当C ++匿名对象替换先前分配的对象时会发生什么？

Question

This question concerns what happens to an object when a variable is assigned to a new object.

Date {
    public:
        Date(int day, int month);
        int day;
        int month;
};

in main:

Date birthday(7,4); //line 1
birthday = Date(5,5); //line 2

My understanding is that line 2's RS returns an anonymous object. My question is, what happens to the object that was created with the values 7,4? Is it replaced in memory by the anonymous object?

Answer 1

You cannot replace some object with another.

What you can do, and what actually happens in your example, is move-assigning from a temporary object to some target-object.

If it was not a temporary object, move-assigning from it would not happen, instead copy-assigning would take place.

Neither changes which object it is, only what value it has.

BTW: Copy-assignment, Move-assignment, copy-construction, move-construction and destruction for your example-class are implicitly defined as member-by-member.