/*      $OpenBSD: except.c,v 1.12 2010/05/08 19:16:33 naddy Exp $       */

#include <sys/types.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <signal.h>
#include <assert.h>
#include <ieeefp.h>
#include <float.h>
#include <err.h>

volatile sig_atomic_t signal_status;

volatile const double one  = 1.0;
volatile const double zero = 0.0;
volatile const double huge = DBL_MAX;
volatile const double tiny = DBL_MIN;

void
sigfpe(int sig, siginfo_t *si, void *v)
{
        char buf[132];

        if (si) {
                snprintf(buf, sizeof(buf), "sigfpe: addr=%p, code=%d\n",
                    si->si_addr, si->si_code);
                write(1, buf, strlen(buf));
        }
        _exit(signal_status);
}


int
main(int argc, char *argv[])
{
        struct sigaction sa;
        volatile double x;

        if (argc != 2) {
                fprintf(stderr, "usage: %s condition\n", argv[0]);
                exit(1);
        }

        /*
         * check to make sure that all exceptions are masked and 
         * that the accumulated exception status is clear.
         */
        assert(fpgetmask() == 0);
        assert(fpgetsticky() == 0);

        memset(&sa, 0, sizeof(sa));
        sa.sa_sigaction = sigfpe;
        sa.sa_flags = SA_SIGINFO;
        sigaction(SIGFPE, &sa, NULL);
        signal_status = 1;

        if (strcmp(argv[1], "fltdiv") == 0) {
                /* trip divide by zero */
                x = one / zero;
                assert(fpgetsticky() & FP_X_DZ);
                fpsetsticky(0);

                /* and now unmask to get a signal */
                signal_status = 0;
                fpsetmask(FP_X_DZ);
                x = one / zero;
        } else if (strcmp(argv[1], "fltinv") == 0) {
                /* trip invalid operation */
                x = zero / zero;
                assert(fpgetsticky() & FP_X_INV);
                fpsetsticky(0);

                /* and now unmask to get a signal */
                signal_status = 0;
                fpsetmask(FP_X_INV);
                x = zero / zero;
        } else if (strcmp(argv[1], "fltovf") == 0) {
                /* trip overflow */
                x = huge * huge;
                assert(fpgetsticky() & FP_X_OFL);
                fpsetsticky(0);

                /* and now unmask to get a signal */
                signal_status = 0;
                fpsetmask(FP_X_OFL);
                x = huge * huge;
        } else if (strcmp(argv[1], "fltund") == 0) {
                /* trip underflow */
                x = tiny * tiny;
                assert(fpgetsticky() & FP_X_UFL);
                fpsetsticky(0);

                /* and now unmask to get a signal */
                signal_status = 0;
                fpsetmask(FP_X_UFL);
                x = tiny * tiny;
        } else {
                errx(1, "unrecognized condition %s", argv[1]);
        }

        /*
         * attempt to trigger the exception on machines where
         * floating-point exceptions are deferred.
         */
        x = one * one;

        errx(1, "signal wasn't caught");
}