Learning immediately: https://edu.csdn.net/course/play/474/8083?utm_source=blogtoedu
Cited as a form of argument time will not allocate new space
The return value is a non-return value of the referenced object when the result of direct access to the stack, i.e., does not perform the copy constructor
The return value is a function of the object class, execution returns to the calling function is not invoked copy constructor
