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  1. #1
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    Post access violation reading location 0x00000000

    hello..
    i am running a thread.but when i try to print anything edit box using the line
    aa.Format("%d",i);
    ts->_this->GetDlgItem(IDC_EDIT3)->SetWindowText(aa);//run time error occurs here.

    my code is compilation error free.but i get an error when i run it as
    access violation reading location 0x00000000

    plz help.

  2. #2
    2kaud's Avatar
    2kaud is offline Super Moderator Power Poster
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    Re: access violation reading location 0x00000000

    You are trying to dereference a pointer that has a value of 0 (null). In the debugger put a breakpoint on that line and examine the contents of the variables. You'll then know which is the one that is 0.
    All advice is offered in good faith only. All my code is tested (unless stated explicitly otherwise) with the latest version of Microsoft Visual Studio (using the supported features of the latest standard) and is offered as examples only - not as production quality. I cannot offer advice regarding any other c/c++ compiler/IDE or incompatibilities with VS. You are ultimately responsible for the effects of your programs and the integrity of the machines they run on. Anything I post, code snippets, advice, etc is licensed as Public Domain https://creativecommons.org/publicdomain/zero/1.0/ and can be used without reference or acknowledgement. Also note that I only provide advice and guidance via the forums - and not via private messages!

    C++23 Compiler: Microsoft VS2022 (17.6.5)

  3. #3
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    Re: access violation reading location 0x00000000

    thanks for the reply..but even though i put a breakpoint on that particular line in debug mode.i am not able check the values of the variables..most of my variables are global variables..plz help.

  4. #4
    2kaud's Avatar
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    Re: access violation reading location 0x00000000

    What compiler/debugger are you using?
    All advice is offered in good faith only. All my code is tested (unless stated explicitly otherwise) with the latest version of Microsoft Visual Studio (using the supported features of the latest standard) and is offered as examples only - not as production quality. I cannot offer advice regarding any other c/c++ compiler/IDE or incompatibilities with VS. You are ultimately responsible for the effects of your programs and the integrity of the machines they run on. Anything I post, code snippets, advice, etc is licensed as Public Domain https://creativecommons.org/publicdomain/zero/1.0/ and can be used without reference or acknowledgement. Also note that I only provide advice and guidance via the forums - and not via private messages!

    C++23 Compiler: Microsoft VS2022 (17.6.5)

  5. #5
    VictorN's Avatar
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    Re: access violation reading location 0x00000000

    Quote Originally Posted by Ramdhyani View Post
    hello..
    i am running a thread.but when i try to print anything edit box using the line
    aa.Format("%d",i);
    ts->_this->GetDlgItem(IDC_EDIT3)->SetWindowText(aa);//run time error occurs here.

    my code is compilation error free.but i get an error when i run it as
    access violation reading location 0x00000000

    plz help.
    1. What is ts?
    2. What is _this?
    3. Are you trying to access the IDC_EDIT3 control from within a worker thread? It appears to be a wrong design. Please, check out this great Joe Newcomer's essay: Using Worker Threads
    Victor Nijegorodov

  6. #6
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    Re: access violation reading location 0x00000000

    vc++ 2010

  7. #7
    2kaud's Avatar
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    Re: access violation reading location 0x00000000

    vc++ 2010
    Then when the break point triggers you should be able to view the contents of the variables - and see which pointer is 0.

    See
    https://blogs.msdn.microsoft.com/dev...visual-studio/
    https://msdn.microsoft.com/en-us/lib...v=vs.100).aspx
    All advice is offered in good faith only. All my code is tested (unless stated explicitly otherwise) with the latest version of Microsoft Visual Studio (using the supported features of the latest standard) and is offered as examples only - not as production quality. I cannot offer advice regarding any other c/c++ compiler/IDE or incompatibilities with VS. You are ultimately responsible for the effects of your programs and the integrity of the machines they run on. Anything I post, code snippets, advice, etc is licensed as Public Domain https://creativecommons.org/publicdomain/zero/1.0/ and can be used without reference or acknowledgement. Also note that I only provide advice and guidance via the forums - and not via private messages!

    C++23 Compiler: Microsoft VS2022 (17.6.5)

  8. #8
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    Re: access violation reading location 0x00000000

    The UI and all its controls should only be modified from the main thread, not from worker threads.
    Marc Gregoire - NuonSoft (http://www.nuonsoft.com)
    My Blog
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    Author of Professional C++, 4th Edition by Wiley/Wrox (includes C++17 features)
    ISBN: 978-1-119-42130-6
    [ http://www.facebook.com/professionalcpp ]

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