[C++] Problema inclusione header

[MacApp]

Forward declaration:

#ifndef A_H
#define A_H

#include"B.h"

class B;
class A{
      B *b;
};

#endif 

#ifndef B_H
#define B_H

#include"A.h"
class A;
class B{
      A *a;    
};    

#endif