一段简单程序从汇编看C指针

首先需要明白的两个概念：

　　　　指针：普通变量的地址

　　　　指针变量：该变量内存放的是指针

程序分析如下：

#include<stdio.h>

void main(){

int a,b;

a = 10;

b = 100;

int *pointa,*pointb;　//声明 *只是表示指针类型 int表示只能指向长度为4字节的int类型

pointa = &a;　　　//指针存放地址，&取地址

pointb = &b;

printf("%d,%d\n",a,b);

printf("%d,%d\n",*pointa,*pointb);　　// *表示去内容，和声明时*含义不同(注意区分)

}

@ILT+0(_main):

00401005 jmp main (00401010) //main作为跳转首地址

0040100A int 3 //类型3(专用:断点中断)中断 机器码0cch　是留给调试工具使用的中断

0040100B int 3

0040100C int 3

0040100D int 3

0040100E int 3

0040100F int 3

--- C:\point.cpp -----------------------------------------------------------------------------------------------------------------

1: #include<stdio.h>

2:

3: void main(){　　　　//调用main 保存原寄存器内容 入栈操作

00401010 push ebp

00401011 mov ebp,esp

00401013 sub esp,50h

00401016 push ebx

00401017 push esi

00401018 push edi

00401019 lea edi,[ebp-50h]

0040101C mov ecx,14h

00401021 mov eax,0CCCCCCCCh

00401026 rep stos dword ptr [edi]

4: int a,b;

5: a = 10;

00401028 mov dword ptr [ebp-4],0Ah //局部变量在不同环境下存放不同内存(即可马上销毁) 入栈ss

6: b = 100;

0040102F mov dword ptr [ebp-8],64h

7: int *pointa,*pointb;

8: pointa = &a;

00401036 lea eax,[ebp-4] //取局部变量a的偏移地址给eax(int 4字节)

00401039 mov dword ptr [ebp-0Ch],eax

9: pointb = &b;

0040103C lea ecx,[ebp-8]

0040103F mov dword ptr [ebp-10h],ecx

10: printf("%d,%d\n",a,b);

00401042 mov edx,dword ptr [ebp-8] //从右到左依此入栈

00401045 push edx

00401046 mov eax,dword ptr [ebp-4]

00401049 push eax

0040104A push offset string "%d,%d\n" (0042201c)

0040104F call printf (004010a0)　//系统调用 004010a0和下面系统调用统一操作

00401054 add esp,0Ch

11: printf("%d,%d\n",*pointa,*pointb);

00401057 mov ecx,dword ptr [ebp-10h]　//取地址 给ecx

0040105A mov edx,dword ptr [ecx]　 //取值 ecx存在要取的值的地址

0040105C push edx

0040105D mov eax,dword ptr [ebp-0Ch]

00401060 mov ecx,dword ptr [eax]

00401062 push ecx

00401063 push offset string "%d,%d\n" (0042201c)

00401068 call printf (004010a0)

0040106D add esp,0Ch

12: }

00401070 pop edi　　　　//恢复现场

00401071 pop esi

00401072 pop ebx

00401073 add esp,50h

00401076 cmp ebp,esp

00401078 call __chkesp (00401120)

0040107D mov esp,ebp

0040107F pop ebp

00401080 ret