usr/src/usr.lib/libF77/traper_.c

/*
char id_traper[] = "@(#)traper_.c       1.1";
 * Arrange to trap integer overflow & floating underflow.
 * Full of Magic! DON'T CHANGE ANYTHING !!
 *
 * To use from f77:
 *      integer oldmsk, traper
 *      oldmsk = traper (mask)
 * where:
 *      mask = 1 to trap integer overflow
 *      mask = 2 to trap floating underflow
 *      mask = 3 to trap both
 *      These 2 bits will be set into the PSW.
 *      The old state will be returned.
 */

long traper_(msk)
long    *msk;
{
        int     old = 0;
#if     vax
#define IOV_MASK        0140
        int     **s = &msk;
        int     psw;

        s -= 5;
        psw = (int)*s;
        old = (psw & IOV_MASK) >> 5;
        psw = (psw & ~IOV_MASK) | ((*msk << 5) & IOV_MASK);
        *s = (int *)psw;
#endif  vax
        return((long)old);
}