QT SERIAL PORT THREADING CRASH APP

[canrollas]

@jsulm

this is functions

[jsulm]

@canrollas As you can see it crashes in executeOrder in file IOThread.cpp line 237 - what is in that line?

[canrollas]

this is execute function

else if(order == 3){
        qInfo()<<"This is general monitor stop";
        // Kill all jedi masters :D
        if(connectionStatus == true){
            if(monitoringStatus == true){
                QByteArray b("0A53");
                QByteArray bytes = QByteArray::fromHex(b);
                serialPort.write(bytes);
                serialPort.waitForBytesWritten();
                qInfo()<<"Stopping the monitoring device!"<<Qt::endl;
                monitoringStatus = false;
                emit sendMonitoringStatus(false);
            }else{
                emit sendMessageToSerialDevice("First start the monitoring device!");
            }
        }else{
            emit sendMessageToSerialDevice("First connect to the device via makcon!");

        }

this is caller function

@jsulm void SerialDevice::connectToCanBus(){

    QString portname ;


    foreach (auto looper, serialPortInfo->availablePorts()) {
        qInfo()<<"This is looping device on the machine:"<<looper.description()<<looper.portName();
        if(looper.description()=="Makersan USB to CAN Converter" || looper.description()=="STMicroelectronics Virtual COM Port" && looper.portName().contains("tty")==true || looper.portName().contains("COM")==true){
            qInfo()<<"The device has found in the loop:"<<looper.description();
            portname = looper.portName();
            thread->setUpSerialPort(looper.portName(),9600);
            thread->addDataCommandToQList(0);

            if(thread->isRunning()==false){
                thread->start();
            }
        }

    }
    if(portname.isEmpty()==true){
        emit sendMessageToMainWindow("Device is not plugged or not detected");
    }


}

[jsulm]

@canrollas Which line in that code is 237 please?

[J.Hilk]

@jsulm 237 is the waitForbytesWritten call

[canrollas]

@jsulm Those are the lines
serialPort.write(bytes);
serialPort.waitForBytesWritten();

[canrollas]

@J-Hilk Can you see where is wrong or etc. ?

[Valentin49]

@jsulm @canrollas
I have the same issue both on Windows 10 and Ubuntu 20.04. Crash occurs on call to waitForBytesWritten()

+1 to solve this bug

[Christian Ehrlicher]

@Valentin49 said in QT SERIAL PORT THREADING CRASH APP:

I have the same issue

then please create a minimal compileable example which reproduces your crash and create a new thread instead hijacking an old one

[glapalme]

Hi, I just stumbled acrros the same issue as yours when switching from Qt5.15.2 MinGW 32-bits to Qt6.3.2 MinGW 64-bits. My application was working fine with Qt5, but was constantly crashing when calling QSerialPort::waitForBytesWritten() when compiling using Qt6.

My original code:

// My QSerialPort object runs in its own thread

QSerialPort *serial = new QSerialPort(this); 
// initializationn of serial object ...

void MySerialClass::write( const QByteArray& bytes )
{
   serial->write(bytes);
   if(!serial->waitForBytesWritten()) 
   {
      qWarning() << "Write timeout!";
   }
}

I found a fix by trial and error: I verify that there is indeed some bytes waiting to be written before calling the function:

void MySerialClass::write( const QByteArray& bytes )
{
   // write() returns the number of bytes that were actually written, or -1 if error
   quint64 bytes_written = serial->write(bytes);
   if(bytes_written != bytes.size() && !serial->waitForBytesWritten()) 
   {
      qWarning() << "Write timeout!";
   }
}

Hope it works for you!