C++对象内存布局--⑩GCC编译器--虚拟继承--菱形继承

//GCC编译器--虚拟继承--菱形继承.cpp
//2010.8.19
//GCC编译器
#include <iostream>
using namespace std;
////////////////////////////////////////////////////////////////
class Base
{
    public:
        Base(int a = 10):a(a)
        {
        }
        virtual void show()
        {
            cout << "Base::show()" << "\t" << a << endl;
        }
        virtual void testA()
        {
            cout << "Base::testA()" << "\t" << a << endl;
        }
    private:
        int a;
};
////////////////////////////////////////////////////////////////
class BaseA : virtual public Base
{
    public:
        BaseA(int b = 20):b(b)
        {
        }
        virtual void showA()
        {
            cout << "BaseA::showA()" << "\t" << b << endl;
        }
        void testA()
        {
            cout << "BaseA::testA()" << "\t" << b << endl;
        }
    private:
        int b;
};
////////////////////////////////////////////////////////////////
class BaseB : virtual public Base
{
    public:
        BaseB(int c = 30):c(c)
        {
        }
        virtual void showB()
        {
            cout << "BaseB::showB()" << "\t" << c << endl;
        }
    private:
        int c;
};
////////////////////////////////////////////////////////////////
class Derived : public BaseA, public BaseB
{
    public:
        Derived(int d = 40):d(d)
        {
        }
        virtual void show()
        {
            cout << "Derived::show()" << "\t" << d << endl;
        }
        virtual void test()
        {
            cout << "Derived::test()" << "\t" << d << endl;
        }
    private:
        int d;
};
////////////////////////////////////////////////////////////////
int main()
{
    Derived obj;
    int** p = (int**)&obj;
    cout << "Derived obj 内存布局：" << endl;
    for (int i = 0; i != sizeof(obj)/4; ++i)
    {
        cout << p[i] << endl;
    }
    cout << endl;
   typedef void (*fun)(void*pThis);//非常重要
        /*通过虚函数表调用函数*/
        /*第一个虚函数表指针。BaseA*/
        ((fun)(p[0][0]))(p);
        ((fun)(p[0][1]))(p);//头两个是BaseA的

        ((fun)(p[0][2]))(p);
        ((fun)(p[0][3]))(p);//后两个是Derived的
        /*第二个虚函数表指针。BaseB*/
        cout << endl;
        ((fun)(p[2][0]))(p+2);
        /*第三个虚函数表指针。Base*/
    cout << endl;
        ((fun)(p[5][0]))(p+5);
        ((fun)(p[5][1]))(p+5);
    return 0;
}
/*
Derived obj 内存布局：
0x472d0c
0x14
0x472d28
0x1e
0x28
0x472d3c
0xa

BaseA::showA()  20
BaseA::testA()  20
Derived::show() 40
Derived::test() 40

BaseB::showB()  30

Derived::show() 40
BaseA::testA()  20
*/