C++菱形继承

简单菱形继承：

#include<iostream>
using namespace std;
 
//sizeof(A) = 4;
//sizoef(B) = 12(变量a,b共8字节，虚基类表指针4 )
//sizeof(C) = 12(变量a,c共8字节，虚基类表指针4 )
 
//sizeof(D) = 24(24,变量a,b,c,d共16，B的虚基类指针4，C的虚基类指针)
 
 
class A{public: int a;};
class B : virtual public A{public: int b;};
class C : virtual public A{public: int c;};
class D : public B, public C{public: int d;};
 
void main()
{
    D d; cout << "sizeof(D) = " << sizeof(D) << endl;
    d.a = 10; d.b = d.c = 20; d.d = 30;
    int* pInt = (int*)(&d);
    for(int i = 0; i < sizeof(D)/sizeof(int); i++){
        if(i == 0 || i == 2)
            cout << "[" << pInt << "] : " << *pInt << "(" << *((int*)(*pInt)) << ")" << endl;
        else
            cout << "[" << pInt << "] : " << *pInt << endl;
        pInt++;
    }
}

复杂菱形继承：

#include<iostream>
using namespace std;
 
//virtual继承基类的好处：
//1、避免保留基类的多个拷贝；
//2、避免二义性
 
 
//顶层（第一层）
class CBase{
public:
    CBase() : iFoo(1){}
    virtual void Fun1(){cout << "CBase::Fun1" << endl;}
    virtual void Fun2(){cout << "CBase::Fun2" << endl;}
    int iFoo;
};
//中间层（第二层）
class CMid1 : virtual public CBase{
public:
    CMid1() : iMid(2){}
    virtual void Fun1(){ cout << "CMid1::Fun1" << endl;}
    virtual void Fun3(){ cout << "CMid1::Fun3" << endl;}
    int iMid;
};
class CMid2 : virtual public CBase{
public:
    CMid2() : iMid(2){}
    virtual void Fun1(){ cout << "CMid2::Fun1" << endl;}
    virtual void Fun3(){ cout << "CMid2::Fun3" << endl;}
    int iMid;
};
//底层（第三层）
class CDerived : public CMid1, public CMid2{
public:
    CDerived() : iBar(3){}
    virtual void Fun1(){ cout << "Derived::Fun1" << endl;}
    virtual void Fun4(){ cout << "Derived::Fun4" << endl;}
    int iBar;
};
 
typedef void (*LPFN)();
void VtableFuns(LPFN* lpfnArr)
{
    for(int i = 0; lpfnArr[i] != NULL; i++){
        cout << "[" << lpfnArr[i] << "] : ";
        lpfnArr[i]();
    }
}
 
void main()
{
    CDerived oDerived;
    cout << "Vtable From CMid1>>>>>>>>>>>>>>>" << endl;
    VtableFuns((LPFN*)*((int*)(&oDerived)));
    cout << "Vtable From CMid2>>>>>>>>>>>>>>>" << endl;
    VtableFuns((LPFN*)*(((int*)&oDerived)+3));
    cout << "Vtable From CBase>>>>>>>>>>>>>>>" << endl;
    VtableFuns((LPFN*)*(((int*)&oDerived)+8));
    cout << endl << ">>>>>>>>>>>>>>>>>>>>>>>>>>>>>>" << endl;
    cout << "sizeof(CDerived) = " << sizeof(CDerived) << endl;
    int* pInt = (int*)(&oDerived);
    for(int i = 0; i < sizeof(CDerived)/sizeof(int); i++){
        if(i == 0 || i == 1 || i == 3 || i == 4 || i == 8){
            cout << "[" << pInt << "] : " << *pInt << "(" << *((int*)(*pInt)) << ")" << endl;
        }
        else{
            cout << "[" << pInt << "] : " << *pInt << endl;
        }
        pInt++;
    }
    cout << "&(oDerived.CMid1::iMid) = " << &(oDerived.CMid1::iMid) << endl;
    cout << "&(oDerived.CMid2::iMid) = " << &(oDerived.CMid2::iMid) << endl;
    cout << ">>>>>>>>>>>>>>>>>>>>>>>>>>>>>>" << endl;
}