitted and @code{Program_Error}
17008 is raised at run time. Otherwise, the effect of calling @code{Current_Task} from an
17009 entry body or interrupt handler is to return the identification of the task
17010 currently executing the code.
17016 "Implementation-defined aspects of
17017 @code{Task_Attributes}. See C.7.2(19)."
17020 There are no implementation-defined aspects of @code{Task_Attributes}.
17026 "Values of all @code{Metrics}. See D(2)."
17029 The metrics information for GNAT depends on the performance of the
17030 underlying operating system. The sources of the run-time for tasking
17031 implementation, together with the output from @emph{-gnatG} can be
17032 used to determine the exact sequence of operating systems calls made
17033 to implement various tasking constructs. Together with appropriate
17034 information on the performance of the underlying operating system,
17035 on the exact target in use, this information can be used to determine
17036 the required metrics.
17042 "The declarations of @code{Any_Priority} and
17043 @code{Priority}. See D.1(11)."
17046 See declarations in file @code{system.ads}.
17052 "Implementation-defined execution resources. See D.1(15)."
17055 There are no implementation-defined execution resources.
17061 "Whether, on a multiprocessor, a task that is waiting for
17062 access to a protected object keeps its processor busy. See D.2.1(3)."
17065 On a multi-processor, a task that is waiting for access to a protected
17066 object does not keep its processor busy.
17072 "The affect of implementation defined execution resources
17073 on task dispatching. See D.2.1(9)."
17076 Tasks map to threads in the threads package used by GNAT. Where possible
17077 and appropriate, these threads correspond to native threads of the
17078 underlying operating system.
17084 "Implementation-defined @emph{policy_identifiers} allowed
17085 in a pragma @code{Task_Dispatching_Policy}. See D.2.2(3)."
17088 There are no implementation-defined policy-identifiers allowed in this
17095 "Implementation-defined aspects of priority inversion. See
17099 Execution of a task cannot be preempted by the implementation processing
17100 of delay expirations for lower priority tasks.
17106 "Implementation-defined task dispatching. See D.2.2(18)."
17109 The policy is the same as that of the underlying threads implementation.
17115 "Implementation-defined @emph{policy_identifiers} allowed
17116 in a pragma @code{Locking_Policy}. See D.3(4)."
17119 The two implementation defined policies permitted in GNAT are
17120 @code{Inheritance_Locking} and @code{Concurrent_Readers_Locking}. On
17121 targets that support the @code{Inheritance_Locking} policy, locking is
17122 implemented by inheritance, i.e., the task owning the lock operates
17123 at a priority equal to the highest priority of any task currently
17124 requesting the lock. On targets that support the
17125 @code{Concurrent_Readers_Locking} policy, locking is implemented with a
17126 read/write lock allowing multiple protected object functions to enter
17133 "Default ceiling priorities. See D.3(10)."
17136 The ceiling priority of protected objects of the type
17137 @code{System.Interrupt_Priority'Last} as described in the Ada
17138 Reference Manual D.3(10),
17144 "The ceiling of any protected object used internally by
17145 the implementation. See D.3(16)."
17148 The ceiling priority of internal protected objects is
17149 @code{System.Priority'Last}.
17155 "Implementation-defined queuing policies. See D.4(1)."
17158 There are no implementation-defined queuing policies.
17164 "On a multiprocessor, any conditions that cause the
17165 completion of an aborted construct to be delayed later than what is
17166 specified for a single processor. See D.6(3)."
17169 The semantics for abort on a multi-processor is the same as on a single
17170 processor, there are no further delays.
17176 "Any operations that implicitly require heap storage
17177 allocation. See D.7(8)."
17180 The only operation that implicitly requires heap storage allocation is
17187 "What happens when a task terminates in the presence of
17188 pragma @code{No_Task_Termination}. See D.7(15)."
17191 Execution is erroneous in that case.
17197 "Implementation-defined aspects of pragma
17198 @code{Restrictions}. See D.7(20)."
17201 There are no such implementation-defined aspects.
17207 "Implementation-defined aspects of package
17208 @code{Real_Time}. See D.8(17)."
17211 There are no implementation defined aspects of package @code{Real_Time}.
17217 "Implementation-defined aspects of
17218 @emph{delay_statements}. See D.9(8)."
17221 Any difference greater than one microsecond will cause the task to be
17222 delayed (see D.9(7)).
17228 "The upper bound on the duration of interrupt blocking
17229 caused by the implementation. See D.12(5)."
17232 The upper bound is determined by the underlying operating system. In
17233 no cases is it more than 10 milliseconds.
17239 "The means for creating and executing distributed
17240 programs. See E(5)."
17243 The GLADE package provides a utility GNATDIST for creating and executing
17244 distributed programs. See the GLADE reference manual for further details.
17250 "Any events that can result in a partition becoming
17251 inaccessible. See E.1(7)."
17254 See the GLADE reference manual for full details on such events.
17260 "The scheduling policies, treatment of priorities, and
17261 management of shared resources between partitions in certain cases. See
17265 See the GLADE reference manual for full details on these aspects of
17266 multi-partition execution.
17272 "Events that cause the version of a compilation unit to
17273 change. See E.3(5)."
17276 Editing the source file of a compilation unit, or the source files of
17277 any units on which it is dependent in a significant way cause the version
17278 to change. No other actions cause the version number to change. All changes
17279 are significant except those which affect only layout, capitalization or
17286 "Whether the execution of the remote subprogram is
17287 immediately aborted as a result of cancellation. See E.4(13)."
17290 See the GLADE reference manual for details on the effect of abort in
17291 a distributed application.
17297 "Implementation-defined aspects of the PCS. See E.5(25)."
17300 See the GLADE reference manual for a full description of all implementation
17301 defined aspects of the PCS.
17307 "Implementation-defined interfaces in the PCS. See
17311 See the GLADE reference manual for a full description of all
17312 implementation defined interfaces.
17318 "The values of named numbers in the package
17319 @code{Decimal}. See F.2(7)."
17323 @multitable {xxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxx}
17366 @emph{Max_Decimal_Digits}
17379 "The value of @code{Max_Picture_Length} in the package
17380 @code{Text_IO.Editing}. See F.3.3(16)."
17389 "The value of @code{Max_Picture_Length} in the package
17390 @code{Wide_Text_IO.Editing}. See F.3.4(5)."
17399 "The accuracy actually achieved by the complex elementary
17400 functions and by other complex arithmetic operations. See G.1(1)."
17403 Standard library functions are used for the complex arithmetic
17404 operations. Only fast math mode is currently supported.
17410 "The sign of a zero result (or a component thereof) from
17411 any operator or function in @code{Numerics.Generic_Complex_Types}, when
17412 @code{Real'Signed_Zeros} is True. See G.1.1(53)."
17415 The signs of zero values are as recommended by the relevant
17416 implementation advice.
17422 "The sign of a zero result (or a component thereof) from
17423 any operator or function in
17424 @code{Numerics.Generic_Complex_Elementary_Functions}, when
17425 @code{Real'Signed_Zeros} is @code{True}. See G.1.2(45)."
17428 The signs of zero values are as recommended by the relevant
17429 implementation advice.
17435 "Whether the strict mode or the relaxed mode is the
17436 default. See G.2(2)."
17439 The strict mode is the default. There is no separate relaxed mode. GNAT
17440 provides a highly efficient implementation of strict mode.
17446 "The result interval in certain cases of fixed-to-float
17447 conversion. See G.2.1(10)."
17450 For cases where the result interval is implementation dependent, the
17451 accuracy is that provided by performing all operations in 64-bit IEEE
17452 floating-point format.
17458 "The result of a floating point arithmetic operation in
17459 overflow situations, when the @code{Machine_Overflows} attribute of the
17460 result type is @code{False}. See G.2.1(13)."
17463 Infinite and NaN values are produced as dictated by the IEEE
17464 floating-point standard.
17465 Note that on machines that are not fully compliant with the IEEE
17466 floating-point standard, such as Alpha, the @emph{-mieee} compiler flag
17467 must be used for achieving IEEE conforming behavior (although at the cost
17468 of a significant performance penalty), so infinite and NaN values are
17469 properly generated.
17475 "The result interval for division (or exponentiation by a
17476 negative exponent), when the floating point hardware implements division
17477 as multiplication by a reciprocal. See G.2.1(16)."
17480 Not relevant, division is IEEE exact.
17486 "The definition of close result set, which determines the
17487 accuracy of certain fixed point multiplications and divisions. See
17491 Operations in the close result set are performed using IEEE long format
17492 floating-point arithmetic. The input operands are converted to
17493 floating-point, the operation is done in floating-point, and the result
17494 is converted to the target type.
17500 "Conditions on a @emph{universal_real} operand of a fixed
17501 point multiplication or division for which the result shall be in the
17502 perfect result set. See G.2.3(22)."
17505 The result is only defined to be in the perfect result set if the result
17506 can be computed by a single scaling operation involving a scale factor
17507 representable in 64 bits.
17513 "The result of a fixed point arithmetic operation in
17514 overflow situations, when the @code{Machine_Overflows} attribute of the
17515 result type is @code{False}. See G.2.3(27)."
17518 Not relevant, @code{Machine_Overflows} is @code{True} for fixed-point
17525 "The result of an elementary function reference in
17526 overflow situations, when the @code{Machine_Overflows} attribute of the
17527 result type is @code{False}. See G.2.4(4)."
17530 IEEE infinite and Nan values are produced as appropriate.
17536 "The value of the angle threshold, within which certain
17537 elementary functions, complex arithmetic operations, and complex
17538 elementary functions yield results conforming to a maximum relative
17539 error bound. See G.2.4(10)."
17542 Information on this subject is not yet available.
17548 "The accuracy of certain elementary functions for
17549 parameters beyond the angle threshold. See G.2.4(10)."
17552 Information on this subject is not yet available.
17558 "The result of a complex arithmetic operation or complex
17559 elementary function reference in overflow situations, when the
17560 @code{Machine_Overflows} attribute of the corresponding real type is
17561 @code{False}. See G.2.6(5)."
17564 IEEE infinite and Nan values are produced as appropriate.
17570 "The accuracy of certain complex arithmetic operations and
17571 certain complex elementary functions for parameters (or components
17572 thereof) beyond the angle threshold. See G.2.6(8)."
17575 Information on those subjects is not yet available.
17581 "Information regarding bounded errors and erroneous
17582 execution. See H.2(1)."
17585 Information on this subject is not yet available.
17591 "Implementation-defined aspects of pragma
17592 @code{Inspection_Point}. See H.3.2(8)."
17595 Pragma @code{Inspection_Point} ensures that the variable is live and can
17596 be examined by the debugger at the inspection point.
17602 "Implementation-defined aspects of pragma
17603 @code{Restrictions}. See H.4(25)."
17606 There are no implementation-defined aspects of pragma @code{Restrictions}. The
17607 use of pragma @code{Restrictions [No_Exceptions]} has no effect on the
17608 generated code. Checks must suppressed by use of pragma @code{Suppress}.
17614 "Any restrictions on pragma @code{Restrictions}. See
17618 There are no restrictions on pragma @code{Restrictions}.
17620 @node Intrinsic Subprograms,Representation Clauses and Pragmas,Implementation Defined Characteristics,Top
17621 @anchor{gnat_rm/intrinsic_subprograms doc}@anchor{259}@anchor{gnat_rm/intrinsic_subprograms intrinsic-subprograms}@anchor{c}@anchor{gnat_rm/intrinsic_subprograms id1}@anchor{25a}
17622 @chapter Intrinsic Subprograms
17625 @geindex Intrinsic Subprograms
17627 GNAT allows a user application program to write the declaration:
17630 pragma Import (Intrinsic, name);
17633 providing that the name corresponds to one of the implemented intrinsic
17634 subprograms in GNAT, and that the parameter profile of the referenced
17635 subprogram meets the requirements. This chapter describes the set of
17636 implemented intrinsic subprograms, and the requirements on parameter profiles.
17637 Note that no body is supplied; as with other uses of pragma Import, the
17638 body is supplied elsewhere (in this case by the compiler itself). Note
17639 that any use of this feature is potentially non-portable, since the
17640 Ada standard does not require Ada compilers to implement this feature.
17643 * Intrinsic Operators::
17644 * Compilation_ISO_Date::
17645 * Compilation_Date::
17646 * Compilation_Time::
17647 * Enclosing_Entity::
17648 * Exception_Information::
17649 * Exception_Message::
17653 * Shifts and Rotates::
17654 * Source_Location::
17658 @node Intrinsic Operators,Compilation_ISO_Date,,Intrinsic Subprograms
17659 @anchor{gnat_rm/intrinsic_subprograms id2}@anchor{25b}@anchor{gnat_rm/intrinsic_subprograms intrinsic-operators}@anchor{25c}
17660 @section Intrinsic Operators
17663 @geindex Intrinsic operator
17665 All the predefined numeric operators in package Standard
17666 in @code{pragma Import (Intrinsic,..)}
17667 declarations. In the binary operator case, the operands must have the same
17668 size. The operand or operands must also be appropriate for
17669 the operator. For example, for addition, the operands must
17670 both be floating-point or both be fixed-point, and the
17671 right operand for @code{"**"} must have a root type of
17672 @code{Standard.Integer'Base}.
17673 You can use an intrinsic operator declaration as in the following example:
17676 type Int1 is new Integer;
17677 type Int2 is new Integer;
17679 function "+" (X1 : Int1; X2 : Int2) return Int1;
17680 function "+" (X1 : Int1; X2 : Int2) return Int2;
17681 pragma Import (Intrinsic, "+");
17684 This declaration would permit 'mixed mode' arithmetic on items
17685 of the differing types @code{Int1} and @code{Int2}.
17686 It is also possible to specify such operators for private types, if the
17687 full views are appropriate arithmetic types.
17689 @node Compilation_ISO_Date,Compilation_Date,Intrinsic Operators,Intrinsic Subprograms
17690 @anchor{gnat_rm/intrinsic_subprograms id3}@anchor{25d}@anchor{gnat_rm/intrinsic_subprograms compilation-iso-date}@anchor{25e}
17691 @section Compilation_ISO_Date
17694 @geindex Compilation_ISO_Date
17696 This intrinsic subprogram is used in the implementation of the
17697 library package @code{GNAT.Source_Info}. The only useful use of the
17698 intrinsic import in this case is the one in this unit, so an
17699 application program should simply call the function
17700 @code{GNAT.Source_Info.Compilation_ISO_Date} to obtain the date of
17701 the current compilation (in local time format YYYY-MM-DD).
17703 @node Compilation_Date,Compilation_Time,Compilation_ISO_Date,Intrinsic Subprograms
17704 @anchor{gnat_rm/intrinsic_subprograms compilation-date}@anchor{25f}@anchor{gnat_rm/intrinsic_subprograms id4}@anchor{260}
17705 @section Compilation_Date
17708 @geindex Compilation_Date
17710 Same as Compilation_ISO_Date, except the string is in the form
17713 @node Compilation_Time,Enclosing_Entity,Compilation_Date,Intrinsic Subprograms
17714 @anchor{gnat_rm/intrinsic_subprograms compilation-time}@anchor{261}@anchor{gnat_rm/intrinsic_subprograms id5}@anchor{262}
17715 @section Compilation_Time
17718 @geindex Compilation_Time
17720 This intrinsic subprogram is used in the implementation of the
17721 library package @code{GNAT.Source_Info}. The only useful use of the
17722 intrinsic import in this case is the one in this unit, so an
17723 application program should simply call the function
17724 @code{GNAT.Source_Info.Compilation_Time} to obtain the time of
17725 the current compilation (in local time format HH:MM:SS).
17727 @node Enclosing_Entity,Exception_Information,Compilation_Time,Intrinsic Subprograms
17728 @anchor{gnat_rm/intrinsic_subprograms id6}@anchor{263}@anchor{gnat_rm/intrinsic_subprograms enclosing-entity}@anchor{264}
17729 @section Enclosing_Entity
17732 @geindex Enclosing_Entity
17734 This intrinsic subprogram is used in the implementation of the
17735 library package @code{GNAT.Source_Info}. The only useful use of the
17736 intrinsic import in this case is the one in this unit, so an
17737 application program should simply call the function
17738 @code{GNAT.Source_Info.Enclosing_Entity} to obtain the name of
17739 the current subprogram, package, task, entry, or protected subprogram.
17741 @node Exception_Information,Exception_Message,Enclosing_Entity,Intrinsic Subprograms
17742 @anchor{gnat_rm/intrinsic_subprograms id7}@anchor{265}@anchor{gnat_rm/intrinsic_subprograms exception-information}@anchor{266}
17743 @section Exception_Information
17746 @geindex Exception_Information'
17748 This intrinsic subprogram is used in the implementation of the
17749 library package @code{GNAT.Current_Exception}. The only useful
17750 use of the intrinsic import in this case is the one in this unit,
17751 so an application program should simply call the function
17752 @code{GNAT.Current_Exception.Exception_Information} to obtain
17753 the exception information associated with the current exception.
17755 @node Exception_Message,Exception_Name,Exception_Information,Intrinsic Subprograms
17756 @anchor{gnat_rm/intrinsic_subprograms exception-message}@anchor{267}@anchor{gnat_rm/intrinsic_subprograms id8}@anchor{268}
17757 @section Exception_Message
17760 @geindex Exception_Message
17762 This intrinsic subprogram is used in the implementation of the
17763 library package @code{GNAT.Current_Exception}. The only useful
17764 use of the intrinsic import in this case is the one in this unit,
17765 so an application program should simply call the function
17766 @code{GNAT.Current_Exception.Exception_Message} to obtain
17767 the message associated with the current exception.
17769 @node Exception_Name,File,Exception_Message,Intrinsic Subprograms
17770 @anchor{gnat_rm/intrinsic_subprograms exception-name}@anchor{269}@anchor{gnat_rm/intrinsic_subprograms id9}@anchor{26a}
17771 @section Exception_Name
17774 @geindex Exception_Name
17776 This intrinsic subprogram is used in the implementation of the
17777 library package @code{GNAT.Current_Exception}. The only useful
17778 use of the intrinsic import in this case is the one in this unit,
17779 so an application program should simply call the function
17780 @code{GNAT.Current_Exception.Exception_Name} to obtain
17781 the name of the current exception.
17783 @node File,Line,Exception_Name,Intrinsic Subprograms
17784 @anchor{gnat_rm/intrinsic_subprograms id10}@anchor{26b}@anchor{gnat_rm/intrinsic_subprograms file}@anchor{26c}
17790 This intrinsic subprogram is used in the implementation of the
17791 library package @code{GNAT.Source_Info}. The only useful use of the
17792 intrinsic import in this case is the one in this unit, so an
17793 application program should simply call the function
17794 @code{GNAT.Source_Info.File} to obtain the name of the current
17797 @node Line,Shifts and Rotates,File,Intrinsic Subprograms
17798 @anchor{gnat_rm/intrinsic_subprograms id11}@anchor{26d}@anchor{gnat_rm/intrinsic_subprograms line}@anchor{26e}
17804 This intrinsic subprogram is used in the implementation of the
17805 library package @code{GNAT.Source_Info}. The only useful use of the
17806 intrinsic import in this case is the one in this unit, so an
17807 application program should simply call the function
17808 @code{GNAT.Source_Info.Line} to obtain the number of the current
17811 @node Shifts and Rotates,Source_Location,Line,Intrinsic Subprograms
17812 @anchor{gnat_rm/intrinsic_subprograms shifts-and-rotates}@anchor{26f}@anchor{gnat_rm/intrinsic_subprograms id12}@anchor{270}
17813 @section Shifts and Rotates
17816 @geindex Shift_Left
17818 @geindex Shift_Right
17820 @geindex Shift_Right_Arithmetic
17822 @geindex Rotate_Left
17824 @geindex Rotate_Right
17826 In standard Ada, the shift and rotate functions are available only
17827 for the predefined modular types in package @code{Interfaces}. However, in
17828 GNAT it is possible to define these functions for any integer
17829 type (signed or modular), as in this example:
17832 function Shift_Left
17834 Amount : Natural) return T;
17837 The function name must be one of
17838 Shift_Left, Shift_Right, Shift_Right_Arithmetic, Rotate_Left, or
17839 Rotate_Right. T must be an integer type. T'Size must be
17840 8, 16, 32 or 64 bits; if T is modular, the modulus
17841 must be 2**8, 2**16, 2**32 or 2**64.
17842 The result type must be the same as the type of @code{Value}.
17843 The shift amount must be Natural.
17844 The formal parameter names can be anything.
17846 A more convenient way of providing these shift operators is to use
17847 the Provide_Shift_Operators pragma, which provides the function declarations
17848 and corresponding pragma Import's for all five shift functions.
17850 @node Source_Location,,Shifts and Rotates,Intrinsic Subprograms
17851 @anchor{gnat_rm/intrinsic_subprograms source-location}@anchor{271}@anchor{gnat_rm/intrinsic_subprograms id13}@anchor{272}
17852 @section Source_Location
17855 @geindex Source_Location
17857 This intrinsic subprogram is used in the implementation of the
17858 library routine @code{GNAT.Source_Info}. The only useful use of the
17859 intrinsic import in this case is the one in this unit, so an
17860 application program should simply call the function
17861 @code{GNAT.Source_Info.Source_Location} to obtain the current
17862 source file location.
17864 @node Representation Clauses and Pragmas,Standard Library Routines,Intrinsic Subprograms,Top
17865 @anchor{gnat_rm/representation_clauses_and_pragmas representation-clauses-and-pragmas}@anchor{d}@anchor{gnat_rm/representation_clauses_and_pragmas doc}@anchor{273}@anchor{gnat_rm/representation_clauses_and_pragmas id1}@anchor{274}
17866 @chapter Representation Clauses and Pragmas
17869 @geindex Representation Clauses
17871 @geindex Representation Clause
17873 @geindex Representation Pragma
17876 @geindex representation
17878 This section describes the representation clauses accepted by GNAT, and
17879 their effect on the representation of corresponding data objects.
17881 GNAT fully implements Annex C (Systems Programming). This means that all
17882 the implementation advice sections in chapter 13 are fully implemented.
17883 However, these sections only require a minimal level of support for
17884 representation clauses. GNAT provides much more extensive capabilities,
17885 and this section describes the additional capabilities provided.
17888 * Alignment Clauses::
17890 * Storage_Size Clauses::
17891 * Size of Variant Record Objects::
17892 * Biased Representation::
17893 * Value_Size and Object_Size Clauses::
17894 * Component_Size Clauses::
17895 * Bit_Order Clauses::
17896 * Effect of Bit_Order on Byte Ordering::
17897 * Pragma Pack for Arrays::
17898 * Pragma Pack for Records::
17899 * Record Representation Clauses::
17900 * Handling of Records with Holes::
17901 * Enumeration Clauses::
17902 * Address Clauses::
17903 * Use of Address Clauses for Memory-Mapped I/O::
17904 * Effect of Convention on Representation::
17905 * Conventions and Anonymous Access Types::
17906 * Determining the Representations chosen by GNAT::
17910 @node Alignment Clauses,Size Clauses,,Representation Clauses and Pragmas
17911 @anchor{gnat_rm/representation_clauses_and_pragmas id2}@anchor{275}@anchor{gnat_rm/representation_clauses_and_pragmas alignment-clauses}@anchor{276}
17912 @section Alignment Clauses
17915 @geindex Alignment Clause
17917 GNAT requires that all alignment clauses specify 0 or a power of 2, and
17918 all default alignments are always a power of 2. Specifying 0 is the
17919 same as specifying 1.
17921 The default alignment values are as follows:
17927 @emph{Elementary Types}.
17929 For elementary types, the alignment is the minimum of the actual size of
17930 objects of the type divided by @code{Storage_Unit},
17931 and the maximum alignment supported by the target.
17932 (This maximum alignment is given by the GNAT-specific attribute
17933 @code{Standard'Maximum_Alignment}; see @ref{18f,,Attribute Maximum_Alignment}.)
17935 @geindex Maximum_Alignment attribute
17937 For example, for type @code{Long_Float}, the object size is 8 bytes, and the
17938 default alignment will be 8 on any target that supports alignments
17939 this large, but on some targets, the maximum alignment may be smaller
17940 than 8, in which case objects of type @code{Long_Float} will be maximally
17946 For arrays, the alignment is equal to the alignment of the component type
17947 for the normal case where no packing or component size is given. If the
17948 array is packed, and the packing is effective (see separate section on
17949 packed arrays), then the alignment will be either 4, 2, or 1 for long packed
17950 arrays or arrays whose length is not known at compile time, depending on
17951 whether the component size is divisible by 4, 2, or is odd. For short packed
17952 arrays, which are handled internally as modular types, the alignment
17953 will be as described for elementary types, e.g. a packed array of length
17954 31 bits will have an object size of four bytes, and an alignment of 4.
17959 For the normal unpacked case, the alignment of a record is equal to
17960 the maximum alignment of any of its components. For tagged records, this
17961 includes the implicit access type used for the tag. If a pragma @code{Pack}
17962 is used and all components are packable (see separate section on pragma
17963 @code{Pack}), then the resulting alignment is 1, unless the layout of the
17964 record makes it profitable to increase it.
17966 A special case is when:
17972 the size of the record is given explicitly, or a
17973 full record representation clause is given, and
17976 the size of the record is 2, 4, or 8 bytes.
17979 In this case, an alignment is chosen to match the
17980 size of the record. For example, if we have:
17983 type Small is record
17986 for Small'Size use 16;
17989 then the default alignment of the record type @code{Small} is 2, not 1. This
17990 leads to more efficient code when the record is treated as a unit, and also
17991 allows the type to specified as @code{Atomic} on architectures requiring
17995 An alignment clause may specify a larger alignment than the default value
17996 up to some maximum value dependent on the target (obtainable by using the
17997 attribute reference @code{Standard'Maximum_Alignment}). It may also specify
17998 a smaller alignment than the default value for enumeration, integer and
17999 fixed point types, as well as for record types, for example
18006 for V'alignment use 1;
18012 The default alignment for the type @code{V} is 4, as a result of the
18013 Integer field in the record, but it is permissible, as shown, to
18014 override the default alignment of the record with a smaller value.
18019 Note that according to the Ada standard, an alignment clause applies only
18020 to the first named subtype. If additional subtypes are declared, then the
18021 compiler is allowed to choose any alignment it likes, and there is no way
18022 to control this choice. Consider:
18025 type R is range 1 .. 10_000;
18026 for R'Alignment use 1;
18027 subtype RS is R range 1 .. 1000;
18030 The alignment clause specifies an alignment of 1 for the first named subtype
18031 @code{R} but this does not necessarily apply to @code{RS}. When writing
18032 portable Ada code, you should avoid writing code that explicitly or
18033 implicitly relies on the alignment of such subtypes.
18035 For the GNAT compiler, if an explicit alignment clause is given, this
18036 value is also used for any subsequent subtypes. So for GNAT, in the
18037 above example, you can count on the alignment of @code{RS} being 1. But this
18038 assumption is non-portable, and other compilers may choose different
18039 alignments for the subtype @code{RS}.
18041 @node Size Clauses,Storage_Size Clauses,Alignment Clauses,Representation Clauses and Pragmas
18042 @anchor{gnat_rm/representation_clauses_and_pragmas id3}@anchor{277}@anchor{gnat_rm/representation_clauses_and_pragmas size-clauses}@anchor{278}
18043 @section Size Clauses
18046 @geindex Size Clause
18048 The default size for a type @code{T} is obtainable through the
18049 language-defined attribute @code{T'Size} and also through the
18050 equivalent GNAT-defined attribute @code{T'Value_Size}.
18051 For objects of type @code{T}, GNAT will generally increase the type size
18052 so that the object size (obtainable through the GNAT-defined attribute
18053 @code{T'Object_Size})
18054 is a multiple of @code{T'Alignment * Storage_Unit}.
18059 type Smallint is range 1 .. 6;
18067 In this example, @code{Smallint'Size} = @code{Smallint'Value_Size} = 3,
18068 as specified by the RM rules,
18069 but objects of this type will have a size of 8
18070 (@code{Smallint'Object_Size} = 8),
18071 since objects by default occupy an integral number
18072 of storage units. On some targets, notably older
18073 versions of the Digital Alpha, the size of stand
18074 alone objects of this type may be 32, reflecting
18075 the inability of the hardware to do byte load/stores.
18077 Similarly, the size of type @code{Rec} is 40 bits
18078 (@code{Rec'Size} = @code{Rec'Value_Size} = 40), but
18079 the alignment is 4, so objects of this type will have
18080 their size increased to 64 bits so that it is a multiple
18081 of the alignment (in bits). This decision is
18082 in accordance with the specific Implementation Advice in RM 13.3(43):
18086 "A @code{Size} clause should be supported for an object if the specified
18087 @code{Size} is at least as large as its subtype's @code{Size}, and corresponds
18088 to a size in storage elements that is a multiple of the object's
18089 @code{Alignment} (if the @code{Alignment} is nonzero)."
18092 An explicit size clause may be used to override the default size by
18093 increasing it. For example, if we have:
18096 type My_Boolean is new Boolean;
18097 for My_Boolean'Size use 32;
18100 then values of this type will always be 32 bits long. In the case of
18101 discrete types, the size can be increased up to 64 bits, with the effect
18102 that the entire specified field is used to hold the value, sign- or
18103 zero-extended as appropriate. If more than 64 bits is specified, then
18104 padding space is allocated after the value, and a warning is issued that
18105 there are unused bits.
18107 Similarly the size of records and arrays may be increased, and the effect
18108 is to add padding bits after the value. This also causes a warning message
18111 The largest Size value permitted in GNAT is 2**31-1. Since this is a
18112 Size in bits, this corresponds to an object of size 256 megabytes (minus
18113 one). This limitation is true on all targets. The reason for this
18114 limitation is that it improves the quality of the code in many cases
18115 if it is known that a Size value can be accommodated in an object of
18118 @node Storage_Size Clauses,Size of Variant Record Objects,Size Clauses,Representation Clauses and Pragmas
18119 @anchor{gnat_rm/representation_clauses_and_pragmas storage-size-clauses}@anchor{279}@anchor{gnat_rm/representation_clauses_and_pragmas id4}@anchor{27a}
18120 @section Storage_Size Clauses
18123 @geindex Storage_Size Clause
18125 For tasks, the @code{Storage_Size} clause specifies the amount of space
18126 to be allocated for the task stack. This cannot be extended, and if the
18127 stack is exhausted, then @code{Storage_Error} will be raised (if stack
18128 checking is enabled). Use a @code{Storage_Size} attribute definition clause,
18129 or a @code{Storage_Size} pragma in the task definition to set the
18130 appropriate required size. A useful technique is to include in every
18131 task definition a pragma of the form:
18134 pragma Storage_Size (Default_Stack_Size);
18137 Then @code{Default_Stack_Size} can be defined in a global package, and
18138 modified as required. Any tasks requiring stack sizes different from the
18139 default can have an appropriate alternative reference in the pragma.
18141 You can also use the @emph{-d} binder switch to modify the default stack
18144 For access types, the @code{Storage_Size} clause specifies the maximum
18145 space available for allocation of objects of the type. If this space is
18146 exceeded then @code{Storage_Error} will be raised by an allocation attempt.
18147 In the case where the access type is declared local to a subprogram, the
18148 use of a @code{Storage_Size} clause triggers automatic use of a special
18149 predefined storage pool (@code{System.Pool_Size}) that ensures that all
18150 space for the pool is automatically reclaimed on exit from the scope in
18151 which the type is declared.
18153 A special case recognized by the compiler is the specification of a
18154 @code{Storage_Size} of zero for an access type. This means that no
18155 items can be allocated from the pool, and this is recognized at compile
18156 time, and all the overhead normally associated with maintaining a fixed
18157 size storage pool is eliminated. Consider the following example:
18161 type R is array (Natural) of Character;
18162 type P is access all R;
18163 for P'Storage_Size use 0;
18164 -- Above access type intended only for interfacing purposes
18168 procedure g (m : P);
18169 pragma Import (C, g);
18179 As indicated in this example, these dummy storage pools are often useful in
18180 connection with interfacing where no object will ever be allocated. If you
18181 compile the above example, you get the warning:
18184 p.adb:16:09: warning: allocation from empty storage pool
18185 p.adb:16:09: warning: Storage_Error will be raised at run time
18188 Of course in practice, there will not be any explicit allocators in the
18189 case of such an access declaration.
18191 @node Size of Variant Record Objects,Biased Representation,Storage_Size Clauses,Representation Clauses and Pragmas
18192 @anchor{gnat_rm/representation_clauses_and_pragmas id5}@anchor{27b}@anchor{gnat_rm/representation_clauses_and_pragmas size-of-variant-record-objects}@anchor{27c}
18193 @section Size of Variant Record Objects
18197 @geindex variant record objects
18199 @geindex Variant record objects
18202 In the case of variant record objects, there is a question whether Size gives
18203 information about a particular variant, or the maximum size required
18204 for any variant. Consider the following program
18207 with Text_IO; use Text_IO;
18209 type R1 (A : Boolean := False) is record
18211 when True => X : Character;
18212 when False => null;
18220 Put_Line (Integer'Image (V1'Size));
18221 Put_Line (Integer'Image (V2'Size));
18225 Here we are dealing with a variant record, where the True variant
18226 requires 16 bits, and the False variant requires 8 bits.
18227 In the above example, both V1 and V2 contain the False variant,
18228 which is only 8 bits long. However, the result of running the
18236 The reason for the difference here is that the discriminant value of
18237 V1 is fixed, and will always be False. It is not possible to assign
18238 a True variant value to V1, therefore 8 bits is sufficient. On the
18239 other hand, in the case of V2, the initial discriminant value is
18240 False (from the default), but it is possible to assign a True
18241 variant value to V2, therefore 16 bits must be allocated for V2
18242 in the general case, even fewer bits may be needed at any particular
18243 point during the program execution.
18245 As can be seen from the output of this program, the @code{'Size}
18246 attribute applied to such an object in GNAT gives the actual allocated
18247 size of the variable, which is the largest size of any of the variants.
18248 The Ada Reference Manual is not completely clear on what choice should
18249 be made here, but the GNAT behavior seems most consistent with the
18250 language in the RM.
18252 In some cases, it may be desirable to obtain the size of the current
18253 variant, rather than the size of the largest variant. This can be
18254 achieved in GNAT by making use of the fact that in the case of a
18255 subprogram parameter, GNAT does indeed return the size of the current
18256 variant (because a subprogram has no way of knowing how much space
18257 is actually allocated for the actual).
18259 Consider the following modified version of the above program:
18262 with Text_IO; use Text_IO;
18264 type R1 (A : Boolean := False) is record
18266 when True => X : Character;
18267 when False => null;
18273 function Size (V : R1) return Integer is
18279 Put_Line (Integer'Image (V2'Size));
18280 Put_Line (Integer'Image (Size (V2)));
18282 Put_Line (Integer'Image (V2'Size));
18283 Put_Line (Integer'Image (Size (V2)));
18287 The output from this program is
18296 Here we see that while the @code{'Size} attribute always returns
18297 the maximum size, regardless of the current variant value, the
18298 @code{Size} function does indeed return the size of the current
18301 @node Biased Representation,Value_Size and Object_Size Clauses,Size of Variant Record Objects,Representation Clauses and Pragmas
18302 @anchor{gnat_rm/representation_clauses_and_pragmas id6}@anchor{27d}@anchor{gnat_rm/representation_clauses_and_pragmas biased-representation}@anchor{27e}
18303 @section Biased Representation
18306 @geindex Size for biased representation
18308 @geindex Biased representation
18310 In the case of scalars with a range starting at other than zero, it is
18311 possible in some cases to specify a size smaller than the default minimum
18312 value, and in such cases, GNAT uses an unsigned biased representation,
18313 in which zero is used to represent the lower bound, and successive values
18314 represent successive values of the type.
18316 For example, suppose we have the declaration:
18319 type Small is range -7 .. -4;
18320 for Small'Size use 2;
18323 Although the default size of type @code{Small} is 4, the @code{Size}
18324 clause is accepted by GNAT and results in the following representation
18328 -7 is represented as 2#00#
18329 -6 is represented as 2#01#
18330 -5 is represented as 2#10#
18331 -4 is represented as 2#11#
18334 Biased representation is only used if the specified @code{Size} clause
18335 cannot be accepted in any other manner. These reduced sizes that force
18336 biased representation can be used for all discrete types except for
18337 enumeration types for which a representation clause is given.
18339 @node Value_Size and Object_Size Clauses,Component_Size Clauses,Biased Representation,Representation Clauses and Pragmas
18340 @anchor{gnat_rm/representation_clauses_and_pragmas id7}@anchor{27f}@anchor{gnat_rm/representation_clauses_and_pragmas value-size-and-object-size-clauses}@anchor{280}
18341 @section Value_Size and Object_Size Clauses
18344 @geindex Value_Size
18346 @geindex Object_Size
18349 @geindex of objects
18351 In Ada 95 and Ada 2005, @code{T'Size} for a type @code{T} is the minimum
18352 number of bits required to hold values of type @code{T}.
18353 Although this interpretation was allowed in Ada 83, it was not required,
18354 and this requirement in practice can cause some significant difficulties.
18355 For example, in most Ada 83 compilers, @code{Natural'Size} was 32.
18356 However, in Ada 95 and Ada 2005,
18357 @code{Natural'Size} is
18358 typically 31. This means that code may change in behavior when moving
18359 from Ada 83 to Ada 95 or Ada 2005. For example, consider:
18362 type Rec is record;
18368 at 0 range 0 .. Natural'Size - 1;
18369 at 0 range Natural'Size .. 2 * Natural'Size - 1;
18373 In the above code, since the typical size of @code{Natural} objects
18374 is 32 bits and @code{Natural'Size} is 31, the above code can cause
18375 unexpected inefficient packing in Ada 95 and Ada 2005, and in general
18376 there are cases where the fact that the object size can exceed the
18377 size of the type causes surprises.
18379 To help get around this problem GNAT provides two implementation
18380 defined attributes, @code{Value_Size} and @code{Object_Size}. When
18381 applied to a type, these attributes yield the size of the type
18382 (corresponding to the RM defined size attribute), and the size of
18383 objects of the type respectively.
18385 The @code{Object_Size} is used for determining the default size of
18386 objects and components. This size value can be referred to using the
18387 @code{Object_Size} attribute. The phrase 'is used' here means that it is
18388 the basis of the determination of the size. The backend is free to
18389 pad this up if necessary for efficiency, e.g., an 8-bit stand-alone
18390 character might be stored in 32 bits on a machine with no efficient
18391 byte access instructions such as the Alpha.
18393 The default rules for the value of @code{Object_Size} for
18394 discrete types are as follows:
18400 The @code{Object_Size} for base subtypes reflect the natural hardware
18401 size in bits (run the compiler with @emph{-gnatS} to find those values
18402 for numeric types). Enumeration types and fixed-point base subtypes have
18403 8, 16, 32, or 64 bits for this size, depending on the range of values
18407 The @code{Object_Size} of a subtype is the same as the
18408 @code{Object_Size} of
18409 the type from which it is obtained.
18412 The @code{Object_Size} of a derived base type is copied from the parent
18413 base type, and the @code{Object_Size} of a derived first subtype is copied
18414 from the parent first subtype.
18417 The @code{Value_Size} attribute
18418 is the (minimum) number of bits required to store a value
18420 This value is used to determine how tightly to pack
18421 records or arrays with components of this type, and also affects
18422 the semantics of unchecked conversion (unchecked conversions where
18423 the @code{Value_Size} values differ generate a warning, and are potentially
18426 The default rules for the value of @code{Value_Size} are as follows:
18432 The @code{Value_Size} for a base subtype is the minimum number of bits
18433 required to store all values of the type (including the sign bit
18434 only if negative values are possible).
18437 If a subtype statically matches the first subtype of a given type, then it has
18438 by default the same @code{Value_Size} as the first subtype. This is a
18439 consequence of RM 13.1(14): "if two subtypes statically match,
18440 then their subtype-specific aspects are the same".)
18443 All other subtypes have a @code{Value_Size} corresponding to the minimum
18444 number of bits required to store all values of the subtype. For
18445 dynamic bounds, it is assumed that the value can range down or up
18446 to the corresponding bound of the ancestor
18449 The RM defined attribute @code{Size} corresponds to the
18450 @code{Value_Size} attribute.
18452 The @code{Size} attribute may be defined for a first-named subtype. This sets
18453 the @code{Value_Size} of
18454 the first-named subtype to the given value, and the
18455 @code{Object_Size} of this first-named subtype to the given value padded up
18456 to an appropriate boundary. It is a consequence of the default rules
18457 above that this @code{Object_Size} will apply to all further subtypes. On the
18458 other hand, @code{Value_Size} is affected only for the first subtype, any
18459 dynamic subtypes obtained from it directly, and any statically matching
18460 subtypes. The @code{Value_Size} of any other static subtypes is not affected.
18462 @code{Value_Size} and
18463 @code{Object_Size} may be explicitly set for any subtype using
18464 an attribute definition clause. Note that the use of these attributes
18465 can cause the RM 13.1(14) rule to be violated. If two access types
18466 reference aliased objects whose subtypes have differing @code{Object_Size}
18467 values as a result of explicit attribute definition clauses, then it
18468 is illegal to convert from one access subtype to the other. For a more
18469 complete description of this additional legality rule, see the
18470 description of the @code{Object_Size} attribute.
18472 To get a feel for the difference, consider the following examples (note
18473 that in each case the base is @code{Short_Short_Integer} with a size of 8):
18476 @multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxx}
18479 Type or subtype declaration
18491 @code{type x1 is range 0 .. 5;}
18503 @code{type x2 is range 0 .. 5;}
18504 @code{for x2'size use 12;}
18516 @code{subtype x3 is x2 range 0 .. 3;}
18528 @code{subtype x4 is x2'base range 0 .. 10;}
18540 @code{dynamic : x2'Base range -64 .. +63;}
18548 @code{subtype x5 is x2 range 0 .. dynamic;}
18560 @code{subtype x6 is x2'base range 0 .. dynamic;}
18573 Note: the entries marked '*' are not actually specified by the Ada
18574 Reference Manual, which has nothing to say about size in the dynamic
18575 case. What GNAT does is to allocate sufficient bits to accommodate any
18576 possible dynamic values for the bounds at run-time.
18578 So far, so good, but GNAT has to obey the RM rules, so the question is
18579 under what conditions must the RM @code{Size} be used.
18580 The following is a list
18581 of the occasions on which the RM @code{Size} must be used:
18587 Component size for packed arrays or records
18590 Value of the attribute @code{Size} for a type
18593 Warning about sizes not matching for unchecked conversion
18596 For record types, the @code{Object_Size} is always a multiple of the
18597 alignment of the type (this is true for all types). In some cases the
18598 @code{Value_Size} can be smaller. Consider:
18607 On a typical 32-bit architecture, the X component will occupy four bytes
18608 and the Y component will occupy one byte, for a total of 5 bytes. As a
18609 result @code{R'Value_Size} will be 40 (bits) since this is the minimum size
18610 required to store a value of this type. For example, it is permissible
18611 to have a component of type R in an array whose component size is
18612 specified to be 40 bits.
18614 However, @code{R'Object_Size} will be 64 (bits). The difference is due to
18615 the alignment requirement for objects of the record type. The X
18616 component will require four-byte alignment because that is what type
18617 Integer requires, whereas the Y component, a Character, will only
18618 require 1-byte alignment. Since the alignment required for X is the
18619 greatest of all the components' alignments, that is the alignment
18620 required for the enclosing record type, i.e., 4 bytes or 32 bits. As
18621 indicated above, the actual object size must be rounded up so that it is
18622 a multiple of the alignment value. Therefore, 40 bits rounded up to the
18623 next multiple of 32 yields 64 bits.
18625 For all other types, the @code{Object_Size}
18626 and @code{Value_Size} are the same (and equivalent to the RM attribute @code{Size}).
18627 Only @code{Size} may be specified for such types.
18629 Note that @code{Value_Size} can be used to force biased representation
18630 for a particular subtype. Consider this example:
18633 type R is (A, B, C, D, E, F);
18634 subtype RAB is R range A .. B;
18635 subtype REF is R range E .. F;
18638 By default, @code{RAB}
18639 has a size of 1 (sufficient to accommodate the representation
18640 of @code{A} and @code{B}, 0 and 1), and @code{REF}
18641 has a size of 3 (sufficient to accommodate the representation
18642 of @code{E} and @code{F}, 4 and 5). But if we add the
18643 following @code{Value_Size} attribute definition clause:
18646 for REF'Value_Size use 1;
18649 then biased representation is forced for @code{REF},
18650 and 0 will represent @code{E} and 1 will represent @code{F}.
18651 A warning is issued when a @code{Value_Size} attribute
18652 definition clause forces biased representation. This
18653 warning can be turned off using @code{-gnatw.B}.
18655 @node Component_Size Clauses,Bit_Order Clauses,Value_Size and Object_Size Clauses,Representation Clauses and Pragmas
18656 @anchor{gnat_rm/representation_clauses_and_pragmas id8}@anchor{281}@anchor{gnat_rm/representation_clauses_and_pragmas component-size-clauses}@anchor{282}
18657 @section Component_Size Clauses
18660 @geindex Component_Size Clause
18662 Normally, the value specified in a component size clause must be consistent
18663 with the subtype of the array component with regard to size and alignment.
18664 In other words, the value specified must be at least equal to the size
18665 of this subtype, and must be a multiple of the alignment value.
18667 In addition, component size clauses are allowed which cause the array
18668 to be packed, by specifying a smaller value. A first case is for
18669 component size values in the range 1 through 63. The value specified
18670 must not be smaller than the Size of the subtype. GNAT will accurately
18671 honor all packing requests in this range. For example, if we have:
18674 type r is array (1 .. 8) of Natural;
18675 for r'Component_Size use 31;
18678 then the resulting array has a length of 31 bytes (248 bits = 8 * 31).
18679 Of course access to the components of such an array is considerably
18680 less efficient than if the natural component size of 32 is used.
18681 A second case is when the subtype of the component is a record type
18682 padded because of its default alignment. For example, if we have:
18691 type a is array (1 .. 8) of r;
18692 for a'Component_Size use 72;
18695 then the resulting array has a length of 72 bytes, instead of 96 bytes
18696 if the alignment of the record (4) was obeyed.
18698 Note that there is no point in giving both a component size clause
18699 and a pragma Pack for the same array type. if such duplicate
18700 clauses are given, the pragma Pack will be ignored.
18702 @node Bit_Order Clauses,Effect of Bit_Order on Byte Ordering,Component_Size Clauses,Representation Clauses and Pragmas
18703 @anchor{gnat_rm/representation_clauses_and_pragmas bit-order-clauses}@anchor{283}@anchor{gnat_rm/representation_clauses_and_pragmas id9}@anchor{284}
18704 @section Bit_Order Clauses
18707 @geindex Bit_Order Clause
18709 @geindex bit ordering
18714 For record subtypes, GNAT permits the specification of the @code{Bit_Order}
18715 attribute. The specification may either correspond to the default bit
18716 order for the target, in which case the specification has no effect and
18717 places no additional restrictions, or it may be for the non-standard
18718 setting (that is the opposite of the default).
18720 In the case where the non-standard value is specified, the effect is
18721 to renumber bits within each byte, but the ordering of bytes is not
18722 affected. There are certain
18723 restrictions placed on component clauses as follows:
18729 Components fitting within a single storage unit.
18731 These are unrestricted, and the effect is merely to renumber bits. For
18732 example if we are on a little-endian machine with @code{Low_Order_First}
18733 being the default, then the following two declarations have exactly
18739 B : Integer range 1 .. 120;
18743 A at 0 range 0 .. 0;
18744 B at 0 range 1 .. 7;
18749 B : Integer range 1 .. 120;
18752 for R2'Bit_Order use High_Order_First;
18755 A at 0 range 7 .. 7;
18756 B at 0 range 0 .. 6;
18760 The useful application here is to write the second declaration with the
18761 @code{Bit_Order} attribute definition clause, and know that it will be treated
18762 the same, regardless of whether the target is little-endian or big-endian.
18765 Components occupying an integral number of bytes.
18767 These are components that exactly fit in two or more bytes. Such component
18768 declarations are allowed, but have no effect, since it is important to realize
18769 that the @code{Bit_Order} specification does not affect the ordering of bytes.
18770 In particular, the following attempt at getting an endian-independent integer
18778 for R2'Bit_Order use High_Order_First;
18781 A at 0 range 0 .. 31;
18785 This declaration will result in a little-endian integer on a
18786 little-endian machine, and a big-endian integer on a big-endian machine.
18787 If byte flipping is required for interoperability between big- and
18788 little-endian machines, this must be explicitly programmed. This capability
18789 is not provided by @code{Bit_Order}.
18792 Components that are positioned across byte boundaries.
18794 but do not occupy an integral number of bytes. Given that bytes are not
18795 reordered, such fields would occupy a non-contiguous sequence of bits
18796 in memory, requiring non-trivial code to reassemble. They are for this
18797 reason not permitted, and any component clause specifying such a layout
18798 will be flagged as illegal by GNAT.
18801 Since the misconception that Bit_Order automatically deals with all
18802 endian-related incompatibilities is a common one, the specification of
18803 a component field that is an integral number of bytes will always
18804 generate a warning. This warning may be suppressed using @code{pragma Warnings (Off)}
18805 if desired. The following section contains additional
18806 details regarding the issue of byte ordering.
18808 @node Effect of Bit_Order on Byte Ordering,Pragma Pack for Arrays,Bit_Order Clauses,Representation Clauses and Pragmas
18809 @anchor{gnat_rm/representation_clauses_and_pragmas id10}@anchor{285}@anchor{gnat_rm/representation_clauses_and_pragmas effect-of-bit-order-on-byte-ordering}@anchor{286}
18810 @section Effect of Bit_Order on Byte Ordering
18813 @geindex byte ordering
18818 In this section we will review the effect of the @code{Bit_Order} attribute
18819 definition clause on byte ordering. Briefly, it has no effect at all, but
18820 a detailed example will be helpful. Before giving this
18821 example, let us review the precise
18822 definition of the effect of defining @code{Bit_Order}. The effect of a
18823 non-standard bit order is described in section 13.5.3 of the Ada
18828 "2 A bit ordering is a method of interpreting the meaning of
18829 the storage place attributes."
18832 To understand the precise definition of storage place attributes in
18833 this context, we visit section 13.5.1 of the manual:
18837 "13 A record_representation_clause (without the mod_clause)
18838 specifies the layout. The storage place attributes (see 13.5.2)
18839 are taken from the values of the position, first_bit, and last_bit
18840 expressions after normalizing those values so that first_bit is
18841 less than Storage_Unit."
18844 The critical point here is that storage places are taken from
18845 the values after normalization, not before. So the @code{Bit_Order}
18846 interpretation applies to normalized values. The interpretation
18847 is described in the later part of the 13.5.3 paragraph:
18851 "2 A bit ordering is a method of interpreting the meaning of
18852 the storage place attributes. High_Order_First (known in the
18853 vernacular as 'big endian') means that the first bit of a
18854 storage element (bit 0) is the most significant bit (interpreting
18855 the sequence of bits that represent a component as an unsigned
18856 integer value). Low_Order_First (known in the vernacular as
18857 'little endian') means the opposite: the first bit is the
18858 least significant."
18861 Note that the numbering is with respect to the bits of a storage
18862 unit. In other words, the specification affects only the numbering
18863 of bits within a single storage unit.
18865 We can make the effect clearer by giving an example.
18867 Suppose that we have an external device which presents two bytes, the first
18868 byte presented, which is the first (low addressed byte) of the two byte
18869 record is called Master, and the second byte is called Slave.
18871 The left most (most significant bit is called Control for each byte, and
18872 the remaining 7 bits are called V1, V2, ... V7, where V7 is the rightmost
18873 (least significant) bit.
18875 On a big-endian machine, we can write the following representation clause
18878 type Data is record
18879 Master_Control : Bit;
18887 Slave_Control : Bit;
18897 for Data use record
18898 Master_Control at 0 range 0 .. 0;
18899 Master_V1 at 0 range 1 .. 1;
18900 Master_V2 at 0 range 2 .. 2;
18901 Master_V3 at 0 range 3 .. 3;
18902 Master_V4 at 0 range 4 .. 4;
18903 Master_V5 at 0 range 5 .. 5;
18904 Master_V6 at 0 range 6 .. 6;
18905 Master_V7 at 0 range 7 .. 7;
18906 Slave_Control at 1 range 0 .. 0;
18907 Slave_V1 at 1 range 1 .. 1;
18908 Slave_V2 at 1 range 2 .. 2;
18909 Slave_V3 at 1 range 3 .. 3;
18910 Slave_V4 at 1 range 4 .. 4;
18911 Slave_V5 at 1 range 5 .. 5;
18912 Slave_V6 at 1 range 6 .. 6;
18913 Slave_V7 at 1 range 7 .. 7;
18917 Now if we move this to a little endian machine, then the bit ordering within
18918 the byte is backwards, so we have to rewrite the record rep clause as:
18921 for Data use record
18922 Master_Control at 0 range 7 .. 7;
18923 Master_V1 at 0 range 6 .. 6;
18924 Master_V2 at 0 range 5 .. 5;
18925 Master_V3 at 0 range 4 .. 4;
18926 Master_V4 at 0 range 3 .. 3;
18927 Master_V5 at 0 range 2 .. 2;
18928 Master_V6 at 0 range 1 .. 1;
18929 Master_V7 at 0 range 0 .. 0;
18930 Slave_Control at 1 range 7 .. 7;
18931 Slave_V1 at 1 range 6 .. 6;
18932 Slave_V2 at 1 range 5 .. 5;
18933 Slave_V3 at 1 range 4 .. 4;
18934 Slave_V4 at 1 range 3 .. 3;
18935 Slave_V5 at 1 range 2 .. 2;
18936 Slave_V6 at 1 range 1 .. 1;
18937 Slave_V7 at 1 range 0 .. 0;
18941 It is a nuisance to have to rewrite the clause, especially if
18942 the code has to be maintained on both machines. However,
18943 this is a case that we can handle with the
18944 @code{Bit_Order} attribute if it is implemented.
18945 Note that the implementation is not required on byte addressed
18946 machines, but it is indeed implemented in GNAT.
18947 This means that we can simply use the
18948 first record clause, together with the declaration
18951 for Data'Bit_Order use High_Order_First;
18954 and the effect is what is desired, namely the layout is exactly the same,
18955 independent of whether the code is compiled on a big-endian or little-endian
18958 The important point to understand is that byte ordering is not affected.
18959 A @code{Bit_Order} attribute definition never affects which byte a field
18960 ends up in, only where it ends up in that byte.
18961 To make this clear, let us rewrite the record rep clause of the previous
18965 for Data'Bit_Order use High_Order_First;
18966 for Data use record
18967 Master_Control at 0 range 0 .. 0;
18968 Master_V1 at 0 range 1 .. 1;
18969 Master_V2 at 0 range 2 .. 2;
18970 Master_V3 at 0 range 3 .. 3;
18971 Master_V4 at 0 range 4 .. 4;
18972 Master_V5 at 0 range 5 .. 5;
18973 Master_V6 at 0 range 6 .. 6;
18974 Master_V7 at 0 range 7 .. 7;
18975 Slave_Control at 0 range 8 .. 8;
18976 Slave_V1 at 0 range 9 .. 9;
18977 Slave_V2 at 0 range 10 .. 10;
18978 Slave_V3 at 0 range 11 .. 11;
18979 Slave_V4 at 0 range 12 .. 12;
18980 Slave_V5 at 0 range 13 .. 13;
18981 Slave_V6 at 0 range 14 .. 14;
18982 Slave_V7 at 0 range 15 .. 15;
18986 This is exactly equivalent to saying (a repeat of the first example):
18989 for Data'Bit_Order use High_Order_First;
18990 for Data use record
18991 Master_Control at 0 range 0 .. 0;
18992 Master_V1 at 0 range 1 .. 1;
18993 Master_V2 at 0 range 2 .. 2;
18994 Master_V3 at 0 range 3 .. 3;
18995 Master_V4 at 0 range 4 .. 4;
18996 Master_V5 at 0 range 5 .. 5;
18997 Master_V6 at 0 range 6 .. 6;
18998 Master_V7 at 0 range 7 .. 7;
18999 Slave_Control at 1 range 0 .. 0;
19000 Slave_V1 at 1 range 1 .. 1;
19001 Slave_V2 at 1 range 2 .. 2;
19002 Slave_V3 at 1 range 3 .. 3;
19003 Slave_V4 at 1 range 4 .. 4;
19004 Slave_V5 at 1 range 5 .. 5;
19005 Slave_V6 at 1 range 6 .. 6;
19006 Slave_V7 at 1 range 7 .. 7;
19010 Why are they equivalent? Well take a specific field, the @code{Slave_V2}
19011 field. The storage place attributes are obtained by normalizing the
19012 values given so that the @code{First_Bit} value is less than 8. After
19013 normalizing the values (0,10,10) we get (1,2,2) which is exactly what
19014 we specified in the other case.
19016 Now one might expect that the @code{Bit_Order} attribute might affect
19017 bit numbering within the entire record component (two bytes in this
19018 case, thus affecting which byte fields end up in), but that is not
19019 the way this feature is defined, it only affects numbering of bits,
19020 not which byte they end up in.
19022 Consequently it never makes sense to specify a starting bit number
19023 greater than 7 (for a byte addressable field) if an attribute
19024 definition for @code{Bit_Order} has been given, and indeed it
19025 may be actively confusing to specify such a value, so the compiler
19026 generates a warning for such usage.
19028 If you do need to control byte ordering then appropriate conditional
19029 values must be used. If in our example, the slave byte came first on
19030 some machines we might write:
19033 Master_Byte_First constant Boolean := ...;
19035 Master_Byte : constant Natural :=
19036 1 - Boolean'Pos (Master_Byte_First);
19037 Slave_Byte : constant Natural :=
19038 Boolean'Pos (Master_Byte_First);
19040 for Data'Bit_Order use High_Order_First;
19041 for Data use record
19042 Master_Control at Master_Byte range 0 .. 0;
19043 Master_V1 at Master_Byte range 1 .. 1;
19044 Master_V2 at Master_Byte range 2 .. 2;
19045 Master_V3 at Master_Byte range 3 .. 3;
19046 Master_V4 at Master_Byte range 4 .. 4;
19047 Master_V5 at Master_Byte range 5 .. 5;
19048 Master_V6 at Master_Byte range 6 .. 6;
19049 Master_V7 at Master_Byte range 7 .. 7;
19050 Slave_Control at Slave_Byte range 0 .. 0;
19051 Slave_V1 at Slave_Byte range 1 .. 1;
19052 Slave_V2 at Slave_Byte range 2 .. 2;
19053 Slave_V3 at Slave_Byte range 3 .. 3;
19054 Slave_V4 at Slave_Byte range 4 .. 4;
19055 Slave_V5 at Slave_Byte range 5 .. 5;
19056 Slave_V6 at Slave_Byte range 6 .. 6;
19057 Slave_V7 at Slave_Byte range 7 .. 7;
19061 Now to switch between machines, all that is necessary is
19062 to set the boolean constant @code{Master_Byte_First} in
19063 an appropriate manner.
19065 @node Pragma Pack for Arrays,Pragma Pack for Records,Effect of Bit_Order on Byte Ordering,Representation Clauses and Pragmas
19066 @anchor{gnat_rm/representation_clauses_and_pragmas pragma-pack-for-arrays}@anchor{287}@anchor{gnat_rm/representation_clauses_and_pragmas id11}@anchor{288}
19067 @section Pragma Pack for Arrays
19070 @geindex Pragma Pack (for arrays)
19072 Pragma @code{Pack} applied to an array has an effect that depends upon whether the
19073 component type is @emph{packable}. For a component type to be @emph{packable}, it must
19074 be one of the following cases:
19080 Any elementary type.
19083 Any small packed array type with a static size.
19086 Any small simple record type with a static size.
19089 For all these cases, if the component subtype size is in the range
19090 1 through 64, then the effect of the pragma @code{Pack} is exactly as though a
19091 component size were specified giving the component subtype size.
19093 All other types are non-packable, they occupy an integral number of storage
19094 units and the only effect of pragma Pack is to remove alignment gaps.
19096 For example if we have:
19099 type r is range 0 .. 17;
19101 type ar is array (1 .. 8) of r;
19105 Then the component size of @code{ar} will be set to 5 (i.e., to @code{r'size},
19106 and the size of the array @code{ar} will be exactly 40 bits).
19108 Note that in some cases this rather fierce approach to packing can produce
19109 unexpected effects. For example, in Ada 95 and Ada 2005,
19110 subtype @code{Natural} typically has a size of 31, meaning that if you
19111 pack an array of @code{Natural}, you get 31-bit
19112 close packing, which saves a few bits, but results in far less efficient
19113 access. Since many other Ada compilers will ignore such a packing request,
19114 GNAT will generate a warning on some uses of pragma @code{Pack} that it guesses
19115 might not be what is intended. You can easily remove this warning by
19116 using an explicit @code{Component_Size} setting instead, which never generates
19117 a warning, since the intention of the programmer is clear in this case.
19119 GNAT treats packed arrays in one of two ways. If the size of the array is
19120 known at compile time and is less than 64 bits, then internally the array
19121 is represented as a single modular type, of exactly the appropriate number
19122 of bits. If the length is greater than 63 bits, or is not known at compile
19123 time, then the packed array is represented as an array of bytes, and the
19124 length is always a multiple of 8 bits.
19126 Note that to represent a packed array as a modular type, the alignment must
19127 be suitable for the modular type involved. For example, on typical machines
19128 a 32-bit packed array will be represented by a 32-bit modular integer with
19129 an alignment of four bytes. If you explicitly override the default alignment
19130 with an alignment clause that is too small, the modular representation
19131 cannot be used. For example, consider the following set of declarations:
19134 type R is range 1 .. 3;
19135 type S is array (1 .. 31) of R;
19136 for S'Component_Size use 2;
19138 for S'Alignment use 1;
19141 If the alignment clause were not present, then a 62-bit modular
19142 representation would be chosen (typically with an alignment of 4 or 8
19143 bytes depending on the target). But the default alignment is overridden
19144 with the explicit alignment clause. This means that the modular
19145 representation cannot be used, and instead the array of bytes
19146 representation must be used, meaning that the length must be a multiple
19147 of 8. Thus the above set of declarations will result in a diagnostic
19148 rejecting the size clause and noting that the minimum size allowed is 64.
19150 @geindex Pragma Pack (for type Natural)
19152 @geindex Pragma Pack warning
19154 One special case that is worth noting occurs when the base type of the
19155 component size is 8/16/32 and the subtype is one bit less. Notably this
19156 occurs with subtype @code{Natural}. Consider:
19159 type Arr is array (1 .. 32) of Natural;
19163 In all commonly used Ada 83 compilers, this pragma Pack would be ignored,
19164 since typically @code{Natural'Size} is 32 in Ada 83, and in any case most
19165 Ada 83 compilers did not attempt 31 bit packing.
19167 In Ada 95 and Ada 2005, @code{Natural'Size} is required to be 31. Furthermore,
19168 GNAT really does pack 31-bit subtype to 31 bits. This may result in a
19169 substantial unintended performance penalty when porting legacy Ada 83 code.
19170 To help prevent this, GNAT generates a warning in such cases. If you really
19171 want 31 bit packing in a case like this, you can set the component size
19175 type Arr is array (1 .. 32) of Natural;
19176 for Arr'Component_Size use 31;
19179 Here 31-bit packing is achieved as required, and no warning is generated,
19180 since in this case the programmer intention is clear.
19182 @node Pragma Pack for Records,Record Representation Clauses,Pragma Pack for Arrays,Representation Clauses and Pragmas
19183 @anchor{gnat_rm/representation_clauses_and_pragmas pragma-pack-for-records}@anchor{289}@anchor{gnat_rm/representation_clauses_and_pragmas id12}@anchor{28a}
19184 @section Pragma Pack for Records
19187 @geindex Pragma Pack (for records)
19189 Pragma @code{Pack} applied to a record will pack the components to reduce
19190 wasted space from alignment gaps and by reducing the amount of space
19191 taken by components. We distinguish between @emph{packable} components and
19192 @emph{non-packable} components.
19193 Components of the following types are considered packable:
19199 Components of an elementary type are packable unless they are aliased,
19200 independent, or of an atomic type.
19203 Small packed arrays, where the size is statically known, are represented
19204 internally as modular integers, and so they are also packable.
19207 Small simple records, where the size is statically known, are also packable.
19210 For all these cases, if the @code{'Size} value is in the range 1 through 64, the
19211 components occupy the exact number of bits corresponding to this value
19212 and are packed with no padding bits, i.e. they can start on an arbitrary
19215 All other types are non-packable, they occupy an integral number of storage
19216 units and the only effect of pragma @code{Pack} is to remove alignment gaps.
19218 For example, consider the record
19221 type Rb1 is array (1 .. 13) of Boolean;
19224 type Rb2 is array (1 .. 65) of Boolean;
19227 type AF is new Float with Atomic;
19240 The representation for the record @code{X2} is as follows:
19243 for X2'Size use 224;
19245 L1 at 0 range 0 .. 0;
19246 L2 at 0 range 1 .. 64;
19247 L3 at 12 range 0 .. 31;
19248 L4 at 16 range 0 .. 0;
19249 L5 at 16 range 1 .. 13;
19250 L6 at 18 range 0 .. 71;
19254 Studying this example, we see that the packable fields @code{L1}
19256 of length equal to their sizes, and placed at specific bit boundaries (and
19257 not byte boundaries) to
19258 eliminate padding. But @code{L3} is of a non-packable float type (because
19259 it is aliased), so it is on the next appropriate alignment boundary.
19261 The next two fields are fully packable, so @code{L4} and @code{L5} are
19262 minimally packed with no gaps. However, type @code{Rb2} is a packed
19263 array that is longer than 64 bits, so it is itself non-packable. Thus
19264 the @code{L6} field is aligned to the next byte boundary, and takes an
19265 integral number of bytes, i.e., 72 bits.
19267 @node Record Representation Clauses,Handling of Records with Holes,Pragma Pack for Records,Representation Clauses and Pragmas
19268 @anchor{gnat_rm/representation_clauses_and_pragmas id13}@anchor{28b}@anchor{gnat_rm/representation_clauses_and_pragmas record-representation-clauses}@anchor{28c}
19269 @section Record Representation Clauses
19272 @geindex Record Representation Clause
19274 Record representation clauses may be given for all record types, including
19275 types obtained by record extension. Component clauses are allowed for any
19276 static component. The restrictions on component clauses depend on the type
19279 @geindex Component Clause
19281 For all components of an elementary type, the only restriction on component
19282 clauses is that the size must be at least the @code{'Size} value of the type
19283 (actually the Value_Size). There are no restrictions due to alignment,
19284 and such components may freely cross storage boundaries.
19286 Packed arrays with a size up to and including 64 bits are represented
19287 internally using a modular type with the appropriate number of bits, and
19288 thus the same lack of restriction applies. For example, if you declare:
19291 type R is array (1 .. 49) of Boolean;
19296 then a component clause for a component of type @code{R} may start on any
19297 specified bit boundary, and may specify a value of 49 bits or greater.
19299 For packed bit arrays that are longer than 64 bits, there are two
19300 cases. If the component size is a power of 2 (1,2,4,8,16,32 bits),
19301 including the important case of single bits or boolean values, then
19302 there are no limitations on placement of such components, and they
19303 may start and end at arbitrary bit boundaries.
19305 If the component size is not a power of 2 (e.g., 3 or 5), then
19306 an array of this type longer than 64 bits must always be placed on
19307 on a storage unit (byte) boundary and occupy an integral number
19308 of storage units (bytes). Any component clause that does not
19309 meet this requirement will be rejected.
19311 Any aliased component, or component of an aliased type, must
19312 have its normal alignment and size. A component clause that
19313 does not meet this requirement will be rejected.
19315 The tag field of a tagged type always occupies an address sized field at
19316 the start of the record. No component clause may attempt to overlay this
19317 tag. When a tagged type appears as a component, the tag field must have
19320 In the case of a record extension @code{T1}, of a type @code{T}, no component clause applied
19321 to the type @code{T1} can specify a storage location that would overlap the first
19322 @code{T'Size} bytes of the record.
19324 For all other component types, including non-bit-packed arrays,
19325 the component can be placed at an arbitrary bit boundary,
19326 so for example, the following is permitted:
19329 type R is array (1 .. 10) of Boolean;
19338 G at 0 range 0 .. 0;
19339 H at 0 range 1 .. 1;
19340 L at 0 range 2 .. 81;
19341 R at 0 range 82 .. 161;
19345 @node Handling of Records with Holes,Enumeration Clauses,Record Representation Clauses,Representation Clauses and Pragmas
19346 @anchor{gnat_rm/representation_clauses_and_pragmas handling-of-records-with-holes}@anchor{28d}@anchor{gnat_rm/representation_clauses_and_pragmas id14}@anchor{28e}
19347 @section Handling of Records with Holes
19350 @geindex Handling of Records with Holes
19352 As a result of alignment considerations, records may contain "holes"
19354 which do not correspond to the data bits of any of the components.
19355 Record representation clauses can also result in holes in records.
19357 GNAT does not attempt to clear these holes, so in record objects,
19358 they should be considered to hold undefined rubbish. The generated
19359 equality routine just tests components so does not access these
19360 undefined bits, and assignment and copy operations may or may not
19361 preserve the contents of these holes (for assignments, the holes
19362 in the target will in practice contain either the bits that are
19363 present in the holes in the source, or the bits that were present
19364 in the target before the assignment).
19366 If it is necessary to ensure that holes in records have all zero
19367 bits, then record objects for which this initialization is desired
19368 should be explicitly set to all zero values using Unchecked_Conversion
19369 or address overlays. For example
19372 type HRec is record
19378 On typical machines, integers need to be aligned on a four-byte
19379 boundary, resulting in three bytes of undefined rubbish following
19380 the 8-bit field for C. To ensure that the hole in a variable of
19381 type HRec is set to all zero bits,
19382 you could for example do:
19385 type Base is record
19386 Dummy1, Dummy2 : Integer := 0;
19391 for RealVar'Address use BaseVar'Address;
19394 Now the 8-bytes of the value of RealVar start out containing all zero
19395 bits. A safer approach is to just define dummy fields, avoiding the
19399 type HRec is record
19401 Dummy1 : Short_Short_Integer := 0;
19402 Dummy2 : Short_Short_Integer := 0;
19403 Dummy3 : Short_Short_Integer := 0;
19408 And to make absolutely sure that the intent of this is followed, you
19409 can use representation clauses:
19412 for Hrec use record
19413 C at 0 range 0 .. 7;
19414 Dummy1 at 1 range 0 .. 7;
19415 Dummy2 at 2 range 0 .. 7;
19416 Dummy3 at 3 range 0 .. 7;
19417 I at 4 range 0 .. 31;
19419 for Hrec'Size use 64;
19422 @node Enumeration Clauses,Address Clauses,Handling of Records with Holes,Representation Clauses and Pragmas
19423 @anchor{gnat_rm/representation_clauses_and_pragmas enumeration-clauses}@anchor{28f}@anchor{gnat_rm/representation_clauses_and_pragmas id15}@anchor{290}
19424 @section Enumeration Clauses
19427 The only restriction on enumeration clauses is that the range of values
19428 must be representable. For the signed case, if one or more of the
19429 representation values are negative, all values must be in the range:
19432 System.Min_Int .. System.Max_Int
19435 For the unsigned case, where all values are nonnegative, the values must
19439 0 .. System.Max_Binary_Modulus;
19442 A @emph{confirming} representation clause is one in which the values range
19443 from 0 in sequence, i.e., a clause that confirms the default representation
19444 for an enumeration type.
19445 Such a confirming representation
19446 is permitted by these rules, and is specially recognized by the compiler so
19447 that no extra overhead results from the use of such a clause.
19449 If an array has an index type which is an enumeration type to which an
19450 enumeration clause has been applied, then the array is stored in a compact
19451 manner. Consider the declarations:
19454 type r is (A, B, C);
19455 for r use (A => 1, B => 5, C => 10);
19456 type t is array (r) of Character;
19459 The array type t corresponds to a vector with exactly three elements and
19460 has a default size equal to @code{3*Character'Size}. This ensures efficient
19461 use of space, but means that accesses to elements of the array will incur
19462 the overhead of converting representation values to the corresponding
19463 positional values, (i.e., the value delivered by the @code{Pos} attribute).
19465 @node Address Clauses,Use of Address Clauses for Memory-Mapped I/O,Enumeration Clauses,Representation Clauses and Pragmas
19466 @anchor{gnat_rm/representation_clauses_and_pragmas id16}@anchor{291}@anchor{gnat_rm/representation_clauses_and_pragmas address-clauses}@anchor{292}
19467 @section Address Clauses
19470 @geindex Address Clause
19472 The reference manual allows a general restriction on representation clauses,
19473 as found in RM 13.1(22):
19477 "An implementation need not support representation
19478 items containing nonstatic expressions, except that
19479 an implementation should support a representation item
19480 for a given entity if each nonstatic expression in the
19481 representation item is a name that statically denotes
19482 a constant declared before the entity."
19485 In practice this is applicable only to address clauses, since this is the
19486 only case in which a nonstatic expression is permitted by the syntax. As
19487 the AARM notes in sections 13.1 (22.a-22.h):
19491 22.a Reason: This is to avoid the following sort of thing:
19493 22.b X : Integer := F(...);
19494 Y : Address := G(...);
19495 for X'Address use Y;
19497 22.c In the above, we have to evaluate the
19498 initialization expression for X before we
19499 know where to put the result. This seems
19500 like an unreasonable implementation burden.
19502 22.d The above code should instead be written
19505 22.e Y : constant Address := G(...);
19506 X : Integer := F(...);
19507 for X'Address use Y;
19509 22.f This allows the expression 'Y' to be safely
19510 evaluated before X is created.
19512 22.g The constant could be a formal parameter of mode in.
19514 22.h An implementation can support other nonstatic
19515 expressions if it wants to. Expressions of type
19516 Address are hardly ever static, but their value
19517 might be known at compile time anyway in many
19521 GNAT does indeed permit many additional cases of nonstatic expressions. In
19522 particular, if the type involved is elementary there are no restrictions
19523 (since in this case, holding a temporary copy of the initialization value,
19524 if one is present, is inexpensive). In addition, if there is no implicit or
19525 explicit initialization, then there are no restrictions. GNAT will reject
19526 only the case where all three of these conditions hold:
19532 The type of the item is non-elementary (e.g., a record or array).
19535 There is explicit or implicit initialization required for the object.
19536 Note that access values are always implicitly initialized.
19539 The address value is nonstatic. Here GNAT is more permissive than the
19540 RM, and allows the address value to be the address of a previously declared
19541 stand-alone variable, as long as it does not itself have an address clause.
19544 Anchor : Some_Initialized_Type;
19545 Overlay : Some_Initialized_Type;
19546 for Overlay'Address use Anchor'Address;
19549 However, the prefix of the address clause cannot be an array component, or
19550 a component of a discriminated record.
19553 As noted above in section 22.h, address values are typically nonstatic. In
19554 particular the To_Address function, even if applied to a literal value, is
19555 a nonstatic function call. To avoid this minor annoyance, GNAT provides
19556 the implementation defined attribute 'To_Address. The following two
19557 expressions have identical values:
19561 @geindex To_Address
19564 To_Address (16#1234_0000#)
19565 System'To_Address (16#1234_0000#);
19568 except that the second form is considered to be a static expression, and
19569 thus when used as an address clause value is always permitted.
19571 Additionally, GNAT treats as static an address clause that is an
19572 unchecked_conversion of a static integer value. This simplifies the porting
19573 of legacy code, and provides a portable equivalent to the GNAT attribute
19576 Another issue with address clauses is the interaction with alignment
19577 requirements. When an address clause is given for an object, the address
19578 value must be consistent with the alignment of the object (which is usually
19579 the same as the alignment of the type of the object). If an address clause
19580 is given that specifies an inappropriately aligned address value, then the
19581 program execution is erroneous.
19583 Since this source of erroneous behavior can have unfortunate effects on
19584 machines with strict alignment requirements, GNAT
19585 checks (at compile time if possible, generating a warning, or at execution
19586 time with a run-time check) that the alignment is appropriate. If the
19587 run-time check fails, then @code{Program_Error} is raised. This run-time
19588 check is suppressed if range checks are suppressed, or if the special GNAT
19589 check Alignment_Check is suppressed, or if
19590 @code{pragma Restrictions (No_Elaboration_Code)} is in effect. It is also
19591 suppressed by default on non-strict alignment machines (such as the x86).
19593 Finally, GNAT does not permit overlaying of objects of class-wide types. In
19594 most cases, the compiler can detect an attempt at such overlays and will
19595 generate a warning at compile time and a Program_Error exception at run time.
19599 An address clause cannot be given for an exported object. More
19600 understandably the real restriction is that objects with an address
19601 clause cannot be exported. This is because such variables are not
19602 defined by the Ada program, so there is no external object to export.
19606 It is permissible to give an address clause and a pragma Import for the
19607 same object. In this case, the variable is not really defined by the
19608 Ada program, so there is no external symbol to be linked. The link name
19609 and the external name are ignored in this case. The reason that we allow this
19610 combination is that it provides a useful idiom to avoid unwanted
19611 initializations on objects with address clauses.
19613 When an address clause is given for an object that has implicit or
19614 explicit initialization, then by default initialization takes place. This
19615 means that the effect of the object declaration is to overwrite the
19616 memory at the specified address. This is almost always not what the
19617 programmer wants, so GNAT will output a warning:
19627 for Ext'Address use System'To_Address (16#1234_1234#);
19629 >>> warning: implicit initialization of "Ext" may
19630 modify overlaid storage
19631 >>> warning: use pragma Import for "Ext" to suppress
19632 initialization (RM B(24))
19637 As indicated by the warning message, the solution is to use a (dummy) pragma
19638 Import to suppress this initialization. The pragma tell the compiler that the
19639 object is declared and initialized elsewhere. The following package compiles
19640 without warnings (and the initialization is suppressed):
19650 for Ext'Address use System'To_Address (16#1234_1234#);
19651 pragma Import (Ada, Ext);
19655 A final issue with address clauses involves their use for overlaying
19656 variables, as in the following example:
19658 @geindex Overlaying of objects
19663 for B'Address use A'Address;
19666 or alternatively, using the form recommended by the RM:
19670 Addr : constant Address := A'Address;
19672 for B'Address use Addr;
19675 In both of these cases, @code{A} and @code{B} become aliased to one another
19676 via the address clause. This use of address clauses to overlay
19677 variables, achieving an effect similar to unchecked conversion
19678 was erroneous in Ada 83, but in Ada 95 and Ada 2005
19679 the effect is implementation defined. Furthermore, the
19680 Ada RM specifically recommends that in a situation
19681 like this, @code{B} should be subject to the following
19682 implementation advice (RM 13.3(19)):
19686 "19 If the Address of an object is specified, or it is imported
19687 or exported, then the implementation should not perform
19688 optimizations based on assumptions of no aliases."
19691 GNAT follows this recommendation, and goes further by also applying
19692 this recommendation to the overlaid variable (@code{A} in the above example)
19693 in this case. This means that the overlay works "as expected", in that
19694 a modification to one of the variables will affect the value of the other.
19696 More generally, GNAT interprets this recommendation conservatively for
19697 address clauses: in the cases other than overlays, it considers that the
19698 object is effectively subject to pragma @code{Volatile} and implements the
19699 associated semantics.
19701 Note that when address clause overlays are used in this way, there is an
19702 issue of unintentional initialization, as shown by this example:
19705 package Overwrite_Record is
19707 A : Character := 'C';
19708 B : Character := 'A';
19710 X : Short_Integer := 3;
19712 for Y'Address use X'Address;
19714 >>> warning: default initialization of "Y" may
19715 modify "X", use pragma Import for "Y" to
19716 suppress initialization (RM B.1(24))
19718 end Overwrite_Record;
19721 Here the default initialization of @code{Y} will clobber the value
19722 of @code{X}, which justifies the warning. The warning notes that
19723 this effect can be eliminated by adding a @code{pragma Import}
19724 which suppresses the initialization:
19727 package Overwrite_Record is
19729 A : Character := 'C';
19730 B : Character := 'A';
19732 X : Short_Integer := 3;
19734 for Y'Address use X'Address;
19735 pragma Import (Ada, Y);
19736 end Overwrite_Record;
19739 Note that the use of @code{pragma Initialize_Scalars} may cause variables to
19740 be initialized when they would not otherwise have been in the absence
19741 of the use of this pragma. This may cause an overlay to have this
19742 unintended clobbering effect. The compiler avoids this for scalar
19743 types, but not for composite objects (where in general the effect
19744 of @code{Initialize_Scalars} is part of the initialization routine
19745 for the composite object:
19748 pragma Initialize_Scalars;
19749 with Ada.Text_IO; use Ada.Text_IO;
19750 procedure Overwrite_Array is
19751 type Arr is array (1 .. 5) of Integer;
19752 X : Arr := (others => 1);
19754 for A'Address use X'Address;
19756 >>> warning: default initialization of "A" may
19757 modify "X", use pragma Import for "A" to
19758 suppress initialization (RM B.1(24))
19761 if X /= Arr'(others => 1) then
19762 Put_Line ("X was clobbered");
19764 Put_Line ("X was not clobbered");
19766 end Overwrite_Array;
19769 The above program generates the warning as shown, and at execution
19770 time, prints @code{X was clobbered}. If the @code{pragma Import} is
19771 added as suggested:
19774 pragma Initialize_Scalars;
19775 with Ada.Text_IO; use Ada.Text_IO;
19776 procedure Overwrite_Array is
19777 type Arr is array (1 .. 5) of Integer;
19778 X : Arr := (others => 1);
19780 for A'Address use X'Address;
19781 pragma Import (Ada, A);
19783 if X /= Arr'(others => 1) then
19784 Put_Line ("X was clobbered");
19786 Put_Line ("X was not clobbered");
19788 end Overwrite_Array;
19791 then the program compiles without the warning and when run will generate
19792 the output @code{X was not clobbered}.
19794 @node Use of Address Clauses for Memory-Mapped I/O,Effect of Convention on Representation,Address Clauses,Representation Clauses and Pragmas
19795 @anchor{gnat_rm/representation_clauses_and_pragmas id17}@anchor{293}@anchor{gnat_rm/representation_clauses_and_pragmas use-of-address-clauses-for-memory-mapped-i-o}@anchor{294}
19796 @section Use of Address Clauses for Memory-Mapped I/O
19799 @geindex Memory-mapped I/O
19801 A common pattern is to use an address clause to map an atomic variable to
19802 a location in memory that corresponds to a memory-mapped I/O operation or
19803 operations, for example:
19806 type Mem_Word is record
19809 pragma Atomic (Mem_Word);
19810 for Mem_Word_Size use 32;
19813 for Mem'Address use some-address;
19820 For a full access (reference or modification) of the variable (Mem) in this
19821 case, as in the above examples, GNAT guarantees that the entire atomic word
19822 will be accessed, in accordance with the RM C.6(15) clause.
19824 A problem arises with a component access such as:
19830 Note that the component A is not declared as atomic. This means that it is
19831 not clear what this assignment means. It could correspond to full word read
19832 and write as given in the first example, or on architectures that supported
19833 such an operation it might be a single byte store instruction. The RM does
19834 not have anything to say in this situation, and GNAT does not make any
19835 guarantee. The code generated may vary from target to target. GNAT will issue
19836 a warning in such a case:
19841 >>> warning: access to non-atomic component of atomic array,
19842 may cause unexpected accesses to atomic object
19845 It is best to be explicit in this situation, by either declaring the
19846 components to be atomic if you want the byte store, or explicitly writing
19847 the full word access sequence if that is what the hardware requires.
19848 Alternatively, if the full word access sequence is required, GNAT also
19849 provides the pragma @code{Volatile_Full_Access} which can be used in lieu of
19850 pragma @code{Atomic} and will give the additional guarantee.
19852 @node Effect of Convention on Representation,Conventions and Anonymous Access Types,Use of Address Clauses for Memory-Mapped I/O,Representation Clauses and Pragmas
19853 @anchor{gnat_rm/representation_clauses_and_pragmas id18}@anchor{295}@anchor{gnat_rm/representation_clauses_and_pragmas effect-of-convention-on-representation}@anchor{296}
19854 @section Effect of Convention on Representation
19857 @geindex Convention
19858 @geindex effect on representation
19860 Normally the specification of a foreign language convention for a type or
19861 an object has no effect on the chosen representation. In particular, the
19862 representation chosen for data in GNAT generally meets the standard system
19863 conventions, and for example records are laid out in a manner that is
19864 consistent with C. This means that specifying convention C (for example)
19867 There are four exceptions to this general rule:
19873 @emph{Convention Fortran and array subtypes}.
19875 If pragma Convention Fortran is specified for an array subtype, then in
19876 accordance with the implementation advice in section 3.6.2(11) of the
19877 Ada Reference Manual, the array will be stored in a Fortran-compatible
19878 column-major manner, instead of the normal default row-major order.
19881 @emph{Convention C and enumeration types}
19883 GNAT normally stores enumeration types in 8, 16, or 32 bits as required
19884 to accommodate all values of the type. For example, for the enumeration
19888 type Color is (Red, Green, Blue);
19891 8 bits is sufficient to store all values of the type, so by default, objects
19892 of type @code{Color} will be represented using 8 bits. However, normal C
19893 convention is to use 32 bits for all enum values in C, since enum values
19894 are essentially of type int. If pragma @code{Convention C} is specified for an
19895 Ada enumeration type, then the size is modified as necessary (usually to
19896 32 bits) to be consistent with the C convention for enum values.
19898 Note that this treatment applies only to types. If Convention C is given for
19899 an enumeration object, where the enumeration type is not Convention C, then
19900 Object_Size bits are allocated. For example, for a normal enumeration type,
19901 with less than 256 elements, only 8 bits will be allocated for the object.
19902 Since this may be a surprise in terms of what C expects, GNAT will issue a
19903 warning in this situation. The warning can be suppressed by giving an explicit
19904 size clause specifying the desired size.
19907 @emph{Convention C/Fortran and Boolean types}
19909 In C, the usual convention for boolean values, that is values used for
19910 conditions, is that zero represents false, and nonzero values represent
19911 true. In Ada, the normal convention is that two specific values, typically
19912 0/1, are used to represent false/true respectively.
19914 Fortran has a similar convention for @code{LOGICAL} values (any nonzero
19915 value represents true).
19917 To accommodate the Fortran and C conventions, if a pragma Convention specifies
19918 C or Fortran convention for a derived Boolean, as in the following example:
19921 type C_Switch is new Boolean;
19922 pragma Convention (C, C_Switch);
19925 then the GNAT generated code will treat any nonzero value as true. For truth
19926 values generated by GNAT, the conventional value 1 will be used for True, but
19927 when one of these values is read, any nonzero value is treated as True.
19930 @node Conventions and Anonymous Access Types,Determining the Representations chosen by GNAT,Effect of Convention on Representation,Representation Clauses and Pragmas
19931 @anchor{gnat_rm/representation_clauses_and_pragmas conventions-and-anonymous-access-types}@anchor{297}@anchor{gnat_rm/representation_clauses_and_pragmas id19}@anchor{298}
19932 @section Conventions and Anonymous Access Types
19935 @geindex Anonymous access types
19937 @geindex Convention for anonymous access types
19939 The RM is not entirely clear on convention handling in a number of cases,
19940 and in particular, it is not clear on the convention to be given to
19941 anonymous access types in general, and in particular what is to be
19942 done for the case of anonymous access-to-subprogram.
19944 In GNAT, we decide that if an explicit Convention is applied
19945 to an object or component, and its type is such an anonymous type,
19946 then the convention will apply to this anonymous type as well. This
19947 seems to make sense since it is anomolous in any case to have a
19948 different convention for an object and its type, and there is clearly
19949 no way to explicitly specify a convention for an anonymous type, since
19950 it doesn't have a name to specify!
19952 Furthermore, we decide that if a convention is applied to a record type,
19953 then this convention is inherited by any of its components that are of an
19954 anonymous access type which do not have an explicitly specified convention.
19956 The following program shows these conventions in action:
19959 package ConvComp is
19960 type Foo is range 1 .. 10;
19962 A : access function (X : Foo) return Integer;
19965 pragma Convention (C, T1);
19968 A : access function (X : Foo) return Integer;
19969 pragma Convention (C, A);
19972 pragma Convention (COBOL, T2);
19975 A : access function (X : Foo) return Integer;
19976 pragma Convention (COBOL, A);
19979 pragma Convention (C, T3);
19982 A : access function (X : Foo) return Integer;
19985 pragma Convention (COBOL, T4);
19987 function F (X : Foo) return Integer;
19988 pragma Convention (C, F);
19990 function F (X : Foo) return Integer is (13);
19992 TV1 : T1 := (F'Access, 12); -- OK
19993 TV2 : T2 := (F'Access, 13); -- OK
19995 TV3 : T3 := (F'Access, 13); -- ERROR
19997 >>> subprogram "F" has wrong convention
19998 >>> does not match access to subprogram declared at line 17
19999 38. TV4 : T4 := (F'Access, 13); -- ERROR
20001 >>> subprogram "F" has wrong convention
20002 >>> does not match access to subprogram declared at line 24
20006 @node Determining the Representations chosen by GNAT,,Conventions and Anonymous Access Types,Representation Clauses and Pragmas
20007 @anchor{gnat_rm/representation_clauses_and_pragmas id20}@anchor{299}@anchor{gnat_rm/representation_clauses_and_pragmas determining-the-representations-chosen-by-gnat}@anchor{29a}
20008 @section Determining the Representations chosen by GNAT
20011 @geindex Representation
20012 @geindex determination of
20014 @geindex -gnatR (gcc)
20016 Although the descriptions in this section are intended to be complete, it is
20017 often easier to simply experiment to see what GNAT accepts and what the
20018 effect is on the layout of types and objects.
20020 As required by the Ada RM, if a representation clause is not accepted, then
20021 it must be rejected as illegal by the compiler. However, when a
20022 representation clause or pragma is accepted, there can still be questions
20023 of what the compiler actually does. For example, if a partial record
20024 representation clause specifies the location of some components and not
20025 others, then where are the non-specified components placed? Or if pragma
20026 @code{Pack} is used on a record, then exactly where are the resulting
20027 fields placed? The section on pragma @code{Pack} in this chapter can be
20028 used to answer the second question, but it is often easier to just see
20029 what the compiler does.
20031 For this purpose, GNAT provides the option @emph{-gnatR}. If you compile
20032 with this option, then the compiler will output information on the actual
20033 representations chosen, in a format similar to source representation
20034 clauses. For example, if we compile the package:
20038 type r (x : boolean) is tagged record
20040 when True => S : String (1 .. 100);
20041 when False => null;
20045 type r2 is new r (false) with record
20050 y2 at 16 range 0 .. 31;
20057 type x1 is array (1 .. 10) of x;
20058 for x1'component_size use 11;
20060 type ia is access integer;
20062 type Rb1 is array (1 .. 13) of Boolean;
20065 type Rb2 is array (1 .. 65) of Boolean;
20080 using the switch @emph{-gnatR} we obtain the following output:
20083 Representation information for unit q
20084 -------------------------------------
20087 for r'Alignment use 4;
20089 x at 4 range 0 .. 7;
20090 _tag at 0 range 0 .. 31;
20091 s at 5 range 0 .. 799;
20094 for r2'Size use 160;
20095 for r2'Alignment use 4;
20097 x at 4 range 0 .. 7;
20098 _tag at 0 range 0 .. 31;
20099 _parent at 0 range 0 .. 63;
20100 y2 at 16 range 0 .. 31;
20104 for x'Alignment use 1;
20106 y at 0 range 0 .. 7;
20109 for x1'Size use 112;
20110 for x1'Alignment use 1;
20111 for x1'Component_Size use 11;
20113 for rb1'Size use 13;
20114 for rb1'Alignment use 2;
20115 for rb1'Component_Size use 1;
20117 for rb2'Size use 72;
20118 for rb2'Alignment use 1;
20119 for rb2'Component_Size use 1;
20121 for x2'Size use 224;
20122 for x2'Alignment use 4;
20124 l1 at 0 range 0 .. 0;
20125 l2 at 0 range 1 .. 64;
20126 l3 at 12 range 0 .. 31;
20127 l4 at 16 range 0 .. 0;
20128 l5 at 16 range 1 .. 13;
20129 l6 at 18 range 0 .. 71;
20133 The Size values are actually the Object_Size, i.e., the default size that
20134 will be allocated for objects of the type.
20135 The @code{??} size for type r indicates that we have a variant record, and the
20136 actual size of objects will depend on the discriminant value.
20138 The Alignment values show the actual alignment chosen by the compiler
20139 for each record or array type.
20141 The record representation clause for type r shows where all fields
20142 are placed, including the compiler generated tag field (whose location
20143 cannot be controlled by the programmer).
20145 The record representation clause for the type extension r2 shows all the
20146 fields present, including the parent field, which is a copy of the fields
20147 of the parent type of r2, i.e., r1.
20149 The component size and size clauses for types rb1 and rb2 show
20150 the exact effect of pragma @code{Pack} on these arrays, and the record
20151 representation clause for type x2 shows how pragma @cite{Pack} affects
20154 In some cases, it may be useful to cut and paste the representation clauses
20155 generated by the compiler into the original source to fix and guarantee
20156 the actual representation to be used.
20158 @node Standard Library Routines,The Implementation of Standard I/O,Representation Clauses and Pragmas,Top
20159 @anchor{gnat_rm/standard_library_routines standard-library-routines}@anchor{e}@anchor{gnat_rm/standard_library_routines doc}@anchor{29b}@anchor{gnat_rm/standard_library_routines id1}@anchor{29c}
20160 @chapter Standard Library Routines
20163 The Ada Reference Manual contains in Annex A a full description of an
20164 extensive set of standard library routines that can be used in any Ada
20165 program, and which must be provided by all Ada compilers. They are
20166 analogous to the standard C library used by C programs.
20168 GNAT implements all of the facilities described in annex A, and for most
20169 purposes the description in the Ada Reference Manual, or appropriate Ada
20170 text book, will be sufficient for making use of these facilities.
20172 In the case of the input-output facilities,
20173 @ref{f,,The Implementation of Standard I/O},
20174 gives details on exactly how GNAT interfaces to the
20175 file system. For the remaining packages, the Ada Reference Manual
20176 should be sufficient. The following is a list of the packages included,
20177 together with a brief description of the functionality that is provided.
20179 For completeness, references are included to other predefined library
20180 routines defined in other sections of the Ada Reference Manual (these are
20181 cross-indexed from Annex A). For further details see the relevant
20182 package declarations in the run-time library. In particular, a few units
20183 are not implemented, as marked by the presence of pragma Unimplemented_Unit,
20184 and in this case the package declaration contains comments explaining why
20185 the unit is not implemented.
20190 @item @code{Ada} @emph{(A.2)}
20192 This is a parent package for all the standard library packages. It is
20193 usually included implicitly in your program, and itself contains no
20194 useful data or routines.
20196 @item @code{Ada.Assertions} @emph{(11.4.2)}
20198 @code{Assertions} provides the @code{Assert} subprograms, and also
20199 the declaration of the @code{Assertion_Error} exception.
20201 @item @code{Ada.Asynchronous_Task_Control} @emph{(D.11)}
20203 @code{Asynchronous_Task_Control} provides low level facilities for task
20204 synchronization. It is typically not implemented. See package spec for details.
20206 @item @code{Ada.Calendar} @emph{(9.6)}
20208 @code{Calendar} provides time of day access, and routines for
20209 manipulating times and durations.
20211 @item @code{Ada.Calendar.Arithmetic} @emph{(9.6.1)}
20213 This package provides additional arithmetic
20214 operations for @code{Calendar}.
20216 @item @code{Ada.Calendar.Formatting} @emph{(9.6.1)}
20218 This package provides formatting operations for @code{Calendar}.
20220 @item @code{Ada.Calendar.Time_Zones} @emph{(9.6.1)}
20222 This package provides additional @code{Calendar} facilities
20223 for handling time zones.
20225 @item @code{Ada.Characters} @emph{(A.3.1)}
20227 This is a dummy parent package that contains no useful entities
20229 @item @code{Ada.Characters.Conversions} @emph{(A.3.2)}
20231 This package provides character conversion functions.
20233 @item @code{Ada.Characters.Handling} @emph{(A.3.2)}
20235 This package provides some basic character handling capabilities,
20236 including classification functions for classes of characters (e.g., test
20237 for letters, or digits).
20239 @item @code{Ada.Characters.Latin_1} @emph{(A.3.3)}
20241 This package includes a complete set of definitions of the characters
20242 that appear in type CHARACTER. It is useful for writing programs that
20243 will run in international environments. For example, if you want an
20244 upper case E with an acute accent in a string, it is often better to use
20245 the definition of @code{UC_E_Acute} in this package. Then your program
20246 will print in an understandable manner even if your environment does not
20247 support these extended characters.
20249 @item @code{Ada.Command_Line} @emph{(A.15)}
20251 This package provides access to the command line parameters and the name
20252 of the current program (analogous to the use of @code{argc} and @code{argv}
20253 in C), and also allows the exit status for the program to be set in a
20254 system-independent manner.
20256 @item @code{Ada.Complex_Text_IO} @emph{(G.1.3)}
20258 This package provides text input and output of complex numbers.
20260 @item @code{Ada.Containers} @emph{(A.18.1)}
20262 A top level package providing a few basic definitions used by all the
20263 following specific child packages that provide specific kinds of
20267 @code{Ada.Containers.Bounded_Priority_Queues} @emph{(A.18.31)}
20269 @code{Ada.Containers.Bounded_Synchronized_Queues} @emph{(A.18.29)}
20271 @code{Ada.Containers.Doubly_Linked_Lists} @emph{(A.18.3)}
20273 @code{Ada.Containers.Generic_Array_Sort} @emph{(A.18.26)}
20275 @code{Ada.Containers.Generic_Constrained_Array_Sort} @emph{(A.18.26)}
20277 @code{Ada.Containers.Generic_Sort} @emph{(A.18.26)}
20279 @code{Ada.Containers.Hashed_Maps} @emph{(A.18.5)}
20281 @code{Ada.Containers.Hashed_Sets} @emph{(A.18.8)}
20283 @code{Ada.Containers.Indefinite_Doubly_Linked_Lists} @emph{(A.18.12)}
20285 @code{Ada.Containers.Indefinite_Hashed_Maps} @emph{(A.18.13)}
20287 @code{Ada.Containers.Indefinite_Hashed_Sets} @emph{(A.18.15)}
20289 @code{Ada.Containers.Indefinite_Holders} @emph{(A.18.18)}
20291 @code{Ada.Containers.Indefinite_Multiway_Trees} @emph{(A.18.17)}
20293 @code{Ada.Containers.Indefinite_Ordered_Maps} @emph{(A.18.14)}
20295 @code{Ada.Containers.Indefinite_Ordered_Sets} @emph{(A.18.16)}
20297 @code{Ada.Containers.Indefinite_Vectors} @emph{(A.18.11)}
20299 @code{Ada.Containers.Multiway_Trees} @emph{(A.18.10)}
20301 @code{Ada.Containers.Ordered_Maps} @emph{(A.18.6)}
20303 @code{Ada.Containers.Ordered_Sets} @emph{(A.18.9)}
20305 @code{Ada.Containers.Synchronized_Queue_Interfaces} @emph{(A.18.27)}
20307 @code{Ada.Containers.Unbounded_Priority_Queues} @emph{(A.18.30)}
20309 @code{Ada.Containers.Unbounded_Synchronized_Queues} @emph{(A.18.28)}
20311 @code{Ada.Containers.Vectors} @emph{(A.18.2)}
20316 @item @code{Ada.Directories} @emph{(A.16)}
20318 This package provides operations on directories.
20320 @item @code{Ada.Directories.Hierarchical_File_Names} @emph{(A.16.1)}
20322 This package provides additional directory operations handling
20323 hiearchical file names.
20325 @item @code{Ada.Directories.Information} @emph{(A.16)}
20327 This is an implementation defined package for additional directory
20328 operations, which is not implemented in GNAT.
20330 @item @code{Ada.Decimal} @emph{(F.2)}
20332 This package provides constants describing the range of decimal numbers
20333 implemented, and also a decimal divide routine (analogous to the COBOL
20334 verb DIVIDE ... GIVING ... REMAINDER ...)
20336 @item @code{Ada.Direct_IO} @emph{(A.8.4)}
20338 This package provides input-output using a model of a set of records of
20339 fixed-length, containing an arbitrary definite Ada type, indexed by an
20340 integer record number.
20342 @item @code{Ada.Dispatching} @emph{(D.2.1)}
20344 A parent package containing definitions for task dispatching operations.
20346 @item @code{Ada.Dispatching.EDF} @emph{(D.2.6)}
20348 Not implemented in GNAT.
20350 @item @code{Ada.Dispatching.Non_Preemptive} @emph{(D.2.4)}
20352 Not implemented in GNAT.
20354 @item @code{Ada.Dispatching.Round_Robin} @emph{(D.2.5)}
20356 Not implemented in GNAT.
20358 @item @code{Ada.Dynamic_Priorities} @emph{(D.5)}
20360 This package allows the priorities of a task to be adjusted dynamically
20361 as the task is running.
20363 @item @code{Ada.Environment_Variables} @emph{(A.17)}
20365 This package provides facilities for accessing environment variables.
20367 @item @code{Ada.Exceptions} @emph{(11.4.1)}
20369 This package provides additional information on exceptions, and also
20370 contains facilities for treating exceptions as data objects, and raising
20371 exceptions with associated messages.
20373 @item @code{Ada.Execution_Time} @emph{(D.14)}
20375 This package provides CPU clock functionalities. It is not implemented on
20376 all targets (see package spec for details).
20378 @item @code{Ada.Execution_Time.Group_Budgets} @emph{(D.14.2)}
20380 Not implemented in GNAT.
20382 @item @code{Ada.Execution_Time.Timers} @emph{(D.14.1)'}
20384 Not implemented in GNAT.
20386 @item @code{Ada.Finalization} @emph{(7.6)}
20388 This package contains the declarations and subprograms to support the
20389 use of controlled types, providing for automatic initialization and
20390 finalization (analogous to the constructors and destructors of C++).
20392 @item @code{Ada.Float_Text_IO} @emph{(A.10.9)}
20394 A library level instantiation of Text_IO.Float_IO for type Float.
20396 @item @code{Ada.Float_Wide_Text_IO} @emph{(A.10.9)}
20398 A library level instantiation of Wide_Text_IO.Float_IO for type Float.
20400 @item @code{Ada.Float_Wide_Wide_Text_IO} @emph{(A.10.9)}
20402 A library level instantiation of Wide_Wide_Text_IO.Float_IO for type Float.
20404 @item @code{Ada.Integer_Text_IO} @emph{(A.10.9)}
20406 A library level instantiation of Text_IO.Integer_IO for type Integer.
20408 @item @code{Ada.Integer_Wide_Text_IO} @emph{(A.10.9)}
20410 A library level instantiation of Wide_Text_IO.Integer_IO for type Integer.
20412 @item @code{Ada.Integer_Wide_Wide_Text_IO} @emph{(A.10.9)}
20414 A library level instantiation of Wide_Wide_Text_IO.Integer_IO for type Integer.
20416 @item @code{Ada.Interrupts} @emph{(C.3.2)}
20418 This package provides facilities for interfacing to interrupts, which
20419 includes the set of signals or conditions that can be raised and
20420 recognized as interrupts.
20422 @item @code{Ada.Interrupts.Names} @emph{(C.3.2)}
20424 This package provides the set of interrupt names (actually signal
20425 or condition names) that can be handled by GNAT.
20427 @item @code{Ada.IO_Exceptions} @emph{(A.13)}
20429 This package defines the set of exceptions that can be raised by use of
20430 the standard IO packages.
20432 @item @code{Ada.Iterator_Interfaces} @emph{(5.5.1)}
20434 This package provides a generic interface to generalized iterators.
20436 @item @code{Ada.Locales} @emph{(A.19)}
20438 This package provides declarations providing information (Language
20439 and Country) about the current locale.
20441 @item @code{Ada.Numerics}
20443 This package contains some standard constants and exceptions used
20444 throughout the numerics packages. Note that the constants pi and e are
20445 defined here, and it is better to use these definitions than rolling
20448 @item @code{Ada.Numerics.Complex_Arrays} @emph{(G.3.2)}
20450 Provides operations on arrays of complex numbers.
20452 @item @code{Ada.Numerics.Complex_Elementary_Functions}
20454 Provides the implementation of standard elementary functions (such as
20455 log and trigonometric functions) operating on complex numbers using the
20456 standard @code{Float} and the @code{Complex} and @code{Imaginary} types
20457 created by the package @code{Numerics.Complex_Types}.
20459 @item @code{Ada.Numerics.Complex_Types}
20461 This is a predefined instantiation of
20462 @code{Numerics.Generic_Complex_Types} using @code{Standard.Float} to
20463 build the type @code{Complex} and @code{Imaginary}.
20465 @item @code{Ada.Numerics.Discrete_Random}
20467 This generic package provides a random number generator suitable for generating
20468 uniformly distributed values of a specified discrete subtype.
20470 @item @code{Ada.Numerics.Float_Random}
20472 This package provides a random number generator suitable for generating
20473 uniformly distributed floating point values in the unit interval.
20475 @item @code{Ada.Numerics.Generic_Complex_Elementary_Functions}
20477 This is a generic version of the package that provides the
20478 implementation of standard elementary functions (such as log and
20479 trigonometric functions) for an arbitrary complex type.
20481 The following predefined instantiations of this package are provided:
20489 @code{Ada.Numerics.Short_Complex_Elementary_Functions}
20494 @code{Ada.Numerics.Complex_Elementary_Functions}
20499 @code{Ada.Numerics.Long_Complex_Elementary_Functions}
20502 @item @code{Ada.Numerics.Generic_Complex_Types}
20504 This is a generic package that allows the creation of complex types,
20505 with associated complex arithmetic operations.
20507 The following predefined instantiations of this package exist
20515 @code{Ada.Numerics.Short_Complex_Complex_Types}
20520 @code{Ada.Numerics.Complex_Complex_Types}
20525 @code{Ada.Numerics.Long_Complex_Complex_Types}
20528 @item @code{Ada.Numerics.Generic_Elementary_Functions}
20530 This is a generic package that provides the implementation of standard
20531 elementary functions (such as log an trigonometric functions) for an
20532 arbitrary float type.
20534 The following predefined instantiations of this package exist
20542 @code{Ada.Numerics.Short_Elementary_Functions}
20547 @code{Ada.Numerics.Elementary_Functions}
20552 @code{Ada.Numerics.Long_Elementary_Functions}
20555 @item @code{Ada.Numerics.Generic_Real_Arrays} @emph{(G.3.1)}
20557 Generic operations on arrays of reals
20559 @item @code{Ada.Numerics.Real_Arrays} @emph{(G.3.1)}
20561 Preinstantiation of Ada.Numerics.Generic_Real_Arrays (Float).
20563 @item @code{Ada.Real_Time} @emph{(D.8)}
20565 This package provides facilities similar to those of @code{Calendar}, but
20566 operating with a finer clock suitable for real time control. Note that
20567 annex D requires that there be no backward clock jumps, and GNAT generally
20568 guarantees this behavior, but of course if the external clock on which
20569 the GNAT runtime depends is deliberately reset by some external event,
20570 then such a backward jump may occur.
20572 @item @code{Ada.Real_Time.Timing_Events} @emph{(D.15)}
20574 Not implemented in GNAT.
20576 @item @code{Ada.Sequential_IO} @emph{(A.8.1)}
20578 This package provides input-output facilities for sequential files,
20579 which can contain a sequence of values of a single type, which can be
20580 any Ada type, including indefinite (unconstrained) types.
20582 @item @code{Ada.Storage_IO} @emph{(A.9)}
20584 This package provides a facility for mapping arbitrary Ada types to and
20585 from a storage buffer. It is primarily intended for the creation of new
20588 @item @code{Ada.Streams} @emph{(13.13.1)}
20590 This is a generic package that provides the basic support for the
20591 concept of streams as used by the stream attributes (@code{Input},
20592 @code{Output}, @code{Read} and @code{Write}).
20594 @item @code{Ada.Streams.Stream_IO} @emph{(A.12.1)}
20596 This package is a specialization of the type @code{Streams} defined in
20597 package @code{Streams} together with a set of operations providing
20598 Stream_IO capability. The Stream_IO model permits both random and
20599 sequential access to a file which can contain an arbitrary set of values
20600 of one or more Ada types.
20602 @item @code{Ada.Strings} @emph{(A.4.1)}
20604 This package provides some basic constants used by the string handling
20607 @item @code{Ada.Strings.Bounded} @emph{(A.4.4)}
20609 This package provides facilities for handling variable length
20610 strings. The bounded model requires a maximum length. It is thus
20611 somewhat more limited than the unbounded model, but avoids the use of
20612 dynamic allocation or finalization.
20614 @item @code{Ada.Strings.Bounded.Equal_Case_Insensitive} @emph{(A.4.10)}
20616 Provides case-insensitive comparisons of bounded strings
20618 @item @code{Ada.Strings.Bounded.Hash} @emph{(A.4.9)}
20620 This package provides a generic hash function for bounded strings
20622 @item @code{Ada.Strings.Bounded.Hash_Case_Insensitive} @emph{(A.4.9)}
20624 This package provides a generic hash function for bounded strings that
20625 converts the string to be hashed to lower case.
20627 @item @code{Ada.Strings.Bounded.Less_Case_Insensitive} @emph{(A.4.10)}
20629 This package provides a comparison function for bounded strings that works
20630 in a case insensitive manner by converting to lower case before the comparison.
20632 @item @code{Ada.Strings.Fixed} @emph{(A.4.3)}
20634 This package provides facilities for handling fixed length strings.
20636 @item @code{Ada.Strings.Fixed.Equal_Case_Insensitive} @emph{(A.4.10)}
20638 This package provides an equality function for fixed strings that compares
20639 the strings after converting both to lower case.
20641 @item @code{Ada.Strings.Fixed.Hash_Case_Insensitive} @emph{(A.4.9)}
20643 This package provides a case insensitive hash function for fixed strings that
20644 converts the string to lower case before computing the hash.
20646 @item @code{Ada.Strings.Fixed.Less_Case_Insensitive} @emph{(A.4.10)}
20648 This package provides a comparison function for fixed strings that works
20649 in a case insensitive manner by converting to lower case before the comparison.
20651 @item @code{Ada.Strings.Hash} @emph{(A.4.9)}
20653 This package provides a hash function for strings.
20655 @item @code{Ada.Strings.Hash_Case_Insensitive} @emph{(A.4.9)}
20657 This package provides a hash function for strings that is case insensitive.
20658 The string is converted to lower case before computing the hash.
20660 @item @code{Ada.Strings.Less_Case_Insensitive} @emph{(A.4.10)}
20662 This package provides a comparison function for\strings that works
20663 in a case insensitive manner by converting to lower case before the comparison.
20665 @item @code{Ada.Strings.Maps} @emph{(A.4.2)}
20667 This package provides facilities for handling character mappings and
20668 arbitrarily defined subsets of characters. For instance it is useful in
20669 defining specialized translation tables.
20671 @item @code{Ada.Strings.Maps.Constants} @emph{(A.4.6)}
20673 This package provides a standard set of predefined mappings and
20674 predefined character sets. For example, the standard upper to lower case
20675 conversion table is found in this package. Note that upper to lower case
20676 conversion is non-trivial if you want to take the entire set of
20677 characters, including extended characters like E with an acute accent,
20678 into account. You should use the mappings in this package (rather than
20679 adding 32 yourself) to do case mappings.
20681 @item @code{Ada.Strings.Unbounded} @emph{(A.4.5)}
20683 This package provides facilities for handling variable length
20684 strings. The unbounded model allows arbitrary length strings, but
20685 requires the use of dynamic allocation and finalization.
20687 @item @code{Ada.Strings.Unbounded.Equal_Case_Insensitive} @emph{(A.4.10)}
20689 Provides case-insensitive comparisons of unbounded strings
20691 @item @code{Ada.Strings.Unbounded.Hash} @emph{(A.4.9)}
20693 This package provides a generic hash function for unbounded strings
20695 @item @code{Ada.Strings.Unbounded.Hash_Case_Insensitive} @emph{(A.4.9)}
20697 This package provides a generic hash function for unbounded strings that
20698 converts the string to be hashed to lower case.
20700 @item @code{Ada.Strings.Unbounded.Less_Case_Insensitive} @emph{(A.4.10)}
20702 This package provides a comparison function for unbounded strings that works
20703 in a case insensitive manner by converting to lower case before the comparison.
20705 @item @code{Ada.Strings.UTF_Encoding} @emph{(A.4.11)}
20707 This package provides basic definitions for dealing with UTF-encoded strings.
20709 @item @code{Ada.Strings.UTF_Encoding.Conversions} @emph{(A.4.11)}
20711 This package provides conversion functions for UTF-encoded strings.
20714 @code{Ada.Strings.UTF_Encoding.Strings} @emph{(A.4.11)}
20716 @code{Ada.Strings.UTF_Encoding.Wide_Strings} @emph{(A.4.11)}
20721 @item @code{Ada.Strings.UTF_Encoding.Wide_Wide_Strings} @emph{(A.4.11)}
20723 These packages provide facilities for handling UTF encodings for
20724 Strings, Wide_Strings and Wide_Wide_Strings.
20727 @code{Ada.Strings.Wide_Bounded} @emph{(A.4.7)}
20729 @code{Ada.Strings.Wide_Fixed} @emph{(A.4.7)}
20731 @code{Ada.Strings.Wide_Maps} @emph{(A.4.7)}
20736 @item @code{Ada.Strings.Wide_Unbounded} @emph{(A.4.7)}
20738 These packages provide analogous capabilities to the corresponding
20739 packages without @code{Wide_} in the name, but operate with the types
20740 @code{Wide_String} and @code{Wide_Character} instead of @code{String}
20741 and @code{Character}. Versions of all the child packages are available.
20744 @code{Ada.Strings.Wide_Wide_Bounded} @emph{(A.4.7)}
20746 @code{Ada.Strings.Wide_Wide_Fixed} @emph{(A.4.7)}
20748 @code{Ada.Strings.Wide_Wide_Maps} @emph{(A.4.7)}
20753 @item @code{Ada.Strings.Wide_Wide_Unbounded} @emph{(A.4.7)}
20755 These packages provide analogous capabilities to the corresponding
20756 packages without @code{Wide_} in the name, but operate with the types
20757 @code{Wide_Wide_String} and @code{Wide_Wide_Character} instead
20758 of @code{String} and @code{Character}.
20760 @item @code{Ada.Synchronous_Barriers} @emph{(D.10.1)}
20762 This package provides facilities for synchronizing tasks at a low level
20765 @item @code{Ada.Synchronous_Task_Control} @emph{(D.10)}
20767 This package provides some standard facilities for controlling task
20768 communication in a synchronous manner.
20770 @item @code{Ada.Synchronous_Task_Control.EDF} @emph{(D.10)}
20772 Not implemented in GNAT.
20774 @item @code{Ada.Tags}
20776 This package contains definitions for manipulation of the tags of tagged
20779 @item @code{Ada.Tags.Generic_Dispatching_Constructor} @emph{(3.9)}
20781 This package provides a way of constructing tagged class-wide values given
20782 only the tag value.
20784 @item @code{Ada.Task_Attributes} @emph{(C.7.2)}
20786 This package provides the capability of associating arbitrary
20787 task-specific data with separate tasks.
20789 @item @code{Ada.Task_Identifification} @emph{(C.7.1)}
20791 This package provides capabilities for task identification.
20793 @item @code{Ada.Task_Termination} @emph{(C.7.3)}
20795 This package provides control over task termination.
20797 @item @code{Ada.Text_IO}
20799 This package provides basic text input-output capabilities for
20800 character, string and numeric data. The subpackages of this
20801 package are listed next. Note that although these are defined
20802 as subpackages in the RM, they are actually transparently
20803 implemented as child packages in GNAT, meaning that they
20804 are only loaded if needed.
20806 @item @code{Ada.Text_IO.Decimal_IO}
20808 Provides input-output facilities for decimal fixed-point types
20810 @item @code{Ada.Text_IO.Enumeration_IO}
20812 Provides input-output facilities for enumeration types.
20814 @item @code{Ada.Text_IO.Fixed_IO}
20816 Provides input-output facilities for ordinary fixed-point types.
20818 @item @code{Ada.Text_IO.Float_IO}
20820 Provides input-output facilities for float types. The following
20821 predefined instantiations of this generic package are available:
20829 @code{Short_Float_Text_IO}
20834 @code{Float_Text_IO}
20839 @code{Long_Float_Text_IO}
20842 @item @code{Ada.Text_IO.Integer_IO}
20844 Provides input-output facilities for integer types. The following
20845 predefined instantiations of this generic package are available:
20851 @code{Short_Short_Integer}
20853 @code{Ada.Short_Short_Integer_Text_IO}
20856 @code{Short_Integer}
20858 @code{Ada.Short_Integer_Text_IO}
20863 @code{Ada.Integer_Text_IO}
20866 @code{Long_Integer}
20868 @code{Ada.Long_Integer_Text_IO}
20871 @code{Long_Long_Integer}
20873 @code{Ada.Long_Long_Integer_Text_IO}
20876 @item @code{Ada.Text_IO.Modular_IO}
20878 Provides input-output facilities for modular (unsigned) types.
20880 @item @code{Ada.Text_IO.Bounded_IO (A.10.11)}
20882 Provides input-output facilities for bounded strings.
20884 @item @code{Ada.Text_IO.Complex_IO (G.1.3)}
20886 This package provides basic text input-output capabilities for complex
20889 @item @code{Ada.Text_IO.Editing (F.3.3)}
20891 This package contains routines for edited output, analogous to the use
20892 of pictures in COBOL. The picture formats used by this package are a
20893 close copy of the facility in COBOL.
20895 @item @code{Ada.Text_IO.Text_Streams (A.12.2)}
20897 This package provides a facility that allows Text_IO files to be treated
20898 as streams, so that the stream attributes can be used for writing
20899 arbitrary data, including binary data, to Text_IO files.
20901 @item @code{Ada.Text_IO.Unbounded_IO (A.10.12)}
20903 This package provides input-output facilities for unbounded strings.
20905 @item @code{Ada.Unchecked_Conversion (13.9)}
20907 This generic package allows arbitrary conversion from one type to
20908 another of the same size, providing for breaking the type safety in
20909 special circumstances.
20911 If the types have the same Size (more accurately the same Value_Size),
20912 then the effect is simply to transfer the bits from the source to the
20913 target type without any modification. This usage is well defined, and
20914 for simple types whose representation is typically the same across
20915 all implementations, gives a portable method of performing such
20918 If the types do not have the same size, then the result is implementation
20919 defined, and thus may be non-portable. The following describes how GNAT
20920 handles such unchecked conversion cases.
20922 If the types are of different sizes, and are both discrete types, then
20923 the effect is of a normal type conversion without any constraint checking.
20924 In particular if the result type has a larger size, the result will be
20925 zero or sign extended. If the result type has a smaller size, the result
20926 will be truncated by ignoring high order bits.
20928 If the types are of different sizes, and are not both discrete types,
20929 then the conversion works as though pointers were created to the source
20930 and target, and the pointer value is converted. The effect is that bits
20931 are copied from successive low order storage units and bits of the source
20932 up to the length of the target type.
20934 A warning is issued if the lengths differ, since the effect in this
20935 case is implementation dependent, and the above behavior may not match
20936 that of some other compiler.
20938 A pointer to one type may be converted to a pointer to another type using
20939 unchecked conversion. The only case in which the effect is undefined is
20940 when one or both pointers are pointers to unconstrained array types. In
20941 this case, the bounds information may get incorrectly transferred, and in
20942 particular, GNAT uses double size pointers for such types, and it is
20943 meaningless to convert between such pointer types. GNAT will issue a
20944 warning if the alignment of the target designated type is more strict
20945 than the alignment of the source designated type (since the result may
20946 be unaligned in this case).
20948 A pointer other than a pointer to an unconstrained array type may be
20949 converted to and from System.Address. Such usage is common in Ada 83
20950 programs, but note that Ada.Address_To_Access_Conversions is the
20951 preferred method of performing such conversions in Ada 95 and Ada 2005.
20953 unchecked conversion nor Ada.Address_To_Access_Conversions should be
20954 used in conjunction with pointers to unconstrained objects, since
20955 the bounds information cannot be handled correctly in this case.
20957 @item @code{Ada.Unchecked_Deallocation} @emph{(13.11.2)}
20959 This generic package allows explicit freeing of storage previously
20960 allocated by use of an allocator.
20962 @item @code{Ada.Wide_Text_IO} @emph{(A.11)}
20964 This package is similar to @code{Ada.Text_IO}, except that the external
20965 file supports wide character representations, and the internal types are
20966 @code{Wide_Character} and @code{Wide_String} instead of @code{Character}
20967 and @code{String}. The corresponding set of nested packages and child
20968 packages are defined.
20970 @item @code{Ada.Wide_Wide_Text_IO} @emph{(A.11)}
20972 This package is similar to @code{Ada.Text_IO}, except that the external
20973 file supports wide character representations, and the internal types are
20974 @code{Wide_Character} and @code{Wide_String} instead of @code{Character}
20975 and @code{String}. The corresponding set of nested packages and child
20976 packages are defined.
20979 For packages in Interfaces and System, all the RM defined packages are
20980 available in GNAT, see the Ada 2012 RM for full details.
20982 @node The Implementation of Standard I/O,The GNAT Library,Standard Library Routines,Top
20983 @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{29d}@anchor{gnat_rm/the_implementation_of_standard_i_o id1}@anchor{29e}
20984 @chapter The Implementation of Standard I/O
20987 GNAT implements all the required input-output facilities described in
20988 A.6 through A.14. These sections of the Ada Reference Manual describe the
20989 required behavior of these packages from the Ada point of view, and if
20990 you are writing a portable Ada program that does not need to know the
20991 exact manner in which Ada maps to the outside world when it comes to
20992 reading or writing external files, then you do not need to read this
20993 chapter. As long as your files are all regular files (not pipes or
20994 devices), and as long as you write and read the files only from Ada, the
20995 description in the Ada Reference Manual is sufficient.
20997 However, if you want to do input-output to pipes or other devices, such
20998 as the keyboard or screen, or if the files you are dealing with are
20999 either generated by some other language, or to be read by some other
21000 language, then you need to know more about the details of how the GNAT
21001 implementation of these input-output facilities behaves.
21003 In this chapter we give a detailed description of exactly how GNAT
21004 interfaces to the file system. As always, the sources of the system are
21005 available to you for answering questions at an even more detailed level,
21006 but for most purposes the information in this chapter will suffice.
21008 Another reason that you may need to know more about how input-output is
21009 implemented arises when you have a program written in mixed languages
21010 where, for example, files are shared between the C and Ada sections of
21011 the same program. GNAT provides some additional facilities, in the form
21012 of additional child library packages, that facilitate this sharing, and
21013 these additional facilities are also described in this chapter.
21016 * Standard I/O Packages::
21022 * Wide_Wide_Text_IO::
21024 * Text Translation::
21026 * Filenames encoding::
21027 * File content encoding::
21029 * Operations on C Streams::
21030 * Interfacing to C Streams::
21034 @node Standard I/O Packages,FORM Strings,,The Implementation of Standard I/O
21035 @anchor{gnat_rm/the_implementation_of_standard_i_o standard-i-o-packages}@anchor{29f}@anchor{gnat_rm/the_implementation_of_standard_i_o id2}@anchor{2a0}
21036 @section Standard I/O Packages
21039 The Standard I/O packages described in Annex A for
21048 Ada.Text_IO.Complex_IO
21051 Ada.Text_IO.Text_Streams
21057 Ada.Wide_Text_IO.Complex_IO
21060 Ada.Wide_Text_IO.Text_Streams
21063 Ada.Wide_Wide_Text_IO
21066 Ada.Wide_Wide_Text_IO.Complex_IO
21069 Ada.Wide_Wide_Text_IO.Text_Streams
21081 are implemented using the C
21082 library streams facility; where
21088 All files are opened using @code{fopen}.
21091 All input/output operations use @code{fread}/@cite{fwrite}.
21094 There is no internal buffering of any kind at the Ada library level. The only
21095 buffering is that provided at the system level in the implementation of the
21096 library routines that support streams. This facilitates shared use of these
21097 streams by mixed language programs. Note though that system level buffering is
21098 explicitly enabled at elaboration of the standard I/O packages and that can
21099 have an impact on mixed language programs, in particular those using I/O before
21100 calling the Ada elaboration routine (e.g., adainit). It is recommended to call
21101 the Ada elaboration routine before performing any I/O or when impractical,
21102 flush the common I/O streams and in particular Standard_Output before
21103 elaborating the Ada code.
21105 @node FORM Strings,Direct_IO,Standard I/O Packages,The Implementation of Standard I/O
21106 @anchor{gnat_rm/the_implementation_of_standard_i_o form-strings}@anchor{2a1}@anchor{gnat_rm/the_implementation_of_standard_i_o id3}@anchor{2a2}
21107 @section FORM Strings
21110 The format of a FORM string in GNAT is:
21113 "keyword=value,keyword=value,...,keyword=value"
21116 where letters may be in upper or lower case, and there are no spaces
21117 between values. The order of the entries is not important. Currently
21118 the following keywords defined.
21121 TEXT_TRANSLATION=[YES|NO|TEXT|BINARY|U8TEXT|WTEXT|U16TEXT]
21123 WCEM=[n|h|u|s|e|8|b]
21124 ENCODING=[UTF8|8BITS]
21127 The use of these parameters is described later in this section. If an
21128 unrecognized keyword appears in a form string, it is silently ignored
21129 and not considered invalid.
21131 @node Direct_IO,Sequential_IO,FORM Strings,The Implementation of Standard I/O
21132 @anchor{gnat_rm/the_implementation_of_standard_i_o direct-io}@anchor{2a3}@anchor{gnat_rm/the_implementation_of_standard_i_o id4}@anchor{2a4}
21136 Direct_IO can only be instantiated for definite types. This is a
21137 restriction of the Ada language, which means that the records are fixed
21138 length (the length being determined by @code{type'Size}, rounded
21139 up to the next storage unit boundary if necessary).
21141 The records of a Direct_IO file are simply written to the file in index
21142 sequence, with the first record starting at offset zero, and subsequent
21143 records following. There is no control information of any kind. For
21144 example, if 32-bit integers are being written, each record takes
21145 4-bytes, so the record at index @code{K} starts at offset
21148 There is no limit on the size of Direct_IO files, they are expanded as
21149 necessary to accommodate whatever records are written to the file.
21151 @node Sequential_IO,Text_IO,Direct_IO,The Implementation of Standard I/O
21152 @anchor{gnat_rm/the_implementation_of_standard_i_o sequential-io}@anchor{2a5}@anchor{gnat_rm/the_implementation_of_standard_i_o id5}@anchor{2a6}
21153 @section Sequential_IO
21156 Sequential_IO may be instantiated with either a definite (constrained)
21157 or indefinite (unconstrained) type.
21159 For the definite type case, the elements written to the file are simply
21160 the memory images of the data values with no control information of any
21161 kind. The resulting file should be read using the same type, no validity
21162 checking is performed on input.
21164 For the indefinite type case, the elements written consist of two
21165 parts. First is the size of the data item, written as the memory image
21166 of a @code{Interfaces.C.size_t} value, followed by the memory image of
21167 the data value. The resulting file can only be read using the same
21168 (unconstrained) type. Normal assignment checks are performed on these
21169 read operations, and if these checks fail, @code{Data_Error} is
21170 raised. In particular, in the array case, the lengths must match, and in
21171 the variant record case, if the variable for a particular read operation
21172 is constrained, the discriminants must match.
21174 Note that it is not possible to use Sequential_IO to write variable
21175 length array items, and then read the data back into different length
21176 arrays. For example, the following will raise @code{Data_Error}:
21179 package IO is new Sequential_IO (String);
21184 IO.Write (F, "hello!")
21185 IO.Reset (F, Mode=>In_File);
21190 On some Ada implementations, this will print @code{hell}, but the program is
21191 clearly incorrect, since there is only one element in the file, and that
21192 element is the string @code{hello!}.
21194 In Ada 95 and Ada 2005, this kind of behavior can be legitimately achieved
21195 using Stream_IO, and this is the preferred mechanism. In particular, the
21196 above program fragment rewritten to use Stream_IO will work correctly.
21198 @node Text_IO,Wide_Text_IO,Sequential_IO,The Implementation of Standard I/O
21199 @anchor{gnat_rm/the_implementation_of_standard_i_o id6}@anchor{2a7}@anchor{gnat_rm/the_implementation_of_standard_i_o text-io}@anchor{2a8}
21203 Text_IO files consist of a stream of characters containing the following
21204 special control characters:
21207 LF (line feed, 16#0A#) Line Mark
21208 FF (form feed, 16#0C#) Page Mark
21211 A canonical Text_IO file is defined as one in which the following
21212 conditions are met:
21218 The character @code{LF} is used only as a line mark, i.e., to mark the end
21222 The character @code{FF} is used only as a page mark, i.e., to mark the
21223 end of a page and consequently can appear only immediately following a
21224 @code{LF} (line mark) character.
21227 The file ends with either @code{LF} (line mark) or @code{LF}-@cite{FF}
21228 (line mark, page mark). In the former case, the page mark is implicitly
21229 assumed to be present.
21232 A file written using Text_IO will be in canonical form provided that no
21233 explicit @code{LF} or @code{FF} characters are written using @code{Put}
21234 or @code{Put_Line}. There will be no @code{FF} character at the end of
21235 the file unless an explicit @code{New_Page} operation was performed
21236 before closing the file.
21238 A canonical Text_IO file that is a regular file (i.e., not a device or a
21239 pipe) can be read using any of the routines in Text_IO. The
21240 semantics in this case will be exactly as defined in the Ada Reference
21241 Manual, and all the routines in Text_IO are fully implemented.
21243 A text file that does not meet the requirements for a canonical Text_IO
21244 file has one of the following:
21250 The file contains @code{FF} characters not immediately following a
21251 @code{LF} character.
21254 The file contains @code{LF} or @code{FF} characters written by
21255 @code{Put} or @code{Put_Line}, which are not logically considered to be
21256 line marks or page marks.
21259 The file ends in a character other than @code{LF} or @code{FF},
21260 i.e., there is no explicit line mark or page mark at the end of the file.
21263 Text_IO can be used to read such non-standard text files but subprograms
21264 to do with line or page numbers do not have defined meanings. In
21265 particular, a @code{FF} character that does not follow a @code{LF}
21266 character may or may not be treated as a page mark from the point of
21267 view of page and line numbering. Every @code{LF} character is considered
21268 to end a line, and there is an implied @code{LF} character at the end of
21272 * Stream Pointer Positioning::
21273 * Reading and Writing Non-Regular Files::
21275 * Treating Text_IO Files as Streams::
21276 * Text_IO Extensions::
21277 * Text_IO Facilities for Unbounded Strings::
21281 @node Stream Pointer Positioning,Reading and Writing Non-Regular Files,,Text_IO
21282 @anchor{gnat_rm/the_implementation_of_standard_i_o id7}@anchor{2a9}@anchor{gnat_rm/the_implementation_of_standard_i_o stream-pointer-positioning}@anchor{2aa}
21283 @subsection Stream Pointer Positioning
21286 @code{Ada.Text_IO} has a definition of current position for a file that
21287 is being read. No internal buffering occurs in Text_IO, and usually the
21288 physical position in the stream used to implement the file corresponds
21289 to this logical position defined by Text_IO. There are two exceptions:
21295 After a call to @code{End_Of_Page} that returns @code{True}, the stream
21296 is positioned past the @code{LF} (line mark) that precedes the page
21297 mark. Text_IO maintains an internal flag so that subsequent read
21298 operations properly handle the logical position which is unchanged by
21299 the @code{End_Of_Page} call.
21302 After a call to @code{End_Of_File} that returns @code{True}, if the
21303 Text_IO file was positioned before the line mark at the end of file
21304 before the call, then the logical position is unchanged, but the stream
21305 is physically positioned right at the end of file (past the line mark,
21306 and past a possible page mark following the line mark. Again Text_IO
21307 maintains internal flags so that subsequent read operations properly
21308 handle the logical position.
21311 These discrepancies have no effect on the observable behavior of
21312 Text_IO, but if a single Ada stream is shared between a C program and
21313 Ada program, or shared (using @code{shared=yes} in the form string)
21314 between two Ada files, then the difference may be observable in some
21317 @node Reading and Writing Non-Regular Files,Get_Immediate,Stream Pointer Positioning,Text_IO
21318 @anchor{gnat_rm/the_implementation_of_standard_i_o reading-and-writing-non-regular-files}@anchor{2ab}@anchor{gnat_rm/the_implementation_of_standard_i_o id8}@anchor{2ac}
21319 @subsection Reading and Writing Non-Regular Files
21322 A non-regular file is a device (such as a keyboard), or a pipe. Text_IO
21323 can be used for reading and writing. Writing is not affected and the
21324 sequence of characters output is identical to the normal file case, but
21325 for reading, the behavior of Text_IO is modified to avoid undesirable
21326 look-ahead as follows:
21328 An input file that is not a regular file is considered to have no page
21329 marks. Any @code{Ascii.FF} characters (the character normally used for a
21330 page mark) appearing in the file are considered to be data
21331 characters. In particular:
21337 @code{Get_Line} and @code{Skip_Line} do not test for a page mark
21338 following a line mark. If a page mark appears, it will be treated as a
21342 This avoids the need to wait for an extra character to be typed or
21343 entered from the pipe to complete one of these operations.
21346 @code{End_Of_Page} always returns @code{False}
21349 @code{End_Of_File} will return @code{False} if there is a page mark at
21350 the end of the file.
21353 Output to non-regular files is the same as for regular files. Page marks
21354 may be written to non-regular files using @code{New_Page}, but as noted
21355 above they will not be treated as page marks on input if the output is
21356 piped to another Ada program.
21358 Another important discrepancy when reading non-regular files is that the end
21359 of file indication is not 'sticky'. If an end of file is entered, e.g., by
21360 pressing the @code{EOT} key,
21362 is signaled once (i.e., the test @code{End_Of_File}
21363 will yield @code{True}, or a read will
21364 raise @code{End_Error}), but then reading can resume
21365 to read data past that end of
21366 file indication, until another end of file indication is entered.
21368 @node Get_Immediate,Treating Text_IO Files as Streams,Reading and Writing Non-Regular Files,Text_IO
21369 @anchor{gnat_rm/the_implementation_of_standard_i_o get-immediate}@anchor{2ad}@anchor{gnat_rm/the_implementation_of_standard_i_o id9}@anchor{2ae}
21370 @subsection Get_Immediate
21373 @geindex Get_Immediate
21375 Get_Immediate returns the next character (including control characters)
21376 from the input file. In particular, Get_Immediate will return LF or FF
21377 characters used as line marks or page marks. Such operations leave the
21378 file positioned past the control character, and it is thus not treated
21379 as having its normal function. This means that page, line and column
21380 counts after this kind of Get_Immediate call are set as though the mark
21381 did not occur. In the case where a Get_Immediate leaves the file
21382 positioned between the line mark and page mark (which is not normally
21383 possible), it is undefined whether the FF character will be treated as a
21386 @node Treating Text_IO Files as Streams,Text_IO Extensions,Get_Immediate,Text_IO
21387 @anchor{gnat_rm/the_implementation_of_standard_i_o id10}@anchor{2af}@anchor{gnat_rm/the_implementation_of_standard_i_o treating-text-io-files-as-streams}@anchor{2b0}
21388 @subsection Treating Text_IO Files as Streams
21391 @geindex Stream files
21393 The package @code{Text_IO.Streams} allows a @code{Text_IO} file to be treated
21394 as a stream. Data written to a @code{Text_IO} file in this stream mode is
21395 binary data. If this binary data contains bytes 16#0A# (@code{LF}) or
21396 16#0C# (@code{FF}), the resulting file may have non-standard
21397 format. Similarly if read operations are used to read from a Text_IO
21398 file treated as a stream, then @code{LF} and @code{FF} characters may be
21399 skipped and the effect is similar to that described above for
21400 @code{Get_Immediate}.
21402 @node Text_IO Extensions,Text_IO Facilities for Unbounded Strings,Treating Text_IO Files as Streams,Text_IO
21403 @anchor{gnat_rm/the_implementation_of_standard_i_o id11}@anchor{2b1}@anchor{gnat_rm/the_implementation_of_standard_i_o text-io-extensions}@anchor{2b2}
21404 @subsection Text_IO Extensions
21407 @geindex Text_IO extensions
21409 A package GNAT.IO_Aux in the GNAT library provides some useful extensions
21410 to the standard @code{Text_IO} package:
21416 function File_Exists (Name : String) return Boolean;
21417 Determines if a file of the given name exists.
21420 function Get_Line return String;
21421 Reads a string from the standard input file. The value returned is exactly
21422 the length of the line that was read.
21425 function Get_Line (File : Ada.Text_IO.File_Type) return String;
21426 Similar, except that the parameter File specifies the file from which
21427 the string is to be read.
21430 @node Text_IO Facilities for Unbounded Strings,,Text_IO Extensions,Text_IO
21431 @anchor{gnat_rm/the_implementation_of_standard_i_o text-io-facilities-for-unbounded-strings}@anchor{2b3}@anchor{gnat_rm/the_implementation_of_standard_i_o id12}@anchor{2b4}
21432 @subsection Text_IO Facilities for Unbounded Strings
21435 @geindex Text_IO for unbounded strings
21437 @geindex Unbounded_String
21438 @geindex Text_IO operations
21440 The package @code{Ada.Strings.Unbounded.Text_IO}
21441 in library files @code{a-suteio.ads/adb} contains some GNAT-specific
21442 subprograms useful for Text_IO operations on unbounded strings:
21448 function Get_Line (File : File_Type) return Unbounded_String;
21449 Reads a line from the specified file
21450 and returns the result as an unbounded string.
21453 procedure Put (File : File_Type; U : Unbounded_String);
21454 Writes the value of the given unbounded string to the specified file
21455 Similar to the effect of
21456 @code{Put (To_String (U))} except that an extra copy is avoided.
21459 procedure Put_Line (File : File_Type; U : Unbounded_String);
21460 Writes the value of the given unbounded string to the specified file,
21461 followed by a @code{New_Line}.
21462 Similar to the effect of @code{Put_Line (To_String (U))} except
21463 that an extra copy is avoided.
21466 In the above procedures, @code{File} is of type @code{Ada.Text_IO.File_Type}
21467 and is optional. If the parameter is omitted, then the standard input or
21468 output file is referenced as appropriate.
21470 The package @code{Ada.Strings.Wide_Unbounded.Wide_Text_IO} in library
21471 files @code{a-swuwti.ads} and @code{a-swuwti.adb} provides similar extended
21472 @code{Wide_Text_IO} functionality for unbounded wide strings.
21474 The package @code{Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO} in library
21475 files @code{a-szuzti.ads} and @code{a-szuzti.adb} provides similar extended
21476 @code{Wide_Wide_Text_IO} functionality for unbounded wide wide strings.
21478 @node Wide_Text_IO,Wide_Wide_Text_IO,Text_IO,The Implementation of Standard I/O
21479 @anchor{gnat_rm/the_implementation_of_standard_i_o wide-text-io}@anchor{2b5}@anchor{gnat_rm/the_implementation_of_standard_i_o id13}@anchor{2b6}
21480 @section Wide_Text_IO
21483 @code{Wide_Text_IO} is similar in most respects to Text_IO, except that
21484 both input and output files may contain special sequences that represent
21485 wide character values. The encoding scheme for a given file may be
21486 specified using a FORM parameter:
21492 as part of the FORM string (WCEM = wide character encoding method),
21493 where @code{x} is one of the following characters
21496 @multitable {xxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxx}
21519 Upper half encoding
21556 The encoding methods match those that
21557 can be used in a source
21558 program, but there is no requirement that the encoding method used for
21559 the source program be the same as the encoding method used for files,
21560 and different files may use different encoding methods.
21562 The default encoding method for the standard files, and for opened files
21563 for which no WCEM parameter is given in the FORM string matches the
21564 wide character encoding specified for the main program (the default
21565 being brackets encoding if no coding method was specified with -gnatW).
21570 @item @emph{Hex Coding}
21572 In this encoding, a wide character is represented by a five character
21583 where @code{a}, @code{b}, @code{c}, @code{d} are the four hexadecimal
21584 characters (using upper case letters) of the wide character code. For
21585 example, ESC A345 is used to represent the wide character with code
21586 16#A345#. This scheme is compatible with use of the full
21587 @code{Wide_Character} set.
21593 @item @emph{Upper Half Coding}
21595 The wide character with encoding 16#abcd#, where the upper bit is on
21596 (i.e., a is in the range 8-F) is represented as two bytes 16#ab# and
21597 16#cd#. The second byte may never be a format control character, but is
21598 not required to be in the upper half. This method can be also used for
21599 shift-JIS or EUC where the internal coding matches the external coding.
21601 @item @emph{Shift JIS Coding}
21603 A wide character is represented by a two character sequence 16#ab# and
21604 16#cd#, with the restrictions described for upper half encoding as
21605 described above. The internal character code is the corresponding JIS
21606 character according to the standard algorithm for Shift-JIS
21607 conversion. Only characters defined in the JIS code set table can be
21608 used with this encoding method.
21610 @item @emph{EUC Coding}
21612 A wide character is represented by a two character sequence 16#ab# and
21613 16#cd#, with both characters being in the upper half. The internal
21614 character code is the corresponding JIS character according to the EUC
21615 encoding algorithm. Only characters defined in the JIS code set table
21616 can be used with this encoding method.
21618 @item @emph{UTF-8 Coding}
21620 A wide character is represented using
21621 UCS Transformation Format 8 (UTF-8) as defined in Annex R of ISO
21622 10646-1/Am.2. Depending on the character value, the representation
21623 is a one, two, or three byte sequence:
21627 16#0000#-16#007f#: 2#0xxxxxxx#
21628 16#0080#-16#07ff#: 2#110xxxxx# 2#10xxxxxx#
21629 16#0800#-16#ffff#: 2#1110xxxx# 2#10xxxxxx# 2#10xxxxxx#
21635 where the @code{xxx} bits correspond to the left-padded bits of the
21636 16-bit character value. Note that all lower half ASCII characters
21637 are represented as ASCII bytes and all upper half characters and
21638 other wide characters are represented as sequences of upper-half
21639 (The full UTF-8 scheme allows for encoding 31-bit characters as
21640 6-byte sequences, but in this implementation, all UTF-8 sequences
21641 of four or more bytes length will raise a Constraint_Error, as
21642 will all invalid UTF-8 sequences.)
21648 @item @emph{Brackets Coding}
21650 In this encoding, a wide character is represented by the following eight
21651 character sequence:
21661 where @code{a}, @code{b}, @code{c}, @code{d} are the four hexadecimal
21662 characters (using uppercase letters) of the wide character code. For
21663 example, @code{["A345"]} is used to represent the wide character with code
21665 This scheme is compatible with use of the full Wide_Character set.
21666 On input, brackets coding can also be used for upper half characters,
21667 e.g., @code{["C1"]} for lower case a. However, on output, brackets notation
21668 is only used for wide characters with a code greater than @code{16#FF#}.
21670 Note that brackets coding is not normally used in the context of
21671 Wide_Text_IO or Wide_Wide_Text_IO, since it is really just designed as
21672 a portable way of encoding source files. In the context of Wide_Text_IO
21673 or Wide_Wide_Text_IO, it can only be used if the file does not contain
21674 any instance of the left bracket character other than to encode wide
21675 character values using the brackets encoding method. In practice it is
21676 expected that some standard wide character encoding method such
21677 as UTF-8 will be used for text input output.
21679 If brackets notation is used, then any occurrence of a left bracket
21680 in the input file which is not the start of a valid wide character
21681 sequence will cause Constraint_Error to be raised. It is possible to
21682 encode a left bracket as ["5B"] and Wide_Text_IO and Wide_Wide_Text_IO
21683 input will interpret this as a left bracket.
21685 However, when a left bracket is output, it will be output as a left bracket
21686 and not as ["5B"]. We make this decision because for normal use of
21687 Wide_Text_IO for outputting messages, it is unpleasant to clobber left
21688 brackets. For example, if we write:
21691 Put_Line ("Start of output [first run]");
21694 we really do not want to have the left bracket in this message clobbered so
21695 that the output reads:
21699 Start of output ["5B"]first run]
21705 In practice brackets encoding is reasonably useful for normal Put_Line use
21706 since we won't get confused between left brackets and wide character
21707 sequences in the output. But for input, or when files are written out
21708 and read back in, it really makes better sense to use one of the standard
21709 encoding methods such as UTF-8.
21712 For the coding schemes other than UTF-8, Hex, or Brackets encoding,
21713 not all wide character
21714 values can be represented. An attempt to output a character that cannot
21715 be represented using the encoding scheme for the file causes
21716 Constraint_Error to be raised. An invalid wide character sequence on
21717 input also causes Constraint_Error to be raised.
21720 * Stream Pointer Positioning: Stream Pointer Positioning<2>.
21721 * Reading and Writing Non-Regular Files: Reading and Writing Non-Regular Files<2>.
21725 @node Stream Pointer Positioning<2>,Reading and Writing Non-Regular Files<2>,,Wide_Text_IO
21726 @anchor{gnat_rm/the_implementation_of_standard_i_o stream-pointer-positioning-1}@anchor{2b7}@anchor{gnat_rm/the_implementation_of_standard_i_o id14}@anchor{2b8}
21727 @subsection Stream Pointer Positioning
21730 @code{Ada.Wide_Text_IO} is similar to @code{Ada.Text_IO} in its handling
21731 of stream pointer positioning (@ref{2a8,,Text_IO}). There is one additional
21734 If @code{Ada.Wide_Text_IO.Look_Ahead} reads a character outside the
21735 normal lower ASCII set (i.e., a character in the range:
21738 Wide_Character'Val (16#0080#) .. Wide_Character'Val (16#FFFF#)
21741 then although the logical position of the file pointer is unchanged by
21742 the @code{Look_Ahead} call, the stream is physically positioned past the
21743 wide character sequence. Again this is to avoid the need for buffering
21744 or backup, and all @code{Wide_Text_IO} routines check the internal
21745 indication that this situation has occurred so that this is not visible
21746 to a normal program using @code{Wide_Text_IO}. However, this discrepancy
21747 can be observed if the wide text file shares a stream with another file.
21749 @node Reading and Writing Non-Regular Files<2>,,Stream Pointer Positioning<2>,Wide_Text_IO
21750 @anchor{gnat_rm/the_implementation_of_standard_i_o reading-and-writing-non-regular-files-1}@anchor{2b9}@anchor{gnat_rm/the_implementation_of_standard_i_o id15}@anchor{2ba}
21751 @subsection Reading and Writing Non-Regular Files
21754 As in the case of Text_IO, when a non-regular file is read, it is
21755 assumed that the file contains no page marks (any form characters are
21756 treated as data characters), and @code{End_Of_Page} always returns
21757 @code{False}. Similarly, the end of file indication is not sticky, so
21758 it is possible to read beyond an end of file.
21760 @node Wide_Wide_Text_IO,Stream_IO,Wide_Text_IO,The Implementation of Standard I/O
21761 @anchor{gnat_rm/the_implementation_of_standard_i_o id16}@anchor{2bb}@anchor{gnat_rm/the_implementation_of_standard_i_o wide-wide-text-io}@anchor{2bc}
21762 @section Wide_Wide_Text_IO
21765 @code{Wide_Wide_Text_IO} is similar in most respects to Text_IO, except that
21766 both input and output files may contain special sequences that represent
21767 wide wide character values. The encoding scheme for a given file may be
21768 specified using a FORM parameter:
21774 as part of the FORM string (WCEM = wide character encoding method),
21775 where @code{x} is one of the following characters
21778 @multitable {xxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxx}
21801 Upper half encoding
21838 The encoding methods match those that
21839 can be used in a source
21840 program, but there is no requirement that the encoding method used for
21841 the source program be the same as the encoding method used for files,
21842 and different files may use different encoding methods.
21844 The default encoding method for the standard files, and for opened files
21845 for which no WCEM parameter is given in the FORM string matches the
21846 wide character encoding specified for the main program (the default
21847 being brackets encoding if no coding method was specified with -gnatW).
21852 @item @emph{UTF-8 Coding}
21854 A wide character is represented using
21855 UCS Transformation Format 8 (UTF-8) as defined in Annex R of ISO
21856 10646-1/Am.2. Depending on the character value, the representation
21857 is a one, two, three, or four byte sequence:
21861 16#000000#-16#00007f#: 2#0xxxxxxx#
21862 16#000080#-16#0007ff#: 2#110xxxxx# 2#10xxxxxx#
21863 16#000800#-16#00ffff#: 2#1110xxxx# 2#10xxxxxx# 2#10xxxxxx#
21864 16#010000#-16#10ffff#: 2#11110xxx# 2#10xxxxxx# 2#10xxxxxx# 2#10xxxxxx#
21870 where the @code{xxx} bits correspond to the left-padded bits of the
21871 21-bit character value. Note that all lower half ASCII characters
21872 are represented as ASCII bytes and all upper half characters and
21873 other wide characters are represented as sequences of upper-half
21880 @item @emph{Brackets Coding}
21882 In this encoding, a wide wide character is represented by the following eight
21883 character sequence if is in wide character range
21893 and by the following ten character sequence if not
21897 [ " a b c d e f " ]
21903 where @code{a}, @code{b}, @code{c}, @code{d}, @code{e}, and @code{f}
21904 are the four or six hexadecimal
21905 characters (using uppercase letters) of the wide wide character code. For
21906 example, @code{["01A345"]} is used to represent the wide wide character
21907 with code @code{16#01A345#}.
21909 This scheme is compatible with use of the full Wide_Wide_Character set.
21910 On input, brackets coding can also be used for upper half characters,
21911 e.g., @code{["C1"]} for lower case a. However, on output, brackets notation
21912 is only used for wide characters with a code greater than @code{16#FF#}.
21915 If is also possible to use the other Wide_Character encoding methods,
21916 such as Shift-JIS, but the other schemes cannot support the full range
21917 of wide wide characters.
21918 An attempt to output a character that cannot
21919 be represented using the encoding scheme for the file causes
21920 Constraint_Error to be raised. An invalid wide character sequence on
21921 input also causes Constraint_Error to be raised.
21924 * Stream Pointer Positioning: Stream Pointer Positioning<3>.
21925 * Reading and Writing Non-Regular Files: Reading and Writing Non-Regular Files<3>.
21929 @node Stream Pointer Positioning<3>,Reading and Writing Non-Regular Files<3>,,Wide_Wide_Text_IO
21930 @anchor{gnat_rm/the_implementation_of_standard_i_o stream-pointer-positioning-2}@anchor{2bd}@anchor{gnat_rm/the_implementation_of_standard_i_o id17}@anchor{2be}
21931 @subsection Stream Pointer Positioning
21934 @code{Ada.Wide_Wide_Text_IO} is similar to @code{Ada.Text_IO} in its handling
21935 of stream pointer positioning (@ref{2a8,,Text_IO}). There is one additional
21938 If @code{Ada.Wide_Wide_Text_IO.Look_Ahead} reads a character outside the
21939 normal lower ASCII set (i.e., a character in the range:
21942 Wide_Wide_Character'Val (16#0080#) .. Wide_Wide_Character'Val (16#10FFFF#)
21945 then although the logical position of the file pointer is unchanged by
21946 the @code{Look_Ahead} call, the stream is physically positioned past the
21947 wide character sequence. Again this is to avoid the need for buffering
21948 or backup, and all @code{Wide_Wide_Text_IO} routines check the internal
21949 indication that this situation has occurred so that this is not visible
21950 to a normal program using @code{Wide_Wide_Text_IO}. However, this discrepancy
21951 can be observed if the wide text file shares a stream with another file.
21953 @node Reading and Writing Non-Regular Files<3>,,Stream Pointer Positioning<3>,Wide_Wide_Text_IO
21954 @anchor{gnat_rm/the_implementation_of_standard_i_o id18}@anchor{2bf}@anchor{gnat_rm/the_implementation_of_standard_i_o reading-and-writing-non-regular-files-2}@anchor{2c0}
21955 @subsection Reading and Writing Non-Regular Files
21958 As in the case of Text_IO, when a non-regular file is read, it is
21959 assumed that the file contains no page marks (any form characters are
21960 treated as data characters), and @code{End_Of_Page} always returns
21961 @code{False}. Similarly, the end of file indication is not sticky, so
21962 it is possible to read beyond an end of file.
21964 @node Stream_IO,Text Translation,Wide_Wide_Text_IO,The Implementation of Standard I/O
21965 @anchor{gnat_rm/the_implementation_of_standard_i_o id19}@anchor{2c1}@anchor{gnat_rm/the_implementation_of_standard_i_o stream-io}@anchor{2c2}
21969 A stream file is a sequence of bytes, where individual elements are
21970 written to the file as described in the Ada Reference Manual. The type
21971 @code{Stream_Element} is simply a byte. There are two ways to read or
21972 write a stream file.
21978 The operations @code{Read} and @code{Write} directly read or write a
21979 sequence of stream elements with no control information.
21982 The stream attributes applied to a stream file transfer data in the
21983 manner described for stream attributes.
21986 @node Text Translation,Shared Files,Stream_IO,The Implementation of Standard I/O
21987 @anchor{gnat_rm/the_implementation_of_standard_i_o id20}@anchor{2c3}@anchor{gnat_rm/the_implementation_of_standard_i_o text-translation}@anchor{2c4}
21988 @section Text Translation
21991 @code{Text_Translation=xxx} may be used as the Form parameter
21992 passed to Text_IO.Create and Text_IO.Open. @code{Text_Translation=xxx}
21993 has no effect on Unix systems. Possible values are:
21999 @code{Yes} or @code{Text} is the default, which means to
22000 translate LF to/from CR/LF on Windows systems.
22002 @code{No} disables this translation; i.e. it
22003 uses binary mode. For output files, @code{Text_Translation=No}
22004 may be used to create Unix-style files on
22008 @code{wtext} translation enabled in Unicode mode.
22009 (corresponds to _O_WTEXT).
22012 @code{u8text} translation enabled in Unicode UTF-8 mode.
22013 (corresponds to O_U8TEXT).
22016 @code{u16text} translation enabled in Unicode UTF-16
22017 mode. (corresponds to_O_U16TEXT).
22020 @node Shared Files,Filenames encoding,Text Translation,The Implementation of Standard I/O
22021 @anchor{gnat_rm/the_implementation_of_standard_i_o id21}@anchor{2c5}@anchor{gnat_rm/the_implementation_of_standard_i_o shared-files}@anchor{2c6}
22022 @section Shared Files
22025 Section A.14 of the Ada Reference Manual allows implementations to
22026 provide a wide variety of behavior if an attempt is made to access the
22027 same external file with two or more internal files.
22029 To provide a full range of functionality, while at the same time
22030 minimizing the problems of portability caused by this implementation
22031 dependence, GNAT handles file sharing as follows:
22037 In the absence of a @code{shared=xxx} form parameter, an attempt
22038 to open two or more files with the same full name is considered an error
22039 and is not supported. The exception @code{Use_Error} will be
22040 raised. Note that a file that is not explicitly closed by the program
22041 remains open until the program terminates.
22044 If the form parameter @code{shared=no} appears in the form string, the
22045 file can be opened or created with its own separate stream identifier,
22046 regardless of whether other files sharing the same external file are
22047 opened. The exact effect depends on how the C stream routines handle
22048 multiple accesses to the same external files using separate streams.
22051 If the form parameter @code{shared=yes} appears in the form string for
22052 each of two or more files opened using the same full name, the same
22053 stream is shared between these files, and the semantics are as described
22054 in Ada Reference Manual, Section A.14.
22057 When a program that opens multiple files with the same name is ported
22058 from another Ada compiler to GNAT, the effect will be that
22059 @code{Use_Error} is raised.
22061 The documentation of the original compiler and the documentation of the
22062 program should then be examined to determine if file sharing was
22063 expected, and @code{shared=xxx} parameters added to @code{Open}
22064 and @code{Create} calls as required.
22066 When a program is ported from GNAT to some other Ada compiler, no
22067 special attention is required unless the @code{shared=xxx} form
22068 parameter is used in the program. In this case, you must examine the
22069 documentation of the new compiler to see if it supports the required
22070 file sharing semantics, and form strings modified appropriately. Of
22071 course it may be the case that the program cannot be ported if the
22072 target compiler does not support the required functionality. The best
22073 approach in writing portable code is to avoid file sharing (and hence
22074 the use of the @code{shared=xxx} parameter in the form string)
22077 One common use of file sharing in Ada 83 is the use of instantiations of
22078 Sequential_IO on the same file with different types, to achieve
22079 heterogeneous input-output. Although this approach will work in GNAT if
22080 @code{shared=yes} is specified, it is preferable in Ada to use Stream_IO
22081 for this purpose (using the stream attributes)
22083 @node Filenames encoding,File content encoding,Shared Files,The Implementation of Standard I/O
22084 @anchor{gnat_rm/the_implementation_of_standard_i_o filenames-encoding}@anchor{2c7}@anchor{gnat_rm/the_implementation_of_standard_i_o id22}@anchor{2c8}
22085 @section Filenames encoding
22088 An encoding form parameter can be used to specify the filename
22089 encoding @code{encoding=xxx}.
22095 If the form parameter @code{encoding=utf8} appears in the form string, the
22096 filename must be encoded in UTF-8.
22099 If the form parameter @code{encoding=8bits} appears in the form
22100 string, the filename must be a standard 8bits string.
22103 In the absence of a @code{encoding=xxx} form parameter, the
22104 encoding is controlled by the @code{GNAT_CODE_PAGE} environment
22105 variable. And if not set @code{utf8} is assumed.
22110 @item @emph{CP_ACP}
22112 The current system Windows ANSI code page.
22114 @item @emph{CP_UTF8}
22119 This encoding form parameter is only supported on the Windows
22120 platform. On the other Operating Systems the run-time is supporting
22123 @node File content encoding,Open Modes,Filenames encoding,The Implementation of Standard I/O
22124 @anchor{gnat_rm/the_implementation_of_standard_i_o file-content-encoding}@anchor{2c9}@anchor{gnat_rm/the_implementation_of_standard_i_o id23}@anchor{2ca}
22125 @section File content encoding
22128 For text files it is possible to specify the encoding to use. This is
22129 controlled by the by the @code{GNAT_CCS_ENCODING} environment
22130 variable. And if not set @code{TEXT} is assumed.
22132 The possible values are those supported on Windows:
22139 Translated text mode
22143 Translated unicode encoding
22145 @item @emph{U16TEXT}
22147 Unicode 16-bit encoding
22149 @item @emph{U8TEXT}
22151 Unicode 8-bit encoding
22154 This encoding is only supported on the Windows platform.
22156 @node Open Modes,Operations on C Streams,File content encoding,The Implementation of Standard I/O
22157 @anchor{gnat_rm/the_implementation_of_standard_i_o open-modes}@anchor{2cb}@anchor{gnat_rm/the_implementation_of_standard_i_o id24}@anchor{2cc}
22158 @section Open Modes
22161 @code{Open} and @code{Create} calls result in a call to @code{fopen}
22162 using the mode shown in the following table:
22165 @multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxx}
22168 @code{Open} and @code{Create} Call Modes
22210 Out_File (Direct_IO)
22222 Out_File (all other cases)
22247 If text file translation is required, then either @code{b} or @code{t}
22248 is added to the mode, depending on the setting of Text. Text file
22249 translation refers to the mapping of CR/LF sequences in an external file
22250 to LF characters internally. This mapping only occurs in DOS and
22251 DOS-like systems, and is not relevant to other systems.
22253 A special case occurs with Stream_IO. As shown in the above table, the
22254 file is initially opened in @code{r} or @code{w} mode for the
22255 @code{In_File} and @code{Out_File} cases. If a @code{Set_Mode} operation
22256 subsequently requires switching from reading to writing or vice-versa,
22257 then the file is reopened in @code{r+} mode to permit the required operation.
22259 @node Operations on C Streams,Interfacing to C Streams,Open Modes,The Implementation of Standard I/O
22260 @anchor{gnat_rm/the_implementation_of_standard_i_o operations-on-c-streams}@anchor{2cd}@anchor{gnat_rm/the_implementation_of_standard_i_o id25}@anchor{2ce}
22261 @section Operations on C Streams
22264 The package @code{Interfaces.C_Streams} provides an Ada program with direct
22265 access to the C library functions for operations on C streams:
22268 package Interfaces.C_Streams is
22269 -- Note: the reason we do not use the types that are in
22270 -- Interfaces.C is that we want to avoid dragging in the
22271 -- code in this unit if possible.
22272 subtype chars is System.Address;
22273 -- Pointer to null-terminated array of characters
22274 subtype FILEs is System.Address;
22275 -- Corresponds to the C type FILE*
22276 subtype voids is System.Address;
22277 -- Corresponds to the C type void*
22278 subtype int is Integer;
22279 subtype long is Long_Integer;
22280 -- Note: the above types are subtypes deliberately, and it
22281 -- is part of this spec that the above correspondences are
22282 -- guaranteed. This means that it is legitimate to, for
22283 -- example, use Integer instead of int. We provide these
22284 -- synonyms for clarity, but in some cases it may be
22285 -- convenient to use the underlying types (for example to
22286 -- avoid an unnecessary dependency of a spec on the spec
22288 type size_t is mod 2 ** Standard'Address_Size;
22289 NULL_Stream : constant FILEs;
22290 -- Value returned (NULL in C) to indicate an
22291 -- fdopen/fopen/tmpfile error
22292 ----------------------------------
22293 -- Constants Defined in stdio.h --
22294 ----------------------------------
22295 EOF : constant int;
22296 -- Used by a number of routines to indicate error or
22298 IOFBF : constant int;
22299 IOLBF : constant int;
22300 IONBF : constant int;
22301 -- Used to indicate buffering mode for setvbuf call
22302 SEEK_CUR : constant int;
22303 SEEK_END : constant int;
22304 SEEK_SET : constant int;
22305 -- Used to indicate origin for fseek call
22306 function stdin return FILEs;
22307 function stdout return FILEs;
22308 function stderr return FILEs;
22309 -- Streams associated with standard files
22310 --------------------------
22311 -- Standard C functions --
22312 --------------------------
22313 -- The functions selected below are ones that are
22314 -- available in UNIX (but not necessarily in ANSI C).
22315 -- These are very thin interfaces
22316 -- which copy exactly the C headers. For more
22317 -- documentation on these functions, see the Microsoft C
22318 -- "Run-Time Library Reference" (Microsoft Press, 1990,
22319 -- ISBN 1-55615-225-6), which includes useful information
22320 -- on system compatibility.
22321 procedure clearerr (stream : FILEs);
22322 function fclose (stream : FILEs) return int;
22323 function fdopen (handle : int; mode : chars) return FILEs;
22324 function feof (stream : FILEs) return int;
22325 function ferror (stream : FILEs) return int;
22326 function fflush (stream : FILEs) return int;
22327 function fgetc (stream : FILEs) return int;
22328 function fgets (strng : chars; n : int; stream : FILEs)
22330 function fileno (stream : FILEs) return int;
22331 function fopen (filename : chars; Mode : chars)
22333 -- Note: to maintain target independence, use
22334 -- text_translation_required, a boolean variable defined in
22335 -- a-sysdep.c to deal with the target dependent text
22336 -- translation requirement. If this variable is set,
22337 -- then b/t should be appended to the standard mode
22338 -- argument to set the text translation mode off or on
22340 function fputc (C : int; stream : FILEs) return int;
22341 function fputs (Strng : chars; Stream : FILEs) return int;
22358 function ftell (stream : FILEs) return long;
22365 function isatty (handle : int) return int;
22366 procedure mktemp (template : chars);
22367 -- The return value (which is just a pointer to template)
22369 procedure rewind (stream : FILEs);
22370 function rmtmp return int;
22378 function tmpfile return FILEs;
22379 function ungetc (c : int; stream : FILEs) return int;
22380 function unlink (filename : chars) return int;
22381 ---------------------
22382 -- Extra functions --
22383 ---------------------
22384 -- These functions supply slightly thicker bindings than
22385 -- those above. They are derived from functions in the
22386 -- C Run-Time Library, but may do a bit more work than
22387 -- just directly calling one of the Library functions.
22388 function is_regular_file (handle : int) return int;
22389 -- Tests if given handle is for a regular file (result 1)
22390 -- or for a non-regular file (pipe or device, result 0).
22391 ---------------------------------
22392 -- Control of Text/Binary Mode --
22393 ---------------------------------
22394 -- If text_translation_required is true, then the following
22395 -- functions may be used to dynamically switch a file from
22396 -- binary to text mode or vice versa. These functions have
22397 -- no effect if text_translation_required is false (i.e., in
22398 -- normal UNIX mode). Use fileno to get a stream handle.
22399 procedure set_binary_mode (handle : int);
22400 procedure set_text_mode (handle : int);
22401 ----------------------------
22402 -- Full Path Name support --
22403 ----------------------------
22404 procedure full_name (nam : chars; buffer : chars);
22405 -- Given a NUL terminated string representing a file
22406 -- name, returns in buffer a NUL terminated string
22407 -- representing the full path name for the file name.
22408 -- On systems where it is relevant the drive is also
22409 -- part of the full path name. It is the responsibility
22410 -- of the caller to pass an actual parameter for buffer
22411 -- that is big enough for any full path name. Use
22412 -- max_path_len given below as the size of buffer.
22413 max_path_len : integer;
22414 -- Maximum length of an allowable full path name on the
22415 -- system, including a terminating NUL character.
22416 end Interfaces.C_Streams;
22419 @node Interfacing to C Streams,,Operations on C Streams,The Implementation of Standard I/O
22420 @anchor{gnat_rm/the_implementation_of_standard_i_o interfacing-to-c-streams}@anchor{2cf}@anchor{gnat_rm/the_implementation_of_standard_i_o id26}@anchor{2d0}
22421 @section Interfacing to C Streams
22424 The packages in this section permit interfacing Ada files to C Stream
22428 with Interfaces.C_Streams;
22429 package Ada.Sequential_IO.C_Streams is
22430 function C_Stream (F : File_Type)
22431 return Interfaces.C_Streams.FILEs;
22433 (File : in out File_Type;
22434 Mode : in File_Mode;
22435 C_Stream : in Interfaces.C_Streams.FILEs;
22436 Form : in String := "");
22437 end Ada.Sequential_IO.C_Streams;
22439 with Interfaces.C_Streams;
22440 package Ada.Direct_IO.C_Streams is
22441 function C_Stream (F : File_Type)
22442 return Interfaces.C_Streams.FILEs;
22444 (File : in out File_Type;
22445 Mode : in File_Mode;
22446 C_Stream : in Interfaces.C_Streams.FILEs;
22447 Form : in String := "");
22448 end Ada.Direct_IO.C_Streams;
22450 with Interfaces.C_Streams;
22451 package Ada.Text_IO.C_Streams is
22452 function C_Stream (F : File_Type)
22453 return Interfaces.C_Streams.FILEs;
22455 (File : in out File_Type;
22456 Mode : in File_Mode;
22457 C_Stream : in Interfaces.C_Streams.FILEs;
22458 Form : in String := "");
22459 end Ada.Text_IO.C_Streams;
22461 with Interfaces.C_Streams;
22462 package Ada.Wide_Text_IO.C_Streams is
22463 function C_Stream (F : File_Type)
22464 return Interfaces.C_Streams.FILEs;
22466 (File : in out File_Type;
22467 Mode : in File_Mode;
22468 C_Stream : in Interfaces.C_Streams.FILEs;
22469 Form : in String := "");
22470 end Ada.Wide_Text_IO.C_Streams;
22472 with Interfaces.C_Streams;
22473 package Ada.Wide_Wide_Text_IO.C_Streams is
22474 function C_Stream (F : File_Type)
22475 return Interfaces.C_Streams.FILEs;
22477 (File : in out File_Type;
22478 Mode : in File_Mode;
22479 C_Stream : in Interfaces.C_Streams.FILEs;
22480 Form : in String := "");
22481 end Ada.Wide_Wide_Text_IO.C_Streams;
22483 with Interfaces.C_Streams;
22484 package Ada.Stream_IO.C_Streams is
22485 function C_Stream (F : File_Type)
22486 return Interfaces.C_Streams.FILEs;
22488 (File : in out File_Type;
22489 Mode : in File_Mode;
22490 C_Stream : in Interfaces.C_Streams.FILEs;
22491 Form : in String := "");
22492 end Ada.Stream_IO.C_Streams;
22495 In each of these six packages, the @code{C_Stream} function obtains the
22496 @code{FILE} pointer from a currently opened Ada file. It is then
22497 possible to use the @code{Interfaces.C_Streams} package to operate on
22498 this stream, or the stream can be passed to a C program which can
22499 operate on it directly. Of course the program is responsible for
22500 ensuring that only appropriate sequences of operations are executed.
22502 One particular use of relevance to an Ada program is that the
22503 @code{setvbuf} function can be used to control the buffering of the
22504 stream used by an Ada file. In the absence of such a call the standard
22505 default buffering is used.
22507 The @code{Open} procedures in these packages open a file giving an
22508 existing C Stream instead of a file name. Typically this stream is
22509 imported from a C program, allowing an Ada file to operate on an
22512 @node The GNAT Library,Interfacing to Other Languages,The Implementation of Standard I/O,Top
22513 @anchor{gnat_rm/the_gnat_library the-gnat-library}@anchor{10}@anchor{gnat_rm/the_gnat_library doc}@anchor{2d1}@anchor{gnat_rm/the_gnat_library id1}@anchor{2d2}
22514 @chapter The GNAT Library
22517 The GNAT library contains a number of general and special purpose packages.
22518 It represents functionality that the GNAT developers have found useful, and
22519 which is made available to GNAT users. The packages described here are fully
22520 supported, and upwards compatibility will be maintained in future releases,
22521 so you can use these facilities with the confidence that the same functionality
22522 will be available in future releases.
22524 The chapter here simply gives a brief summary of the facilities available.
22525 The full documentation is found in the spec file for the package. The full
22526 sources of these library packages, including both spec and body, are provided
22527 with all GNAT releases. For example, to find out the full specifications of
22528 the SPITBOL pattern matching capability, including a full tutorial and
22529 extensive examples, look in the @code{g-spipat.ads} file in the library.
22531 For each entry here, the package name (as it would appear in a @code{with}
22532 clause) is given, followed by the name of the corresponding spec file in
22533 parentheses. The packages are children in four hierarchies, @code{Ada},
22534 @code{Interfaces}, @code{System}, and @code{GNAT}, the latter being a
22535 GNAT-specific hierarchy.
22537 Note that an application program should only use packages in one of these
22538 four hierarchies if the package is defined in the Ada Reference Manual,
22539 or is listed in this section of the GNAT Programmers Reference Manual.
22540 All other units should be considered internal implementation units and
22541 should not be directly @code{with}ed by application code. The use of
22542 a @code{with} clause that references one of these internal implementation
22543 units makes an application potentially dependent on changes in versions
22544 of GNAT, and will generate a warning message.
22547 * Ada.Characters.Latin_9 (a-chlat9.ads): Ada Characters Latin_9 a-chlat9 ads.
22548 * Ada.Characters.Wide_Latin_1 (a-cwila1.ads): Ada Characters Wide_Latin_1 a-cwila1 ads.
22549 * Ada.Characters.Wide_Latin_9 (a-cwila1.ads): Ada Characters Wide_Latin_9 a-cwila1 ads.
22550 * Ada.Characters.Wide_Wide_Latin_1 (a-chzla1.ads): Ada Characters Wide_Wide_Latin_1 a-chzla1 ads.
22551 * Ada.Characters.Wide_Wide_Latin_9 (a-chzla9.ads): Ada Characters Wide_Wide_Latin_9 a-chzla9 ads.
22552 * Ada.Containers.Formal_Doubly_Linked_Lists (a-cfdlli.ads): Ada Containers Formal_Doubly_Linked_Lists a-cfdlli ads.
22553 * Ada.Containers.Formal_Hashed_Maps (a-cfhama.ads): Ada Containers Formal_Hashed_Maps a-cfhama ads.
22554 * Ada.Containers.Formal_Hashed_Sets (a-cfhase.ads): Ada Containers Formal_Hashed_Sets a-cfhase ads.
22555 * Ada.Containers.Formal_Ordered_Maps (a-cforma.ads): Ada Containers Formal_Ordered_Maps a-cforma ads.
22556 * Ada.Containers.Formal_Ordered_Sets (a-cforse.ads): Ada Containers Formal_Ordered_Sets a-cforse ads.
22557 * Ada.Containers.Formal_Vectors (a-cofove.ads): Ada Containers Formal_Vectors a-cofove ads.
22558 * Ada.Containers.Formal_Indefinite_Vectors (a-cfinve.ads): Ada Containers Formal_Indefinite_Vectors a-cfinve ads.
22559 * Ada.Containers.Functional_Vectors (a-cofuve.ads): Ada Containers Functional_Vectors a-cofuve ads.
22560 * Ada.Containers.Functional_Sets (a-cofuse.ads): Ada Containers Functional_Sets a-cofuse ads.
22561 * Ada.Containers.Functional_Maps (a-cofuma.ads): Ada Containers Functional_Maps a-cofuma ads.
22562 * Ada.Containers.Bounded_Holders (a-coboho.ads): Ada Containers Bounded_Holders a-coboho ads.
22563 * Ada.Command_Line.Environment (a-colien.ads): Ada Command_Line Environment a-colien ads.
22564 * Ada.Command_Line.Remove (a-colire.ads): Ada Command_Line Remove a-colire ads.
22565 * Ada.Command_Line.Response_File (a-clrefi.ads): Ada Command_Line Response_File a-clrefi ads.
22566 * Ada.Direct_IO.C_Streams (a-diocst.ads): Ada Direct_IO C_Streams a-diocst ads.
22567 * Ada.Exceptions.Is_Null_Occurrence (a-einuoc.ads): Ada Exceptions Is_Null_Occurrence a-einuoc ads.
22568 * Ada.Exceptions.Last_Chance_Handler (a-elchha.ads): Ada Exceptions Last_Chance_Handler a-elchha ads.
22569 * Ada.Exceptions.Traceback (a-exctra.ads): Ada Exceptions Traceback a-exctra ads.
22570 * Ada.Sequential_IO.C_Streams (a-siocst.ads): Ada Sequential_IO C_Streams a-siocst ads.
22571 * Ada.Streams.Stream_IO.C_Streams (a-ssicst.ads): Ada Streams Stream_IO C_Streams a-ssicst ads.
22572 * Ada.Strings.Unbounded.Text_IO (a-suteio.ads): Ada Strings Unbounded Text_IO a-suteio ads.
22573 * Ada.Strings.Wide_Unbounded.Wide_Text_IO (a-swuwti.ads): Ada Strings Wide_Unbounded Wide_Text_IO a-swuwti ads.
22574 * Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO (a-szuzti.ads): Ada Strings Wide_Wide_Unbounded Wide_Wide_Text_IO a-szuzti ads.
22575 * Ada.Task_Initialization (a-tasini.ads): Ada Task_Initialization a-tasini ads.
22576 * Ada.Text_IO.C_Streams (a-tiocst.ads): Ada Text_IO C_Streams a-tiocst ads.
22577 * Ada.Text_IO.Reset_Standard_Files (a-tirsfi.ads): Ada Text_IO Reset_Standard_Files a-tirsfi ads.
22578 * Ada.Wide_Characters.Unicode (a-wichun.ads): Ada Wide_Characters Unicode a-wichun ads.
22579 * Ada.Wide_Text_IO.C_Streams (a-wtcstr.ads): Ada Wide_Text_IO C_Streams a-wtcstr ads.
22580 * Ada.Wide_Text_IO.Reset_Standard_Files (a-wrstfi.ads): Ada Wide_Text_IO Reset_Standard_Files a-wrstfi ads.
22581 * Ada.Wide_Wide_Characters.Unicode (a-zchuni.ads): Ada Wide_Wide_Characters Unicode a-zchuni ads.
22582 * Ada.Wide_Wide_Text_IO.C_Streams (a-ztcstr.ads): Ada Wide_Wide_Text_IO C_Streams a-ztcstr ads.
22583 * Ada.Wide_Wide_Text_IO.Reset_Standard_Files (a-zrstfi.ads): Ada Wide_Wide_Text_IO Reset_Standard_Files a-zrstfi ads.
22584 * GNAT.Altivec (g-altive.ads): GNAT Altivec g-altive ads.
22585 * GNAT.Altivec.Conversions (g-altcon.ads): GNAT Altivec Conversions g-altcon ads.
22586 * GNAT.Altivec.Vector_Operations (g-alveop.ads): GNAT Altivec Vector_Operations g-alveop ads.
22587 * GNAT.Altivec.Vector_Types (g-alvety.ads): GNAT Altivec Vector_Types g-alvety ads.
22588 * GNAT.Altivec.Vector_Views (g-alvevi.ads): GNAT Altivec Vector_Views g-alvevi ads.
22589 * GNAT.Array_Split (g-arrspl.ads): GNAT Array_Split g-arrspl ads.
22590 * GNAT.AWK (g-awk.ads): GNAT AWK g-awk ads.
22591 * GNAT.Bind_Environment (g-binenv.ads): GNAT Bind_Environment g-binenv ads.
22592 * GNAT.Branch_Prediction (g-brapre.ads): GNAT Branch_Prediction g-brapre ads.
22593 * GNAT.Bounded_Buffers (g-boubuf.ads): GNAT Bounded_Buffers g-boubuf ads.
22594 * GNAT.Bounded_Mailboxes (g-boumai.ads): GNAT Bounded_Mailboxes g-boumai ads.
22595 * GNAT.Bubble_Sort (g-bubsor.ads): GNAT Bubble_Sort g-bubsor ads.
22596 * GNAT.Bubble_Sort_A (g-busora.ads): GNAT Bubble_Sort_A g-busora ads.
22597 * GNAT.Bubble_Sort_G (g-busorg.ads): GNAT Bubble_Sort_G g-busorg ads.
22598 * GNAT.Byte_Order_Mark (g-byorma.ads): GNAT Byte_Order_Mark g-byorma ads.
22599 * GNAT.Byte_Swapping (g-bytswa.ads): GNAT Byte_Swapping g-bytswa ads.
22600 * GNAT.Calendar (g-calend.ads): GNAT Calendar g-calend ads.
22601 * GNAT.Calendar.Time_IO (g-catiio.ads): GNAT Calendar Time_IO g-catiio ads.
22602 * GNAT.CRC32 (g-crc32.ads): GNAT CRC32 g-crc32 ads.
22603 * GNAT.Case_Util (g-casuti.ads): GNAT Case_Util g-casuti ads.
22604 * GNAT.CGI (g-cgi.ads): GNAT CGI g-cgi ads.
22605 * GNAT.CGI.Cookie (g-cgicoo.ads): GNAT CGI Cookie g-cgicoo ads.
22606 * GNAT.CGI.Debug (g-cgideb.ads): GNAT CGI Debug g-cgideb ads.
22607 * GNAT.Command_Line (g-comlin.ads): GNAT Command_Line g-comlin ads.
22608 * GNAT.Compiler_Version (g-comver.ads): GNAT Compiler_Version g-comver ads.
22609 * GNAT.Ctrl_C (g-ctrl_c.ads): GNAT Ctrl_C g-ctrl_c ads.
22610 * GNAT.Current_Exception (g-curexc.ads): GNAT Current_Exception g-curexc ads.
22611 * GNAT.Debug_Pools (g-debpoo.ads): GNAT Debug_Pools g-debpoo ads.
22612 * GNAT.Debug_Utilities (g-debuti.ads): GNAT Debug_Utilities g-debuti ads.
22613 * GNAT.Decode_String (g-decstr.ads): GNAT Decode_String g-decstr ads.
22614 * GNAT.Decode_UTF8_String (g-deutst.ads): GNAT Decode_UTF8_String g-deutst ads.
22615 * GNAT.Directory_Operations (g-dirope.ads): GNAT Directory_Operations g-dirope ads.
22616 * GNAT.Directory_Operations.Iteration (g-diopit.ads): GNAT Directory_Operations Iteration g-diopit ads.
22617 * GNAT.Dynamic_HTables (g-dynhta.ads): GNAT Dynamic_HTables g-dynhta ads.
22618 * GNAT.Dynamic_Tables (g-dyntab.ads): GNAT Dynamic_Tables g-dyntab ads.
22619 * GNAT.Encode_String (g-encstr.ads): GNAT Encode_String g-encstr ads.
22620 * GNAT.Encode_UTF8_String (g-enutst.ads): GNAT Encode_UTF8_String g-enutst ads.
22621 * GNAT.Exception_Actions (g-excact.ads): GNAT Exception_Actions g-excact ads.
22622 * GNAT.Exception_Traces (g-exctra.ads): GNAT Exception_Traces g-exctra ads.
22623 * GNAT.Exceptions (g-except.ads): GNAT Exceptions g-except ads.
22624 * GNAT.Expect (g-expect.ads): GNAT Expect g-expect ads.
22625 * GNAT.Expect.TTY (g-exptty.ads): GNAT Expect TTY g-exptty ads.
22626 * GNAT.Float_Control (g-flocon.ads): GNAT Float_Control g-flocon ads.
22627 * GNAT.Formatted_String (g-forstr.ads): GNAT Formatted_String g-forstr ads.
22628 * GNAT.Heap_Sort (g-heasor.ads): GNAT Heap_Sort g-heasor ads.
22629 * GNAT.Heap_Sort_A (g-hesora.ads): GNAT Heap_Sort_A g-hesora ads.
22630 * GNAT.Heap_Sort_G (g-hesorg.ads): GNAT Heap_Sort_G g-hesorg ads.
22631 * GNAT.HTable (g-htable.ads): GNAT HTable g-htable ads.
22632 * GNAT.IO (g-io.ads): GNAT IO g-io ads.
22633 * GNAT.IO_Aux (g-io_aux.ads): GNAT IO_Aux g-io_aux ads.
22634 * GNAT.Lock_Files (g-locfil.ads): GNAT Lock_Files g-locfil ads.
22635 * GNAT.MBBS_Discrete_Random (g-mbdira.ads): GNAT MBBS_Discrete_Random g-mbdira ads.
22636 * GNAT.MBBS_Float_Random (g-mbflra.ads): GNAT MBBS_Float_Random g-mbflra ads.
22637 * GNAT.MD5 (g-md5.ads): GNAT MD5 g-md5 ads.
22638 * GNAT.Memory_Dump (g-memdum.ads): GNAT Memory_Dump g-memdum ads.
22639 * GNAT.Most_Recent_Exception (g-moreex.ads): GNAT Most_Recent_Exception g-moreex ads.
22640 * GNAT.OS_Lib (g-os_lib.ads): GNAT OS_Lib g-os_lib ads.
22641 * GNAT.Perfect_Hash_Generators (g-pehage.ads): GNAT Perfect_Hash_Generators g-pehage ads.
22642 * GNAT.Random_Numbers (g-rannum.ads): GNAT Random_Numbers g-rannum ads.
22643 * GNAT.Regexp (g-regexp.ads): GNAT Regexp g-regexp ads.
22644 * GNAT.Registry (g-regist.ads): GNAT Registry g-regist ads.
22645 * GNAT.Regpat (g-regpat.ads): GNAT Regpat g-regpat ads.
22646 * GNAT.Rewrite_Data (g-rewdat.ads): GNAT Rewrite_Data g-rewdat ads.
22647 * GNAT.Secondary_Stack_Info (g-sestin.ads): GNAT Secondary_Stack_Info g-sestin ads.
22648 * GNAT.Semaphores (g-semaph.ads): GNAT Semaphores g-semaph ads.
22649 * GNAT.Serial_Communications (g-sercom.ads): GNAT Serial_Communications g-sercom ads.
22650 * GNAT.SHA1 (g-sha1.ads): GNAT SHA1 g-sha1 ads.
22651 * GNAT.SHA224 (g-sha224.ads): GNAT SHA224 g-sha224 ads.
22652 * GNAT.SHA256 (g-sha256.ads): GNAT SHA256 g-sha256 ads.
22653 * GNAT.SHA384 (g-sha384.ads): GNAT SHA384 g-sha384 ads.
22654 * GNAT.SHA512 (g-sha512.ads): GNAT SHA512 g-sha512 ads.
22655 * GNAT.Signals (g-signal.ads): GNAT Signals g-signal ads.
22656 * GNAT.Sockets (g-socket.ads): GNAT Sockets g-socket ads.
22657 * GNAT.Source_Info (g-souinf.ads): GNAT Source_Info g-souinf ads.
22658 * GNAT.Spelling_Checker (g-speche.ads): GNAT Spelling_Checker g-speche ads.
22659 * GNAT.Spelling_Checker_Generic (g-spchge.ads): GNAT Spelling_Checker_Generic g-spchge ads.
22660 * GNAT.Spitbol.Patterns (g-spipat.ads): GNAT Spitbol Patterns g-spipat ads.
22661 * GNAT.Spitbol (g-spitbo.ads): GNAT Spitbol g-spitbo ads.
22662 * GNAT.Spitbol.Table_Boolean (g-sptabo.ads): GNAT Spitbol Table_Boolean g-sptabo ads.
22663 * GNAT.Spitbol.Table_Integer (g-sptain.ads): GNAT Spitbol Table_Integer g-sptain ads.
22664 * GNAT.Spitbol.Table_VString (g-sptavs.ads): GNAT Spitbol Table_VString g-sptavs ads.
22665 * GNAT.SSE (g-sse.ads): GNAT SSE g-sse ads.
22666 * GNAT.SSE.Vector_Types (g-ssvety.ads): GNAT SSE Vector_Types g-ssvety ads.
22667 * GNAT.String_Hash (g-strhas.ads): GNAT String_Hash g-strhas ads.
22668 * GNAT.Strings (g-string.ads): GNAT Strings g-string ads.
22669 * GNAT.String_Split (g-strspl.ads): GNAT String_Split g-strspl ads.
22670 * GNAT.Table (g-table.ads): GNAT Table g-table ads.
22671 * GNAT.Task_Lock (g-tasloc.ads): GNAT Task_Lock g-tasloc ads.
22672 * GNAT.Time_Stamp (g-timsta.ads): GNAT Time_Stamp g-timsta ads.
22673 * GNAT.Threads (g-thread.ads): GNAT Threads g-thread ads.
22674 * GNAT.Traceback (g-traceb.ads): GNAT Traceback g-traceb ads.
22675 * GNAT.Traceback.Symbolic (g-trasym.ads): GNAT Traceback Symbolic g-trasym ads.
22676 * GNAT.UTF_32 (g-table.ads): GNAT UTF_32 g-table ads.
22677 * GNAT.Wide_Spelling_Checker (g-u3spch.ads): GNAT Wide_Spelling_Checker g-u3spch ads.
22678 * GNAT.Wide_Spelling_Checker (g-wispch.ads): GNAT Wide_Spelling_Checker g-wispch ads.
22679 * GNAT.Wide_String_Split (g-wistsp.ads): GNAT Wide_String_Split g-wistsp ads.
22680 * GNAT.Wide_Wide_Spelling_Checker (g-zspche.ads): GNAT Wide_Wide_Spelling_Checker g-zspche ads.
22681 * GNAT.Wide_Wide_String_Split (g-zistsp.ads): GNAT Wide_Wide_String_Split g-zistsp ads.
22682 * Interfaces.C.Extensions (i-cexten.ads): Interfaces C Extensions i-cexten ads.
22683 * Interfaces.C.Streams (i-cstrea.ads): Interfaces C Streams i-cstrea ads.
22684 * Interfaces.Packed_Decimal (i-pacdec.ads): Interfaces Packed_Decimal i-pacdec ads.
22685 * Interfaces.VxWorks (i-vxwork.ads): Interfaces VxWorks i-vxwork ads.
22686 * Interfaces.VxWorks.Int_Connection (i-vxinco.ads): Interfaces VxWorks Int_Connection i-vxinco ads.
22687 * Interfaces.VxWorks.IO (i-vxwoio.ads): Interfaces VxWorks IO i-vxwoio ads.
22688 * System.Address_Image (s-addima.ads): System Address_Image s-addima ads.
22689 * System.Assertions (s-assert.ads): System Assertions s-assert ads.
22690 * System.Atomic_Counters (s-atocou.ads): System Atomic_Counters s-atocou ads.
22691 * System.Memory (s-memory.ads): System Memory s-memory ads.
22692 * System.Multiprocessors (s-multip.ads): System Multiprocessors s-multip ads.
22693 * System.Multiprocessors.Dispatching_Domains (s-mudido.ads): System Multiprocessors Dispatching_Domains s-mudido ads.
22694 * System.Partition_Interface (s-parint.ads): System Partition_Interface s-parint ads.
22695 * System.Pool_Global (s-pooglo.ads): System Pool_Global s-pooglo ads.
22696 * System.Pool_Local (s-pooloc.ads): System Pool_Local s-pooloc ads.
22697 * System.Restrictions (s-restri.ads): System Restrictions s-restri ads.
22698 * System.Rident (s-rident.ads): System Rident s-rident ads.
22699 * System.Strings.Stream_Ops (s-ststop.ads): System Strings Stream_Ops s-ststop ads.
22700 * System.Unsigned_Types (s-unstyp.ads): System Unsigned_Types s-unstyp ads.
22701 * System.Wch_Cnv (s-wchcnv.ads): System Wch_Cnv s-wchcnv ads.
22702 * System.Wch_Con (s-wchcon.ads): System Wch_Con s-wchcon ads.
22706 @node Ada Characters Latin_9 a-chlat9 ads,Ada Characters Wide_Latin_1 a-cwila1 ads,,The GNAT Library
22707 @anchor{gnat_rm/the_gnat_library id2}@anchor{2d3}@anchor{gnat_rm/the_gnat_library ada-characters-latin-9-a-chlat9-ads}@anchor{2d4}
22708 @section @code{Ada.Characters.Latin_9} (@code{a-chlat9.ads})
22711 @geindex Ada.Characters.Latin_9 (a-chlat9.ads)
22713 @geindex Latin_9 constants for Character
22715 This child of @code{Ada.Characters}
22716 provides a set of definitions corresponding to those in the
22717 RM-defined package @code{Ada.Characters.Latin_1} but with the
22718 few modifications required for @code{Latin-9}
22719 The provision of such a package
22720 is specifically authorized by the Ada Reference Manual
22723 @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
22724 @anchor{gnat_rm/the_gnat_library ada-characters-wide-latin-1-a-cwila1-ads}@anchor{2d5}@anchor{gnat_rm/the_gnat_library id3}@anchor{2d6}
22725 @section @code{Ada.Characters.Wide_Latin_1} (@code{a-cwila1.ads})
22728 @geindex Ada.Characters.Wide_Latin_1 (a-cwila1.ads)
22730 @geindex Latin_1 constants for Wide_Character
22732 This child of @code{Ada.Characters}
22733 provides a set of definitions corresponding to those in the
22734 RM-defined package @code{Ada.Characters.Latin_1} but with the
22735 types of the constants being @code{Wide_Character}
22736 instead of @code{Character}. The provision of such a package
22737 is specifically authorized by the Ada Reference Manual
22740 @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
22741 @anchor{gnat_rm/the_gnat_library id4}@anchor{2d7}@anchor{gnat_rm/the_gnat_library ada-characters-wide-latin-9-a-cwila1-ads}@anchor{2d8}
22742 @section @code{Ada.Characters.Wide_Latin_9} (@code{a-cwila1.ads})
22745 @geindex Ada.Characters.Wide_Latin_9 (a-cwila1.ads)
22747 @geindex Latin_9 constants for Wide_Character
22749 This child of @code{Ada.Characters}
22750 provides a set of definitions corresponding to those in the
22751 GNAT defined package @code{Ada.Characters.Latin_9} but with the
22752 types of the constants being @code{Wide_Character}
22753 instead of @code{Character}. The provision of such a package
22754 is specifically authorized by the Ada Reference Manual
22757 @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
22758 @anchor{gnat_rm/the_gnat_library ada-characters-wide-wide-latin-1-a-chzla1-ads}@anchor{2d9}@anchor{gnat_rm/the_gnat_library id5}@anchor{2da}
22759 @section @code{Ada.Characters.Wide_Wide_Latin_1} (@code{a-chzla1.ads})
22762 @geindex Ada.Characters.Wide_Wide_Latin_1 (a-chzla1.ads)
22764 @geindex Latin_1 constants for Wide_Wide_Character
22766 This child of @code{Ada.Characters}
22767 provides a set of definitions corresponding to those in the
22768 RM-defined package @code{Ada.Characters.Latin_1} but with the
22769 types of the constants being @code{Wide_Wide_Character}
22770 instead of @code{Character}. The provision of such a package
22771 is specifically authorized by the Ada Reference Manual
22774 @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
22775 @anchor{gnat_rm/the_gnat_library ada-characters-wide-wide-latin-9-a-chzla9-ads}@anchor{2db}@anchor{gnat_rm/the_gnat_library id6}@anchor{2dc}
22776 @section @code{Ada.Characters.Wide_Wide_Latin_9} (@code{a-chzla9.ads})
22779 @geindex Ada.Characters.Wide_Wide_Latin_9 (a-chzla9.ads)
22781 @geindex Latin_9 constants for Wide_Wide_Character
22783 This child of @code{Ada.Characters}
22784 provides a set of definitions corresponding to those in the
22785 GNAT defined package @code{Ada.Characters.Latin_9} but with the
22786 types of the constants being @code{Wide_Wide_Character}
22787 instead of @code{Character}. The provision of such a package
22788 is specifically authorized by the Ada Reference Manual
22791 @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
22792 @anchor{gnat_rm/the_gnat_library id7}@anchor{2dd}@anchor{gnat_rm/the_gnat_library ada-containers-formal-doubly-linked-lists-a-cfdlli-ads}@anchor{2de}
22793 @section @code{Ada.Containers.Formal_Doubly_Linked_Lists} (@code{a-cfdlli.ads})
22796 @geindex Ada.Containers.Formal_Doubly_Linked_Lists (a-cfdlli.ads)
22798 @geindex Formal container for doubly linked lists
22800 This child of @code{Ada.Containers} defines a modified version of the
22801 Ada 2005 container for doubly linked lists, meant to facilitate formal
22802 verification of code using such containers. The specification of this
22803 unit is compatible with SPARK 2014.
22805 Note that although this container was designed with formal verification
22806 in mind, it may well be generally useful in that it is a simplified more
22807 efficient version than the one defined in the standard. In particular it
22808 does not have the complex overhead required to detect cursor tampering.
22810 @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
22811 @anchor{gnat_rm/the_gnat_library id8}@anchor{2df}@anchor{gnat_rm/the_gnat_library ada-containers-formal-hashed-maps-a-cfhama-ads}@anchor{2e0}
22812 @section @code{Ada.Containers.Formal_Hashed_Maps} (@code{a-cfhama.ads})
22815 @geindex Ada.Containers.Formal_Hashed_Maps (a-cfhama.ads)
22817 @geindex Formal container for hashed maps
22819 This child of @code{Ada.Containers} defines a modified version of the
22820 Ada 2005 container for hashed maps, meant to facilitate formal
22821 verification of code using such containers. The specification of this
22822 unit is compatible with SPARK 2014.
22824 Note that although this container was designed with formal verification
22825 in mind, it may well be generally useful in that it is a simplified more
22826 efficient version than the one defined in the standard. In particular it
22827 does not have the complex overhead required to detect cursor tampering.
22829 @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
22830 @anchor{gnat_rm/the_gnat_library id9}@anchor{2e1}@anchor{gnat_rm/the_gnat_library ada-containers-formal-hashed-sets-a-cfhase-ads}@anchor{2e2}
22831 @section @code{Ada.Containers.Formal_Hashed_Sets} (@code{a-cfhase.ads})
22834 @geindex Ada.Containers.Formal_Hashed_Sets (a-cfhase.ads)
22836 @geindex Formal container for hashed sets
22838 This child of @code{Ada.Containers} defines a modified version of the
22839 Ada 2005 container for hashed sets, meant to facilitate formal
22840 verification of code using such containers. The specification of this
22841 unit is compatible with SPARK 2014.
22843 Note that although this container was designed with formal verification
22844 in mind, it may well be generally useful in that it is a simplified more
22845 efficient version than the one defined in the standard. In particular it
22846 does not have the complex overhead required to detect cursor tampering.
22848 @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
22849 @anchor{gnat_rm/the_gnat_library id10}@anchor{2e3}@anchor{gnat_rm/the_gnat_library ada-containers-formal-ordered-maps-a-cforma-ads}@anchor{2e4}
22850 @section @code{Ada.Containers.Formal_Ordered_Maps} (@code{a-cforma.ads})
22853 @geindex Ada.Containers.Formal_Ordered_Maps (a-cforma.ads)
22855 @geindex Formal container for ordered maps
22857 This child of @code{Ada.Containers} defines a modified version of the
22858 Ada 2005 container for ordered maps, meant to facilitate formal
22859 verification of code using such containers. The specification of this
22860 unit is compatible with SPARK 2014.
22862 Note that although this container was designed with formal verification
22863 in mind, it may well be generally useful in that it is a simplified more
22864 efficient version than the one defined in the standard. In particular it
22865 does not have the complex overhead required to detect cursor tampering.
22867 @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
22868 @anchor{gnat_rm/the_gnat_library ada-containers-formal-ordered-sets-a-cforse-ads}@anchor{2e5}@anchor{gnat_rm/the_gnat_library id11}@anchor{2e6}
22869 @section @code{Ada.Containers.Formal_Ordered_Sets} (@code{a-cforse.ads})
22872 @geindex Ada.Containers.Formal_Ordered_Sets (a-cforse.ads)
22874 @geindex Formal container for ordered sets
22876 This child of @code{Ada.Containers} defines a modified version of the
22877 Ada 2005 container for ordered sets, meant to facilitate formal
22878 verification of code using such containers. The specification of this
22879 unit is compatible with SPARK 2014.
22881 Note that although this container was designed with formal verification
22882 in mind, it may well be generally useful in that it is a simplified more
22883 efficient version than the one defined in the standard. In particular it
22884 does not have the complex overhead required to detect cursor tampering.
22886 @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
22887 @anchor{gnat_rm/the_gnat_library id12}@anchor{2e7}@anchor{gnat_rm/the_gnat_library ada-containers-formal-vectors-a-cofove-ads}@anchor{2e8}
22888 @section @code{Ada.Containers.Formal_Vectors} (@code{a-cofove.ads})
22891 @geindex Ada.Containers.Formal_Vectors (a-cofove.ads)
22893 @geindex Formal container for vectors
22895 This child of @code{Ada.Containers} defines a modified version of the
22896 Ada 2005 container for vectors, meant to facilitate formal
22897 verification of code using such containers. The specification of this
22898 unit is compatible with SPARK 2014.
22900 Note that although this container was designed with formal verification
22901 in mind, it may well be generally useful in that it is a simplified more
22902 efficient version than the one defined in the standard. In particular it
22903 does not have the complex overhead required to detect cursor tampering.
22905 @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
22906 @anchor{gnat_rm/the_gnat_library id13}@anchor{2e9}@anchor{gnat_rm/the_gnat_library ada-containers-formal-indefinite-vectors-a-cfinve-ads}@anchor{2ea}
22907 @section @code{Ada.Containers.Formal_Indefinite_Vectors} (@code{a-cfinve.ads})
22910 @geindex Ada.Containers.Formal_Indefinite_Vectors (a-cfinve.ads)
22912 @geindex Formal container for vectors
22914 This child of @code{Ada.Containers} defines a modified version of the
22915 Ada 2005 container for vectors of indefinite elements, meant to
22916 facilitate formal verification of code using such containers. The
22917 specification of this unit is compatible with SPARK 2014.
22919 Note that although this container was designed with formal verification
22920 in mind, it may well be generally useful in that it is a simplified more
22921 efficient version than the one defined in the standard. In particular it
22922 does not have the complex overhead required to detect cursor tampering.
22924 @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
22925 @anchor{gnat_rm/the_gnat_library id14}@anchor{2eb}@anchor{gnat_rm/the_gnat_library ada-containers-functional-vectors-a-cofuve-ads}@anchor{2ec}
22926 @section @code{Ada.Containers.Functional_Vectors} (@code{a-cofuve.ads})
22929 @geindex Ada.Containers.Functional_Vectors (a-cofuve.ads)
22931 @geindex Functional vectors
22933 This child of @code{Ada.Containers} defines immutable vectors. These
22934 containers are unbounded and may contain indefinite elements. Furthermore, to
22935 be usable in every context, they are neither controlled nor limited. As they
22936 are functional, that is, no primitives are provided which would allow modifying
22937 an existing container, these containers can still be used safely.
22939 Their API features functions creating new containers from existing ones.
22940 As a consequence, these containers are highly inefficient. They are also
22941 memory consuming, as the allocated memory is not reclaimed when the container
22942 is no longer referenced. Thus, they should in general be used in ghost code
22943 and annotations, so that they can be removed from the final executable. The
22944 specification of this unit is compatible with SPARK 2014.
22946 @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
22947 @anchor{gnat_rm/the_gnat_library ada-containers-functional-sets-a-cofuse-ads}@anchor{2ed}@anchor{gnat_rm/the_gnat_library id15}@anchor{2ee}
22948 @section @code{Ada.Containers.Functional_Sets} (@code{a-cofuse.ads})
22951 @geindex Ada.Containers.Functional_Sets (a-cofuse.ads)
22953 @geindex Functional sets
22955 This child of @code{Ada.Containers} defines immutable sets. These containers are
22956 unbounded and may contain indefinite elements. Furthermore, to be usable in
22957 every context, they are neither controlled nor limited. As they are functional,
22958 that is, no primitives are provided which would allow modifying an existing
22959 container, these containers can still be used safely.
22961 Their API features functions creating new containers from existing ones.
22962 As a consequence, these containers are highly inefficient. They are also
22963 memory consuming, as the allocated memory is not reclaimed when the container
22964 is no longer referenced. Thus, they should in general be used in ghost code
22965 and annotations, so that they can be removed from the final executable. The
22966 specification of this unit is compatible with SPARK 2014.
22968 @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
22969 @anchor{gnat_rm/the_gnat_library id16}@anchor{2ef}@anchor{gnat_rm/the_gnat_library ada-containers-functional-maps-a-cofuma-ads}@anchor{2f0}
22970 @section @code{Ada.Containers.Functional_Maps} (@code{a-cofuma.ads})
22973 @geindex Ada.Containers.Functional_Maps (a-cofuma.ads)
22975 @geindex Functional maps
22977 This child of @code{Ada.Containers} defines immutable maps. These containers are
22978 unbounded and may contain indefinite elements. Furthermore, to be usable in
22979 every context, they are neither controlled nor limited. As they are functional,
22980 that is, no primitives are provided which would allow modifying an existing
22981 container, these containers can still be used safely.
22983 Their API features functions creating new containers from existing ones.
22984 As a consequence, these containers are highly inefficient. They are also
22985 memory consuming, as the allocated memory is not reclaimed when the container
22986 is no longer referenced. Thus, they should in general be used in ghost code
22987 and annotations, so that they can be removed from the final executable. The
22988 specification of this unit is compatible with SPARK 2014.
22990 @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
22991 @anchor{gnat_rm/the_gnat_library ada-containers-bounded-holders-a-coboho-ads}@anchor{2f1}@anchor{gnat_rm/the_gnat_library id17}@anchor{2f2}
22992 @section @code{Ada.Containers.Bounded_Holders} (@code{a-coboho.ads})
22995 @geindex Ada.Containers.Bounded_Holders (a-coboho.ads)
22997 @geindex Formal container for vectors
22999 This child of @code{Ada.Containers} defines a modified version of
23000 Indefinite_Holders that avoids heap allocation.
23002 @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
23003 @anchor{gnat_rm/the_gnat_library ada-command-line-environment-a-colien-ads}@anchor{2f3}@anchor{gnat_rm/the_gnat_library id18}@anchor{2f4}
23004 @section @code{Ada.Command_Line.Environment} (@code{a-colien.ads})
23007 @geindex Ada.Command_Line.Environment (a-colien.ads)
23009 @geindex Environment entries
23011 This child of @code{Ada.Command_Line}
23012 provides a mechanism for obtaining environment values on systems
23013 where this concept makes sense.
23015 @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
23016 @anchor{gnat_rm/the_gnat_library id19}@anchor{2f5}@anchor{gnat_rm/the_gnat_library ada-command-line-remove-a-colire-ads}@anchor{2f6}
23017 @section @code{Ada.Command_Line.Remove} (@code{a-colire.ads})
23020 @geindex Ada.Command_Line.Remove (a-colire.ads)
23022 @geindex Removing command line arguments
23024 @geindex Command line
23025 @geindex argument removal
23027 This child of @code{Ada.Command_Line}
23028 provides a mechanism for logically removing
23029 arguments from the argument list. Once removed, an argument is not visible
23030 to further calls on the subprograms in @code{Ada.Command_Line} will not
23031 see the removed argument.
23033 @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
23034 @anchor{gnat_rm/the_gnat_library id20}@anchor{2f7}@anchor{gnat_rm/the_gnat_library ada-command-line-response-file-a-clrefi-ads}@anchor{2f8}
23035 @section @code{Ada.Command_Line.Response_File} (@code{a-clrefi.ads})
23038 @geindex Ada.Command_Line.Response_File (a-clrefi.ads)
23040 @geindex Response file for command line
23042 @geindex Command line
23043 @geindex response file
23045 @geindex Command line
23046 @geindex handling long command lines
23048 This child of @code{Ada.Command_Line} provides a mechanism facilities for
23049 getting command line arguments from a text file, called a "response file".
23050 Using a response file allow passing a set of arguments to an executable longer
23051 than the maximum allowed by the system on the command line.
23053 @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
23054 @anchor{gnat_rm/the_gnat_library id21}@anchor{2f9}@anchor{gnat_rm/the_gnat_library ada-direct-io-c-streams-a-diocst-ads}@anchor{2fa}
23055 @section @code{Ada.Direct_IO.C_Streams} (@code{a-diocst.ads})
23058 @geindex Ada.Direct_IO.C_Streams (a-diocst.ads)
23061 @geindex Interfacing with Direct_IO
23063 This package provides subprograms that allow interfacing between
23064 C streams and @code{Direct_IO}. The stream identifier can be
23065 extracted from a file opened on the Ada side, and an Ada file
23066 can be constructed from a stream opened on the C side.
23068 @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
23069 @anchor{gnat_rm/the_gnat_library id22}@anchor{2fb}@anchor{gnat_rm/the_gnat_library ada-exceptions-is-null-occurrence-a-einuoc-ads}@anchor{2fc}
23070 @section @code{Ada.Exceptions.Is_Null_Occurrence} (@code{a-einuoc.ads})
23073 @geindex Ada.Exceptions.Is_Null_Occurrence (a-einuoc.ads)
23075 @geindex Null_Occurrence
23076 @geindex testing for
23078 This child subprogram provides a way of testing for the null
23079 exception occurrence (@code{Null_Occurrence}) without raising
23082 @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
23083 @anchor{gnat_rm/the_gnat_library id23}@anchor{2fd}@anchor{gnat_rm/the_gnat_library ada-exceptions-last-chance-handler-a-elchha-ads}@anchor{2fe}
23084 @section @code{Ada.Exceptions.Last_Chance_Handler} (@code{a-elchha.ads})
23087 @geindex Ada.Exceptions.Last_Chance_Handler (a-elchha.ads)
23089 @geindex Null_Occurrence
23090 @geindex testing for
23092 This child subprogram is used for handling otherwise unhandled
23093 exceptions (hence the name last chance), and perform clean ups before
23094 terminating the program. Note that this subprogram never returns.
23096 @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
23097 @anchor{gnat_rm/the_gnat_library ada-exceptions-traceback-a-exctra-ads}@anchor{2ff}@anchor{gnat_rm/the_gnat_library id24}@anchor{300}
23098 @section @code{Ada.Exceptions.Traceback} (@code{a-exctra.ads})
23101 @geindex Ada.Exceptions.Traceback (a-exctra.ads)
23103 @geindex Traceback for Exception Occurrence
23105 This child package provides the subprogram (@code{Tracebacks}) to
23106 give a traceback array of addresses based on an exception
23109 @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
23110 @anchor{gnat_rm/the_gnat_library ada-sequential-io-c-streams-a-siocst-ads}@anchor{301}@anchor{gnat_rm/the_gnat_library id25}@anchor{302}
23111 @section @code{Ada.Sequential_IO.C_Streams} (@code{a-siocst.ads})
23114 @geindex Ada.Sequential_IO.C_Streams (a-siocst.ads)
23117 @geindex Interfacing with Sequential_IO
23119 This package provides subprograms that allow interfacing between
23120 C streams and @code{Sequential_IO}. The stream identifier can be
23121 extracted from a file opened on the Ada side, and an Ada file
23122 can be constructed from a stream opened on the C side.
23124 @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
23125 @anchor{gnat_rm/the_gnat_library id26}@anchor{303}@anchor{gnat_rm/the_gnat_library ada-streams-stream-io-c-streams-a-ssicst-ads}@anchor{304}
23126 @section @code{Ada.Streams.Stream_IO.C_Streams} (@code{a-ssicst.ads})
23129 @geindex Ada.Streams.Stream_IO.C_Streams (a-ssicst.ads)
23132 @geindex Interfacing with Stream_IO
23134 This package provides subprograms that allow interfacing between
23135 C streams and @code{Stream_IO}. The stream identifier can be
23136 extracted from a file opened on the Ada side, and an Ada file
23137 can be constructed from a stream opened on the C side.
23139 @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
23140 @anchor{gnat_rm/the_gnat_library ada-strings-unbounded-text-io-a-suteio-ads}@anchor{305}@anchor{gnat_rm/the_gnat_library id27}@anchor{306}
23141 @section @code{Ada.Strings.Unbounded.Text_IO} (@code{a-suteio.ads})
23144 @geindex Ada.Strings.Unbounded.Text_IO (a-suteio.ads)
23146 @geindex Unbounded_String
23147 @geindex IO support
23150 @geindex extensions for unbounded strings
23152 This package provides subprograms for Text_IO for unbounded
23153 strings, avoiding the necessity for an intermediate operation
23154 with ordinary strings.
23156 @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
23157 @anchor{gnat_rm/the_gnat_library id28}@anchor{307}@anchor{gnat_rm/the_gnat_library ada-strings-wide-unbounded-wide-text-io-a-swuwti-ads}@anchor{308}
23158 @section @code{Ada.Strings.Wide_Unbounded.Wide_Text_IO} (@code{a-swuwti.ads})
23161 @geindex Ada.Strings.Wide_Unbounded.Wide_Text_IO (a-swuwti.ads)
23163 @geindex Unbounded_Wide_String
23164 @geindex IO support
23167 @geindex extensions for unbounded wide strings
23169 This package provides subprograms for Text_IO for unbounded
23170 wide strings, avoiding the necessity for an intermediate operation
23171 with ordinary wide strings.
23173 @node Ada Strings Wide_Wide_Unbounded Wide_Wide_Text_IO a-szuzti ads,Ada Task_Initialization a-tasini ads,Ada Strings Wide_Unbounded Wide_Text_IO a-swuwti ads,The GNAT Library
23174 @anchor{gnat_rm/the_gnat_library id29}@anchor{309}@anchor{gnat_rm/the_gnat_library ada-strings-wide-wide-unbounded-wide-wide-text-io-a-szuzti-ads}@anchor{30a}
23175 @section @code{Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO} (@code{a-szuzti.ads})
23178 @geindex Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO (a-szuzti.ads)
23180 @geindex Unbounded_Wide_Wide_String
23181 @geindex IO support
23184 @geindex extensions for unbounded wide wide strings
23186 This package provides subprograms for Text_IO for unbounded
23187 wide wide strings, avoiding the necessity for an intermediate operation
23188 with ordinary wide wide strings.
23190 @node Ada Task_Initialization a-tasini ads,Ada Text_IO C_Streams a-tiocst ads,Ada Strings Wide_Wide_Unbounded Wide_Wide_Text_IO a-szuzti ads,The GNAT Library
23191 @anchor{gnat_rm/the_gnat_library ada-task-initialization-a-tasini-ads}@anchor{30b}@anchor{gnat_rm/the_gnat_library id30}@anchor{30c}
23192 @section @code{Ada.Task_Initialization} (@code{a-tasini.ads})
23195 @geindex Ada.Task_Initialization (a-tasini.ads)
23197 This package provides a way to set a global initialization handler that
23198 is automatically invoked whenever a task is activated. Handlers are
23199 parameterless procedures. Note that such a handler is only invoked for
23200 those tasks activated after the handler is set.
23202 @node Ada Text_IO C_Streams a-tiocst ads,Ada Text_IO Reset_Standard_Files a-tirsfi ads,Ada Task_Initialization a-tasini ads,The GNAT Library
23203 @anchor{gnat_rm/the_gnat_library ada-text-io-c-streams-a-tiocst-ads}@anchor{30d}@anchor{gnat_rm/the_gnat_library id31}@anchor{30e}
23204 @section @code{Ada.Text_IO.C_Streams} (@code{a-tiocst.ads})
23207 @geindex Ada.Text_IO.C_Streams (a-tiocst.ads)
23210 @geindex Interfacing with `@w{`}Text_IO`@w{`}
23212 This package provides subprograms that allow interfacing between
23213 C streams and @code{Text_IO}. The stream identifier can be
23214 extracted from a file opened on the Ada side, and an Ada file
23215 can be constructed from a stream opened on the C side.
23217 @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
23218 @anchor{gnat_rm/the_gnat_library ada-text-io-reset-standard-files-a-tirsfi-ads}@anchor{30f}@anchor{gnat_rm/the_gnat_library id32}@anchor{310}
23219 @section @code{Ada.Text_IO.Reset_Standard_Files} (@code{a-tirsfi.ads})
23222 @geindex Ada.Text_IO.Reset_Standard_Files (a-tirsfi.ads)
23224 @geindex Text_IO resetting standard files
23226 This procedure is used to reset the status of the standard files used
23227 by Ada.Text_IO. This is useful in a situation (such as a restart in an
23228 embedded application) where the status of the files may change during
23229 execution (for example a standard input file may be redefined to be
23232 @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
23233 @anchor{gnat_rm/the_gnat_library id33}@anchor{311}@anchor{gnat_rm/the_gnat_library ada-wide-characters-unicode-a-wichun-ads}@anchor{312}
23234 @section @code{Ada.Wide_Characters.Unicode} (@code{a-wichun.ads})
23237 @geindex Ada.Wide_Characters.Unicode (a-wichun.ads)
23239 @geindex Unicode categorization
23240 @geindex Wide_Character
23242 This package provides subprograms that allow categorization of
23243 Wide_Character values according to Unicode categories.
23245 @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
23246 @anchor{gnat_rm/the_gnat_library id34}@anchor{313}@anchor{gnat_rm/the_gnat_library ada-wide-text-io-c-streams-a-wtcstr-ads}@anchor{314}
23247 @section @code{Ada.Wide_Text_IO.C_Streams} (@code{a-wtcstr.ads})
23250 @geindex Ada.Wide_Text_IO.C_Streams (a-wtcstr.ads)
23253 @geindex Interfacing with `@w{`}Wide_Text_IO`@w{`}
23255 This package provides subprograms that allow interfacing between
23256 C streams and @code{Wide_Text_IO}. The stream identifier can be
23257 extracted from a file opened on the Ada side, and an Ada file
23258 can be constructed from a stream opened on the C side.
23260 @node Ada 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
23261 @anchor{gnat_rm/the_gnat_library ada-wide-text-io-reset-standard-files-a-wrstfi-ads}@anchor{315}@anchor{gnat_rm/the_gnat_library id35}@anchor{316}
23262 @section @code{Ada.Wide_Text_IO.Reset_Standard_Files} (@code{a-wrstfi.ads})
23265 @geindex Ada.Wide_Text_IO.Reset_Standard_Files (a-wrstfi.ads)
23267 @geindex Wide_Text_IO resetting standard files
23269 This procedure is used to reset the status of the standard files used
23270 by Ada.Wide_Text_IO. This is useful in a situation (such as a restart in an
23271 embedded application) where the status of the files may change during
23272 execution (for example a standard input file may be redefined to be
23275 @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
23276 @anchor{gnat_rm/the_gnat_library id36}@anchor{317}@anchor{gnat_rm/the_gnat_library ada-wide-wide-characters-unicode-a-zchuni-ads}@anchor{318}
23277 @section @code{Ada.Wide_Wide_Characters.Unicode} (@code{a-zchuni.ads})
23280 @geindex Ada.Wide_Wide_Characters.Unicode (a-zchuni.ads)
23282 @geindex Unicode categorization
23283 @geindex Wide_Wide_Character
23285 This package provides subprograms that allow categorization of
23286 Wide_Wide_Character values according to Unicode categories.
23288 @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
23289 @anchor{gnat_rm/the_gnat_library id37}@anchor{319}@anchor{gnat_rm/the_gnat_library ada-wide-wide-text-io-c-streams-a-ztcstr-ads}@anchor{31a}
23290 @section @code{Ada.Wide_Wide_Text_IO.C_Streams} (@code{a-ztcstr.ads})
23293 @geindex Ada.Wide_Wide_Text_IO.C_Streams (a-ztcstr.ads)
23296 @geindex Interfacing with `@w{`}Wide_Wide_Text_IO`@w{`}
23298 This package provides subprograms that allow interfacing between
23299 C streams and @code{Wide_Wide_Text_IO}. The stream identifier can be
23300 extracted from a file opened on the Ada side, and an Ada file
23301 can be constructed from a stream opened on the C side.
23303 @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
23304 @anchor{gnat_rm/the_gnat_library ada-wide-wide-text-io-reset-standard-files-a-zrstfi-ads}@anchor{31b}@anchor{gnat_rm/the_gnat_library id38}@anchor{31c}
23305 @section @code{Ada.Wide_Wide_Text_IO.Reset_Standard_Files} (@code{a-zrstfi.ads})
23308 @geindex Ada.Wide_Wide_Text_IO.Reset_Standard_Files (a-zrstfi.ads)
23310 @geindex Wide_Wide_Text_IO resetting standard files
23312 This procedure is used to reset the status of the standard files used
23313 by Ada.Wide_Wide_Text_IO. This is useful in a situation (such as a
23314 restart in an embedded application) where the status of the files may
23315 change during execution (for example a standard input file may be
23316 redefined to be interactive).
23318 @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
23319 @anchor{gnat_rm/the_gnat_library gnat-altivec-g-altive-ads}@anchor{31d}@anchor{gnat_rm/the_gnat_library id39}@anchor{31e}
23320 @section @code{GNAT.Altivec} (@code{g-altive.ads})
23323 @geindex GNAT.Altivec (g-altive.ads)
23327 This is the root package of the GNAT AltiVec binding. It provides
23328 definitions of constants and types common to all the versions of the
23331 @node GNAT Altivec Conversions g-altcon ads,GNAT Altivec Vector_Operations g-alveop ads,GNAT Altivec g-altive ads,The GNAT Library
23332 @anchor{gnat_rm/the_gnat_library gnat-altivec-conversions-g-altcon-ads}@anchor{31f}@anchor{gnat_rm/the_gnat_library id40}@anchor{320}
23333 @section @code{GNAT.Altivec.Conversions} (@code{g-altcon.ads})
23336 @geindex GNAT.Altivec.Conversions (g-altcon.ads)
23340 This package provides the Vector/View conversion routines.
23342 @node GNAT Altivec Vector_Operations g-alveop ads,GNAT Altivec Vector_Types g-alvety ads,GNAT Altivec Conversions g-altcon ads,The GNAT Library
23343 @anchor{gnat_rm/the_gnat_library id41}@anchor{321}@anchor{gnat_rm/the_gnat_library gnat-altivec-vector-operations-g-alveop-ads}@anchor{322}
23344 @section @code{GNAT.Altivec.Vector_Operations} (@code{g-alveop.ads})
23347 @geindex GNAT.Altivec.Vector_Operations (g-alveop.ads)
23351 This package exposes the Ada interface to the AltiVec operations on
23352 vector objects. A soft emulation is included by default in the GNAT
23353 library. The hard binding is provided as a separate package. This unit
23354 is common to both bindings.
23356 @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
23357 @anchor{gnat_rm/the_gnat_library gnat-altivec-vector-types-g-alvety-ads}@anchor{323}@anchor{gnat_rm/the_gnat_library id42}@anchor{324}
23358 @section @code{GNAT.Altivec.Vector_Types} (@code{g-alvety.ads})
23361 @geindex GNAT.Altivec.Vector_Types (g-alvety.ads)
23365 This package exposes the various vector types part of the Ada binding
23366 to AltiVec facilities.
23368 @node GNAT Altivec Vector_Views g-alvevi ads,GNAT Array_Split g-arrspl ads,GNAT Altivec Vector_Types g-alvety ads,The GNAT Library
23369 @anchor{gnat_rm/the_gnat_library gnat-altivec-vector-views-g-alvevi-ads}@anchor{325}@anchor{gnat_rm/the_gnat_library id43}@anchor{326}
23370 @section @code{GNAT.Altivec.Vector_Views} (@code{g-alvevi.ads})
23373 @geindex GNAT.Altivec.Vector_Views (g-alvevi.ads)
23377 This package provides public 'View' data types from/to which private
23378 vector representations can be converted via
23379 GNAT.Altivec.Conversions. This allows convenient access to individual
23380 vector elements and provides a simple way to initialize vector
23383 @node GNAT Array_Split g-arrspl ads,GNAT AWK g-awk ads,GNAT Altivec Vector_Views g-alvevi ads,The GNAT Library
23384 @anchor{gnat_rm/the_gnat_library gnat-array-split-g-arrspl-ads}@anchor{327}@anchor{gnat_rm/the_gnat_library id44}@anchor{328}
23385 @section @code{GNAT.Array_Split} (@code{g-arrspl.ads})
23388 @geindex GNAT.Array_Split (g-arrspl.ads)
23390 @geindex Array splitter
23392 Useful array-manipulation routines: given a set of separators, split
23393 an array wherever the separators appear, and provide direct access
23394 to the resulting slices.
23396 @node GNAT AWK g-awk ads,GNAT Bind_Environment g-binenv ads,GNAT Array_Split g-arrspl ads,The GNAT Library
23397 @anchor{gnat_rm/the_gnat_library id45}@anchor{329}@anchor{gnat_rm/the_gnat_library gnat-awk-g-awk-ads}@anchor{32a}
23398 @section @code{GNAT.AWK} (@code{g-awk.ads})
23401 @geindex GNAT.AWK (g-awk.ads)
23407 Provides AWK-like parsing functions, with an easy interface for parsing one
23408 or more files containing formatted data. The file is viewed as a database
23409 where each record is a line and a field is a data element in this line.
23411 @node GNAT Bind_Environment g-binenv ads,GNAT Branch_Prediction g-brapre ads,GNAT AWK g-awk ads,The GNAT Library
23412 @anchor{gnat_rm/the_gnat_library id46}@anchor{32b}@anchor{gnat_rm/the_gnat_library gnat-bind-environment-g-binenv-ads}@anchor{32c}
23413 @section @code{GNAT.Bind_Environment} (@code{g-binenv.ads})
23416 @geindex GNAT.Bind_Environment (g-binenv.ads)
23418 @geindex Bind environment
23420 Provides access to key=value associations captured at bind time.
23421 These associations can be specified using the @code{-V} binder command
23424 @node GNAT Branch_Prediction g-brapre ads,GNAT Bounded_Buffers g-boubuf ads,GNAT Bind_Environment g-binenv ads,The GNAT Library
23425 @anchor{gnat_rm/the_gnat_library id47}@anchor{32d}@anchor{gnat_rm/the_gnat_library gnat-branch-prediction-g-brapre-ads}@anchor{32e}
23426 @section @code{GNAT.Branch_Prediction} (@code{g-brapre.ads})
23429 @geindex GNAT.Branch_Prediction (g-brapre.ads)
23431 @geindex Branch Prediction
23433 Provides routines giving hints to the branch predictor of the code generator.
23435 @node GNAT Bounded_Buffers g-boubuf ads,GNAT Bounded_Mailboxes g-boumai ads,GNAT Branch_Prediction g-brapre ads,The GNAT Library
23436 @anchor{gnat_rm/the_gnat_library gnat-bounded-buffers-g-boubuf-ads}@anchor{32f}@anchor{gnat_rm/the_gnat_library id48}@anchor{330}
23437 @section @code{GNAT.Bounded_Buffers} (@code{g-boubuf.ads})
23440 @geindex GNAT.Bounded_Buffers (g-boubuf.ads)
23444 @geindex Bounded Buffers
23446 Provides a concurrent generic bounded buffer abstraction. Instances are
23447 useful directly or as parts of the implementations of other abstractions,
23450 @node GNAT Bounded_Mailboxes g-boumai ads,GNAT Bubble_Sort g-bubsor ads,GNAT Bounded_Buffers g-boubuf ads,The GNAT Library
23451 @anchor{gnat_rm/the_gnat_library gnat-bounded-mailboxes-g-boumai-ads}@anchor{331}@anchor{gnat_rm/the_gnat_library id49}@anchor{332}
23452 @section @code{GNAT.Bounded_Mailboxes} (@code{g-boumai.ads})
23455 @geindex GNAT.Bounded_Mailboxes (g-boumai.ads)
23461 Provides a thread-safe asynchronous intertask mailbox communication facility.
23463 @node GNAT Bubble_Sort g-bubsor ads,GNAT Bubble_Sort_A g-busora ads,GNAT Bounded_Mailboxes g-boumai ads,The GNAT Library
23464 @anchor{gnat_rm/the_gnat_library gnat-bubble-sort-g-bubsor-ads}@anchor{333}@anchor{gnat_rm/the_gnat_library id50}@anchor{334}
23465 @section @code{GNAT.Bubble_Sort} (@code{g-bubsor.ads})
23468 @geindex GNAT.Bubble_Sort (g-bubsor.ads)
23472 @geindex Bubble sort
23474 Provides a general implementation of bubble sort usable for sorting arbitrary
23475 data items. Exchange and comparison procedures are provided by passing
23476 access-to-procedure values.
23478 @node GNAT Bubble_Sort_A g-busora ads,GNAT Bubble_Sort_G g-busorg ads,GNAT Bubble_Sort g-bubsor ads,The GNAT Library
23479 @anchor{gnat_rm/the_gnat_library id51}@anchor{335}@anchor{gnat_rm/the_gnat_library gnat-bubble-sort-a-g-busora-ads}@anchor{336}
23480 @section @code{GNAT.Bubble_Sort_A} (@code{g-busora.ads})
23483 @geindex GNAT.Bubble_Sort_A (g-busora.ads)
23487 @geindex Bubble sort
23489 Provides a general implementation of bubble sort usable for sorting arbitrary
23490 data items. Move and comparison procedures are provided by passing
23491 access-to-procedure values. This is an older version, retained for
23492 compatibility. Usually @code{GNAT.Bubble_Sort} will be preferable.
23494 @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
23495 @anchor{gnat_rm/the_gnat_library gnat-bubble-sort-g-g-busorg-ads}@anchor{337}@anchor{gnat_rm/the_gnat_library id52}@anchor{338}
23496 @section @code{GNAT.Bubble_Sort_G} (@code{g-busorg.ads})
23499 @geindex GNAT.Bubble_Sort_G (g-busorg.ads)
23503 @geindex Bubble sort
23505 Similar to @code{Bubble_Sort_A} except that the move and sorting procedures
23506 are provided as generic parameters, this improves efficiency, especially
23507 if the procedures can be inlined, at the expense of duplicating code for
23508 multiple instantiations.
23510 @node GNAT Byte_Order_Mark g-byorma ads,GNAT Byte_Swapping g-bytswa ads,GNAT Bubble_Sort_G g-busorg ads,The GNAT Library
23511 @anchor{gnat_rm/the_gnat_library gnat-byte-order-mark-g-byorma-ads}@anchor{339}@anchor{gnat_rm/the_gnat_library id53}@anchor{33a}
23512 @section @code{GNAT.Byte_Order_Mark} (@code{g-byorma.ads})
23515 @geindex GNAT.Byte_Order_Mark (g-byorma.ads)
23517 @geindex UTF-8 representation
23519 @geindex Wide characte representations
23521 Provides a routine which given a string, reads the start of the string to
23522 see whether it is one of the standard byte order marks (BOM's) which signal
23523 the encoding of the string. The routine includes detection of special XML
23524 sequences for various UCS input formats.
23526 @node GNAT Byte_Swapping g-bytswa ads,GNAT Calendar g-calend ads,GNAT Byte_Order_Mark g-byorma ads,The GNAT Library
23527 @anchor{gnat_rm/the_gnat_library gnat-byte-swapping-g-bytswa-ads}@anchor{33b}@anchor{gnat_rm/the_gnat_library id54}@anchor{33c}
23528 @section @code{GNAT.Byte_Swapping} (@code{g-bytswa.ads})
23531 @geindex GNAT.Byte_Swapping (g-bytswa.ads)
23533 @geindex Byte swapping
23535 @geindex Endianness
23537 General routines for swapping the bytes in 2-, 4-, and 8-byte quantities.
23538 Machine-specific implementations are available in some cases.
23540 @node GNAT Calendar g-calend ads,GNAT Calendar Time_IO g-catiio ads,GNAT Byte_Swapping g-bytswa ads,The GNAT Library
23541 @anchor{gnat_rm/the_gnat_library id55}@anchor{33d}@anchor{gnat_rm/the_gnat_library gnat-calendar-g-calend-ads}@anchor{33e}
23542 @section @code{GNAT.Calendar} (@code{g-calend.ads})
23545 @geindex GNAT.Calendar (g-calend.ads)
23549 Extends the facilities provided by @code{Ada.Calendar} to include handling
23550 of days of the week, an extended @code{Split} and @code{Time_Of} capability.
23551 Also provides conversion of @code{Ada.Calendar.Time} values to and from the
23552 C @code{timeval} format.
23554 @node GNAT Calendar Time_IO g-catiio ads,GNAT CRC32 g-crc32 ads,GNAT Calendar g-calend ads,The GNAT Library
23555 @anchor{gnat_rm/the_gnat_library id56}@anchor{33f}@anchor{gnat_rm/the_gnat_library gnat-calendar-time-io-g-catiio-ads}@anchor{340}
23556 @section @code{GNAT.Calendar.Time_IO} (@code{g-catiio.ads})
23563 @geindex GNAT.Calendar.Time_IO (g-catiio.ads)
23565 @node GNAT CRC32 g-crc32 ads,GNAT Case_Util g-casuti ads,GNAT Calendar Time_IO g-catiio ads,The GNAT Library
23566 @anchor{gnat_rm/the_gnat_library id57}@anchor{341}@anchor{gnat_rm/the_gnat_library gnat-crc32-g-crc32-ads}@anchor{342}
23567 @section @code{GNAT.CRC32} (@code{g-crc32.ads})
23570 @geindex GNAT.CRC32 (g-crc32.ads)
23574 @geindex Cyclic Redundancy Check
23576 This package implements the CRC-32 algorithm. For a full description
23577 of this algorithm see
23578 @emph{Computation of Cyclic Redundancy Checks via Table Look-Up},
23579 @cite{Communications of the ACM}, Vol. 31 No. 8, pp. 1008-1013,
23580 Aug. 1988. Sarwate, D.V.
23582 @node GNAT Case_Util g-casuti ads,GNAT CGI g-cgi ads,GNAT CRC32 g-crc32 ads,The GNAT Library
23583 @anchor{gnat_rm/the_gnat_library id58}@anchor{343}@anchor{gnat_rm/the_gnat_library gnat-case-util-g-casuti-ads}@anchor{344}
23584 @section @code{GNAT.Case_Util} (@code{g-casuti.ads})
23587 @geindex GNAT.Case_Util (g-casuti.ads)
23589 @geindex Casing utilities
23591 @geindex Character handling (`@w{`}GNAT.Case_Util`@w{`})
23593 A set of simple routines for handling upper and lower casing of strings
23594 without the overhead of the full casing tables
23595 in @code{Ada.Characters.Handling}.
23597 @node GNAT CGI g-cgi ads,GNAT CGI Cookie g-cgicoo ads,GNAT Case_Util g-casuti ads,The GNAT Library
23598 @anchor{gnat_rm/the_gnat_library id59}@anchor{345}@anchor{gnat_rm/the_gnat_library gnat-cgi-g-cgi-ads}@anchor{346}
23599 @section @code{GNAT.CGI} (@code{g-cgi.ads})
23602 @geindex GNAT.CGI (g-cgi.ads)
23604 @geindex CGI (Common Gateway Interface)
23606 This is a package for interfacing a GNAT program with a Web server via the
23607 Common Gateway Interface (CGI). Basically this package parses the CGI
23608 parameters, which are a set of key/value pairs sent by the Web server. It
23609 builds a table whose index is the key and provides some services to deal
23612 @node GNAT CGI Cookie g-cgicoo ads,GNAT CGI Debug g-cgideb ads,GNAT CGI g-cgi ads,The GNAT Library
23613 @anchor{gnat_rm/the_gnat_library gnat-cgi-cookie-g-cgicoo-ads}@anchor{347}@anchor{gnat_rm/the_gnat_library id60}@anchor{348}
23614 @section @code{GNAT.CGI.Cookie} (@code{g-cgicoo.ads})
23617 @geindex GNAT.CGI.Cookie (g-cgicoo.ads)
23619 @geindex CGI (Common Gateway Interface) cookie support
23621 @geindex Cookie support in CGI
23623 This is a package to interface a GNAT program with a Web server via the
23624 Common Gateway Interface (CGI). It exports services to deal with Web
23625 cookies (piece of information kept in the Web client software).
23627 @node GNAT CGI Debug g-cgideb ads,GNAT Command_Line g-comlin ads,GNAT CGI Cookie g-cgicoo ads,The GNAT Library
23628 @anchor{gnat_rm/the_gnat_library gnat-cgi-debug-g-cgideb-ads}@anchor{349}@anchor{gnat_rm/the_gnat_library id61}@anchor{34a}
23629 @section @code{GNAT.CGI.Debug} (@code{g-cgideb.ads})
23632 @geindex GNAT.CGI.Debug (g-cgideb.ads)
23634 @geindex CGI (Common Gateway Interface) debugging
23636 This is a package to help debugging CGI (Common Gateway Interface)
23637 programs written in Ada.
23639 @node GNAT Command_Line g-comlin ads,GNAT Compiler_Version g-comver ads,GNAT CGI Debug g-cgideb ads,The GNAT Library
23640 @anchor{gnat_rm/the_gnat_library id62}@anchor{34b}@anchor{gnat_rm/the_gnat_library gnat-command-line-g-comlin-ads}@anchor{34c}
23641 @section @code{GNAT.Command_Line} (@code{g-comlin.ads})
23644 @geindex GNAT.Command_Line (g-comlin.ads)
23646 @geindex Command line
23648 Provides a high level interface to @code{Ada.Command_Line} facilities,
23649 including the ability to scan for named switches with optional parameters
23650 and expand file names using wildcard notations.
23652 @node GNAT Compiler_Version g-comver ads,GNAT Ctrl_C g-ctrl_c ads,GNAT Command_Line g-comlin ads,The GNAT Library
23653 @anchor{gnat_rm/the_gnat_library gnat-compiler-version-g-comver-ads}@anchor{34d}@anchor{gnat_rm/the_gnat_library id63}@anchor{34e}
23654 @section @code{GNAT.Compiler_Version} (@code{g-comver.ads})
23657 @geindex GNAT.Compiler_Version (g-comver.ads)
23659 @geindex Compiler Version
23662 @geindex of compiler
23664 Provides a routine for obtaining the version of the compiler used to
23665 compile the program. More accurately this is the version of the binder
23666 used to bind the program (this will normally be the same as the version
23667 of the compiler if a consistent tool set is used to compile all units
23670 @node GNAT Ctrl_C g-ctrl_c ads,GNAT Current_Exception g-curexc ads,GNAT Compiler_Version g-comver ads,The GNAT Library
23671 @anchor{gnat_rm/the_gnat_library id64}@anchor{34f}@anchor{gnat_rm/the_gnat_library gnat-ctrl-c-g-ctrl-c-ads}@anchor{350}
23672 @section @code{GNAT.Ctrl_C} (@code{g-ctrl_c.ads})
23675 @geindex GNAT.Ctrl_C (g-ctrl_c.ads)
23679 Provides a simple interface to handle Ctrl-C keyboard events.
23681 @node GNAT Current_Exception g-curexc ads,GNAT Debug_Pools g-debpoo ads,GNAT Ctrl_C g-ctrl_c ads,The GNAT Library
23682 @anchor{gnat_rm/the_gnat_library id65}@anchor{351}@anchor{gnat_rm/the_gnat_library gnat-current-exception-g-curexc-ads}@anchor{352}
23683 @section @code{GNAT.Current_Exception} (@code{g-curexc.ads})
23686 @geindex GNAT.Current_Exception (g-curexc.ads)
23688 @geindex Current exception
23690 @geindex Exception retrieval
23692 Provides access to information on the current exception that has been raised
23693 without the need for using the Ada 95 / Ada 2005 exception choice parameter
23694 specification syntax.
23695 This is particularly useful in simulating typical facilities for
23696 obtaining information about exceptions provided by Ada 83 compilers.
23698 @node GNAT Debug_Pools g-debpoo ads,GNAT Debug_Utilities g-debuti ads,GNAT Current_Exception g-curexc ads,The GNAT Library
23699 @anchor{gnat_rm/the_gnat_library gnat-debug-pools-g-debpoo-ads}@anchor{353}@anchor{gnat_rm/the_gnat_library id66}@anchor{354}
23700 @section @code{GNAT.Debug_Pools} (@code{g-debpoo.ads})
23703 @geindex GNAT.Debug_Pools (g-debpoo.ads)
23707 @geindex Debug pools
23709 @geindex Memory corruption debugging
23711 Provide a debugging storage pools that helps tracking memory corruption
23713 See @code{The GNAT Debug_Pool Facility} section in the @cite{GNAT User's Guide}.
23715 @node GNAT Debug_Utilities g-debuti ads,GNAT Decode_String g-decstr ads,GNAT Debug_Pools g-debpoo ads,The GNAT Library
23716 @anchor{gnat_rm/the_gnat_library gnat-debug-utilities-g-debuti-ads}@anchor{355}@anchor{gnat_rm/the_gnat_library id67}@anchor{356}
23717 @section @code{GNAT.Debug_Utilities} (@code{g-debuti.ads})
23720 @geindex GNAT.Debug_Utilities (g-debuti.ads)
23724 Provides a few useful utilities for debugging purposes, including conversion
23725 to and from string images of address values. Supports both C and Ada formats
23726 for hexadecimal literals.
23728 @node GNAT Decode_String g-decstr ads,GNAT Decode_UTF8_String g-deutst ads,GNAT Debug_Utilities g-debuti ads,The GNAT Library
23729 @anchor{gnat_rm/the_gnat_library gnat-decode-string-g-decstr-ads}@anchor{357}@anchor{gnat_rm/the_gnat_library id68}@anchor{358}
23730 @section @code{GNAT.Decode_String} (@code{g-decstr.ads})
23733 @geindex GNAT.Decode_String (g-decstr.ads)
23735 @geindex Decoding strings
23737 @geindex String decoding
23739 @geindex Wide character encoding
23745 A generic package providing routines for decoding wide character and wide wide
23746 character strings encoded as sequences of 8-bit characters using a specified
23747 encoding method. Includes validation routines, and also routines for stepping
23748 to next or previous encoded character in an encoded string.
23749 Useful in conjunction with Unicode character coding. Note there is a
23750 preinstantiation for UTF-8. See next entry.
23752 @node GNAT Decode_UTF8_String g-deutst ads,GNAT Directory_Operations g-dirope ads,GNAT Decode_String g-decstr ads,The GNAT Library
23753 @anchor{gnat_rm/the_gnat_library gnat-decode-utf8-string-g-deutst-ads}@anchor{359}@anchor{gnat_rm/the_gnat_library id69}@anchor{35a}
23754 @section @code{GNAT.Decode_UTF8_String} (@code{g-deutst.ads})
23757 @geindex GNAT.Decode_UTF8_String (g-deutst.ads)
23759 @geindex Decoding strings
23761 @geindex Decoding UTF-8 strings
23763 @geindex UTF-8 string decoding
23765 @geindex Wide character decoding
23771 A preinstantiation of GNAT.Decode_Strings for UTF-8 encoding.
23773 @node GNAT Directory_Operations g-dirope ads,GNAT Directory_Operations Iteration g-diopit ads,GNAT Decode_UTF8_String g-deutst ads,The GNAT Library
23774 @anchor{gnat_rm/the_gnat_library id70}@anchor{35b}@anchor{gnat_rm/the_gnat_library gnat-directory-operations-g-dirope-ads}@anchor{35c}
23775 @section @code{GNAT.Directory_Operations} (@code{g-dirope.ads})
23778 @geindex GNAT.Directory_Operations (g-dirope.ads)
23780 @geindex Directory operations
23782 Provides a set of routines for manipulating directories, including changing
23783 the current directory, making new directories, and scanning the files in a
23786 @node GNAT Directory_Operations Iteration g-diopit ads,GNAT Dynamic_HTables g-dynhta ads,GNAT Directory_Operations g-dirope ads,The GNAT Library
23787 @anchor{gnat_rm/the_gnat_library id71}@anchor{35d}@anchor{gnat_rm/the_gnat_library gnat-directory-operations-iteration-g-diopit-ads}@anchor{35e}
23788 @section @code{GNAT.Directory_Operations.Iteration} (@code{g-diopit.ads})
23791 @geindex GNAT.Directory_Operations.Iteration (g-diopit.ads)
23793 @geindex Directory operations iteration
23795 A child unit of GNAT.Directory_Operations providing additional operations
23796 for iterating through directories.
23798 @node GNAT Dynamic_HTables g-dynhta ads,GNAT Dynamic_Tables g-dyntab ads,GNAT Directory_Operations Iteration g-diopit ads,The GNAT Library
23799 @anchor{gnat_rm/the_gnat_library id72}@anchor{35f}@anchor{gnat_rm/the_gnat_library gnat-dynamic-htables-g-dynhta-ads}@anchor{360}
23800 @section @code{GNAT.Dynamic_HTables} (@code{g-dynhta.ads})
23803 @geindex GNAT.Dynamic_HTables (g-dynhta.ads)
23805 @geindex Hash tables
23807 A generic implementation of hash tables that can be used to hash arbitrary
23808 data. Provided in two forms, a simple form with built in hash functions,
23809 and a more complex form in which the hash function is supplied.
23811 This package provides a facility similar to that of @code{GNAT.HTable},
23812 except that this package declares a type that can be used to define
23813 dynamic instances of the hash table, while an instantiation of
23814 @code{GNAT.HTable} creates a single instance of the hash table.
23816 @node GNAT Dynamic_Tables g-dyntab ads,GNAT Encode_String g-encstr ads,GNAT Dynamic_HTables g-dynhta ads,The GNAT Library
23817 @anchor{gnat_rm/the_gnat_library gnat-dynamic-tables-g-dyntab-ads}@anchor{361}@anchor{gnat_rm/the_gnat_library id73}@anchor{362}
23818 @section @code{GNAT.Dynamic_Tables} (@code{g-dyntab.ads})
23821 @geindex GNAT.Dynamic_Tables (g-dyntab.ads)
23823 @geindex Table implementation
23826 @geindex extendable
23828 A generic package providing a single dimension array abstraction where the
23829 length of the array can be dynamically modified.
23831 This package provides a facility similar to that of @code{GNAT.Table},
23832 except that this package declares a type that can be used to define
23833 dynamic instances of the table, while an instantiation of
23834 @code{GNAT.Table} creates a single instance of the table type.
23836 @node GNAT Encode_String g-encstr ads,GNAT Encode_UTF8_String g-enutst ads,GNAT Dynamic_Tables g-dyntab ads,The GNAT Library
23837 @anchor{gnat_rm/the_gnat_library id74}@anchor{363}@anchor{gnat_rm/the_gnat_library gnat-encode-string-g-encstr-ads}@anchor{364}
23838 @section @code{GNAT.Encode_String} (@code{g-encstr.ads})
23841 @geindex GNAT.Encode_String (g-encstr.ads)
23843 @geindex Encoding strings
23845 @geindex String encoding
23847 @geindex Wide character encoding
23853 A generic package providing routines for encoding wide character and wide
23854 wide character strings as sequences of 8-bit characters using a specified
23855 encoding method. Useful in conjunction with Unicode character coding.
23856 Note there is a preinstantiation for UTF-8. See next entry.
23858 @node GNAT Encode_UTF8_String g-enutst ads,GNAT Exception_Actions g-excact ads,GNAT Encode_String g-encstr ads,The GNAT Library
23859 @anchor{gnat_rm/the_gnat_library gnat-encode-utf8-string-g-enutst-ads}@anchor{365}@anchor{gnat_rm/the_gnat_library id75}@anchor{366}
23860 @section @code{GNAT.Encode_UTF8_String} (@code{g-enutst.ads})
23863 @geindex GNAT.Encode_UTF8_String (g-enutst.ads)
23865 @geindex Encoding strings
23867 @geindex Encoding UTF-8 strings
23869 @geindex UTF-8 string encoding
23871 @geindex Wide character encoding
23877 A preinstantiation of GNAT.Encode_Strings for UTF-8 encoding.
23879 @node GNAT Exception_Actions g-excact ads,GNAT Exception_Traces g-exctra ads,GNAT Encode_UTF8_String g-enutst ads,The GNAT Library
23880 @anchor{gnat_rm/the_gnat_library gnat-exception-actions-g-excact-ads}@anchor{367}@anchor{gnat_rm/the_gnat_library id76}@anchor{368}
23881 @section @code{GNAT.Exception_Actions} (@code{g-excact.ads})
23884 @geindex GNAT.Exception_Actions (g-excact.ads)
23886 @geindex Exception actions
23888 Provides callbacks when an exception is raised. Callbacks can be registered
23889 for specific exceptions, or when any exception is raised. This
23890 can be used for instance to force a core dump to ease debugging.
23892 @node GNAT Exception_Traces g-exctra ads,GNAT Exceptions g-except ads,GNAT Exception_Actions g-excact ads,The GNAT Library
23893 @anchor{gnat_rm/the_gnat_library gnat-exception-traces-g-exctra-ads}@anchor{369}@anchor{gnat_rm/the_gnat_library id77}@anchor{36a}
23894 @section @code{GNAT.Exception_Traces} (@code{g-exctra.ads})
23897 @geindex GNAT.Exception_Traces (g-exctra.ads)
23899 @geindex Exception traces
23903 Provides an interface allowing to control automatic output upon exception
23906 @node GNAT Exceptions g-except ads,GNAT Expect g-expect ads,GNAT Exception_Traces g-exctra ads,The GNAT Library
23907 @anchor{gnat_rm/the_gnat_library id78}@anchor{36b}@anchor{gnat_rm/the_gnat_library gnat-exceptions-g-except-ads}@anchor{36c}
23908 @section @code{GNAT.Exceptions} (@code{g-except.ads})
23911 @geindex GNAT.Exceptions (g-except.ads)
23913 @geindex Exceptions
23916 @geindex Pure packages
23917 @geindex exceptions
23919 Normally it is not possible to raise an exception with
23920 a message from a subprogram in a pure package, since the
23921 necessary types and subprograms are in @code{Ada.Exceptions}
23922 which is not a pure unit. @code{GNAT.Exceptions} provides a
23923 facility for getting around this limitation for a few
23924 predefined exceptions, and for example allow raising
23925 @code{Constraint_Error} with a message from a pure subprogram.
23927 @node GNAT Expect g-expect ads,GNAT Expect TTY g-exptty ads,GNAT Exceptions g-except ads,The GNAT Library
23928 @anchor{gnat_rm/the_gnat_library id79}@anchor{36d}@anchor{gnat_rm/the_gnat_library gnat-expect-g-expect-ads}@anchor{36e}
23929 @section @code{GNAT.Expect} (@code{g-expect.ads})
23932 @geindex GNAT.Expect (g-expect.ads)
23934 Provides a set of subprograms similar to what is available
23935 with the standard Tcl Expect tool.
23936 It allows you to easily spawn and communicate with an external process.
23937 You can send commands or inputs to the process, and compare the output
23938 with some expected regular expression. Currently @code{GNAT.Expect}
23939 is implemented on all native GNAT ports.
23940 It is not implemented for cross ports, and in particular is not
23941 implemented for VxWorks or LynxOS.
23943 @node GNAT Expect TTY g-exptty ads,GNAT Float_Control g-flocon ads,GNAT Expect g-expect ads,The GNAT Library
23944 @anchor{gnat_rm/the_gnat_library id80}@anchor{36f}@anchor{gnat_rm/the_gnat_library gnat-expect-tty-g-exptty-ads}@anchor{370}
23945 @section @code{GNAT.Expect.TTY} (@code{g-exptty.ads})
23948 @geindex GNAT.Expect.TTY (g-exptty.ads)
23950 As GNAT.Expect but using pseudo-terminal.
23951 Currently @code{GNAT.Expect.TTY} is implemented on all native GNAT
23952 ports. It is not implemented for cross ports, and
23953 in particular is not implemented for VxWorks or LynxOS.
23955 @node GNAT Float_Control g-flocon ads,GNAT Formatted_String g-forstr ads,GNAT Expect TTY g-exptty ads,The GNAT Library
23956 @anchor{gnat_rm/the_gnat_library id81}@anchor{371}@anchor{gnat_rm/the_gnat_library gnat-float-control-g-flocon-ads}@anchor{372}
23957 @section @code{GNAT.Float_Control} (@code{g-flocon.ads})
23960 @geindex GNAT.Float_Control (g-flocon.ads)
23962 @geindex Floating-Point Processor
23964 Provides an interface for resetting the floating-point processor into the
23965 mode required for correct semantic operation in Ada. Some third party
23966 library calls may cause this mode to be modified, and the Reset procedure
23967 in this package can be used to reestablish the required mode.
23969 @node GNAT Formatted_String g-forstr ads,GNAT Heap_Sort g-heasor ads,GNAT Float_Control g-flocon ads,The GNAT Library
23970 @anchor{gnat_rm/the_gnat_library id82}@anchor{373}@anchor{gnat_rm/the_gnat_library gnat-formatted-string-g-forstr-ads}@anchor{374}
23971 @section @code{GNAT.Formatted_String} (@code{g-forstr.ads})
23974 @geindex GNAT.Formatted_String (g-forstr.ads)
23976 @geindex Formatted String
23978 Provides support for C/C++ printf() formatted strings. The format is
23979 copied from the printf() routine and should therefore gives identical
23980 output. Some generic routines are provided to be able to use types
23981 derived from Integer, Float or enumerations as values for the
23984 @node GNAT Heap_Sort g-heasor ads,GNAT Heap_Sort_A g-hesora ads,GNAT Formatted_String g-forstr ads,The GNAT Library
23985 @anchor{gnat_rm/the_gnat_library id83}@anchor{375}@anchor{gnat_rm/the_gnat_library gnat-heap-sort-g-heasor-ads}@anchor{376}
23986 @section @code{GNAT.Heap_Sort} (@code{g-heasor.ads})
23989 @geindex GNAT.Heap_Sort (g-heasor.ads)
23993 Provides a general implementation of heap sort usable for sorting arbitrary
23994 data items. Exchange and comparison procedures are provided by passing
23995 access-to-procedure values. The algorithm used is a modified heap sort
23996 that performs approximately N*log(N) comparisons in the worst case.
23998 @node GNAT Heap_Sort_A g-hesora ads,GNAT Heap_Sort_G g-hesorg ads,GNAT Heap_Sort g-heasor ads,The GNAT Library
23999 @anchor{gnat_rm/the_gnat_library gnat-heap-sort-a-g-hesora-ads}@anchor{377}@anchor{gnat_rm/the_gnat_library id84}@anchor{378}
24000 @section @code{GNAT.Heap_Sort_A} (@code{g-hesora.ads})
24003 @geindex GNAT.Heap_Sort_A (g-hesora.ads)
24007 Provides a general implementation of heap sort usable for sorting arbitrary
24008 data items. Move and comparison procedures are provided by passing
24009 access-to-procedure values. The algorithm used is a modified heap sort
24010 that performs approximately N*log(N) comparisons in the worst case.
24011 This differs from @code{GNAT.Heap_Sort} in having a less convenient
24012 interface, but may be slightly more efficient.
24014 @node GNAT Heap_Sort_G g-hesorg ads,GNAT HTable g-htable ads,GNAT Heap_Sort_A g-hesora ads,The GNAT Library
24015 @anchor{gnat_rm/the_gnat_library id85}@anchor{379}@anchor{gnat_rm/the_gnat_library gnat-heap-sort-g-g-hesorg-ads}@anchor{37a}
24016 @section @code{GNAT.Heap_Sort_G} (@code{g-hesorg.ads})
24019 @geindex GNAT.Heap_Sort_G (g-hesorg.ads)
24023 Similar to @code{Heap_Sort_A} except that the move and sorting procedures
24024 are provided as generic parameters, this improves efficiency, especially
24025 if the procedures can be inlined, at the expense of duplicating code for
24026 multiple instantiations.
24028 @node GNAT HTable g-htable ads,GNAT IO g-io ads,GNAT Heap_Sort_G g-hesorg ads,The GNAT Library
24029 @anchor{gnat_rm/the_gnat_library id86}@anchor{37b}@anchor{gnat_rm/the_gnat_library gnat-htable-g-htable-ads}@anchor{37c}
24030 @section @code{GNAT.HTable} (@code{g-htable.ads})
24033 @geindex GNAT.HTable (g-htable.ads)
24035 @geindex Hash tables
24037 A generic implementation of hash tables that can be used to hash arbitrary
24038 data. Provides two approaches, one a simple static approach, and the other
24039 allowing arbitrary dynamic hash tables.
24041 @node GNAT IO g-io ads,GNAT IO_Aux g-io_aux ads,GNAT HTable g-htable ads,The GNAT Library
24042 @anchor{gnat_rm/the_gnat_library id87}@anchor{37d}@anchor{gnat_rm/the_gnat_library gnat-io-g-io-ads}@anchor{37e}
24043 @section @code{GNAT.IO} (@code{g-io.ads})
24046 @geindex GNAT.IO (g-io.ads)
24048 @geindex Simple I/O
24050 @geindex Input/Output facilities
24052 A simple preelaborable input-output package that provides a subset of
24053 simple Text_IO functions for reading characters and strings from
24054 Standard_Input, and writing characters, strings and integers to either
24055 Standard_Output or Standard_Error.
24057 @node GNAT IO_Aux g-io_aux ads,GNAT Lock_Files g-locfil ads,GNAT IO g-io ads,The GNAT Library
24058 @anchor{gnat_rm/the_gnat_library id88}@anchor{37f}@anchor{gnat_rm/the_gnat_library gnat-io-aux-g-io-aux-ads}@anchor{380}
24059 @section @code{GNAT.IO_Aux} (@code{g-io_aux.ads})
24062 @geindex GNAT.IO_Aux (g-io_aux.ads)
24066 @geindex Input/Output facilities
24068 Provides some auxiliary functions for use with Text_IO, including a test
24069 for whether a file exists, and functions for reading a line of text.
24071 @node GNAT Lock_Files g-locfil ads,GNAT MBBS_Discrete_Random g-mbdira ads,GNAT IO_Aux g-io_aux ads,The GNAT Library
24072 @anchor{gnat_rm/the_gnat_library id89}@anchor{381}@anchor{gnat_rm/the_gnat_library gnat-lock-files-g-locfil-ads}@anchor{382}
24073 @section @code{GNAT.Lock_Files} (@code{g-locfil.ads})
24076 @geindex GNAT.Lock_Files (g-locfil.ads)
24078 @geindex File locking
24080 @geindex Locking using files
24082 Provides a general interface for using files as locks. Can be used for
24083 providing program level synchronization.
24085 @node GNAT MBBS_Discrete_Random g-mbdira ads,GNAT MBBS_Float_Random g-mbflra ads,GNAT Lock_Files g-locfil ads,The GNAT Library
24086 @anchor{gnat_rm/the_gnat_library id90}@anchor{383}@anchor{gnat_rm/the_gnat_library gnat-mbbs-discrete-random-g-mbdira-ads}@anchor{384}
24087 @section @code{GNAT.MBBS_Discrete_Random} (@code{g-mbdira.ads})
24090 @geindex GNAT.MBBS_Discrete_Random (g-mbdira.ads)
24092 @geindex Random number generation
24094 The original implementation of @code{Ada.Numerics.Discrete_Random}. Uses
24095 a modified version of the Blum-Blum-Shub generator.
24097 @node GNAT MBBS_Float_Random g-mbflra ads,GNAT MD5 g-md5 ads,GNAT MBBS_Discrete_Random g-mbdira ads,The GNAT Library
24098 @anchor{gnat_rm/the_gnat_library id91}@anchor{385}@anchor{gnat_rm/the_gnat_library gnat-mbbs-float-random-g-mbflra-ads}@anchor{386}
24099 @section @code{GNAT.MBBS_Float_Random} (@code{g-mbflra.ads})
24102 @geindex GNAT.MBBS_Float_Random (g-mbflra.ads)
24104 @geindex Random number generation
24106 The original implementation of @code{Ada.Numerics.Float_Random}. Uses
24107 a modified version of the Blum-Blum-Shub generator.
24109 @node GNAT MD5 g-md5 ads,GNAT Memory_Dump g-memdum ads,GNAT MBBS_Float_Random g-mbflra ads,The GNAT Library
24110 @anchor{gnat_rm/the_gnat_library id92}@anchor{387}@anchor{gnat_rm/the_gnat_library gnat-md5-g-md5-ads}@anchor{388}
24111 @section @code{GNAT.MD5} (@code{g-md5.ads})
24114 @geindex GNAT.MD5 (g-md5.ads)
24116 @geindex Message Digest MD5
24118 Implements the MD5 Message-Digest Algorithm as described in RFC 1321, and
24119 the HMAC-MD5 message authentication function as described in RFC 2104 and
24122 @node GNAT Memory_Dump g-memdum ads,GNAT Most_Recent_Exception g-moreex ads,GNAT MD5 g-md5 ads,The GNAT Library
24123 @anchor{gnat_rm/the_gnat_library id93}@anchor{389}@anchor{gnat_rm/the_gnat_library gnat-memory-dump-g-memdum-ads}@anchor{38a}
24124 @section @code{GNAT.Memory_Dump} (@code{g-memdum.ads})
24127 @geindex GNAT.Memory_Dump (g-memdum.ads)
24129 @geindex Dump Memory
24131 Provides a convenient routine for dumping raw memory to either the
24132 standard output or standard error files. Uses GNAT.IO for actual
24135 @node GNAT Most_Recent_Exception g-moreex ads,GNAT OS_Lib g-os_lib ads,GNAT Memory_Dump g-memdum ads,The GNAT Library
24136 @anchor{gnat_rm/the_gnat_library gnat-most-recent-exception-g-moreex-ads}@anchor{38b}@anchor{gnat_rm/the_gnat_library id94}@anchor{38c}
24137 @section @code{GNAT.Most_Recent_Exception} (@code{g-moreex.ads})
24140 @geindex GNAT.Most_Recent_Exception (g-moreex.ads)
24143 @geindex obtaining most recent
24145 Provides access to the most recently raised exception. Can be used for
24146 various logging purposes, including duplicating functionality of some
24147 Ada 83 implementation dependent extensions.
24149 @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
24150 @anchor{gnat_rm/the_gnat_library gnat-os-lib-g-os-lib-ads}@anchor{38d}@anchor{gnat_rm/the_gnat_library id95}@anchor{38e}
24151 @section @code{GNAT.OS_Lib} (@code{g-os_lib.ads})
24154 @geindex GNAT.OS_Lib (g-os_lib.ads)
24156 @geindex Operating System interface
24158 @geindex Spawn capability
24160 Provides a range of target independent operating system interface functions,
24161 including time/date management, file operations, subprocess management,
24162 including a portable spawn procedure, and access to environment variables
24163 and error return codes.
24165 @node GNAT Perfect_Hash_Generators g-pehage ads,GNAT Random_Numbers g-rannum ads,GNAT OS_Lib g-os_lib ads,The GNAT Library
24166 @anchor{gnat_rm/the_gnat_library gnat-perfect-hash-generators-g-pehage-ads}@anchor{38f}@anchor{gnat_rm/the_gnat_library id96}@anchor{390}
24167 @section @code{GNAT.Perfect_Hash_Generators} (@code{g-pehage.ads})
24170 @geindex GNAT.Perfect_Hash_Generators (g-pehage.ads)
24172 @geindex Hash functions
24174 Provides a generator of static minimal perfect hash functions. No
24175 collisions occur and each item can be retrieved from the table in one
24176 probe (perfect property). The hash table size corresponds to the exact
24177 size of the key set and no larger (minimal property). The key set has to
24178 be know in advance (static property). The hash functions are also order
24179 preserving. If w2 is inserted after w1 in the generator, their
24180 hashcode are in the same order. These hashing functions are very
24181 convenient for use with realtime applications.
24183 @node GNAT Random_Numbers g-rannum ads,GNAT Regexp g-regexp ads,GNAT Perfect_Hash_Generators g-pehage ads,The GNAT Library
24184 @anchor{gnat_rm/the_gnat_library gnat-random-numbers-g-rannum-ads}@anchor{391}@anchor{gnat_rm/the_gnat_library id97}@anchor{392}
24185 @section @code{GNAT.Random_Numbers} (@code{g-rannum.ads})
24188 @geindex GNAT.Random_Numbers (g-rannum.ads)
24190 @geindex Random number generation
24192 Provides random number capabilities which extend those available in the
24193 standard Ada library and are more convenient to use.
24195 @node GNAT Regexp g-regexp ads,GNAT Registry g-regist ads,GNAT Random_Numbers g-rannum ads,The GNAT Library
24196 @anchor{gnat_rm/the_gnat_library id98}@anchor{393}@anchor{gnat_rm/the_gnat_library gnat-regexp-g-regexp-ads}@anchor{258}
24197 @section @code{GNAT.Regexp} (@code{g-regexp.ads})
24200 @geindex GNAT.Regexp (g-regexp.ads)
24202 @geindex Regular expressions
24204 @geindex Pattern matching
24206 A simple implementation of regular expressions, using a subset of regular
24207 expression syntax copied from familiar Unix style utilities. This is the
24208 simplest of the three pattern matching packages provided, and is particularly
24209 suitable for 'file globbing' applications.
24211 @node GNAT Registry g-regist ads,GNAT Regpat g-regpat ads,GNAT Regexp g-regexp ads,The GNAT Library
24212 @anchor{gnat_rm/the_gnat_library id99}@anchor{394}@anchor{gnat_rm/the_gnat_library gnat-registry-g-regist-ads}@anchor{395}
24213 @section @code{GNAT.Registry} (@code{g-regist.ads})
24216 @geindex GNAT.Registry (g-regist.ads)
24218 @geindex Windows Registry
24220 This is a high level binding to the Windows registry. It is possible to
24221 do simple things like reading a key value, creating a new key. For full
24222 registry API, but at a lower level of abstraction, refer to the Win32.Winreg
24223 package provided with the Win32Ada binding
24225 @node GNAT Regpat g-regpat ads,GNAT Rewrite_Data g-rewdat ads,GNAT Registry g-regist ads,The GNAT Library
24226 @anchor{gnat_rm/the_gnat_library id100}@anchor{396}@anchor{gnat_rm/the_gnat_library gnat-regpat-g-regpat-ads}@anchor{397}
24227 @section @code{GNAT.Regpat} (@code{g-regpat.ads})
24230 @geindex GNAT.Regpat (g-regpat.ads)
24232 @geindex Regular expressions
24234 @geindex Pattern matching
24236 A complete implementation of Unix-style regular expression matching, copied
24237 from the original V7 style regular expression library written in C by
24238 Henry Spencer (and binary compatible with this C library).
24240 @node GNAT Rewrite_Data g-rewdat ads,GNAT Secondary_Stack_Info g-sestin ads,GNAT Regpat g-regpat ads,The GNAT Library
24241 @anchor{gnat_rm/the_gnat_library id101}@anchor{398}@anchor{gnat_rm/the_gnat_library gnat-rewrite-data-g-rewdat-ads}@anchor{399}
24242 @section @code{GNAT.Rewrite_Data} (@code{g-rewdat.ads})
24245 @geindex GNAT.Rewrite_Data (g-rewdat.ads)
24247 @geindex Rewrite data
24249 A unit to rewrite on-the-fly string occurrences in a stream of
24250 data. The implementation has a very minimal memory footprint as the
24251 full content to be processed is not loaded into memory all at once. This makes
24252 this interface usable for large files or socket streams.
24254 @node GNAT Secondary_Stack_Info g-sestin ads,GNAT Semaphores g-semaph ads,GNAT Rewrite_Data g-rewdat ads,The GNAT Library
24255 @anchor{gnat_rm/the_gnat_library gnat-secondary-stack-info-g-sestin-ads}@anchor{39a}@anchor{gnat_rm/the_gnat_library id102}@anchor{39b}
24256 @section @code{GNAT.Secondary_Stack_Info} (@code{g-sestin.ads})
24259 @geindex GNAT.Secondary_Stack_Info (g-sestin.ads)
24261 @geindex Secondary Stack Info
24263 Provide the capability to query the high water mark of the current task's
24266 @node GNAT Semaphores g-semaph ads,GNAT Serial_Communications g-sercom ads,GNAT Secondary_Stack_Info g-sestin ads,The GNAT Library
24267 @anchor{gnat_rm/the_gnat_library id103}@anchor{39c}@anchor{gnat_rm/the_gnat_library gnat-semaphores-g-semaph-ads}@anchor{39d}
24268 @section @code{GNAT.Semaphores} (@code{g-semaph.ads})
24271 @geindex GNAT.Semaphores (g-semaph.ads)
24273 @geindex Semaphores
24275 Provides classic counting and binary semaphores using protected types.
24277 @node GNAT Serial_Communications g-sercom ads,GNAT SHA1 g-sha1 ads,GNAT Semaphores g-semaph ads,The GNAT Library
24278 @anchor{gnat_rm/the_gnat_library gnat-serial-communications-g-sercom-ads}@anchor{39e}@anchor{gnat_rm/the_gnat_library id104}@anchor{39f}
24279 @section @code{GNAT.Serial_Communications} (@code{g-sercom.ads})
24282 @geindex GNAT.Serial_Communications (g-sercom.ads)
24284 @geindex Serial_Communications
24286 Provides a simple interface to send and receive data over a serial
24287 port. This is only supported on GNU/Linux and Windows.
24289 @node GNAT SHA1 g-sha1 ads,GNAT SHA224 g-sha224 ads,GNAT Serial_Communications g-sercom ads,The GNAT Library
24290 @anchor{gnat_rm/the_gnat_library gnat-sha1-g-sha1-ads}@anchor{3a0}@anchor{gnat_rm/the_gnat_library id105}@anchor{3a1}
24291 @section @code{GNAT.SHA1} (@code{g-sha1.ads})
24294 @geindex GNAT.SHA1 (g-sha1.ads)
24296 @geindex Secure Hash Algorithm SHA-1
24298 Implements the SHA-1 Secure Hash Algorithm as described in FIPS PUB 180-3
24299 and RFC 3174, and the HMAC-SHA1 message authentication function as described
24300 in RFC 2104 and FIPS PUB 198.
24302 @node GNAT SHA224 g-sha224 ads,GNAT SHA256 g-sha256 ads,GNAT SHA1 g-sha1 ads,The GNAT Library
24303 @anchor{gnat_rm/the_gnat_library gnat-sha224-g-sha224-ads}@anchor{3a2}@anchor{gnat_rm/the_gnat_library id106}@anchor{3a3}
24304 @section @code{GNAT.SHA224} (@code{g-sha224.ads})
24307 @geindex GNAT.SHA224 (g-sha224.ads)
24309 @geindex Secure Hash Algorithm SHA-224
24311 Implements the SHA-224 Secure Hash Algorithm as described in FIPS PUB 180-3,
24312 and the HMAC-SHA224 message authentication function as described
24313 in RFC 2104 and FIPS PUB 198.
24315 @node GNAT SHA256 g-sha256 ads,GNAT SHA384 g-sha384 ads,GNAT SHA224 g-sha224 ads,The GNAT Library
24316 @anchor{gnat_rm/the_gnat_library gnat-sha256-g-sha256-ads}@anchor{3a4}@anchor{gnat_rm/the_gnat_library id107}@anchor{3a5}
24317 @section @code{GNAT.SHA256} (@code{g-sha256.ads})
24320 @geindex GNAT.SHA256 (g-sha256.ads)
24322 @geindex Secure Hash Algorithm SHA-256
24324 Implements the SHA-256 Secure Hash Algorithm as described in FIPS PUB 180-3,
24325 and the HMAC-SHA256 message authentication function as described
24326 in RFC 2104 and FIPS PUB 198.
24328 @node GNAT SHA384 g-sha384 ads,GNAT SHA512 g-sha512 ads,GNAT SHA256 g-sha256 ads,The GNAT Library
24329 @anchor{gnat_rm/the_gnat_library id108}@anchor{3a6}@anchor{gnat_rm/the_gnat_library gnat-sha384-g-sha384-ads}@anchor{3a7}
24330 @section @code{GNAT.SHA384} (@code{g-sha384.ads})
24333 @geindex GNAT.SHA384 (g-sha384.ads)
24335 @geindex Secure Hash Algorithm SHA-384
24337 Implements the SHA-384 Secure Hash Algorithm as described in FIPS PUB 180-3,
24338 and the HMAC-SHA384 message authentication function as described
24339 in RFC 2104 and FIPS PUB 198.
24341 @node GNAT SHA512 g-sha512 ads,GNAT Signals g-signal ads,GNAT SHA384 g-sha384 ads,The GNAT Library
24342 @anchor{gnat_rm/the_gnat_library id109}@anchor{3a8}@anchor{gnat_rm/the_gnat_library gnat-sha512-g-sha512-ads}@anchor{3a9}
24343 @section @code{GNAT.SHA512} (@code{g-sha512.ads})
24346 @geindex GNAT.SHA512 (g-sha512.ads)
24348 @geindex Secure Hash Algorithm SHA-512
24350 Implements the SHA-512 Secure Hash Algorithm as described in FIPS PUB 180-3,
24351 and the HMAC-SHA512 message authentication function as described
24352 in RFC 2104 and FIPS PUB 198.
24354 @node GNAT Signals g-signal ads,GNAT Sockets g-socket ads,GNAT SHA512 g-sha512 ads,The GNAT Library
24355 @anchor{gnat_rm/the_gnat_library gnat-signals-g-signal-ads}@anchor{3aa}@anchor{gnat_rm/the_gnat_library id110}@anchor{3ab}
24356 @section @code{GNAT.Signals} (@code{g-signal.ads})
24359 @geindex GNAT.Signals (g-signal.ads)
24363 Provides the ability to manipulate the blocked status of signals on supported
24366 @node GNAT Sockets g-socket ads,GNAT Source_Info g-souinf ads,GNAT Signals g-signal ads,The GNAT Library
24367 @anchor{gnat_rm/the_gnat_library gnat-sockets-g-socket-ads}@anchor{3ac}@anchor{gnat_rm/the_gnat_library id111}@anchor{3ad}
24368 @section @code{GNAT.Sockets} (@code{g-socket.ads})
24371 @geindex GNAT.Sockets (g-socket.ads)
24375 A high level and portable interface to develop sockets based applications.
24376 This package is based on the sockets thin binding found in
24377 @code{GNAT.Sockets.Thin}. Currently @code{GNAT.Sockets} is implemented
24378 on all native GNAT ports and on VxWorks cross prots. It is not implemented for
24379 the LynxOS cross port.
24381 @node GNAT Source_Info g-souinf ads,GNAT Spelling_Checker g-speche ads,GNAT Sockets g-socket ads,The GNAT Library
24382 @anchor{gnat_rm/the_gnat_library gnat-source-info-g-souinf-ads}@anchor{3ae}@anchor{gnat_rm/the_gnat_library id112}@anchor{3af}
24383 @section @code{GNAT.Source_Info} (@code{g-souinf.ads})
24386 @geindex GNAT.Source_Info (g-souinf.ads)
24388 @geindex Source Information
24390 Provides subprograms that give access to source code information known at
24391 compile time, such as the current file name and line number. Also provides
24392 subprograms yielding the date and time of the current compilation (like the
24393 C macros @code{__DATE__} and @code{__TIME__})
24395 @node GNAT Spelling_Checker g-speche ads,GNAT Spelling_Checker_Generic g-spchge ads,GNAT Source_Info g-souinf ads,The GNAT Library
24396 @anchor{gnat_rm/the_gnat_library gnat-spelling-checker-g-speche-ads}@anchor{3b0}@anchor{gnat_rm/the_gnat_library id113}@anchor{3b1}
24397 @section @code{GNAT.Spelling_Checker} (@code{g-speche.ads})
24400 @geindex GNAT.Spelling_Checker (g-speche.ads)
24402 @geindex Spell checking
24404 Provides a function for determining whether one string is a plausible
24405 near misspelling of another string.
24407 @node GNAT Spelling_Checker_Generic g-spchge ads,GNAT Spitbol Patterns g-spipat ads,GNAT Spelling_Checker g-speche ads,The GNAT Library
24408 @anchor{gnat_rm/the_gnat_library gnat-spelling-checker-generic-g-spchge-ads}@anchor{3b2}@anchor{gnat_rm/the_gnat_library id114}@anchor{3b3}
24409 @section @code{GNAT.Spelling_Checker_Generic} (@code{g-spchge.ads})
24412 @geindex GNAT.Spelling_Checker_Generic (g-spchge.ads)
24414 @geindex Spell checking
24416 Provides a generic function that can be instantiated with a string type for
24417 determining whether one string is a plausible near misspelling of another
24420 @node GNAT Spitbol Patterns g-spipat ads,GNAT Spitbol g-spitbo ads,GNAT Spelling_Checker_Generic g-spchge ads,The GNAT Library
24421 @anchor{gnat_rm/the_gnat_library gnat-spitbol-patterns-g-spipat-ads}@anchor{3b4}@anchor{gnat_rm/the_gnat_library id115}@anchor{3b5}
24422 @section @code{GNAT.Spitbol.Patterns} (@code{g-spipat.ads})
24425 @geindex GNAT.Spitbol.Patterns (g-spipat.ads)
24427 @geindex SPITBOL pattern matching
24429 @geindex Pattern matching
24431 A complete implementation of SNOBOL4 style pattern matching. This is the
24432 most elaborate of the pattern matching packages provided. It fully duplicates
24433 the SNOBOL4 dynamic pattern construction and matching capabilities, using the
24434 efficient algorithm developed by Robert Dewar for the SPITBOL system.
24436 @node GNAT Spitbol g-spitbo ads,GNAT Spitbol Table_Boolean g-sptabo ads,GNAT Spitbol Patterns g-spipat ads,The GNAT Library
24437 @anchor{gnat_rm/the_gnat_library id116}@anchor{3b6}@anchor{gnat_rm/the_gnat_library gnat-spitbol-g-spitbo-ads}@anchor{3b7}
24438 @section @code{GNAT.Spitbol} (@code{g-spitbo.ads})
24441 @geindex GNAT.Spitbol (g-spitbo.ads)
24443 @geindex SPITBOL interface
24445 The top level package of the collection of SPITBOL-style functionality, this
24446 package provides basic SNOBOL4 string manipulation functions, such as
24447 Pad, Reverse, Trim, Substr capability, as well as a generic table function
24448 useful for constructing arbitrary mappings from strings in the style of
24449 the SNOBOL4 TABLE function.
24451 @node GNAT Spitbol Table_Boolean g-sptabo ads,GNAT Spitbol Table_Integer g-sptain ads,GNAT Spitbol g-spitbo ads,The GNAT Library
24452 @anchor{gnat_rm/the_gnat_library gnat-spitbol-table-boolean-g-sptabo-ads}@anchor{3b8}@anchor{gnat_rm/the_gnat_library id117}@anchor{3b9}
24453 @section @code{GNAT.Spitbol.Table_Boolean} (@code{g-sptabo.ads})
24456 @geindex GNAT.Spitbol.Table_Boolean (g-sptabo.ads)
24458 @geindex Sets of strings
24460 @geindex SPITBOL Tables
24462 A library level of instantiation of @code{GNAT.Spitbol.Patterns.Table}
24463 for type @code{Standard.Boolean}, giving an implementation of sets of
24466 @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
24467 @anchor{gnat_rm/the_gnat_library gnat-spitbol-table-integer-g-sptain-ads}@anchor{3ba}@anchor{gnat_rm/the_gnat_library id118}@anchor{3bb}
24468 @section @code{GNAT.Spitbol.Table_Integer} (@code{g-sptain.ads})
24471 @geindex GNAT.Spitbol.Table_Integer (g-sptain.ads)
24473 @geindex Integer maps
24477 @geindex SPITBOL Tables
24479 A library level of instantiation of @code{GNAT.Spitbol.Patterns.Table}
24480 for type @code{Standard.Integer}, giving an implementation of maps
24481 from string to integer values.
24483 @node GNAT Spitbol Table_VString g-sptavs ads,GNAT SSE g-sse ads,GNAT Spitbol Table_Integer g-sptain ads,The GNAT Library
24484 @anchor{gnat_rm/the_gnat_library id119}@anchor{3bc}@anchor{gnat_rm/the_gnat_library gnat-spitbol-table-vstring-g-sptavs-ads}@anchor{3bd}
24485 @section @code{GNAT.Spitbol.Table_VString} (@code{g-sptavs.ads})
24488 @geindex GNAT.Spitbol.Table_VString (g-sptavs.ads)
24490 @geindex String maps
24494 @geindex SPITBOL Tables
24496 A library level of instantiation of @code{GNAT.Spitbol.Patterns.Table} for
24497 a variable length string type, giving an implementation of general
24498 maps from strings to strings.
24500 @node GNAT SSE g-sse ads,GNAT SSE Vector_Types g-ssvety ads,GNAT Spitbol Table_VString g-sptavs ads,The GNAT Library
24501 @anchor{gnat_rm/the_gnat_library id120}@anchor{3be}@anchor{gnat_rm/the_gnat_library gnat-sse-g-sse-ads}@anchor{3bf}
24502 @section @code{GNAT.SSE} (@code{g-sse.ads})
24505 @geindex GNAT.SSE (g-sse.ads)
24507 Root of a set of units aimed at offering Ada bindings to a subset of
24508 the Intel(r) Streaming SIMD Extensions with GNAT on the x86 family of
24509 targets. It exposes vector component types together with a general
24510 introduction to the binding contents and use.
24512 @node GNAT SSE Vector_Types g-ssvety ads,GNAT String_Hash g-strhas ads,GNAT SSE g-sse ads,The GNAT Library
24513 @anchor{gnat_rm/the_gnat_library gnat-sse-vector-types-g-ssvety-ads}@anchor{3c0}@anchor{gnat_rm/the_gnat_library id121}@anchor{3c1}
24514 @section @code{GNAT.SSE.Vector_Types} (@code{g-ssvety.ads})
24517 @geindex GNAT.SSE.Vector_Types (g-ssvety.ads)
24519 SSE vector types for use with SSE related intrinsics.
24521 @node GNAT String_Hash g-strhas ads,GNAT Strings g-string ads,GNAT SSE Vector_Types g-ssvety ads,The GNAT Library
24522 @anchor{gnat_rm/the_gnat_library gnat-string-hash-g-strhas-ads}@anchor{3c2}@anchor{gnat_rm/the_gnat_library id122}@anchor{3c3}
24523 @section @code{GNAT.String_Hash} (@code{g-strhas.ads})
24526 @geindex GNAT.String_Hash (g-strhas.ads)
24528 @geindex Hash functions
24530 Provides a generic hash function working on arrays of scalars. Both the scalar
24531 type and the hash result type are parameters.
24533 @node GNAT Strings g-string ads,GNAT String_Split g-strspl ads,GNAT String_Hash g-strhas ads,The GNAT Library
24534 @anchor{gnat_rm/the_gnat_library id123}@anchor{3c4}@anchor{gnat_rm/the_gnat_library gnat-strings-g-string-ads}@anchor{3c5}
24535 @section @code{GNAT.Strings} (@code{g-string.ads})
24538 @geindex GNAT.Strings (g-string.ads)
24540 Common String access types and related subprograms. Basically it
24541 defines a string access and an array of string access types.
24543 @node GNAT String_Split g-strspl ads,GNAT Table g-table ads,GNAT Strings g-string ads,The GNAT Library
24544 @anchor{gnat_rm/the_gnat_library gnat-string-split-g-strspl-ads}@anchor{3c6}@anchor{gnat_rm/the_gnat_library id124}@anchor{3c7}
24545 @section @code{GNAT.String_Split} (@code{g-strspl.ads})
24548 @geindex GNAT.String_Split (g-strspl.ads)
24550 @geindex String splitter
24552 Useful string manipulation routines: given a set of separators, split
24553 a string wherever the separators appear, and provide direct access
24554 to the resulting slices. This package is instantiated from
24555 @code{GNAT.Array_Split}.
24557 @node GNAT Table g-table ads,GNAT Task_Lock g-tasloc ads,GNAT String_Split g-strspl ads,The GNAT Library
24558 @anchor{gnat_rm/the_gnat_library id125}@anchor{3c8}@anchor{gnat_rm/the_gnat_library gnat-table-g-table-ads}@anchor{3c9}
24559 @section @code{GNAT.Table} (@code{g-table.ads})
24562 @geindex GNAT.Table (g-table.ads)
24564 @geindex Table implementation
24567 @geindex extendable
24569 A generic package providing a single dimension array abstraction where the
24570 length of the array can be dynamically modified.
24572 This package provides a facility similar to that of @code{GNAT.Dynamic_Tables},
24573 except that this package declares a single instance of the table type,
24574 while an instantiation of @code{GNAT.Dynamic_Tables} creates a type that can be
24575 used to define dynamic instances of the table.
24577 @node GNAT Task_Lock g-tasloc ads,GNAT Time_Stamp g-timsta ads,GNAT Table g-table ads,The GNAT Library
24578 @anchor{gnat_rm/the_gnat_library id126}@anchor{3ca}@anchor{gnat_rm/the_gnat_library gnat-task-lock-g-tasloc-ads}@anchor{3cb}
24579 @section @code{GNAT.Task_Lock} (@code{g-tasloc.ads})
24582 @geindex GNAT.Task_Lock (g-tasloc.ads)
24584 @geindex Task synchronization
24586 @geindex Task locking
24590 A very simple facility for locking and unlocking sections of code using a
24591 single global task lock. Appropriate for use in situations where contention
24592 between tasks is very rarely expected.
24594 @node GNAT Time_Stamp g-timsta ads,GNAT Threads g-thread ads,GNAT Task_Lock g-tasloc ads,The GNAT Library
24595 @anchor{gnat_rm/the_gnat_library id127}@anchor{3cc}@anchor{gnat_rm/the_gnat_library gnat-time-stamp-g-timsta-ads}@anchor{3cd}
24596 @section @code{GNAT.Time_Stamp} (@code{g-timsta.ads})
24599 @geindex GNAT.Time_Stamp (g-timsta.ads)
24601 @geindex Time stamp
24603 @geindex Current time
24605 Provides a simple function that returns a string YYYY-MM-DD HH:MM:SS.SS that
24606 represents the current date and time in ISO 8601 format. This is a very simple
24607 routine with minimal code and there are no dependencies on any other unit.
24609 @node GNAT Threads g-thread ads,GNAT Traceback g-traceb ads,GNAT Time_Stamp g-timsta ads,The GNAT Library
24610 @anchor{gnat_rm/the_gnat_library gnat-threads-g-thread-ads}@anchor{3ce}@anchor{gnat_rm/the_gnat_library id128}@anchor{3cf}
24611 @section @code{GNAT.Threads} (@code{g-thread.ads})
24614 @geindex GNAT.Threads (g-thread.ads)
24616 @geindex Foreign threads
24621 Provides facilities for dealing with foreign threads which need to be known
24622 by the GNAT run-time system. Consult the documentation of this package for
24623 further details if your program has threads that are created by a non-Ada
24624 environment which then accesses Ada code.
24626 @node GNAT Traceback g-traceb ads,GNAT Traceback Symbolic g-trasym ads,GNAT Threads g-thread ads,The GNAT Library
24627 @anchor{gnat_rm/the_gnat_library id129}@anchor{3d0}@anchor{gnat_rm/the_gnat_library gnat-traceback-g-traceb-ads}@anchor{3d1}
24628 @section @code{GNAT.Traceback} (@code{g-traceb.ads})
24631 @geindex GNAT.Traceback (g-traceb.ads)
24633 @geindex Trace back facilities
24635 Provides a facility for obtaining non-symbolic traceback information, useful
24636 in various debugging situations.
24638 @node GNAT Traceback Symbolic g-trasym ads,GNAT UTF_32 g-table ads,GNAT Traceback g-traceb ads,The GNAT Library
24639 @anchor{gnat_rm/the_gnat_library id130}@anchor{3d2}@anchor{gnat_rm/the_gnat_library gnat-traceback-symbolic-g-trasym-ads}@anchor{3d3}
24640 @section @code{GNAT.Traceback.Symbolic} (@code{g-trasym.ads})
24643 @geindex GNAT.Traceback.Symbolic (g-trasym.ads)
24645 @geindex Trace back facilities
24647 @node GNAT UTF_32 g-table ads,GNAT Wide_Spelling_Checker g-u3spch ads,GNAT Traceback Symbolic g-trasym ads,The GNAT Library
24648 @anchor{gnat_rm/the_gnat_library id131}@anchor{3d4}@anchor{gnat_rm/the_gnat_library gnat-utf-32-g-table-ads}@anchor{3d5}
24649 @section @code{GNAT.UTF_32} (@code{g-table.ads})
24652 @geindex GNAT.UTF_32 (g-table.ads)
24654 @geindex Wide character codes
24656 This is a package intended to be used in conjunction with the
24657 @code{Wide_Character} type in Ada 95 and the
24658 @code{Wide_Wide_Character} type in Ada 2005 (available
24659 in @code{GNAT} in Ada 2005 mode). This package contains
24660 Unicode categorization routines, as well as lexical
24661 categorization routines corresponding to the Ada 2005
24662 lexical rules for identifiers and strings, and also a
24663 lower case to upper case fold routine corresponding to
24664 the Ada 2005 rules for identifier equivalence.
24666 @node GNAT Wide_Spelling_Checker g-u3spch ads,GNAT Wide_Spelling_Checker g-wispch ads,GNAT UTF_32 g-table ads,The GNAT Library
24667 @anchor{gnat_rm/the_gnat_library gnat-wide-spelling-checker-g-u3spch-ads}@anchor{3d6}@anchor{gnat_rm/the_gnat_library id132}@anchor{3d7}
24668 @section @code{GNAT.Wide_Spelling_Checker} (@code{g-u3spch.ads})
24671 @geindex GNAT.Wide_Spelling_Checker (g-u3spch.ads)
24673 @geindex Spell checking
24675 Provides a function for determining whether one wide wide string is a plausible
24676 near misspelling of another wide wide string, where the strings are represented
24677 using the UTF_32_String type defined in System.Wch_Cnv.
24679 @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
24680 @anchor{gnat_rm/the_gnat_library gnat-wide-spelling-checker-g-wispch-ads}@anchor{3d8}@anchor{gnat_rm/the_gnat_library id133}@anchor{3d9}
24681 @section @code{GNAT.Wide_Spelling_Checker} (@code{g-wispch.ads})
24684 @geindex GNAT.Wide_Spelling_Checker (g-wispch.ads)
24686 @geindex Spell checking
24688 Provides a function for determining whether one wide string is a plausible
24689 near misspelling of another wide string.
24691 @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
24692 @anchor{gnat_rm/the_gnat_library id134}@anchor{3da}@anchor{gnat_rm/the_gnat_library gnat-wide-string-split-g-wistsp-ads}@anchor{3db}
24693 @section @code{GNAT.Wide_String_Split} (@code{g-wistsp.ads})
24696 @geindex GNAT.Wide_String_Split (g-wistsp.ads)
24698 @geindex Wide_String splitter
24700 Useful wide string manipulation routines: given a set of separators, split
24701 a wide string wherever the separators appear, and provide direct access
24702 to the resulting slices. This package is instantiated from
24703 @code{GNAT.Array_Split}.
24705 @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
24706 @anchor{gnat_rm/the_gnat_library gnat-wide-wide-spelling-checker-g-zspche-ads}@anchor{3dc}@anchor{gnat_rm/the_gnat_library id135}@anchor{3dd}
24707 @section @code{GNAT.Wide_Wide_Spelling_Checker} (@code{g-zspche.ads})
24710 @geindex GNAT.Wide_Wide_Spelling_Checker (g-zspche.ads)
24712 @geindex Spell checking
24714 Provides a function for determining whether one wide wide string is a plausible
24715 near misspelling of another wide wide string.
24717 @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
24718 @anchor{gnat_rm/the_gnat_library gnat-wide-wide-string-split-g-zistsp-ads}@anchor{3de}@anchor{gnat_rm/the_gnat_library id136}@anchor{3df}
24719 @section @code{GNAT.Wide_Wide_String_Split} (@code{g-zistsp.ads})
24722 @geindex GNAT.Wide_Wide_String_Split (g-zistsp.ads)
24724 @geindex Wide_Wide_String splitter
24726 Useful wide wide string manipulation routines: given a set of separators, split
24727 a wide wide string wherever the separators appear, and provide direct access
24728 to the resulting slices. This package is instantiated from
24729 @code{GNAT.Array_Split}.
24731 @node Interfaces C Extensions i-cexten ads,Interfaces C Streams i-cstrea ads,GNAT Wide_Wide_String_Split g-zistsp ads,The GNAT Library
24732 @anchor{gnat_rm/the_gnat_library interfaces-c-extensions-i-cexten-ads}@anchor{3e0}@anchor{gnat_rm/the_gnat_library id137}@anchor{3e1}
24733 @section @code{Interfaces.C.Extensions} (@code{i-cexten.ads})
24736 @geindex Interfaces.C.Extensions (i-cexten.ads)
24738 This package contains additional C-related definitions, intended
24739 for use with either manually or automatically generated bindings
24742 @node Interfaces C Streams i-cstrea ads,Interfaces Packed_Decimal i-pacdec ads,Interfaces C Extensions i-cexten ads,The GNAT Library
24743 @anchor{gnat_rm/the_gnat_library id138}@anchor{3e2}@anchor{gnat_rm/the_gnat_library interfaces-c-streams-i-cstrea-ads}@anchor{3e3}
24744 @section @code{Interfaces.C.Streams} (@code{i-cstrea.ads})
24747 @geindex Interfaces.C.Streams (i-cstrea.ads)
24750 @geindex interfacing
24752 This package is a binding for the most commonly used operations
24755 @node Interfaces Packed_Decimal i-pacdec ads,Interfaces VxWorks i-vxwork ads,Interfaces C Streams i-cstrea ads,The GNAT Library
24756 @anchor{gnat_rm/the_gnat_library interfaces-packed-decimal-i-pacdec-ads}@anchor{3e4}@anchor{gnat_rm/the_gnat_library id139}@anchor{3e5}
24757 @section @code{Interfaces.Packed_Decimal} (@code{i-pacdec.ads})
24760 @geindex Interfaces.Packed_Decimal (i-pacdec.ads)
24762 @geindex IBM Packed Format
24764 @geindex Packed Decimal
24766 This package provides a set of routines for conversions to and
24767 from a packed decimal format compatible with that used on IBM
24770 @node Interfaces VxWorks i-vxwork ads,Interfaces VxWorks Int_Connection i-vxinco ads,Interfaces Packed_Decimal i-pacdec ads,The GNAT Library
24771 @anchor{gnat_rm/the_gnat_library interfaces-vxworks-i-vxwork-ads}@anchor{3e6}@anchor{gnat_rm/the_gnat_library id140}@anchor{3e7}
24772 @section @code{Interfaces.VxWorks} (@code{i-vxwork.ads})
24775 @geindex Interfaces.VxWorks (i-vxwork.ads)
24777 @geindex Interfacing to VxWorks
24780 @geindex interfacing
24782 This package provides a limited binding to the VxWorks API.
24783 In particular, it interfaces with the
24784 VxWorks hardware interrupt facilities.
24786 @node Interfaces VxWorks Int_Connection i-vxinco ads,Interfaces VxWorks IO i-vxwoio ads,Interfaces VxWorks i-vxwork ads,The GNAT Library
24787 @anchor{gnat_rm/the_gnat_library interfaces-vxworks-int-connection-i-vxinco-ads}@anchor{3e8}@anchor{gnat_rm/the_gnat_library id141}@anchor{3e9}
24788 @section @code{Interfaces.VxWorks.Int_Connection} (@code{i-vxinco.ads})
24791 @geindex Interfaces.VxWorks.Int_Connection (i-vxinco.ads)
24793 @geindex Interfacing to VxWorks
24796 @geindex interfacing
24798 This package provides a way for users to replace the use of
24799 intConnect() with a custom routine for installing interrupt
24802 @node Interfaces VxWorks IO i-vxwoio ads,System Address_Image s-addima ads,Interfaces VxWorks Int_Connection i-vxinco ads,The GNAT Library
24803 @anchor{gnat_rm/the_gnat_library interfaces-vxworks-io-i-vxwoio-ads}@anchor{3ea}@anchor{gnat_rm/the_gnat_library id142}@anchor{3eb}
24804 @section @code{Interfaces.VxWorks.IO} (@code{i-vxwoio.ads})
24807 @geindex Interfaces.VxWorks.IO (i-vxwoio.ads)
24809 @geindex Interfacing to VxWorks' I/O
24812 @geindex I/O interfacing
24815 @geindex Get_Immediate
24817 @geindex Get_Immediate
24820 This package provides a binding to the ioctl (IO/Control)
24821 function of VxWorks, defining a set of option values and
24822 function codes. A particular use of this package is
24823 to enable the use of Get_Immediate under VxWorks.
24825 @node System Address_Image s-addima ads,System Assertions s-assert ads,Interfaces VxWorks IO i-vxwoio ads,The GNAT Library
24826 @anchor{gnat_rm/the_gnat_library system-address-image-s-addima-ads}@anchor{3ec}@anchor{gnat_rm/the_gnat_library id143}@anchor{3ed}
24827 @section @code{System.Address_Image} (@code{s-addima.ads})
24830 @geindex System.Address_Image (s-addima.ads)
24832 @geindex Address image
24835 @geindex of an address
24837 This function provides a useful debugging
24838 function that gives an (implementation dependent)
24839 string which identifies an address.
24841 @node System Assertions s-assert ads,System Atomic_Counters s-atocou ads,System Address_Image s-addima ads,The GNAT Library
24842 @anchor{gnat_rm/the_gnat_library id144}@anchor{3ee}@anchor{gnat_rm/the_gnat_library system-assertions-s-assert-ads}@anchor{3ef}
24843 @section @code{System.Assertions} (@code{s-assert.ads})
24846 @geindex System.Assertions (s-assert.ads)
24848 @geindex Assertions
24850 @geindex Assert_Failure
24853 This package provides the declaration of the exception raised
24854 by an run-time assertion failure, as well as the routine that
24855 is used internally to raise this assertion.
24857 @node System Atomic_Counters s-atocou ads,System Memory s-memory ads,System Assertions s-assert ads,The GNAT Library
24858 @anchor{gnat_rm/the_gnat_library id145}@anchor{3f0}@anchor{gnat_rm/the_gnat_library system-atomic-counters-s-atocou-ads}@anchor{3f1}
24859 @section @code{System.Atomic_Counters} (@code{s-atocou.ads})
24862 @geindex System.Atomic_Counters (s-atocou.ads)
24864 This package provides the declaration of an atomic counter type,
24865 together with efficient routines (using hardware
24866 synchronization primitives) for incrementing, decrementing,
24867 and testing of these counters. This package is implemented
24868 on most targets, including all Alpha, ia64, PowerPC, SPARC V9,
24869 x86, and x86_64 platforms.
24871 @node System Memory s-memory ads,System Multiprocessors s-multip ads,System Atomic_Counters s-atocou ads,The GNAT Library
24872 @anchor{gnat_rm/the_gnat_library system-memory-s-memory-ads}@anchor{3f2}@anchor{gnat_rm/the_gnat_library id146}@anchor{3f3}
24873 @section @code{System.Memory} (@code{s-memory.ads})
24876 @geindex System.Memory (s-memory.ads)
24878 @geindex Memory allocation
24880 This package provides the interface to the low level routines used
24881 by the generated code for allocation and freeing storage for the
24882 default storage pool (analogous to the C routines malloc and free.
24883 It also provides a reallocation interface analogous to the C routine
24884 realloc. The body of this unit may be modified to provide alternative
24885 allocation mechanisms for the default pool, and in addition, direct
24886 calls to this unit may be made for low level allocation uses (for
24887 example see the body of @code{GNAT.Tables}).
24889 @node System Multiprocessors s-multip ads,System Multiprocessors Dispatching_Domains s-mudido ads,System Memory s-memory ads,The GNAT Library
24890 @anchor{gnat_rm/the_gnat_library id147}@anchor{3f4}@anchor{gnat_rm/the_gnat_library system-multiprocessors-s-multip-ads}@anchor{3f5}
24891 @section @code{System.Multiprocessors} (@code{s-multip.ads})
24894 @geindex System.Multiprocessors (s-multip.ads)
24896 @geindex Multiprocessor interface
24898 This is an Ada 2012 unit defined in the Ada 2012 Reference Manual, but
24899 in GNAT we also make it available in Ada 95 and Ada 2005 (where it is
24900 technically an implementation-defined addition).
24902 @node System Multiprocessors Dispatching_Domains s-mudido ads,System Partition_Interface s-parint ads,System Multiprocessors s-multip ads,The GNAT Library
24903 @anchor{gnat_rm/the_gnat_library system-multiprocessors-dispatching-domains-s-mudido-ads}@anchor{3f6}@anchor{gnat_rm/the_gnat_library id148}@anchor{3f7}
24904 @section @code{System.Multiprocessors.Dispatching_Domains} (@code{s-mudido.ads})
24907 @geindex System.Multiprocessors.Dispatching_Domains (s-mudido.ads)
24909 @geindex Multiprocessor interface
24911 This is an Ada 2012 unit defined in the Ada 2012 Reference Manual, but
24912 in GNAT we also make it available in Ada 95 and Ada 2005 (where it is
24913 technically an implementation-defined addition).
24915 @node System Partition_Interface s-parint ads,System Pool_Global s-pooglo ads,System Multiprocessors Dispatching_Domains s-mudido ads,The GNAT Library
24916 @anchor{gnat_rm/the_gnat_library id149}@anchor{3f8}@anchor{gnat_rm/the_gnat_library system-partition-interface-s-parint-ads}@anchor{3f9}
24917 @section @code{System.Partition_Interface} (@code{s-parint.ads})
24920 @geindex System.Partition_Interface (s-parint.ads)
24922 @geindex Partition interfacing functions
24924 This package provides facilities for partition interfacing. It
24925 is used primarily in a distribution context when using Annex E
24928 @node System Pool_Global s-pooglo ads,System Pool_Local s-pooloc ads,System Partition_Interface s-parint ads,The GNAT Library
24929 @anchor{gnat_rm/the_gnat_library id150}@anchor{3fa}@anchor{gnat_rm/the_gnat_library system-pool-global-s-pooglo-ads}@anchor{3fb}
24930 @section @code{System.Pool_Global} (@code{s-pooglo.ads})
24933 @geindex System.Pool_Global (s-pooglo.ads)
24935 @geindex Storage pool
24938 @geindex Global storage pool
24940 This package provides a storage pool that is equivalent to the default
24941 storage pool used for access types for which no pool is specifically
24942 declared. It uses malloc/free to allocate/free and does not attempt to
24943 do any automatic reclamation.
24945 @node System Pool_Local s-pooloc ads,System Restrictions s-restri ads,System Pool_Global s-pooglo ads,The GNAT Library
24946 @anchor{gnat_rm/the_gnat_library system-pool-local-s-pooloc-ads}@anchor{3fc}@anchor{gnat_rm/the_gnat_library id151}@anchor{3fd}
24947 @section @code{System.Pool_Local} (@code{s-pooloc.ads})
24950 @geindex System.Pool_Local (s-pooloc.ads)
24952 @geindex Storage pool
24955 @geindex Local storage pool
24957 This package provides a storage pool that is intended for use with locally
24958 defined access types. It uses malloc/free for allocate/free, and maintains
24959 a list of allocated blocks, so that all storage allocated for the pool can
24960 be freed automatically when the pool is finalized.
24962 @node System Restrictions s-restri ads,System Rident s-rident ads,System Pool_Local s-pooloc ads,The GNAT Library
24963 @anchor{gnat_rm/the_gnat_library id152}@anchor{3fe}@anchor{gnat_rm/the_gnat_library system-restrictions-s-restri-ads}@anchor{3ff}
24964 @section @code{System.Restrictions} (@code{s-restri.ads})
24967 @geindex System.Restrictions (s-restri.ads)
24969 @geindex Run-time restrictions access
24971 This package provides facilities for accessing at run time
24972 the status of restrictions specified at compile time for
24973 the partition. Information is available both with regard
24974 to actual restrictions specified, and with regard to
24975 compiler determined information on which restrictions
24976 are violated by one or more packages in the partition.
24978 @node System Rident s-rident ads,System Strings Stream_Ops s-ststop ads,System Restrictions s-restri ads,The GNAT Library
24979 @anchor{gnat_rm/the_gnat_library system-rident-s-rident-ads}@anchor{400}@anchor{gnat_rm/the_gnat_library id153}@anchor{401}
24980 @section @code{System.Rident} (@code{s-rident.ads})
24983 @geindex System.Rident (s-rident.ads)
24985 @geindex Restrictions definitions
24987 This package provides definitions of the restrictions
24988 identifiers supported by GNAT, and also the format of
24989 the restrictions provided in package System.Restrictions.
24990 It is not normally necessary to @code{with} this generic package
24991 since the necessary instantiation is included in
24992 package System.Restrictions.
24994 @node System Strings Stream_Ops s-ststop ads,System Unsigned_Types s-unstyp ads,System Rident s-rident ads,The GNAT Library
24995 @anchor{gnat_rm/the_gnat_library id154}@anchor{402}@anchor{gnat_rm/the_gnat_library system-strings-stream-ops-s-ststop-ads}@anchor{403}
24996 @section @code{System.Strings.Stream_Ops} (@code{s-ststop.ads})
24999 @geindex System.Strings.Stream_Ops (s-ststop.ads)
25001 @geindex Stream operations
25003 @geindex String stream operations
25005 This package provides a set of stream subprograms for standard string types.
25006 It is intended primarily to support implicit use of such subprograms when
25007 stream attributes are applied to string types, but the subprograms in this
25008 package can be used directly by application programs.
25010 @node System Unsigned_Types s-unstyp ads,System Wch_Cnv s-wchcnv ads,System Strings Stream_Ops s-ststop ads,The GNAT Library
25011 @anchor{gnat_rm/the_gnat_library system-unsigned-types-s-unstyp-ads}@anchor{404}@anchor{gnat_rm/the_gnat_library id155}@anchor{405}
25012 @section @code{System.Unsigned_Types} (@code{s-unstyp.ads})
25015 @geindex System.Unsigned_Types (s-unstyp.ads)
25017 This package contains definitions of standard unsigned types that
25018 correspond in size to the standard signed types declared in Standard,
25019 and (unlike the types in Interfaces) have corresponding names. It
25020 also contains some related definitions for other specialized types
25021 used by the compiler in connection with packed array types.
25023 @node System Wch_Cnv s-wchcnv ads,System Wch_Con s-wchcon ads,System Unsigned_Types s-unstyp ads,The GNAT Library
25024 @anchor{gnat_rm/the_gnat_library system-wch-cnv-s-wchcnv-ads}@anchor{406}@anchor{gnat_rm/the_gnat_library id156}@anchor{407}
25025 @section @code{System.Wch_Cnv} (@code{s-wchcnv.ads})
25028 @geindex System.Wch_Cnv (s-wchcnv.ads)
25030 @geindex Wide Character
25031 @geindex Representation
25033 @geindex Wide String
25034 @geindex Conversion
25036 @geindex Representation of wide characters
25038 This package provides routines for converting between
25039 wide and wide wide characters and a representation as a value of type
25040 @code{Standard.String}, using a specified wide character
25041 encoding method. It uses definitions in
25042 package @code{System.Wch_Con}.
25044 @node System Wch_Con s-wchcon ads,,System Wch_Cnv s-wchcnv ads,The GNAT Library
25045 @anchor{gnat_rm/the_gnat_library id157}@anchor{408}@anchor{gnat_rm/the_gnat_library system-wch-con-s-wchcon-ads}@anchor{409}
25046 @section @code{System.Wch_Con} (@code{s-wchcon.ads})
25049 @geindex System.Wch_Con (s-wchcon.ads)
25051 This package provides definitions and descriptions of
25052 the various methods used for encoding wide characters
25053 in ordinary strings. These definitions are used by
25054 the package @code{System.Wch_Cnv}.
25056 @node Interfacing to Other Languages,Specialized Needs Annexes,The GNAT Library,Top
25057 @anchor{gnat_rm/interfacing_to_other_languages interfacing-to-other-languages}@anchor{11}@anchor{gnat_rm/interfacing_to_other_languages doc}@anchor{40a}@anchor{gnat_rm/interfacing_to_other_languages id1}@anchor{40b}
25058 @chapter Interfacing to Other Languages
25061 The facilities in Annex B of the Ada Reference Manual are fully
25062 implemented in GNAT, and in addition, a full interface to C++ is
25066 * Interfacing to C::
25067 * Interfacing to C++::
25068 * Interfacing to COBOL::
25069 * Interfacing to Fortran::
25070 * Interfacing to non-GNAT Ada code::
25074 @node Interfacing to C,Interfacing to C++,,Interfacing to Other Languages
25075 @anchor{gnat_rm/interfacing_to_other_languages interfacing-to-c}@anchor{40c}@anchor{gnat_rm/interfacing_to_other_languages id2}@anchor{40d}
25076 @section Interfacing to C
25079 Interfacing to C with GNAT can use one of two approaches:
25085 The types in the package @code{Interfaces.C} may be used.
25088 Standard Ada types may be used directly. This may be less portable to
25089 other compilers, but will work on all GNAT compilers, which guarantee
25090 correspondence between the C and Ada types.
25093 Pragma @code{Convention C} may be applied to Ada types, but mostly has no
25094 effect, since this is the default. The following table shows the
25095 correspondence between Ada scalar types and the corresponding C types.
25098 @multitable {xxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
25117 @code{Short_Integer}
25125 @code{Short_Short_Integer}
25133 @code{Long_Integer}
25141 @code{Long_Long_Integer}
25173 @code{Long_Long_Float}
25177 This is the longest floating-point type supported by the hardware.
25182 Additionally, there are the following general correspondences between Ada
25189 Ada enumeration types map to C enumeration types directly if pragma
25190 @code{Convention C} is specified, which causes them to have a length of
25191 32 bits, except for boolean types which map to C99 @code{bool} and for
25192 which the length is 8 bits.
25193 Without pragma @code{Convention C}, Ada enumeration types map to
25194 8, 16, or 32 bits (i.e., C types @code{signed char}, @code{short},
25195 @code{int}, respectively) depending on the number of values passed.
25196 This is the only case in which pragma @code{Convention C} affects the
25197 representation of an Ada type.
25200 Ada access types map to C pointers, except for the case of pointers to
25201 unconstrained types in Ada, which have no direct C equivalent.
25204 Ada arrays map directly to C arrays.
25207 Ada records map directly to C structures.
25210 Packed Ada records map to C structures where all members are bit fields
25211 of the length corresponding to the @code{type'Size} value in Ada.
25214 @node Interfacing to C++,Interfacing to COBOL,Interfacing to C,Interfacing to Other Languages
25215 @anchor{gnat_rm/interfacing_to_other_languages id4}@anchor{40e}@anchor{gnat_rm/interfacing_to_other_languages id3}@anchor{47}
25216 @section Interfacing to C++
25219 The interface to C++ makes use of the following pragmas, which are
25220 primarily intended to be constructed automatically using a binding generator
25221 tool, although it is possible to construct them by hand.
25223 Using these pragmas it is possible to achieve complete
25224 inter-operability between Ada tagged types and C++ class definitions.
25225 See @ref{7,,Implementation Defined Pragmas}, for more details.
25230 @item @code{pragma CPP_Class ([Entity =>] @emph{LOCAL_NAME})}
25232 The argument denotes an entity in the current declarative region that is
25233 declared as a tagged or untagged record type. It indicates that the type
25234 corresponds to an externally declared C++ class type, and is to be laid
25235 out the same way that C++ would lay out the type.
25237 Note: Pragma @code{CPP_Class} is currently obsolete. It is supported
25238 for backward compatibility but its functionality is available
25239 using pragma @code{Import} with @code{Convention} = @code{CPP}.
25241 @item @code{pragma CPP_Constructor ([Entity =>] @emph{LOCAL_NAME})}
25243 This pragma identifies an imported function (imported in the usual way
25244 with pragma @code{Import}) as corresponding to a C++ constructor.
25247 A few restrictions are placed on the use of the @code{Access} attribute
25248 in conjunction with subprograms subject to convention @code{CPP}: the
25249 attribute may be used neither on primitive operations of a tagged
25250 record type with convention @code{CPP}, imported or not, nor on
25251 subprograms imported with pragma @code{CPP_Constructor}.
25253 In addition, C++ exceptions are propagated and can be handled in an
25254 @code{others} choice of an exception handler. The corresponding Ada
25255 occurrence has no message, and the simple name of the exception identity
25256 contains @code{Foreign_Exception}. Finalization and awaiting dependent
25257 tasks works properly when such foreign exceptions are propagated.
25259 It is also possible to import a C++ exception using the following syntax:
25262 LOCAL_NAME : exception;
25263 pragma Import (Cpp,
25264 [Entity =>] LOCAL_NAME,
25265 [External_Name =>] static_string_EXPRESSION);
25268 The @code{External_Name} is the name of the C++ RTTI symbol. You can then
25269 cover a specific C++ exception in an exception handler.
25271 @node Interfacing to COBOL,Interfacing to Fortran,Interfacing to C++,Interfacing to Other Languages
25272 @anchor{gnat_rm/interfacing_to_other_languages id5}@anchor{40f}@anchor{gnat_rm/interfacing_to_other_languages interfacing-to-cobol}@anchor{410}
25273 @section Interfacing to COBOL
25276 Interfacing to COBOL is achieved as described in section B.4 of
25277 the Ada Reference Manual.
25279 @node Interfacing to Fortran,Interfacing to non-GNAT Ada code,Interfacing to COBOL,Interfacing to Other Languages
25280 @anchor{gnat_rm/interfacing_to_other_languages id6}@anchor{411}@anchor{gnat_rm/interfacing_to_other_languages interfacing-to-fortran}@anchor{412}
25281 @section Interfacing to Fortran
25284 Interfacing to Fortran is achieved as described in section B.5 of the
25285 Ada Reference Manual. The pragma @code{Convention Fortran}, applied to a
25286 multi-dimensional array causes the array to be stored in column-major
25287 order as required for convenient interface to Fortran.
25289 @node Interfacing to non-GNAT Ada code,,Interfacing to Fortran,Interfacing to Other Languages
25290 @anchor{gnat_rm/interfacing_to_other_languages interfacing-to-non-gnat-ada-code}@anchor{413}@anchor{gnat_rm/interfacing_to_other_languages id7}@anchor{414}
25291 @section Interfacing to non-GNAT Ada code
25294 It is possible to specify the convention @code{Ada} in a pragma
25295 @code{Import} or pragma @code{Export}. However this refers to
25296 the calling conventions used by GNAT, which may or may not be
25297 similar enough to those used by some other Ada 83 / Ada 95 / Ada 2005
25298 compiler to allow interoperation.
25300 If arguments types are kept simple, and if the foreign compiler generally
25301 follows system calling conventions, then it may be possible to integrate
25302 files compiled by other Ada compilers, provided that the elaboration
25303 issues are adequately addressed (for example by eliminating the
25304 need for any load time elaboration).
25306 In particular, GNAT running on VMS is designed to
25307 be highly compatible with the DEC Ada 83 compiler, so this is one
25308 case in which it is possible to import foreign units of this type,
25309 provided that the data items passed are restricted to simple scalar
25310 values or simple record types without variants, or simple array
25311 types with fixed bounds.
25313 @node Specialized Needs Annexes,Implementation of Specific Ada Features,Interfacing to Other Languages,Top
25314 @anchor{gnat_rm/specialized_needs_annexes specialized-needs-annexes}@anchor{12}@anchor{gnat_rm/specialized_needs_annexes doc}@anchor{415}@anchor{gnat_rm/specialized_needs_annexes id1}@anchor{416}
25315 @chapter Specialized Needs Annexes
25318 Ada 95, Ada 2005, and Ada 2012 define a number of Specialized Needs Annexes, which are not
25319 required in all implementations. However, as described in this chapter,
25320 GNAT implements all of these annexes:
25325 @item @emph{Systems Programming (Annex C)}
25327 The Systems Programming Annex is fully implemented.
25329 @item @emph{Real-Time Systems (Annex D)}
25331 The Real-Time Systems Annex is fully implemented.
25333 @item @emph{Distributed Systems (Annex E)}
25335 Stub generation is fully implemented in the GNAT compiler. In addition,
25336 a complete compatible PCS is available as part of the GLADE system,
25337 a separate product. When the two
25338 products are used in conjunction, this annex is fully implemented.
25340 @item @emph{Information Systems (Annex F)}
25342 The Information Systems annex is fully implemented.
25344 @item @emph{Numerics (Annex G)}
25346 The Numerics Annex is fully implemented.
25348 @item @emph{Safety and Security / High-Integrity Systems (Annex H)}
25350 The Safety and Security Annex (termed the High-Integrity Systems Annex
25351 in Ada 2005) is fully implemented.
25354 @node Implementation of Specific Ada Features,Implementation of Ada 2012 Features,Specialized Needs Annexes,Top
25355 @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{417}@anchor{gnat_rm/implementation_of_specific_ada_features id1}@anchor{418}
25356 @chapter Implementation of Specific Ada Features
25359 This chapter describes the GNAT implementation of several Ada language
25363 * Machine Code Insertions::
25364 * GNAT Implementation of Tasking::
25365 * GNAT Implementation of Shared Passive Packages::
25366 * Code Generation for Array Aggregates::
25367 * The Size of Discriminated Records with Default Discriminants::
25368 * Strict Conformance to the Ada Reference Manual::
25372 @node Machine Code Insertions,GNAT Implementation of Tasking,,Implementation of Specific Ada Features
25373 @anchor{gnat_rm/implementation_of_specific_ada_features machine-code-insertions}@anchor{169}@anchor{gnat_rm/implementation_of_specific_ada_features id2}@anchor{419}
25374 @section Machine Code Insertions
25377 @geindex Machine Code insertions
25379 Package @code{Machine_Code} provides machine code support as described
25380 in the Ada Reference Manual in two separate forms:
25386 Machine code statements, consisting of qualified expressions that
25387 fit the requirements of RM section 13.8.
25390 An intrinsic callable procedure, providing an alternative mechanism of
25391 including machine instructions in a subprogram.
25394 The two features are similar, and both are closely related to the mechanism
25395 provided by the asm instruction in the GNU C compiler. Full understanding
25396 and use of the facilities in this package requires understanding the asm
25397 instruction, see the section on Extended Asm in
25398 @cite{Using_the_GNU_Compiler_Collection_(GCC)}.
25400 Calls to the function @code{Asm} and the procedure @code{Asm} have identical
25401 semantic restrictions and effects as described below. Both are provided so
25402 that the procedure call can be used as a statement, and the function call
25403 can be used to form a code_statement.
25405 Consider this C @code{asm} instruction:
25408 asm ("fsinx %1 %0" : "=f" (result) : "f" (angle));
25411 The equivalent can be written for GNAT as:
25414 Asm ("fsinx %1 %0",
25415 My_Float'Asm_Output ("=f", result),
25416 My_Float'Asm_Input ("f", angle));
25419 The first argument to @code{Asm} is the assembler template, and is
25420 identical to what is used in GNU C. This string must be a static
25421 expression. The second argument is the output operand list. It is
25422 either a single @code{Asm_Output} attribute reference, or a list of such
25423 references enclosed in parentheses (technically an array aggregate of
25426 The @code{Asm_Output} attribute denotes a function that takes two
25427 parameters. The first is a string, the second is the name of a variable
25428 of the type designated by the attribute prefix. The first (string)
25429 argument is required to be a static expression and designates the
25430 constraint (see the section on Constraints in
25431 @cite{Using_the_GNU_Compiler_Collection_(GCC)})
25432 for the parameter; e.g., what kind of register is required. The second
25433 argument is the variable to be written or updated with the
25434 result. The possible values for constraint are the same as those used in
25435 the RTL, and are dependent on the configuration file used to build the
25436 GCC back end. If there are no output operands, then this argument may
25437 either be omitted, or explicitly given as @code{No_Output_Operands}.
25438 No support is provided for GNU C's symbolic names for output parameters.
25440 The second argument of @code{my_float'Asm_Output} functions as
25441 though it were an @code{out} parameter, which is a little curious, but
25442 all names have the form of expressions, so there is no syntactic
25443 irregularity, even though normally functions would not be permitted
25444 @code{out} parameters. The third argument is the list of input
25445 operands. It is either a single @code{Asm_Input} attribute reference, or
25446 a list of such references enclosed in parentheses (technically an array
25447 aggregate of such references).
25449 The @code{Asm_Input} attribute denotes a function that takes two
25450 parameters. The first is a string, the second is an expression of the
25451 type designated by the prefix. The first (string) argument is required
25452 to be a static expression, and is the constraint for the parameter,
25453 (e.g., what kind of register is required). The second argument is the
25454 value to be used as the input argument. The possible values for the
25455 constraint are the same as those used in the RTL, and are dependent on
25456 the configuration file used to built the GCC back end.
25457 No support is provided for GNU C's symbolic names for input parameters.
25459 If there are no input operands, this argument may either be omitted, or
25460 explicitly given as @code{No_Input_Operands}. The fourth argument, not
25461 present in the above example, is a list of register names, called the
25462 @emph{clobber} argument. This argument, if given, must be a static string
25463 expression, and is a space or comma separated list of names of registers
25464 that must be considered destroyed as a result of the @code{Asm} call. If
25465 this argument is the null string (the default value), then the code
25466 generator assumes that no additional registers are destroyed.
25467 In addition to registers, the special clobbers @code{memory} and
25468 @code{cc} as described in the GNU C docs are both supported.
25470 The fifth argument, not present in the above example, called the
25471 @emph{volatile} argument, is by default @code{False}. It can be set to
25472 the literal value @code{True} to indicate to the code generator that all
25473 optimizations with respect to the instruction specified should be
25474 suppressed, and in particular an instruction that has outputs
25475 will still be generated, even if none of the outputs are
25476 used. See @cite{Using_the_GNU_Compiler_Collection_(GCC)}
25477 for the full description.
25478 Generally it is strongly advisable to use Volatile for any ASM statement
25479 that is missing either input or output operands or to avoid unwanted
25480 optimizations. A warning is generated if this advice is not followed.
25482 No support is provided for GNU C's @code{asm goto} feature.
25484 The @code{Asm} subprograms may be used in two ways. First the procedure
25485 forms can be used anywhere a procedure call would be valid, and
25486 correspond to what the RM calls 'intrinsic' routines. Such calls can
25487 be used to intersperse machine instructions with other Ada statements.
25488 Second, the function forms, which return a dummy value of the limited
25489 private type @code{Asm_Insn}, can be used in code statements, and indeed
25490 this is the only context where such calls are allowed. Code statements
25491 appear as aggregates of the form:
25494 Asm_Insn'(Asm (...));
25495 Asm_Insn'(Asm_Volatile (...));
25498 In accordance with RM rules, such code statements are allowed only
25499 within subprograms whose entire body consists of such statements. It is
25500 not permissible to intermix such statements with other Ada statements.
25502 Typically the form using intrinsic procedure calls is more convenient
25503 and more flexible. The code statement form is provided to meet the RM
25504 suggestion that such a facility should be made available. The following
25505 is the exact syntax of the call to @code{Asm}. As usual, if named notation
25506 is used, the arguments may be given in arbitrary order, following the
25507 normal rules for use of positional and named arguments:
25511 [Template =>] static_string_EXPRESSION
25512 [,[Outputs =>] OUTPUT_OPERAND_LIST ]
25513 [,[Inputs =>] INPUT_OPERAND_LIST ]
25514 [,[Clobber =>] static_string_EXPRESSION ]
25515 [,[Volatile =>] static_boolean_EXPRESSION] )
25517 OUTPUT_OPERAND_LIST ::=
25518 [PREFIX.]No_Output_Operands
25519 | OUTPUT_OPERAND_ATTRIBUTE
25520 | (OUTPUT_OPERAND_ATTRIBUTE @{,OUTPUT_OPERAND_ATTRIBUTE@})
25522 OUTPUT_OPERAND_ATTRIBUTE ::=
25523 SUBTYPE_MARK'Asm_Output (static_string_EXPRESSION, NAME)
25525 INPUT_OPERAND_LIST ::=
25526 [PREFIX.]No_Input_Operands
25527 | INPUT_OPERAND_ATTRIBUTE
25528 | (INPUT_OPERAND_ATTRIBUTE @{,INPUT_OPERAND_ATTRIBUTE@})
25530 INPUT_OPERAND_ATTRIBUTE ::=
25531 SUBTYPE_MARK'Asm_Input (static_string_EXPRESSION, EXPRESSION)
25534 The identifiers @code{No_Input_Operands} and @code{No_Output_Operands}
25535 are declared in the package @code{Machine_Code} and must be referenced
25536 according to normal visibility rules. In particular if there is no
25537 @code{use} clause for this package, then appropriate package name
25538 qualification is required.
25540 @node GNAT Implementation of Tasking,GNAT Implementation of Shared Passive Packages,Machine Code Insertions,Implementation of Specific Ada Features
25541 @anchor{gnat_rm/implementation_of_specific_ada_features id3}@anchor{41a}@anchor{gnat_rm/implementation_of_specific_ada_features gnat-implementation-of-tasking}@anchor{41b}
25542 @section GNAT Implementation of Tasking
25545 This chapter outlines the basic GNAT approach to tasking (in particular,
25546 a multi-layered library for portability) and discusses issues related
25547 to compliance with the Real-Time Systems Annex.
25550 * Mapping Ada Tasks onto the Underlying Kernel Threads::
25551 * Ensuring Compliance with the Real-Time Annex::
25552 * Support for Locking Policies::
25556 @node Mapping Ada Tasks onto the Underlying Kernel Threads,Ensuring Compliance with the Real-Time Annex,,GNAT Implementation of Tasking
25557 @anchor{gnat_rm/implementation_of_specific_ada_features mapping-ada-tasks-onto-the-underlying-kernel-threads}@anchor{41c}@anchor{gnat_rm/implementation_of_specific_ada_features id4}@anchor{41d}
25558 @subsection Mapping Ada Tasks onto the Underlying Kernel Threads
25561 GNAT's run-time support comprises two layers:
25567 GNARL (GNAT Run-time Layer)
25570 GNULL (GNAT Low-level Library)
25573 In GNAT, Ada's tasking services rely on a platform and OS independent
25574 layer known as GNARL. This code is responsible for implementing the
25575 correct semantics of Ada's task creation, rendezvous, protected
25578 GNARL decomposes Ada's tasking semantics into simpler lower level
25579 operations such as create a thread, set the priority of a thread,
25580 yield, create a lock, lock/unlock, etc. The spec for these low-level
25581 operations constitutes GNULLI, the GNULL Interface. This interface is
25582 directly inspired from the POSIX real-time API.
25584 If the underlying executive or OS implements the POSIX standard
25585 faithfully, the GNULL Interface maps as is to the services offered by
25586 the underlying kernel. Otherwise, some target dependent glue code maps
25587 the services offered by the underlying kernel to the semantics expected
25590 Whatever the underlying OS (VxWorks, UNIX, Windows, etc.) the
25591 key point is that each Ada task is mapped on a thread in the underlying
25592 kernel. For example, in the case of VxWorks, one Ada task = one VxWorks task.
25594 In addition Ada task priorities map onto the underlying thread priorities.
25595 Mapping Ada tasks onto the underlying kernel threads has several advantages:
25601 The underlying scheduler is used to schedule the Ada tasks. This
25602 makes Ada tasks as efficient as kernel threads from a scheduling
25606 Interaction with code written in C containing threads is eased
25607 since at the lowest level Ada tasks and C threads map onto the same
25608 underlying kernel concept.
25611 When an Ada task is blocked during I/O the remaining Ada tasks are
25615 On multiprocessor systems Ada tasks can execute in parallel.
25618 Some threads libraries offer a mechanism to fork a new process, with the
25619 child process duplicating the threads from the parent.
25621 support this functionality when the parent contains more than one task.
25623 @geindex Forking a new process
25625 @node Ensuring Compliance with the Real-Time Annex,Support for Locking Policies,Mapping Ada Tasks onto the Underlying Kernel Threads,GNAT Implementation of Tasking
25626 @anchor{gnat_rm/implementation_of_specific_ada_features id5}@anchor{41e}@anchor{gnat_rm/implementation_of_specific_ada_features ensuring-compliance-with-the-real-time-annex}@anchor{41f}
25627 @subsection Ensuring Compliance with the Real-Time Annex
25630 @geindex Real-Time Systems Annex compliance
25632 Although mapping Ada tasks onto
25633 the underlying threads has significant advantages, it does create some
25634 complications when it comes to respecting the scheduling semantics
25635 specified in the real-time annex (Annex D).
25637 For instance the Annex D requirement for the @code{FIFO_Within_Priorities}
25638 scheduling policy states:
25642 @emph{When the active priority of a ready task that is not running
25643 changes, or the setting of its base priority takes effect, the
25644 task is removed from the ready queue for its old active priority
25645 and is added at the tail of the ready queue for its new active
25646 priority, except in the case where the active priority is lowered
25647 due to the loss of inherited priority, in which case the task is
25648 added at the head of the ready queue for its new active priority.}
25651 While most kernels do put tasks at the end of the priority queue when
25652 a task changes its priority, (which respects the main
25653 FIFO_Within_Priorities requirement), almost none keep a thread at the
25654 beginning of its priority queue when its priority drops from the loss
25655 of inherited priority.
25657 As a result most vendors have provided incomplete Annex D implementations.
25659 The GNAT run-time, has a nice cooperative solution to this problem
25660 which ensures that accurate FIFO_Within_Priorities semantics are
25663 The principle is as follows. When an Ada task T is about to start
25664 running, it checks whether some other Ada task R with the same
25665 priority as T has been suspended due to the loss of priority
25666 inheritance. If this is the case, T yields and is placed at the end of
25667 its priority queue. When R arrives at the front of the queue it
25670 Note that this simple scheme preserves the relative order of the tasks
25671 that were ready to execute in the priority queue where R has been
25674 @c Support_for_Locking_Policies
25676 @node Support for Locking Policies,,Ensuring Compliance with the Real-Time Annex,GNAT Implementation of Tasking
25677 @anchor{gnat_rm/implementation_of_specific_ada_features support-for-locking-policies}@anchor{420}
25678 @subsection Support for Locking Policies
25681 This section specifies which policies specified by pragma Locking_Policy
25682 are supported on which platforms.
25684 GNAT supports the standard @code{Ceiling_Locking} policy, and the
25685 implementation defined @code{Inheritance_Locking} and
25686 @code{Concurrent_Readers_Locking} policies.
25688 @code{Ceiling_Locking} is supported on all platforms if the operating system
25689 supports it. In particular, @code{Ceiling_Locking} is not supported on
25691 @code{Inheritance_Locking} is supported on
25696 @code{Concurrent_Readers_Locking} is supported on Linux.
25698 Notes about @code{Ceiling_Locking} on Linux:
25699 If the process is running as 'root', ceiling locking is used.
25700 If the capabilities facility is installed
25701 ("sudo apt-get --assume-yes install libcap-dev" on Ubuntu,
25703 and the program is linked against that library
25705 and the executable file has the cap_sys_nice capability
25706 ("sudo /sbin/setcap cap_sys_nice=ep executable_file_name"),
25707 then ceiling locking is used.
25708 Otherwise, the @code{Ceiling_Locking} policy is ignored.
25710 @node GNAT Implementation of Shared Passive Packages,Code Generation for Array Aggregates,GNAT Implementation of Tasking,Implementation of Specific Ada Features
25711 @anchor{gnat_rm/implementation_of_specific_ada_features id6}@anchor{421}@anchor{gnat_rm/implementation_of_specific_ada_features gnat-implementation-of-shared-passive-packages}@anchor{422}
25712 @section GNAT Implementation of Shared Passive Packages
25715 @geindex Shared passive packages
25717 GNAT fully implements the
25718 @geindex pragma Shared_Passive
25720 @code{Shared_Passive} for
25721 the purpose of designating shared passive packages.
25722 This allows the use of passive partitions in the
25723 context described in the Ada Reference Manual; i.e., for communication
25724 between separate partitions of a distributed application using the
25725 features in Annex E.
25729 @geindex Distribution Systems Annex
25731 However, the implementation approach used by GNAT provides for more
25732 extensive usage as follows:
25737 @item @emph{Communication between separate programs}
25739 This allows separate programs to access the data in passive
25740 partitions, using protected objects for synchronization where
25741 needed. The only requirement is that the two programs have a
25742 common shared file system. It is even possible for programs
25743 running on different machines with different architectures
25744 (e.g., different endianness) to communicate via the data in
25745 a passive partition.
25747 @item @emph{Persistence between program runs}
25749 The data in a passive package can persist from one run of a
25750 program to another, so that a later program sees the final
25751 values stored by a previous run of the same program.
25754 The implementation approach used is to store the data in files. A
25755 separate stream file is created for each object in the package, and
25756 an access to an object causes the corresponding file to be read or
25759 @geindex SHARED_MEMORY_DIRECTORY environment variable
25761 The environment variable @code{SHARED_MEMORY_DIRECTORY} should be
25762 set to the directory to be used for these files.
25763 The files in this directory
25764 have names that correspond to their fully qualified names. For
25765 example, if we have the package
25769 pragma Shared_Passive (X);
25775 and the environment variable is set to @code{/stemp/}, then the files created
25776 will have the names:
25783 These files are created when a value is initially written to the object, and
25784 the files are retained until manually deleted. This provides the persistence
25785 semantics. If no file exists, it means that no partition has assigned a value
25786 to the variable; in this case the initial value declared in the package
25787 will be used. This model ensures that there are no issues in synchronizing
25788 the elaboration process, since elaboration of passive packages elaborates the
25789 initial values, but does not create the files.
25791 The files are written using normal @code{Stream_IO} access.
25792 If you want to be able
25793 to communicate between programs or partitions running on different
25794 architectures, then you should use the XDR versions of the stream attribute
25795 routines, since these are architecture independent.
25797 If active synchronization is required for access to the variables in the
25798 shared passive package, then as described in the Ada Reference Manual, the
25799 package may contain protected objects used for this purpose. In this case
25800 a lock file (whose name is @code{___lock} (three underscores)
25801 is created in the shared memory directory.
25803 @geindex ___lock file (for shared passive packages)
25805 This is used to provide the required locking
25806 semantics for proper protected object synchronization.
25808 @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
25809 @anchor{gnat_rm/implementation_of_specific_ada_features code-generation-for-array-aggregates}@anchor{423}@anchor{gnat_rm/implementation_of_specific_ada_features id7}@anchor{424}
25810 @section Code Generation for Array Aggregates
25813 Aggregates have a rich syntax and allow the user to specify the values of
25814 complex data structures by means of a single construct. As a result, the
25815 code generated for aggregates can be quite complex and involve loops, case
25816 statements and multiple assignments. In the simplest cases, however, the
25817 compiler will recognize aggregates whose components and constraints are
25818 fully static, and in those cases the compiler will generate little or no
25819 executable code. The following is an outline of the code that GNAT generates
25820 for various aggregate constructs. For further details, you will find it
25821 useful to examine the output produced by the -gnatG flag to see the expanded
25822 source that is input to the code generator. You may also want to examine
25823 the assembly code generated at various levels of optimization.
25825 The code generated for aggregates depends on the context, the component values,
25826 and the type. In the context of an object declaration the code generated is
25827 generally simpler than in the case of an assignment. As a general rule, static
25828 component values and static subtypes also lead to simpler code.
25831 * Static constant aggregates with static bounds::
25832 * Constant aggregates with unconstrained nominal types::
25833 * Aggregates with static bounds::
25834 * Aggregates with nonstatic bounds::
25835 * Aggregates in assignment statements::
25839 @node Static constant aggregates with static bounds,Constant aggregates with unconstrained nominal types,,Code Generation for Array Aggregates
25840 @anchor{gnat_rm/implementation_of_specific_ada_features static-constant-aggregates-with-static-bounds}@anchor{425}@anchor{gnat_rm/implementation_of_specific_ada_features id8}@anchor{426}
25841 @subsection Static constant aggregates with static bounds
25844 For the declarations:
25847 type One_Dim is array (1..10) of integer;
25848 ar0 : constant One_Dim := (1, 2, 3, 4, 5, 6, 7, 8, 9, 0);
25851 GNAT generates no executable code: the constant ar0 is placed in static memory.
25852 The same is true for constant aggregates with named associations:
25855 Cr1 : constant One_Dim := (4 => 16, 2 => 4, 3 => 9, 1 => 1, 5 .. 10 => 0);
25856 Cr3 : constant One_Dim := (others => 7777);
25859 The same is true for multidimensional constant arrays such as:
25862 type two_dim is array (1..3, 1..3) of integer;
25863 Unit : constant two_dim := ( (1,0,0), (0,1,0), (0,0,1));
25866 The same is true for arrays of one-dimensional arrays: the following are
25870 type ar1b is array (1..3) of boolean;
25871 type ar_ar is array (1..3) of ar1b;
25872 None : constant ar1b := (others => false); -- fully static
25873 None2 : constant ar_ar := (1..3 => None); -- fully static
25876 However, for multidimensional aggregates with named associations, GNAT will
25877 generate assignments and loops, even if all associations are static. The
25878 following two declarations generate a loop for the first dimension, and
25879 individual component assignments for the second dimension:
25882 Zero1: constant two_dim := (1..3 => (1..3 => 0));
25883 Zero2: constant two_dim := (others => (others => 0));
25886 @node Constant aggregates with unconstrained nominal types,Aggregates with static bounds,Static constant aggregates with static bounds,Code Generation for Array Aggregates
25887 @anchor{gnat_rm/implementation_of_specific_ada_features constant-aggregates-with-unconstrained-nominal-types}@anchor{427}@anchor{gnat_rm/implementation_of_specific_ada_features id9}@anchor{428}
25888 @subsection Constant aggregates with unconstrained nominal types
25891 In such cases the aggregate itself establishes the subtype, so that
25892 associations with @code{others} cannot be used. GNAT determines the
25893 bounds for the actual subtype of the aggregate, and allocates the
25894 aggregate statically as well. No code is generated for the following:
25897 type One_Unc is array (natural range <>) of integer;
25898 Cr_Unc : constant One_Unc := (12,24,36);
25901 @node Aggregates with static bounds,Aggregates with nonstatic bounds,Constant aggregates with unconstrained nominal types,Code Generation for Array Aggregates
25902 @anchor{gnat_rm/implementation_of_specific_ada_features id10}@anchor{429}@anchor{gnat_rm/implementation_of_specific_ada_features aggregates-with-static-bounds}@anchor{42a}
25903 @subsection Aggregates with static bounds
25906 In all previous examples the aggregate was the initial (and immutable) value
25907 of a constant. If the aggregate initializes a variable, then code is generated
25908 for it as a combination of individual assignments and loops over the target
25909 object. The declarations
25912 Cr_Var1 : One_Dim := (2, 5, 7, 11, 0, 0, 0, 0, 0, 0);
25913 Cr_Var2 : One_Dim := (others > -1);
25916 generate the equivalent of
25924 for I in Cr_Var2'range loop
25929 @node Aggregates with nonstatic bounds,Aggregates in assignment statements,Aggregates with static bounds,Code Generation for Array Aggregates
25930 @anchor{gnat_rm/implementation_of_specific_ada_features id11}@anchor{42b}@anchor{gnat_rm/implementation_of_specific_ada_features aggregates-with-nonstatic-bounds}@anchor{42c}
25931 @subsection Aggregates with nonstatic bounds
25934 If the bounds of the aggregate are not statically compatible with the bounds
25935 of the nominal subtype of the target, then constraint checks have to be
25936 generated on the bounds. For a multidimensional array, constraint checks may
25937 have to be applied to sub-arrays individually, if they do not have statically
25938 compatible subtypes.
25940 @node Aggregates in assignment statements,,Aggregates with nonstatic bounds,Code Generation for Array Aggregates
25941 @anchor{gnat_rm/implementation_of_specific_ada_features id12}@anchor{42d}@anchor{gnat_rm/implementation_of_specific_ada_features aggregates-in-assignment-statements}@anchor{42e}
25942 @subsection Aggregates in assignment statements
25945 In general, aggregate assignment requires the construction of a temporary,
25946 and a copy from the temporary to the target of the assignment. This is because
25947 it is not always possible to convert the assignment into a series of individual
25948 component assignments. For example, consider the simple case:
25954 This cannot be converted into:
25961 So the aggregate has to be built first in a separate location, and then
25962 copied into the target. GNAT recognizes simple cases where this intermediate
25963 step is not required, and the assignments can be performed in place, directly
25964 into the target. The following sufficient criteria are applied:
25970 The bounds of the aggregate are static, and the associations are static.
25973 The components of the aggregate are static constants, names of
25974 simple variables that are not renamings, or expressions not involving
25975 indexed components whose operands obey these rules.
25978 If any of these conditions are violated, the aggregate will be built in
25979 a temporary (created either by the front-end or the code generator) and then
25980 that temporary will be copied onto the target.
25982 @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
25983 @anchor{gnat_rm/implementation_of_specific_ada_features id13}@anchor{42f}@anchor{gnat_rm/implementation_of_specific_ada_features the-size-of-discriminated-records-with-default-discriminants}@anchor{430}
25984 @section The Size of Discriminated Records with Default Discriminants
25987 If a discriminated type @code{T} has discriminants with default values, it is
25988 possible to declare an object of this type without providing an explicit
25992 type Size is range 1..100;
25994 type Rec (D : Size := 15) is record
25995 Name : String (1..D);
26001 Such an object is said to be @emph{unconstrained}.
26002 The discriminant of the object
26003 can be modified by a full assignment to the object, as long as it preserves the
26004 relation between the value of the discriminant, and the value of the components
26008 Word := (3, "yes");
26010 Word := (5, "maybe");
26012 Word := (5, "no"); -- raises Constraint_Error
26015 In order to support this behavior efficiently, an unconstrained object is
26016 given the maximum size that any value of the type requires. In the case
26017 above, @code{Word} has storage for the discriminant and for
26018 a @code{String} of length 100.
26019 It is important to note that unconstrained objects do not require dynamic
26020 allocation. It would be an improper implementation to place on the heap those
26021 components whose size depends on discriminants. (This improper implementation
26022 was used by some Ada83 compilers, where the @code{Name} component above
26024 been stored as a pointer to a dynamic string). Following the principle that
26025 dynamic storage management should never be introduced implicitly,
26026 an Ada compiler should reserve the full size for an unconstrained declared
26027 object, and place it on the stack.
26029 This maximum size approach
26030 has been a source of surprise to some users, who expect the default
26031 values of the discriminants to determine the size reserved for an
26032 unconstrained object: "If the default is 15, why should the object occupy
26034 The answer, of course, is that the discriminant may be later modified,
26035 and its full range of values must be taken into account. This is why the
26039 type Rec (D : Positive := 15) is record
26040 Name : String (1..D);
26046 is flagged by the compiler with a warning:
26047 an attempt to create @code{Too_Large} will raise @code{Storage_Error},
26048 because the required size includes @code{Positive'Last}
26049 bytes. As the first example indicates, the proper approach is to declare an
26050 index type of 'reasonable' range so that unconstrained objects are not too
26053 One final wrinkle: if the object is declared to be @code{aliased}, or if it is
26054 created in the heap by means of an allocator, then it is @emph{not}
26056 it is constrained by the default values of the discriminants, and those values
26057 cannot be modified by full assignment. This is because in the presence of
26058 aliasing all views of the object (which may be manipulated by different tasks,
26059 say) must be consistent, so it is imperative that the object, once created,
26062 @node Strict Conformance to the Ada Reference Manual,,The Size of Discriminated Records with Default Discriminants,Implementation of Specific Ada Features
26063 @anchor{gnat_rm/implementation_of_specific_ada_features strict-conformance-to-the-ada-reference-manual}@anchor{431}@anchor{gnat_rm/implementation_of_specific_ada_features id14}@anchor{432}
26064 @section Strict Conformance to the Ada Reference Manual
26067 The dynamic semantics defined by the Ada Reference Manual impose a set of
26068 run-time checks to be generated. By default, the GNAT compiler will insert many
26069 run-time checks into the compiled code, including most of those required by the
26070 Ada Reference Manual. However, there are two checks that are not enabled in
26071 the default mode for efficiency reasons: checks for access before elaboration
26072 on subprogram calls, and stack overflow checking (most operating systems do not
26073 perform this check by default).
26075 Strict conformance to the Ada Reference Manual can be achieved by adding two
26076 compiler options for dynamic checks for access-before-elaboration on subprogram
26077 calls and generic instantiations (@emph{-gnatE}), and stack overflow checking
26078 (@emph{-fstack-check}).
26080 Note that the result of a floating point arithmetic operation in overflow and
26081 invalid situations, when the @code{Machine_Overflows} attribute of the result
26082 type is @code{False}, is to generate IEEE NaN and infinite values. This is the
26083 case for machines compliant with the IEEE floating-point standard, but on
26084 machines that are not fully compliant with this standard, such as Alpha, the
26085 @emph{-mieee} compiler flag must be used for achieving IEEE confirming
26086 behavior (although at the cost of a significant performance penalty), so
26087 infinite and NaN values are properly generated.
26089 @node Implementation of Ada 2012 Features,Obsolescent Features,Implementation of Specific Ada Features,Top
26090 @anchor{gnat_rm/implementation_of_ada_2012_features doc}@anchor{433}@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{434}
26091 @chapter Implementation of Ada 2012 Features
26094 @geindex Ada 2012 implementation status
26096 @geindex -gnat12 option (gcc)
26098 @geindex pragma Ada_2012
26100 @geindex configuration pragma Ada_2012
26102 @geindex Ada_2012 configuration pragma
26104 This chapter contains a complete list of Ada 2012 features that have been
26106 Generally, these features are only
26107 available if the @emph{-gnat12} (Ada 2012 features enabled) option is set,
26108 which is the default behavior,
26109 or if the configuration pragma @code{Ada_2012} is used.
26111 However, new pragmas, attributes, and restrictions are
26112 unconditionally available, since the Ada 95 standard allows the addition of
26113 new pragmas, attributes, and restrictions (there are exceptions, which are
26114 documented in the individual descriptions), and also certain packages
26115 were made available in earlier versions of Ada.
26117 An ISO date (YYYY-MM-DD) appears in parentheses on the description line.
26118 This date shows the implementation date of the feature. Any wavefront
26119 subsequent to this date will contain the indicated feature, as will any
26120 subsequent releases. A date of 0000-00-00 means that GNAT has always
26121 implemented the feature, or implemented it as soon as it appeared as a
26122 binding interpretation.
26124 Each feature corresponds to an Ada Issue ('AI') approved by the Ada
26125 standardization group (ISO/IEC JTC1/SC22/WG9) for inclusion in Ada 2012.
26126 The features are ordered based on the relevant sections of the Ada
26127 Reference Manual ("RM"). When a given AI relates to multiple points
26128 in the RM, the earliest is used.
26130 A complete description of the AIs may be found in
26131 @indicateurl{http://www.ada-auth.org/ai05-summary.html}.
26133 @geindex AI-0176 (Ada 2012 feature)
26139 @emph{AI-0176 Quantified expressions (2010-09-29)}
26141 Both universally and existentially quantified expressions are implemented.
26142 They use the new syntax for iterators proposed in AI05-139-2, as well as
26143 the standard Ada loop syntax.
26145 RM References: 1.01.04 (12) 2.09 (2/2) 4.04 (7) 4.05.09 (0)
26148 @geindex AI-0079 (Ada 2012 feature)
26154 @emph{AI-0079 Allow other_format characters in source (2010-07-10)}
26156 Wide characters in the unicode category @emph{other_format} are now allowed in
26157 source programs between tokens, but not within a token such as an identifier.
26159 RM References: 2.01 (4/2) 2.02 (7)
26162 @geindex AI-0091 (Ada 2012 feature)
26168 @emph{AI-0091 Do not allow other_format in identifiers (0000-00-00)}
26170 Wide characters in the unicode category @emph{other_format} are not permitted
26171 within an identifier, since this can be a security problem. The error
26172 message for this case has been improved to be more specific, but GNAT has
26173 never allowed such characters to appear in identifiers.
26175 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)
26178 @geindex AI-0100 (Ada 2012 feature)
26184 @emph{AI-0100 Placement of pragmas (2010-07-01)}
26186 This AI is an earlier version of AI-163. It simplifies the rules
26187 for legal placement of pragmas. In the case of lists that allow pragmas, if
26188 the list may have no elements, then the list may consist solely of pragmas.
26190 RM References: 2.08 (7)
26193 @geindex AI-0163 (Ada 2012 feature)
26199 @emph{AI-0163 Pragmas in place of null (2010-07-01)}
26201 A statement sequence may be composed entirely of pragmas. It is no longer
26202 necessary to add a dummy @code{null} statement to make the sequence legal.
26204 RM References: 2.08 (7) 2.08 (16)
26207 @geindex AI-0080 (Ada 2012 feature)
26213 @emph{AI-0080 'View of' not needed if clear from context (0000-00-00)}
26215 This is an editorial change only, described as non-testable in the AI.
26217 RM References: 3.01 (7)
26220 @geindex AI-0183 (Ada 2012 feature)
26226 @emph{AI-0183 Aspect specifications (2010-08-16)}
26228 Aspect specifications have been fully implemented except for pre and post-
26229 conditions, and type invariants, which have their own separate AI's. All
26230 forms of declarations listed in the AI are supported. The following is a
26231 list of the aspects supported (with GNAT implementation aspects marked)
26235 @multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxx}
26280 @code{Atomic_Components}
26292 @code{Component_Size}
26298 @code{Contract_Cases}
26306 @code{Discard_Names}
26312 @code{External_Tag}
26318 @code{Favor_Top_Level}
26332 @code{Inline_Always}
26348 @code{Machine_Radix}
26374 @code{Persistent_BSS}
26400 @code{Preelaborable_Initialization}
26406 @code{Pure_Function}
26414 @code{Remote_Access_Type}
26436 @code{Storage_Pool}
26442 @code{Storage_Size}
26460 @code{Suppress_Debug_Info}
26476 @code{Thread_Local_Storage}
26484 @code{Type_Invariant}
26490 @code{Unchecked_Union}
26496 @code{Universal_Aliasing}
26512 @code{Unreferenced}
26520 @code{Unreferenced_Objects}
26548 @code{Volatile_Components}
26565 Note that for aspects with an expression, e.g. @code{Size}, the expression is
26566 treated like a default expression (visibility is analyzed at the point of
26567 occurrence of the aspect, but evaluation of the expression occurs at the
26568 freeze point of the entity involved).
26570 RM References: 3.02.01 (3) 3.02.02 (2) 3.03.01 (2/2) 3.08 (6)
26571 3.09.03 (1.1/2) 6.01 (2/2) 6.07 (2/2) 9.05.02 (2/2) 7.01 (3) 7.03
26572 (2) 7.03 (3) 9.01 (2/2) 9.01 (3/2) 9.04 (2/2) 9.04 (3/2)
26573 9.05.02 (2/2) 11.01 (2) 12.01 (3) 12.03 (2/2) 12.04 (2/2) 12.05 (2)
26574 12.06 (2.1/2) 12.06 (2.2/2) 12.07 (2) 13.01 (0.1/2) 13.03 (5/1)
26578 @geindex AI-0128 (Ada 2012 feature)
26584 @emph{AI-0128 Inequality is a primitive operation (0000-00-00)}
26586 If an equality operator ("=") is declared for a type, then the implicitly
26587 declared inequality operator ("/=") is a primitive operation of the type.
26588 This is the only reasonable interpretation, and is the one always implemented
26589 by GNAT, but the RM was not entirely clear in making this point.
26591 RM References: 3.02.03 (6) 6.06 (6)
26594 @geindex AI-0003 (Ada 2012 feature)
26600 @emph{AI-0003 Qualified expressions as names (2010-07-11)}
26602 In Ada 2012, a qualified expression is considered to be syntactically a name,
26603 meaning that constructs such as @code{A'(F(X)).B} are now legal. This is
26604 useful in disambiguating some cases of overloading.
26606 RM References: 3.03 (11) 3.03 (21) 4.01 (2) 4.04 (7) 4.07 (3)
26610 @geindex AI-0120 (Ada 2012 feature)
26616 @emph{AI-0120 Constant instance of protected object (0000-00-00)}
26618 This is an RM editorial change only. The section that lists objects that are
26619 constant failed to include the current instance of a protected object
26620 within a protected function. This has always been treated as a constant
26623 RM References: 3.03 (21)
26626 @geindex AI-0008 (Ada 2012 feature)
26632 @emph{AI-0008 General access to constrained objects (0000-00-00)}
26634 The wording in the RM implied that if you have a general access to a
26635 constrained object, it could be used to modify the discriminants. This was
26636 obviously not intended. @code{Constraint_Error} should be raised, and GNAT
26637 has always done so in this situation.
26639 RM References: 3.03 (23) 3.10.02 (26/2) 4.01 (9) 6.04.01 (17) 8.05.01 (5/2)
26642 @geindex AI-0093 (Ada 2012 feature)
26648 @emph{AI-0093 Additional rules use immutably limited (0000-00-00)}
26650 This is an editorial change only, to make more widespread use of the Ada 2012
26651 'immutably limited'.
26653 RM References: 3.03 (23.4/3)
26656 @geindex AI-0096 (Ada 2012 feature)
26662 @emph{AI-0096 Deriving from formal private types (2010-07-20)}
26664 In general it is illegal for a type derived from a formal limited type to be
26665 nonlimited. This AI makes an exception to this rule: derivation is legal
26666 if it appears in the private part of the generic, and the formal type is not
26667 tagged. If the type is tagged, the legality check must be applied to the
26668 private part of the package.
26670 RM References: 3.04 (5.1/2) 6.02 (7)
26673 @geindex AI-0181 (Ada 2012 feature)
26679 @emph{AI-0181 Soft hyphen is a non-graphic character (2010-07-23)}
26681 From Ada 2005 on, soft hyphen is considered a non-graphic character, which
26682 means that it has a special name (@code{SOFT_HYPHEN}) in conjunction with the
26683 @code{Image} and @code{Value} attributes for the character types. Strictly
26684 speaking this is an inconsistency with Ada 95, but in practice the use of
26685 these attributes is so obscure that it will not cause problems.
26687 RM References: 3.05.02 (2/2) A.01 (35/2) A.03.03 (21)
26690 @geindex AI-0182 (Ada 2012 feature)
26696 @emph{AI-0182 Additional forms for} @code{Character'Value} @emph{(0000-00-00)}
26698 This AI allows @code{Character'Value} to accept the string @code{'?'} where
26699 @code{?} is any character including non-graphic control characters. GNAT has
26700 always accepted such strings. It also allows strings such as
26701 @code{HEX_00000041} to be accepted, but GNAT does not take advantage of this
26702 permission and raises @code{Constraint_Error}, as is certainly still
26705 RM References: 3.05 (56/2)
26708 @geindex AI-0214 (Ada 2012 feature)
26714 @emph{AI-0214 Defaulted discriminants for limited tagged (2010-10-01)}
26716 Ada 2012 relaxes the restriction that forbids discriminants of tagged types
26717 to have default expressions by allowing them when the type is limited. It
26718 is often useful to define a default value for a discriminant even though
26719 it can't be changed by assignment.
26721 RM References: 3.07 (9.1/2) 3.07.02 (3)
26724 @geindex AI-0102 (Ada 2012 feature)
26730 @emph{AI-0102 Some implicit conversions are illegal (0000-00-00)}
26732 It is illegal to assign an anonymous access constant to an anonymous access
26733 variable. The RM did not have a clear rule to prevent this, but GNAT has
26734 always generated an error for this usage.
26736 RM References: 3.07 (16) 3.07.01 (9) 6.04.01 (6) 8.06 (27/2)
26739 @geindex AI-0158 (Ada 2012 feature)
26745 @emph{AI-0158 Generalizing membership tests (2010-09-16)}
26747 This AI extends the syntax of membership tests to simplify complex conditions
26748 that can be expressed as membership in a subset of values of any type. It
26749 introduces syntax for a list of expressions that may be used in loop contexts
26752 RM References: 3.08.01 (5) 4.04 (3) 4.05.02 (3) 4.05.02 (5) 4.05.02 (27)
26755 @geindex AI-0173 (Ada 2012 feature)
26761 @emph{AI-0173 Testing if tags represent abstract types (2010-07-03)}
26763 The function @code{Ada.Tags.Type_Is_Abstract} returns @code{True} if invoked
26764 with the tag of an abstract type, and @code{False} otherwise.
26766 RM References: 3.09 (7.4/2) 3.09 (12.4/2)
26769 @geindex AI-0076 (Ada 2012 feature)
26775 @emph{AI-0076 function with controlling result (0000-00-00)}
26777 This is an editorial change only. The RM defines calls with controlling
26778 results, but uses the term 'function with controlling result' without an
26779 explicit definition.
26781 RM References: 3.09.02 (2/2)
26784 @geindex AI-0126 (Ada 2012 feature)
26790 @emph{AI-0126 Dispatching with no declared operation (0000-00-00)}
26792 This AI clarifies dispatching rules, and simply confirms that dispatching
26793 executes the operation of the parent type when there is no explicitly or
26794 implicitly declared operation for the descendant type. This has always been
26795 the case in all versions of GNAT.
26797 RM References: 3.09.02 (20/2) 3.09.02 (20.1/2) 3.09.02 (20.2/2)
26800 @geindex AI-0097 (Ada 2012 feature)
26806 @emph{AI-0097 Treatment of abstract null extension (2010-07-19)}
26808 The RM as written implied that in some cases it was possible to create an
26809 object of an abstract type, by having an abstract extension inherit a non-
26810 abstract constructor from its parent type. This mistake has been corrected
26811 in GNAT and in the RM, and this construct is now illegal.
26813 RM References: 3.09.03 (4/2)
26816 @geindex AI-0203 (Ada 2012 feature)
26822 @emph{AI-0203 Extended return cannot be abstract (0000-00-00)}
26824 A return_subtype_indication cannot denote an abstract subtype. GNAT has never
26825 permitted such usage.
26827 RM References: 3.09.03 (8/3)
26830 @geindex AI-0198 (Ada 2012 feature)
26836 @emph{AI-0198 Inheriting abstract operators (0000-00-00)}
26838 This AI resolves a conflict between two rules involving inherited abstract
26839 operations and predefined operators. If a derived numeric type inherits
26840 an abstract operator, it overrides the predefined one. This interpretation
26841 was always the one implemented in GNAT.
26843 RM References: 3.09.03 (4/3)
26846 @geindex AI-0073 (Ada 2012 feature)
26852 @emph{AI-0073 Functions returning abstract types (2010-07-10)}
26854 This AI covers a number of issues regarding returning abstract types. In
26855 particular generic functions cannot have abstract result types or access
26856 result types designated an abstract type. There are some other cases which
26857 are detailed in the AI. Note that this binding interpretation has not been
26858 retrofitted to operate before Ada 2012 mode, since it caused a significant
26859 number of regressions.
26861 RM References: 3.09.03 (8) 3.09.03 (10) 6.05 (8/2)
26864 @geindex AI-0070 (Ada 2012 feature)
26870 @emph{AI-0070 Elaboration of interface types (0000-00-00)}
26872 This is an editorial change only, there are no testable consequences short of
26873 checking for the absence of generated code for an interface declaration.
26875 RM References: 3.09.04 (18/2)
26878 @geindex AI-0208 (Ada 2012 feature)
26884 @emph{AI-0208 Characteristics of incomplete views (0000-00-00)}
26886 The wording in the Ada 2005 RM concerning characteristics of incomplete views
26887 was incorrect and implied that some programs intended to be legal were now
26888 illegal. GNAT had never considered such programs illegal, so it has always
26889 implemented the intent of this AI.
26891 RM References: 3.10.01 (2.4/2) 3.10.01 (2.6/2)
26894 @geindex AI-0162 (Ada 2012 feature)
26900 @emph{AI-0162 Incomplete type completed by partial view (2010-09-15)}
26902 Incomplete types are made more useful by allowing them to be completed by
26903 private types and private extensions.
26905 RM References: 3.10.01 (2.5/2) 3.10.01 (2.6/2) 3.10.01 (3) 3.10.01 (4/2)
26908 @geindex AI-0098 (Ada 2012 feature)
26914 @emph{AI-0098 Anonymous subprogram access restrictions (0000-00-00)}
26916 An unintentional omission in the RM implied some inconsistent restrictions on
26917 the use of anonymous access to subprogram values. These restrictions were not
26918 intentional, and have never been enforced by GNAT.
26920 RM References: 3.10.01 (6) 3.10.01 (9.2/2)
26923 @geindex AI-0199 (Ada 2012 feature)
26929 @emph{AI-0199 Aggregate with anonymous access components (2010-07-14)}
26931 A choice list in a record aggregate can include several components of
26932 (distinct) anonymous access types as long as they have matching designated
26935 RM References: 4.03.01 (16)
26938 @geindex AI-0220 (Ada 2012 feature)
26944 @emph{AI-0220 Needed components for aggregates (0000-00-00)}
26946 This AI addresses a wording problem in the RM that appears to permit some
26947 complex cases of aggregates with nonstatic discriminants. GNAT has always
26948 implemented the intended semantics.
26950 RM References: 4.03.01 (17)
26953 @geindex AI-0147 (Ada 2012 feature)
26959 @emph{AI-0147 Conditional expressions (2009-03-29)}
26961 Conditional expressions are permitted. The form of such an expression is:
26964 (if expr then expr @{elsif expr then expr@} [else expr])
26967 The parentheses can be omitted in contexts where parentheses are present
26968 anyway, such as subprogram arguments and pragma arguments. If the @strong{else}
26969 clause is omitted, @strong{else} @emph{True} is assumed;
26970 thus @code{(if A then B)} is a way to conveniently represent
26971 @emph{(A implies B)} in standard logic.
26973 RM References: 4.03.03 (15) 4.04 (1) 4.04 (7) 4.05.07 (0) 4.07 (2)
26974 4.07 (3) 4.09 (12) 4.09 (33) 5.03 (3) 5.03 (4) 7.05 (2.1/2)
26977 @geindex AI-0037 (Ada 2012 feature)
26983 @emph{AI-0037 Out-of-range box associations in aggregate (0000-00-00)}
26985 This AI confirms that an association of the form @code{Indx => <>} in an
26986 array aggregate must raise @code{Constraint_Error} if @code{Indx}
26987 is out of range. The RM specified a range check on other associations, but
26988 not when the value of the association was defaulted. GNAT has always inserted
26989 a constraint check on the index value.
26991 RM References: 4.03.03 (29)
26994 @geindex AI-0123 (Ada 2012 feature)
27000 @emph{AI-0123 Composability of equality (2010-04-13)}
27002 Equality of untagged record composes, so that the predefined equality for a
27003 composite type that includes a component of some untagged record type
27004 @code{R} uses the equality operation of @code{R} (which may be user-defined
27005 or predefined). This makes the behavior of untagged records identical to that
27006 of tagged types in this respect.
27008 This change is an incompatibility with previous versions of Ada, but it
27009 corrects a non-uniformity that was often a source of confusion. Analysis of
27010 a large number of industrial programs indicates that in those rare cases
27011 where a composite type had an untagged record component with a user-defined
27012 equality, either there was no use of the composite equality, or else the code
27013 expected the same composability as for tagged types, and thus had a bug that
27014 would be fixed by this change.
27016 RM References: 4.05.02 (9.7/2) 4.05.02 (14) 4.05.02 (15) 4.05.02 (24)
27020 @geindex AI-0088 (Ada 2012 feature)
27026 @emph{AI-0088 The value of exponentiation (0000-00-00)}
27028 This AI clarifies the equivalence rule given for the dynamic semantics of
27029 exponentiation: the value of the operation can be obtained by repeated
27030 multiplication, but the operation can be implemented otherwise (for example
27031 using the familiar divide-by-two-and-square algorithm, even if this is less
27032 accurate), and does not imply repeated reads of a volatile base.
27034 RM References: 4.05.06 (11)
27037 @geindex AI-0188 (Ada 2012 feature)
27043 @emph{AI-0188 Case expressions (2010-01-09)}
27045 Case expressions are permitted. This allows use of constructs such as:
27048 X := (case Y is when 1 => 2, when 2 => 3, when others => 31)
27051 RM References: 4.05.07 (0) 4.05.08 (0) 4.09 (12) 4.09 (33)
27054 @geindex AI-0104 (Ada 2012 feature)
27060 @emph{AI-0104 Null exclusion and uninitialized allocator (2010-07-15)}
27062 The assignment @code{Ptr := new not null Some_Ptr;} will raise
27063 @code{Constraint_Error} because the default value of the allocated object is
27064 @strong{null}. This useless construct is illegal in Ada 2012.
27066 RM References: 4.08 (2)
27069 @geindex AI-0157 (Ada 2012 feature)
27075 @emph{AI-0157 Allocation/Deallocation from empty pool (2010-07-11)}
27077 Allocation and Deallocation from an empty storage pool (i.e. allocation or
27078 deallocation of a pointer for which a static storage size clause of zero
27079 has been given) is now illegal and is detected as such. GNAT
27080 previously gave a warning but not an error.
27082 RM References: 4.08 (5.3/2) 13.11.02 (4) 13.11.02 (17)
27085 @geindex AI-0179 (Ada 2012 feature)
27091 @emph{AI-0179 Statement not required after label (2010-04-10)}
27093 It is not necessary to have a statement following a label, so a label
27094 can appear at the end of a statement sequence without the need for putting a
27095 null statement afterwards, but it is not allowable to have only labels and
27096 no real statements in a statement sequence.
27098 RM References: 5.01 (2)
27101 @geindex AI-0139-2 (Ada 2012 feature)
27107 @emph{AI-0139-2 Syntactic sugar for iterators (2010-09-29)}
27109 The new syntax for iterating over arrays and containers is now implemented.
27110 Iteration over containers is for now limited to read-only iterators. Only
27111 default iterators are supported, with the syntax: @code{for Elem of C}.
27113 RM References: 5.05
27116 @geindex AI-0134 (Ada 2012 feature)
27122 @emph{AI-0134 Profiles must match for full conformance (0000-00-00)}
27124 For full conformance, the profiles of anonymous-access-to-subprogram
27125 parameters must match. GNAT has always enforced this rule.
27127 RM References: 6.03.01 (18)
27130 @geindex AI-0207 (Ada 2012 feature)
27136 @emph{AI-0207 Mode conformance and access constant (0000-00-00)}
27138 This AI confirms that access_to_constant indication must match for mode
27139 conformance. This was implemented in GNAT when the qualifier was originally
27140 introduced in Ada 2005.
27142 RM References: 6.03.01 (16/2)
27145 @geindex AI-0046 (Ada 2012 feature)
27151 @emph{AI-0046 Null exclusion match for full conformance (2010-07-17)}
27153 For full conformance, in the case of access parameters, the null exclusion
27154 must match (either both or neither must have @code{not null}).
27156 RM References: 6.03.02 (18)
27159 @geindex AI-0118 (Ada 2012 feature)
27165 @emph{AI-0118 The association of parameter associations (0000-00-00)}
27167 This AI clarifies the rules for named associations in subprogram calls and
27168 generic instantiations. The rules have been in place since Ada 83.
27170 RM References: 6.04.01 (2) 12.03 (9)
27173 @geindex AI-0196 (Ada 2012 feature)
27179 @emph{AI-0196 Null exclusion tests for out parameters (0000-00-00)}
27181 Null exclusion checks are not made for @code{out} parameters when
27182 evaluating the actual parameters. GNAT has never generated these checks.
27184 RM References: 6.04.01 (13)
27187 @geindex AI-0015 (Ada 2012 feature)
27193 @emph{AI-0015 Constant return objects (0000-00-00)}
27195 The return object declared in an @emph{extended_return_statement} may be
27196 declared constant. This was always intended, and GNAT has always allowed it.
27198 RM References: 6.05 (2.1/2) 3.03 (10/2) 3.03 (21) 6.05 (5/2)
27202 @geindex AI-0032 (Ada 2012 feature)
27208 @emph{AI-0032 Extended return for class-wide functions (0000-00-00)}
27210 If a function returns a class-wide type, the object of an extended return
27211 statement can be declared with a specific type that is covered by the class-
27212 wide type. This has been implemented in GNAT since the introduction of
27213 extended returns. Note AI-0103 complements this AI by imposing matching
27214 rules for constrained return types.
27216 RM References: 6.05 (5.2/2) 6.05 (5.3/2) 6.05 (5.6/2) 6.05 (5.8/2)
27220 @geindex AI-0103 (Ada 2012 feature)
27226 @emph{AI-0103 Static matching for extended return (2010-07-23)}
27228 If the return subtype of a function is an elementary type or a constrained
27229 type, the subtype indication in an extended return statement must match
27230 statically this return subtype.
27232 RM References: 6.05 (5.2/2)
27235 @geindex AI-0058 (Ada 2012 feature)
27241 @emph{AI-0058 Abnormal completion of an extended return (0000-00-00)}
27243 The RM had some incorrect wording implying wrong treatment of abnormal
27244 completion in an extended return. GNAT has always implemented the intended
27245 correct semantics as described by this AI.
27247 RM References: 6.05 (22/2)
27250 @geindex AI-0050 (Ada 2012 feature)
27256 @emph{AI-0050 Raising Constraint_Error early for function call (0000-00-00)}
27258 The implementation permissions for raising @code{Constraint_Error} early on a function call
27259 when it was clear an exception would be raised were over-permissive and allowed
27260 mishandling of discriminants in some cases. GNAT did
27261 not take advantage of these incorrect permissions in any case.
27263 RM References: 6.05 (24/2)
27266 @geindex AI-0125 (Ada 2012 feature)
27272 @emph{AI-0125 Nonoverridable operations of an ancestor (2010-09-28)}
27274 In Ada 2012, the declaration of a primitive operation of a type extension
27275 or private extension can also override an inherited primitive that is not
27276 visible at the point of this declaration.
27278 RM References: 7.03.01 (6) 8.03 (23) 8.03.01 (5/2) 8.03.01 (6/2)
27281 @geindex AI-0062 (Ada 2012 feature)
27287 @emph{AI-0062 Null exclusions and deferred constants (0000-00-00)}
27289 A full constant may have a null exclusion even if its associated deferred
27290 constant does not. GNAT has always allowed this.
27292 RM References: 7.04 (6/2) 7.04 (7.1/2)
27295 @geindex AI-0178 (Ada 2012 feature)
27301 @emph{AI-0178 Incomplete views are limited (0000-00-00)}
27303 This AI clarifies the role of incomplete views and plugs an omission in the
27304 RM. GNAT always correctly restricted the use of incomplete views and types.
27306 RM References: 7.05 (3/2) 7.05 (6/2)
27309 @geindex AI-0087 (Ada 2012 feature)
27315 @emph{AI-0087 Actual for formal nonlimited derived type (2010-07-15)}
27317 The actual for a formal nonlimited derived type cannot be limited. In
27318 particular, a formal derived type that extends a limited interface but which
27319 is not explicitly limited cannot be instantiated with a limited type.
27321 RM References: 7.05 (5/2) 12.05.01 (5.1/2)
27324 @geindex AI-0099 (Ada 2012 feature)
27330 @emph{AI-0099 Tag determines whether finalization needed (0000-00-00)}
27332 This AI clarifies that 'needs finalization' is part of dynamic semantics,
27333 and therefore depends on the run-time characteristics of an object (i.e. its
27334 tag) and not on its nominal type. As the AI indicates: "we do not expect
27335 this to affect any implementation'@w{'}.
27337 RM References: 7.06.01 (6) 7.06.01 (7) 7.06.01 (8) 7.06.01 (9/2)
27340 @geindex AI-0064 (Ada 2012 feature)
27346 @emph{AI-0064 Redundant finalization rule (0000-00-00)}
27348 This is an editorial change only. The intended behavior is already checked
27349 by an existing ACATS test, which GNAT has always executed correctly.
27351 RM References: 7.06.01 (17.1/1)
27354 @geindex AI-0026 (Ada 2012 feature)
27360 @emph{AI-0026 Missing rules for Unchecked_Union (2010-07-07)}
27362 Record representation clauses concerning Unchecked_Union types cannot mention
27363 the discriminant of the type. The type of a component declared in the variant
27364 part of an Unchecked_Union cannot be controlled, have controlled components,
27365 nor have protected or task parts. If an Unchecked_Union type is declared
27366 within the body of a generic unit or its descendants, then the type of a
27367 component declared in the variant part cannot be a formal private type or a
27368 formal private extension declared within the same generic unit.
27370 RM References: 7.06 (9.4/2) B.03.03 (9/2) B.03.03 (10/2)
27373 @geindex AI-0205 (Ada 2012 feature)
27379 @emph{AI-0205 Extended return declares visible name (0000-00-00)}
27381 This AI corrects a simple omission in the RM. Return objects have always
27382 been visible within an extended return statement.
27384 RM References: 8.03 (17)
27387 @geindex AI-0042 (Ada 2012 feature)
27393 @emph{AI-0042 Overriding versus implemented-by (0000-00-00)}
27395 This AI fixes a wording gap in the RM. An operation of a synchronized
27396 interface can be implemented by a protected or task entry, but the abstract
27397 operation is not being overridden in the usual sense, and it must be stated
27398 separately that this implementation is legal. This has always been the case
27401 RM References: 9.01 (9.2/2) 9.04 (11.1/2)
27404 @geindex AI-0030 (Ada 2012 feature)
27410 @emph{AI-0030 Requeue on synchronized interfaces (2010-07-19)}
27412 Requeue is permitted to a protected, synchronized or task interface primitive
27413 providing it is known that the overriding operation is an entry. Otherwise
27414 the requeue statement has the same effect as a procedure call. Use of pragma
27415 @code{Implemented} provides a way to impose a static requirement on the
27416 overriding operation by adhering to one of the implementation kinds: entry,
27417 protected procedure or any of the above.
27419 RM References: 9.05 (9) 9.05.04 (2) 9.05.04 (3) 9.05.04 (5)
27420 9.05.04 (6) 9.05.04 (7) 9.05.04 (12)
27423 @geindex AI-0201 (Ada 2012 feature)
27429 @emph{AI-0201 Independence of atomic object components (2010-07-22)}
27431 If an Atomic object has a pragma @code{Pack} or a @code{Component_Size}
27432 attribute, then individual components may not be addressable by independent
27433 tasks. However, if the representation clause has no effect (is confirming),
27434 then independence is not compromised. Furthermore, in GNAT, specification of
27435 other appropriately addressable component sizes (e.g. 16 for 8-bit
27436 characters) also preserves independence. GNAT now gives very clear warnings
27437 both for the declaration of such a type, and for any assignment to its components.
27439 RM References: 9.10 (1/3) C.06 (22/2) C.06 (23/2)
27442 @geindex AI-0009 (Ada 2012 feature)
27448 @emph{AI-0009 Pragma Independent[_Components] (2010-07-23)}
27450 This AI introduces the new pragmas @code{Independent} and
27451 @code{Independent_Components},
27452 which control guaranteeing independence of access to objects and components.
27453 The AI also requires independence not unaffected by confirming rep clauses.
27455 RM References: 9.10 (1) 13.01 (15/1) 13.02 (9) 13.03 (13) C.06 (2)
27456 C.06 (4) C.06 (6) C.06 (9) C.06 (13) C.06 (14)
27459 @geindex AI-0072 (Ada 2012 feature)
27465 @emph{AI-0072 Task signalling using 'Terminated (0000-00-00)}
27467 This AI clarifies that task signalling for reading @code{'Terminated} only
27468 occurs if the result is True. GNAT semantics has always been consistent with
27469 this notion of task signalling.
27471 RM References: 9.10 (6.1/1)
27474 @geindex AI-0108 (Ada 2012 feature)
27480 @emph{AI-0108 Limited incomplete view and discriminants (0000-00-00)}
27482 This AI confirms that an incomplete type from a limited view does not have
27483 discriminants. This has always been the case in GNAT.
27485 RM References: 10.01.01 (12.3/2)
27488 @geindex AI-0129 (Ada 2012 feature)
27494 @emph{AI-0129 Limited views and incomplete types (0000-00-00)}
27496 This AI clarifies the description of limited views: a limited view of a
27497 package includes only one view of a type that has an incomplete declaration
27498 and a full declaration (there is no possible ambiguity in a client package).
27499 This AI also fixes an omission: a nested package in the private part has no
27500 limited view. GNAT always implemented this correctly.
27502 RM References: 10.01.01 (12.2/2) 10.01.01 (12.3/2)
27505 @geindex AI-0077 (Ada 2012 feature)
27511 @emph{AI-0077 Limited withs and scope of declarations (0000-00-00)}
27513 This AI clarifies that a declaration does not include a context clause,
27514 and confirms that it is illegal to have a context in which both a limited
27515 and a nonlimited view of a package are accessible. Such double visibility
27516 was always rejected by GNAT.
27518 RM References: 10.01.02 (12/2) 10.01.02 (21/2) 10.01.02 (22/2)
27521 @geindex AI-0122 (Ada 2012 feature)
27527 @emph{AI-0122 Private with and children of generics (0000-00-00)}
27529 This AI clarifies the visibility of private children of generic units within
27530 instantiations of a parent. GNAT has always handled this correctly.
27532 RM References: 10.01.02 (12/2)
27535 @geindex AI-0040 (Ada 2012 feature)
27541 @emph{AI-0040 Limited with clauses on descendant (0000-00-00)}
27543 This AI confirms that a limited with clause in a child unit cannot name
27544 an ancestor of the unit. This has always been checked in GNAT.
27546 RM References: 10.01.02 (20/2)
27549 @geindex AI-0132 (Ada 2012 feature)
27555 @emph{AI-0132 Placement of library unit pragmas (0000-00-00)}
27557 This AI fills a gap in the description of library unit pragmas. The pragma
27558 clearly must apply to a library unit, even if it does not carry the name
27559 of the enclosing unit. GNAT has always enforced the required check.
27561 RM References: 10.01.05 (7)
27564 @geindex AI-0034 (Ada 2012 feature)
27570 @emph{AI-0034 Categorization of limited views (0000-00-00)}
27572 The RM makes certain limited with clauses illegal because of categorization
27573 considerations, when the corresponding normal with would be legal. This is
27574 not intended, and GNAT has always implemented the recommended behavior.
27576 RM References: 10.02.01 (11/1) 10.02.01 (17/2)
27579 @geindex AI-0035 (Ada 2012 feature)
27585 @emph{AI-0035 Inconsistencies with Pure units (0000-00-00)}
27587 This AI remedies some inconsistencies in the legality rules for Pure units.
27588 Derived access types are legal in a pure unit (on the assumption that the
27589 rule for a zero storage pool size has been enforced on the ancestor type).
27590 The rules are enforced in generic instances and in subunits. GNAT has always
27591 implemented the recommended behavior.
27593 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)
27596 @geindex AI-0219 (Ada 2012 feature)
27602 @emph{AI-0219 Pure permissions and limited parameters (2010-05-25)}
27604 This AI refines the rules for the cases with limited parameters which do not
27605 allow the implementations to omit 'redundant'. GNAT now properly conforms
27606 to the requirements of this binding interpretation.
27608 RM References: 10.02.01 (18/2)
27611 @geindex AI-0043 (Ada 2012 feature)
27617 @emph{AI-0043 Rules about raising exceptions (0000-00-00)}
27619 This AI covers various omissions in the RM regarding the raising of
27620 exceptions. GNAT has always implemented the intended semantics.
27622 RM References: 11.04.01 (10.1/2) 11 (2)
27625 @geindex AI-0200 (Ada 2012 feature)
27631 @emph{AI-0200 Mismatches in formal package declarations (0000-00-00)}
27633 This AI plugs a gap in the RM which appeared to allow some obviously intended
27634 illegal instantiations. GNAT has never allowed these instantiations.
27636 RM References: 12.07 (16)
27639 @geindex AI-0112 (Ada 2012 feature)
27645 @emph{AI-0112 Detection of duplicate pragmas (2010-07-24)}
27647 This AI concerns giving names to various representation aspects, but the
27648 practical effect is simply to make the use of duplicate
27649 @code{Atomic[_Components]},
27650 @code{Volatile[_Components]}, and
27651 @code{Independent[_Components]} pragmas illegal, and GNAT
27652 now performs this required check.
27654 RM References: 13.01 (8)
27657 @geindex AI-0106 (Ada 2012 feature)
27663 @emph{AI-0106 No representation pragmas on generic formals (0000-00-00)}
27665 The RM appeared to allow representation pragmas on generic formal parameters,
27666 but this was not intended, and GNAT has never permitted this usage.
27668 RM References: 13.01 (9.1/1)
27671 @geindex AI-0012 (Ada 2012 feature)
27677 @emph{AI-0012 Pack/Component_Size for aliased/atomic (2010-07-15)}
27679 It is now illegal to give an inappropriate component size or a pragma
27680 @code{Pack} that attempts to change the component size in the case of atomic
27681 or aliased components. Previously GNAT ignored such an attempt with a
27684 RM References: 13.02 (6.1/2) 13.02 (7) C.06 (10) C.06 (11) C.06 (21)
27687 @geindex AI-0039 (Ada 2012 feature)
27693 @emph{AI-0039 Stream attributes cannot be dynamic (0000-00-00)}
27695 The RM permitted the use of dynamic expressions (such as @code{ptr.all})`
27696 for stream attributes, but these were never useful and are now illegal. GNAT
27697 has always regarded such expressions as illegal.
27699 RM References: 13.03 (4) 13.03 (6) 13.13.02 (38/2)
27702 @geindex AI-0095 (Ada 2012 feature)
27708 @emph{AI-0095 Address of intrinsic subprograms (0000-00-00)}
27710 The prefix of @code{'Address} cannot statically denote a subprogram with
27711 convention @code{Intrinsic}. The use of the @code{Address} attribute raises
27712 @code{Program_Error} if the prefix denotes a subprogram with convention
27715 RM References: 13.03 (11/1)
27718 @geindex AI-0116 (Ada 2012 feature)
27724 @emph{AI-0116 Alignment of class-wide objects (0000-00-00)}
27726 This AI requires that the alignment of a class-wide object be no greater
27727 than the alignment of any type in the class. GNAT has always followed this
27730 RM References: 13.03 (29) 13.11 (16)
27733 @geindex AI-0146 (Ada 2012 feature)
27739 @emph{AI-0146 Type invariants (2009-09-21)}
27741 Type invariants may be specified for private types using the aspect notation.
27742 Aspect @code{Type_Invariant} may be specified for any private type,
27743 @code{Type_Invariant'Class} can
27744 only be specified for tagged types, and is inherited by any descendent of the
27745 tagged types. The invariant is a boolean expression that is tested for being
27746 true in the following situations: conversions to the private type, object
27747 declarations for the private type that are default initialized, and
27748 [@strong{in}] @strong{out}
27749 parameters and returned result on return from any primitive operation for
27750 the type that is visible to a client.
27751 GNAT defines the synonyms @code{Invariant} for @code{Type_Invariant} and
27752 @code{Invariant'Class} for @code{Type_Invariant'Class}.
27754 RM References: 13.03.03 (00)
27757 @geindex AI-0078 (Ada 2012 feature)
27763 @emph{AI-0078 Relax Unchecked_Conversion alignment rules (0000-00-00)}
27765 In Ada 2012, compilers are required to support unchecked conversion where the
27766 target alignment is a multiple of the source alignment. GNAT always supported
27767 this case (and indeed all cases of differing alignments, doing copies where
27768 required if the alignment was reduced).
27770 RM References: 13.09 (7)
27773 @geindex AI-0195 (Ada 2012 feature)
27779 @emph{AI-0195 Invalid value handling is implementation defined (2010-07-03)}
27781 The handling of invalid values is now designated to be implementation
27782 defined. This is a documentation change only, requiring Annex M in the GNAT
27783 Reference Manual to document this handling.
27784 In GNAT, checks for invalid values are made
27785 only when necessary to avoid erroneous behavior. Operations like assignments
27786 which cannot cause erroneous behavior ignore the possibility of invalid
27787 values and do not do a check. The date given above applies only to the
27788 documentation change, this behavior has always been implemented by GNAT.
27790 RM References: 13.09.01 (10)
27793 @geindex AI-0193 (Ada 2012 feature)
27799 @emph{AI-0193 Alignment of allocators (2010-09-16)}
27801 This AI introduces a new attribute @code{Max_Alignment_For_Allocation},
27802 analogous to @code{Max_Size_In_Storage_Elements}, but for alignment instead
27805 RM References: 13.11 (16) 13.11 (21) 13.11.01 (0) 13.11.01 (1)
27806 13.11.01 (2) 13.11.01 (3)
27809 @geindex AI-0177 (Ada 2012 feature)
27815 @emph{AI-0177 Parameterized expressions (2010-07-10)}
27817 The new Ada 2012 notion of parameterized expressions is implemented. The form
27821 function-specification is (expression)
27824 This is exactly equivalent to the
27825 corresponding function body that returns the expression, but it can appear
27826 in a package spec. Note that the expression must be parenthesized.
27828 RM References: 13.11.01 (3/2)
27831 @geindex AI-0033 (Ada 2012 feature)
27837 @emph{AI-0033 Attach/Interrupt_Handler in generic (2010-07-24)}
27839 Neither of these two pragmas may appear within a generic template, because
27840 the generic might be instantiated at other than the library level.
27842 RM References: 13.11.02 (16) C.03.01 (7/2) C.03.01 (8/2)
27845 @geindex AI-0161 (Ada 2012 feature)
27851 @emph{AI-0161 Restriction No_Default_Stream_Attributes (2010-09-11)}
27853 A new restriction @code{No_Default_Stream_Attributes} prevents the use of any
27854 of the default stream attributes for elementary types. If this restriction is
27855 in force, then it is necessary to provide explicit subprograms for any
27856 stream attributes used.
27858 RM References: 13.12.01 (4/2) 13.13.02 (40/2) 13.13.02 (52/2)
27861 @geindex AI-0194 (Ada 2012 feature)
27867 @emph{AI-0194 Value of Stream_Size attribute (0000-00-00)}
27869 The @code{Stream_Size} attribute returns the default number of bits in the
27870 stream representation of the given type.
27871 This value is not affected by the presence
27872 of stream subprogram attributes for the type. GNAT has always implemented
27873 this interpretation.
27875 RM References: 13.13.02 (1.2/2)
27878 @geindex AI-0109 (Ada 2012 feature)
27884 @emph{AI-0109 Redundant check in S'Class'Input (0000-00-00)}
27886 This AI is an editorial change only. It removes the need for a tag check
27887 that can never fail.
27889 RM References: 13.13.02 (34/2)
27892 @geindex AI-0007 (Ada 2012 feature)
27898 @emph{AI-0007 Stream read and private scalar types (0000-00-00)}
27900 The RM as written appeared to limit the possibilities of declaring read
27901 attribute procedures for private scalar types. This limitation was not
27902 intended, and has never been enforced by GNAT.
27904 RM References: 13.13.02 (50/2) 13.13.02 (51/2)
27907 @geindex AI-0065 (Ada 2012 feature)
27913 @emph{AI-0065 Remote access types and external streaming (0000-00-00)}
27915 This AI clarifies the fact that all remote access types support external
27916 streaming. This fixes an obvious oversight in the definition of the
27917 language, and GNAT always implemented the intended correct rules.
27919 RM References: 13.13.02 (52/2)
27922 @geindex AI-0019 (Ada 2012 feature)
27928 @emph{AI-0019 Freezing of primitives for tagged types (0000-00-00)}
27930 The RM suggests that primitive subprograms of a specific tagged type are
27931 frozen when the tagged type is frozen. This would be an incompatible change
27932 and is not intended. GNAT has never attempted this kind of freezing and its
27933 behavior is consistent with the recommendation of this AI.
27935 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)
27938 @geindex AI-0017 (Ada 2012 feature)
27944 @emph{AI-0017 Freezing and incomplete types (0000-00-00)}
27946 So-called 'Taft-amendment types' (i.e., types that are completed in package
27947 bodies) are not frozen by the occurrence of bodies in the
27948 enclosing declarative part. GNAT always implemented this properly.
27950 RM References: 13.14 (3/1)
27953 @geindex AI-0060 (Ada 2012 feature)
27959 @emph{AI-0060 Extended definition of remote access types (0000-00-00)}
27961 This AI extends the definition of remote access types to include access
27962 to limited, synchronized, protected or task class-wide interface types.
27963 GNAT already implemented this extension.
27965 RM References: A (4) E.02.02 (9/1) E.02.02 (9.2/1) E.02.02 (14/2) E.02.02 (18)
27968 @geindex AI-0114 (Ada 2012 feature)
27974 @emph{AI-0114 Classification of letters (0000-00-00)}
27976 The code points 170 (@code{FEMININE ORDINAL INDICATOR}),
27977 181 (@code{MICRO SIGN}), and
27978 186 (@code{MASCULINE ORDINAL INDICATOR}) are technically considered
27979 lower case letters by Unicode.
27980 However, they are not allowed in identifiers, and they
27981 return @code{False} to @code{Ada.Characters.Handling.Is_Letter/Is_Lower}.
27982 This behavior is consistent with that defined in Ada 95.
27984 RM References: A.03.02 (59) A.04.06 (7)
27987 @geindex AI-0185 (Ada 2012 feature)
27993 @emph{AI-0185 Ada.Wide_[Wide_]Characters.Handling (2010-07-06)}
27995 Two new packages @code{Ada.Wide_[Wide_]Characters.Handling} provide
27996 classification functions for @code{Wide_Character} and
27997 @code{Wide_Wide_Character}, as well as providing
27998 case folding routines for @code{Wide_[Wide_]Character} and
27999 @code{Wide_[Wide_]String}.
28001 RM References: A.03.05 (0) A.03.06 (0)
28004 @geindex AI-0031 (Ada 2012 feature)
28010 @emph{AI-0031 Add From parameter to Find_Token (2010-07-25)}
28012 A new version of @code{Find_Token} is added to all relevant string packages,
28013 with an extra parameter @code{From}. Instead of starting at the first
28014 character of the string, the search for a matching Token starts at the
28015 character indexed by the value of @code{From}.
28016 These procedures are available in all versions of Ada
28017 but if used in versions earlier than Ada 2012 they will generate a warning
28018 that an Ada 2012 subprogram is being used.
28020 RM References: A.04.03 (16) A.04.03 (67) A.04.03 (68/1) A.04.04 (51)
28024 @geindex AI-0056 (Ada 2012 feature)
28030 @emph{AI-0056 Index on null string returns zero (0000-00-00)}
28032 The wording in the Ada 2005 RM implied an incompatible handling of the
28033 @code{Index} functions, resulting in raising an exception instead of
28034 returning zero in some situations.
28035 This was not intended and has been corrected.
28036 GNAT always returned zero, and is thus consistent with this AI.
28038 RM References: A.04.03 (56.2/2) A.04.03 (58.5/2)
28041 @geindex AI-0137 (Ada 2012 feature)
28047 @emph{AI-0137 String encoding package (2010-03-25)}
28049 The packages @code{Ada.Strings.UTF_Encoding}, together with its child
28050 packages, @code{Conversions}, @code{Strings}, @code{Wide_Strings},
28051 and @code{Wide_Wide_Strings} have been
28052 implemented. These packages (whose documentation can be found in the spec
28053 files @code{a-stuten.ads}, @code{a-suenco.ads}, @code{a-suenst.ads},
28054 @code{a-suewst.ads}, @code{a-suezst.ads}) allow encoding and decoding of
28055 @code{String}, @code{Wide_String}, and @code{Wide_Wide_String}
28056 values using UTF coding schemes (including UTF-8, UTF-16LE, UTF-16BE, and
28057 UTF-16), as well as conversions between the different UTF encodings. With
28058 the exception of @code{Wide_Wide_Strings}, these packages are available in
28059 Ada 95 and Ada 2005 mode as well as Ada 2012 mode.
28060 The @code{Wide_Wide_Strings} package
28061 is available in Ada 2005 mode as well as Ada 2012 mode (but not in Ada 95
28062 mode since it uses @code{Wide_Wide_Character}).
28064 RM References: A.04.11
28067 @geindex AI-0038 (Ada 2012 feature)
28073 @emph{AI-0038 Minor errors in Text_IO (0000-00-00)}
28075 These are minor errors in the description on three points. The intent on
28076 all these points has always been clear, and GNAT has always implemented the
28077 correct intended semantics.
28079 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)
28082 @geindex AI-0044 (Ada 2012 feature)
28088 @emph{AI-0044 Restrictions on container instantiations (0000-00-00)}
28090 This AI places restrictions on allowed instantiations of generic containers.
28091 These restrictions are not checked by the compiler, so there is nothing to
28092 change in the implementation. This affects only the RM documentation.
28094 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)
28097 @geindex AI-0127 (Ada 2012 feature)
28103 @emph{AI-0127 Adding Locale Capabilities (2010-09-29)}
28105 This package provides an interface for identifying the current locale.
28107 RM References: A.19 A.19.01 A.19.02 A.19.03 A.19.05 A.19.06
28108 A.19.07 A.19.08 A.19.09 A.19.10 A.19.11 A.19.12 A.19.13
28111 @geindex AI-0002 (Ada 2012 feature)
28117 @emph{AI-0002 Export C with unconstrained arrays (0000-00-00)}
28119 The compiler is not required to support exporting an Ada subprogram with
28120 convention C if there are parameters or a return type of an unconstrained
28121 array type (such as @code{String}). GNAT allows such declarations but
28122 generates warnings. It is possible, but complicated, to write the
28123 corresponding C code and certainly such code would be specific to GNAT and
28126 RM References: B.01 (17) B.03 (62) B.03 (71.1/2)
28129 @geindex AI05-0216 (Ada 2012 feature)
28135 @emph{AI-0216 No_Task_Hierarchy forbids local tasks (0000-00-00)}
28137 It is clearly the intention that @code{No_Task_Hierarchy} is intended to
28138 forbid tasks declared locally within subprograms, or functions returning task
28139 objects, and that is the implementation that GNAT has always provided.
28140 However the language in the RM was not sufficiently clear on this point.
28141 Thus this is a documentation change in the RM only.
28143 RM References: D.07 (3/3)
28146 @geindex AI-0211 (Ada 2012 feature)
28152 @emph{AI-0211 No_Relative_Delays forbids Set_Handler use (2010-07-09)}
28154 The restriction @code{No_Relative_Delays} forbids any calls to the subprogram
28155 @code{Ada.Real_Time.Timing_Events.Set_Handler}.
28157 RM References: D.07 (5) D.07 (10/2) D.07 (10.4/2) D.07 (10.7/2)
28160 @geindex AI-0190 (Ada 2012 feature)
28166 @emph{AI-0190 pragma Default_Storage_Pool (2010-09-15)}
28168 This AI introduces a new pragma @code{Default_Storage_Pool}, which can be
28169 used to control storage pools globally.
28170 In particular, you can force every access
28171 type that is used for allocation (@strong{new}) to have an explicit storage pool,
28172 or you can declare a pool globally to be used for all access types that lack
28175 RM References: D.07 (8)
28178 @geindex AI-0189 (Ada 2012 feature)
28184 @emph{AI-0189 No_Allocators_After_Elaboration (2010-01-23)}
28186 This AI introduces a new restriction @code{No_Allocators_After_Elaboration},
28187 which says that no dynamic allocation will occur once elaboration is
28189 In general this requires a run-time check, which is not required, and which
28190 GNAT does not attempt. But the static cases of allocators in a task body or
28191 in the body of the main program are detected and flagged at compile or bind
28194 RM References: D.07 (19.1/2) H.04 (23.3/2)
28197 @geindex AI-0171 (Ada 2012 feature)
28203 @emph{AI-0171 Pragma CPU and Ravenscar Profile (2010-09-24)}
28205 A new package @code{System.Multiprocessors} is added, together with the
28206 definition of pragma @code{CPU} for controlling task affinity. A new no
28207 dependence restriction, on @code{System.Multiprocessors.Dispatching_Domains},
28208 is added to the Ravenscar profile.
28210 RM References: D.13.01 (4/2) D.16
28213 @geindex AI-0210 (Ada 2012 feature)
28219 @emph{AI-0210 Correct Timing_Events metric (0000-00-00)}
28221 This is a documentation only issue regarding wording of metric requirements,
28222 that does not affect the implementation of the compiler.
28224 RM References: D.15 (24/2)
28227 @geindex AI-0206 (Ada 2012 feature)
28233 @emph{AI-0206 Remote types packages and preelaborate (2010-07-24)}
28235 Remote types packages are now allowed to depend on preelaborated packages.
28236 This was formerly considered illegal.
28238 RM References: E.02.02 (6)
28241 @geindex AI-0152 (Ada 2012 feature)
28247 @emph{AI-0152 Restriction No_Anonymous_Allocators (2010-09-08)}
28249 Restriction @code{No_Anonymous_Allocators} prevents the use of allocators
28250 where the type of the returned value is an anonymous access type.
28252 RM References: H.04 (8/1)
28255 @node Obsolescent Features,Compatibility and Porting Guide,Implementation of Ada 2012 Features,Top
28256 @anchor{gnat_rm/obsolescent_features id1}@anchor{435}@anchor{gnat_rm/obsolescent_features doc}@anchor{436}@anchor{gnat_rm/obsolescent_features obsolescent-features}@anchor{15}
28257 @chapter Obsolescent Features
28260 This chapter describes features that are provided by GNAT, but are
28261 considered obsolescent since there are preferred ways of achieving
28262 the same effect. These features are provided solely for historical
28263 compatibility purposes.
28266 * pragma No_Run_Time::
28267 * pragma Ravenscar::
28268 * pragma Restricted_Run_Time::
28269 * pragma Task_Info::
28270 * package System.Task_Info (s-tasinf.ads): package System Task_Info s-tasinf ads.
28274 @node pragma No_Run_Time,pragma Ravenscar,,Obsolescent Features
28275 @anchor{gnat_rm/obsolescent_features id2}@anchor{437}@anchor{gnat_rm/obsolescent_features pragma-no-run-time}@anchor{438}
28276 @section pragma No_Run_Time
28279 The pragma @code{No_Run_Time} is used to achieve an affect similar
28280 to the use of the "Zero Foot Print" configurable run time, but without
28281 requiring a specially configured run time. The result of using this
28282 pragma, which must be used for all units in a partition, is to restrict
28283 the use of any language features requiring run-time support code. The
28284 preferred usage is to use an appropriately configured run-time that
28285 includes just those features that are to be made accessible.
28287 @node pragma Ravenscar,pragma Restricted_Run_Time,pragma No_Run_Time,Obsolescent Features
28288 @anchor{gnat_rm/obsolescent_features id3}@anchor{439}@anchor{gnat_rm/obsolescent_features pragma-ravenscar}@anchor{43a}
28289 @section pragma Ravenscar
28292 The pragma @code{Ravenscar} has exactly the same effect as pragma
28293 @code{Profile (Ravenscar)}. The latter usage is preferred since it
28294 is part of the new Ada 2005 standard.
28296 @node pragma Restricted_Run_Time,pragma Task_Info,pragma Ravenscar,Obsolescent Features
28297 @anchor{gnat_rm/obsolescent_features pragma-restricted-run-time}@anchor{43b}@anchor{gnat_rm/obsolescent_features id4}@anchor{43c}
28298 @section pragma Restricted_Run_Time
28301 The pragma @code{Restricted_Run_Time} has exactly the same effect as
28302 pragma @code{Profile (Restricted)}. The latter usage is
28303 preferred since the Ada 2005 pragma @code{Profile} is intended for
28304 this kind of implementation dependent addition.
28306 @node pragma Task_Info,package System Task_Info s-tasinf ads,pragma Restricted_Run_Time,Obsolescent Features
28307 @anchor{gnat_rm/obsolescent_features pragma-task-info}@anchor{43d}@anchor{gnat_rm/obsolescent_features id5}@anchor{43e}
28308 @section pragma Task_Info
28311 The functionality provided by pragma @code{Task_Info} is now part of the
28312 Ada language. The @code{CPU} aspect and the package
28313 @code{System.Multiprocessors} offer a less system-dependent way to specify
28314 task affinity or to query the number of processors.
28319 pragma Task_Info (EXPRESSION);
28322 This pragma appears within a task definition (like pragma
28323 @code{Priority}) and applies to the task in which it appears. The
28324 argument must be of type @code{System.Task_Info.Task_Info_Type}.
28325 The @code{Task_Info} pragma provides system dependent control over
28326 aspects of tasking implementation, for example, the ability to map
28327 tasks to specific processors. For details on the facilities available
28328 for the version of GNAT that you are using, see the documentation
28329 in the spec of package System.Task_Info in the runtime
28332 @node package System Task_Info s-tasinf ads,,pragma Task_Info,Obsolescent Features
28333 @anchor{gnat_rm/obsolescent_features package-system-task-info}@anchor{43f}@anchor{gnat_rm/obsolescent_features package-system-task-info-s-tasinf-ads}@anchor{440}
28334 @section package System.Task_Info (@code{s-tasinf.ads})
28337 This package provides target dependent functionality that is used
28338 to support the @code{Task_Info} pragma. The predefined Ada package
28339 @code{System.Multiprocessors} and the @code{CPU} aspect now provide a
28340 standard replacement for GNAT's @code{Task_Info} functionality.
28342 @node Compatibility and Porting Guide,GNU Free Documentation License,Obsolescent Features,Top
28343 @anchor{gnat_rm/compatibility_and_porting_guide compatibility-and-porting-guide}@anchor{16}@anchor{gnat_rm/compatibility_and_porting_guide doc}@anchor{441}@anchor{gnat_rm/compatibility_and_porting_guide id1}@anchor{442}
28344 @chapter Compatibility and Porting Guide
28347 This chapter presents some guidelines for developing portable Ada code,
28348 describes the compatibility issues that may arise between
28349 GNAT and other Ada compilation systems (including those for Ada 83),
28350 and shows how GNAT can expedite porting
28351 applications developed in other Ada environments.
28354 * Writing Portable Fixed-Point Declarations::
28355 * Compatibility with Ada 83::
28356 * Compatibility between Ada 95 and Ada 2005::
28357 * Implementation-dependent characteristics::
28358 * Compatibility with Other Ada Systems::
28359 * Representation Clauses::
28360 * Compatibility with HP Ada 83::
28364 @node Writing Portable Fixed-Point Declarations,Compatibility with Ada 83,,Compatibility and Porting Guide
28365 @anchor{gnat_rm/compatibility_and_porting_guide id2}@anchor{443}@anchor{gnat_rm/compatibility_and_porting_guide writing-portable-fixed-point-declarations}@anchor{444}
28366 @section Writing Portable Fixed-Point Declarations
28369 The Ada Reference Manual gives an implementation freedom to choose bounds
28370 that are narrower by @code{Small} from the given bounds.
28371 For example, if we write
28374 type F1 is delta 1.0 range -128.0 .. +128.0;
28377 then the implementation is allowed to choose -128.0 .. +127.0 if it
28378 likes, but is not required to do so.
28380 This leads to possible portability problems, so let's have a closer
28381 look at this, and figure out how to avoid these problems.
28383 First, why does this freedom exist, and why would an implementation
28384 take advantage of it? To answer this, take a closer look at the type
28385 declaration for @code{F1} above. If the compiler uses the given bounds,
28386 it would need 9 bits to hold the largest positive value (and typically
28387 that means 16 bits on all machines). But if the implementation chooses
28388 the +127.0 bound then it can fit values of the type in 8 bits.
28390 Why not make the user write +127.0 if that's what is wanted?
28391 The rationale is that if you are thinking of fixed point
28392 as a kind of 'poor man's floating-point', then you don't want
28393 to be thinking about the scaled integers that are used in its
28394 representation. Let's take another example:
28397 type F2 is delta 2.0**(-15) range -1.0 .. +1.0;
28400 Looking at this declaration, it seems casually as though
28401 it should fit in 16 bits, but again that extra positive value
28402 +1.0 has the scaled integer equivalent of 2**15 which is one too
28403 big for signed 16 bits. The implementation can treat this as:
28406 type F2 is delta 2.0**(-15) range -1.0 .. +1.0-(2.0**(-15));
28409 and the Ada language design team felt that this was too annoying
28410 to require. We don't need to debate this decision at this point,
28411 since it is well established (the rule about narrowing the ranges
28414 But the important point is that an implementation is not required
28415 to do this narrowing, so we have a potential portability problem.
28416 We could imagine three types of implementation:
28422 those that narrow the range automatically if they can figure
28423 out that the narrower range will allow storage in a smaller machine unit,
28426 those that will narrow only if forced to by a @code{'Size} clause, and
28429 those that will never narrow.
28432 Now if we are language theoreticians, we can imagine a fourth
28433 approach: to narrow all the time, e.g. to treat
28436 type F3 is delta 1.0 range -10.0 .. +23.0;
28439 as though it had been written:
28442 type F3 is delta 1.0 range -9.0 .. +22.0;
28445 But although technically allowed, such a behavior would be hostile and silly,
28446 and no real compiler would do this. All real compilers will fall into one of
28447 the categories (a), (b) or (c) above.
28449 So, how do you get the compiler to do what you want? The answer is give the
28450 actual bounds you want, and then use a @code{'Small} clause and a
28451 @code{'Size} clause to absolutely pin down what the compiler does.
28452 E.g., for @code{F2} above, we will write:
28455 My_Small : constant := 2.0**(-15);
28456 My_First : constant := -1.0;
28457 My_Last : constant := +1.0 - My_Small;
28459 type F2 is delta My_Small range My_First .. My_Last;
28465 for F2'Small use my_Small;
28466 for F2'Size use 16;
28469 In practice all compilers will do the same thing here and will give you
28470 what you want, so the above declarations are fully portable. If you really
28471 want to play language lawyer and guard against ludicrous behavior by the
28472 compiler you could add
28475 Test1 : constant := 1 / Boolean'Pos (F2'First = My_First);
28476 Test2 : constant := 1 / Boolean'Pos (F2'Last = My_Last);
28479 One or other or both are allowed to be illegal if the compiler is
28480 behaving in a silly manner, but at least the silly compiler will not
28481 get away with silently messing with your (very clear) intentions.
28483 If you follow this scheme you will be guaranteed that your fixed-point
28484 types will be portable.
28486 @node Compatibility with Ada 83,Compatibility between Ada 95 and Ada 2005,Writing Portable Fixed-Point Declarations,Compatibility and Porting Guide
28487 @anchor{gnat_rm/compatibility_and_porting_guide compatibility-with-ada-83}@anchor{445}@anchor{gnat_rm/compatibility_and_porting_guide id3}@anchor{446}
28488 @section Compatibility with Ada 83
28491 @geindex Compatibility (between Ada 83 and Ada 95 / Ada 2005 / Ada 2012)
28493 Ada 95 and the subsequent revisions Ada 2005 and Ada 2012
28494 are highly upwards compatible with Ada 83. In
28495 particular, the design intention was that the difficulties associated
28496 with moving from Ada 83 to later versions of the standard should be no greater
28497 than those that occur when moving from one Ada 83 system to another.
28499 However, there are a number of points at which there are minor
28500 incompatibilities. The @cite{Ada 95 Annotated Reference Manual} contains
28501 full details of these issues as they relate to Ada 95,
28502 and should be consulted for a complete treatment.
28504 following subsections treat the most likely issues to be encountered.
28507 * Legal Ada 83 programs that are illegal in Ada 95::
28508 * More deterministic semantics::
28509 * Changed semantics::
28510 * Other language compatibility issues::
28514 @node Legal Ada 83 programs that are illegal in Ada 95,More deterministic semantics,,Compatibility with Ada 83
28515 @anchor{gnat_rm/compatibility_and_porting_guide id4}@anchor{447}@anchor{gnat_rm/compatibility_and_porting_guide legal-ada-83-programs-that-are-illegal-in-ada-95}@anchor{448}
28516 @subsection Legal Ada 83 programs that are illegal in Ada 95
28519 Some legal Ada 83 programs are illegal (i.e., they will fail to compile) in
28520 Ada 95 and later versions of the standard:
28526 @emph{Character literals}
28528 Some uses of character literals are ambiguous. Since Ada 95 has introduced
28529 @code{Wide_Character} as a new predefined character type, some uses of
28530 character literals that were legal in Ada 83 are illegal in Ada 95.
28534 for Char in 'A' .. 'Z' loop ... end loop;
28537 The problem is that 'A' and 'Z' could be from either
28538 @code{Character} or @code{Wide_Character}. The simplest correction
28539 is to make the type explicit; e.g.:
28542 for Char in Character range 'A' .. 'Z' loop ... end loop;
28546 @emph{New reserved words}
28548 The identifiers @code{abstract}, @code{aliased}, @code{protected},
28549 @code{requeue}, @code{tagged}, and @code{until} are reserved in Ada 95.
28550 Existing Ada 83 code using any of these identifiers must be edited to
28551 use some alternative name.
28554 @emph{Freezing rules}
28556 The rules in Ada 95 are slightly different with regard to the point at
28557 which entities are frozen, and representation pragmas and clauses are
28558 not permitted past the freeze point. This shows up most typically in
28559 the form of an error message complaining that a representation item
28560 appears too late, and the appropriate corrective action is to move
28561 the item nearer to the declaration of the entity to which it refers.
28563 A particular case is that representation pragmas
28564 cannot be applied to a subprogram body. If necessary, a separate subprogram
28565 declaration must be introduced to which the pragma can be applied.
28568 @emph{Optional bodies for library packages}
28570 In Ada 83, a package that did not require a package body was nevertheless
28571 allowed to have one. This lead to certain surprises in compiling large
28572 systems (situations in which the body could be unexpectedly ignored by the
28573 binder). In Ada 95, if a package does not require a body then it is not
28574 permitted to have a body. To fix this problem, simply remove a redundant
28575 body if it is empty, or, if it is non-empty, introduce a dummy declaration
28576 into the spec that makes the body required. One approach is to add a private
28577 part to the package declaration (if necessary), and define a parameterless
28578 procedure called @code{Requires_Body}, which must then be given a dummy
28579 procedure body in the package body, which then becomes required.
28580 Another approach (assuming that this does not introduce elaboration
28581 circularities) is to add an @code{Elaborate_Body} pragma to the package spec,
28582 since one effect of this pragma is to require the presence of a package body.
28585 @emph{Numeric_Error is the same exception as Constraint_Error}
28587 In Ada 95, the exception @code{Numeric_Error} is a renaming of @code{Constraint_Error}.
28588 This means that it is illegal to have separate exception handlers for
28589 the two exceptions. The fix is simply to remove the handler for the
28590 @code{Numeric_Error} case (since even in Ada 83, a compiler was free to raise
28591 @code{Constraint_Error} in place of @code{Numeric_Error} in all cases).
28594 @emph{Indefinite subtypes in generics}
28596 In Ada 83, it was permissible to pass an indefinite type (e.g, @code{String})
28597 as the actual for a generic formal private type, but then the instantiation
28598 would be illegal if there were any instances of declarations of variables
28599 of this type in the generic body. In Ada 95, to avoid this clear violation
28600 of the methodological principle known as the 'contract model',
28601 the generic declaration explicitly indicates whether
28602 or not such instantiations are permitted. If a generic formal parameter
28603 has explicit unknown discriminants, indicated by using @code{(<>)} after the
28604 subtype name, then it can be instantiated with indefinite types, but no
28605 stand-alone variables can be declared of this type. Any attempt to declare
28606 such a variable will result in an illegality at the time the generic is
28607 declared. If the @code{(<>)} notation is not used, then it is illegal
28608 to instantiate the generic with an indefinite type.
28609 This is the potential incompatibility issue when porting Ada 83 code to Ada 95.
28610 It will show up as a compile time error, and
28611 the fix is usually simply to add the @code{(<>)} to the generic declaration.
28614 @node More deterministic semantics,Changed semantics,Legal Ada 83 programs that are illegal in Ada 95,Compatibility with Ada 83
28615 @anchor{gnat_rm/compatibility_and_porting_guide more-deterministic-semantics}@anchor{449}@anchor{gnat_rm/compatibility_and_porting_guide id5}@anchor{44a}
28616 @subsection More deterministic semantics
28625 Conversions from real types to integer types round away from 0. In Ada 83
28626 the conversion Integer(2.5) could deliver either 2 or 3 as its value. This
28627 implementation freedom was intended to support unbiased rounding in
28628 statistical applications, but in practice it interfered with portability.
28629 In Ada 95 the conversion semantics are unambiguous, and rounding away from 0
28630 is required. Numeric code may be affected by this change in semantics.
28631 Note, though, that this issue is no worse than already existed in Ada 83
28632 when porting code from one vendor to another.
28637 The Real-Time Annex introduces a set of policies that define the behavior of
28638 features that were implementation dependent in Ada 83, such as the order in
28639 which open select branches are executed.
28642 @node Changed semantics,Other language compatibility issues,More deterministic semantics,Compatibility with Ada 83
28643 @anchor{gnat_rm/compatibility_and_porting_guide id6}@anchor{44b}@anchor{gnat_rm/compatibility_and_porting_guide changed-semantics}@anchor{44c}
28644 @subsection Changed semantics
28647 The worst kind of incompatibility is one where a program that is legal in
28648 Ada 83 is also legal in Ada 95 but can have an effect in Ada 95 that was not
28649 possible in Ada 83. Fortunately this is extremely rare, but the one
28650 situation that you should be alert to is the change in the predefined type
28651 @code{Character} from 7-bit ASCII to 8-bit Latin-1.
28662 @emph{Range of type `@w{`}Character`@w{`}}
28664 The range of @code{Standard.Character} is now the full 256 characters
28665 of Latin-1, whereas in most Ada 83 implementations it was restricted
28666 to 128 characters. Although some of the effects of
28667 this change will be manifest in compile-time rejection of legal
28668 Ada 83 programs it is possible for a working Ada 83 program to have
28669 a different effect in Ada 95, one that was not permitted in Ada 83.
28670 As an example, the expression
28671 @code{Character'Pos(Character'Last)} returned @code{127} in Ada 83 and now
28672 delivers @code{255} as its value.
28673 In general, you should look at the logic of any
28674 character-processing Ada 83 program and see whether it needs to be adapted
28675 to work correctly with Latin-1. Note that the predefined Ada 95 API has a
28676 character handling package that may be relevant if code needs to be adapted
28677 to account for the additional Latin-1 elements.
28678 The desirable fix is to
28679 modify the program to accommodate the full character set, but in some cases
28680 it may be convenient to define a subtype or derived type of Character that
28681 covers only the restricted range.
28684 @node Other language compatibility issues,,Changed semantics,Compatibility with Ada 83
28685 @anchor{gnat_rm/compatibility_and_porting_guide other-language-compatibility-issues}@anchor{44d}@anchor{gnat_rm/compatibility_and_porting_guide id7}@anchor{44e}
28686 @subsection Other language compatibility issues
28693 @emph{-gnat83} switch
28695 All implementations of GNAT provide a switch that causes GNAT to operate
28696 in Ada 83 mode. In this mode, some but not all compatibility problems
28697 of the type described above are handled automatically. For example, the
28698 new reserved words introduced in Ada 95 and Ada 2005 are treated simply
28699 as identifiers as in Ada 83. However,
28700 in practice, it is usually advisable to make the necessary modifications
28701 to the program to remove the need for using this switch.
28702 See the @code{Compiling Different Versions of Ada} section in
28703 the @cite{GNAT User's Guide}.
28706 Support for removed Ada 83 pragmas and attributes
28708 A number of pragmas and attributes from Ada 83 were removed from Ada 95,
28709 generally because they were replaced by other mechanisms. Ada 95 and Ada 2005
28710 compilers are allowed, but not required, to implement these missing
28711 elements. In contrast with some other compilers, GNAT implements all
28712 such pragmas and attributes, eliminating this compatibility concern. These
28713 include @code{pragma Interface} and the floating point type attributes
28714 (@code{Emax}, @code{Mantissa}, etc.), among other items.
28717 @node Compatibility between Ada 95 and Ada 2005,Implementation-dependent characteristics,Compatibility with Ada 83,Compatibility and Porting Guide
28718 @anchor{gnat_rm/compatibility_and_porting_guide compatibility-between-ada-95-and-ada-2005}@anchor{44f}@anchor{gnat_rm/compatibility_and_porting_guide id8}@anchor{450}
28719 @section Compatibility between Ada 95 and Ada 2005
28722 @geindex Compatibility between Ada 95 and Ada 2005
28724 Although Ada 2005 was designed to be upwards compatible with Ada 95, there are
28725 a number of incompatibilities. Several are enumerated below;
28726 for a complete description please see the
28727 @cite{Annotated Ada 2005 Reference Manual}, or section 9.1.1 in
28728 @cite{Rationale for Ada 2005}.
28734 @emph{New reserved words.}
28736 The words @code{interface}, @code{overriding} and @code{synchronized} are
28737 reserved in Ada 2005.
28738 A pre-Ada 2005 program that uses any of these as an identifier will be
28742 @emph{New declarations in predefined packages.}
28744 A number of packages in the predefined environment contain new declarations:
28745 @code{Ada.Exceptions}, @code{Ada.Real_Time}, @code{Ada.Strings},
28746 @code{Ada.Strings.Fixed}, @code{Ada.Strings.Bounded},
28747 @code{Ada.Strings.Unbounded}, @code{Ada.Strings.Wide_Fixed},
28748 @code{Ada.Strings.Wide_Bounded}, @code{Ada.Strings.Wide_Unbounded},
28749 @code{Ada.Tags}, @code{Ada.Text_IO}, and @code{Interfaces.C}.
28750 If an Ada 95 program does a @code{with} and @code{use} of any of these
28751 packages, the new declarations may cause name clashes.
28754 @emph{Access parameters.}
28756 A nondispatching subprogram with an access parameter cannot be renamed
28757 as a dispatching operation. This was permitted in Ada 95.
28760 @emph{Access types, discriminants, and constraints.}
28762 Rule changes in this area have led to some incompatibilities; for example,
28763 constrained subtypes of some access types are not permitted in Ada 2005.
28766 @emph{Aggregates for limited types.}
28768 The allowance of aggregates for limited types in Ada 2005 raises the
28769 possibility of ambiguities in legal Ada 95 programs, since additional types
28770 now need to be considered in expression resolution.
28773 @emph{Fixed-point multiplication and division.}
28775 Certain expressions involving '*' or '/' for a fixed-point type, which
28776 were legal in Ada 95 and invoked the predefined versions of these operations,
28778 The ambiguity may be resolved either by applying a type conversion to the
28779 expression, or by explicitly invoking the operation from package
28783 @emph{Return-by-reference types.}
28785 The Ada 95 return-by-reference mechanism has been removed. Instead, the user
28786 can declare a function returning a value from an anonymous access type.
28789 @node Implementation-dependent characteristics,Compatibility with Other Ada Systems,Compatibility between Ada 95 and Ada 2005,Compatibility and Porting Guide
28790 @anchor{gnat_rm/compatibility_and_porting_guide implementation-dependent-characteristics}@anchor{451}@anchor{gnat_rm/compatibility_and_porting_guide id9}@anchor{452}
28791 @section Implementation-dependent characteristics
28794 Although the Ada language defines the semantics of each construct as
28795 precisely as practical, in some situations (for example for reasons of
28796 efficiency, or where the effect is heavily dependent on the host or target
28797 platform) the implementation is allowed some freedom. In porting Ada 83
28798 code to GNAT, you need to be aware of whether / how the existing code
28799 exercised such implementation dependencies. Such characteristics fall into
28800 several categories, and GNAT offers specific support in assisting the
28801 transition from certain Ada 83 compilers.
28804 * Implementation-defined pragmas::
28805 * Implementation-defined attributes::
28807 * Elaboration order::
28808 * Target-specific aspects::
28812 @node Implementation-defined pragmas,Implementation-defined attributes,,Implementation-dependent characteristics
28813 @anchor{gnat_rm/compatibility_and_porting_guide implementation-defined-pragmas}@anchor{453}@anchor{gnat_rm/compatibility_and_porting_guide id10}@anchor{454}
28814 @subsection Implementation-defined pragmas
28817 Ada compilers are allowed to supplement the language-defined pragmas, and
28818 these are a potential source of non-portability. All GNAT-defined pragmas
28819 are described in @ref{7,,Implementation Defined Pragmas},
28820 and these include several that are specifically
28821 intended to correspond to other vendors' Ada 83 pragmas.
28822 For migrating from VADS, the pragma @code{Use_VADS_Size} may be useful.
28823 For compatibility with HP Ada 83, GNAT supplies the pragmas
28824 @code{Extend_System}, @code{Ident}, @code{Inline_Generic},
28825 @code{Interface_Name}, @code{Passive}, @code{Suppress_All},
28826 and @code{Volatile}.
28827 Other relevant pragmas include @code{External} and @code{Link_With}.
28828 Some vendor-specific
28829 Ada 83 pragmas (@code{Share_Generic}, @code{Subtitle}, and @code{Title}) are
28831 avoiding compiler rejection of units that contain such pragmas; they are not
28832 relevant in a GNAT context and hence are not otherwise implemented.
28834 @node Implementation-defined attributes,Libraries,Implementation-defined pragmas,Implementation-dependent characteristics
28835 @anchor{gnat_rm/compatibility_and_porting_guide id11}@anchor{455}@anchor{gnat_rm/compatibility_and_porting_guide implementation-defined-attributes}@anchor{456}
28836 @subsection Implementation-defined attributes
28839 Analogous to pragmas, the set of attributes may be extended by an
28840 implementation. All GNAT-defined attributes are described in
28841 @ref{8,,Implementation Defined Attributes},
28842 and these include several that are specifically intended
28843 to correspond to other vendors' Ada 83 attributes. For migrating from VADS,
28844 the attribute @code{VADS_Size} may be useful. For compatibility with HP
28845 Ada 83, GNAT supplies the attributes @code{Bit}, @code{Machine_Size} and
28848 @node Libraries,Elaboration order,Implementation-defined attributes,Implementation-dependent characteristics
28849 @anchor{gnat_rm/compatibility_and_porting_guide libraries}@anchor{457}@anchor{gnat_rm/compatibility_and_porting_guide id12}@anchor{458}
28850 @subsection Libraries
28853 Vendors may supply libraries to supplement the standard Ada API. If Ada 83
28854 code uses vendor-specific libraries then there are several ways to manage
28855 this in Ada 95 and later versions of the standard:
28861 If the source code for the libraries (specs and bodies) are
28862 available, then the libraries can be migrated in the same way as the
28866 If the source code for the specs but not the bodies are
28867 available, then you can reimplement the bodies.
28870 Some features introduced by Ada 95 obviate the need for library support. For
28871 example most Ada 83 vendors supplied a package for unsigned integers. The
28872 Ada 95 modular type feature is the preferred way to handle this need, so
28873 instead of migrating or reimplementing the unsigned integer package it may
28874 be preferable to retrofit the application using modular types.
28877 @node Elaboration order,Target-specific aspects,Libraries,Implementation-dependent characteristics
28878 @anchor{gnat_rm/compatibility_and_porting_guide elaboration-order}@anchor{459}@anchor{gnat_rm/compatibility_and_porting_guide id13}@anchor{45a}
28879 @subsection Elaboration order
28882 The implementation can choose any elaboration order consistent with the unit
28883 dependency relationship. This freedom means that some orders can result in
28884 Program_Error being raised due to an 'Access Before Elaboration': an attempt
28885 to invoke a subprogram before its body has been elaborated, or to instantiate
28886 a generic before the generic body has been elaborated. By default GNAT
28887 attempts to choose a safe order (one that will not encounter access before
28888 elaboration problems) by implicitly inserting @code{Elaborate} or
28889 @code{Elaborate_All} pragmas where
28890 needed. However, this can lead to the creation of elaboration circularities
28891 and a resulting rejection of the program by gnatbind. This issue is
28892 thoroughly described in the @emph{Elaboration Order Handling in GNAT} appendix
28893 in the @cite{GNAT User's Guide}.
28894 In brief, there are several
28895 ways to deal with this situation:
28901 Modify the program to eliminate the circularities, e.g., by moving
28902 elaboration-time code into explicitly-invoked procedures
28905 Constrain the elaboration order by including explicit @code{Elaborate_Body} or
28906 @code{Elaborate} pragmas, and then inhibit the generation of implicit
28907 @code{Elaborate_All}
28908 pragmas either globally (as an effect of the @emph{-gnatE} switch) or locally
28909 (by selectively suppressing elaboration checks via pragma
28910 @code{Suppress(Elaboration_Check)} when it is safe to do so).
28913 @node Target-specific aspects,,Elaboration order,Implementation-dependent characteristics
28914 @anchor{gnat_rm/compatibility_and_porting_guide target-specific-aspects}@anchor{45b}@anchor{gnat_rm/compatibility_and_porting_guide id14}@anchor{45c}
28915 @subsection Target-specific aspects
28918 Low-level applications need to deal with machine addresses, data
28919 representations, interfacing with assembler code, and similar issues. If
28920 such an Ada 83 application is being ported to different target hardware (for
28921 example where the byte endianness has changed) then you will need to
28922 carefully examine the program logic; the porting effort will heavily depend
28923 on the robustness of the original design. Moreover, Ada 95 (and thus
28924 Ada 2005 and Ada 2012) are sometimes
28925 incompatible with typical Ada 83 compiler practices regarding implicit
28926 packing, the meaning of the Size attribute, and the size of access values.
28927 GNAT's approach to these issues is described in @ref{45d,,Representation Clauses}.
28929 @node Compatibility with Other Ada Systems,Representation Clauses,Implementation-dependent characteristics,Compatibility and Porting Guide
28930 @anchor{gnat_rm/compatibility_and_porting_guide id15}@anchor{45e}@anchor{gnat_rm/compatibility_and_porting_guide compatibility-with-other-ada-systems}@anchor{45f}
28931 @section Compatibility with Other Ada Systems
28934 If programs avoid the use of implementation dependent and
28935 implementation defined features, as documented in the
28936 @cite{Ada Reference Manual}, there should be a high degree of portability between
28937 GNAT and other Ada systems. The following are specific items which
28938 have proved troublesome in moving Ada 95 programs from GNAT to other Ada 95
28939 compilers, but do not affect porting code to GNAT.
28940 (As of January 2007, GNAT is the only compiler available for Ada 2005;
28941 the following issues may or may not arise for Ada 2005 programs
28942 when other compilers appear.)
28948 @emph{Ada 83 Pragmas and Attributes}
28950 Ada 95 compilers are allowed, but not required, to implement the missing
28951 Ada 83 pragmas and attributes that are no longer defined in Ada 95.
28952 GNAT implements all such pragmas and attributes, eliminating this as
28953 a compatibility concern, but some other Ada 95 compilers reject these
28954 pragmas and attributes.
28957 @emph{Specialized Needs Annexes}
28959 GNAT implements the full set of special needs annexes. At the
28960 current time, it is the only Ada 95 compiler to do so. This means that
28961 programs making use of these features may not be portable to other Ada
28962 95 compilation systems.
28965 @emph{Representation Clauses}
28967 Some other Ada 95 compilers implement only the minimal set of
28968 representation clauses required by the Ada 95 reference manual. GNAT goes
28969 far beyond this minimal set, as described in the next section.
28972 @node Representation Clauses,Compatibility with HP Ada 83,Compatibility with Other Ada Systems,Compatibility and Porting Guide
28973 @anchor{gnat_rm/compatibility_and_porting_guide representation-clauses}@anchor{45d}@anchor{gnat_rm/compatibility_and_porting_guide id16}@anchor{460}
28974 @section Representation Clauses
28977 The Ada 83 reference manual was quite vague in describing both the minimal
28978 required implementation of representation clauses, and also their precise
28979 effects. Ada 95 (and thus also Ada 2005) are much more explicit, but the
28980 minimal set of capabilities required is still quite limited.
28982 GNAT implements the full required set of capabilities in
28983 Ada 95 and Ada 2005, but also goes much further, and in particular
28984 an effort has been made to be compatible with existing Ada 83 usage to the
28985 greatest extent possible.
28987 A few cases exist in which Ada 83 compiler behavior is incompatible with
28988 the requirements in Ada 95 (and thus also Ada 2005). These are instances of
28989 intentional or accidental dependence on specific implementation dependent
28990 characteristics of these Ada 83 compilers. The following is a list of
28991 the cases most likely to arise in existing Ada 83 code.
28997 @emph{Implicit Packing}
28999 Some Ada 83 compilers allowed a Size specification to cause implicit
29000 packing of an array or record. This could cause expensive implicit
29001 conversions for change of representation in the presence of derived
29002 types, and the Ada design intends to avoid this possibility.
29003 Subsequent AI's were issued to make it clear that such implicit
29004 change of representation in response to a Size clause is inadvisable,
29005 and this recommendation is represented explicitly in the Ada 95 (and Ada 2005)
29006 Reference Manuals as implementation advice that is followed by GNAT.
29007 The problem will show up as an error
29008 message rejecting the size clause. The fix is simply to provide
29009 the explicit pragma @code{Pack}, or for more fine tuned control, provide
29010 a Component_Size clause.
29013 @emph{Meaning of Size Attribute}
29015 The Size attribute in Ada 95 (and Ada 2005) for discrete types is defined as
29016 the minimal number of bits required to hold values of the type. For example,
29017 on a 32-bit machine, the size of @code{Natural} will typically be 31 and not
29018 32 (since no sign bit is required). Some Ada 83 compilers gave 31, and
29019 some 32 in this situation. This problem will usually show up as a compile
29020 time error, but not always. It is a good idea to check all uses of the
29021 'Size attribute when porting Ada 83 code. The GNAT specific attribute
29022 Object_Size can provide a useful way of duplicating the behavior of
29023 some Ada 83 compiler systems.
29026 @emph{Size of Access Types}
29028 A common assumption in Ada 83 code is that an access type is in fact a pointer,
29029 and that therefore it will be the same size as a System.Address value. This
29030 assumption is true for GNAT in most cases with one exception. For the case of
29031 a pointer to an unconstrained array type (where the bounds may vary from one
29032 value of the access type to another), the default is to use a 'fat pointer',
29033 which is represented as two separate pointers, one to the bounds, and one to
29034 the array. This representation has a number of advantages, including improved
29035 efficiency. However, it may cause some difficulties in porting existing Ada 83
29036 code which makes the assumption that, for example, pointers fit in 32 bits on
29037 a machine with 32-bit addressing.
29039 To get around this problem, GNAT also permits the use of 'thin pointers' for
29040 access types in this case (where the designated type is an unconstrained array
29041 type). These thin pointers are indeed the same size as a System.Address value.
29042 To specify a thin pointer, use a size clause for the type, for example:
29045 type X is access all String;
29046 for X'Size use Standard'Address_Size;
29049 which will cause the type X to be represented using a single pointer.
29050 When using this representation, the bounds are right behind the array.
29051 This representation is slightly less efficient, and does not allow quite
29052 such flexibility in the use of foreign pointers or in using the
29053 Unrestricted_Access attribute to create pointers to non-aliased objects.
29054 But for any standard portable use of the access type it will work in
29055 a functionally correct manner and allow porting of existing code.
29056 Note that another way of forcing a thin pointer representation
29057 is to use a component size clause for the element size in an array,
29058 or a record representation clause for an access field in a record.
29060 See the documentation of Unrestricted_Access in the GNAT RM for a
29061 full discussion of possible problems using this attribute in conjunction
29062 with thin pointers.
29065 @node Compatibility with HP Ada 83,,Representation Clauses,Compatibility and Porting Guide
29066 @anchor{gnat_rm/compatibility_and_porting_guide compatibility-with-hp-ada-83}@anchor{461}@anchor{gnat_rm/compatibility_and_porting_guide id17}@anchor{462}
29067 @section Compatibility with HP Ada 83
29070 All the HP Ada 83 pragmas and attributes are recognized, although only a subset
29071 of them can sensibly be implemented. The description of pragmas in
29072 @ref{7,,Implementation Defined Pragmas} indicates whether or not they are
29073 applicable to GNAT.
29079 @emph{Default floating-point representation}
29081 In GNAT, the default floating-point format is IEEE, whereas in HP Ada 83,
29087 the package System in GNAT exactly corresponds to the definition in the
29088 Ada 95 reference manual, which means that it excludes many of the
29089 HP Ada 83 extensions. However, a separate package Aux_DEC is provided
29090 that contains the additional definitions, and a special pragma,
29091 Extend_System allows this package to be treated transparently as an
29092 extension of package System.
29095 @node GNU Free Documentation License,Index,Compatibility and Porting Guide,Top
29096 @anchor{share/gnu_free_documentation_license gnu-fdl}@anchor{1}@anchor{share/gnu_free_documentation_license doc}@anchor{463}@anchor{share/gnu_free_documentation_license gnu-free-documentation-license}@anchor{464}
29097 @chapter GNU Free Documentation License
29100 Version 1.3, 3 November 2008
29102 Copyright 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc
29103 @indicateurl{http://fsf.org/}
29105 Everyone is permitted to copy and distribute verbatim copies of this
29106 license document, but changing it is not allowed.
29110 The purpose of this License is to make a manual, textbook, or other
29111 functional and useful document "free" in the sense of freedom: to
29112 assure everyone the effective freedom to copy and redistribute it,
29113 with or without modifying it, either commercially or noncommercially.
29114 Secondarily, this License preserves for the author and publisher a way
29115 to get credit for their work, while not being considered responsible
29116 for modifications made by others.
29118 This License is a kind of "copyleft", which means that derivative
29119 works of the document must themselves be free in the same sense. It
29120 complements the GNU General Public License, which is a copyleft
29121 license designed for free software.
29123 We have designed this License in order to use it for manuals for free
29124 software, because free software needs free documentation: a free
29125 program should come with manuals providing the same freedoms that the
29126 software does. But this License is not limited to software manuals;
29127 it can be used for any textual work, regardless of subject matter or
29128 whether it is published as a printed book. We recommend this License
29129 principally for works whose purpose is instruction or reference.
29131 @strong{1. APPLICABILITY AND DEFINITIONS}
29133 This License applies to any manual or other work, in any medium, that
29134 contains a notice placed by the copyright holder saying it can be
29135 distributed under the terms of this License. Such a notice grants a
29136 world-wide, royalty-free license, unlimited in duration, to use that
29137 work under the conditions stated herein. The @strong{Document}, below,
29138 refers to any such manual or work. Any member of the public is a
29139 licensee, and is addressed as "@strong{you}". You accept the license if you
29140 copy, modify or distribute the work in a way requiring permission
29141 under copyright law.
29143 A "@strong{Modified Version}" of the Document means any work containing the
29144 Document or a portion of it, either copied verbatim, or with
29145 modifications and/or translated into another language.
29147 A "@strong{Secondary Section}" is a named appendix or a front-matter section of
29148 the Document that deals exclusively with the relationship of the
29149 publishers or authors of the Document to the Document's overall subject
29150 (or to related matters) and contains nothing that could fall directly
29151 within that overall subject. (Thus, if the Document is in part a
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29153 mathematics.) The relationship could be a matter of historical
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29155 commercial, philosophical, ethical or political position regarding
29158 The "@strong{Invariant Sections}" are certain Secondary Sections whose titles
29159 are designated, as being those of Invariant Sections, in the notice
29160 that says that the Document is released under this License. If a
29161 section does not fit the above definition of Secondary then it is not
29162 allowed to be designated as Invariant. The Document may contain zero
29163 Invariant Sections. If the Document does not identify any Invariant
29164 Sections then there are none.
29166 The "@strong{Cover Texts}" are certain short passages of text that are listed,
29167 as Front-Cover Texts or Back-Cover Texts, in the notice that says that
29168 the Document is released under this License. A Front-Cover Text may
29169 be at most 5 words, and a Back-Cover Text may be at most 25 words.
29171 A "@strong{Transparent}" copy of the Document means a machine-readable copy,
29172 represented in a format whose specification is available to the
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29178 to text formatters. A copy made in an otherwise Transparent file
29179 format whose markup, or absence of markup, has been arranged to thwart
29180 or discourage subsequent modification by readers is not Transparent.
29181 An image format is not Transparent if used for any substantial amount
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29184 Examples of suitable formats for Transparent copies include plain
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29186 or XML using a publicly available DTD, and standard-conforming simple
29187 HTML, PostScript or PDF designed for human modification. Examples of
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29189 include proprietary formats that can be read and edited only by
29190 proprietary word processors, SGML or XML for which the DTD and/or
29191 processing tools are not generally available, and the
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29193 processors for output purposes only.
29195 The "@strong{Title Page}" means, for a printed book, the title page itself,
29196 plus such following pages as are needed to hold, legibly, the material
29197 this License requires to appear in the title page. For works in
29198 formats which do not have any title page as such, "Title Page" means
29199 the text near the most prominent appearance of the work's title,
29200 preceding the beginning of the body of the text.
29202 The "@strong{publisher}" means any person or entity that distributes
29203 copies of the Document to the public.
29205 A section "@strong{Entitled XYZ}" means a named subunit of the Document whose
29206 title either is precisely XYZ or contains XYZ in parentheses following
29207 text that translates XYZ in another language. (Here XYZ stands for a
29208 specific section name mentioned below, such as "@strong{Acknowledgements}",
29209 "@strong{Dedications}", "@strong{Endorsements}", or "@strong{History}".)
29210 To "@strong{Preserve the Title}"
29211 of such a section when you modify the Document means that it remains a
29212 section "Entitled XYZ" according to this definition.
29214 The Document may include Warranty Disclaimers next to the notice which
29215 states that this License applies to the Document. These Warranty
29216 Disclaimers are considered to be included by reference in this
29217 License, but only as regards disclaiming warranties: any other
29218 implication that these Warranty Disclaimers may have is void and has
29219 no effect on the meaning of this License.
29221 @strong{2. VERBATIM COPYING}
29223 You may copy and distribute the Document in any medium, either
29224 commercially or noncommercially, provided that this License, the
29225 copyright notices, and the license notice saying this License applies
29226 to the Document are reproduced in all copies, and that you add no other
29227 conditions whatsoever to those of this License. You may not use
29228 technical measures to obstruct or control the reading or further
29229 copying of the copies you make or distribute. However, you may accept
29230 compensation in exchange for copies. If you distribute a large enough
29231 number of copies you must also follow the conditions in section 3.
29233 You may also lend copies, under the same conditions stated above, and
29234 you may publicly display copies.
29236 @strong{3. COPYING IN QUANTITY}
29238 If you publish printed copies (or copies in media that commonly have
29239 printed covers) of the Document, numbering more than 100, and the
29240 Document's license notice requires Cover Texts, you must enclose the
29241 copies in covers that carry, clearly and legibly, all these Cover
29242 Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on
29243 the back cover. Both covers must also clearly and legibly identify
29244 you as the publisher of these copies. The front cover must present
29245 the full title with all words of the title equally prominent and
29246 visible. You may add other material on the covers in addition.
29247 Copying with changes limited to the covers, as long as they preserve
29248 the title of the Document and satisfy these conditions, can be treated
29249 as verbatim copying in other respects.
29251 If the required texts for either cover are too voluminous to fit
29252 legibly, you should put the first ones listed (as many as fit
29253 reasonably) on the actual cover, and continue the rest onto adjacent
29256 If you publish or distribute Opaque copies of the Document numbering
29257 more than 100, you must either include a machine-readable Transparent
29258 copy along with each Opaque copy, or state in or with each Opaque copy
29259 a computer-network location from which the general network-using
29260 public has access to download using public-standard network protocols
29261 a complete Transparent copy of the Document, free of added material.
29262 If you use the latter option, you must take reasonably prudent steps,
29263 when you begin distribution of Opaque copies in quantity, to ensure
29264 that this Transparent copy will remain thus accessible at the stated
29265 location until at least one year after the last time you distribute an
29266 Opaque copy (directly or through your agents or retailers) of that
29267 edition to the public.
29269 It is requested, but not required, that you contact the authors of the
29270 Document well before redistributing any large number of copies, to give
29271 them a chance to provide you with an updated version of the Document.
29273 @strong{4. MODIFICATIONS}
29275 You may copy and distribute a Modified Version of the Document under
29276 the conditions of sections 2 and 3 above, provided that you release
29277 the Modified Version under precisely this License, with the Modified
29278 Version filling the role of the Document, thus licensing distribution
29279 and modification of the Modified Version to whoever possesses a copy
29280 of it. In addition, you must do these things in the Modified Version:
29286 Use in the Title Page (and on the covers, if any) a title distinct
29287 from that of the Document, and from those of previous versions
29288 (which should, if there were any, be listed in the History section
29289 of the Document). You may use the same title as a previous version
29290 if the original publisher of that version gives permission.
29293 List on the Title Page, as authors, one or more persons or entities
29294 responsible for authorship of the modifications in the Modified
29295 Version, together with at least five of the principal authors of the
29296 Document (all of its principal authors, if it has fewer than five),
29297 unless they release you from this requirement.
29300 State on the Title page the name of the publisher of the
29301 Modified Version, as the publisher.
29304 Preserve all the copyright notices of the Document.
29307 Add an appropriate copyright notice for your modifications
29308 adjacent to the other copyright notices.
29311 Include, immediately after the copyright notices, a license notice
29312 giving the public permission to use the Modified Version under the
29313 terms of this License, in the form shown in the Addendum below.
29316 Preserve in that license notice the full lists of Invariant Sections
29317 and required Cover Texts given in the Document's license notice.
29320 Include an unaltered copy of this License.
29323 Preserve the section Entitled "History", Preserve its Title, and add
29324 to it an item stating at least the title, year, new authors, and
29325 publisher of the Modified Version as given on the Title Page. If
29326 there is no section Entitled "History" in the Document, create one
29327 stating the title, year, authors, and publisher of the Document as
29328 given on its Title Page, then add an item describing the Modified
29329 Version as stated in the previous sentence.
29332 Preserve the network location, if any, given in the Document for
29333 public access to a Transparent copy of the Document, and likewise
29334 the network locations given in the Document for previous versions
29335 it was based on. These may be placed in the "History" section.
29336 You may omit a network location for a work that was published at
29337 least four years before the Document itself, or if the original
29338 publisher of the version it refers to gives permission.
29341 For any section Entitled "Acknowledgements" or "Dedications",
29342 Preserve the Title of the section, and preserve in the section all
29343 the substance and tone of each of the contributor acknowledgements
29344 and/or dedications given therein.
29347 Preserve all the Invariant Sections of the Document,
29348 unaltered in their text and in their titles. Section numbers
29349 or the equivalent are not considered part of the section titles.
29352 Delete any section Entitled "Endorsements". Such a section
29353 may not be included in the Modified Version.
29356 Do not retitle any existing section to be Entitled "Endorsements"
29357 or to conflict in title with any Invariant Section.
29360 Preserve any Warranty Disclaimers.
29363 If the Modified Version includes new front-matter sections or
29364 appendices that qualify as Secondary Sections and contain no material
29365 copied from the Document, you may at your option designate some or all
29366 of these sections as invariant. To do this, add their titles to the
29367 list of Invariant Sections in the Modified Version's license notice.
29368 These titles must be distinct from any other section titles.
29370 You may add a section Entitled "Endorsements", provided it contains
29371 nothing but endorsements of your Modified Version by various
29372 parties---for example, statements of peer review or that the text has
29373 been approved by an organization as the authoritative definition of a
29376 You may add a passage of up to five words as a Front-Cover Text, and a
29377 passage of up to 25 words as a Back-Cover Text, to the end of the list
29378 of Cover Texts in the Modified Version. Only one passage of
29379 Front-Cover Text and one of Back-Cover Text may be added by (or
29380 through arrangements made by) any one entity. If the Document already
29381 includes a cover text for the same cover, previously added by you or
29382 by arrangement made by the same entity you are acting on behalf of,
29383 you may not add another; but you may replace the old one, on explicit
29384 permission from the previous publisher that added the old one.
29386 The author(s) and publisher(s) of the Document do not by this License
29387 give permission to use their names for publicity for or to assert or
29388 imply endorsement of any Modified Version.
29390 @strong{5. COMBINING DOCUMENTS}
29392 You may combine the Document with other documents released under this
29393 License, under the terms defined in section 4 above for modified
29394 versions, provided that you include in the combination all of the
29395 Invariant Sections of all of the original documents, unmodified, and
29396 list them all as Invariant Sections of your combined work in its
29397 license notice, and that you preserve all their Warranty Disclaimers.
29399 The combined work need only contain one copy of this License, and
29400 multiple identical Invariant Sections may be replaced with a single
29401 copy. If there are multiple Invariant Sections with the same name but
29402 different contents, make the title of each such section unique by
29403 adding at the end of it, in parentheses, the name of the original
29404 author or publisher of that section if known, or else a unique number.
29405 Make the same adjustment to the section titles in the list of
29406 Invariant Sections in the license notice of the combined work.
29408 In the combination, you must combine any sections Entitled "History"
29409 in the various original documents, forming one section Entitled
29410 "History"; likewise combine any sections Entitled "Acknowledgements",
29411 and any sections Entitled "Dedications". You must delete all sections
29412 Entitled "Endorsements".
29414 @strong{6. COLLECTIONS OF DOCUMENTS}
29416 You may make a collection consisting of the Document and other documents
29417 released under this License, and replace the individual copies of this
29418 License in the various documents with a single copy that is included in
29419 the collection, provided that you follow the rules of this License for
29420 verbatim copying of each of the documents in all other respects.
29422 You may extract a single document from such a collection, and distribute
29423 it individually under this License, provided you insert a copy of this
29424 License into the extracted document, and follow this License in all
29425 other respects regarding verbatim copying of that document.
29427 @strong{7. AGGREGATION WITH INDEPENDENT WORKS}
29429 A compilation of the Document or its derivatives with other separate
29430 and independent documents or works, in or on a volume of a storage or
29431 distribution medium, is called an "aggregate" if the copyright
29432 resulting from the compilation is not used to limit the legal rights
29433 of the compilation's users beyond what the individual works permit.
29434 When the Document is included in an aggregate, this License does not
29435 apply to the other works in the aggregate which are not themselves
29436 derivative works of the Document.
29438 If the Cover Text requirement of section 3 is applicable to these
29439 copies of the Document, then if the Document is less than one half of
29440 the entire aggregate, the Document's Cover Texts may be placed on
29441 covers that bracket the Document within the aggregate, or the
29442 electronic equivalent of covers if the Document is in electronic form.
29443 Otherwise they must appear on printed covers that bracket the whole
29446 @strong{8. TRANSLATION}
29448 Translation is considered a kind of modification, so you may
29449 distribute translations of the Document under the terms of section 4.
29450 Replacing Invariant Sections with translations requires special
29451 permission from their copyright holders, but you may include
29452 translations of some or all Invariant Sections in addition to the
29453 original versions of these Invariant Sections. You may include a
29454 translation of this License, and all the license notices in the
29455 Document, and any Warranty Disclaimers, provided that you also include
29456 the original English version of this License and the original versions
29457 of those notices and disclaimers. In case of a disagreement between
29458 the translation and the original version of this License or a notice
29459 or disclaimer, the original version will prevail.
29461 If a section in the Document is Entitled "Acknowledgements",
29462 "Dedications", or "History", the requirement (section 4) to Preserve
29463 its Title (section 1) will typically require changing the actual
29466 @strong{9. TERMINATION}
29468 You may not copy, modify, sublicense, or distribute the Document
29469 except as expressly provided under this License. Any attempt
29470 otherwise to copy, modify, sublicense, or distribute it is void, and
29471 will automatically terminate your rights under this License.
29473 However, if you cease all violation of this License, then your license
29474 from a particular copyright holder is reinstated (a) provisionally,
29475 unless and until the copyright holder explicitly and finally
29476 terminates your license, and (b) permanently, if the copyright holder
29477 fails to notify you of the violation by some reasonable means prior to
29478 60 days after the cessation.
29480 Moreover, your license from a particular copyright holder is
29481 reinstated permanently if the copyright holder notifies you of the
29482 violation by some reasonable means, this is the first time you have
29483 received notice of violation of this License (for any work) from that
29484 copyright holder, and you cure the violation prior to 30 days after
29485 your receipt of the notice.
29487 Termination of your rights under this section does not terminate the
29488 licenses of parties who have received copies or rights from you under
29489 this License. If your rights have been terminated and not permanently
29490 reinstated, receipt of a copy of some or all of the same material does
29491 not give you any rights to use it.
29493 @strong{10. FUTURE REVISIONS OF THIS LICENSE}
29495 The Free Software Foundation may publish new, revised versions
29496 of the GNU Free Documentation License from time to time. Such new
29497 versions will be similar in spirit to the present version, but may
29498 differ in detail to address new problems or concerns. See
29499 @indicateurl{http://www.gnu.org/copyleft/}.
29501 Each version of the License is given a distinguishing version number.
29502 If the Document specifies that a particular numbered version of this
29503 License "or any later version" applies to it, you have the option of
29504 following the terms and conditions either of that specified version or
29505 of any later version that has been published (not as a draft) by the
29506 Free Software Foundation. If the Document does not specify a version
29507 number of this License, you may choose any version ever published (not
29508 as a draft) by the Free Software Foundation. If the Document
29509 specifies that a proxy can decide which future versions of this
29510 License can be used, that proxy's public statement of acceptance of a
29511 version permanently authorizes you to choose that version for the
29514 @strong{11. RELICENSING}
29516 "Massive Multiauthor Collaboration Site" (or "MMC Site") means any
29517 World Wide Web server that publishes copyrightable works and also
29518 provides prominent facilities for anybody to edit those works. A
29519 public wiki that anybody can edit is an example of such a server. A
29520 "Massive Multiauthor Collaboration" (or "MMC") contained in the
29521 site means any set of copyrightable works thus published on the MMC
29524 "CC-BY-SA" means the Creative Commons Attribution-Share Alike 3.0
29525 license published by Creative Commons Corporation, a not-for-profit
29526 corporation with a principal place of business in San Francisco,
29527 California, as well as future copyleft versions of that license
29528 published by that same organization.
29530 "Incorporate" means to publish or republish a Document, in whole or
29531 in part, as part of another Document.
29533 An MMC is "eligible for relicensing" if it is licensed under this
29534 License, and if all works that were first published under this License
29535 somewhere other than this MMC, and subsequently incorporated in whole
29536 or in part into the MMC, (1) had no cover texts or invariant sections,
29537 and (2) were thus incorporated prior to November 1, 2008.
29539 The operator of an MMC Site may republish an MMC contained in the site
29540 under CC-BY-SA on the same site at any time before August 1, 2009,
29541 provided the MMC is eligible for relicensing.
29543 @strong{ADDENDUM: How to use this License for your documents}
29545 To use this License in a document you have written, include a copy of
29546 the License in the document and put the following copyright and
29547 license notices just after the title page:
29551 Copyright © YEAR YOUR NAME.
29552 Permission is granted to copy, distribute and/or modify this document
29553 under the terms of the GNU Free Documentation License, Version 1.3
29554 or any later version published by the Free Software Foundation;
29555 with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
29556 A copy of the license is included in the section entitled "GNU
29557 Free Documentation License".
29560 If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts,
29561 replace the "with ... Texts." line with this:
29565 with the Invariant Sections being LIST THEIR TITLES, with the
29566 Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST.
29569 If you have Invariant Sections without Cover Texts, or some other
29570 combination of the three, merge those two alternatives to suit the
29573 If your document contains nontrivial examples of program code, we
29574 recommend releasing these examples in parallel under your choice of
29575 free software license, such as the GNU General Public License,
29576 to permit their use in free software.
29578 @node Index,,GNU Free Documentation License,Top