[Bug fortran/85407] New: Replace gcc_assert in module.c:read_module by more helpful diagnostics

["anlauf at gmx dot de" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85407

            Bug ID: 85407
           Summary: Replace gcc_assert in module.c:read_module by more
                    helpful diagnostics
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: anlauf at gmx dot de
  Target Milestone: ---

Created attachment 43939
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=43939&action=edit
Patch

When reading inconsistent module files, an assert can be triggered in
read_module().  The attached patch replaces the assert by an error message
which may be more informative for the user.

See https://gcc.gnu.org/ml/fortran/2018-04/msg00023.html and context
for discussion and proposed Changelog.