No copy on returning a local variable

return_value_optimization.cpp

// How to run it:                                                                                                
// $ g++ --std=c++11 ~/return_value_optimization.cpp && ./a.out                                                  
//                                                                                                               
// Output is                                                                                                     
// copying obj1                                                                                                  
// obj2 is not copied.                                                                                           

#include <iostream>
#include <string>

class MyClass {
public:
  MyClass(std::string label)
    : label_(label) {}

  MyClass(const MyClass& rhs)
    : label_(rhs.label_) {
    std::cout << "copying " << label_ << "\n";
  }

private:
  std::string label_;
};

MyClass fun() {
  MyClass c("obj2");
  return c;
}

int main() {
  MyClass c("obj1");
  MyClass d = c;

  MyClass e = fun();

  return 0;
}

Another way to verify there is no copy happening on return is to get addresses of c in fun() and e in main()`. They have the same address.