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is it possible to somehow make a partial template specification a friend class? I.e. consider you have the following template class template <class T> class X{ T t; }; Now you have partial specializations, for example, for pointers template <class T> class X<T*>{ T* t; }; What I want to accomplish is that every possible X<T*> is a friend class of X<S> for ANY S . I.e. X<A*> should be a friend of X<B> . Of course, I thought about a usual template friend declaration in X: template <class T> class X{ template <class S> friend class X<S*>; } However, this does not compile, g++ tells me this: test4.cpp:34:15: error: specialization of ' template<class T> class X ' must appear at namespace scope test4.cpp:34:21: error: partial specialization ' X<S*> ' declared 'friend' Is this not possible at all or is there some workaround? The reason why I am asking is that I need a constructor in X<T*> that creates this class from an arbitrary X<S> ( S must be a subtype of T ). The code looks like this: template <class T> class X<T*>{ T* t; template<class S> X(X<S> x) : t(&(x.t)) {} //Error, x.t is private } Now, the compiler complains, of course, that x.t is not visibile in the constructor since it is private. This is why I need a partial specialization friend class.

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