Lets look into this snippet and as expected I get In && printed. However, instead of z = x+y if I had written S z(x + y) I don't get the call to "In move". Instead the temporary created inside operator+ seems to be what z is. Maybe the compiler is optimizing it but I don't quite get it.
#include <algorithm>
#include <iostream>
using namespace std;
struct S {
S(int N1) : N(N1) {
cout << "In orig " << N << "\n";
}
S(S& s) {
N = s.N;
cout << "In copy\n";
}
S(S&& s) {
N = s.N;
cout << "In move\n";
}
S const & operator=(S&& s) {
cout << "In &&\n";
}
S operator+(S const & s) {
cout << "In +\n";
return S(N + s.N);
}
int N;
};
int main()
{
S x(33), y(44);
S z = 99; // instead of this line and next try S z(x + y); --> no move constructor??
z = (x + y);
}
