wallch crashes when started for the first time after click on Start

[zasran]

When I login into X Windows wallch starts and shows the opening screen (selection of pics, preview etc.). At that point when I click on Start either nothing happens or it crashes.

It was working fine before upgrade to Ubuntu 14.04.

When I run it again it usually works. The images are same as they were before upgrade to Ubuntu 14.04.

Here's what gdb says about the crash:

Core was generated by `/usr/bin/wallch'.
---Type <return> to continue, or q <return> to quit---
Program terminated with signal SIGFPE, Arithmetic exception.
#0 0x0000000000458897 in ?? ()

...

(gdb) where
#0 0x0000000000458897 in ?? ()
#1 0x0000000000458c1c in ?? ()
#2 0x0000000000458ff0 in ?? ()
#3 0x0000000000459395 in ?? ()
#4 0x00000000004b86fa in ?? ()
#5 0x00000000004b8a13 in ?? ()
#6 0x00007fa49a99d36d in QMetaObject::activate (sender=sender@entry=0x1f84600, signalOffset=<optimized out>,
    local_signal_index=local_signal_index@entry=2, argv=argv@entry=0x7fff29494770) at kernel/qobject.cpp:3584
#7 0x00007fa49a99d7d7 in QMetaObject::activate (sender=sender@entry=0x1f84600,
    m=m@entry=0x7fa49bf5e5c0 <QAbstractButton::staticMetaObject>,
    local_signal_index=local_signal_index@entry=2, argv=argv@entry=0x7fff29494770) at kernel/qobject.cpp:3444
#8 0x00007fa49bbece42 in QAbstractButton::clicked (this=this@entry=0x1f84600, _t1=false)
    at .moc/moc_qabstractbutton.cpp:294
#9 0x00007fa49b976096 in QAbstractButtonPrivate::emitClicked (this=0x1f16790)
    at widgets/qabstractbutton.cpp:542
#10 0x00007fa49b976bae in QAbstractButtonPrivate::click (this=0x1f16790) at widgets/qabstractbutton.cpp:535
#11 0x00007fa49b976d24 in QAbstractButton::mouseReleaseEvent (this=0x1f84600, e=0x7fff29494c50)
    at widgets/qabstractbutton.cpp:1140
#12 0x00007fa49b8baea5 in QWidget::event (this=0x1f84600, event=0x7fff29494c50) at kernel/qwidget.cpp:7946
#13 0x00007fa49b87fc8c in QApplicationPrivate::notify_helper (this=this@entry=0x1caf2f0,
    receiver=receiver@entry=0x1f84600, e=e@entry=0x7fff29494c50) at kernel/qapplication.cpp:3486
#14 0x00007fa49b885b61 in QApplication::notify (this=<optimized out>, receiver=0x1f84600, e=0x7fff29494c50)
    at kernel/qapplication.cpp:3020
#15 0x00007fa49a975c2d in QCoreApplication::notifyInternal (this=0x7fff29495fb0,
    receiver=receiver@entry=0x1f84600, event=event@entry=0x7fff29494c50) at kernel/qcoreapplication.cpp:881
---Type <return> to continue, or q <return> to quit---
#16 0x00007fa49b8839e1 in sendSpontaneousEvent (event=0x7fff29494c50, receiver=0x1f84600)
    at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:235
#17 QApplicationPrivate::sendMouseEvent (receiver=receiver@entry=0x1f84600, event=event@entry=0x7fff29494c50,
    alienWidget=alienWidget@entry=0x1f84600, nativeWidget=0x7fff29495ff0,
    buttonDown=buttonDown@entry=0x7fa49bf6d200 <qt_button_down>, lastMouseReceiver=...,
    spontaneous=spontaneous@entry=true) at kernel/qapplication.cpp:2507
#18 0x00007fa49b8d7bbf in QWidgetWindow::handleMouseEvent (this=this@entry=0x1f6fa10,
    event=event@entry=0x7fff29495080) at kernel/qwidgetwindow.cpp:491
#19 0x00007fa49b8d99bb in QWidgetWindow::event (this=0x1f6fa10, event=0x7fff29495080)
    at kernel/qwidgetwindow.cpp:173
#20 0x00007fa49b87fc8c in QApplicationPrivate::notify_helper (this=this@entry=0x1caf2f0,
    receiver=receiver@entry=0x1f6fa10, e=e@entry=0x7fff29495080) at kernel/qapplication.cpp:3486
#21 0x00007fa49b884e56 in QApplication::notify (this=0x7fff29495fb0, receiver=0x1f6fa10, e=0x7fff29495080)
    at kernel/qapplication.cpp:3236
#22 0x00007fa49a975c2d in QCoreApplication::notifyInternal (this=0x7fff29495fb0,
    receiver=receiver@entry=0x1f6fa10, event=event@entry=0x7fff29495080) at kernel/qcoreapplication.cpp:881
#23 0x00007fa49ae9525c in sendSpontaneousEvent (event=0x7fff29495080, receiver=0x1f6fa10)
    at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:235
#24 QGuiApplicationPrivate::processMouseEvent (e=0x2482530) at kernel/qguiapplication.cpp:1598
#25 0x00007fa49ae96925 in QGuiApplicationPrivate::processWindowSystemEvent (e=e@entry=0x2482530)
    at kernel/qguiapplication.cpp:1409
#26 0x00007fa49ae7f858 in QWindowSystemInterface::sendWindowSystemEvents (flags=...)
    at kernel/qwindowsysteminterface.cpp:575
#27 0x00007fa48743a250 in userEventSourceDispatch (source=<optimized out>)
    at eventdispatchers/qeventdispatcher_glib.cpp:78
---Type <return> to continue, or q <return> to quit---
#28 0x00007fa49e282e04 in g_main_dispatch (context=0x7fa488003000)
    at /build/buildd/glib2.0-2.40.0/./glib/gmain.c:3064
#29 g_main_context_dispatch (context=context@entry=0x7fa488003000)
    at /build/buildd/glib2.0-2.40.0/./glib/gmain.c:3663
#30 0x00007fa49e283048 in g_main_context_iterate (context=context@entry=0x7fa488003000, block=block@entry=1,
    dispatch=dispatch@entry=1, self=<optimized out>) at /build/buildd/glib2.0-2.40.0/./glib/gmain.c:3734
#31 0x00007fa49e2830ec in g_main_context_iteration (context=0x7fa488003000, may_block=1)
    at /build/buildd/glib2.0-2.40.0/./glib/gmain.c:3795
#32 0x00007fa49a9c298c in QEventDispatcherGlib::processEvents (this=0x1d55eb0, flags=...)
    at kernel/qeventdispatcher_glib.cpp:426
#33 0x00007fa49a97496b in QEventLoop::exec (this=this@entry=0x7fff294953f0, flags=..., flags@entry=...)
    at kernel/qeventloop.cpp:212
#34 0x00007fa49a97b0e1 in QCoreApplication::exec () at kernel/qcoreapplication.cpp:1134
#35 0x00000000004a3657 in ?? ()
#36 0x00007fa499b49ec5 in __libc_start_main (main=0x41b830, argc=1, argv=0x7fff29496338, init=<optimized out>,
    fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7fff29496328) at libc-start.c:287
#37 0x000000000041c39a in ?? ()
(gdb)

System info:

Ubuntu 14.04 LTS

$ apt-cache policy wallch
wallch:
  Installed: 4.0-0ubuntu4
  Candidate: 4.0-0ubuntu4
  Version table:
 *** 4.0-0ubuntu4 0
        500 http://us.archive.ubuntu.com/ubuntu/ trusty/universe amd64 Packages
        100 /var/lib/dpkg/status

[Alex Solanos (hakermania)]

Hello zasran and thanks for your bug report.

We are aware the last few days that this bug really exists but no, it is not a huge bug of Wallch as you may understand.

Wallch has been tested a lot and this is one of the core functions of it, so it doesn't really have a bug.

So, what's really happening here? My guess is that there's something wrong with the video drivers. And this is why I believe this:

As many others, I recently upgraded to Ubuntu 14.04 LTS. Firstly I had no drivers installed in my system and Wallch worked smoothly. Then I installed the NVidia drivers and all the Qt applications went completely crazy. To be more specific, the official IDE for creating Qt applications (QtCreator) would crash during its startup with an X server specific error message. Wallch would have the exact same problem as you describe it.

Upon restart, everything was fixed. But this is reported to not work for everybody.

I refuse to mark this as a bug of Wallch though, as it clearly isn't. All Qt applications are affected by it. It is maybe a Qt bug.

Can you please confirm that other Qt Applications misbehave when Wallch misbehaves like that? For example, you can download QtCreator yourself and test it, please?

Thanks again.

[zasran (erik-zasran)]

It does indeed look that the error happens somewhere in Qt (based on function names in gdb stack printout).

Qtcreator runs without errors. Also following QT application run fine: arora, clementine, psi.

However at the moment wallch does not crash either. When I start it and click Start button nothing happens. Then I click Start button again and it works.

Not sure what makes it work or not work (receive SIGFPE). Will try to play with it a bit more, will update the bug if I find anything interesting...

[Alex Solanos (hakermania)]

I tracked down the problem.

It seems to be one of the problems that we did not have in 13.10 but we do have in 14.04, maybe because of slightly different code into the used Qt applications (changes in the Qt libraries were being done till the very last moment of Wallch inclusion into the repos).

So, it is not some else's fault, there are changes that were made, simple as that.

I will try to fix the bug and provide an update through Ubuntu.

[Bruce Pieterse (octoquad)]

I see this in Ubuntu Gnome as well with 15.04. Double-clicking the Start button causes it to crash immediately with the SIGFPE, Arithmetic exception. Single clicking start, causes the application to crash a few seconds later, with everything still functional (not hanging).

I also used apport-bug and upon using the relaunch option, and then clicking start, Wallch behaves correctly.

Stacktrace attached.

[Bruce Pieterse (octoquad)]

This problem is not present in 4.12.

[zasran (erik-zasran)]

I don't see the crashes anymore in 4.10.

[Jake McGregor (jake-mcgregor86)]

I've noticed that Wallch wasn't switching the wallpapers regularly. I have my interval set to 5 minutes, to rotate with pictures I have in a file. After clicking start, it froze and crashed. I'm running 15.04, and I just installed the updates a few minute ago.