Reverse Engineering for Beginners

(avery) #1

CHAPTER 51. C++ CHAPTER 51. C++


push DWORD PTR [esi+12]
push DWORD PTR [esi+8]
push OFFSET $SG40864 ; '2nd element: %d %d'
call edi ; printf
mov eax, DWORD PTR [esi+4] ; operator--: get ->prev pointer
push DWORD PTR [eax+12]
push DWORD PTR [eax+8]
push OFFSET $SG40866 ; '1st element: %d %d'
call edi ; printf
add esp, 64
push OFFSET $SG40867 ; 'removing last element...'
call edi ; printf
mov edx, DWORD PTR [ebx+4]
add esp, 4

; prev=next?
; it is the only element, "garbage one"?
; if yes, do not delete it!
cmp edx, ebx
je SHORT $LN349@main
mov ecx, DWORD PTR [edx+4]
mov eax, DWORD PTR [edx]
mov DWORD PTR [ecx], eax
mov ecx, DWORD PTR [edx]
mov eax, DWORD PTR [edx+4]
push edx
mov DWORD PTR [ecx+4], eax
call ??3@YAXPAX@Z ; operator delete
add esp, 4
mov DWORD PTR _l$[esp+32], 2
$LN349@main:
lea eax, DWORD PTR _l$[esp+28]
push eax
call ?dump_List_val@@YAXPAI@Z ; dump_List_val
mov eax, DWORD PTR [ebx]
add esp, 4
mov DWORD PTR [ebx], ebx
mov DWORD PTR [ebx+4], ebx
cmp eax, ebx
je SHORT $LN412@main
$LL414@main:
mov esi, DWORD PTR [eax]
push eax
call ??3@YAXPAX@Z ; operator delete
add esp, 4
mov eax, esi
cmp esi, ebx
jne SHORT $LL414@main
$LN412@main:
push ebx
call ??3@YAXPAX@Z ; operator delete
add esp, 4
xor eax, eax
pop edi
pop esi
pop ebx
add esp, 16
ret 0
_main ENDP


Unlike GCC, MSVC’s code allocates the dummy element at the start of the function with the help of the “Buynode” function,
it is also used to allocate the rest of the nodes ( GCC’s code allocates the first element in the local stack).


Listing 51.32: The whole output


  • empty list:
    _Myhead=0x003CC258, _Mysize=0
    ptr=0x003CC258 _Next=0x003CC258 _Prev=0x003CC258 x=6226002 y=4522072

  • 3-elements list:
    _Myhead=0x003CC258, _Mysize=3
    ptr=0x003CC258 _Next=0x003CC288 _Prev=0x003CC2A0 x=6226002 y=4522072

Free download pdf