cpp反汇编之控制结构
控制结构主要是关于 if/else switch/case
废话不多说。。献上代码及反汇编分析。。
#include
int main(int argc , char *argv[])
{
int nInt = 9;
// if(0 == nInt)
__asm
{
cmp DWORD PTR [EBP - 4h] , 0 ;
jle __exit;
}
// __asm
{
printf("%d\n" , nInt);
/* push DWORD PTR [EBP - 4h];
push offset string "%d\n";
call printf ;
add esp , 8h ; */
}
/* if(nInt > 9)
{
printf("%d>9\n" , nInt);
}
else if(9 == nInt)
{
printf("nInt = 9\n");
}
else if(8 == nInt)
{
printf("nInt = 8\n");
}
*/
switch(nInt)
{
case 8 :
nInt += 1;
break;
case 9 :
nInt -= 9;
break;
default :
nInt -= 1;
break;
}
switch(nInt = scanf("%d" , &nInt))
{
case 1:
printf("nInt = 1\n");
break;
case 2:
printf("nInt = 2\n");
break;
case 3:
printf("nInt = 3\n");
break;
case 5:
printf("nInt = 5\n");
break;
case 6:
printf("nInt = 6\n");
break;
case 7:
printf("nInt = 7\n");
break;
case 100:
printf("nInt = 100\n");
break;
case 400:
printf("nInt = 400\n");
break;
case 500:
printf("nInt = 500\n");
break;
default:
break;
}
/*
0040D76D lea edx,[ebp-4]
0040D770 push edx
0040D771 push offset string "%d" (0042201c)
0040D776 call scanf (0040fa20)
0040D77B add esp,8
0040D77E mov dword ptr [ebp-4],eax
0040D781 mov eax,dword ptr [ebp-4]
0040D784 mov dword ptr [ebp-0Ch],eax
0040D787 mov ecx,dword ptr [ebp-0Ch]
0040D78A sub ecx,1 // case table index 0->max-1
0040D78D mov dword ptr [ebp-0Ch],ecx
0040D790 cmp dword ptr [ebp-0Ch],6 //maxIndex
0040D794 ja __exit (0040d7f8)
0040D796 mov edx,dword ptr [ebp-0Ch]
0040D799 jmp dword ptr [edx*4+40D80Bh] //case table
47: case 1:
48: printf("nInt = 1\n");
0040D7A0 push offset string "nInt = 1\n" (00422fe0)
0040D7A5 call printf (00401070)
0040D7AA add esp,4
49: break;
0040D7AD jmp __exit (0040d7f8) 执行一个判断就跳转到结尾处
50: case 2:
51: printf("nInt = 2\n");
0040D7AF push offset string "nInt = 2\n" (00422fd4)
0040D7B4 call printf (00401070)
0040D7B9 add esp,4
52: break;
0040D7BC jmp __exit (0040d7f8)
53: case 3:
54: printf("nInt = 3\n");
0040D7BE push offset string "nInt = 3\n" (00422fc8)
0040D7C3 call printf (00401070)
0040D7C8 add esp,4
55: break;
0040D7CB jmp __exit (0040d7f8)
56: case 5:
57: printf("nInt = 5\n");
0040D7CD push offset string "nInt = 5\n" (00422fbc)
0040D7D2 call printf (00401070)
0040D7D7 add esp,4
58: break;
0040D7DA jmp __exit (0040d7f8)
59: case 6:
60: printf("nInt = 6\n");
0040D7DC push offset string "nInt = 6\n" (00422fb0)
0040D7E1 call printf (00401070)
0040D7E6 add esp,4
61: break;
0040D7E9 jmp __exit (0040d7f8)
62: case 7:
63: printf("nInt = 7\n");
0040D7EB push offset string "nInt = 7\n" (00422fa4)
0040D7F0 call printf (00401070)
0040D7F5 add esp,4
64: break;
65: default:
66: break;
67: }
68: __exit:
69: return 0;
0040D7F8 xor eax,eax
线性结构采用数组处理,用索引来引用。 0040FAED lea edx,[ebp-4]
0040FAF0 push edx
0040FAF1 push offset string "%d" (0042201c)
0040FAF6 call scanf (0040fa20)
0040FAFB add esp,8
0040FAFE mov dword ptr [ebp-4],eax
0040FB01 mov eax,dword ptr [ebp-4]
0040FB04 mov dword ptr [ebp-0Ch],eax
0040FB07 cmp dword ptr [ebp-0Ch],64h
0040FB0B jg main+0B4h (0040fb34)
0040FB0D cmp dword ptr [ebp-0Ch],64h #100
0040FB11 je $L554+0Fh (0040fba5)
0040FB17 mov ecx,dword ptr [ebp-0Ch]
0040FB1A sub ecx,1 #index
0040FB1D mov dword ptr [ebp-0Ch],ecx
0040FB20 cmp dword ptr [ebp-0Ch],6 #maxIndex
0040FB24 ja __exit (0040fbd0)
0040FB2A mov edx,dword ptr [ebp-0Ch]
0040FB2D jmp dword ptr [edx*4+40FBE3h]
0040FB34 cmp dword ptr [ebp-0Ch],190h #400
0040FB3B je $L554+1Eh (0040fbb4)
0040FB3D cmp dword ptr [ebp-0Ch],1F4h #500
0040FB44 je $L554+2Dh (0040fbc3)
0040FB46 jmp __exit (0040fbd0)
*/
switch(nInt)
{
case 2:
printf("nInt = 2\n");
break;
case 3:
printf("nInt = 3\n");
break;
case 8:
printf("nInt = 8\n");
break;
case 10:
printf("nInt = 10\n");
break;
case 35:
printf("nInt = 35\n");
break;
case 37:
printf("nInt = 37\n");
break;
case 666:
printf("nInt = 666\n");
break;
}
/*非线性,有另类的就采用二叉树处理。。 /*
0040FBD0 mov eax,dword ptr [ebp-4] nInt -> eax
0040FBD3 mov dword ptr [ebp-10h],eax
0040FBD6 cmp dword ptr [ebp-10h],0Ah > 10
0040FBDA jg $L554+60h (0040fbf6)
0040FBDC cmp dword ptr [ebp-10h],0Ah = 10
0040FBE0 je $L554+0A4h (0040fc3a)
0040FBE2 cmp dword ptr [ebp-10h],2
0040FBE6 je $L554+77h (0040fc0d) = 2
0040FBE8 cmp dword ptr [ebp-10h],3 = 3
0040FBEC je $L554+86h (0040fc1c)
0040FBEE cmp dword ptr [ebp-10h],8
0040FBF2 je $L554+95h (0040fc2b) =8
0040FBF4 jmp __exit (0040fc74) 二叉树右枝
0040FBF6 cmp dword ptr [ebp-10h],23h = 35
0040FBFA je $L554+0B3h (0040fc49)
0040FBFC cmp dword ptr [ebp-10h],25h = 37
0040FC00 je $L554+0C2h (0040fc58)
0040FC02 cmp dword ptr [ebp-10h],29Ah = 666
0040FC09 je $L554+0D1h (0040fc67)
0040FC0B jmp __exit (0040fc74) 左枝结束
*/
__exit:
return 0;
}