[PyKDE] PyQt4/win32 crash

[Phil Thompson]

On Friday 15 September 2006 9:58 pm, K.S.Sreeram wrote:
> [Qt-4.1.4, sip-4.4.5, PyQt-4.0.1, Python-2.4.3, MSVC-7.1]
>
> Hi all,
>
> I've been facing a random crash in my app for sometime, and i've got it
> down to a simple test program. Run the attached script, click "Click Me"
> and close the newly opened window, and it crashes!
>
> I used debug builds and poked around the code, and here's why i think
> its crashing...
>
> The crash happens when a top-level window is closed, and all python
> references to the window are lost in the 'closeEvent' method.
>
> When a window is closed using the close button at the right top of the
> window, the Qt function "QWidgetPrivate::close_helper(mode)" gets called
> with "mode == CloseWithSpontaneousEvent". This function is there in
> src/gui/kernel/qwidget.cpp line 4609.
>
> In this function, close event is sent to the widget if mode is
> CloseWithSpontaneousEvent, as in this case. By the time, the close event
> is handled by the widget, the widget is already deleted because of
> python's gc.
>
> The Qt code seems to check for this case using tests like
> "that.isNull()". But on line 4642, the check for null is not performed
> and the app crashes at that point.
>
> So this looks like it is a bug in Qt itself. But is there someway PyQt
> can workaround this bug?

What if you swap the two lines of MyWindow.closeEvent()?

Phil