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Thread: MVC App crashes in release mode

  1. #1
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    Default MVC App crashes in release mode

    Hi,
    I have an issue in my application, I am working with MVC. I have customised view, model & proxy model.
    When i build this app in debug mode it working fine & cool, But when i build this app in release mode The app is crashing.
    I tried debugging it & found its crashing when it calls proxyModel::columnCount()


    When I debug I see call stack Info as below (Starting from main & crashing at columnCount())

    proxyModel::columnCount(); //App is crashing here
    headeview->setModel(model);
    view->setModel(model);
    .......
    ........
    main()
    my model from qabstractitemmodel:

    Qt Code:
    1. int model::columnCount(const QModelIndex &parent) const
    2. {
    3. return 1;
    4. }
    To copy to clipboard, switch view to plain text mode 

    I have nothing Implemented in proxy except filterAcceptRows()
    Sorry but not able to provide much code. What might gone wrong in my application ??



    And 1 more Qs: Is there simple or standard way to debug MVC, I see debugging MVC is very difficult.
    Thanks :-)

  2. #2
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    Default Re: MVC App crashes in release mode

    In debug mode, the debugger will initialize variables during startup. Pointers are initialized to a known (but non-valid) value, like "0xeaeaeaea". In release mode, this doesn't happen. Variables and especially pointers have random values. So almost certainly the instance of your proxy model that is calling into "columnCount()" is a bad or uninitialized pointer.

    Use the debugger to make sure all of your pointer instances are correct. Make sure you aren't creating your proxy model on the stack and then passing the address of the stack instance in as an argument that is intended to be a heap pointer instead.

  3. #3
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    Default Re: MVC App crashes in release mode

    Quote Originally Posted by prasad_N View Post
    And 1 more Qs: Is there simple or standard way to debug MVC, I see debugging MVC is very difficult.
    The model::columnCount you show is certainly *not* causing your crash. More likely, the pointer to your model has become invalid or not initialized correctly, etc. Please show how you create the model, proxy model, initialize the model in your view, etc.

    Once you get past your current issue, the best method I've found for debugging custom models is:

    http://doc.qt.io/qt-5/modelview.html...with-modeltest
    I write the best type of code possible, code that I want to write, not code that someone tells me to write!

  4. #4
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    Default Re: MVC App crashes in release mode

    Thanks guys.. Did work, problem with uninitialized pointer in constructor & one more silly mistake

    Qt Code:
    1. 1. model::model() : m_parent(nullPtr)
    2. 2. int model::childCount()
    3. {
    4. m_childs.count; //did put return here but, compiler did not warn
    5. }
    To copy to clipboard, switch view to plain text mode 
    Thanks :-)

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