The previous section described the default rules used by GNAT to determine the file name in which a given unit resides. It is usually convenient to follow these default rules, and if you follow them, the compiler knows without being explicitly told where to find all the files it needs.
However, in some cases, particularly when a program is imported from
another Ada compiler environment, it may be more convenient for you
to specify which file names contain which units. GNAT allows
arbitrary file names to be used by means of the Source_File_Name pragma.
The form of this pragma is as shown in the following examples:
pragma Source_File_Name (My_Utilities.Stacks, Spec_File_Name => "myutilst_a.ada"); pragma Source_File_name (My_Utilities.Stacks, Body_File_Name => "myutilst.ada");
As shown in this example, the first argument for the pragma is the unit name (in this example a child unit). The second argument has the form of a named association. The identifier indicates whether the file name is for a spec or a body; the file name itself is given by a string literal.
The source file name pragma is a configuration pragma, which means that
normally you will place it in the gnat.adc
file used to hold configuration
pragmas that apply to a complete compilation environment.
For more details on how the gnat.adc file is created and used
see Handling of Configuration Pragmas.
GNAT allows you to specify completely arbitrary file names using the
source file name pragma. However, if the file name specified has an
extension other than .ads or .adb you must use a
special syntax when compiling the file. The name on the command line
in this case must be preceded by the special sequence -x followed
by a space and the name of the language, here ada, as in:
$ gcc -c -x ada peculiar_file_name.sim
gnatmake handles non-standard file names in the usual manner (the
non-standard file name for the main program is simply used as the
argument to gnatmake). Note that if the extension is also non-standard,
you must include it in the gnatmake command; it may not
be omitted.