关于main函数中的return 0

void my_led_test(void)
{
    rt_thread_t tid;
    /* ????1 */
    tid = rt_thread_create("led",
                           led, RT_NULL,
                           THREAD_STACK_SIZE,
                           THREAD_PRIORITY,
                           THREAD_TIMESLICE);
    if (tid != RT_NULL)
        rt_thread_startup(tid);
}
int main(void)
{
    my_led_test();
    return 0;
}