The package Ada.Command_Line provides access to the command-line
arguments and program name. In order for this interface to operate
correctly, the two variables
int gnat_argc;
char **gnat_argv;
are declared in one of the GNAT library routines. These variables must
be set from the actual argc and argv values passed to the
main program. With no n present, gnatbind
generates the C main program to automatically set these variables.
If the n switch is used, there is no automatic way to
set these variables. If they are not set, the procedures in
Ada.Command_Line will not be available, and any attempt to use
them will raise Constraint_Error. If command line access is
required, your main program must set gnat_argc and
gnat_argv from the argc and argv values passed to
it.