C++對象記憶體布局–⑩GCC編譯器–虛擬繼承–菱形繼承

C++對象記憶體布局--⑩GCC編譯器--虛擬繼承--菱形繼承

//GCC編譯器--虛擬繼承--菱形繼承.cpp//2010.8.19//GCC編譯器#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 記憶體布局：" << 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/*通過虛函數表調用函數*//*第一個虛函數表指標。BaseA*/((fun)(p[0][0]))(p);((fun)(p[0][1]))(p);//頭兩個是BaseA的((fun)(p[0][2]))(p);((fun)(p[0][3]))(p);//後兩個是Derived的/*第二個虛函數表指標。BaseB*/cout << endl;((fun)(p[2][0]))(p+2);/*第三個虛函數表指標。Base*/    cout << endl;((fun)(p[5][0]))(p+5);((fun)(p[5][1]))(p+5);    return 0;}/*Derived obj 記憶體布局：0x472d0c0x140x472d280x1e0x280x472d3c0xaBaseA::showA()  20BaseA::testA()  20Derived::show() 40Derived::test() 40BaseB::showB()  30Derived::show() 40BaseA::testA()  20*/