再议：C++类实例化时的内存分配

#include <iostream>

class A{};
class B{};
class C:public A{
double f;
virtual void fun();

};
class D:public A,public B
{};

class E:public C,public A{};
class F:public A,public C{};

class G:public A{
//double f;
virtual void fun();

};
int main()
{
std::cout << sizeof(A) << std::endl;
std::cout << sizeof(B) << std::endl;
std::cout << sizeof(C) << std::endl;
std::cout << sizeof(D) << std::endl;
std::cout << sizeof(E) << std::endl;
std::cout << sizeof(F) << std::endl;
std::cout << sizeof(double) << std::endl;
std::cout << sizeof(G) << std::endl;
return 0;
}