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8 @settitle GNAT Reference Manual
13 @dircategory GNU Ada Tools
15 * gnat_rm: (gnat_rm.info). gnat_rm
18 @definfoenclose strong,`,'
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24 GNAT Reference Manual , Nov 20, 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::
397 * Attribute Has_Tagged_Values::
399 * Attribute Initialized::
400 * Attribute Integer_Value::
401 * Attribute Invalid_Value::
402 * Attribute Iterable::
404 * Attribute Library_Level::
405 * Attribute Lock_Free::
406 * Attribute Loop_Entry::
407 * Attribute Machine_Size::
408 * Attribute Mantissa::
409 * Attribute Maximum_Alignment::
410 * Attribute Max_Integer_Size::
411 * Attribute Mechanism_Code::
412 * Attribute Null_Parameter::
413 * Attribute Object_Size::
415 * Attribute Passed_By_Reference::
416 * Attribute Pool_Address::
417 * Attribute Range_Length::
418 * Attribute Restriction_Set::
420 * Attribute Safe_Emax::
421 * Attribute Safe_Large::
422 * Attribute Safe_Small::
423 * Attribute Scalar_Storage_Order::
424 * Attribute Simple_Storage_Pool::
426 * Attribute Small_Denominator::
427 * Attribute Small_Numerator::
428 * Attribute Storage_Unit::
429 * Attribute Stub_Type::
430 * Attribute System_Allocator_Alignment::
431 * Attribute Target_Name::
432 * Attribute To_Address::
434 * Attribute Type_Class::
435 * Attribute Type_Key::
436 * Attribute TypeCode::
437 * Attribute Unconstrained_Array::
438 * Attribute Universal_Literal_String::
439 * Attribute Unrestricted_Access::
441 * Attribute Valid_Scalars::
442 * Attribute VADS_Size::
443 * Attribute Value_Size::
444 * Attribute Wchar_T_Size::
445 * Attribute Word_Size::
447 Standard and Implementation Defined Restrictions
449 * Partition-Wide Restrictions::
450 * Program Unit Level Restrictions::
452 Partition-Wide Restrictions
454 * Immediate_Reclamation::
455 * Max_Asynchronous_Select_Nesting::
456 * Max_Entry_Queue_Length::
457 * Max_Protected_Entries::
458 * Max_Select_Alternatives::
459 * Max_Storage_At_Blocking::
462 * No_Abort_Statements::
463 * No_Access_Parameter_Allocators::
464 * No_Access_Subprograms::
466 * No_Anonymous_Allocators::
467 * No_Asynchronous_Control::
470 * No_Default_Initialization::
473 * No_Direct_Boolean_Operators::
475 * No_Dispatching_Calls::
476 * No_Dynamic_Attachment::
477 * No_Dynamic_Priorities::
478 * No_Entry_Calls_In_Elaboration_Code::
479 * No_Enumeration_Maps::
480 * No_Exception_Handlers::
481 * No_Exception_Propagation::
482 * No_Exception_Registration::
486 * No_Floating_Point::
487 * No_Implicit_Conditionals::
488 * No_Implicit_Dynamic_Code::
489 * No_Implicit_Heap_Allocations::
490 * No_Implicit_Protected_Object_Allocations::
491 * No_Implicit_Task_Allocations::
492 * No_Initialize_Scalars::
494 * No_Local_Allocators::
495 * No_Local_Protected_Objects::
496 * No_Local_Timing_Events::
497 * No_Long_Long_Integers::
498 * No_Multiple_Elaboration::
499 * No_Nested_Finalization::
500 * No_Protected_Type_Allocators::
501 * No_Protected_Types::
504 * No_Relative_Delay::
505 * No_Requeue_Statements::
506 * No_Secondary_Stack::
507 * No_Select_Statements::
508 * No_Specific_Termination_Handlers::
509 * No_Specification_of_Aspect::
510 * No_Standard_Allocators_After_Elaboration::
511 * No_Standard_Storage_Pools::
512 * No_Stream_Optimizations::
514 * No_Task_Allocators::
515 * No_Task_At_Interrupt_Priority::
516 * No_Task_Attributes_Package::
517 * No_Task_Hierarchy::
518 * No_Task_Termination::
520 * No_Terminate_Alternatives::
521 * No_Unchecked_Access::
522 * No_Unchecked_Conversion::
523 * No_Unchecked_Deallocation::
527 * Static_Priorities::
528 * Static_Storage_Size::
530 Program Unit Level Restrictions
532 * No_Elaboration_Code::
533 * No_Dynamic_Sized_Objects::
535 * No_Implementation_Aspect_Specifications::
536 * No_Implementation_Attributes::
537 * No_Implementation_Identifiers::
538 * No_Implementation_Pragmas::
539 * No_Implementation_Restrictions::
540 * No_Implementation_Units::
541 * No_Implicit_Aliasing::
542 * No_Implicit_Loops::
543 * No_Obsolescent_Features::
544 * No_Wide_Characters::
545 * Static_Dispatch_Tables::
548 Implementation Advice
550 * RM 1.1.3(20); Error Detection: RM 1 1 3 20 Error Detection.
551 * RM 1.1.3(31); Child Units: RM 1 1 3 31 Child Units.
552 * RM 1.1.5(12); Bounded Errors: RM 1 1 5 12 Bounded Errors.
553 * RM 2.8(16); Pragmas: RM 2 8 16 Pragmas.
554 * RM 2.8(17-19); Pragmas: RM 2 8 17-19 Pragmas.
555 * RM 3.5.2(5); Alternative Character Sets: RM 3 5 2 5 Alternative Character Sets.
556 * RM 3.5.4(28); Integer Types: RM 3 5 4 28 Integer Types.
557 * RM 3.5.4(29); Integer Types: RM 3 5 4 29 Integer Types.
558 * RM 3.5.5(8); Enumeration Values: RM 3 5 5 8 Enumeration Values.
559 * RM 3.5.7(17); Float Types: RM 3 5 7 17 Float Types.
560 * RM 3.6.2(11); Multidimensional Arrays: RM 3 6 2 11 Multidimensional Arrays.
561 * RM 9.6(30-31); Duration'Small: RM 9 6 30-31 Duration'Small.
562 * RM 10.2.1(12); Consistent Representation: RM 10 2 1 12 Consistent Representation.
563 * RM 11.4.1(19); Exception Information: RM 11 4 1 19 Exception Information.
564 * RM 11.5(28); Suppression of Checks: RM 11 5 28 Suppression of Checks.
565 * RM 13.1 (21-24); Representation Clauses: RM 13 1 21-24 Representation Clauses.
566 * RM 13.2(6-8); Packed Types: RM 13 2 6-8 Packed Types.
567 * RM 13.3(14-19); Address Clauses: RM 13 3 14-19 Address Clauses.
568 * RM 13.3(29-35); Alignment Clauses: RM 13 3 29-35 Alignment Clauses.
569 * RM 13.3(42-43); Size Clauses: RM 13 3 42-43 Size Clauses.
570 * RM 13.3(50-56); Size Clauses: RM 13 3 50-56 Size Clauses.
571 * RM 13.3(71-73); Component Size Clauses: RM 13 3 71-73 Component Size Clauses.
572 * RM 13.4(9-10); Enumeration Representation Clauses: RM 13 4 9-10 Enumeration Representation Clauses.
573 * RM 13.5.1(17-22); Record Representation Clauses: RM 13 5 1 17-22 Record Representation Clauses.
574 * RM 13.5.2(5); Storage Place Attributes: RM 13 5 2 5 Storage Place Attributes.
575 * RM 13.5.3(7-8); Bit Ordering: RM 13 5 3 7-8 Bit Ordering.
576 * RM 13.7(37); Address as Private: RM 13 7 37 Address as Private.
577 * RM 13.7.1(16); Address Operations: RM 13 7 1 16 Address Operations.
578 * RM 13.9(14-17); Unchecked Conversion: RM 13 9 14-17 Unchecked Conversion.
579 * RM 13.11(23-25); Implicit Heap Usage: RM 13 11 23-25 Implicit Heap Usage.
580 * RM 13.11.2(17); Unchecked Deallocation: RM 13 11 2 17 Unchecked Deallocation.
581 * RM 13.13.2(1.6); Stream Oriented Attributes: RM 13 13 2 1 6 Stream Oriented Attributes.
582 * RM A.1(52); Names of Predefined Numeric Types: RM A 1 52 Names of Predefined Numeric Types.
583 * RM A.3.2(49); Ada.Characters.Handling: RM A 3 2 49 Ada Characters Handling.
584 * RM A.4.4(106); Bounded-Length String Handling: RM A 4 4 106 Bounded-Length String Handling.
585 * RM A.5.2(46-47); Random Number Generation: RM A 5 2 46-47 Random Number Generation.
586 * RM A.10.7(23); Get_Immediate: RM A 10 7 23 Get_Immediate.
587 * RM B.1(39-41); Pragma Export: RM B 1 39-41 Pragma Export.
588 * RM B.2(12-13); Package Interfaces: RM B 2 12-13 Package Interfaces.
589 * RM B.3(63-71); Interfacing with C: RM B 3 63-71 Interfacing with C.
590 * RM B.4(95-98); Interfacing with COBOL: RM B 4 95-98 Interfacing with COBOL.
591 * RM B.5(22-26); Interfacing with Fortran: RM B 5 22-26 Interfacing with Fortran.
592 * RM C.1(3-5); Access to Machine Operations: RM C 1 3-5 Access to Machine Operations.
593 * RM C.1(10-16); Access to Machine Operations: RM C 1 10-16 Access to Machine Operations.
594 * RM C.3(28); Interrupt Support: RM C 3 28 Interrupt Support.
595 * RM C.3.1(20-21); Protected Procedure Handlers: RM C 3 1 20-21 Protected Procedure Handlers.
596 * RM C.3.2(25); Package Interrupts: RM C 3 2 25 Package Interrupts.
597 * RM C.4(14); Pre-elaboration Requirements: RM C 4 14 Pre-elaboration Requirements.
598 * RM C.5(8); Pragma Discard_Names: RM C 5 8 Pragma Discard_Names.
599 * RM C.7.2(30); The Package Task_Attributes: RM C 7 2 30 The Package Task_Attributes.
600 * RM D.3(17); Locking Policies: RM D 3 17 Locking Policies.
601 * RM D.4(16); Entry Queuing Policies: RM D 4 16 Entry Queuing Policies.
602 * RM D.6(9-10); Preemptive Abort: RM D 6 9-10 Preemptive Abort.
603 * RM D.7(21); Tasking Restrictions: RM D 7 21 Tasking Restrictions.
604 * RM D.8(47-49); Monotonic Time: RM D 8 47-49 Monotonic Time.
605 * RM E.5(28-29); Partition Communication Subsystem: RM E 5 28-29 Partition Communication Subsystem.
606 * RM F(7); COBOL Support: RM F 7 COBOL Support.
607 * RM F.1(2); Decimal Radix Support: RM F 1 2 Decimal Radix Support.
608 * RM G; Numerics: RM G Numerics.
609 * RM G.1.1(56-58); Complex Types: RM G 1 1 56-58 Complex Types.
610 * RM G.1.2(49); Complex Elementary Functions: RM G 1 2 49 Complex Elementary Functions.
611 * RM G.2.4(19); Accuracy Requirements: RM G 2 4 19 Accuracy Requirements.
612 * RM G.2.6(15); Complex Arithmetic Accuracy: RM G 2 6 15 Complex Arithmetic Accuracy.
613 * RM H.6(15/2); Pragma Partition_Elaboration_Policy: RM H 6 15/2 Pragma Partition_Elaboration_Policy.
615 Intrinsic Subprograms
617 * Intrinsic Operators::
618 * Compilation_ISO_Date::
622 * Exception_Information::
623 * Exception_Message::
627 * Shifts and Rotates::
630 Representation Clauses and Pragmas
632 * Alignment Clauses::
634 * Storage_Size Clauses::
635 * Size of Variant Record Objects::
636 * Biased Representation::
637 * Value_Size and Object_Size Clauses::
638 * Component_Size Clauses::
639 * Bit_Order Clauses::
640 * Effect of Bit_Order on Byte Ordering::
641 * Pragma Pack for Arrays::
642 * Pragma Pack for Records::
643 * Record Representation Clauses::
644 * Handling of Records with Holes::
645 * Enumeration Clauses::
647 * Use of Address Clauses for Memory-Mapped I/O::
648 * Effect of Convention on Representation::
649 * Conventions and Anonymous Access Types::
650 * Determining the Representations chosen by GNAT::
652 The Implementation of Standard I/O
654 * Standard I/O Packages::
660 * Wide_Wide_Text_IO::
664 * Filenames encoding::
665 * File content encoding::
667 * Operations on C Streams::
668 * Interfacing to C Streams::
672 * Stream Pointer Positioning::
673 * Reading and Writing Non-Regular Files::
675 * Treating Text_IO Files as Streams::
676 * Text_IO Extensions::
677 * Text_IO Facilities for Unbounded Strings::
681 * Stream Pointer Positioning: Stream Pointer Positioning<2>.
682 * Reading and Writing Non-Regular Files: Reading and Writing Non-Regular Files<2>.
686 * Stream Pointer Positioning: Stream Pointer Positioning<3>.
687 * Reading and Writing Non-Regular Files: Reading and Writing Non-Regular Files<3>.
691 * Ada.Characters.Latin_9 (a-chlat9.ads): Ada Characters Latin_9 a-chlat9 ads.
692 * Ada.Characters.Wide_Latin_1 (a-cwila1.ads): Ada Characters Wide_Latin_1 a-cwila1 ads.
693 * Ada.Characters.Wide_Latin_9 (a-cwila1.ads): Ada Characters Wide_Latin_9 a-cwila1 ads.
694 * Ada.Characters.Wide_Wide_Latin_1 (a-chzla1.ads): Ada Characters Wide_Wide_Latin_1 a-chzla1 ads.
695 * Ada.Characters.Wide_Wide_Latin_9 (a-chzla9.ads): Ada Characters Wide_Wide_Latin_9 a-chzla9 ads.
696 * Ada.Containers.Formal_Doubly_Linked_Lists (a-cfdlli.ads): Ada Containers Formal_Doubly_Linked_Lists a-cfdlli ads.
697 * Ada.Containers.Formal_Hashed_Maps (a-cfhama.ads): Ada Containers Formal_Hashed_Maps a-cfhama ads.
698 * Ada.Containers.Formal_Hashed_Sets (a-cfhase.ads): Ada Containers Formal_Hashed_Sets a-cfhase ads.
699 * Ada.Containers.Formal_Ordered_Maps (a-cforma.ads): Ada Containers Formal_Ordered_Maps a-cforma ads.
700 * Ada.Containers.Formal_Ordered_Sets (a-cforse.ads): Ada Containers Formal_Ordered_Sets a-cforse ads.
701 * Ada.Containers.Formal_Vectors (a-cofove.ads): Ada Containers Formal_Vectors a-cofove ads.
702 * Ada.Containers.Formal_Indefinite_Vectors (a-cfinve.ads): Ada Containers Formal_Indefinite_Vectors a-cfinve ads.
703 * Ada.Containers.Functional_Vectors (a-cofuve.ads): Ada Containers Functional_Vectors a-cofuve ads.
704 * Ada.Containers.Functional_Sets (a-cofuse.ads): Ada Containers Functional_Sets a-cofuse ads.
705 * Ada.Containers.Functional_Maps (a-cofuma.ads): Ada Containers Functional_Maps a-cofuma ads.
706 * Ada.Containers.Bounded_Holders (a-coboho.ads): Ada Containers Bounded_Holders a-coboho ads.
707 * Ada.Command_Line.Environment (a-colien.ads): Ada Command_Line Environment a-colien ads.
708 * Ada.Command_Line.Remove (a-colire.ads): Ada Command_Line Remove a-colire ads.
709 * Ada.Command_Line.Response_File (a-clrefi.ads): Ada Command_Line Response_File a-clrefi ads.
710 * Ada.Direct_IO.C_Streams (a-diocst.ads): Ada Direct_IO C_Streams a-diocst ads.
711 * Ada.Exceptions.Is_Null_Occurrence (a-einuoc.ads): Ada Exceptions Is_Null_Occurrence a-einuoc ads.
712 * Ada.Exceptions.Last_Chance_Handler (a-elchha.ads): Ada Exceptions Last_Chance_Handler a-elchha ads.
713 * Ada.Exceptions.Traceback (a-exctra.ads): Ada Exceptions Traceback a-exctra ads.
714 * Ada.Sequential_IO.C_Streams (a-siocst.ads): Ada Sequential_IO C_Streams a-siocst ads.
715 * Ada.Streams.Stream_IO.C_Streams (a-ssicst.ads): Ada Streams Stream_IO C_Streams a-ssicst ads.
716 * Ada.Strings.Unbounded.Text_IO (a-suteio.ads): Ada Strings Unbounded Text_IO a-suteio ads.
717 * Ada.Strings.Wide_Unbounded.Wide_Text_IO (a-swuwti.ads): Ada Strings Wide_Unbounded Wide_Text_IO a-swuwti ads.
718 * Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO (a-szuzti.ads): Ada Strings Wide_Wide_Unbounded Wide_Wide_Text_IO a-szuzti ads.
719 * Ada.Task_Initialization (a-tasini.ads): Ada Task_Initialization a-tasini ads.
720 * Ada.Text_IO.C_Streams (a-tiocst.ads): Ada Text_IO C_Streams a-tiocst ads.
721 * Ada.Text_IO.Reset_Standard_Files (a-tirsfi.ads): Ada Text_IO Reset_Standard_Files a-tirsfi ads.
722 * Ada.Wide_Characters.Unicode (a-wichun.ads): Ada Wide_Characters Unicode a-wichun ads.
723 * Ada.Wide_Text_IO.C_Streams (a-wtcstr.ads): Ada Wide_Text_IO C_Streams a-wtcstr ads.
724 * Ada.Wide_Text_IO.Reset_Standard_Files (a-wrstfi.ads): Ada Wide_Text_IO Reset_Standard_Files a-wrstfi ads.
725 * Ada.Wide_Wide_Characters.Unicode (a-zchuni.ads): Ada Wide_Wide_Characters Unicode a-zchuni ads.
726 * Ada.Wide_Wide_Text_IO.C_Streams (a-ztcstr.ads): Ada Wide_Wide_Text_IO C_Streams a-ztcstr ads.
727 * Ada.Wide_Wide_Text_IO.Reset_Standard_Files (a-zrstfi.ads): Ada Wide_Wide_Text_IO Reset_Standard_Files a-zrstfi ads.
728 * GNAT.Altivec (g-altive.ads): GNAT Altivec g-altive ads.
729 * GNAT.Altivec.Conversions (g-altcon.ads): GNAT Altivec Conversions g-altcon ads.
730 * GNAT.Altivec.Vector_Operations (g-alveop.ads): GNAT Altivec Vector_Operations g-alveop ads.
731 * GNAT.Altivec.Vector_Types (g-alvety.ads): GNAT Altivec Vector_Types g-alvety ads.
732 * GNAT.Altivec.Vector_Views (g-alvevi.ads): GNAT Altivec Vector_Views g-alvevi ads.
733 * GNAT.Array_Split (g-arrspl.ads): GNAT Array_Split g-arrspl ads.
734 * GNAT.AWK (g-awk.ads): GNAT AWK g-awk ads.
735 * GNAT.Bind_Environment (g-binenv.ads): GNAT Bind_Environment g-binenv ads.
736 * GNAT.Branch_Prediction (g-brapre.ads): GNAT Branch_Prediction g-brapre ads.
737 * GNAT.Bounded_Buffers (g-boubuf.ads): GNAT Bounded_Buffers g-boubuf ads.
738 * GNAT.Bounded_Mailboxes (g-boumai.ads): GNAT Bounded_Mailboxes g-boumai ads.
739 * GNAT.Bubble_Sort (g-bubsor.ads): GNAT Bubble_Sort g-bubsor ads.
740 * GNAT.Bubble_Sort_A (g-busora.ads): GNAT Bubble_Sort_A g-busora ads.
741 * GNAT.Bubble_Sort_G (g-busorg.ads): GNAT Bubble_Sort_G g-busorg ads.
742 * GNAT.Byte_Order_Mark (g-byorma.ads): GNAT Byte_Order_Mark g-byorma ads.
743 * GNAT.Byte_Swapping (g-bytswa.ads): GNAT Byte_Swapping g-bytswa ads.
744 * GNAT.Calendar (g-calend.ads): GNAT Calendar g-calend ads.
745 * GNAT.Calendar.Time_IO (g-catiio.ads): GNAT Calendar Time_IO g-catiio ads.
746 * GNAT.CRC32 (g-crc32.ads): GNAT CRC32 g-crc32 ads.
747 * GNAT.Case_Util (g-casuti.ads): GNAT Case_Util g-casuti ads.
748 * GNAT.CGI (g-cgi.ads): GNAT CGI g-cgi ads.
749 * GNAT.CGI.Cookie (g-cgicoo.ads): GNAT CGI Cookie g-cgicoo ads.
750 * GNAT.CGI.Debug (g-cgideb.ads): GNAT CGI Debug g-cgideb ads.
751 * GNAT.Command_Line (g-comlin.ads): GNAT Command_Line g-comlin ads.
752 * GNAT.Compiler_Version (g-comver.ads): GNAT Compiler_Version g-comver ads.
753 * GNAT.Ctrl_C (g-ctrl_c.ads): GNAT Ctrl_C g-ctrl_c ads.
754 * GNAT.Current_Exception (g-curexc.ads): GNAT Current_Exception g-curexc ads.
755 * GNAT.Debug_Pools (g-debpoo.ads): GNAT Debug_Pools g-debpoo ads.
756 * GNAT.Debug_Utilities (g-debuti.ads): GNAT Debug_Utilities g-debuti ads.
757 * GNAT.Decode_String (g-decstr.ads): GNAT Decode_String g-decstr ads.
758 * GNAT.Decode_UTF8_String (g-deutst.ads): GNAT Decode_UTF8_String g-deutst ads.
759 * GNAT.Directory_Operations (g-dirope.ads): GNAT Directory_Operations g-dirope ads.
760 * GNAT.Directory_Operations.Iteration (g-diopit.ads): GNAT Directory_Operations Iteration g-diopit ads.
761 * GNAT.Dynamic_HTables (g-dynhta.ads): GNAT Dynamic_HTables g-dynhta ads.
762 * GNAT.Dynamic_Tables (g-dyntab.ads): GNAT Dynamic_Tables g-dyntab ads.
763 * GNAT.Encode_String (g-encstr.ads): GNAT Encode_String g-encstr ads.
764 * GNAT.Encode_UTF8_String (g-enutst.ads): GNAT Encode_UTF8_String g-enutst ads.
765 * GNAT.Exception_Actions (g-excact.ads): GNAT Exception_Actions g-excact ads.
766 * GNAT.Exception_Traces (g-exctra.ads): GNAT Exception_Traces g-exctra ads.
767 * GNAT.Exceptions (g-except.ads): GNAT Exceptions g-except ads.
768 * GNAT.Expect (g-expect.ads): GNAT Expect g-expect ads.
769 * GNAT.Expect.TTY (g-exptty.ads): GNAT Expect TTY g-exptty ads.
770 * GNAT.Float_Control (g-flocon.ads): GNAT Float_Control g-flocon ads.
771 * GNAT.Formatted_String (g-forstr.ads): GNAT Formatted_String g-forstr ads.
772 * GNAT.Heap_Sort (g-heasor.ads): GNAT Heap_Sort g-heasor ads.
773 * GNAT.Heap_Sort_A (g-hesora.ads): GNAT Heap_Sort_A g-hesora ads.
774 * GNAT.Heap_Sort_G (g-hesorg.ads): GNAT Heap_Sort_G g-hesorg ads.
775 * GNAT.HTable (g-htable.ads): GNAT HTable g-htable ads.
776 * GNAT.IO (g-io.ads): GNAT IO g-io ads.
777 * GNAT.IO_Aux (g-io_aux.ads): GNAT IO_Aux g-io_aux ads.
778 * GNAT.Lock_Files (g-locfil.ads): GNAT Lock_Files g-locfil ads.
779 * GNAT.MBBS_Discrete_Random (g-mbdira.ads): GNAT MBBS_Discrete_Random g-mbdira ads.
780 * GNAT.MBBS_Float_Random (g-mbflra.ads): GNAT MBBS_Float_Random g-mbflra ads.
781 * GNAT.MD5 (g-md5.ads): GNAT MD5 g-md5 ads.
782 * GNAT.Memory_Dump (g-memdum.ads): GNAT Memory_Dump g-memdum ads.
783 * GNAT.Most_Recent_Exception (g-moreex.ads): GNAT Most_Recent_Exception g-moreex ads.
784 * GNAT.OS_Lib (g-os_lib.ads): GNAT OS_Lib g-os_lib ads.
785 * GNAT.Perfect_Hash_Generators (g-pehage.ads): GNAT Perfect_Hash_Generators g-pehage ads.
786 * GNAT.Random_Numbers (g-rannum.ads): GNAT Random_Numbers g-rannum ads.
787 * GNAT.Regexp (g-regexp.ads): GNAT Regexp g-regexp ads.
788 * GNAT.Registry (g-regist.ads): GNAT Registry g-regist ads.
789 * GNAT.Regpat (g-regpat.ads): GNAT Regpat g-regpat ads.
790 * GNAT.Rewrite_Data (g-rewdat.ads): GNAT Rewrite_Data g-rewdat ads.
791 * GNAT.Secondary_Stack_Info (g-sestin.ads): GNAT Secondary_Stack_Info g-sestin ads.
792 * GNAT.Semaphores (g-semaph.ads): GNAT Semaphores g-semaph ads.
793 * GNAT.Serial_Communications (g-sercom.ads): GNAT Serial_Communications g-sercom ads.
794 * GNAT.SHA1 (g-sha1.ads): GNAT SHA1 g-sha1 ads.
795 * GNAT.SHA224 (g-sha224.ads): GNAT SHA224 g-sha224 ads.
796 * GNAT.SHA256 (g-sha256.ads): GNAT SHA256 g-sha256 ads.
797 * GNAT.SHA384 (g-sha384.ads): GNAT SHA384 g-sha384 ads.
798 * GNAT.SHA512 (g-sha512.ads): GNAT SHA512 g-sha512 ads.
799 * GNAT.Signals (g-signal.ads): GNAT Signals g-signal ads.
800 * GNAT.Sockets (g-socket.ads): GNAT Sockets g-socket ads.
801 * GNAT.Source_Info (g-souinf.ads): GNAT Source_Info g-souinf ads.
802 * GNAT.Spelling_Checker (g-speche.ads): GNAT Spelling_Checker g-speche ads.
803 * GNAT.Spelling_Checker_Generic (g-spchge.ads): GNAT Spelling_Checker_Generic g-spchge ads.
804 * GNAT.Spitbol.Patterns (g-spipat.ads): GNAT Spitbol Patterns g-spipat ads.
805 * GNAT.Spitbol (g-spitbo.ads): GNAT Spitbol g-spitbo ads.
806 * GNAT.Spitbol.Table_Boolean (g-sptabo.ads): GNAT Spitbol Table_Boolean g-sptabo ads.
807 * GNAT.Spitbol.Table_Integer (g-sptain.ads): GNAT Spitbol Table_Integer g-sptain ads.
808 * GNAT.Spitbol.Table_VString (g-sptavs.ads): GNAT Spitbol Table_VString g-sptavs ads.
809 * GNAT.SSE (g-sse.ads): GNAT SSE g-sse ads.
810 * GNAT.SSE.Vector_Types (g-ssvety.ads): GNAT SSE Vector_Types g-ssvety ads.
811 * GNAT.String_Hash (g-strhas.ads): GNAT String_Hash g-strhas ads.
812 * GNAT.Strings (g-string.ads): GNAT Strings g-string ads.
813 * GNAT.String_Split (g-strspl.ads): GNAT String_Split g-strspl ads.
814 * GNAT.Table (g-table.ads): GNAT Table g-table ads.
815 * GNAT.Task_Lock (g-tasloc.ads): GNAT Task_Lock g-tasloc ads.
816 * GNAT.Time_Stamp (g-timsta.ads): GNAT Time_Stamp g-timsta ads.
817 * GNAT.Threads (g-thread.ads): GNAT Threads g-thread ads.
818 * GNAT.Traceback (g-traceb.ads): GNAT Traceback g-traceb ads.
819 * GNAT.Traceback.Symbolic (g-trasym.ads): GNAT Traceback Symbolic g-trasym ads.
820 * GNAT.UTF_32 (g-table.ads): GNAT UTF_32 g-table ads.
821 * GNAT.Wide_Spelling_Checker (g-u3spch.ads): GNAT Wide_Spelling_Checker g-u3spch ads.
822 * GNAT.Wide_Spelling_Checker (g-wispch.ads): GNAT Wide_Spelling_Checker g-wispch ads.
823 * GNAT.Wide_String_Split (g-wistsp.ads): GNAT Wide_String_Split g-wistsp ads.
824 * GNAT.Wide_Wide_Spelling_Checker (g-zspche.ads): GNAT Wide_Wide_Spelling_Checker g-zspche ads.
825 * GNAT.Wide_Wide_String_Split (g-zistsp.ads): GNAT Wide_Wide_String_Split g-zistsp ads.
826 * Interfaces.C.Extensions (i-cexten.ads): Interfaces C Extensions i-cexten ads.
827 * Interfaces.C.Streams (i-cstrea.ads): Interfaces C Streams i-cstrea ads.
828 * Interfaces.Packed_Decimal (i-pacdec.ads): Interfaces Packed_Decimal i-pacdec ads.
829 * Interfaces.VxWorks (i-vxwork.ads): Interfaces VxWorks i-vxwork ads.
830 * Interfaces.VxWorks.Int_Connection (i-vxinco.ads): Interfaces VxWorks Int_Connection i-vxinco ads.
831 * Interfaces.VxWorks.IO (i-vxwoio.ads): Interfaces VxWorks IO i-vxwoio ads.
832 * System.Address_Image (s-addima.ads): System Address_Image s-addima ads.
833 * System.Assertions (s-assert.ads): System Assertions s-assert ads.
834 * System.Atomic_Counters (s-atocou.ads): System Atomic_Counters s-atocou ads.
835 * System.Memory (s-memory.ads): System Memory s-memory ads.
836 * System.Multiprocessors (s-multip.ads): System Multiprocessors s-multip ads.
837 * System.Multiprocessors.Dispatching_Domains (s-mudido.ads): System Multiprocessors Dispatching_Domains s-mudido ads.
838 * System.Partition_Interface (s-parint.ads): System Partition_Interface s-parint ads.
839 * System.Pool_Global (s-pooglo.ads): System Pool_Global s-pooglo ads.
840 * System.Pool_Local (s-pooloc.ads): System Pool_Local s-pooloc ads.
841 * System.Restrictions (s-restri.ads): System Restrictions s-restri ads.
842 * System.Rident (s-rident.ads): System Rident s-rident ads.
843 * System.Strings.Stream_Ops (s-ststop.ads): System Strings Stream_Ops s-ststop ads.
844 * System.Unsigned_Types (s-unstyp.ads): System Unsigned_Types s-unstyp ads.
845 * System.Wch_Cnv (s-wchcnv.ads): System Wch_Cnv s-wchcnv ads.
846 * System.Wch_Con (s-wchcon.ads): System Wch_Con s-wchcon ads.
848 Interfacing to Other Languages
851 * Interfacing to C++::
852 * Interfacing to COBOL::
853 * Interfacing to Fortran::
854 * Interfacing to non-GNAT Ada code::
856 Implementation of Specific Ada Features
858 * Machine Code Insertions::
859 * GNAT Implementation of Tasking::
860 * GNAT Implementation of Shared Passive Packages::
861 * Code Generation for Array Aggregates::
862 * The Size of Discriminated Records with Default Discriminants::
863 * Strict Conformance to the Ada Reference Manual::
865 GNAT Implementation of Tasking
867 * Mapping Ada Tasks onto the Underlying Kernel Threads::
868 * Ensuring Compliance with the Real-Time Annex::
869 * Support for Locking Policies::
871 Code Generation for Array Aggregates
873 * Static constant aggregates with static bounds::
874 * Constant aggregates with unconstrained nominal types::
875 * Aggregates with static bounds::
876 * Aggregates with nonstatic bounds::
877 * Aggregates in assignment statements::
881 * pragma No_Run_Time::
883 * pragma Restricted_Run_Time::
885 * package System.Task_Info (s-tasinf.ads): package System Task_Info s-tasinf ads.
887 Compatibility and Porting Guide
889 * Writing Portable Fixed-Point Declarations::
890 * Compatibility with Ada 83::
891 * Compatibility between Ada 95 and Ada 2005::
892 * Implementation-dependent characteristics::
893 * Compatibility with Other Ada Systems::
894 * Representation Clauses::
895 * Compatibility with HP Ada 83::
897 Compatibility with Ada 83
899 * Legal Ada 83 programs that are illegal in Ada 95::
900 * More deterministic semantics::
901 * Changed semantics::
902 * Other language compatibility issues::
904 Implementation-dependent characteristics
906 * Implementation-defined pragmas::
907 * Implementation-defined attributes::
909 * Elaboration order::
910 * Target-specific aspects::
915 @node About This Guide,Implementation Defined Pragmas,Top,Top
916 @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}
917 @chapter About This Guide
921 This manual contains useful information in writing programs using the
922 GNAT compiler. It includes information on implementation dependent
923 characteristics of GNAT, including all the information required by
924 Annex M of the Ada language standard.
926 GNAT implements Ada 95, Ada 2005 and Ada 2012, and it may also be
927 invoked in Ada 83 compatibility mode.
928 By default, GNAT assumes Ada 2012,
929 but you can override with a compiler switch
930 to explicitly specify the language version.
931 (Please refer to the @emph{GNAT User's Guide} for details on these switches.)
932 Throughout this manual, references to 'Ada' without a year suffix
933 apply to all the Ada versions of the language.
935 Ada is designed to be highly portable.
936 In general, a program will have the same effect even when compiled by
937 different compilers on different platforms.
938 However, since Ada is designed to be used in a
939 wide variety of applications, it also contains a number of system
940 dependent features to be used in interfacing to the external world.
942 @geindex Implementation-dependent features
946 Note: Any program that makes use of implementation-dependent features
947 may be non-portable. You should follow good programming practice and
948 isolate and clearly document any sections of your program that make use
949 of these features in a non-portable manner.
952 * What This Reference Manual Contains::
954 * Related Information::
958 @node What This Reference Manual Contains,Conventions,,About This Guide
959 @anchor{gnat_rm/about_this_guide what-this-reference-manual-contains}@anchor{6}
960 @section What This Reference Manual Contains
963 This reference manual contains the following chapters:
969 @ref{7,,Implementation Defined Pragmas}, lists GNAT implementation-dependent
970 pragmas, which can be used to extend and enhance the functionality of the
974 @ref{8,,Implementation Defined Attributes}, lists GNAT
975 implementation-dependent attributes, which can be used to extend and
976 enhance the functionality of the compiler.
979 @ref{9,,Standard and Implementation Defined Restrictions}, lists GNAT
980 implementation-dependent restrictions, which can be used to extend and
981 enhance the functionality of the compiler.
984 @ref{a,,Implementation Advice}, provides information on generally
985 desirable behavior which are not requirements that all compilers must
986 follow since it cannot be provided on all systems, or which may be
987 undesirable on some systems.
990 @ref{b,,Implementation Defined Characteristics}, provides a guide to
991 minimizing implementation dependent features.
994 @ref{c,,Intrinsic Subprograms}, describes the intrinsic subprograms
995 implemented by GNAT, and how they can be imported into user
996 application programs.
999 @ref{d,,Representation Clauses and Pragmas}, describes in detail the
1000 way that GNAT represents data, and in particular the exact set
1001 of representation clauses and pragmas that is accepted.
1004 @ref{e,,Standard Library Routines}, provides a listing of packages and a
1005 brief description of the functionality that is provided by Ada's
1006 extensive set of standard library routines as implemented by GNAT.
1009 @ref{f,,The Implementation of Standard I/O}, details how the GNAT
1010 implementation of the input-output facilities.
1013 @ref{10,,The GNAT Library}, is a catalog of packages that complement
1014 the Ada predefined library.
1017 @ref{11,,Interfacing to Other Languages}, describes how programs
1018 written in Ada using GNAT can be interfaced to other programming
1022 @ref{12,,Specialized Needs Annexes}, describes the GNAT implementation of all
1023 of the specialized needs annexes.
1026 @ref{13,,Implementation of Specific Ada Features}, discusses issues related
1027 to GNAT's implementation of machine code insertions, tasking, and several
1031 @ref{14,,Implementation of Ada 2012 Features}, describes the status of the
1032 GNAT implementation of the Ada 2012 language standard.
1035 @ref{15,,Obsolescent Features} documents implementation dependent features,
1036 including pragmas and attributes, which are considered obsolescent, since
1037 there are other preferred ways of achieving the same results. These
1038 obsolescent forms are retained for backwards compatibility.
1041 @ref{16,,Compatibility and Porting Guide} presents some guidelines for
1042 developing portable Ada code, describes the compatibility issues that
1043 may arise between GNAT and other Ada compilation systems (including those
1044 for Ada 83), and shows how GNAT can expedite porting applications
1045 developed in other Ada environments.
1048 @ref{1,,GNU Free Documentation License} contains the license for this document.
1051 @geindex Ada 95 Language Reference Manual
1053 @geindex Ada 2005 Language Reference Manual
1055 This reference manual assumes a basic familiarity with the Ada 95 language, as
1057 @cite{International Standard ANSI/ISO/IEC-8652:1995}.
1058 It does not require knowledge of the new features introduced by Ada 2005 or
1060 All three reference manuals are included in the GNAT documentation
1063 @node Conventions,Related Information,What This Reference Manual Contains,About This Guide
1064 @anchor{gnat_rm/about_this_guide conventions}@anchor{17}
1065 @section Conventions
1068 @geindex Conventions
1069 @geindex typographical
1071 @geindex Typographical conventions
1073 Following are examples of the typographical and graphic conventions used
1080 @code{Functions}, @code{utility program names}, @code{standard names},
1096 [optional information or parameters]
1099 Examples are described by text
1102 and then shown this way.
1106 Commands that are entered by the user are shown as preceded by a prompt string
1107 comprising the @code{$} character followed by a space.
1110 @node Related Information,,Conventions,About This Guide
1111 @anchor{gnat_rm/about_this_guide related-information}@anchor{18}
1112 @section Related Information
1115 See the following documents for further information on GNAT:
1121 @cite{GNAT User's Guide for Native Platforms},
1122 which provides information on how to use the
1123 GNAT development environment.
1126 @cite{Ada 95 Reference Manual}, the Ada 95 programming language standard.
1129 @cite{Ada 95 Annotated Reference Manual}, which is an annotated version
1130 of the Ada 95 standard. The annotations describe
1131 detailed aspects of the design decision, and in particular contain useful
1132 sections on Ada 83 compatibility.
1135 @cite{Ada 2005 Reference Manual}, the Ada 2005 programming language standard.
1138 @cite{Ada 2005 Annotated Reference Manual}, which is an annotated version
1139 of the Ada 2005 standard. The annotations describe
1140 detailed aspects of the design decision.
1143 @cite{Ada 2012 Reference Manual}, the Ada 2012 programming language standard.
1146 @cite{DEC Ada@comma{} Technical Overview and Comparison on DIGITAL Platforms},
1147 which contains specific information on compatibility between GNAT and
1151 @cite{DEC Ada@comma{} Language Reference Manual}, part number AA-PYZAB-TK, which
1152 describes in detail the pragmas and attributes provided by the DEC Ada 83
1156 @node Implementation Defined Pragmas,Implementation Defined Aspects,About This Guide,Top
1157 @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}
1158 @chapter Implementation Defined Pragmas
1161 Ada defines a set of pragmas that can be used to supply additional
1162 information to the compiler. These language defined pragmas are
1163 implemented in GNAT and work as described in the Ada Reference Manual.
1165 In addition, Ada allows implementations to define additional pragmas
1166 whose meaning is defined by the implementation. GNAT provides a number
1167 of these implementation-defined pragmas, which can be used to extend
1168 and enhance the functionality of the compiler. This section of the GNAT
1169 Reference Manual describes these additional pragmas.
1171 Note that any program using these pragmas might not be portable to other
1172 compilers (although GNAT implements this set of pragmas on all
1173 platforms). Therefore if portability to other compilers is an important
1174 consideration, the use of these pragmas should be minimized.
1177 * Pragma Abort_Defer::
1178 * Pragma Abstract_State::
1185 * Pragma Aggregate_Individually_Assign::
1186 * Pragma Allow_Integer_Address::
1189 * Pragma Assert_And_Cut::
1190 * Pragma Assertion_Policy::
1192 * Pragma Assume_No_Invalid_Values::
1193 * Pragma Async_Readers::
1194 * Pragma Async_Writers::
1195 * Pragma Attribute_Definition::
1196 * Pragma C_Pass_By_Copy::
1198 * Pragma Check_Float_Overflow::
1199 * Pragma Check_Name::
1200 * Pragma Check_Policy::
1202 * Pragma Common_Object::
1203 * Pragma Compile_Time_Error::
1204 * Pragma Compile_Time_Warning::
1205 * Pragma Compiler_Unit::
1206 * Pragma Compiler_Unit_Warning::
1207 * Pragma Complete_Representation::
1208 * Pragma Complex_Representation::
1209 * Pragma Component_Alignment::
1210 * Pragma Constant_After_Elaboration::
1211 * Pragma Contract_Cases::
1212 * Pragma Convention_Identifier::
1213 * Pragma CPP_Class::
1214 * Pragma CPP_Constructor::
1215 * Pragma CPP_Virtual::
1216 * Pragma CPP_Vtable::
1218 * Pragma Deadline_Floor::
1219 * Pragma Default_Initial_Condition::
1221 * Pragma Debug_Policy::
1222 * Pragma Default_Scalar_Storage_Order::
1223 * Pragma Default_Storage_Pool::
1225 * Pragma Detect_Blocking::
1226 * Pragma Disable_Atomic_Synchronization::
1227 * Pragma Dispatching_Domain::
1228 * Pragma Effective_Reads::
1229 * Pragma Effective_Writes::
1230 * Pragma Elaboration_Checks::
1231 * Pragma Eliminate::
1232 * Pragma Enable_Atomic_Synchronization::
1233 * Pragma Export_Function::
1234 * Pragma Export_Object::
1235 * Pragma Export_Procedure::
1236 * Pragma Export_Value::
1237 * Pragma Export_Valued_Procedure::
1238 * Pragma Extend_System::
1239 * Pragma Extensions_Allowed::
1240 * Pragma Extensions_Visible::
1242 * Pragma External_Name_Casing::
1243 * Pragma Fast_Math::
1244 * Pragma Favor_Top_Level::
1245 * Pragma Finalize_Storage_Only::
1246 * Pragma Float_Representation::
1250 * Pragma Ignore_Pragma::
1251 * Pragma Implementation_Defined::
1252 * Pragma Implemented::
1253 * Pragma Implicit_Packing::
1254 * Pragma Import_Function::
1255 * Pragma Import_Object::
1256 * Pragma Import_Procedure::
1257 * Pragma Import_Valued_Procedure::
1258 * Pragma Independent::
1259 * Pragma Independent_Components::
1260 * Pragma Initial_Condition::
1261 * Pragma Initialize_Scalars::
1262 * Pragma Initializes::
1263 * Pragma Inline_Always::
1264 * Pragma Inline_Generic::
1265 * Pragma Interface::
1266 * Pragma Interface_Name::
1267 * Pragma Interrupt_Handler::
1268 * Pragma Interrupt_State::
1269 * Pragma Invariant::
1270 * Pragma Keep_Names::
1272 * Pragma Link_With::
1273 * Pragma Linker_Alias::
1274 * Pragma Linker_Constructor::
1275 * Pragma Linker_Destructor::
1276 * Pragma Linker_Section::
1277 * Pragma Lock_Free::
1278 * Pragma Loop_Invariant::
1279 * Pragma Loop_Optimize::
1280 * Pragma Loop_Variant::
1281 * Pragma Machine_Attribute::
1283 * Pragma Main_Storage::
1284 * Pragma Max_Queue_Length::
1286 * Pragma No_Caching::
1287 * Pragma No_Component_Reordering::
1288 * Pragma No_Elaboration_Code_All::
1289 * Pragma No_Heap_Finalization::
1290 * Pragma No_Inline::
1291 * Pragma No_Return::
1292 * Pragma No_Strict_Aliasing::
1293 * Pragma No_Tagged_Streams::
1294 * Pragma Normalize_Scalars::
1295 * Pragma Obsolescent::
1296 * Pragma Optimize_Alignment::
1298 * Pragma Overflow_Mode::
1299 * Pragma Overriding_Renamings::
1300 * Pragma Partition_Elaboration_Policy::
1303 * Pragma Persistent_BSS::
1305 * Pragma Postcondition::
1306 * Pragma Post_Class::
1307 * Pragma Rename_Pragma::
1309 * Pragma Precondition::
1310 * Pragma Predicate::
1311 * Pragma Predicate_Failure::
1312 * Pragma Preelaborable_Initialization::
1313 * Pragma Prefix_Exception_Messages::
1314 * Pragma Pre_Class::
1315 * Pragma Priority_Specific_Dispatching::
1317 * Pragma Profile_Warnings::
1318 * Pragma Propagate_Exceptions::
1319 * Pragma Provide_Shift_Operators::
1320 * Pragma Psect_Object::
1321 * Pragma Pure_Function::
1323 * Pragma Ravenscar::
1324 * Pragma Refined_Depends::
1325 * Pragma Refined_Global::
1326 * Pragma Refined_Post::
1327 * Pragma Refined_State::
1328 * Pragma Relative_Deadline::
1329 * Pragma Remote_Access_Type::
1330 * Pragma Restricted_Run_Time::
1331 * Pragma Restriction_Warnings::
1332 * Pragma Reviewable::
1333 * Pragma Secondary_Stack_Size::
1334 * Pragma Share_Generic::
1336 * Pragma Short_Circuit_And_Or::
1337 * Pragma Short_Descriptors::
1338 * Pragma Simple_Storage_Pool_Type::
1339 * Pragma Source_File_Name::
1340 * Pragma Source_File_Name_Project::
1341 * Pragma Source_Reference::
1342 * Pragma SPARK_Mode::
1343 * Pragma Static_Elaboration_Desired::
1344 * Pragma Stream_Convert::
1345 * Pragma Style_Checks::
1348 * Pragma Suppress_All::
1349 * Pragma Suppress_Debug_Info::
1350 * Pragma Suppress_Exception_Locations::
1351 * Pragma Suppress_Initialization::
1352 * Pragma Task_Name::
1353 * Pragma Task_Storage::
1354 * Pragma Test_Case::
1355 * Pragma Thread_Local_Storage::
1356 * Pragma Time_Slice::
1358 * Pragma Type_Invariant::
1359 * Pragma Type_Invariant_Class::
1360 * Pragma Unchecked_Union::
1361 * Pragma Unevaluated_Use_Of_Old::
1362 * Pragma Unimplemented_Unit::
1363 * Pragma Universal_Aliasing::
1364 * Pragma Universal_Data::
1365 * Pragma Unmodified::
1366 * Pragma Unreferenced::
1367 * Pragma Unreferenced_Objects::
1368 * Pragma Unreserve_All_Interrupts::
1369 * Pragma Unsuppress::
1370 * Pragma Use_VADS_Size::
1372 * Pragma Validity_Checks::
1374 * Pragma Volatile_Full_Access::
1375 * Pragma Volatile_Function::
1376 * Pragma Warning_As_Error::
1378 * Pragma Weak_External::
1379 * Pragma Wide_Character_Encoding::
1383 @node Pragma Abort_Defer,Pragma Abstract_State,,Implementation Defined Pragmas
1384 @anchor{gnat_rm/implementation_defined_pragmas pragma-abort-defer}@anchor{1b}
1385 @section Pragma Abort_Defer
1388 @geindex Deferring aborts
1396 This pragma must appear at the start of the statement sequence of a
1397 handled sequence of statements (right after the @code{begin}). It has
1398 the effect of deferring aborts for the sequence of statements (but not
1399 for the declarations or handlers, if any, associated with this statement
1400 sequence). This can also be useful for adding a polling point in Ada code,
1401 where asynchronous abort of tasks is checked when leaving the statement
1402 sequence, and is lighter than, for example, using @code{delay 0.0;}, since with
1403 zero-cost exception handling, propagating exceptions (implicitly used to
1404 implement task abort) cannot be done reliably in an asynchronous way.
1406 An example of usage would be:
1409 -- Add a polling point to check for task aborts
1416 @node Pragma Abstract_State,Pragma Ada_83,Pragma Abort_Defer,Implementation Defined Pragmas
1417 @anchor{gnat_rm/implementation_defined_pragmas pragma-abstract-state}@anchor{1c}@anchor{gnat_rm/implementation_defined_pragmas id2}@anchor{1d}
1418 @section Pragma Abstract_State
1424 pragma Abstract_State (ABSTRACT_STATE_LIST);
1426 ABSTRACT_STATE_LIST ::=
1428 | STATE_NAME_WITH_OPTIONS
1429 | (STATE_NAME_WITH_OPTIONS @{, STATE_NAME_WITH_OPTIONS@} )
1431 STATE_NAME_WITH_OPTIONS ::=
1433 | (STATE_NAME with OPTION_LIST)
1435 OPTION_LIST ::= OPTION @{, OPTION@}
1441 SIMPLE_OPTION ::= Ghost | Synchronous
1443 NAME_VALUE_OPTION ::=
1444 Part_Of => ABSTRACT_STATE
1445 | External [=> EXTERNAL_PROPERTY_LIST]
1447 EXTERNAL_PROPERTY_LIST ::=
1449 | (EXTERNAL_PROPERTY @{, EXTERNAL_PROPERTY@} )
1451 EXTERNAL_PROPERTY ::=
1452 Async_Readers [=> boolean_EXPRESSION]
1453 | Async_Writers [=> boolean_EXPRESSION]
1454 | Effective_Reads [=> boolean_EXPRESSION]
1455 | Effective_Writes [=> boolean_EXPRESSION]
1456 others => boolean_EXPRESSION
1458 STATE_NAME ::= defining_identifier
1460 ABSTRACT_STATE ::= name
1463 For the semantics of this pragma, see the entry for aspect @code{Abstract_State} in
1464 the SPARK 2014 Reference Manual, section 7.1.4.
1466 @node Pragma Ada_83,Pragma Ada_95,Pragma Abstract_State,Implementation Defined Pragmas
1467 @anchor{gnat_rm/implementation_defined_pragmas pragma-ada-83}@anchor{1e}
1468 @section Pragma Ada_83
1477 A configuration pragma that establishes Ada 83 mode for the unit to
1478 which it applies, regardless of the mode set by the command line
1479 switches. In Ada 83 mode, GNAT attempts to be as compatible with
1480 the syntax and semantics of Ada 83, as defined in the original Ada
1481 83 Reference Manual as possible. In particular, the keywords added by Ada 95
1482 and Ada 2005 are not recognized, optional package bodies are allowed,
1483 and generics may name types with unknown discriminants without using
1484 the @code{(<>)} notation. In addition, some but not all of the additional
1485 restrictions of Ada 83 are enforced.
1487 Ada 83 mode is intended for two purposes. Firstly, it allows existing
1488 Ada 83 code to be compiled and adapted to GNAT with less effort.
1489 Secondly, it aids in keeping code backwards compatible with Ada 83.
1490 However, there is no guarantee that code that is processed correctly
1491 by GNAT in Ada 83 mode will in fact compile and execute with an Ada
1492 83 compiler, since GNAT does not enforce all the additional checks
1495 @node Pragma Ada_95,Pragma Ada_05,Pragma Ada_83,Implementation Defined Pragmas
1496 @anchor{gnat_rm/implementation_defined_pragmas pragma-ada-95}@anchor{1f}
1497 @section Pragma Ada_95
1506 A configuration pragma that establishes Ada 95 mode for the unit to which
1507 it applies, regardless of the mode set by the command line switches.
1508 This mode is set automatically for the @code{Ada} and @code{System}
1509 packages and their children, so you need not specify it in these
1510 contexts. This pragma is useful when writing a reusable component that
1511 itself uses Ada 95 features, but which is intended to be usable from
1512 either Ada 83 or Ada 95 programs.
1514 @node Pragma Ada_05,Pragma Ada_2005,Pragma Ada_95,Implementation Defined Pragmas
1515 @anchor{gnat_rm/implementation_defined_pragmas pragma-ada-05}@anchor{20}
1516 @section Pragma Ada_05
1523 pragma Ada_05 (local_NAME);
1526 A configuration pragma that establishes Ada 2005 mode for the unit to which
1527 it applies, regardless of the mode set by the command line switches.
1528 This pragma is useful when writing a reusable component that
1529 itself uses Ada 2005 features, but which is intended to be usable from
1530 either Ada 83 or Ada 95 programs.
1532 The one argument form (which is not a configuration pragma)
1533 is used for managing the transition from
1534 Ada 95 to Ada 2005 in the run-time library. If an entity is marked
1535 as Ada_2005 only, then referencing the entity in Ada_83 or Ada_95
1536 mode will generate a warning. In addition, in Ada_83 or Ada_95
1537 mode, a preference rule is established which does not choose
1538 such an entity unless it is unambiguously specified. This avoids
1539 extra subprograms marked this way from generating ambiguities in
1540 otherwise legal pre-Ada_2005 programs. The one argument form is
1541 intended for exclusive use in the GNAT run-time library.
1543 @node Pragma Ada_2005,Pragma Ada_12,Pragma Ada_05,Implementation Defined Pragmas
1544 @anchor{gnat_rm/implementation_defined_pragmas pragma-ada-2005}@anchor{21}
1545 @section Pragma Ada_2005
1554 This configuration pragma is a synonym for pragma Ada_05 and has the
1555 same syntax and effect.
1557 @node Pragma Ada_12,Pragma Ada_2012,Pragma Ada_2005,Implementation Defined Pragmas
1558 @anchor{gnat_rm/implementation_defined_pragmas pragma-ada-12}@anchor{22}
1559 @section Pragma Ada_12
1566 pragma Ada_12 (local_NAME);
1569 A configuration pragma that establishes Ada 2012 mode for the unit to which
1570 it applies, regardless of the mode set by the command line switches.
1571 This mode is set automatically for the @code{Ada} and @code{System}
1572 packages and their children, so you need not specify it in these
1573 contexts. This pragma is useful when writing a reusable component that
1574 itself uses Ada 2012 features, but which is intended to be usable from
1575 Ada 83, Ada 95, or Ada 2005 programs.
1577 The one argument form, which is not a configuration pragma,
1578 is used for managing the transition from Ada
1579 2005 to Ada 2012 in the run-time library. If an entity is marked
1580 as Ada_2012 only, then referencing the entity in any pre-Ada_2012
1581 mode will generate a warning. In addition, in any pre-Ada_2012
1582 mode, a preference rule is established which does not choose
1583 such an entity unless it is unambiguously specified. This avoids
1584 extra subprograms marked this way from generating ambiguities in
1585 otherwise legal pre-Ada_2012 programs. The one argument form is
1586 intended for exclusive use in the GNAT run-time library.
1588 @node Pragma Ada_2012,Pragma Aggregate_Individually_Assign,Pragma Ada_12,Implementation Defined Pragmas
1589 @anchor{gnat_rm/implementation_defined_pragmas pragma-ada-2012}@anchor{23}
1590 @section Pragma Ada_2012
1599 This configuration pragma is a synonym for pragma Ada_12 and has the
1600 same syntax and effect.
1602 @node Pragma Aggregate_Individually_Assign,Pragma Allow_Integer_Address,Pragma Ada_2012,Implementation Defined Pragmas
1603 @anchor{gnat_rm/implementation_defined_pragmas pragma-aggregate-individually-assign}@anchor{24}
1604 @section Pragma Aggregate_Individually_Assign
1610 pragma Aggregate_Individually_Assign;
1613 Where possible, GNAT will store the binary representation of a record aggregate
1614 in memory for space and performance reasons. This configuration pragma changes
1615 this behavior so that record aggregates are instead always converted into
1616 individual assignment statements.
1618 @node Pragma Allow_Integer_Address,Pragma Annotate,Pragma Aggregate_Individually_Assign,Implementation Defined Pragmas
1619 @anchor{gnat_rm/implementation_defined_pragmas pragma-allow-integer-address}@anchor{25}
1620 @section Pragma Allow_Integer_Address
1626 pragma Allow_Integer_Address;
1629 In almost all versions of GNAT, @code{System.Address} is a private
1630 type in accordance with the implementation advice in the RM. This
1631 means that integer values,
1632 in particular integer literals, are not allowed as address values.
1633 If the configuration pragma
1634 @code{Allow_Integer_Address} is given, then integer expressions may
1635 be used anywhere a value of type @code{System.Address} is required.
1636 The effect is to introduce an implicit unchecked conversion from the
1637 integer value to type @code{System.Address}. The reverse case of using
1638 an address where an integer type is required is handled analogously.
1639 The following example compiles without errors:
1642 pragma Allow_Integer_Address;
1643 with System; use System;
1644 package AddrAsInt is
1647 for X'Address use 16#1240#;
1648 for Y use at 16#3230#;
1649 m : Address := 16#4000#;
1650 n : constant Address := 4000;
1651 p : constant Address := Address (X + Y);
1652 v : Integer := y'Address;
1653 w : constant Integer := Integer (Y'Address);
1654 type R is new integer;
1657 for Z'Address use RR;
1661 Note that pragma @code{Allow_Integer_Address} is ignored if @code{System.Address}
1662 is not a private type. In implementations of @code{GNAT} where
1663 System.Address is a visible integer type,
1664 this pragma serves no purpose but is ignored
1665 rather than rejected to allow common sets of sources to be used
1666 in the two situations.
1668 @node Pragma Annotate,Pragma Assert,Pragma Allow_Integer_Address,Implementation Defined Pragmas
1669 @anchor{gnat_rm/implementation_defined_pragmas pragma-annotate}@anchor{26}@anchor{gnat_rm/implementation_defined_pragmas id3}@anchor{27}
1670 @section Pragma Annotate
1676 pragma Annotate (IDENTIFIER [, IDENTIFIER @{, ARG@}] [, entity => local_NAME]);
1678 ARG ::= NAME | EXPRESSION
1681 This pragma is used to annotate programs. IDENTIFIER identifies
1682 the type of annotation. GNAT verifies that it is an identifier, but does
1683 not otherwise analyze it. The second optional identifier is also left
1684 unanalyzed, and by convention is used to control the action of the tool to
1685 which the annotation is addressed. The remaining ARG arguments
1686 can be either string literals or more generally expressions.
1687 String literals (and concatenations of string literals) are assumed to be
1689 @code{Standard.String} or else @code{Wide_String} or @code{Wide_Wide_String}
1690 depending on the character literals they contain.
1691 All other kinds of arguments are analyzed as expressions, and must be
1692 unambiguous. The last argument if present must have the identifier
1693 @code{Entity} and GNAT verifies that a local name is given.
1695 The analyzed pragma is retained in the tree, but not otherwise processed
1696 by any part of the GNAT compiler, except to generate corresponding note
1697 lines in the generated ALI file. For the format of these note lines, see
1698 the compiler source file lib-writ.ads. This pragma is intended for use by
1699 external tools, including ASIS. The use of pragma Annotate does not
1700 affect the compilation process in any way. This pragma may be used as
1701 a configuration pragma.
1703 @node Pragma Assert,Pragma Assert_And_Cut,Pragma Annotate,Implementation Defined Pragmas
1704 @anchor{gnat_rm/implementation_defined_pragmas pragma-assert}@anchor{28}
1705 @section Pragma Assert
1713 [, string_EXPRESSION]);
1716 The effect of this pragma depends on whether the corresponding command
1717 line switch is set to activate assertions. The pragma expands into code
1718 equivalent to the following:
1721 if assertions-enabled then
1722 if not boolean_EXPRESSION then
1723 System.Assertions.Raise_Assert_Failure
1724 (string_EXPRESSION);
1729 The string argument, if given, is the message that will be associated
1730 with the exception occurrence if the exception is raised. If no second
1731 argument is given, the default message is @code{file}:@code{nnn},
1732 where @code{file} is the name of the source file containing the assert,
1733 and @code{nnn} is the line number of the assert.
1735 Note that, as with the @code{if} statement to which it is equivalent, the
1736 type of the expression is either @code{Standard.Boolean}, or any type derived
1737 from this standard type.
1739 Assert checks can be either checked or ignored. By default they are ignored.
1740 They will be checked if either the command line switch @emph{-gnata} is
1741 used, or if an @code{Assertion_Policy} or @code{Check_Policy} pragma is used
1742 to enable @code{Assert_Checks}.
1744 If assertions are ignored, then there
1745 is no run-time effect (and in particular, any side effects from the
1746 expression will not occur at run time). (The expression is still
1747 analyzed at compile time, and may cause types to be frozen if they are
1748 mentioned here for the first time).
1750 If assertions are checked, then the given expression is tested, and if
1751 it is @code{False} then @code{System.Assertions.Raise_Assert_Failure} is called
1752 which results in the raising of @code{Assert_Failure} with the given message.
1754 You should generally avoid side effects in the expression arguments of
1755 this pragma, because these side effects will turn on and off with the
1756 setting of the assertions mode, resulting in assertions that have an
1757 effect on the program. However, the expressions are analyzed for
1758 semantic correctness whether or not assertions are enabled, so turning
1759 assertions on and off cannot affect the legality of a program.
1761 Note that the implementation defined policy @code{DISABLE}, given in a
1762 pragma @code{Assertion_Policy}, can be used to suppress this semantic analysis.
1764 Note: this is a standard language-defined pragma in versions
1765 of Ada from 2005 on. In GNAT, it is implemented in all versions
1766 of Ada, and the DISABLE policy is an implementation-defined
1769 @node Pragma Assert_And_Cut,Pragma Assertion_Policy,Pragma Assert,Implementation Defined Pragmas
1770 @anchor{gnat_rm/implementation_defined_pragmas pragma-assert-and-cut}@anchor{29}
1771 @section Pragma Assert_And_Cut
1777 pragma Assert_And_Cut (
1779 [, string_EXPRESSION]);
1782 The effect of this pragma is identical to that of pragma @code{Assert},
1783 except that in an @code{Assertion_Policy} pragma, the identifier
1784 @code{Assert_And_Cut} is used to control whether it is ignored or checked
1787 The intention is that this be used within a subprogram when the
1788 given test expresion sums up all the work done so far in the
1789 subprogram, so that the rest of the subprogram can be verified
1790 (informally or formally) using only the entry preconditions,
1791 and the expression in this pragma. This allows dividing up
1792 a subprogram into sections for the purposes of testing or
1793 formal verification. The pragma also serves as useful
1796 @node Pragma Assertion_Policy,Pragma Assume,Pragma Assert_And_Cut,Implementation Defined Pragmas
1797 @anchor{gnat_rm/implementation_defined_pragmas pragma-assertion-policy}@anchor{2a}
1798 @section Pragma Assertion_Policy
1804 pragma Assertion_Policy (CHECK | DISABLE | IGNORE | SUPPRESSIBLE);
1806 pragma Assertion_Policy (
1807 ASSERTION_KIND => POLICY_IDENTIFIER
1808 @{, ASSERTION_KIND => POLICY_IDENTIFIER@});
1810 ASSERTION_KIND ::= RM_ASSERTION_KIND | ID_ASSERTION_KIND
1812 RM_ASSERTION_KIND ::= Assert |
1820 Type_Invariant'Class |
1821 Default_Initial_Condition
1823 ID_ASSERTION_KIND ::= Assertions |
1838 Statement_Assertions |
1841 POLICY_IDENTIFIER ::= Check | Disable | Ignore | Suppressible
1844 This is a standard Ada 2012 pragma that is available as an
1845 implementation-defined pragma in earlier versions of Ada.
1846 The assertion kinds @code{RM_ASSERTION_KIND} are those defined in
1847 the Ada standard. The assertion kinds @code{ID_ASSERTION_KIND}
1848 are implementation defined additions recognized by the GNAT compiler.
1850 The pragma applies in both cases to pragmas and aspects with matching
1851 names, e.g. @code{Pre} applies to the Pre aspect, and @code{Precondition}
1852 applies to both the @code{Precondition} pragma
1853 and the aspect @code{Precondition}. Note that the identifiers for
1854 pragmas Pre_Class and Post_Class are Pre'Class and Post'Class (not
1855 Pre_Class and Post_Class), since these pragmas are intended to be
1856 identical to the corresponding aspects).
1858 If the policy is @code{CHECK}, then assertions are enabled, i.e.
1859 the corresponding pragma or aspect is activated.
1860 If the policy is @code{IGNORE}, then assertions are ignored, i.e.
1861 the corresponding pragma or aspect is deactivated.
1862 This pragma overrides the effect of the @emph{-gnata} switch on the
1864 If the policy is @code{SUPPRESSIBLE}, then assertions are enabled by default,
1865 however, if the @emph{-gnatp} switch is specified all assertions are ignored.
1867 The implementation defined policy @code{DISABLE} is like
1868 @code{IGNORE} except that it completely disables semantic
1869 checking of the corresponding pragma or aspect. This is
1870 useful when the pragma or aspect argument references subprograms
1871 in a with'ed package which is replaced by a dummy package
1872 for the final build.
1874 The implementation defined assertion kind @code{Assertions} applies to all
1875 assertion kinds. The form with no assertion kind given implies this
1876 choice, so it applies to all assertion kinds (RM defined, and
1877 implementation defined).
1879 The implementation defined assertion kind @code{Statement_Assertions}
1880 applies to @code{Assert}, @code{Assert_And_Cut},
1881 @code{Assume}, @code{Loop_Invariant}, and @code{Loop_Variant}.
1883 @node Pragma Assume,Pragma Assume_No_Invalid_Values,Pragma Assertion_Policy,Implementation Defined Pragmas
1884 @anchor{gnat_rm/implementation_defined_pragmas pragma-assume}@anchor{2b}
1885 @section Pragma Assume
1893 [, string_EXPRESSION]);
1896 The effect of this pragma is identical to that of pragma @code{Assert},
1897 except that in an @code{Assertion_Policy} pragma, the identifier
1898 @code{Assume} is used to control whether it is ignored or checked
1901 The intention is that this be used for assumptions about the
1902 external environment. So you cannot expect to verify formally
1903 or informally that the condition is met, this must be
1904 established by examining things outside the program itself.
1905 For example, we may have code that depends on the size of
1906 @code{Long_Long_Integer} being at least 64. So we could write:
1909 pragma Assume (Long_Long_Integer'Size >= 64);
1912 This assumption cannot be proved from the program itself,
1913 but it acts as a useful run-time check that the assumption
1914 is met, and documents the need to ensure that it is met by
1915 reference to information outside the program.
1917 @node Pragma Assume_No_Invalid_Values,Pragma Async_Readers,Pragma Assume,Implementation Defined Pragmas
1918 @anchor{gnat_rm/implementation_defined_pragmas pragma-assume-no-invalid-values}@anchor{2c}
1919 @section Pragma Assume_No_Invalid_Values
1922 @geindex Invalid representations
1924 @geindex Invalid values
1929 pragma Assume_No_Invalid_Values (On | Off);
1932 This is a configuration pragma that controls the assumptions made by the
1933 compiler about the occurrence of invalid representations (invalid values)
1936 The default behavior (corresponding to an Off argument for this pragma), is
1937 to assume that values may in general be invalid unless the compiler can
1938 prove they are valid. Consider the following example:
1941 V1 : Integer range 1 .. 10;
1942 V2 : Integer range 11 .. 20;
1944 for J in V2 .. V1 loop
1949 if V1 and V2 have valid values, then the loop is known at compile
1950 time not to execute since the lower bound must be greater than the
1951 upper bound. However in default mode, no such assumption is made,
1952 and the loop may execute. If @code{Assume_No_Invalid_Values (On)}
1953 is given, the compiler will assume that any occurrence of a variable
1954 other than in an explicit @code{'Valid} test always has a valid
1955 value, and the loop above will be optimized away.
1957 The use of @code{Assume_No_Invalid_Values (On)} is appropriate if
1958 you know your code is free of uninitialized variables and other
1959 possible sources of invalid representations, and may result in
1960 more efficient code. A program that accesses an invalid representation
1961 with this pragma in effect is erroneous, so no guarantees can be made
1964 It is peculiar though permissible to use this pragma in conjunction
1965 with validity checking (-gnatVa). In such cases, accessing invalid
1966 values will generally give an exception, though formally the program
1967 is erroneous so there are no guarantees that this will always be the
1968 case, and it is recommended that these two options not be used together.
1970 @node Pragma Async_Readers,Pragma Async_Writers,Pragma Assume_No_Invalid_Values,Implementation Defined Pragmas
1971 @anchor{gnat_rm/implementation_defined_pragmas pragma-async-readers}@anchor{2d}@anchor{gnat_rm/implementation_defined_pragmas id4}@anchor{2e}
1972 @section Pragma Async_Readers
1978 pragma Async_Readers [ (boolean_EXPRESSION) ];
1981 For the semantics of this pragma, see the entry for aspect @code{Async_Readers} in
1982 the SPARK 2014 Reference Manual, section 7.1.2.
1984 @node Pragma Async_Writers,Pragma Attribute_Definition,Pragma Async_Readers,Implementation Defined Pragmas
1985 @anchor{gnat_rm/implementation_defined_pragmas id5}@anchor{2f}@anchor{gnat_rm/implementation_defined_pragmas pragma-async-writers}@anchor{30}
1986 @section Pragma Async_Writers
1992 pragma Async_Writers [ (boolean_EXPRESSION) ];
1995 For the semantics of this pragma, see the entry for aspect @code{Async_Writers} in
1996 the SPARK 2014 Reference Manual, section 7.1.2.
1998 @node Pragma Attribute_Definition,Pragma C_Pass_By_Copy,Pragma Async_Writers,Implementation Defined Pragmas
1999 @anchor{gnat_rm/implementation_defined_pragmas pragma-attribute-definition}@anchor{31}
2000 @section Pragma Attribute_Definition
2006 pragma Attribute_Definition
2007 ([Attribute =>] ATTRIBUTE_DESIGNATOR,
2008 [Entity =>] LOCAL_NAME,
2009 [Expression =>] EXPRESSION | NAME);
2012 If @code{Attribute} is a known attribute name, this pragma is equivalent to
2013 the attribute definition clause:
2016 for Entity'Attribute use Expression;
2019 If @code{Attribute} is not a recognized attribute name, the pragma is
2020 ignored, and a warning is emitted. This allows source
2021 code to be written that takes advantage of some new attribute, while remaining
2022 compilable with earlier compilers.
2024 @node Pragma C_Pass_By_Copy,Pragma Check,Pragma Attribute_Definition,Implementation Defined Pragmas
2025 @anchor{gnat_rm/implementation_defined_pragmas pragma-c-pass-by-copy}@anchor{32}
2026 @section Pragma C_Pass_By_Copy
2029 @geindex Passing by copy
2034 pragma C_Pass_By_Copy
2035 ([Max_Size =>] static_integer_EXPRESSION);
2038 Normally the default mechanism for passing C convention records to C
2039 convention subprograms is to pass them by reference, as suggested by RM
2040 B.3(69). Use the configuration pragma @code{C_Pass_By_Copy} to change
2041 this default, by requiring that record formal parameters be passed by
2042 copy if all of the following conditions are met:
2048 The size of the record type does not exceed the value specified for
2052 The record type has @code{Convention C}.
2055 The formal parameter has this record type, and the subprogram has a
2056 foreign (non-Ada) convention.
2059 If these conditions are met the argument is passed by copy; i.e., in a
2060 manner consistent with what C expects if the corresponding formal in the
2061 C prototype is a struct (rather than a pointer to a struct).
2063 You can also pass records by copy by specifying the convention
2064 @code{C_Pass_By_Copy} for the record type, or by using the extended
2065 @code{Import} and @code{Export} pragmas, which allow specification of
2066 passing mechanisms on a parameter by parameter basis.
2068 @node Pragma Check,Pragma Check_Float_Overflow,Pragma C_Pass_By_Copy,Implementation Defined Pragmas
2069 @anchor{gnat_rm/implementation_defined_pragmas pragma-check}@anchor{33}
2070 @section Pragma Check
2075 @geindex Named assertions
2081 [Name =>] CHECK_KIND,
2082 [Check =>] Boolean_EXPRESSION
2083 [, [Message =>] string_EXPRESSION] );
2085 CHECK_KIND ::= IDENTIFIER |
2088 Type_Invariant'Class |
2092 This pragma is similar to the predefined pragma @code{Assert} except that an
2093 extra identifier argument is present. In conjunction with pragma
2094 @code{Check_Policy}, this can be used to define groups of assertions that can
2095 be independently controlled. The identifier @code{Assertion} is special, it
2096 refers to the normal set of pragma @code{Assert} statements.
2098 Checks introduced by this pragma are normally deactivated by default. They can
2099 be activated either by the command line option @emph{-gnata}, which turns on
2100 all checks, or individually controlled using pragma @code{Check_Policy}.
2102 The identifiers @code{Assertions} and @code{Statement_Assertions} are not
2103 permitted as check kinds, since this would cause confusion with the use
2104 of these identifiers in @code{Assertion_Policy} and @code{Check_Policy}
2105 pragmas, where they are used to refer to sets of assertions.
2107 @node Pragma Check_Float_Overflow,Pragma Check_Name,Pragma Check,Implementation Defined Pragmas
2108 @anchor{gnat_rm/implementation_defined_pragmas pragma-check-float-overflow}@anchor{34}
2109 @section Pragma Check_Float_Overflow
2112 @geindex Floating-point overflow
2117 pragma Check_Float_Overflow;
2120 In Ada, the predefined floating-point types (@code{Short_Float},
2121 @code{Float}, @code{Long_Float}, @code{Long_Long_Float}) are
2122 defined to be @emph{unconstrained}. This means that even though each
2123 has a well-defined base range, an operation that delivers a result
2124 outside this base range is not required to raise an exception.
2125 This implementation permission accommodates the notion
2126 of infinities in IEEE floating-point, and corresponds to the
2127 efficient execution mode on most machines. GNAT will not raise
2128 overflow exceptions on these machines; instead it will generate
2129 infinities and NaN's as defined in the IEEE standard.
2131 Generating infinities, although efficient, is not always desirable.
2132 Often the preferable approach is to check for overflow, even at the
2133 (perhaps considerable) expense of run-time performance.
2134 This can be accomplished by defining your own constrained floating-point subtypes -- i.e., by supplying explicit
2135 range constraints -- and indeed such a subtype
2136 can have the same base range as its base type. For example:
2139 subtype My_Float is Float range Float'Range;
2142 Here @code{My_Float} has the same range as
2143 @code{Float} but is constrained, so operations on
2144 @code{My_Float} values will be checked for overflow
2147 This style will achieve the desired goal, but
2148 it is often more convenient to be able to simply use
2149 the standard predefined floating-point types as long
2150 as overflow checking could be guaranteed.
2151 The @code{Check_Float_Overflow}
2152 configuration pragma achieves this effect. If a unit is compiled
2153 subject to this configuration pragma, then all operations
2154 on predefined floating-point types including operations on
2155 base types of these floating-point types will be treated as
2156 though those types were constrained, and overflow checks
2157 will be generated. The @code{Constraint_Error}
2158 exception is raised if the result is out of range.
2160 This mode can also be set by use of the compiler
2161 switch @emph{-gnateF}.
2163 @node Pragma Check_Name,Pragma Check_Policy,Pragma Check_Float_Overflow,Implementation Defined Pragmas
2164 @anchor{gnat_rm/implementation_defined_pragmas pragma-check-name}@anchor{35}
2165 @section Pragma Check_Name
2168 @geindex Defining check names
2170 @geindex Check names
2176 pragma Check_Name (check_name_IDENTIFIER);
2179 This is a configuration pragma that defines a new implementation
2180 defined check name (unless IDENTIFIER matches one of the predefined
2181 check names, in which case the pragma has no effect). Check names
2182 are global to a partition, so if two or more configuration pragmas
2183 are present in a partition mentioning the same name, only one new
2184 check name is introduced.
2186 An implementation defined check name introduced with this pragma may
2187 be used in only three contexts: @code{pragma Suppress},
2188 @code{pragma Unsuppress},
2189 and as the prefix of a @code{Check_Name'Enabled} attribute reference. For
2190 any of these three cases, the check name must be visible. A check
2191 name is visible if it is in the configuration pragmas applying to
2192 the current unit, or if it appears at the start of any unit that
2193 is part of the dependency set of the current unit (e.g., units that
2194 are mentioned in @code{with} clauses).
2196 Check names introduced by this pragma are subject to control by compiler
2197 switches (in particular -gnatp) in the usual manner.
2199 @node Pragma Check_Policy,Pragma Comment,Pragma Check_Name,Implementation Defined Pragmas
2200 @anchor{gnat_rm/implementation_defined_pragmas pragma-check-policy}@anchor{36}
2201 @section Pragma Check_Policy
2204 @geindex Controlling assertions
2209 @geindex Check pragma control
2211 @geindex Named assertions
2217 ([Name =>] CHECK_KIND,
2218 [Policy =>] POLICY_IDENTIFIER);
2220 pragma Check_Policy (
2221 CHECK_KIND => POLICY_IDENTIFIER
2222 @{, CHECK_KIND => POLICY_IDENTIFIER@});
2224 ASSERTION_KIND ::= RM_ASSERTION_KIND | ID_ASSERTION_KIND
2226 CHECK_KIND ::= IDENTIFIER |
2229 Type_Invariant'Class |
2232 The identifiers Name and Policy are not allowed as CHECK_KIND values. This
2233 avoids confusion between the two possible syntax forms for this pragma.
2235 POLICY_IDENTIFIER ::= ON | OFF | CHECK | DISABLE | IGNORE
2238 This pragma is used to set the checking policy for assertions (specified
2239 by aspects or pragmas), the @code{Debug} pragma, or additional checks
2240 to be checked using the @code{Check} pragma. It may appear either as
2241 a configuration pragma, or within a declarative part of package. In the
2242 latter case, it applies from the point where it appears to the end of
2243 the declarative region (like pragma @code{Suppress}).
2245 The @code{Check_Policy} pragma is similar to the
2246 predefined @code{Assertion_Policy} pragma,
2247 and if the check kind corresponds to one of the assertion kinds that
2248 are allowed by @code{Assertion_Policy}, then the effect is identical.
2250 If the first argument is Debug, then the policy applies to Debug pragmas,
2251 disabling their effect if the policy is @code{OFF}, @code{DISABLE}, or
2252 @code{IGNORE}, and allowing them to execute with normal semantics if
2253 the policy is @code{ON} or @code{CHECK}. In addition if the policy is
2254 @code{DISABLE}, then the procedure call in @code{Debug} pragmas will
2255 be totally ignored and not analyzed semantically.
2257 Finally the first argument may be some other identifier than the above
2258 possibilities, in which case it controls a set of named assertions
2259 that can be checked using pragma @code{Check}. For example, if the pragma:
2262 pragma Check_Policy (Critical_Error, OFF);
2265 is given, then subsequent @code{Check} pragmas whose first argument is also
2266 @code{Critical_Error} will be disabled.
2268 The check policy is @code{OFF} to turn off corresponding checks, and @code{ON}
2269 to turn on corresponding checks. The default for a set of checks for which no
2270 @code{Check_Policy} is given is @code{OFF} unless the compiler switch
2271 @emph{-gnata} is given, which turns on all checks by default.
2273 The check policy settings @code{CHECK} and @code{IGNORE} are recognized
2274 as synonyms for @code{ON} and @code{OFF}. These synonyms are provided for
2275 compatibility with the standard @code{Assertion_Policy} pragma. The check
2276 policy setting @code{DISABLE} causes the second argument of a corresponding
2277 @code{Check} pragma to be completely ignored and not analyzed.
2279 @node Pragma Comment,Pragma Common_Object,Pragma Check_Policy,Implementation Defined Pragmas
2280 @anchor{gnat_rm/implementation_defined_pragmas pragma-comment}@anchor{37}
2281 @section Pragma Comment
2287 pragma Comment (static_string_EXPRESSION);
2290 This is almost identical in effect to pragma @code{Ident}. It allows the
2291 placement of a comment into the object file and hence into the
2292 executable file if the operating system permits such usage. The
2293 difference is that @code{Comment}, unlike @code{Ident}, has
2294 no limitations on placement of the pragma (it can be placed
2295 anywhere in the main source unit), and if more than one pragma
2296 is used, all comments are retained.
2298 @node Pragma Common_Object,Pragma Compile_Time_Error,Pragma Comment,Implementation Defined Pragmas
2299 @anchor{gnat_rm/implementation_defined_pragmas pragma-common-object}@anchor{38}
2300 @section Pragma Common_Object
2306 pragma Common_Object (
2307 [Internal =>] LOCAL_NAME
2308 [, [External =>] EXTERNAL_SYMBOL]
2309 [, [Size =>] EXTERNAL_SYMBOL] );
2313 | static_string_EXPRESSION
2316 This pragma enables the shared use of variables stored in overlaid
2317 linker areas corresponding to the use of @code{COMMON}
2318 in Fortran. The single
2319 object @code{LOCAL_NAME} is assigned to the area designated by
2320 the @code{External} argument.
2321 You may define a record to correspond to a series
2322 of fields. The @code{Size} argument
2323 is syntax checked in GNAT, but otherwise ignored.
2325 @code{Common_Object} is not supported on all platforms. If no
2326 support is available, then the code generator will issue a message
2327 indicating that the necessary attribute for implementation of this
2328 pragma is not available.
2330 @node Pragma Compile_Time_Error,Pragma Compile_Time_Warning,Pragma Common_Object,Implementation Defined Pragmas
2331 @anchor{gnat_rm/implementation_defined_pragmas pragma-compile-time-error}@anchor{39}@anchor{gnat_rm/implementation_defined_pragmas compile-time-error}@anchor{3a}
2332 @section Pragma Compile_Time_Error
2338 pragma Compile_Time_Error
2339 (boolean_EXPRESSION, static_string_EXPRESSION);
2342 This pragma can be used to generate additional compile time
2344 is particularly useful in generics, where errors can be issued for
2345 specific problematic instantiations. The first parameter is a boolean
2346 expression. The pragma ensures that the value of an expression
2347 is known at compile time, and has the value False. The set of expressions
2348 whose values are known at compile time includes all static boolean
2349 expressions, and also other values which the compiler can determine
2350 at compile time (e.g., the size of a record type set by an explicit
2351 size representation clause, or the value of a variable which was
2352 initialized to a constant and is known not to have been modified).
2353 If these conditions are not met, an error message is generated using
2354 the value given as the second argument. This string value may contain
2355 embedded ASCII.LF characters to break the message into multiple lines.
2357 @node Pragma Compile_Time_Warning,Pragma Compiler_Unit,Pragma Compile_Time_Error,Implementation Defined Pragmas
2358 @anchor{gnat_rm/implementation_defined_pragmas pragma-compile-time-warning}@anchor{3b}
2359 @section Pragma Compile_Time_Warning
2365 pragma Compile_Time_Warning
2366 (boolean_EXPRESSION, static_string_EXPRESSION);
2369 Same as pragma Compile_Time_Error, except a warning is issued instead
2370 of an error message. If switch @emph{-gnatw_C} is used, a warning is only issued
2371 if the value of the expression is known to be True at compile time, not when
2372 the value of the expression is not known at compile time.
2373 Note that if this pragma is used in a package that
2374 is with'ed by a client, the client will get the warning even though it
2375 is issued by a with'ed package (normally warnings in with'ed units are
2376 suppressed, but this is a special exception to that rule).
2378 One typical use is within a generic where compile time known characteristics
2379 of formal parameters are tested, and warnings given appropriately. Another use
2380 with a first parameter of True is to warn a client about use of a package,
2381 for example that it is not fully implemented.
2383 In previous versions of the compiler, combining @emph{-gnatwe} with
2384 Compile_Time_Warning resulted in a fatal error. Now the compiler always emits
2385 a warning. You can use @ref{3a,,Pragma Compile_Time_Error} to force the generation of
2388 @node Pragma Compiler_Unit,Pragma Compiler_Unit_Warning,Pragma Compile_Time_Warning,Implementation Defined Pragmas
2389 @anchor{gnat_rm/implementation_defined_pragmas pragma-compiler-unit}@anchor{3c}
2390 @section Pragma Compiler_Unit
2396 pragma Compiler_Unit;
2399 This pragma is obsolete. It is equivalent to Compiler_Unit_Warning. It is
2400 retained so that old versions of the GNAT run-time that use this pragma can
2401 be compiled with newer versions of the compiler.
2403 @node Pragma Compiler_Unit_Warning,Pragma Complete_Representation,Pragma Compiler_Unit,Implementation Defined Pragmas
2404 @anchor{gnat_rm/implementation_defined_pragmas pragma-compiler-unit-warning}@anchor{3d}
2405 @section Pragma Compiler_Unit_Warning
2411 pragma Compiler_Unit_Warning;
2414 This pragma is intended only for internal use in the GNAT run-time library.
2415 It indicates that the unit is used as part of the compiler build. The effect
2416 is to generate warnings for the use of constructs (for example, conditional
2417 expressions) that would cause trouble when bootstrapping using an older
2418 version of GNAT. For the exact list of restrictions, see the compiler sources
2419 and references to Check_Compiler_Unit.
2421 @node Pragma Complete_Representation,Pragma Complex_Representation,Pragma Compiler_Unit_Warning,Implementation Defined Pragmas
2422 @anchor{gnat_rm/implementation_defined_pragmas pragma-complete-representation}@anchor{3e}
2423 @section Pragma Complete_Representation
2429 pragma Complete_Representation;
2432 This pragma must appear immediately within a record representation
2433 clause. Typical placements are before the first component clause
2434 or after the last component clause. The effect is to give an error
2435 message if any component is missing a component clause. This pragma
2436 may be used to ensure that a record representation clause is
2437 complete, and that this invariant is maintained if fields are
2438 added to the record in the future.
2440 @node Pragma Complex_Representation,Pragma Component_Alignment,Pragma Complete_Representation,Implementation Defined Pragmas
2441 @anchor{gnat_rm/implementation_defined_pragmas pragma-complex-representation}@anchor{3f}
2442 @section Pragma Complex_Representation
2448 pragma Complex_Representation
2449 ([Entity =>] LOCAL_NAME);
2452 The @code{Entity} argument must be the name of a record type which has
2453 two fields of the same floating-point type. The effect of this pragma is
2454 to force gcc to use the special internal complex representation form for
2455 this record, which may be more efficient. Note that this may result in
2456 the code for this type not conforming to standard ABI (application
2457 binary interface) requirements for the handling of record types. For
2458 example, in some environments, there is a requirement for passing
2459 records by pointer, and the use of this pragma may result in passing
2460 this type in floating-point registers.
2462 @node Pragma Component_Alignment,Pragma Constant_After_Elaboration,Pragma Complex_Representation,Implementation Defined Pragmas
2463 @anchor{gnat_rm/implementation_defined_pragmas pragma-component-alignment}@anchor{40}
2464 @section Pragma Component_Alignment
2467 @geindex Alignments of components
2469 @geindex Pragma Component_Alignment
2474 pragma Component_Alignment (
2475 [Form =>] ALIGNMENT_CHOICE
2476 [, [Name =>] type_LOCAL_NAME]);
2478 ALIGNMENT_CHOICE ::=
2485 Specifies the alignment of components in array or record types.
2486 The meaning of the @code{Form} argument is as follows:
2490 @geindex Component_Size (in pragma Component_Alignment)
2496 @item @emph{Component_Size}
2498 Aligns scalar components and subcomponents of the array or record type
2499 on boundaries appropriate to their inherent size (naturally
2500 aligned). For example, 1-byte components are aligned on byte boundaries,
2501 2-byte integer components are aligned on 2-byte boundaries, 4-byte
2502 integer components are aligned on 4-byte boundaries and so on. These
2503 alignment rules correspond to the normal rules for C compilers on all
2504 machines except the VAX.
2506 @geindex Component_Size_4 (in pragma Component_Alignment)
2508 @item @emph{Component_Size_4}
2510 Naturally aligns components with a size of four or fewer
2511 bytes. Components that are larger than 4 bytes are placed on the next
2514 @geindex Storage_Unit (in pragma Component_Alignment)
2516 @item @emph{Storage_Unit}
2518 Specifies that array or record components are byte aligned, i.e.,
2519 aligned on boundaries determined by the value of the constant
2520 @code{System.Storage_Unit}.
2522 @geindex Default (in pragma Component_Alignment)
2524 @item @emph{Default}
2526 Specifies that array or record components are aligned on default
2527 boundaries, appropriate to the underlying hardware or operating system or
2528 both. The @code{Default} choice is the same as @code{Component_Size} (natural
2532 If the @code{Name} parameter is present, @code{type_LOCAL_NAME} must
2533 refer to a local record or array type, and the specified alignment
2534 choice applies to the specified type. The use of
2535 @code{Component_Alignment} together with a pragma @code{Pack} causes the
2536 @code{Component_Alignment} pragma to be ignored. The use of
2537 @code{Component_Alignment} together with a record representation clause
2538 is only effective for fields not specified by the representation clause.
2540 If the @code{Name} parameter is absent, the pragma can be used as either
2541 a configuration pragma, in which case it applies to one or more units in
2542 accordance with the normal rules for configuration pragmas, or it can be
2543 used within a declarative part, in which case it applies to types that
2544 are declared within this declarative part, or within any nested scope
2545 within this declarative part. In either case it specifies the alignment
2546 to be applied to any record or array type which has otherwise standard
2549 If the alignment for a record or array type is not specified (using
2550 pragma @code{Pack}, pragma @code{Component_Alignment}, or a record rep
2551 clause), the GNAT uses the default alignment as described previously.
2553 @node Pragma Constant_After_Elaboration,Pragma Contract_Cases,Pragma Component_Alignment,Implementation Defined Pragmas
2554 @anchor{gnat_rm/implementation_defined_pragmas id6}@anchor{41}@anchor{gnat_rm/implementation_defined_pragmas pragma-constant-after-elaboration}@anchor{42}
2555 @section Pragma Constant_After_Elaboration
2561 pragma Constant_After_Elaboration [ (boolean_EXPRESSION) ];
2564 For the semantics of this pragma, see the entry for aspect
2565 @code{Constant_After_Elaboration} in the SPARK 2014 Reference Manual, section 3.3.1.
2567 @node Pragma Contract_Cases,Pragma Convention_Identifier,Pragma Constant_After_Elaboration,Implementation Defined Pragmas
2568 @anchor{gnat_rm/implementation_defined_pragmas id7}@anchor{43}@anchor{gnat_rm/implementation_defined_pragmas pragma-contract-cases}@anchor{44}
2569 @section Pragma Contract_Cases
2572 @geindex Contract cases
2577 pragma Contract_Cases ((CONTRACT_CASE @{, CONTRACT_CASE));
2579 CONTRACT_CASE ::= CASE_GUARD => CONSEQUENCE
2581 CASE_GUARD ::= boolean_EXPRESSION | others
2583 CONSEQUENCE ::= boolean_EXPRESSION
2586 The @code{Contract_Cases} pragma allows defining fine-grain specifications
2587 that can complement or replace the contract given by a precondition and a
2588 postcondition. Additionally, the @code{Contract_Cases} pragma can be used
2589 by testing and formal verification tools. The compiler checks its validity and,
2590 depending on the assertion policy at the point of declaration of the pragma,
2591 it may insert a check in the executable. For code generation, the contract
2595 pragma Contract_Cases (
2603 C1 : constant Boolean := Cond1; -- evaluated at subprogram entry
2604 C2 : constant Boolean := Cond2; -- evaluated at subprogram entry
2605 pragma Precondition ((C1 and not C2) or (C2 and not C1));
2606 pragma Postcondition (if C1 then Pred1);
2607 pragma Postcondition (if C2 then Pred2);
2610 The precondition ensures that one and only one of the case guards is
2611 satisfied on entry to the subprogram.
2612 The postcondition ensures that for the case guard that was True on entry,
2613 the corresponding consequence is True on exit. Other consequence expressions
2616 A precondition @code{P} and postcondition @code{Q} can also be
2617 expressed as contract cases:
2620 pragma Contract_Cases (P => Q);
2623 The placement and visibility rules for @code{Contract_Cases} pragmas are
2624 identical to those described for preconditions and postconditions.
2626 The compiler checks that boolean expressions given in case guards and
2627 consequences are valid, where the rules for case guards are the same as
2628 the rule for an expression in @code{Precondition} and the rules for
2629 consequences are the same as the rule for an expression in
2630 @code{Postcondition}. In particular, attributes @code{'Old} and
2631 @code{'Result} can only be used within consequence expressions.
2632 The case guard for the last contract case may be @code{others}, to denote
2633 any case not captured by the previous cases. The
2634 following is an example of use within a package spec:
2637 package Math_Functions is
2639 function Sqrt (Arg : Float) return Float;
2640 pragma Contract_Cases (((Arg in 0.0 .. 99.0) => Sqrt'Result < 10.0,
2641 Arg >= 100.0 => Sqrt'Result >= 10.0,
2642 others => Sqrt'Result = 0.0));
2647 The meaning of contract cases is that only one case should apply at each
2648 call, as determined by the corresponding case guard evaluating to True,
2649 and that the consequence for this case should hold when the subprogram
2652 @node Pragma Convention_Identifier,Pragma CPP_Class,Pragma Contract_Cases,Implementation Defined Pragmas
2653 @anchor{gnat_rm/implementation_defined_pragmas pragma-convention-identifier}@anchor{45}
2654 @section Pragma Convention_Identifier
2657 @geindex Conventions
2663 pragma Convention_Identifier (
2664 [Name =>] IDENTIFIER,
2665 [Convention =>] convention_IDENTIFIER);
2668 This pragma provides a mechanism for supplying synonyms for existing
2669 convention identifiers. The @code{Name} identifier can subsequently
2670 be used as a synonym for the given convention in other pragmas (including
2671 for example pragma @code{Import} or another @code{Convention_Identifier}
2672 pragma). As an example of the use of this, suppose you had legacy code
2673 which used Fortran77 as the identifier for Fortran. Then the pragma:
2676 pragma Convention_Identifier (Fortran77, Fortran);
2679 would allow the use of the convention identifier @code{Fortran77} in
2680 subsequent code, avoiding the need to modify the sources. As another
2681 example, you could use this to parameterize convention requirements
2682 according to systems. Suppose you needed to use @code{Stdcall} on
2683 windows systems, and @code{C} on some other system, then you could
2684 define a convention identifier @code{Library} and use a single
2685 @code{Convention_Identifier} pragma to specify which convention
2686 would be used system-wide.
2688 @node Pragma CPP_Class,Pragma CPP_Constructor,Pragma Convention_Identifier,Implementation Defined Pragmas
2689 @anchor{gnat_rm/implementation_defined_pragmas pragma-cpp-class}@anchor{46}
2690 @section Pragma CPP_Class
2693 @geindex Interfacing with C++
2698 pragma CPP_Class ([Entity =>] LOCAL_NAME);
2701 The argument denotes an entity in the current declarative region that is
2702 declared as a record type. It indicates that the type corresponds to an
2703 externally declared C++ class type, and is to be laid out the same way
2704 that C++ would lay out the type. If the C++ class has virtual primitives
2705 then the record must be declared as a tagged record type.
2707 Types for which @code{CPP_Class} is specified do not have assignment or
2708 equality operators defined (such operations can be imported or declared
2709 as subprograms as required). Initialization is allowed only by constructor
2710 functions (see pragma @code{CPP_Constructor}). Such types are implicitly
2711 limited if not explicitly declared as limited or derived from a limited
2712 type, and an error is issued in that case.
2714 See @ref{47,,Interfacing to C++} for related information.
2716 Note: Pragma @code{CPP_Class} is currently obsolete. It is supported
2717 for backward compatibility but its functionality is available
2718 using pragma @code{Import} with @code{Convention} = @code{CPP}.
2720 @node Pragma CPP_Constructor,Pragma CPP_Virtual,Pragma CPP_Class,Implementation Defined Pragmas
2721 @anchor{gnat_rm/implementation_defined_pragmas pragma-cpp-constructor}@anchor{48}
2722 @section Pragma CPP_Constructor
2725 @geindex Interfacing with C++
2730 pragma CPP_Constructor ([Entity =>] LOCAL_NAME
2731 [, [External_Name =>] static_string_EXPRESSION ]
2732 [, [Link_Name =>] static_string_EXPRESSION ]);
2735 This pragma identifies an imported function (imported in the usual way
2736 with pragma @code{Import}) as corresponding to a C++ constructor. If
2737 @code{External_Name} and @code{Link_Name} are not specified then the
2738 @code{Entity} argument is a name that must have been previously mentioned
2739 in a pragma @code{Import} with @code{Convention} = @code{CPP}. Such name
2740 must be of one of the following forms:
2746 @strong{function} @code{Fname} @strong{return} T`
2749 @strong{function} @code{Fname} @strong{return} T'Class
2752 @strong{function} @code{Fname} (...) @strong{return} T`
2755 @strong{function} @code{Fname} (...) @strong{return} T'Class
2758 where @code{T} is a limited record type imported from C++ with pragma
2759 @code{Import} and @code{Convention} = @code{CPP}.
2761 The first two forms import the default constructor, used when an object
2762 of type @code{T} is created on the Ada side with no explicit constructor.
2763 The latter two forms cover all the non-default constructors of the type.
2764 See the GNAT User's Guide for details.
2766 If no constructors are imported, it is impossible to create any objects
2767 on the Ada side and the type is implicitly declared abstract.
2769 Pragma @code{CPP_Constructor} is intended primarily for automatic generation
2770 using an automatic binding generator tool (such as the @code{-fdump-ada-spec}
2772 See @ref{47,,Interfacing to C++} for more related information.
2774 Note: The use of functions returning class-wide types for constructors is
2775 currently obsolete. They are supported for backward compatibility. The
2776 use of functions returning the type T leave the Ada sources more clear
2777 because the imported C++ constructors always return an object of type T;
2778 that is, they never return an object whose type is a descendant of type T.
2780 @node Pragma CPP_Virtual,Pragma CPP_Vtable,Pragma CPP_Constructor,Implementation Defined Pragmas
2781 @anchor{gnat_rm/implementation_defined_pragmas pragma-cpp-virtual}@anchor{49}
2782 @section Pragma CPP_Virtual
2785 @geindex Interfacing to C++
2787 This pragma is now obsolete and, other than generating a warning if warnings
2788 on obsolescent features are enabled, is completely ignored.
2789 It is retained for compatibility
2790 purposes. It used to be required to ensure compoatibility with C++, but
2791 is no longer required for that purpose because GNAT generates
2792 the same object layout as the G++ compiler by default.
2794 See @ref{47,,Interfacing to C++} for related information.
2796 @node Pragma CPP_Vtable,Pragma CPU,Pragma CPP_Virtual,Implementation Defined Pragmas
2797 @anchor{gnat_rm/implementation_defined_pragmas pragma-cpp-vtable}@anchor{4a}
2798 @section Pragma CPP_Vtable
2801 @geindex Interfacing with C++
2803 This pragma is now obsolete and, other than generating a warning if warnings
2804 on obsolescent features are enabled, is completely ignored.
2805 It used to be required to ensure compatibility with C++, but
2806 is no longer required for that purpose because GNAT generates
2807 the same object layout as the G++ compiler by default.
2809 See @ref{47,,Interfacing to C++} for related information.
2811 @node Pragma CPU,Pragma Deadline_Floor,Pragma CPP_Vtable,Implementation Defined Pragmas
2812 @anchor{gnat_rm/implementation_defined_pragmas pragma-cpu}@anchor{4b}
2819 pragma CPU (EXPRESSION);
2822 This pragma is standard in Ada 2012, but is available in all earlier
2823 versions of Ada as an implementation-defined pragma.
2824 See Ada 2012 Reference Manual for details.
2826 @node Pragma Deadline_Floor,Pragma Default_Initial_Condition,Pragma CPU,Implementation Defined Pragmas
2827 @anchor{gnat_rm/implementation_defined_pragmas pragma-deadline-floor}@anchor{4c}
2828 @section Pragma Deadline_Floor
2834 pragma Deadline_Floor (time_span_EXPRESSION);
2837 This pragma applies only to protected types and specifies the floor
2838 deadline inherited by a task when the task enters a protected object.
2839 It is effective only when the EDF scheduling policy is used.
2841 @node Pragma Default_Initial_Condition,Pragma Debug,Pragma Deadline_Floor,Implementation Defined Pragmas
2842 @anchor{gnat_rm/implementation_defined_pragmas id8}@anchor{4d}@anchor{gnat_rm/implementation_defined_pragmas pragma-default-initial-condition}@anchor{4e}
2843 @section Pragma Default_Initial_Condition
2849 pragma Default_Initial_Condition [ (null | boolean_EXPRESSION) ];
2852 For the semantics of this pragma, see the entry for aspect
2853 @code{Default_Initial_Condition} in the SPARK 2014 Reference Manual, section 7.3.3.
2855 @node Pragma Debug,Pragma Debug_Policy,Pragma Default_Initial_Condition,Implementation Defined Pragmas
2856 @anchor{gnat_rm/implementation_defined_pragmas pragma-debug}@anchor{4f}
2857 @section Pragma Debug
2863 pragma Debug ([CONDITION, ]PROCEDURE_CALL_WITHOUT_SEMICOLON);
2865 PROCEDURE_CALL_WITHOUT_SEMICOLON ::=
2867 | PROCEDURE_PREFIX ACTUAL_PARAMETER_PART
2870 The procedure call argument has the syntactic form of an expression, meeting
2871 the syntactic requirements for pragmas.
2873 If debug pragmas are not enabled or if the condition is present and evaluates
2874 to False, this pragma has no effect. If debug pragmas are enabled, the
2875 semantics of the pragma is exactly equivalent to the procedure call statement
2876 corresponding to the argument with a terminating semicolon. Pragmas are
2877 permitted in sequences of declarations, so you can use pragma @code{Debug} to
2878 intersperse calls to debug procedures in the middle of declarations. Debug
2879 pragmas can be enabled either by use of the command line switch @emph{-gnata}
2880 or by use of the pragma @code{Check_Policy} with a first argument of
2883 @node Pragma Debug_Policy,Pragma Default_Scalar_Storage_Order,Pragma Debug,Implementation Defined Pragmas
2884 @anchor{gnat_rm/implementation_defined_pragmas pragma-debug-policy}@anchor{50}
2885 @section Pragma Debug_Policy
2891 pragma Debug_Policy (CHECK | DISABLE | IGNORE | ON | OFF);
2894 This pragma is equivalent to a corresponding @code{Check_Policy} pragma
2895 with a first argument of @code{Debug}. It is retained for historical
2896 compatibility reasons.
2898 @node Pragma Default_Scalar_Storage_Order,Pragma Default_Storage_Pool,Pragma Debug_Policy,Implementation Defined Pragmas
2899 @anchor{gnat_rm/implementation_defined_pragmas pragma-default-scalar-storage-order}@anchor{51}
2900 @section Pragma Default_Scalar_Storage_Order
2903 @geindex Default_Scalar_Storage_Order
2905 @geindex Scalar_Storage_Order
2910 pragma Default_Scalar_Storage_Order (High_Order_First | Low_Order_First);
2913 Normally if no explicit @code{Scalar_Storage_Order} is given for a record
2914 type or array type, then the scalar storage order defaults to the ordinary
2915 default for the target. But this default may be overridden using this pragma.
2916 The pragma may appear as a configuration pragma, or locally within a package
2917 spec or declarative part. In the latter case, it applies to all subsequent
2918 types declared within that package spec or declarative part.
2920 The following example shows the use of this pragma:
2923 pragma Default_Scalar_Storage_Order (High_Order_First);
2924 with System; use System;
2933 for L2'Scalar_Storage_Order use Low_Order_First;
2942 pragma Default_Scalar_Storage_Order (Low_Order_First);
2949 type H4a is new Inner.L4;
2957 In this example record types with names starting with @emph{L} have @cite{Low_Order_First} scalar
2958 storage order, and record types with names starting with @emph{H} have @code{High_Order_First}.
2959 Note that in the case of @code{H4a}, the order is not inherited
2960 from the parent type. Only an explicitly set @code{Scalar_Storage_Order}
2961 gets inherited on type derivation.
2963 If this pragma is used as a configuration pragma which appears within a
2964 configuration pragma file (as opposed to appearing explicitly at the start
2965 of a single unit), then the binder will require that all units in a partition
2966 be compiled in a similar manner, other than run-time units, which are not
2967 affected by this pragma. Note that the use of this form is discouraged because
2968 it may significantly degrade the run-time performance of the software, instead
2969 the default scalar storage order ought to be changed only on a local basis.
2971 @node Pragma Default_Storage_Pool,Pragma Depends,Pragma Default_Scalar_Storage_Order,Implementation Defined Pragmas
2972 @anchor{gnat_rm/implementation_defined_pragmas pragma-default-storage-pool}@anchor{52}
2973 @section Pragma Default_Storage_Pool
2976 @geindex Default_Storage_Pool
2981 pragma Default_Storage_Pool (storage_pool_NAME | null);
2984 This pragma is standard in Ada 2012, but is available in all earlier
2985 versions of Ada as an implementation-defined pragma.
2986 See Ada 2012 Reference Manual for details.
2988 @node Pragma Depends,Pragma Detect_Blocking,Pragma Default_Storage_Pool,Implementation Defined Pragmas
2989 @anchor{gnat_rm/implementation_defined_pragmas pragma-depends}@anchor{53}@anchor{gnat_rm/implementation_defined_pragmas id9}@anchor{54}
2990 @section Pragma Depends
2996 pragma Depends (DEPENDENCY_RELATION);
2998 DEPENDENCY_RELATION ::=
3000 | (DEPENDENCY_CLAUSE @{, DEPENDENCY_CLAUSE@})
3002 DEPENDENCY_CLAUSE ::=
3003 OUTPUT_LIST =>[+] INPUT_LIST
3004 | NULL_DEPENDENCY_CLAUSE
3006 NULL_DEPENDENCY_CLAUSE ::= null => INPUT_LIST
3008 OUTPUT_LIST ::= OUTPUT | (OUTPUT @{, OUTPUT@})
3010 INPUT_LIST ::= null | INPUT | (INPUT @{, INPUT@})
3012 OUTPUT ::= NAME | FUNCTION_RESULT
3015 where FUNCTION_RESULT is a function Result attribute_reference
3018 For the semantics of this pragma, see the entry for aspect @code{Depends} in the
3019 SPARK 2014 Reference Manual, section 6.1.5.
3021 @node Pragma Detect_Blocking,Pragma Disable_Atomic_Synchronization,Pragma Depends,Implementation Defined Pragmas
3022 @anchor{gnat_rm/implementation_defined_pragmas pragma-detect-blocking}@anchor{55}
3023 @section Pragma Detect_Blocking
3029 pragma Detect_Blocking;
3032 This is a standard pragma in Ada 2005, that is available in all earlier
3033 versions of Ada as an implementation-defined pragma.
3035 This is a configuration pragma that forces the detection of potentially
3036 blocking operations within a protected operation, and to raise Program_Error
3039 @node Pragma Disable_Atomic_Synchronization,Pragma Dispatching_Domain,Pragma Detect_Blocking,Implementation Defined Pragmas
3040 @anchor{gnat_rm/implementation_defined_pragmas pragma-disable-atomic-synchronization}@anchor{56}
3041 @section Pragma Disable_Atomic_Synchronization
3044 @geindex Atomic Synchronization
3049 pragma Disable_Atomic_Synchronization [(Entity)];
3052 Ada requires that accesses (reads or writes) of an atomic variable be
3053 regarded as synchronization points in the case of multiple tasks.
3054 Particularly in the case of multi-processors this may require special
3055 handling, e.g. the generation of memory barriers. This capability may
3056 be turned off using this pragma in cases where it is known not to be
3059 The placement and scope rules for this pragma are the same as those
3060 for @code{pragma Suppress}. In particular it can be used as a
3061 configuration pragma, or in a declaration sequence where it applies
3062 till the end of the scope. If an @code{Entity} argument is present,
3063 the action applies only to that entity.
3065 @node Pragma Dispatching_Domain,Pragma Effective_Reads,Pragma Disable_Atomic_Synchronization,Implementation Defined Pragmas
3066 @anchor{gnat_rm/implementation_defined_pragmas pragma-dispatching-domain}@anchor{57}
3067 @section Pragma Dispatching_Domain
3073 pragma Dispatching_Domain (EXPRESSION);
3076 This pragma is standard in Ada 2012, but is available in all earlier
3077 versions of Ada as an implementation-defined pragma.
3078 See Ada 2012 Reference Manual for details.
3080 @node Pragma Effective_Reads,Pragma Effective_Writes,Pragma Dispatching_Domain,Implementation Defined Pragmas
3081 @anchor{gnat_rm/implementation_defined_pragmas id10}@anchor{58}@anchor{gnat_rm/implementation_defined_pragmas pragma-effective-reads}@anchor{59}
3082 @section Pragma Effective_Reads
3088 pragma Effective_Reads [ (boolean_EXPRESSION) ];
3091 For the semantics of this pragma, see the entry for aspect @code{Effective_Reads} in
3092 the SPARK 2014 Reference Manual, section 7.1.2.
3094 @node Pragma Effective_Writes,Pragma Elaboration_Checks,Pragma Effective_Reads,Implementation Defined Pragmas
3095 @anchor{gnat_rm/implementation_defined_pragmas id11}@anchor{5a}@anchor{gnat_rm/implementation_defined_pragmas pragma-effective-writes}@anchor{5b}
3096 @section Pragma Effective_Writes
3102 pragma Effective_Writes [ (boolean_EXPRESSION) ];
3105 For the semantics of this pragma, see the entry for aspect @code{Effective_Writes}
3106 in the SPARK 2014 Reference Manual, section 7.1.2.
3108 @node Pragma Elaboration_Checks,Pragma Eliminate,Pragma Effective_Writes,Implementation Defined Pragmas
3109 @anchor{gnat_rm/implementation_defined_pragmas pragma-elaboration-checks}@anchor{5c}
3110 @section Pragma Elaboration_Checks
3113 @geindex Elaboration control
3118 pragma Elaboration_Checks (Dynamic | Static);
3121 This is a configuration pragma which specifies the elaboration model to be
3122 used during compilation. For more information on the elaboration models of
3123 GNAT, consult the chapter on elaboration order handling in the @emph{GNAT User's
3126 The pragma may appear in the following contexts:
3132 Configuration pragmas file
3135 Prior to the context clauses of a compilation unit's initial declaration
3138 Any other placement of the pragma will result in a warning and the effects of
3139 the offending pragma will be ignored.
3141 If the pragma argument is @code{Dynamic}, then the dynamic elaboration model is in
3142 effect. If the pragma argument is @code{Static}, then the static elaboration model
3145 @node Pragma Eliminate,Pragma Enable_Atomic_Synchronization,Pragma Elaboration_Checks,Implementation Defined Pragmas
3146 @anchor{gnat_rm/implementation_defined_pragmas pragma-eliminate}@anchor{5d}
3147 @section Pragma Eliminate
3150 @geindex Elimination of unused subprograms
3156 [ Unit_Name => ] IDENTIFIER | SELECTED_COMPONENT ,
3157 [ Entity => ] IDENTIFIER |
3158 SELECTED_COMPONENT |
3160 [, Source_Location => SOURCE_TRACE ] );
3162 SOURCE_TRACE ::= STRING_LITERAL
3165 This pragma indicates that the given entity is not used in the program to be
3166 compiled and built, thus allowing the compiler to
3167 eliminate the code or data associated with the named entity. Any reference to
3168 an eliminated entity causes a compile-time or link-time error.
3170 The pragma has the following semantics, where @code{U} is the unit specified by
3171 the @code{Unit_Name} argument and @code{E} is the entity specified by the @code{Entity}
3178 @code{E} must be a subprogram that is explicitly declared either:
3180 o Within @code{U}, or
3182 o Within a generic package that is instantiated in @code{U}, or
3184 o As an instance of generic subprogram instantiated in @code{U}.
3186 Otherwise the pragma is ignored.
3189 If @code{E} is overloaded within @code{U} then, in the absence of a
3190 @code{Source_Location} argument, all overloadings are eliminated.
3193 If @code{E} is overloaded within @code{U} and only some overloadings
3194 are to be eliminated, then each overloading to be eliminated
3195 must be specified in a corresponding pragma @code{Eliminate}
3196 with a @code{Source_Location} argument identifying the line where the
3197 declaration appears, as described below.
3200 If @code{E} is declared as the result of a generic instantiation, then
3201 a @code{Source_Location} argument is needed, as described below
3204 Pragma @code{Eliminate} allows a program to be compiled in a system-independent
3205 manner, so that unused entities are eliminated but without
3206 needing to modify the source text. Normally the required set of
3207 @code{Eliminate} pragmas is constructed automatically using the @code{gnatelim} tool.
3209 Any source file change that removes, splits, or
3210 adds lines may make the set of @code{Eliminate} pragmas invalid because their
3211 @code{Source_Location} argument values may get out of date.
3213 Pragma @code{Eliminate} may be used where the referenced entity is a dispatching
3214 operation. In this case all the subprograms to which the given operation can
3215 dispatch are considered to be unused (are never called as a result of a direct
3216 or a dispatching call).
3218 The string literal given for the source location specifies the line number
3219 of the declaration of the entity, using the following syntax for @code{SOURCE_TRACE}:
3222 SOURCE_TRACE ::= SOURCE_REFERENCE [ LBRACKET SOURCE_TRACE RBRACKET ]
3227 SOURCE_REFERENCE ::= FILE_NAME : LINE_NUMBER
3229 LINE_NUMBER ::= DIGIT @{DIGIT@}
3232 Spaces around the colon in a @code{SOURCE_REFERENCE} are optional.
3234 The source trace that is given as the @code{Source_Location} must obey the
3235 following rules (or else the pragma is ignored), where @code{U} is
3236 the unit @code{U} specified by the @code{Unit_Name} argument and @code{E} is the
3237 subprogram specified by the @code{Entity} argument:
3243 @code{FILE_NAME} is the short name (with no directory
3244 information) of the Ada source file for @code{U}, using the required syntax
3245 for the underlying file system (e.g. case is significant if the underlying
3246 operating system is case sensitive).
3247 If @code{U} is a package and @code{E} is a subprogram declared in the package
3248 specification and its full declaration appears in the package body,
3249 then the relevant source file is the one for the package specification;
3250 analogously if @code{U} is a generic package.
3253 If @code{E} is not declared in a generic instantiation (this includes
3254 generic subprogram instances), the source trace includes only one source
3255 line reference. @code{LINE_NUMBER} gives the line number of the occurrence
3256 of the declaration of @code{E} within the source file (as a decimal literal
3257 without an exponent or point).
3260 If @code{E} is declared by a generic instantiation, its source trace
3261 (from left to right) starts with the source location of the
3262 declaration of @code{E} in the generic unit and ends with the source
3263 location of the instantiation, given in square brackets. This approach is
3264 applied recursively with nested instantiations: the rightmost (nested
3265 most deeply in square brackets) element of the source trace is the location
3266 of the outermost instantiation, and the leftmost element (that is, outside
3267 of any square brackets) is the location of the declaration of @code{E} in
3276 pragma Eliminate (Pkg0, Proc);
3277 -- Eliminate (all overloadings of) Proc in Pkg0
3279 pragma Eliminate (Pkg1, Proc,
3280 Source_Location => "pkg1.ads:8");
3281 -- Eliminate overloading of Proc at line 8 in pkg1.ads
3283 -- Assume the following file contents:
3286 -- 2: type T is private;
3287 -- 3: package Gen_Pkg is
3288 -- 4: procedure Proc(N : T);
3294 -- 2: procedure Q is
3295 -- 3: package Inst_Pkg is new Gen_Pkg(Integer);
3296 -- ... -- No calls on Inst_Pkg.Proc
3299 -- The following pragma eliminates Inst_Pkg.Proc from Q
3300 pragma Eliminate (Q, Proc,
3301 Source_Location => "gen_pkg.ads:4[q.adb:3]");
3305 @node Pragma Enable_Atomic_Synchronization,Pragma Export_Function,Pragma Eliminate,Implementation Defined Pragmas
3306 @anchor{gnat_rm/implementation_defined_pragmas pragma-enable-atomic-synchronization}@anchor{5e}
3307 @section Pragma Enable_Atomic_Synchronization
3310 @geindex Atomic Synchronization
3315 pragma Enable_Atomic_Synchronization [(Entity)];
3318 Ada requires that accesses (reads or writes) of an atomic variable be
3319 regarded as synchronization points in the case of multiple tasks.
3320 Particularly in the case of multi-processors this may require special
3321 handling, e.g. the generation of memory barriers. This synchronization
3322 is performed by default, but can be turned off using
3323 @code{pragma Disable_Atomic_Synchronization}. The
3324 @code{Enable_Atomic_Synchronization} pragma can be used to turn
3327 The placement and scope rules for this pragma are the same as those
3328 for @code{pragma Unsuppress}. In particular it can be used as a
3329 configuration pragma, or in a declaration sequence where it applies
3330 till the end of the scope. If an @code{Entity} argument is present,
3331 the action applies only to that entity.
3333 @node Pragma Export_Function,Pragma Export_Object,Pragma Enable_Atomic_Synchronization,Implementation Defined Pragmas
3334 @anchor{gnat_rm/implementation_defined_pragmas pragma-export-function}@anchor{5f}
3335 @section Pragma Export_Function
3338 @geindex Argument passing mechanisms
3343 pragma Export_Function (
3344 [Internal =>] LOCAL_NAME
3345 [, [External =>] EXTERNAL_SYMBOL]
3346 [, [Parameter_Types =>] PARAMETER_TYPES]
3347 [, [Result_Type =>] result_SUBTYPE_MARK]
3348 [, [Mechanism =>] MECHANISM]
3349 [, [Result_Mechanism =>] MECHANISM_NAME]);
3353 | static_string_EXPRESSION
3358 | TYPE_DESIGNATOR @{, TYPE_DESIGNATOR@}
3362 | subtype_Name ' Access
3366 | (MECHANISM_ASSOCIATION @{, MECHANISM_ASSOCIATION@})
3368 MECHANISM_ASSOCIATION ::=
3369 [formal_parameter_NAME =>] MECHANISM_NAME
3371 MECHANISM_NAME ::= Value | Reference
3374 Use this pragma to make a function externally callable and optionally
3375 provide information on mechanisms to be used for passing parameter and
3376 result values. We recommend, for the purposes of improving portability,
3377 this pragma always be used in conjunction with a separate pragma
3378 @code{Export}, which must precede the pragma @code{Export_Function}.
3379 GNAT does not require a separate pragma @code{Export}, but if none is
3380 present, @code{Convention Ada} is assumed, which is usually
3381 not what is wanted, so it is usually appropriate to use this
3382 pragma in conjunction with a @code{Export} or @code{Convention}
3383 pragma that specifies the desired foreign convention.
3384 Pragma @code{Export_Function}
3385 (and @code{Export}, if present) must appear in the same declarative
3386 region as the function to which they apply.
3388 The @code{internal_name} must uniquely designate the function to which the
3389 pragma applies. If more than one function name exists of this name in
3390 the declarative part you must use the @code{Parameter_Types} and
3391 @code{Result_Type} parameters to achieve the required
3392 unique designation. The @cite{subtype_mark}s in these parameters must
3393 exactly match the subtypes in the corresponding function specification,
3394 using positional notation to match parameters with subtype marks.
3395 The form with an @code{'Access} attribute can be used to match an
3396 anonymous access parameter.
3398 @geindex Suppressing external name
3400 Special treatment is given if the EXTERNAL is an explicit null
3401 string or a static string expressions that evaluates to the null
3402 string. In this case, no external name is generated. This form
3403 still allows the specification of parameter mechanisms.
3405 @node Pragma Export_Object,Pragma Export_Procedure,Pragma Export_Function,Implementation Defined Pragmas
3406 @anchor{gnat_rm/implementation_defined_pragmas pragma-export-object}@anchor{60}
3407 @section Pragma Export_Object
3413 pragma Export_Object
3414 [Internal =>] LOCAL_NAME
3415 [, [External =>] EXTERNAL_SYMBOL]
3416 [, [Size =>] EXTERNAL_SYMBOL]
3420 | static_string_EXPRESSION
3423 This pragma designates an object as exported, and apart from the
3424 extended rules for external symbols, is identical in effect to the use of
3425 the normal @code{Export} pragma applied to an object. You may use a
3426 separate Export pragma (and you probably should from the point of view
3427 of portability), but it is not required. @code{Size} is syntax checked,
3428 but otherwise ignored by GNAT.
3430 @node Pragma Export_Procedure,Pragma Export_Value,Pragma Export_Object,Implementation Defined Pragmas
3431 @anchor{gnat_rm/implementation_defined_pragmas pragma-export-procedure}@anchor{61}
3432 @section Pragma Export_Procedure
3438 pragma Export_Procedure (
3439 [Internal =>] LOCAL_NAME
3440 [, [External =>] EXTERNAL_SYMBOL]
3441 [, [Parameter_Types =>] PARAMETER_TYPES]
3442 [, [Mechanism =>] MECHANISM]);
3446 | static_string_EXPRESSION
3451 | TYPE_DESIGNATOR @{, TYPE_DESIGNATOR@}
3455 | subtype_Name ' Access
3459 | (MECHANISM_ASSOCIATION @{, MECHANISM_ASSOCIATION@})
3461 MECHANISM_ASSOCIATION ::=
3462 [formal_parameter_NAME =>] MECHANISM_NAME
3464 MECHANISM_NAME ::= Value | Reference
3467 This pragma is identical to @code{Export_Function} except that it
3468 applies to a procedure rather than a function and the parameters
3469 @code{Result_Type} and @code{Result_Mechanism} are not permitted.
3470 GNAT does not require a separate pragma @code{Export}, but if none is
3471 present, @code{Convention Ada} is assumed, which is usually
3472 not what is wanted, so it is usually appropriate to use this
3473 pragma in conjunction with a @code{Export} or @code{Convention}
3474 pragma that specifies the desired foreign convention.
3476 @geindex Suppressing external name
3478 Special treatment is given if the EXTERNAL is an explicit null
3479 string or a static string expressions that evaluates to the null
3480 string. In this case, no external name is generated. This form
3481 still allows the specification of parameter mechanisms.
3483 @node Pragma Export_Value,Pragma Export_Valued_Procedure,Pragma Export_Procedure,Implementation Defined Pragmas
3484 @anchor{gnat_rm/implementation_defined_pragmas pragma-export-value}@anchor{62}
3485 @section Pragma Export_Value
3491 pragma Export_Value (
3492 [Value =>] static_integer_EXPRESSION,
3493 [Link_Name =>] static_string_EXPRESSION);
3496 This pragma serves to export a static integer value for external use.
3497 The first argument specifies the value to be exported. The Link_Name
3498 argument specifies the symbolic name to be associated with the integer
3499 value. This pragma is useful for defining a named static value in Ada
3500 that can be referenced in assembly language units to be linked with
3501 the application. This pragma is currently supported only for the
3502 AAMP target and is ignored for other targets.
3504 @node Pragma Export_Valued_Procedure,Pragma Extend_System,Pragma Export_Value,Implementation Defined Pragmas
3505 @anchor{gnat_rm/implementation_defined_pragmas pragma-export-valued-procedure}@anchor{63}
3506 @section Pragma Export_Valued_Procedure
3512 pragma Export_Valued_Procedure (
3513 [Internal =>] LOCAL_NAME
3514 [, [External =>] EXTERNAL_SYMBOL]
3515 [, [Parameter_Types =>] PARAMETER_TYPES]
3516 [, [Mechanism =>] MECHANISM]);
3520 | static_string_EXPRESSION
3525 | TYPE_DESIGNATOR @{, TYPE_DESIGNATOR@}
3529 | subtype_Name ' Access
3533 | (MECHANISM_ASSOCIATION @{, MECHANISM_ASSOCIATION@})
3535 MECHANISM_ASSOCIATION ::=
3536 [formal_parameter_NAME =>] MECHANISM_NAME
3538 MECHANISM_NAME ::= Value | Reference
3541 This pragma is identical to @code{Export_Procedure} except that the
3542 first parameter of @code{LOCAL_NAME}, which must be present, must be of
3543 mode @code{out}, and externally the subprogram is treated as a function
3544 with this parameter as the result of the function. GNAT provides for
3545 this capability to allow the use of @code{out} and @code{in out}
3546 parameters in interfacing to external functions (which are not permitted
3548 GNAT does not require a separate pragma @code{Export}, but if none is
3549 present, @code{Convention Ada} is assumed, which is almost certainly
3550 not what is wanted since the whole point of this pragma is to interface
3551 with foreign language functions, so it is usually appropriate to use this
3552 pragma in conjunction with a @code{Export} or @code{Convention}
3553 pragma that specifies the desired foreign convention.
3555 @geindex Suppressing external name
3557 Special treatment is given if the EXTERNAL is an explicit null
3558 string or a static string expressions that evaluates to the null
3559 string. In this case, no external name is generated. This form
3560 still allows the specification of parameter mechanisms.
3562 @node Pragma Extend_System,Pragma Extensions_Allowed,Pragma Export_Valued_Procedure,Implementation Defined Pragmas
3563 @anchor{gnat_rm/implementation_defined_pragmas pragma-extend-system}@anchor{64}
3564 @section Pragma Extend_System
3575 pragma Extend_System ([Name =>] IDENTIFIER);
3578 This pragma is used to provide backwards compatibility with other
3579 implementations that extend the facilities of package @code{System}. In
3580 GNAT, @code{System} contains only the definitions that are present in
3581 the Ada RM. However, other implementations, notably the DEC Ada 83
3582 implementation, provide many extensions to package @code{System}.
3584 For each such implementation accommodated by this pragma, GNAT provides a
3585 package @code{Aux_@emph{xxx}}, e.g., @code{Aux_DEC} for the DEC Ada 83
3586 implementation, which provides the required additional definitions. You
3587 can use this package in two ways. You can @code{with} it in the normal
3588 way and access entities either by selection or using a @code{use}
3589 clause. In this case no special processing is required.
3591 However, if existing code contains references such as
3592 @code{System.@emph{xxx}} where @emph{xxx} is an entity in the extended
3593 definitions provided in package @code{System}, you may use this pragma
3594 to extend visibility in @code{System} in a non-standard way that
3595 provides greater compatibility with the existing code. Pragma
3596 @code{Extend_System} is a configuration pragma whose single argument is
3597 the name of the package containing the extended definition
3598 (e.g., @code{Aux_DEC} for the DEC Ada case). A unit compiled under
3599 control of this pragma will be processed using special visibility
3600 processing that looks in package @code{System.Aux_@emph{xxx}} where
3601 @code{Aux_@emph{xxx}} is the pragma argument for any entity referenced in
3602 package @code{System}, but not found in package @code{System}.
3604 You can use this pragma either to access a predefined @code{System}
3605 extension supplied with the compiler, for example @code{Aux_DEC} or
3606 you can construct your own extension unit following the above
3607 definition. Note that such a package is a child of @code{System}
3608 and thus is considered part of the implementation.
3609 To compile it you will have to use the @emph{-gnatg} switch
3610 for compiling System units, as explained in the
3613 @node Pragma Extensions_Allowed,Pragma Extensions_Visible,Pragma Extend_System,Implementation Defined Pragmas
3614 @anchor{gnat_rm/implementation_defined_pragmas pragma-extensions-allowed}@anchor{65}
3615 @section Pragma Extensions_Allowed
3618 @geindex Ada Extensions
3620 @geindex GNAT Extensions
3625 pragma Extensions_Allowed (On | Off);
3628 This configuration pragma enables or disables the implementation
3629 extension mode (the use of Off as a parameter cancels the effect
3630 of the @emph{-gnatX} command switch).
3632 In extension mode, the latest version of the Ada language is
3633 implemented (currently Ada 202x), and in addition a small number
3634 of GNAT specific extensions are recognized as follows:
3640 Constrained attribute for generic objects
3642 The @code{Constrained} attribute is permitted for objects of
3643 generic types. The result indicates if the corresponding actual
3647 @code{Static} aspect on intrinsic functions
3649 The Ada 202x @code{Static} aspect can be specified on Intrinsic imported
3650 functions and the compiler will evaluate some of these intrinsic statically,
3651 in particular the @code{Shift_Left} and @code{Shift_Right} intrinsics.
3654 @code{'Reduce} attribute
3656 This attribute part of the Ada 202x language definition is provided for
3657 now under -gnatX to confirm and potentially refine its usage and syntax.
3660 @code{[]} aggregates
3662 This new aggregate syntax for arrays and containers is provided under -gnatX
3663 to experiment and confirm this new language syntax.
3666 @node Pragma Extensions_Visible,Pragma External,Pragma Extensions_Allowed,Implementation Defined Pragmas
3667 @anchor{gnat_rm/implementation_defined_pragmas id12}@anchor{66}@anchor{gnat_rm/implementation_defined_pragmas pragma-extensions-visible}@anchor{67}
3668 @section Pragma Extensions_Visible
3674 pragma Extensions_Visible [ (boolean_EXPRESSION) ];
3677 For the semantics of this pragma, see the entry for aspect @code{Extensions_Visible}
3678 in the SPARK 2014 Reference Manual, section 6.1.7.
3680 @node Pragma External,Pragma External_Name_Casing,Pragma Extensions_Visible,Implementation Defined Pragmas
3681 @anchor{gnat_rm/implementation_defined_pragmas pragma-external}@anchor{68}
3682 @section Pragma External
3689 [ Convention =>] convention_IDENTIFIER,
3690 [ Entity =>] LOCAL_NAME
3691 [, [External_Name =>] static_string_EXPRESSION ]
3692 [, [Link_Name =>] static_string_EXPRESSION ]);
3695 This pragma is identical in syntax and semantics to pragma
3696 @code{Export} as defined in the Ada Reference Manual. It is
3697 provided for compatibility with some Ada 83 compilers that
3698 used this pragma for exactly the same purposes as pragma
3699 @code{Export} before the latter was standardized.
3701 @node Pragma External_Name_Casing,Pragma Fast_Math,Pragma External,Implementation Defined Pragmas
3702 @anchor{gnat_rm/implementation_defined_pragmas pragma-external-name-casing}@anchor{69}
3703 @section Pragma External_Name_Casing
3706 @geindex Dec Ada 83 casing compatibility
3708 @geindex External Names
3711 @geindex Casing of External names
3716 pragma External_Name_Casing (
3717 Uppercase | Lowercase
3718 [, Uppercase | Lowercase | As_Is]);
3721 This pragma provides control over the casing of external names associated
3722 with Import and Export pragmas. There are two cases to consider:
3728 Implicit external names
3730 Implicit external names are derived from identifiers. The most common case
3731 arises when a standard Ada Import or Export pragma is used with only two
3735 pragma Import (C, C_Routine);
3738 Since Ada is a case-insensitive language, the spelling of the identifier in
3739 the Ada source program does not provide any information on the desired
3740 casing of the external name, and so a convention is needed. In GNAT the
3741 default treatment is that such names are converted to all lower case
3742 letters. This corresponds to the normal C style in many environments.
3743 The first argument of pragma @code{External_Name_Casing} can be used to
3744 control this treatment. If @code{Uppercase} is specified, then the name
3745 will be forced to all uppercase letters. If @code{Lowercase} is specified,
3746 then the normal default of all lower case letters will be used.
3748 This same implicit treatment is also used in the case of extended DEC Ada 83
3749 compatible Import and Export pragmas where an external name is explicitly
3750 specified using an identifier rather than a string.
3753 Explicit external names
3755 Explicit external names are given as string literals. The most common case
3756 arises when a standard Ada Import or Export pragma is used with three
3760 pragma Import (C, C_Routine, "C_routine");
3763 In this case, the string literal normally provides the exact casing required
3764 for the external name. The second argument of pragma
3765 @code{External_Name_Casing} may be used to modify this behavior.
3766 If @code{Uppercase} is specified, then the name
3767 will be forced to all uppercase letters. If @code{Lowercase} is specified,
3768 then the name will be forced to all lowercase letters. A specification of
3769 @code{As_Is} provides the normal default behavior in which the casing is
3770 taken from the string provided.
3773 This pragma may appear anywhere that a pragma is valid. In particular, it
3774 can be used as a configuration pragma in the @code{gnat.adc} file, in which
3775 case it applies to all subsequent compilations, or it can be used as a program
3776 unit pragma, in which case it only applies to the current unit, or it can
3777 be used more locally to control individual Import/Export pragmas.
3779 It was primarily intended for use with OpenVMS systems, where many
3780 compilers convert all symbols to upper case by default. For interfacing to
3781 such compilers (e.g., the DEC C compiler), it may be convenient to use
3785 pragma External_Name_Casing (Uppercase, Uppercase);
3788 to enforce the upper casing of all external symbols.
3790 @node Pragma Fast_Math,Pragma Favor_Top_Level,Pragma External_Name_Casing,Implementation Defined Pragmas
3791 @anchor{gnat_rm/implementation_defined_pragmas pragma-fast-math}@anchor{6a}
3792 @section Pragma Fast_Math
3801 This is a configuration pragma which activates a mode in which speed is
3802 considered more important for floating-point operations than absolutely
3803 accurate adherence to the requirements of the standard. Currently the
3804 following operations are affected:
3809 @item @emph{Complex Multiplication}
3811 The normal simple formula for complex multiplication can result in intermediate
3812 overflows for numbers near the end of the range. The Ada standard requires that
3813 this situation be detected and corrected by scaling, but in Fast_Math mode such
3814 cases will simply result in overflow. Note that to take advantage of this you
3815 must instantiate your own version of @code{Ada.Numerics.Generic_Complex_Types}
3816 under control of the pragma, rather than use the preinstantiated versions.
3819 @node Pragma Favor_Top_Level,Pragma Finalize_Storage_Only,Pragma Fast_Math,Implementation Defined Pragmas
3820 @anchor{gnat_rm/implementation_defined_pragmas id13}@anchor{6b}@anchor{gnat_rm/implementation_defined_pragmas pragma-favor-top-level}@anchor{6c}
3821 @section Pragma Favor_Top_Level
3827 pragma Favor_Top_Level (type_NAME);
3830 The argument of pragma @code{Favor_Top_Level} must be a named access-to-subprogram
3831 type. This pragma is an efficiency hint to the compiler, regarding the use of
3832 @code{'Access} or @code{'Unrestricted_Access} on nested (non-library-level) subprograms.
3833 The pragma means that nested subprograms are not used with this type, or are
3834 rare, so that the generated code should be efficient in the top-level case.
3835 When this pragma is used, dynamically generated trampolines may be used on some
3836 targets for nested subprograms. See restriction @code{No_Implicit_Dynamic_Code}.
3838 @node Pragma Finalize_Storage_Only,Pragma Float_Representation,Pragma Favor_Top_Level,Implementation Defined Pragmas
3839 @anchor{gnat_rm/implementation_defined_pragmas pragma-finalize-storage-only}@anchor{6d}
3840 @section Pragma Finalize_Storage_Only
3846 pragma Finalize_Storage_Only (first_subtype_LOCAL_NAME);
3849 The argument of pragma @code{Finalize_Storage_Only} must denote a local type which
3850 is derived from @code{Ada.Finalization.Controlled} or @code{Limited_Controlled}. The
3851 pragma suppresses the call to @code{Finalize} for declared library-level objects
3852 of the argument type. This is mostly useful for types where finalization is
3853 only used to deal with storage reclamation since in most environments it is
3854 not necessary to reclaim memory just before terminating execution, hence the
3855 name. Note that this pragma does not suppress Finalize calls for library-level
3856 heap-allocated objects (see pragma @code{No_Heap_Finalization}).
3858 @node Pragma Float_Representation,Pragma Ghost,Pragma Finalize_Storage_Only,Implementation Defined Pragmas
3859 @anchor{gnat_rm/implementation_defined_pragmas pragma-float-representation}@anchor{6e}
3860 @section Pragma Float_Representation
3866 pragma Float_Representation (FLOAT_REP[, float_type_LOCAL_NAME]);
3868 FLOAT_REP ::= VAX_Float | IEEE_Float
3871 In the one argument form, this pragma is a configuration pragma which
3872 allows control over the internal representation chosen for the predefined
3873 floating point types declared in the packages @code{Standard} and
3874 @code{System}. This pragma is only provided for compatibility and has no effect.
3876 The two argument form specifies the representation to be used for
3877 the specified floating-point type. The argument must
3878 be @code{IEEE_Float} to specify the use of IEEE format, as follows:
3884 For a digits value of 6, 32-bit IEEE short format will be used.
3887 For a digits value of 15, 64-bit IEEE long format will be used.
3890 No other value of digits is permitted.
3893 @node Pragma Ghost,Pragma Global,Pragma Float_Representation,Implementation Defined Pragmas
3894 @anchor{gnat_rm/implementation_defined_pragmas pragma-ghost}@anchor{6f}@anchor{gnat_rm/implementation_defined_pragmas id14}@anchor{70}
3895 @section Pragma Ghost
3901 pragma Ghost [ (boolean_EXPRESSION) ];
3904 For the semantics of this pragma, see the entry for aspect @code{Ghost} in the SPARK
3905 2014 Reference Manual, section 6.9.
3907 @node Pragma Global,Pragma Ident,Pragma Ghost,Implementation Defined Pragmas
3908 @anchor{gnat_rm/implementation_defined_pragmas pragma-global}@anchor{71}@anchor{gnat_rm/implementation_defined_pragmas id15}@anchor{72}
3909 @section Pragma Global
3915 pragma Global (GLOBAL_SPECIFICATION);
3917 GLOBAL_SPECIFICATION ::=
3920 | (MODED_GLOBAL_LIST @{, MODED_GLOBAL_LIST@})
3922 MODED_GLOBAL_LIST ::= MODE_SELECTOR => GLOBAL_LIST
3924 MODE_SELECTOR ::= In_Out | Input | Output | Proof_In
3925 GLOBAL_LIST ::= GLOBAL_ITEM | (GLOBAL_ITEM @{, GLOBAL_ITEM@})
3926 GLOBAL_ITEM ::= NAME
3929 For the semantics of this pragma, see the entry for aspect @code{Global} in the
3930 SPARK 2014 Reference Manual, section 6.1.4.
3932 @node Pragma Ident,Pragma Ignore_Pragma,Pragma Global,Implementation Defined Pragmas
3933 @anchor{gnat_rm/implementation_defined_pragmas pragma-ident}@anchor{73}
3934 @section Pragma Ident
3940 pragma Ident (static_string_EXPRESSION);
3943 This pragma is identical in effect to pragma @code{Comment}. It is provided
3944 for compatibility with other Ada compilers providing this pragma.
3946 @node Pragma Ignore_Pragma,Pragma Implementation_Defined,Pragma Ident,Implementation Defined Pragmas
3947 @anchor{gnat_rm/implementation_defined_pragmas pragma-ignore-pragma}@anchor{74}
3948 @section Pragma Ignore_Pragma
3954 pragma Ignore_Pragma (pragma_IDENTIFIER);
3957 This is a configuration pragma
3958 that takes a single argument that is a simple identifier. Any subsequent
3959 use of a pragma whose pragma identifier matches this argument will be
3960 silently ignored. This may be useful when legacy code or code intended
3961 for compilation with some other compiler contains pragmas that match the
3962 name, but not the exact implementation, of a GNAT pragma. The use of this
3963 pragma allows such pragmas to be ignored, which may be useful in CodePeer
3964 mode, or during porting of legacy code.
3966 @node Pragma Implementation_Defined,Pragma Implemented,Pragma Ignore_Pragma,Implementation Defined Pragmas
3967 @anchor{gnat_rm/implementation_defined_pragmas pragma-implementation-defined}@anchor{75}
3968 @section Pragma Implementation_Defined
3974 pragma Implementation_Defined (local_NAME);
3977 This pragma marks a previously declared entity as implementation-defined.
3978 For an overloaded entity, applies to the most recent homonym.
3981 pragma Implementation_Defined;
3984 The form with no arguments appears anywhere within a scope, most
3985 typically a package spec, and indicates that all entities that are
3986 defined within the package spec are Implementation_Defined.
3988 This pragma is used within the GNAT runtime library to identify
3989 implementation-defined entities introduced in language-defined units,
3990 for the purpose of implementing the No_Implementation_Identifiers
3993 @node Pragma Implemented,Pragma Implicit_Packing,Pragma Implementation_Defined,Implementation Defined Pragmas
3994 @anchor{gnat_rm/implementation_defined_pragmas pragma-implemented}@anchor{76}
3995 @section Pragma Implemented
4001 pragma Implemented (procedure_LOCAL_NAME, implementation_kind);
4003 implementation_kind ::= By_Entry | By_Protected_Procedure | By_Any
4006 This is an Ada 2012 representation pragma which applies to protected, task
4007 and synchronized interface primitives. The use of pragma Implemented provides
4008 a way to impose a static requirement on the overriding operation by adhering
4009 to one of the three implementation kinds: entry, protected procedure or any of
4010 the above. This pragma is available in all earlier versions of Ada as an
4011 implementation-defined pragma.
4014 type Synch_Iface is synchronized interface;
4015 procedure Prim_Op (Obj : in out Iface) is abstract;
4016 pragma Implemented (Prim_Op, By_Protected_Procedure);
4018 protected type Prot_1 is new Synch_Iface with
4019 procedure Prim_Op; -- Legal
4022 protected type Prot_2 is new Synch_Iface with
4023 entry Prim_Op; -- Illegal
4026 task type Task_Typ is new Synch_Iface with
4027 entry Prim_Op; -- Illegal
4031 When applied to the procedure_or_entry_NAME of a requeue statement, pragma
4032 Implemented determines the runtime behavior of the requeue. Implementation kind
4033 By_Entry guarantees that the action of requeueing will proceed from an entry to
4034 another entry. Implementation kind By_Protected_Procedure transforms the
4035 requeue into a dispatching call, thus eliminating the chance of blocking. Kind
4036 By_Any shares the behavior of By_Entry and By_Protected_Procedure depending on
4037 the target's overriding subprogram kind.
4039 @node Pragma Implicit_Packing,Pragma Import_Function,Pragma Implemented,Implementation Defined Pragmas
4040 @anchor{gnat_rm/implementation_defined_pragmas pragma-implicit-packing}@anchor{77}
4041 @section Pragma Implicit_Packing
4044 @geindex Rational Profile
4049 pragma Implicit_Packing;
4052 This is a configuration pragma that requests implicit packing for packed
4053 arrays for which a size clause is given but no explicit pragma Pack or
4054 specification of Component_Size is present. It also applies to records
4055 where no record representation clause is present. Consider this example:
4058 type R is array (0 .. 7) of Boolean;
4062 In accordance with the recommendation in the RM (RM 13.3(53)), a Size clause
4063 does not change the layout of a composite object. So the Size clause in the
4064 above example is normally rejected, since the default layout of the array uses
4065 8-bit components, and thus the array requires a minimum of 64 bits.
4067 If this declaration is compiled in a region of code covered by an occurrence
4068 of the configuration pragma Implicit_Packing, then the Size clause in this
4069 and similar examples will cause implicit packing and thus be accepted. For
4070 this implicit packing to occur, the type in question must be an array of small
4071 components whose size is known at compile time, and the Size clause must
4072 specify the exact size that corresponds to the number of elements in the array
4073 multiplied by the size in bits of the component type (both single and
4074 multi-dimensioned arrays can be controlled with this pragma).
4076 @geindex Array packing
4078 Similarly, the following example shows the use in the record case
4082 a, b, c, d, e, f, g, h : boolean;
4088 Without a pragma Pack, each Boolean field requires 8 bits, so the
4089 minimum size is 72 bits, but with a pragma Pack, 16 bits would be
4090 sufficient. The use of pragma Implicit_Packing allows this record
4091 declaration to compile without an explicit pragma Pack.
4093 @node Pragma Import_Function,Pragma Import_Object,Pragma Implicit_Packing,Implementation Defined Pragmas
4094 @anchor{gnat_rm/implementation_defined_pragmas pragma-import-function}@anchor{78}
4095 @section Pragma Import_Function
4101 pragma Import_Function (
4102 [Internal =>] LOCAL_NAME,
4103 [, [External =>] EXTERNAL_SYMBOL]
4104 [, [Parameter_Types =>] PARAMETER_TYPES]
4105 [, [Result_Type =>] SUBTYPE_MARK]
4106 [, [Mechanism =>] MECHANISM]
4107 [, [Result_Mechanism =>] MECHANISM_NAME]);
4111 | static_string_EXPRESSION
4115 | TYPE_DESIGNATOR @{, TYPE_DESIGNATOR@}
4119 | subtype_Name ' Access
4123 | (MECHANISM_ASSOCIATION @{, MECHANISM_ASSOCIATION@})
4125 MECHANISM_ASSOCIATION ::=
4126 [formal_parameter_NAME =>] MECHANISM_NAME
4133 This pragma is used in conjunction with a pragma @code{Import} to
4134 specify additional information for an imported function. The pragma
4135 @code{Import} (or equivalent pragma @code{Interface}) must precede the
4136 @code{Import_Function} pragma and both must appear in the same
4137 declarative part as the function specification.
4139 The @code{Internal} argument must uniquely designate
4140 the function to which the
4141 pragma applies. If more than one function name exists of this name in
4142 the declarative part you must use the @code{Parameter_Types} and
4143 @code{Result_Type} parameters to achieve the required unique
4144 designation. Subtype marks in these parameters must exactly match the
4145 subtypes in the corresponding function specification, using positional
4146 notation to match parameters with subtype marks.
4147 The form with an @code{'Access} attribute can be used to match an
4148 anonymous access parameter.
4150 You may optionally use the @code{Mechanism} and @code{Result_Mechanism}
4151 parameters to specify passing mechanisms for the
4152 parameters and result. If you specify a single mechanism name, it
4153 applies to all parameters. Otherwise you may specify a mechanism on a
4154 parameter by parameter basis using either positional or named
4155 notation. If the mechanism is not specified, the default mechanism
4158 @node Pragma Import_Object,Pragma Import_Procedure,Pragma Import_Function,Implementation Defined Pragmas
4159 @anchor{gnat_rm/implementation_defined_pragmas pragma-import-object}@anchor{79}
4160 @section Pragma Import_Object
4166 pragma Import_Object
4167 [Internal =>] LOCAL_NAME
4168 [, [External =>] EXTERNAL_SYMBOL]
4169 [, [Size =>] EXTERNAL_SYMBOL]);
4173 | static_string_EXPRESSION
4176 This pragma designates an object as imported, and apart from the
4177 extended rules for external symbols, is identical in effect to the use of
4178 the normal @code{Import} pragma applied to an object. Unlike the
4179 subprogram case, you need not use a separate @code{Import} pragma,
4180 although you may do so (and probably should do so from a portability
4181 point of view). @code{size} is syntax checked, but otherwise ignored by
4184 @node Pragma Import_Procedure,Pragma Import_Valued_Procedure,Pragma Import_Object,Implementation Defined Pragmas
4185 @anchor{gnat_rm/implementation_defined_pragmas pragma-import-procedure}@anchor{7a}
4186 @section Pragma Import_Procedure
4192 pragma Import_Procedure (
4193 [Internal =>] LOCAL_NAME
4194 [, [External =>] EXTERNAL_SYMBOL]
4195 [, [Parameter_Types =>] PARAMETER_TYPES]
4196 [, [Mechanism =>] MECHANISM]);
4200 | static_string_EXPRESSION
4204 | TYPE_DESIGNATOR @{, TYPE_DESIGNATOR@}
4208 | subtype_Name ' Access
4212 | (MECHANISM_ASSOCIATION @{, MECHANISM_ASSOCIATION@})
4214 MECHANISM_ASSOCIATION ::=
4215 [formal_parameter_NAME =>] MECHANISM_NAME
4217 MECHANISM_NAME ::= Value | Reference
4220 This pragma is identical to @code{Import_Function} except that it
4221 applies to a procedure rather than a function and the parameters
4222 @code{Result_Type} and @code{Result_Mechanism} are not permitted.
4224 @node Pragma Import_Valued_Procedure,Pragma Independent,Pragma Import_Procedure,Implementation Defined Pragmas
4225 @anchor{gnat_rm/implementation_defined_pragmas pragma-import-valued-procedure}@anchor{7b}
4226 @section Pragma Import_Valued_Procedure
4232 pragma Import_Valued_Procedure (
4233 [Internal =>] LOCAL_NAME
4234 [, [External =>] EXTERNAL_SYMBOL]
4235 [, [Parameter_Types =>] PARAMETER_TYPES]
4236 [, [Mechanism =>] MECHANISM]);
4240 | static_string_EXPRESSION
4244 | TYPE_DESIGNATOR @{, TYPE_DESIGNATOR@}
4248 | subtype_Name ' Access
4252 | (MECHANISM_ASSOCIATION @{, MECHANISM_ASSOCIATION@})
4254 MECHANISM_ASSOCIATION ::=
4255 [formal_parameter_NAME =>] MECHANISM_NAME
4257 MECHANISM_NAME ::= Value | Reference
4260 This pragma is identical to @code{Import_Procedure} except that the
4261 first parameter of @code{LOCAL_NAME}, which must be present, must be of
4262 mode @code{out}, and externally the subprogram is treated as a function
4263 with this parameter as the result of the function. The purpose of this
4264 capability is to allow the use of @code{out} and @code{in out}
4265 parameters in interfacing to external functions (which are not permitted
4266 in Ada functions). You may optionally use the @code{Mechanism}
4267 parameters to specify passing mechanisms for the parameters.
4268 If you specify a single mechanism name, it applies to all parameters.
4269 Otherwise you may specify a mechanism on a parameter by parameter
4270 basis using either positional or named notation. If the mechanism is not
4271 specified, the default mechanism is used.
4273 Note that it is important to use this pragma in conjunction with a separate
4274 pragma Import that specifies the desired convention, since otherwise the
4275 default convention is Ada, which is almost certainly not what is required.
4277 @node Pragma Independent,Pragma Independent_Components,Pragma Import_Valued_Procedure,Implementation Defined Pragmas
4278 @anchor{gnat_rm/implementation_defined_pragmas pragma-independent}@anchor{7c}
4279 @section Pragma Independent
4285 pragma Independent (Local_NAME);
4288 This pragma is standard in Ada 2012 mode (which also provides an aspect
4289 of the same name). It is also available as an implementation-defined
4290 pragma in all earlier versions. It specifies that the
4291 designated object or all objects of the designated type must be
4292 independently addressable. This means that separate tasks can safely
4293 manipulate such objects. For example, if two components of a record are
4294 independent, then two separate tasks may access these two components.
4296 constraints on the representation of the object (for instance prohibiting
4299 @node Pragma Independent_Components,Pragma Initial_Condition,Pragma Independent,Implementation Defined Pragmas
4300 @anchor{gnat_rm/implementation_defined_pragmas pragma-independent-components}@anchor{7d}
4301 @section Pragma Independent_Components
4307 pragma Independent_Components (Local_NAME);
4310 This pragma is standard in Ada 2012 mode (which also provides an aspect
4311 of the same name). It is also available as an implementation-defined
4312 pragma in all earlier versions. It specifies that the components of the
4313 designated object, or the components of each object of the designated
4315 independently addressable. This means that separate tasks can safely
4316 manipulate separate components in the composite object. This may place
4317 constraints on the representation of the object (for instance prohibiting
4320 @node Pragma Initial_Condition,Pragma Initialize_Scalars,Pragma Independent_Components,Implementation Defined Pragmas
4321 @anchor{gnat_rm/implementation_defined_pragmas id16}@anchor{7e}@anchor{gnat_rm/implementation_defined_pragmas pragma-initial-condition}@anchor{7f}
4322 @section Pragma Initial_Condition
4328 pragma Initial_Condition (boolean_EXPRESSION);
4331 For the semantics of this pragma, see the entry for aspect @code{Initial_Condition}
4332 in the SPARK 2014 Reference Manual, section 7.1.6.
4334 @node Pragma Initialize_Scalars,Pragma Initializes,Pragma Initial_Condition,Implementation Defined Pragmas
4335 @anchor{gnat_rm/implementation_defined_pragmas pragma-initialize-scalars}@anchor{80}
4336 @section Pragma Initialize_Scalars
4339 @geindex debugging with Initialize_Scalars
4344 pragma Initialize_Scalars
4345 [ ( TYPE_VALUE_PAIR @{, TYPE_VALUE_PAIR@} ) ];
4348 SCALAR_TYPE => static_EXPRESSION
4365 This pragma is similar to @code{Normalize_Scalars} conceptually but has two
4366 important differences.
4368 First, there is no requirement for the pragma to be used uniformly in all units
4369 of a partition. In particular, it is fine to use this just for some or all of
4370 the application units of a partition, without needing to recompile the run-time
4371 library. In the case where some units are compiled with the pragma, and some
4372 without, then a declaration of a variable where the type is defined in package
4373 Standard or is locally declared will always be subject to initialization, as
4374 will any declaration of a scalar variable. For composite variables, whether the
4375 variable is initialized may also depend on whether the package in which the
4376 type of the variable is declared is compiled with the pragma.
4378 The other important difference is that the programmer can control the value
4379 used for initializing scalar objects. This effect can be achieved in several
4386 At compile time, the programmer can specify the invalid value for a
4387 particular family of scalar types using the optional arguments of the pragma.
4389 The compile-time approach is intended to optimize the generated code for the
4390 pragma, by possibly using fast operations such as @code{memset}. Note that such
4391 optimizations require using values where the bytes all have the same binary
4395 At bind time, the programmer has several options:
4401 Initialization with invalid values (similar to Normalize_Scalars, though
4402 for Initialize_Scalars it is not always possible to determine the invalid
4403 values in complex cases like signed component fields with nonstandard
4407 Initialization with high values.
4410 Initialization with low values.
4413 Initialization with a specific bit pattern.
4416 See the GNAT User's Guide for binder options for specifying these cases.
4418 The bind-time approach is intended to provide fast turnaround for testing
4419 with different values, without having to recompile the program.
4422 At execution time, the programmer can specify the invalid values using an
4423 environment variable. See the GNAT User's Guide for details.
4425 The execution-time approach is intended to provide fast turnaround for
4426 testing with different values, without having to recompile and rebind the
4430 Note that pragma @code{Initialize_Scalars} is particularly useful in conjunction
4431 with the enhanced validity checking that is now provided in GNAT, which checks
4432 for invalid values under more conditions. Using this feature (see description
4433 of the @emph{-gnatV} flag in the GNAT User's Guide) in conjunction with pragma
4434 @code{Initialize_Scalars} provides a powerful new tool to assist in the detection
4435 of problems caused by uninitialized variables.
4437 Note: the use of @code{Initialize_Scalars} has a fairly extensive effect on the
4438 generated code. This may cause your code to be substantially larger. It may
4439 also cause an increase in the amount of stack required, so it is probably a
4440 good idea to turn on stack checking (see description of stack checking in the
4441 GNAT User's Guide) when using this pragma.
4443 @node Pragma Initializes,Pragma Inline_Always,Pragma Initialize_Scalars,Implementation Defined Pragmas
4444 @anchor{gnat_rm/implementation_defined_pragmas pragma-initializes}@anchor{81}@anchor{gnat_rm/implementation_defined_pragmas id17}@anchor{82}
4445 @section Pragma Initializes
4451 pragma Initializes (INITIALIZATION_LIST);
4453 INITIALIZATION_LIST ::=
4455 | (INITIALIZATION_ITEM @{, INITIALIZATION_ITEM@})
4457 INITIALIZATION_ITEM ::= name [=> INPUT_LIST]
4462 | (INPUT @{, INPUT@})
4467 For the semantics of this pragma, see the entry for aspect @code{Initializes} in the
4468 SPARK 2014 Reference Manual, section 7.1.5.
4470 @node Pragma Inline_Always,Pragma Inline_Generic,Pragma Initializes,Implementation Defined Pragmas
4471 @anchor{gnat_rm/implementation_defined_pragmas id18}@anchor{83}@anchor{gnat_rm/implementation_defined_pragmas pragma-inline-always}@anchor{84}
4472 @section Pragma Inline_Always
4478 pragma Inline_Always (NAME [, NAME]);
4481 Similar to pragma @code{Inline} except that inlining is unconditional.
4482 Inline_Always instructs the compiler to inline every direct call to the
4483 subprogram or else to emit a compilation error, independently of any
4484 option, in particular @emph{-gnatn} or @emph{-gnatN} or the optimization level.
4485 It is an error to take the address or access of @code{NAME}. It is also an error to
4486 apply this pragma to a primitive operation of a tagged type. Thanks to such
4487 restrictions, the compiler is allowed to remove the out-of-line body of @code{NAME}.
4489 @node Pragma Inline_Generic,Pragma Interface,Pragma Inline_Always,Implementation Defined Pragmas
4490 @anchor{gnat_rm/implementation_defined_pragmas pragma-inline-generic}@anchor{85}
4491 @section Pragma Inline_Generic
4497 pragma Inline_Generic (GNAME @{, GNAME@});
4499 GNAME ::= generic_unit_NAME | generic_instance_NAME
4502 This pragma is provided for compatibility with Dec Ada 83. It has
4503 no effect in GNAT (which always inlines generics), other
4504 than to check that the given names are all names of generic units or
4507 @node Pragma Interface,Pragma Interface_Name,Pragma Inline_Generic,Implementation Defined Pragmas
4508 @anchor{gnat_rm/implementation_defined_pragmas pragma-interface}@anchor{86}
4509 @section Pragma Interface
4516 [Convention =>] convention_identifier,
4517 [Entity =>] local_NAME
4518 [, [External_Name =>] static_string_expression]
4519 [, [Link_Name =>] static_string_expression]);
4522 This pragma is identical in syntax and semantics to
4523 the standard Ada pragma @code{Import}. It is provided for compatibility
4524 with Ada 83. The definition is upwards compatible both with pragma
4525 @code{Interface} as defined in the Ada 83 Reference Manual, and also
4526 with some extended implementations of this pragma in certain Ada 83
4527 implementations. The only difference between pragma @code{Interface}
4528 and pragma @code{Import} is that there is special circuitry to allow
4529 both pragmas to appear for the same subprogram entity (normally it
4530 is illegal to have multiple @code{Import} pragmas. This is useful in
4531 maintaining Ada 83/Ada 95 compatibility and is compatible with other
4534 @node Pragma Interface_Name,Pragma Interrupt_Handler,Pragma Interface,Implementation Defined Pragmas
4535 @anchor{gnat_rm/implementation_defined_pragmas pragma-interface-name}@anchor{87}
4536 @section Pragma Interface_Name
4542 pragma Interface_Name (
4543 [Entity =>] LOCAL_NAME
4544 [, [External_Name =>] static_string_EXPRESSION]
4545 [, [Link_Name =>] static_string_EXPRESSION]);
4548 This pragma provides an alternative way of specifying the interface name
4549 for an interfaced subprogram, and is provided for compatibility with Ada
4550 83 compilers that use the pragma for this purpose. You must provide at
4551 least one of @code{External_Name} or @code{Link_Name}.
4553 @node Pragma Interrupt_Handler,Pragma Interrupt_State,Pragma Interface_Name,Implementation Defined Pragmas
4554 @anchor{gnat_rm/implementation_defined_pragmas pragma-interrupt-handler}@anchor{88}
4555 @section Pragma Interrupt_Handler
4561 pragma Interrupt_Handler (procedure_LOCAL_NAME);
4564 This program unit pragma is supported for parameterless protected procedures
4565 as described in Annex C of the Ada Reference Manual. On the AAMP target
4566 the pragma can also be specified for nonprotected parameterless procedures
4567 that are declared at the library level (which includes procedures
4568 declared at the top level of a library package). In the case of AAMP,
4569 when this pragma is applied to a nonprotected procedure, the instruction
4570 @code{IERET} is generated for returns from the procedure, enabling
4571 maskable interrupts, in place of the normal return instruction.
4573 @node Pragma Interrupt_State,Pragma Invariant,Pragma Interrupt_Handler,Implementation Defined Pragmas
4574 @anchor{gnat_rm/implementation_defined_pragmas pragma-interrupt-state}@anchor{89}
4575 @section Pragma Interrupt_State
4581 pragma Interrupt_State
4583 [State =>] SYSTEM | RUNTIME | USER);
4586 Normally certain interrupts are reserved to the implementation. Any attempt
4587 to attach an interrupt causes Program_Error to be raised, as described in
4588 RM C.3.2(22). A typical example is the @code{SIGINT} interrupt used in
4589 many systems for an @code{Ctrl-C} interrupt. Normally this interrupt is
4590 reserved to the implementation, so that @code{Ctrl-C} can be used to
4591 interrupt execution. Additionally, signals such as @code{SIGSEGV},
4592 @code{SIGABRT}, @code{SIGFPE} and @code{SIGILL} are often mapped to specific
4593 Ada exceptions, or used to implement run-time functions such as the
4594 @code{abort} statement and stack overflow checking.
4596 Pragma @code{Interrupt_State} provides a general mechanism for overriding
4597 such uses of interrupts. It subsumes the functionality of pragma
4598 @code{Unreserve_All_Interrupts}. Pragma @code{Interrupt_State} is not
4599 available on Windows. On all other platforms than VxWorks,
4600 it applies to signals; on VxWorks, it applies to vectored hardware interrupts
4601 and may be used to mark interrupts required by the board support package
4604 Interrupts can be in one of three states:
4612 The interrupt is reserved (no Ada handler can be installed), and the
4613 Ada run-time may not install a handler. As a result you are guaranteed
4614 standard system default action if this interrupt is raised. This also allows
4615 installing a low level handler via C APIs such as sigaction(), outside
4621 The interrupt is reserved (no Ada handler can be installed). The run time
4622 is allowed to install a handler for internal control purposes, but is
4623 not required to do so.
4628 The interrupt is unreserved. The user may install an Ada handler via
4629 Ada.Interrupts and pragma Interrupt_Handler or Attach_Handler to provide
4633 These states are the allowed values of the @code{State} parameter of the
4634 pragma. The @code{Name} parameter is a value of the type
4635 @code{Ada.Interrupts.Interrupt_ID}. Typically, it is a name declared in
4636 @code{Ada.Interrupts.Names}.
4638 This is a configuration pragma, and the binder will check that there
4639 are no inconsistencies between different units in a partition in how a
4640 given interrupt is specified. It may appear anywhere a pragma is legal.
4642 The effect is to move the interrupt to the specified state.
4644 By declaring interrupts to be SYSTEM, you guarantee the standard system
4645 action, such as a core dump.
4647 By declaring interrupts to be USER, you guarantee that you can install
4650 Note that certain signals on many operating systems cannot be caught and
4651 handled by applications. In such cases, the pragma is ignored. See the
4652 operating system documentation, or the value of the array @code{Reserved}
4653 declared in the spec of package @code{System.OS_Interface}.
4655 Overriding the default state of signals used by the Ada runtime may interfere
4656 with an application's runtime behavior in the cases of the synchronous signals,
4657 and in the case of the signal used to implement the @code{abort} statement.
4659 @node Pragma Invariant,Pragma Keep_Names,Pragma Interrupt_State,Implementation Defined Pragmas
4660 @anchor{gnat_rm/implementation_defined_pragmas id19}@anchor{8a}@anchor{gnat_rm/implementation_defined_pragmas pragma-invariant}@anchor{8b}
4661 @section Pragma Invariant
4668 ([Entity =>] private_type_LOCAL_NAME,
4669 [Check =>] EXPRESSION
4670 [,[Message =>] String_Expression]);
4673 This pragma provides exactly the same capabilities as the Type_Invariant aspect
4674 defined in AI05-0146-1, and in the Ada 2012 Reference Manual. The
4675 Type_Invariant aspect is fully implemented in Ada 2012 mode, but since it
4676 requires the use of the aspect syntax, which is not available except in 2012
4677 mode, it is not possible to use the Type_Invariant aspect in earlier versions
4678 of Ada. However the Invariant pragma may be used in any version of Ada. Also
4679 note that the aspect Invariant is a synonym in GNAT for the aspect
4680 Type_Invariant, but there is no pragma Type_Invariant.
4682 The pragma must appear within the visible part of the package specification,
4683 after the type to which its Entity argument appears. As with the Invariant
4684 aspect, the Check expression is not analyzed until the end of the visible
4685 part of the package, so it may contain forward references. The Message
4686 argument, if present, provides the exception message used if the invariant
4687 is violated. If no Message parameter is provided, a default message that
4688 identifies the line on which the pragma appears is used.
4690 It is permissible to have multiple Invariants for the same type entity, in
4691 which case they are and'ed together. It is permissible to use this pragma
4692 in Ada 2012 mode, but you cannot have both an invariant aspect and an
4693 invariant pragma for the same entity.
4695 For further details on the use of this pragma, see the Ada 2012 documentation
4696 of the Type_Invariant aspect.
4698 @node Pragma Keep_Names,Pragma License,Pragma Invariant,Implementation Defined Pragmas
4699 @anchor{gnat_rm/implementation_defined_pragmas pragma-keep-names}@anchor{8c}
4700 @section Pragma Keep_Names
4706 pragma Keep_Names ([On =>] enumeration_first_subtype_LOCAL_NAME);
4709 The @code{LOCAL_NAME} argument
4710 must refer to an enumeration first subtype
4711 in the current declarative part. The effect is to retain the enumeration
4712 literal names for use by @code{Image} and @code{Value} even if a global
4713 @code{Discard_Names} pragma applies. This is useful when you want to
4714 generally suppress enumeration literal names and for example you therefore
4715 use a @code{Discard_Names} pragma in the @code{gnat.adc} file, but you
4716 want to retain the names for specific enumeration types.
4718 @node Pragma License,Pragma Link_With,Pragma Keep_Names,Implementation Defined Pragmas
4719 @anchor{gnat_rm/implementation_defined_pragmas pragma-license}@anchor{8d}
4720 @section Pragma License
4723 @geindex License checking
4728 pragma License (Unrestricted | GPL | Modified_GPL | Restricted);
4731 This pragma is provided to allow automated checking for appropriate license
4732 conditions with respect to the standard and modified GPL. A pragma
4733 @code{License}, which is a configuration pragma that typically appears at
4734 the start of a source file or in a separate @code{gnat.adc} file, specifies
4735 the licensing conditions of a unit as follows:
4742 This is used for a unit that can be freely used with no license restrictions.
4743 Examples of such units are public domain units, and units from the Ada
4748 This is used for a unit that is licensed under the unmodified GPL, and which
4749 therefore cannot be @code{with}ed by a restricted unit.
4753 This is used for a unit licensed under the GNAT modified GPL that includes
4754 a special exception paragraph that specifically permits the inclusion of
4755 the unit in programs without requiring the entire program to be released
4760 This is used for a unit that is restricted in that it is not permitted to
4761 depend on units that are licensed under the GPL. Typical examples are
4762 proprietary code that is to be released under more restrictive license
4763 conditions. Note that restricted units are permitted to @code{with} units
4764 which are licensed under the modified GPL (this is the whole point of the
4768 Normally a unit with no @code{License} pragma is considered to have an
4769 unknown license, and no checking is done. However, standard GNAT headers
4770 are recognized, and license information is derived from them as follows.
4772 A GNAT license header starts with a line containing 78 hyphens. The following
4773 comment text is searched for the appearance of any of the following strings.
4775 If the string 'GNU General Public License' is found, then the unit is assumed
4776 to have GPL license, unless the string 'As a special exception' follows, in
4777 which case the license is assumed to be modified GPL.
4779 If one of the strings
4780 'This specification is adapted from the Ada Semantic Interface' or
4781 'This specification is derived from the Ada Reference Manual' is found
4782 then the unit is assumed to be unrestricted.
4784 These default actions means that a program with a restricted license pragma
4785 will automatically get warnings if a GPL unit is inappropriately
4786 @code{with}ed. For example, the program:
4791 procedure Secret_Stuff is
4796 if compiled with pragma @code{License} (@code{Restricted}) in a
4797 @code{gnat.adc} file will generate the warning:
4802 >>> license of withed unit "Sem_Ch3" is incompatible
4804 2. with GNAT.Sockets;
4805 3. procedure Secret_Stuff is
4808 Here we get a warning on @code{Sem_Ch3} since it is part of the GNAT
4809 compiler and is licensed under the
4810 GPL, but no warning for @code{GNAT.Sockets} which is part of the GNAT
4811 run time, and is therefore licensed under the modified GPL.
4813 @node Pragma Link_With,Pragma Linker_Alias,Pragma License,Implementation Defined Pragmas
4814 @anchor{gnat_rm/implementation_defined_pragmas pragma-link-with}@anchor{8e}
4815 @section Pragma Link_With
4821 pragma Link_With (static_string_EXPRESSION @{,static_string_EXPRESSION@});
4824 This pragma is provided for compatibility with certain Ada 83 compilers.
4825 It has exactly the same effect as pragma @code{Linker_Options} except
4826 that spaces occurring within one of the string expressions are treated
4827 as separators. For example, in the following case:
4830 pragma Link_With ("-labc -ldef");
4833 results in passing the strings @code{-labc} and @code{-ldef} as two
4834 separate arguments to the linker. In addition pragma Link_With allows
4835 multiple arguments, with the same effect as successive pragmas.
4837 @node Pragma Linker_Alias,Pragma Linker_Constructor,Pragma Link_With,Implementation Defined Pragmas
4838 @anchor{gnat_rm/implementation_defined_pragmas pragma-linker-alias}@anchor{8f}
4839 @section Pragma Linker_Alias
4845 pragma Linker_Alias (
4846 [Entity =>] LOCAL_NAME,
4847 [Target =>] static_string_EXPRESSION);
4850 @code{LOCAL_NAME} must refer to an object that is declared at the library
4851 level. This pragma establishes the given entity as a linker alias for the
4852 given target. It is equivalent to @code{__attribute__((alias))} in GNU C
4853 and causes @code{LOCAL_NAME} to be emitted as an alias for the symbol
4854 @code{static_string_EXPRESSION} in the object file, that is to say no space
4855 is reserved for @code{LOCAL_NAME} by the assembler and it will be resolved
4856 to the same address as @code{static_string_EXPRESSION} by the linker.
4858 The actual linker name for the target must be used (e.g., the fully
4859 encoded name with qualification in Ada, or the mangled name in C++),
4860 or it must be declared using the C convention with @code{pragma Import}
4861 or @code{pragma Export}.
4863 Not all target machines support this pragma. On some of them it is accepted
4864 only if @code{pragma Weak_External} has been applied to @code{LOCAL_NAME}.
4867 -- Example of the use of pragma Linker_Alias
4871 pragma Export (C, i);
4873 new_name_for_i : Integer;
4874 pragma Linker_Alias (new_name_for_i, "i");
4878 @node Pragma Linker_Constructor,Pragma Linker_Destructor,Pragma Linker_Alias,Implementation Defined Pragmas
4879 @anchor{gnat_rm/implementation_defined_pragmas pragma-linker-constructor}@anchor{90}
4880 @section Pragma Linker_Constructor
4886 pragma Linker_Constructor (procedure_LOCAL_NAME);
4889 @code{procedure_LOCAL_NAME} must refer to a parameterless procedure that
4890 is declared at the library level. A procedure to which this pragma is
4891 applied will be treated as an initialization routine by the linker.
4892 It is equivalent to @code{__attribute__((constructor))} in GNU C and
4893 causes @code{procedure_LOCAL_NAME} to be invoked before the entry point
4894 of the executable is called (or immediately after the shared library is
4895 loaded if the procedure is linked in a shared library), in particular
4896 before the Ada run-time environment is set up.
4898 Because of these specific contexts, the set of operations such a procedure
4899 can perform is very limited and the type of objects it can manipulate is
4900 essentially restricted to the elementary types. In particular, it must only
4901 contain code to which pragma Restrictions (No_Elaboration_Code) applies.
4903 This pragma is used by GNAT to implement auto-initialization of shared Stand
4904 Alone Libraries, which provides a related capability without the restrictions
4905 listed above. Where possible, the use of Stand Alone Libraries is preferable
4906 to the use of this pragma.
4908 @node Pragma Linker_Destructor,Pragma Linker_Section,Pragma Linker_Constructor,Implementation Defined Pragmas
4909 @anchor{gnat_rm/implementation_defined_pragmas pragma-linker-destructor}@anchor{91}
4910 @section Pragma Linker_Destructor
4916 pragma Linker_Destructor (procedure_LOCAL_NAME);
4919 @code{procedure_LOCAL_NAME} must refer to a parameterless procedure that
4920 is declared at the library level. A procedure to which this pragma is
4921 applied will be treated as a finalization routine by the linker.
4922 It is equivalent to @code{__attribute__((destructor))} in GNU C and
4923 causes @code{procedure_LOCAL_NAME} to be invoked after the entry point
4924 of the executable has exited (or immediately before the shared library
4925 is unloaded if the procedure is linked in a shared library), in particular
4926 after the Ada run-time environment is shut down.
4928 See @code{pragma Linker_Constructor} for the set of restrictions that apply
4929 because of these specific contexts.
4931 @node Pragma Linker_Section,Pragma Lock_Free,Pragma Linker_Destructor,Implementation Defined Pragmas
4932 @anchor{gnat_rm/implementation_defined_pragmas id20}@anchor{92}@anchor{gnat_rm/implementation_defined_pragmas pragma-linker-section}@anchor{93}
4933 @section Pragma Linker_Section
4939 pragma Linker_Section (
4940 [Entity =>] LOCAL_NAME,
4941 [Section =>] static_string_EXPRESSION);
4944 @code{LOCAL_NAME} must refer to an object, type, or subprogram that is
4945 declared at the library level. This pragma specifies the name of the
4946 linker section for the given entity. It is equivalent to
4947 @code{__attribute__((section))} in GNU C and causes @code{LOCAL_NAME} to
4948 be placed in the @code{static_string_EXPRESSION} section of the
4949 executable (assuming the linker doesn't rename the section).
4950 GNAT also provides an implementation defined aspect of the same name.
4952 In the case of specifying this aspect for a type, the effect is to
4953 specify the corresponding section for all library-level objects of
4954 the type that do not have an explicit linker section set. Note that
4955 this only applies to whole objects, not to components of composite objects.
4957 In the case of a subprogram, the linker section applies to all previously
4958 declared matching overloaded subprograms in the current declarative part
4959 which do not already have a linker section assigned. The linker section
4960 aspect is useful in this case for specifying different linker sections
4961 for different elements of such an overloaded set.
4963 Note that an empty string specifies that no linker section is specified.
4964 This is not quite the same as omitting the pragma or aspect, since it
4965 can be used to specify that one element of an overloaded set of subprograms
4966 has the default linker section, or that one object of a type for which a
4967 linker section is specified should has the default linker section.
4969 The compiler normally places library-level entities in standard sections
4970 depending on the class: procedures and functions generally go in the
4971 @code{.text} section, initialized variables in the @code{.data} section
4972 and uninitialized variables in the @code{.bss} section.
4974 Other, special sections may exist on given target machines to map special
4975 hardware, for example I/O ports or flash memory. This pragma is a means to
4976 defer the final layout of the executable to the linker, thus fully working
4977 at the symbolic level with the compiler.
4979 Some file formats do not support arbitrary sections so not all target
4980 machines support this pragma. The use of this pragma may cause a program
4981 execution to be erroneous if it is used to place an entity into an
4982 inappropriate section (e.g., a modified variable into the @code{.text}
4983 section). See also @code{pragma Persistent_BSS}.
4986 -- Example of the use of pragma Linker_Section
4990 pragma Volatile (Port_A);
4991 pragma Linker_Section (Port_A, ".bss.port_a");
4994 pragma Volatile (Port_B);
4995 pragma Linker_Section (Port_B, ".bss.port_b");
4997 type Port_Type is new Integer with Linker_Section => ".bss";
4998 PA : Port_Type with Linker_Section => ".bss.PA";
4999 PB : Port_Type; -- ends up in linker section ".bss"
5001 procedure Q with Linker_Section => "Qsection";
5005 @node Pragma Lock_Free,Pragma Loop_Invariant,Pragma Linker_Section,Implementation Defined Pragmas
5006 @anchor{gnat_rm/implementation_defined_pragmas id21}@anchor{94}@anchor{gnat_rm/implementation_defined_pragmas pragma-lock-free}@anchor{95}
5007 @section Pragma Lock_Free
5011 This pragma may be specified for protected types or objects. It specifies that
5012 the implementation of protected operations must be implemented without locks.
5013 Compilation fails if the compiler cannot generate lock-free code for the
5016 The current conditions required to support this pragma are:
5022 Protected type declarations may not contain entries
5025 Protected subprogram declarations may not have nonelementary parameters
5028 In addition, each protected subprogram body must satisfy:
5034 May reference only one protected component
5037 May not reference nonconstant entities outside the protected subprogram
5041 May not contain address representation items, allocators, or quantified
5045 May not contain delay, goto, loop, or procedure-call statements.
5048 May not contain exported and imported entities
5051 May not dereferenced access values
5054 Function calls and attribute references must be static
5057 @node Pragma Loop_Invariant,Pragma Loop_Optimize,Pragma Lock_Free,Implementation Defined Pragmas
5058 @anchor{gnat_rm/implementation_defined_pragmas pragma-loop-invariant}@anchor{96}
5059 @section Pragma Loop_Invariant
5065 pragma Loop_Invariant ( boolean_EXPRESSION );
5068 The effect of this pragma is similar to that of pragma @code{Assert},
5069 except that in an @code{Assertion_Policy} pragma, the identifier
5070 @code{Loop_Invariant} is used to control whether it is ignored or checked
5073 @code{Loop_Invariant} can only appear as one of the items in the sequence
5074 of statements of a loop body, or nested inside block statements that
5075 appear in the sequence of statements of a loop body.
5076 The intention is that it be used to
5077 represent a "loop invariant" assertion, i.e. something that is true each
5078 time through the loop, and which can be used to show that the loop is
5079 achieving its purpose.
5081 Multiple @code{Loop_Invariant} and @code{Loop_Variant} pragmas that
5082 apply to the same loop should be grouped in the same sequence of
5085 To aid in writing such invariants, the special attribute @code{Loop_Entry}
5086 may be used to refer to the value of an expression on entry to the loop. This
5087 attribute can only be used within the expression of a @code{Loop_Invariant}
5088 pragma. For full details, see documentation of attribute @code{Loop_Entry}.
5090 @node Pragma Loop_Optimize,Pragma Loop_Variant,Pragma Loop_Invariant,Implementation Defined Pragmas
5091 @anchor{gnat_rm/implementation_defined_pragmas pragma-loop-optimize}@anchor{97}
5092 @section Pragma Loop_Optimize
5098 pragma Loop_Optimize (OPTIMIZATION_HINT @{, OPTIMIZATION_HINT@});
5100 OPTIMIZATION_HINT ::= Ivdep | No_Unroll | Unroll | No_Vector | Vector
5103 This pragma must appear immediately within a loop statement. It allows the
5104 programmer to specify optimization hints for the enclosing loop. The hints
5105 are not mutually exclusive and can be freely mixed, but not all combinations
5106 will yield a sensible outcome.
5108 There are five supported optimization hints for a loop:
5116 The programmer asserts that there are no loop-carried dependencies
5117 which would prevent consecutive iterations of the loop from being
5118 executed simultaneously.
5123 The loop must not be unrolled. This is a strong hint: the compiler will not
5124 unroll a loop marked with this hint.
5129 The loop should be unrolled. This is a weak hint: the compiler will try to
5130 apply unrolling to this loop preferably to other optimizations, notably
5131 vectorization, but there is no guarantee that the loop will be unrolled.
5136 The loop must not be vectorized. This is a strong hint: the compiler will not
5137 vectorize a loop marked with this hint.
5142 The loop should be vectorized. This is a weak hint: the compiler will try to
5143 apply vectorization to this loop preferably to other optimizations, notably
5144 unrolling, but there is no guarantee that the loop will be vectorized.
5147 These hints do not remove the need to pass the appropriate switches to the
5148 compiler in order to enable the relevant optimizations, that is to say
5149 @emph{-funroll-loops} for unrolling and @emph{-ftree-vectorize} for
5152 @node Pragma Loop_Variant,Pragma Machine_Attribute,Pragma Loop_Optimize,Implementation Defined Pragmas
5153 @anchor{gnat_rm/implementation_defined_pragmas pragma-loop-variant}@anchor{98}
5154 @section Pragma Loop_Variant
5160 pragma Loop_Variant ( LOOP_VARIANT_ITEM @{, LOOP_VARIANT_ITEM @} );
5161 LOOP_VARIANT_ITEM ::= CHANGE_DIRECTION => discrete_EXPRESSION
5162 CHANGE_DIRECTION ::= Increases | Decreases
5165 @code{Loop_Variant} can only appear as one of the items in the sequence
5166 of statements of a loop body, or nested inside block statements that
5167 appear in the sequence of statements of a loop body.
5168 It allows the specification of quantities which must always
5169 decrease or increase in successive iterations of the loop. In its simplest
5170 form, just one expression is specified, whose value must increase or decrease
5171 on each iteration of the loop.
5173 In a more complex form, multiple arguments can be given which are intepreted
5174 in a nesting lexicographic manner. For example:
5177 pragma Loop_Variant (Increases => X, Decreases => Y);
5180 specifies that each time through the loop either X increases, or X stays
5181 the same and Y decreases. A @code{Loop_Variant} pragma ensures that the
5182 loop is making progress. It can be useful in helping to show informally
5183 or prove formally that the loop always terminates.
5185 @code{Loop_Variant} is an assertion whose effect can be controlled using
5186 an @code{Assertion_Policy} with a check name of @code{Loop_Variant}. The
5187 policy can be @code{Check} to enable the loop variant check, @code{Ignore}
5188 to ignore the check (in which case the pragma has no effect on the program),
5189 or @code{Disable} in which case the pragma is not even checked for correct
5192 Multiple @code{Loop_Invariant} and @code{Loop_Variant} pragmas that
5193 apply to the same loop should be grouped in the same sequence of
5196 The @code{Loop_Entry} attribute may be used within the expressions of the
5197 @code{Loop_Variant} pragma to refer to values on entry to the loop.
5199 @node Pragma Machine_Attribute,Pragma Main,Pragma Loop_Variant,Implementation Defined Pragmas
5200 @anchor{gnat_rm/implementation_defined_pragmas pragma-machine-attribute}@anchor{99}
5201 @section Pragma Machine_Attribute
5207 pragma Machine_Attribute (
5208 [Entity =>] LOCAL_NAME,
5209 [Attribute_Name =>] static_string_EXPRESSION
5210 [, [Info =>] static_EXPRESSION @{, static_EXPRESSION@}] );
5213 Machine-dependent attributes can be specified for types and/or
5214 declarations. This pragma is semantically equivalent to
5215 @code{__attribute__((@emph{attribute_name}))} (if @code{info} is not
5216 specified) or @code{__attribute__((@emph{attribute_name(info})))}
5217 or @code{__attribute__((@emph{attribute_name(info,...})))} in GNU C,
5218 where @emph{attribute_name} is recognized by the compiler middle-end
5219 or the @code{TARGET_ATTRIBUTE_TABLE} machine specific macro. Note
5220 that a string literal for the optional parameter @code{info} or the
5221 following ones is transformed by default into an identifier,
5222 which may make this pragma unusable for some attributes.
5223 For further information see @cite{GNU Compiler Collection (GCC) Internals}.
5225 @node Pragma Main,Pragma Main_Storage,Pragma Machine_Attribute,Implementation Defined Pragmas
5226 @anchor{gnat_rm/implementation_defined_pragmas pragma-main}@anchor{9a}
5227 @section Pragma Main
5234 (MAIN_OPTION [, MAIN_OPTION]);
5237 [Stack_Size =>] static_integer_EXPRESSION
5238 | [Task_Stack_Size_Default =>] static_integer_EXPRESSION
5239 | [Time_Slicing_Enabled =>] static_boolean_EXPRESSION
5242 This pragma is provided for compatibility with OpenVMS VAX Systems. It has
5243 no effect in GNAT, other than being syntax checked.
5245 @node Pragma Main_Storage,Pragma Max_Queue_Length,Pragma Main,Implementation Defined Pragmas
5246 @anchor{gnat_rm/implementation_defined_pragmas pragma-main-storage}@anchor{9b}
5247 @section Pragma Main_Storage
5254 (MAIN_STORAGE_OPTION [, MAIN_STORAGE_OPTION]);
5256 MAIN_STORAGE_OPTION ::=
5257 [WORKING_STORAGE =>] static_SIMPLE_EXPRESSION
5258 | [TOP_GUARD =>] static_SIMPLE_EXPRESSION
5261 This pragma is provided for compatibility with OpenVMS VAX Systems. It has
5262 no effect in GNAT, other than being syntax checked.
5264 @node Pragma Max_Queue_Length,Pragma No_Body,Pragma Main_Storage,Implementation Defined Pragmas
5265 @anchor{gnat_rm/implementation_defined_pragmas id22}@anchor{9c}@anchor{gnat_rm/implementation_defined_pragmas pragma-max-queue-length}@anchor{9d}
5266 @section Pragma Max_Queue_Length
5272 pragma Max_Entry_Queue (static_integer_EXPRESSION);
5275 This pragma is used to specify the maximum callers per entry queue for
5276 individual protected entries and entry families. It accepts a single
5277 integer (-1 or more) as a parameter and must appear after the declaration of an
5280 A value of -1 represents no additional restriction on queue length.
5282 @node Pragma No_Body,Pragma No_Caching,Pragma Max_Queue_Length,Implementation Defined Pragmas
5283 @anchor{gnat_rm/implementation_defined_pragmas pragma-no-body}@anchor{9e}
5284 @section Pragma No_Body
5293 There are a number of cases in which a package spec does not require a body,
5294 and in fact a body is not permitted. GNAT will not permit the spec to be
5295 compiled if there is a body around. The pragma No_Body allows you to provide
5296 a body file, even in a case where no body is allowed. The body file must
5297 contain only comments and a single No_Body pragma. This is recognized by
5298 the compiler as indicating that no body is logically present.
5300 This is particularly useful during maintenance when a package is modified in
5301 such a way that a body needed before is no longer needed. The provision of a
5302 dummy body with a No_Body pragma ensures that there is no interference from
5303 earlier versions of the package body.
5305 @node Pragma No_Caching,Pragma No_Component_Reordering,Pragma No_Body,Implementation Defined Pragmas
5306 @anchor{gnat_rm/implementation_defined_pragmas pragma-no-caching}@anchor{9f}@anchor{gnat_rm/implementation_defined_pragmas id23}@anchor{a0}
5307 @section Pragma No_Caching
5313 pragma No_Caching [ (boolean_EXPRESSION) ];
5316 For the semantics of this pragma, see the entry for aspect @code{No_Caching} in
5317 the SPARK 2014 Reference Manual, section 7.1.2.
5319 @node Pragma No_Component_Reordering,Pragma No_Elaboration_Code_All,Pragma No_Caching,Implementation Defined Pragmas
5320 @anchor{gnat_rm/implementation_defined_pragmas pragma-no-component-reordering}@anchor{a1}
5321 @section Pragma No_Component_Reordering
5327 pragma No_Component_Reordering [([Entity =>] type_LOCAL_NAME)];
5330 @code{type_LOCAL_NAME} must refer to a record type declaration in the current
5331 declarative part. The effect is to preclude any reordering of components
5332 for the layout of the record, i.e. the record is laid out by the compiler
5333 in the order in which the components are declared textually. The form with
5334 no argument is a configuration pragma which applies to all record types
5335 declared in units to which the pragma applies and there is a requirement
5336 that this pragma be used consistently within a partition.
5338 @node Pragma No_Elaboration_Code_All,Pragma No_Heap_Finalization,Pragma No_Component_Reordering,Implementation Defined Pragmas
5339 @anchor{gnat_rm/implementation_defined_pragmas id24}@anchor{a2}@anchor{gnat_rm/implementation_defined_pragmas pragma-no-elaboration-code-all}@anchor{a3}
5340 @section Pragma No_Elaboration_Code_All
5346 pragma No_Elaboration_Code_All [(program_unit_NAME)];
5349 This is a program unit pragma (there is also an equivalent aspect of the
5350 same name) that establishes the restriction @code{No_Elaboration_Code} for
5351 the current unit and any extended main source units (body and subunits).
5352 It also has the effect of enforcing a transitive application of this
5353 aspect, so that if any unit is implicitly or explicitly with'ed by the
5354 current unit, it must also have the No_Elaboration_Code_All aspect set.
5355 It may be applied to package or subprogram specs or their generic versions.
5357 @node Pragma No_Heap_Finalization,Pragma No_Inline,Pragma No_Elaboration_Code_All,Implementation Defined Pragmas
5358 @anchor{gnat_rm/implementation_defined_pragmas pragma-no-heap-finalization}@anchor{a4}
5359 @section Pragma No_Heap_Finalization
5365 pragma No_Heap_Finalization [ (first_subtype_LOCAL_NAME) ];
5368 Pragma @code{No_Heap_Finalization} may be used as a configuration pragma or as a
5369 type-specific pragma.
5371 In its configuration form, the pragma must appear within a configuration file
5372 such as gnat.adc, without an argument. The pragma suppresses the call to
5373 @code{Finalize} for heap-allocated objects created through library-level named
5374 access-to-object types in cases where the designated type requires finalization
5377 In its type-specific form, the argument of the pragma must denote a
5378 library-level named access-to-object type. The pragma suppresses the call to
5379 @code{Finalize} for heap-allocated objects created through the specific access type
5380 in cases where the designated type requires finalization actions.
5382 It is still possible to finalize such heap-allocated objects by explicitly
5385 A library-level named access-to-object type declared within a generic unit will
5386 lose its @code{No_Heap_Finalization} pragma when the corresponding instance does not
5387 appear at the library level.
5389 @node Pragma No_Inline,Pragma No_Return,Pragma No_Heap_Finalization,Implementation Defined Pragmas
5390 @anchor{gnat_rm/implementation_defined_pragmas id25}@anchor{a5}@anchor{gnat_rm/implementation_defined_pragmas pragma-no-inline}@anchor{a6}
5391 @section Pragma No_Inline
5397 pragma No_Inline (NAME @{, NAME@});
5400 This pragma suppresses inlining for the callable entity or the instances of
5401 the generic subprogram designated by @code{NAME}, including inlining that
5402 results from the use of pragma @code{Inline}. This pragma is always active,
5403 in particular it is not subject to the use of option @emph{-gnatn} or
5404 @emph{-gnatN}. It is illegal to specify both pragma @code{No_Inline} and
5405 pragma @code{Inline_Always} for the same @code{NAME}.
5407 @node Pragma No_Return,Pragma No_Strict_Aliasing,Pragma No_Inline,Implementation Defined Pragmas
5408 @anchor{gnat_rm/implementation_defined_pragmas pragma-no-return}@anchor{a7}
5409 @section Pragma No_Return
5415 pragma No_Return (procedure_LOCAL_NAME @{, procedure_LOCAL_NAME@});
5418 Each @code{procedure_LOCAL_NAME} argument must refer to one or more procedure
5419 declarations in the current declarative part. A procedure to which this
5420 pragma is applied may not contain any explicit @code{return} statements.
5421 In addition, if the procedure contains any implicit returns from falling
5422 off the end of a statement sequence, then execution of that implicit
5423 return will cause Program_Error to be raised.
5425 One use of this pragma is to identify procedures whose only purpose is to raise
5426 an exception. Another use of this pragma is to suppress incorrect warnings
5427 about missing returns in functions, where the last statement of a function
5428 statement sequence is a call to such a procedure.
5430 Note that in Ada 2005 mode, this pragma is part of the language. It is
5431 available in all earlier versions of Ada as an implementation-defined
5434 @node Pragma No_Strict_Aliasing,Pragma No_Tagged_Streams,Pragma No_Return,Implementation Defined Pragmas
5435 @anchor{gnat_rm/implementation_defined_pragmas pragma-no-strict-aliasing}@anchor{a8}
5436 @section Pragma No_Strict_Aliasing
5442 pragma No_Strict_Aliasing [([Entity =>] type_LOCAL_NAME)];
5445 @code{type_LOCAL_NAME} must refer to an access type
5446 declaration in the current declarative part. The effect is to inhibit
5447 strict aliasing optimization for the given type. The form with no
5448 arguments is a configuration pragma which applies to all access types
5449 declared in units to which the pragma applies. For a detailed
5450 description of the strict aliasing optimization, and the situations
5451 in which it must be suppressed, see the section on Optimization and Strict Aliasing
5452 in the @cite{GNAT User's Guide}.
5454 This pragma currently has no effects on access to unconstrained array types.
5456 @node Pragma No_Tagged_Streams,Pragma Normalize_Scalars,Pragma No_Strict_Aliasing,Implementation Defined Pragmas
5457 @anchor{gnat_rm/implementation_defined_pragmas pragma-no-tagged-streams}@anchor{a9}@anchor{gnat_rm/implementation_defined_pragmas id26}@anchor{aa}
5458 @section Pragma No_Tagged_Streams
5464 pragma No_Tagged_Streams [([Entity =>] tagged_type_LOCAL_NAME)];
5467 Normally when a tagged type is introduced using a full type declaration,
5468 part of the processing includes generating stream access routines to be
5469 used by stream attributes referencing the type (or one of its subtypes
5470 or derived types). This can involve the generation of significant amounts
5471 of code which is wasted space if stream routines are not needed for the
5474 The @code{No_Tagged_Streams} pragma causes the generation of these stream
5475 routines to be skipped, and any attempt to use stream operations on
5476 types subject to this pragma will be statically rejected as illegal.
5478 There are two forms of the pragma. The form with no arguments must appear
5479 in a declarative sequence or in the declarations of a package spec. This
5480 pragma affects all subsequent root tagged types declared in the declaration
5481 sequence, and specifies that no stream routines be generated. The form with
5482 an argument (for which there is also a corresponding aspect) specifies a
5483 single root tagged type for which stream routines are not to be generated.
5485 Once the pragma has been given for a particular root tagged type, all subtypes
5486 and derived types of this type inherit the pragma automatically, so the effect
5487 applies to a complete hierarchy (this is necessary to deal with the class-wide
5488 dispatching versions of the stream routines).
5490 When pragmas @code{Discard_Names} and @code{No_Tagged_Streams} are simultaneously
5491 applied to a tagged type its Expanded_Name and External_Tag are initialized
5492 with empty strings. This is useful to avoid exposing entity names at binary
5493 level but has a negative impact on the debuggability of tagged types.
5495 @node Pragma Normalize_Scalars,Pragma Obsolescent,Pragma No_Tagged_Streams,Implementation Defined Pragmas
5496 @anchor{gnat_rm/implementation_defined_pragmas pragma-normalize-scalars}@anchor{ab}
5497 @section Pragma Normalize_Scalars
5503 pragma Normalize_Scalars;
5506 This is a language defined pragma which is fully implemented in GNAT. The
5507 effect is to cause all scalar objects that are not otherwise initialized
5508 to be initialized. The initial values are implementation dependent and
5514 @item @emph{Standard.Character}
5516 Objects whose root type is Standard.Character are initialized to
5517 Character'Last unless the subtype range excludes NUL (in which case
5518 NUL is used). This choice will always generate an invalid value if
5521 @item @emph{Standard.Wide_Character}
5523 Objects whose root type is Standard.Wide_Character are initialized to
5524 Wide_Character'Last unless the subtype range excludes NUL (in which case
5525 NUL is used). This choice will always generate an invalid value if
5528 @item @emph{Standard.Wide_Wide_Character}
5530 Objects whose root type is Standard.Wide_Wide_Character are initialized to
5531 the invalid value 16#FFFF_FFFF# unless the subtype range excludes NUL (in
5532 which case NUL is used). This choice will always generate an invalid value if
5535 @item @emph{Integer types}
5537 Objects of an integer type are treated differently depending on whether
5538 negative values are present in the subtype. If no negative values are
5539 present, then all one bits is used as the initial value except in the
5540 special case where zero is excluded from the subtype, in which case
5541 all zero bits are used. This choice will always generate an invalid
5542 value if one exists.
5544 For subtypes with negative values present, the largest negative number
5545 is used, except in the unusual case where this largest negative number
5546 is in the subtype, and the largest positive number is not, in which case
5547 the largest positive value is used. This choice will always generate
5548 an invalid value if one exists.
5550 @item @emph{Floating-Point Types}
5552 Objects of all floating-point types are initialized to all 1-bits. For
5553 standard IEEE format, this corresponds to a NaN (not a number) which is
5554 indeed an invalid value.
5556 @item @emph{Fixed-Point Types}
5558 Objects of all fixed-point types are treated as described above for integers,
5559 with the rules applying to the underlying integer value used to represent
5560 the fixed-point value.
5562 @item @emph{Modular types}
5564 Objects of a modular type are initialized to all one bits, except in
5565 the special case where zero is excluded from the subtype, in which
5566 case all zero bits are used. This choice will always generate an
5567 invalid value if one exists.
5569 @item @emph{Enumeration types}
5571 Objects of an enumeration type are initialized to all one-bits, i.e., to
5572 the value @code{2 ** typ'Size - 1} unless the subtype excludes the literal
5573 whose Pos value is zero, in which case a code of zero is used. This choice
5574 will always generate an invalid value if one exists.
5577 @node Pragma Obsolescent,Pragma Optimize_Alignment,Pragma Normalize_Scalars,Implementation Defined Pragmas
5578 @anchor{gnat_rm/implementation_defined_pragmas pragma-obsolescent}@anchor{ac}@anchor{gnat_rm/implementation_defined_pragmas id27}@anchor{ad}
5579 @section Pragma Obsolescent
5587 pragma Obsolescent (
5588 [Message =>] static_string_EXPRESSION
5589 [,[Version =>] Ada_05]]);
5591 pragma Obsolescent (
5593 [,[Message =>] static_string_EXPRESSION
5594 [,[Version =>] Ada_05]] );
5597 This pragma can occur immediately following a declaration of an entity,
5598 including the case of a record component. If no Entity argument is present,
5599 then this declaration is the one to which the pragma applies. If an Entity
5600 parameter is present, it must either match the name of the entity in this
5601 declaration, or alternatively, the pragma can immediately follow an enumeration
5602 type declaration, where the Entity argument names one of the enumeration
5605 This pragma is used to indicate that the named entity
5606 is considered obsolescent and should not be used. Typically this is
5607 used when an API must be modified by eventually removing or modifying
5608 existing subprograms or other entities. The pragma can be used at an
5609 intermediate stage when the entity is still present, but will be
5612 The effect of this pragma is to output a warning message on a reference to
5613 an entity thus marked that the subprogram is obsolescent if the appropriate
5614 warning option in the compiler is activated. If the @code{Message} parameter is
5615 present, then a second warning message is given containing this text. In
5616 addition, a reference to the entity is considered to be a violation of pragma
5617 @code{Restrictions (No_Obsolescent_Features)}.
5619 This pragma can also be used as a program unit pragma for a package,
5620 in which case the entity name is the name of the package, and the
5621 pragma indicates that the entire package is considered
5622 obsolescent. In this case a client @code{with}ing such a package
5623 violates the restriction, and the @code{with} clause is
5624 flagged with warnings if the warning option is set.
5626 If the @code{Version} parameter is present (which must be exactly
5627 the identifier @code{Ada_05}, no other argument is allowed), then the
5628 indication of obsolescence applies only when compiling in Ada 2005
5629 mode. This is primarily intended for dealing with the situations
5630 in the predefined library where subprograms or packages
5631 have become defined as obsolescent in Ada 2005
5632 (e.g., in @code{Ada.Characters.Handling}), but may be used anywhere.
5634 The following examples show typical uses of this pragma:
5638 pragma Obsolescent (p, Message => "use pp instead of p");
5643 pragma Obsolescent ("use q2new instead");
5645 type R is new integer;
5648 Message => "use RR in Ada 2005",
5658 type E is (a, bc, 'd', quack);
5659 pragma Obsolescent (Entity => bc)
5660 pragma Obsolescent (Entity => 'd')
5663 (a, b : character) return character;
5664 pragma Obsolescent (Entity => "+");
5668 Note that, as for all pragmas, if you use a pragma argument identifier,
5669 then all subsequent parameters must also use a pragma argument identifier.
5670 So if you specify @code{Entity =>} for the @code{Entity} argument, and a @code{Message}
5671 argument is present, it must be preceded by @code{Message =>}.
5673 @node Pragma Optimize_Alignment,Pragma Ordered,Pragma Obsolescent,Implementation Defined Pragmas
5674 @anchor{gnat_rm/implementation_defined_pragmas pragma-optimize-alignment}@anchor{ae}
5675 @section Pragma Optimize_Alignment
5679 @geindex default settings
5684 pragma Optimize_Alignment (TIME | SPACE | OFF);
5687 This is a configuration pragma which affects the choice of default alignments
5688 for types and objects where no alignment is explicitly specified. There is a
5689 time/space trade-off in the selection of these values. Large alignments result
5690 in more efficient code, at the expense of larger data space, since sizes have
5691 to be increased to match these alignments. Smaller alignments save space, but
5692 the access code is slower. The normal choice of default alignments for types
5693 and individual alignment promotions for objects (which is what you get if you
5694 do not use this pragma, or if you use an argument of OFF), tries to balance
5695 these two requirements.
5697 Specifying SPACE causes smaller default alignments to be chosen in two cases.
5698 First any packed record is given an alignment of 1. Second, if a size is given
5699 for the type, then the alignment is chosen to avoid increasing this size. For
5711 In the default mode, this type gets an alignment of 4, so that access to the
5712 Integer field X are efficient. But this means that objects of the type end up
5713 with a size of 8 bytes. This is a valid choice, since sizes of objects are
5714 allowed to be bigger than the size of the type, but it can waste space if for
5715 example fields of type R appear in an enclosing record. If the above type is
5716 compiled in @code{Optimize_Alignment (Space)} mode, the alignment is set to 1.
5718 However, there is one case in which SPACE is ignored. If a variable length
5719 record (that is a discriminated record with a component which is an array
5720 whose length depends on a discriminant), has a pragma Pack, then it is not
5721 in general possible to set the alignment of such a record to one, so the
5722 pragma is ignored in this case (with a warning).
5724 Specifying SPACE also disables alignment promotions for standalone objects,
5725 which occur when the compiler increases the alignment of a specific object
5726 without changing the alignment of its type.
5728 Specifying SPACE also disables component reordering in unpacked record types,
5729 which can result in larger sizes in order to meet alignment requirements.
5731 Specifying TIME causes larger default alignments to be chosen in the case of
5732 small types with sizes that are not a power of 2. For example, consider:
5745 The default alignment for this record is normally 1, but if this type is
5746 compiled in @code{Optimize_Alignment (Time)} mode, then the alignment is set
5747 to 4, which wastes space for objects of the type, since they are now 4 bytes
5748 long, but results in more efficient access when the whole record is referenced.
5750 As noted above, this is a configuration pragma, and there is a requirement
5751 that all units in a partition be compiled with a consistent setting of the
5752 optimization setting. This would normally be achieved by use of a configuration
5753 pragma file containing the appropriate setting. The exception to this rule is
5754 that units with an explicit configuration pragma in the same file as the source
5755 unit are excluded from the consistency check, as are all predefined units. The
5756 latter are compiled by default in pragma Optimize_Alignment (Off) mode if no
5757 pragma appears at the start of the file.
5759 @node Pragma Ordered,Pragma Overflow_Mode,Pragma Optimize_Alignment,Implementation Defined Pragmas
5760 @anchor{gnat_rm/implementation_defined_pragmas pragma-ordered}@anchor{af}
5761 @section Pragma Ordered
5767 pragma Ordered (enumeration_first_subtype_LOCAL_NAME);
5770 Most enumeration types are from a conceptual point of view unordered.
5771 For example, consider:
5774 type Color is (Red, Blue, Green, Yellow);
5777 By Ada semantics @code{Blue > Red} and @code{Green > Blue},
5778 but really these relations make no sense; the enumeration type merely
5779 specifies a set of possible colors, and the order is unimportant.
5781 For unordered enumeration types, it is generally a good idea if
5782 clients avoid comparisons (other than equality or inequality) and
5783 explicit ranges. (A @emph{client} is a unit where the type is referenced,
5784 other than the unit where the type is declared, its body, and its subunits.)
5785 For example, if code buried in some client says:
5788 if Current_Color < Yellow then ...
5789 if Current_Color in Blue .. Green then ...
5792 then the client code is relying on the order, which is undesirable.
5793 It makes the code hard to read and creates maintenance difficulties if
5794 entries have to be added to the enumeration type. Instead,
5795 the code in the client should list the possibilities, or an
5796 appropriate subtype should be declared in the unit that declares
5797 the original enumeration type. E.g., the following subtype could
5798 be declared along with the type @code{Color}:
5801 subtype RBG is Color range Red .. Green;
5804 and then the client could write:
5807 if Current_Color in RBG then ...
5808 if Current_Color = Blue or Current_Color = Green then ...
5811 However, some enumeration types are legitimately ordered from a conceptual
5812 point of view. For example, if you declare:
5815 type Day is (Mon, Tue, Wed, Thu, Fri, Sat, Sun);
5818 then the ordering imposed by the language is reasonable, and
5819 clients can depend on it, writing for example:
5822 if D in Mon .. Fri then ...
5826 The pragma @emph{Ordered} is provided to mark enumeration types that
5827 are conceptually ordered, alerting the reader that clients may depend
5828 on the ordering. GNAT provides a pragma to mark enumerations as ordered
5829 rather than one to mark them as unordered, since in our experience,
5830 the great majority of enumeration types are conceptually unordered.
5832 The types @code{Boolean}, @code{Character}, @code{Wide_Character},
5833 and @code{Wide_Wide_Character}
5834 are considered to be ordered types, so each is declared with a
5835 pragma @code{Ordered} in package @code{Standard}.
5837 Normally pragma @code{Ordered} serves only as documentation and a guide for
5838 coding standards, but GNAT provides a warning switch @emph{-gnatw.u} that
5839 requests warnings for inappropriate uses (comparisons and explicit
5840 subranges) for unordered types. If this switch is used, then any
5841 enumeration type not marked with pragma @code{Ordered} will be considered
5842 as unordered, and will generate warnings for inappropriate uses.
5844 Note that generic types are not considered ordered or unordered (since the
5845 template can be instantiated for both cases), so we never generate warnings
5846 for the case of generic enumerated types.
5848 For additional information please refer to the description of the
5849 @emph{-gnatw.u} switch in the GNAT User's Guide.
5851 @node Pragma Overflow_Mode,Pragma Overriding_Renamings,Pragma Ordered,Implementation Defined Pragmas
5852 @anchor{gnat_rm/implementation_defined_pragmas pragma-overflow-mode}@anchor{b0}
5853 @section Pragma Overflow_Mode
5859 pragma Overflow_Mode
5861 [,[Assertions =>] MODE]);
5863 MODE ::= STRICT | MINIMIZED | ELIMINATED
5866 This pragma sets the current overflow mode to the given setting. For details
5867 of the meaning of these modes, please refer to the
5868 'Overflow Check Handling in GNAT' appendix in the
5869 GNAT User's Guide. If only the @code{General} parameter is present,
5870 the given mode applies to all expressions. If both parameters are present,
5871 the @code{General} mode applies to expressions outside assertions, and
5872 the @code{Eliminated} mode applies to expressions within assertions.
5874 The case of the @code{MODE} parameter is ignored,
5875 so @code{MINIMIZED}, @code{Minimized} and
5876 @code{minimized} all have the same effect.
5878 The @code{Overflow_Mode} pragma has the same scoping and placement
5879 rules as pragma @code{Suppress}, so it can occur either as a
5880 configuration pragma, specifying a default for the whole
5881 program, or in a declarative scope, where it applies to the
5882 remaining declarations and statements in that scope.
5884 The pragma @code{Suppress (Overflow_Check)} suppresses
5885 overflow checking, but does not affect the overflow mode.
5887 The pragma @code{Unsuppress (Overflow_Check)} unsuppresses (enables)
5888 overflow checking, but does not affect the overflow mode.
5890 @node Pragma Overriding_Renamings,Pragma Partition_Elaboration_Policy,Pragma Overflow_Mode,Implementation Defined Pragmas
5891 @anchor{gnat_rm/implementation_defined_pragmas pragma-overriding-renamings}@anchor{b1}
5892 @section Pragma Overriding_Renamings
5895 @geindex Rational profile
5897 @geindex Rational compatibility
5902 pragma Overriding_Renamings;
5905 This is a GNAT configuration pragma to simplify porting
5906 legacy code accepted by the Rational
5907 Ada compiler. In the presence of this pragma, a renaming declaration that
5908 renames an inherited operation declared in the same scope is legal if selected
5909 notation is used as in:
5912 pragma Overriding_Renamings;
5917 function F (..) renames R.F;
5922 RM 8.3 (15) stipulates that an overridden operation is not visible within the
5923 declaration of the overriding operation.
5925 @node Pragma Partition_Elaboration_Policy,Pragma Part_Of,Pragma Overriding_Renamings,Implementation Defined Pragmas
5926 @anchor{gnat_rm/implementation_defined_pragmas pragma-partition-elaboration-policy}@anchor{b2}
5927 @section Pragma Partition_Elaboration_Policy
5933 pragma Partition_Elaboration_Policy (POLICY_IDENTIFIER);
5935 POLICY_IDENTIFIER ::= Concurrent | Sequential
5938 This pragma is standard in Ada 2005, but is available in all earlier
5939 versions of Ada as an implementation-defined pragma.
5940 See Ada 2012 Reference Manual for details.
5942 @node Pragma Part_Of,Pragma Passive,Pragma Partition_Elaboration_Policy,Implementation Defined Pragmas
5943 @anchor{gnat_rm/implementation_defined_pragmas id28}@anchor{b3}@anchor{gnat_rm/implementation_defined_pragmas pragma-part-of}@anchor{b4}
5944 @section Pragma Part_Of
5950 pragma Part_Of (ABSTRACT_STATE);
5952 ABSTRACT_STATE ::= NAME
5955 For the semantics of this pragma, see the entry for aspect @code{Part_Of} in the
5956 SPARK 2014 Reference Manual, section 7.2.6.
5958 @node Pragma Passive,Pragma Persistent_BSS,Pragma Part_Of,Implementation Defined Pragmas
5959 @anchor{gnat_rm/implementation_defined_pragmas pragma-passive}@anchor{b5}
5960 @section Pragma Passive
5966 pragma Passive [(Semaphore | No)];
5969 Syntax checked, but otherwise ignored by GNAT. This is recognized for
5970 compatibility with DEC Ada 83 implementations, where it is used within a
5971 task definition to request that a task be made passive. If the argument
5972 @code{Semaphore} is present, or the argument is omitted, then DEC Ada 83
5973 treats the pragma as an assertion that the containing task is passive
5974 and that optimization of context switch with this task is permitted and
5975 desired. If the argument @code{No} is present, the task must not be
5976 optimized. GNAT does not attempt to optimize any tasks in this manner
5977 (since protected objects are available in place of passive tasks).
5979 For more information on the subject of passive tasks, see the section
5980 'Passive Task Optimization' in the GNAT Users Guide.
5982 @node Pragma Persistent_BSS,Pragma Post,Pragma Passive,Implementation Defined Pragmas
5983 @anchor{gnat_rm/implementation_defined_pragmas id29}@anchor{b6}@anchor{gnat_rm/implementation_defined_pragmas pragma-persistent-bss}@anchor{b7}
5984 @section Pragma Persistent_BSS
5990 pragma Persistent_BSS [(LOCAL_NAME)]
5993 This pragma allows selected objects to be placed in the @code{.persistent_bss}
5994 section. On some targets the linker and loader provide for special
5995 treatment of this section, allowing a program to be reloaded without
5996 affecting the contents of this data (hence the name persistent).
5998 There are two forms of usage. If an argument is given, it must be the
5999 local name of a library-level object, with no explicit initialization
6000 and whose type is potentially persistent. If no argument is given, then
6001 the pragma is a configuration pragma, and applies to all library-level
6002 objects with no explicit initialization of potentially persistent types.
6004 A potentially persistent type is a scalar type, or an untagged,
6005 non-discriminated record, all of whose components have no explicit
6006 initialization and are themselves of a potentially persistent type,
6007 or an array, all of whose constraints are static, and whose component
6008 type is potentially persistent.
6010 If this pragma is used on a target where this feature is not supported,
6011 then the pragma will be ignored. See also @code{pragma Linker_Section}.
6013 @node Pragma Post,Pragma Postcondition,Pragma Persistent_BSS,Implementation Defined Pragmas
6014 @anchor{gnat_rm/implementation_defined_pragmas pragma-post}@anchor{b8}
6015 @section Pragma Post
6021 @geindex postconditions
6026 pragma Post (Boolean_Expression);
6029 The @code{Post} pragma is intended to be an exact replacement for
6030 the language-defined
6031 @code{Post} aspect, and shares its restrictions and semantics.
6032 It must appear either immediately following the corresponding
6033 subprogram declaration (only other pragmas may intervene), or
6034 if there is no separate subprogram declaration, then it can
6035 appear at the start of the declarations in a subprogram body
6036 (preceded only by other pragmas).
6038 @node Pragma Postcondition,Pragma Post_Class,Pragma Post,Implementation Defined Pragmas
6039 @anchor{gnat_rm/implementation_defined_pragmas pragma-postcondition}@anchor{b9}
6040 @section Pragma Postcondition
6043 @geindex Postcondition
6046 @geindex postconditions
6051 pragma Postcondition (
6052 [Check =>] Boolean_Expression
6053 [,[Message =>] String_Expression]);
6056 The @code{Postcondition} pragma allows specification of automatic
6057 postcondition checks for subprograms. These checks are similar to
6058 assertions, but are automatically inserted just prior to the return
6059 statements of the subprogram with which they are associated (including
6060 implicit returns at the end of procedure bodies and associated
6061 exception handlers).
6063 In addition, the boolean expression which is the condition which
6064 must be true may contain references to function'Result in the case
6065 of a function to refer to the returned value.
6067 @code{Postcondition} pragmas may appear either immediately following the
6068 (separate) declaration of a subprogram, or at the start of the
6069 declarations of a subprogram body. Only other pragmas may intervene
6070 (that is appear between the subprogram declaration and its
6071 postconditions, or appear before the postcondition in the
6072 declaration sequence in a subprogram body). In the case of a
6073 postcondition appearing after a subprogram declaration, the
6074 formal arguments of the subprogram are visible, and can be
6075 referenced in the postcondition expressions.
6077 The postconditions are collected and automatically tested just
6078 before any return (implicit or explicit) in the subprogram body.
6079 A postcondition is only recognized if postconditions are active
6080 at the time the pragma is encountered. The compiler switch @emph{gnata}
6081 turns on all postconditions by default, and pragma @code{Check_Policy}
6082 with an identifier of @code{Postcondition} can also be used to
6083 control whether postconditions are active.
6085 The general approach is that postconditions are placed in the spec
6086 if they represent functional aspects which make sense to the client.
6087 For example we might have:
6090 function Direction return Integer;
6091 pragma Postcondition
6092 (Direction'Result = +1
6094 Direction'Result = -1);
6097 which serves to document that the result must be +1 or -1, and
6098 will test that this is the case at run time if postcondition
6101 Postconditions within the subprogram body can be used to
6102 check that some internal aspect of the implementation,
6103 not visible to the client, is operating as expected.
6104 For instance if a square root routine keeps an internal
6105 counter of the number of times it is called, then we
6106 might have the following postcondition:
6109 Sqrt_Calls : Natural := 0;
6111 function Sqrt (Arg : Float) return Float is
6112 pragma Postcondition
6113 (Sqrt_Calls = Sqrt_Calls'Old + 1);
6118 As this example, shows, the use of the @code{Old} attribute
6119 is often useful in postconditions to refer to the state on
6120 entry to the subprogram.
6122 Note that postconditions are only checked on normal returns
6123 from the subprogram. If an abnormal return results from
6124 raising an exception, then the postconditions are not checked.
6126 If a postcondition fails, then the exception
6127 @code{System.Assertions.Assert_Failure} is raised. If
6128 a message argument was supplied, then the given string
6129 will be used as the exception message. If no message
6130 argument was supplied, then the default message has
6131 the form "Postcondition failed at file_name:line". The
6132 exception is raised in the context of the subprogram
6133 body, so it is possible to catch postcondition failures
6134 within the subprogram body itself.
6136 Within a package spec, normal visibility rules
6137 in Ada would prevent forward references within a
6138 postcondition pragma to functions defined later in
6139 the same package. This would introduce undesirable
6140 ordering constraints. To avoid this problem, all
6141 postcondition pragmas are analyzed at the end of
6142 the package spec, allowing forward references.
6144 The following example shows that this even allows
6145 mutually recursive postconditions as in:
6148 package Parity_Functions is
6149 function Odd (X : Natural) return Boolean;
6150 pragma Postcondition
6154 (x /= 0 and then Even (X - 1))));
6156 function Even (X : Natural) return Boolean;
6157 pragma Postcondition
6161 (x /= 1 and then Odd (X - 1))));
6163 end Parity_Functions;
6166 There are no restrictions on the complexity or form of
6167 conditions used within @code{Postcondition} pragmas.
6168 The following example shows that it is even possible
6169 to verify performance behavior.
6174 Performance : constant Float;
6175 -- Performance constant set by implementation
6176 -- to match target architecture behavior.
6178 procedure Treesort (Arg : String);
6179 -- Sorts characters of argument using N*logN sort
6180 pragma Postcondition
6181 (Float (Clock - Clock'Old) <=
6182 Float (Arg'Length) *
6183 log (Float (Arg'Length)) *
6188 Note: postcondition pragmas associated with subprograms that are
6189 marked as Inline_Always, or those marked as Inline with front-end
6190 inlining (-gnatN option set) are accepted and legality-checked
6191 by the compiler, but are ignored at run-time even if postcondition
6192 checking is enabled.
6194 Note that pragma @code{Postcondition} differs from the language-defined
6195 @code{Post} aspect (and corresponding @code{Post} pragma) in allowing
6196 multiple occurrences, allowing occurences in the body even if there
6197 is a separate spec, and allowing a second string parameter, and the
6198 use of the pragma identifier @code{Check}. Historically, pragma
6199 @code{Postcondition} was implemented prior to the development of
6200 Ada 2012, and has been retained in its original form for
6201 compatibility purposes.
6203 @node Pragma Post_Class,Pragma Rename_Pragma,Pragma Postcondition,Implementation Defined Pragmas
6204 @anchor{gnat_rm/implementation_defined_pragmas pragma-post-class}@anchor{ba}
6205 @section Pragma Post_Class
6211 @geindex postconditions
6216 pragma Post_Class (Boolean_Expression);
6219 The @code{Post_Class} pragma is intended to be an exact replacement for
6220 the language-defined
6221 @code{Post'Class} aspect, and shares its restrictions and semantics.
6222 It must appear either immediately following the corresponding
6223 subprogram declaration (only other pragmas may intervene), or
6224 if there is no separate subprogram declaration, then it can
6225 appear at the start of the declarations in a subprogram body
6226 (preceded only by other pragmas).
6228 Note: This pragma is called @code{Post_Class} rather than
6229 @code{Post'Class} because the latter would not be strictly
6230 conforming to the allowed syntax for pragmas. The motivation
6231 for provinding pragmas equivalent to the aspects is to allow a program
6232 to be written using the pragmas, and then compiled if necessary
6233 using an Ada compiler that does not recognize the pragmas or
6234 aspects, but is prepared to ignore the pragmas. The assertion
6235 policy that controls this pragma is @code{Post'Class}, not
6238 @node Pragma Rename_Pragma,Pragma Pre,Pragma Post_Class,Implementation Defined Pragmas
6239 @anchor{gnat_rm/implementation_defined_pragmas pragma-rename-pragma}@anchor{bb}
6240 @section Pragma Rename_Pragma
6249 pragma Rename_Pragma (
6250 [New_Name =>] IDENTIFIER,
6251 [Renamed =>] pragma_IDENTIFIER);
6254 This pragma provides a mechanism for supplying new names for existing
6255 pragmas. The @code{New_Name} identifier can subsequently be used as a synonym for
6256 the Renamed pragma. For example, suppose you have code that was originally
6257 developed on a compiler that supports Inline_Only as an implementation defined
6258 pragma. And suppose the semantics of pragma Inline_Only are identical to (or at
6259 least very similar to) the GNAT implementation defined pragma
6260 Inline_Always. You could globally replace Inline_Only with Inline_Always.
6262 However, to avoid that source modification, you could instead add a
6263 configuration pragma:
6266 pragma Rename_Pragma (
6267 New_Name => Inline_Only,
6268 Renamed => Inline_Always);
6271 Then GNAT will treat "pragma Inline_Only ..." as if you had written
6272 "pragma Inline_Always ...".
6274 Pragma Inline_Only will not necessarily mean the same thing as the other Ada
6275 compiler; it's up to you to make sure the semantics are close enough.
6277 @node Pragma Pre,Pragma Precondition,Pragma Rename_Pragma,Implementation Defined Pragmas
6278 @anchor{gnat_rm/implementation_defined_pragmas pragma-pre}@anchor{bc}
6285 @geindex preconditions
6290 pragma Pre (Boolean_Expression);
6293 The @code{Pre} pragma is intended to be an exact replacement for
6294 the language-defined
6295 @code{Pre} aspect, and shares its restrictions and semantics.
6296 It must appear either immediately following the corresponding
6297 subprogram declaration (only other pragmas may intervene), or
6298 if there is no separate subprogram declaration, then it can
6299 appear at the start of the declarations in a subprogram body
6300 (preceded only by other pragmas).
6302 @node Pragma Precondition,Pragma Predicate,Pragma Pre,Implementation Defined Pragmas
6303 @anchor{gnat_rm/implementation_defined_pragmas pragma-precondition}@anchor{bd}
6304 @section Pragma Precondition
6307 @geindex Preconditions
6310 @geindex preconditions
6315 pragma Precondition (
6316 [Check =>] Boolean_Expression
6317 [,[Message =>] String_Expression]);
6320 The @code{Precondition} pragma is similar to @code{Postcondition}
6321 except that the corresponding checks take place immediately upon
6322 entry to the subprogram, and if a precondition fails, the exception
6323 is raised in the context of the caller, and the attribute 'Result
6324 cannot be used within the precondition expression.
6326 Otherwise, the placement and visibility rules are identical to those
6327 described for postconditions. The following is an example of use
6328 within a package spec:
6331 package Math_Functions is
6333 function Sqrt (Arg : Float) return Float;
6334 pragma Precondition (Arg >= 0.0)
6339 @code{Precondition} pragmas may appear either immediately following the
6340 (separate) declaration of a subprogram, or at the start of the
6341 declarations of a subprogram body. Only other pragmas may intervene
6342 (that is appear between the subprogram declaration and its
6343 postconditions, or appear before the postcondition in the
6344 declaration sequence in a subprogram body).
6346 Note: precondition pragmas associated with subprograms that are
6347 marked as Inline_Always, or those marked as Inline with front-end
6348 inlining (-gnatN option set) are accepted and legality-checked
6349 by the compiler, but are ignored at run-time even if precondition
6350 checking is enabled.
6352 Note that pragma @code{Precondition} differs from the language-defined
6353 @code{Pre} aspect (and corresponding @code{Pre} pragma) in allowing
6354 multiple occurrences, allowing occurences in the body even if there
6355 is a separate spec, and allowing a second string parameter, and the
6356 use of the pragma identifier @code{Check}. Historically, pragma
6357 @code{Precondition} was implemented prior to the development of
6358 Ada 2012, and has been retained in its original form for
6359 compatibility purposes.
6361 @node Pragma Predicate,Pragma Predicate_Failure,Pragma Precondition,Implementation Defined Pragmas
6362 @anchor{gnat_rm/implementation_defined_pragmas pragma-predicate}@anchor{be}@anchor{gnat_rm/implementation_defined_pragmas id30}@anchor{bf}
6363 @section Pragma Predicate
6370 ([Entity =>] type_LOCAL_NAME,
6371 [Check =>] EXPRESSION);
6374 This pragma (available in all versions of Ada in GNAT) encompasses both
6375 the @code{Static_Predicate} and @code{Dynamic_Predicate} aspects in
6376 Ada 2012. A predicate is regarded as static if it has an allowed form
6377 for @code{Static_Predicate} and is otherwise treated as a
6378 @code{Dynamic_Predicate}. Otherwise, predicates specified by this
6379 pragma behave exactly as described in the Ada 2012 reference manual.
6380 For example, if we have
6383 type R is range 1 .. 10;
6385 pragma Predicate (Entity => S, Check => S not in 4 .. 6);
6387 pragma Predicate (Entity => Q, Check => F(Q) or G(Q));
6390 the effect is identical to the following Ada 2012 code:
6393 type R is range 1 .. 10;
6395 Static_Predicate => S not in 4 .. 6;
6397 Dynamic_Predicate => F(Q) or G(Q);
6400 Note that there are no pragmas @code{Dynamic_Predicate}
6401 or @code{Static_Predicate}. That is
6402 because these pragmas would affect legality and semantics of
6403 the program and thus do not have a neutral effect if ignored.
6404 The motivation behind providing pragmas equivalent to
6405 corresponding aspects is to allow a program to be written
6406 using the pragmas, and then compiled with a compiler that
6407 will ignore the pragmas. That doesn't work in the case of
6408 static and dynamic predicates, since if the corresponding
6409 pragmas are ignored, then the behavior of the program is
6410 fundamentally changed (for example a membership test
6411 @code{A in B} would not take into account a predicate
6412 defined for subtype B). When following this approach, the
6413 use of predicates should be avoided.
6415 @node Pragma Predicate_Failure,Pragma Preelaborable_Initialization,Pragma Predicate,Implementation Defined Pragmas
6416 @anchor{gnat_rm/implementation_defined_pragmas pragma-predicate-failure}@anchor{c0}
6417 @section Pragma Predicate_Failure
6423 pragma Predicate_Failure
6424 ([Entity =>] type_LOCAL_NAME,
6425 [Message =>] String_Expression);
6428 The @code{Predicate_Failure} pragma is intended to be an exact replacement for
6429 the language-defined
6430 @code{Predicate_Failure} aspect, and shares its restrictions and semantics.
6432 @node Pragma Preelaborable_Initialization,Pragma Prefix_Exception_Messages,Pragma Predicate_Failure,Implementation Defined Pragmas
6433 @anchor{gnat_rm/implementation_defined_pragmas pragma-preelaborable-initialization}@anchor{c1}
6434 @section Pragma Preelaborable_Initialization
6440 pragma Preelaborable_Initialization (DIRECT_NAME);
6443 This pragma is standard in Ada 2005, but is available in all earlier
6444 versions of Ada as an implementation-defined pragma.
6445 See Ada 2012 Reference Manual for details.
6447 @node Pragma Prefix_Exception_Messages,Pragma Pre_Class,Pragma Preelaborable_Initialization,Implementation Defined Pragmas
6448 @anchor{gnat_rm/implementation_defined_pragmas pragma-prefix-exception-messages}@anchor{c2}
6449 @section Pragma Prefix_Exception_Messages
6452 @geindex Prefix_Exception_Messages
6456 @geindex Exception_Message
6461 pragma Prefix_Exception_Messages;
6464 This is an implementation-defined configuration pragma that affects the
6465 behavior of raise statements with a message given as a static string
6466 constant (typically a string literal). In such cases, the string will
6467 be automatically prefixed by the name of the enclosing entity (giving
6468 the package and subprogram containing the raise statement). This helps
6469 to identify where messages are coming from, and this mode is automatic
6470 for the run-time library.
6472 The pragma has no effect if the message is computed with an expression other
6473 than a static string constant, since the assumption in this case is that
6474 the program computes exactly the string it wants. If you still want the
6475 prefixing in this case, you can always call
6476 @code{GNAT.Source_Info.Enclosing_Entity} and prepend the string manually.
6478 @node Pragma Pre_Class,Pragma Priority_Specific_Dispatching,Pragma Prefix_Exception_Messages,Implementation Defined Pragmas
6479 @anchor{gnat_rm/implementation_defined_pragmas pragma-pre-class}@anchor{c3}
6480 @section Pragma Pre_Class
6486 @geindex preconditions
6491 pragma Pre_Class (Boolean_Expression);
6494 The @code{Pre_Class} pragma is intended to be an exact replacement for
6495 the language-defined
6496 @code{Pre'Class} aspect, and shares its restrictions and semantics.
6497 It must appear either immediately following the corresponding
6498 subprogram declaration (only other pragmas may intervene), or
6499 if there is no separate subprogram declaration, then it can
6500 appear at the start of the declarations in a subprogram body
6501 (preceded only by other pragmas).
6503 Note: This pragma is called @code{Pre_Class} rather than
6504 @code{Pre'Class} because the latter would not be strictly
6505 conforming to the allowed syntax for pragmas. The motivation
6506 for providing pragmas equivalent to the aspects is to allow a program
6507 to be written using the pragmas, and then compiled if necessary
6508 using an Ada compiler that does not recognize the pragmas or
6509 aspects, but is prepared to ignore the pragmas. The assertion
6510 policy that controls this pragma is @code{Pre'Class}, not
6513 @node Pragma Priority_Specific_Dispatching,Pragma Profile,Pragma Pre_Class,Implementation Defined Pragmas
6514 @anchor{gnat_rm/implementation_defined_pragmas pragma-priority-specific-dispatching}@anchor{c4}
6515 @section Pragma Priority_Specific_Dispatching
6521 pragma Priority_Specific_Dispatching (
6523 first_priority_EXPRESSION,
6524 last_priority_EXPRESSION)
6526 POLICY_IDENTIFIER ::=
6527 EDF_Across_Priorities |
6528 FIFO_Within_Priorities |
6529 Non_Preemptive_Within_Priorities |
6530 Round_Robin_Within_Priorities
6533 This pragma is standard in Ada 2005, but is available in all earlier
6534 versions of Ada as an implementation-defined pragma.
6535 See Ada 2012 Reference Manual for details.
6537 @node Pragma Profile,Pragma Profile_Warnings,Pragma Priority_Specific_Dispatching,Implementation Defined Pragmas
6538 @anchor{gnat_rm/implementation_defined_pragmas pragma-profile}@anchor{c5}
6539 @section Pragma Profile
6545 pragma Profile (Ravenscar | Restricted | Rational | Jorvik |
6546 GNAT_Extended_Ravenscar | GNAT_Ravenscar_EDF );
6549 This pragma is standard in Ada 2005, but is available in all earlier
6550 versions of Ada as an implementation-defined pragma. This is a
6551 configuration pragma that establishes a set of configuration pragmas
6552 that depend on the argument. @code{Ravenscar} is standard in Ada 2005.
6553 @code{Jorvik} is standard in Ada 202x.
6554 The other possibilities (@code{Restricted}, @code{Rational},
6555 @code{GNAT_Extended_Ravenscar}, @code{GNAT_Ravenscar_EDF})
6556 are implementation-defined. @code{GNAT_Extended_Ravenscar} is an alias for @code{Jorvik}.
6558 The set of configuration pragmas is defined in the following sections.
6564 Pragma Profile (Ravenscar)
6566 The @code{Ravenscar} profile is standard in Ada 2005,
6567 but is available in all earlier
6568 versions of Ada as an implementation-defined pragma. This profile
6569 establishes the following set of configuration pragmas:
6575 @code{Task_Dispatching_Policy (FIFO_Within_Priorities)}
6577 [RM D.2.2] Tasks are dispatched following a preemptive
6578 priority-ordered scheduling policy.
6581 @code{Locking_Policy (Ceiling_Locking)}
6583 [RM D.3] While tasks and interrupts execute a protected action, they inherit
6584 the ceiling priority of the corresponding protected object.
6587 @code{Detect_Blocking}
6589 This pragma forces the detection of potentially blocking operations within a
6590 protected operation, and to raise Program_Error if that happens.
6593 plus the following set of restrictions:
6599 @code{Max_Entry_Queue_Length => 1}
6601 No task can be queued on a protected entry.
6604 @code{Max_Protected_Entries => 1}
6607 @code{Max_Task_Entries => 0}
6609 No rendezvous statements are allowed.
6612 @code{No_Abort_Statements}
6615 @code{No_Dynamic_Attachment}
6618 @code{No_Dynamic_Priorities}
6621 @code{No_Implicit_Heap_Allocations}
6624 @code{No_Local_Protected_Objects}
6627 @code{No_Local_Timing_Events}
6630 @code{No_Protected_Type_Allocators}
6633 @code{No_Relative_Delay}
6636 @code{No_Requeue_Statements}
6639 @code{No_Select_Statements}
6642 @code{No_Specific_Termination_Handlers}
6645 @code{No_Task_Allocators}
6648 @code{No_Task_Hierarchy}
6651 @code{No_Task_Termination}
6654 @code{Simple_Barriers}
6657 The Ravenscar profile also includes the following restrictions that specify
6658 that there are no semantic dependencies on the corresponding predefined
6665 @code{No_Dependence => Ada.Asynchronous_Task_Control}
6668 @code{No_Dependence => Ada.Calendar}
6671 @code{No_Dependence => Ada.Execution_Time.Group_Budget}
6674 @code{No_Dependence => Ada.Execution_Time.Timers}
6677 @code{No_Dependence => Ada.Task_Attributes}
6680 @code{No_Dependence => System.Multiprocessors.Dispatching_Domains}
6683 This set of configuration pragmas and restrictions correspond to the
6684 definition of the 'Ravenscar Profile' for limited tasking, devised and
6685 published by the @cite{International Real-Time Ada Workshop@comma{} 1997}.
6686 A description is also available at
6687 @indicateurl{http://www-users.cs.york.ac.uk/~burns/ravenscar.ps}.
6689 The original definition of the profile was revised at subsequent IRTAW
6690 meetings. It has been included in the ISO
6691 @cite{Guide for the Use of the Ada Programming Language in High Integrity Systems},
6692 and was made part of the Ada 2005 standard.
6693 The formal definition given by
6694 the Ada Rapporteur Group (ARG) can be found in two Ada Issues (AI-249 and
6695 AI-305) available at
6696 @indicateurl{http://www.ada-auth.org/cgi-bin/cvsweb.cgi/ais/ai-00249.txt} and
6697 @indicateurl{http://www.ada-auth.org/cgi-bin/cvsweb.cgi/ais/ai-00305.txt}.
6699 The above set is a superset of the restrictions provided by pragma
6700 @code{Profile (Restricted)}, it includes six additional restrictions
6701 (@code{Simple_Barriers}, @code{No_Select_Statements},
6702 @code{No_Calendar}, @code{No_Implicit_Heap_Allocations},
6703 @code{No_Relative_Delay} and @code{No_Task_Termination}). This means
6704 that pragma @code{Profile (Ravenscar)}, like the pragma
6705 @code{Profile (Restricted)},
6706 automatically causes the use of a simplified,
6707 more efficient version of the tasking run-time library.
6710 Pragma Profile (Jorvik)
6712 @code{Jorvik} is the new profile added to the Ada 202x draft standard,
6713 previously implemented under the name @code{GNAT_Extended_Ravenscar}.
6715 The @code{No_Implicit_Heap_Allocations} restriction has been replaced
6716 by @code{No_Implicit_Task_Allocations} and
6717 @code{No_Implicit_Protected_Object_Allocations}.
6719 The @code{Simple_Barriers} restriction has been replaced by
6720 @code{Pure_Barriers}.
6722 The @code{Max_Protected_Entries}, @code{Max_Entry_Queue_Length}, and
6723 @code{No_Relative_Delay} restrictions have been removed.
6725 Details on the rationale for @code{Jorvik} and implications for use may be
6726 found in @cite{A New Ravenscar-Based Profile} by P. Rogers, J. Ruiz,
6727 T. Gingold and P. Bernardi, in @cite{Reliable Software Technologies -- Ada Europe 2017}, Springer-Verlag Lecture Notes in Computer Science,
6731 Pragma Profile (GNAT_Ravenscar_EDF)
6733 This profile corresponds to the Ravenscar profile but using
6734 EDF_Across_Priority as the Task_Scheduling_Policy.
6737 Pragma Profile (Restricted)
6739 This profile corresponds to the GNAT restricted run time. It
6740 establishes the following set of restrictions:
6746 @code{No_Abort_Statements}
6749 @code{No_Entry_Queue}
6752 @code{No_Task_Hierarchy}
6755 @code{No_Task_Allocators}
6758 @code{No_Dynamic_Priorities}
6761 @code{No_Terminate_Alternatives}
6764 @code{No_Dynamic_Attachment}
6767 @code{No_Protected_Type_Allocators}
6770 @code{No_Local_Protected_Objects}
6773 @code{No_Requeue_Statements}
6776 @code{No_Task_Attributes_Package}
6779 @code{Max_Asynchronous_Select_Nesting = 0}
6782 @code{Max_Task_Entries = 0}
6785 @code{Max_Protected_Entries = 1}
6788 @code{Max_Select_Alternatives = 0}
6791 This set of restrictions causes the automatic selection of a simplified
6792 version of the run time that provides improved performance for the
6793 limited set of tasking functionality permitted by this set of restrictions.
6796 Pragma Profile (Rational)
6798 The Rational profile is intended to facilitate porting legacy code that
6799 compiles with the Rational APEX compiler, even when the code includes non-
6800 conforming Ada constructs. The profile enables the following three pragmas:
6806 @code{pragma Implicit_Packing}
6809 @code{pragma Overriding_Renamings}
6812 @code{pragma Use_VADS_Size}
6816 @node Pragma Profile_Warnings,Pragma Propagate_Exceptions,Pragma Profile,Implementation Defined Pragmas
6817 @anchor{gnat_rm/implementation_defined_pragmas pragma-profile-warnings}@anchor{c6}
6818 @section Pragma Profile_Warnings
6824 pragma Profile_Warnings (Ravenscar | Restricted | Rational);
6827 This is an implementation-defined pragma that is similar in
6828 effect to @code{pragma Profile} except that instead of
6829 generating @code{Restrictions} pragmas, it generates
6830 @code{Restriction_Warnings} pragmas. The result is that
6831 violations of the profile generate warning messages instead
6834 @node Pragma Propagate_Exceptions,Pragma Provide_Shift_Operators,Pragma Profile_Warnings,Implementation Defined Pragmas
6835 @anchor{gnat_rm/implementation_defined_pragmas pragma-propagate-exceptions}@anchor{c7}
6836 @section Pragma Propagate_Exceptions
6839 @geindex Interfacing to C++
6844 pragma Propagate_Exceptions;
6847 This pragma is now obsolete and, other than generating a warning if warnings
6848 on obsolescent features are enabled, is ignored.
6849 It is retained for compatibility
6850 purposes. It used to be used in connection with optimization of
6851 a now-obsolete mechanism for implementation of exceptions.
6853 @node Pragma Provide_Shift_Operators,Pragma Psect_Object,Pragma Propagate_Exceptions,Implementation Defined Pragmas
6854 @anchor{gnat_rm/implementation_defined_pragmas pragma-provide-shift-operators}@anchor{c8}
6855 @section Pragma Provide_Shift_Operators
6858 @geindex Shift operators
6863 pragma Provide_Shift_Operators (integer_first_subtype_LOCAL_NAME);
6866 This pragma can be applied to a first subtype local name that specifies
6867 either an unsigned or signed type. It has the effect of providing the
6868 five shift operators (Shift_Left, Shift_Right, Shift_Right_Arithmetic,
6869 Rotate_Left and Rotate_Right) for the given type. It is similar to
6870 including the function declarations for these five operators, together
6871 with the pragma Import (Intrinsic, ...) statements.
6873 @node Pragma Psect_Object,Pragma Pure_Function,Pragma Provide_Shift_Operators,Implementation Defined Pragmas
6874 @anchor{gnat_rm/implementation_defined_pragmas pragma-psect-object}@anchor{c9}
6875 @section Pragma Psect_Object
6881 pragma Psect_Object (
6882 [Internal =>] LOCAL_NAME,
6883 [, [External =>] EXTERNAL_SYMBOL]
6884 [, [Size =>] EXTERNAL_SYMBOL]);
6888 | static_string_EXPRESSION
6891 This pragma is identical in effect to pragma @code{Common_Object}.
6893 @node Pragma Pure_Function,Pragma Rational,Pragma Psect_Object,Implementation Defined Pragmas
6894 @anchor{gnat_rm/implementation_defined_pragmas pragma-pure-function}@anchor{ca}@anchor{gnat_rm/implementation_defined_pragmas id31}@anchor{cb}
6895 @section Pragma Pure_Function
6901 pragma Pure_Function ([Entity =>] function_LOCAL_NAME);
6904 This pragma appears in the same declarative part as a function
6905 declaration (or a set of function declarations if more than one
6906 overloaded declaration exists, in which case the pragma applies
6907 to all entities). It specifies that the function @code{Entity} is
6908 to be considered pure for the purposes of code generation. This means
6909 that the compiler can assume that there are no side effects, and
6910 in particular that two calls with identical arguments produce the
6911 same result. It also means that the function can be used in an
6914 Note that, quite deliberately, there are no static checks to try
6915 to ensure that this promise is met, so @code{Pure_Function} can be used
6916 with functions that are conceptually pure, even if they do modify
6917 global variables. For example, a square root function that is
6918 instrumented to count the number of times it is called is still
6919 conceptually pure, and can still be optimized, even though it
6920 modifies a global variable (the count). Memo functions are another
6921 example (where a table of previous calls is kept and consulted to
6922 avoid re-computation).
6924 Note also that the normal rules excluding optimization of subprograms
6925 in pure units (when parameter types are descended from System.Address,
6926 or when the full view of a parameter type is limited), do not apply
6927 for the Pure_Function case. If you explicitly specify Pure_Function,
6928 the compiler may optimize away calls with identical arguments, and
6929 if that results in unexpected behavior, the proper action is not to
6930 use the pragma for subprograms that are not (conceptually) pure.
6932 Note: Most functions in a @code{Pure} package are automatically pure, and
6933 there is no need to use pragma @code{Pure_Function} for such functions. One
6934 exception is any function that has at least one formal of type
6935 @code{System.Address} or a type derived from it. Such functions are not
6936 considered pure by default, since the compiler assumes that the
6937 @code{Address} parameter may be functioning as a pointer and that the
6938 referenced data may change even if the address value does not.
6939 Similarly, imported functions are not considered to be pure by default,
6940 since there is no way of checking that they are in fact pure. The use
6941 of pragma @code{Pure_Function} for such a function will override these default
6942 assumption, and cause the compiler to treat a designated subprogram as pure
6945 Note: If pragma @code{Pure_Function} is applied to a renamed function, it
6946 applies to the underlying renamed function. This can be used to
6947 disambiguate cases of overloading where some but not all functions
6948 in a set of overloaded functions are to be designated as pure.
6950 If pragma @code{Pure_Function} is applied to a library-level function, the
6951 function is also considered pure from an optimization point of view, but the
6952 unit is not a Pure unit in the categorization sense. So for example, a function
6953 thus marked is free to @code{with} non-pure units.
6955 @node Pragma Rational,Pragma Ravenscar,Pragma Pure_Function,Implementation Defined Pragmas
6956 @anchor{gnat_rm/implementation_defined_pragmas pragma-rational}@anchor{cc}
6957 @section Pragma Rational
6966 This pragma is considered obsolescent, but is retained for
6967 compatibility purposes. It is equivalent to:
6970 pragma Profile (Rational);
6973 @node Pragma Ravenscar,Pragma Refined_Depends,Pragma Rational,Implementation Defined Pragmas
6974 @anchor{gnat_rm/implementation_defined_pragmas pragma-ravenscar}@anchor{cd}
6975 @section Pragma Ravenscar
6984 This pragma is considered obsolescent, but is retained for
6985 compatibility purposes. It is equivalent to:
6988 pragma Profile (Ravenscar);
6991 which is the preferred method of setting the @code{Ravenscar} profile.
6993 @node Pragma Refined_Depends,Pragma Refined_Global,Pragma Ravenscar,Implementation Defined Pragmas
6994 @anchor{gnat_rm/implementation_defined_pragmas pragma-refined-depends}@anchor{ce}@anchor{gnat_rm/implementation_defined_pragmas id32}@anchor{cf}
6995 @section Pragma Refined_Depends
7001 pragma Refined_Depends (DEPENDENCY_RELATION);
7003 DEPENDENCY_RELATION ::=
7005 | (DEPENDENCY_CLAUSE @{, DEPENDENCY_CLAUSE@})
7007 DEPENDENCY_CLAUSE ::=
7008 OUTPUT_LIST =>[+] INPUT_LIST
7009 | NULL_DEPENDENCY_CLAUSE
7011 NULL_DEPENDENCY_CLAUSE ::= null => INPUT_LIST
7013 OUTPUT_LIST ::= OUTPUT | (OUTPUT @{, OUTPUT@})
7015 INPUT_LIST ::= null | INPUT | (INPUT @{, INPUT@})
7017 OUTPUT ::= NAME | FUNCTION_RESULT
7020 where FUNCTION_RESULT is a function Result attribute_reference
7023 For the semantics of this pragma, see the entry for aspect @code{Refined_Depends} in
7024 the SPARK 2014 Reference Manual, section 6.1.5.
7026 @node Pragma Refined_Global,Pragma Refined_Post,Pragma Refined_Depends,Implementation Defined Pragmas
7027 @anchor{gnat_rm/implementation_defined_pragmas pragma-refined-global}@anchor{d0}@anchor{gnat_rm/implementation_defined_pragmas id33}@anchor{d1}
7028 @section Pragma Refined_Global
7034 pragma Refined_Global (GLOBAL_SPECIFICATION);
7036 GLOBAL_SPECIFICATION ::=
7039 | (MODED_GLOBAL_LIST @{, MODED_GLOBAL_LIST@})
7041 MODED_GLOBAL_LIST ::= MODE_SELECTOR => GLOBAL_LIST
7043 MODE_SELECTOR ::= In_Out | Input | Output | Proof_In
7044 GLOBAL_LIST ::= GLOBAL_ITEM | (GLOBAL_ITEM @{, GLOBAL_ITEM@})
7045 GLOBAL_ITEM ::= NAME
7048 For the semantics of this pragma, see the entry for aspect @code{Refined_Global} in
7049 the SPARK 2014 Reference Manual, section 6.1.4.
7051 @node Pragma Refined_Post,Pragma Refined_State,Pragma Refined_Global,Implementation Defined Pragmas
7052 @anchor{gnat_rm/implementation_defined_pragmas pragma-refined-post}@anchor{d2}@anchor{gnat_rm/implementation_defined_pragmas id34}@anchor{d3}
7053 @section Pragma Refined_Post
7059 pragma Refined_Post (boolean_EXPRESSION);
7062 For the semantics of this pragma, see the entry for aspect @code{Refined_Post} in
7063 the SPARK 2014 Reference Manual, section 7.2.7.
7065 @node Pragma Refined_State,Pragma Relative_Deadline,Pragma Refined_Post,Implementation Defined Pragmas
7066 @anchor{gnat_rm/implementation_defined_pragmas pragma-refined-state}@anchor{d4}@anchor{gnat_rm/implementation_defined_pragmas id35}@anchor{d5}
7067 @section Pragma Refined_State
7073 pragma Refined_State (REFINEMENT_LIST);
7076 (REFINEMENT_CLAUSE @{, REFINEMENT_CLAUSE@})
7078 REFINEMENT_CLAUSE ::= state_NAME => CONSTITUENT_LIST
7080 CONSTITUENT_LIST ::=
7083 | (CONSTITUENT @{, CONSTITUENT@})
7085 CONSTITUENT ::= object_NAME | state_NAME
7088 For the semantics of this pragma, see the entry for aspect @code{Refined_State} in
7089 the SPARK 2014 Reference Manual, section 7.2.2.
7091 @node Pragma Relative_Deadline,Pragma Remote_Access_Type,Pragma Refined_State,Implementation Defined Pragmas
7092 @anchor{gnat_rm/implementation_defined_pragmas pragma-relative-deadline}@anchor{d6}
7093 @section Pragma Relative_Deadline
7099 pragma Relative_Deadline (time_span_EXPRESSION);
7102 This pragma is standard in Ada 2005, but is available in all earlier
7103 versions of Ada as an implementation-defined pragma.
7104 See Ada 2012 Reference Manual for details.
7106 @node Pragma Remote_Access_Type,Pragma Restricted_Run_Time,Pragma Relative_Deadline,Implementation Defined Pragmas
7107 @anchor{gnat_rm/implementation_defined_pragmas id36}@anchor{d7}@anchor{gnat_rm/implementation_defined_pragmas pragma-remote-access-type}@anchor{d8}
7108 @section Pragma Remote_Access_Type
7114 pragma Remote_Access_Type ([Entity =>] formal_access_type_LOCAL_NAME);
7117 This pragma appears in the formal part of a generic declaration.
7118 It specifies an exception to the RM rule from E.2.2(17/2), which forbids
7119 the use of a remote access to class-wide type as actual for a formal
7122 When this pragma applies to a formal access type @code{Entity}, that
7123 type is treated as a remote access to class-wide type in the generic.
7124 It must be a formal general access type, and its designated type must
7125 be the class-wide type of a formal tagged limited private type from the
7126 same generic declaration.
7128 In the generic unit, the formal type is subject to all restrictions
7129 pertaining to remote access to class-wide types. At instantiation, the
7130 actual type must be a remote access to class-wide type.
7132 @node Pragma Restricted_Run_Time,Pragma Restriction_Warnings,Pragma Remote_Access_Type,Implementation Defined Pragmas
7133 @anchor{gnat_rm/implementation_defined_pragmas pragma-restricted-run-time}@anchor{d9}
7134 @section Pragma Restricted_Run_Time
7140 pragma Restricted_Run_Time;
7143 This pragma is considered obsolescent, but is retained for
7144 compatibility purposes. It is equivalent to:
7147 pragma Profile (Restricted);
7150 which is the preferred method of setting the restricted run time
7153 @node Pragma Restriction_Warnings,Pragma Reviewable,Pragma Restricted_Run_Time,Implementation Defined Pragmas
7154 @anchor{gnat_rm/implementation_defined_pragmas pragma-restriction-warnings}@anchor{da}
7155 @section Pragma Restriction_Warnings
7161 pragma Restriction_Warnings
7162 (restriction_IDENTIFIER @{, restriction_IDENTIFIER@});
7165 This pragma allows a series of restriction identifiers to be
7166 specified (the list of allowed identifiers is the same as for
7167 pragma @code{Restrictions}). For each of these identifiers
7168 the compiler checks for violations of the restriction, but
7169 generates a warning message rather than an error message
7170 if the restriction is violated.
7172 One use of this is in situations where you want to know
7173 about violations of a restriction, but you want to ignore some of
7174 these violations. Consider this example, where you want to set
7175 Ada_95 mode and enable style checks, but you want to know about
7176 any other use of implementation pragmas:
7179 pragma Restriction_Warnings (No_Implementation_Pragmas);
7180 pragma Warnings (Off, "violation of No_Implementation_Pragmas");
7182 pragma Style_Checks ("2bfhkM160");
7183 pragma Warnings (On, "violation of No_Implementation_Pragmas");
7186 By including the above lines in a configuration pragmas file,
7187 the Ada_95 and Style_Checks pragmas are accepted without
7188 generating a warning, but any other use of implementation
7189 defined pragmas will cause a warning to be generated.
7191 @node Pragma Reviewable,Pragma Secondary_Stack_Size,Pragma Restriction_Warnings,Implementation Defined Pragmas
7192 @anchor{gnat_rm/implementation_defined_pragmas pragma-reviewable}@anchor{db}
7193 @section Pragma Reviewable
7202 This pragma is an RM-defined standard pragma, but has no effect on the
7203 program being compiled, or on the code generated for the program.
7205 To obtain the required output specified in RM H.3.1, the compiler must be
7206 run with various special switches as follows:
7212 @emph{Where compiler-generated run-time checks remain}
7214 The switch @emph{-gnatGL}
7215 may be used to list the expanded code in pseudo-Ada form.
7216 Runtime checks show up in the listing either as explicit
7217 checks or operators marked with @{@} to indicate a check is present.
7220 @emph{An identification of known exceptions at compile time}
7222 If the program is compiled with @emph{-gnatwa},
7223 the compiler warning messages will indicate all cases where the compiler
7224 detects that an exception is certain to occur at run time.
7227 @emph{Possible reads of uninitialized variables}
7229 The compiler warns of many such cases, but its output is incomplete.
7233 A supplemental static analysis tool
7234 may be used to obtain a comprehensive list of all
7235 possible points at which uninitialized data may be read.
7241 @emph{Where run-time support routines are implicitly invoked}
7243 In the output from @emph{-gnatGL},
7244 run-time calls are explicitly listed as calls to the relevant
7248 @emph{Object code listing}
7250 This may be obtained either by using the @emph{-S} switch,
7251 or the objdump utility.
7254 @emph{Constructs known to be erroneous at compile time}
7256 These are identified by warnings issued by the compiler (use @emph{-gnatwa}).
7259 @emph{Stack usage information}
7261 Static stack usage data (maximum per-subprogram) can be obtained via the
7262 @emph{-fstack-usage} switch to the compiler.
7263 Dynamic stack usage data (per task) can be obtained via the @emph{-u} switch
7272 @emph{Object code listing of entire partition}
7274 This can be obtained by compiling the partition with @emph{-S},
7275 or by applying objdump
7276 to all the object files that are part of the partition.
7279 @emph{A description of the run-time model}
7281 The full sources of the run-time are available, and the documentation of
7282 these routines describes how these run-time routines interface to the
7283 underlying operating system facilities.
7286 @emph{Control and data-flow information}
7290 A supplemental static analysis tool
7291 may be used to obtain complete control and data-flow information, as well as
7292 comprehensive messages identifying possible problems based on this
7295 @node Pragma Secondary_Stack_Size,Pragma Share_Generic,Pragma Reviewable,Implementation Defined Pragmas
7296 @anchor{gnat_rm/implementation_defined_pragmas id37}@anchor{dc}@anchor{gnat_rm/implementation_defined_pragmas pragma-secondary-stack-size}@anchor{dd}
7297 @section Pragma Secondary_Stack_Size
7303 pragma Secondary_Stack_Size (integer_EXPRESSION);
7306 This pragma appears within the task definition of a single task declaration
7307 or a task type declaration (like pragma @code{Storage_Size}) and applies to all
7308 task objects of that type. The argument specifies the size of the secondary
7309 stack to be used by these task objects, and must be of an integer type. The
7310 secondary stack is used to handle functions that return a variable-sized
7311 result, for example a function returning an unconstrained String.
7313 Note this pragma only applies to targets using fixed secondary stacks, like
7314 VxWorks 653 and bare board targets, where a fixed block for the
7315 secondary stack is allocated from the primary stack of the task. By default,
7316 these targets assign a percentage of the primary stack for the secondary stack,
7317 as defined by @code{System.Parameter.Sec_Stack_Percentage}. With this pragma,
7318 an @code{integer_EXPRESSION} of bytes is assigned from the primary stack instead.
7320 For most targets, the pragma does not apply as the secondary stack grows on
7321 demand: allocated as a chain of blocks in the heap. The default size of these
7322 blocks can be modified via the @code{-D} binder option as described in
7323 @cite{GNAT User's Guide}.
7325 Note that no check is made to see if the secondary stack can fit inside the
7328 Note the pragma cannot appear when the restriction @code{No_Secondary_Stack}
7331 @node Pragma Share_Generic,Pragma Shared,Pragma Secondary_Stack_Size,Implementation Defined Pragmas
7332 @anchor{gnat_rm/implementation_defined_pragmas pragma-share-generic}@anchor{de}
7333 @section Pragma Share_Generic
7339 pragma Share_Generic (GNAME @{, GNAME@});
7341 GNAME ::= generic_unit_NAME | generic_instance_NAME
7344 This pragma is provided for compatibility with Dec Ada 83. It has
7345 no effect in GNAT (which does not implement shared generics), other
7346 than to check that the given names are all names of generic units or
7349 @node Pragma Shared,Pragma Short_Circuit_And_Or,Pragma Share_Generic,Implementation Defined Pragmas
7350 @anchor{gnat_rm/implementation_defined_pragmas id38}@anchor{df}@anchor{gnat_rm/implementation_defined_pragmas pragma-shared}@anchor{e0}
7351 @section Pragma Shared
7354 This pragma is provided for compatibility with Ada 83. The syntax and
7355 semantics are identical to pragma Atomic.
7357 @node Pragma Short_Circuit_And_Or,Pragma Short_Descriptors,Pragma Shared,Implementation Defined Pragmas
7358 @anchor{gnat_rm/implementation_defined_pragmas pragma-short-circuit-and-or}@anchor{e1}
7359 @section Pragma Short_Circuit_And_Or
7365 pragma Short_Circuit_And_Or;
7368 This configuration pragma causes any occurrence of the AND operator applied to
7369 operands of type Standard.Boolean to be short-circuited (i.e. the AND operator
7370 is treated as if it were AND THEN). Or is similarly treated as OR ELSE. This
7371 may be useful in the context of certification protocols requiring the use of
7372 short-circuited logical operators. If this configuration pragma occurs locally
7373 within the file being compiled, it applies only to the file being compiled.
7374 There is no requirement that all units in a partition use this option.
7376 @node Pragma Short_Descriptors,Pragma Simple_Storage_Pool_Type,Pragma Short_Circuit_And_Or,Implementation Defined Pragmas
7377 @anchor{gnat_rm/implementation_defined_pragmas pragma-short-descriptors}@anchor{e2}
7378 @section Pragma Short_Descriptors
7384 pragma Short_Descriptors
7387 This pragma is provided for compatibility with other Ada implementations. It
7388 is recognized but ignored by all current versions of GNAT.
7390 @node Pragma Simple_Storage_Pool_Type,Pragma Source_File_Name,Pragma Short_Descriptors,Implementation Defined Pragmas
7391 @anchor{gnat_rm/implementation_defined_pragmas pragma-simple-storage-pool-type}@anchor{e3}@anchor{gnat_rm/implementation_defined_pragmas id39}@anchor{e4}
7392 @section Pragma Simple_Storage_Pool_Type
7395 @geindex Storage pool
7398 @geindex Simple storage pool
7403 pragma Simple_Storage_Pool_Type (type_LOCAL_NAME);
7406 A type can be established as a 'simple storage pool type' by applying
7407 the representation pragma @code{Simple_Storage_Pool_Type} to the type.
7408 A type named in the pragma must be a library-level immutably limited record
7409 type or limited tagged type declared immediately within a package declaration.
7410 The type can also be a limited private type whose full type is allowed as
7411 a simple storage pool type.
7413 For a simple storage pool type @code{SSP}, nonabstract primitive subprograms
7414 @code{Allocate}, @code{Deallocate}, and @code{Storage_Size} can be declared that
7415 are subtype conformant with the following subprogram declarations:
7420 Storage_Address : out System.Address;
7421 Size_In_Storage_Elements : System.Storage_Elements.Storage_Count;
7422 Alignment : System.Storage_Elements.Storage_Count);
7424 procedure Deallocate
7426 Storage_Address : System.Address;
7427 Size_In_Storage_Elements : System.Storage_Elements.Storage_Count;
7428 Alignment : System.Storage_Elements.Storage_Count);
7430 function Storage_Size (Pool : SSP)
7431 return System.Storage_Elements.Storage_Count;
7434 Procedure @code{Allocate} must be declared, whereas @code{Deallocate} and
7435 @code{Storage_Size} are optional. If @code{Deallocate} is not declared, then
7436 applying an unchecked deallocation has no effect other than to set its actual
7437 parameter to null. If @code{Storage_Size} is not declared, then the
7438 @code{Storage_Size} attribute applied to an access type associated with
7439 a pool object of type SSP returns zero. Additional operations can be declared
7440 for a simple storage pool type (such as for supporting a mark/release
7441 storage-management discipline).
7443 An object of a simple storage pool type can be associated with an access
7444 type by specifying the attribute
7445 @ref{e5,,Simple_Storage_Pool}. For example:
7448 My_Pool : My_Simple_Storage_Pool_Type;
7450 type Acc is access My_Data_Type;
7452 for Acc'Simple_Storage_Pool use My_Pool;
7455 See attribute @ref{e5,,Simple_Storage_Pool}
7456 for further details.
7458 @node Pragma Source_File_Name,Pragma Source_File_Name_Project,Pragma Simple_Storage_Pool_Type,Implementation Defined Pragmas
7459 @anchor{gnat_rm/implementation_defined_pragmas pragma-source-file-name}@anchor{e6}@anchor{gnat_rm/implementation_defined_pragmas id40}@anchor{e7}
7460 @section Pragma Source_File_Name
7466 pragma Source_File_Name (
7467 [Unit_Name =>] unit_NAME,
7468 Spec_File_Name => STRING_LITERAL,
7469 [Index => INTEGER_LITERAL]);
7471 pragma Source_File_Name (
7472 [Unit_Name =>] unit_NAME,
7473 Body_File_Name => STRING_LITERAL,
7474 [Index => INTEGER_LITERAL]);
7477 Use this to override the normal naming convention. It is a configuration
7478 pragma, and so has the usual applicability of configuration pragmas
7479 (i.e., it applies to either an entire partition, or to all units in a
7480 compilation, or to a single unit, depending on how it is used.
7481 @code{unit_name} is mapped to @code{file_name_literal}. The identifier for
7482 the second argument is required, and indicates whether this is the file
7483 name for the spec or for the body.
7485 The optional Index argument should be used when a file contains multiple
7486 units, and when you do not want to use @code{gnatchop} to separate then
7487 into multiple files (which is the recommended procedure to limit the
7488 number of recompilations that are needed when some sources change).
7489 For instance, if the source file @code{source.ada} contains
7503 you could use the following configuration pragmas:
7506 pragma Source_File_Name
7507 (B, Spec_File_Name => "source.ada", Index => 1);
7508 pragma Source_File_Name
7509 (A, Body_File_Name => "source.ada", Index => 2);
7512 Note that the @code{gnatname} utility can also be used to generate those
7513 configuration pragmas.
7515 Another form of the @code{Source_File_Name} pragma allows
7516 the specification of patterns defining alternative file naming schemes
7517 to apply to all files.
7520 pragma Source_File_Name
7521 ( [Spec_File_Name =>] STRING_LITERAL
7522 [,[Casing =>] CASING_SPEC]
7523 [,[Dot_Replacement =>] STRING_LITERAL]);
7525 pragma Source_File_Name
7526 ( [Body_File_Name =>] STRING_LITERAL
7527 [,[Casing =>] CASING_SPEC]
7528 [,[Dot_Replacement =>] STRING_LITERAL]);
7530 pragma Source_File_Name
7531 ( [Subunit_File_Name =>] STRING_LITERAL
7532 [,[Casing =>] CASING_SPEC]
7533 [,[Dot_Replacement =>] STRING_LITERAL]);
7535 CASING_SPEC ::= Lowercase | Uppercase | Mixedcase
7538 The first argument is a pattern that contains a single asterisk indicating
7539 the point at which the unit name is to be inserted in the pattern string
7540 to form the file name. The second argument is optional. If present it
7541 specifies the casing of the unit name in the resulting file name string.
7542 The default is lower case. Finally the third argument allows for systematic
7543 replacement of any dots in the unit name by the specified string literal.
7545 Note that Source_File_Name pragmas should not be used if you are using
7546 project files. The reason for this rule is that the project manager is not
7547 aware of these pragmas, and so other tools that use the projet file would not
7548 be aware of the intended naming conventions. If you are using project files,
7549 file naming is controlled by Source_File_Name_Project pragmas, which are
7550 usually supplied automatically by the project manager. A pragma
7551 Source_File_Name cannot appear after a @ref{e8,,Pragma Source_File_Name_Project}.
7553 For more details on the use of the @code{Source_File_Name} pragma, see the
7554 sections on @cite{Using Other File Names} and @cite{Alternative File Naming Schemes}
7555 in the @cite{GNAT User's Guide}.
7557 @node Pragma Source_File_Name_Project,Pragma Source_Reference,Pragma Source_File_Name,Implementation Defined Pragmas
7558 @anchor{gnat_rm/implementation_defined_pragmas pragma-source-file-name-project}@anchor{e8}@anchor{gnat_rm/implementation_defined_pragmas id41}@anchor{e9}
7559 @section Pragma Source_File_Name_Project
7562 This pragma has the same syntax and semantics as pragma Source_File_Name.
7563 It is only allowed as a stand-alone configuration pragma.
7564 It cannot appear after a @ref{e6,,Pragma Source_File_Name}, and
7565 most importantly, once pragma Source_File_Name_Project appears,
7566 no further Source_File_Name pragmas are allowed.
7568 The intention is that Source_File_Name_Project pragmas are always
7569 generated by the Project Manager in a manner consistent with the naming
7570 specified in a project file, and when naming is controlled in this manner,
7571 it is not permissible to attempt to modify this naming scheme using
7572 Source_File_Name or Source_File_Name_Project pragmas (which would not be
7573 known to the project manager).
7575 @node Pragma Source_Reference,Pragma SPARK_Mode,Pragma Source_File_Name_Project,Implementation Defined Pragmas
7576 @anchor{gnat_rm/implementation_defined_pragmas pragma-source-reference}@anchor{ea}
7577 @section Pragma Source_Reference
7583 pragma Source_Reference (INTEGER_LITERAL, STRING_LITERAL);
7586 This pragma must appear as the first line of a source file.
7587 @code{integer_literal} is the logical line number of the line following
7588 the pragma line (for use in error messages and debugging
7589 information). @code{string_literal} is a static string constant that
7590 specifies the file name to be used in error messages and debugging
7591 information. This is most notably used for the output of @code{gnatchop}
7592 with the @emph{-r} switch, to make sure that the original unchopped
7593 source file is the one referred to.
7595 The second argument must be a string literal, it cannot be a static
7596 string expression other than a string literal. This is because its value
7597 is needed for error messages issued by all phases of the compiler.
7599 @node Pragma SPARK_Mode,Pragma Static_Elaboration_Desired,Pragma Source_Reference,Implementation Defined Pragmas
7600 @anchor{gnat_rm/implementation_defined_pragmas pragma-spark-mode}@anchor{eb}@anchor{gnat_rm/implementation_defined_pragmas id42}@anchor{ec}
7601 @section Pragma SPARK_Mode
7607 pragma SPARK_Mode [(On | Off)] ;
7610 In general a program can have some parts that are in SPARK 2014 (and
7611 follow all the rules in the SPARK Reference Manual), and some parts
7612 that are full Ada 2012.
7614 The SPARK_Mode pragma is used to identify which parts are in SPARK
7615 2014 (by default programs are in full Ada). The SPARK_Mode pragma can
7616 be used in the following places:
7622 As a configuration pragma, in which case it sets the default mode for
7623 all units compiled with this pragma.
7626 Immediately following a library-level subprogram spec
7629 Immediately within a library-level package body
7632 Immediately following the @code{private} keyword of a library-level
7636 Immediately following the @code{begin} keyword of a library-level
7640 Immediately within a library-level subprogram body
7643 Normally a subprogram or package spec/body inherits the current mode
7644 that is active at the point it is declared. But this can be overridden
7645 by pragma within the spec or body as above.
7647 The basic consistency rule is that you can't turn SPARK_Mode back
7648 @code{On}, once you have explicitly (with a pragma) turned if
7649 @code{Off}. So the following rules apply:
7651 If a subprogram spec has SPARK_Mode @code{Off}, then the body must
7652 also have SPARK_Mode @code{Off}.
7654 For a package, we have four parts:
7660 the package public declarations
7663 the package private part
7666 the body of the package
7669 the elaboration code after @code{begin}
7672 For a package, the rule is that if you explicitly turn SPARK_Mode
7673 @code{Off} for any part, then all the following parts must have
7674 SPARK_Mode @code{Off}. Note that this may require repeating a pragma
7675 SPARK_Mode (@code{Off}) in the body. For example, if we have a
7676 configuration pragma SPARK_Mode (@code{On}) that turns the mode on by
7677 default everywhere, and one particular package spec has pragma
7678 SPARK_Mode (@code{Off}), then that pragma will need to be repeated in
7681 @node Pragma Static_Elaboration_Desired,Pragma Stream_Convert,Pragma SPARK_Mode,Implementation Defined Pragmas
7682 @anchor{gnat_rm/implementation_defined_pragmas pragma-static-elaboration-desired}@anchor{ed}
7683 @section Pragma Static_Elaboration_Desired
7689 pragma Static_Elaboration_Desired;
7692 This pragma is used to indicate that the compiler should attempt to initialize
7693 statically the objects declared in the library unit to which the pragma applies,
7694 when these objects are initialized (explicitly or implicitly) by an aggregate.
7695 In the absence of this pragma, aggregates in object declarations are expanded
7696 into assignments and loops, even when the aggregate components are static
7697 constants. When the aggregate is present the compiler builds a static expression
7698 that requires no run-time code, so that the initialized object can be placed in
7699 read-only data space. If the components are not static, or the aggregate has
7700 more that 100 components, the compiler emits a warning that the pragma cannot
7701 be obeyed. (See also the restriction No_Implicit_Loops, which supports static
7702 construction of larger aggregates with static components that include an others
7705 @node Pragma Stream_Convert,Pragma Style_Checks,Pragma Static_Elaboration_Desired,Implementation Defined Pragmas
7706 @anchor{gnat_rm/implementation_defined_pragmas pragma-stream-convert}@anchor{ee}
7707 @section Pragma Stream_Convert
7713 pragma Stream_Convert (
7714 [Entity =>] type_LOCAL_NAME,
7715 [Read =>] function_NAME,
7716 [Write =>] function_NAME);
7719 This pragma provides an efficient way of providing user-defined stream
7720 attributes. Not only is it simpler to use than specifying the attributes
7721 directly, but more importantly, it allows the specification to be made in such
7722 a way that the predefined unit Ada.Streams is not loaded unless it is actually
7723 needed (i.e. unless the stream attributes are actually used); the use of
7724 the Stream_Convert pragma adds no overhead at all, unless the stream
7725 attributes are actually used on the designated type.
7727 The first argument specifies the type for which stream functions are
7728 provided. The second parameter provides a function used to read values
7729 of this type. It must name a function whose argument type may be any
7730 subtype, and whose returned type must be the type given as the first
7731 argument to the pragma.
7733 The meaning of the @code{Read} parameter is that if a stream attribute directly
7734 or indirectly specifies reading of the type given as the first parameter,
7735 then a value of the type given as the argument to the Read function is
7736 read from the stream, and then the Read function is used to convert this
7737 to the required target type.
7739 Similarly the @code{Write} parameter specifies how to treat write attributes
7740 that directly or indirectly apply to the type given as the first parameter.
7741 It must have an input parameter of the type specified by the first parameter,
7742 and the return type must be the same as the input type of the Read function.
7743 The effect is to first call the Write function to convert to the given stream
7744 type, and then write the result type to the stream.
7746 The Read and Write functions must not be overloaded subprograms. If necessary
7747 renamings can be supplied to meet this requirement.
7748 The usage of this attribute is best illustrated by a simple example, taken
7749 from the GNAT implementation of package Ada.Strings.Unbounded:
7752 function To_Unbounded (S : String) return Unbounded_String
7753 renames To_Unbounded_String;
7755 pragma Stream_Convert
7756 (Unbounded_String, To_Unbounded, To_String);
7759 The specifications of the referenced functions, as given in the Ada
7760 Reference Manual are:
7763 function To_Unbounded_String (Source : String)
7764 return Unbounded_String;
7766 function To_String (Source : Unbounded_String)
7770 The effect is that if the value of an unbounded string is written to a stream,
7771 then the representation of the item in the stream is in the same format that
7772 would be used for @code{Standard.String'Output}, and this same representation
7773 is expected when a value of this type is read from the stream. Note that the
7774 value written always includes the bounds, even for Unbounded_String'Write,
7775 since Unbounded_String is not an array type.
7777 Note that the @code{Stream_Convert} pragma is not effective in the case of
7778 a derived type of a non-limited tagged type. If such a type is specified then
7779 the pragma is silently ignored, and the default implementation of the stream
7780 attributes is used instead.
7782 @node Pragma Style_Checks,Pragma Subtitle,Pragma Stream_Convert,Implementation Defined Pragmas
7783 @anchor{gnat_rm/implementation_defined_pragmas pragma-style-checks}@anchor{ef}
7784 @section Pragma Style_Checks
7790 pragma Style_Checks (string_LITERAL | ALL_CHECKS |
7791 On | Off [, LOCAL_NAME]);
7794 This pragma is used in conjunction with compiler switches to control the
7795 built in style checking provided by GNAT. The compiler switches, if set,
7796 provide an initial setting for the switches, and this pragma may be used
7797 to modify these settings, or the settings may be provided entirely by
7798 the use of the pragma. This pragma can be used anywhere that a pragma
7799 is legal, including use as a configuration pragma (including use in
7800 the @code{gnat.adc} file).
7802 The form with a string literal specifies which style options are to be
7803 activated. These are additive, so they apply in addition to any previously
7804 set style check options. The codes for the options are the same as those
7805 used in the @emph{-gnaty} switch to @emph{gcc} or @emph{gnatmake}.
7806 For example the following two methods can be used to enable
7814 pragma Style_Checks ("l");
7823 The form @code{ALL_CHECKS} activates all standard checks (its use is equivalent
7824 to the use of the @code{gnaty} switch with no options.
7825 See the @cite{GNAT User's Guide} for details.)
7827 Note: the behavior is slightly different in GNAT mode (@code{-gnatg} used).
7828 In this case, @code{ALL_CHECKS} implies the standard set of GNAT mode style check
7829 options (i.e. equivalent to @code{-gnatyg}).
7831 The forms with @code{Off} and @code{On}
7832 can be used to temporarily disable style checks
7833 as shown in the following example:
7836 pragma Style_Checks ("k"); -- requires keywords in lower case
7837 pragma Style_Checks (Off); -- turn off style checks
7838 NULL; -- this will not generate an error message
7839 pragma Style_Checks (On); -- turn style checks back on
7840 NULL; -- this will generate an error message
7843 Finally the two argument form is allowed only if the first argument is
7844 @code{On} or @code{Off}. The effect is to turn of semantic style checks
7845 for the specified entity, as shown in the following example:
7848 pragma Style_Checks ("r"); -- require consistency of identifier casing
7850 Rf1 : Integer := ARG; -- incorrect, wrong case
7851 pragma Style_Checks (Off, Arg);
7852 Rf2 : Integer := ARG; -- OK, no error
7855 @node Pragma Subtitle,Pragma Suppress,Pragma Style_Checks,Implementation Defined Pragmas
7856 @anchor{gnat_rm/implementation_defined_pragmas pragma-subtitle}@anchor{f0}
7857 @section Pragma Subtitle
7863 pragma Subtitle ([Subtitle =>] STRING_LITERAL);
7866 This pragma is recognized for compatibility with other Ada compilers
7867 but is ignored by GNAT.
7869 @node Pragma Suppress,Pragma Suppress_All,Pragma Subtitle,Implementation Defined Pragmas
7870 @anchor{gnat_rm/implementation_defined_pragmas pragma-suppress}@anchor{f1}
7871 @section Pragma Suppress
7877 pragma Suppress (Identifier [, [On =>] Name]);
7880 This is a standard pragma, and supports all the check names required in
7881 the RM. It is included here because GNAT recognizes some additional check
7882 names that are implementation defined (as permitted by the RM):
7888 @code{Alignment_Check} can be used to suppress alignment checks
7889 on addresses used in address clauses. Such checks can also be suppressed
7890 by suppressing range checks, but the specific use of @code{Alignment_Check}
7891 allows suppression of alignment checks without suppressing other range checks.
7892 Note that @code{Alignment_Check} is suppressed by default on machines (such as
7893 the x86) with non-strict alignment.
7896 @code{Atomic_Synchronization} can be used to suppress the special memory
7897 synchronization instructions that are normally generated for access to
7898 @code{Atomic} variables to ensure correct synchronization between tasks
7899 that use such variables for synchronization purposes.
7902 @code{Duplicated_Tag_Check} Can be used to suppress the check that is generated
7903 for a duplicated tag value when a tagged type is declared.
7906 @code{Container_Checks} Can be used to suppress all checks within Ada.Containers
7907 and instances of its children, including Tampering_Check.
7910 @code{Tampering_Check} Can be used to suppress tampering check in the containers.
7913 @code{Predicate_Check} can be used to control whether predicate checks are
7914 active. It is applicable only to predicates for which the policy is
7915 @code{Check}. Unlike @code{Assertion_Policy}, which determines if a given
7916 predicate is ignored or checked for the whole program, the use of
7917 @code{Suppress} and @code{Unsuppress} with this check name allows a given
7918 predicate to be turned on and off at specific points in the program.
7921 @code{Validity_Check} can be used specifically to control validity checks.
7922 If @code{Suppress} is used to suppress validity checks, then no validity
7923 checks are performed, including those specified by the appropriate compiler
7924 switch or the @code{Validity_Checks} pragma.
7927 Additional check names previously introduced by use of the @code{Check_Name}
7928 pragma are also allowed.
7931 Note that pragma Suppress gives the compiler permission to omit
7932 checks, but does not require the compiler to omit checks. The compiler
7933 will generate checks if they are essentially free, even when they are
7934 suppressed. In particular, if the compiler can prove that a certain
7935 check will necessarily fail, it will generate code to do an
7936 unconditional 'raise', even if checks are suppressed. The compiler
7939 Of course, run-time checks are omitted whenever the compiler can prove
7940 that they will not fail, whether or not checks are suppressed.
7942 @node Pragma Suppress_All,Pragma Suppress_Debug_Info,Pragma Suppress,Implementation Defined Pragmas
7943 @anchor{gnat_rm/implementation_defined_pragmas pragma-suppress-all}@anchor{f2}
7944 @section Pragma Suppress_All
7950 pragma Suppress_All;
7953 This pragma can appear anywhere within a unit.
7954 The effect is to apply @code{Suppress (All_Checks)} to the unit
7955 in which it appears. This pragma is implemented for compatibility with DEC
7956 Ada 83 usage where it appears at the end of a unit, and for compatibility
7957 with Rational Ada, where it appears as a program unit pragma.
7958 The use of the standard Ada pragma @code{Suppress (All_Checks)}
7959 as a normal configuration pragma is the preferred usage in GNAT.
7961 @node Pragma Suppress_Debug_Info,Pragma Suppress_Exception_Locations,Pragma Suppress_All,Implementation Defined Pragmas
7962 @anchor{gnat_rm/implementation_defined_pragmas pragma-suppress-debug-info}@anchor{f3}@anchor{gnat_rm/implementation_defined_pragmas id43}@anchor{f4}
7963 @section Pragma Suppress_Debug_Info
7969 pragma Suppress_Debug_Info ([Entity =>] LOCAL_NAME);
7972 This pragma can be used to suppress generation of debug information
7973 for the specified entity. It is intended primarily for use in debugging
7974 the debugger, and navigating around debugger problems.
7976 @node Pragma Suppress_Exception_Locations,Pragma Suppress_Initialization,Pragma Suppress_Debug_Info,Implementation Defined Pragmas
7977 @anchor{gnat_rm/implementation_defined_pragmas pragma-suppress-exception-locations}@anchor{f5}
7978 @section Pragma Suppress_Exception_Locations
7984 pragma Suppress_Exception_Locations;
7987 In normal mode, a raise statement for an exception by default generates
7988 an exception message giving the file name and line number for the location
7989 of the raise. This is useful for debugging and logging purposes, but this
7990 entails extra space for the strings for the messages. The configuration
7991 pragma @code{Suppress_Exception_Locations} can be used to suppress the
7992 generation of these strings, with the result that space is saved, but the
7993 exception message for such raises is null. This configuration pragma may
7994 appear in a global configuration pragma file, or in a specific unit as
7995 usual. It is not required that this pragma be used consistently within
7996 a partition, so it is fine to have some units within a partition compiled
7997 with this pragma and others compiled in normal mode without it.
7999 @node Pragma Suppress_Initialization,Pragma Task_Name,Pragma Suppress_Exception_Locations,Implementation Defined Pragmas
8000 @anchor{gnat_rm/implementation_defined_pragmas id44}@anchor{f6}@anchor{gnat_rm/implementation_defined_pragmas pragma-suppress-initialization}@anchor{f7}
8001 @section Pragma Suppress_Initialization
8004 @geindex Suppressing initialization
8006 @geindex Initialization
8007 @geindex suppression of
8012 pragma Suppress_Initialization ([Entity =>] variable_or_subtype_Name);
8015 Here variable_or_subtype_Name is the name introduced by a type declaration
8016 or subtype declaration or the name of a variable introduced by an
8019 In the case of a type or subtype
8020 this pragma suppresses any implicit or explicit initialization
8021 for all variables of the given type or subtype,
8022 including initialization resulting from the use of pragmas
8023 Normalize_Scalars or Initialize_Scalars.
8025 This is considered a representation item, so it cannot be given after
8026 the type is frozen. It applies to all subsequent object declarations,
8027 and also any allocator that creates objects of the type.
8029 If the pragma is given for the first subtype, then it is considered
8030 to apply to the base type and all its subtypes. If the pragma is given
8031 for other than a first subtype, then it applies only to the given subtype.
8032 The pragma may not be given after the type is frozen.
8034 Note that this includes eliminating initialization of discriminants
8035 for discriminated types, and tags for tagged types. In these cases,
8036 you will have to use some non-portable mechanism (e.g. address
8037 overlays or unchecked conversion) to achieve required initialization
8038 of these fields before accessing any object of the corresponding type.
8040 For the variable case, implicit initialization for the named variable
8041 is suppressed, just as though its subtype had been given in a pragma
8042 Suppress_Initialization, as described above.
8044 @node Pragma Task_Name,Pragma Task_Storage,Pragma Suppress_Initialization,Implementation Defined Pragmas
8045 @anchor{gnat_rm/implementation_defined_pragmas pragma-task-name}@anchor{f8}
8046 @section Pragma Task_Name
8052 pragma Task_Name (string_EXPRESSION);
8055 This pragma appears within a task definition (like pragma
8056 @code{Priority}) and applies to the task in which it appears. The
8057 argument must be of type String, and provides a name to be used for
8058 the task instance when the task is created. Note that this expression
8059 is not required to be static, and in particular, it can contain
8060 references to task discriminants. This facility can be used to
8061 provide different names for different tasks as they are created,
8062 as illustrated in the example below.
8064 The task name is recorded internally in the run-time structures
8065 and is accessible to tools like the debugger. In addition the
8066 routine @code{Ada.Task_Identification.Image} will return this
8067 string, with a unique task address appended.
8070 -- Example of the use of pragma Task_Name
8072 with Ada.Task_Identification;
8073 use Ada.Task_Identification;
8074 with Text_IO; use Text_IO;
8077 type Astring is access String;
8079 task type Task_Typ (Name : access String) is
8080 pragma Task_Name (Name.all);
8083 task body Task_Typ is
8084 Nam : constant String := Image (Current_Task);
8086 Put_Line ("-->" & Nam (1 .. 14) & "<--");
8089 type Ptr_Task is access Task_Typ;
8090 Task_Var : Ptr_Task;
8094 new Task_Typ (new String'("This is task 1"));
8096 new Task_Typ (new String'("This is task 2"));
8100 @node Pragma Task_Storage,Pragma Test_Case,Pragma Task_Name,Implementation Defined Pragmas
8101 @anchor{gnat_rm/implementation_defined_pragmas pragma-task-storage}@anchor{f9}
8102 @section Pragma Task_Storage
8108 pragma Task_Storage (
8109 [Task_Type =>] LOCAL_NAME,
8110 [Top_Guard =>] static_integer_EXPRESSION);
8113 This pragma specifies the length of the guard area for tasks. The guard
8114 area is an additional storage area allocated to a task. A value of zero
8115 means that either no guard area is created or a minimal guard area is
8116 created, depending on the target. This pragma can appear anywhere a
8117 @code{Storage_Size} attribute definition clause is allowed for a task
8120 @node Pragma Test_Case,Pragma Thread_Local_Storage,Pragma Task_Storage,Implementation Defined Pragmas
8121 @anchor{gnat_rm/implementation_defined_pragmas pragma-test-case}@anchor{fa}@anchor{gnat_rm/implementation_defined_pragmas id45}@anchor{fb}
8122 @section Pragma Test_Case
8131 [Name =>] static_string_Expression
8132 ,[Mode =>] (Nominal | Robustness)
8133 [, Requires => Boolean_Expression]
8134 [, Ensures => Boolean_Expression]);
8137 The @code{Test_Case} pragma allows defining fine-grain specifications
8138 for use by testing tools.
8139 The compiler checks the validity of the @code{Test_Case} pragma, but its
8140 presence does not lead to any modification of the code generated by the
8143 @code{Test_Case} pragmas may only appear immediately following the
8144 (separate) declaration of a subprogram in a package declaration, inside
8145 a package spec unit. Only other pragmas may intervene (that is appear
8146 between the subprogram declaration and a test case).
8148 The compiler checks that boolean expressions given in @code{Requires} and
8149 @code{Ensures} are valid, where the rules for @code{Requires} are the
8150 same as the rule for an expression in @code{Precondition} and the rules
8151 for @code{Ensures} are the same as the rule for an expression in
8152 @code{Postcondition}. In particular, attributes @code{'Old} and
8153 @code{'Result} can only be used within the @code{Ensures}
8154 expression. The following is an example of use within a package spec:
8157 package Math_Functions is
8159 function Sqrt (Arg : Float) return Float;
8160 pragma Test_Case (Name => "Test 1",
8162 Requires => Arg < 10000,
8163 Ensures => Sqrt'Result < 10);
8168 The meaning of a test case is that there is at least one context where
8169 @code{Requires} holds such that, if the associated subprogram is executed in
8170 that context, then @code{Ensures} holds when the subprogram returns.
8171 Mode @code{Nominal} indicates that the input context should also satisfy the
8172 precondition of the subprogram, and the output context should also satisfy its
8173 postcondition. Mode @code{Robustness} indicates that the precondition and
8174 postcondition of the subprogram should be ignored for this test case.
8176 @node Pragma Thread_Local_Storage,Pragma Time_Slice,Pragma Test_Case,Implementation Defined Pragmas
8177 @anchor{gnat_rm/implementation_defined_pragmas pragma-thread-local-storage}@anchor{fc}@anchor{gnat_rm/implementation_defined_pragmas id46}@anchor{fd}
8178 @section Pragma Thread_Local_Storage
8181 @geindex Task specific storage
8183 @geindex TLS (Thread Local Storage)
8185 @geindex Task_Attributes
8190 pragma Thread_Local_Storage ([Entity =>] LOCAL_NAME);
8193 This pragma specifies that the specified entity, which must be
8194 a variable declared in a library-level package, is to be marked as
8195 "Thread Local Storage" (@code{TLS}). On systems supporting this (which
8196 include Windows, Solaris, GNU/Linux, and VxWorks 6), this causes each
8197 thread (and hence each Ada task) to see a distinct copy of the variable.
8199 The variable must not have default initialization, and if there is
8200 an explicit initialization, it must be either @code{null} for an
8201 access variable, a static expression for a scalar variable, or a fully
8202 static aggregate for a composite type, that is to say, an aggregate all
8203 of whose components are static, and which does not include packed or
8204 discriminated components.
8206 This provides a low-level mechanism similar to that provided by
8207 the @code{Ada.Task_Attributes} package, but much more efficient
8208 and is also useful in writing interface code that will interact
8209 with foreign threads.
8211 If this pragma is used on a system where @code{TLS} is not supported,
8212 then an error message will be generated and the program will be rejected.
8214 @node Pragma Time_Slice,Pragma Title,Pragma Thread_Local_Storage,Implementation Defined Pragmas
8215 @anchor{gnat_rm/implementation_defined_pragmas pragma-time-slice}@anchor{fe}
8216 @section Pragma Time_Slice
8222 pragma Time_Slice (static_duration_EXPRESSION);
8225 For implementations of GNAT on operating systems where it is possible
8226 to supply a time slice value, this pragma may be used for this purpose.
8227 It is ignored if it is used in a system that does not allow this control,
8228 or if it appears in other than the main program unit.
8230 @node Pragma Title,Pragma Type_Invariant,Pragma Time_Slice,Implementation Defined Pragmas
8231 @anchor{gnat_rm/implementation_defined_pragmas pragma-title}@anchor{ff}
8232 @section Pragma Title
8238 pragma Title (TITLING_OPTION [, TITLING OPTION]);
8241 [Title =>] STRING_LITERAL,
8242 | [Subtitle =>] STRING_LITERAL
8245 Syntax checked but otherwise ignored by GNAT. This is a listing control
8246 pragma used in DEC Ada 83 implementations to provide a title and/or
8247 subtitle for the program listing. The program listing generated by GNAT
8248 does not have titles or subtitles.
8250 Unlike other pragmas, the full flexibility of named notation is allowed
8251 for this pragma, i.e., the parameters may be given in any order if named
8252 notation is used, and named and positional notation can be mixed
8253 following the normal rules for procedure calls in Ada.
8255 @node Pragma Type_Invariant,Pragma Type_Invariant_Class,Pragma Title,Implementation Defined Pragmas
8256 @anchor{gnat_rm/implementation_defined_pragmas pragma-type-invariant}@anchor{100}
8257 @section Pragma Type_Invariant
8263 pragma Type_Invariant
8264 ([Entity =>] type_LOCAL_NAME,
8265 [Check =>] EXPRESSION);
8268 The @code{Type_Invariant} pragma is intended to be an exact
8269 replacement for the language-defined @code{Type_Invariant}
8270 aspect, and shares its restrictions and semantics. It differs
8271 from the language defined @code{Invariant} pragma in that it
8272 does not permit a string parameter, and it is
8273 controlled by the assertion identifier @code{Type_Invariant}
8274 rather than @code{Invariant}.
8276 @node Pragma Type_Invariant_Class,Pragma Unchecked_Union,Pragma Type_Invariant,Implementation Defined Pragmas
8277 @anchor{gnat_rm/implementation_defined_pragmas id47}@anchor{101}@anchor{gnat_rm/implementation_defined_pragmas pragma-type-invariant-class}@anchor{102}
8278 @section Pragma Type_Invariant_Class
8284 pragma Type_Invariant_Class
8285 ([Entity =>] type_LOCAL_NAME,
8286 [Check =>] EXPRESSION);
8289 The @code{Type_Invariant_Class} pragma is intended to be an exact
8290 replacement for the language-defined @code{Type_Invariant'Class}
8291 aspect, and shares its restrictions and semantics.
8293 Note: This pragma is called @code{Type_Invariant_Class} rather than
8294 @code{Type_Invariant'Class} because the latter would not be strictly
8295 conforming to the allowed syntax for pragmas. The motivation
8296 for providing pragmas equivalent to the aspects is to allow a program
8297 to be written using the pragmas, and then compiled if necessary
8298 using an Ada compiler that does not recognize the pragmas or
8299 aspects, but is prepared to ignore the pragmas. The assertion
8300 policy that controls this pragma is @code{Type_Invariant'Class},
8301 not @code{Type_Invariant_Class}.
8303 @node Pragma Unchecked_Union,Pragma Unevaluated_Use_Of_Old,Pragma Type_Invariant_Class,Implementation Defined Pragmas
8304 @anchor{gnat_rm/implementation_defined_pragmas pragma-unchecked-union}@anchor{103}
8305 @section Pragma Unchecked_Union
8308 @geindex Unions in C
8313 pragma Unchecked_Union (first_subtype_LOCAL_NAME);
8316 This pragma is used to specify a representation of a record type that is
8317 equivalent to a C union. It was introduced as a GNAT implementation defined
8318 pragma in the GNAT Ada 95 mode. Ada 2005 includes an extended version of this
8319 pragma, making it language defined, and GNAT fully implements this extended
8320 version in all language modes (Ada 83, Ada 95, and Ada 2005). For full
8321 details, consult the Ada 2012 Reference Manual, section B.3.3.
8323 @node Pragma Unevaluated_Use_Of_Old,Pragma Unimplemented_Unit,Pragma Unchecked_Union,Implementation Defined Pragmas
8324 @anchor{gnat_rm/implementation_defined_pragmas pragma-unevaluated-use-of-old}@anchor{104}
8325 @section Pragma Unevaluated_Use_Of_Old
8328 @geindex Attribute Old
8330 @geindex Attribute Loop_Entry
8332 @geindex Unevaluated_Use_Of_Old
8337 pragma Unevaluated_Use_Of_Old (Error | Warn | Allow);
8340 This pragma controls the processing of attributes Old and Loop_Entry.
8341 If either of these attributes is used in a potentially unevaluated
8342 expression (e.g. the then or else parts of an if expression), then
8343 normally this usage is considered illegal if the prefix of the attribute
8344 is other than an entity name. The language requires this
8345 behavior for Old, and GNAT copies the same rule for Loop_Entry.
8347 The reason for this rule is that otherwise, we can have a situation
8348 where we save the Old value, and this results in an exception, even
8349 though we might not evaluate the attribute. Consider this example:
8352 package UnevalOld is
8354 procedure U (A : String; C : Boolean) -- ERROR
8355 with Post => (if C then A(1)'Old = K else True);
8359 If procedure U is called with a string with a lower bound of 2, and
8360 C false, then an exception would be raised trying to evaluate A(1)
8361 on entry even though the value would not be actually used.
8363 Although the rule guarantees against this possibility, it is sometimes
8364 too restrictive. For example if we know that the string has a lower
8365 bound of 1, then we will never raise an exception.
8366 The pragma @code{Unevaluated_Use_Of_Old} can be
8367 used to modify this behavior. If the argument is @code{Error} then an
8368 error is given (this is the default RM behavior). If the argument is
8369 @code{Warn} then the usage is allowed as legal but with a warning
8370 that an exception might be raised. If the argument is @code{Allow}
8371 then the usage is allowed as legal without generating a warning.
8373 This pragma may appear as a configuration pragma, or in a declarative
8374 part or package specification. In the latter case it applies to
8375 uses up to the end of the corresponding statement sequence or
8376 sequence of package declarations.
8378 @node Pragma Unimplemented_Unit,Pragma Universal_Aliasing,Pragma Unevaluated_Use_Of_Old,Implementation Defined Pragmas
8379 @anchor{gnat_rm/implementation_defined_pragmas pragma-unimplemented-unit}@anchor{105}
8380 @section Pragma Unimplemented_Unit
8386 pragma Unimplemented_Unit;
8389 If this pragma occurs in a unit that is processed by the compiler, GNAT
8390 aborts with the message @code{xxx not implemented}, where
8391 @code{xxx} is the name of the current compilation unit. This pragma is
8392 intended to allow the compiler to handle unimplemented library units in
8395 The abort only happens if code is being generated. Thus you can use
8396 specs of unimplemented packages in syntax or semantic checking mode.
8398 @node Pragma Universal_Aliasing,Pragma Universal_Data,Pragma Unimplemented_Unit,Implementation Defined Pragmas
8399 @anchor{gnat_rm/implementation_defined_pragmas pragma-universal-aliasing}@anchor{106}@anchor{gnat_rm/implementation_defined_pragmas id48}@anchor{107}
8400 @section Pragma Universal_Aliasing
8406 pragma Universal_Aliasing [([Entity =>] type_LOCAL_NAME)];
8409 @code{type_LOCAL_NAME} must refer to a type declaration in the current
8410 declarative part. The effect is to inhibit strict type-based aliasing
8411 optimization for the given type. In other words, the effect is as though
8412 access types designating this type were subject to pragma No_Strict_Aliasing.
8413 For a detailed description of the strict aliasing optimization, and the
8414 situations in which it must be suppressed, see the section on
8415 @code{Optimization and Strict Aliasing} in the @cite{GNAT User's Guide}.
8417 @node Pragma Universal_Data,Pragma Unmodified,Pragma Universal_Aliasing,Implementation Defined Pragmas
8418 @anchor{gnat_rm/implementation_defined_pragmas pragma-universal-data}@anchor{108}@anchor{gnat_rm/implementation_defined_pragmas id49}@anchor{109}
8419 @section Pragma Universal_Data
8425 pragma Universal_Data [(library_unit_Name)];
8428 This pragma is supported only for the AAMP target and is ignored for
8429 other targets. The pragma specifies that all library-level objects
8430 (Counter 0 data) associated with the library unit are to be accessed
8431 and updated using universal addressing (24-bit addresses for AAMP5)
8432 rather than the default of 16-bit Data Environment (DENV) addressing.
8433 Use of this pragma will generally result in less efficient code for
8434 references to global data associated with the library unit, but
8435 allows such data to be located anywhere in memory. This pragma is
8436 a library unit pragma, but can also be used as a configuration pragma
8437 (including use in the @code{gnat.adc} file). The functionality
8438 of this pragma is also available by applying the -univ switch on the
8439 compilations of units where universal addressing of the data is desired.
8441 @node Pragma Unmodified,Pragma Unreferenced,Pragma Universal_Data,Implementation Defined Pragmas
8442 @anchor{gnat_rm/implementation_defined_pragmas id50}@anchor{10a}@anchor{gnat_rm/implementation_defined_pragmas pragma-unmodified}@anchor{10b}
8443 @section Pragma Unmodified
8452 pragma Unmodified (LOCAL_NAME @{, LOCAL_NAME@});
8455 This pragma signals that the assignable entities (variables,
8456 @code{out} parameters, @code{in out} parameters) whose names are listed are
8457 deliberately not assigned in the current source unit. This
8458 suppresses warnings about the
8459 entities being referenced but not assigned, and in addition a warning will be
8460 generated if one of these entities is in fact assigned in the
8461 same unit as the pragma (or in the corresponding body, or one
8464 This is particularly useful for clearly signaling that a particular
8465 parameter is not modified, even though the spec suggests that it might
8468 For the variable case, warnings are never given for unreferenced variables
8469 whose name contains one of the substrings
8470 @code{DISCARD, DUMMY, IGNORE, JUNK, UNUSED} in any casing. Such names
8471 are typically to be used in cases where such warnings are expected.
8472 Thus it is never necessary to use @code{pragma Unmodified} for such
8473 variables, though it is harmless to do so.
8475 @node Pragma Unreferenced,Pragma Unreferenced_Objects,Pragma Unmodified,Implementation Defined Pragmas
8476 @anchor{gnat_rm/implementation_defined_pragmas pragma-unreferenced}@anchor{10c}@anchor{gnat_rm/implementation_defined_pragmas id51}@anchor{10d}
8477 @section Pragma Unreferenced
8481 @geindex unreferenced
8486 pragma Unreferenced (LOCAL_NAME @{, LOCAL_NAME@});
8487 pragma Unreferenced (library_unit_NAME @{, library_unit_NAME@});
8490 This pragma signals that the entities whose names are listed are
8491 deliberately not referenced in the current source unit after the
8492 occurrence of the pragma. This
8493 suppresses warnings about the
8494 entities being unreferenced, and in addition a warning will be
8495 generated if one of these entities is in fact subsequently referenced in the
8496 same unit as the pragma (or in the corresponding body, or one
8499 This is particularly useful for clearly signaling that a particular
8500 parameter is not referenced in some particular subprogram implementation
8501 and that this is deliberate. It can also be useful in the case of
8502 objects declared only for their initialization or finalization side
8505 If @code{LOCAL_NAME} identifies more than one matching homonym in the
8506 current scope, then the entity most recently declared is the one to which
8507 the pragma applies. Note that in the case of accept formals, the pragma
8508 Unreferenced may appear immediately after the keyword @code{do} which
8509 allows the indication of whether or not accept formals are referenced
8510 or not to be given individually for each accept statement.
8512 The left hand side of an assignment does not count as a reference for the
8513 purpose of this pragma. Thus it is fine to assign to an entity for which
8514 pragma Unreferenced is given.
8516 Note that if a warning is desired for all calls to a given subprogram,
8517 regardless of whether they occur in the same unit as the subprogram
8518 declaration, then this pragma should not be used (calls from another
8519 unit would not be flagged); pragma Obsolescent can be used instead
8520 for this purpose, see @ref{ac,,Pragma Obsolescent}.
8522 The second form of pragma @code{Unreferenced} is used within a context
8523 clause. In this case the arguments must be unit names of units previously
8524 mentioned in @code{with} clauses (similar to the usage of pragma
8525 @code{Elaborate_All}. The effect is to suppress warnings about unreferenced
8526 units and unreferenced entities within these units.
8528 For the variable case, warnings are never given for unreferenced variables
8529 whose name contains one of the substrings
8530 @code{DISCARD, DUMMY, IGNORE, JUNK, UNUSED} in any casing. Such names
8531 are typically to be used in cases where such warnings are expected.
8532 Thus it is never necessary to use @code{pragma Unreferenced} for such
8533 variables, though it is harmless to do so.
8535 @node Pragma Unreferenced_Objects,Pragma Unreserve_All_Interrupts,Pragma Unreferenced,Implementation Defined Pragmas
8536 @anchor{gnat_rm/implementation_defined_pragmas pragma-unreferenced-objects}@anchor{10e}@anchor{gnat_rm/implementation_defined_pragmas id52}@anchor{10f}
8537 @section Pragma Unreferenced_Objects
8541 @geindex unreferenced
8546 pragma Unreferenced_Objects (local_subtype_NAME @{, local_subtype_NAME@});
8549 This pragma signals that for the types or subtypes whose names are
8550 listed, objects which are declared with one of these types or subtypes may
8551 not be referenced, and if no references appear, no warnings are given.
8553 This is particularly useful for objects which are declared solely for their
8554 initialization and finalization effect. Such variables are sometimes referred
8555 to as RAII variables (Resource Acquisition Is Initialization). Using this
8556 pragma on the relevant type (most typically a limited controlled type), the
8557 compiler will automatically suppress unwanted warnings about these variables
8558 not being referenced.
8560 @node Pragma Unreserve_All_Interrupts,Pragma Unsuppress,Pragma Unreferenced_Objects,Implementation Defined Pragmas
8561 @anchor{gnat_rm/implementation_defined_pragmas pragma-unreserve-all-interrupts}@anchor{110}
8562 @section Pragma Unreserve_All_Interrupts
8568 pragma Unreserve_All_Interrupts;
8571 Normally certain interrupts are reserved to the implementation. Any attempt
8572 to attach an interrupt causes Program_Error to be raised, as described in
8573 RM C.3.2(22). A typical example is the @code{SIGINT} interrupt used in
8574 many systems for a @code{Ctrl-C} interrupt. Normally this interrupt is
8575 reserved to the implementation, so that @code{Ctrl-C} can be used to
8576 interrupt execution.
8578 If the pragma @code{Unreserve_All_Interrupts} appears anywhere in any unit in
8579 a program, then all such interrupts are unreserved. This allows the
8580 program to handle these interrupts, but disables their standard
8581 functions. For example, if this pragma is used, then pressing
8582 @code{Ctrl-C} will not automatically interrupt execution. However,
8583 a program can then handle the @code{SIGINT} interrupt as it chooses.
8585 For a full list of the interrupts handled in a specific implementation,
8586 see the source code for the spec of @code{Ada.Interrupts.Names} in
8587 file @code{a-intnam.ads}. This is a target dependent file that contains the
8588 list of interrupts recognized for a given target. The documentation in
8589 this file also specifies what interrupts are affected by the use of
8590 the @code{Unreserve_All_Interrupts} pragma.
8592 For a more general facility for controlling what interrupts can be
8593 handled, see pragma @code{Interrupt_State}, which subsumes the functionality
8594 of the @code{Unreserve_All_Interrupts} pragma.
8596 @node Pragma Unsuppress,Pragma Use_VADS_Size,Pragma Unreserve_All_Interrupts,Implementation Defined Pragmas
8597 @anchor{gnat_rm/implementation_defined_pragmas pragma-unsuppress}@anchor{111}
8598 @section Pragma Unsuppress
8604 pragma Unsuppress (IDENTIFIER [, [On =>] NAME]);
8607 This pragma undoes the effect of a previous pragma @code{Suppress}. If
8608 there is no corresponding pragma @code{Suppress} in effect, it has no
8609 effect. The range of the effect is the same as for pragma
8610 @code{Suppress}. The meaning of the arguments is identical to that used
8611 in pragma @code{Suppress}.
8613 One important application is to ensure that checks are on in cases where
8614 code depends on the checks for its correct functioning, so that the code
8615 will compile correctly even if the compiler switches are set to suppress
8616 checks. For example, in a program that depends on external names of tagged
8617 types and wants to ensure that the duplicated tag check occurs even if all
8618 run-time checks are suppressed by a compiler switch, the following
8619 configuration pragma will ensure this test is not suppressed:
8622 pragma Unsuppress (Duplicated_Tag_Check);
8625 This pragma is standard in Ada 2005. It is available in all earlier versions
8626 of Ada as an implementation-defined pragma.
8628 Note that in addition to the checks defined in the Ada RM, GNAT recogizes a
8629 number of implementation-defined check names. See the description of pragma
8630 @code{Suppress} for full details.
8632 @node Pragma Use_VADS_Size,Pragma Unused,Pragma Unsuppress,Implementation Defined Pragmas
8633 @anchor{gnat_rm/implementation_defined_pragmas pragma-use-vads-size}@anchor{112}
8634 @section Pragma Use_VADS_Size
8638 @geindex VADS compatibility
8640 @geindex Rational profile
8645 pragma Use_VADS_Size;
8648 This is a configuration pragma. In a unit to which it applies, any use
8649 of the 'Size attribute is automatically interpreted as a use of the
8650 'VADS_Size attribute. Note that this may result in incorrect semantic
8651 processing of valid Ada 95 or Ada 2005 programs. This is intended to aid in
8652 the handling of existing code which depends on the interpretation of Size
8653 as implemented in the VADS compiler. See description of the VADS_Size
8654 attribute for further details.
8656 @node Pragma Unused,Pragma Validity_Checks,Pragma Use_VADS_Size,Implementation Defined Pragmas
8657 @anchor{gnat_rm/implementation_defined_pragmas pragma-unused}@anchor{113}@anchor{gnat_rm/implementation_defined_pragmas id53}@anchor{114}
8658 @section Pragma Unused
8667 pragma Unused (LOCAL_NAME @{, LOCAL_NAME@});
8670 This pragma signals that the assignable entities (variables,
8671 @code{out} parameters, and @code{in out} parameters) whose names are listed
8672 deliberately do not get assigned or referenced in the current source unit
8673 after the occurrence of the pragma in the current source unit. This
8674 suppresses warnings about the entities that are unreferenced and/or not
8675 assigned, and, in addition, a warning will be generated if one of these
8676 entities gets assigned or subsequently referenced in the same unit as the
8677 pragma (in the corresponding body or one of its subunits).
8679 This is particularly useful for clearly signaling that a particular
8680 parameter is not modified or referenced, even though the spec suggests
8683 For the variable case, warnings are never given for unreferenced
8684 variables whose name contains one of the substrings
8685 @code{DISCARD, DUMMY, IGNORE, JUNK, UNUSED} in any casing. Such names
8686 are typically to be used in cases where such warnings are expected.
8687 Thus it is never necessary to use @code{pragma Unmodified} for such
8688 variables, though it is harmless to do so.
8690 @node Pragma Validity_Checks,Pragma Volatile,Pragma Unused,Implementation Defined Pragmas
8691 @anchor{gnat_rm/implementation_defined_pragmas pragma-validity-checks}@anchor{115}
8692 @section Pragma Validity_Checks
8698 pragma Validity_Checks (string_LITERAL | ALL_CHECKS | On | Off);
8701 This pragma is used in conjunction with compiler switches to control the
8702 built-in validity checking provided by GNAT. The compiler switches, if set
8703 provide an initial setting for the switches, and this pragma may be used
8704 to modify these settings, or the settings may be provided entirely by
8705 the use of the pragma. This pragma can be used anywhere that a pragma
8706 is legal, including use as a configuration pragma (including use in
8707 the @code{gnat.adc} file).
8709 The form with a string literal specifies which validity options are to be
8710 activated. The validity checks are first set to include only the default
8711 reference manual settings, and then a string of letters in the string
8712 specifies the exact set of options required. The form of this string
8713 is exactly as described for the @emph{-gnatVx} compiler switch (see the
8714 GNAT User's Guide for details). For example the following two
8715 methods can be used to enable validity checking for mode @code{in} and
8716 @code{in out} subprogram parameters:
8723 pragma Validity_Checks ("im");
8728 $ gcc -c -gnatVim ...
8732 The form ALL_CHECKS activates all standard checks (its use is equivalent
8733 to the use of the @code{gnatVa} switch).
8735 The forms with @code{Off} and @code{On} can be used to temporarily disable
8736 validity checks as shown in the following example:
8739 pragma Validity_Checks ("c"); -- validity checks for copies
8740 pragma Validity_Checks (Off); -- turn off validity checks
8741 A := B; -- B will not be validity checked
8742 pragma Validity_Checks (On); -- turn validity checks back on
8743 A := C; -- C will be validity checked
8746 @node Pragma Volatile,Pragma Volatile_Full_Access,Pragma Validity_Checks,Implementation Defined Pragmas
8747 @anchor{gnat_rm/implementation_defined_pragmas id54}@anchor{116}@anchor{gnat_rm/implementation_defined_pragmas pragma-volatile}@anchor{117}
8748 @section Pragma Volatile
8754 pragma Volatile (LOCAL_NAME);
8757 This pragma is defined by the Ada Reference Manual, and the GNAT
8758 implementation is fully conformant with this definition. The reason it
8759 is mentioned in this section is that a pragma of the same name was supplied
8760 in some Ada 83 compilers, including DEC Ada 83. The Ada 95 / Ada 2005
8761 implementation of pragma Volatile is upwards compatible with the
8762 implementation in DEC Ada 83.
8764 @node Pragma Volatile_Full_Access,Pragma Volatile_Function,Pragma Volatile,Implementation Defined Pragmas
8765 @anchor{gnat_rm/implementation_defined_pragmas id55}@anchor{118}@anchor{gnat_rm/implementation_defined_pragmas pragma-volatile-full-access}@anchor{119}
8766 @section Pragma Volatile_Full_Access
8772 pragma Volatile_Full_Access (LOCAL_NAME);
8775 This is similar in effect to pragma Volatile, except that any reference to the
8776 object is guaranteed to be done only with instructions that read or write all
8777 the bits of the object. Furthermore, if the object is of a composite type,
8778 then any reference to a subcomponent of the object is guaranteed to read
8779 and/or write all the bits of the object.
8781 The intention is that this be suitable for use with memory-mapped I/O devices
8782 on some machines. Note that there are two important respects in which this is
8783 different from @code{pragma Atomic}. First a reference to a @code{Volatile_Full_Access}
8784 object is not a sequential action in the RM 9.10 sense and, therefore, does
8785 not create a synchronization point. Second, in the case of @code{pragma Atomic},
8786 there is no guarantee that all the bits will be accessed if the reference
8787 is not to the whole object; the compiler is allowed (and generally will)
8788 access only part of the object in this case.
8790 @node Pragma Volatile_Function,Pragma Warning_As_Error,Pragma Volatile_Full_Access,Implementation Defined Pragmas
8791 @anchor{gnat_rm/implementation_defined_pragmas id56}@anchor{11a}@anchor{gnat_rm/implementation_defined_pragmas pragma-volatile-function}@anchor{11b}
8792 @section Pragma Volatile_Function
8798 pragma Volatile_Function [ (boolean_EXPRESSION) ];
8801 For the semantics of this pragma, see the entry for aspect @code{Volatile_Function}
8802 in the SPARK 2014 Reference Manual, section 7.1.2.
8804 @node Pragma Warning_As_Error,Pragma Warnings,Pragma Volatile_Function,Implementation Defined Pragmas
8805 @anchor{gnat_rm/implementation_defined_pragmas pragma-warning-as-error}@anchor{11c}
8806 @section Pragma Warning_As_Error
8812 pragma Warning_As_Error (static_string_EXPRESSION);
8815 This configuration pragma allows the programmer to specify a set
8816 of warnings that will be treated as errors. Any warning that
8817 matches the pattern given by the pragma argument will be treated
8818 as an error. This gives more precise control than -gnatwe,
8819 which treats warnings as errors.
8821 This pragma can apply to regular warnings (messages enabled by -gnatw)
8822 and to style warnings (messages that start with "(style)",
8825 The pattern may contain asterisks, which match zero or more characters
8826 in the message. For example, you can use @code{pragma Warning_As_Error
8827 ("bits of*unused")} to treat the warning message @code{warning: 960 bits of
8828 "a" unused} as an error. All characters other than asterisk are treated
8829 as literal characters in the match. The match is case insensitive; for
8830 example XYZ matches xyz.
8832 Note that the pattern matches if it occurs anywhere within the warning
8833 message string (it is not necessary to put an asterisk at the start and
8834 the end of the message, since this is implied).
8836 Another possibility for the static_string_EXPRESSION which works whether
8837 or not error tags are enabled (@emph{-gnatw.d}) is to use a single
8838 @emph{-gnatw} tag string, enclosed in brackets,
8839 as shown in the example below, to treat one category of warnings as errors.
8840 Note that if you want to treat multiple categories of warnings as errors,
8841 you can use multiple pragma Warning_As_Error.
8843 The above use of patterns to match the message applies only to warning
8844 messages generated by the front end. This pragma can also be applied to
8845 warnings provided by the back end and mentioned in @ref{11d,,Pragma Warnings}.
8846 By using a single full @emph{-Wxxx} switch in the pragma, such warnings
8847 can also be treated as errors.
8849 The pragma can appear either in a global configuration pragma file
8850 (e.g. @code{gnat.adc}), or at the start of a file. Given a global
8851 configuration pragma file containing:
8854 pragma Warning_As_Error ("[-gnatwj]");
8857 which will treat all obsolescent feature warnings as errors, the
8858 following program compiles as shown (compile options here are
8859 @emph{-gnatwa.d -gnatl -gnatj55}).
8862 1. pragma Warning_As_Error ("*never assigned*");
8863 2. function Warnerr return String is
8866 >>> error: variable "X" is never read and
8867 never assigned [-gnatwv] [warning-as-error]
8871 >>> warning: variable "Y" is assigned but
8872 never read [-gnatwu]
8878 >>> error: use of "%" is an obsolescent
8879 feature (RM J.2(4)), use """ instead
8880 [-gnatwj] [warning-as-error]
8884 8 lines: No errors, 3 warnings (2 treated as errors)
8887 Note that this pragma does not affect the set of warnings issued in
8888 any way, it merely changes the effect of a matching warning if one
8889 is produced as a result of other warnings options. As shown in this
8890 example, if the pragma results in a warning being treated as an error,
8891 the tag is changed from "warning:" to "error:" and the string
8892 "[warning-as-error]" is appended to the end of the message.
8894 @node Pragma Warnings,Pragma Weak_External,Pragma Warning_As_Error,Implementation Defined Pragmas
8895 @anchor{gnat_rm/implementation_defined_pragmas id57}@anchor{11e}@anchor{gnat_rm/implementation_defined_pragmas pragma-warnings}@anchor{11d}
8896 @section Pragma Warnings
8902 pragma Warnings ([TOOL_NAME,] DETAILS [, REASON]);
8904 DETAILS ::= On | Off
8905 DETAILS ::= On | Off, local_NAME
8906 DETAILS ::= static_string_EXPRESSION
8907 DETAILS ::= On | Off, static_string_EXPRESSION
8909 TOOL_NAME ::= GNAT | GNATprove
8911 REASON ::= Reason => STRING_LITERAL @{& STRING_LITERAL@}
8914 Note: in Ada 83 mode, a string literal may be used in place of a static string
8915 expression (which does not exist in Ada 83).
8917 Note if the second argument of @code{DETAILS} is a @code{local_NAME} then the
8918 second form is always understood. If the intention is to use
8919 the fourth form, then you can write @code{NAME & ""} to force the
8920 intepretation as a @emph{static_string_EXPRESSION}.
8922 Note: if the first argument is a valid @code{TOOL_NAME}, it will be interpreted
8923 that way. The use of the @code{TOOL_NAME} argument is relevant only to users
8924 of SPARK and GNATprove, see last part of this section for details.
8926 Normally warnings are enabled, with the output being controlled by
8927 the command line switch. Warnings (@code{Off}) turns off generation of
8928 warnings until a Warnings (@code{On}) is encountered or the end of the
8929 current unit. If generation of warnings is turned off using this
8930 pragma, then some or all of the warning messages are suppressed,
8931 regardless of the setting of the command line switches.
8933 The @code{Reason} parameter may optionally appear as the last argument
8934 in any of the forms of this pragma. It is intended purely for the
8935 purposes of documenting the reason for the @code{Warnings} pragma.
8936 The compiler will check that the argument is a static string but
8937 otherwise ignore this argument. Other tools may provide specialized
8938 processing for this string.
8940 The form with a single argument (or two arguments if Reason present),
8941 where the first argument is @code{ON} or @code{OFF}
8942 may be used as a configuration pragma.
8944 If the @code{LOCAL_NAME} parameter is present, warnings are suppressed for
8945 the specified entity. This suppression is effective from the point where
8946 it occurs till the end of the extended scope of the variable (similar to
8947 the scope of @code{Suppress}). This form cannot be used as a configuration
8950 In the case where the first argument is other than @code{ON} or
8952 the third form with a single static_string_EXPRESSION argument (and possible
8953 reason) provides more precise
8954 control over which warnings are active. The string is a list of letters
8955 specifying which warnings are to be activated and which deactivated. The
8956 code for these letters is the same as the string used in the command
8957 line switch controlling warnings. For a brief summary, use the gnatmake
8958 command with no arguments, which will generate usage information containing
8959 the list of warnings switches supported. For
8960 full details see the section on @code{Warning Message Control} in the
8961 @cite{GNAT User's Guide}.
8962 This form can also be used as a configuration pragma.
8964 The warnings controlled by the @code{-gnatw} switch are generated by the
8965 front end of the compiler. The GCC back end can provide additional warnings
8966 and they are controlled by the @code{-W} switch. Such warnings can be
8967 identified by the appearance of a string of the form @code{[-W@{xxx@}]} in the
8968 message which designates the @code{-W@emph{xxx}} switch that controls the message.
8969 The form with a single @emph{static_string_EXPRESSION} argument also works for these
8970 warnings, but the string must be a single full @code{-W@emph{xxx}} switch in this
8971 case. The above reference lists a few examples of these additional warnings.
8973 The specified warnings will be in effect until the end of the program
8974 or another pragma @code{Warnings} is encountered. The effect of the pragma is
8975 cumulative. Initially the set of warnings is the standard default set
8976 as possibly modified by compiler switches. Then each pragma Warning
8977 modifies this set of warnings as specified. This form of the pragma may
8978 also be used as a configuration pragma.
8980 The fourth form, with an @code{On|Off} parameter and a string, is used to
8981 control individual messages, based on their text. The string argument
8982 is a pattern that is used to match against the text of individual
8983 warning messages (not including the initial "warning: " tag).
8985 The pattern may contain asterisks, which match zero or more characters in
8986 the message. For example, you can use
8987 @code{pragma Warnings (Off, "bits of*unused")} to suppress the warning
8988 message @code{warning: 960 bits of "a" unused}. No other regular
8989 expression notations are permitted. All characters other than asterisk in
8990 these three specific cases are treated as literal characters in the match.
8991 The match is case insensitive, for example XYZ matches xyz.
8993 Note that the pattern matches if it occurs anywhere within the warning
8994 message string (it is not necessary to put an asterisk at the start and
8995 the end of the message, since this is implied).
8997 The above use of patterns to match the message applies only to warning
8998 messages generated by the front end. This form of the pragma with a string
8999 argument can also be used to control warnings provided by the back end and
9000 mentioned above. By using a single full @code{-W@emph{xxx}} switch in the pragma,
9001 such warnings can be turned on and off.
9003 There are two ways to use the pragma in this form. The OFF form can be used
9004 as a configuration pragma. The effect is to suppress all warnings (if any)
9005 that match the pattern string throughout the compilation (or match the
9006 -W switch in the back end case).
9008 The second usage is to suppress a warning locally, and in this case, two
9009 pragmas must appear in sequence:
9012 pragma Warnings (Off, Pattern);
9013 ... code where given warning is to be suppressed
9014 pragma Warnings (On, Pattern);
9017 In this usage, the pattern string must match in the Off and On
9018 pragmas, and (if @emph{-gnatw.w} is given) at least one matching
9019 warning must be suppressed.
9021 Note: if the ON form is not found, then the effect of the OFF form extends
9022 until the end of the file (pragma Warnings is purely textual, so its effect
9023 does not stop at the end of the enclosing scope).
9025 Note: to write a string that will match any warning, use the string
9026 @code{"***"}. It will not work to use a single asterisk or two
9027 asterisks since this looks like an operator name. This form with three
9028 asterisks is similar in effect to specifying @code{pragma Warnings (Off)} except (if @code{-gnatw.w} is given) that a matching
9029 @code{pragma Warnings (On, "***")} will be required. This can be
9030 helpful in avoiding forgetting to turn warnings back on.
9032 Note: the debug flag @code{-gnatd.i} can be
9033 used to cause the compiler to entirely ignore all WARNINGS pragmas. This can
9034 be useful in checking whether obsolete pragmas in existing programs are hiding
9037 Note: pragma Warnings does not affect the processing of style messages. See
9038 separate entry for pragma Style_Checks for control of style messages.
9040 Users of the formal verification tool GNATprove for the SPARK subset of Ada may
9041 use the version of the pragma with a @code{TOOL_NAME} parameter.
9043 If present, @code{TOOL_NAME} is the name of a tool, currently either @code{GNAT} for the
9044 compiler or @code{GNATprove} for the formal verification tool. A given tool only
9045 takes into account pragma Warnings that do not specify a tool name, or that
9046 specify the matching tool name. This makes it possible to disable warnings
9047 selectively for each tool, and as a consequence to detect useless pragma
9048 Warnings with switch @code{-gnatw.w}.
9050 @node Pragma Weak_External,Pragma Wide_Character_Encoding,Pragma Warnings,Implementation Defined Pragmas
9051 @anchor{gnat_rm/implementation_defined_pragmas pragma-weak-external}@anchor{11f}
9052 @section Pragma Weak_External
9058 pragma Weak_External ([Entity =>] LOCAL_NAME);
9061 @code{LOCAL_NAME} must refer to an object that is declared at the library
9062 level. This pragma specifies that the given entity should be marked as a
9063 weak symbol for the linker. It is equivalent to @code{__attribute__((weak))}
9064 in GNU C and causes @code{LOCAL_NAME} to be emitted as a weak symbol instead
9065 of a regular symbol, that is to say a symbol that does not have to be
9066 resolved by the linker if used in conjunction with a pragma Import.
9068 When a weak symbol is not resolved by the linker, its address is set to
9069 zero. This is useful in writing interfaces to external modules that may
9070 or may not be linked in the final executable, for example depending on
9071 configuration settings.
9073 If a program references at run time an entity to which this pragma has been
9074 applied, and the corresponding symbol was not resolved at link time, then
9075 the execution of the program is erroneous. It is not erroneous to take the
9076 Address of such an entity, for example to guard potential references,
9077 as shown in the example below.
9079 Some file formats do not support weak symbols so not all target machines
9080 support this pragma.
9083 -- Example of the use of pragma Weak_External
9085 package External_Module is
9087 pragma Import (C, key);
9088 pragma Weak_External (key);
9089 function Present return boolean;
9090 end External_Module;
9092 with System; use System;
9093 package body External_Module is
9094 function Present return boolean is
9096 return key'Address /= System.Null_Address;
9098 end External_Module;
9101 @node Pragma Wide_Character_Encoding,,Pragma Weak_External,Implementation Defined Pragmas
9102 @anchor{gnat_rm/implementation_defined_pragmas pragma-wide-character-encoding}@anchor{120}
9103 @section Pragma Wide_Character_Encoding
9109 pragma Wide_Character_Encoding (IDENTIFIER | CHARACTER_LITERAL);
9112 This pragma specifies the wide character encoding to be used in program
9113 source text appearing subsequently. It is a configuration pragma, but may
9114 also be used at any point that a pragma is allowed, and it is permissible
9115 to have more than one such pragma in a file, allowing multiple encodings
9116 to appear within the same file.
9118 However, note that the pragma cannot immediately precede the relevant
9119 wide character, because then the previous encoding will still be in
9120 effect, causing "illegal character" errors.
9122 The argument can be an identifier or a character literal. In the identifier
9123 case, it is one of @code{HEX}, @code{UPPER}, @code{SHIFT_JIS},
9124 @code{EUC}, @code{UTF8}, or @code{BRACKETS}. In the character literal
9125 case it is correspondingly one of the characters @code{h}, @code{u},
9126 @code{s}, @code{e}, @code{8}, or @code{b}.
9128 Note that when the pragma is used within a file, it affects only the
9129 encoding within that file, and does not affect withed units, specs,
9132 @node Implementation Defined Aspects,Implementation Defined Attributes,Implementation Defined Pragmas,Top
9133 @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}
9134 @chapter Implementation Defined Aspects
9137 Ada defines (throughout the Ada 2012 reference manual, summarized
9138 in Annex K) a set of aspects that can be specified for certain entities.
9139 These language defined aspects are implemented in GNAT in Ada 2012 mode
9140 and work as described in the Ada 2012 Reference Manual.
9142 In addition, Ada 2012 allows implementations to define additional aspects
9143 whose meaning is defined by the implementation. GNAT provides
9144 a number of these implementation-defined aspects which can be used
9145 to extend and enhance the functionality of the compiler. This section of
9146 the GNAT reference manual describes these additional aspects.
9148 Note that any program using these aspects may not be portable to
9149 other compilers (although GNAT implements this set of aspects on all
9150 platforms). Therefore if portability to other compilers is an important
9151 consideration, you should minimize the use of these aspects.
9153 Note that for many of these aspects, the effect is essentially similar
9154 to the use of a pragma or attribute specification with the same name
9155 applied to the entity. For example, if we write:
9158 type R is range 1 .. 100
9159 with Value_Size => 10;
9162 then the effect is the same as:
9165 type R is range 1 .. 100;
9166 for R'Value_Size use 10;
9172 type R is new Integer
9173 with Shared => True;
9176 then the effect is the same as:
9179 type R is new Integer;
9183 In the documentation below, such cases are simply marked
9184 as being boolean aspects equivalent to the corresponding pragma
9185 or attribute definition clause.
9188 * Aspect Abstract_State::
9190 * Aspect Async_Readers::
9191 * Aspect Async_Writers::
9192 * Aspect Constant_After_Elaboration::
9193 * Aspect Contract_Cases::
9195 * Aspect Default_Initial_Condition::
9196 * Aspect Dimension::
9197 * Aspect Dimension_System::
9198 * Aspect Disable_Controlled::
9199 * Aspect Effective_Reads::
9200 * Aspect Effective_Writes::
9201 * Aspect Extensions_Visible::
9202 * Aspect Favor_Top_Level::
9205 * Aspect Initial_Condition::
9206 * Aspect Initializes::
9207 * Aspect Inline_Always::
9208 * Aspect Invariant::
9209 * Aspect Invariant'Class::
9211 * Aspect Linker_Section::
9212 * Aspect Lock_Free::
9213 * Aspect Max_Queue_Length::
9214 * Aspect No_Caching::
9215 * Aspect No_Elaboration_Code_All::
9216 * Aspect No_Inline::
9217 * Aspect No_Tagged_Streams::
9218 * Aspect Object_Size::
9219 * Aspect Obsolescent::
9221 * Aspect Persistent_BSS::
9222 * Aspect Predicate::
9223 * Aspect Pure_Function::
9224 * Aspect Refined_Depends::
9225 * Aspect Refined_Global::
9226 * Aspect Refined_Post::
9227 * Aspect Refined_State::
9228 * Aspect Relaxed_Initialization::
9229 * Aspect Remote_Access_Type::
9230 * Aspect Secondary_Stack_Size::
9231 * Aspect Scalar_Storage_Order::
9233 * Aspect Simple_Storage_Pool::
9234 * Aspect Simple_Storage_Pool_Type::
9235 * Aspect SPARK_Mode::
9236 * Aspect Suppress_Debug_Info::
9237 * Aspect Suppress_Initialization::
9238 * Aspect Test_Case::
9239 * Aspect Thread_Local_Storage::
9240 * Aspect Universal_Aliasing::
9241 * Aspect Universal_Data::
9242 * Aspect Unmodified::
9243 * Aspect Unreferenced::
9244 * Aspect Unreferenced_Objects::
9245 * Aspect Value_Size::
9246 * Aspect Volatile_Full_Access::
9247 * Aspect Volatile_Function::
9252 @node Aspect Abstract_State,Aspect Annotate,,Implementation Defined Aspects
9253 @anchor{gnat_rm/implementation_defined_aspects aspect-abstract-state}@anchor{124}
9254 @section Aspect Abstract_State
9257 @geindex Abstract_State
9259 This aspect is equivalent to @ref{1c,,pragma Abstract_State}.
9261 @node Aspect Annotate,Aspect Async_Readers,Aspect Abstract_State,Implementation Defined Aspects
9262 @anchor{gnat_rm/implementation_defined_aspects aspect-annotate}@anchor{125}
9263 @section Aspect Annotate
9268 There are three forms of this aspect (where ID is an identifier,
9269 and ARG is a general expression),
9270 corresponding to @ref{26,,pragma Annotate}.
9275 @item @emph{Annotate => ID}
9277 Equivalent to @code{pragma Annotate (ID, Entity => Name);}
9279 @item @emph{Annotate => (ID)}
9281 Equivalent to @code{pragma Annotate (ID, Entity => Name);}
9283 @item @emph{Annotate => (ID ,ID @{, ARG@})}
9285 Equivalent to @code{pragma Annotate (ID, ID @{, ARG@}, Entity => Name);}
9288 @node Aspect Async_Readers,Aspect Async_Writers,Aspect Annotate,Implementation Defined Aspects
9289 @anchor{gnat_rm/implementation_defined_aspects aspect-async-readers}@anchor{126}
9290 @section Aspect Async_Readers
9293 @geindex Async_Readers
9295 This boolean aspect is equivalent to @ref{2d,,pragma Async_Readers}.
9297 @node Aspect Async_Writers,Aspect Constant_After_Elaboration,Aspect Async_Readers,Implementation Defined Aspects
9298 @anchor{gnat_rm/implementation_defined_aspects aspect-async-writers}@anchor{127}
9299 @section Aspect Async_Writers
9302 @geindex Async_Writers
9304 This boolean aspect is equivalent to @ref{30,,pragma Async_Writers}.
9306 @node Aspect Constant_After_Elaboration,Aspect Contract_Cases,Aspect Async_Writers,Implementation Defined Aspects
9307 @anchor{gnat_rm/implementation_defined_aspects aspect-constant-after-elaboration}@anchor{128}
9308 @section Aspect Constant_After_Elaboration
9311 @geindex Constant_After_Elaboration
9313 This aspect is equivalent to @ref{42,,pragma Constant_After_Elaboration}.
9315 @node Aspect Contract_Cases,Aspect Depends,Aspect Constant_After_Elaboration,Implementation Defined Aspects
9316 @anchor{gnat_rm/implementation_defined_aspects aspect-contract-cases}@anchor{129}
9317 @section Aspect Contract_Cases
9320 @geindex Contract_Cases
9322 This aspect is equivalent to @ref{44,,pragma Contract_Cases}, the sequence
9323 of clauses being enclosed in parentheses so that syntactically it is an
9326 @node Aspect Depends,Aspect Default_Initial_Condition,Aspect Contract_Cases,Implementation Defined Aspects
9327 @anchor{gnat_rm/implementation_defined_aspects aspect-depends}@anchor{12a}
9328 @section Aspect Depends
9333 This aspect is equivalent to @ref{53,,pragma Depends}.
9335 @node Aspect Default_Initial_Condition,Aspect Dimension,Aspect Depends,Implementation Defined Aspects
9336 @anchor{gnat_rm/implementation_defined_aspects aspect-default-initial-condition}@anchor{12b}
9337 @section Aspect Default_Initial_Condition
9340 @geindex Default_Initial_Condition
9342 This aspect is equivalent to @ref{4e,,pragma Default_Initial_Condition}.
9344 @node Aspect Dimension,Aspect Dimension_System,Aspect Default_Initial_Condition,Implementation Defined Aspects
9345 @anchor{gnat_rm/implementation_defined_aspects aspect-dimension}@anchor{12c}
9346 @section Aspect Dimension
9351 The @code{Dimension} aspect is used to specify the dimensions of a given
9352 subtype of a dimensioned numeric type. The aspect also specifies a symbol
9353 used when doing formatted output of dimensioned quantities. The syntax is:
9357 ([Symbol =>] SYMBOL, DIMENSION_VALUE @{, DIMENSION_Value@})
9359 SYMBOL ::= STRING_LITERAL | CHARACTER_LITERAL
9363 | others => RATIONAL
9364 | DISCRETE_CHOICE_LIST => RATIONAL
9366 RATIONAL ::= [-] NUMERIC_LITERAL [/ NUMERIC_LITERAL]
9369 This aspect can only be applied to a subtype whose parent type has
9370 a @code{Dimension_System} aspect. The aspect must specify values for
9371 all dimensions of the system. The rational values are the powers of the
9372 corresponding dimensions that are used by the compiler to verify that
9373 physical (numeric) computations are dimensionally consistent. For example,
9374 the computation of a force must result in dimensions (L => 1, M => 1, T => -2).
9375 For further examples of the usage
9376 of this aspect, see package @code{System.Dim.Mks}.
9377 Note that when the dimensioned type is an integer type, then any
9378 dimension value must be an integer literal.
9380 @node Aspect Dimension_System,Aspect Disable_Controlled,Aspect Dimension,Implementation Defined Aspects
9381 @anchor{gnat_rm/implementation_defined_aspects aspect-dimension-system}@anchor{12d}
9382 @section Aspect Dimension_System
9385 @geindex Dimension_System
9387 The @code{Dimension_System} aspect is used to define a system of
9388 dimensions that will be used in subsequent subtype declarations with
9389 @code{Dimension} aspects that reference this system. The syntax is:
9392 with Dimension_System => (DIMENSION @{, DIMENSION@});
9394 DIMENSION ::= ([Unit_Name =>] IDENTIFIER,
9395 [Unit_Symbol =>] SYMBOL,
9396 [Dim_Symbol =>] SYMBOL)
9398 SYMBOL ::= CHARACTER_LITERAL | STRING_LITERAL
9401 This aspect is applied to a type, which must be a numeric derived type
9402 (typically a floating-point type), that
9403 will represent values within the dimension system. Each @code{DIMENSION}
9404 corresponds to one particular dimension. A maximum of 7 dimensions may
9405 be specified. @code{Unit_Name} is the name of the dimension (for example
9406 @code{Meter}). @code{Unit_Symbol} is the shorthand used for quantities
9407 of this dimension (for example @code{m} for @code{Meter}).
9408 @code{Dim_Symbol} gives
9409 the identification within the dimension system (typically this is a
9410 single letter, e.g. @code{L} standing for length for unit name @code{Meter}).
9411 The @code{Unit_Symbol} is used in formatted output of dimensioned quantities.
9412 The @code{Dim_Symbol} is used in error messages when numeric operations have
9413 inconsistent dimensions.
9415 GNAT provides the standard definition of the International MKS system in
9416 the run-time package @code{System.Dim.Mks}. You can easily define
9417 similar packages for cgs units or British units, and define conversion factors
9418 between values in different systems. The MKS system is characterized by the
9422 type Mks_Type is new Long_Long_Float with
9423 Dimension_System => (
9424 (Unit_Name => Meter, Unit_Symbol => 'm', Dim_Symbol => 'L'),
9425 (Unit_Name => Kilogram, Unit_Symbol => "kg", Dim_Symbol => 'M'),
9426 (Unit_Name => Second, Unit_Symbol => 's', Dim_Symbol => 'T'),
9427 (Unit_Name => Ampere, Unit_Symbol => 'A', Dim_Symbol => 'I'),
9428 (Unit_Name => Kelvin, Unit_Symbol => 'K', Dim_Symbol => '@@'),
9429 (Unit_Name => Mole, Unit_Symbol => "mol", Dim_Symbol => 'N'),
9430 (Unit_Name => Candela, Unit_Symbol => "cd", Dim_Symbol => 'J'));
9433 Note that in the above type definition, we use the @code{at} symbol (@code{@@}) to
9434 represent a theta character (avoiding the use of extended Latin-1
9435 characters in this context).
9437 See section 'Performing Dimensionality Analysis in GNAT' in the GNAT Users
9438 Guide for detailed examples of use of the dimension system.
9440 @node Aspect Disable_Controlled,Aspect Effective_Reads,Aspect Dimension_System,Implementation Defined Aspects
9441 @anchor{gnat_rm/implementation_defined_aspects aspect-disable-controlled}@anchor{12e}
9442 @section Aspect Disable_Controlled
9445 @geindex Disable_Controlled
9447 The aspect @code{Disable_Controlled} is defined for controlled record types. If
9448 active, this aspect causes suppression of all related calls to @code{Initialize},
9449 @code{Adjust}, and @code{Finalize}. The intended use is for conditional compilation,
9450 where for example you might want a record to be controlled or not depending on
9451 whether some run-time check is enabled or suppressed.
9453 @node Aspect Effective_Reads,Aspect Effective_Writes,Aspect Disable_Controlled,Implementation Defined Aspects
9454 @anchor{gnat_rm/implementation_defined_aspects aspect-effective-reads}@anchor{12f}
9455 @section Aspect Effective_Reads
9458 @geindex Effective_Reads
9460 This aspect is equivalent to @ref{59,,pragma Effective_Reads}.
9462 @node Aspect Effective_Writes,Aspect Extensions_Visible,Aspect Effective_Reads,Implementation Defined Aspects
9463 @anchor{gnat_rm/implementation_defined_aspects aspect-effective-writes}@anchor{130}
9464 @section Aspect Effective_Writes
9467 @geindex Effective_Writes
9469 This aspect is equivalent to @ref{5b,,pragma Effective_Writes}.
9471 @node Aspect Extensions_Visible,Aspect Favor_Top_Level,Aspect Effective_Writes,Implementation Defined Aspects
9472 @anchor{gnat_rm/implementation_defined_aspects aspect-extensions-visible}@anchor{131}
9473 @section Aspect Extensions_Visible
9476 @geindex Extensions_Visible
9478 This aspect is equivalent to @ref{67,,pragma Extensions_Visible}.
9480 @node Aspect Favor_Top_Level,Aspect Ghost,Aspect Extensions_Visible,Implementation Defined Aspects
9481 @anchor{gnat_rm/implementation_defined_aspects aspect-favor-top-level}@anchor{132}
9482 @section Aspect Favor_Top_Level
9485 @geindex Favor_Top_Level
9487 This boolean aspect is equivalent to @ref{6c,,pragma Favor_Top_Level}.
9489 @node Aspect Ghost,Aspect Global,Aspect Favor_Top_Level,Implementation Defined Aspects
9490 @anchor{gnat_rm/implementation_defined_aspects aspect-ghost}@anchor{133}
9491 @section Aspect Ghost
9496 This aspect is equivalent to @ref{6f,,pragma Ghost}.
9498 @node Aspect Global,Aspect Initial_Condition,Aspect Ghost,Implementation Defined Aspects
9499 @anchor{gnat_rm/implementation_defined_aspects aspect-global}@anchor{134}
9500 @section Aspect Global
9505 This aspect is equivalent to @ref{71,,pragma Global}.
9507 @node Aspect Initial_Condition,Aspect Initializes,Aspect Global,Implementation Defined Aspects
9508 @anchor{gnat_rm/implementation_defined_aspects aspect-initial-condition}@anchor{135}
9509 @section Aspect Initial_Condition
9512 @geindex Initial_Condition
9514 This aspect is equivalent to @ref{7f,,pragma Initial_Condition}.
9516 @node Aspect Initializes,Aspect Inline_Always,Aspect Initial_Condition,Implementation Defined Aspects
9517 @anchor{gnat_rm/implementation_defined_aspects aspect-initializes}@anchor{136}
9518 @section Aspect Initializes
9521 @geindex Initializes
9523 This aspect is equivalent to @ref{81,,pragma Initializes}.
9525 @node Aspect Inline_Always,Aspect Invariant,Aspect Initializes,Implementation Defined Aspects
9526 @anchor{gnat_rm/implementation_defined_aspects aspect-inline-always}@anchor{137}
9527 @section Aspect Inline_Always
9530 @geindex Inline_Always
9532 This boolean aspect is equivalent to @ref{84,,pragma Inline_Always}.
9534 @node Aspect Invariant,Aspect Invariant'Class,Aspect Inline_Always,Implementation Defined Aspects
9535 @anchor{gnat_rm/implementation_defined_aspects aspect-invariant}@anchor{138}
9536 @section Aspect Invariant
9541 This aspect is equivalent to @ref{8b,,pragma Invariant}. It is a
9542 synonym for the language defined aspect @code{Type_Invariant} except
9543 that it is separately controllable using pragma @code{Assertion_Policy}.
9545 @node Aspect Invariant'Class,Aspect Iterable,Aspect Invariant,Implementation Defined Aspects
9546 @anchor{gnat_rm/implementation_defined_aspects aspect-invariant-class}@anchor{139}
9547 @section Aspect Invariant'Class
9550 @geindex Invariant'Class
9552 This aspect is equivalent to @ref{102,,pragma Type_Invariant_Class}. It is a
9553 synonym for the language defined aspect @code{Type_Invariant'Class} except
9554 that it is separately controllable using pragma @code{Assertion_Policy}.
9556 @node Aspect Iterable,Aspect Linker_Section,Aspect Invariant'Class,Implementation Defined Aspects
9557 @anchor{gnat_rm/implementation_defined_aspects aspect-iterable}@anchor{13a}
9558 @section Aspect Iterable
9563 This aspect provides a light-weight mechanism for loops and quantified
9564 expressions over container types, without the overhead imposed by the tampering
9565 checks of standard Ada 2012 iterators. The value of the aspect is an aggregate
9566 with six named components, of which the last three are optional: @code{First},
9567 @code{Next}, @code{Has_Element}, @code{Element}, @code{Last}, and @code{Previous}.
9568 When only the first three components are specified, only the
9569 @code{for .. in} form of iteration over cursors is available. When @code{Element}
9570 is specified, both this form and the @code{for .. of} form of iteration over
9571 elements are available. If the last two components are specified, reverse
9572 iterations over the container can be specified (analogous to what can be done
9573 over predefined containers that support the @code{Reverse_Iterator} interface).
9574 The following is a typical example of use:
9577 type List is private with
9578 Iterable => (First => First_Cursor,
9580 Has_Element => Cursor_Has_Element,
9581 [Element => Get_Element]);
9588 The value denoted by @code{First} must denote a primitive operation of the
9589 container type that returns a @code{Cursor}, which must a be a type declared in
9590 the container package or visible from it. For example:
9594 function First_Cursor (Cont : Container) return Cursor;
9601 The value of @code{Next} is a primitive operation of the container type that takes
9602 both a container and a cursor and yields a cursor. For example:
9606 function Advance (Cont : Container; Position : Cursor) return Cursor;
9613 The value of @code{Has_Element} is a primitive operation of the container type
9614 that takes both a container and a cursor and yields a boolean. For example:
9618 function Cursor_Has_Element (Cont : Container; Position : Cursor) return Boolean;
9625 The value of @code{Element} is a primitive operation of the container type that
9626 takes both a container and a cursor and yields an @code{Element_Type}, which must
9627 be a type declared in the container package or visible from it. For example:
9631 function Get_Element (Cont : Container; Position : Cursor) return Element_Type;
9634 This aspect is used in the GNAT-defined formal container packages.
9636 @node Aspect Linker_Section,Aspect Lock_Free,Aspect Iterable,Implementation Defined Aspects
9637 @anchor{gnat_rm/implementation_defined_aspects aspect-linker-section}@anchor{13b}
9638 @section Aspect Linker_Section
9641 @geindex Linker_Section
9643 This aspect is equivalent to @ref{93,,pragma Linker_Section}.
9645 @node Aspect Lock_Free,Aspect Max_Queue_Length,Aspect Linker_Section,Implementation Defined Aspects
9646 @anchor{gnat_rm/implementation_defined_aspects aspect-lock-free}@anchor{13c}
9647 @section Aspect Lock_Free
9652 This boolean aspect is equivalent to @ref{95,,pragma Lock_Free}.
9654 @node Aspect Max_Queue_Length,Aspect No_Caching,Aspect Lock_Free,Implementation Defined Aspects
9655 @anchor{gnat_rm/implementation_defined_aspects aspect-max-queue-length}@anchor{13d}
9656 @section Aspect Max_Queue_Length
9659 @geindex Max_Queue_Length
9661 This aspect is equivalent to @ref{9d,,pragma Max_Queue_Length}.
9663 @node Aspect No_Caching,Aspect No_Elaboration_Code_All,Aspect Max_Queue_Length,Implementation Defined Aspects
9664 @anchor{gnat_rm/implementation_defined_aspects aspect-no-caching}@anchor{13e}
9665 @section Aspect No_Caching
9670 This boolean aspect is equivalent to @ref{9f,,pragma No_Caching}.
9672 @node Aspect No_Elaboration_Code_All,Aspect No_Inline,Aspect No_Caching,Implementation Defined Aspects
9673 @anchor{gnat_rm/implementation_defined_aspects aspect-no-elaboration-code-all}@anchor{13f}
9674 @section Aspect No_Elaboration_Code_All
9677 @geindex No_Elaboration_Code_All
9679 This aspect is equivalent to @ref{a3,,pragma No_Elaboration_Code_All}
9682 @node Aspect No_Inline,Aspect No_Tagged_Streams,Aspect No_Elaboration_Code_All,Implementation Defined Aspects
9683 @anchor{gnat_rm/implementation_defined_aspects aspect-no-inline}@anchor{140}
9684 @section Aspect No_Inline
9689 This boolean aspect is equivalent to @ref{a6,,pragma No_Inline}.
9691 @node Aspect No_Tagged_Streams,Aspect Object_Size,Aspect No_Inline,Implementation Defined Aspects
9692 @anchor{gnat_rm/implementation_defined_aspects aspect-no-tagged-streams}@anchor{141}
9693 @section Aspect No_Tagged_Streams
9696 @geindex No_Tagged_Streams
9698 This aspect is equivalent to @ref{a9,,pragma No_Tagged_Streams} with an
9699 argument specifying a root tagged type (thus this aspect can only be
9700 applied to such a type).
9702 @node Aspect Object_Size,Aspect Obsolescent,Aspect No_Tagged_Streams,Implementation Defined Aspects
9703 @anchor{gnat_rm/implementation_defined_aspects aspect-object-size}@anchor{142}
9704 @section Aspect Object_Size
9707 @geindex Object_Size
9709 This aspect is equivalent to @ref{143,,attribute Object_Size}.
9711 @node Aspect Obsolescent,Aspect Part_Of,Aspect Object_Size,Implementation Defined Aspects
9712 @anchor{gnat_rm/implementation_defined_aspects aspect-obsolescent}@anchor{144}
9713 @section Aspect Obsolescent
9716 @geindex Obsolsecent
9718 This aspect is equivalent to @ref{ac,,pragma Obsolescent}. Note that the
9719 evaluation of this aspect happens at the point of occurrence, it is not
9720 delayed until the freeze point.
9722 @node Aspect Part_Of,Aspect Persistent_BSS,Aspect Obsolescent,Implementation Defined Aspects
9723 @anchor{gnat_rm/implementation_defined_aspects aspect-part-of}@anchor{145}
9724 @section Aspect Part_Of
9729 This aspect is equivalent to @ref{b4,,pragma Part_Of}.
9731 @node Aspect Persistent_BSS,Aspect Predicate,Aspect Part_Of,Implementation Defined Aspects
9732 @anchor{gnat_rm/implementation_defined_aspects aspect-persistent-bss}@anchor{146}
9733 @section Aspect Persistent_BSS
9736 @geindex Persistent_BSS
9738 This boolean aspect is equivalent to @ref{b7,,pragma Persistent_BSS}.
9740 @node Aspect Predicate,Aspect Pure_Function,Aspect Persistent_BSS,Implementation Defined Aspects
9741 @anchor{gnat_rm/implementation_defined_aspects aspect-predicate}@anchor{147}
9742 @section Aspect Predicate
9747 This aspect is equivalent to @ref{be,,pragma Predicate}. It is thus
9748 similar to the language defined aspects @code{Dynamic_Predicate}
9749 and @code{Static_Predicate} except that whether the resulting
9750 predicate is static or dynamic is controlled by the form of the
9751 expression. It is also separately controllable using pragma
9752 @code{Assertion_Policy}.
9754 @node Aspect Pure_Function,Aspect Refined_Depends,Aspect Predicate,Implementation Defined Aspects
9755 @anchor{gnat_rm/implementation_defined_aspects aspect-pure-function}@anchor{148}
9756 @section Aspect Pure_Function
9759 @geindex Pure_Function
9761 This boolean aspect is equivalent to @ref{ca,,pragma Pure_Function}.
9763 @node Aspect Refined_Depends,Aspect Refined_Global,Aspect Pure_Function,Implementation Defined Aspects
9764 @anchor{gnat_rm/implementation_defined_aspects aspect-refined-depends}@anchor{149}
9765 @section Aspect Refined_Depends
9768 @geindex Refined_Depends
9770 This aspect is equivalent to @ref{ce,,pragma Refined_Depends}.
9772 @node Aspect Refined_Global,Aspect Refined_Post,Aspect Refined_Depends,Implementation Defined Aspects
9773 @anchor{gnat_rm/implementation_defined_aspects aspect-refined-global}@anchor{14a}
9774 @section Aspect Refined_Global
9777 @geindex Refined_Global
9779 This aspect is equivalent to @ref{d0,,pragma Refined_Global}.
9781 @node Aspect Refined_Post,Aspect Refined_State,Aspect Refined_Global,Implementation Defined Aspects
9782 @anchor{gnat_rm/implementation_defined_aspects aspect-refined-post}@anchor{14b}
9783 @section Aspect Refined_Post
9786 @geindex Refined_Post
9788 This aspect is equivalent to @ref{d2,,pragma Refined_Post}.
9790 @node Aspect Refined_State,Aspect Relaxed_Initialization,Aspect Refined_Post,Implementation Defined Aspects
9791 @anchor{gnat_rm/implementation_defined_aspects aspect-refined-state}@anchor{14c}
9792 @section Aspect Refined_State
9795 @geindex Refined_State
9797 This aspect is equivalent to @ref{d4,,pragma Refined_State}.
9799 @node Aspect Relaxed_Initialization,Aspect Remote_Access_Type,Aspect Refined_State,Implementation Defined Aspects
9800 @anchor{gnat_rm/implementation_defined_aspects aspect-relaxed-initialization}@anchor{14d}
9801 @section Aspect Relaxed_Initialization
9804 @geindex Refined_Initialization
9806 For the syntax and semantics of this aspect, see the SPARK 2014 Reference
9807 Manual, section 6.10.
9809 @node Aspect Remote_Access_Type,Aspect Secondary_Stack_Size,Aspect Relaxed_Initialization,Implementation Defined Aspects
9810 @anchor{gnat_rm/implementation_defined_aspects aspect-remote-access-type}@anchor{14e}
9811 @section Aspect Remote_Access_Type
9814 @geindex Remote_Access_Type
9816 This aspect is equivalent to @ref{d8,,pragma Remote_Access_Type}.
9818 @node Aspect Secondary_Stack_Size,Aspect Scalar_Storage_Order,Aspect Remote_Access_Type,Implementation Defined Aspects
9819 @anchor{gnat_rm/implementation_defined_aspects aspect-secondary-stack-size}@anchor{14f}
9820 @section Aspect Secondary_Stack_Size
9823 @geindex Secondary_Stack_Size
9825 This aspect is equivalent to @ref{dd,,pragma Secondary_Stack_Size}.
9827 @node Aspect Scalar_Storage_Order,Aspect Shared,Aspect Secondary_Stack_Size,Implementation Defined Aspects
9828 @anchor{gnat_rm/implementation_defined_aspects aspect-scalar-storage-order}@anchor{150}
9829 @section Aspect Scalar_Storage_Order
9832 @geindex Scalar_Storage_Order
9834 This aspect is equivalent to a @ref{151,,attribute Scalar_Storage_Order}.
9836 @node Aspect Shared,Aspect Simple_Storage_Pool,Aspect Scalar_Storage_Order,Implementation Defined Aspects
9837 @anchor{gnat_rm/implementation_defined_aspects aspect-shared}@anchor{152}
9838 @section Aspect Shared
9843 This boolean aspect is equivalent to @ref{e0,,pragma Shared}
9844 and is thus a synonym for aspect @code{Atomic}.
9846 @node Aspect Simple_Storage_Pool,Aspect Simple_Storage_Pool_Type,Aspect Shared,Implementation Defined Aspects
9847 @anchor{gnat_rm/implementation_defined_aspects aspect-simple-storage-pool}@anchor{153}
9848 @section Aspect Simple_Storage_Pool
9851 @geindex Simple_Storage_Pool
9853 This aspect is equivalent to @ref{e5,,attribute Simple_Storage_Pool}.
9855 @node Aspect Simple_Storage_Pool_Type,Aspect SPARK_Mode,Aspect Simple_Storage_Pool,Implementation Defined Aspects
9856 @anchor{gnat_rm/implementation_defined_aspects aspect-simple-storage-pool-type}@anchor{154}
9857 @section Aspect Simple_Storage_Pool_Type
9860 @geindex Simple_Storage_Pool_Type
9862 This boolean aspect is equivalent to @ref{e3,,pragma Simple_Storage_Pool_Type}.
9864 @node Aspect SPARK_Mode,Aspect Suppress_Debug_Info,Aspect Simple_Storage_Pool_Type,Implementation Defined Aspects
9865 @anchor{gnat_rm/implementation_defined_aspects aspect-spark-mode}@anchor{155}
9866 @section Aspect SPARK_Mode
9871 This aspect is equivalent to @ref{eb,,pragma SPARK_Mode} and
9872 may be specified for either or both of the specification and body
9873 of a subprogram or package.
9875 @node Aspect Suppress_Debug_Info,Aspect Suppress_Initialization,Aspect SPARK_Mode,Implementation Defined Aspects
9876 @anchor{gnat_rm/implementation_defined_aspects aspect-suppress-debug-info}@anchor{156}
9877 @section Aspect Suppress_Debug_Info
9880 @geindex Suppress_Debug_Info
9882 This boolean aspect is equivalent to @ref{f3,,pragma Suppress_Debug_Info}.
9884 @node Aspect Suppress_Initialization,Aspect Test_Case,Aspect Suppress_Debug_Info,Implementation Defined Aspects
9885 @anchor{gnat_rm/implementation_defined_aspects aspect-suppress-initialization}@anchor{157}
9886 @section Aspect Suppress_Initialization
9889 @geindex Suppress_Initialization
9891 This boolean aspect is equivalent to @ref{f7,,pragma Suppress_Initialization}.
9893 @node Aspect Test_Case,Aspect Thread_Local_Storage,Aspect Suppress_Initialization,Implementation Defined Aspects
9894 @anchor{gnat_rm/implementation_defined_aspects aspect-test-case}@anchor{158}
9895 @section Aspect Test_Case
9900 This aspect is equivalent to @ref{fa,,pragma Test_Case}.
9902 @node Aspect Thread_Local_Storage,Aspect Universal_Aliasing,Aspect Test_Case,Implementation Defined Aspects
9903 @anchor{gnat_rm/implementation_defined_aspects aspect-thread-local-storage}@anchor{159}
9904 @section Aspect Thread_Local_Storage
9907 @geindex Thread_Local_Storage
9909 This boolean aspect is equivalent to @ref{fc,,pragma Thread_Local_Storage}.
9911 @node Aspect Universal_Aliasing,Aspect Universal_Data,Aspect Thread_Local_Storage,Implementation Defined Aspects
9912 @anchor{gnat_rm/implementation_defined_aspects aspect-universal-aliasing}@anchor{15a}
9913 @section Aspect Universal_Aliasing
9916 @geindex Universal_Aliasing
9918 This boolean aspect is equivalent to @ref{106,,pragma Universal_Aliasing}.
9920 @node Aspect Universal_Data,Aspect Unmodified,Aspect Universal_Aliasing,Implementation Defined Aspects
9921 @anchor{gnat_rm/implementation_defined_aspects aspect-universal-data}@anchor{15b}
9922 @section Aspect Universal_Data
9925 @geindex Universal_Data
9927 This aspect is equivalent to @ref{108,,pragma Universal_Data}.
9929 @node Aspect Unmodified,Aspect Unreferenced,Aspect Universal_Data,Implementation Defined Aspects
9930 @anchor{gnat_rm/implementation_defined_aspects aspect-unmodified}@anchor{15c}
9931 @section Aspect Unmodified
9936 This boolean aspect is equivalent to @ref{10b,,pragma Unmodified}.
9938 @node Aspect Unreferenced,Aspect Unreferenced_Objects,Aspect Unmodified,Implementation Defined Aspects
9939 @anchor{gnat_rm/implementation_defined_aspects aspect-unreferenced}@anchor{15d}
9940 @section Aspect Unreferenced
9943 @geindex Unreferenced
9945 This boolean aspect is equivalent to @ref{10c,,pragma Unreferenced}.
9947 When using the @code{-gnat2020} switch, this aspect is also supported on formal
9948 parameters, which is in particular the only form possible for expression
9951 @node Aspect Unreferenced_Objects,Aspect Value_Size,Aspect Unreferenced,Implementation Defined Aspects
9952 @anchor{gnat_rm/implementation_defined_aspects aspect-unreferenced-objects}@anchor{15e}
9953 @section Aspect Unreferenced_Objects
9956 @geindex Unreferenced_Objects
9958 This boolean aspect is equivalent to @ref{10e,,pragma Unreferenced_Objects}.
9960 @node Aspect Value_Size,Aspect Volatile_Full_Access,Aspect Unreferenced_Objects,Implementation Defined Aspects
9961 @anchor{gnat_rm/implementation_defined_aspects aspect-value-size}@anchor{15f}
9962 @section Aspect Value_Size
9967 This aspect is equivalent to @ref{160,,attribute Value_Size}.
9969 @node Aspect Volatile_Full_Access,Aspect Volatile_Function,Aspect Value_Size,Implementation Defined Aspects
9970 @anchor{gnat_rm/implementation_defined_aspects aspect-volatile-full-access}@anchor{161}
9971 @section Aspect Volatile_Full_Access
9974 @geindex Volatile_Full_Access
9976 This boolean aspect is equivalent to @ref{119,,pragma Volatile_Full_Access}.
9978 @node Aspect Volatile_Function,Aspect Warnings,Aspect Volatile_Full_Access,Implementation Defined Aspects
9979 @anchor{gnat_rm/implementation_defined_aspects aspect-volatile-function}@anchor{162}
9980 @section Aspect Volatile_Function
9983 @geindex Volatile_Function
9985 This boolean aspect is equivalent to @ref{11b,,pragma Volatile_Function}.
9987 @node Aspect Warnings,,Aspect Volatile_Function,Implementation Defined Aspects
9988 @anchor{gnat_rm/implementation_defined_aspects aspect-warnings}@anchor{163}
9989 @section Aspect Warnings
9994 This aspect is equivalent to the two argument form of @ref{11d,,pragma Warnings},
9995 where the first argument is @code{ON} or @code{OFF} and the second argument
9998 @node Implementation Defined Attributes,Standard and Implementation Defined Restrictions,Implementation Defined Aspects,Top
9999 @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}
10000 @chapter Implementation Defined Attributes
10003 Ada defines (throughout the Ada reference manual,
10004 summarized in Annex K),
10005 a set of attributes that provide useful additional functionality in all
10006 areas of the language. These language defined attributes are implemented
10007 in GNAT and work as described in the Ada Reference Manual.
10009 In addition, Ada allows implementations to define additional
10010 attributes whose meaning is defined by the implementation. GNAT provides
10011 a number of these implementation-dependent attributes which can be used
10012 to extend and enhance the functionality of the compiler. This section of
10013 the GNAT reference manual describes these additional attributes. It also
10014 describes additional implementation-dependent features of standard
10015 language-defined attributes.
10017 Note that any program using these attributes may not be portable to
10018 other compilers (although GNAT implements this set of attributes on all
10019 platforms). Therefore if portability to other compilers is an important
10020 consideration, you should minimize the use of these attributes.
10023 * Attribute Abort_Signal::
10024 * Attribute Address_Size::
10025 * Attribute Asm_Input::
10026 * Attribute Asm_Output::
10027 * Attribute Atomic_Always_Lock_Free::
10029 * Attribute Bit_Position::
10030 * Attribute Code_Address::
10031 * Attribute Compiler_Version::
10032 * Attribute Constrained::
10033 * Attribute Default_Bit_Order::
10034 * Attribute Default_Scalar_Storage_Order::
10035 * Attribute Deref::
10036 * Attribute Descriptor_Size::
10037 * Attribute Elaborated::
10038 * Attribute Elab_Body::
10039 * Attribute Elab_Spec::
10040 * Attribute Elab_Subp_Body::
10042 * Attribute Enabled::
10043 * Attribute Enum_Rep::
10044 * Attribute Enum_Val::
10045 * Attribute Epsilon::
10046 * Attribute Fast_Math::
10047 * Attribute Finalization_Size::
10048 * Attribute Fixed_Value::
10049 * Attribute From_Any::
10050 * Attribute Has_Access_Values::
10051 * Attribute Has_Discriminants::
10052 * Attribute Has_Tagged_Values::
10054 * Attribute Initialized::
10055 * Attribute Integer_Value::
10056 * Attribute Invalid_Value::
10057 * Attribute Iterable::
10058 * Attribute Large::
10059 * Attribute Library_Level::
10060 * Attribute Lock_Free::
10061 * Attribute Loop_Entry::
10062 * Attribute Machine_Size::
10063 * Attribute Mantissa::
10064 * Attribute Maximum_Alignment::
10065 * Attribute Max_Integer_Size::
10066 * Attribute Mechanism_Code::
10067 * Attribute Null_Parameter::
10068 * Attribute Object_Size::
10070 * Attribute Passed_By_Reference::
10071 * Attribute Pool_Address::
10072 * Attribute Range_Length::
10073 * Attribute Restriction_Set::
10074 * Attribute Result::
10075 * Attribute Safe_Emax::
10076 * Attribute Safe_Large::
10077 * Attribute Safe_Small::
10078 * Attribute Scalar_Storage_Order::
10079 * Attribute Simple_Storage_Pool::
10080 * Attribute Small::
10081 * Attribute Small_Denominator::
10082 * Attribute Small_Numerator::
10083 * Attribute Storage_Unit::
10084 * Attribute Stub_Type::
10085 * Attribute System_Allocator_Alignment::
10086 * Attribute Target_Name::
10087 * Attribute To_Address::
10088 * Attribute To_Any::
10089 * Attribute Type_Class::
10090 * Attribute Type_Key::
10091 * Attribute TypeCode::
10092 * Attribute Unconstrained_Array::
10093 * Attribute Universal_Literal_String::
10094 * Attribute Unrestricted_Access::
10095 * Attribute Update::
10096 * Attribute Valid_Scalars::
10097 * Attribute VADS_Size::
10098 * Attribute Value_Size::
10099 * Attribute Wchar_T_Size::
10100 * Attribute Word_Size::
10104 @node Attribute Abort_Signal,Attribute Address_Size,,Implementation Defined Attributes
10105 @anchor{gnat_rm/implementation_defined_attributes attribute-abort-signal}@anchor{166}
10106 @section Attribute Abort_Signal
10109 @geindex Abort_Signal
10111 @code{Standard'Abort_Signal} (@code{Standard} is the only allowed
10112 prefix) provides the entity for the special exception used to signal
10113 task abort or asynchronous transfer of control. Normally this attribute
10114 should only be used in the tasking runtime (it is highly peculiar, and
10115 completely outside the normal semantics of Ada, for a user program to
10116 intercept the abort exception).
10118 @node Attribute Address_Size,Attribute Asm_Input,Attribute Abort_Signal,Implementation Defined Attributes
10119 @anchor{gnat_rm/implementation_defined_attributes attribute-address-size}@anchor{167}
10120 @section Attribute Address_Size
10123 @geindex Size of `@w{`}Address`@w{`}
10125 @geindex Address_Size
10127 @code{Standard'Address_Size} (@code{Standard} is the only allowed
10128 prefix) is a static constant giving the number of bits in an
10129 @code{Address}. It is the same value as System.Address'Size,
10130 but has the advantage of being static, while a direct
10131 reference to System.Address'Size is nonstatic because Address
10134 @node Attribute Asm_Input,Attribute Asm_Output,Attribute Address_Size,Implementation Defined Attributes
10135 @anchor{gnat_rm/implementation_defined_attributes attribute-asm-input}@anchor{168}
10136 @section Attribute Asm_Input
10141 The @code{Asm_Input} attribute denotes a function that takes two
10142 parameters. The first is a string, the second is an expression of the
10143 type designated by the prefix. The first (string) argument is required
10144 to be a static expression, and is the constraint for the parameter,
10145 (e.g., what kind of register is required). The second argument is the
10146 value to be used as the input argument. The possible values for the
10147 constant are the same as those used in the RTL, and are dependent on
10148 the configuration file used to built the GCC back end.
10149 @ref{169,,Machine Code Insertions}
10151 @node Attribute Asm_Output,Attribute Atomic_Always_Lock_Free,Attribute Asm_Input,Implementation Defined Attributes
10152 @anchor{gnat_rm/implementation_defined_attributes attribute-asm-output}@anchor{16a}
10153 @section Attribute Asm_Output
10156 @geindex Asm_Output
10158 The @code{Asm_Output} attribute denotes a function that takes two
10159 parameters. The first is a string, the second is the name of a variable
10160 of the type designated by the attribute prefix. The first (string)
10161 argument is required to be a static expression and designates the
10162 constraint for the parameter (e.g., what kind of register is
10163 required). The second argument is the variable to be updated with the
10164 result. The possible values for constraint are the same as those used in
10165 the RTL, and are dependent on the configuration file used to build the
10166 GCC back end. If there are no output operands, then this argument may
10167 either be omitted, or explicitly given as @code{No_Output_Operands}.
10168 @ref{169,,Machine Code Insertions}
10170 @node Attribute Atomic_Always_Lock_Free,Attribute Bit,Attribute Asm_Output,Implementation Defined Attributes
10171 @anchor{gnat_rm/implementation_defined_attributes attribute-atomic-always-lock-free}@anchor{16b}
10172 @section Attribute Atomic_Always_Lock_Free
10175 @geindex Atomic_Always_Lock_Free
10177 The prefix of the @code{Atomic_Always_Lock_Free} attribute is a type.
10178 The result is a Boolean value which is True if the type has discriminants,
10179 and False otherwise. The result indicate whether atomic operations are
10180 supported by the target for the given type.
10182 @node Attribute Bit,Attribute Bit_Position,Attribute Atomic_Always_Lock_Free,Implementation Defined Attributes
10183 @anchor{gnat_rm/implementation_defined_attributes attribute-bit}@anchor{16c}
10184 @section Attribute Bit
10189 @code{obj'Bit}, where @code{obj} is any object, yields the bit
10190 offset within the storage unit (byte) that contains the first bit of
10191 storage allocated for the object. The value of this attribute is of the
10192 type @emph{universal_integer} and is always a nonnegative number smaller
10193 than @code{System.Storage_Unit}.
10195 For an object that is a variable or a constant allocated in a register,
10196 the value is zero. (The use of this attribute does not force the
10197 allocation of a variable to memory).
10199 For an object that is a formal parameter, this attribute applies
10200 to either the matching actual parameter or to a copy of the
10201 matching actual parameter.
10203 For an access object the value is zero. Note that
10204 @code{obj.all'Bit} is subject to an @code{Access_Check} for the
10205 designated object. Similarly for a record component
10206 @code{X.C'Bit} is subject to a discriminant check and
10207 @code{X(I).Bit} and @code{X(I1..I2)'Bit}
10208 are subject to index checks.
10210 This attribute is designed to be compatible with the DEC Ada 83 definition
10211 and implementation of the @code{Bit} attribute.
10213 @node Attribute Bit_Position,Attribute Code_Address,Attribute Bit,Implementation Defined Attributes
10214 @anchor{gnat_rm/implementation_defined_attributes attribute-bit-position}@anchor{16d}
10215 @section Attribute Bit_Position
10218 @geindex Bit_Position
10220 @code{R.C'Bit_Position}, where @code{R} is a record object and @code{C} is one
10221 of the fields of the record type, yields the bit
10222 offset within the record contains the first bit of
10223 storage allocated for the object. The value of this attribute is of the
10224 type @emph{universal_integer}. The value depends only on the field
10225 @code{C} and is independent of the alignment of
10226 the containing record @code{R}.
10228 @node Attribute Code_Address,Attribute Compiler_Version,Attribute Bit_Position,Implementation Defined Attributes
10229 @anchor{gnat_rm/implementation_defined_attributes attribute-code-address}@anchor{16e}
10230 @section Attribute Code_Address
10233 @geindex Code_Address
10235 @geindex Subprogram address
10237 @geindex Address of subprogram code
10239 The @code{'Address}
10240 attribute may be applied to subprograms in Ada 95 and Ada 2005, but the
10241 intended effect seems to be to provide
10242 an address value which can be used to call the subprogram by means of
10243 an address clause as in the following example:
10249 for L'Address use K'Address;
10250 pragma Import (Ada, L);
10253 A call to @code{L} is then expected to result in a call to @code{K}.
10254 In Ada 83, where there were no access-to-subprogram values, this was
10255 a common work-around for getting the effect of an indirect call.
10256 GNAT implements the above use of @code{Address} and the technique
10257 illustrated by the example code works correctly.
10259 However, for some purposes, it is useful to have the address of the start
10260 of the generated code for the subprogram. On some architectures, this is
10261 not necessarily the same as the @code{Address} value described above.
10262 For example, the @code{Address} value may reference a subprogram
10263 descriptor rather than the subprogram itself.
10265 The @code{'Code_Address} attribute, which can only be applied to
10266 subprogram entities, always returns the address of the start of the
10267 generated code of the specified subprogram, which may or may not be
10268 the same value as is returned by the corresponding @code{'Address}
10271 @node Attribute Compiler_Version,Attribute Constrained,Attribute Code_Address,Implementation Defined Attributes
10272 @anchor{gnat_rm/implementation_defined_attributes attribute-compiler-version}@anchor{16f}
10273 @section Attribute Compiler_Version
10276 @geindex Compiler_Version
10278 @code{Standard'Compiler_Version} (@code{Standard} is the only allowed
10279 prefix) yields a static string identifying the version of the compiler
10280 being used to compile the unit containing the attribute reference.
10282 @node Attribute Constrained,Attribute Default_Bit_Order,Attribute Compiler_Version,Implementation Defined Attributes
10283 @anchor{gnat_rm/implementation_defined_attributes attribute-constrained}@anchor{170}
10284 @section Attribute Constrained
10287 @geindex Constrained
10289 In addition to the usage of this attribute in the Ada RM, GNAT
10290 also permits the use of the @code{'Constrained} attribute
10291 in a generic template
10292 for any type, including types without discriminants. The value of this
10293 attribute in the generic instance when applied to a scalar type or a
10294 record type without discriminants is always @code{True}. This usage is
10295 compatible with older Ada compilers, including notably DEC Ada.
10297 @node Attribute Default_Bit_Order,Attribute Default_Scalar_Storage_Order,Attribute Constrained,Implementation Defined Attributes
10298 @anchor{gnat_rm/implementation_defined_attributes attribute-default-bit-order}@anchor{171}
10299 @section Attribute Default_Bit_Order
10302 @geindex Big endian
10304 @geindex Little endian
10306 @geindex Default_Bit_Order
10308 @code{Standard'Default_Bit_Order} (@code{Standard} is the only
10309 permissible prefix), provides the value @code{System.Default_Bit_Order}
10310 as a @code{Pos} value (0 for @code{High_Order_First}, 1 for
10311 @code{Low_Order_First}). This is used to construct the definition of
10312 @code{Default_Bit_Order} in package @code{System}.
10314 @node Attribute Default_Scalar_Storage_Order,Attribute Deref,Attribute Default_Bit_Order,Implementation Defined Attributes
10315 @anchor{gnat_rm/implementation_defined_attributes attribute-default-scalar-storage-order}@anchor{172}
10316 @section Attribute Default_Scalar_Storage_Order
10319 @geindex Big endian
10321 @geindex Little endian
10323 @geindex Default_Scalar_Storage_Order
10325 @code{Standard'Default_Scalar_Storage_Order} (@code{Standard} is the only
10326 permissible prefix), provides the current value of the default scalar storage
10327 order (as specified using pragma @code{Default_Scalar_Storage_Order}, or
10328 equal to @code{Default_Bit_Order} if unspecified) as a
10329 @code{System.Bit_Order} value. This is a static attribute.
10331 @node Attribute Deref,Attribute Descriptor_Size,Attribute Default_Scalar_Storage_Order,Implementation Defined Attributes
10332 @anchor{gnat_rm/implementation_defined_attributes attribute-deref}@anchor{173}
10333 @section Attribute Deref
10338 The attribute @code{typ'Deref(expr)} where @code{expr} is of type @code{System.Address} yields
10339 the variable of type @code{typ} that is located at the given address. It is similar
10340 to @code{(totyp (expr).all)}, where @code{totyp} is an unchecked conversion from address to
10341 a named access-to-@cite{typ} type, except that it yields a variable, so it can be
10342 used on the left side of an assignment.
10344 @node Attribute Descriptor_Size,Attribute Elaborated,Attribute Deref,Implementation Defined Attributes
10345 @anchor{gnat_rm/implementation_defined_attributes attribute-descriptor-size}@anchor{174}
10346 @section Attribute Descriptor_Size
10349 @geindex Descriptor
10351 @geindex Dope vector
10353 @geindex Descriptor_Size
10355 Nonstatic attribute @code{Descriptor_Size} returns the size in bits of the
10356 descriptor allocated for a type. The result is non-zero only for unconstrained
10357 array types and the returned value is of type universal integer. In GNAT, an
10358 array descriptor contains bounds information and is located immediately before
10359 the first element of the array.
10362 type Unconstr_Array is array (Short_Short_Integer range <>) of Positive;
10363 Put_Line ("Descriptor size = " & Unconstr_Array'Descriptor_Size'Img);
10366 The attribute takes into account any padding due to the alignment of the
10367 component type. In the example above, the descriptor contains two values
10368 of type @code{Short_Short_Integer} representing the low and high bound. But,
10369 since @code{Positive} has an alignment of 4, the size of the descriptor is
10370 @code{2 * Short_Short_Integer'Size} rounded up to the next multiple of 32,
10371 which yields a size of 32 bits, i.e. including 16 bits of padding.
10373 @node Attribute Elaborated,Attribute Elab_Body,Attribute Descriptor_Size,Implementation Defined Attributes
10374 @anchor{gnat_rm/implementation_defined_attributes attribute-elaborated}@anchor{175}
10375 @section Attribute Elaborated
10378 @geindex Elaborated
10380 The prefix of the @code{'Elaborated} attribute must be a unit name. The
10381 value is a Boolean which indicates whether or not the given unit has been
10382 elaborated. This attribute is primarily intended for internal use by the
10383 generated code for dynamic elaboration checking, but it can also be used
10384 in user programs. The value will always be True once elaboration of all
10385 units has been completed. An exception is for units which need no
10386 elaboration, the value is always False for such units.
10388 @node Attribute Elab_Body,Attribute Elab_Spec,Attribute Elaborated,Implementation Defined Attributes
10389 @anchor{gnat_rm/implementation_defined_attributes attribute-elab-body}@anchor{176}
10390 @section Attribute Elab_Body
10395 This attribute can only be applied to a program unit name. It returns
10396 the entity for the corresponding elaboration procedure for elaborating
10397 the body of the referenced unit. This is used in the main generated
10398 elaboration procedure by the binder and is not normally used in any
10399 other context. However, there may be specialized situations in which it
10400 is useful to be able to call this elaboration procedure from Ada code,
10401 e.g., if it is necessary to do selective re-elaboration to fix some
10404 @node Attribute Elab_Spec,Attribute Elab_Subp_Body,Attribute Elab_Body,Implementation Defined Attributes
10405 @anchor{gnat_rm/implementation_defined_attributes attribute-elab-spec}@anchor{177}
10406 @section Attribute Elab_Spec
10411 This attribute can only be applied to a program unit name. It returns
10412 the entity for the corresponding elaboration procedure for elaborating
10413 the spec of the referenced unit. This is used in the main
10414 generated elaboration procedure by the binder and is not normally used
10415 in any other context. However, there may be specialized situations in
10416 which it is useful to be able to call this elaboration procedure from
10417 Ada code, e.g., if it is necessary to do selective re-elaboration to fix
10420 @node Attribute Elab_Subp_Body,Attribute Emax,Attribute Elab_Spec,Implementation Defined Attributes
10421 @anchor{gnat_rm/implementation_defined_attributes attribute-elab-subp-body}@anchor{178}
10422 @section Attribute Elab_Subp_Body
10425 @geindex Elab_Subp_Body
10427 This attribute can only be applied to a library level subprogram
10428 name and is only allowed in CodePeer mode. It returns the entity
10429 for the corresponding elaboration procedure for elaborating the body
10430 of the referenced subprogram unit. This is used in the main generated
10431 elaboration procedure by the binder in CodePeer mode only and is unrecognized
10434 @node Attribute Emax,Attribute Enabled,Attribute Elab_Subp_Body,Implementation Defined Attributes
10435 @anchor{gnat_rm/implementation_defined_attributes attribute-emax}@anchor{179}
10436 @section Attribute Emax
10439 @geindex Ada 83 attributes
10443 The @code{Emax} attribute is provided for compatibility with Ada 83. See
10444 the Ada 83 reference manual for an exact description of the semantics of
10447 @node Attribute Enabled,Attribute Enum_Rep,Attribute Emax,Implementation Defined Attributes
10448 @anchor{gnat_rm/implementation_defined_attributes attribute-enabled}@anchor{17a}
10449 @section Attribute Enabled
10454 The @code{Enabled} attribute allows an application program to check at compile
10455 time to see if the designated check is currently enabled. The prefix is a
10456 simple identifier, referencing any predefined check name (other than
10457 @code{All_Checks}) or a check name introduced by pragma Check_Name. If
10458 no argument is given for the attribute, the check is for the general state
10459 of the check, if an argument is given, then it is an entity name, and the
10460 check indicates whether an @code{Suppress} or @code{Unsuppress} has been
10461 given naming the entity (if not, then the argument is ignored).
10463 Note that instantiations inherit the check status at the point of the
10464 instantiation, so a useful idiom is to have a library package that
10465 introduces a check name with @code{pragma Check_Name}, and then contains
10466 generic packages or subprograms which use the @code{Enabled} attribute
10467 to see if the check is enabled. A user of this package can then issue
10468 a @code{pragma Suppress} or @code{pragma Unsuppress} before instantiating
10469 the package or subprogram, controlling whether the check will be present.
10471 @node Attribute Enum_Rep,Attribute Enum_Val,Attribute Enabled,Implementation Defined Attributes
10472 @anchor{gnat_rm/implementation_defined_attributes attribute-enum-rep}@anchor{17b}
10473 @section Attribute Enum_Rep
10476 @geindex Representation of enums
10480 Note that this attribute is now standard in Ada 202x and is available
10481 as an implementation defined attribute for earlier Ada versions.
10483 For every enumeration subtype @code{S}, @code{S'Enum_Rep} denotes a
10484 function with the following spec:
10487 function S'Enum_Rep (Arg : S'Base) return <Universal_Integer>;
10490 It is also allowable to apply @code{Enum_Rep} directly to an object of an
10491 enumeration type or to a non-overloaded enumeration
10492 literal. In this case @code{S'Enum_Rep} is equivalent to
10493 @code{typ'Enum_Rep(S)} where @code{typ} is the type of the
10494 enumeration literal or object.
10496 The function returns the representation value for the given enumeration
10497 value. This will be equal to value of the @code{Pos} attribute in the
10498 absence of an enumeration representation clause. This is a static
10499 attribute (i.e., the result is static if the argument is static).
10501 @code{S'Enum_Rep} can also be used with integer types and objects,
10502 in which case it simply returns the integer value. The reason for this
10503 is to allow it to be used for @code{(<>)} discrete formal arguments in
10504 a generic unit that can be instantiated with either enumeration types
10505 or integer types. Note that if @code{Enum_Rep} is used on a modular
10506 type whose upper bound exceeds the upper bound of the largest signed
10507 integer type, and the argument is a variable, so that the universal
10508 integer calculation is done at run time, then the call to @code{Enum_Rep}
10509 may raise @code{Constraint_Error}.
10511 @node Attribute Enum_Val,Attribute Epsilon,Attribute Enum_Rep,Implementation Defined Attributes
10512 @anchor{gnat_rm/implementation_defined_attributes attribute-enum-val}@anchor{17c}
10513 @section Attribute Enum_Val
10516 @geindex Representation of enums
10520 Note that this attribute is now standard in Ada 202x and is available
10521 as an implementation defined attribute for earlier Ada versions.
10523 For every enumeration subtype @code{S}, @code{S'Enum_Val} denotes a
10524 function with the following spec:
10527 function S'Enum_Val (Arg : <Universal_Integer>) return S'Base;
10530 The function returns the enumeration value whose representation matches the
10531 argument, or raises Constraint_Error if no enumeration literal of the type
10532 has the matching value.
10533 This will be equal to value of the @code{Val} attribute in the
10534 absence of an enumeration representation clause. This is a static
10535 attribute (i.e., the result is static if the argument is static).
10537 @node Attribute Epsilon,Attribute Fast_Math,Attribute Enum_Val,Implementation Defined Attributes
10538 @anchor{gnat_rm/implementation_defined_attributes attribute-epsilon}@anchor{17d}
10539 @section Attribute Epsilon
10542 @geindex Ada 83 attributes
10546 The @code{Epsilon} attribute is provided for compatibility with Ada 83. See
10547 the Ada 83 reference manual for an exact description of the semantics of
10550 @node Attribute Fast_Math,Attribute Finalization_Size,Attribute Epsilon,Implementation Defined Attributes
10551 @anchor{gnat_rm/implementation_defined_attributes attribute-fast-math}@anchor{17e}
10552 @section Attribute Fast_Math
10557 @code{Standard'Fast_Math} (@code{Standard} is the only allowed
10558 prefix) yields a static Boolean value that is True if pragma
10559 @code{Fast_Math} is active, and False otherwise.
10561 @node Attribute Finalization_Size,Attribute Fixed_Value,Attribute Fast_Math,Implementation Defined Attributes
10562 @anchor{gnat_rm/implementation_defined_attributes attribute-finalization-size}@anchor{17f}
10563 @section Attribute Finalization_Size
10566 @geindex Finalization_Size
10568 The prefix of attribute @code{Finalization_Size} must be an object or
10569 a non-class-wide type. This attribute returns the size of any hidden data
10570 reserved by the compiler to handle finalization-related actions. The type of
10571 the attribute is @emph{universal_integer}.
10573 @code{Finalization_Size} yields a value of zero for a type with no controlled
10574 parts, an object whose type has no controlled parts, or an object of a
10575 class-wide type whose tag denotes a type with no controlled parts.
10577 Note that only heap-allocated objects contain finalization data.
10579 @node Attribute Fixed_Value,Attribute From_Any,Attribute Finalization_Size,Implementation Defined Attributes
10580 @anchor{gnat_rm/implementation_defined_attributes attribute-fixed-value}@anchor{180}
10581 @section Attribute Fixed_Value
10584 @geindex Fixed_Value
10586 For every fixed-point type @code{S}, @code{S'Fixed_Value} denotes a
10587 function with the following specification:
10590 function S'Fixed_Value (Arg : <Universal_Integer>) return S;
10593 The value returned is the fixed-point value @code{V} such that:
10599 The effect is thus similar to first converting the argument to the
10600 integer type used to represent @code{S}, and then doing an unchecked
10601 conversion to the fixed-point type. The difference is
10602 that there are full range checks, to ensure that the result is in range.
10603 This attribute is primarily intended for use in implementation of the
10604 input-output functions for fixed-point values.
10606 @node Attribute From_Any,Attribute Has_Access_Values,Attribute Fixed_Value,Implementation Defined Attributes
10607 @anchor{gnat_rm/implementation_defined_attributes attribute-from-any}@anchor{181}
10608 @section Attribute From_Any
10613 This internal attribute is used for the generation of remote subprogram
10614 stubs in the context of the Distributed Systems Annex.
10616 @node Attribute Has_Access_Values,Attribute Has_Discriminants,Attribute From_Any,Implementation Defined Attributes
10617 @anchor{gnat_rm/implementation_defined_attributes attribute-has-access-values}@anchor{182}
10618 @section Attribute Has_Access_Values
10621 @geindex Access values
10622 @geindex testing for
10624 @geindex Has_Access_Values
10626 The prefix of the @code{Has_Access_Values} attribute is a type. The result
10627 is a Boolean value which is True if the is an access type, or is a composite
10628 type with a component (at any nesting depth) that is an access type, and is
10630 The intended use of this attribute is in conjunction with generic
10631 definitions. If the attribute is applied to a generic private type, it
10632 indicates whether or not the corresponding actual type has access values.
10634 @node Attribute Has_Discriminants,Attribute Has_Tagged_Values,Attribute Has_Access_Values,Implementation Defined Attributes
10635 @anchor{gnat_rm/implementation_defined_attributes attribute-has-discriminants}@anchor{183}
10636 @section Attribute Has_Discriminants
10639 @geindex Discriminants
10640 @geindex testing for
10642 @geindex Has_Discriminants
10644 The prefix of the @code{Has_Discriminants} attribute is a type. The result
10645 is a Boolean value which is True if the type has discriminants, and False
10646 otherwise. The intended use of this attribute is in conjunction with generic
10647 definitions. If the attribute is applied to a generic private type, it
10648 indicates whether or not the corresponding actual type has discriminants.
10650 @node Attribute Has_Tagged_Values,Attribute Img,Attribute Has_Discriminants,Implementation Defined Attributes
10651 @anchor{gnat_rm/implementation_defined_attributes attribute-has-tagged-values}@anchor{184}
10652 @section Attribute Has_Tagged_Values
10655 @geindex Tagged values
10656 @geindex testing for
10658 @geindex Has_Tagged_Values
10660 The prefix of the @code{Has_Tagged_Values} attribute is a type. The result is a
10661 Boolean value which is True if the type is a composite type (array or record)
10662 that is either a tagged type or has a subcomponent that is tagged, and is False
10663 otherwise. The intended use of this attribute is in conjunction with generic
10664 definitions. If the attribute is applied to a generic private type, it
10665 indicates whether or not the corresponding actual type has access values.
10667 @node Attribute Img,Attribute Initialized,Attribute Has_Tagged_Values,Implementation Defined Attributes
10668 @anchor{gnat_rm/implementation_defined_attributes attribute-img}@anchor{185}
10669 @section Attribute Img
10674 The @code{Img} attribute differs from @code{Image} in that, while both can be
10675 applied directly to an object, @code{Img} cannot be applied to types.
10677 Example usage of the attribute:
10680 Put_Line ("X = " & X'Img);
10683 which has the same meaning as the more verbose:
10686 Put_Line ("X = " & T'Image (X));
10689 where @code{T} is the (sub)type of the object @code{X}.
10691 Note that technically, in analogy to @code{Image},
10692 @code{X'Img} returns a parameterless function
10693 that returns the appropriate string when called. This means that
10694 @code{X'Img} can be renamed as a function-returning-string, or used
10695 in an instantiation as a function parameter.
10697 @node Attribute Initialized,Attribute Integer_Value,Attribute Img,Implementation Defined Attributes
10698 @anchor{gnat_rm/implementation_defined_attributes attribute-initialized}@anchor{186}
10699 @section Attribute Initialized
10702 @geindex Initialized
10704 For the syntax and semantics of this attribute, see the SPARK 2014 Reference
10705 Manual, section 6.10.
10707 @node Attribute Integer_Value,Attribute Invalid_Value,Attribute Initialized,Implementation Defined Attributes
10708 @anchor{gnat_rm/implementation_defined_attributes attribute-integer-value}@anchor{187}
10709 @section Attribute Integer_Value
10712 @geindex Integer_Value
10714 For every integer type @code{S}, @code{S'Integer_Value} denotes a
10715 function with the following spec:
10718 function S'Integer_Value (Arg : <Universal_Fixed>) return S;
10721 The value returned is the integer value @code{V}, such that:
10727 where @code{T} is the type of @code{Arg}.
10728 The effect is thus similar to first doing an unchecked conversion from
10729 the fixed-point type to its corresponding implementation type, and then
10730 converting the result to the target integer type. The difference is
10731 that there are full range checks, to ensure that the result is in range.
10732 This attribute is primarily intended for use in implementation of the
10733 standard input-output functions for fixed-point values.
10735 @node Attribute Invalid_Value,Attribute Iterable,Attribute Integer_Value,Implementation Defined Attributes
10736 @anchor{gnat_rm/implementation_defined_attributes attribute-invalid-value}@anchor{188}
10737 @section Attribute Invalid_Value
10740 @geindex Invalid_Value
10742 For every scalar type S, S'Invalid_Value returns an undefined value of the
10743 type. If possible this value is an invalid representation for the type. The
10744 value returned is identical to the value used to initialize an otherwise
10745 uninitialized value of the type if pragma Initialize_Scalars is used,
10746 including the ability to modify the value with the binder -Sxx flag and
10747 relevant environment variables at run time.
10749 @node Attribute Iterable,Attribute Large,Attribute Invalid_Value,Implementation Defined Attributes
10750 @anchor{gnat_rm/implementation_defined_attributes attribute-iterable}@anchor{189}
10751 @section Attribute Iterable
10756 Equivalent to Aspect Iterable.
10758 @node Attribute Large,Attribute Library_Level,Attribute Iterable,Implementation Defined Attributes
10759 @anchor{gnat_rm/implementation_defined_attributes attribute-large}@anchor{18a}
10760 @section Attribute Large
10763 @geindex Ada 83 attributes
10767 The @code{Large} attribute is provided for compatibility with Ada 83. See
10768 the Ada 83 reference manual for an exact description of the semantics of
10771 @node Attribute Library_Level,Attribute Lock_Free,Attribute Large,Implementation Defined Attributes
10772 @anchor{gnat_rm/implementation_defined_attributes attribute-library-level}@anchor{18b}
10773 @section Attribute Library_Level
10776 @geindex Library_Level
10778 @code{P'Library_Level}, where P is an entity name,
10779 returns a Boolean value which is True if the entity is declared
10780 at the library level, and False otherwise. Note that within a
10781 generic instantition, the name of the generic unit denotes the
10782 instance, which means that this attribute can be used to test
10783 if a generic is instantiated at the library level, as shown
10790 pragma Compile_Time_Error
10791 (not Gen'Library_Level,
10792 "Gen can only be instantiated at library level");
10797 @node Attribute Lock_Free,Attribute Loop_Entry,Attribute Library_Level,Implementation Defined Attributes
10798 @anchor{gnat_rm/implementation_defined_attributes attribute-lock-free}@anchor{18c}
10799 @section Attribute Lock_Free
10804 @code{P'Lock_Free}, where P is a protected object, returns True if a
10805 pragma @code{Lock_Free} applies to P.
10807 @node Attribute Loop_Entry,Attribute Machine_Size,Attribute Lock_Free,Implementation Defined Attributes
10808 @anchor{gnat_rm/implementation_defined_attributes attribute-loop-entry}@anchor{18d}
10809 @section Attribute Loop_Entry
10812 @geindex Loop_Entry
10817 X'Loop_Entry [(loop_name)]
10820 The @code{Loop_Entry} attribute is used to refer to the value that an
10821 expression had upon entry to a given loop in much the same way that the
10822 @code{Old} attribute in a subprogram postcondition can be used to refer
10823 to the value an expression had upon entry to the subprogram. The
10824 relevant loop is either identified by the given loop name, or it is the
10825 innermost enclosing loop when no loop name is given.
10827 A @code{Loop_Entry} attribute can only occur within a
10828 @code{Loop_Variant} or @code{Loop_Invariant} pragma. A common use of
10829 @code{Loop_Entry} is to compare the current value of objects with their
10830 initial value at loop entry, in a @code{Loop_Invariant} pragma.
10832 The effect of using @code{X'Loop_Entry} is the same as declaring
10833 a constant initialized with the initial value of @code{X} at loop
10834 entry. This copy is not performed if the loop is not entered, or if the
10835 corresponding pragmas are ignored or disabled.
10837 @node Attribute Machine_Size,Attribute Mantissa,Attribute Loop_Entry,Implementation Defined Attributes
10838 @anchor{gnat_rm/implementation_defined_attributes attribute-machine-size}@anchor{18e}
10839 @section Attribute Machine_Size
10842 @geindex Machine_Size
10844 This attribute is identical to the @code{Object_Size} attribute. It is
10845 provided for compatibility with the DEC Ada 83 attribute of this name.
10847 @node Attribute Mantissa,Attribute Maximum_Alignment,Attribute Machine_Size,Implementation Defined Attributes
10848 @anchor{gnat_rm/implementation_defined_attributes attribute-mantissa}@anchor{18f}
10849 @section Attribute Mantissa
10852 @geindex Ada 83 attributes
10856 The @code{Mantissa} attribute is provided for compatibility with Ada 83. See
10857 the Ada 83 reference manual for an exact description of the semantics of
10860 @node Attribute Maximum_Alignment,Attribute Max_Integer_Size,Attribute Mantissa,Implementation Defined Attributes
10861 @anchor{gnat_rm/implementation_defined_attributes attribute-maximum-alignment}@anchor{190}@anchor{gnat_rm/implementation_defined_attributes id2}@anchor{191}
10862 @section Attribute Maximum_Alignment
10868 @geindex Maximum_Alignment
10870 @code{Standard'Maximum_Alignment} (@code{Standard} is the only
10871 permissible prefix) provides the maximum useful alignment value for the
10872 target. This is a static value that can be used to specify the alignment
10873 for an object, guaranteeing that it is properly aligned in all
10876 @node Attribute Max_Integer_Size,Attribute Mechanism_Code,Attribute Maximum_Alignment,Implementation Defined Attributes
10877 @anchor{gnat_rm/implementation_defined_attributes attribute-max-integer-size}@anchor{192}
10878 @section Attribute Max_Integer_Size
10881 @geindex Max_Integer_Size
10883 @code{Standard'Max_Integer_Size} (@code{Standard} is the only permissible
10884 prefix) provides the size of the largest supported integer type for
10885 the target. The result is a static constant.
10887 @node Attribute Mechanism_Code,Attribute Null_Parameter,Attribute Max_Integer_Size,Implementation Defined Attributes
10888 @anchor{gnat_rm/implementation_defined_attributes attribute-mechanism-code}@anchor{193}
10889 @section Attribute Mechanism_Code
10892 @geindex Return values
10893 @geindex passing mechanism
10895 @geindex Parameters
10896 @geindex passing mechanism
10898 @geindex Mechanism_Code
10900 @code{func'Mechanism_Code} yields an integer code for the
10901 mechanism used for the result of function @code{func}, and
10902 @code{subprog'Mechanism_Code (n)} yields the mechanism
10903 used for formal parameter number @emph{n} (a static integer value, with 1
10904 meaning the first parameter) of subprogram @code{subprog}. The code returned is:
10918 @node Attribute Null_Parameter,Attribute Object_Size,Attribute Mechanism_Code,Implementation Defined Attributes
10919 @anchor{gnat_rm/implementation_defined_attributes attribute-null-parameter}@anchor{194}
10920 @section Attribute Null_Parameter
10923 @geindex Zero address
10926 @geindex Null_Parameter
10928 A reference @code{T'Null_Parameter} denotes an imaginary object of
10929 type or subtype @code{T} allocated at machine address zero. The attribute
10930 is allowed only as the default expression of a formal parameter, or as
10931 an actual expression of a subprogram call. In either case, the
10932 subprogram must be imported.
10934 The identity of the object is represented by the address zero in the
10935 argument list, independent of the passing mechanism (explicit or
10938 This capability is needed to specify that a zero address should be
10939 passed for a record or other composite object passed by reference.
10940 There is no way of indicating this without the @code{Null_Parameter}
10943 @node Attribute Object_Size,Attribute Old,Attribute Null_Parameter,Implementation Defined Attributes
10944 @anchor{gnat_rm/implementation_defined_attributes attribute-object-size}@anchor{143}@anchor{gnat_rm/implementation_defined_attributes id3}@anchor{195}
10945 @section Attribute Object_Size
10949 @geindex used for objects
10951 @geindex Object_Size
10953 The size of an object is not necessarily the same as the size of the type
10954 of an object. This is because by default object sizes are increased to be
10955 a multiple of the alignment of the object. For example,
10956 @code{Natural'Size} is
10957 31, but by default objects of type @code{Natural} will have a size of 32 bits.
10958 Similarly, a record containing an integer and a character:
10967 will have a size of 40 (that is @code{Rec'Size} will be 40). The
10968 alignment will be 4, because of the
10969 integer field, and so the default size of record objects for this type
10970 will be 64 (8 bytes).
10972 If the alignment of the above record is specified to be 1, then the
10973 object size will be 40 (5 bytes). This is true by default, and also
10974 an object size of 40 can be explicitly specified in this case.
10976 A consequence of this capability is that different object sizes can be
10977 given to subtypes that would otherwise be considered in Ada to be
10978 statically matching. But it makes no sense to consider such subtypes
10979 as statically matching. Consequently, GNAT adds a rule
10980 to the static matching rules that requires object sizes to match.
10981 Consider this example:
10984 1. procedure BadAVConvert is
10985 2. type R is new Integer;
10986 3. subtype R1 is R range 1 .. 10;
10987 4. subtype R2 is R range 1 .. 10;
10988 5. for R1'Object_Size use 8;
10989 6. for R2'Object_Size use 16;
10990 7. type R1P is access all R1;
10991 8. type R2P is access all R2;
10992 9. R1PV : R1P := new R1'(4);
10995 12. R2PV := R2P (R1PV);
10997 >>> target designated subtype not compatible with
10998 type "R1" defined at line 3
11003 In the absence of lines 5 and 6,
11004 types @code{R1} and @code{R2} statically match and
11005 hence the conversion on line 12 is legal. But since lines 5 and 6
11006 cause the object sizes to differ, GNAT considers that types
11007 @code{R1} and @code{R2} are not statically matching, and line 12
11008 generates the diagnostic shown above.
11010 Similar additional checks are performed in other contexts requiring
11011 statically matching subtypes.
11013 @node Attribute Old,Attribute Passed_By_Reference,Attribute Object_Size,Implementation Defined Attributes
11014 @anchor{gnat_rm/implementation_defined_attributes attribute-old}@anchor{196}
11015 @section Attribute Old
11020 In addition to the usage of @code{Old} defined in the Ada 2012 RM (usage
11021 within @code{Post} aspect), GNAT also permits the use of this attribute
11022 in implementation defined pragmas @code{Postcondition},
11023 @code{Contract_Cases} and @code{Test_Case}. Also usages of
11024 @code{Old} which would be illegal according to the Ada 2012 RM
11025 definition are allowed under control of
11026 implementation defined pragma @code{Unevaluated_Use_Of_Old}.
11028 @node Attribute Passed_By_Reference,Attribute Pool_Address,Attribute Old,Implementation Defined Attributes
11029 @anchor{gnat_rm/implementation_defined_attributes attribute-passed-by-reference}@anchor{197}
11030 @section Attribute Passed_By_Reference
11033 @geindex Parameters
11034 @geindex when passed by reference
11036 @geindex Passed_By_Reference
11038 @code{typ'Passed_By_Reference} for any subtype @cite{typ} returns
11039 a value of type @code{Boolean} value that is @code{True} if the type is
11040 normally passed by reference and @code{False} if the type is normally
11041 passed by copy in calls. For scalar types, the result is always @code{False}
11042 and is static. For non-scalar types, the result is nonstatic.
11044 @node Attribute Pool_Address,Attribute Range_Length,Attribute Passed_By_Reference,Implementation Defined Attributes
11045 @anchor{gnat_rm/implementation_defined_attributes attribute-pool-address}@anchor{198}
11046 @section Attribute Pool_Address
11049 @geindex Pool_Address
11051 @code{X'Pool_Address} for any object @code{X} returns the address
11052 of X within its storage pool. This is the same as
11053 @code{X'Address}, except that for an unconstrained array whose
11054 bounds are allocated just before the first component,
11055 @code{X'Pool_Address} returns the address of those bounds,
11056 whereas @code{X'Address} returns the address of the first
11059 Here, we are interpreting 'storage pool' broadly to mean
11060 @code{wherever the object is allocated}, which could be a
11061 user-defined storage pool,
11062 the global heap, on the stack, or in a static memory area.
11063 For an object created by @code{new}, @code{Ptr.all'Pool_Address} is
11064 what is passed to @code{Allocate} and returned from @code{Deallocate}.
11066 @node Attribute Range_Length,Attribute Restriction_Set,Attribute Pool_Address,Implementation Defined Attributes
11067 @anchor{gnat_rm/implementation_defined_attributes attribute-range-length}@anchor{199}
11068 @section Attribute Range_Length
11071 @geindex Range_Length
11073 @code{typ'Range_Length} for any discrete type @cite{typ} yields
11074 the number of values represented by the subtype (zero for a null
11075 range). The result is static for static subtypes. @code{Range_Length}
11076 applied to the index subtype of a one dimensional array always gives the
11077 same result as @code{Length} applied to the array itself.
11079 @node Attribute Restriction_Set,Attribute Result,Attribute Range_Length,Implementation Defined Attributes
11080 @anchor{gnat_rm/implementation_defined_attributes attribute-restriction-set}@anchor{19a}
11081 @section Attribute Restriction_Set
11084 @geindex Restriction_Set
11086 @geindex Restrictions
11088 This attribute allows compile time testing of restrictions that
11089 are currently in effect. It is primarily intended for specializing
11090 code in the run-time based on restrictions that are active (e.g.
11091 don't need to save fpt registers if restriction No_Floating_Point
11092 is known to be in effect), but can be used anywhere.
11094 There are two forms:
11097 System'Restriction_Set (partition_boolean_restriction_NAME)
11098 System'Restriction_Set (No_Dependence => library_unit_NAME);
11101 In the case of the first form, the only restriction names
11102 allowed are parameterless restrictions that are checked
11103 for consistency at bind time. For a complete list see the
11104 subtype @code{System.Rident.Partition_Boolean_Restrictions}.
11106 The result returned is True if the restriction is known to
11107 be in effect, and False if the restriction is known not to
11108 be in effect. An important guarantee is that the value of
11109 a Restriction_Set attribute is known to be consistent throughout
11110 all the code of a partition.
11112 This is trivially achieved if the entire partition is compiled
11113 with a consistent set of restriction pragmas. However, the
11114 compilation model does not require this. It is possible to
11115 compile one set of units with one set of pragmas, and another
11116 set of units with another set of pragmas. It is even possible
11117 to compile a spec with one set of pragmas, and then WITH the
11118 same spec with a different set of pragmas. Inconsistencies
11119 in the actual use of the restriction are checked at bind time.
11121 In order to achieve the guarantee of consistency for the
11122 Restriction_Set pragma, we consider that a use of the pragma
11123 that yields False is equivalent to a violation of the
11126 So for example if you write
11129 if System'Restriction_Set (No_Floating_Point) then
11136 And the result is False, so that the else branch is executed,
11137 you can assume that this restriction is not set for any unit
11138 in the partition. This is checked by considering this use of
11139 the restriction pragma to be a violation of the restriction
11140 No_Floating_Point. This means that no other unit can attempt
11141 to set this restriction (if some unit does attempt to set it,
11142 the binder will refuse to bind the partition).
11144 Technical note: The restriction name and the unit name are
11145 intepreted entirely syntactically, as in the corresponding
11146 Restrictions pragma, they are not analyzed semantically,
11147 so they do not have a type.
11149 @node Attribute Result,Attribute Safe_Emax,Attribute Restriction_Set,Implementation Defined Attributes
11150 @anchor{gnat_rm/implementation_defined_attributes attribute-result}@anchor{19b}
11151 @section Attribute Result
11156 @code{function'Result} can only be used with in a Postcondition pragma
11157 for a function. The prefix must be the name of the corresponding function. This
11158 is used to refer to the result of the function in the postcondition expression.
11159 For a further discussion of the use of this attribute and examples of its use,
11160 see the description of pragma Postcondition.
11162 @node Attribute Safe_Emax,Attribute Safe_Large,Attribute Result,Implementation Defined Attributes
11163 @anchor{gnat_rm/implementation_defined_attributes attribute-safe-emax}@anchor{19c}
11164 @section Attribute Safe_Emax
11167 @geindex Ada 83 attributes
11171 The @code{Safe_Emax} attribute is provided for compatibility with Ada 83. See
11172 the Ada 83 reference manual for an exact description of the semantics of
11175 @node Attribute Safe_Large,Attribute Safe_Small,Attribute Safe_Emax,Implementation Defined Attributes
11176 @anchor{gnat_rm/implementation_defined_attributes attribute-safe-large}@anchor{19d}
11177 @section Attribute Safe_Large
11180 @geindex Ada 83 attributes
11182 @geindex Safe_Large
11184 The @code{Safe_Large} attribute is provided for compatibility with Ada 83. See
11185 the Ada 83 reference manual for an exact description of the semantics of
11188 @node Attribute Safe_Small,Attribute Scalar_Storage_Order,Attribute Safe_Large,Implementation Defined Attributes
11189 @anchor{gnat_rm/implementation_defined_attributes attribute-safe-small}@anchor{19e}
11190 @section Attribute Safe_Small
11193 @geindex Ada 83 attributes
11195 @geindex Safe_Small
11197 The @code{Safe_Small} attribute is provided for compatibility with Ada 83. See
11198 the Ada 83 reference manual for an exact description of the semantics of
11201 @node Attribute Scalar_Storage_Order,Attribute Simple_Storage_Pool,Attribute Safe_Small,Implementation Defined Attributes
11202 @anchor{gnat_rm/implementation_defined_attributes id4}@anchor{19f}@anchor{gnat_rm/implementation_defined_attributes attribute-scalar-storage-order}@anchor{151}
11203 @section Attribute Scalar_Storage_Order
11206 @geindex Endianness
11208 @geindex Scalar storage order
11210 @geindex Scalar_Storage_Order
11212 For every array or record type @code{S}, the representation attribute
11213 @code{Scalar_Storage_Order} denotes the order in which storage elements
11214 that make up scalar components are ordered within S. The value given must
11215 be a static expression of type System.Bit_Order. The following is an example
11216 of the use of this feature:
11219 -- Component type definitions
11221 subtype Yr_Type is Natural range 0 .. 127;
11222 subtype Mo_Type is Natural range 1 .. 12;
11223 subtype Da_Type is Natural range 1 .. 31;
11225 -- Record declaration
11227 type Date is record
11228 Years_Since_1980 : Yr_Type;
11230 Day_Of_Month : Da_Type;
11233 -- Record representation clause
11235 for Date use record
11236 Years_Since_1980 at 0 range 0 .. 6;
11237 Month at 0 range 7 .. 10;
11238 Day_Of_Month at 0 range 11 .. 15;
11241 -- Attribute definition clauses
11243 for Date'Bit_Order use System.High_Order_First;
11244 for Date'Scalar_Storage_Order use System.High_Order_First;
11245 -- If Scalar_Storage_Order is specified, it must be consistent with
11246 -- Bit_Order, so it's best to always define the latter explicitly if
11247 -- the former is used.
11250 Other properties are as for the standard representation attribute @code{Bit_Order}
11251 defined by Ada RM 13.5.3(4). The default is @code{System.Default_Bit_Order}.
11253 For a record type @code{T}, if @code{T'Scalar_Storage_Order} is
11254 specified explicitly, it shall be equal to @code{T'Bit_Order}. Note:
11255 this means that if a @code{Scalar_Storage_Order} attribute definition
11256 clause is not confirming, then the type's @code{Bit_Order} shall be
11257 specified explicitly and set to the same value.
11259 Derived types inherit an explicitly set scalar storage order from their parent
11260 types. This may be overridden for the derived type by giving an explicit scalar
11261 storage order for it. However, for a record extension, the derived type must
11262 have the same scalar storage order as the parent type.
11264 A component of a record type that is itself a record or an array and that does
11265 not start and end on a byte boundary must have have the same scalar storage
11266 order as the record type. A component of a bit-packed array type that is itself
11267 a record or an array must have the same scalar storage order as the array type.
11269 No component of a type that has an explicit @code{Scalar_Storage_Order}
11270 attribute definition may be aliased.
11272 A confirming @code{Scalar_Storage_Order} attribute definition clause (i.e.
11273 with a value equal to @code{System.Default_Bit_Order}) has no effect.
11275 If the opposite storage order is specified, then whenever the value of
11276 a scalar component of an object of type @code{S} is read, the storage
11277 elements of the enclosing machine scalar are first reversed (before
11278 retrieving the component value, possibly applying some shift and mask
11279 operatings on the enclosing machine scalar), and the opposite operation
11280 is done for writes.
11282 In that case, the restrictions set forth in 13.5.1(10.3/2) for scalar components
11283 are relaxed. Instead, the following rules apply:
11289 the underlying storage elements are those at positions
11290 @code{(position + first_bit / storage_element_size) .. (position + (last_bit + storage_element_size - 1) / storage_element_size)}
11293 the sequence of underlying storage elements shall have
11294 a size no greater than the largest machine scalar
11297 the enclosing machine scalar is defined as the smallest machine
11298 scalar starting at a position no greater than
11299 @code{position + first_bit / storage_element_size} and covering
11300 storage elements at least up to @code{position + (last_bit + storage_element_size - 1) / storage_element_size`}
11303 the position of the component is interpreted relative to that machine
11307 If no scalar storage order is specified for a type (either directly, or by
11308 inheritance in the case of a derived type), then the default is normally
11309 the native ordering of the target, but this default can be overridden using
11310 pragma @code{Default_Scalar_Storage_Order}.
11312 If a component of @code{T} is itself of a record or array type, the specfied
11313 @code{Scalar_Storage_Order} does @emph{not} apply to that nested type: an explicit
11314 attribute definition clause must be provided for the component type as well
11317 Note that the scalar storage order only affects the in-memory data
11318 representation. It has no effect on the representation used by stream
11321 Note that debuggers may be unable to display the correct value of scalar
11322 components of a type for which the opposite storage order is specified.
11324 @node Attribute Simple_Storage_Pool,Attribute Small,Attribute Scalar_Storage_Order,Implementation Defined Attributes
11325 @anchor{gnat_rm/implementation_defined_attributes attribute-simple-storage-pool}@anchor{e5}@anchor{gnat_rm/implementation_defined_attributes id5}@anchor{1a0}
11326 @section Attribute Simple_Storage_Pool
11329 @geindex Storage pool
11332 @geindex Simple storage pool
11334 @geindex Simple_Storage_Pool
11336 For every nonformal, nonderived access-to-object type @code{Acc}, the
11337 representation attribute @code{Simple_Storage_Pool} may be specified
11338 via an attribute_definition_clause (or by specifying the equivalent aspect):
11341 My_Pool : My_Simple_Storage_Pool_Type;
11343 type Acc is access My_Data_Type;
11345 for Acc'Simple_Storage_Pool use My_Pool;
11348 The name given in an attribute_definition_clause for the
11349 @code{Simple_Storage_Pool} attribute shall denote a variable of
11350 a 'simple storage pool type' (see pragma @cite{Simple_Storage_Pool_Type}).
11352 The use of this attribute is only allowed for a prefix denoting a type
11353 for which it has been specified. The type of the attribute is the type
11354 of the variable specified as the simple storage pool of the access type,
11355 and the attribute denotes that variable.
11357 It is illegal to specify both @code{Storage_Pool} and @code{Simple_Storage_Pool}
11358 for the same access type.
11360 If the @code{Simple_Storage_Pool} attribute has been specified for an access
11361 type, then applying the @code{Storage_Pool} attribute to the type is flagged
11362 with a warning and its evaluation raises the exception @code{Program_Error}.
11364 If the Simple_Storage_Pool attribute has been specified for an access
11365 type @code{S}, then the evaluation of the attribute @code{S'Storage_Size}
11366 returns the result of calling @code{Storage_Size (S'Simple_Storage_Pool)},
11367 which is intended to indicate the number of storage elements reserved for
11368 the simple storage pool. If the Storage_Size function has not been defined
11369 for the simple storage pool type, then this attribute returns zero.
11371 If an access type @code{S} has a specified simple storage pool of type
11372 @code{SSP}, then the evaluation of an allocator for that access type calls
11373 the primitive @code{Allocate} procedure for type @code{SSP}, passing
11374 @code{S'Simple_Storage_Pool} as the pool parameter. The detailed
11375 semantics of such allocators is the same as those defined for allocators
11376 in section 13.11 of the @cite{Ada Reference Manual}, with the term
11377 @emph{simple storage pool} substituted for @emph{storage pool}.
11379 If an access type @code{S} has a specified simple storage pool of type
11380 @code{SSP}, then a call to an instance of the @code{Ada.Unchecked_Deallocation}
11381 for that access type invokes the primitive @code{Deallocate} procedure
11382 for type @code{SSP}, passing @code{S'Simple_Storage_Pool} as the pool
11383 parameter. The detailed semantics of such unchecked deallocations is the same
11384 as defined in section 13.11.2 of the Ada Reference Manual, except that the
11385 term @emph{simple storage pool} is substituted for @emph{storage pool}.
11387 @node Attribute Small,Attribute Small_Denominator,Attribute Simple_Storage_Pool,Implementation Defined Attributes
11388 @anchor{gnat_rm/implementation_defined_attributes attribute-small}@anchor{1a1}
11389 @section Attribute Small
11392 @geindex Ada 83 attributes
11396 The @code{Small} attribute is defined in Ada 95 (and Ada 2005) only for
11398 GNAT also allows this attribute to be applied to floating-point types
11399 for compatibility with Ada 83. See
11400 the Ada 83 reference manual for an exact description of the semantics of
11401 this attribute when applied to floating-point types.
11403 @node Attribute Small_Denominator,Attribute Small_Numerator,Attribute Small,Implementation Defined Attributes
11404 @anchor{gnat_rm/implementation_defined_attributes attribute-small-denominator}@anchor{1a2}
11405 @section Attribute Small_Denominator
11410 @geindex Small_Denominator
11412 @code{typ'Small_Denominator} for any fixed-point subtype @cite{typ} yields the
11413 denominator in the representation of @code{typ'Small} as a rational number
11414 with coprime factors (i.e. as an irreducible fraction).
11416 @node Attribute Small_Numerator,Attribute Storage_Unit,Attribute Small_Denominator,Implementation Defined Attributes
11417 @anchor{gnat_rm/implementation_defined_attributes attribute-small-numerator}@anchor{1a3}
11418 @section Attribute Small_Numerator
11423 @geindex Small_Numerator
11425 @code{typ'Small_Numerator} for any fixed-point subtype @cite{typ} yields the
11426 numerator in the representation of @code{typ'Small} as a rational number
11427 with coprime factors (i.e. as an irreducible fraction).
11429 @node Attribute Storage_Unit,Attribute Stub_Type,Attribute Small_Numerator,Implementation Defined Attributes
11430 @anchor{gnat_rm/implementation_defined_attributes attribute-storage-unit}@anchor{1a4}
11431 @section Attribute Storage_Unit
11434 @geindex Storage_Unit
11436 @code{Standard'Storage_Unit} (@code{Standard} is the only permissible
11437 prefix) provides the same value as @code{System.Storage_Unit}.
11439 @node Attribute Stub_Type,Attribute System_Allocator_Alignment,Attribute Storage_Unit,Implementation Defined Attributes
11440 @anchor{gnat_rm/implementation_defined_attributes attribute-stub-type}@anchor{1a5}
11441 @section Attribute Stub_Type
11446 The GNAT implementation of remote access-to-classwide types is
11447 organized as described in AARM section E.4 (20.t): a value of an RACW type
11448 (designating a remote object) is represented as a normal access
11449 value, pointing to a "stub" object which in turn contains the
11450 necessary information to contact the designated remote object. A
11451 call on any dispatching operation of such a stub object does the
11452 remote call, if necessary, using the information in the stub object
11453 to locate the target partition, etc.
11455 For a prefix @code{T} that denotes a remote access-to-classwide type,
11456 @code{T'Stub_Type} denotes the type of the corresponding stub objects.
11458 By construction, the layout of @code{T'Stub_Type} is identical to that of
11459 type @code{RACW_Stub_Type} declared in the internal implementation-defined
11460 unit @code{System.Partition_Interface}. Use of this attribute will create
11461 an implicit dependency on this unit.
11463 @node Attribute System_Allocator_Alignment,Attribute Target_Name,Attribute Stub_Type,Implementation Defined Attributes
11464 @anchor{gnat_rm/implementation_defined_attributes attribute-system-allocator-alignment}@anchor{1a6}
11465 @section Attribute System_Allocator_Alignment
11471 @geindex System_Allocator_Alignment
11473 @code{Standard'System_Allocator_Alignment} (@code{Standard} is the only
11474 permissible prefix) provides the observable guaranted to be honored by
11475 the system allocator (malloc). This is a static value that can be used
11476 in user storage pools based on malloc either to reject allocation
11477 with alignment too large or to enable a realignment circuitry if the
11478 alignment request is larger than this value.
11480 @node Attribute Target_Name,Attribute To_Address,Attribute System_Allocator_Alignment,Implementation Defined Attributes
11481 @anchor{gnat_rm/implementation_defined_attributes attribute-target-name}@anchor{1a7}
11482 @section Attribute Target_Name
11485 @geindex Target_Name
11487 @code{Standard'Target_Name} (@code{Standard} is the only permissible
11488 prefix) provides a static string value that identifies the target
11489 for the current compilation. For GCC implementations, this is the
11490 standard gcc target name without the terminating slash (for
11491 example, GNAT 5.0 on windows yields "i586-pc-mingw32msv").
11493 @node Attribute To_Address,Attribute To_Any,Attribute Target_Name,Implementation Defined Attributes
11494 @anchor{gnat_rm/implementation_defined_attributes attribute-to-address}@anchor{1a8}
11495 @section Attribute To_Address
11498 @geindex To_Address
11500 The @code{System'To_Address}
11501 (@code{System} is the only permissible prefix)
11502 denotes a function identical to
11503 @code{System.Storage_Elements.To_Address} except that
11504 it is a static attribute. This means that if its argument is
11505 a static expression, then the result of the attribute is a
11506 static expression. This means that such an expression can be
11507 used in contexts (e.g., preelaborable packages) which require a
11508 static expression and where the function call could not be used
11509 (since the function call is always nonstatic, even if its
11510 argument is static). The argument must be in the range
11511 -(2**(m-1)) .. 2**m-1, where m is the memory size
11512 (typically 32 or 64). Negative values are intepreted in a
11513 modular manner (e.g., -1 means the same as 16#FFFF_FFFF# on
11514 a 32 bits machine).
11516 @node Attribute To_Any,Attribute Type_Class,Attribute To_Address,Implementation Defined Attributes
11517 @anchor{gnat_rm/implementation_defined_attributes attribute-to-any}@anchor{1a9}
11518 @section Attribute To_Any
11523 This internal attribute is used for the generation of remote subprogram
11524 stubs in the context of the Distributed Systems Annex.
11526 @node Attribute Type_Class,Attribute Type_Key,Attribute To_Any,Implementation Defined Attributes
11527 @anchor{gnat_rm/implementation_defined_attributes attribute-type-class}@anchor{1aa}
11528 @section Attribute Type_Class
11531 @geindex Type_Class
11533 @code{typ'Type_Class} for any type or subtype @cite{typ} yields
11534 the value of the type class for the full type of @cite{typ}. If
11535 @cite{typ} is a generic formal type, the value is the value for the
11536 corresponding actual subtype. The value of this attribute is of type
11537 @code{System.Aux_DEC.Type_Class}, which has the following definition:
11541 (Type_Class_Enumeration,
11542 Type_Class_Integer,
11543 Type_Class_Fixed_Point,
11544 Type_Class_Floating_Point,
11549 Type_Class_Address);
11552 Protected types yield the value @code{Type_Class_Task}, which thus
11553 applies to all concurrent types. This attribute is designed to
11554 be compatible with the DEC Ada 83 attribute of the same name.
11556 @node Attribute Type_Key,Attribute TypeCode,Attribute Type_Class,Implementation Defined Attributes
11557 @anchor{gnat_rm/implementation_defined_attributes attribute-type-key}@anchor{1ab}
11558 @section Attribute Type_Key
11563 The @code{Type_Key} attribute is applicable to a type or subtype and
11564 yields a value of type Standard.String containing encoded information
11565 about the type or subtype. This provides improved compatibility with
11566 other implementations that support this attribute.
11568 @node Attribute TypeCode,Attribute Unconstrained_Array,Attribute Type_Key,Implementation Defined Attributes
11569 @anchor{gnat_rm/implementation_defined_attributes attribute-typecode}@anchor{1ac}
11570 @section Attribute TypeCode
11575 This internal attribute is used for the generation of remote subprogram
11576 stubs in the context of the Distributed Systems Annex.
11578 @node Attribute Unconstrained_Array,Attribute Universal_Literal_String,Attribute TypeCode,Implementation Defined Attributes
11579 @anchor{gnat_rm/implementation_defined_attributes attribute-unconstrained-array}@anchor{1ad}
11580 @section Attribute Unconstrained_Array
11583 @geindex Unconstrained_Array
11585 The @code{Unconstrained_Array} attribute can be used with a prefix that
11586 denotes any type or subtype. It is a static attribute that yields
11587 @code{True} if the prefix designates an unconstrained array,
11588 and @code{False} otherwise. In a generic instance, the result is
11589 still static, and yields the result of applying this test to the
11592 @node Attribute Universal_Literal_String,Attribute Unrestricted_Access,Attribute Unconstrained_Array,Implementation Defined Attributes
11593 @anchor{gnat_rm/implementation_defined_attributes attribute-universal-literal-string}@anchor{1ae}
11594 @section Attribute Universal_Literal_String
11597 @geindex Named numbers
11598 @geindex representation of
11600 @geindex Universal_Literal_String
11602 The prefix of @code{Universal_Literal_String} must be a named
11603 number. The static result is the string consisting of the characters of
11604 the number as defined in the original source. This allows the user
11605 program to access the actual text of named numbers without intermediate
11606 conversions and without the need to enclose the strings in quotes (which
11607 would preclude their use as numbers).
11609 For example, the following program prints the first 50 digits of pi:
11612 with Text_IO; use Text_IO;
11616 Put (Ada.Numerics.Pi'Universal_Literal_String);
11620 @node Attribute Unrestricted_Access,Attribute Update,Attribute Universal_Literal_String,Implementation Defined Attributes
11621 @anchor{gnat_rm/implementation_defined_attributes attribute-unrestricted-access}@anchor{1af}
11622 @section Attribute Unrestricted_Access
11626 @geindex unrestricted
11628 @geindex Unrestricted_Access
11630 The @code{Unrestricted_Access} attribute is similar to @code{Access}
11631 except that all accessibility and aliased view checks are omitted. This
11632 is a user-beware attribute.
11634 For objects, it is similar to @code{Address}, for which it is a
11635 desirable replacement where the value desired is an access type.
11636 In other words, its effect is similar to first applying the
11637 @code{Address} attribute and then doing an unchecked conversion to a
11638 desired access type.
11640 For subprograms, @code{P'Unrestricted_Access} may be used where
11641 @code{P'Access} would be illegal, to construct a value of a
11642 less-nested named access type that designates a more-nested
11643 subprogram. This value may be used in indirect calls, so long as the
11644 more-nested subprogram still exists; once the subprogram containing it
11645 has returned, such calls are erroneous. For example:
11650 type Less_Nested is not null access procedure;
11651 Global : Less_Nested;
11659 Local_Var : Integer;
11661 procedure More_Nested is
11666 Global := More_Nested'Unrestricted_Access;
11673 When P1 is called from P2, the call via Global is OK, but if P1 were
11674 called after P2 returns, it would be an erroneous use of a dangling
11677 For objects, it is possible to use @code{Unrestricted_Access} for any
11678 type. However, if the result is of an access-to-unconstrained array
11679 subtype, then the resulting pointer has the same scope as the context
11680 of the attribute, and must not be returned to some enclosing scope.
11681 For instance, if a function uses @code{Unrestricted_Access} to create
11682 an access-to-unconstrained-array and returns that value to the caller,
11683 the result will involve dangling pointers. In addition, it is only
11684 valid to create pointers to unconstrained arrays using this attribute
11685 if the pointer has the normal default 'fat' representation where a
11686 pointer has two components, one points to the array and one points to
11687 the bounds. If a size clause is used to force 'thin' representation
11688 for a pointer to unconstrained where there is only space for a single
11689 pointer, then the resulting pointer is not usable.
11691 In the simple case where a direct use of Unrestricted_Access attempts
11692 to make a thin pointer for a non-aliased object, the compiler will
11693 reject the use as illegal, as shown in the following example:
11696 with System; use System;
11697 procedure SliceUA2 is
11698 type A is access all String;
11699 for A'Size use Standard'Address_Size;
11701 procedure P (Arg : A) is
11706 X : String := "hello world!";
11707 X2 : aliased String := "hello world!";
11709 AV : A := X'Unrestricted_Access; -- ERROR
11711 >>> illegal use of Unrestricted_Access attribute
11712 >>> attempt to generate thin pointer to unaliased object
11715 P (X'Unrestricted_Access); -- ERROR
11717 >>> illegal use of Unrestricted_Access attribute
11718 >>> attempt to generate thin pointer to unaliased object
11720 P (X(7 .. 12)'Unrestricted_Access); -- ERROR
11722 >>> illegal use of Unrestricted_Access attribute
11723 >>> attempt to generate thin pointer to unaliased object
11725 P (X2'Unrestricted_Access); -- OK
11729 but other cases cannot be detected by the compiler, and are
11730 considered to be erroneous. Consider the following example:
11733 with System; use System;
11734 with System; use System;
11735 procedure SliceUA is
11736 type AF is access all String;
11738 type A is access all String;
11739 for A'Size use Standard'Address_Size;
11741 procedure P (Arg : A) is
11743 if Arg'Length /= 6 then
11744 raise Program_Error;
11748 X : String := "hello world!";
11749 Y : AF := X (7 .. 12)'Unrestricted_Access;
11756 A normal unconstrained array value
11757 or a constrained array object marked as aliased has the bounds in memory
11758 just before the array, so a thin pointer can retrieve both the data and
11759 the bounds. But in this case, the non-aliased object @code{X} does not have the
11760 bounds before the string. If the size clause for type @code{A}
11761 were not present, then the pointer
11762 would be a fat pointer, where one component is a pointer to the bounds,
11763 and all would be well. But with the size clause present, the conversion from
11764 fat pointer to thin pointer in the call loses the bounds, and so this
11765 is erroneous, and the program likely raises a @code{Program_Error} exception.
11767 In general, it is advisable to completely
11768 avoid mixing the use of thin pointers and the use of
11769 @code{Unrestricted_Access} where the designated type is an
11770 unconstrained array. The use of thin pointers should be restricted to
11771 cases of porting legacy code that implicitly assumes the size of pointers,
11772 and such code should not in any case be using this attribute.
11774 Another erroneous situation arises if the attribute is
11775 applied to a constant. The resulting pointer can be used to access the
11776 constant, but the effect of trying to modify a constant in this manner
11777 is not well-defined. Consider this example:
11780 P : constant Integer := 4;
11781 type R is access all Integer;
11782 RV : R := P'Unrestricted_Access;
11787 Here we attempt to modify the constant P from 4 to 3, but the compiler may
11788 or may not notice this attempt, and subsequent references to P may yield
11789 either the value 3 or the value 4 or the assignment may blow up if the
11790 compiler decides to put P in read-only memory. One particular case where
11791 @code{Unrestricted_Access} can be used in this way is to modify the
11792 value of an @code{in} parameter:
11795 procedure K (S : in String) is
11796 type R is access all Character;
11797 RV : R := S (3)'Unrestricted_Access;
11803 In general this is a risky approach. It may appear to "work" but such uses of
11804 @code{Unrestricted_Access} are potentially non-portable, even from one version
11805 of GNAT to another, so are best avoided if possible.
11807 @node Attribute Update,Attribute Valid_Scalars,Attribute Unrestricted_Access,Implementation Defined Attributes
11808 @anchor{gnat_rm/implementation_defined_attributes attribute-update}@anchor{1b0}
11809 @section Attribute Update
11814 The @code{Update} attribute creates a copy of an array or record value
11815 with one or more modified components. The syntax is:
11818 PREFIX'Update ( RECORD_COMPONENT_ASSOCIATION_LIST )
11819 PREFIX'Update ( ARRAY_COMPONENT_ASSOCIATION @{, ARRAY_COMPONENT_ASSOCIATION @} )
11820 PREFIX'Update ( MULTIDIMENSIONAL_ARRAY_COMPONENT_ASSOCIATION
11821 @{, MULTIDIMENSIONAL_ARRAY_COMPONENT_ASSOCIATION @} )
11823 MULTIDIMENSIONAL_ARRAY_COMPONENT_ASSOCIATION ::= INDEX_EXPRESSION_LIST_LIST => EXPRESSION
11824 INDEX_EXPRESSION_LIST_LIST ::= INDEX_EXPRESSION_LIST @{| INDEX_EXPRESSION_LIST @}
11825 INDEX_EXPRESSION_LIST ::= ( EXPRESSION @{, EXPRESSION @} )
11828 where @code{PREFIX} is the name of an array or record object, the
11829 association list in parentheses does not contain an @code{others}
11830 choice and the box symbol @code{<>} may not appear in any
11831 expression. The effect is to yield a copy of the array or record value
11832 which is unchanged apart from the components mentioned in the
11833 association list, which are changed to the indicated value. The
11834 original value of the array or record value is not affected. For
11838 type Arr is Array (1 .. 5) of Integer;
11840 Avar1 : Arr := (1,2,3,4,5);
11841 Avar2 : Arr := Avar1'Update (2 => 10, 3 .. 4 => 20);
11844 yields a value for @code{Avar2} of 1,10,20,20,5 with @code{Avar1}
11845 begin unmodified. Similarly:
11848 type Rec is A, B, C : Integer;
11850 Rvar1 : Rec := (A => 1, B => 2, C => 3);
11851 Rvar2 : Rec := Rvar1'Update (B => 20);
11854 yields a value for @code{Rvar2} of (A => 1, B => 20, C => 3),
11855 with @code{Rvar1} being unmodifed.
11856 Note that the value of the attribute reference is computed
11857 completely before it is used. This means that if you write:
11860 Avar1 := Avar1'Update (1 => 10, 2 => Function_Call);
11863 then the value of @code{Avar1} is not modified if @code{Function_Call}
11864 raises an exception, unlike the effect of a series of direct assignments
11865 to elements of @code{Avar1}. In general this requires that
11866 two extra complete copies of the object are required, which should be
11867 kept in mind when considering efficiency.
11869 The @code{Update} attribute cannot be applied to prefixes of a limited
11870 type, and cannot reference discriminants in the case of a record type.
11871 The accessibility level of an Update attribute result object is defined
11872 as for an aggregate.
11874 In the record case, no component can be mentioned more than once. In
11875 the array case, two overlapping ranges can appear in the association list,
11876 in which case the modifications are processed left to right.
11878 Multi-dimensional arrays can be modified, as shown by this example:
11881 A : array (1 .. 10, 1 .. 10) of Integer;
11883 A := A'Update ((1, 2) => 20, (3, 4) => 30);
11886 which changes element (1,2) to 20 and (3,4) to 30.
11888 @node Attribute Valid_Scalars,Attribute VADS_Size,Attribute Update,Implementation Defined Attributes
11889 @anchor{gnat_rm/implementation_defined_attributes attribute-valid-scalars}@anchor{1b1}
11890 @section Attribute Valid_Scalars
11893 @geindex Valid_Scalars
11895 The @code{'Valid_Scalars} attribute is intended to make it easier to check the
11896 validity of scalar subcomponents of composite objects. The attribute is defined
11897 for any prefix @code{P} which denotes an object. Prefix @code{P} can be any type
11898 except for tagged private or @code{Unchecked_Union} types. The value of the
11899 attribute is of type @code{Boolean}.
11901 @code{P'Valid_Scalars} yields @code{True} if and only if the evaluation of
11902 @code{C'Valid} yields @code{True} for every scalar subcomponent @code{C} of @code{P}, or if
11903 @code{P} has no scalar subcomponents. Attribute @code{'Valid_Scalars} is equivalent
11904 to attribute @code{'Valid} for scalar types.
11906 It is not specified in what order the subcomponents are checked, nor whether
11907 any more are checked after any one of them is determined to be invalid. If the
11908 prefix @code{P} is of a class-wide type @code{T'Class} (where @code{T} is the associated
11909 specific type), or if the prefix @code{P} is of a specific tagged type @code{T}, then
11910 only the subcomponents of @code{T} are checked; in other words, components of
11911 extensions of @code{T} are not checked even if @code{T'Class (P)'Tag /= T'Tag}.
11913 The compiler will issue a warning if it can be determined at compile time that
11914 the prefix of the attribute has no scalar subcomponents.
11916 Note: @code{Valid_Scalars} can generate a lot of code, especially in the case of
11917 a large variant record. If the attribute is called in many places in the same
11918 program applied to objects of the same type, it can reduce program size to
11919 write a function with a single use of the attribute, and then call that
11920 function from multiple places.
11922 @node Attribute VADS_Size,Attribute Value_Size,Attribute Valid_Scalars,Implementation Defined Attributes
11923 @anchor{gnat_rm/implementation_defined_attributes attribute-vads-size}@anchor{1b2}
11924 @section Attribute VADS_Size
11928 @geindex VADS compatibility
11932 The @code{'VADS_Size} attribute is intended to make it easier to port
11933 legacy code which relies on the semantics of @code{'Size} as implemented
11934 by the VADS Ada 83 compiler. GNAT makes a best effort at duplicating the
11935 same semantic interpretation. In particular, @code{'VADS_Size} applied
11936 to a predefined or other primitive type with no Size clause yields the
11937 Object_Size (for example, @code{Natural'Size} is 32 rather than 31 on
11938 typical machines). In addition @code{'VADS_Size} applied to an object
11939 gives the result that would be obtained by applying the attribute to
11940 the corresponding type.
11942 @node Attribute Value_Size,Attribute Wchar_T_Size,Attribute VADS_Size,Implementation Defined Attributes
11943 @anchor{gnat_rm/implementation_defined_attributes id6}@anchor{1b3}@anchor{gnat_rm/implementation_defined_attributes attribute-value-size}@anchor{160}
11944 @section Attribute Value_Size
11948 @geindex setting for not-first subtype
11950 @geindex Value_Size
11952 @code{type'Value_Size} is the number of bits required to represent
11953 a value of the given subtype. It is the same as @code{type'Size},
11954 but, unlike @code{Size}, may be set for non-first subtypes.
11956 @node Attribute Wchar_T_Size,Attribute Word_Size,Attribute Value_Size,Implementation Defined Attributes
11957 @anchor{gnat_rm/implementation_defined_attributes attribute-wchar-t-size}@anchor{1b4}
11958 @section Attribute Wchar_T_Size
11961 @geindex Wchar_T_Size
11963 @code{Standard'Wchar_T_Size} (@code{Standard} is the only permissible
11964 prefix) provides the size in bits of the C @code{wchar_t} type
11965 primarily for constructing the definition of this type in
11966 package @code{Interfaces.C}. The result is a static constant.
11968 @node Attribute Word_Size,,Attribute Wchar_T_Size,Implementation Defined Attributes
11969 @anchor{gnat_rm/implementation_defined_attributes attribute-word-size}@anchor{1b5}
11970 @section Attribute Word_Size
11975 @code{Standard'Word_Size} (@code{Standard} is the only permissible
11976 prefix) provides the value @code{System.Word_Size}. The result is
11979 @node Standard and Implementation Defined Restrictions,Implementation Advice,Implementation Defined Attributes,Top
11980 @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{1b6}@anchor{gnat_rm/standard_and_implementation_defined_restrictions id1}@anchor{1b7}
11981 @chapter Standard and Implementation Defined Restrictions
11984 All Ada Reference Manual-defined Restriction identifiers are implemented:
11990 language-defined restrictions (see 13.12.1)
11993 tasking restrictions (see D.7)
11996 high integrity restrictions (see H.4)
11999 GNAT implements additional restriction identifiers. All restrictions, whether
12000 language defined or GNAT-specific, are listed in the following.
12003 * Partition-Wide Restrictions::
12004 * Program Unit Level Restrictions::
12008 @node Partition-Wide Restrictions,Program Unit Level Restrictions,,Standard and Implementation Defined Restrictions
12009 @anchor{gnat_rm/standard_and_implementation_defined_restrictions partition-wide-restrictions}@anchor{1b8}@anchor{gnat_rm/standard_and_implementation_defined_restrictions id2}@anchor{1b9}
12010 @section Partition-Wide Restrictions
12013 There are two separate lists of restriction identifiers. The first
12014 set requires consistency throughout a partition (in other words, if the
12015 restriction identifier is used for any compilation unit in the partition,
12016 then all compilation units in the partition must obey the restriction).
12019 * Immediate_Reclamation::
12020 * Max_Asynchronous_Select_Nesting::
12021 * Max_Entry_Queue_Length::
12022 * Max_Protected_Entries::
12023 * Max_Select_Alternatives::
12024 * Max_Storage_At_Blocking::
12025 * Max_Task_Entries::
12027 * No_Abort_Statements::
12028 * No_Access_Parameter_Allocators::
12029 * No_Access_Subprograms::
12031 * No_Anonymous_Allocators::
12032 * No_Asynchronous_Control::
12034 * No_Coextensions::
12035 * No_Default_Initialization::
12038 * No_Direct_Boolean_Operators::
12040 * No_Dispatching_Calls::
12041 * No_Dynamic_Attachment::
12042 * No_Dynamic_Priorities::
12043 * No_Entry_Calls_In_Elaboration_Code::
12044 * No_Enumeration_Maps::
12045 * No_Exception_Handlers::
12046 * No_Exception_Propagation::
12047 * No_Exception_Registration::
12049 * No_Finalization::
12051 * No_Floating_Point::
12052 * No_Implicit_Conditionals::
12053 * No_Implicit_Dynamic_Code::
12054 * No_Implicit_Heap_Allocations::
12055 * No_Implicit_Protected_Object_Allocations::
12056 * No_Implicit_Task_Allocations::
12057 * No_Initialize_Scalars::
12059 * No_Local_Allocators::
12060 * No_Local_Protected_Objects::
12061 * No_Local_Timing_Events::
12062 * No_Long_Long_Integers::
12063 * No_Multiple_Elaboration::
12064 * No_Nested_Finalization::
12065 * No_Protected_Type_Allocators::
12066 * No_Protected_Types::
12069 * No_Relative_Delay::
12070 * No_Requeue_Statements::
12071 * No_Secondary_Stack::
12072 * No_Select_Statements::
12073 * No_Specific_Termination_Handlers::
12074 * No_Specification_of_Aspect::
12075 * No_Standard_Allocators_After_Elaboration::
12076 * No_Standard_Storage_Pools::
12077 * No_Stream_Optimizations::
12079 * No_Task_Allocators::
12080 * No_Task_At_Interrupt_Priority::
12081 * No_Task_Attributes_Package::
12082 * No_Task_Hierarchy::
12083 * No_Task_Termination::
12085 * No_Terminate_Alternatives::
12086 * No_Unchecked_Access::
12087 * No_Unchecked_Conversion::
12088 * No_Unchecked_Deallocation::
12089 * No_Use_Of_Entity::
12091 * Simple_Barriers::
12092 * Static_Priorities::
12093 * Static_Storage_Size::
12097 @node Immediate_Reclamation,Max_Asynchronous_Select_Nesting,,Partition-Wide Restrictions
12098 @anchor{gnat_rm/standard_and_implementation_defined_restrictions immediate-reclamation}@anchor{1ba}
12099 @subsection Immediate_Reclamation
12102 @geindex Immediate_Reclamation
12104 [RM H.4] This restriction ensures that, except for storage occupied by
12105 objects created by allocators and not deallocated via unchecked
12106 deallocation, any storage reserved at run time for an object is
12107 immediately reclaimed when the object no longer exists.
12109 @node Max_Asynchronous_Select_Nesting,Max_Entry_Queue_Length,Immediate_Reclamation,Partition-Wide Restrictions
12110 @anchor{gnat_rm/standard_and_implementation_defined_restrictions max-asynchronous-select-nesting}@anchor{1bb}
12111 @subsection Max_Asynchronous_Select_Nesting
12114 @geindex Max_Asynchronous_Select_Nesting
12116 [RM D.7] Specifies the maximum dynamic nesting level of asynchronous
12117 selects. Violations of this restriction with a value of zero are
12118 detected at compile time. Violations of this restriction with values
12119 other than zero cause Storage_Error to be raised.
12121 @node Max_Entry_Queue_Length,Max_Protected_Entries,Max_Asynchronous_Select_Nesting,Partition-Wide Restrictions
12122 @anchor{gnat_rm/standard_and_implementation_defined_restrictions max-entry-queue-length}@anchor{1bc}
12123 @subsection Max_Entry_Queue_Length
12126 @geindex Max_Entry_Queue_Length
12128 [RM D.7] This restriction is a declaration that any protected entry compiled in
12129 the scope of the restriction has at most the specified number of
12130 tasks waiting on the entry at any one time, and so no queue is required.
12131 Note that this restriction is checked at run time. Violation of this
12132 restriction results in the raising of Program_Error exception at the point of
12135 @geindex Max_Entry_Queue_Depth
12137 The restriction @code{Max_Entry_Queue_Depth} is recognized as a
12138 synonym for @code{Max_Entry_Queue_Length}. This is retained for historical
12139 compatibility purposes (and a warning will be generated for its use if
12140 warnings on obsolescent features are activated).
12142 @node Max_Protected_Entries,Max_Select_Alternatives,Max_Entry_Queue_Length,Partition-Wide Restrictions
12143 @anchor{gnat_rm/standard_and_implementation_defined_restrictions max-protected-entries}@anchor{1bd}
12144 @subsection Max_Protected_Entries
12147 @geindex Max_Protected_Entries
12149 [RM D.7] Specifies the maximum number of entries per protected type. The
12150 bounds of every entry family of a protected unit shall be static, or shall be
12151 defined by a discriminant of a subtype whose corresponding bound is static.
12153 @node Max_Select_Alternatives,Max_Storage_At_Blocking,Max_Protected_Entries,Partition-Wide Restrictions
12154 @anchor{gnat_rm/standard_and_implementation_defined_restrictions max-select-alternatives}@anchor{1be}
12155 @subsection Max_Select_Alternatives
12158 @geindex Max_Select_Alternatives
12160 [RM D.7] Specifies the maximum number of alternatives in a selective accept.
12162 @node Max_Storage_At_Blocking,Max_Task_Entries,Max_Select_Alternatives,Partition-Wide Restrictions
12163 @anchor{gnat_rm/standard_and_implementation_defined_restrictions max-storage-at-blocking}@anchor{1bf}
12164 @subsection Max_Storage_At_Blocking
12167 @geindex Max_Storage_At_Blocking
12169 [RM D.7] Specifies the maximum portion (in storage elements) of a task's
12170 Storage_Size that can be retained by a blocked task. A violation of this
12171 restriction causes Storage_Error to be raised.
12173 @node Max_Task_Entries,Max_Tasks,Max_Storage_At_Blocking,Partition-Wide Restrictions
12174 @anchor{gnat_rm/standard_and_implementation_defined_restrictions max-task-entries}@anchor{1c0}
12175 @subsection Max_Task_Entries
12178 @geindex Max_Task_Entries
12180 [RM D.7] Specifies the maximum number of entries
12181 per task. The bounds of every entry family
12182 of a task unit shall be static, or shall be
12183 defined by a discriminant of a subtype whose
12184 corresponding bound is static.
12186 @node Max_Tasks,No_Abort_Statements,Max_Task_Entries,Partition-Wide Restrictions
12187 @anchor{gnat_rm/standard_and_implementation_defined_restrictions max-tasks}@anchor{1c1}
12188 @subsection Max_Tasks
12193 [RM D.7] Specifies the maximum number of task that may be created, not
12194 counting the creation of the environment task. Violations of this
12195 restriction with a value of zero are detected at compile
12196 time. Violations of this restriction with values other than zero cause
12197 Storage_Error to be raised.
12199 @node No_Abort_Statements,No_Access_Parameter_Allocators,Max_Tasks,Partition-Wide Restrictions
12200 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-abort-statements}@anchor{1c2}
12201 @subsection No_Abort_Statements
12204 @geindex No_Abort_Statements
12206 [RM D.7] There are no abort_statements, and there are
12207 no calls to Task_Identification.Abort_Task.
12209 @node No_Access_Parameter_Allocators,No_Access_Subprograms,No_Abort_Statements,Partition-Wide Restrictions
12210 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-access-parameter-allocators}@anchor{1c3}
12211 @subsection No_Access_Parameter_Allocators
12214 @geindex No_Access_Parameter_Allocators
12216 [RM H.4] This restriction ensures at compile time that there are no
12217 occurrences of an allocator as the actual parameter to an access
12220 @node No_Access_Subprograms,No_Allocators,No_Access_Parameter_Allocators,Partition-Wide Restrictions
12221 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-access-subprograms}@anchor{1c4}
12222 @subsection No_Access_Subprograms
12225 @geindex No_Access_Subprograms
12227 [RM H.4] This restriction ensures at compile time that there are no
12228 declarations of access-to-subprogram types.
12230 @node No_Allocators,No_Anonymous_Allocators,No_Access_Subprograms,Partition-Wide Restrictions
12231 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-allocators}@anchor{1c5}
12232 @subsection No_Allocators
12235 @geindex No_Allocators
12237 [RM H.4] This restriction ensures at compile time that there are no
12238 occurrences of an allocator.
12240 @node No_Anonymous_Allocators,No_Asynchronous_Control,No_Allocators,Partition-Wide Restrictions
12241 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-anonymous-allocators}@anchor{1c6}
12242 @subsection No_Anonymous_Allocators
12245 @geindex No_Anonymous_Allocators
12247 [RM H.4] This restriction ensures at compile time that there are no
12248 occurrences of an allocator of anonymous access type.
12250 @node No_Asynchronous_Control,No_Calendar,No_Anonymous_Allocators,Partition-Wide Restrictions
12251 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-asynchronous-control}@anchor{1c7}
12252 @subsection No_Asynchronous_Control
12255 @geindex No_Asynchronous_Control
12257 [RM J.13] This restriction ensures at compile time that there are no semantic
12258 dependences on the predefined package Asynchronous_Task_Control.
12260 @node No_Calendar,No_Coextensions,No_Asynchronous_Control,Partition-Wide Restrictions
12261 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-calendar}@anchor{1c8}
12262 @subsection No_Calendar
12265 @geindex No_Calendar
12267 [GNAT] This restriction ensures at compile time that there are no semantic
12268 dependences on package Calendar.
12270 @node No_Coextensions,No_Default_Initialization,No_Calendar,Partition-Wide Restrictions
12271 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-coextensions}@anchor{1c9}
12272 @subsection No_Coextensions
12275 @geindex No_Coextensions
12277 [RM H.4] This restriction ensures at compile time that there are no
12278 coextensions. See 3.10.2.
12280 @node No_Default_Initialization,No_Delay,No_Coextensions,Partition-Wide Restrictions
12281 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-default-initialization}@anchor{1ca}
12282 @subsection No_Default_Initialization
12285 @geindex No_Default_Initialization
12287 [GNAT] This restriction prohibits any instance of default initialization
12288 of variables. The binder implements a consistency rule which prevents
12289 any unit compiled without the restriction from with'ing a unit with the
12290 restriction (this allows the generation of initialization procedures to
12291 be skipped, since you can be sure that no call is ever generated to an
12292 initialization procedure in a unit with the restriction active). If used
12293 in conjunction with Initialize_Scalars or Normalize_Scalars, the effect
12294 is to prohibit all cases of variables declared without a specific
12295 initializer (including the case of OUT scalar parameters).
12297 @node No_Delay,No_Dependence,No_Default_Initialization,Partition-Wide Restrictions
12298 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-delay}@anchor{1cb}
12299 @subsection No_Delay
12304 [RM H.4] This restriction ensures at compile time that there are no
12305 delay statements and no semantic dependences on package Calendar.
12307 @node No_Dependence,No_Direct_Boolean_Operators,No_Delay,Partition-Wide Restrictions
12308 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-dependence}@anchor{1cc}
12309 @subsection No_Dependence
12312 @geindex No_Dependence
12314 [RM 13.12.1] This restriction ensures at compile time that there are no
12315 dependences on a library unit.
12317 @node No_Direct_Boolean_Operators,No_Dispatch,No_Dependence,Partition-Wide Restrictions
12318 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-direct-boolean-operators}@anchor{1cd}
12319 @subsection No_Direct_Boolean_Operators
12322 @geindex No_Direct_Boolean_Operators
12324 [GNAT] This restriction ensures that no logical operators (and/or/xor)
12325 are used on operands of type Boolean (or any type derived from Boolean).
12326 This is intended for use in safety critical programs where the certification
12327 protocol requires the use of short-circuit (and then, or else) forms for all
12328 composite boolean operations.
12330 @node No_Dispatch,No_Dispatching_Calls,No_Direct_Boolean_Operators,Partition-Wide Restrictions
12331 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-dispatch}@anchor{1ce}
12332 @subsection No_Dispatch
12335 @geindex No_Dispatch
12337 [RM H.4] This restriction ensures at compile time that there are no
12338 occurrences of @code{T'Class}, for any (tagged) subtype @code{T}.
12340 @node No_Dispatching_Calls,No_Dynamic_Attachment,No_Dispatch,Partition-Wide Restrictions
12341 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-dispatching-calls}@anchor{1cf}
12342 @subsection No_Dispatching_Calls
12345 @geindex No_Dispatching_Calls
12347 [GNAT] This restriction ensures at compile time that the code generated by the
12348 compiler involves no dispatching calls. The use of this restriction allows the
12349 safe use of record extensions, classwide membership tests and other classwide
12350 features not involving implicit dispatching. This restriction ensures that
12351 the code contains no indirect calls through a dispatching mechanism. Note that
12352 this includes internally-generated calls created by the compiler, for example
12353 in the implementation of class-wide objects assignments. The
12354 membership test is allowed in the presence of this restriction, because its
12355 implementation requires no dispatching.
12356 This restriction is comparable to the official Ada restriction
12357 @code{No_Dispatch} except that it is a bit less restrictive in that it allows
12358 all classwide constructs that do not imply dispatching.
12359 The following example indicates constructs that violate this restriction.
12363 type T is tagged record
12366 procedure P (X : T);
12368 type DT is new T with record
12369 More_Data : Natural;
12371 procedure Q (X : DT);
12375 procedure Example is
12376 procedure Test (O : T'Class) is
12377 N : Natural := O'Size;-- Error: Dispatching call
12378 C : T'Class := O; -- Error: implicit Dispatching Call
12380 if O in DT'Class then -- OK : Membership test
12381 Q (DT (O)); -- OK : Type conversion plus direct call
12383 P (O); -- Error: Dispatching call
12389 P (Obj); -- OK : Direct call
12390 P (T (Obj)); -- OK : Type conversion plus direct call
12391 P (T'Class (Obj)); -- Error: Dispatching call
12393 Test (Obj); -- OK : Type conversion
12395 if Obj in T'Class then -- OK : Membership test
12401 @node No_Dynamic_Attachment,No_Dynamic_Priorities,No_Dispatching_Calls,Partition-Wide Restrictions
12402 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-dynamic-attachment}@anchor{1d0}
12403 @subsection No_Dynamic_Attachment
12406 @geindex No_Dynamic_Attachment
12408 [RM D.7] This restriction ensures that there is no call to any of the
12409 operations defined in package Ada.Interrupts
12410 (Is_Reserved, Is_Attached, Current_Handler, Attach_Handler, Exchange_Handler,
12411 Detach_Handler, and Reference).
12413 @geindex No_Dynamic_Interrupts
12415 The restriction @code{No_Dynamic_Interrupts} is recognized as a
12416 synonym for @code{No_Dynamic_Attachment}. This is retained for historical
12417 compatibility purposes (and a warning will be generated for its use if
12418 warnings on obsolescent features are activated).
12420 @node No_Dynamic_Priorities,No_Entry_Calls_In_Elaboration_Code,No_Dynamic_Attachment,Partition-Wide Restrictions
12421 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-dynamic-priorities}@anchor{1d1}
12422 @subsection No_Dynamic_Priorities
12425 @geindex No_Dynamic_Priorities
12427 [RM D.7] There are no semantic dependencies on the package Dynamic_Priorities.
12429 @node No_Entry_Calls_In_Elaboration_Code,No_Enumeration_Maps,No_Dynamic_Priorities,Partition-Wide Restrictions
12430 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-entry-calls-in-elaboration-code}@anchor{1d2}
12431 @subsection No_Entry_Calls_In_Elaboration_Code
12434 @geindex No_Entry_Calls_In_Elaboration_Code
12436 [GNAT] This restriction ensures at compile time that no task or protected entry
12437 calls are made during elaboration code. As a result of the use of this
12438 restriction, the compiler can assume that no code past an accept statement
12439 in a task can be executed at elaboration time.
12441 @node No_Enumeration_Maps,No_Exception_Handlers,No_Entry_Calls_In_Elaboration_Code,Partition-Wide Restrictions
12442 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-enumeration-maps}@anchor{1d3}
12443 @subsection No_Enumeration_Maps
12446 @geindex No_Enumeration_Maps
12448 [GNAT] This restriction ensures at compile time that no operations requiring
12449 enumeration maps are used (that is Image and Value attributes applied
12450 to enumeration types).
12452 @node No_Exception_Handlers,No_Exception_Propagation,No_Enumeration_Maps,Partition-Wide Restrictions
12453 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-exception-handlers}@anchor{1d4}
12454 @subsection No_Exception_Handlers
12457 @geindex No_Exception_Handlers
12459 [GNAT] This restriction ensures at compile time that there are no explicit
12460 exception handlers. It also indicates that no exception propagation will
12461 be provided. In this mode, exceptions may be raised but will result in
12462 an immediate call to the last chance handler, a routine that the user
12463 must define with the following profile:
12466 procedure Last_Chance_Handler
12467 (Source_Location : System.Address; Line : Integer);
12468 pragma Export (C, Last_Chance_Handler,
12469 "__gnat_last_chance_handler");
12472 The parameter is a C null-terminated string representing a message to be
12473 associated with the exception (typically the source location of the raise
12474 statement generated by the compiler). The Line parameter when nonzero
12475 represents the line number in the source program where the raise occurs.
12477 @node No_Exception_Propagation,No_Exception_Registration,No_Exception_Handlers,Partition-Wide Restrictions
12478 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-exception-propagation}@anchor{1d5}
12479 @subsection No_Exception_Propagation
12482 @geindex No_Exception_Propagation
12484 [GNAT] This restriction guarantees that exceptions are never propagated
12485 to an outer subprogram scope. The only case in which an exception may
12486 be raised is when the handler is statically in the same subprogram, so
12487 that the effect of a raise is essentially like a goto statement. Any
12488 other raise statement (implicit or explicit) will be considered
12489 unhandled. Exception handlers are allowed, but may not contain an
12490 exception occurrence identifier (exception choice). In addition, use of
12491 the package GNAT.Current_Exception is not permitted, and reraise
12492 statements (raise with no operand) are not permitted.
12494 @node No_Exception_Registration,No_Exceptions,No_Exception_Propagation,Partition-Wide Restrictions
12495 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-exception-registration}@anchor{1d6}
12496 @subsection No_Exception_Registration
12499 @geindex No_Exception_Registration
12501 [GNAT] This restriction ensures at compile time that no stream operations for
12502 types Exception_Id or Exception_Occurrence are used. This also makes it
12503 impossible to pass exceptions to or from a partition with this restriction
12504 in a distributed environment. If this restriction is active, the generated
12505 code is simplified by omitting the otherwise-required global registration
12506 of exceptions when they are declared.
12508 @node No_Exceptions,No_Finalization,No_Exception_Registration,Partition-Wide Restrictions
12509 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-exceptions}@anchor{1d7}
12510 @subsection No_Exceptions
12513 @geindex No_Exceptions
12515 [RM H.4] This restriction ensures at compile time that there are no
12516 raise statements and no exception handlers and also suppresses the
12517 generation of language-defined run-time checks.
12519 @node No_Finalization,No_Fixed_Point,No_Exceptions,Partition-Wide Restrictions
12520 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-finalization}@anchor{1d8}
12521 @subsection No_Finalization
12524 @geindex No_Finalization
12526 [GNAT] This restriction disables the language features described in
12527 chapter 7.6 of the Ada 2005 RM as well as all form of code generation
12528 performed by the compiler to support these features. The following types
12529 are no longer considered controlled when this restriction is in effect:
12535 @code{Ada.Finalization.Controlled}
12538 @code{Ada.Finalization.Limited_Controlled}
12541 Derivations from @code{Controlled} or @code{Limited_Controlled}
12553 Array and record types with controlled components
12556 The compiler no longer generates code to initialize, finalize or adjust an
12557 object or a nested component, either declared on the stack or on the heap. The
12558 deallocation of a controlled object no longer finalizes its contents.
12560 @node No_Fixed_Point,No_Floating_Point,No_Finalization,Partition-Wide Restrictions
12561 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-fixed-point}@anchor{1d9}
12562 @subsection No_Fixed_Point
12565 @geindex No_Fixed_Point
12567 [RM H.4] This restriction ensures at compile time that there are no
12568 occurrences of fixed point types and operations.
12570 @node No_Floating_Point,No_Implicit_Conditionals,No_Fixed_Point,Partition-Wide Restrictions
12571 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-floating-point}@anchor{1da}
12572 @subsection No_Floating_Point
12575 @geindex No_Floating_Point
12577 [RM H.4] This restriction ensures at compile time that there are no
12578 occurrences of floating point types and operations.
12580 @node No_Implicit_Conditionals,No_Implicit_Dynamic_Code,No_Floating_Point,Partition-Wide Restrictions
12581 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-conditionals}@anchor{1db}
12582 @subsection No_Implicit_Conditionals
12585 @geindex No_Implicit_Conditionals
12587 [GNAT] This restriction ensures that the generated code does not contain any
12588 implicit conditionals, either by modifying the generated code where possible,
12589 or by rejecting any construct that would otherwise generate an implicit
12590 conditional. Note that this check does not include run time constraint
12591 checks, which on some targets may generate implicit conditionals as
12592 well. To control the latter, constraint checks can be suppressed in the
12593 normal manner. Constructs generating implicit conditionals include comparisons
12594 of composite objects and the Max/Min attributes.
12596 @node No_Implicit_Dynamic_Code,No_Implicit_Heap_Allocations,No_Implicit_Conditionals,Partition-Wide Restrictions
12597 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-dynamic-code}@anchor{1dc}
12598 @subsection No_Implicit_Dynamic_Code
12601 @geindex No_Implicit_Dynamic_Code
12603 @geindex trampoline
12605 [GNAT] This restriction prevents the compiler from building 'trampolines'.
12606 This is a structure that is built on the stack and contains dynamic
12607 code to be executed at run time. On some targets, a trampoline is
12608 built for the following features: @code{Access},
12609 @code{Unrestricted_Access}, or @code{Address} of a nested subprogram;
12610 nested task bodies; primitive operations of nested tagged types.
12611 Trampolines do not work on machines that prevent execution of stack
12612 data. For example, on windows systems, enabling DEP (data execution
12613 protection) will cause trampolines to raise an exception.
12614 Trampolines are also quite slow at run time.
12616 On many targets, trampolines have been largely eliminated. Look at the
12617 version of system.ads for your target --- if it has
12618 Always_Compatible_Rep equal to False, then trampolines are largely
12619 eliminated. In particular, a trampoline is built for the following
12620 features: @code{Address} of a nested subprogram;
12621 @code{Access} or @code{Unrestricted_Access} of a nested subprogram,
12622 but only if pragma Favor_Top_Level applies, or the access type has a
12623 foreign-language convention; primitive operations of nested tagged
12626 @node No_Implicit_Heap_Allocations,No_Implicit_Protected_Object_Allocations,No_Implicit_Dynamic_Code,Partition-Wide Restrictions
12627 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-heap-allocations}@anchor{1dd}
12628 @subsection No_Implicit_Heap_Allocations
12631 @geindex No_Implicit_Heap_Allocations
12633 [RM D.7] No constructs are allowed to cause implicit heap allocation.
12635 @node No_Implicit_Protected_Object_Allocations,No_Implicit_Task_Allocations,No_Implicit_Heap_Allocations,Partition-Wide Restrictions
12636 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-protected-object-allocations}@anchor{1de}
12637 @subsection No_Implicit_Protected_Object_Allocations
12640 @geindex No_Implicit_Protected_Object_Allocations
12642 [GNAT] No constructs are allowed to cause implicit heap allocation of a
12645 @node No_Implicit_Task_Allocations,No_Initialize_Scalars,No_Implicit_Protected_Object_Allocations,Partition-Wide Restrictions
12646 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-task-allocations}@anchor{1df}
12647 @subsection No_Implicit_Task_Allocations
12650 @geindex No_Implicit_Task_Allocations
12652 [GNAT] No constructs are allowed to cause implicit heap allocation of a task.
12654 @node No_Initialize_Scalars,No_IO,No_Implicit_Task_Allocations,Partition-Wide Restrictions
12655 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-initialize-scalars}@anchor{1e0}
12656 @subsection No_Initialize_Scalars
12659 @geindex No_Initialize_Scalars
12661 [GNAT] This restriction ensures that no unit in the partition is compiled with
12662 pragma Initialize_Scalars. This allows the generation of more efficient
12663 code, and in particular eliminates dummy null initialization routines that
12664 are otherwise generated for some record and array types.
12666 @node No_IO,No_Local_Allocators,No_Initialize_Scalars,Partition-Wide Restrictions
12667 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-io}@anchor{1e1}
12673 [RM H.4] This restriction ensures at compile time that there are no
12674 dependences on any of the library units Sequential_IO, Direct_IO,
12675 Text_IO, Wide_Text_IO, Wide_Wide_Text_IO, or Stream_IO.
12677 @node No_Local_Allocators,No_Local_Protected_Objects,No_IO,Partition-Wide Restrictions
12678 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-local-allocators}@anchor{1e2}
12679 @subsection No_Local_Allocators
12682 @geindex No_Local_Allocators
12684 [RM H.4] This restriction ensures at compile time that there are no
12685 occurrences of an allocator in subprograms, generic subprograms, tasks,
12688 @node No_Local_Protected_Objects,No_Local_Timing_Events,No_Local_Allocators,Partition-Wide Restrictions
12689 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-local-protected-objects}@anchor{1e3}
12690 @subsection No_Local_Protected_Objects
12693 @geindex No_Local_Protected_Objects
12695 [RM D.7] This restriction ensures at compile time that protected objects are
12696 only declared at the library level.
12698 @node No_Local_Timing_Events,No_Long_Long_Integers,No_Local_Protected_Objects,Partition-Wide Restrictions
12699 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-local-timing-events}@anchor{1e4}
12700 @subsection No_Local_Timing_Events
12703 @geindex No_Local_Timing_Events
12705 [RM D.7] All objects of type Ada.Real_Time.Timing_Events.Timing_Event are
12706 declared at the library level.
12708 @node No_Long_Long_Integers,No_Multiple_Elaboration,No_Local_Timing_Events,Partition-Wide Restrictions
12709 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-long-long-integers}@anchor{1e5}
12710 @subsection No_Long_Long_Integers
12713 @geindex No_Long_Long_Integers
12715 [GNAT] This partition-wide restriction forbids any explicit reference to
12716 type Standard.Long_Long_Integer, and also forbids declaring range types whose
12717 implicit base type is Long_Long_Integer, and modular types whose size exceeds
12720 @node No_Multiple_Elaboration,No_Nested_Finalization,No_Long_Long_Integers,Partition-Wide Restrictions
12721 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-multiple-elaboration}@anchor{1e6}
12722 @subsection No_Multiple_Elaboration
12725 @geindex No_Multiple_Elaboration
12727 [GNAT] When this restriction is active and the static elaboration model is
12728 used, and -fpreserve-control-flow is not used, the compiler is allowed to
12729 suppress the elaboration counter normally associated with the unit, even if
12730 the unit has elaboration code. This counter is typically used to check for
12731 access before elaboration and to control multiple elaboration attempts. If the
12732 restriction is used, then the situations in which multiple elaboration is
12733 possible, including non-Ada main programs and Stand Alone libraries, are not
12734 permitted and will be diagnosed by the binder.
12736 @node No_Nested_Finalization,No_Protected_Type_Allocators,No_Multiple_Elaboration,Partition-Wide Restrictions
12737 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-nested-finalization}@anchor{1e7}
12738 @subsection No_Nested_Finalization
12741 @geindex No_Nested_Finalization
12743 [RM D.7] All objects requiring finalization are declared at the library level.
12745 @node No_Protected_Type_Allocators,No_Protected_Types,No_Nested_Finalization,Partition-Wide Restrictions
12746 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-protected-type-allocators}@anchor{1e8}
12747 @subsection No_Protected_Type_Allocators
12750 @geindex No_Protected_Type_Allocators
12752 [RM D.7] This restriction ensures at compile time that there are no allocator
12753 expressions that attempt to allocate protected objects.
12755 @node No_Protected_Types,No_Recursion,No_Protected_Type_Allocators,Partition-Wide Restrictions
12756 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-protected-types}@anchor{1e9}
12757 @subsection No_Protected_Types
12760 @geindex No_Protected_Types
12762 [RM H.4] This restriction ensures at compile time that there are no
12763 declarations of protected types or protected objects.
12765 @node No_Recursion,No_Reentrancy,No_Protected_Types,Partition-Wide Restrictions
12766 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-recursion}@anchor{1ea}
12767 @subsection No_Recursion
12770 @geindex No_Recursion
12772 [RM H.4] A program execution is erroneous if a subprogram is invoked as
12773 part of its execution.
12775 @node No_Reentrancy,No_Relative_Delay,No_Recursion,Partition-Wide Restrictions
12776 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-reentrancy}@anchor{1eb}
12777 @subsection No_Reentrancy
12780 @geindex No_Reentrancy
12782 [RM H.4] A program execution is erroneous if a subprogram is executed by
12783 two tasks at the same time.
12785 @node No_Relative_Delay,No_Requeue_Statements,No_Reentrancy,Partition-Wide Restrictions
12786 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-relative-delay}@anchor{1ec}
12787 @subsection No_Relative_Delay
12790 @geindex No_Relative_Delay
12792 [RM D.7] This restriction ensures at compile time that there are no delay
12793 relative statements and prevents expressions such as @code{delay 1.23;} from
12794 appearing in source code.
12796 @node No_Requeue_Statements,No_Secondary_Stack,No_Relative_Delay,Partition-Wide Restrictions
12797 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-requeue-statements}@anchor{1ed}
12798 @subsection No_Requeue_Statements
12801 @geindex No_Requeue_Statements
12803 [RM D.7] This restriction ensures at compile time that no requeue statements
12804 are permitted and prevents keyword @code{requeue} from being used in source
12807 @geindex No_Requeue
12809 The restriction @code{No_Requeue} is recognized as a
12810 synonym for @code{No_Requeue_Statements}. This is retained for historical
12811 compatibility purposes (and a warning will be generated for its use if
12812 warnings on oNobsolescent features are activated).
12814 @node No_Secondary_Stack,No_Select_Statements,No_Requeue_Statements,Partition-Wide Restrictions
12815 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-secondary-stack}@anchor{1ee}
12816 @subsection No_Secondary_Stack
12819 @geindex No_Secondary_Stack
12821 [GNAT] This restriction ensures at compile time that the generated code
12822 does not contain any reference to the secondary stack. The secondary
12823 stack is used to implement functions returning unconstrained objects
12824 (arrays or records) on some targets. Suppresses the allocation of
12825 secondary stacks for tasks (excluding the environment task) at run time.
12827 @node No_Select_Statements,No_Specific_Termination_Handlers,No_Secondary_Stack,Partition-Wide Restrictions
12828 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-select-statements}@anchor{1ef}
12829 @subsection No_Select_Statements
12832 @geindex No_Select_Statements
12834 [RM D.7] This restriction ensures at compile time no select statements of any
12835 kind are permitted, that is the keyword @code{select} may not appear.
12837 @node No_Specific_Termination_Handlers,No_Specification_of_Aspect,No_Select_Statements,Partition-Wide Restrictions
12838 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-specific-termination-handlers}@anchor{1f0}
12839 @subsection No_Specific_Termination_Handlers
12842 @geindex No_Specific_Termination_Handlers
12844 [RM D.7] There are no calls to Ada.Task_Termination.Set_Specific_Handler
12845 or to Ada.Task_Termination.Specific_Handler.
12847 @node No_Specification_of_Aspect,No_Standard_Allocators_After_Elaboration,No_Specific_Termination_Handlers,Partition-Wide Restrictions
12848 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-specification-of-aspect}@anchor{1f1}
12849 @subsection No_Specification_of_Aspect
12852 @geindex No_Specification_of_Aspect
12854 [RM 13.12.1] This restriction checks at compile time that no aspect
12855 specification, attribute definition clause, or pragma is given for a
12858 @node No_Standard_Allocators_After_Elaboration,No_Standard_Storage_Pools,No_Specification_of_Aspect,Partition-Wide Restrictions
12859 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-standard-allocators-after-elaboration}@anchor{1f2}
12860 @subsection No_Standard_Allocators_After_Elaboration
12863 @geindex No_Standard_Allocators_After_Elaboration
12865 [RM D.7] Specifies that an allocator using a standard storage pool
12866 should never be evaluated at run time after the elaboration of the
12867 library items of the partition has completed. Otherwise, Storage_Error
12870 @node No_Standard_Storage_Pools,No_Stream_Optimizations,No_Standard_Allocators_After_Elaboration,Partition-Wide Restrictions
12871 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-standard-storage-pools}@anchor{1f3}
12872 @subsection No_Standard_Storage_Pools
12875 @geindex No_Standard_Storage_Pools
12877 [GNAT] This restriction ensures at compile time that no access types
12878 use the standard default storage pool. Any access type declared must
12879 have an explicit Storage_Pool attribute defined specifying a
12880 user-defined storage pool.
12882 @node No_Stream_Optimizations,No_Streams,No_Standard_Storage_Pools,Partition-Wide Restrictions
12883 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-stream-optimizations}@anchor{1f4}
12884 @subsection No_Stream_Optimizations
12887 @geindex No_Stream_Optimizations
12889 [GNAT] This restriction affects the performance of stream operations on types
12890 @code{String}, @code{Wide_String} and @code{Wide_Wide_String}. By default, the
12891 compiler uses block reads and writes when manipulating @code{String} objects
12892 due to their superior performance. When this restriction is in effect, the
12893 compiler performs all IO operations on a per-character basis.
12895 @node No_Streams,No_Task_Allocators,No_Stream_Optimizations,Partition-Wide Restrictions
12896 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-streams}@anchor{1f5}
12897 @subsection No_Streams
12900 @geindex No_Streams
12902 [GNAT] This restriction ensures at compile/bind time that there are no
12903 stream objects created and no use of stream attributes.
12904 This restriction does not forbid dependences on the package
12905 @code{Ada.Streams}. So it is permissible to with
12906 @code{Ada.Streams} (or another package that does so itself)
12907 as long as no actual stream objects are created and no
12908 stream attributes are used.
12910 Note that the use of restriction allows optimization of tagged types,
12911 since they do not need to worry about dispatching stream operations.
12912 To take maximum advantage of this space-saving optimization, any
12913 unit declaring a tagged type should be compiled with the restriction,
12914 though this is not required.
12916 @node No_Task_Allocators,No_Task_At_Interrupt_Priority,No_Streams,Partition-Wide Restrictions
12917 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-task-allocators}@anchor{1f6}
12918 @subsection No_Task_Allocators
12921 @geindex No_Task_Allocators
12923 [RM D.7] There are no allocators for task types
12924 or types containing task subcomponents.
12926 @node No_Task_At_Interrupt_Priority,No_Task_Attributes_Package,No_Task_Allocators,Partition-Wide Restrictions
12927 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-task-at-interrupt-priority}@anchor{1f7}
12928 @subsection No_Task_At_Interrupt_Priority
12931 @geindex No_Task_At_Interrupt_Priority
12933 [GNAT] This restriction ensures at compile time that there is no
12934 Interrupt_Priority aspect or pragma for a task or a task type. As
12935 a consequence, the tasks are always created with a priority below
12936 that an interrupt priority.
12938 @node No_Task_Attributes_Package,No_Task_Hierarchy,No_Task_At_Interrupt_Priority,Partition-Wide Restrictions
12939 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-task-attributes-package}@anchor{1f8}
12940 @subsection No_Task_Attributes_Package
12943 @geindex No_Task_Attributes_Package
12945 [GNAT] This restriction ensures at compile time that there are no implicit or
12946 explicit dependencies on the package @code{Ada.Task_Attributes}.
12948 @geindex No_Task_Attributes
12950 The restriction @code{No_Task_Attributes} is recognized as a synonym
12951 for @code{No_Task_Attributes_Package}. This is retained for historical
12952 compatibility purposes (and a warning will be generated for its use if
12953 warnings on obsolescent features are activated).
12955 @node No_Task_Hierarchy,No_Task_Termination,No_Task_Attributes_Package,Partition-Wide Restrictions
12956 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-task-hierarchy}@anchor{1f9}
12957 @subsection No_Task_Hierarchy
12960 @geindex No_Task_Hierarchy
12962 [RM D.7] All (non-environment) tasks depend
12963 directly on the environment task of the partition.
12965 @node No_Task_Termination,No_Tasking,No_Task_Hierarchy,Partition-Wide Restrictions
12966 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-task-termination}@anchor{1fa}
12967 @subsection No_Task_Termination
12970 @geindex No_Task_Termination
12972 [RM D.7] Tasks that terminate are erroneous.
12974 @node No_Tasking,No_Terminate_Alternatives,No_Task_Termination,Partition-Wide Restrictions
12975 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-tasking}@anchor{1fb}
12976 @subsection No_Tasking
12979 @geindex No_Tasking
12981 [GNAT] This restriction prevents the declaration of tasks or task types
12982 throughout the partition. It is similar in effect to the use of
12983 @code{Max_Tasks => 0} except that violations are caught at compile time
12984 and cause an error message to be output either by the compiler or
12987 @node No_Terminate_Alternatives,No_Unchecked_Access,No_Tasking,Partition-Wide Restrictions
12988 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-terminate-alternatives}@anchor{1fc}
12989 @subsection No_Terminate_Alternatives
12992 @geindex No_Terminate_Alternatives
12994 [RM D.7] There are no selective accepts with terminate alternatives.
12996 @node No_Unchecked_Access,No_Unchecked_Conversion,No_Terminate_Alternatives,Partition-Wide Restrictions
12997 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-unchecked-access}@anchor{1fd}
12998 @subsection No_Unchecked_Access
13001 @geindex No_Unchecked_Access
13003 [RM H.4] This restriction ensures at compile time that there are no
13004 occurrences of the Unchecked_Access attribute.
13006 @node No_Unchecked_Conversion,No_Unchecked_Deallocation,No_Unchecked_Access,Partition-Wide Restrictions
13007 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-unchecked-conversion}@anchor{1fe}
13008 @subsection No_Unchecked_Conversion
13011 @geindex No_Unchecked_Conversion
13013 [RM J.13] This restriction ensures at compile time that there are no semantic
13014 dependences on the predefined generic function Unchecked_Conversion.
13016 @node No_Unchecked_Deallocation,No_Use_Of_Entity,No_Unchecked_Conversion,Partition-Wide Restrictions
13017 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-unchecked-deallocation}@anchor{1ff}
13018 @subsection No_Unchecked_Deallocation
13021 @geindex No_Unchecked_Deallocation
13023 [RM J.13] This restriction ensures at compile time that there are no semantic
13024 dependences on the predefined generic procedure Unchecked_Deallocation.
13026 @node No_Use_Of_Entity,Pure_Barriers,No_Unchecked_Deallocation,Partition-Wide Restrictions
13027 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-use-of-entity}@anchor{200}
13028 @subsection No_Use_Of_Entity
13031 @geindex No_Use_Of_Entity
13033 [GNAT] This restriction ensures at compile time that there are no references
13034 to the entity given in the form
13037 No_Use_Of_Entity => Name
13040 where @code{Name} is the fully qualified entity, for example
13043 No_Use_Of_Entity => Ada.Text_IO.Put_Line
13046 @node Pure_Barriers,Simple_Barriers,No_Use_Of_Entity,Partition-Wide Restrictions
13047 @anchor{gnat_rm/standard_and_implementation_defined_restrictions pure-barriers}@anchor{201}
13048 @subsection Pure_Barriers
13051 @geindex Pure_Barriers
13053 [GNAT] This restriction ensures at compile time that protected entry
13054 barriers are restricted to:
13060 components of the protected object (excluding selection from dereferences),
13063 constant declarations,
13069 enumeration literals,
13078 character literals,
13081 implicitly defined comparison operators,
13084 uses of the Standard."not" operator,
13087 short-circuit operator,
13090 the Count attribute
13093 This restriction is a relaxation of the Simple_Barriers restriction,
13094 but still ensures absence of side effects, exceptions, and recursion
13095 during the evaluation of the barriers.
13097 @node Simple_Barriers,Static_Priorities,Pure_Barriers,Partition-Wide Restrictions
13098 @anchor{gnat_rm/standard_and_implementation_defined_restrictions simple-barriers}@anchor{202}
13099 @subsection Simple_Barriers
13102 @geindex Simple_Barriers
13104 [RM D.7] This restriction ensures at compile time that barriers in entry
13105 declarations for protected types are restricted to either static boolean
13106 expressions or references to simple boolean variables defined in the private
13107 part of the protected type. No other form of entry barriers is permitted.
13109 @geindex Boolean_Entry_Barriers
13111 The restriction @code{Boolean_Entry_Barriers} is recognized as a
13112 synonym for @code{Simple_Barriers}. This is retained for historical
13113 compatibility purposes (and a warning will be generated for its use if
13114 warnings on obsolescent features are activated).
13116 @node Static_Priorities,Static_Storage_Size,Simple_Barriers,Partition-Wide Restrictions
13117 @anchor{gnat_rm/standard_and_implementation_defined_restrictions static-priorities}@anchor{203}
13118 @subsection Static_Priorities
13121 @geindex Static_Priorities
13123 [GNAT] This restriction ensures at compile time that all priority expressions
13124 are static, and that there are no dependences on the package
13125 @code{Ada.Dynamic_Priorities}.
13127 @node Static_Storage_Size,,Static_Priorities,Partition-Wide Restrictions
13128 @anchor{gnat_rm/standard_and_implementation_defined_restrictions static-storage-size}@anchor{204}
13129 @subsection Static_Storage_Size
13132 @geindex Static_Storage_Size
13134 [GNAT] This restriction ensures at compile time that any expression appearing
13135 in a Storage_Size pragma or attribute definition clause is static.
13137 @node Program Unit Level Restrictions,,Partition-Wide Restrictions,Standard and Implementation Defined Restrictions
13138 @anchor{gnat_rm/standard_and_implementation_defined_restrictions program-unit-level-restrictions}@anchor{205}@anchor{gnat_rm/standard_and_implementation_defined_restrictions id3}@anchor{206}
13139 @section Program Unit Level Restrictions
13142 The second set of restriction identifiers
13143 does not require partition-wide consistency.
13144 The restriction may be enforced for a single
13145 compilation unit without any effect on any of the
13146 other compilation units in the partition.
13149 * No_Elaboration_Code::
13150 * No_Dynamic_Sized_Objects::
13152 * No_Implementation_Aspect_Specifications::
13153 * No_Implementation_Attributes::
13154 * No_Implementation_Identifiers::
13155 * No_Implementation_Pragmas::
13156 * No_Implementation_Restrictions::
13157 * No_Implementation_Units::
13158 * No_Implicit_Aliasing::
13159 * No_Implicit_Loops::
13160 * No_Obsolescent_Features::
13161 * No_Wide_Characters::
13162 * Static_Dispatch_Tables::
13167 @node No_Elaboration_Code,No_Dynamic_Sized_Objects,,Program Unit Level Restrictions
13168 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-elaboration-code}@anchor{207}
13169 @subsection No_Elaboration_Code
13172 @geindex No_Elaboration_Code
13174 [GNAT] This restriction ensures at compile time that no elaboration code is
13175 generated. Note that this is not the same condition as is enforced
13176 by pragma @code{Preelaborate}. There are cases in which pragma
13177 @code{Preelaborate} still permits code to be generated (e.g., code
13178 to initialize a large array to all zeroes), and there are cases of units
13179 which do not meet the requirements for pragma @code{Preelaborate},
13180 but for which no elaboration code is generated. Generally, it is
13181 the case that preelaborable units will meet the restrictions, with
13182 the exception of large aggregates initialized with an others_clause,
13183 and exception declarations (which generate calls to a run-time
13184 registry procedure). This restriction is enforced on
13185 a unit by unit basis, it need not be obeyed consistently
13186 throughout a partition.
13188 In the case of aggregates with others, if the aggregate has a dynamic
13189 size, there is no way to eliminate the elaboration code (such dynamic
13190 bounds would be incompatible with @code{Preelaborate} in any case). If
13191 the bounds are static, then use of this restriction actually modifies
13192 the code choice of the compiler to avoid generating a loop, and instead
13193 generate the aggregate statically if possible, no matter how many times
13194 the data for the others clause must be repeatedly generated.
13196 It is not possible to precisely document
13197 the constructs which are compatible with this restriction, since,
13198 unlike most other restrictions, this is not a restriction on the
13199 source code, but a restriction on the generated object code. For
13200 example, if the source contains a declaration:
13203 Val : constant Integer := X;
13206 where X is not a static constant, it may be possible, depending
13207 on complex optimization circuitry, for the compiler to figure
13208 out the value of X at compile time, in which case this initialization
13209 can be done by the loader, and requires no initialization code. It
13210 is not possible to document the precise conditions under which the
13211 optimizer can figure this out.
13213 Note that this the implementation of this restriction requires full
13214 code generation. If it is used in conjunction with "semantics only"
13215 checking, then some cases of violations may be missed.
13217 When this restriction is active, we are not requesting control-flow
13218 preservation with -fpreserve-control-flow, and the static elaboration model is
13219 used, the compiler is allowed to suppress the elaboration counter normally
13220 associated with the unit. This counter is typically used to check for access
13221 before elaboration and to control multiple elaboration attempts.
13223 @node No_Dynamic_Sized_Objects,No_Entry_Queue,No_Elaboration_Code,Program Unit Level Restrictions
13224 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-dynamic-sized-objects}@anchor{208}
13225 @subsection No_Dynamic_Sized_Objects
13228 @geindex No_Dynamic_Sized_Objects
13230 [GNAT] This restriction disallows certain constructs that might lead to the
13231 creation of dynamic-sized composite objects (or array or discriminated type).
13232 An array subtype indication is illegal if the bounds are not static
13233 or references to discriminants of an enclosing type.
13234 A discriminated subtype indication is illegal if the type has
13235 discriminant-dependent array components or a variant part, and the
13236 discriminants are not static. In addition, array and record aggregates are
13237 illegal in corresponding cases. Note that this restriction does not forbid
13238 access discriminants. It is often a good idea to combine this restriction
13239 with No_Secondary_Stack.
13241 @node No_Entry_Queue,No_Implementation_Aspect_Specifications,No_Dynamic_Sized_Objects,Program Unit Level Restrictions
13242 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-entry-queue}@anchor{209}
13243 @subsection No_Entry_Queue
13246 @geindex No_Entry_Queue
13248 [GNAT] This restriction is a declaration that any protected entry compiled in
13249 the scope of the restriction has at most one task waiting on the entry
13250 at any one time, and so no queue is required. This restriction is not
13251 checked at compile time. A program execution is erroneous if an attempt
13252 is made to queue a second task on such an entry.
13254 @node No_Implementation_Aspect_Specifications,No_Implementation_Attributes,No_Entry_Queue,Program Unit Level Restrictions
13255 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implementation-aspect-specifications}@anchor{20a}
13256 @subsection No_Implementation_Aspect_Specifications
13259 @geindex No_Implementation_Aspect_Specifications
13261 [RM 13.12.1] This restriction checks at compile time that no
13262 GNAT-defined aspects are present. With this restriction, the only
13263 aspects that can be used are those defined in the Ada Reference Manual.
13265 @node No_Implementation_Attributes,No_Implementation_Identifiers,No_Implementation_Aspect_Specifications,Program Unit Level Restrictions
13266 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implementation-attributes}@anchor{20b}
13267 @subsection No_Implementation_Attributes
13270 @geindex No_Implementation_Attributes
13272 [RM 13.12.1] This restriction checks at compile time that no
13273 GNAT-defined attributes are present. With this restriction, the only
13274 attributes that can be used are those defined in the Ada Reference
13277 @node No_Implementation_Identifiers,No_Implementation_Pragmas,No_Implementation_Attributes,Program Unit Level Restrictions
13278 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implementation-identifiers}@anchor{20c}
13279 @subsection No_Implementation_Identifiers
13282 @geindex No_Implementation_Identifiers
13284 [RM 13.12.1] This restriction checks at compile time that no
13285 implementation-defined identifiers (marked with pragma Implementation_Defined)
13286 occur within language-defined packages.
13288 @node No_Implementation_Pragmas,No_Implementation_Restrictions,No_Implementation_Identifiers,Program Unit Level Restrictions
13289 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implementation-pragmas}@anchor{20d}
13290 @subsection No_Implementation_Pragmas
13293 @geindex No_Implementation_Pragmas
13295 [RM 13.12.1] This restriction checks at compile time that no
13296 GNAT-defined pragmas are present. With this restriction, the only
13297 pragmas that can be used are those defined in the Ada Reference Manual.
13299 @node No_Implementation_Restrictions,No_Implementation_Units,No_Implementation_Pragmas,Program Unit Level Restrictions
13300 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implementation-restrictions}@anchor{20e}
13301 @subsection No_Implementation_Restrictions
13304 @geindex No_Implementation_Restrictions
13306 [GNAT] This restriction checks at compile time that no GNAT-defined restriction
13307 identifiers (other than @code{No_Implementation_Restrictions} itself)
13308 are present. With this restriction, the only other restriction identifiers
13309 that can be used are those defined in the Ada Reference Manual.
13311 @node No_Implementation_Units,No_Implicit_Aliasing,No_Implementation_Restrictions,Program Unit Level Restrictions
13312 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implementation-units}@anchor{20f}
13313 @subsection No_Implementation_Units
13316 @geindex No_Implementation_Units
13318 [RM 13.12.1] This restriction checks at compile time that there is no
13319 mention in the context clause of any implementation-defined descendants
13320 of packages Ada, Interfaces, or System.
13322 @node No_Implicit_Aliasing,No_Implicit_Loops,No_Implementation_Units,Program Unit Level Restrictions
13323 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-aliasing}@anchor{210}
13324 @subsection No_Implicit_Aliasing
13327 @geindex No_Implicit_Aliasing
13329 [GNAT] This restriction, which is not required to be partition-wide consistent,
13330 requires an explicit aliased keyword for an object to which 'Access,
13331 'Unchecked_Access, or 'Address is applied, and forbids entirely the use of
13332 the 'Unrestricted_Access attribute for objects. Note: the reason that
13333 Unrestricted_Access is forbidden is that it would require the prefix
13334 to be aliased, and in such cases, it can always be replaced by
13335 the standard attribute Unchecked_Access which is preferable.
13337 @node No_Implicit_Loops,No_Obsolescent_Features,No_Implicit_Aliasing,Program Unit Level Restrictions
13338 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-loops}@anchor{211}
13339 @subsection No_Implicit_Loops
13342 @geindex No_Implicit_Loops
13344 [GNAT] This restriction ensures that the generated code of the unit marked
13345 with this restriction does not contain any implicit @code{for} loops, either by
13346 modifying the generated code where possible, or by rejecting any construct
13347 that would otherwise generate an implicit @code{for} loop. If this restriction is
13348 active, it is possible to build large array aggregates with all static
13349 components without generating an intermediate temporary, and without generating
13350 a loop to initialize individual components. Otherwise, a loop is created for
13351 arrays larger than about 5000 scalar components. Note that if this restriction
13352 is set in the spec of a package, it will not apply to its body.
13354 @node No_Obsolescent_Features,No_Wide_Characters,No_Implicit_Loops,Program Unit Level Restrictions
13355 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-obsolescent-features}@anchor{212}
13356 @subsection No_Obsolescent_Features
13359 @geindex No_Obsolescent_Features
13361 [RM 13.12.1] This restriction checks at compile time that no obsolescent
13362 features are used, as defined in Annex J of the Ada Reference Manual.
13364 @node No_Wide_Characters,Static_Dispatch_Tables,No_Obsolescent_Features,Program Unit Level Restrictions
13365 @anchor{gnat_rm/standard_and_implementation_defined_restrictions no-wide-characters}@anchor{213}
13366 @subsection No_Wide_Characters
13369 @geindex No_Wide_Characters
13371 [GNAT] This restriction ensures at compile time that no uses of the types
13372 @code{Wide_Character} or @code{Wide_String} or corresponding wide
13374 appear, and that no wide or wide wide string or character literals
13375 appear in the program (that is literals representing characters not in
13376 type @code{Character}).
13378 @node Static_Dispatch_Tables,SPARK_05,No_Wide_Characters,Program Unit Level Restrictions
13379 @anchor{gnat_rm/standard_and_implementation_defined_restrictions static-dispatch-tables}@anchor{214}
13380 @subsection Static_Dispatch_Tables
13383 @geindex Static_Dispatch_Tables
13385 [GNAT] This restriction checks at compile time that all the artifacts
13386 associated with dispatch tables can be placed in read-only memory.
13388 @node SPARK_05,,Static_Dispatch_Tables,Program Unit Level Restrictions
13389 @anchor{gnat_rm/standard_and_implementation_defined_restrictions spark-05}@anchor{215}
13390 @subsection SPARK_05
13395 [GNAT] This restriction no longer has any effect and is superseded by
13396 SPARK 2014, whose restrictions are checked by the tool GNATprove. To check that
13397 a codebase respects SPARK 2014 restrictions, mark the code with pragma or
13398 aspect @code{SPARK_Mode}, and run the tool GNATprove at Stone assurance level, as
13402 gnatprove -P project.gpr --mode=stone
13408 gnatprove -P project.gpr --mode=check_all
13411 @node Implementation Advice,Implementation Defined Characteristics,Standard and Implementation Defined Restrictions,Top
13412 @anchor{gnat_rm/implementation_advice doc}@anchor{216}@anchor{gnat_rm/implementation_advice implementation-advice}@anchor{a}@anchor{gnat_rm/implementation_advice id1}@anchor{217}
13413 @chapter Implementation Advice
13416 The main text of the Ada Reference Manual describes the required
13417 behavior of all Ada compilers, and the GNAT compiler conforms to
13418 these requirements.
13420 In addition, there are sections throughout the Ada Reference Manual headed
13421 by the phrase 'Implementation advice'. These sections are not normative,
13422 i.e., they do not specify requirements that all compilers must
13423 follow. Rather they provide advice on generally desirable behavior.
13424 They are not requirements, because they describe behavior that cannot
13425 be provided on all systems, or may be undesirable on some systems.
13427 As far as practical, GNAT follows the implementation advice in
13428 the Ada Reference Manual. Each such RM section corresponds to a section
13429 in this chapter whose title specifies the
13430 RM section number and paragraph number and the subject of
13431 the advice. The contents of each section consists of the RM text within
13433 followed by the GNAT interpretation of the advice. Most often, this simply says
13434 'followed', which means that GNAT follows the advice. However, in a
13435 number of cases, GNAT deliberately deviates from this advice, in which
13436 case the text describes what GNAT does and why.
13438 @geindex Error detection
13441 * RM 1.1.3(20); Error Detection: RM 1 1 3 20 Error Detection.
13442 * RM 1.1.3(31); Child Units: RM 1 1 3 31 Child Units.
13443 * RM 1.1.5(12); Bounded Errors: RM 1 1 5 12 Bounded Errors.
13444 * RM 2.8(16); Pragmas: RM 2 8 16 Pragmas.
13445 * RM 2.8(17-19); Pragmas: RM 2 8 17-19 Pragmas.
13446 * RM 3.5.2(5); Alternative Character Sets: RM 3 5 2 5 Alternative Character Sets.
13447 * RM 3.5.4(28); Integer Types: RM 3 5 4 28 Integer Types.
13448 * RM 3.5.4(29); Integer Types: RM 3 5 4 29 Integer Types.
13449 * RM 3.5.5(8); Enumeration Values: RM 3 5 5 8 Enumeration Values.
13450 * RM 3.5.7(17); Float Types: RM 3 5 7 17 Float Types.
13451 * RM 3.6.2(11); Multidimensional Arrays: RM 3 6 2 11 Multidimensional Arrays.
13452 * RM 9.6(30-31); Duration'Small: RM 9 6 30-31 Duration'Small.
13453 * RM 10.2.1(12); Consistent Representation: RM 10 2 1 12 Consistent Representation.
13454 * RM 11.4.1(19); Exception Information: RM 11 4 1 19 Exception Information.
13455 * RM 11.5(28); Suppression of Checks: RM 11 5 28 Suppression of Checks.
13456 * RM 13.1 (21-24); Representation Clauses: RM 13 1 21-24 Representation Clauses.
13457 * RM 13.2(6-8); Packed Types: RM 13 2 6-8 Packed Types.
13458 * RM 13.3(14-19); Address Clauses: RM 13 3 14-19 Address Clauses.
13459 * RM 13.3(29-35); Alignment Clauses: RM 13 3 29-35 Alignment Clauses.
13460 * RM 13.3(42-43); Size Clauses: RM 13 3 42-43 Size Clauses.
13461 * RM 13.3(50-56); Size Clauses: RM 13 3 50-56 Size Clauses.
13462 * RM 13.3(71-73); Component Size Clauses: RM 13 3 71-73 Component Size Clauses.
13463 * RM 13.4(9-10); Enumeration Representation Clauses: RM 13 4 9-10 Enumeration Representation Clauses.
13464 * RM 13.5.1(17-22); Record Representation Clauses: RM 13 5 1 17-22 Record Representation Clauses.
13465 * RM 13.5.2(5); Storage Place Attributes: RM 13 5 2 5 Storage Place Attributes.
13466 * RM 13.5.3(7-8); Bit Ordering: RM 13 5 3 7-8 Bit Ordering.
13467 * RM 13.7(37); Address as Private: RM 13 7 37 Address as Private.
13468 * RM 13.7.1(16); Address Operations: RM 13 7 1 16 Address Operations.
13469 * RM 13.9(14-17); Unchecked Conversion: RM 13 9 14-17 Unchecked Conversion.
13470 * RM 13.11(23-25); Implicit Heap Usage: RM 13 11 23-25 Implicit Heap Usage.
13471 * RM 13.11.2(17); Unchecked Deallocation: RM 13 11 2 17 Unchecked Deallocation.
13472 * RM 13.13.2(1.6); Stream Oriented Attributes: RM 13 13 2 1 6 Stream Oriented Attributes.
13473 * RM A.1(52); Names of Predefined Numeric Types: RM A 1 52 Names of Predefined Numeric Types.
13474 * RM A.3.2(49); Ada.Characters.Handling: RM A 3 2 49 Ada Characters Handling.
13475 * RM A.4.4(106); Bounded-Length String Handling: RM A 4 4 106 Bounded-Length String Handling.
13476 * RM A.5.2(46-47); Random Number Generation: RM A 5 2 46-47 Random Number Generation.
13477 * RM A.10.7(23); Get_Immediate: RM A 10 7 23 Get_Immediate.
13478 * RM B.1(39-41); Pragma Export: RM B 1 39-41 Pragma Export.
13479 * RM B.2(12-13); Package Interfaces: RM B 2 12-13 Package Interfaces.
13480 * RM B.3(63-71); Interfacing with C: RM B 3 63-71 Interfacing with C.
13481 * RM B.4(95-98); Interfacing with COBOL: RM B 4 95-98 Interfacing with COBOL.
13482 * RM B.5(22-26); Interfacing with Fortran: RM B 5 22-26 Interfacing with Fortran.
13483 * RM C.1(3-5); Access to Machine Operations: RM C 1 3-5 Access to Machine Operations.
13484 * RM C.1(10-16); Access to Machine Operations: RM C 1 10-16 Access to Machine Operations.
13485 * RM C.3(28); Interrupt Support: RM C 3 28 Interrupt Support.
13486 * RM C.3.1(20-21); Protected Procedure Handlers: RM C 3 1 20-21 Protected Procedure Handlers.
13487 * RM C.3.2(25); Package Interrupts: RM C 3 2 25 Package Interrupts.
13488 * RM C.4(14); Pre-elaboration Requirements: RM C 4 14 Pre-elaboration Requirements.
13489 * RM C.5(8); Pragma Discard_Names: RM C 5 8 Pragma Discard_Names.
13490 * RM C.7.2(30); The Package Task_Attributes: RM C 7 2 30 The Package Task_Attributes.
13491 * RM D.3(17); Locking Policies: RM D 3 17 Locking Policies.
13492 * RM D.4(16); Entry Queuing Policies: RM D 4 16 Entry Queuing Policies.
13493 * RM D.6(9-10); Preemptive Abort: RM D 6 9-10 Preemptive Abort.
13494 * RM D.7(21); Tasking Restrictions: RM D 7 21 Tasking Restrictions.
13495 * RM D.8(47-49); Monotonic Time: RM D 8 47-49 Monotonic Time.
13496 * RM E.5(28-29); Partition Communication Subsystem: RM E 5 28-29 Partition Communication Subsystem.
13497 * RM F(7); COBOL Support: RM F 7 COBOL Support.
13498 * RM F.1(2); Decimal Radix Support: RM F 1 2 Decimal Radix Support.
13499 * RM G; Numerics: RM G Numerics.
13500 * RM G.1.1(56-58); Complex Types: RM G 1 1 56-58 Complex Types.
13501 * RM G.1.2(49); Complex Elementary Functions: RM G 1 2 49 Complex Elementary Functions.
13502 * RM G.2.4(19); Accuracy Requirements: RM G 2 4 19 Accuracy Requirements.
13503 * RM G.2.6(15); Complex Arithmetic Accuracy: RM G 2 6 15 Complex Arithmetic Accuracy.
13504 * RM H.6(15/2); Pragma Partition_Elaboration_Policy: RM H 6 15/2 Pragma Partition_Elaboration_Policy.
13508 @node RM 1 1 3 20 Error Detection,RM 1 1 3 31 Child Units,,Implementation Advice
13509 @anchor{gnat_rm/implementation_advice rm-1-1-3-20-error-detection}@anchor{218}
13510 @section RM 1.1.3(20): Error Detection
13515 "If an implementation detects the use of an unsupported Specialized Needs
13516 Annex feature at run time, it should raise @code{Program_Error} if
13520 Not relevant. All specialized needs annex features are either supported,
13521 or diagnosed at compile time.
13523 @geindex Child Units
13525 @node RM 1 1 3 31 Child Units,RM 1 1 5 12 Bounded Errors,RM 1 1 3 20 Error Detection,Implementation Advice
13526 @anchor{gnat_rm/implementation_advice rm-1-1-3-31-child-units}@anchor{219}
13527 @section RM 1.1.3(31): Child Units
13532 "If an implementation wishes to provide implementation-defined
13533 extensions to the functionality of a language-defined library unit, it
13534 should normally do so by adding children to the library unit."
13539 @geindex Bounded errors
13541 @node RM 1 1 5 12 Bounded Errors,RM 2 8 16 Pragmas,RM 1 1 3 31 Child Units,Implementation Advice
13542 @anchor{gnat_rm/implementation_advice rm-1-1-5-12-bounded-errors}@anchor{21a}
13543 @section RM 1.1.5(12): Bounded Errors
13548 "If an implementation detects a bounded error or erroneous
13549 execution, it should raise @code{Program_Error}."
13552 Followed in all cases in which the implementation detects a bounded
13553 error or erroneous execution. Not all such situations are detected at
13558 @node RM 2 8 16 Pragmas,RM 2 8 17-19 Pragmas,RM 1 1 5 12 Bounded Errors,Implementation Advice
13559 @anchor{gnat_rm/implementation_advice id2}@anchor{21b}@anchor{gnat_rm/implementation_advice rm-2-8-16-pragmas}@anchor{21c}
13560 @section RM 2.8(16): Pragmas
13565 "Normally, implementation-defined pragmas should have no semantic effect
13566 for error-free programs; that is, if the implementation-defined pragmas
13567 are removed from a working program, the program should still be legal,
13568 and should still have the same semantics."
13571 The following implementation defined pragmas are exceptions to this
13575 @multitable {xxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxx}
13618 @emph{CPP_Constructor}
13634 @emph{Interface_Name}
13642 @emph{Machine_Attribute}
13650 @emph{Unimplemented_Unit}
13658 @emph{Unchecked_Union}
13667 In each of the above cases, it is essential to the purpose of the pragma
13668 that this advice not be followed. For details see
13669 @ref{7,,Implementation Defined Pragmas}.
13671 @node RM 2 8 17-19 Pragmas,RM 3 5 2 5 Alternative Character Sets,RM 2 8 16 Pragmas,Implementation Advice
13672 @anchor{gnat_rm/implementation_advice rm-2-8-17-19-pragmas}@anchor{21d}
13673 @section RM 2.8(17-19): Pragmas
13678 "Normally, an implementation should not define pragmas that can
13679 make an illegal program legal, except as follows:
13685 A pragma used to complete a declaration, such as a pragma @code{Import};
13688 A pragma used to configure the environment by adding, removing, or
13689 replacing @code{library_items}."
13693 See @ref{21c,,RM 2.8(16); Pragmas}.
13695 @geindex Character Sets
13697 @geindex Alternative Character Sets
13699 @node RM 3 5 2 5 Alternative Character Sets,RM 3 5 4 28 Integer Types,RM 2 8 17-19 Pragmas,Implementation Advice
13700 @anchor{gnat_rm/implementation_advice rm-3-5-2-5-alternative-character-sets}@anchor{21e}
13701 @section RM 3.5.2(5): Alternative Character Sets
13706 "If an implementation supports a mode with alternative interpretations
13707 for @code{Character} and @code{Wide_Character}, the set of graphic
13708 characters of @code{Character} should nevertheless remain a proper
13709 subset of the set of graphic characters of @code{Wide_Character}. Any
13710 character set 'localizations' should be reflected in the results of
13711 the subprograms defined in the language-defined package
13712 @code{Characters.Handling} (see A.3) available in such a mode. In a mode with
13713 an alternative interpretation of @code{Character}, the implementation should
13714 also support a corresponding change in what is a legal
13715 @code{identifier_letter}."
13718 Not all wide character modes follow this advice, in particular the JIS
13719 and IEC modes reflect standard usage in Japan, and in these encoding,
13720 the upper half of the Latin-1 set is not part of the wide-character
13721 subset, since the most significant bit is used for wide character
13722 encoding. However, this only applies to the external forms. Internally
13723 there is no such restriction.
13725 @geindex Integer types
13727 @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
13728 @anchor{gnat_rm/implementation_advice rm-3-5-4-28-integer-types}@anchor{21f}
13729 @section RM 3.5.4(28): Integer Types
13734 "An implementation should support @code{Long_Integer} in addition to
13735 @code{Integer} if the target machine supports 32-bit (or longer)
13736 arithmetic. No other named integer subtypes are recommended for package
13737 @code{Standard}. Instead, appropriate named integer subtypes should be
13738 provided in the library package @code{Interfaces} (see B.2)."
13741 @code{Long_Integer} is supported. Other standard integer types are supported
13742 so this advice is not fully followed. These types
13743 are supported for convenient interface to C, and so that all hardware
13744 types of the machine are easily available.
13746 @node RM 3 5 4 29 Integer Types,RM 3 5 5 8 Enumeration Values,RM 3 5 4 28 Integer Types,Implementation Advice
13747 @anchor{gnat_rm/implementation_advice rm-3-5-4-29-integer-types}@anchor{220}
13748 @section RM 3.5.4(29): Integer Types
13753 "An implementation for a two's complement machine should support
13754 modular types with a binary modulus up to @code{System.Max_Int*2+2}. An
13755 implementation should support a non-binary modules up to @code{Integer'Last}."
13760 @geindex Enumeration values
13762 @node RM 3 5 5 8 Enumeration Values,RM 3 5 7 17 Float Types,RM 3 5 4 29 Integer Types,Implementation Advice
13763 @anchor{gnat_rm/implementation_advice rm-3-5-5-8-enumeration-values}@anchor{221}
13764 @section RM 3.5.5(8): Enumeration Values
13769 "For the evaluation of a call on @code{S'Pos} for an enumeration
13770 subtype, if the value of the operand does not correspond to the internal
13771 code for any enumeration literal of its type (perhaps due to an
13772 un-initialized variable), then the implementation should raise
13773 @code{Program_Error}. This is particularly important for enumeration
13774 types with noncontiguous internal codes specified by an
13775 enumeration_representation_clause."
13780 @geindex Float types
13782 @node RM 3 5 7 17 Float Types,RM 3 6 2 11 Multidimensional Arrays,RM 3 5 5 8 Enumeration Values,Implementation Advice
13783 @anchor{gnat_rm/implementation_advice rm-3-5-7-17-float-types}@anchor{222}
13784 @section RM 3.5.7(17): Float Types
13789 "An implementation should support @code{Long_Float} in addition to
13790 @code{Float} if the target machine supports 11 or more digits of
13791 precision. No other named floating point subtypes are recommended for
13792 package @code{Standard}. Instead, appropriate named floating point subtypes
13793 should be provided in the library package @code{Interfaces} (see B.2)."
13796 @code{Short_Float} and @code{Long_Long_Float} are also provided. The
13797 former provides improved compatibility with other implementations
13798 supporting this type. The latter corresponds to the highest precision
13799 floating-point type supported by the hardware. On most machines, this
13800 will be the same as @code{Long_Float}, but on some machines, it will
13801 correspond to the IEEE extended form. The notable case is all x86
13802 implementations, where @code{Long_Long_Float} corresponds to the 80-bit
13803 extended precision format supported in hardware on this processor.
13804 Note that the 128-bit format on SPARC is not supported, since this
13805 is a software rather than a hardware format.
13807 @geindex Multidimensional arrays
13810 @geindex multidimensional
13812 @node RM 3 6 2 11 Multidimensional Arrays,RM 9 6 30-31 Duration'Small,RM 3 5 7 17 Float Types,Implementation Advice
13813 @anchor{gnat_rm/implementation_advice rm-3-6-2-11-multidimensional-arrays}@anchor{223}
13814 @section RM 3.6.2(11): Multidimensional Arrays
13819 "An implementation should normally represent multidimensional arrays in
13820 row-major order, consistent with the notation used for multidimensional
13821 array aggregates (see 4.3.3). However, if a pragma @code{Convention}
13822 (@code{Fortran}, ...) applies to a multidimensional array type, then
13823 column-major order should be used instead (see B.5, @emph{Interfacing with Fortran})."
13828 @geindex Duration'Small
13830 @node RM 9 6 30-31 Duration'Small,RM 10 2 1 12 Consistent Representation,RM 3 6 2 11 Multidimensional Arrays,Implementation Advice
13831 @anchor{gnat_rm/implementation_advice rm-9-6-30-31-duration-small}@anchor{224}
13832 @section RM 9.6(30-31): Duration'Small
13837 "Whenever possible in an implementation, the value of @code{Duration'Small}
13838 should be no greater than 100 microseconds."
13841 Followed. (@code{Duration'Small} = 10**(-9)).
13845 "The time base for @code{delay_relative_statements} should be monotonic;
13846 it need not be the same time base as used for @code{Calendar.Clock}."
13851 @node RM 10 2 1 12 Consistent Representation,RM 11 4 1 19 Exception Information,RM 9 6 30-31 Duration'Small,Implementation Advice
13852 @anchor{gnat_rm/implementation_advice rm-10-2-1-12-consistent-representation}@anchor{225}
13853 @section RM 10.2.1(12): Consistent Representation
13858 "In an implementation, a type declared in a pre-elaborated package should
13859 have the same representation in every elaboration of a given version of
13860 the package, whether the elaborations occur in distinct executions of
13861 the same program, or in executions of distinct programs or partitions
13862 that include the given version."
13865 Followed, except in the case of tagged types. Tagged types involve
13866 implicit pointers to a local copy of a dispatch table, and these pointers
13867 have representations which thus depend on a particular elaboration of the
13868 package. It is not easy to see how it would be possible to follow this
13869 advice without severely impacting efficiency of execution.
13871 @geindex Exception information
13873 @node RM 11 4 1 19 Exception Information,RM 11 5 28 Suppression of Checks,RM 10 2 1 12 Consistent Representation,Implementation Advice
13874 @anchor{gnat_rm/implementation_advice rm-11-4-1-19-exception-information}@anchor{226}
13875 @section RM 11.4.1(19): Exception Information
13880 "@code{Exception_Message} by default and @code{Exception_Information}
13881 should produce information useful for
13882 debugging. @code{Exception_Message} should be short, about one
13883 line. @code{Exception_Information} can be long. @code{Exception_Message}
13884 should not include the
13885 @code{Exception_Name}. @code{Exception_Information} should include both
13886 the @code{Exception_Name} and the @code{Exception_Message}."
13889 Followed. For each exception that doesn't have a specified
13890 @code{Exception_Message}, the compiler generates one containing the location
13891 of the raise statement. This location has the form 'file_name:line', where
13892 file_name is the short file name (without path information) and line is the line
13893 number in the file. Note that in the case of the Zero Cost Exception
13894 mechanism, these messages become redundant with the Exception_Information that
13895 contains a full backtrace of the calling sequence, so they are disabled.
13896 To disable explicitly the generation of the source location message, use the
13897 Pragma @code{Discard_Names}.
13899 @geindex Suppression of checks
13902 @geindex suppression of
13904 @node RM 11 5 28 Suppression of Checks,RM 13 1 21-24 Representation Clauses,RM 11 4 1 19 Exception Information,Implementation Advice
13905 @anchor{gnat_rm/implementation_advice rm-11-5-28-suppression-of-checks}@anchor{227}
13906 @section RM 11.5(28): Suppression of Checks
13911 "The implementation should minimize the code executed for checks that
13912 have been suppressed."
13917 @geindex Representation clauses
13919 @node RM 13 1 21-24 Representation Clauses,RM 13 2 6-8 Packed Types,RM 11 5 28 Suppression of Checks,Implementation Advice
13920 @anchor{gnat_rm/implementation_advice rm-13-1-21-24-representation-clauses}@anchor{228}
13921 @section RM 13.1 (21-24): Representation Clauses
13926 "The recommended level of support for all representation items is
13927 qualified as follows:
13929 An implementation need not support representation items containing
13930 nonstatic expressions, except that an implementation should support a
13931 representation item for a given entity if each nonstatic expression in
13932 the representation item is a name that statically denotes a constant
13933 declared before the entity."
13936 Followed. In fact, GNAT goes beyond the recommended level of support
13937 by allowing nonstatic expressions in some representation clauses even
13938 without the need to declare constants initialized with the values of
13945 for Y'Address use X'Address;>>
13948 "An implementation need not support a specification for the `@w{`}Size`@w{`}
13949 for a given composite subtype, nor the size or storage place for an
13950 object (including a component) of a given composite subtype, unless the
13951 constraints on the subtype and its composite subcomponents (if any) are
13952 all static constraints."
13955 Followed. Size Clauses are not permitted on nonstatic components, as
13960 "An aliased component, or a component whose type is by-reference, should
13961 always be allocated at an addressable location."
13966 @geindex Packed types
13968 @node RM 13 2 6-8 Packed Types,RM 13 3 14-19 Address Clauses,RM 13 1 21-24 Representation Clauses,Implementation Advice
13969 @anchor{gnat_rm/implementation_advice rm-13-2-6-8-packed-types}@anchor{229}
13970 @section RM 13.2(6-8): Packed Types
13975 "If a type is packed, then the implementation should try to minimize
13976 storage allocated to objects of the type, possibly at the expense of
13977 speed of accessing components, subject to reasonable complexity in
13978 addressing calculations.
13980 The recommended level of support pragma @code{Pack} is:
13982 For a packed record type, the components should be packed as tightly as
13983 possible subject to the Sizes of the component subtypes, and subject to
13984 any @emph{record_representation_clause} that applies to the type; the
13985 implementation may, but need not, reorder components or cross aligned
13986 word boundaries to improve the packing. A component whose @code{Size} is
13987 greater than the word size may be allocated an integral number of words."
13990 Followed. Tight packing of arrays is supported for all component sizes
13991 up to 64-bits. If the array component size is 1 (that is to say, if
13992 the component is a boolean type or an enumeration type with two values)
13993 then values of the type are implicitly initialized to zero. This
13994 happens both for objects of the packed type, and for objects that have a
13995 subcomponent of the packed type.
13999 "An implementation should support Address clauses for imported
14005 @geindex Address clauses
14007 @node RM 13 3 14-19 Address Clauses,RM 13 3 29-35 Alignment Clauses,RM 13 2 6-8 Packed Types,Implementation Advice
14008 @anchor{gnat_rm/implementation_advice rm-13-3-14-19-address-clauses}@anchor{22a}
14009 @section RM 13.3(14-19): Address Clauses
14014 "For an array @code{X}, @code{X'Address} should point at the first
14015 component of the array, and not at the array bounds."
14022 "The recommended level of support for the @code{Address} attribute is:
14024 @code{X'Address} should produce a useful result if @code{X} is an
14025 object that is aliased or of a by-reference type, or is an entity whose
14026 @code{Address} has been specified."
14029 Followed. A valid address will be produced even if none of those
14030 conditions have been met. If necessary, the object is forced into
14031 memory to ensure the address is valid.
14035 "An implementation should support @code{Address} clauses for imported
14043 "Objects (including subcomponents) that are aliased or of a by-reference
14044 type should be allocated on storage element boundaries."
14051 "If the @code{Address} of an object is specified, or it is imported or exported,
14052 then the implementation should not perform optimizations based on
14053 assumptions of no aliases."
14058 @geindex Alignment clauses
14060 @node RM 13 3 29-35 Alignment Clauses,RM 13 3 42-43 Size Clauses,RM 13 3 14-19 Address Clauses,Implementation Advice
14061 @anchor{gnat_rm/implementation_advice rm-13-3-29-35-alignment-clauses}@anchor{22b}
14062 @section RM 13.3(29-35): Alignment Clauses
14067 "The recommended level of support for the @code{Alignment} attribute for
14070 An implementation should support specified Alignments that are factors
14071 and multiples of the number of storage elements per word, subject to the
14079 "An implementation need not support specified Alignments for
14080 combinations of Sizes and Alignments that cannot be easily
14081 loaded and stored by available machine instructions."
14088 "An implementation need not support specified Alignments that are
14089 greater than the maximum @code{Alignment} the implementation ever returns by
14097 "The recommended level of support for the @code{Alignment} attribute for
14100 Same as above, for subtypes, but in addition:"
14107 "For stand-alone library-level objects of statically constrained
14108 subtypes, the implementation should support all alignments
14109 supported by the target linker. For example, page alignment is likely to
14110 be supported for such objects, but not for subtypes."
14115 @geindex Size clauses
14117 @node RM 13 3 42-43 Size Clauses,RM 13 3 50-56 Size Clauses,RM 13 3 29-35 Alignment Clauses,Implementation Advice
14118 @anchor{gnat_rm/implementation_advice rm-13-3-42-43-size-clauses}@anchor{22c}
14119 @section RM 13.3(42-43): Size Clauses
14124 "The recommended level of support for the @code{Size} attribute of
14127 A @code{Size} clause should be supported for an object if the specified
14128 @code{Size} is at least as large as its subtype's @code{Size}, and
14129 corresponds to a size in storage elements that is a multiple of the
14130 object's @code{Alignment} (if the @code{Alignment} is nonzero)."
14135 @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
14136 @anchor{gnat_rm/implementation_advice rm-13-3-50-56-size-clauses}@anchor{22d}
14137 @section RM 13.3(50-56): Size Clauses
14142 "If the @code{Size} of a subtype is specified, and allows for efficient
14143 independent addressability (see 9.10) on the target architecture, then
14144 the @code{Size} of the following objects of the subtype should equal the
14145 @code{Size} of the subtype:
14147 Aliased objects (including components)."
14154 "@cite{Size} clause on a composite subtype should not affect the
14155 internal layout of components."
14158 Followed. But note that this can be overridden by use of the implementation
14159 pragma Implicit_Packing in the case of packed arrays.
14163 "The recommended level of support for the @code{Size} attribute of subtypes is:
14165 The @code{Size} (if not specified) of a static discrete or fixed point
14166 subtype should be the number of bits needed to represent each value
14167 belonging to the subtype using an unbiased representation, leaving space
14168 for a sign bit only if the subtype contains negative values. If such a
14169 subtype is a first subtype, then an implementation should support a
14170 specified @code{Size} for it that reflects this representation."
14177 "For a subtype implemented with levels of indirection, the @code{Size}
14178 should include the size of the pointers, but not the size of what they
14184 @geindex Component_Size clauses
14186 @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
14187 @anchor{gnat_rm/implementation_advice rm-13-3-71-73-component-size-clauses}@anchor{22e}
14188 @section RM 13.3(71-73): Component Size Clauses
14193 "The recommended level of support for the @code{Component_Size}
14196 An implementation need not support specified @code{Component_Sizes} that are
14197 less than the @code{Size} of the component subtype."
14204 "An implementation should support specified Component_Sizes that
14205 are factors and multiples of the word size. For such
14206 Component_Sizes, the array should contain no gaps between
14207 components. For other Component_Sizes (if supported), the array
14208 should contain no gaps between components when packing is also
14209 specified; the implementation should forbid this combination in cases
14210 where it cannot support a no-gaps representation."
14215 @geindex Enumeration representation clauses
14217 @geindex Representation clauses
14218 @geindex enumeration
14220 @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
14221 @anchor{gnat_rm/implementation_advice rm-13-4-9-10-enumeration-representation-clauses}@anchor{22f}
14222 @section RM 13.4(9-10): Enumeration Representation Clauses
14227 "The recommended level of support for enumeration representation clauses
14230 An implementation need not support enumeration representation clauses
14231 for boolean types, but should at minimum support the internal codes in
14232 the range @code{System.Min_Int .. System.Max_Int}."
14237 @geindex Record representation clauses
14239 @geindex Representation clauses
14242 @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
14243 @anchor{gnat_rm/implementation_advice rm-13-5-1-17-22-record-representation-clauses}@anchor{230}
14244 @section RM 13.5.1(17-22): Record Representation Clauses
14249 "The recommended level of support for
14250 @emph{record_representation_clause}s is:
14252 An implementation should support storage places that can be extracted
14253 with a load, mask, shift sequence of machine code, and set with a load,
14254 shift, mask, store sequence, given the available machine instructions
14255 and run-time model."
14262 "A storage place should be supported if its size is equal to the
14263 @code{Size} of the component subtype, and it starts and ends on a
14264 boundary that obeys the @code{Alignment} of the component subtype."
14271 "If the default bit ordering applies to the declaration of a given type,
14272 then for a component whose subtype's @code{Size} is less than the word
14273 size, any storage place that does not cross an aligned word boundary
14274 should be supported."
14281 "An implementation may reserve a storage place for the tag field of a
14282 tagged type, and disallow other components from overlapping that place."
14285 Followed. The storage place for the tag field is the beginning of the tagged
14286 record, and its size is Address'Size. GNAT will reject an explicit component
14287 clause for the tag field.
14291 "An implementation need not support a @emph{component_clause} for a
14292 component of an extension part if the storage place is not after the
14293 storage places of all components of the parent type, whether or not
14294 those storage places had been specified."
14297 Followed. The above advice on record representation clauses is followed,
14298 and all mentioned features are implemented.
14300 @geindex Storage place attributes
14302 @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
14303 @anchor{gnat_rm/implementation_advice rm-13-5-2-5-storage-place-attributes}@anchor{231}
14304 @section RM 13.5.2(5): Storage Place Attributes
14309 "If a component is represented using some form of pointer (such as an
14310 offset) to the actual data of the component, and this data is contiguous
14311 with the rest of the object, then the storage place attributes should
14312 reflect the place of the actual data, not the pointer. If a component is
14313 allocated discontinuously from the rest of the object, then a warning
14314 should be generated upon reference to one of its storage place
14318 Followed. There are no such components in GNAT.
14320 @geindex Bit ordering
14322 @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
14323 @anchor{gnat_rm/implementation_advice rm-13-5-3-7-8-bit-ordering}@anchor{232}
14324 @section RM 13.5.3(7-8): Bit Ordering
14329 "The recommended level of support for the non-default bit ordering is:
14331 If @code{Word_Size} = @code{Storage_Unit}, then the implementation
14332 should support the non-default bit ordering in addition to the default
14336 Followed. Word size does not equal storage size in this implementation.
14337 Thus non-default bit ordering is not supported.
14340 @geindex as private type
14342 @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
14343 @anchor{gnat_rm/implementation_advice rm-13-7-37-address-as-private}@anchor{233}
14344 @section RM 13.7(37): Address as Private
14349 "@cite{Address} should be of a private type."
14354 @geindex Operations
14355 @geindex on `@w{`}Address`@w{`}
14358 @geindex operations of
14360 @node RM 13 7 1 16 Address Operations,RM 13 9 14-17 Unchecked Conversion,RM 13 7 37 Address as Private,Implementation Advice
14361 @anchor{gnat_rm/implementation_advice rm-13-7-1-16-address-operations}@anchor{234}
14362 @section RM 13.7.1(16): Address Operations
14367 "Operations in @code{System} and its children should reflect the target
14368 environment semantics as closely as is reasonable. For example, on most
14369 machines, it makes sense for address arithmetic to 'wrap around'.
14370 Operations that do not make sense should raise @code{Program_Error}."
14373 Followed. Address arithmetic is modular arithmetic that wraps around. No
14374 operation raises @code{Program_Error}, since all operations make sense.
14376 @geindex Unchecked conversion
14378 @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
14379 @anchor{gnat_rm/implementation_advice rm-13-9-14-17-unchecked-conversion}@anchor{235}
14380 @section RM 13.9(14-17): Unchecked Conversion
14385 "The @code{Size} of an array object should not include its bounds; hence,
14386 the bounds should not be part of the converted data."
14393 "The implementation should not generate unnecessary run-time checks to
14394 ensure that the representation of @code{S} is a representation of the
14395 target type. It should take advantage of the permission to return by
14396 reference when possible. Restrictions on unchecked conversions should be
14397 avoided unless required by the target environment."
14400 Followed. There are no restrictions on unchecked conversion. A warning is
14401 generated if the source and target types do not have the same size since
14402 the semantics in this case may be target dependent.
14406 "The recommended level of support for unchecked conversions is:
14408 Unchecked conversions should be supported and should be reversible in
14409 the cases where this clause defines the result. To enable meaningful use
14410 of unchecked conversion, a contiguous representation should be used for
14411 elementary subtypes, for statically constrained array subtypes whose
14412 component subtype is one of the subtypes described in this paragraph,
14413 and for record subtypes without discriminants whose component subtypes
14414 are described in this paragraph."
14419 @geindex Heap usage
14422 @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
14423 @anchor{gnat_rm/implementation_advice rm-13-11-23-25-implicit-heap-usage}@anchor{236}
14424 @section RM 13.11(23-25): Implicit Heap Usage
14429 "An implementation should document any cases in which it dynamically
14430 allocates heap storage for a purpose other than the evaluation of an
14434 Followed, the only other points at which heap storage is dynamically
14435 allocated are as follows:
14441 At initial elaboration time, to allocate dynamically sized global
14445 To allocate space for a task when a task is created.
14448 To extend the secondary stack dynamically when needed. The secondary
14449 stack is used for returning variable length results.
14455 "A default (implementation-provided) storage pool for an
14456 access-to-constant type should not have overhead to support deallocation of
14457 individual objects."
14464 "A storage pool for an anonymous access type should be created at the
14465 point of an allocator for the type, and be reclaimed when the designated
14466 object becomes inaccessible."
14471 @geindex Unchecked deallocation
14473 @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
14474 @anchor{gnat_rm/implementation_advice rm-13-11-2-17-unchecked-deallocation}@anchor{237}
14475 @section RM 13.11.2(17): Unchecked Deallocation
14480 "For a standard storage pool, @code{Free} should actually reclaim the
14486 @geindex Stream oriented attributes
14488 @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
14489 @anchor{gnat_rm/implementation_advice rm-13-13-2-1-6-stream-oriented-attributes}@anchor{238}
14490 @section RM 13.13.2(1.6): Stream Oriented Attributes
14495 "If not specified, the value of Stream_Size for an elementary type
14496 should be the number of bits that corresponds to the minimum number of
14497 stream elements required by the first subtype of the type, rounded up
14498 to the nearest factor or multiple of the word size that is also a
14499 multiple of the stream element size."
14502 Followed, except that the number of stream elements is 1, 2, 3, 4 or 8.
14503 The Stream_Size may be used to override the default choice.
14505 The default implementation is based on direct binary representations and is
14506 therefore target- and endianness-dependent. To address this issue, GNAT also
14507 supplies an alternate implementation of the stream attributes @code{Read} and
14508 @code{Write}, which uses the target-independent XDR standard representation for
14509 scalar types. This XDR alternative can be enabled via the binder switch -xdr.
14511 @geindex XDR representation
14513 @geindex Read attribute
14515 @geindex Write attribute
14517 @geindex Stream oriented attributes
14519 @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
14520 @anchor{gnat_rm/implementation_advice rm-a-1-52-names-of-predefined-numeric-types}@anchor{239}
14521 @section RM A.1(52): Names of Predefined Numeric Types
14526 "If an implementation provides additional named predefined integer types,
14527 then the names should end with @code{Integer} as in
14528 @code{Long_Integer}. If an implementation provides additional named
14529 predefined floating point types, then the names should end with
14530 @code{Float} as in @code{Long_Float}."
14535 @geindex Ada.Characters.Handling
14537 @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
14538 @anchor{gnat_rm/implementation_advice rm-a-3-2-49-ada-characters-handling}@anchor{23a}
14539 @section RM A.3.2(49): @code{Ada.Characters.Handling}
14544 "If an implementation provides a localized definition of @code{Character}
14545 or @code{Wide_Character}, then the effects of the subprograms in
14546 @code{Characters.Handling} should reflect the localizations.
14550 Followed. GNAT provides no such localized definitions.
14552 @geindex Bounded-length strings
14554 @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
14555 @anchor{gnat_rm/implementation_advice rm-a-4-4-106-bounded-length-string-handling}@anchor{23b}
14556 @section RM A.4.4(106): Bounded-Length String Handling
14561 "Bounded string objects should not be implemented by implicit pointers
14562 and dynamic allocation."
14565 Followed. No implicit pointers or dynamic allocation are used.
14567 @geindex Random number generation
14569 @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
14570 @anchor{gnat_rm/implementation_advice rm-a-5-2-46-47-random-number-generation}@anchor{23c}
14571 @section RM A.5.2(46-47): Random Number Generation
14576 "Any storage associated with an object of type @code{Generator} should be
14577 reclaimed on exit from the scope of the object."
14584 "If the generator period is sufficiently long in relation to the number
14585 of distinct initiator values, then each possible value of
14586 @code{Initiator} passed to @code{Reset} should initiate a sequence of
14587 random numbers that does not, in a practical sense, overlap the sequence
14588 initiated by any other value. If this is not possible, then the mapping
14589 between initiator values and generator states should be a rapidly
14590 varying function of the initiator value."
14593 Followed. The generator period is sufficiently long for the first
14594 condition here to hold true.
14596 @geindex Get_Immediate
14598 @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
14599 @anchor{gnat_rm/implementation_advice rm-a-10-7-23-get-immediate}@anchor{23d}
14600 @section RM A.10.7(23): @code{Get_Immediate}
14605 "The @code{Get_Immediate} procedures should be implemented with
14606 unbuffered input. For a device such as a keyboard, input should be
14607 available if a key has already been typed, whereas for a disk
14608 file, input should always be available except at end of file. For a file
14609 associated with a keyboard-like device, any line-editing features of the
14610 underlying operating system should be disabled during the execution of
14611 @code{Get_Immediate}."
14614 Followed on all targets except VxWorks. For VxWorks, there is no way to
14615 provide this functionality that does not result in the input buffer being
14616 flushed before the @code{Get_Immediate} call. A special unit
14617 @code{Interfaces.Vxworks.IO} is provided that contains routines to enable
14618 this functionality.
14622 @node RM B 1 39-41 Pragma Export,RM B 2 12-13 Package Interfaces,RM A 10 7 23 Get_Immediate,Implementation Advice
14623 @anchor{gnat_rm/implementation_advice rm-b-1-39-41-pragma-export}@anchor{23e}
14624 @section RM B.1(39-41): Pragma @code{Export}
14629 "If an implementation supports pragma @code{Export} to a given language,
14630 then it should also allow the main subprogram to be written in that
14631 language. It should support some mechanism for invoking the elaboration
14632 of the Ada library units included in the system, and for invoking the
14633 finalization of the environment task. On typical systems, the
14634 recommended mechanism is to provide two subprograms whose link names are
14635 @code{adainit} and @code{adafinal}. @code{adainit} should contain the
14636 elaboration code for library units. @code{adafinal} should contain the
14637 finalization code. These subprograms should have no effect the second
14638 and subsequent time they are called."
14645 "Automatic elaboration of pre-elaborated packages should be
14646 provided when pragma @code{Export} is supported."
14649 Followed when the main program is in Ada. If the main program is in a
14650 foreign language, then
14651 @code{adainit} must be called to elaborate pre-elaborated
14656 "For each supported convention @emph{L} other than @code{Intrinsic}, an
14657 implementation should support @code{Import} and @code{Export} pragmas
14658 for objects of @emph{L}-compatible types and for subprograms, and pragma
14659 @cite{Convention} for @emph{L}-eligible types and for subprograms,
14660 presuming the other language has corresponding features. Pragma
14661 @code{Convention} need not be supported for scalar types."
14666 @geindex Package Interfaces
14668 @geindex Interfaces
14670 @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
14671 @anchor{gnat_rm/implementation_advice rm-b-2-12-13-package-interfaces}@anchor{23f}
14672 @section RM B.2(12-13): Package @code{Interfaces}
14677 "For each implementation-defined convention identifier, there should be a
14678 child package of package Interfaces with the corresponding name. This
14679 package should contain any declarations that would be useful for
14680 interfacing to the language (implementation) represented by the
14681 convention. Any declarations useful for interfacing to any language on
14682 the given hardware architecture should be provided directly in
14683 @code{Interfaces}."
14690 "An implementation supporting an interface to C, COBOL, or Fortran should
14691 provide the corresponding package or packages described in the following
14695 Followed. GNAT provides all the packages described in this section.
14698 @geindex interfacing with
14700 @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
14701 @anchor{gnat_rm/implementation_advice rm-b-3-63-71-interfacing-with-c}@anchor{240}
14702 @section RM B.3(63-71): Interfacing with C
14707 "An implementation should support the following interface correspondences
14708 between Ada and C."
14715 "An Ada procedure corresponds to a void-returning C function."
14722 "An Ada function corresponds to a non-void C function."
14729 "An Ada @code{in} scalar parameter is passed as a scalar argument to a C
14737 "An Ada @code{in} parameter of an access-to-object type with designated
14738 type @code{T} is passed as a @code{t*} argument to a C function,
14739 where @code{t} is the C type corresponding to the Ada type @code{T}."
14746 "An Ada access @code{T} parameter, or an Ada @code{out} or @code{in out}
14747 parameter of an elementary type @code{T}, is passed as a @code{t*}
14748 argument to a C function, where @code{t} is the C type corresponding to
14749 the Ada type @code{T}. In the case of an elementary @code{out} or
14750 @code{in out} parameter, a pointer to a temporary copy is used to
14751 preserve by-copy semantics."
14758 "An Ada parameter of a record type @code{T}, of any mode, is passed as a
14759 @code{t*} argument to a C function, where @code{t} is the C
14760 structure corresponding to the Ada type @code{T}."
14763 Followed. This convention may be overridden by the use of the C_Pass_By_Copy
14764 pragma, or Convention, or by explicitly specifying the mechanism for a given
14765 call using an extended import or export pragma.
14769 "An Ada parameter of an array type with component type @code{T}, of any
14770 mode, is passed as a @code{t*} argument to a C function, where
14771 @code{t} is the C type corresponding to the Ada type @code{T}."
14778 "An Ada parameter of an access-to-subprogram type is passed as a pointer
14779 to a C function whose prototype corresponds to the designated
14780 subprogram's specification."
14786 @geindex interfacing with
14788 @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
14789 @anchor{gnat_rm/implementation_advice rm-b-4-95-98-interfacing-with-cobol}@anchor{241}
14790 @section RM B.4(95-98): Interfacing with COBOL
14795 "An Ada implementation should support the following interface
14796 correspondences between Ada and COBOL."
14803 "An Ada access @code{T} parameter is passed as a @code{BY REFERENCE} data item of
14804 the COBOL type corresponding to @code{T}."
14811 "An Ada in scalar parameter is passed as a @code{BY CONTENT} data item of
14812 the corresponding COBOL type."
14819 "Any other Ada parameter is passed as a @code{BY REFERENCE} data item of the
14820 COBOL type corresponding to the Ada parameter type; for scalars, a local
14821 copy is used if necessary to ensure by-copy semantics."
14827 @geindex interfacing with
14829 @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
14830 @anchor{gnat_rm/implementation_advice rm-b-5-22-26-interfacing-with-fortran}@anchor{242}
14831 @section RM B.5(22-26): Interfacing with Fortran
14836 "An Ada implementation should support the following interface
14837 correspondences between Ada and Fortran:"
14844 "An Ada procedure corresponds to a Fortran subroutine."
14851 "An Ada function corresponds to a Fortran function."
14858 "An Ada parameter of an elementary, array, or record type @code{T} is
14859 passed as a @code{T} argument to a Fortran procedure, where @code{T} is
14860 the Fortran type corresponding to the Ada type @code{T}, and where the
14861 INTENT attribute of the corresponding dummy argument matches the Ada
14862 formal parameter mode; the Fortran implementation's parameter passing
14863 conventions are used. For elementary types, a local copy is used if
14864 necessary to ensure by-copy semantics."
14871 "An Ada parameter of an access-to-subprogram type is passed as a
14872 reference to a Fortran procedure whose interface corresponds to the
14873 designated subprogram's specification."
14878 @geindex Machine operations
14880 @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
14881 @anchor{gnat_rm/implementation_advice rm-c-1-3-5-access-to-machine-operations}@anchor{243}
14882 @section RM C.1(3-5): Access to Machine Operations
14887 "The machine code or intrinsic support should allow access to all
14888 operations normally available to assembly language programmers for the
14889 target environment, including privileged instructions, if any."
14896 "The interfacing pragmas (see Annex B) should support interface to
14897 assembler; the default assembler should be associated with the
14898 convention identifier @code{Assembler}."
14905 "If an entity is exported to assembly language, then the implementation
14906 should allocate it at an addressable location, and should ensure that it
14907 is retained by the linking process, even if not otherwise referenced
14908 from the Ada code. The implementation should assume that any call to a
14909 machine code or assembler subprogram is allowed to read or update every
14910 object that is specified as exported."
14915 @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
14916 @anchor{gnat_rm/implementation_advice rm-c-1-10-16-access-to-machine-operations}@anchor{244}
14917 @section RM C.1(10-16): Access to Machine Operations
14922 "The implementation should ensure that little or no overhead is
14923 associated with calling intrinsic and machine-code subprograms."
14926 Followed for both intrinsics and machine-code subprograms.
14930 "It is recommended that intrinsic subprograms be provided for convenient
14931 access to any machine operations that provide special capabilities or
14932 efficiency and that are not otherwise available through the language
14936 Followed. A full set of machine operation intrinsic subprograms is provided.
14940 "Atomic read-modify-write operations---e.g., test and set, compare and
14941 swap, decrement and test, enqueue/dequeue."
14944 Followed on any target supporting such operations.
14948 "Standard numeric functions---e.g.:, sin, log."
14951 Followed on any target supporting such operations.
14955 "String manipulation operations---e.g.:, translate and test."
14958 Followed on any target supporting such operations.
14962 "Vector operations---e.g.:, compare vector against thresholds."
14965 Followed on any target supporting such operations.
14969 "Direct operations on I/O ports."
14972 Followed on any target supporting such operations.
14974 @geindex Interrupt support
14976 @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
14977 @anchor{gnat_rm/implementation_advice rm-c-3-28-interrupt-support}@anchor{245}
14978 @section RM C.3(28): Interrupt Support
14983 "If the @code{Ceiling_Locking} policy is not in effect, the
14984 implementation should provide means for the application to specify which
14985 interrupts are to be blocked during protected actions, if the underlying
14986 system allows for a finer-grain control of interrupt blocking."
14989 Followed. The underlying system does not allow for finer-grain control
14990 of interrupt blocking.
14992 @geindex Protected procedure handlers
14994 @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
14995 @anchor{gnat_rm/implementation_advice rm-c-3-1-20-21-protected-procedure-handlers}@anchor{246}
14996 @section RM C.3.1(20-21): Protected Procedure Handlers
15001 "Whenever possible, the implementation should allow interrupt handlers to
15002 be called directly by the hardware."
15005 Followed on any target where the underlying operating system permits
15010 "Whenever practical, violations of any
15011 implementation-defined restrictions should be detected before run time."
15014 Followed. Compile time warnings are given when possible.
15016 @geindex Package `@w{`}Interrupts`@w{`}
15018 @geindex Interrupts
15020 @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
15021 @anchor{gnat_rm/implementation_advice rm-c-3-2-25-package-interrupts}@anchor{247}
15022 @section RM C.3.2(25): Package @code{Interrupts}
15027 "If implementation-defined forms of interrupt handler procedures are
15028 supported, such as protected procedures with parameters, then for each
15029 such form of a handler, a type analogous to @code{Parameterless_Handler}
15030 should be specified in a child package of @code{Interrupts}, with the
15031 same operations as in the predefined package Interrupts."
15036 @geindex Pre-elaboration requirements
15038 @node RM C 4 14 Pre-elaboration Requirements,RM C 5 8 Pragma Discard_Names,RM C 3 2 25 Package Interrupts,Implementation Advice
15039 @anchor{gnat_rm/implementation_advice rm-c-4-14-pre-elaboration-requirements}@anchor{248}
15040 @section RM C.4(14): Pre-elaboration Requirements
15045 "It is recommended that pre-elaborated packages be implemented in such a
15046 way that there should be little or no code executed at run time for the
15047 elaboration of entities not already covered by the Implementation
15051 Followed. Executable code is generated in some cases, e.g., loops
15052 to initialize large arrays.
15054 @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
15055 @anchor{gnat_rm/implementation_advice rm-c-5-8-pragma-discard-names}@anchor{249}
15056 @section RM C.5(8): Pragma @code{Discard_Names}
15061 "If the pragma applies to an entity, then the implementation should
15062 reduce the amount of storage used for storing names associated with that
15068 @geindex Package Task_Attributes
15070 @geindex Task_Attributes
15072 @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
15073 @anchor{gnat_rm/implementation_advice rm-c-7-2-30-the-package-task-attributes}@anchor{24a}
15074 @section RM C.7.2(30): The Package Task_Attributes
15079 "Some implementations are targeted to domains in which memory use at run
15080 time must be completely deterministic. For such implementations, it is
15081 recommended that the storage for task attributes will be pre-allocated
15082 statically and not from the heap. This can be accomplished by either
15083 placing restrictions on the number and the size of the task's
15084 attributes, or by using the pre-allocated storage for the first @code{N}
15085 attribute objects, and the heap for the others. In the latter case,
15086 @code{N} should be documented."
15089 Not followed. This implementation is not targeted to such a domain.
15091 @geindex Locking Policies
15093 @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
15094 @anchor{gnat_rm/implementation_advice rm-d-3-17-locking-policies}@anchor{24b}
15095 @section RM D.3(17): Locking Policies
15100 "The implementation should use names that end with @code{_Locking} for
15101 locking policies defined by the implementation."
15104 Followed. Two implementation-defined locking policies are defined,
15105 whose names (@code{Inheritance_Locking} and
15106 @code{Concurrent_Readers_Locking}) follow this suggestion.
15108 @geindex Entry queuing policies
15110 @node RM D 4 16 Entry Queuing Policies,RM D 6 9-10 Preemptive Abort,RM D 3 17 Locking Policies,Implementation Advice
15111 @anchor{gnat_rm/implementation_advice rm-d-4-16-entry-queuing-policies}@anchor{24c}
15112 @section RM D.4(16): Entry Queuing Policies
15117 "Names that end with @code{_Queuing} should be used
15118 for all implementation-defined queuing policies."
15121 Followed. No such implementation-defined queuing policies exist.
15123 @geindex Preemptive abort
15125 @node RM D 6 9-10 Preemptive Abort,RM D 7 21 Tasking Restrictions,RM D 4 16 Entry Queuing Policies,Implementation Advice
15126 @anchor{gnat_rm/implementation_advice rm-d-6-9-10-preemptive-abort}@anchor{24d}
15127 @section RM D.6(9-10): Preemptive Abort
15132 "Even though the @emph{abort_statement} is included in the list of
15133 potentially blocking operations (see 9.5.1), it is recommended that this
15134 statement be implemented in a way that never requires the task executing
15135 the @emph{abort_statement} to block."
15142 "On a multi-processor, the delay associated with aborting a task on
15143 another processor should be bounded; the implementation should use
15144 periodic polling, if necessary, to achieve this."
15149 @geindex Tasking restrictions
15151 @node RM D 7 21 Tasking Restrictions,RM D 8 47-49 Monotonic Time,RM D 6 9-10 Preemptive Abort,Implementation Advice
15152 @anchor{gnat_rm/implementation_advice rm-d-7-21-tasking-restrictions}@anchor{24e}
15153 @section RM D.7(21): Tasking Restrictions
15158 "When feasible, the implementation should take advantage of the specified
15159 restrictions to produce a more efficient implementation."
15162 GNAT currently takes advantage of these restrictions by providing an optimized
15163 run time when the Ravenscar profile and the GNAT restricted run time set
15164 of restrictions are specified. See pragma @code{Profile (Ravenscar)} and
15165 pragma @code{Profile (Restricted)} for more details.
15170 @node RM D 8 47-49 Monotonic Time,RM E 5 28-29 Partition Communication Subsystem,RM D 7 21 Tasking Restrictions,Implementation Advice
15171 @anchor{gnat_rm/implementation_advice rm-d-8-47-49-monotonic-time}@anchor{24f}
15172 @section RM D.8(47-49): Monotonic Time
15177 "When appropriate, implementations should provide configuration
15178 mechanisms to change the value of @code{Tick}."
15181 Such configuration mechanisms are not appropriate to this implementation
15182 and are thus not supported.
15186 "It is recommended that @code{Calendar.Clock} and @code{Real_Time.Clock}
15187 be implemented as transformations of the same time base."
15194 "It is recommended that the best time base which exists in
15195 the underlying system be available to the application through
15196 @code{Clock}. @cite{Best} may mean highest accuracy or largest range."
15201 @geindex Partition communication subsystem
15205 @node RM E 5 28-29 Partition Communication Subsystem,RM F 7 COBOL Support,RM D 8 47-49 Monotonic Time,Implementation Advice
15206 @anchor{gnat_rm/implementation_advice rm-e-5-28-29-partition-communication-subsystem}@anchor{250}
15207 @section RM E.5(28-29): Partition Communication Subsystem
15212 "Whenever possible, the PCS on the called partition should allow for
15213 multiple tasks to call the RPC-receiver with different messages and
15214 should allow them to block until the corresponding subprogram body
15218 Followed by GLADE, a separately supplied PCS that can be used with
15223 "The @code{Write} operation on a stream of type @code{Params_Stream_Type}
15224 should raise @code{Storage_Error} if it runs out of space trying to
15225 write the @code{Item} into the stream."
15228 Followed by GLADE, a separately supplied PCS that can be used with
15231 @geindex COBOL support
15233 @node RM F 7 COBOL Support,RM F 1 2 Decimal Radix Support,RM E 5 28-29 Partition Communication Subsystem,Implementation Advice
15234 @anchor{gnat_rm/implementation_advice rm-f-7-cobol-support}@anchor{251}
15235 @section RM F(7): COBOL Support
15240 "If COBOL (respectively, C) is widely supported in the target
15241 environment, implementations supporting the Information Systems Annex
15242 should provide the child package @code{Interfaces.COBOL} (respectively,
15243 @code{Interfaces.C}) specified in Annex B and should support a
15244 @code{convention_identifier} of COBOL (respectively, C) in the interfacing
15245 pragmas (see Annex B), thus allowing Ada programs to interface with
15246 programs written in that language."
15251 @geindex Decimal radix support
15253 @node RM F 1 2 Decimal Radix Support,RM G Numerics,RM F 7 COBOL Support,Implementation Advice
15254 @anchor{gnat_rm/implementation_advice rm-f-1-2-decimal-radix-support}@anchor{252}
15255 @section RM F.1(2): Decimal Radix Support
15260 "Packed decimal should be used as the internal representation for objects
15261 of subtype @code{S} when @code{S}'Machine_Radix = 10."
15264 Not followed. GNAT ignores @code{S}'Machine_Radix and always uses binary
15269 @node RM G Numerics,RM G 1 1 56-58 Complex Types,RM F 1 2 Decimal Radix Support,Implementation Advice
15270 @anchor{gnat_rm/implementation_advice rm-g-numerics}@anchor{253}
15271 @section RM G: Numerics
15276 "If Fortran (respectively, C) is widely supported in the target
15277 environment, implementations supporting the Numerics Annex
15278 should provide the child package @code{Interfaces.Fortran} (respectively,
15279 @code{Interfaces.C}) specified in Annex B and should support a
15280 @code{convention_identifier} of Fortran (respectively, C) in the interfacing
15281 pragmas (see Annex B), thus allowing Ada programs to interface with
15282 programs written in that language."
15287 @geindex Complex types
15289 @node RM G 1 1 56-58 Complex Types,RM G 1 2 49 Complex Elementary Functions,RM G Numerics,Implementation Advice
15290 @anchor{gnat_rm/implementation_advice rm-g-1-1-56-58-complex-types}@anchor{254}
15291 @section RM G.1.1(56-58): Complex Types
15296 "Because the usual mathematical meaning of multiplication of a complex
15297 operand and a real operand is that of the scaling of both components of
15298 the former by the latter, an implementation should not perform this
15299 operation by first promoting the real operand to complex type and then
15300 performing a full complex multiplication. In systems that, in the
15301 future, support an Ada binding to IEC 559:1989, the latter technique
15302 will not generate the required result when one of the components of the
15303 complex operand is infinite. (Explicit multiplication of the infinite
15304 component by the zero component obtained during promotion yields a NaN
15305 that propagates into the final result.) Analogous advice applies in the
15306 case of multiplication of a complex operand and a pure-imaginary
15307 operand, and in the case of division of a complex operand by a real or
15308 pure-imaginary operand."
15315 "Similarly, because the usual mathematical meaning of addition of a
15316 complex operand and a real operand is that the imaginary operand remains
15317 unchanged, an implementation should not perform this operation by first
15318 promoting the real operand to complex type and then performing a full
15319 complex addition. In implementations in which the @code{Signed_Zeros}
15320 attribute of the component type is @code{True} (and which therefore
15321 conform to IEC 559:1989 in regard to the handling of the sign of zero in
15322 predefined arithmetic operations), the latter technique will not
15323 generate the required result when the imaginary component of the complex
15324 operand is a negatively signed zero. (Explicit addition of the negative
15325 zero to the zero obtained during promotion yields a positive zero.)
15326 Analogous advice applies in the case of addition of a complex operand
15327 and a pure-imaginary operand, and in the case of subtraction of a
15328 complex operand and a real or pure-imaginary operand."
15335 "Implementations in which @code{Real'Signed_Zeros} is @code{True} should
15336 attempt to provide a rational treatment of the signs of zero results and
15337 result components. As one example, the result of the @code{Argument}
15338 function should have the sign of the imaginary component of the
15339 parameter @code{X} when the point represented by that parameter lies on
15340 the positive real axis; as another, the sign of the imaginary component
15341 of the @code{Compose_From_Polar} function should be the same as
15342 (respectively, the opposite of) that of the @code{Argument} parameter when that
15343 parameter has a value of zero and the @code{Modulus} parameter has a
15344 nonnegative (respectively, negative) value."
15349 @geindex Complex elementary functions
15351 @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
15352 @anchor{gnat_rm/implementation_advice rm-g-1-2-49-complex-elementary-functions}@anchor{255}
15353 @section RM G.1.2(49): Complex Elementary Functions
15358 "Implementations in which @code{Complex_Types.Real'Signed_Zeros} is
15359 @code{True} should attempt to provide a rational treatment of the signs
15360 of zero results and result components. For example, many of the complex
15361 elementary functions have components that are odd functions of one of
15362 the parameter components; in these cases, the result component should
15363 have the sign of the parameter component at the origin. Other complex
15364 elementary functions have zero components whose sign is opposite that of
15365 a parameter component at the origin, or is always positive or always
15371 @geindex Accuracy requirements
15373 @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
15374 @anchor{gnat_rm/implementation_advice rm-g-2-4-19-accuracy-requirements}@anchor{256}
15375 @section RM G.2.4(19): Accuracy Requirements
15380 "The versions of the forward trigonometric functions without a
15381 @code{Cycle} parameter should not be implemented by calling the
15382 corresponding version with a @code{Cycle} parameter of
15383 @code{2.0*Numerics.Pi}, since this will not provide the required
15384 accuracy in some portions of the domain. For the same reason, the
15385 version of @code{Log} without a @code{Base} parameter should not be
15386 implemented by calling the corresponding version with a @code{Base}
15387 parameter of @code{Numerics.e}."
15392 @geindex Complex arithmetic accuracy
15395 @geindex complex arithmetic
15397 @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
15398 @anchor{gnat_rm/implementation_advice rm-g-2-6-15-complex-arithmetic-accuracy}@anchor{257}
15399 @section RM G.2.6(15): Complex Arithmetic Accuracy
15404 "The version of the @code{Compose_From_Polar} function without a
15405 @code{Cycle} parameter should not be implemented by calling the
15406 corresponding version with a @code{Cycle} parameter of
15407 @code{2.0*Numerics.Pi}, since this will not provide the required
15408 accuracy in some portions of the domain."
15413 @geindex Sequential elaboration policy
15415 @node RM H 6 15/2 Pragma Partition_Elaboration_Policy,,RM G 2 6 15 Complex Arithmetic Accuracy,Implementation Advice
15416 @anchor{gnat_rm/implementation_advice rm-h-6-15-2-pragma-partition-elaboration-policy}@anchor{258}
15417 @section RM H.6(15/2): Pragma Partition_Elaboration_Policy
15422 "If the partition elaboration policy is @code{Sequential} and the
15423 Environment task becomes permanently blocked during elaboration then the
15424 partition is deadlocked and it is recommended that the partition be
15425 immediately terminated."
15430 @node Implementation Defined Characteristics,Intrinsic Subprograms,Implementation Advice,Top
15431 @anchor{gnat_rm/implementation_defined_characteristics implementation-defined-characteristics}@anchor{b}@anchor{gnat_rm/implementation_defined_characteristics doc}@anchor{259}@anchor{gnat_rm/implementation_defined_characteristics id1}@anchor{25a}
15432 @chapter Implementation Defined Characteristics
15435 In addition to the implementation dependent pragmas and attributes, and the
15436 implementation advice, there are a number of other Ada features that are
15437 potentially implementation dependent and are designated as
15438 implementation-defined. These are mentioned throughout the Ada Reference
15439 Manual, and are summarized in Annex M.
15441 A requirement for conforming Ada compilers is that they provide
15442 documentation describing how the implementation deals with each of these
15443 issues. In this chapter you will find each point in Annex M listed,
15444 followed by a description of how GNAT handles the implementation dependence.
15446 You can use this chapter as a guide to minimizing implementation
15447 dependent features in your programs if portability to other compilers
15448 and other operating systems is an important consideration. The numbers
15449 in each entry below correspond to the paragraph numbers in the Ada
15456 "Whether or not each recommendation given in Implementation
15457 Advice is followed. See 1.1.2(37)."
15460 See @ref{a,,Implementation Advice}.
15466 "Capacity limitations of the implementation. See 1.1.3(3)."
15469 The complexity of programs that can be processed is limited only by the
15470 total amount of available virtual memory, and disk space for the
15471 generated object files.
15477 "Variations from the standard that are impractical to avoid
15478 given the implementation's execution environment. See 1.1.3(6)."
15481 There are no variations from the standard.
15487 "Which code_statements cause external
15488 interactions. See 1.1.3(10)."
15491 Any @emph{code_statement} can potentially cause external interactions.
15497 "The coded representation for the text of an Ada
15498 program. See 2.1(4)."
15501 See separate section on source representation.
15507 "The control functions allowed in comments. See 2.1(14)."
15510 See separate section on source representation.
15516 "The representation for an end of line. See 2.2(2)."
15519 See separate section on source representation.
15525 "Maximum supported line length and lexical element
15526 length. See 2.2(15)."
15529 The maximum line length is 255 characters and the maximum length of
15530 a lexical element is also 255 characters. This is the default setting
15531 if not overridden by the use of compiler switch @emph{-gnaty} (which
15532 sets the maximum to 79) or @emph{-gnatyMnn} which allows the maximum
15533 line length to be specified to be any value up to 32767. The maximum
15534 length of a lexical element is the same as the maximum line length.
15540 "Implementation defined pragmas. See 2.8(14)."
15543 See @ref{7,,Implementation Defined Pragmas}.
15549 "Effect of pragma @code{Optimize}. See 2.8(27)."
15552 Pragma @code{Optimize}, if given with a @code{Time} or @code{Space}
15553 parameter, checks that the optimization flag is set, and aborts if it is
15560 "The sequence of characters of the value returned by
15561 @code{S'Image} when some of the graphic characters of
15562 @code{S'Wide_Image} are not defined in @code{Character}. See
15566 The sequence of characters is as defined by the wide character encoding
15567 method used for the source. See section on source representation for
15574 "The predefined integer types declared in
15575 @code{Standard}. See 3.5.4(25)."
15579 @multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
15590 @emph{Short_Short_Integer}
15598 @emph{Short_Integer}
15614 @emph{Long_Integer}
15618 64-bit signed (on most 64-bit targets,
15619 depending on the C definition of long)
15620 32-bit signed (on all other targets)
15624 @emph{Long_Long_Integer}
15632 @emph{Long_Long_Long_Integer}
15636 128-bit signed (on 64-bit targets)
15637 64-bit signed (on 32-bit targets)
15646 "Any nonstandard integer types and the operators defined
15647 for them. See 3.5.4(26)."
15650 There are no nonstandard integer types.
15656 "Any nonstandard real types and the operators defined for
15657 them. See 3.5.6(8)."
15660 There are no nonstandard real types.
15666 "What combinations of requested decimal precision and range
15667 are supported for floating point types. See 3.5.7(7)."
15670 The precision and range is as defined by the IEEE standard.
15676 "The predefined floating point types declared in
15677 @code{Standard}. See 3.5.7(16)."
15681 @multitable {xxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
15704 (Short) 32 bit IEEE short
15716 @emph{Long_Long_Float}
15720 64 bit IEEE long (80 bit IEEE long on x86 processors)
15729 "The small of an ordinary fixed point type. See 3.5.9(8)."
15732 The small is the largest power of two that does not exceed the delta.
15738 "What combinations of small, range, and digits are
15739 supported for fixed point types. See 3.5.9(10)."
15742 For an ordinary fixed point type, on 32-bit platforms, the small must lie in
15743 2.0**(-80) .. 2.0**80 and the range in -9.0E+36 .. 9.0E+36; any combination
15744 is permitted that does not result in a mantissa larger than 63 bits.
15746 On 64-bit platforms, the small must lie in 2.0**(-127) .. 2.0**127 and the
15747 range in -1.0E+76 .. 1.0E+76; any combination is permitted that does not
15748 result in a mantissa larger than 63 bits, and any combination is permitted
15749 that results in a mantissa between 64 and 127 bits if the small is the
15750 ratio of two integers that lie in 1 .. 2.0**127.
15752 If the small is the ratio of two integers with 64-bit magnitude on 32-bit
15753 platforms and 128-bit magnitude on 64-bit platforms, which is the case if
15754 no @code{small} clause is provided, then the operations of the fixed point
15755 type are entirely implemented by means of integer instructions. In the
15756 other cases, some operations, in particular input and output, may be
15757 implemented by means of floating-point instructions and may be affected
15758 by accuracy issues on architectures other than x86.
15760 For a decimal fixed point type, on 32-bit platforms, the small must lie in
15761 1.0E-18 .. 1.0E+18 and the digits in 1 .. 18. On 64-bit platforms, the
15762 small must lie in 1.0E-38 .. 1.0E+38 and the digits in 1 .. 38.
15768 "The result of @code{Tags.Expanded_Name} for types declared
15769 within an unnamed @emph{block_statement}. See 3.9(10)."
15772 Block numbers of the form @code{B@emph{nnn}}, where @emph{nnn} is a
15773 decimal integer are allocated.
15779 "Implementation-defined attributes. See 4.1.4(12)."
15782 See @ref{8,,Implementation Defined Attributes}.
15788 "Any implementation-defined time types. See 9.6(6)."
15791 There are no implementation-defined time types.
15797 "The time base associated with relative delays."
15800 See 9.6(20). The time base used is that provided by the C library
15801 function @code{gettimeofday}.
15807 "The time base of the type @code{Calendar.Time}. See
15811 The time base used is that provided by the C library function
15812 @code{gettimeofday}.
15818 "The time zone used for package @code{Calendar}
15819 operations. See 9.6(24)."
15822 The time zone used by package @code{Calendar} is the current system time zone
15823 setting for local time, as accessed by the C library function
15830 "Any limit on @emph{delay_until_statements} of
15831 @emph{select_statements}. See 9.6(29)."
15834 There are no such limits.
15840 "Whether or not two non-overlapping parts of a composite
15841 object are independently addressable, in the case where packing, record
15842 layout, or @code{Component_Size} is specified for the object. See
15846 Separate components are independently addressable if they do not share
15847 overlapping storage units.
15853 "The representation for a compilation. See 10.1(2)."
15856 A compilation is represented by a sequence of files presented to the
15857 compiler in a single invocation of the @emph{gcc} command.
15863 "Any restrictions on compilations that contain multiple
15864 compilation_units. See 10.1(4)."
15867 No single file can contain more than one compilation unit, but any
15868 sequence of files can be presented to the compiler as a single
15875 "The mechanisms for creating an environment and for adding
15876 and replacing compilation units. See 10.1.4(3)."
15879 See separate section on compilation model.
15885 "The manner of explicitly assigning library units to a
15886 partition. See 10.2(2)."
15889 If a unit contains an Ada main program, then the Ada units for the partition
15890 are determined by recursive application of the rules in the Ada Reference
15891 Manual section 10.2(2-6). In other words, the Ada units will be those that
15892 are needed by the main program, and then this definition of need is applied
15893 recursively to those units, and the partition contains the transitive
15894 closure determined by this relationship. In short, all the necessary units
15895 are included, with no need to explicitly specify the list. If additional
15896 units are required, e.g., by foreign language units, then all units must be
15897 mentioned in the context clause of one of the needed Ada units.
15899 If the partition contains no main program, or if the main program is in
15900 a language other than Ada, then GNAT
15901 provides the binder options @emph{-z} and @emph{-n} respectively, and in
15902 this case a list of units can be explicitly supplied to the binder for
15903 inclusion in the partition (all units needed by these units will also
15904 be included automatically). For full details on the use of these
15905 options, refer to @emph{GNAT Make Program gnatmake} in the
15906 @cite{GNAT User's Guide}.
15912 "The implementation-defined means, if any, of specifying
15913 which compilation units are needed by a given compilation unit. See
15917 The units needed by a given compilation unit are as defined in
15918 the Ada Reference Manual section 10.2(2-6). There are no
15919 implementation-defined pragmas or other implementation-defined
15920 means for specifying needed units.
15926 "The manner of designating the main subprogram of a
15927 partition. See 10.2(7)."
15930 The main program is designated by providing the name of the
15931 corresponding @code{ALI} file as the input parameter to the binder.
15937 "The order of elaboration of @emph{library_items}. See
15941 The first constraint on ordering is that it meets the requirements of
15942 Chapter 10 of the Ada Reference Manual. This still leaves some
15943 implementation dependent choices, which are resolved by first
15944 elaborating bodies as early as possible (i.e., in preference to specs
15945 where there is a choice), and second by evaluating the immediate with
15946 clauses of a unit to determine the probably best choice, and
15947 third by elaborating in alphabetical order of unit names
15948 where a choice still remains.
15954 "Parameter passing and function return for the main
15955 subprogram. See 10.2(21)."
15958 The main program has no parameters. It may be a procedure, or a function
15959 returning an integer type. In the latter case, the returned integer
15960 value is the return code of the program (overriding any value that
15961 may have been set by a call to @code{Ada.Command_Line.Set_Exit_Status}).
15967 "The mechanisms for building and running partitions. See
15971 GNAT itself supports programs with only a single partition. The GNATDIST
15972 tool provided with the GLADE package (which also includes an implementation
15973 of the PCS) provides a completely flexible method for building and running
15974 programs consisting of multiple partitions. See the separate GLADE manual
15981 "The details of program execution, including program
15982 termination. See 10.2(25)."
15985 See separate section on compilation model.
15991 "The semantics of any non-active partitions supported by the
15992 implementation. See 10.2(28)."
15995 Passive partitions are supported on targets where shared memory is
15996 provided by the operating system. See the GLADE reference manual for
16003 "The information returned by @code{Exception_Message}. See
16007 Exception message returns the null string unless a specific message has
16008 been passed by the program.
16014 "The result of @code{Exceptions.Exception_Name} for types
16015 declared within an unnamed @emph{block_statement}. See 11.4.1(12)."
16018 Blocks have implementation defined names of the form @code{B@emph{nnn}}
16019 where @emph{nnn} is an integer.
16025 "The information returned by
16026 @code{Exception_Information}. See 11.4.1(13)."
16029 @code{Exception_Information} returns a string in the following format:
16032 *Exception_Name:* nnnnn
16035 *Load address:* 0xhhhh
16036 *Call stack traceback locations:*
16037 0xhhhh 0xhhhh 0xhhhh ... 0xhhh
16048 @code{nnnn} is the fully qualified name of the exception in all upper
16049 case letters. This line is always present.
16052 @code{mmmm} is the message (this line present only if message is non-null)
16055 @code{ppp} is the Process Id value as a decimal integer (this line is
16056 present only if the Process Id is nonzero). Currently we are
16057 not making use of this field.
16060 The Load address line, the Call stack traceback locations line and the
16061 following values are present only if at least one traceback location was
16062 recorded. The Load address indicates the address at which the main executable
16063 was loaded; this line may not be present if operating system hasn't relocated
16064 the main executable. The values are given in C style format, with lower case
16065 letters for a-f, and only as many digits present as are necessary.
16066 The line terminator sequence at the end of each line, including
16067 the last line is a single @code{LF} character (@code{16#0A#}).
16075 "Implementation-defined check names. See 11.5(27)."
16078 The implementation defined check names include Alignment_Check,
16079 Atomic_Synchronization, Duplicated_Tag_Check, Container_Checks,
16080 Tampering_Check, Predicate_Check, and Validity_Check. In addition, a user
16081 program can add implementation-defined check names by means of the pragma
16082 Check_Name. See the description of pragma @code{Suppress} for full details.
16088 "The interpretation of each aspect of representation. See
16092 See separate section on data representations.
16098 "Any restrictions placed upon representation items. See
16102 See separate section on data representations.
16108 "The meaning of @code{Size} for indefinite subtypes. See
16112 Size for an indefinite subtype is the maximum possible size, except that
16113 for the case of a subprogram parameter, the size of the parameter object
16114 is the actual size.
16120 "The default external representation for a type tag. See
16124 The default external representation for a type tag is the fully expanded
16125 name of the type in upper case letters.
16131 "What determines whether a compilation unit is the same in
16132 two different partitions. See 13.3(76)."
16135 A compilation unit is the same in two different partitions if and only
16136 if it derives from the same source file.
16142 "Implementation-defined components. See 13.5.1(15)."
16145 The only implementation defined component is the tag for a tagged type,
16146 which contains a pointer to the dispatching table.
16152 "If @code{Word_Size} = @code{Storage_Unit}, the default bit
16153 ordering. See 13.5.3(5)."
16156 @code{Word_Size} (32) is not the same as @code{Storage_Unit} (8) for this
16157 implementation, so no non-default bit ordering is supported. The default
16158 bit ordering corresponds to the natural endianness of the target architecture.
16164 "The contents of the visible part of package @code{System}
16165 and its language-defined children. See 13.7(2)."
16168 See the definition of these packages in files @code{system.ads} and
16169 @code{s-stoele.ads}. Note that two declarations are added to package
16173 Max_Priority : constant Positive := Priority'Last;
16174 Max_Interrupt_Priority : constant Positive := Interrupt_Priority'Last;
16181 "The contents of the visible part of package
16182 @code{System.Machine_Code}, and the meaning of
16183 @emph{code_statements}. See 13.8(7)."
16186 See the definition and documentation in file @code{s-maccod.ads}.
16192 "The effect of unchecked conversion. See 13.9(11)."
16195 Unchecked conversion between types of the same size
16196 results in an uninterpreted transmission of the bits from one type
16197 to the other. If the types are of unequal sizes, then in the case of
16198 discrete types, a shorter source is first zero or sign extended as
16199 necessary, and a shorter target is simply truncated on the left.
16200 For all non-discrete types, the source is first copied if necessary
16201 to ensure that the alignment requirements of the target are met, then
16202 a pointer is constructed to the source value, and the result is obtained
16203 by dereferencing this pointer after converting it to be a pointer to the
16204 target type. Unchecked conversions where the target subtype is an
16205 unconstrained array are not permitted. If the target alignment is
16206 greater than the source alignment, then a copy of the result is
16207 made with appropriate alignment
16213 "The semantics of operations on invalid representations.
16214 See 13.9.2(10-11)."
16217 For assignments and other operations where the use of invalid values cannot
16218 result in erroneous behavior, the compiler ignores the possibility of invalid
16219 values. An exception is raised at the point where an invalid value would
16220 result in erroneous behavior. For example executing:
16223 procedure invalidvals is
16225 Y : Natural range 1 .. 10;
16226 for Y'Address use X'Address;
16227 Z : Natural range 1 .. 10;
16228 A : array (Natural range 1 .. 10) of Integer;
16230 Z := Y; -- no exception
16231 A (Z) := 3; -- exception raised;
16235 As indicated, an exception is raised on the array assignment, but not
16236 on the simple assignment of the invalid negative value from Y to Z.
16242 "The manner of choosing a storage pool for an access type
16243 when @code{Storage_Pool} is not specified for the type. See 13.11(17)."
16246 There are 3 different standard pools used by the compiler when
16247 @code{Storage_Pool} is not specified depending whether the type is local
16248 to a subprogram or defined at the library level and whether
16249 @code{Storage_Size`@w{`}is specified or not. See documentation in the runtime
16250 library units `@w{`}System.Pool_Global}, @code{System.Pool_Size} and
16251 @code{System.Pool_Local} in files @code{s-poosiz.ads},
16252 @code{s-pooglo.ads} and @code{s-pooloc.ads} for full details on the
16253 default pools used.
16259 "Whether or not the implementation provides user-accessible
16260 names for the standard pool type(s). See 13.11(17)."
16263 See documentation in the sources of the run time mentioned in the previous
16264 paragraph. All these pools are accessible by means of @cite{with}ing
16271 "The meaning of @code{Storage_Size}. See 13.11(18)."
16274 @code{Storage_Size} is measured in storage units, and refers to the
16275 total space available for an access type collection, or to the primary
16276 stack space for a task.
16282 "Implementation-defined aspects of storage pools. See
16286 See documentation in the sources of the run time mentioned in the
16287 paragraph about standard storage pools above
16288 for details on GNAT-defined aspects of storage pools.
16294 "The set of restrictions allowed in a pragma
16295 @code{Restrictions}. See 13.12(7)."
16298 See @ref{9,,Standard and Implementation Defined Restrictions}.
16304 "The consequences of violating limitations on
16305 @code{Restrictions} pragmas. See 13.12(9)."
16308 Restrictions that can be checked at compile time result in illegalities
16309 if violated. Currently there are no other consequences of violating
16316 "The representation used by the @code{Read} and
16317 @code{Write} attributes of elementary types in terms of stream
16318 elements. See 13.13.2(9)."
16321 The representation is the in-memory representation of the base type of
16322 the type, using the number of bits corresponding to the
16323 @code{type'Size} value, and the natural ordering of the machine.
16329 "The names and characteristics of the numeric subtypes
16330 declared in the visible part of package @code{Standard}. See A.1(3)."
16333 See items describing the integer and floating-point types supported.
16339 "The string returned by @code{Character_Set_Version}.
16343 @code{Ada.Wide_Characters.Handling.Character_Set_Version} returns
16344 the string "Unicode 4.0", referring to version 4.0 of the
16345 Unicode specification.
16351 "The accuracy actually achieved by the elementary
16352 functions. See A.5.1(1)."
16355 The elementary functions correspond to the functions available in the C
16356 library. Only fast math mode is implemented.
16362 "The sign of a zero result from some of the operators or
16363 functions in @code{Numerics.Generic_Elementary_Functions}, when
16364 @code{Float_Type'Signed_Zeros} is @code{True}. See A.5.1(46)."
16367 The sign of zeroes follows the requirements of the IEEE 754 standard on
16375 @code{Numerics.Float_Random.Max_Image_Width}. See A.5.2(27)."
16378 Maximum image width is 6864, see library file @code{s-rannum.ads}.
16385 @code{Numerics.Discrete_Random.Max_Image_Width}. See A.5.2(27)."
16388 Maximum image width is 6864, see library file @code{s-rannum.ads}.
16394 "The algorithms for random number generation. See
16398 The algorithm is the Mersenne Twister, as documented in the source file
16399 @code{s-rannum.adb}. This version of the algorithm has a period of
16406 "The string representation of a random number generator's
16407 state. See A.5.2(38)."
16410 The value returned by the Image function is the concatenation of
16411 the fixed-width decimal representations of the 624 32-bit integers
16412 of the state vector.
16418 "The minimum time interval between calls to the
16419 time-dependent Reset procedure that are guaranteed to initiate different
16420 random number sequences. See A.5.2(45)."
16423 The minimum period between reset calls to guarantee distinct series of
16424 random numbers is one microsecond.
16430 "The values of the @code{Model_Mantissa},
16431 @code{Model_Emin}, @code{Model_Epsilon}, @code{Model},
16432 @code{Safe_First}, and @code{Safe_Last} attributes, if the Numerics
16433 Annex is not supported. See A.5.3(72)."
16436 Run the compiler with @emph{-gnatS} to produce a listing of package
16437 @code{Standard}, has the values of all numeric attributes.
16443 "Any implementation-defined characteristics of the
16444 input-output packages. See A.7(14)."
16447 There are no special implementation defined characteristics for these
16454 "The value of @code{Buffer_Size} in @code{Storage_IO}. See
16458 All type representations are contiguous, and the @code{Buffer_Size} is
16459 the value of @code{type'Size} rounded up to the next storage unit
16466 "External files for standard input, standard output, and
16467 standard error See A.10(5)."
16470 These files are mapped onto the files provided by the C streams
16471 libraries. See source file @code{i-cstrea.ads} for further details.
16477 "The accuracy of the value produced by @code{Put}. See
16481 If more digits are requested in the output than are represented by the
16482 precision of the value, zeroes are output in the corresponding least
16483 significant digit positions.
16489 "The meaning of @code{Argument_Count}, @code{Argument}, and
16490 @code{Command_Name}. See A.15(1)."
16493 These are mapped onto the @code{argv} and @code{argc} parameters of the
16494 main program in the natural manner.
16500 "The interpretation of the @code{Form} parameter in procedure
16501 @code{Create_Directory}. See A.16(56)."
16504 The @code{Form} parameter is not used.
16510 "The interpretation of the @code{Form} parameter in procedure
16511 @code{Create_Path}. See A.16(60)."
16514 The @code{Form} parameter is not used.
16520 "The interpretation of the @code{Form} parameter in procedure
16521 @code{Copy_File}. See A.16(68)."
16524 The @code{Form} parameter is case-insensitive.
16525 Two fields are recognized in the @code{Form} parameter:
16532 <value> starts immediately after the character '=' and ends with the
16533 character immediately preceding the next comma (',') or with the last
16534 character of the parameter.
16536 The only possible values for preserve= are:
16539 @multitable {xxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
16550 @emph{no_attributes}
16554 Do not try to preserve any file attributes. This is the
16555 default if no preserve= is found in Form.
16559 @emph{all_attributes}
16563 Try to preserve all file attributes (timestamps, access rights).
16571 Preserve the timestamp of the copied file, but not the other
16577 The only possible values for mode= are:
16580 @multitable {xxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
16595 Only do the copy if the destination file does not already exist.
16596 If it already exists, Copy_File fails.
16604 Copy the file in all cases. Overwrite an already existing destination file.
16612 Append the original file to the destination file. If the destination file
16613 does not exist, the destination file is a copy of the source file.
16614 When mode=append, the field preserve=, if it exists, is not taken into account.
16619 If the Form parameter includes one or both of the fields and the value or
16620 values are incorrect, Copy_file fails with Use_Error.
16622 Examples of correct Forms:
16625 Form => "preserve=no_attributes,mode=overwrite" (the default)
16626 Form => "mode=append"
16627 Form => "mode=copy, preserve=all_attributes"
16630 Examples of incorrect Forms:
16633 Form => "preserve=junk"
16634 Form => "mode=internal, preserve=timestamps"
16641 "The interpretation of the @code{Pattern} parameter, when not the null string,
16642 in the @code{Start_Search} and @code{Search} procedures.
16643 See A.16(104) and A.16(112)."
16646 When the @code{Pattern} parameter is not the null string, it is interpreted
16647 according to the syntax of regular expressions as defined in the
16648 @code{GNAT.Regexp} package.
16650 See @ref{25b,,GNAT.Regexp (g-regexp.ads)}.
16656 "Implementation-defined convention names. See B.1(11)."
16659 The following convention names are supported
16662 @multitable {xxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
16681 @emph{Ada_Pass_By_Copy}
16685 Allowed for any types except by-reference types such as limited
16686 records. Compatible with convention Ada, but causes any parameters
16687 with this convention to be passed by copy.
16691 @emph{Ada_Pass_By_Reference}
16695 Allowed for any types except by-copy types such as scalars.
16696 Compatible with convention Ada, but causes any parameters
16697 with this convention to be passed by reference.
16713 Synonym for Assembler
16721 Synonym for Assembler
16733 @emph{C_Pass_By_Copy}
16737 Allowed only for record types, like C, but also notes that record
16738 is to be passed by copy rather than reference.
16750 @emph{C_Plus_Plus (or CPP)}
16762 Treated the same as C
16770 Treated the same as C
16786 For support of pragma @code{Import} with convention Intrinsic, see
16787 separate section on Intrinsic Subprograms.
16795 Stdcall (used for Windows implementations only). This convention correspond
16796 to the WINAPI (previously called Pascal convention) C/C++ convention under
16797 Windows. A routine with this convention cleans the stack before
16798 exit. This pragma cannot be applied to a dispatching call.
16806 Synonym for Stdcall
16814 Synonym for Stdcall
16822 Stubbed is a special convention used to indicate that the body of the
16823 subprogram will be entirely ignored. Any call to the subprogram
16824 is converted into a raise of the @code{Program_Error} exception. If a
16825 pragma @code{Import} specifies convention @code{stubbed} then no body need
16826 be present at all. This convention is useful during development for the
16827 inclusion of subprograms whose body has not yet been written.
16828 In addition, all otherwise unrecognized convention names are also
16829 treated as being synonymous with convention C. In all implementations,
16830 use of such other names results in a warning.
16839 "The meaning of link names. See B.1(36)."
16842 Link names are the actual names used by the linker.
16848 "The manner of choosing link names when neither the link
16849 name nor the address of an imported or exported entity is specified. See
16853 The default linker name is that which would be assigned by the relevant
16854 external language, interpreting the Ada name as being in all lower case
16861 "The effect of pragma @code{Linker_Options}. See B.1(37)."
16864 The string passed to @code{Linker_Options} is presented uninterpreted as
16865 an argument to the link command, unless it contains ASCII.NUL characters.
16866 NUL characters if they appear act as argument separators, so for example
16869 pragma Linker_Options ("-labc" & ASCII.NUL & "-ldef");
16872 causes two separate arguments @code{-labc} and @code{-ldef} to be passed to the
16873 linker. The order of linker options is preserved for a given unit. The final
16874 list of options passed to the linker is in reverse order of the elaboration
16875 order. For example, linker options for a body always appear before the options
16876 from the corresponding package spec.
16882 "The contents of the visible part of package
16883 @code{Interfaces} and its language-defined descendants. See B.2(1)."
16886 See files with prefix @code{i-} in the distributed library.
16892 "Implementation-defined children of package
16893 @code{Interfaces}. The contents of the visible part of package
16894 @code{Interfaces}. See B.2(11)."
16897 See files with prefix @code{i-} in the distributed library.
16903 "The types @code{Floating}, @code{Long_Floating},
16904 @code{Binary}, @code{Long_Binary}, @code{Decimal_ Element}, and
16905 @code{COBOL_Character}; and the initialization of the variables
16906 @code{Ada_To_COBOL} and @code{COBOL_To_Ada}, in
16907 @code{Interfaces.COBOL}. See B.4(50)."
16911 @multitable {xxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
16930 @emph{Long_Floating}
16934 (Floating) Long_Float
16954 @emph{Decimal_Element}
16962 @emph{COBOL_Character}
16971 For initialization, see the file @code{i-cobol.ads} in the distributed library.
16977 "Support for access to machine instructions. See C.1(1)."
16980 See documentation in file @code{s-maccod.ads} in the distributed library.
16986 "Implementation-defined aspects of access to machine
16987 operations. See C.1(9)."
16990 See documentation in file @code{s-maccod.ads} in the distributed library.
16996 "Implementation-defined aspects of interrupts. See C.3(2)."
16999 Interrupts are mapped to signals or conditions as appropriate. See
17001 @code{Ada.Interrupt_Names} in source file @code{a-intnam.ads} for details
17002 on the interrupts supported on a particular target.
17008 "Implementation-defined aspects of pre-elaboration. See
17012 GNAT does not permit a partition to be restarted without reloading,
17013 except under control of the debugger.
17019 "The semantics of pragma @code{Discard_Names}. See C.5(7)."
17022 Pragma @code{Discard_Names} causes names of enumeration literals to
17023 be suppressed. In the presence of this pragma, the Image attribute
17024 provides the image of the Pos of the literal, and Value accepts
17027 For tagged types, when pragmas @code{Discard_Names} and @code{No_Tagged_Streams}
17028 simultaneously apply, their Expanded_Name and External_Tag are initialized
17029 with empty strings. This is useful to avoid exposing entity names at binary
17036 "The result of the @code{Task_Identification.Image}
17037 attribute. See C.7.1(7)."
17040 The result of this attribute is a string that identifies
17041 the object or component that denotes a given task. If a variable @code{Var}
17042 has a task type, the image for this task will have the form @code{Var_@emph{XXXXXXXX}},
17043 where the suffix @emph{XXXXXXXX}
17044 is the hexadecimal representation of the virtual address of the corresponding
17045 task control block. If the variable is an array of tasks, the image of each
17046 task will have the form of an indexed component indicating the position of a
17047 given task in the array, e.g., @code{Group(5)_@emph{XXXXXXX}}. If the task is a
17048 component of a record, the image of the task will have the form of a selected
17049 component. These rules are fully recursive, so that the image of a task that
17050 is a subcomponent of a composite object corresponds to the expression that
17051 designates this task.
17053 If a task is created by an allocator, its image depends on the context. If the
17054 allocator is part of an object declaration, the rules described above are used
17055 to construct its image, and this image is not affected by subsequent
17056 assignments. If the allocator appears within an expression, the image
17057 includes only the name of the task type.
17059 If the configuration pragma Discard_Names is present, or if the restriction
17060 No_Implicit_Heap_Allocation is in effect, the image reduces to
17061 the numeric suffix, that is to say the hexadecimal representation of the
17062 virtual address of the control block of the task.
17068 "The value of @code{Current_Task} when in a protected entry
17069 or interrupt handler. See C.7.1(17)."
17072 Protected entries or interrupt handlers can be executed by any
17073 convenient thread, so the value of @code{Current_Task} is undefined.
17079 "The effect of calling @code{Current_Task} from an entry
17080 body or interrupt handler. See C.7.1(19)."
17083 When GNAT can determine statically that @code{Current_Task} is called directly in
17084 the body of an entry (or barrier) then a warning is emitted and @code{Program_Error}
17085 is raised at run time. Otherwise, the effect of calling @code{Current_Task} from an
17086 entry body or interrupt handler is to return the identification of the task
17087 currently executing the code.
17093 "Implementation-defined aspects of
17094 @code{Task_Attributes}. See C.7.2(19)."
17097 There are no implementation-defined aspects of @code{Task_Attributes}.
17103 "Values of all @code{Metrics}. See D(2)."
17106 The metrics information for GNAT depends on the performance of the
17107 underlying operating system. The sources of the run-time for tasking
17108 implementation, together with the output from @emph{-gnatG} can be
17109 used to determine the exact sequence of operating systems calls made
17110 to implement various tasking constructs. Together with appropriate
17111 information on the performance of the underlying operating system,
17112 on the exact target in use, this information can be used to determine
17113 the required metrics.
17119 "The declarations of @code{Any_Priority} and
17120 @code{Priority}. See D.1(11)."
17123 See declarations in file @code{system.ads}.
17129 "Implementation-defined execution resources. See D.1(15)."
17132 There are no implementation-defined execution resources.
17138 "Whether, on a multiprocessor, a task that is waiting for
17139 access to a protected object keeps its processor busy. See D.2.1(3)."
17142 On a multi-processor, a task that is waiting for access to a protected
17143 object does not keep its processor busy.
17149 "The affect of implementation defined execution resources
17150 on task dispatching. See D.2.1(9)."
17153 Tasks map to threads in the threads package used by GNAT. Where possible
17154 and appropriate, these threads correspond to native threads of the
17155 underlying operating system.
17161 "Implementation-defined @emph{policy_identifiers} allowed
17162 in a pragma @code{Task_Dispatching_Policy}. See D.2.2(3)."
17165 There are no implementation-defined policy-identifiers allowed in this
17172 "Implementation-defined aspects of priority inversion. See
17176 Execution of a task cannot be preempted by the implementation processing
17177 of delay expirations for lower priority tasks.
17183 "Implementation-defined task dispatching. See D.2.2(18)."
17186 The policy is the same as that of the underlying threads implementation.
17192 "Implementation-defined @emph{policy_identifiers} allowed
17193 in a pragma @code{Locking_Policy}. See D.3(4)."
17196 The two implementation defined policies permitted in GNAT are
17197 @code{Inheritance_Locking} and @code{Concurrent_Readers_Locking}. On
17198 targets that support the @code{Inheritance_Locking} policy, locking is
17199 implemented by inheritance, i.e., the task owning the lock operates
17200 at a priority equal to the highest priority of any task currently
17201 requesting the lock. On targets that support the
17202 @code{Concurrent_Readers_Locking} policy, locking is implemented with a
17203 read/write lock allowing multiple protected object functions to enter
17210 "Default ceiling priorities. See D.3(10)."
17213 The ceiling priority of protected objects of the type
17214 @code{System.Interrupt_Priority'Last} as described in the Ada
17215 Reference Manual D.3(10),
17221 "The ceiling of any protected object used internally by
17222 the implementation. See D.3(16)."
17225 The ceiling priority of internal protected objects is
17226 @code{System.Priority'Last}.
17232 "Implementation-defined queuing policies. See D.4(1)."
17235 There are no implementation-defined queuing policies.
17241 "On a multiprocessor, any conditions that cause the
17242 completion of an aborted construct to be delayed later than what is
17243 specified for a single processor. See D.6(3)."
17246 The semantics for abort on a multi-processor is the same as on a single
17247 processor, there are no further delays.
17253 "Any operations that implicitly require heap storage
17254 allocation. See D.7(8)."
17257 The only operation that implicitly requires heap storage allocation is
17264 "What happens when a task terminates in the presence of
17265 pragma @code{No_Task_Termination}. See D.7(15)."
17268 Execution is erroneous in that case.
17274 "Implementation-defined aspects of pragma
17275 @code{Restrictions}. See D.7(20)."
17278 There are no such implementation-defined aspects.
17284 "Implementation-defined aspects of package
17285 @code{Real_Time}. See D.8(17)."
17288 There are no implementation defined aspects of package @code{Real_Time}.
17294 "Implementation-defined aspects of
17295 @emph{delay_statements}. See D.9(8)."
17298 Any difference greater than one microsecond will cause the task to be
17299 delayed (see D.9(7)).
17305 "The upper bound on the duration of interrupt blocking
17306 caused by the implementation. See D.12(5)."
17309 The upper bound is determined by the underlying operating system. In
17310 no cases is it more than 10 milliseconds.
17316 "The means for creating and executing distributed
17317 programs. See E(5)."
17320 The GLADE package provides a utility GNATDIST for creating and executing
17321 distributed programs. See the GLADE reference manual for further details.
17327 "Any events that can result in a partition becoming
17328 inaccessible. See E.1(7)."
17331 See the GLADE reference manual for full details on such events.
17337 "The scheduling policies, treatment of priorities, and
17338 management of shared resources between partitions in certain cases. See
17342 See the GLADE reference manual for full details on these aspects of
17343 multi-partition execution.
17349 "Events that cause the version of a compilation unit to
17350 change. See E.3(5)."
17353 Editing the source file of a compilation unit, or the source files of
17354 any units on which it is dependent in a significant way cause the version
17355 to change. No other actions cause the version number to change. All changes
17356 are significant except those which affect only layout, capitalization or
17363 "Whether the execution of the remote subprogram is
17364 immediately aborted as a result of cancellation. See E.4(13)."
17367 See the GLADE reference manual for details on the effect of abort in
17368 a distributed application.
17374 "Implementation-defined aspects of the PCS. See E.5(25)."
17377 See the GLADE reference manual for a full description of all implementation
17378 defined aspects of the PCS.
17384 "Implementation-defined interfaces in the PCS. See
17388 See the GLADE reference manual for a full description of all
17389 implementation defined interfaces.
17395 "The values of named numbers in the package
17396 @code{Decimal}. See F.2(7)."
17400 @multitable {xxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxx}
17443 @emph{Max_Decimal_Digits}
17456 "The value of @code{Max_Picture_Length} in the package
17457 @code{Text_IO.Editing}. See F.3.3(16)."
17466 "The value of @code{Max_Picture_Length} in the package
17467 @code{Wide_Text_IO.Editing}. See F.3.4(5)."
17476 "The accuracy actually achieved by the complex elementary
17477 functions and by other complex arithmetic operations. See G.1(1)."
17480 Standard library functions are used for the complex arithmetic
17481 operations. Only fast math mode is currently supported.
17487 "The sign of a zero result (or a component thereof) from
17488 any operator or function in @code{Numerics.Generic_Complex_Types}, when
17489 @code{Real'Signed_Zeros} is True. See G.1.1(53)."
17492 The signs of zero values are as recommended by the relevant
17493 implementation advice.
17499 "The sign of a zero result (or a component thereof) from
17500 any operator or function in
17501 @code{Numerics.Generic_Complex_Elementary_Functions}, when
17502 @code{Real'Signed_Zeros} is @code{True}. See G.1.2(45)."
17505 The signs of zero values are as recommended by the relevant
17506 implementation advice.
17512 "Whether the strict mode or the relaxed mode is the
17513 default. See G.2(2)."
17516 The strict mode is the default. There is no separate relaxed mode. GNAT
17517 provides a highly efficient implementation of strict mode.
17523 "The result interval in certain cases of fixed-to-float
17524 conversion. See G.2.1(10)."
17527 For cases where the result interval is implementation dependent, the
17528 accuracy is that provided by performing all operations in 64-bit IEEE
17529 floating-point format.
17535 "The result of a floating point arithmetic operation in
17536 overflow situations, when the @code{Machine_Overflows} attribute of the
17537 result type is @code{False}. See G.2.1(13)."
17540 Infinite and NaN values are produced as dictated by the IEEE
17541 floating-point standard.
17542 Note that on machines that are not fully compliant with the IEEE
17543 floating-point standard, such as Alpha, the @emph{-mieee} compiler flag
17544 must be used for achieving IEEE conforming behavior (although at the cost
17545 of a significant performance penalty), so infinite and NaN values are
17546 properly generated.
17552 "The result interval for division (or exponentiation by a
17553 negative exponent), when the floating point hardware implements division
17554 as multiplication by a reciprocal. See G.2.1(16)."
17557 Not relevant, division is IEEE exact.
17563 "The definition of close result set, which determines the
17564 accuracy of certain fixed point multiplications and divisions. See
17568 Operations in the close result set are performed using IEEE long format
17569 floating-point arithmetic. The input operands are converted to
17570 floating-point, the operation is done in floating-point, and the result
17571 is converted to the target type.
17577 "Conditions on a @emph{universal_real} operand of a fixed
17578 point multiplication or division for which the result shall be in the
17579 perfect result set. See G.2.3(22)."
17582 The result is only defined to be in the perfect result set if the result
17583 can be computed by a single scaling operation involving a scale factor
17584 representable in 64 bits.
17590 "The result of a fixed point arithmetic operation in
17591 overflow situations, when the @code{Machine_Overflows} attribute of the
17592 result type is @code{False}. See G.2.3(27)."
17595 Not relevant, @code{Machine_Overflows} is @code{True} for fixed-point
17602 "The result of an elementary function reference in
17603 overflow situations, when the @code{Machine_Overflows} attribute of the
17604 result type is @code{False}. See G.2.4(4)."
17607 IEEE infinite and Nan values are produced as appropriate.
17613 "The value of the angle threshold, within which certain
17614 elementary functions, complex arithmetic operations, and complex
17615 elementary functions yield results conforming to a maximum relative
17616 error bound. See G.2.4(10)."
17619 Information on this subject is not yet available.
17625 "The accuracy of certain elementary functions for
17626 parameters beyond the angle threshold. See G.2.4(10)."
17629 Information on this subject is not yet available.
17635 "The result of a complex arithmetic operation or complex
17636 elementary function reference in overflow situations, when the
17637 @code{Machine_Overflows} attribute of the corresponding real type is
17638 @code{False}. See G.2.6(5)."
17641 IEEE infinite and Nan values are produced as appropriate.
17647 "The accuracy of certain complex arithmetic operations and
17648 certain complex elementary functions for parameters (or components
17649 thereof) beyond the angle threshold. See G.2.6(8)."
17652 Information on those subjects is not yet available.
17658 "Information regarding bounded errors and erroneous
17659 execution. See H.2(1)."
17662 Information on this subject is not yet available.
17668 "Implementation-defined aspects of pragma
17669 @code{Inspection_Point}. See H.3.2(8)."
17672 Pragma @code{Inspection_Point} ensures that the variable is live and can
17673 be examined by the debugger at the inspection point.
17679 "Implementation-defined aspects of pragma
17680 @code{Restrictions}. See H.4(25)."
17683 There are no implementation-defined aspects of pragma @code{Restrictions}. The
17684 use of pragma @code{Restrictions [No_Exceptions]} has no effect on the
17685 generated code. Checks must suppressed by use of pragma @code{Suppress}.
17691 "Any restrictions on pragma @code{Restrictions}. See
17695 There are no restrictions on pragma @code{Restrictions}.
17697 @node Intrinsic Subprograms,Representation Clauses and Pragmas,Implementation Defined Characteristics,Top
17698 @anchor{gnat_rm/intrinsic_subprograms doc}@anchor{25c}@anchor{gnat_rm/intrinsic_subprograms intrinsic-subprograms}@anchor{c}@anchor{gnat_rm/intrinsic_subprograms id1}@anchor{25d}
17699 @chapter Intrinsic Subprograms
17702 @geindex Intrinsic Subprograms
17704 GNAT allows a user application program to write the declaration:
17707 pragma Import (Intrinsic, name);
17710 providing that the name corresponds to one of the implemented intrinsic
17711 subprograms in GNAT, and that the parameter profile of the referenced
17712 subprogram meets the requirements. This chapter describes the set of
17713 implemented intrinsic subprograms, and the requirements on parameter profiles.
17714 Note that no body is supplied; as with other uses of pragma Import, the
17715 body is supplied elsewhere (in this case by the compiler itself). Note
17716 that any use of this feature is potentially non-portable, since the
17717 Ada standard does not require Ada compilers to implement this feature.
17720 * Intrinsic Operators::
17721 * Compilation_ISO_Date::
17722 * Compilation_Date::
17723 * Compilation_Time::
17724 * Enclosing_Entity::
17725 * Exception_Information::
17726 * Exception_Message::
17730 * Shifts and Rotates::
17731 * Source_Location::
17735 @node Intrinsic Operators,Compilation_ISO_Date,,Intrinsic Subprograms
17736 @anchor{gnat_rm/intrinsic_subprograms id2}@anchor{25e}@anchor{gnat_rm/intrinsic_subprograms intrinsic-operators}@anchor{25f}
17737 @section Intrinsic Operators
17740 @geindex Intrinsic operator
17742 All the predefined numeric operators in package Standard
17743 in @code{pragma Import (Intrinsic,..)}
17744 declarations. In the binary operator case, the operands must have the same
17745 size. The operand or operands must also be appropriate for
17746 the operator. For example, for addition, the operands must
17747 both be floating-point or both be fixed-point, and the
17748 right operand for @code{"**"} must have a root type of
17749 @code{Standard.Integer'Base}.
17750 You can use an intrinsic operator declaration as in the following example:
17753 type Int1 is new Integer;
17754 type Int2 is new Integer;
17756 function "+" (X1 : Int1; X2 : Int2) return Int1;
17757 function "+" (X1 : Int1; X2 : Int2) return Int2;
17758 pragma Import (Intrinsic, "+");
17761 This declaration would permit 'mixed mode' arithmetic on items
17762 of the differing types @code{Int1} and @code{Int2}.
17763 It is also possible to specify such operators for private types, if the
17764 full views are appropriate arithmetic types.
17766 @node Compilation_ISO_Date,Compilation_Date,Intrinsic Operators,Intrinsic Subprograms
17767 @anchor{gnat_rm/intrinsic_subprograms id3}@anchor{260}@anchor{gnat_rm/intrinsic_subprograms compilation-iso-date}@anchor{261}
17768 @section Compilation_ISO_Date
17771 @geindex Compilation_ISO_Date
17773 This intrinsic subprogram is used in the implementation of the
17774 library package @code{GNAT.Source_Info}. The only useful use of the
17775 intrinsic import in this case is the one in this unit, so an
17776 application program should simply call the function
17777 @code{GNAT.Source_Info.Compilation_ISO_Date} to obtain the date of
17778 the current compilation (in local time format YYYY-MM-DD).
17780 @node Compilation_Date,Compilation_Time,Compilation_ISO_Date,Intrinsic Subprograms
17781 @anchor{gnat_rm/intrinsic_subprograms compilation-date}@anchor{262}@anchor{gnat_rm/intrinsic_subprograms id4}@anchor{263}
17782 @section Compilation_Date
17785 @geindex Compilation_Date
17787 Same as Compilation_ISO_Date, except the string is in the form
17790 @node Compilation_Time,Enclosing_Entity,Compilation_Date,Intrinsic Subprograms
17791 @anchor{gnat_rm/intrinsic_subprograms compilation-time}@anchor{264}@anchor{gnat_rm/intrinsic_subprograms id5}@anchor{265}
17792 @section Compilation_Time
17795 @geindex Compilation_Time
17797 This intrinsic subprogram is used in the implementation of the
17798 library package @code{GNAT.Source_Info}. The only useful use of the
17799 intrinsic import in this case is the one in this unit, so an
17800 application program should simply call the function
17801 @code{GNAT.Source_Info.Compilation_Time} to obtain the time of
17802 the current compilation (in local time format HH:MM:SS).
17804 @node Enclosing_Entity,Exception_Information,Compilation_Time,Intrinsic Subprograms
17805 @anchor{gnat_rm/intrinsic_subprograms id6}@anchor{266}@anchor{gnat_rm/intrinsic_subprograms enclosing-entity}@anchor{267}
17806 @section Enclosing_Entity
17809 @geindex Enclosing_Entity
17811 This intrinsic subprogram is used in the implementation of the
17812 library package @code{GNAT.Source_Info}. The only useful use of the
17813 intrinsic import in this case is the one in this unit, so an
17814 application program should simply call the function
17815 @code{GNAT.Source_Info.Enclosing_Entity} to obtain the name of
17816 the current subprogram, package, task, entry, or protected subprogram.
17818 @node Exception_Information,Exception_Message,Enclosing_Entity,Intrinsic Subprograms
17819 @anchor{gnat_rm/intrinsic_subprograms id7}@anchor{268}@anchor{gnat_rm/intrinsic_subprograms exception-information}@anchor{269}
17820 @section Exception_Information
17823 @geindex Exception_Information'
17825 This intrinsic subprogram is used in the implementation of the
17826 library package @code{GNAT.Current_Exception}. The only useful
17827 use of the intrinsic import in this case is the one in this unit,
17828 so an application program should simply call the function
17829 @code{GNAT.Current_Exception.Exception_Information} to obtain
17830 the exception information associated with the current exception.
17832 @node Exception_Message,Exception_Name,Exception_Information,Intrinsic Subprograms
17833 @anchor{gnat_rm/intrinsic_subprograms exception-message}@anchor{26a}@anchor{gnat_rm/intrinsic_subprograms id8}@anchor{26b}
17834 @section Exception_Message
17837 @geindex Exception_Message
17839 This intrinsic subprogram is used in the implementation of the
17840 library package @code{GNAT.Current_Exception}. The only useful
17841 use of the intrinsic import in this case is the one in this unit,
17842 so an application program should simply call the function
17843 @code{GNAT.Current_Exception.Exception_Message} to obtain
17844 the message associated with the current exception.
17846 @node Exception_Name,File,Exception_Message,Intrinsic Subprograms
17847 @anchor{gnat_rm/intrinsic_subprograms exception-name}@anchor{26c}@anchor{gnat_rm/intrinsic_subprograms id9}@anchor{26d}
17848 @section Exception_Name
17851 @geindex Exception_Name
17853 This intrinsic subprogram is used in the implementation of the
17854 library package @code{GNAT.Current_Exception}. The only useful
17855 use of the intrinsic import in this case is the one in this unit,
17856 so an application program should simply call the function
17857 @code{GNAT.Current_Exception.Exception_Name} to obtain
17858 the name of the current exception.
17860 @node File,Line,Exception_Name,Intrinsic Subprograms
17861 @anchor{gnat_rm/intrinsic_subprograms id10}@anchor{26e}@anchor{gnat_rm/intrinsic_subprograms file}@anchor{26f}
17867 This intrinsic subprogram is used in the implementation of the
17868 library package @code{GNAT.Source_Info}. The only useful use of the
17869 intrinsic import in this case is the one in this unit, so an
17870 application program should simply call the function
17871 @code{GNAT.Source_Info.File} to obtain the name of the current
17874 @node Line,Shifts and Rotates,File,Intrinsic Subprograms
17875 @anchor{gnat_rm/intrinsic_subprograms id11}@anchor{270}@anchor{gnat_rm/intrinsic_subprograms line}@anchor{271}
17881 This intrinsic subprogram is used in the implementation of the
17882 library package @code{GNAT.Source_Info}. The only useful use of the
17883 intrinsic import in this case is the one in this unit, so an
17884 application program should simply call the function
17885 @code{GNAT.Source_Info.Line} to obtain the number of the current
17888 @node Shifts and Rotates,Source_Location,Line,Intrinsic Subprograms
17889 @anchor{gnat_rm/intrinsic_subprograms shifts-and-rotates}@anchor{272}@anchor{gnat_rm/intrinsic_subprograms id12}@anchor{273}
17890 @section Shifts and Rotates
17893 @geindex Shift_Left
17895 @geindex Shift_Right
17897 @geindex Shift_Right_Arithmetic
17899 @geindex Rotate_Left
17901 @geindex Rotate_Right
17903 In standard Ada, the shift and rotate functions are available only
17904 for the predefined modular types in package @code{Interfaces}. However, in
17905 GNAT it is possible to define these functions for any integer
17906 type (signed or modular), as in this example:
17909 function Shift_Left
17911 Amount : Natural) return T;
17914 The function name must be one of
17915 Shift_Left, Shift_Right, Shift_Right_Arithmetic, Rotate_Left, or
17916 Rotate_Right. T must be an integer type. T'Size must be
17917 8, 16, 32 or 64 bits; if T is modular, the modulus
17918 must be 2**8, 2**16, 2**32 or 2**64.
17919 The result type must be the same as the type of @code{Value}.
17920 The shift amount must be Natural.
17921 The formal parameter names can be anything.
17923 A more convenient way of providing these shift operators is to use
17924 the Provide_Shift_Operators pragma, which provides the function declarations
17925 and corresponding pragma Import's for all five shift functions. Note that in
17926 using these provided shift operations, shifts performed on negative numbers
17927 will result in modification of the sign bit.
17929 @node Source_Location,,Shifts and Rotates,Intrinsic Subprograms
17930 @anchor{gnat_rm/intrinsic_subprograms source-location}@anchor{274}@anchor{gnat_rm/intrinsic_subprograms id13}@anchor{275}
17931 @section Source_Location
17934 @geindex Source_Location
17936 This intrinsic subprogram is used in the implementation of the
17937 library routine @code{GNAT.Source_Info}. The only useful use of the
17938 intrinsic import in this case is the one in this unit, so an
17939 application program should simply call the function
17940 @code{GNAT.Source_Info.Source_Location} to obtain the current
17941 source file location.
17943 @node Representation Clauses and Pragmas,Standard Library Routines,Intrinsic Subprograms,Top
17944 @anchor{gnat_rm/representation_clauses_and_pragmas representation-clauses-and-pragmas}@anchor{d}@anchor{gnat_rm/representation_clauses_and_pragmas doc}@anchor{276}@anchor{gnat_rm/representation_clauses_and_pragmas id1}@anchor{277}
17945 @chapter Representation Clauses and Pragmas
17948 @geindex Representation Clauses
17950 @geindex Representation Clause
17952 @geindex Representation Pragma
17955 @geindex representation
17957 This section describes the representation clauses accepted by GNAT, and
17958 their effect on the representation of corresponding data objects.
17960 GNAT fully implements Annex C (Systems Programming). This means that all
17961 the implementation advice sections in chapter 13 are fully implemented.
17962 However, these sections only require a minimal level of support for
17963 representation clauses. GNAT provides much more extensive capabilities,
17964 and this section describes the additional capabilities provided.
17967 * Alignment Clauses::
17969 * Storage_Size Clauses::
17970 * Size of Variant Record Objects::
17971 * Biased Representation::
17972 * Value_Size and Object_Size Clauses::
17973 * Component_Size Clauses::
17974 * Bit_Order Clauses::
17975 * Effect of Bit_Order on Byte Ordering::
17976 * Pragma Pack for Arrays::
17977 * Pragma Pack for Records::
17978 * Record Representation Clauses::
17979 * Handling of Records with Holes::
17980 * Enumeration Clauses::
17981 * Address Clauses::
17982 * Use of Address Clauses for Memory-Mapped I/O::
17983 * Effect of Convention on Representation::
17984 * Conventions and Anonymous Access Types::
17985 * Determining the Representations chosen by GNAT::
17989 @node Alignment Clauses,Size Clauses,,Representation Clauses and Pragmas
17990 @anchor{gnat_rm/representation_clauses_and_pragmas id2}@anchor{278}@anchor{gnat_rm/representation_clauses_and_pragmas alignment-clauses}@anchor{279}
17991 @section Alignment Clauses
17994 @geindex Alignment Clause
17996 GNAT requires that all alignment clauses specify 0 or a power of 2, and
17997 all default alignments are always a power of 2. Specifying 0 is the
17998 same as specifying 1.
18000 The default alignment values are as follows:
18006 @emph{Elementary Types}.
18008 For elementary types, the alignment is the minimum of the actual size of
18009 objects of the type divided by @code{Storage_Unit},
18010 and the maximum alignment supported by the target.
18011 (This maximum alignment is given by the GNAT-specific attribute
18012 @code{Standard'Maximum_Alignment}; see @ref{190,,Attribute Maximum_Alignment}.)
18014 @geindex Maximum_Alignment attribute
18016 For example, for type @code{Long_Float}, the object size is 8 bytes, and the
18017 default alignment will be 8 on any target that supports alignments
18018 this large, but on some targets, the maximum alignment may be smaller
18019 than 8, in which case objects of type @code{Long_Float} will be maximally
18025 For arrays, the alignment is equal to the alignment of the component type
18026 for the normal case where no packing or component size is given. If the
18027 array is packed, and the packing is effective (see separate section on
18028 packed arrays), then the alignment will be either 4, 2, or 1 for long packed
18029 arrays or arrays whose length is not known at compile time, depending on
18030 whether the component size is divisible by 4, 2, or is odd. For short packed
18031 arrays, which are handled internally as modular types, the alignment
18032 will be as described for elementary types, e.g. a packed array of length
18033 31 bits will have an object size of four bytes, and an alignment of 4.
18038 For the normal unpacked case, the alignment of a record is equal to
18039 the maximum alignment of any of its components. For tagged records, this
18040 includes the implicit access type used for the tag. If a pragma @code{Pack}
18041 is used and all components are packable (see separate section on pragma
18042 @code{Pack}), then the resulting alignment is 1, unless the layout of the
18043 record makes it profitable to increase it.
18045 A special case is when:
18051 the size of the record is given explicitly, or a
18052 full record representation clause is given, and
18055 the size of the record is 2, 4, or 8 bytes.
18058 In this case, an alignment is chosen to match the
18059 size of the record. For example, if we have:
18062 type Small is record
18065 for Small'Size use 16;
18068 then the default alignment of the record type @code{Small} is 2, not 1. This
18069 leads to more efficient code when the record is treated as a unit, and also
18070 allows the type to specified as @code{Atomic} on architectures requiring
18074 An alignment clause may specify a larger alignment than the default value
18075 up to some maximum value dependent on the target (obtainable by using the
18076 attribute reference @code{Standard'Maximum_Alignment}). It may also specify
18077 a smaller alignment than the default value for enumeration, integer and
18078 fixed point types, as well as for record types, for example
18085 for V'alignment use 1;
18091 The default alignment for the type @code{V} is 4, as a result of the
18092 Integer field in the record, but it is permissible, as shown, to
18093 override the default alignment of the record with a smaller value.
18098 Note that according to the Ada standard, an alignment clause applies only
18099 to the first named subtype. If additional subtypes are declared, then the
18100 compiler is allowed to choose any alignment it likes, and there is no way
18101 to control this choice. Consider:
18104 type R is range 1 .. 10_000;
18105 for R'Alignment use 1;
18106 subtype RS is R range 1 .. 1000;
18109 The alignment clause specifies an alignment of 1 for the first named subtype
18110 @code{R} but this does not necessarily apply to @code{RS}. When writing
18111 portable Ada code, you should avoid writing code that explicitly or
18112 implicitly relies on the alignment of such subtypes.
18114 For the GNAT compiler, if an explicit alignment clause is given, this
18115 value is also used for any subsequent subtypes. So for GNAT, in the
18116 above example, you can count on the alignment of @code{RS} being 1. But this
18117 assumption is non-portable, and other compilers may choose different
18118 alignments for the subtype @code{RS}.
18120 @node Size Clauses,Storage_Size Clauses,Alignment Clauses,Representation Clauses and Pragmas
18121 @anchor{gnat_rm/representation_clauses_and_pragmas id3}@anchor{27a}@anchor{gnat_rm/representation_clauses_and_pragmas size-clauses}@anchor{27b}
18122 @section Size Clauses
18125 @geindex Size Clause
18127 The default size for a type @code{T} is obtainable through the
18128 language-defined attribute @code{T'Size} and also through the
18129 equivalent GNAT-defined attribute @code{T'Value_Size}.
18130 For objects of type @code{T}, GNAT will generally increase the type size
18131 so that the object size (obtainable through the GNAT-defined attribute
18132 @code{T'Object_Size})
18133 is a multiple of @code{T'Alignment * Storage_Unit}.
18138 type Smallint is range 1 .. 6;
18146 In this example, @code{Smallint'Size} = @code{Smallint'Value_Size} = 3,
18147 as specified by the RM rules,
18148 but objects of this type will have a size of 8
18149 (@code{Smallint'Object_Size} = 8),
18150 since objects by default occupy an integral number
18151 of storage units. On some targets, notably older
18152 versions of the Digital Alpha, the size of stand
18153 alone objects of this type may be 32, reflecting
18154 the inability of the hardware to do byte load/stores.
18156 Similarly, the size of type @code{Rec} is 40 bits
18157 (@code{Rec'Size} = @code{Rec'Value_Size} = 40), but
18158 the alignment is 4, so objects of this type will have
18159 their size increased to 64 bits so that it is a multiple
18160 of the alignment (in bits). This decision is
18161 in accordance with the specific Implementation Advice in RM 13.3(43):
18165 "A @code{Size} clause should be supported for an object if the specified
18166 @code{Size} is at least as large as its subtype's @code{Size}, and corresponds
18167 to a size in storage elements that is a multiple of the object's
18168 @code{Alignment} (if the @code{Alignment} is nonzero)."
18171 An explicit size clause may be used to override the default size by
18172 increasing it. For example, if we have:
18175 type My_Boolean is new Boolean;
18176 for My_Boolean'Size use 32;
18179 then values of this type will always be 32-bit long. In the case of discrete
18180 types, the size can be increased up to 64 bits on 32-bit targets and 128 bits
18181 on 64-bit targets, with the effect that the entire specified field is used to
18182 hold the value, sign- or zero-extended as appropriate. If more than 64 bits
18183 or 128 bits resp. is specified, then padding space is allocated after the
18184 value, and a warning is issued that there are unused bits.
18186 Similarly the size of records and arrays may be increased, and the effect
18187 is to add padding bits after the value. This also causes a warning message
18190 The largest Size value permitted in GNAT is 2**31-1. Since this is a
18191 Size in bits, this corresponds to an object of size 256 megabytes (minus
18192 one). This limitation is true on all targets. The reason for this
18193 limitation is that it improves the quality of the code in many cases
18194 if it is known that a Size value can be accommodated in an object of
18197 @node Storage_Size Clauses,Size of Variant Record Objects,Size Clauses,Representation Clauses and Pragmas
18198 @anchor{gnat_rm/representation_clauses_and_pragmas storage-size-clauses}@anchor{27c}@anchor{gnat_rm/representation_clauses_and_pragmas id4}@anchor{27d}
18199 @section Storage_Size Clauses
18202 @geindex Storage_Size Clause
18204 For tasks, the @code{Storage_Size} clause specifies the amount of space
18205 to be allocated for the task stack. This cannot be extended, and if the
18206 stack is exhausted, then @code{Storage_Error} will be raised (if stack
18207 checking is enabled). Use a @code{Storage_Size} attribute definition clause,
18208 or a @code{Storage_Size} pragma in the task definition to set the
18209 appropriate required size. A useful technique is to include in every
18210 task definition a pragma of the form:
18213 pragma Storage_Size (Default_Stack_Size);
18216 Then @code{Default_Stack_Size} can be defined in a global package, and
18217 modified as required. Any tasks requiring stack sizes different from the
18218 default can have an appropriate alternative reference in the pragma.
18220 You can also use the @emph{-d} binder switch to modify the default stack
18223 For access types, the @code{Storage_Size} clause specifies the maximum
18224 space available for allocation of objects of the type. If this space is
18225 exceeded then @code{Storage_Error} will be raised by an allocation attempt.
18226 In the case where the access type is declared local to a subprogram, the
18227 use of a @code{Storage_Size} clause triggers automatic use of a special
18228 predefined storage pool (@code{System.Pool_Size}) that ensures that all
18229 space for the pool is automatically reclaimed on exit from the scope in
18230 which the type is declared.
18232 A special case recognized by the compiler is the specification of a
18233 @code{Storage_Size} of zero for an access type. This means that no
18234 items can be allocated from the pool, and this is recognized at compile
18235 time, and all the overhead normally associated with maintaining a fixed
18236 size storage pool is eliminated. Consider the following example:
18240 type R is array (Natural) of Character;
18241 type P is access all R;
18242 for P'Storage_Size use 0;
18243 -- Above access type intended only for interfacing purposes
18247 procedure g (m : P);
18248 pragma Import (C, g);
18258 As indicated in this example, these dummy storage pools are often useful in
18259 connection with interfacing where no object will ever be allocated. If you
18260 compile the above example, you get the warning:
18263 p.adb:16:09: warning: allocation from empty storage pool
18264 p.adb:16:09: warning: Storage_Error will be raised at run time
18267 Of course in practice, there will not be any explicit allocators in the
18268 case of such an access declaration.
18270 @node Size of Variant Record Objects,Biased Representation,Storage_Size Clauses,Representation Clauses and Pragmas
18271 @anchor{gnat_rm/representation_clauses_and_pragmas id5}@anchor{27e}@anchor{gnat_rm/representation_clauses_and_pragmas size-of-variant-record-objects}@anchor{27f}
18272 @section Size of Variant Record Objects
18276 @geindex variant record objects
18278 @geindex Variant record objects
18281 In the case of variant record objects, there is a question whether Size gives
18282 information about a particular variant, or the maximum size required
18283 for any variant. Consider the following program
18286 with Text_IO; use Text_IO;
18288 type R1 (A : Boolean := False) is record
18290 when True => X : Character;
18291 when False => null;
18299 Put_Line (Integer'Image (V1'Size));
18300 Put_Line (Integer'Image (V2'Size));
18304 Here we are dealing with a variant record, where the True variant
18305 requires 16 bits, and the False variant requires 8 bits.
18306 In the above example, both V1 and V2 contain the False variant,
18307 which is only 8 bits long. However, the result of running the
18315 The reason for the difference here is that the discriminant value of
18316 V1 is fixed, and will always be False. It is not possible to assign
18317 a True variant value to V1, therefore 8 bits is sufficient. On the
18318 other hand, in the case of V2, the initial discriminant value is
18319 False (from the default), but it is possible to assign a True
18320 variant value to V2, therefore 16 bits must be allocated for V2
18321 in the general case, even fewer bits may be needed at any particular
18322 point during the program execution.
18324 As can be seen from the output of this program, the @code{'Size}
18325 attribute applied to such an object in GNAT gives the actual allocated
18326 size of the variable, which is the largest size of any of the variants.
18327 The Ada Reference Manual is not completely clear on what choice should
18328 be made here, but the GNAT behavior seems most consistent with the
18329 language in the RM.
18331 In some cases, it may be desirable to obtain the size of the current
18332 variant, rather than the size of the largest variant. This can be
18333 achieved in GNAT by making use of the fact that in the case of a
18334 subprogram parameter, GNAT does indeed return the size of the current
18335 variant (because a subprogram has no way of knowing how much space
18336 is actually allocated for the actual).
18338 Consider the following modified version of the above program:
18341 with Text_IO; use Text_IO;
18343 type R1 (A : Boolean := False) is record
18345 when True => X : Character;
18346 when False => null;
18352 function Size (V : R1) return Integer is
18358 Put_Line (Integer'Image (V2'Size));
18359 Put_Line (Integer'Image (Size (V2)));
18361 Put_Line (Integer'Image (V2'Size));
18362 Put_Line (Integer'Image (Size (V2)));
18366 The output from this program is
18375 Here we see that while the @code{'Size} attribute always returns
18376 the maximum size, regardless of the current variant value, the
18377 @code{Size} function does indeed return the size of the current
18380 @node Biased Representation,Value_Size and Object_Size Clauses,Size of Variant Record Objects,Representation Clauses and Pragmas
18381 @anchor{gnat_rm/representation_clauses_and_pragmas id6}@anchor{280}@anchor{gnat_rm/representation_clauses_and_pragmas biased-representation}@anchor{281}
18382 @section Biased Representation
18385 @geindex Size for biased representation
18387 @geindex Biased representation
18389 In the case of scalars with a range starting at other than zero, it is
18390 possible in some cases to specify a size smaller than the default minimum
18391 value, and in such cases, GNAT uses an unsigned biased representation,
18392 in which zero is used to represent the lower bound, and successive values
18393 represent successive values of the type.
18395 For example, suppose we have the declaration:
18398 type Small is range -7 .. -4;
18399 for Small'Size use 2;
18402 Although the default size of type @code{Small} is 4, the @code{Size}
18403 clause is accepted by GNAT and results in the following representation
18407 -7 is represented as 2#00#
18408 -6 is represented as 2#01#
18409 -5 is represented as 2#10#
18410 -4 is represented as 2#11#
18413 Biased representation is only used if the specified @code{Size} clause
18414 cannot be accepted in any other manner. These reduced sizes that force
18415 biased representation can be used for all discrete types except for
18416 enumeration types for which a representation clause is given.
18418 @node Value_Size and Object_Size Clauses,Component_Size Clauses,Biased Representation,Representation Clauses and Pragmas
18419 @anchor{gnat_rm/representation_clauses_and_pragmas id7}@anchor{282}@anchor{gnat_rm/representation_clauses_and_pragmas value-size-and-object-size-clauses}@anchor{283}
18420 @section Value_Size and Object_Size Clauses
18423 @geindex Value_Size
18425 @geindex Object_Size
18428 @geindex of objects
18430 In Ada 95 and Ada 2005, @code{T'Size} for a type @code{T} is the minimum
18431 number of bits required to hold values of type @code{T}.
18432 Although this interpretation was allowed in Ada 83, it was not required,
18433 and this requirement in practice can cause some significant difficulties.
18434 For example, in most Ada 83 compilers, @code{Natural'Size} was 32.
18435 However, in Ada 95 and Ada 2005,
18436 @code{Natural'Size} is
18437 typically 31. This means that code may change in behavior when moving
18438 from Ada 83 to Ada 95 or Ada 2005. For example, consider:
18441 type Rec is record;
18447 at 0 range 0 .. Natural'Size - 1;
18448 at 0 range Natural'Size .. 2 * Natural'Size - 1;
18452 In the above code, since the typical size of @code{Natural} objects
18453 is 32 bits and @code{Natural'Size} is 31, the above code can cause
18454 unexpected inefficient packing in Ada 95 and Ada 2005, and in general
18455 there are cases where the fact that the object size can exceed the
18456 size of the type causes surprises.
18458 To help get around this problem GNAT provides two implementation
18459 defined attributes, @code{Value_Size} and @code{Object_Size}. When
18460 applied to a type, these attributes yield the size of the type
18461 (corresponding to the RM defined size attribute), and the size of
18462 objects of the type respectively.
18464 The @code{Object_Size} is used for determining the default size of
18465 objects and components. This size value can be referred to using the
18466 @code{Object_Size} attribute. The phrase 'is used' here means that it is
18467 the basis of the determination of the size. The backend is free to
18468 pad this up if necessary for efficiency, e.g., an 8-bit stand-alone
18469 character might be stored in 32 bits on a machine with no efficient
18470 byte access instructions such as the Alpha.
18472 The default rules for the value of @code{Object_Size} for
18473 discrete types are as follows:
18479 The @code{Object_Size} for base subtypes reflect the natural hardware
18480 size in bits (run the compiler with @emph{-gnatS} to find those values
18481 for numeric types). Enumeration types and fixed-point base subtypes have
18482 8, 16, 32, or 64 bits for this size, depending on the range of values
18486 The @code{Object_Size} of a subtype is the same as the
18487 @code{Object_Size} of
18488 the type from which it is obtained.
18491 The @code{Object_Size} of a derived base type is copied from the parent
18492 base type, and the @code{Object_Size} of a derived first subtype is copied
18493 from the parent first subtype.
18496 The @code{Value_Size} attribute
18497 is the (minimum) number of bits required to store a value
18499 This value is used to determine how tightly to pack
18500 records or arrays with components of this type, and also affects
18501 the semantics of unchecked conversion (unchecked conversions where
18502 the @code{Value_Size} values differ generate a warning, and are potentially
18505 The default rules for the value of @code{Value_Size} are as follows:
18511 The @code{Value_Size} for a base subtype is the minimum number of bits
18512 required to store all values of the type (including the sign bit
18513 only if negative values are possible).
18516 If a subtype statically matches the first subtype of a given type, then it has
18517 by default the same @code{Value_Size} as the first subtype. This is a
18518 consequence of RM 13.1(14): "if two subtypes statically match,
18519 then their subtype-specific aspects are the same".)
18522 All other subtypes have a @code{Value_Size} corresponding to the minimum
18523 number of bits required to store all values of the subtype. For
18524 dynamic bounds, it is assumed that the value can range down or up
18525 to the corresponding bound of the ancestor
18528 The RM defined attribute @code{Size} corresponds to the
18529 @code{Value_Size} attribute.
18531 The @code{Size} attribute may be defined for a first-named subtype. This sets
18532 the @code{Value_Size} of
18533 the first-named subtype to the given value, and the
18534 @code{Object_Size} of this first-named subtype to the given value padded up
18535 to an appropriate boundary. It is a consequence of the default rules
18536 above that this @code{Object_Size} will apply to all further subtypes. On the
18537 other hand, @code{Value_Size} is affected only for the first subtype, any
18538 dynamic subtypes obtained from it directly, and any statically matching
18539 subtypes. The @code{Value_Size} of any other static subtypes is not affected.
18541 @code{Value_Size} and
18542 @code{Object_Size} may be explicitly set for any subtype using
18543 an attribute definition clause. Note that the use of these attributes
18544 can cause the RM 13.1(14) rule to be violated. If two access types
18545 reference aliased objects whose subtypes have differing @code{Object_Size}
18546 values as a result of explicit attribute definition clauses, then it
18547 is illegal to convert from one access subtype to the other. For a more
18548 complete description of this additional legality rule, see the
18549 description of the @code{Object_Size} attribute.
18551 To get a feel for the difference, consider the following examples (note
18552 that in each case the base is @code{Short_Short_Integer} with a size of 8):
18555 @multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxx}
18558 Type or subtype declaration
18570 @code{type x1 is range 0 .. 5;}
18582 @code{type x2 is range 0 .. 5;}
18583 @code{for x2'size use 12;}
18595 @code{subtype x3 is x2 range 0 .. 3;}
18607 @code{subtype x4 is x2'base range 0 .. 10;}
18619 @code{dynamic : x2'Base range -64 .. +63;}
18627 @code{subtype x5 is x2 range 0 .. dynamic;}
18639 @code{subtype x6 is x2'base range 0 .. dynamic;}
18652 Note: the entries marked '*' are not actually specified by the Ada
18653 Reference Manual, which has nothing to say about size in the dynamic
18654 case. What GNAT does is to allocate sufficient bits to accommodate any
18655 possible dynamic values for the bounds at run-time.
18657 So far, so good, but GNAT has to obey the RM rules, so the question is
18658 under what conditions must the RM @code{Size} be used.
18659 The following is a list
18660 of the occasions on which the RM @code{Size} must be used:
18666 Component size for packed arrays or records
18669 Value of the attribute @code{Size} for a type
18672 Warning about sizes not matching for unchecked conversion
18675 For record types, the @code{Object_Size} is always a multiple of the
18676 alignment of the type (this is true for all types). In some cases the
18677 @code{Value_Size} can be smaller. Consider:
18686 On a typical 32-bit architecture, the X component will occupy four bytes
18687 and the Y component will occupy one byte, for a total of 5 bytes. As a
18688 result @code{R'Value_Size} will be 40 (bits) since this is the minimum size
18689 required to store a value of this type. For example, it is permissible
18690 to have a component of type R in an array whose component size is
18691 specified to be 40 bits.
18693 However, @code{R'Object_Size} will be 64 (bits). The difference is due to
18694 the alignment requirement for objects of the record type. The X
18695 component will require four-byte alignment because that is what type
18696 Integer requires, whereas the Y component, a Character, will only
18697 require 1-byte alignment. Since the alignment required for X is the
18698 greatest of all the components' alignments, that is the alignment
18699 required for the enclosing record type, i.e., 4 bytes or 32 bits. As
18700 indicated above, the actual object size must be rounded up so that it is
18701 a multiple of the alignment value. Therefore, 40 bits rounded up to the
18702 next multiple of 32 yields 64 bits.
18704 For all other types, the @code{Object_Size}
18705 and @code{Value_Size} are the same (and equivalent to the RM attribute @code{Size}).
18706 Only @code{Size} may be specified for such types.
18708 Note that @code{Value_Size} can be used to force biased representation
18709 for a particular subtype. Consider this example:
18712 type R is (A, B, C, D, E, F);
18713 subtype RAB is R range A .. B;
18714 subtype REF is R range E .. F;
18717 By default, @code{RAB}
18718 has a size of 1 (sufficient to accommodate the representation
18719 of @code{A} and @code{B}, 0 and 1), and @code{REF}
18720 has a size of 3 (sufficient to accommodate the representation
18721 of @code{E} and @code{F}, 4 and 5). But if we add the
18722 following @code{Value_Size} attribute definition clause:
18725 for REF'Value_Size use 1;
18728 then biased representation is forced for @code{REF},
18729 and 0 will represent @code{E} and 1 will represent @code{F}.
18730 A warning is issued when a @code{Value_Size} attribute
18731 definition clause forces biased representation. This
18732 warning can be turned off using @code{-gnatw.B}.
18734 @node Component_Size Clauses,Bit_Order Clauses,Value_Size and Object_Size Clauses,Representation Clauses and Pragmas
18735 @anchor{gnat_rm/representation_clauses_and_pragmas id8}@anchor{284}@anchor{gnat_rm/representation_clauses_and_pragmas component-size-clauses}@anchor{285}
18736 @section Component_Size Clauses
18739 @geindex Component_Size Clause
18741 Normally, the value specified in a component size clause must be consistent
18742 with the subtype of the array component with regard to size and alignment.
18743 In other words, the value specified must be at least equal to the size
18744 of this subtype, and must be a multiple of the alignment value.
18746 In addition, component size clauses are allowed which cause the array
18747 to be packed, by specifying a smaller value. A first case is for
18748 component size values in the range 1 through 63 on 32-bit targets,
18749 and 1 through 127 on 64-bit targets. The value specified may not
18750 be smaller than the Size of the subtype. GNAT will accurately
18751 honor all packing requests in this range. For example, if we have:
18754 type r is array (1 .. 8) of Natural;
18755 for r'Component_Size use 31;
18758 then the resulting array has a length of 31 bytes (248 bits = 8 * 31).
18759 Of course access to the components of such an array is considerably
18760 less efficient than if the natural component size of 32 is used.
18761 A second case is when the subtype of the component is a record type
18762 padded because of its default alignment. For example, if we have:
18771 type a is array (1 .. 8) of r;
18772 for a'Component_Size use 72;
18775 then the resulting array has a length of 72 bytes, instead of 96 bytes
18776 if the alignment of the record (4) was obeyed.
18778 Note that there is no point in giving both a component size clause
18779 and a pragma Pack for the same array type. if such duplicate
18780 clauses are given, the pragma Pack will be ignored.
18782 @node Bit_Order Clauses,Effect of Bit_Order on Byte Ordering,Component_Size Clauses,Representation Clauses and Pragmas
18783 @anchor{gnat_rm/representation_clauses_and_pragmas bit-order-clauses}@anchor{286}@anchor{gnat_rm/representation_clauses_and_pragmas id9}@anchor{287}
18784 @section Bit_Order Clauses
18787 @geindex Bit_Order Clause
18789 @geindex bit ordering
18794 For record subtypes, GNAT permits the specification of the @code{Bit_Order}
18795 attribute. The specification may either correspond to the default bit
18796 order for the target, in which case the specification has no effect and
18797 places no additional restrictions, or it may be for the non-standard
18798 setting (that is the opposite of the default).
18800 In the case where the non-standard value is specified, the effect is
18801 to renumber bits within each byte, but the ordering of bytes is not
18802 affected. There are certain
18803 restrictions placed on component clauses as follows:
18809 Components fitting within a single storage unit.
18811 These are unrestricted, and the effect is merely to renumber bits. For
18812 example if we are on a little-endian machine with @code{Low_Order_First}
18813 being the default, then the following two declarations have exactly
18819 B : Integer range 1 .. 120;
18823 A at 0 range 0 .. 0;
18824 B at 0 range 1 .. 7;
18829 B : Integer range 1 .. 120;
18832 for R2'Bit_Order use High_Order_First;
18835 A at 0 range 7 .. 7;
18836 B at 0 range 0 .. 6;
18840 The useful application here is to write the second declaration with the
18841 @code{Bit_Order} attribute definition clause, and know that it will be treated
18842 the same, regardless of whether the target is little-endian or big-endian.
18845 Components occupying an integral number of bytes.
18847 These are components that exactly fit in two or more bytes. Such component
18848 declarations are allowed, but have no effect, since it is important to realize
18849 that the @code{Bit_Order} specification does not affect the ordering of bytes.
18850 In particular, the following attempt at getting an endian-independent integer
18858 for R2'Bit_Order use High_Order_First;
18861 A at 0 range 0 .. 31;
18865 This declaration will result in a little-endian integer on a
18866 little-endian machine, and a big-endian integer on a big-endian machine.
18867 If byte flipping is required for interoperability between big- and
18868 little-endian machines, this must be explicitly programmed. This capability
18869 is not provided by @code{Bit_Order}.
18872 Components that are positioned across byte boundaries.
18874 but do not occupy an integral number of bytes. Given that bytes are not
18875 reordered, such fields would occupy a non-contiguous sequence of bits
18876 in memory, requiring non-trivial code to reassemble. They are for this
18877 reason not permitted, and any component clause specifying such a layout
18878 will be flagged as illegal by GNAT.
18881 Since the misconception that Bit_Order automatically deals with all
18882 endian-related incompatibilities is a common one, the specification of
18883 a component field that is an integral number of bytes will always
18884 generate a warning. This warning may be suppressed using @code{pragma Warnings (Off)}
18885 if desired. The following section contains additional
18886 details regarding the issue of byte ordering.
18888 @node Effect of Bit_Order on Byte Ordering,Pragma Pack for Arrays,Bit_Order Clauses,Representation Clauses and Pragmas
18889 @anchor{gnat_rm/representation_clauses_and_pragmas id10}@anchor{288}@anchor{gnat_rm/representation_clauses_and_pragmas effect-of-bit-order-on-byte-ordering}@anchor{289}
18890 @section Effect of Bit_Order on Byte Ordering
18893 @geindex byte ordering
18898 In this section we will review the effect of the @code{Bit_Order} attribute
18899 definition clause on byte ordering. Briefly, it has no effect at all, but
18900 a detailed example will be helpful. Before giving this
18901 example, let us review the precise
18902 definition of the effect of defining @code{Bit_Order}. The effect of a
18903 non-standard bit order is described in section 13.5.3 of the Ada
18908 "2 A bit ordering is a method of interpreting the meaning of
18909 the storage place attributes."
18912 To understand the precise definition of storage place attributes in
18913 this context, we visit section 13.5.1 of the manual:
18917 "13 A record_representation_clause (without the mod_clause)
18918 specifies the layout. The storage place attributes (see 13.5.2)
18919 are taken from the values of the position, first_bit, and last_bit
18920 expressions after normalizing those values so that first_bit is
18921 less than Storage_Unit."
18924 The critical point here is that storage places are taken from
18925 the values after normalization, not before. So the @code{Bit_Order}
18926 interpretation applies to normalized values. The interpretation
18927 is described in the later part of the 13.5.3 paragraph:
18931 "2 A bit ordering is a method of interpreting the meaning of
18932 the storage place attributes. High_Order_First (known in the
18933 vernacular as 'big endian') means that the first bit of a
18934 storage element (bit 0) is the most significant bit (interpreting
18935 the sequence of bits that represent a component as an unsigned
18936 integer value). Low_Order_First (known in the vernacular as
18937 'little endian') means the opposite: the first bit is the
18938 least significant."
18941 Note that the numbering is with respect to the bits of a storage
18942 unit. In other words, the specification affects only the numbering
18943 of bits within a single storage unit.
18945 We can make the effect clearer by giving an example.
18947 Suppose that we have an external device which presents two bytes, the first
18948 byte presented, which is the first (low addressed byte) of the two byte
18949 record is called Master, and the second byte is called Slave.
18951 The left most (most significant bit is called Control for each byte, and
18952 the remaining 7 bits are called V1, V2, ... V7, where V7 is the rightmost
18953 (least significant) bit.
18955 On a big-endian machine, we can write the following representation clause
18958 type Data is record
18959 Master_Control : Bit;
18967 Slave_Control : Bit;
18977 for Data use record
18978 Master_Control at 0 range 0 .. 0;
18979 Master_V1 at 0 range 1 .. 1;
18980 Master_V2 at 0 range 2 .. 2;
18981 Master_V3 at 0 range 3 .. 3;
18982 Master_V4 at 0 range 4 .. 4;
18983 Master_V5 at 0 range 5 .. 5;
18984 Master_V6 at 0 range 6 .. 6;
18985 Master_V7 at 0 range 7 .. 7;
18986 Slave_Control at 1 range 0 .. 0;
18987 Slave_V1 at 1 range 1 .. 1;
18988 Slave_V2 at 1 range 2 .. 2;
18989 Slave_V3 at 1 range 3 .. 3;
18990 Slave_V4 at 1 range 4 .. 4;
18991 Slave_V5 at 1 range 5 .. 5;
18992 Slave_V6 at 1 range 6 .. 6;
18993 Slave_V7 at 1 range 7 .. 7;
18997 Now if we move this to a little endian machine, then the bit ordering within
18998 the byte is backwards, so we have to rewrite the record rep clause as:
19001 for Data use record
19002 Master_Control at 0 range 7 .. 7;
19003 Master_V1 at 0 range 6 .. 6;
19004 Master_V2 at 0 range 5 .. 5;
19005 Master_V3 at 0 range 4 .. 4;
19006 Master_V4 at 0 range 3 .. 3;
19007 Master_V5 at 0 range 2 .. 2;
19008 Master_V6 at 0 range 1 .. 1;
19009 Master_V7 at 0 range 0 .. 0;
19010 Slave_Control at 1 range 7 .. 7;
19011 Slave_V1 at 1 range 6 .. 6;
19012 Slave_V2 at 1 range 5 .. 5;
19013 Slave_V3 at 1 range 4 .. 4;
19014 Slave_V4 at 1 range 3 .. 3;
19015 Slave_V5 at 1 range 2 .. 2;
19016 Slave_V6 at 1 range 1 .. 1;
19017 Slave_V7 at 1 range 0 .. 0;
19021 It is a nuisance to have to rewrite the clause, especially if
19022 the code has to be maintained on both machines. However,
19023 this is a case that we can handle with the
19024 @code{Bit_Order} attribute if it is implemented.
19025 Note that the implementation is not required on byte addressed
19026 machines, but it is indeed implemented in GNAT.
19027 This means that we can simply use the
19028 first record clause, together with the declaration
19031 for Data'Bit_Order use High_Order_First;
19034 and the effect is what is desired, namely the layout is exactly the same,
19035 independent of whether the code is compiled on a big-endian or little-endian
19038 The important point to understand is that byte ordering is not affected.
19039 A @code{Bit_Order} attribute definition never affects which byte a field
19040 ends up in, only where it ends up in that byte.
19041 To make this clear, let us rewrite the record rep clause of the previous
19045 for Data'Bit_Order use High_Order_First;
19046 for Data use record
19047 Master_Control at 0 range 0 .. 0;
19048 Master_V1 at 0 range 1 .. 1;
19049 Master_V2 at 0 range 2 .. 2;
19050 Master_V3 at 0 range 3 .. 3;
19051 Master_V4 at 0 range 4 .. 4;
19052 Master_V5 at 0 range 5 .. 5;
19053 Master_V6 at 0 range 6 .. 6;
19054 Master_V7 at 0 range 7 .. 7;
19055 Slave_Control at 0 range 8 .. 8;
19056 Slave_V1 at 0 range 9 .. 9;
19057 Slave_V2 at 0 range 10 .. 10;
19058 Slave_V3 at 0 range 11 .. 11;
19059 Slave_V4 at 0 range 12 .. 12;
19060 Slave_V5 at 0 range 13 .. 13;
19061 Slave_V6 at 0 range 14 .. 14;
19062 Slave_V7 at 0 range 15 .. 15;
19066 This is exactly equivalent to saying (a repeat of the first example):
19069 for Data'Bit_Order use High_Order_First;
19070 for Data use record
19071 Master_Control at 0 range 0 .. 0;
19072 Master_V1 at 0 range 1 .. 1;
19073 Master_V2 at 0 range 2 .. 2;
19074 Master_V3 at 0 range 3 .. 3;
19075 Master_V4 at 0 range 4 .. 4;
19076 Master_V5 at 0 range 5 .. 5;
19077 Master_V6 at 0 range 6 .. 6;
19078 Master_V7 at 0 range 7 .. 7;
19079 Slave_Control at 1 range 0 .. 0;
19080 Slave_V1 at 1 range 1 .. 1;
19081 Slave_V2 at 1 range 2 .. 2;
19082 Slave_V3 at 1 range 3 .. 3;
19083 Slave_V4 at 1 range 4 .. 4;
19084 Slave_V5 at 1 range 5 .. 5;
19085 Slave_V6 at 1 range 6 .. 6;
19086 Slave_V7 at 1 range 7 .. 7;
19090 Why are they equivalent? Well take a specific field, the @code{Slave_V2}
19091 field. The storage place attributes are obtained by normalizing the
19092 values given so that the @code{First_Bit} value is less than 8. After
19093 normalizing the values (0,10,10) we get (1,2,2) which is exactly what
19094 we specified in the other case.
19096 Now one might expect that the @code{Bit_Order} attribute might affect
19097 bit numbering within the entire record component (two bytes in this
19098 case, thus affecting which byte fields end up in), but that is not
19099 the way this feature is defined, it only affects numbering of bits,
19100 not which byte they end up in.
19102 Consequently it never makes sense to specify a starting bit number
19103 greater than 7 (for a byte addressable field) if an attribute
19104 definition for @code{Bit_Order} has been given, and indeed it
19105 may be actively confusing to specify such a value, so the compiler
19106 generates a warning for such usage.
19108 If you do need to control byte ordering then appropriate conditional
19109 values must be used. If in our example, the slave byte came first on
19110 some machines we might write:
19113 Master_Byte_First constant Boolean := ...;
19115 Master_Byte : constant Natural :=
19116 1 - Boolean'Pos (Master_Byte_First);
19117 Slave_Byte : constant Natural :=
19118 Boolean'Pos (Master_Byte_First);
19120 for Data'Bit_Order use High_Order_First;
19121 for Data use record
19122 Master_Control at Master_Byte range 0 .. 0;
19123 Master_V1 at Master_Byte range 1 .. 1;
19124 Master_V2 at Master_Byte range 2 .. 2;
19125 Master_V3 at Master_Byte range 3 .. 3;
19126 Master_V4 at Master_Byte range 4 .. 4;
19127 Master_V5 at Master_Byte range 5 .. 5;
19128 Master_V6 at Master_Byte range 6 .. 6;
19129 Master_V7 at Master_Byte range 7 .. 7;
19130 Slave_Control at Slave_Byte range 0 .. 0;
19131 Slave_V1 at Slave_Byte range 1 .. 1;
19132 Slave_V2 at Slave_Byte range 2 .. 2;
19133 Slave_V3 at Slave_Byte range 3 .. 3;
19134 Slave_V4 at Slave_Byte range 4 .. 4;
19135 Slave_V5 at Slave_Byte range 5 .. 5;
19136 Slave_V6 at Slave_Byte range 6 .. 6;
19137 Slave_V7 at Slave_Byte range 7 .. 7;
19141 Now to switch between machines, all that is necessary is
19142 to set the boolean constant @code{Master_Byte_First} in
19143 an appropriate manner.
19145 @node Pragma Pack for Arrays,Pragma Pack for Records,Effect of Bit_Order on Byte Ordering,Representation Clauses and Pragmas
19146 @anchor{gnat_rm/representation_clauses_and_pragmas pragma-pack-for-arrays}@anchor{28a}@anchor{gnat_rm/representation_clauses_and_pragmas id11}@anchor{28b}
19147 @section Pragma Pack for Arrays
19150 @geindex Pragma Pack (for arrays)
19152 Pragma @code{Pack} applied to an array has an effect that depends upon whether the
19153 component type is @emph{packable}. For a component type to be @emph{packable}, it must
19154 be one of the following cases:
19160 Any elementary type.
19163 Any small packed array type with a static size.
19166 Any small simple record type with a static size.
19169 For all these cases, if the component subtype size is in the range
19170 1 through 63 on 32-bit targets, and 1 through 127 on 64-bit targets,
19171 then the effect of the pragma @code{Pack} is exactly as though a
19172 component size were specified giving the component subtype size.
19174 All other types are non-packable, they occupy an integral number of storage
19175 units and the only effect of pragma Pack is to remove alignment gaps.
19177 For example if we have:
19180 type r is range 0 .. 17;
19182 type ar is array (1 .. 8) of r;
19186 Then the component size of @code{ar} will be set to 5 (i.e., to @code{r'size},
19187 and the size of the array @code{ar} will be exactly 40 bits).
19189 Note that in some cases this rather fierce approach to packing can produce
19190 unexpected effects. For example, in Ada 95 and Ada 2005,
19191 subtype @code{Natural} typically has a size of 31, meaning that if you
19192 pack an array of @code{Natural}, you get 31-bit
19193 close packing, which saves a few bits, but results in far less efficient
19194 access. Since many other Ada compilers will ignore such a packing request,
19195 GNAT will generate a warning on some uses of pragma @code{Pack} that it guesses
19196 might not be what is intended. You can easily remove this warning by
19197 using an explicit @code{Component_Size} setting instead, which never generates
19198 a warning, since the intention of the programmer is clear in this case.
19200 GNAT treats packed arrays in one of two ways. If the size of the array is
19201 known at compile time and is at most 64 bits on 32-bit targets, and at most
19202 128 bits on 64-bit targets, then internally the array is represented as a
19203 single modular type, of exactly the appropriate number of bits. If the
19204 length is greater than 64 bits on 32-bit targets, and greater than 128
19205 bits on 64-bit targets, or is not known at compile time, then the packed
19206 array is represented as an array of bytes, and its length is always a
19207 multiple of 8 bits.
19209 Note that to represent a packed array as a modular type, the alignment must
19210 be suitable for the modular type involved. For example, on typical machines
19211 a 32-bit packed array will be represented by a 32-bit modular integer with
19212 an alignment of four bytes. If you explicitly override the default alignment
19213 with an alignment clause that is too small, the modular representation
19214 cannot be used. For example, consider the following set of declarations:
19217 type R is range 1 .. 3;
19218 type S is array (1 .. 31) of R;
19219 for S'Component_Size use 2;
19221 for S'Alignment use 1;
19224 If the alignment clause were not present, then a 62-bit modular
19225 representation would be chosen (typically with an alignment of 4 or 8
19226 bytes depending on the target). But the default alignment is overridden
19227 with the explicit alignment clause. This means that the modular
19228 representation cannot be used, and instead the array of bytes
19229 representation must be used, meaning that the length must be a multiple
19230 of 8. Thus the above set of declarations will result in a diagnostic
19231 rejecting the size clause and noting that the minimum size allowed is 64.
19233 @geindex Pragma Pack (for type Natural)
19235 @geindex Pragma Pack warning
19237 One special case that is worth noting occurs when the base type of the
19238 component size is 8/16/32 and the subtype is one bit less. Notably this
19239 occurs with subtype @code{Natural}. Consider:
19242 type Arr is array (1 .. 32) of Natural;
19246 In all commonly used Ada 83 compilers, this pragma Pack would be ignored,
19247 since typically @code{Natural'Size} is 32 in Ada 83, and in any case most
19248 Ada 83 compilers did not attempt 31 bit packing.
19250 In Ada 95 and Ada 2005, @code{Natural'Size} is required to be 31. Furthermore,
19251 GNAT really does pack 31-bit subtype to 31 bits. This may result in a
19252 substantial unintended performance penalty when porting legacy Ada 83 code.
19253 To help prevent this, GNAT generates a warning in such cases. If you really
19254 want 31 bit packing in a case like this, you can set the component size
19258 type Arr is array (1 .. 32) of Natural;
19259 for Arr'Component_Size use 31;
19262 Here 31-bit packing is achieved as required, and no warning is generated,
19263 since in this case the programmer intention is clear.
19265 @node Pragma Pack for Records,Record Representation Clauses,Pragma Pack for Arrays,Representation Clauses and Pragmas
19266 @anchor{gnat_rm/representation_clauses_and_pragmas pragma-pack-for-records}@anchor{28c}@anchor{gnat_rm/representation_clauses_and_pragmas id12}@anchor{28d}
19267 @section Pragma Pack for Records
19270 @geindex Pragma Pack (for records)
19272 Pragma @code{Pack} applied to a record will pack the components to reduce
19273 wasted space from alignment gaps and by reducing the amount of space
19274 taken by components. We distinguish between @emph{packable} components and
19275 @emph{non-packable} components.
19276 Components of the following types are considered packable:
19282 Components of an elementary type are packable unless they are aliased,
19283 independent or atomic.
19286 Small packed arrays, where the size is statically known, are represented
19287 internally as modular integers, and so they are also packable.
19290 Small simple records, where the size is statically known, are also packable.
19293 For all these cases, if the @code{'Size} value is in the range 1 through 64 on
19294 32-bit targets, and 1 through 128 on 64-bit targets, the components occupy
19295 the exact number of bits corresponding to this value and are packed with no
19296 padding bits, i.e. they can start on an arbitrary bit boundary.
19298 All other types are non-packable, they occupy an integral number of storage
19299 units and the only effect of pragma @code{Pack} is to remove alignment gaps.
19301 For example, consider the record
19304 type Rb1 is array (1 .. 13) of Boolean;
19307 type Rb2 is array (1 .. 65) of Boolean;
19310 type AF is new Float with Atomic;
19323 The representation for the record @code{X2} is as follows on 32-bit targets:
19326 for X2'Size use 224;
19328 L1 at 0 range 0 .. 0;
19329 L2 at 0 range 1 .. 64;
19330 L3 at 12 range 0 .. 31;
19331 L4 at 16 range 0 .. 0;
19332 L5 at 16 range 1 .. 13;
19333 L6 at 18 range 0 .. 71;
19337 Studying this example, we see that the packable fields @code{L1}
19338 and @code{L2} are of length equal to their sizes, and placed at
19339 specific bit boundaries (and not byte boundaries) to eliminate
19340 padding. But @code{L3} is of a non-packable float type (because
19341 it is aliased), so it is on the next appropriate alignment boundary.
19343 The next two fields are fully packable, so @code{L4} and @code{L5} are
19344 minimally packed with no gaps. However, type @code{Rb2} is a packed
19345 array that is longer than 64 bits, so it is itself non-packable on
19346 32-bit targets. Thus the @code{L6} field is aligned to the next byte
19347 boundary, and takes an integral number of bytes, i.e., 72 bits.
19349 @node Record Representation Clauses,Handling of Records with Holes,Pragma Pack for Records,Representation Clauses and Pragmas
19350 @anchor{gnat_rm/representation_clauses_and_pragmas id13}@anchor{28e}@anchor{gnat_rm/representation_clauses_and_pragmas record-representation-clauses}@anchor{28f}
19351 @section Record Representation Clauses
19354 @geindex Record Representation Clause
19356 Record representation clauses may be given for all record types, including
19357 types obtained by record extension. Component clauses are allowed for any
19358 static component. The restrictions on component clauses depend on the type
19361 @geindex Component Clause
19363 For all components of an elementary type, the only restriction on component
19364 clauses is that the size must be at least the @code{'Size} value of the type
19365 (actually the Value_Size). There are no restrictions due to alignment,
19366 and such components may freely cross storage boundaries.
19368 Packed arrays with a size up to and including 64 bits on 32-bit targets,
19369 and up to and including 128 bits on 64-bit targets, are represented
19370 internally using a modular type with the appropriate number of bits, and
19371 thus the same lack of restriction applies. For example, if you declare:
19374 type R is array (1 .. 49) of Boolean;
19379 then a component clause for a component of type @code{R} may start on any
19380 specified bit boundary, and may specify a value of 49 bits or greater.
19382 For packed bit arrays that are longer than 64 bits on 32-bit targets,
19383 and longer than 128 bits on 64-bit targets, there are two cases. If the
19384 component size is a power of 2 (1,2,4,8,16,32,64 bits), including the
19385 important case of single bits or boolean values, then there are no
19386 limitations on placement of such components, and they may start and
19387 end at arbitrary bit boundaries.
19389 If the component size is not a power of 2 (e.g., 3 or 5), then an array
19390 of this type must always be placed on on a storage unit (byte) boundary
19391 and occupy an integral number of storage units (bytes). Any component
19392 clause that does not meet this requirement will be rejected.
19394 Any aliased component, or component of an aliased type, must have its
19395 normal alignment and size. A component clause that does not meet this
19396 requirement will be rejected.
19398 The tag field of a tagged type always occupies an address sized field at
19399 the start of the record. No component clause may attempt to overlay this
19400 tag. When a tagged type appears as a component, the tag field must have
19403 In the case of a record extension @code{T1}, of a type @code{T}, no component
19404 clause applied to the type @code{T1} can specify a storage location that
19405 would overlap the first @code{T'Object_Size} bits of the record.
19407 For all other component types, including non-bit-packed arrays,
19408 the component can be placed at an arbitrary bit boundary,
19409 so for example, the following is permitted:
19412 type R is array (1 .. 10) of Boolean;
19421 G at 0 range 0 .. 0;
19422 H at 0 range 1 .. 1;
19423 L at 0 range 2 .. 81;
19424 R at 0 range 82 .. 161;
19428 @node Handling of Records with Holes,Enumeration Clauses,Record Representation Clauses,Representation Clauses and Pragmas
19429 @anchor{gnat_rm/representation_clauses_and_pragmas handling-of-records-with-holes}@anchor{290}@anchor{gnat_rm/representation_clauses_and_pragmas id14}@anchor{291}
19430 @section Handling of Records with Holes
19433 @geindex Handling of Records with Holes
19435 As a result of alignment considerations, records may contain "holes"
19436 or gaps which do not correspond to the data bits of any of the components.
19437 Record representation clauses can also result in holes in records.
19439 GNAT does not attempt to clear these holes, so in record objects,
19440 they should be considered to hold undefined rubbish. The generated
19441 equality routine just tests components so does not access these
19442 undefined bits, and assignment and copy operations may or may not
19443 preserve the contents of these holes (for assignments, the holes
19444 in the target will in practice contain either the bits that are
19445 present in the holes in the source, or the bits that were present
19446 in the target before the assignment).
19448 If it is necessary to ensure that holes in records have all zero
19449 bits, then record objects for which this initialization is desired
19450 should be explicitly set to all zero values using Unchecked_Conversion
19451 or address overlays. For example
19454 type HRec is record
19460 On typical machines, integers need to be aligned on a four-byte
19461 boundary, resulting in three bytes of undefined rubbish following
19462 the 8-bit field for C. To ensure that the hole in a variable of
19463 type HRec is set to all zero bits,
19464 you could for example do:
19467 type Base is record
19468 Dummy1, Dummy2 : Integer := 0;
19473 for RealVar'Address use BaseVar'Address;
19476 Now the 8-bytes of the value of RealVar start out containing all zero
19477 bits. A safer approach is to just define dummy fields, avoiding the
19481 type HRec is record
19483 Dummy1 : Short_Short_Integer := 0;
19484 Dummy2 : Short_Short_Integer := 0;
19485 Dummy3 : Short_Short_Integer := 0;
19490 And to make absolutely sure that the intent of this is followed, you
19491 can use representation clauses:
19494 for Hrec use record
19495 C at 0 range 0 .. 7;
19496 Dummy1 at 1 range 0 .. 7;
19497 Dummy2 at 2 range 0 .. 7;
19498 Dummy3 at 3 range 0 .. 7;
19499 I at 4 range 0 .. 31;
19501 for Hrec'Size use 64;
19504 @node Enumeration Clauses,Address Clauses,Handling of Records with Holes,Representation Clauses and Pragmas
19505 @anchor{gnat_rm/representation_clauses_and_pragmas enumeration-clauses}@anchor{292}@anchor{gnat_rm/representation_clauses_and_pragmas id15}@anchor{293}
19506 @section Enumeration Clauses
19509 The only restriction on enumeration clauses is that the range of values
19510 must be representable. For the signed case, if one or more of the
19511 representation values are negative, all values must be in the range:
19514 System.Min_Int .. System.Max_Int
19517 For the unsigned case, where all values are nonnegative, the values must
19521 0 .. System.Max_Binary_Modulus;
19524 A @emph{confirming} representation clause is one in which the values range
19525 from 0 in sequence, i.e., a clause that confirms the default representation
19526 for an enumeration type.
19527 Such a confirming representation
19528 is permitted by these rules, and is specially recognized by the compiler so
19529 that no extra overhead results from the use of such a clause.
19531 If an array has an index type which is an enumeration type to which an
19532 enumeration clause has been applied, then the array is stored in a compact
19533 manner. Consider the declarations:
19536 type r is (A, B, C);
19537 for r use (A => 1, B => 5, C => 10);
19538 type t is array (r) of Character;
19541 The array type t corresponds to a vector with exactly three elements and
19542 has a default size equal to @code{3*Character'Size}. This ensures efficient
19543 use of space, but means that accesses to elements of the array will incur
19544 the overhead of converting representation values to the corresponding
19545 positional values, (i.e., the value delivered by the @code{Pos} attribute).
19547 @node Address Clauses,Use of Address Clauses for Memory-Mapped I/O,Enumeration Clauses,Representation Clauses and Pragmas
19548 @anchor{gnat_rm/representation_clauses_and_pragmas id16}@anchor{294}@anchor{gnat_rm/representation_clauses_and_pragmas address-clauses}@anchor{295}
19549 @section Address Clauses
19552 @geindex Address Clause
19554 The reference manual allows a general restriction on representation clauses,
19555 as found in RM 13.1(22):
19559 "An implementation need not support representation
19560 items containing nonstatic expressions, except that
19561 an implementation should support a representation item
19562 for a given entity if each nonstatic expression in the
19563 representation item is a name that statically denotes
19564 a constant declared before the entity."
19567 In practice this is applicable only to address clauses, since this is the
19568 only case in which a nonstatic expression is permitted by the syntax. As
19569 the AARM notes in sections 13.1 (22.a-22.h):
19573 22.a Reason: This is to avoid the following sort of thing:
19575 22.b X : Integer := F(...);
19576 Y : Address := G(...);
19577 for X'Address use Y;
19579 22.c In the above, we have to evaluate the
19580 initialization expression for X before we
19581 know where to put the result. This seems
19582 like an unreasonable implementation burden.
19584 22.d The above code should instead be written
19587 22.e Y : constant Address := G(...);
19588 X : Integer := F(...);
19589 for X'Address use Y;
19591 22.f This allows the expression 'Y' to be safely
19592 evaluated before X is created.
19594 22.g The constant could be a formal parameter of mode in.
19596 22.h An implementation can support other nonstatic
19597 expressions if it wants to. Expressions of type
19598 Address are hardly ever static, but their value
19599 might be known at compile time anyway in many
19603 GNAT does indeed permit many additional cases of nonstatic expressions. In
19604 particular, if the type involved is elementary there are no restrictions
19605 (since in this case, holding a temporary copy of the initialization value,
19606 if one is present, is inexpensive). In addition, if there is no implicit or
19607 explicit initialization, then there are no restrictions. GNAT will reject
19608 only the case where all three of these conditions hold:
19614 The type of the item is non-elementary (e.g., a record or array).
19617 There is explicit or implicit initialization required for the object.
19618 Note that access values are always implicitly initialized.
19621 The address value is nonstatic. Here GNAT is more permissive than the
19622 RM, and allows the address value to be the address of a previously declared
19623 stand-alone variable, as long as it does not itself have an address clause.
19626 Anchor : Some_Initialized_Type;
19627 Overlay : Some_Initialized_Type;
19628 for Overlay'Address use Anchor'Address;
19631 However, the prefix of the address clause cannot be an array component, or
19632 a component of a discriminated record.
19635 As noted above in section 22.h, address values are typically nonstatic. In
19636 particular the To_Address function, even if applied to a literal value, is
19637 a nonstatic function call. To avoid this minor annoyance, GNAT provides
19638 the implementation defined attribute 'To_Address. The following two
19639 expressions have identical values:
19643 @geindex To_Address
19646 To_Address (16#1234_0000#)
19647 System'To_Address (16#1234_0000#);
19650 except that the second form is considered to be a static expression, and
19651 thus when used as an address clause value is always permitted.
19653 Additionally, GNAT treats as static an address clause that is an
19654 unchecked_conversion of a static integer value. This simplifies the porting
19655 of legacy code, and provides a portable equivalent to the GNAT attribute
19658 Another issue with address clauses is the interaction with alignment
19659 requirements. When an address clause is given for an object, the address
19660 value must be consistent with the alignment of the object (which is usually
19661 the same as the alignment of the type of the object). If an address clause
19662 is given that specifies an inappropriately aligned address value, then the
19663 program execution is erroneous.
19665 Since this source of erroneous behavior can have unfortunate effects on
19666 machines with strict alignment requirements, GNAT
19667 checks (at compile time if possible, generating a warning, or at execution
19668 time with a run-time check) that the alignment is appropriate. If the
19669 run-time check fails, then @code{Program_Error} is raised. This run-time
19670 check is suppressed if range checks are suppressed, or if the special GNAT
19671 check Alignment_Check is suppressed, or if
19672 @code{pragma Restrictions (No_Elaboration_Code)} is in effect. It is also
19673 suppressed by default on non-strict alignment machines (such as the x86).
19675 Finally, GNAT does not permit overlaying of objects of class-wide types. In
19676 most cases, the compiler can detect an attempt at such overlays and will
19677 generate a warning at compile time and a Program_Error exception at run time.
19681 An address clause cannot be given for an exported object. More
19682 understandably the real restriction is that objects with an address
19683 clause cannot be exported. This is because such variables are not
19684 defined by the Ada program, so there is no external object to export.
19688 It is permissible to give an address clause and a pragma Import for the
19689 same object. In this case, the variable is not really defined by the
19690 Ada program, so there is no external symbol to be linked. The link name
19691 and the external name are ignored in this case. The reason that we allow this
19692 combination is that it provides a useful idiom to avoid unwanted
19693 initializations on objects with address clauses.
19695 When an address clause is given for an object that has implicit or
19696 explicit initialization, then by default initialization takes place. This
19697 means that the effect of the object declaration is to overwrite the
19698 memory at the specified address. This is almost always not what the
19699 programmer wants, so GNAT will output a warning:
19709 for Ext'Address use System'To_Address (16#1234_1234#);
19711 >>> warning: implicit initialization of "Ext" may
19712 modify overlaid storage
19713 >>> warning: use pragma Import for "Ext" to suppress
19714 initialization (RM B(24))
19719 As indicated by the warning message, the solution is to use a (dummy) pragma
19720 Import to suppress this initialization. The pragma tell the compiler that the
19721 object is declared and initialized elsewhere. The following package compiles
19722 without warnings (and the initialization is suppressed):
19732 for Ext'Address use System'To_Address (16#1234_1234#);
19733 pragma Import (Ada, Ext);
19737 A final issue with address clauses involves their use for overlaying
19738 variables, as in the following example:
19740 @geindex Overlaying of objects
19745 for B'Address use A'Address;
19748 or alternatively, using the form recommended by the RM:
19752 Addr : constant Address := A'Address;
19754 for B'Address use Addr;
19757 In both of these cases, @code{A} and @code{B} become aliased to one another
19758 via the address clause. This use of address clauses to overlay
19759 variables, achieving an effect similar to unchecked conversion
19760 was erroneous in Ada 83, but in Ada 95 and Ada 2005
19761 the effect is implementation defined. Furthermore, the
19762 Ada RM specifically recommends that in a situation
19763 like this, @code{B} should be subject to the following
19764 implementation advice (RM 13.3(19)):
19768 "19 If the Address of an object is specified, or it is imported
19769 or exported, then the implementation should not perform
19770 optimizations based on assumptions of no aliases."
19773 GNAT follows this recommendation, and goes further by also applying
19774 this recommendation to the overlaid variable (@code{A} in the above example)
19775 in this case. This means that the overlay works "as expected", in that
19776 a modification to one of the variables will affect the value of the other.
19778 More generally, GNAT interprets this recommendation conservatively for
19779 address clauses: in the cases other than overlays, it considers that the
19780 object is effectively subject to pragma @code{Volatile} and implements the
19781 associated semantics.
19783 Note that when address clause overlays are used in this way, there is an
19784 issue of unintentional initialization, as shown by this example:
19787 package Overwrite_Record is
19789 A : Character := 'C';
19790 B : Character := 'A';
19792 X : Short_Integer := 3;
19794 for Y'Address use X'Address;
19796 >>> warning: default initialization of "Y" may
19797 modify "X", use pragma Import for "Y" to
19798 suppress initialization (RM B.1(24))
19800 end Overwrite_Record;
19803 Here the default initialization of @code{Y} will clobber the value
19804 of @code{X}, which justifies the warning. The warning notes that
19805 this effect can be eliminated by adding a @code{pragma Import}
19806 which suppresses the initialization:
19809 package Overwrite_Record is
19811 A : Character := 'C';
19812 B : Character := 'A';
19814 X : Short_Integer := 3;
19816 for Y'Address use X'Address;
19817 pragma Import (Ada, Y);
19818 end Overwrite_Record;
19821 Note that the use of @code{pragma Initialize_Scalars} may cause variables to
19822 be initialized when they would not otherwise have been in the absence
19823 of the use of this pragma. This may cause an overlay to have this
19824 unintended clobbering effect. The compiler avoids this for scalar
19825 types, but not for composite objects (where in general the effect
19826 of @code{Initialize_Scalars} is part of the initialization routine
19827 for the composite object:
19830 pragma Initialize_Scalars;
19831 with Ada.Text_IO; use Ada.Text_IO;
19832 procedure Overwrite_Array is
19833 type Arr is array (1 .. 5) of Integer;
19834 X : Arr := (others => 1);
19836 for A'Address use X'Address;
19838 >>> warning: default initialization of "A" may
19839 modify "X", use pragma Import for "A" to
19840 suppress initialization (RM B.1(24))
19843 if X /= Arr'(others => 1) then
19844 Put_Line ("X was clobbered");
19846 Put_Line ("X was not clobbered");
19848 end Overwrite_Array;
19851 The above program generates the warning as shown, and at execution
19852 time, prints @code{X was clobbered}. If the @code{pragma Import} is
19853 added as suggested:
19856 pragma Initialize_Scalars;
19857 with Ada.Text_IO; use Ada.Text_IO;
19858 procedure Overwrite_Array is
19859 type Arr is array (1 .. 5) of Integer;
19860 X : Arr := (others => 1);
19862 for A'Address use X'Address;
19863 pragma Import (Ada, A);
19865 if X /= Arr'(others => 1) then
19866 Put_Line ("X was clobbered");
19868 Put_Line ("X was not clobbered");
19870 end Overwrite_Array;
19873 then the program compiles without the warning and when run will generate
19874 the output @code{X was not clobbered}.
19876 @node Use of Address Clauses for Memory-Mapped I/O,Effect of Convention on Representation,Address Clauses,Representation Clauses and Pragmas
19877 @anchor{gnat_rm/representation_clauses_and_pragmas id17}@anchor{296}@anchor{gnat_rm/representation_clauses_and_pragmas use-of-address-clauses-for-memory-mapped-i-o}@anchor{297}
19878 @section Use of Address Clauses for Memory-Mapped I/O
19881 @geindex Memory-mapped I/O
19883 A common pattern is to use an address clause to map an atomic variable to
19884 a location in memory that corresponds to a memory-mapped I/O operation or
19885 operations, for example:
19888 type Mem_Word is record
19891 pragma Atomic (Mem_Word);
19892 for Mem_Word_Size use 32;
19895 for Mem'Address use some-address;
19902 For a full access (reference or modification) of the variable (Mem) in this
19903 case, as in the above examples, GNAT guarantees that the entire atomic word
19904 will be accessed, in accordance with the RM C.6(15) clause.
19906 A problem arises with a component access such as:
19912 Note that the component A is not declared as atomic. This means that it is
19913 not clear what this assignment means. It could correspond to full word read
19914 and write as given in the first example, or on architectures that supported
19915 such an operation it might be a single byte store instruction. The RM does
19916 not have anything to say in this situation, and GNAT does not make any
19917 guarantee. The code generated may vary from target to target. GNAT will issue
19918 a warning in such a case:
19923 >>> warning: access to non-atomic component of atomic array,
19924 may cause unexpected accesses to atomic object
19927 It is best to be explicit in this situation, by either declaring the
19928 components to be atomic if you want the byte store, or explicitly writing
19929 the full word access sequence if that is what the hardware requires.
19930 Alternatively, if the full word access sequence is required, GNAT also
19931 provides the pragma @code{Volatile_Full_Access} which can be used in lieu of
19932 pragma @code{Atomic} and will give the additional guarantee.
19934 @node Effect of Convention on Representation,Conventions and Anonymous Access Types,Use of Address Clauses for Memory-Mapped I/O,Representation Clauses and Pragmas
19935 @anchor{gnat_rm/representation_clauses_and_pragmas id18}@anchor{298}@anchor{gnat_rm/representation_clauses_and_pragmas effect-of-convention-on-representation}@anchor{299}
19936 @section Effect of Convention on Representation
19939 @geindex Convention
19940 @geindex effect on representation
19942 Normally the specification of a foreign language convention for a type or
19943 an object has no effect on the chosen representation. In particular, the
19944 representation chosen for data in GNAT generally meets the standard system
19945 conventions, and for example records are laid out in a manner that is
19946 consistent with C. This means that specifying convention C (for example)
19949 There are four exceptions to this general rule:
19955 @emph{Convention Fortran and array subtypes}.
19957 If pragma Convention Fortran is specified for an array subtype, then in
19958 accordance with the implementation advice in section 3.6.2(11) of the
19959 Ada Reference Manual, the array will be stored in a Fortran-compatible
19960 column-major manner, instead of the normal default row-major order.
19963 @emph{Convention C and enumeration types}
19965 GNAT normally stores enumeration types in 8, 16, or 32 bits as required
19966 to accommodate all values of the type. For example, for the enumeration
19970 type Color is (Red, Green, Blue);
19973 8 bits is sufficient to store all values of the type, so by default, objects
19974 of type @code{Color} will be represented using 8 bits. However, normal C
19975 convention is to use 32 bits for all enum values in C, since enum values
19976 are essentially of type int. If pragma @code{Convention C} is specified for an
19977 Ada enumeration type, then the size is modified as necessary (usually to
19978 32 bits) to be consistent with the C convention for enum values.
19980 Note that this treatment applies only to types. If Convention C is given for
19981 an enumeration object, where the enumeration type is not Convention C, then
19982 Object_Size bits are allocated. For example, for a normal enumeration type,
19983 with less than 256 elements, only 8 bits will be allocated for the object.
19984 Since this may be a surprise in terms of what C expects, GNAT will issue a
19985 warning in this situation. The warning can be suppressed by giving an explicit
19986 size clause specifying the desired size.
19989 @emph{Convention C/Fortran and Boolean types}
19991 In C, the usual convention for boolean values, that is values used for
19992 conditions, is that zero represents false, and nonzero values represent
19993 true. In Ada, the normal convention is that two specific values, typically
19994 0/1, are used to represent false/true respectively.
19996 Fortran has a similar convention for @code{LOGICAL} values (any nonzero
19997 value represents true).
19999 To accommodate the Fortran and C conventions, if a pragma Convention specifies
20000 C or Fortran convention for a derived Boolean, as in the following example:
20003 type C_Switch is new Boolean;
20004 pragma Convention (C, C_Switch);
20007 then the GNAT generated code will treat any nonzero value as true. For truth
20008 values generated by GNAT, the conventional value 1 will be used for True, but
20009 when one of these values is read, any nonzero value is treated as True.
20012 @node Conventions and Anonymous Access Types,Determining the Representations chosen by GNAT,Effect of Convention on Representation,Representation Clauses and Pragmas
20013 @anchor{gnat_rm/representation_clauses_and_pragmas conventions-and-anonymous-access-types}@anchor{29a}@anchor{gnat_rm/representation_clauses_and_pragmas id19}@anchor{29b}
20014 @section Conventions and Anonymous Access Types
20017 @geindex Anonymous access types
20019 @geindex Convention for anonymous access types
20021 The RM is not entirely clear on convention handling in a number of cases,
20022 and in particular, it is not clear on the convention to be given to
20023 anonymous access types in general, and in particular what is to be
20024 done for the case of anonymous access-to-subprogram.
20026 In GNAT, we decide that if an explicit Convention is applied
20027 to an object or component, and its type is such an anonymous type,
20028 then the convention will apply to this anonymous type as well. This
20029 seems to make sense since it is anomolous in any case to have a
20030 different convention for an object and its type, and there is clearly
20031 no way to explicitly specify a convention for an anonymous type, since
20032 it doesn't have a name to specify!
20034 Furthermore, we decide that if a convention is applied to a record type,
20035 then this convention is inherited by any of its components that are of an
20036 anonymous access type which do not have an explicitly specified convention.
20038 The following program shows these conventions in action:
20041 package ConvComp is
20042 type Foo is range 1 .. 10;
20044 A : access function (X : Foo) return Integer;
20047 pragma Convention (C, T1);
20050 A : access function (X : Foo) return Integer;
20051 pragma Convention (C, A);
20054 pragma Convention (COBOL, T2);
20057 A : access function (X : Foo) return Integer;
20058 pragma Convention (COBOL, A);
20061 pragma Convention (C, T3);
20064 A : access function (X : Foo) return Integer;
20067 pragma Convention (COBOL, T4);
20069 function F (X : Foo) return Integer;
20070 pragma Convention (C, F);
20072 function F (X : Foo) return Integer is (13);
20074 TV1 : T1 := (F'Access, 12); -- OK
20075 TV2 : T2 := (F'Access, 13); -- OK
20077 TV3 : T3 := (F'Access, 13); -- ERROR
20079 >>> subprogram "F" has wrong convention
20080 >>> does not match access to subprogram declared at line 17
20081 38. TV4 : T4 := (F'Access, 13); -- ERROR
20083 >>> subprogram "F" has wrong convention
20084 >>> does not match access to subprogram declared at line 24
20088 @node Determining the Representations chosen by GNAT,,Conventions and Anonymous Access Types,Representation Clauses and Pragmas
20089 @anchor{gnat_rm/representation_clauses_and_pragmas id20}@anchor{29c}@anchor{gnat_rm/representation_clauses_and_pragmas determining-the-representations-chosen-by-gnat}@anchor{29d}
20090 @section Determining the Representations chosen by GNAT
20093 @geindex Representation
20094 @geindex determination of
20096 @geindex -gnatR (gcc)
20098 Although the descriptions in this section are intended to be complete, it is
20099 often easier to simply experiment to see what GNAT accepts and what the
20100 effect is on the layout of types and objects.
20102 As required by the Ada RM, if a representation clause is not accepted, then
20103 it must be rejected as illegal by the compiler. However, when a
20104 representation clause or pragma is accepted, there can still be questions
20105 of what the compiler actually does. For example, if a partial record
20106 representation clause specifies the location of some components and not
20107 others, then where are the non-specified components placed? Or if pragma
20108 @code{Pack} is used on a record, then exactly where are the resulting
20109 fields placed? The section on pragma @code{Pack} in this chapter can be
20110 used to answer the second question, but it is often easier to just see
20111 what the compiler does.
20113 For this purpose, GNAT provides the option @emph{-gnatR}. If you compile
20114 with this option, then the compiler will output information on the actual
20115 representations chosen, in a format similar to source representation
20116 clauses. For example, if we compile the package:
20120 type r (x : boolean) is tagged record
20122 when True => S : String (1 .. 100);
20123 when False => null;
20127 type r2 is new r (false) with record
20132 y2 at 16 range 0 .. 31;
20139 type x1 is array (1 .. 10) of x;
20140 for x1'component_size use 11;
20142 type ia is access integer;
20144 type Rb1 is array (1 .. 13) of Boolean;
20147 type Rb2 is array (1 .. 65) of Boolean;
20162 using the switch @emph{-gnatR} we obtain the following output:
20165 Representation information for unit q
20166 -------------------------------------
20169 for r'Alignment use 4;
20171 x at 4 range 0 .. 7;
20172 _tag at 0 range 0 .. 31;
20173 s at 5 range 0 .. 799;
20176 for r2'Size use 160;
20177 for r2'Alignment use 4;
20179 x at 4 range 0 .. 7;
20180 _tag at 0 range 0 .. 31;
20181 _parent at 0 range 0 .. 63;
20182 y2 at 16 range 0 .. 31;
20186 for x'Alignment use 1;
20188 y at 0 range 0 .. 7;
20191 for x1'Size use 112;
20192 for x1'Alignment use 1;
20193 for x1'Component_Size use 11;
20195 for rb1'Size use 13;
20196 for rb1'Alignment use 2;
20197 for rb1'Component_Size use 1;
20199 for rb2'Size use 72;
20200 for rb2'Alignment use 1;
20201 for rb2'Component_Size use 1;
20203 for x2'Size use 224;
20204 for x2'Alignment use 4;
20206 l1 at 0 range 0 .. 0;
20207 l2 at 0 range 1 .. 64;
20208 l3 at 12 range 0 .. 31;
20209 l4 at 16 range 0 .. 0;
20210 l5 at 16 range 1 .. 13;
20211 l6 at 18 range 0 .. 71;
20215 The Size values are actually the Object_Size, i.e., the default size that
20216 will be allocated for objects of the type.
20217 The @code{??} size for type r indicates that we have a variant record, and the
20218 actual size of objects will depend on the discriminant value.
20220 The Alignment values show the actual alignment chosen by the compiler
20221 for each record or array type.
20223 The record representation clause for type r shows where all fields
20224 are placed, including the compiler generated tag field (whose location
20225 cannot be controlled by the programmer).
20227 The record representation clause for the type extension r2 shows all the
20228 fields present, including the parent field, which is a copy of the fields
20229 of the parent type of r2, i.e., r1.
20231 The component size and size clauses for types rb1 and rb2 show
20232 the exact effect of pragma @code{Pack} on these arrays, and the record
20233 representation clause for type x2 shows how pragma @cite{Pack} affects
20236 In some cases, it may be useful to cut and paste the representation clauses
20237 generated by the compiler into the original source to fix and guarantee
20238 the actual representation to be used.
20240 @node Standard Library Routines,The Implementation of Standard I/O,Representation Clauses and Pragmas,Top
20241 @anchor{gnat_rm/standard_library_routines standard-library-routines}@anchor{e}@anchor{gnat_rm/standard_library_routines doc}@anchor{29e}@anchor{gnat_rm/standard_library_routines id1}@anchor{29f}
20242 @chapter Standard Library Routines
20245 The Ada Reference Manual contains in Annex A a full description of an
20246 extensive set of standard library routines that can be used in any Ada
20247 program, and which must be provided by all Ada compilers. They are
20248 analogous to the standard C library used by C programs.
20250 GNAT implements all of the facilities described in annex A, and for most
20251 purposes the description in the Ada Reference Manual, or appropriate Ada
20252 text book, will be sufficient for making use of these facilities.
20254 In the case of the input-output facilities,
20255 @ref{f,,The Implementation of Standard I/O},
20256 gives details on exactly how GNAT interfaces to the
20257 file system. For the remaining packages, the Ada Reference Manual
20258 should be sufficient. The following is a list of the packages included,
20259 together with a brief description of the functionality that is provided.
20261 For completeness, references are included to other predefined library
20262 routines defined in other sections of the Ada Reference Manual (these are
20263 cross-indexed from Annex A). For further details see the relevant
20264 package declarations in the run-time library. In particular, a few units
20265 are not implemented, as marked by the presence of pragma Unimplemented_Unit,
20266 and in this case the package declaration contains comments explaining why
20267 the unit is not implemented.
20272 @item @code{Ada} @emph{(A.2)}
20274 This is a parent package for all the standard library packages. It is
20275 usually included implicitly in your program, and itself contains no
20276 useful data or routines.
20278 @item @code{Ada.Assertions} @emph{(11.4.2)}
20280 @code{Assertions} provides the @code{Assert} subprograms, and also
20281 the declaration of the @code{Assertion_Error} exception.
20283 @item @code{Ada.Asynchronous_Task_Control} @emph{(D.11)}
20285 @code{Asynchronous_Task_Control} provides low level facilities for task
20286 synchronization. It is typically not implemented. See package spec for details.
20288 @item @code{Ada.Calendar} @emph{(9.6)}
20290 @code{Calendar} provides time of day access, and routines for
20291 manipulating times and durations.
20293 @item @code{Ada.Calendar.Arithmetic} @emph{(9.6.1)}
20295 This package provides additional arithmetic
20296 operations for @code{Calendar}.
20298 @item @code{Ada.Calendar.Formatting} @emph{(9.6.1)}
20300 This package provides formatting operations for @code{Calendar}.
20302 @item @code{Ada.Calendar.Time_Zones} @emph{(9.6.1)}
20304 This package provides additional @code{Calendar} facilities
20305 for handling time zones.
20307 @item @code{Ada.Characters} @emph{(A.3.1)}
20309 This is a dummy parent package that contains no useful entities
20311 @item @code{Ada.Characters.Conversions} @emph{(A.3.2)}
20313 This package provides character conversion functions.
20315 @item @code{Ada.Characters.Handling} @emph{(A.3.2)}
20317 This package provides some basic character handling capabilities,
20318 including classification functions for classes of characters (e.g., test
20319 for letters, or digits).
20321 @item @code{Ada.Characters.Latin_1} @emph{(A.3.3)}
20323 This package includes a complete set of definitions of the characters
20324 that appear in type CHARACTER. It is useful for writing programs that
20325 will run in international environments. For example, if you want an
20326 upper case E with an acute accent in a string, it is often better to use
20327 the definition of @code{UC_E_Acute} in this package. Then your program
20328 will print in an understandable manner even if your environment does not
20329 support these extended characters.
20331 @item @code{Ada.Command_Line} @emph{(A.15)}
20333 This package provides access to the command line parameters and the name
20334 of the current program (analogous to the use of @code{argc} and @code{argv}
20335 in C), and also allows the exit status for the program to be set in a
20336 system-independent manner.
20338 @item @code{Ada.Complex_Text_IO} @emph{(G.1.3)}
20340 This package provides text input and output of complex numbers.
20342 @item @code{Ada.Containers} @emph{(A.18.1)}
20344 A top level package providing a few basic definitions used by all the
20345 following specific child packages that provide specific kinds of
20349 @code{Ada.Containers.Bounded_Priority_Queues} @emph{(A.18.31)}
20351 @code{Ada.Containers.Bounded_Synchronized_Queues} @emph{(A.18.29)}
20353 @code{Ada.Containers.Doubly_Linked_Lists} @emph{(A.18.3)}
20355 @code{Ada.Containers.Generic_Array_Sort} @emph{(A.18.26)}
20357 @code{Ada.Containers.Generic_Constrained_Array_Sort} @emph{(A.18.26)}
20359 @code{Ada.Containers.Generic_Sort} @emph{(A.18.26)}
20361 @code{Ada.Containers.Hashed_Maps} @emph{(A.18.5)}
20363 @code{Ada.Containers.Hashed_Sets} @emph{(A.18.8)}
20365 @code{Ada.Containers.Indefinite_Doubly_Linked_Lists} @emph{(A.18.12)}
20367 @code{Ada.Containers.Indefinite_Hashed_Maps} @emph{(A.18.13)}
20369 @code{Ada.Containers.Indefinite_Hashed_Sets} @emph{(A.18.15)}
20371 @code{Ada.Containers.Indefinite_Holders} @emph{(A.18.18)}
20373 @code{Ada.Containers.Indefinite_Multiway_Trees} @emph{(A.18.17)}
20375 @code{Ada.Containers.Indefinite_Ordered_Maps} @emph{(A.18.14)}
20377 @code{Ada.Containers.Indefinite_Ordered_Sets} @emph{(A.18.16)}
20379 @code{Ada.Containers.Indefinite_Vectors} @emph{(A.18.11)}
20381 @code{Ada.Containers.Multiway_Trees} @emph{(A.18.10)}
20383 @code{Ada.Containers.Ordered_Maps} @emph{(A.18.6)}
20385 @code{Ada.Containers.Ordered_Sets} @emph{(A.18.9)}
20387 @code{Ada.Containers.Synchronized_Queue_Interfaces} @emph{(A.18.27)}
20389 @code{Ada.Containers.Unbounded_Priority_Queues} @emph{(A.18.30)}
20391 @code{Ada.Containers.Unbounded_Synchronized_Queues} @emph{(A.18.28)}
20393 @code{Ada.Containers.Vectors} @emph{(A.18.2)}
20398 @item @code{Ada.Directories} @emph{(A.16)}
20400 This package provides operations on directories.
20402 @item @code{Ada.Directories.Hierarchical_File_Names} @emph{(A.16.1)}
20404 This package provides additional directory operations handling
20405 hiearchical file names.
20407 @item @code{Ada.Directories.Information} @emph{(A.16)}
20409 This is an implementation defined package for additional directory
20410 operations, which is not implemented in GNAT.
20412 @item @code{Ada.Decimal} @emph{(F.2)}
20414 This package provides constants describing the range of decimal numbers
20415 implemented, and also a decimal divide routine (analogous to the COBOL
20416 verb DIVIDE ... GIVING ... REMAINDER ...)
20418 @item @code{Ada.Direct_IO} @emph{(A.8.4)}
20420 This package provides input-output using a model of a set of records of
20421 fixed-length, containing an arbitrary definite Ada type, indexed by an
20422 integer record number.
20424 @item @code{Ada.Dispatching} @emph{(D.2.1)}
20426 A parent package containing definitions for task dispatching operations.
20428 @item @code{Ada.Dispatching.EDF} @emph{(D.2.6)}
20430 Not implemented in GNAT.
20432 @item @code{Ada.Dispatching.Non_Preemptive} @emph{(D.2.4)}
20434 Not implemented in GNAT.
20436 @item @code{Ada.Dispatching.Round_Robin} @emph{(D.2.5)}
20438 Not implemented in GNAT.
20440 @item @code{Ada.Dynamic_Priorities} @emph{(D.5)}
20442 This package allows the priorities of a task to be adjusted dynamically
20443 as the task is running.
20445 @item @code{Ada.Environment_Variables} @emph{(A.17)}
20447 This package provides facilities for accessing environment variables.
20449 @item @code{Ada.Exceptions} @emph{(11.4.1)}
20451 This package provides additional information on exceptions, and also
20452 contains facilities for treating exceptions as data objects, and raising
20453 exceptions with associated messages.
20455 @item @code{Ada.Execution_Time} @emph{(D.14)}
20457 This package provides CPU clock functionalities. It is not implemented on
20458 all targets (see package spec for details).
20460 @item @code{Ada.Execution_Time.Group_Budgets} @emph{(D.14.2)}
20462 Not implemented in GNAT.
20464 @item @code{Ada.Execution_Time.Timers} @emph{(D.14.1)'}
20466 Not implemented in GNAT.
20468 @item @code{Ada.Finalization} @emph{(7.6)}
20470 This package contains the declarations and subprograms to support the
20471 use of controlled types, providing for automatic initialization and
20472 finalization (analogous to the constructors and destructors of C++).
20474 @item @code{Ada.Float_Text_IO} @emph{(A.10.9)}
20476 A library level instantiation of Text_IO.Float_IO for type Float.
20478 @item @code{Ada.Float_Wide_Text_IO} @emph{(A.10.9)}
20480 A library level instantiation of Wide_Text_IO.Float_IO for type Float.
20482 @item @code{Ada.Float_Wide_Wide_Text_IO} @emph{(A.10.9)}
20484 A library level instantiation of Wide_Wide_Text_IO.Float_IO for type Float.
20486 @item @code{Ada.Integer_Text_IO} @emph{(A.10.9)}
20488 A library level instantiation of Text_IO.Integer_IO for type Integer.
20490 @item @code{Ada.Integer_Wide_Text_IO} @emph{(A.10.9)}
20492 A library level instantiation of Wide_Text_IO.Integer_IO for type Integer.
20494 @item @code{Ada.Integer_Wide_Wide_Text_IO} @emph{(A.10.9)}
20496 A library level instantiation of Wide_Wide_Text_IO.Integer_IO for type Integer.
20498 @item @code{Ada.Interrupts} @emph{(C.3.2)}
20500 This package provides facilities for interfacing to interrupts, which
20501 includes the set of signals or conditions that can be raised and
20502 recognized as interrupts.
20504 @item @code{Ada.Interrupts.Names} @emph{(C.3.2)}
20506 This package provides the set of interrupt names (actually signal
20507 or condition names) that can be handled by GNAT.
20509 @item @code{Ada.IO_Exceptions} @emph{(A.13)}
20511 This package defines the set of exceptions that can be raised by use of
20512 the standard IO packages.
20514 @item @code{Ada.Iterator_Interfaces} @emph{(5.5.1)}
20516 This package provides a generic interface to generalized iterators.
20518 @item @code{Ada.Locales} @emph{(A.19)}
20520 This package provides declarations providing information (Language
20521 and Country) about the current locale.
20523 @item @code{Ada.Numerics}
20525 This package contains some standard constants and exceptions used
20526 throughout the numerics packages. Note that the constants pi and e are
20527 defined here, and it is better to use these definitions than rolling
20530 @item @code{Ada.Numerics.Complex_Arrays} @emph{(G.3.2)}
20532 Provides operations on arrays of complex numbers.
20534 @item @code{Ada.Numerics.Complex_Elementary_Functions}
20536 Provides the implementation of standard elementary functions (such as
20537 log and trigonometric functions) operating on complex numbers using the
20538 standard @code{Float} and the @code{Complex} and @code{Imaginary} types
20539 created by the package @code{Numerics.Complex_Types}.
20541 @item @code{Ada.Numerics.Complex_Types}
20543 This is a predefined instantiation of
20544 @code{Numerics.Generic_Complex_Types} using @code{Standard.Float} to
20545 build the type @code{Complex} and @code{Imaginary}.
20547 @item @code{Ada.Numerics.Discrete_Random}
20549 This generic package provides a random number generator suitable for generating
20550 uniformly distributed values of a specified discrete subtype.
20552 @item @code{Ada.Numerics.Float_Random}
20554 This package provides a random number generator suitable for generating
20555 uniformly distributed floating point values in the unit interval.
20557 @item @code{Ada.Numerics.Generic_Complex_Elementary_Functions}
20559 This is a generic version of the package that provides the
20560 implementation of standard elementary functions (such as log and
20561 trigonometric functions) for an arbitrary complex type.
20563 The following predefined instantiations of this package are provided:
20571 @code{Ada.Numerics.Short_Complex_Elementary_Functions}
20576 @code{Ada.Numerics.Complex_Elementary_Functions}
20581 @code{Ada.Numerics.Long_Complex_Elementary_Functions}
20584 @item @code{Ada.Numerics.Generic_Complex_Types}
20586 This is a generic package that allows the creation of complex types,
20587 with associated complex arithmetic operations.
20589 The following predefined instantiations of this package exist
20597 @code{Ada.Numerics.Short_Complex_Complex_Types}
20602 @code{Ada.Numerics.Complex_Complex_Types}
20607 @code{Ada.Numerics.Long_Complex_Complex_Types}
20610 @item @code{Ada.Numerics.Generic_Elementary_Functions}
20612 This is a generic package that provides the implementation of standard
20613 elementary functions (such as log an trigonometric functions) for an
20614 arbitrary float type.
20616 The following predefined instantiations of this package exist
20624 @code{Ada.Numerics.Short_Elementary_Functions}
20629 @code{Ada.Numerics.Elementary_Functions}
20634 @code{Ada.Numerics.Long_Elementary_Functions}
20637 @item @code{Ada.Numerics.Generic_Real_Arrays} @emph{(G.3.1)}
20639 Generic operations on arrays of reals
20641 @item @code{Ada.Numerics.Real_Arrays} @emph{(G.3.1)}
20643 Preinstantiation of Ada.Numerics.Generic_Real_Arrays (Float).
20645 @item @code{Ada.Real_Time} @emph{(D.8)}
20647 This package provides facilities similar to those of @code{Calendar}, but
20648 operating with a finer clock suitable for real time control. Note that
20649 annex D requires that there be no backward clock jumps, and GNAT generally
20650 guarantees this behavior, but of course if the external clock on which
20651 the GNAT runtime depends is deliberately reset by some external event,
20652 then such a backward jump may occur.
20654 @item @code{Ada.Real_Time.Timing_Events} @emph{(D.15)}
20656 Not implemented in GNAT.
20658 @item @code{Ada.Sequential_IO} @emph{(A.8.1)}
20660 This package provides input-output facilities for sequential files,
20661 which can contain a sequence of values of a single type, which can be
20662 any Ada type, including indefinite (unconstrained) types.
20664 @item @code{Ada.Storage_IO} @emph{(A.9)}
20666 This package provides a facility for mapping arbitrary Ada types to and
20667 from a storage buffer. It is primarily intended for the creation of new
20670 @item @code{Ada.Streams} @emph{(13.13.1)}
20672 This is a generic package that provides the basic support for the
20673 concept of streams as used by the stream attributes (@code{Input},
20674 @code{Output}, @code{Read} and @code{Write}).
20676 @item @code{Ada.Streams.Stream_IO} @emph{(A.12.1)}
20678 This package is a specialization of the type @code{Streams} defined in
20679 package @code{Streams} together with a set of operations providing
20680 Stream_IO capability. The Stream_IO model permits both random and
20681 sequential access to a file which can contain an arbitrary set of values
20682 of one or more Ada types.
20684 @item @code{Ada.Strings} @emph{(A.4.1)}
20686 This package provides some basic constants used by the string handling
20689 @item @code{Ada.Strings.Bounded} @emph{(A.4.4)}
20691 This package provides facilities for handling variable length
20692 strings. The bounded model requires a maximum length. It is thus
20693 somewhat more limited than the unbounded model, but avoids the use of
20694 dynamic allocation or finalization.
20696 @item @code{Ada.Strings.Bounded.Equal_Case_Insensitive} @emph{(A.4.10)}
20698 Provides case-insensitive comparisons of bounded strings
20700 @item @code{Ada.Strings.Bounded.Hash} @emph{(A.4.9)}
20702 This package provides a generic hash function for bounded strings
20704 @item @code{Ada.Strings.Bounded.Hash_Case_Insensitive} @emph{(A.4.9)}
20706 This package provides a generic hash function for bounded strings that
20707 converts the string to be hashed to lower case.
20709 @item @code{Ada.Strings.Bounded.Less_Case_Insensitive} @emph{(A.4.10)}
20711 This package provides a comparison function for bounded strings that works
20712 in a case insensitive manner by converting to lower case before the comparison.
20714 @item @code{Ada.Strings.Fixed} @emph{(A.4.3)}
20716 This package provides facilities for handling fixed length strings.
20718 @item @code{Ada.Strings.Fixed.Equal_Case_Insensitive} @emph{(A.4.10)}
20720 This package provides an equality function for fixed strings that compares
20721 the strings after converting both to lower case.
20723 @item @code{Ada.Strings.Fixed.Hash_Case_Insensitive} @emph{(A.4.9)}
20725 This package provides a case insensitive hash function for fixed strings that
20726 converts the string to lower case before computing the hash.
20728 @item @code{Ada.Strings.Fixed.Less_Case_Insensitive} @emph{(A.4.10)}
20730 This package provides a comparison function for fixed strings that works
20731 in a case insensitive manner by converting to lower case before the comparison.
20733 @item @code{Ada.Strings.Hash} @emph{(A.4.9)}
20735 This package provides a hash function for strings.
20737 @item @code{Ada.Strings.Hash_Case_Insensitive} @emph{(A.4.9)}
20739 This package provides a hash function for strings that is case insensitive.
20740 The string is converted to lower case before computing the hash.
20742 @item @code{Ada.Strings.Less_Case_Insensitive} @emph{(A.4.10)}
20744 This package provides a comparison function for\strings that works
20745 in a case insensitive manner by converting to lower case before the comparison.
20747 @item @code{Ada.Strings.Maps} @emph{(A.4.2)}
20749 This package provides facilities for handling character mappings and
20750 arbitrarily defined subsets of characters. For instance it is useful in
20751 defining specialized translation tables.
20753 @item @code{Ada.Strings.Maps.Constants} @emph{(A.4.6)}
20755 This package provides a standard set of predefined mappings and
20756 predefined character sets. For example, the standard upper to lower case
20757 conversion table is found in this package. Note that upper to lower case
20758 conversion is non-trivial if you want to take the entire set of
20759 characters, including extended characters like E with an acute accent,
20760 into account. You should use the mappings in this package (rather than
20761 adding 32 yourself) to do case mappings.
20763 @item @code{Ada.Strings.Unbounded} @emph{(A.4.5)}
20765 This package provides facilities for handling variable length
20766 strings. The unbounded model allows arbitrary length strings, but
20767 requires the use of dynamic allocation and finalization.
20769 @item @code{Ada.Strings.Unbounded.Equal_Case_Insensitive} @emph{(A.4.10)}
20771 Provides case-insensitive comparisons of unbounded strings
20773 @item @code{Ada.Strings.Unbounded.Hash} @emph{(A.4.9)}
20775 This package provides a generic hash function for unbounded strings
20777 @item @code{Ada.Strings.Unbounded.Hash_Case_Insensitive} @emph{(A.4.9)}
20779 This package provides a generic hash function for unbounded strings that
20780 converts the string to be hashed to lower case.
20782 @item @code{Ada.Strings.Unbounded.Less_Case_Insensitive} @emph{(A.4.10)}
20784 This package provides a comparison function for unbounded strings that works
20785 in a case insensitive manner by converting to lower case before the comparison.
20787 @item @code{Ada.Strings.UTF_Encoding} @emph{(A.4.11)}
20789 This package provides basic definitions for dealing with UTF-encoded strings.
20791 @item @code{Ada.Strings.UTF_Encoding.Conversions} @emph{(A.4.11)}
20793 This package provides conversion functions for UTF-encoded strings.
20796 @code{Ada.Strings.UTF_Encoding.Strings} @emph{(A.4.11)}
20798 @code{Ada.Strings.UTF_Encoding.Wide_Strings} @emph{(A.4.11)}
20803 @item @code{Ada.Strings.UTF_Encoding.Wide_Wide_Strings} @emph{(A.4.11)}
20805 These packages provide facilities for handling UTF encodings for
20806 Strings, Wide_Strings and Wide_Wide_Strings.
20809 @code{Ada.Strings.Wide_Bounded} @emph{(A.4.7)}
20811 @code{Ada.Strings.Wide_Fixed} @emph{(A.4.7)}
20813 @code{Ada.Strings.Wide_Maps} @emph{(A.4.7)}
20818 @item @code{Ada.Strings.Wide_Unbounded} @emph{(A.4.7)}
20820 These packages provide analogous capabilities to the corresponding
20821 packages without @code{Wide_} in the name, but operate with the types
20822 @code{Wide_String} and @code{Wide_Character} instead of @code{String}
20823 and @code{Character}. Versions of all the child packages are available.
20826 @code{Ada.Strings.Wide_Wide_Bounded} @emph{(A.4.7)}
20828 @code{Ada.Strings.Wide_Wide_Fixed} @emph{(A.4.7)}
20830 @code{Ada.Strings.Wide_Wide_Maps} @emph{(A.4.7)}
20835 @item @code{Ada.Strings.Wide_Wide_Unbounded} @emph{(A.4.7)}
20837 These packages provide analogous capabilities to the corresponding
20838 packages without @code{Wide_} in the name, but operate with the types
20839 @code{Wide_Wide_String} and @code{Wide_Wide_Character} instead
20840 of @code{String} and @code{Character}.
20842 @item @code{Ada.Synchronous_Barriers} @emph{(D.10.1)}
20844 This package provides facilities for synchronizing tasks at a low level
20847 @item @code{Ada.Synchronous_Task_Control} @emph{(D.10)}
20849 This package provides some standard facilities for controlling task
20850 communication in a synchronous manner.
20852 @item @code{Ada.Synchronous_Task_Control.EDF} @emph{(D.10)}
20854 Not implemented in GNAT.
20856 @item @code{Ada.Tags}
20858 This package contains definitions for manipulation of the tags of tagged
20861 @item @code{Ada.Tags.Generic_Dispatching_Constructor} @emph{(3.9)}
20863 This package provides a way of constructing tagged class-wide values given
20864 only the tag value.
20866 @item @code{Ada.Task_Attributes} @emph{(C.7.2)}
20868 This package provides the capability of associating arbitrary
20869 task-specific data with separate tasks.
20871 @item @code{Ada.Task_Identifification} @emph{(C.7.1)}
20873 This package provides capabilities for task identification.
20875 @item @code{Ada.Task_Termination} @emph{(C.7.3)}
20877 This package provides control over task termination.
20879 @item @code{Ada.Text_IO}
20881 This package provides basic text input-output capabilities for
20882 character, string and numeric data. The subpackages of this
20883 package are listed next. Note that although these are defined
20884 as subpackages in the RM, they are actually transparently
20885 implemented as child packages in GNAT, meaning that they
20886 are only loaded if needed.
20888 @item @code{Ada.Text_IO.Decimal_IO}
20890 Provides input-output facilities for decimal fixed-point types
20892 @item @code{Ada.Text_IO.Enumeration_IO}
20894 Provides input-output facilities for enumeration types.
20896 @item @code{Ada.Text_IO.Fixed_IO}
20898 Provides input-output facilities for ordinary fixed-point types.
20900 @item @code{Ada.Text_IO.Float_IO}
20902 Provides input-output facilities for float types. The following
20903 predefined instantiations of this generic package are available:
20911 @code{Short_Float_Text_IO}
20916 @code{Float_Text_IO}
20921 @code{Long_Float_Text_IO}
20924 @item @code{Ada.Text_IO.Integer_IO}
20926 Provides input-output facilities for integer types. The following
20927 predefined instantiations of this generic package are available:
20933 @code{Short_Short_Integer}
20935 @code{Ada.Short_Short_Integer_Text_IO}
20938 @code{Short_Integer}
20940 @code{Ada.Short_Integer_Text_IO}
20945 @code{Ada.Integer_Text_IO}
20948 @code{Long_Integer}
20950 @code{Ada.Long_Integer_Text_IO}
20953 @code{Long_Long_Integer}
20955 @code{Ada.Long_Long_Integer_Text_IO}
20958 @item @code{Ada.Text_IO.Modular_IO}
20960 Provides input-output facilities for modular (unsigned) types.
20962 @item @code{Ada.Text_IO.Bounded_IO (A.10.11)}
20964 Provides input-output facilities for bounded strings.
20966 @item @code{Ada.Text_IO.Complex_IO (G.1.3)}
20968 This package provides basic text input-output capabilities for complex
20971 @item @code{Ada.Text_IO.Editing (F.3.3)}
20973 This package contains routines for edited output, analogous to the use
20974 of pictures in COBOL. The picture formats used by this package are a
20975 close copy of the facility in COBOL.
20977 @item @code{Ada.Text_IO.Text_Streams (A.12.2)}
20979 This package provides a facility that allows Text_IO files to be treated
20980 as streams, so that the stream attributes can be used for writing
20981 arbitrary data, including binary data, to Text_IO files.
20983 @item @code{Ada.Text_IO.Unbounded_IO (A.10.12)}
20985 This package provides input-output facilities for unbounded strings.
20987 @item @code{Ada.Unchecked_Conversion (13.9)}
20989 This generic package allows arbitrary conversion from one type to
20990 another of the same size, providing for breaking the type safety in
20991 special circumstances.
20993 If the types have the same Size (more accurately the same Value_Size),
20994 then the effect is simply to transfer the bits from the source to the
20995 target type without any modification. This usage is well defined, and
20996 for simple types whose representation is typically the same across
20997 all implementations, gives a portable method of performing such
21000 If the types do not have the same size, then the result is implementation
21001 defined, and thus may be non-portable. The following describes how GNAT
21002 handles such unchecked conversion cases.
21004 If the types are of different sizes, and are both discrete types, then
21005 the effect is of a normal type conversion without any constraint checking.
21006 In particular if the result type has a larger size, the result will be
21007 zero or sign extended. If the result type has a smaller size, the result
21008 will be truncated by ignoring high order bits.
21010 If the types are of different sizes, and are not both discrete types,
21011 then the conversion works as though pointers were created to the source
21012 and target, and the pointer value is converted. The effect is that bits
21013 are copied from successive low order storage units and bits of the source
21014 up to the length of the target type.
21016 A warning is issued if the lengths differ, since the effect in this
21017 case is implementation dependent, and the above behavior may not match
21018 that of some other compiler.
21020 A pointer to one type may be converted to a pointer to another type using
21021 unchecked conversion. The only case in which the effect is undefined is
21022 when one or both pointers are pointers to unconstrained array types. In
21023 this case, the bounds information may get incorrectly transferred, and in
21024 particular, GNAT uses double size pointers for such types, and it is
21025 meaningless to convert between such pointer types. GNAT will issue a
21026 warning if the alignment of the target designated type is more strict
21027 than the alignment of the source designated type (since the result may
21028 be unaligned in this case).
21030 A pointer other than a pointer to an unconstrained array type may be
21031 converted to and from System.Address. Such usage is common in Ada 83
21032 programs, but note that Ada.Address_To_Access_Conversions is the
21033 preferred method of performing such conversions in Ada 95 and Ada 2005.
21035 unchecked conversion nor Ada.Address_To_Access_Conversions should be
21036 used in conjunction with pointers to unconstrained objects, since
21037 the bounds information cannot be handled correctly in this case.
21039 @item @code{Ada.Unchecked_Deallocation} @emph{(13.11.2)}
21041 This generic package allows explicit freeing of storage previously
21042 allocated by use of an allocator.
21044 @item @code{Ada.Wide_Text_IO} @emph{(A.11)}
21046 This package is similar to @code{Ada.Text_IO}, except that the external
21047 file supports wide character representations, and the internal types are
21048 @code{Wide_Character} and @code{Wide_String} instead of @code{Character}
21049 and @code{String}. The corresponding set of nested packages and child
21050 packages are defined.
21052 @item @code{Ada.Wide_Wide_Text_IO} @emph{(A.11)}
21054 This package is similar to @code{Ada.Text_IO}, except that the external
21055 file supports wide character representations, and the internal types are
21056 @code{Wide_Character} and @code{Wide_String} instead of @code{Character}
21057 and @code{String}. The corresponding set of nested packages and child
21058 packages are defined.
21061 For packages in Interfaces and System, all the RM defined packages are
21062 available in GNAT, see the Ada 2012 RM for full details.
21064 @node The Implementation of Standard I/O,The GNAT Library,Standard Library Routines,Top
21065 @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{2a0}@anchor{gnat_rm/the_implementation_of_standard_i_o id1}@anchor{2a1}
21066 @chapter The Implementation of Standard I/O
21069 GNAT implements all the required input-output facilities described in
21070 A.6 through A.14. These sections of the Ada Reference Manual describe the
21071 required behavior of these packages from the Ada point of view, and if
21072 you are writing a portable Ada program that does not need to know the
21073 exact manner in which Ada maps to the outside world when it comes to
21074 reading or writing external files, then you do not need to read this
21075 chapter. As long as your files are all regular files (not pipes or
21076 devices), and as long as you write and read the files only from Ada, the
21077 description in the Ada Reference Manual is sufficient.
21079 However, if you want to do input-output to pipes or other devices, such
21080 as the keyboard or screen, or if the files you are dealing with are
21081 either generated by some other language, or to be read by some other
21082 language, then you need to know more about the details of how the GNAT
21083 implementation of these input-output facilities behaves.
21085 In this chapter we give a detailed description of exactly how GNAT
21086 interfaces to the file system. As always, the sources of the system are
21087 available to you for answering questions at an even more detailed level,
21088 but for most purposes the information in this chapter will suffice.
21090 Another reason that you may need to know more about how input-output is
21091 implemented arises when you have a program written in mixed languages
21092 where, for example, files are shared between the C and Ada sections of
21093 the same program. GNAT provides some additional facilities, in the form
21094 of additional child library packages, that facilitate this sharing, and
21095 these additional facilities are also described in this chapter.
21098 * Standard I/O Packages::
21104 * Wide_Wide_Text_IO::
21106 * Text Translation::
21108 * Filenames encoding::
21109 * File content encoding::
21111 * Operations on C Streams::
21112 * Interfacing to C Streams::
21116 @node Standard I/O Packages,FORM Strings,,The Implementation of Standard I/O
21117 @anchor{gnat_rm/the_implementation_of_standard_i_o standard-i-o-packages}@anchor{2a2}@anchor{gnat_rm/the_implementation_of_standard_i_o id2}@anchor{2a3}
21118 @section Standard I/O Packages
21121 The Standard I/O packages described in Annex A for
21130 Ada.Text_IO.Complex_IO
21133 Ada.Text_IO.Text_Streams
21139 Ada.Wide_Text_IO.Complex_IO
21142 Ada.Wide_Text_IO.Text_Streams
21145 Ada.Wide_Wide_Text_IO
21148 Ada.Wide_Wide_Text_IO.Complex_IO
21151 Ada.Wide_Wide_Text_IO.Text_Streams
21163 are implemented using the C
21164 library streams facility; where
21170 All files are opened using @code{fopen}.
21173 All input/output operations use @code{fread}/@cite{fwrite}.
21176 There is no internal buffering of any kind at the Ada library level. The only
21177 buffering is that provided at the system level in the implementation of the
21178 library routines that support streams. This facilitates shared use of these
21179 streams by mixed language programs. Note though that system level buffering is
21180 explicitly enabled at elaboration of the standard I/O packages and that can
21181 have an impact on mixed language programs, in particular those using I/O before
21182 calling the Ada elaboration routine (e.g., adainit). It is recommended to call
21183 the Ada elaboration routine before performing any I/O or when impractical,
21184 flush the common I/O streams and in particular Standard_Output before
21185 elaborating the Ada code.
21187 @node FORM Strings,Direct_IO,Standard I/O Packages,The Implementation of Standard I/O
21188 @anchor{gnat_rm/the_implementation_of_standard_i_o form-strings}@anchor{2a4}@anchor{gnat_rm/the_implementation_of_standard_i_o id3}@anchor{2a5}
21189 @section FORM Strings
21192 The format of a FORM string in GNAT is:
21195 "keyword=value,keyword=value,...,keyword=value"
21198 where letters may be in upper or lower case, and there are no spaces
21199 between values. The order of the entries is not important. Currently
21200 the following keywords defined.
21203 TEXT_TRANSLATION=[YES|NO|TEXT|BINARY|U8TEXT|WTEXT|U16TEXT]
21205 WCEM=[n|h|u|s|e|8|b]
21206 ENCODING=[UTF8|8BITS]
21209 The use of these parameters is described later in this section. If an
21210 unrecognized keyword appears in a form string, it is silently ignored
21211 and not considered invalid.
21213 @node Direct_IO,Sequential_IO,FORM Strings,The Implementation of Standard I/O
21214 @anchor{gnat_rm/the_implementation_of_standard_i_o direct-io}@anchor{2a6}@anchor{gnat_rm/the_implementation_of_standard_i_o id4}@anchor{2a7}
21218 Direct_IO can only be instantiated for definite types. This is a
21219 restriction of the Ada language, which means that the records are fixed
21220 length (the length being determined by @code{type'Size}, rounded
21221 up to the next storage unit boundary if necessary).
21223 The records of a Direct_IO file are simply written to the file in index
21224 sequence, with the first record starting at offset zero, and subsequent
21225 records following. There is no control information of any kind. For
21226 example, if 32-bit integers are being written, each record takes
21227 4-bytes, so the record at index @code{K} starts at offset
21230 There is no limit on the size of Direct_IO files, they are expanded as
21231 necessary to accommodate whatever records are written to the file.
21233 @node Sequential_IO,Text_IO,Direct_IO,The Implementation of Standard I/O
21234 @anchor{gnat_rm/the_implementation_of_standard_i_o sequential-io}@anchor{2a8}@anchor{gnat_rm/the_implementation_of_standard_i_o id5}@anchor{2a9}
21235 @section Sequential_IO
21238 Sequential_IO may be instantiated with either a definite (constrained)
21239 or indefinite (unconstrained) type.
21241 For the definite type case, the elements written to the file are simply
21242 the memory images of the data values with no control information of any
21243 kind. The resulting file should be read using the same type, no validity
21244 checking is performed on input.
21246 For the indefinite type case, the elements written consist of two
21247 parts. First is the size of the data item, written as the memory image
21248 of a @code{Interfaces.C.size_t} value, followed by the memory image of
21249 the data value. The resulting file can only be read using the same
21250 (unconstrained) type. Normal assignment checks are performed on these
21251 read operations, and if these checks fail, @code{Data_Error} is
21252 raised. In particular, in the array case, the lengths must match, and in
21253 the variant record case, if the variable for a particular read operation
21254 is constrained, the discriminants must match.
21256 Note that it is not possible to use Sequential_IO to write variable
21257 length array items, and then read the data back into different length
21258 arrays. For example, the following will raise @code{Data_Error}:
21261 package IO is new Sequential_IO (String);
21266 IO.Write (F, "hello!")
21267 IO.Reset (F, Mode=>In_File);
21272 On some Ada implementations, this will print @code{hell}, but the program is
21273 clearly incorrect, since there is only one element in the file, and that
21274 element is the string @code{hello!}.
21276 In Ada 95 and Ada 2005, this kind of behavior can be legitimately achieved
21277 using Stream_IO, and this is the preferred mechanism. In particular, the
21278 above program fragment rewritten to use Stream_IO will work correctly.
21280 @node Text_IO,Wide_Text_IO,Sequential_IO,The Implementation of Standard I/O
21281 @anchor{gnat_rm/the_implementation_of_standard_i_o id6}@anchor{2aa}@anchor{gnat_rm/the_implementation_of_standard_i_o text-io}@anchor{2ab}
21285 Text_IO files consist of a stream of characters containing the following
21286 special control characters:
21289 LF (line feed, 16#0A#) Line Mark
21290 FF (form feed, 16#0C#) Page Mark
21293 A canonical Text_IO file is defined as one in which the following
21294 conditions are met:
21300 The character @code{LF} is used only as a line mark, i.e., to mark the end
21304 The character @code{FF} is used only as a page mark, i.e., to mark the
21305 end of a page and consequently can appear only immediately following a
21306 @code{LF} (line mark) character.
21309 The file ends with either @code{LF} (line mark) or @code{LF}-@cite{FF}
21310 (line mark, page mark). In the former case, the page mark is implicitly
21311 assumed to be present.
21314 A file written using Text_IO will be in canonical form provided that no
21315 explicit @code{LF} or @code{FF} characters are written using @code{Put}
21316 or @code{Put_Line}. There will be no @code{FF} character at the end of
21317 the file unless an explicit @code{New_Page} operation was performed
21318 before closing the file.
21320 A canonical Text_IO file that is a regular file (i.e., not a device or a
21321 pipe) can be read using any of the routines in Text_IO. The
21322 semantics in this case will be exactly as defined in the Ada Reference
21323 Manual, and all the routines in Text_IO are fully implemented.
21325 A text file that does not meet the requirements for a canonical Text_IO
21326 file has one of the following:
21332 The file contains @code{FF} characters not immediately following a
21333 @code{LF} character.
21336 The file contains @code{LF} or @code{FF} characters written by
21337 @code{Put} or @code{Put_Line}, which are not logically considered to be
21338 line marks or page marks.
21341 The file ends in a character other than @code{LF} or @code{FF},
21342 i.e., there is no explicit line mark or page mark at the end of the file.
21345 Text_IO can be used to read such non-standard text files but subprograms
21346 to do with line or page numbers do not have defined meanings. In
21347 particular, a @code{FF} character that does not follow a @code{LF}
21348 character may or may not be treated as a page mark from the point of
21349 view of page and line numbering. Every @code{LF} character is considered
21350 to end a line, and there is an implied @code{LF} character at the end of
21354 * Stream Pointer Positioning::
21355 * Reading and Writing Non-Regular Files::
21357 * Treating Text_IO Files as Streams::
21358 * Text_IO Extensions::
21359 * Text_IO Facilities for Unbounded Strings::
21363 @node Stream Pointer Positioning,Reading and Writing Non-Regular Files,,Text_IO
21364 @anchor{gnat_rm/the_implementation_of_standard_i_o id7}@anchor{2ac}@anchor{gnat_rm/the_implementation_of_standard_i_o stream-pointer-positioning}@anchor{2ad}
21365 @subsection Stream Pointer Positioning
21368 @code{Ada.Text_IO} has a definition of current position for a file that
21369 is being read. No internal buffering occurs in Text_IO, and usually the
21370 physical position in the stream used to implement the file corresponds
21371 to this logical position defined by Text_IO. There are two exceptions:
21377 After a call to @code{End_Of_Page} that returns @code{True}, the stream
21378 is positioned past the @code{LF} (line mark) that precedes the page
21379 mark. Text_IO maintains an internal flag so that subsequent read
21380 operations properly handle the logical position which is unchanged by
21381 the @code{End_Of_Page} call.
21384 After a call to @code{End_Of_File} that returns @code{True}, if the
21385 Text_IO file was positioned before the line mark at the end of file
21386 before the call, then the logical position is unchanged, but the stream
21387 is physically positioned right at the end of file (past the line mark,
21388 and past a possible page mark following the line mark. Again Text_IO
21389 maintains internal flags so that subsequent read operations properly
21390 handle the logical position.
21393 These discrepancies have no effect on the observable behavior of
21394 Text_IO, but if a single Ada stream is shared between a C program and
21395 Ada program, or shared (using @code{shared=yes} in the form string)
21396 between two Ada files, then the difference may be observable in some
21399 @node Reading and Writing Non-Regular Files,Get_Immediate,Stream Pointer Positioning,Text_IO
21400 @anchor{gnat_rm/the_implementation_of_standard_i_o reading-and-writing-non-regular-files}@anchor{2ae}@anchor{gnat_rm/the_implementation_of_standard_i_o id8}@anchor{2af}
21401 @subsection Reading and Writing Non-Regular Files
21404 A non-regular file is a device (such as a keyboard), or a pipe. Text_IO
21405 can be used for reading and writing. Writing is not affected and the
21406 sequence of characters output is identical to the normal file case, but
21407 for reading, the behavior of Text_IO is modified to avoid undesirable
21408 look-ahead as follows:
21410 An input file that is not a regular file is considered to have no page
21411 marks. Any @code{Ascii.FF} characters (the character normally used for a
21412 page mark) appearing in the file are considered to be data
21413 characters. In particular:
21419 @code{Get_Line} and @code{Skip_Line} do not test for a page mark
21420 following a line mark. If a page mark appears, it will be treated as a
21424 This avoids the need to wait for an extra character to be typed or
21425 entered from the pipe to complete one of these operations.
21428 @code{End_Of_Page} always returns @code{False}
21431 @code{End_Of_File} will return @code{False} if there is a page mark at
21432 the end of the file.
21435 Output to non-regular files is the same as for regular files. Page marks
21436 may be written to non-regular files using @code{New_Page}, but as noted
21437 above they will not be treated as page marks on input if the output is
21438 piped to another Ada program.
21440 Another important discrepancy when reading non-regular files is that the end
21441 of file indication is not 'sticky'. If an end of file is entered, e.g., by
21442 pressing the @code{EOT} key,
21444 is signaled once (i.e., the test @code{End_Of_File}
21445 will yield @code{True}, or a read will
21446 raise @code{End_Error}), but then reading can resume
21447 to read data past that end of
21448 file indication, until another end of file indication is entered.
21450 @node Get_Immediate,Treating Text_IO Files as Streams,Reading and Writing Non-Regular Files,Text_IO
21451 @anchor{gnat_rm/the_implementation_of_standard_i_o get-immediate}@anchor{2b0}@anchor{gnat_rm/the_implementation_of_standard_i_o id9}@anchor{2b1}
21452 @subsection Get_Immediate
21455 @geindex Get_Immediate
21457 Get_Immediate returns the next character (including control characters)
21458 from the input file. In particular, Get_Immediate will return LF or FF
21459 characters used as line marks or page marks. Such operations leave the
21460 file positioned past the control character, and it is thus not treated
21461 as having its normal function. This means that page, line and column
21462 counts after this kind of Get_Immediate call are set as though the mark
21463 did not occur. In the case where a Get_Immediate leaves the file
21464 positioned between the line mark and page mark (which is not normally
21465 possible), it is undefined whether the FF character will be treated as a
21468 @node Treating Text_IO Files as Streams,Text_IO Extensions,Get_Immediate,Text_IO
21469 @anchor{gnat_rm/the_implementation_of_standard_i_o id10}@anchor{2b2}@anchor{gnat_rm/the_implementation_of_standard_i_o treating-text-io-files-as-streams}@anchor{2b3}
21470 @subsection Treating Text_IO Files as Streams
21473 @geindex Stream files
21475 The package @code{Text_IO.Streams} allows a @code{Text_IO} file to be treated
21476 as a stream. Data written to a @code{Text_IO} file in this stream mode is
21477 binary data. If this binary data contains bytes 16#0A# (@code{LF}) or
21478 16#0C# (@code{FF}), the resulting file may have non-standard
21479 format. Similarly if read operations are used to read from a Text_IO
21480 file treated as a stream, then @code{LF} and @code{FF} characters may be
21481 skipped and the effect is similar to that described above for
21482 @code{Get_Immediate}.
21484 @node Text_IO Extensions,Text_IO Facilities for Unbounded Strings,Treating Text_IO Files as Streams,Text_IO
21485 @anchor{gnat_rm/the_implementation_of_standard_i_o id11}@anchor{2b4}@anchor{gnat_rm/the_implementation_of_standard_i_o text-io-extensions}@anchor{2b5}
21486 @subsection Text_IO Extensions
21489 @geindex Text_IO extensions
21491 A package GNAT.IO_Aux in the GNAT library provides some useful extensions
21492 to the standard @code{Text_IO} package:
21498 function File_Exists (Name : String) return Boolean;
21499 Determines if a file of the given name exists.
21502 function Get_Line return String;
21503 Reads a string from the standard input file. The value returned is exactly
21504 the length of the line that was read.
21507 function Get_Line (File : Ada.Text_IO.File_Type) return String;
21508 Similar, except that the parameter File specifies the file from which
21509 the string is to be read.
21512 @node Text_IO Facilities for Unbounded Strings,,Text_IO Extensions,Text_IO
21513 @anchor{gnat_rm/the_implementation_of_standard_i_o text-io-facilities-for-unbounded-strings}@anchor{2b6}@anchor{gnat_rm/the_implementation_of_standard_i_o id12}@anchor{2b7}
21514 @subsection Text_IO Facilities for Unbounded Strings
21517 @geindex Text_IO for unbounded strings
21519 @geindex Unbounded_String
21520 @geindex Text_IO operations
21522 The package @code{Ada.Strings.Unbounded.Text_IO}
21523 in library files @code{a-suteio.ads/adb} contains some GNAT-specific
21524 subprograms useful for Text_IO operations on unbounded strings:
21530 function Get_Line (File : File_Type) return Unbounded_String;
21531 Reads a line from the specified file
21532 and returns the result as an unbounded string.
21535 procedure Put (File : File_Type; U : Unbounded_String);
21536 Writes the value of the given unbounded string to the specified file
21537 Similar to the effect of
21538 @code{Put (To_String (U))} except that an extra copy is avoided.
21541 procedure Put_Line (File : File_Type; U : Unbounded_String);
21542 Writes the value of the given unbounded string to the specified file,
21543 followed by a @code{New_Line}.
21544 Similar to the effect of @code{Put_Line (To_String (U))} except
21545 that an extra copy is avoided.
21548 In the above procedures, @code{File} is of type @code{Ada.Text_IO.File_Type}
21549 and is optional. If the parameter is omitted, then the standard input or
21550 output file is referenced as appropriate.
21552 The package @code{Ada.Strings.Wide_Unbounded.Wide_Text_IO} in library
21553 files @code{a-swuwti.ads} and @code{a-swuwti.adb} provides similar extended
21554 @code{Wide_Text_IO} functionality for unbounded wide strings.
21556 The package @code{Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO} in library
21557 files @code{a-szuzti.ads} and @code{a-szuzti.adb} provides similar extended
21558 @code{Wide_Wide_Text_IO} functionality for unbounded wide wide strings.
21560 @node Wide_Text_IO,Wide_Wide_Text_IO,Text_IO,The Implementation of Standard I/O
21561 @anchor{gnat_rm/the_implementation_of_standard_i_o wide-text-io}@anchor{2b8}@anchor{gnat_rm/the_implementation_of_standard_i_o id13}@anchor{2b9}
21562 @section Wide_Text_IO
21565 @code{Wide_Text_IO} is similar in most respects to Text_IO, except that
21566 both input and output files may contain special sequences that represent
21567 wide character values. The encoding scheme for a given file may be
21568 specified using a FORM parameter:
21574 as part of the FORM string (WCEM = wide character encoding method),
21575 where @code{x} is one of the following characters
21578 @multitable {xxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxx}
21601 Upper half encoding
21638 The encoding methods match those that
21639 can be used in a source
21640 program, but there is no requirement that the encoding method used for
21641 the source program be the same as the encoding method used for files,
21642 and different files may use different encoding methods.
21644 The default encoding method for the standard files, and for opened files
21645 for which no WCEM parameter is given in the FORM string matches the
21646 wide character encoding specified for the main program (the default
21647 being brackets encoding if no coding method was specified with -gnatW).
21652 @item @emph{Hex Coding}
21654 In this encoding, a wide character is represented by a five character
21665 where @code{a}, @code{b}, @code{c}, @code{d} are the four hexadecimal
21666 characters (using upper case letters) of the wide character code. For
21667 example, ESC A345 is used to represent the wide character with code
21668 16#A345#. This scheme is compatible with use of the full
21669 @code{Wide_Character} set.
21675 @item @emph{Upper Half Coding}
21677 The wide character with encoding 16#abcd#, where the upper bit is on
21678 (i.e., a is in the range 8-F) is represented as two bytes 16#ab# and
21679 16#cd#. The second byte may never be a format control character, but is
21680 not required to be in the upper half. This method can be also used for
21681 shift-JIS or EUC where the internal coding matches the external coding.
21683 @item @emph{Shift JIS Coding}
21685 A wide character is represented by a two character sequence 16#ab# and
21686 16#cd#, with the restrictions described for upper half encoding as
21687 described above. The internal character code is the corresponding JIS
21688 character according to the standard algorithm for Shift-JIS
21689 conversion. Only characters defined in the JIS code set table can be
21690 used with this encoding method.
21692 @item @emph{EUC Coding}
21694 A wide character is represented by a two character sequence 16#ab# and
21695 16#cd#, with both characters being in the upper half. The internal
21696 character code is the corresponding JIS character according to the EUC
21697 encoding algorithm. Only characters defined in the JIS code set table
21698 can be used with this encoding method.
21700 @item @emph{UTF-8 Coding}
21702 A wide character is represented using
21703 UCS Transformation Format 8 (UTF-8) as defined in Annex R of ISO
21704 10646-1/Am.2. Depending on the character value, the representation
21705 is a one, two, or three byte sequence:
21709 16#0000#-16#007f#: 2#0xxxxxxx#
21710 16#0080#-16#07ff#: 2#110xxxxx# 2#10xxxxxx#
21711 16#0800#-16#ffff#: 2#1110xxxx# 2#10xxxxxx# 2#10xxxxxx#
21717 where the @code{xxx} bits correspond to the left-padded bits of the
21718 16-bit character value. Note that all lower half ASCII characters
21719 are represented as ASCII bytes and all upper half characters and
21720 other wide characters are represented as sequences of upper-half
21721 (The full UTF-8 scheme allows for encoding 31-bit characters as
21722 6-byte sequences, but in this implementation, all UTF-8 sequences
21723 of four or more bytes length will raise a Constraint_Error, as
21724 will all invalid UTF-8 sequences.)
21730 @item @emph{Brackets Coding}
21732 In this encoding, a wide character is represented by the following eight
21733 character sequence:
21743 where @code{a}, @code{b}, @code{c}, @code{d} are the four hexadecimal
21744 characters (using uppercase letters) of the wide character code. For
21745 example, @code{["A345"]} is used to represent the wide character with code
21747 This scheme is compatible with use of the full Wide_Character set.
21748 On input, brackets coding can also be used for upper half characters,
21749 e.g., @code{["C1"]} for lower case a. However, on output, brackets notation
21750 is only used for wide characters with a code greater than @code{16#FF#}.
21752 Note that brackets coding is not normally used in the context of
21753 Wide_Text_IO or Wide_Wide_Text_IO, since it is really just designed as
21754 a portable way of encoding source files. In the context of Wide_Text_IO
21755 or Wide_Wide_Text_IO, it can only be used if the file does not contain
21756 any instance of the left bracket character other than to encode wide
21757 character values using the brackets encoding method. In practice it is
21758 expected that some standard wide character encoding method such
21759 as UTF-8 will be used for text input output.
21761 If brackets notation is used, then any occurrence of a left bracket
21762 in the input file which is not the start of a valid wide character
21763 sequence will cause Constraint_Error to be raised. It is possible to
21764 encode a left bracket as ["5B"] and Wide_Text_IO and Wide_Wide_Text_IO
21765 input will interpret this as a left bracket.
21767 However, when a left bracket is output, it will be output as a left bracket
21768 and not as ["5B"]. We make this decision because for normal use of
21769 Wide_Text_IO for outputting messages, it is unpleasant to clobber left
21770 brackets. For example, if we write:
21773 Put_Line ("Start of output [first run]");
21776 we really do not want to have the left bracket in this message clobbered so
21777 that the output reads:
21781 Start of output ["5B"]first run]
21787 In practice brackets encoding is reasonably useful for normal Put_Line use
21788 since we won't get confused between left brackets and wide character
21789 sequences in the output. But for input, or when files are written out
21790 and read back in, it really makes better sense to use one of the standard
21791 encoding methods such as UTF-8.
21794 For the coding schemes other than UTF-8, Hex, or Brackets encoding,
21795 not all wide character
21796 values can be represented. An attempt to output a character that cannot
21797 be represented using the encoding scheme for the file causes
21798 Constraint_Error to be raised. An invalid wide character sequence on
21799 input also causes Constraint_Error to be raised.
21802 * Stream Pointer Positioning: Stream Pointer Positioning<2>.
21803 * Reading and Writing Non-Regular Files: Reading and Writing Non-Regular Files<2>.
21807 @node Stream Pointer Positioning<2>,Reading and Writing Non-Regular Files<2>,,Wide_Text_IO
21808 @anchor{gnat_rm/the_implementation_of_standard_i_o stream-pointer-positioning-1}@anchor{2ba}@anchor{gnat_rm/the_implementation_of_standard_i_o id14}@anchor{2bb}
21809 @subsection Stream Pointer Positioning
21812 @code{Ada.Wide_Text_IO} is similar to @code{Ada.Text_IO} in its handling
21813 of stream pointer positioning (@ref{2ab,,Text_IO}). There is one additional
21816 If @code{Ada.Wide_Text_IO.Look_Ahead} reads a character outside the
21817 normal lower ASCII set (i.e., a character in the range:
21820 Wide_Character'Val (16#0080#) .. Wide_Character'Val (16#FFFF#)
21823 then although the logical position of the file pointer is unchanged by
21824 the @code{Look_Ahead} call, the stream is physically positioned past the
21825 wide character sequence. Again this is to avoid the need for buffering
21826 or backup, and all @code{Wide_Text_IO} routines check the internal
21827 indication that this situation has occurred so that this is not visible
21828 to a normal program using @code{Wide_Text_IO}. However, this discrepancy
21829 can be observed if the wide text file shares a stream with another file.
21831 @node Reading and Writing Non-Regular Files<2>,,Stream Pointer Positioning<2>,Wide_Text_IO
21832 @anchor{gnat_rm/the_implementation_of_standard_i_o reading-and-writing-non-regular-files-1}@anchor{2bc}@anchor{gnat_rm/the_implementation_of_standard_i_o id15}@anchor{2bd}
21833 @subsection Reading and Writing Non-Regular Files
21836 As in the case of Text_IO, when a non-regular file is read, it is
21837 assumed that the file contains no page marks (any form characters are
21838 treated as data characters), and @code{End_Of_Page} always returns
21839 @code{False}. Similarly, the end of file indication is not sticky, so
21840 it is possible to read beyond an end of file.
21842 @node Wide_Wide_Text_IO,Stream_IO,Wide_Text_IO,The Implementation of Standard I/O
21843 @anchor{gnat_rm/the_implementation_of_standard_i_o id16}@anchor{2be}@anchor{gnat_rm/the_implementation_of_standard_i_o wide-wide-text-io}@anchor{2bf}
21844 @section Wide_Wide_Text_IO
21847 @code{Wide_Wide_Text_IO} is similar in most respects to Text_IO, except that
21848 both input and output files may contain special sequences that represent
21849 wide wide character values. The encoding scheme for a given file may be
21850 specified using a FORM parameter:
21856 as part of the FORM string (WCEM = wide character encoding method),
21857 where @code{x} is one of the following characters
21860 @multitable {xxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxx}
21883 Upper half encoding
21920 The encoding methods match those that
21921 can be used in a source
21922 program, but there is no requirement that the encoding method used for
21923 the source program be the same as the encoding method used for files,
21924 and different files may use different encoding methods.
21926 The default encoding method for the standard files, and for opened files
21927 for which no WCEM parameter is given in the FORM string matches the
21928 wide character encoding specified for the main program (the default
21929 being brackets encoding if no coding method was specified with -gnatW).
21934 @item @emph{UTF-8 Coding}
21936 A wide character is represented using
21937 UCS Transformation Format 8 (UTF-8) as defined in Annex R of ISO
21938 10646-1/Am.2. Depending on the character value, the representation
21939 is a one, two, three, or four byte sequence:
21943 16#000000#-16#00007f#: 2#0xxxxxxx#
21944 16#000080#-16#0007ff#: 2#110xxxxx# 2#10xxxxxx#
21945 16#000800#-16#00ffff#: 2#1110xxxx# 2#10xxxxxx# 2#10xxxxxx#
21946 16#010000#-16#10ffff#: 2#11110xxx# 2#10xxxxxx# 2#10xxxxxx# 2#10xxxxxx#
21952 where the @code{xxx} bits correspond to the left-padded bits of the
21953 21-bit character value. Note that all lower half ASCII characters
21954 are represented as ASCII bytes and all upper half characters and
21955 other wide characters are represented as sequences of upper-half
21962 @item @emph{Brackets Coding}
21964 In this encoding, a wide wide character is represented by the following eight
21965 character sequence if is in wide character range
21975 and by the following ten character sequence if not
21979 [ " a b c d e f " ]
21985 where @code{a}, @code{b}, @code{c}, @code{d}, @code{e}, and @code{f}
21986 are the four or six hexadecimal
21987 characters (using uppercase letters) of the wide wide character code. For
21988 example, @code{["01A345"]} is used to represent the wide wide character
21989 with code @code{16#01A345#}.
21991 This scheme is compatible with use of the full Wide_Wide_Character set.
21992 On input, brackets coding can also be used for upper half characters,
21993 e.g., @code{["C1"]} for lower case a. However, on output, brackets notation
21994 is only used for wide characters with a code greater than @code{16#FF#}.
21997 If is also possible to use the other Wide_Character encoding methods,
21998 such as Shift-JIS, but the other schemes cannot support the full range
21999 of wide wide characters.
22000 An attempt to output a character that cannot
22001 be represented using the encoding scheme for the file causes
22002 Constraint_Error to be raised. An invalid wide character sequence on
22003 input also causes Constraint_Error to be raised.
22006 * Stream Pointer Positioning: Stream Pointer Positioning<3>.
22007 * Reading and Writing Non-Regular Files: Reading and Writing Non-Regular Files<3>.
22011 @node Stream Pointer Positioning<3>,Reading and Writing Non-Regular Files<3>,,Wide_Wide_Text_IO
22012 @anchor{gnat_rm/the_implementation_of_standard_i_o stream-pointer-positioning-2}@anchor{2c0}@anchor{gnat_rm/the_implementation_of_standard_i_o id17}@anchor{2c1}
22013 @subsection Stream Pointer Positioning
22016 @code{Ada.Wide_Wide_Text_IO} is similar to @code{Ada.Text_IO} in its handling
22017 of stream pointer positioning (@ref{2ab,,Text_IO}). There is one additional
22020 If @code{Ada.Wide_Wide_Text_IO.Look_Ahead} reads a character outside the
22021 normal lower ASCII set (i.e., a character in the range:
22024 Wide_Wide_Character'Val (16#0080#) .. Wide_Wide_Character'Val (16#10FFFF#)
22027 then although the logical position of the file pointer is unchanged by
22028 the @code{Look_Ahead} call, the stream is physically positioned past the
22029 wide character sequence. Again this is to avoid the need for buffering
22030 or backup, and all @code{Wide_Wide_Text_IO} routines check the internal
22031 indication that this situation has occurred so that this is not visible
22032 to a normal program using @code{Wide_Wide_Text_IO}. However, this discrepancy
22033 can be observed if the wide text file shares a stream with another file.
22035 @node Reading and Writing Non-Regular Files<3>,,Stream Pointer Positioning<3>,Wide_Wide_Text_IO
22036 @anchor{gnat_rm/the_implementation_of_standard_i_o id18}@anchor{2c2}@anchor{gnat_rm/the_implementation_of_standard_i_o reading-and-writing-non-regular-files-2}@anchor{2c3}
22037 @subsection Reading and Writing Non-Regular Files
22040 As in the case of Text_IO, when a non-regular file is read, it is
22041 assumed that the file contains no page marks (any form characters are
22042 treated as data characters), and @code{End_Of_Page} always returns
22043 @code{False}. Similarly, the end of file indication is not sticky, so
22044 it is possible to read beyond an end of file.
22046 @node Stream_IO,Text Translation,Wide_Wide_Text_IO,The Implementation of Standard I/O
22047 @anchor{gnat_rm/the_implementation_of_standard_i_o id19}@anchor{2c4}@anchor{gnat_rm/the_implementation_of_standard_i_o stream-io}@anchor{2c5}
22051 A stream file is a sequence of bytes, where individual elements are
22052 written to the file as described in the Ada Reference Manual. The type
22053 @code{Stream_Element} is simply a byte. There are two ways to read or
22054 write a stream file.
22060 The operations @code{Read} and @code{Write} directly read or write a
22061 sequence of stream elements with no control information.
22064 The stream attributes applied to a stream file transfer data in the
22065 manner described for stream attributes.
22068 @node Text Translation,Shared Files,Stream_IO,The Implementation of Standard I/O
22069 @anchor{gnat_rm/the_implementation_of_standard_i_o id20}@anchor{2c6}@anchor{gnat_rm/the_implementation_of_standard_i_o text-translation}@anchor{2c7}
22070 @section Text Translation
22073 @code{Text_Translation=xxx} may be used as the Form parameter
22074 passed to Text_IO.Create and Text_IO.Open. @code{Text_Translation=xxx}
22075 has no effect on Unix systems. Possible values are:
22081 @code{Yes} or @code{Text} is the default, which means to
22082 translate LF to/from CR/LF on Windows systems.
22084 @code{No} disables this translation; i.e. it
22085 uses binary mode. For output files, @code{Text_Translation=No}
22086 may be used to create Unix-style files on
22090 @code{wtext} translation enabled in Unicode mode.
22091 (corresponds to _O_WTEXT).
22094 @code{u8text} translation enabled in Unicode UTF-8 mode.
22095 (corresponds to O_U8TEXT).
22098 @code{u16text} translation enabled in Unicode UTF-16
22099 mode. (corresponds to_O_U16TEXT).
22102 @node Shared Files,Filenames encoding,Text Translation,The Implementation of Standard I/O
22103 @anchor{gnat_rm/the_implementation_of_standard_i_o id21}@anchor{2c8}@anchor{gnat_rm/the_implementation_of_standard_i_o shared-files}@anchor{2c9}
22104 @section Shared Files
22107 Section A.14 of the Ada Reference Manual allows implementations to
22108 provide a wide variety of behavior if an attempt is made to access the
22109 same external file with two or more internal files.
22111 To provide a full range of functionality, while at the same time
22112 minimizing the problems of portability caused by this implementation
22113 dependence, GNAT handles file sharing as follows:
22119 In the absence of a @code{shared=xxx} form parameter, an attempt
22120 to open two or more files with the same full name is considered an error
22121 and is not supported. The exception @code{Use_Error} will be
22122 raised. Note that a file that is not explicitly closed by the program
22123 remains open until the program terminates.
22126 If the form parameter @code{shared=no} appears in the form string, the
22127 file can be opened or created with its own separate stream identifier,
22128 regardless of whether other files sharing the same external file are
22129 opened. The exact effect depends on how the C stream routines handle
22130 multiple accesses to the same external files using separate streams.
22133 If the form parameter @code{shared=yes} appears in the form string for
22134 each of two or more files opened using the same full name, the same
22135 stream is shared between these files, and the semantics are as described
22136 in Ada Reference Manual, Section A.14.
22139 When a program that opens multiple files with the same name is ported
22140 from another Ada compiler to GNAT, the effect will be that
22141 @code{Use_Error} is raised.
22143 The documentation of the original compiler and the documentation of the
22144 program should then be examined to determine if file sharing was
22145 expected, and @code{shared=xxx} parameters added to @code{Open}
22146 and @code{Create} calls as required.
22148 When a program is ported from GNAT to some other Ada compiler, no
22149 special attention is required unless the @code{shared=xxx} form
22150 parameter is used in the program. In this case, you must examine the
22151 documentation of the new compiler to see if it supports the required
22152 file sharing semantics, and form strings modified appropriately. Of
22153 course it may be the case that the program cannot be ported if the
22154 target compiler does not support the required functionality. The best
22155 approach in writing portable code is to avoid file sharing (and hence
22156 the use of the @code{shared=xxx} parameter in the form string)
22159 One common use of file sharing in Ada 83 is the use of instantiations of
22160 Sequential_IO on the same file with different types, to achieve
22161 heterogeneous input-output. Although this approach will work in GNAT if
22162 @code{shared=yes} is specified, it is preferable in Ada to use Stream_IO
22163 for this purpose (using the stream attributes)
22165 @node Filenames encoding,File content encoding,Shared Files,The Implementation of Standard I/O
22166 @anchor{gnat_rm/the_implementation_of_standard_i_o filenames-encoding}@anchor{2ca}@anchor{gnat_rm/the_implementation_of_standard_i_o id22}@anchor{2cb}
22167 @section Filenames encoding
22170 An encoding form parameter can be used to specify the filename
22171 encoding @code{encoding=xxx}.
22177 If the form parameter @code{encoding=utf8} appears in the form string, the
22178 filename must be encoded in UTF-8.
22181 If the form parameter @code{encoding=8bits} appears in the form
22182 string, the filename must be a standard 8bits string.
22185 In the absence of a @code{encoding=xxx} form parameter, the
22186 encoding is controlled by the @code{GNAT_CODE_PAGE} environment
22187 variable. And if not set @code{utf8} is assumed.
22192 @item @emph{CP_ACP}
22194 The current system Windows ANSI code page.
22196 @item @emph{CP_UTF8}
22201 This encoding form parameter is only supported on the Windows
22202 platform. On the other Operating Systems the run-time is supporting
22205 @node File content encoding,Open Modes,Filenames encoding,The Implementation of Standard I/O
22206 @anchor{gnat_rm/the_implementation_of_standard_i_o file-content-encoding}@anchor{2cc}@anchor{gnat_rm/the_implementation_of_standard_i_o id23}@anchor{2cd}
22207 @section File content encoding
22210 For text files it is possible to specify the encoding to use. This is
22211 controlled by the by the @code{GNAT_CCS_ENCODING} environment
22212 variable. And if not set @code{TEXT} is assumed.
22214 The possible values are those supported on Windows:
22221 Translated text mode
22225 Translated unicode encoding
22227 @item @emph{U16TEXT}
22229 Unicode 16-bit encoding
22231 @item @emph{U8TEXT}
22233 Unicode 8-bit encoding
22236 This encoding is only supported on the Windows platform.
22238 @node Open Modes,Operations on C Streams,File content encoding,The Implementation of Standard I/O
22239 @anchor{gnat_rm/the_implementation_of_standard_i_o open-modes}@anchor{2ce}@anchor{gnat_rm/the_implementation_of_standard_i_o id24}@anchor{2cf}
22240 @section Open Modes
22243 @code{Open} and @code{Create} calls result in a call to @code{fopen}
22244 using the mode shown in the following table:
22247 @multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxx}
22250 @code{Open} and @code{Create} Call Modes
22292 Out_File (Direct_IO)
22304 Out_File (all other cases)
22329 If text file translation is required, then either @code{b} or @code{t}
22330 is added to the mode, depending on the setting of Text. Text file
22331 translation refers to the mapping of CR/LF sequences in an external file
22332 to LF characters internally. This mapping only occurs in DOS and
22333 DOS-like systems, and is not relevant to other systems.
22335 A special case occurs with Stream_IO. As shown in the above table, the
22336 file is initially opened in @code{r} or @code{w} mode for the
22337 @code{In_File} and @code{Out_File} cases. If a @code{Set_Mode} operation
22338 subsequently requires switching from reading to writing or vice-versa,
22339 then the file is reopened in @code{r+} mode to permit the required operation.
22341 @node Operations on C Streams,Interfacing to C Streams,Open Modes,The Implementation of Standard I/O
22342 @anchor{gnat_rm/the_implementation_of_standard_i_o operations-on-c-streams}@anchor{2d0}@anchor{gnat_rm/the_implementation_of_standard_i_o id25}@anchor{2d1}
22343 @section Operations on C Streams
22346 The package @code{Interfaces.C_Streams} provides an Ada program with direct
22347 access to the C library functions for operations on C streams:
22350 package Interfaces.C_Streams is
22351 -- Note: the reason we do not use the types that are in
22352 -- Interfaces.C is that we want to avoid dragging in the
22353 -- code in this unit if possible.
22354 subtype chars is System.Address;
22355 -- Pointer to null-terminated array of characters
22356 subtype FILEs is System.Address;
22357 -- Corresponds to the C type FILE*
22358 subtype voids is System.Address;
22359 -- Corresponds to the C type void*
22360 subtype int is Integer;
22361 subtype long is Long_Integer;
22362 -- Note: the above types are subtypes deliberately, and it
22363 -- is part of this spec that the above correspondences are
22364 -- guaranteed. This means that it is legitimate to, for
22365 -- example, use Integer instead of int. We provide these
22366 -- synonyms for clarity, but in some cases it may be
22367 -- convenient to use the underlying types (for example to
22368 -- avoid an unnecessary dependency of a spec on the spec
22370 type size_t is mod 2 ** Standard'Address_Size;
22371 NULL_Stream : constant FILEs;
22372 -- Value returned (NULL in C) to indicate an
22373 -- fdopen/fopen/tmpfile error
22374 ----------------------------------
22375 -- Constants Defined in stdio.h --
22376 ----------------------------------
22377 EOF : constant int;
22378 -- Used by a number of routines to indicate error or
22380 IOFBF : constant int;
22381 IOLBF : constant int;
22382 IONBF : constant int;
22383 -- Used to indicate buffering mode for setvbuf call
22384 SEEK_CUR : constant int;
22385 SEEK_END : constant int;
22386 SEEK_SET : constant int;
22387 -- Used to indicate origin for fseek call
22388 function stdin return FILEs;
22389 function stdout return FILEs;
22390 function stderr return FILEs;
22391 -- Streams associated with standard files
22392 --------------------------
22393 -- Standard C functions --
22394 --------------------------
22395 -- The functions selected below are ones that are
22396 -- available in UNIX (but not necessarily in ANSI C).
22397 -- These are very thin interfaces
22398 -- which copy exactly the C headers. For more
22399 -- documentation on these functions, see the Microsoft C
22400 -- "Run-Time Library Reference" (Microsoft Press, 1990,
22401 -- ISBN 1-55615-225-6), which includes useful information
22402 -- on system compatibility.
22403 procedure clearerr (stream : FILEs);
22404 function fclose (stream : FILEs) return int;
22405 function fdopen (handle : int; mode : chars) return FILEs;
22406 function feof (stream : FILEs) return int;
22407 function ferror (stream : FILEs) return int;
22408 function fflush (stream : FILEs) return int;
22409 function fgetc (stream : FILEs) return int;
22410 function fgets (strng : chars; n : int; stream : FILEs)
22412 function fileno (stream : FILEs) return int;
22413 function fopen (filename : chars; Mode : chars)
22415 -- Note: to maintain target independence, use
22416 -- text_translation_required, a boolean variable defined in
22417 -- a-sysdep.c to deal with the target dependent text
22418 -- translation requirement. If this variable is set,
22419 -- then b/t should be appended to the standard mode
22420 -- argument to set the text translation mode off or on
22422 function fputc (C : int; stream : FILEs) return int;
22423 function fputs (Strng : chars; Stream : FILEs) return int;
22440 function ftell (stream : FILEs) return long;
22447 function isatty (handle : int) return int;
22448 procedure mktemp (template : chars);
22449 -- The return value (which is just a pointer to template)
22451 procedure rewind (stream : FILEs);
22452 function rmtmp return int;
22460 function tmpfile return FILEs;
22461 function ungetc (c : int; stream : FILEs) return int;
22462 function unlink (filename : chars) return int;
22463 ---------------------
22464 -- Extra functions --
22465 ---------------------
22466 -- These functions supply slightly thicker bindings than
22467 -- those above. They are derived from functions in the
22468 -- C Run-Time Library, but may do a bit more work than
22469 -- just directly calling one of the Library functions.
22470 function is_regular_file (handle : int) return int;
22471 -- Tests if given handle is for a regular file (result 1)
22472 -- or for a non-regular file (pipe or device, result 0).
22473 ---------------------------------
22474 -- Control of Text/Binary Mode --
22475 ---------------------------------
22476 -- If text_translation_required is true, then the following
22477 -- functions may be used to dynamically switch a file from
22478 -- binary to text mode or vice versa. These functions have
22479 -- no effect if text_translation_required is false (i.e., in
22480 -- normal UNIX mode). Use fileno to get a stream handle.
22481 procedure set_binary_mode (handle : int);
22482 procedure set_text_mode (handle : int);
22483 ----------------------------
22484 -- Full Path Name support --
22485 ----------------------------
22486 procedure full_name (nam : chars; buffer : chars);
22487 -- Given a NUL terminated string representing a file
22488 -- name, returns in buffer a NUL terminated string
22489 -- representing the full path name for the file name.
22490 -- On systems where it is relevant the drive is also
22491 -- part of the full path name. It is the responsibility
22492 -- of the caller to pass an actual parameter for buffer
22493 -- that is big enough for any full path name. Use
22494 -- max_path_len given below as the size of buffer.
22495 max_path_len : integer;
22496 -- Maximum length of an allowable full path name on the
22497 -- system, including a terminating NUL character.
22498 end Interfaces.C_Streams;
22501 @node Interfacing to C Streams,,Operations on C Streams,The Implementation of Standard I/O
22502 @anchor{gnat_rm/the_implementation_of_standard_i_o interfacing-to-c-streams}@anchor{2d2}@anchor{gnat_rm/the_implementation_of_standard_i_o id26}@anchor{2d3}
22503 @section Interfacing to C Streams
22506 The packages in this section permit interfacing Ada files to C Stream
22510 with Interfaces.C_Streams;
22511 package Ada.Sequential_IO.C_Streams is
22512 function C_Stream (F : File_Type)
22513 return Interfaces.C_Streams.FILEs;
22515 (File : in out File_Type;
22516 Mode : in File_Mode;
22517 C_Stream : in Interfaces.C_Streams.FILEs;
22518 Form : in String := "");
22519 end Ada.Sequential_IO.C_Streams;
22521 with Interfaces.C_Streams;
22522 package Ada.Direct_IO.C_Streams is
22523 function C_Stream (F : File_Type)
22524 return Interfaces.C_Streams.FILEs;
22526 (File : in out File_Type;
22527 Mode : in File_Mode;
22528 C_Stream : in Interfaces.C_Streams.FILEs;
22529 Form : in String := "");
22530 end Ada.Direct_IO.C_Streams;
22532 with Interfaces.C_Streams;
22533 package Ada.Text_IO.C_Streams is
22534 function C_Stream (F : File_Type)
22535 return Interfaces.C_Streams.FILEs;
22537 (File : in out File_Type;
22538 Mode : in File_Mode;
22539 C_Stream : in Interfaces.C_Streams.FILEs;
22540 Form : in String := "");
22541 end Ada.Text_IO.C_Streams;
22543 with Interfaces.C_Streams;
22544 package Ada.Wide_Text_IO.C_Streams is
22545 function C_Stream (F : File_Type)
22546 return Interfaces.C_Streams.FILEs;
22548 (File : in out File_Type;
22549 Mode : in File_Mode;
22550 C_Stream : in Interfaces.C_Streams.FILEs;
22551 Form : in String := "");
22552 end Ada.Wide_Text_IO.C_Streams;
22554 with Interfaces.C_Streams;
22555 package Ada.Wide_Wide_Text_IO.C_Streams is
22556 function C_Stream (F : File_Type)
22557 return Interfaces.C_Streams.FILEs;
22559 (File : in out File_Type;
22560 Mode : in File_Mode;
22561 C_Stream : in Interfaces.C_Streams.FILEs;
22562 Form : in String := "");
22563 end Ada.Wide_Wide_Text_IO.C_Streams;
22565 with Interfaces.C_Streams;
22566 package Ada.Stream_IO.C_Streams is
22567 function C_Stream (F : File_Type)
22568 return Interfaces.C_Streams.FILEs;
22570 (File : in out File_Type;
22571 Mode : in File_Mode;
22572 C_Stream : in Interfaces.C_Streams.FILEs;
22573 Form : in String := "");
22574 end Ada.Stream_IO.C_Streams;
22577 In each of these six packages, the @code{C_Stream} function obtains the
22578 @code{FILE} pointer from a currently opened Ada file. It is then
22579 possible to use the @code{Interfaces.C_Streams} package to operate on
22580 this stream, or the stream can be passed to a C program which can
22581 operate on it directly. Of course the program is responsible for
22582 ensuring that only appropriate sequences of operations are executed.
22584 One particular use of relevance to an Ada program is that the
22585 @code{setvbuf} function can be used to control the buffering of the
22586 stream used by an Ada file. In the absence of such a call the standard
22587 default buffering is used.
22589 The @code{Open} procedures in these packages open a file giving an
22590 existing C Stream instead of a file name. Typically this stream is
22591 imported from a C program, allowing an Ada file to operate on an
22594 @node The GNAT Library,Interfacing to Other Languages,The Implementation of Standard I/O,Top
22595 @anchor{gnat_rm/the_gnat_library the-gnat-library}@anchor{10}@anchor{gnat_rm/the_gnat_library doc}@anchor{2d4}@anchor{gnat_rm/the_gnat_library id1}@anchor{2d5}
22596 @chapter The GNAT Library
22599 The GNAT library contains a number of general and special purpose packages.
22600 It represents functionality that the GNAT developers have found useful, and
22601 which is made available to GNAT users. The packages described here are fully
22602 supported, and upwards compatibility will be maintained in future releases,
22603 so you can use these facilities with the confidence that the same functionality
22604 will be available in future releases.
22606 The chapter here simply gives a brief summary of the facilities available.
22607 The full documentation is found in the spec file for the package. The full
22608 sources of these library packages, including both spec and body, are provided
22609 with all GNAT releases. For example, to find out the full specifications of
22610 the SPITBOL pattern matching capability, including a full tutorial and
22611 extensive examples, look in the @code{g-spipat.ads} file in the library.
22613 For each entry here, the package name (as it would appear in a @code{with}
22614 clause) is given, followed by the name of the corresponding spec file in
22615 parentheses. The packages are children in four hierarchies, @code{Ada},
22616 @code{Interfaces}, @code{System}, and @code{GNAT}, the latter being a
22617 GNAT-specific hierarchy.
22619 Note that an application program should only use packages in one of these
22620 four hierarchies if the package is defined in the Ada Reference Manual,
22621 or is listed in this section of the GNAT Programmers Reference Manual.
22622 All other units should be considered internal implementation units and
22623 should not be directly @code{with}ed by application code. The use of
22624 a @code{with} clause that references one of these internal implementation
22625 units makes an application potentially dependent on changes in versions
22626 of GNAT, and will generate a warning message.
22629 * Ada.Characters.Latin_9 (a-chlat9.ads): Ada Characters Latin_9 a-chlat9 ads.
22630 * Ada.Characters.Wide_Latin_1 (a-cwila1.ads): Ada Characters Wide_Latin_1 a-cwila1 ads.
22631 * Ada.Characters.Wide_Latin_9 (a-cwila1.ads): Ada Characters Wide_Latin_9 a-cwila1 ads.
22632 * Ada.Characters.Wide_Wide_Latin_1 (a-chzla1.ads): Ada Characters Wide_Wide_Latin_1 a-chzla1 ads.
22633 * Ada.Characters.Wide_Wide_Latin_9 (a-chzla9.ads): Ada Characters Wide_Wide_Latin_9 a-chzla9 ads.
22634 * Ada.Containers.Formal_Doubly_Linked_Lists (a-cfdlli.ads): Ada Containers Formal_Doubly_Linked_Lists a-cfdlli ads.
22635 * Ada.Containers.Formal_Hashed_Maps (a-cfhama.ads): Ada Containers Formal_Hashed_Maps a-cfhama ads.
22636 * Ada.Containers.Formal_Hashed_Sets (a-cfhase.ads): Ada Containers Formal_Hashed_Sets a-cfhase ads.
22637 * Ada.Containers.Formal_Ordered_Maps (a-cforma.ads): Ada Containers Formal_Ordered_Maps a-cforma ads.
22638 * Ada.Containers.Formal_Ordered_Sets (a-cforse.ads): Ada Containers Formal_Ordered_Sets a-cforse ads.
22639 * Ada.Containers.Formal_Vectors (a-cofove.ads): Ada Containers Formal_Vectors a-cofove ads.
22640 * Ada.Containers.Formal_Indefinite_Vectors (a-cfinve.ads): Ada Containers Formal_Indefinite_Vectors a-cfinve ads.
22641 * Ada.Containers.Functional_Vectors (a-cofuve.ads): Ada Containers Functional_Vectors a-cofuve ads.
22642 * Ada.Containers.Functional_Sets (a-cofuse.ads): Ada Containers Functional_Sets a-cofuse ads.
22643 * Ada.Containers.Functional_Maps (a-cofuma.ads): Ada Containers Functional_Maps a-cofuma ads.
22644 * Ada.Containers.Bounded_Holders (a-coboho.ads): Ada Containers Bounded_Holders a-coboho ads.
22645 * Ada.Command_Line.Environment (a-colien.ads): Ada Command_Line Environment a-colien ads.
22646 * Ada.Command_Line.Remove (a-colire.ads): Ada Command_Line Remove a-colire ads.
22647 * Ada.Command_Line.Response_File (a-clrefi.ads): Ada Command_Line Response_File a-clrefi ads.
22648 * Ada.Direct_IO.C_Streams (a-diocst.ads): Ada Direct_IO C_Streams a-diocst ads.
22649 * Ada.Exceptions.Is_Null_Occurrence (a-einuoc.ads): Ada Exceptions Is_Null_Occurrence a-einuoc ads.
22650 * Ada.Exceptions.Last_Chance_Handler (a-elchha.ads): Ada Exceptions Last_Chance_Handler a-elchha ads.
22651 * Ada.Exceptions.Traceback (a-exctra.ads): Ada Exceptions Traceback a-exctra ads.
22652 * Ada.Sequential_IO.C_Streams (a-siocst.ads): Ada Sequential_IO C_Streams a-siocst ads.
22653 * Ada.Streams.Stream_IO.C_Streams (a-ssicst.ads): Ada Streams Stream_IO C_Streams a-ssicst ads.
22654 * Ada.Strings.Unbounded.Text_IO (a-suteio.ads): Ada Strings Unbounded Text_IO a-suteio ads.
22655 * Ada.Strings.Wide_Unbounded.Wide_Text_IO (a-swuwti.ads): Ada Strings Wide_Unbounded Wide_Text_IO a-swuwti ads.
22656 * Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO (a-szuzti.ads): Ada Strings Wide_Wide_Unbounded Wide_Wide_Text_IO a-szuzti ads.
22657 * Ada.Task_Initialization (a-tasini.ads): Ada Task_Initialization a-tasini ads.
22658 * Ada.Text_IO.C_Streams (a-tiocst.ads): Ada Text_IO C_Streams a-tiocst ads.
22659 * Ada.Text_IO.Reset_Standard_Files (a-tirsfi.ads): Ada Text_IO Reset_Standard_Files a-tirsfi ads.
22660 * Ada.Wide_Characters.Unicode (a-wichun.ads): Ada Wide_Characters Unicode a-wichun ads.
22661 * Ada.Wide_Text_IO.C_Streams (a-wtcstr.ads): Ada Wide_Text_IO C_Streams a-wtcstr ads.
22662 * Ada.Wide_Text_IO.Reset_Standard_Files (a-wrstfi.ads): Ada Wide_Text_IO Reset_Standard_Files a-wrstfi ads.
22663 * Ada.Wide_Wide_Characters.Unicode (a-zchuni.ads): Ada Wide_Wide_Characters Unicode a-zchuni ads.
22664 * Ada.Wide_Wide_Text_IO.C_Streams (a-ztcstr.ads): Ada Wide_Wide_Text_IO C_Streams a-ztcstr ads.
22665 * Ada.Wide_Wide_Text_IO.Reset_Standard_Files (a-zrstfi.ads): Ada Wide_Wide_Text_IO Reset_Standard_Files a-zrstfi ads.
22666 * GNAT.Altivec (g-altive.ads): GNAT Altivec g-altive ads.
22667 * GNAT.Altivec.Conversions (g-altcon.ads): GNAT Altivec Conversions g-altcon ads.
22668 * GNAT.Altivec.Vector_Operations (g-alveop.ads): GNAT Altivec Vector_Operations g-alveop ads.
22669 * GNAT.Altivec.Vector_Types (g-alvety.ads): GNAT Altivec Vector_Types g-alvety ads.
22670 * GNAT.Altivec.Vector_Views (g-alvevi.ads): GNAT Altivec Vector_Views g-alvevi ads.
22671 * GNAT.Array_Split (g-arrspl.ads): GNAT Array_Split g-arrspl ads.
22672 * GNAT.AWK (g-awk.ads): GNAT AWK g-awk ads.
22673 * GNAT.Bind_Environment (g-binenv.ads): GNAT Bind_Environment g-binenv ads.
22674 * GNAT.Branch_Prediction (g-brapre.ads): GNAT Branch_Prediction g-brapre ads.
22675 * GNAT.Bounded_Buffers (g-boubuf.ads): GNAT Bounded_Buffers g-boubuf ads.
22676 * GNAT.Bounded_Mailboxes (g-boumai.ads): GNAT Bounded_Mailboxes g-boumai ads.
22677 * GNAT.Bubble_Sort (g-bubsor.ads): GNAT Bubble_Sort g-bubsor ads.
22678 * GNAT.Bubble_Sort_A (g-busora.ads): GNAT Bubble_Sort_A g-busora ads.
22679 * GNAT.Bubble_Sort_G (g-busorg.ads): GNAT Bubble_Sort_G g-busorg ads.
22680 * GNAT.Byte_Order_Mark (g-byorma.ads): GNAT Byte_Order_Mark g-byorma ads.
22681 * GNAT.Byte_Swapping (g-bytswa.ads): GNAT Byte_Swapping g-bytswa ads.
22682 * GNAT.Calendar (g-calend.ads): GNAT Calendar g-calend ads.
22683 * GNAT.Calendar.Time_IO (g-catiio.ads): GNAT Calendar Time_IO g-catiio ads.
22684 * GNAT.CRC32 (g-crc32.ads): GNAT CRC32 g-crc32 ads.
22685 * GNAT.Case_Util (g-casuti.ads): GNAT Case_Util g-casuti ads.
22686 * GNAT.CGI (g-cgi.ads): GNAT CGI g-cgi ads.
22687 * GNAT.CGI.Cookie (g-cgicoo.ads): GNAT CGI Cookie g-cgicoo ads.
22688 * GNAT.CGI.Debug (g-cgideb.ads): GNAT CGI Debug g-cgideb ads.
22689 * GNAT.Command_Line (g-comlin.ads): GNAT Command_Line g-comlin ads.
22690 * GNAT.Compiler_Version (g-comver.ads): GNAT Compiler_Version g-comver ads.
22691 * GNAT.Ctrl_C (g-ctrl_c.ads): GNAT Ctrl_C g-ctrl_c ads.
22692 * GNAT.Current_Exception (g-curexc.ads): GNAT Current_Exception g-curexc ads.
22693 * GNAT.Debug_Pools (g-debpoo.ads): GNAT Debug_Pools g-debpoo ads.
22694 * GNAT.Debug_Utilities (g-debuti.ads): GNAT Debug_Utilities g-debuti ads.
22695 * GNAT.Decode_String (g-decstr.ads): GNAT Decode_String g-decstr ads.
22696 * GNAT.Decode_UTF8_String (g-deutst.ads): GNAT Decode_UTF8_String g-deutst ads.
22697 * GNAT.Directory_Operations (g-dirope.ads): GNAT Directory_Operations g-dirope ads.
22698 * GNAT.Directory_Operations.Iteration (g-diopit.ads): GNAT Directory_Operations Iteration g-diopit ads.
22699 * GNAT.Dynamic_HTables (g-dynhta.ads): GNAT Dynamic_HTables g-dynhta ads.
22700 * GNAT.Dynamic_Tables (g-dyntab.ads): GNAT Dynamic_Tables g-dyntab ads.
22701 * GNAT.Encode_String (g-encstr.ads): GNAT Encode_String g-encstr ads.
22702 * GNAT.Encode_UTF8_String (g-enutst.ads): GNAT Encode_UTF8_String g-enutst ads.
22703 * GNAT.Exception_Actions (g-excact.ads): GNAT Exception_Actions g-excact ads.
22704 * GNAT.Exception_Traces (g-exctra.ads): GNAT Exception_Traces g-exctra ads.
22705 * GNAT.Exceptions (g-except.ads): GNAT Exceptions g-except ads.
22706 * GNAT.Expect (g-expect.ads): GNAT Expect g-expect ads.
22707 * GNAT.Expect.TTY (g-exptty.ads): GNAT Expect TTY g-exptty ads.
22708 * GNAT.Float_Control (g-flocon.ads): GNAT Float_Control g-flocon ads.
22709 * GNAT.Formatted_String (g-forstr.ads): GNAT Formatted_String g-forstr ads.
22710 * GNAT.Heap_Sort (g-heasor.ads): GNAT Heap_Sort g-heasor ads.
22711 * GNAT.Heap_Sort_A (g-hesora.ads): GNAT Heap_Sort_A g-hesora ads.
22712 * GNAT.Heap_Sort_G (g-hesorg.ads): GNAT Heap_Sort_G g-hesorg ads.
22713 * GNAT.HTable (g-htable.ads): GNAT HTable g-htable ads.
22714 * GNAT.IO (g-io.ads): GNAT IO g-io ads.
22715 * GNAT.IO_Aux (g-io_aux.ads): GNAT IO_Aux g-io_aux ads.
22716 * GNAT.Lock_Files (g-locfil.ads): GNAT Lock_Files g-locfil ads.
22717 * GNAT.MBBS_Discrete_Random (g-mbdira.ads): GNAT MBBS_Discrete_Random g-mbdira ads.
22718 * GNAT.MBBS_Float_Random (g-mbflra.ads): GNAT MBBS_Float_Random g-mbflra ads.
22719 * GNAT.MD5 (g-md5.ads): GNAT MD5 g-md5 ads.
22720 * GNAT.Memory_Dump (g-memdum.ads): GNAT Memory_Dump g-memdum ads.
22721 * GNAT.Most_Recent_Exception (g-moreex.ads): GNAT Most_Recent_Exception g-moreex ads.
22722 * GNAT.OS_Lib (g-os_lib.ads): GNAT OS_Lib g-os_lib ads.
22723 * GNAT.Perfect_Hash_Generators (g-pehage.ads): GNAT Perfect_Hash_Generators g-pehage ads.
22724 * GNAT.Random_Numbers (g-rannum.ads): GNAT Random_Numbers g-rannum ads.
22725 * GNAT.Regexp (g-regexp.ads): GNAT Regexp g-regexp ads.
22726 * GNAT.Registry (g-regist.ads): GNAT Registry g-regist ads.
22727 * GNAT.Regpat (g-regpat.ads): GNAT Regpat g-regpat ads.
22728 * GNAT.Rewrite_Data (g-rewdat.ads): GNAT Rewrite_Data g-rewdat ads.
22729 * GNAT.Secondary_Stack_Info (g-sestin.ads): GNAT Secondary_Stack_Info g-sestin ads.
22730 * GNAT.Semaphores (g-semaph.ads): GNAT Semaphores g-semaph ads.
22731 * GNAT.Serial_Communications (g-sercom.ads): GNAT Serial_Communications g-sercom ads.
22732 * GNAT.SHA1 (g-sha1.ads): GNAT SHA1 g-sha1 ads.
22733 * GNAT.SHA224 (g-sha224.ads): GNAT SHA224 g-sha224 ads.
22734 * GNAT.SHA256 (g-sha256.ads): GNAT SHA256 g-sha256 ads.
22735 * GNAT.SHA384 (g-sha384.ads): GNAT SHA384 g-sha384 ads.
22736 * GNAT.SHA512 (g-sha512.ads): GNAT SHA512 g-sha512 ads.
22737 * GNAT.Signals (g-signal.ads): GNAT Signals g-signal ads.
22738 * GNAT.Sockets (g-socket.ads): GNAT Sockets g-socket ads.
22739 * GNAT.Source_Info (g-souinf.ads): GNAT Source_Info g-souinf ads.
22740 * GNAT.Spelling_Checker (g-speche.ads): GNAT Spelling_Checker g-speche ads.
22741 * GNAT.Spelling_Checker_Generic (g-spchge.ads): GNAT Spelling_Checker_Generic g-spchge ads.
22742 * GNAT.Spitbol.Patterns (g-spipat.ads): GNAT Spitbol Patterns g-spipat ads.
22743 * GNAT.Spitbol (g-spitbo.ads): GNAT Spitbol g-spitbo ads.
22744 * GNAT.Spitbol.Table_Boolean (g-sptabo.ads): GNAT Spitbol Table_Boolean g-sptabo ads.
22745 * GNAT.Spitbol.Table_Integer (g-sptain.ads): GNAT Spitbol Table_Integer g-sptain ads.
22746 * GNAT.Spitbol.Table_VString (g-sptavs.ads): GNAT Spitbol Table_VString g-sptavs ads.
22747 * GNAT.SSE (g-sse.ads): GNAT SSE g-sse ads.
22748 * GNAT.SSE.Vector_Types (g-ssvety.ads): GNAT SSE Vector_Types g-ssvety ads.
22749 * GNAT.String_Hash (g-strhas.ads): GNAT String_Hash g-strhas ads.
22750 * GNAT.Strings (g-string.ads): GNAT Strings g-string ads.
22751 * GNAT.String_Split (g-strspl.ads): GNAT String_Split g-strspl ads.
22752 * GNAT.Table (g-table.ads): GNAT Table g-table ads.
22753 * GNAT.Task_Lock (g-tasloc.ads): GNAT Task_Lock g-tasloc ads.
22754 * GNAT.Time_Stamp (g-timsta.ads): GNAT Time_Stamp g-timsta ads.
22755 * GNAT.Threads (g-thread.ads): GNAT Threads g-thread ads.
22756 * GNAT.Traceback (g-traceb.ads): GNAT Traceback g-traceb ads.
22757 * GNAT.Traceback.Symbolic (g-trasym.ads): GNAT Traceback Symbolic g-trasym ads.
22758 * GNAT.UTF_32 (g-table.ads): GNAT UTF_32 g-table ads.
22759 * GNAT.Wide_Spelling_Checker (g-u3spch.ads): GNAT Wide_Spelling_Checker g-u3spch ads.
22760 * GNAT.Wide_Spelling_Checker (g-wispch.ads): GNAT Wide_Spelling_Checker g-wispch ads.
22761 * GNAT.Wide_String_Split (g-wistsp.ads): GNAT Wide_String_Split g-wistsp ads.
22762 * GNAT.Wide_Wide_Spelling_Checker (g-zspche.ads): GNAT Wide_Wide_Spelling_Checker g-zspche ads.
22763 * GNAT.Wide_Wide_String_Split (g-zistsp.ads): GNAT Wide_Wide_String_Split g-zistsp ads.
22764 * Interfaces.C.Extensions (i-cexten.ads): Interfaces C Extensions i-cexten ads.
22765 * Interfaces.C.Streams (i-cstrea.ads): Interfaces C Streams i-cstrea ads.
22766 * Interfaces.Packed_Decimal (i-pacdec.ads): Interfaces Packed_Decimal i-pacdec ads.
22767 * Interfaces.VxWorks (i-vxwork.ads): Interfaces VxWorks i-vxwork ads.
22768 * Interfaces.VxWorks.Int_Connection (i-vxinco.ads): Interfaces VxWorks Int_Connection i-vxinco ads.
22769 * Interfaces.VxWorks.IO (i-vxwoio.ads): Interfaces VxWorks IO i-vxwoio ads.
22770 * System.Address_Image (s-addima.ads): System Address_Image s-addima ads.
22771 * System.Assertions (s-assert.ads): System Assertions s-assert ads.
22772 * System.Atomic_Counters (s-atocou.ads): System Atomic_Counters s-atocou ads.
22773 * System.Memory (s-memory.ads): System Memory s-memory ads.
22774 * System.Multiprocessors (s-multip.ads): System Multiprocessors s-multip ads.
22775 * System.Multiprocessors.Dispatching_Domains (s-mudido.ads): System Multiprocessors Dispatching_Domains s-mudido ads.
22776 * System.Partition_Interface (s-parint.ads): System Partition_Interface s-parint ads.
22777 * System.Pool_Global (s-pooglo.ads): System Pool_Global s-pooglo ads.
22778 * System.Pool_Local (s-pooloc.ads): System Pool_Local s-pooloc ads.
22779 * System.Restrictions (s-restri.ads): System Restrictions s-restri ads.
22780 * System.Rident (s-rident.ads): System Rident s-rident ads.
22781 * System.Strings.Stream_Ops (s-ststop.ads): System Strings Stream_Ops s-ststop ads.
22782 * System.Unsigned_Types (s-unstyp.ads): System Unsigned_Types s-unstyp ads.
22783 * System.Wch_Cnv (s-wchcnv.ads): System Wch_Cnv s-wchcnv ads.
22784 * System.Wch_Con (s-wchcon.ads): System Wch_Con s-wchcon ads.
22788 @node Ada Characters Latin_9 a-chlat9 ads,Ada Characters Wide_Latin_1 a-cwila1 ads,,The GNAT Library
22789 @anchor{gnat_rm/the_gnat_library id2}@anchor{2d6}@anchor{gnat_rm/the_gnat_library ada-characters-latin-9-a-chlat9-ads}@anchor{2d7}
22790 @section @code{Ada.Characters.Latin_9} (@code{a-chlat9.ads})
22793 @geindex Ada.Characters.Latin_9 (a-chlat9.ads)
22795 @geindex Latin_9 constants for Character
22797 This child of @code{Ada.Characters}
22798 provides a set of definitions corresponding to those in the
22799 RM-defined package @code{Ada.Characters.Latin_1} but with the
22800 few modifications required for @code{Latin-9}
22801 The provision of such a package
22802 is specifically authorized by the Ada Reference Manual
22805 @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
22806 @anchor{gnat_rm/the_gnat_library ada-characters-wide-latin-1-a-cwila1-ads}@anchor{2d8}@anchor{gnat_rm/the_gnat_library id3}@anchor{2d9}
22807 @section @code{Ada.Characters.Wide_Latin_1} (@code{a-cwila1.ads})
22810 @geindex Ada.Characters.Wide_Latin_1 (a-cwila1.ads)
22812 @geindex Latin_1 constants for Wide_Character
22814 This child of @code{Ada.Characters}
22815 provides a set of definitions corresponding to those in the
22816 RM-defined package @code{Ada.Characters.Latin_1} but with the
22817 types of the constants being @code{Wide_Character}
22818 instead of @code{Character}. The provision of such a package
22819 is specifically authorized by the Ada Reference Manual
22822 @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
22823 @anchor{gnat_rm/the_gnat_library id4}@anchor{2da}@anchor{gnat_rm/the_gnat_library ada-characters-wide-latin-9-a-cwila1-ads}@anchor{2db}
22824 @section @code{Ada.Characters.Wide_Latin_9} (@code{a-cwila1.ads})
22827 @geindex Ada.Characters.Wide_Latin_9 (a-cwila1.ads)
22829 @geindex Latin_9 constants for Wide_Character
22831 This child of @code{Ada.Characters}
22832 provides a set of definitions corresponding to those in the
22833 GNAT defined package @code{Ada.Characters.Latin_9} but with the
22834 types of the constants being @code{Wide_Character}
22835 instead of @code{Character}. The provision of such a package
22836 is specifically authorized by the Ada Reference Manual
22839 @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
22840 @anchor{gnat_rm/the_gnat_library ada-characters-wide-wide-latin-1-a-chzla1-ads}@anchor{2dc}@anchor{gnat_rm/the_gnat_library id5}@anchor{2dd}
22841 @section @code{Ada.Characters.Wide_Wide_Latin_1} (@code{a-chzla1.ads})
22844 @geindex Ada.Characters.Wide_Wide_Latin_1 (a-chzla1.ads)
22846 @geindex Latin_1 constants for Wide_Wide_Character
22848 This child of @code{Ada.Characters}
22849 provides a set of definitions corresponding to those in the
22850 RM-defined package @code{Ada.Characters.Latin_1} but with the
22851 types of the constants being @code{Wide_Wide_Character}
22852 instead of @code{Character}. The provision of such a package
22853 is specifically authorized by the Ada Reference Manual
22856 @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
22857 @anchor{gnat_rm/the_gnat_library ada-characters-wide-wide-latin-9-a-chzla9-ads}@anchor{2de}@anchor{gnat_rm/the_gnat_library id6}@anchor{2df}
22858 @section @code{Ada.Characters.Wide_Wide_Latin_9} (@code{a-chzla9.ads})
22861 @geindex Ada.Characters.Wide_Wide_Latin_9 (a-chzla9.ads)
22863 @geindex Latin_9 constants for Wide_Wide_Character
22865 This child of @code{Ada.Characters}
22866 provides a set of definitions corresponding to those in the
22867 GNAT defined package @code{Ada.Characters.Latin_9} but with the
22868 types of the constants being @code{Wide_Wide_Character}
22869 instead of @code{Character}. The provision of such a package
22870 is specifically authorized by the Ada Reference Manual
22873 @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
22874 @anchor{gnat_rm/the_gnat_library id7}@anchor{2e0}@anchor{gnat_rm/the_gnat_library ada-containers-formal-doubly-linked-lists-a-cfdlli-ads}@anchor{2e1}
22875 @section @code{Ada.Containers.Formal_Doubly_Linked_Lists} (@code{a-cfdlli.ads})
22878 @geindex Ada.Containers.Formal_Doubly_Linked_Lists (a-cfdlli.ads)
22880 @geindex Formal container for doubly linked lists
22882 This child of @code{Ada.Containers} defines a modified version of the
22883 Ada 2005 container for doubly linked lists, meant to facilitate formal
22884 verification of code using such containers. The specification of this
22885 unit is compatible with SPARK 2014.
22887 Note that although this container was designed with formal verification
22888 in mind, it may well be generally useful in that it is a simplified more
22889 efficient version than the one defined in the standard. In particular it
22890 does not have the complex overhead required to detect cursor tampering.
22892 @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
22893 @anchor{gnat_rm/the_gnat_library id8}@anchor{2e2}@anchor{gnat_rm/the_gnat_library ada-containers-formal-hashed-maps-a-cfhama-ads}@anchor{2e3}
22894 @section @code{Ada.Containers.Formal_Hashed_Maps} (@code{a-cfhama.ads})
22897 @geindex Ada.Containers.Formal_Hashed_Maps (a-cfhama.ads)
22899 @geindex Formal container for hashed maps
22901 This child of @code{Ada.Containers} defines a modified version of the
22902 Ada 2005 container for hashed maps, meant to facilitate formal
22903 verification of code using such containers. The specification of this
22904 unit is compatible with SPARK 2014.
22906 Note that although this container was designed with formal verification
22907 in mind, it may well be generally useful in that it is a simplified more
22908 efficient version than the one defined in the standard. In particular it
22909 does not have the complex overhead required to detect cursor tampering.
22911 @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
22912 @anchor{gnat_rm/the_gnat_library id9}@anchor{2e4}@anchor{gnat_rm/the_gnat_library ada-containers-formal-hashed-sets-a-cfhase-ads}@anchor{2e5}
22913 @section @code{Ada.Containers.Formal_Hashed_Sets} (@code{a-cfhase.ads})
22916 @geindex Ada.Containers.Formal_Hashed_Sets (a-cfhase.ads)
22918 @geindex Formal container for hashed sets
22920 This child of @code{Ada.Containers} defines a modified version of the
22921 Ada 2005 container for hashed sets, meant to facilitate formal
22922 verification of code using such containers. The specification of this
22923 unit is compatible with SPARK 2014.
22925 Note that although this container was designed with formal verification
22926 in mind, it may well be generally useful in that it is a simplified more
22927 efficient version than the one defined in the standard. In particular it
22928 does not have the complex overhead required to detect cursor tampering.
22930 @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
22931 @anchor{gnat_rm/the_gnat_library id10}@anchor{2e6}@anchor{gnat_rm/the_gnat_library ada-containers-formal-ordered-maps-a-cforma-ads}@anchor{2e7}
22932 @section @code{Ada.Containers.Formal_Ordered_Maps} (@code{a-cforma.ads})
22935 @geindex Ada.Containers.Formal_Ordered_Maps (a-cforma.ads)
22937 @geindex Formal container for ordered maps
22939 This child of @code{Ada.Containers} defines a modified version of the
22940 Ada 2005 container for ordered maps, meant to facilitate formal
22941 verification of code using such containers. The specification of this
22942 unit is compatible with SPARK 2014.
22944 Note that although this container was designed with formal verification
22945 in mind, it may well be generally useful in that it is a simplified more
22946 efficient version than the one defined in the standard. In particular it
22947 does not have the complex overhead required to detect cursor tampering.
22949 @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
22950 @anchor{gnat_rm/the_gnat_library ada-containers-formal-ordered-sets-a-cforse-ads}@anchor{2e8}@anchor{gnat_rm/the_gnat_library id11}@anchor{2e9}
22951 @section @code{Ada.Containers.Formal_Ordered_Sets} (@code{a-cforse.ads})
22954 @geindex Ada.Containers.Formal_Ordered_Sets (a-cforse.ads)
22956 @geindex Formal container for ordered sets
22958 This child of @code{Ada.Containers} defines a modified version of the
22959 Ada 2005 container for ordered sets, meant to facilitate formal
22960 verification of code using such containers. The specification of this
22961 unit is compatible with SPARK 2014.
22963 Note that although this container was designed with formal verification
22964 in mind, it may well be generally useful in that it is a simplified more
22965 efficient version than the one defined in the standard. In particular it
22966 does not have the complex overhead required to detect cursor tampering.
22968 @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
22969 @anchor{gnat_rm/the_gnat_library id12}@anchor{2ea}@anchor{gnat_rm/the_gnat_library ada-containers-formal-vectors-a-cofove-ads}@anchor{2eb}
22970 @section @code{Ada.Containers.Formal_Vectors} (@code{a-cofove.ads})
22973 @geindex Ada.Containers.Formal_Vectors (a-cofove.ads)
22975 @geindex Formal container for vectors
22977 This child of @code{Ada.Containers} defines a modified version of the
22978 Ada 2005 container for vectors, meant to facilitate formal
22979 verification of code using such containers. The specification of this
22980 unit is compatible with SPARK 2014.
22982 Note that although this container was designed with formal verification
22983 in mind, it may well be generally useful in that it is a simplified more
22984 efficient version than the one defined in the standard. In particular it
22985 does not have the complex overhead required to detect cursor tampering.
22987 @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
22988 @anchor{gnat_rm/the_gnat_library id13}@anchor{2ec}@anchor{gnat_rm/the_gnat_library ada-containers-formal-indefinite-vectors-a-cfinve-ads}@anchor{2ed}
22989 @section @code{Ada.Containers.Formal_Indefinite_Vectors} (@code{a-cfinve.ads})
22992 @geindex Ada.Containers.Formal_Indefinite_Vectors (a-cfinve.ads)
22994 @geindex Formal container for vectors
22996 This child of @code{Ada.Containers} defines a modified version of the
22997 Ada 2005 container for vectors of indefinite elements, meant to
22998 facilitate formal verification of code using such containers. The
22999 specification of this unit is compatible with SPARK 2014.
23001 Note that although this container was designed with formal verification
23002 in mind, it may well be generally useful in that it is a simplified more
23003 efficient version than the one defined in the standard. In particular it
23004 does not have the complex overhead required to detect cursor tampering.
23006 @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
23007 @anchor{gnat_rm/the_gnat_library id14}@anchor{2ee}@anchor{gnat_rm/the_gnat_library ada-containers-functional-vectors-a-cofuve-ads}@anchor{2ef}
23008 @section @code{Ada.Containers.Functional_Vectors} (@code{a-cofuve.ads})
23011 @geindex Ada.Containers.Functional_Vectors (a-cofuve.ads)
23013 @geindex Functional vectors
23015 This child of @code{Ada.Containers} defines immutable vectors. These
23016 containers are unbounded and may contain indefinite elements. Furthermore, to
23017 be usable in every context, they are neither controlled nor limited. As they
23018 are functional, that is, no primitives are provided which would allow modifying
23019 an existing container, these containers can still be used safely.
23021 Their API features functions creating new containers from existing ones.
23022 As a consequence, these containers are highly inefficient. They are also
23023 memory consuming, as the allocated memory is not reclaimed when the container
23024 is no longer referenced. Thus, they should in general be used in ghost code
23025 and annotations, so that they can be removed from the final executable. The
23026 specification of this unit is compatible with SPARK 2014.
23028 @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
23029 @anchor{gnat_rm/the_gnat_library ada-containers-functional-sets-a-cofuse-ads}@anchor{2f0}@anchor{gnat_rm/the_gnat_library id15}@anchor{2f1}
23030 @section @code{Ada.Containers.Functional_Sets} (@code{a-cofuse.ads})
23033 @geindex Ada.Containers.Functional_Sets (a-cofuse.ads)
23035 @geindex Functional sets
23037 This child of @code{Ada.Containers} defines immutable sets. These containers are
23038 unbounded and may contain indefinite elements. Furthermore, to be usable in
23039 every context, they are neither controlled nor limited. As they are functional,
23040 that is, no primitives are provided which would allow modifying an existing
23041 container, these containers can still be used safely.
23043 Their API features functions creating new containers from existing ones.
23044 As a consequence, these containers are highly inefficient. They are also
23045 memory consuming, as the allocated memory is not reclaimed when the container
23046 is no longer referenced. Thus, they should in general be used in ghost code
23047 and annotations, so that they can be removed from the final executable. The
23048 specification of this unit is compatible with SPARK 2014.
23050 @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
23051 @anchor{gnat_rm/the_gnat_library id16}@anchor{2f2}@anchor{gnat_rm/the_gnat_library ada-containers-functional-maps-a-cofuma-ads}@anchor{2f3}
23052 @section @code{Ada.Containers.Functional_Maps} (@code{a-cofuma.ads})
23055 @geindex Ada.Containers.Functional_Maps (a-cofuma.ads)
23057 @geindex Functional maps
23059 This child of @code{Ada.Containers} defines immutable maps. These containers are
23060 unbounded and may contain indefinite elements. Furthermore, to be usable in
23061 every context, they are neither controlled nor limited. As they are functional,
23062 that is, no primitives are provided which would allow modifying an existing
23063 container, these containers can still be used safely.
23065 Their API features functions creating new containers from existing ones.
23066 As a consequence, these containers are highly inefficient. They are also
23067 memory consuming, as the allocated memory is not reclaimed when the container
23068 is no longer referenced. Thus, they should in general be used in ghost code
23069 and annotations, so that they can be removed from the final executable. The
23070 specification of this unit is compatible with SPARK 2014.
23072 @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
23073 @anchor{gnat_rm/the_gnat_library ada-containers-bounded-holders-a-coboho-ads}@anchor{2f4}@anchor{gnat_rm/the_gnat_library id17}@anchor{2f5}
23074 @section @code{Ada.Containers.Bounded_Holders} (@code{a-coboho.ads})
23077 @geindex Ada.Containers.Bounded_Holders (a-coboho.ads)
23079 @geindex Formal container for vectors
23081 This child of @code{Ada.Containers} defines a modified version of
23082 Indefinite_Holders that avoids heap allocation.
23084 @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
23085 @anchor{gnat_rm/the_gnat_library ada-command-line-environment-a-colien-ads}@anchor{2f6}@anchor{gnat_rm/the_gnat_library id18}@anchor{2f7}
23086 @section @code{Ada.Command_Line.Environment} (@code{a-colien.ads})
23089 @geindex Ada.Command_Line.Environment (a-colien.ads)
23091 @geindex Environment entries
23093 This child of @code{Ada.Command_Line}
23094 provides a mechanism for obtaining environment values on systems
23095 where this concept makes sense.
23097 @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
23098 @anchor{gnat_rm/the_gnat_library id19}@anchor{2f8}@anchor{gnat_rm/the_gnat_library ada-command-line-remove-a-colire-ads}@anchor{2f9}
23099 @section @code{Ada.Command_Line.Remove} (@code{a-colire.ads})
23102 @geindex Ada.Command_Line.Remove (a-colire.ads)
23104 @geindex Removing command line arguments
23106 @geindex Command line
23107 @geindex argument removal
23109 This child of @code{Ada.Command_Line}
23110 provides a mechanism for logically removing
23111 arguments from the argument list. Once removed, an argument is not visible
23112 to further calls on the subprograms in @code{Ada.Command_Line} will not
23113 see the removed argument.
23115 @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
23116 @anchor{gnat_rm/the_gnat_library id20}@anchor{2fa}@anchor{gnat_rm/the_gnat_library ada-command-line-response-file-a-clrefi-ads}@anchor{2fb}
23117 @section @code{Ada.Command_Line.Response_File} (@code{a-clrefi.ads})
23120 @geindex Ada.Command_Line.Response_File (a-clrefi.ads)
23122 @geindex Response file for command line
23124 @geindex Command line
23125 @geindex response file
23127 @geindex Command line
23128 @geindex handling long command lines
23130 This child of @code{Ada.Command_Line} provides a mechanism facilities for
23131 getting command line arguments from a text file, called a "response file".
23132 Using a response file allow passing a set of arguments to an executable longer
23133 than the maximum allowed by the system on the command line.
23135 @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
23136 @anchor{gnat_rm/the_gnat_library id21}@anchor{2fc}@anchor{gnat_rm/the_gnat_library ada-direct-io-c-streams-a-diocst-ads}@anchor{2fd}
23137 @section @code{Ada.Direct_IO.C_Streams} (@code{a-diocst.ads})
23140 @geindex Ada.Direct_IO.C_Streams (a-diocst.ads)
23143 @geindex Interfacing with Direct_IO
23145 This package provides subprograms that allow interfacing between
23146 C streams and @code{Direct_IO}. The stream identifier can be
23147 extracted from a file opened on the Ada side, and an Ada file
23148 can be constructed from a stream opened on the C side.
23150 @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
23151 @anchor{gnat_rm/the_gnat_library id22}@anchor{2fe}@anchor{gnat_rm/the_gnat_library ada-exceptions-is-null-occurrence-a-einuoc-ads}@anchor{2ff}
23152 @section @code{Ada.Exceptions.Is_Null_Occurrence} (@code{a-einuoc.ads})
23155 @geindex Ada.Exceptions.Is_Null_Occurrence (a-einuoc.ads)
23157 @geindex Null_Occurrence
23158 @geindex testing for
23160 This child subprogram provides a way of testing for the null
23161 exception occurrence (@code{Null_Occurrence}) without raising
23164 @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
23165 @anchor{gnat_rm/the_gnat_library id23}@anchor{300}@anchor{gnat_rm/the_gnat_library ada-exceptions-last-chance-handler-a-elchha-ads}@anchor{301}
23166 @section @code{Ada.Exceptions.Last_Chance_Handler} (@code{a-elchha.ads})
23169 @geindex Ada.Exceptions.Last_Chance_Handler (a-elchha.ads)
23171 @geindex Null_Occurrence
23172 @geindex testing for
23174 This child subprogram is used for handling otherwise unhandled
23175 exceptions (hence the name last chance), and perform clean ups before
23176 terminating the program. Note that this subprogram never returns.
23178 @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
23179 @anchor{gnat_rm/the_gnat_library ada-exceptions-traceback-a-exctra-ads}@anchor{302}@anchor{gnat_rm/the_gnat_library id24}@anchor{303}
23180 @section @code{Ada.Exceptions.Traceback} (@code{a-exctra.ads})
23183 @geindex Ada.Exceptions.Traceback (a-exctra.ads)
23185 @geindex Traceback for Exception Occurrence
23187 This child package provides the subprogram (@code{Tracebacks}) to
23188 give a traceback array of addresses based on an exception
23191 @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
23192 @anchor{gnat_rm/the_gnat_library ada-sequential-io-c-streams-a-siocst-ads}@anchor{304}@anchor{gnat_rm/the_gnat_library id25}@anchor{305}
23193 @section @code{Ada.Sequential_IO.C_Streams} (@code{a-siocst.ads})
23196 @geindex Ada.Sequential_IO.C_Streams (a-siocst.ads)
23199 @geindex Interfacing with Sequential_IO
23201 This package provides subprograms that allow interfacing between
23202 C streams and @code{Sequential_IO}. The stream identifier can be
23203 extracted from a file opened on the Ada side, and an Ada file
23204 can be constructed from a stream opened on the C side.
23206 @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
23207 @anchor{gnat_rm/the_gnat_library id26}@anchor{306}@anchor{gnat_rm/the_gnat_library ada-streams-stream-io-c-streams-a-ssicst-ads}@anchor{307}
23208 @section @code{Ada.Streams.Stream_IO.C_Streams} (@code{a-ssicst.ads})
23211 @geindex Ada.Streams.Stream_IO.C_Streams (a-ssicst.ads)
23214 @geindex Interfacing with Stream_IO
23216 This package provides subprograms that allow interfacing between
23217 C streams and @code{Stream_IO}. The stream identifier can be
23218 extracted from a file opened on the Ada side, and an Ada file
23219 can be constructed from a stream opened on the C side.
23221 @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
23222 @anchor{gnat_rm/the_gnat_library ada-strings-unbounded-text-io-a-suteio-ads}@anchor{308}@anchor{gnat_rm/the_gnat_library id27}@anchor{309}
23223 @section @code{Ada.Strings.Unbounded.Text_IO} (@code{a-suteio.ads})
23226 @geindex Ada.Strings.Unbounded.Text_IO (a-suteio.ads)
23228 @geindex Unbounded_String
23229 @geindex IO support
23232 @geindex extensions for unbounded strings
23234 This package provides subprograms for Text_IO for unbounded
23235 strings, avoiding the necessity for an intermediate operation
23236 with ordinary strings.
23238 @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
23239 @anchor{gnat_rm/the_gnat_library id28}@anchor{30a}@anchor{gnat_rm/the_gnat_library ada-strings-wide-unbounded-wide-text-io-a-swuwti-ads}@anchor{30b}
23240 @section @code{Ada.Strings.Wide_Unbounded.Wide_Text_IO} (@code{a-swuwti.ads})
23243 @geindex Ada.Strings.Wide_Unbounded.Wide_Text_IO (a-swuwti.ads)
23245 @geindex Unbounded_Wide_String
23246 @geindex IO support
23249 @geindex extensions for unbounded wide strings
23251 This package provides subprograms for Text_IO for unbounded
23252 wide strings, avoiding the necessity for an intermediate operation
23253 with ordinary wide strings.
23255 @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
23256 @anchor{gnat_rm/the_gnat_library id29}@anchor{30c}@anchor{gnat_rm/the_gnat_library ada-strings-wide-wide-unbounded-wide-wide-text-io-a-szuzti-ads}@anchor{30d}
23257 @section @code{Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO} (@code{a-szuzti.ads})
23260 @geindex Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO (a-szuzti.ads)
23262 @geindex Unbounded_Wide_Wide_String
23263 @geindex IO support
23266 @geindex extensions for unbounded wide wide strings
23268 This package provides subprograms for Text_IO for unbounded
23269 wide wide strings, avoiding the necessity for an intermediate operation
23270 with ordinary wide wide strings.
23272 @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
23273 @anchor{gnat_rm/the_gnat_library ada-task-initialization-a-tasini-ads}@anchor{30e}@anchor{gnat_rm/the_gnat_library id30}@anchor{30f}
23274 @section @code{Ada.Task_Initialization} (@code{a-tasini.ads})
23277 @geindex Ada.Task_Initialization (a-tasini.ads)
23279 This package provides a way to set a global initialization handler that
23280 is automatically invoked whenever a task is activated. Handlers are
23281 parameterless procedures. Note that such a handler is only invoked for
23282 those tasks activated after the handler is set.
23284 @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
23285 @anchor{gnat_rm/the_gnat_library ada-text-io-c-streams-a-tiocst-ads}@anchor{310}@anchor{gnat_rm/the_gnat_library id31}@anchor{311}
23286 @section @code{Ada.Text_IO.C_Streams} (@code{a-tiocst.ads})
23289 @geindex Ada.Text_IO.C_Streams (a-tiocst.ads)
23292 @geindex Interfacing with `@w{`}Text_IO`@w{`}
23294 This package provides subprograms that allow interfacing between
23295 C streams and @code{Text_IO}. The stream identifier can be
23296 extracted from a file opened on the Ada side, and an Ada file
23297 can be constructed from a stream opened on the C side.
23299 @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
23300 @anchor{gnat_rm/the_gnat_library ada-text-io-reset-standard-files-a-tirsfi-ads}@anchor{312}@anchor{gnat_rm/the_gnat_library id32}@anchor{313}
23301 @section @code{Ada.Text_IO.Reset_Standard_Files} (@code{a-tirsfi.ads})
23304 @geindex Ada.Text_IO.Reset_Standard_Files (a-tirsfi.ads)
23306 @geindex Text_IO resetting standard files
23308 This procedure is used to reset the status of the standard files used
23309 by Ada.Text_IO. This is useful in a situation (such as a restart in an
23310 embedded application) where the status of the files may change during
23311 execution (for example a standard input file may be redefined to be
23314 @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
23315 @anchor{gnat_rm/the_gnat_library id33}@anchor{314}@anchor{gnat_rm/the_gnat_library ada-wide-characters-unicode-a-wichun-ads}@anchor{315}
23316 @section @code{Ada.Wide_Characters.Unicode} (@code{a-wichun.ads})
23319 @geindex Ada.Wide_Characters.Unicode (a-wichun.ads)
23321 @geindex Unicode categorization
23322 @geindex Wide_Character
23324 This package provides subprograms that allow categorization of
23325 Wide_Character values according to Unicode categories.
23327 @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
23328 @anchor{gnat_rm/the_gnat_library id34}@anchor{316}@anchor{gnat_rm/the_gnat_library ada-wide-text-io-c-streams-a-wtcstr-ads}@anchor{317}
23329 @section @code{Ada.Wide_Text_IO.C_Streams} (@code{a-wtcstr.ads})
23332 @geindex Ada.Wide_Text_IO.C_Streams (a-wtcstr.ads)
23335 @geindex Interfacing with `@w{`}Wide_Text_IO`@w{`}
23337 This package provides subprograms that allow interfacing between
23338 C streams and @code{Wide_Text_IO}. The stream identifier can be
23339 extracted from a file opened on the Ada side, and an Ada file
23340 can be constructed from a stream opened on the C side.
23342 @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
23343 @anchor{gnat_rm/the_gnat_library ada-wide-text-io-reset-standard-files-a-wrstfi-ads}@anchor{318}@anchor{gnat_rm/the_gnat_library id35}@anchor{319}
23344 @section @code{Ada.Wide_Text_IO.Reset_Standard_Files} (@code{a-wrstfi.ads})
23347 @geindex Ada.Wide_Text_IO.Reset_Standard_Files (a-wrstfi.ads)
23349 @geindex Wide_Text_IO resetting standard files
23351 This procedure is used to reset the status of the standard files used
23352 by Ada.Wide_Text_IO. This is useful in a situation (such as a restart in an
23353 embedded application) where the status of the files may change during
23354 execution (for example a standard input file may be redefined to be
23357 @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
23358 @anchor{gnat_rm/the_gnat_library id36}@anchor{31a}@anchor{gnat_rm/the_gnat_library ada-wide-wide-characters-unicode-a-zchuni-ads}@anchor{31b}
23359 @section @code{Ada.Wide_Wide_Characters.Unicode} (@code{a-zchuni.ads})
23362 @geindex Ada.Wide_Wide_Characters.Unicode (a-zchuni.ads)
23364 @geindex Unicode categorization
23365 @geindex Wide_Wide_Character
23367 This package provides subprograms that allow categorization of
23368 Wide_Wide_Character values according to Unicode categories.
23370 @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
23371 @anchor{gnat_rm/the_gnat_library id37}@anchor{31c}@anchor{gnat_rm/the_gnat_library ada-wide-wide-text-io-c-streams-a-ztcstr-ads}@anchor{31d}
23372 @section @code{Ada.Wide_Wide_Text_IO.C_Streams} (@code{a-ztcstr.ads})
23375 @geindex Ada.Wide_Wide_Text_IO.C_Streams (a-ztcstr.ads)
23378 @geindex Interfacing with `@w{`}Wide_Wide_Text_IO`@w{`}
23380 This package provides subprograms that allow interfacing between
23381 C streams and @code{Wide_Wide_Text_IO}. The stream identifier can be
23382 extracted from a file opened on the Ada side, and an Ada file
23383 can be constructed from a stream opened on the C side.
23385 @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
23386 @anchor{gnat_rm/the_gnat_library ada-wide-wide-text-io-reset-standard-files-a-zrstfi-ads}@anchor{31e}@anchor{gnat_rm/the_gnat_library id38}@anchor{31f}
23387 @section @code{Ada.Wide_Wide_Text_IO.Reset_Standard_Files} (@code{a-zrstfi.ads})
23390 @geindex Ada.Wide_Wide_Text_IO.Reset_Standard_Files (a-zrstfi.ads)
23392 @geindex Wide_Wide_Text_IO resetting standard files
23394 This procedure is used to reset the status of the standard files used
23395 by Ada.Wide_Wide_Text_IO. This is useful in a situation (such as a
23396 restart in an embedded application) where the status of the files may
23397 change during execution (for example a standard input file may be
23398 redefined to be interactive).
23400 @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
23401 @anchor{gnat_rm/the_gnat_library gnat-altivec-g-altive-ads}@anchor{320}@anchor{gnat_rm/the_gnat_library id39}@anchor{321}
23402 @section @code{GNAT.Altivec} (@code{g-altive.ads})
23405 @geindex GNAT.Altivec (g-altive.ads)
23409 This is the root package of the GNAT AltiVec binding. It provides
23410 definitions of constants and types common to all the versions of the
23413 @node GNAT Altivec Conversions g-altcon ads,GNAT Altivec Vector_Operations g-alveop ads,GNAT Altivec g-altive ads,The GNAT Library
23414 @anchor{gnat_rm/the_gnat_library gnat-altivec-conversions-g-altcon-ads}@anchor{322}@anchor{gnat_rm/the_gnat_library id40}@anchor{323}
23415 @section @code{GNAT.Altivec.Conversions} (@code{g-altcon.ads})
23418 @geindex GNAT.Altivec.Conversions (g-altcon.ads)
23422 This package provides the Vector/View conversion routines.
23424 @node GNAT Altivec Vector_Operations g-alveop ads,GNAT Altivec Vector_Types g-alvety ads,GNAT Altivec Conversions g-altcon ads,The GNAT Library
23425 @anchor{gnat_rm/the_gnat_library id41}@anchor{324}@anchor{gnat_rm/the_gnat_library gnat-altivec-vector-operations-g-alveop-ads}@anchor{325}
23426 @section @code{GNAT.Altivec.Vector_Operations} (@code{g-alveop.ads})
23429 @geindex GNAT.Altivec.Vector_Operations (g-alveop.ads)
23433 This package exposes the Ada interface to the AltiVec operations on
23434 vector objects. A soft emulation is included by default in the GNAT
23435 library. The hard binding is provided as a separate package. This unit
23436 is common to both bindings.
23438 @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
23439 @anchor{gnat_rm/the_gnat_library gnat-altivec-vector-types-g-alvety-ads}@anchor{326}@anchor{gnat_rm/the_gnat_library id42}@anchor{327}
23440 @section @code{GNAT.Altivec.Vector_Types} (@code{g-alvety.ads})
23443 @geindex GNAT.Altivec.Vector_Types (g-alvety.ads)
23447 This package exposes the various vector types part of the Ada binding
23448 to AltiVec facilities.
23450 @node GNAT Altivec Vector_Views g-alvevi ads,GNAT Array_Split g-arrspl ads,GNAT Altivec Vector_Types g-alvety ads,The GNAT Library
23451 @anchor{gnat_rm/the_gnat_library gnat-altivec-vector-views-g-alvevi-ads}@anchor{328}@anchor{gnat_rm/the_gnat_library id43}@anchor{329}
23452 @section @code{GNAT.Altivec.Vector_Views} (@code{g-alvevi.ads})
23455 @geindex GNAT.Altivec.Vector_Views (g-alvevi.ads)
23459 This package provides public 'View' data types from/to which private
23460 vector representations can be converted via
23461 GNAT.Altivec.Conversions. This allows convenient access to individual
23462 vector elements and provides a simple way to initialize vector
23465 @node GNAT Array_Split g-arrspl ads,GNAT AWK g-awk ads,GNAT Altivec Vector_Views g-alvevi ads,The GNAT Library
23466 @anchor{gnat_rm/the_gnat_library gnat-array-split-g-arrspl-ads}@anchor{32a}@anchor{gnat_rm/the_gnat_library id44}@anchor{32b}
23467 @section @code{GNAT.Array_Split} (@code{g-arrspl.ads})
23470 @geindex GNAT.Array_Split (g-arrspl.ads)
23472 @geindex Array splitter
23474 Useful array-manipulation routines: given a set of separators, split
23475 an array wherever the separators appear, and provide direct access
23476 to the resulting slices.
23478 @node GNAT AWK g-awk ads,GNAT Bind_Environment g-binenv ads,GNAT Array_Split g-arrspl ads,The GNAT Library
23479 @anchor{gnat_rm/the_gnat_library id45}@anchor{32c}@anchor{gnat_rm/the_gnat_library gnat-awk-g-awk-ads}@anchor{32d}
23480 @section @code{GNAT.AWK} (@code{g-awk.ads})
23483 @geindex GNAT.AWK (g-awk.ads)
23489 Provides AWK-like parsing functions, with an easy interface for parsing one
23490 or more files containing formatted data. The file is viewed as a database
23491 where each record is a line and a field is a data element in this line.
23493 @node GNAT Bind_Environment g-binenv ads,GNAT Branch_Prediction g-brapre ads,GNAT AWK g-awk ads,The GNAT Library
23494 @anchor{gnat_rm/the_gnat_library id46}@anchor{32e}@anchor{gnat_rm/the_gnat_library gnat-bind-environment-g-binenv-ads}@anchor{32f}
23495 @section @code{GNAT.Bind_Environment} (@code{g-binenv.ads})
23498 @geindex GNAT.Bind_Environment (g-binenv.ads)
23500 @geindex Bind environment
23502 Provides access to key=value associations captured at bind time.
23503 These associations can be specified using the @code{-V} binder command
23506 @node GNAT Branch_Prediction g-brapre ads,GNAT Bounded_Buffers g-boubuf ads,GNAT Bind_Environment g-binenv ads,The GNAT Library
23507 @anchor{gnat_rm/the_gnat_library id47}@anchor{330}@anchor{gnat_rm/the_gnat_library gnat-branch-prediction-g-brapre-ads}@anchor{331}
23508 @section @code{GNAT.Branch_Prediction} (@code{g-brapre.ads})
23511 @geindex GNAT.Branch_Prediction (g-brapre.ads)
23513 @geindex Branch Prediction
23515 Provides routines giving hints to the branch predictor of the code generator.
23517 @node GNAT Bounded_Buffers g-boubuf ads,GNAT Bounded_Mailboxes g-boumai ads,GNAT Branch_Prediction g-brapre ads,The GNAT Library
23518 @anchor{gnat_rm/the_gnat_library gnat-bounded-buffers-g-boubuf-ads}@anchor{332}@anchor{gnat_rm/the_gnat_library id48}@anchor{333}
23519 @section @code{GNAT.Bounded_Buffers} (@code{g-boubuf.ads})
23522 @geindex GNAT.Bounded_Buffers (g-boubuf.ads)
23526 @geindex Bounded Buffers
23528 Provides a concurrent generic bounded buffer abstraction. Instances are
23529 useful directly or as parts of the implementations of other abstractions,
23532 @node GNAT Bounded_Mailboxes g-boumai ads,GNAT Bubble_Sort g-bubsor ads,GNAT Bounded_Buffers g-boubuf ads,The GNAT Library
23533 @anchor{gnat_rm/the_gnat_library gnat-bounded-mailboxes-g-boumai-ads}@anchor{334}@anchor{gnat_rm/the_gnat_library id49}@anchor{335}
23534 @section @code{GNAT.Bounded_Mailboxes} (@code{g-boumai.ads})
23537 @geindex GNAT.Bounded_Mailboxes (g-boumai.ads)
23543 Provides a thread-safe asynchronous intertask mailbox communication facility.
23545 @node GNAT Bubble_Sort g-bubsor ads,GNAT Bubble_Sort_A g-busora ads,GNAT Bounded_Mailboxes g-boumai ads,The GNAT Library
23546 @anchor{gnat_rm/the_gnat_library gnat-bubble-sort-g-bubsor-ads}@anchor{336}@anchor{gnat_rm/the_gnat_library id50}@anchor{337}
23547 @section @code{GNAT.Bubble_Sort} (@code{g-bubsor.ads})
23550 @geindex GNAT.Bubble_Sort (g-bubsor.ads)
23554 @geindex Bubble sort
23556 Provides a general implementation of bubble sort usable for sorting arbitrary
23557 data items. Exchange and comparison procedures are provided by passing
23558 access-to-procedure values.
23560 @node GNAT Bubble_Sort_A g-busora ads,GNAT Bubble_Sort_G g-busorg ads,GNAT Bubble_Sort g-bubsor ads,The GNAT Library
23561 @anchor{gnat_rm/the_gnat_library id51}@anchor{338}@anchor{gnat_rm/the_gnat_library gnat-bubble-sort-a-g-busora-ads}@anchor{339}
23562 @section @code{GNAT.Bubble_Sort_A} (@code{g-busora.ads})
23565 @geindex GNAT.Bubble_Sort_A (g-busora.ads)
23569 @geindex Bubble sort
23571 Provides a general implementation of bubble sort usable for sorting arbitrary
23572 data items. Move and comparison procedures are provided by passing
23573 access-to-procedure values. This is an older version, retained for
23574 compatibility. Usually @code{GNAT.Bubble_Sort} will be preferable.
23576 @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
23577 @anchor{gnat_rm/the_gnat_library gnat-bubble-sort-g-g-busorg-ads}@anchor{33a}@anchor{gnat_rm/the_gnat_library id52}@anchor{33b}
23578 @section @code{GNAT.Bubble_Sort_G} (@code{g-busorg.ads})
23581 @geindex GNAT.Bubble_Sort_G (g-busorg.ads)
23585 @geindex Bubble sort
23587 Similar to @code{Bubble_Sort_A} except that the move and sorting procedures
23588 are provided as generic parameters, this improves efficiency, especially
23589 if the procedures can be inlined, at the expense of duplicating code for
23590 multiple instantiations.
23592 @node GNAT Byte_Order_Mark g-byorma ads,GNAT Byte_Swapping g-bytswa ads,GNAT Bubble_Sort_G g-busorg ads,The GNAT Library
23593 @anchor{gnat_rm/the_gnat_library gnat-byte-order-mark-g-byorma-ads}@anchor{33c}@anchor{gnat_rm/the_gnat_library id53}@anchor{33d}
23594 @section @code{GNAT.Byte_Order_Mark} (@code{g-byorma.ads})
23597 @geindex GNAT.Byte_Order_Mark (g-byorma.ads)
23599 @geindex UTF-8 representation
23601 @geindex Wide characte representations
23603 Provides a routine which given a string, reads the start of the string to
23604 see whether it is one of the standard byte order marks (BOM's) which signal
23605 the encoding of the string. The routine includes detection of special XML
23606 sequences for various UCS input formats.
23608 @node GNAT Byte_Swapping g-bytswa ads,GNAT Calendar g-calend ads,GNAT Byte_Order_Mark g-byorma ads,The GNAT Library
23609 @anchor{gnat_rm/the_gnat_library gnat-byte-swapping-g-bytswa-ads}@anchor{33e}@anchor{gnat_rm/the_gnat_library id54}@anchor{33f}
23610 @section @code{GNAT.Byte_Swapping} (@code{g-bytswa.ads})
23613 @geindex GNAT.Byte_Swapping (g-bytswa.ads)
23615 @geindex Byte swapping
23617 @geindex Endianness
23619 General routines for swapping the bytes in 2-, 4-, and 8-byte quantities.
23620 Machine-specific implementations are available in some cases.
23622 @node GNAT Calendar g-calend ads,GNAT Calendar Time_IO g-catiio ads,GNAT Byte_Swapping g-bytswa ads,The GNAT Library
23623 @anchor{gnat_rm/the_gnat_library id55}@anchor{340}@anchor{gnat_rm/the_gnat_library gnat-calendar-g-calend-ads}@anchor{341}
23624 @section @code{GNAT.Calendar} (@code{g-calend.ads})
23627 @geindex GNAT.Calendar (g-calend.ads)
23631 Extends the facilities provided by @code{Ada.Calendar} to include handling
23632 of days of the week, an extended @code{Split} and @code{Time_Of} capability.
23633 Also provides conversion of @code{Ada.Calendar.Time} values to and from the
23634 C @code{timeval} format.
23636 @node GNAT Calendar Time_IO g-catiio ads,GNAT CRC32 g-crc32 ads,GNAT Calendar g-calend ads,The GNAT Library
23637 @anchor{gnat_rm/the_gnat_library id56}@anchor{342}@anchor{gnat_rm/the_gnat_library gnat-calendar-time-io-g-catiio-ads}@anchor{343}
23638 @section @code{GNAT.Calendar.Time_IO} (@code{g-catiio.ads})
23645 @geindex GNAT.Calendar.Time_IO (g-catiio.ads)
23647 @node GNAT CRC32 g-crc32 ads,GNAT Case_Util g-casuti ads,GNAT Calendar Time_IO g-catiio ads,The GNAT Library
23648 @anchor{gnat_rm/the_gnat_library id57}@anchor{344}@anchor{gnat_rm/the_gnat_library gnat-crc32-g-crc32-ads}@anchor{345}
23649 @section @code{GNAT.CRC32} (@code{g-crc32.ads})
23652 @geindex GNAT.CRC32 (g-crc32.ads)
23656 @geindex Cyclic Redundancy Check
23658 This package implements the CRC-32 algorithm. For a full description
23659 of this algorithm see
23660 @emph{Computation of Cyclic Redundancy Checks via Table Look-Up},
23661 @cite{Communications of the ACM}, Vol. 31 No. 8, pp. 1008-1013,
23662 Aug. 1988. Sarwate, D.V.
23664 @node GNAT Case_Util g-casuti ads,GNAT CGI g-cgi ads,GNAT CRC32 g-crc32 ads,The GNAT Library
23665 @anchor{gnat_rm/the_gnat_library id58}@anchor{346}@anchor{gnat_rm/the_gnat_library gnat-case-util-g-casuti-ads}@anchor{347}
23666 @section @code{GNAT.Case_Util} (@code{g-casuti.ads})
23669 @geindex GNAT.Case_Util (g-casuti.ads)
23671 @geindex Casing utilities
23673 @geindex Character handling (`@w{`}GNAT.Case_Util`@w{`})
23675 A set of simple routines for handling upper and lower casing of strings
23676 without the overhead of the full casing tables
23677 in @code{Ada.Characters.Handling}.
23679 @node GNAT CGI g-cgi ads,GNAT CGI Cookie g-cgicoo ads,GNAT Case_Util g-casuti ads,The GNAT Library
23680 @anchor{gnat_rm/the_gnat_library id59}@anchor{348}@anchor{gnat_rm/the_gnat_library gnat-cgi-g-cgi-ads}@anchor{349}
23681 @section @code{GNAT.CGI} (@code{g-cgi.ads})
23684 @geindex GNAT.CGI (g-cgi.ads)
23686 @geindex CGI (Common Gateway Interface)
23688 This is a package for interfacing a GNAT program with a Web server via the
23689 Common Gateway Interface (CGI). Basically this package parses the CGI
23690 parameters, which are a set of key/value pairs sent by the Web server. It
23691 builds a table whose index is the key and provides some services to deal
23694 @node GNAT CGI Cookie g-cgicoo ads,GNAT CGI Debug g-cgideb ads,GNAT CGI g-cgi ads,The GNAT Library
23695 @anchor{gnat_rm/the_gnat_library gnat-cgi-cookie-g-cgicoo-ads}@anchor{34a}@anchor{gnat_rm/the_gnat_library id60}@anchor{34b}
23696 @section @code{GNAT.CGI.Cookie} (@code{g-cgicoo.ads})
23699 @geindex GNAT.CGI.Cookie (g-cgicoo.ads)
23701 @geindex CGI (Common Gateway Interface) cookie support
23703 @geindex Cookie support in CGI
23705 This is a package to interface a GNAT program with a Web server via the
23706 Common Gateway Interface (CGI). It exports services to deal with Web
23707 cookies (piece of information kept in the Web client software).
23709 @node GNAT CGI Debug g-cgideb ads,GNAT Command_Line g-comlin ads,GNAT CGI Cookie g-cgicoo ads,The GNAT Library
23710 @anchor{gnat_rm/the_gnat_library gnat-cgi-debug-g-cgideb-ads}@anchor{34c}@anchor{gnat_rm/the_gnat_library id61}@anchor{34d}
23711 @section @code{GNAT.CGI.Debug} (@code{g-cgideb.ads})
23714 @geindex GNAT.CGI.Debug (g-cgideb.ads)
23716 @geindex CGI (Common Gateway Interface) debugging
23718 This is a package to help debugging CGI (Common Gateway Interface)
23719 programs written in Ada.
23721 @node GNAT Command_Line g-comlin ads,GNAT Compiler_Version g-comver ads,GNAT CGI Debug g-cgideb ads,The GNAT Library
23722 @anchor{gnat_rm/the_gnat_library id62}@anchor{34e}@anchor{gnat_rm/the_gnat_library gnat-command-line-g-comlin-ads}@anchor{34f}
23723 @section @code{GNAT.Command_Line} (@code{g-comlin.ads})
23726 @geindex GNAT.Command_Line (g-comlin.ads)
23728 @geindex Command line
23730 Provides a high level interface to @code{Ada.Command_Line} facilities,
23731 including the ability to scan for named switches with optional parameters
23732 and expand file names using wildcard notations.
23734 @node GNAT Compiler_Version g-comver ads,GNAT Ctrl_C g-ctrl_c ads,GNAT Command_Line g-comlin ads,The GNAT Library
23735 @anchor{gnat_rm/the_gnat_library gnat-compiler-version-g-comver-ads}@anchor{350}@anchor{gnat_rm/the_gnat_library id63}@anchor{351}
23736 @section @code{GNAT.Compiler_Version} (@code{g-comver.ads})
23739 @geindex GNAT.Compiler_Version (g-comver.ads)
23741 @geindex Compiler Version
23744 @geindex of compiler
23746 Provides a routine for obtaining the version of the compiler used to
23747 compile the program. More accurately this is the version of the binder
23748 used to bind the program (this will normally be the same as the version
23749 of the compiler if a consistent tool set is used to compile all units
23752 @node GNAT Ctrl_C g-ctrl_c ads,GNAT Current_Exception g-curexc ads,GNAT Compiler_Version g-comver ads,The GNAT Library
23753 @anchor{gnat_rm/the_gnat_library id64}@anchor{352}@anchor{gnat_rm/the_gnat_library gnat-ctrl-c-g-ctrl-c-ads}@anchor{353}
23754 @section @code{GNAT.Ctrl_C} (@code{g-ctrl_c.ads})
23757 @geindex GNAT.Ctrl_C (g-ctrl_c.ads)
23761 Provides a simple interface to handle Ctrl-C keyboard events.
23763 @node GNAT Current_Exception g-curexc ads,GNAT Debug_Pools g-debpoo ads,GNAT Ctrl_C g-ctrl_c ads,The GNAT Library
23764 @anchor{gnat_rm/the_gnat_library id65}@anchor{354}@anchor{gnat_rm/the_gnat_library gnat-current-exception-g-curexc-ads}@anchor{355}
23765 @section @code{GNAT.Current_Exception} (@code{g-curexc.ads})
23768 @geindex GNAT.Current_Exception (g-curexc.ads)
23770 @geindex Current exception
23772 @geindex Exception retrieval
23774 Provides access to information on the current exception that has been raised
23775 without the need for using the Ada 95 / Ada 2005 exception choice parameter
23776 specification syntax.
23777 This is particularly useful in simulating typical facilities for
23778 obtaining information about exceptions provided by Ada 83 compilers.
23780 @node GNAT Debug_Pools g-debpoo ads,GNAT Debug_Utilities g-debuti ads,GNAT Current_Exception g-curexc ads,The GNAT Library
23781 @anchor{gnat_rm/the_gnat_library gnat-debug-pools-g-debpoo-ads}@anchor{356}@anchor{gnat_rm/the_gnat_library id66}@anchor{357}
23782 @section @code{GNAT.Debug_Pools} (@code{g-debpoo.ads})
23785 @geindex GNAT.Debug_Pools (g-debpoo.ads)
23789 @geindex Debug pools
23791 @geindex Memory corruption debugging
23793 Provide a debugging storage pools that helps tracking memory corruption
23795 See @code{The GNAT Debug_Pool Facility} section in the @cite{GNAT User's Guide}.
23797 @node GNAT Debug_Utilities g-debuti ads,GNAT Decode_String g-decstr ads,GNAT Debug_Pools g-debpoo ads,The GNAT Library
23798 @anchor{gnat_rm/the_gnat_library gnat-debug-utilities-g-debuti-ads}@anchor{358}@anchor{gnat_rm/the_gnat_library id67}@anchor{359}
23799 @section @code{GNAT.Debug_Utilities} (@code{g-debuti.ads})
23802 @geindex GNAT.Debug_Utilities (g-debuti.ads)
23806 Provides a few useful utilities for debugging purposes, including conversion
23807 to and from string images of address values. Supports both C and Ada formats
23808 for hexadecimal literals.
23810 @node GNAT Decode_String g-decstr ads,GNAT Decode_UTF8_String g-deutst ads,GNAT Debug_Utilities g-debuti ads,The GNAT Library
23811 @anchor{gnat_rm/the_gnat_library gnat-decode-string-g-decstr-ads}@anchor{35a}@anchor{gnat_rm/the_gnat_library id68}@anchor{35b}
23812 @section @code{GNAT.Decode_String} (@code{g-decstr.ads})
23815 @geindex GNAT.Decode_String (g-decstr.ads)
23817 @geindex Decoding strings
23819 @geindex String decoding
23821 @geindex Wide character encoding
23827 A generic package providing routines for decoding wide character and wide wide
23828 character strings encoded as sequences of 8-bit characters using a specified
23829 encoding method. Includes validation routines, and also routines for stepping
23830 to next or previous encoded character in an encoded string.
23831 Useful in conjunction with Unicode character coding. Note there is a
23832 preinstantiation for UTF-8. See next entry.
23834 @node GNAT Decode_UTF8_String g-deutst ads,GNAT Directory_Operations g-dirope ads,GNAT Decode_String g-decstr ads,The GNAT Library
23835 @anchor{gnat_rm/the_gnat_library gnat-decode-utf8-string-g-deutst-ads}@anchor{35c}@anchor{gnat_rm/the_gnat_library id69}@anchor{35d}
23836 @section @code{GNAT.Decode_UTF8_String} (@code{g-deutst.ads})
23839 @geindex GNAT.Decode_UTF8_String (g-deutst.ads)
23841 @geindex Decoding strings
23843 @geindex Decoding UTF-8 strings
23845 @geindex UTF-8 string decoding
23847 @geindex Wide character decoding
23853 A preinstantiation of GNAT.Decode_Strings for UTF-8 encoding.
23855 @node GNAT Directory_Operations g-dirope ads,GNAT Directory_Operations Iteration g-diopit ads,GNAT Decode_UTF8_String g-deutst ads,The GNAT Library
23856 @anchor{gnat_rm/the_gnat_library id70}@anchor{35e}@anchor{gnat_rm/the_gnat_library gnat-directory-operations-g-dirope-ads}@anchor{35f}
23857 @section @code{GNAT.Directory_Operations} (@code{g-dirope.ads})
23860 @geindex GNAT.Directory_Operations (g-dirope.ads)
23862 @geindex Directory operations
23864 Provides a set of routines for manipulating directories, including changing
23865 the current directory, making new directories, and scanning the files in a
23868 @node GNAT Directory_Operations Iteration g-diopit ads,GNAT Dynamic_HTables g-dynhta ads,GNAT Directory_Operations g-dirope ads,The GNAT Library
23869 @anchor{gnat_rm/the_gnat_library id71}@anchor{360}@anchor{gnat_rm/the_gnat_library gnat-directory-operations-iteration-g-diopit-ads}@anchor{361}
23870 @section @code{GNAT.Directory_Operations.Iteration} (@code{g-diopit.ads})
23873 @geindex GNAT.Directory_Operations.Iteration (g-diopit.ads)
23875 @geindex Directory operations iteration
23877 A child unit of GNAT.Directory_Operations providing additional operations
23878 for iterating through directories.
23880 @node GNAT Dynamic_HTables g-dynhta ads,GNAT Dynamic_Tables g-dyntab ads,GNAT Directory_Operations Iteration g-diopit ads,The GNAT Library
23881 @anchor{gnat_rm/the_gnat_library id72}@anchor{362}@anchor{gnat_rm/the_gnat_library gnat-dynamic-htables-g-dynhta-ads}@anchor{363}
23882 @section @code{GNAT.Dynamic_HTables} (@code{g-dynhta.ads})
23885 @geindex GNAT.Dynamic_HTables (g-dynhta.ads)
23887 @geindex Hash tables
23889 A generic implementation of hash tables that can be used to hash arbitrary
23890 data. Provided in two forms, a simple form with built in hash functions,
23891 and a more complex form in which the hash function is supplied.
23893 This package provides a facility similar to that of @code{GNAT.HTable},
23894 except that this package declares a type that can be used to define
23895 dynamic instances of the hash table, while an instantiation of
23896 @code{GNAT.HTable} creates a single instance of the hash table.
23898 @node GNAT Dynamic_Tables g-dyntab ads,GNAT Encode_String g-encstr ads,GNAT Dynamic_HTables g-dynhta ads,The GNAT Library
23899 @anchor{gnat_rm/the_gnat_library gnat-dynamic-tables-g-dyntab-ads}@anchor{364}@anchor{gnat_rm/the_gnat_library id73}@anchor{365}
23900 @section @code{GNAT.Dynamic_Tables} (@code{g-dyntab.ads})
23903 @geindex GNAT.Dynamic_Tables (g-dyntab.ads)
23905 @geindex Table implementation
23908 @geindex extendable
23910 A generic package providing a single dimension array abstraction where the
23911 length of the array can be dynamically modified.
23913 This package provides a facility similar to that of @code{GNAT.Table},
23914 except that this package declares a type that can be used to define
23915 dynamic instances of the table, while an instantiation of
23916 @code{GNAT.Table} creates a single instance of the table type.
23918 @node GNAT Encode_String g-encstr ads,GNAT Encode_UTF8_String g-enutst ads,GNAT Dynamic_Tables g-dyntab ads,The GNAT Library
23919 @anchor{gnat_rm/the_gnat_library id74}@anchor{366}@anchor{gnat_rm/the_gnat_library gnat-encode-string-g-encstr-ads}@anchor{367}
23920 @section @code{GNAT.Encode_String} (@code{g-encstr.ads})
23923 @geindex GNAT.Encode_String (g-encstr.ads)
23925 @geindex Encoding strings
23927 @geindex String encoding
23929 @geindex Wide character encoding
23935 A generic package providing routines for encoding wide character and wide
23936 wide character strings as sequences of 8-bit characters using a specified
23937 encoding method. Useful in conjunction with Unicode character coding.
23938 Note there is a preinstantiation for UTF-8. See next entry.
23940 @node GNAT Encode_UTF8_String g-enutst ads,GNAT Exception_Actions g-excact ads,GNAT Encode_String g-encstr ads,The GNAT Library
23941 @anchor{gnat_rm/the_gnat_library gnat-encode-utf8-string-g-enutst-ads}@anchor{368}@anchor{gnat_rm/the_gnat_library id75}@anchor{369}
23942 @section @code{GNAT.Encode_UTF8_String} (@code{g-enutst.ads})
23945 @geindex GNAT.Encode_UTF8_String (g-enutst.ads)
23947 @geindex Encoding strings
23949 @geindex Encoding UTF-8 strings
23951 @geindex UTF-8 string encoding
23953 @geindex Wide character encoding
23959 A preinstantiation of GNAT.Encode_Strings for UTF-8 encoding.
23961 @node GNAT Exception_Actions g-excact ads,GNAT Exception_Traces g-exctra ads,GNAT Encode_UTF8_String g-enutst ads,The GNAT Library
23962 @anchor{gnat_rm/the_gnat_library gnat-exception-actions-g-excact-ads}@anchor{36a}@anchor{gnat_rm/the_gnat_library id76}@anchor{36b}
23963 @section @code{GNAT.Exception_Actions} (@code{g-excact.ads})
23966 @geindex GNAT.Exception_Actions (g-excact.ads)
23968 @geindex Exception actions
23970 Provides callbacks when an exception is raised. Callbacks can be registered
23971 for specific exceptions, or when any exception is raised. This
23972 can be used for instance to force a core dump to ease debugging.
23974 @node GNAT Exception_Traces g-exctra ads,GNAT Exceptions g-except ads,GNAT Exception_Actions g-excact ads,The GNAT Library
23975 @anchor{gnat_rm/the_gnat_library gnat-exception-traces-g-exctra-ads}@anchor{36c}@anchor{gnat_rm/the_gnat_library id77}@anchor{36d}
23976 @section @code{GNAT.Exception_Traces} (@code{g-exctra.ads})
23979 @geindex GNAT.Exception_Traces (g-exctra.ads)
23981 @geindex Exception traces
23985 Provides an interface allowing to control automatic output upon exception
23988 @node GNAT Exceptions g-except ads,GNAT Expect g-expect ads,GNAT Exception_Traces g-exctra ads,The GNAT Library
23989 @anchor{gnat_rm/the_gnat_library id78}@anchor{36e}@anchor{gnat_rm/the_gnat_library gnat-exceptions-g-except-ads}@anchor{36f}
23990 @section @code{GNAT.Exceptions} (@code{g-except.ads})
23993 @geindex GNAT.Exceptions (g-except.ads)
23995 @geindex Exceptions
23998 @geindex Pure packages
23999 @geindex exceptions
24001 Normally it is not possible to raise an exception with
24002 a message from a subprogram in a pure package, since the
24003 necessary types and subprograms are in @code{Ada.Exceptions}
24004 which is not a pure unit. @code{GNAT.Exceptions} provides a
24005 facility for getting around this limitation for a few
24006 predefined exceptions, and for example allow raising
24007 @code{Constraint_Error} with a message from a pure subprogram.
24009 @node GNAT Expect g-expect ads,GNAT Expect TTY g-exptty ads,GNAT Exceptions g-except ads,The GNAT Library
24010 @anchor{gnat_rm/the_gnat_library id79}@anchor{370}@anchor{gnat_rm/the_gnat_library gnat-expect-g-expect-ads}@anchor{371}
24011 @section @code{GNAT.Expect} (@code{g-expect.ads})
24014 @geindex GNAT.Expect (g-expect.ads)
24016 Provides a set of subprograms similar to what is available
24017 with the standard Tcl Expect tool.
24018 It allows you to easily spawn and communicate with an external process.
24019 You can send commands or inputs to the process, and compare the output
24020 with some expected regular expression. Currently @code{GNAT.Expect}
24021 is implemented on all native GNAT ports.
24022 It is not implemented for cross ports, and in particular is not
24023 implemented for VxWorks or LynxOS.
24025 @node GNAT Expect TTY g-exptty ads,GNAT Float_Control g-flocon ads,GNAT Expect g-expect ads,The GNAT Library
24026 @anchor{gnat_rm/the_gnat_library id80}@anchor{372}@anchor{gnat_rm/the_gnat_library gnat-expect-tty-g-exptty-ads}@anchor{373}
24027 @section @code{GNAT.Expect.TTY} (@code{g-exptty.ads})
24030 @geindex GNAT.Expect.TTY (g-exptty.ads)
24032 As GNAT.Expect but using pseudo-terminal.
24033 Currently @code{GNAT.Expect.TTY} is implemented on all native GNAT
24034 ports. It is not implemented for cross ports, and
24035 in particular is not implemented for VxWorks or LynxOS.
24037 @node GNAT Float_Control g-flocon ads,GNAT Formatted_String g-forstr ads,GNAT Expect TTY g-exptty ads,The GNAT Library
24038 @anchor{gnat_rm/the_gnat_library id81}@anchor{374}@anchor{gnat_rm/the_gnat_library gnat-float-control-g-flocon-ads}@anchor{375}
24039 @section @code{GNAT.Float_Control} (@code{g-flocon.ads})
24042 @geindex GNAT.Float_Control (g-flocon.ads)
24044 @geindex Floating-Point Processor
24046 Provides an interface for resetting the floating-point processor into the
24047 mode required for correct semantic operation in Ada. Some third party
24048 library calls may cause this mode to be modified, and the Reset procedure
24049 in this package can be used to reestablish the required mode.
24051 @node GNAT Formatted_String g-forstr ads,GNAT Heap_Sort g-heasor ads,GNAT Float_Control g-flocon ads,The GNAT Library
24052 @anchor{gnat_rm/the_gnat_library id82}@anchor{376}@anchor{gnat_rm/the_gnat_library gnat-formatted-string-g-forstr-ads}@anchor{377}
24053 @section @code{GNAT.Formatted_String} (@code{g-forstr.ads})
24056 @geindex GNAT.Formatted_String (g-forstr.ads)
24058 @geindex Formatted String
24060 Provides support for C/C++ printf() formatted strings. The format is
24061 copied from the printf() routine and should therefore gives identical
24062 output. Some generic routines are provided to be able to use types
24063 derived from Integer, Float or enumerations as values for the
24066 @node GNAT Heap_Sort g-heasor ads,GNAT Heap_Sort_A g-hesora ads,GNAT Formatted_String g-forstr ads,The GNAT Library
24067 @anchor{gnat_rm/the_gnat_library id83}@anchor{378}@anchor{gnat_rm/the_gnat_library gnat-heap-sort-g-heasor-ads}@anchor{379}
24068 @section @code{GNAT.Heap_Sort} (@code{g-heasor.ads})
24071 @geindex GNAT.Heap_Sort (g-heasor.ads)
24075 Provides a general implementation of heap sort usable for sorting arbitrary
24076 data items. Exchange and comparison procedures are provided by passing
24077 access-to-procedure values. The algorithm used is a modified heap sort
24078 that performs approximately N*log(N) comparisons in the worst case.
24080 @node GNAT Heap_Sort_A g-hesora ads,GNAT Heap_Sort_G g-hesorg ads,GNAT Heap_Sort g-heasor ads,The GNAT Library
24081 @anchor{gnat_rm/the_gnat_library gnat-heap-sort-a-g-hesora-ads}@anchor{37a}@anchor{gnat_rm/the_gnat_library id84}@anchor{37b}
24082 @section @code{GNAT.Heap_Sort_A} (@code{g-hesora.ads})
24085 @geindex GNAT.Heap_Sort_A (g-hesora.ads)
24089 Provides a general implementation of heap sort usable for sorting arbitrary
24090 data items. Move and comparison procedures are provided by passing
24091 access-to-procedure values. The algorithm used is a modified heap sort
24092 that performs approximately N*log(N) comparisons in the worst case.
24093 This differs from @code{GNAT.Heap_Sort} in having a less convenient
24094 interface, but may be slightly more efficient.
24096 @node GNAT Heap_Sort_G g-hesorg ads,GNAT HTable g-htable ads,GNAT Heap_Sort_A g-hesora ads,The GNAT Library
24097 @anchor{gnat_rm/the_gnat_library id85}@anchor{37c}@anchor{gnat_rm/the_gnat_library gnat-heap-sort-g-g-hesorg-ads}@anchor{37d}
24098 @section @code{GNAT.Heap_Sort_G} (@code{g-hesorg.ads})
24101 @geindex GNAT.Heap_Sort_G (g-hesorg.ads)
24105 Similar to @code{Heap_Sort_A} except that the move and sorting procedures
24106 are provided as generic parameters, this improves efficiency, especially
24107 if the procedures can be inlined, at the expense of duplicating code for
24108 multiple instantiations.
24110 @node GNAT HTable g-htable ads,GNAT IO g-io ads,GNAT Heap_Sort_G g-hesorg ads,The GNAT Library
24111 @anchor{gnat_rm/the_gnat_library id86}@anchor{37e}@anchor{gnat_rm/the_gnat_library gnat-htable-g-htable-ads}@anchor{37f}
24112 @section @code{GNAT.HTable} (@code{g-htable.ads})
24115 @geindex GNAT.HTable (g-htable.ads)
24117 @geindex Hash tables
24119 A generic implementation of hash tables that can be used to hash arbitrary
24120 data. Provides two approaches, one a simple static approach, and the other
24121 allowing arbitrary dynamic hash tables.
24123 @node GNAT IO g-io ads,GNAT IO_Aux g-io_aux ads,GNAT HTable g-htable ads,The GNAT Library
24124 @anchor{gnat_rm/the_gnat_library id87}@anchor{380}@anchor{gnat_rm/the_gnat_library gnat-io-g-io-ads}@anchor{381}
24125 @section @code{GNAT.IO} (@code{g-io.ads})
24128 @geindex GNAT.IO (g-io.ads)
24130 @geindex Simple I/O
24132 @geindex Input/Output facilities
24134 A simple preelaborable input-output package that provides a subset of
24135 simple Text_IO functions for reading characters and strings from
24136 Standard_Input, and writing characters, strings and integers to either
24137 Standard_Output or Standard_Error.
24139 @node GNAT IO_Aux g-io_aux ads,GNAT Lock_Files g-locfil ads,GNAT IO g-io ads,The GNAT Library
24140 @anchor{gnat_rm/the_gnat_library id88}@anchor{382}@anchor{gnat_rm/the_gnat_library gnat-io-aux-g-io-aux-ads}@anchor{383}
24141 @section @code{GNAT.IO_Aux} (@code{g-io_aux.ads})
24144 @geindex GNAT.IO_Aux (g-io_aux.ads)
24148 @geindex Input/Output facilities
24150 Provides some auxiliary functions for use with Text_IO, including a test
24151 for whether a file exists, and functions for reading a line of text.
24153 @node GNAT Lock_Files g-locfil ads,GNAT MBBS_Discrete_Random g-mbdira ads,GNAT IO_Aux g-io_aux ads,The GNAT Library
24154 @anchor{gnat_rm/the_gnat_library id89}@anchor{384}@anchor{gnat_rm/the_gnat_library gnat-lock-files-g-locfil-ads}@anchor{385}
24155 @section @code{GNAT.Lock_Files} (@code{g-locfil.ads})
24158 @geindex GNAT.Lock_Files (g-locfil.ads)
24160 @geindex File locking
24162 @geindex Locking using files
24164 Provides a general interface for using files as locks. Can be used for
24165 providing program level synchronization.
24167 @node GNAT MBBS_Discrete_Random g-mbdira ads,GNAT MBBS_Float_Random g-mbflra ads,GNAT Lock_Files g-locfil ads,The GNAT Library
24168 @anchor{gnat_rm/the_gnat_library id90}@anchor{386}@anchor{gnat_rm/the_gnat_library gnat-mbbs-discrete-random-g-mbdira-ads}@anchor{387}
24169 @section @code{GNAT.MBBS_Discrete_Random} (@code{g-mbdira.ads})
24172 @geindex GNAT.MBBS_Discrete_Random (g-mbdira.ads)
24174 @geindex Random number generation
24176 The original implementation of @code{Ada.Numerics.Discrete_Random}. Uses
24177 a modified version of the Blum-Blum-Shub generator.
24179 @node GNAT MBBS_Float_Random g-mbflra ads,GNAT MD5 g-md5 ads,GNAT MBBS_Discrete_Random g-mbdira ads,The GNAT Library
24180 @anchor{gnat_rm/the_gnat_library id91}@anchor{388}@anchor{gnat_rm/the_gnat_library gnat-mbbs-float-random-g-mbflra-ads}@anchor{389}
24181 @section @code{GNAT.MBBS_Float_Random} (@code{g-mbflra.ads})
24184 @geindex GNAT.MBBS_Float_Random (g-mbflra.ads)
24186 @geindex Random number generation
24188 The original implementation of @code{Ada.Numerics.Float_Random}. Uses
24189 a modified version of the Blum-Blum-Shub generator.
24191 @node GNAT MD5 g-md5 ads,GNAT Memory_Dump g-memdum ads,GNAT MBBS_Float_Random g-mbflra ads,The GNAT Library
24192 @anchor{gnat_rm/the_gnat_library id92}@anchor{38a}@anchor{gnat_rm/the_gnat_library gnat-md5-g-md5-ads}@anchor{38b}
24193 @section @code{GNAT.MD5} (@code{g-md5.ads})
24196 @geindex GNAT.MD5 (g-md5.ads)
24198 @geindex Message Digest MD5
24200 Implements the MD5 Message-Digest Algorithm as described in RFC 1321, and
24201 the HMAC-MD5 message authentication function as described in RFC 2104 and
24204 @node GNAT Memory_Dump g-memdum ads,GNAT Most_Recent_Exception g-moreex ads,GNAT MD5 g-md5 ads,The GNAT Library
24205 @anchor{gnat_rm/the_gnat_library id93}@anchor{38c}@anchor{gnat_rm/the_gnat_library gnat-memory-dump-g-memdum-ads}@anchor{38d}
24206 @section @code{GNAT.Memory_Dump} (@code{g-memdum.ads})
24209 @geindex GNAT.Memory_Dump (g-memdum.ads)
24211 @geindex Dump Memory
24213 Provides a convenient routine for dumping raw memory to either the
24214 standard output or standard error files. Uses GNAT.IO for actual
24217 @node GNAT Most_Recent_Exception g-moreex ads,GNAT OS_Lib g-os_lib ads,GNAT Memory_Dump g-memdum ads,The GNAT Library
24218 @anchor{gnat_rm/the_gnat_library gnat-most-recent-exception-g-moreex-ads}@anchor{38e}@anchor{gnat_rm/the_gnat_library id94}@anchor{38f}
24219 @section @code{GNAT.Most_Recent_Exception} (@code{g-moreex.ads})
24222 @geindex GNAT.Most_Recent_Exception (g-moreex.ads)
24225 @geindex obtaining most recent
24227 Provides access to the most recently raised exception. Can be used for
24228 various logging purposes, including duplicating functionality of some
24229 Ada 83 implementation dependent extensions.
24231 @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
24232 @anchor{gnat_rm/the_gnat_library gnat-os-lib-g-os-lib-ads}@anchor{390}@anchor{gnat_rm/the_gnat_library id95}@anchor{391}
24233 @section @code{GNAT.OS_Lib} (@code{g-os_lib.ads})
24236 @geindex GNAT.OS_Lib (g-os_lib.ads)
24238 @geindex Operating System interface
24240 @geindex Spawn capability
24242 Provides a range of target independent operating system interface functions,
24243 including time/date management, file operations, subprocess management,
24244 including a portable spawn procedure, and access to environment variables
24245 and error return codes.
24247 @node GNAT Perfect_Hash_Generators g-pehage ads,GNAT Random_Numbers g-rannum ads,GNAT OS_Lib g-os_lib ads,The GNAT Library
24248 @anchor{gnat_rm/the_gnat_library gnat-perfect-hash-generators-g-pehage-ads}@anchor{392}@anchor{gnat_rm/the_gnat_library id96}@anchor{393}
24249 @section @code{GNAT.Perfect_Hash_Generators} (@code{g-pehage.ads})
24252 @geindex GNAT.Perfect_Hash_Generators (g-pehage.ads)
24254 @geindex Hash functions
24256 Provides a generator of static minimal perfect hash functions. No
24257 collisions occur and each item can be retrieved from the table in one
24258 probe (perfect property). The hash table size corresponds to the exact
24259 size of the key set and no larger (minimal property). The key set has to
24260 be know in advance (static property). The hash functions are also order
24261 preserving. If w2 is inserted after w1 in the generator, their
24262 hashcode are in the same order. These hashing functions are very
24263 convenient for use with realtime applications.
24265 @node GNAT Random_Numbers g-rannum ads,GNAT Regexp g-regexp ads,GNAT Perfect_Hash_Generators g-pehage ads,The GNAT Library
24266 @anchor{gnat_rm/the_gnat_library gnat-random-numbers-g-rannum-ads}@anchor{394}@anchor{gnat_rm/the_gnat_library id97}@anchor{395}
24267 @section @code{GNAT.Random_Numbers} (@code{g-rannum.ads})
24270 @geindex GNAT.Random_Numbers (g-rannum.ads)
24272 @geindex Random number generation
24274 Provides random number capabilities which extend those available in the
24275 standard Ada library and are more convenient to use.
24277 @node GNAT Regexp g-regexp ads,GNAT Registry g-regist ads,GNAT Random_Numbers g-rannum ads,The GNAT Library
24278 @anchor{gnat_rm/the_gnat_library id98}@anchor{396}@anchor{gnat_rm/the_gnat_library gnat-regexp-g-regexp-ads}@anchor{25b}
24279 @section @code{GNAT.Regexp} (@code{g-regexp.ads})
24282 @geindex GNAT.Regexp (g-regexp.ads)
24284 @geindex Regular expressions
24286 @geindex Pattern matching
24288 A simple implementation of regular expressions, using a subset of regular
24289 expression syntax copied from familiar Unix style utilities. This is the
24290 simplest of the three pattern matching packages provided, and is particularly
24291 suitable for 'file globbing' applications.
24293 @node GNAT Registry g-regist ads,GNAT Regpat g-regpat ads,GNAT Regexp g-regexp ads,The GNAT Library
24294 @anchor{gnat_rm/the_gnat_library id99}@anchor{397}@anchor{gnat_rm/the_gnat_library gnat-registry-g-regist-ads}@anchor{398}
24295 @section @code{GNAT.Registry} (@code{g-regist.ads})
24298 @geindex GNAT.Registry (g-regist.ads)
24300 @geindex Windows Registry
24302 This is a high level binding to the Windows registry. It is possible to
24303 do simple things like reading a key value, creating a new key. For full
24304 registry API, but at a lower level of abstraction, refer to the Win32.Winreg
24305 package provided with the Win32Ada binding
24307 @node GNAT Regpat g-regpat ads,GNAT Rewrite_Data g-rewdat ads,GNAT Registry g-regist ads,The GNAT Library
24308 @anchor{gnat_rm/the_gnat_library id100}@anchor{399}@anchor{gnat_rm/the_gnat_library gnat-regpat-g-regpat-ads}@anchor{39a}
24309 @section @code{GNAT.Regpat} (@code{g-regpat.ads})
24312 @geindex GNAT.Regpat (g-regpat.ads)
24314 @geindex Regular expressions
24316 @geindex Pattern matching
24318 A complete implementation of Unix-style regular expression matching, copied
24319 from the original V7 style regular expression library written in C by
24320 Henry Spencer (and binary compatible with this C library).
24322 @node GNAT Rewrite_Data g-rewdat ads,GNAT Secondary_Stack_Info g-sestin ads,GNAT Regpat g-regpat ads,The GNAT Library
24323 @anchor{gnat_rm/the_gnat_library id101}@anchor{39b}@anchor{gnat_rm/the_gnat_library gnat-rewrite-data-g-rewdat-ads}@anchor{39c}
24324 @section @code{GNAT.Rewrite_Data} (@code{g-rewdat.ads})
24327 @geindex GNAT.Rewrite_Data (g-rewdat.ads)
24329 @geindex Rewrite data
24331 A unit to rewrite on-the-fly string occurrences in a stream of
24332 data. The implementation has a very minimal memory footprint as the
24333 full content to be processed is not loaded into memory all at once. This makes
24334 this interface usable for large files or socket streams.
24336 @node GNAT Secondary_Stack_Info g-sestin ads,GNAT Semaphores g-semaph ads,GNAT Rewrite_Data g-rewdat ads,The GNAT Library
24337 @anchor{gnat_rm/the_gnat_library gnat-secondary-stack-info-g-sestin-ads}@anchor{39d}@anchor{gnat_rm/the_gnat_library id102}@anchor{39e}
24338 @section @code{GNAT.Secondary_Stack_Info} (@code{g-sestin.ads})
24341 @geindex GNAT.Secondary_Stack_Info (g-sestin.ads)
24343 @geindex Secondary Stack Info
24345 Provide the capability to query the high water mark of the current task's
24348 @node GNAT Semaphores g-semaph ads,GNAT Serial_Communications g-sercom ads,GNAT Secondary_Stack_Info g-sestin ads,The GNAT Library
24349 @anchor{gnat_rm/the_gnat_library id103}@anchor{39f}@anchor{gnat_rm/the_gnat_library gnat-semaphores-g-semaph-ads}@anchor{3a0}
24350 @section @code{GNAT.Semaphores} (@code{g-semaph.ads})
24353 @geindex GNAT.Semaphores (g-semaph.ads)
24355 @geindex Semaphores
24357 Provides classic counting and binary semaphores using protected types.
24359 @node GNAT Serial_Communications g-sercom ads,GNAT SHA1 g-sha1 ads,GNAT Semaphores g-semaph ads,The GNAT Library
24360 @anchor{gnat_rm/the_gnat_library gnat-serial-communications-g-sercom-ads}@anchor{3a1}@anchor{gnat_rm/the_gnat_library id104}@anchor{3a2}
24361 @section @code{GNAT.Serial_Communications} (@code{g-sercom.ads})
24364 @geindex GNAT.Serial_Communications (g-sercom.ads)
24366 @geindex Serial_Communications
24368 Provides a simple interface to send and receive data over a serial
24369 port. This is only supported on GNU/Linux and Windows.
24371 @node GNAT SHA1 g-sha1 ads,GNAT SHA224 g-sha224 ads,GNAT Serial_Communications g-sercom ads,The GNAT Library
24372 @anchor{gnat_rm/the_gnat_library gnat-sha1-g-sha1-ads}@anchor{3a3}@anchor{gnat_rm/the_gnat_library id105}@anchor{3a4}
24373 @section @code{GNAT.SHA1} (@code{g-sha1.ads})
24376 @geindex GNAT.SHA1 (g-sha1.ads)
24378 @geindex Secure Hash Algorithm SHA-1
24380 Implements the SHA-1 Secure Hash Algorithm as described in FIPS PUB 180-3
24381 and RFC 3174, and the HMAC-SHA1 message authentication function as described
24382 in RFC 2104 and FIPS PUB 198.
24384 @node GNAT SHA224 g-sha224 ads,GNAT SHA256 g-sha256 ads,GNAT SHA1 g-sha1 ads,The GNAT Library
24385 @anchor{gnat_rm/the_gnat_library gnat-sha224-g-sha224-ads}@anchor{3a5}@anchor{gnat_rm/the_gnat_library id106}@anchor{3a6}
24386 @section @code{GNAT.SHA224} (@code{g-sha224.ads})
24389 @geindex GNAT.SHA224 (g-sha224.ads)
24391 @geindex Secure Hash Algorithm SHA-224
24393 Implements the SHA-224 Secure Hash Algorithm as described in FIPS PUB 180-3,
24394 and the HMAC-SHA224 message authentication function as described
24395 in RFC 2104 and FIPS PUB 198.
24397 @node GNAT SHA256 g-sha256 ads,GNAT SHA384 g-sha384 ads,GNAT SHA224 g-sha224 ads,The GNAT Library
24398 @anchor{gnat_rm/the_gnat_library gnat-sha256-g-sha256-ads}@anchor{3a7}@anchor{gnat_rm/the_gnat_library id107}@anchor{3a8}
24399 @section @code{GNAT.SHA256} (@code{g-sha256.ads})
24402 @geindex GNAT.SHA256 (g-sha256.ads)
24404 @geindex Secure Hash Algorithm SHA-256
24406 Implements the SHA-256 Secure Hash Algorithm as described in FIPS PUB 180-3,
24407 and the HMAC-SHA256 message authentication function as described
24408 in RFC 2104 and FIPS PUB 198.
24410 @node GNAT SHA384 g-sha384 ads,GNAT SHA512 g-sha512 ads,GNAT SHA256 g-sha256 ads,The GNAT Library
24411 @anchor{gnat_rm/the_gnat_library id108}@anchor{3a9}@anchor{gnat_rm/the_gnat_library gnat-sha384-g-sha384-ads}@anchor{3aa}
24412 @section @code{GNAT.SHA384} (@code{g-sha384.ads})
24415 @geindex GNAT.SHA384 (g-sha384.ads)
24417 @geindex Secure Hash Algorithm SHA-384
24419 Implements the SHA-384 Secure Hash Algorithm as described in FIPS PUB 180-3,
24420 and the HMAC-SHA384 message authentication function as described
24421 in RFC 2104 and FIPS PUB 198.
24423 @node GNAT SHA512 g-sha512 ads,GNAT Signals g-signal ads,GNAT SHA384 g-sha384 ads,The GNAT Library
24424 @anchor{gnat_rm/the_gnat_library id109}@anchor{3ab}@anchor{gnat_rm/the_gnat_library gnat-sha512-g-sha512-ads}@anchor{3ac}
24425 @section @code{GNAT.SHA512} (@code{g-sha512.ads})
24428 @geindex GNAT.SHA512 (g-sha512.ads)
24430 @geindex Secure Hash Algorithm SHA-512
24432 Implements the SHA-512 Secure Hash Algorithm as described in FIPS PUB 180-3,
24433 and the HMAC-SHA512 message authentication function as described
24434 in RFC 2104 and FIPS PUB 198.
24436 @node GNAT Signals g-signal ads,GNAT Sockets g-socket ads,GNAT SHA512 g-sha512 ads,The GNAT Library
24437 @anchor{gnat_rm/the_gnat_library gnat-signals-g-signal-ads}@anchor{3ad}@anchor{gnat_rm/the_gnat_library id110}@anchor{3ae}
24438 @section @code{GNAT.Signals} (@code{g-signal.ads})
24441 @geindex GNAT.Signals (g-signal.ads)
24445 Provides the ability to manipulate the blocked status of signals on supported
24448 @node GNAT Sockets g-socket ads,GNAT Source_Info g-souinf ads,GNAT Signals g-signal ads,The GNAT Library
24449 @anchor{gnat_rm/the_gnat_library gnat-sockets-g-socket-ads}@anchor{3af}@anchor{gnat_rm/the_gnat_library id111}@anchor{3b0}
24450 @section @code{GNAT.Sockets} (@code{g-socket.ads})
24453 @geindex GNAT.Sockets (g-socket.ads)
24457 A high level and portable interface to develop sockets based applications.
24458 This package is based on the sockets thin binding found in
24459 @code{GNAT.Sockets.Thin}. Currently @code{GNAT.Sockets} is implemented
24460 on all native GNAT ports and on VxWorks cross prots. It is not implemented for
24461 the LynxOS cross port.
24463 @node GNAT Source_Info g-souinf ads,GNAT Spelling_Checker g-speche ads,GNAT Sockets g-socket ads,The GNAT Library
24464 @anchor{gnat_rm/the_gnat_library gnat-source-info-g-souinf-ads}@anchor{3b1}@anchor{gnat_rm/the_gnat_library id112}@anchor{3b2}
24465 @section @code{GNAT.Source_Info} (@code{g-souinf.ads})
24468 @geindex GNAT.Source_Info (g-souinf.ads)
24470 @geindex Source Information
24472 Provides subprograms that give access to source code information known at
24473 compile time, such as the current file name and line number. Also provides
24474 subprograms yielding the date and time of the current compilation (like the
24475 C macros @code{__DATE__} and @code{__TIME__})
24477 @node GNAT Spelling_Checker g-speche ads,GNAT Spelling_Checker_Generic g-spchge ads,GNAT Source_Info g-souinf ads,The GNAT Library
24478 @anchor{gnat_rm/the_gnat_library gnat-spelling-checker-g-speche-ads}@anchor{3b3}@anchor{gnat_rm/the_gnat_library id113}@anchor{3b4}
24479 @section @code{GNAT.Spelling_Checker} (@code{g-speche.ads})
24482 @geindex GNAT.Spelling_Checker (g-speche.ads)
24484 @geindex Spell checking
24486 Provides a function for determining whether one string is a plausible
24487 near misspelling of another string.
24489 @node GNAT Spelling_Checker_Generic g-spchge ads,GNAT Spitbol Patterns g-spipat ads,GNAT Spelling_Checker g-speche ads,The GNAT Library
24490 @anchor{gnat_rm/the_gnat_library gnat-spelling-checker-generic-g-spchge-ads}@anchor{3b5}@anchor{gnat_rm/the_gnat_library id114}@anchor{3b6}
24491 @section @code{GNAT.Spelling_Checker_Generic} (@code{g-spchge.ads})
24494 @geindex GNAT.Spelling_Checker_Generic (g-spchge.ads)
24496 @geindex Spell checking
24498 Provides a generic function that can be instantiated with a string type for
24499 determining whether one string is a plausible near misspelling of another
24502 @node GNAT Spitbol Patterns g-spipat ads,GNAT Spitbol g-spitbo ads,GNAT Spelling_Checker_Generic g-spchge ads,The GNAT Library
24503 @anchor{gnat_rm/the_gnat_library gnat-spitbol-patterns-g-spipat-ads}@anchor{3b7}@anchor{gnat_rm/the_gnat_library id115}@anchor{3b8}
24504 @section @code{GNAT.Spitbol.Patterns} (@code{g-spipat.ads})
24507 @geindex GNAT.Spitbol.Patterns (g-spipat.ads)
24509 @geindex SPITBOL pattern matching
24511 @geindex Pattern matching
24513 A complete implementation of SNOBOL4 style pattern matching. This is the
24514 most elaborate of the pattern matching packages provided. It fully duplicates
24515 the SNOBOL4 dynamic pattern construction and matching capabilities, using the
24516 efficient algorithm developed by Robert Dewar for the SPITBOL system.
24518 @node GNAT Spitbol g-spitbo ads,GNAT Spitbol Table_Boolean g-sptabo ads,GNAT Spitbol Patterns g-spipat ads,The GNAT Library
24519 @anchor{gnat_rm/the_gnat_library id116}@anchor{3b9}@anchor{gnat_rm/the_gnat_library gnat-spitbol-g-spitbo-ads}@anchor{3ba}
24520 @section @code{GNAT.Spitbol} (@code{g-spitbo.ads})
24523 @geindex GNAT.Spitbol (g-spitbo.ads)
24525 @geindex SPITBOL interface
24527 The top level package of the collection of SPITBOL-style functionality, this
24528 package provides basic SNOBOL4 string manipulation functions, such as
24529 Pad, Reverse, Trim, Substr capability, as well as a generic table function
24530 useful for constructing arbitrary mappings from strings in the style of
24531 the SNOBOL4 TABLE function.
24533 @node GNAT Spitbol Table_Boolean g-sptabo ads,GNAT Spitbol Table_Integer g-sptain ads,GNAT Spitbol g-spitbo ads,The GNAT Library
24534 @anchor{gnat_rm/the_gnat_library gnat-spitbol-table-boolean-g-sptabo-ads}@anchor{3bb}@anchor{gnat_rm/the_gnat_library id117}@anchor{3bc}
24535 @section @code{GNAT.Spitbol.Table_Boolean} (@code{g-sptabo.ads})
24538 @geindex GNAT.Spitbol.Table_Boolean (g-sptabo.ads)
24540 @geindex Sets of strings
24542 @geindex SPITBOL Tables
24544 A library level of instantiation of @code{GNAT.Spitbol.Patterns.Table}
24545 for type @code{Standard.Boolean}, giving an implementation of sets of
24548 @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
24549 @anchor{gnat_rm/the_gnat_library gnat-spitbol-table-integer-g-sptain-ads}@anchor{3bd}@anchor{gnat_rm/the_gnat_library id118}@anchor{3be}
24550 @section @code{GNAT.Spitbol.Table_Integer} (@code{g-sptain.ads})
24553 @geindex GNAT.Spitbol.Table_Integer (g-sptain.ads)
24555 @geindex Integer maps
24559 @geindex SPITBOL Tables
24561 A library level of instantiation of @code{GNAT.Spitbol.Patterns.Table}
24562 for type @code{Standard.Integer}, giving an implementation of maps
24563 from string to integer values.
24565 @node GNAT Spitbol Table_VString g-sptavs ads,GNAT SSE g-sse ads,GNAT Spitbol Table_Integer g-sptain ads,The GNAT Library
24566 @anchor{gnat_rm/the_gnat_library id119}@anchor{3bf}@anchor{gnat_rm/the_gnat_library gnat-spitbol-table-vstring-g-sptavs-ads}@anchor{3c0}
24567 @section @code{GNAT.Spitbol.Table_VString} (@code{g-sptavs.ads})
24570 @geindex GNAT.Spitbol.Table_VString (g-sptavs.ads)
24572 @geindex String maps
24576 @geindex SPITBOL Tables
24578 A library level of instantiation of @code{GNAT.Spitbol.Patterns.Table} for
24579 a variable length string type, giving an implementation of general
24580 maps from strings to strings.
24582 @node GNAT SSE g-sse ads,GNAT SSE Vector_Types g-ssvety ads,GNAT Spitbol Table_VString g-sptavs ads,The GNAT Library
24583 @anchor{gnat_rm/the_gnat_library id120}@anchor{3c1}@anchor{gnat_rm/the_gnat_library gnat-sse-g-sse-ads}@anchor{3c2}
24584 @section @code{GNAT.SSE} (@code{g-sse.ads})
24587 @geindex GNAT.SSE (g-sse.ads)
24589 Root of a set of units aimed at offering Ada bindings to a subset of
24590 the Intel(r) Streaming SIMD Extensions with GNAT on the x86 family of
24591 targets. It exposes vector component types together with a general
24592 introduction to the binding contents and use.
24594 @node GNAT SSE Vector_Types g-ssvety ads,GNAT String_Hash g-strhas ads,GNAT SSE g-sse ads,The GNAT Library
24595 @anchor{gnat_rm/the_gnat_library gnat-sse-vector-types-g-ssvety-ads}@anchor{3c3}@anchor{gnat_rm/the_gnat_library id121}@anchor{3c4}
24596 @section @code{GNAT.SSE.Vector_Types} (@code{g-ssvety.ads})
24599 @geindex GNAT.SSE.Vector_Types (g-ssvety.ads)
24601 SSE vector types for use with SSE related intrinsics.
24603 @node GNAT String_Hash g-strhas ads,GNAT Strings g-string ads,GNAT SSE Vector_Types g-ssvety ads,The GNAT Library
24604 @anchor{gnat_rm/the_gnat_library gnat-string-hash-g-strhas-ads}@anchor{3c5}@anchor{gnat_rm/the_gnat_library id122}@anchor{3c6}
24605 @section @code{GNAT.String_Hash} (@code{g-strhas.ads})
24608 @geindex GNAT.String_Hash (g-strhas.ads)
24610 @geindex Hash functions
24612 Provides a generic hash function working on arrays of scalars. Both the scalar
24613 type and the hash result type are parameters.
24615 @node GNAT Strings g-string ads,GNAT String_Split g-strspl ads,GNAT String_Hash g-strhas ads,The GNAT Library
24616 @anchor{gnat_rm/the_gnat_library id123}@anchor{3c7}@anchor{gnat_rm/the_gnat_library gnat-strings-g-string-ads}@anchor{3c8}
24617 @section @code{GNAT.Strings} (@code{g-string.ads})
24620 @geindex GNAT.Strings (g-string.ads)
24622 Common String access types and related subprograms. Basically it
24623 defines a string access and an array of string access types.
24625 @node GNAT String_Split g-strspl ads,GNAT Table g-table ads,GNAT Strings g-string ads,The GNAT Library
24626 @anchor{gnat_rm/the_gnat_library gnat-string-split-g-strspl-ads}@anchor{3c9}@anchor{gnat_rm/the_gnat_library id124}@anchor{3ca}
24627 @section @code{GNAT.String_Split} (@code{g-strspl.ads})
24630 @geindex GNAT.String_Split (g-strspl.ads)
24632 @geindex String splitter
24634 Useful string manipulation routines: given a set of separators, split
24635 a string wherever the separators appear, and provide direct access
24636 to the resulting slices. This package is instantiated from
24637 @code{GNAT.Array_Split}.
24639 @node GNAT Table g-table ads,GNAT Task_Lock g-tasloc ads,GNAT String_Split g-strspl ads,The GNAT Library
24640 @anchor{gnat_rm/the_gnat_library id125}@anchor{3cb}@anchor{gnat_rm/the_gnat_library gnat-table-g-table-ads}@anchor{3cc}
24641 @section @code{GNAT.Table} (@code{g-table.ads})
24644 @geindex GNAT.Table (g-table.ads)
24646 @geindex Table implementation
24649 @geindex extendable
24651 A generic package providing a single dimension array abstraction where the
24652 length of the array can be dynamically modified.
24654 This package provides a facility similar to that of @code{GNAT.Dynamic_Tables},
24655 except that this package declares a single instance of the table type,
24656 while an instantiation of @code{GNAT.Dynamic_Tables} creates a type that can be
24657 used to define dynamic instances of the table.
24659 @node GNAT Task_Lock g-tasloc ads,GNAT Time_Stamp g-timsta ads,GNAT Table g-table ads,The GNAT Library
24660 @anchor{gnat_rm/the_gnat_library id126}@anchor{3cd}@anchor{gnat_rm/the_gnat_library gnat-task-lock-g-tasloc-ads}@anchor{3ce}
24661 @section @code{GNAT.Task_Lock} (@code{g-tasloc.ads})
24664 @geindex GNAT.Task_Lock (g-tasloc.ads)
24666 @geindex Task synchronization
24668 @geindex Task locking
24672 A very simple facility for locking and unlocking sections of code using a
24673 single global task lock. Appropriate for use in situations where contention
24674 between tasks is very rarely expected.
24676 @node GNAT Time_Stamp g-timsta ads,GNAT Threads g-thread ads,GNAT Task_Lock g-tasloc ads,The GNAT Library
24677 @anchor{gnat_rm/the_gnat_library id127}@anchor{3cf}@anchor{gnat_rm/the_gnat_library gnat-time-stamp-g-timsta-ads}@anchor{3d0}
24678 @section @code{GNAT.Time_Stamp} (@code{g-timsta.ads})
24681 @geindex GNAT.Time_Stamp (g-timsta.ads)
24683 @geindex Time stamp
24685 @geindex Current time
24687 Provides a simple function that returns a string YYYY-MM-DD HH:MM:SS.SS that
24688 represents the current date and time in ISO 8601 format. This is a very simple
24689 routine with minimal code and there are no dependencies on any other unit.
24691 @node GNAT Threads g-thread ads,GNAT Traceback g-traceb ads,GNAT Time_Stamp g-timsta ads,The GNAT Library
24692 @anchor{gnat_rm/the_gnat_library gnat-threads-g-thread-ads}@anchor{3d1}@anchor{gnat_rm/the_gnat_library id128}@anchor{3d2}
24693 @section @code{GNAT.Threads} (@code{g-thread.ads})
24696 @geindex GNAT.Threads (g-thread.ads)
24698 @geindex Foreign threads
24703 Provides facilities for dealing with foreign threads which need to be known
24704 by the GNAT run-time system. Consult the documentation of this package for
24705 further details if your program has threads that are created by a non-Ada
24706 environment which then accesses Ada code.
24708 @node GNAT Traceback g-traceb ads,GNAT Traceback Symbolic g-trasym ads,GNAT Threads g-thread ads,The GNAT Library
24709 @anchor{gnat_rm/the_gnat_library id129}@anchor{3d3}@anchor{gnat_rm/the_gnat_library gnat-traceback-g-traceb-ads}@anchor{3d4}
24710 @section @code{GNAT.Traceback} (@code{g-traceb.ads})
24713 @geindex GNAT.Traceback (g-traceb.ads)
24715 @geindex Trace back facilities
24717 Provides a facility for obtaining non-symbolic traceback information, useful
24718 in various debugging situations.
24720 @node GNAT Traceback Symbolic g-trasym ads,GNAT UTF_32 g-table ads,GNAT Traceback g-traceb ads,The GNAT Library
24721 @anchor{gnat_rm/the_gnat_library id130}@anchor{3d5}@anchor{gnat_rm/the_gnat_library gnat-traceback-symbolic-g-trasym-ads}@anchor{3d6}
24722 @section @code{GNAT.Traceback.Symbolic} (@code{g-trasym.ads})
24725 @geindex GNAT.Traceback.Symbolic (g-trasym.ads)
24727 @geindex Trace back facilities
24729 @node GNAT UTF_32 g-table ads,GNAT Wide_Spelling_Checker g-u3spch ads,GNAT Traceback Symbolic g-trasym ads,The GNAT Library
24730 @anchor{gnat_rm/the_gnat_library id131}@anchor{3d7}@anchor{gnat_rm/the_gnat_library gnat-utf-32-g-table-ads}@anchor{3d8}
24731 @section @code{GNAT.UTF_32} (@code{g-table.ads})
24734 @geindex GNAT.UTF_32 (g-table.ads)
24736 @geindex Wide character codes
24738 This is a package intended to be used in conjunction with the
24739 @code{Wide_Character} type in Ada 95 and the
24740 @code{Wide_Wide_Character} type in Ada 2005 (available
24741 in @code{GNAT} in Ada 2005 mode). This package contains
24742 Unicode categorization routines, as well as lexical
24743 categorization routines corresponding to the Ada 2005
24744 lexical rules for identifiers and strings, and also a
24745 lower case to upper case fold routine corresponding to
24746 the Ada 2005 rules for identifier equivalence.
24748 @node GNAT Wide_Spelling_Checker g-u3spch ads,GNAT Wide_Spelling_Checker g-wispch ads,GNAT UTF_32 g-table ads,The GNAT Library
24749 @anchor{gnat_rm/the_gnat_library gnat-wide-spelling-checker-g-u3spch-ads}@anchor{3d9}@anchor{gnat_rm/the_gnat_library id132}@anchor{3da}
24750 @section @code{GNAT.Wide_Spelling_Checker} (@code{g-u3spch.ads})
24753 @geindex GNAT.Wide_Spelling_Checker (g-u3spch.ads)
24755 @geindex Spell checking
24757 Provides a function for determining whether one wide wide string is a plausible
24758 near misspelling of another wide wide string, where the strings are represented
24759 using the UTF_32_String type defined in System.Wch_Cnv.
24761 @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
24762 @anchor{gnat_rm/the_gnat_library gnat-wide-spelling-checker-g-wispch-ads}@anchor{3db}@anchor{gnat_rm/the_gnat_library id133}@anchor{3dc}
24763 @section @code{GNAT.Wide_Spelling_Checker} (@code{g-wispch.ads})
24766 @geindex GNAT.Wide_Spelling_Checker (g-wispch.ads)
24768 @geindex Spell checking
24770 Provides a function for determining whether one wide string is a plausible
24771 near misspelling of another wide string.
24773 @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
24774 @anchor{gnat_rm/the_gnat_library id134}@anchor{3dd}@anchor{gnat_rm/the_gnat_library gnat-wide-string-split-g-wistsp-ads}@anchor{3de}
24775 @section @code{GNAT.Wide_String_Split} (@code{g-wistsp.ads})
24778 @geindex GNAT.Wide_String_Split (g-wistsp.ads)
24780 @geindex Wide_String splitter
24782 Useful wide string manipulation routines: given a set of separators, split
24783 a wide string wherever the separators appear, and provide direct access
24784 to the resulting slices. This package is instantiated from
24785 @code{GNAT.Array_Split}.
24787 @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
24788 @anchor{gnat_rm/the_gnat_library gnat-wide-wide-spelling-checker-g-zspche-ads}@anchor{3df}@anchor{gnat_rm/the_gnat_library id135}@anchor{3e0}
24789 @section @code{GNAT.Wide_Wide_Spelling_Checker} (@code{g-zspche.ads})
24792 @geindex GNAT.Wide_Wide_Spelling_Checker (g-zspche.ads)
24794 @geindex Spell checking
24796 Provides a function for determining whether one wide wide string is a plausible
24797 near misspelling of another wide wide string.
24799 @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
24800 @anchor{gnat_rm/the_gnat_library gnat-wide-wide-string-split-g-zistsp-ads}@anchor{3e1}@anchor{gnat_rm/the_gnat_library id136}@anchor{3e2}
24801 @section @code{GNAT.Wide_Wide_String_Split} (@code{g-zistsp.ads})
24804 @geindex GNAT.Wide_Wide_String_Split (g-zistsp.ads)
24806 @geindex Wide_Wide_String splitter
24808 Useful wide wide string manipulation routines: given a set of separators, split
24809 a wide wide string wherever the separators appear, and provide direct access
24810 to the resulting slices. This package is instantiated from
24811 @code{GNAT.Array_Split}.
24813 @node Interfaces C Extensions i-cexten ads,Interfaces C Streams i-cstrea ads,GNAT Wide_Wide_String_Split g-zistsp ads,The GNAT Library
24814 @anchor{gnat_rm/the_gnat_library interfaces-c-extensions-i-cexten-ads}@anchor{3e3}@anchor{gnat_rm/the_gnat_library id137}@anchor{3e4}
24815 @section @code{Interfaces.C.Extensions} (@code{i-cexten.ads})
24818 @geindex Interfaces.C.Extensions (i-cexten.ads)
24820 This package contains additional C-related definitions, intended
24821 for use with either manually or automatically generated bindings
24824 @node Interfaces C Streams i-cstrea ads,Interfaces Packed_Decimal i-pacdec ads,Interfaces C Extensions i-cexten ads,The GNAT Library
24825 @anchor{gnat_rm/the_gnat_library id138}@anchor{3e5}@anchor{gnat_rm/the_gnat_library interfaces-c-streams-i-cstrea-ads}@anchor{3e6}
24826 @section @code{Interfaces.C.Streams} (@code{i-cstrea.ads})
24829 @geindex Interfaces.C.Streams (i-cstrea.ads)
24832 @geindex interfacing
24834 This package is a binding for the most commonly used operations
24837 @node Interfaces Packed_Decimal i-pacdec ads,Interfaces VxWorks i-vxwork ads,Interfaces C Streams i-cstrea ads,The GNAT Library
24838 @anchor{gnat_rm/the_gnat_library interfaces-packed-decimal-i-pacdec-ads}@anchor{3e7}@anchor{gnat_rm/the_gnat_library id139}@anchor{3e8}
24839 @section @code{Interfaces.Packed_Decimal} (@code{i-pacdec.ads})
24842 @geindex Interfaces.Packed_Decimal (i-pacdec.ads)
24844 @geindex IBM Packed Format
24846 @geindex Packed Decimal
24848 This package provides a set of routines for conversions to and
24849 from a packed decimal format compatible with that used on IBM
24852 @node Interfaces VxWorks i-vxwork ads,Interfaces VxWorks Int_Connection i-vxinco ads,Interfaces Packed_Decimal i-pacdec ads,The GNAT Library
24853 @anchor{gnat_rm/the_gnat_library interfaces-vxworks-i-vxwork-ads}@anchor{3e9}@anchor{gnat_rm/the_gnat_library id140}@anchor{3ea}
24854 @section @code{Interfaces.VxWorks} (@code{i-vxwork.ads})
24857 @geindex Interfaces.VxWorks (i-vxwork.ads)
24859 @geindex Interfacing to VxWorks
24862 @geindex interfacing
24864 This package provides a limited binding to the VxWorks API.
24865 In particular, it interfaces with the
24866 VxWorks hardware interrupt facilities.
24868 @node Interfaces VxWorks Int_Connection i-vxinco ads,Interfaces VxWorks IO i-vxwoio ads,Interfaces VxWorks i-vxwork ads,The GNAT Library
24869 @anchor{gnat_rm/the_gnat_library interfaces-vxworks-int-connection-i-vxinco-ads}@anchor{3eb}@anchor{gnat_rm/the_gnat_library id141}@anchor{3ec}
24870 @section @code{Interfaces.VxWorks.Int_Connection} (@code{i-vxinco.ads})
24873 @geindex Interfaces.VxWorks.Int_Connection (i-vxinco.ads)
24875 @geindex Interfacing to VxWorks
24878 @geindex interfacing
24880 This package provides a way for users to replace the use of
24881 intConnect() with a custom routine for installing interrupt
24884 @node Interfaces VxWorks IO i-vxwoio ads,System Address_Image s-addima ads,Interfaces VxWorks Int_Connection i-vxinco ads,The GNAT Library
24885 @anchor{gnat_rm/the_gnat_library interfaces-vxworks-io-i-vxwoio-ads}@anchor{3ed}@anchor{gnat_rm/the_gnat_library id142}@anchor{3ee}
24886 @section @code{Interfaces.VxWorks.IO} (@code{i-vxwoio.ads})
24889 @geindex Interfaces.VxWorks.IO (i-vxwoio.ads)
24891 @geindex Interfacing to VxWorks' I/O
24894 @geindex I/O interfacing
24897 @geindex Get_Immediate
24899 @geindex Get_Immediate
24902 This package provides a binding to the ioctl (IO/Control)
24903 function of VxWorks, defining a set of option values and
24904 function codes. A particular use of this package is
24905 to enable the use of Get_Immediate under VxWorks.
24907 @node System Address_Image s-addima ads,System Assertions s-assert ads,Interfaces VxWorks IO i-vxwoio ads,The GNAT Library
24908 @anchor{gnat_rm/the_gnat_library system-address-image-s-addima-ads}@anchor{3ef}@anchor{gnat_rm/the_gnat_library id143}@anchor{3f0}
24909 @section @code{System.Address_Image} (@code{s-addima.ads})
24912 @geindex System.Address_Image (s-addima.ads)
24914 @geindex Address image
24917 @geindex of an address
24919 This function provides a useful debugging
24920 function that gives an (implementation dependent)
24921 string which identifies an address.
24923 @node System Assertions s-assert ads,System Atomic_Counters s-atocou ads,System Address_Image s-addima ads,The GNAT Library
24924 @anchor{gnat_rm/the_gnat_library id144}@anchor{3f1}@anchor{gnat_rm/the_gnat_library system-assertions-s-assert-ads}@anchor{3f2}
24925 @section @code{System.Assertions} (@code{s-assert.ads})
24928 @geindex System.Assertions (s-assert.ads)
24930 @geindex Assertions
24932 @geindex Assert_Failure
24935 This package provides the declaration of the exception raised
24936 by an run-time assertion failure, as well as the routine that
24937 is used internally to raise this assertion.
24939 @node System Atomic_Counters s-atocou ads,System Memory s-memory ads,System Assertions s-assert ads,The GNAT Library
24940 @anchor{gnat_rm/the_gnat_library id145}@anchor{3f3}@anchor{gnat_rm/the_gnat_library system-atomic-counters-s-atocou-ads}@anchor{3f4}
24941 @section @code{System.Atomic_Counters} (@code{s-atocou.ads})
24944 @geindex System.Atomic_Counters (s-atocou.ads)
24946 This package provides the declaration of an atomic counter type,
24947 together with efficient routines (using hardware
24948 synchronization primitives) for incrementing, decrementing,
24949 and testing of these counters. This package is implemented
24950 on most targets, including all Alpha, ia64, PowerPC, SPARC V9,
24951 x86, and x86_64 platforms.
24953 @node System Memory s-memory ads,System Multiprocessors s-multip ads,System Atomic_Counters s-atocou ads,The GNAT Library
24954 @anchor{gnat_rm/the_gnat_library system-memory-s-memory-ads}@anchor{3f5}@anchor{gnat_rm/the_gnat_library id146}@anchor{3f6}
24955 @section @code{System.Memory} (@code{s-memory.ads})
24958 @geindex System.Memory (s-memory.ads)
24960 @geindex Memory allocation
24962 This package provides the interface to the low level routines used
24963 by the generated code for allocation and freeing storage for the
24964 default storage pool (analogous to the C routines malloc and free.
24965 It also provides a reallocation interface analogous to the C routine
24966 realloc. The body of this unit may be modified to provide alternative
24967 allocation mechanisms for the default pool, and in addition, direct
24968 calls to this unit may be made for low level allocation uses (for
24969 example see the body of @code{GNAT.Tables}).
24971 @node System Multiprocessors s-multip ads,System Multiprocessors Dispatching_Domains s-mudido ads,System Memory s-memory ads,The GNAT Library
24972 @anchor{gnat_rm/the_gnat_library id147}@anchor{3f7}@anchor{gnat_rm/the_gnat_library system-multiprocessors-s-multip-ads}@anchor{3f8}
24973 @section @code{System.Multiprocessors} (@code{s-multip.ads})
24976 @geindex System.Multiprocessors (s-multip.ads)
24978 @geindex Multiprocessor interface
24980 This is an Ada 2012 unit defined in the Ada 2012 Reference Manual, but
24981 in GNAT we also make it available in Ada 95 and Ada 2005 (where it is
24982 technically an implementation-defined addition).
24984 @node System Multiprocessors Dispatching_Domains s-mudido ads,System Partition_Interface s-parint ads,System Multiprocessors s-multip ads,The GNAT Library
24985 @anchor{gnat_rm/the_gnat_library system-multiprocessors-dispatching-domains-s-mudido-ads}@anchor{3f9}@anchor{gnat_rm/the_gnat_library id148}@anchor{3fa}
24986 @section @code{System.Multiprocessors.Dispatching_Domains} (@code{s-mudido.ads})
24989 @geindex System.Multiprocessors.Dispatching_Domains (s-mudido.ads)
24991 @geindex Multiprocessor interface
24993 This is an Ada 2012 unit defined in the Ada 2012 Reference Manual, but
24994 in GNAT we also make it available in Ada 95 and Ada 2005 (where it is
24995 technically an implementation-defined addition).
24997 @node System Partition_Interface s-parint ads,System Pool_Global s-pooglo ads,System Multiprocessors Dispatching_Domains s-mudido ads,The GNAT Library
24998 @anchor{gnat_rm/the_gnat_library id149}@anchor{3fb}@anchor{gnat_rm/the_gnat_library system-partition-interface-s-parint-ads}@anchor{3fc}
24999 @section @code{System.Partition_Interface} (@code{s-parint.ads})
25002 @geindex System.Partition_Interface (s-parint.ads)
25004 @geindex Partition interfacing functions
25006 This package provides facilities for partition interfacing. It
25007 is used primarily in a distribution context when using Annex E
25010 @node System Pool_Global s-pooglo ads,System Pool_Local s-pooloc ads,System Partition_Interface s-parint ads,The GNAT Library
25011 @anchor{gnat_rm/the_gnat_library id150}@anchor{3fd}@anchor{gnat_rm/the_gnat_library system-pool-global-s-pooglo-ads}@anchor{3fe}
25012 @section @code{System.Pool_Global} (@code{s-pooglo.ads})
25015 @geindex System.Pool_Global (s-pooglo.ads)
25017 @geindex Storage pool
25020 @geindex Global storage pool
25022 This package provides a storage pool that is equivalent to the default
25023 storage pool used for access types for which no pool is specifically
25024 declared. It uses malloc/free to allocate/free and does not attempt to
25025 do any automatic reclamation.
25027 @node System Pool_Local s-pooloc ads,System Restrictions s-restri ads,System Pool_Global s-pooglo ads,The GNAT Library
25028 @anchor{gnat_rm/the_gnat_library system-pool-local-s-pooloc-ads}@anchor{3ff}@anchor{gnat_rm/the_gnat_library id151}@anchor{400}
25029 @section @code{System.Pool_Local} (@code{s-pooloc.ads})
25032 @geindex System.Pool_Local (s-pooloc.ads)
25034 @geindex Storage pool
25037 @geindex Local storage pool
25039 This package provides a storage pool that is intended for use with locally
25040 defined access types. It uses malloc/free for allocate/free, and maintains
25041 a list of allocated blocks, so that all storage allocated for the pool can
25042 be freed automatically when the pool is finalized.
25044 @node System Restrictions s-restri ads,System Rident s-rident ads,System Pool_Local s-pooloc ads,The GNAT Library
25045 @anchor{gnat_rm/the_gnat_library id152}@anchor{401}@anchor{gnat_rm/the_gnat_library system-restrictions-s-restri-ads}@anchor{402}
25046 @section @code{System.Restrictions} (@code{s-restri.ads})
25049 @geindex System.Restrictions (s-restri.ads)
25051 @geindex Run-time restrictions access
25053 This package provides facilities for accessing at run time
25054 the status of restrictions specified at compile time for
25055 the partition. Information is available both with regard
25056 to actual restrictions specified, and with regard to
25057 compiler determined information on which restrictions
25058 are violated by one or more packages in the partition.
25060 @node System Rident s-rident ads,System Strings Stream_Ops s-ststop ads,System Restrictions s-restri ads,The GNAT Library
25061 @anchor{gnat_rm/the_gnat_library system-rident-s-rident-ads}@anchor{403}@anchor{gnat_rm/the_gnat_library id153}@anchor{404}
25062 @section @code{System.Rident} (@code{s-rident.ads})
25065 @geindex System.Rident (s-rident.ads)
25067 @geindex Restrictions definitions
25069 This package provides definitions of the restrictions
25070 identifiers supported by GNAT, and also the format of
25071 the restrictions provided in package System.Restrictions.
25072 It is not normally necessary to @code{with} this generic package
25073 since the necessary instantiation is included in
25074 package System.Restrictions.
25076 @node System Strings Stream_Ops s-ststop ads,System Unsigned_Types s-unstyp ads,System Rident s-rident ads,The GNAT Library
25077 @anchor{gnat_rm/the_gnat_library id154}@anchor{405}@anchor{gnat_rm/the_gnat_library system-strings-stream-ops-s-ststop-ads}@anchor{406}
25078 @section @code{System.Strings.Stream_Ops} (@code{s-ststop.ads})
25081 @geindex System.Strings.Stream_Ops (s-ststop.ads)
25083 @geindex Stream operations
25085 @geindex String stream operations
25087 This package provides a set of stream subprograms for standard string types.
25088 It is intended primarily to support implicit use of such subprograms when
25089 stream attributes are applied to string types, but the subprograms in this
25090 package can be used directly by application programs.
25092 @node System Unsigned_Types s-unstyp ads,System Wch_Cnv s-wchcnv ads,System Strings Stream_Ops s-ststop ads,The GNAT Library
25093 @anchor{gnat_rm/the_gnat_library system-unsigned-types-s-unstyp-ads}@anchor{407}@anchor{gnat_rm/the_gnat_library id155}@anchor{408}
25094 @section @code{System.Unsigned_Types} (@code{s-unstyp.ads})
25097 @geindex System.Unsigned_Types (s-unstyp.ads)
25099 This package contains definitions of standard unsigned types that
25100 correspond in size to the standard signed types declared in Standard,
25101 and (unlike the types in Interfaces) have corresponding names. It
25102 also contains some related definitions for other specialized types
25103 used by the compiler in connection with packed array types.
25105 @node System Wch_Cnv s-wchcnv ads,System Wch_Con s-wchcon ads,System Unsigned_Types s-unstyp ads,The GNAT Library
25106 @anchor{gnat_rm/the_gnat_library system-wch-cnv-s-wchcnv-ads}@anchor{409}@anchor{gnat_rm/the_gnat_library id156}@anchor{40a}
25107 @section @code{System.Wch_Cnv} (@code{s-wchcnv.ads})
25110 @geindex System.Wch_Cnv (s-wchcnv.ads)
25112 @geindex Wide Character
25113 @geindex Representation
25115 @geindex Wide String
25116 @geindex Conversion
25118 @geindex Representation of wide characters
25120 This package provides routines for converting between
25121 wide and wide wide characters and a representation as a value of type
25122 @code{Standard.String}, using a specified wide character
25123 encoding method. It uses definitions in
25124 package @code{System.Wch_Con}.
25126 @node System Wch_Con s-wchcon ads,,System Wch_Cnv s-wchcnv ads,The GNAT Library
25127 @anchor{gnat_rm/the_gnat_library id157}@anchor{40b}@anchor{gnat_rm/the_gnat_library system-wch-con-s-wchcon-ads}@anchor{40c}
25128 @section @code{System.Wch_Con} (@code{s-wchcon.ads})
25131 @geindex System.Wch_Con (s-wchcon.ads)
25133 This package provides definitions and descriptions of
25134 the various methods used for encoding wide characters
25135 in ordinary strings. These definitions are used by
25136 the package @code{System.Wch_Cnv}.
25138 @node Interfacing to Other Languages,Specialized Needs Annexes,The GNAT Library,Top
25139 @anchor{gnat_rm/interfacing_to_other_languages interfacing-to-other-languages}@anchor{11}@anchor{gnat_rm/interfacing_to_other_languages doc}@anchor{40d}@anchor{gnat_rm/interfacing_to_other_languages id1}@anchor{40e}
25140 @chapter Interfacing to Other Languages
25143 The facilities in Annex B of the Ada Reference Manual are fully
25144 implemented in GNAT, and in addition, a full interface to C++ is
25148 * Interfacing to C::
25149 * Interfacing to C++::
25150 * Interfacing to COBOL::
25151 * Interfacing to Fortran::
25152 * Interfacing to non-GNAT Ada code::
25156 @node Interfacing to C,Interfacing to C++,,Interfacing to Other Languages
25157 @anchor{gnat_rm/interfacing_to_other_languages interfacing-to-c}@anchor{40f}@anchor{gnat_rm/interfacing_to_other_languages id2}@anchor{410}
25158 @section Interfacing to C
25161 Interfacing to C with GNAT can use one of two approaches:
25167 The types in the package @code{Interfaces.C} may be used.
25170 Standard Ada types may be used directly. This may be less portable to
25171 other compilers, but will work on all GNAT compilers, which guarantee
25172 correspondence between the C and Ada types.
25175 Pragma @code{Convention C} may be applied to Ada types, but mostly has no
25176 effect, since this is the default. The following table shows the
25177 correspondence between Ada scalar types and the corresponding C types.
25180 @multitable {xxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
25199 @code{Short_Integer}
25207 @code{Short_Short_Integer}
25215 @code{Long_Integer}
25223 @code{Long_Long_Integer}
25255 @code{Long_Long_Float}
25259 This is the longest floating-point type supported by the hardware.
25264 Additionally, there are the following general correspondences between Ada
25271 Ada enumeration types map to C enumeration types directly if pragma
25272 @code{Convention C} is specified, which causes them to have a length of
25273 32 bits, except for boolean types which map to C99 @code{bool} and for
25274 which the length is 8 bits.
25275 Without pragma @code{Convention C}, Ada enumeration types map to
25276 8, 16, or 32 bits (i.e., C types @code{signed char}, @code{short},
25277 @code{int}, respectively) depending on the number of values passed.
25278 This is the only case in which pragma @code{Convention C} affects the
25279 representation of an Ada type.
25282 Ada access types map to C pointers, except for the case of pointers to
25283 unconstrained types in Ada, which have no direct C equivalent.
25286 Ada arrays map directly to C arrays.
25289 Ada records map directly to C structures.
25292 Packed Ada records map to C structures where all members are bit fields
25293 of the length corresponding to the @code{type'Size} value in Ada.
25296 @node Interfacing to C++,Interfacing to COBOL,Interfacing to C,Interfacing to Other Languages
25297 @anchor{gnat_rm/interfacing_to_other_languages id4}@anchor{411}@anchor{gnat_rm/interfacing_to_other_languages id3}@anchor{47}
25298 @section Interfacing to C++
25301 The interface to C++ makes use of the following pragmas, which are
25302 primarily intended to be constructed automatically using a binding generator
25303 tool, although it is possible to construct them by hand.
25305 Using these pragmas it is possible to achieve complete
25306 inter-operability between Ada tagged types and C++ class definitions.
25307 See @ref{7,,Implementation Defined Pragmas}, for more details.
25312 @item @code{pragma CPP_Class ([Entity =>] @emph{LOCAL_NAME})}
25314 The argument denotes an entity in the current declarative region that is
25315 declared as a tagged or untagged record type. It indicates that the type
25316 corresponds to an externally declared C++ class type, and is to be laid
25317 out the same way that C++ would lay out the type.
25319 Note: Pragma @code{CPP_Class} is currently obsolete. It is supported
25320 for backward compatibility but its functionality is available
25321 using pragma @code{Import} with @code{Convention} = @code{CPP}.
25323 @item @code{pragma CPP_Constructor ([Entity =>] @emph{LOCAL_NAME})}
25325 This pragma identifies an imported function (imported in the usual way
25326 with pragma @code{Import}) as corresponding to a C++ constructor.
25329 A few restrictions are placed on the use of the @code{Access} attribute
25330 in conjunction with subprograms subject to convention @code{CPP}: the
25331 attribute may be used neither on primitive operations of a tagged
25332 record type with convention @code{CPP}, imported or not, nor on
25333 subprograms imported with pragma @code{CPP_Constructor}.
25335 In addition, C++ exceptions are propagated and can be handled in an
25336 @code{others} choice of an exception handler. The corresponding Ada
25337 occurrence has no message, and the simple name of the exception identity
25338 contains @code{Foreign_Exception}. Finalization and awaiting dependent
25339 tasks works properly when such foreign exceptions are propagated.
25341 It is also possible to import a C++ exception using the following syntax:
25344 LOCAL_NAME : exception;
25345 pragma Import (Cpp,
25346 [Entity =>] LOCAL_NAME,
25347 [External_Name =>] static_string_EXPRESSION);
25350 The @code{External_Name} is the name of the C++ RTTI symbol. You can then
25351 cover a specific C++ exception in an exception handler.
25353 @node Interfacing to COBOL,Interfacing to Fortran,Interfacing to C++,Interfacing to Other Languages
25354 @anchor{gnat_rm/interfacing_to_other_languages id5}@anchor{412}@anchor{gnat_rm/interfacing_to_other_languages interfacing-to-cobol}@anchor{413}
25355 @section Interfacing to COBOL
25358 Interfacing to COBOL is achieved as described in section B.4 of
25359 the Ada Reference Manual.
25361 @node Interfacing to Fortran,Interfacing to non-GNAT Ada code,Interfacing to COBOL,Interfacing to Other Languages
25362 @anchor{gnat_rm/interfacing_to_other_languages id6}@anchor{414}@anchor{gnat_rm/interfacing_to_other_languages interfacing-to-fortran}@anchor{415}
25363 @section Interfacing to Fortran
25366 Interfacing to Fortran is achieved as described in section B.5 of the
25367 Ada Reference Manual. The pragma @code{Convention Fortran}, applied to a
25368 multi-dimensional array causes the array to be stored in column-major
25369 order as required for convenient interface to Fortran.
25371 @node Interfacing to non-GNAT Ada code,,Interfacing to Fortran,Interfacing to Other Languages
25372 @anchor{gnat_rm/interfacing_to_other_languages interfacing-to-non-gnat-ada-code}@anchor{416}@anchor{gnat_rm/interfacing_to_other_languages id7}@anchor{417}
25373 @section Interfacing to non-GNAT Ada code
25376 It is possible to specify the convention @code{Ada} in a pragma
25377 @code{Import} or pragma @code{Export}. However this refers to
25378 the calling conventions used by GNAT, which may or may not be
25379 similar enough to those used by some other Ada 83 / Ada 95 / Ada 2005
25380 compiler to allow interoperation.
25382 If arguments types are kept simple, and if the foreign compiler generally
25383 follows system calling conventions, then it may be possible to integrate
25384 files compiled by other Ada compilers, provided that the elaboration
25385 issues are adequately addressed (for example by eliminating the
25386 need for any load time elaboration).
25388 In particular, GNAT running on VMS is designed to
25389 be highly compatible with the DEC Ada 83 compiler, so this is one
25390 case in which it is possible to import foreign units of this type,
25391 provided that the data items passed are restricted to simple scalar
25392 values or simple record types without variants, or simple array
25393 types with fixed bounds.
25395 @node Specialized Needs Annexes,Implementation of Specific Ada Features,Interfacing to Other Languages,Top
25396 @anchor{gnat_rm/specialized_needs_annexes specialized-needs-annexes}@anchor{12}@anchor{gnat_rm/specialized_needs_annexes doc}@anchor{418}@anchor{gnat_rm/specialized_needs_annexes id1}@anchor{419}
25397 @chapter Specialized Needs Annexes
25400 Ada 95, Ada 2005, and Ada 2012 define a number of Specialized Needs Annexes, which are not
25401 required in all implementations. However, as described in this chapter,
25402 GNAT implements all of these annexes:
25407 @item @emph{Systems Programming (Annex C)}
25409 The Systems Programming Annex is fully implemented.
25411 @item @emph{Real-Time Systems (Annex D)}
25413 The Real-Time Systems Annex is fully implemented.
25415 @item @emph{Distributed Systems (Annex E)}
25417 Stub generation is fully implemented in the GNAT compiler. In addition,
25418 a complete compatible PCS is available as part of the GLADE system,
25419 a separate product. When the two
25420 products are used in conjunction, this annex is fully implemented.
25422 @item @emph{Information Systems (Annex F)}
25424 The Information Systems annex is fully implemented.
25426 @item @emph{Numerics (Annex G)}
25428 The Numerics Annex is fully implemented.
25430 @item @emph{Safety and Security / High-Integrity Systems (Annex H)}
25432 The Safety and Security Annex (termed the High-Integrity Systems Annex
25433 in Ada 2005) is fully implemented.
25436 @node Implementation of Specific Ada Features,Implementation of Ada 2012 Features,Specialized Needs Annexes,Top
25437 @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{41a}@anchor{gnat_rm/implementation_of_specific_ada_features id1}@anchor{41b}
25438 @chapter Implementation of Specific Ada Features
25441 This chapter describes the GNAT implementation of several Ada language
25445 * Machine Code Insertions::
25446 * GNAT Implementation of Tasking::
25447 * GNAT Implementation of Shared Passive Packages::
25448 * Code Generation for Array Aggregates::
25449 * The Size of Discriminated Records with Default Discriminants::
25450 * Strict Conformance to the Ada Reference Manual::
25454 @node Machine Code Insertions,GNAT Implementation of Tasking,,Implementation of Specific Ada Features
25455 @anchor{gnat_rm/implementation_of_specific_ada_features machine-code-insertions}@anchor{169}@anchor{gnat_rm/implementation_of_specific_ada_features id2}@anchor{41c}
25456 @section Machine Code Insertions
25459 @geindex Machine Code insertions
25461 Package @code{Machine_Code} provides machine code support as described
25462 in the Ada Reference Manual in two separate forms:
25468 Machine code statements, consisting of qualified expressions that
25469 fit the requirements of RM section 13.8.
25472 An intrinsic callable procedure, providing an alternative mechanism of
25473 including machine instructions in a subprogram.
25476 The two features are similar, and both are closely related to the mechanism
25477 provided by the asm instruction in the GNU C compiler. Full understanding
25478 and use of the facilities in this package requires understanding the asm
25479 instruction, see the section on Extended Asm in
25480 @cite{Using_the_GNU_Compiler_Collection_(GCC)}.
25482 Calls to the function @code{Asm} and the procedure @code{Asm} have identical
25483 semantic restrictions and effects as described below. Both are provided so
25484 that the procedure call can be used as a statement, and the function call
25485 can be used to form a code_statement.
25487 Consider this C @code{asm} instruction:
25490 asm ("fsinx %1 %0" : "=f" (result) : "f" (angle));
25493 The equivalent can be written for GNAT as:
25496 Asm ("fsinx %1 %0",
25497 My_Float'Asm_Output ("=f", result),
25498 My_Float'Asm_Input ("f", angle));
25501 The first argument to @code{Asm} is the assembler template, and is
25502 identical to what is used in GNU C. This string must be a static
25503 expression. The second argument is the output operand list. It is
25504 either a single @code{Asm_Output} attribute reference, or a list of such
25505 references enclosed in parentheses (technically an array aggregate of
25508 The @code{Asm_Output} attribute denotes a function that takes two
25509 parameters. The first is a string, the second is the name of a variable
25510 of the type designated by the attribute prefix. The first (string)
25511 argument is required to be a static expression and designates the
25512 constraint (see the section on Constraints in
25513 @cite{Using_the_GNU_Compiler_Collection_(GCC)})
25514 for the parameter; e.g., what kind of register is required. The second
25515 argument is the variable to be written or updated with the
25516 result. The possible values for constraint are the same as those used in
25517 the RTL, and are dependent on the configuration file used to build the
25518 GCC back end. If there are no output operands, then this argument may
25519 either be omitted, or explicitly given as @code{No_Output_Operands}.
25520 No support is provided for GNU C's symbolic names for output parameters.
25522 The second argument of @code{my_float'Asm_Output} functions as
25523 though it were an @code{out} parameter, which is a little curious, but
25524 all names have the form of expressions, so there is no syntactic
25525 irregularity, even though normally functions would not be permitted
25526 @code{out} parameters. The third argument is the list of input
25527 operands. It is either a single @code{Asm_Input} attribute reference, or
25528 a list of such references enclosed in parentheses (technically an array
25529 aggregate of such references).
25531 The @code{Asm_Input} attribute denotes a function that takes two
25532 parameters. The first is a string, the second is an expression of the
25533 type designated by the prefix. The first (string) argument is required
25534 to be a static expression, and is the constraint for the parameter,
25535 (e.g., what kind of register is required). The second argument is the
25536 value to be used as the input argument. The possible values for the
25537 constraint are the same as those used in the RTL, and are dependent on
25538 the configuration file used to built the GCC back end.
25539 No support is provided for GNU C's symbolic names for input parameters.
25541 If there are no input operands, this argument may either be omitted, or
25542 explicitly given as @code{No_Input_Operands}. The fourth argument, not
25543 present in the above example, is a list of register names, called the
25544 @emph{clobber} argument. This argument, if given, must be a static string
25545 expression, and is a space or comma separated list of names of registers
25546 that must be considered destroyed as a result of the @code{Asm} call. If
25547 this argument is the null string (the default value), then the code
25548 generator assumes that no additional registers are destroyed.
25549 In addition to registers, the special clobbers @code{memory} and
25550 @code{cc} as described in the GNU C docs are both supported.
25552 The fifth argument, not present in the above example, called the
25553 @emph{volatile} argument, is by default @code{False}. It can be set to
25554 the literal value @code{True} to indicate to the code generator that all
25555 optimizations with respect to the instruction specified should be
25556 suppressed, and in particular an instruction that has outputs
25557 will still be generated, even if none of the outputs are
25558 used. See @cite{Using_the_GNU_Compiler_Collection_(GCC)}
25559 for the full description.
25560 Generally it is strongly advisable to use Volatile for any ASM statement
25561 that is missing either input or output operands or to avoid unwanted
25562 optimizations. A warning is generated if this advice is not followed.
25564 No support is provided for GNU C's @code{asm goto} feature.
25566 The @code{Asm} subprograms may be used in two ways. First the procedure
25567 forms can be used anywhere a procedure call would be valid, and
25568 correspond to what the RM calls 'intrinsic' routines. Such calls can
25569 be used to intersperse machine instructions with other Ada statements.
25570 Second, the function forms, which return a dummy value of the limited
25571 private type @code{Asm_Insn}, can be used in code statements, and indeed
25572 this is the only context where such calls are allowed. Code statements
25573 appear as aggregates of the form:
25576 Asm_Insn'(Asm (...));
25577 Asm_Insn'(Asm_Volatile (...));
25580 In accordance with RM rules, such code statements are allowed only
25581 within subprograms whose entire body consists of such statements. It is
25582 not permissible to intermix such statements with other Ada statements.
25584 Typically the form using intrinsic procedure calls is more convenient
25585 and more flexible. The code statement form is provided to meet the RM
25586 suggestion that such a facility should be made available. The following
25587 is the exact syntax of the call to @code{Asm}. As usual, if named notation
25588 is used, the arguments may be given in arbitrary order, following the
25589 normal rules for use of positional and named arguments:
25593 [Template =>] static_string_EXPRESSION
25594 [,[Outputs =>] OUTPUT_OPERAND_LIST ]
25595 [,[Inputs =>] INPUT_OPERAND_LIST ]
25596 [,[Clobber =>] static_string_EXPRESSION ]
25597 [,[Volatile =>] static_boolean_EXPRESSION] )
25599 OUTPUT_OPERAND_LIST ::=
25600 [PREFIX.]No_Output_Operands
25601 | OUTPUT_OPERAND_ATTRIBUTE
25602 | (OUTPUT_OPERAND_ATTRIBUTE @{,OUTPUT_OPERAND_ATTRIBUTE@})
25604 OUTPUT_OPERAND_ATTRIBUTE ::=
25605 SUBTYPE_MARK'Asm_Output (static_string_EXPRESSION, NAME)
25607 INPUT_OPERAND_LIST ::=
25608 [PREFIX.]No_Input_Operands
25609 | INPUT_OPERAND_ATTRIBUTE
25610 | (INPUT_OPERAND_ATTRIBUTE @{,INPUT_OPERAND_ATTRIBUTE@})
25612 INPUT_OPERAND_ATTRIBUTE ::=
25613 SUBTYPE_MARK'Asm_Input (static_string_EXPRESSION, EXPRESSION)
25616 The identifiers @code{No_Input_Operands} and @code{No_Output_Operands}
25617 are declared in the package @code{Machine_Code} and must be referenced
25618 according to normal visibility rules. In particular if there is no
25619 @code{use} clause for this package, then appropriate package name
25620 qualification is required.
25622 @node GNAT Implementation of Tasking,GNAT Implementation of Shared Passive Packages,Machine Code Insertions,Implementation of Specific Ada Features
25623 @anchor{gnat_rm/implementation_of_specific_ada_features id3}@anchor{41d}@anchor{gnat_rm/implementation_of_specific_ada_features gnat-implementation-of-tasking}@anchor{41e}
25624 @section GNAT Implementation of Tasking
25627 This chapter outlines the basic GNAT approach to tasking (in particular,
25628 a multi-layered library for portability) and discusses issues related
25629 to compliance with the Real-Time Systems Annex.
25632 * Mapping Ada Tasks onto the Underlying Kernel Threads::
25633 * Ensuring Compliance with the Real-Time Annex::
25634 * Support for Locking Policies::
25638 @node Mapping Ada Tasks onto the Underlying Kernel Threads,Ensuring Compliance with the Real-Time Annex,,GNAT Implementation of Tasking
25639 @anchor{gnat_rm/implementation_of_specific_ada_features mapping-ada-tasks-onto-the-underlying-kernel-threads}@anchor{41f}@anchor{gnat_rm/implementation_of_specific_ada_features id4}@anchor{420}
25640 @subsection Mapping Ada Tasks onto the Underlying Kernel Threads
25643 GNAT's run-time support comprises two layers:
25649 GNARL (GNAT Run-time Layer)
25652 GNULL (GNAT Low-level Library)
25655 In GNAT, Ada's tasking services rely on a platform and OS independent
25656 layer known as GNARL. This code is responsible for implementing the
25657 correct semantics of Ada's task creation, rendezvous, protected
25660 GNARL decomposes Ada's tasking semantics into simpler lower level
25661 operations such as create a thread, set the priority of a thread,
25662 yield, create a lock, lock/unlock, etc. The spec for these low-level
25663 operations constitutes GNULLI, the GNULL Interface. This interface is
25664 directly inspired from the POSIX real-time API.
25666 If the underlying executive or OS implements the POSIX standard
25667 faithfully, the GNULL Interface maps as is to the services offered by
25668 the underlying kernel. Otherwise, some target dependent glue code maps
25669 the services offered by the underlying kernel to the semantics expected
25672 Whatever the underlying OS (VxWorks, UNIX, Windows, etc.) the
25673 key point is that each Ada task is mapped on a thread in the underlying
25674 kernel. For example, in the case of VxWorks, one Ada task = one VxWorks task.
25676 In addition Ada task priorities map onto the underlying thread priorities.
25677 Mapping Ada tasks onto the underlying kernel threads has several advantages:
25683 The underlying scheduler is used to schedule the Ada tasks. This
25684 makes Ada tasks as efficient as kernel threads from a scheduling
25688 Interaction with code written in C containing threads is eased
25689 since at the lowest level Ada tasks and C threads map onto the same
25690 underlying kernel concept.
25693 When an Ada task is blocked during I/O the remaining Ada tasks are
25697 On multiprocessor systems Ada tasks can execute in parallel.
25700 Some threads libraries offer a mechanism to fork a new process, with the
25701 child process duplicating the threads from the parent.
25703 support this functionality when the parent contains more than one task.
25705 @geindex Forking a new process
25707 @node Ensuring Compliance with the Real-Time Annex,Support for Locking Policies,Mapping Ada Tasks onto the Underlying Kernel Threads,GNAT Implementation of Tasking
25708 @anchor{gnat_rm/implementation_of_specific_ada_features id5}@anchor{421}@anchor{gnat_rm/implementation_of_specific_ada_features ensuring-compliance-with-the-real-time-annex}@anchor{422}
25709 @subsection Ensuring Compliance with the Real-Time Annex
25712 @geindex Real-Time Systems Annex compliance
25714 Although mapping Ada tasks onto
25715 the underlying threads has significant advantages, it does create some
25716 complications when it comes to respecting the scheduling semantics
25717 specified in the real-time annex (Annex D).
25719 For instance the Annex D requirement for the @code{FIFO_Within_Priorities}
25720 scheduling policy states:
25724 @emph{When the active priority of a ready task that is not running
25725 changes, or the setting of its base priority takes effect, the
25726 task is removed from the ready queue for its old active priority
25727 and is added at the tail of the ready queue for its new active
25728 priority, except in the case where the active priority is lowered
25729 due to the loss of inherited priority, in which case the task is
25730 added at the head of the ready queue for its new active priority.}
25733 While most kernels do put tasks at the end of the priority queue when
25734 a task changes its priority, (which respects the main
25735 FIFO_Within_Priorities requirement), almost none keep a thread at the
25736 beginning of its priority queue when its priority drops from the loss
25737 of inherited priority.
25739 As a result most vendors have provided incomplete Annex D implementations.
25741 The GNAT run-time, has a nice cooperative solution to this problem
25742 which ensures that accurate FIFO_Within_Priorities semantics are
25745 The principle is as follows. When an Ada task T is about to start
25746 running, it checks whether some other Ada task R with the same
25747 priority as T has been suspended due to the loss of priority
25748 inheritance. If this is the case, T yields and is placed at the end of
25749 its priority queue. When R arrives at the front of the queue it
25752 Note that this simple scheme preserves the relative order of the tasks
25753 that were ready to execute in the priority queue where R has been
25756 @c Support_for_Locking_Policies
25758 @node Support for Locking Policies,,Ensuring Compliance with the Real-Time Annex,GNAT Implementation of Tasking
25759 @anchor{gnat_rm/implementation_of_specific_ada_features support-for-locking-policies}@anchor{423}
25760 @subsection Support for Locking Policies
25763 This section specifies which policies specified by pragma Locking_Policy
25764 are supported on which platforms.
25766 GNAT supports the standard @code{Ceiling_Locking} policy, and the
25767 implementation defined @code{Inheritance_Locking} and
25768 @code{Concurrent_Readers_Locking} policies.
25770 @code{Ceiling_Locking} is supported on all platforms if the operating system
25771 supports it. In particular, @code{Ceiling_Locking} is not supported on
25773 @code{Inheritance_Locking} is supported on
25778 @code{Concurrent_Readers_Locking} is supported on Linux.
25780 Notes about @code{Ceiling_Locking} on Linux:
25781 If the process is running as 'root', ceiling locking is used.
25782 If the capabilities facility is installed
25783 ("sudo apt-get --assume-yes install libcap-dev" on Ubuntu,
25785 and the program is linked against that library
25787 and the executable file has the cap_sys_nice capability
25788 ("sudo /sbin/setcap cap_sys_nice=ep executable_file_name"),
25789 then ceiling locking is used.
25790 Otherwise, the @code{Ceiling_Locking} policy is ignored.
25792 @node GNAT Implementation of Shared Passive Packages,Code Generation for Array Aggregates,GNAT Implementation of Tasking,Implementation of Specific Ada Features
25793 @anchor{gnat_rm/implementation_of_specific_ada_features id6}@anchor{424}@anchor{gnat_rm/implementation_of_specific_ada_features gnat-implementation-of-shared-passive-packages}@anchor{425}
25794 @section GNAT Implementation of Shared Passive Packages
25797 @geindex Shared passive packages
25799 GNAT fully implements the
25800 @geindex pragma Shared_Passive
25802 @code{Shared_Passive} for
25803 the purpose of designating shared passive packages.
25804 This allows the use of passive partitions in the
25805 context described in the Ada Reference Manual; i.e., for communication
25806 between separate partitions of a distributed application using the
25807 features in Annex E.
25811 @geindex Distribution Systems Annex
25813 However, the implementation approach used by GNAT provides for more
25814 extensive usage as follows:
25819 @item @emph{Communication between separate programs}
25821 This allows separate programs to access the data in passive
25822 partitions, using protected objects for synchronization where
25823 needed. The only requirement is that the two programs have a
25824 common shared file system. It is even possible for programs
25825 running on different machines with different architectures
25826 (e.g., different endianness) to communicate via the data in
25827 a passive partition.
25829 @item @emph{Persistence between program runs}
25831 The data in a passive package can persist from one run of a
25832 program to another, so that a later program sees the final
25833 values stored by a previous run of the same program.
25836 The implementation approach used is to store the data in files. A
25837 separate stream file is created for each object in the package, and
25838 an access to an object causes the corresponding file to be read or
25841 @geindex SHARED_MEMORY_DIRECTORY environment variable
25843 The environment variable @code{SHARED_MEMORY_DIRECTORY} should be
25844 set to the directory to be used for these files.
25845 The files in this directory
25846 have names that correspond to their fully qualified names. For
25847 example, if we have the package
25851 pragma Shared_Passive (X);
25857 and the environment variable is set to @code{/stemp/}, then the files created
25858 will have the names:
25865 These files are created when a value is initially written to the object, and
25866 the files are retained until manually deleted. This provides the persistence
25867 semantics. If no file exists, it means that no partition has assigned a value
25868 to the variable; in this case the initial value declared in the package
25869 will be used. This model ensures that there are no issues in synchronizing
25870 the elaboration process, since elaboration of passive packages elaborates the
25871 initial values, but does not create the files.
25873 The files are written using normal @code{Stream_IO} access.
25874 If you want to be able
25875 to communicate between programs or partitions running on different
25876 architectures, then you should use the XDR versions of the stream attribute
25877 routines, since these are architecture independent.
25879 If active synchronization is required for access to the variables in the
25880 shared passive package, then as described in the Ada Reference Manual, the
25881 package may contain protected objects used for this purpose. In this case
25882 a lock file (whose name is @code{___lock} (three underscores)
25883 is created in the shared memory directory.
25885 @geindex ___lock file (for shared passive packages)
25887 This is used to provide the required locking
25888 semantics for proper protected object synchronization.
25890 @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
25891 @anchor{gnat_rm/implementation_of_specific_ada_features code-generation-for-array-aggregates}@anchor{426}@anchor{gnat_rm/implementation_of_specific_ada_features id7}@anchor{427}
25892 @section Code Generation for Array Aggregates
25895 Aggregates have a rich syntax and allow the user to specify the values of
25896 complex data structures by means of a single construct. As a result, the
25897 code generated for aggregates can be quite complex and involve loops, case
25898 statements and multiple assignments. In the simplest cases, however, the
25899 compiler will recognize aggregates whose components and constraints are
25900 fully static, and in those cases the compiler will generate little or no
25901 executable code. The following is an outline of the code that GNAT generates
25902 for various aggregate constructs. For further details, you will find it
25903 useful to examine the output produced by the -gnatG flag to see the expanded
25904 source that is input to the code generator. You may also want to examine
25905 the assembly code generated at various levels of optimization.
25907 The code generated for aggregates depends on the context, the component values,
25908 and the type. In the context of an object declaration the code generated is
25909 generally simpler than in the case of an assignment. As a general rule, static
25910 component values and static subtypes also lead to simpler code.
25913 * Static constant aggregates with static bounds::
25914 * Constant aggregates with unconstrained nominal types::
25915 * Aggregates with static bounds::
25916 * Aggregates with nonstatic bounds::
25917 * Aggregates in assignment statements::
25921 @node Static constant aggregates with static bounds,Constant aggregates with unconstrained nominal types,,Code Generation for Array Aggregates
25922 @anchor{gnat_rm/implementation_of_specific_ada_features static-constant-aggregates-with-static-bounds}@anchor{428}@anchor{gnat_rm/implementation_of_specific_ada_features id8}@anchor{429}
25923 @subsection Static constant aggregates with static bounds
25926 For the declarations:
25929 type One_Dim is array (1..10) of integer;
25930 ar0 : constant One_Dim := (1, 2, 3, 4, 5, 6, 7, 8, 9, 0);
25933 GNAT generates no executable code: the constant ar0 is placed in static memory.
25934 The same is true for constant aggregates with named associations:
25937 Cr1 : constant One_Dim := (4 => 16, 2 => 4, 3 => 9, 1 => 1, 5 .. 10 => 0);
25938 Cr3 : constant One_Dim := (others => 7777);
25941 The same is true for multidimensional constant arrays such as:
25944 type two_dim is array (1..3, 1..3) of integer;
25945 Unit : constant two_dim := ( (1,0,0), (0,1,0), (0,0,1));
25948 The same is true for arrays of one-dimensional arrays: the following are
25952 type ar1b is array (1..3) of boolean;
25953 type ar_ar is array (1..3) of ar1b;
25954 None : constant ar1b := (others => false); -- fully static
25955 None2 : constant ar_ar := (1..3 => None); -- fully static
25958 However, for multidimensional aggregates with named associations, GNAT will
25959 generate assignments and loops, even if all associations are static. The
25960 following two declarations generate a loop for the first dimension, and
25961 individual component assignments for the second dimension:
25964 Zero1: constant two_dim := (1..3 => (1..3 => 0));
25965 Zero2: constant two_dim := (others => (others => 0));
25968 @node Constant aggregates with unconstrained nominal types,Aggregates with static bounds,Static constant aggregates with static bounds,Code Generation for Array Aggregates
25969 @anchor{gnat_rm/implementation_of_specific_ada_features constant-aggregates-with-unconstrained-nominal-types}@anchor{42a}@anchor{gnat_rm/implementation_of_specific_ada_features id9}@anchor{42b}
25970 @subsection Constant aggregates with unconstrained nominal types
25973 In such cases the aggregate itself establishes the subtype, so that
25974 associations with @code{others} cannot be used. GNAT determines the
25975 bounds for the actual subtype of the aggregate, and allocates the
25976 aggregate statically as well. No code is generated for the following:
25979 type One_Unc is array (natural range <>) of integer;
25980 Cr_Unc : constant One_Unc := (12,24,36);
25983 @node Aggregates with static bounds,Aggregates with nonstatic bounds,Constant aggregates with unconstrained nominal types,Code Generation for Array Aggregates
25984 @anchor{gnat_rm/implementation_of_specific_ada_features id10}@anchor{42c}@anchor{gnat_rm/implementation_of_specific_ada_features aggregates-with-static-bounds}@anchor{42d}
25985 @subsection Aggregates with static bounds
25988 In all previous examples the aggregate was the initial (and immutable) value
25989 of a constant. If the aggregate initializes a variable, then code is generated
25990 for it as a combination of individual assignments and loops over the target
25991 object. The declarations
25994 Cr_Var1 : One_Dim := (2, 5, 7, 11, 0, 0, 0, 0, 0, 0);
25995 Cr_Var2 : One_Dim := (others > -1);
25998 generate the equivalent of
26006 for I in Cr_Var2'range loop
26011 @node Aggregates with nonstatic bounds,Aggregates in assignment statements,Aggregates with static bounds,Code Generation for Array Aggregates
26012 @anchor{gnat_rm/implementation_of_specific_ada_features id11}@anchor{42e}@anchor{gnat_rm/implementation_of_specific_ada_features aggregates-with-nonstatic-bounds}@anchor{42f}
26013 @subsection Aggregates with nonstatic bounds
26016 If the bounds of the aggregate are not statically compatible with the bounds
26017 of the nominal subtype of the target, then constraint checks have to be
26018 generated on the bounds. For a multidimensional array, constraint checks may
26019 have to be applied to sub-arrays individually, if they do not have statically
26020 compatible subtypes.
26022 @node Aggregates in assignment statements,,Aggregates with nonstatic bounds,Code Generation for Array Aggregates
26023 @anchor{gnat_rm/implementation_of_specific_ada_features id12}@anchor{430}@anchor{gnat_rm/implementation_of_specific_ada_features aggregates-in-assignment-statements}@anchor{431}
26024 @subsection Aggregates in assignment statements
26027 In general, aggregate assignment requires the construction of a temporary,
26028 and a copy from the temporary to the target of the assignment. This is because
26029 it is not always possible to convert the assignment into a series of individual
26030 component assignments. For example, consider the simple case:
26036 This cannot be converted into:
26043 So the aggregate has to be built first in a separate location, and then
26044 copied into the target. GNAT recognizes simple cases where this intermediate
26045 step is not required, and the assignments can be performed in place, directly
26046 into the target. The following sufficient criteria are applied:
26052 The bounds of the aggregate are static, and the associations are static.
26055 The components of the aggregate are static constants, names of
26056 simple variables that are not renamings, or expressions not involving
26057 indexed components whose operands obey these rules.
26060 If any of these conditions are violated, the aggregate will be built in
26061 a temporary (created either by the front-end or the code generator) and then
26062 that temporary will be copied onto the target.
26064 @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
26065 @anchor{gnat_rm/implementation_of_specific_ada_features id13}@anchor{432}@anchor{gnat_rm/implementation_of_specific_ada_features the-size-of-discriminated-records-with-default-discriminants}@anchor{433}
26066 @section The Size of Discriminated Records with Default Discriminants
26069 If a discriminated type @code{T} has discriminants with default values, it is
26070 possible to declare an object of this type without providing an explicit
26074 type Size is range 1..100;
26076 type Rec (D : Size := 15) is record
26077 Name : String (1..D);
26083 Such an object is said to be @emph{unconstrained}.
26084 The discriminant of the object
26085 can be modified by a full assignment to the object, as long as it preserves the
26086 relation between the value of the discriminant, and the value of the components
26090 Word := (3, "yes");
26092 Word := (5, "maybe");
26094 Word := (5, "no"); -- raises Constraint_Error
26097 In order to support this behavior efficiently, an unconstrained object is
26098 given the maximum size that any value of the type requires. In the case
26099 above, @code{Word} has storage for the discriminant and for
26100 a @code{String} of length 100.
26101 It is important to note that unconstrained objects do not require dynamic
26102 allocation. It would be an improper implementation to place on the heap those
26103 components whose size depends on discriminants. (This improper implementation
26104 was used by some Ada83 compilers, where the @code{Name} component above
26106 been stored as a pointer to a dynamic string). Following the principle that
26107 dynamic storage management should never be introduced implicitly,
26108 an Ada compiler should reserve the full size for an unconstrained declared
26109 object, and place it on the stack.
26111 This maximum size approach
26112 has been a source of surprise to some users, who expect the default
26113 values of the discriminants to determine the size reserved for an
26114 unconstrained object: "If the default is 15, why should the object occupy
26116 The answer, of course, is that the discriminant may be later modified,
26117 and its full range of values must be taken into account. This is why the
26121 type Rec (D : Positive := 15) is record
26122 Name : String (1..D);
26128 is flagged by the compiler with a warning:
26129 an attempt to create @code{Too_Large} will raise @code{Storage_Error},
26130 because the required size includes @code{Positive'Last}
26131 bytes. As the first example indicates, the proper approach is to declare an
26132 index type of 'reasonable' range so that unconstrained objects are not too
26135 One final wrinkle: if the object is declared to be @code{aliased}, or if it is
26136 created in the heap by means of an allocator, then it is @emph{not}
26138 it is constrained by the default values of the discriminants, and those values
26139 cannot be modified by full assignment. This is because in the presence of
26140 aliasing all views of the object (which may be manipulated by different tasks,
26141 say) must be consistent, so it is imperative that the object, once created,
26144 @node Strict Conformance to the Ada Reference Manual,,The Size of Discriminated Records with Default Discriminants,Implementation of Specific Ada Features
26145 @anchor{gnat_rm/implementation_of_specific_ada_features strict-conformance-to-the-ada-reference-manual}@anchor{434}@anchor{gnat_rm/implementation_of_specific_ada_features id14}@anchor{435}
26146 @section Strict Conformance to the Ada Reference Manual
26149 The dynamic semantics defined by the Ada Reference Manual impose a set of
26150 run-time checks to be generated. By default, the GNAT compiler will insert many
26151 run-time checks into the compiled code, including most of those required by the
26152 Ada Reference Manual. However, there are two checks that are not enabled in
26153 the default mode for efficiency reasons: checks for access before elaboration
26154 on subprogram calls, and stack overflow checking (most operating systems do not
26155 perform this check by default).
26157 Strict conformance to the Ada Reference Manual can be achieved by adding two
26158 compiler options for dynamic checks for access-before-elaboration on subprogram
26159 calls and generic instantiations (@emph{-gnatE}), and stack overflow checking
26160 (@emph{-fstack-check}).
26162 Note that the result of a floating point arithmetic operation in overflow and
26163 invalid situations, when the @code{Machine_Overflows} attribute of the result
26164 type is @code{False}, is to generate IEEE NaN and infinite values. This is the
26165 case for machines compliant with the IEEE floating-point standard, but on
26166 machines that are not fully compliant with this standard, such as Alpha, the
26167 @emph{-mieee} compiler flag must be used for achieving IEEE confirming
26168 behavior (although at the cost of a significant performance penalty), so
26169 infinite and NaN values are properly generated.
26171 @node Implementation of Ada 2012 Features,Obsolescent Features,Implementation of Specific Ada Features,Top
26172 @anchor{gnat_rm/implementation_of_ada_2012_features doc}@anchor{436}@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{437}
26173 @chapter Implementation of Ada 2012 Features
26176 @geindex Ada 2012 implementation status
26178 @geindex -gnat12 option (gcc)
26180 @geindex pragma Ada_2012
26182 @geindex configuration pragma Ada_2012
26184 @geindex Ada_2012 configuration pragma
26186 This chapter contains a complete list of Ada 2012 features that have been
26188 Generally, these features are only
26189 available if the @emph{-gnat12} (Ada 2012 features enabled) option is set,
26190 which is the default behavior,
26191 or if the configuration pragma @code{Ada_2012} is used.
26193 However, new pragmas, attributes, and restrictions are
26194 unconditionally available, since the Ada 95 standard allows the addition of
26195 new pragmas, attributes, and restrictions (there are exceptions, which are
26196 documented in the individual descriptions), and also certain packages
26197 were made available in earlier versions of Ada.
26199 An ISO date (YYYY-MM-DD) appears in parentheses on the description line.
26200 This date shows the implementation date of the feature. Any wavefront
26201 subsequent to this date will contain the indicated feature, as will any
26202 subsequent releases. A date of 0000-00-00 means that GNAT has always
26203 implemented the feature, or implemented it as soon as it appeared as a
26204 binding interpretation.
26206 Each feature corresponds to an Ada Issue ('AI') approved by the Ada
26207 standardization group (ISO/IEC JTC1/SC22/WG9) for inclusion in Ada 2012.
26208 The features are ordered based on the relevant sections of the Ada
26209 Reference Manual ("RM"). When a given AI relates to multiple points
26210 in the RM, the earliest is used.
26212 A complete description of the AIs may be found in
26213 @indicateurl{http://www.ada-auth.org/ai05-summary.html}.
26215 @geindex AI-0176 (Ada 2012 feature)
26221 @emph{AI-0176 Quantified expressions (2010-09-29)}
26223 Both universally and existentially quantified expressions are implemented.
26224 They use the new syntax for iterators proposed in AI05-139-2, as well as
26225 the standard Ada loop syntax.
26227 RM References: 1.01.04 (12) 2.09 (2/2) 4.04 (7) 4.05.09 (0)
26230 @geindex AI-0079 (Ada 2012 feature)
26236 @emph{AI-0079 Allow other_format characters in source (2010-07-10)}
26238 Wide characters in the unicode category @emph{other_format} are now allowed in
26239 source programs between tokens, but not within a token such as an identifier.
26241 RM References: 2.01 (4/2) 2.02 (7)
26244 @geindex AI-0091 (Ada 2012 feature)
26250 @emph{AI-0091 Do not allow other_format in identifiers (0000-00-00)}
26252 Wide characters in the unicode category @emph{other_format} are not permitted
26253 within an identifier, since this can be a security problem. The error
26254 message for this case has been improved to be more specific, but GNAT has
26255 never allowed such characters to appear in identifiers.
26257 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)
26260 @geindex AI-0100 (Ada 2012 feature)
26266 @emph{AI-0100 Placement of pragmas (2010-07-01)}
26268 This AI is an earlier version of AI-163. It simplifies the rules
26269 for legal placement of pragmas. In the case of lists that allow pragmas, if
26270 the list may have no elements, then the list may consist solely of pragmas.
26272 RM References: 2.08 (7)
26275 @geindex AI-0163 (Ada 2012 feature)
26281 @emph{AI-0163 Pragmas in place of null (2010-07-01)}
26283 A statement sequence may be composed entirely of pragmas. It is no longer
26284 necessary to add a dummy @code{null} statement to make the sequence legal.
26286 RM References: 2.08 (7) 2.08 (16)
26289 @geindex AI-0080 (Ada 2012 feature)
26295 @emph{AI-0080 'View of' not needed if clear from context (0000-00-00)}
26297 This is an editorial change only, described as non-testable in the AI.
26299 RM References: 3.01 (7)
26302 @geindex AI-0183 (Ada 2012 feature)
26308 @emph{AI-0183 Aspect specifications (2010-08-16)}
26310 Aspect specifications have been fully implemented except for pre and post-
26311 conditions, and type invariants, which have their own separate AI's. All
26312 forms of declarations listed in the AI are supported. The following is a
26313 list of the aspects supported (with GNAT implementation aspects marked)
26317 @multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxx}
26362 @code{Atomic_Components}
26374 @code{Component_Size}
26380 @code{Contract_Cases}
26388 @code{Discard_Names}
26394 @code{External_Tag}
26400 @code{Favor_Top_Level}
26414 @code{Inline_Always}
26430 @code{Machine_Radix}
26456 @code{Persistent_BSS}
26482 @code{Preelaborable_Initialization}
26488 @code{Pure_Function}
26496 @code{Remote_Access_Type}
26518 @code{Storage_Pool}
26524 @code{Storage_Size}
26542 @code{Suppress_Debug_Info}
26558 @code{Thread_Local_Storage}
26566 @code{Type_Invariant}
26572 @code{Unchecked_Union}
26578 @code{Universal_Aliasing}
26594 @code{Unreferenced}
26602 @code{Unreferenced_Objects}
26630 @code{Volatile_Components}
26647 Note that for aspects with an expression, e.g. @code{Size}, the expression is
26648 treated like a default expression (visibility is analyzed at the point of
26649 occurrence of the aspect, but evaluation of the expression occurs at the
26650 freeze point of the entity involved).
26652 RM References: 3.02.01 (3) 3.02.02 (2) 3.03.01 (2/2) 3.08 (6)
26653 3.09.03 (1.1/2) 6.01 (2/2) 6.07 (2/2) 9.05.02 (2/2) 7.01 (3) 7.03
26654 (2) 7.03 (3) 9.01 (2/2) 9.01 (3/2) 9.04 (2/2) 9.04 (3/2)
26655 9.05.02 (2/2) 11.01 (2) 12.01 (3) 12.03 (2/2) 12.04 (2/2) 12.05 (2)
26656 12.06 (2.1/2) 12.06 (2.2/2) 12.07 (2) 13.01 (0.1/2) 13.03 (5/1)
26660 @geindex AI-0128 (Ada 2012 feature)
26666 @emph{AI-0128 Inequality is a primitive operation (0000-00-00)}
26668 If an equality operator ("=") is declared for a type, then the implicitly
26669 declared inequality operator ("/=") is a primitive operation of the type.
26670 This is the only reasonable interpretation, and is the one always implemented
26671 by GNAT, but the RM was not entirely clear in making this point.
26673 RM References: 3.02.03 (6) 6.06 (6)
26676 @geindex AI-0003 (Ada 2012 feature)
26682 @emph{AI-0003 Qualified expressions as names (2010-07-11)}
26684 In Ada 2012, a qualified expression is considered to be syntactically a name,
26685 meaning that constructs such as @code{A'(F(X)).B} are now legal. This is
26686 useful in disambiguating some cases of overloading.
26688 RM References: 3.03 (11) 3.03 (21) 4.01 (2) 4.04 (7) 4.07 (3)
26692 @geindex AI-0120 (Ada 2012 feature)
26698 @emph{AI-0120 Constant instance of protected object (0000-00-00)}
26700 This is an RM editorial change only. The section that lists objects that are
26701 constant failed to include the current instance of a protected object
26702 within a protected function. This has always been treated as a constant
26705 RM References: 3.03 (21)
26708 @geindex AI-0008 (Ada 2012 feature)
26714 @emph{AI-0008 General access to constrained objects (0000-00-00)}
26716 The wording in the RM implied that if you have a general access to a
26717 constrained object, it could be used to modify the discriminants. This was
26718 obviously not intended. @code{Constraint_Error} should be raised, and GNAT
26719 has always done so in this situation.
26721 RM References: 3.03 (23) 3.10.02 (26/2) 4.01 (9) 6.04.01 (17) 8.05.01 (5/2)
26724 @geindex AI-0093 (Ada 2012 feature)
26730 @emph{AI-0093 Additional rules use immutably limited (0000-00-00)}
26732 This is an editorial change only, to make more widespread use of the Ada 2012
26733 'immutably limited'.
26735 RM References: 3.03 (23.4/3)
26738 @geindex AI-0096 (Ada 2012 feature)
26744 @emph{AI-0096 Deriving from formal private types (2010-07-20)}
26746 In general it is illegal for a type derived from a formal limited type to be
26747 nonlimited. This AI makes an exception to this rule: derivation is legal
26748 if it appears in the private part of the generic, and the formal type is not
26749 tagged. If the type is tagged, the legality check must be applied to the
26750 private part of the package.
26752 RM References: 3.04 (5.1/2) 6.02 (7)
26755 @geindex AI-0181 (Ada 2012 feature)
26761 @emph{AI-0181 Soft hyphen is a non-graphic character (2010-07-23)}
26763 From Ada 2005 on, soft hyphen is considered a non-graphic character, which
26764 means that it has a special name (@code{SOFT_HYPHEN}) in conjunction with the
26765 @code{Image} and @code{Value} attributes for the character types. Strictly
26766 speaking this is an inconsistency with Ada 95, but in practice the use of
26767 these attributes is so obscure that it will not cause problems.
26769 RM References: 3.05.02 (2/2) A.01 (35/2) A.03.03 (21)
26772 @geindex AI-0182 (Ada 2012 feature)
26778 @emph{AI-0182 Additional forms for} @code{Character'Value} @emph{(0000-00-00)}
26780 This AI allows @code{Character'Value} to accept the string @code{'?'} where
26781 @code{?} is any character including non-graphic control characters. GNAT has
26782 always accepted such strings. It also allows strings such as
26783 @code{HEX_00000041} to be accepted, but GNAT does not take advantage of this
26784 permission and raises @code{Constraint_Error}, as is certainly still
26787 RM References: 3.05 (56/2)
26790 @geindex AI-0214 (Ada 2012 feature)
26796 @emph{AI-0214 Defaulted discriminants for limited tagged (2010-10-01)}
26798 Ada 2012 relaxes the restriction that forbids discriminants of tagged types
26799 to have default expressions by allowing them when the type is limited. It
26800 is often useful to define a default value for a discriminant even though
26801 it can't be changed by assignment.
26803 RM References: 3.07 (9.1/2) 3.07.02 (3)
26806 @geindex AI-0102 (Ada 2012 feature)
26812 @emph{AI-0102 Some implicit conversions are illegal (0000-00-00)}
26814 It is illegal to assign an anonymous access constant to an anonymous access
26815 variable. The RM did not have a clear rule to prevent this, but GNAT has
26816 always generated an error for this usage.
26818 RM References: 3.07 (16) 3.07.01 (9) 6.04.01 (6) 8.06 (27/2)
26821 @geindex AI-0158 (Ada 2012 feature)
26827 @emph{AI-0158 Generalizing membership tests (2010-09-16)}
26829 This AI extends the syntax of membership tests to simplify complex conditions
26830 that can be expressed as membership in a subset of values of any type. It
26831 introduces syntax for a list of expressions that may be used in loop contexts
26834 RM References: 3.08.01 (5) 4.04 (3) 4.05.02 (3) 4.05.02 (5) 4.05.02 (27)
26837 @geindex AI-0173 (Ada 2012 feature)
26843 @emph{AI-0173 Testing if tags represent abstract types (2010-07-03)}
26845 The function @code{Ada.Tags.Type_Is_Abstract} returns @code{True} if invoked
26846 with the tag of an abstract type, and @code{False} otherwise.
26848 RM References: 3.09 (7.4/2) 3.09 (12.4/2)
26851 @geindex AI-0076 (Ada 2012 feature)
26857 @emph{AI-0076 function with controlling result (0000-00-00)}
26859 This is an editorial change only. The RM defines calls with controlling
26860 results, but uses the term 'function with controlling result' without an
26861 explicit definition.
26863 RM References: 3.09.02 (2/2)
26866 @geindex AI-0126 (Ada 2012 feature)
26872 @emph{AI-0126 Dispatching with no declared operation (0000-00-00)}
26874 This AI clarifies dispatching rules, and simply confirms that dispatching
26875 executes the operation of the parent type when there is no explicitly or
26876 implicitly declared operation for the descendant type. This has always been
26877 the case in all versions of GNAT.
26879 RM References: 3.09.02 (20/2) 3.09.02 (20.1/2) 3.09.02 (20.2/2)
26882 @geindex AI-0097 (Ada 2012 feature)
26888 @emph{AI-0097 Treatment of abstract null extension (2010-07-19)}
26890 The RM as written implied that in some cases it was possible to create an
26891 object of an abstract type, by having an abstract extension inherit a non-
26892 abstract constructor from its parent type. This mistake has been corrected
26893 in GNAT and in the RM, and this construct is now illegal.
26895 RM References: 3.09.03 (4/2)
26898 @geindex AI-0203 (Ada 2012 feature)
26904 @emph{AI-0203 Extended return cannot be abstract (0000-00-00)}
26906 A return_subtype_indication cannot denote an abstract subtype. GNAT has never
26907 permitted such usage.
26909 RM References: 3.09.03 (8/3)
26912 @geindex AI-0198 (Ada 2012 feature)
26918 @emph{AI-0198 Inheriting abstract operators (0000-00-00)}
26920 This AI resolves a conflict between two rules involving inherited abstract
26921 operations and predefined operators. If a derived numeric type inherits
26922 an abstract operator, it overrides the predefined one. This interpretation
26923 was always the one implemented in GNAT.
26925 RM References: 3.09.03 (4/3)
26928 @geindex AI-0073 (Ada 2012 feature)
26934 @emph{AI-0073 Functions returning abstract types (2010-07-10)}
26936 This AI covers a number of issues regarding returning abstract types. In
26937 particular generic functions cannot have abstract result types or access
26938 result types designated an abstract type. There are some other cases which
26939 are detailed in the AI. Note that this binding interpretation has not been
26940 retrofitted to operate before Ada 2012 mode, since it caused a significant
26941 number of regressions.
26943 RM References: 3.09.03 (8) 3.09.03 (10) 6.05 (8/2)
26946 @geindex AI-0070 (Ada 2012 feature)
26952 @emph{AI-0070 Elaboration of interface types (0000-00-00)}
26954 This is an editorial change only, there are no testable consequences short of
26955 checking for the absence of generated code for an interface declaration.
26957 RM References: 3.09.04 (18/2)
26960 @geindex AI-0208 (Ada 2012 feature)
26966 @emph{AI-0208 Characteristics of incomplete views (0000-00-00)}
26968 The wording in the Ada 2005 RM concerning characteristics of incomplete views
26969 was incorrect and implied that some programs intended to be legal were now
26970 illegal. GNAT had never considered such programs illegal, so it has always
26971 implemented the intent of this AI.
26973 RM References: 3.10.01 (2.4/2) 3.10.01 (2.6/2)
26976 @geindex AI-0162 (Ada 2012 feature)
26982 @emph{AI-0162 Incomplete type completed by partial view (2010-09-15)}
26984 Incomplete types are made more useful by allowing them to be completed by
26985 private types and private extensions.
26987 RM References: 3.10.01 (2.5/2) 3.10.01 (2.6/2) 3.10.01 (3) 3.10.01 (4/2)
26990 @geindex AI-0098 (Ada 2012 feature)
26996 @emph{AI-0098 Anonymous subprogram access restrictions (0000-00-00)}
26998 An unintentional omission in the RM implied some inconsistent restrictions on
26999 the use of anonymous access to subprogram values. These restrictions were not
27000 intentional, and have never been enforced by GNAT.
27002 RM References: 3.10.01 (6) 3.10.01 (9.2/2)
27005 @geindex AI-0199 (Ada 2012 feature)
27011 @emph{AI-0199 Aggregate with anonymous access components (2010-07-14)}
27013 A choice list in a record aggregate can include several components of
27014 (distinct) anonymous access types as long as they have matching designated
27017 RM References: 4.03.01 (16)
27020 @geindex AI-0220 (Ada 2012 feature)
27026 @emph{AI-0220 Needed components for aggregates (0000-00-00)}
27028 This AI addresses a wording problem in the RM that appears to permit some
27029 complex cases of aggregates with nonstatic discriminants. GNAT has always
27030 implemented the intended semantics.
27032 RM References: 4.03.01 (17)
27035 @geindex AI-0147 (Ada 2012 feature)
27041 @emph{AI-0147 Conditional expressions (2009-03-29)}
27043 Conditional expressions are permitted. The form of such an expression is:
27046 (if expr then expr @{elsif expr then expr@} [else expr])
27049 The parentheses can be omitted in contexts where parentheses are present
27050 anyway, such as subprogram arguments and pragma arguments. If the @strong{else}
27051 clause is omitted, @strong{else} @emph{True} is assumed;
27052 thus @code{(if A then B)} is a way to conveniently represent
27053 @emph{(A implies B)} in standard logic.
27055 RM References: 4.03.03 (15) 4.04 (1) 4.04 (7) 4.05.07 (0) 4.07 (2)
27056 4.07 (3) 4.09 (12) 4.09 (33) 5.03 (3) 5.03 (4) 7.05 (2.1/2)
27059 @geindex AI-0037 (Ada 2012 feature)
27065 @emph{AI-0037 Out-of-range box associations in aggregate (0000-00-00)}
27067 This AI confirms that an association of the form @code{Indx => <>} in an
27068 array aggregate must raise @code{Constraint_Error} if @code{Indx}
27069 is out of range. The RM specified a range check on other associations, but
27070 not when the value of the association was defaulted. GNAT has always inserted
27071 a constraint check on the index value.
27073 RM References: 4.03.03 (29)
27076 @geindex AI-0123 (Ada 2012 feature)
27082 @emph{AI-0123 Composability of equality (2010-04-13)}
27084 Equality of untagged record composes, so that the predefined equality for a
27085 composite type that includes a component of some untagged record type
27086 @code{R} uses the equality operation of @code{R} (which may be user-defined
27087 or predefined). This makes the behavior of untagged records identical to that
27088 of tagged types in this respect.
27090 This change is an incompatibility with previous versions of Ada, but it
27091 corrects a non-uniformity that was often a source of confusion. Analysis of
27092 a large number of industrial programs indicates that in those rare cases
27093 where a composite type had an untagged record component with a user-defined
27094 equality, either there was no use of the composite equality, or else the code
27095 expected the same composability as for tagged types, and thus had a bug that
27096 would be fixed by this change.
27098 RM References: 4.05.02 (9.7/2) 4.05.02 (14) 4.05.02 (15) 4.05.02 (24)
27102 @geindex AI-0088 (Ada 2012 feature)
27108 @emph{AI-0088 The value of exponentiation (0000-00-00)}
27110 This AI clarifies the equivalence rule given for the dynamic semantics of
27111 exponentiation: the value of the operation can be obtained by repeated
27112 multiplication, but the operation can be implemented otherwise (for example
27113 using the familiar divide-by-two-and-square algorithm, even if this is less
27114 accurate), and does not imply repeated reads of a volatile base.
27116 RM References: 4.05.06 (11)
27119 @geindex AI-0188 (Ada 2012 feature)
27125 @emph{AI-0188 Case expressions (2010-01-09)}
27127 Case expressions are permitted. This allows use of constructs such as:
27130 X := (case Y is when 1 => 2, when 2 => 3, when others => 31)
27133 RM References: 4.05.07 (0) 4.05.08 (0) 4.09 (12) 4.09 (33)
27136 @geindex AI-0104 (Ada 2012 feature)
27142 @emph{AI-0104 Null exclusion and uninitialized allocator (2010-07-15)}
27144 The assignment @code{Ptr := new not null Some_Ptr;} will raise
27145 @code{Constraint_Error} because the default value of the allocated object is
27146 @strong{null}. This useless construct is illegal in Ada 2012.
27148 RM References: 4.08 (2)
27151 @geindex AI-0157 (Ada 2012 feature)
27157 @emph{AI-0157 Allocation/Deallocation from empty pool (2010-07-11)}
27159 Allocation and Deallocation from an empty storage pool (i.e. allocation or
27160 deallocation of a pointer for which a static storage size clause of zero
27161 has been given) is now illegal and is detected as such. GNAT
27162 previously gave a warning but not an error.
27164 RM References: 4.08 (5.3/2) 13.11.02 (4) 13.11.02 (17)
27167 @geindex AI-0179 (Ada 2012 feature)
27173 @emph{AI-0179 Statement not required after label (2010-04-10)}
27175 It is not necessary to have a statement following a label, so a label
27176 can appear at the end of a statement sequence without the need for putting a
27177 null statement afterwards, but it is not allowable to have only labels and
27178 no real statements in a statement sequence.
27180 RM References: 5.01 (2)
27183 @geindex AI-0139-2 (Ada 2012 feature)
27189 @emph{AI-0139-2 Syntactic sugar for iterators (2010-09-29)}
27191 The new syntax for iterating over arrays and containers is now implemented.
27192 Iteration over containers is for now limited to read-only iterators. Only
27193 default iterators are supported, with the syntax: @code{for Elem of C}.
27195 RM References: 5.05
27198 @geindex AI-0134 (Ada 2012 feature)
27204 @emph{AI-0134 Profiles must match for full conformance (0000-00-00)}
27206 For full conformance, the profiles of anonymous-access-to-subprogram
27207 parameters must match. GNAT has always enforced this rule.
27209 RM References: 6.03.01 (18)
27212 @geindex AI-0207 (Ada 2012 feature)
27218 @emph{AI-0207 Mode conformance and access constant (0000-00-00)}
27220 This AI confirms that access_to_constant indication must match for mode
27221 conformance. This was implemented in GNAT when the qualifier was originally
27222 introduced in Ada 2005.
27224 RM References: 6.03.01 (16/2)
27227 @geindex AI-0046 (Ada 2012 feature)
27233 @emph{AI-0046 Null exclusion match for full conformance (2010-07-17)}
27235 For full conformance, in the case of access parameters, the null exclusion
27236 must match (either both or neither must have @code{not null}).
27238 RM References: 6.03.02 (18)
27241 @geindex AI-0118 (Ada 2012 feature)
27247 @emph{AI-0118 The association of parameter associations (0000-00-00)}
27249 This AI clarifies the rules for named associations in subprogram calls and
27250 generic instantiations. The rules have been in place since Ada 83.
27252 RM References: 6.04.01 (2) 12.03 (9)
27255 @geindex AI-0196 (Ada 2012 feature)
27261 @emph{AI-0196 Null exclusion tests for out parameters (0000-00-00)}
27263 Null exclusion checks are not made for @code{out} parameters when
27264 evaluating the actual parameters. GNAT has never generated these checks.
27266 RM References: 6.04.01 (13)
27269 @geindex AI-0015 (Ada 2012 feature)
27275 @emph{AI-0015 Constant return objects (0000-00-00)}
27277 The return object declared in an @emph{extended_return_statement} may be
27278 declared constant. This was always intended, and GNAT has always allowed it.
27280 RM References: 6.05 (2.1/2) 3.03 (10/2) 3.03 (21) 6.05 (5/2)
27284 @geindex AI-0032 (Ada 2012 feature)
27290 @emph{AI-0032 Extended return for class-wide functions (0000-00-00)}
27292 If a function returns a class-wide type, the object of an extended return
27293 statement can be declared with a specific type that is covered by the class-
27294 wide type. This has been implemented in GNAT since the introduction of
27295 extended returns. Note AI-0103 complements this AI by imposing matching
27296 rules for constrained return types.
27298 RM References: 6.05 (5.2/2) 6.05 (5.3/2) 6.05 (5.6/2) 6.05 (5.8/2)
27302 @geindex AI-0103 (Ada 2012 feature)
27308 @emph{AI-0103 Static matching for extended return (2010-07-23)}
27310 If the return subtype of a function is an elementary type or a constrained
27311 type, the subtype indication in an extended return statement must match
27312 statically this return subtype.
27314 RM References: 6.05 (5.2/2)
27317 @geindex AI-0058 (Ada 2012 feature)
27323 @emph{AI-0058 Abnormal completion of an extended return (0000-00-00)}
27325 The RM had some incorrect wording implying wrong treatment of abnormal
27326 completion in an extended return. GNAT has always implemented the intended
27327 correct semantics as described by this AI.
27329 RM References: 6.05 (22/2)
27332 @geindex AI-0050 (Ada 2012 feature)
27338 @emph{AI-0050 Raising Constraint_Error early for function call (0000-00-00)}
27340 The implementation permissions for raising @code{Constraint_Error} early on a function call
27341 when it was clear an exception would be raised were over-permissive and allowed
27342 mishandling of discriminants in some cases. GNAT did
27343 not take advantage of these incorrect permissions in any case.
27345 RM References: 6.05 (24/2)
27348 @geindex AI-0125 (Ada 2012 feature)
27354 @emph{AI-0125 Nonoverridable operations of an ancestor (2010-09-28)}
27356 In Ada 2012, the declaration of a primitive operation of a type extension
27357 or private extension can also override an inherited primitive that is not
27358 visible at the point of this declaration.
27360 RM References: 7.03.01 (6) 8.03 (23) 8.03.01 (5/2) 8.03.01 (6/2)
27363 @geindex AI-0062 (Ada 2012 feature)
27369 @emph{AI-0062 Null exclusions and deferred constants (0000-00-00)}
27371 A full constant may have a null exclusion even if its associated deferred
27372 constant does not. GNAT has always allowed this.
27374 RM References: 7.04 (6/2) 7.04 (7.1/2)
27377 @geindex AI-0178 (Ada 2012 feature)
27383 @emph{AI-0178 Incomplete views are limited (0000-00-00)}
27385 This AI clarifies the role of incomplete views and plugs an omission in the
27386 RM. GNAT always correctly restricted the use of incomplete views and types.
27388 RM References: 7.05 (3/2) 7.05 (6/2)
27391 @geindex AI-0087 (Ada 2012 feature)
27397 @emph{AI-0087 Actual for formal nonlimited derived type (2010-07-15)}
27399 The actual for a formal nonlimited derived type cannot be limited. In
27400 particular, a formal derived type that extends a limited interface but which
27401 is not explicitly limited cannot be instantiated with a limited type.
27403 RM References: 7.05 (5/2) 12.05.01 (5.1/2)
27406 @geindex AI-0099 (Ada 2012 feature)
27412 @emph{AI-0099 Tag determines whether finalization needed (0000-00-00)}
27414 This AI clarifies that 'needs finalization' is part of dynamic semantics,
27415 and therefore depends on the run-time characteristics of an object (i.e. its
27416 tag) and not on its nominal type. As the AI indicates: "we do not expect
27417 this to affect any implementation'@w{'}.
27419 RM References: 7.06.01 (6) 7.06.01 (7) 7.06.01 (8) 7.06.01 (9/2)
27422 @geindex AI-0064 (Ada 2012 feature)
27428 @emph{AI-0064 Redundant finalization rule (0000-00-00)}
27430 This is an editorial change only. The intended behavior is already checked
27431 by an existing ACATS test, which GNAT has always executed correctly.
27433 RM References: 7.06.01 (17.1/1)
27436 @geindex AI-0026 (Ada 2012 feature)
27442 @emph{AI-0026 Missing rules for Unchecked_Union (2010-07-07)}
27444 Record representation clauses concerning Unchecked_Union types cannot mention
27445 the discriminant of the type. The type of a component declared in the variant
27446 part of an Unchecked_Union cannot be controlled, have controlled components,
27447 nor have protected or task parts. If an Unchecked_Union type is declared
27448 within the body of a generic unit or its descendants, then the type of a
27449 component declared in the variant part cannot be a formal private type or a
27450 formal private extension declared within the same generic unit.
27452 RM References: 7.06 (9.4/2) B.03.03 (9/2) B.03.03 (10/2)
27455 @geindex AI-0205 (Ada 2012 feature)
27461 @emph{AI-0205 Extended return declares visible name (0000-00-00)}
27463 This AI corrects a simple omission in the RM. Return objects have always
27464 been visible within an extended return statement.
27466 RM References: 8.03 (17)
27469 @geindex AI-0042 (Ada 2012 feature)
27475 @emph{AI-0042 Overriding versus implemented-by (0000-00-00)}
27477 This AI fixes a wording gap in the RM. An operation of a synchronized
27478 interface can be implemented by a protected or task entry, but the abstract
27479 operation is not being overridden in the usual sense, and it must be stated
27480 separately that this implementation is legal. This has always been the case
27483 RM References: 9.01 (9.2/2) 9.04 (11.1/2)
27486 @geindex AI-0030 (Ada 2012 feature)
27492 @emph{AI-0030 Requeue on synchronized interfaces (2010-07-19)}
27494 Requeue is permitted to a protected, synchronized or task interface primitive
27495 providing it is known that the overriding operation is an entry. Otherwise
27496 the requeue statement has the same effect as a procedure call. Use of pragma
27497 @code{Implemented} provides a way to impose a static requirement on the
27498 overriding operation by adhering to one of the implementation kinds: entry,
27499 protected procedure or any of the above.
27501 RM References: 9.05 (9) 9.05.04 (2) 9.05.04 (3) 9.05.04 (5)
27502 9.05.04 (6) 9.05.04 (7) 9.05.04 (12)
27505 @geindex AI-0201 (Ada 2012 feature)
27511 @emph{AI-0201 Independence of atomic object components (2010-07-22)}
27513 If an Atomic object has a pragma @code{Pack} or a @code{Component_Size}
27514 attribute, then individual components may not be addressable by independent
27515 tasks. However, if the representation clause has no effect (is confirming),
27516 then independence is not compromised. Furthermore, in GNAT, specification of
27517 other appropriately addressable component sizes (e.g. 16 for 8-bit
27518 characters) also preserves independence. GNAT now gives very clear warnings
27519 both for the declaration of such a type, and for any assignment to its components.
27521 RM References: 9.10 (1/3) C.06 (22/2) C.06 (23/2)
27524 @geindex AI-0009 (Ada 2012 feature)
27530 @emph{AI-0009 Pragma Independent[_Components] (2010-07-23)}
27532 This AI introduces the new pragmas @code{Independent} and
27533 @code{Independent_Components},
27534 which control guaranteeing independence of access to objects and components.
27535 The AI also requires independence not unaffected by confirming rep clauses.
27537 RM References: 9.10 (1) 13.01 (15/1) 13.02 (9) 13.03 (13) C.06 (2)
27538 C.06 (4) C.06 (6) C.06 (9) C.06 (13) C.06 (14)
27541 @geindex AI-0072 (Ada 2012 feature)
27547 @emph{AI-0072 Task signalling using 'Terminated (0000-00-00)}
27549 This AI clarifies that task signalling for reading @code{'Terminated} only
27550 occurs if the result is True. GNAT semantics has always been consistent with
27551 this notion of task signalling.
27553 RM References: 9.10 (6.1/1)
27556 @geindex AI-0108 (Ada 2012 feature)
27562 @emph{AI-0108 Limited incomplete view and discriminants (0000-00-00)}
27564 This AI confirms that an incomplete type from a limited view does not have
27565 discriminants. This has always been the case in GNAT.
27567 RM References: 10.01.01 (12.3/2)
27570 @geindex AI-0129 (Ada 2012 feature)
27576 @emph{AI-0129 Limited views and incomplete types (0000-00-00)}
27578 This AI clarifies the description of limited views: a limited view of a
27579 package includes only one view of a type that has an incomplete declaration
27580 and a full declaration (there is no possible ambiguity in a client package).
27581 This AI also fixes an omission: a nested package in the private part has no
27582 limited view. GNAT always implemented this correctly.
27584 RM References: 10.01.01 (12.2/2) 10.01.01 (12.3/2)
27587 @geindex AI-0077 (Ada 2012 feature)
27593 @emph{AI-0077 Limited withs and scope of declarations (0000-00-00)}
27595 This AI clarifies that a declaration does not include a context clause,
27596 and confirms that it is illegal to have a context in which both a limited
27597 and a nonlimited view of a package are accessible. Such double visibility
27598 was always rejected by GNAT.
27600 RM References: 10.01.02 (12/2) 10.01.02 (21/2) 10.01.02 (22/2)
27603 @geindex AI-0122 (Ada 2012 feature)
27609 @emph{AI-0122 Private with and children of generics (0000-00-00)}
27611 This AI clarifies the visibility of private children of generic units within
27612 instantiations of a parent. GNAT has always handled this correctly.
27614 RM References: 10.01.02 (12/2)
27617 @geindex AI-0040 (Ada 2012 feature)
27623 @emph{AI-0040 Limited with clauses on descendant (0000-00-00)}
27625 This AI confirms that a limited with clause in a child unit cannot name
27626 an ancestor of the unit. This has always been checked in GNAT.
27628 RM References: 10.01.02 (20/2)
27631 @geindex AI-0132 (Ada 2012 feature)
27637 @emph{AI-0132 Placement of library unit pragmas (0000-00-00)}
27639 This AI fills a gap in the description of library unit pragmas. The pragma
27640 clearly must apply to a library unit, even if it does not carry the name
27641 of the enclosing unit. GNAT has always enforced the required check.
27643 RM References: 10.01.05 (7)
27646 @geindex AI-0034 (Ada 2012 feature)
27652 @emph{AI-0034 Categorization of limited views (0000-00-00)}
27654 The RM makes certain limited with clauses illegal because of categorization
27655 considerations, when the corresponding normal with would be legal. This is
27656 not intended, and GNAT has always implemented the recommended behavior.
27658 RM References: 10.02.01 (11/1) 10.02.01 (17/2)
27661 @geindex AI-0035 (Ada 2012 feature)
27667 @emph{AI-0035 Inconsistencies with Pure units (0000-00-00)}
27669 This AI remedies some inconsistencies in the legality rules for Pure units.
27670 Derived access types are legal in a pure unit (on the assumption that the
27671 rule for a zero storage pool size has been enforced on the ancestor type).
27672 The rules are enforced in generic instances and in subunits. GNAT has always
27673 implemented the recommended behavior.
27675 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)
27678 @geindex AI-0219 (Ada 2012 feature)
27684 @emph{AI-0219 Pure permissions and limited parameters (2010-05-25)}
27686 This AI refines the rules for the cases with limited parameters which do not
27687 allow the implementations to omit 'redundant'. GNAT now properly conforms
27688 to the requirements of this binding interpretation.
27690 RM References: 10.02.01 (18/2)
27693 @geindex AI-0043 (Ada 2012 feature)
27699 @emph{AI-0043 Rules about raising exceptions (0000-00-00)}
27701 This AI covers various omissions in the RM regarding the raising of
27702 exceptions. GNAT has always implemented the intended semantics.
27704 RM References: 11.04.01 (10.1/2) 11 (2)
27707 @geindex AI-0200 (Ada 2012 feature)
27713 @emph{AI-0200 Mismatches in formal package declarations (0000-00-00)}
27715 This AI plugs a gap in the RM which appeared to allow some obviously intended
27716 illegal instantiations. GNAT has never allowed these instantiations.
27718 RM References: 12.07 (16)
27721 @geindex AI-0112 (Ada 2012 feature)
27727 @emph{AI-0112 Detection of duplicate pragmas (2010-07-24)}
27729 This AI concerns giving names to various representation aspects, but the
27730 practical effect is simply to make the use of duplicate
27731 @code{Atomic[_Components]},
27732 @code{Volatile[_Components]}, and
27733 @code{Independent[_Components]} pragmas illegal, and GNAT
27734 now performs this required check.
27736 RM References: 13.01 (8)
27739 @geindex AI-0106 (Ada 2012 feature)
27745 @emph{AI-0106 No representation pragmas on generic formals (0000-00-00)}
27747 The RM appeared to allow representation pragmas on generic formal parameters,
27748 but this was not intended, and GNAT has never permitted this usage.
27750 RM References: 13.01 (9.1/1)
27753 @geindex AI-0012 (Ada 2012 feature)
27759 @emph{AI-0012 Pack/Component_Size for aliased/atomic (2010-07-15)}
27761 It is now illegal to give an inappropriate component size or a pragma
27762 @code{Pack} that attempts to change the component size in the case of atomic
27763 or aliased components. Previously GNAT ignored such an attempt with a
27766 RM References: 13.02 (6.1/2) 13.02 (7) C.06 (10) C.06 (11) C.06 (21)
27769 @geindex AI-0039 (Ada 2012 feature)
27775 @emph{AI-0039 Stream attributes cannot be dynamic (0000-00-00)}
27777 The RM permitted the use of dynamic expressions (such as @code{ptr.all})`
27778 for stream attributes, but these were never useful and are now illegal. GNAT
27779 has always regarded such expressions as illegal.
27781 RM References: 13.03 (4) 13.03 (6) 13.13.02 (38/2)
27784 @geindex AI-0095 (Ada 2012 feature)
27790 @emph{AI-0095 Address of intrinsic subprograms (0000-00-00)}
27792 The prefix of @code{'Address} cannot statically denote a subprogram with
27793 convention @code{Intrinsic}. The use of the @code{Address} attribute raises
27794 @code{Program_Error} if the prefix denotes a subprogram with convention
27797 RM References: 13.03 (11/1)
27800 @geindex AI-0116 (Ada 2012 feature)
27806 @emph{AI-0116 Alignment of class-wide objects (0000-00-00)}
27808 This AI requires that the alignment of a class-wide object be no greater
27809 than the alignment of any type in the class. GNAT has always followed this
27812 RM References: 13.03 (29) 13.11 (16)
27815 @geindex AI-0146 (Ada 2012 feature)
27821 @emph{AI-0146 Type invariants (2009-09-21)}
27823 Type invariants may be specified for private types using the aspect notation.
27824 Aspect @code{Type_Invariant} may be specified for any private type,
27825 @code{Type_Invariant'Class} can
27826 only be specified for tagged types, and is inherited by any descendent of the
27827 tagged types. The invariant is a boolean expression that is tested for being
27828 true in the following situations: conversions to the private type, object
27829 declarations for the private type that are default initialized, and
27830 [@strong{in}] @strong{out}
27831 parameters and returned result on return from any primitive operation for
27832 the type that is visible to a client.
27833 GNAT defines the synonyms @code{Invariant} for @code{Type_Invariant} and
27834 @code{Invariant'Class} for @code{Type_Invariant'Class}.
27836 RM References: 13.03.03 (00)
27839 @geindex AI-0078 (Ada 2012 feature)
27845 @emph{AI-0078 Relax Unchecked_Conversion alignment rules (0000-00-00)}
27847 In Ada 2012, compilers are required to support unchecked conversion where the
27848 target alignment is a multiple of the source alignment. GNAT always supported
27849 this case (and indeed all cases of differing alignments, doing copies where
27850 required if the alignment was reduced).
27852 RM References: 13.09 (7)
27855 @geindex AI-0195 (Ada 2012 feature)
27861 @emph{AI-0195 Invalid value handling is implementation defined (2010-07-03)}
27863 The handling of invalid values is now designated to be implementation
27864 defined. This is a documentation change only, requiring Annex M in the GNAT
27865 Reference Manual to document this handling.
27866 In GNAT, checks for invalid values are made
27867 only when necessary to avoid erroneous behavior. Operations like assignments
27868 which cannot cause erroneous behavior ignore the possibility of invalid
27869 values and do not do a check. The date given above applies only to the
27870 documentation change, this behavior has always been implemented by GNAT.
27872 RM References: 13.09.01 (10)
27875 @geindex AI-0193 (Ada 2012 feature)
27881 @emph{AI-0193 Alignment of allocators (2010-09-16)}
27883 This AI introduces a new attribute @code{Max_Alignment_For_Allocation},
27884 analogous to @code{Max_Size_In_Storage_Elements}, but for alignment instead
27887 RM References: 13.11 (16) 13.11 (21) 13.11.01 (0) 13.11.01 (1)
27888 13.11.01 (2) 13.11.01 (3)
27891 @geindex AI-0177 (Ada 2012 feature)
27897 @emph{AI-0177 Parameterized expressions (2010-07-10)}
27899 The new Ada 2012 notion of parameterized expressions is implemented. The form
27903 function-specification is (expression)
27906 This is exactly equivalent to the
27907 corresponding function body that returns the expression, but it can appear
27908 in a package spec. Note that the expression must be parenthesized.
27910 RM References: 13.11.01 (3/2)
27913 @geindex AI-0033 (Ada 2012 feature)
27919 @emph{AI-0033 Attach/Interrupt_Handler in generic (2010-07-24)}
27921 Neither of these two pragmas may appear within a generic template, because
27922 the generic might be instantiated at other than the library level.
27924 RM References: 13.11.02 (16) C.03.01 (7/2) C.03.01 (8/2)
27927 @geindex AI-0161 (Ada 2012 feature)
27933 @emph{AI-0161 Restriction No_Default_Stream_Attributes (2010-09-11)}
27935 A new restriction @code{No_Default_Stream_Attributes} prevents the use of any
27936 of the default stream attributes for elementary types. If this restriction is
27937 in force, then it is necessary to provide explicit subprograms for any
27938 stream attributes used.
27940 RM References: 13.12.01 (4/2) 13.13.02 (40/2) 13.13.02 (52/2)
27943 @geindex AI-0194 (Ada 2012 feature)
27949 @emph{AI-0194 Value of Stream_Size attribute (0000-00-00)}
27951 The @code{Stream_Size} attribute returns the default number of bits in the
27952 stream representation of the given type.
27953 This value is not affected by the presence
27954 of stream subprogram attributes for the type. GNAT has always implemented
27955 this interpretation.
27957 RM References: 13.13.02 (1.2/2)
27960 @geindex AI-0109 (Ada 2012 feature)
27966 @emph{AI-0109 Redundant check in S'Class'Input (0000-00-00)}
27968 This AI is an editorial change only. It removes the need for a tag check
27969 that can never fail.
27971 RM References: 13.13.02 (34/2)
27974 @geindex AI-0007 (Ada 2012 feature)
27980 @emph{AI-0007 Stream read and private scalar types (0000-00-00)}
27982 The RM as written appeared to limit the possibilities of declaring read
27983 attribute procedures for private scalar types. This limitation was not
27984 intended, and has never been enforced by GNAT.
27986 RM References: 13.13.02 (50/2) 13.13.02 (51/2)
27989 @geindex AI-0065 (Ada 2012 feature)
27995 @emph{AI-0065 Remote access types and external streaming (0000-00-00)}
27997 This AI clarifies the fact that all remote access types support external
27998 streaming. This fixes an obvious oversight in the definition of the
27999 language, and GNAT always implemented the intended correct rules.
28001 RM References: 13.13.02 (52/2)
28004 @geindex AI-0019 (Ada 2012 feature)
28010 @emph{AI-0019 Freezing of primitives for tagged types (0000-00-00)}
28012 The RM suggests that primitive subprograms of a specific tagged type are
28013 frozen when the tagged type is frozen. This would be an incompatible change
28014 and is not intended. GNAT has never attempted this kind of freezing and its
28015 behavior is consistent with the recommendation of this AI.
28017 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)
28020 @geindex AI-0017 (Ada 2012 feature)
28026 @emph{AI-0017 Freezing and incomplete types (0000-00-00)}
28028 So-called 'Taft-amendment types' (i.e., types that are completed in package
28029 bodies) are not frozen by the occurrence of bodies in the
28030 enclosing declarative part. GNAT always implemented this properly.
28032 RM References: 13.14 (3/1)
28035 @geindex AI-0060 (Ada 2012 feature)
28041 @emph{AI-0060 Extended definition of remote access types (0000-00-00)}
28043 This AI extends the definition of remote access types to include access
28044 to limited, synchronized, protected or task class-wide interface types.
28045 GNAT already implemented this extension.
28047 RM References: A (4) E.02.02 (9/1) E.02.02 (9.2/1) E.02.02 (14/2) E.02.02 (18)
28050 @geindex AI-0114 (Ada 2012 feature)
28056 @emph{AI-0114 Classification of letters (0000-00-00)}
28058 The code points 170 (@code{FEMININE ORDINAL INDICATOR}),
28059 181 (@code{MICRO SIGN}), and
28060 186 (@code{MASCULINE ORDINAL INDICATOR}) are technically considered
28061 lower case letters by Unicode.
28062 However, they are not allowed in identifiers, and they
28063 return @code{False} to @code{Ada.Characters.Handling.Is_Letter/Is_Lower}.
28064 This behavior is consistent with that defined in Ada 95.
28066 RM References: A.03.02 (59) A.04.06 (7)
28069 @geindex AI-0185 (Ada 2012 feature)
28075 @emph{AI-0185 Ada.Wide_[Wide_]Characters.Handling (2010-07-06)}
28077 Two new packages @code{Ada.Wide_[Wide_]Characters.Handling} provide
28078 classification functions for @code{Wide_Character} and
28079 @code{Wide_Wide_Character}, as well as providing
28080 case folding routines for @code{Wide_[Wide_]Character} and
28081 @code{Wide_[Wide_]String}.
28083 RM References: A.03.05 (0) A.03.06 (0)
28086 @geindex AI-0031 (Ada 2012 feature)
28092 @emph{AI-0031 Add From parameter to Find_Token (2010-07-25)}
28094 A new version of @code{Find_Token} is added to all relevant string packages,
28095 with an extra parameter @code{From}. Instead of starting at the first
28096 character of the string, the search for a matching Token starts at the
28097 character indexed by the value of @code{From}.
28098 These procedures are available in all versions of Ada
28099 but if used in versions earlier than Ada 2012 they will generate a warning
28100 that an Ada 2012 subprogram is being used.
28102 RM References: A.04.03 (16) A.04.03 (67) A.04.03 (68/1) A.04.04 (51)
28106 @geindex AI-0056 (Ada 2012 feature)
28112 @emph{AI-0056 Index on null string returns zero (0000-00-00)}
28114 The wording in the Ada 2005 RM implied an incompatible handling of the
28115 @code{Index} functions, resulting in raising an exception instead of
28116 returning zero in some situations.
28117 This was not intended and has been corrected.
28118 GNAT always returned zero, and is thus consistent with this AI.
28120 RM References: A.04.03 (56.2/2) A.04.03 (58.5/2)
28123 @geindex AI-0137 (Ada 2012 feature)
28129 @emph{AI-0137 String encoding package (2010-03-25)}
28131 The packages @code{Ada.Strings.UTF_Encoding}, together with its child
28132 packages, @code{Conversions}, @code{Strings}, @code{Wide_Strings},
28133 and @code{Wide_Wide_Strings} have been
28134 implemented. These packages (whose documentation can be found in the spec
28135 files @code{a-stuten.ads}, @code{a-suenco.ads}, @code{a-suenst.ads},
28136 @code{a-suewst.ads}, @code{a-suezst.ads}) allow encoding and decoding of
28137 @code{String}, @code{Wide_String}, and @code{Wide_Wide_String}
28138 values using UTF coding schemes (including UTF-8, UTF-16LE, UTF-16BE, and
28139 UTF-16), as well as conversions between the different UTF encodings. With
28140 the exception of @code{Wide_Wide_Strings}, these packages are available in
28141 Ada 95 and Ada 2005 mode as well as Ada 2012 mode.
28142 The @code{Wide_Wide_Strings} package
28143 is available in Ada 2005 mode as well as Ada 2012 mode (but not in Ada 95
28144 mode since it uses @code{Wide_Wide_Character}).
28146 RM References: A.04.11
28149 @geindex AI-0038 (Ada 2012 feature)
28155 @emph{AI-0038 Minor errors in Text_IO (0000-00-00)}
28157 These are minor errors in the description on three points. The intent on
28158 all these points has always been clear, and GNAT has always implemented the
28159 correct intended semantics.
28161 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)
28164 @geindex AI-0044 (Ada 2012 feature)
28170 @emph{AI-0044 Restrictions on container instantiations (0000-00-00)}
28172 This AI places restrictions on allowed instantiations of generic containers.
28173 These restrictions are not checked by the compiler, so there is nothing to
28174 change in the implementation. This affects only the RM documentation.
28176 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)
28179 @geindex AI-0127 (Ada 2012 feature)
28185 @emph{AI-0127 Adding Locale Capabilities (2010-09-29)}
28187 This package provides an interface for identifying the current locale.
28189 RM References: A.19 A.19.01 A.19.02 A.19.03 A.19.05 A.19.06
28190 A.19.07 A.19.08 A.19.09 A.19.10 A.19.11 A.19.12 A.19.13
28193 @geindex AI-0002 (Ada 2012 feature)
28199 @emph{AI-0002 Export C with unconstrained arrays (0000-00-00)}
28201 The compiler is not required to support exporting an Ada subprogram with
28202 convention C if there are parameters or a return type of an unconstrained
28203 array type (such as @code{String}). GNAT allows such declarations but
28204 generates warnings. It is possible, but complicated, to write the
28205 corresponding C code and certainly such code would be specific to GNAT and
28208 RM References: B.01 (17) B.03 (62) B.03 (71.1/2)
28211 @geindex AI05-0216 (Ada 2012 feature)
28217 @emph{AI-0216 No_Task_Hierarchy forbids local tasks (0000-00-00)}
28219 It is clearly the intention that @code{No_Task_Hierarchy} is intended to
28220 forbid tasks declared locally within subprograms, or functions returning task
28221 objects, and that is the implementation that GNAT has always provided.
28222 However the language in the RM was not sufficiently clear on this point.
28223 Thus this is a documentation change in the RM only.
28225 RM References: D.07 (3/3)
28228 @geindex AI-0211 (Ada 2012 feature)
28234 @emph{AI-0211 No_Relative_Delays forbids Set_Handler use (2010-07-09)}
28236 The restriction @code{No_Relative_Delays} forbids any calls to the subprogram
28237 @code{Ada.Real_Time.Timing_Events.Set_Handler}.
28239 RM References: D.07 (5) D.07 (10/2) D.07 (10.4/2) D.07 (10.7/2)
28242 @geindex AI-0190 (Ada 2012 feature)
28248 @emph{AI-0190 pragma Default_Storage_Pool (2010-09-15)}
28250 This AI introduces a new pragma @code{Default_Storage_Pool}, which can be
28251 used to control storage pools globally.
28252 In particular, you can force every access
28253 type that is used for allocation (@strong{new}) to have an explicit storage pool,
28254 or you can declare a pool globally to be used for all access types that lack
28257 RM References: D.07 (8)
28260 @geindex AI-0189 (Ada 2012 feature)
28266 @emph{AI-0189 No_Allocators_After_Elaboration (2010-01-23)}
28268 This AI introduces a new restriction @code{No_Allocators_After_Elaboration},
28269 which says that no dynamic allocation will occur once elaboration is
28271 In general this requires a run-time check, which is not required, and which
28272 GNAT does not attempt. But the static cases of allocators in a task body or
28273 in the body of the main program are detected and flagged at compile or bind
28276 RM References: D.07 (19.1/2) H.04 (23.3/2)
28279 @geindex AI-0171 (Ada 2012 feature)
28285 @emph{AI-0171 Pragma CPU and Ravenscar Profile (2010-09-24)}
28287 A new package @code{System.Multiprocessors} is added, together with the
28288 definition of pragma @code{CPU} for controlling task affinity. A new no
28289 dependence restriction, on @code{System.Multiprocessors.Dispatching_Domains},
28290 is added to the Ravenscar profile.
28292 RM References: D.13.01 (4/2) D.16
28295 @geindex AI-0210 (Ada 2012 feature)
28301 @emph{AI-0210 Correct Timing_Events metric (0000-00-00)}
28303 This is a documentation only issue regarding wording of metric requirements,
28304 that does not affect the implementation of the compiler.
28306 RM References: D.15 (24/2)
28309 @geindex AI-0206 (Ada 2012 feature)
28315 @emph{AI-0206 Remote types packages and preelaborate (2010-07-24)}
28317 Remote types packages are now allowed to depend on preelaborated packages.
28318 This was formerly considered illegal.
28320 RM References: E.02.02 (6)
28323 @geindex AI-0152 (Ada 2012 feature)
28329 @emph{AI-0152 Restriction No_Anonymous_Allocators (2010-09-08)}
28331 Restriction @code{No_Anonymous_Allocators} prevents the use of allocators
28332 where the type of the returned value is an anonymous access type.
28334 RM References: H.04 (8/1)
28337 @node Obsolescent Features,Compatibility and Porting Guide,Implementation of Ada 2012 Features,Top
28338 @anchor{gnat_rm/obsolescent_features id1}@anchor{438}@anchor{gnat_rm/obsolescent_features doc}@anchor{439}@anchor{gnat_rm/obsolescent_features obsolescent-features}@anchor{15}
28339 @chapter Obsolescent Features
28342 This chapter describes features that are provided by GNAT, but are
28343 considered obsolescent since there are preferred ways of achieving
28344 the same effect. These features are provided solely for historical
28345 compatibility purposes.
28348 * pragma No_Run_Time::
28349 * pragma Ravenscar::
28350 * pragma Restricted_Run_Time::
28351 * pragma Task_Info::
28352 * package System.Task_Info (s-tasinf.ads): package System Task_Info s-tasinf ads.
28356 @node pragma No_Run_Time,pragma Ravenscar,,Obsolescent Features
28357 @anchor{gnat_rm/obsolescent_features id2}@anchor{43a}@anchor{gnat_rm/obsolescent_features pragma-no-run-time}@anchor{43b}
28358 @section pragma No_Run_Time
28361 The pragma @code{No_Run_Time} is used to achieve an affect similar
28362 to the use of the "Zero Foot Print" configurable run time, but without
28363 requiring a specially configured run time. The result of using this
28364 pragma, which must be used for all units in a partition, is to restrict
28365 the use of any language features requiring run-time support code. The
28366 preferred usage is to use an appropriately configured run-time that
28367 includes just those features that are to be made accessible.
28369 @node pragma Ravenscar,pragma Restricted_Run_Time,pragma No_Run_Time,Obsolescent Features
28370 @anchor{gnat_rm/obsolescent_features id3}@anchor{43c}@anchor{gnat_rm/obsolescent_features pragma-ravenscar}@anchor{43d}
28371 @section pragma Ravenscar
28374 The pragma @code{Ravenscar} has exactly the same effect as pragma
28375 @code{Profile (Ravenscar)}. The latter usage is preferred since it
28376 is part of the new Ada 2005 standard.
28378 @node pragma Restricted_Run_Time,pragma Task_Info,pragma Ravenscar,Obsolescent Features
28379 @anchor{gnat_rm/obsolescent_features pragma-restricted-run-time}@anchor{43e}@anchor{gnat_rm/obsolescent_features id4}@anchor{43f}
28380 @section pragma Restricted_Run_Time
28383 The pragma @code{Restricted_Run_Time} has exactly the same effect as
28384 pragma @code{Profile (Restricted)}. The latter usage is
28385 preferred since the Ada 2005 pragma @code{Profile} is intended for
28386 this kind of implementation dependent addition.
28388 @node pragma Task_Info,package System Task_Info s-tasinf ads,pragma Restricted_Run_Time,Obsolescent Features
28389 @anchor{gnat_rm/obsolescent_features pragma-task-info}@anchor{440}@anchor{gnat_rm/obsolescent_features id5}@anchor{441}
28390 @section pragma Task_Info
28393 The functionality provided by pragma @code{Task_Info} is now part of the
28394 Ada language. The @code{CPU} aspect and the package
28395 @code{System.Multiprocessors} offer a less system-dependent way to specify
28396 task affinity or to query the number of processors.
28401 pragma Task_Info (EXPRESSION);
28404 This pragma appears within a task definition (like pragma
28405 @code{Priority}) and applies to the task in which it appears. The
28406 argument must be of type @code{System.Task_Info.Task_Info_Type}.
28407 The @code{Task_Info} pragma provides system dependent control over
28408 aspects of tasking implementation, for example, the ability to map
28409 tasks to specific processors. For details on the facilities available
28410 for the version of GNAT that you are using, see the documentation
28411 in the spec of package System.Task_Info in the runtime
28414 @node package System Task_Info s-tasinf ads,,pragma Task_Info,Obsolescent Features
28415 @anchor{gnat_rm/obsolescent_features package-system-task-info}@anchor{442}@anchor{gnat_rm/obsolescent_features package-system-task-info-s-tasinf-ads}@anchor{443}
28416 @section package System.Task_Info (@code{s-tasinf.ads})
28419 This package provides target dependent functionality that is used
28420 to support the @code{Task_Info} pragma. The predefined Ada package
28421 @code{System.Multiprocessors} and the @code{CPU} aspect now provide a
28422 standard replacement for GNAT's @code{Task_Info} functionality.
28424 @node Compatibility and Porting Guide,GNU Free Documentation License,Obsolescent Features,Top
28425 @anchor{gnat_rm/compatibility_and_porting_guide compatibility-and-porting-guide}@anchor{16}@anchor{gnat_rm/compatibility_and_porting_guide doc}@anchor{444}@anchor{gnat_rm/compatibility_and_porting_guide id1}@anchor{445}
28426 @chapter Compatibility and Porting Guide
28429 This chapter presents some guidelines for developing portable Ada code,
28430 describes the compatibility issues that may arise between
28431 GNAT and other Ada compilation systems (including those for Ada 83),
28432 and shows how GNAT can expedite porting
28433 applications developed in other Ada environments.
28436 * Writing Portable Fixed-Point Declarations::
28437 * Compatibility with Ada 83::
28438 * Compatibility between Ada 95 and Ada 2005::
28439 * Implementation-dependent characteristics::
28440 * Compatibility with Other Ada Systems::
28441 * Representation Clauses::
28442 * Compatibility with HP Ada 83::
28446 @node Writing Portable Fixed-Point Declarations,Compatibility with Ada 83,,Compatibility and Porting Guide
28447 @anchor{gnat_rm/compatibility_and_porting_guide id2}@anchor{446}@anchor{gnat_rm/compatibility_and_porting_guide writing-portable-fixed-point-declarations}@anchor{447}
28448 @section Writing Portable Fixed-Point Declarations
28451 The Ada Reference Manual gives an implementation freedom to choose bounds
28452 that are narrower by @code{Small} from the given bounds.
28453 For example, if we write
28456 type F1 is delta 1.0 range -128.0 .. +128.0;
28459 then the implementation is allowed to choose -128.0 .. +127.0 if it
28460 likes, but is not required to do so.
28462 This leads to possible portability problems, so let's have a closer
28463 look at this, and figure out how to avoid these problems.
28465 First, why does this freedom exist, and why would an implementation
28466 take advantage of it? To answer this, take a closer look at the type
28467 declaration for @code{F1} above. If the compiler uses the given bounds,
28468 it would need 9 bits to hold the largest positive value (and typically
28469 that means 16 bits on all machines). But if the implementation chooses
28470 the +127.0 bound then it can fit values of the type in 8 bits.
28472 Why not make the user write +127.0 if that's what is wanted?
28473 The rationale is that if you are thinking of fixed point
28474 as a kind of 'poor man's floating-point', then you don't want
28475 to be thinking about the scaled integers that are used in its
28476 representation. Let's take another example:
28479 type F2 is delta 2.0**(-15) range -1.0 .. +1.0;
28482 Looking at this declaration, it seems casually as though
28483 it should fit in 16 bits, but again that extra positive value
28484 +1.0 has the scaled integer equivalent of 2**15 which is one too
28485 big for signed 16 bits. The implementation can treat this as:
28488 type F2 is delta 2.0**(-15) range -1.0 .. +1.0-(2.0**(-15));
28491 and the Ada language design team felt that this was too annoying
28492 to require. We don't need to debate this decision at this point,
28493 since it is well established (the rule about narrowing the ranges
28496 But the important point is that an implementation is not required
28497 to do this narrowing, so we have a potential portability problem.
28498 We could imagine three types of implementation:
28504 those that narrow the range automatically if they can figure
28505 out that the narrower range will allow storage in a smaller machine unit,
28508 those that will narrow only if forced to by a @code{'Size} clause, and
28511 those that will never narrow.
28514 Now if we are language theoreticians, we can imagine a fourth
28515 approach: to narrow all the time, e.g. to treat
28518 type F3 is delta 1.0 range -10.0 .. +23.0;
28521 as though it had been written:
28524 type F3 is delta 1.0 range -9.0 .. +22.0;
28527 But although technically allowed, such a behavior would be hostile and silly,
28528 and no real compiler would do this. All real compilers will fall into one of
28529 the categories (a), (b) or (c) above.
28531 So, how do you get the compiler to do what you want? The answer is give the
28532 actual bounds you want, and then use a @code{'Small} clause and a
28533 @code{'Size} clause to absolutely pin down what the compiler does.
28534 E.g., for @code{F2} above, we will write:
28537 My_Small : constant := 2.0**(-15);
28538 My_First : constant := -1.0;
28539 My_Last : constant := +1.0 - My_Small;
28541 type F2 is delta My_Small range My_First .. My_Last;
28547 for F2'Small use my_Small;
28548 for F2'Size use 16;
28551 In practice all compilers will do the same thing here and will give you
28552 what you want, so the above declarations are fully portable. If you really
28553 want to play language lawyer and guard against ludicrous behavior by the
28554 compiler you could add
28557 Test1 : constant := 1 / Boolean'Pos (F2'First = My_First);
28558 Test2 : constant := 1 / Boolean'Pos (F2'Last = My_Last);
28561 One or other or both are allowed to be illegal if the compiler is
28562 behaving in a silly manner, but at least the silly compiler will not
28563 get away with silently messing with your (very clear) intentions.
28565 If you follow this scheme you will be guaranteed that your fixed-point
28566 types will be portable.
28568 @node Compatibility with Ada 83,Compatibility between Ada 95 and Ada 2005,Writing Portable Fixed-Point Declarations,Compatibility and Porting Guide
28569 @anchor{gnat_rm/compatibility_and_porting_guide compatibility-with-ada-83}@anchor{448}@anchor{gnat_rm/compatibility_and_porting_guide id3}@anchor{449}
28570 @section Compatibility with Ada 83
28573 @geindex Compatibility (between Ada 83 and Ada 95 / Ada 2005 / Ada 2012)
28575 Ada 95 and the subsequent revisions Ada 2005 and Ada 2012
28576 are highly upwards compatible with Ada 83. In
28577 particular, the design intention was that the difficulties associated
28578 with moving from Ada 83 to later versions of the standard should be no greater
28579 than those that occur when moving from one Ada 83 system to another.
28581 However, there are a number of points at which there are minor
28582 incompatibilities. The @cite{Ada 95 Annotated Reference Manual} contains
28583 full details of these issues as they relate to Ada 95,
28584 and should be consulted for a complete treatment.
28586 following subsections treat the most likely issues to be encountered.
28589 * Legal Ada 83 programs that are illegal in Ada 95::
28590 * More deterministic semantics::
28591 * Changed semantics::
28592 * Other language compatibility issues::
28596 @node Legal Ada 83 programs that are illegal in Ada 95,More deterministic semantics,,Compatibility with Ada 83
28597 @anchor{gnat_rm/compatibility_and_porting_guide id4}@anchor{44a}@anchor{gnat_rm/compatibility_and_porting_guide legal-ada-83-programs-that-are-illegal-in-ada-95}@anchor{44b}
28598 @subsection Legal Ada 83 programs that are illegal in Ada 95
28601 Some legal Ada 83 programs are illegal (i.e., they will fail to compile) in
28602 Ada 95 and later versions of the standard:
28608 @emph{Character literals}
28610 Some uses of character literals are ambiguous. Since Ada 95 has introduced
28611 @code{Wide_Character} as a new predefined character type, some uses of
28612 character literals that were legal in Ada 83 are illegal in Ada 95.
28616 for Char in 'A' .. 'Z' loop ... end loop;
28619 The problem is that 'A' and 'Z' could be from either
28620 @code{Character} or @code{Wide_Character}. The simplest correction
28621 is to make the type explicit; e.g.:
28624 for Char in Character range 'A' .. 'Z' loop ... end loop;
28628 @emph{New reserved words}
28630 The identifiers @code{abstract}, @code{aliased}, @code{protected},
28631 @code{requeue}, @code{tagged}, and @code{until} are reserved in Ada 95.
28632 Existing Ada 83 code using any of these identifiers must be edited to
28633 use some alternative name.
28636 @emph{Freezing rules}
28638 The rules in Ada 95 are slightly different with regard to the point at
28639 which entities are frozen, and representation pragmas and clauses are
28640 not permitted past the freeze point. This shows up most typically in
28641 the form of an error message complaining that a representation item
28642 appears too late, and the appropriate corrective action is to move
28643 the item nearer to the declaration of the entity to which it refers.
28645 A particular case is that representation pragmas
28646 cannot be applied to a subprogram body. If necessary, a separate subprogram
28647 declaration must be introduced to which the pragma can be applied.
28650 @emph{Optional bodies for library packages}
28652 In Ada 83, a package that did not require a package body was nevertheless
28653 allowed to have one. This lead to certain surprises in compiling large
28654 systems (situations in which the body could be unexpectedly ignored by the
28655 binder). In Ada 95, if a package does not require a body then it is not
28656 permitted to have a body. To fix this problem, simply remove a redundant
28657 body if it is empty, or, if it is non-empty, introduce a dummy declaration
28658 into the spec that makes the body required. One approach is to add a private
28659 part to the package declaration (if necessary), and define a parameterless
28660 procedure called @code{Requires_Body}, which must then be given a dummy
28661 procedure body in the package body, which then becomes required.
28662 Another approach (assuming that this does not introduce elaboration
28663 circularities) is to add an @code{Elaborate_Body} pragma to the package spec,
28664 since one effect of this pragma is to require the presence of a package body.
28667 @emph{Numeric_Error is the same exception as Constraint_Error}
28669 In Ada 95, the exception @code{Numeric_Error} is a renaming of @code{Constraint_Error}.
28670 This means that it is illegal to have separate exception handlers for
28671 the two exceptions. The fix is simply to remove the handler for the
28672 @code{Numeric_Error} case (since even in Ada 83, a compiler was free to raise
28673 @code{Constraint_Error} in place of @code{Numeric_Error} in all cases).
28676 @emph{Indefinite subtypes in generics}
28678 In Ada 83, it was permissible to pass an indefinite type (e.g, @code{String})
28679 as the actual for a generic formal private type, but then the instantiation
28680 would be illegal if there were any instances of declarations of variables
28681 of this type in the generic body. In Ada 95, to avoid this clear violation
28682 of the methodological principle known as the 'contract model',
28683 the generic declaration explicitly indicates whether
28684 or not such instantiations are permitted. If a generic formal parameter
28685 has explicit unknown discriminants, indicated by using @code{(<>)} after the
28686 subtype name, then it can be instantiated with indefinite types, but no
28687 stand-alone variables can be declared of this type. Any attempt to declare
28688 such a variable will result in an illegality at the time the generic is
28689 declared. If the @code{(<>)} notation is not used, then it is illegal
28690 to instantiate the generic with an indefinite type.
28691 This is the potential incompatibility issue when porting Ada 83 code to Ada 95.
28692 It will show up as a compile time error, and
28693 the fix is usually simply to add the @code{(<>)} to the generic declaration.
28696 @node More deterministic semantics,Changed semantics,Legal Ada 83 programs that are illegal in Ada 95,Compatibility with Ada 83
28697 @anchor{gnat_rm/compatibility_and_porting_guide more-deterministic-semantics}@anchor{44c}@anchor{gnat_rm/compatibility_and_porting_guide id5}@anchor{44d}
28698 @subsection More deterministic semantics
28707 Conversions from real types to integer types round away from 0. In Ada 83
28708 the conversion Integer(2.5) could deliver either 2 or 3 as its value. This
28709 implementation freedom was intended to support unbiased rounding in
28710 statistical applications, but in practice it interfered with portability.
28711 In Ada 95 the conversion semantics are unambiguous, and rounding away from 0
28712 is required. Numeric code may be affected by this change in semantics.
28713 Note, though, that this issue is no worse than already existed in Ada 83
28714 when porting code from one vendor to another.
28719 The Real-Time Annex introduces a set of policies that define the behavior of
28720 features that were implementation dependent in Ada 83, such as the order in
28721 which open select branches are executed.
28724 @node Changed semantics,Other language compatibility issues,More deterministic semantics,Compatibility with Ada 83
28725 @anchor{gnat_rm/compatibility_and_porting_guide id6}@anchor{44e}@anchor{gnat_rm/compatibility_and_porting_guide changed-semantics}@anchor{44f}
28726 @subsection Changed semantics
28729 The worst kind of incompatibility is one where a program that is legal in
28730 Ada 83 is also legal in Ada 95 but can have an effect in Ada 95 that was not
28731 possible in Ada 83. Fortunately this is extremely rare, but the one
28732 situation that you should be alert to is the change in the predefined type
28733 @code{Character} from 7-bit ASCII to 8-bit Latin-1.
28744 @emph{Range of type `@w{`}Character`@w{`}}
28746 The range of @code{Standard.Character} is now the full 256 characters
28747 of Latin-1, whereas in most Ada 83 implementations it was restricted
28748 to 128 characters. Although some of the effects of
28749 this change will be manifest in compile-time rejection of legal
28750 Ada 83 programs it is possible for a working Ada 83 program to have
28751 a different effect in Ada 95, one that was not permitted in Ada 83.
28752 As an example, the expression
28753 @code{Character'Pos(Character'Last)} returned @code{127} in Ada 83 and now
28754 delivers @code{255} as its value.
28755 In general, you should look at the logic of any
28756 character-processing Ada 83 program and see whether it needs to be adapted
28757 to work correctly with Latin-1. Note that the predefined Ada 95 API has a
28758 character handling package that may be relevant if code needs to be adapted
28759 to account for the additional Latin-1 elements.
28760 The desirable fix is to
28761 modify the program to accommodate the full character set, but in some cases
28762 it may be convenient to define a subtype or derived type of Character that
28763 covers only the restricted range.
28766 @node Other language compatibility issues,,Changed semantics,Compatibility with Ada 83
28767 @anchor{gnat_rm/compatibility_and_porting_guide other-language-compatibility-issues}@anchor{450}@anchor{gnat_rm/compatibility_and_porting_guide id7}@anchor{451}
28768 @subsection Other language compatibility issues
28775 @emph{-gnat83} switch
28777 All implementations of GNAT provide a switch that causes GNAT to operate
28778 in Ada 83 mode. In this mode, some but not all compatibility problems
28779 of the type described above are handled automatically. For example, the
28780 new reserved words introduced in Ada 95 and Ada 2005 are treated simply
28781 as identifiers as in Ada 83. However,
28782 in practice, it is usually advisable to make the necessary modifications
28783 to the program to remove the need for using this switch.
28784 See the @code{Compiling Different Versions of Ada} section in
28785 the @cite{GNAT User's Guide}.
28788 Support for removed Ada 83 pragmas and attributes
28790 A number of pragmas and attributes from Ada 83 were removed from Ada 95,
28791 generally because they were replaced by other mechanisms. Ada 95 and Ada 2005
28792 compilers are allowed, but not required, to implement these missing
28793 elements. In contrast with some other compilers, GNAT implements all
28794 such pragmas and attributes, eliminating this compatibility concern. These
28795 include @code{pragma Interface} and the floating point type attributes
28796 (@code{Emax}, @code{Mantissa}, etc.), among other items.
28799 @node Compatibility between Ada 95 and Ada 2005,Implementation-dependent characteristics,Compatibility with Ada 83,Compatibility and Porting Guide
28800 @anchor{gnat_rm/compatibility_and_porting_guide compatibility-between-ada-95-and-ada-2005}@anchor{452}@anchor{gnat_rm/compatibility_and_porting_guide id8}@anchor{453}
28801 @section Compatibility between Ada 95 and Ada 2005
28804 @geindex Compatibility between Ada 95 and Ada 2005
28806 Although Ada 2005 was designed to be upwards compatible with Ada 95, there are
28807 a number of incompatibilities. Several are enumerated below;
28808 for a complete description please see the
28809 @cite{Annotated Ada 2005 Reference Manual}, or section 9.1.1 in
28810 @cite{Rationale for Ada 2005}.
28816 @emph{New reserved words.}
28818 The words @code{interface}, @code{overriding} and @code{synchronized} are
28819 reserved in Ada 2005.
28820 A pre-Ada 2005 program that uses any of these as an identifier will be
28824 @emph{New declarations in predefined packages.}
28826 A number of packages in the predefined environment contain new declarations:
28827 @code{Ada.Exceptions}, @code{Ada.Real_Time}, @code{Ada.Strings},
28828 @code{Ada.Strings.Fixed}, @code{Ada.Strings.Bounded},
28829 @code{Ada.Strings.Unbounded}, @code{Ada.Strings.Wide_Fixed},
28830 @code{Ada.Strings.Wide_Bounded}, @code{Ada.Strings.Wide_Unbounded},
28831 @code{Ada.Tags}, @code{Ada.Text_IO}, and @code{Interfaces.C}.
28832 If an Ada 95 program does a @code{with} and @code{use} of any of these
28833 packages, the new declarations may cause name clashes.
28836 @emph{Access parameters.}
28838 A nondispatching subprogram with an access parameter cannot be renamed
28839 as a dispatching operation. This was permitted in Ada 95.
28842 @emph{Access types, discriminants, and constraints.}
28844 Rule changes in this area have led to some incompatibilities; for example,
28845 constrained subtypes of some access types are not permitted in Ada 2005.
28848 @emph{Aggregates for limited types.}
28850 The allowance of aggregates for limited types in Ada 2005 raises the
28851 possibility of ambiguities in legal Ada 95 programs, since additional types
28852 now need to be considered in expression resolution.
28855 @emph{Fixed-point multiplication and division.}
28857 Certain expressions involving '*' or '/' for a fixed-point type, which
28858 were legal in Ada 95 and invoked the predefined versions of these operations,
28860 The ambiguity may be resolved either by applying a type conversion to the
28861 expression, or by explicitly invoking the operation from package
28865 @emph{Return-by-reference types.}
28867 The Ada 95 return-by-reference mechanism has been removed. Instead, the user
28868 can declare a function returning a value from an anonymous access type.
28871 @node Implementation-dependent characteristics,Compatibility with Other Ada Systems,Compatibility between Ada 95 and Ada 2005,Compatibility and Porting Guide
28872 @anchor{gnat_rm/compatibility_and_porting_guide implementation-dependent-characteristics}@anchor{454}@anchor{gnat_rm/compatibility_and_porting_guide id9}@anchor{455}
28873 @section Implementation-dependent characteristics
28876 Although the Ada language defines the semantics of each construct as
28877 precisely as practical, in some situations (for example for reasons of
28878 efficiency, or where the effect is heavily dependent on the host or target
28879 platform) the implementation is allowed some freedom. In porting Ada 83
28880 code to GNAT, you need to be aware of whether / how the existing code
28881 exercised such implementation dependencies. Such characteristics fall into
28882 several categories, and GNAT offers specific support in assisting the
28883 transition from certain Ada 83 compilers.
28886 * Implementation-defined pragmas::
28887 * Implementation-defined attributes::
28889 * Elaboration order::
28890 * Target-specific aspects::
28894 @node Implementation-defined pragmas,Implementation-defined attributes,,Implementation-dependent characteristics
28895 @anchor{gnat_rm/compatibility_and_porting_guide implementation-defined-pragmas}@anchor{456}@anchor{gnat_rm/compatibility_and_porting_guide id10}@anchor{457}
28896 @subsection Implementation-defined pragmas
28899 Ada compilers are allowed to supplement the language-defined pragmas, and
28900 these are a potential source of non-portability. All GNAT-defined pragmas
28901 are described in @ref{7,,Implementation Defined Pragmas},
28902 and these include several that are specifically
28903 intended to correspond to other vendors' Ada 83 pragmas.
28904 For migrating from VADS, the pragma @code{Use_VADS_Size} may be useful.
28905 For compatibility with HP Ada 83, GNAT supplies the pragmas
28906 @code{Extend_System}, @code{Ident}, @code{Inline_Generic},
28907 @code{Interface_Name}, @code{Passive}, @code{Suppress_All},
28908 and @code{Volatile}.
28909 Other relevant pragmas include @code{External} and @code{Link_With}.
28910 Some vendor-specific
28911 Ada 83 pragmas (@code{Share_Generic}, @code{Subtitle}, and @code{Title}) are
28913 avoiding compiler rejection of units that contain such pragmas; they are not
28914 relevant in a GNAT context and hence are not otherwise implemented.
28916 @node Implementation-defined attributes,Libraries,Implementation-defined pragmas,Implementation-dependent characteristics
28917 @anchor{gnat_rm/compatibility_and_porting_guide id11}@anchor{458}@anchor{gnat_rm/compatibility_and_porting_guide implementation-defined-attributes}@anchor{459}
28918 @subsection Implementation-defined attributes
28921 Analogous to pragmas, the set of attributes may be extended by an
28922 implementation. All GNAT-defined attributes are described in
28923 @ref{8,,Implementation Defined Attributes},
28924 and these include several that are specifically intended
28925 to correspond to other vendors' Ada 83 attributes. For migrating from VADS,
28926 the attribute @code{VADS_Size} may be useful. For compatibility with HP
28927 Ada 83, GNAT supplies the attributes @code{Bit}, @code{Machine_Size} and
28930 @node Libraries,Elaboration order,Implementation-defined attributes,Implementation-dependent characteristics
28931 @anchor{gnat_rm/compatibility_and_porting_guide libraries}@anchor{45a}@anchor{gnat_rm/compatibility_and_porting_guide id12}@anchor{45b}
28932 @subsection Libraries
28935 Vendors may supply libraries to supplement the standard Ada API. If Ada 83
28936 code uses vendor-specific libraries then there are several ways to manage
28937 this in Ada 95 and later versions of the standard:
28943 If the source code for the libraries (specs and bodies) are
28944 available, then the libraries can be migrated in the same way as the
28948 If the source code for the specs but not the bodies are
28949 available, then you can reimplement the bodies.
28952 Some features introduced by Ada 95 obviate the need for library support. For
28953 example most Ada 83 vendors supplied a package for unsigned integers. The
28954 Ada 95 modular type feature is the preferred way to handle this need, so
28955 instead of migrating or reimplementing the unsigned integer package it may
28956 be preferable to retrofit the application using modular types.
28959 @node Elaboration order,Target-specific aspects,Libraries,Implementation-dependent characteristics
28960 @anchor{gnat_rm/compatibility_and_porting_guide elaboration-order}@anchor{45c}@anchor{gnat_rm/compatibility_and_porting_guide id13}@anchor{45d}
28961 @subsection Elaboration order
28964 The implementation can choose any elaboration order consistent with the unit
28965 dependency relationship. This freedom means that some orders can result in
28966 Program_Error being raised due to an 'Access Before Elaboration': an attempt
28967 to invoke a subprogram before its body has been elaborated, or to instantiate
28968 a generic before the generic body has been elaborated. By default GNAT
28969 attempts to choose a safe order (one that will not encounter access before
28970 elaboration problems) by implicitly inserting @code{Elaborate} or
28971 @code{Elaborate_All} pragmas where
28972 needed. However, this can lead to the creation of elaboration circularities
28973 and a resulting rejection of the program by gnatbind. This issue is
28974 thoroughly described in the @emph{Elaboration Order Handling in GNAT} appendix
28975 in the @cite{GNAT User's Guide}.
28976 In brief, there are several
28977 ways to deal with this situation:
28983 Modify the program to eliminate the circularities, e.g., by moving
28984 elaboration-time code into explicitly-invoked procedures
28987 Constrain the elaboration order by including explicit @code{Elaborate_Body} or
28988 @code{Elaborate} pragmas, and then inhibit the generation of implicit
28989 @code{Elaborate_All}
28990 pragmas either globally (as an effect of the @emph{-gnatE} switch) or locally
28991 (by selectively suppressing elaboration checks via pragma
28992 @code{Suppress(Elaboration_Check)} when it is safe to do so).
28995 @node Target-specific aspects,,Elaboration order,Implementation-dependent characteristics
28996 @anchor{gnat_rm/compatibility_and_porting_guide target-specific-aspects}@anchor{45e}@anchor{gnat_rm/compatibility_and_porting_guide id14}@anchor{45f}
28997 @subsection Target-specific aspects
29000 Low-level applications need to deal with machine addresses, data
29001 representations, interfacing with assembler code, and similar issues. If
29002 such an Ada 83 application is being ported to different target hardware (for
29003 example where the byte endianness has changed) then you will need to
29004 carefully examine the program logic; the porting effort will heavily depend
29005 on the robustness of the original design. Moreover, Ada 95 (and thus
29006 Ada 2005 and Ada 2012) are sometimes
29007 incompatible with typical Ada 83 compiler practices regarding implicit
29008 packing, the meaning of the Size attribute, and the size of access values.
29009 GNAT's approach to these issues is described in @ref{460,,Representation Clauses}.
29011 @node Compatibility with Other Ada Systems,Representation Clauses,Implementation-dependent characteristics,Compatibility and Porting Guide
29012 @anchor{gnat_rm/compatibility_and_porting_guide id15}@anchor{461}@anchor{gnat_rm/compatibility_and_porting_guide compatibility-with-other-ada-systems}@anchor{462}
29013 @section Compatibility with Other Ada Systems
29016 If programs avoid the use of implementation dependent and
29017 implementation defined features, as documented in the
29018 @cite{Ada Reference Manual}, there should be a high degree of portability between
29019 GNAT and other Ada systems. The following are specific items which
29020 have proved troublesome in moving Ada 95 programs from GNAT to other Ada 95
29021 compilers, but do not affect porting code to GNAT.
29022 (As of January 2007, GNAT is the only compiler available for Ada 2005;
29023 the following issues may or may not arise for Ada 2005 programs
29024 when other compilers appear.)
29030 @emph{Ada 83 Pragmas and Attributes}
29032 Ada 95 compilers are allowed, but not required, to implement the missing
29033 Ada 83 pragmas and attributes that are no longer defined in Ada 95.
29034 GNAT implements all such pragmas and attributes, eliminating this as
29035 a compatibility concern, but some other Ada 95 compilers reject these
29036 pragmas and attributes.
29039 @emph{Specialized Needs Annexes}
29041 GNAT implements the full set of special needs annexes. At the
29042 current time, it is the only Ada 95 compiler to do so. This means that
29043 programs making use of these features may not be portable to other Ada
29044 95 compilation systems.
29047 @emph{Representation Clauses}
29049 Some other Ada 95 compilers implement only the minimal set of
29050 representation clauses required by the Ada 95 reference manual. GNAT goes
29051 far beyond this minimal set, as described in the next section.
29054 @node Representation Clauses,Compatibility with HP Ada 83,Compatibility with Other Ada Systems,Compatibility and Porting Guide
29055 @anchor{gnat_rm/compatibility_and_porting_guide representation-clauses}@anchor{460}@anchor{gnat_rm/compatibility_and_porting_guide id16}@anchor{463}
29056 @section Representation Clauses
29059 The Ada 83 reference manual was quite vague in describing both the minimal
29060 required implementation of representation clauses, and also their precise
29061 effects. Ada 95 (and thus also Ada 2005) are much more explicit, but the
29062 minimal set of capabilities required is still quite limited.
29064 GNAT implements the full required set of capabilities in
29065 Ada 95 and Ada 2005, but also goes much further, and in particular
29066 an effort has been made to be compatible with existing Ada 83 usage to the
29067 greatest extent possible.
29069 A few cases exist in which Ada 83 compiler behavior is incompatible with
29070 the requirements in Ada 95 (and thus also Ada 2005). These are instances of
29071 intentional or accidental dependence on specific implementation dependent
29072 characteristics of these Ada 83 compilers. The following is a list of
29073 the cases most likely to arise in existing Ada 83 code.
29079 @emph{Implicit Packing}
29081 Some Ada 83 compilers allowed a Size specification to cause implicit
29082 packing of an array or record. This could cause expensive implicit
29083 conversions for change of representation in the presence of derived
29084 types, and the Ada design intends to avoid this possibility.
29085 Subsequent AI's were issued to make it clear that such implicit
29086 change of representation in response to a Size clause is inadvisable,
29087 and this recommendation is represented explicitly in the Ada 95 (and Ada 2005)
29088 Reference Manuals as implementation advice that is followed by GNAT.
29089 The problem will show up as an error
29090 message rejecting the size clause. The fix is simply to provide
29091 the explicit pragma @code{Pack}, or for more fine tuned control, provide
29092 a Component_Size clause.
29095 @emph{Meaning of Size Attribute}
29097 The Size attribute in Ada 95 (and Ada 2005) for discrete types is defined as
29098 the minimal number of bits required to hold values of the type. For example,
29099 on a 32-bit machine, the size of @code{Natural} will typically be 31 and not
29100 32 (since no sign bit is required). Some Ada 83 compilers gave 31, and
29101 some 32 in this situation. This problem will usually show up as a compile
29102 time error, but not always. It is a good idea to check all uses of the
29103 'Size attribute when porting Ada 83 code. The GNAT specific attribute
29104 Object_Size can provide a useful way of duplicating the behavior of
29105 some Ada 83 compiler systems.
29108 @emph{Size of Access Types}
29110 A common assumption in Ada 83 code is that an access type is in fact a pointer,
29111 and that therefore it will be the same size as a System.Address value. This
29112 assumption is true for GNAT in most cases with one exception. For the case of
29113 a pointer to an unconstrained array type (where the bounds may vary from one
29114 value of the access type to another), the default is to use a 'fat pointer',
29115 which is represented as two separate pointers, one to the bounds, and one to
29116 the array. This representation has a number of advantages, including improved
29117 efficiency. However, it may cause some difficulties in porting existing Ada 83
29118 code which makes the assumption that, for example, pointers fit in 32 bits on
29119 a machine with 32-bit addressing.
29121 To get around this problem, GNAT also permits the use of 'thin pointers' for
29122 access types in this case (where the designated type is an unconstrained array
29123 type). These thin pointers are indeed the same size as a System.Address value.
29124 To specify a thin pointer, use a size clause for the type, for example:
29127 type X is access all String;
29128 for X'Size use Standard'Address_Size;
29131 which will cause the type X to be represented using a single pointer.
29132 When using this representation, the bounds are right behind the array.
29133 This representation is slightly less efficient, and does not allow quite
29134 such flexibility in the use of foreign pointers or in using the
29135 Unrestricted_Access attribute to create pointers to non-aliased objects.
29136 But for any standard portable use of the access type it will work in
29137 a functionally correct manner and allow porting of existing code.
29138 Note that another way of forcing a thin pointer representation
29139 is to use a component size clause for the element size in an array,
29140 or a record representation clause for an access field in a record.
29142 See the documentation of Unrestricted_Access in the GNAT RM for a
29143 full discussion of possible problems using this attribute in conjunction
29144 with thin pointers.
29147 @node Compatibility with HP Ada 83,,Representation Clauses,Compatibility and Porting Guide
29148 @anchor{gnat_rm/compatibility_and_porting_guide compatibility-with-hp-ada-83}@anchor{464}@anchor{gnat_rm/compatibility_and_porting_guide id17}@anchor{465}
29149 @section Compatibility with HP Ada 83
29152 All the HP Ada 83 pragmas and attributes are recognized, although only a subset
29153 of them can sensibly be implemented. The description of pragmas in
29154 @ref{7,,Implementation Defined Pragmas} indicates whether or not they are
29155 applicable to GNAT.
29161 @emph{Default floating-point representation}
29163 In GNAT, the default floating-point format is IEEE, whereas in HP Ada 83,
29169 the package System in GNAT exactly corresponds to the definition in the
29170 Ada 95 reference manual, which means that it excludes many of the
29171 HP Ada 83 extensions. However, a separate package Aux_DEC is provided
29172 that contains the additional definitions, and a special pragma,
29173 Extend_System allows this package to be treated transparently as an
29174 extension of package System.
29177 @node GNU Free Documentation License,Index,Compatibility and Porting Guide,Top
29178 @anchor{share/gnu_free_documentation_license gnu-fdl}@anchor{1}@anchor{share/gnu_free_documentation_license doc}@anchor{466}@anchor{share/gnu_free_documentation_license gnu-free-documentation-license}@anchor{467}
29179 @chapter GNU Free Documentation License
29182 Version 1.3, 3 November 2008
29184 Copyright 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc
29185 @indicateurl{http://fsf.org/}
29187 Everyone is permitted to copy and distribute verbatim copies of this
29188 license document, but changing it is not allowed.
29192 The purpose of this License is to make a manual, textbook, or other
29193 functional and useful document "free" in the sense of freedom: to
29194 assure everyone the effective freedom to copy and redistribute it,
29195 with or without modifying it, either commercially or noncommercially.
29196 Secondarily, this License preserves for the author and publisher a way
29197 to get credit for their work, while not being considered responsible
29198 for modifications made by others.
29200 This License is a kind of "copyleft", which means that derivative
29201 works of the document must themselves be free in the same sense. It
29202 complements the GNU General Public License, which is a copyleft
29203 license designed for free software.
29205 We have designed this License in order to use it for manuals for free
29206 software, because free software needs free documentation: a free
29207 program should come with manuals providing the same freedoms that the
29208 software does. But this License is not limited to software manuals;
29209 it can be used for any textual work, regardless of subject matter or
29210 whether it is published as a printed book. We recommend this License
29211 principally for works whose purpose is instruction or reference.
29213 @strong{1. APPLICABILITY AND DEFINITIONS}
29215 This License applies to any manual or other work, in any medium, that
29216 contains a notice placed by the copyright holder saying it can be
29217 distributed under the terms of this License. Such a notice grants a
29218 world-wide, royalty-free license, unlimited in duration, to use that
29219 work under the conditions stated herein. The @strong{Document}, below,
29220 refers to any such manual or work. Any member of the public is a
29221 licensee, and is addressed as "@strong{you}". You accept the license if you
29222 copy, modify or distribute the work in a way requiring permission
29223 under copyright law.
29225 A "@strong{Modified Version}" of the Document means any work containing the
29226 Document or a portion of it, either copied verbatim, or with
29227 modifications and/or translated into another language.
29229 A "@strong{Secondary Section}" is a named appendix or a front-matter section of
29230 the Document that deals exclusively with the relationship of the
29231 publishers or authors of the Document to the Document's overall subject
29232 (or to related matters) and contains nothing that could fall directly
29233 within that overall subject. (Thus, if the Document is in part a
29234 textbook of mathematics, a Secondary Section may not explain any
29235 mathematics.) The relationship could be a matter of historical
29236 connection with the subject or with related matters, or of legal,
29237 commercial, philosophical, ethical or political position regarding
29240 The "@strong{Invariant Sections}" are certain Secondary Sections whose titles
29241 are designated, as being those of Invariant Sections, in the notice
29242 that says that the Document is released under this License. If a
29243 section does not fit the above definition of Secondary then it is not
29244 allowed to be designated as Invariant. The Document may contain zero
29245 Invariant Sections. If the Document does not identify any Invariant
29246 Sections then there are none.
29248 The "@strong{Cover Texts}" are certain short passages of text that are listed,
29249 as Front-Cover Texts or Back-Cover Texts, in the notice that says that
29250 the Document is released under this License. A Front-Cover Text may
29251 be at most 5 words, and a Back-Cover Text may be at most 25 words.
29253 A "@strong{Transparent}" copy of the Document means a machine-readable copy,
29254 represented in a format whose specification is available to the
29255 general public, that is suitable for revising the document
29256 straightforwardly with generic text editors or (for images composed of
29257 pixels) generic paint programs or (for drawings) some widely available
29258 drawing editor, and that is suitable for input to text formatters or
29259 for automatic translation to a variety of formats suitable for input
29260 to text formatters. A copy made in an otherwise Transparent file
29261 format whose markup, or absence of markup, has been arranged to thwart
29262 or discourage subsequent modification by readers is not Transparent.
29263 An image format is not Transparent if used for any substantial amount
29264 of text. A copy that is not "Transparent" is called @strong{Opaque}.
29266 Examples of suitable formats for Transparent copies include plain
29267 ASCII without markup, Texinfo input format, LaTeX input format, SGML
29268 or XML using a publicly available DTD, and standard-conforming simple
29269 HTML, PostScript or PDF designed for human modification. Examples of
29270 transparent image formats include PNG, XCF and JPG. Opaque formats
29271 include proprietary formats that can be read and edited only by
29272 proprietary word processors, SGML or XML for which the DTD and/or
29273 processing tools are not generally available, and the
29274 machine-generated HTML, PostScript or PDF produced by some word
29275 processors for output purposes only.
29277 The "@strong{Title Page}" means, for a printed book, the title page itself,
29278 plus such following pages as are needed to hold, legibly, the material
29279 this License requires to appear in the title page. For works in
29280 formats which do not have any title page as such, "Title Page" means
29281 the text near the most prominent appearance of the work's title,
29282 preceding the beginning of the body of the text.
29284 The "@strong{publisher}" means any person or entity that distributes
29285 copies of the Document to the public.
29287 A section "@strong{Entitled XYZ}" means a named subunit of the Document whose
29288 title either is precisely XYZ or contains XYZ in parentheses following
29289 text that translates XYZ in another language. (Here XYZ stands for a
29290 specific section name mentioned below, such as "@strong{Acknowledgements}",
29291 "@strong{Dedications}", "@strong{Endorsements}", or "@strong{History}".)
29292 To "@strong{Preserve the Title}"
29293 of such a section when you modify the Document means that it remains a
29294 section "Entitled XYZ" according to this definition.
29296 The Document may include Warranty Disclaimers next to the notice which
29297 states that this License applies to the Document. These Warranty
29298 Disclaimers are considered to be included by reference in this
29299 License, but only as regards disclaiming warranties: any other
29300 implication that these Warranty Disclaimers may have is void and has
29301 no effect on the meaning of this License.
29303 @strong{2. VERBATIM COPYING}
29305 You may copy and distribute the Document in any medium, either
29306 commercially or noncommercially, provided that this License, the
29307 copyright notices, and the license notice saying this License applies
29308 to the Document are reproduced in all copies, and that you add no other
29309 conditions whatsoever to those of this License. You may not use
29310 technical measures to obstruct or control the reading or further
29311 copying of the copies you make or distribute. However, you may accept
29312 compensation in exchange for copies. If you distribute a large enough
29313 number of copies you must also follow the conditions in section 3.
29315 You may also lend copies, under the same conditions stated above, and
29316 you may publicly display copies.
29318 @strong{3. COPYING IN QUANTITY}
29320 If you publish printed copies (or copies in media that commonly have
29321 printed covers) of the Document, numbering more than 100, and the
29322 Document's license notice requires Cover Texts, you must enclose the
29323 copies in covers that carry, clearly and legibly, all these Cover
29324 Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on
29325 the back cover. Both covers must also clearly and legibly identify
29326 you as the publisher of these copies. The front cover must present
29327 the full title with all words of the title equally prominent and
29328 visible. You may add other material on the covers in addition.
29329 Copying with changes limited to the covers, as long as they preserve
29330 the title of the Document and satisfy these conditions, can be treated
29331 as verbatim copying in other respects.
29333 If the required texts for either cover are too voluminous to fit
29334 legibly, you should put the first ones listed (as many as fit
29335 reasonably) on the actual cover, and continue the rest onto adjacent
29338 If you publish or distribute Opaque copies of the Document numbering
29339 more than 100, you must either include a machine-readable Transparent
29340 copy along with each Opaque copy, or state in or with each Opaque copy
29341 a computer-network location from which the general network-using
29342 public has access to download using public-standard network protocols
29343 a complete Transparent copy of the Document, free of added material.
29344 If you use the latter option, you must take reasonably prudent steps,
29345 when you begin distribution of Opaque copies in quantity, to ensure
29346 that this Transparent copy will remain thus accessible at the stated
29347 location until at least one year after the last time you distribute an
29348 Opaque copy (directly or through your agents or retailers) of that
29349 edition to the public.
29351 It is requested, but not required, that you contact the authors of the
29352 Document well before redistributing any large number of copies, to give
29353 them a chance to provide you with an updated version of the Document.
29355 @strong{4. MODIFICATIONS}
29357 You may copy and distribute a Modified Version of the Document under
29358 the conditions of sections 2 and 3 above, provided that you release
29359 the Modified Version under precisely this License, with the Modified
29360 Version filling the role of the Document, thus licensing distribution
29361 and modification of the Modified Version to whoever possesses a copy
29362 of it. In addition, you must do these things in the Modified Version:
29368 Use in the Title Page (and on the covers, if any) a title distinct
29369 from that of the Document, and from those of previous versions
29370 (which should, if there were any, be listed in the History section
29371 of the Document). You may use the same title as a previous version
29372 if the original publisher of that version gives permission.
29375 List on the Title Page, as authors, one or more persons or entities
29376 responsible for authorship of the modifications in the Modified
29377 Version, together with at least five of the principal authors of the
29378 Document (all of its principal authors, if it has fewer than five),
29379 unless they release you from this requirement.
29382 State on the Title page the name of the publisher of the
29383 Modified Version, as the publisher.
29386 Preserve all the copyright notices of the Document.
29389 Add an appropriate copyright notice for your modifications
29390 adjacent to the other copyright notices.
29393 Include, immediately after the copyright notices, a license notice
29394 giving the public permission to use the Modified Version under the
29395 terms of this License, in the form shown in the Addendum below.
29398 Preserve in that license notice the full lists of Invariant Sections
29399 and required Cover Texts given in the Document's license notice.
29402 Include an unaltered copy of this License.
29405 Preserve the section Entitled "History", Preserve its Title, and add
29406 to it an item stating at least the title, year, new authors, and
29407 publisher of the Modified Version as given on the Title Page. If
29408 there is no section Entitled "History" in the Document, create one
29409 stating the title, year, authors, and publisher of the Document as
29410 given on its Title Page, then add an item describing the Modified
29411 Version as stated in the previous sentence.
29414 Preserve the network location, if any, given in the Document for
29415 public access to a Transparent copy of the Document, and likewise
29416 the network locations given in the Document for previous versions
29417 it was based on. These may be placed in the "History" section.
29418 You may omit a network location for a work that was published at
29419 least four years before the Document itself, or if the original
29420 publisher of the version it refers to gives permission.
29423 For any section Entitled "Acknowledgements" or "Dedications",
29424 Preserve the Title of the section, and preserve in the section all
29425 the substance and tone of each of the contributor acknowledgements
29426 and/or dedications given therein.
29429 Preserve all the Invariant Sections of the Document,
29430 unaltered in their text and in their titles. Section numbers
29431 or the equivalent are not considered part of the section titles.
29434 Delete any section Entitled "Endorsements". Such a section
29435 may not be included in the Modified Version.
29438 Do not retitle any existing section to be Entitled "Endorsements"
29439 or to conflict in title with any Invariant Section.
29442 Preserve any Warranty Disclaimers.
29445 If the Modified Version includes new front-matter sections or
29446 appendices that qualify as Secondary Sections and contain no material
29447 copied from the Document, you may at your option designate some or all
29448 of these sections as invariant. To do this, add their titles to the
29449 list of Invariant Sections in the Modified Version's license notice.
29450 These titles must be distinct from any other section titles.
29452 You may add a section Entitled "Endorsements", provided it contains
29453 nothing but endorsements of your Modified Version by various
29454 parties---for example, statements of peer review or that the text has
29455 been approved by an organization as the authoritative definition of a
29458 You may add a passage of up to five words as a Front-Cover Text, and a
29459 passage of up to 25 words as a Back-Cover Text, to the end of the list
29460 of Cover Texts in the Modified Version. Only one passage of
29461 Front-Cover Text and one of Back-Cover Text may be added by (or
29462 through arrangements made by) any one entity. If the Document already
29463 includes a cover text for the same cover, previously added by you or
29464 by arrangement made by the same entity you are acting on behalf of,
29465 you may not add another; but you may replace the old one, on explicit
29466 permission from the previous publisher that added the old one.
29468 The author(s) and publisher(s) of the Document do not by this License
29469 give permission to use their names for publicity for or to assert or
29470 imply endorsement of any Modified Version.
29472 @strong{5. COMBINING DOCUMENTS}
29474 You may combine the Document with other documents released under this
29475 License, under the terms defined in section 4 above for modified
29476 versions, provided that you include in the combination all of the
29477 Invariant Sections of all of the original documents, unmodified, and
29478 list them all as Invariant Sections of your combined work in its
29479 license notice, and that you preserve all their Warranty Disclaimers.
29481 The combined work need only contain one copy of this License, and
29482 multiple identical Invariant Sections may be replaced with a single
29483 copy. If there are multiple Invariant Sections with the same name but
29484 different contents, make the title of each such section unique by
29485 adding at the end of it, in parentheses, the name of the original
29486 author or publisher of that section if known, or else a unique number.
29487 Make the same adjustment to the section titles in the list of
29488 Invariant Sections in the license notice of the combined work.
29490 In the combination, you must combine any sections Entitled "History"
29491 in the various original documents, forming one section Entitled
29492 "History"; likewise combine any sections Entitled "Acknowledgements",
29493 and any sections Entitled "Dedications". You must delete all sections
29494 Entitled "Endorsements".
29496 @strong{6. COLLECTIONS OF DOCUMENTS}
29498 You may make a collection consisting of the Document and other documents
29499 released under this License, and replace the individual copies of this
29500 License in the various documents with a single copy that is included in
29501 the collection, provided that you follow the rules of this License for
29502 verbatim copying of each of the documents in all other respects.
29504 You may extract a single document from such a collection, and distribute
29505 it individually under this License, provided you insert a copy of this
29506 License into the extracted document, and follow this License in all
29507 other respects regarding verbatim copying of that document.
29509 @strong{7. AGGREGATION WITH INDEPENDENT WORKS}
29511 A compilation of the Document or its derivatives with other separate
29512 and independent documents or works, in or on a volume of a storage or
29513 distribution medium, is called an "aggregate" if the copyright
29514 resulting from the compilation is not used to limit the legal rights
29515 of the compilation's users beyond what the individual works permit.
29516 When the Document is included in an aggregate, this License does not
29517 apply to the other works in the aggregate which are not themselves
29518 derivative works of the Document.
29520 If the Cover Text requirement of section 3 is applicable to these
29521 copies of the Document, then if the Document is less than one half of
29522 the entire aggregate, the Document's Cover Texts may be placed on
29523 covers that bracket the Document within the aggregate, or the
29524 electronic equivalent of covers if the Document is in electronic form.
29525 Otherwise they must appear on printed covers that bracket the whole
29528 @strong{8. TRANSLATION}
29530 Translation is considered a kind of modification, so you may
29531 distribute translations of the Document under the terms of section 4.
29532 Replacing Invariant Sections with translations requires special
29533 permission from their copyright holders, but you may include
29534 translations of some or all Invariant Sections in addition to the
29535 original versions of these Invariant Sections. You may include a
29536 translation of this License, and all the license notices in the
29537 Document, and any Warranty Disclaimers, provided that you also include
29538 the original English version of this License and the original versions
29539 of those notices and disclaimers. In case of a disagreement between
29540 the translation and the original version of this License or a notice
29541 or disclaimer, the original version will prevail.
29543 If a section in the Document is Entitled "Acknowledgements",
29544 "Dedications", or "History", the requirement (section 4) to Preserve
29545 its Title (section 1) will typically require changing the actual
29548 @strong{9. TERMINATION}
29550 You may not copy, modify, sublicense, or distribute the Document
29551 except as expressly provided under this License. Any attempt
29552 otherwise to copy, modify, sublicense, or distribute it is void, and
29553 will automatically terminate your rights under this License.
29555 However, if you cease all violation of this License, then your license
29556 from a particular copyright holder is reinstated (a) provisionally,
29557 unless and until the copyright holder explicitly and finally
29558 terminates your license, and (b) permanently, if the copyright holder
29559 fails to notify you of the violation by some reasonable means prior to
29560 60 days after the cessation.
29562 Moreover, your license from a particular copyright holder is
29563 reinstated permanently if the copyright holder notifies you of the
29564 violation by some reasonable means, this is the first time you have
29565 received notice of violation of this License (for any work) from that
29566 copyright holder, and you cure the violation prior to 30 days after
29567 your receipt of the notice.
29569 Termination of your rights under this section does not terminate the
29570 licenses of parties who have received copies or rights from you under
29571 this License. If your rights have been terminated and not permanently
29572 reinstated, receipt of a copy of some or all of the same material does
29573 not give you any rights to use it.
29575 @strong{10. FUTURE REVISIONS OF THIS LICENSE}
29577 The Free Software Foundation may publish new, revised versions
29578 of the GNU Free Documentation License from time to time. Such new
29579 versions will be similar in spirit to the present version, but may
29580 differ in detail to address new problems or concerns. See
29581 @indicateurl{http://www.gnu.org/copyleft/}.
29583 Each version of the License is given a distinguishing version number.
29584 If the Document specifies that a particular numbered version of this
29585 License "or any later version" applies to it, you have the option of
29586 following the terms and conditions either of that specified version or
29587 of any later version that has been published (not as a draft) by the
29588 Free Software Foundation. If the Document does not specify a version
29589 number of this License, you may choose any version ever published (not
29590 as a draft) by the Free Software Foundation. If the Document
29591 specifies that a proxy can decide which future versions of this
29592 License can be used, that proxy's public statement of acceptance of a
29593 version permanently authorizes you to choose that version for the
29596 @strong{11. RELICENSING}
29598 "Massive Multiauthor Collaboration Site" (or "MMC Site") means any
29599 World Wide Web server that publishes copyrightable works and also
29600 provides prominent facilities for anybody to edit those works. A
29601 public wiki that anybody can edit is an example of such a server. A
29602 "Massive Multiauthor Collaboration" (or "MMC") contained in the
29603 site means any set of copyrightable works thus published on the MMC
29606 "CC-BY-SA" means the Creative Commons Attribution-Share Alike 3.0
29607 license published by Creative Commons Corporation, a not-for-profit
29608 corporation with a principal place of business in San Francisco,
29609 California, as well as future copyleft versions of that license
29610 published by that same organization.
29612 "Incorporate" means to publish or republish a Document, in whole or
29613 in part, as part of another Document.
29615 An MMC is "eligible for relicensing" if it is licensed under this
29616 License, and if all works that were first published under this License
29617 somewhere other than this MMC, and subsequently incorporated in whole
29618 or in part into the MMC, (1) had no cover texts or invariant sections,
29619 and (2) were thus incorporated prior to November 1, 2008.
29621 The operator of an MMC Site may republish an MMC contained in the site
29622 under CC-BY-SA on the same site at any time before August 1, 2009,
29623 provided the MMC is eligible for relicensing.
29625 @strong{ADDENDUM: How to use this License for your documents}
29627 To use this License in a document you have written, include a copy of
29628 the License in the document and put the following copyright and
29629 license notices just after the title page:
29633 Copyright © YEAR YOUR NAME.
29634 Permission is granted to copy, distribute and/or modify this document
29635 under the terms of the GNU Free Documentation License, Version 1.3
29636 or any later version published by the Free Software Foundation;
29637 with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
29638 A copy of the license is included in the section entitled "GNU
29639 Free Documentation License".
29642 If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts,
29643 replace the "with ... Texts." line with this:
29647 with the Invariant Sections being LIST THEIR TITLES, with the
29648 Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST.
29651 If you have Invariant Sections without Cover Texts, or some other
29652 combination of the three, merge those two alternatives to suit the
29655 If your document contains nontrivial examples of program code, we
29656 recommend releasing these examples in parallel under your choice of
29657 free software license, such as the GNU General Public License,
29658 to permit their use in free software.
29660 @node Index,,GNU Free Documentation License,Top