C++對(duì)象內(nèi)存布局--⑤GCC編譯器--單個(gè)虛擬繼承

　　測(cè)試GNU的GCC編譯器在處理虛擬繼承上跟VS不同的地方。派生類的虛函數(shù)表跟虛基類表合并。

//GCC編譯器--單個(gè)虛擬繼承.cpp //2010.8.18 //虛基類表到底是那個(gè)？，還是說(shuō)派生類的虛函數(shù)表的上邊和下邊都是？ //GCC編譯器 #include <iostream> using namespace std; // class Base {public:Base(int a = 10):a(a){cout << "Base::Base()" << endl;}virtual void show1(){cout << "Base::show1()" << endl;cout << a << endl;}private:int a; }; // class Derived : virtual public Base {public:Derived(int b = 100):b(b){cout << "Derived::derived()" << endl;}virtual void show2(){cout << "Derived::show2()" << endl;cout << b << endl;}private:int b; }; // int main() {Derived obj;int** p = (int**)&obj;cout << "虛擬繼承了基類的派生類的對(duì)象內(nèi)存布局：" <<endl;for (int i = 0; i != sizeof(obj)/4; ++i){cout << p[i] << endl;}typedef void (*fun)(void*pThis);//this指針?lè)浅Ｖ匾猚out << endl << "第一虛函數(shù)表第一項(xiàng)，虛函數(shù)Derived::show2()地址：" << (int*)p[0][0] << endl;((fun)(p[0][0]))(p);cout << "第二虛函數(shù)表第一項(xiàng)，虛函數(shù)Base::show1()地址 ：" << (int*)p[2][0] << endl;((fun)(p[2][0]))(p+2);cout << endl << "派生類虛函數(shù)表指針往低地址方向?qū)ぶ?#xff1a;" << endl;cout << "p[0][-1] = " << (int*)p[0][-1] << endl;cout << "p[0][-2] = " << (int*)p[0][-2] << endl;cout << "p[0][-3] = " << (int*)p[0][-3] << endl;cout << endl << "派生類虛函數(shù)表指針往高地址方向?qū)ぶ?#xff1a;" << endl;cout << "p[0][0] = " << (int*)p[0][0] << "(這個(gè)是show2()函數(shù)地址)" << endl;cout << "p[0][1] = " << (int*)p[0][1] << endl;cout << "p[0][2] = " << (int*)p[0][2] << endl;cout << "p[0][3] = " << (int*)p[0][3] << endl;cout << endl << "是否往高方向?qū)ふ液屯胤较驅(qū)ふ宜业降亩际翘摶惐砟?#xff1f;" << endl;//system("pause");return 0; } /* Base::Base() Derived::derived() 虛擬繼承了基類的派生類的對(duì)象內(nèi)存布局： 0x472d4c 0x64 0x472d5c 0xa第一虛函數(shù)表第一項(xiàng)，虛函數(shù)Derived::show2()地址：0x41cd50 Derived::show2() 100 第二虛函數(shù)表第一項(xiàng)，虛函數(shù)Base::show1()地址 ：0x41ccbc Base::show1() 10派生類虛函數(shù)表指針往低地址方向?qū)ぶ?#xff1a; p[0][-1] = 0x471388 p[0][-2] = 0 p[0][-3] = 0x8派生類虛函數(shù)表指針往高地址方向?qū)ぶ?#xff1a; p[0][0] = 0x41cd50(這個(gè)是show2()函數(shù)地址) p[0][1] = 0 p[0][2] = 0xfffffff8 p[0][3] = 0x471388是否往高方向?qū)ふ液屯胤较驅(qū)ふ宜业降亩际翘摶惐砟?#xff1f; */

轉(zhuǎn)載于:https://www.cnblogs.com/cswuyg/archive/2010/08/20/1804087.html

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