Why the return value of Api-Function doesnt work?

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ronnie

Joined: 22 Nov 2006
Posts: 5

ronnie 22 Nov 2006, 15:38

HI this is my code:

Code:

format MS COFF


extrn '__imp__MessageBoxA@16' as MessageBox:dword
extrn '__imp__ExitProcess@4' as ExitProcess:dword


section '.text' code readable executable
public _4compiler
_4compiler:
push 0
push _S1
push _S2
push 0
call [MessageBox]

MOV   dword [v_test],eax   <--------- here is the Error !

push 0
push _S1
push [v_test]
push 0
call [MessageBox]

push 0
call [ExitProcess]
ret

section '.data' Data readable writeable
_S1       db     "Test",0
_S2       db     "Testbox !",0

Why the compiler says to me that there is an undefined symbol ???

22 Nov 2006, 15:38

LocoDelAssembly
Your code has a bug

Joined: 06 May 2005
Posts: 4624
Location: Argentina

LocoDelAssembly 22 Nov 2006, 15:43

Because you didn't define it

add a "v_test dd ?" at .data section

[edit] BTW, MessageBox doesn't return a pointer to a string so I think that your second call to MessageBox will not work (unless I'm missing something)[/edit]

22 Nov 2006, 15:43

ronnie

Joined: 22 Nov 2006
Posts: 5

ronnie 22 Nov 2006, 16:47

yes , thats the point now : which api-function can convert numbers to strings?

22 Nov 2006, 16:47

vid
Verbosity in development

Joined: 05 Sep 2003
Posts: 7105
Location: Slovakia

vid 22 Nov 2006, 17:46

wsprintf

22 Nov 2006, 17:46

LocoDelAssembly
Your code has a bug

Joined: 06 May 2005
Posts: 4624
Location: Argentina

LocoDelAssembly 22 Nov 2006, 17:47

Code:

push [v_test]
push fmt
push buffer
call [wsprintf]
add esp, 12 ; Because wsprintf uses cdecl calling convention
.
.
.
fmt db "%d"
buffer rb 12

(The last part should go in data section)

Not tested but the point is you can use wsprintf Very Happy

(or doing you own IntToStr)

22 Nov 2006, 17:47

ronnie

Joined: 22 Nov 2006
Posts: 5

ronnie 22 Nov 2006, 22:07

extrn '__imp__ExitProcess@4' as ExitProcess:dword

for ExitProcess and for wsprintf ??

22 Nov 2006, 22:07

LocoDelAssembly
Your code has a bug

Joined: 06 May 2005
Posts: 4624
Location: Argentina

LocoDelAssembly 23 Nov 2006, 02:21

I never use COFF format so I don't know, try with just '__imp__wsprintf' or '__imp__wsprintf@' or '__imp__wsprintf@8', I think that one of these should work

23 Nov 2006, 02:21

vid
Verbosity in development

Joined: 05 Sep 2003
Posts: 7105
Location: Slovakia

vid 23 Nov 2006, 03:30

just look into appropriate .lib file. It should be kernel32.lib or user32.lib, my quess

23 Nov 2006, 03:30

madmatt

Joined: 07 Oct 2003
Posts: 1045
Location: Michigan, USA

madmatt 23 Nov 2006, 06:32

ronnie: you can import the crtdll.dll just like the kernel32.dll, which contain the various printf functions that you need to print integers and floats

23 Nov 2006, 06:32

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