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| author | mir3636 |
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| date | Thu, 25 Oct 2018 07:37:49 +0900 |
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\input texinfo @c -*-texinfo-*- @c %**start of header @setfilename gnat_ugn.info @documentencoding UTF-8 @ifinfo @*Generated by Sphinx 1.4.6.@* @end ifinfo @settitle GNAT User's Guide for Native Platforms @defindex ge @paragraphindent 0 @exampleindent 4 @finalout @dircategory GNU Ada Tools @direntry * gnat_ugn: (gnat_ugn.info). gnat_ugn @end direntry @definfoenclose strong,`,' @definfoenclose emph,`,' @c %**end of header @copying @quotation GNAT User's Guide for Native Platforms , Aug 20, 2018 AdaCore Copyright @copyright{} 2008-2018, Free Software Foundation @end quotation @end copying @titlepage @title GNAT User's Guide for Native Platforms @insertcopying @end titlepage @contents @c %** start of user preamble @c %** end of user preamble @ifnottex @node Top @top GNAT User's Guide for Native Platforms @insertcopying @end ifnottex @c %**start of body @anchor{gnat_ugn doc}@anchor{0} @emph{GNAT, The GNU Ada Development Environment} @include gcc-common.texi GCC version @value{version-GCC}@* AdaCore Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, with the Front-Cover Texts being "GNAT User's Guide for Native Platforms", and with no Back-Cover Texts. A copy of the license is included in the section entitled @ref{1,,GNU Free Documentation License}. @menu * About This Guide:: * Getting Started with GNAT:: * The GNAT Compilation Model:: * Building Executable Programs with GNAT:: * GNAT Utility Programs:: * GNAT and Program Execution:: * Platform-Specific Information:: * Example of Binder Output File:: * Elaboration Order Handling in GNAT:: * Inline Assembler:: * GNU Free Documentation License:: * Index:: @detailmenu --- The Detailed Node Listing --- About This Guide * What This Guide Contains:: * What You Should Know before Reading This Guide:: * Related Information:: * A Note to Readers of Previous Versions of the Manual:: * Conventions:: Getting Started with GNAT * Running GNAT:: * Running a Simple Ada Program:: * Running a Program with Multiple Units:: * Using the gnatmake Utility:: The GNAT Compilation Model * Source Representation:: * Foreign Language Representation:: * File Naming Topics and Utilities:: * Configuration Pragmas:: * Generating Object Files:: * Source Dependencies:: * The Ada Library Information Files:: * Binding an Ada Program:: * GNAT and Libraries:: * Conditional Compilation:: * Mixed Language Programming:: * GNAT and Other Compilation Models:: * Using GNAT Files with External Tools:: Foreign Language Representation * Latin-1:: * Other 8-Bit Codes:: * Wide_Character Encodings:: * Wide_Wide_Character Encodings:: File Naming Topics and Utilities * File Naming Rules:: * Using Other File Names:: * Alternative File Naming Schemes:: * Handling Arbitrary File Naming Conventions with gnatname:: * File Name Krunching with gnatkr:: * Renaming Files with gnatchop:: Handling Arbitrary File Naming Conventions with gnatname * Arbitrary File Naming Conventions:: * Running gnatname:: * Switches for gnatname:: * Examples of gnatname Usage:: File Name Krunching with gnatkr * About gnatkr:: * Using gnatkr:: * Krunching Method:: * Examples of gnatkr Usage:: Renaming Files with gnatchop * Handling Files with Multiple Units:: * Operating gnatchop in Compilation Mode:: * Command Line for gnatchop:: * Switches for gnatchop:: * Examples of gnatchop Usage:: Configuration Pragmas * Handling of Configuration Pragmas:: * The Configuration Pragmas Files:: GNAT and Libraries * Introduction to Libraries in GNAT:: * General Ada Libraries:: * Stand-alone Ada Libraries:: * Rebuilding the GNAT Run-Time Library:: General Ada Libraries * Building a library:: * Installing a library:: * Using a library:: Stand-alone Ada Libraries * Introduction to Stand-alone Libraries:: * Building a Stand-alone Library:: * Creating a Stand-alone Library to be used in a non-Ada context:: * Restrictions in Stand-alone Libraries:: Conditional Compilation * Modeling Conditional Compilation in Ada:: * Preprocessing with gnatprep:: * Integrated Preprocessing:: Modeling Conditional Compilation in Ada * Use of Boolean Constants:: * Debugging - A Special Case:: * Conditionalizing Declarations:: * Use of Alternative Implementations:: * Preprocessing:: Preprocessing with gnatprep * Preprocessing Symbols:: * Using gnatprep:: * Switches for gnatprep:: * Form of Definitions File:: * Form of Input Text for gnatprep:: Mixed Language Programming * Interfacing to C:: * Calling Conventions:: * Building Mixed Ada and C++ Programs:: * Generating Ada Bindings for C and C++ headers:: * Generating C Headers for Ada Specifications:: Building Mixed Ada and C++ Programs * Interfacing to C++:: * Linking a Mixed C++ & Ada Program:: * A Simple Example:: * Interfacing with C++ constructors:: * Interfacing with C++ at the Class Level:: Generating Ada Bindings for C and C++ headers * Running the Binding Generator:: * Generating Bindings for C++ Headers:: * Switches:: Generating C Headers for Ada Specifications * Running the C Header Generator:: GNAT and Other Compilation Models * Comparison between GNAT and C/C++ Compilation Models:: * Comparison between GNAT and Conventional Ada Library Models:: Using GNAT Files with External Tools * Using Other Utility Programs with GNAT:: * The External Symbol Naming Scheme of GNAT:: Building Executable Programs with GNAT * Building with gnatmake:: * Compiling with gcc:: * Compiler Switches:: * Linker Switches:: * Binding with gnatbind:: * Linking with gnatlink:: * Using the GNU make Utility:: Building with gnatmake * Running gnatmake:: * Switches for gnatmake:: * Mode Switches for gnatmake:: * Notes on the Command Line:: * How gnatmake Works:: * Examples of gnatmake Usage:: Compiling with gcc * Compiling Programs:: * Search Paths and the Run-Time Library (RTL): Search Paths and the Run-Time Library RTL. * Order of Compilation Issues:: * Examples:: Compiler Switches * Alphabetical List of All Switches:: * Output and Error Message Control:: * Warning Message Control:: * Debugging and Assertion Control:: * Validity Checking:: * Style Checking:: * Run-Time Checks:: * Using gcc for Syntax Checking:: * Using gcc for Semantic Checking:: * Compiling Different Versions of Ada:: * Character Set Control:: * File Naming Control:: * Subprogram Inlining Control:: * Auxiliary Output Control:: * Debugging Control:: * Exception Handling Control:: * Units to Sources Mapping Files:: * Code Generation Control:: Binding with gnatbind * Running gnatbind:: * Switches for gnatbind:: * Command-Line Access:: * Search Paths for gnatbind:: * Examples of gnatbind Usage:: Switches for gnatbind * Consistency-Checking Modes:: * Binder Error Message Control:: * Elaboration Control:: * Output Control:: * Dynamic Allocation Control:: * Binding with Non-Ada Main Programs:: * Binding Programs with No Main Subprogram:: Linking with gnatlink * Running gnatlink:: * Switches for gnatlink:: Using the GNU make Utility * Using gnatmake in a Makefile:: * Automatically Creating a List of Directories:: * Generating the Command Line Switches:: * Overcoming Command Line Length Limits:: GNAT Utility Programs * The File Cleanup Utility gnatclean:: * The GNAT Library Browser gnatls:: * The Cross-Referencing Tools gnatxref and gnatfind:: * The Ada to HTML Converter gnathtml:: The File Cleanup Utility gnatclean * Running gnatclean:: * Switches for gnatclean:: The GNAT Library Browser gnatls * Running gnatls:: * Switches for gnatls:: * Example of gnatls Usage:: The Cross-Referencing Tools gnatxref and gnatfind * gnatxref Switches:: * gnatfind Switches:: * Configuration Files for gnatxref and gnatfind:: * Regular Expressions in gnatfind and gnatxref:: * Examples of gnatxref Usage:: * Examples of gnatfind Usage:: Examples of gnatxref Usage * General Usage:: * Using gnatxref with vi:: The Ada to HTML Converter gnathtml * Invoking gnathtml:: * Installing gnathtml:: GNAT and Program Execution * Running and Debugging Ada Programs:: * Profiling:: * Improving Performance:: * Overflow Check Handling in GNAT:: * Performing Dimensionality Analysis in GNAT:: * Stack Related Facilities:: * Memory Management Issues:: Running and Debugging Ada Programs * The GNAT Debugger GDB:: * Running GDB:: * Introduction to GDB Commands:: * Using Ada Expressions:: * Calling User-Defined Subprograms:: * Using the next Command in a Function:: * Stopping When Ada Exceptions Are Raised:: * Ada Tasks:: * Debugging Generic Units:: * Remote Debugging with gdbserver:: * GNAT Abnormal Termination or Failure to Terminate:: * Naming Conventions for GNAT Source Files:: * Getting Internal Debugging Information:: * Stack Traceback:: * Pretty-Printers for the GNAT runtime:: Stack Traceback * Non-Symbolic Traceback:: * Symbolic Traceback:: Profiling * Profiling an Ada Program with gprof:: Profiling an Ada Program with gprof * Compilation for profiling:: * Program execution:: * Running gprof:: * Interpretation of profiling results:: Improving Performance * Performance Considerations:: * Text_IO Suggestions:: * Reducing Size of Executables with Unused Subprogram/Data Elimination:: Performance Considerations * Controlling Run-Time Checks:: * Use of Restrictions:: * Optimization Levels:: * Debugging Optimized Code:: * Inlining of Subprograms:: * Floating_Point_Operations:: * Vectorization of loops:: * Other Optimization Switches:: * Optimization and Strict Aliasing:: * Aliased Variables and Optimization:: * Atomic Variables and Optimization:: * Passive Task Optimization:: Reducing Size of Executables with Unused Subprogram/Data Elimination * About unused subprogram/data elimination:: * Compilation options:: * Example of unused subprogram/data elimination:: Overflow Check Handling in GNAT * Background:: * Management of Overflows in GNAT:: * Specifying the Desired Mode:: * Default Settings:: * Implementation Notes:: Stack Related Facilities * Stack Overflow Checking:: * Static Stack Usage Analysis:: * Dynamic Stack Usage Analysis:: Memory Management Issues * Some Useful Memory Pools:: * The GNAT Debug Pool Facility:: Platform-Specific Information * Run-Time Libraries:: * Specifying a Run-Time Library:: * GNU/Linux Topics:: * Microsoft Windows Topics:: * Mac OS Topics:: Run-Time Libraries * Summary of Run-Time Configurations:: Specifying a Run-Time Library * Choosing the Scheduling Policy:: GNU/Linux Topics * Required Packages on GNU/Linux:: Microsoft Windows Topics * Using GNAT on Windows:: * Using a network installation of GNAT:: * CONSOLE and WINDOWS subsystems:: * Temporary Files:: * Disabling Command Line Argument Expansion:: * Mixed-Language Programming on Windows:: * Windows Specific Add-Ons:: Mixed-Language Programming on Windows * Windows Calling Conventions:: * Introduction to Dynamic Link Libraries (DLLs): Introduction to Dynamic Link Libraries DLLs. * Using DLLs with GNAT:: * Building DLLs with GNAT Project files:: * Building DLLs with GNAT:: * Building DLLs with gnatdll:: * Ada DLLs and Finalization:: * Creating a Spec for Ada DLLs:: * GNAT and Windows Resources:: * Using GNAT DLLs from Microsoft Visual Studio Applications:: * Debugging a DLL:: * Setting Stack Size from gnatlink:: * Setting Heap Size from gnatlink:: Windows Calling Conventions * C Calling Convention:: * Stdcall Calling Convention:: * Win32 Calling Convention:: * DLL Calling Convention:: Using DLLs with GNAT * Creating an Ada Spec for the DLL Services:: * Creating an Import Library:: Building DLLs with gnatdll * Limitations When Using Ada DLLs from Ada:: * Exporting Ada Entities:: * Ada DLLs and Elaboration:: Creating a Spec for Ada DLLs * Creating the Definition File:: * Using gnatdll:: GNAT and Windows Resources * Building Resources:: * Compiling Resources:: * Using Resources:: Debugging a DLL * Program and DLL Both Built with GCC/GNAT:: * Program Built with Foreign Tools and DLL Built with GCC/GNAT:: Windows Specific Add-Ons * Win32Ada:: * wPOSIX:: Mac OS Topics * Codesigning the Debugger:: Elaboration Order Handling in GNAT * Elaboration Code:: * Elaboration Order:: * Checking the Elaboration Order:: * Controlling the Elaboration Order in Ada:: * Controlling the Elaboration Order in GNAT:: * Common Elaboration-model Traits:: * Dynamic Elaboration Model in GNAT:: * Static Elaboration Model in GNAT:: * SPARK Elaboration Model in GNAT:: * Legacy Elaboration Model in GNAT:: * Mixing Elaboration Models:: * Elaboration Circularities:: * Resolving Elaboration Circularities:: * Resolving Task Issues:: * Elaboration-related Compiler Switches:: * Summary of Procedures for Elaboration Control:: * Inspecting the Chosen Elaboration Order:: Inline Assembler * Basic Assembler Syntax:: * A Simple Example of Inline Assembler:: * Output Variables in Inline Assembler:: * Input Variables in Inline Assembler:: * Inlining Inline Assembler Code:: * Other Asm Functionality:: Other Asm Functionality * The Clobber Parameter:: * The Volatile Parameter:: @end detailmenu @end menu @node About This Guide,Getting Started with GNAT,Top,Top @anchor{gnat_ugn/about_this_guide about-this-guide}@anchor{2}@anchor{gnat_ugn/about_this_guide doc}@anchor{3}@anchor{gnat_ugn/about_this_guide gnat-user-s-guide-for-native-platforms}@anchor{4}@anchor{gnat_ugn/about_this_guide id1}@anchor{5} @chapter About This Guide This guide describes the use of GNAT, a compiler and software development toolset for the full Ada programming language. It documents the features of the compiler and tools, and explains how to use them to build Ada applications. GNAT implements Ada 95, Ada 2005 and Ada 2012, and it may also be invoked in Ada 83 compatibility mode. By default, GNAT assumes Ada 2012, but you can override with a compiler switch (@ref{6,,Compiling Different Versions of Ada}) to explicitly specify the language version. Throughout this manual, references to 'Ada' without a year suffix apply to all Ada 95/2005/2012 versions of the language. @menu * What This Guide Contains:: * What You Should Know before Reading This Guide:: * Related Information:: * A Note to Readers of Previous Versions of the Manual:: * Conventions:: @end menu @node What This Guide Contains,What You Should Know before Reading This Guide,,About This Guide @anchor{gnat_ugn/about_this_guide what-this-guide-contains}@anchor{7} @section What This Guide Contains This guide contains the following chapters: @itemize * @item @ref{8,,Getting Started with GNAT} describes how to get started compiling and running Ada programs with the GNAT Ada programming environment. @item @ref{9,,The GNAT Compilation Model} describes the compilation model used by GNAT. @item @ref{a,,Building Executable Programs with GNAT} describes how to use the main GNAT tools to build executable programs, and it also gives examples of using the GNU make utility with GNAT. @item @ref{b,,GNAT Utility Programs} explains the various utility programs that are included in the GNAT environment @item @ref{c,,GNAT and Program Execution} covers a number of topics related to running, debugging, and tuning the performace of programs developed with GNAT @end itemize Appendices cover several additional topics: @itemize * @item @ref{d,,Platform-Specific Information} describes the different run-time library implementations and also presents information on how to use GNAT on several specific platforms @item @ref{e,,Example of Binder Output File} shows the source code for the binder output file for a sample program. @item @ref{f,,Elaboration Order Handling in GNAT} describes how GNAT helps you deal with elaboration order issues. @item @ref{10,,Inline Assembler} shows how to use the inline assembly facility in an Ada program. @end itemize @node What You Should Know before Reading This Guide,Related Information,What This Guide Contains,About This Guide @anchor{gnat_ugn/about_this_guide what-you-should-know-before-reading-this-guide}@anchor{11} @section What You Should Know before Reading This Guide @geindex Ada 95 Language Reference Manual @geindex Ada 2005 Language Reference Manual This guide 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 features introduced by Ada 2005 or Ada 2012. Reference manuals for Ada 95, Ada 2005, and Ada 2012 are included in the GNAT documentation package. @node Related Information,A Note to Readers of Previous Versions of the Manual,What You Should Know before Reading This Guide,About This Guide @anchor{gnat_ugn/about_this_guide related-information}@anchor{12} @section Related Information For further information about Ada and related tools, please refer to the following documents: @itemize * @item @cite{Ada 95 Reference Manual}, @cite{Ada 2005 Reference Manual}, and @cite{Ada 2012 Reference Manual}, which contain reference material for the several revisions of the Ada language standard. @item @cite{GNAT Reference_Manual}, which contains all reference material for the GNAT implementation of Ada. @item @cite{Using the GNAT Programming Studio}, which describes the GPS Integrated Development Environment. @item @cite{GNAT Programming Studio Tutorial}, which introduces the main GPS features through examples. @item @cite{Debugging with GDB}, for all details on the use of the GNU source-level debugger. @item @cite{GNU Emacs Manual}, for full information on the extensible editor and programming environment Emacs. @end itemize @node A Note to Readers of Previous Versions of the Manual,Conventions,Related Information,About This Guide @anchor{gnat_ugn/about_this_guide a-note-to-readers-of-previous-versions-of-the-manual}@anchor{13} @section A Note to Readers of Previous Versions of the Manual In early 2015 the GNAT manuals were transitioned to the reStructuredText (rst) / Sphinx documentation generator technology. During that process the @cite{GNAT User's Guide} was reorganized so that related topics would be described together in the same chapter or appendix. Here's a summary of the major changes realized in the new document structure. @itemize * @item @ref{9,,The GNAT Compilation Model} has been extended so that it now covers the following material: @itemize - @item The @code{gnatname}, @code{gnatkr}, and @code{gnatchop} tools @item @ref{14,,Configuration Pragmas} @item @ref{15,,GNAT and Libraries} @item @ref{16,,Conditional Compilation} including @ref{17,,Preprocessing with gnatprep} and @ref{18,,Integrated Preprocessing} @item @ref{19,,Generating Ada Bindings for C and C++ headers} @item @ref{1a,,Using GNAT Files with External Tools} @end itemize @item @ref{a,,Building Executable Programs with GNAT} is a new chapter consolidating the following content: @itemize - @item @ref{1b,,Building with gnatmake} @item @ref{1c,,Compiling with gcc} @item @ref{1d,,Binding with gnatbind} @item @ref{1e,,Linking with gnatlink} @item @ref{1f,,Using the GNU make Utility} @end itemize @item @ref{b,,GNAT Utility Programs} is a new chapter consolidating the information about several GNAT tools: @itemize - @item @ref{20,,The File Cleanup Utility gnatclean} @item @ref{21,,The GNAT Library Browser gnatls} @item @ref{22,,The Cross-Referencing Tools gnatxref and gnatfind} @item @ref{23,,The Ada to HTML Converter gnathtml} @end itemize @item @ref{c,,GNAT and Program Execution} is a new chapter consolidating the following: @itemize - @item @ref{24,,Running and Debugging Ada Programs} @item @ref{25,,Profiling} @item @ref{26,,Improving Performance} @item @ref{27,,Overflow Check Handling in GNAT} @item @ref{28,,Performing Dimensionality Analysis in GNAT} @item @ref{29,,Stack Related Facilities} @item @ref{2a,,Memory Management Issues} @end itemize @item @ref{d,,Platform-Specific Information} is a new appendix consolidating the following: @itemize - @item @ref{2b,,Run-Time Libraries} @item @ref{2c,,Microsoft Windows Topics} @item @ref{2d,,Mac OS Topics} @end itemize @item The @emph{Compatibility and Porting Guide} appendix has been moved to the @cite{GNAT Reference Manual}. It now includes a section @emph{Writing Portable Fixed-Point Declarations} which was previously a separate chapter in the @cite{GNAT User's Guide}. @end itemize @node Conventions,,A Note to Readers of Previous Versions of the Manual,About This Guide @anchor{gnat_ugn/about_this_guide conventions}@anchor{2e} @section Conventions @geindex Conventions @geindex typographical @geindex Typographical conventions Following are examples of the typographical and graphic conventions used in this guide: @itemize * @item @code{Functions}, @code{utility program names}, @code{standard names}, and @code{classes}. @item @code{Option flags} @item @code{File names} @item @code{Variables} @item @emph{Emphasis} @item [optional information or parameters] @item Examples are described by text @example and then shown this way. @end example @item Commands that are entered by the user are shown as preceded by a prompt string comprising the @code{$} character followed by a space. @item Full file names are shown with the '/' character as the directory separator; e.g., @code{parent-dir/subdir/myfile.adb}. If you are using GNAT on a Windows platform, please note that the '\' character should be used instead. @end itemize @node Getting Started with GNAT,The GNAT Compilation Model,About This Guide,Top @anchor{gnat_ugn/getting_started_with_gnat getting-started-with-gnat}@anchor{8}@anchor{gnat_ugn/getting_started_with_gnat doc}@anchor{2f}@anchor{gnat_ugn/getting_started_with_gnat id1}@anchor{30} @chapter Getting Started with GNAT This chapter describes how to use GNAT's command line interface to build executable Ada programs. On most platforms a visually oriented Integrated Development Environment is also available, the GNAT Programming Studio (GPS). GPS offers a graphical "look and feel", support for development in other programming languages, comprehensive browsing features, and many other capabilities. For information on GPS please refer to @cite{Using the GNAT Programming Studio}. @menu * Running GNAT:: * Running a Simple Ada Program:: * Running a Program with Multiple Units:: * Using the gnatmake Utility:: @end menu @node Running GNAT,Running a Simple Ada Program,,Getting Started with GNAT @anchor{gnat_ugn/getting_started_with_gnat running-gnat}@anchor{31}@anchor{gnat_ugn/getting_started_with_gnat id2}@anchor{32} @section Running GNAT Three steps are needed to create an executable file from an Ada source file: @itemize * @item The source file(s) must be compiled. @item The file(s) must be bound using the GNAT binder. @item All appropriate object files must be linked to produce an executable. @end itemize All three steps are most commonly handled by using the @code{gnatmake} utility program that, given the name of the main program, automatically performs the necessary compilation, binding and linking steps. @node Running a Simple Ada Program,Running a Program with Multiple Units,Running GNAT,Getting Started with GNAT @anchor{gnat_ugn/getting_started_with_gnat running-a-simple-ada-program}@anchor{33}@anchor{gnat_ugn/getting_started_with_gnat id3}@anchor{34} @section Running a Simple Ada Program Any text editor may be used to prepare an Ada program. (If Emacs is used, the optional Ada mode may be helpful in laying out the program.) The program text is a normal text file. We will assume in our initial example that you have used your editor to prepare the following standard format text file: @example with Ada.Text_IO; use Ada.Text_IO; procedure Hello is begin Put_Line ("Hello WORLD!"); end Hello; @end example This file should be named @code{hello.adb}. With the normal default file naming conventions, GNAT requires that each file contain a single compilation unit whose file name is the unit name, with periods replaced by hyphens; the extension is @code{ads} for a spec and @code{adb} for a body. You can override this default file naming convention by use of the special pragma @code{Source_File_Name} (for further information please see @ref{35,,Using Other File Names}). Alternatively, if you want to rename your files according to this default convention, which is probably more convenient if you will be using GNAT for all your compilations, then the @code{gnatchop} utility can be used to generate correctly-named source files (see @ref{36,,Renaming Files with gnatchop}). You can compile the program using the following command (@code{$} is used as the command prompt in the examples in this document): @example $ gcc -c hello.adb @end example @code{gcc} is the command used to run the compiler. This compiler is capable of compiling programs in several languages, including Ada and C. It assumes that you have given it an Ada program if the file extension is either @code{.ads} or @code{.adb}, and it will then call the GNAT compiler to compile the specified file. The @code{-c} switch is required. It tells @code{gcc} to only do a compilation. (For C programs, @code{gcc} can also do linking, but this capability is not used directly for Ada programs, so the @code{-c} switch must always be present.) This compile command generates a file @code{hello.o}, which is the object file corresponding to your Ada program. It also generates an 'Ada Library Information' file @code{hello.ali}, which contains additional information used to check that an Ada program is consistent. To build an executable file, use @code{gnatbind} to bind the program and @code{gnatlink} to link it. The argument to both @code{gnatbind} and @code{gnatlink} is the name of the @code{ALI} file, but the default extension of @code{.ali} can be omitted. This means that in the most common case, the argument is simply the name of the main program: @example $ gnatbind hello $ gnatlink hello @end example A simpler method of carrying out these steps is to use @code{gnatmake}, a master program that invokes all the required compilation, binding and linking tools in the correct order. In particular, @code{gnatmake} automatically recompiles any sources that have been modified since they were last compiled, or sources that depend on such modified sources, so that 'version skew' is avoided. @geindex Version skew (avoided by `@w{`}gnatmake`@w{`}) @example $ gnatmake hello.adb @end example The result is an executable program called @code{hello}, which can be run by entering: @example $ hello @end example assuming that the current directory is on the search path for executable programs. and, if all has gone well, you will see: @example Hello WORLD! @end example appear in response to this command. @node Running a Program with Multiple Units,Using the gnatmake Utility,Running a Simple Ada Program,Getting Started with GNAT @anchor{gnat_ugn/getting_started_with_gnat id4}@anchor{37}@anchor{gnat_ugn/getting_started_with_gnat running-a-program-with-multiple-units}@anchor{38} @section Running a Program with Multiple Units Consider a slightly more complicated example that has three files: a main program, and the spec and body of a package: @example package Greetings is procedure Hello; procedure Goodbye; end Greetings; with Ada.Text_IO; use Ada.Text_IO; package body Greetings is procedure Hello is begin Put_Line ("Hello WORLD!"); end Hello; procedure Goodbye is begin Put_Line ("Goodbye WORLD!"); end Goodbye; end Greetings; with Greetings; procedure Gmain is begin Greetings.Hello; Greetings.Goodbye; end Gmain; @end example Following the one-unit-per-file rule, place this program in the following three separate files: @table @asis @item @emph{greetings.ads} spec of package @code{Greetings} @item @emph{greetings.adb} body of package @code{Greetings} @item @emph{gmain.adb} body of main program @end table To build an executable version of this program, we could use four separate steps to compile, bind, and link the program, as follows: @example $ gcc -c gmain.adb $ gcc -c greetings.adb $ gnatbind gmain $ gnatlink gmain @end example Note that there is no required order of compilation when using GNAT. In particular it is perfectly fine to compile the main program first. Also, it is not necessary to compile package specs in the case where there is an accompanying body; you only need to compile the body. If you want to submit these files to the compiler for semantic checking and not code generation, then use the @code{-gnatc} switch: @example $ gcc -c greetings.ads -gnatc @end example Although the compilation can be done in separate steps as in the above example, in practice it is almost always more convenient to use the @code{gnatmake} tool. All you need to know in this case is the name of the main program's source file. The effect of the above four commands can be achieved with a single one: @example $ gnatmake gmain.adb @end example In the next section we discuss the advantages of using @code{gnatmake} in more detail. @node Using the gnatmake Utility,,Running a Program with Multiple Units,Getting Started with GNAT @anchor{gnat_ugn/getting_started_with_gnat using-the-gnatmake-utility}@anchor{39}@anchor{gnat_ugn/getting_started_with_gnat id5}@anchor{3a} @section Using the @code{gnatmake} Utility If you work on a program by compiling single components at a time using @code{gcc}, you typically keep track of the units you modify. In order to build a consistent system, you compile not only these units, but also any units that depend on the units you have modified. For example, in the preceding case, if you edit @code{gmain.adb}, you only need to recompile that file. But if you edit @code{greetings.ads}, you must recompile both @code{greetings.adb} and @code{gmain.adb}, because both files contain units that depend on @code{greetings.ads}. @code{gnatbind} will warn you if you forget one of these compilation steps, so that it is impossible to generate an inconsistent program as a result of forgetting to do a compilation. Nevertheless it is tedious and error-prone to keep track of dependencies among units. One approach to handle the dependency-bookkeeping is to use a makefile. However, makefiles present maintenance problems of their own: if the dependencies change as you change the program, you must make sure that the makefile is kept up-to-date manually, which is also an error-prone process. The @code{gnatmake} utility takes care of these details automatically. Invoke it using either one of the following forms: @example $ gnatmake gmain.adb $ gnatmake gmain @end example The argument is the name of the file containing the main program; you may omit the extension. @code{gnatmake} examines the environment, automatically recompiles any files that need recompiling, and binds and links the resulting set of object files, generating the executable file, @code{gmain}. In a large program, it can be extremely helpful to use @code{gnatmake}, because working out by hand what needs to be recompiled can be difficult. Note that @code{gnatmake} takes into account all the Ada rules that establish dependencies among units. These include dependencies that result from inlining subprogram bodies, and from generic instantiation. Unlike some other Ada make tools, @code{gnatmake} does not rely on the dependencies that were found by the compiler on a previous compilation, which may possibly be wrong when sources change. @code{gnatmake} determines the exact set of dependencies from scratch each time it is run. @c -- Example: A |withing| unit has a |with| clause, it |withs| a |withed| unit @node The GNAT Compilation Model,Building Executable Programs with GNAT,Getting Started with GNAT,Top @anchor{gnat_ugn/the_gnat_compilation_model doc}@anchor{3b}@anchor{gnat_ugn/the_gnat_compilation_model the-gnat-compilation-model}@anchor{9}@anchor{gnat_ugn/the_gnat_compilation_model id1}@anchor{3c} @chapter The GNAT Compilation Model @geindex GNAT compilation model @geindex Compilation model This chapter describes the compilation model used by GNAT. Although similar to that used by other languages such as C and C++, this model is substantially different from the traditional Ada compilation models, which are based on a centralized program library. The chapter covers the following material: @itemize * @item Topics related to source file makeup and naming @itemize * @item @ref{3d,,Source Representation} @item @ref{3e,,Foreign Language Representation} @item @ref{3f,,File Naming Topics and Utilities} @end itemize @item @ref{14,,Configuration Pragmas} @item @ref{40,,Generating Object Files} @item @ref{41,,Source Dependencies} @item @ref{42,,The Ada Library Information Files} @item @ref{43,,Binding an Ada Program} @item @ref{15,,GNAT and Libraries} @item @ref{16,,Conditional Compilation} @item @ref{44,,Mixed Language Programming} @item @ref{45,,GNAT and Other Compilation Models} @item @ref{1a,,Using GNAT Files with External Tools} @end itemize @menu * Source Representation:: * Foreign Language Representation:: * File Naming Topics and Utilities:: * Configuration Pragmas:: * Generating Object Files:: * Source Dependencies:: * The Ada Library Information Files:: * Binding an Ada Program:: * GNAT and Libraries:: * Conditional Compilation:: * Mixed Language Programming:: * GNAT and Other Compilation Models:: * Using GNAT Files with External Tools:: @end menu @node Source Representation,Foreign Language Representation,,The GNAT Compilation Model @anchor{gnat_ugn/the_gnat_compilation_model source-representation}@anchor{3d}@anchor{gnat_ugn/the_gnat_compilation_model id2}@anchor{46} @section Source Representation @geindex Latin-1 @geindex VT @geindex HT @geindex CR @geindex LF @geindex FF Ada source programs are represented in standard text files, using Latin-1 coding. Latin-1 is an 8-bit code that includes the familiar 7-bit ASCII set, plus additional characters used for representing foreign languages (see @ref{3e,,Foreign Language Representation} for support of non-USA character sets). The format effector characters are represented using their standard ASCII encodings, as follows: @quotation @multitable {xxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxx} @item Character @tab Effect @tab Code @item @code{VT} @tab Vertical tab @tab @code{16#0B#} @item @code{HT} @tab Horizontal tab @tab @code{16#09#} @item @code{CR} @tab Carriage return @tab @code{16#0D#} @item @code{LF} @tab Line feed @tab @code{16#0A#} @item @code{FF} @tab Form feed @tab @code{16#0C#} @end multitable @end quotation Source files are in standard text file format. In addition, GNAT will recognize a wide variety of stream formats, in which the end of physical lines is marked by any of the following sequences: @code{LF}, @code{CR}, @code{CR-LF}, or @code{LF-CR}. This is useful in accommodating files that are imported from other operating systems. @geindex End of source file; Source file@comma{} end @geindex SUB (control character) The end of a source file is normally represented by the physical end of file. However, the control character @code{16#1A#} (@code{SUB}) is also recognized as signalling the end of the source file. Again, this is provided for compatibility with other operating systems where this code is used to represent the end of file. @geindex spec (definition) @geindex compilation (definition) Each file contains a single Ada compilation unit, including any pragmas associated with the unit. For example, this means you must place a package declaration (a package @emph{spec}) and the corresponding body in separate files. An Ada @emph{compilation} (which is a sequence of compilation units) is represented using a sequence of files. Similarly, you will place each subunit or child unit in a separate file. @node Foreign Language Representation,File Naming Topics and Utilities,Source Representation,The GNAT Compilation Model @anchor{gnat_ugn/the_gnat_compilation_model foreign-language-representation}@anchor{3e}@anchor{gnat_ugn/the_gnat_compilation_model id3}@anchor{47} @section Foreign Language Representation GNAT supports the standard character sets defined in Ada as well as several other non-standard character sets for use in localized versions of the compiler (@ref{48,,Character Set Control}). @menu * Latin-1:: * Other 8-Bit Codes:: * Wide_Character Encodings:: * Wide_Wide_Character Encodings:: @end menu @node Latin-1,Other 8-Bit Codes,,Foreign Language Representation @anchor{gnat_ugn/the_gnat_compilation_model id4}@anchor{49}@anchor{gnat_ugn/the_gnat_compilation_model latin-1}@anchor{4a} @subsection Latin-1 @geindex Latin-1 The basic character set is Latin-1. This character set is defined by ISO standard 8859, part 1. The lower half (character codes @code{16#00#} ... @code{16#7F#)} is identical to standard ASCII coding, but the upper half is used to represent additional characters. These include extended letters used by European languages, such as French accents, the vowels with umlauts used in German, and the extra letter A-ring used in Swedish. @geindex Ada.Characters.Latin_1 For a complete list of Latin-1 codes and their encodings, see the source file of library unit @code{Ada.Characters.Latin_1} in file @code{a-chlat1.ads}. You may use any of these extended characters freely in character or string literals. In addition, the extended characters that represent letters can be used in identifiers. @node Other 8-Bit Codes,Wide_Character Encodings,Latin-1,Foreign Language Representation @anchor{gnat_ugn/the_gnat_compilation_model other-8-bit-codes}@anchor{4b}@anchor{gnat_ugn/the_gnat_compilation_model id5}@anchor{4c} @subsection Other 8-Bit Codes GNAT also supports several other 8-bit coding schemes: @geindex Latin-2 @geindex ISO 8859-2 @table @asis @item @emph{ISO 8859-2 (Latin-2)} Latin-2 letters allowed in identifiers, with uppercase and lowercase equivalence. @end table @geindex Latin-3 @geindex ISO 8859-3 @table @asis @item @emph{ISO 8859-3 (Latin-3)} Latin-3 letters allowed in identifiers, with uppercase and lowercase equivalence. @end table @geindex Latin-4 @geindex ISO 8859-4 @table @asis @item @emph{ISO 8859-4 (Latin-4)} Latin-4 letters allowed in identifiers, with uppercase and lowercase equivalence. @end table @geindex ISO 8859-5 @geindex Cyrillic @table @asis @item @emph{ISO 8859-5 (Cyrillic)} ISO 8859-5 letters (Cyrillic) allowed in identifiers, with uppercase and lowercase equivalence. @end table @geindex ISO 8859-15 @geindex Latin-9 @table @asis @item @emph{ISO 8859-15 (Latin-9)} ISO 8859-15 (Latin-9) letters allowed in identifiers, with uppercase and lowercase equivalence @end table @geindex code page 437 (IBM PC) @table @asis @item @emph{IBM PC (code page 437)} This code page is the normal default for PCs in the U.S. It corresponds to the original IBM PC character set. This set has some, but not all, of the extended Latin-1 letters, but these letters do not have the same encoding as Latin-1. In this mode, these letters are allowed in identifiers with uppercase and lowercase equivalence. @end table @geindex code page 850 (IBM PC) @table @asis @item @emph{IBM PC (code page 850)} This code page is a modification of 437 extended to include all the Latin-1 letters, but still not with the usual Latin-1 encoding. In this mode, all these letters are allowed in identifiers with uppercase and lowercase equivalence. @item @emph{Full Upper 8-bit} Any character in the range 80-FF allowed in identifiers, and all are considered distinct. In other words, there are no uppercase and lowercase equivalences in this range. This is useful in conjunction with certain encoding schemes used for some foreign character sets (e.g., the typical method of representing Chinese characters on the PC). @item @emph{No Upper-Half} No upper-half characters in the range 80-FF are allowed in identifiers. This gives Ada 83 compatibility for identifier names. @end table For precise data on the encodings permitted, and the uppercase and lowercase equivalences that are recognized, see the file @code{csets.adb} in the GNAT compiler sources. You will need to obtain a full source release of GNAT to obtain this file. @node Wide_Character Encodings,Wide_Wide_Character Encodings,Other 8-Bit Codes,Foreign Language Representation @anchor{gnat_ugn/the_gnat_compilation_model id6}@anchor{4d}@anchor{gnat_ugn/the_gnat_compilation_model wide-character-encodings}@anchor{4e} @subsection Wide_Character Encodings GNAT allows wide character codes to appear in character and string literals, and also optionally in identifiers, by means of the following possible encoding schemes: @table @asis @item @emph{Hex Coding} In this encoding, a wide character is represented by the following five character sequence: @example ESC a b c d @end example where @code{a}, @code{b}, @code{c}, @code{d} are the four hexadecimal characters (using uppercase letters) of the wide character code. For example, ESC 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. @item @emph{Upper-Half Coding} @geindex Upper-Half Coding The wide character with encoding @code{16#abcd#} where the upper bit is on (in other words, 'a' is in the range 8-F) is represented as two bytes, @code{16#ab#} and @code{16#cd#}. The second byte cannot 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 @emph{Shift JIS Coding} @geindex Shift JIS Coding A wide character is represented by a two-character sequence, @code{16#ab#} and @code{16#cd#}, with the restrictions described for upper-half encoding as 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 used with this encoding method. @item @emph{EUC Coding} @geindex EUC Coding A wide character is represented by a two-character sequence @code{16#ab#} and @code{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 can be used with this encoding method. @item @emph{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, or three byte sequence: @example 16#0000#-16#007f#: 2#0xxxxxxx# 16#0080#-16#07ff#: 2#110xxxxx# 2#10xxxxxx# 16#0800#-16#ffff#: 2#1110xxxx# 2#10xxxxxx# 2#10xxxxxx# @end example where the @code{xxx} bits correspond to the left-padded bits of the 16-bit character value. Note that all lower half ASCII characters are represented as ASCII bytes and all upper half characters and 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, and in the following section on wide wide characters, the use of these sequences is documented). @item @emph{Brackets Coding} In this encoding, a wide character is represented by the following eight character sequence: @example [ " a b c d " ] @end example where @code{a}, @code{b}, @code{c}, @code{d} are the four hexadecimal characters (using uppercase letters) of the wide character code. For example, ['A345'] is used to represent the wide character with code @code{16#A345#}. It is also possible (though not required) to use the Brackets coding for upper half characters. For example, the code @code{16#A3#} can be represented as @code{['A3']}. This scheme is compatible with use of the full Wide_Character set, and is also the method used for wide character encoding in some standard ACATS (Ada Conformity Assessment Test Suite) test suite distributions. @end table @cartouche @quotation Note Some of these coding schemes do not permit the full use of the Ada character set. For example, neither Shift JIS nor EUC allow the use of the upper half of the Latin-1 set. @end quotation @end cartouche @node Wide_Wide_Character Encodings,,Wide_Character Encodings,Foreign Language Representation @anchor{gnat_ugn/the_gnat_compilation_model id7}@anchor{4f}@anchor{gnat_ugn/the_gnat_compilation_model wide-wide-character-encodings}@anchor{50} @subsection Wide_Wide_Character Encodings GNAT allows wide wide character codes to appear in character and string literals, and also optionally in identifiers, by means of the following possible encoding schemes: @table @asis @item @emph{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 of character codes with values greater than 16#FFFF# is a is a four, five, or six byte sequence: @example 16#01_0000#-16#10_FFFF#: 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx 16#0020_0000#-16#03FF_FFFF#: 111110xx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx 16#0400_0000#-16#7FFF_FFFF#: 1111110x 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx @end example where the @code{xxx} bits correspond to the left-padded bits of the 32-bit character value. @item @emph{Brackets Coding} In this encoding, a wide wide character is represented by the following ten or twelve byte character sequence: @example [ " a b c d e f " ] [ " a b c d e f g h " ] @end example where @code{a-h} are the six or eight hexadecimal characters (using uppercase letters) of the wide wide character code. For example, ["1F4567"] is used to represent the wide wide character with code @code{16#001F_4567#}. This scheme is compatible with use of the full Wide_Wide_Character set, and is also the method used for wide wide character encoding in some standard ACATS (Ada Conformity Assessment Test Suite) test suite distributions. @end table @node File Naming Topics and Utilities,Configuration Pragmas,Foreign Language Representation,The GNAT Compilation Model @anchor{gnat_ugn/the_gnat_compilation_model id8}@anchor{51}@anchor{gnat_ugn/the_gnat_compilation_model file-naming-topics-and-utilities}@anchor{3f} @section File Naming Topics and Utilities GNAT has a default file naming scheme and also provides the user with a high degree of control over how the names and extensions of the source files correspond to the Ada compilation units that they contain. @menu * File Naming Rules:: * Using Other File Names:: * Alternative File Naming Schemes:: * Handling Arbitrary File Naming Conventions with gnatname:: * File Name Krunching with gnatkr:: * Renaming Files with gnatchop:: @end menu @node File Naming Rules,Using Other File Names,,File Naming Topics and Utilities @anchor{gnat_ugn/the_gnat_compilation_model file-naming-rules}@anchor{52}@anchor{gnat_ugn/the_gnat_compilation_model id9}@anchor{53} @subsection File Naming Rules The default file name is determined by the name of the unit that the file contains. The name is formed by taking the full expanded name of the unit and replacing the separating dots with hyphens and using lowercase for all letters. An exception arises if the file name generated by the above rules starts with one of the characters @code{a}, @code{g}, @code{i}, or @code{s}, and the second character is a minus. In this case, the character tilde is used in place of the minus. The reason for this special rule is to avoid clashes with the standard names for child units of the packages System, Ada, Interfaces, and GNAT, which use the prefixes @code{s-}, @code{a-}, @code{i-}, and @code{g-}, respectively. The file extension is @code{.ads} for a spec and @code{.adb} for a body. The following table shows some examples of these rules. @quotation @multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} @item Source File @tab Ada Compilation Unit @item @code{main.ads} @tab Main (spec) @item @code{main.adb} @tab Main (body) @item @code{arith_functions.ads} @tab Arith_Functions (package spec) @item @code{arith_functions.adb} @tab Arith_Functions (package body) @item @code{func-spec.ads} @tab Func.Spec (child package spec) @item @code{func-spec.adb} @tab Func.Spec (child package body) @item @code{main-sub.adb} @tab Sub (subunit of Main) @item @code{a~bad.adb} @tab A.Bad (child package body) @end multitable @end quotation Following these rules can result in excessively long file names if corresponding unit names are long (for example, if child units or subunits are heavily nested). An option is available to shorten such long file names (called file name 'krunching'). This may be particularly useful when programs being developed with GNAT are to be used on operating systems with limited file name lengths. @ref{54,,Using gnatkr}. Of course, no file shortening algorithm can guarantee uniqueness over all possible unit names; if file name krunching is used, it is your responsibility to ensure no name clashes occur. Alternatively you can specify the exact file names that you want used, as described in the next section. Finally, if your Ada programs are migrating from a compiler with a different naming convention, you can use the gnatchop utility to produce source files that follow the GNAT naming conventions. (For details see @ref{36,,Renaming Files with gnatchop}.) Note: in the case of Windows or Mac OS operating systems, case is not significant. So for example on Windows if the canonical name is @code{main-sub.adb}, you can use the file name @code{Main-Sub.adb} instead. However, case is significant for other operating systems, so for example, if you want to use other than canonically cased file names on a Unix system, you need to follow the procedures described in the next section. @node Using Other File Names,Alternative File Naming Schemes,File Naming Rules,File Naming Topics and Utilities @anchor{gnat_ugn/the_gnat_compilation_model id10}@anchor{55}@anchor{gnat_ugn/the_gnat_compilation_model using-other-file-names}@anchor{35} @subsection Using Other File Names @geindex File names In the previous section, we have described the default rules used by GNAT to determine the file name in which a given unit resides. It is often convenient to follow these default rules, and if you follow them, the compiler knows without being explicitly told where to find all the files it needs. @geindex Source_File_Name pragma However, in some cases, particularly when a program is imported from another Ada compiler environment, it may be more convenient for the programmer to specify which file names contain which units. GNAT allows arbitrary file names to be used by means of the Source_File_Name pragma. The form of this pragma is as shown in the following examples: @example pragma Source_File_Name (My_Utilities.Stacks, Spec_File_Name => "myutilst_a.ada"); pragma Source_File_name (My_Utilities.Stacks, Body_File_Name => "myutilst.ada"); @end example As shown in this example, the first argument for the pragma is the unit name (in this example a child unit). The second argument has the form of a named association. The identifier indicates whether the file name is for a spec or a body; the file name itself is given by a string literal. The source file name pragma is a configuration pragma, which means that normally it will be placed in the @code{gnat.adc} file used to hold configuration pragmas that apply to a complete compilation environment. For more details on how the @code{gnat.adc} file is created and used see @ref{56,,Handling of Configuration Pragmas}. @geindex gnat.adc GNAT allows completely arbitrary file names to be specified using the source file name pragma. However, if the file name specified has an extension other than @code{.ads} or @code{.adb} it is necessary to use a special syntax when compiling the file. The name in this case must be preceded by the special sequence @code{-x} followed by a space and the name of the language, here @code{ada}, as in: @example $ gcc -c -x ada peculiar_file_name.sim @end example @code{gnatmake} handles non-standard file names in the usual manner (the non-standard file name for the main program is simply used as the argument to gnatmake). Note that if the extension is also non-standard, then it must be included in the @code{gnatmake} command, it may not be omitted. @node Alternative File Naming Schemes,Handling Arbitrary File Naming Conventions with gnatname,Using Other File Names,File Naming Topics and Utilities @anchor{gnat_ugn/the_gnat_compilation_model id11}@anchor{57}@anchor{gnat_ugn/the_gnat_compilation_model alternative-file-naming-schemes}@anchor{58} @subsection Alternative File Naming Schemes @geindex File naming schemes @geindex alternative @geindex File names The previous section described the use of the @code{Source_File_Name} pragma to allow arbitrary names to be assigned to individual source files. However, this approach requires one pragma for each file, and especially in large systems can result in very long @code{gnat.adc} files, and also create a maintenance problem. @geindex Source_File_Name pragma GNAT also provides a facility for specifying systematic file naming schemes other than the standard default naming scheme previously described. An alternative scheme for naming is specified by the use of @code{Source_File_Name} pragmas having the following format: @example pragma Source_File_Name ( Spec_File_Name => FILE_NAME_PATTERN [ , Casing => CASING_SPEC] [ , Dot_Replacement => STRING_LITERAL ] ); pragma Source_File_Name ( Body_File_Name => FILE_NAME_PATTERN [ , Casing => CASING_SPEC ] [ , Dot_Replacement => STRING_LITERAL ] ) ; pragma Source_File_Name ( Subunit_File_Name => FILE_NAME_PATTERN [ , Casing => CASING_SPEC ] [ , Dot_Replacement => STRING_LITERAL ] ) ; FILE_NAME_PATTERN ::= STRING_LITERAL CASING_SPEC ::= Lowercase | Uppercase | Mixedcase @end example The @code{FILE_NAME_PATTERN} string shows how the file name is constructed. It contains a single asterisk character, and the unit name is substituted systematically for this asterisk. The optional parameter @code{Casing} indicates whether the unit name is to be all upper-case letters, all lower-case letters, or mixed-case. If no @code{Casing} parameter is used, then the default is all lower-case. The optional @code{Dot_Replacement} string is used to replace any periods that occur in subunit or child unit names. If no @code{Dot_Replacement} argument is used then separating dots appear unchanged in the resulting file name. Although the above syntax indicates that the @code{Casing} argument must appear before the @code{Dot_Replacement} argument, but it is also permissible to write these arguments in the opposite order. As indicated, it is possible to specify different naming schemes for bodies, specs, and subunits. Quite often the rule for subunits is the same as the rule for bodies, in which case, there is no need to give a separate @code{Subunit_File_Name} rule, and in this case the @code{Body_File_name} rule is used for subunits as well. The separate rule for subunits can also be used to implement the rather unusual case of a compilation environment (e.g., a single directory) which contains a subunit and a child unit with the same unit name. Although both units cannot appear in the same partition, the Ada Reference Manual allows (but does not require) the possibility of the two units coexisting in the same environment. The file name translation works in the following steps: @itemize * @item If there is a specific @code{Source_File_Name} pragma for the given unit, then this is always used, and any general pattern rules are ignored. @item If there is a pattern type @code{Source_File_Name} pragma that applies to the unit, then the resulting file name will be used if the file exists. If more than one pattern matches, the latest one will be tried first, and the first attempt resulting in a reference to a file that exists will be used. @item If no pattern type @code{Source_File_Name} pragma that applies to the unit for which the corresponding file exists, then the standard GNAT default naming rules are used. @end itemize As an example of the use of this mechanism, consider a commonly used scheme in which file names are all lower case, with separating periods copied unchanged to the resulting file name, and specs end with @code{.1.ada}, and bodies end with @code{.2.ada}. GNAT will follow this scheme if the following two pragmas appear: @example pragma Source_File_Name (Spec_File_Name => ".1.ada"); pragma Source_File_Name (Body_File_Name => ".2.ada"); @end example The default GNAT scheme is actually implemented by providing the following default pragmas internally: @example pragma Source_File_Name (Spec_File_Name => ".ads", Dot_Replacement => "-"); pragma Source_File_Name (Body_File_Name => ".adb", Dot_Replacement => "-"); @end example Our final example implements a scheme typically used with one of the Ada 83 compilers, where the separator character for subunits was '__' (two underscores), specs were identified by adding @code{_.ADA}, bodies by adding @code{.ADA}, and subunits by adding @code{.SEP}. All file names were upper case. Child units were not present of course since this was an Ada 83 compiler, but it seems reasonable to extend this scheme to use the same double underscore separator for child units. @example pragma Source_File_Name (Spec_File_Name => "_.ADA", Dot_Replacement => "__", Casing = Uppercase); pragma Source_File_Name (Body_File_Name => ".ADA", Dot_Replacement => "__", Casing = Uppercase); pragma Source_File_Name (Subunit_File_Name => ".SEP", Dot_Replacement => "__", Casing = Uppercase); @end example @geindex gnatname @node Handling Arbitrary File Naming Conventions with gnatname,File Name Krunching with gnatkr,Alternative File Naming Schemes,File Naming Topics and Utilities @anchor{gnat_ugn/the_gnat_compilation_model handling-arbitrary-file-naming-conventions-with-gnatname}@anchor{59}@anchor{gnat_ugn/the_gnat_compilation_model id12}@anchor{5a} @subsection Handling Arbitrary File Naming Conventions with @code{gnatname} @geindex File Naming Conventions @menu * Arbitrary File Naming Conventions:: * Running gnatname:: * Switches for gnatname:: * Examples of gnatname Usage:: @end menu @node Arbitrary File Naming Conventions,Running gnatname,,Handling Arbitrary File Naming Conventions with gnatname @anchor{gnat_ugn/the_gnat_compilation_model arbitrary-file-naming-conventions}@anchor{5b}@anchor{gnat_ugn/the_gnat_compilation_model id13}@anchor{5c} @subsubsection Arbitrary File Naming Conventions The GNAT compiler must be able to know the source file name of a compilation unit. When using the standard GNAT default file naming conventions (@code{.ads} for specs, @code{.adb} for bodies), the GNAT compiler does not need additional information. When the source file names do not follow the standard GNAT default file naming conventions, the GNAT compiler must be given additional information through a configuration pragmas file (@ref{14,,Configuration Pragmas}) or a project file. When the non-standard file naming conventions are well-defined, a small number of pragmas @code{Source_File_Name} specifying a naming pattern (@ref{58,,Alternative File Naming Schemes}) may be sufficient. However, if the file naming conventions are irregular or arbitrary, a number of pragma @code{Source_File_Name} for individual compilation units must be defined. To help maintain the correspondence between compilation unit names and source file names within the compiler, GNAT provides a tool @code{gnatname} to generate the required pragmas for a set of files. @node Running gnatname,Switches for gnatname,Arbitrary File Naming Conventions,Handling Arbitrary File Naming Conventions with gnatname @anchor{gnat_ugn/the_gnat_compilation_model running-gnatname}@anchor{5d}@anchor{gnat_ugn/the_gnat_compilation_model id14}@anchor{5e} @subsubsection Running @code{gnatname} The usual form of the @code{gnatname} command is: @example $ gnatname [ switches ] naming_pattern [ naming_patterns ] [--and [ switches ] naming_pattern [ naming_patterns ]] @end example All of the arguments are optional. If invoked without any argument, @code{gnatname} will display its usage. When used with at least one naming pattern, @code{gnatname} will attempt to find all the compilation units in files that follow at least one of the naming patterns. To find these compilation units, @code{gnatname} will use the GNAT compiler in syntax-check-only mode on all regular files. One or several Naming Patterns may be given as arguments to @code{gnatname}. Each Naming Pattern is enclosed between double quotes (or single quotes on Windows). A Naming Pattern is a regular expression similar to the wildcard patterns used in file names by the Unix shells or the DOS prompt. @code{gnatname} may be called with several sections of directories/patterns. Sections are separated by the switch @code{--and}. In each section, there must be at least one pattern. If no directory is specified in a section, the current directory (or the project directory if @code{-P} is used) is implied. The options other that the directory switches and the patterns apply globally even if they are in different sections. Examples of Naming Patterns are: @example "*.[12].ada" "*.ad[sb]*" "body_*" "spec_*" @end example For a more complete description of the syntax of Naming Patterns, see the second kind of regular expressions described in @code{g-regexp.ads} (the 'Glob' regular expressions). When invoked without the switch @code{-P}, @code{gnatname} will create a configuration pragmas file @code{gnat.adc} in the current working directory, with pragmas @code{Source_File_Name} for each file that contains a valid Ada unit. @node Switches for gnatname,Examples of gnatname Usage,Running gnatname,Handling Arbitrary File Naming Conventions with gnatname @anchor{gnat_ugn/the_gnat_compilation_model id15}@anchor{5f}@anchor{gnat_ugn/the_gnat_compilation_model switches-for-gnatname}@anchor{60} @subsubsection Switches for @code{gnatname} Switches for @code{gnatname} must precede any specified Naming Pattern. You may specify any of the following switches to @code{gnatname}: @geindex --version (gnatname) @table @asis @item @code{--version} Display Copyright and version, then exit disregarding all other options. @end table @geindex --help (gnatname) @table @asis @item @code{--help} If @code{--version} was not used, display usage, then exit disregarding all other options. @item @code{--subdirs=@emph{dir}} Real object, library or exec directories are subdirectories <dir> of the specified ones. @item @code{--no-backup} Do not create a backup copy of an existing project file. @item @code{--and} Start another section of directories/patterns. @end table @geindex -c (gnatname) @table @asis @item @code{-c@emph{filename}} Create a configuration pragmas file @code{filename} (instead of the default @code{gnat.adc}). There may be zero, one or more space between @code{-c} and @code{filename}. @code{filename} may include directory information. @code{filename} must be writable. There may be only one switch @code{-c}. When a switch @code{-c} is specified, no switch @code{-P} may be specified (see below). @end table @geindex -d (gnatname) @table @asis @item @code{-d@emph{dir}} Look for source files in directory @code{dir}. There may be zero, one or more spaces between @code{-d} and @code{dir}. @code{dir} may end with @code{/**}, that is it may be of the form @code{root_dir/**}. In this case, the directory @code{root_dir} and all of its subdirectories, recursively, have to be searched for sources. When a switch @code{-d} is specified, the current working directory will not be searched for source files, unless it is explicitly specified with a @code{-d} or @code{-D} switch. Several switches @code{-d} may be specified. If @code{dir} is a relative path, it is relative to the directory of the configuration pragmas file specified with switch @code{-c}, or to the directory of the project file specified with switch @code{-P} or, if neither switch @code{-c} nor switch @code{-P} are specified, it is relative to the current working directory. The directory specified with switch @code{-d} must exist and be readable. @end table @geindex -D (gnatname) @table @asis @item @code{-D@emph{filename}} Look for source files in all directories listed in text file @code{filename}. There may be zero, one or more spaces between @code{-D} and @code{filename}. @code{filename} must be an existing, readable text file. Each nonempty line in @code{filename} must be a directory. Specifying switch @code{-D} is equivalent to specifying as many switches @code{-d} as there are nonempty lines in @code{file}. @item @code{-eL} Follow symbolic links when processing project files. @geindex -f (gnatname) @item @code{-f@emph{pattern}} Foreign patterns. Using this switch, it is possible to add sources of languages other than Ada to the list of sources of a project file. It is only useful if a -P switch is used. For example, @example gnatname -Pprj -f"*.c" "*.ada" @end example will look for Ada units in all files with the @code{.ada} extension, and will add to the list of file for project @code{prj.gpr} the C files with extension @code{.c}. @geindex -h (gnatname) @item @code{-h} Output usage (help) information. The output is written to @code{stdout}. @geindex -P (gnatname) @item @code{-P@emph{proj}} Create or update project file @code{proj}. There may be zero, one or more space between @code{-P} and @code{proj}. @code{proj} may include directory information. @code{proj} must be writable. There may be only one switch @code{-P}. When a switch @code{-P} is specified, no switch @code{-c} may be specified. On all platforms, except on VMS, when @code{gnatname} is invoked for an existing project file <proj>.gpr, a backup copy of the project file is created in the project directory with file name <proj>.gpr.saved_x. 'x' is the first non negative number that makes this backup copy a new file. @geindex -v (gnatname) @item @code{-v} Verbose mode. Output detailed explanation of behavior to @code{stdout}. This includes name of the file written, the name of the directories to search and, for each file in those directories whose name matches at least one of the Naming Patterns, an indication of whether the file contains a unit, and if so the name of the unit. @end table @geindex -v -v (gnatname) @table @asis @item @code{-v -v} Very Verbose mode. In addition to the output produced in verbose mode, for each file in the searched directories whose name matches none of the Naming Patterns, an indication is given that there is no match. @geindex -x (gnatname) @item @code{-x@emph{pattern}} Excluded patterns. Using this switch, it is possible to exclude some files that would match the name patterns. For example, @example gnatname -x "*_nt.ada" "*.ada" @end example will look for Ada units in all files with the @code{.ada} extension, except those whose names end with @code{_nt.ada}. @end table @node Examples of gnatname Usage,,Switches for gnatname,Handling Arbitrary File Naming Conventions with gnatname @anchor{gnat_ugn/the_gnat_compilation_model examples-of-gnatname-usage}@anchor{61}@anchor{gnat_ugn/the_gnat_compilation_model id16}@anchor{62} @subsubsection Examples of @code{gnatname} Usage @example $ gnatname -c /home/me/names.adc -d sources "[a-z]*.ada*" @end example In this example, the directory @code{/home/me} must already exist and be writable. In addition, the directory @code{/home/me/sources} (specified by @code{-d sources}) must exist and be readable. Note the optional spaces after @code{-c} and @code{-d}. @example $ gnatname -P/home/me/proj -x "*_nt_body.ada" -dsources -dsources/plus -Dcommon_dirs.txt "body_*" "spec_*" @end example Note that several switches @code{-d} may be used, even in conjunction with one or several switches @code{-D}. Several Naming Patterns and one excluded pattern are used in this example. @node File Name Krunching with gnatkr,Renaming Files with gnatchop,Handling Arbitrary File Naming Conventions with gnatname,File Naming Topics and Utilities @anchor{gnat_ugn/the_gnat_compilation_model file-name-krunching-with-gnatkr}@anchor{63}@anchor{gnat_ugn/the_gnat_compilation_model id17}@anchor{64} @subsection File Name Krunching with @code{gnatkr} @geindex gnatkr This section discusses the method used by the compiler to shorten the default file names chosen for Ada units so that they do not exceed the maximum length permitted. It also describes the @code{gnatkr} utility that can be used to determine the result of applying this shortening. @menu * About gnatkr:: * Using gnatkr:: * Krunching Method:: * Examples of gnatkr Usage:: @end menu @node About gnatkr,Using gnatkr,,File Name Krunching with gnatkr @anchor{gnat_ugn/the_gnat_compilation_model id18}@anchor{65}@anchor{gnat_ugn/the_gnat_compilation_model about-gnatkr}@anchor{66} @subsubsection About @code{gnatkr} The default file naming rule in GNAT is that the file name must be derived from the unit name. The exact default rule is as follows: @itemize * @item Take the unit name and replace all dots by hyphens. @item If such a replacement occurs in the second character position of a name, and the first character is @code{a}, @code{g}, @code{s}, or @code{i}, then replace the dot by the character @code{~} (tilde) instead of a minus. The reason for this exception is to avoid clashes with the standard names for children of System, Ada, Interfaces, and GNAT, which use the prefixes @code{s-}, @code{a-}, @code{i-}, and @code{g-}, respectively. @end itemize The @code{-gnatk@emph{nn}} switch of the compiler activates a 'krunching' circuit that limits file names to nn characters (where nn is a decimal integer). The @code{gnatkr} utility can be used to determine the krunched name for a given file, when krunched to a specified maximum length. @node Using gnatkr,Krunching Method,About gnatkr,File Name Krunching with gnatkr @anchor{gnat_ugn/the_gnat_compilation_model id19}@anchor{67}@anchor{gnat_ugn/the_gnat_compilation_model using-gnatkr}@anchor{54} @subsubsection Using @code{gnatkr} The @code{gnatkr} command has the form: @example $ gnatkr name [ length ] @end example @code{name} is the uncrunched file name, derived from the name of the unit in the standard manner described in the previous section (i.e., in particular all dots are replaced by hyphens). The file name may or may not have an extension (defined as a suffix of the form period followed by arbitrary characters other than period). If an extension is present then it will be preserved in the output. For example, when krunching @code{hellofile.ads} to eight characters, the result will be hellofil.ads. Note: for compatibility with previous versions of @code{gnatkr} dots may appear in the name instead of hyphens, but the last dot will always be taken as the start of an extension. So if @code{gnatkr} is given an argument such as @code{Hello.World.adb} it will be treated exactly as if the first period had been a hyphen, and for example krunching to eight characters gives the result @code{hellworl.adb}. Note that the result is always all lower case. Characters of the other case are folded as required. @code{length} represents the length of the krunched name. The default when no argument is given is 8 characters. A length of zero stands for unlimited, in other words do not chop except for system files where the implied crunching length is always eight characters. The output is the krunched name. The output has an extension only if the original argument was a file name with an extension. @node Krunching Method,Examples of gnatkr Usage,Using gnatkr,File Name Krunching with gnatkr @anchor{gnat_ugn/the_gnat_compilation_model id20}@anchor{68}@anchor{gnat_ugn/the_gnat_compilation_model krunching-method}@anchor{69} @subsubsection Krunching Method The initial file name is determined by the name of the unit that the file contains. The name is formed by taking the full expanded name of the unit and replacing the separating dots with hyphens and using lowercase for all letters, except that a hyphen in the second character position is replaced by a tilde if the first character is @code{a}, @code{i}, @code{g}, or @code{s}. The extension is @code{.ads} for a spec and @code{.adb} for a body. Krunching does not affect the extension, but the file name is shortened to the specified length by following these rules: @itemize * @item The name is divided into segments separated by hyphens, tildes or underscores and all hyphens, tildes, and underscores are eliminated. If this leaves the name short enough, we are done. @item If the name is too long, the longest segment is located (left-most if there are two of equal length), and shortened by dropping its last character. This is repeated until the name is short enough. As an example, consider the krunching of @code{our-strings-wide_fixed.adb} to fit the name into 8 characters as required by some operating systems: @example our-strings-wide_fixed 22 our strings wide fixed 19 our string wide fixed 18 our strin wide fixed 17 our stri wide fixed 16 our stri wide fixe 15 our str wide fixe 14 our str wid fixe 13 our str wid fix 12 ou str wid fix 11 ou st wid fix 10 ou st wi fix 9 ou st wi fi 8 Final file name: oustwifi.adb @end example @item The file names for all predefined units are always krunched to eight characters. The krunching of these predefined units uses the following special prefix replacements: @multitable {xxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxx} @item Prefix @tab Replacement @item @code{ada-} @tab @code{a-} @item @code{gnat-} @tab @code{g-} @item @code{interfac es-} @tab @code{i-} @item @code{system-} @tab @code{s-} @end multitable These system files have a hyphen in the second character position. That is why normal user files replace such a character with a tilde, to avoid confusion with system file names. As an example of this special rule, consider @code{ada-strings-wide_fixed.adb}, which gets krunched as follows: @example ada-strings-wide_fixed 22 a- strings wide fixed 18 a- string wide fixed 17 a- strin wide fixed 16 a- stri wide fixed 15 a- stri wide fixe 14 a- str wide fixe 13 a- str wid fixe 12 a- str wid fix 11 a- st wid fix 10 a- st wi fix 9 a- st wi fi 8 Final file name: a-stwifi.adb @end example @end itemize Of course no file shortening algorithm can guarantee uniqueness over all possible unit names, and if file name krunching is used then it is your responsibility to ensure that no name clashes occur. The utility program @code{gnatkr} is supplied for conveniently determining the krunched name of a file. @node Examples of gnatkr Usage,,Krunching Method,File Name Krunching with gnatkr @anchor{gnat_ugn/the_gnat_compilation_model id21}@anchor{6a}@anchor{gnat_ugn/the_gnat_compilation_model examples-of-gnatkr-usage}@anchor{6b} @subsubsection Examples of @code{gnatkr} Usage @example $ gnatkr very_long_unit_name.ads --> velounna.ads $ gnatkr grandparent-parent-child.ads --> grparchi.ads $ gnatkr Grandparent.Parent.Child.ads --> grparchi.ads $ gnatkr grandparent-parent-child --> grparchi $ gnatkr very_long_unit_name.ads/count=6 --> vlunna.ads $ gnatkr very_long_unit_name.ads/count=0 --> very_long_unit_name.ads @end example @node Renaming Files with gnatchop,,File Name Krunching with gnatkr,File Naming Topics and Utilities @anchor{gnat_ugn/the_gnat_compilation_model id22}@anchor{6c}@anchor{gnat_ugn/the_gnat_compilation_model renaming-files-with-gnatchop}@anchor{36} @subsection Renaming Files with @code{gnatchop} @geindex gnatchop This section discusses how to handle files with multiple units by using the @code{gnatchop} utility. This utility is also useful in renaming files to meet the standard GNAT default file naming conventions. @menu * Handling Files with Multiple Units:: * Operating gnatchop in Compilation Mode:: * Command Line for gnatchop:: * Switches for gnatchop:: * Examples of gnatchop Usage:: @end menu @node Handling Files with Multiple Units,Operating gnatchop in Compilation Mode,,Renaming Files with gnatchop @anchor{gnat_ugn/the_gnat_compilation_model id23}@anchor{6d}@anchor{gnat_ugn/the_gnat_compilation_model handling-files-with-multiple-units}@anchor{6e} @subsubsection Handling Files with Multiple Units The basic compilation model of GNAT requires that a file submitted to the compiler have only one unit and there be a strict correspondence between the file name and the unit name. The @code{gnatchop} utility allows both of these rules to be relaxed, allowing GNAT to process files which contain multiple compilation units and files with arbitrary file names. @code{gnatchop} reads the specified file and generates one or more output files, containing one unit per file. The unit and the file name correspond, as required by GNAT. If you want to permanently restructure a set of 'foreign' files so that they match the GNAT rules, and do the remaining development using the GNAT structure, you can simply use @code{gnatchop} once, generate the new set of files and work with them from that point on. Alternatively, if you want to keep your files in the 'foreign' format, perhaps to maintain compatibility with some other Ada compilation system, you can set up a procedure where you use @code{gnatchop} each time you compile, regarding the source files that it writes as temporary files that you throw away. Note that if your file containing multiple units starts with a byte order mark (BOM) specifying UTF-8 encoding, then the files generated by gnatchop will each start with a copy of this BOM, meaning that they can be compiled automatically in UTF-8 mode without needing to specify an explicit encoding. @node Operating gnatchop in Compilation Mode,Command Line for gnatchop,Handling Files with Multiple Units,Renaming Files with gnatchop @anchor{gnat_ugn/the_gnat_compilation_model operating-gnatchop-in-compilation-mode}@anchor{6f}@anchor{gnat_ugn/the_gnat_compilation_model id24}@anchor{70} @subsubsection Operating gnatchop in Compilation Mode The basic function of @code{gnatchop} is to take a file with multiple units and split it into separate files. The boundary between files is reasonably clear, except for the issue of comments and pragmas. In default mode, the rule is that any pragmas between units belong to the previous unit, except that configuration pragmas always belong to the following unit. Any comments belong to the following unit. These rules almost always result in the right choice of the split point without needing to mark it explicitly and most users will find this default to be what they want. In this default mode it is incorrect to submit a file containing only configuration pragmas, or one that ends in configuration pragmas, to @code{gnatchop}. However, using a special option to activate 'compilation mode', @code{gnatchop} can perform another function, which is to provide exactly the semantics required by the RM for handling of configuration pragmas in a compilation. In the absence of configuration pragmas (at the main file level), this option has no effect, but it causes such configuration pragmas to be handled in a quite different manner. First, in compilation mode, if @code{gnatchop} is given a file that consists of only configuration pragmas, then this file is appended to the @code{gnat.adc} file in the current directory. This behavior provides the required behavior described in the RM for the actions to be taken on submitting such a file to the compiler, namely that these pragmas should apply to all subsequent compilations in the same compilation environment. Using GNAT, the current directory, possibly containing a @code{gnat.adc} file is the representation of a compilation environment. For more information on the @code{gnat.adc} file, see @ref{56,,Handling of Configuration Pragmas}. Second, in compilation mode, if @code{gnatchop} is given a file that starts with configuration pragmas, and contains one or more units, then these configuration pragmas are prepended to each of the chopped files. This behavior provides the required behavior described in the RM for the actions to be taken on compiling such a file, namely that the pragmas apply to all units in the compilation, but not to subsequently compiled units. Finally, if configuration pragmas appear between units, they are appended to the previous unit. This results in the previous unit being illegal, since the compiler does not accept configuration pragmas that follow a unit. This provides the required RM behavior that forbids configuration pragmas other than those preceding the first compilation unit of a compilation. For most purposes, @code{gnatchop} will be used in default mode. The compilation mode described above is used only if you need exactly accurate behavior with respect to compilations, and you have files that contain multiple units and configuration pragmas. In this circumstance the use of @code{gnatchop} with the compilation mode switch provides the required behavior, and is for example the mode in which GNAT processes the ACVC tests. @node Command Line for gnatchop,Switches for gnatchop,Operating gnatchop in Compilation Mode,Renaming Files with gnatchop @anchor{gnat_ugn/the_gnat_compilation_model id25}@anchor{71}@anchor{gnat_ugn/the_gnat_compilation_model command-line-for-gnatchop}@anchor{72} @subsubsection Command Line for @code{gnatchop} The @code{gnatchop} command has the form: @example $ gnatchop switches file_name [file_name ...] [directory] @end example The only required argument is the file name of the file to be chopped. There are no restrictions on the form of this file name. The file itself contains one or more Ada units, in normal GNAT format, concatenated together. As shown, more than one file may be presented to be chopped. When run in default mode, @code{gnatchop} generates one output file in the current directory for each unit in each of the files. @code{directory}, if specified, gives the name of the directory to which the output files will be written. If it is not specified, all files are written to the current directory. For example, given a file called @code{hellofiles} containing @example procedure Hello; with Ada.Text_IO; use Ada.Text_IO; procedure Hello is begin Put_Line ("Hello"); end Hello; @end example the command @example $ gnatchop hellofiles @end example generates two files in the current directory, one called @code{hello.ads} containing the single line that is the procedure spec, and the other called @code{hello.adb} containing the remaining text. The original file is not affected. The generated files can be compiled in the normal manner. When gnatchop is invoked on a file that is empty or that contains only empty lines and/or comments, gnatchop will not fail, but will not produce any new sources. For example, given a file called @code{toto.txt} containing @example -- Just a comment @end example the command @example $ gnatchop toto.txt @end example will not produce any new file and will result in the following warnings: @example toto.txt:1:01: warning: empty file, contains no compilation units no compilation units found no source files written @end example @node Switches for gnatchop,Examples of gnatchop Usage,Command Line for gnatchop,Renaming Files with gnatchop @anchor{gnat_ugn/the_gnat_compilation_model switches-for-gnatchop}@anchor{73}@anchor{gnat_ugn/the_gnat_compilation_model id26}@anchor{74} @subsubsection Switches for @code{gnatchop} @code{gnatchop} recognizes the following switches: @geindex --version (gnatchop) @table @asis @item @code{--version} Display Copyright and version, then exit disregarding all other options. @end table @geindex --help (gnatchop) @table @asis @item @code{--help} If @code{--version} was not used, display usage, then exit disregarding all other options. @end table @geindex -c (gnatchop) @table @asis @item @code{-c} Causes @code{gnatchop} to operate in compilation mode, in which configuration pragmas are handled according to strict RM rules. See previous section for a full description of this mode. @item @code{-gnat@emph{xxx}} This passes the given @code{-gnat@emph{xxx}} switch to @code{gnat} which is used to parse the given file. Not all @emph{xxx} options make sense, but for example, the use of @code{-gnati2} allows @code{gnatchop} to process a source file that uses Latin-2 coding for identifiers. @item @code{-h} Causes @code{gnatchop} to generate a brief help summary to the standard output file showing usage information. @end table @geindex -k (gnatchop) @table @asis @item @code{-k@emph{mm}} Limit generated file names to the specified number @code{mm} of characters. This is useful if the resulting set of files is required to be interoperable with systems which limit the length of file names. No space is allowed between the @code{-k} and the numeric value. The numeric value may be omitted in which case a default of @code{-k8}, suitable for use with DOS-like file systems, is used. If no @code{-k} switch is present then there is no limit on the length of file names. @end table @geindex -p (gnatchop) @table @asis @item @code{-p} Causes the file modification time stamp of the input file to be preserved and used for the time stamp of the output file(s). This may be useful for preserving coherency of time stamps in an environment where @code{gnatchop} is used as part of a standard build process. @end table @geindex -q (gnatchop) @table @asis @item @code{-q} Causes output of informational messages indicating the set of generated files to be suppressed. Warnings and error messages are unaffected. @end table @geindex -r (gnatchop) @geindex Source_Reference pragmas @table @asis @item @code{-r} Generate @code{Source_Reference} pragmas. Use this switch if the output files are regarded as temporary and development is to be done in terms of the original unchopped file. This switch causes @code{Source_Reference} pragmas to be inserted into each of the generated files to refers back to the original file name and line number. The result is that all error messages refer back to the original unchopped file. In addition, the debugging information placed into the object file (when the @code{-g} switch of @code{gcc} or @code{gnatmake} is specified) also refers back to this original file so that tools like profilers and debuggers will give information in terms of the original unchopped file. If the original file to be chopped itself contains a @code{Source_Reference} pragma referencing a third file, then gnatchop respects this pragma, and the generated @code{Source_Reference} pragmas in the chopped file refer to the original file, with appropriate line numbers. This is particularly useful when @code{gnatchop} is used in conjunction with @code{gnatprep} to compile files that contain preprocessing statements and multiple units. @end table @geindex -v (gnatchop) @table @asis @item @code{-v} Causes @code{gnatchop} to operate in verbose mode. The version number and copyright notice are output, as well as exact copies of the gnat1 commands spawned to obtain the chop control information. @end table @geindex -w (gnatchop) @table @asis @item @code{-w} Overwrite existing file names. Normally @code{gnatchop} regards it as a fatal error if there is already a file with the same name as a file it would otherwise output, in other words if the files to be chopped contain duplicated units. This switch bypasses this check, and causes all but the last instance of such duplicated units to be skipped. @end table @geindex --GCC= (gnatchop) @table @asis @item @code{--GCC=@emph{xxxx}} Specify the path of the GNAT parser to be used. When this switch is used, no attempt is made to add the prefix to the GNAT parser executable. @end table @node Examples of gnatchop Usage,,Switches for gnatchop,Renaming Files with gnatchop @anchor{gnat_ugn/the_gnat_compilation_model id27}@anchor{75}@anchor{gnat_ugn/the_gnat_compilation_model examples-of-gnatchop-usage}@anchor{76} @subsubsection Examples of @code{gnatchop} Usage @example $ gnatchop -w hello_s.ada prerelease/files @end example Chops the source file @code{hello_s.ada}. The output files will be placed in the directory @code{prerelease/files}, overwriting any files with matching names in that directory (no files in the current directory are modified). @example $ gnatchop archive @end example Chops the source file @code{archive} into the current directory. One useful application of @code{gnatchop} is in sending sets of sources around, for example in email messages. The required sources are simply concatenated (for example, using a Unix @code{cat} command), and then @code{gnatchop} is used at the other end to reconstitute the original file names. @example $ gnatchop file1 file2 file3 direc @end example Chops all units in files @code{file1}, @code{file2}, @code{file3}, placing the resulting files in the directory @code{direc}. Note that if any units occur more than once anywhere within this set of files, an error message is generated, and no files are written. To override this check, use the @code{-w} switch, in which case the last occurrence in the last file will be the one that is output, and earlier duplicate occurrences for a given unit will be skipped. @node Configuration Pragmas,Generating Object Files,File Naming Topics and Utilities,The GNAT Compilation Model @anchor{gnat_ugn/the_gnat_compilation_model id28}@anchor{77}@anchor{gnat_ugn/the_gnat_compilation_model configuration-pragmas}@anchor{14} @section Configuration Pragmas @geindex Configuration pragmas @geindex Pragmas @geindex configuration Configuration pragmas include those pragmas described as such in the Ada Reference Manual, as well as implementation-dependent pragmas that are configuration pragmas. See the @code{Implementation_Defined_Pragmas} chapter in the @cite{GNAT_Reference_Manual} for details on these additional GNAT-specific configuration pragmas. Most notably, the pragma @code{Source_File_Name}, which allows specifying non-default names for source files, is a configuration pragma. The following is a complete list of configuration pragmas recognized by GNAT: @example Ada_83 Ada_95 Ada_05 Ada_2005 Ada_12 Ada_2012 Allow_Integer_Address Annotate Assertion_Policy Assume_No_Invalid_Values C_Pass_By_Copy Check_Float_Overflow Check_Name Check_Policy Compile_Time_Error Compile_Time_Warning Compiler_Unit Compiler_Unit_Warning Component_Alignment Convention_Identifier Debug_Policy Detect_Blocking Default_Scalar_Storage_Order Default_Storage_Pool Disable_Atomic_Synchronization Discard_Names Elaboration_Checks Eliminate Enable_Atomic_Synchronization Extend_System Extensions_Allowed External_Name_Casing Fast_Math Favor_Top_Level Ignore_Pragma Implicit_Packing Initialize_Scalars Interrupt_State License Locking_Policy No_Component_Reordering No_Heap_Finalization No_Run_Time No_Strict_Aliasing Normalize_Scalars Optimize_Alignment Overflow_Mode Overriding_Renamings Partition_Elaboration_Policy Persistent_BSS Polling Prefix_Exception_Messages Priority_Specific_Dispatching Profile Profile_Warnings Propagate_Exceptions Queuing_Policy Rational Ravenscar Rename_Pragma Restricted_Run_Time Restrictions Restrictions_Warnings Reviewable Short_Circuit_And_Or Short_Descriptors Source_File_Name Source_File_Name_Project SPARK_Mode Style_Checks Suppress Suppress_Exception_Locations Task_Dispatching_Policy Unevaluated_Use_Of_Old Universal_Data Unsuppress Use_VADS_Size Validity_Checks Warning_As_Error Warnings Wide_Character_Encoding @end example @menu * Handling of Configuration Pragmas:: * The Configuration Pragmas Files:: @end menu @node Handling of Configuration Pragmas,The Configuration Pragmas Files,,Configuration Pragmas @anchor{gnat_ugn/the_gnat_compilation_model id29}@anchor{78}@anchor{gnat_ugn/the_gnat_compilation_model handling-of-configuration-pragmas}@anchor{56} @subsection Handling of Configuration Pragmas Configuration pragmas may either appear at the start of a compilation unit, or they can appear in a configuration pragma file to apply to all compilations performed in a given compilation environment. GNAT also provides the @code{gnatchop} utility to provide an automatic way to handle configuration pragmas following the semantics for compilations (that is, files with multiple units), described in the RM. See @ref{6f,,Operating gnatchop in Compilation Mode} for details. However, for most purposes, it will be more convenient to edit the @code{gnat.adc} file that contains configuration pragmas directly, as described in the following section. In the case of @code{Restrictions} pragmas appearing as configuration pragmas in individual compilation units, the exact handling depends on the type of restriction. Restrictions that require partition-wide consistency (like @code{No_Tasking}) are recognized wherever they appear and can be freely inherited, e.g. from a @emph{with}ed unit to the @emph{with}ing unit. This makes sense since the binder will in any case insist on seeing consistent use, so any unit not conforming to any restrictions that are anywhere in the partition will be rejected, and you might as well find that out at compile time rather than at bind time. For restrictions that do not require partition-wide consistency, e.g. SPARK or No_Implementation_Attributes, in general the restriction applies only to the unit in which the pragma appears, and not to any other units. The exception is No_Elaboration_Code which always applies to the entire object file from a compilation, i.e. to the body, spec, and all subunits. This restriction can be specified in a configuration pragma file, or it can be on the body and/or the spec (in eithe case it applies to all the relevant units). It can appear on a subunit only if it has previously appeared in the body of spec. @node The Configuration Pragmas Files,,Handling of Configuration Pragmas,Configuration Pragmas @anchor{gnat_ugn/the_gnat_compilation_model the-configuration-pragmas-files}@anchor{79}@anchor{gnat_ugn/the_gnat_compilation_model id30}@anchor{7a} @subsection The Configuration Pragmas Files @geindex gnat.adc In GNAT a compilation environment is defined by the current directory at the time that a compile command is given. This current directory is searched for a file whose name is @code{gnat.adc}. If this file is present, it is expected to contain one or more configuration pragmas that will be applied to the current compilation. However, if the switch @code{-gnatA} is used, @code{gnat.adc} is not considered. When taken into account, @code{gnat.adc} is added to the dependencies, so that if @code{gnat.adc} is modified later, an invocation of @code{gnatmake} will recompile the source. Configuration pragmas may be entered into the @code{gnat.adc} file either by running @code{gnatchop} on a source file that consists only of configuration pragmas, or more conveniently by direct editing of the @code{gnat.adc} file, which is a standard format source file. Besides @code{gnat.adc}, additional files containing configuration pragmas may be applied to the current compilation using the switch @code{-gnatec=@emph{path}} where @code{path} must designate an existing file that contains only configuration pragmas. These configuration pragmas are in addition to those found in @code{gnat.adc} (provided @code{gnat.adc} is present and switch @code{-gnatA} is not used). It is allowable to specify several switches @code{-gnatec=}, all of which will be taken into account. Files containing configuration pragmas specified with switches @code{-gnatec=} are added to the dependencies, unless they are temporary files. A file is considered temporary if its name ends in @code{.tmp} or @code{.TMP}. Certain tools follow this naming convention because they pass information to @code{gcc} via temporary files that are immediately deleted; it doesn't make sense to depend on a file that no longer exists. Such tools include @code{gprbuild}, @code{gnatmake}, and @code{gnatcheck}. If you are using project file, a separate mechanism is provided using project attributes. @c --Comment @c See :ref:`Specifying_Configuration_Pragmas` for more details. @node Generating Object Files,Source Dependencies,Configuration Pragmas,The GNAT Compilation Model @anchor{gnat_ugn/the_gnat_compilation_model generating-object-files}@anchor{40}@anchor{gnat_ugn/the_gnat_compilation_model id31}@anchor{7b} @section Generating Object Files An Ada program consists of a set of source files, and the first step in compiling the program is to generate the corresponding object files. These are generated by compiling a subset of these source files. The files you need to compile are the following: @itemize * @item If a package spec has no body, compile the package spec to produce the object file for the package. @item If a package has both a spec and a body, compile the body to produce the object file for the package. The source file for the package spec need not be compiled in this case because there is only one object file, which contains the code for both the spec and body of the package. @item For a subprogram, compile the subprogram body to produce the object file for the subprogram. The spec, if one is present, is as usual in a separate file, and need not be compiled. @end itemize @geindex Subunits @itemize * @item In the case of subunits, only compile the parent unit. A single object file is generated for the entire subunit tree, which includes all the subunits. @item Compile child units independently of their parent units (though, of course, the spec of all the ancestor unit must be present in order to compile a child unit). @geindex Generics @item Compile generic units in the same manner as any other units. The object files in this case are small dummy files that contain at most the flag used for elaboration checking. This is because GNAT always handles generic instantiation by means of macro expansion. However, it is still necessary to compile generic units, for dependency checking and elaboration purposes. @end itemize The preceding rules describe the set of files that must be compiled to generate the object files for a program. Each object file has the same name as the corresponding source file, except that the extension is @code{.o} as usual. You may wish to compile other files for the purpose of checking their syntactic and semantic correctness. For example, in the case where a package has a separate spec and body, you would not normally compile the spec. However, it is convenient in practice to compile the spec to make sure it is error-free before compiling clients of this spec, because such compilations will fail if there is an error in the spec. GNAT provides an option for compiling such files purely for the purposes of checking correctness; such compilations are not required as part of the process of building a program. To compile a file in this checking mode, use the @code{-gnatc} switch. @node Source Dependencies,The Ada Library Information Files,Generating Object Files,The GNAT Compilation Model @anchor{gnat_ugn/the_gnat_compilation_model id32}@anchor{7c}@anchor{gnat_ugn/the_gnat_compilation_model source-dependencies}@anchor{41} @section Source Dependencies A given object file clearly depends on the source file which is compiled to produce it. Here we are using "depends" in the sense of a typical @code{make} utility; in other words, an object file depends on a source file if changes to the source file require the object file to be recompiled. In addition to this basic dependency, a given object may depend on additional source files as follows: @itemize * @item If a file being compiled @emph{with}s a unit @code{X}, the object file depends on the file containing the spec of unit @code{X}. This includes files that are @emph{with}ed implicitly either because they are parents of @emph{with}ed child units or they are run-time units required by the language constructs used in a particular unit. @item If a file being compiled instantiates a library level generic unit, the object file depends on both the spec and body files for this generic unit. @item If a file being compiled instantiates a generic unit defined within a package, the object file depends on the body file for the package as well as the spec file. @end itemize @geindex Inline @geindex -gnatn switch @itemize * @item If a file being compiled contains a call to a subprogram for which pragma @code{Inline} applies and inlining is activated with the @code{-gnatn} switch, the object file depends on the file containing the body of this subprogram as well as on the file containing the spec. Note that for inlining to actually occur as a result of the use of this switch, it is necessary to compile in optimizing mode. @geindex -gnatN switch The use of @code{-gnatN} activates inlining optimization that is performed by the front end of the compiler. This inlining does not require that the code generation be optimized. Like @code{-gnatn}, the use of this switch generates additional dependencies. When using a gcc-based back end (in practice this means using any version of GNAT other than for the JVM, .NET or GNAAMP platforms), then the use of @code{-gnatN} is deprecated, and the use of @code{-gnatn} is preferred. Historically front end inlining was more extensive than the gcc back end inlining, but that is no longer the case. @item If an object file @code{O} depends on the proper body of a subunit through inlining or instantiation, it depends on the parent unit of the subunit. This means that any modification of the parent unit or one of its subunits affects the compilation of @code{O}. @item The object file for a parent unit depends on all its subunit body files. @item The previous two rules meant that for purposes of computing dependencies and recompilation, a body and all its subunits are treated as an indivisible whole. These rules are applied transitively: if unit @code{A} @emph{with}s unit @code{B}, whose elaboration calls an inlined procedure in package @code{C}, the object file for unit @code{A} will depend on the body of @code{C}, in file @code{c.adb}. The set of dependent files described by these rules includes all the files on which the unit is semantically dependent, as dictated by the Ada language standard. However, it is a superset of what the standard describes, because it includes generic, inline, and subunit dependencies. An object file must be recreated by recompiling the corresponding source file if any of the source files on which it depends are modified. For example, if the @code{make} utility is used to control compilation, the rule for an Ada object file must mention all the source files on which the object file depends, according to the above definition. The determination of the necessary recompilations is done automatically when one uses @code{gnatmake}. @end itemize @node The Ada Library Information Files,Binding an Ada Program,Source Dependencies,The GNAT Compilation Model @anchor{gnat_ugn/the_gnat_compilation_model id33}@anchor{7d}@anchor{gnat_ugn/the_gnat_compilation_model the-ada-library-information-files}@anchor{42} @section The Ada Library Information Files @geindex Ada Library Information files @geindex ALI files Each compilation actually generates two output files. The first of these is the normal object file that has a @code{.o} extension. The second is a text file containing full dependency information. It has the same name as the source file, but an @code{.ali} extension. This file is known as the Ada Library Information (@code{ALI}) file. The following information is contained in the @code{ALI} file. @itemize * @item Version information (indicates which version of GNAT was used to compile the unit(s) in question) @item Main program information (including priority and time slice settings, as well as the wide character encoding used during compilation). @item List of arguments used in the @code{gcc} command for the compilation @item Attributes of the unit, including configuration pragmas used, an indication of whether the compilation was successful, exception model used etc. @item A list of relevant restrictions applying to the unit (used for consistency) checking. @item Categorization information (e.g., use of pragma @code{Pure}). @item Information on all @emph{with}ed units, including presence of @code{Elaborate} or @code{Elaborate_All} pragmas. @item Information from any @code{Linker_Options} pragmas used in the unit @item Information on the use of @code{Body_Version} or @code{Version} attributes in the unit. @item Dependency information. This is a list of files, together with time stamp and checksum information. These are files on which the unit depends in the sense that recompilation is required if any of these units are modified. @item Cross-reference data. Contains information on all entities referenced in the unit. Used by tools like @code{gnatxref} and @code{gnatfind} to provide cross-reference information. @end itemize For a full detailed description of the format of the @code{ALI} file, see the source of the body of unit @code{Lib.Writ}, contained in file @code{lib-writ.adb} in the GNAT compiler sources. @node Binding an Ada Program,GNAT and Libraries,The Ada Library Information Files,The GNAT Compilation Model @anchor{gnat_ugn/the_gnat_compilation_model id34}@anchor{7e}@anchor{gnat_ugn/the_gnat_compilation_model binding-an-ada-program}@anchor{43} @section Binding an Ada Program When using languages such as C and C++, once the source files have been compiled the only remaining step in building an executable program is linking the object modules together. This means that it is possible to link an inconsistent version of a program, in which two units have included different versions of the same header. The rules of Ada do not permit such an inconsistent program to be built. For example, if two clients have different versions of the same package, it is illegal to build a program containing these two clients. These rules are enforced by the GNAT binder, which also determines an elaboration order consistent with the Ada rules. The GNAT binder is run after all the object files for a program have been created. It is given the name of the main program unit, and from this it determines the set of units required by the program, by reading the corresponding ALI files. It generates error messages if the program is inconsistent or if no valid order of elaboration exists. If no errors are detected, the binder produces a main program, in Ada by default, that contains calls to the elaboration procedures of those compilation unit that require them, followed by a call to the main program. This Ada program is compiled to generate the object file for the main program. The name of the Ada file is @code{b~xxx}.adb` (with the corresponding spec @code{b~xxx}.ads`) where @code{xxx} is the name of the main program unit. Finally, the linker is used to build the resulting executable program, using the object from the main program from the bind step as well as the object files for the Ada units of the program. @node GNAT and Libraries,Conditional Compilation,Binding an Ada Program,The GNAT Compilation Model @anchor{gnat_ugn/the_gnat_compilation_model gnat-and-libraries}@anchor{15}@anchor{gnat_ugn/the_gnat_compilation_model id35}@anchor{7f} @section GNAT and Libraries @geindex Library building and using This section describes how to build and use libraries with GNAT, and also shows how to recompile the GNAT run-time library. You should be familiar with the Project Manager facility (see the @emph{GNAT_Project_Manager} chapter of the @emph{GPRbuild User's Guide}) before reading this chapter. @menu * Introduction to Libraries in GNAT:: * General Ada Libraries:: * Stand-alone Ada Libraries:: * Rebuilding the GNAT Run-Time Library:: @end menu @node Introduction to Libraries in GNAT,General Ada Libraries,,GNAT and Libraries @anchor{gnat_ugn/the_gnat_compilation_model introduction-to-libraries-in-gnat}@anchor{80}@anchor{gnat_ugn/the_gnat_compilation_model id36}@anchor{81} @subsection Introduction to Libraries in GNAT A library is, conceptually, a collection of objects which does not have its own main thread of execution, but rather provides certain services to the applications that use it. A library can be either statically linked with the application, in which case its code is directly included in the application, or, on platforms that support it, be dynamically linked, in which case its code is shared by all applications making use of this library. GNAT supports both types of libraries. In the static case, the compiled code can be provided in different ways. The simplest approach is to provide directly the set of objects resulting from compilation of the library source files. Alternatively, you can group the objects into an archive using whatever commands are provided by the operating system. For the latter case, the objects are grouped into a shared library. In the GNAT environment, a library has three types of components: @itemize * @item Source files, @item @code{ALI} files (see @ref{42,,The Ada Library Information Files}), and @item Object files, an archive or a shared library. @end itemize A GNAT library may expose all its source files, which is useful for documentation purposes. Alternatively, it may expose only the units needed by an external user to make use of the library. That is to say, the specs reflecting the library services along with all the units needed to compile those specs, which can include generic bodies or any body implementing an inlined routine. In the case of @emph{stand-alone libraries} those exposed units are called @emph{interface units} (@ref{82,,Stand-alone Ada Libraries}). All compilation units comprising an application, including those in a library, need to be elaborated in an order partially defined by Ada's semantics. GNAT computes the elaboration order from the @code{ALI} files and this is why they constitute a mandatory part of GNAT libraries. @emph{Stand-alone libraries} are the exception to this rule because a specific library elaboration routine is produced independently of the application(s) using the library. @node General Ada Libraries,Stand-alone Ada Libraries,Introduction to Libraries in GNAT,GNAT and Libraries @anchor{gnat_ugn/the_gnat_compilation_model general-ada-libraries}@anchor{83}@anchor{gnat_ugn/the_gnat_compilation_model id37}@anchor{84} @subsection General Ada Libraries @menu * Building a library:: * Installing a library:: * Using a library:: @end menu @node Building a library,Installing a library,,General Ada Libraries @anchor{gnat_ugn/the_gnat_compilation_model building-a-library}@anchor{85}@anchor{gnat_ugn/the_gnat_compilation_model id38}@anchor{86} @subsubsection Building a library The easiest way to build a library is to use the Project Manager, which supports a special type of project called a @emph{Library Project} (see the @emph{Library Projects} section in the @emph{GNAT Project Manager} chapter of the @emph{GPRbuild User's Guide}). A project is considered a library project, when two project-level attributes are defined in it: @code{Library_Name} and @code{Library_Dir}. In order to control different aspects of library configuration, additional optional project-level attributes can be specified: @itemize * @item @table @asis @item @code{Library_Kind} This attribute controls whether the library is to be static or dynamic @end table @item @table @asis @item @code{Library_Version} This attribute specifies the library version; this value is used during dynamic linking of shared libraries to determine if the currently installed versions of the binaries are compatible. @end table @item @code{Library_Options} @item @table @asis @item @code{Library_GCC} These attributes specify additional low-level options to be used during library generation, and redefine the actual application used to generate library. @end table @end itemize The GNAT Project Manager takes full care of the library maintenance task, including recompilation of the source files for which objects do not exist or are not up to date, assembly of the library archive, and installation of the library (i.e., copying associated source, object and @code{ALI} files to the specified location). Here is a simple library project file: @example project My_Lib is for Source_Dirs use ("src1", "src2"); for Object_Dir use "obj"; for Library_Name use "mylib"; for Library_Dir use "lib"; for Library_Kind use "dynamic"; end My_lib; @end example and the compilation command to build and install the library: @example $ gnatmake -Pmy_lib @end example It is not entirely trivial to perform manually all the steps required to produce a library. We recommend that you use the GNAT Project Manager for this task. In special cases where this is not desired, the necessary steps are discussed below. There are various possibilities for compiling the units that make up the library: for example with a Makefile (@ref{1f,,Using the GNU make Utility}) or with a conventional script. For simple libraries, it is also possible to create a dummy main program which depends upon all the packages that comprise the interface of the library. This dummy main program can then be given to @code{gnatmake}, which will ensure that all necessary objects are built. After this task is accomplished, you should follow the standard procedure of the underlying operating system to produce the static or shared library. Here is an example of such a dummy program: @example with My_Lib.Service1; with My_Lib.Service2; with My_Lib.Service3; procedure My_Lib_Dummy is begin null; end; @end example Here are the generic commands that will build an archive or a shared library. @example # compiling the library $ gnatmake -c my_lib_dummy.adb # we don't need the dummy object itself $ rm my_lib_dummy.o my_lib_dummy.ali # create an archive with the remaining objects $ ar rc libmy_lib.a *.o # some systems may require "ranlib" to be run as well # or create a shared library $ gcc -shared -o libmy_lib.so *.o # some systems may require the code to have been compiled with -fPIC # remove the object files that are now in the library $ rm *.o # Make the ALI files read-only so that gnatmake will not try to # regenerate the objects that are in the library $ chmod -w *.ali @end example Please note that the library must have a name of the form @code{lib@emph{xxx}.a} or @code{lib@emph{xxx}.so} (or @code{lib@emph{xxx}.dll} on Windows) in order to be accessed by the directive @code{-l@emph{xxx}} at link time. @node Installing a library,Using a library,Building a library,General Ada Libraries @anchor{gnat_ugn/the_gnat_compilation_model installing-a-library}@anchor{87}@anchor{gnat_ugn/the_gnat_compilation_model id39}@anchor{88} @subsubsection Installing a library @geindex ADA_PROJECT_PATH @geindex GPR_PROJECT_PATH If you use project files, library installation is part of the library build process (see the @emph{Installing a Library with Project Files} section of the @emph{GNAT Project Manager} chapter of the @emph{GPRbuild User's Guide}). When project files are not an option, it is also possible, but not recommended, to install the library so that the sources needed to use the library are on the Ada source path and the ALI files & libraries be on the Ada Object path (see @ref{89,,Search Paths and the Run-Time Library (RTL)}. Alternatively, the system administrator can place general-purpose libraries in the default compiler paths, by specifying the libraries' location in the configuration files @code{ada_source_path} and @code{ada_object_path}. These configuration files must be located in the GNAT installation tree at the same place as the gcc spec file. The location of the gcc spec file can be determined as follows: @example $ gcc -v @end example The configuration files mentioned above have a simple format: each line must contain one unique directory name. Those names are added to the corresponding path in their order of appearance in the file. The names can be either absolute or relative; in the latter case, they are relative to where theses files are located. The files @code{ada_source_path} and @code{ada_object_path} might not be present in a GNAT installation, in which case, GNAT will look for its run-time library in the directories @code{adainclude} (for the sources) and @code{adalib} (for the objects and @code{ALI} files). When the files exist, the compiler does not look in @code{adainclude} and @code{adalib}, and thus the @code{ada_source_path} file must contain the location for the GNAT run-time sources (which can simply be @code{adainclude}). In the same way, the @code{ada_object_path} file must contain the location for the GNAT run-time objects (which can simply be @code{adalib}). You can also specify a new default path to the run-time library at compilation time with the switch @code{--RTS=rts-path}. You can thus choose / change the run-time library you want your program to be compiled with. This switch is recognized by @code{gcc}, @code{gnatmake}, @code{gnatbind}, @code{gnatls}, @code{gnatfind} and @code{gnatxref}. It is possible to install a library before or after the standard GNAT library, by reordering the lines in the configuration files. In general, a library must be installed before the GNAT library if it redefines any part of it. @node Using a library,,Installing a library,General Ada Libraries @anchor{gnat_ugn/the_gnat_compilation_model using-a-library}@anchor{8a}@anchor{gnat_ugn/the_gnat_compilation_model id40}@anchor{8b} @subsubsection Using a library Once again, the project facility greatly simplifies the use of libraries. In this context, using a library is just a matter of adding a @emph{with} clause in the user project. For instance, to make use of the library @code{My_Lib} shown in examples in earlier sections, you can write: @example with "my_lib"; project My_Proj is ... end My_Proj; @end example Even if you have a third-party, non-Ada library, you can still use GNAT's Project Manager facility to provide a wrapper for it. For example, the following project, when @emph{with}ed by your main project, will link with the third-party library @code{liba.a}: @example project Liba is for Externally_Built use "true"; for Source_Files use (); for Library_Dir use "lib"; for Library_Name use "a"; for Library_Kind use "static"; end Liba; @end example This is an alternative to the use of @code{pragma Linker_Options}. It is especially interesting in the context of systems with several interdependent static libraries where finding a proper linker order is not easy and best be left to the tools having visibility over project dependence information. In order to use an Ada library manually, you need to make sure that this library is on both your source and object path (see @ref{89,,Search Paths and the Run-Time Library (RTL)} and @ref{8c,,Search Paths for gnatbind}). Furthermore, when the objects are grouped in an archive or a shared library, you need to specify the desired library at link time. For example, you can use the library @code{mylib} installed in @code{/dir/my_lib_src} and @code{/dir/my_lib_obj} with the following commands: @example $ gnatmake -aI/dir/my_lib_src -aO/dir/my_lib_obj my_appl \\ -largs -lmy_lib @end example This can be expressed more simply: @example $ gnatmake my_appl @end example when the following conditions are met: @itemize * @item @code{/dir/my_lib_src} has been added by the user to the environment variable @geindex ADA_INCLUDE_PATH @geindex environment variable; ADA_INCLUDE_PATH @code{ADA_INCLUDE_PATH}, or by the administrator to the file @code{ada_source_path} @item @code{/dir/my_lib_obj} has been added by the user to the environment variable @geindex ADA_OBJECTS_PATH @geindex environment variable; ADA_OBJECTS_PATH @code{ADA_OBJECTS_PATH}, or by the administrator to the file @code{ada_object_path} @item a pragma @code{Linker_Options} has been added to one of the sources. For example: @example pragma Linker_Options ("-lmy_lib"); @end example @end itemize Note that you may also load a library dynamically at run time given its filename, as illustrated in the GNAT @code{plugins} example in the directory @code{share/examples/gnat/plugins} within the GNAT install area. @node Stand-alone Ada Libraries,Rebuilding the GNAT Run-Time Library,General Ada Libraries,GNAT and Libraries @anchor{gnat_ugn/the_gnat_compilation_model stand-alone-ada-libraries}@anchor{82}@anchor{gnat_ugn/the_gnat_compilation_model id41}@anchor{8d} @subsection Stand-alone Ada Libraries @geindex Stand-alone libraries @menu * Introduction to Stand-alone Libraries:: * Building a Stand-alone Library:: * Creating a Stand-alone Library to be used in a non-Ada context:: * Restrictions in Stand-alone Libraries:: @end menu @node Introduction to Stand-alone Libraries,Building a Stand-alone Library,,Stand-alone Ada Libraries @anchor{gnat_ugn/the_gnat_compilation_model introduction-to-stand-alone-libraries}@anchor{8e}@anchor{gnat_ugn/the_gnat_compilation_model id42}@anchor{8f} @subsubsection Introduction to Stand-alone Libraries A Stand-alone Library (abbreviated 'SAL') is a library that contains the necessary code to elaborate the Ada units that are included in the library. In contrast with an ordinary library, which consists of all sources, objects and @code{ALI} files of the library, a SAL may specify a restricted subset of compilation units to serve as a library interface. In this case, the fully self-sufficient set of files will normally consist of an objects archive, the sources of interface units' specs, and the @code{ALI} files of interface units. If an interface spec contains a generic unit or an inlined subprogram, the body's source must also be provided; if the units that must be provided in the source form depend on other units, the source and @code{ALI} files of those must also be provided. The main purpose of a SAL is to minimize the recompilation overhead of client applications when a new version of the library is installed. Specifically, if the interface sources have not changed, client applications do not need to be recompiled. If, furthermore, a SAL is provided in the shared form and its version, controlled by @code{Library_Version} attribute, is not changed, then the clients do not need to be relinked. SALs also allow the library providers to minimize the amount of library source text exposed to the clients. Such 'information hiding' might be useful or necessary for various reasons. Stand-alone libraries are also well suited to be used in an executable whose main routine is not written in Ada. @node Building a Stand-alone Library,Creating a Stand-alone Library to be used in a non-Ada context,Introduction to Stand-alone Libraries,Stand-alone Ada Libraries @anchor{gnat_ugn/the_gnat_compilation_model id43}@anchor{90}@anchor{gnat_ugn/the_gnat_compilation_model building-a-stand-alone-library}@anchor{91} @subsubsection Building a Stand-alone Library GNAT's Project facility provides a simple way of building and installing stand-alone libraries; see the @emph{Stand-alone Library Projects} section in the @emph{GNAT Project Manager} chapter of the @emph{GPRbuild User's Guide}. To be a Stand-alone Library Project, in addition to the two attributes that make a project a Library Project (@code{Library_Name} and @code{Library_Dir}; see the @emph{Library Projects} section in the @emph{GNAT Project Manager} chapter of the @emph{GPRbuild User's Guide}), the attribute @code{Library_Interface} must be defined. For example: @example for Library_Dir use "lib_dir"; for Library_Name use "dummy"; for Library_Interface use ("int1", "int1.child"); @end example Attribute @code{Library_Interface} has a non-empty string list value, each string in the list designating a unit contained in an immediate source of the project file. When a Stand-alone Library is built, first the binder is invoked to build a package whose name depends on the library name (@code{b~dummy.ads/b} in the example above). This binder-generated package includes initialization and finalization procedures whose names depend on the library name (@code{dummyinit} and @code{dummyfinal} in the example above). The object corresponding to this package is included in the library. You must ensure timely (e.g., prior to any use of interfaces in the SAL) calling of these procedures if a static SAL is built, or if a shared SAL is built with the project-level attribute @code{Library_Auto_Init} set to @code{"false"}. For a Stand-Alone Library, only the @code{ALI} files of the Interface Units (those that are listed in attribute @code{Library_Interface}) are copied to the Library Directory. As a consequence, only the Interface Units may be imported from Ada units outside of the library. If other units are imported, the binding phase will fail. It is also possible to build an encapsulated library where not only the code to elaborate and finalize the library is embedded but also ensuring that the library is linked only against static libraries. So an encapsulated library only depends on system libraries, all other code, including the GNAT runtime, is embedded. To build an encapsulated library the attribute @code{Library_Standalone} must be set to @code{encapsulated}: @example for Library_Dir use "lib_dir"; for Library_Name use "dummy"; for Library_Kind use "dynamic"; for Library_Interface use ("int1", "int1.child"); for Library_Standalone use "encapsulated"; @end example The default value for this attribute is @code{standard} in which case a stand-alone library is built. The attribute @code{Library_Src_Dir} may be specified for a Stand-Alone Library. @code{Library_Src_Dir} is a simple attribute that has a single string value. Its value must be the path (absolute or relative to the project directory) of an existing directory. This directory cannot be the object directory or one of the source directories, but it can be the same as the library directory. The sources of the Interface Units of the library that are needed by an Ada client of the library will be copied to the designated directory, called the Interface Copy directory. These sources include the specs of the Interface Units, but they may also include bodies and subunits, when pragmas @code{Inline} or @code{Inline_Always} are used, or when there is a generic unit in the spec. Before the sources are copied to the Interface Copy directory, an attempt is made to delete all files in the Interface Copy directory. Building stand-alone libraries by hand is somewhat tedious, but for those occasions when it is necessary here are the steps that you need to perform: @itemize * @item Compile all library sources. @item Invoke the binder with the switch @code{-n} (No Ada main program), with all the @code{ALI} files of the interfaces, and with the switch @code{-L} to give specific names to the @code{init} and @code{final} procedures. For example: @example $ gnatbind -n int1.ali int2.ali -Lsal1 @end example @item Compile the binder generated file: @example $ gcc -c b~int2.adb @end example @item Link the dynamic library with all the necessary object files, indicating to the linker the names of the @code{init} (and possibly @code{final}) procedures for automatic initialization (and finalization). The built library should be placed in a directory different from the object directory. @item Copy the @code{ALI} files of the interface to the library directory, add in this copy an indication that it is an interface to a SAL (i.e., add a word @code{SL} on the line in the @code{ALI} file that starts with letter 'P') and make the modified copy of the @code{ALI} file read-only. @end itemize Using SALs is not different from using other libraries (see @ref{8a,,Using a library}). @node Creating a Stand-alone Library to be used in a non-Ada context,Restrictions in Stand-alone Libraries,Building a Stand-alone Library,Stand-alone Ada Libraries @anchor{gnat_ugn/the_gnat_compilation_model creating-a-stand-alone-library-to-be-used-in-a-non-ada-context}@anchor{92}@anchor{gnat_ugn/the_gnat_compilation_model id44}@anchor{93} @subsubsection Creating a Stand-alone Library to be used in a non-Ada context It is easy to adapt the SAL build procedure discussed above for use of a SAL in a non-Ada context. The only extra step required is to ensure that library interface subprograms are compatible with the main program, by means of @code{pragma Export} or @code{pragma Convention}. Here is an example of simple library interface for use with C main program: @example package My_Package is procedure Do_Something; pragma Export (C, Do_Something, "do_something"); procedure Do_Something_Else; pragma Export (C, Do_Something_Else, "do_something_else"); end My_Package; @end example On the foreign language side, you must provide a 'foreign' view of the library interface; remember that it should contain elaboration routines in addition to interface subprograms. The example below shows the content of @code{mylib_interface.h} (note that there is no rule for the naming of this file, any name can be used) @example /* the library elaboration procedure */ extern void mylibinit (void); /* the library finalization procedure */ extern void mylibfinal (void); /* the interface exported by the library */ extern void do_something (void); extern void do_something_else (void); @end example Libraries built as explained above can be used from any program, provided that the elaboration procedures (named @code{mylibinit} in the previous example) are called before the library services are used. Any number of libraries can be used simultaneously, as long as the elaboration procedure of each library is called. Below is an example of a C program that uses the @code{mylib} library. @example #include "mylib_interface.h" int main (void) @{ /* First, elaborate the library before using it */ mylibinit (); /* Main program, using the library exported entities */ do_something (); do_something_else (); /* Library finalization at the end of the program */ mylibfinal (); return 0; @} @end example Note that invoking any library finalization procedure generated by @code{gnatbind} shuts down the Ada run-time environment. Consequently, the finalization of all Ada libraries must be performed at the end of the program. No call to these libraries or to the Ada run-time library should be made after the finalization phase. Note also that special care must be taken with multi-tasks applications. The initialization and finalization routines are not protected against concurrent access. If such requirement is needed it must be ensured at the application level using a specific operating system services like a mutex or a critical-section. @node Restrictions in Stand-alone Libraries,,Creating a Stand-alone Library to be used in a non-Ada context,Stand-alone Ada Libraries @anchor{gnat_ugn/the_gnat_compilation_model id45}@anchor{94}@anchor{gnat_ugn/the_gnat_compilation_model restrictions-in-stand-alone-libraries}@anchor{95} @subsubsection Restrictions in Stand-alone Libraries The pragmas listed below should be used with caution inside libraries, as they can create incompatibilities with other Ada libraries: @itemize * @item pragma @code{Locking_Policy} @item pragma @code{Partition_Elaboration_Policy} @item pragma @code{Queuing_Policy} @item pragma @code{Task_Dispatching_Policy} @item pragma @code{Unreserve_All_Interrupts} @end itemize When using a library that contains such pragmas, the user must make sure that all libraries use the same pragmas with the same values. Otherwise, @code{Program_Error} will be raised during the elaboration of the conflicting libraries. The usage of these pragmas and its consequences for the user should therefore be well documented. Similarly, the traceback in the exception occurrence mechanism should be enabled or disabled in a consistent manner across all libraries. Otherwise, Program_Error will be raised during the elaboration of the conflicting libraries. If the @code{Version} or @code{Body_Version} attributes are used inside a library, then you need to perform a @code{gnatbind} step that specifies all @code{ALI} files in all libraries, so that version identifiers can be properly computed. In practice these attributes are rarely used, so this is unlikely to be a consideration. @node Rebuilding the GNAT Run-Time Library,,Stand-alone Ada Libraries,GNAT and Libraries @anchor{gnat_ugn/the_gnat_compilation_model id46}@anchor{96}@anchor{gnat_ugn/the_gnat_compilation_model rebuilding-the-gnat-run-time-library}@anchor{97} @subsection Rebuilding the GNAT Run-Time Library @geindex GNAT Run-Time Library @geindex rebuilding @geindex Building the GNAT Run-Time Library @geindex Rebuilding the GNAT Run-Time Library @geindex Run-Time Library @geindex rebuilding It may be useful to recompile the GNAT library in various contexts, the most important one being the use of partition-wide configuration pragmas such as @code{Normalize_Scalars}. A special Makefile called @code{Makefile.adalib} is provided to that effect and can be found in the directory containing the GNAT library. The location of this directory depends on the way the GNAT environment has been installed and can be determined by means of the command: @example $ gnatls -v @end example The last entry in the object search path usually contains the gnat library. This Makefile contains its own documentation and in particular the set of instructions needed to rebuild a new library and to use it. @geindex Conditional compilation @node Conditional Compilation,Mixed Language Programming,GNAT and Libraries,The GNAT Compilation Model @anchor{gnat_ugn/the_gnat_compilation_model id47}@anchor{98}@anchor{gnat_ugn/the_gnat_compilation_model conditional-compilation}@anchor{16} @section Conditional Compilation This section presents some guidelines for modeling conditional compilation in Ada and describes the gnatprep preprocessor utility. @geindex Conditional compilation @menu * Modeling Conditional Compilation in Ada:: * Preprocessing with gnatprep:: * Integrated Preprocessing:: @end menu @node Modeling Conditional Compilation in Ada,Preprocessing with gnatprep,,Conditional Compilation @anchor{gnat_ugn/the_gnat_compilation_model modeling-conditional-compilation-in-ada}@anchor{99}@anchor{gnat_ugn/the_gnat_compilation_model id48}@anchor{9a} @subsection Modeling Conditional Compilation in Ada It is often necessary to arrange for a single source program to serve multiple purposes, where it is compiled in different ways to achieve these different goals. Some examples of the need for this feature are @itemize * @item Adapting a program to a different hardware environment @item Adapting a program to a different target architecture @item Turning debugging features on and off @item Arranging for a program to compile with different compilers @end itemize In C, or C++, the typical approach would be to use the preprocessor that is defined as part of the language. The Ada language does not contain such a feature. This is not an oversight, but rather a very deliberate design decision, based on the experience that overuse of the preprocessing features in C and C++ can result in programs that are extremely difficult to maintain. For example, if we have ten switches that can be on or off, this means that there are a thousand separate programs, any one of which might not even be syntactically correct, and even if syntactically correct, the resulting program might not work correctly. Testing all combinations can quickly become impossible. Nevertheless, the need to tailor programs certainly exists, and in this section we will discuss how this can be achieved using Ada in general, and GNAT in particular. @menu * Use of Boolean Constants:: * Debugging - A Special Case:: * Conditionalizing Declarations:: * Use of Alternative Implementations:: * Preprocessing:: @end menu @node Use of Boolean Constants,Debugging - A Special Case,,Modeling Conditional Compilation in Ada @anchor{gnat_ugn/the_gnat_compilation_model id49}@anchor{9b}@anchor{gnat_ugn/the_gnat_compilation_model use-of-boolean-constants}@anchor{9c} @subsubsection Use of Boolean Constants In the case where the difference is simply which code sequence is executed, the cleanest solution is to use Boolean constants to control which code is executed. @example FP_Initialize_Required : constant Boolean := True; ... if FP_Initialize_Required then ... end if; @end example Not only will the code inside the @code{if} statement not be executed if the constant Boolean is @code{False}, but it will also be completely deleted from the program. However, the code is only deleted after the @code{if} statement has been checked for syntactic and semantic correctness. (In contrast, with preprocessors the code is deleted before the compiler ever gets to see it, so it is not checked until the switch is turned on.) @geindex Preprocessors (contrasted with conditional compilation) Typically the Boolean constants will be in a separate package, something like: @example package Config is FP_Initialize_Required : constant Boolean := True; Reset_Available : constant Boolean := False; ... end Config; @end example The @code{Config} package exists in multiple forms for the various targets, with an appropriate script selecting the version of @code{Config} needed. Then any other unit requiring conditional compilation can do a @emph{with} of @code{Config} to make the constants visible. @node Debugging - A Special Case,Conditionalizing Declarations,Use of Boolean Constants,Modeling Conditional Compilation in Ada @anchor{gnat_ugn/the_gnat_compilation_model debugging-a-special-case}@anchor{9d}@anchor{gnat_ugn/the_gnat_compilation_model id50}@anchor{9e} @subsubsection Debugging - A Special Case A common use of conditional code is to execute statements (for example dynamic checks, or output of intermediate results) under control of a debug switch, so that the debugging behavior can be turned on and off. This can be done using a Boolean constant to control whether the code is active: @example if Debugging then Put_Line ("got to the first stage!"); end if; @end example or @example if Debugging and then Temperature > 999.0 then raise Temperature_Crazy; end if; @end example @geindex pragma Assert Since this is a common case, there are special features to deal with this in a convenient manner. For the case of tests, Ada 2005 has added a pragma @code{Assert} that can be used for such tests. This pragma is modeled on the @code{Assert} pragma that has always been available in GNAT, so this feature may be used with GNAT even if you are not using Ada 2005 features. The use of pragma @code{Assert} is described in the @cite{GNAT_Reference_Manual}, but as an example, the last test could be written: @example pragma Assert (Temperature <= 999.0, "Temperature Crazy"); @end example or simply @example pragma Assert (Temperature <= 999.0); @end example In both cases, if assertions are active and the temperature is excessive, the exception @code{Assert_Failure} will be raised, with the given string in the first case or a string indicating the location of the pragma in the second case used as the exception message. @geindex pragma Assertion_Policy You can turn assertions on and off by using the @code{Assertion_Policy} pragma. @geindex -gnata switch This is an Ada 2005 pragma which is implemented in all modes by GNAT. Alternatively, you can use the @code{-gnata} switch to enable assertions from the command line, which applies to all versions of Ada. @geindex pragma Debug For the example above with the @code{Put_Line}, the GNAT-specific pragma @code{Debug} can be used: @example pragma Debug (Put_Line ("got to the first stage!")); @end example If debug pragmas are enabled, the argument, which must be of the form of a procedure call, is executed (in this case, @code{Put_Line} will be called). Only one call can be present, but of course a special debugging procedure containing any code you like can be included in the program and then called in a pragma @code{Debug} argument as needed. One advantage of pragma @code{Debug} over the @code{if Debugging then} construct is that pragma @code{Debug} can appear in declarative contexts, such as at the very beginning of a procedure, before local declarations have been elaborated. @geindex pragma Debug_Policy Debug pragmas are enabled using either the @code{-gnata} switch that also controls assertions, or with a separate Debug_Policy pragma. The latter pragma is new in the Ada 2005 versions of GNAT (but it can be used in Ada 95 and Ada 83 programs as well), and is analogous to pragma @code{Assertion_Policy} to control assertions. @code{Assertion_Policy} and @code{Debug_Policy} are configuration pragmas, and thus they can appear in @code{gnat.adc} if you are not using a project file, or in the file designated to contain configuration pragmas in a project file. They then apply to all subsequent compilations. In practice the use of the @code{-gnata} switch is often the most convenient method of controlling the status of these pragmas. Note that a pragma is not a statement, so in contexts where a statement sequence is required, you can't just write a pragma on its own. You have to add a @code{null} statement. @example if ... then ... -- some statements else pragma Assert (Num_Cases < 10); null; end if; @end example @node Conditionalizing Declarations,Use of Alternative Implementations,Debugging - A Special Case,Modeling Conditional Compilation in Ada @anchor{gnat_ugn/the_gnat_compilation_model conditionalizing-declarations}@anchor{9f}@anchor{gnat_ugn/the_gnat_compilation_model id51}@anchor{a0} @subsubsection Conditionalizing Declarations In some cases it may be necessary to conditionalize declarations to meet different requirements. For example we might want a bit string whose length is set to meet some hardware message requirement. This may be possible using declare blocks controlled by conditional constants: @example if Small_Machine then declare X : Bit_String (1 .. 10); begin ... end; else declare X : Large_Bit_String (1 .. 1000); begin ... end; end if; @end example Note that in this approach, both declarations are analyzed by the compiler so this can only be used where both declarations are legal, even though one of them will not be used. Another approach is to define integer constants, e.g., @code{Bits_Per_Word}, or Boolean constants, e.g., @code{Little_Endian}, and then write declarations that are parameterized by these constants. For example @example for Rec use Field1 at 0 range Boolean'Pos (Little_Endian) * 10 .. Bits_Per_Word; end record; @end example If @code{Bits_Per_Word} is set to 32, this generates either @example for Rec use Field1 at 0 range 0 .. 32; end record; @end example for the big endian case, or @example for Rec use record Field1 at 0 range 10 .. 32; end record; @end example for the little endian case. Since a powerful subset of Ada expression notation is usable for creating static constants, clever use of this feature can often solve quite difficult problems in conditionalizing compilation (note incidentally that in Ada 95, the little endian constant was introduced as @code{System.Default_Bit_Order}, so you do not need to define this one yourself). @node Use of Alternative Implementations,Preprocessing,Conditionalizing Declarations,Modeling Conditional Compilation in Ada @anchor{gnat_ugn/the_gnat_compilation_model use-of-alternative-implementations}@anchor{a1}@anchor{gnat_ugn/the_gnat_compilation_model id52}@anchor{a2} @subsubsection Use of Alternative Implementations In some cases, none of the approaches described above are adequate. This can occur for example if the set of declarations required is radically different for two different configurations. In this situation, the official Ada way of dealing with conditionalizing such code is to write separate units for the different cases. As long as this does not result in excessive duplication of code, this can be done without creating maintenance problems. The approach is to share common code as far as possible, and then isolate the code and declarations that are different. Subunits are often a convenient method for breaking out a piece of a unit that is to be conditionalized, with separate files for different versions of the subunit for different targets, where the build script selects the right one to give to the compiler. @geindex Subunits (and conditional compilation) As an example, consider a situation where a new feature in Ada 2005 allows something to be done in a really nice way. But your code must be able to compile with an Ada 95 compiler. Conceptually you want to say: @example if Ada_2005 then ... neat Ada 2005 code else ... not quite as neat Ada 95 code end if; @end example where @code{Ada_2005} is a Boolean constant. But this won't work when @code{Ada_2005} is set to @code{False}, since the @code{then} clause will be illegal for an Ada 95 compiler. (Recall that although such unreachable code would eventually be deleted by the compiler, it still needs to be legal. If it uses features introduced in Ada 2005, it will be illegal in Ada 95.) So instead we write @example procedure Insert is separate; @end example Then we have two files for the subunit @code{Insert}, with the two sets of code. If the package containing this is called @code{File_Queries}, then we might have two files @itemize * @item @code{file_queries-insert-2005.adb} @item @code{file_queries-insert-95.adb} @end itemize and the build script renames the appropriate file to @code{file_queries-insert.adb} and then carries out the compilation. This can also be done with project files' naming schemes. For example: @example for body ("File_Queries.Insert") use "file_queries-insert-2005.ada"; @end example Note also that with project files it is desirable to use a different extension than @code{ads} / @code{adb} for alternative versions. Otherwise a naming conflict may arise through another commonly used feature: to declare as part of the project a set of directories containing all the sources obeying the default naming scheme. The use of alternative units is certainly feasible in all situations, and for example the Ada part of the GNAT run-time is conditionalized based on the target architecture using this approach. As a specific example, consider the implementation of the AST feature in VMS. There is one spec: @code{s-asthan.ads} which is the same for all architectures, and three bodies: @itemize * @item @table @asis @item @code{s-asthan.adb} used for all non-VMS operating systems @end table @item @table @asis @item @code{s-asthan-vms-alpha.adb} used for VMS on the Alpha @end table @item @table @asis @item @code{s-asthan-vms-ia64.adb} used for VMS on the ia64 @end table @end itemize The dummy version @code{s-asthan.adb} simply raises exceptions noting that this operating system feature is not available, and the two remaining versions interface with the corresponding versions of VMS to provide VMS-compatible AST handling. The GNAT build script knows the architecture and operating system, and automatically selects the right version, renaming it if necessary to @code{s-asthan.adb} before the run-time build. Another style for arranging alternative implementations is through Ada's access-to-subprogram facility. In case some functionality is to be conditionally included, you can declare an access-to-procedure variable @code{Ref} that is initialized to designate a 'do nothing' procedure, and then invoke @code{Ref.all} when appropriate. In some library package, set @code{Ref} to @code{Proc'Access} for some procedure @code{Proc} that performs the relevant processing. The initialization only occurs if the library package is included in the program. The same idea can also be implemented using tagged types and dispatching calls. @node Preprocessing,,Use of Alternative Implementations,Modeling Conditional Compilation in Ada @anchor{gnat_ugn/the_gnat_compilation_model preprocessing}@anchor{a3}@anchor{gnat_ugn/the_gnat_compilation_model id53}@anchor{a4} @subsubsection Preprocessing @geindex Preprocessing Although it is quite possible to conditionalize code without the use of C-style preprocessing, as described earlier in this section, it is nevertheless convenient in some cases to use the C approach. Moreover, older Ada compilers have often provided some preprocessing capability, so legacy code may depend on this approach, even though it is not standard. To accommodate such use, GNAT provides a preprocessor (modeled to a large extent on the various preprocessors that have been used with legacy code on other compilers, to enable easier transition). @geindex gnatprep The preprocessor may be used in two separate modes. It can be used quite separately from the compiler, to generate a separate output source file that is then fed to the compiler as a separate step. This is the @code{gnatprep} utility, whose use is fully described in @ref{17,,Preprocessing with gnatprep}. The preprocessing language allows such constructs as @example #if DEBUG or else (PRIORITY > 4) then sequence of declarations #else completely different sequence of declarations #end if; @end example The values of the symbols @code{DEBUG} and @code{PRIORITY} can be defined either on the command line or in a separate file. The other way of running the preprocessor is even closer to the C style and often more convenient. In this approach the preprocessing is integrated into the compilation process. The compiler is given the preprocessor input which includes @code{#if} lines etc, and then the compiler carries out the preprocessing internally and processes the resulting output. For more details on this approach, see @ref{18,,Integrated Preprocessing}. @node Preprocessing with gnatprep,Integrated Preprocessing,Modeling Conditional Compilation in Ada,Conditional Compilation @anchor{gnat_ugn/the_gnat_compilation_model id54}@anchor{a5}@anchor{gnat_ugn/the_gnat_compilation_model preprocessing-with-gnatprep}@anchor{17} @subsection Preprocessing with @code{gnatprep} @geindex gnatprep @geindex Preprocessing (gnatprep) This section discusses how to use GNAT's @code{gnatprep} utility for simple preprocessing. Although designed for use with GNAT, @code{gnatprep} does not depend on any special GNAT features. For further discussion of conditional compilation in general, see @ref{16,,Conditional Compilation}. @menu * Preprocessing Symbols:: * Using gnatprep:: * Switches for gnatprep:: * Form of Definitions File:: * Form of Input Text for gnatprep:: @end menu @node Preprocessing Symbols,Using gnatprep,,Preprocessing with gnatprep @anchor{gnat_ugn/the_gnat_compilation_model id55}@anchor{a6}@anchor{gnat_ugn/the_gnat_compilation_model preprocessing-symbols}@anchor{a7} @subsubsection Preprocessing Symbols Preprocessing symbols are defined in @emph{definition files} and referenced in the sources to be preprocessed. A preprocessing symbol is an identifier, following normal Ada (case-insensitive) rules for its syntax, with the restriction that all characters need to be in the ASCII set (no accented letters). @node Using gnatprep,Switches for gnatprep,Preprocessing Symbols,Preprocessing with gnatprep @anchor{gnat_ugn/the_gnat_compilation_model using-gnatprep}@anchor{a8}@anchor{gnat_ugn/the_gnat_compilation_model id56}@anchor{a9} @subsubsection Using @code{gnatprep} To call @code{gnatprep} use: @example $ gnatprep [ switches ] infile outfile [ deffile ] @end example where @itemize * @item @table @asis @item @emph{switches} is an optional sequence of switches as described in the next section. @end table @item @table @asis @item @emph{infile} is the full name of the input file, which is an Ada source file containing preprocessor directives. @end table @item @table @asis @item @emph{outfile} is the full name of the output file, which is an Ada source in standard Ada form. When used with GNAT, this file name will normally have an @code{ads} or @code{adb} suffix. @end table @item @table @asis @item @code{deffile} is the full name of a text file containing definitions of preprocessing symbols to be referenced by the preprocessor. This argument is optional, and can be replaced by the use of the @code{-D} switch. @end table @end itemize @node Switches for gnatprep,Form of Definitions File,Using gnatprep,Preprocessing with gnatprep @anchor{gnat_ugn/the_gnat_compilation_model switches-for-gnatprep}@anchor{aa}@anchor{gnat_ugn/the_gnat_compilation_model id57}@anchor{ab} @subsubsection Switches for @code{gnatprep} @geindex --version (gnatprep) @table @asis @item @code{--version} Display Copyright and version, then exit disregarding all other options. @end table @geindex --help (gnatprep) @table @asis @item @code{--help} If @code{--version} was not used, display usage and then exit disregarding all other options. @end table @geindex -b (gnatprep) @table @asis @item @code{-b} Causes both preprocessor lines and the lines deleted by preprocessing to be replaced by blank lines in the output source file, preserving line numbers in the output file. @end table @geindex -c (gnatprep) @table @asis @item @code{-c} Causes both preprocessor lines and the lines deleted by preprocessing to be retained in the output source as comments marked with the special string @code{"--! "}. This option will result in line numbers being preserved in the output file. @end table @geindex -C (gnatprep) @table @asis @item @code{-C} Causes comments to be scanned. Normally comments are ignored by gnatprep. If this option is specified, then comments are scanned and any $symbol substitutions performed as in program text. This is particularly useful when structured comments are used (e.g., for programs written in a pre-2014 version of the SPARK Ada subset). Note that this switch is not available when doing integrated preprocessing (it would be useless in this context since comments are ignored by the compiler in any case). @end table @geindex -D (gnatprep) @table @asis @item @code{-D@emph{symbol}[=@emph{value}]} Defines a new preprocessing symbol with the specified value. If no value is given on the command line, then symbol is considered to be @code{True}. This switch can be used in place of a definition file. @end table @geindex -r (gnatprep) @table @asis @item @code{-r} Causes a @code{Source_Reference} pragma to be generated that references the original input file, so that error messages will use the file name of this original file. The use of this switch implies that preprocessor lines are not to be removed from the file, so its use will force @code{-b} mode if @code{-c} has not been specified explicitly. Note that if the file to be preprocessed contains multiple units, then it will be necessary to @code{gnatchop} the output file from @code{gnatprep}. If a @code{Source_Reference} pragma is present in the preprocessed file, it will be respected by @code{gnatchop -r} so that the final chopped files will correctly refer to the original input source file for @code{gnatprep}. @end table @geindex -s (gnatprep) @table @asis @item @code{-s} Causes a sorted list of symbol names and values to be listed on the standard output file. @end table @geindex -T (gnatprep) @table @asis @item @code{-T} Use LF as line terminators when writing files. By default the line terminator of the host (LF under unix, CR/LF under Windows) is used. @end table @geindex -u (gnatprep) @table @asis @item @code{-u} Causes undefined symbols to be treated as having the value FALSE in the context of a preprocessor test. In the absence of this option, an undefined symbol in a @code{#if} or @code{#elsif} test will be treated as an error. @end table @geindex -v (gnatprep) @table @asis @item @code{-v} Verbose mode: generates more output about work done. @end table Note: if neither @code{-b} nor @code{-c} is present, then preprocessor lines and deleted lines are completely removed from the output, unless -r is specified, in which case -b is assumed. @node Form of Definitions File,Form of Input Text for gnatprep,Switches for gnatprep,Preprocessing with gnatprep @anchor{gnat_ugn/the_gnat_compilation_model form-of-definitions-file}@anchor{ac}@anchor{gnat_ugn/the_gnat_compilation_model id58}@anchor{ad} @subsubsection Form of Definitions File The definitions file contains lines of the form: @example symbol := value @end example where @code{symbol} is a preprocessing symbol, and @code{value} is one of the following: @itemize * @item Empty, corresponding to a null substitution, @item A string literal using normal Ada syntax, or @item Any sequence of characters from the set @{letters, digits, period, underline@}. @end itemize Comment lines may also appear in the definitions file, starting with the usual @code{--}, and comments may be added to the definitions lines. @node Form of Input Text for gnatprep,,Form of Definitions File,Preprocessing with gnatprep @anchor{gnat_ugn/the_gnat_compilation_model id59}@anchor{ae}@anchor{gnat_ugn/the_gnat_compilation_model form-of-input-text-for-gnatprep}@anchor{af} @subsubsection Form of Input Text for @code{gnatprep} The input text may contain preprocessor conditional inclusion lines, as well as general symbol substitution sequences. The preprocessor conditional inclusion commands have the form: @example #if <expression> [then] lines #elsif <expression> [then] lines #elsif <expression> [then] lines ... #else lines #end if; @end example In this example, <expression> is defined by the following grammar: @example <expression> ::= <symbol> <expression> ::= <symbol> = "<value>" <expression> ::= <symbol> = <symbol> <expression> ::= <symbol> = <integer> <expression> ::= <symbol> > <integer> <expression> ::= <symbol> >= <integer> <expression> ::= <symbol> < <integer> <expression> ::= <symbol> <= <integer> <expression> ::= <symbol> 'Defined <expression> ::= not <expression> <expression> ::= <expression> and <expression> <expression> ::= <expression> or <expression> <expression> ::= <expression> and then <expression> <expression> ::= <expression> or else <expression> <expression> ::= ( <expression> ) @end example Note the following restriction: it is not allowed to have "and" or "or" following "not" in the same expression without parentheses. For example, this is not allowed: @example not X or Y @end example This can be expressed instead as one of the following forms: @example (not X) or Y not (X or Y) @end example For the first test (<expression> ::= <symbol>) the symbol must have either the value true or false, that is to say the right-hand of the symbol definition must be one of the (case-insensitive) literals @code{True} or @code{False}. If the value is true, then the corresponding lines are included, and if the value is false, they are excluded. When comparing a symbol to an integer, the integer is any non negative literal integer as defined in the Ada Reference Manual, such as 3, 16#FF# or 2#11#. The symbol value must also be a non negative integer. Integer values in the range 0 .. 2**31-1 are supported. The test (<expression> ::= <symbol>'Defined) is true only if the symbol has been defined in the definition file or by a @code{-D} switch on the command line. Otherwise, the test is false. The equality tests are case insensitive, as are all the preprocessor lines. If the symbol referenced is not defined in the symbol definitions file, then the effect depends on whether or not switch @code{-u} is specified. If so, then the symbol is treated as if it had the value false and the test fails. If this switch is not specified, then it is an error to reference an undefined symbol. It is also an error to reference a symbol that is defined with a value other than @code{True} or @code{False}. The use of the @code{not} operator inverts the sense of this logical test. The @code{not} operator cannot be combined with the @code{or} or @code{and} operators, without parentheses. For example, "if not X or Y then" is not allowed, but "if (not X) or Y then" and "if not (X or Y) then" are. The @code{then} keyword is optional as shown The @code{#} must be the first non-blank character on a line, but otherwise the format is free form. Spaces or tabs may appear between the @code{#} and the keyword. The keywords and the symbols are case insensitive as in normal Ada code. Comments may be used on a preprocessor line, but other than that, no other tokens may appear on a preprocessor line. Any number of @code{elsif} clauses can be present, including none at all. The @code{else} is optional, as in Ada. The @code{#} marking the start of a preprocessor line must be the first non-blank character on the line, i.e., it must be preceded only by spaces or horizontal tabs. Symbol substitution outside of preprocessor lines is obtained by using the sequence: @example $symbol @end example anywhere within a source line, except in a comment or within a string literal. The identifier following the @code{$} must match one of the symbols defined in the symbol definition file, and the result is to substitute the value of the symbol in place of @code{$symbol} in the output file. Note that although the substitution of strings within a string literal is not possible, it is possible to have a symbol whose defined value is a string literal. So instead of setting XYZ to @code{hello} and writing: @example Header : String := "$XYZ"; @end example you should set XYZ to @code{"hello"} and write: @example Header : String := $XYZ; @end example and then the substitution will occur as desired. @node Integrated Preprocessing,,Preprocessing with gnatprep,Conditional Compilation @anchor{gnat_ugn/the_gnat_compilation_model id60}@anchor{b0}@anchor{gnat_ugn/the_gnat_compilation_model integrated-preprocessing}@anchor{18} @subsection Integrated Preprocessing As noted above, a file to be preprocessed consists of Ada source code in which preprocessing lines have been inserted. However, instead of using @code{gnatprep} to explicitly preprocess a file as a separate step before compilation, you can carry out the preprocessing implicitly as part of compilation. Such @emph{integrated preprocessing}, which is the common style with C, is performed when either or both of the following switches are passed to the compiler: @quotation @itemize * @item @code{-gnatep}, which specifies the @emph{preprocessor data file}. This file dictates how the source files will be preprocessed (e.g., which symbol definition files apply to which sources). @item @code{-gnateD}, which defines values for preprocessing symbols. @end itemize @end quotation Integrated preprocessing applies only to Ada source files, it is not available for configuration pragma files. With integrated preprocessing, the output from the preprocessor is not, by default, written to any external file. Instead it is passed internally to the compiler. To preserve the result of preprocessing in a file, either run @code{gnatprep} in standalone mode or else supply the @code{-gnateG} switch (described below) to the compiler. When using project files: @quotation @itemize * @item the builder switch @code{-x} should be used if any Ada source is compiled with @code{gnatep=}, so that the compiler finds the @emph{preprocessor data file}. @item the preprocessing data file and the symbol definition files should be located in the source directories of the project. @end itemize @end quotation Note that the @code{gnatmake} switch @code{-m} will almost always trigger recompilation for sources that are preprocessed, because @code{gnatmake} cannot compute the checksum of the source after preprocessing. The actual preprocessing function is described in detail in @ref{17,,Preprocessing with gnatprep}. This section explains the switches that relate to integrated preprocessing. @geindex -gnatep (gcc) @table @asis @item @code{-gnatep=@emph{preprocessor_data_file}} This switch specifies the file name (without directory information) of the preprocessor data file. Either place this file in one of the source directories, or, when using project files, reference the project file's directory via the @code{project_name'Project_Dir} project attribute; e.g: @quotation @example project Prj is package Compiler is for Switches ("Ada") use ("-gnatep=" & Prj'Project_Dir & "prep.def"); end Compiler; end Prj; @end example @end quotation A preprocessor data file is a text file that contains @emph{preprocessor control lines}. A preprocessor control line directs the preprocessing of either a particular source file, or, analogous to @code{others} in Ada, all sources not specified elsewhere in the preprocessor data file. A preprocessor control line can optionally identify a @emph{definition file} that assigns values to preprocessor symbols, as well as a list of switches that relate to preprocessing. Empty lines and comments (using Ada syntax) are also permitted, with no semantic effect. Here's an example of a preprocessor data file: @quotation @example "toto.adb" "prep.def" -u -- Preprocess toto.adb, using definition file prep.def -- Undefined symbols are treated as False * -c -DVERSION=V101 -- Preprocess all other sources without using a definition file -- Suppressed lined are commented -- Symbol VERSION has the value V101 "tata.adb" "prep2.def" -s -- Preprocess tata.adb, using definition file prep2.def -- List all symbols with their values @end example @end quotation A preprocessor control line has the following syntax: @quotation @example <preprocessor_control_line> ::= <preprocessor_input> [ <definition_file_name> ] @{ <switch> @} <preprocessor_input> ::= <source_file_name> | '*' <definition_file_name> ::= <string_literal> <source_file_name> := <string_literal> <switch> := (See below for list) @end example @end quotation Thus each preprocessor control line starts with either a literal string or the character '*': @itemize * @item A literal string is the file name (without directory information) of the source file that will be input to the preprocessor. @item The character '*' is a wild-card indicator; the additional parameters on the line indicate the preprocessing for all the sources that are not specified explicitly on other lines (the order of the lines is not significant). @end itemize It is an error to have two lines with the same file name or two lines starting with the character '*'. After the file name or '*', an optional literal string specifies the name of the definition file to be used for preprocessing (@ref{ac,,Form of Definitions File}). The definition files are found by the compiler in one of the source directories. In some cases, when compiling a source in a directory other than the current directory, if the definition file is in the current directory, it may be necessary to add the current directory as a source directory through the @code{-I} switch; otherwise the compiler would not find the definition file. Finally, switches similar to those of @code{gnatprep} may optionally appear: @table @asis @item @code{-b} Causes both preprocessor lines and the lines deleted by preprocessing to be replaced by blank lines, preserving the line number. This switch is always implied; however, if specified after @code{-c} it cancels the effect of @code{-c}. @item @code{-c} Causes both preprocessor lines and the lines deleted by preprocessing to be retained as comments marked with the special string '@cite{--!}'. @item @code{-D@emph{symbol}=@emph{new_value}} Define or redefine @code{symbol} to have @code{new_value} as its value. The permitted form for @code{symbol} is either an Ada identifier, or any Ada reserved word aside from @code{if}, @code{else}, @code{elsif}, @code{end}, @code{and}, @code{or} and @code{then}. The permitted form for @code{new_value} is a literal string, an Ada identifier or any Ada reserved word. A symbol declared with this switch replaces a symbol with the same name defined in a definition file. @item @code{-s} Causes a sorted list of symbol names and values to be listed on the standard output file. @item @code{-u} Causes undefined symbols to be treated as having the value @code{FALSE} in the context of a preprocessor test. In the absence of this option, an undefined symbol in a @code{#if} or @code{#elsif} test will be treated as an error. @end table @end table @geindex -gnateD (gcc) @table @asis @item @code{-gnateD@emph{symbol}[=@emph{new_value}]} Define or redefine @code{symbol} to have @code{new_value} as its value. If no value is supplied, then the value of @code{symbol} is @code{True}. The form of @code{symbol} is an identifier, following normal Ada (case-insensitive) rules for its syntax, and @code{new_value} is either an arbitrary string between double quotes or any sequence (including an empty sequence) of characters from the set (letters, digits, period, underline). Ada reserved words may be used as symbols, with the exceptions of @code{if}, @code{else}, @code{elsif}, @code{end}, @code{and}, @code{or} and @code{then}. Examples: @quotation @example -gnateDToto=Tata -gnateDFoo -gnateDFoo=\"Foo-Bar\" @end example @end quotation A symbol declared with this switch on the command line replaces a symbol with the same name either in a definition file or specified with a switch @code{-D} in the preprocessor data file. This switch is similar to switch @code{-D} of @code{gnatprep}. @item @code{-gnateG} When integrated preprocessing is performed on source file @code{filename.extension}, create or overwrite @code{filename.extension.prep} to contain the result of the preprocessing. For example if the source file is @code{foo.adb} then the output file will be @code{foo.adb.prep}. @end table @node Mixed Language Programming,GNAT and Other Compilation Models,Conditional Compilation,The GNAT Compilation Model @anchor{gnat_ugn/the_gnat_compilation_model mixed-language-programming}@anchor{44}@anchor{gnat_ugn/the_gnat_compilation_model id61}@anchor{b1} @section Mixed Language Programming @geindex Mixed Language Programming This section describes how to develop a mixed-language program, with a focus on combining Ada with C or C++. @menu * Interfacing to C:: * Calling Conventions:: * Building Mixed Ada and C++ Programs:: * Generating Ada Bindings for C and C++ headers:: * Generating C Headers for Ada Specifications:: @end menu @node Interfacing to C,Calling Conventions,,Mixed Language Programming @anchor{gnat_ugn/the_gnat_compilation_model interfacing-to-c}@anchor{b2}@anchor{gnat_ugn/the_gnat_compilation_model id62}@anchor{b3} @subsection Interfacing to C Interfacing Ada with a foreign language such as C involves using compiler directives to import and/or export entity definitions in each language -- using @code{extern} statements in C, for instance, and the @code{Import}, @code{Export}, and @code{Convention} pragmas in Ada. A full treatment of these topics is provided in Appendix B, section 1 of the Ada Reference Manual. There are two ways to build a program using GNAT that contains some Ada sources and some foreign language sources, depending on whether or not the main subprogram is written in Ada. Here is a source example with the main subprogram in Ada: @example /* file1.c */ #include <stdio.h> void print_num (int num) @{ printf ("num is %d.\\n", num); return; @} @end example @example /* file2.c */ /* num_from_Ada is declared in my_main.adb */ extern int num_from_Ada; int get_num (void) @{ return num_from_Ada; @} @end example @example -- my_main.adb procedure My_Main is -- Declare then export an Integer entity called num_from_Ada My_Num : Integer := 10; pragma Export (C, My_Num, "num_from_Ada"); -- Declare an Ada function spec for Get_Num, then use -- C function get_num for the implementation. function Get_Num return Integer; pragma Import (C, Get_Num, "get_num"); -- Declare an Ada procedure spec for Print_Num, then use -- C function print_num for the implementation. procedure Print_Num (Num : Integer); pragma Import (C, Print_Num, "print_num"); begin Print_Num (Get_Num); end My_Main; @end example To build this example: @itemize * @item First compile the foreign language files to generate object files: @example $ gcc -c file1.c $ gcc -c file2.c @end example @item Then, compile the Ada units to produce a set of object files and ALI files: @example $ gnatmake -c my_main.adb @end example @item Run the Ada binder on the Ada main program: @example $ gnatbind my_main.ali @end example @item Link the Ada main program, the Ada objects and the other language objects: @example $ gnatlink my_main.ali file1.o file2.o @end example @end itemize The last three steps can be grouped in a single command: @example $ gnatmake my_main.adb -largs file1.o file2.o @end example @geindex Binder output file If the main program is in a language other than Ada, then you may have more than one entry point into the Ada subsystem. You must use a special binder option to generate callable routines that initialize and finalize the Ada units (@ref{b4,,Binding with Non-Ada Main Programs}). Calls to the initialization and finalization routines must be inserted in the main program, or some other appropriate point in the code. The call to initialize the Ada units must occur before the first Ada subprogram is called, and the call to finalize the Ada units must occur after the last Ada subprogram returns. The binder will place the initialization and finalization subprograms into the @code{b~xxx.adb} file where they can be accessed by your C sources. To illustrate, we have the following example: @example /* main.c */ extern void adainit (void); extern void adafinal (void); extern int add (int, int); extern int sub (int, int); int main (int argc, char *argv[]) @{ int a = 21, b = 7; adainit(); /* Should print "21 + 7 = 28" */ printf ("%d + %d = %d\\n", a, b, add (a, b)); /* Should print "21 - 7 = 14" */ printf ("%d - %d = %d\\n", a, b, sub (a, b)); adafinal(); @} @end example @example -- unit1.ads package Unit1 is function Add (A, B : Integer) return Integer; pragma Export (C, Add, "add"); end Unit1; @end example @example -- unit1.adb package body Unit1 is function Add (A, B : Integer) return Integer is begin return A + B; end Add; end Unit1; @end example @example -- unit2.ads package Unit2 is function Sub (A, B : Integer) return Integer; pragma Export (C, Sub, "sub"); end Unit2; @end example @example -- unit2.adb package body Unit2 is function Sub (A, B : Integer) return Integer is begin return A - B; end Sub; end Unit2; @end example The build procedure for this application is similar to the last example's: @itemize * @item First, compile the foreign language files to generate object files: @example $ gcc -c main.c @end example @item Next, compile the Ada units to produce a set of object files and ALI files: @example $ gnatmake -c unit1.adb $ gnatmake -c unit2.adb @end example @item Run the Ada binder on every generated ALI file. Make sure to use the @code{-n} option to specify a foreign main program: @example $ gnatbind -n unit1.ali unit2.ali @end example @item Link the Ada main program, the Ada objects and the foreign language objects. You need only list the last ALI file here: @example $ gnatlink unit2.ali main.o -o exec_file @end example This procedure yields a binary executable called @code{exec_file}. @end itemize Depending on the circumstances (for example when your non-Ada main object does not provide symbol @code{main}), you may also need to instruct the GNAT linker not to include the standard startup objects by passing the @code{-nostartfiles} switch to @code{gnatlink}. @node Calling Conventions,Building Mixed Ada and C++ Programs,Interfacing to C,Mixed Language Programming @anchor{gnat_ugn/the_gnat_compilation_model calling-conventions}@anchor{b5}@anchor{gnat_ugn/the_gnat_compilation_model id63}@anchor{b6} @subsection Calling Conventions @geindex Foreign Languages @geindex Calling Conventions GNAT follows standard calling sequence conventions and will thus interface to any other language that also follows these conventions. The following Convention identifiers are recognized by GNAT: @geindex Interfacing to Ada @geindex Other Ada compilers @geindex Convention Ada @table @asis @item @code{Ada} This indicates that the standard Ada calling sequence will be used and all Ada data items may be passed without any limitations in the case where GNAT is used to generate both the caller and callee. It is also possible to mix GNAT generated code and code generated by another Ada compiler. In this case, the data types should be restricted to simple cases, including primitive types. Whether complex data types can be passed depends on the situation. Probably it is safe to pass simple arrays, such as arrays of integers or floats. Records may or may not work, depending on whether both compilers lay them out identically. Complex structures involving variant records, access parameters, tasks, or protected types, are unlikely to be able to be passed. Note that in the case of GNAT running on a platform that supports HP Ada 83, a higher degree of compatibility can be guaranteed, and in particular records are laid out in an identical manner in the two compilers. Note also that if output from two different compilers is mixed, the program is responsible for dealing with elaboration issues. Probably the safest approach is to write the main program in the version of Ada other than GNAT, so that it takes care of its own elaboration requirements, and then call the GNAT-generated adainit procedure to ensure elaboration of the GNAT components. Consult the documentation of the other Ada compiler for further details on elaboration. However, it is not possible to mix the tasking run time of GNAT and HP Ada 83, All the tasking operations must either be entirely within GNAT compiled sections of the program, or entirely within HP Ada 83 compiled sections of the program. @end table @geindex Interfacing to Assembly @geindex Convention Assembler @table @asis @item @code{Assembler} Specifies assembler as the convention. In practice this has the same effect as convention Ada (but is not equivalent in the sense of being considered the same convention). @end table @geindex Convention Asm @geindex Asm @table @asis @item @code{Asm} Equivalent to Assembler. @geindex Interfacing to COBOL @geindex Convention COBOL @end table @geindex COBOL @table @asis @item @code{COBOL} Data will be passed according to the conventions described in section B.4 of the Ada Reference Manual. @end table @geindex C @geindex Interfacing to C @geindex Convention C @table @asis @item @code{C} Data will be passed according to the conventions described in section B.3 of the Ada Reference Manual. A note on interfacing to a C 'varargs' function: @quotation @geindex C varargs function @geindex Interfacing to C varargs function @geindex varargs function interfaces In C, @code{varargs} allows a function to take a variable number of arguments. There is no direct equivalent in this to Ada. One approach that can be used is to create a C wrapper for each different profile and then interface to this C wrapper. For example, to print an @code{int} value using @code{printf}, create a C function @code{printfi} that takes two arguments, a pointer to a string and an int, and calls @code{printf}. Then in the Ada program, use pragma @code{Import} to interface to @code{printfi}. It may work on some platforms to directly interface to a @code{varargs} function by providing a specific Ada profile for a particular call. However, this does not work on all platforms, since there is no guarantee that the calling sequence for a two argument normal C function is the same as for calling a @code{varargs} C function with the same two arguments. @end quotation @end table @geindex Convention Default @geindex Default @table @asis @item @code{Default} Equivalent to C. @end table @geindex Convention External @geindex External @table @asis @item @code{External} Equivalent to C. @end table @geindex C++ @geindex Interfacing to C++ @geindex Convention C++ @table @asis @item @code{C_Plus_Plus} (or @code{CPP}) This stands for C++. For most purposes this is identical to C. See the separate description of the specialized GNAT pragmas relating to C++ interfacing for further details. @end table @geindex Fortran @geindex Interfacing to Fortran @geindex Convention Fortran @table @asis @item @code{Fortran} Data will be passed according to the conventions described in section B.5 of the Ada Reference Manual. @item @code{Intrinsic} This applies to an intrinsic operation, as defined in the Ada Reference Manual. If a pragma Import (Intrinsic) applies to a subprogram, this means that the body of the subprogram is provided by the compiler itself, usually by means of an efficient code sequence, and that the user does not supply an explicit body for it. In an application program, the pragma may be applied to the following sets of names: @itemize * @item Rotate_Left, Rotate_Right, Shift_Left, Shift_Right, Shift_Right_Arithmetic. The corresponding subprogram declaration must have two formal parameters. The first one must be a signed integer type or a modular type with a binary modulus, and the second parameter must be of type Natural. The return type must be the same as the type of the first argument. The size of this type can only be 8, 16, 32, or 64. @item Binary arithmetic operators: '+', '-', '*', '/'. The corresponding operator declaration must have parameters and result type that have the same root numeric type (for example, all three are long_float types). This simplifies the definition of operations that use type checking to perform dimensional checks: @end itemize @example type Distance is new Long_Float; type Time is new Long_Float; type Velocity is new Long_Float; function "/" (D : Distance; T : Time) return Velocity; pragma Import (Intrinsic, "/"); This common idiom is often programmed with a generic definition and an explicit body. The pragma makes it simpler to introduce such declarations. It incurs no overhead in compilation time or code size, because it is implemented as a single machine instruction. @end example @itemize * @item General subprogram entities. This is used to bind an Ada subprogram declaration to a compiler builtin by name with back-ends where such interfaces are available. A typical example is the set of @code{__builtin} functions exposed by the GCC back-end, as in the following example: @example function builtin_sqrt (F : Float) return Float; pragma Import (Intrinsic, builtin_sqrt, "__builtin_sqrtf"); @end example Most of the GCC builtins are accessible this way, and as for other import conventions (e.g. C), it is the user's responsibility to ensure that the Ada subprogram profile matches the underlying builtin expectations. @end itemize @end table @geindex Stdcall @geindex Convention Stdcall @table @asis @item @code{Stdcall} This is relevant only to Windows implementations of GNAT, and specifies that the @code{Stdcall} calling sequence will be used, as defined by the NT API. Nevertheless, to ease building cross-platform bindings this convention will be handled as a @code{C} calling convention on non-Windows platforms. @end table @geindex DLL @geindex Convention DLL @table @asis @item @code{DLL} This is equivalent to @code{Stdcall}. @end table @geindex Win32 @geindex Convention Win32 @table @asis @item @code{Win32} This is equivalent to @code{Stdcall}. @end table @geindex Stubbed @geindex Convention Stubbed @table @asis @item @code{Stubbed} This is a special convention that indicates that the compiler should provide a stub body that raises @code{Program_Error}. @end table GNAT additionally provides a useful pragma @code{Convention_Identifier} that can be used to parameterize conventions and allow additional synonyms to be specified. For example if you have legacy code in which the convention identifier Fortran77 was used for Fortran, you can use the configuration pragma: @example pragma Convention_Identifier (Fortran77, Fortran); @end example And from now on the identifier Fortran77 may be used as a convention identifier (for example in an @code{Import} pragma) with the same meaning as Fortran. @node Building Mixed Ada and C++ Programs,Generating Ada Bindings for C and C++ headers,Calling Conventions,Mixed Language Programming @anchor{gnat_ugn/the_gnat_compilation_model id64}@anchor{b7}@anchor{gnat_ugn/the_gnat_compilation_model building-mixed-ada-and-c-programs}@anchor{b8} @subsection Building Mixed Ada and C++ Programs A programmer inexperienced with mixed-language development may find that building an application containing both Ada and C++ code can be a challenge. This section gives a few hints that should make this task easier. @menu * Interfacing to C++:: * Linking a Mixed C++ & Ada Program:: * A Simple Example:: * Interfacing with C++ constructors:: * Interfacing with C++ at the Class Level:: @end menu @node Interfacing to C++,Linking a Mixed C++ & Ada Program,,Building Mixed Ada and C++ Programs @anchor{gnat_ugn/the_gnat_compilation_model id65}@anchor{b9}@anchor{gnat_ugn/the_gnat_compilation_model id66}@anchor{ba} @subsubsection Interfacing to C++ GNAT supports interfacing with the G++ compiler (or any C++ compiler generating code that is compatible with the G++ Application Binary Interface ---see @indicateurl{http://www.codesourcery.com/archives/cxx-abi}). Interfacing can be done at 3 levels: simple data, subprograms, and classes. In the first two cases, GNAT offers a specific @code{Convention C_Plus_Plus} (or @code{CPP}) that behaves exactly like @code{Convention C}. Usually, C++ mangles the names of subprograms. To generate proper mangled names automatically, see @ref{19,,Generating Ada Bindings for C and C++ headers}). This problem can also be addressed manually in two ways: @itemize * @item by modifying the C++ code in order to force a C convention using the @code{extern "C"} syntax. @item by figuring out the mangled name (using e.g. @code{nm}) and using it as the Link_Name argument of the pragma import. @end itemize Interfacing at the class level can be achieved by using the GNAT specific pragmas such as @code{CPP_Constructor}. See the @cite{GNAT_Reference_Manual} for additional information. @node Linking a Mixed C++ & Ada Program,A Simple Example,Interfacing to C++,Building Mixed Ada and C++ Programs @anchor{gnat_ugn/the_gnat_compilation_model linking-a-mixed-c-ada-program}@anchor{bb}@anchor{gnat_ugn/the_gnat_compilation_model linking-a-mixed-c-and-ada-program}@anchor{bc} @subsubsection Linking a Mixed C++ & Ada Program Usually the linker of the C++ development system must be used to link mixed applications because most C++ systems will resolve elaboration issues (such as calling constructors on global class instances) transparently during the link phase. GNAT has been adapted to ease the use of a foreign linker for the last phase. Three cases can be considered: @itemize * @item Using GNAT and G++ (GNU C++ compiler) from the same GCC installation: The C++ linker can simply be called by using the C++ specific driver called @code{g++}. Note that if the C++ code uses inline functions, you will need to compile your C++ code with the @code{-fkeep-inline-functions} switch in order to provide an existing function implementation that the Ada code can link with. @example $ g++ -c -fkeep-inline-functions file1.C $ g++ -c -fkeep-inline-functions file2.C $ gnatmake ada_unit -largs file1.o file2.o --LINK=g++ @end example @item Using GNAT and G++ from two different GCC installations: If both compilers are on the :envvar`PATH`, the previous method may be used. It is important to note that environment variables such as @geindex C_INCLUDE_PATH @geindex environment variable; C_INCLUDE_PATH @code{C_INCLUDE_PATH}, @geindex GCC_EXEC_PREFIX @geindex environment variable; GCC_EXEC_PREFIX @code{GCC_EXEC_PREFIX}, @geindex BINUTILS_ROOT @geindex environment variable; BINUTILS_ROOT @code{BINUTILS_ROOT}, and @geindex GCC_ROOT @geindex environment variable; GCC_ROOT @code{GCC_ROOT} will affect both compilers at the same time and may make one of the two compilers operate improperly if set during invocation of the wrong compiler. It is also very important that the linker uses the proper @code{libgcc.a} GCC library -- that is, the one from the C++ compiler installation. The implicit link command as suggested in the @code{gnatmake} command from the former example can be replaced by an explicit link command with the full-verbosity option in order to verify which library is used: @example $ gnatbind ada_unit $ gnatlink -v -v ada_unit file1.o file2.o --LINK=c++ @end example If there is a problem due to interfering environment variables, it can be worked around by using an intermediate script. The following example shows the proper script to use when GNAT has not been installed at its default location and g++ has been installed at its default location: @example $ cat ./my_script #!/bin/sh unset BINUTILS_ROOT unset GCC_ROOT c++ $* $ gnatlink -v -v ada_unit file1.o file2.o --LINK=./my_script @end example @item Using a non-GNU C++ compiler: The commands previously described can be used to insure that the C++ linker is used. Nonetheless, you need to add a few more parameters to the link command line, depending on the exception mechanism used. If the @code{setjmp} / @code{longjmp} exception mechanism is used, only the paths to the @code{libgcc} libraries are required: @example $ cat ./my_script #!/bin/sh CC $* gcc -print-file-name=libgcc.a gcc -print-file-name=libgcc_eh.a $ gnatlink ada_unit file1.o file2.o --LINK=./my_script @end example where CC is the name of the non-GNU C++ compiler. If the "zero cost" exception mechanism is used, and the platform supports automatic registration of exception tables (e.g., Solaris), paths to more objects are required: @example $ cat ./my_script #!/bin/sh CC gcc -print-file-name=crtbegin.o $* \\ gcc -print-file-name=libgcc.a gcc -print-file-name=libgcc_eh.a \\ gcc -print-file-name=crtend.o $ gnatlink ada_unit file1.o file2.o --LINK=./my_script @end example If the "zero cost exception" mechanism is used, and the platform doesn't support automatic registration of exception tables (e.g., HP-UX or AIX), the simple approach described above will not work and a pre-linking phase using GNAT will be necessary. @end itemize Another alternative is to use the @code{gprbuild} multi-language builder which has a large knowledge base and knows how to link Ada and C++ code together automatically in most cases. @node A Simple Example,Interfacing with C++ constructors,Linking a Mixed C++ & Ada Program,Building Mixed Ada and C++ Programs @anchor{gnat_ugn/the_gnat_compilation_model id67}@anchor{bd}@anchor{gnat_ugn/the_gnat_compilation_model a-simple-example}@anchor{be} @subsubsection A Simple Example The following example, provided as part of the GNAT examples, shows how to achieve procedural interfacing between Ada and C++ in both directions. The C++ class A has two methods. The first method is exported to Ada by the means of an extern C wrapper function. The second method calls an Ada subprogram. On the Ada side, The C++ calls are modelled by a limited record with a layout comparable to the C++ class. The Ada subprogram, in turn, calls the C++ method. So, starting from the C++ main program, the process passes back and forth between the two languages. Here are the compilation commands: @example $ gnatmake -c simple_cpp_interface $ g++ -c cpp_main.C $ g++ -c ex7.C $ gnatbind -n simple_cpp_interface $ gnatlink simple_cpp_interface -o cpp_main --LINK=g++ -lstdc++ ex7.o cpp_main.o @end example Here are the corresponding sources: @example //cpp_main.C #include "ex7.h" extern "C" @{ void adainit (void); void adafinal (void); void method1 (A *t); @} void method1 (A *t) @{ t->method1 (); @} int main () @{ A obj; adainit (); obj.method2 (3030); adafinal (); @} @end example @example //ex7.h class Origin @{ public: int o_value; @}; class A : public Origin @{ public: void method1 (void); void method2 (int v); A(); int a_value; @}; @end example @example //ex7.C #include "ex7.h" #include <stdio.h> extern "C" @{ void ada_method2 (A *t, int v);@} void A::method1 (void) @{ a_value = 2020; printf ("in A::method1, a_value = %d \\n",a_value); @} void A::method2 (int v) @{ ada_method2 (this, v); printf ("in A::method2, a_value = %d \\n",a_value); @} A::A(void) @{ a_value = 1010; printf ("in A::A, a_value = %d \\n",a_value); @} @end example @example -- simple_cpp_interface.ads with System; package Simple_Cpp_Interface is type A is limited record Vptr : System.Address; O_Value : Integer; A_Value : Integer; end record; pragma Convention (C, A); procedure Method1 (This : in out A); pragma Import (C, Method1); procedure Ada_Method2 (This : in out A; V : Integer); pragma Export (C, Ada_Method2); end Simple_Cpp_Interface; @end example @example -- simple_cpp_interface.adb package body Simple_Cpp_Interface is procedure Ada_Method2 (This : in out A; V : Integer) is begin Method1 (This); This.A_Value := V; end Ada_Method2; end Simple_Cpp_Interface; @end example @node Interfacing with C++ constructors,Interfacing with C++ at the Class Level,A Simple Example,Building Mixed Ada and C++ Programs @anchor{gnat_ugn/the_gnat_compilation_model id68}@anchor{bf}@anchor{gnat_ugn/the_gnat_compilation_model interfacing-with-c-constructors}@anchor{c0} @subsubsection Interfacing with C++ constructors In order to interface with C++ constructors GNAT provides the @code{pragma CPP_Constructor} (see the @cite{GNAT_Reference_Manual} for additional information). In this section we present some common uses of C++ constructors in mixed-languages programs in GNAT. Let us assume that we need to interface with the following C++ class: @example class Root @{ public: int a_value; int b_value; virtual int Get_Value (); Root(); // Default constructor Root(int v); // 1st non-default constructor Root(int v, int w); // 2nd non-default constructor @}; @end example For this purpose we can write the following package spec (further information on how to build this spec is available in @ref{c1,,Interfacing with C++ at the Class Level} and @ref{19,,Generating Ada Bindings for C and C++ headers}). @example with Interfaces.C; use Interfaces.C; package Pkg_Root is type Root is tagged limited record A_Value : int; B_Value : int; end record; pragma Import (CPP, Root); function Get_Value (Obj : Root) return int; pragma Import (CPP, Get_Value); function Constructor return Root; pragma Cpp_Constructor (Constructor, "_ZN4RootC1Ev"); function Constructor (v : Integer) return Root; pragma Cpp_Constructor (Constructor, "_ZN4RootC1Ei"); function Constructor (v, w : Integer) return Root; pragma Cpp_Constructor (Constructor, "_ZN4RootC1Eii"); end Pkg_Root; @end example On the Ada side the constructor is represented by a function (whose name is arbitrary) that returns the classwide type corresponding to the imported C++ class. Although the constructor is described as a function, 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 object properly initialized. Constructors can only appear in the following contexts: @itemize * @item On the right side of an initialization of an object of type @code{T}. @item On the right side of an initialization of a record component of type @code{T}. @item In an Ada 2005 limited aggregate. @item In an Ada 2005 nested limited aggregate. @item In an Ada 2005 limited aggregate that initializes an object built in place by an extended return statement. @end itemize In a declaration of an object whose type is a class imported from C++, either the default C++ constructor is implicitly called by GNAT, or else the required C++ constructor must be explicitly called in the expression that initializes the object. For example: @example Obj1 : Root; Obj2 : Root := Constructor; Obj3 : Root := Constructor (v => 10); Obj4 : Root := Constructor (30, 40); @end example The first two declarations are equivalent: in both cases the default C++ constructor is invoked (in the former case the call to the constructor is implicit, and in the latter case the call is explicit in the object declaration). @code{Obj3} is initialized by the C++ non-default constructor that takes an integer argument, and @code{Obj4} is initialized by the non-default C++ constructor that takes two integers. Let us derive the imported C++ class in the Ada side. For example: @example type DT is new Root with record C_Value : Natural := 2009; end record; @end example In this case the components DT inherited from the C++ side must be initialized by a C++ constructor, and the additional Ada components of type DT are initialized by GNAT. The initialization of such an object is done either by default, or by means of a function returning an aggregate of type DT, or by means of an extension aggregate. @example Obj5 : DT; Obj6 : DT := Function_Returning_DT (50); Obj7 : DT := (Constructor (30,40) with C_Value => 50); @end example The declaration of @code{Obj5} invokes the default constructors: the C++ default constructor of the parent type takes care of the initialization of the components inherited from Root, and GNAT takes care of the default initialization of the additional Ada components of type DT (that is, @code{C_Value} is initialized to value 2009). The order of invocation of the constructors is consistent with the order of elaboration required by Ada and C++. That is, the constructor of the parent type is always called before the constructor of the derived type. Let us now consider a record that has components whose type is imported from C++. For example: @example type Rec1 is limited record Data1 : Root := Constructor (10); Value : Natural := 1000; end record; type Rec2 (D : Integer := 20) is limited record Rec : Rec1; Data2 : Root := Constructor (D, 30); end record; @end example The initialization of an object of type @code{Rec2} will call the non-default C++ constructors specified for the imported components. For example: @example Obj8 : Rec2 (40); @end example Using Ada 2005 we can use limited aggregates to initialize an object invoking C++ constructors that differ from those specified in the type declarations. For example: @example Obj9 : Rec2 := (Rec => (Data1 => Constructor (15, 16), others => <>), others => <>); @end example The above declaration uses an Ada 2005 limited aggregate to initialize @code{Obj9}, and the C++ constructor that has two integer arguments is invoked to initialize the @code{Data1} component instead of the constructor specified in the declaration of type @code{Rec1}. In Ada 2005 the box in the aggregate indicates that unspecified components are initialized using the expression (if any) available in the component declaration. That is, in this case discriminant @code{D} is initialized to value @code{20}, @code{Value} is initialized to value 1000, and the non-default C++ constructor that handles two integers takes care of initializing component @code{Data2} with values @code{20,30}. In Ada 2005 we can use the extended return statement to build the Ada equivalent to C++ non-default constructors. For example: @example function Constructor (V : Integer) return Rec2 is begin return Obj : Rec2 := (Rec => (Data1 => Constructor (V, 20), others => <>), others => <>) do -- Further actions required for construction of -- objects of type Rec2 ... end record; end Constructor; @end example In this example the extended return statement construct is used to build in place the returned object whose components are initialized by means of a limited aggregate. Any further action associated with the constructor can be placed inside the construct. @node Interfacing with C++ at the Class Level,,Interfacing with C++ constructors,Building Mixed Ada and C++ Programs @anchor{gnat_ugn/the_gnat_compilation_model interfacing-with-c-at-the-class-level}@anchor{c1}@anchor{gnat_ugn/the_gnat_compilation_model id69}@anchor{c2} @subsubsection Interfacing with C++ at the Class Level In this section we demonstrate the GNAT features for interfacing with C++ by means of an example making use of Ada 2005 abstract interface types. This example consists of a classification of animals; classes have been used to model our main classification of animals, and interfaces provide support for the management of secondary classifications. We first demonstrate a case in which the types and constructors are defined on the C++ side and imported from the Ada side, and latter the reverse case. The root of our derivation will be the @code{Animal} class, with a single private attribute (the @code{Age} of the animal), a constructor, and two public primitives to set and get the value of this attribute. @example class Animal @{ public: virtual void Set_Age (int New_Age); virtual int Age (); Animal() @{Age_Count = 0;@}; private: int Age_Count; @}; @end example Abstract interface types are defined in C++ by means of classes with pure virtual functions and no data members. In our example we will use two interfaces that provide support for the common management of @code{Carnivore} and @code{Domestic} animals: @example class Carnivore @{ public: virtual int Number_Of_Teeth () = 0; @}; class Domestic @{ public: virtual void Set_Owner (char* Name) = 0; @}; @end example Using these declarations, we can now say that a @code{Dog} is an animal that is both Carnivore and Domestic, that is: @example class Dog : Animal, Carnivore, Domestic @{ public: virtual int Number_Of_Teeth (); virtual void Set_Owner (char* Name); Dog(); // Constructor private: int Tooth_Count; char *Owner; @}; @end example In the following examples we will assume that the previous declarations are located in a file named @code{animals.h}. The following package demonstrates how to import these C++ declarations from the Ada side: @example with Interfaces.C.Strings; use Interfaces.C.Strings; package Animals is type Carnivore is limited interface; pragma Convention (C_Plus_Plus, Carnivore); function Number_Of_Teeth (X : Carnivore) return Natural is abstract; type Domestic is limited interface; pragma Convention (C_Plus_Plus, Domestic); procedure Set_Owner (X : in out Domestic; Name : Chars_Ptr) is abstract; type Animal is tagged limited record Age : Natural; end record; pragma Import (C_Plus_Plus, Animal); procedure Set_Age (X : in out Animal; Age : Integer); pragma Import (C_Plus_Plus, Set_Age); function Age (X : Animal) return Integer; pragma Import (C_Plus_Plus, Age); function New_Animal return Animal; pragma CPP_Constructor (New_Animal); pragma Import (CPP, New_Animal, "_ZN6AnimalC1Ev"); type Dog is new Animal and Carnivore and Domestic with record Tooth_Count : Natural; Owner : Chars_Ptr; end record; pragma Import (C_Plus_Plus, Dog); function Number_Of_Teeth (A : Dog) return Natural; pragma Import (C_Plus_Plus, Number_Of_Teeth); procedure Set_Owner (A : in out Dog; Name : Chars_Ptr); pragma Import (C_Plus_Plus, Set_Owner); function New_Dog return Dog; pragma CPP_Constructor (New_Dog); pragma Import (CPP, New_Dog, "_ZN3DogC2Ev"); end Animals; @end example Thanks to the compatibility between GNAT run-time structures and the C++ ABI, interfacing with these C++ classes is easy. The only requirement is that all the primitives and components must be declared exactly in the same order in the two languages. Regarding the abstract interfaces, we must indicate to the GNAT compiler by means of a @code{pragma Convention (C_Plus_Plus)}, the convention used to pass the arguments to the called primitives will be the same as for C++. For the imported classes we use @code{pragma Import} with convention @code{C_Plus_Plus} to indicate that they have been defined on the C++ side; this is required because the dispatch table associated with these tagged types will be built in the C++ side and therefore will not contain the predefined Ada primitives which Ada would otherwise expect. As the reader can see there is no need to indicate the C++ mangled names associated with each subprogram because it is assumed that all the calls to these primitives will be dispatching calls. The only exception is the constructor, which must be registered with the compiler by means of @code{pragma CPP_Constructor} and needs to provide its associated C++ mangled name because the Ada compiler generates direct calls to it. With the above packages we can now declare objects of type Dog on the Ada side and dispatch calls to the corresponding subprograms on the C++ side. We can also extend the tagged type Dog with further fields and primitives, and override some of its C++ primitives on the Ada side. For example, here we have a type derivation defined on the Ada side that inherits all the dispatching primitives of the ancestor from the C++ side. @example with Animals; use Animals; package Vaccinated_Animals is type Vaccinated_Dog is new Dog with null record; function Vaccination_Expired (A : Vaccinated_Dog) return Boolean; end Vaccinated_Animals; @end example It is important to note that, because of the ABI compatibility, the programmer does not need to add any further information to indicate either the object layout or the dispatch table entry associated with each dispatching operation. Now let us define all the types and constructors on the Ada side and export them to C++, using the same hierarchy of our previous example: @example with Interfaces.C.Strings; use Interfaces.C.Strings; package Animals is type Carnivore is limited interface; pragma Convention (C_Plus_Plus, Carnivore); function Number_Of_Teeth (X : Carnivore) return Natural is abstract; type Domestic is limited interface; pragma Convention (C_Plus_Plus, Domestic); procedure Set_Owner (X : in out Domestic; Name : Chars_Ptr) is abstract; type Animal is tagged record Age : Natural; end record; pragma Convention (C_Plus_Plus, Animal); procedure Set_Age (X : in out Animal; Age : Integer); pragma Export (C_Plus_Plus, Set_Age); function Age (X : Animal) return Integer; pragma Export (C_Plus_Plus, Age); function New_Animal return Animal'Class; pragma Export (C_Plus_Plus, New_Animal); type Dog is new Animal and Carnivore and Domestic with record Tooth_Count : Natural; Owner : String (1 .. 30); end record; pragma Convention (C_Plus_Plus, Dog); function Number_Of_Teeth (A : Dog) return Natural; pragma Export (C_Plus_Plus, Number_Of_Teeth); procedure Set_Owner (A : in out Dog; Name : Chars_Ptr); pragma Export (C_Plus_Plus, Set_Owner); function New_Dog return Dog'Class; pragma Export (C_Plus_Plus, New_Dog); end Animals; @end example Compared with our previous example the only differences are the use of @code{pragma Convention} (instead of @code{pragma Import}), and the use of @code{pragma Export} to indicate to the GNAT compiler that the primitives will be available to C++. Thanks to the ABI compatibility, on the C++ side there is nothing else to be done; as explained above, the only requirement is that all the primitives and components are declared in exactly the same order. For completeness, let us see a brief C++ main program that uses the declarations available in @code{animals.h} (presented in our first example) to import and use the declarations from the Ada side, properly initializing and finalizing the Ada run-time system along the way: @example #include "animals.h" #include <iostream> using namespace std; void Check_Carnivore (Carnivore *obj) @{...@} void Check_Domestic (Domestic *obj) @{...@} void Check_Animal (Animal *obj) @{...@} void Check_Dog (Dog *obj) @{...@} extern "C" @{ void adainit (void); void adafinal (void); Dog* new_dog (); @} void test () @{ Dog *obj = new_dog(); // Ada constructor Check_Carnivore (obj); // Check secondary DT Check_Domestic (obj); // Check secondary DT Check_Animal (obj); // Check primary DT Check_Dog (obj); // Check primary DT @} int main () @{ adainit (); test(); adafinal (); return 0; @} @end example @node Generating Ada Bindings for C and C++ headers,Generating C Headers for Ada Specifications,Building Mixed Ada and C++ Programs,Mixed Language Programming @anchor{gnat_ugn/the_gnat_compilation_model id70}@anchor{c3}@anchor{gnat_ugn/the_gnat_compilation_model generating-ada-bindings-for-c-and-c-headers}@anchor{19} @subsection Generating Ada Bindings for C and C++ headers @geindex Binding generation (for C and C++ headers) @geindex C headers (binding generation) @geindex C++ headers (binding generation) GNAT includes a binding generator for C and C++ headers which is intended to do 95% of the tedious work of generating Ada specs from C or C++ header files. Note that this capability is not intended to generate 100% correct Ada specs, and will is some cases require manual adjustments, although it can often be used out of the box in practice. Some of the known limitations include: @itemize * @item only very simple character constant macros are translated into Ada constants. Function macros (macros with arguments) are partially translated as comments, to be completed manually if needed. @item some extensions (e.g. vector types) are not supported @item pointers to pointers or complex structures are mapped to System.Address @item identifiers with identical name (except casing) will generate compilation errors (e.g. @code{shm_get} vs @code{SHM_GET}). @end itemize The code generated is using the Ada 2005 syntax, which makes it easier to interface with other languages than previous versions of Ada. @menu * Running the Binding Generator:: * Generating Bindings for C++ Headers:: * Switches:: @end menu @node Running the Binding Generator,Generating Bindings for C++ Headers,,Generating Ada Bindings for C and C++ headers @anchor{gnat_ugn/the_gnat_compilation_model id71}@anchor{c4}@anchor{gnat_ugn/the_gnat_compilation_model running-the-binding-generator}@anchor{c5} @subsubsection Running the Binding Generator The binding generator is part of the @code{gcc} compiler and can be invoked via the @code{-fdump-ada-spec} switch, which will generate Ada spec files for the header files specified on the command line, and all header files needed by these files transitively. For example: @example $ g++ -c -fdump-ada-spec -C /usr/include/time.h $ gcc -c -gnat05 *.ads @end example will generate, under GNU/Linux, the following files: @code{time_h.ads}, @code{bits_time_h.ads}, @code{stddef_h.ads}, @code{bits_types_h.ads} which correspond to the files @code{/usr/include/time.h}, @code{/usr/include/bits/time.h}, etc..., and will then compile these Ada specs in Ada 2005 mode. The @code{-C} switch tells @code{gcc} to extract comments from headers, and will attempt to generate corresponding Ada comments. If you want to generate a single Ada file and not the transitive closure, you can use instead the @code{-fdump-ada-spec-slim} switch. You can optionally specify a parent unit, of which all generated units will be children, using @code{-fada-spec-parent=@emph{unit}}. Note that we recommend when possible to use the @emph{g++} driver to generate bindings, even for most C headers, since this will in general generate better Ada specs. For generating bindings for C++ headers, it is mandatory to use the @emph{g++} command, or @emph{gcc -x c++} which is equivalent in this case. If @emph{g++} cannot work on your C headers because of incompatibilities between C and C++, then you can fallback to @code{gcc} instead. For an example of better bindings generated from the C++ front-end, the name of the parameters (when available) are actually ignored by the C front-end. Consider the following C header: @example extern void foo (int variable); @end example with the C front-end, @code{variable} is ignored, and the above is handled as: @example extern void foo (int); @end example generating a generic: @example procedure foo (param1 : int); @end example with the C++ front-end, the name is available, and we generate: @example procedure foo (variable : int); @end example In some cases, the generated bindings will be more complete or more meaningful when defining some macros, which you can do via the @code{-D} switch. This is for example the case with @code{Xlib.h} under GNU/Linux: @example $ g++ -c -fdump-ada-spec -DXLIB_ILLEGAL_ACCESS -C /usr/include/X11/Xlib.h @end example The above will generate more complete bindings than a straight call without the @code{-DXLIB_ILLEGAL_ACCESS} switch. In other cases, it is not possible to parse a header file in a stand-alone manner, because other include files need to be included first. In this case, the solution is to create a small header file including the needed @code{#include} and possible @code{#define} directives. For example, to generate Ada bindings for @code{readline/readline.h}, you need to first include @code{stdio.h}, so you can create a file with the following two lines in e.g. @code{readline1.h}: @example #include <stdio.h> #include <readline/readline.h> @end example and then generate Ada bindings from this file: @example $ g++ -c -fdump-ada-spec readline1.h @end example @node Generating Bindings for C++ Headers,Switches,Running the Binding Generator,Generating Ada Bindings for C and C++ headers @anchor{gnat_ugn/the_gnat_compilation_model id72}@anchor{c6}@anchor{gnat_ugn/the_gnat_compilation_model generating-bindings-for-c-headers}@anchor{c7} @subsubsection Generating Bindings for C++ Headers Generating bindings for C++ headers is done using the same options, always with the @emph{g++} compiler. Note that generating Ada spec from C++ headers is a much more complex job and support for C++ headers is much more limited that support for C headers. As a result, you will need to modify the resulting bindings by hand more extensively when using C++ headers. In this mode, C++ classes will be mapped to Ada tagged types, constructors will be mapped using the @code{CPP_Constructor} pragma, and when possible, multiple inheritance of abstract classes will be mapped to Ada interfaces (see the @emph{Interfacing to C++} section in the @cite{GNAT Reference Manual} for additional information on interfacing to C++). For example, given the following C++ header file: @example class Carnivore @{ public: virtual int Number_Of_Teeth () = 0; @}; class Domestic @{ public: virtual void Set_Owner (char* Name) = 0; @}; class Animal @{ public: int Age_Count; virtual void Set_Age (int New_Age); @}; class Dog : Animal, Carnivore, Domestic @{ public: int Tooth_Count; char *Owner; virtual int Number_Of_Teeth (); virtual void Set_Owner (char* Name); Dog(); @}; @end example The corresponding Ada code is generated: @example package Class_Carnivore is type Carnivore is limited interface; pragma Import (CPP, Carnivore); function Number_Of_Teeth (this : access Carnivore) return int is abstract; end; use Class_Carnivore; package Class_Domestic is type Domestic is limited interface; pragma Import (CPP, Domestic); procedure Set_Owner (this : access Domestic; Name : Interfaces.C.Strings.chars_ptr) is abstract; end; use Class_Domestic; package Class_Animal is type Animal is tagged limited record Age_Count : aliased int; end record; pragma Import (CPP, Animal); procedure Set_Age (this : access Animal; New_Age : int); pragma Import (CPP, Set_Age, "_ZN6Animal7Set_AgeEi"); end; use Class_Animal; package Class_Dog is type Dog is new Animal and Carnivore and Domestic with record Tooth_Count : aliased int; Owner : Interfaces.C.Strings.chars_ptr; end record; pragma Import (CPP, Dog); function Number_Of_Teeth (this : access Dog) return int; pragma Import (CPP, Number_Of_Teeth, "_ZN3Dog15Number_Of_TeethEv"); procedure Set_Owner (this : access Dog; Name : Interfaces.C.Strings.chars_ptr); pragma Import (CPP, Set_Owner, "_ZN3Dog9Set_OwnerEPc"); function New_Dog return Dog; pragma CPP_Constructor (New_Dog); pragma Import (CPP, New_Dog, "_ZN3DogC1Ev"); end; use Class_Dog; @end example @node Switches,,Generating Bindings for C++ Headers,Generating Ada Bindings for C and C++ headers @anchor{gnat_ugn/the_gnat_compilation_model switches}@anchor{c8}@anchor{gnat_ugn/the_gnat_compilation_model switches-for-ada-binding-generation}@anchor{c9} @subsubsection Switches @geindex -fdump-ada-spec (gcc) @table @asis @item @code{-fdump-ada-spec} Generate Ada spec files for the given header files transitively (including all header files that these headers depend upon). @end table @geindex -fdump-ada-spec-slim (gcc) @table @asis @item @code{-fdump-ada-spec-slim} Generate Ada spec files for the header files specified on the command line only. @end table @geindex -fada-spec-parent (gcc) @table @asis @item @code{-fada-spec-parent=@emph{unit}} Specifies that all files generated by @code{-fdump-ada-spec} are to be child units of the specified parent unit. @end table @geindex -C (gcc) @table @asis @item @code{-C} Extract comments from headers and generate Ada comments in the Ada spec files. @end table @node Generating C Headers for Ada Specifications,,Generating Ada Bindings for C and C++ headers,Mixed Language Programming @anchor{gnat_ugn/the_gnat_compilation_model generating-c-headers-for-ada-specifications}@anchor{ca}@anchor{gnat_ugn/the_gnat_compilation_model id73}@anchor{cb} @subsection Generating C Headers for Ada Specifications @geindex Binding generation (for Ada specs) @geindex C headers (binding generation) GNAT includes a C header generator for Ada specifications which supports Ada types that have a direct mapping to C types. This includes in particular support for: @itemize * @item Scalar types @item Constrained arrays @item Records (untagged) @item Composition of the above types @item Constant declarations @item Object declarations @item Subprogram declarations @end itemize @menu * Running the C Header Generator:: @end menu @node Running the C Header Generator,,,Generating C Headers for Ada Specifications @anchor{gnat_ugn/the_gnat_compilation_model running-the-c-header-generator}@anchor{cc} @subsubsection Running the C Header Generator The C header generator is part of the GNAT compiler and can be invoked via the @code{-gnatceg} combination of switches, which will generate a @code{.h} file corresponding to the given input file (Ada spec or body). Note that only spec files are processed in any case, so giving a spec or a body file as input is equivalent. For example: @example $ gcc -c -gnatceg pack1.ads @end example will generate a self-contained file called @code{pack1.h} including common definitions from the Ada Standard package, followed by the definitions included in @code{pack1.ads}, as well as all the other units withed by this file. For instance, given the following Ada files: @example package Pack2 is type Int is range 1 .. 10; end Pack2; @end example @example with Pack2; package Pack1 is type Rec is record Field1, Field2 : Pack2.Int; end record; Global : Rec := (1, 2); procedure Proc1 (R : Rec); procedure Proc2 (R : in out Rec); end Pack1; @end example The above @code{gcc} command will generate the following @code{pack1.h} file: @example /* Standard definitions skipped */ #ifndef PACK2_ADS #define PACK2_ADS typedef short_short_integer pack2__TintB; typedef pack2__TintB pack2__int; #endif /* PACK2_ADS */ #ifndef PACK1_ADS #define PACK1_ADS typedef struct _pack1__rec @{ pack2__int field1; pack2__int field2; @} pack1__rec; extern pack1__rec pack1__global; extern void pack1__proc1(const pack1__rec r); extern void pack1__proc2(pack1__rec *r); #endif /* PACK1_ADS */ @end example You can then @code{include} @code{pack1.h} from a C source file and use the types, call subprograms, reference objects, and constants. @node GNAT and Other Compilation Models,Using GNAT Files with External Tools,Mixed Language Programming,The GNAT Compilation Model @anchor{gnat_ugn/the_gnat_compilation_model id74}@anchor{cd}@anchor{gnat_ugn/the_gnat_compilation_model gnat-and-other-compilation-models}@anchor{45} @section GNAT and Other Compilation Models This section compares the GNAT model with the approaches taken in other environents, first the C/C++ model and then the mechanism that has been used in other Ada systems, in particular those traditionally used for Ada 83. @menu * Comparison between GNAT and C/C++ Compilation Models:: * Comparison between GNAT and Conventional Ada Library Models:: @end menu @node Comparison between GNAT and C/C++ Compilation Models,Comparison between GNAT and Conventional Ada Library Models,,GNAT and Other Compilation Models @anchor{gnat_ugn/the_gnat_compilation_model comparison-between-gnat-and-c-c-compilation-models}@anchor{ce}@anchor{gnat_ugn/the_gnat_compilation_model id75}@anchor{cf} @subsection Comparison between GNAT and C/C++ Compilation Models The GNAT model of compilation is close to the C and C++ models. You can think of Ada specs as corresponding to header files in C. As in C, you don't need to compile specs; they are compiled when they are used. The Ada @emph{with} is similar in effect to the @code{#include} of a C header. One notable difference is that, in Ada, you may compile specs separately to check them for semantic and syntactic accuracy. This is not always possible with C headers because they are fragments of programs that have less specific syntactic or semantic rules. The other major difference is the requirement for running the binder, which performs two important functions. First, it checks for consistency. In C or C++, the only defense against assembling inconsistent programs lies outside the compiler, in a makefile, for example. The binder satisfies the Ada requirement that it be impossible to construct an inconsistent program when the compiler is used in normal mode. @geindex Elaboration order control The other important function of the binder is to deal with elaboration issues. There are also elaboration issues in C++ that are handled automatically. This automatic handling has the advantage of being simpler to use, but the C++ programmer has no control over elaboration. Where @code{gnatbind} might complain there was no valid order of elaboration, a C++ compiler would simply construct a program that malfunctioned at run time. @node Comparison between GNAT and Conventional Ada Library Models,,Comparison between GNAT and C/C++ Compilation Models,GNAT and Other Compilation Models @anchor{gnat_ugn/the_gnat_compilation_model comparison-between-gnat-and-conventional-ada-library-models}@anchor{d0}@anchor{gnat_ugn/the_gnat_compilation_model id76}@anchor{d1} @subsection Comparison between GNAT and Conventional Ada Library Models This section is intended for Ada programmers who have used an Ada compiler implementing the traditional Ada library model, as described in the Ada Reference Manual. @geindex GNAT library In GNAT, there is no 'library' in the normal sense. Instead, the set of source files themselves acts as the library. Compiling Ada programs does not generate any centralized information, but rather an object file and a ALI file, which are of interest only to the binder and linker. In a traditional system, the compiler reads information not only from the source file being compiled, but also from the centralized library. This means that the effect of a compilation depends on what has been previously compiled. In particular: @itemize * @item When a unit is @emph{with}ed, the unit seen by the compiler corresponds to the version of the unit most recently compiled into the library. @item Inlining is effective only if the necessary body has already been compiled into the library. @item Compiling a unit may obsolete other units in the library. @end itemize In GNAT, compiling one unit never affects the compilation of any other units because the compiler reads only source files. Only changes to source files can affect the results of a compilation. In particular: @itemize * @item When a unit is @emph{with}ed, the unit seen by the compiler corresponds to the source version of the unit that is currently accessible to the compiler. @geindex Inlining @item Inlining requires the appropriate source files for the package or subprogram bodies to be available to the compiler. Inlining is always effective, independent of the order in which units are compiled. @item Compiling a unit never affects any other compilations. The editing of sources may cause previous compilations to be out of date if they depended on the source file being modified. @end itemize The most important result of these differences is that order of compilation is never significant in GNAT. There is no situation in which one is required to do one compilation before another. What shows up as order of compilation requirements in the traditional Ada library becomes, in GNAT, simple source dependencies; in other words, there is only a set of rules saying what source files must be present when a file is compiled. @node Using GNAT Files with External Tools,,GNAT and Other Compilation Models,The GNAT Compilation Model @anchor{gnat_ugn/the_gnat_compilation_model using-gnat-files-with-external-tools}@anchor{1a}@anchor{gnat_ugn/the_gnat_compilation_model id77}@anchor{d2} @section Using GNAT Files with External Tools This section explains how files that are produced by GNAT may be used with tools designed for other languages. @menu * Using Other Utility Programs with GNAT:: * The External Symbol Naming Scheme of GNAT:: @end menu @node Using Other Utility Programs with GNAT,The External Symbol Naming Scheme of GNAT,,Using GNAT Files with External Tools @anchor{gnat_ugn/the_gnat_compilation_model using-other-utility-programs-with-gnat}@anchor{d3}@anchor{gnat_ugn/the_gnat_compilation_model id78}@anchor{d4} @subsection Using Other Utility Programs with GNAT The object files generated by GNAT are in standard system format and in particular the debugging information uses this format. This means programs generated by GNAT can be used with existing utilities that depend on these formats. In general, any utility program that works with C will also often work with Ada programs generated by GNAT. This includes software utilities such as gprof (a profiling program), gdb (the FSF debugger), and utilities such as Purify. @node The External Symbol Naming Scheme of GNAT,,Using Other Utility Programs with GNAT,Using GNAT Files with External Tools @anchor{gnat_ugn/the_gnat_compilation_model the-external-symbol-naming-scheme-of-gnat}@anchor{d5}@anchor{gnat_ugn/the_gnat_compilation_model id79}@anchor{d6} @subsection The External Symbol Naming Scheme of GNAT In order to interpret the output from GNAT, when using tools that are originally intended for use with other languages, it is useful to understand the conventions used to generate link names from the Ada entity names. All link names are in all lowercase letters. With the exception of library procedure names, the mechanism used is simply to use the full expanded Ada name with dots replaced by double underscores. For example, suppose we have the following package spec: @example package QRS is MN : Integer; end QRS; @end example @geindex pragma Export The variable @code{MN} has a full expanded Ada name of @code{QRS.MN}, so the corresponding link name is @code{qrs__mn}. Of course if a @code{pragma Export} is used this may be overridden: @example package Exports is Var1 : Integer; pragma Export (Var1, C, External_Name => "var1_name"); Var2 : Integer; pragma Export (Var2, C, Link_Name => "var2_link_name"); end Exports; @end example In this case, the link name for @code{Var1} is whatever link name the C compiler would assign for the C function @code{var1_name}. This typically would be either @code{var1_name} or @code{_var1_name}, depending on operating system conventions, but other possibilities exist. The link name for @code{Var2} is @code{var2_link_name}, and this is not operating system dependent. One exception occurs for library level procedures. A potential ambiguity arises between the required name @code{_main} for the C main program, and the name we would otherwise assign to an Ada library level procedure called @code{Main} (which might well not be the main program). To avoid this ambiguity, we attach the prefix @code{_ada_} to such names. So if we have a library level procedure such as: @example procedure Hello (S : String); @end example the external name of this procedure will be @code{_ada_hello}. @c -- Example: A |withing| unit has a |with| clause, it |withs| a |withed| unit @node Building Executable Programs with GNAT,GNAT Utility Programs,The GNAT Compilation Model,Top @anchor{gnat_ugn/building_executable_programs_with_gnat building-executable-programs-with-gnat}@anchor{a}@anchor{gnat_ugn/building_executable_programs_with_gnat doc}@anchor{d7}@anchor{gnat_ugn/building_executable_programs_with_gnat id1}@anchor{d8} @chapter Building Executable Programs with GNAT This chapter describes first the gnatmake tool (@ref{1b,,Building with gnatmake}), which automatically determines the set of sources needed by an Ada compilation unit and executes the necessary (re)compilations, binding and linking. It also explains how to use each tool individually: the compiler (gcc, see @ref{1c,,Compiling with gcc}), binder (gnatbind, see @ref{1d,,Binding with gnatbind}), and linker (gnatlink, see @ref{1e,,Linking with gnatlink}) to build executable programs. Finally, this chapter provides examples of how to make use of the general GNU make mechanism in a GNAT context (see @ref{1f,,Using the GNU make Utility}). @menu * Building with gnatmake:: * Compiling with gcc:: * Compiler Switches:: * Linker Switches:: * Binding with gnatbind:: * Linking with gnatlink:: * Using the GNU make Utility:: @end menu @node Building with gnatmake,Compiling with gcc,,Building Executable Programs with GNAT @anchor{gnat_ugn/building_executable_programs_with_gnat the-gnat-make-program-gnatmake}@anchor{1b}@anchor{gnat_ugn/building_executable_programs_with_gnat building-with-gnatmake}@anchor{d9} @section Building with @code{gnatmake} @geindex gnatmake A typical development cycle when working on an Ada program consists of the following steps: @enumerate @item Edit some sources to fix bugs; @item Add enhancements; @item Compile all sources affected; @item Rebind and relink; and @item Test. @end enumerate @geindex Dependency rules (compilation) The third step in particular can be tricky, because not only do the modified files have to be compiled, but any files depending on these files must also be recompiled. The dependency rules in Ada can be quite complex, especially in the presence of overloading, @code{use} clauses, generics and inlined subprograms. @code{gnatmake} automatically takes care of the third and fourth steps of this process. It determines which sources need to be compiled, compiles them, and binds and links the resulting object files. Unlike some other Ada make programs, the dependencies are always accurately recomputed from the new sources. The source based approach of the GNAT compilation model makes this possible. This means that if changes to the source program cause corresponding changes in dependencies, they will always be tracked exactly correctly by @code{gnatmake}. Note that for advanced forms of project structure, we recommend creating a project file as explained in the @emph{GNAT_Project_Manager} chapter in the @emph{GPRbuild User's Guide}, and using the @code{gprbuild} tool which supports building with project files and works similarly to @code{gnatmake}. @menu * Running gnatmake:: * Switches for gnatmake:: * Mode Switches for gnatmake:: * Notes on the Command Line:: * How gnatmake Works:: * Examples of gnatmake Usage:: @end menu @node Running gnatmake,Switches for gnatmake,,Building with gnatmake @anchor{gnat_ugn/building_executable_programs_with_gnat running-gnatmake}@anchor{da}@anchor{gnat_ugn/building_executable_programs_with_gnat id2}@anchor{db} @subsection Running @code{gnatmake} The usual form of the @code{gnatmake} command is @example $ gnatmake [<switches>] <file_name> [<file_names>] [<mode_switches>] @end example The only required argument is one @code{file_name}, which specifies a compilation unit that is a main program. Several @code{file_names} can be specified: this will result in several executables being built. If @code{switches} are present, they can be placed before the first @code{file_name}, between @code{file_names} or after the last @code{file_name}. If @code{mode_switches} are present, they must always be placed after the last @code{file_name} and all @code{switches}. If you are using standard file extensions (@code{.adb} and @code{.ads}), then the extension may be omitted from the @code{file_name} arguments. However, if you are using non-standard extensions, then it is required that the extension be given. A relative or absolute directory path can be specified in a @code{file_name}, in which case, the input source file will be searched for in the specified directory only. Otherwise, the input source file will first be searched in the directory where @code{gnatmake} was invoked and if it is not found, it will be search on the source path of the compiler as described in @ref{89,,Search Paths and the Run-Time Library (RTL)}. All @code{gnatmake} output (except when you specify @code{-M}) is sent to @code{stderr}. The output produced by the @code{-M} switch is sent to @code{stdout}. @node Switches for gnatmake,Mode Switches for gnatmake,Running gnatmake,Building with gnatmake @anchor{gnat_ugn/building_executable_programs_with_gnat switches-for-gnatmake}@anchor{dc}@anchor{gnat_ugn/building_executable_programs_with_gnat id3}@anchor{dd} @subsection Switches for @code{gnatmake} You may specify any of the following switches to @code{gnatmake}: @geindex --version (gnatmake) @table @asis @item @code{--version} Display Copyright and version, then exit disregarding all other options. @end table @geindex --help (gnatmake) @table @asis @item @code{--help} If @code{--version} was not used, display usage, then exit disregarding all other options. @end table @geindex --GCC=compiler_name (gnatmake) @table @asis @item @code{--GCC=@emph{compiler_name}} Program used for compiling. The default is @code{gcc}. You need to use quotes around @code{compiler_name} if @code{compiler_name} contains spaces or other separator characters. As an example @code{--GCC="foo -x -y"} will instruct @code{gnatmake} to use @code{foo -x -y} as your compiler. A limitation of this syntax is that the name and path name of the executable itself must not include any embedded spaces. Note that switch @code{-c} is always inserted after your command name. Thus in the above example the compiler command that will be used by @code{gnatmake} will be @code{foo -c -x -y}. If several @code{--GCC=compiler_name} are used, only the last @code{compiler_name} is taken into account. However, all the additional switches are also taken into account. Thus, @code{--GCC="foo -x -y" --GCC="bar -z -t"} is equivalent to @code{--GCC="bar -x -y -z -t"}. @end table @geindex --GNATBIND=binder_name (gnatmake) @table @asis @item @code{--GNATBIND=@emph{binder_name}} Program used for binding. The default is @code{gnatbind}. You need to use quotes around @code{binder_name} if @code{binder_name} contains spaces or other separator characters. As an example @code{--GNATBIND="bar -x -y"} will instruct @code{gnatmake} to use @code{bar -x -y} as your binder. Binder switches that are normally appended by @code{gnatmake} to @code{gnatbind} are now appended to the end of @code{bar -x -y}. A limitation of this syntax is that the name and path name of the executable itself must not include any embedded spaces. @end table @geindex --GNATLINK=linker_name (gnatmake) @table @asis @item @code{--GNATLINK=@emph{linker_name}} Program used for linking. The default is @code{gnatlink}. You need to use quotes around @code{linker_name} if @code{linker_name} contains spaces or other separator characters. As an example @code{--GNATLINK="lan -x -y"} will instruct @code{gnatmake} to use @code{lan -x -y} as your linker. Linker switches that are normally appended by @code{gnatmake} to @code{gnatlink} are now appended to the end of @code{lan -x -y}. A limitation of this syntax is that the name and path name of the executable itself must not include any embedded spaces. @item @code{--create-map-file} When linking an executable, create a map file. The name of the map file has the same name as the executable with extension ".map". @item @code{--create-map-file=@emph{mapfile}} When linking an executable, create a map file with the specified name. @end table @geindex --create-missing-dirs (gnatmake) @table @asis @item @code{--create-missing-dirs} When using project files (@code{-P@emph{project}}), automatically create missing object directories, library directories and exec directories. @item @code{--single-compile-per-obj-dir} Disallow simultaneous compilations in the same object directory when project files are used. @item @code{--subdirs=@emph{subdir}} Actual object directory of each project file is the subdirectory subdir of the object directory specified or defaulted in the project file. @item @code{--unchecked-shared-lib-imports} By default, shared library projects are not allowed to import static library projects. When this switch is used on the command line, this restriction is relaxed. @item @code{--source-info=@emph{source info file}} Specify a source info file. This switch is active only when project files are used. If the source info file is specified as a relative path, then it is relative to the object directory of the main project. If the source info file does not exist, then after the Project Manager has successfully parsed and processed the project files and found the sources, it creates the source info file. If the source info file already exists and can be read successfully, then the Project Manager will get all the needed information about the sources from the source info file and will not look for them. This reduces the time to process the project files, especially when looking for sources that take a long time. If the source info file exists but cannot be parsed successfully, the Project Manager will attempt to recreate it. If the Project Manager fails to create the source info file, a message is issued, but gnatmake does not fail. @code{gnatmake} "trusts" the source info file. This means that if the source files have changed (addition, deletion, moving to a different source directory), then the source info file need to be deleted and recreated. @end table @geindex -a (gnatmake) @table @asis @item @code{-a} Consider all files in the make process, even the GNAT internal system files (for example, the predefined Ada library files), as well as any locked files. Locked files are files whose ALI file is write-protected. By default, @code{gnatmake} does not check these files, because the assumption is that the GNAT internal files are properly up to date, and also that any write protected ALI files have been properly installed. Note that if there is an installation problem, such that one of these files is not up to date, it will be properly caught by the binder. You may have to specify this switch if you are working on GNAT itself. The switch @code{-a} is also useful in conjunction with @code{-f} if you need to recompile an entire application, including run-time files, using special configuration pragmas, such as a @code{Normalize_Scalars} pragma. By default @code{gnatmake -a} compiles all GNAT internal files with @code{gcc -c -gnatpg} rather than @code{gcc -c}. @end table @geindex -b (gnatmake) @table @asis @item @code{-b} Bind only. Can be combined with @code{-c} to do compilation and binding, but no link. Can be combined with @code{-l} to do binding and linking. When not combined with @code{-c} all the units in the closure of the main program must have been previously compiled and must be up to date. The root unit specified by @code{file_name} may be given without extension, with the source extension or, if no GNAT Project File is specified, with the ALI file extension. @end table @geindex -c (gnatmake) @table @asis @item @code{-c} Compile only. Do not perform binding, except when @code{-b} is also specified. Do not perform linking, except if both @code{-b} and @code{-l} are also specified. If the root unit specified by @code{file_name} is not a main unit, this is the default. Otherwise @code{gnatmake} will attempt binding and linking unless all objects are up to date and the executable is more recent than the objects. @end table @geindex -C (gnatmake) @table @asis @item @code{-C} Use a temporary mapping file. A mapping file is a way to communicate to the compiler two mappings: from unit names to file names (without any directory information) and from file names to path names (with full directory information). A mapping file can make the compiler's file searches faster, especially if there are many source directories, or the sources are read over a slow network connection. If @code{-P} is used, a mapping file is always used, so @code{-C} is unnecessary; in this case the mapping file is initially populated based on the project file. If @code{-C} is used without @code{-P}, the mapping file is initially empty. Each invocation of the compiler will add any newly accessed sources to the mapping file. @end table @geindex -C= (gnatmake) @table @asis @item @code{-C=@emph{file}} Use a specific mapping file. The file, specified as a path name (absolute or relative) by this switch, should already exist, otherwise the switch is ineffective. The specified mapping file will be communicated to the compiler. This switch is not compatible with a project file (-P`file`) or with multiple compiling processes (-jnnn, when nnn is greater than 1). @end table @geindex -d (gnatmake) @table @asis @item @code{-d} Display progress for each source, up to date or not, as a single line: @example completed x out of y (zz%) @end example If the file needs to be compiled this is displayed after the invocation of the compiler. These lines are displayed even in quiet output mode. @end table @geindex -D (gnatmake) @table @asis @item @code{-D @emph{dir}} Put all object files and ALI file in directory @code{dir}. If the @code{-D} switch is not used, all object files and ALI files go in the current working directory. This switch cannot be used when using a project file. @end table @geindex -eI (gnatmake) @table @asis @item @code{-eI@emph{nnn}} Indicates that the main source is a multi-unit source and the rank of the unit in the source file is nnn. nnn needs to be a positive number and a valid index in the source. This switch cannot be used when @code{gnatmake} is invoked for several mains. @end table @geindex -eL (gnatmake) @geindex symbolic links @table @asis @item @code{-eL} Follow all symbolic links when processing project files. This should be used if your project uses symbolic links for files or directories, but is not needed in other cases. @geindex naming scheme This also assumes that no directory matches the naming scheme for files (for instance that you do not have a directory called "sources.ads" when using the default GNAT naming scheme). When you do not have to use this switch (i.e., by default), gnatmake is able to save a lot of system calls (several per source file and object file), which can result in a significant speed up to load and manipulate a project file, especially when using source files from a remote system. @end table @geindex -eS (gnatmake) @table @asis @item @code{-eS} Output the commands for the compiler, the binder and the linker on standard output, instead of standard error. @end table @geindex -f (gnatmake) @table @asis @item @code{-f} Force recompilations. Recompile all sources, even though some object files may be up to date, but don't recompile predefined or GNAT internal files or locked files (files with a write-protected ALI file), unless the @code{-a} switch is also specified. @end table @geindex -F (gnatmake) @table @asis @item @code{-F} When using project files, if some errors or warnings are detected during parsing and verbose mode is not in effect (no use of switch -v), then error lines start with the full path name of the project file, rather than its simple file name. @end table @geindex -g (gnatmake) @table @asis @item @code{-g} Enable debugging. This switch is simply passed to the compiler and to the linker. @end table @geindex -i (gnatmake) @table @asis @item @code{-i} In normal mode, @code{gnatmake} compiles all object files and ALI files into the current directory. If the @code{-i} switch is used, then instead object files and ALI files that already exist are overwritten in place. This means that once a large project is organized into separate directories in the desired manner, then @code{gnatmake} will automatically maintain and update this organization. If no ALI files are found on the Ada object path (see @ref{89,,Search Paths and the Run-Time Library (RTL)}), the new object and ALI files are created in the directory containing the source being compiled. If another organization is desired, where objects and sources are kept in different directories, a useful technique is to create dummy ALI files in the desired directories. When detecting such a dummy file, @code{gnatmake} will be forced to recompile the corresponding source file, and it will be put the resulting object and ALI files in the directory where it found the dummy file. @end table @geindex -j (gnatmake) @geindex Parallel make @table @asis @item @code{-j@emph{n}} Use @code{n} processes to carry out the (re)compilations. On a multiprocessor machine compilations will occur in parallel. If @code{n} is 0, then the maximum number of parallel compilations is the number of core processors on the platform. In the event of compilation errors, messages from various compilations might get interspersed (but @code{gnatmake} will give you the full ordered list of failing compiles at the end). If this is problematic, rerun the make process with n set to 1 to get a clean list of messages. @end table @geindex -k (gnatmake) @table @asis @item @code{-k} Keep going. Continue as much as possible after a compilation error. To ease the programmer's task in case of compilation errors, the list of sources for which the compile fails is given when @code{gnatmake} terminates. If @code{gnatmake} is invoked with several @code{file_names} and with this switch, if there are compilation errors when building an executable, @code{gnatmake} will not attempt to build the following executables. @end table @geindex -l (gnatmake) @table @asis @item @code{-l} Link only. Can be combined with @code{-b} to binding and linking. Linking will not be performed if combined with @code{-c} but not with @code{-b}. When not combined with @code{-b} all the units in the closure of the main program must have been previously compiled and must be up to date, and the main program needs to have been bound. The root unit specified by @code{file_name} may be given without extension, with the source extension or, if no GNAT Project File is specified, with the ALI file extension. @end table @geindex -m (gnatmake) @table @asis @item @code{-m} Specify that the minimum necessary amount of recompilations be performed. In this mode @code{gnatmake} ignores time stamp differences when the only modifications to a source file consist in adding/removing comments, empty lines, spaces or tabs. This means that if you have changed the comments in a source file or have simply reformatted it, using this switch will tell @code{gnatmake} not to recompile files that depend on it (provided other sources on which these files depend have undergone no semantic modifications). Note that the debugging information may be out of date with respect to the sources if the @code{-m} switch causes a compilation to be switched, so the use of this switch represents a trade-off between compilation time and accurate debugging information. @end table @geindex Dependencies @geindex producing list @geindex -M (gnatmake) @table @asis @item @code{-M} Check if all objects are up to date. If they are, output the object dependences to @code{stdout} in a form that can be directly exploited in a @code{Makefile}. By default, each source file is prefixed with its (relative or absolute) directory name. This name is whatever you specified in the various @code{-aI} and @code{-I} switches. If you use @code{gnatmake -M} @code{-q} (see below), only the source file names, without relative paths, are output. If you just specify the @code{-M} switch, dependencies of the GNAT internal system files are omitted. This is typically what you want. If you also specify the @code{-a} switch, dependencies of the GNAT internal files are also listed. Note that dependencies of the objects in external Ada libraries (see switch @code{-aL@emph{dir}} in the following list) are never reported. @end table @geindex -n (gnatmake) @table @asis @item @code{-n} Don't compile, bind, or link. Checks if all objects are up to date. If they are not, the full name of the first file that needs to be recompiled is printed. Repeated use of this option, followed by compiling the indicated source file, will eventually result in recompiling all required units. @end table @geindex -o (gnatmake) @table @asis @item @code{-o @emph{exec_name}} Output executable name. The name of the final executable program will be @code{exec_name}. If the @code{-o} switch is omitted the default name for the executable will be the name of the input file in appropriate form for an executable file on the host system. This switch cannot be used when invoking @code{gnatmake} with several @code{file_names}. @end table @geindex -p (gnatmake) @table @asis @item @code{-p} Same as @code{--create-missing-dirs} @end table @geindex -P (gnatmake) @table @asis @item @code{-P@emph{project}} Use project file @code{project}. Only one such switch can be used. @end table @c -- Comment: @c :ref:`gnatmake_and_Project_Files`. @geindex -q (gnatmake) @table @asis @item @code{-q} Quiet. When this flag is not set, the commands carried out by @code{gnatmake} are displayed. @end table @geindex -s (gnatmake) @table @asis @item @code{-s} Recompile if compiler switches have changed since last compilation. All compiler switches but -I and -o are taken into account in the following way: orders between different 'first letter' switches are ignored, but orders between same switches are taken into account. For example, @code{-O -O2} is different than @code{-O2 -O}, but @code{-g -O} is equivalent to @code{-O -g}. This switch is recommended when Integrated Preprocessing is used. @end table @geindex -u (gnatmake) @table @asis @item @code{-u} Unique. Recompile at most the main files. It implies -c. Combined with -f, it is equivalent to calling the compiler directly. Note that using -u with a project file and no main has a special meaning. @end table @c --Comment @c (See :ref:`Project_Files_and_Main_Subprograms`.) @geindex -U (gnatmake) @table @asis @item @code{-U} When used without a project file or with one or several mains on the command line, is equivalent to -u. When used with a project file and no main on the command line, all sources of all project files are checked and compiled if not up to date, and libraries are rebuilt, if necessary. @end table @geindex -v (gnatmake) @table @asis @item @code{-v} Verbose. Display the reason for all recompilations @code{gnatmake} decides are necessary, with the highest verbosity level. @end table @geindex -vl (gnatmake) @table @asis @item @code{-vl} Verbosity level Low. Display fewer lines than in verbosity Medium. @end table @geindex -vm (gnatmake) @table @asis @item @code{-vm} Verbosity level Medium. Potentially display fewer lines than in verbosity High. @end table @geindex -vm (gnatmake) @table @asis @item @code{-vh} Verbosity level High. Equivalent to -v. @item @code{-vP@emph{x}} Indicate the verbosity of the parsing of GNAT project files. See @ref{de,,Switches Related to Project Files}. @end table @geindex -x (gnatmake) @table @asis @item @code{-x} Indicate that sources that are not part of any Project File may be compiled. Normally, when using Project Files, only sources that are part of a Project File may be compile. When this switch is used, a source outside of all Project Files may be compiled. The ALI file and the object file will be put in the object directory of the main Project. The compilation switches used will only be those specified on the command line. Even when @code{-x} is used, mains specified on the command line need to be sources of a project file. @item @code{-X@emph{name}=@emph{value}} Indicate that external variable @code{name} has the value @code{value}. The Project Manager will use this value for occurrences of @code{external(name)} when parsing the project file. @ref{de,,Switches Related to Project Files}. @end table @geindex -z (gnatmake) @table @asis @item @code{-z} No main subprogram. Bind and link the program even if the unit name given on the command line is a package name. The resulting executable will execute the elaboration routines of the package and its closure, then the finalization routines. @end table @subsubheading GCC switches Any uppercase or multi-character switch that is not a @code{gnatmake} switch is passed to @code{gcc} (e.g., @code{-O}, @code{-gnato,} etc.) @subsubheading Source and library search path switches @geindex -aI (gnatmake) @table @asis @item @code{-aI@emph{dir}} When looking for source files also look in directory @code{dir}. The order in which source files search is undertaken is described in @ref{89,,Search Paths and the Run-Time Library (RTL)}. @end table @geindex -aL (gnatmake) @table @asis @item @code{-aL@emph{dir}} Consider @code{dir} as being an externally provided Ada library. Instructs @code{gnatmake} to skip compilation units whose @code{.ALI} files have been located in directory @code{dir}. This allows you to have missing bodies for the units in @code{dir} and to ignore out of date bodies for the same units. You still need to specify the location of the specs for these units by using the switches @code{-aI@emph{dir}} or @code{-I@emph{dir}}. Note: this switch is provided for compatibility with previous versions of @code{gnatmake}. The easier method of causing standard libraries to be excluded from consideration is to write-protect the corresponding ALI files. @end table @geindex -aO (gnatmake) @table @asis @item @code{-aO@emph{dir}} When searching for library and object files, look in directory @code{dir}. The order in which library files are searched is described in @ref{8c,,Search Paths for gnatbind}. @end table @geindex Search paths @geindex for gnatmake @geindex -A (gnatmake) @table @asis @item @code{-A@emph{dir}} Equivalent to @code{-aL@emph{dir}} @code{-aI@emph{dir}}. @geindex -I (gnatmake) @item @code{-I@emph{dir}} Equivalent to @code{-aO@emph{dir} -aI@emph{dir}}. @end table @geindex -I- (gnatmake) @geindex Source files @geindex suppressing search @table @asis @item @code{-I-} Do not look for source files in the directory containing the source file named in the command line. Do not look for ALI or object files in the directory where @code{gnatmake} was invoked. @end table @geindex -L (gnatmake) @geindex Linker libraries @table @asis @item @code{-L@emph{dir}} Add directory @code{dir} to the list of directories in which the linker will search for libraries. This is equivalent to @code{-largs} @code{-L@emph{dir}}. Furthermore, under Windows, the sources pointed to by the libraries path set in the registry are not searched for. @end table @geindex -nostdinc (gnatmake) @table @asis @item @code{-nostdinc} Do not look for source files in the system default directory. @end table @geindex -nostdlib (gnatmake) @table @asis @item @code{-nostdlib} Do not look for library files in the system default directory. @end table @geindex --RTS (gnatmake) @table @asis @item @code{--RTS=@emph{rts-path}} Specifies the default location of the run-time library. GNAT looks for the run-time in the following directories, and stops as soon as a valid run-time is found (@code{adainclude} or @code{ada_source_path}, and @code{adalib} or @code{ada_object_path} present): @itemize * @item @emph{<current directory>/$rts_path} @item @emph{<default-search-dir>/$rts_path} @item @emph{<default-search-dir>/rts-$rts_path} @item The selected path is handled like a normal RTS path. @end itemize @end table @node Mode Switches for gnatmake,Notes on the Command Line,Switches for gnatmake,Building with gnatmake @anchor{gnat_ugn/building_executable_programs_with_gnat id4}@anchor{df}@anchor{gnat_ugn/building_executable_programs_with_gnat mode-switches-for-gnatmake}@anchor{e0} @subsection Mode Switches for @code{gnatmake} The mode switches (referred to as @code{mode_switches}) allow the inclusion of switches that are to be passed to the compiler itself, the binder or the linker. The effect of a mode switch is to cause all subsequent switches up to the end of the switch list, or up to the next mode switch, to be interpreted as switches to be passed on to the designated component of GNAT. @geindex -cargs (gnatmake) @table @asis @item @code{-cargs @emph{switches}} Compiler switches. Here @code{switches} is a list of switches that are valid switches for @code{gcc}. They will be passed on to all compile steps performed by @code{gnatmake}. @end table @geindex -bargs (gnatmake) @table @asis @item @code{-bargs @emph{switches}} Binder switches. Here @code{switches} is a list of switches that are valid switches for @code{gnatbind}. They will be passed on to all bind steps performed by @code{gnatmake}. @end table @geindex -largs (gnatmake) @table @asis @item @code{-largs @emph{switches}} Linker switches. Here @code{switches} is a list of switches that are valid switches for @code{gnatlink}. They will be passed on to all link steps performed by @code{gnatmake}. @end table @geindex -margs (gnatmake) @table @asis @item @code{-margs @emph{switches}} Make switches. The switches are directly interpreted by @code{gnatmake}, regardless of any previous occurrence of @code{-cargs}, @code{-bargs} or @code{-largs}. @end table @node Notes on the Command Line,How gnatmake Works,Mode Switches for gnatmake,Building with gnatmake @anchor{gnat_ugn/building_executable_programs_with_gnat id5}@anchor{e1}@anchor{gnat_ugn/building_executable_programs_with_gnat notes-on-the-command-line}@anchor{e2} @subsection Notes on the Command Line This section contains some additional useful notes on the operation of the @code{gnatmake} command. @geindex Recompilation (by gnatmake) @itemize * @item If @code{gnatmake} finds no ALI files, it recompiles the main program and all other units required by the main program. This means that @code{gnatmake} can be used for the initial compile, as well as during subsequent steps of the development cycle. @item If you enter @code{gnatmake foo.adb}, where @code{foo} is a subunit or body of a generic unit, @code{gnatmake} recompiles @code{foo.adb} (because it finds no ALI) and stops, issuing a warning. @item In @code{gnatmake} the switch @code{-I} is used to specify both source and library file paths. Use @code{-aI} instead if you just want to specify source paths only and @code{-aO} if you want to specify library paths only. @item @code{gnatmake} will ignore any files whose ALI file is write-protected. This may conveniently be used to exclude standard libraries from consideration and in particular it means that the use of the @code{-f} switch will not recompile these files unless @code{-a} is also specified. @item @code{gnatmake} has been designed to make the use of Ada libraries particularly convenient. Assume you have an Ada library organized as follows: @emph{obj-dir} contains the objects and ALI files for of your Ada compilation units, whereas @emph{include-dir} contains the specs of these units, but no bodies. Then to compile a unit stored in @code{main.adb}, which uses this Ada library you would just type: @example $ gnatmake -aI`include-dir` -aL`obj-dir` main @end example @item Using @code{gnatmake} along with the @code{-m (minimal recompilation)} switch provides a mechanism for avoiding unnecessary recompilations. Using this switch, you can update the comments/format of your source files without having to recompile everything. Note, however, that adding or deleting lines in a source files may render its debugging info obsolete. If the file in question is a spec, the impact is rather limited, as that debugging info will only be useful during the elaboration phase of your program. For bodies the impact can be more significant. In all events, your debugger will warn you if a source file is more recent than the corresponding object, and alert you to the fact that the debugging information may be out of date. @end itemize @node How gnatmake Works,Examples of gnatmake Usage,Notes on the Command Line,Building with gnatmake @anchor{gnat_ugn/building_executable_programs_with_gnat id6}@anchor{e3}@anchor{gnat_ugn/building_executable_programs_with_gnat how-gnatmake-works}@anchor{e4} @subsection How @code{gnatmake} Works Generally @code{gnatmake} automatically performs all necessary recompilations and you don't need to worry about how it works. However, it may be useful to have some basic understanding of the @code{gnatmake} approach and in particular to understand how it uses the results of previous compilations without incorrectly depending on them. First a definition: an object file is considered @emph{up to date} if the corresponding ALI file exists and if all the source files listed in the dependency section of this ALI file have time stamps matching those in the ALI file. This means that neither the source file itself nor any files that it depends on have been modified, and hence there is no need to recompile this file. @code{gnatmake} works by first checking if the specified main unit is up to date. If so, no compilations are required for the main unit. If not, @code{gnatmake} compiles the main program to build a new ALI file that reflects the latest sources. Then the ALI file of the main unit is examined to find all the source files on which the main program depends, and @code{gnatmake} recursively applies the above procedure on all these files. This process ensures that @code{gnatmake} only trusts the dependencies in an existing ALI file if they are known to be correct. Otherwise it always recompiles to determine a new, guaranteed accurate set of dependencies. As a result the program is compiled 'upside down' from what may be more familiar as the required order of compilation in some other Ada systems. In particular, clients are compiled before the units on which they depend. The ability of GNAT to compile in any order is critical in allowing an order of compilation to be chosen that guarantees that @code{gnatmake} will recompute a correct set of new dependencies if necessary. When invoking @code{gnatmake} with several @code{file_names}, if a unit is imported by several of the executables, it will be recompiled at most once. Note: when using non-standard naming conventions (@ref{35,,Using Other File Names}), changing through a configuration pragmas file the version of a source and invoking @code{gnatmake} to recompile may have no effect, if the previous version of the source is still accessible by @code{gnatmake}. It may be necessary to use the switch -f. @node Examples of gnatmake Usage,,How gnatmake Works,Building with gnatmake @anchor{gnat_ugn/building_executable_programs_with_gnat examples-of-gnatmake-usage}@anchor{e5}@anchor{gnat_ugn/building_executable_programs_with_gnat id7}@anchor{e6} @subsection Examples of @code{gnatmake} Usage @table @asis @item @emph{gnatmake hello.adb} Compile all files necessary to bind and link the main program @code{hello.adb} (containing unit @code{Hello}) and bind and link the resulting object files to generate an executable file @code{hello}. @item @emph{gnatmake main1 main2 main3} Compile all files necessary to bind and link the main programs @code{main1.adb} (containing unit @code{Main1}), @code{main2.adb} (containing unit @code{Main2}) and @code{main3.adb} (containing unit @code{Main3}) and bind and link the resulting object files to generate three executable files @code{main1}, @code{main2} and @code{main3}. @item @emph{gnatmake -q Main_Unit -cargs -O2 -bargs -l} Compile all files necessary to bind and link the main program unit @code{Main_Unit} (from file @code{main_unit.adb}). All compilations will be done with optimization level 2 and the order of elaboration will be listed by the binder. @code{gnatmake} will operate in quiet mode, not displaying commands it is executing. @end table @node Compiling with gcc,Compiler Switches,Building with gnatmake,Building Executable Programs with GNAT @anchor{gnat_ugn/building_executable_programs_with_gnat compiling-with-gcc}@anchor{1c}@anchor{gnat_ugn/building_executable_programs_with_gnat id8}@anchor{e7} @section Compiling with @code{gcc} This section discusses how to compile Ada programs using the @code{gcc} command. It also describes the set of switches that can be used to control the behavior of the compiler. @menu * Compiling Programs:: * Search Paths and the Run-Time Library (RTL): Search Paths and the Run-Time Library RTL. * Order of Compilation Issues:: * Examples:: @end menu @node Compiling Programs,Search Paths and the Run-Time Library RTL,,Compiling with gcc @anchor{gnat_ugn/building_executable_programs_with_gnat compiling-programs}@anchor{e8}@anchor{gnat_ugn/building_executable_programs_with_gnat id9}@anchor{e9} @subsection Compiling Programs The first step in creating an executable program is to compile the units of the program using the @code{gcc} command. You must compile the following files: @itemize * @item the body file (@code{.adb}) for a library level subprogram or generic subprogram @item the spec file (@code{.ads}) for a library level package or generic package that has no body @item the body file (@code{.adb}) for a library level package or generic package that has a body @end itemize You need @emph{not} compile the following files @itemize * @item the spec of a library unit which has a body @item subunits @end itemize because they are compiled as part of compiling related units. GNAT package specs when the corresponding body is compiled, and subunits when the parent is compiled. @geindex cannot generate code If you attempt to compile any of these files, you will get one of the following error messages (where @code{fff} is the name of the file you compiled): @quotation @example cannot generate code for file `@w{`}fff`@w{`} (package spec) to check package spec, use -gnatc cannot generate code for file `@w{`}fff`@w{`} (missing subunits) to check parent unit, use -gnatc cannot generate code for file `@w{`}fff`@w{`} (subprogram spec) to check subprogram spec, use -gnatc cannot generate code for file `@w{`}fff`@w{`} (subunit) to check subunit, use -gnatc @end example @end quotation As indicated by the above error messages, if you want to submit one of these files to the compiler to check for correct semantics without generating code, then use the @code{-gnatc} switch. The basic command for compiling a file containing an Ada unit is: @example $ gcc -c [switches] <file name> @end example where @code{file name} is the name of the Ada file (usually having an extension @code{.ads} for a spec or @code{.adb} for a body). You specify the @code{-c} switch to tell @code{gcc} to compile, but not link, the file. The result of a successful compilation is an object file, which has the same name as the source file but an extension of @code{.o} and an Ada Library Information (ALI) file, which also has the same name as the source file, but with @code{.ali} as the extension. GNAT creates these two output files in the current directory, but you may specify a source file in any directory using an absolute or relative path specification containing the directory information. TESTING: the @code{--foobar@emph{NN}} switch @geindex gnat1 @code{gcc} is actually a driver program that looks at the extensions of the file arguments and loads the appropriate compiler. For example, the GNU C compiler is @code{cc1}, and the Ada compiler is @code{gnat1}. These programs are in directories known to the driver program (in some configurations via environment variables you set), but need not be in your path. The @code{gcc} driver also calls the assembler and any other utilities needed to complete the generation of the required object files. It is possible to supply several file names on the same @code{gcc} command. This causes @code{gcc} to call the appropriate compiler for each file. For example, the following command lists two separate files to be compiled: @example $ gcc -c x.adb y.adb @end example calls @code{gnat1} (the Ada compiler) twice to compile @code{x.adb} and @code{y.adb}. The compiler generates two object files @code{x.o} and @code{y.o} and the two ALI files @code{x.ali} and @code{y.ali}. Any switches apply to all the files listed, see @ref{ea,,Compiler Switches} for a list of available @code{gcc} switches. @node Search Paths and the Run-Time Library RTL,Order of Compilation Issues,Compiling Programs,Compiling with gcc @anchor{gnat_ugn/building_executable_programs_with_gnat id10}@anchor{eb}@anchor{gnat_ugn/building_executable_programs_with_gnat search-paths-and-the-run-time-library-rtl}@anchor{89} @subsection Search Paths and the Run-Time Library (RTL) With the GNAT source-based library system, the compiler must be able to find source files for units that are needed by the unit being compiled. Search paths are used to guide this process. The compiler compiles one source file whose name must be given explicitly on the command line. In other words, no searching is done for this file. To find all other source files that are needed (the most common being the specs of units), the compiler examines the following directories, in the following order: @itemize * @item The directory containing the source file of the main unit being compiled (the file name on the command line). @item Each directory named by an @code{-I} switch given on the @code{gcc} command line, in the order given. @geindex ADA_PRJ_INCLUDE_FILE @item Each of the directories listed in the text file whose name is given by the @geindex ADA_PRJ_INCLUDE_FILE @geindex environment variable; ADA_PRJ_INCLUDE_FILE @code{ADA_PRJ_INCLUDE_FILE} environment variable. @geindex ADA_PRJ_INCLUDE_FILE @geindex environment variable; ADA_PRJ_INCLUDE_FILE @code{ADA_PRJ_INCLUDE_FILE} is normally set by gnatmake or by the gnat driver when project files are used. It should not normally be set by other means. @geindex ADA_INCLUDE_PATH @item Each of the directories listed in the value of the @geindex ADA_INCLUDE_PATH @geindex environment variable; ADA_INCLUDE_PATH @code{ADA_INCLUDE_PATH} environment variable. Construct this value exactly as the @geindex PATH @geindex environment variable; PATH @code{PATH} environment variable: a list of directory names separated by colons (semicolons when working with the NT version). @item The content of the @code{ada_source_path} file which is part of the GNAT installation tree and is used to store standard libraries such as the GNAT Run Time Library (RTL) source files. @ref{87,,Installing a library} @end itemize Specifying the switch @code{-I-} inhibits the use of the directory containing the source file named in the command line. You can still have this directory on your search path, but in this case it must be explicitly requested with a @code{-I} switch. Specifying the switch @code{-nostdinc} inhibits the search of the default location for the GNAT Run Time Library (RTL) source files. The compiler outputs its object files and ALI files in the current working directory. Caution: The object file can be redirected with the @code{-o} switch; however, @code{gcc} and @code{gnat1} have not been coordinated on this so the @code{ALI} file will not go to the right place. Therefore, you should avoid using the @code{-o} switch. @geindex System.IO The packages @code{Ada}, @code{System}, and @code{Interfaces} and their children make up the GNAT RTL, together with the simple @code{System.IO} package used in the @code{"Hello World"} example. The sources for these units are needed by the compiler and are kept together in one directory. Not all of the bodies are needed, but all of the sources are kept together anyway. In a normal installation, you need not specify these directory names when compiling or binding. Either the environment variables or the built-in defaults cause these files to be found. In addition to the language-defined hierarchies (@code{System}, @code{Ada} and @code{Interfaces}), the GNAT distribution provides a fourth hierarchy, consisting of child units of @code{GNAT}. This is a collection of generally useful types, subprograms, etc. See the @cite{GNAT_Reference_Manual} for further details. Besides simplifying access to the RTL, a major use of search paths is in compiling sources from multiple directories. This can make development environments much more flexible. @node Order of Compilation Issues,Examples,Search Paths and the Run-Time Library RTL,Compiling with gcc @anchor{gnat_ugn/building_executable_programs_with_gnat id11}@anchor{ec}@anchor{gnat_ugn/building_executable_programs_with_gnat order-of-compilation-issues}@anchor{ed} @subsection Order of Compilation Issues If, in our earlier example, there was a spec for the @code{hello} procedure, it would be contained in the file @code{hello.ads}; yet this file would not have to be explicitly compiled. This is the result of the model we chose to implement library management. Some of the consequences of this model are as follows: @itemize * @item There is no point in compiling specs (except for package specs with no bodies) because these are compiled as needed by clients. If you attempt a useless compilation, you will receive an error message. It is also useless to compile subunits because they are compiled as needed by the parent. @item There are no order of compilation requirements: performing a compilation never obsoletes anything. The only way you can obsolete something and require recompilations is to modify one of the source files on which it depends. @item There is no library as such, apart from the ALI files (@ref{42,,The Ada Library Information Files}, for information on the format of these files). For now we find it convenient to create separate ALI files, but eventually the information therein may be incorporated into the object file directly. @item When you compile a unit, the source files for the specs of all units that it @emph{with}s, all its subunits, and the bodies of any generics it instantiates must be available (reachable by the search-paths mechanism described above), or you will receive a fatal error message. @end itemize @node Examples,,Order of Compilation Issues,Compiling with gcc @anchor{gnat_ugn/building_executable_programs_with_gnat id12}@anchor{ee}@anchor{gnat_ugn/building_executable_programs_with_gnat examples}@anchor{ef} @subsection Examples The following are some typical Ada compilation command line examples: @example $ gcc -c xyz.adb @end example Compile body in file @code{xyz.adb} with all default options. @example $ gcc -c -O2 -gnata xyz-def.adb @end example Compile the child unit package in file @code{xyz-def.adb} with extensive optimizations, and pragma @code{Assert}/@cite{Debug} statements enabled. @example $ gcc -c -gnatc abc-def.adb @end example Compile the subunit in file @code{abc-def.adb} in semantic-checking-only mode. @node Compiler Switches,Linker Switches,Compiling with gcc,Building Executable Programs with GNAT @anchor{gnat_ugn/building_executable_programs_with_gnat compiler-switches}@anchor{f0}@anchor{gnat_ugn/building_executable_programs_with_gnat switches-for-gcc}@anchor{ea} @section Compiler Switches The @code{gcc} command accepts switches that control the compilation process. These switches are fully described in this section: first an alphabetical listing of all switches with a brief description, and then functionally grouped sets of switches with more detailed information. More switches exist for GCC than those documented here, especially for specific targets. However, their use is not recommended as they may change code generation in ways that are incompatible with the Ada run-time library, or can cause inconsistencies between compilation units. @menu * Alphabetical List of All Switches:: * Output and Error Message Control:: * Warning Message Control:: * Debugging and Assertion Control:: * Validity Checking:: * Style Checking:: * Run-Time Checks:: * Using gcc for Syntax Checking:: * Using gcc for Semantic Checking:: * Compiling Different Versions of Ada:: * Character Set Control:: * File Naming Control:: * Subprogram Inlining Control:: * Auxiliary Output Control:: * Debugging Control:: * Exception Handling Control:: * Units to Sources Mapping Files:: * Code Generation Control:: @end menu @node Alphabetical List of All Switches,Output and Error Message Control,,Compiler Switches @anchor{gnat_ugn/building_executable_programs_with_gnat id13}@anchor{f1}@anchor{gnat_ugn/building_executable_programs_with_gnat alphabetical-list-of-all-switches}@anchor{f2} @subsection Alphabetical List of All Switches @geindex -b (gcc) @table @asis @item @code{-b @emph{target}} Compile your program to run on @code{target}, which is the name of a system configuration. You must have a GNAT cross-compiler built if @code{target} is not the same as your host system. @end table @geindex -B (gcc) @table @asis @item @code{-B@emph{dir}} Load compiler executables (for example, @code{gnat1}, the Ada compiler) from @code{dir} instead of the default location. Only use this switch when multiple versions of the GNAT compiler are available. See the "Options for Directory Search" section in the @cite{Using the GNU Compiler Collection (GCC)} manual for further details. You would normally use the @code{-b} or @code{-V} switch instead. @end table @geindex -c (gcc) @table @asis @item @code{-c} Compile. Always use this switch when compiling Ada programs. Note: for some other languages when using @code{gcc}, notably in the case of C and C++, it is possible to use use @code{gcc} without a @code{-c} switch to compile and link in one step. In the case of GNAT, you cannot use this approach, because the binder must be run and @code{gcc} cannot be used to run the GNAT binder. @end table @geindex -fcallgraph-info (gcc) @table @asis @item @code{-fcallgraph-info[=su,da]} Makes the compiler output callgraph information for the program, on a per-file basis. The information is generated in the VCG format. It can be decorated with additional, per-node and/or per-edge information, if a list of comma-separated markers is additionally specified. When the @code{su} marker is specified, the callgraph is decorated with stack usage information; it is equivalent to @code{-fstack-usage}. When the @code{da} marker is specified, the callgraph is decorated with information about dynamically allocated objects. @end table @geindex -fdump-scos (gcc) @table @asis @item @code{-fdump-scos} Generates SCO (Source Coverage Obligation) information in the ALI file. This information is used by advanced coverage tools. See unit @code{SCOs} in the compiler sources for details in files @code{scos.ads} and @code{scos.adb}. @end table @geindex -flto (gcc) @table @asis @item @code{-flto[=@emph{n}]} Enables Link Time Optimization. This switch must be used in conjunction with the @code{-Ox} switches (but not with the @code{-gnatn} switch since it is a full replacement for the latter) and instructs the compiler to defer most optimizations until the link stage. The advantage of this approach is that the compiler can do a whole-program analysis and choose the best interprocedural optimization strategy based on a complete view of the program, instead of a fragmentary view with the usual approach. This can also speed up the compilation of big programs and reduce the size of the executable, compared with a traditional per-unit compilation with inlining across units enabled by the @code{-gnatn} switch. The drawback of this approach is that it may require more memory and that the debugging information generated by -g with it might be hardly usable. The switch, as well as the accompanying @code{-Ox} switches, must be specified both for the compilation and the link phases. If the @code{n} parameter is specified, the optimization and final code generation at link time are executed using @code{n} parallel jobs by means of an installed @code{make} program. @end table @geindex -fno-inline (gcc) @table @asis @item @code{-fno-inline} Suppresses all inlining, unless requested with pragma @code{Inline_Always}. The effect is enforced regardless of other optimization or inlining switches. Note that inlining can also be suppressed on a finer-grained basis with pragma @code{No_Inline}. @end table @geindex -fno-inline-functions (gcc) @table @asis @item @code{-fno-inline-functions} Suppresses automatic inlining of subprograms, which is enabled if @code{-O3} is used. @end table @geindex -fno-inline-small-functions (gcc) @table @asis @item @code{-fno-inline-small-functions} Suppresses automatic inlining of small subprograms, which is enabled if @code{-O2} is used. @end table @geindex -fno-inline-functions-called-once (gcc) @table @asis @item @code{-fno-inline-functions-called-once} Suppresses inlining of subprograms local to the unit and called once from within it, which is enabled if @code{-O1} is used. @end table @geindex -fno-ivopts (gcc) @table @asis @item @code{-fno-ivopts} Suppresses high-level loop induction variable optimizations, which are enabled if @code{-O1} is used. These optimizations are generally profitable but, for some specific cases of loops with numerous uses of the iteration variable that follow a common pattern, they may end up destroying the regularity that could be exploited at a lower level and thus producing inferior code. @end table @geindex -fno-strict-aliasing (gcc) @table @asis @item @code{-fno-strict-aliasing} Causes the compiler to avoid assumptions regarding non-aliasing of objects of different types. See @ref{f3,,Optimization and Strict Aliasing} for details. @end table @geindex -fno-strict-overflow (gcc) @table @asis @item @code{-fno-strict-overflow} Causes the compiler to avoid assumptions regarding the rules of signed integer overflow. These rules specify that signed integer overflow will result in a Constraint_Error exception at run time and are enforced in default mode by the compiler, so this switch should not be necessary in normal operating mode. It might be useful in conjunction with @code{-gnato0} for very peculiar cases of low-level programming. @end table @geindex -fstack-check (gcc) @table @asis @item @code{-fstack-check} Activates stack checking. See @ref{f4,,Stack Overflow Checking} for details. @end table @geindex -fstack-usage (gcc) @table @asis @item @code{-fstack-usage} Makes the compiler output stack usage information for the program, on a per-subprogram basis. See @ref{f5,,Static Stack Usage Analysis} for details. @end table @geindex -g (gcc) @table @asis @item @code{-g} Generate debugging information. This information is stored in the object file and copied from there to the final executable file by the linker, where it can be read by the debugger. You must use the @code{-g} switch if you plan on using the debugger. @end table @geindex -gnat05 (gcc) @table @asis @item @code{-gnat05} Allow full Ada 2005 features. @end table @geindex -gnat12 (gcc) @table @asis @item @code{-gnat12} Allow full Ada 2012 features. @end table @geindex -gnat83 (gcc) @geindex -gnat2005 (gcc) @table @asis @item @code{-gnat2005} Allow full Ada 2005 features (same as @code{-gnat05}) @end table @geindex -gnat2012 (gcc) @table @asis @item @code{-gnat2012} Allow full Ada 2012 features (same as @code{-gnat12}) @item @code{-gnat83} Enforce Ada 83 restrictions. @end table @geindex -gnat95 (gcc) @table @asis @item @code{-gnat95} Enforce Ada 95 restrictions. Note: for compatibility with some Ada 95 compilers which support only the @code{overriding} keyword of Ada 2005, the @code{-gnatd.D} switch can be used along with @code{-gnat95} to achieve a similar effect with GNAT. @code{-gnatd.D} instructs GNAT to consider @code{overriding} as a keyword and handle its associated semantic checks, even in Ada 95 mode. @end table @geindex -gnata (gcc) @table @asis @item @code{-gnata} Assertions enabled. @code{Pragma Assert} and @code{pragma Debug} to be activated. Note that these pragmas can also be controlled using the configuration pragmas @code{Assertion_Policy} and @code{Debug_Policy}. It also activates pragmas @code{Check}, @code{Precondition}, and @code{Postcondition}. Note that these pragmas can also be controlled using the configuration pragma @code{Check_Policy}. In Ada 2012, it also activates all assertions defined in the RM as aspects: preconditions, postconditions, type invariants and (sub)type predicates. In all Ada modes, corresponding pragmas for type invariants and (sub)type predicates are also activated. The default is that all these assertions are disabled, and have no effect, other than being checked for syntactic validity, and in the case of subtype predicates, constructions such as membership tests still test predicates even if assertions are turned off. @end table @geindex -gnatA (gcc) @table @asis @item @code{-gnatA} Avoid processing @code{gnat.adc}. If a @code{gnat.adc} file is present, it will be ignored. @end table @geindex -gnatb (gcc) @table @asis @item @code{-gnatb} Generate brief messages to @code{stderr} even if verbose mode set. @end table @geindex -gnatB (gcc) @table @asis @item @code{-gnatB} Assume no invalid (bad) values except for 'Valid attribute use (@ref{f6,,Validity Checking}). @end table @geindex -gnatc (gcc) @table @asis @item @code{-gnatc} Check syntax and semantics only (no code generation attempted). When the compiler is invoked by @code{gnatmake}, if the switch @code{-gnatc} is only given to the compiler (after @code{-cargs} or in package Compiler of the project file, @code{gnatmake} will fail because it will not find the object file after compilation. If @code{gnatmake} is called with @code{-gnatc} as a builder switch (before @code{-cargs} or in package Builder of the project file) then @code{gnatmake} will not fail because it will not look for the object files after compilation, and it will not try to build and link. @end table @geindex -gnatC (gcc) @table @asis @item @code{-gnatC} Generate CodePeer intermediate format (no code generation attempted). This switch will generate an intermediate representation suitable for use by CodePeer (@code{.scil} files). This switch is not compatible with code generation (it will, among other things, disable some switches such as -gnatn, and enable others such as -gnata). @end table @geindex -gnatd (gcc) @table @asis @item @code{-gnatd} Specify debug options for the compiler. The string of characters after the @code{-gnatd} specify the specific debug options. The possible characters are 0-9, a-z, A-Z, optionally preceded by a dot. See compiler source file @code{debug.adb} for details of the implemented debug options. Certain debug options are relevant to applications programmers, and these are documented at appropriate points in this users guide. @end table @geindex -gnatD[nn] (gcc) @table @asis @item @code{-gnatD} Create expanded source files for source level debugging. This switch also suppresses generation of cross-reference information (see @code{-gnatx}). Note that this switch is not allowed if a previous -gnatR switch has been given, since these two switches are not compatible. @end table @geindex -gnateA (gcc) @table @asis @item @code{-gnateA} Check that the actual parameters of a subprogram call are not aliases of one another. To qualify as aliasing, the actuals must denote objects of a composite type, their memory locations must be identical or overlapping, and at least one of the corresponding formal parameters must be of mode OUT or IN OUT. @example type Rec_Typ is record Data : Integer := 0; end record; function Self (Val : Rec_Typ) return Rec_Typ is begin return Val; end Self; procedure Detect_Aliasing (Val_1 : in out Rec_Typ; Val_2 : Rec_Typ) is begin null; end Detect_Aliasing; Obj : Rec_Typ; Detect_Aliasing (Obj, Obj); Detect_Aliasing (Obj, Self (Obj)); @end example In the example above, the first call to @code{Detect_Aliasing} fails with a @code{Program_Error} at run time because the actuals for @code{Val_1} and @code{Val_2} denote the same object. The second call executes without raising an exception because @code{Self(Obj)} produces an anonymous object which does not share the memory location of @code{Obj}. @end table @geindex -gnatec (gcc) @table @asis @item @code{-gnatec=@emph{path}} Specify a configuration pragma file (the equal sign is optional) (@ref{79,,The Configuration Pragmas Files}). @end table @geindex -gnateC (gcc) @table @asis @item @code{-gnateC} Generate CodePeer messages in a compiler-like format. This switch is only effective if @code{-gnatcC} is also specified and requires an installation of CodePeer. @end table @geindex -gnated (gcc) @table @asis @item @code{-gnated} Disable atomic synchronization @end table @geindex -gnateD (gcc) @table @asis @item @code{-gnateDsymbol[=@emph{value}]} Defines a symbol, associated with @code{value}, for preprocessing. (@ref{18,,Integrated Preprocessing}). @end table @geindex -gnateE (gcc) @table @asis @item @code{-gnateE} Generate extra information in exception messages. In particular, display extra column information and the value and range associated with index and range check failures, and extra column information for access checks. In cases where the compiler is able to determine at compile time that a check will fail, it gives a warning, and the extra information is not produced at run time. @end table @geindex -gnatef (gcc) @table @asis @item @code{-gnatef} Display full source path name in brief error messages. @end table @geindex -gnateF (gcc) @table @asis @item @code{-gnateF} Check for overflow on all floating-point operations, including those for unconstrained predefined types. See description of pragma @code{Check_Float_Overflow} in GNAT RM. @end table @geindex -gnateg (gcc) @code{-gnateg} @code{-gnatceg} @quotation The @code{-gnatc} switch must always be specified before this switch, e.g. @code{-gnatceg}. Generate a C header from the Ada input file. See @ref{ca,,Generating C Headers for Ada Specifications} for more information. @end quotation @geindex -gnateG (gcc) @table @asis @item @code{-gnateG} Save result of preprocessing in a text file. @end table @geindex -gnatei (gcc) @table @asis @item @code{-gnatei@emph{nnn}} Set maximum number of instantiations during compilation of a single unit to @code{nnn}. This may be useful in increasing the default maximum of 8000 for the rare case when a single unit legitimately exceeds this limit. @end table @geindex -gnateI (gcc) @table @asis @item @code{-gnateI@emph{nnn}} Indicates that the source is a multi-unit source and that the index of the unit to compile is @code{nnn}. @code{nnn} needs to be a positive number and need to be a valid index in the multi-unit source. @end table @geindex -gnatel (gcc) @table @asis @item @code{-gnatel} This switch can be used with the static elaboration model to issue info messages showing where implicit @code{pragma Elaborate} and @code{pragma Elaborate_All} are generated. This is useful in diagnosing elaboration circularities caused by these implicit pragmas when using the static elaboration model. See See the section in this guide on elaboration checking for further details. These messages are not generated by default, and are intended only for temporary use when debugging circularity problems. @end table @geindex -gnatel (gcc) @table @asis @item @code{-gnateL} This switch turns off the info messages about implicit elaboration pragmas. @end table @geindex -gnatem (gcc) @table @asis @item @code{-gnatem=@emph{path}} Specify a mapping file (the equal sign is optional) (@ref{f7,,Units to Sources Mapping Files}). @end table @geindex -gnatep (gcc) @table @asis @item @code{-gnatep=@emph{file}} Specify a preprocessing data file (the equal sign is optional) (@ref{18,,Integrated Preprocessing}). @end table @geindex -gnateP (gcc) @table @asis @item @code{-gnateP} Turn categorization dependency errors into warnings. Ada requires that units that WITH one another have compatible categories, for example a Pure unit cannot WITH a Preelaborate unit. If this switch is used, these errors become warnings (which can be ignored, or suppressed in the usual manner). This can be useful in some specialized circumstances such as the temporary use of special test software. @end table @geindex -gnateS (gcc) @table @asis @item @code{-gnateS} Synonym of @code{-fdump-scos}, kept for backwards compatibility. @end table @geindex -gnatet=file (gcc) @table @asis @item @code{-gnatet=@emph{path}} Generate target dependent information. The format of the output file is described in the section about switch @code{-gnateT}. @end table @geindex -gnateT (gcc) @table @asis @item @code{-gnateT=@emph{path}} Read target dependent information, such as endianness or sizes and alignments of base type. If this switch is passed, the default target dependent information of the compiler is replaced by the one read from the input file. This is used by tools other than the compiler, e.g. to do semantic analysis of programs that will run on some other target than the machine on which the tool is run. The following target dependent values should be defined, where @code{Nat} denotes a natural integer value, @code{Pos} denotes a positive integer value, and fields marked with a question mark are boolean fields, where a value of 0 is False, and a value of 1 is True: @example Bits_BE : Nat; -- Bits stored big-endian? Bits_Per_Unit : Pos; -- Bits in a storage unit Bits_Per_Word : Pos; -- Bits in a word Bytes_BE : Nat; -- Bytes stored big-endian? Char_Size : Pos; -- Standard.Character'Size Double_Float_Alignment : Nat; -- Alignment of double float Double_Scalar_Alignment : Nat; -- Alignment of double length scalar Double_Size : Pos; -- Standard.Long_Float'Size Float_Size : Pos; -- Standard.Float'Size Float_Words_BE : Nat; -- Float words stored big-endian? Int_Size : Pos; -- Standard.Integer'Size Long_Double_Size : Pos; -- Standard.Long_Long_Float'Size Long_Long_Size : Pos; -- Standard.Long_Long_Integer'Size Long_Size : Pos; -- Standard.Long_Integer'Size Maximum_Alignment : Pos; -- Maximum permitted alignment Max_Unaligned_Field : Pos; -- Maximum size for unaligned bit field Pointer_Size : Pos; -- System.Address'Size Short_Enums : Nat; -- Foreign enums use short size? Short_Size : Pos; -- Standard.Short_Integer'Size Strict_Alignment : Nat; -- Strict alignment? System_Allocator_Alignment : Nat; -- Alignment for malloc calls Wchar_T_Size : Pos; -- Interfaces.C.wchar_t'Size Words_BE : Nat; -- Words stored big-endian? @end example @code{Bits_Per_Unit} is the number of bits in a storage unit, the equivalent of GCC macro @code{BITS_PER_UNIT} documented as follows: @cite{Define this macro to be the number of bits in an addressable storage unit (byte); normally 8.} @code{Bits_Per_Word} is the number of bits in a machine word, the equivalent of GCC macro @code{BITS_PER_WORD} documented as follows: @cite{Number of bits in a word; normally 32.} @code{Double_Scalar_Alignment} is the alignment for a scalar whose size is two machine words. It should be the same as the alignment for C @code{long_long} on most targets. @code{Maximum_Alignment} is the maximum alignment that the compiler might choose by default for a type or object, which is also the maximum alignment that can be specified in GNAT. It is computed for GCC backends as @code{BIGGEST_ALIGNMENT / BITS_PER_UNIT} where GCC macro @code{BIGGEST_ALIGNMENT} is documented as follows: @cite{Biggest alignment that any data type can require on this machine@comma{} in bits.} @code{Max_Unaligned_Field} is the maximum size for unaligned bit field, which is 64 for the majority of GCC targets (but can be different on some targets like AAMP). @code{Strict_Alignment} is the equivalent of GCC macro @code{STRICT_ALIGNMENT} documented as follows: @cite{Define this macro to be the value 1 if instructions will fail to work if given data not on the nominal alignment. If instructions will merely go slower in that case@comma{} define this macro as 0.} @code{System_Allocator_Alignment} is the guaranteed alignment of data returned by calls to @code{malloc}. The format of the input file is as follows. First come the values of the variables defined above, with one line per value: @example name value @end example where @code{name} is the name of the parameter, spelled out in full, and cased as in the above list, and @code{value} is an unsigned decimal integer. Two or more blanks separates the name from the value. All the variables must be present, in alphabetical order (i.e. the same order as the list above). Then there is a blank line to separate the two parts of the file. Then come the lines showing the floating-point types to be registered, with one line per registered mode: @example name digs float_rep size alignment @end example where @code{name} is the string name of the type (which can have single spaces embedded in the name (e.g. long double), @code{digs} is the number of digits for the floating-point type, @code{float_rep} is the float representation (I/V/A for IEEE-754-Binary, Vax_Native, AAMP), @code{size} is the size in bits, @code{alignment} is the alignment in bits. The name is followed by at least two blanks, fields are separated by at least one blank, and a LF character immediately follows the alignment field. Here is an example of a target parameterization file: @example Bits_BE 0 Bits_Per_Unit 8 Bits_Per_Word 64 Bytes_BE 0 Char_Size 8 Double_Float_Alignment 0 Double_Scalar_Alignment 0 Double_Size 64 Float_Size 32 Float_Words_BE 0 Int_Size 64 Long_Double_Size 128 Long_Long_Size 64 Long_Size 64 Maximum_Alignment 16 Max_Unaligned_Field 64 Pointer_Size 64 Short_Size 16 Strict_Alignment 0 System_Allocator_Alignment 16 Wchar_T_Size 32 Words_BE 0 float 15 I 64 64 double 15 I 64 64 long double 18 I 80 128 TF 33 I 128 128 @end example @end table @geindex -gnateu (gcc) @table @asis @item @code{-gnateu} Ignore unrecognized validity, warning, and style switches that appear after this switch is given. This may be useful when compiling sources developed on a later version of the compiler with an earlier version. Of course the earlier version must support this switch. @end table @geindex -gnateV (gcc) @table @asis @item @code{-gnateV} Check that all actual parameters of a subprogram call are valid according to the rules of validity checking (@ref{f6,,Validity Checking}). @end table @geindex -gnateY (gcc) @table @asis @item @code{-gnateY} Ignore all STYLE_CHECKS pragmas. Full legality checks are still carried out, but the pragmas have no effect on what style checks are active. This allows all style checking options to be controlled from the command line. @end table @geindex -gnatE (gcc) @table @asis @item @code{-gnatE} Full dynamic elaboration checks. @end table @geindex -gnatf (gcc) @table @asis @item @code{-gnatf} Full errors. Multiple errors per line, all undefined references, do not attempt to suppress cascaded errors. @end table @geindex -gnatF (gcc) @table @asis @item @code{-gnatF} Externals names are folded to all uppercase. @end table @geindex -gnatg (gcc) @table @asis @item @code{-gnatg} Internal GNAT implementation mode. This should not be used for applications programs, it is intended only for use by the compiler and its run-time library. For documentation, see the GNAT sources. Note that @code{-gnatg} implies @code{-gnatw.ge} and @code{-gnatyg} so that all standard warnings and all standard style options are turned on. All warnings and style messages are treated as errors. @end table @geindex -gnatG[nn] (gcc) @table @asis @item @code{-gnatG=nn} List generated expanded code in source form. @end table @geindex -gnath (gcc) @table @asis @item @code{-gnath} Output usage information. The output is written to @code{stdout}. @end table @geindex -gnatH (gcc) @table @asis @item @code{-gnatH} Legacy elaboration-checking mode enabled. When this switch is in effect, the pre-18.x access-before-elaboration model becomes the de facto model. @end table @geindex -gnati (gcc) @table @asis @item @code{-gnati@emph{c}} Identifier character set (@code{c} = 1/2/3/4/8/9/p/f/n/w). For details of the possible selections for @code{c}, see @ref{48,,Character Set Control}. @end table @geindex -gnatI (gcc) @table @asis @item @code{-gnatI} Ignore representation clauses. When this switch is used, representation clauses are treated as comments. This is useful when initially porting code where you want to ignore rep clause problems, and also for compiling foreign code (particularly for use with ASIS). The representation clauses that are ignored are: enumeration_representation_clause, record_representation_clause, and attribute_definition_clause for the following attributes: Address, Alignment, Bit_Order, Component_Size, Machine_Radix, Object_Size, Scalar_Storage_Order, Size, Small, Stream_Size, and Value_Size. Pragma Default_Scalar_Storage_Order is also ignored. Note that this option should be used only for compiling -- the code is likely to malfunction at run time. Note that when @code{-gnatct} is used to generate trees for input into ASIS tools, these representation clauses are removed from the tree and ignored. This means that the tool will not see them. @end table @geindex -gnatjnn (gcc) @table @asis @item @code{-gnatj@emph{nn}} Reformat error messages to fit on @code{nn} character lines @end table @geindex -gnatJ (gcc) @table @asis @item @code{-gnatJ} Permissive elaboration-checking mode enabled. When this switch is in effect, the post-18.x access-before-elaboration model ignores potential issues with: @itemize - @item Accept statements @item Activations of tasks defined in instances @item Assertion pragmas @item Calls from within an instance to its enclosing context @item Calls through generic formal parameters @item Calls to subprograms defined in instances @item Entry calls @item Indirect calls using 'Access @item Requeue statements @item Select statements @item Synchronous task suspension @end itemize and does not emit compile-time diagnostics or run-time checks. @end table @geindex -gnatk (gcc) @table @asis @item @code{-gnatk=@emph{n}} Limit file names to @code{n} (1-999) characters (@code{k} = krunch). @end table @geindex -gnatl (gcc) @table @asis @item @code{-gnatl} Output full source listing with embedded error messages. @end table @geindex -gnatL (gcc) @table @asis @item @code{-gnatL} Used in conjunction with -gnatG or -gnatD to intersperse original source lines (as comment lines with line numbers) in the expanded source output. @end table @geindex -gnatm (gcc) @table @asis @item @code{-gnatm=@emph{n}} Limit number of detected error or warning messages to @code{n} where @code{n} is in the range 1..999999. The default setting if no switch is given is 9999. If the number of warnings reaches this limit, then a message is output and further warnings are suppressed, but the compilation is continued. If the number of error messages reaches this limit, then a message is output and the compilation is abandoned. The equal sign here is optional. A value of zero means that no limit applies. @end table @geindex -gnatn (gcc) @table @asis @item @code{-gnatn[12]} Activate inlining across units for subprograms for which pragma @code{Inline} is specified. This inlining is performed by the GCC back-end. An optional digit sets the inlining level: 1 for moderate inlining across units or 2 for full inlining across units. If no inlining level is specified, the compiler will pick it based on the optimization level. @end table @geindex -gnatN (gcc) @table @asis @item @code{-gnatN} Activate front end inlining for subprograms for which pragma @code{Inline} is specified. This inlining is performed by the front end and will be visible in the @code{-gnatG} output. When using a gcc-based back end (in practice this means using any version of GNAT other than the JGNAT, .NET or GNAAMP versions), then the use of @code{-gnatN} is deprecated, and the use of @code{-gnatn} is preferred. Historically front end inlining was more extensive than the gcc back end inlining, but that is no longer the case. @end table @geindex -gnato0 (gcc) @table @asis @item @code{-gnato0} Suppresses overflow checking. This causes the behavior of the compiler to match the default for older versions where overflow checking was suppressed by default. This is equivalent to having @code{pragma Suppress (Overflow_Check)} in a configuration pragma file. @end table @geindex -gnato?? (gcc) @table @asis @item @code{-gnato??} Set default mode for handling generation of code to avoid intermediate arithmetic overflow. Here @code{??} is two digits, a single digit, or nothing. Each digit is one of the digits @code{1} through @code{3}: @multitable {xxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} @item Digit @tab Interpretation @item @emph{1} @tab All intermediate overflows checked against base type (@code{STRICT}) @item @emph{2} @tab Minimize intermediate overflows (@code{MINIMIZED}) @item @emph{3} @tab Eliminate intermediate overflows (@code{ELIMINATED}) @end multitable If only one digit appears, then it applies to all cases; if two digits are given, then the first applies outside assertions, pre/postconditions, and type invariants, and the second applies within assertions, pre/postconditions, and type invariants. If no digits follow the @code{-gnato}, then it is equivalent to @code{-gnato11}, causing all intermediate overflows to be handled in strict mode. This switch also causes arithmetic overflow checking to be performed (as though @code{pragma Unsuppress (Overflow_Check)} had been specified). The default if no option @code{-gnato} is given is that overflow handling is in @code{STRICT} mode (computations done using the base type), and that overflow checking is enabled. Note that division by zero is a separate check that is not controlled by this switch (divide-by-zero checking is on by default). See also @ref{f8,,Specifying the Desired Mode}. @end table @geindex -gnatp (gcc) @table @asis @item @code{-gnatp} Suppress all checks. See @ref{f9,,Run-Time Checks} for details. This switch has no effect if cancelled by a subsequent @code{-gnat-p} switch. @end table @geindex -gnat-p (gcc) @table @asis @item @code{-gnat-p} Cancel effect of previous @code{-gnatp} switch. @end table @geindex -gnatP (gcc) @table @asis @item @code{-gnatP} Enable polling. This is required on some systems (notably Windows NT) to obtain asynchronous abort and asynchronous transfer of control capability. See @code{Pragma_Polling} in the @cite{GNAT_Reference_Manual} for full details. @end table @geindex -gnatq (gcc) @table @asis @item @code{-gnatq} Don't quit. Try semantics, even if parse errors. @end table @geindex -gnatQ (gcc) @table @asis @item @code{-gnatQ} Don't quit. Generate @code{ALI} and tree files even if illegalities. Note that code generation is still suppressed in the presence of any errors, so even with @code{-gnatQ} no object file is generated. @end table @geindex -gnatr (gcc) @table @asis @item @code{-gnatr} Treat pragma Restrictions as Restriction_Warnings. @end table @geindex -gnatR (gcc) @table @asis @item @code{-gnatR[0|1|2|3][e][j][m][s]} Output representation information for declared types, objects and subprograms. Note that this switch is not allowed if a previous @code{-gnatD} switch has been given, since these two switches are not compatible. @end table @geindex -gnats (gcc) @table @asis @item @code{-gnats} Syntax check only. @end table @geindex -gnatS (gcc) @table @asis @item @code{-gnatS} Print package Standard. @end table @geindex -gnatt (gcc) @table @asis @item @code{-gnatt} Generate tree output file. @end table @geindex -gnatT (gcc) @table @asis @item @code{-gnatT@emph{nnn}} All compiler tables start at @code{nnn} times usual starting size. @end table @geindex -gnatu (gcc) @table @asis @item @code{-gnatu} List units for this compilation. @end table @geindex -gnatU (gcc) @table @asis @item @code{-gnatU} Tag all error messages with the unique string 'error:' @end table @geindex -gnatv (gcc) @table @asis @item @code{-gnatv} Verbose mode. Full error output with source lines to @code{stdout}. @end table @geindex -gnatV (gcc) @table @asis @item @code{-gnatV} Control level of validity checking (@ref{f6,,Validity Checking}). @end table @geindex -gnatw (gcc) @table @asis @item @code{-gnatw@emph{xxx}} Warning mode where @code{xxx} is a string of option letters that denotes the exact warnings that are enabled or disabled (@ref{fa,,Warning Message Control}). @end table @geindex -gnatW (gcc) @table @asis @item @code{-gnatW@emph{e}} Wide character encoding method (@code{e}=n/h/u/s/e/8). @end table @geindex -gnatx (gcc) @table @asis @item @code{-gnatx} Suppress generation of cross-reference information. @end table @geindex -gnatX (gcc) @table @asis @item @code{-gnatX} Enable GNAT implementation extensions and latest Ada version. @end table @geindex -gnaty (gcc) @table @asis @item @code{-gnaty} Enable built-in style checks (@ref{fb,,Style Checking}). @end table @geindex -gnatz (gcc) @table @asis @item @code{-gnatz@emph{m}} Distribution stub generation and compilation (@code{m}=r/c for receiver/caller stubs). @end table @geindex -I (gcc) @table @asis @item @code{-I@emph{dir}} @geindex RTL Direct GNAT to search the @code{dir} directory for source files needed by the current compilation (see @ref{89,,Search Paths and the Run-Time Library (RTL)}). @end table @geindex -I- (gcc) @table @asis @item @code{-I-} @geindex RTL Except for the source file named in the command line, do not look for source files in the directory containing the source file named in the command line (see @ref{89,,Search Paths and the Run-Time Library (RTL)}). @end table @geindex -o (gcc) @table @asis @item @code{-o @emph{file}} This switch is used in @code{gcc} to redirect the generated object file and its associated ALI file. Beware of this switch with GNAT, because it may cause the object file and ALI file to have different names which in turn may confuse the binder and the linker. @end table @geindex -nostdinc (gcc) @table @asis @item @code{-nostdinc} Inhibit the search of the default location for the GNAT Run Time Library (RTL) source files. @end table @geindex -nostdlib (gcc) @table @asis @item @code{-nostdlib} Inhibit the search of the default location for the GNAT Run Time Library (RTL) ALI files. @end table @geindex -O (gcc) @table @asis @item @code{-O[@emph{n}]} @code{n} controls the optimization level: @multitable {xxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} @item @emph{n} @tab Effect @item @emph{0} @tab No optimization, the default setting if no @code{-O} appears @item @emph{1} @tab Normal optimization, the default if you specify @code{-O} without an operand. A good compromise between code quality and compilation time. @item @emph{2} @tab Extensive optimization, may improve execution time, possibly at the cost of substantially increased compilation time. @item @emph{3} @tab Same as @code{-O2}, and also includes inline expansion for small subprograms in the same unit. @item @emph{s} @tab Optimize space usage @end multitable See also @ref{fc,,Optimization Levels}. @end table @geindex -pass-exit-codes (gcc) @table @asis @item @code{-pass-exit-codes} Catch exit codes from the compiler and use the most meaningful as exit status. @end table @geindex --RTS (gcc) @table @asis @item @code{--RTS=@emph{rts-path}} Specifies the default location of the run-time library. Same meaning as the equivalent @code{gnatmake} flag (@ref{dc,,Switches for gnatmake}). @end table @geindex -S (gcc) @table @asis @item @code{-S} Used in place of @code{-c} to cause the assembler source file to be generated, using @code{.s} as the extension, instead of the object file. This may be useful if you need to examine the generated assembly code. @end table @geindex -fverbose-asm (gcc) @table @asis @item @code{-fverbose-asm} Used in conjunction with @code{-S} to cause the generated assembly code file to be annotated with variable names, making it significantly easier to follow. @end table @geindex -v (gcc) @table @asis @item @code{-v} Show commands generated by the @code{gcc} driver. Normally used only for debugging purposes or if you need to be sure what version of the compiler you are executing. @end table @geindex -V (gcc) @table @asis @item @code{-V @emph{ver}} Execute @code{ver} version of the compiler. This is the @code{gcc} version, not the GNAT version. @end table @geindex -w (gcc) @table @asis @item @code{-w} Turn off warnings generated by the back end of the compiler. Use of this switch also causes the default for front end warnings to be set to suppress (as though @code{-gnatws} had appeared at the start of the options). @end table @geindex Combining GNAT switches You may combine a sequence of GNAT switches into a single switch. For example, the combined switch @quotation @example -gnatofi3 @end example @end quotation is equivalent to specifying the following sequence of switches: @quotation @example -gnato -gnatf -gnati3 @end example @end quotation The following restrictions apply to the combination of switches in this manner: @itemize * @item The switch @code{-gnatc} if combined with other switches must come first in the string. @item The switch @code{-gnats} if combined with other switches must come first in the string. @item The switches @code{-gnatzc} and @code{-gnatzr} may not be combined with any other switches, and only one of them may appear in the command line. @item The switch @code{-gnat-p} may not be combined with any other switch. @item Once a 'y' appears in the string (that is a use of the @code{-gnaty} switch), then all further characters in the switch are interpreted as style modifiers (see description of @code{-gnaty}). @item Once a 'd' appears in the string (that is a use of the @code{-gnatd} switch), then all further characters in the switch are interpreted as debug flags (see description of @code{-gnatd}). @item Once a 'w' appears in the string (that is a use of the @code{-gnatw} switch), then all further characters in the switch are interpreted as warning mode modifiers (see description of @code{-gnatw}). @item Once a 'V' appears in the string (that is a use of the @code{-gnatV} switch), then all further characters in the switch are interpreted as validity checking options (@ref{f6,,Validity Checking}). @item Option 'em', 'ec', 'ep', 'l=' and 'R' must be the last options in a combined list of options. @end itemize @node Output and Error Message Control,Warning Message Control,Alphabetical List of All Switches,Compiler Switches @anchor{gnat_ugn/building_executable_programs_with_gnat id14}@anchor{fd}@anchor{gnat_ugn/building_executable_programs_with_gnat output-and-error-message-control}@anchor{fe} @subsection Output and Error Message Control @geindex stderr The standard default format for error messages is called 'brief format'. Brief format messages are written to @code{stderr} (the standard error file) and have the following form: @example e.adb:3:04: Incorrect spelling of keyword "function" e.adb:4:20: ";" should be "is" @end example The first integer after the file name is the line number in the file, and the second integer is the column number within the line. @code{GPS} can parse the error messages and point to the referenced character. The following switches provide control over the error message format: @geindex -gnatv (gcc) @table @asis @item @code{-gnatv} The @code{v} stands for verbose. The effect of this setting is to write long-format error messages to @code{stdout} (the standard output file. The same program compiled with the @code{-gnatv} switch would generate: @example 3. funcion X (Q : Integer) | >>> Incorrect spelling of keyword "function" 4. return Integer; | >>> ";" should be "is" @end example The vertical bar indicates the location of the error, and the @code{>>>} prefix can be used to search for error messages. When this switch is used the only source lines output are those with errors. @end table @geindex -gnatl (gcc) @table @asis @item @code{-gnatl} The @code{l} stands for list. This switch causes a full listing of the file to be generated. In the case where a body is compiled, the corresponding spec is also listed, along with any subunits. Typical output from compiling a package body @code{p.adb} might look like: @example Compiling: p.adb 1. package body p is 2. procedure a; 3. procedure a is separate; 4. begin 5. null | >>> missing ";" 6. end; Compiling: p.ads 1. package p is 2. pragma Elaborate_Body | >>> missing ";" 3. end p; Compiling: p-a.adb 1. separate p | >>> missing "(" 2. procedure a is 3. begin 4. null | >>> missing ";" 5. end; @end example When you specify the @code{-gnatv} or @code{-gnatl} switches and standard output is redirected, a brief summary is written to @code{stderr} (standard error) giving the number of error messages and warning messages generated. @end table @geindex -gnatl=fname (gcc) @table @asis @item @code{-gnatl=@emph{fname}} This has the same effect as @code{-gnatl} except that the output is written to a file instead of to standard output. If the given name @code{fname} does not start with a period, then it is the full name of the file to be written. If @code{fname} is an extension, it is appended to the name of the file being compiled. For example, if file @code{xyz.adb} is compiled with @code{-gnatl=.lst}, then the output is written to file xyz.adb.lst. @end table @geindex -gnatU (gcc) @table @asis @item @code{-gnatU} This switch forces all error messages to be preceded by the unique string 'error:'. This means that error messages take a few more characters in space, but allows easy searching for and identification of error messages. @end table @geindex -gnatb (gcc) @table @asis @item @code{-gnatb} The @code{b} stands for brief. This switch causes GNAT to generate the brief format error messages to @code{stderr} (the standard error file) as well as the verbose format message or full listing (which as usual is written to @code{stdout} (the standard output file). @end table @geindex -gnatm (gcc) @table @asis @item @code{-gnatm=@emph{n}} The @code{m} stands for maximum. @code{n} is a decimal integer in the range of 1 to 999999 and limits the number of error or warning messages to be generated. For example, using @code{-gnatm2} might yield @example e.adb:3:04: Incorrect spelling of keyword "function" e.adb:5:35: missing ".." fatal error: maximum number of errors detected compilation abandoned @end example The default setting if no switch is given is 9999. If the number of warnings reaches this limit, then a message is output and further warnings are suppressed, but the compilation is continued. If the number of error messages reaches this limit, then a message is output and the compilation is abandoned. A value of zero means that no limit applies. Note that the equal sign is optional, so the switches @code{-gnatm2} and @code{-gnatm=2} are equivalent. @end table @geindex -gnatf (gcc) @table @asis @item @code{-gnatf} @geindex Error messages @geindex suppressing The @code{f} stands for full. Normally, the compiler suppresses error messages that are likely to be redundant. This switch causes all error messages to be generated. In particular, in the case of references to undefined variables. If a given variable is referenced several times, the normal format of messages is @example e.adb:7:07: "V" is undefined (more references follow) @end example where the parenthetical comment warns that there are additional references to the variable @code{V}. Compiling the same program with the @code{-gnatf} switch yields @example e.adb:7:07: "V" is undefined e.adb:8:07: "V" is undefined e.adb:8:12: "V" is undefined e.adb:8:16: "V" is undefined e.adb:9:07: "V" is undefined e.adb:9:12: "V" is undefined @end example The @code{-gnatf} switch also generates additional information for some error messages. Some examples are: @itemize * @item Details on possibly non-portable unchecked conversion @item List possible interpretations for ambiguous calls @item Additional details on incorrect parameters @end itemize @end table @geindex -gnatjnn (gcc) @table @asis @item @code{-gnatjnn} In normal operation mode (or if @code{-gnatj0} is used), then error messages with continuation lines are treated as though the continuation lines were separate messages (and so a warning with two continuation lines counts as three warnings, and is listed as three separate messages). If the @code{-gnatjnn} switch is used with a positive value for nn, then messages are output in a different manner. A message and all its continuation lines are treated as a unit, and count as only one warning or message in the statistics totals. Furthermore, the message is reformatted so that no line is longer than nn characters. @end table @geindex -gnatq (gcc) @table @asis @item @code{-gnatq} The @code{q} stands for quit (really 'don't quit'). In normal operation mode, the compiler first parses the program and determines if there are any syntax errors. If there are, appropriate error messages are generated and compilation is immediately terminated. This switch tells GNAT to continue with semantic analysis even if syntax errors have been found. This may enable the detection of more errors in a single run. On the other hand, the semantic analyzer is more likely to encounter some internal fatal error when given a syntactically invalid tree. @end table @geindex -gnatQ (gcc) @table @asis @item @code{-gnatQ} In normal operation mode, the @code{ALI} file is not generated if any illegalities are detected in the program. The use of @code{-gnatQ} forces generation of the @code{ALI} file. This file is marked as being in error, so it cannot be used for binding purposes, but it does contain reasonably complete cross-reference information, and thus may be useful for use by tools (e.g., semantic browsing tools or integrated development environments) that are driven from the @code{ALI} file. This switch implies @code{-gnatq}, since the semantic phase must be run to get a meaningful ALI file. In addition, if @code{-gnatt} is also specified, then the tree file is generated even if there are illegalities. It may be useful in this case to also specify @code{-gnatq} to ensure that full semantic processing occurs. The resulting tree file can be processed by ASIS, for the purpose of providing partial information about illegal units, but if the error causes the tree to be badly malformed, then ASIS may crash during the analysis. When @code{-gnatQ} is used and the generated @code{ALI} file is marked as being in error, @code{gnatmake} will attempt to recompile the source when it finds such an @code{ALI} file, including with switch @code{-gnatc}. Note that @code{-gnatQ} has no effect if @code{-gnats} is specified, since ALI files are never generated if @code{-gnats} is set. @end table @node Warning Message Control,Debugging and Assertion Control,Output and Error Message Control,Compiler Switches @anchor{gnat_ugn/building_executable_programs_with_gnat warning-message-control}@anchor{fa}@anchor{gnat_ugn/building_executable_programs_with_gnat id15}@anchor{ff} @subsection Warning Message Control @geindex Warning messages In addition to error messages, which correspond to illegalities as defined in the Ada Reference Manual, the compiler detects two kinds of warning situations. First, the compiler considers some constructs suspicious and generates a warning message to alert you to a possible error. Second, if the compiler detects a situation that is sure to raise an exception at run time, it generates a warning message. The following shows an example of warning messages: @example e.adb:4:24: warning: creation of object may raise Storage_Error e.adb:10:17: warning: static value out of range e.adb:10:17: warning: "Constraint_Error" will be raised at run time @end example GNAT considers a large number of situations as appropriate for the generation of warning messages. As always, warnings are not definite indications of errors. For example, if you do an out-of-range assignment with the deliberate intention of raising a @code{Constraint_Error} exception, then the warning that may be issued does not indicate an error. Some of the situations for which GNAT issues warnings (at least some of the time) are given in the following list. This list is not complete, and new warnings are often added to subsequent versions of GNAT. The list is intended to give a general idea of the kinds of warnings that are generated. @itemize * @item Possible infinitely recursive calls @item Out-of-range values being assigned @item Possible order of elaboration problems @item Size not a multiple of alignment for a record type @item Assertions (pragma Assert) that are sure to fail @item Unreachable code @item Address clauses with possibly unaligned values, or where an attempt is made to overlay a smaller variable with a larger one. @item Fixed-point type declarations with a null range @item Direct_IO or Sequential_IO instantiated with a type that has access values @item Variables that are never assigned a value @item Variables that are referenced before being initialized @item Task entries with no corresponding @code{accept} statement @item Duplicate accepts for the same task entry in a @code{select} @item Objects that take too much storage @item Unchecked conversion between types of differing sizes @item Missing @code{return} statement along some execution path in a function @item Incorrect (unrecognized) pragmas @item Incorrect external names @item Allocation from empty storage pool @item Potentially blocking operation in protected type @item Suspicious parenthesization of expressions @item Mismatching bounds in an aggregate @item Attempt to return local value by reference @item Premature instantiation of a generic body @item Attempt to pack aliased components @item Out of bounds array subscripts @item Wrong length on string assignment @item Violations of style rules if style checking is enabled @item Unused @emph{with} clauses @item @code{Bit_Order} usage that does not have any effect @item @code{Standard.Duration} used to resolve universal fixed expression @item Dereference of possibly null value @item Declaration that is likely to cause storage error @item Internal GNAT unit @emph{with}ed by application unit @item Values known to be out of range at compile time @item Unreferenced or unmodified variables. Note that a special exemption applies to variables which contain any of the substrings @code{DISCARD, DUMMY, IGNORE, JUNK, UNUSED}, in any casing. Such variables are considered likely to be intentionally used in a situation where otherwise a warning would be given, so warnings of this kind are always suppressed for such variables. @item Address overlays that could clobber memory @item Unexpected initialization when address clause present @item Bad alignment for address clause @item Useless type conversions @item Redundant assignment statements and other redundant constructs @item Useless exception handlers @item Accidental hiding of name by child unit @item Access before elaboration detected at compile time @item A range in a @code{for} loop that is known to be null or might be null @end itemize The following section lists compiler switches that are available to control the handling of warning messages. It is also possible to exercise much finer control over what warnings are issued and suppressed using the GNAT pragma Warnings (see the description of the pragma in the @cite{GNAT_Reference_manual}). @geindex -gnatwa (gcc) @table @asis @item @code{-gnatwa} @emph{Activate most optional warnings.} This switch activates most optional warning messages. See the remaining list in this section for details on optional warning messages that can be individually controlled. The warnings that are not turned on by this switch are: @itemize * @item @code{-gnatwd} (implicit dereferencing) @item @code{-gnatw.d} (tag warnings with -gnatw switch) @item @code{-gnatwh} (hiding) @item @code{-gnatw.h} (holes in record layouts) @item @code{-gnatw.j} (late primitives of tagged types) @item @code{-gnatw.k} (redefinition of names in standard) @item @code{-gnatwl} (elaboration warnings) @item @code{-gnatw.l} (inherited aspects) @item @code{-gnatw.n} (atomic synchronization) @item @code{-gnatwo} (address clause overlay) @item @code{-gnatw.o} (values set by out parameters ignored) @item @code{-gnatw.q} (questionable layout of record types) @item @code{-gnatw.s} (overridden size clause) @item @code{-gnatwt} (tracking of deleted conditional code) @item @code{-gnatw.u} (unordered enumeration) @item @code{-gnatw.w} (use of Warnings Off) @item @code{-gnatw.y} (reasons for package needing body) @end itemize All other optional warnings are turned on. @end table @geindex -gnatwA (gcc) @table @asis @item @code{-gnatwA} @emph{Suppress all optional errors.} This switch suppresses all optional warning messages, see remaining list in this section for details on optional warning messages that can be individually controlled. Note that unlike switch @code{-gnatws}, the use of switch @code{-gnatwA} does not suppress warnings that are normally given unconditionally and cannot be individually controlled (for example, the warning about a missing exit path in a function). Also, again unlike switch @code{-gnatws}, warnings suppressed by the use of switch @code{-gnatwA} can be individually turned back on. For example the use of switch @code{-gnatwA} followed by switch @code{-gnatwd} will suppress all optional warnings except the warnings for implicit dereferencing. @end table @geindex -gnatw.a (gcc) @table @asis @item @code{-gnatw.a} @emph{Activate warnings on failing assertions.} @geindex Assert failures This switch activates warnings for assertions where the compiler can tell at compile time that the assertion will fail. Note that this warning is given even if assertions are disabled. The default is that such warnings are generated. @end table @geindex -gnatw.A (gcc) @table @asis @item @code{-gnatw.A} @emph{Suppress warnings on failing assertions.} @geindex Assert failures This switch suppresses warnings for assertions where the compiler can tell at compile time that the assertion will fail. @end table @geindex -gnatwb (gcc) @table @asis @item @code{-gnatwb} @emph{Activate warnings on bad fixed values.} @geindex Bad fixed values @geindex Fixed-point Small value @geindex Small value This switch activates warnings for static fixed-point expressions whose value is not an exact multiple of Small. Such values are implementation dependent, since an implementation is free to choose either of the multiples that surround the value. GNAT always chooses the closer one, but this is not required behavior, and it is better to specify a value that is an exact multiple, ensuring predictable execution. The default is that such warnings are not generated. @end table @geindex -gnatwB (gcc) @table @asis @item @code{-gnatwB} @emph{Suppress warnings on bad fixed values.} This switch suppresses warnings for static fixed-point expressions whose value is not an exact multiple of Small. @end table @geindex -gnatw.b (gcc) @table @asis @item @code{-gnatw.b} @emph{Activate warnings on biased representation.} @geindex Biased representation This switch activates warnings when a size clause, value size clause, component clause, or component size clause forces the use of biased representation for an integer type (e.g. representing a range of 10..11 in a single bit by using 0/1 to represent 10/11). The default is that such warnings are generated. @end table @geindex -gnatwB (gcc) @table @asis @item @code{-gnatw.B} @emph{Suppress warnings on biased representation.} This switch suppresses warnings for representation clauses that force the use of biased representation. @end table @geindex -gnatwc (gcc) @table @asis @item @code{-gnatwc} @emph{Activate warnings on conditionals.} @geindex Conditionals @geindex constant This switch activates warnings for conditional expressions used in tests that are known to be True or False at compile time. The default is that such warnings are not generated. Note that this warning does not get issued for the use of boolean variables or constants whose values are known at compile time, since this is a standard technique for conditional compilation in Ada, and this would generate too many false positive warnings. This warning option also activates a special test for comparisons using the operators '>=' and' <='. If the compiler can tell that only the equality condition is possible, then it will warn that the '>' or '<' part of the test is useless and that the operator could be replaced by '='. An example would be comparing a @code{Natural} variable <= 0. This warning option also generates warnings if one or both tests is optimized away in a membership test for integer values if the result can be determined at compile time. Range tests on enumeration types are not included, since it is common for such tests to include an end point. This warning can also be turned on using @code{-gnatwa}. @end table @geindex -gnatwC (gcc) @table @asis @item @code{-gnatwC} @emph{Suppress warnings on conditionals.} This switch suppresses warnings for conditional expressions used in tests that are known to be True or False at compile time. @end table @geindex -gnatw.c (gcc) @table @asis @item @code{-gnatw.c} @emph{Activate warnings on missing component clauses.} @geindex Component clause @geindex missing This switch activates warnings for record components where a record representation clause is present and has component clauses for the majority, but not all, of the components. A warning is given for each component for which no component clause is present. @end table @geindex -gnatwC (gcc) @table @asis @item @code{-gnatw.C} @emph{Suppress warnings on missing component clauses.} This switch suppresses warnings for record components that are missing a component clause in the situation described above. @end table @geindex -gnatwd (gcc) @table @asis @item @code{-gnatwd} @emph{Activate warnings on implicit dereferencing.} If this switch is set, then the use of a prefix of an access type in an indexed component, slice, or selected component without an explicit @code{.all} will generate a warning. With this warning enabled, access checks occur only at points where an explicit @code{.all} appears in the source code (assuming no warnings are generated as a result of this switch). The default is that such warnings are not generated. @end table @geindex -gnatwD (gcc) @table @asis @item @code{-gnatwD} @emph{Suppress warnings on implicit dereferencing.} @geindex Implicit dereferencing @geindex Dereferencing @geindex implicit This switch suppresses warnings for implicit dereferences in indexed components, slices, and selected components. @end table @geindex -gnatw.d (gcc) @table @asis @item @code{-gnatw.d} @emph{Activate tagging of warning and info messages.} If this switch is set, then warning messages are tagged, with one of the following strings: @quotation @itemize - @item @emph{[-gnatw?]} Used to tag warnings controlled by the switch @code{-gnatwx} where x is a letter a-z. @item @emph{[-gnatw.?]} Used to tag warnings controlled by the switch @code{-gnatw.x} where x is a letter a-z. @item @emph{[-gnatel]} Used to tag elaboration information (info) messages generated when the static model of elaboration is used and the @code{-gnatel} switch is set. @item @emph{[restriction warning]} Used to tag warning messages for restriction violations, activated by use of the pragma @code{Restriction_Warnings}. @item @emph{[warning-as-error]} Used to tag warning messages that have been converted to error messages by use of the pragma Warning_As_Error. Note that such warnings are prefixed by the string "error: " rather than "warning: ". @item @emph{[enabled by default]} Used to tag all other warnings that are always given by default, unless warnings are completely suppressed using pragma @emph{Warnings(Off)} or the switch @code{-gnatws}. @end itemize @end quotation @end table @geindex -gnatw.d (gcc) @table @asis @item @code{-gnatw.D} @emph{Deactivate tagging of warning and info messages messages.} If this switch is set, then warning messages return to the default mode in which warnings and info messages are not tagged as described above for @code{-gnatw.d}. @end table @geindex -gnatwe (gcc) @geindex Warnings @geindex treat as error @table @asis @item @code{-gnatwe} @emph{Treat warnings and style checks as errors.} This switch causes warning messages and style check messages to be treated as errors. The warning string still appears, but the warning messages are counted as errors, and prevent the generation of an object file. Note that this is the only -gnatw switch that affects the handling of style check messages. Note also that this switch has no effect on info (information) messages, which are not treated as errors if this switch is present. @end table @geindex -gnatw.e (gcc) @table @asis @item @code{-gnatw.e} @emph{Activate every optional warning.} @geindex Warnings @geindex activate every optional warning This switch activates all optional warnings, including those which are not activated by @code{-gnatwa}. The use of this switch is not recommended for normal use. If you turn this switch on, it is almost certain that you will get large numbers of useless warnings. The warnings that are excluded from @code{-gnatwa} are typically highly specialized warnings that are suitable for use only in code that has been specifically designed according to specialized coding rules. @end table @geindex -gnatwE (gcc) @geindex Warnings @geindex treat as error @table @asis @item @code{-gnatwE} @emph{Treat all run-time exception warnings as errors.} This switch causes warning messages regarding errors that will be raised during run-time execution to be treated as errors. @end table @geindex -gnatwf (gcc) @table @asis @item @code{-gnatwf} @emph{Activate warnings on unreferenced formals.} @geindex Formals @geindex unreferenced This switch causes a warning to be generated if a formal parameter is not referenced in the body of the subprogram. This warning can also be turned on using @code{-gnatwu}. The default is that these warnings are not generated. @end table @geindex -gnatwF (gcc) @table @asis @item @code{-gnatwF} @emph{Suppress warnings on unreferenced formals.} This switch suppresses warnings for unreferenced formal parameters. Note that the combination @code{-gnatwu} followed by @code{-gnatwF} has the effect of warning on unreferenced entities other than subprogram formals. @end table @geindex -gnatwg (gcc) @table @asis @item @code{-gnatwg} @emph{Activate warnings on unrecognized pragmas.} @geindex Pragmas @geindex unrecognized This switch causes a warning to be generated if an unrecognized pragma is encountered. Apart from issuing this warning, the pragma is ignored and has no effect. The default is that such warnings are issued (satisfying the Ada Reference Manual requirement that such warnings appear). @end table @geindex -gnatwG (gcc) @table @asis @item @code{-gnatwG} @emph{Suppress warnings on unrecognized pragmas.} This switch suppresses warnings for unrecognized pragmas. @end table @geindex -gnatw.g (gcc) @table @asis @item @code{-gnatw.g} @emph{Warnings used for GNAT sources.} This switch sets the warning categories that are used by the standard GNAT style. Currently this is equivalent to @code{-gnatwAao.q.s.CI.V.X.Z} but more warnings may be added in the future without advanced notice. @end table @geindex -gnatwh (gcc) @table @asis @item @code{-gnatwh} @emph{Activate warnings on hiding.} @geindex Hiding of Declarations This switch activates warnings on hiding declarations that are considered potentially confusing. Not all cases of hiding cause warnings; for example an overriding declaration hides an implicit declaration, which is just normal code. The default is that warnings on hiding are not generated. @end table @geindex -gnatwH (gcc) @table @asis @item @code{-gnatwH} @emph{Suppress warnings on hiding.} This switch suppresses warnings on hiding declarations. @end table @geindex -gnatw.h (gcc) @table @asis @item @code{-gnatw.h} @emph{Activate warnings on holes/gaps in records.} @geindex Record Representation (gaps) This switch activates warnings on component clauses in record representation clauses that leave holes (gaps) in the record layout. If this warning option is active, then record representation clauses should specify a contiguous layout, adding unused fill fields if needed. @end table @geindex -gnatw.H (gcc) @table @asis @item @code{-gnatw.H} @emph{Suppress warnings on holes/gaps in records.} This switch suppresses warnings on component clauses in record representation clauses that leave holes (haps) in the record layout. @end table @geindex -gnatwi (gcc) @table @asis @item @code{-gnatwi} @emph{Activate warnings on implementation units.} This switch activates warnings for a @emph{with} of an internal GNAT implementation unit, defined as any unit from the @code{Ada}, @code{Interfaces}, @code{GNAT}, or @code{System} hierarchies that is not documented in either the Ada Reference Manual or the GNAT Programmer's Reference Manual. Such units are intended only for internal implementation purposes and should not be @emph{with}ed by user programs. The default is that such warnings are generated @end table @geindex -gnatwI (gcc) @table @asis @item @code{-gnatwI} @emph{Disable warnings on implementation units.} This switch disables warnings for a @emph{with} of an internal GNAT implementation unit. @end table @geindex -gnatw.i (gcc) @table @asis @item @code{-gnatw.i} @emph{Activate warnings on overlapping actuals.} This switch enables a warning on statically detectable overlapping actuals in a subprogram call, when one of the actuals is an in-out parameter, and the types of the actuals are not by-copy types. This warning is off by default. @end table @geindex -gnatw.I (gcc) @table @asis @item @code{-gnatw.I} @emph{Disable warnings on overlapping actuals.} This switch disables warnings on overlapping actuals in a call.. @end table @geindex -gnatwj (gcc) @table @asis @item @code{-gnatwj} @emph{Activate warnings on obsolescent features (Annex J).} @geindex Features @geindex obsolescent @geindex Obsolescent features If this warning option is activated, then warnings are generated for calls to subprograms marked with @code{pragma Obsolescent} and for use of features in Annex J of the Ada Reference Manual. In the case of Annex J, not all features are flagged. In particular use of the renamed packages (like @code{Text_IO}) and use of package @code{ASCII} are not flagged, since these are very common and would generate many annoying positive warnings. The default is that such warnings are not generated. In addition to the above cases, warnings are also generated for GNAT features that have been provided in past versions but which have been superseded (typically by features in the new Ada standard). For example, @code{pragma Ravenscar} will be flagged since its function is replaced by @code{pragma Profile(Ravenscar)}, and @code{pragma Interface_Name} will be flagged since its function is replaced by @code{pragma Import}. Note that this warning option functions differently from the restriction @code{No_Obsolescent_Features} in two respects. First, the restriction applies only to annex J features. Second, the restriction does flag uses of package @code{ASCII}. @end table @geindex -gnatwJ (gcc) @table @asis @item @code{-gnatwJ} @emph{Suppress warnings on obsolescent features (Annex J).} This switch disables warnings on use of obsolescent features. @end table @geindex -gnatw.j (gcc) @table @asis @item @code{-gnatw.j} @emph{Activate warnings on late declarations of tagged type primitives.} This switch activates warnings on visible primitives added to a tagged type after deriving a private extension from it. @end table @geindex -gnatw.J (gcc) @table @asis @item @code{-gnatw.J} @emph{Suppress warnings on late declarations of tagged type primitives.} This switch suppresses warnings on visible primitives added to a tagged type after deriving a private extension from it. @end table @geindex -gnatwk (gcc) @table @asis @item @code{-gnatwk} @emph{Activate warnings on variables that could be constants.} This switch activates warnings for variables that are initialized but never modified, and then could be declared constants. The default is that such warnings are not given. @end table @geindex -gnatwK (gcc) @table @asis @item @code{-gnatwK} @emph{Suppress warnings on variables that could be constants.} This switch disables warnings on variables that could be declared constants. @end table @geindex -gnatw.k (gcc) @table @asis @item @code{-gnatw.k} @emph{Activate warnings on redefinition of names in standard.} This switch activates warnings for declarations that declare a name that is defined in package Standard. Such declarations can be confusing, especially since the names in package Standard continue to be directly visible, meaning that use visibiliy on such redeclared names does not work as expected. Names of discriminants and components in records are not included in this check. @end table @geindex -gnatwK (gcc) @table @asis @item @code{-gnatw.K} @emph{Suppress warnings on redefinition of names in standard.} This switch activates warnings for declarations that declare a name that is defined in package Standard. @end table @geindex -gnatwl (gcc) @table @asis @item @code{-gnatwl} @emph{Activate warnings for elaboration pragmas.} @geindex Elaboration @geindex warnings This switch activates warnings for possible elaboration problems, including suspicious use of @code{Elaborate} pragmas, when using the static elaboration model, and possible situations that may raise @code{Program_Error} when using the dynamic elaboration model. See the section in this guide on elaboration checking for further details. The default is that such warnings are not generated. @end table @geindex -gnatwL (gcc) @table @asis @item @code{-gnatwL} @emph{Suppress warnings for elaboration pragmas.} This switch suppresses warnings for possible elaboration problems. @end table @geindex -gnatw.l (gcc) @table @asis @item @code{-gnatw.l} @emph{List inherited aspects.} This switch causes the compiler to list inherited invariants, preconditions, and postconditions from Type_Invariant'Class, Invariant'Class, Pre'Class, and Post'Class aspects. Also list inherited subtype predicates. @end table @geindex -gnatw.L (gcc) @table @asis @item @code{-gnatw.L} @emph{Suppress listing of inherited aspects.} This switch suppresses listing of inherited aspects. @end table @geindex -gnatwm (gcc) @table @asis @item @code{-gnatwm} @emph{Activate warnings on modified but unreferenced variables.} This switch activates warnings for variables that are assigned (using an initialization value or with one or more assignment statements) but whose value is never read. The warning is suppressed for volatile variables and also for variables that are renamings of other variables or for which an address clause is given. The default is that these warnings are not given. @end table @geindex -gnatwM (gcc) @table @asis @item @code{-gnatwM} @emph{Disable warnings on modified but unreferenced variables.} This switch disables warnings for variables that are assigned or initialized, but never read. @end table @geindex -gnatw.m (gcc) @table @asis @item @code{-gnatw.m} @emph{Activate warnings on suspicious modulus values.} This switch activates warnings for modulus values that seem suspicious. The cases caught are where the size is the same as the modulus (e.g. a modulus of 7 with a size of 7 bits), and modulus values of 32 or 64 with no size clause. The guess in both cases is that 2**x was intended rather than x. In addition expressions of the form 2*x for small x generate a warning (the almost certainly accurate guess being that 2**x was intended). The default is that these warnings are given. @end table @geindex -gnatw.M (gcc) @table @asis @item @code{-gnatw.M} @emph{Disable warnings on suspicious modulus values.} This switch disables warnings for suspicious modulus values. @end table @geindex -gnatwn (gcc) @table @asis @item @code{-gnatwn} @emph{Set normal warnings mode.} This switch sets normal warning mode, in which enabled warnings are issued and treated as warnings rather than errors. This is the default mode. the switch @code{-gnatwn} can be used to cancel the effect of an explicit @code{-gnatws} or @code{-gnatwe}. It also cancels the effect of the implicit @code{-gnatwe} that is activated by the use of @code{-gnatg}. @end table @geindex -gnatw.n (gcc) @geindex Atomic Synchronization @geindex warnings @table @asis @item @code{-gnatw.n} @emph{Activate warnings on atomic synchronization.} This switch actives warnings when an access to an atomic variable requires the generation of atomic synchronization code. These warnings are off by default. @end table @geindex -gnatw.N (gcc) @table @asis @item @code{-gnatw.N} @emph{Suppress warnings on atomic synchronization.} @geindex Atomic Synchronization @geindex warnings This switch suppresses warnings when an access to an atomic variable requires the generation of atomic synchronization code. @end table @geindex -gnatwo (gcc) @geindex Address Clauses @geindex warnings @table @asis @item @code{-gnatwo} @emph{Activate warnings on address clause overlays.} This switch activates warnings for possibly unintended initialization effects of defining address clauses that cause one variable to overlap another. The default is that such warnings are generated. @end table @geindex -gnatwO (gcc) @table @asis @item @code{-gnatwO} @emph{Suppress warnings on address clause overlays.} This switch suppresses warnings on possibly unintended initialization effects of defining address clauses that cause one variable to overlap another. @end table @geindex -gnatw.o (gcc) @table @asis @item @code{-gnatw.o} @emph{Activate warnings on modified but unreferenced out parameters.} This switch activates warnings for variables that are modified by using them as actuals for a call to a procedure with an out mode formal, where the resulting assigned value is never read. It is applicable in the case where there is more than one out mode formal. If there is only one out mode formal, the warning is issued by default (controlled by -gnatwu). The warning is suppressed for volatile variables and also for variables that are renamings of other variables or for which an address clause is given. The default is that these warnings are not given. @end table @geindex -gnatw.O (gcc) @table @asis @item @code{-gnatw.O} @emph{Disable warnings on modified but unreferenced out parameters.} This switch suppresses warnings for variables that are modified by using them as actuals for a call to a procedure with an out mode formal, where the resulting assigned value is never read. @end table @geindex -gnatwp (gcc) @geindex Inlining @geindex warnings @table @asis @item @code{-gnatwp} @emph{Activate warnings on ineffective pragma Inlines.} This switch activates warnings for failure of front end inlining (activated by @code{-gnatN}) to inline a particular call. There are many reasons for not being able to inline a call, including most commonly that the call is too complex to inline. The default is that such warnings are not given. Warnings on ineffective inlining by the gcc back-end can be activated separately, using the gcc switch -Winline. @end table @geindex -gnatwP (gcc) @table @asis @item @code{-gnatwP} @emph{Suppress warnings on ineffective pragma Inlines.} This switch suppresses warnings on ineffective pragma Inlines. If the inlining mechanism cannot inline a call, it will simply ignore the request silently. @end table @geindex -gnatw.p (gcc) @geindex Parameter order @geindex warnings @table @asis @item @code{-gnatw.p} @emph{Activate warnings on parameter ordering.} This switch activates warnings for cases of suspicious parameter ordering when the list of arguments are all simple identifiers that match the names of the formals, but are in a different order. The warning is suppressed if any use of named parameter notation is used, so this is the appropriate way to suppress a false positive (and serves to emphasize that the "misordering" is deliberate). The default is that such warnings are not given. @end table @geindex -gnatw.P (gcc) @table @asis @item @code{-gnatw.P} @emph{Suppress warnings on parameter ordering.} This switch suppresses warnings on cases of suspicious parameter ordering. @end table @geindex -gnatwq (gcc) @geindex Parentheses @geindex warnings @table @asis @item @code{-gnatwq} @emph{Activate warnings on questionable missing parentheses.} This switch activates warnings for cases where parentheses are not used and the result is potential ambiguity from a readers point of view. For example (not a > b) when a and b are modular means ((not a) > b) and very likely the programmer intended (not (a > b)). Similarly (-x mod 5) means (-(x mod 5)) and quite likely ((-x) mod 5) was intended. In such situations it seems best to follow the rule of always parenthesizing to make the association clear, and this warning switch warns if such parentheses are not present. The default is that these warnings are given. @end table @geindex -gnatwQ (gcc) @table @asis @item @code{-gnatwQ} @emph{Suppress warnings on questionable missing parentheses.} This switch suppresses warnings for cases where the association is not clear and the use of parentheses is preferred. @end table @geindex -gnatw.q (gcc) @geindex Layout @geindex warnings @table @asis @item @code{-gnatw.q} @emph{Activate warnings on questionable layout of record types.} This switch activates warnings for cases where the default layout of a record type, that is to say the layout of its components in textual order of the source code, would very likely cause inefficiencies in the code generated by the compiler, both in terms of space and speed during execution. One warning is issued for each problematic component without representation clause in the nonvariant part and then in each variant recursively, if any. The purpose of these warnings is neither to prescribe an optimal layout nor to force the use of representation clauses, but rather to get rid of the most blatant inefficiencies in the layout. Therefore, the default layout is matched against the following synthetic ordered layout and the deviations are flagged on a component-by-component basis: @itemize * @item first all components or groups of components whose length is fixed and a multiple of the storage unit, @item then the remaining components whose length is fixed and not a multiple of the storage unit, @item then the remaining components whose length doesn't depend on discriminants (that is to say, with variable but uniform length for all objects), @item then all components whose length depends on discriminants, @item finally the variant part (if any), @end itemize for the nonvariant part and for each variant recursively, if any. The exact wording of the warning depends on whether the compiler is allowed to reorder the components in the record type or precluded from doing it by means of pragma @code{No_Component_Reordering}. The default is that these warnings are not given. @end table @geindex -gnatw.Q (gcc) @table @asis @item @code{-gnatw.Q} @emph{Suppress warnings on questionable layout of record types.} This switch suppresses warnings for cases where the default layout of a record type would very likely cause inefficiencies. @end table @geindex -gnatwr (gcc) @table @asis @item @code{-gnatwr} @emph{Activate warnings on redundant constructs.} This switch activates warnings for redundant constructs. The following is the current list of constructs regarded as redundant: @itemize * @item Assignment of an item to itself. @item Type conversion that converts an expression to its own type. @item Use of the attribute @code{Base} where @code{typ'Base} is the same as @code{typ}. @item Use of pragma @code{Pack} when all components are placed by a record representation clause. @item Exception handler containing only a reraise statement (raise with no operand) which has no effect. @item Use of the operator abs on an operand that is known at compile time to be non-negative @item Comparison of an object or (unary or binary) operation of boolean type to an explicit True value. @end itemize The default is that warnings for redundant constructs are not given. @end table @geindex -gnatwR (gcc) @table @asis @item @code{-gnatwR} @emph{Suppress warnings on redundant constructs.} This switch suppresses warnings for redundant constructs. @end table @geindex -gnatw.r (gcc) @table @asis @item @code{-gnatw.r} @emph{Activate warnings for object renaming function.} This switch activates warnings for an object renaming that renames a function call, which is equivalent to a constant declaration (as opposed to renaming the function itself). The default is that these warnings are given. @end table @geindex -gnatwT (gcc) @table @asis @item @code{-gnatw.R} @emph{Suppress warnings for object renaming function.} This switch suppresses warnings for object renaming function. @end table @geindex -gnatws (gcc) @table @asis @item @code{-gnatws} @emph{Suppress all warnings.} This switch completely suppresses the output of all warning messages from the GNAT front end, including both warnings that can be controlled by switches described in this section, and those that are normally given unconditionally. The effect of this suppress action can only be cancelled by a subsequent use of the switch @code{-gnatwn}. Note that switch @code{-gnatws} does not suppress warnings from the @code{gcc} back end. To suppress these back end warnings as well, use the switch @code{-w} in addition to @code{-gnatws}. Also this switch has no effect on the handling of style check messages. @end table @geindex -gnatw.s (gcc) @geindex Record Representation (component sizes) @table @asis @item @code{-gnatw.s} @emph{Activate warnings on overridden size clauses.} This switch activates warnings on component clauses in record representation clauses where the length given overrides that specified by an explicit size clause for the component type. A warning is similarly given in the array case if a specified component size overrides an explicit size clause for the array component type. @end table @geindex -gnatw.S (gcc) @table @asis @item @code{-gnatw.S} @emph{Suppress warnings on overridden size clauses.} This switch suppresses warnings on component clauses in record representation clauses that override size clauses, and similar warnings when an array component size overrides a size clause. @end table @geindex -gnatwt (gcc) @geindex Deactivated code @geindex warnings @geindex Deleted code @geindex warnings @table @asis @item @code{-gnatwt} @emph{Activate warnings for tracking of deleted conditional code.} This switch activates warnings for tracking of code in conditionals (IF and CASE statements) that is detected to be dead code which cannot be executed, and which is removed by the front end. This warning is off by default. This may be useful for detecting deactivated code in certified applications. @end table @geindex -gnatwT (gcc) @table @asis @item @code{-gnatwT} @emph{Suppress warnings for tracking of deleted conditional code.} This switch suppresses warnings for tracking of deleted conditional code. @end table @geindex -gnatw.t (gcc) @table @asis @item @code{-gnatw.t} @emph{Activate warnings on suspicious contracts.} This switch activates warnings on suspicious contracts. This includes warnings on suspicious postconditions (whether a pragma @code{Postcondition} or a @code{Post} aspect in Ada 2012) and suspicious contract cases (pragma or aspect @code{Contract_Cases}). A function postcondition or contract case is suspicious when no postcondition or contract case for this function mentions the result of the function. A procedure postcondition or contract case is suspicious when it only refers to the pre-state of the procedure, because in that case it should rather be expressed as a precondition. This switch also controls warnings on suspicious cases of expressions typically found in contracts like quantified expressions and uses of Update attribute. The default is that such warnings are generated. @end table @geindex -gnatw.T (gcc) @table @asis @item @code{-gnatw.T} @emph{Suppress warnings on suspicious contracts.} This switch suppresses warnings on suspicious contracts. @end table @geindex -gnatwu (gcc) @table @asis @item @code{-gnatwu} @emph{Activate warnings on unused entities.} This switch activates warnings to be generated for entities that are declared but not referenced, and for units that are @emph{with}ed and not referenced. In the case of packages, a warning is also generated if no entities in the package are referenced. This means that if a with'ed package is referenced but the only references are in @code{use} clauses or @code{renames} declarations, a warning is still generated. A warning is also generated for a generic package that is @emph{with}ed but never instantiated. In the case where a package or subprogram body is compiled, and there is a @emph{with} on the corresponding spec that is only referenced in the body, a warning is also generated, noting that the @emph{with} can be moved to the body. The default is that such warnings are not generated. This switch also activates warnings on unreferenced formals (it includes the effect of @code{-gnatwf}). @end table @geindex -gnatwU (gcc) @table @asis @item @code{-gnatwU} @emph{Suppress warnings on unused entities.} This switch suppresses warnings for unused entities and packages. It also turns off warnings on unreferenced formals (and thus includes the effect of @code{-gnatwF}). @end table @geindex -gnatw.u (gcc) @table @asis @item @code{-gnatw.u} @emph{Activate warnings on unordered enumeration types.} This switch causes enumeration types to be considered as conceptually unordered, unless an explicit pragma @code{Ordered} is given for the type. The effect is to generate warnings in clients that use explicit comparisons or subranges, since these constructs both treat objects of the type as ordered. (A @emph{client} is defined as a unit that is other than the unit in which the type is declared, or its body or subunits.) Please refer to the description of pragma @code{Ordered} in the @cite{GNAT Reference Manual} for further details. The default is that such warnings are not generated. @end table @geindex -gnatw.U (gcc) @table @asis @item @code{-gnatw.U} @emph{Deactivate warnings on unordered enumeration types.} This switch causes all enumeration types to be considered as ordered, so that no warnings are given for comparisons or subranges for any type. @end table @geindex -gnatwv (gcc) @geindex Unassigned variable warnings @table @asis @item @code{-gnatwv} @emph{Activate warnings on unassigned variables.} This switch activates warnings for access to variables which may not be properly initialized. The default is that such warnings are generated. @end table @geindex -gnatwV (gcc) @table @asis @item @code{-gnatwV} @emph{Suppress warnings on unassigned variables.} This switch suppresses warnings for access to variables which may not be properly initialized. For variables of a composite type, the warning can also be suppressed in Ada 2005 by using a default initialization with a box. For example, if Table is an array of records whose components are only partially uninitialized, then the following code: @example Tab : Table := (others => <>); @end example will suppress warnings on subsequent statements that access components of variable Tab. @end table @geindex -gnatw.v (gcc) @geindex bit order warnings @table @asis @item @code{-gnatw.v} @emph{Activate info messages for non-default bit order.} This switch activates messages (labeled "info", they are not warnings, just informational messages) about the effects of non-default bit-order on records to which a component clause is applied. The effect of specifying non-default bit ordering is a bit subtle (and changed with Ada 2005), so these messages, which are given by default, are useful in understanding the exact consequences of using this feature. @end table @geindex -gnatw.V (gcc) @table @asis @item @code{-gnatw.V} @emph{Suppress info messages for non-default bit order.} This switch suppresses information messages for the effects of specifying non-default bit order on record components with component clauses. @end table @geindex -gnatww (gcc) @geindex String indexing warnings @table @asis @item @code{-gnatww} @emph{Activate warnings on wrong low bound assumption.} This switch activates warnings for indexing an unconstrained string parameter with a literal or S'Length. This is a case where the code is assuming that the low bound is one, which is in general not true (for example when a slice is passed). The default is that such warnings are generated. @end table @geindex -gnatwW (gcc) @table @asis @item @code{-gnatwW} @emph{Suppress warnings on wrong low bound assumption.} This switch suppresses warnings for indexing an unconstrained string parameter with a literal or S'Length. Note that this warning can also be suppressed in a particular case by adding an assertion that the lower bound is 1, as shown in the following example: @example procedure K (S : String) is pragma Assert (S'First = 1); ... @end example @end table @geindex -gnatw.w (gcc) @geindex Warnings Off control @table @asis @item @code{-gnatw.w} @emph{Activate warnings on Warnings Off pragmas.} This switch activates warnings for use of @code{pragma Warnings (Off, entity)} where either the pragma is entirely useless (because it suppresses no warnings), or it could be replaced by @code{pragma Unreferenced} or @code{pragma Unmodified}. Also activates warnings for the case of Warnings (Off, String), where either there is no matching Warnings (On, String), or the Warnings (Off) did not suppress any warning. The default is that these warnings are not given. @end table @geindex -gnatw.W (gcc) @table @asis @item @code{-gnatw.W} @emph{Suppress warnings on unnecessary Warnings Off pragmas.} This switch suppresses warnings for use of @code{pragma Warnings (Off, ...)}. @end table @geindex -gnatwx (gcc) @geindex Export/Import pragma warnings @table @asis @item @code{-gnatwx} @emph{Activate warnings on Export/Import pragmas.} This switch activates warnings on Export/Import pragmas when the compiler detects a possible conflict between the Ada and foreign language calling sequences. For example, the use of default parameters in a convention C procedure is dubious because the C compiler cannot supply the proper default, so a warning is issued. The default is that such warnings are generated. @end table @geindex -gnatwX (gcc) @table @asis @item @code{-gnatwX} @emph{Suppress warnings on Export/Import pragmas.} This switch suppresses warnings on Export/Import pragmas. The sense of this is that you are telling the compiler that you know what you are doing in writing the pragma, and it should not complain at you. @end table @geindex -gnatwm (gcc) @table @asis @item @code{-gnatw.x} @emph{Activate warnings for No_Exception_Propagation mode.} This switch activates warnings for exception usage when pragma Restrictions (No_Exception_Propagation) is in effect. Warnings are given for implicit or explicit exception raises which are not covered by a local handler, and for exception handlers which do not cover a local raise. The default is that these warnings are given for units that contain exception handlers. @item @code{-gnatw.X} @emph{Disable warnings for No_Exception_Propagation mode.} This switch disables warnings for exception usage when pragma Restrictions (No_Exception_Propagation) is in effect. @end table @geindex -gnatwy (gcc) @geindex Ada compatibility issues warnings @table @asis @item @code{-gnatwy} @emph{Activate warnings for Ada compatibility issues.} For the most part, newer versions of Ada are upwards compatible with older versions. For example, Ada 2005 programs will almost always work when compiled as Ada 2012. However there are some exceptions (for example the fact that @code{some} is now a reserved word in Ada 2012). This switch activates several warnings to help in identifying and correcting such incompatibilities. The default is that these warnings are generated. Note that at one point Ada 2005 was called Ada 0Y, hence the choice of character. @end table @geindex -gnatwY (gcc) @geindex Ada compatibility issues warnings @table @asis @item @code{-gnatwY} @emph{Disable warnings for Ada compatibility issues.} This switch suppresses the warnings intended to help in identifying incompatibilities between Ada language versions. @end table @geindex -gnatw.y (gcc) @geindex Package spec needing body @table @asis @item @code{-gnatw.y} @emph{Activate information messages for why package spec needs body.} There are a number of cases in which a package spec needs a body. For example, the use of pragma Elaborate_Body, or the declaration of a procedure specification requiring a completion. This switch causes information messages to be output showing why a package specification requires a body. This can be useful in the case of a large package specification which is unexpectedly requiring a body. The default is that such information messages are not output. @end table @geindex -gnatw.Y (gcc) @geindex No information messages for why package spec needs body @table @asis @item @code{-gnatw.Y} @emph{Disable information messages for why package spec needs body.} This switch suppresses the output of information messages showing why a package specification needs a body. @end table @geindex -gnatwz (gcc) @geindex Unchecked_Conversion warnings @table @asis @item @code{-gnatwz} @emph{Activate warnings on unchecked conversions.} This switch activates warnings for unchecked conversions where the types are known at compile time to have different sizes. The default is that such warnings are generated. Warnings are also generated for subprogram pointers with different conventions. @end table @geindex -gnatwZ (gcc) @table @asis @item @code{-gnatwZ} @emph{Suppress warnings on unchecked conversions.} This switch suppresses warnings for unchecked conversions where the types are known at compile time to have different sizes or conventions. @end table @geindex -gnatw.z (gcc) @geindex Size/Alignment warnings @table @asis @item @code{-gnatw.z} @emph{Activate warnings for size not a multiple of alignment.} This switch activates warnings for cases of record types with specified @code{Size} and @code{Alignment} attributes where the size is not a multiple of the alignment, resulting in an object size that is greater than the specified size. The default is that such warnings are generated. @end table @geindex -gnatw.Z (gcc) @geindex Size/Alignment warnings @table @asis @item @code{-gnatw.Z} @emph{Suppress warnings for size not a multiple of alignment.} This switch suppresses warnings for cases of record types with specified @code{Size} and @code{Alignment} attributes where the size is not a multiple of the alignment, resulting in an object size that is greater than the specified size. The warning can also be suppressed by giving an explicit @code{Object_Size} value. @end table @geindex -Wunused (gcc) @table @asis @item @code{-Wunused} The warnings controlled by the @code{-gnatw} switch are generated by the front end of the compiler. The GCC back end can provide additional warnings and they are controlled by the @code{-W} switch. For example, @code{-Wunused} activates back end warnings for entities that are declared but not referenced. @end table @geindex -Wuninitialized (gcc) @table @asis @item @code{-Wuninitialized} Similarly, @code{-Wuninitialized} activates the back end warning for uninitialized variables. This switch must be used in conjunction with an optimization level greater than zero. @end table @geindex -Wstack-usage (gcc) @table @asis @item @code{-Wstack-usage=@emph{len}} Warn if the stack usage of a subprogram might be larger than @code{len} bytes. See @ref{f5,,Static Stack Usage Analysis} for details. @end table @geindex -Wall (gcc) @table @asis @item @code{-Wall} This switch enables most warnings from the GCC back end. The code generator detects a number of warning situations that are missed by the GNAT front end, and this switch can be used to activate them. The use of this switch also sets the default front end warning mode to @code{-gnatwa}, that is, most front end warnings activated as well. @end table @geindex -w (gcc) @table @asis @item @code{-w} Conversely, this switch suppresses warnings from the GCC back end. The use of this switch also sets the default front end warning mode to @code{-gnatws}, that is, front end warnings suppressed as well. @end table @geindex -Werror (gcc) @table @asis @item @code{-Werror} This switch causes warnings from the GCC back end to be treated as errors. The warning string still appears, but the warning messages are counted as errors, and prevent the generation of an object file. @end table A string of warning parameters can be used in the same parameter. For example: @example -gnatwaGe @end example will turn on all optional warnings except for unrecognized pragma warnings, and also specify that warnings should be treated as errors. When no switch @code{-gnatw} is used, this is equivalent to: @quotation @itemize * @item @code{-gnatw.a} @item @code{-gnatwB} @item @code{-gnatw.b} @item @code{-gnatwC} @item @code{-gnatw.C} @item @code{-gnatwD} @item @code{-gnatw.D} @item @code{-gnatwF} @item @code{-gnatw.F} @item @code{-gnatwg} @item @code{-gnatwH} @item @code{-gnatw.H} @item @code{-gnatwi} @item @code{-gnatwJ} @item @code{-gnatw.J} @item @code{-gnatwK} @item @code{-gnatw.K} @item @code{-gnatwL} @item @code{-gnatw.L} @item @code{-gnatwM} @item @code{-gnatw.m} @item @code{-gnatwn} @item @code{-gnatw.N} @item @code{-gnatwo} @item @code{-gnatw.O} @item @code{-gnatwP} @item @code{-gnatw.P} @item @code{-gnatwq} @item @code{-gnatw.Q} @item @code{-gnatwR} @item @code{-gnatw.R} @item @code{-gnatw.S} @item @code{-gnatwT} @item @code{-gnatw.t} @item @code{-gnatwU} @item @code{-gnatw.U} @item @code{-gnatwv} @item @code{-gnatw.v} @item @code{-gnatww} @item @code{-gnatw.W} @item @code{-gnatwx} @item @code{-gnatw.X} @item @code{-gnatwy} @item @code{-gnatw.Y} @item @code{-gnatwz} @item @code{-gnatw.z} @end itemize @end quotation @node Debugging and Assertion Control,Validity Checking,Warning Message Control,Compiler Switches @anchor{gnat_ugn/building_executable_programs_with_gnat debugging-and-assertion-control}@anchor{100}@anchor{gnat_ugn/building_executable_programs_with_gnat id16}@anchor{101} @subsection Debugging and Assertion Control @geindex -gnata (gcc) @table @asis @item @code{-gnata} @geindex Assert @geindex Debug @geindex Assertions @geindex Precondition @geindex Postcondition @geindex Type invariants @geindex Subtype predicates The @code{-gnata} option is equivalent to the following @code{Assertion_Policy} pragma: @example pragma Assertion_Policy (Check); @end example Which is a shorthand for: @example pragma Assertion_Policy (Assert => Check, Static_Predicate => Check, Dynamic_Predicate => Check, Pre => Check, Pre'Class => Check, Post => Check, Post'Class => Check, Type_Invariant => Check, Type_Invariant'Class => Check); @end example The pragmas @code{Assert} and @code{Debug} normally have no effect and are ignored. This switch, where @code{a} stands for 'assert', causes pragmas @code{Assert} and @code{Debug} to be activated. This switch also causes preconditions, postconditions, subtype predicates, and type invariants to be activated. The pragmas have the form: @example pragma Assert (<Boolean-expression> [, <static-string-expression>]) pragma Debug (<procedure call>) pragma Type_Invariant (<type-local-name>, <Boolean-expression>) pragma Predicate (<type-local-name>, <Boolean-expression>) pragma Precondition (<Boolean-expression>, <string-expression>) pragma Postcondition (<Boolean-expression>, <string-expression>) @end example The aspects have the form: @example with [Pre|Post|Type_Invariant|Dynamic_Predicate|Static_Predicate] => <Boolean-expression>; @end example The @code{Assert} pragma causes @code{Boolean-expression} to be tested. If the result is @code{True}, the pragma has no effect (other than possible side effects from evaluating the expression). If the result is @code{False}, the exception @code{Assert_Failure} declared in the package @code{System.Assertions} is raised (passing @code{static-string-expression}, if present, as the message associated with the exception). If no string expression is given, the default is a string containing the file name and line number of the pragma. The @code{Debug} pragma causes @code{procedure} to be called. Note that @code{pragma Debug} may appear within a declaration sequence, allowing debugging procedures to be called between declarations. For the aspect specification, the @code{Boolean-expression} is evaluated. If the result is @code{True}, the aspect has no effect. If the result is @code{False}, the exception @code{Assert_Failure} is raised. @end table @node Validity Checking,Style Checking,Debugging and Assertion Control,Compiler Switches @anchor{gnat_ugn/building_executable_programs_with_gnat validity-checking}@anchor{f6}@anchor{gnat_ugn/building_executable_programs_with_gnat id17}@anchor{102} @subsection Validity Checking @geindex Validity Checking The Ada Reference Manual defines the concept of invalid values (see RM 13.9.1). The primary source of invalid values is uninitialized variables. A scalar variable that is left uninitialized may contain an invalid value; the concept of invalid does not apply to access or composite types. It is an error to read an invalid value, but the RM does not require run-time checks to detect such errors, except for some minimal checking to prevent erroneous execution (i.e. unpredictable behavior). This corresponds to the @code{-gnatVd} switch below, which is the default. For example, by default, if the expression of a case statement is invalid, it will raise Constraint_Error rather than causing a wild jump, and if an array index on the left-hand side of an assignment is invalid, it will raise Constraint_Error rather than overwriting an arbitrary memory location. The @code{-gnatVa} may be used to enable additional validity checks, which are not required by the RM. These checks are often very expensive (which is why the RM does not require them). These checks are useful in tracking down uninitialized variables, but they are not usually recommended for production builds, and in particular we do not recommend using these extra validity checking options in combination with optimization, since this can confuse the optimizer. If performance is a consideration, leading to the need to optimize, then the validity checking options should not be used. The other @code{-gnatV@emph{x}} switches below allow finer-grained control; you can enable whichever validity checks you desire. However, for most debugging purposes, @code{-gnatVa} is sufficient, and the default @code{-gnatVd} (i.e. standard Ada behavior) is usually sufficient for non-debugging use. The @code{-gnatB} switch tells the compiler to assume that all values are valid (that is, within their declared subtype range) except in the context of a use of the Valid attribute. This means the compiler can generate more efficient code, since the range of values is better known at compile time. However, an uninitialized variable can cause wild jumps and memory corruption in this mode. The @code{-gnatV@emph{x}} switch allows control over the validity checking mode as described below. The @code{x} argument is a string of letters that indicate validity checks that are performed or not performed in addition to the default checks required by Ada as described above. @geindex -gnatVa (gcc) @table @asis @item @code{-gnatVa} @emph{All validity checks.} All validity checks are turned on. That is, @code{-gnatVa} is equivalent to @code{gnatVcdfimorst}. @end table @geindex -gnatVc (gcc) @table @asis @item @code{-gnatVc} @emph{Validity checks for copies.} The right hand side of assignments, and the initializing values of object declarations are validity checked. @end table @geindex -gnatVd (gcc) @table @asis @item @code{-gnatVd} @emph{Default (RM) validity checks.} Some validity checks are done by default following normal Ada semantics (RM 13.9.1 (9-11)). A check is done in case statements that the expression is within the range of the subtype. If it is not, Constraint_Error is raised. For assignments to array components, a check is done that the expression used as index is within the range. If it is not, Constraint_Error is raised. Both these validity checks may be turned off using switch @code{-gnatVD}. They are turned on by default. If @code{-gnatVD} is specified, a subsequent switch @code{-gnatVd} will leave the checks turned on. Switch @code{-gnatVD} should be used only if you are sure that all such expressions have valid values. If you use this switch and invalid values are present, then the program is erroneous, and wild jumps or memory overwriting may occur. @end table @geindex -gnatVe (gcc) @table @asis @item @code{-gnatVe} @emph{Validity checks for elementary components.} In the absence of this switch, assignments to record or array components are not validity checked, even if validity checks for assignments generally (@code{-gnatVc}) are turned on. In Ada, assignment of composite values do not require valid data, but assignment of individual components does. So for example, there is a difference between copying the elements of an array with a slice assignment, compared to assigning element by element in a loop. This switch allows you to turn off validity checking for components, even when they are assigned component by component. @end table @geindex -gnatVf (gcc) @table @asis @item @code{-gnatVf} @emph{Validity checks for floating-point values.} In the absence of this switch, validity checking occurs only for discrete values. If @code{-gnatVf} is specified, then validity checking also applies for floating-point values, and NaNs and infinities are considered invalid, as well as out of range values for constrained types. Note that this means that standard IEEE infinity mode is not allowed. The exact contexts in which floating-point values are checked depends on the setting of other options. For example, @code{-gnatVif} or @code{-gnatVfi} (the order does not matter) specifies that floating-point parameters of mode @code{in} should be validity checked. @end table @geindex -gnatVi (gcc) @table @asis @item @code{-gnatVi} @emph{Validity checks for `@w{`}in`@w{`} mode parameters.} Arguments for parameters of mode @code{in} are validity checked in function and procedure calls at the point of call. @end table @geindex -gnatVm (gcc) @table @asis @item @code{-gnatVm} @emph{Validity checks for `@w{`}in out`@w{`} mode parameters.} Arguments for parameters of mode @code{in out} are validity checked in procedure calls at the point of call. The @code{'m'} here stands for modify, since this concerns parameters that can be modified by the call. Note that there is no specific option to test @code{out} parameters, but any reference within the subprogram will be tested in the usual manner, and if an invalid value is copied back, any reference to it will be subject to validity checking. @end table @geindex -gnatVn (gcc) @table @asis @item @code{-gnatVn} @emph{No validity checks.} This switch turns off all validity checking, including the default checking for case statements and left hand side subscripts. Note that the use of the switch @code{-gnatp} suppresses all run-time checks, including validity checks, and thus implies @code{-gnatVn}. When this switch is used, it cancels any other @code{-gnatV} previously issued. @end table @geindex -gnatVo (gcc) @table @asis @item @code{-gnatVo} @emph{Validity checks for operator and attribute operands.} Arguments for predefined operators and attributes are validity checked. This includes all operators in package @code{Standard}, the shift operators defined as intrinsic in package @code{Interfaces} and operands for attributes such as @code{Pos}. Checks are also made on individual component values for composite comparisons, and on the expressions in type conversions and qualified expressions. Checks are also made on explicit ranges using @code{..} (e.g., slices, loops etc). @end table @geindex -gnatVp (gcc) @table @asis @item @code{-gnatVp} @emph{Validity checks for parameters.} This controls the treatment of parameters within a subprogram (as opposed to @code{-gnatVi} and @code{-gnatVm} which control validity testing of parameters on a call. If either of these call options is used, then normally an assumption is made within a subprogram that the input arguments have been validity checking at the point of call, and do not need checking again within a subprogram). If @code{-gnatVp} is set, then this assumption is not made, and parameters are not assumed to be valid, so their validity will be checked (or rechecked) within the subprogram. @end table @geindex -gnatVr (gcc) @table @asis @item @code{-gnatVr} @emph{Validity checks for function returns.} The expression in @code{return} statements in functions is validity checked. @end table @geindex -gnatVs (gcc) @table @asis @item @code{-gnatVs} @emph{Validity checks for subscripts.} All subscripts expressions are checked for validity, whether they appear on the right side or left side (in default mode only left side subscripts are validity checked). @end table @geindex -gnatVt (gcc) @table @asis @item @code{-gnatVt} @emph{Validity checks for tests.} Expressions used as conditions in @code{if}, @code{while} or @code{exit} statements are checked, as well as guard expressions in entry calls. @end table The @code{-gnatV} switch may be followed by a string of letters to turn on a series of validity checking options. For example, @code{-gnatVcr} specifies that in addition to the default validity checking, copies and function return expressions are to be validity checked. In order to make it easier to specify the desired combination of effects, the upper case letters @code{CDFIMORST} may be used to turn off the corresponding lower case option. Thus @code{-gnatVaM} turns on all validity checking options except for checking of @code{in out} parameters. The specification of additional validity checking generates extra code (and in the case of @code{-gnatVa} the code expansion can be substantial). However, these additional checks can be very useful in detecting uninitialized variables, incorrect use of unchecked conversion, and other errors leading to invalid values. The use of pragma @code{Initialize_Scalars} is useful in conjunction with the extra validity checking, since this ensures that wherever possible uninitialized variables have invalid values. See also the pragma @code{Validity_Checks} which allows modification of the validity checking mode at the program source level, and also allows for temporary disabling of validity checks. @node Style Checking,Run-Time Checks,Validity Checking,Compiler Switches @anchor{gnat_ugn/building_executable_programs_with_gnat id18}@anchor{103}@anchor{gnat_ugn/building_executable_programs_with_gnat style-checking}@anchor{fb} @subsection Style Checking @geindex Style checking @geindex -gnaty (gcc) The @code{-gnatyx} switch causes the compiler to enforce specified style rules. A limited set of style rules has been used in writing the GNAT sources themselves. This switch allows user programs to activate all or some of these checks. If the source program fails a specified style check, an appropriate message is given, preceded by the character sequence '(style)'. This message does not prevent successful compilation (unless the @code{-gnatwe} switch is used). Note that this is by no means intended to be a general facility for checking arbitrary coding standards. It is simply an embedding of the style rules we have chosen for the GNAT sources. If you are starting a project which does not have established style standards, you may find it useful to adopt the entire set of GNAT coding standards, or some subset of them. The string @code{x} is a sequence of letters or digits indicating the particular style checks to be performed. The following checks are defined: @geindex -gnaty[0-9] (gcc) @table @asis @item @code{-gnaty0} @emph{Specify indentation level.} If a digit from 1-9 appears in the string after @code{-gnaty} then proper indentation is checked, with the digit indicating the indentation level required. A value of zero turns off this style check. The general style of required indentation is as specified by the examples in the Ada Reference Manual. Full line comments must be aligned with the @code{--} starting on a column that is a multiple of the alignment level, or they may be aligned the same way as the following non-blank line (this is useful when full line comments appear in the middle of a statement, or they may be aligned with the source line on the previous non-blank line. @end table @geindex -gnatya (gcc) @table @asis @item @code{-gnatya} @emph{Check attribute casing.} Attribute names, including the case of keywords such as @code{digits} used as attributes names, must be written in mixed case, that is, the initial letter and any letter following an underscore must be uppercase. All other letters must be lowercase. @end table @geindex -gnatyA (gcc) @table @asis @item @code{-gnatyA} @emph{Use of array index numbers in array attributes.} When using the array attributes First, Last, Range, or Length, the index number must be omitted for one-dimensional arrays and is required for multi-dimensional arrays. @end table @geindex -gnatyb (gcc) @table @asis @item @code{-gnatyb} @emph{Blanks not allowed at statement end.} Trailing blanks are not allowed at the end of statements. The purpose of this rule, together with h (no horizontal tabs), is to enforce a canonical format for the use of blanks to separate source tokens. @end table @geindex -gnatyB (gcc) @table @asis @item @code{-gnatyB} @emph{Check Boolean operators.} The use of AND/OR operators is not permitted except in the cases of modular operands, array operands, and simple stand-alone boolean variables or boolean constants. In all other cases @code{and then}/@cite{or else} are required. @end table @geindex -gnatyc (gcc) @table @asis @item @code{-gnatyc} @emph{Check comments, double space.} Comments must meet the following set of rules: @itemize * @item The @code{--} that starts the column must either start in column one, or else at least one blank must precede this sequence. @item Comments that follow other tokens on a line must have at least one blank following the @code{--} at the start of the comment. @item Full line comments must have at least two blanks following the @code{--} that starts the comment, with the following exceptions. @item A line consisting only of the @code{--} characters, possibly preceded by blanks is permitted. @item A comment starting with @code{--x} where @code{x} is a special character is permitted. This allows proper processing of the output from specialized tools such as @code{gnatprep} (where @code{--!} is used) and in earlier versions of the SPARK annotation language (where @code{--#} is used). For the purposes of this rule, a special character is defined as being in one of the ASCII ranges @code{16#21#...16#2F#} or @code{16#3A#...16#3F#}. Note that this usage is not permitted in GNAT implementation units (i.e., when @code{-gnatg} is used). @item A line consisting entirely of minus signs, possibly preceded by blanks, is permitted. This allows the construction of box comments where lines of minus signs are used to form the top and bottom of the box. @item A comment that starts and ends with @code{--} is permitted as long as at least one blank follows the initial @code{--}. Together with the preceding rule, this allows the construction of box comments, as shown in the following example: @example --------------------------- -- This is a box comment -- -- with two text lines. -- --------------------------- @end example @end itemize @end table @geindex -gnatyC (gcc) @table @asis @item @code{-gnatyC} @emph{Check comments, single space.} This is identical to @code{c} except that only one space is required following the @code{--} of a comment instead of two. @end table @geindex -gnatyd (gcc) @table @asis @item @code{-gnatyd} @emph{Check no DOS line terminators present.} All lines must be terminated by a single ASCII.LF character (in particular the DOS line terminator sequence CR/LF is not allowed). @end table @geindex -gnatye (gcc) @table @asis @item @code{-gnatye} @emph{Check end/exit labels.} Optional labels on @code{end} statements ending subprograms and on @code{exit} statements exiting named loops, are required to be present. @end table @geindex -gnatyf (gcc) @table @asis @item @code{-gnatyf} @emph{No form feeds or vertical tabs.} Neither form feeds nor vertical tab characters are permitted in the source text. @end table @geindex -gnatyg (gcc) @table @asis @item @code{-gnatyg} @emph{GNAT style mode.} The set of style check switches is set to match that used by the GNAT sources. This may be useful when developing code that is eventually intended to be incorporated into GNAT. Currently this is equivalent to @code{-gnatwydISux}) but additional style switches may be added to this set in the future without advance notice. @end table @geindex -gnatyh (gcc) @table @asis @item @code{-gnatyh} @emph{No horizontal tabs.} Horizontal tab characters are not permitted in the source text. Together with the b (no blanks at end of line) check, this enforces a canonical form for the use of blanks to separate source tokens. @end table @geindex -gnatyi (gcc) @table @asis @item @code{-gnatyi} @emph{Check if-then layout.} The keyword @code{then} must appear either on the same line as corresponding @code{if}, or on a line on its own, lined up under the @code{if}. @end table @geindex -gnatyI (gcc) @table @asis @item @code{-gnatyI} @emph{check mode IN keywords.} Mode @code{in} (the default mode) is not allowed to be given explicitly. @code{in out} is fine, but not @code{in} on its own. @end table @geindex -gnatyk (gcc) @table @asis @item @code{-gnatyk} @emph{Check keyword casing.} All keywords must be in lower case (with the exception of keywords such as @code{digits} used as attribute names to which this check does not apply). @end table @geindex -gnatyl (gcc) @table @asis @item @code{-gnatyl} @emph{Check layout.} Layout of statement and declaration constructs must follow the recommendations in the Ada Reference Manual, as indicated by the form of the syntax rules. For example an @code{else} keyword must be lined up with the corresponding @code{if} keyword. There are two respects in which the style rule enforced by this check option are more liberal than those in the Ada Reference Manual. First in the case of record declarations, it is permissible to put the @code{record} keyword on the same line as the @code{type} keyword, and then the @code{end} in @code{end record} must line up under @code{type}. This is also permitted when the type declaration is split on two lines. For example, any of the following three layouts is acceptable: @example type q is record a : integer; b : integer; end record; type q is record a : integer; b : integer; end record; type q is record a : integer; b : integer; end record; @end example Second, in the case of a block statement, a permitted alternative is to put the block label on the same line as the @code{declare} or @code{begin} keyword, and then line the @code{end} keyword up under the block label. For example both the following are permitted: @example Block : declare A : Integer := 3; begin Proc (A, A); end Block; Block : declare A : Integer := 3; begin Proc (A, A); end Block; @end example The same alternative format is allowed for loops. For example, both of the following are permitted: @example Clear : while J < 10 loop A (J) := 0; end loop Clear; Clear : while J < 10 loop A (J) := 0; end loop Clear; @end example @end table @geindex -gnatyLnnn (gcc) @table @asis @item @code{-gnatyL} @emph{Set maximum nesting level.} The maximum level of nesting of constructs (including subprograms, loops, blocks, packages, and conditionals) may not exceed the given value @emph{nnn}. A value of zero disconnects this style check. @end table @geindex -gnatym (gcc) @table @asis @item @code{-gnatym} @emph{Check maximum line length.} The length of source lines must not exceed 79 characters, including any trailing blanks. The value of 79 allows convenient display on an 80 character wide device or window, allowing for possible special treatment of 80 character lines. Note that this count is of characters in the source text. This means that a tab character counts as one character in this count and a wide character sequence counts as a single character (however many bytes are needed in the encoding). @end table @geindex -gnatyMnnn (gcc) @table @asis @item @code{-gnatyM} @emph{Set maximum line length.} The length of lines must not exceed the given value @emph{nnn}. The maximum value that can be specified is 32767. If neither style option for setting the line length is used, then the default is 255. This also controls the maximum length of lexical elements, where the only restriction is that they must fit on a single line. @end table @geindex -gnatyn (gcc) @table @asis @item @code{-gnatyn} @emph{Check casing of entities in Standard.} Any identifier from Standard must be cased to match the presentation in the Ada Reference Manual (for example, @code{Integer} and @code{ASCII.NUL}). @end table @geindex -gnatyN (gcc) @table @asis @item @code{-gnatyN} @emph{Turn off all style checks.} All style check options are turned off. @end table @geindex -gnatyo (gcc) @table @asis @item @code{-gnatyo} @emph{Check order of subprogram bodies.} All subprogram bodies in a given scope (e.g., a package body) must be in alphabetical order. The ordering rule uses normal Ada rules for comparing strings, ignoring casing of letters, except that if there is a trailing numeric suffix, then the value of this suffix is used in the ordering (e.g., Junk2 comes before Junk10). @end table @geindex -gnatyO (gcc) @table @asis @item @code{-gnatyO} @emph{Check that overriding subprograms are explicitly marked as such.} This applies to all subprograms of a derived type that override a primitive operation of the type, for both tagged and untagged types. In particular, the declaration of a primitive operation of a type extension that overrides an inherited operation must carry an overriding indicator. Another case is the declaration of a function that overrides a predefined operator (such as an equality operator). @end table @geindex -gnatyp (gcc) @table @asis @item @code{-gnatyp} @emph{Check pragma casing.} Pragma names must be written in mixed case, that is, the initial letter and any letter following an underscore must be uppercase. All other letters must be lowercase. An exception is that SPARK_Mode is allowed as an alternative for Spark_Mode. @end table @geindex -gnatyr (gcc) @table @asis @item @code{-gnatyr} @emph{Check references.} All identifier references must be cased in the same way as the corresponding declaration. No specific casing style is imposed on identifiers. The only requirement is for consistency of references with declarations. @end table @geindex -gnatys (gcc) @table @asis @item @code{-gnatys} @emph{Check separate specs.} Separate declarations ('specs') are required for subprograms (a body is not allowed to serve as its own declaration). The only exception is that parameterless library level procedures are not required to have a separate declaration. This exception covers the most frequent form of main program procedures. @end table @geindex -gnatyS (gcc) @table @asis @item @code{-gnatyS} @emph{Check no statements after then/else.} No statements are allowed on the same line as a @code{then} or @code{else} keyword following the keyword in an @code{if} statement. @code{or else} and @code{and then} are not affected, and a special exception allows a pragma to appear after @code{else}. @end table @geindex -gnatyt (gcc) @table @asis @item @code{-gnatyt} @emph{Check token spacing.} The following token spacing rules are enforced: @itemize * @item The keywords @code{abs} and @code{not} must be followed by a space. @item The token @code{=>} must be surrounded by spaces. @item The token @code{<>} must be preceded by a space or a left parenthesis. @item Binary operators other than @code{**} must be surrounded by spaces. There is no restriction on the layout of the @code{**} binary operator. @item Colon must be surrounded by spaces. @item Colon-equal (assignment, initialization) must be surrounded by spaces. @item Comma must be the first non-blank character on the line, or be immediately preceded by a non-blank character, and must be followed by a space. @item If the token preceding a left parenthesis ends with a letter or digit, then a space must separate the two tokens. @item If the token following a right parenthesis starts with a letter or digit, then a space must separate the two tokens. @item A right parenthesis must either be the first non-blank character on a line, or it must be preceded by a non-blank character. @item A semicolon must not be preceded by a space, and must not be followed by a non-blank character. @item A unary plus or minus may not be followed by a space. @item A vertical bar must be surrounded by spaces. @end itemize Exactly one blank (and no other white space) must appear between a @code{not} token and a following @code{in} token. @end table @geindex -gnatyu (gcc) @table @asis @item @code{-gnatyu} @emph{Check unnecessary blank lines.} Unnecessary blank lines are not allowed. A blank line is considered unnecessary if it appears at the end of the file, or if more than one blank line occurs in sequence. @end table @geindex -gnatyx (gcc) @table @asis @item @code{-gnatyx} @emph{Check extra parentheses.}