[Bug fortran/88511] passing allocatable character through two levels of procedure calls fails

[stephen at soliday dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88511

--- Comment #1 from Stephen Soliday <stephen at soliday dot com> ---
One of the respondents in Stack overflow posted this reduced version of my code
that also reproduces the segmentation fault.

program main
  implicit none
  character(:), allocatable :: txt

  call sub1(txt)
  print *, "main ", len(txt), txt      ! prints: main 0 (or throws segfault)

contains
  subroutine sub1(txt)
    character(:), allocatable, optional, intent(out) :: txt
    call sub2(txt)
    print *, "sub1 ", len(txt), txt    ! prints: sub1 0 (or throws segfault)
  end subroutine sub1
  subroutine sub2(txt)
    character(:), allocatable, optional, intent(out) :: txt
    if(present(txt)) txt = "message"
    print *, "sub2 ", len(txt), txt    ! prints: sub2 7 message
  end subroutine sub2
end program main