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

 Message        <Context> allowing two different enumeration types to
                be compatible is a language extension.

 Description    The Compaq C compiler allows two objects of different
                enumeration types to be compatible.  The C standard
                specifies that enumeration types are distinct types.
                Therefore this program is not standard compliant and
                other C compilers may not accept it.

 User Action    Use the same enumeration type or cast one type to the
                other.