\input texinfo @c -*-texinfo-*-
-@input texiplus
@c %**start of header
@c o
@c G N A T _ RM o
@c o
+@c Copyright (C) 1995-2007, Free Software Foundation o
@c o
-@c Copyright (C) 1992-2001 Ada Core Technologies, Inc. o
-@c o
-@c GNAT is free software; you can redistribute it and/or modify it under o
-@c terms of the GNU General Public License as published by the Free Soft- o
-@c ware Foundation; either version 2, or (at your option) any later ver- o
-@c sion. GNAT is distributed in the hope that it will be useful, but WITH- o
-@c OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY o
-@c or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License o
-@c for more details. You should have received a copy of the GNU General o
-@c Public License distributed with GNAT; see file COPYING. If not, write o
-@c to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, o
-@c MA 02111-1307, USA. o
@c o
@c GNAT is maintained by Ada Core Technologies Inc (http://www.gnat.com). o
@c o
@c oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo
@setfilename gnat_rm.info
-@settitle GNAT Reference Manual
-@setchapternewpage odd
-@syncodeindex fn cp
-@titlepage
+@set EDITION GNAT
+@set DEFAULTLANGUAGEVERSION Ada 2005
+@set NONDEFAULTLANGUAGEVERSION Ada 95
+@settitle GNAT Reference Manual
-@title GNAT Reference Manual
-@subtitle GNAT, The GNU Ada 95 Compiler
-@subtitle Version 3.15w
-@subtitle Date: $Date: 2001/12/18 00:03:37 $
-@author Ada Core Technologies, Inc.
+@setchapternewpage odd
+@syncodeindex fn cp
-@page
-@vskip 0pt plus 1filll
+@include gcc-common.texi
+@dircategory GNU Ada tools
+@direntry
+* GNAT Reference Manual: (gnat_rm). Reference Manual for GNU Ada tools.
+@end direntry
-Copyright @copyright{} 1995-2001, Ada Core Technologies
+@copying
+Copyright @copyright{} 1995-2007, 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
+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''.
-
-Silicon Graphics and IRIS are registered trademarks
-and IRIX is a trademark of Silicon Graphics, Inc.
+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
-IBM PC is a trademark of International
-Business Machines Corporation.
-
-UNIX is a registered trademark of AT&T
-Bell Laboratories.
-DIGITAL
-
-VADS is a registered trademark of Rational Software Inc.
+@titlepage
+@title GNAT Reference Manual
+@subtitle GNAT, The GNU Ada Compiler
+@versionsubtitle
+@author AdaCore
+@page
+@vskip 0pt plus 1filll
-The following are trademarks of Digital Equipment Corporation:
-DEC, DEC Ada, DECthreads, Digital, OpenVMS, and VAX@.
+@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
-
-Version 3.14a
-
-Date: $Date: 2001/12/18 00:03:37 $
-
-Ada Core Technologies, Inc.
-
-
-Copyright @copyright{} 1995-2001, Ada Core Technologies
-
-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".
-
-
-Silicon Graphics and IRIS are registered trademarks
-and IRIX is a trademark of Silicon Graphics, Inc.
-
-IBM PC is a trademark of International
-Business Machines Corporation.
-
-UNIX is a registered trademark of AT&T
-Bell Laboratories.
-DIGITAL
-
-VADS is a registered trademark of Rational Software Inc.
+@noindent
+GNAT, The GNU Ada Compiler@*
+GCC version @value{version-GCC}@*
-The following are trademarks of Digital Equipment Corporation:
-DEC, DEC Ada, DECthreads, Digital, OpenVMS, and VAX@.
+@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 (g-io.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.Os2lib.Threads (i-os2thr.ads)::
* Interfaces.Packed_Decimal (i-pacdec.ads)::
* Interfaces.VxWorks (i-vxwork.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 be 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
and @code{classes}.
@item
-@samp{Option flags}
+@code{Option flags}
@item
-@file{File Names}, @file{button names}, and @file{field names}.
+@file{File Names}, @samp{button names}, and @samp{field names}.
@item
-@var{Variables}.
+@code{Variables}.
@item
@emph{Emphasis}.
@noindent
Commands that are entered by the user are preceded in this manual by the
-characters "$ " (dollar sign followed by space). If your system uses this
+characters @samp{$ } (dollar sign followed by space). If your system uses this
sequence as a prompt, then the commands will appear exactly as you see them
-in the manual. If your system uses some other prompt, then the command will
-appear with the $ replaced by whatever prompt character you are using.
+in the manual. If your system uses some other prompt, then the command will
+appear with the @samp{$} replaced by whatever prompt character you are using.
@node Related Information
@unnumberedsec Related Information
-See the following documents for further information on GNAT
+@noindent
+See the following documents for further information on GNAT:
@itemize @bullet
@item
@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
-information to the compiler. These language defined pragmas are
-implemented in GNAT and work as described in the Ada 95 Reference
+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 Reference
Manual.
-In addition, Ada 95 allows implementations to define additional pragmas
-whose meaning is defined by the implementation. GNAT provides a number
+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
+and enhance the functionality of the compiler. This section of the GNAT
Reference Manual describes these additional pragmas.
Note that any program using these pragmas may not be portable to other
compilers (although GNAT implements this set of pragmas on all
-platforms). Therefore if portability to other compilers is an important
+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
@noindent
This pragma must appear at the start of the statement sequence of a
-handled sequence of statements (right after the @code{begin}). It has
+handled sequence of statements (right after the @code{begin}). It has
the effect of deferring aborts for the sequence of statements (but not
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
@noindent
A configuration pragma that establishes Ada 83 mode for the unit to
which it applies, regardless of the mode set by the command line
-switches. In Ada 83 mode, GNAT attempts to be as compatible with
+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 (<>) notation. In addition, some but not all of the additional
+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 mode is intended for two purposes. Firstly, it allows existing
+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
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
+contexts. This pragma is useful when writing a reusable component that
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
@end smallexample
@noindent
-This pragma is used to annotate programs. @var{identifier} identifies
-the type of annotation. GNAT verifies this is an identifier, but does
-not otherwise analyze it. The @var{arg} argument
+This pragma is used to annotate programs. @var{identifier} identifies
+the type of annotation. GNAT verifies this is an identifier, but does
+not otherwise analyze it. The @var{arg} argument
can be either a string literal or an
-expression. String literals are assumed to be of type
-@code{Standard.String}. Names of entities are simply analyzed as entity
-names. All other expressions are analyzed as expressions, and must be
+expression. String literals are assumed to be of type
+@code{Standard.String}. Names of entities are simply analyzed as entity
+names. All other expressions are analyzed as expressions, and must be
unambiguous.
The analyzed pragma is retained in the tree, but not otherwise processed
-by any part of the GNAT compiler. This pragma is intended for use by
+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
The effect of this pragma depends on whether the corresponding command
-line switch is set to activate assertions. The pragma expands into code
+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
@noindent
The string argument, if given, is the message that will be associated
-with the exception occurrence if the exception is raised. If no second
+with the exception occurrence if the exception is raised. If no second
argument is given, the default message is @samp{@var{file}:@var{nnn}},
where @var{file} is the name of the source file containing the assert,
-and @var{nnn} is the line number of the assert. A pragma is not a
+and @var{nnn} is the line number of the assert. A pragma is not a
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");
null;
@end smallexample
@noindent
-Note that, as with the if statement to which it is equivalent, the
-type of the expression is either Standard.Boolean, or any type derived
+Note that, as with the @code{if} statement to which it is equivalent, the
+type of the expression is either @code{Standard.Boolean}, or any type derived
from this standard type.
If assertions are disabled (switch @code{-gnata} not used), then there
is no effect (and in particular, any side effects from the expression
-are suppressed). More precisely it is not quite true that the pragma
+are suppressed). More precisely it is not quite true that the pragma
has no effect, since the expression is analyzed, and may cause types
to be frozen if they are mentioned here for the first time.
If assertions are enabled, then the given expression is tested, and if
-it is @code{False} then System.Assertions.Raise_Assert_Failure is called
-which results in the raising of Assert_Failure with the given message.
+it is @code{False} then @code{System.Assertions.Raise_Assert_Failure} is called
+which results in the raising of @code{Assert_Failure} with the given message.
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
-avoid side effects in the expression arguments of this pragma. However,
+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
+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
+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
+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
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
@noindent
Normally the default mechanism for passing C convention records to C
convention subprograms is to pass them by reference, as suggested by RM
-B.3(69). Use the configuration pragma @code{C_Pass_By_Copy} to change
+B.3(69). Use the configuration pragma @code{C_Pass_By_Copy} to change
this default, by requiring that record formal parameters be passed by
copy if all of the following conditions are met:
@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
@noindent
-This is almost identical in effect to pragma Ident. It allows the
+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 Comment, unlike 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).
-
+executable file if the operating system permits such usage. The
+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
+of fields. The @var{size} argument
is syntax checked in GNAT, but otherwise ignored.
-@code{Common_Object} is not supported on all platforms. If no
+@code{Common_Object} is not supported on all platforms. If no
support is available, then the code generator will issue a message
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
The @var{Entity} argument must be the name of a record type which has
-two fields of the same floating-point type. The effect of this pragma is
+two fields of the same floating-point type. The effect of this pragma is
to force gcc to use the special internal complex representation form for
-this record, which may be more efficient. Note that this may result in
+this record, which may be more efficient. Note that this may result in
the code for this type not conforming to standard ABI (application
-binary interface) requirements for the handling of record types. For
+binary interface) requirements for the handling of record types. For
example, in some environments, there is a requirement for passing
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
@item Component_Size
Aligns scalar components and subcomponents of the array or record type
on boundaries appropriate to their inherent size (naturally
-aligned). For example, 1-byte components are aligned on byte boundaries,
+aligned). For example, 1-byte components are aligned on byte boundaries,
2-byte integer components are aligned on 2-byte boundaries, 4-byte
-integer components are aligned on 4-byte boundaries and so on. These
+integer components are aligned on 4-byte boundaries and so on. These
alignment rules correspond to the normal rules for C compilers on all
machines except the VAX@.
@findex Component_Size_4
@item Component_Size_4
Naturally aligns components with a size of four or fewer
-bytes. Components that are larger than 4 bytes are placed on the next
+bytes. Components that are larger than 4 bytes are placed on the next
4-byte boundary.
@findex Storage_Unit
@item Default
Specifies that array or record components are aligned on default
boundaries, appropriate to the underlying hardware or operating system or
-both. For OpenVMS VAX systems, the @code{Default} choice is the same as
-the @code{Storage_Unit} choice (byte alignment). For all other systems,
+both. For OpenVMS VAX systems, the @code{Default} choice is the same as
+the @code{Storage_Unit} choice (byte alignment). For all other systems,
the @code{Default} choice is the same as @code{Component_Size} (natural
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
+choice applies to the specified type. The use of
@code{Component_Alignment} together with a pragma @code{Pack} causes the
-@code{Component_Alignment} pragma to be ignored. The use of
+@code{Component_Alignment} pragma to be ignored. The use of
@code{Component_Alignment} together with a record representation clause
is only effective for fields not specified by the representation clause.
accordance with the normal rules for configuration pragmas, or it can be
used within a declarative part, in which case it applies to types that
are declared within this declarative part, or within any nested scope
-within this declarative part. In either case it specifies the alignment
+within this declarative part. In either case it specifies the alignment
to be applied to any record or array type which has otherwise standard
representation.
If the alignment for a record or array type is not specified (using
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
+@noindent
+Syntax:
+
+@smallexample @c ada
+pragma Convention_Identifier (
+ [Name =>] IDENTIFIER,
+ [Convention =>] convention_IDENTIFIER);
+@end smallexample
+
+@noindent
+This pragma provides a mechanism for supplying synonyms for existing
+convention identifiers. The @code{Name} identifier can subsequently
+be used as a synonym for the given convention in other pragmas (including
+for example pragma @code{Import} or another @code{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 @c ada
+pragma Convention_Identifier (Fortran77, Fortran);
+@end smallexample
+
+@noindent
+would allow the use of the convention identifier @code{Fortran77} in
+subsequent code, avoiding the need to modify the sources. As another
+example, you could use this to parametrize convention requirements
+according to systems. Suppose you needed to use @code{Stdcall} on
+windows systems, and @code{C} on some other system, then you could
+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. Ada Core Technologies does
-not currently supply such a
-tool; See @ref{Interfacing to C++} for more details.
+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 Import) as corresponding to a C++
-constructor. The argument is a name that must have been
-previously mentioned in a pragma
-Import with @var{Convention 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
where @var{T} is a tagged type to which the pragma @code{CPP_Class} applies.
The first form is the default constructor, used when an object of type
-@var{T} is created on the Ada side with no explicit constructor. Other
+@var{T} is created on the Ada side with no explicit constructor. Other
constructors (including the copy constructor, which is simply a special
case of the second form in which the one and only argument is of type
@var{T}), can only appear in two contexts:
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
-level. GNAT issues the appropriate call, whatever it is, to get the
+level. GNAT issues the appropriate call, whatever it is, to get the
object properly initialized.
In the case of derived objects, you may use one of two possible forms
@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
+expressions in the Ada declaration. In the second case, the given
constructor is called and the extension aggregate indicates the explicit
values of the extension fields.
If no constructors are imported, it is impossible to create any objects
-on the Ada side. If no default constructor is imported, only the
+on the Ada side. If no default constructor is imported, only the
initialization forms using an explicit call to a constructor are
permitted.
Pragma @code{CPP_Constructor} is intended primarily for automatic generation
-using an automatic binding generator tool. Ada Core Technologies does
-not currently supply such a
-tool; See @ref{Interfacing to C++} for more details.
+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. Ada Core Technologies does
-not currently supply such a
-tool; See @ref{Interfacing to C++} for more details.
+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
+This pragma is now obsolete has has no effect because GNAT generates
+the same object layout than the G++ compiler.
+
+See @ref{Interfacing to C++} for related information.
+
+@node Pragma Debug
+@unnumberedsec Pragma Debug
+@findex Debug
@noindent
Syntax:
-@smallexample
-pragma CPP_Vtable (
- [Entity =>] ENTITY,
- [Vtable_Ptr =>] vtable_ENTITY,
- [Entry_Count =>] static_integer_EXPRESSION);
+@smallexample @c ada
+pragma Debug ([CONDITION, ]PROCEDURE_CALL_WITHOUT_SEMICOLON);
+
+PROCEDURE_CALL_WITHOUT_SEMICOLON ::=
+ PROCEDURE_NAME
+| PROCEDURE_PREFIX ACTUAL_PARAMETER_PART
@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.
+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:
-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).
+@smallexample @c ada
+pragma Debug_Policy (CHECK | IGNORE);
+@end smallexample
-Pragma @code{CPP_Vtable} is intended primarily for automatic generation
-using an automatic binding generator tool. Ada Core Technologies does
-not currently supply such a
-tool; See @ref{Interfacing to C++} for more details.
+@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.
-@findex Debug
-@item pragma Debug
+@node Pragma Detect_Blocking
+@unnumberedsec Pragma Detect_Blocking
+@findex Detect_Blocking
@noindent
Syntax:
-@smallexample
-pragma Debug (PROCEDURE_CALL_STATEMENT);
+@smallexample @c ada
+pragma Detect_Blocking;
@end smallexample
@noindent
-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. 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.
+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
-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 GNAT Users Guide.
-
+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);
pragma Eliminate (
[Unit_Name =>] IDENTIFIER |
- SELECTED_COMPONENT
+ SELECTED_COMPONENT,
[Entity =>] IDENTIFIER |
SELECTED_COMPONENT |
- STRING_LITERAL]
- [,[Parameter_Types =>] PARAMETER_TYPES]
- [,[Result_Type =>] result_SUBTYPE_NAME]]);
+ STRING_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
+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 third and fourth parameters are optionally used to distinguish
-between overloaded subprograms, 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.
+
+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
+
+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.
+
+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 intention of pragma Eliminate is to allow a program to be compiled
+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 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 Eliminate.
+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}.
Note that the reason this pragma takes string literals where names might
-be expected is that a pragma Eliminate can appear in a context where the
+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]);
@end smallexample
@noindent
-This pragma is implemented only in the OpenVMS implementation of GNAT@. It
+This pragma is implemented only in the OpenVMS implementation of GNAT@. It
causes the specified exception to be propagated outside of the Ada program,
so that it can be handled by programs written in other OpenVMS languages.
This pragma establishes an external name for an Ada exception and makes the
-name available to the OpenVMS Linker as a global symbol. For further details
+name available to the OpenVMS Linker as a global symbol. For further details
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,
+result values. We recommend, for the purposes of improving portability,
this pragma always be used in conjunction with a separate pragma
@code{Export}, which must precede the pragma @code{Export_Function}.
GNAT does not require a separate pragma @code{Export}, but if none is
region as the function to which they apply.
@var{internal_name} must uniquely designate the function to which the
-pragma applies. If more than one function name exists of this name in
+pragma applies. If more than one function name exists of this name in
the declarative part you must use the @code{Parameter_Types} and
@code{Result_Type} parameters is mandatory to achieve the required
-unique designation. @var{subtype_ mark}s in these parameters must
+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
+the normal @code{Export} pragma applied to an object. You may use a
separate Export pragma (and you probably should from the point of view
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
+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}
parameters in interfacing to external functions (which are not permitted
in Ada functions).
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
@noindent
This pragma is used to provide backwards compatibility with other
-implementations that extend the facilities of package @code{System}. In
+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
package @code{Aux_@var{xxx}}, e.g.@: @code{Aux_DEC} for the DEC Ada 83
-implementation, which provides the required additional definitions. You
+implementation, which provides the required additional definitions. You
can use this package in two ways. You can @code{with} it in the normal
way and access entities either by selection or using a @code{use}
-clause. In this case no special processing is required.
+clause. In this case no special processing is required.
However, if existing code contains references such as
@code{System.@var{xxx}} where @var{xxx} is an entity in the extended
definitions provided in package @code{System}, you may use this pragma
to extend visibility in @code{System} in a non-standard way that
-provides greater compatibility with the existing code. Pragma
+provides greater compatibility with the existing code. Pragma
@code{Extend_System} is a configuration pragma whose single argument is
the name of the package containing the extended definition
-(e.g.@: @code{Aux_DEC} for the DEC Ada case). A unit compiled under
+(e.g.@: @code{Aux_DEC} for the DEC Ada case). A unit compiled under
control of this pragma will be processed using special visibility
processing that looks in package @code{System.Aux_@var{xxx}} where
@code{Aux_@var{xxx}} is the pragma argument for any entity referenced in
You can use this pragma either to access a predefined @code{System}
extension supplied with the compiler, for example @code{Aux_DEC} or
you can construct your own extension unit following the above
-definition. Note that such a package is a child of @code{System}
-and thus is considered part of the implementation. To compile
+definition. Note that such a package is a child of @code{System}
+and thus is considered part of the implementation. To compile
it you will have to use the appropriate switch for compiling
-system units. See the GNAT User's Guide for details.
+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
@noindent
This pragma is identical in syntax and semantics to pragma
-@code{Export} as defined in the Ada Reference Manual. It is
+@code{Export} as defined in the Ada Reference Manual. It is
provided for compatibility with some Ada 83 compilers that
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]);
@noindent
This pragma provides control over the casing of external names associated
-with Import and Export pragmas. There are two cases to consider:
+with Import and Export pragmas. There are two cases to consider:
@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
+Implicit external names are derived from identifiers. The most common case
+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
+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
-letters. This corresponds to the normal C style in many environments.
+letters. This corresponds to the normal C style in many environments.
The first argument of pragma @code{External_Name_Casing} can be used to
-control this treatment. If @code{Uppercase} is specified, then the name
-will be forced to all uppercase letters. If @code{Lowercase} is specified,
+control this treatment. If @code{Uppercase} is specified, then the name
+will be forced to all uppercase letters. If @code{Lowercase} is specified,
then the normal default of all lower case letters will be used.
This same implicit treatment is also used in the case of extended DEC Ada 83
specified using an identifier rather than a string.
@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
+Explicit external names are given as string literals. The most common case
+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
+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
@code{As_Is} provides the normal default behavior in which the casing is
taken from the string provided.
@end table
@noindent
-This pragma may appear anywhere that a pragma is valid. in particular, it
-can be used as a configuration pragma in the @code{gnat.adc} file, in which
+This pragma may appear anywhere that a pragma is valid. In particular, it
+can be used as a configuration pragma in the @file{gnat.adc} file, in which
case it applies to all subsequent compilations, or it can be used as a program
unit pragma, in which case it only applies to the current unit, or it can
be used more locally to control individual Import/Export pragmas.
-It is primarily intended for use with @code{OpenVMS} systems, where many
-compilers convert all symbols to upper case by default. For interfacing to
+It is primarily intended for use with OpenVMS systems, where many
+compilers convert all symbols to upper case by default. For interfacing to
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
This pragma allows the compiler not to emit a Finalize call for objects
-defined at the library level. This is mostly useful for types where
+defined at the library level. This is mostly useful for types where
finalization is only used to deal with storage reclamation since in most
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.
-@cindex OpenVMS
-@findex Import_Exception
-@item pragma Import_Exception
+@node Pragma Implicit_Packing
+@unnumberedsec Pragma Implicit_Packing
+@findex Implicit_Packing
@noindent
Syntax:
-@smallexample
-pragma Import_Exception (
- [Internal =>] LOCAL_NAME,
- [, [External =>] EXTERNAL_SYMBOL,]
- [, [Form =>] Ada | VMS]
- [, [Code =>] static_integer_EXPRESSION]);
+@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
+@noindent
+Syntax:
+
+@smallexample @c ada
+pragma Import_Exception (
+ [Internal =>] local_NAME,
+ [, [External =>] EXTERNAL_SYMBOL,]
+ [, [Form =>] Ada | VMS]
+ [, [Code =>] static_integer_EXPRESSION]);
EXTERNAL_SYMBOL ::=
IDENTIFIER
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
+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
+pragma applies. If more than one function name exists of this name in
the declarative part you must use the @code{Parameter_Types} and
@var{Result_Type} parameters to achieve the required unique
-designation. Subtype marks in these parameters must exactly match the
+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
-parameters and result. If you specify a single mechanism name, it
+parameters and result. If you specify a single mechanism name, it
applies to all parameters. Otherwise you may specify a mechanism on a
parameter by parameter basis using either positional or named
-notation. If the mechanism is not specified, the default mechanism
+notation. If the mechanism is not specified, the default mechanism
is used.
@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
are optional, meaning that they are not passed at the generated code
level (this is distinct from the notion of optional parameters in Ada
where the parameters are passed anyway with the designated optional
-parameters). All optional parameters must be of mode @code{IN} and have
+parameters). All optional parameters must be of mode @code{IN} and have
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
the normal @code{Import} pragma applied to an object. Unlike the
subprogram case, you need not use a separate @code{Import} pragma,
although you may do so (and probably should do so from a portability
-point of view). @var{size} is syntax checked, but otherwise ignored by
+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
+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}
parameters in interfacing to external functions (which are not permitted
in Ada functions). You may optionally use the @code{Mechanism}
parameters to specify passing mechanisms for the parameters.
If you specify a single mechanism name, it applies to all parameters.
Otherwise you may specify a mechanism on a parameter by parameter
-basis using either positional or named notation. If the mechanism is not
+basis using either positional or named notation. If the mechanism is not
specified, the default mechanism is used.
Note that it is important to use this pragma in conjunction with a separate
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
-two important differences. First, there is no requirement for the pragma
+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,
without needing to recompile the run-time library.
In the case where some units are compiled with the pragma, and some without,
then a declaration of a variable where the type is defined in package
Standard or is locally declared will always be subject to initialization,
-as will any declaration of a scalar variable. For composite variables,
+as will any declaration of a scalar variable. For composite variables,
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
-low values, or with a specified bit pattern. See the users guide for binder
+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.
This means that you can compile a program, and then without having to
recompile the program, you can run it with different values being used
for initializing otherwise uninitialized values, to test if your program
-behavior depends on the choice. Of course the behavior should not change,
+behavior depends on the choice. Of course the behavior should not change,
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 @code{GNAT}, which checks for invalid values under more conditions.
-Using this feature (see description of the @code{-gnatv} flag in the
+in GNAT, which checks for invalid values under more conditions.
+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.
+Similar to pragma @code{Inline} except that inlining is not subject to
+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
This is implemented for compatibility with DEC Ada 83 and is recognized,
-but otherwise ignored, by GNAT@. All generic instantiations are inlined
+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
-with Ada 83. The definition is upwards compatible both with pragma
+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
@noindent
This pragma provides an alternative way of specifying the interface name
for an interfaced subprogram, and is provided for compatibility with Ada
-83 compilers that use the pragma for this purpose. You must provide at
+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 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
-depend on units that are licensed under the GPL@. Typical examples are
+depend on units that are licensed under the GPL@. Typical examples are
proprietary code that is to be released under more restrictive license
-conditions. Note that restricted units are permitted to @code{with} units
+conditions. Note that restricted units are permitted to @code{with} units
which are licensed under the modified GPL (this is the whole point of the
modified GPL).
@noindent
Normally a unit with no @code{License} pragma is considered to have an
-unknown license, and no checking is done. However, standard GNAT headers
+unknown license, and no checking is done. However, standard GNAT headers
are recognized, and license information is derived from them as follows.
@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.
+A GNAT license header starts with a line containing 78 hyphens. The following
+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
+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 derived from the Ada Reference Manual" is found
+``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
@noindent
These default actions means that a program with a restricted license pragma
will automatically get warnings if a GPL unit is inappropriately
-@code{with}'ed. For example, the program:
+@code{with}'ed. For example, the program:
-@smallexample
+@smallexample @c ada
with Sem_Ch3;
with GNAT.Sockets;
procedure Secret_Stuff is
-...
+ @dots{}
end Secret_Stuff
@end smallexample
@file{gnat.adc} file will generate the warning:
@smallexample
-1. with Sem_Ch3;
+1. with Sem_Ch3;
|
>>> license of withed unit "Sem_Ch3" is incompatible
-2. with GNAT.Sockets;
-3. procedure Secret_Stuff is
+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
@noindent
results in passing the strings @code{-labc} and @code{-ldef} as two
-separate arguments to the linker.
+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 High
-Integrity product documentation 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 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.
+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
This pragma is implemented only in the OpenVMS implementation of GNAT@.
It allows control over the internal representation chosen for the predefined
type @code{Long_Float} and for floating point type representations with
-@code{digits} specified in the range 7 .. 15.
+@code{digits} specified in the range 7 through 15.
For further details on this pragma, see the
-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 Users Guide for details on the use of this command.
+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
+
+@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 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
-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, where @code{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.
+@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
-no effect in GNAT, other than being syntax checked. Note that the pragma
+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
-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.
+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.
+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.
-Another use of this pragma is to suppress incorrect warnings about
-missing returns in functions, where the last statement of a function
+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.
-@findex Passive
-@item pragma Passive
+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
-pragma Passive ([Semaphore | No]);
+@smallexample @c ada
+pragma No_Strict_Aliasing [([Entity =>] type_LOCAL_NAME)];
@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
-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).
+@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.
-@findex Polling
-@item pragma Polling
+@node Pragma Normalize_Scalars
+@unnumberedsec Pragma Normalize_Scalars
+@findex Normalize_Scalars
@noindent
Syntax:
-@smallexample
-pragma Polling (ON | OFF);
+@smallexample @c ada
+pragma Normalize_Scalars;
@end smallexample
@noindent
-This pragma controls the generation of polling code. This is normally off.
-If @code{pragma Polling (ON)} is used then periodic calls are generated to
-the routine Ada.Exceptions.Poll. This routine is a separate unit in the
-runtime library, and can be found in file a-excpol.adb.
+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.
-Pragma polling can appear as a configuration pragma (for example it can be
-placed in the gnat.adc file) to enable polling globally, or it can be used
-in the statement or declaration sequence to control polling more locally.
+@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.
-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 Poll
-routine is called frequently, and places an upper bound (determined by
-the complexity of the code) on the period between two Poll calls.
+@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.
-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 Ada.Exceptions package that can be found
-in files a-except.ads/adb.
+@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.
-A standard alternative unit (called 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 Poll
-in this file makes a call to the appropriate runtime routine to test for
-an abort condition.
+@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.
-Note that polling can also be enabled by use of the -gnatP switch. See
-the GNAT User's Guide for details.
+@end table
-@findex Propagate_Exceptions
-@cindex Zero Cost Exceptions
-@item pragma Propagate_Exceptions
+@node Pragma Obsolescent
+@unnumberedsec Pragma Obsolescent
+@findex Obsolescent
@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 longjmp/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 longjmp/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.
+@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
-@findex Psect_Object
-@item pragma Psect_Object
@noindent
-Syntax:
+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).
-@smallexample
-pragma Psect_Object
- [Internal =>] LOCAL_NAME,
- [, [External =>] EXTERNAL_SYMBOL]
- [, [Size =>] EXTERNAL_SYMBOL]
+@node Pragma Passive
+@unnumberedsec Pragma Passive
+@findex Passive
+@noindent
+Syntax:
-EXTERNAL_SYMBOL ::=
- IDENTIFIER
-| static_string_EXPRESSION
+@smallexample @c ada
+pragma Passive [(Semaphore | No)];
@end smallexample
@noindent
-This pragma is identical in effect to pragma @code{Common_Object}.
+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 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 Pure_Function
-@item pragma Pure_Function
+@node Pragma Persistent_BSS
+@unnumberedsec Pragma Persistent_BSS
+@findex Persistent_BSS
@noindent
Syntax:
-@smallexample
-pragma Pure_Function ([Entity =>] function_LOCAL_NAME);
+@smallexample @c ada
+pragma Persistent_BSS [(local_NAME)]
@end smallexample
-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.
+@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).
-Note that, quite deliberately, there are no static checks to try
-to ensure that this promise is met, so @var{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).
+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.
-@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 Pure_Function for such a function will override this default
-assumption, and cause the compiler to treat such a function as pure.
+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.
-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 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}.
-@findex Ravenscar
-@item pragma Ravenscar
+@node Pragma Polling
+@unnumberedsec Pragma Polling
+@findex Polling
@noindent
Syntax:
-@smallexample
-pragma Ravenscar
+@smallexample @c ada
+pragma Polling (ON | OFF);
@end smallexample
@noindent
-A configuration pragma that establishes the following set of restrictions:
+This pragma controls the generation of polling code. This is normally off.
+If @code{pragma Polling (ON)} is used then periodic calls are generated to
+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}.
-@table @code
-@item No_Abort_Statements
-[RM D.7] There are no abort_statements, and there are
-no calls to Task_Identification.Abort_Task.
+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.
-@item No_Select_Statements
-There are no select_statements.
+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.
-@item No_Task_Hierarchy
-[RM D.7] All (non-environment) tasks depend
-directly on the environment task of the partition.
+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}.
-@item No_Task_Allocators
-[RM D.7] There are no allocators for task types
-or types containing task subcomponents.
+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.
-@item No_Dynamic_Priorities
-[RM D.7] There are no semantic dependencies on the package Dynamic_Priorities.
+Note that polling can also be enabled by use of the @code{-gnatP} switch. See
+the @cite{GNAT User's Guide} for details.
-@item No_Terminate_Alternatives
-[RM D.7] There are no selective_accepts with terminate_alternatives
+@node Pragma Profile (Ravenscar)
+@unnumberedsec Pragma Profile (Ravenscar)
+@findex Ravenscar
+@noindent
+Syntax:
-@item No_Dynamic_Interrupts
-There are no semantic dependencies on Ada.Interrupts.
+@smallexample @c ada
+pragma Profile (Ravenscar);
+@end smallexample
-@item No_Protected_Type_Allocators
-There are no allocators for protected types or
-types containing protected subcomponents.
+@noindent
+A configuration pragma that establishes the following set of configuration
+pragmas:
-@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].
+@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
-@item Static_Storage_Size
-The expression for pragma Storage_Size is static.
+plus the following set of restrictions:
-@item Boolean_Entry_Barriers
-Entry barrier condition expressions shall be boolean
-objects which are declared in the protected type
-which contains the entry.
+@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.
-@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 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.
@item Max_Task_Entries = 0
[RM D.7] Specifies the maximum number of entries
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
+the Profile (Ravenscar), the value of Max_Task_Entries is always
0 (zero).
-@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_Abort_Statements
+[RM D.7] There are no abort_statements, and there are
+no calls to Task_Identification.Abort_Task.
-@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_Asynchronous_Control
+[RM D.7] There are no semantic dependences on the package
+Asynchronous_Task_Control.
+
+@item No_Calendar
+There are no semantic dependencies on the package Ada.Calendar.
+
+@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_Implicit_Heap_Allocations
+[RM D.7] No constructs are allowed to cause implicit heap allocation.
+
+@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_Relative_Delay
+There are no delay_relative statements.
+
+@item No_Requeue_Statements
+Requeue statements are not allowed.
+
+@item No_Select_Statements
+There are no select_statements.
+
+@item No_Task_Allocators
+[RM D.7] There are no allocators for task types
+or types containing task subcomponents.
+
+@item No_Task_Attributes_Package
+There are no semantic dependencies on the Ada.Task_Attributes package.
+
+@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 International
-Workshop On Real Time Ada", 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 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{No_Relative_Delay} and @code{No_Task_Termination}). This means
-that pragma Ravenscar, like the pragma Restricted_Run_Time, automatically
-causes the use of a simplified, more efficient version of the tasking
-run-time system.
+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.
-@findex Restricted_Run_Time
-@item pragma Restricted_Run_Time
+The above set is a superset of the restrictions provided by pragma
+@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{Profile (Ravenscar)}, like the pragma
+@code{Profile (Restricted)},
+automatically causes the use of a simplified,
+more efficient version of the tasking run-time system.
+
+@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);
@end smallexample
@noindent
-Use this to override the normal naming convention. It is a configuration
+Use this to override the normal naming convention. It is a configuration
pragma, and so has the usual applicability of configuration pragmas
(i.e.@: it applies to either an entire partition, or to all units in a
compilation, or to a single unit, depending on how it is used.
-@var{unit_name} is mapped to @var{file_name_literal}. The identifier for
+@var{unit_name} is mapped to @var{file_name_literal}. The identifier for
the second argument is required, and indicates whether this is the file
name for the spec or for the body.
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]
@noindent
The first argument is a pattern that contains a single asterisk indicating
the point at which the unit name is to be inserted in the pattern string
-to form the file name. The second argument is optional. If present it
+to form the file name. The second argument is optional. If present it
specifies the casing of the unit name in the resulting file name string.
-The default is lower case. Finally the third argument allows for systematic
+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 "Alternative File
-Naming Schemes" in the GNAT User's Guide.
+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
This pragma must appear as the first line of a source file.
@var{integer_literal} is the logical line number of the line following
the pragma line (for use in error messages and debugging
-information). @var{string_literal} is a static string constant that
+information). @var{string_literal} is a static string constant that
specifies the file name to be used in error messages and debugging
-information. This is most notably used for the output of @code{gnatchop}
-with the @samp{-r} switch, to make sure that the original unchopped
+information. This is most notably used for the output of @code{gnatchop}
+with the @code{-r} switch, to make sure that the original unchopped
source file is the one referred to.
The second argument must be a string literal, it cannot be a static
-string expression other than a string literal. This is because its value
+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
This pragma provides an efficient way of providing stream functions for
-types defined in packages. Not only is it simpler to use than declaring
+types defined in packages. Not only is it simpler to use than declaring
the necessary functions with attribute representation clauses, but more
significantly, it allows the declaration to made in such a way that the
-stream packages are not loaded unless they are needed. The use of
+stream packages are not loaded unless they are needed. The use of
the Stream_Convert pragma adds no overhead at all, unless the stream
attributes are actually used on the designated type.
The first argument specifies the type for which stream functions are
-provided. The second parameter provides a function used to read values
-of this type. It must name a function whose argument type may be any
+provided. The second parameter provides a function used to read values
+of this type. It must name a function whose argument type may be any
subtype, and whose returned type must be the type given as the first
argument to the pragma.
The effect is to first call the Write function to convert to the given stream
type, and then write the result type to the stream.
-The Read and Write functions must not be overloaded subprograms. If necessary
+The Read and Write functions must not be overloaded subprograms. If necessary
renamings can be supplied to meet this requirement.
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
+the use of the pragma. This pragma can be used anywhere that a pragma
is legal, including use as a configuration pragma (including use in
the @file{gnat.adc} file).
The form with a string literal specifies which style options are to be
-activated. These are additive, so they apply in addition to any previously
-set style check options. The codes for the options are the same as those
-used in the @code{-gnaty} switch on the @code{gcc} or @code{gnatmake}
-line. For example the following two methods can be used to enable
+activated. These are additive, so they apply in addition to any previously
+set style check options. The codes for the options are the same as those
+used in the @code{-gnaty} switch to @code{gcc} or @code{gnatmake}.
+For example the following two methods can be used to enable
layout checking:
-@smallexample
+@itemize @bullet
+@item
+@smallexample @c ada
pragma Style_Checks ("l");
-gcc -c -gnatyl ...
@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
-to the use of the @code{gnaty} switch with no options. See GNAT User's
+to the use of the @code{gnaty} switch with no options. See GNAT User's
Guide for details.
The forms with @code{Off} and @code{On}
can be used to temporarily disable style checks
as shown in the following example:
-@smallexample
+@smallexample @c ada
@iftex
@leftskip=0cm
@end iftex
@noindent
Finally the two argument form is allowed only if the first argument is
-@code{On} or @code{Off}. The effect is to turn of semantic style checks
+@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
@noindent
This pragma can only appear immediately following a compilation
-unit. The effect is to apply @code{Suppress (All_Checks)} to the unit
-which it follows. This pragma is implemented for compatibility with DEC
-Ada 83 usage. The use of pragma @code{Suppress (All_Checks)} as a normal
+unit. The effect is to apply @code{Suppress (All_Checks)} to the unit
+which it follows. This pragma is implemented for compatibility with DEC
+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
@noindent
This pragma appears within a task definition (like pragma
-@code{Priority}) and applies to the task in which it appears. The
+@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
-tasks to specific processors. For details on the facilities available
+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
@noindent
This pragma appears within a task definition (like pragma
-@code{Priority}) and applies to the task in which it appears. The
+@code{Priority}) and applies to the task in which it appears. The
argument must be of type String, and provides a name to be used for
-the task instance when the task is created. Note that this expression
+the task instance when the task is created. Note that this expression
is not required to be static, and in particular, it can contain
-references to task discriminants. This facility can be used to
+references to task discriminants. This facility can be used to
provide different names for different tasks as they are created,
as illustrated in the example below.
The task name is recorded internally in the run-time structures
-and is accessible to tools like the debugger. In addition the
+and is accessible to tools like the debugger. In addition the
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
-created, depending on the target. This pragma can appear anywhere a
+created, depending on the target. This pragma can appear anywhere a
@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 ::=
@end smallexample
@noindent
-Syntax checked but otherwise ignored by GNAT@. This is a listing control
+Syntax checked but otherwise ignored by GNAT@. This is a listing control
pragma used in DEC Ada 83 implementations to provide a title and/or
-subtitle for the program listing. The program listing generated by GNAT
+subtitle for the program listing. The program listing generated by GNAT
does not have titles or subtitles.
Unlike other pragmas, the full flexibility of named notation is allowed
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
+@cindex Warnings, unreferenced
+@noindent
+Syntax:
+
+@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 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 in the
+same unit as the pragma (or in the corresponding body, or one
+of its subunits).
+
+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
+current scope, then the entity most recently declared is the one to which
+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
@noindent
-Normally certain interrupts are reserved to the implementation. Any attempt
+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 @code{Ctrl-C} interrupt. Normally this interrupt is
-reserved to the implementation, so that @code{Ctrl-C} can be used to
+RM C.3.2(22). A typical example is the @code{SIGINT} interrupt used in
+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.
-If the pragma Unreserve_All_Interrupts appears anywhere in any unit in
-a program, then all such interrupts are unreserved. This allows the
+If the pragma @code{Unreserve_All_Interrupts} appears anywhere in any unit in
+a program, then all such interrupts are unreserved. This allows the
program to handle these interrupts, but disables their standard
-functions. For example, if this pragma is used, then pressing
-@code{Ctrl-C} will not automatically interrupt execution. However,
+functions. For example, if this pragma is used, then pressing
+@kbd{Ctrl-C} will not automatically interrupt execution. However,
a program can then handle the @code{SIGINT} interrupt as it chooses.
For a full list of the interrupts handled in a specific implementation,
-see the source code for the specification of Ada.Interrupts.Names in
-file a-intnam.ads. This is a target dependent file that contains the
-list of interrupts recognized for a given target. The documentation in
+see the source code for the specification of @code{Ada.Interrupts.Names} in
+file @file{a-intnam.ads}. This is a target dependent file that contains the
+list of interrupts recognized for a given target. The documentation in
this file also specifies what interrupts are affected by the use of
-the Unreserve_All_Interrupts pragma.
+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
@noindent
-This pragma undoes the effect of a previous pragma @code{Suppress}. If
+This pragma undoes the effect of a previous pragma @code{Suppress}. If
there is no corresponding pragma @code{Suppress} in effect, it has no
-effect. The range of the effect is the same as for pragma
-@code{Suppress}. The meaning of the arguments is identical to that used
+effect. The range of the effect is the same as for pragma
+@code{Suppress}. The meaning of the arguments is identical to that used
in pragma @code{Suppress}.
One important application is to ensure that checks are on in cases where
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
@noindent
-This is a configuration pragma. In a unit to which it applies, any use
+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
-as implemented in the VADS compiler. See description of the VADS_Size
+'VADS_Size attribute. Note that this may result in incorrect semantic
+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
+the use of the pragma. This pragma can be used anywhere that a pragma
is legal, including use as a configuration pragma (including use in
the @file{gnat.adc} file).
The form with a string literal specifies which validity options are to be
-activated. The validity checks are first set to include only the default
+activated. The validity checks are first set to include only the default
reference manual settings, and then a string of letters in the string
-specifies the exact set of options required. The form of this string
+specifies the exact set of options required. The form of this string
is exactly as described for the @code{-gnatVx} compiler switch (see the
-GNAT users guide for details). For example the following two methods
+GNAT users guide for details). For example the following two methods
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");
-gcc -c -gnatVim ...
@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
to the use of the @code{gnatva} switch.
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
-implementation is fully conformant with this definition. The reason it
+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
Normally warnings are enabled, with the output being controlled by
-the command line switch. Warnings (@code{Off}) turns off generation of
+the command line switch. Warnings (@code{Off}) turns off generation of
warnings until a Warnings (@code{On}) is encountered or the end of the
-current unit. If generation of warnings is turned off using this
+current unit. If generation of warnings is turned off using this
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
-the specified entity. This suppression is effective from the point where
+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.
+areas of the language. These language defined attributes are implemented
+in GNAT and work as described in the Ada Reference Manual.
-In addition, Ada 95 allows implementations to define additional
-attributes whose meaning is defined by the implementation. GNAT provides
+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
+to extend and enhance the functionality of the compiler. This section of
the GNAT reference manual describes these additional attributes.
Note that any program using these attributes may not be portable to
other compilers (although GNAT implements this set of attributes on all
-platforms). Therefore if portability to other compilers is an important
+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
-task abort or asynchronous transfer of control. Normally this attribute
+task abort or asynchronous transfer of control. Normally this attribute
should only be used in the tasking runtime (it is highly peculiar, and
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
-type designated by the prefix. The first (string) argument is required
+type designated by the prefix. The first (string) argument is required
to be a static expression, and is the constraint for the parameter,
-(e.g.@: what kind of register is required). The second argument is the
-value to be used as the input argument. The possible values for the
+(e.g.@: what kind of register is required). The second argument is the
+value to be used as the input argument. The possible values for the
constant are the same as those used in the RTL, and are dependent on
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
-of the type designated by the attribute prefix. The first (string)
+of the type designated by the attribute prefix. The first (string)
argument is required to be a static expression and designates the
constraint for the parameter (e.g.@: what kind of register is
-required). The second argument is the variable to be updated with the
-result. The possible values for constraint are the same as those used in
+required). The second argument is the variable to be updated with the
+result. The possible values for constraint are the same as those used in
the RTL, and are dependent on the configuration file used to build the
GCC back end. If there are no output operands, then this argument may
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
+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
(declared in the predefined package System, as extended by the use of
-pragma Extend_System (Aux_DEC)). This value enables the given entry to
-be called when an AST occurs. For further details, refer to the DEC Ada
-Language Reference Manual, section 9.12a.
+pragma @code{Extend_System (Aux_DEC)}). This value enables the given entry to
+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
+storage allocated for the object. The value of this attribute is of the
type @code{Universal_Integer}, and is always a non-negative number not
exceeding the value of @code{System.Storage_Unit}.
For an object that is a variable or a constant allocated in a register,
-the value is zero. (The use of this attribute does not force the
+the value is zero. (The use of this attribute does not force the
allocation of a variable to memory).
For an object that is a formal parameter, this attribute applies
to either the matching actual parameter or to a copy of the
matching actual parameter.
-For an access object the value is zero. Note that
+For an access object the value is zero. Note that
@code{@var{obj}.all'Bit} is subject to an @code{Access_Check} for the
-designated object. Similarly for a record component
+designated object. Similarly for a record component
@code{@var{X}.@var{C}'Bit} is subject to a discriminant check and
@code{@var{X}(@var{I}).Bit} and @code{@var{X}(@var{I1}..@var{I2})'Bit}
are subject to index checks.
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
offset within the record contains the first bit of
-storage allocated for the object. The value of this attribute is of the
-type @code{Universal_Integer}. The value depends only on the field
+storage allocated for the object. The value of this attribute is of the
+type @code{Universal_Integer}. The value depends only on the field
@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
-procedure K is ...
+@smallexample @c ada
+procedure K is @dots{}
procedure L;
for L'Address use K'Address;
@end smallexample
@noindent
-A call to L is then expected to result in a call to 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 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 Address value described above. For example,
-the Address value may reference a subprogram descriptor rather than the
-subprogram itself.
+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.
-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}
as a @code{Pos} value (0 for @code{High_Order_First}, 1 for
-@code{Low_Order_First}). This is used to construct the definition of
+@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
+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
+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.
+in user programs. The value will always be True once elaboration of all
+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
+This attribute can only be applied to a program unit name. It returns
the entity for the corresponding elaboration procedure for elaborating
-the body of the referenced unit. This is used in the main generated
+the body of the referenced unit. This is used in the main generated
elaboration procedure by the binder and is not normally used in any
other context. However, there may be specialized situations in which it
is useful to be able to call this elaboration procedure from Ada code,
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
+This attribute can only be applied to a program unit name. It returns
the entity for the corresponding elaboration procedure for elaborating
-the specification of the referenced unit. This is used in the main
+the specification of the referenced unit. This is used in the main
generated elaboration procedure by the binder and is not normally used
in any other context. However, there may be specialized situations in
which it is useful to be able to call this elaboration procedure from
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 @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 Enum_Rep directly to an object of an
+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.
The function returns the representation value for the given enumeration
-value. This will be equal to value of the @code{Pos} attribute in the
-absence of an enumeration representation clause. This is a static
+value. This will be equal to value of the @code{Pos} attribute in the
+absence of an enumeration representation clause. This is a static
attribute (i.e.@: the result is static if the argument is static).
-@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 (<>) discrete formal arguments in a generic unit that
-can be instantiated with either enumeration types or integer types. Note
-that if 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 @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
+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
-otherwise. The intended use of this attribute is in conjunction with generic
-definitions. If the attribute is applied to a generic private type, it
+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 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
+@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 @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
+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 @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
+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
@code{@var{subprogram}'Mechanism_Code (@var{n})} yields the mechanism
used for formal parameter number @var{n} (a static integer value with 1
-meaning the first parameter) of @var{subprogram}. The code returned is:
+meaning the first parameter) of @var{subprogram}. The code returned is:
@table @asis
@item 1
by descriptor (NCA: non-contiguous array)
@end table
+@noindent
+Values from 3 through 10 are only relevant to Digital OpenVMS implementations.
@cindex OpenVMS
-Values from 3-10 are only relevant to Digital OpenVMS implementations.
+@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
+type or subtype @var{T} allocated at machine address zero. The attribute
is allowed only as the default expression of a formal parameter, or as
-an actual expression of a subprogram call. In either case, the
+an actual expression of a subprogram call. In either case, the
subprogram must be imported.
The identity of the object is represented by the address zero in the
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,
+of an object. This is because by default object sizes are increased to be
+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).
The @code{@var{type}'Object_Size} attribute
has been added to GNAT to allow the
-default object size of a type to be easily determined. For example,
+default object size of a type to be easily determined. For example,
@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
+64. Note also that, unlike the situation with the
+@code{Size} attribute as defined in the Ada RM, the
@code{Object_Size} attribute can be specified individually
-for different subtypes. For example:
+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;
@noindent
In this example, @code{R'Object_Size} and @code{R1'Object_Size} are both
32 since the default object size for a subtype is the same as the object size
-for the parent subtype. This means that objects of type @code{R}
+for the parent subtype. This means that objects of type @code{R}
or @code{R1} will
-by default be 32 bits (four bytes). But objects of type
+by default be 32 bits (four bytes). But objects of type
@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
normally passed by reference and @code{False} if the type is normally
-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.
+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
-range). The result is static for static subtypes. @code{Range_Length}
+range). The result is static for static subtypes. @code{Range_Length}
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 @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 @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
+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
+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
+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
+the value of the type class for the full type of @var{type}. If
@var{type} is a generic formal type, the value is the value for the
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,
@noindent
Protected types yield the value @code{Type_Class_Task}, which thus
-applies to all concurrent types. This attribute is designed to
+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
-table when zero cost exception handling is used. This attribute is
-intended only for use within the GNAT implementation. See the unit
-@code{Ada.Exceptions} in files @file{a-except.ads,a-except.adb}
+denotes a library package. It yields the address of the unit exception
+table when zero cost exception handling is used. This attribute is
+intended only for use within the GNAT implementation. See the unit
+@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
-the number as defined in the original source. This allows the user
+number. The static result is the string consisting of the characters of
+the number as defined in the original source. This allows the user
program to access the actual text of named numbers without intermediate
conversions and without the need to enclose the strings in quotes (which
-would preclude their use as numbers). This is used internally for the
+would preclude their use as numbers). This is used internally for the
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
+except that all accessibility and aliased view checks are omitted. This
is a user-beware attribute. It is similar to
@code{Address}, for which it is a desirable replacement where the value
-desired is an access type. In other words, its effect is identical to
+desired is an access type. In other words, its effect is identical to
first applying the @code{Address} attribute and then doing an unchecked
-conversion to a desired access type. In GNAT, but not necessarily in
+conversion to a desired access type. In GNAT, but not necessarily in
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
-by the VADS Ada 83 compiler. GNAT makes a best effort at duplicating the
-same semantic interpretation. In particular, @code{'VADS_Size} applied
+by the VADS Ada 83 compiler. GNAT makes a best effort at duplicating the
+same semantic interpretation. In particular, @code{'VADS_Size} applied
to a predefined or other primitive type with no Size clause yields the
Object_Size (for example, @code{Natural'Size} is 32 rather than 31 on
-typical machines). In addition @code{'VADS_Size} applied to an object
+typical machines). In addition @code{'VADS_Size} applied to an object
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},
+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
-follow. Rather they provide advice on generally desirable behavior. You
-may wonder why they are not requirements. The most typical answer is
+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
-``followed'', which means that GNAT follows the advice. However, in a
+by the GNAT interpretation of this advice. Most often, this simply says
+``followed'', which means that GNAT follows the advice. However, in a
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
Annex feature at run time, it should raise @code{Program_Error} if
feasible.
@end cartouche
-Not relevant. All specialized needs annex features are either supported,
+Not relevant. All specialized needs annex features are either supported,
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
execution, it should raise @code{Program_Error}.
@end cartouche
Followed in all cases in which the implementation detects a bounded
-error or erroneous execution. Not all such situations are detected at
+error or erroneous execution. Not all such situations are detected at
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
+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
for @code{Character} and @code{Wide_Character}, the set of graphic
characters of @code{Character} should nevertheless remain a proper
-subset of the set of graphic characters of @code{Wide_Character}. Any
+subset of the set of graphic characters of @code{Wide_Character}. Any
character set ``localizations'' should be reflected in the results of
the subprograms defined in the language-defined package
-@code{Characters.Handling} (see A.3) available in such a mode. In a mode with
+@code{Characters.Handling} (see A.3) available in such a mode. In a mode with
an alternative interpretation of @code{Character}, the implementation should
also support a corresponding change in what is a legal
@code{identifier_letter}.
and IEC modes reflect standard usage in Japan, and in these encoding,
the upper half of the Latin-1 set is not part of the wide-character
subset, since the most significant bit is used for wide character
-encoding. However, this only applies to the external forms. Internally
+encoding. However, this only applies to the external forms. Internally
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
An implementation should support @code{Long_Integer} in addition to
@code{Integer} if the target machine supports 32-bit (or longer)
-arithmetic. No other named integer subtypes are recommended for package
-@code{Standard}. Instead, appropriate named integer subtypes should be
+arithmetic. No other named integer subtypes are recommended for package
+@code{Standard}. Instead, appropriate named integer subtypes should be
provided in the library package @code{Interfaces} (see B.2).
@end cartouche
-@code{Long_Integer} is supported. Other standard integer types are supported
-so this advice is not fully followed. These types
+@code{Long_Integer} is supported. Other standard integer types are supported
+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
An implementation for a two's complement machine should support
-modular types with a binary modulus up to @code{System.Max_Int*2+2}. An
+modular types with a binary modulus up to @code{System.Max_Int*2+2}. An
implementation should support a non-binary modules up to @code{Integer'Last}.
@end 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
subtype, if the value of the operand does not correspond to the internal
code for any enumeration literal of its type (perhaps due to an
un-initialized variable), then the implementation should raise
-@code{Program_Error}. This is particularly important for enumeration
+@code{Program_Error}. This is particularly important for enumeration
types with noncontiguous internal codes specified by an
enumeration_representation_clause.
@end cartouche
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
@code{Float} if the target machine supports 11 or more digits of
-precision. No other named floating point subtypes are recommended for
-package @code{Standard}. Instead, appropriate named floating point subtypes
+precision. No other named floating point subtypes are recommended for
+package @code{Standard}. Instead, appropriate named floating point subtypes
should be provided in the library package @code{Interfaces} (see B.2).
@end cartouche
-@code{Short_Float} and @code{Long_Long_Float} are also provided. The
+@code{Short_Float} and @code{Long_Long_Float} are also provided. The
former provides improved compatibility with other implementations
-supporting this type. The latter corresponds to the highest precision
-floating-point type supported by the hardware. On most machines, this
+supporting this type. The latter corresponds to the highest precision
+floating-point type supported by the hardware. On most machines, this
will be the same as @code{Long_Float}, but on some machines, it will
-correspond to the IEEE extended form. The notable case is all ia32
+correspond to the IEEE extended form. The notable case is all ia32
(x86) implementations, where @code{Long_Long_Float} corresponds to
the 80-bit extended precision format supported in hardware on this
-processor. Note that the 128-bit format on SPARC is not supported,
+processor. Note that the 128-bit format on SPARC is not supported,
since this is a software rather than a hardware format.
@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
row-major order, consistent with the notation used for multidimensional
-array aggregates (see 4.3.3). However, if a pragma @code{Convention}
-(@code{Fortran}, ...) applies to a multidimensional array type, then
+array aggregates (see 4.3.3). However, if a pragma @code{Convention}
+(@code{Fortran}, @dots{}) applies to a multidimensional array type, then
column-major order should be used instead (see B.5, ``Interfacing with
Fortran'').
@end cartouche
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}
should be no greater than 100 microseconds.
@end cartouche
-Followed. (@code{Duration'Small} = 10**(-9)).
+Followed. (@code{Duration'Small} = 10**(@minus{}9)).
@sp 1
@cartouche
@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
the same program, or in executions of distinct programs or partitions
that include the given version.
@end cartouche
-Followed, except in the case of tagged types. Tagged types involve
+Followed, except in the case of tagged types. Tagged types involve
implicit pointers to a local copy of a dispatch table, and these pointers
have representations which thus depend on a particular elaboration of the
-package. It is not easy to see how it would be possible to follow this
+package. It is not easy to see how it would be possible to follow this
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}
should produce information useful for
-debugging. @code{Exception_Message} should be short, about one
-line. @code{Exception_Information} can be long. @code{Exception_Message}
+debugging. @code{Exception_Message} should be short, about one
+line. @code{Exception_Information} can be long. @code{Exception_Message}
should not include the
-@code{Exception_Name}. @code{Exception_Information} should include both
+@code{Exception_Name}. @code{Exception_Information} should include both
the @code{Exception_Name} and the @code{Exception_Message}.
@end cartouche
-Followed. For each exception that doesn't have a specified
+Followed. For each exception that doesn't have a specified
@code{Exception_Message}, the compiler generates one containing the location
-of the raise statement. This location has the form "file:line", where
+of the raise statement. This location has the form ``file:line'', where
file is the short file name (without path information) and line is the line
-number in the file. Note that in the case of the Zero Cost Exception
+number in the file. Note that in the case of the Zero Cost Exception
mechanism, these messages become redundant with the Exception_Information that
contains a full backtrace of the calling sequence, so they are disabled.
To disable explicitly the generation of the source location message, use the
@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
constraints on the subtype and its composite subcomponents (if any) are
all static constraints.
@end cartouche
-Followed. Size Clauses are not permitted on non-static components, as
+Followed. Size Clauses are not permitted on non-static components, as
described above.
@sp 1
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
possible subject to the Sizes of the component subtypes, and subject to
any @code{record_representation_clause} that applies to the type; the
implementation may, but need not, reorder components or cross aligned
-word boundaries to improve the packing. A component whose @code{Size} is
+word boundaries to improve the packing. A component whose @code{Size} is
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.
+Followed. Tight packing of arrays is supported for all component sizes
+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
subtypes, the implementation should support all @code{Alignment}s
-supported by the target linker. For example, page alignment is likely to
+supported by the target linker. For example, page alignment is likely to
be supported for such objects, but not for subtypes.
@end cartouche
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
The @code{Size} (if not specified) of a static discrete or fixed point
subtype should be the number of bits needed to represent each value
belonging to the subtype using an unbiased representation, leaving space
-for a sign bit only if the subtype contains negative values. If such a
+for a sign bit only if the subtype contains negative values. If such a
subtype is a first subtype, then an implementation should support a
specified @code{Size} for it that reflects this representation.
@end 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}
@sp 1
@cartouche
An implementation should support specified @code{Component_Size}s that
-are factors and multiples of the word size. For such
+are factors and multiples of the word size. For such
@code{Component_Size}s, the array should contain no gaps between
-components. For other @code{Component_Size}s (if supported), the array
+components. For other @code{Component_Size}s (if supported), the array
should contain no gaps between components when packing is also
specified; the implementation should forbid this combination in cases
where it cannot support a no-gaps representation.
@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,
An implementation may reserve a storage place for the tag field of a
tagged type, and disallow other components from overlapping that place.
@end cartouche
-Followed. The storage place for the tag field is the beginning of the tagged
-record, and its size is Address'Size. GNAT will reject an explicit component
+Followed. The storage place for the tag field is the beginning of the tagged
+record, and its size is Address'Size. GNAT will reject an explicit component
clause for the tag field.
@sp 1
storage places of all components of the parent type, whether or not
those storage places had been specified.
@end cartouche
-Followed. The above advice on record representation clauses is followed,
+Followed. The above advice on record representation clauses is followed,
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
offset) to the actual data of the component, and this data is contiguous
with the rest of the object, then the storage place attributes should
-reflect the place of the actual data, not the pointer. If a component is
+reflect the place of the actual data, not the pointer. If a component is
allocated discontinuously from the rest of the object, then a warning
should be generated upon reference to one of its storage place
attributes.
@end cartouche
-Followed. There are no such components in GNAT@.
+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:
should support the non-default bit ordering in addition to the default
bit ordering.
@end cartouche
-Followed. Word size does not equal storage size in this implementation.
+Followed. Word size does not equal storage size in this implementation.
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
-environment semantics as closely as is reasonable. For example, on most
-machines, it makes sense for address arithmetic to ``wrap around.''
+environment semantics as closely as is reasonable. For example, on most
+machines, it makes sense for address arithmetic to ``wrap around''.
Operations that do not make sense should raise @code{Program_Error}.
@end cartouche
-Followed. Address arithmetic is modular arithmetic that wraps around. No
+Followed. Address arithmetic is modular arithmetic that wraps around. No
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
The implementation should not generate unnecessary run-time checks to
ensure that the representation of @var{S} is a representation of the
-target type. It should take advantage of the permission to return by
-reference when possible. Restrictions on unchecked conversions should be
+target type. It should take advantage of the permission to return by
+reference when possible. Restrictions on unchecked conversions should be
avoided unless required by the target environment.
@end cartouche
-Followed. There are no restrictions on unchecked conversion. A warning is
+Followed. There are no restrictions on unchecked conversion. A warning is
generated if the source and target types do not have the same size since
the semantics in this case may be target dependent.
@sp 1
@cartouche
Unchecked conversions should be supported and should be reversible in
-the cases where this clause defines the result. To enable meaningful use
+the cases where this clause defines the result. To enable meaningful use
of unchecked conversion, a contiguous representation should be used for
elementary subtypes, for statically constrained array subtypes whose
component subtype is one of the subtypes described in this paragraph,
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
To allocate space for a task when a task is created.
@item
-To extend the secondary stack dynamically when needed. The secondary
+To extend the secondary stack dynamically when needed. The secondary
stack is used for returning variable length results.
@end itemize
@sp 1
@cartouche
-A default (implementation-provided) storage pool for an access-to-
-constant type should not have overhead to support de-allocation of
+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
normal in-memory representation should be used by @code{Read} and
-@code{Write} for scalar objects. Otherwise, @code{Read} and @code{Write}
+@code{Write} for scalar objects. Otherwise, @code{Read} and @code{Write}
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,
then the names should end with @samp{Integer} as in
-@samp{Long_Integer}. If an implementation provides additional named
+@samp{Long_Integer}. If an implementation provides additional named
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}
or @code{Wide_Character}, then the effects of the subprograms in
-@code{Characters.Handling} should reflect the localizations. See also
+@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
of distinct initiator values, then each possible value of
@code{Initiator} passed to @code{Reset} should initiate a sequence of
random numbers that does not, in a practical sense, overlap the sequence
-initiated by any other value. If this is not possible, then the mapping
+initiated by any other value. If this is not possible, then the mapping
between initiator values and generator states should be a rapidly
varying function of the initiator value.
@end cartouche
-Followed. The generator period is sufficiently long for the first
-condition here to hold true.
+Followed. The generator period is sufficiently long for the first
+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
-unbuffered input. For a device such as a keyboard, input should be
+unbuffered input. For a device such as a keyboard, input should be
@dfn{available} if a key has already been typed, whereas for a disk
-file, input should always be available except at end of file. For a file
+file, input should always be available except at end of file. For a file
associated with a keyboard-like device, any line-editing features of the
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,
then it should also allow the main subprogram to be written in that
-language. It should support some mechanism for invoking the elaboration
+language. It should support some mechanism for invoking the elaboration
of the Ada library units included in the system, and for invoking the
-finalization of the environment task. On typical systems, the
+finalization of the environment task. On typical systems, the
recommended mechanism is to provide two subprograms whose link names are
-@code{adainit} and @code{adafinal}. @code{adainit} should contain the
-elaboration code for library units. @code{adafinal} should contain the
-finalization code. These subprograms should have no effect the second
+@code{adainit} and @code{adafinal}. @code{adainit} should contain the
+elaboration code for library units. @code{adafinal} should contain the
+finalization code. These subprograms should have no effect the second
and subsequent time they are called.
@end cartouche
-Followed.
+Followed.
@sp 1
@cartouche
Automatic elaboration of pre-elaborated packages should be
-provided when pragma Export is supported.
+provided when pragma @code{Export} is supported.
@end cartouche
-Followed when the main program is in Ada. If the main program is in a
+Followed when the main program is in Ada. If the main program is in a
foreign language, then
@code{adainit} must be called to elaborate pre-elaborated
packages.
implementation should support @code{Import} and @code{Export} pragmas
for objects of @var{L}-compatible types and for subprograms, and pragma
@code{Convention} for @var{L}-eligible types and for subprograms,
-presuming the other language has corresponding features. Pragma
+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
-child package of package Interfaces with the corresponding name. This
+child package of package Interfaces with the corresponding name. This
package should contain any declarations that would be useful for
interfacing to the language (implementation) represented by the
-convention. Any declarations useful for interfacing to any language on
+convention. Any declarations useful for interfacing to any language on
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
+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
An Ada access @var{T} parameter, or an Ada @code{out} or @code{in out}
parameter of an elementary 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}. In the case of an elementary @code{out} or
+the Ada type @var{T}. In the case of an elementary @code{out} or
@code{in out} parameter, a pointer to a temporary copy is used to
preserve by-copy semantics.
@end cartouche
-Followed.
+Followed.
@sp 1
@cartouche
@code{@var{t}*} argument to a C function, where @var{t} is the C
structure corresponding to the Ada type @var{T}.
@end cartouche
-Followed. This convention may be overridden by the use of the C_Pass_By_Copy
+Followed. This convention may be overridden by the use of the C_Pass_By_Copy
pragma, or Convention, or by explicitly specifying the mechanism for a given
call using an extended import or export pragma.
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
@sp 1
@cartouche
-An Ada access @var{T} parameter is passed as a ``BY REFERENCE'' data item of
+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 ``BY CONTENT'' data item of
+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
-Any other Ada parameter is passed as a ``BY REFERENCE'' data item of the
+Any other Ada parameter is passed as a @samp{BY REFERENCE} data item of the
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
the Fortran type corresponding to the Ada type @var{T}, and where the
INTENT attribute of the corresponding dummy argument matches the Ada
formal parameter mode; the Fortran implementation's parameter passing
-conventions are used. For elementary types, a local copy is used if
+conventions are used. For elementary types, a local copy is used if
necessary to ensure by-copy semantics.
@end cartouche
Followed.
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
If an entity is exported to assembly language, then the implementation
should allocate it at an addressable location, and should ensure that it
is retained by the linking process, even if not otherwise referenced
-from the Ada code. The implementation should assume that any call to a
+from the Ada code. The implementation should assume that any call to a
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
efficiency and that are not otherwise available through the language
constructs.
@end cartouche
-Followed. A full set of machine operation intrinsic subprograms is provided.
+Followed. A full set of machine operation intrinsic subprograms is provided.
@sp 1
@cartouche
-Atomic read-modify-write operations -- e.g.@:, test and set, compare and
+Atomic read-modify-write operations---e.g.@:, test and set, compare and
swap, decrement and test, enqueue/dequeue.
@end cartouche
Followed on any target supporting such operations.
@sp 1
@cartouche
-Standard numeric functions -- e.g.@:, sin, log.
+Standard numeric functions---e.g.@:, sin, log.
@end cartouche
Followed on any target supporting such operations.
@sp 1
@cartouche
-String manipulation operations -- e.g.@:, translate and test.
+String manipulation operations---e.g.@:, translate and test.
@end cartouche
Followed on any target supporting such operations.
@sp 1
@cartouche
-Vector operations -- e.g.@:, compare vector against thresholds.
+Vector operations---e.g.@:, compare vector against thresholds.
@end cartouche
Followed on any target supporting such operations.
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
interrupts are to be blocked during protected actions, if the underlying
system allows for a finer-grain control of interrupt blocking.
@end cartouche
-Followed. The underlying system does not allow for finer-grain control
+Followed. The underlying system does not allow for finer-grain control
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
elaboration of entities not already covered by the Implementation
Requirements.
@end cartouche
-Followed. Executable code is generated in some cases, e.g.@: loops
+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
-time must be completely deterministic. For such implementations, it is
+time must be completely deterministic. For such implementations, it is
recommended that the storage for task attributes will be pre-allocated
-statically and not from the heap. This can be accomplished by either
+statically and not from the heap. This can be accomplished by either
placing restrictions on the number and the size of the task's
attributes, or by using the pre-allocated storage for the first @var{N}
-attribute objects, and the heap for the others. In the latter case,
+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
The implementation should use names that end with @samp{_Locking} for
locking policies defined by the implementation.
@end cartouche
-Followed. A single implementation-defined locking policy is defined,
+Followed. A single implementation-defined locking policy is defined,
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
It is recommended that the @dfn{best} time base which exists in
the underlying system be available to the application through
-@code{Clock}. @dfn{Best} may mean highest accuracy or largest range.
+@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. For information on GLADE, contact Ada Core Technologies.
+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@. For information on GLADE, contact Ada Core Technologies.
+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
of subtype @var{S} when @var{S}'Machine_Radix = 10.
@end cartouche
-Not followed. GNAT ignores @var{S}'Machine_Radix and always uses binary
+Not followed. GNAT ignores @var{S}'Machine_Radix and always uses binary
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 a real operand is that of the scaling of both components of
the former by the latter, an implementation should not perform this
operation by first promoting the real operand to complex type and then
-performing a full complex multiplication. In systems that, in the
+performing a full complex multiplication. In systems that, in the
future, support an Ada binding to IEC 559:1989, the latter technique
will not generate the required result when one of the components of the
-complex operand is infinite. (Explicit multiplication of the infinite
+complex operand is infinite. (Explicit multiplication of the infinite
component by the zero component obtained during promotion yields a NaN
that propagates into the final result.) Analogous advice applies in the
case of multiplication of a complex operand and a pure-imaginary
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
complex operand and a real operand is that the imaginary operand remains
unchanged, an implementation should not perform this operation by first
promoting the real operand to complex type and then performing a full
-complex addition. In implementations in which the @code{Signed_Zeros}
+complex addition. In implementations in which the @code{Signed_Zeros}
attribute of the component type is @code{True} (and which therefore
conform to IEC 559:1989 in regard to the handling of the sign of zero in
predefined arithmetic operations), the latter technique will not
generate the required result when the imaginary component of the complex
-operand is a negatively signed zero. (Explicit addition of the negative
+operand is a negatively signed zero. (Explicit addition of the negative
zero to the zero obtained during promotion yields a positive zero.)
Analogous advice applies in the case of addition of a complex operand
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
Implementations in which @code{Real'Signed_Zeros} is @code{True} should
attempt to provide a rational treatment of the signs of zero results and
-result components. As one example, the result of the @code{Argument}
+result components. As one example, the result of the @code{Argument}
function should have the sign of the imaginary component of the
parameter @code{X} when the point represented by that parameter lies on
the positive real axis; as another, the sign of the imaginary component
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
@code{True} should attempt to provide a rational treatment of the signs
-of zero results and result components. For example, many of the complex
+of zero results and result components. For example, many of the complex
elementary functions have components that are odd functions of one of
the parameter components; in these cases, the result component should
-have the sign of the parameter component at the origin. Other complex
+have the sign of the parameter component at the origin. Other complex
elementary functions have zero components whose sign is opposite that of
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
@code{Cycle} parameter should not be implemented by calling the
corresponding version with a @code{Cycle} parameter of
@code{2.0*Numerics.Pi}, since this will not provide the required
-accuracy in some portions of the domain. For the same reason, the
+accuracy in some portions of the domain. For the same reason, the
version of @code{Log} without a @code{Base} parameter should not be
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
-issues. In this chapter, you will find each point in annex M listed
+issues. In this chapter, you will find each point in annex M listed
followed by a description in italic font of how GNAT
@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
@cartouche
@noindent
@strong{2}. Whether or not each recommendation given in Implementation
-Advice is followed. See 1.1.2(37).
+Advice is followed. See 1.1.2(37).
@end cartouche
@noindent
@xref{Implementation Advice}.
@sp 1
@cartouche
@noindent
-@strong{3}. Capacity limitations of the implementation. See 1.1.3(3).
+@strong{3}. Capacity limitations of the implementation. See 1.1.3(3).
@end cartouche
@noindent
The complexity of programs that can be processed is limited only by the
@cartouche
@noindent
@strong{4}. Variations from the standard that are impractical to avoid
-given the implementation's execution environment. See 1.1.3(6).
+given the implementation's execution environment. See 1.1.3(6).
@end cartouche
@noindent
There are no variations from the standard.
@cartouche
@noindent
@strong{5}. Which @code{code_statement}s cause external
-interactions. See 1.1.3(10).
+interactions. See 1.1.3(10).
@end cartouche
@noindent
Any @code{code_statement} can potentially cause external interactions.
@cartouche
@noindent
@strong{6}. The coded representation for the text of an Ada
-program. See 2.1(4).
+program. See 2.1(4).
@end cartouche
@noindent
See separate section on source representation.
@sp 1
@cartouche
@noindent
-@strong{7}. The control functions allowed in comments. See 2.1(14).
+@strong{7}. The control functions allowed in comments. See 2.1(14).
@end cartouche
@noindent
See separate section on source representation.
@sp 1
@cartouche
@noindent
-@strong{8}. The representation for an end of line. See 2.2(2).
+@strong{8}. The representation for an end of line. See 2.2(2).
@end cartouche
@noindent
See separate section on source representation.
@cartouche
@noindent
@strong{9}. Maximum supported line length and lexical element
-length. See 2.2(15).
+length. See 2.2(15).
@end cartouche
@noindent
The maximum line length is 255 characters an the maximum length of a
@sp 1
@cartouche
@noindent
-@strong{10}. Implementation defined pragmas. See 2.8(14).
+@strong{10}. Implementation defined pragmas. See 2.8(14).
@end cartouche
@noindent
@sp 1
@cartouche
@noindent
-@strong{11}. Effect of pragma @code{Optimize}. See 2.8(27).
+@strong{11}. Effect of pragma @code{Optimize}. See 2.8(27).
@end cartouche
@noindent
Pragma @code{Optimize}, if given with a @code{Time} or @code{Space}
@noindent
@strong{12}. The sequence of characters of the value returned by
@code{@var{S}'Image} when some of the graphic characters of
-@code{@var{S}'Wide_Image} are not defined in @code{Character}. See
+@code{@var{S}'Wide_Image} are not defined in @code{Character}. See
3.5(37).
@end cartouche
@noindent
The sequence of characters is as defined by the wide character encoding
-method used for the source. See section on source representation for
+method used for the source. See section on source representation for
further details.
@sp 1
@cartouche
@noindent
@strong{13}. The predefined integer types declared in
-@code{Standard}. See 3.5.4(25).
+@code{Standard}. See 3.5.4(25).
@end cartouche
@noindent
@table @code
@cartouche
@noindent
@strong{14}. Any nonstandard integer types and the operators defined
-for them. See 3.5.4(26).
+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
@noindent
@strong{15}. Any nonstandard real types and the operators defined for
-them. See 3.5.6(8).
+them. See 3.5.6(8).
@end cartouche
@noindent
-There are no nonstandard real types.
+There are no nonstandard real types.
@sp 1
@cartouche
@noindent
@strong{16}. What combinations of requested decimal precision and range
-are supported for floating point types. See 3.5.7(7).
+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
@noindent
@strong{17}. The predefined floating point types declared in
-@code{Standard}. See 3.5.7(16).
+@code{Standard}. See 3.5.7(16).
@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
@sp 1
@cartouche
@noindent
-@strong{18}. The small of an ordinary fixed point type. See 3.5.9(8).
+@strong{18}. The small of an ordinary fixed point type. See 3.5.9(8).
@end cartouche
@noindent
-@code{Fine_Delta} is 2**(-63)
+@code{Fine_Delta} is 2**(@minus{}63)
@sp 1
@cartouche
@noindent
@strong{19}. What combinations of small, range, and digits are
-supported for fixed point types. See 3.5.9(10).
+supported for fixed point types. See 3.5.9(10).
@end cartouche
@noindent
Any combinations are permitted that do not result in a small less than
@code{Fine_Delta} and do not result in a mantissa larger than 63 bits.
If the mantissa is larger than 53 bits on machines where Long_Long_Float
is 64 bits (true of all architectures except ia32), then the output from
-Text_IO is accurate to only 53 bits, rather than the full mantissa. This
+Text_IO is accurate to only 53 bits, rather than the full mantissa. This
is because floating-point conversions are used to convert fixed point.
@sp 1
@cartouche
@noindent
@strong{20}. The result of @code{Tags.Expanded_Name} for types declared
-within an unnamed @code{block_statement}. See 3.9(10).
+within an unnamed @code{block_statement}. See 3.9(10).
@end cartouche
@noindent
Block numbers of the form @code{B@var{nnn}}, where @var{nnn} is a
@sp 1
@cartouche
@noindent
-@strong{21}. Implementation-defined attributes. See 4.1.4(12).
+@strong{21}. Implementation-defined attributes. See 4.1.4(12).
@end cartouche
@noindent
@xref{Implementation Defined Attributes}.
@sp 1
@cartouche
@noindent
-@strong{22}. Any implementation-defined time types. See 9.6(6).
+@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
@strong{23}. The time base associated with relative delays.
@end cartouche
@noindent
-See 9.6(20). The time base used is that provided by the C library
+See 9.6(20). The time base used is that provided by the C library
function @code{gettimeofday}.
@sp 1
@cartouche
@noindent
-@strong{24}. The time base of the type @code{Calendar.Time}. See
+@strong{24}. The time base of the type @code{Calendar.Time}. See
9.6(23).
@end cartouche
@noindent
@cartouche
@noindent
@strong{25}. The time zone used for package @code{Calendar}
-operations. See 9.6(24).
+operations. See 9.6(24).
@end cartouche
@noindent
The time zone used by package @code{Calendar} is the current system time zone
@cartouche
@noindent
@strong{26}. Any limit on @code{delay_until_statements} of
-@code{select_statements}. See 9.6(29).
+@code{select_statements}. See 9.6(29).
@end cartouche
@noindent
-There are no such limits.
+There are no such limits.
@sp 1
@cartouche
@noindent
@strong{27}. Whether or not two non overlapping parts of a composite
object are independently addressable, in the case where packing, record
-layout, or @code{Component_Size} is specified for the object. See
+layout, or @code{Component_Size} is specified for the object. See
9.10(1).
@end cartouche
@noindent
@sp 1
@cartouche
@noindent
-@strong{28}. The representation for a compilation. See 10.1(2).
+@strong{28}. The representation for a compilation. See 10.1(2).
@end cartouche
@noindent
A compilation is represented by a sequence of files presented to the
-compiler in a single invocation of the @file{gcc} command.
+compiler in a single invocation of the @code{gcc} command.
@sp 1
@cartouche
@noindent
@strong{29}. Any restrictions on compilations that contain multiple
-compilation_units. See 10.1(4).
+compilation_units. See 10.1(4).
@end cartouche
@noindent
No single file can contain more than one compilation unit, but any
@cartouche
@noindent
@strong{30}. The mechanisms for creating an environment and for adding
-and replacing compilation units. See 10.1.4(3).
+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
@noindent
@strong{31}. The manner of explicitly assigning library units to a
-partition. See 10.2(2).
+partition. See 10.2(2).
@end cartouche
@noindent
If a unit contains an Ada main program, then the Ada units for the partition
are determined by recursive application of the rules in the Ada Reference
-Manual section 10.2(2-6). In other words, the Ada units will be those that
+Manual section 10.2(2-6). In other words, the Ada units will be those that
are needed by the main program, and then this definition of need is applied
recursively to those units, and the partition contains the transitive
-closure determined by this relationship. In short, all the necessary units
-are included, with no need to explicitly specify the list. If additional
+closure determined by this relationship. In short, all the necessary units
+are included, with no need to explicitly specify the list. If additional
units are required, e.g.@: by foreign language units, then all units must be
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 -z and -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 User 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
@noindent
@strong{32}. The implementation-defined means, if any, of specifying
-which compilation units are needed by a given compilation unit. See
+which compilation units are needed by a given compilation unit. See
10.2(2).
@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.
@cartouche
@noindent
@strong{33}. The manner of designating the main subprogram of a
-partition. See 10.2(7).
+partition. See 10.2(7).
@end cartouche
@noindent
The main program is designated by providing the name of the
-corresponding ali file as the input parameter to the binder.
+corresponding @file{ALI} file as the input parameter to the binder.
@sp 1
@cartouche
@noindent
-@strong{34}. The order of elaboration of @code{library_items}. See
+@strong{34}. The order of elaboration of @code{library_items}. See
10.2(18).
@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
@cartouche
@noindent
@strong{35}. Parameter passing and function return for the main
-subprogram. See 10.2(21).
+subprogram. See 10.2(21).
@end cartouche
@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.
+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 (overriding any value that
+may have been set by a call to @code{Ada.Command_Line.Set_Exit_Status}).
@sp 1
@cartouche
@noindent
-@strong{36}. The mechanisms for building and running partitions. See
+@strong{36}. The mechanisms for building and running partitions. See
10.2(24).
@end cartouche
@noindent
-GNAT itself supports programs with only a single partition. The GNATDIST
+GNAT itself supports programs with only a single partition. The GNATDIST
tool provided with the GLADE package (which also includes an implementation
of the PCS) provides a completely flexible method for building and running
-programs consisting of multiple partitions. See the separate GLADE manual
+programs consisting of multiple partitions. See the separate GLADE manual
for details.
@sp 1
@cartouche
@noindent
@strong{37}. The details of program execution, including program
-termination. See 10.2(25).
+termination. See 10.2(25).
@end cartouche
@noindent
See separate section on compilation model.
@cartouche
@noindent
@strong{38}. The semantics of any non-active partitions supported by the
-implementation. See 10.2(28).
+implementation. See 10.2(28).
@end cartouche
@noindent
Passive partitions are supported on targets where shared memory is
-provided by the operating system. See the GLADE reference manual for
+provided by the operating system. See the GLADE reference manual for
further details.
@sp 1
@cartouche
@noindent
-@strong{39}. The information returned by @code{Exception_Message}. See
+@strong{39}. The information returned by @code{Exception_Message}. See
11.4.1(10).
@end cartouche
@noindent
@cartouche
@noindent
@strong{40}. The result of @code{Exceptions.Exception_Name} for types
-declared within an unnamed @code{block_statement}. See 11.4.1(12).
+declared within an unnamed @code{block_statement}. See 11.4.1(12).
@end cartouche
@noindent
Blocks have implementation defined names of the form @code{B@var{nnn}}
@cartouche
@noindent
@strong{41}. The information returned by
-@code{Exception_Information}. See 11.4.1(13).
+@code{Exception_Information}. See 11.4.1(13).
@end cartouche
@noindent
-@code{Exception_Information} contains the expanded name of the exception
-in upper case, and no other information.
+@code{Exception_Information} returns a string in the following format:
+
+@smallexample
+@emph{Exception_Name:} nnnnn
+@emph{Message:} mmmmm
+@emph{PID:} ppp
+@emph{Call stack traceback locations:}
+0xhhhh 0xhhhh 0xhhhh ... 0xhhh
+@end smallexample
+
+@noindent
+where
+
+@itemize @bullet
+@item
+@code{nnnn} is the fully qualified name of the exception in all upper
+case letters. This line is always present.
+
+@item
+@code{mmmm} is the message (this line present only if message is non-null)
+
+@item
+@code{ppp} is the Process Id value as a decimal integer (this line is
+present only if the Process Id is nonzero). Currently we are
+not making use of this field.
+
+@item
+The Call stack traceback locations line and the following values
+are present only if at least one traceback location was recorded.
+The values are given in C style format, with lower case letters
+for a-f, and only as many digits present as are necessary.
+@end itemize
+
+@noindent
+The line terminator sequence at the end of each line, including
+the last line is a single @code{LF} character (@code{16#0A#}).
@sp 1
@cartouche
@noindent
-@strong{42}. Implementation-defined check names. See 11.5(27).
+@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
@noindent
-@strong{43}. The interpretation of each aspect of representation. See
+@strong{43}. The interpretation of each aspect of representation. See
13.1(20).
@end cartouche
@noindent
@sp 1
@cartouche
@noindent
-@strong{44}. Any restrictions placed upon representation items. See
+@strong{44}. Any restrictions placed upon representation items. See
13.1(20).
@end cartouche
@noindent
@sp 1
@cartouche
@noindent
-@strong{45}. The meaning of @code{Size} for indefinite subtypes. See
+@strong{45}. The meaning of @code{Size} for indefinite subtypes. See
13.3(48).
@end cartouche
@noindent
@sp 1
@cartouche
@noindent
-@strong{46}. The default external representation for a type tag. See
+@strong{46}. The default external representation for a type tag. See
13.3(75).
@end cartouche
@noindent
@cartouche
@noindent
@strong{47}. What determines whether a compilation unit is the same in
-two different partitions. See 13.3(76).
+two different partitions. See 13.3(76).
@end cartouche
@noindent
A compilation unit is the same in two different partitions if and only
@sp 1
@cartouche
@noindent
-@strong{48}. Implementation-defined components. See 13.5.1(15).
+@strong{48}. Implementation-defined components. See 13.5.1(15).
@end cartouche
@noindent
The only implementation defined component is the tag for a tagged type,
@cartouche
@noindent
@strong{49}. If @code{Word_Size} = @code{Storage_Unit}, the default bit
-ordering. See 13.5.3(5).
+ordering. See 13.5.3(5).
@end cartouche
@noindent
@code{Word_Size} (32) is not the same as @code{Storage_Unit} (8) for this
-implementation, so no non-default bit ordering is supported. The default
+implementation, so no non-default bit ordering is supported. The default
bit ordering corresponds to the natural endianness of the target architecture.
@sp 1
@cartouche
@noindent
@strong{50}. The contents of the visible part of package @code{System}
-and its language-defined children. See 13.7(2).
+and its language-defined children. See 13.7(2).
@end cartouche
@noindent
See the definition of these packages in files @file{system.ads} and
@noindent
@strong{51}. The contents of the visible part of package
@code{System.Machine_Code}, and the meaning of
-@code{code_statements}. See 13.8(7).
+@code{code_statements}. See 13.8(7).
@end cartouche
@noindent
See the definition and documentation in file @file{s-maccod.ads}.
@sp 1
@cartouche
@noindent
-@strong{52}. The effect of unchecked conversion. See 13.9(11).
+@strong{52}. The effect of unchecked conversion. See 13.9(11).
@end cartouche
@noindent
Unchecked conversion between types of the same size
-and 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
+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.
For all non-discrete types, the source is first copied if necessary
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
@noindent
@strong{53}. The manner of choosing a storage pool for an access type
-when @code{Storage_Pool} is not specified for the type. See 13.11(17).
+when @code{Storage_Pool} is not specified for the type. See 13.11(17).
@end cartouche
@noindent
There are 3 different standard pools used by the compiler when
@code{Storage_Pool} is not specified depending whether the type is local
to a subprogram or defined at the library level and whether
-@code{Storage_Size}is specified or not. See documentation in the runtime
+@code{Storage_Size}is specified or not. See documentation in the runtime
library units @code{System.Pool_Global}, @code{System.Pool_Size} and
@code{System.Pool_Local} in files @file{s-poosiz.ads},
@file{s-pooglo.ads} and @file{s-pooloc.ads} for full details on the
@cartouche
@noindent
@strong{54}. Whether or not the implementation provides user-accessible
-names for the standard pool type(s). See 13.11(17).
+names for the standard pool type(s). See 13.11(17).
@end cartouche
@noindent
See documentation in the sources of the run time mentioned in paragraph
-@strong{53} . All these pools are accessible by means of @code{with}'ing
+@strong{53} . All these pools are accessible by means of @code{with}'ing
these units.
@sp 1
@cartouche
@noindent
-@strong{55}. The meaning of @code{Storage_Size}. See 13.11(18).
+@strong{55}. The meaning of @code{Storage_Size}. See 13.11(18).
@end cartouche
@noindent
@code{Storage_Size} is measured in storage units, and refers to the
@sp 1
@cartouche
@noindent
-@strong{56}. Implementation-defined aspects of storage pools. See
+@strong{56}. Implementation-defined aspects of storage pools. See
13.11(22).
@end cartouche
@noindent
@cartouche
@noindent
@strong{57}. The set of restrictions allowed in a pragma
-@code{Restrictions}. See 13.12(7).
+@code{Restrictions}. See 13.12(7).
@end cartouche
@noindent
-All RM defined Restriction identifiers are implemented. The following
-additional restriction identifiers are provided. There are two separate
-lists of implementation dependent restriction identifiers. The first
+All RM defined Restriction identifiers are implemented. The following
+additional restriction identifiers are provided. There are two separate
+lists of implementation dependent restriction identifiers. The first
set requires consistency throughout a partition (in other words, if the
restriction identifier is used for any compilation unit in the partition,
then all compilation units in the partition must obey the restriction.
@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 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
-at any one time, and so no queue is required. This restriction is not
-checked at compile time. A program execution is erroneous if an attempt
+at any one time, and so no queue is required. This restriction is not
+checked at compile time. A program execution is erroneous if an attempt
is made to queue more than the specified number of tasks on such an entry.
@item No_Calendar
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_Entry_Calls_In_Elaboration_Code
@findex No_Entry_Calls_In_Elaboration_Code
This restriction ensures at compile time that no task or protected entry
-calls are made during elaboration code. As a result of the use of this
+calls are made during elaboration code. As a result of the use of this
restriction, the compiler can assume that no code past an accept statement
in a task can be executed at elaboration time.
@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 GNORT Reference Manual.
+@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
This restriction ensures at compile time that there are no allocator
expressions that attempt to allocate protected objects.
+@item No_Secondary_Stack
+@findex No_Secondary_Stack
+This restriction ensures at compile time that the generated code does not
+contain any reference to the secondary stack. The secondary stack is used
+to implement functions returning unconstrained objects (arrays or records)
+on some targets.
+
@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 Ravenscar).
+profile for limited tasking (see also pragma @code{Profile (Ravenscar)}).
@item No_Standard_Storage_Pools
@findex No_Standard_Storage_Pools
This restriction ensures at compile time that no access types
-use the standard default storage pool. Any access type declared must
+use the standard default storage pool. Any access type declared must
have an explicit Storage_Pool attribute defined specifying a
user-defined storage pool.
@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}.
This restriction ensures at compile time that no terminate alternatives
appear in any task body.
-@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 No_Tasking
+@findex No_Tasking
+This restriction prevents the declaration of tasks or task types throughout
+the partition. It is similar in effect to the use of @code{Max_Tasks => 0}
+except that violations are caught at compile time and cause an error message
+to be output either by the compiler or binder.
@item Static_Priorities
@findex Static_Priorities
@item No_Elaboration_Code
@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 Preelaborate. There are cases in which pragma 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 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
+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). 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
the scope of the restriction has at most one task waiting on the entry
-at any one time, and so no queue is required. This restriction is not
-checked at compile time. A program execution is erroneous if an attempt
+at any one time, and so no queue is required. This restriction is not
+checked at compile time. A program execution is erroneous if an attempt
is made to queue a second task on such an entry.
@item No_Implementation_Attributes
@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 present. With this restriction, the only attributes that can be used
+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 present. With this restriction, the only pragmas that can be used
+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.
+are present. With this restriction, the only other restriction identifiers
+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
@cartouche
@noindent
@strong{58}. The consequences of violating limitations on
-@code{Restrictions} pragmas. See 13.12(9).
+@code{Restrictions} pragmas. See 13.12(9).
@end cartouche
@noindent
Restrictions that can be checked at compile time result in illegalities
-if violated. Currently there are no other consequences of violating
+if violated. Currently there are no other consequences of violating
restrictions.
@sp 1
@noindent
@strong{59}. The representation used by the @code{Read} and
@code{Write} attributes of elementary types in terms of stream
-elements. See 13.13.2(9).
+elements. See 13.13.2(9).
@end cartouche
@noindent
The representation is the in-memory representation of the base type of
@cartouche
@noindent
@strong{60}. The names and characteristics of the numeric subtypes
-declared in the visible part of package @code{Standard}. See A.1(3).
+declared in the visible part of package @code{Standard}. See A.1(3).
@end cartouche
@noindent
See items describing the integer and floating-point types supported.
@cartouche
@noindent
@strong{61}. The accuracy actually achieved by the elementary
-functions. See A.5.1(1).
+functions. See A.5.1(1).
@end cartouche
@noindent
The elementary functions correspond to the functions available in the C
-library. Only fast math mode is implemented.
+library. Only fast math mode is implemented.
@sp 1
@cartouche
@noindent
@strong{62}. The sign of a zero result from some of the operators or
functions in @code{Numerics.Generic_Elementary_Functions}, when
-@code{Float_Type'Signed_Zeros} is @code{True}. See A.5.1(46).
+@code{Float_Type'Signed_Zeros} is @code{True}. See A.5.1(46).
@end cartouche
@noindent
The sign of zeroes follows the requirements of the IEEE 754 standard on
@cartouche
@noindent
@strong{63}. The value of
-@code{Numerics.Float_Random.Max_Image_Width}. See A.5.2(27).
+@code{Numerics.Float_Random.Max_Image_Width}. See A.5.2(27).
@end cartouche
@noindent
Maximum image width is 649, see library file @file{a-numran.ads}.
@cartouche
@noindent
@strong{64}. The value of
-@code{Numerics.Discrete_Random.Max_Image_Width}. See A.5.2(27).
+@code{Numerics.Discrete_Random.Max_Image_Width}. See A.5.2(27).
@end cartouche
@noindent
Maximum image width is 80, see library file @file{a-nudira.ads}.
@sp 1
@cartouche
@noindent
-@strong{65}. The algorithms for random number generation. See
+@strong{65}. The algorithms for random number generation. See
A.5.2(32).
@end cartouche
@noindent
@cartouche
@noindent
@strong{66}. The string representation of a random number generator's
-state. See A.5.2(38).
+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
@noindent
@strong{67}. The minimum time interval between calls to the
time-dependent Reset procedure that are guaranteed to initiate different
-random number sequences. See A.5.2(45).
+random number sequences. See A.5.2(45).
@end cartouche
@noindent
The minimum period between reset calls to guarantee distinct series of
@strong{68}. The values of the @code{Model_Mantissa},
@code{Model_Emin}, @code{Model_Epsilon}, @code{Model},
@code{Safe_First}, and @code{Safe_Last} attributes, if the Numerics
-Annex is not supported. See A.5.3(72).
+Annex is not supported. See A.5.3(72).
@end cartouche
@noindent
See the source file @file{ttypef.ads} for the values of all numeric
@cartouche
@noindent
@strong{69}. Any implementation-defined characteristics of the
-input-output packages. See A.7(14).
+input-output packages. See A.7(14).
@end cartouche
@noindent
There are no special implementation defined characteristics for these
@sp 1
@cartouche
@noindent
-@strong{70}. The value of @code{Buffer_Size} in @code{Storage_IO}. See
+@strong{70}. The value of @code{Buffer_Size} in @code{Storage_IO}. See
A.9(10).
@end cartouche
@noindent
@end cartouche
@noindent
These files are mapped onto the files provided by the C streams
-libraries. See source file @file{i-cstrea.ads} for further details.
+libraries. See source file @file{i-cstrea.ads} for further details.
@sp 1
@cartouche
@noindent
-@strong{72}. The accuracy of the value produced by @code{Put}. See
+@strong{72}. The accuracy of the value produced by @code{Put}. See
A.10.9(36).
@end cartouche
@noindent
@cartouche
@noindent
@strong{73}. The meaning of @code{Argument_Count}, @code{Argument}, and
-@code{Command_Name}. See A.15(1).
+@code{Command_Name}. See A.15(1).
@end cartouche
@noindent
These are mapped onto the @code{argv} and @code{argc} parameters of the
@sp 1
@cartouche
@noindent
-@strong{74}. Implementation-defined convention names. See B.1(11).
+@strong{74}. Implementation-defined convention names. See B.1(11).
@end cartouche
@noindent
The following convention names are supported
@table @code
@item Ada
Ada
-@item Asm
-Assembly language
-@item Assembler
-Assembly language
+@item Assembler
+Assembly language
+@item Asm
+Synonym for Assembler
+@item Assembly
+Synonym for Assembler
@item C
C
@item C_Pass_By_Copy
-Treated like C, except for record types
-@item COBOL
-COBOL
-@item CPP
-C++
+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 C_Plus_Plus (or CPP)
+C++
@item Default
Treated the same as C
-@item DLL
-DLL (used for Windows implementations only) is handled like the Stdcall
-convention. This convention is used to access variables and functions
-(with Stdcall convention) in a DLL@.
-@item Win32
-Win32 (used for Windows implementations only) is handled like the Stdcall
-convention. This convention is used to access variables and functions
-(with Stdcall convention) in a DLL@.
@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
-Stdcall (used for Windows implementations only). This convention correspond
+@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 clean the stack before exit.
+Windows. A function with this convention cleans the stack before exit.
+@item DLL
+Synonym for Stdcall
+@item Win32
+Synonym for Stdcall
@item Stubbed
Stubbed is a special convention used to indicate that the body of the
-subprogram will be entirely ignored. Any call to the subprogram
-is converted into a raise of the @code{Program_Error} exception. If a
+subprogram will be entirely ignored. Any call to the subprogram
+is converted into a raise of the @code{Program_Error} exception. If a
pragma @code{Import} specifies convention @code{stubbed} then no body need
-be present at all. This convention is useful during development for the
+be present at all. This convention is useful during development for the
inclusion of subprograms whose body has not yet been written.
@end table
@noindent
In addition, all otherwise unrecognized convention names are also
-treated as being synonymous with convention C@. In all implementations
-except for VMS, use of such other names results in a warning. In VMS
+treated as being synonymous with convention C@. In all implementations
+except for VMS, use of such other names results in a warning. In VMS
implementations, these names are accepted silently.
@sp 1
@cartouche
@noindent
-@strong{75}. The meaning of link names. See B.1(36).
+@strong{75}. The meaning of link names. See B.1(36).
@end cartouche
@noindent
Link names are the actual names used by the linker.
@cartouche
@noindent
@strong{76}. The manner of choosing link names when neither the link
-name nor the address of an imported or exported entity is specified. See
+name nor the address of an imported or exported entity is specified. See
B.1(36).
@end cartouche
@noindent
@sp 1
@cartouche
@noindent
-@strong{77}. The effect of pragma @code{Linker_Options}. See B.1(37).
+@strong{77}. The effect of pragma @code{Linker_Options}. See B.1(37).
@end cartouche
@noindent
The string passed to @code{Linker_Options} is presented uninterpreted as
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
@noindent
-causes two separate arguments "-labc" and "-ldef" to be passed to the
-linker with a guarantee that the order is preserved (no such guarantee
-exists for the use of separate Linker_Options pragmas).
-
-In addition, GNAT allow multiple arguments to @code{Linker_Options}
-with exactly the same meaning, so the above pragma could also be
-written as:
-
-@smallexample
-pragma Linker_Options ("-labc", "-ldef");
-@end smallexample
-
-@noindent
-The above multiple argument form is a GNAT extension.
+causes two separate arguments @code{-labc} and @code{-ldef} to be passed to the
+linker. The order of linker options is preserved for a given unit. The final
+list of options passed to the linker is in reverse order of the elaboration
+order. For example, linker options fo a body always appear before the options
+from the corresponding package spec.
@sp 1
@cartouche
@noindent
@strong{78}. The contents of the visible part of package
-@code{Interfaces} and its language-defined descendants. See B.2(1).
+@code{Interfaces} and its language-defined descendants. See B.2(1).
@end cartouche
@noindent
See files with prefix @file{i-} in the distributed library.
@cartouche
@noindent
@strong{79}. Implementation-defined children of package
-@code{Interfaces}. The contents of the visible part of package
-@code{Interfaces}. See B.2(11).
+@code{Interfaces}. The contents of the visible part of package
+@code{Interfaces}. See B.2(11).
@end cartouche
@noindent
See files with prefix @file{i-} in the distributed library.
@code{Binary}, @code{Long_Binary}, @code{Decimal_ Element}, and
@code{COBOL_Character}; and the initialization of the variables
@code{Ada_To_COBOL} and @code{COBOL_To_Ada}, in
-@code{Interfaces.COBOL}. See B.4(50).
+@code{Interfaces.COBOL}. See B.4(50).
@end cartouche
@noindent
@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
@cartouche
@noindent
-@strong{81}. Support for access to machine instructions. See C.1(1).
+@strong{81}. Support for access to machine instructions. See C.1(1).
@end cartouche
@noindent
See documentation in file @file{s-maccod.ads} in the distributed library.
@cartouche
@noindent
@strong{82}. Implementation-defined aspects of access to machine
-operations. See C.1(9).
+operations. See C.1(9).
@end cartouche
@noindent
See documentation in file @file{s-maccod.ads} in the distributed library.
@sp 1
@cartouche
@noindent
-@strong{83}. Implementation-defined aspects of interrupts. See C.3(2).
+@strong{83}. Implementation-defined aspects of interrupts. See C.3(2).
@end cartouche
@noindent
-Interrupts are mapped to signals or conditions as appropriate. See
+Interrupts are mapped to signals or conditions as appropriate. See
definition of unit
@code{Ada.Interrupt_Names} in source file @file{a-intnam.ads} for details
on the interrupts supported on a particular target.
@sp 1
@cartouche
@noindent
-@strong{84}. Implementation-defined aspects of pre-elaboration. See
+@strong{84}. Implementation-defined aspects of pre-elaboration. See
C.4(13).
@end cartouche
@noindent
@sp 1
@cartouche
@noindent
-@strong{85}. The semantics of pragma @code{Discard_Names}. See C.5(7).
+@strong{85}. The semantics of pragma @code{Discard_Names}. See C.5(7).
@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.
@cartouche
@noindent
@strong{86}. The result of the @code{Task_Identification.Image}
-attribute. See C.7.1(7).
+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
@strong{87}. The value of @code{Current_Task} when in a protected entry
-or interrupt handler. See C.7.1(17).
+or interrupt handler. See C.7.1(17).
@end cartouche
@noindent
Protected entries or interrupt handlers can be executed by any
@cartouche
@noindent
@strong{88}. The effect of calling @code{Current_Task} from an entry
-body or interrupt handler. See C.7.1(19).
+body or interrupt handler. See C.7.1(19).
@end cartouche
@noindent
The effect of calling @code{Current_Task} from an entry body or
@cartouche
@noindent
@strong{89}. Implementation-defined aspects of
-@code{Task_Attributes}. See C.7.2(19).
+@code{Task_Attributes}. See C.7.2(19).
@end cartouche
@noindent
There are no implementation-defined aspects of @code{Task_Attributes}.
@sp 1
@cartouche
@noindent
-@strong{90}. Values of all @code{Metrics}. See D(2).
+@strong{90}. Values of all @code{Metrics}. See D(2).
@end cartouche
@noindent
The metrics information for GNAT depends on the performance of the
-underlying operating system. The sources of the run-time for tasking
+underlying operating system. The sources of the run-time for tasking
implementation, together with the output from @code{-gnatG} can be
used to determine the exact sequence of operating systems calls made
-to implement various tasking constructs. Together with appropriate
+to implement various tasking constructs. Together with appropriate
information on the performance of the underlying operating system,
on the exact target in use, this information can be used to determine
the required metrics.
@cartouche
@noindent
@strong{91}. The declarations of @code{Any_Priority} and
-@code{Priority}. See D.1(11).
+@code{Priority}. See D.1(11).
@end cartouche
@noindent
See declarations in file @file{system.ads}.
@sp 1
@cartouche
@noindent
-@strong{92}. Implementation-defined execution resources. See D.1(15).
+@strong{92}. Implementation-defined execution resources. See D.1(15).
@end cartouche
@noindent
There are no implementation-defined execution resources.
@cartouche
@noindent
@strong{93}. Whether, on a multiprocessor, a task that is waiting for
-access to a protected object keeps its processor busy. See D.2.1(3).
+access to a protected object keeps its processor busy. See D.2.1(3).
@end cartouche
@noindent
On a multi-processor, a task that is waiting for access to a protected
@cartouche
@noindent
@strong{94}. The affect of implementation defined execution resources
-on task dispatching. See D.2.1(9).
+on task dispatching. See D.2.1(9).
@end cartouche
@noindent
@c SGI info
Tasks map to IRIX threads, and the dispatching policy is as defined by
the IRIX implementation of threads.
@end ignore
-Tasks map to threads in the threads package used by GNAT@. Where possible
+Tasks map to threads in the threads package used by GNAT@. Where possible
and appropriate, these threads correspond to native threads of the
underlying operating system.
@cartouche
@noindent
@strong{95}. Implementation-defined @code{policy_identifiers} allowed
-in a pragma @code{Task_Dispatching_Policy}. See D.2.2(3).
+in a pragma @code{Task_Dispatching_Policy}. See D.2.2(3).
@end cartouche
@noindent
There are no implementation-defined policy-identifiers allowed in this
@sp 1
@cartouche
@noindent
-@strong{96}. Implementation-defined aspects of priority inversion. See
+@strong{96}. Implementation-defined aspects of priority inversion. See
D.2.2(16).
@end cartouche
@noindent
@sp 1
@cartouche
@noindent
-@strong{97}. Implementation defined task dispatching. See D.2.2(18).
+@strong{97}. Implementation defined task dispatching. See D.2.2(18).
@end cartouche
@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.
@cartouche
@noindent
@strong{98}. Implementation-defined @code{policy_identifiers} allowed
-in a pragma @code{Locking_Policy}. See D.3(4).
+in a pragma @code{Locking_Policy}. See D.3(4).
@end cartouche
@noindent
The only implementation defined policy permitted in GNAT is
-@code{Inheritance_Locking}. On targets that support this policy, locking
+@code{Inheritance_Locking}. On targets that support this policy, locking
is implemented by inheritance, i.e.@: the task owning the lock operates
at a priority equal to the highest priority of any task currently
requesting the lock.
@sp 1
@cartouche
@noindent
-@strong{99}. Default ceiling priorities. See D.3(10).
+@strong{99}. Default ceiling priorities. See D.3(10).
@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
@cartouche
@noindent
@strong{100}. The ceiling of any protected object used internally by
-the implementation. See D.3(16).
+the implementation. See D.3(16).
@end cartouche
@noindent
The ceiling priority of internal protected objects is
@sp 1
@cartouche
@noindent
-@strong{101}. Implementation-defined queuing policies. See D.4(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
@noindent
@strong{102}. On a multiprocessor, any conditions that cause the
completion of an aborted construct to be delayed later than what is
-specified for a single processor. See D.6(3).
+specified for a single processor. See D.6(3).
@end cartouche
@noindent
The semantics for abort on a multi-processor is the same as on a single
@cartouche
@noindent
@strong{103}. Any operations that implicitly require heap storage
-allocation. See D.7(8).
+allocation. See D.7(8).
@end cartouche
@noindent
The only operation that implicitly requires heap storage allocation is
@cartouche
@noindent
@strong{104}. Implementation-defined aspects of pragma
-@code{Restrictions}. See D.7(20).
+@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
@noindent
@strong{105}. Implementation-defined aspects of package
-@code{Real_Time}. See D.8(17).
+@code{Real_Time}. See D.8(17).
@end cartouche
@noindent
There are no implementation defined aspects of package @code{Real_Time}.
@cartouche
@noindent
@strong{106}. Implementation-defined aspects of
-@code{delay_statements}. See D.9(8).
+@code{delay_statements}. See D.9(8).
@end cartouche
@noindent
Any difference greater than one microsecond will cause the task to be
@cartouche
@noindent
@strong{107}. The upper bound on the duration of interrupt blocking
-caused by the implementation. See D.12(5).
+caused by the implementation. See D.12(5).
@end cartouche
@noindent
-The upper bound is determined by the underlying operating system. In
+The upper bound is determined by the underlying operating system. In
no cases is it more than 10 milliseconds.
@sp 1
@cartouche
@noindent
@strong{108}. The means for creating and executing distributed
-programs. See E(5).
+programs. See E(5).
@end cartouche
@noindent
The GLADE package provides a utility GNATDIST for creating and executing
-distributed programs. See the GLADE reference manual for further details.
+distributed programs. See the GLADE reference manual for further details.
@sp 1
@cartouche
@noindent
@strong{109}. Any events that can result in a partition becoming
-inaccessible. See E.1(7).
+inaccessible. See E.1(7).
@end cartouche
@noindent
See the GLADE reference manual for full details on such events.
@cartouche
@noindent
@strong{110}. The scheduling policies, treatment of priorities, and
-management of shared resources between partitions in certain cases. See
+management of shared resources between partitions in certain cases. See
E.1(11).
@end cartouche
@noindent
@cartouche
@noindent
@strong{111}. Events that cause the version of a compilation unit to
-change. See E.3(5).
+change. See E.3(5).
@end cartouche
@noindent
Editing the source file of a compilation unit, or the source files of
any units on which it is dependent in a significant way cause the version
-to change. No other actions cause the version number to change. All changes
+to change. No other actions cause the version number to change. All changes
are significant except those which affect only layout, capitalization or
comments.
@cartouche
@noindent
@strong{112}. Whether the execution of the remote subprogram is
-immediately aborted as a result of cancellation. See E.4(13).
+immediately aborted as a result of cancellation. See E.4(13).
@end cartouche
@noindent
See the GLADE reference manual for details on the effect of abort in
@sp 1
@cartouche
@noindent
-@strong{113}. Implementation-defined aspects of the PCS@. See E.5(25).
+@strong{113}. Implementation-defined aspects of the PCS@. See E.5(25).
@end cartouche
@noindent
See the GLADE reference manual for a full description of all implementation
@sp 1
@cartouche
@noindent
-@strong{114}. Implementation-defined interfaces in the PCS@. See
+@strong{114}. Implementation-defined interfaces in the PCS@. See
E.5(26).
@end cartouche
@noindent
@cartouche
@noindent
@strong{115}. The values of named numbers in the package
-@code{Decimal}. See F.2(7).
+@code{Decimal}. See F.2(7).
@end cartouche
@noindent
@table @code
@cartouche
@noindent
@strong{116}. The value of @code{Max_Picture_Length} in the package
-@code{Text_IO.Editing}. See F.3.3(16).
+@code{Text_IO.Editing}. See F.3.3(16).
@end cartouche
@noindent
64
@cartouche
@noindent
@strong{117}. The value of @code{Max_Picture_Length} in the package
-@code{Wide_Text_IO.Editing}. See F.3.4(5).
+@code{Wide_Text_IO.Editing}. See F.3.4(5).
@end cartouche
@noindent
64
@cartouche
@noindent
@strong{118}. The accuracy actually achieved by the complex elementary
-functions and by other complex arithmetic operations. See G.1(1).
+functions and by other complex arithmetic operations. See G.1(1).
@end cartouche
@noindent
Standard library functions are used for the complex arithmetic
-operations. Only fast math mode is currently supported.
+operations. Only fast math mode is currently supported.
@sp 1
@cartouche
@noindent
@strong{119}. The sign of a zero result (or a component thereof) from
any operator or function in @code{Numerics.Generic_Complex_Types}, when
-@code{Real'Signed_Zeros} is True. See G.1.1(53).
+@code{Real'Signed_Zeros} is True. See G.1.1(53).
@end cartouche
@noindent
The signs of zero values are as recommended by the relevant
@strong{120}. The sign of a zero result (or a component thereof) from
any operator or function in
@code{Numerics.Generic_Complex_Elementary_Functions}, when
-@code{Real'Signed_Zeros} is @code{True}. See G.1.2(45).
+@code{Real'Signed_Zeros} is @code{True}. See G.1.2(45).
@end cartouche
@noindent
The signs of zero values are as recommended by the relevant
@cartouche
@noindent
@strong{121}. Whether the strict mode or the relaxed mode is the
-default. See G.2(2).
+default. See G.2(2).
@end cartouche
@noindent
-The strict mode is the default. There is no separate relaxed mode. GNAT
+The strict mode is the default. There is no separate relaxed mode. GNAT
provides a highly efficient implementation of strict mode.
@sp 1
@cartouche
@noindent
@strong{122}. The result interval in certain cases of fixed-to-float
-conversion. See G.2.1(10).
+conversion. See G.2.1(10).
@end cartouche
@noindent
For cases where the result interval is implementation dependent, the
@noindent
@strong{123}. The result of a floating point arithmetic operation in
overflow situations, when the @code{Machine_Overflows} attribute of the
-result type is @code{False}. See G.2.1(13).
+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
@strong{124}. The result interval for division (or exponentiation by a
negative exponent), when the floating point hardware implements division
-as multiplication by a reciprocal. See G.2.1(16).
+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
@noindent
@strong{125}. The definition of close result set, which determines the
-accuracy of certain fixed point multiplications and divisions. See
+accuracy of certain fixed point multiplications and divisions. See
G.2.3(5).
@end cartouche
@noindent
Operations in the close result set are performed using IEEE long format
-floating-point arithmetic. The input operands are converted to
+floating-point arithmetic. The input operands are converted to
floating-point, the operation is done in floating-point, and the result
is converted to the target type.
@noindent
@strong{126}. Conditions on a @code{universal_real} operand of a fixed
point multiplication or division for which the result shall be in the
-perfect result set. See G.2.3(22).
+perfect result set. See G.2.3(22).
@end cartouche
@noindent
The result is only defined to be in the perfect result set if the result
@noindent
@strong{127}. The result of a fixed point arithmetic operation in
overflow situations, when the @code{Machine_Overflows} attribute of the
-result type is @code{False}. See G.2.3(27).
+result type is @code{False}. See G.2.3(27).
@end cartouche
@noindent
Not relevant, @code{Machine_Overflows} is @code{True} for fixed-point
@noindent
@strong{128}. The result of an elementary function reference in
overflow situations, when the @code{Machine_Overflows} attribute of the
-result type is @code{False}. See G.2.4(4).
+result type is @code{False}. See G.2.4(4).
@end cartouche
@noindent
IEEE infinite and Nan values are produced as appropriate.
@strong{129}. The value of the angle threshold, within which certain
elementary functions, complex arithmetic operations, and complex
elementary functions yield results conforming to a maximum relative
-error bound. See G.2.4(10).
+error bound. See G.2.4(10).
@end cartouche
@noindent
Information on this subject is not yet available.
@cartouche
@noindent
@strong{130}. The accuracy of certain elementary functions for
-parameters beyond the angle threshold. See G.2.4(10).
+parameters beyond the angle threshold. See G.2.4(10).
@end cartouche
@noindent
Information on this subject is not yet available.
@strong{131}. The result of a complex arithmetic operation or complex
elementary function reference in overflow situations, when the
@code{Machine_Overflows} attribute of the corresponding real type is
-@code{False}. See G.2.6(5).
+@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
@noindent
@strong{132}. The accuracy of certain complex arithmetic operations and
certain complex elementary functions for parameters (or components
-thereof) beyond the angle threshold. See G.2.6(8).
+thereof) beyond the angle threshold. See G.2.6(8).
@end cartouche
@noindent
Information on those subjects is not yet available.
@cartouche
@noindent
@strong{133}. Information regarding bounded errors and erroneous
-execution. See H.2(1).
+execution. See H.2(1).
@end cartouche
@noindent
Information on this subject is not yet available.
@cartouche
@noindent
@strong{134}. Implementation-defined aspects of pragma
-@code{Inspection_Point}. See H.3.2(8).
+@code{Inspection_Point}. See H.3.2(8).
@end cartouche
@noindent
Pragma @code{Inspection_Point} ensures that the variable is live and can
@cartouche
@noindent
@strong{135}. Implementation-defined aspects of pragma
-@code{Restrictions}. See H.4(25).
+@code{Restrictions}. See H.4(25).
@end cartouche
@noindent
-There are no implementation-defined aspects of pragma @code{Restrictions}. The
+There are no implementation-defined aspects of pragma @code{Restrictions}. The
use of pragma @code{Restrictions [No_Exceptions]} has no effect on the
-generated code. Checks must suppressed by use of pragma @code{Suppress}.
+generated code. Checks must suppressed by use of pragma @code{Suppress}.
@sp 1
@cartouche
@noindent
-@strong{136}. Any restrictions on pragma @code{Restrictions}. See
+@strong{136}. Any restrictions on pragma @code{Restrictions}. See
H.4(27).
@end cartouche
@noindent
* 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
@noindent
providing that the name corresponds to one of the implemented intrinsic
subprograms in GNAT, and that the parameter profile of the referenced
-subprogram meets the requirements. This chapter describes the set of
+subprogram meets the requirements. This chapter describes the set of
implemented intrinsic subprograms, and the requirements on parameter profiles.
Note that no body is supplied; as with other uses of pragma Import, the
-body is supplied elsewhere (in this case by the compiler itself). Note
+body is supplied elsewhere (in this case by the compiler itself). Note
that any use of this feature is potentially non-portable, since the
Ada standard does not require Ada compilers to implement this feature.
@cindex Intrinsic operator
@noindent
-All predefined operators can be used 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
-both be floating-point or both be fixed-point. You can use an intrinsic
-operator declaration as in the following example:
+All the predefined numeric operators in package Standard
+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
+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;
@end smallexample
@noindent
-This declaration would permit "mixed mode" arithmetic on items
-of the differing types Int1 and Int2.
+This declaration would permit ``mixed mode'' arithmetic on items
+of the differing types @code{Int1} and @code{Int2}.
+It is also possible to specify such operators for private types, if the
+full views are appropriate arithmetic types.
@node Enclosing_Entity
@section Enclosing_Entity
@cindex Enclosing_Entity
@noindent
This intrinsic subprogram is used in the implementation of the
-library routine @code{GNAT.Source_Info}. The only useful use of the
+library routine @code{GNAT.Source_Info}. The only useful use of the
intrinsic import in this case is the one in this unit, so an
application program should simply call the function
@code{GNAT.Source_Info.Enclosing_Entity} to obtain the name of
@cindex Exception_Information'
@noindent
This intrinsic subprogram is used in the implementation of the
-library routine @code{GNAT.Current_Exception}. The only useful
+library routine @code{GNAT.Current_Exception}. The only useful
use of the intrinsic import in this case is the one in this unit,
so an application program should simply call the function
@code{GNAT.Current_Exception.Exception_Information} to obtain
@cindex Exception_Message
@noindent
This intrinsic subprogram is used in the implementation of the
-library routine @code{GNAT.Current_Exception}. The only useful
+library routine @code{GNAT.Current_Exception}. The only useful
use of the intrinsic import in this case is the one in this unit,
so an application program should simply call the function
@code{GNAT.Current_Exception.Exception_Message} to obtain
@cindex Exception_Name
@noindent
This intrinsic subprogram is used in the implementation of the
-library routine @code{GNAT.Current_Exception}. The only useful
+library routine @code{GNAT.Current_Exception}. The only useful
use of the intrinsic import in this case is the one in this unit,
so an application program should simply call the function
@code{GNAT.Current_Exception.Exception_Name} to obtain
@cindex File
@noindent
This intrinsic subprogram is used in the implementation of the
-library routine @code{GNAT.Source_Info}. The only useful use of the
+library routine @code{GNAT.Source_Info}. The only useful use of the
intrinsic import in this case is the one in this unit, so an
application program should simply call the function
@code{GNAT.Source_Info.File} to obtain the name of the current
@cindex Line
@noindent
This intrinsic subprogram is used in the implementation of the
-library routine @code{GNAT.Source_Info}. The only useful use of the
+library routine @code{GNAT.Source_Info}. The only useful use of the
intrinsic import in this case is the one in this unit, so an
application program should simply call the function
@code{GNAT.Source_Info.Line} to obtain the number of the current
@section Rotate_Left
@cindex Rotate_Left
@noindent
-In standard Ada 95, the @code{Rotate_Left} function is available only
-for the predefined modular types in package @code{Interfaces}. However, in
+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)
@noindent
The requirements are that the profile be exactly as in the example
-above. The only modifications allowed are in the formal parameter
+above. The only modifications allowed are in the formal parameter
names, and in the type of @code{Value} and the return type, which
must be the same, and must be either a signed integer type, or
a modular integer type with a binary modulus, and the size must
-be 8. 16, 32 or 64 bits.
+be 8. 16, 32 or 64 bits.
@node Rotate_Right
@section Rotate_Right
@cindex Source_Location
@noindent
This intrinsic subprogram is used in the implementation of the
-library routine @code{GNAT.Source_Info}. The only useful use of the
+library routine @code{GNAT.Source_Info}. The only useful use of the
intrinsic import in this case is the one in this unit, so an
application program should simply call the function
@code{GNAT.Source_Info.Source_Location} to obtain the current
This section describes the representation clauses accepted by GNAT, and
their effect on the representation of corresponding data objects.
-GNAT fully implements Annex C (Systems Programming). This means that all
+GNAT fully implements Annex C (Systems Programming). This means that all
the implementation advice sections in chapter 13 are fully implemented.
However, these sections only require a minimal level of support for
-representation clauses. GNAT provides much more extensive capabilities,
+representation clauses. GNAT provides much more extensive capabilities,
and this section describes the additional capabilities provided.
@node Alignment Clauses
@noindent
GNAT requires that all alignment clauses specify a power of 2, and all
-default alignments are always a power of 2. The default alignment
+default alignments are always a power of 2. The default alignment
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
+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
packed arrays), then the alignment will be one for long packed arrays,
-or arrays whose length is not known at compile time. For short packed
+or arrays whose length is not known at compile time. For short packed
arrays, which are handled internally as modular types, the alignment
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 Pack is
-used and all fields are packable (see separate section on pragma Pack),
+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:
+@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 @c ada
+ type Small is record
+ A, B : Character;
+ end record;
+ for Small'Size use 16;
+@end smallexample
@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
+then the default alignment of the record type @code{Small} is 2, not 1. This
+leads to more efficient code when the record is treated as a unit, and also
+allows the type to specified as @code{Atomic} on architectures requiring
+strict alignment.
-@smallexample
- type v is record
- a : integer;
- end record;
+@end itemize
- for v use record
- a at 0 range 0 .. 31;
+@noindent
+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
+
+@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
+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:
+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
+zero-extended as appropriate. If more than 64 bits is specified, then
padding space is allocated after the value, and a warning is issued that
there are unused bits.
Similarly the size of records and arrays may be increased, and the effect
-is to add padding bits after the value. This also causes a warning message
+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**32-1. 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
+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
if it is known that a Size value can be accommodated in an object of
type Integer.
@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,
+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). 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
+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
+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.
In the case where the access type is declared local to a subprogram, the
use of a @code{Storage_Size} clause triggers automatic use of a special
which the type is declared.
A special case recognized by the compiler is the specification of a
-@code{Storage_Size} of zero for an access type. This means that no
+@code{Storage_Size} of zero for an access type. This means that no
items can be allocated from the pool, and this is recognized at compile
time, and all the overhead normally associated with maintaining a fixed
-size storage pool is eliminated. Consider the following example:
+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;
end;
@end smallexample
@noindent
As indicated in this example, these dummy storage pools are often useful in
-connection with interfacing where no object will ever be allocated. If you
+connection with interfacing where no object will ever be allocated. If you
compile the above example, you get the warning:
@smallexample
@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
+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;
Here we are dealing with a variant record, where the True variant
requires 16 bits, and the False variant requires 8 bits.
In the above example, both V1 and V2 contain the False variant,
-which is only 8 bits long. However, the result of running the
+which is only 8 bits long. However, the result of running the
program is:
@smallexample
@noindent
The reason for the difference here is that the discriminant value of
-V1 is fixed, and will always be False. It is not possible to assign
-a True variant value to V1, therefore 8 bits is sufficient. On the
+V1 is fixed, and will always be False. It is not possible to assign
+a True variant value to V1, therefore 8 bits is sufficient. On the
other hand, in the case of V2, the initial discriminant value is
False (from the default), but it is possible to assign a True
variant value to V2, therefore 16 bits must be allocated for V2
language in the RM@.
In some cases, it may be desirable to obtain the size of the current
-variant, rather than the size of the largest variant. This can be
+variant, rather than the size of the largest variant. This can be
achieved in GNAT by making use of the fact that in the case of a
subprogram parameter, GNAT does indeed return the size of the current
variant (because a subprogram has no way of knowing how much space
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
@noindent
In the case of scalars with a range starting at other than zero, it is
possible in some cases to specify a size smaller than the default minimum
-value, and in such cases, @code{GNAT} uses an unsigned biased representation,
+value, and in such cases, GNAT uses an unsigned biased representation,
in which zero is used to represent the lower bound, and successive values
represent successive values of the type.
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
+cannot be accepted in any other manner. These reduced sizes that force
+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:
+typically 31. This means that code may change in behavior when moving
+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.
The @code{Object_Size} is used for determining the default size of
-objects and components. This size value can be referred to using the
-@code{Object_Size} attribute. The phrase "is used" here means that it is
-the basis of the determination of the size. The backend is free to
+objects and components. This size value can be referred to using the
+@code{Object_Size} attribute. The phrase ``is used'' here means that it is
+the basis of the determination of the size. The backend is free to
pad this up if necessary for efficiency, e.g.@: an 8-bit stand-alone
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 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
@item
If a subtype statically matches the first subtype of a given type, then it has
-by default the same @code{Value_Size} as the first subtype. This is a
-consequence of RM 13.1(14) ("if two subtypes statically match,
-then their subtype-specific aspects are the same".)
+by default the same @code{Value_Size} as the first subtype. This is a
+consequence of RM 13.1(14) (``if two subtypes statically match,
+then their subtype-specific aspects are the same''.)
@item
All other subtypes have a @code{Value_Size} corresponding to the minimum
-number of bits required to store all values of the subtype. For
+number of bits required to store all values of the subtype. For
dynamic bounds, it is assumed that the value can range down or up
to the corresponding bound of the ancestor
@end itemize
The RM defined attribute @code{Size} corresponds to the
@code{Value_Size} attribute.
-The @code{Size} attribute may be defined for a first-named subtype. This sets
+The @code{Size} attribute may be defined for a first-named subtype. This sets
the @code{Value_Size} of
the first-named subtype to the given value, and the
@code{Object_Size} of this first-named subtype to the given value padded up
-to an appropriate boundary. It is a consequence of the default rules
-above that this @code{Object_Size} will apply to all further subtypes. On the
+to an appropriate boundary. It is a consequence of the default rules
+above that this @code{Object_Size} will apply to all further subtypes. On the
other hand, @code{Value_Size} is affected only for the first subtype, any
dynamic subtypes obtained from it directly, and any statically matching
-subtypes. The @code{Value_Size} of any other static subtypes is not affected.
+subtypes. The @code{Value_Size} of any other static subtypes is not affected.
@code{Value_Size} and
@code{Object_Size} may be explicitly set for any subtype using
-an attribute definition clause. Note that the use of these attributes
-can cause the RM 13.1(14) rule to be violated. If two access types
+an attribute definition clause. Note that the use of these attributes
+can cause the RM 13.1(14) rule to be violated. If two access types
reference aliased objects whose subtypes have differing @code{Object_Size}
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 x1 is range 0 .. 5; 8 3
-type x2 is range 0..5;
-for x2'size use 12; 12 12
+type x2 is range 0 .. 5;
+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.
In addition, component size clauses are allowed which cause the array
-to be packed, by specifying a smaller value. The cases in which this
-is allowed are for component size values in the range 1-63. The value
-specified must not be smaller than the Size of the subtype. GNAT will
-accurately honor all packing requests in this range. For example, if
+to be packed, by specifying a smaller value. The cases in which this
+is allowed are for component size values in the range 1 through 63. The value
+specified must not be smaller than the Size of the subtype. GNAT will
+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
@noindent
For record subtypes, GNAT permits the specification of the @code{Bit_Order}
-attribute. The specification may either correspond to the default bit
+attribute. The specification may either correspond to the default bit
order for the target, in which case the specification has no effect and
places no additional restrictions, or it may be for the non-standard
setting (that is the opposite of the default).
In the case where the non-standard value is specified, the effect is
to renumber bits within each byte, but the ordering of bytes is not
-affected. There are certain
+affected. There are certain
restrictions placed on component clauses as follows:
@itemize @bullet
@item Components fitting within a single storage unit.
@noindent
-These are unrestricted, and the effect is merely to renumber bits. For
+These are unrestricted, and the effect is merely to renumber bits. For
example if we are on a little-endian machine with @code{Low_Order_First}
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;
@item Components occupying an integral number of bytes.
@noindent
-These are components that exactly fit in two or more bytes. Such component
+These are components that exactly fit in two or more bytes. Such component
declarations are allowed, but have no effect, since it is important to realize
that the @code{Bit_Order} specification does not affect the ordering of bytes.
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;
This declaration will result in a little-endian integer on a
little-endian machine, and a big-endian integer on a big-endian machine.
If byte flipping is required for interoperability between big- and
-little-endian machines, this must be explicitly programmed. This capability
+little-endian machines, this must be explicitly programmed. This capability
is not provided by @code{Bit_Order}.
@item Components that are positioned across byte boundaries
@noindent
-but do not occupy an integral number of bytes. Given that bytes are not
+but do not occupy an integral number of bytes. Given that bytes are not
reordered, such fields would occupy a non-contiguous sequence of bits
-in memory, requiring non-trivial code to reassemble. They are for this
+in memory, requiring non-trivial code to reassemble. They are for this
reason not permitted, and any component clause specifying such a layout
will be flagged as illegal by GNAT@.
Since the misconception that Bit_Order automatically deals with all
endian-related incompatibilities is a common one, the specification of
a component field that is an integral number of bytes will always
-generate a warning. This warning may be suppressed using
-@code{pragma Suppress} if desired. The following section contains additional
+generate a warning. This warning may be suppressed using
+@code{pragma Suppress} if desired. The following section contains additional
details regarding the issue of byte ordering.
@node Effect of Bit_Order on Byte Ordering
@noindent
In this section we will review the effect of the @code{Bit_Order} attribute
-definition clause on byte ordering. Briefly, it has no effect at all, but
-a detailed example will be helpful. Before giving this
+definition clause on byte ordering. Briefly, it has no effect at all, but
+a detailed example will be helpful. Before giving this
example, let us review the precise
-definition of the effect of defining @code{Bit_Order}. The effect of a
+definition of the effect of defining @code{Bit_Order}. The effect of a
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)
+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
-the values after normalization, not before. So the @code{Bit_Order}
-interpretation applies to normalized values. The interpretation
+the values after normalization, not before. So the @code{Bit_Order}
+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
+vernacular as ``big endian'') means that the first bit of a
storage element (bit 0) is the most significant bit (interpreting
the sequence of bits that represent a component as an unsigned
-integer value). Low_Order_First (known in the vernacular as
-"little endian") means the opposite: the first bit is the
+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
-unit. In other words, the specification affects only the numbering
+unit. In other words, the specification affects only the numbering
of bits within a single storage unit.
We can make the effect clearer by giving an example.
record is called Master, and the second byte is called Slave.
The left most (most significant bit is called Control for each byte, and
-the remaing 7 bits are called V1, V2 .. V7, where V7 is the right most
-(least significant bit).
+the remaining 7 bits are called V1, V2, @dots{} V7, where V7 is the rightmost
+(least significant) bit.
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,
+the code has to be maintained on both machines. However,
this is a case that we can handle with the
@code{Bit_Order} attribute if it is implemented.
Note that the implementation is not required on byte addressed
-machines, but it is indeed implemented in @code{GNAT}.
+machines, but it is indeed implemented in GNAT.
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
@noindent
and the effect is what is desired, namely the layout is exactly the same,
-independent of whether the code is compiled on a big-endial or little-endian
+independent of whether the code is compiled on a big-endian or little-endian
machine.
The important point to understand is that byte ordering is not affected.
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;
- Master_V1 at 0 range 1 .. 1;
- Master_V2 at 0 range 2 .. 2;
- Master_V3 at 0 range 3 .. 3;
- Master_V4 at 0 range 4 .. 4;
- Master_V5 at 0 range 5 .. 5;
- Master_V6 at 0 range 6 .. 6;
- Master_V7 at 0 range 7 .. 7;
- Slave_Control at 0 range 8 .. 8;
- Slave_V1 at 0 range 9 .. 9;
+ Master_Control at 0 range 0 .. 0;
+ Master_V1 at 0 range 1 .. 1;
+ Master_V2 at 0 range 2 .. 2;
+ Master_V3 at 0 range 3 .. 3;
+ Master_V4 at 0 range 4 .. 4;
+ Master_V5 at 0 range 5 .. 5;
+ Master_V6 at 0 range 6 .. 6;
+ Master_V7 at 0 range 7 .. 7;
+ Slave_Control at 0 range 8 .. 8;
+ Slave_V1 at 0 range 9 .. 9;
Slave_V2 at 0 range 10 .. 10;
Slave_V3 at 0 range 11 .. 11;
Slave_V4 at 0 range 12 .. 12;
@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;
@noindent
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
+field. The storage place attributes are obtained by normalizing the
+values given so that the @code{First_Bit} value is less than 8. After
+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
generates a warning for such usage.
If you do need to control byte ordering then appropriate conditional
-values must be used. If in our example, the slave byte came first on
+values must be used. If in our example, the slave byte came first on
some machines we might write:
-@smallexample
- Master_Byte_First constant Boolean := ...;
+@smallexample @c ada
+ Master_Byte_First constant Boolean := @dots{};
Master_Byte : constant Natural :=
1 - Boolean'Pos (Master_Byte_First);
@cindex Pragma Pack (for arrays)
@noindent
-Pragma Pack applied to an array has no effect unless the component type
-is packable. For a component type to be packable, it must be one of the
+Pragma @code{Pack} applied to an array has no effect unless the component type
+is packable. For a component type to be packable, it must be one of the
following cases:
@itemize @bullet
@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
@noindent
For all these cases, if the component subtype size is in the range
-1- 63, then the effect of the pragma Pack is exactly as though a
+1 through 63, then the effect of the pragma @code{Pack} is exactly as though a
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 Pack that it guesses
-might not be what is intended. You can easily remove this warning by
-using an explicit Component_Size setting instead, which never generates
+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
+might not be what is intended. You can easily remove this warning by
+using an explicit @code{Component_Size} setting instead, which never generates
a warning, since the intention of the programmer is clear in this case.
-GNAT treats packed arrays in one of two ways. If the size of the array is
+GNAT treats packed arrays in one of two ways. If the size of the array is
known at compile time and is less than 64 bits, then internally the array
is represented as a single modular type, of exactly the appropriate number
-of bits. If the length is greater than 63 bits, or is not known at compile
+of bits. If the length is greater than 63 bits, or is not known at compile
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 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;
+ l1 at 0 range 0 .. 0;
l2 at 0 range 1 .. 64;
l3 at 12 range 0 .. 31;
- l4 at 16 range 0 .. 0;
+ l4 at 16 range 0 .. 0;
l5 at 16 range 1 .. 13;
l6 at 18 range 0 .. 71;
end record;
and @code{l2} are
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.
+eliminate padding. But @code{l3} is of a non-packable float type, so
+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
-array that is longer than 64 bits, so it is itself non-packable. Thus
+minimally packed with no gaps. However, type @code{Rb2} is a packed
+array that is longer than 64 bits, so it is itself non-packable. Thus
the @code{l6} field is aligned to the next byte boundary, and takes an
integral number of bytes, i.e.@: 72 bits.
@noindent
Record representation clauses may be given for all record types, including
-types obtained by record extension. Component clauses are allowed for any
-static component. The restrictions on component clauses depend on the type
+types obtained by record extension. Component clauses are allowed for any
+static component. The restrictions on component clauses depend on the type
of the component.
@cindex Component Clause
For all components of an elementary type, the only restriction on component
clauses is that the size must be at least the 'Size value of the type
-(actually the Value_Size). There are no restrictions due to alignment,
+(actually the Value_Size). There are no restrictions due to alignment,
and such components may freely cross storage boundaries.
-Packed arrays with a size up to and including 64-bits are represented
+Packed arrays with a size up to and including 64 bits are represented
internally using a modular type with the appropriate number of bits, and
-thus the same lack of restriction applies. For example, if you declare:
+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.
+the start of the record. No component clause may attempt to overlay this
+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
The only restriction on enumeration clauses is that the range of values
-must be representable. For the signed case, if one or more of the
+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
@noindent
-A "confirming" representation clause is one in which the values range
+A @emph{confirming} representation clause is one in which the values range
from 0 in sequence, i.e.@: a clause that confirms the default representation
for an enumeration type.
Such a confirming representation
If an array has an index type which is an enumeration type to which an
enumeration clause has been applied, then the array is stored in a compact
-manner. Consider the declarations:
+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;
@noindent
The array type t corresponds to a vector with exactly three elements and
-has a default size equal to @code{3*Character'Size}. This ensures efficient
+has a default size equal to @code{3*Character'Size}. This ensures efficient
use of space, but means that accesses to elements of the array will incur
the overhead of converting representation values to the corresponding
-positional values, (i.e.@: the value delivered by the @code{Pos} attribute).
+positional values, (i.e.@: the value delivered by the @code{Pos} attribute).
@node Address Clauses
@section Address Clauses
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
+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(...);
- Y : Address := G(...);
+ 22.b X : Integer := F(@dots{});
+ Y : Address := G(@dots{});
for X'Address use Y;
22.c In the above, we have to evaluate the
initialization expression for X before we
- know where to put the result. This seems
+ know where to put the result. This seems
like an unreasonable implementation burden.
22.d The above code should instead be written
like this:
- 22.e Y : constant Address := G(...);
- X : Integer := F(...);
+ 22.e Y : constant Address := G(@dots{});
+ X : Integer := F(@dots{});
for X'Address use Y;
22.f This allows the expression ``Y'' to be safely
22.g The constant could be a formal parameter of mode in.
22.h An implementation can support other nonstatic
- expressions if it wants to. Expressions of type
+ expressions if it wants to. Expressions of type
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
+GNAT does indeed permit many additional cases of non-static expressions. In
particular, if the type involved is elementary there are no restrictions
(since in this case, holding a temporary copy of the initialization value,
-if one is present, is inexpensive). In addition, if there is no implicit or
-explicit initialization, then there are no restrictions. GNAT will reject
+if one is present, is inexpensive). In addition, if there is no implicit or
+explicit initialization, then there are no restrictions. GNAT will reject
only the case where all three of these conditions hold:
@itemize @bullet
@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
+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.
@end itemize
@noindent
-As noted above in section 22.h, address values are typically non-static. In
+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
+a non-static function call. To avoid this minor annoyance, GNAT provides
+the implementation defined attribute 'To_Address. The following two
expressions have identical values:
@findex Attribute
@findex To_Address
-@smallexample
+@smallexample @c ada
To_Address (16#1234_0000#)
System'To_Address (16#1234_0000#);
@end smallexample
@noindent
Additionally, GNAT treats as static an address clause that is an
-unchecked_conversion of a static integer value. This simplifies the porting
+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
+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.
+clause cannot be exported. This is because such variables are not
+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
-same object. In this case, the variable is not really defined by the
-Ada program, so there is no external symbol to be linked. The link name
-and the external name are ignored in this case. The reason that we allow this
+same object. In this case, the variable is not really defined by the
+Ada program, so there is no external symbol to be linked. The link name
+and the external name are ignored in this case. The reason that we allow this
combination is that it provides a useful idiom to avoid unwanted
initializations on objects with address clauses.
When an address clause is given for an object that has implicit or
-explicit initialization, then by default initialization takes place. This
+explicit initialization, then by default initialization takes place. This
means that the effect of the object declaration is to overwrite the
-memory at the specified address. This is almost always not what the
+memory at the specified address. This is almost always not what the
programmer wants, so GNAT will output a warning:
@smallexample
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
@noindent
As indicated by the warning message, the solution is to use a (dummy) pragma
-Import to suppress this initialization. The pragma tell the compiler that the
-object is declared and initialized elsewhere. The following package compiles
+Import to suppress this initialization. The pragma tell the compiler that the
+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
@noindent
Normally the specification of a foreign language convention for a type or
-an object has no effect on the chosen representation. In particular, the
+an object has no effect on the chosen representation. In particular, the
representation chosen for data in GNAT generally meets the standard system
conventions, and for example records are laid out in a manner that is
-consistent with C@. This means that specifying convention C (for example)
+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
@item Convention C and enumeration types
GNAT normally stores enumeration types in 8, 16, or 32 bits as required
-to accommodate all values of the type. For example, for the enumeration
+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
@noindent
8 bits is sufficient to store all values of the type, so by default, objects
-of type @code{Color} will be represented using 8 bits. However, normal C
-convention is to use 32-bits for all enum values in C, since enum values
-are essentially of type int. If pragma Convention C is specified for an
+of type @code{Color} will be represented using 8 bits. However, normal C
+convention is to use 32 bits for all enum values in C, since enum values
+are essentially of type int. If pragma @code{Convention C} is specified for an
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
-true. In Ada, the normal convention is that two specific values, typically
+true. In Ada, the normal convention is that two specific values, typically
0/1, are used to represent false/true respectively.
Fortran has a similar convention for @code{LOGICAL} values (any nonzero
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
@noindent
-then the GNAT generated code will treat any nonzero value as true. For truth
+then the GNAT generated code will treat any nonzero value as true. For truth
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
@section Determining the Representations chosen by GNAT
@cindex Representation, determination of
-@cindex -gnatR switch
+@cindex @code{-gnatR} switch
@noindent
Although the descriptions in this section are intended to be complete, it is
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 pack is used on a
-record, then exactly where are the resulting fields placed? The section
-on pragma 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
+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:
+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
for r'Size use ??;
for r'Alignment use 4;
for r use record
- x at 4 range 0 .. 7;
+ x at 4 range 0 .. 7;
_tag at 0 range 0 .. 31;
s at 5 range 0 .. 799;
end record;
for r2'Size use 160;
for r2'Alignment use 4;
for r2 use record
- x at 4 range 0 .. 7;
+ x at 4 range 0 .. 7;
_tag at 0 range 0 .. 31;
_parent at 0 range 0 .. 63;
y2 at 16 range 0 .. 31;
for x'Size use 8;
for x'Alignment use 1;
for x use record
- y at 0 range 0 .. 7;
+ y at 0 range 0 .. 7;
end record;
for x1'Size use 112;
for x2'Size use 224;
for x2'Alignment use 4;
for x2 use record
- l1 at 0 range 0 .. 0;
+ l1 at 0 range 0 .. 0;
l2 at 0 range 1 .. 64;
l3 at 12 range 0 .. 31;
- l4 at 16 range 0 .. 0;
+ l4 at 16 range 0 .. 0;
l5 at 16 range 1 .. 13;
l6 at 18 range 0 .. 71;
end record;
of the parent type of r2, i.e.@: r1.
The component size and size clauses for types rb1 and rb2 show
-the exact effect of pragma Pack on these arrays, and the record
-representation clause for type x2 shows how pragma Pack affects
+the exact effect of pragma @code{Pack} on these arrays, and the record
+representation clause for type x2 shows how pragma @code{Pack} affects
this record type.
In some cases, it may be useful to cut and paste the representation clauses
@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
+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
-should be sufficient. The following is a list of the packages included,
+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)
-This is a parent package for all the standard library packages. It is
+This is a parent package for all the standard library packages. It is
usually included implicitly in your program, and itself contains no
useful data or routines.
@item Ada.Characters.Latin_1 (A.3.3)
This package includes a complete set of definitions of the characters
-that appear in type CHARACTER@. It is useful for writing programs that
-will run in international environments. For example, if you want an
+that appear in type CHARACTER@. It is useful for writing programs that
+will run in international environments. For example, if you want an
upper case E with an acute accent in a string, it is often better to use
-the definition of @code{UC_E_Acute} in this package. Then your program
+the definition of @code{UC_E_Acute} in this package. Then your program
will print in an understandable manner even if your environment does not
support these extended characters.
@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 argc and 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)
@item Ada.Numerics
This package contains some standard constants and exceptions used
-throughout the numerics packages. Note that the constants pi and e are
+throughout the numerics packages. Note that the constants pi and e are
defined here, and it is better to use these definitions than rolling
your own.
@item Ada.Numerics.Generic_Complex_Elementary_Functions
This is a generic version of the package that provides the
-implementation of standard elementary functions (such as log an
+implementation of standard elementary functions (such as log and
trigonometric functions) for an arbitrary complex type.
-The following predefined instantiations of this package exist
+The following predefined instantiations of this package are provided:
@table @code
@item Short_Float
@item Ada.Real_Time (D.8)
This package provides facilities similar to those of @code{Calendar}, but
-operating with a finer clock suitable for real time control.
+operating with a finer clock suitable for real time control. Note that
+annex D requires that there be no backward clock jumps, and GNAT generally
+guarantees this behavior, but of course if the external clock on which
+the GNAT runtime depends is deliberately reset by some external event,
+then such a backward jump may occur.
@item Ada.Sequential_IO (A.8.1)
This package provides input-output facilities for sequential files,
@item Ada.Storage_IO (A.9)
This package provides a facility for mapping arbitrary Ada types to and
-from a storage buffer. It is primarily intended for the creation of new
+from a storage buffer. It is primarily intended for the creation of new
IO packages.
@item Ada.Streams (13.13.1)
@item Ada.Streams.Stream_IO (A.12.1)
This package is a specialization of the type @code{Streams} defined in
package @code{Streams} together with a set of operations providing
-Stream_IO capability. The Stream_IO model permits both random and
+Stream_IO capability. The Stream_IO model permits both random and
sequential access to a file which can contain an arbitrary set of values
of one or more Ada types.
@item Ada.Strings.Bounded (A.4.4)
This package provides facilities for handling variable length
-strings. The bounded model requires a maximum length. It is thus
+strings. The bounded model requires a maximum length. It is thus
somewhat more limited than the unbounded model, but avoids the use of
dynamic allocation or finalization.
@item Ada.Strings.Maps (A.4.2)
This package provides facilities for handling character mappings and
-arbitrarily defined subsets of characters. For instance it is useful in
+arbitrarily defined subsets of characters. For instance it is useful in
defining specialized translation tables.
@item Ada.Strings.Maps.Constants (A.4.6)
This package provides a standard set of predefined mappings and
-predefined character sets. For example, the standard upper to lower case
-conversion table is found in this package. Note that upper to lower case
+predefined character sets. For example, the standard upper to lower case
+conversion table is found in this package. Note that upper to lower case
conversion is non-trivial if you want to take the entire set of
characters, including extended characters like E with an acute accent,
-into account. You should use the mappings in this package (rather than
+into account. You should use the mappings in this package (rather than
adding 32 yourself) to do case mappings.
@item Ada.Strings.Unbounded (A.4.5)
This package provides facilities for handling variable length
-strings. The unbounded model allows arbitrary length strings, but
+strings. The unbounded model allows arbitrary length strings, but
requires the use of dynamic allocation and finalization.
@item Ada.Strings.Wide_Bounded (A.4.7)
@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
This package provides basic text input-output capabilities for
-character, string and numeric data. The subpackages of this
+character, string and numeric data. The subpackages of this
package are listed next.
@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
Provides input-output facilities for ordinary fixed-point types.
@item Ada.Text_IO.Float_IO
-Provides input-output facilities for float types. The following
+Provides input-output facilities for float types. The following
predefined instantiations of this generic package are available:
@table @code
@end table
@item Ada.Text_IO.Integer_IO
-Provides input-output facilities for integer types. The following
+Provides input-output facilities for integer types. The following
predefined instantiations of this generic package are available:
@table @code
@item Ada.Text_IO.Editing (F.3.3)
This package contains routines for edited output, analogous to the use
-of pictures in COBOL@. The picture formats used by this package are a
+of pictures in COBOL@. The picture formats used by this package are a
close copy of the facility in COBOL@.
@item Ada.Text_IO.Text_Streams (A.12.2)
If the types have the same Size (more accurately the same Value_Size),
then the effect is simply to transfer the bits from the source to the
-target type without any modification. This usage is well defined, and
+target type without any modification. This usage is well defined, and
for simple types whose representation is typically the same across
all implementations, gives a portable method of performing such
conversions.
If the types do not have the same size, then the result is implementation
-defined, and thus may be non-portable. The following describes how GNAT
+defined, and thus may be non-portable. The following describes how GNAT
handles such unchecked conversion cases.
If the types are of different sizes, and are both discrete types, then
the effect is of a normal type conversion without any constraint checking.
In particular if the result type has a larger size, the result will be
-zero or sign extended. If the result type has a smaller size, the result
+zero or sign extended. If the result type has a smaller size, the result
will be truncated by ignoring high order bits.
If the types are of different sizes, and are not both discrete types,
then the conversion works as though pointers were created to the source
-and target, and the pointer value is converted. The effect is that bits
+and target, and the pointer value is converted. The effect is that bits
are copied from successive low order storage units and bits of the source
up to the length of the target type.
that of some other compiler.
A pointer to one type may be converted to a pointer to another type using
-unchecked conversion. The only case in which the effect is undefined is
-when one or both pointers are pointers to unconstrained array types. In
+unchecked conversion. The only case in which the effect is undefined is
+when one or both pointers are pointers to unconstrained array types. In
this case, the bounds information may get incorrectly transferred, and in
particular, GNAT uses double size pointers for such types, and it is
-meaningless to convert between such pointer types. GNAT will issue a
+meaningless to convert between such pointer types. GNAT will issue a
warning if the alignment of the target designated type is more strict
than the alignment of the source designated type (since the result may
be unaligned in this case).
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
+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}, 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.
+and @code{String}. It contains generic subpackages listed next.
@item Ada.Wide_Text_IO.Decimal_IO
Provides input-output facilities for decimal fixed-point types
Provides input-output facilities for ordinary fixed-point types.
@item Ada.Wide_Text_IO.Float_IO
-Provides input-output facilities for float types. The following
+Provides input-output facilities for float types. The following
predefined instantiations of this generic package are available:
@table @code
@end table
@item Ada.Wide_Text_IO.Integer_IO
-Provides input-output facilities for integer types. The following
+Provides input-output facilities for integer types. The following
predefined instantiations of this generic package are available:
@table @code
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
+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
implementation of these input-output facilities behaves.
In this chapter we give a detailed description of exactly how GNAT
-interfaces to the file system. As always, the sources of the system are
+interfaces to the file system. As always, the sources of the system are
available to you for answering questions at an even more detailed level,
but for most purposes the information in this chapter will suffice.
Another reason that you may need to know more about how input-output is
implemented arises when you have a program written in mixed languages
where, for example, files are shared between the C and Ada sections of
-the same program. GNAT provides some additional facilities, in the form
+the same program. GNAT provides some additional facilities, in the form
of additional child library packages, that facilitate this sharing, and
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
The format of a FORM string in GNAT is:
@smallexample
-"keyword=value,keyword=value,...,keyword=value"
+"keyword=value,keyword=value,@dots{},keyword=value"
@end smallexample
@noindent
where letters may be in upper or lower case, and there are no spaces
-between values. The order of the entries is not important. Currently
+between values. The order of the entries is not important. Currently
there are two keywords defined.
@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
@section Direct_IO
@noindent
-Direct_IO can only be instantiated for definite types. This is a
+Direct_IO can only be instantiated for definite types. This is a
restriction of the Ada language, which means that the records are fixed
length (the length being determined by @code{@var{type}'Size}, rounded
up to the next storage unit boundary if necessary).
The records of a Direct_IO file are simply written to the file in index
sequence, with the first record starting at offset zero, and subsequent
-records following. There is no control information of any kind. For
+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 (@var{K} -
-1)*4.
+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
necessary to accommodate whatever records are written to the file.
For the definite type case, the elements written to the file are simply
the memory images of the data values with no control information of any
-kind. The resulting file should be read using the same type, no validity
+kind. The resulting file should be read using the same type, no validity
checking is performed on input.
For the indefinite type case, the elements written consist of two
-parts. First is the size of the data item, written as the memory image
+parts. First is the size of the data item, written as the memory image
of a @code{Interfaces.C.size_t} value, followed by the memory image of
-the data value. The resulting file can only be read using the same
-(unconstrained) type. Normal assignment checks are performed on these
+the data value. The resulting file can only be read using the same
+(unconstrained) type. Normal assignment checks are performed on these
read operations, and if these checks fail, @code{Data_Error} is
-raised. In particular, in the array case, the lengths must match, and in
+raised. In particular, in the array case, the lengths must match, and in
the variant record case, if the variable for a particular read operation
is constrained, the discriminants must match.
Note that it is not possible to use Sequential_IO to write variable
length array items, and then read the data back into different length
-arrays. For example, the following will raise @code{Data_Error}:
+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);
- ...
+ @dots{}
IO.Create (F)
IO.Write (F, "hello!")
IO.Reset (F, Mode=>In_File);
@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:
@item
The file ends with either @code{LF} (line mark) or @code{LF}-@code{FF}
-(line mark, page mark). In the former case, the page mark is implicitly
+(line mark, page mark). In the former case, the page mark is implicitly
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
+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
+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}
character may or may not be treated as a page mark from the point of
-view of page and line numbering. Every @code{LF} character is considered
+view of page and line numbering. Every @code{LF} character is considered
to end a line, and there is an implied @code{LF} character at the end of
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
@code{Ada.Text_IO} has a definition of current position for a file that
-is being read. No internal buffering occurs in Text_IO, and usually the
+is being read. No internal buffering occurs in Text_IO, and usually the
physical position in the stream used to implement the file corresponds
-to this logical position defined by Text_IO@. There are two exceptions:
+to this logical position defined by Text_IO@. There are two exceptions:
@itemize @bullet
@item
After a call to @code{End_Of_Page} that returns @code{True}, the stream
is positioned past the @code{LF} (line mark) that precedes the page
-mark. Text_IO maintains an internal flag so that subsequent read
+mark. Text_IO maintains an internal flag so that subsequent read
operations properly handle the logical position which is unchanged by
the @code{End_Of_Page} call.
Text_IO file was positioned before the line mark at the end of file
before the call, then the logical position is unchanged, but the stream
is physically positioned right at the end of file (past the line mark,
-and past a possible page mark following the line mark. Again Text_IO
+and past a possible page mark following the line mark. Again Text_IO
maintains internal flags so that subsequent read operations properly
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)
@subsection Reading and Writing Non-Regular Files
@noindent
-A non-regular file is a device (such as a keyboard), or a pipe. Text_IO
-can be used for reading and writing. Writing is not affected and the
+A non-regular file is a device (such as a keyboard), or a pipe. Text_IO
+can be used for reading and writing. Writing is not affected and the
sequence of characters output is identical to the normal file case, but
for reading, the behavior of Text_IO is modified to avoid undesirable
look-ahead as follows:
An input file that is not a regular file is considered to have no page
-marks. Any @code{Ascii.FF} characters (the character normally used for a
+marks. Any @code{Ascii.FF} characters (the character normally used for a
page mark) appearing in the file are considered to be data
-characters. In particular:
+characters. In particular:
@itemize @bullet
@item
@code{Get_Line} and @code{Skip_Line} do not test for a page mark
-following a line mark. If a page mark appears, it will be treated as a
+following a line mark. If a page mark appears, it will be treated as a
data character.
@item
the end of the file.
@end itemize
-Output to non-regular files is the same as for regular files. Page marks
+@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
piped to another Ada program.
Another important discrepancy when reading non-regular files is that the end
-of file indication is not "sticky". If an end of file is entered, e.g.@: by
-pressing the @code{EOT} key,
+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
@noindent
Get_Immediate returns the next character (including control characters)
-from the input file. In particular, Get_Immediate will return LF or FF
-characters used as line marks or page marks. Such operations leave the
+from the input file. In particular, Get_Immediate will return LF or FF
+characters used as line marks or page marks. Such operations leave the
file positioned past the control character, and it is thus not treated
-as having its normal function. This means that page, line and column
+as having its normal function. This means that page, line and column
counts after this kind of Get_Immediate call are set as though the mark
-did not occur. In the case where a Get_Immediate leaves the file
+did not occur. In the case where a Get_Immediate leaves the file
positioned between the line mark and page mark (which is not normally
possible), it is undefined whether the FF character will be treated as a
page mark.
@noindent
The package @code{Text_IO.Streams} allows a Text_IO file to be treated
-as a stream. Data written to a Text_IO file in this stream mode is
-binary data. If this binary data contains bytes 16#0A# (@code{LF}) or
+as a stream. Data written to a Text_IO file in this stream mode is
+binary data. If this binary data contains bytes 16#0A# (@code{LF}) or
16#0C# (@code{FF}), the resulting file may have non-standard
-format. Similarly if read operations are used to read from a Text_IO
+format. Similarly if read operations are used to read from a Text_IO
file treated as a stream, then @code{LF} and @code{FF} characters may be
skipped and the effect is similar to that described above for
@code{Get_Immediate}.
@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
+Reads a string from the standard input file. The value returned is exactly
the length of the line that was read.
@item function Get_Line (File : Ada.Text_IO.File_Type) return String;
@noindent
In the above procedures, @code{File} is of type @code{Ada.Text_IO.File_Type}
-and is optional. If the parameter is omitted, then the standard input or
+and is optional. If the parameter is omitted, then the standard input or
output file is referenced as appropriate.
The package @code{Ada.Strings.Wide_Unbounded.Wide_Text_IO} in library
-files @code{a-swuwti.ads/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
@noindent
@code{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 character values. The encoding scheme for a given file may be
+wide character values. The encoding scheme for a given file may be
specified using a FORM parameter:
@smallexample
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
+characters (using upper case letters) of the wide character code. For
example, ESC A345 is used to represent the wide character with code
-16#A345#. This scheme is compatible with use of the full
+16#A345#. This scheme is compatible with use of the full
@code{Wide_Character} set.
@item Upper Half Coding
The wide character with encoding 16#abcd#, where the upper bit is on
(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.
+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.
@item Shift JIS Coding
A wide character is represented by a two character sequence 16#ab# and
16#cd#, with the restrictions described for upper half encoding as
-described above. The internal character code is the corresponding JIS
+described above. The internal character code is the corresponding JIS
character according to the standard algorithm for Shift-JIS
-conversion. Only characters defined in the JIS code set table can be
+conversion. Only characters defined in the JIS code set table can be
used with this encoding method.
@item EUC Coding
A wide character is represented by a two character sequence 16#ab# and
-16#cd#, with both characters being in the upper half. The internal
+16#cd#, with both characters being in the upper half. The internal
character code is the corresponding JIS character according to the EUC
-encoding algorithm. Only characters defined in the JIS code set table
+encoding algorithm. Only characters defined in the JIS code set table
can be used with this encoding method.
@item UTF-8 Coding
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
+16-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
(The full UTF-8 scheme allows for encoding 31-bit characters as
6-byte sequences, but in this implementation, all UTF-8 sequences
of four or more bytes length will raise a Constraint_Error, as
-will all illegal UTF-8 sequences.)
+will all invalid UTF-8 sequences.)
@item Brackets Coding
In this encoding, a wide character is represented by the following eight
[ " a b c d " ]
@end smallexample
-Where @code{a}, @code{b}, @code{c}, @code{d} are the four hexadecimal
-characters (using uppercase letters) of the wide character code. For
+@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#}.
This scheme is compatible with use of the full 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
+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
+values can be represented. 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
+Constraint_Error to be raised. An invalid wide character sequence on
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
@noindent
@code{Ada.Wide_Text_IO} is similar to @code{Ada.Text_IO} in its handling
-of stream pointer positioning (@pxref{Text_IO}). There is one additional
+of stream pointer positioning (@pxref{Text_IO}). There is one additional
case:
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
@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
+wide character sequence. Again this is to avoid the need for buffering
or backup, and all @code{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_Text_IO}. However, this discrepancy
+to a normal program using @code{Wide_Text_IO}. However, this discrepancy
can be observed if the wide text file shares a stream with another file.
@node Wide_Text_IO Reading and Writing Non-Regular Files
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
+@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
@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
-@code{Stream_Element} is simply a byte. There are two ways to read or
+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.
@itemize @bullet
@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.
@item
In the absence of a @samp{shared=@var{xxx}} form parameter, an attempt
to open two or more files with the same full name is considered an error
-and is not supported. The exception @code{Use_Error} will be
-raised. Note that a file that is not explicitly closed by the program
+and is not supported. The exception @code{Use_Error} will be
+raised. Note that a file that is not explicitly closed by the program
remains open until the program terminates.
@item
If the form parameter @samp{shared=no} appears in the form string, the
file can be opened or created with its own separate stream identifier,
regardless of whether other files sharing the same external file are
-opened. The exact effect depends on how the C stream routines handle
+opened. The exact effect depends on how the C stream routines handle
multiple accesses to the same external files using separate streams.
@item
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.
When a program is ported from GNAT to some other Ada compiler, no
special attention is required unless the @samp{shared=@var{xxx}} form
-parameter is used in the program. In this case, you must examine the
+parameter is used in the program. In this case, you must examine the
documentation of the new compiler to see if it supports the required
-file sharing semantics, and form strings modified appropriately. Of
+file sharing semantics, and form strings modified appropriately. Of
course it may be the case that the program cannot be ported if the
-target compiler does not support the required functionality. The best
+target compiler does not support the required functionality. The best
approach in writing portable code is to avoid file sharing (and hence
the use of the @samp{shared=@var{xxx}} parameter in the form string)
completely.
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
+heterogeneous input-output. Although this approach will work in GNAT if
+@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
+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
-to LF characters internally. This mapping only occurs in DOS and
+to LF characters internally. This mapping only occurs in DOS and
DOS-like systems, and is not relevant to other systems.
-A special case occurs with Stream_IO@. As shown in the above table, the
+A special case occurs with Stream_IO@. As shown in the above table, the
file is initially opened in @samp{r} or @samp{w} mode for the
-@code{In_File} and @code{Out_File} cases. If a @code{Set_Mode} operation
+@code{In_File} and @code{Out_File} cases. If a @code{Set_Mode} operation
subsequently requires switching from reading to writing or vice-versa,
then the file is reopened in @samp{r+} mode to permit the required operation.
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
subtype long is Long_Integer;
-- Note: the above types are subtypes deliberately, and it
-- is part of this spec that the above correspondences are
- -- guaranteed. This means that it is legitimate to, for
- -- example, use Integer instead of int. We provide these
+ -- guaranteed. This means that it is legitimate to, for
+ -- example, use Integer instead of int. We provide these
-- synonyms for clarity, but in some cases it may be
-- convenient to use the underlying types (for example to
-- avoid an unnecessary dependency of a spec on the spec
-- 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;
--------------------------
-- The functions selected below are ones that are
-- 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
+ -- 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
-- "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;
---------------------------------
-- If text_translation_required is true, then the following
-- functions may be used to dynamically switch a file from
- -- binary to text mode or vice versa. These functions have
- -- no effect if text_translation_required is false (i.e. in
- -- normal UNIX mode). Use fileno to get a stream handle.
+ -- binary to text mode or vice versa. These functions have
+ -- no effect if text_translation_required is false (i.e. in
+ -- normal UNIX mode). Use fileno to get a stream handle.
procedure set_binary_mode (handle : int);
procedure set_text_mode (handle : 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
+ -- that is big enough for any full path name. Use
-- max_path_len given below as the size of buffer.
max_path_len : integer;
-- Maximum length of an allowable full path name on the
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
-@code{FILE} pointer from a currently opened Ada file. It is then
+@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
-operate on it directly. Of course the program is responsible for
+operate on it directly. Of course the program is responsible for
ensuring that only appropriate sequences of operations are executed.
One particular use of relevance to an Ada program is that the
@code{setvbuf} function can be used to control the buffering of the
-stream used by an Ada file. In the absence of such a call the standard
+stream used by an Ada file. In the absence of such a call the standard
default buffering is used.
The @code{Open} procedures in these packages open a file giving an
-existing C Stream instead of a file name. Typically this stream is
+existing C Stream instead of a file name. Typically this stream is
imported from a C program, allowing an Ada file to operate on an
existing C file.
@noindent
The GNAT library contains a number of general and special purpose packages.
It represents functionality that the GNAT developers have found useful, and
-which is made available to GNAT users. The packages described here are fully
+which is made available to GNAT users. The packages described here are fully
supported, and upwards compatibility will be maintained in future releases,
so you can use these facilities with the confidence that the same functionality
will be available in future releases.
The chapter here simply gives a brief summary of the facilities available.
-The full documentation is found in the spec file for the package. The full
+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
-extensive examples, look in the g-spipat.ads file in the library.
+with all GNAT releases. For example, to find out the full specifications of
+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}
clause) is given, followed by the name of the corresponding spec file in
-parentheses. The packages are children in four hierarchies, @code{Ada},
+parentheses. The packages are children in four hierarchies, @code{Ada},
@code{Interfaces}, @code{System}, and @code{GNAT}, the latter being a
GNAT-specific hierarchy.
four hierarchies if the package is defined in the Ada Reference Manual,
or is listed in this section of the GNAT Programmers Reference Manual.
All other units should be considered internal implementation units and
-should not be directly @code{with}'ed by application code. The use of
+should not be directly @code{with}'ed by application code. The use of
a @code{with} statement that references one of these internal implementation
units makes an application potentially dependent on changes in versions
of GNAT, and will generate a warning message.
@menu
+* 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 (g-io.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.Os2lib.Threads (i-os2thr.ads)::
* Interfaces.Packed_Decimal (i-pacdec.ads)::
* Interfaces.VxWorks (i-vxwork.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)::
@end menu
+@node Ada.Characters.Latin_9 (a-chlat9.ads)
+@section @code{Ada.Characters.Latin_9} (@file{a-chlat9.ads})
+@cindex @code{Ada.Characters.Latin_9} (@file{a-chlat9.ads})
+@cindex Latin_9 constants for 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
+few modifications required for @code{Latin-9}
+The provision of such a package
+is specifically authorized by the Ada Reference Manual
+(RM A.3.3(27)).
+
@node Ada.Characters.Wide_Latin_1 (a-cwila1.ads)
-@section Ada.Characters.Wide_Latin_1 (a-cwila1.ads)
-@cindex Ada.Characters.Wide_Latin_1 (a-cwila1.ads)
-@cindex Latin_1 constants for Wide_Character
+@section @code{Ada.Characters.Wide_Latin_1} (@file{a-cwila1.ads})
+@cindex @code{Ada.Characters.Wide_Latin_1} (@file{a-cwila1.ads})
+@cindex Latin_1 constants for 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_Character}
-instead of @code{Character}. The provision of such a package
+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.Command_Line.Remove (a-colire.ads)
-@section Ada.Command_Line.Remove (a-colire.ads)
-@cindex Ada.Command_Line.Remove (a-colire.ads)
-@cindex Removing command line arguments
-@cindex Command line, argument removal
+@node Ada.Characters.Wide_Latin_9 (a-cwila9.ads)
+@section @code{Ada.Characters.Wide_Latin_9} (@file{a-cwila1.ads})
+@cindex @code{Ada.Characters.Wide_Latin_9} (@file{a-cwila1.ads})
+@cindex Latin_9 constants for Wide_Character
@noindent
-This child of @code{Ada.Command_Line}
-provides a mechanism for logically removing
-arguments from the argument list. Once removed, an argument is not visible
-to further calls on the subprograms in @code{Ada.Command_Line} will not
-see the removed argument.
+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_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.Direct_IO.C_Streams (a-diocst.ads)
-@section Ada.Direct_IO.C_Streams (a-diocst.ads)
-@cindex Ada.Direct_IO.C_Streams (a-diocst.ads)
-@cindex C Streams, Interfacing with Direct_IO
+@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 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
+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})
+@cindex @code{Ada.Command_Line.Remove} (@file{a-colire.ads})
+@cindex Removing command line arguments
+@cindex Command line, argument removal
+
+@noindent
+This child of @code{Ada.Command_Line}
+provides a mechanism for logically removing
+arguments from the argument list. Once removed, an argument is not visible
+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
+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.
@node Ada.Exceptions.Is_Null_Occurrence (a-einuoc.ads)
-@section Ada.Exceptions.Is_Null_Occurrence (a-einuoc.ads)
-@cindex Ada.Exceptions.Is_Null_Occurrence (a-einuoc.ads)
-@cindex Null_Occurrence, testing for
+@section @code{Ada.Exceptions.Is_Null_Occurrence} (@file{a-einuoc.ads})
+@cindex @code{Ada.Exceptions.Is_Null_Occurrence} (@file{a-einuoc.ads})
+@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 Ada.Sequential_IO.C_Streams (a-siocst.ads)
-@cindex Ada.Sequential_IO.C_Streams (a-siocst.ads)
-@cindex C Streams, Interfacing with Sequential_IO
+@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
-C streams and @code{Sequential_IO}. The stream identifier can be
+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.
@node Ada.Streams.Stream_IO.C_Streams (a-ssicst.ads)
-@section Ada.Streams.Stream_IO.C_Streams (a-ssicst.ads)
-@cindex Ada.Streams.Stream_IO.C_Streams (a-ssicst.ads)
-@cindex C Streams, Interfacing with Stream_IO
+@section @code{Ada.Streams.Stream_IO.C_Streams} (@file{a-ssicst.ads})
+@cindex @code{Ada.Streams.Stream_IO.C_Streams} (@file{a-ssicst.ads})
+@cindex C Streams, Interfacing with Stream_IO
@noindent
-This package provides subprograms that allow interfacing between
-C streams and @code{Stream_IO}. The stream identifier can be
+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.
@node Ada.Strings.Unbounded.Text_IO (a-suteio.ads)
-@section Ada.Strings.Unbounded.Text_IO (a-suteio.ads)
-@cindex Ada.Strings.Unbounded.Text_IO (a-suteio.ads)
-@cindex Unbounded_String, IO support
-@cindex Text_IO, extensions for unbounded strings
+@section @code{Ada.Strings.Unbounded.Text_IO} (@file{a-suteio.ads})
+@cindex @code{Ada.Strings.Unbounded.Text_IO} (@file{a-suteio.ads})
+@cindex @code{Unbounded_String}, IO support
+@cindex @code{Text_IO}, extensions for unbounded strings
@noindent
This package provides subprograms for Text_IO for unbounded
with ordinary strings.
@node Ada.Strings.Wide_Unbounded.Wide_Text_IO (a-swuwti.ads)
-@section Ada.Strings.Wide_Unbounded.Wide_Text_IO (a-swuwti.ads)
-@cindex Ada.Strings.Wide_Unbounded.Wide_Text_IO (a-swuwti.ads)
-@cindex Unbounded_Wide_String, IO support
-@cindex Text_IO, extensions for unbounded wide strings
+@section @code{Ada.Strings.Wide_Unbounded.Wide_Text_IO} (@file{a-swuwti.ads})
+@cindex @code{Ada.Strings.Wide_Unbounded.Wide_Text_IO} (@file{a-swuwti.ads})
+@cindex @code{Unbounded_Wide_String}, IO support
+@cindex @code{Text_IO}, extensions for unbounded wide strings
@noindent
This package provides subprograms for Text_IO for unbounded
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 Ada.Text_IO.C_Streams (a-tiocst.ads)
-@cindex Ada.Text_IO.C_Streams (a-tiocst.ads)
-@cindex C Streams, Interfacing with Text_IO
+@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
-C streams and @code{Text_IO}. The stream identifier can be
+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.
@node Ada.Wide_Text_IO.C_Streams (a-wtcstr.ads)
-@section Ada.Wide_Text_IO.C_Streams (a-wtcstr.ads)
-@cindex Ada.Wide_Text_IO.C_Streams (a-wtcstr.ads)
-@cindex C Streams, Interfacing with Wide_Text_IO
+@section @code{Ada.Wide_Text_IO.C_Streams} (@file{a-wtcstr.ads})
+@cindex @code{Ada.Wide_Text_IO.C_Streams} (@file{a-wtcstr.ads})
+@cindex C Streams, Interfacing with @code{Wide_Text_IO}
+
+@noindent
+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_Text_IO}. The stream identifier can be
+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 GNAT.AWK (g-awk.ads)
-@cindex GNAT.AWK (g-awk.ads)
+@section @code{GNAT.AWK} (@file{g-awk.ads})
+@cindex @code{GNAT.AWK} (@file{g-awk.ads})
@cindex Parsing
+@cindex AWK
@noindent
Provides AWK-like parsing functions, with an easy interface for parsing one
-or more files containing formatted data. The file is viewed as a database
+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.Bubble_Sort_A (g-busora.ads)
-@section GNAT.Bubble_Sort_A (g-busora.ads)
-@cindex GNAT.Bubble_Sort_A (g-busora.ads)
+@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. Move and comparison procedures are provided by passing
+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})
+@cindex Sorting
+@cindex Bubble sort
+
+@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. 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 GNAT.Bubble_Sort_G (g-busorg.ads)
-@cindex GNAT.Bubble_Sort_G (g-busorg.ads)
+@section @code{GNAT.Bubble_Sort_G} (@file{g-busorg.ads})
+@cindex @code{GNAT.Bubble_Sort_G} (@file{g-busorg.ads})
@cindex Sorting
+@cindex Bubble sort
@noindent
Similar to @code{Bubble_Sort_A} except that the move and sorting procedures
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 GNAT.Calendar (g-calend.ads)
-@cindex GNAT.Calendar (g-calend.ads)
-@cindex Calendar
+@section @code{GNAT.Calendar} (@file{g-calend.ads})
+@cindex @code{GNAT.Calendar} (@file{g-calend.ads})
+@cindex @code{Calendar}
@noindent
Extends the facilities provided by @code{Ada.Calendar} to include handling
C @code{timeval} format.
@node GNAT.Calendar.Time_IO (g-catiio.ads)
-@section GNAT.Calendar.Time_IO (g-catiio.ads)
-@cindex Calendar
+@section @code{GNAT.Calendar.Time_IO} (@file{g-catiio.ads})
+@cindex @code{Calendar}
@cindex Time
-@cindex GNAT.Calendar.Time_IO (g-catiio.ads)
+@cindex @code{GNAT.Calendar.Time_IO} (@file{g-catiio.ads})
@node GNAT.CRC32 (g-crc32.ads)
-@section GNAT.CRC32 (g-crc32.ads)
-@cindex GNAT.CRC32 (g-crc32.ads)
+@section @code{GNAT.CRC32} (@file{g-crc32.ads})
+@cindex @code{GNAT.CRC32} (@file{g-crc32.ads})
@cindex CRC32
+@cindex Cyclic Redundancy Check
@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", 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.
+This package implements the CRC-32 algorithm. For a full description
+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 GNAT.Case_Util (g-casuti.ads)
-@cindex GNAT.Case_Util (g-casuti.ads)
+@section @code{GNAT.Case_Util} (@file{g-casuti.ads})
+@cindex @code{GNAT.Case_Util} (@file{g-casuti.ads})
@cindex Casing utilities
+@cindex Character handling (@code{GNAT.Case_Util})
@noindent
A set of simple routines for handling upper and lower casing of strings
in @code{Ada.Characters.Handling}.
@node GNAT.CGI (g-cgi.ads)
-@section GNAT.CGI (g-cgi.ads)
-@cindex GNAT.CGI (g-cgi.ads)
+@section @code{GNAT.CGI} (@file{g-cgi.ads})
+@cindex @code{GNAT.CGI} (@file{g-cgi.ads})
@cindex CGI (Common Gateway Interface)
@noindent
This is a package for interfacing a GNAT program with a Web server via the
-Common Gateway Interface (CGI). Basically this package parse the CGI
-parameters which are a set of key/value pairs sent by the Web server. It
+Common Gateway Interface (CGI)@. Basically this package parses the CGI
+parameters, which are a set of key/value pairs sent by the Web server. It
builds a table whose index is the key and provides some services to deal
with this table.
@node GNAT.CGI.Cookie (g-cgicoo.ads)
-@section GNAT.CGI.Cookie (g-cgicoo.ads)
-@cindex GNAT.CGI.Cookie (g-cgicoo.ads)
-@cindex CGI (Common Gateway Interface) Cookie support
+@section @code{GNAT.CGI.Cookie} (@file{g-cgicoo.ads})
+@cindex @code{GNAT.CGI.Cookie} (@file{g-cgicoo.ads})
+@cindex CGI (Common Gateway Interface) cookie support
+@cindex Cookie support in CGI
@noindent
This is a package to interface a GNAT program with a Web server via the
-Common Gateway Interface (CGI). It exports services to deal with Web
+Common Gateway Interface (CGI). It exports services to deal with Web
cookies (piece of information kept in the Web client software).
@node GNAT.CGI.Debug (g-cgideb.ads)
-@section GNAT.CGI.Debug (g-cgideb.ads)
-@cindex GNAT.CGI.Debug (g-cgideb.ads)
+@section @code{GNAT.CGI.Debug} (@file{g-cgideb.ads})
+@cindex @code{GNAT.CGI.Debug} (@file{g-cgideb.ads})
@cindex CGI (Common Gateway Interface) debugging
@noindent
programs written in Ada.
@node GNAT.Command_Line (g-comlin.ads)
-@section GNAT.Command_Line (g-comlin.ads)
-@cindex GNAT.Command_Line (g-comlin.ads)
+@section @code{GNAT.Command_Line} (@file{g-comlin.ads})
+@cindex @code{GNAT.Command_Line} (@file{g-comlin.ads})
@cindex Command line
@noindent
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 GNAT.Current_Exception (g-curexc.ads)
-@cindex GNAT.Current_Exception (g-curexc.ads)
+@section @code{GNAT.Current_Exception} (@file{g-curexc.ads})
+@cindex @code{GNAT.Current_Exception} (@file{g-curexc.ads})
@cindex Current exception
@cindex Exception retrieval
@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 mimicking 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)
-@section GNAT.Debug_Pools (g-debpoo.ads)
-@cindex GNAT.Debug_Pools (g-debpoo.ads)
+@section @code{GNAT.Debug_Pools} (@file{g-debpoo.ads})
+@cindex @code{GNAT.Debug_Pools} (@file{g-debpoo.ads})
@cindex Debugging
+@cindex Debug pools
+@cindex Memory corruption debugging
@noindent
Provide a debugging storage pools that helps tracking memory corruption
-problems. See section "Finding memory problems with GNAT Debug Pool" in
-the GNAT User's guide.
+problems. See section ``Finding memory problems with GNAT Debug Pool'' in
+the @cite{GNAT User's Guide}.
@node GNAT.Debug_Utilities (g-debuti.ads)
-@section GNAT.Debug_Utilities (g-debuti.ads)
-@cindex GNAT.Debug_Utilities (g-debuti.ads)
+@section @code{GNAT.Debug_Utilities} (@file{g-debuti.ads})
+@cindex @code{GNAT.Debug_Utilities} (@file{g-debuti.ads})
@cindex Debugging
@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 GNAT.Directory_Operations (g-dirope.ads)
-@cindex 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 GNAT.Dynamic_Tables (g-dyntab.ads)
-@cindex GNAT.Dynamic_Tables (g-dyntab.ads)
+@section @code{GNAT.Dynamic_Tables} (@file{g-dyntab.ads})
+@cindex @code{GNAT.Dynamic_Tables} (@file{g-dyntab.ads})
@cindex Table implementation
@cindex Arrays, extendable
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 GNAT.Exception_Traces (g-exctra.ads)
-@cindex GNAT.Exception_Traces (g-exctra.ads)
+@section @code{GNAT.Exception_Traces} (@file{g-exctra.ads})
+@cindex @code{GNAT.Exception_Traces} (@file{g-exctra.ads})
@cindex Exception traces
@cindex Debugging
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 GNAT.Expect (g-expect.ads)
-@cindex GNAT.Expect (g-expect.ads)
+@section @code{GNAT.Expect} (@file{g-expect.ads})
+@cindex @code{GNAT.Expect} (@file{g-expect.ads})
@noindent
Provides a set of subprograms similar to what is available
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)
-@section GNAT.Float_Control (g-flocon.ads)
-@cindex GNAT.Float_Control (g-flocon.ads)
+@section @code{GNAT.Float_Control} (@file{g-flocon.ads})
+@cindex @code{GNAT.Float_Control} (@file{g-flocon.ads})
@cindex Floating-Point Processor
@noindent
Provides an interface for resetting the floating-point processor into the
-mode required for correct semantic operation in Ada. Some third party
+mode required for correct semantic operation in Ada. Some third party
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 GNAT.Heap_Sort_A (g-hesora.ads)
-@cindex 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})
@cindex Sorting
@noindent
Provides a general implementation of heap sort usable for sorting arbitrary
data items. Move and comparison procedures are provided by passing
-access-to-procedure values. The algorithm used is a modified heap sort
+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 GNAT.Heap_Sort_G (g-hesorg.ads)
-@cindex GNAT.Heap_Sort_G (g-hesorg.ads)
+@section @code{GNAT.Heap_Sort_G} (@file{g-hesorg.ads})
+@cindex @code{GNAT.Heap_Sort_G} (@file{g-hesorg.ads})
@cindex Sorting
@noindent
multiple instantiations.
@node GNAT.HTable (g-htable.ads)
-@section GNAT.HTable (g-htable.ads)
-@cindex GNAT.HTable (g-htable.ads)
+@section @code{GNAT.HTable} (@file{g-htable.ads})
+@cindex @code{GNAT.HTable} (@file{g-htable.ads})
@cindex Hash tables
@noindent
A generic implementation of hash tables that can be used to hash arbitrary
-data. Provides two approaches, one a simple static approach, and the other
+data. Provides two approaches, one a simple static approach, and the other
allowing arbitrary dynamic hash tables.
@node GNAT.IO (g-io.ads)
-@section GNAT.IO (g-io.ads)
-@cindex GNAT.IO (g-io.ads)
+@section @code{GNAT.IO} (@file{g-io.ads})
+@cindex @code{GNAT.IO} (@file{g-io.ads})
@cindex Simple I/O
@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.
@node GNAT.IO_Aux (g-io_aux.ads)
-@section GNAT.IO_Aux (g-io_aux.ads)
-@cindex GNAT.IO_Aux (g-io_aux.ads)
+@section @code{GNAT.IO_Aux} (@file{g-io_aux.ads})
+@cindex @code{GNAT.IO_Aux} (@file{g-io_aux.ads})
@cindex Text_IO
@cindex Input/Output facilities
for whether a file exists, and functions for reading a line of text.
@node GNAT.Lock_Files (g-locfil.ads)
-@section GNAT.Lock_Files (g-locfil.ads)
-@cindex GNAT.Lock_Files (g-locfil.ads)
+@section @code{GNAT.Lock_Files} (@file{g-locfil.ads})
+@cindex @code{GNAT.Lock_Files} (@file{g-locfil.ads})
@cindex File locking
@cindex Locking using files
@noindent
-Provides a general interface for using files as locks. Can be used for
-providing program level synchronization.
+Provides a general interface for using files as locks. Can be used for
+providing program level synchronization.
+
+@node GNAT.MD5 (g-md5.ads)
+@section @code{GNAT.MD5} (@file{g-md5.ads})
+@cindex @code{GNAT.MD5} (@file{g-md5.ads})
+@cindex Message Digest MD5
+
+@noindent
+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 GNAT.Most_Recent_Exception (g-moreex.ads)
-@cindex GNAT.Most_Recent_Exception (g-moreex.ads)
+@section @code{GNAT.Most_Recent_Exception} (@file{g-moreex.ads})
+@cindex @code{GNAT.Most_Recent_Exception} (@file{g-moreex.ads})
@cindex Exception, obtaining most recent
@noindent
-Provides access to the most recently raised exception. Can be used for
+Provides access to the most recently raised exception. Can be used for
various logging purposes, including duplicating functionality of some
Ada 83 implementation dependent extensions.
@node GNAT.OS_Lib (g-os_lib.ads)
-@section GNAT.OS_Lib (g-os_lib.ads)
-@cindex GNAT.OS_Lib (g-os_lib.ads)
+@section @code{GNAT.OS_Lib} (@file{g-os_lib.ads})
+@cindex @code{GNAT.OS_Lib} (@file{g-os_lib.ads})
@cindex Operating System interface
@cindex Spawn capability
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 GNAT.Regexp (g-regexp.ads)
-@cindex GNAT.Regexp (g-regexp.ads)
+@section @code{GNAT.Regexp} (@file{g-regexp.ads})
+@cindex @code{GNAT.Regexp} (@file{g-regexp.ads})
@cindex Regular expressions
@cindex Pattern matching
@noindent
A simple implementation of regular expressions, using a subset of regular
-expression syntax copied from familiar Unix style utilities. This is the
+expression syntax copied from familiar Unix style utilities. This is the
simples of the three pattern matching packages provided, and is particularly
-suitable for "file globbing" applications.
+suitable for ``file globbing'' applications.
@node GNAT.Registry (g-regist.ads)
-@section GNAT.Registry (g-regist.ads)
-@cindex GNAT.Registry (g-regist.ads)
+@section @code{GNAT.Registry} (@file{g-regist.ads})
+@cindex @code{GNAT.Registry} (@file{g-regist.ads})
@cindex Windows Registry
@noindent
-This is a high level binding to the Windows registry. It is possible to
-do simple things like reading a key value, creating a new key. For full
+This is a high level binding to the Windows registry. It is possible to
+do simple things like reading a key value, creating a new key. For full
registry API, but at a lower level of abstraction, refer to the Win32.Winreg
package provided with the Win32Ada binding
@node GNAT.Regpat (g-regpat.ads)
-@section GNAT.Regpat (g-regpat.ads)
-@cindex GNAT.Regpat (g-regpat.ads)
+@section @code{GNAT.Regpat} (@file{g-regpat.ads})
+@cindex @code{GNAT.Regpat} (@file{g-regpat.ads})
@cindex Regular expressions
@cindex Pattern matching
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 GNAT.Sockets (g-socket.ads)
-@cindex GNAT.Sockets (g-socket.ads)
+@section @code{GNAT.Sockets} (@file{g-socket.ads})
+@cindex @code{GNAT.Sockets} (@file{g-socket.ads})
@cindex Sockets
@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 cross ports, and in particular is not
-implemented for VxWorks or LynxOS@.
+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 GNAT.Source_Info (g-souinf.ads)
-@cindex GNAT.Source_Info (g-souinf.ads)
+@section @code{GNAT.Source_Info} (@file{g-souinf.ads})
+@cindex @code{GNAT.Source_Info} (@file{g-souinf.ads})
@cindex Source Information
@noindent
compile time, such as the current file name and line number.
@node GNAT.Spell_Checker (g-speche.ads)
-@section GNAT.Spell_Checker (g-speche.ads)
-@cindex GNAT.Spell_Checker (g-speche.ads)
+@section @code{GNAT.Spell_Checker} (@file{g-speche.ads})
+@cindex @code{GNAT.Spell_Checker} (@file{g-speche.ads})
@cindex Spell checking
@noindent
near misspelling of another string.
@node GNAT.Spitbol.Patterns (g-spipat.ads)
-@section GNAT.Spitbol.Patterns (g-spipat.ads)
-@cindex GNAT.Spitbol.Patterns (g-spipat.ads)
+@section @code{GNAT.Spitbol.Patterns} (@file{g-spipat.ads})
+@cindex @code{GNAT.Spitbol.Patterns} (@file{g-spipat.ads})
@cindex SPITBOL pattern matching
@cindex Pattern matching
@noindent
-A complete implementation of SNOBOL4 style pattern matching. This is the
-most elaborate of the pattern matching packages provided. It fully duplicates
+A complete implementation of SNOBOL4 style pattern matching. This is the
+most elaborate of the pattern matching packages provided. It fully duplicates
the SNOBOL4 dynamic pattern construction and matching capabilities, using the
efficient algorithm developed by Robert Dewar for the SPITBOL system.
@node GNAT.Spitbol (g-spitbo.ads)
-@section GNAT.Spitbol (g-spitbo.ads)
-@cindex GNAT.Spitbol (g-spitbo.ads)
+@section @code{GNAT.Spitbol} (@file{g-spitbo.ads})
+@cindex @code{GNAT.Spitbol} (@file{g-spitbo.ads})
@cindex SPITBOL interface
@noindent
the SNOBOL4 TABLE function.
@node GNAT.Spitbol.Table_Boolean (g-sptabo.ads)
-@section GNAT.Spitbol.Table_Boolean (g-sptabo.ads)
-@cindex GNAT.Spitbol.Table_Boolean (g-sptabo.ads)
+@section @code{GNAT.Spitbol.Table_Boolean} (@file{g-sptabo.ads})
+@cindex @code{GNAT.Spitbol.Table_Boolean} (@file{g-sptabo.ads})
@cindex Sets of strings
@cindex SPITBOL Tables
string values.
@node GNAT.Spitbol.Table_Integer (g-sptain.ads)
-@section GNAT.Spitbol.Table_Integer (g-sptain.ads)
-@cindex GNAT.Spitbol.Table_Integer (g-sptain.ads)
+@section @code{GNAT.Spitbol.Table_Integer} (@file{g-sptain.ads})
+@cindex @code{GNAT.Spitbol.Table_Integer} (@file{g-sptain.ads})
@cindex Integer maps
@cindex Maps
@cindex SPITBOL Tables
from string to integer values.
@node GNAT.Spitbol.Table_VString (g-sptavs.ads)
-@section GNAT.Spitbol.Table_VString (g-sptavs.ads)
-@cindex GNAT.Spitbol.Table_VString (g-sptavs.ads)
+@section @code{GNAT.Spitbol.Table_VString} (@file{g-sptavs.ads})
+@cindex @code{GNAT.Spitbol.Table_VString} (@file{g-sptavs.ads})
@cindex String maps
@cindex Maps
@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 GNAT.Table (g-table.ads)
-@cindex GNAT.Table (g-table.ads)
+@section @code{GNAT.Table} (@file{g-table.ads})
+@cindex @code{GNAT.Table} (@file{g-table.ads})
@cindex Table implementation
@cindex Arrays, extendable
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)
-@section GNAT.Task_Lock (g-tasloc.ads)
-@cindex GNAT.Task_Lock (g-tasloc.ads)
+@section @code{GNAT.Task_Lock} (@file{g-tasloc.ads})
+@cindex @code{GNAT.Task_Lock} (@file{g-tasloc.ads})
@cindex Task synchronization
@cindex Task locking
@cindex Locking
@noindent
A very simple facility for locking and unlocking sections of code using a
-single global task lock. Appropriate for use in situations where contention
+single global task lock. Appropriate for use in situations where contention
between tasks is very rarely expected.
@node GNAT.Threads (g-thread.ads)
-@section GNAT.Threads (g-thread.ads)
-@cindex GNAT.Threads (g-thread.ads)
+@section @code{GNAT.Threads} (@file{g-thread.ads})
+@cindex @code{GNAT.Threads} (@file{g-thread.ads})
@cindex Foreign threads
@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 GNAT.Traceback (g-traceb.ads)
-@cindex GNAT.Traceback (g-traceb.ads)
+@section @code{GNAT.Traceback} (@file{g-traceb.ads})
+@cindex @code{GNAT.Traceback} (@file{g-traceb.ads})
@cindex Trace back facilities
@noindent
in various debugging situations.
@node GNAT.Traceback.Symbolic (g-trasym.ads)
-@section GNAT.Traceback.Symbolic (g-trasym.ads)
-@cindex GNAT.Traceback.Symbolic (g-trasym.ads)
+@section @code{GNAT.Traceback.Symbolic} (@file{g-trasym.ads})
+@cindex @code{GNAT.Traceback.Symbolic} (@file{g-trasym.ads})
@cindex Trace back facilities
@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 Interfaces.C.Extensions (i-cexten.ads)
-@cindex Interfaces.C.Extensions (i-cexten.ads)
+@section @code{Interfaces.C.Extensions} (@file{i-cexten.ads})
+@cindex @code{Interfaces.C.Extensions} (@file{i-cexten.ads})
@noindent
This package contains additional C-related definitions, intended
to C libraries.
@node Interfaces.C.Streams (i-cstrea.ads)
-@section Interfaces.C.Streams (i-cstrea.ads)
-@cindex Interfaces.C.Streams (i-cstrea.ads)
+@section @code{Interfaces.C.Streams} (@file{i-cstrea.ads})
+@cindex @code{Interfaces.C.Streams} (@file{i-cstrea.ads})
@cindex C streams, interfacing
@noindent
on C streams.
@node Interfaces.CPP (i-cpp.ads)
-@section Interfaces.CPP (i-cpp.ads)
-@cindex Interfaces.CPP (i-cpp.ads)
+@section @code{Interfaces.CPP} (@file{i-cpp.ads})
+@cindex @code{Interfaces.CPP} (@file{i-cpp.ads})
@cindex C++ interfacing
@cindex Interfacing, to C++
@noindent
-This package provides facilities for use in interfacing to C++. It
+This package provides facilities for use in interfacing to C++. It
is primarily intended to be used in connection with automated tools
for the generation of C++ interfaces.
@node Interfaces.Os2lib (i-os2lib.ads)
-@section Interfaces.Os2lib (i-os2lib.ads)
-@cindex Interfaces.Os2lib (i-os2lib.ads)
+@section @code{Interfaces.Os2lib} (@file{i-os2lib.ads})
+@cindex @code{Interfaces.Os2lib} (@file{i-os2lib.ads})
@cindex Interfacing, to OS/2
@cindex OS/2 interfacing
various @file{<bse@.h>} files.
@node Interfaces.Os2lib.Errors (i-os2err.ads)
-@section Interfaces.Os2lib.Errors (i-os2err.ads)
-@cindex Interfaces.Os2lib.Errors (i-os2err.ads)
+@section @code{Interfaces.Os2lib.Errors} (@file{i-os2err.ads})
+@cindex @code{Interfaces.Os2lib.Errors} (@file{i-os2err.ads})
@cindex OS/2 Error codes
@cindex Interfacing, to OS/2
@cindex OS/2 interfacing
This package provides definitions of the OS/2 error codes.
@node Interfaces.Os2lib.Synchronization (i-os2syn.ads)
-@section Interfaces.Os2lib.Synchronization (i-os2syn.ads)
-@cindex Interfaces.Os2lib.Synchronization (i-os2syn.ads)
+@section @code{Interfaces.Os2lib.Synchronization} (@file{i-os2syn.ads})
+@cindex @code{Interfaces.Os2lib.Synchronization} (@file{i-os2syn.ads})
@cindex Interfacing, to OS/2
@cindex Synchronization, OS/2
@cindex OS/2 synchronization primitives
to the @code{OS/2} synchronization primitives.
@node Interfaces.Os2lib.Threads (i-os2thr.ads)
-@section Interfaces.Os2lib.Threads (i-os2thr.ads)
-@cindex Interfaces.Os2lib.Threads (i-os2thr.ads)
+@section @code{Interfaces.Os2lib.Threads} (@file{i-os2thr.ads})
+@cindex @code{Interfaces.Os2lib.Threads} (@file{i-os2thr.ads})
@cindex Interfacing, to OS/2
@cindex Thread control, OS/2
@cindex OS/2 thread interfacing
to the @code{OS/2} thread primitives.
@node Interfaces.Packed_Decimal (i-pacdec.ads)
-@section Interfaces.Packed_Decimal (i-pacdec.ads)
-@cindex Interfaces.Packed_Decimal (i-pacdec.ads)
+@section @code{Interfaces.Packed_Decimal} (@file{i-pacdec.ads})
+@cindex @code{Interfaces.Packed_Decimal} (@file{i-pacdec.ads})
@cindex IBM Packed Format
@cindex Packed Decimal
mainframes.
@node Interfaces.VxWorks (i-vxwork.ads)
-@section Interfaces.VxWorks (i-vxwork.ads)
-@cindex Interfaces.VxWorks (i-vxwork.ads)
+@section @code{Interfaces.VxWorks} (@file{i-vxwork.ads})
+@cindex @code{Interfaces.VxWorks} (@file{i-vxwork.ads})
@cindex Interfacing to VxWorks
@cindex VxWorks, interfacing
@noindent
-This package provides a limited binding to the VxWorks API
+This package provides a limited binding to the VxWorks API.
In particular, it interfaces with the
-VxWorks hardware interrupt facilities
+VxWorks hardware interrupt facilities.
+
+@node Interfaces.VxWorks.IO (i-vxwoio.ads)
+@section @code{Interfaces.VxWorks.IO} (@file{i-vxwoio.ads})
+@cindex @code{Interfaces.VxWorks.IO} (@file{i-vxwoio.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 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 System.Address_Image (s-addima.ads)
-@cindex System.Address_Image (s-addima.ads)
+@section @code{System.Address_Image} (@file{s-addima.ads})
+@cindex @code{System.Address_Image} (@file{s-addima.ads})
@cindex Address image
@cindex Image, of an address
string which identifies an address.
@node System.Assertions (s-assert.ads)
-@section System.Assertions (s-assert.ads)
-@cindex System.Assertions (s-assert.ads)
-@cindex Assertions
-@cindex Assert_Failure, exception
+@section @code{System.Assertions} (@file{s-assert.ads})
+@cindex @code{System.Assertions} (@file{s-assert.ads})
+@cindex Assertions
+@cindex Assert_Failure, exception
@noindent
This package provides the declaration of the exception raised
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 System.Partition_Interface (s-parint.ads)
-@cindex System.Partition_Interface (s-parint.ads)
-@cindex Partition intefacing functions
+@section @code{System.Partition_Interface} (@file{s-parint.ads})
+@cindex @code{System.Partition_Interface} (@file{s-parint.ads})
+@cindex Partition interfacing functions
@noindent
-This package provides facilities for partition interfacing. It
+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 System.Task_Info (s-tasinf.ads)
-@cindex System.Task_Info (s-tasinf.ads)
-@cindex Task_Info pragma
+@section @code{System.Task_Info} (@file{s-tasinf.ads})
+@cindex @code{System.Task_Info} (@file{s-tasinf.ads})
+@cindex Task_Info pragma
@noindent
This package provides target dependent functionality that is used
to support the @code{Task_Info} pragma
@node System.Wch_Cnv (s-wchcnv.ads)
-@section System.Wch_Cnv (s-wchcnv.ads)
-@cindex System.Wch_Cnv (s-wchcnv.ads)
+@section @code{System.Wch_Cnv} (@file{s-wchcnv.ads})
+@cindex @code{System.Wch_Cnv} (@file{s-wchcnv.ads})
@cindex Wide Character, Representation
@cindex Wide String, Conversion
@cindex Representation of wide characters
@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. Uses definitions in
-package @code{System.Wch_Con}
+encoding method. It uses definitions in
+package @code{System.Wch_Con}.
@node System.Wch_Con (s-wchcon.ads)
-@section System.Wch_Con (s-wchcon.ads)
-@cindex System.Wch_Con (s-wchcon.ads)
+@section @code{System.Wch_Con} (@file{s-wchcon.ads})
+@cindex @code{System.Wch_Con} (@file{s-wchcon.ads})
@noindent
This package provides definitions and descriptions of
the various methods used for encoding wide characters
-in ordinary strings. These definitions are used by
+in ordinary strings. These definitions are used by
the package @code{System.Wch_Cnv}.
@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
+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
-effect, since this is the default. The following table shows the
+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.
@table @code
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 signed char, short, 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.
+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.
@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
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
-multi- dimensional array causes the array to be stored in column-major
+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 Ada in a pragma Import or
-pragma 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
-provided by the asm instruction in the GNU C compiler. Full understanding
+@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 GNU CC} 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 GNU CC documentation is the C @code{asm}
+The first example given in the GCC documentation is the C @code{asm}
instruction:
@smallexample
asm ("fsinx %1 %0" : "=f" (result) : "f" (angle));
@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 CC@. This string must be a static
-expression. The second argument is the output operand list. It 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
either a single @code{Asm_Output} attribute reference, or a list of such
references enclosed in parentheses (technically an array aggregate of
such references).
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
-of the type designated by the attribute prefix. The first (string)
+of the type designated by the attribute prefix. The first (string)
argument is required to be a static expression and designates the
constraint for the parameter (e.g.@: what kind of register is
-required). The second argument is the variable to be updated with the
-result. The possible values for constraint are the same as those used in
+required). The second argument is the variable to be updated with the
+result. The possible values for constraint are the same as those used in
the RTL, and are dependent on the configuration file used to build the
GCC back end. If there are no output operands, then this argument may
either be omitted, or explicitly given as @code{No_Output_Operands}.
all names have the form of expressions, so there is no syntactic
irregularity, even though normally functions would not be permitted
@code{out} parameters. The third argument is the list of input
-operands. It is either a single @code{Asm_Input} attribute reference, or
+operands. It is either a single @code{Asm_Input} attribute reference, or
a list of such references enclosed in parentheses (technically an array
aggregate of such references).
The @code{Asm_Input} attribute denotes a function that takes two
parameters. The first is a string, the second is an expression of the
-type designated by the prefix. The first (string) argument is required
+type designated by the prefix. The first (string) argument is required
to be a static expression, and is the constraint for the parameter,
-(e.g.@: what kind of register is required). The second argument is the
-value to be used as the input argument. The possible values for the
+(e.g.@: what kind of register is required). The second argument is the
+value to be used as the input argument. The possible values for the
constant are the same as those used in the RTL, and are dependent on
the configuration file used to built the GCC back end.
If there are no input operands, this argument may either be omitted, or
explicitly given as @code{No_Input_Operands}. The fourth argument, not
present in the above example, is a list of register names, called the
-@dfn{clobber} argument. This argument, if given, must be a static string
+@dfn{clobber} argument. This argument, if given, must be a static string
expression, and is a space or comma separated list of names of registers
-that must be considered destroyed as a result of the @code{Asm} call. If
+that must be considered destroyed as a result of the @code{Asm} call. If
this argument is the null string (the default value), then the code
generator assumes that no additional registers are destroyed.
The fifth argument, not present in the above example, called the
-@dfn{volatile} argument, is by default @code{False}. It can be set to
+@dfn{volatile} argument, is by default @code{False}. It can be set to
the literal value @code{True} to indicate to the code generator that all
optimizations with respect to the instruction specified should be
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.
+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
+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
-correspond to what the RM calls ``intrinsic'' routines. Such calls can
+correspond to what the RM calls ``intrinsic'' routines. Such calls can
be used to intersperse machine instructions with other Ada statements.
Second, the function forms, which return a dummy value of the limited
private type @code{Asm_Insn}, can be used in code statements, and indeed
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
+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
+layer known as GNARL@. This code is responsible for implementing the
correct semantics of Ada's task creation, rendezvous, protected
operations etc.
GNARL decomposes Ada's tasking semantics into simpler lower level
operations such as create a thread, set the priority of a thread,
-yield, create a lock, lock/unlock, etc. The spec for these low-level
-operations constitutes GNULLI, the GNULL Interface. This interface is
+yield, create a lock, lock/unlock, etc. The spec for these low-level
+operations constitutes GNULLI, the GNULL Interface. This interface is
directly inspired from the POSIX real-time API@.
If the underlying executive or OS implements the POSIX standard
faithfully, the GNULL Interface maps as is to the services offered by
-the underlying kernel. Otherwise, some target dependent glue code maps
+the underlying kernel. Otherwise, some target dependent glue code maps
the services offered by the underlying kernel to the semantics expected
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
-kernel. For example, in the case of VxWorks
-
- 1 Ada task = 1 VxWorks task
+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
+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
which ensures that accurate FIFO_Within_Priorities semantics are
respected.
-The principle is as follows. When an Ada task T is about to start
+The principle is as follows. When an Ada task T is about to start
running, it checks whether some other Ada task R with the same
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.
+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.
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
-complex data structures by means of a single construct. As a result, the
+
+@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
+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
+executable code. The following is an outline of the code that GNAT generates
+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
+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
+@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
-
-The same is true for arrays of one-dimensional arrays: the following are
-static:
-
-@smallexample
-type ar1b is array (1..3) of boolean;
+@end smallexample
+
+@noindent
+The same is true for arrays of one-dimensional arrays: the following are
+static:
+
+@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
+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 "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
+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);
+object. The declarations
+
+@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
+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
-component assignments. For example, consider the simple case:
-
-@smallexample
-@end smallexample
+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
+component assignments. For example, consider the simple case:
+
+@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
+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:
+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 @code{GNAT} compiler. In addition,
-a complete compatible PCS is available as part of the @code{GLADE} system,
-a separate product available from Ada Core Technologies. 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
-@node Compatibility Guide
-@chapter Compatibility Guide
+@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
-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.
+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 Strict Conformance to the Ada Reference Manual
+@section Strict Conformance to the Ada Reference Manual
+
+@noindent
+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
+@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 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.
-
-@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 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 Numeric_Error is now the same as Constraint_Error
-In Ada 95, the exception Numeric_Error is a renaming of 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
-Numeric_Error case (since even in Ada 83, a compiler was free to raise
-Constraint_Error in place of Numeric_Error in all cases).
-
-@item Indefinite subtypes in generics
-In Ada 83, it was permissible to pass an indefinite type (e.g.@: 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 (<>) 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
-(<>) 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 (<>) 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 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
-type X is access all String;
-for X'Size use Standard'Address_Size;
+typed_string_declaration ::=
+ @b{type} <typed_string_>_simple_name @b{is}
+ ( string_literal @{, 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.
+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
+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
+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.
-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:
+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.
+
+@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
+
+package_specification ::=
+ @b{package} package_identifier @b{is}
+ @{simple_declarative_item@}
+ @b{end} package_identifier ;
-function To_Address_Long (X : Unsigned_Longword)
- return Address;
-pragma Pure_Function (To_Address_Long);
+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
-This means that programs using TO_ADDRESS for UNSIGNED_LONGWORD must
-change the name to TO_ADDRESS_LONG@.
+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}:
-@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.
+@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
-For full details on these and other less significant compatibility issues,
-see appendix E of the Digital publication entitled "DEC Ada, Technical
-Overview and Comparison on DIGITAL Platforms".
+@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
+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.
+
+@end table
+
+@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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