Quick introduction to reverse engineering for beginners

push ecx
mov DWORD PTR _this$[ebp], ecx
mov eax, DWORD PTR _this$[ebp]
mov ecx, DWORD PTR _a$[ebp]
mov DWORD PTR [eax], ecx
mov edx, DWORD PTR _this$[ebp]
mov eax, DWORD PTR _b$[ebp]
mov DWORD PTR [edx+4], eax
mov eax, DWORD PTR _this$[ebp]
mov esp, ebp
pop ebp
ret 8
??0c@@QAE@HH@Z ENDP ; c::c
Constructors are just functions, they use pointer to structure in ECX, moving the pointer into own local
variable, however, it’s not necessary.
Now dump() method:
_this$ = -4 ; size = 4
?dump@c@@QAEXXZ PROC ; c::dump, COMDAT
; _this$ = ecx
push ebp
mov ebp, esp
push ecx
mov DWORD PTR _this$[ebp], ecx
mov eax, DWORD PTR _this$[ebp]
mov ecx, DWORD PTR [eax+4]
push ecx
mov edx, DWORD PTR _this$[ebp]
mov eax, DWORD PTR [edx]
push eax
push OFFSET ??_C@_07NJBDCIEC@?$CFd?$DL?5?$CFd?6?$AA@
call _printf
add esp, 12 ; 0000000cH
mov esp, ebp
pop ebp
ret 0
?dump@c@@QAEXXZ ENDP ; c::dump
Simple enough: dump() taking pointer to the structure containing two int’s in ECX, takes two values from
it and passing it into printf().
The code is much shorter if compiled with optimization (/Ox):
??0c@@QAE@XZ PROC ; c::c, COMDAT
; _this$ = ecx
mov eax, ecx
mov DWORD PTR [eax], 667 ; 0000029bH
mov DWORD PTR [eax+4], 999 ; 000003e7H
ret 0
??0c@@QAE@XZ ENDP ; c::c
_a$ = 8 ; size = 4
_b$ = 12 ; size = 4
??0c@@QAE@HH@Z PROC ; c::c, COMDAT
; _this$ = ecx
mov edx, DWORD PTR _b$[esp-4]
81