dynamic_cast的有效性问题

/******************************************************************** 
 file name : CLK.h 
 author  :   Clark/陈泽丹 
 created :   2011-12-12 
 purpose :   测试dynamic_cast的转换有效性
 测试结果发现dynamic_cast的只能在 [根结点, 实例化对象所处的类] 的路径上才能成功转换
*********************************************************************/ 
#include <iostream>

using namespace std;

#define DECLARE_CLASS_CREATE(class_name) static char* getName() { return #class_name; }; 

template<class T_TYPE>
class T2T
{
public:
	typedef T_TYPE CUR_TYPE;
};

class Root
{
public:
	DECLARE_CLASS_CREATE(Root)
	virtual void show(){} 
};
class Root_1Ex:public Root
{
public:
	DECLARE_CLASS_CREATE(Root_1Ex)
};
class Root_1Ex_1Ex:public Root_1Ex
{
public:
	DECLARE_CLASS_CREATE(Root_1Ex_1Ex)
};
class Root_2Ex:public Root
{
public:
	DECLARE_CLASS_CREATE(Root_2Ex)
};

template<class T_Base, class T_Ex, class T_Test>
void Test_Dynamic_Cast(T_Base obj1, T_Ex obj2, T_Test obj3)
{
	cout<<"-----------------------------------------------------------"<<endl;
	T_Base::CUR_TYPE* pBase = new T_Ex::CUR_TYPE();
	if( NULL != pBase)
	{
		cout<<"Succeed: "<<T_Base::CUR_TYPE::getName()<<" = new "<< T_Ex::CUR_TYPE::getName()<<endl;
	}
	else
	{
		cout<<"Failed: "<<T_Base::CUR_TYPE::getName()<<" = new "<< T_Ex::CUR_TYPE::getName()<<endl;
	}

	T_Test::CUR_TYPE* pTest = dynamic_cast<T_Test::CUR_TYPE*>(pBase);
	if( NULL != pTest)
	{
		cout<<"Succeed: "<<"dynamic_cast<"<< T_Test::CUR_TYPE::getName()<<"*>("<<T_Base::CUR_TYPE::getName()<<")"<<endl;
	}
	else
	{
		cout<<"Failed: "<<"dynamic_cast<"<< T_Test::CUR_TYPE::getName()<<"*>("<<T_Base::CUR_TYPE::getName()<<")"<<endl;
	}
	cout<<"-----------------------------------------------------------"<<endl;
	cout<<endl;
}

void main()
{
	Test_Dynamic_Cast(T2T<Root>(), T2T<Root_1Ex>(), T2T<Root_1Ex>());
	Test_Dynamic_Cast(T2T<Root>(), T2T<Root_1Ex>(), T2T<Root_1Ex_1Ex>());
	Test_Dynamic_Cast(T2T<Root>(), T2T<Root_1Ex>(), T2T<Root_2Ex>());
	Test_Dynamic_Cast(T2T<Root>(), T2T<Root_1Ex_1Ex>(), T2T<Root_1Ex>());
	system("pause");
}

 运行结果:

-----------------------------------------------------------
Succeed: Root = new Root_1Ex
Succeed: dynamic_cast<Root_1Ex*>(Root)
-----------------------------------------------------------

-----------------------------------------------------------
Succeed: Root = new Root_1Ex
Failed: dynamic_cast<Root_1Ex_1Ex*>(Root)
-----------------------------------------------------------

-----------------------------------------------------------
Succeed: Root = new Root_1Ex
Failed: dynamic_cast<Root_2Ex*>(Root)
-----------------------------------------------------------

-----------------------------------------------------------
Succeed: Root = new Root_1Ex_1Ex
Succeed: dynamic_cast<Root_1Ex*>(Root)
-----------------------------------------------------------