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10.13.2 The GNAT Driver and Project Files

A number of GNAT tools, other than gnatmake are project-aware: gnatbind, gnatfind, gnatlink, gnatls and gnatxref. However, none of these tools can be invoked directly with a project file switch (-P). They need to be invoke through the gnat driver.

The gnat driver is a front-end that accepts a number of commands and call the corresponding tool. It has been designed initially for VMS to convert VMS style qualifiers to Unix style switches, but it is now available to all the GNAT supported platforms.

On non VMS platforms, the gnat driver accepts the following commands (case insensitive):

Note that the compiler is invoked using the command gnatmake -f -u.

Following the command, you may put switches and arguments for the invoked tool.

       gnat bind -C main.ali
       gnat ls -a main
       gnat chop foo.txt

In addition, for command BIND, FIND, LS or LIST, LINK and XREF, the project file related switches (-P, -X and -vPx) may be used in addition to the switches of the invoking tool.

For each of these command, there is possibly a package in the main project that corresponds to the invoked tool.

Package Gnatls has a unique attribute Switches, a simple variable with a string list value. It contains switches for the invocation of gnatls.

     project Proj1 is
        package gnatls is
           for Switches use ("-a", "-v");
        end gnatls;
     end Proj1;

All other packages contains a switch Default_Switches, an associative array, indexed by the programming language (case insensitive) and having a string list value. Default_Switches ("Ada") contains the switches for the invocation of the tool corresponding to the package.

     project Proj is
        for Source_Dirs use ("./**");
        package gnatls is
           for Switches use ("-a", "-v");
        end gnatls;
        package Binder is
           for Default_Switches ("Ada") use ("-C", "-e");
        end Binder;
        package Linker is
           for Default_Switches ("Ada") use ("-C");
        end Linker;
        package Finder is
           for Default_Switches ("Ada") use ("-a", "-f");
        end Finder;
        package Cross_Reference is
           for Default_Switches ("Ada") use ("-a", "-f", "-d", "-u");
        end Cross_Reference;
     end Proj;

With the above project file, commands such as

        gnat ls -Pproj main
        gnat xref -Pproj main
        gnat bind -Pproj main.ali

will set up the environment properly and invoke the tool with the switches found in the package corresponding to the tool.