c++ - Preserving referenceness when passing variadic arguments -

consider following code snippet:

class base { public:      template <typename...ts>     void fun(ts... vs)     {         cout << "base::fun" << endl;         cout << __funcsig__ << endl;     } };  template <typename...ts> class derived : public base { public:     void dfun(ts... vs)     {         cout << "derived::dfun" << endl;         cout << __funcsig__ << endl;         fun(vs...);     } };  int main() {     int = 10;     int & = i;     derived<int, int &> d;     d.dfun(i, a); } 

on running above code in vs2013, types deduced paramater pack values in derived::dfun (int, int&) in base::fun (int, int). why referenceness lost when passing arguments?

if dfun , fun free functions, referenceness preserved. why difference?

if change signature of base::fun base::fun(ts&&... vs), referenceness preserved again.

during template deduction reference types deduced type refer to. int& deduced int. causing behaviour seeing.

see here more detailed explication.