externs

[Martin Stjernholm, Roxen IS @ Pike developers forum]

Or maybe reading 0 is correct, if one takes the analogy with undefined
functions one step further:

  class B
  {
    extern int i;
    void f();
    void x() {werror ("i: %O, f: %O\n", i, f);}
  }

  int main()
  {
    B()->x(); // Writes "i: 0, f: 0"
  }

But I still would rather have B::i an alias for A::i (and i) in C in
my first example.