language: C++11 (gcc-4.7.2)
date: 728 days 12 hours ago
link:
visibility: private 
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#include <iostream>
 
struct S
{
  S() {}
  S(const S&) { std::cout << "Copy" << std::endl; }
  S(S&&) { std::cout << "Move" << std::endl; }
};
 
S f1(S a) {
  return a;
}
 
S f2(const S& a) {
  return a;
}
 
#define DELAY(x) [&]{ return x; }
 
template <class F>
S f3(F a) {
  return a();
}
 
int main()
{
  S t;
  std::cout << "Without delay:" << std::endl;
  S s1 = f1(t);
  std::cout << "With delay:" << std::endl;
  S s2 = f3(DELAY(t));
  std::cout << "Without delay pass by ref:" << std::endl;
  S s3 = f2(t);
  std::cout << "Without delay pass by ref (temporary) (should have 0 copies, will get 1):" << std::endl;
  S s4 = f2(S());
  std::cout << "With delay (temporary) (no copies, best):" << std::endl;
  S s5 = f3(DELAY(S()));
}