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  4. Access violation on adding QWidget to QTabWidget in Qt5.4
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Access violation on adding QWidget to QTabWidget in Qt5.4

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  • S Offline
    S Offline
    SergejK
    wrote on last edited by
    #1

    I recently upgraded to Qt5.4 and after adding to a QTabWidget this problem occurred:

    First-chance exception at 0x000007FEDEE6A30A (Qt5Guid.dll) in MyApp.exe: 0xC0000005: Access violation reading location 0x0000000000000008

    On continuing, application runs fine.
    Fortunately I also found a quick fix relatively fast by trying to set some application attribute that just sounded right:

    Qt::AA_ImmediateWidgetCreation

    Problem is that in the documentation it is indicated that this attribute is obsolete and is no longer supported.
    I wonder if there is anything I am missing.

    @
    void MainWindow::addEditorTab()
    {
    // CustomTabWidget inherits QWidget
    CustomTabWidget* tab = new CustomTabWidget();
    // tabs is a QTabWidget*
    tabs->addTab( tab, tab->icon(), tab->title() ); // <-- access violation
    }

    int main( int argc, char *argv[] )
    {
    ...
    QApplication app(argc, argv);
    app.setAttribute( Qt::AA_DontCreateNativeWidgetSiblings ); //< fixes another bug
    app.setAttribute( Qt::AA_ImmediateWidgetCreation); // < This fixes access violation
    ...
    }
    @

    In the callstack there are calls to qwindowsd.dll. This bug does not occur on Mac Osx.
    Here the last part of the callstack:

    @Qt5Guid.dll!000007fedee6a30a()
    Qt5Guid.dll!000007fedee5fff3()
    Qt5Guid.dll!000007fedee6a22a()
    Qt5Guid.dll!000007fedef06853()
    Qt5Guid.dll!000007fedee92ba3()
    Qt5Guid.dll!000007fedee9368e()
    qwindowsd.dll!QWindowsWindow::handleGeometryChange() Line 1397 C++
    qwindowsd.dll!QWindowsWindow::handleMoved() Line 1355 C++
    qwindowsd.dll!QWindowsContext::windowsProc(HWND__ * hwnd, unsigned int message, QtWindows::WindowsEventType et, unsigned __int64 wParam, __int64 lParam, int64 * result) Line 986 C++
    qwindowsd.dll!qWindowsWndProc(HWND
    * hwnd, unsigned int message, unsigned __int64 wParam, int64 lParam) Line 1236 C++
    [External Code]
    qwindowsd.dll!qWindowsWndProc(HWND
    * hwnd, unsigned int message, unsigned __int64 wParam, int64 lParam) Line 1245 C++
    [External Code]
    qwindowsd.dll!WindowCreationData::initialize(HWND
    * hwnd, bool frameChange, double opacityLevel) Line 669 C++
    qwindowsd.dll!QWindowsWindow::setWindowFlags_sys(QFlags<enum Qt::WindowType> wt, unsigned int flags) Line 1549 C++
    qwindowsd.dll!QWindowsWindow::setParent_sys(const QPlatformWindow * parent) Line 1259 C++@

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    • SGaistS Offline
      SGaistS Offline
      SGaist
      Lifetime Qt Champion
      wrote on last edited by
      #2

      Hi and welcome to devnet,

      What is the tabs variable ?

      Did you initialiaze it ?

      Interested in AI ? www.idiap.ch
      Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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      • S Offline
        S Offline
        SergejK
        wrote on last edited by
        #3

        Hi,
        thanks for the reply and welcome.
        As I stated in the comment above tabs is a QTabWidget*.
        It is a member of Ui_MainWindow, generated from the UI-File.
        MainWindow inherits QMainWindow and Ui::MainWindow.
        setupUi( this ) is called in the constructor of MainWindow, where tabs is initialized.
        addEditorTab() is called after the user double-clicks an item in a TreeWidget, long after MainWindow-initialization.

        Also note that this bug does not occur on Osx or Qt5.3.

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        • R Offline
          R Offline
          Rondog
          wrote on last edited by
          #4

          I haven't seen this problem on Qt 5.4.0 on Windows. My application uses QTabWidget with a number of custom widgets. I just double checked to be sure.

          The devil is in the details. In my case I am using a virtual machine (Xp x86) guest on OS X, compiler is MinGW, release build only. I compiled Qt from source.

          Maybe you are mixing DLL files? Have you tried this with just a basic QWidget* added to QTabWidget? Do you get the same error with the release build (not Qt5Guid,qwindowsd)?

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          • S Offline
            S Offline
            SergejK
            wrote on last edited by
            #5

            Hey,
            I found the cause!
            In the initialisation process inside the constructor of CustomTabWidget windowHandle()->winId() is called, which makes the QWidget native.
            Maybe there is a problem with adding widgets as tabs that are already native?
            Anyway I moved initialization to an init-function after tab is inserted, which fixes the problem for me.
            Thank you all for the help!

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            • SGaistS Offline
              SGaistS Offline
              SGaist
              Lifetime Qt Champion
              wrote on last edited by
              #6

              [quote author="SergejK" date="1423485248"]Hi,
              thanks for the reply and welcome.
              As I stated in the comment above tabs is a QTabWidget*.
              It is a member of Ui_MainWindow, generated from the UI-File.
              [/quote]

              Can you show me where ? After several re-reads I can't find it.

              Anyway, so it only happens on Windows since 5.4, do I get you right ?

              Interested in AI ? www.idiap.ch
              Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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              • S Offline
                S Offline
                SergejK
                wrote on last edited by
                #7

                [quote author="SGaist" date="1423520133"][quote author="SergejK" date="1423485248"]Hi,
                thanks for the reply and welcome.
                As I stated in the comment above tabs is a QTabWidget*.
                It is a member of Ui_MainWindow, generated from the UI-File.
                [/quote]

                Can you show me where ? After several re-reads I can't find it.
                [/quote]
                line 5 in the first code section, its a comment.
                [quote author="SGaist" date="1423520133"]
                Anyway, so it only happens on Windows since 5.4, do I get you right ?
                [/quote]
                Yes and it seems to be caused by making the widget native before inserting as tab.
                If you can reproduce it, maybe it is a bug in Qt.
                Otherwise I am ok with the quick fix by adding the tab first, then making it native.

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                • SGaistS Offline
                  SGaistS Offline
                  SGaist
                  Lifetime Qt Champion
                  wrote on last edited by
                  #8

                  [quote author="SergejK" date="1423560584"][quote author="SGaist" date="1423520133"][quote author="SergejK" date="1423485248"]Hi,
                  thanks for the reply and welcome.
                  As I stated in the comment above tabs is a QTabWidget*.
                  It is a member of Ui_MainWindow, generated from the UI-File.
                  [/quote]

                  Can you show me where ? After several re-reads I can't find it.
                  [/quote]
                  line 5 in the first code section, its a comment.
                  [/quote]

                  Ok, but neither it nor the code mention any UI file

                  Can you create a minimal compilable example that reproduces this behavior ?

                  Interested in AI ? www.idiap.ch
                  Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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                  • S Offline
                    S Offline
                    SergejK
                    wrote on last edited by
                    #9

                    Oh, sorry for the misunderstanding. I only meant the first part is mentioned in the comments.

                    Ok, I can reproduce the error with the following lines of code:
                    @
                    int main( int argc, char *argv[] )
                    {
                    QApplication app(argc, argv);

                    QMainWindow* mainWindow= new QMainWindow();
                    QWidget *centralwidget = new QWidget(mainWindow);
                    QHBoxLayout* horizontalLayout = new QHBoxLayout(centralwidget);
                    QTabWidget * tabs = new QTabWidget(centralwidget);
                    horizontalLayout->addWidget(tabs);
                    
                    QWidget* customTab = new QWidget();
                    customTab->windowHandle()->winId();
                    tabs->addTab(customTab, "name");
                    

                    }@

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                    • SGaistS Offline
                      SGaistS Offline
                      SGaist
                      Lifetime Qt Champion
                      wrote on last edited by
                      #10

                      Then you should check the "bug report system":http://bugreports.qt.io to see if it's something known

                      Interested in AI ? www.idiap.ch
                      Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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