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From: "kargl at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
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Date: Fri, 14 Oct 2022 18:51:22 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D107266

--- Comment #3 from kargl at gcc dot gnu.org ---
(In reply to kargl from comment #2)
> (In reply to Tobias Burnus from comment #1)
> > Better example:
> >=20
> > character(kind=3D4) function f(x) bind(C)
> >   character(kind=3D4), value :: x
> > end
> >=20
> >=20
> > Has the dump:
> >=20
> > __attribute__((fn spec (". w ")))
> > character(kind=3D1) f (character(kind=3D1) x)
> > {
> >   (void) 0;
> > }
> >=20
> >=20
> > Note the change to kind=3D1
>=20
> So, you want gfortran to reject the function.
>=20
> It gets real ugly with
>=20
> function f(x) bind(C) result(a)
>    character(kind=3D4) a
>    character(kind=3D4), value :: x
>    a =3D x
> end
>=20
> leading to
>=20
> __attribute__((fn spec (". w ")))
> character(kind=3D1) f (character(kind=3D1) x)
> {
>   character(kind=3D1) a;
>=20
>   *(character(kind=3D4) *) &a =3D *(character(kind=3D4) *) &x;
>   return a;
> }

Looks like resolve.cc:resolve_symbol() might be able to dela with this.
For my function with the result variable one has

(gdb) p *sym
$4 =3D {name =3D 0x2041ec100 "f", module =3D 0x0, declared_at =3D {
    nextc =3D 0x203a38160, lb =3D 0x203a38140}, ts =3D {type =3D BT_UNKNOWN=
, kind =3D 0,=20
...
    in_equivalence =3D 0, function =3D 1, subroutine =3D 0, procedure =3D 0=
,=20
    generic =3D 0, generic_copy =3D 0, implicit_type =3D 0, untyped =3D 0,=
=20
    is_bind_c =3D 1, extension =3D 0, is_class =3D 0, class_ok =3D 0, vtab =
=3D 0,=20
...
   value =3D 0x0, as =3D 0x0, result =3D 0x203a57600, components =3D 0x0,=20

(gdb) p *sym->result
$5 =3D {name =3D 0x2041ec110 "a", module =3D 0x0, declared_at =3D {
    nextc =3D 0x203a381dc, lb =3D 0x203a38140}, ts =3D {type =3D BT_CHARACT=
ER,=20
    kind =3D 4, u =3D {derived =3D 0x203a245a0, cl =3D 0x203a245a0, pad =3D=
 60966304},=20
...
    dummy =3D 0, result =3D 1, assign =3D 0, threadprivate =3D 0,=20

so gfortran can check for kind=3D4 versus kind=3D1 (aka C_CHAR).=