[Bug fortran/78398] New: missing warnings and inconsistencies with -Wuninitialized

[janus at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78398

            Bug ID: 78398
           Summary: missing warnings and inconsistencies with
                    -Wuninitialized
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: janus at gcc dot gnu.org
  Target Milestone: ---

Please consider the following example:


subroutine s1
  integer :: i,j
  j = i               ! warning here
  print *,i           ! none here
end

module m
contains
  subroutine s2
    integer :: i,j
    j = i               ! warning here
    print *,i           ! none here
  end
end module

program p
contains
  subroutine s3
    integer :: i,j
    j = i               ! none here
    print *,i           ! none here
  end
end


Compiling this with -Wuninitialized correctly produces two warnings on the
marked lines (with gfortran 5, 6 and trunk), but four warnings are missing.

Two things are inconsistent here:
1) The subroutines s1,s2,s3 are completely identical. If the routine is
alone-standing or inside a module, we get a warning. But if it is contained in
a program, the warning is gone.
2) We get a warning when an uninitialized variable is used in an assignment,
but not in a print statement.