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Details

Type: Bug
Resolution: Fixed
Priority: P1: Critical
Fix Version/s: 6.7.3, 6.8.0 Beta2, 6.9.0 FF
Affects Version/s: 6.7.0, 6.7.1, 6.8
Component/s: Widgets: Widgets and Dialogs
Labels:
None

Platform/s:

All
Commits:
006cbf658 (dev), f0f9cc602 (6.8), 0673dde3f (6.7)

Description

Steps to reproduce:

Run the program below:

#include <iostream>
#include <QApplication>
#include <QTabWidget>
#include <QWindow>
#include <QQuickWidget>

class MyWindow : public QWindow
{
public:
    MyWindow() {
        std::cerr << "MyWindow::MyWindow(). this=" << std::hex << this << std::endl;
    }

    ~MyWindow() {
        std::cerr << "MyWindow::~MyWindow(). this=" << std::hex << this << std::endl;
    }
};

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);

    QTabWidget tab_widget;
    tab_widget.show();

    const auto w1 = QWidget::createWindowContainer(new MyWindow(), &tab_widget);
    tab_widget.addTab(w1, QStringLiteral("MyWindow tab"));

    // Trigger condition. During the execution of this statement MyWindow will unexpectedly
    // be deleted.
    tab_widget.addTab(new QQuickWidget(), QStringLiteral("QQuickWidget tab"));

    return QCoreApplication::exec();
}

Expected result:

The program runs

Actual result:

The program crashes.

The program crashes because the MyWindow instanced added via QWidget::createWindowContainer() is unexpectedly deleted when the second tab, "QQuickWidget tab", is added. This happens because of the call to newtlw->destroy() in the following code from https://code.qt.io/cgit/qt/qtbase.git/commit/?id=68a4c5da9a080101cccd8a3b2edb1c908da0ca8e

void QWidget::setParent(QWidget *parent, Qt::WindowFlags f)
{
    ...

    if (oldtlw != newtlw) {
        ...
        if (q_evaluateRhiConfig(this, nullptr, &surfaceType)) {
        ...

            if (recreate) {
                const auto windowStateBeforeDestroy = newtlw->windowState();
                const auto visibilityBeforeDestroy = newtlw->isVisible();
                newtlw->destroy(); // <--- Causes the window created with QWidget::createWindowContainer() to be deleted
                newtlw->create();
                Q_ASSERT(newtlw->windowHandle());
                newtlw->windowHandle()->setWindowStates(windowStateBeforeDestroy);
                QWidgetPrivate::get(newtlw)->setVisible(visibilityBeforeDestroy);
            }

The stacktrace for the destruction of the MyWindow instance:

MyWindow::~MyWindow(MyWindow * const this) (/home/ts/src/easyviz/qtutility/examples/example2.cc:15)
MyWindow::~MyWindow(MyWindow * const this) (/home/ts/src/easyviz/qtutility/examples/example2.cc:16)
libQt6Core.so.6!QObjectPrivate::deleteChildren(QObjectPrivate * const this) (/home/ts/src/qt5-2/qtbase/src/corelib/kernel/qobject.cpp:2216)
libQt6Core.so.6!QObject::~QObject(QObject * const this) (/home/ts/src/qt5-2/qtbase/src/corelib/kernel/qobject.cpp:1168)
libQt6Gui.so.6!QWindow::~QWindow(QWindow * const this) (/home/ts/src/qt5-2/qtbase/src/gui/kernel/qwindow.cpp:203)
libQt6Widgets.so.6!QWidgetWindow::~QWidgetWindow(QWidgetWindow * const this) (/home/ts/src/qt5-2/qtbase/src/widgets/kernel/qwidgetwindow.cpp:156)
libQt6Widgets.so.6!QWidgetWindow::~QWidgetWindow(QWidgetWindow * const this) (/home/ts/src/qt5-2/qtbase/src/widgets/kernel/qwidgetwindow.cpp:156)
libQt6Widgets.so.6!QWidgetPrivate::deleteTLSysExtra(QWidgetPrivate * const this) (/home/ts/src/qt5-2/qtbase/src/widgets/kernel/qwidget.cpp:1705)
libQt6Widgets.so.6!QWidget::destroy(QWidget * const this, bool destroyWindow, bool destroySubWindows) (/home/ts/src/qt5-2/qtbase/src/widgets/kernel/qwidget.cpp:12585)
libQt6Widgets.so.6!QWidget::setParent(QWidget * const this, QWidget * parent, Qt::WindowFlags f) (/home/ts/src/qt5-2/qtbase/src/widgets/kernel/qwidget.cpp:10929)
libQt6Widgets.so.6!QWidget::setParent(QWidget * const this, QWidget * parent) (/home/ts/src/qt5-2/qtbase/src/widgets/kernel/qwidget.cpp:10710)
libQt6Widgets.so.6!QLayout::addChildWidget(QLayout * const this, QWidget * w) (/home/ts/src/qt5-2/qtbase/src/widgets/kernel/qlayout.cpp:863)
libQt6Widgets.so.6!QStackedLayout::insertWidget(QStackedLayout * const this, int index, QWidget * widget) (/home/ts/src/qt5-2/qtbase/src/widgets/kernel/qstackedlayout.cpp:191)
libQt6Widgets.so.6!QStackedWidget::insertWidget(QStackedWidget * const this, int index, QWidget * widget) (/home/ts/src/qt5-2/qtbase/src/widgets/widgets/qstackedwidget.cpp:146)
libQt6Widgets.so.6!QTabWidget::insertTab(QTabWidget * const this, int index, QWidget * w, const QIcon & icon, const QString & label) (/home/ts/src/qt5-2/qtbase/src/widgets/widgets/qtabwidget.cpp:440)
libQt6Widgets.so.6!QTabWidget::insertTab(QTabWidget * const this, int index, QWidget * w, const QString & label) (/home/ts/src/qt5-2/qtbase/src/widgets/widgets/qtabwidget.cpp:419)
libQt6Widgets.so.6!QTabWidget::addTab(QTabWidget * const this, QWidget * child, const QString & label) (/home/ts/src/qt5-2/qtbase/src/widgets/widgets/qtabwidget.cpp:363)
main(int argc, char ** argv) (/home/ts/src/easyviz/qtutility/examples/example2.cc:31)

The problem reproduces on both the platforms I have access to, Linux and Windows, with exactly the same stacktrace.