Shouldn't destructors be called when this object returns (and not as a pointer)?

Question

I have a function:

static Bwah boo(){ Bwah bwah; return bwah; } 

And the main function:

 int main(){ Bwah boo = Assigner::boo(); cout << "got here.." << endl; } 

The destructor in Bwah is called only once, after printing "received here". Is this a guarantee or is it a compiler optimization?

Answer 1

This is an optimization called Return Value Optimization (RVO). This is a normal optimization, but you cannot rely on it.

Here are two really great links for learning more:

• First, a really detailed article about passing by value, rvalue semantics, return value optimization and rvalue links, as well as the move constructor and assignment in C ++ 0x
• Secondly, a good old backup version of Wikipedia and their record in return value optimization .

The Wikipedia article, in particular, directly relates to your question. But in another article, the whole question is considered in more detail.