/*      $OpenBSD: fpu.c,v 1.3 2021/06/17 12:55:38 kettenis Exp $        */

#include <err.h>
#include <fenv.h>
#include <stdlib.h>

int
main(int argc, char *argv[])
{
        fexcept_t flag;
        int rv;

        /* Set up the FPU control word register. */
        rv = fesetround(FE_UPWARD);
        if (rv != 0)
                errx(2, "fesetround FE_UPWARD returned %d", rv);
        fedisableexcept(FE_ALL_EXCEPT);
        feenableexcept(FE_DIVBYZERO);

        /* Set the FPU exception flags. */
        flag = FE_OVERFLOW;
        rv = fesetexceptflag(&flag, FE_ALL_EXCEPT);
        if (rv != 0)
                errx(2, "fesetexceptflag returned %d", rv);

        /* Schedule another process, to check if kernel preserves state. */
        rv = system("true");
        if (rv == -1)
                err(2, "system");
        if (rv != 0)
                errx(2, "true: %d", rv);

        /* Verify that the FPU control word is preserved. */
        rv = fegetround();
        if (rv != FE_UPWARD)
                errx(1, "fegetround returned %d, not FE_UPWARD", rv);
#if !defined(__arm__) && !defined(__aarch64__) && !defined(__riscv)
        rv = fegetexcept();
        if (rv != FE_DIVBYZERO)
                errx(1, "fegetexcept returned %d, not FE_DIVBYZERO",
                    rv);
#endif

        /* Verify that the FPU exception flags weren't clobbered. */
        flag = 0;
        rv = fegetexceptflag(&flag, FE_ALL_EXCEPT);
        if (rv != 0)
                errx(2, "fegetexceptflag returned %d", rv);
        if (flag != FE_OVERFLOW)
                errx(1, "except flag is %d, no FE_OVERFLOW", rv);

        return (0);
}