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

 Message        <Context> accepting an identifier enclosed in
                parentheses as the second argument to va_start is a
                language extension.

 Description    The C standard states that the second argument to
                va_start must be an identifier.  For compatibility
                with other C compilers, Compaq C will accept an
                identifier enclosed in parentheses.  Be aware that
                this program does not conform to the standard and may
                be rejected by other compilers.

 User Action    Remove the parentheses.