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When using a project file, you can invoke gnatmake with several main subprograms, by specifying their source files on the command line. Each of these needs to be an immediate source file of the project.

         gnatmake -Pprj main1 main2 main3

When using a project file, you can also invoke gnatmake without explicitly specifying any main, and the effect depends on whether you have defined the 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) containing a main subprogram.

If the Main attribute is defined in a project file as a non-empty string list and the switch -u is not used on the command line, then invoking gnatmake with this project file but without any main on the command line is equivalent to invoking gnatmake with all the file names in the Main attribute on the command line.


        project Prj is
           for Main use ("main1", "main2", "main3");
        end Prj;

With this project file, "gnatmake -Pprj" is equivalent to "gnatmake -Pprj main1 main2 main3".

When the project attribute Main is not specified, or is specified as an empty string list, or when the switch -u is used on the command line, then invoking 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 -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 -u switch is applied to all of the immediate sources of themain project file.