大会：在C语言程序

的变量内存地址，这是我的C代码大会：在C语言程序

C:\Codes>gdb test -q 
Reading symbols from C:\Codes\test.exe...done. 
(gdb) list 1,15 
1  #include<stdio.h> 
2 
3  int main() 
4  { 
5    int a = 12345; 
6    int b = 0x12345; 
7    printf("+-----+-------+---------+----------+\n"); 
8    printf("| Var | Dec | Hex  | Address |\n"); 
9    printf("+-----+-------+---------+----------+\n"); 
10    printf("| a | %d | 0x%x | %p |\n",a,a,&a); 
11    printf("| b | %d | 0x%x | %p |\n",b,b,&b); 
12    printf("+-----+-------+---------+----------+\n"); 
13 
14    return 0; 
15  } 
(gdb) set disassembly-flavor intel

这是标准输出

C:\Codes>test 
+-----+-------+---------+----------+ 
| Var | Dec | Hex  | Address | 
+-----+-------+---------+----------+ 
| a | 12345 | 0x3039 | 0022FF4C | 
| b | 74565 | 0x12345 | 0022FF48 | 
+-----+-------+---------+----------+

这是我所看到的在GDB

(gdb) break 7 
Breakpoint 1 at 0x40135e: file test.c, line 7. 
(gdb) run 
Starting program: C:\Codes/test.exe 
[New Thread 4044.0xab0] 

Breakpoint 1, main() at test.c:7 
7    printf("+-----+-------+---------+----------+\n"); 
(gdb) disassemble 
Dump of assembler code for function main: 
    0x00401340 <+0>:  push ebp 
    0x00401341 <+1>:  mov ebp,esp 
    0x00401343 <+3>:  and esp,0xfffffff0 
    0x00401346 <+6>:  sub esp,0x20 
    0x00401349 <+9>:  call 0x401990 <__main> 
    0x0040134e <+14>: mov DWORD PTR [esp+0x1c],0x3039 
    0x00401356 <+22>: mov DWORD PTR [esp+0x18],0x12345 
=> 0x0040135e <+30>: mov DWORD PTR [esp],0x403024 
    0x00401365 <+37>: call 0x401c00 <puts> 
    0x0040136a <+42>: mov DWORD PTR [esp],0x40304c 
    0x00401371 <+49>: call 0x401c00 <puts> 
    0x00401376 <+54>: mov DWORD PTR [esp],0x403024 
    0x0040137d <+61>: call 0x401c00 <puts> 
    0x00401382 <+66>: mov edx,DWORD PTR [esp+0x1c] 
    0x00401386 <+70>: mov eax,DWORD PTR [esp+0x1c] 
    0x0040138a <+74>: lea ecx,[esp+0x1c] 
    0x0040138e <+78>: mov DWORD PTR [esp+0xc],ecx 
    0x00401392 <+82>: mov DWORD PTR [esp+0x8],edx 
    0x00401396 <+86>: mov DWORD PTR [esp+0x4],eax 
    0x0040139a <+90>: mov DWORD PTR [esp],0x403071 
    0x004013a1 <+97>: call 0x401c08 <printf> 
    0x004013a6 <+102>: mov edx,DWORD PTR [esp+0x18] 
    0x004013aa <+106>: mov eax,DWORD PTR [esp+0x18] 
    0x004013ae <+110>: lea ecx,[esp+0x18] 
    0x004013b2 <+114>: mov DWORD PTR [esp+0xc],ecx 
    0x004013b6 <+118>: mov DWORD PTR [esp+0x8],edx 
    0x004013ba <+122>: mov DWORD PTR [esp+0x4],eax 
    0x004013be <+126>: mov DWORD PTR [esp],0x40308c 
    0x004013c5 <+133>: call 0x401c08 <printf> 
    0x004013ca <+138>: mov DWORD PTR [esp],0x403024 
    0x004013d1 <+145>: call 0x401c00 <puts> 
    0x004013d6 <+150>: mov eax,0x0 
    0x004013db <+155>: leave 
    0x004013dc <+156>: ret 
End of assembler dump. 
(gdb)

变量地址a & b应该是在0x22ff4c & 0x22ff48分别

(gdb) print &a 
$1 = (int *) 0x22ff4c 

(gdb) print &b 
$2 = (int *) 0x22ff48

不过，如果你看看下面的GDB拆卸输出，地址是不是0x22ff4c & 0x22ff48，但0x0040134e & 0x00401356

0x0040134e <+14>: mov DWORD PTR [esp+0x1c],0x3039 
    0x00401356 <+22>: mov DWORD PTR [esp+0x18],0x12345

我也对这个调试x32dbg，但也获得相同的地址。

我很困惑。 0x0040134e & 0x00401356如果它们不是变量的存储地址a & b？

来源

2017-07-02 Charlotte Russell

0x0040134e <+14>: mov DWORD PTR [esp+0x1c],0x3039 
0x00401356 <+22>: mov DWORD PTR [esp+0x18],0x12345

没有，0x0040134e和0x00401356不变量a和b地址。相反，它们是代码中的指令地址，即instruction pointer IP。 a和b被初始化在这些行：

0x0040134e <+14>: mov DWORD PTR [esp+0x1c],0x3039 
0x00401356 <+22>: mov DWORD PTR [esp+0x18],0x12345

这里a和b地址分别是esp+0x1c和esp+0x18其中esp是stack pointer。作为地址你得到0x22ff4c和0x22ff48从中你可以轻松地扣除当前esp是0x22ff4c - 0x1c。

请注意，这个答案忽略了底层的虚拟内存管理或操作系统，即其他相关的内存管理问题上最架构0x22ff4c和0x22ff48将虚拟内存地址，而不是你的RAM的真实物理地址。

来源

2017-07-02 03:40:41 taskinoor

大会：在C语言程序

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