派生类重载问题

 条件一：B继承A，C继承B

class A
{
public:
	void pp() { cout << "A" << endl; }
};

class B : public A
{
public:
	void pp() { cout << "B" << endl; }
};

class C : public B
{
public:
	void pp() { cout << "C" << endl; }
};

条件二：存在两个重载函数：

void pp(B*b)

void pp(A*a)

问题：pp(new C)进哪个重载函数

Coding: 

class A
{
public:
	void pp() { cout << "A" << endl; }
};

class B : public A
{
public:
	void pp() { cout << "B" << endl; }
};

class C : public B
{
public:
	void pp() { cout << "C" << endl; }
};

class D : public A
{
public:
	void pp() { cout << "D" << endl; }
};

void pp(B*b)
{
	b->pp();
	cout << "BPP" << endl;
}

void pp(A* a)
{
	a->pp();
	cout << "APP" << endl;
}



int main()
{
	pp(new C);

    return 0;
}

输出结果：

C
BPP

 单线多继承下：

class D : public B ,public A
{
public:
	virtual void pp() { cout << "D" << endl; }
};

int main()
{
	pp(new D);

    return 0;
}

输出：

D
BPP

多继承下：

class A
{
public:
	virtual void pp() { cout << "A" << endl; }
};

class AA
{
public:
	virtual void pp() { cout << "AA" << endl; }
};

class D : public A ,public AA
{
public:
	virtual void pp() { cout << "D" << endl; }
};

void pp(A* a)
{
	a->pp();
	cout << "APP" << endl;
}

void pp(AA* a)
{
	a->pp();
	cout << "APP" << endl;
}

int main()
{
	pp(new D);

    return 0;
}

结果：

编译报错：pp对重载函数的调用不明确

结论：

重载派生，就近原则。无法确定时，会编译报错