C++对象内存布局⑨VS编译器虚拟继承菱形继承

C++对象内存布局--⑨VS编译器--虚拟继承--菱形继承

//VS编译器--虚拟继承--菱形继承.cpp
//2010.8.19
//VS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 sizeof = " << sizeof(obj) << endl;
    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 (__thiscall *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);

	//第二个虚函数表指针。BaseB
	cout << endl;
	((fun)(p[3][0]))(p+3);
	//第三个虚函数表指针。Base
    cout << endl;
	((fun)(p[8][0]))(p+8);
	((fun)(p[8][1]))(p+8);
	system("pause");
    return 0;
}
/*
Derived obj sizeof = 40
Derived obj 内存布局：
0041A200
0041A210
00000014
0041A1F8
0041A208
0000001E
00000028
00000000
0041A1EC
0000000A

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

BaseB::showB()  30

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