[Bug fortran/94672] [10 Regression] gfortran/OpenMP chokes on PRESENT(array) despite of SHARED(array): Error: ‘array’ not specified in enclosing ‘parallel’

["jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94672

--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Further examples, one for which should be rejected:
subroutine s1 (array)
  real, optional :: array(:)
  !$omp parallel default(none)          ! { dg-error "" }
  if (.not.present (array)) stop 1      ! { dg-error "" }
  !$omp end parallel
end subroutine
subroutine s2 (arg)
  real, optional :: arg
  !$omp parallel default(none)          ! { dg-error "" }
  if (.not.present (arg)) stop 1        ! { dg-error "" }
  !$omp end parallel
end subroutine
subroutine s3 (arg)
  real, value, optional :: arg
  !$omp parallel default(none)          ! { dg-error "" }
  if (.not.present (arg)) stop 1        ! { dg-error "" }
  !$omp end parallel
end subroutine

and one that should be accepted:

subroutine s1 (array)
  real, optional :: array(:)
  !$omp parallel default(none) firstprivate (array)
  if (present (array)) array(:) = 3
  !$omp end parallel
end subroutine
subroutine s2 (array)
  real, optional :: array(:)
  !$omp parallel default(none) shared (array)
  !$omp master
  if (present (array)) array(:) = 3
  !$omp end master
  !$omp end parallel
end subroutine
subroutine s3 (array)
  real, optional :: array(:)
  !$omp parallel default(none) private (array)
  if (present (array)) array(:) = 3
  !$omp end parallel
end subroutine
subroutine s4 (arg)
  real, optional :: arg
  !$omp parallel default(none) firstprivate (arg)
  if (present (arg)) arg = 3
  !$omp end parallel
end subroutine
subroutine s5 (arg)
  real, optional :: arg
  !$omp parallel default(none) shared (arg)
  !$omp master
  if (present (arg)) arg = 3
  !$omp end master
  !$omp end parallel
end subroutine
subroutine s6 (arg)
  real, optional :: arg
  !$omp parallel default(none) private (arg)
  if (present (arg)) arg = 3
  !$omp end parallel
end subroutine
subroutine s7 (arg)
  real, value, optional :: arg
  !$omp parallel default(none) firstprivate (arg)
  if (present (arg)) arg = 3
  !$omp end parallel
end subroutine
subroutine s8 (arg)
  real, value, optional :: arg
  !$omp parallel default(none) shared (arg)
  !$omp master
  if (present (arg)) arg = 3
  !$omp end master
  !$omp end parallel
end subroutine
subroutine s9 (arg)
  real, value, optional :: arg
  !$omp parallel default(none) private (arg)
  if (present (arg)) arg = 3
  !$omp end parallel
end subroutine

etc. Note, even just adding the artificial firstprivate clause is not enough,
the data sharing on the OPTIONAL parameters doesn't work as the standard says
so.
E.g. for private clause on OPTIONAL scalar without VALUE, we set the privatized
arg to &arg.1 and then compare that in the present check against NULL (which it
always is).
The spec says:
"If a list item that appears in a directive or clause is an optional dummy
argument that is not present, the directive or clause for that list item is
ignored.
If the variable referenced inside a construct is an optional dummy argument
that is not present, any explicitly determined, implicitly determined, or
predetermined data-sharing and data-mapping attribute rules for that variable
are ignored. Otherwise, if the variable is an optional dummy argument that is
present, it is present inside the construct."