[Bug fortran/78661] [OOP] Namelist output missing object designator under DTIO

[janus at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78661

--- Comment #7 from janus at gcc dot gnu.org ---
So, here is a corrected test for the polymorphic case:

MODULE m
  IMPLICIT NONE
  TYPE :: t
    CHARACTER :: c
  CONTAINS
    PROCEDURE :: write_formatted
    GENERIC :: WRITE(FORMATTED) => write_formatted
    PROCEDURE :: read_formatted
    GENERIC :: READ(FORMATTED) => read_formatted
  END TYPE
CONTAINS
  SUBROUTINE write_formatted(dtv, unit, iotype, v_list, iostat, iomsg)
    CLASS(t), INTENT(IN) :: dtv
    INTEGER, INTENT(IN) :: unit
    CHARACTER(*), INTENT(IN) :: iotype
    INTEGER, INTENT(IN) :: v_list(:)
    INTEGER, INTENT(OUT) :: iostat
    CHARACTER(*), INTENT(INOUT) :: iomsg
    WRITE (unit, "(A)", IOSTAT=iostat, IOMSG=iomsg) dtv%c
  END SUBROUTINE
  SUBROUTINE read_formatted(dtv, unit, iotype, v_list, iostat, iomsg)
    CLASS(t), INTENT(INOUT) :: dtv
    INTEGER, INTENT(IN) :: unit
    CHARACTER(*), INTENT(IN) :: iotype
    INTEGER, INTENT(IN) :: v_list(:)
    INTEGER, INTENT(OUT) :: iostat
    CHARACTER(*), INTENT(INOUT) :: iomsg
    READ (unit, "(A)", IOSTAT=iostat, IOMSG=iomsg) dtv%c
  END SUBROUTINE read_formatted
END MODULE

PROGRAM p
  USE m
  IMPLICIT NONE
  class(t), allocatable :: x
  NAMELIST /nml/ x
  x = t('a')
  WRITE (*, nml)
END


It currently prints (with my patch from comment 4, but probably also without):

&NML
 X=
 /

Apparently 'write_formatted' is not called. The dump for the non-poly version
from comment 0/3 shows:

_gfortran_st_set_nml_dtio_var (&dt_parm.3, x, &"x"[1]{lb: 1 sz: 1}, 0, 0, 40,
write_formatted, (void *) &__vtab_m_T);

But for the polymorphic version it has:

_gfortran_st_set_nml_dtio_var (&dt_parm.3, &x, &"x"[1]{lb: 1 sz: 1}, 0, 0, 56,
0B, 0B);

Neither the DTIO procedure nor the vtab is called. The DTIO procedure we need
here is "x._vptr->write_formatted".

Btw why do we actually pass the vtab in the first case?