c++中虚函数指针，虚基类指针在派生过程不会复制吗？

Question

我电脑运行结果是4,4,4,8,4，按这个看，基类的虚函数指针似乎不会在派生类中复制？

#include <string>
#include <iostream>
#include <string.h>
#include <stdio.h>
using namespace std;

class A {
public:
    virtual int fun() {return 1;}
};

class E : public A {
public:
    virtual int fun() {return 5;}
};

class B : virtual public A {
public:
    virtual int fun() {return 2;}
};

class C : virtual public A {
public:
    virtual int fun() {return 3;}
};

class D : public B, public C {
public:
    virtual int fun() {return 4;}
};


int main()
{
    cout << sizeof(A) << endl;    // 4
    cout << sizeof(B) << endl;    // 4
    cout << sizeof(C) << endl;    // 4
    cout << sizeof(D) << endl;    // 8
    cout << sizeof(E) << endl;    // 4

    return 0;
}

Answer 1

是覆盖不是复制