static void segvHandler(int signo, siginfo_t* info, void* ctxt) {
	sigset_t mask;
	int i;

	if (sigemptyset(&mask) < 0) {
		die("sigemptyset");
	}
	if (sigaddset(&mask, SIGSEGV) < 0) {
		die("sigaddset");
	}
	i = sigprocmask(SIG_UNBLOCK, &mask, NULL);
	if (i != 0) {
		fprintf(stderr, "sigprocmask: %s\n", strerror(i));
		exit(EXIT_FAILURE);
	}

	// Don't try this at home.

	int i;

	// Call an arbitrary function that requires the stack to be properly aligned.
	callWithVarargs("dummy arg", 3.1415);

	if (sigemptyset(&mask) < 0) {
		die("sigemptyset");
	}
	if (sigaddset(&mask, SIGSEGV) < 0) {
		die("sigaddset");
	}
	i = sigprocmask(SIG_UNBLOCK, &mask, NULL);
	if (i != 0) {
		fprintf(stderr, "sigprocmask: %s\n", strerror(i));
		exit(EXIT_FAILURE);
	}

	// Don't try this at home.

	_SIG_BLOCK   = 1
	_SIG_UNBLOCK = 2
	_SIG_SETMASK = 3
)

type sigset [4]uint32

var sigset_all = sigset{^uint32(0), ^uint32(0), ^uint32(0), ^uint32(0)}

//go:nosplit
//go:nowritebarrierrec
func sigaddset(mask *sigset, i int) {
	(*mask)[(i-1)/32] |= 1 << ((uint32(i) - 1) & 31)
}

func sigdelset(mask *sigset, i int) {
	(*mask)[(i-1)/32] &^= 1 << ((uint32(i) - 1) & 31)
}

//go:nosplit

	_SS_DISABLE  = 2
	_NSIG        = 65
	_SIG_BLOCK   = 0
	_SIG_UNBLOCK = 1
	_SIG_SETMASK = 2
)

type sigset uint64

var sigset_all = sigset(^uint64(0))

//go:nosplit
//go:nowritebarrierrec
func sigaddset(mask *sigset, i int) {
	if i > 64 {
		throw("unexpected signal greater than 64")
	}
	*mask |= 1 << (uint(i) - 1)
}

func sigdelset(mask *sigset, i int) {
	if i > 64 {

// rt_sigprocmask crashes if we get it wrong, so if binaries
// are running, this is right.
type sigset [2]uint32

var sigset_all = sigset{^uint32(0), ^uint32(0)}

//go:nosplit
//go:nowritebarrierrec
func sigaddset(mask *sigset, i int) {
	(*mask)[(i-1)/32] |= 1 << ((uint32(i) - 1) & 31)
}

func sigdelset(mask *sigset, i int) {
	(*mask)[(i-1)/32] &^= 1 << ((uint32(i) - 1) & 31)
}

//go:nosplit

int CheckBlocked() {
	sigset_t mask;
	sigprocmask(SIG_BLOCK, NULL, &mask);
	return sigismember(&mask, SIGIO);
}

static void* sigthreadfunc(void* unused) {
	sigset_t mask;
	sigemptyset(&mask);
	sigaddset(&mask, SIGIO);
	sigprocmask(SIG_BLOCK, &mask, NULL);
	IntoGoAndBack();
	return NULL;
}

int RunSigThread() {
	int tries;
	pthread_t thread;
	int r;
	struct timespec ts;

	_NSIG        = 129
	_SIG_BLOCK   = 1
	_SIG_UNBLOCK = 2
	_SIG_SETMASK = 3
)

type sigset [2]uint64

var sigset_all = sigset{^uint64(0), ^uint64(0)}

//go:nosplit
//go:nowritebarrierrec
func sigaddset(mask *sigset, i int) {
	(*mask)[(i-1)/64] |= 1 << ((uint32(i) - 1) & 63)
}

func sigdelset(mask *sigset, i int) {
	(*mask)[(i-1)/64] &^= 1 << ((uint32(i) - 1) & 63)
}

//go:nosplit

		} else {
			act.sa_handler = (void(*)(int))(goact->handler);
		}
		sigemptyset(&act.sa_mask);
		for (i = 0; i < 8 * sizeof(goact->mask); i++) {
			if (goact->mask.__bits[i/32] & ((uint32_t)(1)<<(i&31))) {
				sigaddset(&act.sa_mask, i+1);
			}
		}
		act.sa_flags = goact->flags;
	}

	ret = sigaction(signum, goact ? &act : NULL, oldgoact ? &oldact : NULL);
	if (ret == -1) {

		} else {
			act.sa_handler = (void(*)(int))(goact->handler);
		}
		sigemptyset(&act.sa_mask);
		for (i = 0; i < 8 * sizeof(goact->mask); i++) {
			if (goact->mask & ((uint64_t)(1)<<i)) {
				sigaddset(&act.sa_mask, (int)(i+1));
			}
		}
		act.sa_flags = (int)(goact->flags & ~(uint64_t)SA_RESTORER);
	}

	ret = sigaction((int)signum, goact ? &act : NULL, oldgoact ? &oldact : NULL);
	if (ret == -1) {

		// Therefore, raisebadsignal won't raise SIGPIPE again if
		// it was deliver in a non-Go thread.
		c.set_sigcode(_SI_USER)
	}
}

//go:nosplit
//go:nowritebarrierrec
func sigaddset(mask *sigset, i int) {
	(*mask)[(i-1)/64] |= 1 << ((uint32(i) - 1) & 63)
}

func sigdelset(mask *sigset, i int) {
	(*mask)[(i-1)/64] &^= 1 << ((uint32(i) - 1) & 63)
}