关于内存偏移量

只看该作者 · 2013-10-30 18:49

在程序员面试宝典上有这么一道题：

#include <string.h>
#include <iostream.h>
#include <stdio.h>

class A
{
public:
A(){m_a = 1; m_b = 2;}
~A(){};
void fun(){printf("%d%d",m_a,m_b);}
public:
int m_a;
int m_b;
};

class B
{
public:
B(){m_c = 3;}
~B();
void fun(){printf("%d",m_c);}
public:
int m_c;
};

int tmain(void)
{
      A a;
      B *pb = (B*)(&a);
      cout << &a << endl;          //0x22ff58
      cout << &(a.m_a) << endl;    //print the address of the a.m_a 0x22ff58
printf("%p\n",&A::m_a);       //print the offset from m_a to the beginning A object
                                    //address 00000000
printf("%p\n",&A::m_b);       //print the offset from m_a to the beginning A object
                                    //address 00000004
printf("%p\n",&B::m_cn);    //print the offset from m_c to the beginning B object
                                    //address 00000000
system("PAUSE");
return 0;
}

我的问题是：
（1）为什么内存的偏移是从成员变量开始？成员函数放在哪了呢？比如printf("%p\n",&A::fun);输出的是个
很大的偏移量，为什么？
（2）类在内存中具体是怎么保存的？