Copy constructor not called when initializing an object with return value of a function

Question

Consider the following code:

#include 

using namespace std;

class A
{
    public:
        int a;
        A(): a(5)
        {
           cout &l         


        

Answer 1

The copy that is elided is the copy of the temporary return value into b. Without elision the return value is initialized from a and copied to b. Instead, the temporary that would otherwise hold the return value is constructed into b and initialized with a. [class.copy]/31:

when a temporary class object that has not been bound to a reference (12.2) would be copied/moved to a class object with the same cv-unqualified type, the copy/move operation can be omitted by constructing the temporary object directly into the target of the omitted copy/move

You can observe this if you add an additional output in fun:

A fun(A a)
{
    cout << "fun!" << endl;
    return a;
}

Then with the elision you'll get

[…]
fun!
Copy Constructor

And without:

[…]
fun!
Copy Constructor
Copy Constructor