VMS Help CC, Messages, CMPPTRFUNVOID  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 Message        <Context> accepting the [in]equality comparison of a
                pointer to void and a pointer to function type is a
                language extension.

 Description    Under the C standard, it is a constraint violation to
                perform an [in]equality comparison between a pointer
                to void and a pointer to function type.  Therefore
                this code may not be accepted by other compilers.

 User Action    Cast one of the pointers to the type of the other.