copy constructor is not called??

Answer 1

The compiler is permitted to elide the call to a copy constructor when an object is returned from a function.

That is, it is not required to actually call the copy constructor: it can just construct the object to be returned in whatever place the object needs to be to be returned from the function.

Answer 2

I believe you've encountered return value optimization (RVO) http://en.wikipedia.org/wiki/Return_value_optimization

Answer 3

It's legal to ellide copies, even when the copy constructor has side effects. It's called RVO (there's also one for named (comment: thanks) values, NRVO) and is explicitly allowed by the Standard.

Answer 4

It looks like RVO (Return Value Optimization). Your compiler sees that you are not doing anything with the 'b' instance nor with its returned copy so it removes it (object copy operation) from the compiled output.

Answer 5

Hi,

The web-wide famous C++ FAQ Lite (which you can find here for instance) is a must-read for every C++ programmer.

Your question probably corresponds to that one :
[10.9] Does return-by-value mean extra copies and extra overhead?