How to close a local QDialog?

[MorrisLiang]

My application shows an icon in system tray which allows user to quit the application. Sometimes, my app will popup a dialog to let user verify.

void MyWidget::showWarning()
{
    QDialog dialog;
    ...
    ...
    int result = dialog.exec();
    if(result == QDialog::Accepted)
    {
       ...
    }
}

void MyWidget::showWarning()
{
    QDialog dialog;
    ...
    ...
    int result = dialog.exec();
    if(result == QDialog::Accepted)
    {
       ...
    }
}

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The problem is, if the local QDialog object is executing when user quits the app.MyWidget will be deleted before the line

if(result == QDialog::Accepted)

if(result == QDialog::Accepted)

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is called, which makes the app crash.

So, how do I safely finish the QDialog when the user quits the app?