conv1.c

this is a gcc file, you can download it and learn its usetility, for further detail please look at t

// Build don't link:

template <class T>
struct S1 {};

struct S2
{
  template <class T>
  operator S1<T>*();
};

struct D: public S1<int> {
};

void f()
{
  S2 s;
  (D*) s; // ERROR - cannot convert
}