In C++, why isn't it possible to friend a template class member function using the template type of another class?

Question

In other words, why does this compile fine :

template
class A{
  public:
    void f();
};

class B{
  friend void A::f();
};

tem         


        

Answer 1

Specializing template class member function without specializing whole template class is special case when you are allowed to specialize non-template member function, so maybe GCC is confused, and I don't know the reasons, but somehow you can't declare friendship to specialized non-template member of template class. Temporary solution would be to specialize whole class template for this to work.

//class template A
template
class A{
  public:
    void f();
};

//class A
template<>
class A{
  public:
    void f();
};

Then, define A::f:

For class B:

void A::f(){
      B* var = new B();
      (void)(var);
}

For template class B:

void A::f(){
      B* var = new B();
      (void)(var);
}

But I think Clang is right here, there should be no problems for such friend declaration. It's probably a bug in GCC.