[Bug fortran/36058] Not allowing pointers to derived types in COMMON

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

------- Comment #1 from burnus at gcc dot gnu dot org  2008-04-27 08:01 -------
gfortran's rejection is in line with g95, NAG f95, ifort, openf95, sunf95 and
ifort.

I think gfortran is right and the sequence (or bind(C)) attribute is needed.

The reason is the same as for the following program:

  type my_t
    integer :: x, y, z
  end type my_t
  type(my_t) :: tt
  call foo(tt)
contains
subroutine foo(t)
  type foo_t
    integer :: x, y, z
  end type foo_t
  type(foo_t) :: t
end subroutine
end

foo_t and my_t are different, incompatible types without SEQUENCE. From that
point of view, it makes sense to reject your example.

Additionally, I think the following also applies to pointers. ("my_wwsptr" is
of a derived type [albeit with pointer attribute].)

"C589 (R558) If a common-block-object is of a derived type, it shall be a
sequence type (4.5.1) or a type with the BIND attribute and it shall have no
default initialization."

 * * *

If one now adds "SEQUENCE", gfortran rejects it as there is a default
initialization; in principle this it can be allowed as the default
initialization does not happen for pointers to derived types (only for its
targets). However, I believe that C589 also applies in this case.

The such modified program is rejected by NAG f95, sunf95, openf95, g95 and
gfortran, but ifort accepts the program.

 * * *

In conclustion, I think both error messages of gfortran are correct.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36058