fork download

copy

#include <iostream>
 
template <typename Derived>
struct A
{
  static void do_thing() { Derived::do_thing_impl(); }
};
 
struct B : public A<B>
{
  friend A<B>;
 protected:
  static void do_thing_impl() { std::cout << "B impl" << std::endl; }
};
 
struct C : public A<C>
{
  friend A<C>;
 protected:
  static void do_thing_impl() { std::cout << "C impl" << std::endl; }
};
 
struct D : public A<D>
{
 friend A<D>;
};
 
int main() 
{
 A<B>::do_thing();
 A<C>::do_thing();
 A<D>::do_thing();
 
 return (0);
}

prog.cpp: In instantiation of ‘static void A<Derived>::do_thing() [with Derived = D]’:
prog.cpp:32:8:   required from here
prog.cpp:6:51: error: ‘do_thing_impl’ is not a member of ‘D’
   static void do_thing() { Derived::do_thing_impl(); }
                                                   ^

Standard output is empty