*** This bug has been marked as a duplicate of bug 242116 ***

backtraces are different. This crash is caused by clicking maximize button, other crash is caused by closing a window.

both traces end on:
QGraphicsScene::mouseReleaseEvent() -> QGraphicsItem::update() -> QGraphicsItemPrivate::invalidateParentGraphicsEffectsRecursively (this=0x0)

the maximize causes a reset which sets the buttons, apparently invoking (on a rough look on the code) a deletion of the former ones, long story short_

AuroraeButton::mouseReleaseEvent() can cause self deletion through "emit clicked();" which you want to emit after the update and baseclass call... :-P

yes that's what I just figured out, too. I guess for clicks on close buttons that happens, too - also I'm not able to reproduce it there.

damn it - if I ensure that the internal handling is called before emitting the signal, it just dies somewhere else:

Application: KWin (kwin), signal: Segmentation fault
The current source language is "auto; currently asm".
[KCrash Handler]
#6  0x00007f2a882440b4 in QAbstractScrollArea::viewport (this=0x2ed06c0) at widgets/qabstractscrollarea.cpp:568
#7  0x00007f2a883feb81 in QGraphicsView::mouseReleaseEvent (this=0x2ed06c0, event=<value optimized out>) at graphicsview/qgraphicsview.cpp:3267
#8  0x00007f2a87e12602 in QWidget::event (this=0x2ed06c0, event=0x7fff59ef39b0) at kernel/qwidget.cpp:8044
#9  0x00007f2a881b9946 in QFrame::event (this=0x2ed06c0, e=0x7fff59ef39b0) at widgets/qframe.cpp:557
#10 0x00007f2a883fcdab in QGraphicsView::viewportEvent (this=0x2ed06c0, event=0x7fff59ef39b0) at graphicsview/qgraphicsview.cpp:2787
#11 0x00007f2a88e92577 in QCoreApplicationPrivate::sendThroughObjectEventFilters (this=<value optimized out>, receiver=0x2ed5ea0, event=0x7fff59ef39b0) at kernel/qcoreapplication.cpp:841
#12 0x00007f2a87dbc2fc in QApplicationPrivate::notify_helper (this=0x2616d20, receiver=0x2ed5ea0, e=0x7fff59ef39b0) at kernel/qapplication.cpp:4298
#13 0x00007f2a87dc2fdb in QApplication::notify (this=0x7fff59ef4510, receiver=0x2ed5ea0, e=0x7fff59ef39b0) at kernel/qapplication.cpp:3867
#14 0x00007f2a89b48bb6 in KApplication::notify (this=0x7fff59ef4510, receiver=0x2ed5ea0, event=0x7fff59ef39b0) at /opt/kde/src/KDE/kdelibs/kdeui/kernel/kapplication.cpp:302
#15 0x00007f2a88e9315c in QCoreApplication::notifyInternal (this=0x7fff59ef4510, receiver=0x2ed5ea0, event=0x7fff59ef39b0) at kernel/qcoreapplication.cpp:726
#16 0x00007f2a87dc21be in QCoreApplication::sendEvent (receiver=0x2ed5ea0, event=0x7fff59ef39b0, alienWidget=0x0, nativeWidget=0x2ed5ea0, buttonDown=<value optimized out>, 
    lastMouseReceiver=<value optimized out>, spontaneous=true) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:215
#17 QApplicationPrivate::sendMouseEvent (receiver=0x2ed5ea0, event=0x7fff59ef39b0, alienWidget=0x0, nativeWidget=0x2ed5ea0, buttonDown=<value optimized out>, lastMouseReceiver=<value optimized out>, 
    spontaneous=true) at kernel/qapplication.cpp:2967
#18 0x00007f2a87e4203b in QETWidget::translateMouseEvent (this=0x2ed5ea0, event=<value optimized out>) at kernel/qapplication_x11.cpp:4380
#19 0x00007f2a87e409ac in QApplication::x11ProcessEvent (this=<value optimized out>, event=0x7fff59ef4130) at kernel/qapplication_x11.cpp:3513
#20 0x00007f2a87e6c552 in x11EventSourceDispatch (s=0x261aa60, callback=<value optimized out>, user_data=<value optimized out>) at kernel/qguieventdispatcher_glib.cpp:146
#21 0x00007f2a80a0f6c2 in g_main_context_dispatch () from /lib/libglib-2.0.so.0
#22 0x00007f2a80a13538 in ?? () from /lib/libglib-2.0.so.0
#23 0x00007f2a80a136ec in g_main_context_iteration () from /lib/libglib-2.0.so.0
#24 0x00007f2a88ebc713 in QEventDispatcherGlib::processEvents (this=0x25f3970, flags=<value optimized out>) at kernel/qeventdispatcher_glib.cpp:412
#25 0x00007f2a87e6c14e in QGuiEventDispatcherGlib::processEvents (this=0x2ed06c0, flags=<value optimized out>) at kernel/qguieventdispatcher_glib.cpp:204
#26 0x00007f2a88e91a82 in QEventLoop::processEvents (this=<value optimized out>, flags=) at kernel/qeventloop.cpp:149
#27 0x00007f2a88e91e5c in QEventLoop::exec (this=0x7fff59ef4450, flags=) at kernel/qeventloop.cpp:201
#28 0x00007f2a88e96aeb in QCoreApplication::exec () at kernel/qcoreapplication.cpp:1003
#29 0x00007f2a8b3c62c2 in kdemain (argc=<value optimized out>, argv=<value optimized out>) at /opt/kde/src/KDE/kdebase/workspace/kwin/main.cpp:527
#30 0x00007f2a85129c4d in __libc_start_main (main=<value optimized out>, argc=<value optimized out>, ubp_av=<value optimized out>, init=<value optimized out>, fini=<value optimized out>, 
    rtld_fini=<value optimized out>, stack_end=0x7fff59ef4b18) at libc-start.c:228
#31 0x0000000000400849 in _start ()

try "event->accept()" to prevent further handling.

however i don't know how QGraphicsStuff handles this, so it might actually be required to take the item out of moc and use a deleteLater() on it (or pass the click signal through a QTimer::singleShot to get it outside the current event loop

From Qt documentation: Calling QEvent::ignore() or QEvent::accept() on event has no effect. It get's further processed and it just crashes somewhere else. I tried with deleteLater and the singleShot and it always just crashed somewhere else.

I have now a solution which solves this crash (and probably the other ones, too) but causes kwin to crash on shutdown:

diff --git a/client.cpp b/client.cpp
index 61656c2..c2c17cf 100644
--- a/client.cpp
+++ b/client.cpp
@@ -374,7 +374,7 @@ void Client::destroyDecoration()
     QRect oldgeom = geometry();
     if( decoration != NULL )
         {
-        delete decoration;
+        decoration->deleteLater();
         decoration = NULL;
         QPoint grav = calculateGravitation( true );
         border_left = border_right = border_top = border_bottom = 0;

SVN commit 1139942 by graesslin:

Defer deletion of the AuroraeScene and View to the next event loop. It is possible that the scene get's deleted before processing mouse events is finished which causes crashes.
BUG: 242165
FIXED-IN: 4.5.0
CCBUG: 241876
CCBUG: 242116

 M  +8 -1      aurorae.cpp  
 M  +1 -0      aurorae.h  


WebSVN link: http://websvn.kde.org/?view=rev&revision=1139942

*** Bug 269237 has been marked as a duplicate of this bug. ***

re-appeared in 4.6.n (some git master i presume)
reopening for the moment... :-(

i just counterchecked. this bug does not occur in kwin 4.6.0, just in 4.6.1

*** Bug 271435 has been marked as a duplicate of this bug. ***

I don't think it is the same crash as the duplicate is an assert while the original crash was a crash.

*** Bug 280704 has been marked as a duplicate of this bug. ***