How to correct use QtConcurrent::run

shav · wrote on 8 Mar 2015, 22:06

Hi,

In QML I've called this:

    MenuItem {
        id: openLogMenuItem
        text: qsTr("Open...")
        shortcut: StandardKey.Open

        onTriggered: {
            if(openFileDialog !== null)
            {
                openFileDialog.accepted.connect(function () {
                    manager.openFile(openFileDialog.fileUrl);
                    manager.viewer.settingsManager.addRecentFile(openFileDialog.fileUrl.toString());
                });
                openFileDialog.open();
            }
        }
    }

Also I've connected slot:

MdlManager {
    id: mdlManager

    onMdlLogParserDidStart: {
        spinnerView.running = true;
        cententViewLoader.setSource("");
    }

    onMdlLogParserDidFinished: {
        spinnerView.running = false;
        if(parser !== null)
        {
            var options = { manager: loggerInfoView.mdl};
            cententViewLoader.setSource("Components/MdlCentralWidget.qml", options);
        }
    }

    onMdlLogParserErrorDetected: {
        spinnerView.running = false;
    }
}

In C++ I have method:

Q_INVOKABLE inline void openFile(QString file){m_lvManager->parseLogFile(file);}

And Connected slot:

    m_lvManager = new MdlLogViewerManager();
    m_lvManager->setParent(this);
    connect(m_lvManager->getParser(), &MdlLogParser::parserDidStart, this, [this]() {
        emit mdlLogParserDidStart();
    });
    connect(m_lvManager->getParser(), &MdlLogParser::parserDidFinished, this, [this](MdlLogParser* obj) {
        emit mdlLogParserDidFinished(obj);
    });
    connect(m_lvManager->getParser(), &MdlLogParser::errorChanged, this, [this](MdlLogParserError* obj) {
        emit mdlLogParserErrorDetected(obj);
    });
    connect(m_lvManager->getSettingsManager(), &ShavSettingsManager::settingsLoaded, this, [this](bool flag, ShavSettingsManager* settings) {
        emit mdlSettingsLoaded(flag, settings);
    });

And source code for method "parsingLogFile":

void MdlLogParser::parsingLogFile(QString fPath)
{
    try
    {
        m_wasParsed = false;
        m_logFileFolder.clear();
        m_logFilePath = fPath.replace("file://", "");
        QString logFileName = m_logFilePath.split("/").last();
        m_logFileFolder = m_logFilePath;
        m_logFileFolder.replace(logFileName, "");

        m_classes.clear();
        m_frameworksList.clear();
        m_sessions.clear();
        m_methods.clear();
        m_messages.clear();
        m_systemMessage.clear();
        m_images.clear();
        m_viewsStructures.clear();

        emit parserDidStart();
        QtConcurrent::run(this, &MdlLogParser::readLogFileContents);
    }
    catch(std::exception& exception)
    {
        ShavNotificationCenter::defaultManger()->postNotification(SHAV_NC_EXCEPTION_DETECTED, QVariant(exception.what()));
    }
}

shav · 13 Mar 2015, 19:50

Hi, everyone!

I still have problem with threads in my project, but now it's strange and I don't know why this happens.

I've changed code in my project and now I have class which reading file, the content from file unzip and decoding using AES decode algorithm from QCA library. In result class generate QVariantMap object which return to main program by signal. The code of all operation looks like:

if(!m_logFilePath.isEmpty())
{
    m_logFilePath = m_logFilePath.replace("file://", "");
    QFile file(m_logFilePath);
    if(file.exists())
    {
        if(file.open(QIODevice::ReadOnly | QIODevice::Text))
        {
            QTextStream stream(&file);
            QString content = stream.readAll();

            if(!content.isNull())
            {
                QByteArray compressedDatas = QByteArray::fromBase64(content.toUtf8());
                QString fileContent = QString(uncompressDatas(compressedDatas));        //Trying to decompress source datas

                QString decodedString;
                if(!fileContent.isEmpty()) //If source datas was compressed.
                {
                    decodedString = decode(fileContent, m_aesKey, m_aesIv);
                }
                else        //If source datas doen't compressed we trying to decode withot decompress.
                {
                    decodedString = decode(compressedDatas, m_aesKey, m_aesIv);
                }

                //Start convert to Objects
                if(!decodedString.isNull())
                {
                    QString crashString("Crash=Y");
                    bool wasCrash = false;
                    if(decodedString.startsWith(crashString, Qt::CaseInsensitive))
                    {
                        wasCrash = true;
                    }

                    decodedString = QString("[") + decodedString.mid(crashString.length(),
                                                                     decodedString.length()-crashString.length()-1) + QString("]");

                    QJsonDocument doc = QJsonDocument::fromJson(decodedString.toUtf8());
                    if(!doc.isEmpty())
                    {
                        QVariant data = doc.toVariant();
                        QList<QVariant> list = data.toList();

                        if(!list.isEmpty())
                        {
                            QVariantMap jsonObj, crashImage, startSession;
                            QVariantList methods, viewsList, classes, messageList, systemsList, frameworks, images, loggerMessagesList, loggerExceptionsList, sessions;

                            foreach(QVariant item, list)
                            {
                                QVariantMap obj = item.toMap();
                                QString componentType = obj.value(QString("componentType")).toString();
                                QString action = obj.value(QString("action")).toString();

                                if(componentType == QString("DeviceInfo"))
                                {
                                    jsonObj["deviceInfo"] = obj;
                                }
                                else if(componentType == QString("ApplicationInfo"))
                                {
                                    jsonObj["appInfo"] = obj;
                                }
                                else if(componentType == QString("LoggerInfo"))
                                {
                                    jsonObj["loggerInfo"] = obj;
                                }
                                else if(componentType == QString("Crash"))
                                {
                                    jsonObj["crashLog"] = obj;
                                }
                                else if(componentType == QString("StatisticObject"))
                                {
                                    jsonObj["statistic"] = obj;
                                }
                                else if(componentType == QString("Method"))
                                {
                                    methods.append(obj);
                                }
                                else if(componentType == QString("LibImages"))
                                {
                                    frameworks = obj["list"].toList();
                                }
                                else if(componentType == QString("Image"))
                                {
                                    images.append(obj);

                                    bool isCrash = obj["forCrash"].toBool();
                                    if(isCrash)
                                    {
                                        crashImage = obj;
                                    }
                                }
                                else if(componentType == QString("ViewStructure"))
                                {
                                    viewsList.append(obj);
                                }
                                else if(componentType == QString("LoggerMessage"))
                                {
                                    if(action == QString("Exception"))
                                    {
                                        loggerExceptionsList.append(obj);
                                    }
                                    else
                                    {
                                        loggerMessagesList.append(obj);
                                    }
                                }
                                else if(componentType == QString("Message"))
                                {
                                    messageList.append(obj);
                                }
                                else if(componentType == QString("SystemMessage"))
                                {
                                    systemsList.append(obj);
                                }
                                else if(componentType == QString("Class"))
                                {
                                    classes.append(obj);
                                }
                                else if(componentType == QString("Session"))
                                {
                                    if(action == QString("SessionStart"))
                                    {
                                        startSession = obj;
                                    }
                                    else if(action == QString("SessionFinished"))
                                    {
                                        QVariantMap map = startSession;
                                        map["start"] = startSession["timestamp"];
                                        map["end"] = obj["timestamp"];
                                        map["length"] = (obj["timestamp"].toDouble() - startSession["timestamp"].toDouble());
                                        sessions.append(map);
                                    }
                                }
                            }


                            QString path = m_logFilePath;
                            QString logFile = m_logFilePath.split("/").last();
                            QString logFileFolder = path.replace(logFile, "");

                            jsonObj["logFilePath"] = m_logFilePath;
                            jsonObj["logFileFolder"] = logFileFolder;
                            jsonObj["logContent"] = decodedString;
                            jsonObj["wasCrash"] = wasCrash;

                            jsonObj["classes"] = classes;
                            jsonObj["methods"] = methods;
                            jsonObj["viewsStructures"] = viewsList;
                            jsonObj["messages"] = messageList;
                            jsonObj["systemMessage"] = systemsList;
                            jsonObj["frameworksList"] = frameworks;
                            jsonObj["images"] = images;
                            jsonObj["sessions"] = sessions;

                            QVariantMap crashLog = jsonObj["crashLog"].toMap();
                            crashLog["image"] = crashImage;
                            jsonObj["crashLog"] = crashLog;

                            QVariantMap loggerInfo = jsonObj["loggerInfo"].toMap();
                            loggerInfo["messages"] = loggerMessagesList;
                            loggerInfo["exceptions"] = loggerExceptionsList;
                            jsonObj["loggerInfo"] = loggerInfo;

                            emit fileReaderDidFinish(jsonObj);
                        }
                    }
                }
            }
        }
    }
}

emit fileReaderDidFinish(QVariant());

When I need to use class I've called this code:

    if(!file.isEmpty())
    {
        emit m_parser->parserDidStart();

        QThread* thread = new QThread(this);
        MdlFileReader* fileReader = new MdlFileReader(file, m_settingsManager->getAesKey(), m_settingsManager->getAesInventoryKey());
        fileReader->moveToThread(thread);
        connect(fileReader, &MdlFileReader::fileReaderDidFinish, this, [this, file](QVariant jsonObj) {

            if(!jsonObj.isNull())
            {
                m_parser->updateFromJSONObject(jsonObj);
            }
        }, Qt::QueuedConnection);
        connect(thread, &QThread::started, fileReader, &MdlFileReader::startParseFile);
        thread->start();
    }

The problem is sometimes this code works and application does't crash. But sometimes application crashes. It's could happens every second time when I load application (without rebuild).

I've also tried QtConcurrent::run but no luck.

Full crash report looks like:

Process:               MdlViewer [6460]
Path:                  /Volumes/VOLUME/*/MdlViewer.app/Contents/MacOS/MdlViewer
Identifier:            com.shav.MdlViewer
Version:               1.0.0 (1.0.0)
Code Type:             X86-64 (Native)
Parent Process:        Qt Creator [6229]
Responsible:           Qt Creator [6229]
User ID:               501

Date/Time:             2015-03-13 20:35:02.729 +0200
OS Version:            Mac OS X 10.10.2 (14C1510)
Report Version:        11
Anonymous UUID:        01BBAAA2-2A09-5EF9-08B9-47ED5259279D


Time Awake Since Boot: 39000 seconds

Crashed Thread:        0  Dispatch queue: com.apple.main-thread

Exception Type:        EXC_BAD_ACCESS (SIGSEGV)
Exception Codes:       EXC_I386_GPFLT

Thread 0 Crashed:: Dispatch queue: com.apple.main-thread
0   org.qt-project.QtQml          	0x000000010795c5ea QV4::QObjectWrapper::wrap(QV4::ExecutionEngine*, QObject*) + 42
1   org.qt-project.QtQml          	0x000000010795ac72 QV4::QObjectWrapper::getProperty(QObject*, QV4::ExecutionContext*, QQmlPropertyData*, bool) + 1602
2   org.qt-project.QtQml          	0x000000010795a41c QV4::QObjectWrapper::getQmlProperty(QV4::ExecutionContext*, QQmlContextData*, QV4::String*, QV4::QObjectWrapper::RevisionMode, bool*, bool) + 636
3   org.qt-project.QtQml          	0x000000010795e266 QV4::QObjectWrapper::get(QV4::Managed*, QV4::String*, bool*) + 70
4   org.qt-project.QtQml          	0x0000000107969f29 QV4::Runtime::getProperty(QV4::ExecutionContext*, QV4::ValueRef, QV4::String*) + 105
5   ???                           	0x0000000112f7c9b9 0 + 4613196217
6   org.qt-project.QtQml          	0x000000010791b190 QV4::SimpleScriptFunction::call(QV4::Managed*, QV4::CallData*) + 528
7   org.qt-project.QtQml          	0x0000000107a0145e QQmlJavaScriptExpression::evaluate(QQmlContextData*, QV4::ValueRef, QV4::CallData*, bool*) + 622
8   org.qt-project.QtQml          	0x00000001079a8142 QQmlBoundSignalExpression::evaluate(void**) + 2258
9   org.qt-project.QtQml          	0x00000001079a8b68 QQmlBoundSignal_callback(QQmlNotifierEndpoint*, void**) + 440
10  org.qt-project.QtQml          	0x00000001079e345c QQmlNotifier::emitNotify(QQmlNotifierEndpoint*, void**) + 92
11  org.qt-project.QtQml          	0x0000000107984711 QQmlData::signalEmitted(QAbstractDeclarativeData*, QObject*, int, void**) + 753
12  org.qt-project.QtCore         	0x0000000107467cb7 QMetaObject::activate(QObject*, int, int, void**) + 183
13  libqtquickcontrolsplugin.dylib	0x000000010fe15285 QQuickMenuItem::qt_static_metacall(QObject*, QMetaObject::Call, int, void**) + 517
14  org.qt-project.QtCore         	0x00000001074687ab QMetaObject::activate(QObject*, int, int, void**) + 2987
15  libqtquickcontrolsplugin.dylib	0x000000010fe12cfd QQuickAction::triggered(QObject*) + 61
16  libqtquickcontrolsplugin.dylib	0x000000010fe152a1 QQuickMenuItem::qt_static_metacall(QObject*, QMetaObject::Call, int, void**) + 545
17  org.qt-project.QtCore         	0x0000000107461393 QObject::event(QEvent*) + 755
18  org.qt-project.QtWidgets      	0x0000000107e2632b QApplicationPrivate::notify_helper(QObject*, QEvent*) + 251
19  org.qt-project.QtWidgets      	0x0000000107e29648 QApplication::notify(QObject*, QEvent*) + 8136
20  org.qt-project.QtCore         	0x0000000107436a5b QCoreApplicationPrivate::sendPostedEvents(QObject*, int, QThreadData*) + 971
21  libqcocoa.dylib               	0x000000010aea0b8e QCocoaEventDispatcherPrivate::processPostedEvents() + 190
22  libqcocoa.dylib               	0x000000010aea1411 QCocoaEventDispatcherPrivate::postedEventsSourceCallback(void*) + 33
23  com.apple.CoreFoundation      	0x00007fff8f285681 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 17
24  com.apple.CoreFoundation      	0x00007fff8f27780d __CFRunLoopDoSources0 + 269
25  com.apple.CoreFoundation      	0x00007fff8f276e3f __CFRunLoopRun + 927
26  com.apple.CoreFoundation      	0x00007fff8f276858 CFRunLoopRunSpecific + 296
27  com.apple.HIToolbox           	0x00007fff8e010aef RunCurrentEventLoopInMode + 235
28  com.apple.HIToolbox           	0x00007fff8e01076e ReceiveNextEventCommon + 179
29  com.apple.HIToolbox           	0x00007fff8e0106ab _BlockUntilNextEventMatchingListInModeWithFilter + 71
30  com.apple.AppKit              	0x00007fff8c903f81 _DPSNextEvent + 964
31  com.apple.AppKit              	0x00007fff8c903730 -[NSApplication nextEventMatchingMask:untilDate:inMode:dequeue:] + 194
32  com.apple.AppKit              	0x00007fff8c8f7593 -[NSApplication run] + 594
33  libqcocoa.dylib               	0x000000010aea02fd QCocoaEventDispatcher::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) + 2189
34  org.qt-project.QtCore         	0x000000010743337d QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) + 381
35  org.qt-project.QtCore         	0x000000010743635a QCoreApplication::exec() + 346
36  com.shav.MdlViewer            	0x00000001067ebe57 main + 663
37  com.shav.MdlViewer            	0x00000001067ebbb4 start + 52

What I do wrong? Thanks for the any help!

jalomic · 13 Mar 2015, 20:13

@shav Where is objects deletion?

http://doc.qt.io/qt-5/qthread.html Documentation contains very useful examles

shav · replied to jalomic on 13 Mar 2015, 20:13

@jalomic Thanks for the reply!

I've added the attribute to my main class which must separate thread as

    /** Thread for read file.*/
    QThread* m_thread;

In constructor of my class I've aded this line to create thread instance like this:

    m_thread = new QThread(this);

and method where I'm using this thread looks like this:

        MdlFileReader* fileReader = new MdlFileReader(file, m_settingsManager->getAesKey(), m_settingsManager->getAesInventoryKey());
        fileReader->moveToThread(m_thread);
        connect(fileReader, &MdlFileReader::fileReaderDidFinish, this, [this](QVariant jsonObj) {

            m_thread->quit();
            m_thread->wait();

            if(!jsonObj.isNull())
            {
                m_parser->updateFromJSONObject(jsonObj);
            }
        });

        connect(m_thread, &QThread::started, fileReader, &MdlFileReader::startParseFile);
        m_thread->start();

in destructor of my main class I've added this line:

    m_thread->deleteLater();

By the way how I can call slot from main thread if signal send from separate thread? Maybe problem is that I'm updating GUI in separate thread? Because in QML I have slot which uses Loader to load QML file. This slot called when file was parse and ready to use.

SGaist · wrote on 13 Mar 2015, 21:14

The connection should be queued, so the slot will be executed in the receiver thread (hence the use of signals and slots to transmit information for the GUI part to update)

I wonder if your object gets garbage collected

shav · 14 Mar 2015, 07:18

Thanks! But I've tried this and this didn't help me to solved problem :-(

About GC I'll check.

jalomic · 14 Mar 2015, 17:49

@shav connect(m_thread, &QThread::finished, fileReader, &QObject::deleteLater);

shav · replied to jalomic on 14 Mar 2015, 17:49

@jalomic Thanks I'll try this.

SGaist · 16 Mar 2015, 10:32

About the ownership: here is the doc

shav · replied to SGaist on 16 Mar 2015, 10:32

@SGaist Thanks for the link! I'll check it!