In order to profile a program the first step is to tell the compiler
to generate the necessary profiling information. The compiler switch to be used
is -pg, which must be added to other compilation switches. This
switch needs to be specified both during compilation and link stages, and can
be specified once when using gnatmake:
$ gnatmake -f -pg -P my_project
Note that only the objects that were compiled with the -pg switch will
be profiled; if you need to profile your whole project, use the -f
gnatmake switch to force full recompilation.