Application don` t exit (maybe it cause qfuture?)

qtenjoyer

I'm writing my own messenger, and after updating the frontend to qml, I noticed that the application no longer terminates when the window is closed, although I even explicitly set setQuitOnLastWindowClosed in QGuiApplication. After I added an onClosing slot to the ApplicationWindow type qml, and associated the quit signal QQmlApplicationEngine with QGuiApplication::quit, this did not give any result, then I associated this signal with the lambda, through qDebug I saw that it was called, and that qApp->quit() was called also, but does not give a way out. Then I used std::exit, everything worked, but the QWaitCondition: Destroyed while threads are still waiting log appeared.

In general, as I understand it, QtConcurrent does not allow the application to close, which is necessary for an asynchronous connection with the server. I don't want to use std::exit, it's still probably not safe, how can I ignore the threads in the application and close them with quit? exit doesn't work either, by the way.

jsulm

@qtenjoyer How exactly do you use threads?
You should stop your threads when your application is closing.

qtenjoyer

@jsulm
I have a Connection class, inside of which there is a restoreConnection method, and it already uses QtConcurrent::run to asynchronously establish a connection to the server. Below is the method code

void Connection::restoreConnection() noexcept {
    if (m_socket)
        m_socket->deleteLater();
    QFuture<void> future = QtConcurrent::run([this]() {
        m_socket = new QTcpSocket(nullptr);
        while (true) {
            m_socket->connectToHost(ip::ServerIp, ip::ServerPort);
            if (m_socket->waitForConnected()) {
                qDebug() << "Succesfull connected to server";
                AbstractNetworkSocket::initializeFromSocket(m_socket);
                if (isAuthenticated()) {
                    auto request = outgoingRequestFlags(
                        PacketType::Login,
                        this,
                        PacketFlags(PacketFlags::AuthorizationRequest),
                        << getUserId() << utils::makeSHA256Hash(getPassword())
                    );
                    request->onCompleted([this](OutgoingRequestProxy& proxy) {
                        QUuid token;
                        proxy >> token;
                        setToken(token);
                        emit authentificated(); 
                    });
                    request->onError(replyes::incorrentLogin,[this]() -> void {
                        emit invalidAuthentificate();
                    });
                    request->onError([request](ReplyStatus status) -> void {
                        request->tryAgain();
                    });
                }
                return;
            }
            qCritical() << "Retry connect to server..";
        }
    });
}

JonB

@qtenjoyer

@jsulm said in Application don` t exit (maybe it cause qfuture?):

You should stop your threads when your application is closing.

jsulm

@qtenjoyer said in Application don` t exit (maybe it cause qfuture?):

QFuture<void> future = QtConcurrent::run(this {

Try to call https://doc.qt.io/qt-6/qfuture.html#cancel on that future if it is still running (when you close your app).

qtenjoyer

@jsulm
you can’t cancel qfuture that was launched via qtconcurrent::run, I ended up doing without using a thread at all, I just did connectToHost in restoreConnection without waiting, connected onConnect for the socket and processed all the logic there