\input texinfo @c -*-texinfo-*-
-@input texiplus
@c %**start of header
@c o
@c G N A T _ RM o
@c o
-@c $Revision: 1.254 $
-@c o
-@c Copyright (C) 1995-2002 Free Software Foundation o
+@c Copyright (C) 1995-2007, Free Software Foundation o
@c o
@c o
@c GNAT is maintained by Ada Core Technologies Inc (http://www.gnat.com). o
@c oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo
@setfilename gnat_rm.info
+
+@set EDITION GNAT
+@set DEFAULTLANGUAGEVERSION Ada 2005
+@set NONDEFAULTLANGUAGEVERSION Ada 95
+
@settitle GNAT Reference Manual
+
@setchapternewpage odd
@syncodeindex fn cp
+@include gcc-common.texi
+
@dircategory GNU Ada tools
@direntry
* GNAT Reference Manual: (gnat_rm). Reference Manual for GNU Ada tools.
@end direntry
-@titlepage
+@copying
+Copyright @copyright{} 1995-2007, Free Software Foundation
-@title GNAT Reference Manual
-@subtitle GNAT, The GNU Ada 95 Compiler
-@ifset vxworks
-@title Version 3.16w
-@end ifset
-@ifclear vxworks
-@subtitle Version 3.16w
-@end ifclear
-@author Ada Core Technologies, Inc.
+Permission is granted to copy, distribute and/or modify this document
+under the terms of the GNU Free Documentation License, Version 1.2
+or any later version published by the Free Software Foundation;
+with the Invariant Sections being ``GNU Free Documentation License'',
+with the Front-Cover Texts being ``GNAT Reference Manual'', and with
+no Back-Cover Texts. A copy of the license is included in the section
+entitled ``GNU Free Documentation License''.
+@end copying
+@titlepage
+@title GNAT Reference Manual
+@subtitle GNAT, The GNU Ada Compiler
+@versionsubtitle
+@author AdaCore
@page
@vskip 0pt plus 1filll
-
-Copyright @copyright{} 1995-2001, Free Software Foundation
-
-Permission is granted to copy, distribute and/or modify this document
-under the terms of the GNU Free Documentation License, Version 1.1
-or any later version published by the Free Software Foundation;
-with the Invariant Sections being ``GNU Free Documentation License'', with the
-Front-Cover Texts being ``GNAT Reference Manual'', and with no Back-Cover Texts.
-A copy of the license is included in the section entitled ``GNU
-Free Documentation License''.
-
+@insertcopying
@end titlepage
-@ifinfo
+
+@ifnottex
@node Top, About This Guide, (dir), (dir)
@top GNAT Reference Manual
-
+@noindent
GNAT Reference Manual
-GNAT, The GNU Ada 95 Compiler
-
-@ifset vxworks
-Version 3.16w
-@end ifset
-@ifclear vxworks
-Version 3.16w
-@end ifclear
-
-Ada Core Technologies, Inc.
-
-
-Copyright @copyright{} 1995-2001, Free Software Foundation
-
-Permission is granted to copy, distribute and/or modify this document
-under the terms of the GNU Free Documentation License, Version 1.1
-or any later version published by the Free Software Foundation;
-with the Invariant Sections being ``GNU Free Documentation License'', with the
-Front-Cover Texts being ``GNAT Reference Manual'', and with no Back-Cover Texts.
-A copy of the license is included in the section entitled ``GNU
-Free Documentation License''.
+@noindent
+GNAT, The GNU Ada Compiler@*
+GCC version @value{version-GCC}@*
+@noindent
+AdaCore
@menu
-* About This Guide::
-* Implementation Defined Pragmas::
-* Implementation Defined Attributes::
-* Implementation Advice::
-* Implementation Defined Characteristics::
+* About This Guide::
+* Implementation Defined Pragmas::
+* Implementation Defined Attributes::
+* Implementation Advice::
+* Implementation Defined Characteristics::
* Intrinsic Subprograms::
* Representation Clauses and Pragmas::
-* Standard Library Routines::
-* The Implementation of Standard I/O::
+* Standard Library Routines::
+* The Implementation of Standard I/O::
* The GNAT Library::
-* Interfacing to Other Languages::
-* Machine Code Insertions::
-* GNAT Implementation of Tasking::
-* Code generation for array aggregates::
-* Specialized Needs Annexes::
-* Compatibility Guide::
+* Interfacing to Other Languages::
+* Specialized Needs Annexes::
+* Implementation of Specific Ada Features::
+* Project File Reference::
+* Obsolescent Features::
* GNU Free Documentation License::
-* Index::
+* Index::
--- The Detailed Node Listing ---
About This Guide
-* What This Reference Manual Contains::
-* Related Information::
+* What This Reference Manual Contains::
+* Related Information::
+
+Implementation Defined Pragmas
+
+* Pragma Abort_Defer::
+* Pragma Ada_83::
+* Pragma Ada_95::
+* Pragma Ada_05::
+* Pragma Ada_2005::
+* Pragma Annotate::
+* Pragma Assert::
+* Pragma Ast_Entry::
+* Pragma C_Pass_By_Copy::
+* Pragma Check_Name::
+* Pragma Comment::
+* Pragma Common_Object::
+* Pragma Compile_Time_Error::
+* Pragma Compile_Time_Warning::
+* Pragma Complete_Representation::
+* Pragma Complex_Representation::
+* Pragma Component_Alignment::
+* Pragma Convention_Identifier::
+* Pragma CPP_Class::
+* Pragma CPP_Constructor::
+* Pragma CPP_Virtual::
+* Pragma CPP_Vtable::
+* Pragma Debug::
+* Pragma Debug_Policy::
+* Pragma Detect_Blocking::
+* Pragma Elaboration_Checks::
+* Pragma Eliminate::
+* Pragma Export_Exception::
+* Pragma Export_Function::
+* Pragma Export_Object::
+* Pragma Export_Procedure::
+* Pragma Export_Value::
+* Pragma Export_Valued_Procedure::
+* Pragma Extend_System::
+* Pragma External::
+* Pragma External_Name_Casing::
+* Pragma Finalize_Storage_Only::
+* Pragma Float_Representation::
+* Pragma Ident::
+* Pragma Implicit_Packing::
+* Pragma Import_Exception::
+* Pragma Import_Function::
+* Pragma Import_Object::
+* Pragma Import_Procedure::
+* Pragma Import_Valued_Procedure::
+* Pragma Initialize_Scalars::
+* Pragma Inline_Always::
+* Pragma Inline_Generic::
+* Pragma Interface::
+* Pragma Interface_Name::
+* Pragma Interrupt_Handler::
+* Pragma Interrupt_State::
+* Pragma Keep_Names::
+* Pragma License::
+* Pragma Link_With::
+* Pragma Linker_Alias::
+* Pragma Linker_Constructor::
+* Pragma Linker_Destructor::
+* Pragma Linker_Section::
+* Pragma Long_Float::
+* Pragma Machine_Attribute::
+* Pragma Main::
+* Pragma Main_Storage::
+* Pragma No_Body::
+* Pragma No_Return::
+* Pragma No_Strict_Aliasing ::
+* Pragma Normalize_Scalars::
+* Pragma Obsolescent::
+* Pragma Passive::
+* Pragma Persistent_BSS::
+* Pragma Polling::
+* Pragma Profile (Ravenscar)::
+* Pragma Profile (Restricted)::
+* Pragma Psect_Object::
+* Pragma Pure_Function::
+* Pragma Restriction_Warnings::
+* Pragma Source_File_Name::
+* Pragma Source_File_Name_Project::
+* Pragma Source_Reference::
+* Pragma Stream_Convert::
+* Pragma Style_Checks::
+* Pragma Subtitle::
+* Pragma Suppress::
+* Pragma Suppress_All::
+* Pragma Suppress_Exception_Locations::
+* Pragma Suppress_Initialization::
+* Pragma Task_Info::
+* Pragma Task_Name::
+* Pragma Task_Storage::
+* Pragma Time_Slice::
+* Pragma Title::
+* Pragma Unchecked_Union::
+* Pragma Unimplemented_Unit::
+* Pragma Universal_Aliasing ::
+* Pragma Universal_Data::
+* Pragma Unreferenced::
+* Pragma Unreferenced_Objects::
+* Pragma Unreserve_All_Interrupts::
+* Pragma Unsuppress::
+* Pragma Use_VADS_Size::
+* Pragma Validity_Checks::
+* Pragma Volatile::
+* Pragma Warnings::
+* Pragma Weak_External::
+* Pragma Wide_Character_Encoding::
+
+Implementation Defined Attributes
+
+* Abort_Signal::
+* Address_Size::
+* Asm_Input::
+* Asm_Output::
+* AST_Entry::
+* Bit::
+* Bit_Position::
+* Code_Address::
+* Default_Bit_Order::
+* Elaborated::
+* Elab_Body::
+* Elab_Spec::
+* Emax::
+* Enabled::
+* Enum_Rep::
+* Epsilon::
+* Fixed_Value::
+* Has_Access_Values::
+* Has_Discriminants::
+* Img::
+* Integer_Value::
+* Large::
+* Machine_Size::
+* Mantissa::
+* Max_Interrupt_Priority::
+* Max_Priority::
+* Maximum_Alignment::
+* Mechanism_Code::
+* Null_Parameter::
+* Object_Size::
+* Passed_By_Reference::
+* Range_Length::
+* Safe_Emax::
+* Safe_Large::
+* Small::
+* Storage_Unit::
+* Stub_Type::
+* Target_Name::
+* Tick::
+* To_Address::
+* Type_Class::
+* UET_Address::
+* Unconstrained_Array::
+* Universal_Literal_String::
+* Unrestricted_Access::
+* VADS_Size::
+* Value_Size::
+* Wchar_T_Size::
+* Word_Size::
The Implementation of Standard I/O
-* Standard I/O Packages::
-* FORM Strings::
-* Direct_IO::
-* Sequential_IO::
-* Text_IO::
-* Wide_Text_IO::
-* Stream_IO::
-* Shared Files::
-* Open Modes::
-* Operations on C Streams::
-* Interfacing to C Streams::
+* Standard I/O Packages::
+* FORM Strings::
+* Direct_IO::
+* Sequential_IO::
+* Text_IO::
+* Wide_Text_IO::
+* Wide_Wide_Text_IO::
+* Stream_IO::
+* Shared Files::
+* Filenames encoding::
+* Open Modes::
+* Operations on C Streams::
+* Interfacing to C Streams::
The GNAT Library
* Ada.Characters.Latin_9 (a-chlat9.ads)::
* Ada.Characters.Wide_Latin_1 (a-cwila1.ads)::
* Ada.Characters.Wide_Latin_9 (a-cwila9.ads)::
+* Ada.Characters.Wide_Wide_Latin_1 (a-czila1.ads)::
+* Ada.Characters.Wide_Wide_Latin_9 (a-czila9.ads)::
* Ada.Command_Line.Remove (a-colire.ads)::
+* Ada.Command_Line.Environment (a-colien.ads)::
* Ada.Direct_IO.C_Streams (a-diocst.ads)::
* Ada.Exceptions.Is_Null_Occurrence (a-einuoc.ads)::
+* Ada.Exceptions.Traceback (a-exctra.ads)::
* Ada.Sequential_IO.C_Streams (a-siocst.ads)::
* Ada.Streams.Stream_IO.C_Streams (a-ssicst.ads)::
* Ada.Strings.Unbounded.Text_IO (a-suteio.ads)::
* Ada.Strings.Wide_Unbounded.Wide_Text_IO (a-swuwti.ads)::
+* Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO (a-szuzti.ads)::
* Ada.Text_IO.C_Streams (a-tiocst.ads)::
* Ada.Wide_Text_IO.C_Streams (a-wtcstr.ads)::
+* Ada.Wide_Wide_Text_IO.C_Streams (a-ztcstr.ads)::
+* GNAT.Altivec (g-altive.ads)::
+* GNAT.Altivec.Conversions (g-altcon.ads)::
+* GNAT.Altivec.Vector_Operations (g-alveop.ads)::
+* GNAT.Altivec.Vector_Types (g-alvety.ads)::
+* GNAT.Altivec.Vector_Views (g-alvevi.ads)::
+* GNAT.Array_Split (g-arrspl.ads)::
* GNAT.AWK (g-awk.ads)::
+* GNAT.Bounded_Buffers (g-boubuf.ads)::
+* GNAT.Bounded_Mailboxes (g-boumai.ads)::
+* GNAT.Bubble_Sort (g-bubsor.ads)::
* GNAT.Bubble_Sort_A (g-busora.ads)::
* GNAT.Bubble_Sort_G (g-busorg.ads)::
+* GNAT.Byte_Swapping (g-bytswa.ads)::
* GNAT.Calendar (g-calend.ads)::
* GNAT.Calendar.Time_IO (g-catiio.ads)::
* GNAT.Case_Util (g-casuti.ads)::
* GNAT.CGI.Cookie (g-cgicoo.ads)::
* GNAT.CGI.Debug (g-cgideb.ads)::
* GNAT.Command_Line (g-comlin.ads)::
+* GNAT.Compiler_Version (g-comver.ads)::
+* GNAT.Ctrl_C (g-ctrl_c.ads)::
* GNAT.CRC32 (g-crc32.ads)::
* GNAT.Current_Exception (g-curexc.ads)::
* GNAT.Debug_Pools (g-debpoo.ads)::
* GNAT.Debug_Utilities (g-debuti.ads)::
* GNAT.Directory_Operations (g-dirope.ads)::
+* GNAT.Dynamic_HTables (g-dynhta.ads)::
* GNAT.Dynamic_Tables (g-dyntab.ads)::
+* GNAT.Exception_Actions (g-excact.ads)::
* GNAT.Exception_Traces (g-exctra.ads)::
+* GNAT.Exceptions (g-except.ads)::
* GNAT.Expect (g-expect.ads)::
* GNAT.Float_Control (g-flocon.ads)::
+* GNAT.Heap_Sort (g-heasor.ads)::
* GNAT.Heap_Sort_A (g-hesora.ads)::
* GNAT.Heap_Sort_G (g-hesorg.ads)::
* GNAT.HTable (g-htable.ads)::
* GNAT.IO_Aux (g-io_aux.ads)::
* GNAT.Lock_Files (g-locfil.ads)::
* GNAT.MD5 (g-md5.ads)::
+* GNAT.Memory_Dump (g-memdum.ads)::
* GNAT.Most_Recent_Exception (g-moreex.ads)::
* GNAT.OS_Lib (g-os_lib.ads)::
+* GNAT.Perfect_Hash_Generators (g-pehage.ads)::
* GNAT.Regexp (g-regexp.ads)::
* GNAT.Registry (g-regist.ads)::
* GNAT.Regpat (g-regpat.ads)::
+* GNAT.Secondary_Stack_Info (g-sestin.ads)::
+* GNAT.Semaphores (g-semaph.ads)::
+* GNAT.SHA1 (g-sha1.ads)::
+* GNAT.Signals (g-signal.ads)::
* GNAT.Sockets (g-socket.ads)::
* GNAT.Source_Info (g-souinf.ads)::
* GNAT.Spell_Checker (g-speche.ads)::
* GNAT.Spitbol.Table_Boolean (g-sptabo.ads)::
* GNAT.Spitbol.Table_Integer (g-sptain.ads)::
* GNAT.Spitbol.Table_VString (g-sptavs.ads)::
+* GNAT.Strings (g-string.ads)::
+* GNAT.String_Split (g-strspl.ads)::
* GNAT.Table (g-table.ads)::
* GNAT.Task_Lock (g-tasloc.ads)::
* GNAT.Threads (g-thread.ads)::
* GNAT.Traceback (g-traceb.ads)::
* GNAT.Traceback.Symbolic (g-trasym.ads)::
+* GNAT.Wide_String_Split (g-wistsp.ads)::
+* GNAT.Wide_Wide_String_Split (g-zistsp.ads)::
* Interfaces.C.Extensions (i-cexten.ads)::
* Interfaces.C.Streams (i-cstrea.ads)::
* Interfaces.CPP (i-cpp.ads)::
* Interfaces.VxWorks.IO (i-vxwoio.ads)::
* System.Address_Image (s-addima.ads)::
* System.Assertions (s-assert.ads)::
+* System.Memory (s-memory.ads)::
* System.Partition_Interface (s-parint.ads)::
+* System.Restrictions (s-restri.ads)::
+* System.Rident (s-rident.ads)::
* System.Task_Info (s-tasinf.ads)::
* System.Wch_Cnv (s-wchcnv.ads)::
* System.Wch_Con (s-wchcon.ads)::
Text_IO
-* Text_IO Stream Pointer Positioning::
-* Text_IO Reading and Writing Non-Regular Files::
-* Get_Immediate::
+* Text_IO Stream Pointer Positioning::
+* Text_IO Reading and Writing Non-Regular Files::
+* Get_Immediate::
* Treating Text_IO Files as Streams::
* Text_IO Extensions::
* Text_IO Facilities for Unbounded Strings::
Wide_Text_IO
-* Wide_Text_IO Stream Pointer Positioning::
-* Wide_Text_IO Reading and Writing Non-Regular Files::
+* Wide_Text_IO Stream Pointer Positioning::
+* Wide_Text_IO Reading and Writing Non-Regular Files::
+
+Wide_Wide_Text_IO
+
+* Wide_Wide_Text_IO Stream Pointer Positioning::
+* Wide_Wide_Text_IO Reading and Writing Non-Regular Files::
Interfacing to Other Languages
* Interfacing to C::
-* Interfacing to C++::
-* Interfacing to COBOL::
-* Interfacing to Fortran::
+* Interfacing to C++::
+* Interfacing to COBOL::
+* Interfacing to Fortran::
* Interfacing to non-GNAT Ada code::
-GNAT Implementation of Tasking
+Specialized Needs Annexes
-* Mapping Ada Tasks onto the Underlying Kernel Threads::
-* Ensuring Compliance with the Real-Time Annex::
+Implementation of Specific Ada Features
+* Machine Code Insertions::
+* GNAT Implementation of Tasking::
+* GNAT Implementation of Shared Passive Packages::
+* Code Generation for Array Aggregates::
+* The Size of Discriminated Records with Default Discriminants::
+* Strict Conformance to the Ada Reference Manual::
+
+Project File Reference
+
+Obsolescent Features
+
+GNU Free Documentation License
+
+Index
@end menu
-@end ifinfo
+@end ifnottex
@node About This Guide
@unnumbered About This Guide
@noindent
This manual contains useful information in writing programs using the
-GNAT compiler. It includes information on implementation dependent
-characteristics of GNAT, including all the information required by Annex
-M of the standard.
-
-Ada 95 is designed to be highly portable,and guarantees that, for most
-programs, Ada 95 compilers behave in exactly the same manner on
-different machines. However, since Ada 95 is designed to be used in a
+@value{EDITION} compiler. It includes information on implementation dependent
+characteristics of @value{EDITION}, including all the information required by
+Annex M of the Ada language standard.
+
+@value{EDITION} implements Ada 95 and Ada 2005, and it may also be invoked in
+Ada 83 compatibility mode.
+By default, @value{EDITION} assumes @value{DEFAULTLANGUAGEVERSION},
+but you can override with a compiler switch
+to explicitly specify the language version.
+(Please refer to the section ``Compiling Different Versions of Ada'', in
+@cite{@value{EDITION} User's Guide}, for details on these switches.)
+Throughout this manual, references to ``Ada'' without a year suffix
+apply to both the Ada 95 and Ada 2005 versions of the language.
+
+Ada is designed to be highly portable.
+In general, a program will have the same effect even when compiled by
+different compilers on different platforms.
+However, since Ada is designed to be used in a
wide variety of applications, it also contains a number of system
-dependent features to Functbe used in interfacing to the external world.
-
-@c Maybe put the following in platform-specific section
-@ignore
-@cindex ProDev Ada
-This reference manual discusses how these features are implemented for
-use in ProDev Ada running on the IRIX 5.3 or greater operating systems.
-@end ignore
-
+dependent features to be used in interfacing to the external world.
@cindex Implementation-dependent features
@cindex Portability
+
Note: Any program that makes use of implementation-dependent features
may be non-portable. You should follow good programming practice and
isolate and clearly document any sections of your program that make use
of these features in a non-portable manner.
+@ifset PROEDITION
+For ease of exposition, ``GNAT Pro'' will be referred to simply as
+``GNAT'' in the remainder of this document.
+@end ifset
+
@menu
-* What This Reference Manual Contains::
+* What This Reference Manual Contains::
* Conventions::
-* Related Information::
+* Related Information::
@end menu
@node What This Reference Manual Contains
@unnumberedsec What This Reference Manual Contains
+@noindent
This reference manual contains the following chapters:
@itemize @bullet
@item
-@ref{Implementation Defined Pragmas} lists GNAT implementation-dependent
+@ref{Implementation Defined Pragmas}, lists GNAT implementation-dependent
pragmas, which can be used to extend and enhance the functionality of the
compiler.
@item
-@ref{Implementation Defined Attributes} lists GNAT
+@ref{Implementation Defined Attributes}, lists GNAT
implementation-dependent attributes which can be used to extend and
enhance the functionality of the compiler.
@item
-@ref{Implementation Advice} provides information on generally
+@ref{Implementation Advice}, provides information on generally
desirable behavior which are not requirements that all compilers must
follow since it cannot be provided on all systems, or which may be
undesirable on some systems.
@item
-@ref{Implementation Defined Characteristics} provides a guide to
+@ref{Implementation Defined Characteristics}, provides a guide to
minimizing implementation dependent features.
@item
-@ref{Intrinsic Subprograms} describes the intrinsic subprograms
+@ref{Intrinsic Subprograms}, describes the intrinsic subprograms
implemented by GNAT, and how they can be imported into user
application programs.
@item
-@ref{Representation Clauses and Pragmas} describes in detail the
+@ref{Representation Clauses and Pragmas}, describes in detail the
way that GNAT represents data, and in particular the exact set
of representation clauses and pragmas that is accepted.
@item
-@ref{Standard Library Routines} provides a listing of packages and a
+@ref{Standard Library Routines}, provides a listing of packages and a
brief description of the functionality that is provided by Ada's
extensive set of standard library routines as implemented by GNAT@.
@item
-@ref{The Implementation of Standard I/O} details how the GNAT
+@ref{The Implementation of Standard I/O}, details how the GNAT
implementation of the input-output facilities.
@item
-@ref{Interfacing to Other Languages} describes how programs
+@ref{The GNAT Library}, is a catalog of packages that complement
+the Ada predefined library.
+
+@item
+@ref{Interfacing to Other Languages}, describes how programs
written in Ada using GNAT can be interfaced to other programming
languages.
+@ref{Specialized Needs Annexes}, describes the GNAT implementation of all
+of the specialized needs annexes.
+
+@item
+@ref{Implementation of Specific Ada Features}, discusses issues related
+to GNAT's implementation of machine code insertions, tasking, and several
+other features.
+
@item
-@ref{Specialized Needs Annexes} describes the GNAT implementation of all
-of the special needs annexes.
+@ref{Project File Reference}, presents the syntax and semantics
+of project files.
@item
-@ref{Compatibility Guide} includes sections on compatibility of GNAT with
-other Ada 83 and Ada 95 compilation systems, to assist in porting code
-from other environments.
+@ref{Obsolescent Features} documents implementation dependent features,
+including pragmas and attributes, which are considered obsolescent, since
+there are other preferred ways of achieving the same results. These
+obsolescent forms are retained for backwards compatibility.
+
@end itemize
-@cindex Ada 95 ISO/ANSI Standard
-This reference manual assumes that you are familiar with Ada 95
-language, as described in the International Standard
-ANSI/ISO/IEC-8652:1995, Jan 1995.
+@cindex Ada 95 Language Reference Manual
+@cindex Ada 2005 Language Reference Manual
+@noindent
+This reference manual assumes a basic familiarity with the Ada 95 language, as
+described in the International Standard ANSI/ISO/IEC-8652:1995,
+January 1995.
+It does not require knowledge of the new features introduced by Ada 2005,
+(officially known as ISO/IEC 8652:1995 with Technical Corrigendum 1
+and Amendment 1).
+Both reference manuals are included in the GNAT documentation
+package.
@node Conventions
@unnumberedsec Conventions
@node Related Information
@unnumberedsec Related Information
+@noindent
See the following documents for further information on GNAT:
@itemize @bullet
@item
@cite{Ada 95 Annotated Reference Manual}, which is an annotated version
-of the standard reference manual cited above. The annotations describe
+of the Ada 95 standard. The annotations describe
detailed aspects of the design decision, and in particular contain useful
sections on Ada 83 compatibility.
@item
+@cite{Ada 2005 Reference Manual}, which contains all reference
+material for the Ada 2005 programming language.
+
+@item
+@cite{Ada 2005 Annotated Reference Manual}, which is an annotated version
+of the Ada 2005 standard. The annotations describe
+detailed aspects of the design decision, and in particular contain useful
+sections on Ada 83 and Ada 95 compatibility.
+
+@item
@cite{DEC Ada, Technical Overview and Comparison on DIGITAL Platforms},
which contains specific information on compatibility between GNAT and
DEC Ada 83 systems.
@chapter Implementation Defined Pragmas
@noindent
-Ada 95 defines a set of pragmas that can be used to supply additional
+Ada defines a set of pragmas that can be used to supply additional
information to the compiler. These language defined pragmas are
-implemented in GNAT and work as described in the Ada 95 Reference
+implemented in GNAT and work as described in the Ada Reference
Manual.
-In addition, Ada 95 allows implementations to define additional pragmas
+In addition, Ada allows implementations to define additional pragmas
whose meaning is defined by the implementation. GNAT provides a number
of these implementation-dependent pragmas which can be used to extend
and enhance the functionality of the compiler. This section of the GNAT
platforms). Therefore if portability to other compilers is an important
consideration, the use of these pragmas should be minimized.
-@table @code
+@menu
+* Pragma Abort_Defer::
+* Pragma Ada_83::
+* Pragma Ada_95::
+* Pragma Ada_05::
+* Pragma Ada_2005::
+* Pragma Annotate::
+* Pragma Assert::
+* Pragma Ast_Entry::
+* Pragma C_Pass_By_Copy::
+* Pragma Check_Name::
+* Pragma Comment::
+* Pragma Common_Object::
+* Pragma Compile_Time_Error::
+* Pragma Compile_Time_Warning::
+* Pragma Complete_Representation::
+* Pragma Complex_Representation::
+* Pragma Component_Alignment::
+* Pragma Convention_Identifier::
+* Pragma CPP_Class::
+* Pragma CPP_Constructor::
+* Pragma CPP_Virtual::
+* Pragma CPP_Vtable::
+* Pragma Debug::
+* Pragma Debug_Policy::
+* Pragma Detect_Blocking::
+* Pragma Elaboration_Checks::
+* Pragma Eliminate::
+* Pragma Export_Exception::
+* Pragma Export_Function::
+* Pragma Export_Object::
+* Pragma Export_Procedure::
+* Pragma Export_Value::
+* Pragma Export_Valued_Procedure::
+* Pragma Extend_System::
+* Pragma External::
+* Pragma External_Name_Casing::
+* Pragma Finalize_Storage_Only::
+* Pragma Float_Representation::
+* Pragma Ident::
+* Pragma Implicit_Packing::
+* Pragma Import_Exception::
+* Pragma Import_Function::
+* Pragma Import_Object::
+* Pragma Import_Procedure::
+* Pragma Import_Valued_Procedure::
+* Pragma Initialize_Scalars::
+* Pragma Inline_Always::
+* Pragma Inline_Generic::
+* Pragma Interface::
+* Pragma Interface_Name::
+* Pragma Interrupt_Handler::
+* Pragma Interrupt_State::
+* Pragma Keep_Names::
+* Pragma License::
+* Pragma Link_With::
+* Pragma Linker_Alias::
+* Pragma Linker_Constructor::
+* Pragma Linker_Destructor::
+* Pragma Linker_Section::
+* Pragma Long_Float::
+* Pragma Machine_Attribute::
+* Pragma Main::
+* Pragma Main_Storage::
+* Pragma No_Body::
+* Pragma No_Return::
+* Pragma No_Strict_Aliasing::
+* Pragma Normalize_Scalars::
+* Pragma Obsolescent::
+* Pragma Passive::
+* Pragma Persistent_BSS::
+* Pragma Polling::
+* Pragma Profile (Ravenscar)::
+* Pragma Profile (Restricted)::
+* Pragma Psect_Object::
+* Pragma Pure_Function::
+* Pragma Restriction_Warnings::
+* Pragma Source_File_Name::
+* Pragma Source_File_Name_Project::
+* Pragma Source_Reference::
+* Pragma Stream_Convert::
+* Pragma Style_Checks::
+* Pragma Subtitle::
+* Pragma Suppress::
+* Pragma Suppress_All::
+* Pragma Suppress_Exception_Locations::
+* Pragma Suppress_Initialization::
+* Pragma Task_Info::
+* Pragma Task_Name::
+* Pragma Task_Storage::
+* Pragma Time_Slice::
+* Pragma Title::
+* Pragma Unchecked_Union::
+* Pragma Unimplemented_Unit::
+* Pragma Universal_Aliasing ::
+* Pragma Universal_Data::
+* Pragma Unreferenced::
+* Pragma Unreferenced_Objects::
+* Pragma Unreserve_All_Interrupts::
+* Pragma Unsuppress::
+* Pragma Use_VADS_Size::
+* Pragma Validity_Checks::
+* Pragma Volatile::
+* Pragma Warnings::
+* Pragma Weak_External::
+* Pragma Wide_Character_Encoding::
+@end menu
+@node Pragma Abort_Defer
+@unnumberedsec Pragma Abort_Defer
@findex Abort_Defer
@cindex Deferring aborts
-@item pragma Abort_Defer
@noindent
Syntax:
-
@smallexample
pragma Abort_Defer;
@end smallexample
for the declarations or handlers, if any, associated with this statement
sequence).
-@item pragma Ada_83
+@node Pragma Ada_83
+@unnumberedsec Pragma Ada_83
@findex Ada_83
@noindent
Syntax:
-
-@smallexample
+@smallexample @c ada
pragma Ada_83;
@end smallexample
which it applies, regardless of the mode set by the command line
switches. In Ada 83 mode, GNAT attempts to be as compatible with
the syntax and semantics of Ada 83, as defined in the original Ada
-83 Reference Manual as possible. In particular, the new Ada 95
-keywords are not recognized, optional package bodies are allowed,
+83 Reference Manual as possible. In particular, the keywords added by Ada 95
+(and Ada 2005) are not recognized, optional package bodies are allowed,
and generics may name types with unknown discriminants without using
the @code{(<>)} notation. In addition, some but not all of the additional
restrictions of Ada 83 are enforced.
Ada 83 mode is intended for two purposes. Firstly, it allows existing
-legacy Ada 83 code to be compiled and adapted to GNAT with less effort.
-Secondly, it aids in keeping code backwards compatible with Ada 83.
+Ada 83 code to be compiled and adapted to GNAT with less effort.
+Secondly, it aids in keeping code backwards compatible with Ada 83.
However, there is no guarantee that code that is processed correctly
by GNAT in Ada 83 mode will in fact compile and execute with an Ada
83 compiler, since GNAT does not enforce all the additional checks
required by Ada 83.
+@node Pragma Ada_95
+@unnumberedsec Pragma Ada_95
@findex Ada_95
-@item pragma Ada_95
@noindent
Syntax:
-
-@smallexample
+@smallexample @c ada
pragma Ada_95;
@end smallexample
itself uses Ada 95 features, but which is intended to be usable from
either Ada 83 or Ada 95 programs.
-@findex Annotate
-@item pragma Annotate
+@node Pragma Ada_05
+@unnumberedsec Pragma Ada_05
+@findex Ada_05
@noindent
Syntax:
+@smallexample @c ada
+pragma Ada_05;
+@end smallexample
-@smallexample
+@noindent
+A configuration pragma that establishes Ada 2005 mode for the unit to which
+it applies, regardless of the mode set by the command line switches.
+This mode is set automatically for the @code{Ada} and @code{System}
+packages and their children, so you need not specify it in these
+contexts. This pragma is useful when writing a reusable component that
+itself uses Ada 2005 features, but which is intended to be usable from
+either Ada 83 or Ada 95 programs.
+
+@node Pragma Ada_2005
+@unnumberedsec Pragma Ada_2005
+@findex Ada_2005
+@noindent
+Syntax:
+@smallexample @c ada
+pragma Ada_2005;
+@end smallexample
+
+@noindent
+This configuration pragma is a synonym for pragma Ada_05 and has the
+same syntax and effect.
+
+@node Pragma Annotate
+@unnumberedsec Pragma Annotate
+@findex Annotate
+@noindent
+Syntax:
+@smallexample @c ada
pragma Annotate (IDENTIFIER @{, ARG@});
ARG ::= NAME | EXPRESSION
by any part of the GNAT compiler. This pragma is intended for use by
external tools, including ASIS@.
+@node Pragma Assert
+@unnumberedsec Pragma Assert
@findex Assert
-@item pragma Assert
@noindent
Syntax:
-
-@smallexample
+@smallexample @c ada
pragma Assert (
boolean_EXPRESSION
- [, static_string_EXPRESSION])
+ [, static_string_EXPRESSION]);
@end smallexample
@noindent
line switch is set to activate assertions. The pragma expands into code
equivalent to the following:
-@smallexample
+@smallexample @c ada
if assertions-enabled then
if not boolean_EXPRESSION then
System.Assertions.Raise_Assert_Failure
- (string_EXPRESSION);
+ (string_EXPRESSION);
end if;
end if;
@end smallexample
statement, so if a statement sequence contains nothing but a pragma
assert, then a null statement is required in addition, as in:
-@smallexample
+@smallexample @c ada
@dots{}
if J > 3 then
pragma Assert (K > 3, "Bad value for K");
If the boolean expression has side effects, these side effects will turn
on and off with the setting of the assertions mode, resulting in
-assertions that have an effect on the program. You should generally
+assertions that have an effect on the program. You should generally
avoid side effects in the expression arguments of this pragma. However,
the expressions are analyzed for semantic correctness whether or not
assertions are enabled, so turning assertions on and off cannot affect
the legality of a program.
+@node Pragma Ast_Entry
+@unnumberedsec Pragma Ast_Entry
@cindex OpenVMS
@findex Ast_Entry
-@item pragma Ast_Entry
@noindent
Syntax:
-
-@smallexample
+@smallexample @c ada
pragma AST_Entry (entry_IDENTIFIER);
@end smallexample
@noindent
This pragma is implemented only in the OpenVMS implementation of GNAT@. The
argument is the simple name of a single entry; at most one @code{AST_Entry}
-pragma is allowed for any given entry. This pragma must be used in
+pragma is allowed for any given entry. This pragma must be used in
conjunction with the @code{AST_Entry} attribute, and is only allowed after
the entry declaration and in the same task type specification or single task
as the entry to which it applies. This pragma specifies that the given entry
may be used to handle an OpenVMS asynchronous system trap (@code{AST})
resulting from an OpenVMS system service call. The pragma does not affect
-normal use of the entry. For further details on this pragma, see the
+normal use of the entry. For further details on this pragma, see the
DEC Ada Language Reference Manual, section 9.12a.
+@node Pragma C_Pass_By_Copy
+@unnumberedsec Pragma C_Pass_By_Copy
@cindex Passing by copy
@findex C_Pass_By_Copy
-@item pragma C_Pass_By_Copy
@noindent
Syntax:
-
-@smallexample
+@smallexample @c ada
pragma C_Pass_By_Copy
([Max_Size =>] static_integer_EXPRESSION);
@end smallexample
@code{Import} and @code{Export} pragmas, which allow specification of
passing mechanisms on a parameter by parameter basis.
+@node Pragma Check_Name
+@unnumberedsec Pragma Check_Name
+@cindex Defining check names
+@cindex Check names, defining
+@findex Check_Name
+@noindent
+Syntax:
+@smallexample @c ada
+pragma Check_Name (check_name_IDENTIFIER);
+@end smallexample
+
+@noindent
+This is a configuration pragma which defines a new implementation
+defined check name (unless IDENTIFIER matches one of the predefined
+check names, in which case the pragma has no effect). Check names
+are global to a partition, so if two more more configuration pragmas
+are present in a partition mentioning the same name, only one new
+check name is introduced.
+
+An implementation defined check name introduced with this pragma may
+be used in only three contexts: @code{pragma Suppress},
+@code{pragma Unsuppress},
+and as the prefix of a @code{Check_Name'Enabled} attribute reference. For
+any of these three cases, the check name must be visible. A check
+name is visible if it is in the configuration pragmas applying to
+the current unit, or if it appears at the start of any unit that
+is part of the dependency set of the current unit (e.g. units that
+are mentioned in @code{with} clauses.
+
+Normally the default mechanism for passing C convention records to C
+@node Pragma Comment
+@unnumberedsec Pragma Comment
@findex Comment
-@item pragma Comment
@noindent
Syntax:
-@smallexample
+@smallexample @c ada
pragma Comment (static_string_EXPRESSION);
@end smallexample
This is almost identical in effect to pragma @code{Ident}. It allows the
placement of a comment into the object file and hence into the
executable file if the operating system permits such usage. The
-difference is that @code{Comment}, unlike @code{Ident}, has no limit on the
-length of the string argument, and no limitations on placement
-of the pragma (it can be placed anywhere in the main source unit).
+difference is that @code{Comment}, unlike @code{Ident}, has
+no limitations on placement of the pragma (it can be placed
+anywhere in the main source unit), and if more than one pragma
+is used, all comments are retained.
+@node Pragma Common_Object
+@unnumberedsec Pragma Common_Object
@findex Common_Object
-@item pragma Common_Object
@noindent
Syntax:
-@smallexample
+@smallexample @c ada
pragma Common_Object (
- [Internal =>] LOCAL_NAME,
+ [Internal =>] local_NAME,
[, [External =>] EXTERNAL_SYMBOL]
- [, [Size =>] EXTERNAL_SYMBOL] )
+ [, [Size =>] EXTERNAL_SYMBOL] );
EXTERNAL_SYMBOL ::=
IDENTIFIER
This pragma enables the shared use of variables stored in overlaid
linker areas corresponding to the use of @code{COMMON}
in Fortran. The single
-object @var{local_name} is assigned to the area designated by
+object @var{local_NAME} is assigned to the area designated by
the @var{External} argument.
You may define a record to correspond to a series
of fields. The @var{size} argument
indicating that the necessary attribute for implementation of this
pragma is not available.
+@node Pragma Compile_Time_Error
+@unnumberedsec Pragma Compile_Time_Error
+@findex Compile_Time_Error
+@noindent
+Syntax:
+
+@smallexample @c ada
+pragma Compile_Time_Error
+ (boolean_EXPRESSION, static_string_EXPRESSION);
+@end smallexample
+
+@noindent
+This pragma can be used to generate additional compile time
+error messages. It
+is particularly useful in generics, where errors can be issued for
+specific problematic instantiations. The first parameter is a boolean
+expression. The pragma is effective only if the value of this expression
+is known at compile time, and has the value True. The set of expressions
+whose values are known at compile time includes all static boolean
+expressions, and also other values which the compiler can determine
+at compile time (e.g. the size of a record type set by an explicit
+size representation clause, or the value of a variable which was
+initialized to a constant and is known not to have been modified).
+If these conditions are met, an error message is generated using
+the value given as the second argument. This string value may contain
+embedded ASCII.LF characters to break the message into multiple lines.
+
+@node Pragma Compile_Time_Warning
+@unnumberedsec Pragma Compile_Time_Warning
+@findex Compile_Time_Warning
+@noindent
+Syntax:
+
+@smallexample @c ada
+pragma Compile_Time_Warning
+ (boolean_EXPRESSION, static_string_EXPRESSION);
+@end smallexample
+
+@noindent
+This pragma can be used to generate additional compile time warnings. It
+is particularly useful in generics, where warnings can be issued for
+specific problematic instantiations. The first parameter is a boolean
+expression. The pragma is effective only if the value of this expression
+is known at compile time, and has the value True. The set of expressions
+whose values are known at compile time includes all static boolean
+expressions, and also other values which the compiler can determine
+at compile time (e.g. the size of a record type set by an explicit
+size representation clause, or the value of a variable which was
+initialized to a constant and is known not to have been modified).
+If these conditions are met, a warning message is generated using
+the value given as the second argument. This string value may contain
+embedded ASCII.LF characters to break the message into multiple lines.
+
+@node Pragma Complete_Representation
+@unnumberedsec Pragma Complete_Representation
+@findex Complete_Representation
+@noindent
+Syntax:
+
+@smallexample @c ada
+pragma Complete_Representation;
+@end smallexample
+
+@noindent
+This pragma must appear immediately within a record representation
+clause. Typical placements are before the first component clause
+or after the last component clause. The effect is to give an error
+message if any component is missing a component clause. This pragma
+may be used to ensure that a record representation clause is
+complete, and that this invariant is maintained if fields are
+added to the record in the future.
+
+@node Pragma Complex_Representation
+@unnumberedsec Pragma Complex_Representation
@findex Complex_Representation
-@item pragma Complex_Representation
@noindent
Syntax:
-@smallexample
+@smallexample @c ada
pragma Complex_Representation
- ([Entity =>] LOCAL_NAME);
+ ([Entity =>] local_NAME);
@end smallexample
@noindent
records by pointer, and the use of this pragma may result in passing
this type in floating-point registers.
+@node Pragma Component_Alignment
+@unnumberedsec Pragma Component_Alignment
@cindex Alignments of components
@findex Component_Alignment
-@item pragma Component_Alignment
@noindent
Syntax:
-@smallexample
+@smallexample @c ada
pragma Component_Alignment (
[Form =>] ALIGNMENT_CHOICE
- [, [Name =>] type_LOCAL_NAME]);
+ [, [Name =>] type_local_NAME]);
ALIGNMENT_CHOICE ::=
Component_Size
alignment).
@end table
-If the @code{Name} parameter is present, @var{type_local_name} must
+@noindent
+If the @code{Name} parameter is present, @var{type_local_NAME} must
refer to a local record or array type, and the specified alignment
choice applies to the specified type. The use of
@code{Component_Alignment} together with a pragma @code{Pack} causes the
pragma @code{Pack}, pragma @code{Component_Alignment}, or a record rep
clause), the GNAT uses the default alignment as described previously.
+@node Pragma Convention_Identifier
+@unnumberedsec Pragma Convention_Identifier
@findex Convention_Identifier
@cindex Conventions, synonyms
-@item pragma Convention_Identifier
@noindent
Syntax:
-@smallexample
+@smallexample @c ada
pragma Convention_Identifier (
[Name =>] IDENTIFIER,
[Convention =>] convention_IDENTIFIER);
pragma). As an example of the use of this, suppose you had legacy code
which used Fortran77 as the identifier for Fortran. Then the pragma:
-@smallexample
-pragma Convention_Indentifier (Fortran77, Fortran);
+@smallexample @c ada
+pragma Convention_Identifier (Fortran77, Fortran);
@end smallexample
@noindent
define a convention identifier @code{Library} and use a single
@code{Convention_Identifier} pragma to specify which convention
would be used system-wide.
-
+
+@node Pragma CPP_Class
+@unnumberedsec Pragma CPP_Class
@findex CPP_Class
@cindex Interfacing with C++
-@item pragma CPP_Class
@noindent
Syntax:
-@smallexample
-pragma CPP_Class ([Entity =>] LOCAL_NAME);
+@smallexample @c ada
+pragma CPP_Class ([Entity =>] local_NAME);
@end smallexample
@noindent
-The argument denotes an entity in the current declarative region
-that is declared as a tagged or untagged record type. It indicates that
-the type corresponds to an externally declared C++ class type, and is to
-be laid out the same way that C++ would lay out the type.
-
-If (and only if) the type is tagged, at least one component in the
-record must be of type @code{Interfaces.CPP.Vtable_Ptr}, corresponding
-to the C++ Vtable (or Vtables in the case of multiple inheritance) used
-for dispatching.
+The argument denotes an entity in the current declarative region that is
+declared as a tagged record type. It indicates that the type corresponds
+to an externally declared C++ class type, and is to be laid out the same
+way that C++ would lay out the type.
Types for which @code{CPP_Class} is specified do not have assignment or
equality operators defined (such operations can be imported or declared
-as subprograms as required). Initialization is allowed only by
-constructor functions (see pragma @code{CPP_Constructor}).
+as subprograms as required). Initialization is allowed only by constructor
+functions (see pragma @code{CPP_Constructor}). Such types are implicitly
+limited if not explicitly declared as limited or derived from a limited
+type, and a warning is issued in that case.
Pragma @code{CPP_Class} is intended primarily for automatic generation
-using an automatic binding generator tool.
+using an automatic binding generator tool.
See @ref{Interfacing to C++} for related information.
+Note: Pragma @code{CPP_Class} is currently obsolete. It is supported
+for backward compatibility but its functionality is available
+using pragma @code{Import} with @code{Convention} = @code{CPP}.
+
+@node Pragma CPP_Constructor
+@unnumberedsec Pragma CPP_Constructor
@cindex Interfacing with C++
@findex CPP_Constructor
-@item pragma CPP_Constructor
@noindent
Syntax:
-@smallexample
-pragma CPP_Constructor ([Entity =>] LOCAL_NAME);
+@smallexample @c ada
+pragma CPP_Constructor ([Entity =>] local_NAME
+ [, [External_Name =>] static_string_EXPRESSION ]
+ [, [Link_Name =>] static_string_EXPRESSION ]);
@end smallexample
@noindent
This pragma identifies an imported function (imported in the usual way
-with pragma @code{Import}) as corresponding to a C++
-constructor. The argument is a name that must have been
-previously mentioned in a pragma @code{Import}
-with @code{Convention} = @code{CPP}, and must be of one of the following
-forms:
+with pragma @code{Import}) as corresponding to a C++ constructor. If
+@code{External_Name} and @code{Link_Name} are not specified then the
+@code{Entity} argument is a name that must have been previously mentioned
+in a pragma @code{Import} with @code{Convention} = @code{CPP}. Such name
+must be of one of the following forms:
@itemize @bullet
@item
In an extension aggregate for an object of a type derived from @var{T}.
@end itemize
+@noindent
Although the constructor is described as a function that returns a value
on the Ada side, it is typically a procedure with an extra implicit
argument (the object being initialized) at the implementation
@itemize @bullet
@item @code{New_Object : Derived_T}
-@item @code{New_Object : Derived_T := (@var{constructor-function-call with} @dots{})}
+@item @code{New_Object : Derived_T := (@var{constructor-call with} @dots{})}
@end itemize
+@noindent
In the first case the default constructor is called and extension fields
if any are initialized according to the default initialization
expressions in the Ada declaration. In the second case, the given
permitted.
Pragma @code{CPP_Constructor} is intended primarily for automatic generation
-using an automatic binding generator tool.
+using an automatic binding generator tool.
See @ref{Interfacing to C++} for more related information.
+@node Pragma CPP_Virtual
+@unnumberedsec Pragma CPP_Virtual
@cindex Interfacing to C++
@findex CPP_Virtual
-@item pragma CPP_Virtual
@noindent
-Syntax:
+This pragma is now obsolete has has no effect because GNAT generates
+the same object layout than the G++ compiler.
-@smallexample
-pragma CPP_Virtual
- [Entity =>] ENTITY,
- [, [Vtable_Ptr =>] vtable_ENTITY,]
- [, [Position =>] static_integer_EXPRESSION])
-@end smallexample
-
-This pragma serves the same function as pragma @code{Import} in that
-case of a virtual function imported from C++. The @var{Entity} argument
-must be a
-primitive subprogram of a tagged type to which pragma @code{CPP_Class}
-applies. The @var{Vtable_Ptr} argument specifies
-the Vtable_Ptr component which contains the
-entry for this virtual function. The @var{Position} argument
-is the sequential number
-counting virtual functions for this Vtable starting at 1.
-
-The @code{Vtable_Ptr} and @code{Position} arguments may be omitted if
-there is one Vtable_Ptr present (single inheritance case) and all
-virtual functions are imported. In that case the compiler can deduce both
-these values.
-
-No @code{External_Name} or @code{Link_Name} arguments are required for a
-virtual function, since it is always accessed indirectly via the
-appropriate Vtable entry.
-
-Pragma @code{CPP_Virtual} is intended primarily for automatic generation
-using an automatic binding generator tool.
See @ref{Interfacing to C++} for related information.
+@node Pragma CPP_Vtable
+@unnumberedsec Pragma CPP_Vtable
@cindex Interfacing with C++
@findex CPP_Vtable
-@item pragma CPP_Vtable
-@noindent
-Syntax:
-
-@smallexample
-pragma CPP_Vtable (
- [Entity =>] ENTITY,
- [Vtable_Ptr =>] vtable_ENTITY,
- [Entry_Count =>] static_integer_EXPRESSION);
-@end smallexample
-
@noindent
-Given a record to which the pragma @code{CPP_Class} applies,
-this pragma can be specified for each component of type
-@code{CPP.Interfaces.Vtable_Ptr}.
-@var{Entity} is the tagged type, @var{Vtable_Ptr}
-is the record field of type @code{Vtable_Ptr}, and @var{Entry_Count} is
-the number of virtual functions on the C++ side. Not all of these
-functions need to be imported on the Ada side.
-
-You may omit the @code{CPP_Vtable} pragma if there is only one
-@code{Vtable_Ptr} component in the record and all virtual functions are
-imported on the Ada side (the default value for the entry count in this
-case is simply the total number of virtual functions).
+This pragma is now obsolete has has no effect because GNAT generates
+the same object layout than the G++ compiler.
-Pragma @code{CPP_Vtable} is intended primarily for automatic generation
-using an automatic binding generator tool.
See @ref{Interfacing to C++} for related information.
+@node Pragma Debug
+@unnumberedsec Pragma Debug
@findex Debug
-@item pragma Debug
@noindent
Syntax:
-@smallexample
-pragma Debug (PROCEDURE_CALL_WITHOUT_SEMICOLON);
+@smallexample @c ada
+pragma Debug ([CONDITION, ]PROCEDURE_CALL_WITHOUT_SEMICOLON);
PROCEDURE_CALL_WITHOUT_SEMICOLON ::=
PROCEDURE_NAME
@end smallexample
@noindent
-The argument has the syntactic form of an expression, meeting the
-syntactic requirements for pragmas.
+The procedure call argument has the syntactic form of an expression, meeting
+the syntactic requirements for pragmas.
+
+If debug pragmas are not enabled or if the condition is present and evaluates
+to False, this pragma has no effect. If debug pragmas are enabled, the
+semantics of the pragma is exactly equivalent to the procedure call statement
+corresponding to the argument with a terminating semicolon. Pragmas are
+permitted in sequences of declarations, so you can use pragma @code{Debug} to
+intersperse calls to debug procedures in the middle of declarations. Debug
+pragmas can be enabled either by use of the command line switch @code{-gnata}
+or by use of the configuration pragma @code{Debug_Policy}.
+
+@node Pragma Debug_Policy
+@unnumberedsec Pragma Debug_Policy
+@findex Debug_Policy
+@noindent
+Syntax:
+
+@smallexample @c ada
+pragma Debug_Policy (CHECK | IGNORE);
+@end smallexample
+
+@noindent
+If the argument is @code{CHECK}, then pragma @code{DEBUG} is enabled.
+If the argument is @code{IGNORE}, then pragma @code{DEBUG} is ignored.
+This pragma overrides the effect of the @code{-gnata} switch on the
+command line.
+
+@node Pragma Detect_Blocking
+@unnumberedsec Pragma Detect_Blocking
+@findex Detect_Blocking
+@noindent
+Syntax:
+
+@smallexample @c ada
+pragma Detect_Blocking;
+@end smallexample
-If assertions are not enabled on the command line, this pragma has no
-effect. If asserts are enabled, the semantics of the pragma is exactly
-equivalent to the procedure call statement corresponding to the argument
-with a terminating semicolon. Pragmas are permitted in sequences of
-declarations, so you can use pragma @code{Debug} to intersperse calls to
-debug procedures in the middle of declarations.
+@noindent
+This is a configuration pragma that forces the detection of potentially
+blocking operations within a protected operation, and to raise Program_Error
+if that happens.
+@node Pragma Elaboration_Checks
+@unnumberedsec Pragma Elaboration_Checks
@cindex Elaboration control
@findex Elaboration_Checks
-@item pragma Elaboration_Checks
@noindent
Syntax:
-@smallexample
-pragma Elaboration_Checks (RM | Static);
+@smallexample @c ada
+pragma Elaboration_Checks (Dynamic | Static);
@end smallexample
@noindent
This is a configuration pragma that provides control over the
elaboration model used by the compilation affected by the
-pragma. If the parameter is RM, then the dynamic elaboration
+pragma. If the parameter is @code{Dynamic},
+then the dynamic elaboration
model described in the Ada Reference Manual is used, as though
the @code{-gnatE} switch had been specified on the command
-line. If the parameter is Static, then the default GNAT static
+line. If the parameter is @code{Static}, then the default GNAT static
model is used. This configuration pragma overrides the setting
of the command line. For full details on the elaboration models
used by the GNAT compiler, see section ``Elaboration Order
Handling in GNAT'' in the @cite{GNAT User's Guide}.
+@node Pragma Eliminate
+@unnumberedsec Pragma Eliminate
@cindex Elimination of unused subprograms
@findex Eliminate
-@item pragma Eliminate
@noindent
Syntax:
-@smallexample
+@smallexample @c ada
pragma Eliminate (
[Unit_Name =>] IDENTIFIER |
SELECTED_COMPONENT);
[Entity =>] IDENTIFIER |
SELECTED_COMPONENT |
STRING_LITERAL
- [,[Parameter_Types =>] PARAMETER_TYPES]
- [,[Result_Type =>] result_SUBTYPE_NAME]
- [,[Homonym_Number =>] INTEGER_LITERAL]);
+ [,OVERLOADING_RESOLUTION]);
+
+OVERLOADING_RESOLUTION ::= PARAMETER_AND_RESULT_TYPE_PROFILE |
+ SOURCE_LOCATION
+
+PARAMETER_AND_RESULT_TYPE_PROFILE ::= PROCEDURE_PROFILE |
+ FUNCTION_PROFILE
+
+PROCEDURE_PROFILE ::= Parameter_Types => PARAMETER_TYPES
+
+FUNCTION_PROFILE ::= [Parameter_Types => PARAMETER_TYPES,]
+ Result_Type => result_SUBTYPE_NAME]
PARAMETER_TYPES ::= (SUBTYPE_NAME @{, SUBTYPE_NAME@})
-SUBTYPE_NAME ::= STRING_LITERAL
+SUBTYPE_NAME ::= STRING_VALUE
+
+SOURCE_LOCATION ::= Source_Location => SOURCE_TRACE
+SOURCE_TRACE ::= STRING_VALUE
+
+STRING_VALUE ::= STRING_LITERAL @{& STRING_LITERAL@}
@end smallexample
@noindent
This pragma indicates that the given entity is not used outside the
-compilation unit it is defined in. The entity may be either a subprogram
-or a variable.
+compilation unit it is defined in. The entity must be an explicitly declared
+subprogram; this includes generic subprogram instances and
+subprograms declared in generic package instances.
If the entity to be eliminated is a library level subprogram, then
the first form of pragma @code{Eliminate} is used with only a single argument.
library level unit to be eliminated.
In all other cases, both @code{Unit_Name} and @code{Entity} arguments
-are required. item is an entity of a library package, then the first
+are required. If item is an entity of a library package, then the first
argument specifies the unit name, and the second argument specifies
the particular entity. If the second argument is in string form, it must
correspond to the internal manner in which GNAT stores entity names (see
compilation unit Namet in the compiler sources for details).
-The remaining parameters are optionally used to distinguish
-between overloaded subprograms. There are two ways of doing this.
+The remaining parameters (OVERLOADING_RESOLUTION) are optionally used
+to distinguish between overloaded subprograms. If a pragma does not contain
+the OVERLOADING_RESOLUTION parameter(s), it is applied to all the overloaded
+subprograms denoted by the first two parameters.
+
+Use PARAMETER_AND_RESULT_TYPE_PROFILE to specify the profile of the subprogram
+to be eliminated in a manner similar to that used for the extended
+@code{Import} and @code{Export} pragmas, except that the subtype names are
+always given as strings. At the moment, this form of distinguishing
+overloaded subprograms is implemented only partially, so we do not recommend
+using it for practical subprogram elimination.
+
+Note that in case of a parameterless procedure its profile is represented
+as @code{Parameter_Types => ("")}
+
+Alternatively, the @code{Source_Location} parameter is used to specify
+which overloaded alternative is to be eliminated by pointing to the
+location of the DEFINING_PROGRAM_UNIT_NAME of this subprogram in the
+source text. The string literal (or concatenation of string literals)
+given as SOURCE_TRACE must have the following format:
+
+@smallexample @c ada
+SOURCE_TRACE ::= SOURCE_LOCATION@{LBRACKET SOURCE_LOCATION RBRACKET@}
+
+LBRACKET ::= [
+RBRACKET ::= ]
+
+SOURCE_LOCATION ::= FILE_NAME:LINE_NUMBER
+FILE_NAME ::= STRING_LITERAL
+LINE_NUMBER ::= DIGIT @{DIGIT@}
+@end smallexample
-Use @code{Parameter_Types} and @code{Result_Type} to specify the
-profile of the subprogram to be eliminated in a manner similar to that
-used for
-the extended @code{Import} and @code{Export} pragmas, except that the
-subtype names are always given as string literals, again corresponding
-to the internal manner in which GNAT stores entity names.
+SOURCE_TRACE should be the short name of the source file (with no directory
+information), and LINE_NUMBER is supposed to point to the line where the
+defining name of the subprogram is located.
-Alternatively, the @code{Homonym_Number} parameter is used to specify
-which overloaded alternative is to be eliminated. A value of 1 indicates
-the first subprogram (in lexical order), 2 indicates the second etc.
+For the subprograms that are not a part of generic instantiations, only one
+SOURCE_LOCATION is used. If a subprogram is declared in a package
+instantiation, SOURCE_TRACE contains two SOURCE_LOCATIONs, the first one is
+the location of the (DEFINING_PROGRAM_UNIT_NAME of the) instantiation, and the
+second one denotes the declaration of the corresponding subprogram in the
+generic package. This approach is recursively used to create SOURCE_LOCATIONs
+in case of nested instantiations.
The effect of the pragma is to allow the compiler to eliminate
-the code or data associated with the named entity. Any reference to
+the code or data associated with the named entity. Any reference to
an eliminated entity outside the compilation unit it is defined in,
causes a compile time or link time error.
-The parameters of this pragma may be given in any order, as long as
-the usual rules for use of named parameters and position parameters
-are used.
-
The intention of pragma @code{Eliminate} is to allow a program to be compiled
in a system independent manner, with unused entities eliminated, without
the requirement of modifying the source text. Normally the required set
-of @code{Eliminate} pragmas is constructed automatically using the gnatelim tool.
-Elimination of unused entities local to a compilation unit is automatic,
-without requiring the use of pragma @code{Eliminate}.
+of @code{Eliminate} pragmas is constructed automatically using the gnatelim
+tool. Elimination of unused entities local to a compilation unit is
+automatic, without requiring the use of pragma @code{Eliminate}.
Note that the reason this pragma takes string literals where names might
be expected is that a pragma @code{Eliminate} can appear in a context where the
relevant names are not visible.
+Note that any change in the source files that includes removing, splitting of
+adding lines may make the set of Eliminate pragmas using SOURCE_LOCATION
+parameter illegal.
+
+It is legal to use pragma Eliminate where the referenced entity is a
+dispatching operation, but it is not clear what this would mean, since
+in general the call does not know which entity is actually being called.
+Consequently, a pragma Eliminate for a dispatching operation is ignored.
+
+@node Pragma Export_Exception
+@unnumberedsec Pragma Export_Exception
@cindex OpenVMS
@findex Export_Exception
-@item pragma Export_Exception
@noindent
Syntax:
-@smallexample
+@smallexample @c ada
pragma Export_Exception (
- [Internal =>] LOCAL_NAME,
+ [Internal =>] local_NAME,
[, [External =>] EXTERNAL_SYMBOL,]
[, [Form =>] Ada | VMS]
[, [Code =>] static_integer_EXPRESSION]);
on this pragma, see the
DEC Ada Language Reference Manual, section 13.9a3.2.
+@node Pragma Export_Function
+@unnumberedsec Pragma Export_Function
@cindex Argument passing mechanisms
@findex Export_Function
-@item pragma Export_Function @dots{}
@noindent
Syntax:
-@smallexample
+@smallexample @c ada
pragma Export_Function (
- [Internal =>] LOCAL_NAME,
+ [Internal =>] local_NAME,
[, [External =>] EXTERNAL_SYMBOL]
[, [Parameter_Types =>] PARAMETER_TYPES]
[, [Result_Type =>] result_SUBTYPE_MARK]
EXTERNAL_SYMBOL ::=
IDENTIFIER
| static_string_EXPRESSION
+| ""
PARAMETER_TYPES ::=
null
-| SUBTYPE_MARK @{, SUBTYPE_MARK@}
+| TYPE_DESIGNATOR @{, TYPE_DESIGNATOR@}
+
+TYPE_DESIGNATOR ::=
+ subtype_NAME
+| subtype_Name ' Access
MECHANISM ::=
MECHANISM_NAME
| Reference
| Descriptor [([Class =>] CLASS_NAME)]
-CLASS_NAME ::= ubs | ubsb | uba | s | sb | a | nca
+CLASS_NAME ::= ubs | ubsb | uba | s | sb | a
@end smallexample
+@noindent
Use this pragma to make a function externally callable and optionally
provide information on mechanisms to be used for passing parameter and
result values. We recommend, for the purposes of improving portability,
unique designation. @var{subtype_ mark}s in these parameters must
exactly match the subtypes in the corresponding function specification,
using positional notation to match parameters with subtype marks.
+The form with an @code{'Access} attribute can be used to match an
+anonymous access parameter.
+
@cindex OpenVMS
@cindex Passing by descriptor
Passing by descriptor is supported only on the OpenVMS ports of GNAT@.
+@cindex Suppressing external name
+Special treatment is given if the EXTERNAL is an explicit null
+string or a static string expressions that evaluates to the null
+string. In this case, no external name is generated. This form
+still allows the specification of parameter mechanisms.
+
+@node Pragma Export_Object
+@unnumberedsec Pragma Export_Object
@findex Export_Object
-@item pragma Export_Object @dots{}
@noindent
Syntax:
-@smallexample
+@smallexample @c ada
pragma Export_Object
- [Internal =>] LOCAL_NAME,
+ [Internal =>] local_NAME,
[, [External =>] EXTERNAL_SYMBOL]
[, [Size =>] EXTERNAL_SYMBOL]
| static_string_EXPRESSION
@end smallexample
+@noindent
This pragma designates an object as exported, and apart from the
extended rules for external symbols, is identical in effect to the use of
the normal @code{Export} pragma applied to an object. You may use a
of portability), but it is not required. @var{Size} is syntax checked,
but otherwise ignored by GNAT@.
+@node Pragma Export_Procedure
+@unnumberedsec Pragma Export_Procedure
@findex Export_Procedure
-@item pragma Export_Procedure @dots{}
@noindent
Syntax:
-@smallexample
+@smallexample @c ada
pragma Export_Procedure (
- [Internal =>] LOCAL_NAME
+ [Internal =>] local_NAME
[, [External =>] EXTERNAL_SYMBOL]
[, [Parameter_Types =>] PARAMETER_TYPES]
[, [Mechanism =>] MECHANISM]);
EXTERNAL_SYMBOL ::=
IDENTIFIER
| static_string_EXPRESSION
+| ""
PARAMETER_TYPES ::=
null
-| SUBTYPE_MARK @{, SUBTYPE_MARK@}
+| TYPE_DESIGNATOR @{, TYPE_DESIGNATOR@}
+
+TYPE_DESIGNATOR ::=
+ subtype_NAME
+| subtype_Name ' Access
MECHANISM ::=
MECHANISM_NAME
| Reference
| Descriptor [([Class =>] CLASS_NAME)]
-CLASS_NAME ::= ubs | ubsb | uba | s | sb | a | nca
+CLASS_NAME ::= ubs | ubsb | uba | s | sb | a
@end smallexample
@noindent
pragma in conjunction with a @code{Export} or @code{Convention}
pragma that specifies the desired foreign convention.
+@cindex OpenVMS
+@cindex Passing by descriptor
+Passing by descriptor is supported only on the OpenVMS ports of GNAT@.
+
+@cindex Suppressing external name
+Special treatment is given if the EXTERNAL is an explicit null
+string or a static string expressions that evaluates to the null
+string. In this case, no external name is generated. This form
+still allows the specification of parameter mechanisms.
+
+@node Pragma Export_Value
+@unnumberedsec Pragma Export_Value
+@findex Export_Value
+@noindent
+Syntax:
+
+@smallexample @c ada
+pragma Export_Value (
+ [Value =>] static_integer_EXPRESSION,
+ [Link_Name =>] static_string_EXPRESSION);
+@end smallexample
+
+@noindent
+This pragma serves to export a static integer value for external use.
+The first argument specifies the value to be exported. The Link_Name
+argument specifies the symbolic name to be associated with the integer
+value. This pragma is useful for defining a named static value in Ada
+that can be referenced in assembly language units to be linked with
+the application. This pragma is currently supported only for the
+AAMP target and is ignored for other targets.
+
+@node Pragma Export_Valued_Procedure
+@unnumberedsec Pragma Export_Valued_Procedure
@findex Export_Valued_Procedure
-@item pragma Export_Valued_Procedure
@noindent
Syntax:
-@smallexample
+@smallexample @c ada
pragma Export_Valued_Procedure (
- [Internal =>] LOCAL_NAME
+ [Internal =>] local_NAME
[, [External =>] EXTERNAL_SYMBOL]
[, [Parameter_Types =>] PARAMETER_TYPES]
[, [Mechanism =>] MECHANISM]);
EXTERNAL_SYMBOL ::=
IDENTIFIER
| static_string_EXPRESSION
+| ""
PARAMETER_TYPES ::=
null
-| SUBTYPE_MARK @{, SUBTYPE_MARK@}
+| TYPE_DESIGNATOR @{, TYPE_DESIGNATOR@}
+
+TYPE_DESIGNATOR ::=
+ subtype_NAME
+| subtype_Name ' Access
MECHANISM ::=
MECHANISM_NAME
| Reference
| Descriptor [([Class =>] CLASS_NAME)]
-CLASS_NAME ::= ubs | ubsb | uba | s | sb | a | nca
+CLASS_NAME ::= ubs | ubsb | uba | s | sb | a
@end smallexample
+@noindent
This pragma is identical to @code{Export_Procedure} except that the
-first parameter of @var{local_name}, which must be present, must be of
+first parameter of @var{local_NAME}, which must be present, must be of
mode @code{OUT}, and externally the subprogram is treated as a function
with this parameter as the result of the function. GNAT provides for
this capability to allow the use of @code{OUT} and @code{IN OUT}
pragma in conjunction with a @code{Export} or @code{Convention}
pragma that specifies the desired foreign convention.
+@cindex OpenVMS
+@cindex Passing by descriptor
+Passing by descriptor is supported only on the OpenVMS ports of GNAT@.
+
+@cindex Suppressing external name
+Special treatment is given if the EXTERNAL is an explicit null
+string or a static string expressions that evaluates to the null
+string. In this case, no external name is generated. This form
+still allows the specification of parameter mechanisms.
+
+@node Pragma Extend_System
+@unnumberedsec Pragma Extend_System
@cindex @code{system}, extending
@cindex Dec Ada 83
@findex Extend_System
-@item pragma Extend_System
@noindent
Syntax:
-@smallexample
+@smallexample @c ada
pragma Extend_System ([Name =>] IDENTIFIER);
@end smallexample
This pragma is used to provide backwards compatibility with other
implementations that extend the facilities of package @code{System}. In
GNAT, @code{System} contains only the definitions that are present in
-the Ada 95 RM@. However, other implementations, notably the DEC Ada 83
+the Ada RM@. However, other implementations, notably the DEC Ada 83
implementation, provide many extensions to package @code{System}.
For each such implementation accommodated by this pragma, GNAT provides a
it you will have to use the appropriate switch for compiling
system units. See the GNAT User's Guide for details.
+@node Pragma External
+@unnumberedsec Pragma External
@findex External
-@item pragma External
@noindent
Syntax:
-@smallexample
+@smallexample @c ada
pragma External (
[ Convention =>] convention_IDENTIFIER,
[ Entity =>] local_NAME
used this pragma for exactly the same purposes as pragma
@code{Export} before the latter was standardized.
+@node Pragma External_Name_Casing
+@unnumberedsec Pragma External_Name_Casing
@cindex Dec Ada 83 casing compatibility
@cindex External Names, casing
@cindex Casing of External names
@findex External_Name_Casing
-@item pragma External_Name_Casing
@noindent
Syntax:
-@smallexample
+@smallexample @c ada
pragma External_Name_Casing (
Uppercase | Lowercase
[, Uppercase | Lowercase | As_Is]);
@table @asis
@item Implicit external names
Implicit external names are derived from identifiers. The most common case
-arises when a standard Ada 95 Import or Export pragma is used with only two
+arises when a standard Ada Import or Export pragma is used with only two
arguments, as in:
-@smallexample
+@smallexample @c ada
pragma Import (C, C_Routine);
@end smallexample
@noindent
-Since Ada is a case insensitive language, the spelling of the identifier in
+Since Ada is a case-insensitive language, the spelling of the identifier in
the Ada source program does not provide any information on the desired
casing of the external name, and so a convention is needed. In GNAT the
default treatment is that such names are converted to all lower case
@item Explicit external names
Explicit external names are given as string literals. The most common case
-arises when a standard Ada 95 Import or Export pragma is used with three
+arises when a standard Ada Import or Export pragma is used with three
arguments, as in:
-@smallexample
+@smallexample @c ada
pragma Import (C, C_Routine, "C_routine");
@end smallexample
@noindent
In this case, the string literal normally provides the exact casing required
-for the external name. The second argument of pragma
-@code{External_Name_Casing} may be used to modify this behavior.
+for the external name. The second argument of pragma
+@code{External_Name_Casing} may be used to modify this behavior.
If @code{Uppercase} is specified, then the name
will be forced to all uppercase letters. If @code{Lowercase} is specified,
then the name will be forced to all lowercase letters. A specification of
such compilers (e.g.@: the DEC C compiler), it may be convenient to use
the pragma:
-@smallexample
+@smallexample @c ada
pragma External_Name_Casing (Uppercase, Uppercase);
@end smallexample
@noindent
-to enforce the upper casing of all external symbols.
+to enforce the upper casing of all external symbols.
+@node Pragma Finalize_Storage_Only
+@unnumberedsec Pragma Finalize_Storage_Only
@findex Finalize_Storage_Only
-@item pragma Finalize_Storage_Only
@noindent
Syntax:
-@smallexample
-pragma Finalize_Storage_Only (first_subtype_LOCAL_NAME);
+@smallexample @c ada
+pragma Finalize_Storage_Only (first_subtype_local_NAME);
@end smallexample
@noindent
environments it is not necessary to reclaim memory just before terminating
execution, hence the name.
+@node Pragma Float_Representation
+@unnumberedsec Pragma Float_Representation
@cindex OpenVMS
@findex Float_Representation
-@item pragma Float_Representation
@noindent
Syntax:
-@smallexample
-pragma Float_Representation (FLOAT_REP);
+@smallexample @c ada
+pragma Float_Representation (FLOAT_REP[, float_type_LOCAL_NAME]);
FLOAT_REP ::= VAX_Float | IEEE_Float
@end smallexample
@noindent
-This pragma is implemented only in the OpenVMS implementation of GNAT@.
-It allows control over the internal representation chosen for the predefined
+In the one argument form, this pragma is a configuration pragma which
+allows control over the internal representation chosen for the predefined
floating point types declared in the packages @code{Standard} and
-@code{System}. For further details on this pragma, see the
-DEC Ada Language Reference Manual, section 3.5.7a. Note that to use this
-pragma, the standard runtime libraries must be recompiled. See the
+@code{System}. On all systems other than OpenVMS, the argument must
+be @code{IEEE_Float} and the pragma has no effect. On OpenVMS, the
+argument may be @code{VAX_Float} to specify the use of the VAX float
+format for the floating-point types in Standard. This requires that
+the standard runtime libraries be recompiled. See the
description of the @code{GNAT LIBRARY} command in the OpenVMS version
of the GNAT Users Guide for details on the use of this command.
+The two argument form specifies the representation to be used for
+the specified floating-point type. On all systems other than OpenVMS,
+the argument must
+be @code{IEEE_Float} and the pragma has no effect. On OpenVMS, the
+argument may be @code{VAX_Float} to specify the use of the VAX float
+format, as follows:
+
+@itemize @bullet
+@item
+For digits values up to 6, F float format will be used.
+@item
+For digits values from 7 to 9, G float format will be used.
+@item
+For digits values from 10 to 15, F float format will be used.
+@item
+Digits values above 15 are not allowed.
+@end itemize
+
+@node Pragma Ident
+@unnumberedsec Pragma Ident
@findex Ident
-@item pragma Ident
@noindent
Syntax:
-@smallexample
+@smallexample @c ada
pragma Ident (static_string_EXPRESSION);
@end smallexample
@noindent
This pragma provides a string identification in the generated object file,
if the system supports the concept of this kind of identification string.
-The maximum permitted length of the string literal is 31 characters.
This pragma is allowed only in the outermost declarative part or
-declarative items of a compilation unit.
+declarative items of a compilation unit. If more than one @code{Ident}
+pragma is given, only the last one processed is effective.
@cindex OpenVMS
On OpenVMS systems, the effect of the pragma is identical to the effect of
-the DEC Ada 83 pragma of the same name.
+the DEC Ada 83 pragma of the same name. Note that in DEC Ada 83, the
+maximum allowed length is 31 characters, so if it is important to
+maintain compatibility with this compiler, you should obey this length
+limit.
+
+@node Pragma Implicit_Packing
+@unnumberedsec Pragma Implicit_Packing
+@findex Implicit_Packing
+@noindent
+Syntax:
+
+@smallexample @c ada
+pragma Implicit_Packing;
+@end smallexample
+
+@noindent
+This is a configuration pragma that requests implicit packing for packed
+arrays for which a size clause is given but no explicit pragma Pack or
+specification of Component_Size is present. Consider this example:
+
+@smallexample @c ada
+type R is array (0 .. 7) of Boolean;
+for R'Size use 8;
+@end smallexample
+@noindent
+In accordance with the recommendation in the RM (RM 13.3(53)), a Size clause
+does not change the layout of a composite object. So the Size clause in the
+above example is normally rejected, since the default layout of the array uses
+8-bit components, and thus the array requires a minimum of 64 bits.
+
+If this declaration is compiled in a region of code covered by an occurrence
+of the configuration pragma Implicit_Packing, then the Size clause in this
+and similar examples will cause implicit packing and thus be accepted. For
+this implicit packing to occur, the type in question must be an array of small
+components whose size is known at compile time, and the Size clause must
+specify the exact size that corresponds to the length of the array multiplied
+by the size in bits of the component type.
+@cindex Array packing
+
+@node Pragma Import_Exception
+@unnumberedsec Pragma Import_Exception
@cindex OpenVMS
@findex Import_Exception
-@item pragma Import_Exception
@noindent
Syntax:
-@smallexample
+@smallexample @c ada
pragma Import_Exception (
- [Internal =>] LOCAL_NAME,
+ [Internal =>] local_NAME,
[, [External =>] EXTERNAL_SYMBOL,]
[, [Form =>] Ada | VMS]
[, [Code =>] static_integer_EXPRESSION]);
For further details on this pragma, see the
DEC Ada Language Reference Manual, section 13.9a.3.1.
+@node Pragma Import_Function
+@unnumberedsec Pragma Import_Function
@findex Import_Function
-@item pragma Import_Function @dots{}
@noindent
Syntax:
-@smallexample
+@smallexample @c ada
pragma Import_Function (
- [Internal =>] LOCAL_NAME,
+ [Internal =>] local_NAME,
[, [External =>] EXTERNAL_SYMBOL]
[, [Parameter_Types =>] PARAMETER_TYPES]
[, [Result_Type =>] SUBTYPE_MARK]
PARAMETER_TYPES ::=
null
-| SUBTYPE_MARK @{, SUBTYPE_MARK@}
+| TYPE_DESIGNATOR @{, TYPE_DESIGNATOR@}
+
+TYPE_DESIGNATOR ::=
+ subtype_NAME
+| subtype_Name ' Access
MECHANISM ::=
MECHANISM_NAME
CLASS_NAME ::= ubs | ubsb | uba | s | sb | a | nca
@end smallexample
+@noindent
This pragma is used in conjunction with a pragma @code{Import} to
specify additional information for an imported function. The pragma
@code{Import} (or equivalent pragma @code{Interface}) must precede the
@code{Import_Function} pragma and both must appear in the same
declarative part as the function specification.
-The @var{Internal_Name} argument must uniquely designate
+The @var{Internal} argument must uniquely designate
the function to which the
pragma applies. If more than one function name exists of this name in
the declarative part you must use the @code{Parameter_Types} and
designation. Subtype marks in these parameters must exactly match the
subtypes in the corresponding function specification, using positional
notation to match parameters with subtype marks.
+The form with an @code{'Access} attribute can be used to match an
+anonymous access parameter.
You may optionally use the @var{Mechanism} and @var{Result_Mechanism}
parameters to specify passing mechanisms for the
@cindex OpenVMS
@cindex Passing by descriptor
-Passing by descriptor is supported only on the to OpenVMS ports of GNAT@.
+Passing by descriptor is supported only on the OpenVMS ports of GNAT@.
@code{First_Optional_Parameter} applies only to OpenVMS ports of GNAT@.
It specifies that the designated parameter and all following parameters
default parameter values that are either known at compile time
expressions, or uses of the @code{'Null_Parameter} attribute.
+@node Pragma Import_Object
+@unnumberedsec Pragma Import_Object
@findex Import_Object
-@item pragma Import_Object
@noindent
Syntax:
-@smallexample
+@smallexample @c ada
pragma Import_Object
- [Internal =>] LOCAL_NAME,
+ [Internal =>] local_NAME,
[, [External =>] EXTERNAL_SYMBOL],
- [, [Size =>] EXTERNAL_SYMBOL])
+ [, [Size =>] EXTERNAL_SYMBOL]);
EXTERNAL_SYMBOL ::=
IDENTIFIER
point of view). @var{size} is syntax checked, but otherwise ignored by
GNAT@.
+@node Pragma Import_Procedure
+@unnumberedsec Pragma Import_Procedure
@findex Import_Procedure
-@item pragma Import_Procedure
@noindent
Syntax:
-@smallexample
+@smallexample @c ada
pragma Import_Procedure (
- [Internal =>] LOCAL_NAME,
+ [Internal =>] local_NAME,
[, [External =>] EXTERNAL_SYMBOL]
[, [Parameter_Types =>] PARAMETER_TYPES]
[, [Mechanism =>] MECHANISM]
PARAMETER_TYPES ::=
null
-| SUBTYPE_MARK @{, SUBTYPE_MARK@}
+| TYPE_DESIGNATOR @{, TYPE_DESIGNATOR@}
+
+TYPE_DESIGNATOR ::=
+ subtype_NAME
+| subtype_Name ' Access
MECHANISM ::=
MECHANISM_NAME
applies to a procedure rather than a function and the parameters
@code{Result_Type} and @code{Result_Mechanism} are not permitted.
+@node Pragma Import_Valued_Procedure
+@unnumberedsec Pragma Import_Valued_Procedure
@findex Import_Valued_Procedure
-@item pragma Import_Valued_Procedure @dots{}
@noindent
Syntax:
-@smallexample
+@smallexample @c ada
pragma Import_Valued_Procedure (
- [Internal =>] LOCAL_NAME,
+ [Internal =>] local_NAME,
[, [External =>] EXTERNAL_SYMBOL]
[, [Parameter_Types =>] PARAMETER_TYPES]
[, [Mechanism =>] MECHANISM]
PARAMETER_TYPES ::=
null
-| SUBTYPE_MARK @{, SUBTYPE_MARK@}
+| TYPE_DESIGNATOR @{, TYPE_DESIGNATOR@}
+
+TYPE_DESIGNATOR ::=
+ subtype_NAME
+| subtype_Name ' Access
MECHANISM ::=
MECHANISM_NAME
@noindent
This pragma is identical to @code{Import_Procedure} except that the
-first parameter of @var{local_name}, which must be present, must be of
+first parameter of @var{local_NAME}, which must be present, must be of
mode @code{OUT}, and externally the subprogram is treated as a function
with this parameter as the result of the function. The purpose of this
capability is to allow the use of @code{OUT} and @code{IN OUT}
pragma Import that specifies the desired convention, since otherwise the
default convention is Ada, which is almost certainly not what is required.
+@node Pragma Initialize_Scalars
+@unnumberedsec Pragma Initialize_Scalars
@findex Initialize_Scalars
@cindex debugging with Initialize_Scalars
-@item pragma Initialize_Scalars
@noindent
Syntax:
-@smallexample
+@smallexample @c ada
pragma Initialize_Scalars;
@end smallexample
@noindent
-This pragma is similar to @code{Normalize_Scalars} conceptually but has
+This pragma is similar to @code{Normalize_Scalars} conceptually but has
two important differences. First, there is no requirement for the pragma
to be used uniformly in all units of a partition, in particular, it is fine
to use this just for some or all of the application units of a partition,
whether the variable is initialized may also depend on whether the package
in which the type of the variable is declared is compiled with the pragma.
-The other important difference is that there is control over the value used
-for initializing scalar objects. At bind time, you can select whether to
-initialize with invalid values (like Normalize_Scalars), or with high or
+The other important difference is that you can control the value used
+for initializing scalar objects. At bind time, you can select several
+options for initialization. You can
+initialize with invalid values (similar to Normalize_Scalars, though for
+Initialize_Scalars it is not always possible to determine the invalid
+values in complex cases like signed component fields with non-standard
+sizes). You can also initialize with high or
low values, or with a specified bit pattern. See the users guide for binder
options for specifying these cases.
and if it does, then most likely you have an erroneous reference to an
uninitialized value.
+It is even possible to change the value at execution time eliminating even
+the need to rebind with a different switch using an environment variable.
+See the GNAT users guide for details.
+
Note that pragma @code{Initialize_Scalars} is particularly useful in
conjunction with the enhanced validity checking that is now provided
in GNAT, which checks for invalid values under more conditions.
-Using this feature (see description of the @code{-gnatv} flag in the
+Using this feature (see description of the @code{-gnatV} flag in the
users guide) in conjunction with pragma @code{Initialize_Scalars}
provides a powerful new tool to assist in the detection of problems
caused by uninitialized variables.
+Note: the use of @code{Initialize_Scalars} has a fairly extensive
+effect on the generated code. This may cause your code to be
+substantially larger. It may also cause an increase in the amount
+of stack required, so it is probably a good idea to turn on stack
+checking (see description of stack checking in the GNAT users guide)
+when using this pragma.
+
+@node Pragma Inline_Always
+@unnumberedsec Pragma Inline_Always
@findex Inline_Always
-@item pragma Inline_Always
@noindent
Syntax:
-@smallexample
+@smallexample @c ada
pragma Inline_Always (NAME [, NAME]);
@end smallexample
@noindent
Similar to pragma @code{Inline} except that inlining is not subject to
-the use of option @code{-gnatn} for inter-unit inlining.
+the use of option @code{-gnatn} and the inlining happens regardless of
+whether this option is used.
+@node Pragma Inline_Generic
+@unnumberedsec Pragma Inline_Generic
@findex Inline_Generic
-@item pragma Inline_Generic
@noindent
Syntax:
-@smallexample
-pragma Inline_Generic (generic_package_NAME)
+@smallexample @c ada
+pragma Inline_Generic (generic_package_NAME);
@end smallexample
@noindent
but otherwise ignored, by GNAT@. All generic instantiations are inlined
by default when using GNAT@.
+@node Pragma Interface
+@unnumberedsec Pragma Interface
@findex Interface
-@item pragma Interface
@noindent
Syntax:
-@smallexample
+@smallexample @c ada
pragma Interface (
[Convention =>] convention_identifier,
- [Entity =>] local_name
+ [Entity =>] local_NAME
[, [External_Name =>] static_string_expression],
[, [Link_Name =>] static_string_expression]);
@end smallexample
@noindent
This pragma is identical in syntax and semantics to
-the standard Ada 95 pragma @code{Import}. It is provided for compatibility
+the standard Ada pragma @code{Import}. It is provided for compatibility
with Ada 83. The definition is upwards compatible both with pragma
@code{Interface} as defined in the Ada 83 Reference Manual, and also
with some extended implementations of this pragma in certain Ada 83
implementations.
+@node Pragma Interface_Name
+@unnumberedsec Pragma Interface_Name
@findex Interface_Name
-@item pragma Interface_Name
@noindent
Syntax:
-@smallexample
-pragma Interface_Name (
- [Entity =>] LOCAL_NAME
+@smallexample @c ada
+pragma Interface_Name (
+ [Entity =>] local_NAME
[, [External_Name =>] static_string_EXPRESSION]
[, [Link_Name =>] static_string_EXPRESSION]);
@end smallexample
83 compilers that use the pragma for this purpose. You must provide at
least one of @var{External_Name} or @var{Link_Name}.
+@node Pragma Interrupt_Handler
+@unnumberedsec Pragma Interrupt_Handler
+@findex Interrupt_Handler
+@noindent
+Syntax:
+
+@smallexample @c ada
+pragma Interrupt_Handler (procedure_local_NAME);
+@end smallexample
+
+@noindent
+This program unit pragma is supported for parameterless protected procedures
+as described in Annex C of the Ada Reference Manual. On the AAMP target
+the pragma can also be specified for nonprotected parameterless procedures
+that are declared at the library level (which includes procedures
+declared at the top level of a library package). In the case of AAMP,
+when this pragma is applied to a nonprotected procedure, the instruction
+@code{IERET} is generated for returns from the procedure, enabling
+maskable interrupts, in place of the normal return instruction.
+
+@node Pragma Interrupt_State
+@unnumberedsec Pragma Interrupt_State
+@findex Interrupt_State
+@noindent
+Syntax:
+
+@smallexample @c ada
+pragma Interrupt_State (Name => value, State => SYSTEM | RUNTIME | USER);
+@end smallexample
+
+@noindent
+Normally certain interrupts are reserved to the implementation. Any attempt
+to attach an interrupt causes Program_Error to be raised, as described in
+RM C.3.2(22). A typical example is the @code{SIGINT} interrupt used in
+many systems for an @kbd{Ctrl-C} interrupt. Normally this interrupt is
+reserved to the implementation, so that @kbd{Ctrl-C} can be used to
+interrupt execution. Additionally, signals such as @code{SIGSEGV},
+@code{SIGABRT}, @code{SIGFPE} and @code{SIGILL} are often mapped to specific
+Ada exceptions, or used to implement run-time functions such as the
+@code{abort} statement and stack overflow checking.
+
+Pragma @code{Interrupt_State} provides a general mechanism for overriding
+such uses of interrupts. It subsumes the functionality of pragma
+@code{Unreserve_All_Interrupts}. Pragma @code{Interrupt_State} is not
+available on OS/2, Windows or VMS. On all other platforms than VxWorks,
+it applies to signals; on VxWorks, it applies to vectored hardware interrupts
+and may be used to mark interrupts required by the board support package
+as reserved.
+
+Interrupts can be in one of three states:
+@itemize @bullet
+@item System
+
+The interrupt is reserved (no Ada handler can be installed), and the
+Ada run-time may not install a handler. As a result you are guaranteed
+standard system default action if this interrupt is raised.
+
+@item Runtime
+
+The interrupt is reserved (no Ada handler can be installed). The run time
+is allowed to install a handler for internal control purposes, but is
+not required to do so.
+
+@item User
+
+The interrupt is unreserved. The user may install a handler to provide
+some other action.
+@end itemize
+
+@noindent
+These states are the allowed values of the @code{State} parameter of the
+pragma. The @code{Name} parameter is a value of the type
+@code{Ada.Interrupts.Interrupt_ID}. Typically, it is a name declared in
+@code{Ada.Interrupts.Names}.
+
+This is a configuration pragma, and the binder will check that there
+are no inconsistencies between different units in a partition in how a
+given interrupt is specified. It may appear anywhere a pragma is legal.
+
+The effect is to move the interrupt to the specified state.
+
+By declaring interrupts to be SYSTEM, you guarantee the standard system
+action, such as a core dump.
+
+By declaring interrupts to be USER, you guarantee that you can install
+a handler.
+
+Note that certain signals on many operating systems cannot be caught and
+handled by applications. In such cases, the pragma is ignored. See the
+operating system documentation, or the value of the array @code{Reserved}
+declared in the specification of package @code{System.OS_Interface}.
+
+Overriding the default state of signals used by the Ada runtime may interfere
+with an application's runtime behavior in the cases of the synchronous signals,
+and in the case of the signal used to implement the @code{abort} statement.
+
+@node Pragma Keep_Names
+@unnumberedsec Pragma Keep_Names
+@findex Keep_Names
+@noindent
+Syntax:
+
+@smallexample @c ada
+pragma Keep_Names ([On =>] enumeration_first_subtype_local_NAME);
+@end smallexample
+
+@noindent
+The @var{local_NAME} argument
+must refer to an enumeration first subtype
+in the current declarative part. The effect is to retain the enumeration
+literal names for use by @code{Image} and @code{Value} even if a global
+@code{Discard_Names} pragma applies. This is useful when you want to
+generally suppress enumeration literal names and for example you therefore
+use a @code{Discard_Names} pragma in the @file{gnat.adc} file, but you
+want to retain the names for specific enumeration types.
+
+@node Pragma License
+@unnumberedsec Pragma License
@findex License
-@item pragma License
@cindex License checking
@noindent
Syntax:
-@smallexample
+@smallexample @c ada
pragma License (Unrestricted | GPL | Modified_GPL | Restricted);
@end smallexample
@noindent
This pragma is provided to allow automated checking for appropriate license
-conditions with respect to the standard and modified GPL@. A pragma @code{License},
-which is a configuration pragma that typically appears at the start of a
-source file or in a separate @file{gnat.adc} file, specifies the licensing
-conditions of a unit as follows:
+conditions with respect to the standard and modified GPL@. A pragma
+@code{License}, which is a configuration pragma that typically appears at
+the start of a source file or in a separate @file{gnat.adc} file, specifies
+the licensing conditions of a unit as follows:
@itemize @bullet
@item Unrestricted
This is used for a unit licensed under the GNAT modified GPL that includes
a special exception paragraph that specifically permits the inclusion of
the unit in programs without requiring the entire program to be released
-under the GPL@. This is the license used for the GNAT run-time which ensures
-that the run-time can be used freely in any program without GPL concerns.
+under the GPL@.
@item Restricted
This is used for a unit that is restricted in that it is not permitted to
@itemize @bullet
A GNAT license header starts with a line containing 78 hyphens. The following
-comment text is searched for the appearence of any of the following strings.
+comment text is searched for the appearance of any of the following strings.
If the string ``GNU General Public License'' is found, then the unit is assumed
to have GPL license, unless the string ``As a special exception'' follows, in
which case the license is assumed to be modified GPL@.
If one of the strings
-``This specification is adapated from the Ada Semantic Interface'' or
+``This specification is adapted from the Ada Semantic Interface'' or
``This specification is derived from the Ada Reference Manual'' is found
then the unit is assumed to be unrestricted.
@end itemize
will automatically get warnings if a GPL unit is inappropriately
@code{with}'ed. For example, the program:
-@smallexample
+@smallexample @c ada
with Sem_Ch3;
with GNAT.Sockets;
procedure Secret_Stuff is
-@dots{}
+ @dots{}
end Secret_Stuff
@end smallexample
2. with GNAT.Sockets;
3. procedure Secret_Stuff is
@end smallexample
+
@noindent
Here we get a warning on @code{Sem_Ch3} since it is part of the GNAT
compiler and is licensed under the
-GPL, but no warning for @code{GNAT.Sockets} which is part of the GNAT
+GPL, but no warning for @code{GNAT.Sockets} which is part of the GNAT
run time, and is therefore licensed under the modified GPL@.
+@node Pragma Link_With
+@unnumberedsec Pragma Link_With
@findex Link_With
-@item pragma Link_With
@noindent
Syntax:
-@smallexample
+@smallexample @c ada
pragma Link_With (static_string_EXPRESSION @{,static_string_EXPRESSION@});
@end smallexample
that spaces occurring within one of the string expressions are treated
as separators. For example, in the following case:
-@smallexample
+@smallexample @c ada
pragma Link_With ("-labc -ldef");
@end smallexample
separate arguments to the linker. In addition pragma Link_With allows
multiple arguments, with the same effect as successive pragmas.
+@node Pragma Linker_Alias
+@unnumberedsec Pragma Linker_Alias
@findex Linker_Alias
-@item pragma Linker_Alias
@noindent
Syntax:
-@smallexample
+@smallexample @c ada
pragma Linker_Alias (
- [Entity =>] LOCAL_NAME
- [Alias =>] static_string_EXPRESSION);
+ [Entity =>] local_NAME
+ [Target =>] static_string_EXPRESSION);
@end smallexample
@noindent
-This pragma establishes a linker alias for the given named entity. For
-further details on the exact effect, consult the GCC manual.
+@var{local_NAME} must refer to an object that is declared at the library
+level. This pragma establishes the given entity as a linker alias for the
+given target. It is equivalent to @code{__attribute__((alias))} in GNU C
+and causes @var{local_NAME} to be emitted as an alias for the symbol
+@var{static_string_EXPRESSION} in the object file, that is to say no space
+is reserved for @var{local_NAME} by the assembler and it will be resolved
+to the same address as @var{static_string_EXPRESSION} by the linker.
-@findex Linker_Section
-@item pragma Linker_Section
-@noindent
-Syntax:
+The actual linker name for the target must be used (e.g. the fully
+encoded name with qualification in Ada, or the mangled name in C++),
+or it must be declared using the C convention with @code{pragma Import}
+or @code{pragma Export}.
-@smallexample
-pragma Linker_Section (
- [Entity =>] LOCAL_NAME
- [Section =>] static_string_EXPRESSION);
-@end smallexample
+Not all target machines support this pragma. On some of them it is accepted
+only if @code{pragma Weak_External} has been applied to @var{local_NAME}.
-@noindent
-This pragma specifies the name of the linker section for the given entity.
-For further details on the exact effect, consult the GCC manual.
+@smallexample @c ada
+-- Example of the use of pragma Linker_Alias
+
+package p is
+ i : Integer := 1;
+ pragma Export (C, i);
+
+ new_name_for_i : Integer;
+ pragma Linker_Alias (new_name_for_i, "i");
+end p;
+@end smallexample
-@findex No_Run_Time
-@item pragma No_Run_Time
+@node Pragma Linker_Constructor
+@unnumberedsec Pragma Linker_Constructor
+@findex Linker_Constructor
@noindent
Syntax:
-@smallexample
-pragma No_Run_Time;
+@smallexample @c ada
+pragma Linker_Constructor (procedure_LOCAL_NAME);
@end smallexample
@noindent
-This is a configuration pragma that makes sure the user code does not
-use nor need anything from the GNAT run time. This is mostly useful in
-context where code certification is required. Please consult the
-@cite{GNAT Pro High-Integrity Edition User's Guide} for additional information.
+@var{procedure_local_NAME} must refer to a parameterless procedure that
+is declared at the library level. A procedure to which this pragma is
+applied will be treated as an initialization routine by the linker.
+It is equivalent to @code{__attribute__((constructor))} in GNU C and
+causes @var{procedure_LOCAL_NAME} to be invoked before the entry point
+of the executable is called (or immediately after the shared library is
+loaded if the procedure is linked in a shared library), in particular
+before the Ada run-time environment is set up.
-@findex Normalize_Scalars
-@item pragma Normalize_Scalars
+Because of these specific contexts, the set of operations such a procedure
+can perform is very limited and the type of objects it can manipulate is
+essentially restricted to the elementary types. In particular, it must only
+contain code to which pragma Restrictions (No_Elaboration_Code) applies.
+
+This pragma is used by GNAT to implement auto-initialization of shared Stand
+Alone Libraries, which provides a related capability without the restrictions
+listed above. Where possible, the use of Stand Alone Libraries is preferable
+to the use of this pragma.
+
+@node Pragma Linker_Destructor
+@unnumberedsec Pragma Linker_Destructor
+@findex Linker_Destructor
@noindent
Syntax:
-@smallexample
-pragma Normalize_Scalars;
+@smallexample @c ada
+pragma Linker_Destructor (procedure_LOCAL_NAME);
@end smallexample
@noindent
-This is a language defined pragma which is fully implemented in GNAT@. The
-effect is to cause all scalar objects that are not otherwise initialized
-to be initialized. The initial values are implementation dependent and
-are as follows:
-
-@table @code
-@item Standard.Character
-@noindent
-Objects whose root type is Standard.Character are initialized to
-Character'Last. This will be out of range of the subtype only if
-the subtype range excludes this value.
+@var{procedure_local_NAME} must refer to a parameterless procedure that
+is declared at the library level. A procedure to which this pragma is
+applied will be treated as a finalization routine by the linker.
+It is equivalent to @code{__attribute__((destructor))} in GNU C and
+causes @var{procedure_LOCAL_NAME} to be invoked after the entry point
+of the executable has exited (or immediately before the shared library
+is unloaded if the procedure is linked in a shared library), in particular
+after the Ada run-time environment is shut down.
-@item Standard.Wide_Character
-@noindent
-Objects whose root type is Standard.Wide_Character are initialized to
-Wide_Character'Last. This will be out of range of the subtype only if
-the subtype range excludes this value.
+See @code{pragma Linker_Constructor} for the set of restrictions that apply
+because of these specific contexts.
-@item Integer types
+@node Pragma Linker_Section
+@unnumberedsec Pragma Linker_Section
+@findex Linker_Section
@noindent
-Objects of an integer type are initialized to base_type'First, where
-base_type is the base type of the object type. This will be out of range
-of the subtype only if the subtype range excludes this value. For example,
-if you declare the subtype:
+Syntax:
-@smallexample
-subtype Ityp is integer range 1 .. 10;
+@smallexample @c ada
+pragma Linker_Section (
+ [Entity =>] local_NAME
+ [Section =>] static_string_EXPRESSION);
@end smallexample
@noindent
-then objects of type x will be initialized to Integer'First, a negative
-number that is certainly outside the range of subtype @code{Ityp}.
+@var{local_NAME} must refer to an object that is declared at the library
+level. This pragma specifies the name of the linker section for the given
+entity. It is equivalent to @code{__attribute__((section))} in GNU C and
+causes @var{local_NAME} to be placed in the @var{static_string_EXPRESSION}
+section of the executable (assuming the linker doesn't rename the section).
-@item Real types
-Objects of all real types (fixed and floating) are initialized to
-base_type'First, where base_Type is the base type of the object type.
-This will be out of range of the subtype only if the subtype range
-excludes this value.
+The compiler normally places library-level objects in standard sections
+depending on their type: procedures and functions generally go in the
+@code{.text} section, initialized variables in the @code{.data} section
+and uninitialized variables in the @code{.bss} section.
-@item Modular types
-Objects of a modular type are initialized to typ'Last. This will be out
-of range of the subtype only if the subtype excludes this value.
+Other, special sections may exist on given target machines to map special
+hardware, for example I/O ports or flash memory. This pragma is a means to
+defer the final layout of the executable to the linker, thus fully working
+at the symbolic level with the compiler.
-@item Enumeration types
-Objects of an enumeration type are initialized to all one-bits, i.e.@: to
-the value @code{2 ** typ'Size - 1}. This will be out of range of the enumeration
-subtype in all cases except where the subtype contains exactly
-2**8, 2**16, or 2**32 elements.
+Some file formats do not support arbitrary sections so not all target
+machines support this pragma. The use of this pragma may cause a program
+execution to be erroneous if it is used to place an entity into an
+inappropriate section (e.g. a modified variable into the @code{.text}
+section). See also @code{pragma Persistent_BSS}.
-@end table
+@smallexample @c ada
+-- Example of the use of pragma Linker_Section
+package IO_Card is
+ Port_A : Integer;
+ pragma Volatile (Port_A);
+ pragma Linker_Section (Port_A, ".bss.port_a");
+
+ Port_B : Integer;
+ pragma Volatile (Port_B);
+ pragma Linker_Section (Port_B, ".bss.port_b");
+end IO_Card;
+@end smallexample
+
+@node Pragma Long_Float
+@unnumberedsec Pragma Long_Float
@cindex OpenVMS
@findex Long_Float
-@item pragma Long_Float
@noindent
Syntax:
-@smallexample
+@smallexample @c ada
pragma Long_Float (FLOAT_FORMAT);
FLOAT_FORMAT ::= D_Float | G_Float
type @code{Long_Float} and for floating point type representations with
@code{digits} specified in the range 7 through 15.
For further details on this pragma, see the
-@cite{DEC Ada Language Reference Manual}, section 3.5.7b. Note that to use this
-pragma, the standard runtime libraries must be recompiled. See the
+@cite{DEC Ada Language Reference Manual}, section 3.5.7b. Note that to use
+this pragma, the standard runtime libraries must be recompiled. See the
description of the @code{GNAT LIBRARY} command in the OpenVMS version
of the GNAT User's Guide for details on the use of this command.
+@node Pragma Machine_Attribute
+@unnumberedsec Pragma Machine_Attribute
@findex Machine_Attribute
-@item pragma Machine_Attribute @dots{}
@noindent
Syntax:
-@smallexample
+@smallexample @c ada
pragma Machine_Attribute (
[Attribute_Name =>] string_EXPRESSION,
- [Entity =>] LOCAL_NAME);
+ [Entity =>] local_NAME);
@end smallexample
-Machine dependent attributes can be specified for types and/or
-declarations. Currently only subprogram entities are supported. This
-pragma is semantically equivalent to
-@code{__attribute__((@var{string_expression}))} in GNU C,
+@noindent
+Machine-dependent attributes can be specified for types and/or
+declarations. This pragma is semantically equivalent to
+@code{__attribute__((@var{string_expression}))} in GNU C,
where @code{@var{string_expression}} is
-recognized by the GNU C macros @code{VALID_MACHINE_TYPE_ATTRIBUTE} and
-@code{VALID_MACHINE_DECL_ATTRIBUTE} which are defined in the
-configuration header file @file{tm.h} for each machine. See the GCC
-manual for further information.
+recognized by the target macro @code{TARGET_ATTRIBUTE_TABLE} which is
+defined for each machine. See the GCC manual for further information.
+It is not possible to specify attributes defined by other languages,
+only attributes defined by the machine the code is intended to run on.
+
+@node Pragma Main
+@unnumberedsec Pragma Main
+@cindex OpenVMS
+@findex Main
+@noindent
+Syntax:
+
+@smallexample @c ada
+pragma Main
+ (MAIN_OPTION [, MAIN_OPTION]);
+
+MAIN_OPTION ::=
+ [STACK_SIZE =>] static_integer_EXPRESSION
+| [TASK_STACK_SIZE_DEFAULT =>] static_integer_EXPRESSION
+| [TIME_SLICING_ENABLED =>] static_boolean_EXPRESSION
+@end smallexample
+
+@noindent
+This pragma is provided for compatibility with OpenVMS VAX Systems. It has
+no effect in GNAT, other than being syntax checked.
+@node Pragma Main_Storage
+@unnumberedsec Pragma Main_Storage
@cindex OpenVMS
@findex Main_Storage
-@item pragma Main_Storage
@noindent
Syntax:
-@smallexample
+@smallexample @c ada
pragma Main_Storage
(MAIN_STORAGE_OPTION [, MAIN_STORAGE_OPTION]);
MAIN_STORAGE_OPTION ::=
[WORKING_STORAGE =>] static_SIMPLE_EXPRESSION
| [TOP_GUARD =>] static_SIMPLE_EXPRESSION
-
@end smallexample
@noindent
-This pragma is provided for compatibility with OpenVMS Vax Systems. It has
+This pragma is provided for compatibility with OpenVMS VAX Systems. It has
no effect in GNAT, other than being syntax checked. Note that the pragma
also has no effect in DEC Ada 83 for OpenVMS Alpha Systems.
+@node Pragma No_Body
+@unnumberedsec Pragma No_Body
+@findex No_Body
+@noindent
+Syntax:
+
+@smallexample @c ada
+pragma No_Body;
+@end smallexample
+
+@noindent
+There are a number of cases in which a package spec does not require a body,
+and in fact a body is not permitted. GNAT will not permit the spec to be
+compiled if there is a body around. The pragma No_Body allows you to provide
+a body file, even in a case where no body is allowed. The body file must
+contain only comments and a single No_Body pragma. This is recognized by
+the compiler as indicating that no body is logically present.
+
+This is particularly useful during maintenance when a package is modified in
+such a way that a body needed before is no longer needed. The provision of a
+dummy body with a No_Body pragma ensures that there is no inteference from
+earlier versions of the package body.
+
+@node Pragma No_Return
+@unnumberedsec Pragma No_Return
@findex No_Return
-@item pragma No_Return
@noindent
Syntax:
-@smallexample
-pragma No_Return (procedure_LOCAL_NAME);
+@smallexample @c ada
+pragma No_Return (procedure_local_NAME @{, procedure_local_NAME@});
@end smallexample
@noindent
-@var{procedure_local_NAME} must refer to one or more procedure
+Each @var{procedure_local_NAME} argument must refer to one or more procedure
declarations in the current declarative part. A procedure to which this
-pragma is applied may not contain any explicit @code{return} statements,
-and also may not contain any implicit return statements from falling off
-the end of a statement sequence. One use of this pragma is to identify
-procedures whose only purpose is to raise an exception.
-
-Another use of this pragma is to suppress incorrect warnings about
-missing returns in functions, where the last statement of a function
+pragma is applied may not contain any explicit @code{return} statements.
+In addition, if the procedure contains any implicit returns from falling
+off the end of a statement sequence, then execution of that implicit
+return will cause Program_Error to be raised.
+
+One use of this pragma is to identify procedures whose only purpose is to raise
+an exception. Another use of this pragma is to suppress incorrect warnings
+about missing returns in functions, where the last statement of a function
statement sequence is a call to such a procedure.
+Note that in Ada 2005 mode, this pragma is part of the language, and is
+identical in effect to the pragma as implemented in Ada 95 mode.
+
+@node Pragma No_Strict_Aliasing
+@unnumberedsec Pragma No_Strict_Aliasing
+@findex No_Strict_Aliasing
+@noindent
+Syntax:
+
+@smallexample @c ada
+pragma No_Strict_Aliasing [([Entity =>] type_LOCAL_NAME)];
+@end smallexample
+
+@noindent
+@var{type_LOCAL_NAME} must refer to an access type
+declaration in the current declarative part. The effect is to inhibit
+strict aliasing optimization for the given type. The form with no
+arguments is a configuration pragma which applies to all access types
+declared in units to which the pragma applies. For a detailed
+description of the strict aliasing optimization, and the situations
+in which it must be suppressed, see section
+``Optimization and Strict Aliasing'' in the @value{EDITION} User's Guide.
+
+@node Pragma Normalize_Scalars
+@unnumberedsec Pragma Normalize_Scalars
+@findex Normalize_Scalars
+@noindent
+Syntax:
+
+@smallexample @c ada
+pragma Normalize_Scalars;
+@end smallexample
+
+@noindent
+This is a language defined pragma which is fully implemented in GNAT@. The
+effect is to cause all scalar objects that are not otherwise initialized
+to be initialized. The initial values are implementation dependent and
+are as follows:
+
+@table @code
+@item Standard.Character
+@noindent
+Objects whose root type is Standard.Character are initialized to
+Character'Last unless the subtype range excludes NUL (in which case
+NUL is used). This choice will always generate an invalid value if
+one exists.
+
+@item Standard.Wide_Character
+@noindent
+Objects whose root type is Standard.Wide_Character are initialized to
+Wide_Character'Last unless the subtype range excludes NUL (in which case
+NUL is used). This choice will always generate an invalid value if
+one exists.
+
+@item Standard.Wide_Wide_Character
+@noindent
+Objects whose root type is Standard.Wide_Wide_Character are initialized to
+the invalid value 16#FFFF_FFFF# unless the subtype range excludes NUL (in
+which case NUL is used). This choice will always generate an invalid value if
+one exists.
+
+@item Integer types
+@noindent
+Objects of an integer type are treated differently depending on whether
+negative values are present in the subtype. If no negative values are
+present, then all one bits is used as the initial value except in the
+special case where zero is excluded from the subtype, in which case
+all zero bits are used. This choice will always generate an invalid
+value if one exists.
+
+For subtypes with negative values present, the largest negative number
+is used, except in the unusual case where this largest negative number
+is in the subtype, and the largest positive number is not, in which case
+the largest positive value is used. This choice will always generate
+an invalid value if one exists.
+
+@item Floating-Point Types
+Objects of all floating-point types are initialized to all 1-bits. For
+standard IEEE format, this corresponds to a NaN (not a number) which is
+indeed an invalid value.
+
+@item Fixed-Point Types
+Objects of all fixed-point types are treated as described above for integers,
+with the rules applying to the underlying integer value used to represent
+the fixed-point value.
+
+@item Modular types
+Objects of a modular type are initialized to all one bits, except in
+the special case where zero is excluded from the subtype, in which
+case all zero bits are used. This choice will always generate an
+invalid value if one exists.
+
+@item Enumeration types
+Objects of an enumeration type are initialized to all one-bits, i.e.@: to
+the value @code{2 ** typ'Size - 1} unless the subtype excludes the literal
+whose Pos value is zero, in which case a code of zero is used. This choice
+will always generate an invalid value if one exists.
+
+@end table
+
+@node Pragma Obsolescent
+@unnumberedsec Pragma Obsolescent
+@findex Obsolescent
+@noindent
+Syntax:
+
+@smallexample @c ada
+pragma Obsolescent
+ (Entity => NAME [, static_string_EXPRESSION [,Ada_05]]);
+@end smallexample
+
+@noindent
+This pragma can occur immediately following a declaration of an entity,
+including the case of a record component, and usually the Entity name
+must match the name of the entity declared by this declaration.
+Alternatively, the pragma can immediately follow an
+enumeration type declaration, where the entity argument names one of the
+enumeration literals.
+
+This pragma is used to indicate that the named entity
+is considered obsolescent and should not be used. Typically this is
+used when an API must be modified by eventually removing or modifying
+existing subprograms or other entities. The pragma can be used at an
+intermediate stage when the entity is still present, but will be
+removed later.
+
+The effect of this pragma is to output a warning message on
+a call to a program thus marked that the
+subprogram is obsolescent if the appropriate warning option in the
+compiler is activated. If the string parameter is present, then a second
+warning message is given containing this text.
+In addition, a call to such a program is considered a violation of
+pragma Restrictions (No_Obsolescent_Features).
+
+This pragma can also be used as a program unit pragma for a package,
+in which case the entity name is the name of the package, and the
+pragma indicates that the entire package is considered
+obsolescent. In this case a client @code{with}'ing such a package
+violates the restriction, and the @code{with} statement is
+flagged with warnings if the warning option is set.
+
+If the optional third parameter is present (which must be exactly
+the identifier Ada_05, no other argument is allowed), then the
+indication of obsolescence applies only when compiling in Ada 2005
+mode. This is primarily intended for dealing with the situations
+in the predefined library where subprograms or packages
+have become defined as obsolescent in Ada 2005
+(e.g. in Ada.Characters.Handling), but may be used anywhere.
+
+The following examples show typical uses of this pragma:
+
+@smallexample @c ada
+package p is
+ pragma Obsolescent
+ (Entity => p, "use pp instead of p");
+end p;
+
+package q is
+ procedure q2;
+ pragma Obsolescent
+ (Entity => q2, "use q2new instead");
+
+ type R is new integer;
+ pragma Obsolescent
+ (Entity => R, "use RR in Ada 2005", Ada_05);
+
+ type M is record
+ F1 : Integer;
+ F2 : Integer;
+ pragma Obsolescent (Entity => F2);
+ F3 : Integer;
+ end record;
+
+ type E is (a, bc, 'd', quack);
+ pragma Obsolescent (Entity => bc)
+ pragma Obsolescent (Entity => 'd')
+
+ function "+"
+ (a, b : character) return character;
+ pragma Obsolescent (Entity => "+");
+end;
+@end smallexample
+
+@noindent
+In an earlier version of GNAT, the Entity parameter was not required,
+and this form is still accepted for compatibility purposes. If the
+Entity parameter is omitted, then the pragma applies to the declaration
+immediately preceding the pragma (this form cannot be used for the
+enumeration literal case).
+
+@node Pragma Passive
+@unnumberedsec Pragma Passive
@findex Passive
-@item pragma Passive
@noindent
Syntax:
-@smallexample
-pragma Passive ([Semaphore | No]);
+@smallexample @c ada
+pragma Passive [(Semaphore | No)];
@end smallexample
@noindent
Syntax checked, but otherwise ignored by GNAT@. This is recognized for
compatibility with DEC Ada 83 implementations, where it is used within a
task definition to request that a task be made passive. If the argument
-@code{Semaphore} is present, or no argument is omitted, then DEC Ada 83
+@code{Semaphore} is present, or the argument is omitted, then DEC Ada 83
treats the pragma as an assertion that the containing task is passive
and that optimization of context switch with this task is permitted and
desired. If the argument @code{No} is present, the task must not be
optimized. GNAT does not attempt to optimize any tasks in this manner
(since protected objects are available in place of passive tasks).
-@findex Polling
-@item pragma Polling
+@node Pragma Persistent_BSS
+@unnumberedsec Pragma Persistent_BSS
+@findex Persistent_BSS
@noindent
Syntax:
-@smallexample
+@smallexample @c ada
+pragma Persistent_BSS [(local_NAME)]
+@end smallexample
+
+@noindent
+This pragma allows selected objects to be placed in the @code{.persistent_bss}
+section. On some targets the linker and loader provide for special
+treatment of this section, allowing a program to be reloaded without
+affecting the contents of this data (hence the name persistent).
+
+There are two forms of usage. If an argument is given, it must be the
+local name of a library level object, with no explicit initialization
+and whose type is potentially persistent. If no argument is given, then
+the pragma is a configuration pragma, and applies to all library level
+objects with no explicit initialization of potentially persistent types.
+
+A potentially persistent type is a scalar type, or a non-tagged,
+non-discriminated record, all of whose components have no explicit
+initialization and are themselves of a potentially persistent type,
+or an array, all of whose constraints are static, and whose component
+type is potentially persistent.
+
+If this pragma is used on a target where this feature is not supported,
+then the pragma will be ignored. See also @code{pragma Linker_Section}.
+
+@node Pragma Polling
+@unnumberedsec Pragma Polling
+@findex Polling
+@noindent
+Syntax:
+
+@smallexample @c ada
pragma Polling (ON | OFF);
@end smallexample
the routine @code{Ada.Exceptions.Poll}. This routine is a separate unit in the
runtime library, and can be found in file @file{a-excpol.adb}.
-Pragma @code{Polling} can appear as a configuration pragma (for example it can be
-placed in the @file{gnat.adc} file) to enable polling globally, or it can be used
-in the statement or declaration sequence to control polling more locally.
+Pragma @code{Polling} can appear as a configuration pragma (for example it
+can be placed in the @file{gnat.adc} file) to enable polling globally, or it
+can be used in the statement or declaration sequence to control polling
+more locally.
A call to the polling routine is generated at the start of every loop and
at the start of every subprogram call. This guarantees that the @code{Poll}
routine is called frequently, and places an upper bound (determined by
the complexity of the code) on the period between two @code{Poll} calls.
-The primary purpose of the polling interface is to enable asynchronous
+The primary purpose of the polling interface is to enable asynchronous
aborts on targets that cannot otherwise support it (for example Windows
NT), but it may be used for any other purpose requiring periodic polling.
The standard version is null, and can be replaced by a user program. This
-will require re-compilation of the @code{Ada.Exceptions} package that can be found
-in files @file{a-except.ads} and @file{a-except.adb}.
+will require re-compilation of the @code{Ada.Exceptions} package that can
+be found in files @file{a-except.ads} and @file{a-except.adb}.
A standard alternative unit (in file @file{4wexcpol.adb} in the standard GNAT
distribution) is used to enable the asynchronous abort capability on
-targets that do not normally support the capability. The version of @code{Poll}
-in this file makes a call to the appropriate runtime routine to test for
-an abort condition.
+targets that do not normally support the capability. The version of
+@code{Poll} in this file makes a call to the appropriate runtime routine
+to test for an abort condition.
Note that polling can also be enabled by use of the @code{-gnatP} switch. See
the @cite{GNAT User's Guide} for details.
-@findex Propagate_Exceptions
-@cindex Zero Cost Exceptions
-@item pragma Propagate_Exceptions
-@noindent
-Syntax:
-
-@smallexample
-pragma Propagate_Exceptions (subprogram_LOCAL_NAME);
-@end smallexample
-
-@noindent
-This pragma indicates that the given entity, which is the name of an
-imported foreign-language subprogram may receive an Ada exception,
-and that the exception should be propagated. It is relevant only if
-zero cost exception handling is in use, and is thus never needed if
-the alternative @code{longjmp} / @code{setjmp} implementation of exceptions is used
-(although it is harmless to use it in such cases).
-
-The implementation of fast exceptions always properly propagates
-exceptions through Ada code, as described in the Ada Reference Manual.
-However, this manual is silent about the propagation of exceptions
-through foreign code. For example, consider the
-situation where @code{P1} calls
-@code{P2}, and @code{P2} calls @code{P3}, where
-@code{P1} and @code{P3} are in Ada, but @code{P2} is in C@.
-@code{P3} raises an Ada exception. The question is whether or not
-it will be propagated through @code{P2} and can be handled in
-@code{P1}.
-
-For the @code{longjmp} / @code{setjmp} implementation of exceptions, the answer is
-always yes. For some targets on which zero cost exception handling
-is implemented, the answer is also always yes. However, there are
-some targets, notably in the current version all x86 architecture
-targets, in which the answer is that such propagation does not
-happen automatically. If such propagation is required on these
-targets, it is mandatory to use @code{Propagate_Exceptions} to
-name all foreign language routines through which Ada exceptions
-may be propagated.
-
-@findex Psect_Object
-@item pragma Psect_Object
+@node Pragma Profile (Ravenscar)
+@unnumberedsec Pragma Profile (Ravenscar)
+@findex Ravenscar
@noindent
Syntax:
-@smallexample
-pragma Psect_Object
- [Internal =>] LOCAL_NAME,
- [, [External =>] EXTERNAL_SYMBOL]
- [, [Size =>] EXTERNAL_SYMBOL]
-
-EXTERNAL_SYMBOL ::=
- IDENTIFIER
-| static_string_EXPRESSION
+@smallexample @c ada
+pragma Profile (Ravenscar);
@end smallexample
@noindent
-This pragma is identical in effect to pragma @code{Common_Object}.
+A configuration pragma that establishes the following set of configuration
+pragmas:
-@findex Pure_Function
-@item pragma Pure_Function
+@table @code
+@item Task_Dispatching_Policy (FIFO_Within_Priorities)
+[RM D.2.2] Tasks are dispatched following a preemptive
+priority-ordered scheduling policy.
+
+@item Locking_Policy (Ceiling_Locking)
+[RM D.3] While tasks and interrupts execute a protected action, they inherit
+the ceiling priority of the corresponding protected object.
+@c
+@c @item Detect_Blocking
+@c This pragma forces the detection of potentially blocking operations within a
+@c protected operation, and to raise Program_Error if that happens.
+@end table
@noindent
-Syntax:
-@smallexample
-pragma Pure_Function ([Entity =>] function_LOCAL_NAME);
-@end smallexample
+plus the following set of restrictions:
-This pragma appears in the same declarative part as a function
-declaration (or a set of function declarations if more than one
-overloaded declaration exists, in which case the pragma applies
-to all entities). If specifies that the function @code{Entity} is
-to be considered pure for the purposes of code generation. This means
-that the compiler can assume that there are no side effects, and
-in particular that two calls with identical arguments produce the
-same result. It also means that the function can be used in an
-address clause.
+@table @code
+@item Max_Entry_Queue_Length = 1
+Defines the maximum number of calls that are queued on a (protected) entry.
+Note that this restrictions is checked at run time. Violation of this
+restriction results in the raising of Program_Error exception at the point of
+the call. For the Profile (Ravenscar) the value of Max_Entry_Queue_Length is
+always 1 and hence no task can be queued on a protected entry.
-Note that, quite deliberately, there are no static checks to try
-to ensure that this promise is met, so @code{Pure_Function} can be used
-with functions that are conceptually pure, even if they do modify
-global variables. For example, a square root function that is
-instrumented to count the number of times it is called is still
-conceptually pure, and can still be optimized, even though it
-modifies a global variable (the count). Memo functions are another
-example (where a table of previous calls is kept and consulted to
-avoid re-computation).
+@item Max_Protected_Entries = 1
+[RM D.7] Specifies the maximum number of entries per protected type. The
+bounds of every entry family of a protected unit shall be static, or shall be
+defined by a discriminant of a subtype whose corresponding bound is static.
+For the Profile (Ravenscar) the value of Max_Protected_Entries is always 1.
-@findex Pure
-Note: Most functions in a @code{Pure} package are automatically pure, and
-there is no need to use pragma @code{Pure_Function} for such functions. An
-exception is any function that has at least one formal of type
-@code{System.Address} or a type derived from it. Such functions are not
-considered pure by default, since the compiler assumes that the
-@code{Address} parameter may be functioning as a pointer and that the
-referenced data may change even if the address value does not. The use
-of pragma @code{Pure_Function} for such a function will override this default
-assumption, and cause the compiler to treat such a function as pure.
+@item Max_Task_Entries = 0
+[RM D.7] Specifies the maximum number of entries
+per task. The bounds of every entry family
+of a task unit shall be static, or shall be
+defined by a discriminant of a subtype whose
+corresponding bound is static. A value of zero
+indicates that no rendezvous are possible. For
+the Profile (Ravenscar), the value of Max_Task_Entries is always
+0 (zero).
-Note: If pragma @code{Pure_Function} is applied to a renamed function, it
-applies to the underlying renamed function. This can be used to
-disambiguate cases of overloading where some but not all functions
-in a set of overloaded functions are to be designated as pure.
+@item No_Abort_Statements
+[RM D.7] There are no abort_statements, and there are
+no calls to Task_Identification.Abort_Task.
-@findex Ravenscar
-@item pragma Ravenscar
-@noindent
-Syntax:
-
-@smallexample
-pragma Ravenscar
-@end smallexample
-
-@noindent
-A configuration pragma that establishes the following set of restrictions:
-
-@table @code
-@item No_Abort_Statements
-[RM D.7] There are no abort_statements, and there are
-no calls to Task_Identification.Abort_Task.
-
-@item No_Select_Statements
-There are no select_statements.
+@item No_Asynchronous_Control
+[RM D.7] There are no semantic dependences on the package
+Asynchronous_Task_Control.
-@item No_Task_Hierarchy
-[RM D.7] All (non-environment) tasks depend
-directly on the environment task of the partition.
+@item No_Calendar
+There are no semantic dependencies on the package Ada.Calendar.
-@item No_Task_Allocators
-[RM D.7] There are no allocators for task types
-or types containing task subcomponents.
+@item No_Dynamic_Attachment
+There is no call to any of the operations defined in package Ada.Interrupts
+(Is_Reserved, Is_Attached, Current_Handler, Attach_Handler, Exchange_Handler,
+Detach_Handler, and Reference).
@item No_Dynamic_Priorities
[RM D.7] There are no semantic dependencies on the package Dynamic_Priorities.
-@item No_Terminate_Alternatives
-[RM D.7] There are no selective_accepts with terminate_alternatives
+@item No_Implicit_Heap_Allocations
+[RM D.7] No constructs are allowed to cause implicit heap allocation.
-@item No_Dynamic_Interrupts
-There are no semantic dependencies on Ada.Interrupts.
+@item No_Local_Protected_Objects
+Protected objects and access types that designate
+such objects shall be declared only at library level.
@item No_Protected_Type_Allocators
There are no allocators for protected types or
types containing protected subcomponents.
-@item No_Local_Protected_Objects
-Protected objects and access types that designate
-such objects shall be declared only at library level.
-
-@item No_Requeue
-Requeue statements are not allowed.
-
-@item No_Calendar
-There are no semantic dependencies on the package Ada.Calendar.
-
@item No_Relative_Delay
-There are no delay_relative_statements.
-
-@item No_Task_Attributes
-There are no semantic dependencies on the Ada.Task_Attributes package and
-there are no references to the attributes Callable and Terminated [RM 9.9].
+There are no delay_relative statements.
-@item Static_Storage_Size
-The expression for pragma Storage_Size is static.
-
-@item Boolean_Entry_Barriers
-Entry barrier condition expressions shall be boolean
-objects which are declared in the protected type
-which contains the entry.
+@item No_Requeue_Statements
+Requeue statements are not allowed.
-@item Max_Asynchronous_Select_Nesting = 0
-[RM D.7] Specifies the maximum dynamic nesting level of asynchronous_selects.
-A value of zero prevents the use of any asynchronous_select.
+@item No_Select_Statements
+There are no select_statements.
-@item Max_Task_Entries = 0
-[RM D.7] Specifies the maximum number of entries
-per task. The bounds of every entry family
-of a task unit shall be static, or shall be
-defined by a discriminant of a subtype whose
-corresponding bound is static. A value of zero
-indicates that no rendezvous are possible. For
-the Ravenscar pragma, the value of Max_Task_Entries is always
-0 (zero).
+@item No_Task_Allocators
+[RM D.7] There are no allocators for task types
+or types containing task subcomponents.
-@item Max_Protected_Entries = 1
-[RM D.7] Specifies the maximum number of entries per
-protected type. The bounds of every entry family of
-a protected unit shall be static, or shall be defined
-by a discriminant of a subtype whose corresponding
-bound is static. For the Ravenscar pragma the value of
-Max_Protected_Entries is always 1.
+@item No_Task_Attributes_Package
+There are no semantic dependencies on the Ada.Task_Attributes package.
-@item Max_Select_Alternatives = 0
-[RM D.7] Specifies the maximum number of alternatives in a selective_accept.
-For the Ravenscar pragma the value if always 0.
+@item No_Task_Hierarchy
+[RM D.7] All (non-environment) tasks depend
+directly on the environment task of the partition.
@item No_Task_Termination
Tasks which terminate are erroneous.
-@item No_Entry_Queue
-No task can be queued on a protected entry. Note that this restrictions is
-checked at run time. The violation of this restriction generates a
-Program_Error exception.
+@item Simple_Barriers
+Entry barrier condition expressions shall be either static
+boolean expressions or boolean objects which are declared in
+the protected type which contains the entry.
@end table
@noindent
-This set of restrictions corresponds to the definition of the ``Ravenscar
-Profile'' for limited tasking, devised and published by the @cite{International
-Real-Time Ada Workshop}, 1997.
+This set of configuration pragmas and restrictions correspond to the
+definition of the ``Ravenscar Profile'' for limited tasking, devised and
+published by the @cite{International Real-Time Ada Workshop}, 1997,
+and whose most recent description is available at
+@url{http://www-users.cs.york.ac.uk/~burns/ravenscar.ps}.
+
+The original definition of the profile was revised at subsequent IRTAW
+meetings. It has been included in the ISO
+@cite{Guide for the Use of the Ada Programming Language in High
+Integrity Systems}, and has been approved by ISO/IEC/SC22/WG9 for inclusion in
+the next revision of the standard. The formal definition given by
+the Ada Rapporteur Group (ARG) can be found in two Ada Issues (AI-249 and
+AI-305) available at
+@url{http://www.ada-auth.org/cgi-bin/cvsweb.cgi/AIs/AI-00249.TXT} and
+@url{http://www.ada-auth.org/cgi-bin/cvsweb.cgi/AIs/AI-00305.TXT}
+respectively.
The above set is a superset of the restrictions provided by pragma
-@code{Restricted_Run_Time}, it includes six additional restrictions
-(@code{Boolean_Entry_Barriers}, @code{No_Select_Statements},
-@code{No_Calendar}, @code{Static_Storage_Size},
+@code{Profile (Restricted)}, it includes six additional restrictions
+(@code{Simple_Barriers}, @code{No_Select_Statements},
+@code{No_Calendar}, @code{No_Implicit_Heap_Allocations},
@code{No_Relative_Delay} and @code{No_Task_Termination}). This means
-that pragma @code{Ravenscar}, like the pragma @code{Restricted_Run_Time}, automatically
-causes the use of a simplified, more efficient version of the tasking
-run-time system.
+that pragma @code{Profile (Ravenscar)}, like the pragma
+@code{Profile (Restricted)},
+automatically causes the use of a simplified,
+more efficient version of the tasking run-time system.
-@findex Restricted_Run_Time
-@item pragma Restricted_Run_Time
+@node Pragma Profile (Restricted)
+@unnumberedsec Pragma Profile (Restricted)
+@findex Restricted Run Time
@noindent
Syntax:
-@smallexample
-pragma Restricted_Run_Time
+@smallexample @c ada
+pragma Profile (Restricted);
@end smallexample
@noindent
@itemize @bullet
@item No_Abort_Statements
-@item No_Asynchronous_Control
@item No_Entry_Queue
@item No_Task_Hierarchy
@item No_Task_Allocators
@item No_Dynamic_Priorities
@item No_Terminate_Alternatives
-@item No_Dynamic_Interrupts
+@item No_Dynamic_Attachment
@item No_Protected_Type_Allocators
@item No_Local_Protected_Objects
-@item No_Requeue
-@item No_Task_Attributes
+@item No_Requeue_Statements
+@item No_Task_Attributes_Package
@item Max_Asynchronous_Select_Nesting = 0
@item Max_Task_Entries = 0
@item Max_Protected_Entries = 1
version of the run time that provides improved performance for the
limited set of tasking functionality permitted by this set of restrictions.
-@findex Share_Generic
-@item pragma Share_Generic
+@node Pragma Psect_Object
+@unnumberedsec Pragma Psect_Object
+@findex Psect_Object
@noindent
Syntax:
-@smallexample
-pragma Share_Generic (NAME @{, NAME@});
+@smallexample @c ada
+pragma Psect_Object (
+ [Internal =>] local_NAME,
+ [, [External =>] EXTERNAL_SYMBOL]
+ [, [Size =>] EXTERNAL_SYMBOL]);
+
+EXTERNAL_SYMBOL ::=
+ IDENTIFIER
+| static_string_EXPRESSION
@end smallexample
@noindent
-This pragma is recognized for compatibility with other Ada compilers
-but is ignored by GNAT@. GNAT does not provide the capability for
-sharing of generic code. All generic instantiations result in making
-an inlined copy of the template with appropriate substitutions.
+This pragma is identical in effect to pragma @code{Common_Object}.
+@node Pragma Pure_Function
+@unnumberedsec Pragma Pure_Function
+@findex Pure_Function
+@noindent
+Syntax:
+
+@smallexample @c ada
+pragma Pure_Function ([Entity =>] function_local_NAME);
+@end smallexample
+
+@noindent
+This pragma appears in the same declarative part as a function
+declaration (or a set of function declarations if more than one
+overloaded declaration exists, in which case the pragma applies
+to all entities). It specifies that the function @code{Entity} is
+to be considered pure for the purposes of code generation. This means
+that the compiler can assume that there are no side effects, and
+in particular that two calls with identical arguments produce the
+same result. It also means that the function can be used in an
+address clause.
+
+Note that, quite deliberately, there are no static checks to try
+to ensure that this promise is met, so @code{Pure_Function} can be used
+with functions that are conceptually pure, even if they do modify
+global variables. For example, a square root function that is
+instrumented to count the number of times it is called is still
+conceptually pure, and can still be optimized, even though it
+modifies a global variable (the count). Memo functions are another
+example (where a table of previous calls is kept and consulted to
+avoid re-computation).
+
+@findex Pure
+Note: Most functions in a @code{Pure} package are automatically pure, and
+there is no need to use pragma @code{Pure_Function} for such functions. One
+exception is any function that has at least one formal of type
+@code{System.Address} or a type derived from it. Such functions are not
+considered pure by default, since the compiler assumes that the
+@code{Address} parameter may be functioning as a pointer and that the
+referenced data may change even if the address value does not.
+Similarly, imported functions are not considered to be pure by default,
+since there is no way of checking that they are in fact pure. The use
+of pragma @code{Pure_Function} for such a function will override these default
+assumption, and cause the compiler to treat a designated subprogram as pure
+in these cases.
+
+Note: If pragma @code{Pure_Function} is applied to a renamed function, it
+applies to the underlying renamed function. This can be used to
+disambiguate cases of overloading where some but not all functions
+in a set of overloaded functions are to be designated as pure.
+
+If pragma @code{Pure_Function} is applied to a library level function, the
+function is also considered pure from an optimization point of view, but the
+unit is not a Pure unit in the categorization sense. So for example, a function
+thus marked is free to @code{with} non-pure units.
+
+@node Pragma Restriction_Warnings
+@unnumberedsec Pragma Restriction_Warnings
+@findex Restriction_Warnings
+@noindent
+Syntax:
+
+@smallexample @c ada
+pragma Restriction_Warnings
+ (restriction_IDENTIFIER @{, restriction_IDENTIFIER@});
+@end smallexample
+
+@noindent
+This pragma allows a series of restriction identifiers to be
+specified (the list of allowed identifiers is the same as for
+pragma @code{Restrictions}). For each of these identifiers
+the compiler checks for violations of the restriction, but
+generates a warning message rather than an error message
+if the restriction is violated.
+
+@node Pragma Source_File_Name
+@unnumberedsec Pragma Source_File_Name
@findex Source_File_Name
-@item pragma Source_File_Name
@noindent
Syntax:
-@smallexample
+@smallexample @c ada
pragma Source_File_Name (
[Unit_Name =>] unit_NAME,
Spec_File_Name => STRING_LITERAL);
Another form of the @code{Source_File_Name} pragma allows
the specification of patterns defining alternative file naming schemes
-to apply to all files.
+to apply to all files.
-@smallexample
+@smallexample @c ada
pragma Source_File_Name
(Spec_File_Name => STRING_LITERAL
[,Casing => CASING_SPEC]
The default is lower case. Finally the third argument allows for systematic
replacement of any dots in the unit name by the specified string literal.
+A pragma Source_File_Name cannot appear after a
+@ref{Pragma Source_File_Name_Project}.
+
For more details on the use of the @code{Source_File_Name} pragma,
-see the sections ``Using Other File Names'' and
+see the sections ``Using Other File Names'' and
``Alternative File Naming Schemes'' in the @cite{GNAT User's Guide}.
+@node Pragma Source_File_Name_Project
+@unnumberedsec Pragma Source_File_Name_Project
+@findex Source_File_Name_Project
+@noindent
+
+This pragma has the same syntax and semantics as pragma Source_File_Name.
+It is only allowed as a stand alone configuration pragma.
+It cannot appear after a @ref{Pragma Source_File_Name}, and
+most importantly, once pragma Source_File_Name_Project appears,
+no further Source_File_Name pragmas are allowed.
+
+The intention is that Source_File_Name_Project pragmas are always
+generated by the Project Manager in a manner consistent with the naming
+specified in a project file, and when naming is controlled in this manner,
+it is not permissible to attempt to modify this naming scheme using
+Source_File_Name pragmas (which would not be known to the project manager).
+
+@node Pragma Source_Reference
+@unnumberedsec Pragma Source_Reference
@findex Source_Reference
-@item pragma Source_Reference
@noindent
Syntax:
-@smallexample
-pragma Source_Reference (INTEGER_LITERAL,
- STRING_LITERAL);
+@smallexample @c ada
+pragma Source_Reference (INTEGER_LITERAL, STRING_LITERAL);
@end smallexample
@noindent
string expression other than a string literal. This is because its value
is needed for error messages issued by all phases of the compiler.
+@node Pragma Stream_Convert
+@unnumberedsec Pragma Stream_Convert
@findex Stream_Convert
-@item pragma Stream_Convert
@noindent
Syntax:
-@smallexample
+@smallexample @c ada
pragma Stream_Convert (
- [Entity =>] type_LOCAL_NAME,
+ [Entity =>] type_local_NAME,
[Read =>] function_NAME,
- [Write =>] function NAME);
+ [Write =>] function_NAME);
@end smallexample
@noindent
The usage of this attribute is best illustrated by a simple example, taken
from the GNAT implementation of package Ada.Strings.Unbounded:
-@smallexample
+@smallexample @c ada
function To_Unbounded (S : String)
return Unbounded_String
renames To_Unbounded_String;
@end smallexample
@noindent
-The specifications of the referenced functions, as given in the Ada 95
+The specifications of the referenced functions, as given in the Ada
Reference Manual are:
-@smallexample
+@smallexample @c ada
function To_Unbounded_String (Source : String)
return Unbounded_String;
format used for @code{Standard.String}, and this same representation is
expected when a value of this type is read from the stream.
+@node Pragma Style_Checks
+@unnumberedsec Pragma Style_Checks
@findex Style_Checks
-@item pragma Style_Checks
@noindent
Syntax:
-@smallexample
+@smallexample @c ada
pragma Style_Checks (string_LITERAL | ALL_CHECKS |
- On | Off [, LOCAL_NAME]);
+ On | Off [, local_NAME]);
@end smallexample
@noindent
This pragma is used in conjunction with compiler switches to control the
-built in style checking provided by GNAT@. The compiler switches, if set
+built in style checking provided by GNAT@. The compiler switches, if set,
provide an initial setting for the switches, and this pragma may be used
to modify these settings, or the settings may be provided entirely by
the use of the pragma. This pragma can be used anywhere that a pragma
For example the following two methods can be used to enable
layout checking:
-@smallexample
+@itemize @bullet
+@item
+@smallexample @c ada
pragma Style_Checks ("l");
+@end smallexample
+
+@item
+@smallexample
gcc -c -gnatyl @dots{}
@end smallexample
+@end itemize
@noindent
The form ALL_CHECKS activates all standard checks (its use is equivalent
can be used to temporarily disable style checks
as shown in the following example:
-@smallexample
+@smallexample @c ada
@iftex
@leftskip=0cm
@end iftex
@code{On} or @code{Off}. The effect is to turn of semantic style checks
for the specified entity, as shown in the following example:
-@smallexample
+@smallexample @c ada
@iftex
@leftskip=0cm
@end iftex
Rf2 : Integer := ARG; -- OK, no error
@end smallexample
+@node Pragma Subtitle
+@unnumberedsec Pragma Subtitle
@findex Subtitle
-@item pragma Subtitle
@noindent
Syntax:
-@smallexample
+@smallexample @c ada
pragma Subtitle ([Subtitle =>] STRING_LITERAL);
@end smallexample
This pragma is recognized for compatibility with other Ada compilers
but is ignored by GNAT@.
+@node Pragma Suppress
+@unnumberedsec Pragma Suppress
+@findex Suppress
+@noindent
+Syntax:
+
+@smallexample @c ada
+pragma Suppress (Identifier [, [On =>] Name]);
+@end smallexample
+
+@noindent
+This is a standard pragma, and supports all the check names required in
+the RM. It is included here because GNAT recognizes one additional check
+name: @code{Alignment_Check} which can be used to suppress alignment checks
+on addresses used in address clauses. Such checks can also be suppressed
+by suppressing range checks, but the specific use of @code{Alignment_Check}
+allows suppression of alignment checks without suppressing other range checks.
+
+@node Pragma Suppress_All
+@unnumberedsec Pragma Suppress_All
@findex Suppress_All
-@item pragma Suppress_All
@noindent
Syntax:
-@smallexample
+@smallexample @c ada
pragma Suppress_All;
@end smallexample
Ada 83 usage. The use of pragma @code{Suppress (All_Checks)} as a normal
configuration pragma is the preferred usage in GNAT@.
+@node Pragma Suppress_Exception_Locations
+@unnumberedsec Pragma Suppress_Exception_Locations
+@findex Suppress_Exception_Locations
+@noindent
+Syntax:
+
+@smallexample @c ada
+pragma Suppress_Exception_Locations;
+@end smallexample
+
+@noindent
+In normal mode, a raise statement for an exception by default generates
+an exception message giving the file name and line number for the location
+of the raise. This is useful for debugging and logging purposes, but this
+entails extra space for the strings for the messages. The configuration
+pragma @code{Suppress_Exception_Locations} can be used to suppress the
+generation of these strings, with the result that space is saved, but the
+exception message for such raises is null. This configuration pragma may
+appear in a global configuration pragma file, or in a specific unit as
+usual. It is not required that this pragma be used consistently within
+a partition, so it is fine to have some units within a partition compiled
+with this pragma and others compiled in normal mode without it.
+
+@node Pragma Suppress_Initialization
+@unnumberedsec Pragma Suppress_Initialization
@findex Suppress_Initialization
@cindex Suppressing initialization
@cindex Initialization, suppression of
-@item pragma Suppress_Initialization
@noindent
Syntax:
-@smallexample
+@smallexample @c ada
pragma Suppress_Initialization ([Entity =>] type_Name);
@end smallexample
This pragma suppresses any implicit or explicit initialization
associated with the given type name for all variables of this type.
+@node Pragma Task_Info
+@unnumberedsec Pragma Task_Info
@findex Task_Info
-@item pragma Task_Info
@noindent
Syntax
-@smallexample
+@smallexample @c ada
pragma Task_Info (EXPRESSION);
@end smallexample
@code{Priority}) and applies to the task in which it appears. The
argument must be of type @code{System.Task_Info.Task_Info_Type}.
The @code{Task_Info} pragma provides system dependent control over
-aspect of tasking implementation, for example, the ability to map
+aspects of tasking implementation, for example, the ability to map
tasks to specific processors. For details on the facilities available
for the version of GNAT that you are using, see the documentation
in the specification of package System.Task_Info in the runtime
library.
+@node Pragma Task_Name
+@unnumberedsec Pragma Task_Name
@findex Task_Name
-@item pragma Task_Name
@noindent
Syntax
-@smallexample
+@smallexample @c ada
pragma Task_Name (string_EXPRESSION);
@end smallexample
routine @code{Ada.Task_Identification.Image} will return this
string, with a unique task address appended.
-@smallexample
+@smallexample @c ada
-- Example of the use of pragma Task_Name
with Ada.Task_Identification;
task type Task_Typ (Name : access String) is
pragma Task_Name (Name.all);
end Task_Typ;
-
+
task body Task_Typ is
Nam : constant String := Image (Current_Task);
begin
Put_Line ("-->" & Nam (1 .. 14) & "<--");
end Task_Typ;
-
+
type Ptr_Task is access Task_Typ;
Task_Var : Ptr_Task;
end;
@end smallexample
+@node Pragma Task_Storage
+@unnumberedsec Pragma Task_Storage
@findex Task_Storage
-@item pragma Task_Storage
Syntax:
-@smallexample
-pragma Task_Storage
- [Task_Type =>] LOCAL_NAME,
+@smallexample @c ada
+pragma Task_Storage (
+ [Task_Type =>] local_NAME,
[Top_Guard =>] static_integer_EXPRESSION);
@end smallexample
+@noindent
This pragma specifies the length of the guard area for tasks. The guard
area is an additional storage area allocated to a task. A value of zero
means that either no guard area is created or a minimal guard area is
@code{Storage_Size} attribute definition clause is allowed for a task
type.
+@node Pragma Time_Slice
+@unnumberedsec Pragma Time_Slice
@findex Time_Slice
-@item pragma Time_Slice
@noindent
Syntax:
-@smallexample
+@smallexample @c ada
pragma Time_Slice (static_duration_EXPRESSION);
@end smallexample
Note that the effect of this pragma is identical to the effect of the
DEC Ada 83 pragma of the same name when operating under OpenVMS systems.
+@node Pragma Title
+@unnumberedsec Pragma Title
@findex Title
-@item pragma Title
@noindent
Syntax:
-@smallexample
+@smallexample @c ada
pragma Title (TITLING_OPTION [, TITLING OPTION]);
TITLING_OPTION ::=
notation is used, and named and positional notation can be mixed
following the normal rules for procedure calls in Ada.
+@node Pragma Unchecked_Union
+@unnumberedsec Pragma Unchecked_Union
@cindex Unions in C
@findex Unchecked_Union
-@item pragma Unchecked_Union
@noindent
Syntax:
-@smallexample
-pragma Unchecked_Union (first_subtype_LOCAL_NAME)
+@smallexample @c ada
+pragma Unchecked_Union (first_subtype_local_NAME);
@end smallexample
@noindent
-This pragma is used to declare that the specified type should be represented
-in a manner
-equivalent to a C union type, and is intended only for use in
-interfacing with C code that uses union types. In Ada terms, the named
-type must obey the following rules:
-
-@itemize @bullet
-@item
-It is a non-tagged non-limited record type.
-@item
-It has a single discrete discriminant with a default value.
-@item
-The component list consists of a single variant part.
-@item
-Each variant has a component list with a single component.
-@item
-No nested variants are allowed.
-@item
-No component has an explicit default value.
-@item
-No component has a non-static constraint.
-@end itemize
-
-In addition, given a type that meets the above requirements, the
-following restrictions apply to its use throughout the program:
-
-@itemize @bullet
-@item
-The discriminant name can be mentioned only in an aggregate.
-@item
-No subtypes may be created of this type.
-@item
-The type may not be constrained by giving a discriminant value.
-@item
-The type cannot be passed as the actual for a generic formal with a
-discriminant.
-@end itemize
-
-Equality and inequality operations on @code{unchecked_unions} are not
-available, since there is no discriminant to compare and the compiler
-does not even know how many bits to compare. It is implementation
-dependent whether this is detected at compile time as an illegality or
-whether it is undetected and considered to be an erroneous construct. In
-GNAT, a direct comparison is illegal, but GNAT does not attempt to catch
-the composite case (where two composites are compared that contain an
-unchecked union component), so such comparisons are simply considered
-erroneous.
-
-The layout of the resulting type corresponds exactly to a C union, where
-each branch of the union corresponds to a single variant in the Ada
-record. The semantics of the Ada program is not changed in any way by
-the pragma, i.e.@: provided the above restrictions are followed, and no
-erroneous incorrect references to fields or erroneous comparisons occur,
-the semantics is exactly as described by the Ada reference manual.
-Pragma @code{Suppress (Discriminant_Check)} applies implicitly to the
-type and the default convention is C
+This pragma is used to specify a representation of a record type that is
+equivalent to a C union. It was introduced as a GNAT implementation defined
+pragma in the GNAT Ada 95 mode. Ada 2005 includes an extended version of this
+pragma, making it language defined, and GNAT fully implements this extended
+version in all language modes (Ada 83, Ada 95, and Ada 2005). For full
+details, consult the Ada 2005 Reference Manual, section B.3.3.
+@node Pragma Unimplemented_Unit
+@unnumberedsec Pragma Unimplemented_Unit
@findex Unimplemented_Unit
-@item pragma Unimplemented_Unit
@noindent
Syntax:
-@smallexample
+@smallexample @c ada
pragma Unimplemented_Unit;
@end smallexample
The abort only happens if code is being generated. Thus you can use
specs of unimplemented packages in syntax or semantic checking mode.
+@node Pragma Universal_Aliasing
+@unnumberedsec Pragma Universal_Aliasing
+@findex Universal_Aliasing
+@noindent
+Syntax:
+
+@smallexample @c ada
+pragma Universal_Aliasing [([Entity =>] type_LOCAL_NAME)];
+@end smallexample
+
+@noindent
+@var{type_LOCAL_NAME} must refer to a type declaration in the current
+declarative part. The effect is to inhibit strict type-based aliasing
+optimization for the given type. In other words, the effect is as though
+access types designating this type were subject to pragma No_Strict_Aliasing.
+For a detailed description of the strict aliasing optimization, and the
+situations in which it must be suppressed, see section
+``Optimization and Strict Aliasing'' in the @value{EDITION} User's Guide.
+
+@node Pragma Universal_Data
+@unnumberedsec Pragma Universal_Data
+@findex Universal_Data
+@noindent
+Syntax:
+
+@smallexample @c ada
+pragma Universal_Data [(library_unit_Name)];
+@end smallexample
+
+@noindent
+This pragma is supported only for the AAMP target and is ignored for
+other targets. The pragma specifies that all library-level objects
+(Counter 0 data) associated with the library unit are to be accessed
+and updated using universal addressing (24-bit addresses for AAMP5)
+rather than the default of 16-bit Data Environment (DENV) addressing.
+Use of this pragma will generally result in less efficient code for
+references to global data associated with the library unit, but
+allows such data to be located anywhere in memory. This pragma is
+a library unit pragma, but can also be used as a configuration pragma
+(including use in the @file{gnat.adc} file). The functionality
+of this pragma is also available by applying the -univ switch on the
+compilations of units where universal addressing of the data is desired.
+
+@node Pragma Unreferenced
+@unnumberedsec Pragma Unreferenced
@findex Unreferenced
-@item pragma Unreferenced
@cindex Warnings, unreferenced
@noindent
Syntax:
-@smallexample
-pragma Unreferenced (local_Name @{, local_Name@});
+@smallexample @c ada
+pragma Unreferenced (local_NAME @{, local_NAME@});
+pragma Unreferenced (library_unit_NAME @{, library_unit_NAME@});
@end smallexample
@noindent
This pragma signals that the entities whose names are listed are
-deliberately not referenced. This suppresses warnings about the
+deliberately not referenced in the current source unit. This
+suppresses warnings about the
entities being unreferenced, and in addition a warning will be
-generated if one of these entities is in fact referenced.
+generated if one of these entities is in fact referenced in the
+same unit as the pragma (or in the corresponding body, or one
+of its subunits).
-This is particularly useful for clearly signalling that a particular
+This is particularly useful for clearly signaling that a particular
parameter is not referenced in some particular subprogram implementation
and that this is deliberate. It can also be useful in the case of
objects declared only for their initialization or finalization side
effects.
-If @code{local_Name} identifies more than one matching homonym in the
+If @code{local_NAME} identifies more than one matching homonym in the
current scope, then the entity most recently declared is the one to which
-the pragma applies.
+the pragma applies. Note that in the case of accept formals, the pragma
+Unreferenced may appear immediately after the keyword @code{do} which
+allows the indication of whether or not accept formals are referenced
+or not to be given individually for each accept statement.
+
+The left hand side of an assignment does not count as a reference for the
+purpose of this pragma. Thus it is fine to assign to an entity for which
+pragma Unreferenced is given.
+
+Note that if a warning is desired for all calls to a given subprogram,
+regardless of whether they occur in the same unit as the subprogram
+declaration, then this pragma should not be used (calls from another
+unit would not be flagged); pragma Obsolescent can be used instead
+for this purpose, see @xref{Pragma Obsolescent}.
+
+The second form of pragma @code{Unreferenced} is used within a context
+clause. In this case the arguments must be unit names of units previously
+mentioned in @code{with} clauses (similar to the usage of pragma
+@code{Elaborate_All}. The effect is to suppress warnings about unreferenced
+units.
+
+@node Pragma Unreferenced_Objects
+@unnumberedsec Pragma Unreferenced_Objects
+@findex Unreferenced_Objects
+@cindex Warnings, unreferenced
+@noindent
+Syntax:
+
+@smallexample @c ada
+pragma Unreferenced_Objects (local_subtype_NAME @{, local_subtype_NAME@});
+@end smallexample
+
+@noindent
+This pragma signals that for the types or subtypes whose names are
+listed, objects which are declared with one of these types or subtypes may
+not be referenced, and if no references appear, no warnings are given.
+
+This is particularly useful for objects which are declared solely for their
+initialization and finalization effect. Such variables are sometimes referred
+to as RAII variables (Resource Acquisition Is Initialization). Using this
+pragma on the relevant type (most typically a limited controlled type), the
+compiler will automatically suppress unwanted warnings about these variables
+not being referenced.
+@node Pragma Unreserve_All_Interrupts
+@unnumberedsec Pragma Unreserve_All_Interrupts
@findex Unreserve_All_Interrupts
-@item pragma Unreserve_All_Interrupts
@noindent
Syntax:
-@smallexample
+@smallexample @c ada
pragma Unreserve_All_Interrupts;
@end smallexample
Normally certain interrupts are reserved to the implementation. Any attempt
to attach an interrupt causes Program_Error to be raised, as described in
RM C.3.2(22). A typical example is the @code{SIGINT} interrupt used in
-many systems for an @kbd{Ctrl-C} interrupt. Normally this interrupt is
+many systems for a @kbd{Ctrl-C} interrupt. Normally this interrupt is
reserved to the implementation, so that @kbd{Ctrl-C} can be used to
interrupt execution.
this file also specifies what interrupts are affected by the use of
the @code{Unreserve_All_Interrupts} pragma.
+For a more general facility for controlling what interrupts can be
+handled, see pragma @code{Interrupt_State}, which subsumes the functionality
+of the @code{Unreserve_All_Interrupts} pragma.
+
+@node Pragma Unsuppress
+@unnumberedsec Pragma Unsuppress
@findex Unsuppress
-@item pragma Unsuppress
@noindent
Syntax:
-@smallexample
+@smallexample @c ada
pragma Unsuppress (IDENTIFIER [, [On =>] NAME]);
@end smallexample
will compile correctly even if the compiler switches are set to suppress
checks.
+@node Pragma Use_VADS_Size
+@unnumberedsec Pragma Use_VADS_Size
@cindex @code{Size}, VADS compatibility
@findex Use_VADS_Size
-@item pragma Use_VADS_Size
@noindent
Syntax:
-@smallexample
+@smallexample @c ada
pragma Use_VADS_Size;
@end smallexample
This is a configuration pragma. In a unit to which it applies, any use
of the 'Size attribute is automatically interpreted as a use of the
'VADS_Size attribute. Note that this may result in incorrect semantic
-processing of valid Ada 95 programs. This is intended to aid in the
-handling of legacy code which depends on the interpretation of Size
+processing of valid Ada 95 or Ada 2005 programs. This is intended to aid in
+the handling of existing code which depends on the interpretation of Size
as implemented in the VADS compiler. See description of the VADS_Size
attribute for further details.
+@node Pragma Validity_Checks
+@unnumberedsec Pragma Validity_Checks
@findex Validity_Checks
-@item pragma Validity_Checks
@noindent
Syntax:
-@smallexample
+@smallexample @c ada
pragma Validity_Checks (string_LITERAL | ALL_CHECKS | On | Off);
@end smallexample
@noindent
This pragma is used in conjunction with compiler switches to control the
-built in validity checking provided by GNAT@. The compiler switches, if set
+built-in validity checking provided by GNAT@. The compiler switches, if set
provide an initial setting for the switches, and this pragma may be used
to modify these settings, or the settings may be provided entirely by
the use of the pragma. This pragma can be used anywhere that a pragma
can be used to enable validity checking for mode @code{in} and
@code{in out} subprogram parameters:
-@smallexample
+@itemize @bullet
+@item
+@smallexample @c ada
pragma Validity_Checks ("im");
+@end smallexample
+
+@item
+@smallexample
gcc -c -gnatVim @dots{}
@end smallexample
+@end itemize
@noindent
The form ALL_CHECKS activates all standard checks (its use is equivalent
can be used to temporarily disable validity checks
as shown in the following example:
-@smallexample
+@smallexample @c ada
@iftex
@leftskip=0cm
@end iftex
A := C; -- C will be validity checked
@end smallexample
+@node Pragma Volatile
+@unnumberedsec Pragma Volatile
@findex Volatile
-@item pragma Volatile
@noindent
Syntax:
-@smallexample
-pragma Volatile (local_NAME)
+@smallexample @c ada
+pragma Volatile (local_NAME);
@end smallexample
@noindent
-This pragma is defined by the Ada 95 Reference Manual, and the GNAT
+This pragma is defined by the Ada Reference Manual, and the GNAT
implementation is fully conformant with this definition. The reason it
is mentioned in this section is that a pragma of the same name was supplied
-in some Ada 83 compilers, including DEC Ada 83. The Ada 95 implementation
-of pragma Volatile is upwards compatible with the implementation in
-Dec Ada 83.
+in some Ada 83 compilers, including DEC Ada 83. The Ada 95 / Ada 2005
+implementation of pragma Volatile is upwards compatible with the
+implementation in DEC Ada 83.
+@node Pragma Warnings
+@unnumberedsec Pragma Warnings
@findex Warnings
-@item pragma Warnings
@noindent
Syntax:
-@smallexample
-pragma Warnings (On | Off [, LOCAL_NAME]);
+@smallexample @c ada
+pragma Warnings (On | Off);
+pragma Warnings (On | Off, local_NAME);
+pragma Warnings (static_string_EXPRESSION);
+pragma Warnings (On | Off, static_string_EXPRESSION);
@end smallexample
@noindent
pragma, then no warning messages are output, regardless of the
setting of the command line switches.
-The form with a single argument is a configuration pragma.
+The form with a single argument may be used as a configuration pragma.
-If the @var{local_name} parameter is present, warnings are suppressed for
+If the @var{local_NAME} parameter is present, warnings are suppressed for
the specified entity. This suppression is effective from the point where
it occurs till the end of the extended scope of the variable (similar to
the scope of @code{Suppress}).
+The form with a single static_string_EXPRESSION argument provides more precise
+control over which warnings are active. The string is a list of letters
+specifying which warnings are to be activated and which deactivated. The
+code for these letters is the same as the string used in the command
+line switch controlling warnings. The following is a brief summary. For
+full details see the GNAT Users Guide:
+
+@smallexample
+a turn on all optional warnings (except d,h,l)
+A turn off all optional warnings
+b turn on warnings for bad fixed value (not multiple of small)
+B turn off warnings for bad fixed value (not multiple of small)
+c turn on warnings for constant conditional
+C turn off warnings for constant conditional
+d turn on warnings for implicit dereference
+D turn off warnings for implicit dereference
+e treat all warnings as errors
+f turn on warnings for unreferenced formal
+F turn off warnings for unreferenced formal
+g turn on warnings for unrecognized pragma
+G turn off warnings for unrecognized pragma
+h turn on warnings for hiding variable
+H turn off warnings for hiding variable
+i turn on warnings for implementation unit
+I turn off warnings for implementation unit
+j turn on warnings for obsolescent (annex J) feature
+J turn off warnings for obsolescent (annex J) feature
+k turn on warnings on constant variable
+K turn off warnings on constant variable
+l turn on warnings for missing elaboration pragma
+L turn off warnings for missing elaboration pragma
+m turn on warnings for variable assigned but not read
+M turn off warnings for variable assigned but not read
+n normal warning mode (cancels -gnatws/-gnatwe)
+o turn on warnings for address clause overlay
+O turn off warnings for address clause overlay
+p turn on warnings for ineffective pragma Inline
+P turn off warnings for ineffective pragma Inline
+q turn on warnings for questionable missing parentheses
+Q turn off warnings for questionable missing parentheses
+r turn on warnings for redundant construct
+R turn off warnings for redundant construct
+s suppress all warnings
+t turn on warnings for tracking deleted code
+T turn off warnings for tracking deleted code
+u turn on warnings for unused entity
+U turn off warnings for unused entity
+v turn on warnings for unassigned variable
+V turn off warnings for unassigned variable
+w turn on warnings for wrong low bound assumption
+W turn off warnings for wrong low bound assumption
+x turn on warnings for export/import
+X turn off warnings for export/import
+y turn on warnings for Ada 2005 incompatibility
+Y turn off warnings for Ada 2005 incompatibility
+z turn on size/align warnings for unchecked conversion
+Z turn off size/align warnings for unchecked conversion
+@end smallexample
+
+@noindent
+The specified warnings will be in effect until the end of the program
+or another pragma Warnings is encountered. The effect of the pragma is
+cumulative. Initially the set of warnings is the standard default set
+as possibly modified by compiler switches. Then each pragma Warning
+modifies this set of warnings as specified. This form of the pragma may
+also be used as a configuration pragma.
+
+The fourth form, with an On|Off parameter and a string, is used to
+control individual messages, based on their text. The string argument
+is a pattern that is used to match against the text of individual
+warning messages (not including the initial "warnings: " tag).
+
+The pattern may start with an asterisk, which matches otherwise unmatched
+characters at the start of the message, and it may also end with an asterisk
+which matches otherwise unmatched characters at the end of the message. For
+example, the string "*alignment*" could be used to match any warnings about
+alignment problems. Within the string, the sequence "*" can be used to match
+any sequence of characters enclosed in quotation marks. No other regular
+expression notations are permitted. All characters other than asterisk in
+these three specific cases are treated as literal characters in the match.
+
+There are two ways to use this pragma. The OFF form can be used as a
+configuration pragma. The effect is to suppress all warnings (if any)
+that match the pattern string throughout the compilation.
+
+The second usage is to suppress a warning locally, and in this case, two
+pragmas must appear in sequence:
+
+@smallexample @c ada
+pragma Warnings (Off, Pattern);
+.. code where given warning is to be suppressed
+pragma Warnings (On, Pattern);
+@end smallexample
+
+@noindent
+In this usage, the pattern string must match in the Off and On pragmas,
+and at least one matching warning must be suppressed.
+
+@node Pragma Weak_External
+@unnumberedsec Pragma Weak_External
@findex Weak_External
-@item pragma Weak_External
@noindent
Syntax:
-@smallexample
-pragma Weak_External ([Entity =>] LOCAL_NAME);
+@smallexample @c ada
+pragma Weak_External ([Entity =>] local_NAME);
@end smallexample
@noindent
-This pragma specifies that the given entity should be marked as a weak
-external (one that does not have to be resolved) for the linker. For
-further details, consult the GCC manual.
-@end table
+@var{local_NAME} must refer to an object that is declared at the library
+level. This pragma specifies that the given entity should be marked as a
+weak symbol for the linker. It is equivalent to @code{__attribute__((weak))}
+in GNU C and causes @var{local_NAME} to be emitted as a weak symbol instead
+of a regular symbol, that is to say a symbol that does not have to be
+resolved by the linker if used in conjunction with a pragma Import.
+
+When a weak symbol is not resolved by the linker, its address is set to
+zero. This is useful in writing interfaces to external modules that may
+or may not be linked in the final executable, for example depending on
+configuration settings.
+
+If a program references at run time an entity to which this pragma has been
+applied, and the corresponding symbol was not resolved at link time, then
+the execution of the program is erroneous. It is not erroneous to take the
+Address of such an entity, for example to guard potential references,
+as shown in the example below.
+
+Some file formats do not support weak symbols so not all target machines
+support this pragma.
+
+@smallexample @c ada
+-- Example of the use of pragma Weak_External
+
+package External_Module is
+ key : Integer;
+ pragma Import (C, key);
+ pragma Weak_External (key);
+ function Present return boolean;
+end External_Module;
+
+with System; use System;
+package body External_Module is
+ function Present return boolean is
+ begin
+ return key'Address /= System.Null_Address;
+ end Present;
+end External_Module;
+@end smallexample
+
+@node Pragma Wide_Character_Encoding
+@unnumberedsec Pragma Wide_Character_Encoding
+@findex Wide_Character_Encoding
+@noindent
+Syntax:
+
+@smallexample @c ada
+pragma Wide_Character_Encoding (IDENTIFIER | CHARACTER_LITERAL);
+@end smallexample
+
+@noindent
+This pragma specifies the wide character encoding to be used in program
+source text appearing subsequently. It is a configuration pragma, but may
+also be used at any point that a pragma is allowed, and it is permissible
+to have more than one such pragma in a file, allowing multiple encodings
+to appear within the same file.
+
+The argument can be an identifier or a character literal. In the identifier
+case, it is one of @code{HEX}, @code{UPPER}, @code{SHIFT_JIS},
+@code{EUC}, @code{UTF8}, or @code{BRACKETS}. In the character literal
+case it is correspondingly one of the characters h,u,s,e,8,b.
+
+Note that when the pragma is used within a file, it affects only the
+encoding within that file, and does not affect withed units, specs,
+or subunits.
@node Implementation Defined Attributes
@chapter Implementation Defined Attributes
-Ada 95 defines (throughout the Ada 95 reference manual,
-summarized in annex K),
+Ada defines (throughout the Ada reference manual,
+summarized in Annex K),
a set of attributes that provide useful additional functionality in all
areas of the language. These language defined attributes are implemented
-in GNAT and work as described in the Ada 95 Reference Manual.
+in GNAT and work as described in the Ada Reference Manual.
-In addition, Ada 95 allows implementations to define additional
+In addition, Ada allows implementations to define additional
attributes whose meaning is defined by the implementation. GNAT provides
a number of these implementation-dependent attributes which can be used
to extend and enhance the functionality of the compiler. This section of
platforms). Therefore if portability to other compilers is an important
consideration, you should minimize the use of these attributes.
-@table @code
+@menu
+* Abort_Signal::
+* Address_Size::
+* Asm_Input::
+* Asm_Output::
+* AST_Entry::
+* Bit::
+* Bit_Position::
+* Code_Address::
+* Default_Bit_Order::
+* Elaborated::
+* Elab_Body::
+* Elab_Spec::
+* Emax::
+* Enabled::
+* Enum_Rep::
+* Epsilon::
+* Fixed_Value::
+* Has_Access_Values::
+* Has_Discriminants::
+* Img::
+* Integer_Value::
+* Large::
+* Machine_Size::
+* Mantissa::
+* Max_Interrupt_Priority::
+* Max_Priority::
+* Maximum_Alignment::
+* Mechanism_Code::
+* Null_Parameter::
+* Object_Size::
+* Passed_By_Reference::
+* Range_Length::
+* Safe_Emax::
+* Safe_Large::
+* Small::
+* Storage_Unit::
+* Stub_Type::
+* Target_Name::
+* Tick::
+* To_Address::
+* Type_Class::
+* UET_Address::
+* Unconstrained_Array::
+* Universal_Literal_String::
+* Unrestricted_Access::
+* VADS_Size::
+* Value_Size::
+* Wchar_T_Size::
+* Word_Size::
+@end menu
+
+@node Abort_Signal
+@unnumberedsec Abort_Signal
@findex Abort_Signal
-@item Abort_Signal
@noindent
@code{Standard'Abort_Signal} (@code{Standard} is the only allowed
prefix) provides the entity for the special exception used to signal
completely outside the normal semantics of Ada, for a user program to
intercept the abort exception).
+@node Address_Size
+@unnumberedsec Address_Size
@cindex Size of @code{Address}
@findex Address_Size
-@item Address_Size
@noindent
@code{Standard'Address_Size} (@code{Standard} is the only allowed
prefix) is a static constant giving the number of bits in an
-@code{Address}. It is used primarily for constructing the definition of
-@code{Memory_Size} in package @code{Standard}, but may be freely used in user
-programs and has the advantage of being static, while a direct
+@code{Address}. It is the same value as System.Address'Size,
+but has the advantage of being static, while a direct
reference to System.Address'Size is non-static because Address
is a private type.
+@node Asm_Input
+@unnumberedsec Asm_Input
@findex Asm_Input
-@item Asm_Input
@noindent
The @code{Asm_Input} attribute denotes a function that takes two
parameters. The first is a string, the second is an expression of the
the configuration file used to built the GCC back end.
@ref{Machine Code Insertions}
+@node Asm_Output
+@unnumberedsec Asm_Output
@findex Asm_Output
-@item Asm_Output
@noindent
The @code{Asm_Output} attribute denotes a function that takes two
parameters. The first is a string, the second is the name of a variable
either be omitted, or explicitly given as @code{No_Output_Operands}.
@ref{Machine Code Insertions}
+@node AST_Entry
+@unnumberedsec AST_Entry
@cindex OpenVMS
@findex AST_Entry
-@item AST_Entry
@noindent
This attribute is implemented only in OpenVMS versions of GNAT@. Applied to
the name of an entry, it yields a value of the predefined type AST_Handler
be called when an AST occurs. For further details, refer to the @cite{DEC Ada
Language Reference Manual}, section 9.12a.
+@node Bit
+@unnumberedsec Bit
@findex Bit
-@item Bit
@code{@var{obj}'Bit}, where @var{obj} is any object, yields the bit
offset within the storage unit (byte) that contains the first bit of
storage allocated for the object. The value of this attribute is of the
This attribute is designed to be compatible with the DEC Ada 83 definition
and implementation of the @code{Bit} attribute.
+@node Bit_Position
+@unnumberedsec Bit_Position
@findex Bit_Position
-@item Bit_Position
@noindent
@code{@var{R.C}'Bit}, where @var{R} is a record object and C is one
of the fields of the record type, yields the bit
@var{C} and is independent of the alignment of
the containing record @var{R}.
+@node Code_Address
+@unnumberedsec Code_Address
@findex Code_Address
@cindex Subprogram address
@cindex Address of subprogram code
-@item Code_Address
@noindent
The @code{'Address}
-attribute may be applied to subprograms in Ada 95, but the
-intended effect from the Ada 95 reference manual seems to be to provide
+attribute may be applied to subprograms in Ada 95 and Ada 2005, but the
+intended effect seems to be to provide
an address value which can be used to call the subprogram by means of
an address clause as in the following example:
-@smallexample
+@smallexample @c ada
procedure K is @dots{}
procedure L;
@end smallexample
@noindent
-A call to @code{L} is then expected to result in a call to @code{K}@. In Ada 83, where
-there were no access-to-subprogram values, this was a common work around
-for getting the effect of an indirect call.
-GNAT implements the above use of @code{Address} and the technique illustrated
-by the example code works correctly.
+A call to @code{L} is then expected to result in a call to @code{K}@.
+In Ada 83, where there were no access-to-subprogram values, this was
+a common work-around for getting the effect of an indirect call.
+GNAT implements the above use of @code{Address} and the technique
+illustrated by the example code works correctly.
However, for some purposes, it is useful to have the address of the start
of the generated code for the subprogram. On some architectures, this is
-not necessarily the same as the @code{Address} value described above. For example,
-the @code{Address} value may reference a subprogram descriptor rather than the
-subprogram itself.
+not necessarily the same as the @code{Address} value described above.
+For example, the @code{Address} value may reference a subprogram
+descriptor rather than the subprogram itself.
-The @code{'Code_Address} attribute, which can only be applied to
-subprogram entities, always returns the address of the start of the
+The @code{'Code_Address} attribute, which can only be applied to
+subprogram entities, always returns the address of the start of the
generated code of the specified subprogram, which may or may not be
the same value as is returned by the corresponding @code{'Address}
attribute.
+@node Default_Bit_Order
+@unnumberedsec Default_Bit_Order
@cindex Big endian
@cindex Little endian
@findex Default_Bit_Order
-@item Default_Bit_Order
@noindent
@code{Standard'Default_Bit_Order} (@code{Standard} is the only
permissible prefix), provides the value @code{System.Default_Bit_Order}
@code{Low_Order_First}). This is used to construct the definition of
@code{Default_Bit_Order} in package @code{System}.
+@node Elaborated
+@unnumberedsec Elaborated
@findex Elaborated
-@item Elaborated
@noindent
The prefix of the @code{'Elaborated} attribute must be a unit name. The
value is a Boolean which indicates whether or not the given unit has been
elaborated. This attribute is primarily intended for internal use by the
generated code for dynamic elaboration checking, but it can also be used
in user programs. The value will always be True once elaboration of all
-units has been completed.
+units has been completed. An exception is for units which need no
+elaboration, the value is always False for such units.
+@node Elab_Body
+@unnumberedsec Elab_Body
@findex Elab_Body
-@item Elab_Body
@noindent
This attribute can only be applied to a program unit name. It returns
the entity for the corresponding elaboration procedure for elaborating
e.g.@: if it is necessary to do selective re-elaboration to fix some
error.
+@node Elab_Spec
+@unnumberedsec Elab_Spec
@findex Elab_Spec
-@item Elab_Spec
@noindent
This attribute can only be applied to a program unit name. It returns
the entity for the corresponding elaboration procedure for elaborating
Ada code, e.g.@: if it is necessary to do selective re-elaboration to fix
some error.
+@node Emax
+@unnumberedsec Emax
@cindex Ada 83 attributes
@findex Emax
-@item Emax
@noindent
The @code{Emax} attribute is provided for compatibility with Ada 83. See
the Ada 83 reference manual for an exact description of the semantics of
this attribute.
+@node Enabled
+@unnumberedsec Enabled
+@findex Enabled
+@noindent
+The @code{Enabled} attribute allows an application program to check at compile
+time to see if the designated check is currently enabled. The prefix is a
+simple identifier, referencing any predefined check name (other than
+@code{All_Checks}) or a check name introduced by pragma Check_Name. If
+no argument is given for the attribute, the check is for the general state
+of the check, if an argument is given, then it is an entity name, and the
+check indicates whether an @code{Suppress} or @code{Unsuppress} has been
+given naming the entity (if not, then the argument is ignored).
+
+Note that instantiations inherit the check status at the point of the
+instantiation, so a useful idiom is to have a library package that
+introduces a check name with @code{pragma Check_Name}, and then contains
+generic packages or subprograms which use the @code{Enabled} attribute
+to see if the check is enabled. A user of this package can then issue
+a @code{pragma Suppress} or @code{pragma Unsuppress} before instantiating
+the package or subprogram, controlling whether the check will be present.
+
+@node Enum_Rep
+@unnumberedsec Enum_Rep
@cindex Representation of enums
@findex Enum_Rep
-@item Enum_Rep
@noindent
For every enumeration subtype @var{S}, @code{@var{S}'Enum_Rep} denotes a
-function with the following specification:
+function with the following spec:
-@smallexample
+@smallexample @c ada
function @var{S}'Enum_Rep (Arg : @var{S}'Base)
- return Universal_Integer;
+ return @i{Universal_Integer};
@end smallexample
@noindent
It is also allowable to apply @code{Enum_Rep} directly to an object of an
enumeration type or to a non-overloaded enumeration
-literal. In this case @code{@var{S}'Enum_Rep} is equivalent to
+literal. In this case @code{@var{S}'Enum_Rep} is equivalent to
@code{@var{typ}'Enum_Rep(@var{S})} where @var{typ} is the type of the
enumeration literal or object.
absence of an enumeration representation clause. This is a static
attribute (i.e.@: the result is static if the argument is static).
-@code{@var{S}'Enum_Rep} can also be used with integer types and objects, in which
-case it simply returns the integer value. The reason for this is to allow
-it to be used for @code{(<>)} discrete formal arguments in a generic unit that
-can be instantiated with either enumeration types or integer types. Note
-that if @code{Enum_Rep} is used on a modular type whose upper bound exceeds the
-upper bound of the largest signed integer type, and the argument is a
-variable, so that the universal integer calculation is done at run-time,
-then the call to @code{Enum_Rep} may raise @code{Constraint_Error}.
-
+@code{@var{S}'Enum_Rep} can also be used with integer types and objects,
+in which case it simply returns the integer value. The reason for this
+is to allow it to be used for @code{(<>)} discrete formal arguments in
+a generic unit that can be instantiated with either enumeration types
+or integer types. Note that if @code{Enum_Rep} is used on a modular
+type whose upper bound exceeds the upper bound of the largest signed
+integer type, and the argument is a variable, so that the universal
+integer calculation is done at run time, then the call to @code{Enum_Rep}
+may raise @code{Constraint_Error}.
+
+@node Epsilon
+@unnumberedsec Epsilon
@cindex Ada 83 attributes
@findex Epsilon
-@item Epsilon
@noindent
The @code{Epsilon} attribute is provided for compatibility with Ada 83. See
the Ada 83 reference manual for an exact description of the semantics of
this attribute.
+@node Fixed_Value
+@unnumberedsec Fixed_Value
@findex Fixed_Value
-@item Fixed_Value
@noindent
For every fixed-point type @var{S}, @code{@var{S}'Fixed_Value} denotes a
function with the following specification:
-@smallexample
-function @var{S}'Fixed_Value (Arg : Universal_Integer)
+@smallexample @c ada
+function @var{S}'Fixed_Value (Arg : @i{Universal_Integer})
return @var{S};
@end smallexample
@noindent
The value returned is the fixed-point value @var{V} such that
-@smallexample
+@smallexample @c ada
@var{V} = Arg * @var{S}'Small
@end smallexample
@noindent
-The effect is thus equivalent to first converting the argument to the
+The effect is thus similar to first converting the argument to the
integer type used to represent @var{S}, and then doing an unchecked
-conversion to the fixed-point type. This attribute is primarily intended
-for use in implementation of the input-output functions for fixed-point
-values.
+conversion to the fixed-point type. The difference is
+that there are full range checks, to ensure that the result is in range.
+This attribute is primarily intended for use in implementation of the
+input-output functions for fixed-point values.
+
+@node Has_Access_Values
+@unnumberedsec Has_Access_Values
+@cindex Access values, testing for
+@findex Has_Access_Values
+@noindent
+The prefix of the @code{Has_Access_Values} attribute is a type. The result
+is a Boolean value which is True if the is an access type, or is a composite
+type with a component (at any nesting depth) that is an access type, and is
+False otherwise.
+The intended use of this attribute is in conjunction with generic
+definitions. If the attribute is applied to a generic private type, it
+indicates whether or not the corresponding actual type has access values.
+@node Has_Discriminants
+@unnumberedsec Has_Discriminants
@cindex Discriminants, testing for
@findex Has_Discriminants
-@item Has_Discriminants
@noindent
The prefix of the @code{Has_Discriminants} attribute is a type. The result
is a Boolean value which is True if the type has discriminants, and False
definitions. If the attribute is applied to a generic private type, it
indicates whether or not the corresponding actual type has discriminants.
+@node Img
+@unnumberedsec Img
@findex Img
-@item Img
@noindent
The @code{Img} attribute differs from @code{Image} in that it may be
applied to objects as well as types, in which case it gives the
@code{Image} for the subtype of the object. This is convenient for
debugging:
-@smallexample
+@smallexample @c ada
Put_Line ("X = " & X'Img);
@end smallexample
@noindent
has the same meaning as the more verbose:
-@smallexample
-Put_Line ("X = " & @var{type}'Image (X));
+@smallexample @c ada
+Put_Line ("X = " & @var{T}'Image (X));
@end smallexample
-where @var{type} is the subtype of the object X@.
+@noindent
+where @var{T} is the (sub)type of the object @code{X}.
+@node Integer_Value
+@unnumberedsec Integer_Value
@findex Integer_Value
-@item Integer_Value
@noindent
For every integer type @var{S}, @code{@var{S}'Integer_Value} denotes a
-function with the following specification:
+function with the following spec:
-@smallexample
-function @var{S}'Integer_Value (Arg : Universal_Fixed)
+@smallexample @c ada
+function @var{S}'Integer_Value (Arg : @i{Universal_Fixed})
return @var{S};
@end smallexample
@noindent
The value returned is the integer value @var{V}, such that
-@smallexample
-Arg = @var{V} * @var{type}'Small
+@smallexample @c ada
+Arg = @var{V} * @var{T}'Small
@end smallexample
@noindent
-The effect is thus equivalent to first doing an unchecked convert from
+where @var{T} is the type of @code{Arg}.
+The effect is thus similar to first doing an unchecked conversion from
the fixed-point type to its corresponding implementation type, and then
-converting the result to the target integer type. This attribute is
-primarily intended for use in implementation of the standard
-input-output functions for fixed-point values.
+converting the result to the target integer type. The difference is
+that there are full range checks, to ensure that the result is in range.
+This attribute is primarily intended for use in implementation of the
+standard input-output functions for fixed-point values.
+@node Large
+@unnumberedsec Large
@cindex Ada 83 attributes
@findex Large
-@item Large
@noindent
The @code{Large} attribute is provided for compatibility with Ada 83. See
the Ada 83 reference manual for an exact description of the semantics of
this attribute.
+@node Machine_Size
+@unnumberedsec Machine_Size
@findex Machine_Size
-@item Machine_Size
@noindent
This attribute is identical to the @code{Object_Size} attribute. It is
provided for compatibility with the DEC Ada 83 attribute of this name.
-
+
+@node Mantissa
+@unnumberedsec Mantissa
@cindex Ada 83 attributes
@findex Mantissa
-@item Mantissa
@noindent
The @code{Mantissa} attribute is provided for compatibility with Ada 83. See
the Ada 83 reference manual for an exact description of the semantics of
this attribute.
+@node Max_Interrupt_Priority
+@unnumberedsec Max_Interrupt_Priority
@cindex Interrupt priority, maximum
@findex Max_Interrupt_Priority
-@item Max_Interrupt_Priority
@noindent
@code{Standard'Max_Interrupt_Priority} (@code{Standard} is the only
-permissible prefix), provides the value
-@code{System.Max_Interrupt_Priority} and is intended primarily for
-constructing this definition in package @code{System}.
+permissible prefix), provides the same value as
+@code{System.Max_Interrupt_Priority}.
+@node Max_Priority
+@unnumberedsec Max_Priority
@cindex Priority, maximum
@findex Max_Priority
-@item Max_Priority
@noindent
@code{Standard'Max_Priority} (@code{Standard} is the only permissible
-prefix) provides the value @code{System.Max_Priority} and is intended
-primarily for constructing this definition in package @code{System}.
+prefix) provides the same value as @code{System.Max_Priority}.
+@node Maximum_Alignment
+@unnumberedsec Maximum_Alignment
@cindex Alignment, maximum
@findex Maximum_Alignment
-@item Maximum_Alignment
@noindent
@code{Standard'Maximum_Alignment} (@code{Standard} is the only
permissible prefix) provides the maximum useful alignment value for the
target. This is a static value that can be used to specify the alignment
for an object, guaranteeing that it is properly aligned in all
-cases. This is useful when an external object is imported and its
-alignment requirements are unknown.
+cases.
+@node Mechanism_Code
+@unnumberedsec Mechanism_Code
@cindex Return values, passing mechanism
@cindex Parameters, passing mechanism
@findex Mechanism_Code
-@item Mechanism_Code
@noindent
@code{@var{function}'Mechanism_Code} yields an integer code for the
mechanism used for the result of function, and
by descriptor (NCA: non-contiguous array)
@end table
-@cindex OpenVMS
+@noindent
Values from 3 through 10 are only relevant to Digital OpenVMS implementations.
+@cindex OpenVMS
+@node Null_Parameter
+@unnumberedsec Null_Parameter
@cindex Zero address, passing
@findex Null_Parameter
-@item Null_Parameter
@noindent
A reference @code{@var{T}'Null_Parameter} denotes an imaginary object of
type or subtype @var{T} allocated at machine address zero. The attribute
There is no way of indicating this without the @code{Null_Parameter}
attribute.
+@node Object_Size
+@unnumberedsec Object_Size
@cindex Size, used for objects
@findex Object_Size
-@item Object_Size
@noindent
The size of an object is not necessarily the same as the size of the type
of an object. This is because by default object sizes are increased to be
-a multiple of the alignment of the object. For example,
+a multiple of the alignment of the object. For example,
@code{Natural'Size} is
31, but by default objects of type @code{Natural} will have a size of 32 bits.
Similarly, a record containing an integer and a character:
-@smallexample
+@smallexample @c ada
type Rec is record
I : Integer;
C : Character;
@end smallexample
@noindent
-will have a size of 40 (that is @code{Rec'Size} will be 40. The
+will have a size of 40 (that is @code{Rec'Size} will be 40. The
alignment will be 4, because of the
integer field, and so the default size of record objects for this type
will be 64 (8 bytes).
@code{Natural'Object_Size} is 32, and
@code{Rec'Object_Size} (for the record type in the above example) will be
64. Note also that, unlike the situation with the
-@code{Size} attribute as defined in the Ada RM, the
+@code{Size} attribute as defined in the Ada RM, the
@code{Object_Size} attribute can be specified individually
for different subtypes. For example:
-@smallexample
+@smallexample @c ada
type R is new Integer;
subtype R1 is R range 1 .. 10;
subtype R2 is R range 1 .. 10;
@code{R2} will be only
8 bits (one byte), since @code{R2'Object_Size} has been set to 8.
+Although @code{Object_Size} does properly reflect the default object size
+value, it is not necessarily the case that all objects will be of this size
+in a case where it is not specified explicitly. The compiler is free to
+increase the size and alignment of stand alone objects to improve efficiency
+of the generated code and sometimes does so in the case of large composite
+objects. If the size of a stand alone object is critical to the
+application, it should be specified explicitly.
+
+@node Passed_By_Reference
+@unnumberedsec Passed_By_Reference
@cindex Parameters, when passed by reference
@findex Passed_By_Reference
-@item Passed_By_Reference
@noindent
@code{@var{type}'Passed_By_Reference} for any subtype @var{type} returns
a value of type @code{Boolean} value that is @code{True} if the type is
passed by copy in calls. For scalar types, the result is always @code{False}
and is static. For non-scalar types, the result is non-static.
+@node Range_Length
+@unnumberedsec Range_Length
@findex Range_Length
-@item Range_Length
@noindent
@code{@var{type}'Range_Length} for any discrete type @var{type} yields
the number of values represented by the subtype (zero for a null
applied to the index subtype of a one dimensional array always gives the
same result as @code{Range} applied to the array itself.
+@node Safe_Emax
+@unnumberedsec Safe_Emax
@cindex Ada 83 attributes
@findex Safe_Emax
-@item Safe_Emax
@noindent
The @code{Safe_Emax} attribute is provided for compatibility with Ada 83. See
the Ada 83 reference manual for an exact description of the semantics of
this attribute.
+@node Safe_Large
+@unnumberedsec Safe_Large
@cindex Ada 83 attributes
@findex Safe_Large
-@item Safe_Large
-@noindent
-The @code{Safe_Large} attribute is provided for compatibility with Ada 83. See
-the Ada 83 reference manual for an exact description of the semantics of
-this attribute.
-
-@cindex Ada 83 attributes
-@findex Safe_Large
-@item Safe_Large
@noindent
The @code{Safe_Large} attribute is provided for compatibility with Ada 83. See
the Ada 83 reference manual for an exact description of the semantics of
this attribute.
+@node Small
+@unnumberedsec Small
@cindex Ada 83 attributes
@findex Small
-@item Small
@noindent
-The @code{Small} attribute is defined in Ada 95 only for fixed-point types.
+The @code{Small} attribute is defined in Ada 95 (and Ada 2005) only for
+fixed-point types.
GNAT also allows this attribute to be applied to floating-point types
for compatibility with Ada 83. See
the Ada 83 reference manual for an exact description of the semantics of
this attribute when applied to floating-point types.
+@node Storage_Unit
+@unnumberedsec Storage_Unit
@findex Storage_Unit
-@item Storage_Unit
@noindent
@code{Standard'Storage_Unit} (@code{Standard} is the only permissible
-prefix) provides the value @code{System.Storage_Unit} and is intended
-primarily for constructing this definition in package @code{System}.
-
+prefix) provides the same value as @code{System.Storage_Unit}.
+
+@node Stub_Type
+@unnumberedsec Stub_Type
+@findex Stub_Type
+@noindent
+The GNAT implementation of remote access-to-classwide types is
+organized as described in AARM section E.4 (20.t): a value of an RACW type
+(designating a remote object) is represented as a normal access
+value, pointing to a "stub" object which in turn contains the
+necessary information to contact the designated remote object. A
+call on any dispatching operation of such a stub object does the
+remote call, if necessary, using the information in the stub object
+to locate the target partition, etc.
+
+For a prefix @code{T} that denotes a remote access-to-classwide type,
+@code{T'Stub_Type} denotes the type of the corresponding stub objects.
+
+By construction, the layout of @code{T'Stub_Type} is identical to that of
+type @code{RACW_Stub_Type} declared in the internal implementation-defined
+unit @code{System.Partition_Interface}. Use of this attribute will create
+an implicit dependency on this unit.
+
+@node Target_Name
+@unnumberedsec Target_Name
+@findex Target_Name
+@noindent
+@code{Standard'Target_Name} (@code{Standard} is the only permissible
+prefix) provides a static string value that identifies the target
+for the current compilation. For GCC implementations, this is the
+standard gcc target name without the terminating slash (for
+example, GNAT 5.0 on windows yields "i586-pc-mingw32msv").
+
+@node Tick
+@unnumberedsec Tick
@findex Tick
-@item Tick
@noindent
@code{Standard'Tick} (@code{Standard} is the only permissible prefix)
-provides the value of @code{System.Tick} and is intended primarily for
-constructing this definition in package @code{System}.
+provides the same value as @code{System.Tick},
+@node To_Address
+@unnumberedsec To_Address
@findex To_Address
-@item To_Address
@noindent
The @code{System'To_Address}
(@code{System} is the only permissible prefix)
-denotes a function identical to
+denotes a function identical to
@code{System.Storage_Elements.To_Address} except that
it is a static attribute. This means that if its argument is
a static expression, then the result of the attribute is a
static expression. The result is that such an expression can be
used in contexts (e.g.@: preelaborable packages) which require a
static expression and where the function call could not be used
-(since the function call is always non-static, even if its
+(since the function call is always non-static, even if its
argument is static).
+@node Type_Class
+@unnumberedsec Type_Class
@findex Type_Class
-@item Type_Class
@noindent
@code{@var{type}'Type_Class} for any type or subtype @var{type} yields
the value of the type class for the full type of @var{type}. If
corresponding actual subtype. The value of this attribute is of type
@code{System.Aux_DEC.Type_Class}, which has the following definition:
-@smallexample
+@smallexample @c ada
type Type_Class is
(Type_Class_Enumeration,
Type_Class_Integer,
applies to all concurrent types. This attribute is designed to
be compatible with the DEC Ada 83 attribute of the same name.
+@node UET_Address
+@unnumberedsec UET_Address
@findex UET_Address
-@item UET_Address
@noindent
The @code{UET_Address} attribute can only be used for a prefix which
denotes a library package. It yields the address of the unit exception
@code{Ada.Exceptions} in files @file{a-except.ads} and @file{a-except.adb}
for details on how this attribute is used in the implementation.
+@node Unconstrained_Array
+@unnumberedsec Unconstrained_Array
+@findex Unconstrained_Array
+@noindent
+The @code{Unconstrained_Array} attribute can be used with a prefix that
+denotes any type or subtype. It is a static attribute that yields
+@code{True} if the prefix designates an unconstrained array,
+and @code{False} otherwise. In a generic instance, the result is
+still static, and yields the result of applying this test to the
+generic actual.
+
+@node Universal_Literal_String
+@unnumberedsec Universal_Literal_String
@cindex Named numbers, representation of
@findex Universal_Literal_String
-@item Universal_Literal_String
@noindent
The prefix of @code{Universal_Literal_String} must be a named
number. The static result is the string consisting of the characters of
construction of values of the floating-point attributes from the file
@file{ttypef.ads}, but may also be used by user programs.
+For example, the following program prints the first 50 digits of pi:
+
+@smallexample @c ada
+with Text_IO; use Text_IO;
+with Ada.Numerics;
+procedure Pi is
+begin
+ Put (Ada.Numerics.Pi'Universal_Literal_String);
+end;
+@end smallexample
+
+@node Unrestricted_Access
+@unnumberedsec Unrestricted_Access
@cindex @code{Access}, unrestricted
@findex Unrestricted_Access
-@item Unrestricted_Access
@noindent
The @code{Unrestricted_Access} attribute is similar to @code{Access}
except that all accessibility and aliased view checks are omitted. This
other implementations, the use of static chains for inner level
subprograms means that @code{Unrestricted_Access} applied to a
subprogram yields a value that can be called as long as the subprogram
-is in scope (normal Ada 95 accessibility rules restrict this usage).
-
+is in scope (normal Ada accessibility rules restrict this usage).
+
+It is possible to use @code{Unrestricted_Access} for any type, but care
+must be exercised if it is used to create pointers to unconstrained
+objects. In this case, the resulting pointer has the same scope as the
+context of the attribute, and may not be returned to some enclosing
+scope. For instance, a function cannot use @code{Unrestricted_Access}
+to create a unconstrained pointer and then return that value to the
+caller.
+
+@node VADS_Size
+@unnumberedsec VADS_Size
@cindex @code{Size}, VADS compatibility
@findex VADS_Size
-@item VADS_Size
@noindent
The @code{'VADS_Size} attribute is intended to make it easier to port
legacy code which relies on the semantics of @code{'Size} as implemented
gives the result that would be obtained by applying the attribute to
the corresponding type.
+@node Value_Size
+@unnumberedsec Value_Size
@cindex @code{Size}, setting for not-first subtype
@findex Value_Size
-@item Value_Size
@code{@var{type}'Value_Size} is the number of bits required to represent
a value of the given subtype. It is the same as @code{@var{type}'Size},
but, unlike @code{Size}, may be set for non-first subtypes.
+@node Wchar_T_Size
+@unnumberedsec Wchar_T_Size
@findex Wchar_T_Size
-@item Wchar_T_Size
@code{Standard'Wchar_T_Size} (@code{Standard} is the only permissible
-prefix) provides the size in bits of the C @code{wchar_t} type
-primarily for constructing the definition of this type in
+prefix) provides the size in bits of the C @code{wchar_t} type
+primarily for constructing the definition of this type in
package @code{Interfaces.C}.
+@node Word_Size
+@unnumberedsec Word_Size
@findex Word_Size
-@item Word_Size
@code{Standard'Word_Size} (@code{Standard} is the only permissible
-prefix) provides the value @code{System.Word_Size} and is intended
-primarily for constructing this definition in package @code{System}.
-@end table
+prefix) provides the value @code{System.Word_Size}.
+
+@c ------------------------
@node Implementation Advice
@chapter Implementation Advice
-The main text of the Ada 95 Reference Manual describes the required
-behavior of all Ada 95 compilers, and the GNAT compiler conforms to
+@noindent
+The main text of the Ada Reference Manual describes the required
+behavior of all Ada compilers, and the GNAT compiler conforms to
these requirements.
-In addition, there are sections throughout the Ada 95
-reference manual headed
-by the phrase ``implementation advice''. These sections are not normative,
-i.e.@: they do not specify requirements that all compilers must
+In addition, there are sections throughout the Ada Reference Manual headed
+by the phrase ``Implementation advice''. These sections are not normative,
+i.e., they do not specify requirements that all compilers must
follow. Rather they provide advice on generally desirable behavior. You
may wonder why they are not requirements. The most typical answer is
that they describe behavior that seems generally desirable, but cannot
be provided on all systems, or which may be undesirable on some systems.
As far as practical, GNAT follows the implementation advice sections in
-the Ada 95 Reference Manual. This chapter contains a table giving the
+the Ada Reference Manual. This chapter contains a table giving the
reference manual section number, paragraph number and several keywords
for each advice. Each entry consists of the text of the advice followed
by the GNAT interpretation of this advice. Most often, this simply says
number of cases, GNAT deliberately deviates from this advice, in which
case the text describes what GNAT does and why.
-@table @strong
@cindex Error detection
-@item 1.1.3(20): Error Detection
+@unnumberedsec 1.1.3(20): Error Detection
@sp 1
@cartouche
If an implementation detects the use of an unsupported Specialized Needs
or diagnosed at compile time.
@cindex Child Units
-@item 1.1.3(31): Child Units
+@unnumberedsec 1.1.3(31): Child Units
@sp 1
@cartouche
If an implementation wishes to provide implementation-defined
Followed.
@cindex Bounded errors
-@item 1.1.5(12): Bounded Errors
+@unnumberedsec 1.1.5(12): Bounded Errors
@sp 1
@cartouche
If an implementation detects a bounded error or erroneous
runtime.
@cindex Pragmas
-@item 2.8(16): Pragmas
+@unnumberedsec 2.8(16): Pragmas
@sp 1
@cartouche
Normally, implementation-defined pragmas should have no semantic effect
Affects semantics
@item CPP_Constructor
Affects semantics
-@item CPP_Virtual
-Affects semantics
-@item CPP_Vtable
-Affects semantics
@item Debug
Affects semantics
@item Interface_Name
Affects semantics
@end table
+@noindent
In each of the above cases, it is essential to the purpose of the pragma
that this advice not be followed. For details see the separate section
on implementation defined pragmas.
-@item 2.8(17-19): Pragmas
+@unnumberedsec 2.8(17-19): Pragmas
@sp 1
@cartouche
Normally, an implementation should not define pragmas that can
@cindex Character Sets
@cindex Alternative Character Sets
-@item 3.5.2(5): Alternative Character Sets
+@unnumberedsec 3.5.2(5): Alternative Character Sets
@sp 1
@cartouche
If an implementation supports a mode with alternative interpretations
there is no such restriction.
@cindex Integer types
-@item 3.5.4(28): Integer Types
+@unnumberedsec 3.5.4(28): Integer Types
@sp 1
@cartouche
so this advice is not fully followed. These types
are supported for convenient interface to C, and so that all hardware
types of the machine are easily available.
-@item 3.5.4(29): Integer Types
+@unnumberedsec 3.5.4(29): Integer Types
@sp 1
@cartouche
Followed.
@cindex Enumeration values
-@item 3.5.5(8): Enumeration Values
+@unnumberedsec 3.5.5(8): Enumeration Values
@sp 1
@cartouche
For the evaluation of a call on @code{@var{S}'Pos} for an enumeration
Followed.
@cindex Float types
-@item 3.5.7(17): Float Types
+@unnumberedsec 3.5.7(17): Float Types
@sp 1
@cartouche
An implementation should support @code{Long_Float} in addition to
@cindex Multidimensional arrays
@cindex Arrays, multidimensional
-@item 3.6.2(11): Multidimensional Arrays
+@unnumberedsec 3.6.2(11): Multidimensional Arrays
@sp 1
@cartouche
An implementation should normally represent multidimensional arrays in
Followed.
@findex Duration'Small
-@item 9.6(30-31): Duration'Small
+@unnumberedsec 9.6(30-31): Duration'Small
@sp 1
@cartouche
Whenever possible in an implementation, the value of @code{Duration'Small}
@end cartouche
Followed.
-@item 10.2.1(12): Consistent Representation
+@unnumberedsec 10.2.1(12): Consistent Representation
@sp 1
@cartouche
In an implementation, a type declared in a pre-elaborated package should
advice without severely impacting efficiency of execution.
@cindex Exception information
-@item 11.4.1(19): Exception Information
+@unnumberedsec 11.4.1(19): Exception Information
@sp 1
@cartouche
@code{Exception_Message} by default and @code{Exception_Information}
@cindex Suppression of checks
@cindex Checks, suppression of
-@item 11.5(28): Suppression of Checks
+@unnumberedsec 11.5(28): Suppression of Checks
@sp 1
@cartouche
The implementation should minimize the code executed for checks that
Followed.
@cindex Representation clauses
-@item 13.1 (21-24): Representation Clauses
+@unnumberedsec 13.1 (21-24): Representation Clauses
@sp 1
@cartouche
The recommended level of support for all representation items is
the representation item is a name that statically denotes a constant
declared before the entity.
@end cartouche
-Followed. GNAT does not support non-static expressions in representation
-clauses unless they are constants declared before the entity. For
-example:
+Followed. In fact, GNAT goes beyond the recommended level of support
+by allowing nonstatic expressions in some representation clauses even
+without the need to declare constants initialized with the values of
+such expressions.
+For example:
-@smallexample
-X : typ;
-for X'Address use To_address (16#2000#);
+@smallexample @c ada
+ X : Integer;
+ Y : Float;
+ for Y'Address use X'Address;>>
@end smallexample
-@noindent
-will be rejected, since the To_Address expression is non-static. Instead
-write:
-
-@smallexample
-X_Address : constant Address : =
-To_Address ((16#2000#);
-X : typ;
-for X'Address use X_Address;
-@end smallexample
@sp 1
@cartouche
Followed.
@cindex Packed types
-@item 13.2(6-8): Packed Types
+@unnumberedsec 13.2(6-8): Packed Types
@sp 1
@cartouche
If a type is packed, then the implementation should try to minimize
greater than the word size may be allocated an integral number of words.
@end cartouche
Followed. Tight packing of arrays is supported for all component sizes
-up to 64-bits.
+up to 64-bits. If the array component size is 1 (that is to say, if
+the component is a boolean type or an enumeration type with two values)
+then values of the type are implicitly initialized to zero. This
+happens both for objects of the packed type, and for objects that have a
+subcomponent of the packed type.
@sp 1
@cartouche
@end cartouche
Followed.
@cindex @code{Address} clauses
-@item 13.3(14-19): Address Clauses
+@unnumberedsec 13.3(14-19): Address Clauses
@sp 1
@cartouche
subprograms.
@end cartouche
Followed.
-
+
@sp 1
@cartouche
Objects (including subcomponents) that are aliased or of a by-reference
type should be allocated on storage element boundaries.
@end cartouche
Followed.
-
+
@sp 1
@cartouche
If the @code{Address} of an object is specified, or it is imported or exported,
Followed.
@cindex @code{Alignment} clauses
-@item 13.3(29-35): Alignment Clauses
+@unnumberedsec 13.3(29-35): Alignment Clauses
@sp 1
@cartouche
The recommended level of support for the @code{Alignment} attribute for
following:
@end cartouche
Followed.
-
+
@sp 1
@cartouche
An implementation need not support specified @code{Alignment}s for
loaded and stored by available machine instructions.
@end cartouche
Followed.
-
+
@sp 1
@cartouche
An implementation need not support specified @code{Alignment}s that are
Same as above, for subtypes, but in addition:
@end cartouche
Followed.
-
+
@sp 1
@cartouche
For stand-alone library-level objects of statically constrained
Followed.
@cindex @code{Size} clauses
-@item 13.3(42-43): Size Clauses
+@unnumberedsec 13.3(42-43): Size Clauses
@sp 1
@cartouche
The recommended level of support for the @code{Size} attribute of
@end cartouche
Followed.
-@item 13.3(50-56): Size Clauses
+@unnumberedsec 13.3(50-56): Size Clauses
@sp 1
@cartouche
If the @code{Size} of a subtype is specified, and allows for efficient
@code{Size} clause on a composite subtype should not affect the
internal layout of components.
@end cartouche
-Followed.
+Followed. But note that this can be overridden by use of the implementation
+pragma Implicit_Packing in the case of packed arrays.
@sp 1
@cartouche
Followed.
@cindex @code{Component_Size} clauses
-@item 13.3(71-73): Component Size Clauses
+@unnumberedsec 13.3(71-73): Component Size Clauses
@sp 1
@cartouche
The recommended level of support for the @code{Component_Size}
@cindex Enumeration representation clauses
@cindex Representation clauses, enumeration
-@item 13.4(9-10): Enumeration Representation Clauses
+@unnumberedsec 13.4(9-10): Enumeration Representation Clauses
@sp 1
@cartouche
The recommended level of support for enumeration representation clauses
@cindex Record representation clauses
@cindex Representation clauses, records
-@item 13.5.1(17-22): Record Representation Clauses
+@unnumberedsec 13.5.1(17-22): Record Representation Clauses
@sp 1
@cartouche
The recommended level of support for
boundary that obeys the @code{Alignment} of the component subtype.
@end cartouche
Followed.
-
+
@sp 1
@cartouche
If the default bit ordering applies to the declaration of a given type,
and all mentioned features are implemented.
@cindex Storage place attributes
-@item 13.5.2(5): Storage Place Attributes
+@unnumberedsec 13.5.2(5): Storage Place Attributes
@sp 1
@cartouche
If a component is represented using some form of pointer (such as an
Followed. There are no such components in GNAT@.
@cindex Bit ordering
-@item 13.5.3(7-8): Bit Ordering
+@unnumberedsec 13.5.3(7-8): Bit Ordering
@sp 1
@cartouche
The recommended level of support for the non-default bit ordering is:
Thus non-default bit ordering is not supported.
@cindex @code{Address}, as private type
-@item 13.7(37): Address as Private
+@unnumberedsec 13.7(37): Address as Private
@sp 1
@cartouche
@code{Address} should be of a private type.
@cindex Operations, on @code{Address}
@cindex @code{Address}, operations of
-@item 13.7.1(16): Address Operations
+@unnumberedsec 13.7.1(16): Address Operations
@sp 1
@cartouche
Operations in @code{System} and its children should reflect the target
operation raises @code{Program_Error}, since all operations make sense.
@cindex Unchecked conversion
-@item 13.9(14-17): Unchecked Conversion
+@unnumberedsec 13.9(14-17): Unchecked Conversion
@sp 1
@cartouche
The @code{Size} of an array object should not include its bounds; hence,
the bounds should not be part of the converted data.
@end cartouche
-Followed.
+Followed.
@sp 1
@cartouche
and for record subtypes without discriminants whose component subtypes
are described in this paragraph.
@end cartouche
-Followed.
+Followed.
@cindex Heap usage, implicit
-@item 13.11(23-25): Implicit Heap Usage
+@unnumberedsec 13.11(23-25): Implicit Heap Usage
@sp 1
@cartouche
An implementation should document any cases in which it dynamically
@sp 1
@cartouche
-A default (implementation-provided) storage pool for an
+A default (implementation-provided) storage pool for an
access-to-constant type should not have overhead to support deallocation of
individual objects.
@end cartouche
-Followed.
+Followed.
@sp 1
@cartouche
point of an allocator for the type, and be reclaimed when the designated
object becomes inaccessible.
@end cartouche
-Followed.
+Followed.
@cindex Unchecked deallocation
-@item 13.11.2(17): Unchecked De-allocation
+@unnumberedsec 13.11.2(17): Unchecked De-allocation
@sp 1
@cartouche
For a standard storage pool, @code{Free} should actually reclaim the
storage.
@end cartouche
-Followed.
+Followed.
@cindex Stream oriented attributes
-@item 13.13.2(17): Stream Oriented Attributes
+@unnumberedsec 13.13.2(17): Stream Oriented Attributes
@sp 1
@cartouche
If a stream element is the same size as a storage element, then the
should use the smallest number of stream elements needed to represent
all values in the base range of the scalar type.
@end cartouche
-Followed. In particular, the interpretation chosen is that of AI-195,
-which specifies that the size to be used is that of the first subtype.
-@item A.1(52): Implementation Advice
+Followed. By default, GNAT uses the interpretation suggested by AI-195,
+which specifies using the size of the first subtype.
+However, such an implementation is based on direct binary
+representations and is therefore target- and endianness-dependent.
+To address this issue, GNAT also supplies an alternate implementation
+of the stream attributes @code{Read} and @code{Write},
+which uses the target-independent XDR standard representation
+for scalar types.
+@cindex XDR representation
+@cindex @code{Read} attribute
+@cindex @code{Write} attribute
+@cindex Stream oriented attributes
+The XDR implementation is provided as an alternative body of the
+@code{System.Stream_Attributes} package, in the file
+@file{s-strxdr.adb} in the GNAT library.
+There is no @file{s-strxdr.ads} file.
+In order to install the XDR implementation, do the following:
+@enumerate
+@item Replace the default implementation of the
+@code{System.Stream_Attributes} package with the XDR implementation.
+For example on a Unix platform issue the commands:
+@smallexample
+$ mv s-stratt.adb s-strold.adb
+$ mv s-strxdr.adb s-stratt.adb
+@end smallexample
+
+@item
+Rebuild the GNAT run-time library as documented in the
+@cite{GNAT User's Guide}
+@end enumerate
+
+@unnumberedsec A.1(52): Names of Predefined Numeric Types
@sp 1
@cartouche
If an implementation provides additional named predefined integer types,
predefined floating point types, then the names should end with
@samp{Float} as in @samp{Long_Float}.
@end cartouche
-Followed.
+Followed.
@findex Ada.Characters.Handling
-@item A.3.2(49): @code{Ada.Characters.Handling}
+@unnumberedsec A.3.2(49): @code{Ada.Characters.Handling}
@sp 1
@cartouche
If an implementation provides a localized definition of @code{Character}
@code{Characters.Handling} should reflect the localizations. See also
3.5.2.
@end cartouche
-Followed. GNAT provides no such localized definitions.
+Followed. GNAT provides no such localized definitions.
@cindex Bounded-length strings
-@item A.4.4(106): Bounded-Length String Handling
+@unnumberedsec A.4.4(106): Bounded-Length String Handling
@sp 1
@cartouche
Bounded string objects should not be implemented by implicit pointers
and dynamic allocation.
@end cartouche
-Followed. No implicit pointers or dynamic allocation are used.
+Followed. No implicit pointers or dynamic allocation are used.
@cindex Random number generation
-@item A.5.2(46-47): Random Number Generation
+@unnumberedsec A.5.2(46-47): Random Number Generation
@sp 1
@cartouche
Any storage associated with an object of type @code{Generator} should be
reclaimed on exit from the scope of the object.
@end cartouche
-Followed.
+Followed.
@sp 1
@cartouche
varying function of the initiator value.
@end cartouche
Followed. The generator period is sufficiently long for the first
-condition here to hold true.
+condition here to hold true.
@findex Get_Immediate
-@item A.10.7(23): @code{Get_Immediate}
+@unnumberedsec A.10.7(23): @code{Get_Immediate}
@sp 1
@cartouche
The @code{Get_Immediate} procedures should be implemented with
underlying operating system should be disabled during the execution of
@code{Get_Immediate}.
@end cartouche
-Followed.
+Followed on all targets except VxWorks. For VxWorks, there is no way to
+provide this functionality that does not result in the input buffer being
+flushed before the @code{Get_Immediate} call. A special unit
+@code{Interfaces.Vxworks.IO} is provided that contains routines to enable
+this functionality.
@findex Export
-@item B.1(39-41): Pragma @code{Export}
+@unnumberedsec B.1(39-41): Pragma @code{Export}
@sp 1
@cartouche
If an implementation supports pragma @code{Export} to a given language,
finalization code. These subprograms should have no effect the second
and subsequent time they are called.
@end cartouche
-Followed.
+Followed.
@sp 1
@cartouche
presuming the other language has corresponding features. Pragma
@code{Convention} need not be supported for scalar types.
@end cartouche
-Followed.
+Followed.
@cindex Package @code{Interfaces}
@findex Interfaces
-@item B.2(12-13): Package @code{Interfaces}
+@unnumberedsec B.2(12-13): Package @code{Interfaces}
@sp 1
@cartouche
For each implementation-defined convention identifier, there should be a
the given hardware architecture should be provided directly in
@code{Interfaces}.
@end cartouche
-Followed. An additional package not defined
-in the Ada 95 Reference Manual is @code{Interfaces.CPP}, used
+Followed. An additional package not defined
+in the Ada Reference Manual is @code{Interfaces.CPP}, used
for interfacing to C++.
@sp 1
provide the corresponding package or packages described in the following
clauses.
@end cartouche
-Followed. GNAT provides all the packages described in this section.
+Followed. GNAT provides all the packages described in this section.
@cindex C, interfacing with
-@item B.3(63-71): Interfacing with C
+@unnumberedsec B.3(63-71): Interfacing with C
@sp 1
@cartouche
An implementation should support the following interface correspondences
@cartouche
An Ada procedure corresponds to a void-returning C function.
@end cartouche
-Followed.
+Followed.
@sp 1
@cartouche
An Ada function corresponds to a non-void C function.
@end cartouche
-Followed.
+Followed.
@sp 1
@cartouche
An Ada @code{in} scalar parameter is passed as a scalar argument to a C
function.
@end cartouche
-Followed.
+Followed.
@sp 1
@cartouche
type @var{T} is passed as a @code{@var{t}*} argument to a C function,
where @var{t} is the C type corresponding to the Ada type @var{T}.
@end cartouche
-Followed.
+Followed.
@sp 1
@cartouche
@code{in out} parameter, a pointer to a temporary copy is used to
preserve by-copy semantics.
@end cartouche
-Followed.
+Followed.
@sp 1
@cartouche
mode, is passed as a @code{@var{t}*} argument to a C function, where
@var{t} is the C type corresponding to the Ada type @var{T}.
@end cartouche
-Followed.
+Followed.
@sp 1
@cartouche
to a C function whose prototype corresponds to the designated
subprogram's specification.
@end cartouche
-Followed.
+Followed.
@cindex COBOL, interfacing with
-@item B.4(95-98): Interfacing with COBOL
+@unnumberedsec B.4(95-98): Interfacing with COBOL
@sp 1
@cartouche
An Ada implementation should support the following interface
An Ada access @var{T} parameter is passed as a @samp{BY REFERENCE} data item of
the COBOL type corresponding to @var{T}.
@end cartouche
-Followed.
+Followed.
@sp 1
@cartouche
An Ada in scalar parameter is passed as a @samp{BY CONTENT} data item of
the corresponding COBOL type.
@end cartouche
-Followed.
+Followed.
@sp 1
@cartouche
COBOL type corresponding to the Ada parameter type; for scalars, a local
copy is used if necessary to ensure by-copy semantics.
@end cartouche
-Followed.
+Followed.
@cindex Fortran, interfacing with
-@item B.5(22-26): Interfacing with Fortran
+@unnumberedsec B.5(22-26): Interfacing with Fortran
@sp 1
@cartouche
An Ada implementation should support the following interface
Followed.
@cindex Machine operations
-@item C.1(3-5): Access to Machine Operations
+@unnumberedsec C.1(3-5): Access to Machine Operations
@sp 1
@cartouche
The machine code or intrinsic support should allow access to all
assembler; the default assembler should be associated with the
convention identifier @code{Assembler}.
@end cartouche
-Followed.
+Followed.
@sp 1
@cartouche
machine code or assembler subprogram is allowed to read or update every
object that is specified as exported.
@end cartouche
-Followed.
+Followed.
-@item C.1(10-16): Access to Machine Operations
+@unnumberedsec C.1(10-16): Access to Machine Operations
@sp 1
@cartouche
The implementation should ensure that little or no overhead is
Followed on any target supporting such operations.
@cindex Interrupt support
-@item C.3(28): Interrupt Support
+@unnumberedsec C.3(28): Interrupt Support
@sp 1
@cartouche
If the @code{Ceiling_Locking} policy is not in effect, the
of interrupt blocking.
@cindex Protected procedure handlers
-@item C.3.1(20-21): Protected Procedure Handlers
+@unnumberedsec C.3.1(20-21): Protected Procedure Handlers
@sp 1
@cartouche
Whenever possible, the implementation should allow interrupt handlers to
@end cartouche
@c SGI info:
@ignore
-This is never possible under IRIX, so this is followed by default.
+This is never possible under IRIX, so this is followed by default.
@end ignore
Followed on any target where the underlying operating system permits
such direct calls.
Whenever practical, violations of any
implementation-defined restrictions should be detected before run time.
@end cartouche
-Followed. Compile time warnings are given when possible.
+Followed. Compile time warnings are given when possible.
@cindex Package @code{Interrupts}
@findex Interrupts
-@item C.3.2(25): Package @code{Interrupts}
+@unnumberedsec C.3.2(25): Package @code{Interrupts}
@sp 1
@cartouche
should be specified in a child package of @code{Interrupts}, with the
same operations as in the predefined package Interrupts.
@end cartouche
-Followed.
+Followed.
@cindex Pre-elaboration requirements
-@item C.4(14): Pre-elaboration Requirements
+@unnumberedsec C.4(14): Pre-elaboration Requirements
@sp 1
@cartouche
It is recommended that pre-elaborated packages be implemented in such a
Followed. Executable code is generated in some cases, e.g.@: loops
to initialize large arrays.
-@item C.5(8): Pragma @code{Discard_Names}
+@unnumberedsec C.5(8): Pragma @code{Discard_Names}
@sp 1
@cartouche
@cindex Package @code{Task_Attributes}
@findex Task_Attributes
-@item C.7.2(30): The Package Task_Attributes
+@unnumberedsec C.7.2(30): The Package Task_Attributes
@sp 1
@cartouche
Some implementations are targeted to domains in which memory use at run
attribute objects, and the heap for the others. In the latter case,
@var{N} should be documented.
@end cartouche
-Not followed. This implementation is not targeted to such a domain.
+Not followed. This implementation is not targeted to such a domain.
@cindex Locking Policies
-@item D.3(17): Locking Policies
+@unnumberedsec D.3(17): Locking Policies
@sp 1
@cartouche
whose name (@code{Inheritance_Locking}) follows this suggestion.
@cindex Entry queuing policies
-@item D.4(16): Entry Queuing Policies
+@unnumberedsec D.4(16): Entry Queuing Policies
@sp 1
@cartouche
Names that end with @samp{_Queuing} should be used
for all implementation-defined queuing policies.
@end cartouche
-Followed. No such implementation-defined queueing policies exist.
+Followed. No such implementation-defined queuing policies exist.
@cindex Preemptive abort
-@item D.6(9-10): Preemptive Abort
+@unnumberedsec D.6(9-10): Preemptive Abort
@sp 1
@cartouche
Even though the @code{abort_statement} is included in the list of
statement be implemented in a way that never requires the task executing
the @code{abort_statement} to block.
@end cartouche
-Followed.
+Followed.
@sp 1
@cartouche
another processor should be bounded; the implementation should use
periodic polling, if necessary, to achieve this.
@end cartouche
-Followed.
+Followed.
@cindex Tasking restrictions
-@item D.7(21): Tasking Restrictions
+@unnumberedsec D.7(21): Tasking Restrictions
@sp 1
@cartouche
When feasible, the implementation should take advantage of the specified
@end cartouche
GNAT currently takes advantage of these restrictions by providing an optimized
run time when the Ravenscar profile and the GNAT restricted run time set
-of restrictions are specified. See pragma @code{Ravenscar} and pragma
-@code{Restricted_Run_Time} for more details.
+of restrictions are specified. See pragma @code{Profile (Ravenscar)} and
+pragma @code{Profile (Restricted)} for more details.
@cindex Time, monotonic
-@item D.8(47-49): Monotonic Time
+@unnumberedsec D.8(47-49): Monotonic Time
@sp 1
@cartouche
When appropriate, implementations should provide configuration
It is recommended that @code{Calendar.Clock} and @code{Real_Time.Clock}
be implemented as transformations of the same time base.
@end cartouche
-Followed.
+Followed.
@sp 1
@cartouche
the underlying system be available to the application through
@code{Clock}. @dfn{Best} may mean highest accuracy or largest range.
@end cartouche
-Followed.
+Followed.
@cindex Partition communication subsystem
@cindex PCS
-@item E.5(28-29): Partition Communication Subsystem
+@unnumberedsec E.5(28-29): Partition Communication Subsystem
@sp 1
@cartouche
Whenever possible, the PCS on the called partition should allow for
returns.
@end cartouche
Followed by GLADE, a separately supplied PCS that can be used with
-GNAT.
+GNAT.
@sp 1
@cartouche
write the @code{Item} into the stream.
@end cartouche
Followed by GLADE, a separately supplied PCS that can be used with
-GNAT@.
+GNAT@.
@cindex COBOL support
-@item F(7): COBOL Support
+@unnumberedsec F(7): COBOL Support
@sp 1
@cartouche
If COBOL (respectively, C) is widely supported in the target
pragmas (see Annex B), thus allowing Ada programs to interface with
programs written in that language.
@end cartouche
-Followed.
+Followed.
@cindex Decimal radix support
-@item F.1(2): Decimal Radix Support
+@unnumberedsec F.1(2): Decimal Radix Support
@sp 1
@cartouche
Packed decimal should be used as the internal representation for objects
representations.
@cindex Numerics
-@item G: Numerics
+@unnumberedsec G: Numerics
@sp 2
@cartouche
If Fortran (respectively, C) is widely supported in the target
Followed.
@cindex Complex types
-@item G.1.1(56-58): Complex Types
+@unnumberedsec G.1.1(56-58): Complex Types
@sp 2
@cartouche
Because the usual mathematical meaning of multiplication of a complex
operand, and in the case of division of a complex operand by a real or
pure-imaginary operand.
@end cartouche
-Not followed.
+Not followed.
@sp 1
@cartouche
and a pure-imaginary operand, and in the case of subtraction of a
complex operand and a real or pure-imaginary operand.
@end cartouche
-Not followed.
+Not followed.
@sp 1
@cartouche
parameter has a value of zero and the @code{Modulus} parameter has a
nonnegative (respectively, negative) value.
@end cartouche
-Followed.
+Followed.
@cindex Complex elementary functions
-@item G.1.2(49): Complex Elementary Functions
+@unnumberedsec G.1.2(49): Complex Elementary Functions
@sp 1
@cartouche
Implementations in which @code{Complex_Types.Real'Signed_Zeros} is
a parameter component at the origin, or is always positive or always
negative.
@end cartouche
-Followed.
+Followed.
@cindex Accuracy requirements
-@item G.2.4(19): Accuracy Requirements
+@unnumberedsec G.2.4(19): Accuracy Requirements
@sp 1
@cartouche
The versions of the forward trigonometric functions without a
implemented by calling the corresponding version with a @code{Base}
parameter of @code{Numerics.e}.
@end cartouche
-Followed.
+Followed.
@cindex Complex arithmetic accuracy
@cindex Accuracy, complex arithmetic
-@item G.2.6(15): Complex Arithmetic Accuracy
+@unnumberedsec G.2.6(15): Complex Arithmetic Accuracy
@sp 1
@cartouche
@end cartouche
Followed.
-@end table
+@c -----------------------------------------
@node Implementation Defined Characteristics
@chapter Implementation Defined Characteristics
+
+@noindent
In addition to the implementation dependent pragmas and attributes, and
-the implementation advice, there are a number of other features of Ada
-95 that are potentially implementation dependent. These are mentioned
-throughout the Ada 95 Reference Manual, and are summarized in annex M@.
+the implementation advice, there are a number of other Ada features
+that are potentially implementation dependent. These are mentioned
+throughout the Ada Reference Manual, and are summarized in annex M@.
A requirement for conforming Ada compilers is that they provide
documentation describing how the implementation deals with each of these
@c SGI info:
@ignore
in the ProDev Ada
-implementation on IRIX 5.3 operating system or greater
+implementation on IRIX 5.3 operating system or greater
@end ignore
handles the implementation dependence.
You can use this chapter as a guide to minimizing implementation
dependent features in your programs if portability to other compilers
and other operating systems is an important consideration. The numbers
-in each section below correspond to the paragraph number in the Ada 95
+in each section below correspond to the paragraph number in the Ada
Reference Manual.
@sp 1
for them. See 3.5.4(26).
@end cartouche
@noindent
-There are no nonstandard integer types.
+There are no nonstandard integer types.
@sp 1
@cartouche
them. See 3.5.6(8).
@end cartouche
@noindent
-There are no nonstandard real types.
+There are no nonstandard real types.
@sp 1
@cartouche
are supported for floating point types. See 3.5.7(7).
@end cartouche
@noindent
-The precision and range is as defined by the IEEE standard.
+The precision and range is as defined by the IEEE standard.
@sp 1
@cartouche
@end cartouche
@noindent
@table @code
-@item Short_Float
+@item Short_Float
32 bit IEEE short
-@item Float
-(Short) 32 bit IEEE short
-@item Long_Float
-64 bit IEEE long
-@item Long_Long_Float
+@item Float
+(Short) 32 bit IEEE short
+@item Long_Float
+64 bit IEEE long
+@item Long_Long_Float
64 bit IEEE long (80 bit IEEE long on x86 processors)
@end table
@strong{18}. The small of an ordinary fixed point type. See 3.5.9(8).
@end cartouche
@noindent
-@code{Fine_Delta} is 2**(@minus{}63)
+@code{Fine_Delta} is 2**(@minus{}63)
@sp 1
@cartouche
@strong{22}. Any implementation-defined time types. See 9.6(6).
@end cartouche
@noindent
-There are no implementation-defined time types.
+There are no implementation-defined time types.
@sp 1
@cartouche
@code{select_statements}. See 9.6(29).
@end cartouche
@noindent
-There are no such limits.
+There are no such limits.
@sp 1
@cartouche
and replacing compilation units. See 10.1.4(3).
@end cartouche
@noindent
-See separate section on compilation model.
+See separate section on compilation model.
@sp 1
@cartouche
mentioned in the context clause of one of the needed Ada units.
If the partition contains no main program, or if the main program is in
-a language other than Ada, then GNAT
-provides the binder options @code{-z} and @code{-n} respectively, and in this case a
-list of units can be explicitly supplied to the binder for inclusion in
-the partition (all units needed by these units will also be included
-automatically). For full details on the use of these options, refer to
-the @cite{GNAT User's Guide} sections on Binding and Linking.
+a language other than Ada, then GNAT
+provides the binder options @code{-z} and @code{-n} respectively, and in
+this case a list of units can be explicitly supplied to the binder for
+inclusion in the partition (all units needed by these units will also
+be included automatically). For full details on the use of these
+options, refer to the @cite{GNAT User's Guide} sections on Binding
+and Linking.
@sp 1
@cartouche
@end cartouche
@noindent
The units needed by a given compilation unit are as defined in
-the Ada Reference Manual section 10.2(2-6). There are no
+the Ada Reference Manual section 10.2(2-6). There are no
implementation-defined pragmas or other implementation-defined
means for specifying needed units.
@end cartouche
@noindent
The first constraint on ordering is that it meets the requirements of
-chapter 10 of the Ada 95 Reference Manual. This still leaves some
+Chapter 10 of the Ada Reference Manual. This still leaves some
implementation dependent choices, which are resolved by first
-elaborating bodies as early as possible (i.e.@: in preference to specs
+elaborating bodies as early as possible (i.e., in preference to specs
where there is a choice), and second by evaluating the immediate with
clauses of a unit to determine the probably best choice, and
third by elaborating in alphabetical order of unit names
@noindent
The main program has no parameters. It may be a procedure, or a function
returning an integer type. In the latter case, the returned integer
-value is the return code of the program.
+value is the return code of the program (overriding any value that
+may have been set by a call to @code{Ada.Command_Line.Set_Exit_Status}).
@sp 1
@cartouche
@item
@code{ppp} is the Process Id value as a decimal integer (this line is
-present only if the Process Id is non-zero). Currently we are
+present only if the Process Id is nonzero). Currently we are
not making use of this field.
@item
@strong{42}. Implementation-defined check names. See 11.5(27).
@end cartouche
@noindent
-No implementation-defined check names are supported.
+The implementation defined check name Alignment_Check controls checking of
+address clause values for proper alignment (that is, the address supplied
+must be consistent with the alignment of the type).
+
+In addition, a user program can add implementation-defined check names
+by means of the pragma Check_Name.
@sp 1
@cartouche
@end cartouche
@noindent
Unchecked conversion between types of the same size
-and results in an uninterpreted transmission of the bits from one type
+results in an uninterpreted transmission of the bits from one type
to the other. If the types are of unequal sizes, then in the case of
discrete types, a shorter source is first zero or sign extended as
necessary, and a shorter target is simply truncated on the left.
to ensure that the alignment requirements of the target are met, then
a pointer is constructed to the source value, and the result is obtained
by dereferencing this pointer after converting it to be a pointer to the
-target type.
+target type. Unchecked conversions where the target subtype is an
+unconstrained array are not permitted. If the target alignment is
+greater than the source alignment, then a copy of the result is
+made with appropriate alignment
@sp 1
@cartouche
@table @code
-@item Boolean_Entry_Barriers
-@findex Boolean_Entry_Barriers
+@item Simple_Barriers
+@findex Simple_Barriers
This restriction ensures at compile time that barriers in entry declarations
-for protected types are restricted to references to simple boolean variables
-defined in the private part of the protected type. No other form of entry
-barriers is permitted. This is one of the restrictions of the Ravenscar
-profile for limited tasking (see also pragma @code{Ravenscar}).
-
-@item Max_Entry_Queue_Depth => Expr
-@findex Max_Entry_Queue_Depth
+for protected types are restricted to either static boolean expressions or
+references to simple boolean variables defined in the private part of the
+protected type. No other form of entry barriers is permitted. This is one
+of the restrictions of the Ravenscar profile for limited tasking (see also
+pragma @code{Profile (Ravenscar)}).
+
+@item Max_Entry_Queue_Length => Expr
+@findex Max_Entry_Queue_Length
This restriction is a declaration that any protected entry compiled in
the scope of the restriction has at most the specified number of
tasks waiting on the entry
This restriction ensures at compile time that there is no implicit or
explicit dependence on the package @code{Ada.Calendar}.
-@item No_Dynamic_Interrupts
-@findex No_Dynamic_Interrupts
-This restriction ensures at compile time that there is no attempt to
-dynamically associate interrupts. Only static association is allowed.
+@item No_Direct_Boolean_Operators
+@findex No_Direct_Boolean_Operators
+This restriction ensures that no logical (and/or/xor) or comparison
+operators are used on operands of type Boolean (or any type derived
+from Boolean). This is intended for use in safety critical programs
+where the certification protocol requires the use of short-circuit
+(and then, or else) forms for all composite boolean operations.
+
+@item No_Dispatching_Calls
+@findex No_Dispatching_Calls
+This restriction ensures at compile time that the code generated by the
+compiler involves no dispatching calls. The use of this restriction allows the
+safe use of record extensions, classwide membership tests and other classwide
+features not involving implicit dispatching. This restriction ensures that
+the code contains no indirect calls through a dispatching mechanism. Note that
+this includes internally-generated calls created by the compiler, for example
+in the implementation of class-wide objects assignments. The
+membership test is allowed in the presence of this restriction, because its
+implementation requires no dispatching.
+This restriction is comparable to the official Ada restriction
+@code{No_Dispatch} except that it is a bit less restrictive in that it allows
+all classwide constructs that do not imply dispatching.
+The following example indicates constructs that violate this restriction.
+
+@smallexample
+package Pkg is
+ type T is tagged record
+ Data : Natural;
+ end record;
+ procedure P (X : T);
+
+ type DT is new T with record
+ More_Data : Natural;
+ end record;
+ procedure Q (X : DT);
+end Pkg;
+
+with Pkg; use Pkg;
+procedure Example is
+ procedure Test (O : T'Class) is
+ N : Natural := O'Size;-- Error: Dispatching call
+ C : T'Class := O; -- Error: implicit Dispatching Call
+ begin
+ if O in DT'Class then -- OK : Membership test
+ Q (DT (O)); -- OK : Type conversion plus direct call
+ else
+ P (O); -- Error: Dispatching call
+ end if;
+ end Test;
+
+ Obj : DT;
+begin
+ P (Obj); -- OK : Direct call
+ P (T (Obj)); -- OK : Type conversion plus direct call
+ P (T'Class (Obj)); -- Error: Dispatching call
+
+ Test (Obj); -- OK : Type conversion
+
+ if Obj in T'Class then -- OK : Membership test
+ null;
+ end if;
+end Example;
+@end smallexample
+
+@item No_Dynamic_Attachment
+@findex No_Dynamic_Attachment
+This restriction ensures that there is no call to any of the operations
+defined in package Ada.Interrupts.
@item No_Enumeration_Maps
@findex No_Enumeration_Maps
@item No_Exception_Handlers
@findex No_Exception_Handlers
This restriction ensures at compile time that there are no explicit
-exception handlers.
+exception handlers. It also indicates that no exception propagation will
+be provided. In this mode, exceptions may be raised but will result in
+an immediate call to the last chance handler, a routine that the user
+must define with the following profile:
+
+ procedure Last_Chance_Handler
+ (Source_Location : System.Address; Line : Integer);
+ pragma Export (C, Last_Chance_Handler,
+ "__gnat_last_chance_handler");
+
+ The parameter is a C null-terminated string representing a message to be
+ associated with the exception (typically the source location of the raise
+ statement generated by the compiler). The Line parameter when nonzero
+ represents the line number in the source program where the raise occurs.
+
+@item No_Exception_Propagation
+@findex No_Exception_Propagation
+This restriction guarantees that exceptions are never propagated to an outer
+subprogram scope). The only case in which an exception may be raised is when
+the handler is statically in the same subprogram, so that the effect of a raise
+is essentially like a goto statement. Any other raise statement (implicit or
+explicit) will be considered unhandled. Exception handlers are allowed, but may
+not contain an exception occurrence identifier (exception choice). In addition
+use of the package GNAT.Current_Exception is not permitted, and reraise
+statements (raise with no operand) are not permitted.
+
+@item No_Exception_Registration
+@findex No_Exception_Registration
+This restriction ensures at compile time that no stream operations for
+types Exception_Id or Exception_Occurrence are used. This also makes it
+impossible to pass exceptions to or from a partition with this restriction
+in a distributed environment. If this exception is active, then the generated
+code is simplified by omitting the otherwise-required global registration
+of exceptions when they are declared.
@item No_Implicit_Conditionals
@findex No_Implicit_Conditionals
This restriction ensures that the generated code does not contain any
implicit conditionals, either by modifying the generated code where possible,
or by rejecting any construct that would otherwise generate an implicit
-conditional. The details and use of this restriction are described in
-more detail in the High Integrity product documentation.
+conditional. Note that this check does not include run time constraint
+checks, which on some targets may generate implicit conditionals as
+well. To control the latter, constraint checks can be suppressed in the
+normal manner. Constructs generating implicit conditionals include comparisons
+of composite objects and the Max/Min attributes.
+
+@item No_Implicit_Dynamic_Code
+@findex No_Implicit_Dynamic_Code
+This restriction prevents the compiler from building ``trampolines''.
+This is a structure that is built on the stack and contains dynamic
+code to be executed at run time. On some targets, a trampoline is
+built for the following features: @code{Access},
+@code{Unrestricted_Access}, or @code{Address} of a nested subprogram;
+nested task bodies; primitive operations of nested tagged types.
+Trampolines do not work on machines that prevent execution of stack
+data. For example, on windows systems, enabling DEP (data execution
+protection) will cause trampolines to raise an exception.
@item No_Implicit_Loops
@findex No_Implicit_Loops
implicit @code{for} loops, either by modifying
the generated code where possible,
or by rejecting any construct that would otherwise generate an implicit
-@code{for} loop. The details and use of this restriction are described in
-more detail in the High Integrity product documentation.
+@code{for} loop. If this restriction is active, it is possible to build
+large array aggregates with all static components without generating an
+intermediate temporary, and without generating a loop to initialize individual
+components..Otherwise, a loop is created for arrays larger than about 5000
+scalar components.
+
+@item No_Initialize_Scalars
+@findex No_Initialize_Scalars
+This restriction ensures that no unit in the partition is compiled with
+pragma Initialize_Scalars. This allows the generation of more efficient
+code, and in particular eliminates dummy null initialization routines that
+are otherwise generated for some record and array types.
@item No_Local_Protected_Objects
@findex No_Local_Protected_Objects
contain any reference to the secondary stack. The secondary stack is used
to implement functions returning unconstrained objects (arrays or records)
on some targets.
-The details and use of this restriction are described in
-more detail in the High Integrity product documentation.
@item No_Select_Statements
@findex No_Select_Statements
This restriction ensures at compile time no select statements of any kind
-are permitted, that is the keyword @code{select} may not appear.
+are permitted, that is the keyword @code{select} may not appear.
This is one of the restrictions of the Ravenscar
-profile for limited tasking (see also pragma @code{Ravenscar}).
+profile for limited tasking (see also pragma @code{Profile (Ravenscar)}).
@item No_Standard_Storage_Pools
@findex No_Standard_Storage_Pools
@item No_Streams
@findex No_Streams
-This restriction ensures at compile time that there are no implicit or
-explicit dependencies on the package @code{Ada.Streams}.
-
-@item No_Task_Attributes
-@findex No_Task_Attributes
+This restriction ensures at compile/bind time that there are no
+stream objects created (and therefore no actual stream operations).
+This restriction does not forbid dependences on the package
+@code{Ada.Streams}. So it is permissible to with
+@code{Ada.Streams} (or another package that does so itself)
+as long as no actual stream objects are created.
+
+@item No_Task_Attributes_Package
+@findex No_Task_Attributes_Package
This restriction ensures at compile time that there are no implicit or
explicit dependencies on the package @code{Ada.Task_Attributes}.
except that violations are caught at compile time and cause an error message
to be output either by the compiler or binder.
-@item No_Wide_Characters
-@findex No_Wide_Characters
-This restriction ensures at compile time that no uses of the types
-@code{Wide_Character} or @code{Wide_String}
-appear, and that no wide character literals
-appear in the program (that is literals representing characters not in
-type @code{Character}.
-
@item Static_Priorities
@findex Static_Priorities
This restriction ensures at compile time that all priority expressions
@findex No_Elaboration_Code
This restriction ensures at compile time that no elaboration code is
generated. Note that this is not the same condition as is enforced
-by pragma @code{Preelaborate}. There are cases in which pragma @code{Preelaborate}
-still permits code to be generated (e.g.@: code to initialize a large
-array to all zeroes), and there are cases of units which do not meet
-the requirements for pragma @code{Preelaborate}, but for which no elaboration
-code is generated. Generally, it is the case that preelaborable units
-will meet the restrictions, with the exception of large aggregates
-initialized with an others_clause, and exception declarations (which
-generate calls to a run-time registry procedure). Note that this restriction
-is enforced on a unit by unit basis, it need not be obeyed consistently
+by pragma @code{Preelaborate}. There are cases in which pragma
+@code{Preelaborate} still permits code to be generated (e.g.@: code
+to initialize a large array to all zeroes), and there are cases of units
+which do not meet the requirements for pragma @code{Preelaborate},
+but for which no elaboration code is generated. Generally, it is
+the case that preelaborable units will meet the restrictions, with
+the exception of large aggregates initialized with an others_clause,
+and exception declarations (which generate calls to a run-time
+registry procedure). This restriction is enforced on
+a unit by unit basis, it need not be obeyed consistently
throughout a partition.
+In the case of aggregates with others, if the aggregate has a dynamic
+size, there is no way to eliminate the elaboration code (such dynamic
+bounds would be incompatible with @code{Preelaborate} in any case). If
+the bounds are static, then use of this restriction actually modifies
+the code choice of the compiler to avoid generating a loop, and instead
+generate the aggregate statically if possible, no matter how many times
+the data for the others clause must be repeatedly generated.
+
+It is not possible to precisely document
+the constructs which are compatible with this restriction, since,
+unlike most other restrictions, this is not a restriction on the
+source code, but a restriction on the generated object code. For
+example, if the source contains a declaration:
+
+@smallexample
+ Val : constant Integer := X;
+@end smallexample
+
+@noindent
+where X is not a static constant, it may be possible, depending
+on complex optimization circuitry, for the compiler to figure
+out the value of X at compile time, in which case this initialization
+can be done by the loader, and requires no initialization code. It
+is not possible to document the precise conditions under which the
+optimizer can figure this out.
+
+Note that this the implementation of this restriction requires full
+code generation. If it is used in conjunction with "semantics only"
+checking, then some cases of violations may be missed.
+
@item No_Entry_Queue
@findex No_Entry_Queue
This restriction is a declaration that any protected entry compiled in
@findex No_Implementation_Attributes
This restriction checks at compile time that no GNAT-defined attributes
are present. With this restriction, the only attributes that can be used
-are those defined in the Ada 95 Reference Manual.
+are those defined in the Ada Reference Manual.
@item No_Implementation_Pragmas
@findex No_Implementation_Pragmas
This restriction checks at compile time that no GNAT-defined pragmas
are present. With this restriction, the only pragmas that can be used
-are those defined in the Ada 95 Reference Manual.
+are those defined in the Ada Reference Manual.
@item No_Implementation_Restrictions
@findex No_Implementation_Restrictions
This restriction checks at compile time that no GNAT-defined restriction
identifiers (other than @code{No_Implementation_Restrictions} itself)
are present. With this restriction, the only other restriction identifiers
-that can be used are those defined in the Ada 95 Reference Manual.
+that can be used are those defined in the Ada Reference Manual.
+
+@item No_Wide_Characters
+@findex No_Wide_Characters
+This restriction ensures at compile time that no uses of the types
+@code{Wide_Character} or @code{Wide_String} or corresponding wide
+wide types
+appear, and that no wide or wide wide string or character literals
+appear in the program (that is literals representing characters not in
+type @code{Character}.
@end table
state. See A.5.2(38).
@end cartouche
@noindent
-See the documentation contained in the file @file{a-numran.adb}.
+See the documentation contained in the file @file{a-numran.adb}.
@sp 1
@cartouche
@table @code
@item Ada
Ada
-@item Assembler
-Assembly language
-@item Asm
+@item Assembler
+Assembly language
+@item Asm
Synonym for Assembler
-@item Assembly
+@item Assembly
Synonym for Assembler
@item C
C
@item C_Pass_By_Copy
Allowed only for record types, like C, but also notes that record
is to be passed by copy rather than reference.
-@item COBOL
-COBOL
-@item CPP
-C++
+@item COBOL
+COBOL
+@item C_Plus_Plus (or CPP)
+C++
@item Default
Treated the same as C
@item External
Treated the same as C
-@item Fortran
-Fortran
-@item Intrinsic
+@item Fortran
+Fortran
+@item Intrinsic
For support of pragma @code{Import} with convention Intrinsic, see
separate section on Intrinsic Subprograms.
-@item Stdcall
+@item Stdcall
Stdcall (used for Windows implementations only). This convention correspond
to the WINAPI (previously called Pascal convention) C/C++ convention under
Windows. A function with this convention cleans the stack before exit.
an argument to the link command, unless it contains Ascii.NUL characters.
NUL characters if they appear act as argument separators, so for example
-@smallexample
+@smallexample @c ada
pragma Linker_Options ("-labc" & ASCII.Nul & "-ldef");
@end smallexample
@table @code
@item Floating
Float
-@item Long_Floating
-(Floating) Long_Float
-@item Binary
-Integer
-@item Long_Binary
-Long_Long_Integer
-@item Decimal_Element
-Character
-@item COBOL_Character
-Character
+@item Long_Floating
+(Floating) Long_Float
+@item Binary
+Integer
+@item Long_Binary
+Long_Long_Integer
+@item Decimal_Element
+Character
+@item COBOL_Character
+Character
@end table
+@noindent
For initialization, see the file @file{i-cobol.ads} in the distributed library.
@sp 1
@end cartouche
@noindent
Pragma @code{Discard_Names} causes names of enumeration literals to
-be suppressed. In the presence of this pragma, the Image attribute
+be suppressed. In the presence of this pragma, the Image attribute
provides the image of the Pos of the literal, and Value accepts
Pos values.
attribute. See C.7.1(7).
@end cartouche
@noindent
-The result of this attribute is an 8-digit hexadecimal string
-representing the virtual address of the task control block.
-
+The result of this attribute is a string that identifies
+the object or component that denotes a given task. If a variable Var has a task
+type, the image for this task will have the form Var_XXXXXXXX, where the
+suffix
+is the hexadecimal representation of the virtual address of the corresponding
+task control block. If the variable is an array of tasks, the image of each
+task will have the form of an indexed component indicating the position of a
+given task in the array, eg. Group(5)_XXXXXXX. If the task is a
+component of a record, the image of the task will have the form of a selected
+component. These rules are fully recursive, so that the image of a task that
+is a subcomponent of a composite object corresponds to the expression that
+designates this task.
+@noindent
+If a task is created by an allocator, its image depends on the context. If the
+allocator is part of an object declaration, the rules described above are used
+to construct its image, and this image is not affected by subsequent
+assignments. If the allocator appears within an expression, the image
+includes only the name of the task type.
+@noindent
+If the configuration pragma Discard_Names is present, or if the restriction
+No_Implicit_Heap_Allocation is in effect, the image reduces to
+the numeric suffix, that is to say the hexadecimal representation of the
+virtual address of the control block of the task.
@sp 1
@cartouche
@noindent
@noindent
@c SGI info:
@ignore
-Tasks map to IRIX threads, and the dispatching policy is as defied by
+Tasks map to IRIX threads, and the dispatching policy is as defined by
the IRIX implementation of threads.
@end ignore
The policy is the same as that of the underlying threads implementation.
@end cartouche
@noindent
The ceiling priority of protected objects of the type
-@code{System.Interrupt_Priority'Last} as described in the Ada 95
+@code{System.Interrupt_Priority'Last} as described in the Ada
Reference Manual D.3(10),
@sp 1
@strong{101}. Implementation-defined queuing policies. See D.4(1).
@end cartouche
@noindent
-There are no implementation-defined queueing policies.
+There are no implementation-defined queuing policies.
@sp 1
@cartouche
@code{Restrictions}. See D.7(20).
@end cartouche
@noindent
-There are no such implementation-defined aspects.
+There are no such implementation-defined aspects.
@sp 1
@cartouche
result type is @code{False}. See G.2.1(13).
@end cartouche
@noindent
-Infinite and Nan values are produced as dictated by the IEEE
+Infinite and NaN values are produced as dictated by the IEEE
floating-point standard.
+Note that on machines that are not fully compliant with the IEEE
+floating-point standard, such as Alpha, the @option{-mieee} compiler flag
+must be used for achieving IEEE confirming behavior (although at the cost
+of a significant performance penalty), so infinite and NaN values are
+properly generated.
+
@sp 1
@cartouche
@noindent
as multiplication by a reciprocal. See G.2.1(16).
@end cartouche
@noindent
-Not relevant, division is IEEE exact.
+Not relevant, division is IEEE exact.
@sp 1
@cartouche
@code{False}. See G.2.6(5).
@end cartouche
@noindent
-IEEE infinite and Nan values are produced as appropriate.
+IEEE infinite and Nan values are produced as appropriate.
@sp 1
@cartouche
* Source_Location::
@end menu
+@noindent
GNAT allows a user application program to write the declaration:
-@smallexample
+@smallexample @c ada
pragma Import (Intrinsic, name);
@end smallexample
in @code{pragma Import (Intrinsic,..)}
declarations. In the binary operator case, the operands must have the same
size. The operand or operands must also be appropriate for
-the operator. For example, for addition, the operands must
+the operator. For example, for addition, the operands must
both be floating-point or both be fixed-point, and the
right operand for @code{"**"} must have a root type of
@code{Standard.Integer'Base}.
You can use an intrinsic operator declaration as in the following example:
-@smallexample
+@smallexample @c ada
type Int1 is new Integer;
type Int2 is new Integer;
@section Rotate_Left
@cindex Rotate_Left
@noindent
-In standard Ada 95, the @code{Rotate_Left} function is available only
+In standard Ada, the @code{Rotate_Left} function is available only
for the predefined modular types in package @code{Interfaces}. However, in
GNAT it is possible to define a Rotate_Left function for a user
defined modular type or any signed integer type as in this example:
-@smallexample
+@smallexample @c ada
function Shift_Left
(Value : My_Modular_Type;
Amount : Natural)
values are as follows:
@itemize @bullet
-@item Primitive Types
-For primitive types, the alignment is the maximum of the actual size of
-objects of the type, and the maximum alignment supported by the target.
-For example, for type Long_Float, the object size is 8 bytes, and the
+@item @emph{Primitive Types}.
+For primitive types, the alignment is the minimum of the actual size of
+objects of the type divided by @code{Storage_Unit},
+and the maximum alignment supported by the target.
+(This maximum alignment is given by the GNAT-specific attribute
+@code{Standard'Maximum_Alignment}; see @ref{Maximum_Alignment}.)
+@cindex @code{Maximum_Alignment} attribute
+For example, for type @code{Long_Float}, the object size is 8 bytes, and the
default alignment will be 8 on any target that supports alignments
this large, but on some targets, the maximum alignment may be smaller
-than 8, in which case objects of type Long_Float will be maximally
+than 8, in which case objects of type @code{Long_Float} will be maximally
aligned.
-@item Arrays
+@item @emph{Arrays}.
For arrays, the alignment is equal to the alignment of the component type
for the normal case where no packing or component size is given. If the
array is packed, and the packing is effective (see separate section on
will be as described for primitive types, e.g.@: a packed array of length
31 bits will have an object size of four bytes, and an alignment of 4.
-@item Records
+@item @emph{Records}.
For the normal non-packed case, the alignment of a record is equal to
the maximum alignment of any of its components. For tagged records, this
includes the implicit access type used for the tag. If a pragma @code{Pack} is
used and all fields are packable (see separate section on pragma @code{Pack}),
then the resulting alignment is 1.
-A special case is when the size of the record is given explicitly, or a
-full record representation clause is given, and the size of the record
-is 2, 4, or 8 bytes. In this case, an alignment is chosen to match the
+A special case is when:
+@itemize @bullet
+@item
+the size of the record is given explicitly, or a
+full record representation clause is given, and
+@item
+the size of the record is 2, 4, or 8 bytes.
+@end itemize
+@noindent
+In this case, an alignment is chosen to match the
size of the record. For example, if we have:
-@smallexample
+@smallexample @c ada
type Small is record
A, B : Character;
end record;
+ for Small'Size use 16;
@end smallexample
@noindent
@end itemize
@noindent
-An alignment clause may
-always specify a larger alignment than the default value, up to some
-maximum value dependent on the target (obtainable by using the
-attribute reference System'Maximum_Alignment). The only case in which
-it is permissible to specify a smaller alignment than the default value
-is in the case of a record for which a record representation clause is
-given. In this case, packable fields for which a component clause is
-given still result in a default alignment corresponding to the original
-type, but this may be overridden, since these components in fact only
-require an alignment of one byte. For example, given
-
-@smallexample
- type v is record
- a : integer;
- end record;
+An alignment clause may specify a larger alignment than the default value
+up to some maximum value dependent on the target (obtainable by using the
+attribute reference @code{Standard'Maximum_Alignment}). It may also specify
+a smaller alignment than the default value, for example
- for v use record
- a at 0 range 0 .. 31;
+@smallexample @c ada
+ type V is record
+ A : Integer;
end record;
- for v'alignment use 1;
+ for V'alignment use 1;
@end smallexample
@noindent
@cindex Alignment, default
-The default alignment for the type @code{v} is 4, as a result of the
-integer field in the record, but since this field is placed with a
-component clause, it is permissible, as shown, to override the default
-alignment of the record to a smaller value.
+The default alignment for the type @code{V} is 4, as a result of the
+Integer field in the record, but it is permissible, as shown, to
+override the default alignment of the record with a smaller value.
@node Size Clauses
@section Size Clauses
@cindex Size Clause
@noindent
-The default size of types is as specified in the reference manual. For
-objects, GNAT will generally increase the type size so that the object
-size is a multiple of storage units, and also a multiple of the
-alignment. For example
+The default size for a type @code{T} is obtainable through the
+language-defined attribute @code{T'Size} and also through the
+equivalent GNAT-defined attribute @code{T'Value_Size}.
+For objects of type @code{T}, GNAT will generally increase the type size
+so that the object size (obtainable through the GNAT-defined attribute
+@code{T'Object_Size})
+is a multiple of @code{T'Alignment * Storage_Unit}.
+For example
-@smallexample
+@smallexample @c ada
type Smallint is range 1 .. 6;
type Rec is record
- y1 : integer;
- y2 : boolean;
+ Y1 : integer;
+ Y2 : boolean;
end record;
@end smallexample
@noindent
-In this example, @code{Smallint}
-has a size of 3, as specified by the RM rules,
-but objects of this type will have a size of 8,
+In this example, @code{Smallint'Size} = @code{Smallint'Value_Size} = 3,
+as specified by the RM rules,
+but objects of this type will have a size of 8
+(@code{Smallint'Object_Size} = 8),
since objects by default occupy an integral number
of storage units. On some targets, notably older
versions of the Digital Alpha, the size of stand
alone objects of this type may be 32, reflecting
the inability of the hardware to do byte load/stores.
-Similarly, the size of type @code{Rec} is 40 bits, but
+Similarly, the size of type @code{Rec} is 40 bits
+(@code{Rec'Size} = @code{Rec'Value_Size} = 40), but
the alignment is 4, so objects of this type will have
their size increased to 64 bits so that it is a multiple
-of the alignment. The reason for this decision, which is
-in accordance with the specific note in RM 13.3(43):
+of the alignment (in bits). This decision is
+in accordance with the specific Implementation Advice in RM 13.3(43):
-@smallexample
-A Size clause should be supported for an object if the specified
-Size is at least as large as its subtype's Size, and corresponds
+@quotation
+A @code{Size} clause should be supported for an object if the specified
+@code{Size} is at least as large as its subtype's @code{Size}, and corresponds
to a size in storage elements that is a multiple of the object's
-Alignment (if the Alignment is nonzero).
-@end smallexample
+@code{Alignment} (if the @code{Alignment} is nonzero).
+@end quotation
@noindent
An explicit size clause may be used to override the default size by
increasing it. For example, if we have:
-@smallexample
+@smallexample @c ada
type My_Boolean is new Boolean;
for My_Boolean'Size use 32;
@end smallexample
@noindent
-then objects of this type will always be 32 bits long. In the case of
+then values of this type will always be 32 bits long. In the case of
discrete types, the size can be increased up to 64 bits, with the effect
that the entire specified field is used to hold the value, sign- or
zero-extended as appropriate. If more than 64 bits is specified, then
is to add padding bits after the value. This also causes a warning message
to be generated.
-The largest Size value permitted in GNAT is 2**32@minus{}1. Since this is a
+The largest Size value permitted in GNAT is 2**31@minus{}1. Since this is a
Size in bits, this corresponds to an object of size 256 megabytes (minus
one). This limitation is true on all targets. The reason for this
limitation is that it improves the quality of the code in many cases
@noindent
For tasks, the @code{Storage_Size} clause specifies the amount of space
to be allocated for the task stack. This cannot be extended, and if the
-stack is exhausted, then @code{Storage_Error} will be raised if stack
-checking is enabled. If the default size of 20K bytes is insufficient,
-then you need to use a @code{Storage_Size} attribute definition clause,
+stack is exhausted, then @code{Storage_Error} will be raised (if stack
+checking is enabled). Use a @code{Storage_Size} attribute definition clause,
or a @code{Storage_Size} pragma in the task definition to set the
appropriate required size. A useful technique is to include in every
task definition a pragma of the form:
-@smallexample
+@smallexample @c ada
pragma Storage_Size (Default_Stack_Size);
@end smallexample
@noindent
-Then Default_Stack_Size can be defined in a global package, and modified
-as required. Any tasks requiring different task stack sizes from the
+Then @code{Default_Stack_Size} can be defined in a global package, and
+modified as required. Any tasks requiring stack sizes different from the
default can have an appropriate alternative reference in the pragma.
+You can also use the @code{-d} binder switch to modify the default stack
+size.
+
For access types, the @code{Storage_Size} clause specifies the maximum
space available for allocation of objects of the type. If this space is
exceeded then @code{Storage_Error} will be raised by an allocation attempt.
time, and all the overhead normally associated with maintaining a fixed
size storage pool is eliminated. Consider the following example:
-@smallexample
+@smallexample @c ada
procedure p is
type R is array (Natural) of Character;
type P is access all R;
for P'Storage_Size use 0;
-- Above access type intended only for interfacing purposes
-
+
y : P;
-
+
procedure g (m : P);
pragma Import (C, g);
-
+
-- @dots{}
-
+
begin
-- @dots{}
y := new R;
@cindex Variant record objects, size
@noindent
-An issue arises in the case of variant record objects of whether Size gives
+In the case of variant record objects, there is a question whether Size gives
information about a particular variant, or the maximum size required
for any variant. Consider the following program
-@smallexample
+@smallexample @c ada
with Text_IO; use Text_IO;
procedure q is
type R1 (A : Boolean := False) is record
when False => null;
end case;
end record;
-
+
V1 : R1 (False);
V2 : R1;
Consider the following modified version of the above program:
-@smallexample
+@smallexample @c ada
with Text_IO; use Text_IO;
procedure q is
type R1 (A : Boolean := False) is record
when False => null;
end case;
end record;
-
+
V2 : R1;
function Size (V : R1) return Integer is
For example, suppose we have the declaration:
-@smallexample
+@smallexample @c ada
type Small is range -7 .. -4;
for Small'Size use 2;
@end smallexample
@noindent
Biased representation is only used if the specified @code{Size} clause
cannot be accepted in any other manner. These reduced sizes that force
-biased representation can be used for all discrete types except for
+biased representation can be used for all discrete types except for
enumeration types for which a representation clause is given.
@node Value_Size and Object_Size Clauses
@cindex Size, of objects
@noindent
-In Ada 95, the @code{Size} of a discrete type is the minimum number of bits
-required to hold values of the type. Although this interpretation was
-allowed in Ada 83, it was not required, and this requirement in practice
-can cause some significant difficulties. For example, in most Ada 83
-compilers, @code{Natural'Size} was 32. However, in Ada-95,
+In Ada 95 and Ada 2005, @code{T'Size} for a type @code{T} is the minimum
+number of bits required to hold values of type @code{T}.
+Although this interpretation was allowed in Ada 83, it was not required,
+and this requirement in practice can cause some significant difficulties.
+For example, in most Ada 83 compilers, @code{Natural'Size} was 32.
+However, in Ada 95 and Ada 2005,
@code{Natural'Size} is
typically 31. This means that code may change in behavior when moving
-from Ada 83 to Ada 95. For example, consider:
+from Ada 83 to Ada 95 or Ada 2005. For example, consider:
-@smallexample
+@smallexample @c ada
type Rec is record;
A : Natural;
B : Natural;
end record;
for Rec use record
- for A use at 0 range 0 .. Natural'Size - 1;
- for B use at 0 range Natural'Size .. 2 * Natural'Size - 1;
+ at 0 range 0 .. Natural'Size - 1;
+ at 0 range Natural'Size .. 2 * Natural'Size - 1;
end record;
@end smallexample
@noindent
In the above code, since the typical size of @code{Natural} objects
is 32 bits and @code{Natural'Size} is 31, the above code can cause
-unexpected inefficient packing in Ada 95, and in general there are
-surprising cases where the fact that the object size can exceed the
+unexpected inefficient packing in Ada 95 and Ada 2005, and in general
+there are cases where the fact that the object size can exceed the
size of the type causes surprises.
To help get around this problem GNAT provides two implementation
-dependent attributes @code{Value_Size} and @code{Object_Size}. When
+defined attributes, @code{Value_Size} and @code{Object_Size}. When
applied to a type, these attributes yield the size of the type
(corresponding to the RM defined size attribute), and the size of
objects of the type respectively.
character might be stored in 32 bits on a machine with no efficient
byte access instructions such as the Alpha.
-The default rules for the value of @code{Object_Size} for fixed-point and
+The default rules for the value of @code{Object_Size} for
discrete types are as follows:
@itemize @bullet
@item
The @code{Object_Size} for base subtypes reflect the natural hardware
-size in bits (run the utility @code{gnatpsta} to find those values for numeric types).
-Enumeration types and fixed-point base subtypes have 8, 16, 32 or 64
-bits for this size, depending on the range of values to be stored.
+size in bits (run the compiler with @option{-gnatS} to find those values
+for numeric types). Enumeration types and fixed-point base subtypes have
+8, 16, 32 or 64 bits for this size, depending on the range of values
+to be stored.
@item
The @code{Object_Size} of a subtype is the same as the
@noindent
The @code{Value_Size} attribute
-is the number of bits required to store a value
-of the type. This size can be referred to using the @code{Value_Size}
-attribute. This value is used to determine how tightly to pack
+is the (minimum) number of bits required to store a value
+of the type.
+This value is used to determine how tightly to pack
records or arrays with components of this type, and also affects
the semantics of unchecked conversion (unchecked conversions where
the @code{Value_Size} values differ generate a warning, and are potentially
values as a result of explicit attribute definition clauses, then it
is erroneous to convert from one access subtype to the other.
-At the implementation level, Esize stores the Object_SIze and the
+At the implementation level, Esize stores the Object_Size and the
RM_Size field stores the @code{Value_Size} (and hence the value of the
@code{Size} attribute,
which, as noted above, is equivalent to @code{Value_Size}).
To get a feel for the difference, consider the following examples (note
-that in each case the base is short_short_integer with a size of 8):
+that in each case the base is @code{Short_Short_Integer} with a size of 8):
@smallexample
Object_Size Value_Size
type x1 is range 0 .. 5; 8 3
type x2 is range 0 .. 5;
-for x2'size use 12; 12 12
+for x2'size use 12; 16 12
-subtype x3 is x2 range 0 .. 3; 12 2
+subtype x3 is x2 range 0 .. 3; 16 2
subtype x4 is x2'base range 0 .. 10; 8 4
-subtype x5 is x2 range 0 .. dynamic; 12 (7)
+subtype x5 is x2 range 0 .. dynamic; 16 3*
-subtype x6 is x2'base range 0 .. dynamic; 8 (7)
+subtype x6 is x2'base range 0 .. dynamic; 8 3*
@end smallexample
@noindent
-Note: the entries marked (7) are not actually specified by the Ada 95 RM,
-but it seems in the spirit of the RM rules to allocate the minimum number
-of bits known to be large enough to hold the given range of values.
+Note: the entries marked ``3*'' are not actually specified by the Ada
+Reference Manual, but it seems in the spirit of the RM rules to allocate
+the minimum number of bits (here 3, given the range for @code{x2})
+known to be large enough to hold the given range of values.
So far, so good, but GNAT has to obey the RM rules, so the question is
under what conditions must the RM @code{Size} be used.
@end itemize
@noindent
-For types other than discrete and fixed-point types, the @code{Object_Size}
+For record types, the @code{Object_Size} is always a multiple of the
+alignment of the type (this is true for all types). In some cases the
+@code{Value_Size} can be smaller. Consider:
+
+@smallexample
+ type R is record
+ X : Integer;
+ Y : Character;
+ end record;
+@end smallexample
+
+@noindent
+On a typical 32-bit architecture, the X component will be four bytes, and
+require four-byte alignment, and the Y component will be one byte. In this
+case @code{R'Value_Size} will be 40 (bits) since this is the minimum size
+required to store a value of this type, and for example, it is permissible
+to have a component of type R in an outer record whose component size is
+specified to be 48 bits. However, @code{R'Object_Size} will be 64 (bits),
+since it must be rounded up so that this value is a multiple of the
+alignment (4 bytes = 32 bits).
+
+@noindent
+For all other types, the @code{Object_Size}
and Value_Size are the same (and equivalent to the RM attribute @code{Size}).
Only @code{Size} may be specified for such types.
@cindex Component_Size Clause
@noindent
-Normally, the value specified in a component clause must be consistent
+Normally, the value specified in a component size clause must be consistent
with the subtype of the array component with regard to size and alignment.
In other words, the value specified must be at least equal to the size
of this subtype, and must be a multiple of the alignment value.
accurately honor all packing requests in this range. For example, if
we have:
-@smallexample
+@smallexample @c ada
type r is array (1 .. 8) of Natural;
-for r'Size use 31;
+for r'Component_Size use 31;
@end smallexample
@noindent
Of course access to the components of such an array is considerably
less efficient than if the natural component size of 32 is used.
+Note that there is no point in giving both a component size clause
+and a pragma Pack for the same array type. if such duplicate
+clauses are given, the pragma Pack will be ignored.
+
@node Bit_Order Clauses
@section Bit_Order Clauses
@cindex Bit_Order Clause
being the default, then the following two declarations have exactly
the same effect:
-@smallexample
+@smallexample @c ada
type R1 is record
A : Boolean;
B : Integer range 1 .. 120;
In particular, the following attempt at getting an endian-independent integer
does not work:
-@smallexample
+@smallexample @c ada
type R2 is record
A : Integer;
end record;
non-standard bit order is described in section 15.5.3 of the Ada
Reference Manual:
-@smallexample
+@quotation
2 A bit ordering is a method of interpreting the meaning of
the storage place attributes.
-@end smallexample
+@end quotation
@noindent
To understand the precise definition of storage place attributes in
this context, we visit section 13.5.1 of the manual:
-@smallexample
+@quotation
13 A record_representation_clause (without the mod_clause)
specifies the layout. The storage place attributes (see 13.5.2)
are taken from the values of the position, first_bit, and last_bit
expressions after normalizing those values so that first_bit is
less than Storage_Unit.
-@end smallexample
+@end quotation
@noindent
The critical point here is that storage places are taken from
interpretation applies to normalized values. The interpretation
is described in the later part of the 15.5.3 paragraph:
-@smallexample
+@quotation
2 A bit ordering is a method of interpreting the meaning of
the storage place attributes. High_Order_First (known in the
vernacular as ``big endian'') means that the first bit of a
integer value). Low_Order_First (known in the vernacular as
``little endian'') means the opposite: the first bit is the
least significant.
-@end smallexample
+@end quotation
@noindent
Note that the numbering is with respect to the bits of a storage
On a big-endian machine, we can write the following representation clause
-@smallexample
+@smallexample @c ada
type Data is record
Master_Control : Bit;
Master_V1 : Bit;
Now if we move this to a little endian machine, then the bit ordering within
the byte is backwards, so we have to rewrite the record rep clause as:
-@smallexample
+@smallexample @c ada
for Data use record
Master_Control at 0 range 7 .. 7;
Master_V1 at 0 range 6 .. 6;
end record;
@end smallexample
+@noindent
It is a nuisance to have to rewrite the clause, especially if
the code has to be maintained on both machines. However,
this is a case that we can handle with the
This means that we can simply use the
first record clause, together with the declaration
-@smallexample
+@smallexample @c ada
for Data'Bit_Order use High_Order_First;
@end smallexample
To make this clear, let us rewrite the record rep clause of the previous
example as:
-@smallexample
+@smallexample @c ada
for Data'Bit_Order use High_Order_First;
for Data use record
Master_Control at 0 range 0 .. 0;
@noindent
This is exactly equivalent to saying (a repeat of the first example):
-@smallexample
+@smallexample @c ada
for Data'Bit_Order use High_Order_First;
for Data use record
Master_Control at 0 range 0 .. 0;
Why are they equivalent? Well take a specific field, the @code{Slave_V2}
field. The storage place attributes are obtained by normalizing the
values given so that the @code{First_Bit} value is less than 8. After
-nromalizing the values (0,10,10) we get (1,2,2) which is exactly what
+normalizing the values (0,10,10) we get (1,2,2) which is exactly what
we specified in the other case.
Now one might expect that the @code{Bit_Order} attribute might affect
values must be used. If in our example, the slave byte came first on
some machines we might write:
-@smallexample
+@smallexample @c ada
Master_Byte_First constant Boolean := @dots{};
Master_Byte : constant Natural :=
@item
Any scalar type
@item
-Any fixed-point type
-@item
Any type whose size is specified with a size clause
@item
Any packed array type with a static size
component size were specified giving the component subtype size.
For example if we have:
-@smallexample
+@smallexample @c ada
type r is range 0 .. 17;
-
+
type ar is array (1 .. 8) of r;
pragma Pack (ar);
@end smallexample
and the size of the array @code{ar} will be exactly 40 bits.
Note that in some cases this rather fierce approach to packing can produce
-unexpected effects. For example, in Ada 95, type Natural typically has a
-size of 31, meaning that if you pack an array of Natural, you get 31-bit
+unexpected effects. For example, in Ada 95 and Ada 2005,
+subtype @code{Natural} typically has a size of 31, meaning that if you
+pack an array of @code{Natural}, you get 31-bit
close packing, which saves a few bits, but results in far less efficient
access. Since many other Ada compilers will ignore such a packing request,
GNAT will generate a warning on some uses of pragma @code{Pack} that it guesses
time, then the packed array is represented as an array of bytes, and the
length is always a multiple of 8 bits.
+Note that to represent a packed array as a modular type, the alignment must
+be suitable for the modular type involved. For example, on typical machines
+a 32-bit packed array will be represented by a 32-bit modular integer with
+an alignment of four bytes. If you explicitly override the default alignment
+with an alignment clause that is too small, the modular representation
+cannot be used. For example, consider the following set of declarations:
+
+@smallexample @c ada
+ type R is range 1 .. 3;
+ type S is array (1 .. 31) of R;
+ for S'Component_Size use 2;
+ for S'Size use 62;
+ for S'Alignment use 1;
+@end smallexample
+
+@noindent
+If the alignment clause were not present, then a 62-bit modular
+representation would be chosen (typically with an alignment of 4 or 8
+bytes depending on the target). But the default alignment is overridden
+with the explicit alignment clause. This means that the modular
+representation cannot be used, and instead the array of bytes
+representation must be used, meaning that the length must be a multiple
+of 8. Thus the above set of declarations will result in a diagnostic
+rejecting the size clause and noting that the minimum size allowed is 64.
+
+@cindex Pragma Pack (for type Natural)
+@cindex Pragma Pack warning
+
+One special case that is worth noting occurs when the base type of the
+component size is 8/16/32 and the subtype is one bit less. Notably this
+occurs with subtype @code{Natural}. Consider:
+
+@smallexample @c ada
+ type Arr is array (1 .. 32) of Natural;
+ pragma Pack (Arr);
+@end smallexample
+
+@noindent
+In all commonly used Ada 83 compilers, this pragma Pack would be ignored,
+since typically @code{Natural'Size} is 32 in Ada 83, and in any case most
+Ada 83 compilers did not attempt 31 bit packing.
+
+In Ada 95 and Ada 2005, @code{Natural'Size} is required to be 31. Furthermore,
+GNAT really does pack 31-bit subtype to 31 bits. This may result in a
+substantial unintended performance penalty when porting legacy Ada 83 code.
+To help prevent this, GNAT generates a warning in such cases. If you really
+want 31 bit packing in a case like this, you can set the component size
+explicitly:
+
+@smallexample @c ada
+ type Arr is array (1 .. 32) of Natural;
+ for Arr'Component_Size use 31;
+@end smallexample
+
+@noindent
+Here 31-bit packing is achieved as required, and no warning is generated,
+since in this case the programmer intention is clear.
+
@node Pragma Pack for Records
@section Pragma Pack for Records
@cindex Pragma Pack (for records)
@noindent
-Pragma @code{Pack} applied to a record will pack the components to reduce wasted
-space from alignment gaps and by reducing the amount of space taken by
-components. We distinguish between package components and non-packable
-components. Components of the following types are considered packable:
-
+Pragma @code{Pack} applied to a record will pack the components to reduce
+wasted space from alignment gaps and by reducing the amount of space
+taken by components. We distinguish between @emph{packable} components and
+@emph{non-packable} components.
+Components of the following types are considered packable:
@itemize @bullet
@item
-All scalar types are packable.
-
-@item
-All fixed-point types are represented internally as integers, and
-are packable.
+All primitive types are packable.
@item
Small packed arrays, whose size does not exceed 64 bits, and where the
can start on an arbitrary bit boundary.
All other types are non-packable, they occupy an integral number of
-storage units, and
+storage units, and
are placed at a boundary corresponding to their alignment requirements.
For example, consider the record
-@smallexample
+@smallexample @c ada
type Rb1 is array (1 .. 13) of Boolean;
pragma Pack (rb1);
@noindent
The representation for the record x2 is as follows:
-@smallexample
+@smallexample @c ada
for x2'Size use 224;
for x2 use record
l1 at 0 range 0 .. 0;
of length equal to their sizes, and placed at specific bit boundaries (and
not byte boundaries) to
eliminate padding. But @code{l3} is of a non-packable float type, so
-it is on the next appropriate alignment boundary.
+it is on the next appropriate alignment boundary.
The next two fields are fully packable, so @code{l4} and @code{l5} are
minimally packed with no gaps. However, type @code{Rb2} is a packed
internally using a modular type with the appropriate number of bits, and
thus the same lack of restriction applies. For example, if you declare:
-@smallexample
+@smallexample @c ada
type R is array (1 .. 49) of Boolean;
pragma Pack (R);
for R'Size use 49;
then a component clause for a component of type R may start on any
specified bit boundary, and may specify a value of 49 bits or greater.
-For non-primitive types, including packed arrays with a size greater than
-64 bits, component clauses must respect the alignment requirement of the
-type, in particular, always starting on a byte boundary, and the length
-must be a multiple of the storage unit.
+For packed bit arrays that are longer than 64 bits, there are two
+cases. If the component size is a power of 2 (1,2,4,8,16,32 bits),
+including the important case of single bits or boolean values, then
+there are no limitations on placement of such components, and they
+may start and end at arbitrary bit boundaries.
+
+If the component size is not a power of 2 (e.g. 3 or 5), then
+an array of this type longer than 64 bits must always be placed on
+on a storage unit (byte) boundary and occupy an integral number
+of storage units (bytes). Any component clause that does not
+meet this requirement will be rejected.
+
+Any aliased component, or component of an aliased type, must
+have its normal alignment and size. A component clause that
+does not meet this requirement will be rejected.
The tag field of a tagged type always occupies an address sized field at
the start of the record. No component clause may attempt to overlay this
-tag.
+tag. When a tagged type appears as a component, the tag field must have
+proper alignment
In the case of a record extension T1, of a type T, no component clause applied
to the type T1 can specify a storage location that would overlap the first
T'Size bytes of the record.
+For all other component types, including non-bit-packed arrays,
+the component can be placed at an arbitrary bit boundary,
+so for example, the following is permitted:
+
+@smallexample @c ada
+ type R is array (1 .. 10) of Boolean;
+ for R'Size use 80;
+
+ type Q is record
+ G, H : Boolean;
+ L, M : R;
+ end record;
+
+ for Q use record
+ G at 0 range 0 .. 0;
+ H at 0 range 1 .. 1;
+ L at 0 range 2 .. 81;
+ R at 0 range 82 .. 161;
+ end record;
+@end smallexample
+
+@noindent
+Note: the above rules apply to recent releases of GNAT 5.
+In GNAT 3, there are more severe restrictions on larger components.
+For non-primitive types, including packed arrays with a size greater than
+64 bits, component clauses must respect the alignment requirement of the
+type, in particular, always starting on a byte boundary, and the length
+must be a multiple of the storage unit.
+
@node Enumeration Clauses
@section Enumeration Clauses
must be representable. For the signed case, if one or more of the
representation values are negative, all values must be in the range:
-@smallexample
+@smallexample @c ada
System.Min_Int .. System.Max_Int
@end smallexample
For the unsigned case, where all values are non negative, the values must
be in the range:
-@smallexample
+@smallexample @c ada
0 .. System.Max_Binary_Modulus;
@end smallexample
enumeration clause has been applied, then the array is stored in a compact
manner. Consider the declarations:
-@smallexample
+@smallexample @c ada
type r is (A, B, C);
for r use (A => 1, B => 5, C => 10);
type t is array (r) of Character;
The reference manual allows a general restriction on representation clauses,
as found in RM 13.1(22):
-@smallexample
- An implementation need not support representation
- items containing nonstatic expressions, except that
- an implementation should support a representation item
- for a given entity if each nonstatic expression in the
- representation item is a name that statically denotes
- a constant declared before the entity.
-@end smallexample
+@quotation
+An implementation need not support representation
+items containing nonstatic expressions, except that
+an implementation should support a representation item
+for a given entity if each nonstatic expression in the
+representation item is a name that statically denotes
+a constant declared before the entity.
+@end quotation
@noindent
In practice this is applicable only to address clauses, since this is the
only case in which a non-static expression is permitted by the syntax. As
the AARM notes in sections 13.1 (22.a-22.h):
-@smallexample
- 22.a Reason: This is to avoid the following sort
- of thing:
+@display
+ 22.a Reason: This is to avoid the following sort of thing:
22.b X : Integer := F(@dots{});
Y : Address := G(@dots{});
Address are hardly ever static, but their value
might be known at compile time anyway in many
cases.
-@end smallexample
+@end display
@noindent
GNAT does indeed permit many additional cases of non-static expressions. In
@item
There is explicit or implicit initialization required for the object.
+Note that access values are always implicitly initialized, and also
+in GNAT, certain bit-packed arrays (those having a dynamic length or
+a length greater than 64) will also be implicitly initialized to zero.
@item
The address value is non-static. Here GNAT is more permissive than the
RM, and allows the address value to be the address of a previously declared
stand-alone variable, as long as it does not itself have an address clause.
-@smallexample
- Anchor : Some_Initialized_Type;
+@smallexample @c ada
+ Anchor : Some_Initialized_Type;
Overlay : Some_Initialized_Type;
for Overlay'Address use Anchor'Address;
@end smallexample
+@noindent
However, the prefix of the address clause cannot be an array component, or
a component of a discriminated record.
As noted above in section 22.h, address values are typically non-static. In
particular the To_Address function, even if applied to a literal value, is
a non-static function call. To avoid this minor annoyance, GNAT provides
-the implementation defined attribute 'To_Address. The following two
+the implementation defined attribute 'To_Address. The following two
expressions have identical values:
-Another issue with address clauses is the interaction with alignment
-requirements. When an address clause is given for an object, the address
-value must be consistent with the alignment of the object (which is usually
-the same as the alignment of the type of the object). If an address clause
-is given that specifies an inappropriately aligned address value, then the
-program execution is erroneous.
-
-Since this source of erroneous behavior can have unfortunate effects, GNAT
-checks (at compile time if possible, generating a warning, or at execution
-time with a run-time check) that the alignment is appropriate. If the
-run-time check fails, then @code{Program_Error} is raised. This run-time
-check is suppressed if range checks are suppressed, or if
-@code{pragma Restrictions (No_Elaboration_Code)} is in effect.
-
-@findex Attribute
-@findex To_Address
-@smallexample
- To_Address (16#1234_0000#)
- System'To_Address (16#1234_0000#);
-@end smallexample
+@findex Attribute
+@findex To_Address
+@smallexample @c ada
+ To_Address (16#1234_0000#)
+ System'To_Address (16#1234_0000#);
+@end smallexample
@noindent
except that the second form is considered to be a static expression, and
Additionally, GNAT treats as static an address clause that is an
unchecked_conversion of a static integer value. This simplifies the porting
of legacy code, and provides a portable equivalent to the GNAT attribute
-To_Address.
+@code{To_Address}.
+
+Another issue with address clauses is the interaction with alignment
+requirements. When an address clause is given for an object, the address
+value must be consistent with the alignment of the object (which is usually
+the same as the alignment of the type of the object). If an address clause
+is given that specifies an inappropriately aligned address value, then the
+program execution is erroneous.
+
+Since this source of erroneous behavior can have unfortunate effects, GNAT
+checks (at compile time if possible, generating a warning, or at execution
+time with a run-time check) that the alignment is appropriate. If the
+run-time check fails, then @code{Program_Error} is raised. This run-time
+check is suppressed if range checks are suppressed, or if the special GNAT
+check Alignment_Check is suppressed, or if
+@code{pragma Restrictions (No_Elaboration_Code)} is in effect.
+
+Finally, GNAT does not permit overlaying of objects of controlled types or
+composite types containing a controlled component. In most cases, the compiler
+can detect an attempt at such overlays and will generate a warning at compile
+time and a Program_Error exception at run time.
@findex Export
An address clause cannot be given for an exported object. More
understandably the real restriction is that objects with an address
clause cannot be exported. This is because such variables are not
-defined by the Ada program, so there is no external object so export.
+defined by the Ada program, so there is no external object to export.
@findex Import
It is permissible to give an address clause and a pragma Import for the
type R is record
M : Integer := 0;
end record;
-
+
Ext : R;
for Ext'Address use System'To_Address (16#1234_1234#);
|
modify overlaid storage
>>> warning: use pragma Import for "Ext" to suppress
initialization (RM B(24))
-
+
end G;
@end smallexample
object is declared and initialized elsewhere. The following package compiles
without warnings (and the initialization is suppressed):
-@smallexample
+@smallexample @c ada
with System;
package G is
type R is record
M : Integer := 0;
end record;
-
+
Ext : R;
for Ext'Address use System'To_Address (16#1234_1234#);
pragma Import (Ada, Ext);
end G;
@end smallexample
+@noindent
+A final issue with address clauses involves their use for overlaying
+variables, as in the following example:
+@cindex Overlaying of objects
+
+@smallexample @c ada
+ A : Integer;
+ B : Integer;
+ for B'Address use A'Address;
+@end smallexample
+
+@noindent
+or alternatively, using the form recommended by the RM:
+
+@smallexample @c ada
+ A : Integer;
+ Addr : constant Address := A'Address;
+ B : Integer;
+ for B'Address use Addr;
+@end smallexample
+
+@noindent
+In both of these cases, @code{A}
+and @code{B} become aliased to one another via the
+address clause. This use of address clauses to overlay
+variables, achieving an effect similar to unchecked
+conversion was erroneous in Ada 83, but in Ada 95 and Ada 2005
+the effect is implementation defined. Furthermore, the
+Ada RM specifically recommends that in a situation
+like this, @code{B} should be subject to the following
+implementation advice (RM 13.3(19)):
+
+@quotation
+19 If the Address of an object is specified, or it is imported
+ or exported, then the implementation should not perform
+ optimizations based on assumptions of no aliases.
+@end quotation
+
+@noindent
+GNAT follows this recommendation, and goes further by also applying
+this recommendation to the overlaid variable (@code{A}
+in the above example) in this case. This means that the overlay
+works "as expected", in that a modification to one of the variables
+will affect the value of the other.
+
@node Effect of Convention on Representation
@section Effect of Convention on Representation
@cindex Convention, effect on representation
consistent with C@. This means that specifying convention C (for example)
has no effect.
-There are three exceptions to this general rule:
+There are four exceptions to this general rule:
@itemize @bullet
to accommodate all values of the type. For example, for the enumeration
type declared by:
-@smallexample
+@smallexample @c ada
type Color is (Red, Green, Blue);
@end smallexample
Ada enumeration type, then the size is modified as necessary (usually to
32 bits) to be consistent with the C convention for enum values.
+Note that this treatment applies only to types. If Convention C is given for
+an enumeration object, where the enumeration type is not Convention C, then
+Object_Size bits are allocated. For example, for a normal enumeration type,
+with less than 256 elements, only 8 bits will be allocated for the object.
+Since this may be a surprise in terms of what C expects, GNAT will issue a
+warning in this situation. The warning can be suppressed by giving an explicit
+size clause specifying the desired size.
+
@item Convention C/Fortran and Boolean types
In C, the usual convention for boolean values, that is values used for
conditions, is that zero represents false, and nonzero values represent
To accommodate the Fortran and C conventions, if a pragma Convention specifies
C or Fortran convention for a derived Boolean, as in the following example:
-@smallexample
+@smallexample @c ada
type C_Switch is new Boolean;
pragma Convention (C, C_Switch);
@end smallexample
values generated by GNAT, the conventional value 1 will be used for True, but
when one of these values is read, any nonzero value is treated as True.
+@item Access types on OpenVMS
+For 64-bit OpenVMS systems, access types (other than those for unconstrained
+arrays) are 64-bits long. An exception to this rule is for the case of
+C-convention access types where there is no explicit size clause present (or
+inherited for derived types). In this case, GNAT chooses to make these
+pointers 32-bits, which provides an easier path for migration of 32-bit legacy
+code. size clause specifying 64-bits must be used to obtain a 64-bit pointer.
+
@end itemize
@node Determining the Representations chosen by GNAT
effect is on the layout of types and objects.
As required by the Ada RM, if a representation clause is not accepted, then
-it must be rejected as illegal by the compiler. However, when a representation
-clause or pragma is accepted, there can still be questions of what the
-compiler actually does. For example, if a partial record representation
-clause specifies the location of some components and not others, then where
-are the non-specified components placed? Or if pragma @code{Pack} is used on a
-record, then exactly where are the resulting fields placed? The section
-on pragma @code{Pack} in this chapter can be used to answer the second question,
-but it is often easier to just see what the compiler does.
+it must be rejected as illegal by the compiler. However, when a
+representation clause or pragma is accepted, there can still be questions
+of what the compiler actually does. For example, if a partial record
+representation clause specifies the location of some components and not
+others, then where are the non-specified components placed? Or if pragma
+@code{Pack} is used on a record, then exactly where are the resulting
+fields placed? The section on pragma @code{Pack} in this chapter can be
+used to answer the second question, but it is often easier to just see
+what the compiler does.
For this purpose, GNAT provides the option @code{-gnatR}. If you compile
with this option, then the compiler will output information on the actual
representations chosen, in a format similar to source representation
clauses. For example, if we compile the package:
-@smallexample
+@smallexample @c ada
package q is
type r (x : boolean) is tagged record
case x is
@chapter Standard Library Routines
@noindent
-The Ada 95 Reference Manual contains in Annex A a full description of an
+The Ada Reference Manual contains in Annex A a full description of an
extensive set of standard library routines that can be used in any Ada
program, and which must be provided by all Ada compilers. They are
analogous to the standard C library used by C programs.
GNAT implements all of the facilities described in annex A, and for most
-purposes the description in the Ada 95
-reference manual, or appropriate Ada
+purposes the description in the Ada Reference Manual, or appropriate Ada
text book, will be sufficient for making use of these facilities.
-In the case of the input-output facilities, @xref{The Implementation of
-Standard I/O}, gives details on exactly how GNAT interfaces to the
-file system. For the remaining packages, the Ada 95 reference manual
+In the case of the input-output facilities,
+@xref{The Implementation of Standard I/O},
+gives details on exactly how GNAT interfaces to the
+file system. For the remaining packages, the Ada Reference Manual
should be sufficient. The following is a list of the packages included,
together with a brief description of the functionality that is provided.
For completeness, references are included to other predefined library
-routines defined in other sections of the Ada 95 reference manual (these are
-cross-indexed from annex A).
+routines defined in other sections of the Ada Reference Manual (these are
+cross-indexed from Annex A).
@table @code
@item Ada (A.2)
@item Ada.Command_Line (A.15)
This package provides access to the command line parameters and the name
-of the current program (analogous to the use of @code{argc} and @code{argv} in C), and
-also allows the exit status for the program to be set in a
+of the current program (analogous to the use of @code{argc} and @code{argv}
+in C), and also allows the exit status for the program to be set in a
system-independent manner.
@item Ada.Decimal (F.2)
@itemx Ada.Strings.Wide_Maps (A.4.7)
@itemx Ada.Strings.Wide_Maps.Constants (A.4.7)
@itemx Ada.Strings.Wide_Unbounded (A.4.7)
-These package provide analogous capabilities to the corresponding
+These packages provide analogous capabilities to the corresponding
packages without @samp{Wide_} in the name, but operate with the types
@code{Wide_String} and @code{Wide_Character} instead of @code{String}
and @code{Character}.
+@item Ada.Strings.Wide_Wide_Bounded (A.4.7)
+@itemx Ada.Strings.Wide_Wide_Fixed (A.4.7)
+@itemx Ada.Strings.Wide_Wide_Maps (A.4.7)
+@itemx Ada.Strings.Wide_Wide_Maps.Constants (A.4.7)
+@itemx Ada.Strings.Wide_Wide_Unbounded (A.4.7)
+These packages provide analogous capabilities to the corresponding
+packages without @samp{Wide_} in the name, but operate with the types
+@code{Wide_Wide_String} and @code{Wide_Wide_Character} instead
+of @code{String} and @code{Character}.
+
@item Ada.Synchronous_Task_Control (D.10)
This package provides some standard facilities for controlling task
communication in a synchronous manner.
@item Ada.Text_IO.Decimal_IO
Provides input-output facilities for decimal fixed-point types
-@item Ada.Text_IO.Enumeration_IO
+@item Ada.Text_IO.Enumeration_IO
Provides input-output facilities for enumeration types.
@item Ada.Text_IO.Fixed_IO
A pointer other than a pointer to an unconstrained array type may be
converted to and from System.Address. Such usage is common in Ada 83
programs, but note that Ada.Address_To_Access_Conversions is the
-preferred method of performing such conversions in Ada 95. Neither
+preferred method of performing such conversions in Ada 95 and Ada 2005.
+Neither
unchecked conversion nor Ada.Address_To_Access_Conversions should be
used in conjunction with pointers to unconstrained objects, since
the bounds information cannot be handled correctly in this case.
This package is similar to @code{Ada.Text_IO.Streams}, except that the
types are @code{Wide_Character} and @code{Wide_String} instead of
@code{Character} and @code{String}.
+
+@item Ada.Wide_Wide_Text_IO (A.11)
+This package is similar to @code{Ada.Text_IO}, except that the external
+file supports wide character representations, and the internal types are
+@code{Wide_Character} and @code{Wide_String} instead of @code{Character}
+and @code{String}. It contains generic subpackages listed next.
+
+@item Ada.Wide_Wide_Text_IO.Decimal_IO
+Provides input-output facilities for decimal fixed-point types
+
+@item Ada.Wide_Wide_Text_IO.Enumeration_IO
+Provides input-output facilities for enumeration types.
+
+@item Ada.Wide_Wide_Text_IO.Fixed_IO
+Provides input-output facilities for ordinary fixed-point types.
+
+@item Ada.Wide_Wide_Text_IO.Float_IO
+Provides input-output facilities for float types. The following
+predefined instantiations of this generic package are available:
+
+@table @code
+@item Short_Float
+@code{Short_Float_Wide_Wide_Text_IO}
+@item Float
+@code{Float_Wide_Wide_Text_IO}
+@item Long_Float
+@code{Long_Float_Wide_Wide_Text_IO}
+@end table
+
+@item Ada.Wide_Wide_Text_IO.Integer_IO
+Provides input-output facilities for integer types. The following
+predefined instantiations of this generic package are available:
+
+@table @code
+@item Short_Short_Integer
+@code{Ada.Short_Short_Integer_Wide_Wide_Text_IO}
+@item Short_Integer
+@code{Ada.Short_Integer_Wide_Wide_Text_IO}
+@item Integer
+@code{Ada.Integer_Wide_Wide_Text_IO}
+@item Long_Integer
+@code{Ada.Long_Integer_Wide_Wide_Text_IO}
+@item Long_Long_Integer
+@code{Ada.Long_Long_Integer_Wide_Wide_Text_IO}
+@end table
+
+@item Ada.Wide_Wide_Text_IO.Modular_IO
+Provides input-output facilities for modular (unsigned) types
+
+@item Ada.Wide_Wide_Text_IO.Complex_IO (G.1.3)
+This package is similar to @code{Ada.Text_IO.Complex_IO}, except that the
+external file supports wide character representations.
+
+@item Ada.Wide_Wide_Text_IO.Editing (F.3.4)
+This package is similar to @code{Ada.Text_IO.Editing}, except that the
+types are @code{Wide_Character} and @code{Wide_String} instead of
+@code{Character} and @code{String}.
+
+@item Ada.Wide_Wide_Text_IO.Streams (A.12.3)
+This package is similar to @code{Ada.Text_IO.Streams}, except that the
+types are @code{Wide_Character} and @code{Wide_String} instead of
+@code{Character} and @code{String}.
@end table
+
+
+
@node The Implementation of Standard I/O
@chapter The Implementation of Standard I/O
@noindent
GNAT implements all the required input-output facilities described in
-A.6 through A.14. These sections of the Ada 95 reference manual describe the
+A.6 through A.14. These sections of the Ada Reference Manual describe the
required behavior of these packages from the Ada point of view, and if
you are writing a portable Ada program that does not need to know the
exact manner in which Ada maps to the outside world when it comes to
reading or writing external files, then you do not need to read this
chapter. As long as your files are all regular files (not pipes or
devices), and as long as you write and read the files only from Ada, the
-description in the Ada 95 reference manual is sufficient.
+description in the Ada Reference Manual is sufficient.
However, if you want to do input-output to pipes or other devices, such
as the keyboard or screen, or if the files you are dealing with are
these additional facilities are also described in this chapter.
@menu
-* Standard I/O Packages::
-* FORM Strings::
-* Direct_IO::
-* Sequential_IO::
-* Text_IO::
-* Wide_Text_IO::
-* Stream_IO::
-* Shared Files::
-* Open Modes::
-* Operations on C Streams::
-* Interfacing to C Streams::
+* Standard I/O Packages::
+* FORM Strings::
+* Direct_IO::
+* Sequential_IO::
+* Text_IO::
+* Wide_Text_IO::
+* Wide_Wide_Text_IO::
+* Stream_IO::
+* Shared Files::
+* Filenames encoding::
+* Open Modes::
+* Operations on C Streams::
+* Interfacing to C Streams::
@end menu
@node Standard I/O Packages
@item
Ada.Text_IO.Complex_IO
@item
-Ada.Text_IO.Text_Streams,
+Ada.Text_IO.Text_Streams
@item
Ada.Wide_Text_IO
@item
-Ada.Wide_Text_IO.Complex_IO,
+Ada.Wide_Text_IO.Complex_IO
@item
Ada.Wide_Text_IO.Text_Streams
@item
+Ada.Wide_Wide_Text_IO
+@item
+Ada.Wide_Wide_Text_IO.Complex_IO
+@item
+Ada.Wide_Wide_Text_IO.Text_Streams
+@item
Ada.Stream_IO
@item
Ada.Sequential_IO
All input/output operations use @code{fread}/@code{fwrite}.
@end itemize
-There is no internal buffering of any kind at the Ada library level. The
-only buffering is that provided at the system level in the
-implementation of the C library routines that support streams. This
-facilitates shared use of these streams by mixed language programs.
+@noindent
+There is no internal buffering of any kind at the Ada library level. The only
+buffering is that provided at the system level in the implementation of the
+library routines that support streams. This facilitates shared use of these
+streams by mixed language programs. Note though that system level buffering is
+explicitly enabled at elaboration of the standard I/O packages and that can
+have an impact on mixed language programs, in particular those using I/O before
+calling the Ada elaboration routine (e.g. adainit). It is recommended to call
+the Ada elaboration routine before performing any I/O or when impractical,
+flush the common I/O streams and in particular Standard_Output before
+elaborating the Ada code.
@node FORM Strings
@section FORM Strings
@smallexample
SHARED=[YES|NO]
-WCEM=[n|h|u|s\e]
+WCEM=[n|h|u|s|e|8|b]
@end smallexample
+@noindent
The use of these parameters is described later in this section.
@node Direct_IO
sequence, with the first record starting at offset zero, and subsequent
records following. There is no control information of any kind. For
example, if 32-bit integers are being written, each record takes
-4-bytes, so the record at index @var{K} starts at offset
+4-bytes, so the record at index @var{K} starts at offset
(@var{K}@minus{}1)*4.
There is no limit on the size of Direct_IO files, they are expanded as
length array items, and then read the data back into different length
arrays. For example, the following will raise @code{Data_Error}:
-@smallexample
+@smallexample @c ada
package IO is new Sequential_IO (String);
F : IO.File_Type;
S : String (1..4);
@end smallexample
-On some Ada implementations, this will print @samp{hell}, but the program is
+@noindent
+On some Ada implementations, this will print @code{hell}, but the program is
clearly incorrect, since there is only one element in the file, and that
-element is the string @samp{hello!}.
+element is the string @code{hello!}.
-In Ada 95, this kind of behavior can be legitimately achieved using
-Stream_IO, and this is the preferred mechanism. In particular, the above
-program fragment rewritten to use Stream_IO will work correctly.
+In Ada 95 and Ada 2005, this kind of behavior can be legitimately achieved
+using Stream_IO, and this is the preferred mechanism. In particular, the
+above program fragment rewritten to use Stream_IO will work correctly.
@node Text_IO
@section Text_IO
FF (form feed, 16#0C#) Page Mark
@end smallexample
+@noindent
A canonical Text_IO file is defined as one in which the following
conditions are met:
assumed to be present.
@end itemize
+@noindent
A file written using Text_IO will be in canonical form provided that no
explicit @code{LF} or @code{FF} characters are written using @code{Put}
or @code{Put_Line}. There will be no @code{FF} character at the end of
the file unless an explicit @code{New_Page} operation was performed
before closing the file.
-A canonical Text_IO file that is a regular file, i.e.@: not a device or a
-pipe, can be read using any of the routines in Text_IO@. The
-semantics in this case will be exactly as defined in the Ada 95 reference
-manual and all the routines in Text_IO are fully implemented.
+A canonical Text_IO file that is a regular file (i.e., not a device or a
+pipe) can be read using any of the routines in Text_IO@. The
+semantics in this case will be exactly as defined in the Ada Reference
+Manual, and all the routines in Text_IO are fully implemented.
A text file that does not meet the requirements for a canonical Text_IO
file has one of the following:
i.e.@: there is no explicit line mark or page mark at the end of the file.
@end itemize
+@noindent
Text_IO can be used to read such non-standard text files but subprograms
to do with line or page numbers do not have defined meanings. In
particular, a @code{FF} character that does not follow a @code{LF}
the file.
@menu
-* Text_IO Stream Pointer Positioning::
-* Text_IO Reading and Writing Non-Regular Files::
-* Get_Immediate::
+* Text_IO Stream Pointer Positioning::
+* Text_IO Reading and Writing Non-Regular Files::
+* Get_Immediate::
* Treating Text_IO Files as Streams::
* Text_IO Extensions::
* Text_IO Facilities for Unbounded Strings::
@end menu
-@node Text_IO Stream Pointer Positioning
+@node Text_IO Stream Pointer Positioning
@subsection Stream Pointer Positioning
@noindent
handle the logical position.
@end itemize
+@noindent
These discrepancies have no effect on the observable behavior of
Text_IO, but if a single Ada stream is shared between a C program and
Ada program, or shared (using @samp{shared=yes} in the form string)
the end of the file.
@end itemize
+@noindent
Output to non-regular files is the same as for regular files. Page marks
may be written to non-regular files using @code{New_Page}, but as noted
above they will not be treated as page marks on input if the output is
of file indication is not ``sticky''. If an end of file is entered, e.g.@: by
pressing the @key{EOT} key,
then end of file
-is signalled once (i.e.@: the test @code{End_Of_File}
+is signaled once (i.e.@: the test @code{End_Of_File}
will yield @code{True}, or a read will
raise @code{End_Error}), but then reading can resume
to read data past that end of
@itemize @bullet
@item function File_Exists (Name : String) return Boolean;
-Determines if a file of the given name exists and can be successfully
-opened (without actually performing the open operation).
+Determines if a file of the given name exists.
@item function Get_Line return String;
Reads a string from the standard input file. The value returned is exactly
output file is referenced as appropriate.
The package @code{Ada.Strings.Wide_Unbounded.Wide_Text_IO} in library
-files @file{a-swuwti.ads} and @file{a-swuwti.adb} provides similar extended @code{Wide_Text_IO}
-functionality for unbounded wide strings.
+files @file{a-swuwti.ads} and @file{a-swuwti.adb} provides similar extended
+@code{Wide_Text_IO} functionality for unbounded wide strings.
+
+The package @code{Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO} in library
+files @file{a-szuzti.ads} and @file{a-szuzti.adb} provides similar extended
+@code{Wide_Wide_Text_IO} functionality for unbounded wide wide strings.
@node Wide_Text_IO
@section Wide_Text_IO
Brackets encoding
@end table
+@noindent
The encoding methods match those that
can be used in a source
program, but there is no requirement that the encoding method used for
ESC a b c d
@end smallexample
+@noindent
where @var{a}, @var{b}, @var{c}, @var{d} are the four hexadecimal
characters (using upper case letters) of the wide character code. For
example, ESC A345 is used to represent the wide character with code
(i.e.@: a is in the range 8-F) is represented as two bytes 16#ab# and
16#cd#. The second byte may never be a format control character, but is
not required to be in the upper half. This method can be also used for
-shift-JIS or EUC where the internal coding matches the external coding.
+shift-JIS or EUC where the internal coding matches the external coding.
@item Shift JIS Coding
A wide character is represented by a two character sequence 16#ab# and
16#0800#-16#ffff#: 2#1110xxxx# 2#10xxxxxx# 2#10xxxxxx#
@end smallexample
+@noindent
where the xxx bits correspond to the left-padded bits of the
16-bit character value. Note that all lower half ASCII characters
are represented as ASCII bytes and all upper half characters and
[ " a b c d " ]
@end smallexample
-Where @code{a}, @code{b}, @code{c}, @code{d} are the four hexadecimal
+@noindent
+where @code{a}, @code{b}, @code{c}, @code{d} are the four hexadecimal
characters (using uppercase letters) of the wide character code. For
example, @code{["A345"]} is used to represent the wide character with code
@code{16#A345#}.
e.g.@: @code{["C1"]} for lower case a. However, on output, brackets notation
is only used for wide characters with a code greater than @code{16#FF#}.
+Note that brackets coding is not normally used in the context of
+Wide_Text_IO or Wide_Wide_Text_IO, since it is really just designed as
+a portable way of encoding source files. In the context of Wide_Text_IO
+or Wide_Wide_Text_IO, it can only be used if the file does not contain
+any instance of the left bracket character other than to encode wide
+character values using the brackets encoding method. In practice it is
+expected that some standard wide character encoding method such
+as UTF-8 will be used for text input output.
+
+If brackets notation is used, then any occurrence of a left bracket
+in the input file which is not the start of a valid wide character
+sequence will cause Constraint_Error to be raised. It is possible to
+encode a left bracket as ["5B"] and Wide_Text_IO and Wide_Wide_Text_IO
+input will interpret this as a left bracket.
+
+However, when a left bracket is output, it will be output as a left bracket
+and not as ["5B"]. We make this decision because for normal use of
+Wide_Text_IO for outputting messages, it is unpleasant to clobber left
+brackets. For example, if we write:
+
+@smallexample
+ Put_Line ("Start of output [first run]");
+@end smallexample
+
+@noindent
+we really do not want to have the left bracket in this message clobbered so
+that the output reads:
+
+@smallexample
+ Start of output ["5B"]first run]
+@end smallexample
+
+@noindent
+In practice brackets encoding is reasonably useful for normal Put_Line use
+since we won't get confused between left brackets and wide character
+sequences in the output. But for input, or when files are written out
+and read back in, it really makes better sense to use one of the standard
+encoding methods such as UTF-8.
+
@end table
-For the coding schemes other than Hex and Brackets encoding,
+@noindent
+For the coding schemes other than UTF-8, Hex, or Brackets encoding,
not all wide character
values can be represented. An attempt to output a character that cannot
be represented using the encoding scheme for the file causes
input also causes Constraint_Error to be raised.
@menu
-* Wide_Text_IO Stream Pointer Positioning::
-* Wide_Text_IO Reading and Writing Non-Regular Files::
+* Wide_Text_IO Stream Pointer Positioning::
+* Wide_Text_IO Reading and Writing Non-Regular Files::
@end menu
@node Wide_Text_IO Stream Pointer Positioning
If @code{Ada.Wide_Text_IO.Look_Ahead} reads a character outside the
normal lower ASCII set (i.e.@: a character in the range:
-@smallexample
+@smallexample @c ada
Wide_Character'Val (16#0080#) .. Wide_Character'Val (16#FFFF#)
@end smallexample
@code{False}. Similarly, the end of file indication is not sticky, so
it is possible to read beyond an end of file.
+@node Wide_Wide_Text_IO
+@section Wide_Wide_Text_IO
+
+@noindent
+@code{Wide_Wide_Text_IO} is similar in most respects to Text_IO, except that
+both input and output files may contain special sequences that represent
+wide wide character values. The encoding scheme for a given file may be
+specified using a FORM parameter:
+
+@smallexample
+WCEM=@var{x}
+@end smallexample
+
+@noindent
+as part of the FORM string (WCEM = wide character encoding method),
+where @var{x} is one of the following characters
+
+@table @samp
+@item h
+Hex ESC encoding
+@item u
+Upper half encoding
+@item s
+Shift-JIS encoding
+@item e
+EUC Encoding
+@item 8
+UTF-8 encoding
+@item b
+Brackets encoding
+@end table
+
+@noindent
+The encoding methods match those that
+can be used in a source
+program, but there is no requirement that the encoding method used for
+the source program be the same as the encoding method used for files,
+and different files may use different encoding methods.
+
+The default encoding method for the standard files, and for opened files
+for which no WCEM parameter is given in the FORM string matches the
+wide character encoding specified for the main program (the default
+being brackets encoding if no coding method was specified with -gnatW).
+
+@table @asis
+
+@item UTF-8 Coding
+A wide character is represented using
+UCS Transformation Format 8 (UTF-8) as defined in Annex R of ISO
+10646-1/Am.2. Depending on the character value, the representation
+is a one, two, three, or four byte sequence:
+
+@smallexample
+16#000000#-16#00007f#: 2#0xxxxxxx#
+16#000080#-16#0007ff#: 2#110xxxxx# 2#10xxxxxx#
+16#000800#-16#00ffff#: 2#1110xxxx# 2#10xxxxxx# 2#10xxxxxx#
+16#010000#-16#10ffff#: 2#11110xxx# 2#10xxxxxx# 2#10xxxxxx# 2#10xxxxxx#
+@end smallexample
+
+@noindent
+where the xxx bits correspond to the left-padded bits of the
+21-bit character value. Note that all lower half ASCII characters
+are represented as ASCII bytes and all upper half characters and
+other wide characters are represented as sequences of upper-half
+characters.
+
+@item Brackets Coding
+In this encoding, a wide wide character is represented by the following eight
+character sequence if is in wide character range
+
+@smallexample
+[ " a b c d " ]
+@end smallexample
+
+and by the following ten character sequence if not
+
+@smallexample
+[ " a b c d e f " ]
+@end smallexample
+
+@noindent
+where @code{a}, @code{b}, @code{c}, @code{d}, @code{e}, and @code{f}
+are the four or six hexadecimal
+characters (using uppercase letters) of the wide wide character code. For
+example, @code{["01A345"]} is used to represent the wide wide character
+with code @code{16#01A345#}.
+
+This scheme is compatible with use of the full Wide_Wide_Character set.
+On input, brackets coding can also be used for upper half characters,
+e.g.@: @code{["C1"]} for lower case a. However, on output, brackets notation
+is only used for wide characters with a code greater than @code{16#FF#}.
+
+@end table
+
+@noindent
+If is also possible to use the other Wide_Character encoding methods,
+such as Shift-JIS, but the other schemes cannot support the full range
+of wide wide characters.
+An attempt to output a character that cannot
+be represented using the encoding scheme for the file causes
+Constraint_Error to be raised. An invalid wide character sequence on
+input also causes Constraint_Error to be raised.
+
+@menu
+* Wide_Wide_Text_IO Stream Pointer Positioning::
+* Wide_Wide_Text_IO Reading and Writing Non-Regular Files::
+@end menu
+
+@node Wide_Wide_Text_IO Stream Pointer Positioning
+@subsection Stream Pointer Positioning
+
+@noindent
+@code{Ada.Wide_Wide_Text_IO} is similar to @code{Ada.Text_IO} in its handling
+of stream pointer positioning (@pxref{Text_IO}). There is one additional
+case:
+
+If @code{Ada.Wide_Wide_Text_IO.Look_Ahead} reads a character outside the
+normal lower ASCII set (i.e.@: a character in the range:
+
+@smallexample @c ada
+Wide_Wide_Character'Val (16#0080#) .. Wide_Wide_Character'Val (16#10FFFF#)
+@end smallexample
+
+@noindent
+then although the logical position of the file pointer is unchanged by
+the @code{Look_Ahead} call, the stream is physically positioned past the
+wide character sequence. Again this is to avoid the need for buffering
+or backup, and all @code{Wide_Wide_Text_IO} routines check the internal
+indication that this situation has occurred so that this is not visible
+to a normal program using @code{Wide_Wide_Text_IO}. However, this discrepancy
+can be observed if the wide text file shares a stream with another file.
+
+@node Wide_Wide_Text_IO Reading and Writing Non-Regular Files
+@subsection Reading and Writing Non-Regular Files
+
+@noindent
+As in the case of Text_IO, when a non-regular file is read, it is
+assumed that the file contains no page marks (any form characters are
+treated as data characters), and @code{End_Of_Page} always returns
+@code{False}. Similarly, the end of file indication is not sticky, so
+it is possible to read beyond an end of file.
+
@node Stream_IO
@section Stream_IO
@noindent
A stream file is a sequence of bytes, where individual elements are
-written to the file as described in the Ada 95 reference manual. The type
+written to the file as described in the Ada Reference Manual. The type
@code{Stream_Element} is simply a byte. There are two ways to read or
write a stream file.
@section Shared Files
@noindent
-Section A.14 of the Ada 95 Reference Manual allows implementations to
+Section A.14 of the Ada Reference Manual allows implementations to
provide a wide variety of behavior if an attempt is made to access the
same external file with two or more internal files.
If the form parameter @samp{shared=yes} appears in the form string for
each of two or more files opened using the same full name, the same
stream is shared between these files, and the semantics are as described
-in Ada 95 Reference Manual, Section A.14.
+in Ada Reference Manual, Section A.14.
@end itemize
+@noindent
When a program that opens multiple files with the same name is ported
from another Ada compiler to GNAT, the effect will be that
@code{Use_Error} is raised.
One common use of file sharing in Ada 83 is the use of instantiations of
Sequential_IO on the same file with different types, to achieve
heterogeneous input-output. Although this approach will work in GNAT if
-@samp{shared=yes} is specified, it is preferable in Ada 95 to use Stream_IO
+@samp{shared=yes} is specified, it is preferable in Ada to use Stream_IO
for this purpose (using the stream attributes)
+@node Filenames encoding
+@section Filenames encoding
+
+@noindent
+An encoding form parameter can be used to specify the filename
+encoding @samp{encoding=@var{xxx}}.
+
+@itemize @bullet
+@item
+If the form parameter @samp{encoding=utf8} appears in the form string, the
+filename must be encoded in UTF-8.
+
+@item
+If the form parameter @samp{encoding=8bits} appears in the form
+string, the filename must be a standard 8bits string.
+@end itemize
+
+In the absence of a @samp{encoding=@var{xxx}} form parameter, the
+value UTF-8 is used. This encoding form parameter is only supported on
+the Windows platform. On the other Operating Systems the runtime is
+supporting UTF-8 natively.
+
@node Open Modes
@section Open Modes
@noindent
@code{Open} and @code{Create} calls result in a call to @code{fopen}
-using the mode shown in Table 6.1
+using the mode shown in the following table:
@sp 2
-@center Table 6-1 @code{Open} and @code{Create} Call Modes
+@center @code{Open} and @code{Create} Call Modes
@smallexample
@b{OPEN } @b{CREATE}
Append_File "r+" "w+"
Inout_File "r+" "w+"
@end smallexample
+@noindent
If text file translation is required, then either @samp{b} or @samp{t}
is added to the mode, depending on the setting of Text. Text file
translation refers to the mapping of CR/LF sequences in an external file
The package @code{Interfaces.C_Streams} provides an Ada program with direct
access to the C library functions for operations on C streams:
-@smallexample
+@smallexample @c adanocomment
package Interfaces.C_Streams is
-- Note: the reason we do not use the types that are in
-- Interfaces.C is that we want to avoid dragging in the
-- Constants Defined in stdio.h --
----------------------------------
EOF : constant int;
- -- Used by a number of routines to indicate error or
+ -- Used by a number of routines to indicate error or
-- end of file
IOFBF : constant int;
IOLBF : constant int;
-- available in DOS, OS/2, UNIX and Xenix (but not
-- necessarily in ANSI C). These are very thin interfaces
-- which copy exactly the C headers. For more
- -- documentation on these functions, see the Microsoft C
+ -- documentation on these functions, see the Microsoft C
-- "Run-Time Library Reference" (Microsoft Press, 1990,
-- ISBN 1-55615-225-6), which includes useful information
-- on system compatibility.
procedure clearerr (stream : FILEs);
function fclose (stream : FILEs) return int;
- function fdopen (handle : int; mode : chars) return FILEs;
- function feof (stream : FILEs) return int;
- function ferror (stream : FILEs) return int;
- function fflush (stream : FILEs) return int;
- function fgetc (stream : FILEs) return int;
- function fgets (strng : chars; n : int; stream : FILEs)
- return chars;
- function fileno (stream : FILEs) return int;
- function fopen (filename : chars; Mode : chars)
+ function fdopen (handle : int; mode : chars) return FILEs;
+ function feof (stream : FILEs) return int;
+ function ferror (stream : FILEs) return int;
+ function fflush (stream : FILEs) return int;
+ function fgetc (stream : FILEs) return int;
+ function fgets (strng : chars; n : int; stream : FILEs)
+ return chars;
+ function fileno (stream : FILEs) return int;
+ function fopen (filename : chars; Mode : chars)
return FILEs;
-- Note: to maintain target independence, use
-- text_translation_required, a boolean variable defined in
-- a-sysdep.c to deal with the target dependent text
- -- translation requirement. If this variable is set,
+ -- translation requirement. If this variable is set,
-- then b/t should be appended to the standard mode
- -- argument to set the text translation mode off or on
+ -- argument to set the text translation mode off or on
-- as required.
function fputc (C : int; stream : FILEs) return int;
function fputs (Strng : chars; Stream : FILEs) return int;
size : size_t;
count : size_t;
stream : FILEs)
- return size_t;
+ return size_t;
function isatty (handle : int) return int;
procedure mktemp (template : chars);
-- The return value (which is just a pointer to template)
-- Extra functions --
---------------------
-- These functions supply slightly thicker bindings than
- -- those above. They are derived from functions in the
+ -- those above. They are derived from functions in the
-- C Run-Time Library, but may do a bit more work than
-- just directly calling one of the Library functions.
function is_regular_file (handle : int) return int;
procedure full_name (nam : chars; buffer : chars);
-- Given a NUL terminated string representing a file
-- name, returns in buffer a NUL terminated string
- -- representing the full path name for the file name.
+ -- representing the full path name for the file name.
-- On systems where it is relevant the drive is also
- -- part of the full path name. It is the responsibility
+ -- part of the full path name. It is the responsibility
-- of the caller to pass an actual parameter for buffer
-- that is big enough for any full path name. Use
-- max_path_len given below as the size of buffer.
The packages in this section permit interfacing Ada files to C Stream
operations.
-@smallexample
+@smallexample @c ada
with Interfaces.C_Streams;
package Ada.Sequential_IO.C_Streams is
- function C_Stream (F : File_Type)
+ function C_Stream (F : File_Type)
return Interfaces.C_Streams.FILEs;
procedure Open
(File : in out File_Type;
with Interfaces.C_Streams;
package Ada.Direct_IO.C_Streams is
- function C_Stream (F : File_Type)
+ function C_Stream (F : File_Type)
return Interfaces.C_Streams.FILEs;
procedure Open
(File : in out File_Type;
with Interfaces.C_Streams;
package Ada.Wide_Text_IO.C_Streams is
- function C_Stream (F : File_Type)
+ function C_Stream (F : File_Type)
return Interfaces.C_Streams.FILEs;
procedure Open
(File : in out File_Type;
Form : in String := "");
end Ada.Wide_Text_IO.C_Streams;
+ with Interfaces.C_Streams;
+ package Ada.Wide_Wide_Text_IO.C_Streams is
+ function C_Stream (F : File_Type)
+ return Interfaces.C_Streams.FILEs;
+ procedure Open
+ (File : in out File_Type;
+ Mode : in File_Mode;
+ C_Stream : in Interfaces.C_Streams.FILEs;
+ Form : in String := "");
+ end Ada.Wide_Wide_Text_IO.C_Streams;
+
with Interfaces.C_Streams;
package Ada.Stream_IO.C_Streams is
function C_Stream (F : File_Type)
end Ada.Stream_IO.C_Streams;
@end smallexample
-In each of these five packages, the @code{C_Stream} function obtains the
+@noindent
+In each of these six packages, the @code{C_Stream} function obtains the
@code{FILE} pointer from a currently opened Ada file. It is then
possible to use the @code{Interfaces.C_Streams} package to operate on
this stream, or the stream can be passed to a C program which can
The full documentation is found in the spec file for the package. The full
sources of these library packages, including both spec and body, are provided
with all GNAT releases. For example, to find out the full specifications of
-the SPITBOL pattern matching capability, including a full tutorial and
+the SPITBOL pattern matching capability, including a full tutorial and
extensive examples, look in the @file{g-spipat.ads} file in the library.
For each entry here, the package name (as it would appear in a @code{with}
* Ada.Characters.Latin_9 (a-chlat9.ads)::
* Ada.Characters.Wide_Latin_1 (a-cwila1.ads)::
* Ada.Characters.Wide_Latin_9 (a-cwila9.ads)::
+* Ada.Characters.Wide_Wide_Latin_1 (a-czila1.ads)::
+* Ada.Characters.Wide_Wide_Latin_9 (a-czila9.ads)::
* Ada.Command_Line.Remove (a-colire.ads)::
+* Ada.Command_Line.Environment (a-colien.ads)::
* Ada.Direct_IO.C_Streams (a-diocst.ads)::
* Ada.Exceptions.Is_Null_Occurrence (a-einuoc.ads)::
+* Ada.Exceptions.Traceback (a-exctra.ads)::
* Ada.Sequential_IO.C_Streams (a-siocst.ads)::
* Ada.Streams.Stream_IO.C_Streams (a-ssicst.ads)::
* Ada.Strings.Unbounded.Text_IO (a-suteio.ads)::
* Ada.Strings.Wide_Unbounded.Wide_Text_IO (a-swuwti.ads)::
+* Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO (a-szuzti.ads)::
* Ada.Text_IO.C_Streams (a-tiocst.ads)::
* Ada.Wide_Text_IO.C_Streams (a-wtcstr.ads)::
+* Ada.Wide_Wide_Text_IO.C_Streams (a-ztcstr.ads)::
+* GNAT.Altivec (g-altive.ads)::
+* GNAT.Altivec.Conversions (g-altcon.ads)::
+* GNAT.Altivec.Vector_Operations (g-alveop.ads)::
+* GNAT.Altivec.Vector_Types (g-alvety.ads)::
+* GNAT.Altivec.Vector_Views (g-alvevi.ads)::
+* GNAT.Array_Split (g-arrspl.ads)::
* GNAT.AWK (g-awk.ads)::
+* GNAT.Bounded_Buffers (g-boubuf.ads)::
+* GNAT.Bounded_Mailboxes (g-boumai.ads)::
+* GNAT.Bubble_Sort (g-bubsor.ads)::
* GNAT.Bubble_Sort_A (g-busora.ads)::
* GNAT.Bubble_Sort_G (g-busorg.ads)::
+* GNAT.Byte_Swapping (g-bytswa.ads)::
* GNAT.Calendar (g-calend.ads)::
* GNAT.Calendar.Time_IO (g-catiio.ads)::
* GNAT.CRC32 (g-crc32.ads)::
* GNAT.CGI.Cookie (g-cgicoo.ads)::
* GNAT.CGI.Debug (g-cgideb.ads)::
* GNAT.Command_Line (g-comlin.ads)::
+* GNAT.Compiler_Version (g-comver.ads)::
+* GNAT.Ctrl_C (g-ctrl_c.ads)::
* GNAT.Current_Exception (g-curexc.ads)::
* GNAT.Debug_Pools (g-debpoo.ads)::
* GNAT.Debug_Utilities (g-debuti.ads)::
* GNAT.Directory_Operations (g-dirope.ads)::
+* GNAT.Dynamic_HTables (g-dynhta.ads)::
* GNAT.Dynamic_Tables (g-dyntab.ads)::
+* GNAT.Exception_Actions (g-excact.ads)::
* GNAT.Exception_Traces (g-exctra.ads)::
+* GNAT.Exceptions (g-except.ads)::
* GNAT.Expect (g-expect.ads)::
* GNAT.Float_Control (g-flocon.ads)::
+* GNAT.Heap_Sort (g-heasor.ads)::
* GNAT.Heap_Sort_A (g-hesora.ads)::
* GNAT.Heap_Sort_G (g-hesorg.ads)::
* GNAT.HTable (g-htable.ads)::
* GNAT.IO_Aux (g-io_aux.ads)::
* GNAT.Lock_Files (g-locfil.ads)::
* GNAT.MD5 (g-md5.ads)::
+* GNAT.Memory_Dump (g-memdum.ads)::
* GNAT.Most_Recent_Exception (g-moreex.ads)::
* GNAT.OS_Lib (g-os_lib.ads)::
+* GNAT.Perfect_Hash_Generators (g-pehage.ads)::
* GNAT.Regexp (g-regexp.ads)::
* GNAT.Registry (g-regist.ads)::
* GNAT.Regpat (g-regpat.ads)::
+* GNAT.Secondary_Stack_Info (g-sestin.ads)::
+* GNAT.Semaphores (g-semaph.ads)::
+* GNAT.SHA1 (g-sha1.ads)::
+* GNAT.Signals (g-signal.ads)::
* GNAT.Sockets (g-socket.ads)::
* GNAT.Source_Info (g-souinf.ads)::
* GNAT.Spell_Checker (g-speche.ads)::
* GNAT.Spitbol.Table_Boolean (g-sptabo.ads)::
* GNAT.Spitbol.Table_Integer (g-sptain.ads)::
* GNAT.Spitbol.Table_VString (g-sptavs.ads)::
+* GNAT.Strings (g-string.ads)::
+* GNAT.String_Split (g-strspl.ads)::
+* GNAT.UTF_32 (g-utf_32.ads)::
* GNAT.Table (g-table.ads)::
* GNAT.Task_Lock (g-tasloc.ads)::
* GNAT.Threads (g-thread.ads)::
* GNAT.Traceback (g-traceb.ads)::
* GNAT.Traceback.Symbolic (g-trasym.ads)::
+* GNAT.Wide_String_Split (g-wistsp.ads)::
+* GNAT.Wide_Wide_String_Split (g-zistsp.ads)::
* Interfaces.C.Extensions (i-cexten.ads)::
* Interfaces.C.Streams (i-cstrea.ads)::
* Interfaces.CPP (i-cpp.ads)::
* Interfaces.VxWorks.IO (i-vxwoio.ads)::
* System.Address_Image (s-addima.ads)::
* System.Assertions (s-assert.ads)::
+* System.Memory (s-memory.ads)::
* System.Partition_Interface (s-parint.ads)::
+* System.Restrictions (s-restri.ads)::
+* System.Rident (s-rident.ads)::
* System.Task_Info (s-tasinf.ads)::
* System.Wch_Cnv (s-wchcnv.ads)::
* System.Wch_Con (s-wchcon.ads)::
few modifications required for @code{Latin-9}
The provision of such a package
is specifically authorized by the Ada Reference Manual
-(RM A.3(27)).
+(RM A.3.3(27)).
@node Ada.Characters.Wide_Latin_1 (a-cwila1.ads)
@section @code{Ada.Characters.Wide_Latin_1} (@file{a-cwila1.ads})
types of the constants being @code{Wide_Character}
instead of @code{Character}. The provision of such a package
is specifically authorized by the Ada Reference Manual
-(RM A.3(27)).
+(RM A.3.3(27)).
@node Ada.Characters.Wide_Latin_9 (a-cwila9.ads)
@section @code{Ada.Characters.Wide_Latin_9} (@file{a-cwila1.ads})
types of the constants being @code{Wide_Character}
instead of @code{Character}. The provision of such a package
is specifically authorized by the Ada Reference Manual
-(RM A.3(27)).
+(RM A.3.3(27)).
+
+@node Ada.Characters.Wide_Wide_Latin_1 (a-czila1.ads)
+@section @code{Ada.Characters.Wide_Wide_Latin_1} (@file{a-czila1.ads})
+@cindex @code{Ada.Characters.Wide_Wide_Latin_1} (@file{a-czila1.ads})
+@cindex Latin_1 constants for Wide_Wide_Character
+
+@noindent
+This child of @code{Ada.Characters}
+provides a set of definitions corresponding to those in the
+RM-defined package @code{Ada.Characters.Latin_1} but with the
+types of the constants being @code{Wide_Wide_Character}
+instead of @code{Character}. The provision of such a package
+is specifically authorized by the Ada Reference Manual
+(RM A.3.3(27)).
+
+@node Ada.Characters.Wide_Wide_Latin_9 (a-czila9.ads)
+@section @code{Ada.Characters.Wide_Wide_Latin_9} (@file{a-czila9.ads})
+@cindex @code{Ada.Characters.Wide_Wide_Latin_9} (@file{a-czila9.ads})
+@cindex Latin_9 constants for Wide_Wide_Character
+
+@noindent
+This child of @code{Ada.Characters}
+provides a set of definitions corresponding to those in the
+GNAT defined package @code{Ada.Characters.Latin_9} but with the
+types of the constants being @code{Wide_Wide_Character}
+instead of @code{Character}. The provision of such a package
+is specifically authorized by the Ada Reference Manual
+(RM A.3.3(27)).
@node Ada.Command_Line.Remove (a-colire.ads)
@section @code{Ada.Command_Line.Remove} (@file{a-colire.ads})
to further calls on the subprograms in @code{Ada.Command_Line} will not
see the removed argument.
+@node Ada.Command_Line.Environment (a-colien.ads)
+@section @code{Ada.Command_Line.Environment} (@file{a-colien.ads})
+@cindex @code{Ada.Command_Line.Environment} (@file{a-colien.ads})
+@cindex Environment entries
+
+@noindent
+This child of @code{Ada.Command_Line}
+provides a mechanism for obtaining environment values on systems
+where this concept makes sense.
+
@node Ada.Direct_IO.C_Streams (a-diocst.ads)
@section @code{Ada.Direct_IO.C_Streams} (@file{a-diocst.ads})
@cindex @code{Ada.Direct_IO.C_Streams} (@file{a-diocst.ads})
@cindex C Streams, Interfacing with Direct_IO
@noindent
-This package provides subprograms that allow interfacing between
+This package provides subprograms that allow interfacing between
C streams and @code{Direct_IO}. The stream identifier can be
extracted from a file opened on the Ada side, and an Ada file
can be constructed from a stream opened on the C side.
@cindex Null_Occurrence, testing for
@noindent
-This child subprogram provides a way of testing for the null
+This child subprogram provides a way of testing for the null
exception occurrence (@code{Null_Occurrence}) without raising
an exception.
+@node Ada.Exceptions.Traceback (a-exctra.ads)
+@section @code{Ada.Exceptions.Traceback} (@file{a-exctra.ads})
+@cindex @code{Ada.Exceptions.Traceback} (@file{a-exctra.ads})
+@cindex Traceback for Exception Occurrence
+
+@noindent
+This child package provides the subprogram (@code{Tracebacks}) to
+give a traceback array of addresses based on an exception
+occurrence.
+
@node Ada.Sequential_IO.C_Streams (a-siocst.ads)
@section @code{Ada.Sequential_IO.C_Streams} (@file{a-siocst.ads})
@cindex @code{Ada.Sequential_IO.C_Streams} (@file{a-siocst.ads})
@cindex C Streams, Interfacing with Sequential_IO
@noindent
-This package provides subprograms that allow interfacing between
+This package provides subprograms that allow interfacing between
C streams and @code{Sequential_IO}. The stream identifier can be
extracted from a file opened on the Ada side, and an Ada file
can be constructed from a stream opened on the C side.
@cindex C Streams, Interfacing with Stream_IO
@noindent
-This package provides subprograms that allow interfacing between
+This package provides subprograms that allow interfacing between
C streams and @code{Stream_IO}. The stream identifier can be
extracted from a file opened on the Ada side, and an Ada file
can be constructed from a stream opened on the C side.
wide strings, avoiding the necessity for an intermediate operation
with ordinary wide strings.
+@node Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO (a-szuzti.ads)
+@section @code{Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO} (@file{a-szuzti.ads})
+@cindex @code{Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO} (@file{a-szuzti.ads})
+@cindex @code{Unbounded_Wide_Wide_String}, IO support
+@cindex @code{Text_IO}, extensions for unbounded wide wide strings
+
+@noindent
+This package provides subprograms for Text_IO for unbounded
+wide wide strings, avoiding the necessity for an intermediate operation
+with ordinary wide wide strings.
+
@node Ada.Text_IO.C_Streams (a-tiocst.ads)
@section @code{Ada.Text_IO.C_Streams} (@file{a-tiocst.ads})
@cindex @code{Ada.Text_IO.C_Streams} (@file{a-tiocst.ads})
@cindex C Streams, Interfacing with @code{Text_IO}
@noindent
-This package provides subprograms that allow interfacing between
+This package provides subprograms that allow interfacing between
C streams and @code{Text_IO}. The stream identifier can be
extracted from a file opened on the Ada side, and an Ada file
can be constructed from a stream opened on the C side.
@cindex C Streams, Interfacing with @code{Wide_Text_IO}
@noindent
-This package provides subprograms that allow interfacing between
+This package provides subprograms that allow interfacing between
C streams and @code{Wide_Text_IO}. The stream identifier can be
extracted from a file opened on the Ada side, and an Ada file
can be constructed from a stream opened on the C side.
+@node Ada.Wide_Wide_Text_IO.C_Streams (a-ztcstr.ads)
+@section @code{Ada.Wide_Wide_Text_IO.C_Streams} (@file{a-ztcstr.ads})
+@cindex @code{Ada.Wide_Wide_Text_IO.C_Streams} (@file{a-ztcstr.ads})
+@cindex C Streams, Interfacing with @code{Wide_Wide_Text_IO}
+
+@noindent
+This package provides subprograms that allow interfacing between
+C streams and @code{Wide_Wide_Text_IO}. The stream identifier can be
+extracted from a file opened on the Ada side, and an Ada file
+can be constructed from a stream opened on the C side.
+
+@node GNAT.Altivec (g-altive.ads)
+@section @code{GNAT.Altivec} (@file{g-altive.ads})
+@cindex @code{GNAT.Altivec} (@file{g-altive.ads})
+@cindex AltiVec
+
+@noindent
+This is the root package of the GNAT AltiVec binding. It provides
+definitions of constants and types common to all the versions of the
+binding.
+
+@node GNAT.Altivec.Conversions (g-altcon.ads)
+@section @code{GNAT.Altivec.Conversions} (@file{g-altcon.ads})
+@cindex @code{GNAT.Altivec.Conversions} (@file{g-altcon.ads})
+@cindex AltiVec
+
+@noindent
+This package provides the Vector/View conversion routines.
+
+@node GNAT.Altivec.Vector_Operations (g-alveop.ads)
+@section @code{GNAT.Altivec.Vector_Operations} (@file{g-alveop.ads})
+@cindex @code{GNAT.Altivec.Vector_Operations} (@file{g-alveop.ads})
+@cindex AltiVec
+
+@noindent
+This package exposes the Ada interface to the AltiVec operations on
+vector objects. A soft emulation is included by default in the GNAT
+library. The hard binding is provided as a separate package. This unit
+is common to both bindings.
+
+@node GNAT.Altivec.Vector_Types (g-alvety.ads)
+@section @code{GNAT.Altivec.Vector_Types} (@file{g-alvety.ads})
+@cindex @code{GNAT.Altivec.Vector_Types} (@file{g-alvety.ads})
+@cindex AltiVec
+
+@noindent
+This package exposes the various vector types part of the Ada binding
+to AltiVec facilities.
+
+@node GNAT.Altivec.Vector_Views (g-alvevi.ads)
+@section @code{GNAT.Altivec.Vector_Views} (@file{g-alvevi.ads})
+@cindex @code{GNAT.Altivec.Vector_Views} (@file{g-alvevi.ads})
+@cindex AltiVec
+
+@noindent
+This package provides public 'View' data types from/to which private
+vector representations can be converted via
+GNAT.Altivec.Conversions. This allows convenient access to individual
+vector elements and provides a simple way to initialize vector
+objects.
+
+@node GNAT.Array_Split (g-arrspl.ads)
+@section @code{GNAT.Array_Split} (@file{g-arrspl.ads})
+@cindex @code{GNAT.Array_Split} (@file{g-arrspl.ads})
+@cindex Array splitter
+
+@noindent
+Useful array-manipulation routines: given a set of separators, split
+an array wherever the separators appear, and provide direct access
+to the resulting slices.
+
@node GNAT.AWK (g-awk.ads)
@section @code{GNAT.AWK} (@file{g-awk.ads})
@cindex @code{GNAT.AWK} (@file{g-awk.ads})
or more files containing formatted data. The file is viewed as a database
where each record is a line and a field is a data element in this line.
+@node GNAT.Bounded_Buffers (g-boubuf.ads)
+@section @code{GNAT.Bounded_Buffers} (@file{g-boubuf.ads})
+@cindex @code{GNAT.Bounded_Buffers} (@file{g-boubuf.ads})
+@cindex Parsing
+@cindex Bounded Buffers
+
+@noindent
+Provides a concurrent generic bounded buffer abstraction. Instances are
+useful directly or as parts of the implementations of other abstractions,
+such as mailboxes.
+
+@node GNAT.Bounded_Mailboxes (g-boumai.ads)
+@section @code{GNAT.Bounded_Mailboxes} (@file{g-boumai.ads})
+@cindex @code{GNAT.Bounded_Mailboxes} (@file{g-boumai.ads})
+@cindex Parsing
+@cindex Mailboxes
+
+@noindent
+Provides a thread-safe asynchronous intertask mailbox communication facility.
+
+@node GNAT.Bubble_Sort (g-bubsor.ads)
+@section @code{GNAT.Bubble_Sort} (@file{g-bubsor.ads})
+@cindex @code{GNAT.Bubble_Sort} (@file{g-bubsor.ads})
+@cindex Sorting
+@cindex Bubble sort
+
+@noindent
+Provides a general implementation of bubble sort usable for sorting arbitrary
+data items. Exchange and comparison procedures are provided by passing
+access-to-procedure values.
+
@node GNAT.Bubble_Sort_A (g-busora.ads)
@section @code{GNAT.Bubble_Sort_A} (@file{g-busora.ads})
@cindex @code{GNAT.Bubble_Sort_A} (@file{g-busora.ads})
@noindent
Provides a general implementation of bubble sort usable for sorting arbitrary
data items. Move and comparison procedures are provided by passing
-access-to-procedure values.
+access-to-procedure values. This is an older version, retained for
+compatibility. Usually @code{GNAT.Bubble_Sort} will be preferable.
@node GNAT.Bubble_Sort_G (g-busorg.ads)
@section @code{GNAT.Bubble_Sort_G} (@file{g-busorg.ads})
if the procedures can be inlined, at the expense of duplicating code for
multiple instantiations.
+@node GNAT.Byte_Swapping (g-bytswa.ads)
+@section @code{GNAT.Byte_Swapping} (@file{g-bytswa.ads})
+@cindex @code{GNAT.Byte_Swapping} (@file{g-bytswa.ads})
+@cindex Byte swapping
+@cindex Endian
+
+@noindent
+General routines for swapping the bytes in 2-, 4-, and 8-byte quantities.
+Machine-specific implementations are available in some cases.
+
@node GNAT.Calendar (g-calend.ads)
@section @code{GNAT.Calendar} (@file{g-calend.ads})
@cindex @code{GNAT.Calendar} (@file{g-calend.ads})
@noindent
This package implements the CRC-32 algorithm. For a full description
-of this algorithm you should have a look at:
-``Computation of Cyclic Redundancy Checks via Table Look-Up'', @cite{Communications
-of the ACM}, Vol.@: 31 No.@: 8, pp.@: 1008-1013, Aug.@: 1988. Sarwate, D.V@.
-
-@noindent
-Provides an extended capability for formatted output of time values with
-full user control over the format. Modeled on the GNU Date specification.
+of this algorithm see
+``Computation of Cyclic Redundancy Checks via Table Look-Up'',
+@cite{Communications of the ACM}, Vol.@: 31 No.@: 8, pp.@: 1008-1013,
+Aug.@: 1988. Sarwate, D.V@.
@node GNAT.Case_Util (g-casuti.ads)
@section @code{GNAT.Case_Util} (@file{g-casuti.ads})
including the ability to scan for named switches with optional parameters
and expand file names using wild card notations.
+@node GNAT.Compiler_Version (g-comver.ads)
+@section @code{GNAT.Compiler_Version} (@file{g-comver.ads})
+@cindex @code{GNAT.Compiler_Version} (@file{g-comver.ads})
+@cindex Compiler Version
+@cindex Version, of compiler
+
+@noindent
+Provides a routine for obtaining the version of the compiler used to
+compile the program. More accurately this is the version of the binder
+used to bind the program (this will normally be the same as the version
+of the compiler if a consistent tool set is used to compile all units
+of a partition).
+
+@node GNAT.Ctrl_C (g-ctrl_c.ads)
+@section @code{GNAT.Ctrl_C} (@file{g-ctrl_c.ads})
+@cindex @code{GNAT.Ctrl_C} (@file{g-ctrl_c.ads})
+@cindex Interrupt
+
+@noindent
+Provides a simple interface to handle Ctrl-C keyboard events.
+
@node GNAT.Current_Exception (g-curexc.ads)
@section @code{GNAT.Current_Exception} (@file{g-curexc.ads})
@cindex @code{GNAT.Current_Exception} (@file{g-curexc.ads})
@noindent
Provides access to information on the current exception that has been raised
-without the need for using the Ada-95 exception choice parameter specification
-syntax. This is particularly useful in simulating typical facilities for
+without the need for using the Ada 95 / Ada 2005 exception choice parameter
+specification syntax.
+This is particularly useful in simulating typical facilities for
obtaining information about exceptions provided by Ada 83 compilers.
@node GNAT.Debug_Pools (g-debpoo.ads)
@noindent
Provides a few useful utilities for debugging purposes, including conversion
-to and from string images of address values.
+to and from string images of address values. Supports both C and Ada formats
+for hexadecimal literals.
@node GNAT.Directory_Operations (g-dirope.ads)
-@section @code{GNAT.Directory_Operations} (g-dirope.ads)
-@cindex @code{GNAT.Directory_Operations} (g-dirope.ads)
+@section @code{GNAT.Directory_Operations} (@file{g-dirope.ads})
+@cindex @code{GNAT.Directory_Operations} (@file{g-dirope.ads})
@cindex Directory operations
@noindent
the current directory, making new directories, and scanning the files in a
directory.
+@node GNAT.Dynamic_HTables (g-dynhta.ads)
+@section @code{GNAT.Dynamic_HTables} (@file{g-dynhta.ads})
+@cindex @code{GNAT.Dynamic_HTables} (@file{g-dynhta.ads})
+@cindex Hash tables
+
+@noindent
+A generic implementation of hash tables that can be used to hash arbitrary
+data. Provided in two forms, a simple form with built in hash functions,
+and a more complex form in which the hash function is supplied.
+
+@noindent
+This package provides a facility similar to that of @code{GNAT.HTable},
+except that this package declares a type that can be used to define
+dynamic instances of the hash table, while an instantiation of
+@code{GNAT.HTable} creates a single instance of the hash table.
+
@node GNAT.Dynamic_Tables (g-dyntab.ads)
@section @code{GNAT.Dynamic_Tables} (@file{g-dyntab.ads})
@cindex @code{GNAT.Dynamic_Tables} (@file{g-dyntab.ads})
length of the array can be dynamically modified.
@noindent
-This package provides a facility similar to that of GNAT.Table, except
-that this package declares a type that can be used to define dynamic
-instances of the table, while an instantiation of GNAT.Table creates a
-single instance of the table type.
+This package provides a facility similar to that of @code{GNAT.Table},
+except that this package declares a type that can be used to define
+dynamic instances of the table, while an instantiation of
+@code{GNAT.Table} creates a single instance of the table type.
+
+@node GNAT.Exception_Actions (g-excact.ads)
+@section @code{GNAT.Exception_Actions} (@file{g-excact.ads})
+@cindex @code{GNAT.Exception_Actions} (@file{g-excact.ads})
+@cindex Exception actions
+
+@noindent
+Provides callbacks when an exception is raised. Callbacks can be registered
+for specific exceptions, or when any exception is raised. This
+can be used for instance to force a core dump to ease debugging.
@node GNAT.Exception_Traces (g-exctra.ads)
@section @code{GNAT.Exception_Traces} (@file{g-exctra.ads})
Provides an interface allowing to control automatic output upon exception
occurrences.
+@node GNAT.Exceptions (g-except.ads)
+@section @code{GNAT.Exceptions} (@file{g-expect.ads})
+@cindex @code{GNAT.Exceptions} (@file{g-expect.ads})
+@cindex Exceptions, Pure
+@cindex Pure packages, exceptions
+
+@noindent
+Normally it is not possible to raise an exception with
+a message from a subprogram in a pure package, since the
+necessary types and subprograms are in @code{Ada.Exceptions}
+which is not a pure unit. @code{GNAT.Exceptions} provides a
+facility for getting around this limitation for a few
+predefined exceptions, and for example allow raising
+@code{Constraint_Error} with a message from a pure subprogram.
+
@node GNAT.Expect (g-expect.ads)
@section @code{GNAT.Expect} (@file{g-expect.ads})
@cindex @code{GNAT.Expect} (@file{g-expect.ads})
with the standard Tcl Expect tool.
It allows you to easily spawn and communicate with an external process.
You can send commands or inputs to the process, and compare the output
-with some expected regular expression.
-Currently GNAT.Expect is implemented on all native GNAT ports except for
-OpenVMS@. It is not implemented for cross ports, and in particular is not
+with some expected regular expression. Currently @code{GNAT.Expect}
+is implemented on all native GNAT ports except for OpenVMS@.
+It is not implemented for cross ports, and in particular is not
implemented for VxWorks or LynxOS@.
@node GNAT.Float_Control (g-flocon.ads)
library calls may cause this mode to be modified, and the Reset procedure
in this package can be used to reestablish the required mode.
+@node GNAT.Heap_Sort (g-heasor.ads)
+@section @code{GNAT.Heap_Sort} (@file{g-heasor.ads})
+@cindex @code{GNAT.Heap_Sort} (@file{g-heasor.ads})
+@cindex Sorting
+
+@noindent
+Provides a general implementation of heap sort usable for sorting arbitrary
+data items. Exchange and comparison procedures are provided by passing
+access-to-procedure values. The algorithm used is a modified heap sort
+that performs approximately N*log(N) comparisons in the worst case.
+
@node GNAT.Heap_Sort_A (g-hesora.ads)
@section @code{GNAT.Heap_Sort_A} (@file{g-hesora.ads})
@cindex @code{GNAT.Heap_Sort_A} (@file{g-hesora.ads})
@noindent
Provides a general implementation of heap sort usable for sorting arbitrary
-data items. Move and comparison procedures are provided by passing
+data items. Move and comparison procedures are provided by passing
access-to-procedure values. The algorithm used is a modified heap sort
that performs approximately N*log(N) comparisons in the worst case.
+This differs from @code{GNAT.Heap_Sort} in having a less convenient
+interface, but may be slightly more efficient.
@node GNAT.Heap_Sort_G (g-hesorg.ads)
@section @code{GNAT.Heap_Sort_G} (@file{g-hesorg.ads})
@cindex Input/Output facilities
@noindent
-A simple preealborable input-output package that provides a subset of
+A simple preelaborable input-output package that provides a subset of
simple Text_IO functions for reading characters and strings from
Standard_Input, and writing characters, strings and integers to either
Standard_Output or Standard_Error.
@noindent
Provides a general interface for using files as locks. Can be used for
-providing program level synchronization.
+providing program level synchronization.
@node GNAT.MD5 (g-md5.ads)
@section @code{GNAT.MD5} (@file{g-md5.ads})
@cindex Message Digest MD5
@noindent
-Implements the MD5 Message-Digest Algorithm as described in RFC 1321.
+Implements the MD5 Message-Digest Algorithm as described in RFC 1321.
+
+@node GNAT.Memory_Dump (g-memdum.ads)
+@section @code{GNAT.Memory_Dump} (@file{g-memdum.ads})
+@cindex @code{GNAT.Memory_Dump} (@file{g-memdum.ads})
+@cindex Dump Memory
+
+@noindent
+Provides a convenient routine for dumping raw memory to either the
+standard output or standard error files. Uses GNAT.IO for actual
+output.
@node GNAT.Most_Recent_Exception (g-moreex.ads)
@section @code{GNAT.Most_Recent_Exception} (@file{g-moreex.ads})
including a portable spawn procedure, and access to environment variables
and error return codes.
+@node GNAT.Perfect_Hash_Generators (g-pehage.ads)
+@section @code{GNAT.Perfect_Hash_Generators} (@file{g-pehage.ads})
+@cindex @code{GNAT.Perfect_Hash_Generators} (@file{g-pehage.ads})
+@cindex Hash functions
+
+@noindent
+Provides a generator of static minimal perfect hash functions. No
+collisions occur and each item can be retrieved from the table in one
+probe (perfect property). The hash table size corresponds to the exact
+size of the key set and no larger (minimal property). The key set has to
+be know in advance (static property). The hash functions are also order
+preserving. If w2 is inserted after w1 in the generator, their
+hashcode are in the same order. These hashing functions are very
+convenient for use with realtime applications.
+
@node GNAT.Regexp (g-regexp.ads)
@section @code{GNAT.Regexp} (@file{g-regexp.ads})
@cindex @code{GNAT.Regexp} (@file{g-regexp.ads})
from the original V7 style regular expression library written in C by
Henry Spencer (and binary compatible with this C library).
+@node GNAT.Secondary_Stack_Info (g-sestin.ads)
+@section @code{GNAT.Secondary_Stack_Info} (@file{g-sestin.ads})
+@cindex @code{GNAT.Secondary_Stack_Info} (@file{g-sestin.ads})
+@cindex Secondary Stack Info
+
+@noindent
+Provide the capability to query the high water mark of the current task's
+secondary stack.
+
+@node GNAT.Semaphores (g-semaph.ads)
+@section @code{GNAT.Semaphores} (@file{g-semaph.ads})
+@cindex @code{GNAT.Semaphores} (@file{g-semaph.ads})
+@cindex Semaphores
+
+@noindent
+Provides classic counting and binary semaphores using protected types.
+
+@node GNAT.SHA1 (g-sha1.ads)
+@section @code{GNAT.SHA1} (@file{g-sha1.ads})
+@cindex @code{GNAT.SHA1} (@file{g-sha1.ads})
+@cindex Secure Hash Algorithm SHA-1
+
+@noindent
+Implements the SHA-1 Secure Hash Algorithm as described in RFC 3174.
+
+@node GNAT.Signals (g-signal.ads)
+@section @code{GNAT.Signals} (@file{g-signal.ads})
+@cindex @code{GNAT.Signals} (@file{g-signal.ads})
+@cindex Signals
+
+@noindent
+Provides the ability to manipulate the blocked status of signals on supported
+targets.
+
@node GNAT.Sockets (g-socket.ads)
@section @code{GNAT.Sockets} (@file{g-socket.ads})
@cindex @code{GNAT.Sockets} (@file{g-socket.ads})
@noindent
A high level and portable interface to develop sockets based applications.
-This package is based on the sockets thin binding found in GNAT.Sockets.Thin.
-Currently GNAT.Sockets is implemented on all native GNAT ports except for
-OpenVMS@. It is not implemented for the LynxOS@ cross port.
+This package is based on the sockets thin binding found in
+@code{GNAT.Sockets.Thin}. Currently @code{GNAT.Sockets} is implemented
+on all native GNAT ports except for OpenVMS@. It is not implemented
+for the LynxOS@ cross port.
@node GNAT.Source_Info (g-souinf.ads)
@section @code{GNAT.Source_Info} (@file{g-souinf.ads})
@cindex SPITBOL Tables
@noindent
-A library level of instantiation of GNAT.Spitbol.Patterns.Table for
+A library level of instantiation of @code{GNAT.Spitbol.Patterns.Table} for
a variable length string type, giving an implementation of general
maps from strings to strings.
+@node GNAT.Strings (g-string.ads)
+@section @code{GNAT.Strings} (@file{g-string.ads})
+@cindex @code{GNAT.Strings} (@file{g-string.ads})
+
+@noindent
+Common String access types and related subprograms. Basically it
+defines a string access and an array of string access types.
+
+@node GNAT.String_Split (g-strspl.ads)
+@section @code{GNAT.String_Split} (@file{g-strspl.ads})
+@cindex @code{GNAT.String_Split} (@file{g-strspl.ads})
+@cindex String splitter
+
+@noindent
+Useful string manipulation routines: given a set of separators, split
+a string wherever the separators appear, and provide direct access
+to the resulting slices. This package is instantiated from
+@code{GNAT.Array_Split}.
+
+@node GNAT.UTF_32 (g-utf_32.ads)
+@section @code{GNAT.UTF_32} (@file{g-table.ads})
+@cindex @code{GNAT.UTF_32} (@file{g-table.ads})
+@cindex Wide character codes
+
+@noindent
+This is a package intended to be used in conjunction with the
+@code{Wide_Character} type in Ada 95 and the
+@code{Wide_Wide_Character} type in Ada 2005 (available
+in @code{GNAT} in Ada 2005 mode). This package contains
+Unicode categorization routines, as well as lexical
+categorization routines corresponding to the Ada 2005
+lexical rules for identifiers and strings, and also a
+lower case to upper case fold routine corresponding to
+the Ada 2005 rules for identifier equivalence.
+
@node GNAT.Table (g-table.ads)
@section @code{GNAT.Table} (@file{g-table.ads})
@cindex @code{GNAT.Table} (@file{g-table.ads})
length of the array can be dynamically modified.
@noindent
-This package provides a facility similar to that of GNAT.Dynamic_Tables,
+This package provides a facility similar to that of @code{GNAT.Dynamic_Tables},
except that this package declares a single instance of the table type,
-while an instantiation of GNAT.Dynamic_Tables creates a type that can be
+while an instantiation of @code{GNAT.Dynamic_Tables} creates a type that can be
used to define dynamic instances of the table.
@node GNAT.Task_Lock (g-tasloc.ads)
@cindex Threads, foreign
@noindent
-Provides facilities for creating and destroying threads with explicit calls.
-These threads are known to the GNAT run-time system. These subprograms are
-exported C-convention procedures intended to be called from foreign code.
-By using these primitives rather than directly calling operating systems
-routines, compatibility with the Ada tasking runt-time is provided.
+Provides facilities for dealing with foreign threads which need to be known
+by the GNAT run-time system. Consult the documentation of this package for
+further details if your program has threads that are created by a non-Ada
+environment which then accesses Ada code.
@node GNAT.Traceback (g-traceb.ads)
@section @code{GNAT.Traceback} (@file{g-traceb.ads})
@noindent
Provides symbolic traceback information that includes the subprogram
-name and line number information.
+name and line number information. Note that this capability is not available
+on all targets, see g-trasym.ads for list of supported targets.
+
+@node GNAT.Wide_String_Split (g-wistsp.ads)
+@section @code{GNAT.Wide_String_Split} (@file{g-wistsp.ads})
+@cindex @code{GNAT.Wide_String_Split} (@file{g-wistsp.ads})
+@cindex Wide_String splitter
+
+@noindent
+Useful wide string manipulation routines: given a set of separators, split
+a wide string wherever the separators appear, and provide direct access
+to the resulting slices. This package is instantiated from
+@code{GNAT.Array_Split}.
+
+@node GNAT.Wide_Wide_String_Split (g-zistsp.ads)
+@section @code{GNAT.Wide_Wide_String_Split} (@file{g-zistsp.ads})
+@cindex @code{GNAT.Wide_Wide_String_Split} (@file{g-zistsp.ads})
+@cindex Wide_Wide_String splitter
+
+@noindent
+Useful wide wide string manipulation routines: given a set of separators, split
+a wide wide string wherever the separators appear, and provide direct access
+to the resulting slices. This package is instantiated from
+@code{GNAT.Array_Split}.
@node Interfaces.C.Extensions (i-cexten.ads)
@section @code{Interfaces.C.Extensions} (@file{i-cexten.ads})
@cindex Interfacing to VxWorks' I/O
@cindex VxWorks, I/O interfacing
@cindex VxWorks, Get_Immediate
+@cindex Get_Immediate, VxWorks
@noindent
-This package provides a limited binding to the VxWorks' I/O API.
-In particular, it provides procedures that enable the use of
-Get_Immediate under VxWorks.
+This package provides a binding to the ioctl (IO/Control)
+function of VxWorks, defining a set of option values and
+function codes. A particular use of this package is
+to enable the use of Get_Immediate under VxWorks.
@node System.Address_Image (s-addima.ads)
@section @code{System.Address_Image} (@file{s-addima.ads})
by an run-time assertion failure, as well as the routine that
is used internally to raise this assertion.
+@node System.Memory (s-memory.ads)
+@section @code{System.Memory} (@file{s-memory.ads})
+@cindex @code{System.Memory} (@file{s-memory.ads})
+@cindex Memory allocation
+
+@noindent
+This package provides the interface to the low level routines used
+by the generated code for allocation and freeing storage for the
+default storage pool (analogous to the C routines malloc and free.
+It also provides a reallocation interface analogous to the C routine
+realloc. The body of this unit may be modified to provide alternative
+allocation mechanisms for the default pool, and in addition, direct
+calls to this unit may be made for low level allocation uses (for
+example see the body of @code{GNAT.Tables}).
+
@node System.Partition_Interface (s-parint.ads)
@section @code{System.Partition_Interface} (@file{s-parint.ads})
@cindex @code{System.Partition_Interface} (@file{s-parint.ads})
-@cindex Partition intefacing functions
+@cindex Partition interfacing functions
@noindent
This package provides facilities for partition interfacing. It
is used primarily in a distribution context when using Annex E
with @code{GLADE}.
+@node System.Restrictions (s-restri.ads)
+@section @code{System.Restrictions} (@file{s-restri.ads})
+@cindex @code{System.Restrictions} (@file{s-restri.ads})
+@cindex Run-time restrictions access
+
+@noindent
+This package provides facilities for accessing at run time
+the status of restrictions specified at compile time for
+the partition. Information is available both with regard
+to actual restrictions specified, and with regard to
+compiler determined information on which restrictions
+are violated by one or more packages in the partition.
+
+@node System.Rident (s-rident.ads)
+@section @code{System.Rident} (@file{s-rident.ads})
+@cindex @code{System.Rident} (@file{s-rident.ads})
+@cindex Restrictions definitions
+
+@noindent
+This package provides definitions of the restrictions
+identifiers supported by GNAT, and also the format of
+the restrictions provided in package System.Restrictions.
+It is not normally necessary to @code{with} this generic package
+since the necessary instantiation is included in
+package System.Restrictions.
+
@node System.Task_Info (s-tasinf.ads)
@section @code{System.Task_Info} (@file{s-tasinf.ads})
@cindex @code{System.Task_Info} (@file{s-tasinf.ads})
@noindent
This package provides routines for converting between
-wide characters and a representation as a value of type
+wide and wide wide characters and a representation as a value of type
@code{Standard.String}, using a specified wide character
encoding method. It uses definitions in
package @code{System.Wch_Con}.
@node Interfacing to Other Languages
@chapter Interfacing to Other Languages
@noindent
-The facilities in annex B of the Ada 95 Reference Manual are fully
+The facilities in annex B of the Ada Reference Manual are fully
implemented in GNAT, and in addition, a full interface to C++ is
provided.
@menu
-* Interfacing to C::
-* Interfacing to C++::
-* Interfacing to COBOL::
-* Interfacing to Fortran::
+* Interfacing to C::
+* Interfacing to C++::
+* Interfacing to COBOL::
+* Interfacing to Fortran::
* Interfacing to non-GNAT Ada code::
@end menu
@noindent
Interfacing to C with GNAT can use one of two approaches:
-@enumerate
+@itemize @bullet
@item
The types in the package @code{Interfaces.C} may be used.
@item
Standard Ada types may be used directly. This may be less portable to
other compilers, but will work on all GNAT compilers, which guarantee
correspondence between the C and Ada types.
-@end enumerate
+@end itemize
@noindent
-Pragma @code{Convention C} maybe applied to Ada types, but mostly has no
+Pragma @code{Convention C} may be applied to Ada types, but mostly has no
effect, since this is the default. The following table shows the
correspondence between Ada scalar types and the corresponding C types.
This is the longest floating-point type supported by the hardware.
@end table
+@noindent
+Additionally, there are the following general correspondences between Ada
+and C types:
@itemize @bullet
@item
Ada enumeration types map to C enumeration types directly if pragma
@code{Convention C} is specified, which causes them to have int
length. Without pragma @code{Convention C}, Ada enumeration types map to
-8, 16, or 32 bits (i.e.@: C types @code{signed char}, @code{short}, @code{int}, respectively)
-depending on the number of values passed. This is the only case in which
-pragma @code{Convention C} affects the representation of an Ada type.
+8, 16, or 32 bits (i.e.@: C types @code{signed char}, @code{short},
+@code{int}, respectively) depending on the number of values passed.
+This is the only case in which pragma @code{Convention C} affects the
+representation of an Ada type.
@item
Ada access types map to C pointers, except for the case of pointers to
@noindent
The interface to C++ makes use of the following pragmas, which are
primarily intended to be constructed automatically using a binding generator
-tool, although it is possible to construct them by hand. Ada Core
-Technologies does not currently supply a suitable binding generator tool.
+tool, although it is possible to construct them by hand. No suitable binding
+generator tool is supplied with GNAT though.
Using these pragmas it is possible to achieve complete
-inter-operability between Ada tagged types and C class definitions.
-See @ref{Implementation Defined Pragmas} for more details.
+inter-operability between Ada tagged types and C++ class definitions.
+See @ref{Implementation Defined Pragmas}, for more details.
@table @code
-@item pragma CPP_Class ([Entity =>] @var{local_name})
+@item pragma CPP_Class ([Entity =>] @var{local_NAME})
The argument denotes an entity in the current declarative region that is
-declared as a tagged or untagged record type. It indicates that the type
+declared as a tagged or untagged record type. It indicates that the type
corresponds to an externally declared C++ class type, and is to be laid
out the same way that C++ would lay out the type.
-@item pragma CPP_Constructor ([Entity =>] @var{local_name})
+Note: Pragma @code{CPP_Class} is currently obsolete. It is supported
+for backward compatibility but its functionality is available
+using pragma @code{Import} with @code{Convention} = @code{CPP}.
+
+@item pragma CPP_Constructor ([Entity =>] @var{local_NAME})
This pragma identifies an imported function (imported in the usual way
with pragma @code{Import}) as corresponding to a C++ constructor.
-
-@item pragma CPP_Vtable @dots{}
-One @code{CPP_Vtable} pragma can be present for each component of type
-@code{CPP.Interfaces.Vtable_Ptr} in a record to which pragma @code{CPP_Class}
-applies.
@end table
@node Interfacing to COBOL
@noindent
Interfacing to COBOL is achieved as described in section B.4 of
-the Ada 95 reference manual.
+the Ada Reference Manual.
@node Interfacing to Fortran
@section Interfacing to Fortran
@noindent
Interfacing to Fortran is achieved as described in section B.5 of the
-reference manual. The pragma @code{Convention Fortran}, applied to a
+Ada Reference Manual. The pragma @code{Convention Fortran}, applied to a
multi-dimensional array causes the array to be stored in column-major
order as required for convenient interface to Fortran.
@node Interfacing to non-GNAT Ada code
@section Interfacing to non-GNAT Ada code
-It is possible to specify the convention @code{Ada} in a pragma @code{Import} or
-pragma @code{Export}. However this refers to the calling conventions used
-by GNAT, which may or may not be similar enough to those used by
-some other Ada 83 or Ada 95 compiler to allow interoperation.
+It is possible to specify the convention @code{Ada} in a pragma
+@code{Import} or pragma @code{Export}. However this refers to
+the calling conventions used by GNAT, which may or may not be
+similar enough to those used by some other Ada 83 / Ada 95 / Ada 2005
+compiler to allow interoperation.
If arguments types are kept simple, and if the foreign compiler generally
follows system calling conventions, then it may be possible to integrate
files compiled by other Ada compilers, provided that the elaboration
-issues are adequately addressed (for example by eliminating the
+issues are adequately addressed (for example by eliminating the
need for any load time elaboration).
In particular, GNAT running on VMS is designed to
values or simple record types without variants, or simple array
types with fixed bounds.
+@node Specialized Needs Annexes
+@chapter Specialized Needs Annexes
+
+@noindent
+Ada 95 and Ada 2005 define a number of Specialized Needs Annexes, which are not
+required in all implementations. However, as described in this chapter,
+GNAT implements all of these annexes:
+
+@table @asis
+@item Systems Programming (Annex C)
+The Systems Programming Annex is fully implemented.
+
+@item Real-Time Systems (Annex D)
+The Real-Time Systems Annex is fully implemented.
+
+@item Distributed Systems (Annex E)
+Stub generation is fully implemented in the GNAT compiler. In addition,
+a complete compatible PCS is available as part of the GLADE system,
+a separate product. When the two
+products are used in conjunction, this annex is fully implemented.
+
+@item Information Systems (Annex F)
+The Information Systems annex is fully implemented.
+
+@item Numerics (Annex G)
+The Numerics Annex is fully implemented.
+
+@item Safety and Security / High-Integrity Systems (Annex H)
+The Safety and Security Annex (termed the High-Integrity Systems Annex
+in Ada 2005) is fully implemented.
+@end table
+
+@node Implementation of Specific Ada Features
+@chapter Implementation of Specific Ada Features
+
+@noindent
+This chapter describes the GNAT implementation of several Ada language
+facilities.
+
+@menu
+* Machine Code Insertions::
+* GNAT Implementation of Tasking::
+* GNAT Implementation of Shared Passive Packages::
+* Code Generation for Array Aggregates::
+* The Size of Discriminated Records with Default Discriminants::
+* Strict Conformance to the Ada Reference Manual::
+@end menu
+
@node Machine Code Insertions
-@chapter Machine Code Insertions
+@section Machine Code Insertions
+@cindex Machine Code insertions
@noindent
Package @code{Machine_Code} provides machine code support as described
-in the Ada 95 Reference Manual in two separate forms:
+in the Ada Reference Manual in two separate forms:
@itemize @bullet
@item
Machine code statements, consisting of qualified expressions that
including machine instructions in a subprogram.
@end itemize
-The two features are similar, and both closely related to the mechanism
+@noindent
+The two features are similar, and both are closely related to the mechanism
provided by the asm instruction in the GNU C compiler. Full understanding
and use of the facilities in this package requires understanding the asm
-instruction as described in
-@cite{Using and Porting the GNU Compiler Collection (GCC)} by Richard
-Stallman. Calls to the function @code{Asm} and the procedure @code{Asm}
-have identical semantic restrictions and effects as described below.
-Both are provided so that the procedure call can be used as a statement,
-and the function call can be used to form a code_statement.
+instruction as described in @cite{Using the GNU Compiler Collection (GCC)}
+by Richard Stallman. The relevant section is titled ``Extensions to the C
+Language Family'' @result{} ``Assembler Instructions with C Expression
+Operands''.
+
+Calls to the function @code{Asm} and the procedure @code{Asm} have identical
+semantic restrictions and effects as described below. Both are provided so
+that the procedure call can be used as a statement, and the function call
+can be used to form a code_statement.
The first example given in the GCC documentation is the C @code{asm}
instruction:
@noindent
The equivalent can be written for GNAT as:
-@smallexample
+@smallexample @c ada
Asm ("fsinx %1 %0",
My_Float'Asm_Output ("=f", result),
My_Float'Asm_Input ("f", angle));
@end smallexample
+@noindent
The first argument to @code{Asm} is the assembler template, and is
identical to what is used in GNU C@. This string must be a static
expression. The second argument is the output operand list. It is
suppressed, and that in particular, for an instruction that has outputs,
the instruction will still be generated, even if none of the outputs are
used. See the full description in the GCC manual for further details.
+Generally it is strongly advisable to use Volatile for any ASM statement
+that is missing either input or output operands, or when two or more ASM
+statements appear in sequence, to avoid unwanted optimizations. A warning
+is generated if this advice is not followed.
The @code{Asm} subprograms may be used in two ways. First the procedure
forms can be used anywhere a procedure call would be valid, and
this is the only context where such calls are allowed. Code statements
appear as aggregates of the form:
-@smallexample
+@smallexample @c ada
Asm_Insn'(Asm (@dots{}));
Asm_Insn'(Asm_Volatile (@dots{}));
@end smallexample
+@noindent
In accordance with RM rules, such code statements are allowed only
within subprograms whose entire body consists of such statements. It is
not permissible to intermix such statements with other Ada statements.
Typically the form using intrinsic procedure calls is more convenient
and more flexible. The code statement form is provided to meet the RM
suggestion that such a facility should be made available. The following
-is the exact syntax of the call to @code{Asm} (of course if named notation is
-used, the arguments may be given in arbitrary order, following the
+is the exact syntax of the call to @code{Asm}. As usual, if named notation
+is used, the arguments may be given in arbitrary order, following the
normal rules for use of positional and named arguments)
@smallexample
[,[Inputs =>] INPUT_OPERAND_LIST ]
[,[Clobber =>] static_string_EXPRESSION ]
[,[Volatile =>] static_boolean_EXPRESSION] )
+
OUTPUT_OPERAND_LIST ::=
- No_Output_Operands
+ [PREFIX.]No_Output_Operands
| OUTPUT_OPERAND_ATTRIBUTE
| (OUTPUT_OPERAND_ATTRIBUTE @{,OUTPUT_OPERAND_ATTRIBUTE@})
+
OUTPUT_OPERAND_ATTRIBUTE ::=
SUBTYPE_MARK'Asm_Output (static_string_EXPRESSION, NAME)
+
INPUT_OPERAND_LIST ::=
- No_Input_Operands
+ [PREFIX.]No_Input_Operands
| INPUT_OPERAND_ATTRIBUTE
| (INPUT_OPERAND_ATTRIBUTE @{,INPUT_OPERAND_ATTRIBUTE@})
+
INPUT_OPERAND_ATTRIBUTE ::=
SUBTYPE_MARK'Asm_Input (static_string_EXPRESSION, EXPRESSION)
@end smallexample
+@noindent
+The identifiers @code{No_Input_Operands} and @code{No_Output_Operands}
+are declared in the package @code{Machine_Code} and must be referenced
+according to normal visibility rules. In particular if there is no
+@code{use} clause for this package, then appropriate package name
+qualification is required.
+
@node GNAT Implementation of Tasking
-@chapter GNAT Implementation of Tasking
+@section GNAT Implementation of Tasking
+
+@noindent
+This chapter outlines the basic GNAT approach to tasking (in particular,
+a multi-layered library for portability) and discusses issues related
+to compliance with the Real-Time Systems Annex.
+
@menu
* Mapping Ada Tasks onto the Underlying Kernel Threads::
* Ensuring Compliance with the Real-Time Annex::
@end menu
@node Mapping Ada Tasks onto the Underlying Kernel Threads
-@section Mapping Ada Tasks onto the Underlying Kernel Threads
+@subsection Mapping Ada Tasks onto the Underlying Kernel Threads
-GNAT run-time system comprises two layers:
+@noindent
+GNAT's run-time support comprises two layers:
@itemize @bullet
-@item GNARL (GNAT Run-time Layer)
+@item GNARL (GNAT Run-time Layer)
@item GNULL (GNAT Low-level Library)
@end itemize
+@noindent
In GNAT, Ada's tasking services rely on a platform and OS independent
layer known as GNARL@. This code is responsible for implementing the
correct semantics of Ada's task creation, rendezvous, protected
by GNARL@.
Whatever the underlying OS (VxWorks, UNIX, OS/2, Windows NT, etc.) the
-key point is that each Ada task is mapped on a thread in the underlying
+key point is that each Ada task is mapped on a thread in the underlying
kernel. For example, in the case of VxWorks, one Ada task = one VxWorks task.
In addition Ada task priorities map onto the underlying thread priorities.
Mapping Ada tasks onto the underlying kernel threads has several advantages:
-@enumerate
-
+@itemize @bullet
@item
The underlying scheduler is used to schedule the Ada tasks. This
makes Ada tasks as efficient as kernel threads from a scheduling
-standpoint.
+standpoint.
@item
Interaction with code written in C containing threads is eased
able to proceed.
@item
-On multi-processor systems Ada Tasks can execute in parallel.
-@end enumerate
+On multiprocessor systems Ada tasks can execute in parallel.
+@end itemize
+
+@noindent
+Some threads libraries offer a mechanism to fork a new process, with the
+child process duplicating the threads from the parent.
+GNAT does not
+support this functionality when the parent contains more than one task.
+@cindex Forking a new process
@node Ensuring Compliance with the Real-Time Annex
-@section Ensuring Compliance with the Real-Time Annex
+@subsection Ensuring Compliance with the Real-Time Annex
+@cindex Real-Time Systems Annex compliance
-The reader will be quick to notice that while mapping Ada tasks onto
+@noindent
+Although mapping Ada tasks onto
the underlying threads has significant advantages, it does create some
complications when it comes to respecting the scheduling semantics
specified in the real-time annex (Annex D).
-For instance Annex D requires that for the FIFO_Within_Priorities
-scheduling policy we have:
+For instance the Annex D requirement for the @code{FIFO_Within_Priorities}
+scheduling policy states:
-@smallexample
-When the active priority of a ready task that is not running
+@quotation
+@emph{When the active priority of a ready task that is not running
changes, or the setting of its base priority takes effect, the
task is removed from the ready queue for its old active priority
and is added at the tail of the ready queue for its new active
priority, except in the case where the active priority is lowered
due to the loss of inherited priority, in which case the task is
-added at the head of the ready queue for its new active priority.
-@end smallexample
+added at the head of the ready queue for its new active priority.}
+@end quotation
+@noindent
While most kernels do put tasks at the end of the priority queue when
a task changes its priority, (which respects the main
FIFO_Within_Priorities requirement), almost none keep a thread at the
priority as T has been suspended due to the loss of priority
inheritance. If this is the case, T yields and is placed at the end of
its priority queue. When R arrives at the front of the queue it
-executes.
+executes.
Note that this simple scheme preserves the relative order of the tasks
that were ready to execute in the priority queue where R has been
placed at the end.
-@node Code generation for array aggregates
-@chapter Code generation for array aggregates
+@node GNAT Implementation of Shared Passive Packages
+@section GNAT Implementation of Shared Passive Packages
+@cindex Shared passive packages
+
+@noindent
+GNAT fully implements the pragma @code{Shared_Passive} for
+@cindex pragma @code{Shared_Passive}
+the purpose of designating shared passive packages.
+This allows the use of passive partitions in the
+context described in the Ada Reference Manual; i.e. for communication
+between separate partitions of a distributed application using the
+features in Annex E.
+@cindex Annex E
+@cindex Distribution Systems Annex
+
+However, the implementation approach used by GNAT provides for more
+extensive usage as follows:
+
+@table @emph
+@item Communication between separate programs
+
+This allows separate programs to access the data in passive
+partitions, using protected objects for synchronization where
+needed. The only requirement is that the two programs have a
+common shared file system. It is even possible for programs
+running on different machines with different architectures
+(e.g. different endianness) to communicate via the data in
+a passive partition.
+
+@item Persistence between program runs
+
+The data in a passive package can persist from one run of a
+program to another, so that a later program sees the final
+values stored by a previous run of the same program.
+
+@end table
+
+@noindent
+The implementation approach used is to store the data in files. A
+separate stream file is created for each object in the package, and
+an access to an object causes the corresponding file to be read or
+written.
+
+The environment variable @code{SHARED_MEMORY_DIRECTORY} should be
+@cindex @code{SHARED_MEMORY_DIRECTORY} environment variable
+set to the directory to be used for these files.
+The files in this directory
+have names that correspond to their fully qualified names. For
+example, if we have the package
+
+@smallexample @c ada
+package X is
+ pragma Shared_Passive (X);
+ Y : Integer;
+ Z : Float;
+end X;
+@end smallexample
+
+@noindent
+and the environment variable is set to @code{/stemp/}, then the files created
+will have the names:
+
+@smallexample
+/stemp/x.y
+/stemp/x.z
+@end smallexample
+
+@noindent
+These files are created when a value is initially written to the object, and
+the files are retained until manually deleted. This provides the persistence
+semantics. If no file exists, it means that no partition has assigned a value
+to the variable; in this case the initial value declared in the package
+will be used. This model ensures that there are no issues in synchronizing
+the elaboration process, since elaboration of passive packages elaborates the
+initial values, but does not create the files.
+
+The files are written using normal @code{Stream_IO} access.
+If you want to be able
+to communicate between programs or partitions running on different
+architectures, then you should use the XDR versions of the stream attribute
+routines, since these are architecture independent.
+
+If active synchronization is required for access to the variables in the
+shared passive package, then as described in the Ada Reference Manual, the
+package may contain protected objects used for this purpose. In this case
+a lock file (whose name is @file{___lock} (three underscores)
+is created in the shared memory directory.
+@cindex @file{___lock} file (for shared passive packages)
+This is used to provide the required locking
+semantics for proper protected object synchronization.
+
+As of January 2003, GNAT supports shared passive packages on all platforms
+except for OpenVMS.
+
+@node Code Generation for Array Aggregates
+@section Code Generation for Array Aggregates
@menu
* Static constant aggregates with static bounds::
-* Constant aggregates with an unconstrained nominal types::
+* Constant aggregates with unconstrained nominal types::
* Aggregates with static bounds::
* Aggregates with non-static bounds::
-* Aggregates in assignments statements::
+* Aggregates in assignment statements::
@end menu
-
-Aggregate have a rich syntax and allow the user to specify the values of
+
+@noindent
+Aggregates have a rich syntax and allow the user to specify the values of
complex data structures by means of a single construct. As a result, the
code generated for aggregates can be quite complex and involve loops, case
statements and multiple assignments. In the simplest cases, however, the
compiler will recognize aggregates whose components and constraints are
fully static, and in those cases the compiler will generate little or no
executable code. The following is an outline of the code that GNAT generates
-for various aggregate constructs. For further details, the user will find it
+for various aggregate constructs. For further details, you will find it
useful to examine the output produced by the -gnatG flag to see the expanded
-source that is input to the code generator. The user will also want to examine
+source that is input to the code generator. You may also want to examine
the assembly code generated at various levels of optimization.
The code generated for aggregates depends on the context, the component values,
and the type. In the context of an object declaration the code generated is
generally simpler than in the case of an assignment. As a general rule, static
component values and static subtypes also lead to simpler code.
-
+
@node Static constant aggregates with static bounds
-@section Static constant aggregates with static bounds
-
- For the declarations:
-@smallexample
+@subsection Static constant aggregates with static bounds
+
+@noindent
+For the declarations:
+@smallexample @c ada
type One_Dim is array (1..10) of integer;
- ar0 : constant One_Dim := ( 1, 2, 3, 4, 5, 6, 7, 8, 9, 0);
-@end smallexample
+ ar0 : constant One_Dim := (1, 2, 3, 4, 5, 6, 7, 8, 9, 0);
+@end smallexample
+@noindent
GNAT generates no executable code: the constant ar0 is placed in static memory.
The same is true for constant aggregates with named associations:
-
-@smallexample
- Cr1 : constant One_Dim := (4 => 16, 2 => 4, 3 => 9, 1=> 1);
+
+@smallexample @c ada
+ Cr1 : constant One_Dim := (4 => 16, 2 => 4, 3 => 9, 1 => 1, 5 .. 10 => 0);
Cr3 : constant One_Dim := (others => 7777);
-@end smallexample
-
- The same is true for multidimensional constant arrays such as:
-
-@smallexample
- type two_dim is array (1..3, 1..3) of integer;
+@end smallexample
+
+@noindent
+The same is true for multidimensional constant arrays such as:
+
+@smallexample @c ada
+ type two_dim is array (1..3, 1..3) of integer;
Unit : constant two_dim := ( (1,0,0), (0,1,0), (0,0,1));
-@end smallexample
-
+@end smallexample
+
+@noindent
The same is true for arrays of one-dimensional arrays: the following are
static:
-
-@smallexample
-type ar1b is array (1..3) of boolean;
+
+@smallexample @c ada
+type ar1b is array (1..3) of boolean;
type ar_ar is array (1..3) of ar1b;
-None : constant ar1b := (others => false); -- fully static
+None : constant ar1b := (others => false); -- fully static
None2 : constant ar_ar := (1..3 => None); -- fully static
-@end smallexample
-
+@end smallexample
+
+@noindent
However, for multidimensional aggregates with named associations, GNAT will
generate assignments and loops, even if all associations are static. The
following two declarations generate a loop for the first dimension, and
individual component assignments for the second dimension:
-
-@smallexample
+
+@smallexample @c ada
Zero1: constant two_dim := (1..3 => (1..3 => 0));
-Zero2: constant two_dim := (others => (others => 0));
-@end smallexample
-
-@node Constant aggregates with an unconstrained nominal types
-@section Constant aggregates with an unconstrained nominal types
-
-In such cases the aggregate itself establishes the subtype, so that associations
-with @code{others} cannot be used. GNAT determines the bounds for the actual
-subtype of the aggregate, and allocates the aggregate statically as well. No
-code is generated for the following:
-
-@smallexample
+Zero2: constant two_dim := (others => (others => 0));
+@end smallexample
+
+@node Constant aggregates with unconstrained nominal types
+@subsection Constant aggregates with unconstrained nominal types
+
+@noindent
+In such cases the aggregate itself establishes the subtype, so that
+associations with @code{others} cannot be used. GNAT determines the
+bounds for the actual subtype of the aggregate, and allocates the
+aggregate statically as well. No code is generated for the following:
+
+@smallexample @c ada
type One_Unc is array (natural range <>) of integer;
Cr_Unc : constant One_Unc := (12,24,36);
-@end smallexample
-
+@end smallexample
+
@node Aggregates with static bounds
-@section Aggregates with static bounds
-
+@subsection Aggregates with static bounds
+
+@noindent
In all previous examples the aggregate was the initial (and immutable) value
of a constant. If the aggregate initializes a variable, then code is generated
for it as a combination of individual assignments and loops over the target
object. The declarations
-
-@smallexample
- Cr_Var1 : One_Dim := (2, 5, 7, 11);
+
+@smallexample @c ada
+ Cr_Var1 : One_Dim := (2, 5, 7, 11, 0, 0, 0, 0, 0, 0);
Cr_Var2 : One_Dim := (others > -1);
-@end smallexample
-
+@end smallexample
+
+@noindent
generate the equivalent of
-
-@smallexample
+
+@smallexample @c ada
Cr_Var1 (1) := 2;
Cr_Var1 (2) := 3;
Cr_Var1 (3) := 5;
Cr_Var1 (4) := 11;
-
+
for I in Cr_Var2'range loop
Cr_Var2 (I) := =-1;
end loop;
-@end smallexample
-
+@end smallexample
+
@node Aggregates with non-static bounds
-@section Aggregates with non-static bounds
-
+@subsection Aggregates with non-static bounds
+
+@noindent
If the bounds of the aggregate are not statically compatible with the bounds
of the nominal subtype of the target, then constraint checks have to be
generated on the bounds. For a multidimensional array, constraint checks may
have to be applied to sub-arrays individually, if they do not have statically
compatible subtypes.
-
-@node Aggregates in assignments statements
-@section Aggregates in assignments statements
-
+
+@node Aggregates in assignment statements
+@subsection Aggregates in assignment statements
+
+@noindent
In general, aggregate assignment requires the construction of a temporary,
and a copy from the temporary to the target of the assignment. This is because
-it is not always possible to convert the assignment into a series of individual
+it is not always possible to convert the assignment into a series of individual
component assignments. For example, consider the simple case:
-
-@smallexample
-@end smallexample
+
+@smallexample @c ada
A := (A(2), A(1));
-
+@end smallexample
+
+@noindent
This cannot be converted into:
-
-@smallexample
+
+@smallexample @c ada
A(1) := A(2);
A(2) := A(1);
-@end smallexample
-
+@end smallexample
+
+@noindent
So the aggregate has to be built first in a separate location, and then
copied into the target. GNAT recognizes simple cases where this intermediate
step is not required, and the assignments can be performed in place, directly
into the target. The following sufficient criteria are applied:
-@enumerate
-@item The bounds of the aggregate are static, and the associations are static.
-@item The components of the aggregate are static constants, names of
- simple variables that are not renamings, or expressions not involving
- indexed components whose operands obey these rules.
-@end enumerate
-
+@itemize @bullet
+@item
+The bounds of the aggregate are static, and the associations are static.
+@item
+The components of the aggregate are static constants, names of
+simple variables that are not renamings, or expressions not involving
+indexed components whose operands obey these rules.
+@end itemize
+
+@noindent
If any of these conditions are violated, the aggregate will be built in
a temporary (created either by the front-end or the code generator) and then
that temporary will be copied onto the target.
-
-
-@node Specialized Needs Annexes
-@chapter Specialized Needs Annexes
+
+
+@node The Size of Discriminated Records with Default Discriminants
+@section The Size of Discriminated Records with Default Discriminants
@noindent
-Ada 95 defines a number of specialized needs annexes, which are not
-required in all implementations. However, as described in this chapter,
-GNAT implements all of these special needs annexes:
+If a discriminated type @code{T} has discriminants with default values, it is
+possible to declare an object of this type without providing an explicit
+constraint:
-@table @asis
-@item Systems Programming (Annex C)
-The Systems Programming Annex is fully implemented.
+@smallexample @c ada
+@group
+type Size is range 1..100;
-@item Real-Time Systems (Annex D)
-The Real-Time Systems Annex is fully implemented.
+type Rec (D : Size := 15) is record
+ Name : String (1..D);
+end T;
-@item Distributed Systems (Annex E)
-Stub generation is fully implemented in the GNAT compiler. In addition,
-a complete compatible PCS is available as part of the GLADE system,
-a separate product. When the two
-products are used in conjunction, this annex is fully implemented.
+Word : Rec;
+@end group
+@end smallexample
-@item Information Systems (Annex F)
-The Information Systems annex is fully implemented.
+@noindent
+Such an object is said to be @emph{unconstrained}.
+The discriminant of the object
+can be modified by a full assignment to the object, as long as it preserves the
+relation between the value of the discriminant, and the value of the components
+that depend on it:
-@item Numerics (Annex G)
-The Numerics Annex is fully implemented.
+@smallexample @c ada
+@group
+Word := (3, "yes");
-@item Safety and Security (Annex H)
-The Safety and Security annex is fully implemented.
+Word := (5, "maybe");
-@end table
+Word := (5, "no"); -- raises Constraint_Error
+@end group
+@end smallexample
+
+@noindent
+In order to support this behavior efficiently, an unconstrained object is
+given the maximum size that any value of the type requires. In the case
+above, @code{Word} has storage for the discriminant and for
+a @code{String} of length 100.
+It is important to note that unconstrained objects do not require dynamic
+allocation. It would be an improper implementation to place on the heap those
+components whose size depends on discriminants. (This improper implementation
+was used by some Ada83 compilers, where the @code{Name} component above
+would have
+been stored as a pointer to a dynamic string). Following the principle that
+dynamic storage management should never be introduced implicitly,
+an Ada compiler should reserve the full size for an unconstrained declared
+object, and place it on the stack.
+
+This maximum size approach
+has been a source of surprise to some users, who expect the default
+values of the discriminants to determine the size reserved for an
+unconstrained object: ``If the default is 15, why should the object occupy
+a larger size?''
+The answer, of course, is that the discriminant may be later modified,
+and its full range of values must be taken into account. This is why the
+declaration:
+
+@smallexample
+@group
+type Rec (D : Positive := 15) is record
+ Name : String (1..D);
+end record;
+
+Too_Large : Rec;
+@end group
+@end smallexample
+
+@noindent
+is flagged by the compiler with a warning:
+an attempt to create @code{Too_Large} will raise @code{Storage_Error},
+because the required size includes @code{Positive'Last}
+bytes. As the first example indicates, the proper approach is to declare an
+index type of ``reasonable'' range so that unconstrained objects are not too
+large.
+
+One final wrinkle: if the object is declared to be @code{aliased}, or if it is
+created in the heap by means of an allocator, then it is @emph{not}
+unconstrained:
+it is constrained by the default values of the discriminants, and those values
+cannot be modified by full assignment. This is because in the presence of
+aliasing all views of the object (which may be manipulated by different tasks,
+say) must be consistent, so it is imperative that the object, once created,
+remain invariant.
-@node Compatibility Guide
-@chapter Compatibility Guide
+@node Strict Conformance to the Ada Reference Manual
+@section Strict Conformance to the Ada Reference Manual
@noindent
-This chapter contains sections that describe compatibility issues between
-GNAT and other Ada 83 and Ada 95 compilation systems, to aid in porting
-applications developed in other Ada environments.
+The dynamic semantics defined by the Ada Reference Manual impose a set of
+run-time checks to be generated. By default, the GNAT compiler will insert many
+run-time checks into the compiled code, including most of those required by the
+Ada Reference Manual. However, there are three checks that are not enabled
+in the default mode for efficiency reasons: arithmetic overflow checking for
+integer operations (including division by zero), checks for access before
+elaboration on subprogram calls, and stack overflow checking (most operating
+systems do not perform this check by default).
+
+Strict conformance to the Ada Reference Manual can be achieved by adding
+three compiler options for overflow checking for integer operations
+(@option{-gnato}), dynamic checks for access-before-elaboration on subprogram
+calls and generic instantiations (@option{-gnatE}), and stack overflow
+checking (@option{-fstack-check}).
+
+Note that the result of a floating point arithmetic operation in overflow and
+invalid situations, when the @code{Machine_Overflows} attribute of the result
+type is @code{False}, is to generate IEEE NaN and infinite values. This is the
+case for machines compliant with the IEEE floating-point standard, but on
+machines that are not fully compliant with this standard, such as Alpha, the
+@option{-mieee} compiler flag must be used for achieving IEEE confirming
+behavior (although at the cost of a significant performance penalty), so
+infinite and and NaN values are properly generated.
+
+
+@node Project File Reference
+@chapter Project File Reference
+
+@noindent
+This chapter describes the syntax and semantics of project files.
+Project files specify the options to be used when building a system.
+Project files can specify global settings for all tools,
+as well as tool-specific settings.
+See the chapter on project files in the GNAT Users guide for examples of use.
@menu
-* Compatibility with Ada 83::
-* Compatibility with DEC Ada 83::
-* Compatibility with Other Ada 95 Systems::
-* Representation Clauses::
+* Reserved Words::
+* Lexical Elements::
+* Declarations::
+* Empty declarations::
+* Typed string declarations::
+* Variables::
+* Expressions::
+* Attributes::
+* Project Attributes::
+* Attribute References::
+* External Values::
+* Case Construction::
+* Packages::
+* Package Renamings::
+* Projects::
+* Project Extensions::
+* Project File Elaboration::
@end menu
-@node Compatibility with Ada 83
-@section Compatibility with Ada 83
-@cindex Compatibility (between Ada 83 and Ada 95)
+@node Reserved Words
+@section Reserved Words
@noindent
-Ada 95 is designed to be highly upwards compatible with Ada 83. In
-particular, the design intention is that the difficulties associated
-with moving from Ada 83 to Ada 95 should be no greater than those
-that occur when moving from one Ada 83 system to another.
+All Ada reserved words are reserved in project files, and cannot be used
+as variable names or project names. In addition, the following are
+also reserved in project files:
-However, there are a number of points at which there are minor
-incompatibilities. The Ada 95 Annotated Reference Manual contains
-full details of these issues,
-and should be consulted for a complete treatment.
-In practice the
-following are the most likely issues to be encountered.
+@itemize
+@item @code{extends}
-@table @asis
-@item Character range
-The range of @code{Standard.Character} is now the full 256 characters of Latin-1,
-whereas in most Ada 83 implementations it was restricted to 128 characters.
-This may show up as compile time or runtime errors. The desirable fix is to
-adapt the program to accommodate the full character set, but in some cases
-it may be convenient to define a subtype or derived type of Character that
-covers only the restricted range.
-@cindex Latin-1
-
-@item New reserved words
-The identifiers @code{abstract}, @code{aliased}, @code{protected},
-@code{requeue}, @code{tagged}, and @code{until} are reserved in Ada 95.
-Existing Ada 83 code using any of these identifiers must be edited to
-use some alternative name.
-
-@item Freezing rules
-The rules in Ada 95 are slightly different with regard to the point at
-which entities are frozen, and representation pragmas and clauses are
-not permitted past the freeze point. This shows up most typically in
-the form of an error message complaining that a representation item
-appears too late, and the appropriate corrective action is to move
-the item nearer to the declaration of the entity to which it refers.
-
-A particular case is that representation pragmas (including the
-extended DEC Ada 83 compatibility pragmas such as @code{Export_Procedure}), cannot
-be applied to a subprogram body. If necessary, a separate subprogram
-declaration must be introduced to which the pragma can be applied.
-
-@item Optional bodies for library packages
-In Ada 83, a package that did not require a package body was nevertheless
-allowed to have one. This lead to certain surprises in compiling large
-systems (situations in which the body could be unexpectedly ignored). In
-Ada 95, if a package does not require a body then it is not permitted to
-have a body. To fix this problem, simply remove a redundant body if it
-is empty, or, if it is non-empty, introduce a dummy declaration into the
-spec that makes the body required. One approach is to add a private part
-to the package declaration (if necessary), and define a parameterless
-procedure called Requires_Body, which must then be given a dummy
-procedure body in the package body, which then becomes required.
-
-@item @code{Numeric_Error} is now the same as @code{Constraint_Error}
-In Ada 95, the exception @code{Numeric_Error} is a renaming of @code{Constraint_Error}.
-This means that it is illegal to have separate exception handlers for
-the two exceptions. The fix is simply to remove the handler for the
-@code{Numeric_Error} case (since even in Ada 83, a compiler was free to raise
-@code{Constraint_Error} in place of @code{Numeric_Error} in all cases).
-
-@item Indefinite subtypes in generics
-In Ada 83, it was permissible to pass an indefinite type (e.g.@: @code{String}) as
-the actual for a generic formal private type, but then the instantiation
-would be illegal if there were any instances of declarations of variables
-of this type in the generic body. In Ada 95, to avoid this clear violation
-of the contract model, the generic declaration clearly indicates whether
-or not such instantiations are permitted. If a generic formal parameter
-has explicit unknown discriminants, indicated by using @code{(<>)} after the
-type name, then it can be instantiated with indefinite types, but no
-variables can be declared of this type. Any attempt to declare a variable
-will result in an illegality at the time the generic is declared. If the
-@code{(<>)} notation is not used, then it is illegal to instantiate the generic
-with an indefinite type. This will show up as a compile time error, and
-the fix is usually simply to add the @code{(<>)} to the generic declaration.
-@end table
+@item @code{external}
-All implementations of GNAT provide a switch that causes GNAT to operate
-in Ada 83 mode. In this mode, some but not all compatibility problems
-of the type described above are handled automatically. For example, the
-new Ada 95 protected keywords are not recognized in this mode. However,
-in practice, it is usually advisable to make the necessary modifications
-to the program to remove the need for using this switch.
+@item @code{project}
-@node Compatibility with Other Ada 95 Systems
-@section Compatibility with Other Ada 95 Systems
+@end itemize
+
+@node Lexical Elements
+@section Lexical Elements
@noindent
-Providing that programs avoid the use of implementation dependent and
-implementation defined features of Ada 95, as documented in the Ada 95
-reference manual, there should be a high degree of portability between
-GNAT and other Ada 95 systems. The following are specific items which
-have proved troublesome in moving GNAT programs to other Ada 95
-compilers, but do not affect porting code to GNAT@.
+Rules for identifiers are the same as in Ada. Identifiers
+are case-insensitive. Strings are case sensitive, except where noted.
+Comments have the same form as in Ada.
-@table @asis
-@item Ada 83 Pragmas and Attributes
-Ada 95 compilers are allowed, but not required, to implement the missing
-Ada 83 pragmas and attributes that are no longer defined in Ada 95.
-GNAT implements all such pragmas and attributes, eliminating this as
-a compatibility concern, but some other Ada 95 compilers reject these
-pragmas and attributes.
-
-@item Special-needs Annexes
-GNAT implements the full set of special needs annexes. At the
-current time, it is the only Ada 95 compiler to do so. This means that
-programs making use of these features may not be portable to other Ada
-95 compilation systems.
-
-@item Representation Clauses
-Some other Ada 95 compilers implement only the minimal set of
-representation clauses required by the Ada 95 reference manual. GNAT goes
-far beyond this minimal set, as described in the next section.
-@end table
+@noindent
+Syntax:
+
+@smallexample
+simple_name ::=
+ identifier
-@node Representation Clauses
-@section Representation Clauses
+name ::=
+ simple_name @{. simple_name@}
+@end smallexample
+
+@node Declarations
+@section Declarations
@noindent
-The Ada 83 reference manual was quite vague in describing both the minimal
-required implementation of representation clauses, and also their precise
-effects. The Ada 95 reference manual is much more explicit, but the minimal
-set of capabilities required in Ada 95 is quite limited.
+Declarations introduce new entities that denote types, variables, attributes,
+and packages. Some declarations can only appear immediately within a project
+declaration. Others can appear within a project or within a package.
-GNAT implements the full required set of capabilities described in the
-Ada 95 reference manual, but also goes much beyond this, and in particular
-an effort has been made to be compatible with existing Ada 83 usage to the
-greatest extent possible.
+Syntax:
+@smallexample
+declarative_item ::=
+ simple_declarative_item |
+ typed_string_declaration |
+ package_declaration
-A few cases exist in which Ada 83 compiler behavior is incompatible with
-requirements in the Ada 95 reference manual. These are instances of
-intentional or accidental dependence on specific implementation dependent
-characteristics of these Ada 83 compilers. The following is a list of
-the cases most likely to arise in existing legacy Ada 83 code.
+simple_declarative_item ::=
+ variable_declaration |
+ typed_variable_declaration |
+ attribute_declaration |
+ case_construction |
+ empty_declaration
+@end smallexample
-@table @asis
-@item Implicit Packing
-Some Ada 83 compilers allowed a Size specification to cause implicit
-packing of an array or record. This could cause expensive implicit
-conversions for change of representation in the presence of derived
-types, and the Ada design intends to avoid this possibility.
-Subsequent AI's were issued to make it clear that such implicit
-change of representation in response to a Size clause is inadvisable,
-and this recommendation is represented explicitly in the Ada 95 RM
-as implementation advice that is followed by GNAT@.
-The problem will show up as an error
-message rejecting the size clause. The fix is simply to provide
-the explicit pragma @code{Pack}, or for more fine tuned control, provide
-a Component_Size clause.
-
-@item Meaning of Size Attribute
-The Size attribute in Ada 95 for discrete types is defined as being the
-minimal number of bits required to hold values of the type. For example,
-on a 32-bit machine, the size of Natural will typically be 31 and not
-32 (since no sign bit is required). Some Ada 83 compilers gave 31, and
-some 32 in this situation. This problem will usually show up as a compile
-time error, but not always. It is a good idea to check all uses of the
-'Size attribute when porting Ada 83 code. The GNAT specific attribute
-Object_Size can provide a useful way of duplicating the behavior of
-some Ada 83 compiler systems.
-
-@item Size of Access Types
-A common assumption in Ada 83 code is that an access type is in fact a pointer,
-and that therefore it will be the same size as a System.Address value. This
-assumption is true for GNAT in most cases with one exception. For the case of
-a pointer to an unconstrained array type (where the bounds may vary from one
-value of the access type to another), the default is to use a ``fat pointer'',
-which is represented as two separate pointers, one to the bounds, and one to
-the array. This representation has a number of advantages, including improved
-efficiency. However, it may cause some difficulties in porting existing Ada 83
-code which makes the assumption that, for example, pointers fit in 32 bits on
-a machine with 32-bit addressing.
-
-To get around this problem, GNAT also permits the use of ``thin pointers'' for
-access types in this case (where the designated type is an unconstrained array
-type). These thin pointers are indeed the same size as a System.Address value.
-To specify a thin pointer, use a size clause for the type, for example:
+@node Empty declarations
+@section Empty declarations
+
+@smallexample
+empty_declaration ::=
+ @b{null} ;
+@end smallexample
+
+An empty declaration is allowed anywhere a declaration is allowed.
+It has no effect.
+
+@node Typed string declarations
+@section Typed string declarations
+
+@noindent
+Typed strings are sequences of string literals. Typed strings are the only
+named types in project files. They are used in case constructions, where they
+provide support for conditional attribute definitions.
+
+Syntax:
+@smallexample
+typed_string_declaration ::=
+ @b{type} <typed_string_>_simple_name @b{is}
+ ( string_literal @{, string_literal@} );
+@end smallexample
+
+@noindent
+A typed string declaration can only appear immediately within a project
+declaration.
+
+All the string literals in a typed string declaration must be distinct.
+
+@node Variables
+@section Variables
+
+@noindent
+Variables denote values, and appear as constituents of expressions.
+
+@smallexample
+typed_variable_declaration ::=
+ <typed_variable_>simple_name : <typed_string_>name := string_expression ;
+
+variable_declaration ::=
+ <variable_>simple_name := expression;
+@end smallexample
+
+@noindent
+The elaboration of a variable declaration introduces the variable and
+assigns to it the value of the expression. The name of the variable is
+available after the assignment symbol.
+
+@noindent
+A typed_variable can only be declare once.
+
+@noindent
+a non typed variable can be declared multiple times.
+@noindent
+Before the completion of its first declaration, the value of variable
+is the null string.
+
+@node Expressions
+@section Expressions
+
+@noindent
+An expression is a formula that defines a computation or retrieval of a value.
+In a project file the value of an expression is either a string or a list
+of strings. A string value in an expression is either a literal, the current
+value of a variable, an external value, an attribute reference, or a
+concatenation operation.
+
+Syntax:
+
+@smallexample
+expression ::=
+ term @{& term@}
+
+term ::=
+ string_literal |
+ string_list |
+ <variable_>name |
+ external_value |
+ attribute_reference
+
+string_literal ::=
+ (same as Ada)
+
+string_list ::=
+ ( <string_>expression @{ , <string_>expression @} )
+@end smallexample
+
+@subsection Concatenation
+@noindent
+The following concatenation functions are defined:
+
+@smallexample @c ada
+ function "&" (X : String; Y : String) return String;
+ function "&" (X : String_List; Y : String) return String_List;
+ function "&" (X : String_List; Y : String_List) return String_List;
+@end smallexample
+
+@node Attributes
+@section Attributes
+
+@noindent
+An attribute declaration defines a property of a project or package. This
+property can later be queried by means of an attribute reference.
+Attribute values are strings or string lists.
+
+Some attributes are associative arrays. These attributes are mappings whose
+domain is a set of strings. These attributes are declared one association
+at a time, by specifying a point in the domain and the corresponding image
+of the attribute. They may also be declared as a full associative array,
+getting the same associations as the corresponding attribute in an imported
+or extended project.
+
+Attributes that are not associative arrays are called simple attributes.
+
+Syntax:
@smallexample
-type X is access all String;
-for X'Size use Standard'Address_Size;
+attribute_declaration ::=
+ full_associative_array_declaration |
+ @b{for} attribute_designator @b{use} expression ;
+
+full_associative_array_declaration ::=
+ @b{for} <associative_array_attribute_>simple_name @b{use}
+ <project_>simple_name [ . <package_>simple_Name ] ' <attribute_>simple_name ;
+
+attribute_designator ::=
+ <simple_attribute_>simple_name |
+ <associative_array_attribute_>simple_name ( string_literal )
@end smallexample
@noindent
-which will cause the type X to be represented using a single pointer. When using
-this representation, the bounds are right behind the array. This representation
-is slightly less efficient, and does not allow quite such flexibility in the
-use of foreign pointers or in using the Unrestricted_Access attribute to create
-pointers to non-aliased objects. But for any standard portable use of the access
-type it will work in a functionally correct manner and allow porting of existing
-code. Note that another way of forcing a thin pointer representation is to use
-a component size clause for the element size in an array, or a record
-representation clause for an access field in a record.
+Some attributes are project-specific, and can only appear immediately within
+a project declaration. Others are package-specific, and can only appear within
+the proper package.
+
+The expression in an attribute definition must be a string or a string_list.
+The string literal appearing in the attribute_designator of an associative
+array attribute is case-insensitive.
+
+@node Project Attributes
+@section Project Attributes
+
+@noindent
+The following attributes apply to a project. All of them are simple
+attributes.
+
+@table @code
+@item Object_Dir
+Expression must be a path name. The attribute defines the
+directory in which the object files created by the build are to be placed. If
+not specified, object files are placed in the project directory.
+
+@item Exec_Dir
+Expression must be a path name. The attribute defines the
+directory in which the executables created by the build are to be placed.
+If not specified, executables are placed in the object directory.
+
+@item Source_Dirs
+Expression must be a list of path names. The attribute
+defines the directories in which the source files for the project are to be
+found. If not specified, source files are found in the project directory.
+If a string in the list ends with "/**", then the directory that precedes
+"/**" and all of its subdirectories (recursively) are included in the list
+of source directories.
+
+@item Excluded_Source_Dirs
+Expression must be a list of strings. Each entry designates a directory that
+is not to be included in the list of source directories of the project.
+This is normally used when there are strings ending with "/**" in the value
+of attribute Source_Dirs.
+
+@item Source_Files
+Expression must be a list of file names. The attribute
+defines the individual files, in the project directory, which are to be used
+as sources for the project. File names are path_names that contain no directory
+information. If the project has no sources the attribute must be declared
+explicitly with an empty list.
+
+@item Excluded_Source_Files (Locally_Removed_Files)
+Expression must be a list of strings that are legal file names.
+Each file name must designate a source that would normally be a source file
+in the source directories of the project or, if the project file is an
+extending project file, inherited by the current project file. It cannot
+designate an immediate source that is not inherited. Each of the source files
+in the list are not considered to be sources of the project file: they are not
+inherited. Attribute Locally_Removed_Files is obsolescent, attribute
+Excluded_Source_Files is preferred.
+
+@item Source_List_File
+Expression must a single path name. The attribute
+defines a text file that contains a list of source file names to be used
+as sources for the project
+
+@item Library_Dir
+Expression must be a path name. The attribute defines the
+directory in which a library is to be built. The directory must exist, must
+be distinct from the project's object directory, and must be writable.
+
+@item Library_Name
+Expression must be a string that is a legal file name,
+without extension. The attribute defines a string that is used to generate
+the name of the library to be built by the project.
+
+@item Library_Kind
+Argument must be a string value that must be one of the
+following @code{"static"}, @code{"dynamic"} or @code{"relocatable"}. This
+string is case-insensitive. If this attribute is not specified, the library is
+a static library. Otherwise, the library may be dynamic or relocatable. This
+distinction is operating-system dependent.
+
+@item Library_Version
+Expression must be a string value whose interpretation
+is platform dependent. On UNIX, it is used only for dynamic/relocatable
+libraries as the internal name of the library (the @code{"soname"}). If the
+library file name (built from the @code{Library_Name}) is different from the
+@code{Library_Version}, then the library file will be a symbolic link to the
+actual file whose name will be @code{Library_Version}.
+
+@item Library_Interface
+Expression must be a string list. Each element of the string list
+must designate a unit of the project.
+If this attribute is present in a Library Project File, then the project
+file is a Stand-alone Library_Project_File.
+
+@item Library_Auto_Init
+Expression must be a single string "true" or "false", case-insensitive.
+If this attribute is present in a Stand-alone Library Project File,
+it indicates if initialization is automatic when the dynamic library
+is loaded.
+
+@item Library_Options
+Expression must be a string list. Indicates additional switches that
+are to be used when building a shared library.
+
+@item Library_GCC
+Expression must be a single string. Designates an alternative to "gcc"
+for building shared libraries.
+
+@item Library_Src_Dir
+Expression must be a path name. The attribute defines the
+directory in which the sources of the interfaces of a Stand-alone Library will
+be copied. The directory must exist, must be distinct from the project's
+object directory and source directories of all projects in the project tree,
+and must be writable.
+
+@item Library_Src_Dir
+Expression must be a path name. The attribute defines the
+directory in which the ALI files of a Library will
+be copied. The directory must exist, must be distinct from the project's
+object directory and source directories of all projects in the project tree,
+and must be writable.
+
+@item Library_Symbol_File
+Expression must be a single string. Its value is the single file name of a
+symbol file to be created when building a stand-alone library when the
+symbol policy is either "compliant", "controlled" or "restricted",
+on platforms that support symbol control, such as VMS. When symbol policy
+is "direct", then a file with this name must exist in the object directory.
+
+@item Library_Reference_Symbol_File
+Expression must be a single string. Its value is the path name of a
+reference symbol file that is read when the symbol policy is either
+"compliant" or "controlled", on platforms that support symbol control,
+such as VMS, when building a stand-alone library. The path may be an absolute
+path or a path relative to the project directory.
+
+@item Library_Symbol_Policy
+Expression must be a single string. Its case-insensitive value can only be
+"autonomous", "default", "compliant", "controlled", "restricted" or "direct".
+
+This attribute is not taken into account on all platforms. It controls the
+policy for exported symbols and, on some platforms (like VMS) that have the
+notions of major and minor IDs built in the library files, it controls
+the setting of these IDs.
+
+"autonomous" or "default": exported symbols are not controlled.
+
+"compliant": if attribute Library_Reference_Symbol_File is not defined, then
+it is equivalent to policy "autonomous". If there are exported symbols in
+the reference symbol file that are not in the object files of the interfaces,
+the major ID of the library is increased. If there are symbols in the
+object files of the interfaces that are not in the reference symbol file,
+these symbols are put at the end of the list in the newly created symbol file
+and the minor ID is increased.
+
+"controlled": the attribute Library_Reference_Symbol_File must be defined.
+The library will fail to build if the exported symbols in the object files of
+the interfaces do not match exactly the symbol in the symbol file.
+
+"restricted": The attribute Library_Symbol_File must be defined. The library
+will fail to build if there are symbols in the symbol file that are not in
+the exported symbols of the object files of the interfaces. Additional symbols
+in the object files are not added to the symbol file.
+
+"direct": The attribute Library_Symbol_File must be defined and must designate
+an existing file in the object directory. This symbol file is passed directly
+to the underlying linker without any symbol processing.
+
+@item Main
+Expression must be a list of strings that are legal file names.
+These file names designate existing compilation units in the source directory
+that are legal main subprograms.
+
+When a project file is elaborated, as part of the execution of a gnatmake
+command, one or several executables are built and placed in the Exec_Dir.
+If the gnatmake command does not include explicit file names, the executables
+that are built correspond to the files specified by this attribute.
+
+@item Externally_Built
+Expression must be a single string. Its value must be either "true" of "false",
+case-insensitive. The default is "false". When the value of this attribute is
+"true", no attempt is made to compile the sources or to build the library,
+when the project is a library project.
+
+@item Main_Language
+This is a simple attribute. Its value is a string that specifies the
+language of the main program.
+
+@item Languages
+Expression must be a string list. Each string designates
+a programming language that is known to GNAT. The strings are case-insensitive.
+
@end table
-@node Compatibility with DEC Ada 83
-@section Compatibility with DEC Ada 83
+@node Attribute References
+@section Attribute References
@noindent
-The VMS version of GNAT fully implements all the pragmas and attributes
-provided by DEC Ada 83, as well as providing the standard DEC Ada 83
-libraries, including Starlet. In addition, data layouts and parameter
-passing conventions are highly compatible. This means that porting
-existing DEC Ada 83 code to GNAT in VMS systems should be easier than
-most other porting efforts. The following are some of the most
-significant differences between GNAT and DEC Ada 83.
+Attribute references are used to retrieve the value of previously defined
+attribute for a package or project.
+Syntax:
+@smallexample
+attribute_reference ::=
+ attribute_prefix ' <simple_attribute_>simple_name [ ( string_literal ) ]
-@table @asis
-@item Default floating-point representation
-In GNAT, the default floating-point format is IEEE, whereas in DEC Ada 83,
-it is VMS format. GNAT does implement the necessary pragmas
-(Long_Float, Float_Representation) for changing this default.
+attribute_prefix ::=
+ @b{project} |
+ <project_simple_name | package_identifier |
+ <project_>simple_name . package_identifier
+@end smallexample
-@item System
-The package System in GNAT exactly corresponds to the definition in the
-Ada 95 reference manual, which means that it excludes many of the
-DEC Ada 83 extensions. However, a separate package Aux_DEC is provided
-that contains the additional definitions, and a special pragma,
-Extend_System allows this package to be treated transparently as an
-extension of package System.
-
-@item To_Address
-The definitions provided by Aux_DEC are exactly compatible with those
-in the DEC Ada 83 version of System, with one exception. DEC Ada provides
-the following declarations:
+@noindent
+If an attribute has not been specified for a given package or project, its
+value is the null string or the empty list.
+@node External Values
+@section External Values
+
+@noindent
+An external value is an expression whose value is obtained from the command
+that invoked the processing of the current project file (typically a
+gnatmake command).
+
+Syntax:
@smallexample
-TO_ADDRESS(INTEGER)
-TO_ADDRESS(UNSIGNED_LONGWORD)
-TO_ADDRESS(universal_integer)
+external_value ::=
+ @b{external} ( string_literal [, string_literal] )
@end smallexample
@noindent
-The version of TO_ADDRESS taking a universal integer argument is in fact
-an extension to Ada 83 not strictly compatible with the reference manual.
-In GNAT, we are constrained to be exactly compatible with the standard,
-and this means we cannot provide this capability. In DEC Ada 83, the
-point of this definition is to deal with a call like:
+The first string_literal is the string to be used on the command line or
+in the environment to specify the external value. The second string_literal,
+if present, is the default to use if there is no specification for this
+external value either on the command line or in the environment.
+
+@node Case Construction
+@section Case Construction
+@noindent
+A case construction supports attribute and variable declarations that depend
+on the value of a previously declared variable.
+
+Syntax:
@smallexample
- TO_ADDRESS (16#12777#);
+case_construction ::=
+ @b{case} <typed_variable_>name @b{is}
+ @{case_item@}
+ @b{end case} ;
+
+case_item ::=
+ @b{when} discrete_choice_list =>
+ @{case_construction |
+ attribute_declaration |
+ variable_declaration |
+ empty_declaration@}
+
+discrete_choice_list ::=
+ string_literal @{| string_literal@} |
+ @b{others}
@end smallexample
@noindent
-Normally, according to the Ada 83 standard, one would expect this to be
-ambiguous, since it matches both the INTEGER and UNSIGNED_LONGWORD forms
-of TO_ADDRESS@. However, in DEC Ada 83, there is no ambiguity, since the
-definition using universal_integer takes precedence.
+Inside a case construction, variable declarations must be for variables that
+have already been declared before the case construction.
+
+All choices in a choice list must be distinct. The choice lists of two
+distinct alternatives must be disjoint. Unlike Ada, the choice lists of all
+alternatives do not need to include all values of the type. An @code{others}
+choice must appear last in the list of alternatives.
-In GNAT, since the version with universal_integer cannot be supplied, it is
-not possible to be 100% compatible. Since there are many programs using
-numeric constants for the argument to TO_ADDRESS, the decision in GNAT was
-to change the name of the function in the UNSIGNED_LONGWORD case, so the
-declarations provided in the GNAT version of AUX_Dec are:
+@node Packages
+@section Packages
+
+@noindent
+A package provides a grouping of variable declarations and attribute
+declarations to be used when invoking various GNAT tools. The name of
+the package indicates the tool(s) to which it applies.
+Syntax:
@smallexample
-function To_Address (X : Integer) return Address;
-pragma Pure_Function (To_Address);
+package_declaration ::=
+ package_specification | package_renaming
-function To_Address_Long (X : Unsigned_Longword)
- return Address;
-pragma Pure_Function (To_Address_Long);
+package_specification ::=
+ @b{package} package_identifier @b{is}
+ @{simple_declarative_item@}
+ @b{end} package_identifier ;
+
+package_identifier ::=
+ @code{Naming} | @code{Builder} | @code{Compiler} | @code{Binder} |
+ @code{Linker} | @code{Finder} | @code{Cross_Reference} |
+ @code{gnatls} | @code{IDE} | @code{Pretty_Printer}
@end smallexample
+@subsection Package Naming
+
+@noindent
+The attributes of a @code{Naming} package specifies the naming conventions
+that apply to the source files in a project. When invoking other GNAT tools,
+they will use the sources in the source directories that satisfy these
+naming conventions.
+
+The following attributes apply to a @code{Naming} package:
+
+@table @code
+@item Casing
+This is a simple attribute whose value is a string. Legal values of this
+string are @code{"lowercase"}, @code{"uppercase"} or @code{"mixedcase"}.
+These strings are themselves case insensitive.
+
+@noindent
+If @code{Casing} is not specified, then the default is @code{"lowercase"}.
+
+@item Dot_Replacement
+This is a simple attribute whose string value satisfies the following
+requirements:
+
+@itemize @bullet
+@item It must not be empty
+@item It cannot start or end with an alphanumeric character
+@item It cannot be a single underscore
+@item It cannot start with an underscore followed by an alphanumeric
+@item It cannot contain a dot @code{'.'} if longer than one character
+@end itemize
+
+@noindent
+If @code{Dot_Replacement} is not specified, then the default is @code{"-"}.
+
+@item Spec_Suffix
+This is an associative array attribute, defined on language names,
+whose image is a string that must satisfy the following
+conditions:
+
+@itemize @bullet
+@item It must not be empty
+@item It cannot start with an alphanumeric character
+@item It cannot start with an underscore followed by an alphanumeric character
+@end itemize
+
+@noindent
+For Ada, the attribute denotes the suffix used in file names that contain
+library unit declarations, that is to say units that are package and
+subprogram declarations. If @code{Spec_Suffix ("Ada")} is not
+specified, then the default is @code{".ads"}.
+
+For C and C++, the attribute denotes the suffix used in file names that
+contain prototypes.
+
+@item Body_Suffix
+This is an associative array attribute defined on language names,
+whose image is a string that must satisfy the following
+conditions:
+
+@itemize @bullet
+@item It must not be empty
+@item It cannot start with an alphanumeric character
+@item It cannot start with an underscore followed by an alphanumeric character
+@item It cannot be a suffix of @code{Spec_Suffix}
+@end itemize
+
+@noindent
+For Ada, the attribute denotes the suffix used in file names that contain
+library bodies, that is to say units that are package and subprogram bodies.
+If @code{Body_Suffix ("Ada")} is not specified, then the default is
+@code{".adb"}.
+
+For C and C++, the attribute denotes the suffix used in file names that contain
+source code.
+
+@item Separate_Suffix
+This is a simple attribute whose value satisfies the same conditions as
+@code{Body_Suffix}.
+
+This attribute is specific to Ada. It denotes the suffix used in file names
+that contain separate bodies. If it is not specified, then it defaults to same
+value as @code{Body_Suffix ("Ada")}.
+
+@item Spec
+This is an associative array attribute, specific to Ada, defined over
+compilation unit names. The image is a string that is the name of the file
+that contains that library unit. The file name is case sensitive if the
+conventions of the host operating system require it.
+
+@item Body
+This is an associative array attribute, specific to Ada, defined over
+compilation unit names. The image is a string that is the name of the file
+that contains the library unit body for the named unit. The file name is case
+sensitive if the conventions of the host operating system require it.
+
+@item Specification_Exceptions
+This is an associative array attribute defined on language names,
+whose value is a list of strings.
+
+This attribute is not significant for Ada.
+
+For C and C++, each string in the list denotes the name of a file that
+contains prototypes, but whose suffix is not necessarily the
+@code{Spec_Suffix} for the language.
+
+@item Implementation_Exceptions
+This is an associative array attribute defined on language names,
+whose value is a list of strings.
+
+This attribute is not significant for Ada.
+
+For C and C++, each string in the list denotes the name of a file that
+contains source code, but whose suffix is not necessarily the
+@code{Body_Suffix} for the language.
+@end table
+
+The following attributes of package @code{Naming} are obsolescent. They are
+kept as synonyms of other attributes for compatibility with previous versions
+of the Project Manager.
+
+@table @code
+@item Specification_Suffix
+This is a synonym of @code{Spec_Suffix}.
+
+@item Implementation_Suffix
+This is a synonym of @code{Body_Suffix}.
+
+@item Specification
+This is a synonym of @code{Spec}.
+
+@item Implementation
+This is a synonym of @code{Body}.
+@end table
+
+@subsection package Compiler
+
+@noindent
+The attributes of the @code{Compiler} package specify the compilation options
+to be used by the underlying compiler.
+
+@table @code
+@item Default_Switches
+This is an associative array attribute. Its
+domain is a set of language names. Its range is a string list that
+specifies the compilation options to be used when compiling a component
+written in that language, for which no file-specific switches have been
+specified.
+
+@item Switches
+This is an associative array attribute. Its domain is
+a set of file names. Its range is a string list that specifies the
+compilation options to be used when compiling the named file. If a file
+is not specified in the Switches attribute, it is compiled with the
+options specified by Default_Switches of its language, if defined.
+
+@item Local_Configuration_Pragmas.
+This is a simple attribute, whose
+value is a path name that designates a file containing configuration pragmas
+to be used for all invocations of the compiler for immediate sources of the
+project.
+@end table
+
+@subsection package Builder
+
+@noindent
+The attributes of package @code{Builder} specify the compilation, binding, and
+linking options to be used when building an executable for a project. The
+following attributes apply to package @code{Builder}:
+
+@table @code
+@item Default_Switches
+This is an associative array attribute. Its
+domain is a set of language names. Its range is a string list that
+specifies options to be used when building a main
+written in that language, for which no file-specific switches have been
+specified.
+
+@item Switches
+This is an associative array attribute. Its domain is
+a set of file names. Its range is a string list that specifies
+options to be used when building the named main file. If a main file
+is not specified in the Switches attribute, it is built with the
+options specified by Default_Switches of its language, if defined.
+
+@item Global_Configuration_Pragmas
+This is a simple attribute, whose
+value is a path name that designates a file that contains configuration pragmas
+to be used in every build of an executable. If both local and global
+configuration pragmas are specified, a compilation makes use of both sets.
+
+
+@item Executable
+This is an associative array attribute. Its domain is
+a set of main source file names. Its range is a simple string that specifies
+the executable file name to be used when linking the specified main source.
+If a main source is not specified in the Executable attribute, the executable
+file name is deducted from the main source file name.
+This attribute has no effect if its value is the empty string.
+
+@item Executable_Suffix
+This is a simple attribute whose value is the suffix to be added to
+the executables that don't have an attribute Executable specified.
+@end table
+
+@subsection package Gnatls
+
+@noindent
+The attributes of package @code{Gnatls} specify the tool options to be used
+when invoking the library browser @command{gnatls}.
+The following attributes apply to package @code{Gnatls}:
+
+@table @code
+@item Switches
+This is a single attribute with a string list value. Each non empty string
+in the list is an option when invoking @code{gnatls}.
+@end table
+
+@subsection package Binder
+
+@noindent
+The attributes of package @code{Binder} specify the options to be used
+when invoking the binder in the construction of an executable.
+The following attributes apply to package @code{Binder}:
+
+@table @code
+@item Default_Switches
+This is an associative array attribute. Its
+domain is a set of language names. Its range is a string list that
+specifies options to be used when binding a main
+written in that language, for which no file-specific switches have been
+specified.
+
+@item Switches
+This is an associative array attribute. Its domain is
+a set of file names. Its range is a string list that specifies
+options to be used when binding the named main file. If a main file
+is not specified in the Switches attribute, it is bound with the
+options specified by Default_Switches of its language, if defined.
+@end table
+
+@subsection package Linker
+
+@noindent
+The attributes of package @code{Linker} specify the options to be used when
+invoking the linker in the construction of an executable.
+The following attributes apply to package @code{Linker}:
+
+@table @code
+@item Default_Switches
+This is an associative array attribute. Its
+domain is a set of language names. Its range is a string list that
+specifies options to be used when linking a main
+written in that language, for which no file-specific switches have been
+specified.
+
+@item Switches
+This is an associative array attribute. Its domain is
+a set of file names. Its range is a string list that specifies
+options to be used when linking the named main file. If a main file
+is not specified in the Switches attribute, it is linked with the
+options specified by Default_Switches of its language, if defined.
+
+@item Linker_Options
+This is a string list attribute. Its value specifies additional options that
+be given to the linker when linking an executable. This attribute is not
+used in the main project, only in projects imported directly or indirectly.
+
+@end table
+
+@subsection package Cross_Reference
+
@noindent
-This means that programs using TO_ADDRESS for UNSIGNED_LONGWORD must
-change the name to TO_ADDRESS_LONG@.
+The attributes of package @code{Cross_Reference} specify the tool options
+to be used
+when invoking the library tool @command{gnatxref}.
+The following attributes apply to package @code{Cross_Reference}:
+
+@table @code
+@item Default_Switches
+This is an associative array attribute. Its
+domain is a set of language names. Its range is a string list that
+specifies options to be used when calling @command{gnatxref} on a source
+written in that language, for which no file-specific switches have been
+specified.
+
+@item Switches
+This is an associative array attribute. Its domain is
+a set of file names. Its range is a string list that specifies
+options to be used when calling @command{gnatxref} on the named main source.
+If a source is not specified in the Switches attribute, @command{gnatxref} will
+be called with the options specified by Default_Switches of its language,
+if defined.
+@end table
+
+@subsection package Finder
+
+@noindent
+The attributes of package @code{Finder} specify the tool options to be used
+when invoking the search tool @command{gnatfind}.
+The following attributes apply to package @code{Finder}:
+
+@table @code
+@item Default_Switches
+This is an associative array attribute. Its
+domain is a set of language names. Its range is a string list that
+specifies options to be used when calling @command{gnatfind} on a source
+written in that language, for which no file-specific switches have been
+specified.
+
+@item Switches
+This is an associative array attribute. Its domain is
+a set of file names. Its range is a string list that specifies
+options to be used when calling @command{gnatfind} on the named main source.
+If a source is not specified in the Switches attribute, @command{gnatfind} will
+be called with the options specified by Default_Switches of its language,
+if defined.
+@end table
+
+@subsection package Pretty_Printer
+
+@noindent
+The attributes of package @code{Pretty_Printer}
+specify the tool options to be used
+when invoking the formatting tool @command{gnatpp}.
+The following attributes apply to package @code{Pretty_Printer}:
+
+@table @code
+@item Default_switches
+This is an associative array attribute. Its
+domain is a set of language names. Its range is a string list that
+specifies options to be used when calling @command{gnatpp} on a source
+written in that language, for which no file-specific switches have been
+specified.
+
+@item Switches
+This is an associative array attribute. Its domain is
+a set of file names. Its range is a string list that specifies
+options to be used when calling @command{gnatpp} on the named main source.
+If a source is not specified in the Switches attribute, @command{gnatpp} will
+be called with the options specified by Default_Switches of its language,
+if defined.
+@end table
+
+@subsection package gnatstub
+
+@noindent
+The attributes of package @code{gnatstub}
+specify the tool options to be used
+when invoking the tool @command{gnatstub}.
+The following attributes apply to package @code{gnatstub}:
+
+@table @code
+@item Default_switches
+This is an associative array attribute. Its
+domain is a set of language names. Its range is a string list that
+specifies options to be used when calling @command{gnatstub} on a source
+written in that language, for which no file-specific switches have been
+specified.
+
+@item Switches
+This is an associative array attribute. Its domain is
+a set of file names. Its range is a string list that specifies
+options to be used when calling @command{gnatstub} on the named main source.
+If a source is not specified in the Switches attribute, @command{gnatpp} will
+be called with the options specified by Default_Switches of its language,
+if defined.
+@end table
+
+@subsection package Eliminate
+
+@noindent
+The attributes of package @code{Eliminate}
+specify the tool options to be used
+when invoking the tool @command{gnatelim}.
+The following attributes apply to package @code{Eliminate}:
+
+@table @code
+@item Default_switches
+This is an associative array attribute. Its
+domain is a set of language names. Its range is a string list that
+specifies options to be used when calling @command{gnatelim} on a source
+written in that language, for which no file-specific switches have been
+specified.
+
+@item Switches
+This is an associative array attribute. Its domain is
+a set of file names. Its range is a string list that specifies
+options to be used when calling @command{gnatelim} on the named main source.
+If a source is not specified in the Switches attribute, @command{gnatelim} will
+be called with the options specified by Default_Switches of its language,
+if defined.
+@end table
+
+@subsection package Metrics
+
+@noindent
+The attributes of package @code{Metrics}
+specify the tool options to be used
+when invoking the tool @command{gnatmetric}.
+The following attributes apply to package @code{Metrics}:
+
+@table @code
+@item Default_switches
+This is an associative array attribute. Its
+domain is a set of language names. Its range is a string list that
+specifies options to be used when calling @command{gnatmetric} on a source
+written in that language, for which no file-specific switches have been
+specified.
+
+@item Switches
+This is an associative array attribute. Its domain is
+a set of file names. Its range is a string list that specifies
+options to be used when calling @command{gnatmetric} on the named main source.
+If a source is not specified in the Switches attribute, @command{gnatmetric}
+will be called with the options specified by Default_Switches of its language,
+if defined.
+@end table
+
+@subsection package IDE
+
+@noindent
+The attributes of package @code{IDE} specify the options to be used when using
+an Integrated Development Environment such as @command{GPS}.
+
+@table @code
+@item Remote_Host
+This is a simple attribute. Its value is a string that designates the remote
+host in a cross-compilation environment, to be used for remote compilation and
+debugging. This field should not be specified when running on the local
+machine.
+
+@item Program_Host
+This is a simple attribute. Its value is a string that specifies the
+name of IP address of the embedded target in a cross-compilation environment,
+on which the program should execute.
+
+@item Communication_Protocol
+This is a simple string attribute. Its value is the name of the protocol
+to use to communicate with the target in a cross-compilation environment,
+e.g. @code{"wtx"} or @code{"vxworks"}.
+
+@item Compiler_Command
+This is an associative array attribute, whose domain is a language name. Its
+value is string that denotes the command to be used to invoke the compiler.
+The value of @code{Compiler_Command ("Ada")} is expected to be compatible with
+gnatmake, in particular in the handling of switches.
+
+@item Debugger_Command
+This is simple attribute, Its value is a string that specifies the name of
+the debugger to be used, such as gdb, powerpc-wrs-vxworks-gdb or gdb-4.
+
+@item Default_Switches
+This is an associative array attribute. Its indexes are the name of the
+external tools that the GNAT Programming System (GPS) is supporting. Its
+value is a list of switches to use when invoking that tool.
+
+@item Gnatlist
+This is a simple attribute. Its value is a string that specifies the name
+of the @command{gnatls} utility to be used to retrieve information about the
+predefined path; e.g., @code{"gnatls"}, @code{"powerpc-wrs-vxworks-gnatls"}.
+
+@item VCS_Kind
+This is a simple attribute. Its value is a string used to specify the
+Version Control System (VCS) to be used for this project, e.g CVS, RCS
+ClearCase or Perforce.
+
+@item VCS_File_Check
+This is a simple attribute. Its value is a string that specifies the
+command used by the VCS to check the validity of a file, either
+when the user explicitly asks for a check, or as a sanity check before
+doing the check-in.
+
+@item VCS_Log_Check
+This is a simple attribute. Its value is a string that specifies
+the command used by the VCS to check the validity of a log file.
+
+@item VCS_Repository_Root
+The VCS repository root path. This is used to create tags or branches
+of the repository. For subversion the value should be the @code{URL}
+as specified to check-out the working copy of the repository.
+
+@item VCS_Patch_Root
+The local root directory to use for building patch file. All patch chunks
+will be relative to this path. The root project directory is used if
+this value is not defined.
-@item Task_Id values
-The Task_Id values assigned will be different in the two systems, and GNAT
-does not provide a specified value for the Task_Id of the environment task,
-which in GNAT is treated like any other declared task.
@end table
-For full details on these and other less significant compatibility issues,
-see appendix E of the Digital publication entitled @cite{DEC Ada, Technical
-Overview and Comparison on DIGITAL Platforms}.
+@node Package Renamings
+@section Package Renamings
+
+@noindent
+A package can be defined by a renaming declaration. The new package renames
+a package declared in a different project file, and has the same attributes
+as the package it renames.
+Syntax:
+@smallexample
+package_renaming ::==
+ @b{package} package_identifier @b{renames}
+ <project_>simple_name.package_identifier ;
+@end smallexample
+
+@noindent
+The package_identifier of the renamed package must be the same as the
+package_identifier. The project whose name is the prefix of the renamed
+package must contain a package declaration with this name. This project
+must appear in the context_clause of the enclosing project declaration,
+or be the parent project of the enclosing child project.
+
+@node Projects
+@section Projects
+
+@noindent
+A project file specifies a set of rules for constructing a software system.
+A project file can be self-contained, or depend on other project files.
+Dependencies are expressed through a context clause that names other projects.
+
+Syntax:
+
+@smallexample
+project ::=
+ context_clause project_declaration
+
+project_declaration ::=
+ simple_project_declaration | project_extension
+
+simple_project_declaration ::=
+ @b{project} <project_>simple_name @b{is}
+ @{declarative_item@}
+ @b{end} <project_>simple_name;
+
+context_clause ::=
+ @{with_clause@}
+
+with_clause ::=
+ [@b{limited}] @b{with} path_name @{ , path_name @} ;
+
+path_name ::=
+ string_literal
+@end smallexample
+
+@noindent
+A path name denotes a project file. A path name can be absolute or relative.
+An absolute path name includes a sequence of directories, in the syntax of
+the host operating system, that identifies uniquely the project file in the
+file system. A relative path name identifies the project file, relative
+to the directory that contains the current project, or relative to a
+directory listed in the environment variable ADA_PROJECT_PATH.
+Path names are case sensitive if file names in the host operating system
+are case sensitive.
+
+The syntax of the environment variable ADA_PROJECT_PATH is a list of
+directory names separated by colons (semicolons on Windows).
+
+A given project name can appear only once in a context_clause.
+
+It is illegal for a project imported by a context clause to refer, directly
+or indirectly, to the project in which this context clause appears (the
+dependency graph cannot contain cycles), except when one of the with_clause
+in the cycle is a @code{limited with}.
+
+@node Project Extensions
+@section Project Extensions
+
+@noindent
+A project extension introduces a new project, which inherits the declarations
+of another project.
+Syntax:
+@smallexample
+
+project_extension ::=
+ @b{project} <project_>simple_name @b{extends} path_name @b{is}
+ @{declarative_item@}
+ @b{end} <project_>simple_name;
+@end smallexample
+
+@noindent
+The project extension declares a child project. The child project inherits
+all the declarations and all the files of the parent project, These inherited
+declaration can be overridden in the child project, by means of suitable
+declarations.
+
+@node Project File Elaboration
+@section Project File Elaboration
+
+@noindent
+A project file is processed as part of the invocation of a gnat tool that
+uses the project option. Elaboration of the process file consists in the
+sequential elaboration of all its declarations. The computed values of
+attributes and variables in the project are then used to establish the
+environment in which the gnat tool will execute.
+
+@node Obsolescent Features
+@chapter Obsolescent Features
+
+@noindent
+This chapter describes features that are provided by GNAT, but are
+considered obsolescent since there are preferred ways of achieving
+the same effect. These features are provided solely for historical
+compatibility purposes.
+
+@menu
+* pragma No_Run_Time::
+* pragma Ravenscar::
+* pragma Restricted_Run_Time::
+@end menu
+
+@node pragma No_Run_Time
+@section pragma No_Run_Time
+
+The pragma @code{No_Run_Time} is used to achieve an affect similar
+to the use of the "Zero Foot Print" configurable run time, but without
+requiring a specially configured run time. The result of using this
+pragma, which must be used for all units in a partition, is to restrict
+the use of any language features requiring run-time support code. The
+preferred usage is to use an appropriately configured run-time that
+includes just those features that are to be made accessible.
+
+@node pragma Ravenscar
+@section pragma Ravenscar
+
+The pragma @code{Ravenscar} has exactly the same effect as pragma
+@code{Profile (Ravenscar)}. The latter usage is preferred since it
+is part of the new Ada 2005 standard.
+
+@node pragma Restricted_Run_Time
+@section pragma Restricted_Run_Time
-For GNAT running on other than VMS systems, all the DEC Ada 83 pragmas and
-attributes are recognized, although only a subset of them can sensibly
-be implemented. The description of pragmas in this reference manual
-indicates whether or not they are applicable to non-VMS systems.
+The pragma @code{Restricted_Run_Time} has exactly the same effect as
+pragma @code{Profile (Restricted)}. The latter usage is
+preferred since the Ada 2005 pragma @code{Profile} is intended for
+this kind of implementation dependent addition.
-@include gfdl.texi
+@include fdl.texi
@c GNU Free Documentation License
@node Index,,GNU Free Documentation License, Top
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