空指针调用成员函数

#include <iostream> 
using namespace std; 
class test 
{ 
public: 
	test(int i){ m_i=i;} 
	test(){} 
	void hello() 
	{ 
		if(NULL == this)
		{
			cout << "null == this" << endl;
		}

		printf("hello\n"); 		
	} 
private: 
	int m_i; 
}; 
int main() 
{ 
	test *p=new test(); 
	p->hello(); 
	delete p;
	p=NULL;	

	p->hello(); 
} 

 运行结果:

 

hello

null == this

hello