Created attachment 53860 [details]
File that fail to be loaded in cantor and crash the program

it loads just fine here.
Are you using the latest trunk-version of Cantor?

I'm using the trunk-version and i've compiled it on ubuntu maverick 64bit

Hi,
Could you please start Cantor in a terminal, and send me all of the debugging output it gives you (please make sure that the debugging output is enabled by running "kdebugdialog" and enable anything related to cantor), so I can get a better picture of what might be going wrong? Thanks.

joxer@aurora:~$ cantor
Connecting to deprecated signal QDBusConnectionInterface::serviceOwnerChanged(QString,QString,QString)
QMetaObject::invokeMethod: No such method KUniqueApplication::loadCommandLineOptionsForNewInstance()
kbuildsycoca4 running...
kbuildsycoca4(7609) VFolderMenu::loadDoc: Parse error in  "/home/joxer/.config/menus/applications-merged/xdg-desktop-menu-dummy.menu" , line  1 , col  1 :  "unexpected end of file" 
kbuildsycoca4(7609) KBuildServiceFactory::collectInheritedServices: parent mimetype not found: "text/generic" 
kbuildsycoca4(7609) KBuildServiceFactory::collectInheritedServices: parent mimetype not found: "text/generic" 
kbuildsycoca4(7609) KBuildServiceFactory::collectInheritedServices: parent mimetype not found: "text/generic" 
cantor(7571)/kdecore (KLibrary) findLibraryInternal: plugins should not have a 'lib' prefix: "libcantorpart.so"
cantor(7571)/kdecore (KLibrary) kde4Factory: The library "/usr/lib/kde4/libcantorpart.so" does not offer a qt_plugin_instance function.
Object::disconnect: Unexpected null parameter
QLayout: Attempting to add QLayout "" to VariableManagerWidget "", which already has a layout
cantor(7571)/kdecore (services) KMimeTypeFactory::parseMagic: Now parsing  "/usr/share/mime/magic"
cantor(7571)/kdecore (services) KMimeTypeFactory::parseMagic: Now parsing  "/home/joxer/.local/share/mime/magic"
QLayout: Attempting to add QLayout "" to VariableManagerWidget "", which already has a layout
cantor(7571) KXMLGUI::ActionList::plug: Index  4  is not within range (0 -  2 
KCrash: Application 'cantor' crashing...
KCrash: Attempting to start /usr/lib/kde4/libexec/drkonqi from kdeinit
sock_file=/home/joxer/.kde/socket-aurora/kdeinit4__0

[1]+  Fermato                 cantor
joxer@aurora:~$ fg
bash: fg: il job è terminato
[1]+  Exit 253                cantor
joxer@aurora:~$ fg
bash: fg: attuale: job inesistente
joxer@aurora:~$ cantor
cantor(7871)/kdecore (KLibrary) findLibraryInternal: plugins should not have a 'lib' prefix: "libcantorpart.so"
cantor(7871)/kdecore (KLibrary) kde4Factory: The library "/usr/lib/kde4/libcantorpart.so" does not offer a qt_plugin_instance function.
Object::disconnect: Unexpected null parameter
QLayout: Attempting to add QLayout "" to VariableManagerWidget "", which already has a layout
cantor(7871)/kdecore (services) KMimeTypeFactory::parseMagic: Now parsing  "/usr/share/mime/magic"
cantor(7871)/kdecore (services) KMimeTypeFactory::parseMagic: Now parsing  "/home/joxer/.local/share/mime/magic"
QLayout: Attempting to add QLayout "" to VariableManagerWidget "", which already has a layout
cantor(7871) KXMLGUI::ActionList::plug: Index  4  is not within range (0 -  2 
KCrash: Application 'cantor' crashing...
KCrash: Attempting to start /usr/lib/kde4/libexec/drkonqi from kdeinit
sock_file=/home/joxer/.kde/socket-aurora/kdeinit4__0

[1]+  Fermato                 cantor
joxer@aurora:~$ 82	../sysdeps/unix/syscall-template.S: No such file or directory.
drkonqi(7903) BacktraceGenerator::~BacktraceGenerator: Killing running debugger instance 

[1]+  Exit 253                cantor


this is the output to terminal

Hi,
this debugging output doesn't contain anything that actually comes from Cantor (there should be a lot more lines, starting with cantor(something) ), it is all just output by some of the KDE libraries. Did you enable cantors debugging output? Please run kdebugdialog and enable cantor there.
Thanks

[Comment from a bug triager]
From bug 259868:
- What I was doing when the application crashed:
Cantor crashes right after selecting a Sage worksheet in the open file dialog
and clicking 'open'.

Backtrace:
[KCrash Handler]
#6  d_func (this=0x0, row=0, col=0) at text/qtexttable.h:137
#7  QTextTable::cellAt (this=0x0, row=0, col=0) at text/qtexttable.cpp:590
#8  0x00007f5715a5305e in CommandEntry::updatePrompt (this=0x739c70) at
/usr/src/debug/kdeedu-4.5.85/cantor/src/commandentry.cpp:818
#9  0x00007f5715a43cfc in CommandEntry::qt_metacall (this=0x739c70,
_c=QMetaObject::InvokeMetaMethod, _id=<value optimized out>, _a=0x7fffb0ef14a0)
    at /usr/src/debug/kdeedu-4.5.85/build/cantor/src/moc_commandentry.cpp:88
#10 0x00007f572635afef in QMetaObject::activate (sender=0xbb9b20, m=<value
optimized out>, local_signal_index=<value optimized out>, argv=0x0) at
kernel/qobject.cpp:3272
#11 0x00007f5715a4c696 in enableExpressionNumbering (this=0xbb9b20) at
/usr/src/debug/kdeedu-4.5.85/cantor/src/worksheet.cpp:820
#12 Worksheet::loginToSession (this=0xbb9b20) at
/usr/src/debug/kdeedu-4.5.85/cantor/src/worksheet.cpp:107
#13 0x00007f5715a4fe1d in Worksheet::qt_metacall (this=0xbb9b20,
_c=QMetaObject::InvokeMetaMethod, _id=37, _a=0xbf58c0) at
/usr/src/debug/kdeedu-4.5.85/build/cantor/src/worksheet.moc:191
#14 0x00007f5726359c6a in QObject::event (this=0xbb9b20, e=<value optimized
out>) at kernel/qobject.cpp:1211
#15 0x00007f5725754e4d in QWidget::event (this=0xbb9b20, event=0x1260b70) at
kernel/qwidget.cpp:8659
#16 0x00007f5725b02246 in QFrame::event (this=0xbb9b20, e=0x1260b70) at
widgets/qframe.cpp:557
#17 0x00007f5725b833eb in QAbstractScrollArea::event (this=0xbb9b20,
e=0x1260b70) at widgets/qabstractscrollarea.cpp:996
#18 0x00007f5725b6fa10 in QTextEdit::event (this=0xbb9b20, e=0x1260b70) at
widgets/qtextedit.cpp:1070
#19 0x00007f5715a4bf15 in Worksheet::event (this=0xbb9b20, event=0x1260b70) at
/usr/src/debug/kdeedu-4.5.85/cantor/src/worksheet.cpp:148
...

*** Bug 250335 has been marked as a duplicate of this bug. ***

*** Bug 259868 has been marked as a duplicate of this bug. ***

Could anyone who can reproduce this crash attach his cantorrc file (it can be found somewhere like ~/.kde/share/config/cantorrc ), thanks

Hello,
I have the same problem, but with nearly any cantor file.

Workaraound:
- start cantor
- enter: 
  sin(x) <shift><enter>
  in the default worksheet
- now open the file, that you want to use 

Result:
no crash

I forgot to mention:

I use Ubuntu 10.10, 32 bit, cantor from kde 4.6.1 together with sage.

Crash info:
Thread 1 (Thread 0xb76fa710 (LWP 8490)):
[KCrash Handler]
#7  d_func (this=0x0, row=0, col=0) at text/qtexttable.h:137
#8  QTextTable::cellAt (this=0x0, row=0, col=0) at text/qtexttable.cpp:590
#9  0x07e255d2 in CommandEntry::updatePrompt (this=0xa313250) at ../../../cantor/src/commandentry.cpp:818
#10 0x07e1210b in CommandEntry::qt_metacall (this=0xa313250, _c=QMetaObject::InvokeMetaMethod, _id=10, _a=0xbfbe432c) at moc_commandentry.cpp:88
#11 0x0616f8ca in QMetaObject::metacall (object=0xa313250, cl=QMetaObject::InvokeMetaMethod, idx=10, argv=0xbfbe432c) at kernel/qmetaobject.cpp:237
#12 0x061826ad in QMetaObject::activate (sender=0xa202850, m=0x7e32770, local_signal_index=3, argv=0xbfbe4204) at kernel/qobject.cpp:3280
#13 0x07e1b757 in Worksheet::updatePrompt (this=0xa202850) at ./worksheet.moc:231
#14 0x07e1ba12 in enableExpressionNumbering (this=0xa202850) at ../../../cantor/src/worksheet.cpp:820
#15 Worksheet::loginToSession (this=0xa202850) at ../../../cantor/src/worksheet.cpp:107
#16 0x07e20794 in Worksheet::qt_metacall (this=0xa202850, _c=QMetaObject::InvokeMetaMethod, _id=37, _a=0xa52d960) at ./worksheet.moc:191
#17 0x0616f8ca in QMetaObject::metacall (object=0xa202850, cl=QMetaObject::InvokeMetaMethod, idx=171, argv=0xa52d960) at kernel/qmetaobject.cpp:237
#18 0x0617adf6 in QMetaCallEvent::placeMetaCall (this=0xa38f8c0, object=0xa202850) at kernel/qobject.cpp:534
#19 0x0617c6a2 in QObject::event (this=0xa202850, e=0x0) at kernel/qobject.cpp:1219
#20 0x01170936 in QWidget::event (this=0xa202850, event=0xa38f8c0) at kernel/qwidget.cpp:8646
#21 0x01592763 in QFrame::event (this=0xa202850, e=0xa38f8c0) at widgets/qframe.cpp:557
#22 0x01630487 in QAbstractScrollArea::event (this=0xa202850, e=0xa38f8c0) at widgets/qabstractscrollarea.cpp:996
#23 0x016191cd in QTextEdit::event (this=0xa202850, e=0xa38f8c0) at widgets/qtextedit.cpp:1070
#24 0x0058cea3 in KTextEdit::event (this=0xa202850, ev=0xa38f8c0) at ../../kdeui/widgets/ktextedit.cpp:329
#25 0x07e1bc43 in Worksheet::event (this=0xa202850, event=0xa38f8c0) at ../../../cantor/src/worksheet.cpp:148
#26 0x01112fdc in QApplicationPrivate::notify_helper (this=0xa0033a0, receiver=0xa202850, e=0xa38f8c0) at kernel/qapplication.cpp:4396
#27 0x011190e9 in QApplication::notify (this=0xbfbe4fe8, receiver=0xa202850, e=0xa38f8c0) at kernel/qapplication.cpp:4361
#28 0x004707da in KApplication::notify (this=0xbfbe4fe8, receiver=0xa202850, event=0xa38f8c0) at ../../kdeui/kernel/kapplication.cpp:311
#29 0x06169b3b in QCoreApplication::notifyInternal (this=0xbfbe4fe8, receiver=0xa202850, event=0xa38f8c0) at kernel/qcoreapplication.cpp:732
#30 0x0616cd8b in sendEvent (receiver=0x0, event_type=0, data=0x9fede98) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:215
#31 QCoreApplicationPrivate::sendPostedEvents (receiver=0x0, event_type=0, data=0x9fede98) at kernel/qcoreapplication.cpp:1373
#32 0x0616cf4d in QCoreApplication::sendPostedEvents (receiver=0x0, event_type=0) at kernel/qcoreapplication.cpp:1266
#33 0x06198a74 in sendPostedEvents (s=0xa004f70) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:220
#34 postEventSourceDispatch (s=0xa004f70) at kernel/qeventdispatcher_glib.cpp:277
#35 0x01c30855 in g_main_context_dispatch () from /lib/libglib-2.0.so.0
#36 0x01c34668 in ?? () from /lib/libglib-2.0.so.0
#37 0x01c34848 in g_main_context_iteration () from /lib/libglib-2.0.so.0
#38 0x06198565 in QEventDispatcherGlib::processEvents (this=0x9fedb58, flags=...) at kernel/qeventdispatcher_glib.cpp:415
#39 0x011d4be5 in QGuiEventDispatcherGlib::processEvents (this=0x9fedb58, flags=...) at kernel/qguieventdispatcher_glib.cpp:204
#40 0x06168609 in QEventLoop::processEvents (this=0xbfbe4f44, flags=) at kernel/qeventloop.cpp:149
#41 0x06168a8a in QEventLoop::exec (this=0xbfbe4f44, flags=...) at kernel/qeventloop.cpp:201
#42 0x0616d00f in QCoreApplication::exec () at kernel/qcoreapplication.cpp:1009
#43 0x01111e07 in QApplication::exec () at kernel/qapplication.cpp:3672
#44 0x0804fe9f in main (argc=3, argv=0xbfbe5164) at ../../../cantor/src/main.cpp:87

Bug still present with kde 4.6.2.

Created attachment 58939 [details]
New crash information added by DrKonqi

cantor (0.2) on KDE Platform 4.6.2 (4.6.2) using Qt 4.7.2

- What I was doing when the application crashed: 
I'm trying to open an example of Maxima worksheet. But the cantor crashed

- Custom settings of the application:

-- Backtrace (Reduced):
#6  d_func (this=0x0, row=0, col=0) at text/qtexttable.h:137
#7  QTextTable::cellAt (this=0x0, row=0, col=0) at text/qtexttable.cpp:590
#8  0x00007f5c2ab34c3a in CommandEntry::updatePrompt (this=0x1e1ec30) at ../../../cantor/src/commandentry.cpp:818
#9  0x00007f5c2ab258ac in CommandEntry::qt_metacall (this=0x1e1ec30, _c=QMetaObject::InvokeMetaMethod, _id=<value optimized out>, _a=0x7fff258355a0) at moc_commandentry.cpp:88
[...]
#11 0x00007f5c2ab2e2b6 in enableExpressionNumbering (this=0x164d850) at ../../../cantor/src/worksheet.cpp:820

*** Bug 271158 has been marked as a duplicate of this bug. ***

Hi,
I compiled cantor from the source. I enabled cantor with "kdebugdialog". Now I get the following crash log, when I open a one-line octave file, that just contains the command "pi":

Wird gestartet: /home/ufechner/cantor/cantor/build/src/cantor
cantor(11682)/kdecore (KSycoca) KSycocaPrivate::openDatabase: Trying to open ksycoca from "/var/tmp/kdecache-ufechner/ksycoca4"
cantor(11682) OctaveBackend::OctaveBackend:
cantor(11682) SageBackend::SageBackend: Creating SageBackend
cantor(11682) NullBackend::NullBackend: Creating NullBackend
cantor(11682) MaximaBackend::MaximaBackend: Creating MaximaBackend
cantor(11682) RBackend::RBackend: Creating RBackend
cantor(11682)/kdecore (kdelibs) KStandardDirs::findExe: findExe(): returning  "/usr/bin/octave"
cantor(11682)/kdecore (kdelibs) KStandardDirs::findExe: findExe(): returning  "/usr/bin/maxima"
cantor(11682)/kdecore (KLibrary) findLibraryInternal: plugins should not have a 'lib' prefix: "libcantorpart.so"
cantor(11682) CantorPart::CantorPart: Created a CantorPart
cantor(11682) CantorPart::CantorPart: Backend  "Sage"  offers extensions:  ("HistoryExtension", "ScriptExtension", "CASExtension", "CalculusExtension", "LinearAlgebraExtension", "PlotExtension")
cantor(11682) SageBackend::createSession: Spawning a new Sage session
cantor(11682) SageSession::SageSession:
cantor(11682)/kparts KParts::ReadWritePart::setModified: setModified( false )
cantor(11682) CantorPart::loadAssistants: loading assistants...
cantor(11682) CantorPart::loadAssistants: found service "Plot3d"
cantor(11682) CantorPart::loadAssistants: created it
cantor(11682) CantorPart::loadAssistants: plugin  "Plot3d"  requires  ("PlotExtension")
cantor(11682) CantorPart::loadAssistants: plugin  "Plot3d"  is    supported by  "Sage"
cantor(11682) CantorPart::loadAssistants: found service "AdvancedPlot"
cantor(11682) CantorPart::loadAssistants: created it
cantor(11682) CantorPart::loadAssistants: plugin  "AdvancedPlot"  requires  ("AdvancedPlotExtension")
cantor(11682) CantorPart::loadAssistants: plugin  "AdvancedPlot"  is   not   supported by  "Sage"
cantor(11682) CantorPart::loadAssistants: found service "Skript ausführen"
cantor(11682) CantorPart::loadAssistants: created it
cantor(11682) CantorPart::loadAssistants: plugin  "Skript ausführen"  requires  ("ScriptExtension")
cantor(11682) CantorPart::loadAssistants: plugin  "Skript ausführen"  is    supported by  "Sage"
cantor(11682) CantorPart::loadAssistants: found service "Plot2d"
cantor(11682) CantorPart::loadAssistants: created it
cantor(11682) CantorPart::loadAssistants: plugin  "Plot2d"  requires  ("PlotExtension")
cantor(11682) CantorPart::loadAssistants: plugin  "Plot2d"  is    supported by  "Sage"
cantor(11682) CantorPart::loadAssistants: found service "Differenzieren"
cantor(11682) CantorPart::loadAssistants: created it
cantor(11682) CantorPart::loadAssistants: plugin  "Differenzieren"  requires  ("CalculusExtension")
cantor(11682) CantorPart::loadAssistants: plugin  "Differenzieren"  is    supported by  "Sage"
cantor(11682) CantorPart::loadAssistants: found service "Integrieren"
cantor(11682) CantorPart::loadAssistants: created it
cantor(11682) CantorPart::loadAssistants: plugin  "Integrieren"  requires  ("CalculusExtension")
cantor(11682) CantorPart::loadAssistants: plugin  "Integrieren"  is    supported by  "Sage"
cantor(11682) CantorPart::loadAssistants: found service "Matrix invertieren"
cantor(11682) CantorPart::loadAssistants: created it
cantor(11682) CantorPart::loadAssistants: plugin  "Matrix invertieren"  requires  ("LinearAlgebraExtension", "HistoryExtension")
cantor(11682) CantorPart::loadAssistants: plugin  "Matrix invertieren"  is    supported by  "Sage"
cantor(11682) CantorPart::loadAssistants: found service "Matrix erstellen"
cantor(11682) CantorPart::loadAssistants: created it
cantor(11682) CantorPart::loadAssistants: plugin  "Matrix erstellen"  requires  ("LinearAlgebraExtension")
cantor(11682) CantorPart::loadAssistants: plugin  "Matrix erstellen"  is    supported by  "Sage"
cantor(11682) CantorPart::loadAssistants: found service "Eigenvektoren"
cantor(11682) CantorPart::loadAssistants: created it
cantor(11682) CantorPart::loadAssistants: plugin  "Eigenvektoren"  requires  ("LinearAlgebraExtension", "HistoryExtension")
cantor(11682) CantorPart::loadAssistants: plugin  "Eigenvektoren"  is    supported by  "Sage"
cantor(11682) CantorPart::loadAssistants: found service "Eigenwerte"
cantor(11682) CantorPart::loadAssistants: created it
cantor(11682) CantorPart::loadAssistants: plugin  "Eigenwerte"  requires  ("LinearAlgebraExtension", "HistoryExtension")
cantor(11682) CantorPart::loadAssistants: plugin  "Eigenwerte"  is    supported by  "Sage"
cantor(11682) CantorPart::loadAssistants: found service "Lösen"
cantor(11682) CantorPart::loadAssistants: created it
cantor(11682) CantorPart::loadAssistants: plugin  "Lösen"  requires  ("CASExtension")
cantor(11682) CantorPart::loadAssistants: plugin  "Lösen"  is    supported by  "Sage"
cantor(11682) Cantor::PanelPluginHandler::loadPlugins: loading panel plugins for session of type  "Sage"
cantor(11682) Cantor::PanelPluginHandler::loadPlugins: found service "Hilfe"
cantor(11682) Cantor::PanelPluginHandler::loadPlugins: created it
cantor(11682) Cantor::PanelPluginHandler::loadPlugins: plugin  "Hilfe"  requires  ()
cantor(11682) SageBackend::capabilities: Requesting capabilities of SageSession
cantor(11682) Cantor::PanelPluginHandler::loadPlugins: plugin  "Hilfe"  is    supported
cantor(11682) Cantor::PanelPlugin::setSession: setting session to  0x893e458
cantor(11682) Cantor::PanelPluginHandler::loadPlugins: found service "Variablen-Verwaltung"
cantor(11682) Cantor::PanelPluginHandler::loadPlugins: created it
cantor(11682) Cantor::PanelPluginHandler::loadPlugins: plugin  "Variablen-Verwaltung"  requires  ("VariableManagementExtension")
cantor(11682) Cantor::PanelPluginHandler::loadPlugins: plugin  "Variablen-Verwaltung"  is   not   supported
cantor(11682) SageBackend::capabilities: Requesting capabilities of SageSession
cantor(11682) SageBackend::capabilities: Requesting capabilities of SageSession
Object::disconnect: Unexpected null parameter
cantor(11682) CantorShell::updatePanel: updating panels
cantor(11682) CantorShell::updatePanel: adding panel for  "Hilfe"
cantor(11682)/kdeui (kdelibs): Attempt to use QAction "" with KXMLGUIFactory! 
cantor(11682) SageSession::login: login
cantor(11682) SageSession::evaluateExpression: evaluating:  "sage.misc.latex.pretty_print_default(true);_;__IP.outputcache()"
cantor(11682) SageExpression::SageExpression:
cantor(11682) SageExpression::evaluate: evaluating  "sage.misc.latex.pretty_print_default(true);_;__IP.outputcache()"
cantor(11682) CantorPart::worksheetStatusChanged: wsStatusChange 0
cantor(11682) SageSession::readStdOut: out:  "----------------------------------------------------------------------
| Sage Version 4.6.2, Release Date: 2011-02-25                       |
| Type notebook() for the GUI, and license() for information.        |
----------------------------------------------------------------------
"
cantor(11682) SageSession::readStdOut: out:  "sage: "
cantor(11682) SageSession::readStdOut: out:  "sage: sage: "
cantor(11682) SageSession::readStdOut: out:  "sage: "
cantor(11682) SageSession::readStdOut: out:  "sage: "
cantor(11682) SageSession::readStdOut: out:  "sage: sage: "
cantor(11682) SageSession::readStdOut: out:  "sage: "
cantor(11682) SageSession::readStdOut: out:  "____TMP_DIR____ /home/ufechner/.sage//temp/dell_laptop/11708/
sage: "
cantor(11682) SageSession::readStdOut: tmp path:  "/home/ufechner/.sage//temp/dell_laptop/11708/"
cantor(11682) SageSession::readStdOut: out:  "____END_OF_INIT____
sage: "
cantor(11682) SageSession::readStdOut: initialized
cantor(11682) SageSession::runFirstExpression: writing  "sage.misc.latex.pretty_print_default(true);_;__IP.outputcache()"  to the process
cantor(11682) CantorPart::worksheetStatusChanged: wsStatusChange 1
cantor(11682) Worksheet::appendEntry: Entry Appended
cantor(11682) SageSession::readStdOut: out:  "<html><span class="math">\newcommand{\Bold}[1]{\mathbf{#1}}</span></html>
sage: "
cantor(11682) SageExpression::parseOutput: got prompt 73    -1
cantor(11682) SageExpression::evalFinished: evaluation finished
cantor(11682) SageExpression::evalFinished: "<html><span class="math">\newcommand{\Bold}[1]{\mathbf{#1}}</span></html>"
cantor(11682) Cantor::Expression::setResult: settting result to a type  1  result
cantor(11682) Cantor::Expression::renderResultAsLatex: rendering as latex
cantor(11682) Cantor::Expression::renderResultAsLatex: checking if it really is a formula that can be typeset
cantor(11682) Cantor::Expression::renderResultAsLatex: fileName:  "/tmp/kde-ufechner/cantor/X11682.tex"
cantor(11682)/kdecore (kdelibs) KStandardDirs::findExe: findExe(): returning  "/usr/bin/latex"
cantor(11682)/kdecore (kdelibs) KStandardDirs::findExe: findExe(): returning  "/usr/bin/dvips"
cantor(11682) CantorPart::worksheetStatusChanged: wsStatusChange 1
QProcess: Destroyed while process is still running.
cantor(11682)/kio (bookmarks) KBookmarkManager::KBookmarkManager: starting KDirWatch for  "/home/ufechner/.local/share//user-places.xbel"
cantor(11682)/kio (KDirListerCache) KDirListerCache::listDir: Listing directory: KUrl("trash:/")
cantor(11682)/kio (Scheduler) KIO::SchedulerPrivate::doJob: KIO::SimpleJob(0x89b0ca8)
cantor(11682)/kio (Scheduler) KIO::SchedulerPrivate::protoQ: creating ProtoQueue instance for "trash"
cantor(11682)/kio (Scheduler) KIO::ProtoQueue::ProtoQueue: m_maxConnectionsTotal: 2 m_maxConnectionsPerHost: 2
cantor(11682)/kio (Scheduler) KIO::SchedulerPrivate::doJob: KIO::SimpleJob(0x8d33a10)
cantor(11682)/kio (Scheduler) KIO::SchedulerPrivate::protoQ: creating ProtoQueue instance for "file"
cantor(11682)/kio (Scheduler) KIO::ProtoQueue::ProtoQueue: m_maxConnectionsTotal: 50 m_maxConnectionsPerHost: 50
cantor(11682)/kio (KDirListerCache) KDirListerCache::listDir: Entry currently being listed: KUrl("trash:/") by (KDirLister(0x8a80748) )
cantor(11682)/kio (KDirListerCache) KDirListerCache::stopListingUrl: KDirLister(0x8c4b5f8)  url= KUrl("trash:/")
cantor(11682)/kio (Slave) KIO::Slave::createSlave: createSlave "trash" for KUrl("trash:/")
cantor(11682)/kio (KIOConnection) KIO::ConnectionServer::listenForRemote: Listening on  "local:/tmp/ksocket-ufechner/cantora11682.slave-socket"
cantor(11682)/kio (Slave) KIO::Slave::createSlave: createSlave "file" for KUrl("file:///mnt/data/Dropbox/Cantor")
cantor(11682)/kio (KIOConnection) KIO::ConnectionServer::listenForRemote: Listening on  "local:/tmp/ksocket-ufechner/cantorV11682.slave-socket"
cantor(11682)/kio (Scheduler) KIO::SchedulerPrivate::jobFinished: KIO::StatJob(0x8d33a10) KIO::Slave(0x89b01b8)
cantor(11682)/kio (KDirListerCache) KDirListerCache::listDir: Listing directory: KUrl("file:///mnt/data/Dropbox/Cantor")
cantor(11682)/kio (Scheduler) KIO::SchedulerPrivate::doJob: KIO::SimpleJob(0x8d54ab8)
cantor(11682)/kio (KDirListerCache) KDirListerCache::stopListingUrl: KDirLister(0x8cd38c0)  url= KUrl("file:///mnt/data/Dropbox/Cantor")
cantor(11682)/kio (Scheduler) KIO::SchedulerPrivate::cancelJob: KIO::ListJob(0x8d54ab8) QObject(0x0)
cantor(11682)/kio (Scheduler) KIO::SchedulerPrivate::jobFinished: KIO::ListJob(0x8d54ab8) QObject(0x0)
cantor(11682)/kio (KDirListerCache) KDirListerCache::slotResult: finished listing KUrl("file:///mnt/data/Dropbox/Cantor")
cantor(11682)/kio (KDirListerCache) KDirListerCache::listDir: Listing directory: KUrl("file:///mnt/data/Dropbox/Cantor")
cantor(11682)/kio (Scheduler) KIO::SchedulerPrivate::doJob: KIO::SimpleJob(0x8d773b8)
cantor(11682)/kio (Scheduler) KIO::SchedulerPrivate::jobFinished: KIO::ListJob(0x89b0ca8) KIO::Slave(0x8d5cc68)
cantor(11682)/kio (KDirListerCache) KDirListerCache::slotResult: finished listing KUrl("trash:/")
cantor(11682)/kio (Scheduler) KIO::SchedulerPrivate::jobFinished: KIO::ListJob(0x8d773b8) KIO::Slave(0x89b01b8)
cantor(11682)/kio (KDirListerCache) KDirListerCache::slotResult: finished listing KUrl("file:///mnt/data/Dropbox/Cantor")
cantor(11682)/kio (Scheduler) KIO::SchedulerPrivate::doJob: KIO::SimpleJob(0x8d320e8)
cantor(11682)/kio (Scheduler) KIO::SchedulerPrivate::jobFinished: KIO::StatJob(0x8d320e8) KIO::Slave(0x89b01b8)
cantor(11682)/kio (KDirListerCache) KDirListerCache::stopListingUrl: KDirLister(0x8cd38c0)  url= KUrl("file:///mnt/data/Dropbox/Cantor")
cantor(11682)/kio (KDirListerCache) KDirListerCache::stopListingUrl: KDirLister(0x8cd38c0)  url= KUrl("file:///mnt/data/Dropbox/Cantor")
cantor(11682)/kio (KDirListerCache) KDirListerCache::forgetDirs: KDirLister(0x8cd38c0)  item moved into cache:  KUrl("file:///mnt/data/Dropbox/Cantor")
cantor(11682)/kio (KDirListerCache) KDirListerCache::stopListingUrl: KDirLister(0x8a80748)  url= KUrl("trash:/")
cantor(11682)/kio (KDirListerCache) KDirListerCache::forgetDirs: KDirLister(0x8a80748)  item moved into cache:  KUrl("trash:/")
cantor(11682) Worksheet::load: read:  "<!DOCTYPE CantorWorksheet>
<Worksheet backend="Sage">
 <Expression>
  <Command>sin(x)</Command>
  <Result type="latex" filename="PR6216.eps">\begin{eqnarray*}\newcommand{\Bold}[1]{\mathbf{#1}}\sin\left(x\right)\end{eqnarray*}</Result>
 </Expression>
 <Expression>
  <Command>sqrt(x)</Command>
  <Result type="latex" filename="nT6216.eps">\begin{eqnarray*}\newcommand{\Bold}[1]{\mathbf{#1}}\sqrt{x}\end{eqnarray*}</Result>
 </Expression>
 <Expression>
  <Command>x=var('x')</Command>
  <Result type="text"></Result>
 </Expression>
 <Expression>
  <Command>eqn=x^2</Command>
  <Result type="text"></Result>
 </Expression>
 <Expression>
  <Command>eqn</Command>
  <Result type="latex" filename="uF6216.eps">\begin{eqnarray*}\newcommand{\Bold}[1]{\mathbf{#1}}x^{2}\end{eqnarray*}</Result>
 </Expression>
 <Expression>
  <Command>x^2</Command>
  <Result type="latex" filename="Vm6216.eps">\begin{eqnarray*}\newcommand{\Bold}[1]{\mathbf{#1}}x^{2}\end{eqnarray*}</Result>
 </Expression>
 <Expression>
  <Command>sqrt(x^2)</Command>
  <Result type="latex" filename="BQ6216.eps">\begin{eqnarray*}\newcommand{\Bold}[1]{\mathbf{#1}}\sqrt{x^{2}}\end{eqnarray*}</Result>
 </Expression>
</Worksheet>
"
cantor(11682) Worksheet::load: "Worksheet"
cantor(11682) SageBackend::createSession: Spawning a new Sage session
cantor(11682) SageSession::SageSession:
cantor(11682) Worksheet::load: loading entries
cantor(11682) Worksheet::appendEntry: Entry Appended
cantor(11682) Cantor::Expression::setResult: settting result to a type  7  result
cantor(11682) CommandEntry::update: setting cell to  "<img src="file:///tmp/kde-ufechner/cantor//PR6216.eps" />"
cantor(11682) ResultProxy::insertResult: inserting new format
cantor(11682) ResultProxy::renderEps: rendering eps file:  KUrl("file:///tmp/kde-ufechner/cantor//PR6216.eps")
cantor(11682) ResultProxy::renderEps: dimension:  34 x 14
cantor(11682) Worksheet::appendEntry: Entry Appended
cantor(11682) Cantor::Expression::setResult: settting result to a type  7  result
cantor(11682) CommandEntry::update: setting cell to  "<img src="file:///tmp/kde-ufechner/cantor//nT6216.eps" />"
cantor(11682) ResultProxy::insertResult: inserting new format
cantor(11682) ResultProxy::renderEps: rendering eps file:  KUrl("file:///tmp/kde-ufechner/cantor//nT6216.eps")
cantor(11682) ResultProxy::renderEps: dimension:  23 x 14
cantor(11682) Worksheet::appendEntry: Entry Appended
cantor(11682) Cantor::Expression::setResult: settting result to a type  1  result
cantor(11682) CommandEntry::update: setting cell to  ""
cantor(11682) ResultProxy::insertResult: inserting new format
cantor(11682) Worksheet::appendEntry: Entry Appended
cantor(11682) Cantor::Expression::setResult: settting result to a type  1  result
cantor(11682) CommandEntry::update: setting cell to  ""
cantor(11682) ResultProxy::insertResult: inserting new format
cantor(11682) Worksheet::appendEntry: Entry Appended
cantor(11682) Cantor::Expression::setResult: settting result to a type  7  result
cantor(11682) CommandEntry::update: setting cell to  "<img src="file:///tmp/kde-ufechner/cantor//uF6216.eps" />"
cantor(11682) ResultProxy::insertResult: inserting new format
cantor(11682) ResultProxy::renderEps: rendering eps file:  KUrl("file:///tmp/kde-ufechner/cantor//uF6216.eps")
cantor(11682) ResultProxy::renderEps: dimension:  13 x 12
cantor(11682) Worksheet::appendEntry: Entry Appended
cantor(11682) Cantor::Expression::setResult: settting result to a type  7  result
cantor(11682) CommandEntry::update: setting cell to  "<img src="file:///tmp/kde-ufechner/cantor//Vm6216.eps" />"
cantor(11682) ResultProxy::insertResult: inserting new format
cantor(11682) ResultProxy::renderEps: rendering eps file:  KUrl("file:///tmp/kde-ufechner/cantor//Vm6216.eps")
cantor(11682) ResultProxy::renderEps: dimension:  13 x 12
cantor(11682) Worksheet::appendEntry: Entry Appended
cantor(11682) Cantor::Expression::setResult: settting result to a type  7  result
cantor(11682) CommandEntry::update: setting cell to  "<img src="file:///tmp/kde-ufechner/cantor//BQ6216.eps" />"
cantor(11682) ResultProxy::insertResult: inserting new format
cantor(11682) ResultProxy::renderEps: rendering eps file:  KUrl("file:///tmp/kde-ufechner/cantor//BQ6216.eps")
cantor(11682) ResultProxy::renderEps: dimension:  26 x 14
cantor(11682) CantorPart::loadAssistants: loading assistants...
cantor(11682) CantorPart::loadAssistants: found service "Plot3d"
cantor(11682) CantorPart::loadAssistants: created it
cantor(11682) CantorPart::loadAssistants: plugin  "Plot3d"  requires  ("PlotExtension")
cantor(11682) CantorPart::loadAssistants: plugin  "Plot3d"  is    supported by  "Sage"
cantor(11682) CantorPart::loadAssistants: found service "AdvancedPlot"
cantor(11682) CantorPart::loadAssistants: created it
cantor(11682) CantorPart::loadAssistants: plugin  "AdvancedPlot"  requires  ("AdvancedPlotExtension")
cantor(11682) CantorPart::loadAssistants: plugin  "AdvancedPlot"  is   not   supported by  "Sage"
cantor(11682) CantorPart::loadAssistants: found service "Skript ausführen"
cantor(11682) CantorPart::loadAssistants: created it
cantor(11682) CantorPart::loadAssistants: plugin  "Skript ausführen"  requires  ("ScriptExtension")
cantor(11682) CantorPart::loadAssistants: plugin  "Skript ausführen"  is    supported by  "Sage"
cantor(11682) CantorPart::loadAssistants: found service "Plot2d"
cantor(11682) CantorPart::loadAssistants: created it
cantor(11682) CantorPart::loadAssistants: plugin  "Plot2d"  requires  ("PlotExtension")
cantor(11682) CantorPart::loadAssistants: plugin  "Plot2d"  is    supported by  "Sage"
cantor(11682) CantorPart::loadAssistants: found service "Differenzieren"
cantor(11682) CantorPart::loadAssistants: created it
cantor(11682) CantorPart::loadAssistants: plugin  "Differenzieren"  requires  ("CalculusExtension")
cantor(11682) CantorPart::loadAssistants: plugin  "Differenzieren"  is    supported by  "Sage"
cantor(11682) CantorPart::loadAssistants: found service "Integrieren"
cantor(11682) CantorPart::loadAssistants: created it
cantor(11682) CantorPart::loadAssistants: plugin  "Integrieren"  requires  ("CalculusExtension")
cantor(11682) CantorPart::loadAssistants: plugin  "Integrieren"  is    supported by  "Sage"
cantor(11682) CantorPart::loadAssistants: found service "Matrix invertieren"
cantor(11682) CantorPart::loadAssistants: created it
cantor(11682) CantorPart::loadAssistants: plugin  "Matrix invertieren"  requires  ("LinearAlgebraExtension", "HistoryExtension")
cantor(11682) CantorPart::loadAssistants: plugin  "Matrix invertieren"  is    supported by  "Sage"
cantor(11682) CantorPart::loadAssistants: found service "Matrix erstellen"
cantor(11682) CantorPart::loadAssistants: created it
cantor(11682) CantorPart::loadAssistants: plugin  "Matrix erstellen"  requires  ("LinearAlgebraExtension")
cantor(11682) CantorPart::loadAssistants: plugin  "Matrix erstellen"  is    supported by  "Sage"
cantor(11682) CantorPart::loadAssistants: found service "Eigenvektoren"
cantor(11682) CantorPart::loadAssistants: created it
cantor(11682) CantorPart::loadAssistants: plugin  "Eigenvektoren"  requires  ("LinearAlgebraExtension", "HistoryExtension")
cantor(11682) CantorPart::loadAssistants: plugin  "Eigenvektoren"  is    supported by  "Sage"
cantor(11682) CantorPart::loadAssistants: found service "Eigenwerte"
cantor(11682) CantorPart::loadAssistants: created it
cantor(11682) CantorPart::loadAssistants: plugin  "Eigenwerte"  requires  ("LinearAlgebraExtension", "HistoryExtension")
cantor(11682) CantorPart::loadAssistants: plugin  "Eigenwerte"  is    supported by  "Sage"
cantor(11682) CantorPart::loadAssistants: found service "Lösen"
cantor(11682) CantorPart::loadAssistants: created it
cantor(11682) CantorPart::loadAssistants: plugin  "Lösen"  requires  ("CASExtension")
cantor(11682) CantorPart::loadAssistants: plugin  "Lösen"  is    supported by  "Sage"
cantor(11682) Cantor::PanelPluginHandler::loadPlugins: loading panel plugins for session of type  "Sage"
cantor(11682) Cantor::PanelPluginHandler::loadPlugins: found service "Hilfe"
cantor(11682) Cantor::PanelPluginHandler::loadPlugins: created it
cantor(11682) Cantor::PanelPluginHandler::loadPlugins: plugin  "Hilfe"  requires  ()
cantor(11682) SageBackend::capabilities: Requesting capabilities of SageSession
cantor(11682) Cantor::PanelPluginHandler::loadPlugins: plugin  "Hilfe"  is    supported
cantor(11682) Cantor::PanelPlugin::setSession: setting session to  0x8da5e58
cantor(11682) Cantor::PanelPluginHandler::loadPlugins: found service "Variablen-Verwaltung"
cantor(11682) Cantor::PanelPluginHandler::loadPlugins: created it
cantor(11682) Cantor::PanelPluginHandler::loadPlugins: plugin  "Variablen-Verwaltung"  requires  ("VariableManagementExtension")
cantor(11682) Cantor::PanelPluginHandler::loadPlugins: plugin  "Variablen-Verwaltung"  is   not   supported
cantor(11682) CantorShell::updatePanel: updating panels
cantor(11682) CantorShell::updatePanel: adding panel for  "Hilfe"
cantor(11682)/kdeui (kdelibs): Attempt to use QAction "" with KXMLGUIFactory! 
cantor(11682) SageBackend::capabilities: Requesting capabilities of SageSession
cantor(11682) SageBackend::capabilities: Requesting capabilities of SageSession
cantor(11682) SageSession::login: login
KCrash: Application 'cantor' crashing...
KCrash: Attempting to start /usr/lib/kde4/libexec/drkonqi from kdeinit
QSocketNotifier: Invalid socket 32 and type 'Read', disabling...
QSocketNotifier: Invalid socket 43 and type 'Read', disabling...
*** Beendet mit Rückgabewert: 253 ***

The same error, when I open a sage file. No error, if I first enter "sin(x)" after starting cantor and before loading a file.

Regards: 
Uwe

Sorry, in the last comment I posted the crash log, using the sage backend.

Here the crash log when opening the simple octave worksheet:
Application: Cantor (cantor), signal: Segmentation fault
[Current thread is 1 (Thread 0xb5044930 (LWP 13600))]

Thread 4 (Thread 0xb4a8eb70 (LWP 13601)):
#0  0xb773b424 in __kernel_vsyscall ()
#1  0xb59a2df6 in __poll (fds=0xb5a39ff4, nfds=1, timeout=-1) at ../sysdeps/unix/sysv/linux/poll.c:87
#2  0xb541aa1b in g_poll () from /lib/libglib-2.0.so.0
#3  0xb540d43c in ?? () from /lib/libglib-2.0.so.0
#4  0xb540dba7 in g_main_loop_run () from /lib/libglib-2.0.so.0
#5  0xb4bbb9c4 in ?? () from /usr/lib/libgio-2.0.so.0
#6  0xb543448f in ?? () from /lib/libglib-2.0.so.0
#7  0xb5549cc9 in start_thread (arg=0xb4a8eb70) at pthread_create.c:304
#8  0xb59b169e in clone () at ../sysdeps/unix/sysv/linux/i386/clone.S:130

Thread 3 (Thread 0xaaeebb70 (LWP 13628)):
#0  0xb773b424 in __kernel_vsyscall ()
#1  0xb59a2df6 in __poll (fds=0xb5a39ff4, nfds=1, timeout=-1) at ../sysdeps/unix/sysv/linux/poll.c:87
#2  0xb541aa1b in g_poll () from /lib/libglib-2.0.so.0
#3  0xb540d43c in ?? () from /lib/libglib-2.0.so.0
#4  0xb540d848 in g_main_context_iteration () from /lib/libglib-2.0.so.0
#5  0xb5e7059f in QEventDispatcherGlib::processEvents (this=0x966e1f8, flags=...) at kernel/qeventdispatcher_glib.cpp:417
#6  0xb5e40609 in QEventLoop::processEvents (this=0xaaeeb290, flags=) at kernel/qeventloop.cpp:149
#7  0xb5e40a8a in QEventLoop::exec (this=0xaaeeb290, flags=...) at kernel/qeventloop.cpp:201
#8  0xb5d3cb7e in QThread::exec (this=0x98308a8) at thread/qthread.cpp:490
#9  0xb5e1f35b in QInotifyFileSystemWatcherEngine::run (this=0x98308a8) at io/qfilesystemwatcher_inotify.cpp:248
#10 0xb5d3fdf9 in QThreadPrivate::start (arg=0x98308a8) at thread/qthread_unix.cpp:266
#11 0xb5549cc9 in start_thread (arg=0xaaeebb70) at pthread_create.c:304
#12 0xb59b169e in clone () at ../sysdeps/unix/sysv/linux/i386/clone.S:130

Thread 2 (Thread 0xaa623b70 (LWP 13630)):
#0  0xb773b424 in __kernel_vsyscall ()
#1  0xb59a2df6 in __poll (fds=0xb5a39ff4, nfds=1, timeout=-1) at ../sysdeps/unix/sysv/linux/poll.c:87
#2  0xb541aa1b in g_poll () from /lib/libglib-2.0.so.0
#3  0xb540d43c in ?? () from /lib/libglib-2.0.so.0
#4  0xb540d848 in g_main_context_iteration () from /lib/libglib-2.0.so.0
#5  0xb5e7059f in QEventDispatcherGlib::processEvents (this=0x98b0b88, flags=...) at kernel/qeventdispatcher_glib.cpp:417
#6  0xb5e40609 in QEventLoop::processEvents (this=0xaa623290, flags=) at kernel/qeventloop.cpp:149
#7  0xb5e40a8a in QEventLoop::exec (this=0xaa623290, flags=...) at kernel/qeventloop.cpp:201
#8  0xb5d3cb7e in QThread::exec (this=0x98b0fc8) at thread/qthread.cpp:490
#9  0xb5e1f35b in QInotifyFileSystemWatcherEngine::run (this=0x98b0fc8) at io/qfilesystemwatcher_inotify.cpp:248
#10 0xb5d3fdf9 in QThreadPrivate::start (arg=0x98b0fc8) at thread/qthread_unix.cpp:266
#11 0xb5549cc9 in start_thread (arg=0xaa623b70) at pthread_create.c:304
#12 0xb59b169e in clone () at ../sysdeps/unix/sysv/linux/i386/clone.S:130

Thread 1 (Thread 0xb5044930 (LWP 13600)):
[KCrash Handler]
#7  d_func (this=0x0, row=0, col=0) at text/qtexttable.h:137
#8  QTextTable::cellAt (this=0x0, row=0, col=0) at text/qtexttable.cpp:590
#9  0xb12b2a61 in CommandEntry::updatePrompt (this=0x967cec8) at /home/ufechner/cantor/cantor/src/commandentry.cpp:823
#10 0xb129c7ea in CommandEntry::qt_metacall (this=0x967cec8, _c=QMetaObject::InvokeMetaMethod, _id=1, _a=0xbff5f65c) at /home/ufechner/cantor/cantor/build/src/moc_commandentry.cpp:88
#11 0xb5e478ca in QMetaObject::metacall (object=0x967cec8, cl=QMetaObject::InvokeMetaMethod, idx=10, argv=0xbff5f65c) at kernel/qmetaobject.cpp:237
#12 0xb5e5a6ad in QMetaObject::activate (sender=0x95301e8, m=0xb12c1730, local_signal_index=3, argv=0xbff5f564) at kernel/qobject.cpp:3280
#13 0xb12abb43 in Worksheet::updatePrompt (this=0x95301e8) at /home/ufechner/cantor/cantor/build/src/worksheet.moc:233
#14 0xb12ab151 in Worksheet::enableExpressionNumbering (this=0x95301e8, enable=false) at /home/ufechner/cantor/cantor/src/worksheet.cpp:824
#15 0xb12a74eb in Worksheet::loginToSession (this=0x95301e8) at /home/ufechner/cantor/cantor/src/worksheet.cpp:107
#16 0xb12ab908 in Worksheet::qt_metacall (this=0x95301e8, _c=QMetaObject::InvokeMetaMethod, _id=38, _a=0x9998840) at /home/ufechner/cantor/cantor/build/src/worksheet.moc:193
#17 0xb5e478ca in QMetaObject::metacall (object=0x95301e8, cl=QMetaObject::InvokeMetaMethod, idx=172, argv=0x9998840) at kernel/qmetaobject.cpp:237
#18 0xb5e52df6 in QMetaCallEvent::placeMetaCall (this=0x93a7660, object=0x95301e8) at kernel/qobject.cpp:534
#19 0xb5e546a2 in QObject::event (this=0x95301e8, e=0x0) at kernel/qobject.cpp:1219
#20 0xb6400936 in QWidget::event (this=0x95301e8, event=0x93a7660) at kernel/qwidget.cpp:8646
#21 0xb6822763 in QFrame::event (this=0x95301e8, e=0x93a7660) at widgets/qframe.cpp:557
#22 0xb68c0487 in QAbstractScrollArea::event (this=0x95301e8, e=0x93a7660) at widgets/qabstractscrollarea.cpp:996
#23 0xb68a91cd in QTextEdit::event (this=0x95301e8, e=0x93a7660) at widgets/qtextedit.cpp:1070
#24 0xb763cee3 in KTextEdit::event (this=0x95301e8, ev=0x93a7660) at ../../kdeui/widgets/ktextedit.cpp:329
#25 0xb12a77ab in Worksheet::event (this=0x95301e8, event=0x93a7660) at /home/ufechner/cantor/cantor/src/worksheet.cpp:148
#26 0xb63a2fdc in QApplicationPrivate::notify_helper (this=0x920e9b8, receiver=0x95301e8, e=0x93a7660) at kernel/qapplication.cpp:4396
#27 0xb63a90e9 in QApplication::notify (this=0xbff60310, receiver=0x95301e8, e=0x93a7660) at kernel/qapplication.cpp:4361
#28 0xb752082a in KApplication::notify (this=0xbff60310, receiver=0x95301e8, event=0x93a7660) at ../../kdeui/kernel/kapplication.cpp:311
#29 0xb5e41b3b in QCoreApplication::notifyInternal (this=0xbff60310, receiver=0x95301e8, event=0x93a7660) at kernel/qcoreapplication.cpp:732
#30 0xb5e44d8b in sendEvent (receiver=0x0, event_type=0, data=0x91f58b8) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:215
#31 QCoreApplicationPrivate::sendPostedEvents (receiver=0x0, event_type=0, data=0x91f58b8) at kernel/qcoreapplication.cpp:1373
#32 0xb5e44f4d in QCoreApplication::sendPostedEvents (receiver=0x0, event_type=0) at kernel/qcoreapplication.cpp:1266
#33 0xb5e70a74 in sendPostedEvents (s=0x92110f0) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:220
#34 postEventSourceDispatch (s=0x92110f0) at kernel/qeventdispatcher_glib.cpp:277
#35 0xb5409855 in g_main_context_dispatch () from /lib/libglib-2.0.so.0
#36 0xb540d668 in ?? () from /lib/libglib-2.0.so.0
#37 0xb540d848 in g_main_context_iteration () from /lib/libglib-2.0.so.0
#38 0xb5e70565 in QEventDispatcherGlib::processEvents (this=0x91f5368, flags=...) at kernel/qeventdispatcher_glib.cpp:415
#39 0xb6464be5 in QGuiEventDispatcherGlib::processEvents (this=0x91f5368, flags=...) at kernel/qguieventdispatcher_glib.cpp:204
#40 0xb5e40609 in QEventLoop::processEvents (this=0xbff60294, flags=) at kernel/qeventloop.cpp:149
#41 0xb5e40a8a in QEventLoop::exec (this=0xbff60294, flags=...) at kernel/qeventloop.cpp:201
#42 0xb5e4500f in QCoreApplication::exec () at kernel/qcoreapplication.cpp:1009
#43 0xb63a1e07 in QApplication::exec () at kernel/qapplication.cpp:3672
#44 0x08050469 in main (argc=3, argv=0xbff60494) at /home/ufechner/cantor/cantor/src/main.cpp:87

Regards:

Uwe

Partial solution:
If I change the line:
    QTimer::singleShot(0, this, SLOT(loginToSession()));
into:
    QTimer::singleShot(1, this, SLOT(loginToSession()));
(file: worksheet.cpp, method: void Worksheet::load(const QString& filename ))

than cantor doesn't crash any more.
One problem remains:
Every file, that is opened, has an additional, empty command entry at the end.

Created attachment 59973 [details]
patch, that fixes but 258286 for me (on ubuntu 10.10, kde 4.6.2)

The patch works for me. It fixes a race condition, but I don't understand the real reason for this bug, therefore there might be a cleaner solution).
It also fixes the issue, that an empty command entry was added, when loading any worksheet. Tested on a Core Duo laptop with a 32 bit Ubuntu.

Created attachment 59990 [details]
possible fix

Hi,
thanks for your work on this. I've had some closer look on the crash, and how you fixed it, and I think I now finally understand where this race-conditioin/crash comes from. Its because in the load() method, the worksheet is cleared using the TextEntry::clear(), and then relying on all the WorksheetEntries deleting themselves, which they do, but only as soon as Qt processes the events again.
In the case for loading this is not enough, as it can happen that the signal for updating the prompt is placed before the event to delete the old entry, but there is no more valid table for the entry to write to, so CRASH.
Can you please test if the attached patch fixes this behaviour for you?

*** Bug 272551 has been marked as a duplicate of this bug. ***

Created attachment 60565 [details]
New crash information added by DrKonqi

cantor (0.2) on KDE Platform 4.6.3 (4.6.3) using Qt 4.7.2

- What I was doing when the application crashed:
I downloaded several example files to open in Cantor/Maxima, but every time I try to open, it crashes.

-- Backtrace (Reduced):
#7  d_func (this=0x0, row=0, col=0) at text/qtexttable.h:137
#8  QTextTable::cellAt (this=0x0, row=0, col=0) at text/qtexttable.cpp:590
#9  0xb11666c2 in CommandEntry::updatePrompt (this=0x9410148) at ../../../cantor/src/commandentry.cpp:818
#10 0xb115521b in CommandEntry::qt_metacall (this=0x9410148, _c=QMetaObject::InvokeMetaMethod, _id=<value optimized out>, _a=0xbf845f6c) at moc_commandentry.cpp:88
[...]
#13 0xb115eee7 in Worksheet::updatePrompt (this=0x91e3e98) at ./worksheet.moc:231

Git commit 484f8c60dadb41575406373c0f7012093ebd0399 by Alexander Rieder.
Committed on 02/06/2011 at 23:50.
Pushed by arieder into branch 'master'.

fix crash when loading worksheets
CCBUG: 258286

M  +18   -7    src/worksheet.cpp     

http://commits.kde.org/cantor/484f8c60dadb41575406373c0f7012093ebd0399

I commited the patch I posted earlier. Can anyone please confirm that the crash is indeed fixed now (as I can not reproduce here), so I can close this bug report?

I updated my source code to the newest revision and was not able to reproduce this bug any longer.

Closing, as my fix seems to work.

Created attachment 63370 [details]
New crash information added by DrKonqi

cantor (0.2) on KDE Platform 4.7.1 (4.7.1) using Qt 4.7.4

- What I was doing when the application crashed:

Openning a Sage sheet without actually having Sage installed, Cantor still segfaults, using latest KDE 4.7.1 and Qt 4.7.4

-- Backtrace (Reduced):
#6  0x00007fc21bd574c8 in QTextTable::cellAt(int, int) const () from /usr/lib/libQtGui.so.4
#7  0x00007fc20cdc50fe in CommandEntry::updatePrompt (this=0x3226b40) at /chakra/desktop-testing/kdeedu-cantor/src/cantor-4.7.1/src/commandentry.cpp:823
#8  0x00007fc20cdb5c7c in CommandEntry::qt_metacall (this=0x3226b40, _c=QMetaObject::InvokeMetaMethod, _id=<value optimized out>, _a=0x7fffaf62c7c0)
    at /chakra/desktop-testing/kdeedu-cantor/src/cantor-4.7.1/src/moc_commandentry.cpp:88
[...]
#10 0x00007fc20cdbe6d6 in Worksheet::enableExpressionNumbering (this=0x1e9f060) at /chakra/desktop-testing/kdeedu-cantor/src/cantor-4.7.1/src/worksheet.cpp:824
#11 Worksheet::loginToSession (this=0x1e9f060) at /chakra/desktop-testing/kdeedu-cantor/src/cantor-4.7.1/src/worksheet.cpp:107

Created attachment 65027 [details]
New crash information added by DrKonqi

cantor (0.2) on KDE Platform 4.7.2 (4.7.2) using Qt 4.7.4

- What I was doing when the application crashed:

This crash continues to occur using the version of Cantor available in the Ubuntu Software Center.

-- Backtrace (Reduced):
#6  0x00007f535e064298 in QTextTable::cellAt(int, int) const () from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#7  0x00007f53432540d8 in CommandEntry::updatePrompt (this=0x1741120) at ../../src/commandentry.cpp:823
#8  0x00007f5343244b4c in CommandEntry::qt_metacall (this=0x1741120, _c=QMetaObject::InvokeMetaMethod, _id=<optimized out>, _a=0x7fffc3d2ec30) at moc_commandentry.cpp:88
[...]
#10 0x00007f534324d6d6 in enableExpressionNumbering (enable=<optimized out>, this=0x14b22e0) at ../../src/worksheet.cpp:824
#11 Worksheet::loginToSession (this=0x14b22e0) at ../../src/worksheet.cpp:107

For me, this still happens as well. KDE 4.7.2, Ubuntu 11.10, simlilar crash dump (cellAt via enableExpressionNumbering), and with similar conditions: If and only if there is a worksheet with no content, no matter if it's at startup or created later via File/New, there is a crash. Closing the empty worksheet and then opening a file works fine.

This is on an i7 (quad-core).

Crash still happening on 4.7.2, see duplicate. Which version should have the fix?

*** Bug 287069 has been marked as a duplicate of this bug. ***

Hi,
I just checked, and it looks like the fix didn't get into the 4.7 branch. I must have forgotten to backport it. Sorry.

Git commit a353985e7abc480baf37cf6b450e7a9669f386eb by Alexander Rieder.
Committed on 02/06/2011 at 23:50.
Pushed by arieder into branch 'KDE/4.7'.

fix crash when loading worksheets
CCBUG: 258286

M  +18   -7    src/worksheet.cpp

http://commits.kde.org/cantor/a353985e7abc480baf37cf6b450e7a9669f386eb

I just backported the fix to the 4.7 branch, it should be available with KDE 4.7.4 which will be released on December 6, 2011. Please let me now if you still experience the crash with the new version.

Created attachment 70412 [details]
New crash information added by DrKonqi

cantor (0.2) on KDE Platform 4.6.5 (4.6.5) using Qt 4.7.2

- What I was doing when the application crashed:
Opening a sage file in cantor when it crashed.

-- Backtrace (Reduced):
#7  d_func (this=0x0, row=0, col=0) at text/qtexttable.h:137
#8  QTextTable::cellAt (this=0x0, row=0, col=0) at text/qtexttable.cpp:590
#9  0x023a56c2 in CommandEntry::updatePrompt (this=0x9eb99a0) at ../../../cantor/src/commandentry.cpp:818
#10 0x02393ebb in CommandEntry::qt_metacall (this=0x9eb99a0, _c=QMetaObject::InvokeMetaMethod, _id=<value optimized out>, _a=0xbfd76dbc) at moc_commandentry.cpp:88
[...]
#13 0x0239dee7 in Worksheet::updatePrompt (this=0x9f28a20) at ./worksheet.moc:231