class Class2;
class Class1 : public BaseClass
.......#include "class1.h"
#include "class2.h"
.....#include "class3.h"
class Class2
.....#include "class2.h"
......#include "class1.h"
class Class2;
class Class3 : public Class1
.....#include "class3.h"
#include "class2.h"