@set gprconfig GPRconfig @c ------ projects.texi @c Copyright (C) 2002-2012, Free Software Foundation, Inc. @c This file is shared between the GNAT user's guide and gprbuild. It is not @c compilable on its own, you should instead compile the other two manuals. @c For that reason, there is no toplevel @menu @c --------------------------------------------- @node GNAT Project Manager @chapter GNAT Project Manager @c --------------------------------------------- @noindent @menu * Introduction:: * Building With Projects:: * Organizing Projects into Subsystems:: * Scenarios in Projects:: * Library Projects:: * Project Extension:: * Aggregate Projects:: * Aggregate Library Projects:: * Project File Reference:: @end menu @c --------------------------------------------- @node Introduction @section Introduction @c --------------------------------------------- @noindent This chapter describes GNAT's @emph{Project Manager}, a facility that allows you to manage complex builds involving a number of source files, directories, and options for different system configurations. In particular, project files allow you to specify: @itemize @bullet @item The directory or set of directories containing the source files, and/or the names of the specific source files themselves @item The directory in which the compiler's output (@file{ALI} files, object files, tree files, etc.) is to be placed @item The directory in which the executable programs are to be placed @item Switch settings for any of the project-enabled tools; you can apply these settings either globally or to individual compilation units. @item The source files containing the main subprogram(s) to be built @item The source programming language(s) @item Source file naming conventions; you can specify these either globally or for individual compilation units (@pxref{Naming Schemes}). @item Change any of the above settings depending on external values, thus enabling the reuse of the projects in various @b{scenarios} (@pxref{Scenarios in Projects}). @item Automatically build libraries as part of the build process (@pxref{Library Projects}). @end itemize @noindent Project files are written in a syntax close to that of Ada, using familiar notions such as packages, context clauses, declarations, default values, assignments, and inheritance (@pxref{Project File Reference}). Project files can be built hierarchically from other project files, simplifying complex system integration and project reuse (@pxref{Organizing Projects into Subsystems}). @itemize @bullet @item One project can import other projects containing needed source files. More generally, the Project Manager lets you structure large development efforts into hierarchical subsystems, where build decisions are delegated to the subsystem level, and thus different compilation environments (switch settings) used for different subsystems. @item You can organize GNAT projects in a hierarchy: a child project can extend a parent project, inheriting the parent's source files and optionally overriding any of them with alternative versions (@pxref{Project Extension}). @end itemize @noindent Several tools support project files, generally in addition to specifying the information on the command line itself). They share common switches to control the loading of the project (in particular @option{^-P^/PROJECT_FILE=^@emph{projectfile}} and @option{^-X^/EXTERNAL_REFERENCE=^@emph{vbl}=@emph{value}}). @xref{Switches Related to Project Files}. The Project Manager supports a wide range of development strategies, for systems of all sizes. Here are some typical practices that are easily handled: @itemize @bullet @item Using a common set of source files and generating object files in different directories via different switch settings. It can be used for instance, for generating separate sets of object files for debugging and for production. @item Using a mostly-shared set of source files with different versions of some units or subunits. It can be used for instance, for grouping and hiding @end itemize @noindent all OS dependencies in a small number of implementation units. Project files can be used to achieve some of the effects of a source versioning system (for example, defining separate projects for the different sets of sources that comprise different releases) but the Project Manager is independent of any source configuration management tool that might be used by the developers. The various sections below introduce the different concepts related to projects. Each section starts with examples and use cases, and then goes into the details of related project file capabilities. @c --------------------------------------------- @node Building With Projects @section Building With Projects @c --------------------------------------------- @noindent In its simplest form, a unique project is used to build a single executable. This section concentrates on such a simple setup. Later sections will extend this basic model to more complex setups. The following concepts are the foundation of project files, and will be further detailed later in this documentation. They are summarized here as a reference. @table @asis @item @b{Project file}: A text file using an Ada-like syntax, generally using the @file{.gpr} extension. It defines build-related characteristics of an application. The characteristics include the list of sources, the location of those sources, the location for the generated object files, the name of the main program, and the options for the various tools involved in the build process. @item @b{Project attribute}: A specific project characteristic is defined by an attribute clause. Its value is a string or a sequence of strings. All settings in a project are defined through a list of predefined attributes with precise semantics. @xref{Attributes}. @item @b{Package in a project}: Global attributes are defined at the top level of a project. Attributes affecting specific tools are grouped in a package whose name is related to tool's function. The most common packages are @code{Builder}, @code{Compiler}, @code{Binder}, and @code{Linker}. @xref{Packages}. @item @b{Project variables}: In addition to attributes, a project can use variables to store intermediate values and avoid duplication in complex expressions. It can be initialized with a value coming from the environment. A frequent use of variables is to define scenarios. @xref{External Values}, @xref{Scenarios in Projects}, and @xref{Variables}. @item @b{Source files} and @b{source directories}: A source file is associated with a language through a naming convention. For instance, @code{foo.c} is typically the name of a C source file; @code{bar.ads} or @code{bar.1.ada} are two common naming conventions for a file containing an Ada spec. A compilation unit is often composed of a main source file and potentially several auxiliary ones, such as header files in C. The naming conventions can be user defined @xref{Naming Schemes}, and will drive the builder to call the appropriate compiler for the given source file. Source files are searched for in the source directories associated with the project through the @b{Source_Dirs} attribute. By default, all the files (in these source directories) following the naming conventions associated with the declared languages are considered to be part of the project. It is also possible to limit the list of source files using the @b{Source_Files} or @b{Source_List_File} attributes. Note that those last two attributes only accept basenames with no directory information. @item @b{Object files} and @b{object directory}: An object file is an intermediate file produced by the compiler from a compilation unit. It is used by post-compilation tools to produce final executables or libraries. Object files produced in the context of a given project are stored in a single directory that can be specified by the @b{Object_Dir} attribute. In order to store objects in two or more object directories, the system must be split into distinct subsystems with their own project file. @end table The following subsections introduce gradually all the attributes of interest for simple build needs. Here is the simple setup that will be used in the following examples. The Ada source files @file{pack.ads}, @file{pack.adb}, and @file{proc.adb} are in the @file{common/} directory. The file @file{proc.adb} contains an Ada main subprogram @code{Proc} that @code{with}s package @code{Pack}. We want to compile these source files with the switch @option{-O2}, and put the resulting files in the directory @file{obj/}. @smallexample @group ^common/^[COMMON]^ pack.ads pack.adb proc.adb @end group @group ^common/release/^[COMMON.RELEASE]^ proc.ali, proc.o pack.ali, pack.o @end group @end smallexample @noindent Our project is to be called @emph{Build}. The name of the file is the name of the project (case-insensitive) with the @file{.gpr} extension, therefore the project file name is @file{build.gpr}. This is not mandatory, but a warning is issued when this convention is not followed. This is a very simple example, and as stated above, a single project file is enough for it. We will thus create a new file, that for now should contain the following code: @smallexample @b{project} Build @b{is} @b{end} Build; @end smallexample @menu * Source Files and Directories:: * Object and Exec Directory:: * Main Subprograms:: * Tools Options in Project Files:: * Compiling with Project Files:: * Executable File Names:: * Avoid Duplication With Variables:: * Naming Schemes:: @end menu @c --------------------------------------------- @node Source Files and Directories @subsection Source Files and Directories @c --------------------------------------------- @noindent When you create a new project, the first thing to describe is how to find the corresponding source files. This is the only settings that are needed by all the tools that will use this project (builder, compiler, binder and linker for the compilation, IDEs to edit the source files,@dots{}). @cindex Source directories First step is to declare the source directories, which are the directories to be searched to find source files. In the case of the example, the @file{common} directory is the only source directory. @cindex @code{Source_Dirs} There are several ways of defining source directories: @itemize @bullet @item When the attribute @b{Source_Dirs} is not used, a project contains a single source directory which is the one where the project file itself resides. In our example, if @file{build.gpr} is placed in the @file{common} directory, the project has the needed implicit source directory. @item The attribute @b{Source_Dirs} can be set to a list of path names, one for each of the source directories. Such paths can either be absolute names (for instance @file{"/usr/local/common/"} on UNIX), or relative to the directory in which the project file resides (for instance "." if @file{build.gpr} is inside @file{common/}, or "common" if it is one level up). Each of the source directories must exist and be readable. @cindex portability The syntax for directories is platform specific. For portability, however, the project manager will always properly translate UNIX-like path names to the native format of specific platform. For instance, when the same project file is to be used both on Unix and Windows, "/" should be used as the directory separator rather than "\". @item The attribute @b{Source_Dirs} can automatically include subdirectories using a special syntax inspired by some UNIX shells. If any of the path in the list ends with @emph{"**"}, then that path and all its subdirectories (recursively) are included in the list of source directories. For instance, @file{**} and @file{./**} represent the complete directory tree rooted at ".". @cindex Source directories, recursive @cindex @code{Excluded_Source_Dirs} When using that construct, it can sometimes be convenient to also use the attribute @b{Excluded_Source_Dirs}, which is also a list of paths. Each entry specifies a directory whose immediate content, not including subdirs, is to be excluded. It is also possible to exclude a complete directory subtree using the "**" notation. @cindex @code{Ignore_Source_Sub_Dirs} It is often desirable to remove, from the source directories, directory subtrees rooted at some subdirectories. An example is the subdirectories created by a Version Control System such as Subversion that creates directory subtrees .svn/**. To do that, attribute @b{Ignore_Source_Sub_Dirs} can be used. It specifies the list of simple file names for the root of these undesirable directory subtrees. @end itemize @noindent When applied to the simple example, and because we generally prefer to have the project file at the toplevel directory rather than mixed with the sources, we will create the following file @smallexample build.gpr @b{project} Build @b{is} @b{for} Source_Dirs @b{use} ("common"); -- <<<< @b{end} Build; @end smallexample @noindent Once source directories have been specified, one may need to indicate source files of interest. By default, all source files present in the source directories are considered by the project manager. When this is not desired, it is possible to specify the list of sources to consider explicitly. In such a case, only source file base names are indicated and not their absolute or relative path names. The project manager is in charge of locating the specified source files in the specified source directories. @itemize @bullet @item By default, the project manager search for all source files of all specified languages in all the source directories. Since the project manager was initially developed for Ada environments, the default language is usually Ada and the above project file is complete: it defines without ambiguity the sources composing the project: that is to say, all the sources in subdirectory "common" for the default language (Ada) using the default naming convention. @cindex @code{Languages} However, when compiling a multi-language application, or a pure C application, the project manager must be told which languages are of interest, which is done by setting the @b{Languages} attribute to a list of strings, each of which is the name of a language. Tools like @command{gnatmake} only know about Ada, while other tools like @command{gprbuild} know about many more languages such as C, C++, Fortran, assembly and others can be added dynamically. @cindex Naming scheme Even when using only Ada, the default naming might not be suitable. Indeed, how does the project manager recognizes an "Ada file" from any other file? Project files can describe the naming scheme used for source files, and override the default (@pxref{Naming Schemes}). The default is the standard GNAT extension (@file{.adb} for bodies and @file{.ads} for specs), which is what is used in our example, explaining why no naming scheme is explicitly specified. @xref{Naming Schemes}. @item @code{Source Files} @cindex @code{Source_Files} In some cases, source directories might contain files that should not be included in a project. One can specify the explicit list of file names to be considered through the @b{Source_Files} attribute. When this attribute is defined, instead of looking at every file in the source directories, the project manager takes only those names into consideration reports errors if they cannot be found in the source directories or does not correspond to the naming scheme. @item For various reasons, it is sometimes useful to have a project with no sources (most of the time because the attributes defined in the project file will be reused in other projects, as explained in @pxref{Organizing Projects into Subsystems}. To do this, the attribute @emph{Source_Files} is set to the empty list, i.e. @code{()}. Alternatively, @emph{Source_Dirs} can be set to the empty list, with the same result. @item @code{Source_List_File} @cindex @code{Source_List_File} If there is a great number of files, it might be more convenient to use the attribute @b{Source_List_File}, which specifies the full path of a file. This file must contain a list of source file names (one per line, no directory information) that are searched as if they had been defined through @emph{Source_Files}. Such a file can easily be created through external tools. A warning is issued if both attributes @code{Source_Files} and @code{Source_List_File} are given explicit values. In this case, the attribute @code{Source_Files} prevails. @item @code{Excluded_Source_Files} @cindex @code{Excluded_Source_Files} @cindex @code{Locally_Removed_Files} @cindex @code{Excluded_Source_List_File} Specifying an explicit list of files is not always convenient.It might be more convenient to use the default search rules with specific exceptions. This can be done thanks to the attribute @b{Excluded_Source_Files} (or its synonym @b{Locally_Removed_Files}). Its value is the list of file names that should not be taken into account. This attribute is often used when extending a project, @xref{Project Extension}. A similar attribute @b{Excluded_Source_List_File} plays the same role but takes the name of file containing file names similarly to @code{Source_List_File}. @end itemize @noindent In most simple cases, such as the above example, the default source file search behavior provides the expected result, and we do not need to add anything after setting @code{Source_Dirs}. The project manager automatically finds @file{pack.ads}, @file{pack.adb} and @file{proc.adb} as source files of the project. Note that it is considered an error for a project file to have no sources attached to it unless explicitly declared as mentioned above. If the order of the source directories is known statically, that is if @code{"**"} is not used in the string list @code{Source_Dirs}, then there may be several files with the same source file name sitting in different directories of the project. In this case, only the file in the first directory is considered as a source of the project and the others are hidden. If @code{"**"} is used in the string list @code{Source_Dirs}, it is an error to have several files with the same source file name in the same directory @code{"**"} subtree, since there would be an ambiguity as to which one should be used. However, two files with the same source file name may exist in two single directories or directory subtrees. In this case, the one in the first directory or directory subtree is a source of the project. @c --------------------------------------------- @node Object and Exec Directory @subsection Object and Exec Directory @c --------------------------------------------- @noindent The next step when writing a project is to indicate where the compiler should put the object files. In fact, the compiler and other tools might create several different kind of files (for GNAT, there is the object file and the ALI file for instance). One of the important concepts in projects is that most tools may consider source directories as read-only and do not attempt to create new or temporary files there. Instead, all files are created in the object directory. It is of course not true for project-aware IDEs, whose purpose it is to create the source files. @cindex @code{Object_Dir} The object directory is specified through the @b{Object_Dir} attribute. Its value is the path to the object directory, either absolute or relative to the directory containing the project file. This directory must already exist and be readable and writable, although some tools have a switch to create the directory if needed (See the switch @code{-p} for @command{gnatmake} and @command{gprbuild}). If the attribute @code{Object_Dir} is not specified, it defaults to the project directory, that is the directory containing the project file. For our example, we can specify the object dir in this way: @smallexample @b{project} Build @b{is} @b{for} Source_Dirs @b{use} ("common"); @b{for} Object_Dir @b{use} "obj"; -- <<<< @b{end} Build; @end smallexample @noindent As mentioned earlier, there is a single object directory per project. As a result, if you have an existing system where the object files are spread in several directories, you can either move all of them into the same directory if you want to build it with a single project file, or study the section on subsystems (@pxref{Organizing Projects into Subsystems}) to see how each separate object directory can be associated with one of the subsystem constituting the application. When the @command{linker} is called, it usually creates an executable. By default, this executable is placed in the object directory of the project. It might be convenient to store it in its own directory. @cindex @code{Exec_Dir} This can be done through the @code{Exec_Dir} attribute, which, like @emph{Object_Dir} contains a single absolute or relative path and must point to an existing and writable directory, unless you ask the tool to create it on your behalf. When not specified, It defaults to the object directory and therefore to the project file's directory if neither @emph{Object_Dir} nor @emph{Exec_Dir} was specified. In the case of the example, let's place the executable in the root of the hierarchy, ie the same directory as @file{build.gpr}. Hence the project file is now @smallexample @b{project} Build @b{is} @b{for} Source_Dirs @b{use} ("common"); @b{for} Object_Dir @b{use} "obj"; @b{for} Exec_Dir @b{use} "."; -- <<<< @b{end} Build; @end smallexample @c --------------------------------------------- @node Main Subprograms @subsection Main Subprograms @c --------------------------------------------- @noindent In the previous section, executables were mentioned. The project manager needs to be taught what they are. In a project file, an executable is indicated by pointing to source file of the main subprogram. In C this is the file that contains the @code{main} function, and in Ada the file that contains the main unit. There can be any number of such main files within a given project, and thus several executables can be built in the context of a single project file. Of course, one given executable might not (and in fact will not) need all the source files referenced by the project. As opposed to other build environments such as @command{makefile}, one does not need to specify the list of dependencies of each executable, the project-aware builders knows enough of the semantics of the languages to build ands link only the necessary elements. @cindex @code{Main} The list of main files is specified via the @b{Main} attribute. It contains a list of file names (no directories). If a project defines this attribute, it is not necessary to identify main files on the command line when invoking a builder, and editors like @command{GPS} will be able to create extra menus to spawn or debug the corresponding executables. @smallexample @b{project} Build @b{is} @b{for} Source_Dirs @b{use} ("common"); @b{for} Object_Dir @b{use} "obj"; @b{for} Exec_Dir @b{use} "."; @b{for} Main @b{use} ("proc.adb"); -- <<<< @b{end} Build; @end smallexample @noindent If this attribute is defined in the project, then spawning the builder with a command such as @smallexample gnatmake ^-Pbuild^/PROJECT_FILE=build^ @end smallexample @noindent automatically builds all the executables corresponding to the files listed in the @emph{Main} attribute. It is possible to specify one or more executables on the command line to build a subset of them. @c --------------------------------------------- @node Tools Options in Project Files @subsection Tools Options in Project Files @c --------------------------------------------- @noindent We now have a project file that fully describes our environment, and can be used to build the application with a simple @command{gnatmake} command as seen in the previous section. In fact, the empty project we showed immediately at the beginning (with no attribute at all) could already fulfill that need if it was put in the @file{common} directory. Of course, we always want more control. This section will show you how to specify the compilation switches that the various tools involved in the building of the executable should use. @cindex command line length Since source names and locations are described into the project file, it is not necessary to use switches on the command line for this purpose (switches such as -I for gcc). This removes a major source of command line length overflow. Clearly, the builders will have to communicate this information one way or another to the underlying compilers and tools they call but they usually use response files for this and thus should not be subject to command line overflows. Several tools are participating to the creation of an executable: the compiler produces object files from the source files; the binder (in the Ada case) creates an source file that takes care, among other things, of elaboration issues and global variables initialization; and the linker gathers everything into a single executable that users can execute. All these tools are known by the project manager and will be called with user defined switches from the project files. However, we need to introduce a new project file concept to express which switches to be used for any of the tools involved in the build. @cindex project file packages A project file is subdivided into zero or more @b{packages}, each of which contains the attributes specific to one tool (or one set of tools). Project files use an Ada-like syntax for packages. Package names permitted in project files are restricted to a predefined set (@pxref{Packages}), and the contents of packages are limited to a small set of constructs and attributes (@pxref{Attributes}). Our example project file can be extended with the following empty packages. At this stage, they could all be omitted since they are empty, but they show which packages would be involved in the build process. @smallexample @b{project} Build @b{is} @b{for} Source_Dirs @b{use} ("common"); @b{for} Object_Dir @b{use} "obj"; @b{for} Exec_Dir @b{use} "."; @b{for} Main @b{use} ("proc.adb"); @b{package} Builder @b{is} --<<< for gnatmake and gprbuild @b{end} Builder; @b{package} Compiler @b{is} --<<< for the compiler @b{end} Compiler; @b{package} Binder @b{is} --<<< for the binder @b{end} Binder; @b{package} Linker @b{is} --<<< for the linker @b{end} Linker; @b{end} Build; @end smallexample @noindent Let's first examine the compiler switches. As stated in the initial description of the example, we want to compile all files with @option{-O2}. This is a compiler switch, although it is usual, on the command line, to pass it to the builder which then passes it to the compiler. It is recommended to use directly the right package, which will make the setup easier to understand for other people. Several attributes can be used to specify the switches: @table @asis @item @b{Default_Switches}: @cindex @code{Default_Switches} This is the first mention in this manual of an @b{indexed attribute}. When this attribute is defined, one must supply an @emph{index} in the form of a literal string. In the case of @emph{Default_Switches}, the index is the name of the language to which the switches apply (since a different compiler will likely be used for each language, and each compiler has its own set of switches). The value of the attribute is a list of switches. In this example, we want to compile all Ada source files with the @option{-O2} switch, and the resulting project file is as follows (only the @code{Compiler} package is shown): @smallexample @b{package} Compiler @b{is} @b{for} Default_Switches ("Ada") @b{use} ("-O2"); @b{end} Compiler; @end smallexample @item @b{Switches}: @cindex @code{Switches} in some cases, we might want to use specific switches for one or more files. For instance, compiling @file{proc.adb} might not be possible at high level of optimization because of a compiler issue. In such a case, the @emph{Switches} attribute (indexed on the file name) can be used and will override the switches defined by @emph{Default_Switches}. Our project file would become: @smallexample @b{package} Compiler @b{is} @b{for} Default_Switches ("Ada") @b{use} ("-O2"); @b{for} Switches ("proc.adb") @b{use} ("-O0"); @b{end} Compiler; @end smallexample @noindent @code{Switches} may take a pattern as an index, such as in: @smallexample @b{package} Compiler @b{is} @b{for} Default_Switches ("Ada") @b{use} ("-O2"); @b{for} Switches ("pkg*") @b{use} ("-O0"); @b{end} Compiler; @end smallexample @noindent Sources @file{pkg.adb} and @file{pkg-child.adb} would be compiled with -O0, not -O2. @noindent @code{Switches} can also be given a language name as index instead of a file name in which case it has the same semantics as @emph{Default_Switches}. However, indexes with wild cards are never valid for language name. @item @b{Local_Configuration_Pragmas}: @cindex @code{Local_Configuration_Pragmas} this attribute may specify the path of a file containing configuration pragmas for use by the Ada compiler, such as @code{pragma Restrictions (No_Tasking)}. These pragmas will be used for all the sources of the project. @end table The switches for the other tools are defined in a similar manner through the @b{Default_Switches} and @b{Switches} attributes, respectively in the @emph{Builder} package (for @command{gnatmake} and @command{gprbuild}), the @emph{Binder} package (binding Ada executables) and the @emph{Linker} package (for linking executables). @c --------------------------------------------- @node Compiling with Project Files @subsection Compiling with Project Files @c --------------------------------------------- @noindent Now that our project files are written, let's build our executable. Here is the command we would use from the command line: @smallexample gnatmake ^-Pbuild^/PROJECT_FILE=build^ @end smallexample @noindent This will automatically build the executables specified through the @emph{Main} attribute: for each, it will compile or recompile the sources for which the object file does not exist or is not up-to-date; it will then run the binder; and finally run the linker to create the executable itself. @command{gnatmake} only knows how to handle Ada files. By using @command{gprbuild} as a builder, you could automatically manage C files the same way: create the file @file{utils.c} in the @file{common} directory, set the attribute @emph{Languages} to @code{"(Ada, C)"}, and run @smallexample gprbuild ^-Pbuild^/PROJECT_FILE=build^ @end smallexample @noindent Gprbuild knows how to recompile the C files and will recompile them only if one of their dependencies has changed. No direct indication on how to build the various elements is given in the project file, which describes the project properties rather than a set of actions to be executed. Here is the invocation of @command{gprbuild} when building a multi-language program: @smallexample $ gprbuild -Pbuild gcc -c proc.adb gcc -c pack.adb gcc -c utils.c gprbind proc ... gcc proc.o -o proc @end smallexample @noindent Notice the three steps described earlier: @itemize @bullet @item The first three gcc commands correspond to the compilation phase. @item The gprbind command corresponds to the post-compilation phase. @item The last gcc command corresponds to the final link. @end itemize @noindent @cindex @option{-v} option (for GPRbuild) The default output of GPRbuild's execution is kept reasonably simple and easy to understand. In particular, some of the less frequently used commands are not shown, and some parameters are abbreviated. So it is not possible to rerun the effect of the @command{gprbuild} command by cut-and-pasting its output. GPRbuild's option @code{-v} provides a much more verbose output which includes, among other information, more complete compilation, post-compilation and link commands. @c --------------------------------------------- @node Executable File Names @subsection Executable File Names @c --------------------------------------------- @noindent @cindex @code{Executable} By default, the executable name corresponding to a main file is computed from the main source file name. Through the attribute @b{Builder.Executable}, it is possible to change this default. For instance, instead of building @command{proc} (or @command{proc.exe} on Windows), we could configure our project file to build "proc1" (resp proc1.exe) with the following addition: @smallexample @c projectfile project Build is ... -- same as before package Builder is for Executable ("proc.adb") use "proc1"; end Builder end Build; @end smallexample @noindent @cindex @code{Executable_Suffix} Attribute @b{Executable_Suffix}, when specified, may change the suffix of the executable files, when no attribute @code{Executable} applies: its value replace the platform-specific executable suffix. The default executable suffix is empty on UNIX and ".exe" on Windows. It is also possible to change the name of the produced executable by using the command line switch @option{-o}. When several mains are defined in the project, it is not possible to use the @option{-o} switch and the only way to change the names of the executable is provided by Attributes @code{Executable} and @code{Executable_Suffix}. @c --------------------------------------------- @node Avoid Duplication With Variables @subsection Avoid Duplication With Variables @c --------------------------------------------- @noindent To illustrate some other project capabilities, here is a slightly more complex project using similar sources and a main program in C: @smallexample @c projectfile project C_Main is for Languages use ("Ada", "C"); for Source_Dirs use ("common"); for Object_Dir use "obj"; for Main use ("main.c"); package Compiler is C_Switches := ("-pedantic"); for Default_Switches ("C") use C_Switches; for Default_Switches ("Ada") use ("-gnaty"); for Switches ("main.c") use C_Switches & ("-g"); end Compiler; end C_Main; @end smallexample @noindent This project has many similarities with the previous one. As expected, its @code{Main} attribute now refers to a C source. The attribute @emph{Exec_Dir} is now omitted, thus the resulting executable will be put in the directory @file{obj}. The most noticeable difference is the use of a variable in the @emph{Compiler} package to store settings used in several attributes. This avoids text duplication, and eases maintenance (a single place to modify if we want to add new switches for C files). We will revisit the use of variables in the context of scenarios (@pxref{Scenarios in Projects}). In this example, we see how the file @file{main.c} can be compiled with the switches used for all the other C files, plus @option{-g}. In this specific situation the use of a variable could have been replaced by a reference to the @code{Default_Switches} attribute: @smallexample @c projectfile for Switches ("c_main.c") use Compiler'Default_Switches ("C") & ("-g"); @end smallexample @noindent Note the tick (@emph{'}) used to refer to attributes defined in a package. Here is the output of the GPRbuild command using this project: @smallexample $gprbuild -Pc_main gcc -c -pedantic -g main.c gcc -c -gnaty proc.adb gcc -c -gnaty pack.adb gcc -c -pedantic utils.c gprbind main.bexch ... gcc main.o -o main @end smallexample @noindent The default switches for Ada sources, the default switches for C sources (in the compilation of @file{lib.c}), and the specific switches for @file{main.c} have all been taken into account. @c --------------------------------------------- @node Naming Schemes @subsection Naming Schemes @c --------------------------------------------- @noindent Sometimes an Ada software system is ported from one compilation environment to another (say GNAT), and the file are not named using the default GNAT conventions. Instead of changing all the file names, which for a variety of reasons might not be possible, you can define the relevant file naming scheme in the @b{Naming} package of your project file. The naming scheme has two distinct goals for the project manager: it allows finding of source files when searching in the source directories, and given a source file name it makes it possible to guess the associated language, and thus the compiler to use. Note that the use by the Ada compiler of pragmas Source_File_Name is not supported when using project files. You must use the features described in this paragraph. You can however specify other configuration pragmas (@pxref{Specifying Configuration Pragmas}). The following attributes can be defined in package @code{Naming}: @table @asis @item @b{Casing}: @cindex @code{Casing} Its value must be one of @code{"lowercase"} (the default if unspecified), @code{"uppercase"} or @code{"mixedcase"}. It describes the casing of file names with regards to the Ada unit name. Given an Ada unit My_Unit, the file name will respectively be @file{my_unit.adb} (lowercase), @file{MY_UNIT.ADB} (uppercase) or @file{My_Unit.adb} (mixedcase). On Windows, file names are case insensitive, so this attribute is irrelevant. @item @b{Dot_Replacement}: @cindex @code{Dot_Replacement} This attribute specifies the string that should replace the "." in unit names. Its default value is @code{"-"} so that a unit @code{Parent.Child} is expected to be found in the file @file{parent-child.adb}. The replacement string must satisfy the following requirements to avoid ambiguities in the naming scheme: @itemize - @item It must not be empty @item It cannot start or end with an alphanumeric character @item It cannot be a single underscore @item It cannot start with an underscore followed by an alphanumeric @item It cannot contain a dot @code{'.'} except if the entire string is @code{"."} @end itemize @item @b{Spec_Suffix} and @b{Specification_Suffix}: @cindex @code{Spec_Suffix} @cindex @code{Specification_Suffix} For Ada, these attributes give the suffix used in file names that contain specifications. For other languages, they give the extension for files that contain declaration (header files in C for instance). The attribute is indexed on the language. The two attributes are equivalent, but the latter is obsolescent. If @code{Spec_Suffix ("Ada")} is not specified, then the default is @code{"^.ads^.ADS^"}. The value must satisfy the following requirements: @itemize - @item It must not be empty @item It cannot start with an alphanumeric character @item It cannot start with an underscore followed by an alphanumeric character @item It must include at least one dot @end itemize @item @b{Body_Suffix} and @b{Implementation_Suffix}: @cindex @code{Body_Suffix} @cindex @code{Implementation_Suffix} These attributes give the extension used for file names that contain code (bodies in Ada). They are indexed on the language. The second version is obsolescent and fully replaced by the first attribute. These attributes must satisfy the same requirements as @code{Spec_Suffix}. In addition, they must be different from any of the values in @code{Spec_Suffix}. If @code{Body_Suffix ("Ada")} is not specified, then the default is @code{"^.adb^.ADB^"}. If @code{Body_Suffix ("Ada")} and @code{Spec_Suffix ("Ada")} end with the same string, then a file name that ends with the longest of these two suffixes will be a body if the longest suffix is @code{Body_Suffix ("Ada")} or a spec if the longest suffix is @code{Spec_Suffix ("Ada")}. If the suffix does not start with a '.', a file with a name exactly equal to the suffix will also be part of the project (for instance if you define the suffix as @code{Makefile}, a file called @file{Makefile} will be part of the project. This capability is usually not interesting when building. However, it might become useful when a project is also used to find the list of source files in an editor, like the GNAT Programming System (GPS). @item @b{Separate_Suffix}: @cindex @code{Separate_Suffix} This attribute is specific to Ada. It denotes the suffix used in file names that contain separate bodies. If it is not specified, then it defaults to same value as @code{Body_Suffix ("Ada")}. The same rules apply as for the @code{Body_Suffix} attribute. The only accepted index is "Ada". @item @b{Spec} or @b{Specification}: @cindex @code{Spec} @cindex @code{Specification} This attribute @code{Spec} can be used to define the source file name for a given Ada compilation unit's spec. The index is the literal name of the Ada unit (case insensitive). The value is the literal base name of the file that contains this unit's spec (case sensitive or insensitive depending on the operating system). This attribute allows the definition of exceptions to the general naming scheme, in case some files do not follow the usual convention. When a source file contains several units, the relative position of the unit can be indicated. The first unit in the file is at position 1 @smallexample @c projectfile for Spec ("MyPack.MyChild") use "mypack.mychild.spec"; for Spec ("top") use "foo.a" at 1; for Spec ("foo") use "foo.a" at 2; @end smallexample @item @b{Body} or @b{Implementation}: @cindex @code{Body} @cindex @code{Implementation} These attribute play the same role as @emph{Spec} for Ada bodies. @item @b{Specification_Exceptions} and @b{Implementation_Exceptions}: @cindex @code{Specification_Exceptions} @cindex @code{Implementation_Exceptions} These attributes define exceptions to the naming scheme for languages other than Ada. They are indexed on the language name, and contain a list of file names respectively for headers and source code. @end table @ifclear vms For example, the following package models the Apex file naming rules: @smallexample @c projectfile @group package Naming is for Casing use "lowercase"; for Dot_Replacement use "."; for Spec_Suffix ("Ada") use ".1.ada"; for Body_Suffix ("Ada") use ".2.ada"; end Naming; @end group @end smallexample @end ifclear @ifset vms For example, the following package models the DEC Ada file naming rules: @smallexample @c projectfile @group package Naming is for Casing use "lowercase"; for Dot_Replacement use "__"; for Spec_Suffix ("Ada") use "_.ada"; for Body_Suffix ("Ada") use ".ada"; end Naming; @end group @end smallexample @noindent (Note that @code{Casing} is @code{"lowercase"} because GNAT gets the file names in lower case) @end ifset @c --------------------------------------------- @node Organizing Projects into Subsystems @section Organizing Projects into Subsystems @c --------------------------------------------- @noindent A @b{subsystem} is a coherent part of the complete system to be built. It is represented by a set of sources and one single object directory. A system can be composed of a single subsystem when it is simple as we have seen in the first section. Complex systems are usually composed of several interdependent subsystems. A subsystem is dependent on another subsystem if knowledge of the other one is required to build it, and in particular if visibility on some of the sources of this other subsystem is required. Each subsystem is usually represented by its own project file. In this section, the previous example is being extended. Let's assume some sources of our @code{Build} project depend on other sources. For instance, when building a graphical interface, it is usual to depend upon a graphical library toolkit such as GtkAda. Furthermore, we also need sources from a logging module we had previously written. @menu * Project Dependencies:: * Cyclic Project Dependencies:: * Sharing Between Projects:: * Global Attributes:: @end menu @c --------------------------------------------- @node Project Dependencies @subsection Project Dependencies @c --------------------------------------------- @noindent GtkAda comes with its own project file (appropriately called @file{gtkada.gpr}), and we will assume we have already built a project called @file{logging.gpr} for the logging module. With the information provided so far in @file{build.gpr}, building the application would fail with an error indicating that the gtkada and logging units that are relied upon by the sources of this project cannot be found. This is easily solved by adding the following @b{with} clauses at the beginning of our project: @smallexample @c projectfile with "gtkada.gpr"; with "a/b/logging.gpr"; project Build is ... -- as before end Build; @end smallexample @noindent @cindex @code{Externally_Built} When such a project is compiled, @command{gnatmake} will automatically check the other projects and recompile their sources when needed. It will also recompile the sources from @code{Build} when needed, and finally create the executable. In some cases, the implementation units needed to recompile a project are not available, or come from some third-party and you do not want to recompile it yourself. In this case, the attribute @b{Externally_Built} to "true" can be set, indicating to the builder that this project can be assumed to be up-to-date, and should not be considered for recompilation. In Ada, if the sources of this externally built project were compiled with another version of the compiler or with incompatible options, the binder will issue an error. The project's @code{with} clause has several effects. It provides source visibility between projects during the compilation process. It also guarantees that the necessary object files from @code{Logging} and @code{GtkAda} are available when linking @code{Build}. As can be seen in this example, the syntax for importing projects is similar to the syntax for importing compilation units in Ada. However, project files use literal strings instead of names, and the @code{with} clause identifies project files rather than packages. Each literal string after @code{with} is the path (absolute or relative) to a project file. The @code{.gpr} extension is optional, although we recommend adding it. If no extension is specified, and no project file with the @file{^.gpr^.GPR^} extension is found, then the file is searched for exactly as written in the @code{with} clause, that is with no extension. As mentioned above, the path after a @code{with} has to be a literal string, and you cannot use concatenation, or lookup the value of external variables to change the directories from which a project is loaded. A solution if you need something like this is to use aggregate projects (@pxref{Aggregate Projects}). @cindex project path When a relative path or a base name is used, the project files are searched relative to each of the directories in the @b{project path}. This path includes all the directories found with the following algorithm, in that order, as soon as a matching file is found, the search stops: @itemize @bullet @item First, the file is searched relative to the directory that contains the current project file. @item @cindex @code{ADA_PROJECT_PATH} @cindex @code{GPR_PROJECT_PATH} Then it is searched relative to all the directories specified in the ^environment variables^logical names^ @b{GPR_PROJECT_PATH} and @b{ADA_PROJECT_PATH} (in that order) if they exist. The former is recommended, the latter is kept for backward compatibility. @item Finally, it is searched relative to the default project directories. Such directories depends on the tool used. The different locations searched in the specified order are: @itemize @bullet @item @file{//lib/gnat} (for @command{gnatmake} in all cases, and for @command{gprbuild} if option @option{--target} is specified) @item @file{/share/gpr/} (for @command{gnatmake} and @command{gprbuild}) @item @file{/lib/gnat/} (for @command{gnatmake} and @command{gprbuild}) @end itemize In our example, @file{gtkada.gpr} is found in the predefined directory if it was installed at the same root as GNAT. @end itemize @noindent Some tools also support extending the project path from the command line, generally through the @option{-aP}. You can see the value of the project path by using the @command{gnatls -v} command. Any symbolic link will be fully resolved in the directory of the importing project file before the imported project file is examined. Any source file in the imported project can be used by the sources of the importing project, transitively. Thus if @code{A} imports @code{B}, which imports @code{C}, the sources of @code{A} may depend on the sources of @code{C}, even if @code{A} does not import @code{C} explicitly. However, this is not recommended, because if and when @code{B} ceases to import @code{C}, some sources in @code{A} will no longer compile. @command{gprbuild} has a switch @option{--no-indirect-imports} that will report such indirect dependencies. One very important aspect of a project hierarchy is that @b{a given source can only belong to one project} (otherwise the project manager would not know which settings apply to it and when to recompile it). It means that different project files do not usually share source directories or when they do, they need to specify precisely which project owns which sources using attribute @code{Source_Files} or equivalent. By contrast, 2 projects can each own a source with the same base file name as long as they live in different directories. The latter is not true for Ada Sources because of the correlation between source files and Ada units. @c --------------------------------------------- @node Cyclic Project Dependencies @subsection Cyclic Project Dependencies @c --------------------------------------------- @noindent Cyclic dependencies are mostly forbidden: if @code{A} imports @code{B} (directly or indirectly) then @code{B} is not allowed to import @code{A}. However, there are cases when cyclic dependencies would be beneficial. For these cases, another form of import between projects exists: the @b{limited with}. A project @code{A} that imports a project @code{B} with a straight @code{with} may also be imported, directly or indirectly, by @code{B} through a @code{limited with}. The difference between straight @code{with} and @code{limited with} is that the name of a project imported with a @code{limited with} cannot be used in the project importing it. In particular, its packages cannot be renamed and its variables cannot be referred to. @smallexample @c 0projectfile with "b.gpr"; with "c.gpr"; project A is For Exec_Dir use B'Exec_Dir; -- ok end A; limited with "a.gpr"; -- Cyclic dependency: A -> B -> A project B is For Exec_Dir use A'Exec_Dir; -- not ok end B; with "d.gpr"; project C is end C; limited with "a.gpr"; -- Cyclic dependency: A -> C -> D -> A project D is For Exec_Dir use A'Exec_Dir; -- not ok end D; @end smallexample @c --------------------------------------------- @node Sharing Between Projects @subsection Sharing Between Projects @c --------------------------------------------- @noindent When building an application, it is common to have similar needs in several of the projects corresponding to the subsystems under construction. For instance, they will all have the same compilation switches. As seen before (@pxref{Tools Options in Project Files}), setting compilation switches for all sources of a subsystem is simple: it is just a matter of adding a @code{Compiler.Default_Switches} attribute to each project files with the same value. Of course, that means duplication of data, and both places need to be changed in order to recompile the whole application with different switches. It can become a real problem if there are many subsystems and thus many project files to edit. There are two main approaches to avoiding this duplication: @itemize @bullet @item Since @file{build.gpr} imports @file{logging.gpr}, we could change it to reference the attribute in Logging, either through a package renaming, or by referencing the attribute. The following example shows both cases: @smallexample @c projectfile project Logging is package Compiler is for Switches ("Ada") use ("-O2"); end Compiler; package Binder is for Switches ("Ada") use ("-E"); end Binder; end Logging; with "logging.gpr"; project Build is package Compiler renames Logging.Compiler; package Binder is for Switches ("Ada") use Logging.Binder'Switches ("Ada"); end Binder; end Build; @end smallexample @noindent The solution used for @code{Compiler} gets the same value for all attributes of the package, but you cannot modify anything from the package (adding extra switches or some exceptions). The second version is more flexible, but more verbose. If you need to refer to the value of a variable in an imported project, rather than an attribute, the syntax is similar but uses a "." rather than an apostrophe. For instance: @smallexample @c projectfile with "imported"; project Main is Var1 := Imported.Var; end Main; @end smallexample @item The second approach is to define the switches in a third project. That project is setup without any sources (so that, as opposed to the first example, none of the project plays a special role), and will only be used to define the attributes. Such a project is typically called @file{shared.gpr}. @smallexample @c projectfile abstract project Shared is for Source_Files use (); -- no project package Compiler is for Switches ("Ada") use ("-O2"); end Compiler; end Shared; with "shared.gpr"; project Logging is package Compiler renames Shared.Compiler; end Logging; with "shared.gpr"; project Build is package Compiler renames Shared.Compiler; end Build; @end smallexample @noindent As for the first example, we could have chosen to set the attributes one by one rather than to rename a package. The reason we explicitly indicate that @code{Shared} has no sources is so that it can be created in any directory and we are sure it shares no sources with @code{Build} or @code{Logging}, which of course would be invalid. @cindex project qualifier Note the additional use of the @b{abstract} qualifier in @file{shared.gpr}. This qualifier is optional, but helps convey the message that we do not intend this project to have sources (@pxref{Qualified Projects} for more qualifiers). @end itemize @c --------------------------------------------- @node Global Attributes @subsection Global Attributes @c --------------------------------------------- @noindent We have already seen many examples of attributes used to specify a special option of one of the tools involved in the build process. Most of those attributes are project specific. That it to say, they only affect the invocation of tools on the sources of the project where they are defined. There are a few additional attributes that apply to all projects in a hierarchy as long as they are defined on the "main" project. The main project is the project explicitly mentioned on the command-line. The project hierarchy is the "with"-closure of the main project. Here is a list of commonly used global attributes: @table @asis @item @b{Builder.Global_Configuration_Pragmas}: @cindex @code{Global_Configuration_Pragmas} This attribute points to a file that contains configuration pragmas to use when building executables. These pragmas apply for all executables build from this project hierarchy. As we have seen before, additional pragmas can be specified on a per-project basis by setting the @code{Compiler.Local_Configuration_Pragmas} attribute. @item @b{Builder.Global_Compilation_Switches}: @cindex @code{Global_Compilation_Switches} This attribute is a list of compiler switches to use when compiling any source file in the project hierarchy. These switches are used in addition to the ones defined in the @code{Compiler} package, which only apply to the sources of the corresponding project. This attribute is indexed on the name of the language. @end table Using such global capabilities is convenient. It can also lead to unexpected behavior. Especially when several subsystems are shared among different main projects and the different global attributes are not compatible. Note that using aggregate projects can be a safer and more powerful replacement to global attributes. @c --------------------------------------------- @node Scenarios in Projects @section Scenarios in Projects @c --------------------------------------------- @noindent Various aspects of the projects can be modified based on @b{scenarios}. These are user-defined modes that change the behavior of a project. Typical examples are the setup of platform-specific compiler options, or the use of a debug and a release mode (the former would activate the generation of debug information, when the second will focus on improving code optimization). Let's enhance our example to support a debug and a release modes.The issue is to let the user choose what kind of system he is building: use @option{-g} as compiler switches in debug mode and @option{-O2} in release mode. We will also setup the projects so that we do not share the same object directory in both modes, otherwise switching from one to the other might trigger more recompilations than needed or mix objects from the 2 modes. One naive approach is to create two different project files, say @file{build_debug.gpr} and @file{build_release.gpr}, that set the appropriate attributes as explained in previous sections. This solution does not scale well, because in presence of multiple projects depending on each other, you will also have to duplicate the complete hierarchy and adapt the project files to point to the right copies. @cindex scenarios Instead, project files support the notion of scenarios controlled by external values. Such values can come from several sources (in decreasing order of priority): @table @asis @item @b{Command line}: @cindex @option{-X} When launching @command{gnatmake} or @command{gprbuild}, the user can pass extra @option{-X} switches to define the external value. In our case, the command line might look like @smallexample gnatmake -Pbuild.gpr -Xmode=debug or gnatmake -Pbuild.gpr -Xmode=release @end smallexample @item @b{^Environment variables^Logical names^}: When the external value does not come from the command line, it can come from the value of ^environment variables^logical names^ of the appropriate name. In our case, if ^an environment variable^a logical name^ called "mode" exist, its value will be taken into account. @item @b{External function second parameter} @end table @cindex @code{external} We now need to get that value in the project. The general form is to use the predefined function @b{external} which returns the current value of the external. For instance, we could setup the object directory to point to either @file{obj/debug} or @file{obj/release} by changing our project to @smallexample @c projectfile project Build is for Object_Dir use "obj/" & external ("mode", "debug"); ... -- as before end Build; @end smallexample @noindent The second parameter to @code{external} is optional, and is the default value to use if "mode" is not set from the command line or the environment. In order to set the switches according to the different scenarios, other constructs have to be introduced such as typed variables and case statements. @cindex typed variable @cindex case statement A @b{typed variable} is a variable that can take only a limited number of values, similar to an enumeration in Ada. Such a variable can then be used in a @b{case statement} and create conditional sections in the project. The following example shows how this can be done: @smallexample @c projectfile project Build is type Mode_Type is ("debug", "release"); -- all possible values Mode : Mode_Type := external ("mode", "debug"); -- a typed variable package Compiler is case Mode is when "debug" => for Switches ("Ada") use ("-g"); when "release" => for Switches ("Ada") use ("-O2"); end case; end Compiler; end Build; @end smallexample @noindent The project has suddenly grown in size, but has become much more flexible. @code{Mode_Type} defines the only valid values for the @code{mode} variable. If any other value is read from the environment, an error is reported and the project is considered as invalid. The @code{Mode} variable is initialized with an external value defaulting to @code{"debug"}. This default could be omitted and that would force the user to define the value. Finally, we can use a case statement to set the switches depending on the scenario the user has chosen. Most aspects of the projects can depend on scenarios. The notable exception are project dependencies (@code{with} clauses), which may not depend on a scenario. Scenarios work the same way with @b{project hierarchies}: you can either duplicate a variable similar to @code{Mode} in each of the project (as long as the first argument to @code{external} is always the same and the type is the same), or simply set the variable in the @file{shared.gpr} project (@pxref{Sharing Between Projects}). @c --------------------------------------------- @node Library Projects @section Library Projects @c --------------------------------------------- @noindent So far, we have seen examples of projects that create executables. However, it is also possible to create libraries instead. A @b{library} is a specific type of subsystem where, for convenience, objects are grouped together using system-specific means such as archives or windows DLLs. Library projects provide a system- and language-independent way of building both @b{static} and @b{dynamic} libraries. They also support the concept of @b{standalone libraries} (SAL) which offers two significant properties: the elaboration (e.g. initialization) of the library is either automatic or very simple; a change in the implementation part of the library implies minimal post-compilation actions on the complete system and potentially no action at all for the rest of the system in the case of dynamic SALs. The GNAT Project Manager takes complete care of the library build, rebuild and installation tasks, 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 @file{ALI} files to the specified location). @menu * Building Libraries:: * Using Library Projects:: * Stand-alone Library Projects:: * Installing a library with project files:: @end menu @c --------------------------------------------- @node Building Libraries @subsection Building Libraries @c --------------------------------------------- @noindent Let's enhance our example and transform the @code{logging} subsystem into a library. In order to do so, a few changes need to be made to @file{logging.gpr}. A number of specific attributes needs to be defined: at least @code{Library_Name} and @code{Library_Dir}; in addition, a number of other attributes can be used to specify specific aspects of the library. For readability, it is also recommended (although not mandatory), to use the qualifier @code{library} in front of the @code{project} keyword. @table @asis @item @b{Library_Name}: @cindex @code{Library_Name} This attribute is the name of the library to be built. There is no restriction on the name of a library imposed by the project manager, except for stand-alone libraries whose names must follow the syntax of Ada identifiers; however, there may be system specific restrictions on the name. In general, it is recommended to stick to alphanumeric characters (and possibly single underscores) to help portability. @item @b{Library_Dir}: @cindex @code{Library_Dir} This attribute is the path (absolute or relative) of the directory where the library is to be installed. In the process of building a library, the sources are compiled, the object files end up in the explicit or implicit @code{Object_Dir} directory. When all sources of a library are compiled, some of the compilation artifacts, including the library itself, are copied to the library_dir directory. This directory must exists and be writable. It must also be different from the object directory so that cleanup activities in the Library_Dir do not affect recompilation needs. @end table Here is the new version of @file{logging.gpr} that makes it a library: @smallexample @c projectfile library project Logging is -- "library" is optional for Library_Name use "logging"; -- will create "liblogging.a" on Unix for Object_Dir use "obj"; for Library_Dir use "lib"; -- different from object_dir end Logging; @end smallexample @noindent Once the above two attributes are defined, the library project is valid and is enough for building a library with default characteristics. Other library-related attributes can be used to change the defaults: @table @asis @item @b{Library_Kind}: @cindex @code{Library_Kind} The value of this attribute must be either @code{"static"}, @code{"dynamic"} or @code{"relocatable"} (the latter is a synonym for dynamic). It indicates which kind of library should be build (the default is to build a static library, that is an archive of object files that can potentially be linked into a static executable). When the library is set to be dynamic, a separate image is created that will be loaded independently, usually at the start of the main program execution. Support for dynamic libraries is very platform specific, for instance on Windows it takes the form of a DLL while on GNU/Linux, it is a dynamic elf image whose suffix is usually @file{.so}. Library project files, on the other hand, can be written in a platform independent way so that the same project file can be used to build a library on different operating systems. If you need to build both a static and a dynamic library, it is recommended use two different object directories, since in some cases some extra code needs to be generated for the latter. For such cases, one can either define two different project files, or a single one which uses scenarios to indicate at the various kinds of library to be build and their corresponding object_dir. @cindex @code{Library_ALI_Dir} @item @b{Library_ALI_Dir}: This attribute may be specified to indicate the directory where the ALI files of the library are installed. By default, they are copied into the @code{Library_Dir} directory, but as for the executables where we have a separate @code{Exec_Dir} attribute, you might want to put them in a separate directory since there can be hundreds of them. The same restrictions as for the @code{Library_Dir} attribute apply. @cindex @code{Library_Version} @item @b{Library_Version}: This attribute is platform dependent, and has no effect on VMS and Windows. On Unix, it is used only for dynamic libraries as the internal name of the library (the @code{"soname"}). If the library file name (built from the @code{Library_Name}) is different from the @code{Library_Version}, then the library file will be a symbolic link to the actual file whose name will be @code{Library_Version}. This follows the usual installation schemes for dynamic libraries on many Unix systems. @smallexample @c projectfile @group project Logging is Version := "1"; for Library_Dir use "lib"; for Library_Name use "logging"; for Library_Kind use "dynamic"; for Library_Version use "liblogging.so." & Version; end Logging; @end group @end smallexample @noindent After the compilation, the directory @file{lib} will contain both a @file{libdummy.so.1} library and a symbolic link to it called @file{libdummy.so}. @cindex @code{Library_GCC} @item @b{Library_GCC}: This attribute is the name of the tool to use instead of "gcc" to link shared libraries. A common use of this attribute is to define a wrapper script that accomplishes specific actions before calling gcc (which itself is calling the linker to build the library image). @item @b{Library_Options}: @cindex @code{Library_Options} This attribute may be used to specify additional switches (last switches) when linking a shared library. @item @b{Leading_Library_Options}: @cindex @code{Leading_Library_Options} This attribute, that is taken into account only by @command{gprbuild}, may be used to specified leading options (first switches) when linking a shared library. @cindex @code{Linker_Options} @item @b{Linker.Linker_Options}: This attribute specifies additional switches to be given to the linker when linking an executable. It is ignored when defined in the main project and taken into account in all other projects that are imported directly or indirectly. These switches complement the @code{Linker.Switches} defined in the main project. This is useful when a particular subsystem depends on an external library: adding this dependency as a @code{Linker_Options} in the project of the subsystem is more convenient than adding it to all the @code{Linker.Switches} of the main projects that depend upon this subsystem. @end table @c --------------------------------------------- @node Using Library Projects @subsection Using Library Projects @c --------------------------------------------- @noindent When the builder detects that a project file is a library project file, it recompiles all sources of the project that need recompilation and rebuild the library if any of the sources have been recompiled. It then groups all object files into a single file, which is a shared or a static library. This library can later on be linked with multiple executables. Note that the use of shard libraries reduces the size of the final executable and can also reduce the memory footprint at execution time when the library is shared among several executables. It is also possible to build @b{multi-language libraries}. When using @command{gprbuild} as a builder, multi-language library projects allow naturally the creation of multi-language libraries . @command{gnatmake}, does not try to compile non Ada sources. However, when the project is multi-language, it will automatically link all object files found in the object directory, whether or not they were compiled from an Ada source file. This specific behavior does not apply to Ada-only projects which only take into account the objects corresponding to the sources of the project. A non-library project can import a library project. When the builder is invoked on the former, the library of the latter is only rebuilt when absolutely necessary. For instance, if a unit of the library is not up-to-date but non of the executables need this unit, then the unit is not recompiled and the library is not reassembled. For instance, let's assume in our example that logging has the following sources: @file{log1.ads}, @file{log1.adb}, @file{log2.ads} and @file{log2.adb}. If @file{log1.adb} has been modified, then the library @file{liblogging} will be rebuilt when compiling all the sources of @code{Build} only if @file{proc.ads}, @file{pack.ads} or @file{pack.adb} include a @code{"with Log1"}. To ensure that all the sources in the @code{Logging} library are up to date, and that all the sources of @code{Build} are also up to date, the following two commands needs to be used: @smallexample gnatmake -Plogging.gpr gnatmake -Pbuild.gpr @end smallexample @noindent All @file{ALI} files will also be copied from the object directory to the library directory. To build executables, @command{gnatmake} will use the library rather than the individual object files. @ifclear vms Library projects can also be useful to describe a library that need to be used but, for some reason, cannot be rebuilt. For instance, it is the case when some of the library sources are not available. Such library projects need simply to use the @code{Externally_Built} attribute as in the example below: @smallexample @c projectfile library project Extern_Lib is for Languages use ("Ada", "C"); for Source_Dirs use ("lib_src"); for Library_Dir use "lib2"; for Library_Kind use "dynamic"; for Library_Name use "l2"; for Externally_Built use "true"; -- <<<< end Extern_Lib; @end smallexample @noindent In the case of externally built libraries, the @code{Object_Dir} attribute does not need to be specified because it will never be used. The main effect of using such an externally built library project is mostly to affect the linker command in order to reference the desired library. It can also be achieved by using @code{Linker.Linker_Options} or @code{Linker.Switches} in the project corresponding to the subsystem needing this external library. This latter method is more straightforward in simple cases but when several subsystems depend upon the same external library, finding the proper place for the @code{Linker.Linker_Options} might not be easy and if it is not placed properly, the final link command is likely to present ordering issues. In such a situation, it is better to use the externally built library project so that all other subsystems depending on it can declare this dependency thanks to a project @code{with} clause, which in turn will trigger the builder to find the proper order of libraries in the final link command. @end ifclear @c --------------------------------------------- @node Stand-alone Library Projects @subsection Stand-alone Library Projects @c --------------------------------------------- @noindent @cindex standalone libraries A @b{stand-alone library} is a library that contains the necessary code to elaborate the Ada units that are included in the library. A stand-alone library is a convenient way to add an Ada subsystem to a more global system whose main is not in Ada since it makes the elaboration of the Ada part mostly transparent. However, stand-alone libraries are also useful when the main is in Ada: they provide a means for minimizing relinking & redeployment of complex systems when localized changes are made. The name of a stand-alone library, specified with attribute @code{Library_Name}, must have the syntax of an Ada identifier. The most prominent characteristic of a stand-alone library is that it offers a distinction between interface units and implementation units. Only the former are visible to units outside the library. A stand-alone library project is thus characterised by a third attribute, usually @b{Library_Interface}, in addition to the two attributes that make a project a Library Project (@code{Library_Name} and @code{Library_Dir}). This third attribute may also be @b{Interfaces}. @b{Library_Interface} only works when the interface is in Ada and takes a list of units as parameter. @b{Interfaces} works for any supported language and takes a list of sources as parameter. @table @asis @item @b{Library_Interface}: @cindex @code{Library_Interface} This attribute defines an explicit subset of the units of the project. Units from projects importing this library project may only "with" units whose sources are listed in the @code{Library_Interface}. Other sources are considered implementation units. @smallexample @c projectfile @group for Library_Dir use "lib"; for Library_Name use "loggin"; for Library_Interface use ("lib1", "lib2"); -- unit names @end group @end smallexample @item @b{Interfaces} This attribute defines an explicit subset of the source files of a project. Sources from projects importing this project, can only depend on sources from this subset. This attribute can be used on non library projects. It can also be used as a replacement for attribute @code{Library_Interface}, in which case, units have to be replaced by source files. For multi-language library projects, it is the only way to make the project a Stand-Alone Library project whose interface is not purely Ada. @item @b{Library_Standalone}: @cindex @code{Library_Standalone} This attribute defines the kind of standalone library to build. Values are either @code{standard} (the default), @code{no} or @code{encapsulated}. When @code{standard} is used the code to elaborate and finalize the library is embedded, when @code{encapsulated} is used the library can furthermore only depends on static libraries (including the GNAT runtime). This attribute can be set to @code{no} to make it clear that the library should not be standalone in which case the @code{Library_Interface} should not defined. @smallexample @c projectfile @group for Library_Dir use "lib"; for Library_Name use "loggin"; for Library_Interface use ("lib1", "lib2"); -- unit names for Library_Standalone use "encapsulated"; @end group @end smallexample @end table In order to include the elaboration code in the stand-alone library, the binder is invoked on the closure of the library units creating a package whose name depends on the library name (^b~logging.ads/b^B$LOGGING.ADS/B^ in the example). This binder-generated package includes @b{initialization} and @b{finalization} procedures whose names depend on the library name (@code{logginginit} and @code{loggingfinal} in the example). The object corresponding to this package is included in the library. @table @asis @item @b{Library_Auto_Init}: @cindex @code{Library_Auto_Init} A dynamic stand-alone Library is automatically initialized if automatic initialization of Stand-alone Libraries is supported on the platform and if attribute @b{Library_Auto_Init} is not specified or is specified with the value "true". A static Stand-alone Library is never automatically initialized. Specifying "false" for this attribute prevent automatic initialization. When a non-automatically initialized stand-alone library is used in an executable, its initialization procedure must be called before any service of the library is used. When the main subprogram is in Ada, it may mean that the initialization procedure has to be called during elaboration of another package. @item @b{Library_Dir}: @cindex @code{Library_Dir} For a stand-alone library, only the @file{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. @item @b{Binder.Default_Switches}: When a stand-alone library is bound, the switches that are specified in the attribute @b{Binder.Default_Switches ("Ada")} are used in the call to @command{gnatbind}. @item @b{Library_Src_Dir}: @cindex @code{Library_Src_Dir} This attribute defines the location (absolute or relative to the project directory) where the sources of the interface units are copied at installation time. These sources includes the specs of the interface units along with the closure of sources necessary to compile them successfully. That may include bodies and subunits, when pragmas @code{Inline} are used, or when there is a generic units in the spec. This directory cannot point to the object directory or one of the source directories, but it can point to the library directory, which is the default value for this attribute. @item @b{Library_Symbol_Policy}: @cindex @code{Library_Symbol_Policy} This attribute controls the export of symbols and, on some platforms (like VMS) that have the notions of major and minor IDs built in the library files, it controls the setting of these IDs. It is not supported on all platforms (where it will just have no effect). It may have one of the following values: @itemize - @item @code{"autonomous"} or @code{"default"}: exported symbols are not controlled @item @code{"compliant"}: if attribute @b{Library_Reference_Symbol_File} is not defined, then it is equivalent to policy "autonomous". If there are exported symbols in the reference symbol file that are not in the object files of the interfaces, the major ID of the library is increased. If there are symbols in the object files of the interfaces that are not in the reference symbol file, these symbols are put at the end of the list in the newly created symbol file and the minor ID is increased. @item @code{"controlled"}: the attribute @b{Library_Reference_Symbol_File} must be defined. The library will fail to build if the exported symbols in the object files of the interfaces do not match exactly the symbol in the symbol file. @item @code{"restricted"}: The attribute @b{Library_Symbol_File} must be defined. The library will fail to build if there are symbols in the symbol file that are not in the exported symbols of the object files of the interfaces. Additional symbols in the object files are not added to the symbol file. @item @code{"direct"}: The attribute @b{Library_Symbol_File} must be defined and must designate an existing file in the object directory. This symbol file is passed directly to the underlying linker without any symbol processing. @end itemize @item @b{Library_Reference_Symbol_File} @cindex @code{Library_Reference_Symbol_File} This attribute may define the path name of a reference symbol file that is read when the symbol policy is either "compliant" or "controlled", on platforms that support symbol control, such as VMS, when building a stand-alone library. The path may be an absolute path or a path relative to the project directory. @item @b{Library_Symbol_File} @cindex @code{Library_Symbol_File} This attribute may define the name of the symbol file to be created when building a stand-alone library when the symbol policy is either "compliant", "controlled" or "restricted", on platforms that support symbol control, such as VMS. When symbol policy is "direct", then a file with this name must exist in the object directory. @end table @c --------------------------------------------- @node Installing a library with project files @subsection Installing a library with project files @c --------------------------------------------- @noindent When using project files, library installation is part of the library build process. Thus no further action is needed in order to make use of the libraries that are built as part of the general application build. A usable version of the library is installed in the directory specified by the @code{Library_Dir} attribute of the library project file. You may want to install a library in a context different from where the library is built. This situation arises with third party suppliers, who may want to distribute a library in binary form where the user is not expected to be able to recompile the library. The simplest option in this case is to provide a project file slightly different from the one used to build the library, by using the @code{externally_built} attribute. @ref{Using Library Projects} @c --------------------------------------------- @node Project Extension @section Project Extension @c --------------------------------------------- @noindent During development of a large system, it is sometimes necessary to use modified versions of some of the source files, without changing the original sources. This can be achieved through the @b{project extension} facility. Suppose for instance that our example @code{Build} project is build every night for the whole team, in some shared directory. A developer usually need to work on a small part of the system, and might not want to have a copy of all the sources and all the object files (mostly because that would require too much disk space, time to recompile everything). He prefers to be able to override some of the source files in his directory, while taking advantage of all the object files generated at night. Another example can be taken from large software systems, where it is common to have multiple implementations of a common interface; in Ada terms, multiple versions of a package body for the same spec. For example, one implementation might be safe for use in tasking programs, while another might only be used in sequential applications. This can be modeled in GNAT using the concept of @emph{project extension}. If one project (the ``child'') @emph{extends} another project (the ``parent'') then by default all source files of the parent project are inherited by the child, but the child project can override any of the parent's source files with new versions, and can also add new files or remove unnecessary ones. This facility is the project analog of a type extension in object-oriented programming. Project hierarchies are permitted (an extending project may itself be extended), and a project that extends a project can also import other projects. A third example is that of using project extensions to provide different versions of the same system. For instance, assume that a @code{Common} project is used by two development branches. One of the branches has now been frozen, and no further change can be done to it or to @code{Common}. However, the other development branch still needs evolution of @code{Common}. Project extensions provide a flexible solution to create a new version of a subsystem while sharing and reusing as much as possible from the original one. A project extension inherits implicitly all the sources and objects from the project it extends. It is possible to create a new version of some of the sources in one of the additional source dirs of the extending project. Those new versions hide the original versions. Adding new sources or removing existing ones is also possible. Here is an example on how to extend the project @code{Build} from previous examples: @smallexample @c projectfile project Work extends "../bld/build.gpr" is end Work; @end smallexample @noindent The project after @b{extends} is the one being extended. As usual, it can be specified using an absolute path, or a path relative to any of the directories in the project path (@pxref{Project Dependencies}). This project does not specify source or object directories, so the default value for these attribute will be used that is to say the current directory (where project @code{Work} is placed). We can already compile that project with @smallexample gnatmake -Pwork @end smallexample @noindent If no sources have been placed in the current directory, this command won't do anything, since this project does not change the sources it inherited from @code{Build}, therefore all the object files in @code{Build} and its dependencies are still valid and are reused automatically. Suppose we now want to supply an alternate version of @file{pack.adb} but use the existing versions of @file{pack.ads} and @file{proc.adb}. We can create the new file Work's current directory (likely by copying the one from the @code{Build} project and making changes to it. If new packages are needed at the same time, we simply create new files in the source directory of the extending project. When we recompile, @command{gnatmake} will now automatically recompile this file (thus creating @file{pack.o} in the current directory) and any file that depends on it (thus creating @file{proc.o}). Finally, the executable is also linked locally. Note that we could have obtained the desired behavior using project import rather than project inheritance. A @code{base} project would contain the sources for @file{pack.ads} and @file{proc.adb}, and @code{Work} would import @code{base} and add @file{pack.adb}. In this scenario, @code{base} cannot contain the original version of @file{pack.adb} otherwise there would be 2 versions of the same unit in the closure of the project and this is not allowed. Generally speaking, it is not recommended to put the spec and the body of a unit in different projects since this affects their autonomy and reusability. In a project file that extends another project, it is possible to indicate that an inherited source is @b{not part} of the sources of the extending project. This is necessary sometimes when a package spec has been overridden and no longer requires a body: in this case, it is necessary to indicate that the inherited body is not part of the sources of the project, otherwise there will be a compilation error when compiling the spec. @cindex @code{Excluded_Source_Files} @cindex @code{Excluded_Source_List_File} For that purpose, the attribute @b{Excluded_Source_Files} is used. Its value is a list of file names. It is also possible to use attribute @code{Excluded_Source_List_File}. Its value is the path of a text file containing one file name per line. @smallexample @c @projectfile project Work extends "../bld/build.gpr" is for Source_Files use ("pack.ads"); -- New spec of Pkg does not need a completion for Excluded_Source_Files use ("pack.adb"); end Work; @end smallexample @noindent All packages that are not declared in the extending project are inherited from the project being extended, with their attributes, with the exception of @code{Linker'Linker_Options} which is never inherited. In particular, an extending project retains all the switches specified in the project being extended. At the project level, if they are not declared in the extending project, some attributes are inherited from the project being extended. They are: @code{Languages}, @code{Main} (for a root non library project) and @code{Library_Name} (for a project extending a library project) @menu * Project Hierarchy Extension:: @end menu @c --------------------------------------------- @node Project Hierarchy Extension @subsection Project Hierarchy Extension @c --------------------------------------------- @noindent One of the fundamental restrictions in project extension is the following: @b{A project is not allowed to import directly or indirectly at the same time an extending project and one of its ancestors}. By means of example, consider the following hierarchy of projects. @smallexample a.gpr contains package A1 b.gpr, imports a.gpr and contains B1, which depends on A1 c.gpr, imports b.gpr and contains C1, which depends on B1 @end smallexample @noindent If we want to locally extend the packages @code{A1} and @code{C1}, we need to create several extending projects: @smallexample a_ext.gpr which extends a.gpr, and overrides A1 b_ext.gpr which extends b.gpr and imports a_ext.gpr c_ext.gpr which extends c.gpr, imports b_ext.gpr and overrides C1 @end smallexample @noindent @smallexample @c projectfile project A_Ext extends "a.gpr" is for Source_Files use ("a1.adb", "a1.ads"); end A_Ext; with "a_ext.gpr"; project B_Ext extends "b.gpr" is end B_Ext; with "b_ext.gpr"; project C_Ext extends "c.gpr" is for Source_Files use ("c1.adb"); end C_Ext; @end smallexample @noindent The extension @file{b_ext.gpr} is required, even though we are not overriding any of the sources of @file{b.gpr} because otherwise @file{c_expr.gpr} would import @file{b.gpr} which itself knows nothing about @file{a_ext.gpr}. @cindex extends all When extending a large system spanning multiple projects, it is often inconvenient to extend every project in the hierarchy that is impacted by a small change introduced in a low layer. In such cases, it is possible to create an @b{implicit extension} of entire hierarchy using @b{extends all} relationship. When the project is extended using @code{extends all} inheritance, all projects that are imported by it, both directly and indirectly, are considered virtually extended. That is, the project manager creates implicit projects that extend every project in the hierarchy; all these implicit projects do not control sources on their own and use the object directory of the "extending all" project. It is possible to explicitly extend one or more projects in the hierarchy in order to modify the sources. These extending projects must be imported by the "extending all" project, which will replace the corresponding virtual projects with the explicit ones. When building such a project hierarchy extension, the project manager will ensure that both modified sources and sources in implicit extending projects that depend on them, are recompiled. Thus, in our example we could create the following projects instead: @smallexample a_ext.gpr, extends a.gpr and overrides A1 c_ext.gpr, "extends all" c.gpr, imports a_ext.gpr and overrides C1 @end smallexample @noindent @smallexample @c projectfile project A_Ext extends "a.gpr" is for Source_Files use ("a1.adb", "a1.ads"); end A_Ext; with "a_ext.gpr"; project C_Ext extends all "c.gpr" is for Source_Files use ("c1.adb"); end C_Ext; @end smallexample @noindent When building project @file{c_ext.gpr}, the entire modified project space is considered for recompilation, including the sources of @file{b.gpr} that are impacted by the changes in @code{A1} and @code{C1}. @c --------------------------------------------- @node Aggregate Projects @section Aggregate Projects @c --------------------------------------------- @noindent Aggregate projects are an extension of the project paradigm, and are meant to solve a few specific use cases that cannot be solved directly using standard projects. This section will go over a few of these use cases to try and explain what you can use aggregate projects for. @menu * Building all main programs from a single project tree:: * Building a set of projects with a single command:: * Define a build environment:: * Performance improvements in builder:: * Syntax of aggregate projects:: * package Builder in aggregate projects:: @end menu @c ----------------------------------------------------------- @node Building all main programs from a single project tree @subsection Building all main programs from a single project tree @c ----------------------------------------------------------- Most often, an application is organized into modules and submodules, which are very conveniently represented as a project tree or graph (the root project A @code{with}s the projects for each modules (say B and C), which in turn @code{with} projects for submodules. Very often, modules will build their own executables (for testing purposes for instance), or libraries (for easier reuse in various contexts). However, if you build your project through gnatmake or gprbuild, using a syntax similar to @smallexample gprbuild -PA.gpr @end smallexample this will only rebuild the main programs of project A, not those of the imported projects B and C. Therefore you have to spawn several gnatmake commands, one per project, to build all executables. This is a little inconvenient, but more importantly is inefficient (since gnatmake needs to do duplicate work to ensure that sources are up-to-date, and cannot easily compile things in parallel when using the -j switch). Also libraries are always rebuild when building a project. You could therefore define an aggregate project Agg that groups A, B and C. Then, when you build with @smallexample gprbuild -PAgg.gpr @end smallexample this will build all mains from A, B and C. @smallexample @c projectfile aggregate project Agg is for Project_Files use ("a.gpr", "b.gpr", "c.gpr"); end Agg; @end smallexample If B or C do not define any main program (through their Main attribute), all their sources are build. When you do not group them in the aggregate project, only those sources that are needed by A will be build. If you add a main to a project P not already explicitly referenced in the aggregate project, you will need to add "p.gpr" in the list of project files for the aggregate project, or the main will not be built when building the aggregate project. @c --------------------------------------------------------- @node Building a set of projects with a single command @subsection Building a set of projects with a single command @c --------------------------------------------------------- One other case is when you have multiple applications and libraries that are build independently from each other (but they can be build in parallel). For instance, you have a project tree rooted at A, and another one (which might share some subprojects) rooted at B. Using only gprbuild, you could do @smallexample gprbuild -PA.gpr gprbuild -PB.gpr @end smallexample to build both. But again, gprbuild has to do some duplicate work for those files that are shared between the two, and cannot truly build things in parallel efficiently. If the two projects are really independent, share no sources other than through a common subproject, and have no source files with a common basename, you could create a project C that imports A and B. But these restrictions are often too strong, and one has to build them independently. An aggregate project does not have these limitations, and can aggregate two project trees that have common sources. @smallexample Aggregate projects can group projects with duplicate file names @end smallexample This scenario is particularly useful in environment like VxWork 653 where the applications running in the multiple partitions can be build in parallel through a single gprbuild command. This also works nicely with Annex E. @smallexample Aggregate projects can be used to build multiple partitions @end smallexample @c --------------------------------------------- @node Define a build environment @subsection Define a build environment @c --------------------------------------------- The environment variables at the time you launch gprbuild or gprbuild will influence the view these tools have of the project (PATH to find the compiler, ADA_PROJECT_PATH or GPR_PROJECT_PATH to find the projects, environment variables that are referenced in project files through the "external" statement,...). Several command line switches can be used to override those (-X or -aP), but on some systems and with some projects, this might make the command line too long, and on all systems often make it hard to read. An aggregate project can be used to set the environment for all projects build through that aggregate. One of the nice aspects is that you can put the aggregate project under configuration management, and make sure all your user have a consistent environment when building. The syntax looks like @smallexample @c projectfile aggregate project Agg is for Project_Files use ("A.gpr", "B.gpr"); for Project_Path use ("../dir1", "../dir1/dir2"); for External ("BUILD") use "PRODUCTION"; package Builder is for Switches ("Ada") use ("-q"); end Builder; end Agg; @end smallexample One of the often requested features in projects is to be able to reference external variables in @code{with} statements, as in @smallexample @c projectfile with external("SETUP") & "path/prj.gpr"; -- ILLEGAL project MyProject is ... end MyProject; @end smallexample For various reasons, this isn't authorized. But using aggregate projects provide an elegant solution. For instance, you could use a project file like: @smallexample @c projectfile aggregate project Agg is for Project_Path use (external("SETUP") % "path"); for Project_Files use ("myproject.gpr"); end Agg; with "prj.gpr"; -- searched on Agg'Project_Path project MyProject is ... end MyProject; @end smallexample @c -------------------------------------------- @node Performance improvements in builder @subsection Performance improvements in builder @c -------------------------------------------- The loading of aggregate projects is optimized in gprbuild and gnatmake, so that all files are searched for only once on the disk (thus reducing the number of system calls and contributing to faster compilation times especially on systems with sources on remote servers). As part of the loading, gprbuild and gnatmake compute how and where a source file should be compiled, and even if it is found several times in the aggregated projects it will be compiled only once. Since there is no ambiguity as to which switches should be used, files can be compiled in parallel (through the usual -j switch) and this can be done while maximizing the use of CPUs (compared to launching multiple gprbuild and gnatmake commands in parallel). @c ------------------------------------- @node Syntax of aggregate projects @subsection Syntax of aggregate projects @c ------------------------------------- An aggregate project follows the general syntax of project files. The recommended extension is still @file{.gpr}. However, a special @code{aggregate} qualifier must be put before the keyword @code{project}. An aggregate project cannot @code{with} any other project (standard or aggregate), except an abstract project which can be used to share attribute values. Building other aggregate projects from an aggregate project is done through the Project_Files attribute (see below). An aggregate project does not have any source files directly (only through other standard projects). Therefore a number of the standard attributes and packages are forbidden in an aggregate project. Here is the (non exhaustive) list: @itemize @bullet @item Languages @item Source_Files, Source_List_File and other attributes dealing with list of sources. @item Source_Dirs, Exec_Dir and Object_Dir @item Library_Dir, Library_Name and other library-related attributes @item Main @item Roots @item Externally_Built @item Inherit_Source_Path @item Excluded_Source_Dirs @item Locally_Removed_Files @item Excluded_Source_Files @item Excluded_Source_List_File @item Interfaces @end itemize The only package that is authorized (albeit optional) is Builder. Other packages (in particular Compiler, Binder and Linker) are forbidden. It is an error to have any of these (and such an error prevents the proper loading of the aggregate project). Three new attributes have been created, which can only be used in the context of aggregate projects: @table @asis @item @b{Project_Files}: @cindex @code{Project_Files} This attribute is compulsory (or else we are not aggregating any project, and thus not doing anything). It specifies a list of @file{.gpr} files that are grouped in the aggregate. The list may be empty. The project files can be either other aggregate projects, or standard projects. When grouping standard projects, you can have both the root of a project tree (and you do not need to specify all its imported projects), and any project within the tree. Basically, the idea is to specify all those projects that have main programs you want to build and link, or libraries you want to build. You can even specify projects that do not use the Main attribute nor the @code{Library_*} attributes, and the result will be to build all their source files (not just the ones needed by other projects). The file can include paths (absolute or relative). Paths are relative to the location of the aggregate project file itself (if you use a base name, we expect to find the .gpr file in the same directory as the aggregate project file). The extension @file{.gpr} is mandatory, since this attribute contains file names, not project names. Paths can also include the @code{"*"} and @code{"**"} globbing patterns. The latter indicates that any subdirectory (recursively) will be searched for matching files. The latter (@code{"**"}) can only occur at the last position in the directory part (ie @code{"a/**/*.gpr"} is supported, but not @code{"**/a/*.gpr"}). Starting the pattern with @code{"**"} is equivalent to starting with @code{"./**"}. For now, the pattern @code{"*"} is only allowed in the filename part, not in the directory part. This is mostly for efficiency reasons to limit the number of system calls that are needed. Here are a few valid examples: @smallexample @c projectfile for Project_Files use ("a.gpr", "subdir/b.gpr"); -- two specific projects relative to the directory of agg.gpr for Project_Files use ("**/*.gpr"); -- all projects recursively @end smallexample @item @b{Project_Path}: @cindex @code{Project_Path} This attribute can be used to specify a list of directories in which to look for project files in @code{with} statements. When you specify a project in Project_Files say @code{"x/y/a.gpr"}), and this projects imports a project "b.gpr", only b.gpr is searched in the project path. a.gpr must be exactly at /x/y/a.gpr. This attribute, however, does not affect the search for the aggregated project files specified with @code{Project_Files}. Each aggregate project has its own (that is if agg1.gpr includes agg2.gpr, they can potentially both have a different project path). This project path is defined as the concatenation, in that order, of the current directory, followed by the command line -aP switches, then the directories from the Project_Path attribute, then the directories from the GPR_PROJECT_PATH and ADA_PROJECT_PATH env. variables, and finally the predefined directories. In the example above, agg2.gpr's project path is not influenced by the attribute agg1'Project_Path, nor is agg1 influenced by agg2'Project_Path. This can potentially lead to errors. In the following example: @smallexample +---------------+ +----------------+ | Agg1.gpr |-=--includes--=-->| Agg2.gpr | | 'project_path| | 'project_path | | | | | +---------------+ +----------------+ : : includes includes : : v v +-------+ +---------+ | P.gpr |<---------- withs --------| Q.gpr | +-------+---------\ +---------+ | | withs | | | v v +-------+ +---------+ | R.gpr | | R'.gpr | +-------+ +---------+ @end smallexample When looking for p.gpr, both aggregates find the same physical file on the disk. However, it might happen that with their different project paths, both aggregate projects would in fact find a different r.gpr. Since we have a common project (p.gpr) "with"ing two different r.gpr, this will be reported as an error by the builder. Directories are relative to the location of the aggregate project file. Here are a few valid examples: @smallexample @c projectfile for Project_Path use ("/usr/local/gpr", "gpr/"); @end smallexample @item @b{External}: @cindex @code{External} This attribute can be used to set the value of environment variables as retrieved through the @code{external} statement in projects. It does not affect the environment variables themselves (so for instance you cannot use it to change the value of your PATH as seen from the spawned compiler). This attribute affects the external values as seen in the rest of the aggreate projects, and in the aggregated projects. The exact value of external a variable comes from one of three sources (each level overrides the previous levels): @itemize @bullet @item An External attribute in aggregate project, for instance @code{for External ("BUILD_MODE") use "DEBUG"}; @item Environment variables These override the value given by the attribute, so that users can override the value set in the (presumably shared with others in his team) aggregate project. @item The -X command line switch to gprbuild and gnatmake This always takes precedence. @end itemize This attribute is only taken into account in the main aggregate project (i.e. the one specified on the command line to gprbuild or natmake), and ignored in other aggregate projects. It is invalid in standard projects. The goal is to have a consistent value in all projects that are build through the aggregate, which would not be the case in the diamond case: A groups the aggregate projects B and C, which both (either directly or indirectly) build the project P. If B and C could set different values for the environment variables, we would have two different views of P, which in particular might impact the list of source files in P. @end table @c ---------------------------------------------- @node package Builder in aggregate projects @subsection package Builder in aggregate projects @c ---------------------------------------------- As we mentioned before, only the package Builder can be specified in an aggregate project. In this package, only the following attributes are valid: @table @asis @item @b{Switches}: @cindex @code{Switches} This attribute gives the list of switches to use for the builder (gprbuild or gnatmake), depending on the language of the main file. For instance, @smallexample @c projectfile for Switches ("Ada") use ("-d", "-p"); for Switches ("C") use ("-p"); @end smallexample These switches are only read from the main aggregate project (the one passed on the command line), and ignored in all other aggregate projects or projects. It can only contain builder switches, not compiler switches. @item @b{Global_Compilation_Switches} @cindex @code{Global_Compilation_Switches} This attribute gives the list of compiler switches for the various languages. For instance, @smallexample @c projectfile for Global_Compilation_Switches ("Ada") use ("-O1", "-g"); for Global_Compilation_Switches ("C") use ("-O2"); @end smallexample This attribute is only taken into account in the aggregate project specified on the command line, not in other aggregate projects. In the projects grouped by that aggregate, the attribute Builder.Global_Compilation_Switches is also ignored. However, the attribute Compiler.Default_Switches will be taken into account (but that of the aggregate have higher priority). The attribute Compiler.Switches is also taken into account and can be used to override the switches for a specific file. As a result, it always has priority. The rules are meant to avoid ambiguities when compiling. For instance, aggregate project Agg groups the projects A and B, that both depend on C. Here is an extra for all of these projects: @smallexample @c projectfile aggregate project Agg is for Project_Files use ("a.gpr", "b.gpr"); package Builder is for Global_Compilation_Switches ("Ada") use ("-O2"); end Builder; end Agg; with "c.gpr"; project A is package Builder is for Global_Compilation_Switches ("Ada") use ("-O1"); -- ignored end Builder; package Compiler is for Default_Switches ("Ada") use ("-O1", "-g"); for Switches ("a_file1.adb") use ("-O0"); end Compiler; end A; with "c.gpr"; project B is package Compiler is for Default_Switches ("Ada") use ("-O0"); end Compiler; end B; project C is package Compiler is for Default_Switches ("Ada") use ("-O3", "-gnatn"); for Switches ("c_file1.adb") use ("-O0", "-g"); end Compiler; end C; @end smallexample then the following switches are used: @itemize @bullet @item all files from project A except a_file1.adb are compiled with "-O2 -g", since the aggregate project has priority. @item the file a_file1.adb is compiled with "-O0", since the Compiler.Switches has priority @item all files from project B are compiled with "-O2", since the aggregate project has priority @item all files from C are compiled with "-O2 -gnatn", except for c_file1.adb which is compiled with "-O0 -g" @end itemize Even though C is seen through two paths (through A and through B), the switches used by the compiler are unambiguous. @item @b{Global_Configuration_Pragmas} @cindex @code{Global_Configuration_Pragmas} This attribute can be used to specify a file containing configuration pragmas, to be passed to the compiler. Since we ignore the package Builder in other aggregate projects and projects, only those pragmas defined in the main aggregate project will be taken into account. Projects can locally add to those by using the @code{Compiler.Local_Configuration_Pragmas} attribute if they need. @end table For projects that are build through the aggregate, the package Builder is ignored, except for the Executable attribute which specifies the name of the executables resulting from the link of the main programs, and for the Executable_Suffix. @c --------------------------------------------- @node Aggregate Library Projects @section Aggregate Library Projects @c --------------------------------------------- @noindent Aggregate library projects make it possible to build a single library using object files built using other standard or library projects. This gives the flexibility to describe an application as having multiple modules (a GUI, database access, ...) using different project files (so possibly built with different compiler options) and yet create a single library (static or relocatable) out of the corresponding object files. @menu * Building aggregate library projects:: * Syntax of aggregate library projects:: @end menu @c --------------------------------------------- @node Building aggregate library projects @subsection Building aggregate library projects @c --------------------------------------------- For example, we can define an aggregate project Agg that groups A, B and C: @smallexample @c projectfile aggregate library project Agg is for Project_Files use ("a.gpr", "b.gpr", "c.gpr"); for Library_Name use ("agg"); for Library_Dir use ("lagg"); end Agg; @end smallexample Then, when you build with: @smallexample gprbuild agg.gpr @end smallexample This will build all units from projects A, B and C and will create a static library named @file{libagg.a} into the @file{lagg} directory. An aggregate library project has the same set of restriction as a standard library project. Note that a shared aggregate library project cannot aggregates a static library project. In platforms where a compiler option is required to create relocatable object files, a Builder package in the aggregate library project may be used: @smallexample @c projectfile aggregate library project Agg is for Project_Files use ("a.gpr", "b.gpr", "c.gpr"); for Library_Name use ("agg"); for Library_Dir use ("lagg"); for Library_Kind use "relocatable"; package Builder is for Global_Compilation_Switches ("Ada") use ("-fPIC"); end Builder; end Agg; @end smallexample With the above aggregate library Builder package, the @code{-fPIC} option will be passed to the compiler when building any source code from projects @file{a.gpr}, @file{b.gpr} and @file{c.gpr}. @c --------------------------------------------- @node Syntax of aggregate library projects @subsection Syntax of aggregate library projects @c --------------------------------------------- An aggregate library project follows the general syntax of project files. The recommended extension is still @file{.gpr}. However, a special @code{aggregate library} qualifier must be put before the keyword @code{project}. An aggregate library project cannot @code{with} any other project (standard or aggregate), except an abstract project which can be used to share attribute values. An aggregate library project does not have any source files directly (only through other standard projects). Therefore a number of the standard attributes and packages are forbidden in an aggregate library project. Here is the (non exhaustive) list: @itemize @bullet @item Languages @item Source_Files, Source_List_File and other attributes dealing with list of sources. @item Source_Dirs, Exec_Dir and Object_Dir @item Main @item Roots @item Externally_Built @item Inherit_Source_Path @item Excluded_Source_Dirs @item Locally_Removed_Files @item Excluded_Source_Files @item Excluded_Source_List_File @item Interfaces @end itemize The only package that is authorized (albeit optional) is Builder. The Project_Files attribute (See @pxref{Aggregate Projects}) is used to described the aggregated projects whose object files have to be included into the aggregate library. @c --------------------------------------------- @node Project File Reference @section Project File Reference @c --------------------------------------------- @noindent This section describes the syntactic structure of project files, the various constructs that can be used. Finally, it ends with a summary of all available attributes. @menu * Project Declaration:: * Qualified Projects:: * Declarations:: * Packages:: * Expressions:: * External Values:: * Typed String Declaration:: * Variables:: * Attributes:: * Case Statements:: @end menu @c --------------------------------------------- @node Project Declaration @subsection Project Declaration @c --------------------------------------------- @noindent Project files have an Ada-like syntax. The minimal project file is: @smallexample @c projectfile @group project Empty is end Empty; @end group @end smallexample @noindent The identifier @code{Empty} is the name of the project. This project name must be present after the reserved word @code{end} at the end of the project file, followed by a semi-colon. @b{Identifiers} (i.e.@: the user-defined names such as project or variable names) have the same syntax as Ada identifiers: they must start with a letter, and be followed by zero or more letters, digits or underscore characters; it is also illegal to have two underscores next to each other. Identifiers are always case-insensitive ("Name" is the same as "name"). @smallexample simple_name ::= identifier name ::= simple_name @{ . simple_name @} @end smallexample @noindent @b{Strings} are used for values of attributes or as indexes for these attributes. They are in general case sensitive, except when noted otherwise (in particular, strings representing file names will be case insensitive on some systems, so that "file.adb" and "File.adb" both represent the same file). @b{Reserved words} are the same as for standard Ada 95, and cannot be used for identifiers. In particular, the following words are currently used in project files, but others could be added later on. In bold are the extra reserved words in project files: @code{all, at, case, end, for, is, limited, null, others, package, renames, type, use, when, with, @b{extends}, @b{external}, @b{project}}. @b{Comments} in project files have the same syntax as in Ada, two consecutive hyphens through the end of the line. A project may be an @b{independent project}, entirely defined by a single project file. Any source file in an independent project depends only on the predefined library and other source files in the same project. But a project may also depend on other projects, either by importing them through @b{with clauses}, or by @b{extending} at most one other project. Both types of dependency can be used in the same project. A path name denotes a project file. It can be absolute or relative. An absolute path name includes a sequence of directories, in the syntax of the host operating system, that identifies uniquely the project file in the file system. A relative path name identifies the project file, relative to the directory that contains the current project, or relative to a directory listed in the environment variables ADA_PROJECT_PATH and GPR_PROJECT_PATH. Path names are case sensitive if file names in the host operating system are case sensitive. As a special case, the directory separator can always be "/" even on Windows systems, so that project files can be made portable across architectures. The syntax of the environment variable ADA_PROJECT_PATH and GPR_PROJECT_PATH is a list of directory names separated by colons on UNIX and semicolons on Windows. A given project name can appear only once in a context clause. It is illegal for a project imported by a context clause to refer, directly or indirectly, to the project in which this context clause appears (the dependency graph cannot contain cycles), except when one of the with clause in the cycle is a @b{limited with}. @c ??? Need more details here @smallexample @c projectfile with "other_project.gpr"; project My_Project extends "extended.gpr" is end My_Project; @end smallexample @noindent These dependencies form a @b{directed graph}, potentially cyclic when using @b{limited with}. The subprogram reflecting the @b{extends} relations is a tree. A project's @b{immediate sources} are the source files directly defined by that project, either implicitly by residing in the project source directories, or explicitly through any of the source-related attributes. More generally, a project sources are the immediate sources of the project together with the immediate sources (unless overridden) of any project on which it depends directly or indirectly. A @b{project hierarchy} can be created, where projects are children of other projects. The name of such a child project must be @code{Parent.Child}, where @code{Parent} is the name of the parent project. In particular, this makes all @code{with} clauses of the parent project automatically visible in the child project. @smallexample project ::= context_clause project_declaration context_clause ::= @{with_clause@} with_clause ::= @i{with} path_name @{ , path_name @} ; path_name ::= string_literal project_declaration ::= simple_project_declaration | project_extension simple_project_declaration ::= @i{project} @i{}name @i{is} @{declarative_item@} @i{end} simple_name; @end smallexample @c --------------------------------------------- @node Qualified Projects @subsection Qualified Projects @c --------------------------------------------- @noindent Before the reserved @code{project}, there may be one or two @b{qualifiers}, that is identifiers or reserved words, to qualify the project. The current list of qualifiers is: @table @asis @item @b{abstract}: qualifies a project with no sources. Such a project must either have no declaration of attributes @code{Source_Dirs}, @code{Source_Files}, @code{Languages} or @code{Source_List_File}, or one of @code{Source_Dirs}, @code{Source_Files}, or @code{Languages} must be declared as empty. If it extends another project, the project it extends must also be a qualified abstract project. @item @b{standard}: a standard project is a non library project with sources. This is the default (implicit) qualifier. @item @b{aggregate}: a project whose sources are aggregated from other project files. @item @b{aggregate library}: a library whose sources are aggregated from other project or library project files. @item @b{library}: a library project must declare both attributes @code{Library_Name} and @code{Library_Dir}. @item @b{configuration}: a configuration project cannot be in a project tree. It describes compilers and other tools to @code{gprbuild}. @end table @c --------------------------------------------- @node Declarations @subsection Declarations @c --------------------------------------------- @noindent Declarations introduce new entities that denote types, variables, attributes, and packages. Some declarations can only appear immediately within a project declaration. Others can appear within a project or within a package. @smallexample declarative_item ::= simple_declarative_item | typed_string_declaration | package_declaration simple_declarative_item ::= variable_declaration | typed_variable_declaration | attribute_declaration | case_construction | empty_declaration empty_declaration ::= @i{null} ; @end smallexample @noindent An empty declaration is allowed anywhere a declaration is allowed. It has no effect. @c --------------------------------------------- @node Packages @subsection Packages @c --------------------------------------------- @noindent A project file may contain @b{packages}, that group attributes (typically all the attributes that are used by one of the GNAT tools). A package with a given name may only appear once in a project file. The following packages are currently supported in project files (See @pxref{Attributes} for the list of attributes that each can contain). @table @code @item Binder This package specifies characteristics useful when invoking the binder either directly via the @command{gnat} driver or when using a builder such as @command{gnatmake} or @command{gprbuild}. @xref{Main Subprograms}. @item Builder This package specifies the compilation options used when building an executable or a library for a project. Most of the options should be set in one of @code{Compiler}, @code{Binder} or @code{Linker} packages, but there are some general options that should be defined in this package. @xref{Main Subprograms}, and @pxref{Executable File Names} in particular. @item Check This package specifies the options used when calling the checking tool @command{gnatcheck} via the @command{gnat} driver. Its attribute @b{Default_Switches} has the same semantics as for the package @code{Builder}. The first string should always be @code{-rules} to specify that all the other options belong to the @code{-rules} section of the parameters to @command{gnatcheck}. @item Compiler This package specifies the compilation options used by the compiler for each languages. @xref{Tools Options in Project Files}. @item Cross_Reference This package specifies the options used when calling the library tool @command{gnatxref} via the @command{gnat} driver. Its attributes @b{Default_Switches} and @b{Switches} have the same semantics as for the package @code{Builder}. @item Eliminate This package specifies the options used when calling the tool @command{gnatelim} via the @command{gnat} driver. Its attributes @b{Default_Switches} and @b{Switches} have the same semantics as for the package @code{Builder}. @item Finder This package specifies the options used when calling the search tool @command{gnatfind} via the @command{gnat} driver. Its attributes @b{Default_Switches} and @b{Switches} have the same semantics as for the package @code{Builder}. @item Gnatls This package the options to use when invoking @command{gnatls} via the @command{gnat} driver. @item Gnatstub This package specifies the options used when calling the tool @command{gnatstub} via the @command{gnat} driver. Its attributes @b{Default_Switches} and @b{Switches} have the same semantics as for the package @code{Builder}. @item IDE This package specifies the options used when starting an integrated development environment, for instance @command{GPS} or @command{Gnatbench}. @xref{The Development Environments}. @item Linker This package specifies the options used by the linker. @xref{Main Subprograms}. @item Makefile @cindex Makefile package in projects This package is used by the GPS plugin Makefile.py. See the documentation in that plugin (from GPS: /Tools/Plug-ins). @item Metrics This package specifies the options used when calling the tool @command{gnatmetric} via the @command{gnat} driver. Its attributes @b{Default_Switches} and @b{Switches} have the same semantics as for the package @code{Builder}. @item Naming This package specifies the naming conventions that apply to the source files in a project. In particular, these conventions are used to automatically find all source files in the source directories, or given a file name to find out its language for proper processing. @xref{Naming Schemes}. @item Pretty_Printer This package specifies the options used when calling the formatting tool @command{gnatpp} via the @command{gnat} driver. Its attributes @b{Default_Switches} and @b{Switches} have the same semantics as for the package @code{Builder}. @item Stack This package specifies the options used when calling the tool @command{gnatstack} via the @command{gnat} driver. Its attributes @b{Default_Switches} and @b{Switches} have the same semantics as for the package @code{Builder}. @item Synchronize This package specifies the options used when calling the tool @command{gnatsync} via the @command{gnat} driver. @end table In its simplest form, a package may be empty: @smallexample @c projectfile @group project Simple is package Builder is end Builder; end Simple; @end group @end smallexample @noindent A package may contain @b{attribute declarations}, @b{variable declarations} and @b{case constructions}, as will be described below. When there is ambiguity between a project name and a package name, the name always designates the project. To avoid possible confusion, it is always a good idea to avoid naming a project with one of the names allowed for packages or any name that starts with @code{gnat}. A package can also be defined by a @b{renaming declaration}. The new package renames a package declared in a different project file, and has the same attributes as the package it renames. The name of the renamed package must be the same as the name of the renaming package. The project must contain a package declaration with this name, and the project must appear in the context clause of the current project, or be its parent project. It is not possible to add or override attributes to the renaming project. If you need to do so, you should use an @b{extending declaration} (see below). Packages that are renamed in other project files often come from project files that have no sources: they are just used as templates. Any modification in the template will be reflected automatically in all the project files that rename a package from the template. This is a very common way to share settings between projects. Finally, a package can also be defined by an @b{extending declaration}. This is similar to a @b{renaming declaration}, except that it is possible to add or override attributes. @smallexample package_declaration ::= package_spec | package_renaming | package_extension package_spec ::= @i{package} @i{}simple_name @i{is} @{simple_declarative_item@} @i{end} package_identifier ; package_renaming ::== @i{package} @i{}simple_name @i{renames} @i{}simple_name.package_identifier ; package_extension ::== @i{package} @i{}simple_name @i{extends} @i{}simple_name.package_identifier @i{is} @{simple_declarative_item@} @i{end} package_identifier ; @end smallexample @c --------------------------------------------- @node Expressions @subsection Expressions @c --------------------------------------------- @noindent An expression is any value that can be assigned to an attribute or a variable. It is either a literal value, or a construct requiring runtime computation by the project manager. In a project file, the computed value of an expression is either a string or a list of strings. A string value is one of: @itemize @bullet @item A literal string, for instance @code{"comm/my_proj.gpr"} @item The name of a variable that evaluates to a string (@pxref{Variables}) @item The name of an attribute that evaluates to a string (@pxref{Attributes}) @item An external reference (@pxref{External Values}) @item A concatenation of the above, as in @code{"prefix_" & Var}. @end itemize @noindent A list of strings is one of the following: @itemize @bullet @item A parenthesized comma-separated list of zero or more string expressions, for instance @code{(File_Name, "gnat.adc", File_Name & ".orig")} or @code{()}. @item The name of a variable that evaluates to a list of strings @item The name of an attribute that evaluates to a list of strings @item A concatenation of a list of strings and a string (as defined above), for instance @code{("A", "B") & "C"} @item A concatenation of two lists of strings @end itemize @noindent The following is the grammar for expressions @smallexample string_literal ::= "@{string_element@}" -- Same as Ada string_expression ::= string_literal | @i{variable_}name | external_value | attribute_reference | ( string_expression @{ & string_expression @} ) string_list ::= ( string_expression @{ , string_expression @} ) | @i{string_variable}_name | @i{string_}attribute_reference term ::= string_expression | string_list expression ::= term @{ & term @} -- Concatenation @end smallexample @noindent Concatenation involves strings and list of strings. As soon as a list of strings is involved, the result of the concatenation is a list of strings. The following Ada declarations show the existing operators: @smallexample @c ada function "&" (X : String; Y : String) return String; function "&" (X : String_List; Y : String) return String_List; function "&" (X : String_List; Y : String_List) return String_List; @end smallexample @noindent Here are some specific examples: @smallexample @c projectfile @group List := () & File_Name; -- One string in this list List2 := List & (File_Name & ".orig"); -- Two strings Big_List := List & Lists2; -- Three strings Illegal := "gnat.adc" & List2; -- Illegal, must start with list @end group @end smallexample @c --------------------------------------------- @node External Values @subsection External Values @c --------------------------------------------- @noindent An external value is an expression whose value is obtained from the command that invoked the processing of the current project file (typically a gnatmake or gprbuild command). There are two kinds of external values, one that returns a single string, and one that returns a string list. The syntax of a single string external value is: @smallexample external_value ::= @i{external} ( string_literal [, string_literal] ) @end smallexample @noindent The first string_literal is the string to be used on the command line or in the environment to specify the external value. The second string_literal, if present, is the default to use if there is no specification for this external value either on the command line or in the environment. Typically, the external value will either exist in the ^environment variables^logical name^ or be specified on the command line through the @option{^-X^/EXTERNAL_REFERENCE=^@emph{vbl}=@emph{value}} switch. If both are specified, then the command line value is used, so that a user can more easily override the value. The function @code{external} always returns a string. It is an error if the value was not found in the environment and no default was specified in the call to @code{external}. An external reference may be part of a string expression or of a string list expression, and can therefore appear in a variable declaration or an attribute declaration. Most of the time, this construct is used to initialize typed variables, which are then used in @b{case} statements to control the value assigned to attributes in various scenarios. Thus such variables are often called @b{scenario variables}. The syntax for a string list external value is: @smallexample external_value ::= @i{external_as_list} ( string_literal , string_literal ) @end smallexample @noindent The first string_literal is the string to be used on the command line or in the environment to specify the external value. The second string_literal is the separator between each component of the string list. If the external value does not exist in the environment or on the command line, the result is an empty list. This is also the case, if the separator is an empty string or if the external value is only one separator. Any separator at the beginning or at the end of the external value is discarded. Then, if there is no separator in the external value, the result is a string list with only one string. Otherwise, any string between the beginning and the first separator, between two consecutive separators and between the last separator and the end are components of the string list. @smallexample @i{external_as_list} ("SWITCHES", ",") @end smallexample @noindent If the external value is "-O2,-g", the result is ("-O2", "-g"). If the external value is ",-O2,-g,", the result is also ("-O2", "-g"). if the external value is "-gnav", the result is ("-gnatv"). If the external value is ",,", the result is (""). If the external value is ",", the result is (), the empty string list. @c --------------------------------------------- @node Typed String Declaration @subsection Typed String Declaration @c --------------------------------------------- @noindent A @b{type declaration} introduces a discrete set of string literals. If a string variable is declared to have this type, its value is restricted to the given set of literals. These are the only named types in project files. A string type may only be declared at the project level, not inside a package. @smallexample typed_string_declaration ::= @i{type} @i{}_simple_name @i{is} ( string_literal @{, string_literal@} ); @end smallexample @noindent The string literals in the list are case sensitive and must all be different. They may include any graphic characters allowed in Ada, including spaces. Here is an example of a string type declaration: @smallexample @c projectfile type OS is ("NT", "nt", "Unix", "GNU/Linux", "other OS"); @end smallexample @noindent Variables of a string type are called @b{typed variables}; all other variables are called @b{untyped variables}. Typed variables are particularly useful in @code{case} constructions, to support conditional attribute declarations. (@pxref{Case Statements}). A string type may be referenced by its name if it has been declared in the same project file, or by an expanded name whose prefix is the name of the project in which it is declared. @c --------------------------------------------- @node Variables @subsection Variables @c --------------------------------------------- @noindent @b{Variables} store values (strings or list of strings) and can appear as part of an expression. The declaration of a variable creates the variable and assigns the value of the expression to it. The name of the variable is available immediately after the assignment symbol, if you need to reuse its old value to compute the new value. Before the completion of its first declaration, the value of a variable defaults to the empty string (""). A @b{typed} variable can be used as part of a @b{case} expression to compute the value, but it can only be declared once in the project file, so that all case statements see the same value for the variable. This provides more consistency and makes the project easier to understand. The syntax for its declaration is identical to the Ada syntax for an object declaration. In effect, a typed variable acts as a constant. An @b{untyped} variable can be declared and overridden multiple times within the same project. It is declared implicitly through an Ada assignment. The first declaration establishes the kind of the variable (string or list of strings) and successive declarations must respect the initial kind. Assignments are executed in the order in which they appear, so the new value replaces the old one and any subsequent reference to the variable uses the new value. A variable may be declared at the project file level, or within a package. @smallexample typed_variable_declaration ::= @i{}simple_name : @i{}name := string_expression; variable_declaration ::= @i{}simple_name := expression; @end smallexample @noindent Here are some examples of variable declarations: @smallexample @c projectfile @group This_OS : OS := external ("OS"); -- a typed variable declaration That_OS := "GNU/Linux"; -- an untyped variable declaration Name := "readme.txt"; Save_Name := Name & ".saved"; Empty_List := (); List_With_One_Element := ("-gnaty"); List_With_Two_Elements := List_With_One_Element & "-gnatg"; Long_List := ("main.ada", "pack1_.ada", "pack1.ada", "pack2_.ada"); @end group @end smallexample @noindent A @b{variable reference} may take several forms: @itemize @bullet @item The simple variable name, for a variable in the current package (if any) or in the current project @item An expanded name, whose prefix is a context name. @end itemize @noindent A @b{context} may be one of the following: @itemize @bullet @item The name of an existing package in the current project @item The name of an imported project of the current project @item The name of an ancestor project (i.e., a project extended by the current project, either directly or indirectly) @item An expanded name whose prefix is an imported/parent project name, and whose selector is a package name in that project. @end itemize @c --------------------------------------------- @node Attributes @subsection Attributes @c --------------------------------------------- @noindent A project (and its packages) may have @b{attributes} that define the project's properties. Some attributes have values that are strings; others have values that are string lists. @smallexample attribute_declaration ::= simple_attribute_declaration | indexed_attribute_declaration simple_attribute_declaration ::= @i{for} attribute_designator @i{use} expression ; indexed_attribute_declaration ::= @i{for} @i{}simple_name ( string_literal) @i{use} expression ; attribute_designator ::= @i{}simple_name | @i{}simple_name ( string_literal ) @end smallexample @noindent There are two categories of attributes: @b{simple attributes} and @b{indexed attributes}. Each simple attribute has a default value: the empty string (for string attributes) and the empty list (for string list attributes). An attribute declaration defines a new value for an attribute, and overrides the previous value. The syntax of a simple attribute declaration is similar to that of an attribute definition clause in Ada. Some attributes are indexed. These attributes are mappings whose domain is a set of strings. They are declared one association at a time, by specifying a point in the domain and the corresponding image of the attribute. Like untyped variables and simple attributes, indexed attributes may be declared several times. Each declaration supplies a new value for the attribute, and replaces the previous setting. Here are some examples of attribute declarations: @smallexample @c projectfile -- simple attributes for Object_Dir use "objects"; for Source_Dirs use ("units", "test/drivers"); -- indexed attributes for Body ("main") use "Main.ada"; for Switches ("main.ada") use ("-v", "-gnatv"); for Switches ("main.ada") use Builder'Switches ("main.ada") & "-g"; -- indexed attributes copy (from package Builder in project Default) -- The package name must always be specified, even if it is the current -- package. for Default_Switches use Default.Builder'Default_Switches; @end smallexample @noindent Attributes references may be appear anywhere in expressions, and are used to retrieve the value previously assigned to the attribute. If an attribute has not been set in a given package or project, its value defaults to the empty string or the empty list. @smallexample attribute_reference ::= attribute_prefix ' @i{_}simple_name [ (string_literal) ] attribute_prefix ::= @i{project} | @i{}simple_name | package_identifier | @i{}simple_name . package_identifier @end smallexample @noindent Examples are: @smallexample @c projectfile project'Object_Dir Naming'Dot_Replacement Imported_Project'Source_Dirs Imported_Project.Naming'Casing Builder'Default_Switches ("Ada") @end smallexample @noindent The prefix of an attribute may be: @itemize @bullet @item @code{project} for an attribute of the current project @item The name of an existing package of the current project @item The name of an imported project @item The name of a parent project that is extended by the current project @item An expanded name whose prefix is imported/parent project name, and whose selector is a package name @end itemize @noindent Legal attribute names are listed below, including the package in which they must be declared. These names are case-insensitive. The semantics for the attributes is explained in great details in other sections. The column @emph{index} indicates whether the attribute is an indexed attribute, and when it is whether its index is case sensitive (sensitive) or not (insensitive), or if case sensitivity depends is the same as file names sensitivity on the system (file). The text is between brackets ([]) if the index is optional. @multitable @columnfractions .3 .1 .2 .4 @headitem Attribute Name @tab Value @tab Package @tab Index @headitem General attributes @tab @tab @tab @pxref{Building With Projects} @item Name @tab string @tab - @tab (Read-only, name of project) @item Project_Dir @tab string @tab - @tab (Read-only, directory of project) @item Source_Files @tab list @tab - @tab - @item Source_Dirs @tab list @tab - @tab - @item Source_List_File @tab string @tab - @tab - @item Locally_Removed_Files @tab list @tab - @tab - @item Excluded_Source_Files @tab list @tab - @tab - @item Object_Dir @tab string @tab - @tab - @item Exec_Dir @tab string @tab - @tab - @item Excluded_Source_Dirs @tab list @tab - @tab - @item Excluded_Source_Files @tab list @tab - @tab - @item Excluded_Source_List_File @tab list @tab - @tab - @item Inherit_Source_Path @tab list @tab - @tab insensitive @item Languages @tab list @tab - @tab - @item Main @tab list @tab - @tab - @item Main_Language @tab string @tab - @tab - @item Externally_Built @tab string @tab - @tab - @item Roots @tab list @tab - @tab file @headitem Library-related attributes @tab @tab @tab @pxref{Library Projects} @item Library_Dir @tab string @tab - @tab - @item Library_Name @tab string @tab - @tab - @item Library_Kind @tab string @tab - @tab - @item Library_Version @tab string @tab - @tab - @item Library_Interface @tab string @tab - @tab - @item Library_Auto_Init @tab string @tab - @tab - @item Library_Options @tab list @tab - @tab - @item Leading_Library_Options @tab list @tab - @tab - @item Library_Src_Dir @tab string @tab - @tab - @item Library_ALI_Dir @tab string @tab - @tab - @item Library_GCC @tab string @tab - @tab - @item Library_Symbol_File @tab string @tab - @tab - @item Library_Symbol_Policy @tab string @tab - @tab - @item Library_Reference_Symbol_File @tab string @tab - @tab - @item Interfaces @tab list @tab - @tab - @headitem Naming @tab @tab @tab @pxref{Naming Schemes} @item Spec_Suffix @tab string @tab Naming @tab insensitive (language) @item Body_Suffix @tab string @tab Naming @tab insensitive (language) @item Separate_Suffix @tab string @tab Naming @tab - @item Casing @tab string @tab Naming @tab - @item Dot_Replacement @tab string @tab Naming @tab - @item Spec @tab string @tab Naming @tab insensitive (Ada unit) @item Body @tab string @tab Naming @tab insensitive (Ada unit) @item Specification_Exceptions @tab list @tab Naming @tab insensitive (language) @item Implementation_Exceptions @tab list @tab Naming @tab insensitive (language) @headitem Building @tab @tab @tab @pxref{Switches and Project Files} @item Default_Switches @tab list @tab Builder, Compiler, Binder, Linker, Cross_Reference, Finder, Pretty_Printer, gnatstub, Check, Synchronize, Eliminate, Metrics, IDE @tab insensitive (language name) @item Switches @tab list @tab Builder, Compiler, Binder, Linker, Cross_Reference, Finder, gnatls, Pretty_Printer, gnatstub, Check, Synchronize, Eliminate, Metrics, Stack @tab [file] (file name) @item Local_Configuration_Pragmas @tab string @tab Compiler @tab - @item Local_Config_File @tab string @tab insensitive @tab - @item Global_Configuration_Pragmas @tab list @tab Builder @tab - @item Global_Compilation_Switches @tab list @tab Builder @tab language @item Executable @tab string @tab Builder @tab [file] @item Executable_Suffix @tab string @tab Builder @tab - @item Global_Config_File @tab string @tab Builder @tab insensitive (language) @headitem IDE (used and created by GPS) @tab @tab @tab @item Remote_Host @tab string @tab IDE @tab - @item Program_Host @tab string @tab IDE @tab - @item Communication_Protocol @tab string @tab IDE @tab - @item Compiler_Command @tab string @tab IDE @tab insensitive (language) @item Debugger_Command @tab string @tab IDE @tab - @item Gnatlist @tab string @tab IDE @tab - @item Gnat @tab string @tab IDE @tab - @item VCS_Kind @tab string @tab IDE @tab - @item VCS_File_Check @tab string @tab IDE @tab - @item VCS_Log_Check @tab string @tab IDE @tab - @item Documentation_Dir @tab string @tab IDE @tab - @headitem Configuration files @tab @tab @tab See gprbuild manual @item Default_Language @tab string @tab - @tab - @item Run_Path_Option @tab list @tab - @tab - @item Run_Path_Origin @tab string @tab - @tab - @item Separate_Run_Path_Options @tab string @tab - @tab - @item Toolchain_Version @tab string @tab - @tab insensitive @item Toolchain_Description @tab string @tab - @tab insensitive @item Object_Generated @tab string @tab - @tab insensitive @item Objects_Linked @tab string @tab - @tab insensitive @item Target @tab string @tab - @tab - @item Library_Builder @tab string @tab - @tab - @item Library_Support @tab string @tab - @tab - @item Archive_Builder @tab list @tab - @tab - @item Archive_Builder_Append_Option @tab list @tab - @tab - @item Archive_Indexer @tab list @tab - @tab - @item Archive_Suffix @tab string @tab - @tab - @item Library_Partial_Linker @tab list @tab - @tab - @item Shared_Library_Prefix @tab string @tab - @tab - @item Shared_Library_Suffix @tab string @tab - @tab - @item Symbolic_Link_Supported @tab string @tab - @tab - @item Library_Major_Minor_Id_Supported @tab string @tab - @tab - @item Library_Auto_Init_Supported @tab string @tab - @tab - @item Shared_Library_Minimum_Switches @tab list @tab - @tab - @item Library_Version_Switches @tab list @tab - @tab - @item Library_Install_Name_Option @tab string @tab - @tab - @item Runtime_Library_Dir @tab string @tab - @tab insensitive @item Runtime_Source_Dir @tab string @tab - @tab insensitive @item Driver @tab string @tab Compiler,Binder,Linker @tab insensitive (language) @item Required_Switches @tab list @tab Compiler,Binder,Linker @tab insensitive (language) @item Leading_Required_Switches @tab list @tab Compiler @tab insensitive (language) @item Trailing_Required_Switches @tab list @tab Compiler @tab insensitive (language) @item Pic_Options @tab list @tab Compiler @tab insensitive (language) @item Path_Syntax @tab string @tab Compiler @tab insensitive (language) @item Object_File_Suffix @tab string @tab Compiler @tab insensitive (language) @item Object_File_Switches @tab list @tab Compiler @tab insensitive (language) @item Multi_Unit_Switches @tab list @tab Compiler @tab insensitive (language) @item Multi_Unit_Object_Separator @tab string @tab Compiler @tab insensitive (language) @item Mapping_File_Switches @tab list @tab Compiler @tab insensitive (language) @item Mapping_Spec_Suffix @tab string @tab Compiler @tab insensitive (language) @item Mapping_body_Suffix @tab string @tab Compiler @tab insensitive (language) @item Config_File_Switches @tab list @tab Compiler @tab insensitive (language) @item Config_Body_File_Name @tab string @tab Compiler @tab insensitive (language) @item Config_Body_File_Name_Index @tab string @tab Compiler @tab insensitive (language) @item Config_Body_File_Name_Pattern @tab string @tab Compiler @tab insensitive (language) @item Config_Spec_File_Name @tab string @tab Compiler @tab insensitive (language) @item Config_Spec_File_Name_Index @tab string @tab Compiler @tab insensitive (language) @item Config_Spec_File_Name_Pattern @tab string @tab Compiler @tab insensitive (language) @item Config_File_Unique @tab string @tab Compiler @tab insensitive (language) @item Dependency_Switches @tab list @tab Compiler @tab insensitive (language) @item Dependency_Driver @tab list @tab Compiler @tab insensitive (language) @item Include_Switches @tab list @tab Compiler @tab insensitive (language) @item Include_Path @tab string @tab Compiler @tab insensitive (language) @item Include_Path_File @tab string @tab Compiler @tab insensitive (language) @item Prefix @tab string @tab Binder @tab insensitive (language) @item Objects_Path @tab string @tab Binder @tab insensitive (language) @item Objects_Path_File @tab string @tab Binder @tab insensitive (language) @item Linker_Options @tab list @tab Linker @tab - @item Leading_Switches @tab list @tab Linker @tab - @item Map_File_Options @tab string @tab Linker @tab - @item Executable_Switches @tab list @tab Linker @tab - @item Lib_Dir_Switch @tab string @tab Linker @tab - @item Lib_Name_Switch @tab string @tab Linker @tab - @item Max_Command_Line_Length @tab string @tab Linker @tab - @item Response_File_Format @tab string @tab Linker @tab - @item Response_File_Switches @tab list @tab Linker @tab - @end multitable @c --------------------------------------------- @node Case Statements @subsection Case Statements @c --------------------------------------------- @noindent A @b{case} statement is used in a project file to effect conditional behavior. Through this statement, you can set the value of attributes and variables depending on the value previously assigned to a typed variable. All choices in a choice list must be distinct. Unlike Ada, the choice lists of all alternatives do not need to include all values of the type. An @code{others} choice must appear last in the list of alternatives. The syntax of a @code{case} construction is based on the Ada case statement (although the @code{null} statement for empty alternatives is optional). The case expression must be a typed string variable, whose value is often given by an external reference (@pxref{External Values}). Each alternative starts with the reserved word @code{when}, either a list of literal strings separated by the @code{"|"} character or the reserved word @code{others}, and the @code{"=>"} token. Each literal string must belong to the string type that is the type of the case variable. After each @code{=>}, there are zero or more statements. The only statements allowed in a case construction are other case statements, attribute declarations and variable declarations. String type declarations and package declarations are not allowed. Variable declarations are restricted to variables that have already been declared before the case construction. @smallexample case_statement ::= @i{case} @i{}name @i{is} @{case_item@} @i{end case} ; case_item ::= @i{when} discrete_choice_list => @{case_statement | attribute_declaration | variable_declaration | empty_declaration@} discrete_choice_list ::= string_literal @{| string_literal@} | @i{others} @end smallexample @noindent Here is a typical example: @smallexample @c projectfile @group project MyProj is type OS_Type is ("GNU/Linux", "Unix", "NT", "VMS"); OS : OS_Type := external ("OS", "GNU/Linux"); package Compiler is case OS is when "GNU/Linux" | "Unix" => for Switches ("Ada") use ("-gnath"); when "NT" => for Switches ("Ada") use ("-gnatP"); when others => null; end case; end Compiler; end MyProj; @end group @end smallexample @c --------------------------------------------- @node Tools Supporting Project Files @chapter Tools Supporting Project Files @c --------------------------------------------- @noindent @menu * gnatmake and Project Files:: * The GNAT Driver and Project Files:: * The Development Environments:: @end menu @c --------------------------------------------- @node gnatmake and Project Files @section gnatmake and Project Files @c --------------------------------------------- @noindent This section covers several topics related to @command{gnatmake} and project files: defining ^switches^switches^ for @command{gnatmake} and for the tools that it invokes; specifying configuration pragmas; the use of the @code{Main} attribute; building and rebuilding library project files. @menu * Switches Related to Project Files:: * Switches and Project Files:: * Specifying Configuration Pragmas:: * Project Files and Main Subprograms:: * Library Project Files:: @end menu @c --------------------------------------------- @node Switches Related to Project Files @subsection Switches Related to Project Files @c --------------------------------------------- @noindent The following switches are used by GNAT tools that support project files: @table @option @item ^-P^/PROJECT_FILE=^@var{project} @cindex @option{^-P^/PROJECT_FILE^} (any project-aware tool) Indicates the name of a project file. This project file will be parsed with the verbosity indicated by @option{^-vP^MESSAGE_PROJECT_FILES=^@emph{x}}, if any, and using the external references indicated by @option{^-X^/EXTERNAL_REFERENCE^} switches, if any. @ifclear vms There may zero, one or more spaces between @option{-P} and @var{project}. @end ifclear There must be only one @option{^-P^/PROJECT_FILE^} switch on the command line. Since the Project Manager parses the project file only after all the switches on the command line are checked, the order of the switches @option{^-P^/PROJECT_FILE^}, @option{^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}} or @option{^-X^/EXTERNAL_REFERENCE^} is not significant. @item ^-X^/EXTERNAL_REFERENCE=^@var{name=value} @cindex @option{^-X^/EXTERNAL_REFERENCE^} (any project-aware tool) Indicates that external variable @var{name} has the value @var{value}. The Project Manager will use this value for occurrences of @code{external(name)} when parsing the project file. @ifclear vms If @var{name} or @var{value} includes a space, then @var{name=value} should be put between quotes. @smallexample -XOS=NT -X"user=John Doe" @end smallexample @end ifclear Several @option{^-X^/EXTERNAL_REFERENCE^} switches can be used simultaneously. If several @option{^-X^/EXTERNAL_REFERENCE^} switches specify the same @var{name}, only the last one is used. An external variable specified with a @option{^-X^/EXTERNAL_REFERENCE^} switch takes precedence over the value of the same name in the environment. @item ^-vP^/MESSAGES_PROJECT_FILE=^@emph{x} @cindex @option{^-vP^/MESSAGES_PROJECT_FILE^} (any project-aware tool) Indicates the verbosity of the parsing of GNAT project files. @ifclear vms @option{-vP0} means Default; @option{-vP1} means Medium; @option{-vP2} means High. @end ifclear @ifset vms There are three possible options for this qualifier: DEFAULT, MEDIUM and HIGH. @end ifset The default is ^Default^DEFAULT^: no output for syntactically correct project files. If several @option{^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}} switches are present, only the last one is used. @item ^-aP^/ADD_PROJECT_SEARCH_DIR=^ @cindex @option{^-aP^/ADD_PROJECT_SEARCH_DIR=^} (any project-aware tool) Add directory at the beginning of the project search path, in order, after the current working directory. @ifclear vms @item -eL @cindex @option{-eL} (any project-aware tool) Follow all symbolic links when processing project files. @end ifclear @item ^--subdirs^/SUBDIRS^= @cindex @option{^--subdirs^/SUBDIRS^=} (gnatmake and gnatclean) This switch is recognized by gnatmake and gnatclean. It indicate that the real directories (except the source directories) are the subdirectories of the directories specified in the project files. This applies in particular to object directories, library directories and exec directories. If the subdirectories do not exist, they are created automatically. @end table @c --------------------------------------------- @node Switches and Project Files @subsection Switches and Project Files @c --------------------------------------------- @noindent @ifset vms It is not currently possible to specify VMS style qualifiers in the project files; only Unix style ^switches^switches^ may be specified. @end ifset For each of the packages @code{Builder}, @code{Compiler}, @code{Binder}, and @code{Linker}, you can specify a @code{^Default_Switches^Default_Switches^} attribute, a @code{Switches} attribute, or both; as their names imply, these ^switch^switch^-related attributes affect the ^switches^switches^ that are used for each of these GNAT components when @command{gnatmake} is invoked. As will be explained below, these component-specific ^switches^switches^ precede the ^switches^switches^ provided on the @command{gnatmake} command line. The @code{^Default_Switches^Default_Switches^} attribute is an attribute indexed by language name (case insensitive) whose value is a string list. For example: @smallexample @c projectfile @group package Compiler is for ^Default_Switches^Default_Switches^ ("Ada") use ("^-gnaty^-gnaty^", "^-v^-v^"); end Compiler; @end group @end smallexample @noindent The @code{Switches} attribute is indexed on a file name (which may or may not be case sensitive, depending on the operating system) whose value is a string list. For example: @smallexample @c projectfile @group package Builder is for Switches ("main1.adb") use ("^-O2^-O2^"); for Switches ("main2.adb") use ("^-g^-g^"); end Builder; @end group @end smallexample @noindent For the @code{Builder} package, the file names must designate source files for main subprograms. For the @code{Binder} and @code{Linker} packages, the file names must designate @file{ALI} or source files for main subprograms. In each case just the file name without an explicit extension is acceptable. For each tool used in a program build (@command{gnatmake}, the compiler, the binder, and the linker), the corresponding package @dfn{contributes} a set of ^switches^switches^ for each file on which the tool is invoked, based on the ^switch^switch^-related attributes defined in the package. In particular, the ^switches^switches^ that each of these packages contributes for a given file @var{f} comprise: @itemize @bullet @item the value of attribute @code{Switches (@var{f})}, if it is specified in the package for the given file, @item otherwise, the value of @code{^Default_Switches^Default_Switches^ ("Ada")}, if it is specified in the package. @end itemize @noindent If neither of these attributes is defined in the package, then the package does not contribute any ^switches^switches^ for the given file. When @command{gnatmake} is invoked on a file, the ^switches^switches^ comprise two sets, in the following order: those contributed for the file by the @code{Builder} package; and the switches passed on the command line. When @command{gnatmake} invokes a tool (compiler, binder, linker) on a file, the ^switches^switches^ passed to the tool comprise three sets, in the following order: @enumerate @item the applicable ^switches^switches^ contributed for the file by the @code{Builder} package in the project file supplied on the command line; @item those contributed for the file by the package (in the relevant project file -- see below) corresponding to the tool; and @item the applicable switches passed on the command line. @end enumerate The term @emph{applicable ^switches^switches^} reflects the fact that @command{gnatmake} ^switches^switches^ may or may not be passed to individual tools, depending on the individual ^switch^switch^. @command{gnatmake} may invoke the compiler on source files from different projects. The Project Manager will use the appropriate project file to determine the @code{Compiler} package for each source file being compiled. Likewise for the @code{Binder} and @code{Linker} packages. As an example, consider the following package in a project file: @smallexample @c projectfile @group project Proj1 is package Compiler is for ^Default_Switches^Default_Switches^ ("Ada") use ("^-g^-g^"); for Switches ("a.adb") use ("^-O1^-O1^"); for Switches ("b.adb") use ("^-O2^-O2^", "^-gnaty^-gnaty^"); end Compiler; end Proj1; @end group @end smallexample @noindent If @command{gnatmake} is invoked with this project file, and it needs to compile, say, the files @file{a.adb}, @file{b.adb}, and @file{c.adb}, then @file{a.adb} will be compiled with the ^switch^switch^ @option{^-O1^-O1^}, @file{b.adb} with ^switches^switches^ @option{^-O2^-O2^} and @option{^-gnaty^-gnaty^}, and @file{c.adb} with @option{^-g^-g^}. The following example illustrates the ordering of the ^switches^switches^ contributed by different packages: @smallexample @c projectfile @group project Proj2 is package Builder is for Switches ("main.adb") use ("^-g^-g^", "^-O1^-)1^", "^-f^-f^"); end Builder; @end group @group package Compiler is for Switches ("main.adb") use ("^-O2^-O2^"); end Compiler; end Proj2; @end group @end smallexample @noindent If you issue the command: @smallexample gnatmake ^-Pproj2^/PROJECT_FILE=PROJ2^ -O0 main @end smallexample @noindent then the compiler will be invoked on @file{main.adb} with the following sequence of ^switches^switches^ @smallexample ^-g -O1 -O2 -O0^-g -O1 -O2 -O0^ @end smallexample @noindent with the last @option{^-O^-O^} ^switch^switch^ having precedence over the earlier ones; several other ^switches^switches^ (such as @option{^-c^-c^}) are added implicitly. The ^switches^switches^ @option{^-g^-g^} and @option{^-O1^-O1^} are contributed by package @code{Builder}, @option{^-O2^-O2^} is contributed by the package @code{Compiler} and @option{^-O0^-O0^} comes from the command line. The @option{^-g^-g^} ^switch^switch^ will also be passed in the invocation of @command{Gnatlink.} A final example illustrates switch contributions from packages in different project files: @smallexample @c projectfile @group project Proj3 is for Source_Files use ("pack.ads", "pack.adb"); package Compiler is for ^Default_Switches^Default_Switches^ ("Ada") use ("^-gnata^-gnata^"); end Compiler; end Proj3; @end group @group with "Proj3"; project Proj4 is for Source_Files use ("foo_main.adb", "bar_main.adb"); package Builder is for Switches ("foo_main.adb") use ("^-s^-s^", "^-g^-g^"); end Builder; end Proj4; @end group @group -- Ada source file: with Pack; procedure Foo_Main is @dots{} end Foo_Main; @end group @end smallexample @noindent If the command is @smallexample gnatmake ^-PProj4^/PROJECT_FILE=PROJ4^ foo_main.adb -cargs -gnato @end smallexample @noindent then the ^switches^switches^ passed to the compiler for @file{foo_main.adb} are @option{^-g^-g^} (contributed by the package @code{Proj4.Builder}) and @option{^-gnato^-gnato^} (passed on the command line). When the imported package @code{Pack} is compiled, the ^switches^switches^ used are @option{^-g^-g^} from @code{Proj4.Builder}, @option{^-gnata^-gnata^} (contributed from package @code{Proj3.Compiler}, and @option{^-gnato^-gnato^} from the command line. When using @command{gnatmake} with project files, some ^switches^switches^ or arguments may be expressed as relative paths. As the working directory where compilation occurs may change, these relative paths are converted to absolute paths. For the ^switches^switches^ found in a project file, the relative paths are relative to the project file directory, for the switches on the command line, they are relative to the directory where @command{gnatmake} is invoked. The ^switches^switches^ for which this occurs are: ^-I^-I^, ^-A^-A^, ^-L^-L^, ^-aO^-aO^, ^-aL^-aL^, ^-aI^-aI^, as well as all arguments that are not switches (arguments to ^switch^switch^ ^-o^-o^, object files specified in package @code{Linker} or after -largs on the command line). The exception to this rule is the ^switch^switch^ ^--RTS=^--RTS=^ for which a relative path argument is never converted. @c --------------------------------------------- @node Specifying Configuration Pragmas @subsection Specifying Configuration Pragmas @c --------------------------------------------- @noindent When using @command{gnatmake} with project files, if there exists a file @file{gnat.adc} that contains configuration pragmas, this file will be ignored. Configuration pragmas can be defined by means of the following attributes in project files: @code{Global_Configuration_Pragmas} in package @code{Builder} and @code{Local_Configuration_Pragmas} in package @code{Compiler}. Both these attributes are single string attributes. Their values is the path name of a file containing configuration pragmas. If a path name is relative, then it is relative to the project directory of the project file where the attribute is defined. When compiling a source, the configuration pragmas used are, in order, those listed in the file designated by attribute @code{Global_Configuration_Pragmas} in package @code{Builder} of the main project file, if it is specified, and those listed in the file designated by attribute @code{Local_Configuration_Pragmas} in package @code{Compiler} of the project file of the source, if it exists. @c --------------------------------------------- @node Project Files and Main Subprograms @subsection Project Files and Main Subprograms @c --------------------------------------------- @noindent When using a project file, you can invoke @command{gnatmake} with one or several main subprograms, by specifying their source files on the command line. @smallexample gnatmake ^-P^/PROJECT_FILE=^prj main1.adb main2.adb main3.adb @end smallexample @noindent Each of these needs to be a source file of the same project, except when the switch ^-u^/UNIQUE^ is used. When ^-u^/UNIQUE^ is not used, all the mains need to be sources of the same project, one of the project in the tree rooted at the project specified on the command line. The package @code{Builder} of this common project, the "main project" is the one that is considered by @command{gnatmake}. When ^-u^/UNIQUE^ is used, the specified source files may be in projects imported directly or indirectly by the project specified on the command line. Note that if such a source file is not part of the project specified on the command line, the ^switches^switches^ found in package @code{Builder} of the project specified on the command line, if any, that are transmitted to the compiler will still be used, not those found in the project file of the source file. When using a project file, you can also invoke @command{gnatmake} without explicitly specifying any main, and the effect depends on whether you have defined the @code{Main} attribute. This attribute has a string list value, where each element in the list is the name of a source file (the file extension is optional) that contains a unit that can be a main subprogram. If the @code{Main} attribute is defined in a project file as a non-empty string list and the switch @option{^-u^/UNIQUE^} is not used on the command line, then invoking @command{gnatmake} with this project file but without any main on the command line is equivalent to invoking @command{gnatmake} with all the file names in the @code{Main} attribute on the command line. Example: @smallexample @c projectfile @group project Prj is for Main use ("main1.adb", "main2.adb", "main3.adb"); end Prj; @end group @end smallexample @noindent With this project file, @code{"gnatmake ^-Pprj^/PROJECT_FILE=PRJ^"} is equivalent to @code{"gnatmake ^-Pprj^/PROJECT_FILE=PRJ^ main1.adb main2.adb main3.adb"}. When the project attribute @code{Main} is not specified, or is specified as an empty string list, or when the switch @option{-u} is used on the command line, then invoking @command{gnatmake} with no main on the command line will result in all immediate sources of the project file being checked, and potentially recompiled. Depending on the presence of the switch @option{-u}, sources from other project files on which the immediate sources of the main project file depend are also checked and potentially recompiled. In other words, the @option{-u} switch is applied to all of the immediate sources of the main project file. When no main is specified on the command line and attribute @code{Main} exists and includes several mains, or when several mains are specified on the command line, the default ^switches^switches^ in package @code{Builder} will be used for all mains, even if there are specific ^switches^switches^ specified for one or several mains. But the ^switches^switches^ from package @code{Binder} or @code{Linker} will be the specific ^switches^switches^ for each main, if they are specified. @c --------------------------------------------- @node Library Project Files @subsection Library Project Files @c --------------------------------------------- @noindent When @command{gnatmake} is invoked with a main project file that is a library project file, it is not allowed to specify one or more mains on the command line. When a library project file is specified, switches ^-b^/ACTION=BIND^ and ^-l^/ACTION=LINK^ have special meanings. @itemize @bullet @item ^-b^/ACTION=BIND^ is only allowed for stand-alone libraries. It indicates to @command{gnatmake} that @command{gnatbind} should be invoked for the library. @item ^-l^/ACTION=LINK^ may be used for all library projects. It indicates to @command{gnatmake} that the binder generated file should be compiled (in the case of a stand-alone library) and that the library should be built. @end itemize @c --------------------------------------------- @node The GNAT Driver and Project Files @section The GNAT Driver and Project Files @c --------------------------------------------- @noindent A number of GNAT tools, other than @command{^gnatmake^gnatmake^} can benefit from project files: (@command{^gnatbind^gnatbind^}, @command{^gnatcheck^gnatcheck^}, @command{^gnatclean^gnatclean^}, @command{^gnatelim^gnatelim^}, @command{^gnatfind^gnatfind^}, @command{^gnatlink^gnatlink^}, @command{^gnatls^gnatls^}, @command{^gnatmetric^gnatmetric^}, @command{^gnatpp^gnatpp^}, @command{^gnatstub^gnatstub^}, and @command{^gnatxref^gnatxref^}). However, none of these tools can be invoked directly with a project file switch (@option{^-P^/PROJECT_FILE=^}). They must be invoked through the @command{gnat} driver. The @command{gnat} driver is a wrapper that accepts a number of commands and calls the corresponding tool. It was designed initially for VMS platforms (to convert VMS qualifiers to Unix-style switches), but it is now available on all GNAT platforms. On non-VMS platforms, the @command{gnat} driver accepts the following commands (case insensitive): @itemize @bullet @item BIND to invoke @command{^gnatbind^gnatbind^} @item CHOP to invoke @command{^gnatchop^gnatchop^} @item CLEAN to invoke @command{^gnatclean^gnatclean^} @item COMP or COMPILE to invoke the compiler @item ELIM to invoke @command{^gnatelim^gnatelim^} @item FIND to invoke @command{^gnatfind^gnatfind^} @item KR or KRUNCH to invoke @command{^gnatkr^gnatkr^} @item LINK to invoke @command{^gnatlink^gnatlink^} @item LS or LIST to invoke @command{^gnatls^gnatls^} @item MAKE to invoke @command{^gnatmake^gnatmake^} @item NAME to invoke @command{^gnatname^gnatname^} @item PREP or PREPROCESS to invoke @command{^gnatprep^gnatprep^} @item PP or PRETTY to invoke @command{^gnatpp^gnatpp^} @item METRIC to invoke @command{^gnatmetric^gnatmetric^} @item STUB to invoke @command{^gnatstub^gnatstub^} @item XREF to invoke @command{^gnatxref^gnatxref^} @end itemize @noindent (note that the compiler is invoked using the command @command{^gnatmake -f -u -c^gnatmake -f -u -c^}). On non-VMS platforms, between @command{gnat} and the command, two special switches may be used: @itemize @bullet @item @command{-v} to display the invocation of the tool. @item @command{-dn} to prevent the @command{gnat} driver from removing the temporary files it has created. These temporary files are configuration files and temporary file list files. @end itemize @noindent The command may be followed by switches and arguments for the invoked tool. @smallexample gnat bind -C main.ali gnat ls -a main gnat chop foo.txt @end smallexample @noindent Switches may also be put in text files, one switch per line, and the text files may be specified with their path name preceded by '@@'. @smallexample gnat bind @@args.txt main.ali @end smallexample @noindent In addition, for commands BIND, COMP or COMPILE, FIND, ELIM, LS or LIST, LINK, METRIC, PP or PRETTY, STUB and XREF, the project file related switches (@option{^-P^/PROJECT_FILE^}, @option{^-X^/EXTERNAL_REFERENCE^} and @option{^-vP^/MESSAGES_PROJECT_FILE=^x}) may be used in addition to the switches of the invoking tool. When GNAT PP or GNAT PRETTY is used with a project file, but with no source specified on the command line, it invokes @command{^gnatpp^gnatpp^} with all the immediate sources of the specified project file. When GNAT METRIC is used with a project file, but with no source specified on the command line, it invokes @command{^gnatmetric^gnatmetric^} with all the immediate sources of the specified project file and with @option{^-d^/DIRECTORY^} with the parameter pointing to the object directory of the project. In addition, when GNAT PP, GNAT PRETTY or GNAT METRIC is used with a project file, no source is specified on the command line and switch ^-U^/ALL_PROJECTS^ is specified on the command line, then the underlying tool (^gnatpp^gnatpp^ or ^gnatmetric^gnatmetric^) is invoked for all sources of all projects, not only for the immediate sources of the main project. @ifclear vms (-U stands for Universal or Union of the project files of the project tree) @end ifclear For each of the following commands, there is optionally a corresponding package in the main project. @itemize @bullet @item package @code{Binder} for command BIND (invoking @code{^gnatbind^gnatbind^}) @item package @code{Check} for command CHECK (invoking @code{^gnatcheck^gnatcheck^}) @item package @code{Compiler} for command COMP or COMPILE (invoking the compiler) @item package @code{Cross_Reference} for command XREF (invoking @code{^gnatxref^gnatxref^}) @item package @code{Eliminate} for command ELIM (invoking @code{^gnatelim^gnatelim^}) @item package @code{Finder} for command FIND (invoking @code{^gnatfind^gnatfind^}) @item package @code{Gnatls} for command LS or LIST (invoking @code{^gnatls^gnatls^}) @item package @code{Gnatstub} for command STUB (invoking @code{^gnatstub^gnatstub^}) @item package @code{Linker} for command LINK (invoking @code{^gnatlink^gnatlink^}) @item package @code{Check} for command CHECK (invoking @code{^gnatcheck^gnatcheck^}) @item package @code{Metrics} for command METRIC (invoking @code{^gnatmetric^gnatmetric^}) @item package @code{Pretty_Printer} for command PP or PRETTY (invoking @code{^gnatpp^gnatpp^}) @end itemize @noindent Package @code{Gnatls} has a unique attribute @code{Switches}, a simple variable with a string list value. It contains ^switches^switches^ for the invocation of @code{^gnatls^gnatls^}. @smallexample @c projectfile @group project Proj1 is package gnatls is for Switches use ("^-a^-a^", "^-v^-v^"); end gnatls; end Proj1; @end group @end smallexample @noindent All other packages have two attribute @code{Switches} and @code{^Default_Switches^Default_Switches^}. @code{Switches} is an indexed attribute, indexed by the source file name, that has a string list value: the ^switches^switches^ to be used when the tool corresponding to the package is invoked for the specific source file. @code{^Default_Switches^Default_Switches^} is an attribute, indexed by the programming language that has a string list value. @code{^Default_Switches^Default_Switches^ ("Ada")} contains the ^switches^switches^ for the invocation of the tool corresponding to the package, except if a specific @code{Switches} attribute is specified for the source file. @smallexample @c projectfile @group project Proj is for Source_Dirs use ("**"); package gnatls is for Switches use ("^-a^-a^", "^-v^-v^"); end gnatls; @end group @group package Compiler is for ^Default_Switches^Default_Switches^ ("Ada") use ("^-gnatv^-gnatv^", "^-gnatwa^-gnatwa^"); end Binder; @end group @group package Binder is for ^Default_Switches^Default_Switches^ ("Ada") use ("^-C^-C^", "^-e^-e^"); end Binder; @end group @group package Linker is for ^Default_Switches^Default_Switches^ ("Ada") use ("^-C^-C^"); for Switches ("main.adb") use ("^-C^-C^", "^-v^-v^", "^-v^-v^"); end Linker; @end group @group package Finder is for ^Default_Switches^Default_Switches^ ("Ada") use ("^-a^-a^", "^-f^-f^"); end Finder; @end group @group package Cross_Reference is for ^Default_Switches^Default_Switches^ ("Ada") use ("^-a^-a^", "^-f^-f^", "^-d^-d^", "^-u^-u^"); end Cross_Reference; end Proj; @end group @end smallexample @noindent With the above project file, commands such as @smallexample ^gnat comp -Pproj main^GNAT COMP /PROJECT_FILE=PROJ MAIN^ ^gnat ls -Pproj main^GNAT LIST /PROJECT_FILE=PROJ MAIN^ ^gnat xref -Pproj main^GNAT XREF /PROJECT_FILE=PROJ MAIN^ ^gnat bind -Pproj main.ali^GNAT BIND /PROJECT_FILE=PROJ MAIN.ALI^ ^gnat link -Pproj main.ali^GNAT LINK /PROJECT_FILE=PROJ MAIN.ALI^ @end smallexample @noindent will set up the environment properly and invoke the tool with the switches found in the package corresponding to the tool: @code{^Default_Switches^Default_Switches^ ("Ada")} for all tools, except @code{Switches ("main.adb")} for @code{^gnatlink^gnatlink^}. It is also possible to invoke some of the tools, (@code{^gnatcheck^gnatcheck^}, @code{^gnatmetric^gnatmetric^}, and @code{^gnatpp^gnatpp^}) on a set of project units thanks to the combination of the switches @option{-P}, @option{-U} and possibly the main unit when one is interested in its closure. For instance, @smallexample gnat metric -Pproj @end smallexample @noindent will compute the metrics for all the immediate units of project @code{proj}. @smallexample gnat metric -Pproj -U @end smallexample @noindent will compute the metrics for all the units of the closure of projects rooted at @code{proj}. @smallexample gnat metric -Pproj -U main_unit @end smallexample @noindent will compute the metrics for the closure of units rooted at @code{main_unit}. This last possibility relies implicitly on @command{gnatbind}'s option @option{-R}. But if the argument files for the tool invoked by the @command{gnat} driver are explicitly specified either directly or through the tool @option{-files} option, then the tool is called only for these explicitly specified files. @c --------------------------------------------- @node The Development Environments @section The Development Environments @c --------------------------------------------- @noindent See the appropriate manuals for more details. These environments will store a number of settings in the project itself, when they are meant to be shared by the whole team working on the project. Here are the attributes defined in the package @b{IDE} in projects. @table @code @item Remote_Host This is a simple attribute. Its value is a string that designates the remote host in a cross-compilation environment, to be used for remote compilation and debugging. This field should not be specified when running on the local machine. @item Program_Host This is a simple attribute. Its value is a string that specifies the name of IP address of the embedded target in a cross-compilation environment, on which the program should execute. @item Communication_Protocol This is a simple string attribute. Its value is the name of the protocol to use to communicate with the target in a cross-compilation environment, e.g.@: @code{"wtx"} or @code{"vxworks"}. @item Compiler_Command This is an associative array attribute, whose domain is a language name. Its value is string that denotes the command to be used to invoke the compiler. The value of @code{Compiler_Command ("Ada")} is expected to be compatible with gnatmake, in particular in the handling of switches. @item Debugger_Command This is simple attribute, Its value is a string that specifies the name of the debugger to be used, such as gdb, powerpc-wrs-vxworks-gdb or gdb-4. @item Default_Switches This is an associative array attribute. Its indexes are the name of the external tools that the GNAT Programming System (GPS) is supporting. Its value is a list of switches to use when invoking that tool. @item Gnatlist This is a simple attribute. Its value is a string that specifies the name of the @command{gnatls} utility to be used to retrieve information about the predefined path; e.g., @code{"gnatls"}, @code{"powerpc-wrs-vxworks-gnatls"}. @item VCS_Kind This is a simple attribute. Its value is a string used to specify the Version Control System (VCS) to be used for this project, e.g.@: CVS, RCS ClearCase or Perforce. @item Gnat This is a simple attribute. Its value is a string that specifies the name of the @command{gnat} utility to be used when executing various tools from GPS, in particular @code{"gnat pp"}, @code{"gnat stub"},@dots{} @item VCS_File_Check This is a simple attribute. Its value is a string that specifies the command used by the VCS to check the validity of a file, either when the user explicitly asks for a check, or as a sanity check before doing the check-in. @item VCS_Log_Check This is a simple attribute. Its value is a string that specifies the command used by the VCS to check the validity of a log file. @item VCS_Repository_Root The VCS repository root path. This is used to create tags or branches of the repository. For subversion the value should be the @code{URL} as specified to check-out the working copy of the repository. @item VCS_Patch_Root The local root directory to use for building patch file. All patch chunks will be relative to this path. The root project directory is used if this value is not defined. @end table