QSerialPort crash on write()

  • Hello,

    I find that this code runs fine in Debug mode but in Release mode causes my program to crash a few seconds after opening.

    If remove the line that writes to the serial port then it doesn't crash.

    I can't figure out why it is crashing!

        // Serial port connection
        m_serialPort = new QSerialPort(this);
        connect(m_serialPort, &QSerialPort::readyRead, this, &MyClass::readSerialData);
    void MyClass::openSerialPort()
        QString portName = "";
        const QList<QSerialPortInfo> infos = QSerialPortInfo::availablePorts();
        for (const QSerialPortInfo &info : infos) {
            if (info.isBusy() == false) {
                portName = info.portName();
        if (m_serialPort->open(QIODevice::ReadWrite)) {
            // connected
        } else {
            qWarning() << "Cannot open serial port";
        m_serialPort->write("TESTWRITE", 9);

  • Qt Champions 2018

    can you try replacing m_serialPort->write("TESTWRITE", 9); with

    QTextStream portStream(m_serialPort);
    portStream << "TESTWRITE";

  • Thanks for the suggestion VRonin.

    I tried this but still causes program to crash after 10 or 15 seconds.

  • Lifetime Qt Champion


    Can you show a stack trace ?

  • Qt Champions 2018

    @SGaist said in QSerialPort crash on write():

    Can you show a stack trace ?

    Can you get a meaningful stack trace in release mode?

    BTW the problem does not appear to be in this snippet

  • Lifetime Qt Champion

    Indeed, it's harder. I somehow missed the "Release" part...

    On a side note, it's pretty unusual to call write if the port opening failed.

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