#include <iostream>
#include <cstring>
using namespace std;
class A
{
private:
    int num;
public:
    A(){}
    A(int num){this->num=num;}
    virtual ~A(){}
};
int main()
{
    A a;
    cout<<sizeof(a)<<endl;
    return 0;
}

只要是虚函数，就一定是4字节吗