Perl_do_shmio(pTHX_ I32 optype, SV **mark, SV **sp)
{
#ifdef HAS_SHM
    char *shm;
    struct shmid_ds shmds;
    const I32 id = SvIVx(*++mark);
    SV * const mstr = *++mark;
    const I32 mpos = SvIVx(*++mark);
    const I32 msize = SvIVx(*++mark);

##</code><code>##

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);