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> Windows > Simple addition program |
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typedef 27 Jan 2014, 16:55
1st. don't use scanf.
2nd. Use cinvoke or if you have to use call with a C function, restore the stack. 3rd. Use ConsoleAlloc, GetConsoleHandle, ReadFile/WriteFile, 4th. Use atoi (or make your onwn) |
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27 Jan 2014, 16:55 |
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Isamaul 27 Jan 2014, 17:20
I modified source to get loop.
No errors now Code: format PE console entry start include 'win32a.inc' proc Addition stdcall uses ecx edx, a:DWORD mov ecx, [a] mov edx, [sum] add ecx, edx mov [sum],ecx ret endp section '.data' data readable writeable RequestInput db "Write number: ", 0 Result db "Sum: %d", 0 input dd "%s", 0 sum dd "%d", 0 number dd ? section '.text' code readable executable start: mov [sum],0 ;;set sum to 0 at start inputCall: push RequestInput call [printf] push number ;; push variable push input ;; get input call [scanf] ;; do scanf ;; atoi cinvoke atoi, number mov [number],eax checkIfZero: mov ecx, [number] ;; get inserted number cmp ecx,0 ;; check if 0 je results ;go to results if 0 push [number] ;; not 0, we can sum, push number into stack call Addition ;; get addition jmp inputCall ;; loop results: push [sum] push Result call [printf] call [getchar] push 0 call [ExitProcess] section '.idata' import data readable library msvcrt, 'MSVCRT.DLL', \ kernel, 'KERNEL32.DLL' import msvcrt, \ printf, 'printf', \ scanf, 'scanf', \ getchar, 'getchar',\ atoi, 'atoi' import kernel, \ ExitProcess, 'ExitProcess' I am new into this, so i do not know what typedef, are you talking about. 1. What should i use instead of scanf, and where can i learn more about that? 2. Why should I? 3. For what should i use that? |
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27 Jan 2014, 17:20 |
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typedef 27 Jan 2014, 19:44
Sorry for misleading you with the ConsoleAlloc API. When you specify the EXE type in the PE header as console, the system will spawn the console for you. I thought this was marked as GUI.
Another thing, don't use atoi as it doesn't report errors. Instead strtol will return if there was an error or not. Anyway, Quote:
1. Instead of using scanf, read a fixed amount of bytes from the console. Say 12 (12 bytes = 12 possible digits (LONG)). Then, with that fixed buffer, use something like strtol to do the conversion. 2. I suggest reading calling conventions and the stack : http://en.wikipedia.org/wiki/X86_calling_conventions 3. Using scanf will always expect the input to be what the format specifier indicates. So if you use %d (signed int), and type a string (ie qwerty instead of 1234) in the console, you will get garbage and your app will likely crash. Code: format PE console entry start include 'win32a.inc' FIRST_PARAMETER EQU DWORD[EBP+0x08] SECOND_PARAMETER EQU DWORD[EBP+0x0C] section '.data' data readable writeable RequestInput db "Enter number [0 to quit] > ", 0 fmt db "Sum : %d", 10,13,0 buffer db 16 dup(0) bytes_read dd 0 section '.text' code readable executable ; ; __stdcall signed int Addition (signed int a, signed int b) ; Addition: push ebp mov ebp, esp ; setting up our stack frame. mov ecx, FIRST_PARAMETER ; get a mov eax, SECOND_PARAMETER ; get b add eax, ecx ; adds ECX to EAX and result is stored in EAX pop ebp ; restore old stack frame pointer ret 4 * 2 ; POP 2 DWORD values from stack start: push -10 ; Get standard input handle call [GetStdHandle] mov ebx, eax xor esi, esi .input: push RequestInput call [printf] add esp, 4 ; restore the stack ; read 12 bytes from console push NULL push bytes_read push 12 ; bytes to read push buffer push ebx ; console handle call [ReadFile] ; now attempt to convert the buffer to number push 10 ; Our RADIX push NULL ; NULL push buffer call [strtol] add esp, 4 ; 0 could be an error or completion signal test eax, eax je .show_results .add_number: ; add number push esi push eax call Addition mov esi, eax ; sum += Addition (input, sum); jmp .input .show_results: push esi push fmt call [printf] add esp, 4*2 ; pause the console call [getchar] push 0x0 call [ExitProcess] section '.idata' import data readable library msvcrt, 'MSVCRT.DLL', \ kernel, 'KERNEL32.DLL' import msvcrt, \ printf, 'printf', \ getchar, 'getchar', \ strtol,'strtol' import kernel, \ ExitProcess, 'ExitProcess',\ GetStdHandle,'GetStdHandle',\ ReadFile,'ReadFile' |
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27 Jan 2014, 19:44 |
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