#define _DEFAULT_SOURCE
#include <assert.h>
#include <errno.h>
#include <fenv.h>
#include <setjmp.h>
#include <signal.h>
#include <stdio.h>
#include <string.h>


static int sExceptions = 0;
static int sLastCode = -1;
static jmp_buf sJmpBuf;


static void
signal_handler(int signal, siginfo_t* siginfo, void*)
{
        sExceptions++;
        sLastCode = siginfo->si_code;

        longjmp(sJmpBuf, 1);
}


int main()
{
        fenv_t exceptenv;
        long double volatile nanl, resultl;

        struct sigaction action = {};
        sigemptyset(&action.sa_mask);
        action.sa_flags = SA_SIGINFO | SA_NODEFER | SA_NOMASK;
        action.sa_sigaction = signal_handler;
        if (sigaction(SIGFPE, &action, NULL) == -1) {
                fprintf(stderr, "failed to install signal handler: %s\n",
                        strerror(errno));
                return 1;
        }

        assert(feclearexcept(FE_ALL_EXCEPT) == 0);

        // Test 1: switching to an fenv with an exception raised triggers SIGFPE
        // (but not a kernel panic.)
        if (feenableexcept(FE_INVALID) == -1) {
                fputs("trapping floating-point exceptions are not supported on this machine.\n", stderr);
                return -1;
        }

        assert(fegetenv(&exceptenv) == 0);
        assert(fesetenv(FE_DFL_ENV) == 0);

        assert(feraiseexcept(FE_INVALID) == 0);

        assert(sExceptions == 0);
        if (setjmp(sJmpBuf) == 0) {
                assert(feupdateenv(&exceptenv) == 0);
        } else {
                assert(feclearexcept(FE_INVALID) == 0);
                assert(feupdateenv(&exceptenv) == 0);
        }
        assert(sExceptions == 1);
        assert(sLastCode == FPE_FLTINV);

        // Test 2: long signaling NaNs also trigger SIGFPE
        // (but again no kernel panic.)
        nanl = __builtin_nansl("");
        assert(sExceptions == 1);
        if (setjmp(sJmpBuf) == 0) {
                resultl = nanl + 42.0L;
        } else {
                assert(feclearexcept(FE_ALL_EXCEPT) == 0);
        }
        assert(sExceptions == 2);
        assert(sLastCode == FPE_FLTINV);

        // Test 3: Overflow triggers SIGFPE, with the right code.
        if (feenableexcept(FE_OVERFLOW) == -1) {
                fputs("FE_OVERFLOW is not supported on this machine.\n", stderr);
                return 0;
        }

        if (setjmp(sJmpBuf) == 0) {
                float volatile top = FLT_MAX;
                float volatile result = top * top;
        }
        assert(sExceptions == 3);
        assert(sLastCode == FPE_FLTOVF);

        return 0;
}