C++ 虚继承加上虚函数的类对象布局

单独的虚继承，单独的虚函数的类对象模型布局我们已经讨论过，接下来两者结合的对象布局如下，先看代码

代码

#include<iostream>
using namespace std;
class Base 
{
public:
	virtual void show(){cout<<"base show()"<<endl;}
public:
	int ma;
};

class Derived : virtual public Base
{
public:

	virtual void show(){cout<<"Derived show()"<<endl;}
public:
	int mb;
};

int main()
{

	return 0;
}

1、先按照常规布局，不考虑虚继承，布局如下

1>  class Derived	size(12):
1>  	+---
1>  	| +--- (base class Base)
1>   0	| | {vfptr}
1>   4	| | ma
1>  	| +---
1>   8	| mb
1>  	+---

2、再考虑虚继承，将虚基类对象整体放在最下面，然后再原来的位置放vbptr

1>  class Derived	size(16):
1>  	+---
1>   0	| {vbptr}
1>   4	| mb
1>  	+---
1>  	+--- (virtual base Base)
1>   8	| {vfptr}
1>  12	| ma
1>  	+---
1>  
1>  Derived::$vbtable@:
1>   0	| 0
1>   1	| 8 (Derivedd(Derived+0)Base)