Output is different for R-value and L-value. Why?

Posted by Leonid Volnitsky on Stack Overflow See other posts from Stack Overflow or by Leonid Volnitsky
Published on 2012-09-01T09:28:33Z Indexed on 2012/09/01 9:38 UTC
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Can someone explain to me why output for R-value is different from L-value?

#include <iostream>
#include <vector>
using namespace std;

template<typename Ct>
struct  ct_wrapper {
    Ct&& ct; // R or L ref
    explicit ct_wrapper(Ct&& ct) 
      : ct(std::forward<Ct>(ct)) { std::cout <<  this->ct[1];};
};

int main() {

    // L-val
    vector<int> v{1,2,3};
    ct_wrapper<vector<int>&> lv(v);
    cout << endl << lv.ct[0] << lv.ct[1] << lv.ct[2] << endl;

    // R-val
    ct_wrapper<vector<int>&&> rv(vector<int>{1,2,3});
    cout << endl << rv.ct[0] << rv.ct[1] << rv.ct[2] << endl;
}

Output (same for gcc48 and clang32):

2
123
2
003

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