很久以前收藏的原文地址找不到了。

单继承对象内存分配：

#include 
     
      using namespace std;class Base1{public:    long ibase1;    int ibase12;    Base1():ibase1(10),ibase12(100) {}    virtual void f()    {        cout << "Base1::f()" << endl;    }    virtual void g()    {        cout << "Base1::g()" << endl;    }    virtual void h()    {        cout << "Base1::h()" << endl;    }};class Base2{public:    int ibase2;    long ibasee21;    Base2():ibase2(20),ibasee21(21) {}    virtual void f()    {        cout << "Base2::f()" << endl;    }    virtual void g()    {        cout << "Base2::g()" << endl;    }    virtual void h()    {        cout << "Base2::h()" << endl;    }};class Base3{public:    int ibase3;    Base3():ibase3(30) {}    virtual void f()    {        cout << "Base3::f()" << endl;    }    virtual void g()    {        cout << "Base3::g()" << endl;    }    virtual void h()    {        cout << "Base3::h()" << endl;    }};class Derive : public Base1, public Base2, public Base3{public:    int iderive;    Derive():iderive(100) {}    virtual void f()    {        cout << "Derive::f()" << endl;    }    virtual void g1()    {        cout << "Derive::g1()" << endl;    }};typedef void(*Fun)(void);Fun pFun;int main(){    Derive d;    int** pVtab = (int**)&d;     cout << "[0] Base1::_vptr->" << endl;    pFun = (Fun)pVtab[0][0];    cout << "     [0] ";    pFun();    pFun = (Fun)pVtab[0][1];    cout << "     [1] ";    pFun();    pFun = (Fun)pVtab[0][2];    cout << "     [2] ";    pFun();    pFun = (Fun)pVtab[0][3];    cout << "     [3] ";    pFun();    pFun = (Fun)pVtab[0][4];    cout << "     [4] ";    cout<
      
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重复继承内存分配：

 

#include 
     
      using namespace std;class B{    public:        int ib;        char cb;    public:        B():ib(0),cb('B') {}        virtual void f() { cout << "B::f()" << endl;}        virtual void Bf() { cout << "B::Bf()" << endl;}};class B1 :  public B{    public:        int ib1;        char cb1;    public:        B1():ib1(11),cb1('1') {}        virtual void f() { cout << "B1::f()" << endl;}        virtual void f1() { cout << "B1::f1()" << endl;}        virtual void Bf1() { cout << "B1::Bf1()" << endl;};class B2:  public B{    public:        int ib2;        char cb2;    public:        B2():ib2(12),cb2('2') {}        virtual void f() { cout << "B2::f()" << endl;}        virtual void f2() { cout << "B2::f2()" << endl;}        virtual void Bf2() { cout << "B2::Bf2()" << endl;}};class D : public B1, public B2{    public:        int id;        char cd;    public:        D():id(100),cd('D') {}        virtual void f() { cout << "D::f()" << endl;}        virtual void f1() { cout << "D::f1()" << endl;}        virtual void f2() { cout << "D::f2()" << endl;}        virtual void Df() { cout << "D::Df()" << endl;}}; typedef void(*Fun)(void);    int** pVtab = NULL;    Fun pFun = NULL;int main(){     D d;    pVtab = (int**)&d;    cout << "[0] D::B1::_vptr->" << endl;    pFun = (Fun)pVtab[0][0];    cout << "     [0] ";    pFun();    pFun = (Fun)pVtab[0][1];    cout << "     [1] ";    pFun();    pFun = (Fun)pVtab[0][2];    cout << "     [2] ";    pFun();    pFun = (Fun)pVtab[0][3];    cout << "     [3] ";    pFun();    pFun = (Fun)pVtab[0][4];    cout << "     [4] ";    pFun();    pFun = (Fun)pVtab[0][5];    cout << "     [5] 0x" << pFun << endl;    cout << "[1] B::ib = " << (int)pVtab[1] << endl;    cout << "[2] B::cb = " << (char)pVtab[2] << endl;    cout << "[3] B1::ib1 = " << (int)pVtab[3] << endl;    cout << "[4] B1::cb1 = " << (char)pVtab[4] << endl;     cout << "[5] D::B2::_vptr->" << endl;    pFun = (Fun)pVtab[5][0];    cout << "     [0] ";    pFun();    pFun = (Fun)pVtab[5][1];    cout << "     [1] ";    pFun();    pFun = (Fun)pVtab[5][2];    cout << "     [2] ";    pFun();    pFun = (Fun)pVtab[5][3];    cout << "     [3] ";    pFun();    pFun = (Fun)pVtab[5][4];    cout << "     [4] 0x" << pFun << endl;    cout << "[6] B::ib = " << (int)pVtab[6] << endl;    cout << "[7] B::cb = " << (char)pVtab[7] << endl;    cout << "[8] B2::ib2 = " << (int)pVtab[8] << endl;    cout << "[9] B2::cb2 = " << (char)pVtab[9] << endl;    cout << "[10] D::id = " << (int)pVtab[10] << endl;    cout << "[11] D::cd = " << (char)pVtab[11] << endl;}
     

我们可以看见，最顶端的父类B其成员变量存在于B1和B2中，并被D给继承下去了。而在D中，其有B1和B2的实例，于是B的成员在D的实例中存在两份，一份是B1继承而来的，另一份是B2继承而来的。所以，如果我们使用以下语句，则会产生二义性编译错误：

 

D d;

d.ib = 0;               //二义性错误

d.B1::ib = 1;           //正确

d.B2::ib = 2;           //正确

 

注意，上面例程中的最后两条语句存取的是两个变量。虽然我们消除了二义性的编译错误，但B类在D中还是有两个实例，这种继承造成了数据的重复，我们叫这种继承为重复继承。重复的基类数据成员可能并不是我们想要的。所以，C++引入了虚基类的概念。

 钻石型多重虚拟继承内存分配：

#include 
     
      using namespace std;class B{public:    int ib;    char cb;public:    B():ib(0),cb('B') {}    virtual void f()    {        cout << "B::f()" << endl;    }    virtual void Bf()    {        cout << "B::Bf()" << endl;    }};class B1 : virtual public B//虚拟继承{public:    int ib1;    char cb1;public:    B1():ib1(11),cb1('1') {}    virtual void f()    {        cout << "B1::f()" << endl;    }    virtual void f1()    {        cout << "B1::f1()" << endl;    }    virtual void Bf1()    {        cout << "B1::Bf1()" << endl;    }};class B2:  virtual public B//虚拟继承{public:    int ib2;    char cb2;public:    B2():ib2(12),cb2('2') {}    virtual void f()　　 {        cout << "B2::f()" << endl;    }    virtual void f2()    {      cout << "B2::f2()" << endl;    }    virtual void Bf2()    {        cout << "B2::Bf2()" << endl;    }};class D : public B1, public B2{public:    int id;    char cd;public:    D():id(100),cd('D') {}    virtual void f()    {        cout << "D::f()" << endl;    }    virtual void f1()    {        cout << "D::f1()" << endl;    }    virtual void f2()    {        cout << "D::f2()" << endl;    }    virtual void Df()    {        cout << "D::Df()" << endl;    }};typedef void(*Fun)(void);int** pVtab = NULL;Fun pFun = NULL;int main(){    D dd;     pVtab = (int**)ⅆ    cout << "[0] D::B1::_vptr->" << endl;    pFun = (Fun)pVtab[0][0];    cout << "     [0] ";    pFun(); //D::f1();    pFun = (Fun)pVtab[0][1];    cout << "     [1] ";    pFun(); //B1::Bf1();    pFun = (Fun)pVtab[0][2];    cout << "     [2] ";    pFun(); //D::Df();    pFun = (Fun)pVtab[0][3];    cout << "     [3] ";    cout << pFun << endl;    //cout << pVtab[4][2] << endl;    cout << "[1] = 0x";    cout <<  (int*)((&dd)+1) <
      
       " << endl;    pFun = (Fun)pVtab[4][0];    cout << "     [0] ";    pFun(); //D::f2();    pFun = (Fun)pVtab[4][1];    cout << "     [1] ";    pFun(); //B2::Bf2();    pFun = (Fun)pVtab[4][2];    cout << "     [2] ";    cout << pFun << endl;    cout << "[5] = 0x";    cout << *((int*)(&dd)+5) << endl; // ???    cout << "[6] B2::ib2 = ";    cout << (int)*((int*)(&dd)+6) <
       
        " << endl;    pFun = (Fun)pVtab[11][0];    cout << "     [0] ";    pFun(); //D::f();    pFun = (Fun)pVtab[11][1];    cout << "     [1] ";    pFun(); //B::Bf();    pFun = (Fun)pVtab[11][2];    cout << "     [2] ";    cout << pFun << endl;    cout << "[12] B::ib = ";    cout << *((int*)(&dd)+12) << endl; //B::ib    cout << "[13] B::cb = ";    cout << (char)*((int*)(&dd)+13) <