int pthread_create(pthread_t *thread, const pthread_attr_t *attr,void *(*start_routine) (void *), void *arg);
void *(*start_routine) (void *),
1、start_routine是标识符
2、*start_routine说明start_routine是指针。是什么指针?
3、(*start_routine)()说明start_routine是函数指针。函数原型是什么?
4、(*start_routine)(void *)说明函数的参数类型是void*
5、void *(*start_routine)(void *);说明函数的返回值类型是void*