空类与多重继承占用空间大小

虚继承涉及虚表（虚指针），所以sizeof(C) = 8

#include <iostream>
using namespace std;

class A{};
class A2{};
class B:public A
{};

class C:public virtual B
{};

class D:public A,public A2
{};

int main(int argc,char *argv[])
{
    cout << "sizeof(A)" << sizeof(A) <<endl;//1
    cout << "sizeof(B)" << sizeof(B) <<endl;//1
    cout << "sizeof(C)" << sizeof(C) <<endl;//8
    cout << "sizeof(D)" << sizeof(D) <<endl;//1
    return 0;
    
}