C++:空指针访问类方法

#include <iostream>
using std::cout;
using std::endl;

class NullPointerCall
{
public:
	void func1()
	{	cout << "func1()" << endl;	}

	void func2(int ix)
	{	cout << "ix = " << ix << endl;	}

	void func3(/*  NullPointerCall* const this   */)
	{	cout << "_ix = " << this->_ix << endl;	}

private:
	int _ix;
};

 
int main(void)
{
	NullPointerCall * p = nullptr;
	p->func1();//NullPointerCall::func1(p);
	p->func2(10);// NullPointerCall::func2(p, 10);
	//p->func3();//error   p->func3(p);
	
	NullPointerCall np;
	np.func1();//NullPointerCall::func1(&np);
	np.func2(10);
	np.func3();//np.func3(&np); 
	return 0;
}