QT SERIAL PORT THREADING CRASH APP

[canrollas]

@jsulm Sir,look you have answered my other question same way. I need thread in my specific situation ( can not be explained ) .

[jsulm]

@canrollas Then please run through debugger until it crashes and post the stack trace here. Debugging is the first thing to do in case of a crash.

[jsulm]

@canrollas Also, where do you call setUpSerialPort? You need to understand that you should create all needed variables (like serialPort) inside run() method, else they will live in the thread which starts your io thread.

[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!