Assigning the value and copy constructor

Question

In line
MyClass res = op1 + op2;
do we call operator= or copy constructor?
Other question is what happens to object that is instantiated inside operator+ code?
We obviously made two new objects, one is res and the other inside operator+ method, which is later assigned to res variable.

Answer 1

Regarding first question, a copy constructor is called as you are assigning op1+op2 at the time of declaring the variable res. Had it been

MyClass res;
res = op1+op2;

operator= would have been invoked.

The object created inside the operator+ method is a local variable and will go out of scope as soon as it gets assigned to res.

Answer 2

Thanks Ravi.

So all other variables declared inside a function dies immediately after function call. Except for variable that is returned as a result, which lives a bit longer, just after it is assigned to some other variable. And I guess that destructor is called on that instance.

Answer 3

Yes, all the variables which are stored on stack memory (not created using dynamic memory allocation) gets destroyed after the function call. Destructor also gets called.