Le 27/11/2010 21:27, Warp nous fit lire :
> Le_Forgeron <jgr### [at] freefr> wrote:
>> (2) is not allowed because a() of A is protected, so can only be called
>> by the object itself (in a gross simplification).

I did write "in a gross simplification", didn't I ?

>   Needless to say, gcc (and probably most other C++ compilers) will give
> an error for that, so it just cannot be done. If you need to call the
> protected section of the object, take a pointer of the derived type,
> because that's what it has to be.
> 

Or "just" make B a friend of A. Or in fact, only the needed function of
B can be a friend of A.

Now, I would question the design any way for such function b
(as it is bypassing the objects' boundaries), but sometimes it's simpler
than redesign everything.

  class B;

  class A
  {
      protected:
          void a() {}
      friend void B::b(); // more restricted than "friend B;"
  };

  class B : public A
  {
      protected:
          void b(A* other)
          {
              this->a();  // (1)
              other->a(); // (2)
          }
  };

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