[Kde-pim] need help with dynamic_cast failing

[Jason 'vanRijn' Kasper]

re, all.

I've seen a few bug reports about this, and it seems that it's mostly (only?) 
on debian-based systems.  Anyway, I'm out of my C++ element, so I'd really 
appreciate some help from the gurus.  =:)

KPilot has a subclass of QCustomEvent that's declared and defined in 
lib/kpilotdevicelink.cc.  This subclass has a few basic additional data 
private elements (2 ints and a QString), as well as a few public methods.  
This little class (DeviceCommEvent) runs from a separate thread and is used 
to pass status and message updates to the main GUI thread for user feedback, 
etc., with code like this:

QApplication::postEvent(link(),
  new DeviceCommEvent(EventLogProgress, QString::null, 30));

This is received by the main thread with this:

void KPilotDeviceLink::customEvent(QCustomEvent *e) ...

and inside that method, after checking the QCustomEvent::type(), I try a 
dynamic_cast like this:

DeviceCommEvent* t = dynamic_cast<DeviceCommEvent*>(e);

Now, after that I check to make sure that t is valid, but what's happening is 
that the dynamic_cast itself is segfaulting.  I didn't think that that was 
supposed to happen.

If anyone could help me understand why a dynamic_cast would be segfaulting and 
how I can fix it, I'd really, really, really, really, really appreciate it!!  
=:)

Thanks!!!
	

(gdb) thread apply all bt
 
Thread 2 (Thread -1236108400 (LWP 3308)):
#0  0xffffe410 in __kernel_vsyscall ()
#1  0xb75f38fc in pthread_cond_timedwait@@GLIBC_2.3.2 () 
from /lib/tls/i686/cmov/libpthread.so.0
#2  0xb7a025de in ?? () from /usr/lib/libqt-mt.so.3
#3  0xb6527298 in ?? ()
#4  0xb65272c8 in ?? ()
#5  0xb6527304 in ?? ()
#6  0xb75ce339 in DeviceMap::showList (this=0xb652730c) 
at /tmp/kdepim-3.5.7enterprise20070926/kpilot/lib/kpilotdevicelink.cc:109
#7  0xb7a0281c in QThread::sleep () from /usr/lib/libqt-mt.so.3
#8  0xb75cd5c2 in DeviceCommThread::run (this=0x80d7210) 
at /tmp/kdepim-3.5.7enterprise20070926/kpilot/lib/kpilotdevicelink.cc:628
#9  0xb7a03069 in QThreadInstance::start () from /usr/lib/libqt-mt.so.3
#10 0xb75ef46b in start_thread () from /lib/tls/i686/cmov/libpthread.so.0
#11 0xb6d8373e in clone () from /lib/tls/i686/cmov/libc.so.6
 
Thread 1 (Thread -1233549632 (LWP 3305)):
#0  0xb6ee47ae in __dynamic_cast () from /usr/lib/libstdc++.so.6
#1  0xb75caa9a in KPilotDeviceLink::customEvent (this=0x80e6dd0, e=0x80e4bc0)
    at /tmp/kdepim-3.5.7enterprise20070926/kpilot/lib/kpilotdevicelink.cc:727
#2  0xb7a72f95 in QObject::event () from /usr/lib/libqt-mt.so.3
#3  0xb7a0aaf0 in QApplication::internalNotify () from /usr/lib/libqt-mt.so.3
#4  0xb7a0c91f in QApplication::notify () from /usr/lib/libqt-mt.so.3
#5  0xb6c29ca2 in KApplication::notify () from /usr/lib/libkdecore.so.4
#6  0xb799d209 in QApplication::sendEvent () from /usr/lib/libqt-mt.so.3
#7  0xb7a0bb28 in QApplication::sendPostedEvents () 
from /usr/lib/libqt-mt.so.3
#8  0xb7a0bc30 in QApplication::sendPostedEvents () 
from /usr/lib/libqt-mt.so.3
#9  0xb79b1101 in QEventLoop::processEvents () from /usr/lib/libqt-mt.so.3
#10 0xb7a251ce in QEventLoop::enterLoop () from /usr/lib/libqt-mt.so.3
#11 0xb7a24fde in QEventLoop::exec () from /usr/lib/libqt-mt.so.3
#12 0xb7a0c699 in QApplication::exec () from /usr/lib/libqt-mt.so.3
#13 0x0807b9ac in main (argc=134762064, argv=0xbfbbd444) 
at /tmp/kdepim-3.5.7enterprise20070926/kpilot/kpilot/pilotDaemon.cc:1400

-- 
 -[ Jason 'vanRijn' Kasper    //  http://movingparts.net ]-
 -[ KDE PIM Developer         //  http://www.kde.org  ]-
 -[ bash fun -> :(){ :|:&};:  //  Numbers 6:22-26 ]-
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