Weird MessageBox

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roticv

Joined: 19 Jun 2003
Posts: 374
Location: Singapore

roticv 04 Oct 2003, 14:31

At some part of my code there is a call to messagebox. However it always crashes with

---------------------------
myapplication.exe - Application Error
---------------------------
The instruction at "0x77fcb032" referenced memory at "0x007e0049". The memory could not be "written".

Click on OK to terminate the program
---------------------------
OK
---------------------------

The only way I found out that removes this error is by placing a call to the MessageBox at entrypoint. Does anyone knows what went wrong?

04 Oct 2003, 14:31

roticv

Joined: 19 Jun 2003
Posts: 374
Location: Singapore

roticv 04 Oct 2003, 14:39

Just to add, in ollydbg, the problem does not persist. grr.

04 Oct 2003, 14:39

Yawgmoth

Joined: 20 Aug 2003
Posts: 37

Yawgmoth 04 Oct 2003, 18:18

Post your code.

04 Oct 2003, 18:18

roticv

Joined: 19 Jun 2003
Posts: 374
Location: Singapore

roticv 05 Oct 2003, 04:24

Code:

        or      ecx, -1
        mov     edi, Invalid
        push    0C3F97523h        ;decrypt string in stack
        push    0F348041h
        mov     eax, esp
        call    eax
        pop     eax
        pop     eax             ;empty stack
        invoke  MessageBox,0,Invalid,0,0

05 Oct 2003, 04:24

MazeGen

Joined: 06 Oct 2003
Posts: 977
Location: Czechoslovakia

MazeGen 06 Oct 2003, 08:22

Quote:

The instruction at "0x77fcb032" referenced memory at "0x007e0049". The memory could not be "written".

Looks really weird. What about that:

Code:

0x77fcb032 disassembly (reverse order):
32 B0 FC 77 .. ..    XOR DH,[EAX+....77FC]   ; referenced to 007e0049?

Is your de/crypting routine all right?

Else it may get out of synchronization:

Code:

32 B0              ???
FC                       CLD
77 xx            JA $+xx

Code:

32                      ???
B0 FC            MOV AL,FC
77 xx              JA $+xx

_________________
x86asm.net

06 Oct 2003, 08:22

roticv

Joined: 19 Jun 2003
Posts: 374
Location: Singapore

roticv 06 Oct 2003, 14:02

I do not know what is wrong. The weird thing is that no such error exist in ollydbg, making the debugging pain in the a**. Yes, the decrypting routine is definitely correct. At the beginning, the following snipplet works well for me, but after coding another 300 lines I got that weird error. The only way I could get rid of it is to put a messagebox somewhere before it.

06 Oct 2003, 14:02

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