throw("pthread_attr_init")
	}

	if pthread_attr_setstacksize(&attr, threadStackSize) != 0 {
		throw("pthread_attr_getstacksize")
	}

	if pthread_attr_setdetachstate(&attr, _PTHREAD_CREATE_DETACHED) != 0 {
		throw("pthread_attr_setdetachstate")
	}

	// Disable signals during create, so that the new thread starts
	// with signals disabled. It will enable them in minit.

	sigfillset(&ign);
	pthread_sigmask(SIG_SETMASK, &ign, &oset);

	// Start a thread to handle exceptions.
	uintptr_t port_set = (uintptr_t)mach_exception_handler_port_set;
	pthread_attr_init(&attr);
	pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
	ret = _cgo_try_pthread_create(&thr, &attr, mach_exception_handler, (void*)port_set);

	pthread_sigmask(SIG_SETMASK, &oset, nil);

	if (ret) {