Segfault when closing

[The-Compiler]

We still have some segfaults when closing, usually with a corrupted stack trace:

#5  0x00007fffde97a700 in ?? ()
#6  0x00007ffff57573be in ?? () from /usr/lib/libQt5Core.so.5
Backtrace stopped: previous frame inner to this frame (corrupt stack?)

There's an user who can reproduce it by letting qutebrowser run on duckduckgo for ~10 hours and then closing it with the "x"-button in his window manager.

Maybe a solution is to delete the QApplication object properly.

References:

http://python.6.x6.nabble.com/Application-crash-on-exit-under-Linux-td5067510.html
http://stackoverflow.com/questions/5506781/pyqt4-application-on-windows-is-crashing-on-exit
http://qt-project.org/forums/viewthread/27196
http://stackoverflow.com/questions/11945183/what-are-good-practices-for-avoiding-crashes-hangs-in-pyqt
https://github.com/Xinkai/XwareDesktop/issues/25

[The-Compiler]

Some attempted fixes are in the segfault branch, but it's not tested yet if they fix the issue.

[The-Compiler]

Xinkai/XwareDesktop does this:

-    sys.exit(app.exec())
+    code = app.exec()
+    for w in QApplication.topLevelWindows():
+        del w
+    del app
+    sys.exit(code)

[The-Compiler]

I tried to reproduce it (on the master branch) with no luck. About 8 hours of running with Arch, Debian VM and Ubuntu VM, and closing via the close-button worked normally.

[The-Compiler]

Maybe related: http://www.riverbankcomputing.com/pipermail/pyqt/2014-October/034941.html

[The-Compiler]

http://pyqt.sourceforge.net/Docs/PyQt5/pyqt4_differences.html#object-destruction-on-exit

[The-Compiler]

Another one:

#0  QString (other=..., this=0x7f5a68bbcca0) at ../../include/QtCore/../../src/corelib/tools/qstring.h:814
#1  dbusServiceString () at qdbusintegrator.cpp:82
#2  QDBusConnectionPrivate::isServiceRegisteredByThread (this=0x2c4fea0, serviceName=...) at qdbusintegrator.cpp:2494
#3  0x00007f5a6b72956e in QDBusConnectionPrivate::sendWithReply (this=0x2c4fea0, message=..., sendMode=1, timeout=-1) at qdbusintegrator.cpp:1940
#4  0x00007f5a6b7159eb in QDBusConnection::call (this=0x7f5a1401a790, message=..., mode=<optimized out>, timeout=<optimized out>) at qdbusconnection.cpp:584
#5  0x00007f5a6b733bf8 in QDBusAbstractInterfacePrivate::property (this=0x7f5a1401a720, mp=..., returnValuePtr=0x1e) at qdbusabstractinterface.cpp:146
#6  0x00007f5a6b735c96 in QDBusAbstractInterfaceBase::qt_metacall (this=this@entry=0x7f5a1401a680, _c=_c@entry=QMetaObject::ReadProperty, _id=<optimized out>, _a=_a@entry=0x7f5a68bbd1c0) at qdbusabstractinterface.cpp:257
#7  0x00007f5a6b735e45 in QDBusAbstractInterface::qt_metacall (this=this@entry=0x7f5a1401a680, _c=_c@entry=QMetaObject::ReadProperty, _id=<optimized out>, _a=_a@entry=0x7f5a68bbd1c0) at .moc/moc_qdbusabstractinterface.cpp:95
#8  0x00007f5a6b737cc1 in QDBusInterface::qt_metacall (this=0x7f5a1401a680, _c=QMetaObject::ReadProperty, _id=<optimized out>, _a=0x7f5a68bbd1c0) at qdbusinterface.cpp:262
#9  0x00007f5a80920507 in QMetaProperty::read (this=this@entry=0x7f5a68bbd260, object=object@entry=0x7f5a1401a680) at kernel/qmetaobject.cpp:2848
#10 0x00007f5a809425f7 in QObject::property (this=0x7f5a1401a680, name=name@entry=0x7f5a23be3cf7 "Ssid") at kernel/qobject.cpp:3861
#11 0x00007f5a23bc7a6f in QNetworkManagerInterfaceAccessPoint::ssid (this=<optimized out>) at qnetworkmanagerservice.cpp:266
#12 0x00007f5a23bd4514 in QNetworkManagerEngine::newAccessPoint (this=0x2c5c470, path=..., objectPath=...) at qnetworkmanagerengine.cpp:563
#13 0x00007f5a23be2bf5 in QNetworkManagerEngine::qt_static_metacall (_o=0x7f5a1401cc80, _c=45516704, _id=30, _a=0x1) at .moc/moc_qnetworkmanagerengine.cpp:142
#14 0x00007f5a8094365d in QMetaObject::activate (sender=0x7f5a14003740, signalOffset=<optimized out>, local_signal_index=local_signal_index@entry=1, argv=argv@entry=0x7f5a68bbd520) at kernel/qobject.cpp:3681
#15 0x00007f5a80943ac7 in QMetaObject::activate (sender=<optimized out>, m=m@entry=0x7f5a23ded840 <QNetworkManagerInterfaceDeviceWireless::staticMetaObject>, local_signal_index=local_signal_index@entry=1, 
    argv=argv@entry=0x7f5a68bbd520) at kernel/qobject.cpp:3547
#16 0x00007f5a23be0aea in QNetworkManagerInterfaceDeviceWireless::accessPointAdded (this=<optimized out>, _t1=..., _t2=...) at .moc/moc_qnetworkmanagerservice.cpp:700
#17 0x00007f5a23be1ac6 in QNetworkManagerInterfaceDeviceWireless::qt_static_metacall (_o=0x7f5a14003740, _c=45516704, _id=30, _a=0x1) at .moc/moc_qnetworkmanagerservice.cpp:607
#18 0x00007f5a8094365d in QMetaObject::activate (sender=sender@entry=0x7f5a140081c0, signalOffset=<optimized out>, local_signal_index=local_signal_index@entry=1, argv=argv@entry=0x7f5a68bbd6a0) at kernel/qobject.cpp:3681
#19 0x00007f5a80943ac7 in QMetaObject::activate (sender=sender@entry=0x7f5a140081c0, m=m@entry=0x7f5a23ded140 <QNmDBusHelper::staticMetaObject>, local_signal_index=local_signal_index@entry=1, argv=argv@entry=0x7f5a68bbd6a0)
    at kernel/qobject.cpp:3547
#20 0x00007f5a23bdfe3a in QNmDBusHelper::pathForAccessPointAdded (this=this@entry=0x7f5a140081c0, _t1=..., _t2=...) at .moc/moc_qnmdbushelper.cpp:234
#21 0x00007f5a23bc5c76 in QNmDBusHelper::slotAccessPointAdded (this=0x7f5a140081c0, path=...) at qnmdbushelper.cpp:83
#22 0x00007f5a23be02ca in QNmDBusHelper::qt_static_metacall (_o=0x7f5a140081c0, _c=45516704, _c@entry=QMetaObject::InvokeMetaMethod, _id=30, _id@entry=6, _a=0x1, _a@entry=0x7f5a68bbd8c0) at .moc/moc_qnmdbushelper.cpp:111
#23 0x00007f5a23be05e3 in QNmDBusHelper::qt_metacall (this=0x7f5a140081c0, _c=QMetaObject::InvokeMetaMethod, _id=6, _a=0x7f5a68bbd8c0) at .moc/moc_qnmdbushelper.cpp:213
#24 0x00007f5a6b725a47 in QDBusConnectionPrivate::deliverCall (this=0x7f5a1401cc80, object=0x2b687a0, msg=..., metaTypes=..., slotIdx=335574247) at qdbusintegrator.cpp:991
#25 0x00007f5a8094452a in QObject::event (this=0x7f5a140081c0, e=<optimized out>) at kernel/qobject.cpp:1241
#26 0x00007f5a6f05df3c in QApplicationPrivate::notify_helper (this=0x29c3840, receiver=0x7f5a140081c0, e=0x2fabfe0) at kernel/qapplication.cpp:3499
#27 0x00007f5a6f063380 in QApplication::notify (this=0x2665b70, receiver=0x7f5a140081c0, e=0x2fabfe0) at kernel/qapplication.cpp:3282
#28 0x00007f5a6fa4738c in sipQApplication::notify (this=0x2665b70, a0=0x7f5a140081c0, a1=0x2fabfe0) at sipQtWidgetsQApplication.cpp:349
#29 0x00007f5a8091498b in QCoreApplication::notifyInternal (this=0x2665b70, receiver=0x7f5a140081c0, event=event@entry=0x2fabfe0) at kernel/qcoreapplication.cpp:935
#30 0x00007f5a80916953 in sendEvent (event=0x2fabfe0, receiver=<optimized out>) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:237
#31 QCoreApplicationPrivate::sendPostedEvents (receiver=receiver@entry=0x0, event_type=event_type@entry=0, data=0x2c4ea00) at kernel/qcoreapplication.cpp:1539
#32 0x00007f5a80916f58 in QCoreApplication::sendPostedEvents (receiver=receiver@entry=0x0, event_type=event_type@entry=0) at kernel/qcoreapplication.cpp:1397
#33 0x00007f5a8096bf43 in postEventSourceDispatch (s=0x7f5a140012f0) at kernel/qeventdispatcher_glib.cpp:279
#34 0x00007f5a82230a0d in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#35 0x00007f5a82230cf8 in ?? () from /usr/lib/libglib-2.0.so.0
#36 0x00007f5a82230dac in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#37 0x00007f5a8096c337 in QEventDispatcherGlib::processEvents (this=0x7f5a140008e0, flags=...) at kernel/qeventdispatcher_glib.cpp:426
#38 0x00007f5a809123b2 in QEventLoop::exec (this=this@entry=0x7f5a68bbdec0, flags=..., flags@entry=...) at kernel/qeventloop.cpp:212
#39 0x00007f5a80723354 in QThread::exec (this=<optimized out>) at thread/qthread.cpp:511
#40 0x00007f5a8072837e in QThreadPrivate::start (arg=0x2aad780) at thread/qthread_unix.cpp:345
#41 0x00007f5a85f23314 in start_thread () from /usr/lib/libpthread.so.0
#42 0x00007f5a85c615bd in clone () from /usr/lib/libc.so.6

[The-Compiler]

Removing this from v0.1 - one source of crashes has been identified and fixed at least.

[The-Compiler]

Another one, with v0.1 on Windows when restarting from exception handler:

Qt5WebKit!QWebSettings::QWebSettings+1632 
Qt5WebKit!QWebSettings::~QWebSettings+30 
Qt5WebKit!QWebPageAdapter::~QWebPageAdapter+41 
Qt5WebKitWidgets!QWebPage::setViewportSize+1f4 
Qt5WebKitWidgets!QWebPage::~QWebPage+26 
QtWebKitWidgets!PyInit_QtWebKitWidgets+177e2 
Qt5WebKitWidgets!QWebView::metaObject+f3 
Qt5WebKitWidgets!QWebView::qt_metacall+34e 
Qt5WebKitWidgets!QWebView::~QWebView+31 
QtWebKitWidgets!PyInit_QtWebKitWidgets+20fad 
Qt5Core!QObject::event+86 
Qt5Widgets!QWidget::event+d4b 
QtWebKitWidgets!PyInit_QtWebKitWidgets+1c0dd 
Qt5Widgets!QApplicationPrivate::notify_helper+f6 
Qt5Widgets!QApplication::notify+1eca 
QtWidgets!PyInit_QtWidgets+2e7a8 
Qt5Core!QCoreApplication::notifyInternal+6f 
Qt5Core!QCoreApplicationPrivate::sendPostedEvents+258 
Qt5Core!QAbstractEventDispatcherPrivate::QAbstractEventDispatcherPrivate+e0 
Qt5Core!QThread::wait+12e 
Qt5Core!QThreadPoolPrivate::reset+cd 
Qt5Core!QThreadPool::waitForDone+25 
Qt5Network!QHostInfo::~QHostInfo+5f0 
Qt5Network!QHostInfo::~QHostInfo+923 
Qt5Network!QHostInfo::~QHostInfo+a14 
Qt5Network!QUdpSocket::metaObject+1a5b 
Qt5Network!QUdpSocket::metaObject+cb7 
Qt5Network!QUdpSocket::metaObject+f01 
ntdll!LdrShutdownProcess+1db 
ntdll!RtlExitUserProcess+90 
msvcr100!cinit+20d 
python34!PyOS_URandom+1af945 
python34!PyOS_URandom+1afad1 
python34!PyOS_URandom+1afc5c 
QtCore!PyInit_QtCore+127b4e 
QtCore!PyInit_QtCore+127c26 
Qt5Core!QMetaObject::activate+622 
QtCore!PyInit_QtCore+1242fa 
QtCore!PyInit_QtCore+124499 
python34!PyOS_URandom+fcd3d 
...
python34!PyOS_URandom+16ef3b 
sip!PyInit_sip+1410 
QtCore+2c23 
QtCore!PyInit_QtCore+b5901 
Qt5Core!QCoreApplicationPrivate::sendThroughApplicationEventFilters+f5 
Qt5Widgets!QApplicationPrivate::notify_helper+1e 
Qt5Widgets!QApplication::notify+1eca 
QtWidgets!PyInit_QtWidgets+2e7a8 
Qt5Core!QCoreApplication::notifyInternal+6f 
Qt5Gui!QGuiApplicationPrivate::processKeyEvent+a9 
Qt5Gui!QGuiApplicationPrivate::processWindowSystemEvent+1a1 
Qt5Gui!QWindowSystemInterface::sendWindowSystemEvents+73 
Qt5Core!QEventDispatcherWin32Private::QEventDispatcherWin32Private+378 
user32!UserCallWinProcCheckWow+1ad 
user32!DispatchMessageWorker+3b5 
Qt5Core!QEventDispatcherWin32::processEvents+426 
qwindows+1fcd1 
Qt5Core!QEventLoop::exec+1cd 
Qt5Core!QCoreApplication::exec+189 

[arp242]

Observed after leaving it open on :help for about 20 minutes and pressing <C-q>.

#0  0x00007fe501d2266d in QNetworkConfigurationManagerPrivate::pollEngines() () from /usr/lib/libQt5Network.so.5
#1  0x00007fe501d8cdcd in ?? () from /usr/lib/libQt5Network.so.5
#2  0x00007fe5102c5ff9 in QMetaObject::activate(QObject*, int, int, void**) () from /usr/lib/libQt5Core.so.5
#3  0x00007fe5102d3df8 in QTimer::timerEvent(QTimerEvent*) () from /usr/lib/libQt5Core.so.5
#4  0x00007fe5102c6d13 in QObject::event(QEvent*) () from /usr/lib/libQt5Core.so.5
#5  0x00007fe50b3ec3dc in QApplicationPrivate::notify_helper(QObject*, QEvent*) () from /usr/lib/libQt5Widgets.so.5
#6  0x00007fe50b3f1820 in QApplication::notify(QObject*, QEvent*) () from /usr/lib/libQt5Widgets.so.5
#7  0x00007fe50bd3219e in ?? () from /usr/lib/python3.4/site-packages/PyQt5/QtWidgets.so
#8  0x00007fe5102959eb in QCoreApplication::notifyInternal(QObject*, QEvent*) () from /usr/lib/libQt5Core.so.5
#9  0x00007fe5102eccdd in QTimerInfoList::activateTimers() () from /usr/lib/libQt5Core.so.5
#10 0x00007fe5102ed121 in ?? () from /usr/lib/libQt5Core.so.5
#11 0x00007fe5118fe9fd in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#12 0x00007fe5118fece0 in ?? () from /usr/lib/libglib-2.0.so.0
#13 0x00007fe5118fed8c in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#14 0x00007fe5102eddfc in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/libQt5Core.so.5
#15 0x00007fe510293482 in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/libQt5Core.so.5
#16 0x00007fe5100a51f4 in QThread::exec() () from /usr/lib/libQt5Core.so.5
#17 0x00007fe5100aa18e in ?? () from /usr/lib/libQt5Core.so.5
#18 0x00007fe5182ec354 in start_thread () from /usr/lib/libpthread.so.0
#19 0x00007fe51802abfd in clone () from /usr/lib/libc.so.6

Qt 5.4.1

[The-Compiler]

This one seems to be a Qt bug which was fixed for Qt 5.4.2, which should be released in the next few days.

[fosskers]

If it helps at all, I notice quite often that systemd-coredump goes nuts when I close qutebrowser. I'm on xmonad and close it with super+shift+c, as per the default.

[The-Compiler]

It seems a lot better to me now (with recent Qt/PyQt versions) as it used to be, so I'm closing this and hope it's indeed the case.

[The-Compiler]

Old code with some stuff I tried from the segfault branch:

commit b7b1fe9518688bc668fd65a993f53dde73c5277c
Author: Florian Bruhin <git@the-compiler.org>
Date:   Mon Oct 13 08:22:12 2014 +0200

    Fix downloadModel rowCount

diff --git a/qutebrowser/models/downloadmodel.py b/qutebrowser/models/downloadmodel.py
index f7f1138..a256ac7 100644
--- a/qutebrowser/models/downloadmodel.py
+++ b/qutebrowser/models/downloadmodel.py
@@ -105,4 +105,9 @@ class DownloadModel(QAbstractListModel):
         if parent.isValid():
             # We don't have children
             return 0
-        return len(objreg.get('download-manager').downloads)
+        try:
+            download_manager = objreg.get('download-manager')
+        except KeyError:
+            return 0
+        else:
+            return len(download_manager.downloads)

commit d74345d77e05c292ee1f25530432ab27764e5f93
Author: Florian Bruhin <git@the-compiler.org>
Date:   Mon Oct 13 04:10:24 2014 +0200

    quick fix for KeyError on shutdown

diff --git a/qutebrowser/widgets/mainwindow.py b/qutebrowser/widgets/mainwindow.py
index d8dd816..199b1b3 100644
--- a/qutebrowser/widgets/mainwindow.py
+++ b/qutebrowser/widgets/mainwindow.py
@@ -160,9 +160,12 @@ class MainWindow(QWidget):
             e: The QResizeEvent
         """
         super().resizeEvent(e)
-        self.resize_completion()
-        self._downloadview.updateGeometry()
-        self._tabbed_browser.tabBar().refresh()
+        try:
+            self.resize_completion()
+            self._downloadview.updateGeometry()
+            self._tabbed_browser.tabBar().refresh()
+        except KeyError:
+            pass

     def closeEvent(self, e):
         """Override closeEvent to display a confirmation if needed."""

commit 725468414b47cce898a57cda8b78b4effa964cee
Author: Florian Bruhin <git@the-compiler.org>
Date:   Tue Sep 30 06:32:41 2014 +0200

    Make exit debugging a lot more verbose

diff --git a/qutebrowser/app.py b/qutebrowser/app.py
index 04a81ba..ed69d1f 100644
--- a/qutebrowser/app.py
+++ b/qutebrowser/app.py
@@ -19,6 +19,7 @@

 """Initialization of qutebrowser and application-wide things."""

+import gc
 import os
 import sys
 import subprocess
@@ -660,6 +661,10 @@ class Application(QApplication):
         # pylint: disable=too-many-branches, too-many-statements
         # FIXME refactor this
         log.destroy.debug("Stage 2 of shutting down...")
+        if self._args.debug_exit:
+            print("Now logging shutdown.", file=sys.stderr)
+            debug.trace_lines(True)
+            gc.set_debug(gc.DEBUG_LEAK)
         # Remove eventfilter
         try:
             log.destroy.debug("Removing eventfilter...")
@@ -733,7 +738,4 @@ class Application(QApplication):
     def exit(self, status):
         """Extend QApplication::exit to log the event."""
         log.destroy.debug("Now calling QApplication::exit.")
-        if self._args.debug_exit:
-            print("Now logging late shutdown.", file=sys.stderr)
-            debug.trace_lines(True)
         super().exit(status)

commit 59640888afe0fee60b89445235c8550b13a62ccc
Author: Florian Bruhin <git@the-compiler.org>
Date:   Tue Sep 30 06:17:09 2014 +0200

    Clear object registries on shutdown.

diff --git a/qutebrowser/app.py b/qutebrowser/app.py
index b28703e..04a81ba 100644
--- a/qutebrowser/app.py
+++ b/qutebrowser/app.py
@@ -722,6 +722,8 @@ class Application(QApplication):
         # If we don't kill our custom handler here we might get segfaults
         log.destroy.debug("Deactiving message handler...")
         qInstallMessageHandler(None)
+        log.destroy.debug("Cleaning up object registry...")
+        objreg.clear()
         # Now we can hopefully quit without segfaults
         log.destroy.debug("Deferring QApplication::exit...")
         # We use a singleshot timer to exit here to minimize the likelyhood of
diff --git a/qutebrowser/utils/objreg.py b/qutebrowser/utils/objreg.py
index 6f233cc..b94dcdd 100644
--- a/qutebrowser/utils/objreg.py
+++ b/qutebrowser/utils/objreg.py
@@ -84,6 +84,12 @@ meta_registry = ObjectRegistry()
 meta_registry['global'] = global_registry


+def clear():
+    """Clear all object registries on shutdown."""
+    global_registry.clear()
+    meta_registry.clear()
+
+
 def _get_registry(scope):
     """Get the correct registry for a given scope."""
     if scope == 'global':
diff --git a/qutebrowser/widgets/webview.py b/qutebrowser/widgets/webview.py
index 71cbfab..f7e6ded 100644
--- a/qutebrowser/widgets/webview.py
+++ b/qutebrowser/widgets/webview.py
@@ -260,6 +260,7 @@ class WebView(QWebView):
         # Copied from:
         # https://code.google.com/p/webscraping/source/browse/webkit.py#325
         self.setPage(None)
+        self.registry.clear()

     def openurl(self, url):
         """Open a URL in the browser.

commit 8e4af9bce2f7e6675ae57f2650ae0e230a184fd3
Author: Florian Bruhin <git@the-compiler.org>
Date:   Tue Sep 30 06:16:59 2014 +0200

    Delete reference to app explicitely.

diff --git a/qutebrowser/qutebrowser.py b/qutebrowser/qutebrowser.py
index e2f1578..c9269b7 100644
--- a/qutebrowser/qutebrowser.py
+++ b/qutebrowser/qutebrowser.py
@@ -114,4 +114,5 @@ def main():
     QtWidgets.qApp = app
     ret = app.exec_()
     QtWidgets.qApp = None
+    del app
     return ret