Modify the gcc exit code for warning

[disquisitiones via Gcc-help <gcc-help@xxxxxxxxxxx>]

Hi,

I would like to modify the exit code returned by gcc in case of warning
from 0 to some other value, but I'm not familiar with the gcc large source
code base.

Could you provide an hint to which is the file in the gcc source code that
I should modify for modifying the exit value?

Many thanks,

Luca