[Bug fortran/62226] New: Encode CPP options in lang.opt

[manu at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62226

            Bug ID: 62226
           Summary: Encode CPP options in lang.opt
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: manu at gcc dot gnu.org

Created attachment 33378
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=33378&action=edit
patch to handle CPP() per language

I recently added a new feature to .opt files to encode CPP options and handle
them transparently. Unfortunately, it does not work with Fortran because
Fortran does not use the common options machinery.

Steps to fix:

* Fortran should use the common options machinery (at least for those options
that are CPP options).

* Apply the attached patch.

* Add a call to Fortran_cpp_handle_option_auto and init_global_opts_from_cpp
somewhere appropriate in the Fortran FE.

Features like #pragma diagnostics and -fdiagnostics-show-option rely on this,
so it is a prerequisite for fixing PR44054.