On &&

gistfile1.cpp

class Report
{
public:
    Report() : i_am_dead(false) { cout << "  Report();" << endl; }
    Report(const Report & ) { cout << "  Report(const Report&);" << endl; };
    Report(Report && h) { cout << "  Report(&&);" << endl; h.i_am_dead = true; }
    Report & operator = (const Report&) { cout << "  Report::=(const Report&);" << endl; return *this; };
    ~Report() { cout << "  ~Report() i_am_dead=" << i_am_dead << endl; }
    bool i_am_dead;
};

template <typename Tc, typename T>
void push1 ( Tc & c, T t )
{
    c.push_back(move(t));
}

template <typename Tc, typename T>
void push2 ( Tc & c, const T & t )
{
    c.push_back(t);
}

template <typename Tc, typename T>
void push3 ( Tc & c, T && t )
{
    c.push_back(forward<T>(t));
}

Report f(int bla) {
    return Report();
}

int main(int argc, const char * argv[])
{
    cout << "push1" << endl;
    {
        vector<Report> a;
        Report b;
        push1(a, b);
    }
    
    cout << "push2" << endl;
    {
        vector<Report> a;
        Report b;
        push2(a, b);
    }
    
    cout << "push3" << endl;
    {
        vector<Report> a;
        Report b;
        push3(a, b);
    }
    
    cout << "push1 with a temporary returned from f" << endl;
    {
        vector<Report> a;
        push1(a, f(123));
    }
    
    cout << "push2 with a temporary returned from f" << endl;
    {
        vector<Report> a;
        push2(a, f(123));
    }
    
    cout << "push3 with a temporary returned from f" << endl;
    {
        vector<Report> a;
        push3(a, f(123));
    }
}

/*
push1
  Report();
  Report(const Report&);
  Report(&&);
  ~Report() i_am_dead=1
  ~Report() i_am_dead=0
  ~Report() i_am_dead=0
push2
  Report();
  Report(const Report&);
  ~Report() i_am_dead=0
  ~Report() i_am_dead=0
push3
  Report();
  Report(const Report&);
  ~Report() i_am_dead=0
  ~Report() i_am_dead=0
push1 with a temporary returned from f
  Report();
  Report(&&);
  ~Report() i_am_dead=1
  ~Report() i_am_dead=0
push2 with a temporary returned from f
  Report();
  Report(const Report&);
  ~Report() i_am_dead=0
  ~Report() i_am_dead=0
push3 with a temporary returned from f
  Report();
  Report(&&);
  ~Report() i_am_dead=1
  ~Report() i_am_dead=0
*/