x                  Pointer to the retrieved message.
    s                  Pointer to the default message string.
                       Indicates that the function is not able
                       to retrieve the requested message from
                       the catalog. This condition can arise if
                       the requested pair (set_d, msg_id) does
                       not represent an existing message from the
                       open catalog, or it indicates that an error
                       occurred. If an error occurred, the function
                       sets errno to one of the following values:

                       o  EBADF - The catalog descriptor is not
                          valid.

                       o  EVMSRR - An OpenVMS I/O read error;
                          the OpenVMS error code can be found in
                          vaxc$errno.