How can a class inherit itself? [duplicate]

Question

I don't understand the following code:

template <int _id> class Model;

template <int _id> class Model : public Model<0> { ... };

So, class Model derives from itself it seems. This doesn't compile with EDG or Gcc (error: invalid use of incomplete type ‘class Model<0>’), but Visual Studio accepts it. What compiler is right and for what reason?

Answer 1

So, class Model derives from itself it seems.

The class doesn't inherit itself. Every instatiation of Model<N> is a different, unrelated class.

This doesn't compile with EDG or Gcc (error: invalid use of incomplete type ‘class Model<0>’), but Visual Studio accepts it. What compiler is right and for what reason?

GCC is correct, at the point of usage, Model<0> is incomplete. Inheritance requires a complete class declaration.