int
do_msgrcv(arglast)
int *arglast;
{
#ifdef HAS_MSG
    register STR **st = stack->ary_array;
    register int sp = arglast[0];
    STR *mstr;
    char *mbuf;
    long mtype;
    int id, msize, flags, ret;

    id = (int)str_gnum(st[++sp]);
    mstr = st[++sp];
    msize = (int)str_gnum(st[++sp]);
    mtype = (long)str_gnum(st[++sp]);
    flags = (int)str_gnum(st[++sp]);
    mbuf = str_get(mstr);
    if (mstr->str_cur < sizeof(long)+msize+1) {
	STR_GROW(mstr, sizeof(long)+msize+1);
	mbuf = str_get(mstr);
    }
    errno = 0;
    ret = msgrcv(id, (struct msgbuf *)mbuf, msize, mtype, flags);
    if (ret >= 0) {
	mstr->str_cur = sizeof(long)+ret;
	mstr->str_ptr[sizeof(long)+ret] = '\0';
    }
    return ret;
#else
    fatal("msgrcv not implemented");
#endif
}