我有以下用例(实际上没有意义，因为它是从现实生活中的工作示例中最小化的，但我认为它在技术上仍然是正确的):

class Dialog : public QDialog
{
public:
  Dialog(QWidget* parent)
    : QDialog(parent)
    {
      new Q3ListView(this); // this will crash
//    new QWidget(this);    // this won't crash
    }
};

根据添加到 Dialog 的内容，程序是否会在删除 Dialog 实例时崩溃(如代码片段中的注释所示)，但仅当主窗口的标志已被修改。下面是 MainWindow 类的代码，它使用了 Dialog:

class MainWindow : public QMainWindow
{
public:
  // the fact that the widget (dialog) below 
  // has no chance to show seems irrelevant. 
  // In the real scenario I have, the widget is shown on 
  // the screen and is closed by the user. 
  // I've just put the whole sequence of pieces of code 
  // that result from signal/slot calls, that in turn 
  // result from a point&click scenario in our application 
  // into the following function for brevity.
  void go()
    {        
      auto dialog = new Dialog(this);
      dialog->show();
      dialog->close();
      
      disableAlwaysOnTop();

      delete dialog; // or dialog->deleteLater();
    }

  void disableAlwaysOnTop()
    {
      setAttribute(Qt::WA_Resized, true);

      Qt::WindowFlags flags = windowFlags();
      setWindowFlags(flags ^ (Qt::CustomizeWindowHint | Qt::WindowStaysOnTopHint));

      setVisible(true);
    }
};

和main的实现:

int main(int argc, char** argv)
{
  QApplication app(argc, argv);
  MainWindow mainWindow;
  mainWindow.show();
  mainWindow.go();
  return app.exec();
}

所有行似乎都是重现崩溃的必要条件。

这是 Qt 中的错误，还是我做错了什么？

允许手动删除小部件的子项，并且它们应该自动从其父项中注销，如下面手册中的引述所示。在我的真实案例中，小部件被删除以从 GUI 中消失，并且它适用于其他小部件组合。如上面的评论所示，将 delete dialog; 更改为 dialog->deleteLater(); 没有帮助。

从 Qt 的后备存储中删除 Q3ListView 实例似乎有问题，这里是堆栈跟踪:

QtGuid4.dll!QWidgetBackingStore::staticContents(QWidget * parent, const QRect & withinClipRect) Line 499 C++

QtGuid4.dll!QWidgetBackingStore::sync() Line 1200 C++

QtGuid4.dll!QWidgetPrivate::syncBackingStore() Line 1896 C++

QtGuid4.dll!QWidget::event(QEvent * event) Line 8694 C++

QtGuid4.dll!QMainWindow::event(QEvent * event) Line 1479 C++

QtGuid4.dll!QApplicationPrivate::notify_helper(QObject * receiver, QEvent * e) Line 4565 C++

QtGuid4.dll!QApplication::notify(QObject * receiver, QEvent * e) Line 4530 C++

QtCored4.dll!QCoreApplication::notifyInternal(QObject * receiver, QEvent * event) Line 955 C++

QtCored4.dll!QCoreApplication::sendEvent(QObject * receiver, QEvent * event) Line 231 C++

QtCored4.dll!QCoreApplicationPrivate::sendPostedEvents(QObject * receiver, int event_type, QThreadData * data) Line 1579 C++

QtCored4.dll!qt_internal_proc(HWND__ * hwnd, unsigned int message, unsigned __int64 wp, __int64 lp) Line 498 C++

[External Code]

QtCored4.dll!QEventDispatcherWin32::processEvents(QFlags flags) Line 823 C++

QtGuid4.dll!QGuiEventDispatcherWin32::processEvents(QFlags flags) Line 1216 C++

QtCored4.dll!QEventLoop::processEvents(QFlags flags) Line 150 C++

QtCored4.dll!QEventLoop::exec(QFlags flags) Line 204 C++

QtCored4.dll!QCoreApplication::exec() Line 1227 C++

QtGuid4.dll!QApplication::exec() Line 3824 C++

qt_bug.exe!main(int argc, char * * argv) Line 60 C++

还有一段 Qt 代码试图在堆栈跟踪中指示的行中使用指向已删除对象的指针:

for (int i = 0; i < count; ++i) {
    QWidget *w = staticWidgets.at(i);
    QWidgetPrivate *wd = w->d_func();
    if (!wd->isOpaque || !wd->extra || wd->extra->staticContentsSize.isEmpty()  // ****
        || !w->isVisible() || (parent && !parent->isAncestorOf(w))) {
        continue;
    }

(wd 指向在注释标记的行删除的对象)。

免责声明: 我知道存在更优雅的解决方案，但这是遗留代码，根据 Qt's manual :

You can also delete child objects yourself, and they will remove themselves from their parents.

此代码有效。

我们在 Windows 7(MSVC 2010 SP1、CL 16)、Windows 8(MSVC 2013 U4、CL 18)和 Fedora 20(GCC 4.8.3)上重现了这个问题。

最佳答案

我已经提交了 bug report .由于它涉及旧版本的库，因此不希望它会被修复。

无论如何，我们都在陆续删除 Qt3Support，因此建议大家 ;)

关于c++ - Q3ListView 是否无法从 Qt 后备存储中注销或代码错误？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/31414774/