Access violation on adding QWidget to QTabWidget in Qt5.4



  • 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    Problem is that in the documentation it is indicated that this attribute is obsolete and is no longer supported.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++@


  • Lifetime Qt Champion

    Hi and welcome to devnet,

    What is the tabs variable ?

    Did you initialiaze it ?



  • 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.



  • 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)?



  • 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!


  • Lifetime Qt Champion

    [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 ?



  • [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.


  • Lifetime Qt Champion

    [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 ?



  • 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");
    

    }@


  • Lifetime Qt Champion

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


Log in to reply
 

Looks like your connection to Qt Forum was lost, please wait while we try to reconnect.