什么是菱形继承带来的二义性问题

首先来看一下这段代码：

#include<iostream>
using namespace std;

class Grandam
{
public:
    void introduce_self()
    {
        cout << "I am grandam." << endl;
    }
};

class Mother :public Grandam
{
public:
    void introduce_self()
    {
        cout << "I am mother." << endl;
    }
};

class Aunt :public Grandam
{
public:
    void introduce_self()
    {
        cout << "I am aunt." << endl;
    }
};

class Daughter :public Mother,public Aunt
{
public:
    void introduce_self()
    {
        cout << "I am daughter." << endl;
    }
};

int main()
{
    Grandam* ptr;
    Daughter d;
    ptr = &d;
    ptr->introduce_self();
    return 0;
}

对该程序进行编译，出现如图问题：

这就是二义性问题，Mother和Aunt都继承了Grandam，而Daughter多继承了Mother和Aunt，这样在调用对象d时，编译器不知道要调用来自Mother里的成员函数introduce_self()，还是来自Aunt里的introduce_self()，所以编译时会出错。

二义性的解决方法过程详细分析，见下篇文章：
http://blog.csdn.net/lxp_mujinhuakai/article/details/69427582