c++ virtual的作用

<span style="font-family: Arial, Helvetica, sans-serif;">using namespace std;</span>

class C
{
public:
	C()
	{
		cout << "construct c" << endl;
	}
	virtual ~C()
	{
		cout << "delete c" << endl;
	}
	virtual void showc()
	{
		cout << "show c" << endl;
	}


};
class D : public  C
{
public:
	D(){
		cout << "construct d" << endl;
	}
	~D()
	{
		cout << "delete d" << endl;
	}
	void showd()
	{
		cout << "show d" << endl;
	}
};
int main()
{
	C* c = new D;
	c->showc();
	delete c;
	return 0;
}

注意：如果去掉基函數裏面析構函數的virtual時候，那麼D類析構的時候就調用不了~C（）造成內存泄露。所以基函數一般都默認的加virtual，起到默認的繼承作用，new誰的對象，類析構的時候就調用誰的析構函數。運行結果如上圖所示。