templates - C++ calling the right virtual function -

i have problem following situation:

 template<class t> class { public: virtual int  f() { return 1; } };  class basea : public a<basea> {}; class deriveda : public basea, public a<deriveda> {}; 

and when do:

 basea* b1 = new deriveda; b1->f(); 

it calls a<basea>::f() instead of a<deriveda>::f() , don't know how fix it.

additional info op: homework problem class a can freely changed, classes basea , deriveda cannot changed.

then following 1 solution, based on dominance in virtual inheritance hierarhcy:

#include <iostream> #include <typeinfo> using namespace std;  struct basea;  struct {     virtual auto  f()         -> int = 0; };  template<class t> class     : public virtual { public:     virtual auto  f()         -> int override     { cout << typeid( t ).name() << '\n'; return 1; } };  template<> class a<basea>: public virtual {};  class basea : public a<basea> {}; class deriveda : public basea, public a<deriveda> {};  auto main() -> int {     basea* b1 = new deriveda;     b1->f(); }