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

 Message        <Context> compatibility of a pointer to void and a
                pointer to a function is not portable under the C
                standard.

 Description    The C standard defines pointer to void as being
                assignment compatible only with pointers to object or
                incomplete types.  An implementation may represent
                function pointers in a way that cannot be stored in a
                pointer to void (or vice-versa).  Thus even an
                explicit cast between a function pointer and a
                pointer to void is not portable.

 User Action    If a generic pointer to function is needed, declare a
                typedef for some pointer to function type, and always
                use explicit casts to assign to and from that type.