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

 Message        The declaration of "<name1>" will map to the same
                external name as the declaration of "<name2>" at
                <where>.

 Description    The compiler has detected a case where two different
                names in a program will map to the same external name
                in the output object file.  This can cause
                unpredictable results at runtime.  This will most
                often happen when the /NAMES=UPPERCASE or
                /NAMES=LOWERCASE qualifier causes two names with
                different case spellings to map to the same external
                name.

 User Action    Either use the /NAMES=AS_IS qualifier, or modify one
                of the names.