This would work.  But it's a real hack...

And perhaps this does belong on comp.std.c++, since this solution
*really* should not be allowed.  It works by means of doing funky
pointer arithmetic inside of the subclass...

ie, either doing "((b *) & a)->a::do()" should be forbidden inside class
B, or it should be possible to access protected members in a instance of
that class inside of a subclass...

Granted, you could make class B a friend of class A, but there are
occasions where you really don't want to have to modify class A to do
this...

Example:

class A
{
  ...
protected:   //  Make do() a protected member, only this class
             //  & subclasses can access do().
  void do();
  ...
};

class B : public A // This can be public, protected, or private inheritance
{
  ...
  public :
    ...
    void doit()
      { A a;  // Make this a instance of A, not a pointer, for clarity.
        ((b *) & a)->a::do();   // This is allowed, and actually works...
      };
    ...
};

But
void main()
{
  A* a;
  a->do(); // This is forbidden at compile time.
}

Hello,

I have a problem with the method of the class A... Let me give you an example :

class A
{
  ...
  void do();
  ...
};

class B : public A
{
  ...
  public :
    ...
    void doit()
      { A* a;
        a->do(); I want to allow this situation...
      };
    ...
};

But
void main()
{
  A* a;
  a->do(); I want to forbide this situation...

So, I don't want to allow to use the do() method of the class A, except if I am in the classes A or B (even if, I use an instance of A in this classes, like in the example).

I want to know how I can implement the do() method of the class A to have this kind of particular situation.

I expect you understand this strange case...

Thanks in advance.

DAVID.