//fprintf(stderr, "runtime/cgo: _cgo_sys_thread_start: fn=%p, g=%p\n", ts->fn, ts->g); // debug
	sigfillset(&ign);
	pthread_sigmask(SIG_SETMASK, &ign, &oset);

	size = pthread_get_stacksize_np(pthread_self());
	pthread_attr_init(&attr);
	pthread_attr_setstacksize(&attr, size);
	// Leave stacklo=0 and set stackhi=size; mstart will do the rest.
	ts->g->stackhi = size;
	err = _cgo_try_pthread_create(&p, &attr, threadentry, ts);

	if false {
		print("newosproc stk=", stk, " m=", mp, " g=", mp.g0, " id=", mp.id, " ostk=", &mp, "\n")
	}

	// Initialize an attribute object.
	var attr pthreadattr
	var err int32
	err = pthread_attr_init(&attr)
	if err != 0 {
		writeErrStr(failthreadcreate)
		exit(1)
	}

	// Find out OS stack size for our own stack guard.
	var stacksize uintptr
	if pthread_attr_getstacksize(&attr, &stacksize) != 0 {

	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);

	return int32(r)
}

func pthread_attr_init1(attr uintptr) int32

//go:nosplit
func pthread_attr_init(attr *pthread_attr) int32 {
	gp := getg()

	// Check the validity of g because without a g during
	// newosproc0.
	if gp != nil {
		r, _ := syscall1(&libpthread_attr_init, uintptr(unsafe.Pointer(attr)))
		return int32(r)
	}

	return pthread_attr_init1(uintptr(unsafe.Pointer(attr)))
}

// and then call the underlying libc function.  They are defined in sys_darwin_$ARCH.s.

//go:nosplit
//go:cgo_unsafe_args
func pthread_attr_init(attr *pthreadattr) int32 {
	ret := libcCall(unsafe.Pointer(abi.FuncPCABI0(pthread_attr_init_trampoline)), unsafe.Pointer(&attr))
	KeepAlive(attr)
	return ret
}
func pthread_attr_init_trampoline()