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Thread: How to avoid OutputDebugString() message box?

  1. #1
    GuangZor
    Guest

    Angry How to avoid OutputDebugString() message box?

    When I run a game executable, which is compiled in Debug mode, everytime it calls OutputDebugStringA() I get a message box containing strange characters:



    The API is called everytime the game loads a resource/file, then you can imagine how annoying is to keep pressing ESC/or pressing OK button many times, everytime I need to run the game.

    My OllyDBG settings:
    "Option -> Events -> BP on Debug String" -> Unchecked

    olydbg.ini:
    Code:
    Stop on new DLL=0
    Stop on DLL unload=0
    Stop on new thread=0
    Stop on thread end=0
    Stop on debug string=0
    Any ideas?
    I promise that I have read the FAQ and tried to use the Search to answer my question.

  2. #2
    Hi GuangZor,
    Well the proper debug string is output in the status bar, but without seeing the code where it is then put into the MessageBox it is hard to determine what exactly is wrong. Possibly MessageBoxW is used, or simply a corrupted register or missing debug text.
    But if you just want to get rid of the messagebox, just nop the call to it, and the parameters.
    Or alternatively you could try writing Ret 4 at the entry to the OutputDebugStringA Api, maybe it won't show the messagebox if no debug string is sent?

    Have fun!
    BoB

  3. #3
    GuangZor
    Guest

    Post

    Hi BoB,

    I forced a RETN 4 at OutputDebugStringA, as you have suggested, and now I'm able to run without any message boxes! This API is calling RaiseException() all the times for this specified game.

    Thanks for your hint!
    I promise that I have read the FAQ and tried to use the Search to answer my question.

  4. #4
    Hi GuangZor,
    You're welcome, glad to hear it worked

    Have fun!
    BoB

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