VMS Help CC, Messages, CVTU32TO64  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 Message        <Context> an unsigned 32-bit integer constant that
                has its high-order bit set has been converted to a
                signed 64-bit type.  The conversion will not
                sign-extend.

 Description    This message indicates a conversion that may produce
                unexpected results on this platform because the
                destination type is a 64-bit type instead of a 32-bit
                type.

 User Action    If this is the intended behavior, first cast the
                constant to an unsigned 64-bit type.