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

 Message        The name "<name>" cannot be a user-defined macro.

 Description    The code has tried to #define either a macro that is
                predefined by the C standard or the DEFINED
                preprocessing keyword.  This is not allowed.  The
                #define will be ignored.

 User Action    Remove the #define directive.