if (optype == OP_SHMREAD) {
    char *mbuf;
    /* suppress warning when reading into undef var (tchrist 3/Mar/00) */
    SvGETMAGIC(mstr);
    SvUPGRADE(mstr, SVt_PV);
    if (! SvOK(mstr))
        SvPVCLEAR(mstr);
    SvPOK_only(mstr);
    mbuf = SvGROW(mstr, (STRLEN)msize+1);

    Copy(shm + mpos, mbuf, msize, char);