Application randomly crashes on segmentation fault.

[Hudek]

Hello guys,

when running a qt5 app it sometimes crashes on segmentation fault. This happens on random places in application and I have not been able to pinpoint why. I went forward to debugging it with gdc and got this output:

Program received signal SIGSEGV, Segmentation fault.
0xb5dd2580 in QV4::QObjectWrapper::wrap(QV4::ExecutionEngine*, QObject*) () from /usr/share/qt5.9.6/lib/libQt5Qml.so.5
(gdb) bt
#0 0xb5dd2580 in QV4::QObjectWrapper::wrap(QV4::ExecutionEngine*, QObject*) () from /usr/share/qt5.9.6/lib/libQt5Qml.so.5
#1 0xb5dcd2f4 in QV4::ExecutionEngine::fromVariant(QVariant const&) () from /usr/share/qt5.9.6/lib/libQt5Qml.so.5
#2 0xb5e184c5 in QV4::QmlContextWrapper::get(QV4::Managed const*, QV4::String*, bool*) () from /usr/share/qt5.9.6/lib/libQt5Qml.so.5
#3 0xb5dd63a1 in QV4::ExecutionContext::getProperty(QV4::String*) () from /usr/share/qt5.9.6/lib/libQt5Qml.so.5
#4 0xb5e6a962 in QV4::Runtime::method_getActivationProperty(QV4::ExecutionEngine*, int) () from /usr/share/qt5.9.6/lib/libQt5Qml.so.5
#5 0xac7e1d9d in ?? ()
#6 0xb5dd76e9 in QV4::ExecutionContext::simpleCall(QV4::Scope&, QV4::CallData*, QV4::Function*) () from /usr/share/qt5.9.6/lib/libQt5Qml.so.5
#7 0xb5f0d8ce in QQmlJavaScriptExpression::evaluate(QV4::CallData*, bool*, QV4::Scope&) () from /usr/share/qt5.9.6/lib/libQt5Qml.so.5
#8 0xb5e9f73f in QQmlBoundSignalExpression::evaluate(void**) () from /usr/share/qt5.9.6/lib/libQt5Qml.so.5
#9 0xb5ea08d1 in ?? () from /usr/share/qt5.9.6/lib/libQt5Qml.so.5
#10 0xb5ee92a2 in QQmlNotifier::emitNotify(QQmlNotifierEndpoint*, void**) () from /usr/share/qt5.9.6/lib/libQt5Qml.so.5
#11 0xb5e81638 in QQmlData::signalEmitted(QAbstractDeclarativeData*, QObject*, int, void**) () from /usr/share/qt5.9.6/lib/libQt5Qml.so.5
#12 0xb57ada54 in QMetaObject::activate(QObject*, int, int, void**) () from /usr/share/qt5.9.6/lib/libQt5Core.so.5
#13 0xb57ae4db in QMetaObject::activate(QObject*, QMetaObject const*, int, void**) () from /usr/share/qt5.9.6/lib/libQt5Core.so.5
#14 0xaa095ac5 in QQuickWebView::urlChanged() () from /usr/share/qt5.9.6/qml/QtWebKit/../../lib/libQt5WebKit.so.5
#15 0xaa098f54 in QQuickWebView::emitUrlChangeIfNeeded() () from /usr/share/qt5.9.6/qml/QtWebKit/../../lib/libQt5WebKit.so.5
#16 0xaa09c4f1 in QQuickWebViewPrivate::didStartProvisionalLoadForFrame(OpaqueWKPage const*, OpaqueWKFrame const*, void const*, void const*) () from /usr/share/qt5.9.6/qml/QtWebKit/../../lib/libQt5WebKit.so.5
#17 0xa9fcb06e in WebKit::WebLoaderClient::didStartProvisionalLoadForFrame(WebKit::WebPageProxy*, WebKit::WebFrameProxy*, WebKit::APIObject*) () from /usr/share/qt5.9.6/qml/QtWebKit/../../lib/libQt5WebKit.so.5
#18 0xa9fee1d3 in WebKit::WebPageProxy::didStartProvisionalLoadForFrame(unsigned long long, WTF::String const&, WTF::String const&, CoreIPC::MessageDecoder&) () from /usr/share/qt5.9.6/qml/QtWebKit/../../lib/libQt5WebKit.so.5
#19 0xaa0d0754 in void CoreIPC::handleMessageVariadic<Messages::WebPageProxy::DidStartProvisionalLoadForFrame, WebKit::WebPageProxy, void (WebKit::WebPageProxy::)(unsigned long long, WTF::String const&, WTF::String const&, CoreIPC::MessageDecoder&)>(CoreIPC::MessageDecoder&, WebKit::WebPageProxy, void (WebKit::WebPageProxy::)(unsigned long long, WTF::String const&, WTF::String const&, CoreIPC::MessageDecoder&)) ()
from /usr/share/qt5.9.6/qml/QtWebKit/../../lib/libQt5WebKit.so.5
#20 0xaa0dae8b in WebKit::WebPageProxy::didReceiveMessage(CoreIPC::Connection, CoreIPC::MessageDecoder&) () from /usr/share/qt5.9.6/qml/QtWebKit/../../lib/libQt5WebKit.so.5
#21 0xa9f2416b in CoreIPC::MessageReceiverMap::dispatchMessage(CoreIPC::Connection*, CoreIPC::MessageDecoder&) () from /usr/share/qt5.9.6/qml/QtWebKit/../../lib/libQt5WebKit.so.5
#22 0xa9f3f35e in WebKit::ChildProcessProxy::dispatchMessage(CoreIPC::Connection*, CoreIPC::MessageDecoder&) () from /usr/share/qt5.9.6/qml/QtWebKit/../../lib/libQt5WebKit.so.5
#23 0xa9ff582e in WebKit::WebProcessProxy::didReceiveMessage(CoreIPC::Connection*, CoreIPC::MessageDecoder&) () from /usr/share/qt5.9.6/qml/QtWebKit/../../lib/libQt5WebKit.so.5
#24 0xa9f1e73c in CoreIPC::Connection::dispatchMessage(WTF::PassOwnPtrCoreIPC::MessageDecoder) () from /usr/share/qt5.9.6/qml/QtWebKit/../../lib/libQt5WebKit.so.5
#25 0xa9f1e89d in CoreIPC::Connection::dispatchOneMessage() () from /usr/share/qt5.9.6/qml/QtWebKit/../../lib/libQt5WebKit.so.5
#26 0xa9f1d692 in WTF::BoundFunctionImpl<WTF::FunctionWrapper<void (CoreIPC::Connection::)()>, void (CoreIPC::Connection)>::operator()() () from /usr/share/qt5.9.6/qml/QtWebKit/../../lib/libQt5WebKit.so.5
#27 0xaa3a238c in WebCore::RunLoop::performWork() () from /usr/share/qt5.9.6/qml/QtWebKit/../../lib/libQt5WebKit.so.5
#28 0xaa476a37 in WebCore::RunLoop::TimerObject::qt_static_metacall(QObject*, QMetaObject::Call, int, void**) () from /usr/share/qt5.9.6/qml/QtWebKit/../../lib/libQt5WebKit.so.5
#29 0xb57aadeb in QMetaCallEvent::placeMetaCall(QObject*) () from /usr/share/qt5.9.6/lib/libQt5Core.so.5
#30 0xb57af2bd in QObject::event(QEvent*) () from /usr/share/qt5.9.6/lib/libQt5Core.so.5
#31 0xb66bf22c in QApplicationPrivate::notify_helper(QObject*, QEvent*) () from /usr/share/qt5.9.6/lib/libQt5Widgets.so.5
#32 0xb66c6d24 in QApplication::notify(QObject*, QEvent*) () from /usr/share/qt5.9.6/lib/libQt5Widgets.so.5
#33 0xb577f3f3 in QCoreApplication::notifyInternal2(QObject*, QEvent*) () from /usr/share/qt5.9.6/lib/libQt5Core.so.5
#34 0xb5781c3c in QCoreApplicationPrivate::sendPostedEvents(QObject*, int, QThreadData*) () from /usr/share/qt5.9.6/lib/libQt5Core.so.5
#35 0xb57d5a55 in QEventDispatcherUNIX::processEvents(QFlagsQEventLoop::ProcessEventsFlag) () from /usr/share/qt5.9.6/lib/libQt5Core.so.5
#36 0xb346e2a5 in ?? () from /usr/share/qt5.9.6/plugins/platforms/../../lib/libQt5XcbQpa.so.5
#37 0xb577cea9 in QEventLoop::processEvents(QFlagsQEventLoop::ProcessEventsFlag) () from /usr/share/qt5.9.6/lib/libQt5Core.so.5
#38 0xb577d304 in QEventLoop::exec(QFlagsQEventLoop::ProcessEventsFlag) () from /usr/share/qt5.9.6/lib/libQt5Core.so.5
#39 0xb57864a9 in QCoreApplication::exec() () from /usr/share/qt5.9.6/lib/libQt5Core.so.5
#40 0xb6125ef4 in QGuiApplication::exec() () from /usr/share/qt5.9.6/lib/libQt5Gui.so.5
#41 0xb66bf184 in QApplication::exec() () from /usr/share/qt5.9.6/lib/libQt5Widgets.so.5
#42 0x08060468 in main ()

Anyone has any idea what could this be caused by?
Thanks.

[Cobra91151]

Hello!

Add the code below in your main.cpp and run the application in a debug mode:

Code:

#ifdef QT_DEBUG
    qputenv("QT_FATAL_WARNINGS", "1");
    qputenv("QT_MESSAGE_PATTERN",
            "Type: %{type}\nProduct Name: %{appname}\nFile: %{file}\nLine: %{line}\nMethod: %{function}\nThreadID: %{threadid}\nThreadPtr: %{qthreadptr}\nMessage: %{message}");
#endif

OR

#ifdef QT_DEBUG
    qputenv("QT_FATAL_WARNINGS", "1");
    qSetMessagePattern("Type: %{type}\nProduct Name: %{appname}\nFile: %{file}\nLine: %{line}\nMethod: %{function}\nThreadID: %{threadid}\nThreadPtr: %{qthreadptr}\nMessage: %{message}");
#endif

It should display more information about the crashes. Happy coding!

[JonB]

@Cobra91151
In that case, can't the first one be done just by setting the environment variables and running the application, without code changing/recompiling?

Oh, do you mean the OP will need to recompile to have a debug version?

[Cobra91151]

@JonB

It is better to run this code in a debug mode. Running in a release mode could display different results.

[Hudek]

Thanks for the reply, I'll give it a try.

[davidcastagnetoa]

I have had the same error with the same library "libQt5Qml.so.5". I have tried various alternatives, and in my case, that error occurred when I executed a function in QML, which was supposed to create a custom component previously created in another directory, inside main.qml. In the end, the only thing that solved the problem was migrating to QT6. In my case, I was using Python, so switching from PySide2 to PySide6 solved the problem. Try using QT6 instead of QT5. Good luck