http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54667
--- Comment #2 from janus at gcc dot gnu.org 2012-09-22 08:53:51 UTC --- The question is if it is really valid. At first sight both F03 and F08 only specify that FPTR, i.e. the second argument to C_F_POINTER, shall be a pointer with INTENT(OUT). However, there are additional constraints depending on the actual value of CPTR: "(1) If the value of CPTR is the C address of an interoperable data entity, FPTR shall be a data pointer with type and type parame- ters interoperable with the type of the entity. ..." "(2) If the value of CPTR is the result of a reference to C LOC with a noninteroperable argument X, FPTR shall be a nonpolymorphic scalar pointer with the same type and type parameters as X. ..." While it would be nontrivial to fully enforce these constraints by a runtime check, I think they might effectively mean that FPTR must not be polymorphic: In the second case this constraint is spelled out explicitly, and the first case demands that FPTR shall be interoperable. But polymorphic objects are by definition not interoperable.
