[Bug fortran/78300] New: Failure to compile a Fortran-2003 code with an optional dummy procedure argument.

[liakhdi at ornl dot gov]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78300

            Bug ID: 78300
           Summary: Failure to compile a Fortran-2003 code with an
                    optional dummy procedure argument.
           Product: gcc
           Version: 6.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: liakhdi at ornl dot gov
  Target Milestone: ---

Source code: https://gitlab.com/DmitryLyakh/GFC.git

The minimal reproducer can be created by taking only three source files from
GFC:
gfortran -c dil_basic.F90
gfortran -c timers.F90
gfortran -c -DNO_GNU gfc_base.F90 (GFORTRAN fails to compile if you define
-DNO_GNU)

If you look inside gfc_base.F90 line 240 (subroutine ContElemConstruct), you
will see the exact place where the compile error occurs. For some reason, it
has problems with an optional dummy procedure argument. I believe this is a
compiler bug. All other compilers I tried compile and run the code fine (Cray,
PGI, XL, probably Intel as well).

Please help fixing this problem in gfortran. Thanks!