[Bug fortran/88299] [9 Regression] COMMON in a legacy module produces bogus warnings in dependent code

[anlauf at gmx dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88299

--- Comment #1 from Harald Anlauf <anlauf at gmx dot de> ---
The warning was introduced in:

r260705 | janus | 2018-05-25 08:09:10 +0200 (Fri, 25 May 2018) | 16 lines

2018-05-25  Janus Weil  <janus@gcc.gnu.org>

        PR fortran/85839
        * match.c (gfc_match_block_data): Call gfc_notify_std to warn about
        an obsolescent feature in Fortran 2018.
        (gfc_match_equivalence): Ditto.
        * resolve.c (resolve_common_blocks): Ditto.
        (gfc_resolve_forall): Ditto.
        * symbol.c (gfc_define_st_label): Ditto.


Maybe the warning can be restricted to those files / compilation units
where the COMMON is declared?

The COMMON unfortunately pollutes all upstream module files (*.mod),
even if no symbol is imported (see e.g. mod2 in the testcase).