[PyQt] Strange crash with pan on qtghraphichview

Hans-Peter Jansen hpj at urpla.net
Mon Nov 29 19:40:09 GMT 2010

On Monday 29 November 2010, 18:53:55 Matteo Boscolo wrote:
>   Hi All,
> I got some strange crash in my qt open source application PythonCAD.
> I have implemented QGraphicsView and QGraphicsScene to render the
> line arc ellipse .. of my application.
> Randomly I have some crash from the qt library and I can't make any
> debug on it because the crash is not on the python code, and no error
> is raised from the framework, I have just a crash and the application
> goes down
> Can anybody help me on this issue ?

The first step would be running your app under gdb control. It boils 
down to installing the debug packages of Qt, python, sip and PyQt at 
least, and then: 

$ gdb python
(gdb) set args qtcrash.py
(gdb) run
Starting program: /usr/bin/python qtcrash.py
[Thread debugging using libthread_db enabled]
[New Thread 0xb456bb90 (LWP 10895)]
[New Thread 0xb3a43b90 (LWP 10897)]
Program received signal SIGSEGV, Segmentation fault.
QCoreApplication::postEvent (receiver=0x8218f00, event=0x8304bd0, priority=0) at kernel/qcoreapplication.cpp:1133
1133        QThreadData *data = *pdata;
Current language:  auto; currently c++
(gdb) bt
#0  QCoreApplication::postEvent (receiver=0x8218f00, event=0x8304bd0, priority=0) at kernel/qcoreapplication.cpp:1133
#1  0xb7811eec in QCoreApplication::postEvent (receiver=0x8218f00, event=0x8304bd0) at kernel/qcoreapplication.cpp:1094
#2  0xb7820dd7 in QObject::deleteLater (this=0x8218f00) at kernel/qobject.cpp:2123
#3  0xb55e2203 in WebCore::QNetworkReplyHandler::finish() () from /usr/lib/libQtWebKit.so.4
#4  0xb55e2848 in WebCore::QNetworkReplyHandler::qt_metacall(QMetaObject::Call, int, void**) ()
   from /usr/lib/libQtWebKit.so.4
#5  0xb7815215 in QMetaObject::metacall (object=0x8218f00, cl=QMetaObject::InvokeMetaMethod, idx=5, argv=0xbfffdc88)
    at kernel/qmetaobject.cpp:237
#6  0xb7827e93 in QMetaObject::activate (sender=0x8218f00, m=0xb4b3b46c, local_signal_index=1, argv=0x0)
    at kernel/qobject.cpp:3272
#7  0xb4af8917 in QNetworkReply::finished (this=0x8218f00) at .moc/release-shared/moc_qnetworkreply.cpp:152
#8  0xb4a86eff in QNetworkReplyImplPrivate::finished (this=0x81fd248) at access/qnetworkreplyimpl.cpp:657
#9  0xb4a6a810 in QNetworkAccessBackend::finished (this=0x81fd190) at access/qnetworkaccessbackend.cpp:309
#10 0xb4a712f1 in QNetworkAccessHttpBackend::finished (this=0x81fd190) at access/qnetworkaccesshttpbackend.cpp:338
#11 0xb4a718e4 in QNetworkAccessHttpBackend::replyFinished (this=0x81fd190) at access/qnetworkaccesshttpbackend.cpp:773
#12 0xb4a86c49 in QNetworkReplyImplPrivate::handleNotifications (this=0x81fd248) at access/qnetworkreplyimpl.cpp:367
#13 0xb4a86ce6 in QNetworkReplyImpl::event (this=0x8218f00, e=0x8207550) at access/qnetworkreplyimpl.cpp:867

Post the backtrace.


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