[PyKDE] Re: Q___Style wrapper

[Phil Thompson]

On Friday 12 May 2006 3:12 pm, david at boddie.org.uk wrote:
> On Thu, 11 May 2006 17:13:54, Mike Rovner wrote:
> > David Boddie wrote:
> > > It looks like something expects to be deleted or garbage collected when
> > > the QApplication is destroyed, but that maybe the Python interpreter
> > > has already been shut down (interp is zero in frame #0).
> >
> > Agree.
> >
> > > If you can show us your .sip file for the QWindowsStyle binding then
> > > maybe it will become clearer just what's happening.
> >
> > I did ;) It's included in my original message.
>
> Looks like I didn't scroll down far enough. :-/
>
> I think your original backtrace probably gives us the information we need.
> Still, I compiled SIP, PyQt, and ExtraStyles (my name for the new module)
> with debugging symbols, and got the following backtrace:
>
> #0  PyThreadState_New (interp=0x0) at Python/pystate.c:194
> #1  0xb7ee1560 in PyGILState_Ensure () at Python/pystate.c:489
> #2  0xb7e21c8c in sip_api_common_dtor (sipSelf=0xb7b40b2c) at siplib.c:3014
> #3  0xb674a860 in ~sipQWindowsStyle (this=0x8230768) at
> sipExtraStylesQWindowsStyle.cpp:46
> #4  0xb6e05400 in ~QApplication (this=0x80faf90) at
> kernel/qapplication.cpp:854
> #5  0xb780b198 in ~sipQApplication (this=0x80faf90) at
> sipQtGuipart3.cpp:47410 #6  0xb752018c in sipDelayedDtors
> (ddlist=0x8142c00) at qapplication.sip:396 #7  0xb7e1e76c in finalise () at
> siplib.c:883
> #8  0xb7ee366a in Py_Finalize () at Python/pythonrun.c:1564
> #9  0xb7eea3b3 in Py_Main (argc=1, argv=0xbf854964) at Modules/main.c:504
> #10 0x08048654 in main (argc=2, argv=0xbf854964) at Modules/python.c:23
>
> Frame 4 looks interesting:
>
> (gdb) f 4
> #4  0xb6e05400 in ~QApplication (this=0x80faf90) at
> kernel/qapplication.cpp:854
> 854         delete QApplicationPrivate::app_style;
> Current language:  auto; currently c++
> (gdb) l
> 849         QApplicationPrivate::set_pal = 0;
> 850         app_palettes()->clear();
> 851         delete QApplicationPrivate::app_font;
> 852         QApplicationPrivate::app_font = 0;
> 853         app_fonts()->clear();
> 854         delete QApplicationPrivate::app_style;
> 855         QApplicationPrivate::app_style = 0;
> 856         delete QApplicationPrivate::app_icon;
> 857         QApplicationPrivate::app_icon = 0;
> 858     #ifndef QT_NO_CURSOR
>
> So, the style is being deleted here, so in frame 3 the QWindowsStyle
> wrapper is destroyed.
>
> I think the problem is that all this is happening after Python has been
> shut down, maybe because QApplication is defined using the /DelayDtor/
> annotation in sip/QtGui/qapplication.sip. Just to test my theory, I
> removed the annotation (but not the annotation for QCoreApplication), and
> I didn't get a segfault on exit.
>
> Maybe someone with more experience can suggest a workaround, or perhaps
> there's room for some changes in the QApplication wrapper. I expect that
> there was a good reason to use the annotation there, though perhaps just
> keeping it for QCoreApplication is sufficient to solve any previous issues.

The /DelayDtor/ triggers the bug, but omitting it doesn't fix it.

Hopefully fixed properly in tonight's SIP snapshot.

Phil