/sys$common/syshlp/helplib.hlb CC, Messages, CANNOTUNDEF  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 Message        Cannot #undef a macro that is currently expanding.

 Description    The program is trying to #undef the same macro it is
                currently expanding.  The #undef will be ignored.

 User Action    Remove the #undef, or move it after the expansion of
                the macro.